JP7335772B2 - Methacrylic resins, methacrylic resin compositions, molded articles, optical parts and automobile parts - Google Patents

Description

TECHNICAL FIELD The present invention relates to methacrylic resins, methacrylic resin compositions, molded articles, optical parts, and automobile parts.

In recent years, methacrylic resins, in addition to their excellent transparency and surface hardness, have low birefringence, which is an optical property. Optical resin for optical materials such as optical discs, optical films, plastic substrates, etc., such as flat panel displays such as flat panel displays, small infrared sensors, fine optical waveguides, ultra-small lenses, pickup lenses for DVD/Blue Ray discs that handle short wavelength light. and the market is expanding significantly.

In particular, a methacrylic resin containing a structural unit having a ring structure in its main chain and a composition containing the methacrylic resin are known to have excellent performance in terms of both heat resistance and optical properties. (See, for example, Patent Document 1), the demand is rapidly increasing year by year. However, methacrylic resins having structural units having a ring structure in the main chain, which have improved heat resistance and optical properties as described above, are sometimes colored due to the absorption of light in the visible light range due to the ring structure, etc. There is a problem that the Therefore, in order to obtain a methacrylic resin having a cyclic structure in the main chain with little coloration and high transparency, the substances that cause coloring contained in the raw materials are reduced, and the unreacted cyclic monomers remaining in the methacrylic resin are reduced. A method for doing so is disclosed.

Regarding coloring-causing substances in raw materials, for example, Patent Document 2 discloses that resin coloring is achieved by reducing the content of various N-phenylmaleamic acids and N-phenylsuccinimides contained in N-phenylmaleimide. There is a description that it can prevent silver streaks.

Further, in Patent Document 3, by reducing the content of primary amines and the content of 2-amino-N-substituted succinimides in N-substituted maleimides, coloring of N-substituted maleimides is prevented, and in turn, N-substituted maleimides are prevented from being colored. It is disclosed that the color tone of transparent resins using maleimide as a monomer can also be improved.

As a method for reducing unreacted monomers in a methacrylic resin, for example, in Patent Document 4, a monomer component containing an N-substituted maleimide (a) and a methacrylic acid ester (b) is used, and the monomer Unreacted monomers present in the reaction system at the end of the supply of the monomer components in a production method in which a part of the components are supplied to initiate polymerization and then the remainder of the monomer component is supplied during polymerization. By controlling the ratio of the N-substituted maleimide (a) in the component to be lower than the ratio of the N-substituted maleimide (a) in the total supply amount of the monomer component, the amount of residual N-substituted maleimide monomer is reduced. A method for obtaining a heat-resistant methacrylic resin having a reduced weight, excellent transparency, and little coloration has been proposed.

Further, in Patent Document 5, in a methacrylic acid ester-based monomer/maleimide monomer polymerization system using a sulfur-based chain transfer agent such as mercaptan, by allowing an acidic substance to exist in the reaction system, residual maleimide There have been proposed methods for suppressing coloration by reducing analogue monomers and maleimide analogue monomers generated by heating during molding and the like.

WO2011/149088 WO2012/128255 JP-A-6-135931 JP-A-9-324016 JP-A-2001-233919

However, in recent years, as the application has expanded from optical film applications to thick molded products such as lenses and molded plates, thick molded products have a longer optical path length, so molded products with less coloring. It is desired to provide a composition that provides

When using a methacrylic resin composition with a relatively high glass transition temperature to prepare a thick molded body such as a lens by injection molding, a high temperature and high fluidity are required to obtain a low birefringence molded body. Since it is necessary to perform molding under such conditions, the inside of a thick molded product is exposed to high temperatures for a long period of time, and there is an increased concern that color tone will deteriorate.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a methacrylic resin and a methacrylic resin composition which are raw materials for molded articles having excellent color tone in a long optical path. In particular, a methacrylic resin composition that uses a methacrylic resin composition with a relatively high glass transition temperature and can obtain a molded body with low birefringence and little coloration even in a thick molded body such as a lens obtained by injection molding. and a methacrylic resin composition.

The inventors of the present invention have made intensive studies to solve the above problems, and found that there is a correlation between the content of fluorescent substances commonly contained in methacrylic resins having a ring structure in the main chain and the coloring in the manufacturing process. I found Then, the present inventors have found that a molded product with a good color tone can be obtained by controlling the fluorescence emission intensity of a methacrylic resin within a certain range, and have completed the present invention.

That is, the present invention is as follows.
[1]
A methacrylic resin having a structural unit (X) having a ring structure in its main chain,
The structural unit (X) is a structural unit derived from N-cyclohexylmaleimide or N-phenylmaleimide ,
Glass transition temperature (Tg) is more than 120 ° C. and 160 ° C. or less,
When the chloroform solution containing 2.0% by mass of the methacrylic resin was spectroscopically analyzed, the emission intensity at 514 nm obtained at an excitation wavelength of 436 nm and a slit width of 2 nm was 30 × 10 ^-10 mol/ in terms of the concentration of the ethanol solution of fluorescein. L or less ,
The methacrylic resin contains a structural unit derived from a methacrylic acid ester monomer, and the content of the structural unit derived from the methacrylic acid ester monomer is 50 to 97% by mass with respect to 100% by mass of the methacrylic resin, The content of structural units derived from N-cyclohexylmaleimide or N-phenylmaleimide is 5 to 40% by mass with respect to 100% by mass of the methacrylic resin,
The methacrylate ester monomer is methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid Cyclopentyl, cyclohexyl methacrylate, cyclooctyl methacrylate, tricyclodecyl methacrylate, dicyclooctyl methacrylate, tricyclododecyl methacrylate, isobornyl methacrylate, phenyl methacrylate, benzyl methacrylate, 1-phenylethyl methacrylate, methacrylic acid at least one selected from 2-phenoxyethyl, 3-phenylpropyl methacrylate, and 2,4,6-tribromophenyl methacrylate ;
A methacrylic resin characterized by:

[2]
The methacrylic resin according to [1], wherein the luminescence intensity is 1×10 ⁻¹⁰ mol/L or more and 20×10 ⁻¹⁰ mol/L or less in terms of concentration of ethanol solution of fluorescein.

[3]
When the chloroform solution containing 2.0% by mass of the methacrylic resin was spectroscopically analyzed, the emission intensity at 458 nm obtained at an excitation wavelength of 365 nm and a slit width of 2 nm was obtained by dissolving quinine sulfate dihydrate in a 1 mol / L dilute sulfuric acid solution. The methacrylic resin of [1] or [2], which is 4×10 ⁻⁹ mol/L or more and 6×10 ⁻⁹ mol/L or less in terms of concentration of the solution.

[4]
The methacrylic resin according to any one of [1] to [3], having an absolute value of photoelastic coefficient of 3.0×10 ⁻¹² Pa ⁻¹ or less.

[5]
A methacrylic resin composition comprising the methacrylic resin according to any one of [1] to [4] .

[6]
A molded article comprising the methacrylic resin composition of [5] .

[7]
An optical component comprising the molded product of [6] .

[8]
The optical component of [7] , which is a light guide plate.

[9]
The optical component of [7] , which is a lens.

[ 10 ]
An automobile part comprising the molded article of [6] .

According to the present invention, it is possible to provide a methacrylic resin and a methacrylic resin composition that serve as raw materials for molded articles having excellent color tone in a long optical path.
In particular, the methacrylic resin and methacrylic resin composition of the present embodiment preferably have high heat resistance, highly controlled birefringence, and improved color tone.

FIG. 1 is a diagram showing a concentration-intensity approximation line and a concentration-intensity conversion formula for a fluorescein/ethanol solution in Examples. FIG. 2 is a diagram showing a concentration-intensity approximation line and a concentration-intensity conversion formula for a solution obtained by dissolving quinine sulfate dihydrate in a 1 mol/L dilute sulfuric acid solution in Examples.

Hereinafter, the mode for carrying out the present invention (hereinafter referred to as "this embodiment") will be described in detail, but the present invention is not limited to the following description, and within the scope of the gist Various modifications can be made.

[Methacrylic resin]
The methacrylic resin in the present embodiment contains a structural unit (X) having a ring structure in its main chain and a structural unit derived from a methacrylic acid ester monomer. In the methacrylic resin of the present embodiment, the main chain may consist of only the structural unit (X) having a ring structure and the structural unit derived from the methacrylic acid ester monomer.

Each structural unit will be described below.

- Structural Unit Derived from Methacrylic Acid Ester Monomer -
Examples of structural units derived from methacrylic acid ester monomers include structural units derived from monomers selected from the following methacrylic acid esters. Examples of methacrylates include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, and methacrylic acid. Cyclopentyl, cyclohexyl methacrylate, cyclooctyl methacrylate, tricyclodecyl methacrylate, dicyclooctyl methacrylate, tricyclododecyl methacrylate, isobornyl methacrylate, phenyl methacrylate, benzyl methacrylate, 1-phenylethyl methacrylate, methacrylic acid 2-phenoxyethyl, 3-phenylpropyl methacrylate, 2,4,6-tribromophenyl methacrylate and the like.
These monomers may be used alone or in combination of two or more.
As the structural unit derived from the methacrylic acid ester monomer, structural units derived from methyl methacrylate and benzyl methacrylate are preferable from the viewpoint of excellent transparency and weather resistance of the resulting methacrylic resin.
Structural units derived from methacrylic acid ester monomers may be contained alone or in combination of two or more.

The content of the structural unit derived from the methacrylic acid ester monomer is the methacrylic resin from the viewpoint of sufficiently imparting heat resistance to the methacrylic resin by the structural unit (X) having a ring structure in the main chain described later. 100% by mass, preferably 50 to 97% by mass, more preferably 55 to 97% by mass, even more preferably 55 to 95% by mass, even more preferably 60 to 93% by mass, particularly preferably 60 to 90% by mass %.

The content of structural units derived from methacrylic acid ester monomers can be determined by ¹ H-NMR measurement and ¹³ C-NMR measurement. ¹ H-NMR measurement and ¹³ C-NMR measurement can be performed at a measurement temperature of 40° C. using, for example, CDCl ₃ or DMSO-d ₆ as a measurement solvent.

The structural unit (X) having a ring structure in its main chain is described below.
The structural unit (X) having a ring structure in the main chain may contain at least one selected from the group consisting of a structural unit derived from an N-substituted maleimide monomer, a glutarimide-based structural unit, and a lactone ring structural unit. More preferably, it consists only of structural units selected from the group consisting of structural units derived from N-substituted maleimide monomers, glutarimide-based structural units, and lactone ring structural units. Structural units (X) having a ring structure in the main chain may be of one type or a combination of two or more types.

-Structural unit derived from N-substituted maleimide monomer-
Next, structural units derived from N-substituted maleimide monomers will be described.
The structural unit derived from the N-substituted maleimide monomer may be at least one structural unit selected from the group consisting of structural units represented by the following formula (1) and structural units represented by the following formula (2), Preferably, it is formed from both structural units represented by the following formula (1) and the following formula (2).

式（１）中、Ｒ¹は、炭素数７～１４のアリールアルキル基、炭素数６～１４のアリール基のいずれかを示し、Ｒ²及びＲ³は、それぞれ独立に、水素原子、酸素原子、硫黄原子、炭素数１～１２のアルキル基又は炭素数６～１４のアリール基のいずれかを示す。
また、Ｒ²またはＲ³がアリール基の場合には、Ｒ²またはＲ³は置換基としてハロゲン原子を含んでいてもよい。
また、Ｒ¹は、ハロゲン原子、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基、ニトロ基、ベンジル基等の置換基で置換されていてもよい。

In formula (1), R ¹ represents either an arylalkyl group having 7 to 14 carbon atoms or an aryl group having 6 to 14 carbon atoms, and R ² and R ³ each independently represent a hydrogen atom or an oxygen atom. , a sulfur atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms.
Also, when R ² or R ³ is an aryl group, R ² or R ³ may contain a halogen atom as a substituent.
Also, R ¹ may be substituted with a substituent such as a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a nitro group, or a benzyl group.

式（２）中、Ｒ⁴は、水素原子、炭素数３～１２のシクロアルキル基、炭素数１～１２のアルキル基のいずれかを示し、Ｒ⁵及びＲ⁶は、それぞれ独立に、水素原子、酸素原子、硫黄原子、炭素数１～１２のアルキル基、又は炭素数６～１４のアリール基のいずれかを示す。

In formula (2), R ⁴ represents a hydrogen atom, a cycloalkyl group having 3 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms, and R ⁵ and R ⁶ each independently represent a hydrogen atom. , an oxygen atom, a sulfur atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms.

Specific examples are shown below.
Examples of monomers (N-arylmaleimides, N-aromatically substituted maleimides, etc.) forming the structural unit represented by formula (1) include N-phenylmaleimide, N-benzylmaleimide, N-(2 -chlorophenyl)maleimide, N-(4-chlorophenyl)maleimide, N-(4-bromophenyl)maleimide, N-(2-methylphenyl)maleimide, N-(2,6-dimethylphenyl)maleimide, N-(2 -ethylphenyl)maleimide, N-(2-methoxyphenyl)maleimide, N-(2-nitrophenyl)maleimide, N-(2,4,6-trimethylphenyl)maleimide, N-(4-benzylphenyl)maleimide, N-(2,4,6-tribromophenyl)maleimide, N-naphthylmaleimide, N-anthracenylmaleimide, 3-methyl-1-phenyl-1H-pyrrole-2,5-dione, 3,4-dimethyl -1-phenyl-1H-pyrrole-2,5-dione, 1,3-diphenyl-1H-pyrrole-2,5-dione, 1,3,4-triphenyl-1H-pyrrole-2,5-dione, etc. are mentioned.
Among these monomers, N-phenylmaleimide and N-benzylmaleimide are preferable because the obtained methacrylic resin has excellent heat resistance and optical properties such as birefringence.
These monomers may be used alone or in combination of two or more.

Examples of the monomer forming the structural unit represented by formula (2) include N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, N-isopropylmaleimide, Nn-butylmaleimide, N-isobutylmaleimide, Ns-butylmaleimide, Nt-butylmaleimide, Nn-pentylmaleimide, Nn-hexylmaleimide, Nn-heptylmaleimide, Nn-octylmaleimide, N-lauryl maleimide, N-cyclopentylmaleimide, N-cyclohexylmaleimide, 1-cyclohexyl-3-methyl-1H-pyrrole-2,5-dione, 1-cyclohexyl-3,4-dimethyl-1H-pyrrole-2,5-dione, 1-cyclohexyl-3-phenyl-1H-pyrrole-2,5-dione, 1-cyclohexyl-3,4-diphenyl-1H-pyrrole-2,5-dione and the like.
Among these monomers, N-methylmaleimide, N-ethylmaleimide, N-isopropylmaleimide, and N-cyclohexylmaleimide are preferred from the viewpoint of excellent weather resistance of methacrylic resins. N-cyclohexylmaleimide is particularly preferred because of its excellent hygroscopicity.
These monomers can be used alone or in combination of two or more.

In the methacrylic resin of the present embodiment, the combined use of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) expresses highly controlled birefringence properties. It is particularly preferable in terms of obtaining.

The molar ratio of the content (X1) of the structural unit represented by formula (1) to the content (X2) of the structural unit represented by formula (2), (X1/X2), is preferably greater than 0 and 15 Below, more preferably more than 0 and 10 or less.
When the molar ratio (X1/X2) is within this range, the methacrylic resin of the present embodiment maintains transparency, is not accompanied by yellowing, and does not impair environmental resistance, and exhibits good heat resistance and good heat resistance. It expresses photoelastic properties.

The content of the structural unit derived from the N-substituted maleimide monomer is preferably in the range of 5 to 40% by mass, more preferably 5 to 35% by mass, based on 100% by mass of the methacrylic resin.
Within this range, the methacrylic resin has a more sufficient effect of improving heat resistance, and more favorable effects of improving weather resistance, low water absorption, and optical properties. When the content of the structural unit derived from the N-substituted maleimide monomer is 40% by mass or less, the reactivity of the monomer component is lowered during the polymerization reaction, and the amount of unreacted residual monomer is large. It is effective in preventing the physical properties of the methacrylic resin from deteriorating.

The methacrylic resin having a structural unit derived from an N-substituted maleimide monomer in the present embodiment can be copolymerized with a methacrylic acid ester monomer and an N-substituted maleimide monomer as long as the object of the present invention is not impaired. may contain structural units derived from other monomers.

For example, other copolymerizable monomers include aromatic vinyl; unsaturated nitrile; cyclohexyl group, benzyl group, or acrylic acid ester having an alkyl group having 1 to 18 carbon atoms; glycidyl compound; acids; and the like.
Examples of the aromatic vinyl include styrene, α-methylstyrene, divinylbenzene and the like.
Examples of the unsaturated nitrile include acrylonitrile, methacrylonitrile, ethacrylonitrile, and the like.
Examples of the acrylate include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, and butyl acrylate.
Glycidyl (meth)acrylate etc. are mentioned as said glycidyl compound.
Examples of the unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and semi-esterified products or anhydrides thereof.
The structural unit derived from the other copolymerizable monomer may have only one type, or may have two or more types.

The content of structural units derived from these other copolymerizable monomers is preferably 0 to 10% by mass, more preferably 0 to 9% by mass, based on 100% by mass of the methacrylic resin. It is preferably 0 to 8% by mass, and more preferably 0 to 8% by mass.
When the content of structural units derived from other monomers is within this range, the molding processability and mechanical properties of the resin can be improved without impairing the inherent effect of introducing a ring structure into the main chain, which is preferable.

The content of structural units derived from the N-substituted maleimide monomer and the content of structural units derived from other copolymerizable monomers should be determined by ¹ H-NMR measurement and ¹³ C-NMR measurement. can be done. ¹ H-NMR measurement and ¹³ C-NMR measurement can be performed at a measurement temperature of 40° C. using, for example, CDCl ₃ or DMSO-d ₆ as a measurement solvent.

- Glutarimide structural unit -
Examples of methacrylic resins having a glutarimide-based structural unit in the main chain include, for example, JP-A-2006-249202, JP-A-2007-009182, JP-A-2007-009191, JP-A-2011-186482, Examples thereof include methacrylic resins having a glutarimide-based structural unit, which are described in Republished Patent No. 2012/114718, etc., and can be formed by the method described in the publication.
The glutarimide-based structural unit that constitutes the methacrylic resin of this embodiment may be formed after the resin is polymerized.

上記一般式（３）において、好ましくはＲ⁷及びＲ⁸は、それぞれ独立して、水素原子又はメチル基であり、Ｒ⁹は、水素原子、メチル基、ブチル基、シクロヘキシル基のいずれかであり、より好ましくは、Ｒ⁷は、メチル基であり、Ｒ⁸は、水素であり、Ｒ⁹は、メチル基である。
グルタルイミド系構造単位は、単一の種類のみを含んでいてもよいし、複数の種類を含んでいてもよい。 Specifically, the glutarimide-based structural unit may be represented by the following general formula (3).

In general formula (3) above, preferably R ⁷ and R ⁸ are each independently a hydrogen atom or a methyl group, and R ⁹ is a hydrogen atom, a methyl group, a butyl group, or a cyclohexyl group. , more preferably, R ⁷ is a methyl group, R ⁸ is hydrogen and R ⁹ is a methyl group.
The glutarimide-based structural unit may contain only a single type, or may contain a plurality of types.

In the methacrylic resin having a glutarimide structural unit, the content of the glutarimide structural unit is preferably in the range of 5 to 70% by mass, more preferably 5 to 60% by mass, based on 100% by mass of the methacrylic resin. is in the range.
When the content of the glutarimide-based structural unit is within the above range, it is preferable because a resin having excellent moldability, heat resistance, and optical properties can be obtained.
The content of the glutarimide-based structural unit in the methacrylic resin can be determined using the method described in the aforementioned patent document.

A methacrylic resin having a glutarimide structural unit may further contain an aromatic vinyl monomer unit, if necessary.
Examples of the aromatic vinyl monomer include, but are not limited to, styrene and α-methylstyrene, with styrene being preferred.

The content of the aromatic vinyl unit in the methacrylic resin having a glutarimide structural unit is not particularly limited, but is preferably 0 to 20% by mass based on 100% by mass of the methacrylic resin having a glutarimide structural unit.
When the content of the aromatic vinyl unit is within the above range, it is possible to achieve both heat resistance and excellent photoelastic properties, which is preferable.

- Lactone ring structural unit -
Methacrylic resins having a lactone ring structural unit in the main chain, for example, JP-A-2001-151814, JP-A-2004-168882, JP-A-2005-146084, JP-A-2006-96960, JP-A-2006-96960 It can be formed by methods described in JP-A-2006-171464, JP-A-2007-63541, JP-A-2007-297620, JP-A-2010-180305, and the like.
The lactone ring structural unit constituting the methacrylic resin of the present embodiment may be formed after resin polymerization.

上記一般式（４）において、Ｒ¹⁰、Ｒ¹¹及びＲ¹²は、互いに独立して、水素原子、又は炭素数１～２０の有機残基である。 As the lactone ring structural unit in the present embodiment, a six-membered ring is preferable because the stability of the ring structure is excellent.
As the 6-membered lactone ring structural unit, for example, a structure represented by the following general formula (4) is particularly preferred.

In general formula (4) above, R ¹⁰ , R ¹¹ and R ¹² are each independently a hydrogen atom or an organic residue having 1 to 20 carbon atoms.

Examples of organic residues include saturated aliphatic hydrocarbon groups (alkyl groups, etc.) having 1 to 20 carbon atoms such as methyl group, ethyl group and propyl group; saturated aliphatic hydrocarbon groups (alkenyl groups, etc.); aromatic hydrocarbon groups having 6 to 20 carbon atoms such as phenyl groups and naphthyl groups (aryl groups, etc.); these saturated aliphatic hydrocarbon groups, unsaturated aliphatic hydrocarbons a group in which one or more hydrogen atoms in an aromatic hydrocarbon group are substituted with at least one group selected from the group consisting of a hydroxy group, a carboxyl group, an ether group, and an ester group; and the like.

The lactone ring structural unit is obtained, for example, by copolymerizing an acrylic monomer having a hydroxy group and a methacrylic acid ester monomer such as methyl methacrylate to form a hydroxy group and an ester group or a carboxyl group in the molecular chain. can be formed by causing dealcoholization (esterification) or dehydration condensation (hereinafter also referred to as "cyclization condensation reaction") between these hydroxy groups and ester groups or carboxyl groups after introducing .

Examples of acrylic acid-based monomers having a hydroxy group used for polymerization include 2-(hydroxymethyl)acrylic acid, 2-(hydroxyethyl)acrylic acid, and alkyl 2-(hydroxymethyl)acrylate (e.g., 2- (Hydroxymethyl) methyl acrylate, 2-(hydroxymethyl) ethyl acrylate, 2-(hydroxymethyl) isopropyl acrylate, 2-(hydroxymethyl) n-butyl acrylate, 2-(hydroxymethyl) t-acrylate butyl), 2-(hydroxyethyl)alkyl acrylate, etc., preferably 2-(hydroxymethyl)acrylic acid or 2-(hydroxymethyl)alkyl acrylate, which are monomers having a hydroxyalkyl moiety. , and particularly preferably methyl 2-(hydroxymethyl)acrylate and ethyl 2-(hydroxymethyl)acrylate.

The content of the lactone ring structural unit in the methacrylic resin having the lactone ring structural unit in the main chain is preferably 5 to 40% by mass, more preferably 5 to 35% by mass, based on 100% by mass of the methacrylic resin. %.
When the content of the lactone ring structural unit is within this range, the effects of introducing the ring structure, such as improved solvent resistance and improved surface hardness, can be exhibited while maintaining moldability.
In addition, the content of the lactone ring structure in the methacrylic resin can be determined using the method described in the aforementioned patent document.

A methacrylic resin having a lactone ring structural unit may have structural units derived from other monomers copolymerizable with the methacrylic acid ester monomer and the acrylic acid monomer having a hydroxy group. good.

Examples of such other copolymerizable monomers include styrene, vinyltoluene, α-methylstyrene, α-hydroxymethylstyrene, α-hydroxyethylstyrene, acrylonitrile, methacrylonitrile, methallyl alcohol, ethylene. , propylene, 4-methyl-1-pentene, vinyl acetate, 2-hydroxymethyl-1-butene, methyl vinyl ketone, N-vinylpyrrolidone, N-vinylcarbazole and other monomers having a polymerizable double bond. mentioned.
These other monomers (constituent units) may have only one kind, or may have two or more kinds.

The content of structural units derived from these other copolymerizable monomers is preferably 0 to 20% by mass with respect to 100% by mass of the methacrylic resin, and from the viewpoint of weather resistance, 10% by mass. %, more preferably less than 7% by mass.
The methacrylic resin in the present embodiment may have only one structural unit derived from another copolymerizable monomer, or may have two or more structural units.

The methacrylic resin in the present embodiment preferably has at least one structural unit selected from the group consisting of N-substituted maleimide monomer-derived structural units, glutarimide structural units, and lactone ring structural units. In particular, it is particularly preferable to have a structural unit derived from an N-substituted maleimide monomer, because optical properties such as photoelastic coefficient can be controlled to a high degree without blending with other thermoplastic resins. Moreover, it is particularly preferable to contain a glutarimide-based structural unit in applications where high strength is required.

-Characteristics of methacrylic resin-
--Glass-transition temperature--
The glass transition temperature (Tg) of the methacrylic resin in this embodiment is more than 120° C. and 160° C. or less.
If the glass transition temperature of the methacrylic resin exceeds 120 ° C., it is easier to obtain necessary and sufficient heat resistance for optical parts such as lens moldings in recent years, automotive parts such as in-vehicle displays, and film moldings for liquid crystal displays. can get to The glass transition temperature (Tg) is more preferably 125° C. or higher, and still more preferably 130° C. or higher, from the viewpoint of dimensional stability under the environmental temperature of use.
On the other hand, when the glass transition temperature (Tg) of the methacrylic resin is 160° C. or less, melt processing at extremely high temperatures is avoided, thermal decomposition of the resin is suppressed, and good products can be obtained. The glass transition temperature (Tg) is preferably 150° C. or lower, more preferably 140° C. or lower, from the viewpoint of further obtaining the above effects.
The glass transition temperature (Tg) can be determined by measuring according to JIS-K7121. Specifically, it can be determined by the method described in Examples below.

--Molecular weight and molecular weight distribution--
In the methacrylic resin of the present embodiment, the weight average molecular weight (Mw) in terms of polymethyl methacrylate measured by gel permeation chromatography (GPC) is preferably in the range of 100,000 to 170,000, more preferably It is in the range of 100,000 to 150,000, more preferably in the range of 120,000 to 150,000. When the weight average molecular weight (Mw) is within the above range, the balance between mechanical strength and fluidity is also excellent.
The weight-average molecular weight (Mw), number-average molecular weight (Mn) and Z-average molecular weight (Mz) of the methacrylic resin can be measured using the following equipment and conditions.
・ Measuring device: Gel permeation chromatography (HLC-8320GPC) manufactured by Tosoh Corporation
·Measurement condition:
Column: One TSKguard column SuperH-H, two TSKgel SuperHM-M, and one TSKgel SuperH2500 are connected in series and used.
Column temperature: 40°C
Developing solvent: tetrahydrofuran, flow rate: 0.6 mL/min, 2,6-di-t-butyl-4-methylphenol (BHT) is added at 0.1 g/L as an internal standard.
Detector: RI (differential refraction) detector Detection sensitivity: 3.0 mV/min Sample: 0.02 g of methacrylic resin in 20 mL of tetrahydrofuran solution Injection volume: 10 μL
Standard sample for calibration curve: The following 10 types of polymethyl methacrylate (manufactured by Polymer Laboratories; PMMA Calibration Kit MM-10) with known monodisperse weight peak molecular weights and different molecular weights are used.
Weight peak molecular weight (Mp)
Standard sample 1 1,916,000
Standard sample 2 625,500
Standard sample 3 298,900
Standard sample 4 138,600
Standard sample 5 60,150
Standard sample 6 27,600
Standard sample 7 10,290
Standard sample 8 5,000
Standard sample 9 2,810
Standard sample 10 850
Under the above conditions, the RI detection intensity is measured with respect to the elution time of the methacrylic resin.
Based on each calibration curve obtained by measuring the calibration curve standard sample, the weight average molecular weight (Mw), number average molecular weight (Mn), and Z average molecular weight (Mz) of the methacrylic resin are determined, and the values is used to determine the molecular weight distribution (Mw/Mn) and (Mz/Mw).

--Methanol-insoluble matter--
The ratio of the amount of the methanol-insoluble matter of the methacrylic resin in the present embodiment to the total amount of 100% by weight of the methanol-insoluble matter and the methanol-soluble matter is preferably 95% by weight or more, more preferably 95.5% by mass or more, more preferably 96% by mass or more, still more preferably 96.5% by mass or more, particularly preferably 97% by mass or more, most preferably 97.5% by mass That's it. By setting the proportion of the methanol-insoluble matter to 95% by mass or more, troubles during molding such as contamination of cast rolls during film molding and generation of silver streaks during injection molding can be suppressed.
The methanol-insoluble matter and the methanol-soluble matter are reprecipitated by making the methacrylic resin into a chloroform solution and dropping the solution into a large excess amount of methanol. obtained by drying
Specifically, it can be obtained as follows. After dissolving 5 g of methacrylic resin in 100 mL of chloroform, the solution is placed in a dropping funnel and added dropwise over about 1 hour to 1 L of methanol being stirred using a stirrer to reprecipitate. After dropping the entire amount, the solution is allowed to stand for 1 hour, and then suction filtration is performed using a membrane filter (manufactured by Advantech Toyo Co., Ltd., T050A090C) as a filter. The filtrate is vacuum-dried at 60° C. for 16 hours to obtain a methanol-insoluble matter. In addition, the filtrate is a rotary evaporator, the bath temperature is set to 40 ° C., the degree of vacuum is gradually lowered from the initial setting of 390 Torr to 30 Torr, and the solvent is removed. is collected and used as a methanol soluble matter. The mass of the methanol-insoluble matter and the mass of the methanol-soluble matter are each weighed, and the ratio (mass %) (methanol soluble fraction) is calculated.

-- Photoelastic coefficient C _R --
The absolute value of the photoelastic coefficient C _R of the methacrylic resin having a ring structure in the main chain of the present embodiment is preferably 3.0×10 ⁻¹² Pa ⁻¹ or less, more preferably 2.0×10 ⁻¹² Pa ⁻¹ or less, more preferably 1.5×10 ⁻¹² Pa ⁻¹ or less, and still more preferably 1.0×10 ⁻¹² Pa ⁻¹ or less. The photoelastic coefficient is described in various documents (see, for example, Kagaku Sosetsu, No. 39, 1998 (published by Gakkai Publishing Center)), and is defined by the following formulas (ia) and (ib) is. It can be seen that the closer the value of the photoelastic coefficient C _R is to zero, the smaller the change in birefringence due to external force.
C _R =|Δn|/σ _R (ia)
|Δn|=|nx−ny| (i−b)
(Wherein, C _R is the photoelastic coefficient, σ _R is the tensile stress, |Δn| is the absolute value of birefringence, nx is the refractive index in the stretching direction, ny is the direction perpendicular to the stretching direction in the plane , respectively.)
If the absolute value of the photoelastic coefficient C _R of the methacrylic resin of the present embodiment is 3.0×10 ⁻¹² Pa ⁻¹ or less, residual stress during molding and when the molded body is fitted into a product as a part Since the birefringence caused by the generated stress is sufficiently small, clear images and images can be obtained even when used as optical parts or automobile parts.
The photoelastic coefficient C _R is measured by forming a press film from the methacrylic resin using a vacuum compression molding machine. Specifically, it can be determined by the method described in Examples below.

-- fluorescence intensity --
Evaluation of the luminescence intensity (fluorescence luminescence intensity) of the methacrylic resin in this embodiment can be performed by the following two methods (i) and (ii).
(i) fluorescein concentration in a fluorescein/ethanol solution and fluorescence emission intensity at 514 nm obtained by spectroscopic analysis of this at an excitation wavelength of 436 nm and a slit width of 2 nm; The fluorescence emission intensity obtained when spectroscopically analyzing the chloroform solution of the resin is converted into the concentration of the fluorescein/ethanol solution. That is, in the present embodiment, the fluorescence emission intensity at 514 nm obtained when a 2.0% by mass chloroform solution of a methacrylic resin is spectroscopically analyzed at an excitation wavelength of 436 nm and a slit width of 2 nm is converted into a fluorescein/ethanol solution concentration. The concentration of fluorescein obtained in the process is 30×10 ⁻¹⁰ mol/L or less, preferably 1×10 ⁻¹⁰ mol/L or more and 20×10 ⁻¹⁰ mol/L or less, more preferably 1×10 ⁻¹⁰ mol or less. /L or more and 18×10 ⁻¹⁰ mol/L or less, more preferably 1×10 ⁻¹⁰ mol/L or more and 10×10 ⁻¹⁰ mol/L or less. When the concentration is 30×10 ⁻¹⁰ mol/L or less, a molded piece with little coloration can be molded even in a thick-walled molded product. Moreover, it is preferable that the content is equal to or higher than the lower limit because blue light can be reduced. The fluorescein concentration in the fluorescein/ethanol solution when obtaining the concentration-strength conversion formula was between 0 mol/L and 1.0×10 ⁻⁶ mol/L.
(ii) Quinine sulfate concentration in a solution in which quinine sulfate dihydrate is dissolved in a 1 mol/L dilute sulfuric acid solution, and the fluorescence emission intensity at 458 nm obtained when this is spectroscopically analyzed at an excitation wavelength of 365 nm and a slit width of 2 nm. Using the concentration-intensity conversion formula obtained from and, the fluorescence emission intensity obtained when the chloroform solution of the methacrylic resin is spectroscopically analyzed is the solution obtained by dissolving quinine sulfate dihydrate in a 1 mol / L dilute sulfuric acid solution. It is performed by converting to the quinine sulfate concentration in the medium. That is, in the present embodiment, the fluorescence emission intensity at 458 nm obtained when a 2.0% by mass chloroform solution of methacrylic resin is spectroscopically analyzed at an excitation wavelength of 365 nm and a slit width of 2 nm is measured by adding 1 mol of quinine sulfate dihydrate. The concentration of quinine sulfate obtained when converted to the concentration of a solution dissolved in a /L dilute sulfuric acid solution is preferably 4×10 ⁻⁹ mol/L or more and 6×10 ⁻⁹ mol/L or less. . A concentration of 4×10 ⁻⁹ mol/L or more is preferable because the YI of the methacrylic resin is reduced by the effect of blue light emission at 458 nm. On the other hand, if it exceeds 6×10 ⁻⁹ mol/L, the intensity of the absorption band around 365 nm becomes high and the YI becomes large, which is not preferable.
The measurement was performed using a fluorescence spectrophotometer (Fluorolog 3-22, manufactured by Horiba JobinYvon) using a xenon lamp as a light source and a PMT as a detector. The time constant was 0.2 s, the measurement mode was Sc/Rc, which normalizes the emission intensity with the excitation light intensity of each wavelength, and the observation was performed at 90° using a quartz cell with an optical path length of 1 cm. The quinine sulfate concentration in the quinine sulfate/diluted sulfuric acid solution when obtaining the concentration-strength conversion formula was between 0 mol/L and 1.0×10 ⁻⁶ mol/L.
For example, the above emission intensity can be reduced by lowering the shear rate in the devolatilization step in the production of the methacrylic resin, impurities (2-amino-N-substituted succinimide, etc.) in the N-substituted maleimide monomer of the polymerization raw material. can be adjusted to the above range by lowering the content ratio of

[Method for producing methacrylic resin]
A method for producing a methacrylic resin according to this embodiment will be described below.
-Method for Producing Methacrylic Resin Containing Structural Unit Derived from N-Substituted Maleimide Monomer-
Methods for producing a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer in its main chain (hereinafter sometimes referred to as "maleimide copolymer") include bulk polymerization, solution polymerization, suspension Any of polymerization method, precipitation polymerization method and emulsion polymerization method can be mentioned, preferably suspension polymerization method, bulk polymerization method and solution polymerization method, more preferably solution polymerization method.

In the production method of the present embodiment, any of batch polymerization method, semi-batch method, and continuous polymerization method can be used as the polymerization method.
In the present embodiment, a method of charging a part of the monomers into the reactor before starting the polymerization, starting the polymerization by adding a polymerization initiator, and then supplying the remainder of the monomers, a so-called semi-batch polymerization method. Law can be preferably used.

In order for a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer to exhibit a predetermined fluorescence emission intensity, (1) an N-substituted maleimide monomer in which the content of specific impurities is controlled as a raw material; (2) applying a polymerization method that reduces the amount of unreacted N-substituted maleimide remaining after the completion of polymerization, (3) applying a devolatilization method with a reduced shear rate, etc. At least Among them, it is preferable to select a manufacturing method that combines (1) and (3) or select a manufacturing method that combines the three.

--Control of impurities in N-substituted maleimide--
One of the impurities in the N-substituted maleimide that imparts fluorescence to the methacrylic resin is 2-amino-N-substituted succinimide produced by the reaction of the N-substituted maleimide with a primary amine. 2-Amino-N-substituted succinimide itself not only has fluorescence emission properties, and although the detailed denaturation mechanism is unknown, it can be heated to 300° C. or higher or subjected to a shearing devolatilization device. , the inventors' study revealed that a thermally denatured product having fluorescence emission was generated. That is, 2-amino-N-substituted succinimide contained in N-substituted maleimide should be reduced, and in the production of methacrylic resin, devolatilization should be performed at 300° C. or less using a devolatilization device that does not have a rotating part. is preferable for controlling the fluorescence emission intensity of the methacrylic resin.

Methods for controlling impurities in the N-substituted maleimide include providing a pretreatment step for washing (washing step) and/or dehydrating (dehydrating step) the N-substituted maleimide. The pretreatment step may be only water washing, or may be a combination of water washing and dehydration. Moreover, washing with water and dehydration may be performed once each, or may be performed multiple times. The pretreatment step may further include a concentration adjustment step of adjusting the concentration of the N-substituted maleimide solution obtained in the dehydration step.
For example, in the present embodiment, the 2-amino-N-substituted succinimide in the N-substituted maleimide is removed by the water washing step shown below, and water is removed in the subsequent dehydration step to control fluorescence emission intensity, In addition, an N-substituted maleimide solution suitable for preparing a methacrylic resin having good color tone can be obtained.

In the water washing step, for example, the N-substituted maleimide is dissolved in a water-insoluble organic solvent, separated into an organic layer and an aqueous layer, and the organic layer is washed with one or more of an acidic aqueous solution, water, and an alkaline aqueous solution, A method of mixing and washing by a batch system, a continuous system, or both of these systems, and then separating the organic layer and the aqueous layer can be adopted. The amount of 2-amino-N-substituted succinimide in the organic layer after the water washing step is preferably 5 ppm by mass or less, more preferably 0.1 ppm by mass, when the amount of N-substituted maleimide in the organic layer is 100% by mass. It is more than 1 mass ppm or less. When the amount of 2-amino-N-substituted succinimide in the organic layer is within this range, the fluorescence emission intensity of the methacrylic resin can be controlled within a predetermined range, and the methacrylic resin has a good color tone even in a molded article having a long optical path length. It is preferable because the system resin and the composition of the resin can be obtained. It is also preferable from the viewpoint of cost in cleaning. When the dehydration step is not provided, the organic layer containing the N-substituted maleimide obtained in the water washing step may be used as the N-substituted maleimide solution in the polymerization step.

The water-insoluble organic solvent to be used is not particularly limited as long as it dissolves N-substituted maleimide and 2-amino-N-substituted succinimide, undergoes phase separation from water, and has an azeotropic point with water. Specific examples of solvents that can be used include aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as normal-hexane and cyclohexane; and halogenated hydrocarbons such as chloroform and dichloroethane.

The concentration of the N-substituted maleimide in the organic layer is preferably 0.5% by mass or more and 30% by mass or less, more preferably 10% by mass or more and 25% by mass or less, and even more preferably 20% by mass or more and 25% by mass or less. is.
The water used may be any of sewage, pure water, and tap water.
Moreover, the acidity of the acidic aqueous solution and the alkaline aqueous solution is not limited.
The temperature for mixing and washing the organic layer and the aqueous layer may be 40°C or higher, preferably 40°C or higher and 80°C or lower, more preferably 50°C or higher and 60°C or lower.
The weight ratio of the water layer to the organic layer is preferably 5% by mass or more and 300% by mass or less, more preferably 10% by mass or more and 200% by mass, and even more preferably 30% by mass, when the weight of the organic layer is 100% by mass. It is more than 100 mass % or less.
When the organic layer concentration, liquid temperature, and water layer weight ratio are within these ranges, the reaction between the N-substituted maleimide and water is difficult to proceed, and the 2-amino-N-substituted succinimide is extracted to the water layer side. preferred because it is easy.

In the case of batchwise cleaning, the reaction tank used may be either stainless steel or glass lined, or a reaction tank other than these may be used. Also, the shape of the stirring blade is not particularly limited. As specific stirring blades, for example, 3 swept back blades, 4 paddle blades, 4 inclined paddle blades, 6 turbine blades, and anchor blades can be used. can be used. The stirring time is preferably 10 minutes or more and 120 minutes or less, more preferably 30 minutes or more and 60 minutes or less. When the stirring time is within this range, the stirring efficiency and the extraction efficiency of the 2-amino-N-substituted succinimide into the aqueous layer are improved, and the 2-amino-N-substituted succinimide in the N-substituted maleimide can be further reduced. Therefore, it is preferable.

In the case of continuous washing, an empty tower, a packed tower, or a tray tower can be used, and a static mixer such as a static mixer or a rotary mixer such as a dynamic mixer can also be used. The contact time between the organic layer and the aqueous layer is preferably set to 1 second or more and 60 minutes or less, more preferably 30 seconds or more and 10 minutes or less. The contact time within this range is preferable because the reaction between the N-substituted maleimide and water is less likely to proceed and the 2-amino-N-substituted succinimide is easily extracted to the water layer side.

In the dehydration step, the organic layer is provided in a reaction vessel and heated under reduced pressure to remove moisture. Pressure and temperature are not particularly limited as long as the solvent and water used form an azeotropic composition.

The amount of water in the organic layer after the dehydration step is preferably 100 ppm by mass or less when the weight of the organic layer is 100% by mass. When the amount of water after the dehydration step is within this range, deterioration of color tone due to water during polymerization of the methacrylic resin can be suppressed, and the amount of solvent distilled off together with water can be reduced, which is preferable from the viewpoint of cost. The organic layer containing the N-substituted maleimide obtained in the dehydration step may be used in the polymerization step as an N-substituted maleimide solution, or the N-substituted maleimide solution whose concentration has been adjusted in the concentration adjustment step may be used in the polymerization step. may

In the concentration adjustment step, for example, the organic layer of the N-substituted maleimide obtained in the dehydration step or the like may be diluted with the water-insoluble organic solvent. The water-insoluble organic solvent used in the concentration adjustment step is preferably the same as the water-insoluble organic solvent used in the water washing step.

The N-substituted maleimide solution obtained in the pretreatment step is preferably a solution of the water-insoluble organic solvent (organic layer).
In the N-substituted maleimide solution obtained in the pretreatment step, the mass ratio of 2-amino-N-substituted succinimide contained in the N-substituted maleimide solution is the N-substituted maleimide solution contained in the N-substituted maleimide solution. It is preferably 5 ppm by mass or less, more preferably 0.1 ppm by mass or more and 1 mass ppm or less with respect to 100% by mass of maleimide.
The amount of water contained in the N-substituted maleimide solution obtained in the pretreatment step is preferably 200 ppm by mass or less, more preferably 100 to 200 ppm by mass, based on 100% by mass of the N-substituted maleimide solution. is.
The mass ratio of the N-substituted maleimide contained in the N-substituted maleimide solution obtained in the pretreatment step is preferably 5 to 30% by mass with respect to 100% by mass of the N-substituted maleimide solution, and more preferably. is 5 to 25% by mass. This range is preferable because the N-substituted maleimide is less likely to precipitate and can be transferred as a uniform solution.
When a plurality of types of N-substituted maleimide solutions are used in the polymerization step, the mixture of the plurality of types of N-substituted maleimide solutions contains the above 2-amino-N-substituted succinimide mass ratio, the above water content, and/or the above N- It is preferable that the weight ratio of the substituted maleimide is satisfied, and each N-substituted maleimide solution satisfies the weight ratio of the 2-amino-N-substituted succinimide, the water content, and/or the weight ratio of the N-substituted maleimide. more preferred.

By adopting the water washing step and the dehydration step of the N-substituted maleimide as described above, the amount of 2-amino-N-substituted succinimide having fluorescent light emission is reduced and the water that causes deterioration of the color tone of the methacrylic resin is removed. It is possible to obtain a methacrylic resin and a composition of the resin having a good color tone even in a molded article having a long optical path length.
In the polymerization step, the N-substituted maleimide solution obtained in the pretreatment step is mixed with a methacrylic acid ester monomer, an arbitrary monomer, a polymerization initiator, a polymerization solvent, a chain transfer agent, and the like to obtain a monomer. The mixed solution may be used for polymerization.

--Reduction of unreacted N-substituted maleimide at the end of polymerization--
If unreacted N-substituted maleimide exists at the end of polymerization of methacrylic resin, the low-molecular-weight compound containing N-substituted maleimide as its structural unit exhibits fluorescence emission in a heated devolatilization device or the like, although the detailed mechanism is unknown. The inventors have found that reaction by-products having

In order to control the fluorescence emission intensity of the methacrylic resin within a predetermined range, the total mass of the unreacted N-substituted maleimide remaining after the completion of polymerization is 1000 ppm by mass with respect to 100% by mass of the polymerization solution at the completion of polymerization. or less, more preferably 10 mass ppm or more and 500 mass ppm or less.
Further, when N-arylmaleimides such as N-phenylmaleimide are used as the N-substituted maleimide, the total mass of unreacted N-arylmaleimides remaining after the completion of polymerization is 100 masses of the polymerization solution at the completion of polymerization. %, preferably 500 mass ppm or less, more preferably 10 mass ppm or more and 500 mass ppm or less, and still more preferably 10 mass ppm or more and 50 mass ppm or less.
These ranges are preferable because the fluorescence intensity of the methacrylic resin can be suppressed within a predetermined range. In order to reduce the amount of unreacted N-substituted maleimide to less than 10 ppm by mass, it is necessary to raise the polymerization temperature or increase the amount of the initiator. It is not preferable because it causes deterioration of the color tone of the resin.

As a means for controlling the amount of unreacted N-substituted maleimide after completion of polymerization within the above range, a semi-batch polymerization method can be mentioned. In the semi-batch polymerization method, in the polymerization step, after 30 minutes from the start of addition of the polymerization initiator, all monomers that contribute to the polymerization (for example, methacrylic acid esters, N-substituted maleimides, and any other monomers It is preferable to add 5 to 35% by mass of a methacrylic acid ester monomer to the total mass of 100% by mass. In other words, 65 to 95% by mass of 100% by mass of the total mass of all monomers to be donated to polymerization is charged into the reactor before adding the polymerization initiator, and after 30 minutes from the start of addition of the polymerization initiator It is preferable to additionally add the remaining 5 to 35% by mass of the methacrylic acid ester monomer. The amount of the methacrylic acid ester monomer to be additionally added is more preferably 10 to 30% by mass based on 100% by mass of the total mass of all the monomers donating to the polymerization. When the amount of the additionally added methacrylic acid ester monomer is within these ranges, the unreacted N-substituted maleimide reacts with the additionally added methacrylic acid ester monomer, and the amount of unreacted N-substituted maleimide after the completion of polymerization is reduced. It is preferable because it can be controlled within a predetermined range.
The starting point of the additional addition of the monomer, the speed of the additional addition, etc. may be appropriately selected according to the polymerization conversion rate. In addition to the methacrylic acid ester monomer, a monomer containing an N-substituted maleimide monomer and other monomers within a range that does not inhibit the effect of the present invention and the reduction of the amount of unreacted N-substituted maleimide Additional body mixture may be added.
By adopting the semi-batch polymerization method as described above, it is possible to reduce the amount of unreacted N-substituted maleimide monomers in the second half of the polymerization and to minimize the generation of fluorescent substances in the devolatilization step. Therefore, it is possible to obtain a methacrylic resin and a composition of the resin having a good color tone even in a molded article having a long optical path length, which is preferable.

Hereinafter, as an example of a method for producing a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer (hereinafter sometimes referred to as a "maleimide copolymer"), radical The case of production by polymerization will be specifically described.
In the semi-batch polymerization method, the total mass of all monomers (methacrylic acid ester, N-substituted maleimide, and any other monomers) donated to the polymerization after 30 minutes from the start of addition of the polymerization initiator is Based on 100% by mass, it is preferable to additionally add 5 to 35% by mass of the methacrylic acid ester monomer. In other words, 65 to 95% by mass of 100% by mass of the total mass of all monomers to be donated to the polymerization is charged into the reactor before the start of polymerization, and 30 minutes after the start of addition of the polymerization initiator, methacrylic acid is added. It is preferable to additionally add 5 to 35% by mass of the remaining ester monomer.
The amount of the methacrylic acid ester monomer to be additionally added is more preferably 10 to 30% by mass based on 100% by mass of the total mass of all the monomers donating to the polymerization.
The starting point of additional addition of the monomer, the speed of additional addition, etc. may be appropriately selected according to the polymerization conversion rate.
Further, in addition to the methacrylic acid ester monomer, it contains an N-substituted maleimide monomer and other monomers within a range that does not hinder the effects of the present invention and the conversion rate of the N-substituted maleimide monomer. Additional monomer mixtures may be added.

By adopting the semi-batch polymerization method as described above, it becomes possible to increase the conversion rate of the unreacted N-substituted maleimide monomer at the latter half of the polymerization, and the light transmittance of the molded article having a long optical path length can be improved. It is preferable because it is excellent, the molecular weight distribution of the obtained polymer can be easily controlled, and a resin having fluidity suitable for injection molding and a composition of the resin can be obtained.

The polymerization solvent to be used is not particularly limited as long as it can increase the solubility of the maleimide copolymer obtained by polymerization and maintain the viscosity of the reaction solution appropriately for the purpose of preventing gelation or the like.
Specific polymerization solvents include aromatic hydrocarbons such as toluene, xylene, ethylbenzene and isopropylbenzene; ketones such as methylisobutylketone, butylcellosolve, methylethylketone and cyclohexanone; polar solvents such as dimethylformamide and 2-methylpyrrolidone. can be used.
Alcohols such as methanol, ethanol, and isopropanol may also be used as a polymerization solvent as long as they do not inhibit the dissolution of the polymerization product during polymerization.

The amount of the solvent during polymerization is not particularly limited as long as it is an amount that can be easily removed without causing precipitation of the copolymer or the monomers used during production. When the total amount of is 100% by mass, it is preferably 10 to 200% by mass. More preferably 25 to 150% by mass, still more preferably 40 to 100% by mass, still more preferably 50 to 100% by mass.

In the present embodiment, when the total amount of the monomers to be blended is 100% by mass, the amount of solvent during polymerization is within the range of 100% by mass or less, and the solvent concentration is appropriately changed during polymerization. A method can also be preferably used.
More specifically, 40 to 60% by mass is blended at the beginning of polymerization, the remaining 60 to 40% by mass is blended during polymerization, and finally, the total amount of the monomers to be blended is 100% by mass. In this case, a method of adjusting the amount of the solvent to be in the range of 100% by mass or less can be exemplified.
By adopting this method, it is possible to increase the polymerization conversion rate, control the molecular weight distribution, and have excellent injection moldability. It is preferable because the resulting resin and resin composition can be obtained.

In solution polymerization, it is important to reduce the dissolved oxygen concentration in the polymerization solution as much as possible. For example, the dissolved oxygen concentration is preferably 10 ppm or less. The dissolved oxygen concentration can be measured, for example, using a dissolved oxygen meter DO meter B-505 (manufactured by Iijima Denshi Kogyo Co., Ltd.). As a method for reducing the dissolved oxygen concentration, a method of bubbling an inert gas into the polymerization solution, and an operation of pressurizing the container containing the polymerization solution to about 0.2 MPa with an inert gas before polymerization and then releasing the pressure are repeated. A method such as passing an inert gas through a container containing a polymerization solution can be selected as appropriate.

The polymerization temperature is not particularly limited as long as it is a temperature at which polymerization proceeds. More preferably 90 to 150°C, still more preferably 100 to 150°C. From the viewpoint of productivity, the temperature is preferably 70° C. or higher, and preferably 180° C. or lower in order to suppress side reactions during polymerization and obtain a polymer having a desired molecular weight and quality.

In addition, the polymerization time is not particularly limited as long as it is a time that can obtain the required degree of polymerization at the required conversion rate, but from the viewpoint of productivity etc., it is preferably 2 to 15 hours. More preferably 3 to 12 hours, still more preferably 4 to 10 hours.

Any initiator generally used in radical polymerization can be used as the polymerization initiator. Examples include cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, and benzoyl peroxide. Oxide, organic peroxides such as t-butylperoxyisopropyl carbonate, t-amylperoxy-2-ethylhexanoate, t-amylperoxyisononanoate, 1,1-di(t-butylperoxy)cyclohexane substance; 2,2′-azobis(isobutyronitrile), 1,1′-azobis(cyclohexanecarbonitrile), 2,2′-azobis(2,4-dimethylvaleronitrile), dimethyl-2,2′- azo compounds such as azobisisobutyrate; and the like.
These may be used alone or in combination of two or more.

The amount of the polymerization initiator to be added may be 0.01 to 1% by mass, preferably 0.05 to 0.5% by mass, when the total amount of monomers used for polymerization is 100% by mass. be.

The method of adding the polymerization initiator is not particularly limited as long as it is adjusted to the concentration of the monomers remaining in the polymerization solution rather than being added at a constant rate, and is variable, and may be added continuously or intermittently. good too. When the polymerization initiator is intermittently added, the amount added per unit time is not taken into consideration during the period when the polymerization initiator is not added.
In the present embodiment, the type and amount of the polymerization initiator, and the It is preferable to appropriately select the polymerization temperature and the like.
By adopting these methods, it is possible to suppress the amount of oligomers and low-molecular-weight products produced in the latter stage of polymerization, and to suppress overheating during polymerization, thereby stabilizing polymerization.
During the polymerization reaction, if necessary, a chain transfer agent may be added for polymerization.

As the chain transfer agent, a chain transfer agent used in general radical polymerization can be used. mercaptan compounds; halogen compounds such as carbon tetrachloride, methylene chloride and bromoform; unsaturated hydrocarbon compounds such as α-methylstyrene dimer, α-terpinene, dipentene and terpinolene;
These may be used alone or in combination of two or more.

These chain transfer agents may be added at any stage as long as the polymerization reaction is in progress, and are not particularly limited.

The amount of chain transfer agent to be added may be 0.01 to 1% by mass, preferably 0.05 to 0.5% by mass, when the total amount of monomers used for polymerization is 100% by mass.

A method for recovering a polymer from a polymerization liquid obtained by solution polymerization includes a method of separating a polymerization solvent and unreacted monomers through a process called a devolatilization process and recovering a polymerization product. . Here, the devolatilization step refers to a step of removing volatile matter such as a polymerization solvent, residual monomers, and reaction by-products under heating and reduced pressure conditions.

In the present embodiment, it is preferable to control the content of the unreacted N-substituted maleimide monomer contained in the polymerization solution containing the methacrylic resin to be subjected to the devolatilization step to a certain concentration or less. Details are as described in "Reduction of unreacted N-substituted maleimide at the end of polymerization" above. or by changing the addition rate of the polymerization initiator according to the concentration of unreacted monomers in the polymerization solution; A method of additionally adding another monomer highly reactive with the N-substituted maleimide monomer remaining in the reaction; a method of adding a compound highly reactive with the N-substituted maleimide such as α-terpinene at the end of the polymerization. etc. can also be used.

As a method for determining the residual concentration of the N-substituted maleimide monomer remaining in the polymerization solution containing the methacrylic resin, for example, a part of the polymerization solution is sampled and weighed, and this sample is dissolved in chloroform. A mass% solution is prepared, n-decane is added as an internal standard substance, and the concentration of the N-substituted maleimide monomer remaining in the sample is measured using gas chromatography (GC-2010 manufactured by Shimadzu Corporation). can be obtained by As more specific measurement conditions, those described in Examples below can be used.

As the apparatus used in the devolatilization step, it is preferable to use a devolatilization apparatus having a heat exchanger and a reduced pressure vessel as its main structure and having no rotating part.
Specifically, a devolatilization tank having a configuration in which a decompression unit is attached to a decompression vessel having a size that allows devolatilization and a heat exchanger disposed on the top thereof, and a gear pump for discharging the polymer after devolatilization. It is possible to employ a devolatilization device composed of a discharge device such as
The above-mentioned devolatilization device transfers the polymerization solution to a heat exchanger placed in the upper part of the decompression vessel and heated. After being preheated in a heat exchanger or the like, the mixture is supplied to a devolatilization tank under heating and reduced pressure to separate and remove the polymerization solvent, unreacted raw material mixture, polymerization by-products, etc., and the copolymer. As described above, by using a devolatilization device that does not have a rotating part, it is possible to suppress the low-molecular-weight fluorescence-emitting reaction by-products derived from the unreacted N-substituted maleimide, and to reduce the fluorescence intensity to a predetermined level. is preferable because it can be controlled within the range of Moreover, it is preferable because a methacrylic resin having a good color tone can be obtained.
Examples of the apparatus having the rotating part include thin-film evaporators such as Wiplen and Exeva manufactured by Kobelco Eco-Solutions Co., Ltd., Contra and inclined blade Contra manufactured by Hitachi, Ltd.; extruders with vents; By not providing a rotating part, shearing during devolatilization can be reduced, and a resin with even lower fluorescence emission can be obtained.
In the devolatilization step in the present embodiment, the shear rate applied to the polymerization solution is preferably 20 s ^-1 or less, more preferably 10 s ^-1 or less, and 0.1 s ^-1 or more and 10 s ^-1 or less. It is even more preferable to implement. By setting the shear rate to 0.1 s ⁻¹ or more, the flow of the molten resin does not become too slow, and deterioration of color tone due to an increase in residence time can be suppressed. Further, by setting the time to 20 s ⁻¹ or less, it is possible to suppress the generation of fluorescent reaction by-products due to shearing.
Here, for example, the shear rate γ in the extruder is calculated by the following formula.
γ=(π×D×N)/H
(In the formula, D is the screw diameter (m), N is the number of screw revolutions per second, and H is the screw groove depth (m).)
Moreover, in the case of a flat plate type channel, the shear rate γ is calculated by the following formula.
γ=(6×Q)/(w×h ² )
(In the formula, Q is the volumetric flow rate (m ³ /s) passing through the plate-shaped channel, w is the width of the plate-shaped channel (m), and h is the distance between the plates (m).)

In this embodiment, it is preferable to use a flat heat exchanger having a flat flow path and a heater as the heat exchanger arranged in the upper part of the pressure reducing vessel. More preferably, it is a planar heat exchanger having a planar flow path having a laminated structure having a plurality of slit-shaped flow paths having a rectangular cross section on the same plane, and a heater.
The polymerization solution supplied to the devolatilization device is sent from the central portion of the heat exchanger to the slit-like channel and heated. The heated polymerization solution is supplied from the slit-shaped channel into a vacuum container integrated with a heat exchanger under reduced pressure, and flash-evaporated.
Such a devolatilization method is sometimes referred to as flash devolatilization, and in the present invention, hereinafter also referred to as flash devolatilization.
It is also possible to adopt a method of installing two or more of the devolatilizing devices described above in series to perform devolatilization in two or more stages.

The temperature range for heating with a heat exchanger attached to the devolatilization device may be 100°C or higher and 300°C or lower, preferably Tg + 100°C to Tg + 160°C, more preferably Tg + 110°C to Tg + 150°C. . The temperature range of the devolatilization tank heated and kept warm may be 100°C or higher and 300°C or lower, preferably Tg + 100°C to Tg + 160°C, more preferably Tg + 110°C to Tg + 150°C. When the temperatures of the heat exchanger and the devolatilization tank are within this range, the thermal denaturation of the remaining 2-amino-N-substituted succinimide can be suppressed, and the production of fluorescent substances can be suppressed, which is preferable. Moreover, it is effective in preventing an increase in residual volatile matter, and is preferable because it improves the thermal stability and product quality of the obtained methacrylic resin. Here, the above Tg refers to the glass transition temperature of the obtained methacrylic resin.

The degree of vacuum in the devolatilization tank may be in the range of 5 to 300 Torr, preferably in the range of 10 to 200 Torr. When the degree of vacuum is 300 Torr or less, the unreacted monomer or the mixture of the unreacted monomer and the polymerization solvent can be efficiently separated and removed, and the thermal stability and quality of the resulting thermoplastic copolymer can be improved. not decrease. Industrial implementation is easier when the degree of vacuum is 5 Torr or more.

The average residence time in the devolatilization tank is 5 to 60 minutes, preferably 5 to 45 minutes. When the average residence time is within this range, volatilization can be efficiently performed, and coloration and decomposition due to thermal denaturation of the polymer can be suppressed, which is preferable.

The polymer recovered through the devolatilization process is processed into pellets in a process called granulation process.
In the granulation step, the molten resin is extruded into strands by at least one delivery granulator selected from gear pumps, single-screw extruders, twin-screw extruders, etc., having a perforated die as ancillary equipment. , a cold cut method, an aerial hot cut method, an underwater strand cut method, and an underwater cut method, and processed into pellets. From the viewpoint of suppressing the production of fluorescence-emitting reaction by-products due to shearing, it is preferable to select a conveying device with a low shearing speed without using an extruder.

In this embodiment, in order to obtain a highly controlled methacrylic resin composition, the composition in a molten state at a high temperature is prevented from being exposed to air as much as possible, and the composition can be quickly cooled and solidified. It is preferable to use the granular method.
In that case, the molten resin temperature should be as low as possible, the residence time from the exit of the multi-hole die to the surface of the cooling water should be minimized, and the temperature of the cooling water should be as high as possible. It is more preferable to carry out granulation with
For example, the molten resin temperature is preferably 220 to 280° C., more preferably 230 to 270° C., and the residence time from the exit of the multi-hole die to the cooling water surface is preferably within 5 seconds, more preferably within 3 seconds. The temperature of the cooling water is preferably 30-80°C, more preferably 40-60°C.
A methacrylic resin with less coloration and a low moisture content and a composition thereof can be obtained by carrying out the process within these molten resin temperature and cooling water temperature ranges, which is preferable.

Regarding the content of the monomers remaining in the methacrylic resin after the devolatilization step, the smaller the content, the better from the viewpoint of thermal stability and product quality. Specifically, the content of the methacrylic acid ester monomer is preferably 3000 mass ppm or less, more preferably 2000 mass ppm or less. The total content of N-substituted maleimide monomers is preferably 200 mass ppm or less, more preferably 100 mass ppm or less.
Moreover, the content of the residual polymerization solvent is preferably 500 mass ppm or less, more preferably 300 mass ppm or less.

-Method for Producing Methacrylic Resin Containing Glutarimide Structural Unit-
Examples of the method for producing a methacrylic resin having a glutarimide-based structural unit in its main chain include bulk polymerization, solution polymerization, suspension polymerization, precipitation polymerization, and emulsion polymerization, preferably. They are suspension polymerization, bulk polymerization and solution polymerization, and more preferably solution polymerization.
In the production method of the present embodiment, any of batch polymerization method, semi-batch method, and continuous polymerization method can be used as the polymerization method.
In the production method of the present embodiment, it is preferable to polymerize the monomers by radical polymerization.

Methacrylic resins having a glutarimide-based structural unit in the main chain are, for example, JP-A-2006-249202, JP-A-2007-009182, JP-A-2007-009191, JP-A-2011-186482, International It is a methacrylic resin having a glutarimide structural unit, which is described in Japanese Unexamined Patent Publication No. 2012/114718, etc., and can be formed by the method described in the publication.

Hereinafter, as an example of a method for producing a methacrylic resin having a glutarimide-based structural unit, a case of production by batch-type radical polymerization using a solution polymerization method will be specifically described.
First, a (meth)acrylate polymer is produced by polymerizing a (meth)acrylate such as methyl methacrylate. When an aromatic vinyl unit is included in a methacrylic resin having a glutarimide-based structural unit, a (meth)acrylic acid ester and an aromatic vinyl (e.g., styrene) are copolymerized to form a (meth)acrylic acid ester-aromatic to produce a group vinyl copolymer.

Examples of solvents used for polymerization include aromatic hydrocarbons such as toluene, xylene and ethylbenzene; ketones such as methyl ethyl ketone and methyl isobutyl ketone; and the like.
These solvents may be used alone or in combination of two or more.
The amount of the solvent used during polymerization is not particularly limited as long as the polymerization proceeds, the copolymer and the monomer used do not precipitate during production, and the amount can be easily removed. When the total amount is 100% by mass, it is preferably 10 to 200% by mass. More preferably 25 to 200% by mass, still more preferably 50 to 200% by mass, still more preferably 50 to 150% by mass.

The polymerization temperature is not particularly limited as long as it is a temperature at which the polymerization proceeds. More preferably 90 to 150°C, still more preferably 100 to 140°C, and even more preferably 100 to 130°C. From the viewpoint of productivity, the temperature is preferably 70° C. or higher, and preferably 180° C. or lower in order to suppress side reactions during polymerization and obtain a polymer having a desired molecular weight and quality.

The polymerization time is not particularly limited as long as the target conversion rate is satisfied, but from the viewpoint of productivity, etc., it is preferably 0.5 to 15 hours, more preferably 2 to 12 hours, and still more preferably 4 hours. ~10 hours.

During the polymerization reaction, if necessary, a polymerization initiator or a chain transfer agent may be added for polymerization.
Although the polymerization initiator is not particularly limited, for example, the polymerization initiator disclosed in the method for preparing a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer can be used.
These polymerization initiators may be used alone or in combination of two or more.
These polymerization initiators may be added at any stage as long as the polymerization reaction is in progress.
The amount of the polymerization initiator to be added may be appropriately set according to the combination of monomers, reaction conditions, etc., and is not particularly limited, but when the total amount of monomers used for polymerization is 100% by mass In addition, it may be 0.01 to 1% by mass, preferably 0.05 to 0.5% by mass.
As the chain transfer agent, a chain transfer agent used in general radical polymerization can be used. For example, the chain transfer agent disclosed in the method for preparing a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer can be used. can.
These may be used alone or in combination of two or more.
These chain transfer agents may be added at any stage as long as the polymerization reaction is in progress, and are not particularly limited.
The amount of the chain transfer agent to be added is not particularly limited as long as the desired degree of polymerization can be obtained under the polymerization conditions used, but the total amount of the monomers used in the polymerization is preferably 100% by mass. 0.01 to 1% by mass, preferably 0.05 to 0.5% by mass.
A suitable method for adding the polymerization initiator and the chain transfer agent in the polymerization step may be, for example, the method described in the method for preparing the methacrylic resin having structural units derived from the N-substituted maleimide monomer.
The dissolved oxygen concentration in the polymerization solution may be, for example, the value disclosed in the method for preparing a methacrylic resin having a structural unit derived from the N-substituted maleimide monomer.

Next, the (meth)acrylic acid ester polymer or the methacrylic acid ester-aromatic vinyl copolymer is reacted with an imidizing agent to perform an imidization reaction (imidization step). Thereby, a methacrylic resin having a glutarimide structural unit can be produced.

The imidizing agent is not particularly limited as long as it can form the glutarimide-based structural unit represented by the general formula (3).
Specifically, ammonia or primary amine can be used as the imidizing agent. Examples of the primary amine include aliphatic hydrocarbon group-containing primary amines such as methylamine, ethylamine, n-propylamine, i-propylamine, n-butylamine, i-butylamine, tert-butylamine, and n-hexylamine; alicyclic hydrocarbon group-containing primary amines such as cyclohexylamine;
Among the above imidization agents, ammonia, methylamine, and cyclohexylamine are preferably used, and methylamine is particularly preferably used, from the viewpoint of cost and physical properties.
In this imidization step, the content of the glutarimide-based structural unit in the obtained methacrylic resin having the glutarimide-based structural unit can be adjusted by adjusting the addition ratio of the imidizing agent.

The method for carrying out the imidization reaction is not particularly limited, but a conventionally known method can be used. For example, the imidization reaction can be advanced by using an extruder or a batch reactor.
Although the extruder is not particularly limited, for example, a single-screw extruder, a twin-screw extruder, a multi-screw extruder, or the like can be used.
Among them, it is preferable to use a twin-screw extruder. A twin-screw extruder can facilitate mixing of the starting polymer and the imidizing agent.
Examples of the twin-screw extruder include a non-intermeshing co-rotating type, an intermeshing co-rotating type, a non-intermeshing counter-rotating type, and an intermeshing counter-rotating type.
The extruders exemplified above may be used alone, or may be used by connecting a plurality of them in series.
In addition, the extruder to be used is equipped with a vent port capable of reducing pressure to atmospheric pressure or less, because it is possible to remove the imidizing agent of the reaction, by-products such as methanol, or monomers. preferable.

In producing a methacrylic resin having a glutarimide structural unit, in addition to the imidization step, an esterification step of treating the carboxyl groups of the resin with an esterification agent such as dimethyl carbonate can be included. In that case, a catalyst such as trimethylamine, triethylamine or tributylamine may be used in combination for the treatment.
The esterification step can be advanced by using, for example, an extruder or a batch-type reaction tank, like the imidization step.
For the purpose of removing excessive esterifying agent, by-products such as methanol, or monomers, the apparatus used is preferably equipped with a vent port capable of reducing pressure to atmospheric pressure or lower.

The methacrylic resin that has undergone the imidization process and, if necessary, the esterification process, is melted and extruded into strands from an extruder equipped with a multi-hole die. It is processed into pellets by a water cutting method or the like.
Further, in order to reduce the number of foreign substances in the resin, the methacrylic resin is dissolved in an organic solvent such as toluene, methyl ethyl ketone, methylene chloride, the obtained methacrylic resin solution is filtered, and then the organic solvent is devolatilized. It is also preferred to use a method.

From the viewpoint of reducing fluorescence intensity (content of fluorescent light-emitting substance), it is preferable to imidize the polymerization solution after completion of polymerization in a batch-type reaction tank and not use a twin-screw extruder that receives shear force.
The imidization reaction is preferably carried out at 130 to 250°C, more preferably at 150 to 230°C, even more preferably at 160 to 220°C, and even more preferably at 170 to 200°C. preferable. The reaction time is preferably 10 minutes to 5 hours, more preferably 30 minutes to 2 hours.
After the imidization step, after undergoing an esterification step as necessary, after devolatilization by a devolatilization method with reduced shear described in the method for preparing a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer. , pelletizing is preferable from the viewpoint of reducing fluorescence intensity.

-Method for Producing Methacrylic Resin Containing Lactone Ring Structural Unit-
As a method for producing a methacrylic resin having a lactone ring structural unit in the main chain, a method of forming a lactone ring structure by a cyclization reaction after polymerization is used. It is preferable to polymerize the monomers by radical polymerization in the polymerization method.
In the production method of the present embodiment, any of batch polymerization method, semi-batch method, and continuous polymerization method can be used as the polymerization method.

Methacrylic resins having a lactone ring structural unit in the main chain, for example, JP-A-2001-151814, JP-A-2004-168882, JP-A-2005-146084, JP-A-2006-96960, JP-A-2006-96960 It can be formed by methods described in JP-A-2006-171464, JP-A-2007-63541, JP-A-2007-297620, JP-A-2010-180305, and the like.

Hereinafter, as an example of a method for producing a methacrylic resin having a lactone ring structural unit, a case of production by radical polymerization in a batch system using a solution polymerization method will be specifically described.
As a method for producing a methacrylic resin having a lactone ring structural unit, a method of forming a lactone ring structure by a cyclization reaction after polymerization is used, but solution polymerization using a solvent is preferable in terms of promoting the cyclization reaction. .

Examples of solvents used for polymerization include aromatic hydrocarbons such as toluene, xylene and ethylbenzene; ketones such as methyl ethyl ketone and methyl isobutyl ketone; and the like.
These solvents may be used alone or in combination of two or more.

The amount of solvent during polymerization is not particularly limited as long as it is a condition that allows polymerization to proceed and gelation can be suppressed. %, more preferably 100 to 200% by mass.
In order to sufficiently suppress the gelation of the polymerization liquid and promote the cyclization reaction after polymerization, polymerization is carried out so that the concentration of the produced polymer in the reaction mixture obtained after polymerization is 50% by mass or less. is preferred. Moreover, it is preferable to appropriately add a polymerization solvent to the reaction mixture to control the above concentration to 50% by mass or less.
The method for appropriately adding the polymerization solvent to the reaction mixture is not particularly limited. For example, the polymerization solvent may be added continuously or may be added intermittently.
The polymerization solvent to be added may be a single solvent of only one kind or a mixed solvent of two or more kinds.

The polymerization temperature is not particularly limited as long as it is a temperature at which polymerization proceeds.

The polymerization time is not particularly limited as long as the target conversion rate is satisfied, but from the viewpoint of productivity and the like, it is preferably 0.5 to 10 hours, more preferably 1 to 8 hours.

During the polymerization reaction, if necessary, a polymerization initiator or a chain transfer agent may be added for polymerization.
Although the polymerization initiator is not particularly limited, for example, the polymerization initiator disclosed in the method for preparing a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer can be used.
These polymerization initiators may be used alone or in combination of two or more.
These polymerization initiators may be added at any stage as long as the polymerization reaction is in progress.
The amount of the polymerization initiator to be added may be appropriately set according to the combination of monomers, reaction conditions, etc., and is not particularly limited, but when the total amount of monomers used for polymerization is 100% by mass In addition, it may be 0.05 to 1% by mass.
As the chain transfer agent, a chain transfer agent used in general radical polymerization can be used. For example, the chain transfer agent disclosed in the method for preparing a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer can be used. can.
These may be used alone or in combination of two or more.
These chain transfer agents may be added at any stage as long as the polymerization reaction is in progress, and are not particularly limited.
The amount of the chain transfer agent to be added is not particularly limited as long as the desired degree of polymerization can be obtained under the polymerization conditions used, but the total amount of the monomers used in the polymerization is preferably 100% by mass. 0.05 to 1% by mass.
A suitable method for adding the polymerization initiator and the chain transfer agent in the polymerization step may be, for example, the method described in the method for preparing the methacrylic resin having structural units derived from the N-substituted maleimide monomer.

The dissolved oxygen concentration in the polymerization solution may be, for example, the value disclosed in the method for preparing a methacrylic resin having a structural unit derived from the N-substituted maleimide monomer.
A methacrylic resin having a lactone ring structural unit in the present embodiment can be obtained by performing a cyclization reaction after completion of the polymerization reaction. Therefore, it is preferable to subject the polymerization reaction solution to the lactone cyclization reaction in a state containing the solvent without removing the polymerization solvent.
The copolymer obtained by polymerization is heat-treated to cause a cyclization condensation reaction between the hydroxyl group (hydroxyl group) and the ester group present in the molecular chain of the copolymer to form a lactone ring structure. to form
In the heat treatment for forming the lactone ring structure, a reaction apparatus equipped with a vacuum device or a devolatilization device, an extruder equipped with a devolatilization device, or the like can be used to remove alcohol that may be by-produced by cyclization condensation. .

When forming the lactone ring structure, if necessary, heat treatment may be performed using a cyclization condensation catalyst in order to promote the cyclization condensation reaction.
Specific examples of cyclization condensation catalysts include methyl phosphite, ethyl phosphite, phenyl phosphite, dimethyl phosphite, diethyl phosphite, diphenyl phosphite, trimethyl phosphite, Phosphite monoalkyl esters, dialkyl esters or triesters such as triethyl phosphate; methyl phosphate, ethyl phosphate, 2-ethylhexyl phosphate, octyl phosphate, isodecyl phosphate, lauryl phosphate, stearyl phosphate, phosphoric acid isostearyl phosphate, dimethyl phosphate, diethyl phosphate, di-2-ethylhexyl phosphate, diisodecyl phosphate, dilauryl phosphate, distearyl phosphate, diisostearyl phosphate, trimethyl phosphate, triethyl phosphate, triisodecyl phosphate, phosphoric acid monoalkyl esters, dialkyl esters or trialkyl esters such as trilauryl phosphate, tristearyl phosphate and triisostearyl phosphate; organic zinc compounds such as zinc acetate, zinc propionate and zinc octyl;
These may be used alone or in combination of two or more.

The amount of the cyclization condensation catalyst to be used is not particularly limited. It is 1% by mass.
When the amount of the catalyst used is 0.01% by mass or more, it is effective for improving the reaction rate of the cyclization condensation reaction, and when the amount of the catalyst used is 3% by mass or less, the resulting polymer is colored. It is also effective in preventing cross-linking of the polymer and making melt molding difficult.

The timing of addition of the cyclization condensation catalyst is not particularly limited. For example, it may be added at the beginning of the cyclization condensation reaction, during the reaction, or both. good.
It is also preferable to perform devolatilization at the same time when the cyclization condensation reaction is performed in the presence of a solvent.

The device used when the cyclization condensation reaction and the devolatilization step are performed at the same time is not particularly limited, but a devolatilization device consisting of a heat exchanger and a devolatilization tank, a vented extruder, or a devolatilization A device and an extruder arranged in series are preferred, and a vented twin-screw extruder is more preferred.

As the vented twin-screw extruder to be used, a vented extruder having a plurality of vent ports is preferable.
When using a vented extruder, the reaction processing temperature is preferably 150 to 350°C, more preferably 200 to 300°C. If the reaction treatment temperature is lower than 150°C, the cyclization condensation reaction may be insufficient and the residual volatile matter may increase. Conversely, if the reaction treatment temperature exceeds 350° C., the resulting polymer may be colored or decomposed.
The degree of vacuum when using a vented extruder is preferably 10 to 500 Torr, more preferably 10 to 300 Torr. When the degree of vacuum exceeds 500 Torr, volatile matter tends to remain. Conversely, if the degree of vacuum is less than 10 Torr, industrial implementation may become difficult.

For the purpose of deactivating the remaining cyclization condensation catalyst during the cyclization condensation reaction, it is also preferable to add an alkaline earth metal and/or amphoteric metal salt of an organic acid during granulation.
Examples of alkaline earth metal and/or amphoteric metal salts of organic acids that can be used include calcium acetylacetate, calcium stearate, zinc acetate, zinc octylate, and zinc 2-ethylhexylate.
After undergoing the cyclization condensation reaction process, the methacrylic resin is melted and extruded into strands from an extruder equipped with a multi-hole die, and is cut by a cold cut method, an air hot cut method, an underwater strand cut method, and an underwater cut method. Process into pellets.
The lactonization for forming the lactone ring structural unit described above may be performed after the production of the resin and before the production of the resin composition (described later). It may be performed in conjunction with melt-kneading with.

From the viewpoint of reducing fluorescence intensity (content of fluorescent light-emitting substance), the polymerization solution after completion of polymerization is lactonized in a batch-type reaction tank in the same manner as in the method for producing a methacrylic resin having a glutarimide-based structural unit, It is preferred not to use a twin-screw extruder that is subjected to shear forces.
After the lactonization step, pelletization after devolatilization by the devolatilization method with reduced shear described in the method for preparing a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer reduces the fluorescence intensity. It is preferable from the point of view.

[Methacrylic resin composition]
The methacrylic resin composition of the present embodiment contains the above-described methacrylic resin containing a structural unit (X) having a ring structure in the main chain, and various additives within a range that does not significantly impair the effects of the present invention. may contain.

-Additive-
Additives are not particularly limited, but include, for example, antioxidants, light stabilizers such as hindered amine light stabilizers, ultraviolet absorbers, release agents, other thermoplastic resins, paraffin-based process oils, and naphthene-based process oils. Oil, aromatic process oil, paraffin, organic polysiloxane, softeners/plasticizers such as mineral oil, flame retardants, antistatic agents, organic fibers, inorganic fillers such as pigments such as iron oxide, glass fiber, carbon fiber , reinforcing agents such as metal whiskers, coloring agents; organic phosphorous compounds such as phosphites, phosphonites and phosphates; other additives; or mixtures thereof.

--Antioxidant--
The methacrylic resin composition of the present embodiment preferably contains an antioxidant that suppresses deterioration and coloration during molding or during use.
Examples of the antioxidant include, but are not limited to, hindered phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and the like.
These antioxidants may be used singly or in combination of two or more.
The methacrylic resin or methacrylic resin composition of the present embodiment is suitably used in various applications such as melt extrusion, injection molding, and film molding. The heat history received during processing varies depending on the processing method, but it ranges from several tens of seconds for extruders to several tens of minutes to several hours for thick product molding and sheet molding. Various. When subjected to a long heat history, it is necessary to increase the amount of heat stabilizer added in order to obtain the desired heat stability.

Therefore, from the viewpoint of suppressing the bleeding out of the heat stabilizer and preventing the film from sticking to the roll during film formation, it is preferable to use a plurality of types of heat stabilizers in combination. It is preferable to use together at least one selected from antioxidants and a hindered phenol-based antioxidant.
Examples of hindered phenol antioxidants include, but are not limited to, pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], thiodiethylene bis [3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3,3′,3 '',5,5',5''-hexa-tert-butyl-a,a',a''-(mesitylene-2,4,6-triyl)tri-p-cresol, 4,6-bis( octylthiomethyl)-o-cresol, 4,6-bis(dodecylthiomethyl)-o-cresol, ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate ], hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris[(4-tert-butyl-3-hydroxy-2,6-xylin)methyl ]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3 ,5-triazin-2-ylamine)phenol, 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylic acid, acrylic acid 2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl and the like.
In particular pentaerythritol terakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2-[1-(2-Hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate is preferred.

In addition, the hindered phenolic antioxidant as the antioxidant may be a commercially available phenolic antioxidant, and such commercially available phenolic antioxidants are limited to the following. However, for example, Irganox 1010 (Irganox 1010: pentaerythritol tetrakis [3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate], manufactured by BASF), Irganox 1076 (Irganox 1076: Octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, manufactured by BASF), Irganox 1330 (Irganox 1330: 3,3′,3″,5,5′,5′) '-Hexa-t-butyl-a,a',a''-(mesitylene-2,4,6-triyl)tri-p-cresol, manufactured by BASF), Irganox 3114 (Irganox3114: 1,3,5 -tris(3,5-di-t-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, manufactured by BASF), Irganox 3125 (Irganox 3125, manufactured by BASF), Adekastab AO-60 (pentaerythritol tetrakis [3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], manufactured by ADEKA), Adekastab AO-80 (3 , 9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro [5.5] Undecane, manufactured by ADEKA), Sumilizer BHT (Sumilizer BHT, manufactured by Sumitomo Chemical), Cyanox 1790 (Cyanox 1790, manufactured by Cytec), Sumilizer GA-80 (Sumilizer GA-80, manufactured by Sumitomo Chemical), Sumilizer GS (Sumilizer GS: 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, manufactured by Sumitomo Chemical), Sumilizer GM (Sumilizer GM: 2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl acrylate, manufactured by Sumitomo Chemical), vitamin E (manufactured by Eisai), and the like.
Among these commercially available phenolic antioxidants, Irganox 1010, Adekastab AO-60, Adekastab AO-80, Irganox 1076, Sumilizer GS, etc. are preferable from the viewpoint of the effect of imparting thermal stability to the resin.
These may be used individually by 1 type, or may be used in combination of 2 or more types.

Further, the phosphorus antioxidant as the antioxidant is not limited to the following, but for example, tris(2,4-di-t-butylphenyl)phosphite, bis(2,4- Bis(1,1-dimethylethyl)-6-methylphenyl)ethyl ester phosphorous acid, tetrakis(2,4-di-t-butylphenyl)(1,1-biphenyl)-4,4'-diylbisphosph Phonite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, bis(2,4 -dicumylphenyl)pentaerythritol-diphosphite, tetrakis(2,4-t-butylphenyl)(1,1-biphenyl)-4,4'-diylbisphosphonite, di-t-butyl-m-cresyl- Phosphonite, 4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin)-6-yloxy]propyl]-2 -methyl-6-tert-butylphenol and the like.

Furthermore, a commercially available phosphorus antioxidant may be used as the phosphorus antioxidant, and examples of such commercially available phosphorus antioxidants include, but are not limited to, Irgafos 168 ( Irgafos 168: tris (2,4-di-t-butylphenyl) phosphite, manufactured by BASF), Irgafos 12 (Irgafos 12: tris [2-[[2,4,8,10-tetra-t-butyldibenzo[ d, f][1,3,2]dioxaphosphefin-6-yl]oxy]ethyl]amine, manufactured by BASF), Irgafos 38 (Irgafos 38: bis(2,4-bis(1,1-dimethyl Ethyl)-6-methylphenyl) ethyl ester phosphorous acid, manufactured by BASF), Adekastab 329K (ADK STAB-229K, manufactured by ADEKA), Adekastab PEP-36 (ADK STAB PEP-36, manufactured by ADEKA), Adekastab PEP-36A ( ADK STAB PEP-36A, manufactured by ADEKA), ADEKA STAB PEP-8 (ADK STAB PEP-8, manufactured by ADEKA), ADEKA STAB HP-10 (ADK STAB HP-10, manufactured by ADEKA), ADEKA STAB 2112 (ADK STAB 2112, manufactured by ADEKA) ), ADEKA STAB 1178 (ADKA STAB 1178, made by ADEKA), ADEKA STAB 1500 (ADK STAB 1500, made by ADEKA), Sandstab P-EPQ (made by Clariant), Weston 618 (Weston 618, made by GE), Weston 619G (Weston 619G, made by GE ), Ultranox 626 (manufactured by GE), Sumilizer GP: 4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3, 2] Dioxaphosphepin)-6-yloxy]propyl]-2-methyl-6-tert-butylphenol, manufactured by Sumitomo Chemical), HCA (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10 - oxide, manufactured by Sanko Co., Ltd.) and the like.
Among these commercially available phosphorus-based antioxidants, Irgafos 168, Adekastab PEP-36, Adekastab PEP-36A, and Adekastab HP are considered effective in imparting thermal stability to the resin and in combination with various antioxidants. -10 and Adekastab 1178 are preferred, and Adekastab PEP-36A and Adekastab PEP-36 are particularly preferred.
These phosphorus-based antioxidants may be used alone or in combination of two or more.

In addition, the sulfur-based antioxidant as the antioxidant is not limited to the following, but for example, 2,4-bis(dodecylthiomethyl)-6-methylphenol (Irganox 1726, BASF ), 2,4-bis(octylthiomethyl)-6-methylphenol (Irganox 1520L, manufactured by BASF), 2,2-bis{[3-(dodecylthio)-1-oxoporopoxy]methyl}propane-1 ,3-diylbis[3-dodecylthio]propionate] (adekastab AO-412S, manufactured by ADEKA), 2,2-bis{[3-(dodecylthio)-1-oxoporopoxy]methyl}propane-1,3-diylbis[3 -dodecylthio]propionate] (Cheminox PLS, manufactured by Chemipro Kasei Co., Ltd.), di(tridecyl) 3,3′-thiodipropionate (AO-503, manufactured by ADEKA), and the like.
Among these commercially available sulfur antioxidants, Adekastab AO-412S and Cheminox PLS are preferred from the viewpoints of thermal stability imparting effect in the resin, combined effect with various antioxidants, and handleability.
These sulfur-based antioxidants may be used alone or in combination of two or more.

The content of the antioxidant may be any amount as long as the effect of improving the thermal stability is obtained, and if the content is excessive, problems such as bleeding out during processing may occur. Based on 100% by mass of the system resin, it is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 1% by mass or less, even more preferably 0.8% by mass or less. It is preferably 0.01 to 0.8% by mass, particularly preferably 0.01 to 0.5% by mass.

The timing of adding the antioxidant is not particularly limited, a method of starting polymerization after adding it to the monomer solution before polymerization, a method of adding and mixing with the polymer solution after polymerization and then subjecting it to a devolatilization step, and devolatilization. Examples thereof include a method of adding and mixing with the polymer in a molten state and then pelletizing, and a method of adding and mixing the pellets after devolatilization and pelletizing when they are melt-extruded again. Among these, from the viewpoint of preventing thermal deterioration and coloration in the devolatilization process, it is possible to add and mix the polymer solution after polymerization, add an antioxidant before the devolatilization process, and then subject it to the devolatilization process. preferable.

--Hindered amine light stabilizer--
The methacrylic resin composition of this embodiment can contain a hindered amine light stabilizer.
Although the hindered amine light stabilizer is not particularly limited, it is preferably a compound containing three or more ring structures. Here, the ring structure is preferably at least one selected from the group consisting of aromatic rings, aliphatic rings, aromatic heterocycles and non-aromatic heterocycles, and two or more ring structures are contained in one compound. If so, they may be the same or different from each other.
Examples of the hindered amine light stabilizer include, but are not limited to, bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis (1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl 1,2,2,6,6 -pentamethyl-4-piperidyl sebacate mixture, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, N,N'-bis(2,2,6,6-tetramethyl-4- piperidyl)-N,N'-diformylhexamethylenediamine, dibutylamine/1,3,5-triazine/N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)-1, Polycondensate of 6-hexamethylenediamine and N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine, poly[{6-(1,1,3,3-tetramethylbutyl)amino- 1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl)imino} hexamethylene {(2,2,6,6-tetramethyl-4- piperidyl)imino}], tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate, tetrakis(2,2,6,6-tetramethyl -4-piperidyl)butane-1,2,3,4-tetracarboxylate, 1,2,2,6,6-pentamethyl-4-piperidiol and β,β,β',β'-tetramethyl-2, 4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol reactant, 2,2,6,6-tetramethyl-4-piperidiol and β,β,β',β'- Tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol reactant, bis(1-undecanoxy-2,2,6,6-tetramethylpiperidine-4- yl) carbonate, 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, 2,2,6,6-tetramethyl-4-piperidyl methacrylate and the like.
Among them, bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl containing 3 or more ring structures ] Butylmalonate, dibutylamine/1,3,5-triazine/N,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexamethylenediamine and N-( Polycondensate of 2,2,6,6-tetramethyl-4-piperidyl)butylamine, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2 ,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl)imino}], 1,2 ,2,6,6-pentamethyl-4-piperidiol and β,β,β',β'-tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol Reactants, 2,2,6,6-tetramethyl-4-piperidiol and β,β,β',β'-tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane-3 ,9-diethanol is preferred.

The content of the hindered amine light stabilizer may be any amount as long as the effect of improving the light stability is obtained, and if the content is excessive, problems such as bleeding out during processing may occur. , with respect to 100% by mass of the methacrylic resin, it is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 1% by mass or less, and even more preferably 0.8% by mass or less, More preferably 0.01 to 0.8% by mass, particularly preferably 0.01 to 0.5% by mass.

--Ultraviolet absorber--
The methacrylic resin composition of this embodiment can contain an ultraviolet absorber.
Although the ultraviolet absorber is not particularly limited, it is preferably an ultraviolet absorber having a maximum absorption wavelength of 280 to 380 nm. Examples include benzotriazole compounds, benzotriazine compounds, benzophenone compounds, and oxybenzophenone compounds. , benzoate-based compounds, phenol-based compounds, oxazole-based compounds, cyanoacrylate-based compounds, benzoxazinone-based compounds, and the like.
Benzotriazole compounds include 2,2′-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol], 2-(3, 5-di-tert-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(2H-benzotriazol-2-yl)-p-cresol, 2-(2H-benzotriazol-2-yl)- 4,6-bis(1-methyl-1-phenylethyl)phenol, 2-benzotriazol-2-yl-4,6-di-tert-butylphenol, 2-[5-chloro(2H)-benzotriazole-2 -yl]-4-methyl-6-t-butylphenol, 2-(2H-benzotriazol-2-yl)-4,6-di-t-butylphenol, 2-(2H-benzotriazol-2-yl)- 4-(1,1,3,3-tetramethylbutyl)phenol, 2-(2H-benzotriazol-2-yl)-4-methyl-6-(3,4,5,6-tetrahydrophthalimidylmethyl) ) phenol, reaction product of methyl 3-(3-(2H-benzotriazol-2-yl)-5-t-butyl-4-hydroxyphenyl)propionate/polyethylene glycol 300, 2-(2H-benzotriazole-2 -yl)-6-(linear and branched dodecyl)-4-methylphenol, 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α, α-dimethylbenzyl)phenyl]-2H-benzotriazole, 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy-C7-9 side chain and linear alkyl esters.
Among these, benzotriazole-based compounds having a molecular weight of 400 or more are preferable. registered trademark) 234 (manufactured by BASF).

Benzotriazine compounds include 2-mono(hydroxyphenyl)-1,3,5-triazine compounds, 2,4-bis(hydroxyphenyl)-1,3,5-triazine compounds, 2,4,6-tris (Hydroxyphenyl)-1,3,5-triazine compounds, specifically 2,4-diphenyl-6-(2-hydroxy-4-methoxyphenyl)-1,3,5-triazine, 2 ,4-diphenyl-6-(2-hydroxy-4-ethoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-(2-hydroxy-4-propoxyphenyl)-1,3,5-triazine , 2,4-diphenyl-(2-hydroxy-4-butoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-butoxyphenyl)-1,3,5 -triazine, 2,4-diphenyl-6-(2-hydroxy-4-hexyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-octyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-dodecyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy- 4-benzyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-butoxyethoxy)-1,3,5-triazine, 2,4-bis(2- hydroxy-4-butoxyphenyl)-6-(2,4-dibutoxyphenyl)-1,3-5-triazine, 2,4,6-tris(2-hydroxy-4-methoxyphenyl)-1,3, 5-triazine, 2,4,6-tris(2-hydroxy-4-ethoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-propoxyphenyl)-1, 3,5-triazine, 2,4,6-tris(2-hydroxy-4-butoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-butoxyphenyl)- 1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-hexyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-octyl oxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-dodecyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy -4-benzyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-ethoxyethoxyphenyl)-1,3,5-triazine, 2,4,6-tris (2-hydroxy-4-butoxyethoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-propoxyethoxyphenyl)-1,3,5-triazine, 2,4 ,6-tris(2-hydroxy-4-methoxycarbonylpropyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-ethoxycarbonylethyloxyphenyl)-1,3 ,5-triazine, 2,4,6-tris(2-hydroxy-4-(1-(2-ethoxyhexyloxy)-1-oxopropan-2-yloxy)phenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-methoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-ethoxyphenyl )-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-propoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2- hydroxy-3-methyl-4-butoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-butoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-hexyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-octyl oxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-dodecyloxyphenyl)-1,3,5-triazine, 2,4,6-tris (2-hydroxy-3-methyl-4-benzyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-ethoxyethoxyphenyl)-1,3 ,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-butoxyethoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3- methyl-4-propoxyethoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-methoxycarbonylpropyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-ethoxycarbonylethyloxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4 -(1-(2-ethoxyhexyloxy)-1-oxopropan-2-yloxy)phenyl)-1,3,5-triazine and the like.
As the benzotriazine-based compound, commercially available products may be used, for example, Kemisorb 102 (manufactured by Chemipro Kasei Co., Ltd.), LA-F70 (manufactured by ADEKA Corporation), LA-46 (manufactured by ADEKA Corporation), Tinuvin 405 (BASF Corporation). (manufactured by BASF), Tinuvin 460 (manufactured by BASF), Tinuvin 479 (manufactured by BASF), Tinuvin 1577FF (manufactured by BASF) and the like can be used.
Among them, 2,4-bis(2,4-dimethylphenyl)-6-[2-hydroxy-4-(3-alkyloxy -2-hydroxypropyloxy)-5-α-cumylphenyl]-s-triazine skeleton ("alkyloxy" means a long-chain alkyloxy group such as octyloxy, nonyloxy, decyloxy, etc.). It can be preferably used.

As the UV absorber, benzotriazole-based compounds and benzotriazine-based compounds having a molecular weight of 400 or more are preferable from the viewpoint of compatibility with resins and volatility when heated. Benzotriazine-based compounds are particularly preferred from the viewpoint of inhibiting decomposition by.
Further, the melting point (Tm) of the ultraviolet absorber is preferably 80° C. or higher, more preferably 100° C. or higher, still more preferably 130° C. or higher, and further preferably 160° C. or higher. more preferred.
The UV absorber preferably has a weight loss rate of 50% or less, more preferably 30% or less, and 15% or less when the temperature is increased from 23° C. to 260° C. at a rate of 20° C./min. is more preferably 10% or less, and even more preferably 5% or less.
These ultraviolet absorbers may be used alone or in combination of two or more. By using two types of ultraviolet absorbers having different structures together, it is possible to absorb ultraviolet rays in a wide wavelength range.
The content of the ultraviolet absorber is not particularly limited as long as it does not impair heat resistance, moist heat resistance, thermal stability, and moldability and exhibits the effects of the present invention, but 100 mass of methacrylic resin %, preferably 0.1 to 5% by mass, preferably 0.2 to 4% by mass or less, more preferably 0.25 to 3% by mass, and even more preferably 0.3 to It is 3% by mass. Within this range, the balance between ultraviolet absorption performance, moldability, and the like is excellent.

--Release agent--
The methacrylic resin composition of this embodiment can contain a release agent. Examples of the release agent include, but are not limited to, fatty acid esters, fatty acid amides, fatty acid metal salts, hydrocarbon-based lubricants, alcohol-based lubricants, polyalkylene glycols, carboxylic acid esters, carbonized Hydrogen-based paraffinic mineral oils and the like are included.
Fatty acid esters that can be used as the release agent are not particularly limited, and conventionally known ones can be used.

Examples of fatty acid esters include fatty acids having 12 to 32 carbon atoms such as lauric acid, palmitic acid, heptadecanoic acid, stearic acid, oleic acid, arachidic acid and behenic acid, and monovalent fatty acids such as palmityl alcohol, stearyl alcohol and behenyl alcohol. Ester compounds with fatty alcohols and polyhydric fatty alcohols such as glycerin, pentaerythritol, dipentaerythritol and sorbitan; Complex esters of fatty acids, polybasic organic acids and monohydric fatty alcohols or polyhydric fatty alcohols A compound or the like can be used.
Examples of such fatty acid esters include cetyl palmitate, butyl stearate, stearyl stearate, stearyl citrate, glycerin monocaprylate, glycerin monocaprate, glycerin monolaurate, glycerin monopalmitate, glycerin dipalmitate, Glycerin Monostearate, Glycerin Distearate, Glycerin Tristearate, Glycerin Monooleate, Glycerin Dioleate, Glycerin Trioleate, Glycerin Monolinoleate, Glycerin Monobehenate, Glycerin Mono 12-Hydroxystearate, Glycerin di-12 - hydroxystearate, glycerine tri-12-hydroxystearate, glycerine diacetomonostearate, glycerine citrate fatty acid ester, pentaerythritol adipate stearate, montanic acid partially saponified ester, pentaerythritol tetrastearate, dipentaerythritol hexa Stearate, sorbitan tristearate and the like can be mentioned.
These fatty acid esters can be used singly or in combination of two or more.
Examples of commercially available products include Rikemal series, Poem series, Rikester series, Rikemaster series manufactured by Riken Vitamin Co., Ltd., Excel series manufactured by Kao Corporation, Rheodor series, Excepal series, and Coconard series. Rikemar S-100, Rikemar H-100, Poem V-100, Rikemar B-100, Rikemar HC-100, Rikemar S-200, Poem B-200, Rikester EW-200, Rikester EW-400, Excel S -95, Rheodol MS-50 and the like.

Fatty acid amides are also not particularly limited, and conventionally known ones can be used.
Examples of fatty acid amides include saturated fatty acid amides such as lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide and hydroxystearic acid amide; unsaturated fatty acid amides such as oleic acid amide, erucic acid amide and ricinoleic acid amide. substituted amides such as N-stearyl stearamide, N-oleyl oleic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, N-stearyl erucic acid amide, N-oleyl palmitic acid amide; Methylol stearic acid amides, methylolamides such as methylolbehenamide; stearic acid amide, ethylenebisbehenamide, hexamethylenebisstearic acid amide, hexamethylenebisbehenic acid amide, hexamethylenebishydroxystearic acid amide, N,N'-distearyladipic acid amide, N,N'-distearyl saturated fatty acid bisamides such as sebacic acid amide; unsaturated fatty acid bisamides such as ethylenebisoleic acid amide, hexamethylenebisoleic acid amide, N,N'-dioleyladipic acid amide, N,N'-dioleylsebacic acid amide; Aromatic bisamides such as m-xylylenebisstearic acid amide and N,N'-distearylisophthalic acid amide can be used.
These fatty acid amides can be used singly or in combination of two or more.
Commercially available products include, for example, Diamid series (manufactured by Nippon Kasei Co., Ltd.), Amide series (manufactured by Nippon Kasei Co., Ltd.), Nikka Amide series (manufactured by Nippon Kasei Co., Ltd.), Methylolamide series, Bisamide series, Slipax series (Nippon Kasei Co., Ltd.). Co., Ltd.), Kaowax series (manufactured by Kao Corporation), fatty acid amide series (manufactured by Kao Corporation), ethylenebisstearate amides (manufactured by Dainichi Chemical Industry Co., Ltd.), and the like.

Fatty acid metal salts refer to metal salts of higher fatty acids, such as lithium stearate, magnesium stearate, calcium stearate, calcium laurate, calcium ricinoleate, strontium stearate, barium stearate, barium laurate, barium ricinoleate, zinc stearate, zinc laurate, zinc ricinoleate, zinc 2-ethylhexoate, lead stearate, dibasic lead stearate, lead naphthenate, calcium 12-hydroxystearate, lithium 12-hydroxystearate, Among these, calcium stearate, magnesium stearate, and zinc stearate are particularly preferred because the resulting transparent resin composition has excellent processability and extremely excellent transparency.
Examples of commercially available products include SZ series, SC series, SM series, SA series manufactured by Sakai Chemical Industry Co., Ltd., and the like.
When using the fatty acid metal salt, the content is preferably 0.2% by mass or less with respect to 100% by mass of the methacrylic resin composition from the viewpoint of maintaining transparency.

The release agents may be used singly or in combination of two or more.
The release agent to be used preferably has a decomposition initiation temperature of 200° C. or higher. Here, the decomposition initiation temperature can be measured by the 1% weight loss temperature by TGA.
The content of the mold release agent is sufficient as long as it is effective as a mold release agent; if the content is excessive, problems such as bleed-out during processing and poor extrusion due to screw slippage may occur. Therefore, it is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and even more preferably 0.8% by mass, based on 100% by mass of the methacrylic resin. % or less, even more preferably 0.01 to 0.8% by mass, particularly preferably 0.01 to 0.5% by mass. When added in an amount within the above range, the decrease in transparency due to the addition of a mold release agent is suppressed, and mold release defects during injection molding and sticking to metal rolls during sheet molding tend to be suppressed. preferable.

--other thermoplastics--
The methacrylic resin composition of the present embodiment may contain a thermoplastic resin other than the methacrylic resin for the purpose of adjusting the birefringence and improving flexibility without impairing the object of the present invention.

Other thermoplastic resins include, for example, polyacrylates such as polybutyl acrylate; polystyrene, styrene-methyl methacrylate copolymer, styrene-butyl acrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene Styrene-based polymers such as block copolymers; etc., acrylic rubber particles having a three- to four-layer structure; JP-B-60-17406, a rubbery polymer disclosed in JP-A-8-245854; , methacrylic rubber-containing graft copolymer particles obtained by multistage polymerization;
Among these, from the viewpoint of obtaining good optical properties and mechanical properties, it is preferable to use a composition compatible with a styrene-acrylonitrile copolymer or a methacrylic resin containing a structural unit (X) having a ring structure in the main chain. A rubber-containing graft copolymer particle having a graft portion on its surface layer is preferred.

The average particle size of the acrylic rubber particles, the methacrylic rubber-containing graft copolymer particles, and the rubbery polymer described above is selected from the viewpoint of enhancing the impact strength, optical properties, etc. of the film obtained from the composition of the present embodiment. Therefore, it is preferably 0.03 to 1 μm, more preferably 0.05 to 0.5 μm.

The content of the other thermoplastic resin is preferably 0 to 50% by mass, more preferably 0 to 25% by mass, based on 100% by mass of the methacrylic resin.

[Method for producing methacrylic resin composition]
A method for producing the methacrylic resin composition of the present embodiment is not particularly limited as long as a composition satisfying the requirements of the present invention can be obtained. For example, a method of kneading using a kneader such as an extruder, a heating roll, a kneader, a roller mixer, or a Banbury mixer can be used. Among them, kneading by an extruder is preferable in terms of productivity. The kneading temperature may follow the preferred processing temperature of the polymer constituting the methacrylic resin and other resins to be mixed, and is generally in the range of 140 to 300.degree. Also, the extruder is preferably provided with a vent port for the purpose of reducing volatile matter.

Here, in the methacrylic resin composition of the present embodiment, the residual solvent amount (residual solvent amount) is preferably less than 1000 ppm by mass, more preferably less than 800 ppm by mass, and even more preferably 700 ppm by mass. is less than
Here, the residual solvent refers to the polymerization solvent used during polymerization (excluding alcohols), and the solvent used to re-dissolve the resin obtained by polymerization to form a solution. , Examples of the polymerization solvent include aromatic hydrocarbons such as toluene, xylene, ethylbenzene, and isopropylbenzene; ketones such as methyl isobutyl ketone, butyl cellosolve, methyl ethyl ketone, and cyclohexanone; Examples of solvents used for redissolving include toluene, methyl ethyl ketone, and methylene chloride.

In the methacrylic resin composition of the present embodiment, the residual alcohol content (residual alcohol content) is preferably less than 500 mass ppm, more preferably less than 400 mass ppm, and still more preferably less than 350 mass ppm. .
Here, the residual alcohol refers to an alcohol by-produced by the cyclization condensation reaction, and specific examples thereof include aliphatic alcohols such as methanol, ethanol, and isopropanol.
The residual solvent amount and the residual alcohol amount can be measured by gas chromatography.

Further, when the methacrylic resin composition of the present embodiment is used for film applications, etc., the polymerization reaction step, liquid-liquid separation step, liquid-solid separation step, devolatilization step, and granulation are carried out for the purpose of reducing foreign matter. and in any one or more of the molding steps, for example, a sintered filter, a pleated filter, a leaf disk type polymer filter, etc. with a filtration accuracy of 1.5 to 20 μm are added to the filtration device to prepare. is also a preferred method.

Whichever method is selected, it is preferable to prepare the composition after reducing oxygen and water as much as possible.
For example, the dissolved oxygen concentration in the polymerization solution in solution polymerization is preferably less than 300 ppm in the polymerization process, and in the preparation method using an extruder or the like, the oxygen concentration in the extruder is less than 1% by volume. preferably less than 0.8% by volume. The water content of the methacrylic resin is adjusted to preferably 1000 mass ppm or less, more preferably 500 mass ppm or less.
Within these ranges, it is relatively easy to prepare a composition that satisfies the requirements of the present invention, which is advantageous.

Glass transition temperature (Tg), weight average molecular weight (Mw), number average molecular weight (Mn) of the methacrylic resin composition, total amount of methanol soluble content and methanol insoluble content The ratio to 100% by mass, the photoelastic coefficient C _R , and the luminous intensity may be the same as those described above for the methacrylic resin.

- Method for producing methacrylic resin molding -
Various molding methods such as extrusion molding, injection molding, compression molding, calender molding, inflation molding, and hollow molding can be used as the method for producing the molded article (methacrylic resin molded article) of the present embodiment.
Various molded articles using the methacrylic resin of the present embodiment or the resin composition thereof can be further subjected to surface functionalization treatment such as antireflection treatment, transparent conductive treatment, electromagnetic wave shielding treatment, and gas barrier treatment.
Surface functionalization treatments such as hard coat treatment, antireflection treatment, transparent conductive treatment, electromagnetic wave shielding treatment, and gas barrier treatment are further applied to the surface of various molded articles using the methacrylic resin of the present embodiment and its resin composition. can also be done. Although the thickness of these functional layers is not particularly limited, it is usually used in the range of 0.01 to 10 μm.
As the hard coat layer applied to the surface, for example, a silicone-based curable resin, an organic polymer composite inorganic fine particle-containing curable resin, an acrylate such as a urethane acrylate, an epoxy acrylate, a multifunctional acrylate, and a photopolymerization initiator are mixed in an organic solvent. A coating liquid dissolved or dispersed in a conventionally known coating method is applied on a film or sheet obtained from the methacrylic resin composition of the present embodiment, dried, and photocured.
In addition, in order to improve the adhesion before applying the hard coat layer, for example, an easy adhesion layer containing inorganic fine particles in its composition, a primer layer, an anchor layer, etc. are provided in advance, and then the hard coat layer is formed. methods can also be used.
The anti-glare layer to be applied to the surface is formed by forming an ink from fine particles of silica, melamine resin, acrylic resin, etc., applying the ink onto another functional layer by a conventionally known coating method, and curing the ink with heat or light. Let
The antireflection layer to be applied to the surface includes thin films of inorganic substances such as metal oxides, fluorides, silicides, borides, nitrides, and sulfides, and resins having different refractive indices such as acrylic resins and fluorine resins. can be exemplified by laminating a single layer or multiple layers, and a lamination of thin layers containing fine composite particles of an inorganic compound and an organic compound can also be used.

-Characteristics of methacrylic resin moldings-
The YI (yellowness index) of the methacrylic resin molded article in the present embodiment at an optical path length of 80 mm is preferably 17.0 or less, more preferably 15.0 or less, and still more preferably 14.0 or less. is. When the YI at the optical path length of 80 mm is within this range, it is possible to obtain a suitable color tone even for a long optical path molding such as a light guide plate.
YI can be measured according to JIS K 7373 using a long-path spectral transmission colorimeter (manufactured by Nippon Denshoku Co., Ltd., ASA1). More specifically, it can be measured by the method described in Examples below.

-Application of methacrylic resin moldings-
Applications of the methacrylic resin molding include, for example, household goods, OA equipment, AV equipment, battery electrical equipment, lighting equipment, automobile parts, housings, sanitary such as sanitary ware substitutes, and optical parts.
Examples of automobile parts include tail lamps, meter covers, head lamps, light guide bars, lenses, and front plates of car navigation systems. It is preferable that the automobile component of the present embodiment includes the molded article.
Optical parts include light guide plates, diffusion plates, polarizing plate protective films, quarter-wave plates, and half-wave plates used in displays such as liquid crystal displays, plasma displays, organic EL displays, field emission displays, and rear projection televisions. , a viewing angle control film, a retardation film such as a liquid crystal optical compensation film, a display front plate, a display substrate, a lens, a touch panel, etc., and can be suitably used for a transparent substrate used in a solar cell. In addition, in the field of optical communication systems, optical exchange systems, optical measurement systems, or in optical products such as head-mounted displays and liquid crystal projectors, waveguides, lenses, optical fibers, optical fiber coating materials, LED lenses, lens covers, etc. can also be used for
It can also be used as a modifier for other resins.

EXAMPLES Hereinafter, the content of the present invention will be specifically described with reference to examples and comparative examples. In addition, the present invention is not limited to the following examples.

(Determination of 1.2-cyclohexylamino-N-cyclohexylsuccinimide)
N-cyclohexylmaleimide or N-cyclohexylmaleimide/meta-xylene solution was sampled and weighed, N-cyclohexylmaleimide 25% by mass meta-xylene solution was prepared, isopropyl benzoate was added as an internal standard substance, and gas chromatography (Shimadzu Using Seisakusho GC-2014), measurement was performed under the following conditions and determined.
Detector: FID
Column used: HP-5ms
Measurement conditions: After holding at 80°C for 5 minutes, heating up to 300°C at a heating rate of 10°C/min, then holding for 5 minutes

(Quantification of 2.2-anilino-N-phenylsuccinimide)
N-phenylmaleimide or N-phenylmaleimide/meta-xylene solution was collected and weighed, N-phenylmaleimide 10 mass% meta-xylene solution was prepared, isopropyl benzoate was added as an internal standard substance, and liquid chromatography (Waters Using UPLC H-class manufactured by Co., Ltd., measurement was performed under the following conditions and determined.
Detector: PDA (detection wavelength: 210 nm to 300 nm)
Column used: ACQUITY UPLC HSS T3
Column temperature: 40°C
Mobile phase: 50% acetonitrile aqueous solution containing 0.1% formic acid Flow rate: 0.4 mL/min

(3. Determination of residual amount of N-substituted maleimide monomer)
A part of the analysis object (polymerized solution after polymerization or methacrylic resin pellet) is collected and weighed, this sample is dissolved in chloroform to prepare a 5% by mass solution, and n-decane is added as an internal standard substance. Then, using gas chromatography (Shimadzu Corporation GC-2010), measurement was performed under the following conditions and determined.
Detector: FID
Column used: ZB-1
Measurement conditions: After holding at 45°C for 5 minutes, heating up to 300°C at a heating rate of 20°C/min, then holding for 15 minutes

(4. Analysis of structural units)
Unless otherwise specified, each structural unit in the methacrylic resins produced in Examples and Comparative Examples described later was determined by ¹ H-NMR measurement and ¹³ C-NMR measurement for each structure of the methacrylic resin and the methacrylic resin composition. Units were identified and their abundance calculated. The measurement conditions for ¹ H-NMR measurement and ¹³ C-NMR measurement are as follows.
・Measurement equipment: DPX-400 manufactured by Bruker Co., Ltd.
・Measurement solvent: CDCl ₃ or d ₆ -DMSO
・Measurement temperature: 40°C

(5. Glass transition temperature)
The glass transition temperature (Tg) (°C) of the methacrylic resin was measured according to JIS-K7121.
First, from a sample that had been conditioned under standard conditions (23° C., 65% RH) (left at 23° C. for 1 week), 4 points (4 locations) were cut out of about 10 mg each as test pieces.
Next, a differential scanning calorimeter (Diamond DSC manufactured by PerkinElmer Japan Co., Ltd.) was used under the condition of a nitrogen gas flow rate of 25 mL / min, where the temperature was raised from room temperature (23 ° C.) to 200 ° C. at 10 ° C. / min. After heating (first heating) and holding at 200 ° C. for 5 minutes to completely melt the sample, the temperature was lowered from 200 ° C. to 40 ° C. at 10 ° C./min, held at 40 ° C. for 5 minutes, and further , Among the DSC curves drawn during the temperature increase (secondary temperature increase) under the above temperature increase conditions, the stepwise change partial curve at the time of the secondary temperature increase and the extension line of each baseline are equidistant in the vertical axis direction The point of intersection with a straight line (midpoint glass transition temperature) was measured as the glass transition temperature (Tg) (°C). Measurement was performed at 4 points per sample, and the arithmetic average of the 4 points (rounded off to the nearest whole number) was used as the measured value.

(6. Molecular weight and molecular weight distribution)
The weight-average molecular weight (Mw), number-average molecular weight (Mn), and Z-average molecular weight (Mz) of the methacrylic resins produced in Examples and Comparative Examples described below were measured using the following equipment and conditions.・ Measuring device: Gel permeation chromatography (HLC-8320GPC) manufactured by Tosoh Corporation
·Measurement condition:
Columns: One TSKguard column SuperH-H, two TSKgel SuperHM-M, and one TSKgel SuperH2500 were connected in series and used.
Column temperature: 40°C
Developing solvent: tetrahydrofuran, flow rate: 0.6 mL/min, 2,6-di-t-butyl-4-methylphenol (BHT) was added at 0.1 g/L as an internal standard.
Detector: RI (differential refraction) detector Detection sensitivity: 3.0 mV/min Sample: Tetrahydrofuran 20 mL solution of 0.02 g of methacrylic resin Injection volume: 10 μL
Standard sample for calibration curve: The following 10 types of polymethyl methacrylate (manufactured by Polymer Laboratories; PMMA Calibration Kit MM-10) with known monodisperse weight peak molecular weights and different molecular weights were used.
Weight peak molecular weight (Mp)
Standard sample 1 1,916,000
Standard sample 2 625,500
Standard sample 3 298,900
Standard sample 4 138,600
Standard sample 5 60,150
Standard sample 6 27,600
Standard sample 7 10,290
Standard sample 8 5,000
Standard sample 9 2,810
Standard sample 10 850
Under the above conditions, the RI detection intensity was measured with respect to the elution time of the methacrylic resin.
Based on each calibration curve obtained by measuring the calibration curve standard sample, the weight average molecular weight (Mw), number average molecular weight (Mn), and Z average molecular weight (Mz) of the methacrylic resin composition are determined, Using that value, the molecular weight distribution (Mw/Mn) and (Mz/Mw) were determined.

(7. Photoelastic coefficient)
The methacrylic resins obtained in Examples and Comparative Examples were formed into press films using a vacuum compression molding machine to prepare measurement samples.
As specific sample preparation conditions, a vacuum compression molding machine (manufactured by Shindo Kinzoku Kogyo Co., Ltd., SFV-30 type) was used, and after preheating at 260 ° C. under reduced pressure (about 10 kPa) for 10 minutes, the resin was heated at 260 ° C. After compressing at about 10 MPa for 5 minutes and releasing the reduced pressure and press pressure, the mixture was transferred to a cooling compression molding machine and solidified by cooling. The obtained press film was aged for 24 hours or more in a constant temperature and humidity room adjusted to 23° C. and 60% humidity, and then cut into test pieces for measurement (thickness: about 150 μm, width: 6 mm).
The photoelastic coefficient C _R (Pa ⁻¹ ) was measured using a birefringence measuring device described in detail in Polymer Engineering and Science 1999, 39, 2349-2357.
The film-shaped test piece was similarly placed in a film tensioning device (manufactured by Imoto Seisakusho) installed in a constant temperature and humidity chamber with a chuck distance of 50 mm. Next, the birefringence measuring device (RETS-100, manufactured by Otsuka Electronics Co., Ltd.) was placed so that the laser light path was positioned at the center of the film, and the strain rate was 50% / min (between chucks: 50 mm, chuck movement speed: The birefringence of the specimen was measured while applying a tensile stress at 5 mm/min).
From the relationship between the absolute value of birefringence (|Δn|) and the tensile stress (σ _R ) obtained from the measurement, the slope of the straight line is obtained by least-squares approximation, and the photoelastic coefficient (C _R ) (Pa ^-1 ) is calculated. Calculated. The data for the tensile stress of 2.5 MPa≦σ _R ≦10 MPa was used for the calculation.
C _R =|Δn|/σ _R
Here, the absolute value of birefringence (|Δn|) is the value shown below.
|Δn|=|nx−ny|
(nx: refractive index in the stretching direction, ny: refractive index in the direction perpendicular to the stretching direction in the plane)

(8. Fluorescence Emission Intensity)
The methacrylic resins obtained in Examples and Comparative Examples were weighed in a glass sample bottle, chloroform was added, and the methacrylic resin was shaken at a speed of 800 times per minute for 30 minutes with a shaker. A 0% by mass chloroform solution was prepared. The fluorescence emission intensity was evaluated by the following two methods (i) and (ii).
(i) Using the concentration-intensity conversion formula obtained from the concentration of a fluorescein/ethanol solution and the fluorescence emission intensity at 514 nm obtained when this is spectroscopically analyzed at an excitation wavelength of 436 nm and a slit width of 2 nm, the methacrylic resin of 2. The fluorescence emission intensity obtained when the 0% by mass chloroform solution was spectroscopically analyzed was converted to the fluorescein/ethanol solution concentration.
Specifically, the emission intensity at 514 nm (shown in Table 1) of each of ethanol and 5×10 ⁻⁸ mol/L and 1×10 ⁻⁶ mol/L fluorescein/ethanol solutions was measured, and the ethanol background (BG ) A linear approximation straight line (shown in FIG. 1) was obtained using the values with correction, and this was used as the concentration-intensity conversion formula. Using this formula, the emission intensity of a 2.0% by mass chloroform solution of the methacrylic resin composition was converted into concentration and evaluated.
(ii) Concentration of quinine sulfate dihydrate dissolved in 1 mol/L dilute sulfuric acid solution, and fluorescence emission intensity at 458 nm obtained by spectroscopic analysis at an excitation wavelength of 365 nm and a slit width of 2 nm. Using the concentration-intensity conversion formula, the fluorescence emission intensity obtained when a 2.0% by mass chloroform solution of methacrylic resin was spectroscopically analyzed was calculated using a solution in which quinine sulfate dihydrate was dissolved in a 1 mol/L dilute sulfuric acid solution. converted to the concentration of
Specifically, the emission intensity at 458 nm of 1 mol/L diluted sulfuric acid and 1×10 ⁻⁷ mol/L and 1×10 ⁻⁶ mol/L quinine sulfate dihydrate/diluted sulfuric acid solutions (shown in Table 2) ) was measured, and a linear approximation straight line (shown in FIG. 2) was obtained using the values with dilute sulfuric acid background (BG) correction, and this was used as a concentration-intensity conversion formula. Using this formula, the emission intensity of a 2.0% by mass chloroform solution of methacrylic resin was converted into concentration and evaluated.
Fluorescence was measured using a fluorescence spectrophotometer (Fluorolog 3-22, manufactured by Horiba Jobin Yvon) using a xenon lamp as a light source and a PMT as a detector. The time constant was 0.2 s, the measurement mode was Sc/Rc, which normalizes the emission intensity with the excitation light intensity of each wavelength, and the observation was performed at 90° using a quartz cell with an optical path length of 1 cm.

(9. Color tone (YI) in length direction of injection molded body)
-Evaluation with injection molded plate-
Using an injection molding machine "AUTO SHOT Model 15A" manufactured by FANUC CORPORATION, under the conditions of a cylinder temperature of 270 ° C and a mold temperature of 90 ° C, a strip-shaped test piece with a thickness of 3 mm × width of 12 mm × length of 124 mm was produced. .
The obtained molded piece was cut to 80 mm in the longitudinal direction, and the longitudinal direction of the molded piece was cut using a grinder (Megaro Technica Co., Ltd., Plabeauty) at a cutter rotation speed of 8500 rpm and a feed rate of 1 m / min. Both end faces perpendicular to the direction were polished.
YI in the longitudinal direction (optical path length 80 mm) was measured using a long optical path spectral transmission colorimeter (manufactured by Nippon Denshoku Co., Ltd., ASA1) for the molded piece subjected to the polishing treatment. YI was measured in a wavelength range of 380 to 780 nm according to JIS K 7373.

(10. Solution YI)
The methacrylic resins or molded pieces obtained in Examples and Comparative Examples were used as a 20 w/v% chloroform solution (i.e., a solution prepared in such a ratio that 10 g of the sample was dissolved in chloroform to make a 50 mL solution), It was used as a measurement sample. Using an ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation, UV-2500PC), measurement wavelength 380 to 780 nm, slit width 2 nm, viewing angle 10 ° with 10 cm optical path length cell, auxiliary illuminant C used, reference object: chloroform , transmittance measurements were performed.
According to JIS K 7373, using the XYZ color system, the following formula YI = 100 (1.2769X-1.0592Z) / Y
YI (yellowness index) was calculated by

[material]
Raw materials used in Examples and Comparative Examples to be described later are shown below.
[[monomer]]
・Methyl methacrylate (MMA): Asahi Kasei Corporation ・N-phenylmaleimide (phMI, mass ratio of 2-anilino-N-phenylsuccinimide (APSI) to phMI mass: 60 mass ppm): Nippon Shokubai Co., Ltd. ・N-cyclohexyl Maleimide (chMI, mass ratio of 2-cyclohexylamino-N-cyclohexylsuccinimide (CCSI) to chMI mass 80 mass ppm): Nippon Shokubai Co., Ltd. Styrene: Asahi Kasei Co., Ltd.

-Water washing step and dehydration step of N-substituted maleimide-
The 2-amino-N-substituted succinimide was removed by the following water washing method, and the contained water was removed by the dehydration method.

--N-cyclohexylmaleimide washing step and dehydration step--
--- Reduction of CCSI in N-cyclohexylmaleimide to 5 mass ppm or less ---
250.0 kg of chMI and 750.0 kg of meta-xylene (hereinafter referred to as mXy) were weighed and added to a 2.0 m ³ glass-lined reactor equipped with a jacket temperature control device and three swept back impellers as stirring impellers. Steam was blown in to raise the temperature of the solution in the reactor to 56° C. and the solution was stirred to obtain an organic layer. Then, 350.0 kg of 2% by mass sulfuric acid water was weighed and added to the reactor, and the solution temperature was kept at 56° C. and stirred at 100 rpm for 10 minutes. Stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was discharged into a drum can.
The same operation was repeated twice, and the operation of washing the organic layer with aqueous sulfuric acid was performed three times in total. When the amount of CCSI in the organic layer was quantified by gas chromatography, it was 4.9 ppm by mass relative to chMI in the organic layer.
After that, 350.0 kg of ion-exchanged water was added to the reactor, the solution temperature was kept at 55° C., and the mixture was stirred at 100 rpm for 10 minutes. Stirring was stopped, the mixture was allowed to stand for 20 minutes, and the aqueous layer was discharged into a drum can.
The same operation was repeated once more, and the operation of washing the organic layer with ion-exchanged water was performed twice in total. When the amount of CCSI in the organic layer was quantified by gas chromatography, it was 4.6 mass ppm relative to chMI in the organic layer. The temperature of the solution was kept at 50° C., and the pressure in the reactor was gradually reduced while stirring at 100 rpm to set the pressure in the reactor to 5 kPa. After that, the temperature of the solution was raised to 60° C. and azeotropic dehydration was performed. 131.6 kg of the water/mXy mixed solution was distilled off, and the water concentration in the organic layer was quantified using a Karl Fischer moisture meter, and was 102 mass ppm relative to the mass of the organic phase.
mXy for concentration adjustment was added to the organic layer to obtain 1034.3 kg of an organic layer with chMI of 24.0 mass %, water concentration of 191 mass ppm, and CCSI of 4.6 mass ppm relative to the mass of chMI.
--- Reduction of CCSI in N-cyclohexylmaleimide to 1 mass ppm or less ---
80.0 kg of chMI and 240.0 kg of meta-xylene (hereinafter referred to as mXy) were weighed, and added to a 0.50 m ³ glass-lined reactor equipped with a jacket temperature control device and Kobelco Eco-Solutions full zone stirring blades. Steam was blown into the reactor to raise the temperature of the solution in the reactor to 55° C., and the mixture was stirred to obtain an organic layer. Then, 112.0 kg of 2% by mass sulfuric acid water was weighed and added to the reactor, and the solution temperature was kept at 55° C. and stirred at 100 rpm for 30 minutes. Stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was discharged into a drum can.
The same operation was repeated three times, and the operation of washing the organic layer with aqueous sulfuric acid was performed four times in total. When the amount of CCSI in the organic layer was quantified by gas chromatography, it was 0.57 mass ppm with respect to chMI in the organic layer.
After that, 112.0 kg of ion-exchanged water was added to the reactor, the solution temperature was kept at 55° C., and the mixture was stirred at 100 rpm for 30 minutes. Stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was discharged into a drum can.
The temperature of the solution was kept at 50° C., and the pressure in the reactor was gradually reduced while stirring at 100 rpm to set the pressure in the reactor to 5 kPa. After that, the temperature of the solution was raised to 60° C., and azeotropic dehydration was performed. 54 kg of the water/mXy mixed solution was distilled off, and the water concentration in the organic layer was quantified using a Karl Fischer moisture meter, which was 46 ppm by mass relative to the mass of the organic phase.
mXy for concentration adjustment was added to the organic layer to obtain 384.0 kg of an organic layer with chMI of 20.3 mass %, water concentration of 125 mass ppm, and CCSI of 0.60 mass ppm relative to the mass of chMI.

--N-phenylmaleimide washing step and dehydration step--
--- Reduction of APSI in N-phenylmaleimide to 5 mass ppm or less ---
150.0 kg of pHMI and 720.0 kg of mXy were weighed and added to a 2.0 m ³ glass lined reactor equipped with a jacket temperature control device and three retreating blades as stirring blades. The temperature was raised to 55° C. and stirred to obtain an organic layer. Next, 336.0 kg of 7% by mass sodium bicarbonate water was weighed and added to the reactor, and the solution temperature was kept at 55° C. and stirred at 100 rpm for 10 minutes. Stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was discharged into a drum can.
Then, 336.0 kg of ion-exchanged water was added to the reactor, the solution temperature was kept at 55° C., and the mixture was stirred at 100 rpm for 10 minutes. Stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was discharged into a drum can.
After that, 336.0 kg of 2 mass % sulfuric acid water was weighed and added to the reactor, and the solution temperature was kept at 55° C. and stirred at 100 rpm for 10 minutes. Stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was discharged into a drum can.
An operation of washing with ion-exchanged water was performed twice in the same manner as described above.
When the amount of APSI in the organic layer was quantified by liquid chromatography, it was 3.6 mass ppm relative to the pHMI in the organic layer.
The temperature of the solution was kept at 50° C., and the pressure in the reactor was gradually reduced while stirring at 100 rpm to set the pressure in the reactor to 5 kPa. After that, the temperature of the solution was raised to 55° C., and azeotropic dehydration was performed. 190 kg of the water/mXy mixed solution was distilled off, and the water concentration in the organic layer was quantified using a Karl Fischer moisture meter, and it was 47 mass ppm based on the mass of the organic layer.
mXy for concentration adjustment was added to the organic layer to obtain 1340.7 kg of an organic layer having a phMI of 10.8% by mass, a water concentration of 170 mass ppm, and an APSI of 3.4 mass ppm relative to the mass of phMI.
--- Reduction of APSI in N-phenylmaleimide to 1 mass ppm or less ---
50.0 kg of phMI and 240.0 kg of mXy were weighed and added to a 0.50 m ³ glass-lined reactor equipped with a jacket temperature control device and Kobelco Eco-Solutions full zone stirring blades. was raised to 55° C. and stirred to obtain an organic layer. Next, 112.0 kg of 7% by mass sodium bicarbonate water was weighed and added to the reactor, and the solution temperature was kept at 55° C. and stirred at 100 rpm for 15 minutes. Stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was discharged into a drum can. The same operation was repeated once more, and the operation of washing the organic layer with sodium bicarbonate water was performed twice in total.
Then, 112.0 kg of ion-exchanged water was added to the reactor, the solution temperature was kept at 55° C., and the mixture was stirred at 100 rpm for 30 minutes. Stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was discharged into a drum can.
After that, 112.0 kg of 2 mass % sulfuric acid water was weighed and added to the reactor, and the solution temperature was kept at 55° C. and stirred at 100 rpm for 30 minutes. Stirring was stopped, the mixture was allowed to stand for 10 minutes, and the aqueous layer was discharged into a drum can. The same operation was repeated twice, and the operation of washing the organic layer with aqueous sulfuric acid was performed three times in total.
An operation of washing with ion-exchanged water was performed twice in the same manner as described above.
When the amount of APSI in the organic layer was quantified by liquid chromatography, it was 0.37 ppm by mass relative to the pHMI in the organic layer.
The temperature of the solution was kept at 50° C., and the pressure in the reactor was gradually reduced while stirring at 100 rpm to set the pressure in the reactor to 5 kPa. After that, the temperature of the solution was raised to 55° C., and azeotropic dehydration was performed. 72 kg of the water/mXy mixture was distilled off, and the water concentration in the organic layer was quantified using a Karl Fischer moisture meter, and was 60 mass ppm based on the mass of the organic layer.
mXy for concentration adjustment was added to the organic layer to obtain 432.8 kg of an organic layer having a phMI of 10.3 mass %, a water concentration of 180 mass ppm, and an APSI of 0.42 mass ppm relative to the mass of phMI.

[[polymerization initiator]]
・ 1,1-di (t-butylperoxy) cyclohexane: "Perhexa C" manufactured by NOF Corporation
[[chain transfer agent]]
・ n-octyl mercaptan: manufactured by Kao Corporation [[Hindered phenolic antioxidant]]
・ Irganox 1076: manufactured by BASF [[phosphorus antioxidant]]
・ Irgafos 168 (melting point 180 to 190 ° C.): manufactured by BASF

[Example 1]
508.7 kg of a phMI 10.3% by mass meta-xylene (hereinafter referred to as mXy) solution (containing APSI 0.42 mass ppm) that has undergone the above steps multiple times and has undergone a water washing step and a dehydration step is weighed, and the temperature is controlled by a jacket. It was added to a 1.25 m ³ reactor equipped with an apparatus and a stirring blade, and 312.8 kg of mXy was distilled off under reduced pressure while stirring at a solution temperature of 60° C. and an internal reactor pressure of 5 kPa. Next, the reactor was returned to normal pressure, and 81.8 kg of 20.3 mass % mXy solution of chMI (containing 0.60 mass ppm of CCSI) and 38.3 kg of mXy which had undergone the water washing process and the dehydration process were charged. Further, 326.1 kg of MMA and 0.66 kg of n-octyl mercaptan as a chain transfer agent were weighed, added and stirred to obtain a monomer mixed solution.
123.0 kg of mXy was then weighed and added to Tank 1.
Further, 165.0 kg of MMA and 80.0 kg of mXy were weighed into tank 2 and stirred to obtain a monomer solution for addition.
The contents of the reactor are bubbled with nitrogen at a rate of 30 L/min for 1 hour, and each of tanks 1 and 2 is bubbled with nitrogen at a rate of 10 L/min for 30 minutes to remove dissolved oxygen. did.
After that, steam was blown into the jacket to raise the temperature of the solution in the reactor to 124°C, and while stirring at 50 rpm, 0.35 kg of 1,1-di(t-butylperoxy)cyclohexane was dissolved in 3.025 kg of mXy. The polymerization initiator solution was added at a rate of 1 kg/hour to initiate polymerization, and mXy was added from tank 1 at 30.75 kg/hour for 4 hours.
During the polymerization, the temperature of the solution in the reactor was controlled at 124±2° C. by adjusting the temperature with a jacket.
After 4 to 6 hours, a monomer solution containing MMA was added from tank 2 at a rate of 122.5 kg/hour.
Further, the initiator solution was added at a rate of 0.25 kg/hour 0.5 hours after the initiation of polymerization, 0.75 kg/hour after 4 hours, and 0.5 kg/hour after 6 hours. Addition of the solution was stopped and polymerization was continued for another 3 hours to obtain a polymerization solution containing a methacrylic resin having a ring structural unit in its main chain.
As a result of evaluating the amount of N-substituted maleimide contained in the resulting polymerization solution, it contained 340 ppm by mass of phMI and 120 ppm by mass of chMI.
To this polymerization solution, 0.1% by weight of Irganox 1076 and 0.05% by weight of Irgafos 168 were added with stirring based on 100% by weight of the polymer contained in the solution.
The polymerization solution containing the antioxidant was filtered by passing it through a filter made of SUS316L metal fiber and having a filtration accuracy of 2 μm.
In order to recover the polymer from the polymerization solution, the device used in the devolatilization process is a flat plate heat exchanger with a flat plate slit-shaped channel and a heat medium channel, and a SUS heat medium jacket with an internal volume of about 0.3 m ³ . A devolatilization device having no rotating part and comprising a vacuum vessel (hereinafter referred to as a devolatilization tank) was used.
A solution containing a polymer obtained by polymerization was supplied to a heat exchanger installed at the top of a vacuum vessel at a rate of 30 liters/hour, heated to 260°C, and then the internal temperature was 260°C and the degree of vacuum was 30 Torr. It was supplied to a devolatilization tank heated and decompressed to 1000 rpm and subjected to devolatilization treatment. The shear rate in the devolatilization device was calculated to be 5.3 s ^-1 from the shape of the device and the operating conditions.
After devolatilization, the polymer was pressurized with a gear pump from the bottom of the devolatilization tank, extruded through a strand die, cooled with water, and pelletized to obtain methacrylic resin composition pellets.
When the composition of the obtained pellet-shaped polymer was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 88.1% by mass, 9.0% by mass, and 2.9% by mass, respectively. there were. Also, the weight average molecular weight was 102,000 and Mw/Mn was 2.12. Other physical properties are shown in Table 3.

[Example 2]
Using a 10.3% by mass mXy solution of phMI (containing 0.42 ppm by mass of APSI) and a 20.3% by mass mXy solution of chMI (containing 0.60 ppm by mass of CCSI) that had undergone a water washing step and a dehydration step, Example 1 and A mixed solution of 39.6 kg of phMI, 59.5 kg of chMI and 247.0 kg of mXy was obtained through the same operation. 296.0 kg of MMA and 0.390 kg of n-octyl mercaptan were added thereto to prepare a monomer mixture solution, and then, in the same manner as in Example 1, methacrylic resin composition pellets were obtained.
As a result of evaluating the amount of N-substituted maleimide contained in the obtained polymerization solution, it contained 80 ppm by mass of phMI and 460 ppm by mass of chMI.
When the composition of the obtained pellet-shaped polymer was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 83.1% by mass, 6.8% by mass, and 10.1% by mass, respectively. there were. Also, the weight average molecular weight was 151,000 and the Mw/Mn was 2.14. Other physical properties are shown in Table 3.

[Example 3]
Using a 10.3% by mass mXy solution of phMI (containing 0.42 ppm by mass of APSI) and a 20.3% by mass mXy solution of chMI (containing 0.60 ppm by mass of CCSI) that had undergone a water washing step and a dehydration step, Example 1 and A mixed solution of 5.6 kg of phMI, 187.2 kg of chMI and 247.0 kg of mXy was obtained through the same operation. 184.2 kg of MMA, 53.1 kg of styrene and 0.280 kg of n-octyl mercaptan were added to prepare a monomer mixed solution.
123.0 kg of mXy was then weighed and added to Tank 1.
Further, 130.0 kg of MMA and 80.0 kg of mXy were weighed into tank 2 and stirred to obtain a monomer solution for addition.
Thereafter, in the same manner as in Example 1, methacrylic resin composition pellets were obtained.
As a result of evaluating the amount of N-substituted maleimide contained in the obtained polymerization solution, it contained 30 ppm by mass of phMI and 250 ppm by mass of chMI.
When the composition of the obtained pellet-shaped polymer was confirmed, the structural units derived from MMA, phMI, chMI, and styrene monomers were 57.2% by mass, 0.8% by mass, and 33.0% by mass, respectively. %, 9.0% by mass. Also, the weight average molecular weight was 130,000, Mw/Mn was 2.33, and the glass transition temperature was 150°C. Other physical properties are shown in Table 3.

[Example 4]
Using a 10.3% by mass mXy solution of phMI (containing 0.42 ppm by mass of APSI) and a 20.3% by mass mXy solution of chMI (containing 0.60 ppm by mass of CCSI) that had undergone a water washing step and a dehydration step, Example 1 and A mixed solution of 52.4 kg of phMI, 16.6 kg of chMI and 450.0 kg of mXy was obtained through the same operation. 491.1 kg of MMA and 0.660 kg of n-octylmercaptan were added to prepare a monomer mixed solution.
The contents of the reactor were bubbled with nitrogen at a rate of 30 L/min for 1 hour to remove dissolved oxygen.
After that, steam was blown into the jacket to raise the temperature of the solution in the reactor to 124°C, and while stirring at 50 rpm, 0.23 kg of 1,1-di(t-butylperoxy)cyclohexane was dissolved in 1.82 kg of mXy. A polymerization initiator solution was prepared, and polymerization was initiated by adding this solution at a rate of 1 kg/hour. Furthermore, the initiator solution was added to 0.5 kg/h after 0.5 hours, 0.42 kg/h after 1 hour, 0.35 kg/h after 2 hours, 0.14 kg/h after 3 hours, and 0.14 kg/h after 4 hours. The addition rate was lowered to 13 kg/hour, and the addition was stopped 7 hours after the initiation of polymerization.
During the polymerization, the temperature of the solution in the reactor was controlled at 124±2° C. by adjusting the temperature with a jacket.
After 15 hours from the initiation of polymerization, a polymerization solution containing a methacrylic resin having a ring structure in its main chain was obtained.
As a result of evaluating the amount of N-substituted maleimide contained in the resulting polymerization solution, it contained 6,300 mass ppm of phMI and 2,150 mass ppm of chMI.
To this polymerization solution, 0.1% by weight of Irganox 1076 and 0.05% by weight of Irgafos 168 were added with stirring based on 100% by weight of the polymer contained in the solution.
The polymerization solution containing this antioxidant was filtered by passing it through a filter made of SUS316L metal fiber and having a filtration accuracy of 2 μm.
In order to recover the polymer from the polymerization solution, the device used in the devolatilization process is a flat plate heat exchanger with a flat plate slit-shaped channel and a heat medium channel, and a SUS heat medium jacket with an internal volume of about 0.3 m ³ . A devolatilization device having no rotating part and comprising a vacuum vessel (hereinafter referred to as a devolatilization tank) was used.
A solution containing a polymer obtained by polymerization was supplied to a heat exchanger installed at the top of a vacuum vessel at a rate of 30 liters/hour, heated to 260°C, and then the internal temperature was 260°C and the degree of vacuum was 30 Torr. It was supplied to a devolatilization tank heated and decompressed to 1000 rpm and subjected to devolatilization treatment. The shear rate in the devolatilization device was calculated to be 5.3 s ^-1 from the shape of the device and the operating conditions.
After devolatilization, the polymer was pressurized with a gear pump from the bottom of the devolatilization tank, extruded through a strand die, cooled with water, and pelletized to obtain methacrylic resin composition pellets.
When the composition of the obtained pellet-shaped polymer was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 88.3% by mass, 9.0% by mass, and 2.7% by mass, respectively. there were. Further, the weight average molecular weight was 113,000, Mw/Mn was 2.25, and the glass transition temperature was 135°C. Other physical properties are shown in Table 3.

[Example 5]
Monomer mixture using a 10.8 mass% mXy solution of phMI (containing APSI 3.4 mass ppm) and a 24.0 mass% mXy solution of chMI (containing CCSI 4.6 mass ppm) that have undergone a water washing step and a dehydration step. In order to adjust the monomer concentration in the solution to that of Example 1, the same procedure as in Example 1 was carried out, except that the weight of mXy to be distilled off under reduced pressure and the weight of mXy to be added were changed. A methacrylic resin composition pellet having
As a result of evaluating the amount of N-substituted maleimide contained in the obtained polymerization solution, it contained 320 ppm by mass of phMI and 110 ppm by mass of chMI.
When the composition of the obtained pellet-shaped polymer was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 88.1% by mass, 9.1% by mass, and 2.8% by mass, respectively. there were. Also, the weight average molecular weight was 102,000, Mw/Mn was 2.13, and the glass transition temperature was 132°C. Other physical properties are shown in Table 3.

[Example 6]
On both sides of the injection molded plate obtained in Example 1, Acier E50PG manufactured by Nidek Co., Ltd. was spray-coated, dried, and then irradiated with ultraviolet rays of about 1000 mJ/cm ² using a high-pressure mercury lamp to obtain a film thickness of about 3 μm. A hard coat layer was formed. Furthermore, an antireflection layer was formed by depositing TiO ₂ (thickness 12 nm), SiO ₂ (thickness 37 nm), TiO ₂ (thickness 117 nm), and SiO ₂ (thickness 88 nm) in this order by vacuum deposition.
The total light transmittance of the injection-molded plate obtained in Example 1 was 91.7%, while the total light transmittance of the injection-molded plate on which the hard coat layer and the antireflection layer were formed was 97.4%. It was good.
When a cross-cut test was conducted according to JIS K5600-5-6, no peeling of the hard coat layer was observed.
Next, the injection molded plate on which the hard coat layer and the antireflection layer were formed was placed in a constant temperature and humidity chamber at a temperature of 80 ° C. and a relative humidity of 80% for 500 hours, and then the total light transmittance was measured and the cross-cut test was performed in the same manner. However, no change from before the constant temperature and humidity test was observed.

[Example 7]
400.3 kg of MMA, 100.2 kg of styrene, 0.396 kg of n-dodecyl mercaptan (equivalent to 800 ppm by mass with respect to the total mass of all monomers put into the polymerization system), and 500.4 kg of toluene were weighed, and the jacket temperature was adjusted. It was added to a 1.25 m ³ reactor equipped with a regulator and a stirring blade and stirred to obtain a mixed monomer solution.
Then, the solution in the reactor was bubbled with nitrogen at a rate of 30 L/min for 1 hour to remove dissolved oxygen.
Thereafter, steam was blown into the jacket to raise the temperature of the solution in the reactor to 120° C., and while stirring at 50 rpm, 0.253 kg of 1,1-di(t-amylperoxy)cyclohexane was dissolved in 4.748 kg of mXy. Polymerization was initiated by adding the resulting polymerization initiator solution at a rate of 1.0 kg/hour for 5 hours. Thus, the polymerization initiator was not added at the initial stage, but was added at a constant addition rate for a certain period of time.
During the polymerization, the temperature of the solution in the reactor was controlled at 120±2° C. by adjusting the temperature with a jacket.
After 6 hours from the start of the polymerization, the polymerization solution was sampled, and the polymerization conversion rate was analyzed from the concentration of the remaining monomer, and it was 96%. (polymerization time = 6 hours).
After that, 250 kg of toluene was added to the polymerization solution for dilution, and after completion of the polymerization, the liquid temperature was lowered to 50°C.
Next, a mixed liquid consisting of 165 kg of monomethylamine and 165 kg of methanol was added dropwise into the reactor at room temperature, the liquid temperature was raised to 190° C., and the mixture was stirred under pressure for 2 hours to allow the glutarimide cyclization reaction to proceed. The liquid temperature was lowered to 110° C., the pressure in the reactor was reduced, unreacted monomethylamine and methanol, and part of the toluene were distilled off, and an approximately 50% by mass toluene solution of the glutarimide cyclized methacrylic polymer was obtained. Obtained.
To this polymer solution, 0.1% by weight of Irganox 1010 and 0.05% by weight of Irgafos 168 were added with stirring based on 100% by weight of the polymer contained in the solution.
The polymer solution containing the antioxidant was filtered by passing it through a filter made of SUS316L metal fiber and having a filtration accuracy of 2 μm.
In order to recover the polymer from the polymer solution, the equipment used in the devolatilization process consists of a plate-type heat exchanger having a flat plate slit-shaped channel and a heat medium channel, and a SUS heat medium jacket with an internal volume of about 0.3 m ³ . A devolatilization device having no rotating part, which is composed of a reduced pressure vessel (hereinafter referred to as a devolatilization tank) and a devolatilization tank, was used.
A solution containing a polymer obtained by polymerization is supplied to a heat exchanger installed at the top of a vacuum vessel at a rate of 30 liters/hour, heated to 250°C, and then the internal temperature is 250°C and the degree of vacuum is 30 Torr. It was supplied to a devolatilization tank heated and decompressed to 1000 rpm and subjected to devolatilization treatment. The shear rate in the devolatilization device was calculated to be 5.3 s ^-1 from the shape of the device and the operating conditions.
After devolatilization, the polymer was pressurized with a gear pump from the bottom of the devolatilization tank, extruded through a strand die, cooled with water, and pelletized to obtain a methacrylic resin having a glutarimide structural unit. Physical properties are shown in Table 3.

[Example 8]
A methacrylic resin having a glutarimide structural unit was obtained in the same manner as in Example 7, except that the liquid temperature during the glutarimide cyclization reaction was changed from 190°C to 220°C.

[Comparative Example 1]
Using a 10.3% by mass mXy solution of phMI (containing 0.42 ppm by mass of APSI) and a 20.3% by mass mXy solution of chMI (containing 0.60 ppm by mass of CCSI) that had undergone a water washing step and a dehydration step, Example 1 and A mixed solution of 39.6 kg of phMI, 59.7 kg of chMI and 236.9 kg of mXy was obtained through the same operation. 340.7 kg of MMA and 0.275 kg of n-octyl mercaptan were added to prepare a monomer mixed solution.
Next, 123.1 kg of mXy was weighed to prepare tank 1 for additional solvent.
Further, 110.0 kg of MMA and 90.0 kg of mXy were weighed into tank 2 and stirred to obtain an additional MMA solution.
The contents of the reactor are bubbled with nitrogen at a rate of 30 L/min for 1 hour, and each of tanks 1 and 2 is bubbled with nitrogen at a rate of 10 L/min for 30 minutes to remove dissolved oxygen. did.
After that, steam was blown into the jacket to raise the temperature of the solution in the reactor to 128°C, and while stirring at 50 rpm, 0.371 kg of 1,1-di(t-butylperoxy)cyclohexane was dissolved in 3.004 kg of mXy. Polymerization was initiated by adding the polymerization initiator solution obtained at a rate of 1 kg/hour.
During the polymerization, the temperature of the solution in the reactor was controlled at 128±2° C. by adjusting the temperature with a jacket. Thirty minutes after the initiation of polymerization, the initiator solution addition rate was reduced to 0.25 kg/hr, and mXy was added from tank 1 at 30.78 kg/hr for 3.5 hours.
Then, 4 hours after the initiation of polymerization, the rate of addition of the initiator solution was increased to 0.75 kg/hour, and 100 kg/hour of MMA solution for addition was added from tank 2 for 2 hours.
Further, after 6 hours from the initiation of polymerization, the addition rate of the initiator solution was reduced to 0.5 kg/hour, and after 7 hours from the initiation of polymerization, the addition was stopped.
After 8 hours from the initiation of polymerization, a polymerization solution containing a methacrylic resin was obtained.
As a result of evaluating the amount of N-substituted maleimide contained in the resulting polymerization solution, it contained 240 ppm by mass of phMI and 1010 ppm by mass of chMI.
Next, devolatilization was performed by introducing the obtained polymer solution into a twin-screw extruder equipped with a plurality of vent ports for devolatilization. The obtained copolymer solution was supplied to the twin-screw extruder at a rate of 10 kg/h in terms of resin, and the conditions were a barrel temperature of 260° C., a screw rotation speed of 150 rpm, and a degree of vacuum of 10 to 40 Torr. The resin devolatilized by the twin-screw extruder was extruded through a strand die, cooled with water, and pelletized to obtain a methacrylic resin. The shear rate in the devolatilization device was calculated to be 80 s ^-1 from the shape of the device and the operating conditions.
When the composition of the obtained pellet-shaped polymer was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 80.9% by mass, 7.7% by mass, and 11.4% by mass, respectively. there were. Moreover, the weight average molecular weight was 149,000 and Mw/Mn was 2.26. Other physical properties are shown in Table 3.

[Comparative Example 2]
MMA 335.5 kg, phMI (commercially available, unrefined) 37.4 kg, chMI (commercially available, unrefined) 67.1 kg, chain transfer agent n-octyl mercaptan 0.300 kg, mXy 236.9 kg The mixture was weighed, added to a 1.25 m ³ reactor equipped with a temperature control device using a jacket and a stirring blade, and stirred to obtain a mixed monomer solution.
Next, 123.1 kg of mXy was weighed to prepare tank 1 for additional solvent.
Further, 110.0 kg of MMA and 90.0 kg of mXy were weighed into tank 2 and stirred to obtain an additional MMA solution.
The contents of the reactor are bubbled with nitrogen at a rate of 30 L/min for 1 hour, and each of tanks 1 and 2 is bubbled with nitrogen at a rate of 10 L/min for 30 minutes to remove dissolved oxygen. did.
After that, steam was blown into the jacket to raise the temperature of the solution in the reactor to 123° C., and while stirring at 50 rpm, 0.481 kg of 1,1-di(t-butylperoxy)cyclohexane was dissolved in 2.644 kg of mXy. Polymerization was initiated by adding the polymerization initiator solution obtained at a rate of 1 kg/hour.
During the polymerization, the temperature of the solution in the reactor was controlled at 123±2° C. by adjusting the temperature with a jacket. Thirty minutes after the initiation of polymerization, the initiator solution addition rate was reduced to 0.25 kg/hr, and mXy was added from tank 1 at 30.78 kg/hr for 3.5 hours.
Then, 4 hours after the initiation of polymerization, the rate of addition of the initiator solution was increased to 0.75 kg/hour, and 100 kg/hour of MMA solution for addition was added from tank 2 for 2 hours.
Furthermore, 6 hours after the initiation of polymerization, the addition rate of the initiator solution was reduced to 0.25 kg/hour, and 7 hours after the initiation of polymerization, the addition was stopped.
After 8 hours from the initiation of polymerization, a polymerization solution containing a methacrylic resin was obtained.
As a result of evaluating the amount of N-substituted maleimide contained in the obtained polymerization solution, it contained 340 ppm by mass of phMI and 1480 ppm by mass of chMI.
Next, the obtained polymer solution was devolatilized by supplying it to a concentrator having no rotating part, which consisted of a tubular heat exchanger preheated to 250° C. and a vaporization tank. The degree of vacuum in the vaporization tank was set to 10 to 15 Torr. The resin flowing down the vaporization tank was discharged with a screw pump, extruded through a strand die, cooled with water, and pelletized to obtain a methacrylic resin. The shear rate in the devolatilization device was calculated to be 5.3 s ^-1 from the shape of the device and the operating conditions.
When the composition of the obtained pellet-shaped polymer was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 80.0% by mass, 7.2% by mass, and 12.8% by mass, respectively. there were. Moreover, the weight average molecular weight was 137,000 and Mw/Mn was 2.32. Other physical properties are shown in Table 3.

[Comparative Example 3]
Using a 10.3% by mass mXy solution of phMI (containing 0.42 ppm by mass of APSI) and a 20.3% by mass mXy solution of chMI (containing 0.60 ppm by mass of CCSI) that had undergone a water washing step and a dehydration step, Example 1 and A mixed solution of 45.0 kg of phMI, 30.0 kg of chMI and 247.0 kg of mXy was obtained through the same operation. 485.1 kg of MMA and 0.660 kg of n-octylmercaptan were added to prepare a monomer mixed solution.
The contents of the reactor were bubbled with nitrogen at a rate of 30 L/min for 1 hour to remove dissolved oxygen.
After that, steam was blown into the jacket to raise the temperature of the solution in the reactor to 124°C, and while stirring at 50 rpm, 0.23 kg of 1,1-di(t-butylperoxy)cyclohexane was dissolved in 1.82 kg of mXy. A polymerization initiator solution was prepared, and polymerization was initiated by adding this solution at a rate of 1 kg/hour. Furthermore, the initiator solution was added to 0.5 kg/h after 0.5 hours, 0.42 kg/h after 1 hour, 0.35 kg/h after 2 hours, 0.14 kg/h after 3 hours, and 0.14 kg/h after 4 hours. The addition rate was lowered to 13 kg/hour, and the addition was stopped 7 hours after the start of polymerization.
During the polymerization, the temperature of the solution in the reactor was controlled at 124±2° C. by adjusting the temperature with a jacket.
After 15 hours from the initiation of polymerization, a polymerization solution containing a methacrylic resin having a ring structure in its main chain was obtained.
As a result of evaluating the amount of N-substituted maleimide contained in the obtained polymerization solution, it contained 6500 mass ppm of phMI and 2260 mass ppm of chMI.
To this polymerization solution, 0.1% by weight of Irganox 1076 and 0.05% by weight of Irgafos 168 were added with stirring based on 100% by weight of the polymer contained in the solution.
This antioxidant-added polymerization solution is supplied to a concentrating device consisting of a tubular heat exchanger preheated to 170° C. and a vaporization tank to increase the concentration of the polymer contained in the solution to 70% by mass. The obtained polymerized solution was supplied to a thin film evaporator having a rotating part with a heat transfer area of 0.2 m ² to devolatilize.
At this time, the temperature in the apparatus is 280 ° C., the supply amount is 30 L / hr, the rotation speed is 400 rpm, and the vacuum degree is 30 Torr. , to obtain methacrylic resin composition pellets. The shear rate in the thin film evaporator having a rotating part was calculated to be 3.2×10 ³ s ^-1 from the device shape and operating conditions.
When the composition of the obtained pellet-shaped polymer was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 87.3% by mass, 7.7% by mass, and 5.0% by mass, respectively. there were. Further, the weight average molecular weight was 152,000, Mw/Mn was 2.05, and the glass transition temperature was 135°C. Other physical properties are shown in Table 3.

[Comparative Example 4]
400.3 kg of MMA, 100.2 kg of styrene, 0.396 kg of n-dodecyl mercaptan (equivalent to 800 ppm by mass with respect to the total mass of all monomers put into the polymerization system), and 500.4 kg of toluene were weighed, and the jacket temperature was adjusted. It was added to a 1.25 m ³ reactor equipped with a regulator and a stirring blade and stirred to obtain a mixed monomer solution.
Then, the solution in the reactor was bubbled with nitrogen at a rate of 30 L/min for 1 hour to remove dissolved oxygen.
Thereafter, steam was blown into the jacket to raise the temperature of the solution in the reactor to 120° C., and while stirring at 50 rpm, 0.253 kg of 1,1-di(t-amylperoxy)cyclohexane was dissolved in 4.748 kg of mXy. Polymerization was initiated by adding the resulting polymerization initiator solution at a rate of 1.0 kg/hour for 5 hours. Thus, the polymerization initiator was not added at the initial stage, but was added at a constant addition rate for a certain period of time.
During the polymerization, the temperature of the solution in the reactor was controlled at 120±2° C. by adjusting the temperature with a jacket.
After 6 hours from the start of the polymerization, the polymerization solution was sampled, and the polymerization conversion rate was analyzed from the concentration of the remaining monomer, and it was 96%. (polymerization time = 6 hours).
After that, this polymerization solution was supplied to a concentrator consisting of a tubular heat exchanger preheated to 170° C. and a vaporization tank to increase the concentration of the polymer contained in the solution to 70% by mass.
The obtained polymerized solution was supplied to a thin film evaporator having a heat transfer area of 0.2 m ² for devolatilization.
At this time, the temperature in the apparatus is 280 ° C., the supply amount is 30 L / hr, the rotation speed is 400 rpm, and the vacuum degree is 30 Torr. to obtain a methacrylic resin. The shear rate in the thin film evaporator having a rotating part was calculated to be 3.2×10 ³ s ^-1 from the device shape and operating conditions.
Using the obtained methacrylic resin, using monomethylamine as an imidizing agent, and using an intermeshing co-rotating twin-screw extruder with a diameter of 15 mm and L/D = 90, it has a glutarimide-based structural unit. A methacrylic resin was produced.
At that time, the oxygen concentration in the extruder was made 1% or less by flowing nitrogen gas from the popper. The temperature of each temperature control zone of the extruder was set to 250° C., the screw rotation speed was 300 rpm, MS resin was supplied at 1 kg/hour, and the amount of monomethylamine supplied was 20% by mass based on 100% by mass of methacrylic resin. A methacrylic resin was charged from a hopper, melted and filled with a kneading block, and then monomethylamine was injected from a nozzle. A seal ring was placed at the end of the reaction zone and filled with resin. By-products and excess methylamine after the reaction were removed by reducing the degree of vacuum at the vent port to 60 Torr. The resin coming out as a strand from a die provided at the outlet of the extruder was cooled in a water tank and then pelletized by a pelletizer. The shear rate in the extruder was 160 s ^-1 calculated from the device shape and operating conditions.
Next, in an apparatus having a rotating part, which is an intermeshing co-rotating twin-screw extruder with a diameter of 15 mm and L/D = 90, the temperature of each temperature control zone of the extruder was set to 230 ° C. and the screw rotation speed was 150 rpm. Under the conditions of , the pellets obtained above are charged from the hopper at a supply rate of 1 kg / hr, and the resin is melted and filled with a kneading block, and then 100% by mass of the pelletized resin is discharged from the nozzle. 0.8% by mass of dimethyl carbonate was injected. A reverse flight was placed at the end of the reaction zone to fill with resin. By-products and excess dimethyl carbonate after the reaction were removed by reducing the degree of vacuum at the vent port to 100 Torr. The shear rate in the extruder was 80 s ^-1 calculated from the device shape and operating conditions.
The resin coming out as a strand from the die provided at the outlet of the extruder was cooled in a water tank and then pelletized again by a pelletizer to obtain a methacrylic resin having glutarimide structural units.

[Comparative Example 5]
Before devolatilizing the polymerization solution obtained in Comparative Example 1 with a twin-screw devolatilizing extruder, it was supplied to a concentrator consisting of a tubular heat exchanger and a vaporization tank preheated to 170 ° C., and contained in the solution A methacrylic resin was obtained in the same manner as in Comparative Example 1 except that the concentration of the polymer was increased to 70% by mass and then supplied to the twin-screw devolatilizing extruder.

[Comparative Example 6]
The polymerization solution obtained in Comparative Example 1 is desolvated by steam distillation, pulverized, dried, passed through an extruder under conditions of a barrel temperature of 260 ° C. and a screw rotation speed of 100 rpm, and the strand is water-cooled and pelletized to obtain a methacrylic resin. Obtained. The shear rate in the extruder was 53 s ^-1 calculated from the device shape and operating conditions.

As can be seen from Table 3, the methacrylic resin moldings of Examples have improved color tone in the long optical path.
On the other hand, in the comparative example, the color tone of the methacrylic resin and the solution of the methacrylic resin molded article was good, but the color tone of the methacrylic resin molded article in the long optical path was impaired.

The methacrylic resin and the methacrylic resin composition of the present invention not only have high heat resistance and excellent birefringence, but also extremely excellent color tone and transparency.
Molded articles for optical components obtained using the methacrylic resin composition of the present invention are, for example, smart phones, PDAs, tablet PCs, light guide plates used in displays such as liquid crystal televisions, display front plates, touch panels, smart phones, Lenses for tablet PC cameras, etc., optical lens parts for head-mounted displays, liquid crystal projectors, etc., such as prism elements, waveguides, lenses, especially small thin and uneven thickness optical lenses, optical fibers, coating materials for optical fibers, lenses, Examples include Fresnel lenses, phase plates with microlens arrays, optical cover components, and the like. Automotive parts include light guide plates for in-vehicle displays; in-vehicle meter panels; car navigation front panels, combiners, optical cover parts and other optical parts for head-up displays; in-vehicle camera lenses, light guide bars, etc. In addition, it can be particularly preferably used as parts for display devices for digital signage, etc., in which information is displayed on a thin display connected to a network for the purpose of publicity, advertising, etc., in locations such as camera focusing screens, outdoors, stores, public institutions, and transportation facilities. can.

Claims (10)

A methacrylic resin having a structural unit (X) having a ring structure in its main chain,
The structural unit (X) is a structural unit derived from N-cyclohexylmaleimide or N-phenylmaleimide ,
Glass transition temperature (Tg) is more than 120 ° C. and 160 ° C. or less,
When the chloroform solution containing 2.0% by mass of the methacrylic resin was spectroscopically analyzed, the emission intensity at 514 nm obtained at an excitation wavelength of 436 nm and a slit width of 2 nm was 30 × 10 ^-10 mol/ in terms of the concentration of the ethanol solution of fluorescein. L or less ,
The methacrylic resin contains a structural unit derived from a methacrylic acid ester monomer, and the content of the structural unit derived from the methacrylic acid ester monomer is 50 to 97% by mass with respect to 100% by mass of the methacrylic resin, The content of structural units derived from N-cyclohexylmaleimide or N-phenylmaleimide is 5 to 40% by mass with respect to 100% by mass of the methacrylic resin,
The methacrylate ester monomer is methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid Cyclopentyl, cyclohexyl methacrylate, cyclooctyl methacrylate, tricyclodecyl methacrylate, dicyclooctyl methacrylate, tricyclododecyl methacrylate, isobornyl methacrylate, phenyl methacrylate, benzyl methacrylate, 1-phenylethyl methacrylate, methacrylic acid at least one selected from 2-phenoxyethyl, 3-phenylpropyl methacrylate, and 2,4,6-tribromophenyl methacrylate ;
A methacrylic resin characterized by: 2. The methacrylic resin according to claim 1, wherein the emission intensity is 1×10 ⁻¹⁰ mol/L or more and 20×10 ⁻¹⁰ mol/L or less in terms of concentration of ethanol solution of fluorescein. When the chloroform solution containing 2.0% by mass of the methacrylic resin was spectroscopically analyzed, the emission intensity at 458 nm obtained at an excitation wavelength of 365 nm and a slit width of 2 nm was obtained by dissolving quinine sulfate dihydrate in a 1 mol / L dilute sulfuric acid solution. 3. The methacrylic resin according to claim 1, which is 4×10 ⁻⁹ mol/L or more and 6×10 ⁻⁹ mol/L or less in terms of the concentration of the solution. The methacrylic resin according to any one of claims 1 to 3, which has an absolute value of photoelastic coefficient of 3.0 × 10 ^-12 Pa ^-1 or less. A methacrylic resin composition comprising the methacrylic resin according to any one of claims 1 to 4 . A molded article comprising the methacrylic resin composition according to claim 5 . An optical component comprising the molded article according to claim 6 . 8. The optical component according to claim 7 , which is a light guide plate. 8. An optical component according to claim 7 , which is a lens. An automobile part comprising the molded article according to claim 6 .

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