JP2010037386A - Shock-resistant methacrylic resin cast plate and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shock-resistant methacrylic resin cast plate having excellent shock resistance, improved heating processability and sufficient practical heat resistance, and to provide a rational manufacturing method of the plate. <P>SOLUTION: The methacrylic resin cast plate includes: a methacrylic polymer (A), which is a polymer of a monomer mixture containing 85 to 97 mass% of methylmethacrylate and 3 to 15 mass% of methylacrylate and has a weight average molecular weight of 100,000 to 500,000; and a multilayered structure polymer (B), which is a multilayered structure polymer consisting of a rubber polymer having a crosslinked structure with a hard resin component grafted thereto and is dispersed in the above methacrylic polymer (A). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a methacrylic resin cast plate having excellent impact resistance and heat processability, and a method for producing the same.

Since the methacrylic resin cast plate has excellent transparency, good weather resistance, and mechanical properties, it is widely used in applications such as lighting equipment, signboards, building materials, and game machine covers. However, the impact strength is not always satisfactory and there has been a strong demand for improvement.
As a method for improving the impact resistance of a methacrylic resin cast plate, Patent Document 1 discloses that a polymer obtained by grafting a hard resin component to a rubbery polymer having a crosslinked structure is dispersed in a methyl methacrylate resin. A cast plate is disclosed.
Patent Document 2 discloses a syrup in which a methyl methacrylate polymer having an average molecular weight of 10,000 to 300,000 is dissolved in a monomer having methyl methacrylate as a main component and a multilayered elastic body is further dispersed. A method for producing a methacrylic resin cast plate that is injected into a polymer and polymerized is disclosed.

Japanese Patent Laid-Open No. 01-252653 Japanese Patent Laid-Open No. 08-151498

  However, the methacrylic resin cast plate obtained by the above-mentioned method is superior in impact resistance as compared with the one made of methyl methacrylate resin alone, but the softening temperature is relatively high when molding by heating. There is a problem in workability because it is high and fluidity is not sufficient.

  In view of the above circumstances, the problem to be solved by the present invention is a methacrylic resin cast plate having excellent impact resistance, improved heat workability, and sufficient practical heat resistance, and its rational Providing a simple manufacturing method.

  As a result of intensive studies to solve the above problems, the present inventors have found that a methacrylic resin cast plate having the following configuration and a method for producing a methacrylic resin cast plate can solve the above problems.

That is, the present invention is as follows.
[1]
A polymer of a monomer mixture containing 85 to 97% by mass of methyl methacrylate and 3 to 15% by mass of methyl acrylate, and a methacrylic polymer (A) having a weight average molecular weight of 100 to 500,000;
A multilayer structure polymer in which a hard resin component is grafted to a rubbery polymer having a crosslinked structure, the multilayer structure polymer (B) dispersed in the methacrylic polymer (A);
Methacrylic resin cast board containing
[2]
The methacrylic resin cast plate according to the above [1], comprising 5 to 30 parts by mass of the multilayer polymer (B) with respect to 100 parts by mass of the methacrylic polymer (A).
[3]
To 100 parts by mass of a monomer mixture containing 85 to 97% by mass of methyl methacrylate and 3 to 15% by mass of methyl acrylate,
A method for producing a methacrylic resin cast plate, comprising a step of dispersing 5 to 30 parts by mass of a multilayer structure polymer (B) obtained by grafting a hard resin component onto a rubbery polymer having a cross-linked structure and performing cast polymerization.

  According to the present invention, it is possible to provide a methacrylic resin cast plate having improved impact resistance and heat processability and good practical heat resistance, and a rational manufacturing method thereof.

  Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as the present embodiment) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

The methacrylic resin cast plate of this embodiment is
A polymer of a monomer mixture containing 85 to 97% by mass of methyl methacrylate and 3 to 15% by mass of methyl acrylate, and a methacrylic polymer (A) having a weight average molecular weight of 100 to 500,000; A methacrylic polymer comprising a multilayered polymer obtained by grafting a hard resin component to a rubbery polymer having a crosslinked structure, the multilayered polymer (B) dispersed in the methacrylic polymer (A). It is a resin cast board.

[Methacrylic polymer (A)]
The methacrylic polymer (A) in the present embodiment is a polymer of a monomer mixture containing 85 to 97% by mass of methyl methacrylate and 3 to 15% by mass of methyl acrylate, and has a weight average molecular weight. It is adjusted to the range of 100,000 to 500,000.

  Methyl methacrylate contained in the monomer mixture at a content of 85 to 97% by mass in order to maintain the characteristics such as good weather resistance and mechanical properties that the methacrylic resin cast plate originally has. is important.

  When the content of methyl methacrylate is less than 85% by mass, the weather resistance and mechanical properties are lowered, and when it exceeds 97% by mass, the impact resistance of the resulting cast plate is lowered, and the polymer obtained The softening temperature is high and the fluidity is insufficient.

  Methyl acrylate contained in the monomer mixture at a content of 3 to 15% by mass improves the impact resistance of the resulting cast plate and moderately lowers the softening temperature of the resulting polymer to improve fluidity. It is important to improve.

  When the content of methyl acrylate is less than 3% by mass, it is difficult to obtain the above-described effect. When the content exceeds 15% by mass, the softening temperature becomes too low, and as a result, a methacrylic resin cast plate is practical. Insufficient heat-resistant temperature cannot be maintained.

  The monomer mixture may contain other monomers copolymerizable therewith in addition to methyl methacrylate and methyl acrylate, if necessary. Examples of such other monomers include other acrylates other than methyl acrylate such as ethyl acrylate and butyl acrylate, monofunctional monomers such as styrene, alkylene glycol di (meth) acrylate, trimethylol propane tri And polyfunctional monomers such as (meth) acrylate and divinylbenzene.

  The content of the other monomers described above is appropriately determined in order to maintain the balance of physical properties such as weather resistance, mechanical properties, thermal formation, and heat resistance of the resulting methacrylic resin cast plate. Preferably it is 10 mass% or less with respect to the whole, More preferably, it is 5 mass% or less.

  Moreover, well-known additives, such as a stabilizer, a ultraviolet absorber, a mold release agent, a light-diffusion agent, a coloring agent, can also be added to a monomer mixture as needed.

  In the present embodiment, the weight average molecular weight of the methacrylic polymer (A) which is a polymer of a monomer mixture containing 85 to 97% by mass of methyl methacrylate and 3 to 15% by weight of methyl acrylate is 10 to 50. It is important to make it ten thousand. By adjusting the weight average molecular weight of the methacrylic polymer (A) to 100,000 to 500,000, the impact resistance performance of the resulting methacrylic resin cast plate is improved, and the heat processability is improved by improving the fluidity of the cast plate. Can be greatly improved. If the weight average molecular weight is less than 100,000, the mechanical strength, solvent resistance, etc. will be reduced, causing practical problems. If it exceeds 500,000, the impact resistance of the cast plate will be reduced and the fluidity will be improved. It becomes virtually impossible to obtain.

  Here, the weight average molecular weight of the methacrylic polymer (A) refers to a value measured by gel permeation chromatography.

[Multilayer structure polymer (B)]
The multilayer structure polymer (B) in the present embodiment is obtained by grafting a hard resin component to a rubbery polymer having a crosslinked structure. As such a multilayer structure polymer, for example, as disclosed in JP-B-60-17406,
As a first layer, a copolymer having a glass transition temperature of 25 ° C. or higher obtained by polymerizing methyl methacrylate alone or a mixture of methyl methacrylate and a monomer copolymerizable therewith,
The second layer is mainly composed of an alkyl acrylate that forms a polymer having a glass transition temperature of 25 ° C. or less when polymerized alone, and at least a monomer and a polyfunctional monomer copolymerizable therewith. One, a rubbery polymer obtained by polymerizing a polyfunctional grafting agent,
As the third layer, a polymer obtained by polymerizing a mixture of monomers mainly composed of methyl methacrylate that forms a hard resin component having a glass transition temperature of 25 ° C. or higher when polymerized alone, and copolymerizable therewith. When,
And a multilayer structure graft copolymer composed of three layers.

  As the number of layers of the multilayer structure polymer (B) is larger, it is possible to obtain a rubber-like polymer whose elasticity is controlled within a suitable range. What consists of three layers is preferable.

  In the multilayer structure graft copolymer composed of three layers, monomers that can be copolymerized with methyl methacrylate include known (meth) acrylic acid, (meth) acrylates other than methyl methacrylate, styrene, α-methyl Monofunctional monomers such as styrene, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, Polyfunctional monomers such as triallyl isocyanurate, diallyl maleate, and divinylbenzene are listed. The said monomer can be used 1 type or in combination of 2 or more types as needed.

  The second layer of the multilayer structure graft copolymer composed of three layers is a rubber-like copolymer exhibiting rubber elasticity, and is important for imparting excellent impact strength to the cast plate.

  The alkyl acrylate that forms the second layer is not particularly limited, and for example, one or more of methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, and the like can be used in combination. Among these, n-butyl acrylate and 2-ethylhexyl acrylate are preferable.

  In addition, other monomers that can be copolymerized with these alkyl acrylates are not particularly limited, and general monomers can be used. Styrene or a derivative thereof is preferably used from the viewpoint of improving transparency by matching with the coalescence (A).

  In the case where the multilayer structure polymer (B) in the present embodiment is composed of three layers, the rubber-like polymer having a crosslinked structure contained in the multilayer structure polymer refers to this second layer, and is a multifunctional single polymer. It means a rubber-like polymer in which a crosslinked structure is formed by copolymerizing a monomer.

  The cross-linked structure in the rubber-like polymer is necessary for imparting appropriate rubber elasticity and maintaining its form in a dispersed state without being dissolved in the monomer mixture in the cast polymerization step described later.

  As the polyfunctional monomer for forming a crosslinked structure, the compounds exemplified as those copolymerizable with methyl methacrylate and methyl acrylate can be used, and the amount used is 0 with respect to the entire second layer. .1 to 5% by mass. When the amount of the polyfunctional monomer used is less than 0.1% by mass, a sufficient crosslinking effect cannot be obtained, and when it exceeds 5% by mass, the crosslinking is too strong, both of which are preferable because the rubber elastic effect is reduced. Absent. Further, if the amount used is less than 0.1% by mass, the rubbery polymer is dissolved or greatly swelled in the cast polymerization step described later, which is not preferable because the rubber elastic body cannot be maintained.

  Furthermore, a polyfunctional grafting agent for forming a graft bond that closes the affinity with the polymer of the third layer is used for the second layer.

  The polyfunctional grafting agent is a polyfunctional monomer having different functional groups, and examples thereof include allyl esters such as acrylic acid, methacrylic acid, maleic acid, and fumaric acid. Among them, allyl acrylate and allyl methacrylate are exemplified. preferable. The usage-amount of a polyfunctional grafting agent is the range of 0.1-3 mass% with respect to the whole 2nd layer. If the amount of the polyfunctional grafting agent used is less than 0.1% by mass, a sufficient graft effect cannot be obtained, and if it exceeds 3% by mass, the rubber elasticity is lowered, which is not preferable.

  In the polymerization of the third layer, the molecular weight can be adjusted using a chain transfer agent in order to improve the affinity with the methacrylic polymer (A).

  In order to improve the transparency of the methacrylic resin cast plate, it is necessary to match the refractive indexes of the multilayer structure polymer (B) and the methacrylic resin (A) dispersed in the cast plate. It is extremely difficult to completely match the refractive index of the second layer, which is a copolymer containing alkyl acrylate as a main component, with that of the methacrylic resin (A). In order to match the refractive index, for example, when alkyl acrylate and styrene or its derivatives are copolymerized in the second layer, the refractive index becomes substantially equal in a certain temperature range and the transparency is improved, but the temperature is changed. A refractive index shift occurs and transparency is deteriorated.

  As a means for avoiding this, it is possible to provide a first layer whose refractive index is substantially the same as that of the methacrylic resin. When the first layer does not exist, the transparency tends to be remarkably lowered. Further, reducing the thickness of the second layer is also effective in preventing the deterioration of transparency.

  The multilayer structure polymer (B) in the present embodiment is preferably obtained by emulsion polymerization. Specifically, when the multilayer polymer (B) is composed of three layers, in the presence of an emulsifier and an initiator, the monomer mixture of the first layer is first added to complete the polymerization, and then The second layer monomer mixture is added to complete the polymerization, and then the third layer monomer mixture is added to complete the polymerization, thereby easily obtaining a multilayer structure polymer (particle) as a latex. be able to.

  The multilayer structure polymer (particles) can be recovered from the latex as a powder by a known method such as salting out, spray drying, freeze drying and the like.

  When the multilayer polymer is a polymer composed of three layers, aggregation of the powders can be avoided by providing a hard resin component in the third layer.

  The average particle size of the multilayer structure polymer (B) is preferably 0.1 to 1 μm. If the average particle size of the multilayer structure polymer is less than 0.1 μm, sufficient impact strength tends to be difficult to obtain, and if it exceeds 1 μm, fine ripples appear on the surface of the finally obtained methacrylic cast plate. When the defects appear in the shape, the specularity is hindered, and further, when molded by heating, there is a risk that the stretched portion has a significant decrease in surface gloss and impairs transparency. In order to obtain sufficient impact strength and good surface gloss, the average particle size of the multilayer structure polymer is more preferably 0.1 to 0.5 μm.

  The compounding amount of the multilayer structure polymer (B) in the methacrylic resin cast plate of the present embodiment is preferably 5 to 30 parts by mass, more preferably 7 to 100 parts by mass with respect to 100 parts by mass of the methacrylic polymer (A). The impact resistance varies depending on the amount of the multilayer polymer. When the blending amount of the multilayer structure polymer is less than 5 parts by mass, the impact resistance of the resulting methacrylic resin cast plate tends to decrease. There is a tendency that the viscosity of the mixed solution in which the multilayer structure polymer is dispersed in the mixture becomes too large and it is difficult to perform the polymerization.

[Method for producing methacrylic resin cast plate]
The method for producing a methacrylic resin cast plate of the present embodiment is a rubber-like material having a crosslinked structure in 100 parts by mass of a monomer mixture containing 85 to 97% by mass of methyl methacrylate and 3 to 15% by mass of methyl acrylate. It includes a step of cast polymerization by dispersing 5 to 30 parts by mass of the multilayer structure polymer (B) in which the hard resin component is grafted to the polymer.

  Cast polymerization to obtain a methacrylic resin cast plate is performed by, for example, two glass plates facing each other in parallel, or a seal material that prevents liquid leakage such as soft vinyl chloride around the metal plate and a clamp that holds the seal. It is carried out by polymerizing a so-called cell having a gap in a state in which a mixed solution in which the above-mentioned multilayer structure polymer (B) is dispersed is sealed in a monomer mixture containing methyl methacrylate and methyl acrylate. be able to.

  Initiators used for cast polymerization include peroxide radical initiators such as dilauroyl peroxide, dibenzoyl peroxide, t-butylperoxy 2-ethylhexanoate, and 2,2′-azobisiso Azo radical initiators such as butyronitrile, 2,2′-azobis (2,4-dimethyl-valeronitrile), 1,1-azobis (1-cyclohexanecarbonitrile) can be used, and these are independent. However, two or more types may be used in combination.

  Moreover, you may use it as a redox type | system | group initiator combining the said radical initiator and a suitable reducing agent.

  These initiators are usually used in the range of 0.01 to 1% by mass with respect to the monomer mixture.

  Furthermore, in order to adjust the molecular weight of the methacrylic resin (A), a known chain transfer agent may be used. Examples of the chain transfer agent include n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, 2-ethylhexyl thioglycolate, ethylene glycol dithioglycolate, trimethylolpropane tris (thioglycolate), pentaerythritol tetrakis (thioglycolate). Mercaptans such as (Rate) are preferably used. These chain transfer agents may be used alone or in combination of two or more.

  A chain transfer agent is normally used in 0.01-0.5 mass% with respect to a monomer mixture.

  The cell gap is determined by the desired thickness of the cast plate, but is generally set in the range of 1 to 20 mm.

  Polymerization is started by heating the cell. However, since methyl methacrylate is an exothermic polymerization reaction, if the heat of reaction is insufficiently removed or uneven heat builds up, the cast plate surface May cause a defect or a defect due to internal foaming. In order to avoid these problems, in general, circulating hot water that can easily adjust the temperature and can smoothly remove heat during the polymerization reaction or circulating hot air having a sufficient wind speed is applied as the heat medium. .

  In the heat treatment stage for completing the polymerization, it is preferable to apply hot air heated by boiler steam, electric heat, or the like, which can be controlled in a relatively high temperature range.

  The conditions for the polymerization can be appropriately determined depending on the initiator to be used, the type and amount of the chain transfer agent, the composition of the monomer mixture, and the desired cast plate thickness. Usually, the temperature range is 30 to 80 ° C. Yes, the polymerization time is 1 to several tens of hours.

  In the heat treatment stage, the temperature range is usually 110 to 140 ° C. and the treatment time is 1 to 5 hours.

  After completion of the polymerization and heat treatment, the glass plate or metal plate constituting the cell can be removed to obtain a methacrylic resin cast plate.

Hereinafter, the present embodiment will be described in more detail with reference to examples. However, the present embodiment is not limited to the examples described below.
Evaluation of the obtained cast board was implemented with the following method.
(1) Charpy impact strength: ISO179 / 1fU
(2) Vicat softening temperature: ISO306B50
(3) Rockwell hardness: ISO2039-2 (M scale surface hardness)
(4) Total light transmittance, haze: JIS K 7105
(5) Transparency:
According to the visual judgment, ◎ if there is little cloudiness and high transparency, ◎ very slightly cloudy, but ○ that can be used practically without problems for transparent applications, and those that are cloudy and difficult to use for transparent applications X.
(6) Thermoformability:
The cast plate heated to a surface temperature of 170 ° C. was vacuum-formed using a cylindrical concave mold having a diameter of 100 mm and a depth of 50 mm provided with a vacuum hole, and the mold reproducibility of the bottom corner was relatively evaluated.
As a reference example 1, the moldability was better than this, and when the corner R became smaller, evaluations 2 to 4 were given depending on the degree. R in the reference example was 30 mm, and in the case of evaluation of 4, the corner R was 5 mm or less.
(7) Weight average molecular weight:
A gel permeation chromatography LC-908 manufactured by Nippon Analytical Industries, Ltd. was used, 0.45 g of a sample was dissolved in 15 mL of chloroform, and the weight average molecular weight was measured using the same chloroform as a developing solvent. At this time, the multilayer structure polymer as a rubber component was previously removed with a filter.

[Production of multilayer structure polymer]
First layer monomer component is methyl methacrylate 33.51 (mass% is shown below), n-butyl acrylate 2.14, allyl methacrylate 0.04, second layer monomer component is n-butyl acrylate Except for 32.54, styrene 7.03, diethylene glycol diacrylate 0.08, allyl methacrylate 0.84, and the third layer monomer component of methyl methacrylate 22.36, n-butyl acrylate 1.46 A multilayer structure polymer having a three-layer structure was obtained by the same method as that described in Example 1 of JP-B-60-17406.

[Production of methacrylic resin cast board]
[Example 1]
Monomer containing 89.8% by weight of methyl methacrylate, 10% by weight of methyl acrylate, 0.1% by weight of 2,2′-azobis (2,4-dimethyl-valeronitrile), 0.1% by weight of n-octyl mercaptan To 100 parts by mass of the mixture, 15 parts by mass of the multilayer polymer was added little by little with stirring with a screw-type stirring blade at room temperature to obtain a uniform dispersion.
A soft polyvinyl chloride tube was set around the two tempered glass plates, and the dispersion liquid in which dissolved air was removed under reduced pressure was injected into a cell having an interval of 5 mm held by a clamp.
The cell was placed in circulating warm water adjusted to 40 ° C. for 10 hours, and then placed in 70 ° C. warm water for 2 hours. Further, after being placed in a circulating hot air at 120 ° C. for 2 hours, it was cooled to room temperature to obtain a methacrylic resin cast plate.
The obtained cast plate had good light transparency with a total light transmittance of 92% and a haze of 0.9%.
The weight average molecular weight of the polymer excluding the multilayer structure polymer was 260,000.

[Examples 2 and 3]
Implementation was performed except that the amount of methyl acrylate used was 5% by mass (Example 2) and 7% by mass (Example 3), and the amount of methyl methacrylate was adjusted to 100% by mass in the entire monomer mixture. A methacrylic resin cast plate was obtained in the same manner as in Example 1.
The weight average molecular weights of the polymers excluding the multilayer structure polymer were 270,000 (Example 2) and 260,000 (Example 3), respectively.

[Example 4]
A methacrylic resin cast plate was obtained in the same manner as in Example 1 except that the amount of n-octyl mercaptan used was 0.06% by mass.
The weight average molecular weight of the polymer excluding the multilayer structure polymer was 400,000.

[Examples 5 and 6]
A methacrylic resin cast plate was obtained in the same manner as in Example 1 except that the blending amounts of the rubber-like polymers were 10 parts by mass (Example 5) and 20 parts by mass (Example 6), respectively.
The weight average molecular weights of the polymers excluding the multilayer structure polymer were 270,000 (Example 5) and 280,000 (Example 6), respectively.

[Comparative Example 1]
A methacrylic resin cast plate was obtained in the same manner as in Example 1 except that the multilayer structure polymer (rubber-like polymer powder) was not used.
The weight average molecular weight of the polymer was 270,000.

[Comparative Example 2]
A methacrylic resin cast plate was obtained in the same manner as in Example 1 except that 99.8% by mass of methyl methacrylate was used as the monomer.
The weight average molecular weight of the polymer excluding the multilayer structure polymer was 260,000.

[Comparative Examples 3 and 4]
A methacrylic resin cast plate was prepared in the same manner as in Example 1 except that n-octyl mercaptan was not added (Comparative Example 3) and that n-octyl mercaptan was 0.02% by mass (Comparative Example 4). Got.
The weight average molecular weights of the polymers excluding the multilayer structure polymer were 3.7 million (Comparative Example 3) and 650,000 (Comparative Example 4), respectively.

[Comparative Examples 5 and 6]
A methacrylic resin cast plate was obtained in the same manner as in Example 1 except that 10% by mass of ethyl acrylate (Comparative Example 5) and 10% by mass of butyl acrylate (Comparative Example 6) were used instead of methyl acrylate. .
The weight average molecular weights of the polymers excluding the multilayer structure polymer were 280,000 (Comparative Example 5) and 300,000 (Comparative Example 6), respectively.

[Reference Example 1]
A general-purpose acrylic cast board containing no rubber component (manufactured by Asahi Kasei Chemicals Corporation: trade name Delaglass K, thickness 5 mm) was used.

The results of evaluation are summarized in Table 1.
In Table 1, rubber (parts) represents the added mass part of the multilayered polymer with respect to 100 parts by mass of the monomer mixture, and comonomer (%) represents methyl acrylate (MA) and ethyl acrylate (EA) in the monomer mixture. Or n-OM represents the mass proportion added to the monomer mixture of n-octyl mercaptan.

As is clear from the results in Table 1, all of the methacrylic resin cast plates obtained in Examples 1 to 6 have good impact strength, heat resistance, surface hardness, transparency, and excellent performance balance. The moldability was also good.
On the other hand, since the cast board of Comparative Example 1 did not contain a multilayer structure polymer, the impact strength (impact resistance) was inferior.
The cast board of Comparative Example 2 had a problem in transparency because it had a total light transmittance of 91% and a haze of 5.1% and was cloudy. Moreover, impact strength was also inferior compared with the cast board of the Example.
The cast plates of Comparative Examples 3 and 4 have polymer weight average molecular weights of 37,000,000 (Comparative Example 3) and 650,000 (Comparative Example 4), respectively, excluding the multilayer structure polymer. The impact strength was inferior compared with the cast board of the Example.
The cast plates of Comparative Examples 5 and 6 had low Vicat softening temperature and Rockwell hardness as compared to the Examples, and had a problem in performance balance.

  The methacrylic resin cast plate of the present invention has good transparency, impact strength, heat resistance, and surface hardness, and has industrial applicability in fields such as lighting equipment, signboards, and building materials.

Claims (3)

A polymer of a monomer mixture containing 85 to 97% by mass of methyl methacrylate and 3 to 15% by mass of methyl acrylate, and a methacrylic polymer (A) having a weight average molecular weight of 100 to 500,000;
A multilayer structure polymer in which a hard resin component is grafted to a rubbery polymer having a crosslinked structure, the multilayer structure polymer (B) dispersed in the methacrylic polymer (A);
Methacrylic resin cast board containing   The methacrylic resin cast board according to claim 1, comprising 5 to 30 parts by mass of the multilayer polymer (B) with respect to 100 parts by mass of the methacrylic polymer (A). To 100 parts by mass of a monomer mixture containing 85 to 97% by mass of methyl methacrylate and 3 to 15% by mass of methyl acrylate,
A method for producing a methacrylic resin cast plate, comprising a step of dispersing 5 to 30 parts by mass of a multilayer structure polymer (B) obtained by grafting a hard resin component onto a rubbery polymer having a cross-linked structure and performing cast polymerization.