JP7332678B2 - Method for producing (meth)acrylic polymer coagulate and molded article - Google Patents

Description

The present invention relates to a method for producing a (meth)acrylic polymer coagulate having excellent resistance to hot water whitening from a polymer latex obtained by emulsion polymerization. It relates to a method for producing a (meth)acrylic polymer coagulate. The present invention also relates to a molded article of the (meth)acrylic polymer solidified product obtained by the above-described production method.

Acrylic multi-layer structure polymer particles have been conventionally referred to as core-shell type polymers, and have a layer made of a crosslinked elastic body inside and a layer made of a thermoplastic resin component as the outermost layer. It is known that it is used for modifying thermoplastic resins such as acrylic resins, and is particularly useful as a modifier for imparting impact resistance. However, the addition of multi-layer structure polymer particles improves the impact resistance, but lowers the heat resistance, lowers the surface hardness, bend whitening, hot water whitening, etc., and further improvement is desired.

In particular, in building material applications, whitening due to hot water impairs the appearance peculiar to acrylic resins, so improvement is desired.

As a method for improving hot water whitening resistance, a method of reducing the content of water-soluble substances to 200 ppm or less (Patent Document 1) and a method of reducing the residual amount of cations derived from the coagulant to 180 ppm or less (Patent Document 2) ) are being considered. However, the expected effect is not obtained for hot water of 100°C.

In order to facilitate the removal of water-soluble substances during dehydration and to reduce troubles in the production process, studies have been conducted to increase the bulk density of the coagulate and reduce fine particles. As a method for obtaining a coagulate with high bulk density and few fine particles, there is a method of adjusting the pH of the emulsion polymerization latex (Patent Document 3), and a nonionic water-soluble A method of spraying or dripping an emulsion polymerized latex containing a polymer thickener (Patent Document 4) has been studied.

JP 2003-277528 Patent No. 4080076 JP 2017-61646 JP 2017-61645

An object of the present invention is to ameliorate the effect of whitening of an emulsion polymerized resin due to hot water.

As a result of repeated studies to achieve the above object, the present invention including the following aspects has been completed.
[1]
Steps 1 to 3 below
Step 1: A latex (B) containing (meth)acrylic multilayer structure particles (A) obtained by an emulsion polymerization method and an aqueous coagulant solution are continuously supplied to a coagulation tank (1) and mixed. ) a salting-out step of obtaining a salting-out slurry containing soft aggregates of the acrylic multilayer structure particles (A);
Step 2: A granulation step in which the salting-out slurry obtained in step 1 and washing water are supplied to the flocculation tank (2) and hard flocculated at an internal liquid temperature higher than that of the flocculation tank (1) (here, the washing Water is supplied so that the solid content concentration in the coagulation tank (2) is less than 2/3 of the solid content concentration in the coagulation tank (1));
Step 3: Step of washing, dehydrating and drying the aggregates of the (meth)acrylic multilayer structure particles (A) obtained in Step 2;
A method for producing a (meth)acrylic polymer coagulum.
[2]
The production method according to [1], wherein the internal liquid of the coagulation tank (2) has a solid content concentration of less than 10% by mass.
[3]
The production method according to [1] or [2], wherein the (meth)acrylic multilayer structure particles (A) are particles having a three-layer structure consisting of an innermost layer c, an intermediate layer i, and an outermost layer o.
[4]
(Meth)acrylic multilayer structure particles (A), innermost layer composed of hard polymer c having 50 to 100% by mass of methacrylate units, 40 to 99.9% by mass of acrylate units, and polyfunctional an intermediate layer composed of a soft polymer i having a monomer unit content of 0.1 to 5% by mass and a glass transition temperature of less than 25° C., and a methacrylic acid ester unit content of 80 to 100% by mass, and The production method according to [3], wherein the outermost layer has a three-layer structure composed of a hard polymer o having a glass transition temperature of 80° C. or higher.
[5]
[3] or [4], wherein the temperature of the liquid inside the aggregation tank (2) is lower than the glass transition temperature of the outermost layer o of the (meth)acrylic multilayer structure particles (A) + 10°C. manufacturing method.
[6]
The production method according to any one of [1] to [5], wherein the coagulant is at least one selected from the group consisting of magnesium sulfate, calcium chloride, aluminum sulfate and calcium acetate.
[7]
The production method according to any one of [1] to [6], wherein the amount of (meth)acrylic polymer aggregates having a particle size of 20 μm or less in the aggregation tank (1) is 1 to 7% by mass.
[8]
The (meth)acrylic polymer coagulate obtained by the method according to any one of [1] to [7] is formed into a plate-shaped molded article having a thickness of 1 mm, and the plate-shaped molded article is placed in hot water at 98° C. for 4 hours. A molded product of (meth)acrylic multilayer structure particles (A) which is immersed and has a haze difference (ΔH) of less than 1.0% before and after immersion.

In the production method of the present invention, the solid content concentration in the salting-out slurry obtained in step 1 is relatively high, and the temperature of the coagulation tank (1) is lower than the temperature of the coagulation tank (2). The system multilayer structure particles (A) are flocculated with a weak cohesive force, and incorporation of impurities other than the particles (eg, emulsifier, polymerization initiator residue, coagulant, etc.) into the flocculated material is suppressed. On the other hand, in step 2, the salting-out slurry is diluted with washing water to reduce the solid content concentration, and the temperature of the liquid inside the flocculation tank (2) is raised above that of the flocculation tank (1), thereby ) to agglomerate the particles more strongly (hard agglomeration). At this time, since the concentration of impurities is lowered, the amount of impurities taken into hard agglomerates (granules) is suppressed, and as a result, hot water whitening is suppressed.

By a two-step aggregation process consisting of soft aggregation of the (meth)acrylic multilayer structure particles (A) in the aggregation tank (1) and hard aggregation of the (meth)acrylic multilayer structure particles (A) in the aggregation tank (2) The resulting coagulum and molded articles obtained by molding the coagulate are excellent in resistance to hot water whitening, and are particularly suitable for use as building materials.

In this specification, the liquid in the aggregation tank (1) contains latex (B), a coagulant, and water, which are mixed in the aggregation tank (1) to form (meth)acrylic multilayer structure particles ( Soft agglomerates of A) are deposited to form a salting-out slurry. This salting-out slurry is sent to a flocculation tank (2), where soft agglomerates are fused together to obtain hard agglomerates (granules or coagulates).

The aggregation tank (1) and the aggregation tank (2) are connected in series, and the salting-out slurry containing the aggregates of the (meth)acrylic multilayer structure particles (A) is transferred from the aggregation tank (1) to the aggregation tank (2). is supplied. In a preferred embodiment of the present invention, the coagulation tank (1) and the coagulation tank (2) are each equipped with a mixing device so that the internal liquid can be stirred. Mixing devices include, for example, stirring blades and those provided with stirring blades. Although not wishing to be bound by theory, in the aggregation tank (1), precipitation of aggregates of the (meth)acrylic multilayer structure particles (A) occurs due to the high coagulant concentration and high solid content concentration. It is believed by the inventors that rapidly, the salted-out slurry forms a large number of small-sized agglomerates, and that the small particles are loosely bound together to form large-sized particles with a low bulk density. It is desirable that the liquid temperature inside the coagulation tank (1) is lower than the Tg (glass transition temperature) of the outermost layer of the particles (A). ) will flocculate. On the other hand, in the coagulation tank (2), the temperature of the internal liquid is higher than that in the coagulation tank (1), particularly higher than the Tg of the outermost layer of the particles (A), By reducing the concentration of impurities such as residues, it is possible to fuse the flocculated substances while suppressing the incorporation of impurities, thereby obtaining a hard agglomerated coagulated substance with a small amount of impurities.

The method for producing a (meth)acrylic polymer coagulate of the present invention includes the following steps 1 to 3.
Step 1: A latex (B) containing (meth)acrylic multilayer structure particles (A) obtained by an emulsion polymerization method and an aqueous coagulant solution are continuously supplied to a coagulation tank (1) and mixed. ) a salting-out step of obtaining a salting-out slurry containing soft aggregates of the acrylic multilayer structure particles (A);
Step 2: A granulation step in which the salting-out slurry obtained in step 1 and washing water are supplied to the flocculation tank (2) and hard flocculated at an internal liquid temperature higher than that of the flocculation tank (1) (here, the washing Water is supplied so that the solid content concentration in the coagulation tank (2) is less than 2/3 of the solid content concentration in the coagulation tank (1));
Step 3: A step of washing, dehydrating and drying the aggregates of the (meth)acrylic multilayer structure particles (A) obtained in Step 2.

In step 1, a salting-out slurry containing soft aggregates of (meth)acrylic multilayer structure particles (A) is obtained. The coagulant destroys the electric double layer formed on the surface of the latex particles by the emulsifier to form aggregates. The concentration of the coagulation liquid in the coagulation tank (1) is high, and a large number of aggregates with small particle diameters are generated. In addition, the amount of impurities incorporated in the flocculated material of the (meth)acrylic multilayer structure particles (A) is suppressed, which is one of the reasons for improving the resistance to hot water whitening.

In step 2, the salting-out slurry is diluted with washing water, and the concentration of components other than particles (A), such as emulsifiers, polymerization initiator residues, and coagulants, decreases. In particular, the amount of impurities taken into the solidified product during hard aggregation caused by the inner liquid temperature above the Tg of the outermost layer of the particles (A) is suppressed. In the production method of the present invention, a combination of flocculation due to the low internal liquid temperature and high coagulant concentration in step 1 and hard aggregation due to the high internal liquid temperature and low impurity concentration in step 2 produces a (meth)acrylic polymer solidified product. can effectively suppress the incorporation of impurities into Since this impurity causes hot water whitening, as a result, the present invention can greatly improve the hot water whitening resistance of the coagulum.

In the flocculation tank (2), the washing water and the salting-out slurry are mixed, thereby lowering the solid content concentration and the coagulant concentration. Specifically, the solid content concentration of the liquid inside the flocculation tank (2) is less than 2/3 of the solid content concentration of the flocculation tank (1), preferably 7/11 or less, 5/8 or less, or 3/5 or less. , 7/12 or less, 6/11 or less, or 1/2 or less.

Washing and dehydration in step 3 can remove water-soluble components such as coagulants, emulsifiers and polymerization initiator residues. Washing and dehydration can be performed, for example, using a filter press, a belt press, a Guina centrifuge, a screw decanter centrifuge, or the like. From the viewpoint of productivity and washing efficiency, it is preferable to use a screw decanter centrifuge. It is preferable to wash and dehydrate the granules at least twice. As the number of times of washing and dehydration increases, the amount of remaining water-soluble components decreases. However, from the viewpoint of productivity, the number of times of washing and dehydration is preferably 3 or less.

The granules obtained in step 2 are washed and dried after dehydration so that the water content is preferably less than 0.2% by mass, more preferably less than 0.1% by mass. The higher the moisture content, the more the multi-layered acrylic polymer undergoes an ester hydrolysis reaction during melt extrusion molding, which tends to generate a carboxyl group in the molecular chain.

The coagulant used in step 1 includes an inorganic acid or its salt, or an organic acid or its salt that has the property of being able to coagulate and coagulate the latex (B). In step 1, an aqueous solution of these coagulants is used. be done. Examples of specific inorganic acids, inorganic acid salts, organic acids or organic acid salts include sodium chloride, potassium chloride, lithium chloride, sodium bromide, potassium bromide, lithium bromide, potassium iodide, iodide Alkali metal halides such as sodium; Alkali metal sulfates such as potassium sulfate and sodium sulfate; Ammonium sulfate; Ammonium chloride; Alkali metal nitrates such as sodium nitrate and potassium nitrate; , copper sulfate, barium chloride, ferrous chloride, ferric chloride, magnesium chloride, ferric sulfate, aluminum sulfate, potassium alum, iron alum, etc. These coagulants may be used alone or in combination of two or more. used as Among these, aqueous solutions of salts of monovalent or divalent inorganic acids such as sodium chloride, potassium chloride, sodium sulfate, ammonium chloride, calcium chloride, magnesium chloride, magnesium sulfate, barium chloride, and calcium acetate can be suitably used, Magnesium sulfate, calcium chloride, aluminum sulfate, and calcium acetate are more preferred. The concentration of the aqueous coagulant solution supplied to the aggregation tank (1) is preferably 5-20 mass %, more preferably 10-15 mass %. The concentration of the coagulant in the mixture containing the latex (B) and the coagulant in the coagulation tank (1) is preferably 0.2 to 5.0% by mass, more preferably 0.3 to 2.0% by mass. .

The solid content concentration of the latex (B) supplied to the coagulation tank (1) is preferably 10-60% by mass, more preferably 30-50% by mass.

A desired amount of water is added so that the liquid inside the coagulation tank (1) for supplying the latex (B) and the aqueous coagulant solution preferably has a solid content concentration of 5 to 30% by mass, more preferably 7 to 20% by mass. to add.

In a preferred embodiment of the present invention, the mixture (inner liquid) containing the latex (B) and coagulant in the coagulation tank (1) is stirred by a mixing device equipped with stirring blades, stirring blades and the like.

The temperature of the liquid inside the coagulation tank (1) is preferably 70 to 100°C, more preferably 75 to 95°C, still more preferably 75 to 85°C. The temperature of the liquid inside the aggregation tank (1) is preferably lower than the Tg of the outermost layer of the particles (A).

The average particle size of the aggregates of the (meth)acrylic multilayer structure particles (A) in the salting-out slurry in the aggregation tank (1) is preferably 10 to 400 μm, more preferably 50 to 300 μm, and the bulk specific gravity is , preferably 0.1 to 0.6 g/cm ³ , more preferably 0.2 to 0.4 g/cm ³ .

The residence time of the mixture in the coagulation tank (1) is not particularly limited, but is preferably 0.3 to 2 hours, more preferably 0.5 to 1.5 hours.

In the cumulative particle size distribution of the aggregates of the (meth)acrylic multilayer structure particles (A) in the salting-out slurry in the aggregation tank (1), D ₂₀ (20 μm or less) is preferably 1 to 7%, D ₅₀ (50 μm or less) is preferably 1.5 to 20%.

The solid content concentration in the mixture (internal liquid) in the aggregation tank (2) is preferably 3 to 20% by mass, more preferably 4.5 to 13.5% by mass.

In a preferred embodiment of the present invention, the mixture of the slurry in the flocculation tank (2) and the washing water is agitated by a stirring blade or a mixing device equipped with a stirring blade.

The temperature of the liquid inside the coagulation tank (2) is preferably 80-110°C, more preferably 85-100°C, still more preferably 90-98°C. The liquid temperature in the coagulation tank (2) is preferably 5 to 20°C higher than the liquid temperature in the coagulation tank (1), more preferably 7 to 15°C higher.

The average particle size of the coagulate of the (meth)acrylic multilayer structure particles (A) produced in the aggregation tank (2) is preferably 50 to 400 μm, more preferably 100 to 300 μm.

In this specification, the average particle size of aggregates and the cumulative particle size distribution of aggregates can be measured by a light scattering method (laser diffraction/scattering method, dynamic light scattering method). It can be measured using a laser diffraction/scattering particle size distribution analyzer LA-920V2 manufactured by Co., Ltd.

The bulk specific gravity of the solidified (meth)acrylic multilayer structure particles (A) produced in the aggregation tank (2) is preferably 0.2-0.6 g/cm ³ , more preferably 0.3-0. .5 g/cm ³ . The bulk specific gravity of the solidified (meth)acrylic multilayer structure particles (A) produced in the coagulation tank (2) is determined by the (meth)acrylic multilayer structure particles ( It is preferably 0.05 to 0.3 g/cm ³ larger, more preferably 0.07 to 0.2 g/cm ³ larger than the bulk specific gravity of the aggregates in A).

The residence time of the mixture in the flocculation tank (2) is preferably 0.3 to 2 hours (h), more preferably 0.5 to 1.5 hours.

The (meth)acrylic polymer coagulate obtained in the present invention is formed into a plate-shaped molded article having a thickness of 1 mm, and the haze difference (ΔH) before and after immersion in hot water at 98° C. for 4 hours. is preferably less than 1.0%, more preferably 0.9% or less. The haze is measured using a test piece having an optical path length of 1 mm according to JIS K7136.

The (meth)acrylic polymer granules obtained in Step 2 are washed with water, dehydrated and dried in accordance with conventional methods to obtain a (meth)acrylic polymer coagulate as powder. The moisture content of the obtained coagulate powder is 0.01-0.3% by mass, more preferably 0.05-0.2% by mass.

In a preferred embodiment of the present invention, the (meth)acrylic multilayer structure particles (A) obtained by emulsion polymerization are particles having a three-layer structure consisting of an innermost layer c, an intermediate layer i, and an outermost layer o. The temperature of the liquid inside the aggregation tank (2) is preferably less than the glass transition temperature Tg of the outermost layer o + 10°C. More preferably, the liquid temperature in the coagulation tank (2) is Tg+1°C to Tg+9°C. The temperature of the liquid inside the coagulation tank (1) is preferably Tg-20°C to Tg-0°C, more preferably Tg-15°C to Tg-5°C, of the outermost layer o.

The (meth)acrylic multilayer structure particles (A) have 2 to 5 layers, preferably 2 to 4 layers, and particularly preferably 3 layers.

In the present specification, hard polymer c, mixture c, and latex c mean the hard polymer, mixture, and latex of the innermost layer (core), and hard polymer i, mixture i, and latex i of the intermediate layer (core). Hard polymer, mixture, latex means hard polymer o, mixture o, latex o means the outermost hard polymer, mixture, latex.

As the layer structure of the (meth)acrylic multilayer structure particles (A), for example, a core-shell multilayer structure is preferable. The core-shell multilayer structure (meth)acrylic multilayer structure particles (A) can be obtained, for example, by melt-kneading a three-layer granule composed of an innermost layer c, an intermediate layer i and an outermost layer o. In one preferred embodiment of the invention, the innermost and intermediate layers, and the intermediate and outermost layers are composed of different polymers. It is preferable that the innermost layer and the intermediate layer and the intermediate layer and the outermost layer are in contact with each other without a gap. The polymer forming the intermediate layer is preferably softer than the polymer forming the innermost layer and the polymer forming the outermost layer.

In one preferred embodiment of the present invention, it is more preferred that the hard polymer constitutes the innermost layer c, the soft polymer constitutes the intermediate layer i, and the hard polymer constitutes the outermost layer o. The glass transition temperature of the hard polymer c constituting the outermost layer is preferably 60 to 105°C, more preferably 70 to 100°C. The glass transition temperature of the soft polymer i constituting the intermediate layer is preferably -60 to 0°C, more preferably -40 to -10°C.

The hard polymer c may be composed of a structural unit derived from a methacrylic acid ester (hereinafter referred to as a methacrylic acid ester unit), and a methacrylic acid ester unit and a structural unit derived from an acrylic ester (hereinafter referred to as an acrylic ester unit) and, if necessary, a structural unit derived from a polyfunctional monomer (hereinafter referred to as a polyfunctional monomer unit). The polyfunctional monomer unit includes a structural unit derived from a grafting agent (hereinafter referred to as a grafting agent unit or a structural unit derived from a cross-linking agent (hereinafter referred to as a cross-linking agent unit).

The amount of methacrylic acid ester units in the hard polymer c is preferably 50 to 100% by mass, more preferably 50 to 80% by mass, based on the total units of the hard polymer c.

The amount of structural units derived from an acrylic acid ester in the hard polymer c is preferably 0 to 50% by mass, more preferably 10 to 50% by mass, based on the total units of the hard polymer c. The number of carbon atoms in the ester portion (OR) in the acrylic acid ester is preferably 1-8. The smaller the amount of acrylic acid ester units, the lower the thermal decomposition resistance of the (meth)acrylic polymer solidified product. The hot water whitening resistance of the produced film tends to decrease.

The amount of grafting agent units in the rigid polymer c is preferably 0.01 to 1% by weight, more preferably 0.1 to 0.5% by weight, based on the total units of the rigid polymer c. The smaller the amount of grafting agent units, the lower the bonding strength between the hard polymer c and the soft polymer i. The impact resistance of the produced film tends to decrease.

In one preferred embodiment of the invention, the flexible polymer i is composed of acrylate units and grafting agent units and optionally methacrylate units, crosslinker units and other monomer units. It is a polymer that is

The amount of acrylate units in the flexible polymer i is preferably 10 to 100% by weight, more preferably 20 to 90% by weight, based on the total units of the flexible polymer i. The ester portion (OR) in the acrylic acid ester preferably has 1 to 8 carbon atoms. The smaller the amount of acrylic acid ester units, the lower the impact resistance of the film produced using the (meth)acrylic polymer coagulate. Films made with coalesced coagulum tend to be less stress whitening resistant and less transparent.

The amount of grafting agent units in the flexible polymer i is preferably 0.1-10% by weight, more preferably 0.5-5% by weight, based on the total units of the flexible polymer i. The smaller the amount of grafting agent units, the lower the stress whitening resistance of the film. impact resistance tends to decrease.

The amount of methacrylic acid ester units in the flexible polymer i is preferably 0 to 50% by mass, more preferably 0 to 20% by mass, based on the total units of the flexible polymer i. As the amount of methacrylic acid ester units increases, the impact resistance of the film produced using the (meth)acrylic polymer coagulate tends to decrease.

The hard polymer o is a polymer composed of methacrylate units and acrylate units. The rigid polymer o preferably does not contain polyfunctional monomer units. Since it does not contain polyfunctional monomer units, the hard polymer o dissolves in acetone.

The amount of methacrylic acid ester units in the hard polymer o is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, based on the total units of the hard polymer o. The smaller the amount of methacrylate ester units, the lower the stress whitening resistance of the film, and the larger the amount of structural units derived from methyl methacrylate, the lower the thermal decomposition resistance of the (meth)acrylic polymer coagulate. Tend.

The amount of acrylate units in the hard polymer o is preferably 0 to 50% by mass, more preferably 0 to 30% by mass, based on the total units of the hard polymer o. The ester portion (OR) in the acrylic acid ester preferably has 1 to 8 carbon atoms. The smaller the amount of acrylic acid ester units, the lower the thermal decomposition resistance of the multi-layer structure acrylic polymer. stress whitening resistance tends to decrease.

The hard polymer o has a glass transition temperature of preferably 80° C. or higher, more preferably 85° C. or higher. There is a tendency that the higher the glass transition temperature of the hard polymer o, the better the hot water resistance or boiling water whitening resistance of the film.

In a further preferred embodiment of the present invention, the (meth)acrylic multilayer structure particles (A) obtained by emulsion polymerization have an innermost layer composed of a hard polymer c having 50 to 100% by mass of methacrylate ester units. , an intermediate layer comprising a soft polymer i having 40 to 99.9% by mass of acrylate units and 0.1 to 5% by mass of polyfunctional monomer units and having a glass transition temperature of less than 25°C, and methacrylic It has a three-layer structure consisting of an outermost layer made of a hard polymer o having an acid ester unit content of 80 to 100% by mass and a glass transition temperature of 80° C. or higher.

Examples of acrylic acid esters used in hard polymer c, soft polymer i and hard polymer o include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate and t-butyl acrylate. , n-butylmethyl acrylate, n-heptyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate and the like. These acrylic acid esters can be used singly or in combination of two or more. Among these, methyl acrylate and/or n-butyl acrylate are preferred.

The grafting agent used for the hard polymer c and the soft polymer i mainly has the role of chemically bonding the hard polymer c and the soft polymer i and the soft polymer i and the hard polymer o. Furthermore, it is a monomer thought to play a role in assisting the formation of a crosslinked structure in the hard polymer c or the soft polymer i.

A grafting agent is a monomer having two or more different polymerizable groups. Grafting agents include, for example, allyl methacrylate, allyl acrylate, mono- or di-allyl maleate, mono- or di-allyl fumarate, crotyl acrylate, crotyl methacrylate, and the like. These grafting agents can be used singly or in combination of two or more. Among these, allyl methacrylate improves the bonding ability between the hard polymer c and the soft polymer i or between the soft polymer i and the hard polymer o, thereby improving the stress whitening resistance and transparency of the film. It is preferably used because it is excellent in the effect of improving the properties.

The cross-linking agent used for the hard polymer c and the soft polymer i is a monomer that is considered to play a major role in forming a cross-linked structure in the hard polymer c or the soft polymer i.

The cross-linking agent is a monomer having two or more polymerizable groups of the same type, and examples thereof include diacryl compounds, dimethacryl compounds, diallyl compounds, divinyl compounds, diene compounds, and trivinyl compounds. Examples of cross-linking agents include ethylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, divinylbenzene, trivinylbenzene, ethylene glycol diallyl ether. , propylene glycol diallyl ether, butadiene, and the like. These cross-linking agents can be used singly or in combination of two or more.

Other polymerizable monomers used for the hard polymer c and the soft polymer i may be any vinyl-based monomer that can be copolymerized with a methacrylic acid ester or an acrylic acid ester. , p-methylstyrene, o-methylstyrene, aromatic vinyl monomers such as vinylnaphthalene, unsaturated nitrile monomers such as acrylonitrile, olefinic monomers such as ethylene and propylene, vinyl chloride, vinylidene chloride, Vinyl halide monomers such as vinylidene fluoride, acrylic acid, methacrylic acid, unsaturated carboxylic acid monomers such as maleic anhydride, vinyl acetate, N-propylmaleimide, N-cyclohexylmaleimide, No- Maleimide-based monomers such as chlorophenylmaleimide can be mentioned, and these compounds can be used alone or in combination of two or more.

Further, the coagulate obtained by the production method of the present invention has a melt flow rate of preferably 0.5 to 20 g/10 min, more preferably 0.8 to 10 g/10 min at 230° C. under a load of 3.8 kg. minutes. The lower the melt flow rate of the multi-layered acrylic polymer, the lower the fluidity and film moldability of the multi-layered acrylic polymer. The higher the melt flow rate of the multilayer structure acrylic polymer, the lower the mechanical properties of the film.

The method for producing the latex (B) containing the (meth)acrylic multilayer structure particles (A) is not particularly limited. For example, a hard polymer c, a soft polymer i, and a hard polymer o can be sequentially formed by emulsion polymerization, such as seed emulsion polymerization, to obtain a latex (B).

The coagulum of the present invention may be mixed with other thermoplastic resins and extruded. Other thermoplastic resins include polycarbonate-based polymers, vinyl chloride-based polymers, vinylidene fluoride-based polymers, vinyl acetate-based polymers, maleic acid-based copolymers, acrylic resins, ABS resins, AES resins, and AS resins. etc. can be mentioned. The mass ratio of other thermoplastic resin/coagulum is preferably from 0/100 to 35/65, more preferably from 0/100 to 20/80.

The coagulum of the present invention may be mixed with an acrylic resin and extruded. The acrylic resin/coagulum mass ratio is preferably 0/100 to 35/65, more preferably 0/100 to 20/80. If it is in this range, the film formability will be good.

The acrylic resin that can be used as necessary in extrusion molding is a resin having a structural unit derived from methyl methacrylate and, if necessary, a structural unit derived from an acrylic acid ester.

The amount of structural units derived from methyl methacrylate in the acrylic resin is preferably 85 to 100% by mass, more preferably 92 to 100% by mass, based on the mass of all structural units in the acrylic resin. The amount of structural units derived from an acrylic acid ester in the acrylic resin is preferably 0 to 15% by mass, more preferably 0 to 8% by mass, based on the mass of all structural units in the acrylic resin.

Examples of acrylic acid esters in acrylic resins include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, s-butyl acrylate, t-butyl acrylate, amyl acrylate, isoamyl acrylate, n- Hexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate, cyclohexyl acrylate, norbornenyl acrylate, isobornyl acrylate, benzyl acrylate, phenoxyethyl acrylate, 2-hydroxyethyl acrylate, 2-ethoxyethyl acrylate , glycidyl acrylate, allyl acrylate, phenyl acrylate, and the like. Among these, acrylic acid esters having 1 to 6 carbon atoms are preferred.

The acrylic resin that is optionally used for extrusion molding preferably has a glass transition temperature of 95° C. or higher, more preferably 100° C. or higher, and even more preferably 105° C. or higher. The acrylic resin preferably has a melt flow rate of 0.5 to 20 g/10 minutes, more preferably 0.8 to 10 g/10 minutes at 230° C. under a load of 3.8 kg.

The acrylic resin is not particularly limited by its manufacturing method. For example, it can be produced by a known polymerization method such as a radical polymerization method or an anion polymerization method. Adjustments to the aforementioned characteristic values of acrylic resins are made by adjusting the polymerization conditions, specifically the polymerization temperature, polymerization time, type and amount of chain transfer agent, type and amount of polymerization initiator, etc. It can be done by Adjustment of resin properties by adjusting polymerization conditions is a technique well known to those skilled in the art.

The coagulate and acrylic resin obtained by the production method of the present invention are preferably pelletized in order to facilitate transportation, storage, molding, and the like. An extruder used for pelletizing the multilayer structure acrylic polymer preferably has a vent. Preferably the vent is a vacuum vent or an open vent. At least one vent is preferably provided downstream of the resin melting start portion. The pressure in the vacuum vent is preferably 30 Torr or less, more preferably 15 Torr or less, still more preferably 9 Torr or less, and most preferably 6 Torr or less. If the pressure at the vacuum vent is within the above range, the devolatilization efficiency is good, and residual moisture and monomers can be reduced.

The extruder used for pelletization is preferably of the single screw type. A single-screw extruder imparts a small shearing energy to a multi-layer structure acrylic polymer or the like, and can suppress thermal decomposition of the polymer. Preferably, the screw configuration is full flight.

The cylinder heating temperature of the extruder used for pelletization is preferably 210-270°C, more preferably 220-260°C, still more preferably 230-250°C. The residence time in the extruder is preferably 7 minutes or less, more preferably 5 minutes or less, even more preferably 3 minutes or less. The higher the cylinder heating temperature or the longer the residence time, the greater the shear energy given to the multi-layer structure acrylic polymer, etc., the more likely the thermal decomposition of the polymer will proceed, and the hot water whitening resistance of the film tends to decrease.

It is preferable to dry the coagulum and acrylic resin to reduce the moisture content before extruding. The moisture content of the multilayer structure acrylic polymer and the acrylic resin before being subjected to extrusion molding is preferably less than 0.2% by mass, more preferably less than 0.1% by mass. The higher the water content, the more likely silver streaks and deterioration of hot water whitening resistance are caused.

For the coagulate and acrylic resin, if necessary, known resin additives such as ultraviolet absorbers, antioxidants, light stabilizers, anti-aging agents, plasticizers, polymer processing aids, lubricants, dyes, pigments, etc. agents may be included. The total content of resin additives is preferably 20% by mass or less with respect to 100% by mass as the total amount of the coagulate and the acrylic resin. The resin additive may be added, for example, to the molten coagulum and acrylic resin in the film forming machine, or may be dry-blended into the pelletized coagulum or acrylic resin, or may be added to the coagulate. may be added when pelletizing the product or acrylic resin (masterbatch method).

It is preferable that the coagulate and the acrylic resin contain an ultraviolet absorber. Examples of UV absorbers include reactive UV absorbers such as 2-[2-hydroxy-5-(2-methacryloyloxyethyl)phenyl]-2H-1,2,3-benzotriazole. The content of the ultraviolet absorber is preferably 0.05 to 5 parts by mass with respect to 100 parts by mass as the total amount of the solidified material and the acrylic resin.

When the solidified product of the present invention is used as a molded product, it can be molded into a plate shape, a film shape, or the like by heat melting, extrusion molding, injection molding, or other general molding methods.

The extruder used for film formation is preferably vented. Preferably the vent is a vacuum vent or an open vent. At least one vent is preferably provided downstream of the resin melting start portion. The pressure in the vacuum vent is preferably 30 Torr or less, more preferably 15 Torr or less, even more preferably 9 Torr or less, and most preferably 6 Torr or less. The extruder used for film formation is preferably of the single-screw or co-rotating twin-screw type.

The cylinder heating temperature of the extruder used for film formation is preferably 220 to 300°C, more preferably 230 to 290°C, still more preferably 240 to 280°C. The residence time in the extruder used for film formation is preferably 7 minutes or less, more preferably 5 minutes or less, even more preferably 3 minutes or less. The higher the cylinder heating temperature or the longer the residence time, the greater the shear energy given to the multi-layer structure acrylic polymer, etc., the more likely the thermal decomposition of the polymer will proceed, and the hot water whitening resistance of the film tends to decrease. Therefore, extrusion molding for film formation is preferably carried out with a residence time in the extruder of 5 minutes or less and a resin temperature of 280° C. or less.

The resin film obtained from the coagulate of the present invention has excellent impact resistance, excellent stress whitening resistance, does not cause whitening even when bent, has excellent hot water whitening resistance and boiling water whitening resistance, and is excellent in hot water whitening resistance. No whitening occurs when exposed to boiling water. The resin film obtained from the coagulate of the present invention also has excellent adhesion to other polymers, particularly thermoplastic polymers.

The resin film obtained from the coagulate of the present invention preferably has a thickness of 10 to 500 μm, more preferably 20 to 400 μm, still more preferably 30 to 300 μm.

A laminate using the coagulate obtained by the production method of the present invention has at least one layer using the coagulate of the present invention and at least one layer made of another thermoplastic polymer.

Other thermoplastic polymers used in the laminates of the present invention are not particularly limited. Other thermoplastic polymers include polycarbonate-based polymer, vinyl chloride-based polymer, vinylidene fluoride-based polymer, vinyl acetate-based polymer, maleic acid-based copolymer, methacrylic resin, ABS resin, AES resin, or AS. Resin is preferable because it has good adhesiveness with the resin film of the present invention. Thermoplastic polymer molded articles may be planar molded articles such as films, sheets and plates, linear molded articles such as tubes and rods, lenses, prisms, containers and the like. It may be a molded product of various shapes such as.

The laminate of the present invention is not particularly limited by its manufacturing method. The laminate is formed by, for example, co-extrusion molding the multilayer structure acrylic polymer and another thermoplastic polymer, thereby coating the multilayer structure acrylic resin on the other thermoplastic polymer molded product. Other thermoplastic polymer moldings are performed by extruding other thermoplastic polymer moldings by placing them in a desired mold, and by injecting or injecting the multilayer structure acrylic polymer into said mold after melting it. The multi-layered acrylic resin described above is placed on the product and press-molded, or the resin film containing the coagulate obtained by the production method of the present invention is heat-sealed to another thermoplastic polymer molded product. Or it can be obtained by gluing.

The present invention will be described in more detail below with reference to polymerization examples, production examples, examples, and comparative examples. However, the present invention is not limited by them. In addition, "part" represents a mass part below.

[Glass transition temperature measurement]
The glass transition temperature (Tg) of the hard polymer is measured in accordance with JIS K7121 by manufacturing only the hard polymer under the same conditions as in the process of forming the hard polymer during the manufacturing process of the polymer particles. is the intermediate glass transition temperature.

The glass transition temperature (Tg) of the soft polymer is measured in accordance with JIS K7121 by manufacturing only the soft polymer under the same conditions as in the process of forming the soft polymer during the manufacturing process of the polymer particles. is the intermediate glass transition temperature.

[Warm water whitening resistance]
The coagulate was hot-pressed to prepare a flat plate-shaped molded article having a thickness of 1 mm, and the haze of the flat plate was measured. The flat plate was immersed in hot water at 98°C for 4 hours, and the haze was measured before and after immersion. The difference between the haze after immersion in warm water and the haze before immersion in warm water was defined as Δhaze.

[Volume average particle size]
Regarding the slurry containing the coagulum, the volume average particle size (herein referred to as the “average particle size”) is determined by a light scattering method using a laser diffraction/scattering particle size distribution analyzer LA-920V2 manufactured by Horiba, Ltd. The proportion of particles below 20 μm was determined.

[Bulk specific gravity]
The coagulum was filled into a 100 cc graduated cylinder with tapping and weighed to determine the bulk specific gravity.

<Polymerization Example 1>
200 parts of ion-exchanged water was placed in a glass-lined reaction vessel equipped with a condenser, a thermometer and a stirrer, and then 1.3 parts of sodium dodecylbenzenesulfonate and 0.05 part of sodium carbonate were added and dissolved. let me The inside of the reaction vessel was replaced with nitrogen gas to make it substantially free of oxygen. After that, the inside of the reaction vessel was heated to bring the aqueous solution to 80°C.

To the aqueous solution, 0.01 part of potassium persulfate was added, and after stirring for 5 minutes, 2.50 parts of methyl methacrylate (MMA), 2.50 parts of butyl acrylate (BA) and 0.5 parts of allyl methacrylate (ALMA) were added. 01 part of the mixture c was continuously added dropwise over 15 minutes, and after the completion of the dropwise addition of the mixture c, the emulsion polymerization was carried out for 25 minutes to obtain a latex c.

To Latex c was then added 0.095 parts of potassium persulfate, followed by 1.5 parts of methyl methacrylate (MMA), 28.5 parts of butyl acrylate (BA) and 0.90 parts of allyl methacrylate (ALMA). A mixture i consisting of was continuously fed dropwise over a period of 60 minutes. After the addition of the mixture i was completed, the mixture was maintained for 30 minutes, and seed emulsion polymerization was carried out to obtain a latex i.

To this latex i was then added a mixture o of 56.9 parts of methyl methacrylate (MMA), 8.1 parts of butyl acrylate (BA) and 0.19 parts of n-octyl mercaptan (OM) over 100 minutes. It was fed dropwise continuously. After the addition of the mixture o was completed, the mixture was held for 60 minutes, and seed emulsion polymerization was carried out to obtain a latex I-1 containing the (meth)acrylic multilayer structure particles (A).

The hard polymer o constituting the outermost layer of the (meth)acrylic multilayer structure particles (A) had a Tg of 87°C.

Table 1 shows the composition of the (meth)acrylic multilayer structure particles (A) contained in the latex I-1.

<Production Example 1>
100 parts of latex I-1 and 146.5 parts of deionized water were added to a coagulation tank (1) equipped with a Maxblend impeller stirrer, stirred at a stirring speed of 246 rpm, and the reactor was heated to 80°C. did. 0.41 part of a 1.2% by mass aqueous solution of magnesium sulfate was added thereto, and the mixture was stirred for 60 minutes to obtain a salting-out slurry No.1.

<Production Example 2>
The solid content concentration, stirring rotation speed, heating temperature, and magnesium sulfate aqueous solution addition concentration in the aggregation tank (1) were changed as shown in Table 2, and the mixture was stirred for 60 minutes to obtain salting-out slurry No.2.

<Example 1>
The slurry and ion-exchanged water are charged into a coagulation tank (2) equipped with another Maxblend impeller stirrer so that the solid content concentration of the slurry No. 1 is 7.5% by mass, and the stirring speed is 400 rpm. and heated to 90° C. and stirred for 60 minutes. After that, it was washed with water twice, dehydrated and dried to obtain a (meth)acrylic polymer coagulate.

<Example 2>
A (meth)acrylic polymer coagulate was obtained in the same manner as in Example 1 except that the solid content concentration at the time of aggregation was changed to 5% by mass and the stirring rotation speed was changed to 300 rpm.

<Comparative Example 1>
A (meth)acrylic polymer coagulate was obtained in the same manner as in Example 1, except that the temperature during aggregation was changed to 97°C.

<Comparative Example 2>
A (meth)acrylic polymer coagulate was obtained in the same manner as in Example 1 except that the solid content concentration of the slurry during aggregation was changed to 10% by mass and the stirring time during aggregation was changed to 20 minutes.

<Comparative Example 3>
A (meth)acrylic polymer coagulate was obtained in the same manner as in Example 1, except that the temperature during aggregation in Example 1 was changed to 85° C. and the solid content concentration of the slurry was changed to 15% by mass.

<Comparative Example 4>
A (meth)acrylic polymer coagulate was obtained in the same manner as in Example 1, except that the temperature during aggregation in Example 1 was changed to 80° C. and the solid content concentration of the slurry was changed to 15% by mass.

<Comparative Example 5>
A (meth)acrylic polymer coagulate was obtained in the same manner as in Example 1, except that salting-out slurry No. 2 was used.

Claims (8)

Steps 1 to 3 below
Step 1: A latex (B) containing (meth)acrylic multilayer structure particles (A) obtained by an emulsion polymerization method and an aqueous coagulant solution are continuously supplied to a coagulation tank (1) and mixed. ) a salting-out step of obtaining a salting-out slurry containing soft aggregates of the acrylic multilayer structure particles (A);
Step 2: A granulation step in which the salting-out slurry obtained in step 1 and washing water are supplied to the flocculation tank (2) and hard flocculated at an internal liquid temperature higher than that of the flocculation tank (1) (here, the washing Water is supplied so that the solid content concentration in the coagulation tank (2) is less than 2/3 of the solid content concentration in the coagulation tank (1));
Step 3: Step of washing, dehydrating and drying the aggregates of the (meth)acrylic multilayer structure particles (A) obtained in Step 2;
A method for producing a (meth)acrylic polymer coagulum. 2. The production method according to claim 1, wherein the solid content concentration of the liquid inside the coagulation tank (2) is less than 10% by mass. 3. The production method according to claim 1 or 2, wherein the (meth)acrylic multilayer structure particles (A) are particles having a three-layer structure comprising an innermost layer c, an intermediate layer i, and an outermost layer o. (Meth)acrylic multilayer structure particles (A), innermost layer composed of hard polymer c having 50 to 100% by mass of methacrylate units, 40 to 99.9% by mass of acrylate units, and polyfunctional an intermediate layer composed of a soft polymer i having a monomer unit content of 0.1 to 5% by mass and a glass transition temperature of less than 25° C., and a methacrylic acid ester unit content of 80 to 100% by mass, and 4. The production method according to claim 3, wherein the outermost layer comprises a hard polymer o having a glass transition temperature of 80[deg.] C. or higher and has a three-layer structure. 5. The production according to claim 3 or 4, characterized in that the temperature of the liquid inside the aggregation tank (2) is less than the glass transition temperature of the outermost layer o of the (meth)acrylic multilayer structure particles (A) + 10°C. Method. The production method according to any one of claims 1 to 5, wherein the coagulant is at least one selected from the group consisting of magnesium sulfate, calcium chloride, aluminum sulfate and calcium acetate. The production method according to any one of claims 1 to 6, wherein the amount of (meth)acrylic polymer aggregates having a particle size of 20 µm or less in the aggregation tank (1) is 1 to 7% by mass. A step of producing a (meth)acrylic polymer coagulate by the method according to any one of claims 1 to 7, and
Including the step of molding the (meth)acrylic polymer coagulate,
A method for producing a molded article of (meth)acrylic multilayer structure particles (A), comprising:
When the (meth)acrylic polymer solidified product is formed into a plate-shaped molded article having a thickness of 1 mm and the plate-shaped molded article is immersed in hot water of 98°C for 4 hours, the haze difference (ΔH) before and after the immersion is 1.0. A method for producing a molded product of (meth)acrylic multilayer structure particles (A), wherein the content is less than 0% .