Methacrylic resin composition

Abstract

Provided is a methacrylic resin composition for forming a resin film having excellent thermal stability and sufficient mechanical strength such as crack resistance while maintaining optical characteristics such as transparency and color tone. The methacrylic resin composition contains a methacrylic resin and crosslinked particles, the glass transition temperature of the methacrylic resin is 120 DEG C or more, the syndiotacticity represented by triad is 55% or more and less than 65%, and the 5% weight loss temperature of the methacrylic resin composition is 334 DEG C or more.

Description

Technical Field

[0001] The invention relates to a methacrylic resin composition. Background Art

[0002] Methacrylic resin has excellent transparency, weather resistance, processability, etc., and is therefore widely used in various fields. In particular, since a resin film obtained by molding a methacrylic resin has excellent optical properties, it is used for optical purposes such as display devices. As for the production of the resin film, a method of extruding a molten methacrylic resin in a film form and winding it at the same time is known (for example, refer to Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2008-229901 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, resin films produced using methacrylic resins not only lack thermal stability but also lack sufficient mechanical strength such as crack resistance.

[0008] An object of the present invention is to provide a methacrylic resin composition for forming a resin film having excellent thermal stability and sufficient mechanical strength such as crack resistance while maintaining optical properties such as transparency and color tone.

[0009] Solutions to the problem

[0010] Specific methods for solving the above-mentioned problems include the following implementations.

[0011] <1>

[0012] A methacrylic resin composition, comprising:

[0013] Methacrylic resin, and

[0014] Cross-linked particles,

[0015] The methacrylic resin has a glass transition temperature of 120° C. or higher, and a syndiotacticity expressed by a triad of 55% or higher and less than 65%;

[0016] The methacrylic resin composition has a 5% weight loss temperature of 334° C. or higher.

[0017] <2>

[0018] according to <1> The methacrylic resin composition, wherein

[0019] The methacrylic resin composition has a 5% weight loss temperature of 335° C. or higher.

[0020] <3>

[0021] according to <1> or <2> The methacrylic resin composition, wherein

[0022] The thermal weight loss rate when exposed to 280°C for 15 minutes in a nitrogen atmosphere was less than 1.0%.

[0023] <4>

[0024] according to <1> ~ <3> The methacrylic resin composition according to any one of the preceding claims, wherein

[0025] The cross-linked particles are acrylic cross-linked particles.

[0026] <5>

[0027] according to <4> The methacrylic resin composition, wherein

[0028] The acrylic cross-linked particles are core-shell polymers.

[0029] <6>

[0030] according to <4> The methacrylic resin composition, wherein

[0031] The acrylic cross-linked particles are acrylic rubber particles.

[0032] <7>

[0033] according to <6> The methacrylic resin composition, wherein

[0034] The acrylic rubber particles are core-shell type elastomers having a core layer containing a rubbery polymer and a shell layer containing a glassy polymer.

[0035] <8>

[0036] according to <1> ~ <7> The methacrylic resin composition according to any one of the preceding claims, wherein

[0037] The mass ratio of the methacrylic resin to the cross-linked particles is 99.9:0.1 to 65:35.

[0038] <9>

[0039] according to <1> ~ <8> The methacrylic resin composition according to any one of the preceding claims, wherein

[0040] The weight average molecular weight of the methacrylic resin is 70,000 to 250,000.

[0041] <10>

[0042] according to <1> ~ <9> The methacrylic resin composition according to any one of the preceding claims, wherein

[0043] The methacrylic resin has a molecular weight distribution (Mw / Mn) of more than 1.5.

[0044] <11>

[0045] according to <1> ~ <10> The methacrylic resin composition further comprises an ultraviolet absorber.

[0046] <12>

[0047] according to <1> ~ <11> The methacrylic resin composition according to any one of the preceding claims, wherein

[0048] The ratio of the terminal double bonds in the methacrylic resin to the structural units derived from methyl methacrylate is 0.004 mol % or less.

[0049] <13>

[0050] A particle comprising <1> ~ <12> The methacrylic resin composition described above.

[0051] <14>

[0052] A resin film comprising <1> ~ <12> The methacrylic resin composition described above.

[0053] <15>

[0054] An optical film comprising <1> ~ <12> The methacrylic resin composition described above.

[0055] <16>

[0056] according to <15> The optical film, wherein

[0057] The static friction coefficient measured in accordance with JIS K7125 is 2.00 or less.

[0058] <17>

[0059] according to <15> or <16> The optical film has a haze of less than 1.0%.

[0060] <18>

[0061] according to <15> ~ <17> The optical film has an internal haze of less than 1.0%.

[0062] <19>

[0063] according to <15> ~ <18> The optical film as described in any one of the preceding claims, wherein:

[0064] The optical film is a polarizer protective film.

[0065] Effects of the Invention

[0066] According to the present invention, there is provided a methacrylic resin composition for forming a resin film having excellent thermal stability and sufficient mechanical strength such as crack resistance while maintaining optical properties such as transparency and color tone. DETAILED DESCRIPTION

[0067] Hereinafter, specific embodiments to which the present invention is applied will be described in detail. Unless otherwise specified, the symbol "to" used to indicate a numerical range means that the lower limit and the upper limit of the range are included.

[0068] (Methacrylic Resin)

[0069] In the methacrylic resin of the present embodiment, the ratio of the structural unit derived from methyl methacrylate is 98% by mass or more, and the ratio of the structural unit derived from the monomer other than methyl methacrylate is preferably 2% by mass or less. In the methacrylic resin of the present embodiment, the ratio of the structural unit derived from methyl methacrylate is preferably 99% by mass or more, more preferably 100% by mass (i.e., homopolymer of methyl methacrylate). It should be noted that the structural unit derived from methyl methacrylate is represented by the following formula.

[0070] [Chemistry 1]

[0071]

[0072] Examples of monomers other than methyl methacrylate include alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate; aryl acrylates such as phenyl acrylate; cycloalkyl acrylates such as cyclohexyl acrylate and norbornene acrylate; alkyl methacrylates other than methyl methacrylate such as ethyl methacrylate, propyl methacrylate, and butyl methacrylate; aryl methacrylates such as phenyl methacrylate; cycloalkyl methacrylates such as cyclohexyl methacrylate and norbornene methacrylate; aromatic vinyl compounds such as styrene and α-methylstyrene; acrylamide; methacrylamide; acrylonitrile; methacrylonitrile; and the like.

[0073] The methacrylic resin of the present embodiment has a syndiotacticity (rr) expressed by a triad of 55% or more, preferably 56% or more, and more preferably 57% or more. When the syndiotacticity (rr) expressed by a triad is 55% or more, the glass transition temperature (Tg) of the methacrylic resin increases, and the heat resistance tends to be improved. In addition, from the viewpoint of the molding temperature, the toughness of the molded body, and the secondary processability, the syndiotacticity (rr) is less than 65%, and more preferably 63% or less.

[0074] The syndiotacticity (rr) is the ratio of two chains (diad) of a chain (triad) of three consecutive structural units to be racemic (rr). It should be noted that the chains (diad) of structural units in the polymer molecule with the same stereo configuration are called meso, and the opposite are called racemo, which are indicated as m and r, respectively.

[0075] As described in the examples below, the measurement was performed in deuterated chloroform at 22°C for 16 cumulative times. 1 H-NMR spectrum, when tetramethylsilane (TMS) is 0 ppm, the area (X) of the 0.60-0.95 ppm region and the area (Y) of the 0.60-1.25 ppm region are measured from the above spectrum, and the syndiotacticity (rr) can be calculated by the formula: (X / Y)×100.

[0076] The glass transition temperature (Tg) of the methacrylic resin of the present embodiment is 120° C. or higher, preferably higher than 120° C., more preferably 121° C. or higher, and further preferably 122° C. or higher. The upper limit of the glass transition temperature (Tg) is not particularly limited, but is preferably 135° C. or lower, and may be 130° C. or lower, from the viewpoint of the molding temperature and the secondary processability of the molded body.

[0077] The glass transition temperature (Tg) in this specification is a midpoint glass transition temperature obtained from a DSC curve, and this temperature is measured by the method described in Examples described later.

[0078] It should be noted that the syndiotacticity (rr) and glass transition temperature (Tg) of the methacrylic resin can be controlled by adjusting the polymerization temperature during the synthesis of the methacrylic resin. For example, it is preferred to lower the polymerization temperature to increase the syndiotacticity (rr) and glass transition temperature (Tg) of the methacrylic resin. In addition, the glass transition temperature (Tg) can also be controlled by adjusting the molecular weight of the methacrylic resin.

[0079] The methacrylic resin of the present embodiment may include a terminal structure represented by the following formula (1) derived from a polymerization initiator.

[0080] [Chemistry 2]

[0081]

[0082] (Where R 1 , R 2 , and R 3 Each independently represents an alkyl group, a substituted alkyl group, an ester group, or an amide group. 1 , R 2 , and R 3 At least one of R represents an ester group or an amide group. 1 , R 2 , and R 3 Two of them can be bonded to each other to form an alicyclic structure. * indicates the bonding position with the structural unit derived from the monomer. )

[0083] Examples of the alkyl group include linear or branched alkyl groups having 1 to 6 carbon atoms. Examples of the substituent group which may or may not have an alkyl group include a hydroxyl group, a carboxyl group, an alkoxy group, and a halogen atom.

[0084] Examples of the ester group include -COOR 4 The group represented by R 4 It represents an alkyl group having 1 to 6 carbon atoms, which may or may not have a substituent such as a hydroxyl group, a carboxyl group, an alkoxy group or a halogen atom.

[0085] Examples of the amide group include -C(O)NR 5 The group represented by R 5 It represents an alkyl group or cycloalkyl group having 1 to 6 carbon atoms, or an alkenyl group having 2 to 6 carbon atoms, and may or may not have a substituent such as a hydroxyl group, a carboxyl group, an alkoxy group, or a halogen atom.

[0086] When synthesizing a methacrylic resin, by using a non-nitrile azo polymerization initiator represented by the following formula (2), the terminal structure represented by the above formula (1) can be introduced into the methacrylic resin molecule. 1 , R 2 , and R 3 The same meaning as in the above formula (1). Compared with the case where a polymerization initiator other than a non-nitrile azo polymerization initiator (e.g., a nitrile azo polymerization initiator) is used, the methacrylic resin obtained by using such a non-nitrile azo polymerization initiator tends to have increased thermal stability. In addition, compared with a nitrile azo polymerization initiator, a non-nitrile azo polymerization initiator tends to have lower toxicity of the initiator itself and the decomposition product, and is therefore also preferred from this point of view.

[0087] [Chemistry 3]

[0088]

[0089] Examples of the non-nitrile azo polymerization initiator represented by the formula (2) include 2,2'-azobis(isobutyric acid) dimethyl ester, 1,1'-azobis(cyclohexanecarboxylic acid methyl ester), 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2'-azobis(N-cyclohexyl-2-methylpropionamide), 2,2'-azobis{2-methyl-N-[2-(1-hydroxyethyl)]propionamide}, and 2,2'-azobis{2-methyl-N-[2-(1-hydroxybutyl)]propionamide}. Among them, at least one selected from 2,2'-azobis(isobutyric acid) dimethyl ester and 1,1'-azobis(cyclohexanecarboxylic acid methyl ester) is preferred from the viewpoints of half-life temperature, cost, and the like.

[0090] In addition, in the methacrylic resin of the present embodiment, the ratio of the terminal double bonds relative to the structural units derived from methyl methacrylate is preferably 0.020 mol% or less, more preferably 0.015 mol% or less, still more preferably 0.010 mol% or less, further preferably 0.006 mol% or less, and particularly preferably 0.004 mol% or less. When the ratio of the terminal double bonds is within the above range, the methacrylic resin tends to have improved thermal stability.

[0091] As shown in the manufacturing method described later, the methacrylic resin of the present embodiment can be manufactured by a free radical polymerization method. The methacrylic resin manufactured by the free radical polymerization method contains terminal double bonds generated by a disproportionation termination reaction in polymerization, a hydrogen extraction reaction of a monomer by a polymerization initiator, and the like. Since the terminal double bonds have an effect on the thermal stability of the resin, the proportion thereof is preferably low. The proportion of the terminal double bonds is controlled by the method described later, and when it can be reduced to a range of 0.001 mol% or more and 0.020 mol% or less, the thermal stability of the methacrylic resin tends to be greatly improved.

[0092] According to the following examples, the conditions of deuterated chloroform, 20°C, and 8192 cumulative times were used for determination. 1 In the H-NMR spectrum, the ratio of the terminal double bond to the structural unit derived from methyl methacrylate can be calculated as follows: the sum (X) of the areas of the peaks (5.47 to 5.53 ppm and 6.21 ppm) derived from the terminal double bond portion of the methacrylic resin and the area (Y) of the peak (0.5 to 1.25 ppm) derived from the α-methyl group of the methacrylic resin are measured from the spectrum, and then calculated by the formula: [(3×X) / (2×Y)]×100.

[0093] It should be noted that the proportion of terminal double bonds in the methacrylic resin can be controlled by adjusting the amount of polymerization initiator and chain transfer agent used, polymerization temperature, polymerization time, etc. when synthesizing the methacrylic resin. For example, it is preferred to reduce the amount of polymerization initiator used, increase the amount of chain transfer agent used, lower the polymerization temperature, and extend the polymerization time to reduce the proportion of terminal double bonds.

[0094] As described above, the methacrylic resin of the present embodiment has excellent thermal stability. The thermal weight loss rate of the methacrylic resin of the present embodiment when exposed to a nitrogen atmosphere at 280° C. for 15 minutes is preferably less than 2.5%, more preferably less than 2.3%. The thermal weight loss rate is measured by the method described in the examples described below.

[0095] The weight average molecular weight (Mw) of the methacrylic resin of the present embodiment is preferably 70,000 to 250,000, and more preferably 90,000 to 150,000. When the weight average molecular weight (Mw) of the methacrylic resin is 70,000 or more, the obtained molded body tends to have improved mechanical properties; when the weight average molecular weight (Mw) of the methacrylic resin is 250,000 or less, the moldability tends to be improved.

[0096] In addition, the methacrylic resin of the present embodiment has a dispersion (Mw / Mn) which is a ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of preferably more than 1.5, more preferably 1.6 to 2.5, and particularly preferably 1.7 to 2.2. When the dispersion (Mw / Mn) of the methacrylic resin exceeds 1.5, the methacrylic resin tends to have improved fluidity and easy molding; when the dispersion (Mw / Mn) of the methacrylic resin is 2.5 or less, the obtained molded body tends to have improved mechanical properties such as impact resistance, toughness, and bending resistance.

[0097] The weight average molecular weight (Mw) and number average molecular weight (Mn) in this specification are values ​​converted to standard polystyrene measured by gel permeation chromatography (GPC), and are measured by the method described in Examples below.

[0098] It should be noted that the weight average molecular weight (Mw) and number average molecular weight (Mn) of the methacrylic resin can be controlled by adjusting the type and amount of the polymerization initiator and the chain transfer agent used when synthesizing the methacrylic resin.

[0099] The methacrylic resin of the present embodiment is not only excellent in thermal stability, but also expected to be suitable for reuse after being discarded, i.e., recycling. As a recycling method for methacrylic resin, for example, chemical recycling (a method of recovering decomposition oil as a decomposition product by thermal decomposition and reusing it in chemical raw materials or fuel) is known. In general, in order to improve the heat resistance and thermal stability of methacrylic resin, a cyclic structure can be introduced into the molecular structure of methacrylic resin, and a monomer with a rigid structure can be copolymerized. However, these structures become impurities in chemical recycling, and are therefore not preferred. In this regard, the methacrylic resin of the present embodiment is expected to have a high yield as a monomer recovered from decomposition oil due to the large ratio of the structural unit derived from methyl methacrylate, and is expected to show good chemical recyclability.

[0100] (Method for producing methacrylic resin)

[0101] The method for producing the methacrylic resin of the present embodiment includes a polymerization step: for example, a monomer mixture containing 98% by mass or more of methyl methacrylate is polymerized at a temperature below 100° C. and in the presence of a non-nitrile azo polymerization initiator (hereinafter referred to as a “polymerization initiator”) and a chain transfer agent until 90% or more of the resulting methacrylic resin is generated. Here, “until 90% or more of the resulting methacrylic resin is generated” means that when the polymerization reaction reaches a conversion rate of 100%, “the conversion rate reaches at least 90%”, for example, when the polymerization reaction is terminated at a conversion rate of 50%, “the conversion rate reaches at least 45%”. After 90% or more of the resulting methacrylic resin is generated, the polymerization temperature may be increased to more than 100° C. in order to reduce the residual monomer components and inactivate the residual polymerization initiator. A conventionally known polymerization method may be used as a method for producing the methacrylic resin, for example, a free radical polymerization method such as a continuous bulk polymerization method, a solution polymerization method, an emulsion polymerization method, an emulsifier-free (soap-free) emulsion polymerization method, and a suspension polymerization method may be used. Among them, from the viewpoints of the degree of freedom in structural design of the methacrylic resin, simplicity of polymerization, productivity, etc., a production method involving aqueous polymerization is preferred, suspension polymerization and emulsion polymerization are more preferred, and suspension polymerization is still more preferred.

[0102] It should be noted that when the methacrylic resin of the present embodiment is manufactured by water-based polymerization, it is also advantageous from the viewpoint of impurities in the resin. For example, in anionic solution polymerization, an organometallic compound is used as a polymerization initiator, so the metal ions derived from the organometallic compound remain in the resin at about hundreds of mass ppm. On the other hand, in water-based polymerization, an organometallic compound is not used as a polymerization initiator, so the total amount of residual metal ions in the resin can be made to be less than 100 mass ppm. When carrying out water-based polymerization, the content of Al in the resin is preferably less than 1 mass ppm, and the content of Li is preferably less than 1 mass ppm. In addition, in water-based polymerization, it is also not necessary to remove the process of residual metal ions, and the economy is excellent. Further, with regard to water-based polymerization, for example, organic solvents such as aliphatic hydrocarbons and alicyclic hydrocarbons used in anionic solution polymerization are not used, so it is also excellent in terms of environment.

[0103] (Suspension polymerization)

[0104] The suspension polymerization method is to synthesize a methacrylic resin in an aqueous suspension mixed with water, a monomer mixture, a dispersant, a polymerization initiator, a chain transfer agent, and optionally other additives. The order of mixing the components is not particularly limited. For example, the components can be mixed simultaneously to prepare an aqueous suspension. Alternatively, after preparing an aqueous solution by mixing water, a polymerization initiator, and optionally other additives, a monomer mixture and a chain transfer agent are added, and then a dispersant is added to prepare an aqueous suspension. The mass ratio of the obtained methacrylic resin to water (methacrylic resin / water) is preferably 1.0 / 0.6 to 1.0 / 3.0.

[0105] The content of methyl methacrylate used as the monomer mixture is 98% by mass or more, preferably 99% by mass or more, and more preferably 100% by mass.

[0106] As dispersants, for example, inorganic salts that are poorly soluble in water, such as calcium phosphate, magnesium pyrophosphate, hydroxyapatite, and kaolin, and water-soluble polymers, such as polyvinyl alcohol, methylcellulose, polyacrylamide, and polyvinyl pyrrolidone, can be cited. When inorganic salts that are poorly soluble in water are used as dispersants, it is effective to use them in combination with anionic surfactants such as sodium α-olefin sulfonate and sodium dodecylbenzene sulfonate. These dispersants can also be added during the polymerization process as needed.

[0107] As the non-nitrile polymerization initiator, for example, a non-nitrile azo polymerization initiator represented by the above formula (2) can be cited. Among the non-nitrile azo polymerization initiators represented by the above formula (2), from the viewpoints of half-life temperature, cost, etc., at least one selected from 2,2'-azobis(isobutyric acid)dimethyl ester and 1,1'-azobis(cyclohexanecarboxylic acid methyl ester) is preferred.

[0108] It should be noted that, as polymerization initiators generally used in free radical polymerization methods, azo polymerization initiators, peroxide polymerization initiators, etc. can be cited. It is known that the free radicals generated by the polymerization initiator, in addition to the addition reaction with the monomer, will also cause a hydrogenation reaction when there is a substance that easily donates hydrogen. In this regard, since the azo polymerization initiator can only generate alkyl free radicals, the azo polymerization initiator has a lower hydrogenation energy than the peroxide polymerization initiator. Here, the polymerization initiator has a high hydrogenation energy. For example, when methyl methacrylate is used as a monomer, the free radicals generated by the polymerization initiator extract hydrogen from the α-methyl group of methyl methacrylate and the methyl group of the ester, and the free radicals on the newly generated α-methyl group and the methyl group of the ester are polymerized. As a result, it is easy to generate a polymer in which the double bond derived from the monomer structure remains at the end. Therefore, when a polymerization initiator with high hydrogenation energy is used, the resulting methacrylic resin tends to have insufficient thermal stability. Therefore, in order to obtain a methacrylic resin with high thermal stability, an azo polymerization initiator is more preferred than a peroxide polymerization initiator.

[0109] The hydrogen abstraction energy of the polymerization initiator can be measured, for example, by a radical trapping method using an α-methylstyrene dimer (ie, an α-methylstyrene dimer trapping method).

[0110] Relative to the total amount of 100 parts by mass of the monomer mixture, the amount of the polymerization initiator used is preferably 0.1 parts by mass or less, more preferably 0.05 parts by mass or less, and further preferably 0.04 parts by mass or less. The lower limit of the amount of the polymerization initiator used is not particularly limited, but from the viewpoint of polymerization rate, it is preferably 0.001 parts by mass or more relative to the total amount of 100 parts by mass of the monomer mixture.

[0111] Examples of the chain transfer agent include: primary alkyl mercaptan chain transfer agents such as n-butyl mercaptan, n-octyl mercaptan, n-hexadecyl mercaptan, n-dodecyl mercaptan, and n-tetradecyl mercaptan; secondary alkyl mercaptan chain transfer agents such as sec-butyl mercaptan and sec-dodecyl mercaptan; tertiary alkyl mercaptan chain transfer agents such as tert-dodecyl mercaptan and tert-tetradecyl mercaptan; thioglycolates such as 2-acetyl thioglycolate, ethylene glycol dimercaptoacetate, trimethylolpropane tris(thioglycolate), and pentaerythritol tetra(thioglycolate); thiophenol, tetraethylthiuram disulfide, pentaphenylethane, acrolein, methacrolein, allyl alcohol, carbon tetrachloride, vinyl bromide, styrene oligomers (α-methylstyrene dimer, etc.), terpinolene, etc. These chain transfer agents may be used alone or in combination of two or more.

[0112] Among these chain transfer agents, alkyl mercaptan chain transfer agents and thioglycolates are preferred from the viewpoints of handleability, stability, thermal stability of the resulting methacrylic resin, etc. As the alkyl mercaptan chain transfer agent, n-octyl mercaptan is more preferred, and as the thioglycolate, 2-hexyl thioglycolate is more preferred.

[0113] The amount of the chain transfer agent used is 0.10 mol% or more, preferably 0.15 mol% or more, based on the total amount of the monomer mixture. The upper limit of the amount of the chain transfer agent used is not particularly limited, but is preferably 0.45 mol% or less, based on the total amount of the monomer mixture.

[0114] By using the chain transfer agent in the above-mentioned usage amount, a methacrylic resin containing a structure derived from the chain transfer agent can be obtained. The structure derived from the chain transfer agent refers to, for example, when an alkyl mercaptan chain transfer agent or thioglycolate is used, a structure generated by the reaction of a propagating free radical with hydrogen of the alkyl mercaptan chain transfer agent or thioglycolate (i.e., a saturated bond terminal structure), a resin structure generated by the reaction of a sulfhydryl radical generated by hydrogen extraction of the alkyl mercaptan chain transfer agent or thioglycolate with a monomer (i.e., a resin structure containing sulfur), etc. With respect to the methacrylic resin of the present embodiment, from the viewpoint of the thermal stability of the resin, the amount of sulfur contained in the resin, i.e., the amount of bonded sulfur atoms, is preferably 0.05 mol% or more, more preferably 0.10 mol% or more. Among them, the amount of bonded sulfur atoms is the amount of structural units derived from the monomer in the methacrylic resin.

[0115] In order to reduce the proportion of terminal double bonds of the obtained methacrylic resin and improve thermal stability, the ratio of the total mol amount of the chain transfer agent to the total mol amount of the polymerization initiator is 2.0 or more. The ratio of the total mol amount of the chain transfer agent to the total mol amount of the polymerization initiator is preferably 4.0 or more, more preferably 8.0 or more, and further preferably 10 or more. The upper limit of the ratio of the total mol amount of the chain transfer agent to the total mol amount of the polymerization initiator is not particularly limited, and is, for example, preferably 50 or less.

[0116] From the viewpoint of controlling the syndiotacticity of the obtained methacrylic resin and productivity, the polymerization temperature when synthesizing the methacrylic resin is 100° C. or less, preferably 20 to 100° C., more preferably 30 to 95° C., further preferably 50 to 90° C., and particularly preferably 60 to 85° C. After the main reaction in the first stage polymerization is completed, the temperature may be raised to a higher temperature than the first stage to carry out post-polymerization in order to reduce residual monomers.

[0117] It should be noted that, in order to start polymerization with a small amount of polymerization initiator, it is preferred to reduce the amount of dissolved oxygen and carry out the polymerization reaction. The amount of dissolved oxygen in the raw materials of the polymerization is preferably less than 10ppm, more preferably less than 5ppm, further preferably less than 4ppm, and particularly preferably less than 2ppm. By making the amount of dissolved oxygen in such a range, the polymerization reaction proceeds smoothly, and in addition, the molded body of the methacrylic resin has a tendency to be suppressed in coloring. As a method for removing dissolved oxygen in the raw materials of the polymerization, for example, it can be cited: before heating to a given polymerization temperature, during heating, and after heating, an inert gas such as nitrogen is continuously fed into the reaction vessel. In order to remove dissolved oxygen from the raw materials added during the polymerization process, it is preferred to additionally pass an inert gas into these raw materials.

[0118] When the monomer mixture contains a polymerization inhibitor, in order to allow the polymerization reaction to proceed smoothly, the polymerization inhibitor is preferably removed in advance by distillation, alkali extraction, or using an adsorbent such as alumina, silica gel, molecular sieves, activated carbon, ion exchange resins, zeolite, acid clay, etc.

[0119] In order to remove the dispersant, the suspension containing the methacrylic resin obtained by suspension polymerization may be subjected to a washing operation such as acid washing, water washing, alkali washing, etc. The most appropriate number of washing operations may be selected in consideration of the work efficiency and the efficiency of removing the dispersant, and the number of washing operations may be once or multiple times.

[0120] As a method for separating the methacrylic resin from the suspension containing the methacrylic resin, a conventionally known dehydration method can be adopted, for example, a method using a centrifuge, a method of removing water by suction on a porous belt or a filter membrane, etc.

[0121] The methacrylic resin in a water-containing state obtained by the above dehydration can be dried and recovered by a conventionally known method. Examples of drying methods include: hot air drying in which hot air is sent into an empty tank by a hot air blower, a blower heater, etc.; vacuum drying in which the system is depressurized and the temperature is raised as needed; drum drying in which the obtained methacrylic resin is rotated in a container to remove moisture; and spin drying in which the methacrylic resin is dried using centrifugal force. These drying methods may be implemented alone or in combination of two or more.

[0122] (Emulsion polymerization method)

[0123] The emulsion polymerization method synthesizes the methacrylic resin in an emulsion prepared by mixing water, a monomer mixture, an emulsifier, a polymerization initiator, a chain transfer agent, and optionally other additives.

[0124] The monomer mixture contains methyl methacrylate in an amount of 98% by mass or more, preferably 99% by mass or more, and more preferably 100% by mass.

[0125] As emulsifiers, there can be mentioned: for example, anionic surfactants such as alkyl sulfonates, alkylbenzene sulfonates, dialkyl sulfosuccinates, α-olefin sulfonates, naphthalene sulfonate-formaldehyde condensates, alkylnaphthalene sulfonates, N-methyl-N-acyltaurates, phosphate ester salts (polyoxyethylene alkyl ether phosphates, etc.); nonionic surfactants, etc. In addition, as the above-mentioned salts, there can be mentioned: lithium salts, sodium salts, potassium salts, calcium salts, magnesium salts, etc. These emulsifiers can be used alone or in combination of two or more. It should be noted that the emulsifier used in the emulsion polymerization can also remain in the final methacrylic resin.

[0126] When the pH of the emulsion deviates from neutrality and becomes acidic or alkaline, an appropriate pH adjuster may be used to prevent hydrolysis of methyl methacrylate as a monomer or a structural unit derived from methyl methacrylate in a methacrylic resin obtained by polymerization. Examples of the pH adjuster include boric acid-potassium chloride-potassium hydroxide, potassium dihydrogen phosphate-sodium hydrogen phosphate, boric acid-potassium chloride-potassium carbonate, citric acid-potassium hydrogen citrate, potassium dihydrogen phosphate-boric acid, sodium dihydrogen phosphate-citric acid, and the like.

[0127] The polymerization initiator and the chain transfer agent may be the same as those in the above-mentioned suspension polymerization method.

[0128] In order to reduce the proportion of terminal double bonds of the obtained methacrylic resin and improve thermal stability, the ratio of the total mol amount of the chain transfer agent to the total mol amount of the polymerization initiator is 2.0 or more. The ratio of the total mol amount of the chain transfer agent to the total mol amount of the polymerization initiator is preferably 4.0 or more, more preferably 8.0 or more, and further preferably 10 or more. The upper limit of the ratio of the total mol amount of the chain transfer agent to the total mol amount of the polymerization initiator is not particularly limited, and is, for example, preferably 50 or less.

[0129] The solid or powdered methacrylic resin can be obtained by the following well-known methods: by heating and drying or spray drying the latex of the methacrylic resin obtained by emulsion polymerization; or by adding a water-soluble electrolyte such as a salt or an acid to the latex to make it coagulate, and further heat-treating it, separating the resin component from the aqueous phase, and drying it. The above-mentioned salt is not particularly limited, and is preferably a divalent salt. Specifically, calcium salts such as calcium chloride and calcium acetate; magnesium salts such as magnesium chloride and magnesium sulfate, etc. can be cited. Among these salts, magnesium salts such as magnesium chloride and magnesium sulfate are preferred. It is also possible to add generally added additives such as anti-aging agents and ultraviolet absorbers during coagulation.

[0130] Before the coagulation operation, the latex is preferably filtered through a filter, mesh, etc. to remove minute polymer scale. This can reduce shrinkage cavities, foreign matter, etc. caused by minute polymer scale when the methacrylic resin is molded into a molded body.

[0131] In this embodiment, the methacrylic resin obtained by aqueous polymerization may be in the form of a powder, a granular body, or a powder and granular body containing both powder and granular body. Regarding the primary particles constituting the powder, granular body, and powder and granular body, when preparing primary particles with an average particle size of about 10 to 1000 μm, suspension polymerization is preferred; and when preparing primary particles with an average particle size of about 50 to 500 nm, emulsion polymerization is preferred. The powder, granular body, and powder and granular body may also contain an aggregate as an aggregate of the above primary particles.

[0132] After the polymerization is completed, volatile components such as residual monomers, residual oligomers, and chain transfer agents in the methacrylic resin can be removed as needed. The removal method is not particularly limited, and heating devolatilization is preferred. As a devolatilization method, it can be cited: for example, treatment using an extruder equipped with a vent. The vent of the extruder is preferably a vacuum vent or an open vent, and the screw of the extruder is preferably a twin screw. Compared with a single screw, a twin screw has greater shear energy for the resin and a greater degree of surface renewal, so it can be devolatilized more efficiently. The barrel heating temperature of the extruder is preferably 150 to 270°C, more preferably 160 to 260°C, and further preferably 180 to 250°C. By making the barrel heating temperature below 270°C, the thermal decomposition of the methacrylic resin can be suppressed.

[0133] (Cross-linked particles)

[0134] By using a methacrylic resin composition containing crosslinked particles, a resin film having excellent transparency and color tone and excellent mechanical strength such as bending resistance can be obtained. The crosslinked particles are preferably acrylic crosslinked particles. The acrylic crosslinked particles are described below.

[0135] The acrylic cross-linked particles are not particularly limited, and hard or soft acrylic cross-linked particles can be widely used, and can be either monolayer or multilayer. As hard acrylic cross-linked particles, methacrylates such as methyl methacrylate in the raw materials and polyfunctional monomers having more than two non-cooperating double bonds can be used, but acrylic rubber particles with excellent thermal stability can also be used. As acrylic rubber particles, core-shell elastomers are preferably used, and the elastomer has a core layer containing a rubbery polymer and a shell layer containing a glassy polymer (also referred to as a hard polymer).

[0136] The acrylic crosslinked particles can be formed of, for example, a multilayer structure polymer, or a graft copolymer called a core-shell polymer.

[0137] The multilayer structure polymer is a polymer (core-shell type polymer) having a polymer layer (shell layer) obtained by polymerizing a monomer mixture in the presence of polymer particles (core layer).

[0138] In the case of acrylic crosslinked particles, the average particle size of the core layer can be 125 to 400 nm. When the average particle size of the core layer is 125 nm or more, the strength of the manufactured resin film can be excellent. In addition, when it is below 400 nm, the transparency, appearance, optical properties, etc. of the manufactured resin film are excellent. The average particle size of the core layer is preferably 130 to 380 nm, and particularly preferably 200 to 260 nm. In the state of the polymer latex of the core layer before the polymerization shell layer, the light scattering of 546 nm wavelength is measured using a spectrophotometer to calculate the average particle size of the core layer of the acrylic crosslinked particles of the present invention.

[0139] According to a preferred embodiment of the present invention, the acrylic crosslinked particles can be obtained by the method described in International Publication No. WO2018 / 212227. The polymer layer formed by the polymerization stage (I) to the polymerization stage (II) is equivalent to the core layer, and the polymer layer formed by the polymerization stage (III) and thereafter is equivalent to the shell layer.

[0140] (I) Polymerization stage

[0141] In the polymerization stage (I), the following substances are preferably polymerized to obtain a hard polymer (I): a monomer mixture (a) consisting of 40 to 100 mass % of methacrylate (a-1) and 60 to 0 mass % of other monomers (a-2) having double bonds copolymerizable therewith, and 0.01 to 10 mass parts of a multifunctional monomer relative to a total of 100 mass parts of the above-mentioned (a-1) and (a-2), and 0.1 to 4.0 mass parts of a chain transfer agent.

[0142] As the other monomer having a copolymerizable double bond (hereinafter sometimes referred to as a "copolymerizable monomer"), an alkyl acrylate having an alkyl group with 1 to 12 carbon atoms and / or an aromatic vinyl monomer is preferred.

[0143] The monomer mixture (a) is preferably composed of 40 to 100% by mass of methacrylate, 0 to 35% by mass of acrylate, 0 to 10% by mass of aromatic vinyl monomer, and 0 to 15% by mass of other monomers having a copolymerizable double bond, and is particularly preferably composed of 51 to 96.8% by mass of methacrylate, 3.1 to 29% by mass of acrylate, 0.1 to 10% by mass of aromatic vinyl monomer, and 0 to 10% by mass of other monomers having a copolymerizable double bond. Within this range, the depolymerization of the zipper during high-temperature molding can be suppressed to improve thermal stability, and the obtained acrylic crosslinked particles can be combined with methacrylic resin without impairing the optical properties of the methacrylic resin, such as transparency and color tone.

[0144] Examples of the methacrylate include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, isobornyl methacrylate, phenyl methacrylate, and benzyl methacrylate. Among them, alkyl methacrylates having an alkyl group with 1 to 4 carbon atoms, such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and tert-butyl methacrylate are preferred. These may be used alone or in combination of two or more, and methyl methacrylate is particularly preferred.

[0145] The above-mentioned other monomers having a copolymerizable double bond are preferably at least one selected from the group consisting of acrylic acid esters, aromatic vinyl monomers, and copolymerizable monomers other than (meth) acrylic acid esters and aromatic vinyl monomers, and more preferably one or more monomers selected from the group consisting of acrylic acid alkyl esters having 1 to 12 carbon atoms in the alkyl group, aromatic vinyl monomers, and copolymerizable monomers other than (meth) acrylic acid esters and aromatic vinyl monomers. As the above-mentioned other monomers having a copolymerizable double bond, acrylic acid alkyl esters having 1 to 12 carbon atoms in the alkyl group and / or aromatic vinyl monomers are preferred.

[0146] In the polymerization stage (I), the amount of the multifunctional monomer used is preferably 0.01 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, and most preferably 0.01 to 2 parts by mass relative to 100 parts by mass of the total of the above (a-1) and (a-2). When the amount of the multifunctional monomer used is 0.01 parts by mass or more, the transparency of the obtained film is improved, and when it is 10 parts by mass or less, excellent mechanical properties can be imparted to the film.

[0147] As the polyfunctional monomer, any monomer known as a crosslinking agent or a crosslinking monomer can be used. As the crosslinking monomer, it is more preferable to use allyl methacrylate alone or in combination with other polyfunctional monomers.

[0148] In the present invention, in the polymerization step (I), the monomer mixture (a) and the mixture of the polyfunctional monomer are polymerized in the presence of a chain transfer agent to obtain the hard polymer (I).

[0149] The chain transfer agent used in the polymerization step (I) is not particularly limited, and any chain transfer agent known in the art can be used. These can be used alone or in combination of two or more.

[0150] When the chain transfer agent contains a sulfur component, the thermal stability of the acrylic crosslinked particles is improved, so alkyl mercaptan chain transfer agents and thiophenol are preferred, and alkyl mercaptan chain transfer agents are more preferred. Among them, n-octyl mercaptan and n-dodecyl mercaptan are preferred, and n-octyl mercaptan is particularly preferred.

[0151] The hard polymer (I) obtained in the polymerization step (I) of the acrylic crosslinked particles preferably has an alkylthiol group derived from an alkylthiol chain transfer agent, and more preferably has a primary and / or secondary alkylthiol chain transfer agent derived from a primary and / or secondary alkylthiol chain transfer agent. The alkylthiol group refers to a structure represented by the chemical formula RS- (R is an alkyl group), and the primary and / or secondary alkylthiol group means that the above R represents a primary and / or secondary alkyl group.

[0152] (II) Polymerization stage

[0153] In the polymerization stage (II), the soft polymer (II) is preferably obtained by polymerizing the following substances: a monomer mixture (b) consisting of 60 to 100 mass % of an acrylate (b-1) and 0 to 40 mass % of other monomers (b-2) having a double bond copolymerizable therewith, and 0.1 to 5 mass parts of a multifunctional monomer relative to a total of 100 mass parts of the above (b-1) and (b-2), and 0 to 2.0 mass parts of a chain transfer agent.

[0154] As the other monomer having a copolymerizable double bond, at least one selected from methacrylic acid esters and other monomers having a copolymerizable double bond is preferred.

[0155] As the acrylic acid ester, preferably, an alkyl acrylic acid ester having an alkyl group with 1 to 12 carbon atoms, for example, ethyl acrylate, n-butyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, etc. can be mentioned. These acrylic acid esters can be used alone or in combination of two or more. As the alkyl acrylic acid ester, preferably, n-butyl acrylate, a combination of n-butyl acrylate and ethyl acrylate, and a combination of n-butyl acrylate and 2-ethylhexyl acrylate are also preferred. In particular, in the acrylic acid ester used in the polymerization stage (II), the content ratio of n-butyl acrylate is preferably 50 to 100% by mass, and particularly preferably 80 to 100% by mass.

[0156] The methacrylate, other monomers having copolymerizable double bonds, multifunctional monomers and chain transfer agents used in the polymerization step (II) are the same as those described in the polymerization step (I) above. In the polymerization step (II), a chain transfer agent may or may not be used, but preferably not used.

[0157] (III) Polymerization stage

[0158] In the polymerization stage (III), the following substances are preferably polymerized to obtain a hard polymer (III): a monomer mixture (c) consisting of 60 to 100 mass % of methacrylate (c-1) and 40 to 0 mass % of other monomers (c-2) having double bonds copolymerizable therewith, and 0 to 10 mass parts of a multifunctional monomer relative to a total of 100 mass parts of the above-mentioned (c-1) and (c-2), and 0 to 6 mass parts of a chain transfer agent.

[0159] In order to lower the glass transition temperature of the hard polymer (III) formed in the polymerization step (III), the monomer mixture (c) preferably contains an acrylate. In the monomer mixture (c), the amount of the acrylate used is preferably 0 to 40% by mass, more preferably 10 to 40% by mass, and most preferably 20 to 30% by mass.

[0160] In the acrylic cross-linked particles, the hard polymer (III) has a structure graft-bonded to the hard polymer (I) and / or the soft polymer (II). The hard polymer (III) may be graft-bonded to the hard polymer (I) and / or the soft polymer (II) as a whole, or a portion of the hard polymer (III) may be graft-bonded to the hard polymer (I) and / or the soft polymer (II), and the remainder exists in the form of a polymer component (free polymer) that is not graft-bonded to any of the hard polymer (I) and the soft polymer (II). The ungrafted polymer component may also constitute a portion of the acrylic cross-linked particles.

[0161] The methacrylate, other monomers having copolymerizable double bonds, multifunctional monomers and chain transfer agents used in the polymerization stage (III) are the same as those described in the polymerization stage (I) above. In the polymerization stage (III), the multifunctional monomer and / or chain transfer agent may or may not be used, but preferably not used.

[0162] (IV) Polymerization stage

[0163] In the polymerization stage (IV), the following substances are preferably polymerized to obtain a hard polymer (IV): a monomer mixture (d) consisting of 40 to 100 mass % of methacrylate (d-1), 0 to 60 mass % of acrylate (d-2), and 0 to 5 mass % of other monomers (d-3) having copolymerizable double bonds, as well as 0 to 10 mass parts of a multifunctional monomer and 0 to 6 mass parts of a chain transfer agent relative to a total of 100 mass parts of the above-mentioned (d-1), (d-2) and (d-3).

[0164] In order to lower the glass transition temperature of the hard polymer (IV) formed in the polymerization step (IV), the amount of the acrylic acid ester (d-2) used is preferably 0 to 55% by mass, particularly preferably 15 to 40% by mass, and most preferably 20 to 40% by mass.

[0165] The methacrylate, acrylate, other monomers having a copolymerizable double bond, polyfunctional monomers and chain transfer agents used in the polymerization stage (IV) may be the same as those described in (I) to (III) above. In the polymerization stage (IV), the polyfunctional monomer and / or chain transfer agent may or may not be used, but preferably not used.

[0166] In the above preferred embodiment of the acrylic cross-linked particles, the hard polymer (IV) may have a structure graft-bonded to the hard polymer (I) and / or the soft polymer (II) and / or the hard polymer (III). The hard polymer (IV) may be graft-bonded to the hard polymer (I) and / or the soft polymer (II) and / or the hard polymer (III) as a whole, or a part of the hard polymer (IV) may be graft-bonded to the hard polymer (I) and / or the soft polymer (II) and / or the hard polymer (III), and the remaining part may exist in a form not graft-bonded to any of the hard polymer (I), the soft polymer (II) and the hard polymer (III). The ungrafted polymer component also constitutes a part of the acrylic cross-linked particles.

[0167] The acrylic crosslinked particles can be produced by performing ordinary emulsion polymerization using a known emulsifier.

[0168] From the viewpoint of improving the thermal stability of the resin film formed using the methacrylic resin composition of the present invention, the polymerization initiator used in the polymerization for obtaining the acrylic crosslinked particles is preferably a polymerization initiator having a 10-hour half-life temperature of 100°C or less. The polymerization initiator is not particularly limited as long as it has a 10-hour half-life temperature of 100°C or less, and the 10-hour half-life temperature of the polymerization initiator is preferably 100°C or less, more preferably 80°C or less, and particularly preferably 75°C or less. In addition, persulfates are preferred, for example, potassium persulfate, sodium persulfate, ammonium persulfate, etc. Among them, potassium persulfate is particularly preferred.

[0169] The polymerization initiator is preferably used in the polymerization of the polymerization stage (I), and more preferably used in the polymerization stage using a chain transfer agent. In addition, it is particularly preferred to use the polymerization initiator in the entire polymerization stage of the acrylic crosslinked particles.

[0170] The total amount of the polymerization initiator used is preferably 0.01 to 1.0 parts by mass, particularly preferably 0.01 to 0.2 parts by mass, relative to 100 parts by mass of the total amount of the monomer mixture constituting the acrylic crosslinked particles. When the acrylic crosslinked particles are obtained by three polymerization stages (I) to (III), the monomer mixture of each polymerization stage (I) to (III) is set to 100 parts by mass, and the amount of each polymerization initiator used is preferably 0.01 to 1.85 parts by mass in the polymerization stage (I), 0.01 to 0.6 parts by mass in the polymerization stage (II), and 0.01 to 0.90 parts by mass in the polymerization stage (III), particularly preferably 0.01 to 0.2 parts by mass in the polymerization stage (I), 0.01 to 0.4 parts by mass in the polymerization stage (II), and 0.01 to 0.2 parts by mass in the polymerization stage (III). In addition, the amount of the polymerization initiator used in the polymerization stage (I) is preferably more than 1% by mass and less than 29% by mass relative to the total amount of the polymerization initiator used.

[0171] In the present invention, the core layer of the acrylic crosslinked particles refers to the crosslinked structure polymer obtained by polymerization until the (II) polymerization stage (therefore, the outermost layer of the core layer is a soft polymer formed by the (II) polymerization stage), and the shell layer refers to the hard polymer obtained by polymerization after the (II) polymerization stage.

[0172] The latex for acrylic crosslinked particles thus obtained can be used to obtain solid or powdered acrylic crosslinked particles by the following well-known methods: spray drying, or coagulation by adding a water-soluble electrolyte such as a salt or an acid, followed by heat treatment, separation of the resin component from the aqueous phase, appropriate washing and drying.

[0173] The term "soft" as used herein means that the glass transition temperature of the polymer is lower than 10° C. From the viewpoint of improving the impact resistance such as crack resistance, the glass transition temperature of the soft polymer is preferably lower than 0° C., more preferably lower than -20° C.

[0174] In addition, the term "hard" in the present application means that the glass transition temperature of the polymer is 10° C. or higher.

[0175] The glass transition temperature of the hard polymer (polymer formed by the (III) polymerization stage or the (IV) polymerization stage) constituting the shell layer (when the shell layer is multi-layered, it is the layer with the highest glass transition temperature among the multi-layered layers) of the acrylic crosslinked particles is preferably 10°C to 92°C.

[0176] In the present application, the glass transition temperatures of "soft" and "hard" polymers are the values ​​described in Polymer Hand Book (J. Brandrup, Interscience 1989) and calculated using the Fox equation (for example, 105° C. for polymethyl methacrylate and −54° C. for polybutyl acrylate).

[0177] According to a preferred embodiment of the present invention, the polymer (I) obtained in the polymerization stage (I) is a hard polymer, the polymer (II) obtained in the polymerization stage (II) is a soft polymer, and the polymer (III) obtained in the polymerization stage (III) is a hard polymer. In addition, the polymer (IV) obtained in the polymerization stage (IV) is a hard polymer. The acrylic cross-linked particles having such a structure can well balance the appearance, transparency, weather resistance, gloss, processability, thermal stability, etc. when various thermoplastic acrylic resins are mixed. Thus, a film can be provided that does not damage the excellent color tone, appearance, transparency peculiar to the mixed thermoplastic acrylic resins, and has excellent thermal stability, weather resistance, gloss, processability, etc.

[0178] (Methacrylic resin composition)

[0179] The methacrylic resin composition of the present embodiment contains the methacrylic resin of the present embodiment described above and acrylic crosslinked particles.

[0180] In the resin composition of the present embodiment, the mixing ratio of the methacrylic resin and the acrylic crosslinked particles varies depending on the use of the molded article, and the mass ratio of the methacrylic resin to the acrylic crosslinked particles is preferably 99.9:0.1 to 65:35. When the acrylic crosslinked particles are core-shell type particles, the mass ratio of the methacrylic resin to the acrylic crosslinked particles is preferably 95:5 to 65:35, and further, the mass ratio of the methacrylic resin to the acrylic crosslinked particles is more preferably 90:10 to 60:40.

[0181] When the amount of the methacrylic resin is 65 parts by mass or more relative to 100 parts by mass of the total amount of the two components of the methacrylic resin and the acrylic crosslinked particles, the properties of the methacrylic resin can be fully exhibited, and when it is 95 parts by mass or less, the mechanical strength of the methacrylic resin can be sufficiently improved.

[0182] The 5% weight loss temperature (Td5) of the methacrylic resin composition is 334° C. or higher, more preferably 335° C. or higher, further preferably 336° C. or higher, and particularly preferably 337° C. or higher. When the 5% weight loss temperature (Td5) of the methacrylic resin composition is 334° C. or higher, it is considered that the methacrylic resin composition and the resin film formed from the methacrylic resin composition have excellent resistance to thermal decomposition. The 5% weight loss temperature (Td5) is measured by a thermogravimetric analyzer (manufactured by Hitachi High-Tech Science Co., Ltd., STA7200).

[0183] The retention heat stability of the methacrylic resin composition is preferably such that the weight loss rate of heat when exposed to 280°C for 15 minutes in a nitrogen atmosphere is less than 1.0%. The retention heat stability can be evaluated using a thermogravimetric analyzer (manufactured by Hitachi High-Tech Science Co., Ltd., STA7200).

[0184] From the viewpoint of further improving the light resistance of the obtained molded article, the methacrylic resin composition of the present embodiment preferably contains an ultraviolet absorber. The ultraviolet absorber is not particularly limited, and ultraviolet absorbers conventionally mixed with various resins can be used. Examples of the ultraviolet absorber include benzotriazole compounds, triazine compounds, oxalic acid anilide compounds, cyanoacrylate compounds, salicylate compounds, and benzophenone compounds. Among these compounds, triazine compounds are preferred from the viewpoint of the light resistance of the methacrylic resin composition.

[0185] Examples of the triazine compound include 2,4-diphenyl-6-(2-hydroxyphenyl-4-hexyloxyphenyl)-1,3,5-triazine, 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl]-5-(octyloxy)phenol, 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(hexyl)oxy]phenol, 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]phenol, and 2,4,6-tris(2-hydroxy-4-alkoxy-3-methylphenyl)-1,3,5-triazine. The alkoxy group of 2,4,6-tris(2-hydroxy-4-alkoxy-3-methylphenyl)-1,3,5-triazine is preferably a linear or branched alkoxy group having 1 to 10 carbon atoms. Specific examples of 2,4,6-tris(2-hydroxy-4-alkoxy-3-methylphenyl)-1,3,5-triazine include 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine.

[0186] Among these triazine compounds, 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]phenol and 2,4,6-tris(2-hydroxy-4-alkoxy-3-methylphenyl)-1,3,5-triazine are preferred. 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]phenol can be obtained as ADEKASTAB LA-46 (manufactured by ADEKA Corporation). 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine can be obtained as ADEKASTAB LA-F70 (manufactured by ADEKA Corporation). These ultraviolet absorbers may be used alone or in combination of two or more.

[0187] When the methacrylic resin composition of the present embodiment contains an ultraviolet absorber, the amount used varies depending on the type of ultraviolet absorber, the conditions of use, etc., and is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 3 parts by mass relative to 100 parts by mass of the methacrylic resin. When the amount of the ultraviolet absorber used is 0.1 parts by mass or more, the ultraviolet absorption effect can be improved. In addition, when the amount of the ultraviolet absorber used is 5 parts by mass or less, the coloring of the obtained molded body can be suppressed, and the deterioration of the transparency caused by the increase in the haze of the molded body can be suppressed.

[0188] The methacrylic resin composition of the present embodiment may further include: light stabilizers, heat stabilizers, matting agents, light diffusers, colorants, dyes, pigments, antistatic agents, heat ray reflective materials, lubricants, plasticizers, stabilizers, flame retardants, mold release agents, polymer processing aids, antioxidants, fillers and other known additives, and resins other than methacrylic resins. As resins other than methacrylic resins, for example, styrene resins such as acrylonitrile styrene resins and styrene maleic anhydride resins; polycarbonate resins; polyvinyl acetal resins; cellulose acylate resins; fluorine resins such as polyvinylidene fluoride and polyfluoroalkyl (meth) acrylic resins; silicone resins; polyolefin resins; polyethylene terephthalate resins; polybutylene terephthalate resins, etc.

[0189] In order to adjust the orientation birefringence of the molded article, the methacrylic resin composition of the present embodiment may contain inorganic fine particles having birefringence as described in Japanese Patent No. 3648201, Japanese Patent No. 4336586, etc., or a low molecular weight compound having birefringence of 5000 or less (preferably 1000 or less) as described in Japanese Patent No. 3696649.

[0190] The form of the methacrylic resin composition of the present embodiment is not particularly limited, and may be in the form of a powder, a granular body, a powder or granular body including both a powder and a granular body, or may be in the form of granules.

[0191] (Molding body)

[0192] The methacrylic resin composition of the present embodiment can be formed into a molded body by a known molding method. Examples of the molding method include: melt molding methods such as T-die method (lamination method, co-extrusion method, etc.), blown film molding method (co-extrusion method, etc.), compression molding method, blow molding method, calendaring method, vacuum molding method, injection molding method (insert method, two-color method, pressing method, core method, sandwich method, etc.); solution casting method, etc.

[0193] (resin film)

[0194] The resin film of the present embodiment is produced, for example, by using the methacrylic resin composition of the present embodiment described above and using a melt extrusion method. When the resin film is produced by the melt extrusion method, first, the methacrylic resin composition of the present embodiment is preliminarily dried, then supplied to an extruder, heated and melted, and then supplied to a T-die. Next, the methacrylic resin composition supplied to the T-die is extruded into a sheet-like molten resin, which is cooled and solidified using a cooling roll or the like, thereby obtaining a resin film.

[0195] The thickness of the resin film of the present embodiment is, for example, preferably 500 μm or less, more preferably 300 μm or less, and further preferably 200 μm or less. In addition, the thickness of the resin film of the present embodiment is, for example, preferably 10 μm or more, more preferably 30 μm or more, further preferably 50 μm or more, and particularly preferably 60 μm or more. When the thickness of the resin film is within the above range, when the resin film is used for vacuum forming, it has the advantages that it is not easy to deform and the stretched part is not easy to break. Furthermore, it also has the advantage of being able to manufacture a resin film with uniform optical properties and good transparency.

[0196] The total light transmittance of the resin film of this embodiment is preferably 85% or more, more preferably 88% or more, and further preferably 90% or more. When the total light transmittance is within the above range, the transparency is high and thus the film can be suitably used for optical applications requiring light transmittance.

[0197] The glass transition temperature of the resin film of the present embodiment is preferably 120° C. or higher, more preferably higher than 120° C., further preferably 121° C. or higher, and particularly preferably 122° C. or higher. When the glass transition temperature is within the above range, the heat resistance of the resin film becomes sufficient.

[0198] In the resin film of the present embodiment, the static friction coefficient between the surface and the back of the film is preferably 2.00 or less, more preferably 1.50 or less, and particularly preferably 1.20 or less. When the static friction coefficient between the surface and the back is 2.00 or less, adhesion of the film in the form of a film roll is suppressed, which is preferred.

[0199] Here, the static friction coefficient refers to the static friction coefficient measured under the conditions of bringing the front and back surfaces of the resin film into contact with each other, with a load of 200 g, a contact area of ​​60 mm×60 mm, and a measurement speed of 100 mm / min.

[0200] The haze of the resin film of the present embodiment is preferably 2.0% or less, more preferably 1.5% or less, further preferably 1.3% or less, and particularly preferably 1.0% or less. In addition, the internal haze of the resin film is preferably 1.5% or less, more preferably 1.0% or less, further preferably 0.5% or less, and particularly preferably 0.4% or less. When the haze and internal haze are within the above ranges, the transparency is high, so it can be suitably used for optical applications requiring light transmittance. It should be noted that the haze includes the haze inside the film and the haze on the film surface (exterior), which are expressed as internal haze and external haze, respectively.

[0201] The yellowness index YI (Yellow Index) of the resin film of the present embodiment is preferably 1.2 or less, and more preferably 1.0 or less. When YI is within the above range, the transparency is high, and thus the resin film can be suitably used for optical applications requiring light transmittance.

[0202] From the viewpoint of further improving light resistance, the resin film of the present embodiment preferably contains an ultraviolet absorber. The purpose of the ultraviolet absorber is to improve light resistance by absorbing ultraviolet rays with a wavelength of 400 nm or less. For the resin film of the present embodiment, the transmittance at a wavelength of 380 nm is preferably in the range of 2 to 30%, more preferably in the range of 4 to 20%, and even more preferably in the range of 5 to 10%.

[0203] When the proportion of crosslinked particles in the methacrylic resin composition used in the manufacture of the resin film of the present embodiment increases, the mechanical strength of the resin film, such as bending resistance, tends to be improved. Specifically, when the proportion of the crosslinked particles is 10 parts by mass or more relative to 100 parts by mass of the total of the methacrylic resin and the crosslinked particles in the methacrylic resin composition, a resin film having excellent mechanical strength, such as bending resistance, can be obtained.

[0204] The resin film of the present embodiment can be suitably used for optical films such as polarizer protective films. When the resin film of the present embodiment is used as a polarizer protective film, it is preferably small in optical anisotropy. In particular, not only the optical anisotropy in the in-plane direction (long direction, width direction) of the resin film, but also the optical anisotropy in the thickness direction is preferably small. That is, the absolute values ​​of the in-plane phase difference and the thickness direction phase difference are preferably small. For example, when the measurement wavelength is set to 590nm, the absolute value of the in-plane phase difference is preferably less than 20nm, more preferably less than 15nm. In addition, the absolute value of the thickness direction phase difference is preferably less than 50nm, more preferably less than 20nm, and further preferably less than 15nm.

[0205] Phase difference is an index value calculated based on birefringence. The in-plane phase difference (Re) and the thickness direction phase difference (Rth) can be calculated by the following formulas. For an ideal resin film that is completely optically isotropic in three dimensions, the in-plane phase difference Re and the thickness direction phase difference Rth are both 0.

[0206] Re=(nx-ny)×d

[0207] Rth=〔(nx+ny) / 2-nz〕×d

[0208] In the above formula, nx, ny, and nz represent the refractive index of each axis direction when the in-plane stretching direction (orientation direction of the polymer chain) is the X axis, the direction perpendicular to the X axis is the Y axis, and the thickness direction of the resin film is the Z axis. In addition, d represents the thickness of the resin film, and nx-ny represents the orientation birefringence. It should be noted that the MD direction of the film is the X axis, and when the film is stretched, the stretching direction is the X axis.

[0209] The orientation birefringence value of the resin film of the present embodiment is preferably -5.0×10 -4 ~5.0×10 -4 , more preferably -4.0×10 -4 ~4.0×10 -4 , more preferably -3.8×10 -4 ~3.8×10 -4 When the orientation birefringence is within the above range, birefringence does not occur during molding, and there is a tendency that stable optical characteristics can be obtained.

[0210] (Stretch)

[0211] The resin film of this embodiment may be further stretched. By stretching the resin film, it is possible to improve the mechanical strength and film thickness accuracy of the resin film.

[0212] When the resin film of the present embodiment is stretched, the methacrylic resin composition of the present embodiment is first formed into an unstretched resin film and then uniaxially stretched or biaxially stretched. Thus, a stretched film (uniaxially stretched film or biaxially stretched film) can be produced.

[0213] The stretch ratio of the stretched film is not particularly limited and is appropriately determined according to the mechanical strength, surface properties, thickness accuracy, etc. of the stretched film to be manufactured. It is also related to the stretching temperature, but in general, the stretch ratio is preferably selected from the range of 1.1 to 5 times, more preferably from the range of 1.3 to 4 times, and further preferably from the range of 1.5 to 3 times. When the stretch ratio is within the above range, there is a tendency to greatly improve the mechanical properties of the film, such as elongation, tear propagation strength, and bending fatigue resistance.

[0214] (use)

[0215] The resin film of the present embodiment can be used for various purposes such as transportation machinery, solar cell components, civil engineering and construction components, daily sundries, electrical and electronic equipment, optical components, and medical supplies. In particular, the resin film of the present embodiment has excellent heat resistance and optical properties, so it can be suitably used for optical purposes. As optical uses, for example, front panels (cover windows) of various display devices, diffusion plates, polarizer protective films, polarizing plate protective films, phase difference films, light diffusion films, optical isotropic films, etc. can be cited.

[0216] Among them, the resin film of this embodiment can be suitably used as a polarizer protective film, or a front panel (cover window) of a display device. When the resin film of this embodiment is used as a front panel (cover window) of various display devices, a functional coating layer such as a primer layer and a hard coating layer can be formed on at least one main surface of the resin film as needed. In addition, when the resin film of this embodiment is used as a polarizer protective film, the resin film of this embodiment is bonded to a polarizer to form a polarizing plate. The polarizer is not particularly limited, and any polarizer known in the past can be used. The polarizing plate is used in display devices such as liquid crystal display devices and organic EL display devices.

[0217] Example

[0218] Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to the following Examples. It should be noted that the measurement methods of various physical properties described in Examples and Comparative Examples are as follows.

[0219] (1) Polymerization conversion rate (conversion rate)

[0220] The polymerization conversion rate was determined by a gravimetric method from the ratio of the weight of the solid content remaining after drying to the weight of the added monomer. The solid content weight was determined by drying the resin beads in an oven heated to 150° C. for 30 minutes.

[0221] Conversion rate (%) = (weight of solid content / weight of added monomer) × 100

[0222] (2) Average particle size of cross-linked particles

[0223] The average particle size was measured in a latex state using a U-5100 proportional beam spectrophotometer manufactured by Hitachi High-Technologies Co., Ltd., and was determined by utilizing light scattering at a wavelength of 546 nm.

[0224] (3) Regularity of triplet representation (rr)

[0225] The methacrylic acid resin was measured using a nuclear magnetic resonance apparatus (AVANCEIII 400 MHz, manufactured by Bruker) in a deuterated chloroform solution at 22°C for 16 times. 1 H-NMR spectrum. The area (X) of the 0.60-0.95 ppm region when tetramethylsilane (TMS) is 0 ppm and the area (Y) of the 0.60-1.25 ppm region were measured from the spectrum, and then the syndiotacticity (rr) expressed by the triad was calculated using the formula: (X / Y)×100.

[0226] (4) Average molecular weight and molecular weight distribution

[0227] The weight average molecular weight (Mw), number average molecular weight (Mn), and the ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn), which is an index of molecular weight distribution, of the methacrylic resin were calculated by using the standard polystyrene conversion method of gel permeation chromatography (GPC). Specifically, a sample solution prepared by dissolving 4 mg of methacrylic resin in 2 mL of chloroform was used and analyzed using the following apparatus and conditions.

[0228] Measuring machine: HLC-8220GPC (Tosoh)

[0229] Detector: RI detector

[0230] Solvent: Chloroform

[0231] Guard column: KF-G 4A (manufactured by Resonac Co., Ltd.)

[0232] Analytical column: KF-806M and KF-806L manufactured by Resonac Co., Ltd. connected in series

[0233] Flow rate: 1mL / min

[0234] Measurement temperature: 40℃

[0235] Standard material: Standard polystyrene (Tosoh)

[0236] (5) Terminal double bond amount

[0237] As a pretreatment, methacrylic acid resin was dissolved in dichloromethane, and the solution was dropped into methanol to precipitate and purify the resin. The resin after filtering and precipitating was recovered by suction, and then dried for analysis. 20 mg of the dried methacrylic acid resin was dissolved in 0.6-0.7 mL of deuterated chloroform to prepare a solution, and the NMR was measured using a nuclear magnetic resonance device (made by Bruker, AVANCE NEO 700 MHz). 1 H-NMR. The measurement temperature was set to 20°C, the cumulative number of times was 8192, and the Excitation Sculpting (ES) method, which is a solvent elimination method, was used to measure while eliminating the peak derived from the methoxy group of the methacrylic resin (3.60 ppm, the value when the chemical shift of the solvent peak is 7.26 ppm). 1 The total area (X) of the peaks derived from the terminal double bonds of the methacrylic resin (5.47 to 5.53 ppm and 6.21 ppm) and the area (Y) of the peak derived from the α-methyl group of the methacrylic resin (0.5 to 1.25 ppm) were measured from the H-NMR spectrum, and then the ratio of the terminal double bonds of the methacrylic resin was calculated by the formula: [(3×X) / (2×Y)]×100.

[0238] (6) Glass transition temperature (Tg)

[0239] The glass transition temperature of the methacrylic resin composition particles was measured by the following method. Using a differential scanning calorimeter (DSC; manufactured by Hitachi High-Tech Science Co., Ltd., DSC7000X), the temperature was first increased from 40°C to 160°C at a heating rate of 10°C / min at a nitrogen flow rate of 40 mL / min, and after cooling to 40°C, the temperature was increased from 40°C to 160°C at a heating rate of 10°C / min for the second time. DSC measurement was performed under these conditions. Then, the midpoint glass transition temperature (the temperature of the point where a straight line with equal distances from both the straight line extrapolating the baseline before the inflection point to the high temperature side and the straight line extrapolating the baseline after the inflection point to the low temperature side intersects with the curve of the glass transition step-shaped change portion) was read from the DSC curve measured at the second heating.

[0240] (7) 5% weight loss temperature (Td5)

[0241] The 5% weight loss temperature (Td5) of the methacrylic resin composition particles and the crosslinked particle powder was measured using a thermogravimetric analyzer (manufactured by Hitachi High-Tech Science Co., Ltd., STA7200). First, the temperature was raised from 40°C to 190°C at a heating rate of 10°C / min under a nitrogen gas flow of 200 mL / min, then cooled to 40°C, and then the temperature was raised from 40°C to 500°C at a heating rate of 10°C / min. The temperature at which the sample weight obtained from the thermogravimetric (TG) curve measured at the second heating time decreased to 95% of the temperature at the start of the second heating time was taken as the 5% weight loss temperature (Td5).

[0242] (8) Retention thermal stability

[0243] The retention thermal stability of the methacrylic resin composition particles was evaluated using a thermogravimetric analyzer (manufactured by Hitachi High-Tech Science, STA7200). First, heat treatment was performed under the following conditions: under a nitrogen gas flow of 200 mL / min, the temperature was raised from 40°C to 190°C at a heating rate of 10°C / min, and maintained at 190°C for 2.0 to 2.5 minutes. Next, the mass change under the following conditions was recorded: after cooling to 40°C, the temperature was raised from 40°C to 280°C at a heating rate of 10°C / min, and maintained at 280°C for 30 minutes. The mass of the sample when the temperature reached 280°C was set as X 0 , the mass when kept at 280℃ for 15 minutes is set as X 15 , by the formula: [(X 0 -X15 ) / X 0 The retention thermal stability was evaluated by the mass reduction rate calculated by ]×100.

[0244] (9) Total light transmittance

[0245] The total light transmittance of the stretched resin film was measured using a haze meter (HZ-V3, manufactured by SUGA Testing Instruments Co., Ltd.) in accordance with JIS K7361-1.

[0246] (10) Haze, internal haze

[0247] The haze of the stretched resin film was measured using a haze meter (HZ-V3, manufactured by SUGA Testing Instruments Co., Ltd.) according to JIS K7136. In addition, glycerol was placed on both sides of the resin film, and then the film was sandwiched between two pieces of glass and the same measurement was performed. The obtained value was the internal haze. The obtained result was converted to a film thickness of 40 μm.

[0248] (11) Yellowness Index (YI)

[0249] The yellowness index (YI) of the stretched resin film was measured using a spectrophotometer (SC-P, manufactured by SUGA Test Instruments Co., Ltd.) in accordance with JIS K7373. The obtained result was converted to an equivalent of a film thickness of 40 μm.

[0250] (12) b* value

[0251] The b* value of the stretched resin film was measured using a spectrophotometer (SC-P, manufactured by SUGA Test Instruments Co., Ltd.) in accordance with JIS Z8781-4.

[0252] (13) Light transmittance at a wavelength of 380 nm

[0253] The light transmittance of the stretched resin film at a wavelength of 380 nm was measured using an ultraviolet-visible spectrophotometer (V-560, manufactured by JASCO Corporation).

[0254] (14) Static friction coefficient

[0255] The measurement was carried out according to JIS K7125. The A side of the stretched resin film was fixed on a smooth stainless steel plate, and the B side of the stretched resin film was adhered to a 60×60 mm, 200 g screw with double-sided tape. The load sensor was used to read the load when the screw was moved at a speed of 100 mm / min through the pulley, and the static friction coefficient was calculated. The film was changed and the measurement was performed 5 times, and the average value was calculated.

[0256] (15) MIT bending test

[0257] The stretched resin film was cut into strips with a width of 15 mm and used as test pieces. The test piece was measured using a MIT bending fatigue tester model D manufactured by Toyo Seiki Co., Ltd., with a test load of 1.96 N, a speed of 175 times / min, a curvature radius R of the bending fixture of 0.38 mm, and a left and right bending angle of 135°. The number of reciprocating bends at which the test piece broke was calculated. The measurement was performed 5 times in the MD direction and TD direction respectively, and the arithmetic average was used as the MIT reciprocating bend number.

[0258] (Manufacture of methacrylic resin (resin A))

[0259] In a 4-liter glass reactor equipped with an H-type stirring blade type stirrer, 150 parts by mass of deionized water, 0.20 parts by mass of calcium phosphate as a dispersant, 0.0075 parts by mass of sodium α-olefin sulfonate, and 0.30 parts by mass of sodium chloride were added. Under a nitrogen atmosphere, 100 parts by mass of methyl methacrylate (MMA), 0.289 parts by mass of n-octyl mercaptan (n-OM) as a chain transfer agent, and 0.074 parts by mass of 2,2'-azobis(isobutyric acid) dimethyl ester (Fuji Film Wako Pure Chemical Industries, Ltd., V-601) as a polymerization initiator were added to the reactor at the same time while stirring at 250 rpm. Thereafter, the liquid temperature in the reactor was raised to 70°C to start polymerization. 0.10 parts by mass of calcium phosphate was added to the reaction solution after 2 hours from the start of polymerization. A heat peak accompanied by a gel effect was observed 4 hours and 20 minutes after the start of polymerization. The temperature was raised to 95°C 7 hours after the start of polymerization. The conversion rate was 93% 7 hours after the start of polymerization. After 2 hours at 95°C, the reactor was cooled to room temperature to terminate the polymerization. The conversion rate at the end of the polymerization was 99%.

[0260] The methacrylic resin bead dispersion obtained by the above polymerization was acid-washed and water-washed with 1N hydrochloric acid in an amount 0.1 times the weight ratio of the added monomer to remove the dispersant, and then dehydrated and dried to obtain bead-shaped methacrylic resin (resin A).

[0261] (Production of acrylic crosslinked particles (1))

[0262] Into an 8 L polymerization apparatus equipped with a stirrer, 175 parts by mass of deionized water, 0.01 parts by mass of polyoxyethylene lauryl ether phosphoric acid, 0.5 parts by mass of boric acid, and 0.05 parts by mass of sodium carbonate were added.

[0263] After the inside of the polymerization machine was fully replaced with nitrogen, the internal temperature was set to 80°C, and 26% of (I) shown in Table 1 was added to the polymerization machine at once, followed by the addition of 0.06 parts by mass of sodium formaldehyde sulfoxylate, 0.006 parts by mass of ethylenediaminetetraacetic acid-2-sodium, 0.001 parts by mass of ferrous sulfate, and 0.02 parts by mass of tert-butyl hydroperoxide. After 15 minutes, 0.03 parts by mass of tert-butyl hydroperoxide was added, and the polymerization was further continued for 15 minutes. Then, 0.01 parts by mass of sodium hydroxide was added in the form of a 2% aqueous solution, and 0.09 parts by mass of polyoxyethylene lauryl ether phosphoric acid was added, and the remaining 74% of (I) was continuously added within 60 minutes. By adding 0.07 parts by mass of tert-butyl hydroperoxide 30 minutes after the addition was completed, the polymerization was further continued for 30 minutes, and the polymer of (I) was obtained.

[0264] Thereafter, 0.03 parts by mass of sodium hydroxide and 0.08 parts by mass of potassium persulfate were added in the form of a 2% aqueous solution, and (II) shown in Table 1 was then added continuously over 150 minutes. After the addition was completed, 0.02 parts by mass of potassium persulfate were added in the form of a 2% aqueous solution, and polymerization was continued for 120 minutes to obtain a polymer of (II). The average particle size was 225 nm.

[0265] Thereafter, 0.02 parts by mass of potassium persulfate was added in the form of a 2% aqueous solution, and (III-1) shown in Table 1 was continuously added over 45 minutes, and polymerization was further continued for 30 minutes.

[0266] Thereafter, (III-2) shown in Table 1 was continuously added over 25 minutes, and polymerization was further continued for 60 minutes to obtain a latex of acrylic crosslinked particles (1). The obtained latex was salted out and coagulated with magnesium chloride, washed with water, and dried to obtain white powdery acrylic crosslinked particles (1). The Td5 of the acrylic crosslinked particles (1) was 294°C.

[0267] (Production of acrylic crosslinked particles (2))

[0268] Into an 8 L polymerization apparatus equipped with a stirrer, 180 parts by mass of deionized water, 0.003 parts by mass of polyoxyethylene lauryl ether phosphoric acid, 0.5 parts by mass of boric acid, 0.05 parts by mass of sodium carbonate, and 0.01 parts by mass of sodium hydroxide were added.

[0269] After the inside of the polymerization machine was fully replaced with nitrogen, the internal temperature was set to 80°C, 0.03 parts by mass of potassium persulfate was added as a 2% aqueous solution, and (I) shown in Table 1 was continuously added over 81 minutes. The polymerization was further continued for 60 minutes to obtain a polymer of (I).

[0270] Thereafter, 0.03 parts by mass of sodium hydroxide and 0.08 parts by mass of potassium persulfate were added in the form of a 2% aqueous solution, and then (II) shown in Table 1 was continuously added over 150 minutes. After the addition was completed, 0.02 parts by mass of pure potassium persulfate was added in the form of a 2% aqueous solution, and polymerization was continued for 120 minutes to obtain a polymer of (II). The average particle size was 224 nm.

[0271] Thereafter, 0.02 parts by mass of potassium persulfate was added in the form of a 2% aqueous solution, and (III) shown in Table 1 was continuously added over 70 minutes, and polymerization was further continued for 60 minutes to obtain a latex of acrylic crosslinked particles (2). The obtained latex was salted out and coagulated by magnesium chloride, washed with water, and dried to obtain white powdery acrylic crosslinked particles (2). The Td5 of the acrylic crosslinked particles (2) was 338°C.

[0272] [Table 1]

[0273]

[0274] <Example 1>

[0275] A mixture of 90 parts by mass of methacrylic resin (resin A) and 10 parts by mass of acrylic crosslinked particles (1) was manually mixed and extruded at a resin temperature of 255° C. through an intermeshing co-rotating twin-screw extruder (manufactured by Technovel Corporation, KZW15TWIN-45MG, L / D=45) having a diameter of 15 mm. The resin extruded in the form of strands from a die head provided at the outlet of the extruder was cooled in a water tank and pelletized by a pelletizer to obtain resin composition pellets.

[0276] The obtained resin composition pellets were dried at 90°C for 4 hours and then extruded at a resin temperature of 240°C using an intermeshing co-rotating twin-screw extruder (manufactured by Technovel, KZW15TWIN-45MG, L / D=45) equipped with a T-die with a diameter of 15 mm at the extruder outlet. The sheet-like molten resin extruded from the T-die was cooled by a cooling roll to obtain a resin film with a width of 130 mm and a thickness of 160 μm. At this time, the surface in contact with the casting roll was defined as the B surface, and the other surface was defined as the A surface.

[0277] From the obtained resin film, a small piece of 100mm×100mm was cut in a manner that both sides were parallel to the extrusion direction. The small piece was placed in a pantograph twin-screw stretching device, and at 135°C, the twin-screw stretching was performed at 2 times in the direction parallel to the extrusion direction and in the direction perpendicular to the extrusion direction. The stretching speed in each direction was set to 100mm / min. Thereafter, it was taken out at room temperature and quenched to obtain a stretched film with a thickness of 38μm. The physical properties of the resin composition particles and the stretched film are shown in Table 2.

[0278] <Examples 2 and 3>

[0279] Resin composition particles and stretched films were obtained by the same method as in Example 1, except that 80 parts by mass of methacrylic resin (resin A), 20 parts by mass of acrylic crosslinked particles (1), 70 parts by mass of methacrylic resin (resin A), and 30 parts by mass of acrylic crosslinked particles (1) were used instead of 90 parts by mass of methacrylic resin (resin A) and 10 parts by mass of acrylic crosslinked particles (1) in Example 1. The thickness of the stretched films was 36 μm and 39 μm, respectively. The physical properties are shown in Table 2.

[0280] <Example 4>

[0281] Resin composition particles and a stretched film having a thickness of 39 μm were obtained by the same method as in Example 1 except that 80 parts by mass of methacrylic resin (resin A) and 20 parts by mass of acrylic crosslinked particles (2) were used instead of 90 parts by mass of methacrylic resin (resin A) and 10 parts by mass of acrylic crosslinked particles (1). The physical properties are shown in Table 2.

[0282] <Example 5>

[0283] Resin composition pellets and a stretched film having a thickness of 40 μm were obtained by the same method as in Example 1, except that 80 parts by mass of methacrylic resin (resin A), 20 parts by mass of acrylic crosslinked particles (1), and 0.7 parts by mass of an ultraviolet absorber (ADEKA STAB LA-F70 manufactured by ADEKA Corporation) were used instead of 90 parts by mass of methacrylic resin (resin A) and 10 parts by mass of acrylic crosslinked particles (1). The physical properties are shown in Table 2.

[0284] <Example 6>

[0285] Resin composition particles and a stretched film having a thickness of 40 μm were obtained by the same method as in Example 1 except that 99.9 parts by mass of methacrylic resin (resin A) and 0.1 parts by mass of acrylic crosslinked particles (2) were used instead of 90 parts by mass of methacrylic resin (resin A) and 10 parts by mass of acrylic crosslinked particles (1). The physical properties are shown in Table 2.

[0286] <Example 7>

[0287] Resin composition particles and a stretched film having a thickness of 38 μm were obtained by the same method as in Example 1, except that 99 parts by mass of methacrylic resin (resin A) and 1 part by mass of acrylic crosslinked particles (2) were used instead of 90 parts by mass of methacrylic resin (resin A) and 10 parts by mass of acrylic crosslinked particles (1). The physical properties are shown in Table 2.

[0288] <Example 8>

[0289] Resin composition particles and a stretched film having a thickness of 41 μm were obtained by the same method as in Example 1 except that 95 parts by mass of methacrylic resin (resin A) and 5 parts by mass of acrylic crosslinked particles (2) were used instead of 90 parts by mass of methacrylic resin (resin A) and 10 parts by mass of acrylic crosslinked particles (1). The physical properties are shown in Table 2.

[0290] <Comparative Example 1>

[0291] Resin composition particles and a stretched film having a thickness of 39 μm were obtained by the same method as in Example 1 except that 100 parts by mass of methacrylic resin (resin A) was used instead of 90 parts by mass of methacrylic resin (resin A) and 10 parts by mass of acrylic crosslinked particles (1). The physical properties are shown in Table 2.

[0292] The thermal decomposition resistance (Td5, retention thermal stability) of the resin composition pellets was low and the static friction coefficient of the stretched film was high compared to Examples 1 to 8. In addition, the MIT reciprocating folding number of the stretched film was low and the folding resistance was poor compared to Examples 1 to 5.

[0293] <Comparative Example 2>

[0294] 100 parts by mass of pellets of methacrylic resin (resin B) (manufactured by Kuraray Co., Ltd., Parapet HR-S) were dried at 90° C. for 4 hours and then extruded at a resin temperature of 240° C. using an intermeshing co-rotating twin-screw extruder (manufactured by Technovel Co., Ltd., KZW15TWIN-45MG, L / D=45) having a T-die at the extruder outlet and a diameter of 15 mm. The sheet-like molten resin extruded from the T-die was cooled by a cooling roll to obtain a resin film having a width of 130 mm and a thickness of 160 μm.

[0295] From the obtained resin film, a small piece of 100 mm × 100 mm was cut in a manner that both sides were parallel to the extrusion direction. The small piece was placed in a pantograph twin-screw stretching device, and the twin-screw stretching was performed at 135°C in a direction parallel to the extrusion direction and in a direction perpendicular to the extrusion direction at a rate of 2 times. The stretching speed in each direction was set to 100 mm / min. Thereafter, it was taken out at room temperature and quenched to obtain a stretched film with a thickness of 37 m. The physical properties of the resin pellets and the stretched film are shown in Table 2.

[0296] Compared with Examples 1 to 8, the thermal decomposition resistance (Td5, retention thermal stability) of the resin composition particles was low, the heat resistance (glass transition temperature) was also insufficient, and the static friction coefficient of the stretched film was also high. In addition, compared with Examples 1 to 5, the MIT reciprocating bending number of the stretched film was low, and the bending resistance was poor.

[0297] <Comparative Example 3>

[0298] Resin composition particles and a stretched film having a thickness of 39 μm were obtained by the same method as in Example 1 except that 80 parts by mass of methacrylic resin (resin B) particles and 20 parts by mass of acrylic crosslinked particles (1) were used instead of 90 parts by mass of methacrylic resin (resin A) and 10 parts by mass of acrylic crosslinked particles (1). The physical properties are shown in Table 2. Compared with Examples 1 to 8, the resin composition particles had low thermal decomposition resistance (retention heat stability), low glass transition temperature, insufficient heat resistance, and a high static friction coefficient of the stretched film.

[0299]

[0300] As can be seen from the above results, the methacrylic resin composition specified in the present invention has high thermal decomposition resistance, so it is excellent from the viewpoint of not being easy to thermally decompose when using an extruder for molding. In addition, due to the high glass transition temperature, when using an extruder for filming, the speed of cooling and solidification by the casting roll is fast and the processability is excellent. In addition, the surprising result is that the Td5 of the resin composition particles obtained by combining methacrylic resin and acrylic acid crosslinked particles is higher than the Td5 of any one of the methacrylic resin monomer and the acrylic acid crosslinked particle monomer. In addition, the resin film made by the methacrylic resin composition has excellent heat resistance while maintaining the excellent optical properties (transparency, color tone) of methacrylic resin, and, due to the low static friction coefficient, when curled into a roll, it is not easy to cause wrinkles and wrinkles caused by contact between the films, and has good winding (sliding property), which is useful as an optical film. In addition, when the proportion of acrylic acid crosslinked particles in the methacrylic resin composition increases, a resin film with improved bending resistance and excellent mechanical strength of the resin film made by the methacrylic resin composition can be obtained. Furthermore, it is possible to impart further excellent light resistance by adding an ultraviolet absorber as shown in Example 5. In addition, in the methacrylic resin composition defined in the present invention, the content of methyl methacrylate can be made very high, and therefore, it is also a useful material from the viewpoint of recycling such as material recycling and chemical recycling.

Claims

1. A methacrylic resin composition, comprising: Methacrylic resin, and Cross-linked particles, in, The methacrylic resin has a glass transition temperature of 120° C. or higher, and a syndiotacticity expressed by a triad of 55% or higher and less than 65%; The methacrylic resin composition has a 5% weight loss temperature of 334° C. or higher.

2. The methacrylic resin composition according to claim 1, wherein The methacrylic resin composition has a 5% weight loss temperature of 335° C. or higher.

3. The methacrylic resin composition according to claim 1 or 2, wherein The thermal weight loss rate when exposed to 280°C for 15 minutes in a nitrogen atmosphere was less than 1.0%.

4. The methacrylic resin composition according to claim 1 or 2, wherein The cross-linked particles are acrylic cross-linked particles.

5. The methacrylic resin composition according to claim 4, wherein The acrylic cross-linked particles are core-shell polymers.

6. The methacrylic resin composition according to claim 4, wherein The acrylic cross-linked particles are acrylic rubber particles.

7. The methacrylic resin composition according to claim 6, wherein The acrylic rubber particles are core-shell type elastomers having a core layer containing a rubbery polymer and a shell layer containing a glassy polymer.

8. The methacrylic resin composition according to claim 1 or 2, wherein The mass ratio of the methacrylic resin to the cross-linked particles is 99.9:0.1 to 65:

35.

9. The methacrylic resin composition according to claim 1 or 2, wherein The weight average molecular weight of the methacrylic resin is 70,000 to 250,000.

10. The methacrylic resin composition according to claim 1 or 2, wherein The methacrylic resin has a molecular weight distribution (Mw / Mn) of more than 1.

5. 11 . The methacrylic resin composition according to claim 1 , further comprising an ultraviolet absorber.

12. The methacrylic resin composition according to claim 1 or 2, wherein The ratio of the terminal double bonds in the methacrylic resin to the structural units derived from methyl methacrylate is 0.004 mol % or less. 13 . Particles comprising the methacrylic resin composition according to claim 1 or 2 . 14 . A resin film comprising the methacrylic resin composition according to claim 1 . 15 . An optical film comprising the methacrylic resin composition according to claim 1 .

16. The optical film according to claim 15, wherein: The static friction coefficient measured in accordance with JIS K7125 is 2.00 or less. 17 . The optical film according to claim 15 , which has a haze of 1.0% or less. The optical film according to claim 15 , which has an internal haze of 1.0% or less.

19. The optical film according to claim 15, wherein: The optical film is a polarizer protective film.

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