Methacrylic polymer, its production method, and molded body

Abstract

To provide a methacrylic polymer which has high heat resistance, a high coefficient of elasticity, a not high coefficient of water absorption, and good heat and warm water stability.SOLUTION: A methacrylic copolymer comprises: 15-83 mass% of methyl methacrylate units; 7-35 mass% of α-methylstyrene units; 0-20 mass% of maleic anhydride units (M); 10-65 mass% of structural units (R) having in the main chain at least one or more ring structures selected from the group consisting of a lactone ring unit, a glutaric anhydride unit, an N-substituted or -unsubstituted glutarimide unit, and an N-substituted or -unsubstituted maleimide unit; and 0-20 mass% of other vinylic monomer units (C) copolymerizable with methyl methacrylate units.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a methacrylic polymer, a method for producing the same, and a molded article including a film, an optical film, and a laminate. [Background technology]

[0002] Methacrylic resins are excellent in transparency, weather resistance, surface hardness, etc. By molding acrylic resin compositions containing such methacrylic resins, various components used in display components, electronic and electrical components, transportation equipment parts, etc. In recent years, there has been a demand for higher performance in various components, and there is a strong demand for improvements in heat resistance and elastic modulus in particular.

[0003] Random copolymers of methyl methacrylate and α-methylstyrene have long been known to improve the heat resistance and elastic modulus of (meth)acrylic resins. However, α-methylstyrene is not homopolymerizable by radical polymerization under industrial conditions and has low copolymerizability with other monomers, making it difficult to produce the copolymer. For example, Patent Document 1 discloses a copolymer synthesized by a batch-type bulk polymerization method, but the polymerization time is very long and the productivity is low.

[0004] A method for copolymerizing maleic anhydride with the copolymer (a random copolymer of methyl methacrylate and α-methylstyrene) is known as a method for increasing the polymerization rate and further improving heat resistance. For example, Patent Document 2 discloses a method for copolymerizing methyl methacrylate with α-methylstyrene and maleic anhydride. Patent Document 3 discloses a method for copolymerizing methyl methacrylate with α-methylstyrene, maleic anhydride and styrene. These copolymerized polymers of α-methylstyrene copolymer and maleic anhydride have a fast polymerization rate and also have high heat resistance, but they are susceptible to chemical reactions and decomposition in response to heat or hot water, which significantly limits their use during molding and processing. Furthermore, they suffer from the drawback of causing a deterioration in physical properties when processed products are exposed to water or water vapor or exposed to high temperatures and humidity.

[0005] Imidization reactions have been proposed as a method for improving thermal decomposition resistance and suppressing deterioration of physical properties under high temperature and humidity. Patent Document 4 discloses a method for producing an imidized resin of a copolymer consisting of an aromatic vinyl monomer, maleic anhydride, and methyl methacrylate as a vinyl monomer copolymerizable therewith. Patent Document 5 also discloses an imidized resin of a terpolymer of methyl methacrylate, styrene, and maleic anhydride, and a resin composition thereof.

[0006] In all of the disclosed examples, thermal stability is improved, but water absorption and coloration easily occur due to the high imidization rate. As described above, there is room for further investigation into methods for achieving a higher level of balance between heat resistance, high elastic modulus, heat and hot water stability, and low water absorption. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] US Patent 3135723 [Patent Document 2] Special Publication No. 45-31953 [Patent Document 3] Special Publication No. 61-36764 [Patent Document 4] Special Publication No. 60-45642 [Patent Document 5] Japanese Patent Application Laid-Open No. 2006-124592 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above circumstances, an object of the present invention is to provide a methacrylic polymer having high heat resistance, high elastic modulus, low water absorption, and good stability to heat and hot water. [Means for solving the problem]

[0009] As a result of investigations conducted to achieve the above object, the present invention has been completed, including the following aspects. [1] A methacrylic copolymer comprising 15 to 83 mass% of methyl methacrylate units, 7 to 35 mass% of α-methylstyrene units, 0 to 20 mass% of maleic anhydride units (M), 10 to 65 mass% of structural units (R) having at least one ring structure in the main chain selected from the group consisting of lactone ring units, glutaric anhydride units, N-substituted or unsubstituted glutarimide units, and N-substituted or unsubstituted maleimide units, and 0 to 20 mass% of other vinyl monomer units (C) copolymerizable with methyl methacrylate. [2] The methacrylic copolymer according to [1], wherein the structural unit (R) is an N-substituted or unsubstituted glutarimide unit represented by formula (I): [ka] (In formula (I), R 1 are each independently a hydrogen atom or a methyl group, and R 2 is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an organic group having 6 to 15 carbon atoms and containing an aromatic ring. [3] The methacrylic copolymer according to any one of [1] and [2], wherein the structural unit (R) is an N-substituted or unsubstituted maleimide unit represented by formula (II): [ka] (In formula (II), R 3 is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an organic group having 6 to 15 carbon atoms and containing an aromatic ring. [4] The methacrylic copolymer according to any one of [1] to [3], wherein the other vinyl monomer unit (C) copolymerizable with the methyl methacrylate unit is formed of at least one monomer selected from the group consisting of an acrylic acid ester monomer, an aromatic vinyl monomer, and a vinyl cyanide monomer. [5] The methacrylic copolymer according to any one of [1] to [4], wherein the other vinyl monomer unit (C) copolymerizable with the methyl methacrylate unit is formed of at least one selected from the group consisting of methyl acrylate, ethyl acrylate, styrene, and acrylonitrile. [6] The methacrylic copolymer according to any one of [1] to [5], which contains 0.1 to 3 mass % of maleic anhydride units (M). [7] The methacrylic copolymer according to any one of [1] to [6], wherein the mass ratio of the maleic anhydride unit (M) to the structural unit (R) having in its main chain at least one ring structure selected from the group consisting of a lactone ring unit, a glutaric anhydride unit, an N-substituted or unsubstituted glutarimide unit, and an N-substituted or unsubstituted maleimide unit, {100×(M) / (R)}, is in the range of 0 to 20%. [8] The methacrylic copolymer according to any one of [1] to [7], which has a glass transition temperature of 140°C or higher. [9] A methacrylic copolymer composition containing the copolymer according to any one of [1] to [8].

[10] A molded article comprising the methacrylic copolymer according to any one of [1] to [8] or the methacrylic copolymer composition according to [9].

[11] A film comprising the methacrylic copolymer according to any one of [1] to [8] or the methacrylic copolymer composition according to [9].

[12] An optical film comprising the methacrylic copolymer according to any one of [1] to [8] or the methacrylic copolymer composition according to [9].

[13]

[14] A laminate having a layer containing the methacrylic copolymer according to any one of [1] to [8] or the methacrylic copolymer composition according to [9], and a layer containing another material. A method for producing a methacrylic copolymer according to any one of [1] to [8], comprising the steps of: continuously supplying a reaction raw material containing a monomer mixture containing 50 to 92 mass% of methyl methacrylate, 7 to 30 mass% of α-methylstyrene units, 1 to 20 mass% of maleic anhydride units (M), and 0 to 20 mass% of other vinyl monomer units (C) copolymerizable with the methyl methacrylate units, to a tank reactor; polymerizing in the tank reactor to a polymerization conversion rate of 30 to 60 mass% to obtain a reaction product; removing the monomer mixture from the reaction product; and subjecting the obtained precursor polymer to a ring structure-forming reaction.

[15]

[15] The method for producing a methacrylic copolymer according to

[14] , wherein the ring structure-forming reaction is an imide cyclization reaction in which an imidizing agent is added to a precursor polymer in an extruder, and the mixture is kneaded and reacted. [Effects of the Invention]

[0010] According to the present invention, it is possible to obtain a methacrylic polymer that has excellent stability in heat and hot water, high heat resistance, high elastic modulus, and low water absorption. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Methacrylic copolymer) The methacrylic copolymer of the present invention contains methyl methacrylate units, α-methylstyrene units, and a structural unit (R). The methacrylic copolymer of the present invention may further contain maleic anhydride units (M) and other vinyl monomer units (C) copolymerizable with methyl methacrylate. The other vinyl monomer units (C) copolymerizable with methyl methacrylate may be methacrylamide units represented by the following formula (A) or 2-(hydroxyalkyl)acrylate units represented by the following formula (B).

[0012] [ka] (In the formula, R 4 , R 6 , R 7 is defined below)

[0013] In the methacrylic copolymer of the present invention, the proportion of methyl methacrylate units relative to all structural units is preferably 15 to 83 mass%, more preferably 30 to 80 mass%, and even more preferably 35 to 75 mass%. If the proportion of methyl methacrylate units is less than this range, the total light transmittance of the resulting methacrylic copolymer will be reduced, and if the proportion of methyl methacrylate units is greater than this range, the heat resistance of the resulting methacrylic copolymer will be reduced.

[0014] The methacrylic copolymer of the present invention preferably has an α-methylstyrene unit content of 7 to 35% by mass, more preferably 8 to 30% by mass, and even more preferably 11 to 25% by mass, based on the total structural units. If the α-methylstyrene unit content is less than this range, the saturated water absorption of the resulting methacrylic copolymer will be high. Furthermore, a methacrylic copolymer having an α-methylstyrene unit content of more than 35% by mass will have low polymerizability and reduced productivity. Furthermore, this will inhibit the glutarimidization reaction caused by the intramolecular cyclization of structural units derived from two adjacent (meth)acrylic acids, as described below.

[0015] The methacrylic copolymer of the present invention preferably has a maleic anhydride unit (M) content of 0 to 20% by mass, more preferably 0.05 to 10% by mass, and even more preferably 0.1 to 3% by mass, based on the total structural units. A methacrylic copolymer having a maleic anhydride unit content of more than 20% by mass has poor hot water stability.

[0016] The structural unit (R) is a structural unit having at least one ring structure selected from the group consisting of a lactone ring unit, a glutaric anhydride unit, an N-substituted or unsubstituted glutarimide unit, and an N-substituted or unsubstituted maleimide unit in the main chain. The methacrylic copolymer of the present invention may contain, in the main chain, a methacrylic acid amide unit represented by the above formula (A) and / or a 2-(hydroxyalkyl)acrylic acid ester unit represented by the above formula (B).

[0017] A lactone ring unit is a structural unit containing a >CH-OC(=O)- group in the ring structure. The structural unit containing a >CH-OC(=O)- group in the ring structure preferably has 4 to 8, more preferably 5 to 6, and most preferably 6, ring constituent elements. Examples of structural units containing a >CH-OC(=O)- group in the ring structure include lactonediyl structural units such as a β-propiolactonediyl structural unit, a γ-butyrolactonediyl structural unit, and a δ-valerolactonediyl structural unit. A structural unit containing a >CH-OC(=O)- group in the ring structure can be obtained, for example, by intramolecular cyclization of a polymer having a hydroxy group and an ester group with the hydroxy group and the ester group. Note that ">C" in the formula means that the carbon atom C has two bonds.

[0018] For example, an example of the δ-valerolactonediyl structural unit is a structural unit represented by formula (IV).

[0019] [ka]

[0020] In formula (IV), R 8 , R 9 and R 10 are each independently a hydrogen atom or an organic group having 1 to 20 carbon atoms, preferably a hydrogen atom or an organic group having 1 to 10 carbon atoms, and more preferably a hydrogen atom or an organic group having 1 to 5 carbon atoms. The organic group is not particularly limited as long as it has 1 to 20 carbon atoms, and examples thereof include a linear or branched alkyl group, a linear or branched aryl group, a -COOCH3 group, and a -CN group. The organic group may contain a heteroatom such as an oxygen atom. R 8 is preferably a methyl group, and R 9 is preferably a -COOCH3 group, and R 10 is preferably a hydrogen atom.

[0021] The lactone ring unit can be incorporated into the methacrylic copolymer by the methods described in JP-A Nos. 2000-230016, 2001-151814, 2002-120326, 2002-254544, and 2005-146084, for example, by intramolecular cyclization of a structural unit derived from a 2-(hydroxyalkyl)acrylate ester with a structural unit derived from methyl (meth)acrylate.

[0022] The glutaric anhydride unit is a unit having a 2,6-dioxodihydropyrandiyl structure. An example of the unit having a 2,6-dioxodihydropyrandiyl structure is a structural unit represented by formula (V).

[0023] [ka] In formula (II), R 11 are each independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and are preferably a methyl group.

[0024] The unit having a 2,6-dioxodihydropyrandiyl structure can be incorporated into the methacrylic copolymer by methods described in JP 2007-197703 A, JP 2010-96919 A, and the like, for example, by intramolecular cyclization of two adjacent structural units derived from (meth)acrylic acid, or intramolecular cyclization of a structural unit derived from (meth)acrylic acid and a structural unit derived from methyl (meth)acrylate.

[0025] The N-substituted or unsubstituted glutarimide unit is a unit having an N-substituted or unsubstituted 2,6-dioxopiperidinediyl structure. An example of a unit having an N-substituted or unsubstituted 2,6-dioxopiperidinediyl structure is a structural unit represented by formula (I).

[0026] [ka] In formula (I), R1 are each independently a hydrogen atom or a methyl group, and two R 1 Preferably, both R are methyl groups. 2 is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an organic group having 6 to 15 carbon atoms and containing an aromatic ring, and is preferably a hydrogen atom, a methyl group, an n-butyl group, a cyclohexyl group, or a benzyl group, and more preferably a methyl group, an n-butyl group, or a cyclohexyl group. The structural unit represented by formula (I) can be prepared by, for example, reacting the corresponding acid anhydride (IIa) with R 2 It may be produced by a reaction of an imidizing agent represented by NH2, or by an intramolecular cyclization reaction of a copolymer having a partial structure of formula (III). It is preferable to heat the copolymer to convert the structural unit represented by formula (III) into the structural unit represented by formula (I) by the intramolecular cyclization reaction. Scheme (i) [ka] (In the formula, R 1 , R 2 is as defined above.)

[0027] N-substituted or unsubstituted glutarimide units can be obtained by reacting two adjacent structural units derived from methyl methacrylate or glutaric anhydride units with an imidizing agent such as ammonia, aliphatic hydrocarbon group-containing amines such as methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, tert-butylamine, or n-hexylamine, aromatic hydrocarbon group-containing amines such as aniline, toluidine, or trichloroaniline, alicyclic hydrocarbon group-containing amines such as cyclohexylamine, urea, 1,3-dimethylurea, 1,3-diethylurea, or 1,3-dipropylurea. Among these, methylamine is preferred. During this imidization reaction, some of the methyl methacrylate units may be hydrolyzed to form carboxyl groups, and these carboxyl groups are preferably converted back to the original methyl methacrylate units by an esterification reaction involving treatment with an esterifying agent. The esterifying agent is not particularly limited as long as it can exhibit the effects of the present invention, but dimethyl carbonate and trimethyl acetate are preferably used. In addition to the esterifying agent, a tertiary amine such as trimethylamine, triethylamine, or tributylamine can also be used as a catalyst.

[0028] The N-substituted or unsubstituted maleimide unit is a unit having an N-substituted or unsubstituted 2,5-pyrrolidinedione structure. An example of a unit having an N-substituted or unsubstituted 2,5-pyrrolidinedione structure is a structural unit represented by formula (II).

[0029] [ka] (In formula (II), R 3 is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an organic group having 6 to 15 carbon atoms and containing an aromatic ring. The structural unit represented by formula (II) is a compound of maleic anhydride (M) and R 3 It is produced by the reaction of an imidizing agent represented by NH2.

[0030] N-substituted or unsubstituted maleimide units can be obtained by methods described in JP-B Nos. 61-026924, 7-042332, 9-100322, and 2001-329021, specifically by reacting maleic anhydride units with an imidizing agent such as ammonia, aliphatic hydrocarbon group-containing amines such as methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, tert-butylamine, and n-hexylamine, aromatic hydrocarbon group-containing amines such as aniline, toluidine, and trichloroaniline, alicyclic hydrocarbon group-containing amines such as cyclohexylamine, urea, 1,3-dimethylurea, 1,3-diethylurea, and 1,3-dipropylurea. Among these, methylamine is preferred.

[0031] In the methacrylic copolymer of the present invention, the proportion of the structural unit (R) relative to all structural units is preferably 10 to 65 mass%, more preferably 12 to 62 mass%, and even more preferably 14 to 60 mass%. As the content of the structural unit (R) increases, the thermal decomposition resistance of the methacrylic copolymer improves, but the melt viscosity increases and molding processability tends to decrease.

[0032] Examples of the other vinyl monomer units (C) copolymerizable with methyl methacrylate units (hereinafter sometimes referred to as (C) monomer units) include acrylate ester monomer units (C-1), aromatic vinyl monomer units (C-2), vinyl cyanide monomer units (C-3), and other monomer units (C-4). The other vinyl monomer units (C) copolymerizable with methyl methacrylate units may be used alone or in combination of two or more.

[0033] The (C) monomer unit can be selected appropriately depending on the properties required for the methacrylic copolymer of the present invention. When properties such as thermal stability, fluidity, chemical resistance, optical properties, and compatibility with other resins are particularly required, at least one selected from the group consisting of an acrylic acid ester monomer unit, an aromatic vinyl monomer unit, and a vinyl cyanide monomer unit is preferred.

[0034] The acrylic acid ester monomer unit (C-1) constituting the methacrylic copolymer of the present invention is not particularly limited, but from the viewpoints of heat resistance, fluidity, heat resistance stability, productivity, etc., methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, 2-ethylhexyl acrylate, benzyl acrylate, cyclohexyl acrylate, phenyl acrylate, etc. are preferred, more preferably methyl acrylate, ethyl acrylate, n-butyl acrylate, and even more preferably methyl acrylate and ethyl acrylate from the viewpoint of productivity. The acrylic acid ester monomer unit (C-1) may be used alone or in combination of two or more kinds.

[0035] When the acrylic acid ester monomer unit (C-1) is used, its content is preferably 20% or less, more preferably 10% or less, of the total structural units, from the viewpoint of heat resistance and thermal stability.

[0036] The aromatic vinyl monomer unit (C-2) constituting the methacrylic copolymer of the present invention is not particularly limited as long as it is other than α-methylstyrene. However, from the viewpoints of heat resistance, flowability, heat stability, productivity, etc., styrene (St), o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, 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, isopropenyltoluene, isopropenylethylbenzene, isopropenylpropylbenzene, isopropenylpropylbenzene, isopropenylbutylbenzene, isopropenylbenzylbenzene, isopropenylhexylbenzene, isopropenyloctylbenzene, etc. are preferred, and from the viewpoint of productivity, styrene is more preferred. The aromatic vinyl monomer unit (C-2) may be used alone or in combination of two or more kinds.

[0037] When the aromatic vinyl monomer unit (C-2) is used, its content is preferably 20% or less, more preferably 15% or less, based on the total structural units, from the viewpoint of heat resistance and thermal stability.

[0038] The vinyl cyanide monomer unit (C-3) constituting the methacrylic copolymer of the present invention is not particularly limited, but from the viewpoints of heat resistance, flowability, heat stability, chemical resistance, productivity, etc., acrylonitrile (AN), methacrylonitrile, vinylidene cyanide, etc. are preferred, and among these, acrylonitrile is preferred from the viewpoints of easy availability and imparting chemical resistance. The vinyl cyanide monomer unit (C-3) may be used alone or in combination of two or more kinds.

[0039] When vinyl cyanide monomer units (C-3) are used, their content is preferably 20% or less, more preferably 10% or less, based on the total structural units, from the viewpoint of heat resistance and thermal stability.

[0040] The monomer forming the monomer unit (C-4) other than (C-1) to (C-3) constituting the methacrylic copolymer of the present invention is not particularly limited, and may be a monomer corresponding to the methacrylic acid amide unit represented by formula (A) or a monomer corresponding to the 2-(hydroxyalkyl)acrylic acid ester unit represented by formula (B). Examples include amides such as acrylamide and methacrylamide; ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, or ethylene glycol oligomers thereof, in which both terminal hydroxyl groups are esterified with acrylic acid or methacrylic acid; neopentyl glycol di(meth)acrylate, di(meth)acrylate, or other ethylene glycol di(meth)acrylate, in which the hydroxyl groups of two alcohols are esterified with acrylic acid or methacrylic acid; trimethylolpropane, pentaerythritol, or other polyhydric alcohol derivatives are esterified with acrylic acid or methacrylic acid; and polyfunctional monomers such as divinylbenzene.

[0041] Among the monomers constituting the above-mentioned (C) monomer unit, at least one selected from the group consisting of methyl acrylate (MA), ethyl acrylate, styrene, and acrylonitrile is preferred from the viewpoint of availability.

[0042] In the methacrylic copolymer of the present invention, the proportion of other vinyl monomer units (C) copolymerizable with methyl methacrylate units is preferably 0 to 20% by mass, more preferably 0 to 15% by mass, and even more preferably 0 to 10% by mass, based on the total structural units. A methacrylic copolymer having a proportion of other vinyl monomer units (C) copolymerizable with methyl methacrylate units exceeding 20% ​​by mass has reduced heat resistance and rigidity. The proportions of methyl methacrylate units, α-methylstyrene units, maleic anhydride units (M), structural units (R), and monomer units (C) are as follows: 1 H-NMR, 13 It can be measured by C-NMR or the like.

[0043] From the viewpoint of heat resistance and warm water resistance, the methacrylic copolymer of the present invention preferably has a mass ratio of maleic anhydride units (M) to structural units (R) having at least one ring structure in the main chain selected from the group consisting of lactone ring units, glutaric anhydride units, and N-substituted or unsubstituted glutarimide units, {100×(M) / (R)}, in the range of 0 to 20% and more preferably 0 to 10% by mass.

[0044] The methacrylic copolymer of the present invention has a weight average molecular weight (Mw) of preferably 40,000 to 200,000, more preferably 50,000 to 180,000, and even more preferably 55,000 to 160,000. When Mw is 40,000 or more, the strength, toughness, etc. of the molded article of the present invention are improved. When Mw is 200,000 or less, the flowability of the methacrylic copolymer of the present invention is improved, and molding processability is improved.

[0045] The weight average molecular weight (Mw) is a value calculated by converting a chromatogram measured by gel permeation chromatography into the molecular weight of standard polystyrene.

[0046] The methacrylic copolymer of the present invention preferably has an acid value of 0.01 to 0.30 mmol / g, more preferably 0.05 to 0.28 mmol / g. The acid value is proportional to the content of carboxylic acid units and carboxylic anhydride units in the methacrylic copolymer. The acid value can be calculated, for example, by the method described in JP-A-2005-23272. When the acid value is within the above range, the copolymer has an excellent balance of heat resistance, mechanical properties, and moldability.

[0047] The methacrylic copolymer of the present invention has a glass transition temperature in which the lower limit is preferably 140°C, more preferably 141°C, and even more preferably 142°C, and the upper limit is not particularly limited, but is preferably 170°C. In this specification, the "glass transition temperature (Tg)" is measured in accordance with JIS K7121. Specifically, the temperature is raised once to 230°C, then cooled to room temperature, and then the DSC curve is measured under conditions of raising the temperature from room temperature to 230°C at a rate of 10°C / min. The midpoint of the DSC curve measured during the second temperature rise is determined as the "glass transition temperature (Tg)."

[0048] The saturated water absorption of the methacrylic copolymer of the present invention can be measured under the following conditions. The methacrylic copolymer is press-molded into a sheet with a thickness of 1.0 mm. A 50 mm x 50 mm test piece is cut from the center of the press-molded sheet and dried in a dryer at 80°C for at least 16 hours. The dried test piece is cooled to room temperature in a desiccator and then weighed to the nearest 0.1 mg. This weight is the initial weight, Wo. The test piece is immersed in distilled water at 23°C for 24 hours, after which it is removed from the water and all surface moisture is wiped off with a clean, dry cloth or filter paper. Within 1 minute of removing it from the water, the test piece is weighed again to the nearest 0.1 mg. The test piece is then reimmersed and weighed again after 24 hours using the same method as above. The weight at which the weight change of the test piece is within 0.02% of Wo is defined as the saturated weight, Ws. The saturated water absorption can be calculated using Equation (2).

[0049]

number

[0050] The methacrylic copolymer of the present invention has a 1% thermal weight loss temperature under a nitrogen atmosphere of preferably 300°C or higher, more preferably 310°C or higher. The 1% thermal weight loss temperature can be measured using a thermogravimetric analyzer (TGA). The 1% thermal weight loss temperature can be determined as the temperature at which the weight loss is 1% relative to the charged weight.

[0051] (Methacrylic copolymer manufacturing method) The methacrylic copolymer of the present invention can be obtained by a method including a ring structure-forming reaction of a copolymer (hereinafter sometimes referred to as a precursor polymer) of methyl methacrylate (MMA), α-methylstyrene (αMSt), maleic anhydride (Mah), and optionally other vinyl monomers. That is, the production method of the present invention comprises the steps of continuously supplying a reaction raw material containing a monomer mixture containing 50 to 92 mass% of methyl methacrylate, 30 to 7 mass% of α-methylstyrene, 1 to 20 mass% of maleic anhydride, and 0 to 20 mass% of other copolymerizable vinyl monomers, a radical polymerization initiator, and, if necessary, a chain transfer agent, to a tank reactor; bulk polymerizing the monomer mixture in the tank reactor to a polymerization conversion of 30 to 60 mass% to obtain a reaction product; removing the monomer mixture from the reaction product to obtain a precursor polymer; and subjecting the obtained precursor polymer to a ring structure-forming reaction, and each step can be carried out by a known technique.

[0052] The precursor polymer is polymerized from reaction raw materials including a monomer mixture, a radical polymerization initiator, and optionally a chain transfer agent, and the monomer mixture contains 50 to 92 mass %, preferably 55 to 90 mass %, of methyl methacrylate. The content of α-methylstyrene is 30 to 7 mass %, preferably 25 to 10 mass %, the content of maleic anhydride is 1 to 20 mass %, preferably 3 to 15 mass %, and the content of copolymerizable monomer is 0 to 20 mass %, preferably 0 to 10 mass %. The copolymerizable monomer is not particularly limited, and may be a monomer corresponding to the methacrylic acid amide unit represented by formula (A) or a monomer corresponding to the 2-(hydroxyalkyl)acrylic acid ester unit represented by formula (B). Examples of the copolymerizable monomer include alkyl methacrylates other than methyl methacrylate, such as ethyl methacrylate and butyl methacrylate; aryl methacrylates, such as phenyl methacrylate; cycloalkyl methacrylates, such as cyclohexyl methacrylate and norbornenyl methacrylate; aryl acrylates, such as phenyl acrylate; cycloalkyl acrylates, such as cyclohexyl acrylate and norbornenyl acrylate; aromatic vinyl monomers, such as styrene; acrylamide; methacrylamide; acrylonitrile; and methacrylonitrile; and other vinyl monomers having only one polymerizable alkenyl group in one molecule.

[0053] The monomer mixture preferably has b* of -1 to 2, more preferably -0.5 to 1.5. When b* is within this range, molding the resulting methacrylic copolymer composition is advantageous in that it allows for the production of molded articles with little coloration at high production efficiency. Note that b* is a value measured in accordance with the International Commission on Illumination (CIE) standard (1976) or JIS Z-8722. The monomer mixture removed from the reaction product in the step of removing the monomer mixture in the reaction product can be recovered and reused in the present invention. If the b* of the recovered monomer mixture becomes high due to heat applied during recovery, it is preferable to purify it by an appropriate method to bring the b* into the above-mentioned range.

[0054] The polymerization initiator used in the present invention is not particularly limited as long as it generates reactive radicals. For example, t-hexylperoxyisopropyl monocarbonate, t-hexylperoxy 2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, t-butylperoxypivalate, t-hexylperoxypivalate, t-butylperoxyneodecanoate, t-hexylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, 1,1-bis(t-hexylperoxy)cyclohexane, benzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, lauroyl peroxide, 2,2'-azobis(2-methylpropionitrile), 2,2'-azobis(2-methylbutyronitrile), and dimethyl 2,2'-azobis(2-methylpropionate) are preferred; Examples include t-hexylperoxy 2-ethylhexanoate, 1,1-bis(t-hexylperoxy)cyclohexane, and dimethyl 2,2'-azobis(2-methylpropionate).

[0055] The polymerization initiator used in the present invention has an average uncleaved initiator concentration (I) of 5.1 × 10 at the polymerization temperature in a tank reactor described below. -5 ~2.4×10 -4 (mol / L) range is desirable.

[0056] The amount of the polymerization initiator used is adjusted to the polymerization temperature and added to the monomer mixture so as to achieve the above initiator concentration (I).

[0057] Examples of chain transfer agents used in the present invention include alkyl mercaptans such as n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, 1,4-butanedithiol, 1,6-hexanedithiol, ethylene glycol bisthiopropionate, butanediol bisthioglycolate, butanediol bisthiopropionate, hexanediol bisthioglycolate, hexanediol bisthiopropionate, trimethylolpropane tris-(β-thiopropionate), and pentaerythritol tetrakisthiopropionate; and terpinolene. Among these, monofunctional alkyl mercaptans such as n-octyl mercaptan and n-dodecyl mercaptan are preferred. These chain transfer agents can be used alone or in combination of two or more. The amount of chain transfer agent used is preferably 0 to 1 part by mass, more preferably 0.01 to 0.8 parts by mass, and even more preferably 0.02 to 0.6 parts by mass, per 100 parts by mass of the monomer mixture.

[0058] In principle, no solvent is used in bulk polymerization. However, if it is necessary to adjust the viscosity of the reaction solution, a solvent can be added to the monomer mixture. Preferred solvents include aromatic hydrocarbons such as benzene, toluene, and ethylbenzene, and ketones such as methyl ethyl ketone and methyl isobutyl ketone. These solvents can be used alone or in combination of two or more. The amount of such solvents used is preferably 30 parts by mass or less, more preferably 10 parts by mass or less, per 100 parts by mass of the monomer mixture.

[0059] The reaction raw materials used in the present invention preferably have a dissolved oxygen content of 10 ppm or less, more preferably 5 ppm or less, even more preferably 4 ppm or less, and most preferably 3 ppm or less. When the dissolved oxygen content is within this range, the polymerization reaction proceeds smoothly, and molded products free of silver streaks and coloration are more likely to be obtained.

[0060] The temperature inside the tank reactor, i.e., the temperature of the liquid inside the reaction tank, is preferably 110 to 140° C., more preferably 114 to 135° C. If the temperature is higher than this range, it becomes difficult to produce high molecular weight compounds containing α-methylstyrene, which causes a decrease in heat resistance.

[0061] In the method for producing a methacrylic copolymer composition of the present invention, the water content in the reaction solution in the tank reactor is preferably 1000 ppm or less, more preferably 700 ppm or less, and even more preferably 280 ppm or less. By keeping the water content at 1000 ppm or less, it is possible to suppress the generation of resin foreign matter of several μm to several tens of μm during the polymerization reaction, and when the resulting methacrylic copolymer composition is formed into a film or sheet by melt molding, it is possible to significantly reduce the occurrence of defects with an outer diameter of several tens of μm that are caused by the resin foreign matter.

[0062] In the tank reactor, bulk polymerization is preferably carried out until the polymerization conversion rate reaches 30 to 60% by mass, and more preferably 35 to 55% by mass.

[0063] The average residence time (θ) of the reaction raw materials in the tank reactor is preferably 1.5 to 5 hours, more preferably 2 to 4.5 hours, and even more preferably 2.5 to 4 hours. If the average residence time is too short, the amount of polymerization initiator required increases. Furthermore, an increase in the amount of polymerization initiator tends to make it difficult to control the polymerization reaction and to control the molecular weight. On the other hand, if the average residence time is too long, it takes time for the reaction to reach a steady state, and productivity tends to decrease. The average residence time can be adjusted by the capacity of the tank reactor and the amount of reaction raw materials supplied.

[0064] The bulk polymerization is preferably carried out in an inert gas atmosphere such as nitrogen gas.

[0065] The production method of the present invention includes a step of removing the monomer mixture from the reaction product. Here, the reaction product is not limited to a reaction product obtained by bulk polymerization in a tank reactor. It may also be a reaction product obtained, if necessary, in a separate reactor connected downstream of the tank reactor. That is, a reaction product in which the unreacted monomer mixture in the reaction product obtained by bulk polymerization in a tank reactor is further polymerized in a separate reactor to increase the polymerization conversion. In addition, in this step, the solvent is also removed simultaneously, if necessary. While the removal method is not particularly limited, thermal devolatilization is preferred. Examples of thermal devolatilization include equilibrium flash evaporation and adiabatic flash evaporation, with adiabatic flash evaporation being preferred. The temperature at which adiabatic flash evaporation is performed is preferably 200 to 280°C, more preferably 220 to 280°C, and even more preferably 220 to 270°C. If the adiabatic flash evaporation is performed at a temperature below 200°C, devolatilization takes a long time, resulting in insufficient devolatilization, which can cause poor appearance, such as silver streaks, on the molded product. On the other hand, if the temperature at which the adiabatic flash evaporation method is performed exceeds 280°C, the methacrylic copolymer composition tends to become discolored and undergo depolymerization due to oxidation, burning, decomposition, etc. The adiabatic flash evaporation method may be performed in multiple stages. In this case, the reaction product flowing through the heat transfer tube is heated with vapor from the flash-evaporated monomer mixture, and the heated reaction product is supplied to a low-pressure flash tank for flash evaporation. The reaction product can be pressurized using a pump or the like. After removing the monomer mixture, the methacrylic copolymer composition can be pelletized or powdered according to known methods to facilitate handling as a molding material. The content of the monomer mixture in the methacrylic copolymer composition obtained by the present invention is preferably 1% by mass or less, more preferably 0.5% by mass or less.

[0066] The precursor polymer preferably has a glass transition temperature of 124°C as a lower limit, more preferably 125°C, and even more preferably 127°C, and preferably 150°C as an upper limit. The glass transition temperature can be changed by adjusting the molecular weight, the amount of α-methylstyrene copolymerized, the amount of maleic anhydride copolymerized, etc. The higher the glass transition temperature of the precursor polymer, the better the heat resistance. A methacrylic copolymer obtained using a precursor polymer with a high glass transition temperature has high heat resistance even with a small amount of structural unit (R), and is therefore less likely to cause deterioration in saturated water absorption, etc.

[0067] The precursor polymer is not particularly limited as long as it has a total content of structural units derived from methyl methacrylate of 50 to 92% by mass, a total content of structural units derived from α-methylstyrene of 35 to 7% by mass, and a total content of structural units derived from maleic anhydride of 1 to 20% by mass. From the viewpoints of polymerizability, transparency, etc., the total content of structural units derived from methyl methacrylate in the precursor polymer is preferably 50 to 92% by mass, more preferably 55 to 91% by mass, and most preferably 60 to 90% by mass.

[0068] From the viewpoints of heat resistance, polymerizability, water absorption, etc., the total content of structural units derived from α-methylstyrene in the precursor polymer is preferably 7% by mass or more and 27% by mass or less, more preferably 8% by mass or more and 25% by mass or less. If the structural units derived from α-methylstyrene are less than this range, sufficient heat resistance cannot be obtained, and if they are more than this range, polymerizability is significantly reduced.

[0069] From the viewpoints of heat resistance, polymerizability, thermal stability, etc., the total content of structural units derived from maleic anhydride in the precursor polymer is preferably 1% by mass or more and 18% by mass or less, more preferably 2% by mass or more and 15% by mass or less. If the amount of structural units derived from maleic anhydride is less than this range, sufficient heat resistance cannot be obtained, and if it is more than this range, significant yellowing occurs.

[0070] The precursor polymer preferably has a polystyrene-equivalent weight-average molecular weight (Mw) of 30,000 to 200,000, more preferably 40,000 to 180,000, and even more preferably 50,000 to 160,000, in a chromatogram obtained by gel permeation chromatography. If the weight-average molecular weight (Mw) is lower than this range, the resulting molded article will be brittle, while if it is higher than this range, productivity will be reduced. Mw can be controlled by adjusting the type, amount, and timing of addition of the polymerization initiator and chain transfer agent (optional components) used in producing the precursor polymer.

[0071] The ring structure-forming reaction can be carried out using, for example, an extruder. Examples of extruders include single-screw extruders, twin-screw extruders, and multi-screw extruders. From the viewpoint of mixing performance, twin-screw extruders are preferred. Twin-screw extruders include non-intermeshing co-rotating extruders, intermeshing co-rotating extruders, non-intermeshing counter-rotating extruders, and intermeshing counter-rotating extruders. Intermeshing co-rotating extruders are preferred because they are capable of high-speed rotation and can efficiently promote mixing. These extruders may be used alone or connected in series.

[0072] In the ring structure forming reaction using an extruder, for example, a precursor polymer as a raw material is introduced into the raw material inlet of the extruder, the precursor polymer is melted, and the cylinder is filled with the precursor polymer. Then, an imidizing agent (optional component) and the like are injected into the extruder using an addition pump, thereby allowing the ring structure forming reaction to proceed in the extruder. When an imidizing agent is used, the structural unit (R) contains an N-substituted or unsubstituted glutarimide unit and an N-substituted or unsubstituted maleimide unit, and may contain a lactone ring unit and / or a glutaric anhydride unit as necessary. When an imidizing agent is not used, the structural unit (R) is composed of a lactone ring unit and / or a glutaric anhydride unit. A preferred imidizing agent is R 4 -NH2(R 4is as defined above). The imidizing agent is used in an amount of 1.6 to 30 parts by mass, preferably 2.0 to 12 parts by mass, per 100 parts by mass of the methacrylic copolymer. When the amount of the imidizing agent used is within the above range, the by-production of methacrylic acid amide units can be suppressed.

[0073] The resin temperature in the reaction zone of the extruder is preferably in the range of 180 to 280°C, and more preferably in the range of 200 to 280°C. If the resin temperature in the reaction zone is below 180°C, the heat resistance of the methacrylic copolymer tends to decrease due to a decrease in the reaction efficiency of the ring structure-forming reaction and the by-production of methacrylic acid amide units. If the resin temperature in the reaction zone exceeds 280°C, the resin decomposition becomes significant, and the mechanical strength, such as the tensile break strength, of the resulting molded article made of the methacrylic copolymer, and films including optical films, laminates, etc., tends to decrease. The reaction zone in the extruder refers to the region from the injection position of the imidizing agent, etc., in the extruder cylinder to the resin discharge port (die section).

[0074] By extending the reaction time in the reaction zone of the extruder, the ring structure-forming reaction can be promoted. The reaction time in the reaction zone of the extruder is preferably longer than 10 seconds, and more preferably longer than 30 seconds. If the reaction time is shorter than 10 seconds, the ring structure-forming reaction may hardly proceed.

[0075] The resin pressure in the extruder is preferably in the range of atmospheric pressure to 50 MPa, and more preferably in the range of 1 to 30 MPa. If it is 50 MPa or higher, it exceeds the limit of the mechanical pressure resistance of a normal extruder, and special equipment will be required, which is not preferable from the viewpoint of cost.

[0076] It is preferable to use an extruder having a vent hole that can reduce the pressure to below atmospheric pressure. With such a configuration, unreacted materials, by-products such as methanol, and monomers can be removed, and the heat resistance of a molded article containing the methacrylic copolymer of the present invention tends to be improved.

[0077] For the ring structure-forming reaction, a reaction apparatus suitable for high viscosity, such as a horizontal twin-screw reaction apparatus like Bivolac manufactured by Sumitomo Heavy Industries, Ltd. or a vertical twin-screw stirring tank like Superblend, can be suitably used instead of an extruder.

[0078] During the ring structure-forming reaction, carboxyl groups may be by-produced in the methacrylic copolymer. These carboxyl groups may be converted to ester groups using an esterifying agent or catalyst, as necessary. This reduces resin foaming during the production of optical films. While the ester groups vary depending on the esterifying agent and catalyst used, they preferably contain methyl methacrylate units from the viewpoints of reducing the resin melt viscosity during melt molding, the reactivity of esterification, and the heat resistance of the resin after esterification. Dimethyl carbonate is a preferred esterifying agent from the viewpoints of cost, reactivity, etc.

[0079] The amount of the esterifying agent added can be set, for example, so that the acid value of the methacrylic copolymer becomes a desired value.

[0080] In addition to the esterifying agent, a catalyst can also be used in combination. The type of catalyst is not particularly limited, but examples thereof include amine compounds such as trimethylamine, triethylamine, monomethyldiethylamine, dimethylmonoethylamine, and dimethylbenzylamine. Among these, triethylamine is preferred from the viewpoints of cost, reactivity, etc.

[0081] (Methacrylic copolymer composition) The methacrylic copolymer composition of the present invention may contain other polymers as long as the effects of the present invention are not impaired. Examples of other polymers include polyolefin resins such as polyethylene, polypropylene, polybutene-1, poly-4-methylpentene-1, and polynorbornene; ethylene ionomers; styrene resins such as polystyrene, styrene-maleic anhydride copolymer, high-impact polystyrene, AS resin, ABS resin, AES resin, AAS resin, ACS resin, and MBS resin; methyl methacrylate-styrene copolymers; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polyamides such as nylon 6, nylon 66, and polyamide elastomers; polyvinyl chloride, polyvinylidene chloride, Examples of other polymers that can be contained in the resin composition of the present invention include polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyacetal, polyvinylidene fluoride, polyurethane, phenoxy resin, modified polyphenylene ether, polyphenylene sulfide, silicone-modified resin; silicone rubber; acrylic multilayer copolymer elastomer; acrylic thermoplastic elastomers such as diblock copolymers and triblock copolymers of methyl methacrylate polymer block-n-butyl acrylate polymer block; (hydrogenated) styrene thermoplastic elastomers such as SEPS, SEBS, and SIS; and olefin rubbers such as IR, EPR, and EPDM. The amount of other polymers that can be contained in the resin composition of the present invention is preferably 10% by mass or less, more preferably 5% by mass or less, and most preferably 0% by mass.

[0082] Additives commonly used in resin compositions may be included within the scope of the present invention, provided that the objectives of the present invention are not impaired. Examples of additives include fillers, antioxidants, heat deterioration inhibitors, UV absorbers, light stabilizers, lubricants, mold release agents, polymer processing aids, antistatic agents, flame retardants, colorants, dyes, pigments, light diffusing agents, organic dyes, matting agents, impact resistance modifiers, and fluorescent materials. The total amount of such additives other than fillers is preferably 7% by mass or less, more preferably 5% by mass or less, and even more preferably 4% by mass or less.

[0083] Examples of the filler include calcium carbonate, talc, carbon black, titanium oxide, silica, clay, barium sulfate, magnesium carbonate, etc. The amount of the filler that can be contained in the methacrylic copolymer composition of the present invention is preferably 3% by mass or less, more preferably 1.5% by mass or less.

[0084] The antioxidant is effective in preventing oxidative degradation of the resin by itself in the presence of oxygen. Examples include phosphorus-based antioxidants, hindered phenol-based antioxidants, and thioether-based antioxidants. These antioxidants may be used alone or in combination of two or more.

[0085] The heat deterioration inhibitor can prevent the thermal deterioration of a resin by capturing polymer radicals that are generated when the resin is exposed to high heat in a substantially oxygen-free state. Suitable examples of the heat deterioration inhibitor include 2-tert-butyl-6-(3'-tert-butyl-5'-methyl-hydroxybenzyl)-4-methylphenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd.; trade name: Sumilizer GM), 2,4-di-tert-amyl-6-(3',5'-di-tert-amyl-2'-hydroxy-α-methylbenzyl)phenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd.; trade name: Sumilizer GS), 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol (manufactured by BASF; trade name: Irganox 565), and tetrakis[methylene-3-(dodecylthio)propionate]methane (manufactured by ADEKA; trade name: AO-412S).

[0086] An ultraviolet absorber is a compound that has the ability to absorb ultraviolet rays and is said to have the function of converting light energy into heat energy. Examples of ultraviolet absorbers include benzophenones, benzotriazoles, triazines, benzoates, salicylates, cyanoacrylates, oxalic anilides, malonic acid esters, and formamidines. These may be used alone or in combination of two or more. Among these, benzotriazoles, triazines, or compounds having a maximum molar absorption coefficient ε at a wavelength of 380 to 450 nm are preferred. max 1200dm 3 mol -1 cm -1 The following ultraviolet absorbers are preferred:

[0087] Light stabilizers are compounds that are said to have the function of capturing radicals generated mainly by oxidation due to light. Suitable light stabilizers include hindered amines such as compounds having a 2,2,6,6-tetraalkylpiperidine skeleton.

[0088] Examples of the lubricant include stearic acid, behenic acid, stearamidic acid, methylene bisstearamide, hydroxystearic acid triglyceride, paraffin wax, ketone wax, octyl alcohol, and hydrogenated oil.

[0089] Examples of the release agent include higher alcohols such as cetyl alcohol and stearyl alcohol; and higher fatty acid esters of glycerin such as stearic acid monoglyceride and stearic acid diglyceride. In the present invention, it is preferable to use a combination of a higher alcohol and a glycerin fatty acid monoester as the release agent. When a combination of a higher alcohol and a glycerin fatty acid monoester is used, the ratio thereof is not particularly limited, but the mass ratio of the amount of higher alcohol used to the amount of glycerin fatty acid monoester used is preferably 2.5:1 to 3.5:1, and more preferably 2.8:1 to 3.2:1.

[0090] Polymer processing aids typically use polymer particles (non-crosslinked rubber particles) with a particle size of 0.05 to 0.5 μm, which can be produced by emulsion polymerization. The polymer particles may be single-layer particles made of a polymer with a single composition ratio and a single intrinsic viscosity, or may be multi-layer particles made of two or more polymers with different composition ratios or intrinsic viscosities. Examples of the antistatic agent include alkyl sulfonates such as sodium heptyl sulfonate, sodium octyl sulfonate, sodium nonyl sulfonate, sodium decyl sulfonate, sodium dodecyl sulfonate, sodium cetyl sulfonate, sodium octadecyl sulfonate, sodium diheptyl sulfonate, potassium heptyl sulfonate, potassium octyl sulfonate, potassium nonyl sulfonate, potassium decyl sulfonate, potassium dodecyl sulfonate, potassium cetyl sulfonate, potassium octadecyl sulfonate, potassium diheptyl sulfonate, lithium heptyl sulfonate, lithium octyl sulfonate, lithium nonyl sulfonate, lithium decyl sulfonate, lithium dodecyl sulfonate, lithium cetyl sulfonate, lithium octadecyl sulfonate, and lithium diheptyl sulfonate. Examples of the flame retardant include metal hydrates having a hydroxyl group or crystal water, such as magnesium hydroxide, aluminum hydroxide, hydrated aluminum silicate, hydrated magnesium silicate, and hydrotalcite; phosphate compounds, such as polyamine phosphate and phosphate esters; and silicon compounds. Of these, preferred are phosphate ester-based flame retardants, such as trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, tripentyl phosphate, trihexyl phosphate, tricyclohexyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, dimethylethyl phosphate, methyldibutyl phosphate, ethyldipropyl phosphate, and hydroxyphenyldiphenyl phosphate. Examples of dyes and pigments include red organic pigments such as Para Red, Fire Red, Pyrazolone Red, Thioindiko Red, and Perylene Red; blue organic pigments such as Cyanine Blue and Indanthrene Blue; and green organic pigments such as Cyanine Green and Naphthol Green. One or more of these can be used.

[0091] As the organic dye, a compound having a function of converting ultraviolet light into visible light is preferably used. Examples of the light diffusing agent and the matting agent include glass particles, polysiloxane-based crosslinked particles, crosslinked polymer particles, talc, calcium carbonate, and barium sulfate. Examples of the fluorescent substance include fluorescent pigments, fluorescent dyes, fluorescent white dyes, fluorescent brighteners, and fluorescent bleaches.

[0092] The methacrylic copolymer composition of the present invention is not particularly limited by its production method, and can be produced, for example, by melt-kneading the methacrylic copolymer of the present invention with additives such as an ultraviolet absorber, and optionally other polymers. The melt-kneading can be carried out using a melt-kneading device such as a kneader-ruder, an extruder, a mixing roll, or a Banbury mixer. The temperature during kneading can be appropriately set depending on the softening temperatures of the methacrylic copolymer and other polymers, and can be set, for example, to 150 to 300°C. The shear rate during kneading can be set, for example, to 10 to 5,000 sec -1 can be set to.

[0093] The methacrylic copolymer composition of the present invention can be made into a form such as pellets in order to improve convenience in storage, transportation, or molding.

[0094] (Molded body) The molded article of the present invention comprises the methacrylic copolymer or methacrylic copolymer composition of the present invention. The method for producing the molded article of the present invention is not particularly limited. Examples include melt molding methods such as the T-die method (lamination method, coextrusion method, etc.), inflation method (coextrusion method, etc.), compression molding, blow molding, calendar molding, vacuum molding, and injection molding (insert method, two-color method, press method, core-back method, sandwich method, etc.), as well as solution casting. Among these, the T-die method, inflation method, and injection molding are preferred from the standpoints of productivity and cost. While there are no limitations on the type of molded article, films (flat molded articles with a thickness of 5 μm to 250 μm) and sheets (flat molded articles with a thickness of more than 250 μm) are preferred, with films being particularly preferred.

[0095] The film, which is one form of the molded article of the present invention, can be produced by a solution casting method, a melt casting method, an extrusion molding method, an inflation molding method, a blow molding method, or the like. Among these, the extrusion molding method is preferred from the viewpoint of being able to obtain a film that has excellent transparency, improved toughness, excellent handleability, and an excellent balance between toughness, surface hardness, and rigidity. The temperature of the molten resin discharged from the extruder is preferably set to 160 to 270°C, more preferably 220 to 260°C.

[0096] Among extrusion molding methods, the T-die method is preferred from the viewpoint of obtaining a film with good surface smoothness, good mirror gloss, and low haze. In this T-die method, the molten resin discharged from the T-die after passing through an extruder, a gear pump, a polymer filter, and a mixer is preferably sandwiched between two or more mirror-finished rolls or mirror-finished belts to be molded into a film. When sandwiching the resin between the mirror-finished rolls or mirror-finished belts, a bank may or may not be formed. The die has a function for automatically adjusting the lip opening, and the air gap is preferably 100 mm or less. The mirror-finished roll or mirror-finished belt is preferably made of metal. Examples of mirror-finished rolls include rigid metal rolls and elastic metal rolls. It is preferable to use a combination of a rigid metal roll and an elastic metal roll. The surface temperatures of both mirror-finished rolls or mirror-finished belts are preferably 130°C or lower. At least one of the pair of mirror-finished rolls or mirror-finished belts preferably has a surface temperature of 60°C or higher. Setting the surface temperature within this range allows the molten resin extruded from the extruder to be cooled at a rate faster than natural cooling, facilitating the production of a film with excellent surface smoothness and low haze. The linear pressure between the pair of rolls or belts is preferably 10 N / mm or higher, more preferably 30 N / mm or higher. The thickness of the unstretched film obtained by extrusion molding is preferably 10 to 300 μm. The haze of the film at a thickness of 100 μm is preferably 0.7% or lower, more preferably 0.5% or lower, and even more preferably 0.3% or lower.

[0097] The unstretched film obtained as described above may be subjected to a stretching treatment. Stretching treatment increases the mechanical strength, resulting in a film that is less susceptible to cracking. The stretching method is not particularly limited, and examples include simultaneous biaxial stretching, sequential biaxial stretching, and tubular stretching. From the viewpoint of obtaining a film that can be uniformly stretched and has high strength, the lower limit of the temperature during stretching is 10°C higher than the glass transition temperature of the methacrylic copolymer or methacrylic copolymer composition, and the upper limit of the temperature during stretching is 40°C higher than the glass transition temperature of the methacrylic copolymer or methacrylic copolymer composition. Stretching is usually performed at a rate of 100 to 5000% / min. After stretching, heat setting can be performed to obtain a film with little thermal shrinkage. The thickness of the stretched film is preferably 10 to 200 μm.

[0098] A functional layer may be provided on the surface of the film, which is one embodiment of the molded article of the present invention. Examples of the functional layer include a hard coat layer, an antiglare layer, an antireflection layer, an antisticking layer, a diffusion layer, an antiglare layer, an antistatic layer, an antifouling layer, and a slippery layer such as a layer containing fine particles.

[0099] It is also preferable to provide an undercoat layer on at least one side of the film of the present invention in order to improve the adhesion strength with the functional layer or to improve the adhesive strength when laminated with other films via an adhesive or pressure-sensitive adhesive.

[0100] The methacrylic copolymer or methacrylic copolymer composition of the present invention is suitable as a molding material. The molded article of the present invention can be made into components for various applications. Specific applications include, for example, signboard components and marking films such as advertising towers, stand signs, side signs, transom signs, and rooftop signs; display components such as showcases, partitions, and store displays; lighting components such as fluorescent light covers, mood lighting covers, lampshades, illuminated ceilings, illuminated walls, and chandeliers; interior components such as furniture, pendants, and mirrors; architectural components such as doors, domes, safety window glass, partitions, staircase slats, balcony slats, and roofs of leisure buildings; transportation-related components such as aircraft windshields, pilot visors, motorcycle and motorboat windshields, bus sunshades, automobile side visors, rear visors, head wings, headlight covers, automobile interior components, and automobile exterior components such as bumpers; audiovisual nameplates, stereo covers, and televisions. Examples of applications include electronic equipment parts such as Levi's protective masks, vending machines, mobile phones, and personal computers; medical equipment parts such as incubators and X-ray parts; equipment parts such as machine covers, instrument covers, laboratory equipment, rulers, dials, and observation windows; optical parts such as liquid crystal protection plates, light guide plates, light guide films, Fresnel lenses, lenticular lenses, front panels for various displays, and diffusers; transportation parts such as road signs, information boards, curved mirrors, and soundproof walls; and other products such as greenhouses, large aquariums, box-shaped aquariums, bathroom components, clock panels, bathtubs, sanitary products, desk mats, game parts, toys, musical instruments, face protection masks for welding, solar cell back sheets, front sheets for flexible solar cells, and decorative films.

[0101] A laminate can be obtained by laminating a layer containing the methacrylic copolymer or methacrylic copolymer composition of the present invention with another material (e.g., a layer containing another thermoplastic copolymer). Examples of other materials that can be used in the laminate include steel, plastic (e.g., thermoplastic resin), wood, and glass. The laminate obtained by the present invention can be suitably used for wallpaper, automobile interior surface, automobile exterior surface such as bumpers, mobile phone surface, furniture surface, personal computer surface, vending machine surface, bathroom surface such as bathtub, and the like.

[0102] The film, which is one embodiment of the molded article of the present invention, has high transparency and heat resistance and is therefore suitable for optical applications, and is particularly suitable for applications such as polarizer protective films, liquid crystal protective plates, surface materials for portable information terminals, display window protective films for portable information terminals, light-guiding films, transparent conductive films with silver nanowires or carbon nanotubes applied to their surfaces, and front panels for various displays. Because the film of the present invention has high transparency and heat resistance, it can also be used for applications other than optical applications, such as infrared-blocking films, security films, shatterproof films, decorative films, metal-decorated films, shrink films, and in-mold label films.

[0103] When a film, which is one form of the molded article of the present invention, is used as a polarizer protective film or a retardation film, it may be laminated on only one side or both sides of a polarizer film. When laminating with a polarizer film, it can be laminated via an adhesive layer or a pressure-sensitive adhesive layer. As the polarizer film, a stretched film made of a polyvinyl alcohol resin and iodine can be used, and its film thickness is preferably 1 to 100 μm. [Example]

[0104] The present invention will now be described in more detail with reference to examples, although the present invention is not limited to these examples.

[0105] Measurements of physical properties etc. were carried out by the following methods.

[0106] (polymerization conversion rate) A gas chromatograph GC-14A manufactured by Shimadzu Corporation was connected to an INERTCAP1 column manufactured by GL Sciences Inc. (df=0.4 μm, 0.25 mm I.D.×60 m), and analysis was performed under the following conditions, and calculations were made based on the results. injection temperature=250℃ detector temperature=250℃ Temperature conditions: Hold at 60°C for 5 minutes → Heat to 250°C at 10°C / min → Hold at 250°C for 10 minutes

[0107] (Weight average molecular weight) The weight-average molecular weight (Mw) of the resin obtained in the Production Examples was determined by GPC (gel permeation chromatography). A sample solution was prepared by dissolving 4 mg of the resin to be measured in 5 ml of tetrahydrofuran. The column oven temperature was set to 40°C, and 20 μl of the sample solution was injected into the instrument at an eluent flow rate of 0.35 ml / min. The chromatogram was measured. Ten standard polystyrenes with molecular weights ranging from 400 to 5,000,000 were measured by GPC, and a calibration curve showing the relationship between retention time and molecular weight was created. The Mw of the resin to be measured was determined based on this calibration curve. The value corresponding to the molecular weight of the standard polystyrene from the chromatogram measured by GPC was taken as the molecular weight of the copolymer. Apparatus: Tosoh GPC HLC-8320 Separation column: TSKguardcolumSuperHZ-H, TSKgelHZM-M, and TSKgelSuperHZ4000 manufactured by Tosoh Corporation connected in series Eluent: tetrahydrofuran Eluent flow rate: 0.35 ml / min Column temperature: 40℃ Detection method: Refractive index (RI)

[0108] (Composition of each unit in the copolymer) 13The carbon ratios of the phenyl group of the α-methylstyrene unit, the methoxy group of the methyl methacrylate unit, and the carbonyl group of the maleic anhydride unit were determined by C-NMR, and the composition of each unit was calculated from this. The carbon ratios of the cyano group bonded to the carbon at the α-position were determined for copolymers containing acrylonitrile units, and the phenyl group bonded to the carbon at the α-position was determined for copolymers containing styrene units, and the composition of each unit was calculated from this. The copolymer containing methyl acrylate units was 13 In addition to C-NMR, the composition of each unit was calculated by determining the methyl acrylate unit by pyrolysis gas chromatography.

[0109] (glass transition temperature; Tg) The resins obtained in the Production Examples, Examples, and Comparative Examples were dissolved in chloroform and reprecipitated with methanol, and the precipitated resins were then vacuum-dried at 80°C for at least 12 hours. The vacuum-dried resins were measured in accordance with JIS K7121 using a differential scanning calorimeter (Shimadzu Corporation, DSC-50 (product number)) by heating them once to 250°C, then cooling to room temperature, and then heating them from room temperature to 200°C at a rate of 10°C / min. The midpoint glass transition temperature determined from the DSC curve measured during the second heating run was defined as the glass transition temperature in the present invention.

[0110] (Imidization rate) 1 The copolymer was analyzed using H-NMR (Bruker; product name: ULTRA SHIELD 400 PLUS). 1 H-NMR measurement was performed, and the imidization rate (R) was calculated using the following formula from the area A of the peak at around 3.5 to 3.8 ppm derived from the O-CH3 group of methyl methacrylate and the area B of the peak at around 3.0 to 3.3 ppm derived from the N-CH3 groups of glutarimide and maleimide. Imidization rate (R) (%) = [B / (A+B)] x 100

[0111] (Amount of maleic anhydride in methacrylic copolymer) Using an infrared spectrophotometer, 1780 cm -1The absorption intensity of the peaks originating from the carbonyl of maleic anhydride in the vicinity of 1685 cm -1 The imidization rate of maleic anhydride (R m % by mole was calculated. 13 The amount of maleic anhydride (m; mass %) in the resins obtained in the Examples and Comparative Examples was calculated from the amount of maleic anhydride (m; mass %) in the Production Examples determined by C-NMR and the imidization rate using the following formula: Amount of maleic anhydride (M; mass %) in the resins obtained in the Examples and Comparative Examples: Amount of maleic anhydride (M) = m × (100 - R m ) / 100

[0112] (1% thermogravimetric reduction temperature) The resins obtained in the Production Examples, Examples, and Comparative Examples were dissolved in chloroform and reprecipitated with methanol, and the precipitated resins were then vacuum dried for 12 hours or more at 80° C. The vacuum-dried resins were heated at a rate of 10° C. / min in a nitrogen atmosphere using a thermogravimetric analyzer (Shimadzu Corporation, TGA-50), and the temperature at which a 1% weight loss occurred was recorded as the 1% thermal weight loss temperature (° C.).

[0113] (flexural modulus) The resins obtained in the Production Examples, Examples, and Comparative Examples were press-molded and then machined to obtain test pieces 4 mm thick, 80 mm long, and 10 mm wide. Each test piece was subjected to three-point bending at 23°C using an autograph (manufactured by Shimadzu Corporation) in accordance with the method described in JIS K7171, and the flexural modulus (MPa) was measured.

[0114] (saturated water absorption rate) The resins obtained in the examples and comparative examples were press-molded and then machined to obtain test pieces with a thickness of 1 mm and a side length of 50 mm. The test pieces were vacuum-dried for 24 hours at a temperature of 80°C and 5 mmHg. The test pieces were then allowed to cool in a desiccator. The test pieces were removed from the desiccator and their masses (initial masses) were immediately measured. The test pieces were then immersed in distilled water at 23°C. The test pieces were removed from the water, the water adhering to the surface was wiped off, and the masses were measured. Immersion in distilled water and mass measurements were repeated until no mass change occurred. The saturated water absorption (23°C) was calculated from the mass (absorbed mass) when no mass change occurred and the initial mass using the following formula: Saturated water absorption rate (23℃) (%) = [(absorbed mass - initial mass) / initial mass] × 100

[0115] (Surface hardness) The resins obtained in the examples and comparative examples were press-molded and then machined to obtain test pieces with a thickness of 3 mm and a side length of 50 mm. Using a moving-table pencil scratch tester (Model P) (manufactured by Toyo Seiki Co., Ltd.), a pencil lead was pressed against the surface of each test piece at an angle of 45 degrees and a load of 750 g to check for the presence or absence of scratches. The hardness of the pencil lead was gradually increased, and the hardness of the lead one level softer than the hardness at which scratches were observed was recorded as the pencil scratch hardness. 〇: Pencil hardness is 3H or higher ×: Pencil hardness is 2H or less

[0116] (Hot water resistance) The resins obtained in the examples and comparative examples were press-molded and then machined to obtain test pieces with a thickness of 1 mm and a side length of 50 mm. The test pieces were vacuum-dried for 24 hours at 80°C and 5 mmHg. The test pieces were then allowed to cool in a desiccator. The test pieces were removed from the desiccator and their masses (initial masses) were measured immediately. The test pieces were then immersed in distilled water at 80°C. The test pieces were removed from the water, the water adhering to the surface was wiped off, and the masses were measured. Immersion in distilled water and mass measurements were repeated until no change in mass was observed. The saturated water absorption (80°C) was calculated from the mass (absorbed mass) when no change in mass was observed and the initial mass using the following formula: Saturated water absorption rate (80℃) (%) = [(absorbed mass - initial mass) / initial mass] × 100 The warm water resistance was evaluated from the ratio of saturated water absorption (23°C) to saturated water absorption (80°C). ◎: Saturated water absorption rate (80℃) / Saturated water absorption rate (23℃) is less than 1.5 ○: Saturated water absorption (80℃) / Saturated water absorption (23℃) is 1.5 or more and less than 2 ×: Saturated water absorption (80°C) / Saturated water absorption (23°C) is 2 or more

[0117] (Moldability) Using an injection molding machine (M-100C, manufactured by Meiki Seisakusho Co., Ltd.), the acrylic resin compositions obtained in the Examples and Comparative Examples were injection molded under conditions of a cylinder temperature of 280°C, a mold temperature of 80°C, and a molding cycle of 2 minutes to produce flat plates measuring 200 mm in length, 60 mm in width, and 0.6 mm in thickness. The appearance of the flat plates was visually observed. The quality of moldability was judged based on the presence or absence of molding defects such as sink marks due to insufficient fluidity or silver spots due to insufficient thermal decomposition resistance. ◎: No sink marks on molded products and no silver spots ○: Slight sink marks or silver spots on the molded product ×: Sink marks or silver spots on molded products

[0118] <Examples of various materials> The precursor polymer (B) used was the material shown below. Precursor polymer (B): Denka Resify (Mw = 80,000, styrene / maleic anhydride / MMA = 56% / 18% / 26%, Tg = 134°C, 1% weight loss temperature = 340°C, flexural modulus = 3,590 MPa)

[0119] (Production example: precursor polymer) <Production Examples 1 to 8> The precursor polymers Aa to Ah were produced by the following method. The purified monomers, 2,2'-azobis(2-methylpropionitrile) (AIBN) and n-octyl mercaptan (n-OM) were charged in the proportions shown in Table 1 into an autoclave equipped with a stirrer and dissolved uniformly to obtain the polymerization raw materials. The polymerization raw materials were continuously fed from an autoclave at a rate of 1.5 kg / hr to a tank reactor controlled at the polymerization temperature listed in Table 1. The bulk polymerization reaction was carried out with an average residence time of 2 to 3 hours. A liquid containing a methacrylic copolymer was continuously discharged from the tank reactor. The polymerization conversion rate was as shown in Table 1. The liquid discharged from the reactor was then heated to 230°C and fed to a twin-screw extruder controlled at 240°C. Volatiles, primarily consisting of unreacted monomers, were separated and removed in the twin-screw extruder, and the methacrylic copolymer was extruded into strands. The strands were cut with a pelletizer to obtain a precursor polymer. The weight-average molecular weight (Mw), the proportion of each unit component, the glass transition temperature (Tg), the 1% weight loss temperature, and the flexural modulus of the resulting precursor polymer were measured. The results are shown in Table 1. The following abbreviations are used in Table 1: MMA: methyl methacrylate αMSt: α-methylstyrene Mah: Maleic anhydride MA: methyl acrylate St: styrene AN: Acrylonitrile

[0120] [Table 1]

[0121] Example 1 A twin-screw extruder (manufactured by The Japan Steel Works, Ltd.; trade name: TEX30α-77AW-3V) was used. The extruder consisted of a transport section, a melt-kneading section, a devolatilizing section, and a discharge section. The screw speed was set at 100 rpm and the temperature at 230°C. The precursor polymer [Aa] was fed at 10 kg / hr into the transport section. Monomethylamine was injected at 1.0 kg / hr into the melt-kneading section, which was equipped with a kneading block, through the extruder's additive supply port. The precursor polymer [Aa] and monomethylamine were reacted. The melt-kneading section consisted mostly of kneading disks, each equipped with a sealing element at both ends. In the devolatilizing section, which was set at 37 Torr (approximately 5 kPa), by-products and excess monomethylamine were volatilized from the molten resin that had passed through the melt-kneading section and discharged through multiple vents. The molten resin extruded as a strand from a die at the end of the twin-screw extruder's discharge section was cooled in a water bath and then cut with a pelletizer to obtain pellets of methacrylic copolymer [1]. The methacrylic copolymer [1] had an imidization rate (proportion of structural units (R)) of 17 wt% and a maleic anhydride (M) content of 0 wt%. The physical properties of the methacrylic copolymer (Aa) are shown in Table 2.

[0122] <Example 2> A methacrylic copolymer [2] was obtained in the same manner as in Example 1, except that the precursor polymer [Ab] was used instead of the precursor polymer [Aa]. The physical properties of the methacrylic copolymer [2] are shown in Table 2.

[0123] Example 3 A methacrylic copolymer [3] was obtained in the same manner as in Example 1, except that the precursor polymer [Ac] was used instead of the precursor polymer [Aa]. The physical properties of the methacrylic copolymer [3] are shown in Table 2.

[0124] Example 4 Except for adding monomethylamine at a rate of 2.0 kg / hr, a methacrylic copolymer [4] was obtained in the same manner as in Example 1. The physical properties of the methacrylic copolymer [4] are shown in Table 2.

[0125] <Example 5> A methacrylic copolymer [5] was obtained in the same manner as in Example 1, except that precursor polymer [Ab] was used instead of precursor polymer [Aa] and monomethylamine was added at a rate of 2.6 kg / hr. The physical properties of the methacrylic copolymer [5] are shown in Table 2.

[0126] Example 6 A methacrylic copolymer [6] was obtained in the same manner as in Example 1, except that the precursor polymer [Ad] was used instead of the precursor polymer [Aa] and the monomethylamine was added at a rate of 0.7 kg / hr. The physical properties of the methacrylic copolymer [6] are shown in Table 2.

[0127] Example 7 A methacrylic copolymer [7] was obtained in the same manner as in Example 1, except that the precursor polymer [Ae] was used instead of the precursor polymer [Aa]. The physical properties of the methacrylic copolymer [7] are shown in Table 2.

[0128] Example 8 A methacrylic copolymer [8] was obtained in the same manner as in Example 1, except that precursor polymer [Ae] was used instead of precursor polymer [Aa] and monomethylamine was added at a rate of 2.7 kg / hr. The physical properties of the methacrylic copolymer [8] are shown in Table 2.

[0129] Example 9 A methacrylic copolymer [9] was obtained in the same manner as in Example 1, except that precursor polymer [Af] was used instead of precursor polymer [Aa] and monomethylamine was added at a rate of 2.8 kg / hr. The physical properties of the methacrylic copolymer [9] are shown in Table 2.

[0130] Example 10 A methacrylic copolymer

[10] was obtained in the same manner as in Example 1, except that precursor polymer [Ag] was used instead of precursor polymer [Aa] and monomethylamine was added at a rate of 2.9 kg / hr. The physical properties of the methacrylic copolymer

[10] are shown in Table 2.

[0131] [Table 2]

[0132] <Comparative Example 1> A methacrylic copolymer

[11] was obtained in the same manner as in Example 1, except that precursor polymer [Ah] was used instead of precursor polymer [Aa] and monomethylamine was added at a rate of 0.5 kg / hr. The physical properties of the methacrylic copolymer

[11] are shown in Table 3.

[0133] <Comparative Example 2> A methacrylic copolymer

[12] was obtained in the same manner as in Example 1, except that precursor polymer [Ag] was used instead of precursor polymer [Aa] and monomethylamine was added at a rate of 0.5 kg / hr. The physical properties of the methacrylic copolymer

[12] are shown in Table 3.

[0134] <Comparative Example 3> A methacrylic copolymer

[13] was obtained in the same manner as in Example 1, except that precursor polymer [Ab] was used instead of precursor polymer [Aa] and monomethylamine was added at a rate of 0.1 kg / hr. The physical properties of the methacrylic copolymer

[13] are shown in Table 3.

[0135] <Comparative Example 4> A methacrylic copolymer

[14] was obtained in the same manner as in Example 1, except that precursor polymer [Ab] was used instead of precursor polymer [Aa] and monomethylamine was added at a rate of 3.8 kg / hr. The physical properties of the methacrylic copolymer

[14] are shown in Table 3.

[0136] <Comparative Example 5> A methacrylic copolymer

[15] was obtained in the same manner as in Example 1, except that precursor polymer [B] was used instead of precursor polymer [Aa] and monomethylamine was added at a rate of 0.3 kg / hr. The physical properties of the methacrylic copolymer

[15] are shown in Table 3.

[0137] [Table 3]

[0138] The methacrylic copolymers obtained in Examples 1 to 10 have high heat resistance, rigidity, and thermal decomposition resistance, and also have excellent surface hardness, hot water resistance, and moldability, making them suitable for use as molding materials and optical components such as polarizer protective films. On the other hand, the methacrylic copolymers obtained in Comparative Examples 1 to 5 are outside the scope of the present invention and are therefore inferior to the copolymers of the present invention in any of the following aspects: poor thermal decomposition resistance, excessively high saturated water absorption, or poor hot water resistance and moldability.

Claims

1. A polarizer protective film containing a methacrylic copolymer having 15 to 83 mass% of methyl methacrylate units, 7 to 35 mass% of α-methylstyrene units, 10 to 65 mass% of N-substituted glutarimide units (R) represented by formula (I), and 0 to 20 mass% of other vinyl monomer units (C) copolymerizable with methyl methacrylate, wherein the methacrylic copolymer contains 0 mass% of maleic anhydride units (M). 【Chemistry 1】 (In formula (I), R １ are each independently a hydrogen atom or a methyl group, and R ２ is an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an organic group having 6 to 15 carbon atoms and containing an aromatic ring.

2. 2. The polarizer protective film according to claim 1, wherein the other vinyl-based monomer unit (C) copolymerizable with the methyl methacrylate unit is formed from at least one selected from the group consisting of an acrylic acid ester monomer, an aromatic vinyl monomer, and a vinyl cyanide monomer.

3. 3. The polarizer protective film according to claim 1, wherein the other vinyl-based monomer unit (C) copolymerizable with the methyl methacrylate unit is formed from at least one selected from the group consisting of methyl acrylate, ethyl acrylate, styrene, and acrylonitrile.

4. 4. The polarizer protective film according to claim 1, wherein the methacrylic copolymer has a glass transition temperature of 140° C. or higher.

5. A polarizer protective film comprising a methacrylic copolymer composition containing a methacrylic copolymer having 15 to 83 mass% of methyl methacrylate units, 7 to 35 mass% of α-methylstyrene units, 10 to 65 mass% of N-substituted glutarimide units (R) represented by formula (I), and 0 to 20 mass% of other vinyl monomer units (C) copolymerizable with methyl methacrylate, wherein the methacrylic copolymer contains 0 mass% of maleic anhydride units (M). 【Chemistry 2】 (In formula (I), R １ are each independently a hydrogen atom or a methyl group, and R ２ is an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an organic group having 6 to 15 carbon atoms and containing an aromatic ring.

6. A laminate comprising a layer made of the polarizer protective film according to any one of claims 1 to 5 and a layer containing another material.

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