JP7187343B2 - Method for producing methacrylic resin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a methacrylic resin having high heat resistance, highly controlled birefringence, excellent color tone and transparency, and a method for producing the same.

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

In particular, methacrylic resins having a ring structure in the main chain and compositions containing the methacrylic resins are known to have excellent performance in both heat resistance and optical properties (for example, patent Reference 1), the demand is rapidly increasing year by year. However, methacrylic resins having a ring structure in the main chain with 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., and the transmittance is reduced. There are problems like this. Therefore, in order to obtain a methacrylic resin having a ring structure in its main chain, which is less colored and has high transparency, a method for reducing the unreacted cyclic monomer remaining in the methacrylic resin has been disclosed.

For example, in Patent Document 2, a monomer component containing an N-substituted maleimide (a) and a methacrylic acid ester (b) is used, and a part of the monomer component is supplied to initiate polymerization, followed by polymerization. In the production method in which the remainder of the monomer component is supplied midway, the ratio of the N-substituted maleimide (a) in the unreacted monomer component present in the reaction system at the end of the supply of the monomer component is By controlling the ratio of the N-substituted maleimide (a) in the total amount of the monomer component supplied to be less than the amount of the residual N-substituted maleimide monomer, the amount of the residual N-substituted maleimide monomer is reduced, and the heat resistant product with excellent transparency and little coloration. A method for obtaining a methacrylic resin has been proposed.

Further, in Patent Document 3, the content of unreacted N-substituted maleimide in the copolymer obtained by carrying out polymerization in the presence of a specific polymerization initiator without using other polymerization initiators in combination is disclosed. There has been proposed a method for obtaining an N-substituted maleimide-containing methacrylic resin having a low content, excellent heat resistance, and little coloration.

Furthermore, in Patent Document 4, 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.

As another method for obtaining a less colored methacrylic resin having a ring structure in its main chain, a method for suppressing impurities present in raw materials and impurities generated during polymerization has been disclosed.
For example, in Patent Document 5, by polymerizing a monomer component containing an N-substituted maleimide in the presence of a non-radical polymerizable acid anhydride and/or a non-radical polymerizable carboxylic acid, A method has been proposed in which a reaction with an amine component, which is an impurity in the polyimide, is converted into an amide, thereby making it difficult to cause oxidative coloring.

Further, in Patent Document 6, in a method for producing a heat-resistant acrylic resin copolymerized with maleimide monomers, coloring impurities generated during copolymerization are suppressed by adding a specific alcohol during polymerization. A method is proposed.

Furthermore, in Patent Document 7, in a methacrylic resin containing a structural unit derived from an N-substituted maleimide monomer in the main chain, the amount of the N-substituted maleimide monomer remaining in the polymerization system at the end of the polymerization and the methacrylic acid ester A method of reducing the amount of coloring oligomers remaining in the methacrylic resin and improving the color tone of the resin has been proposed by controlling the amount of the monomer to absorb light at a wavelength of 400 nm in the methanol-soluble matter.

WO2011/149088 JP-A-9-324016 JP-A-9-12640 JP-A-2001-233919 JP-A-10-45852 JP-A-5-310853 Japanese Unexamined Patent Application Publication No. 2018-9141

However, in recent years, as its use has expanded from optical film applications to thick molded body applications such as lenses and molded plates, for example, even for molded body applications with a long optical path length, it is less colored and It has been desired to provide a resin capable of exhibiting high transparency.

Patent Documents 2, 3, and 4 focus on N-substituted maleimide, which has a strong coloring property as a monomer itself, as a method for reducing coloration, and reduce the amount of N-substituted maleimide remaining in the methacrylic resin and perform molding. Attention has been paid to the amount of N-substituted maleimide due to heat history such as processing, and a method of solving the problem by reducing it has been proposed.
However, as described above, it has been found that the degree of coloration and transparency of the methacrylic resin are insufficient for expanding the use of molded articles having a long optical path length, for example.

Moreover, Patent Documents 5 and 6 propose a method of suppressing the formation of coloring impurities by adding a specific compound during copolymerization. However, due to the influence of the compound added and the substance produced by reaction therewith, the light transmittance may be lowered in the use of a molded article having a long optical path length.

In Patent Document 7, although the degree of coloring is improved by reducing the amount of coloring oligomers, further improvement may be required when used for molded articles with long optical paths.

Therefore, it is strongly desired to further improve the colorability and transparency of methacrylic resins.
An object of the present invention is to provide a methacrylic resin having high heat resistance, highly controlled birefringence, and excellent color tone and transparency.

The inventors of the present invention have made intensive studies to solve the above-described problems of the prior art. The present inventors have found that a high transparency can be achieved with a small amount, and have made the present invention.

That is, the present invention is as follows.
[1]
Including a hydrogenation step of hydrogenating the methacrylic resin,
A method for producing a methacrylic resin having a ring structure in its main chain, having a glass transition temperature of more than 120° C. and not more than 160° C. and a photoelastic coefficient of −3×10 ⁻¹² to +3×10 ⁻¹² Pa ⁻¹ .
[2]
The method for producing a methacrylic resin according to [1], wherein the amount of change in the photoelastic coefficient of the methacrylic resin due to the hydrogenation step is 0.30×10 ⁻¹² Pa ⁻¹ or less.
[3]
The method for producing a methacrylic resin according to [1] or [2], wherein the hydrogenation catalyst used in the hydrogenation step is a heterogeneous catalyst.
[4]
The method for producing a methacrylic resin according to [3], wherein the heterogeneous catalyst is a palladium catalyst.
[5]
The method for producing a methacrylic resin according to any one of [1] to [4], wherein in the hydrogenation step, the hydrogen pressure is set to 0.2 to 5 MPa and the reaction is performed at 20 to 100° C. for 0.1 to 4 hours.

According to the present invention, it is possible to provide a method for producing a methacrylic resin having high heat resistance, highly controlled birefringence, and excellent color tone and transparency.

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 of the present embodiment is a methacrylic resin containing a methacrylic acid ester monomer unit (A) and a structural unit (B) having a ring structure in its main chain. The structural unit (B) having a ring structure in the main chain includes a structural unit (B-1) derived from an N-substituted maleimide monomer, a glutarimide structural unit (B-2), and a lactone ring structural unit (B-3 ), etc. Optionally, other vinyl-based monomer units (C) copolymerizable with methacrylic acid ester monomers are also included.

Each monomer structural unit will be described below.

- Structural unit (A) derived from methacrylic acid ester monomer -
First, the structural unit (A) derived from the methacrylic acid ester monomer will be described.
The structural unit (A) derived from a methacrylic acid ester monomer is formed, for example, from a monomer selected from methacrylic acid esters shown below.
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.
Among the above methacrylic acid esters, methyl methacrylate and benzyl methacrylate are preferable because the methacrylic resin to be obtained has excellent transparency and weather resistance.
Structural units (A) derived from methacrylic acid ester monomers may be contained alone or in combination of two or more.

The content of the structural unit (A) derived from the methacrylic acid ester monomer is, from the viewpoint of sufficiently imparting heat resistance to the methacrylic resin by the structural unit (B) having a ring structure in the main chain described later, The methacrylic resin is 100% by mass, preferably 50 to 97% by mass, more preferably 55 to 97% by mass, even more preferably 55 to 95% by mass, still more preferably 60 to 93% by mass, particularly preferably 60% by mass. ~90% by mass.
The content of the structural unit (A) derived from the methacrylic acid ester monomer 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, for example, using CDCl ₃ or DMSO-d ₆ as a measurement solvent at a measurement temperature of 40°C.

The structural unit (B) having a ring structure in its main chain is described below.
-Structural unit (B) having a ring structure in the main chain-
-- Structural unit (B-1) derived from N-substituted maleimide monomer --
Next, the structural unit (B-1) derived from the N-substituted maleimide monomer will be explained.
The structural unit (B-1) derived from the N-substituted maleimide monomer is at least selected from monomers represented by the following formula (1) and/or monomers represented by the following formula (2) It may be one, and is preferably formed from both monomers represented by the following formula (1) and the following formula (2).

式（１）中、Ｒ^１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、Ｒ^２及びＲ^３は、それぞれ独立に、水素原子、炭素数１～１２のアルキル基、炭素数６～１４のアリール基のいずれかを示す。
また、Ｒ^２がアリール基の場合には、Ｒ^２は、置換基としてハロゲンを含んでいてもよい。
また、Ｒ^１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 a carbon number. It represents either an alkyl group of 1 to 12 or an aryl group of 6 to 14 carbon atoms.
Moreover, when R ² is an aryl group, R ² may contain a halogen as a substituent.
In addition, 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、Ｒ^４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、Ｒ^５及びＲ^６は、それぞれ独立に、水素原子、炭素数１～１８のアルキル基、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 alkyl group having 1 to 18 carbon atoms, or an aryl group having 6 to 14 carbon atoms.

Specific examples are shown below.
Examples of the monomer represented by formula (1) include N-phenylmaleimide, N-benzylmaleimide, N-(2-chlorophenyl)maleimide, N-(4-chlorophenyl)maleimide, N-(4-bromo Phenyl)maleimide, N-(2-methylphenyl)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 and the like.
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 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-laurylmaleimide, N-stearyl maleimide, N-cyclopentylmaleimide, N-cyclohexylmaleimide, 1-cyclohexyl-3-methyl-1-phenyl-1H-pyrrole-2,5-dione, 1-cyclohexyl-3,4-dimethyl-1-phenyl-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 monomer represented by the formula (1) and the monomer represented by the formula (2) provides highly controlled birefringence properties. It is particularly preferable because it can be expressed.
The molar ratio (B1/ B2) is preferably greater than 0 and 15 or less, more preferably greater than 0 and 10 or less.
When the molar ratio B1/B2 is in this range, the methacrylic resin molded article of the present embodiment maintains transparency, does not yellow, and does not impair environmental resistance, and has good heat resistance and good heat resistance. It expresses photoelastic properties.

The content of the structural unit (B-1) derived from the N-substituted maleimide monomer is not particularly limited as long as the resulting composition satisfies the range of the glass transition temperature of the present embodiment. 100% by mass, preferably in the range of 5 to 40% by mass, more preferably in the range of 5 to 35% by mass.
Within this range, the methacrylic resin molded article 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 deterioration of the physical properties of the methacrylic resin molded product due to deterioration.

-- Glutarimide structural unit (B-2) --
Methacrylic resins having a glutarimide-based structural unit in the main chain, for example, JP-A-2006-249202, JP-A-2007-009182, JP-A-2007-009191, JP-A-2011-186482, Re It is a methacrylic resin having a glutarimide-based structural unit, which is described in Japanese Patent Publication 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.
Specifically, the glutarimide-based structural unit may be represented by the following general formula (3).

上記一般式（３）において、好ましくはＲ^７及びＲ^８は、それぞれ独立して、水素又はメチル基であり、Ｒ^９は、水素、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、Ｒ^７は、メチル基であり、Ｒ^８は、水素であり、Ｒ^９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。
グルタルイミド系構造単位を有するメタクリル系樹脂において、グルタルイミド系構造単位の含有量については、本実施形態の組成物として好ましいガラス転移温度の範囲を満たすものであれば特に制限はないが、メタクリル系樹脂を１００質量％として、好ましくは５～７０質量％の範囲、より好ましくは５～６０質量％の範囲である。
グルタルイミド系構造単位の含有量が上記範囲にあると、成形加工性、耐熱性、及び光学特性の良好な樹脂が得られることから好ましい。
グルタルイミド系構造単位を有するメタクリル系樹脂は、必要に応じて、芳香族ビニル単量体単位をさらに含んでいてもよい。
芳香族ビニル単量体としては特に限定されないが、スチレン、α－メチルスチレンが挙げられ、スチレンが好ましい。
グルタルイミド系構造単位を有するメタクリル系樹脂における芳香族ビニル単位の含有量としては、特に限定されないが、グルタルイミド系構造単位を有するメタクリル系樹脂を１００質量％として、０～２０質量％が好ましい。
芳香族ビニル単位の含有量が上記範囲にあると、耐熱性と優れた光弾性特性との両立が可能となり好ましい。

In general formula (3) above, preferably R ⁷ and R ⁸ are each independently hydrogen or a methyl group, R ⁹ is hydrogen, a methyl group, a butyl group, or a cyclohexyl group, and more Preferably, ^R7 is a methyl group, ^R8 is hydrogen and ^R9 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-based structural unit, the content of the glutarimide-based structural unit is not particularly limited as long as it satisfies the preferred glass transition temperature range for the composition of the present embodiment. Based on 100% by mass of the resin, the content is preferably in the range of 5 to 70% by mass, more preferably in the range of 5 to 60% by mass.
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.
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 (B-3)--
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.
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 preferable.

上記一般式（４）において、Ｒ^１０、Ｒ^１１及びＲ^１２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。
有機残基としては、例えば、メチル基、エチル基、プロピル基等の炭素数１～２０の飽和脂肪族炭化水素基（アルキル基等）；エテニル基、プロペニル基等の炭素数２～２０の不飽和脂肪族炭化水素基（アルケニル基等）；フェニル基、ナフチル基等の炭素数６～２０の芳香族炭化水素基（アリール基等）；これら飽和脂肪族炭化水素基、不飽和脂肪族炭化水素基、芳香族炭化水素基における水素原子の一つ以上が、ヒドロキシ基、カルボキシル基、エーテル基、エステル基からなる群から選ばれる少なくとも１種の基により置換された基；等が挙げられる。
ラクトン環構造は、例えば、ヒドロキシ基を有するアクリル酸系単量体と、メタクリル酸メチル等のメタクリル酸エステル単量体とを共重合して、分子鎖にヒドロキシ基とエステル基又はカルボキシル基とを導入した後、これらヒドロキシ基とエステル基又はカルボキシル基との間で、脱アルコール（エステル化）又は脱水縮合（以下、「環化縮合反応」ともいう）を生じさせることにより形成することができる。
重合に用いるヒドロキシ基を有するアクリル酸系単量体としては、例えば、２－（ヒドロキシメチル）アクリル酸、２－（ヒドロキシエチル）アクリル酸、２－（ヒドロキシメチル）アクリル酸アルキル（例えば、２－（ヒドロキシメチル）アクリル酸メチル、２－（ヒドロキシメチル）アクリル酸エチル、２－（ヒドロキシメチル）アクリル酸イソプロピル、２－（ヒドロキシメチル）アクリル酸ｎ－ブチル、２－（ヒドロキシメチル）アクリル酸ｔ－ブチル）、２－（ヒドロキシエチル）アクリル酸アルキル等が挙げられ、好ましくは、ヒドロキシアリル部位を有する単量体である２－（ヒドロキシメチル）アクリル酸や２－（ヒドロキシメチル）アクリル酸アルキルであり、特に好ましくは２－（ヒドロキシメチル）アクリル酸メチル、２－（ヒドロキシメチル）アクリル酸エチルである。

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 structure 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. After introduction, it 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.
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 hydroxyallyl 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 not particularly limited as long as it satisfies the range of the glass transition temperature of the methacrylic resin of the present embodiment. It is preferably 5 to 40% by mass, more preferably 5 to 35% by mass, based on 100% by mass.
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.

The content of the structural unit (B) having a ring structure in the main chain is 3, based on 100% by mass of the methacrylic resin, from the viewpoint of the heat resistance, thermal stability, strength, and fluidity of the methacrylic resin of the present embodiment. to 40% by mass, the lower limit is more preferably 5% by mass or more, still more preferably 7% by mass or more, and even more preferably 8% by mass or more, and the upper limit is more preferably It is 30% by mass or less, more preferably 28% by mass or less, even more preferably 25% by mass or less, particularly preferably 20% by mass or less, even more preferably 18% by mass or less, and most preferably less than 15% by mass.

-Other vinyl-based monomer unit (C) copolymerizable with methacrylic acid ester monomer-
Other vinyl-based monomer units (C) copolymerizable with methacrylic acid ester monomers that can constitute the methacrylic resin of the present embodiment (hereinafter sometimes referred to as (C) monomer units) .) include an aromatic vinyl-based monomer unit (C-1), an acrylic ester monomer unit (C-2), a vinyl cyanide-based monomer unit (C-3), and other units A mer unit (C-4) is included.
Other vinyl-based monomer units (C) copolymerizable with methacrylic acid ester monomers may be used singly or in combination of two or more.
The (C) monomer unit can be appropriately selected according to the properties required for the methacrylic resin, but properties such as thermal stability, fluidity, mechanical properties, and chemical resistance are particularly required. is selected from the group consisting of an aromatic vinyl-based monomer unit (C-1), an acrylate monomer unit (C-2), and a vinyl cyanide-based monomer unit (C-3) At least one is preferred.

[Aromatic vinyl-based monomer unit (C-1)]
The monomer forming the aromatic vinyl-based monomer unit (C-1) constituting the methacrylic resin of the present embodiment is not particularly limited, but is represented by the following general formula (5) Aromatic vinyl monomers are preferred.

前記一般式（４）中、Ｒ^１３は、水素原子、又は炭素数が１～６のアルキル基を表し、当該アルキル基は、例えば、水酸基で置換されていてもよい。
Ｒ^１４は、水素原子、炭素数が１～１２のアルキル基、炭素数が１～１２のアルコキシ基、炭素数が６～８のアリール基、炭素数が６～８のアリーロキシ基からなる群より選択されるいずれかであり、Ｒ^２は、全て同じ基であっても、異なる基であってもよい。また、Ｒ^１４同士で環構造を形成してもよい。
ｎは、０～５の整数を表す。

In general formula (4), R ¹³ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and the alkyl group may be substituted with, for example, a hydroxyl group.
R ¹⁴ is selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 8 carbon atoms, and an aryloxy group having 6 to 8 carbon atoms. Any selected, and R ² may all be the same group or different groups. Also, R ¹⁴ may form a ring structure together.
n represents an integer of 0 to 5;

Specific examples of the monomer represented by the general formula (5) are not particularly limited, but styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethyl styrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene, o-ethylstyrene, p-tert-butylstyrene, 1-vinylnaphthalene, 2-vinylnaphthalene, 1,1-diphenylethylene, isopropenylbenzene (α-methylstyrene), isopropenyltoluene, isopropenylethylbenzene, isopropenylpropylbenzene, isopropenylbutylbenzene, isopropenylpentylbenzene, isopropenylhexylbenzene, isopropenyloctylbenzene, α-hydroxymethylstyrene, α-hydroxyethylstyrene and the like.
Among the above, styrene and isopropenylbenzene are preferable, and styrene is more preferable from the viewpoints of imparting fluidity and reducing unreacted monomers by improving polymerization conversion.
These may be appropriately selected according to the properties required for the methacrylic resin of the present embodiment.

When the aromatic vinyl-based monomer unit (C-1) is used, the content is, considering heat resistance, reduction of residual monomer species, and balance of fluidity, (A) monomer unit and (B) When the total amount with the structural unit is 100% by mass, it is preferably 23% by mass or less, more preferably 20% by mass or less, still more preferably 18% by mass or less, and even more preferably 15% by mass or less, Even more preferably, it is 10% by mass or less.

When the aromatic vinyl-based monomer unit (C-1) is used in combination with the maleimide-based structural unit (B-1) described above, the (C-1) monomer relative to the content of the (B-1) structural unit The ratio (mass ratio) of the unit content (that is, (C-1) content / (B-1) content) is determined from the viewpoint of processing fluidity and the effect of reducing silver streaks by reducing residual monomers. , 0.3 to 5.
Here, from the viewpoint of maintaining good color tone and heat resistance, the upper limit is preferably 5 or less, more preferably 3 or less, and even more preferably 1 or less. From the viewpoint of reducing residual monomers, the lower limit is preferably 0.3 or more, more preferably 0.4 or more.
The aromatic vinyl-based monomer (C-1) described above may be used alone or in combination of two or more.

[Acrylic acid ester monomer unit (C-2)]
The monomer forming the acrylic acid ester monomer unit (C-2) constituting the methacrylic resin of the present embodiment is not particularly limited, but acrylic represented by the following general formula (6) Acid ester monomers are preferred.

前記一般式（６）中、Ｒ^１５は、水素原子、又は炭素数が１～１２のアルコキシ基を表し、Ｒ^１６は、炭素数が１～１８のアルキル基、炭素数が３～１２のシクロアルキル基、炭素数が６～１４のアリール基のいずれかを表す。

In the general formula (6), R ¹⁵ represents a hydrogen atom or an alkoxy group having 1 to 12 carbon atoms, R ¹⁶ represents an alkyl group having 1 to 18 carbon atoms, a cyclo It represents either an alkyl group or an aryl group having 6 to 14 carbon atoms.

As a monomer for forming the acrylic acid ester monomer unit (C-2), in the methacrylic resin for the film of the present embodiment, weather resistance, heat resistance, fluidity, and heat stability are improved. From the point of view, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate and the like are preferable. Methyl acrylate, ethyl acrylate and n-butyl acrylate are more preferred, and methyl acrylate and ethyl acrylate are more preferred from the viewpoint of availability.
The acrylic acid ester monomer units (C-2) may be used singly or in combination of two or more.

The content when the acrylic acid ester monomer unit (C-2) is used is, from the viewpoint of heat resistance and thermal stability, the total amount of the (A) monomer unit and the (B) structural unit to 100. In terms of % by mass, it is preferably 5% by mass or less, more preferably 3% by mass or less.

[Vinyl cyanide-based monomer unit (C-3)]
The monomer forming the vinyl cyanide monomer unit (C-3) constituting the methacrylic resin of the present embodiment is not particularly limited, but examples include acrylonitrile, methacrylonitrile, ethacrylonitrile, Nitrile, vinylidene cyanide, and the like can be mentioned, and among them, acrylonitrile is preferable from the viewpoint of availability and imparting chemical resistance.
The vinyl cyanide-based monomer units (C-3) may be used alone or in combination of two or more.

When the vinyl cyanide-based monomer unit (C-3) is used, the content is the total amount of the (A) monomer unit and (B) structural unit from the viewpoint of maintaining solvent resistance and heat resistance. 100% by mass, the content is preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less.

[monomer unit (C-4) other than (C-1) to (C-3)]
The monomer forming the monomer unit (C-4) other than (C-1) to (C-3) constituting the methacrylic resin of the present embodiment is not particularly limited. , acrylamide, amides such as methacrylamide; glycidyl compounds such as glycidyl (meth)acrylate, allyl glycidyl ether; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and their half esters compounds or anhydrides; unsaturated alcohols such as methallyl alcohol and allyl alcohol; olefins such as ethylene, propylene and 4-methyl-1-pentene; vinyl acetate, 2-hydroxymethyl-1-butene, methyl vinyl ketone, Vinyl compounds other than those mentioned above, such as N-vinylpyrrolidone and N-vinylcarbazole, and vinylidene compounds are included.
Furthermore, crosslinkable compounds having multiple reactive double bonds include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and the like. Esterification of both terminal hydroxyl groups of ethylene glycol or its oligomer with acrylic acid or methacrylic acid; neopentyl glycol di(meth)acrylate, di(meth)acrylate, etc., with acrylic acid or methacrylic acid for the hydroxyl groups of two alcohols esterified ones; polyhydric alcohol derivatives such as trimethylolpropane and pentaerythritol esterified with acrylic acid or methacrylic acid; and polyfunctional monomers such as divinylbenzene.

Among the monomers constituting the (C) monomer unit described above, at least one selected from the group consisting of methyl acrylate, ethyl acrylate, styrene, and acrylonitrile is preferable from the viewpoint of availability.

The content of other vinyl-based monomer units (C) that can be copolymerized with the methacrylic acid ester monomer is 100% by mass of the methacrylic resin from the viewpoint of enhancing the effect of imparting heat resistance by the structural unit (B). is 0 to 20% by mass, preferably 0 to 18% by mass, more preferably 0 to 15% by mass.
In particular, when using a crosslinkable polyfunctional (meth)acrylate having a plurality of reactive double bonds as the monomer unit (C), the content of the monomer unit (C) is the fluidity of the polymer. From the viewpoint of , it is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and still more preferably 0.2% by mass or less.

In particular, in the present embodiment, from the viewpoint of the heat resistance and optical properties of the methacrylic resin molded product, when the total amount of the (B) structural unit and the (C) monomer unit is 100% by mass, (B) The content of structural units is 45 to 100% by mass. At this time, the content of the (C) structural unit is 0 to 55% by mass. The content of the (B) structural unit is preferably 50 to 100% by mass, more preferably 50 to 90% by mass, still more preferably 50 to 80% by mass.

The properties of the methacrylic resin of this embodiment are described below.

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 possible to more easily obtain necessary and sufficient heat resistance as an optical film for lens moldings and film moldings for liquid crystal displays in recent years. 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 for the reasons described above.
The glass transition temperature (Tg) can be determined by measuring according to JIS-K7121. Specifically, it can be measured using the method described in the examples below.

The content of the component having light absorption at a wavelength of 400 nm in the methanol-soluble portion of the methacrylic resin in the present embodiment is preferably 0.6% by mass or less, more preferably 0.5% by mass or less, and further It is preferably 0.4% by mass or less, still more preferably 0.3% by mass or less, and particularly preferably 0.1% by mass or less.
By setting the ratio of the component having light absorption at a wavelength of 400 nm to 0.5% by mass or less, it is possible to obtain a molded product that has a good color tone and is suitable for optical applications.
The content of a component having an absorbance at a wavelength of 400 nm in the methanol-soluble matter was determined by GPC measurement using a UV detector at a wavelength of 400 nm, while obtaining the total peak area of the methanol-soluble matter. A calibration curve based on the polymer is prepared, and the content of the component having an absorbance at a wavelength of 400 nm in the methanol-soluble matter can be calculated as mass% in terms of N-phenylmaleimide by conventional analysis. can.
Specifically, it will be described in detail in Examples described later.
The methanol-soluble and methanol-insoluble components are reprecipitated by making a chloroform solution of the methacrylic resin and dropping the solution into methanol, separating the filtrate and the filtered matter, and then drying each of them. Specifically, it can be obtained by the method described in Examples below.

The content of the component having a molecular weight of 2000 or less in the methanol-soluble portion of the methacrylic resin in the present embodiment is preferably 40% by mass or less, more preferably 30% by mass or less, and 20% by mass or less. It is even more preferable to have
By setting the content of the component with a molecular weight of 2000 or less in the methanol-soluble matter to 40% by mass or less, it is possible to obtain a molded product with a good color tone, and it is possible to prevent stains on the cast roll during film molding and during injection molding. It is possible to suppress troubles during molding such as generation of silver streaks.
The content of components with a molecular weight of 2,000 or less in the methanol-soluble matter is calculated by measuring the methanol-soluble matter with GPC using an RI detector and calculating the ratio of the elution area with a molecular weight of 2,000 or less to the total peak area. be. Specifically, it can be obtained by the method described in Examples below.

The ratio of the amount of methanol-soluble content of the methacrylic resin in the present embodiment to the total amount of 100% by mass of the amount of methanol-soluble content and the amount of methanol-insoluble content is preferably 5% by mass or less, more preferably It is 4% by mass or less, more preferably 3.5% by mass or less, and even more preferably 3% by mass or less.
By setting the ratio of the soluble content to 5% by mass or less, troubles during molding such as contamination of cast rolls during film molding and generation of silver streaks during injection molding can be suppressed.
The details of the methanol-soluble matter and the methanol-insoluble matter are as described above.

In the methacrylic resin in 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 65,000 to 300,000, more preferably It is in the range of 100,000 to 220,000, more preferably in the range of 120,000 to 180,000.
When the weight average molecular weight (Mw) is within the above range, the balance between mechanical strength and fluidity is also excellent.
Regarding the ratio between the weight average molecular weight (Mw) and the number average molecular weight (Mn), which are parameters representing the molecular weight distribution, in the methacrylic resin of the present embodiment, considering the balance between fluidity and mechanical strength, , Mw/Mn is preferably 1.5 to 3.0, more preferably 1.6 to 2.5, even more preferably 1.6 to 2.3.
The weight-average molecular weight and number-average molecular weight of the methacrylic resin can be measured by the methods described in Examples below.

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, preferably 2.0×10 ⁻¹² Pa ⁻¹ or less, and 1 It is more preferably 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 _CR 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 birefringence, nx is the refractive index in the stretching direction, ny is the refractive index in the direction perpendicular to the stretching direction in the plane, are shown 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, birefringence due to residual stress during molding when formed into a molded body such as a lens can be suppressed.
Specifically, the photoelastic coefficient _CR of the methacrylic resin can be determined by the method described in Examples below.

The methacrylic resin in the present embodiment preferably has a YI of 0 to 1.2 at an optical path length of 3 mm, more preferably 0 to 1.1, and still more preferably 0 to 1.1.
In addition, the total light transmittance at an optical path length of 3 mm measured under the same conditions as the conditions for measuring YI is preferably 90 to 93%, more preferably 91 to 93%, and still more preferably 92 to 93%. is.
When the YI and the total light transmittance at an optical path length of 3 mm are within this range, practically sufficient color tone and transmittance can be obtained in a relatively thin molded article such as a sheet.
The YI and the total light transmittance at an optical path length of 3 mm can be measured by the method described in Examples below.

The methacrylic resin in the present embodiment preferably has a YI of 0 to 15, more preferably 0 to 12, and even more preferably 0 to 10 at an optical path length of 80 mm.
When the YI at the optical path length of 80 mm is within this range, it is possible to obtain color tone and transparency suitable for use in long optical path moldings such as light guide plates.
YI at an optical path length of 80 mm can be measured by the method described in Examples below.

(Method for producing methacrylic resin)
A method for producing the methacrylic resin of the present embodiment will be described below.
Methods for producing methacrylic resins having structural units derived from N-substituted maleimide monomers in the main chain include bulk polymerization, solution polymerization, suspension polymerization, precipitation polymerization, and emulsion polymerization. methods, 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 polymerization 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.

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"), production is carried out by radical polymerization using a solution polymerization method. A case of doing so will be specifically described.

In the present embodiment, a method of charging a part of the monomers into the reactor before the start of polymerization, starting polymerization by adding a polymerization initiator, and then supplying the remainder of the monomers, a so-called semi-batch polymerization method. A method (also called a semi-batch method) can be preferably used. Employing this method tends to make it easier to control the molecular weight distribution and composition distribution of the resulting polymer. Further, by adopting a semi-batch polymerization method as described in JP-A-2018-9141, the amount of coloring oligomer before hydrogenation can be further reduced.

In the production of a maleimide copolymer, the ratio of the amount of monomer used in the initial charge (at the start of polymerization) to the amount of monomer added after the start of polymerization (amount of monomer at the start of polymerization: polymerization The amount of monomer added after initiation) is preferably in the range of 1:9 to 8:2, more preferably in the range of 2:8 to 7.5:2.5, and further It is preferably in the range of 3:7 to 5:5.
If the amount ratio of the monomers is within the above range, it becomes possible to appropriately select the mixed composition of the monomers in the initial charge, taking into consideration the copolymerization reactivity of each monomer used during copolymerization. It tends to be easier to control the composition distribution of the resulting polymer.

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.
These may be used individually by 1 type, or may be used in combination of 2 or more types.

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 parts by mass, it is preferably 10 to 200 parts by mass. More preferably 25 to 200 parts by mass, still more preferably 50 to 200 parts by mass, still more preferably 50 to 150 parts by mass.

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 140°C, still more preferably 100 to 130°C.

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 0.5 to 10 hours. It is preferably 1 to 8 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.

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 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 part by mass, preferably 0.05 to 0.5 parts by mass, when the total amount of monomers used for polymerization is 100 parts by mass. be.
These polymerization initiators may be added at any stage as long as the polymerization reaction is in progress.

In the present embodiment, the type of the initiator, the amount of the initiator, the polymerization temperature, etc. are adjusted so that the ratio of the total amount of radicals generated from the polymerization initiator to the total amount of unreacted monomers remaining in the reaction system is always below a certain value. is preferably selected as appropriate.

In particular, in the present embodiment, at least once in the first half of the time from the start of addition of the polymerization initiator to the end of addition (polymerization initiator addition time), the addition amount of the polymerization initiator per unit time is It is preferable to make it smaller than the addition amount per unit time.
By adopting this method, 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.

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 part by mass, preferably 0.05 to 0.5 part by mass, when the total amount of monomers used for polymerization is 100 parts by mass.

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 using, for example, 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 method for recovering the polymer from the polymerization liquid obtained by solution polymerization is not particularly limited. After adding the polymerization liquid in the presence of an excess amount, treatment with a homogenizer (emulsification dispersion) is performed, and unreacted monomers are subjected to pretreatment such as liquid-liquid extraction and solid-liquid extraction. a method of separating from the polymerization liquid; or a method of separating the polymerization solvent and unreacted monomers via a step called devolatilization step to recover the polymerization product; and the like.
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.

Devices used in the devolatilization process include, for example, a devolatilization device consisting of a tubular heat exchanger and a devolatilization tank; thin film evaporators such as Wiblen and Exeba manufactured by Kobelco Eco-Solutions Co., Ltd., Contra and inclined blade Contra manufactured by Hitachi; A vented extruder with sufficient residence time and surface area to exhibit devolatilization performance;
A devolatilization step or the like using a devolatilization device in which two or more of these devices are combined can also be used.

The treatment temperature in the devolatilizer is preferably 150 to 350°C, more preferably 170 to 300°C, still more preferably 200 to 280°C. When this temperature is 150° C. or higher, it is effective to prevent the residual volatile matter from increasing. Conversely, if this temperature is 350° C. or less, there is little possibility that the obtained methacrylic resin will be colored or decomposed.

The degree of vacuum in the devolatilizer may be in the range of 10 to 500 Torr, preferably in the range of 10 to 300 Torr. When the degree of vacuum is 500 Torr or less, volatile matter tends to be less likely to remain, and when the degree of vacuum is 10 Torr or more, industrial implementation is easier.

The treatment time is appropriately selected according to the amount of residual volatile matter, but the shorter the time, the better, in order to suppress the coloring and decomposition of the resulting methacrylic resin.

The polymer recovered through the devolatilization step may be processed into pellets in a step called granulation step.
In the granulation step, the molten resin may be extruded into strands from a perforated die and processed into pellets by a cold cut method, an air hot cut method, an underwater strand cut method, and an underwater cut method.

When a vented extruder is employed as the devolatilization device, the devolatilization step and the granulation step may be combined.

Next, an example of a method for producing a methacrylic resin having a glutarimide structural unit will be described.

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-based 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 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.

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 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 reaction tank.
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 non-intermeshing co-rotating, intermeshing co-rotating, non-intermeshing counter-rotating and intermeshing counter-rotating.

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 that can be reduced 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. At that time, 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. and processed into pellets.
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.

Hereinafter, a method for producing a methacrylic resin containing a lactone ring structural unit (B-2) as the structural unit (B) having a ring structure in the main chain will be described in detail.
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 producing by radical polymerization using a solution polymerization method will be specifically described.

As the method for producing the methacrylic resin having the lactone ring structural unit (B-2) in the main chain in the present embodiment, solution polymerization using a solvent is preferable in terms of promoting the cyclization reaction. Here, the lactone ring structure may be formed by a cyclization reaction after polymerization.
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
During 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;
These may be used alone or in combination of two or more.

The amount of the cyclization condensation catalyst used is not particularly limited. 1 part by mass.
If the amount used is less than 0.01 part by mass, the reaction rate of the cyclization condensation reaction may not be sufficiently improved. Conversely, if the amount of the catalyst used exceeds 3 parts by mass, the resulting polymer may be colored or the polymer may be crosslinked, 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 passing through the cyclization condensation reaction process, the methacrylic resin is melted and extruded into strands from an extruder equipped with a multi-hole die, and processed into pellets by a cold cut method, an air hot cut method, and an underwater cut method. .
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.

The methacrylic resin in the present embodiment preferably has at least one ring 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.

≪Hydrogenation process≫
The method for producing a methacrylic resin in this embodiment includes a hydrogenation step of hydrogenating the methacrylic resin in order to obtain a good color tone in the resin.

In the production of methacrylic resins having a ring structure in the main chain, side reactions in the polymerization process, cyclization process, etc., generate low molecular weight products containing conjugated double bonds, oligomer components, oxidation degradation products, etc. It is thought that the part causes coloring in the methacrylic resin. A polymer with a good color tone can be obtained by decolorizing these coloring-causing substances by a hydrogenation reaction.

In the hydrogenation step of the present embodiment, when a cyclization reaction for forming a ring structure in the main chain is performed after the polymerization step or after polymerization, the polymerization solution after the cyclization reaction is directly provided, or the polymerization solution is diluted. It can be provided after or after concentration, and it can also be provided after re-dissolving the resin obtained after the devolatilization step or after the granulation step in an organic solvent.
From the viewpoint of reducing the heat history in the devolatilization/granulation step, it is preferable to subject the polymerization liquid after the polymerization step to the hydrogenation step as it is, or after dilution or concentration. In addition, since it is thought that a coloring component may be formed when a ring structure is introduced into the main chain of the methacrylic resin, the hydrogenation step is carried out after the polymerization step or the cyclization reaction step related to the introduction of the ring structure. is preferred.

The hydrogenation reaction is carried out in a usual manner by adding a hydrogenation catalyst to a solution of a methacrylic resin, and adding hydrogen gas at normal pressure to 30 MPa, preferably 0.2 to 15 MPa, at 0 to 180 ° C., preferably 20 to It is carried out by acting at 150° C. for 0.1 to 24 hours, preferably 0.2 to 12 hours.

As the hydrogenation catalyst, those used for hydrogenation reactions of ordinary olefinic compounds can be used. As this hydrogenation catalyst, a heterogeneous catalyst and a homogeneous catalyst are known.

Examples of heterogeneous catalysts include solid catalysts in which catalytic substances such as palladium, platinum, nickel, rhodium and ruthenium are supported on carriers such as carbon, silica, alumina and titania.

Homogeneous catalysts include nickel naphthenate-triethylaluminum, nickel acetylacetonate-triethylaluminum, cobalt-n-butyllithium octenoate, titanocene dichloride-diethylaluminum monochloride, cobalt acetate-triethylaluminum, rhodium acetate, chlorotris (Triphenylphosphine)rhodium and the like can be mentioned.

When a heterogeneous catalyst having a particle size of 0.2 μm or more, that is, substantially free of particles having a particle size of less than 0.2 μm is used, the heterogeneous catalyst can be easily removed by filtration. preferable.

From these hydrogenation catalysts and hydrogenation conditions, catalysts and reaction conditions that do not substantially hydrogenate carbonyl groups and phenyl groups in the methacrylic resin may be selected.
Here, not substantially hydrogenating the carbonyl group or phenyl group in the methacrylic resin means that the hydrogenation rate of the carbonyl group or phenyl group before and after the reaction is 5% or less, preferably 1% or less. Say things.
Moreover, when these functional groups are not substantially hydrogenated, the amount of change in the photoelastic coefficient due to the hydrogenation reaction is sufficiently small.
The difference in the photoelastic coefficient due to the presence or absence of the hydrogenation reaction, in other words, the amount of change in the photoelastic coefficient of the methacrylic resin due to the hydrogenation process is preferably 0.3×10 ⁻¹² Pa ⁻¹ or less, and more preferably. is 0.2×10 ⁻¹² Pa ⁻¹ or less, more preferably 0.1×10 ⁻¹² Pa ⁻¹ or less.

In this embodiment, in order not to hydrogenate the carbonyl group and phenyl group in the methacrylic resin, a palladium catalyst, which is a heterogeneous catalyst, is used, and the hydrogen pressure is 0.2 to 5 MPa and the hydrogen pressure is 0.1 to 4 at 20 to 100 ° C. Time reaction is preferred.
The lower limit of the hydrogen pressure is preferably 0.3 MPa or more and 0.4 MPa or more, and the upper limit is preferably 2 MPa or less and 1 MPa or less.
The lower limit of the reaction temperature is preferably 50° C. or higher and 60° C. or higher, and is preferably 90° C. or lower and 80° C. or lower.
The lower limit of the reaction time is preferably 0.2 hours or more and 0.5 hours or more, and is preferably 3 hours or less and 2 hours or less.

The hydrogenation reaction solvent is not particularly limited as long as it has a high solubility for the methacrylic resin, maintains an appropriate viscosity, and does not interfere with the hydrogenation reaction.
Specific reaction solvents include aromatic hydrocarbons such as toluene, xylene, ethylbenzene, and isopropylbenzene; aliphatic hydrocarbons such as n-pentane and hexane; alicyclic hydrocarbons such as cyclohexane and decalin; Ketones such as ketones, butyl cellosolve, methyl ethyl ketone and cyclohexanone; halogenated hydrocarbons such as methylene dichloride and dichloroethane;
These may be used individually by 1 type, or may be used in combination of 2 or more types.

The concentration of the solution in the hydrogenation reaction is not particularly limited as long as it has an appropriate viscosity during the hydrogenation reaction. % is more preferred.

Through such a hydrogenation reaction step, the content of the component having light absorption at a wavelength of 400 nm in the methanol-soluble portion of the methacrylic resin can be easily reduced to 0.5% by mass or less.

After completion of the hydrogenation reaction, the catalyst may be removed by conventional methods such as centrifugation and filtration. The method of centrifugation or filtration is not particularly limited as long as the conditions are such that the used catalyst can be removed. Among them, removal by filtration is preferable because it is simple and efficient.
In the case of filtration, pressure filtration or suction filtration may be used, and from the viewpoint of efficiency, it is preferable to use a filter aid such as diatomaceous earth or perlite. An adsorbent for transition metal atoms derived from the polymerization catalyst may be used as a filter aid.

The method for recovering the methacrylic resin from the hydrogenation reaction solution after the hydrogenation reaction is not particularly limited. After adding the polymerization liquid in the presence of a large amount, treatment with a homogenizer (emulsification dispersion) is performed, and unreacted monomers are subjected to pretreatment such as liquid-liquid extraction and solid-liquid extraction to obtain the polymerization liquid. Alternatively, a method of separating the solvent and unreacted monomers through a step called devolatilization step and recovering the hydrogenated methacrylic resin; and the like.
Here, the devolatilization step refers to a step of removing volatile matter such as solvent, residual monomers and reaction by-products under heating and reduced pressure conditions.

Devices used in the devolatilization process include, for example, a devolatilization device consisting of a tubular heat exchanger and a devolatilization tank; thin film evaporators such as Wyblen and Exeva manufactured by Kobelco Eco-Solutions Co., Ltd., Contra and inclined blade Contra manufactured by Hitachi; A vented extruder with sufficient residence time and surface area to exhibit vaporization performance;
A devolatilization step or the like using a devolatilization device in which two or more of these devices are combined can also be used.

The treatment temperature in the devolatilizer is preferably 150 to 350°C, more preferably 170 to 300°C, still more preferably 200 to 280°C. By setting the temperature to the lower limit temperature or higher, residual volatile matter can be suppressed, and by setting the temperature to the upper limit temperature or lower, coloring and decomposition of the obtained methacrylic resin can be suppressed.

The degree of vacuum in the devolatilizer is preferably in the range of 10-500 Torr, more preferably in the range of 10-300 Torr. By making the degree of vacuum equal to or lower than the upper limit, the residual amount of volatile matter can be suppressed. Moreover, a degree of vacuum equal to or higher than the lower limit is practical for industrial implementation.

The treatment time is appropriately selected according to the amount of residual volatile matter, but the shorter the treatment time, the better, in order to suppress the coloring and decomposition of the obtained methacrylic resin.

The hydrogenated methacrylic resin recovered through the devolatilization step may be processed into pellets in a step called granulation step.
In the granulation step, the molten resin may be extruded into strands from a perforated die and processed into pellets by a cold cut method, an air hot cut method, an underwater strand cut method, and an underwater cut method.

When a vented extruder is employed as the devolatilization device, the devolatilization step and the granulation step may be combined.

(Methacrylic resin composition)
The methacrylic resin composition of the present embodiment may contain a methacrylic resin composition containing the methacrylic resin of the present embodiment described above. The methacrylic resin composition may optionally contain additives in addition to the methacrylic resin of the present embodiment described above, and may also contain thermoplastic resins other than methacrylic resins, rubbery polymers etc. may be included.

-Additive-
The methacrylic resin composition according to this embodiment may contain various additives as long as the effects of the present invention are not significantly impaired.
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 according to this 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. The methacrylic resin 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. 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, such as a phosphorus antioxidant and a sulfur antioxidant. It is preferable to use together at least one selected from the antioxidants and a hindered phenol-based antioxidant.
These antioxidants may be used singly or in combination of two or more.

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-xyline)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 phenol-based antioxidant as the antioxidant may be a commercially available phenol-based antioxidant, and such a commercially available phenol-based antioxidant is 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-based 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.

Further, 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] (ADEKA STAB 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 parts by mass of the system resin, it is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, still more preferably 1 part by mass or less, even more preferably 0.8 parts by mass or less. It is preferably 0.01 to 0.8 parts by mass, particularly preferably 0.01 to 0.5 parts 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-1,6 - polycondensation product of 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 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 reactant, bis(1-undecanoxy-2,2,6,6-tetramethylpiperidin-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-(2 , 2,6,6-tetramethyl-4-piperidyl)butylamine polycondensate, 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 reactant , 2,2,6,6-tetramethyl-4-piperidiol and β,β,β',β'-tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane-3,9 - the diethanol reactant is preferred.

The content of the hindered amine photostabilizer may be any amount as long as the effect of improving photostability can be obtained, and if the content is excessive, problems such as bleeding out during processing may occur. , with respect to 100 parts by mass of the methacrylic resin, it is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, still more preferably 1 part by mass or less, still more preferably 0.8 parts by mass or less, More preferably 0.01 to 0.8 parts by mass, particularly preferably 0.01 to 0.5 parts 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-octyloxyphenyl)-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-methoxycarbonylpropyloxy phenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-3-methyl-4-ethoxycarbonylethyloxyphenyl)-1,3,5-triazine, 2,4,6- and tris(2-hydroxy-3-methyl-4-(1-(2-ethoxyhexyloxy)-1-oxopropan-2-yloxy)phenyl)-1,3,5-triazine.
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 molding processability, and is an amount that exhibits the effects of the present invention. It is preferably 0.1 to 5 parts by mass, preferably 0.2 to 4 parts by mass or less, more preferably 0.25 to 3 parts by mass, and even more preferably 0.3 to 3 parts 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 ester-based lubricants include cetyl palmitate, butyl stearate, stearyl stearate, stearyl citrate, glycerin monocaprylate, glycerin monocaprate, glycerin monolaurate, glycerin monopalmitate, glycerin dipalmi. Tate, 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 citric acid fatty acid ester, pentaerythritol adipate stearate, montanic acid partially saponified ester, pentaerythritol tetrastearate, dipenta Erythritol hexastearate, sorbitan tristearate and the like can be mentioned.
These fatty acid ester-based lubricants 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 amide-based lubricants are also not particularly limited, and conventionally known ones can be used.
Examples of fatty acid amide lubricants 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. fatty acid amides; 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 Methylolamides such as stearamide and methylolbehenamide; Bishydroxystearic acid amide, ethylenebisbehenic acid amide, hexamethylenebisstearic acid amide, hexamethylenebisbehenic acid amide, hexamethylenebishydroxystearic acid amide, N,N'-distearyladipic acid amide, N,N'- Saturated fatty acid bisamides such as distearylsebacamide; unsaturated fatty acids such as ethylenebisoleic acid amide, hexamethylenebisoleic acid amide, N,N'-dioleyladipate, and N,N'-dioleylsebacic acid amide Bisamides; aromatic bisamides such as m-xylylenebisstearic acid amide and N,N'-distearyl isophthalic acid amide.
These fatty acid amide release agents can be used singly or in combination of two or more.
Examples of commercially available products include 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, and 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 release agent may be any amount as long as it is effective as a release agent. If the content is excessive, problems such as bleeding out during processing and extrusion failure due to screw slippage will occur. Therefore, it is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, still more preferably 1 part by mass or less, and still more preferably 0.8 parts by mass with respect to 100 parts by mass of the methacrylic resin. parts by mass or less, more preferably 0.01 to 0.8 parts by mass, particularly preferably 0.01 to 0.5 parts by mass. When added in an amount within the above range, a decrease in transparency due to the addition of a mold release agent is suppressed, and mold release failure during injection molding and sticking to metal rolls during sheet molding tend to be suppressed. preferable.

- Other thermoplastic resins -
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 mentioned above enhances the impact strength, optical properties, etc. of the molded article obtained from the composition of the present embodiment. From the point of view, 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 parts by mass, more preferably 0 to 25 parts by mass, based on 100 parts by mass of the methacrylic resin.

(Method for producing methacrylic resin composition)
Examples of the method for producing the methacrylic resin composition include a method of kneading using a kneader such as an extruder, a heating roll, a kneader, a roller mixer, or a Banbury mixer. 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.
The glass transition temperature (Tg), weight average molecular weight (Mw), number average molecular weight (Mn), orientation birefringence, and photoelastic coefficient _CR of the methacrylic resin composition are the same as those described above for the methacrylic resin. you can

(Molded body)
The molded article of the present embodiment may contain the methacrylic resin of the present embodiment, or may contain the methacrylic resin composition of the present embodiment.

(Manufacturing method of compact)
Various molding methods such as extrusion molding, injection molding, compression molding, calender molding, inflation molding, and blow molding can be used as the method for producing the molded article of the present embodiment. Among them, it is preferable to apply injection molding and injection compression molding from the viewpoint of productivity.
In general, the injection molding method consists of (1) an injection process in which the resin is melted and filled into the temperature-controlled cavity of the mold, and (2) pressure is applied to the cavity until the gate is sealed, and the injection process fills the cavity. (3) A cooling process in which the molded product is held until the resin is cooled after releasing the holding pressure, ( 4) It consists of opening the mold and removing the cooled part.

At this time, the molding temperature is in the range of Tg+100° C. to Tg+160° C., preferably in the range of Tg+110° C. to Tg+150° C., based on the glass transition temperature of the methacrylic resin composition. Here, the molding temperature refers to the controlled temperature of the band heater wound around the injection nozzle.
The mold temperature is in the range of Tg-70°C to Tg, preferably in the range of Tg-50°C to Tg-20°C, based on the glass transition temperature (Tg) of the methacrylic resin composition. preferable.

Also, the injection speed can be appropriately selected depending on the thickness and dimensions of the injection-molded article to be obtained, and can be appropriately selected, for example, from the range of 200 to 1000 mm/sec.
Further, the pressure for holding pressure can be appropriately selected depending on the shape of the injection molded article to be obtained, and can be appropriately selected within the range of, for example, 30 to 120 MPa. In the case of a thin-walled compact that solidifies quickly, there are cases where no holding pressure is applied.
Here, the pressure for holding pressure is the pressure maintained by the screw for further sending out the molten resin from the gate after the molten resin is filled.

Injection compression molding involves opening the mold slightly at the start of injection molding and filling the mold with molten resin at high speed and low pressure. It is an injection molding method in which a compression and holding pressure step is added, and it is possible to mold a molded product with excellent surface characteristics and optical characteristics.
When it is desired to obtain a thinner injection-molded article, for example, a thickness of less than 1 mm and a diagonal dimension of more than 100 mm, injection compression molding is employed to obtain a molded article having excellent optical characteristics and color tone. It is particularly preferred because it can be obtained.

In addition, when the injection-molded article obtained using the methacrylic resin composition of the present embodiment is used as a light guide plate, the article may have fine irregularities formed on its surface. By providing such fine unevenness, it is preferable that there is no need to separately provide a reflective layer by printing or the like. Fine unevenness is not particularly limited, but unevenness with clear structural units such as cuboids, cylinders, elliptical cylinders, triangular prisms, spherical surfaces, and aspherical surfaces, and uneven shapes such as satin and hairline shapes, Concavities and convexities whose structural units are unclear or a combination thereof, and concavities and convexities whose structural units are clear but whose shapes, particularly sizes, are varied. As for the shape of the unevenness, the height of the shape or the concave portion is 0.1 to 500 μm, and the pitch distance between the unevenness is 10 to 1000 μm.

Surface functions such as hard coat treatment, anti-glare treatment, anti-reflection treatment, transparent conductive treatment, electromagnetic wave shielding treatment, gas barrier treatment, etc. are applied to the surface of various molded products using the methacrylic resin of the present embodiment and its resin composition. Further processing can be performed.
Although the thickness of these functional layers is not particularly limited, it is usually used in the range of 0.01 to 10 μm.

When hard coating is applied to the surface of the molded product, examples of the hard coating layer to be applied to the surface include silicone-based curable resins, organic polymer composite inorganic fine particle-containing curable resins, urethane acrylates, epoxy acrylates, polyfunctional acrylates, and the like. A coating solution obtained by dissolving or dispersing the acrylate and the photopolymerization initiator in an organic solvent is applied to the film or sheet obtained from the methacrylic resin composition of the present embodiment by a conventionally known coating method, and dried. It is formed by applying and photocuring.
In addition, before applying the hard coat layer, in order to improve the adhesiveness, for example, a method of forming the hard coat layer after providing an easy adhesion layer, a primer layer, an anchor layer, etc. containing inorganic fine particles in its composition in advance. can also be used.
The antiglare layer to be applied to the surface is formed by making ink from fine particles of silica, melamine resin, acrylic resin, etc., applying the ink onto other functional layers 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.

(Application of compact)
A molded article made of the methacrylic resin composition of the present invention can be suitably used for applications such as optical parts in household goods, OA equipment, AV equipment, battery electrical components, lighting equipment, automobile parts, and the like.
Optical components in household goods, OA equipment, AV equipment, battery electrical components, lighting equipment, etc. include, for example, smartphones, PDAs, tablet PCs, light guide plates used in displays such as liquid crystal televisions, display front panels, touch panels, and more. Lenses for smartphones, 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, optical fiber coating materials , lenses, Fresnel lenses, phase plates with microlens arrays, optical cover components, and the like.
Optical parts for automobile 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. be done.
In addition to the above, it can also be used as parts for digital signage display devices that transmit information to thin displays connected to networks for the purpose of publicity, advertising, etc., in places such as camera focusing screens, outdoors, stores, public institutions, and transportation facilities. It can be preferably used.

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.

<1. Measurement of polymerization conversion>
A part of the polymerization liquid in Examples and Comparative Examples was collected, and the amount of monomer remaining in this polymerization liquid sample was dissolved in chloroform to prepare a 5% by mass solution, and n was used as an internal standard substance. -Add decane and measure the concentration of monomers remaining in the sample using gas chromatography (GC-2010 manufactured by Shimadzu Corporation), and determine the total mass (a) of the monomers remaining in the polymerization solution. asked. Then, from this total mass (a) and the total mass (b) when it is assumed that the total amount of the added monomers remained in the polymerization solution by the time the sample was collected, the calculation formula (ba)/ The polymerization conversion rate (%) was calculated from b×100.

<2. Analysis of Structural Units>
Unless otherwise specified in each example described later, by ¹ H-NMR measurement and ¹³ C-NMR measurement, the structural unit of the produced methacrylic resin was identified and its abundance was calculated. The measurement conditions for ¹ H-NMR measurement and ¹³ C-NMR measurement are as follows.
・Measuring equipment: JNM-ECZ400S manufactured by JEOL Ltd.
・Measurement solvent: CDCl ₃ or DMSO-d ₆
When the ring structure of the methacrylic resin is a lactone ring structure, it was confirmed by the methods described in JP-A-2001-151814 and JP-A-2007-297620.

<3. Measurement of molecular weight and molecular weight distribution>
The weight-average molecular weight (Mw) and number-average molecular weight (Mn) 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, 0.1 g/L of 2,6-di-t-butyl-4-methylphenol (BHT) was added as an internal standard.
Detector: RI (differential refraction) detector, detection sensitivity: 3.0 mV/min Sample: 0.02 g of methacrylic resin or tetrahydrofuran solution of methacrylic resin in 20 mL. Injection volume: 10 μL
Standard sample for calibration curve: The following 10 types of polymethyl methacrylate (manufactured by Polymer Laboratories; PMMACalibration 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.
The weight average molecular weight (Mw) and number average molecular weight (Mn) of the methacrylic resin were obtained based on the calibration curve obtained by measuring the standard sample for calibration curve.

<4. 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 (primary temperature rise) 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 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.

<5. Measurement of photoelastic coefficient _CR >
The methacrylic resins obtained in Production Examples, Examples, and Comparative Examples were formed into press films using a vacuum compression molding machine to obtain samples for measurement.
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 cured for 24 hours or longer 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 the test piece for measurement prepared above and a birefringence measuring apparatus described in detail in Polymer Engineering and Science 1999, 39, 2349-2357.
A 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 optical path of the device was positioned at the center of the film. The birefringence of the test piece was measured at a wavelength of 550 nm while applying .
From the relationship between the birefringence (Δn) and the tensile stress (σ _R ) obtained from the measurement, the slope of the straight line was determined by least squares approximation, and the photoelastic coefficient (C _R ) (Pa ⁻¹ ) was calculated. For the calculation, the data when the tensile stress is between 2.5 MPa≦σ _R ≦10 MPa was used.
C _R =Δn/σ _R
Here, the 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)

<6. Measurement of the amount of methanol-soluble matter and the amount of methanol-insoluble matter>
After dissolving 5 g of the methacrylic resin obtained in Examples and Comparative Examples in 100 mL of chloroform, the solution was placed in a dropping funnel and added dropwise over about 1 hour to 1 L of methanol being stirred using a stirrer. and reprecipitated. After dropping the entire amount, the mixture was allowed to stand still for 1 hour, and suction filtration was performed using a membrane filter (T05A090C manufactured by Advantech Toyo Co., Ltd.) as a filter.
The filtrate was vacuum-dried at 60° C. for 16 hours to obtain a methanol-insoluble matter. In addition, the filtrate was removed using a rotary evaporator at a bath temperature of 40° C., and the degree of vacuum was gradually lowered from the initial setting of 390 Torr to a final 30 Torr to remove the solvent. The soluble matter was collected and used as the methanol soluble matter.
The mass of methanol-insoluble matter and the mass of methanol-soluble matter are each weighed, and the ratio (mass %) (methanol soluble fraction) was calculated.

<7. Contents of Components Absorbing at a Wavelength of 400 nm, Components with a Molecular Weight of 2000 or Less, and N-Phenylmaleimide Monomers in the Methanol-soluble Content>
(7-1) Calculation of Content of Component Absorbing at Wavelength of 400 nm The methanol-soluble matter obtained by the above reprecipitation was used as a THF solution having a concentration of 0.030 g/mL.
This methanol soluble matter solution was subjected to gel permeation chromatography (GPC) measurement according to the method described in "3. Measurement of molecular weight and molecular weight distribution". However, as a detector, in addition to the RI detector, a UV detector (manufactured by Tosoh Corporation, UV-8020, a light source of a tungsten lamp and a wavelength of 400 nm) was also used.
Specifically, first, by GPC measurement using a UV detector (wavelength 400 nm), the molecular weight distribution of the methanol-soluble matter was measured, and the total peak area was obtained. Separately, GPC measurement using a UV detector (wavelength 400 nm) was also performed for the N-phenylmaleimide monomer to prepare a calibration curve between sample concentration and peak area. Using this calibration curve, the amount of the component having an absorbance at 400 nm in the methanol-soluble matter was determined as the amount in terms of N-phenylmaleimide. From the mass ratio of the converted amount to the methanol-soluble matter, the content of the component having light absorption at a wavelength of 400 nm in the methanol-soluble matter (mass% in terms of N-phenylmaleimide) was determined.
(7-2) Calculation of the content of components with a molecular weight of 2000 or less The above reprecipitated soluble matter is a THF solution with a concentration of 0.030 g / mL, and according to "3. Measurement of molecular weight and molecular weight distribution", RI as a detector GPC measurements were performed using a detector.
Using the separately measured peak elution time of standard PMMA with a weight peak molecular weight of 2000, the elution area with a molecular weight of 2000 or less is calculated from the measurement results of the RI detector, and from the ratio to the total peak area, the molecular weight contained in the methanol soluble The content (% by mass) of the components of 2000 or less was calculated.
(7-3) Calculation of content of N-phenylmaleimide monomer The content (% by mass) of the N-phenylmaleimide monomer in the methanol-soluble matter was also <1. Measurement of polymerization conversion rate> was calculated by measurement using gas chromatography according to the method described in section.

<8. Measurement of color tone of molded piece>
(8-1) Measurement of YI and total light transmittance at an optical path length of 3 mm The methacrylic resins obtained in the examples and comparative examples described below were molded by an injection molding machine (AUTO SHOT C Series MODEL 15A, manufactured by FANUC Co., Ltd.). A rectangular test piece having a thickness of 3 mm, a width of 12 mm, and a length of 124 mm was produced under conditions of a molding temperature of 250°C and a mold temperature of 90°C.
Using a spectral colorimeter (SD-5000, manufactured by Nippon Denshoku Industries Co., Ltd.), the obtained molded piece is sandwiched so that the light source passes in the thickness direction of the molded piece, and a D65 light source 10 ° YI with an optical path length of 3 mm. (in accordance with JIS K7373) and total light transmittance (in accordance with JIS K7361-1) (%) were measured. Three measurements were made and the average value was used.
(8-2) Measurement of YI at an optical path length of 80 mm The methacrylic resins obtained in Examples and Comparative Examples described below are molded using an injection molding machine (AUTO SHOT C Series MODEL 15A, manufactured by FANUC Co., Ltd.). A strip-shaped test piece having a thickness of 4 mm, a width of 10 mm, and a length of 80 mm was produced under conditions of 250° C. and a mold temperature of 90° C.
The mold was mirror-finished. The mold has slide cores that open in the direction of the long side, and adopts a structure with no draft angle.
A test piece was obtained in which the color tone could be measured with transmitted light having an optical path length of 80 mm in the long side direction, with the two mirror-finished end faces perpendicular to the long side direction as the entrance and exit surfaces.
Using a color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd., ASA-1), the obtained test piece was measured for YI at a C light source of 2° and an optical path length of 80 mm.

[material]
Raw materials used in Production Examples and Production Comparative Examples to be described later are shown below.
[[monomer]]
・Methyl methacrylate: manufactured by Asahi Kasei Corporation ・N-Phenylmaleimide (phMI): manufactured by Nippon Shokubai Co., Ltd. ・N-Cyclohexylmaleimide (chMI): manufactured by Nippon Shokubai Co., Ltd. [[polymerization initiator]]
・ 1,1-di (t-butylperoxy) cyclohexane: "Perhexa C" manufactured by NOF Corporation
[[chain transfer agent]]
・ n-octyl mercaptan: manufactured by Kao Corporation [[Antioxidant]]
・ Pentaerythritol = tetrakis [3-(3',5'-di-tert-butyl-4'-hydroxyphenyl) propionate]: BASF "Irganox1010"
- Tris (2,4-di-t-butylphenyl) phosphite: "Irgafos168" manufactured by BASF

[Manufacturing example]
340.7 kg of methyl methacrylate (hereinafter referred to as MMA), 39.6 kg of N-phenylmaleimide (hereinafter referred to as phMI), 59.7 kg of N-cyclohexylmaleimide (hereinafter referred to as chMI), and n-octyl mercaptan as a chain transfer agent. 0.275 kg and 236.9 kg of meta-xylene (hereinafter referred to as mXy) were weighed and added to a 1.25 m ³ reactor equipped with a jacket temperature control device and stirring blades 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 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.
After 3 hours, 4 hours, and 8 hours (at the end of polymerization) from the start of polymerization, the polymer solution was sampled, and the polymerization conversion rate was analyzed from the concentration of the remaining monomers. MMA 87.7%, phMI 84.6%, chMI 74.7%, 4 hours later MMA 92.9%, phMI 90.3%, chMI 84.1%, 8 hours later MMA 92.2%, phMI 99.4%, chMI 98.9%. was 3%.
Further, the methacrylic resin obtained after the polymerization was treated in the same manner as in Comparative Example 1 described later, and the photoelastic coefficient C _R thereof was measured to be −0.11×10 ⁻¹² Pa ^−1. .

[Example 1]
160 kg of the polymer solution obtained in the production example was transferred to another 1.25 m ³ reactor and diluted with an additional 533 kg of meta-xylene. After adding 4.3 kg of 5% Pd carbon powder (dry product) manufactured by NE Chemcat to this, the inside of the reactor was pressurized to 0.5 MPa with hydrogen, and the pressure was lowered twice to perform hydrogen substitution. Then, after pressurizing the inside of the reactor to 0.4 MPa with hydrogen, the solution temperature was raised to 70° C. and a hydrogenation reaction was carried out for 2 hours. After that, the temperature was quickly lowered to 40° C., the inside of the reactor was replaced with nitrogen, and the catalyst was removed by filtering the solution through a membrane filter with a filtration accuracy of 0.2 μm.
Next, devolatilization was performed by introducing the obtained 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 then pelletized to obtain a hydrogenated methacrylic resin.
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 148,000 and Mw/Mn was 2.28. Other physical properties are shown in Table 1.

[Comparative Example 1]
Volatilization was performed by introducing the polymer solution obtained in the Production Example 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.
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 1.

As shown in Table 1, the methacrylic resin of the present embodiment has a low YI in the long optical path of the molded product obtained, and has excellent color tone and high transmittance. Also, it can be suitably used for automobile parts such as tail lamps, meter covers, and head lamps.

The methacrylic resin of the present invention has high heat resistance, highly controlled birefringence, and excellent color tone and transparency.
The methacrylic resin of the present invention is used as an optical material, for example, in displays such as liquid crystal displays, plasma displays, organic EL displays, field emission displays, rear projection televisions, light guide plates, diffusion plates, and polarizing plate protective films; Retardation plates such as /4 wavelength plates and 1/2 wavelength plates; Liquid crystal optical compensation films such as viewing angle control films; Display front panels; Display substrates; Lenses; Substrates; waveguides, lenses, lens arrays, optical fibers, optical fiber coating materials in the fields of optical communication systems, optical exchange systems, optical measurement systems, or optical products such as head-mounted displays and liquid crystal projectors; LED lenses; lens covers etc., household goods, OA equipment, AV equipment, battery electrical equipment, lighting equipment; tail lamps, meter covers, head lamps, light guide bars, automotive parts such as lenses; housing applications; It can be used preferably.

Claims (5)

Including a hydrogenation step of hydrogenating the methacrylic resin,
A method for producing a methacrylic resin having a ring structure in its main chain, having a glass transition temperature of more than 120° C. and not more than 160° C. and a photoelastic coefficient of −3×10 ⁻¹² to +3×10 ⁻¹² Pa ⁻¹ . 2. The method for producing a methacrylic resin according to claim 1, wherein the amount of change in photoelastic coefficient of said methacrylic resin due to said hydrogenation step is 0.30×10 ⁻¹² Pa ⁻¹ or less. 3. The method for producing a methacrylic resin according to claim 1, wherein the hydrogenation catalyst used in the hydrogenation step is a heterogeneous catalyst. 4. The method for producing a methacrylic resin according to claim 3, wherein said heterogeneous catalyst is a palladium catalyst. The method for producing a methacrylic resin according to any one of claims 1 to 4, wherein in the hydrogenation step, the hydrogen pressure is 0.2 to 5 MPa and the reaction is performed at 20 to 100°C for 0.1 to 4 hours.