Method for manufacturing acrylic resin, acrylic resin film, and acrylic resin molded product

Abstract

The present invention provides a method for manufacturing acrylic resins, acrylic resin films, and acrylic resin molded articles that exhibit excellent resistance to roll contamination and heat resistance during film formation. [Solution] The method for producing an acrylic resin molded article includes a step of melt-molding an acrylic resin using an extruder, the resin containing methyl methacrylate units and having one or more ring structures selected from the group consisting of glutarimide rings, lactone rings, maleic anhydride rings, glutaric acid anhydride rings, and maleimide rings in its main chain. If the content of methyl methacrylate dimers in the acrylic resin and the content of methyl methacrylate dimers in the acrylic resin molded article are A [ppm by weight] and B [ppm by weight], respectively, then the formula [(AB) / A] × 100 The reduction rate of methyl methacrylate dimers calculated by this method is 50% or more.

Description

[Technical Field]

[0001] The present invention relates to a method for producing acrylic resin, acrylic resin film, and acrylic resin molded articles. [Background technology]

[0002] Acrylic resin is used in optical films such as polarizer protective films and phase difference films because of its excellent transparency, color tone, appearance, heat resistance, and processability.

[0003] Patent Document 1 describes a method for producing a methacrylic copolymer, comprising the steps of continuously supplying a raw material liquid to a tank reactor, obtaining a reaction product by bulk polymerization in the tank reactor, and continuously withdrawing the reaction product from the tank reactor to remove volatile components from the reaction product. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2019 / 093385 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in recent years, with the improvement of optical film performance, there has been a growing demand for higher quality optical films. On the other hand, when methacrylic copolymers described in Patent Document 1 are manufactured by the melt extrusion method, the cast rolls may become contaminated. This is presumed to be because when methacrylic copolymers are produced by bulk polymerization, low molecular weight components such as methyl methacrylate dimers are generated, and these low molecular weight components bleed out during film formation.

[0006] The present invention aims to provide a method for producing acrylic resin, acrylic resin film, and acrylic resin molded articles that exhibit excellent resistance to roll contamination and heat resistance during film formation. [Means for solving the problem]

[0007] (1) A method for producing an acrylic resin molded article, comprising the step of melt-molding an acrylic resin using an extruder, wherein the acrylic resin contains methyl methacrylate units and has one or more ring structures selected from the group consisting of a glutarimide ring, a lactone ring, a maleic anhydride ring, a glutaric acid anhydride ring, and a maleimide ring in its main chain, and the content of methyl methacrylate dimers in the acrylic resin and the content of methyl methacrylate dimers in the acrylic resin molded article are A [ppm by weight] and B [ppm by weight], respectively, and the formula [(AB) / A] × 100 A method for producing an acrylic resin molded article, wherein the reduction rate of methyl methacrylate dimers calculated by the method is 50% or more.

[0008] (2) A method for producing an acrylic resin molded article, comprising the step of melt-molding an acrylic resin containing methyl methacrylate units and having a glass transition temperature of 120°C or higher using an extruder, wherein the content of methyl methacrylate dimers in the acrylic resin and the content of methyl methacrylate dimers in the acrylic resin molded article are A [ppm by weight] and B [ppm by weight], respectively, and the formula [(AB) / A] × 100 A method for producing an acrylic resin molded article, wherein the reduction rate of methyl methacrylate dimers calculated by the method is 50% or more.

[0009] (3) The method for manufacturing an acrylic resin molded article according to (1) or (2), wherein the acrylic resin molded article is a pellet or a film.

[0010] (4) The method for producing an acrylic resin molded article according to any one of (1) to (3), wherein the acrylic resin has a molecular weight dispersion (Mw / Mn) of 1.60 or more.

[0011] (5) The method for producing an acrylic resin molded article according to any one of (1) to (4), wherein the acrylic resin molded article has a methyl methacrylate dimer content of less than 200 ppm by weight.

[0012] (6) A method for producing an acrylic resin molded article according to any one of (1) to (5), wherein a 2 cm square test piece cut from a 160 μm thick film made by molding the acrylic resin molded article is placed in a glass petri dish with a diameter of 4 cm and a height of 1 cm, and a glass plate covered on its entire surface with aluminum foil is placed over the glass petri dish, and the mixture is heated at 285°C for 1 hour, and the relative fluorescence emission intensity of the volatile substances transferred to the surface of the aluminum foil is less than 2000 RFU.

[0013] (7) A method for producing an acrylic resin molded article according to any one of (1) to (6), further comprising the steps of polymerizing methyl methacrylate in a solvent or dispersion medium to obtain a polymer, and reacting the polymer to obtain the acrylic resin.

[0014] (8) A method for producing an acrylic resin molded article according to (7), wherein the methyl methacrylate is polymerized by solution polymerization, suspension polymerization, or emulsion polymerization.

[0015] (9) An acrylic resin containing methyl methacrylate units, having one or more ring structures selected from the group consisting of glutarimide rings, lactone rings, maleic anhydride rings, glutaric acid anhydride rings, and maleimide rings in its main chain, and having a methyl methacrylate dimer content of less than 200 ppm by weight.

[0016] (10) The acrylic resin according to (9), wherein a 2 cm square test piece cut from a 160 μm thick film formed by molding the acrylic resin is placed in a glass petri dish with a diameter of 4 cm and a height of 1 cm, and a glass plate covered with aluminum foil is placed over the glass petri dish, and the mixture is heated at 285°C for 1 hour, and the relative fluorescence emission intensity of the volatile substances transferred to the surface of the aluminum foil is less than 2000 RFU.

[0017] The acrylic resin according to (9) or (10), having a molecular weight distribution (Mw / Mn) of 1.60 or more.

[0018] (12) An acrylic resin film containing a resin including a methyl methacrylate unit and containing one or more ring structures selected from the group consisting of a glutarimide ring, a lactone ring, a maleic anhydride ring, a glutaric anhydride ring, and a maleimide ring in the main chain, and having a content of methyl methacrylate dimer of less than 200 ppm by weight.

[0019] (13) The acrylic resin film according to (12), having an internal haze of 0.30% or less.

[0020] (14) The acrylic resin film according to (12) or (13), which is a polarizer protection film.

[0021] (15) An acrylic resin including a methyl methacrylate unit, having a glass transition temperature of 120°C or more, and having a content of methyl methacrylate dimer of less than 200 ppm by weight.

[0022] (16) An acrylic resin film containing a resin including a methyl methacrylate unit and having a glass transition temperature of 120°C or more, and having a content of methyl methacrylate dimer of less than 200 ppm by weight.

[0023] (17) The acrylic resin film according to (16), having a water contact angle at 23°C of less than 70°.

Advantages of the Invention

[0024] According to the present invention, it is possible to provide a method for producing an acrylic resin, an acrylic resin film, and an acrylic resin molded body, which are excellent in roll contamination resistance and heat resistance during film formation.

Modes for Carrying Out the Invention

[0025] Hereinafter, embodiments of the present invention will be described.

[0026] (First form of acrylic resin) The acrylic resin of this embodiment contains methyl methacrylate units and includes one or more ring structures selected from the group consisting of glutarimide rings, lactone rings, maleic anhydride rings, glutaric acid anhydride rings, and maleimide rings in its main chain. As a result, the heat resistance of the acrylic resin of this embodiment is enhanced.

[0027] In this specification and in the claims, acrylic resin means a resin that contains methyl methacrylate units and may also contain other constituent units. The constituent units other than methyl methacrylate units are not particularly limited, but include, for example, alkyl (meth)acrylate units other than methyl methacrylate units; aromatic vinyl units such as styrene units and methylstyrene units; (meth)acrylonitrile units; and constituent units including ring structures, as described later.

[0028] The methyl methacrylate dimer content in the acrylic resin of this embodiment is less than 200 ppm by weight, and preferably less than 150 ppm by weight. Because the methyl methacrylate dimer content in the acrylic resin of this embodiment is less than 200 ppm by weight, the roll contamination resistance and heat resistance during film formation of the acrylic resin of this embodiment are improved. Here, it is presumed that the roll contamination resistance during film formation of the acrylic resin of this embodiment is improved because the amount of methyl methacrylate dimer bleed-out is reduced even when the acrylic resin of this embodiment is formed by the melt extrusion film formation method.

[0029] Furthermore, in order to suppress the formation of methyl methacrylate dimers when synthesizing the acrylic resin of this embodiment, it is necessary to reduce the frequency of contact between radicals when polymerizing methyl methacrylate. In polymerization methods using solvents or dispersion media such as suspension polymerization, emulsion polymerization, and solution polymerization, the concentration of monomers in the polymerization system is low, so the frequency of contact between radicals decreases, and the generation of dimers tends to be suppressed. Moreover, in aqueous polymerization methods using dispersants or surfactants such as suspension polymerization and emulsion polymerization, radicals are generated in the aqueous phase or at the interface with the aqueous phase, and monomers are present in the particles or droplets, so the frequency of contact between radicals decreases even further, and the generation of dimers tends to be suppressed.

[0030] Furthermore, in order to suppress the formation of methyl methacrylate dimers when synthesizing the acrylic resin of this embodiment, it is necessary to control the polymerization temperature to a low level when polymerizing methyl methacrylate, from the viewpoint of suppressing the rapid generation of radicals. Here, in polymerization methods that use solvents or dispersion media, such as suspension polymerization, emulsion polymerization, and solution polymerization, the solvent or dispersion media absorbs the heat of polymerization, and the increase in viscosity of the polymerization system is small, so it is not necessary to raise the polymerization temperature in order to maintain the polymerization rate. On the other hand, in polymerization methods that do not use solvents or dispersion media, such as bulk polymerization, the concentration of monomers in the polymerization system is high, so the viscosity tends to increase rapidly as polymerization progresses, hindering the diffusion of radicals, and therefore it is necessary to raise the polymerization temperature in order to maintain the polymerization rate. These factors are presumed to affect the formation of methyl methacrylate dimers. In addition, in continuous bulk polymerization, unreacted monomers are heated and recovered after the polymer is synthesized, which is a factor that increases the formation of methyl methacrylate dimers.

[0031] There are no particular limitations on the method for polymerizing methyl methacrylate, but examples include solution polymerization, suspension polymerization, and emulsion polymerization. Among these, suspension polymerization and emulsion polymerization are preferred because they allow the polymerization temperature to be kept low by using water, which has high heat removal efficiency, and because the presence of monomers in the particles or droplets reduces the frequency of contact between radicals.

[0032] A 2cm square test piece cut from a 160μm thick film formed from the acrylic resin of this embodiment is placed in a glass petri dish with a diameter of 4cm and a height of 1cm. A glass plate completely covered with aluminum foil is placed over the glass petri dish, and the sample is heated at 285°C for 1 hour. The relative fluorescence emission intensity of the volatile substances transferred to the surface of the aluminum foil is preferably less than 2000 RFU, and more preferably less than 1500 RFU. A relative fluorescence emission intensity of less than 2000 RFU of the volatile substances improves the roll contamination resistance of the acrylic resin during film formation in this embodiment. The relative fluorescence emission intensity of the volatile substances is, for example, 500 RFU or more.

[0033] The molecular weight dispersibility (Mw / Mn) of the acrylic resin in this embodiment is preferably 1.60 or higher, more preferably 1.70 or higher, even more preferably 1.80 or higher, and even more preferably greater than 1.80. When the molecular weight dispersibility of the acrylic resin in this embodiment is 1.60 or higher, the roll stain resistance during film formation of the acrylic resin in this embodiment is improved. For example, the molecular weight dispersibility (Mw / Mn) of the acrylic resin in this embodiment is 2.00 or lower. Furthermore, the weight-average molecular weight (Mw) of the acrylic resin in this embodiment is not particularly limited, but for example, it is 50,000 or more and 200,000 or less.

[0034] In this embodiment, the methyl methacrylate dimer content in the acrylic resin is D1 [ppm by weight], and the shear rate is 24 s. -1 If D2 [ppm by weight] is the content of methyl methacrylate dimer after heating the acrylic resin of this embodiment for 1 hour at the temperature at which the melt viscosity of the acrylic resin of this embodiment becomes 7000 Poise, then the formula D2 - D1 ≤ 1000 It is preferable that the following conditions be met: D2 - D1 ≤ 500 It is more preferable that the following conditions are met. If (D2-D1) is 1000 or less, the roll contamination resistance of the acrylic resin during film formation in this embodiment will be improved. Note that (D2-D1) is, for example, 100 or more.

[0035] The glass transition temperature of the acrylic resin in this embodiment is preferably 120°C or higher, more preferably greater than 120°C, even more preferably 121°C or higher, and even more preferably 122°C or higher. When the glass transition temperature of the acrylic resin in this embodiment is 120°C or higher, the heat resistance of the acrylic resin film is increased. Furthermore, the glass transition temperature of the acrylic resin in this embodiment is preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 145°C or lower.

[0036] The following describes acrylic resins containing a glutarimide ring or lactone ring in their main chain.

[0037] Acrylic resins containing a glutarimide ring as the main chain include, for example, a constituent unit represented by the following formula (1) and a methyl methacrylate unit.

[0038] [ka] (In the formula, R 1 and R 2 Each is independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R 3 (This is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or a cycloalkyl group having 3 to 12 carbon atoms.)

[0039] Acrylic resins containing the constituent units represented by formula (1) and methyl methacrylate units can be manufactured using known methods. An example of a method for manufacturing acrylic resins containing the constituent units represented by formula (1) and methyl methacrylate units is described below.

[0040] First, methyl methacrylate is homopolymerized to obtain polymethyl methacrylate. Next, using a twin-screw extruder equipped with a die at the outlet, the polymethyl methacrylate is melted, imidized, and the strand is extruded from the die. Next, the strand is cooled in a water bath, and then pelletized using a pelletizer to obtain imidized polymethyl methacrylate. Next, using a twin-screw extruder equipped with a die at the outlet, the imidized polymethyl methacrylate is melted, esterified, and the strand is extruded from the die. Next, the strand is cooled in a water bath, and then pelletized using a pelletizer to obtain an acrylic resin containing constituent units represented by formula (1) and methyl methacrylate units.

[0041] The imidizing agent used when imidizing polymethyl methacrylate is not particularly limited, but examples include ammonia and primary amines represented by the following formula (2). Among these, ammonia and monomethylamine are preferred. In this case, the imidization rate of polymethyl methacrylate is not particularly limited, but can be appropriately set according to the glass transition temperature of the acrylic resin.

[0042] R 3 NH2(2) (In the formula, R 3 This is equivalent to equation (1).

[0043] Examples of esterifying agents used when esterifying imidized polymethyl methacrylate include dimethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, diphenyl carbonate, dimethyl sulfate, methyltoluenesulfonate, methyltrifluoromethylsulfonate, methyl acetate, methanol, ethanol, methyl isocyanate, p-chlorophenyl isocyanate, and dimethylcarbodiimide. Examples include dimethyl-t-butylsilyl chloride, isopropenyl acetate, dimethylurea, tetramethylammonium hydroxide, dimethyldiethoxysilane, tetra-n-butoxysilane, dimethyl(trimethylsilane) phosphite, trimethyl phosphite, trimethyl phosphate, tricresyl phosphate, diazomethane, ethylene oxide, propylene oxide, cyclohexene oxide, 2-ethylhexylglycidyl ether, phenylglycidyl ether, and benzylglycidyl ether. Among these, dimethyl carbonate is preferred.

[0044] Acrylic resins containing a lactone ring in the main chain can be obtained, for example, by copolymerizing a monomer represented by the following formula (3) with methyl methacrylate, and then heat-treating the copolymer to form a lactone ring.

[0045] [ka] (In the formula, R 4 and R 5 Each of these is independently either a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

[0046] Examples of monomers represented by formula (3) include methyl 2-(hydroxymethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, isopropyl 2-(hydroxymethyl)acrylate, n-butyl 2-(hydroxymethyl)acrylate, and t-butyl 2-(hydroxymethyl)acrylate, and two or more may be used in combination. Among these, methyl 2-(hydroxymethyl)acrylate and ethyl 2-(hydroxymethyl)acrylate are preferred, and methyl 2-(hydroxymethyl)acrylate is particularly preferred.

[0047] The copolymerization method for the monomer represented by formula (3) and methyl methacrylate is not particularly limited, as long as it is possible to keep the content of methyl methacrylate dimer in the acrylic resin below 200 ppm by weight. Examples include suspension polymerization and emulsion polymerization.

[0048] Furthermore, as acrylic resins containing ring structures other than glutarimide rings and lactone rings in the main chain, known acrylic resins used in acrylic resin films can be used.

[0049] The content of structural units containing one or more ring structures selected from the group consisting of glutarimide rings, lactone rings, maleic anhydride rings, glutaric acid anhydride rings, and maleimide rings in the acrylic resin is preferably 1% by weight or more and 70% by weight or less, more preferably 2% by weight or more and 50% by weight or less, and even more preferably 4% by weight or more and 30% by weight or less. When the content of structural units containing one or more ring structures selected from the group consisting of glutarimide rings, lactone rings, maleic anhydride rings, glutaric acid anhydride rings, and maleimide rings in the acrylic resin is 2% by weight or more, the heat resistance of the acrylic resin film is increased, and when it is 50% by weight or less, the processability of the acrylic resin film is increased.

[0050] (First aspect of acrylic resin film) The acrylic resin film of this embodiment contains methyl methacrylate units and a resin whose main chain contains one or more ring structures selected from the group consisting of glutarimide rings, lactone rings, maleic anhydride rings, glutaric acid anhydride rings, and maleimide rings. As a result, the heat resistance of the acrylic resin film of this embodiment is increased.

[0051] The methyl methacrylate dimer content in the acrylic resin film of this embodiment is less than 200 ppm by weight, and preferably less than 100 ppm by weight. Because the methyl methacrylate dimer content in the acrylic resin film of this embodiment is less than 200 ppm by weight, the roll contamination resistance and heat resistance of the acrylic resin film of this embodiment during film formation are improved.

[0052] The internal haze of the acrylic resin film in this embodiment is preferably 0.30% or less, and more preferably 0.25% or less. When the internal haze of the acrylic resin film in this embodiment is 0.30% or less, the optical properties of the acrylic resin film in this embodiment are improved. For example, the internal haze of the acrylic resin film in this embodiment is 0.10% or more. Furthermore, the haze of the acrylic resin film in this embodiment is not particularly limited, but for example, it is 0.10% or more and 0.35% or less.

[0053] The contact angle of the acrylic resin film of this embodiment with respect to water at 23°C is preferably less than 70°, more preferably 69° or less, and even more preferably 68° or less. When the contact angle of the acrylic resin film of this embodiment with respect to water at 23°C is less than 70°, good coatability can be obtained when applying a water-based coating agent such as an easy-to-use adhesive to the acrylic resin film of this embodiment. In addition, the roll stain resistance during film formation of the acrylic resin film of this embodiment tends to improve. These results are presumed to be due to the fact that the surface of an acrylic resin film containing acrylic resin produced by water polymerization tends to be hydrophilic, making it easily compatible with water-based coating agents, and also because hydrophobic methyl methacrylate dimers are less likely to migrate to the hydrophilic surface.

[0054] The number of foreign objects present in a 20cm square area of ​​the acrylic resin film of this embodiment is preferably less than 5, and more preferably less than 2. When the number of foreign objects present in a 20cm square area of ​​the acrylic resin film of this embodiment is less than 5, the optical properties of the acrylic resin film of this embodiment are improved. Here, the major axis of the foreign objects is 30 μm or more.

[0055] The glass transition temperature of the resin contained in the acrylic resin film of this embodiment is preferably 120°C or higher, more preferably greater than 120°C, even more preferably 121°C or higher, and even more preferably 122°C or higher. When the glass transition temperature of the resin contained in the acrylic resin film of this embodiment is 120°C or higher, the heat resistance of the acrylic resin film of this embodiment is increased. For example, the glass transition temperature of the resin contained in the acrylic resin of this embodiment is 130°C or lower.

[0056] The acrylic resin film of this embodiment is not particularly limited in its applications, but examples include optical films such as polarizer protective films and phase difference films.

[0057] (Method of manufacturing acrylic resin film) The acrylic resin film of this embodiment can be manufactured using known methods. An example of a method for manufacturing the acrylic resin film of this embodiment will be described below.

[0058] First, the acrylic resin of this embodiment is melted using an extruder equipped with a T-die at the outlet, then the sheet is extruded from the T-die and cooled with a cooling roll to obtain a raw film. Next, the raw film is biaxially stretched to obtain the acrylic resin film of this embodiment. At this time, the biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching.

[0059] The temperature at which the raw film is biaxially stretched is preferably (Tg+5)°C to (Tg+20)°C, more preferably (Tg+6)°C to (Tg+18)°C, and even more preferably (Tg+7)°C to (Tg+15)°C, when Tg is the glass transition temperature of the acrylic resin in this embodiment. The surface ratio at which the raw film is biaxially stretched is not particularly limited, but for example, it is between 2 and 10 times. The stretching speed at which the raw film is biaxially stretched is not particularly limited, but for example, it is between 1.1 times / min and 100 times / min. When the raw film is sequentially biaxially stretched, the stretching speed of the first stage and the stretching speed of the second stage may be the same or different. In sequential biaxial stretching, the first stage stretching is usually in the longitudinal direction (MD direction), and the second stage stretching is in the width direction (TD direction).

[0060] (Second aspect of acrylic resin) The acrylic resin in this embodiment contains methyl methacrylate units and has a glass transition temperature of 120°C or higher. Therefore, the heat resistance of the acrylic resin film is increased.

[0061] The glass transition temperature of the acrylic resin in this embodiment is 120°C or higher, but is preferably greater than 120°C, more preferably 121°C or higher, and even more preferably 122°C or higher. Furthermore, the glass transition temperature of the acrylic resin in this embodiment is preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 145°C or lower.

[0062] The methyl methacrylate dimer content in the acrylic resin of this embodiment is less than 200 ppm by weight, preferably less than 180 ppm by weight, more preferably 160 ppm by weight or less, even more preferably less than 150 ppm by weight, and even more preferably 100 ppm by weight or less. Because the methyl methacrylate dimer content in the acrylic resin of this embodiment is less than 200 ppm by weight, the roll stain resistance and heat resistance of the acrylic resin of this embodiment during film formation are improved.

[0063] Furthermore, the acrylic resin of this embodiment may also possess the characteristics of the first embodiment of the acrylic resin described above.

[0064] (Second aspect of acrylic resin film) The acrylic resin film of this embodiment contains methyl methacrylate units and a resin having a glass transition temperature of 120°C or higher. Therefore, the heat resistance of the acrylic resin film of this embodiment is enhanced.

[0065] The glass transition temperature of the resin contained in the acrylic resin film of this embodiment is 120°C or higher, but is preferably greater than 120°C, more preferably 121°C or higher, and even more preferably 122°C or higher. Furthermore, the glass transition temperature of the resin contained in the acrylic resin film of this embodiment is preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 145°C or lower.

[0066] The methyl methacrylate dimer content in the acrylic resin film of this embodiment is less than 200 ppm by weight, and preferably less than 150 ppm by weight. Because the methyl methacrylate dimer content in the acrylic resin film of this embodiment is less than 200 ppm by weight, the roll contamination resistance and heat resistance of the acrylic resin film of this embodiment during film formation are improved.

[0067] Furthermore, the acrylic resin film of this embodiment may also possess the characteristics of the first embodiment of the acrylic resin film described above.

[0068] (Method for manufacturing acrylic resin molded products) A first aspect of the method for producing an acrylic resin molded article of this embodiment includes a step of melt-molding an acrylic resin using an extruder, the acrylic resin containing methyl methacrylate units and having one or more ring structures selected from the group consisting of glutarimide rings, lactone rings, maleic anhydride rings, glutaric acid anhydride rings, and maleimide rings in its main chain. In this case, it is preferable to supply the acrylic resin to the extruder, but if the molded article is a pellet, the raw material resin for the acrylic resin (for example, a polymer described later) may be supplied to the extruder and the acrylic resin may be melt-molded, or the acrylic resin having a ring structure in its main chain (for example, beads) may be supplied to the extruder and melt-molded.

[0069] A second aspect of the method for producing an acrylic resin molded article according to this embodiment includes a step of melt-molding an acrylic resin containing methyl methacrylate units and having a glass transition temperature of 120°C or higher using an extruder.

[0070] If the content of methyl methacrylate dimer in the acrylic resin and the content of methyl methacrylate dimer in the molded acrylic resin are A [ppm by weight] and B [ppm by weight], respectively, then the formula [(AB) / A] × 100 The reduction rate of methyl methacrylate dimers calculated by this method is 50% or more, preferably 60% or more, more preferably 75% or more, even more preferably 80% or more, and even more preferably 90% or more. Because the reduction rate of methyl methacrylate dimers is 50% or more, the roll stain resistance of the acrylic resin molded article is improved.

[0071] The acrylic resin molded product is not particularly limited, but examples include pellets and films.

[0072] The molecular weight dispersibility (Mw / Mn) of the acrylic resin is preferably 1.60 or higher, more preferably 1.70 or higher, even more preferably 1.80 or higher, and even more preferably greater than 1.80. When the molecular weight dispersibility of the acrylic resin is 1.60 or higher, the roll contamination resistance during film formation of the acrylic resin molded product is improved. For example, the molecular weight dispersibility (Mw / Mn) of the acrylic resin is 2.00 or lower. The weight-average molecular weight (Mw) of the acrylic resin is not particularly limited, but for example, it is 50,000 to 200,000.

[0073] The content of methyl methacrylate dimer in the acrylic resin molded article is preferably less than 200 ppm by weight, and more preferably less than 150 ppm by weight. When the content of methyl methacrylate dimer in the acrylic resin molded article is less than 200 ppm by weight, the roll contamination resistance and heat resistance of the acrylic resin molded article during film formation are improved.

[0074] A 2cm square test piece cut from a 160μm thick film formed from an acrylic resin molded body is placed in a glass petri dish with a diameter of 4cm and a height of 1cm. A glass plate completely covered with aluminum foil is placed over the glass petri dish, and the test is heated at 285°C for 1 hour. The relative fluorescence emission intensity of the volatile substances transferred to the surface of the aluminum foil is preferably less than 2000 RFU, and more preferably less than 1500 RFU. A relative fluorescence emission intensity of less than 2000 RFU of the volatile substances improves the roll contamination resistance during film formation of the acrylic resin molded body. For example, the relative fluorescence emission intensity of the volatile substances is 500 RFU or higher.

[0075] The method for producing the acrylic resin molded article of this embodiment may further include the steps of polymerizing methyl methacrylate in a solvent or dispersion medium to obtain a polymer, and reacting the polymer to obtain the acrylic resin of this embodiment. The polymer is not particularly limited as long as it contains methyl methacrylate units, but examples include polymethyl methacrylate.

[0076] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and the above embodiments may be modified as appropriate within the scope of the spirit of the present invention. [Examples]

[0077] (polymerization rate) The polymerization conversion rate [%] was determined by the gravimetric method, based on the ratio of the solid content weight of the polymerization solution to the weight of the added monomer. The solid content weight of the polymerization solution was determined by drying it in an oven set to 150°C for 30 minutes.

[0078] (Glass transition temperature Tg) The glass transition temperature of the resin composition was measured using a differential scanning calorimetry system (DSC7000X, manufactured by Hitachi High-Tech Science). Specifically, the temperature was first raised from 40°C to 160°C at a heating rate of 10°C / min under a nitrogen flow rate of 40 mL / min, then cooled to 40°C, and then raised again from 40°C to 160°C at a heating rate of 10°C / min. Next, the glass transition temperature Tg (midpoint glass transition temperature) was read from the DSC curve measured during the second heating cycle. Here, the midpoint glass transition temperature is the temperature at the point where a line equidistant in the vertical axis direction from both the line obtained by extrapolating the baseline before the inflection point of the DSC curve to the higher temperature side, and the line obtained by extrapolating the baseline after the inflection point of the DSC curve to the lower temperature side, intersects with the stepwise change portion of the glass transition in the DSC curve.

[0079] (Content of methyl methacrylate (MMA) dimer) The MMA dimer content in acrylic resin or acrylic resin film was measured using a gas chromatograph GC2010 (Shimadzu Corporation) and a column RTX-1 (RESTEK) with a liquid phase thickness of 5 μm, a length of 30 μm, and an inner diameter of 0.5 mm, under the following measurement conditions. Measurement sample: 1g acrylic resin or acrylic resin film, 20g methylene chloride Evaporation chamber temperature: 200℃ Detector temperature: 270℃ Column oven temperature profile: 1) Hold at 35°C for 5 minutes. 2) Heat the temperature to 70°C at a rate of 5°C / minute. 3) Heat to 270°C at a heating rate of 20°C / min and maintain the temperature for 40 minutes. Gas flow rates: Helium (30 ml / min), Air (400 ml / min), Hydrogen (40 ml / min)

[0080] Furthermore, based on a pre-prepared calibration curve for MMA, the amount of MMA dimer was determined from the area of ​​the peak detected at the retention time corresponding to dimethyl 1-hexene-2,5-dicarboxylate in the gas chromatogram.

[0081] (Decrease rate of methyl methacrylate (MMA) dimers) If the content of methyl methacrylate dimer in acrylic resin and the content of methyl methacrylate dimer in acrylic resin molded product (film) are A [ppm by weight] and B [ppm by weight], respectively, then the formula [(AB) / A] × 100 The percentage decrease in methyl methacrylate dimer was calculated using this method.

[0082] (Weight-average molecular weight (Mw) and molecular weight dispersion (Mw / Mn)) Using a high-speed GPC instrument HLC-8420GPC (manufactured by Tosoh Corporation), the weight-average molecular weight (Mw) and molecular weight dispersion (Mw / Mn) of acrylic resin were calculated using the standard polystyrene equivalent method. Specifically, a sample solution prepared by dissolving 15 mg of acrylic resin in 10 mL of tetrahydrofuran was used, and the analysis was performed under the following conditions. Detector: RI detector Solvent: tetrahydrofuran Guard column: TSKguardcolumn SuperH-L Analysis columns: TSKgel SuperH5000, TSKgel SuperH4000, TSKgel SuperH3000, TSKgel SuperH2000 Measurement temperature: 40℃ Standard material: Standard polystyrene (manufactured by Tosoh Corporation)

[0083] (Total light transmittance) Using a haze meter NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), in accordance with JIS7361-1, the total light transmittance of the acrylic resin film was measured.

[0084] (Haze) Using a haze meter NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), in accordance with JIS7136:2000, the haze of the acrylic resin film was measured.

[0085] (Internal haze) Using a haze meter NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), in accordance with JIS7136:2000, the internal haze of the acrylic resin film was measured. Specifically, first, in order to cancel the influence of surface scattering of the acrylic resin film, glycerin was dropped on the front and back of the film, then sandwiched with a glass plate, and the haze was measured with the interface between the film and the glass plate filled with glycerin. Next, the haze of the glass plate measured in advance was subtracted to obtain the internal haze of the acrylic resin film.

[0086] (In-plane retardation Re and thickness-direction retardation Rth) After cutting out a 40 mm × 40 mm test piece from the acrylic resin film, using a retardation measuring device KOBRA-WR (manufactured by Oji Scientific Instruments Co., Ltd.), in an environment of temperature 23 ± 2°C and humidity 50 ± 5%, the in-plane retardation Re at a wavelength of 590 nm and an incident angle of 0° was measured. Next, using a digital indicator (manufactured by Mitutoyo), the thickness d of the test piece was measured, and using a precision Abbe refractometer NAR-3T (manufactured by Atago), the refractive index n was measured. Next, after obtaining the three-dimensional refractive indices nx, ny, and nz from the in-plane retardation Re and the retardation in the 40° tilt direction, the formula Rth = |(nx + ny) / 2 - nz| × d was used to calculate the thickness-direction retardation Rth.

[0087] (Content of structural unit containing glutarimide ring) Using a nuclear magnetic resonance apparatus AvanceIII (manufactured by BRUKER) with a proton resonance frequency of 400 MHz, for the acrylic resin 1The H-NMR spectrum was measured. Next, the acrylic resin 1 The molar ratio of methyl methacrylate units to constituent units containing glutarimide rings was determined from the peak area ratio of the 1H-NMR spectrum. This ratio was then converted to weight to calculate the content of constituent units containing glutarimide rings. In this case, the molar ratio was determined from the peak area derived from the O-CH3 proton of methyl methacrylate units around 3.5-3.8 ppm and the peak area derived from the N-CH3 proton of constituent units containing glutarimide rings around 3.0-3.3 ppm.

[0088] (Content of constituent units containing lactone rings) Using tetrahydrofuran as a good solvent and hexane as a poor solvent, the acrylic resin was reprecipitated and purified, then dried in a hot air oven at 75°C for 10 hours. The content of constituent units containing lactone rings was then determined according to the method described in

[0228] of Japanese Patent Application Publication No. 2021-42353.

[0089] (Roll stain resistance) Acrylic resin was supplied to a 15mm diameter, L / D=45 meshing type co-rotating twin-screw extruder KZW15TWIN-45MG (manufactured by Technovel), equipped with a T-die at the outlet. Acrylic resin film was continuously produced for 1 hour under the conditions of a feeder rotation speed of 65 rpm, a screw rotation speed of 300 rpm, and an extrusion temperature of 270°C. During this process, the sheet extruded from the T-die was cooled and wound via a cast roll set to 110°C to produce a film with a thickness of 100 μm. Before film production, the surface of the cast roll was wiped with a nonwoven fabric wiper impregnated with chloroform. After the acrylic resin film was produced, the contamination status of the cast roll surface was visually observed to evaluate the roll contamination resistance. The evaluation criteria for roll contamination resistance are as follows. A: If no white, hazy contamination is observed on the surface of the cast roll. B: If a white, hazy contamination is observed on the surface of the cast roll.

[0090] (Relative fluorescence emission intensity of volatile substances) A 2cm square test piece was cut from a 160μm thick acrylic resin film and placed in a glass petri dish with a diameter of 4cm and a height of 1cm. Next, a 5cm square glass plate, completely covered with aluminum foil, was placed over the glass petri dish. The petri dish was then placed on a hot plate set to 285°C and heated for 1 hour. After removing the glass plate, the relative fluorescence emission intensity of volatile substances transferred to the surface of the aluminum foil was measured using a metal surface cleanliness tester (CleanoSpecter) (manufactured by SITA). The metal surface cleanliness tester measures relative fluorescence emission intensity by irradiating with UV light and detecting the fluorescence emission of organic substances. The amount of organic substances transferred to the surface of the aluminum foil can be quantified by the magnitude of the emission intensity. Relative fluorescence emission intensity is expressed in units of RFU (Relative fluorescence units), and a lower RFU value means a smaller amount of transferred organic substances. The measurement range of the metal surface cleanliness tester is 0 to 2,000 RFU.

[0091] (Changes in the content of methyl methacrylate dimer before and after retention (D2-D1)) Using a Capillograph 1D and a capillary die (manufactured by Toyo Seiki Seisakusho) with a length of 10 mm and a hole diameter of 1 mm, the shear rate was 24 s. -1 Under these conditions, a correlation curve showing the relationship between the temperature and melt viscosity of the acrylic resin was obtained. Next, the temperature T [°C] at which the melt viscosity of the acrylic resin becomes 7000 Poise was determined by interpolation or extrapolation. Using a Capillograph 1D and a capillary die with a length of 10 mm and a hole diameter of 1 mm (manufactured by Toyo Seiki Seisakusho), acrylic resin was allowed to remain in a barrel for 1 hour under the condition T [°C]. The content of methyl methacrylate dimer D2 [ppm by weight] in the extruded strand was then determined by the analytical method described above. Similarly, the content of methyl methacrylate dimer D1 [ppm by weight] in the acrylic resin before retention was also determined, and the change in the content of methyl methacrylate dimer (D2-D1) [ppm by weight] before and after retention was calculated.

[0092] (water contact angle) The water contact angle of an acrylic resin film at 23°C was determined using the droplet method with an automatic contact angle meter SImage AUTO 100 (manufactured by Excimer) in Auto Mode. The contact angle with water was measured 10 times at different measurement positions on the surface of the acrylic resin film, and the average value for n=10 was used.

[0093] (Example 1) (Manufacturing of acrylic resin A) In a 4L glass reactor equipped with an H-type agitator, 150 parts by weight of deionized water, 0.20 parts by weight of tricalcium phosphate, 0.0075 parts by weight of sodium α-olefin sulfonate, and 0.30 parts by weight of sodium chloride were charged as dispersants. Next, under a nitrogen atmosphere, while stirring at 250 rpm, 100 parts by weight of methyl methacrylate, 0.289 parts by weight of n-octyl mercaptan as a chain transfer agent, and 0.074 parts by weight of 2,2'-azobis(isobutyrate)dimethyl V-601 (manufactured by Fujifilm Wako Pure Chemical Industries) as a polymerization initiator were added to the reactor. Subsequently, the temperature of the liquid in the reactor was raised to 70°C to start polymerization. Two hours after the start of polymerization, 0.10 parts by weight of tricalcium phosphate was added to the polymerization solution. At this time, an exothermic peak associated with the gel effect was observed 4 hours and 20 minutes after the start of polymerization. Seven hours after the start of polymerization, the temperature was increased to 95°C. At the seven-hour mark, the polymerization conversion rate was 93%. Two hours after the temperature reached 95°C, the reactor was cooled to room temperature to terminate polymerization and obtain an acrylic resin dispersion. At this point, the polymerization conversion rate was 99%. Next, the acrylic resin dispersion was washed with 0.1 times the weight of the charged monomer in 1N hydrochloric acid, and then washed with water to remove the dispersant. After washing with water, the acrylic resin was dehydrated and dried to obtain bead-shaped acrylic resin.

[0094] A 40mm diameter, L / D=90 meshing type co-rotating twin-screw extruder equipped with a die at the outlet was used. Each temperature control zone was set to 250-280°C, and the screw rotation speed was set to 85 rpm. Bead-shaped acrylic resin was melted and filled using a kneading block. Next, 1.8 wt% monomethylamine (manufactured by Mitsubishi Gas Chemical) was injected into the acrylic resin through a nozzle to imidize it. Then, the strand extruded from the die was cooled in a water bath and pelletized in a pelletizer to obtain pellets of acrylic resin A. Acrylic resin A had an Mw of 101,300, an Mw / Mn ratio of 1.72, and a glutarimide ring content of 6 wt%.

[0095] (Manufacturing of acrylic resin film A) Acrylic resin A pellets were supplied to a 15mm diameter, L / D=45 meshing type coaxial rotating twin-screw extruder KZW15TWIN-45MG (manufactured by Technovel) equipped with a T-die at the outlet, and a film was formed by melt extrusion film formation at an extrusion temperature of 260°C. At this time, the sheet discharged from the T-die was cooled and wound via a cast roll to obtain a raw film roll with a width of 160 mm and a thickness of 160 μm. Next, a 100 mm × 100 mm film was cut from the raw film roll so that two sides were parallel to the extrusion direction. Then, the film was set in a pantograph type biaxial stretching device and simultaneously biaxially stretched at a stretching temperature of 142°C and a stretching speed of 100 mm / min so that the stretching ratio in the direction parallel and perpendicular to the extrusion direction was 2 times. After that, it was removed and cooled at room temperature to obtain acrylic resin film A with a thickness of 40 μm.

[0096] (Example 2) (Manufacturing of acrylic resin B) In an 8L glass reactor equipped with a paddle-type stirrer, 350 parts by weight of deionized water, 0.004 parts by weight of sodium hydroxide, and 0.2 parts by weight of sodium dioctyl sulfosuccinate were charged. Under a nitrogen atmosphere, the reactor temperature was raised to 60°C while stirring at 140 rpm. Next, 0.1 parts by weight of t-butyl hydroperoxide was added to the reactor, followed by the sequential addition of a mixed aqueous solution of 0.0055 parts by weight of ethylenediaminetetraacetic acid disodium, 0.0015 parts by weight of ferrous sulfate heptahydrate, and 0.1 parts by weight of sodium sulfoxylate formaldehyde. Then, a monomer mixture consisting of 80 parts by weight of methyl methacrylate, 20 parts by weight of ethyl 2-(hydroxymethyl)acrylate, and 0.3 parts by weight of 2-ethylhexyl thioglycolate was continuously added to the reactor over 240 minutes for polymerization. At this time, 30 minutes after adding the monomer mixture, 0.7 parts by weight of sodium dioctyl sulfosuccinate was continuously added to the reactor. Also, 90 minutes after adding the monomer mixture, the stirring speed was changed to 165 rpm. Furthermore, 150 minutes after adding the monomer mixture, 0.1 parts by weight of sodium sulfoxylate / formaldehyde and 0.1 parts by weight of t-butyl hydroperoxide were added to the reactor in sequence. After polymerization for 15 minutes following the completion of the monomer mixture addition, 0.05 parts by weight of sodium sulfoxylate / formaldehyde and 0.05 parts by weight of t-butyl hydroperoxide were added to the reactor in sequence. Next, the temperature in the reactor was raised to 80°C and polymerization was carried out for 30 minutes, after which 0.05 parts by weight of sodium sulfoxylate / formaldehyde and 0.05 parts by weight of t-butyl hydroperoxide were added to the reactor in sequence and polymerization was carried out for 30 minutes. Next, the reactor temperature was cooled to room temperature to complete the polymerization and obtain acrylic resin latex. At this point, the polymerization conversion rate was 99.2%.

[0097] An aqueous magnesium chloride solution, prepared by dissolving 3 parts by weight of magnesium chloride in 200 parts by weight of deionized water, was added to a stainless steel container. The solution was then heated to 95°C while stirring with a paddle-type stirrer. Next, 100 parts by weight (solid content) of acrylic resin latex was added to the aqueous magnesium chloride solution, and the acrylic resin latex was allowed to solidify. Then, 325 parts by weight of deionized water was added, the solution was heated to 98°C, and stirred for 1 minute to obtain an acrylic resin slurry. After the solution was cooled to room temperature, the acrylic resin slurry was vacuum filtered to remove water, obtaining a cake-like acrylic resin containing a small amount of water. Next, the cake-like acrylic resin was dried at 75°C for 10 hours using a hot air dryer to obtain a white powdered acrylic resin.

[0098] White powdered acrylic resin was dispersed in ethanol to a concentration of 25% by weight and stirred for 30 minutes. The ethanol was then removed by vacuum filtration to obtain acrylic resin containing a small amount of ethanol. Next, the obtained acrylic resin was dispersed in deionized water to a concentration of 25% by weight and stirred for 30 minutes. The water was then removed by vacuum filtration. Next, the acrylic resin was dried in a hot air dryer at 75°C for 10 hours to obtain white powdered acrylic resin from which impurities had been removed. Next, the obtained acrylic resin was spread in a stainless steel container and heated in a hot air dryer at 200°C for 1 hour. Next, the acrylic resin that had solidified after heating was crushed using a mixer to obtain granular acrylic resin B. Acrylic resin B had an Mw of 86,000, an Mw / Mn ratio of 1.84, and a content of 24% by weight of constituent units containing lactone rings. Furthermore, the acrylic resin having hydroxyl groups and ester groups, which is a precursor of acrylic resin B, undergoes a cyclization condensation reaction between the hydroxyl groups and ester groups upon heating, forming structural units containing lactone rings.

[0099] (Manufacturing of acrylic resin film B) Granular acrylic resin B was supplied to a 15mm diameter, L / D=45 meshing type coaxial rotary twin-screw extruder KZW15TWIN-45MG (manufactured by Technovel) equipped with a T-die at the outlet, and a film was formed by melt extrusion at an extrusion temperature of 260°C. At this time, the sheet discharged from the T-die was cooled and wound via a cast roll to obtain a raw film roll with a width of 160mm and a thickness of 160μm. Next, a 100mm x 100mm film was cut from the raw film roll so that two sides were parallel to the extrusion direction. Then, the film was set in a pantograph type biaxial stretching device and simultaneously biaxially stretched at a stretching temperature of 137°C and a stretching speed of 100mm / min so that the stretching ratio in the direction parallel and perpendicular to the extrusion direction was doubled. After that, it was removed and cooled at room temperature to obtain an acrylic resin film B with a thickness of 40μm.

[0100] (Comparative Example 1) (Manufacturing of acrylic resin C) Except for using PMMA resin Sumipex MH (manufactured by Sumitomo Chemical) as the acrylic resin supplied to the interlocking co-rotating twin-screw extruder, pellets of acrylic resin C were obtained in the same manner as in the production of acrylic resin A. Acrylic resin C had an Mw of 115,000, an Mw / Mn ratio of 1.58, and a glutarimide ring content of 5.8% by weight.

[0101] (Manufacturing of acrylic resin film C) Acrylic resin film C was obtained in the same manner as (manufacturing of acrylic resin film A), except that pellets of acrylic resin C were used instead of pellets of acrylic resin A, and the stretching temperature was changed to 129°C.

[0102] (Comparative Example 2) (Manufacturing of acrylic resin D) Except for using PMMA resin Acrypet VH5 (manufactured by Mitsubishi Chemical) as the acrylic resin supplied to the interlocking co-rotating twin-screw extruder, pellets of acrylic resin D were obtained in the same manner as in the production of acrylic resin A. Acrylic resin D had an Mw of 81,500, an Mw / Mn ratio of 1.57, and a glutarimide ring content of 5.9% by weight.

[0103] (Manufacturing of acrylic resin film D) Acrylic resin film D was obtained in the same manner as (manufacturing of acrylic resin film A), except that pellets of acrylic resin D were used instead of pellets of acrylic resin A, and the stretching temperature was changed to 134°C.

[0104] Table 1 shows the evaluation results for the roll stain resistance of acrylic resin film.

[0105] [Table 1]

[0106] Table 1 shows that the acrylic resin and acrylic resin film of Examples 1 and 2 exhibit high resistance to roll contamination and heat resistance during film formation.

[0107] In contrast, the acrylic resin of Comparative Example 1 has an MMA dimer content of 600 ppm by weight, resulting in low resistance to roll contamination and heat during film formation. Furthermore, the acrylic resin film of Comparative Example 1 has an MMA dimer content of 400 ppm by weight, a high water contact angle of 70°, and a reduction rate of 33.3% in MMA dimers, resulting in low resistance to roll contamination and heat during film formation.

[0108] The acrylic resin of Comparative Example 2 has an MMA dimer content of 450 ppm by weight, resulting in low resistance to roll contamination and heat during film formation. Furthermore, the acrylic resin film of Comparative Example 2 has an MMA dimer content of 250 ppm by weight, a high water contact angle of 72°, and a reduction rate of 44.4% in MMA dimers, resulting in low resistance to roll contamination and heat during film formation.

Claims

1. A method for manufacturing an acrylic resin molded article, The process includes melt molding an acrylic resin containing methyl methacrylate units and having one or more ring structures selected from the group consisting of glutarimide rings, lactone rings, maleic anhydride rings, glutaric acid anhydride rings, and maleimide rings in its main chain, using an extruder. If the content of methyl methacrylate dimer in the acrylic resin and the content of methyl methacrylate dimer in the acrylic resin molded product are A [ppm by weight] and B [ppm by weight], respectively, then the formula [(A-B) / A]×100 A method for producing an acrylic resin molded article, wherein the reduction rate of methyl methacrylate dimers calculated by the method is 50% or more.

2. A method for manufacturing an acrylic resin molded article, The process includes a step of melt-molding an acrylic resin containing methyl methacrylate units and having a glass transition temperature of 120°C or higher using an extruder. If the content of methyl methacrylate dimer in the acrylic resin and the content of methyl methacrylate dimer in the acrylic resin molded product are A [ppm by weight] and B [ppm by weight], respectively, then the formula [(A-B) / A]×100 A method for producing an acrylic resin molded article, wherein the reduction rate of methyl methacrylate dimers calculated by the method is 50% or more.

3. The method for manufacturing an acrylic resin molded article according to claim 1 or 2, wherein the acrylic resin molded article is a pellet or a film.

4. The method for producing an acrylic resin molded article according to claim 1 or 2, wherein the acrylic resin has a molecular weight dispersion (Mw / Mn) of 1.60 or more.

5. The method for producing an acrylic resin molded article according to claim 1 or 2, wherein the acrylic resin molded article has a methyl methacrylate dimer content of less than 200 ppm by weight.

6. A method for producing an acrylic resin molded article according to claim 1 or 2, wherein a 2 cm square test piece cut from a 160 μm thick film made by molding the acrylic resin molded article is placed in a glass petri dish with a diameter of 4 cm and a height of 1 cm, and a glass plate covered entirely with aluminum foil is placed over the glass petri dish, and the mixture is heated at 285°C for 1 hour, and the relative fluorescence emission intensity of the volatile substances transferred to the surface of the aluminum foil is less than 2000 RFU.

7. A step of polymerizing methyl methacrylate in a solvent or dispersion medium to obtain a polymer, A method for producing an acrylic resin molded article according to claim 1 or 2, further comprising the step of reacting the polymer to obtain the acrylic resin.

8. A method for producing an acrylic resin molded article according to claim 7, wherein the methyl methacrylate is polymerized by solution polymerization, suspension polymerization, or emulsion polymerization.

9. Contains methyl methacrylate units, The main chain contains one or more ring structures selected from the group consisting of a glutarimide ring, a lactone ring, a maleic anhydride ring, a glutaric acid anhydride ring, and a maleimide ring. An acrylic resin having a methyl methacrylate dimer content of less than 200 ppm by weight.

10. The acrylic resin according to claim 9, wherein a 2 cm square test piece cut from a 160 μm thick film formed by molding the acrylic resin is placed in a glass petri dish with a diameter of 4 cm and a height of 1 cm, and a glass plate covered entirely with aluminum foil is placed over the glass petri dish, and the mixture is heated at 285°C for 1 hour, and the relative fluorescence emission intensity of the volatile substances transferred to the surface of the aluminum foil is less than 2000 RFU.

11. The acrylic resin according to claim 9 or 10, wherein the molecular weight dispersion (Mw / Mn) is 1.60 or higher.

12. The resin contains methyl methacrylate units and includes one or more ring structures selected from the group consisting of glutarimide rings, lactone rings, maleic anhydride rings, glutaric acid anhydride rings, and maleimide rings in its main chain. An acrylic resin film having a methyl methacrylate dimer content of less than 200 ppm by weight.

13. The acrylic resin film according to claim 12, wherein the internal haze is 0.30% or less.

14. The acrylic resin film according to claim 12 or 13, which is a polarizer protective film.

15. Contains methyl methacrylate units, The glass transition temperature is 120°C or higher. An acrylic resin having a methyl methacrylate dimer content of less than 200 ppm by weight.

16. The acrylic resin contains methyl methacrylate units and has a glass transition temperature of 120°C or higher. An acrylic resin film having a methyl methacrylate dimer content of less than 200 ppm by weight.

17. The acrylic resin film according to claim 16, wherein the water contact angle at 23°C is less than 70°.

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