Methacrylic resin composition

Abstract

To provide a methacrylic resin composition for use in the formation of a resin film which retains optical properties such as transparency and color tone while exhibiting superior heat resistance and adequate mechanical strength such as crack resistance.SOLUTION: A methacrylic resin composition comprises a methacrylic resin and crosslinked particles. The methacrylic resin has a glass transition temperature of 120°C or more and a triad-based syndiotacticity of 55% or more and less than 65%. The methacrylic resin composition has a 5% weight loss temperature of 334°C or more.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Methacrylic resin has excellent transparency, weather resistance, processability, etc., and is thus widely used in various fields. In particular, a resin film obtained by molding methacrylic resin is also used for optical applications such as display devices due to its excellent optical properties. In the production of the resin film, methods such as extruding the molten methacrylic resin into a film shape and winding it up are known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, a resin film produced using methacrylic resin lacks thermal stability and does not sufficiently have mechanical strength such as crack resistance.

[0005] An object of the present invention is to provide a methacrylic resin composition for forming a resin film that is excellent in thermal stability and sufficiently has mechanical strength such as crack resistance while maintaining optical properties such as transparency and color tone.

Means for Solving the Problems

[0006] Specific means for solving the above problems include the following embodiments. <1> A methacrylic resin composition comprising a methacrylic resin and crosslinked particles, The methacrylic resin has a glass transition temperature of 120 °C or higher and a syndiotacticity of triple-chain display of 55% or more 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 <1>, wherein the 5% weight loss temperature of the methacrylic resin composition is 335 °C or higher. <3> The methacrylic resin composition according to <1> or <2>, wherein the thermogravimetric reduction rate when exposed to 280 °C for 15 minutes in a nitrogen gas atmosphere is less than 1.0%. <4> The methacrylic resin composition according to any one of <1> to <3>, wherein the crosslinked particles are acrylic crosslinked particles. <5> The methacrylic resin composition according to <4>, wherein the acrylic crosslinked particles are core-shell polymers. <6> The methacrylic resin composition according to <4>, wherein the acrylic crosslinked particles are acrylic rubber particles. <7> The methacrylic resin composition according to <6>, wherein the acrylic rubber particles are core-shell elastomers having a core layer made of a rubbery polymer and a shell layer made of a glassy polymer. <8> The methacrylic resin composition according to any one of <1> to <7>, wherein the mass ratio of the methacrylic resin to the crosslinked particles is 99.9:0.1 to 65:35. <9> The methacrylic resin composition according to any one of <1> to <8>, wherein the weight average molecular weight of the methacrylic resin is 70,000 to 250,000. <10> The methacrylic resin composition according to any one of <1> to <9>, wherein the molecular weight distribution (Mw / Mn) of the methacrylic resin exceeds 1.5. <11> The methacrylic resin composition according to any one of <1> to <10>, further comprising an ultraviolet absorber. <12> An optical film comprising the methacrylic resin composition according to any one of <1> to <11>. <13> The optical film according to <12>, wherein the optical film is a polarizer protection film.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a methacrylic resin composition for forming a resin film that has excellent thermal stability and sufficient mechanical strength such as crack resistance while maintaining optical properties such as transparency and color tone.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, specific embodiments to which the present invention is applied will be described in detail. The symbol "~" representing a numerical range is used with the intention of including the lower and upper limits of the range unless otherwise specified.

[0009] (Methacrylic resin) The methacrylic resin according to this embodiment preferably has a proportion of structural units derived from methyl methacrylate of 98% by mass or more and a proportion of structural units derived from monomers other than methyl methacrylate of 2% by mass or less. The methacrylic resin according to this embodiment preferably has a proportion of structural units derived from methyl methacrylate of 99% by mass or more, and more preferably 100% by mass (that is, a homopolymer of methyl methacrylate). The structural unit derived from methyl methacrylate is represented by the following formula.

[0010]

Chemical formula

[0011] 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 norbornenyl 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 norbornenyl methacrylate; aromatic vinyl compounds such as styrene and α-methylstyrene; acrylamide; methacrylamide; acrylonitrile; methacrylonitrile; and the like.

[0012] The methacrylic resin according to this embodiment has a syndiotacticity (rr) of 55% or more in the triad display, preferably 56% or more, and more preferably 57% or more. When the syndiotacticity (rr) in the triad display is 55% or more, the glass transition temperature (Tg) of the methacrylic resin tends to be high and the heat resistance tends to improve. Also, the syndiotacticity (rr) is less than 65% from the viewpoints of the molding processing temperature and the toughness and secondary processability of the molded article, and more preferably 63% or less.

[0013] The syndiotacticity (rr) is the ratio in which the two chains (diads) of the chain of three consecutive structural units (triads) are both racemo (rr). In the chain (diad) of the structural unit in the polymer molecule, those with the same configuration are called meso and those with the opposite configuration are called racemo, and are denoted as m and r, respectively.

[0014] The syndiotacticity (rr) is as described in the examples below, in deuterated chloroform, at 22°C, and with an integration number of 16 times. 1Measure the 1H-NMR spectrum, and measure the area (X) in the region of 0.60 to 0.95 ppm and the area (Y) in the region of 0.60 to 1.25 ppm when tetramethylsilane (TMS) is set to 0 ppm from the spectrum, and it can be calculated by the formula: (X / Y) × 100.

[0015] Moreover, the methacrylic resin according to the present embodiment has a glass transition temperature (Tg) of 120 °C or higher, preferably higher than 120 °C, more preferably 121 °C or higher, and even more preferably 122 °C or higher. The upper limit of the glass transition temperature (Tg) is not particularly limited, but from the viewpoints of the molding processing temperature and the secondary processability of the molded body, it is preferably 135 °C or lower, and may be 130 °C or lower.

[0016] The glass transition temperature (Tg) in this specification is the midpoint glass transition temperature determined from the DSC curve, and is measured by the method described in the examples below.

[0017] Note that the syndiotacticity (rr) and the glass transition temperature (Tg) of the methacrylic resin can be controlled by adjusting the polymerization temperature when synthesizing the methacrylic resin. For example, lowering the polymerization temperature is preferable for increasing the syndiotacticity (rr) of the methacrylic resin and raising the glass transition temperature (Tg). Also, the glass transition temperature (Tg) can be controlled by adjusting the molecular weight of the methacrylic resin.

[0018] Moreover, the methacrylic resin according to the present embodiment can contain a terminal structure represented by the following formula (1) derived from a polymerization initiator.

[0019] [Chemical formula] (In the formula, R 1 , R 2 , and R 3 each independently represents an alkyl group, a substituted alkyl group, an ester group, or an amide group. However, R 1 , R 2, and R 3 At least one of them represents an ester group or an amide group. R 1 , R 2 , and R 3 Two of them may be bonded to each other to form an alicyclic structure. * indicates a bond to a structural unit derived from a monomer.)

[0020] Examples of the alkyl group include linear or branched alkyl groups having 1 to 6 carbon atoms. Examples of the substituent that the alkyl group may have include a hydroxy group, a carboxy group, an alkoxy group, a halogen atom, and the like.

[0021] Examples of the ester group include a group represented by -COOR 4 . R 4 represents an alkyl group having 1 to 6 carbon atoms, and may have substituents such as a hydroxy group, a carboxy group, an alkoxy group, and a halogen atom.

[0022] Examples of the amide group include a group represented by -C(O)NR 5 . R 5 represents an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group, or an alkenyl group having 2 to 6 carbon atoms, and may have substituents such as a hydroxy group, a carboxy group, an alkoxy group, and a halogen atom.

[0023] The terminal structure represented by the above formula (1) can be introduced into the molecule of the methacrylic resin by using a non-nitrile azo polymerization initiator represented by the following formula (2) when synthesizing the methacrylic resin. R 1 , R 2 , and R 3 in the formula has the same meaning as in the above formula (1). By using such a non-nitrile azo polymerization initiator, the thermal stability of the obtained methacrylic resin tends to be improved as compared with the case of using a polymerization initiator other than the non-nitrile azo polymerization initiator (for example, a nitrile azo polymerization initiator). In addition, it is also preferable that the non-nitrile azo polymerization initiator has a lower toxicity of the initiator itself and decomposition products as compared with the nitrile azo polymerization initiator.

[0024] [Chem.]

[0025] Examples of the non-nitrile azo polymerization initiator represented by the above formula (2) include dimethyl 2,2'-azobis(isobutyrate), methyl 1,1'-azobis(cyclohexanecarboxylate), 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}, 2,2'-azobis{2-methyl-N-[2-(1-hydroxybutyl)]propionamide}, and the like. Among these, from the viewpoints of half-life temperature, cost, etc., at least one selected from dimethyl 2,2'-azobis(isobutyrate) and methyl 1,1'-azobis(cyclohexanecarboxylate) is preferable.

[0026] Further, in the methacrylic resin according to the present embodiment, the ratio of the terminal double bond to the structural unit derived from methyl methacrylate is preferably less than 0.020 mol%, more preferably less than 0.015 mol%, still more preferably less than 0.010 mol%, and even more preferably less than 0.006 mol%. If the ratio of the terminal double bond is within the above range, the thermal stability of the methacrylic resin tends to be improved.

[0027] The methacrylic resin according to this embodiment can be produced by a radical polymerization method as shown in the production method described later. The methacrylic resin produced by the radical polymerization method contains terminal double bonds generated by disproportionation termination reaction during polymerization, hydrogen abstraction reaction of monomers by a polymerization initiator, etc. Since the terminal double bonds affect the thermal stability of the resin, it is preferable that the proportion thereof is small. If the proportion of the terminal double bonds can be reduced to a range of 0.001 mol% or more and less than 0.020 mol% by the method described later, the thermal stability of the methacrylic resin tends to be greatly improved.

[0028] The proportion of the terminal double bonds to the structural unit derived from methyl methacrylate is, as described in the examples described later, in deuterated chloroform at 20 ° C. under the conditions of an integration number of 8,192 times 1 an 1H-NMR spectrum is measured, and from the spectrum, the total area (X) 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, and it can be calculated by the formula: [(3 × X) / (2 × Y)] × 100.

[0029] Note that the proportion of the terminal double bonds of the methacrylic resin can be controlled by adjusting the usage amounts of the polymerization initiator and the chain transfer agent, the polymerization temperature, the polymerization time, etc. when synthesizing the methacrylic resin. For example, reducing the usage amount of the polymerization initiator, increasing the usage amount of the chain transfer agent, lowering the polymerization temperature, and lengthening the polymerization time are preferable for reducing the proportion of the terminal double bonds.

[0030] As described above, the methacrylic resin according to this embodiment has excellent thermal stability. The methacrylic resin according to this embodiment preferably has a thermogravimetric weight loss rate of less than 2.5% when exposed to 280 ° C. for 15 minutes in a nitrogen gas atmosphere, and more preferably less than 2.3%. This thermogravimetric weight loss rate is measured by the method described in the examples described later.

[0031] The methacrylic resin according to this embodiment preferably has a weight average molecular weight (Mw) of 70,000 to 250,000, more preferably 90,000 to 150,000. When the weight average molecular weight (Mw) of the methacrylic resin is 70,000 or more, the mechanical properties of the resulting molded article tend to improve. When the weight average molecular weight (Mw) of the methacrylic resin is 250,000 or less, the moldability tends to improve.

[0032] Also, the methacrylic resin according to this embodiment preferably has a dispersity (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), exceeding 1.5, more preferably 1.6 to 2.5, and particularly preferably 1.7 to 2.2. When the dispersity (Mw / Mn) of the methacrylic resin exceeds 1.5, the fluidity of the methacrylic resin tends to improve and it becomes easier to mold. When the dispersity (Mw / Mn) of the methacrylic resin is 2.5 or less, the mechanical properties such as impact resistance, toughness, and flexural resistance of the resulting molded article tend to improve.

[0033] The weight average molecular weight (Mw) and number average molecular weight (Mn) in this specification are values in terms of standard polystyrene measured by gel permeation chromatography (GPC) and are measured by the method described in the examples below.

[0034] Note that the weight average molecular weight (Mw) and number average molecular weight (Mn) of the methacrylic resin can be controlled by adjusting the types and amounts used of the polymerization initiator and chain transfer agent when synthesizing the methacrylic resin.

[0035] The methacrylic resin according to this embodiment is not only excellent in thermal stability but also expected to be suitable for reuse, i.e., recycling, after disposal. As a recycling method of methacrylic resin, for example, chemical recycling (a method of recovering cracked oil as a decomposition product by thermal decomposition and reusing it as a chemical raw material or fuel) is known. Generally, in order to improve the heat resistance and thermal stability of methacrylic resin, a cyclic structure is introduced into the molecular structure of methacrylic resin, or a monomer having a rigid structure is copolymerized. However, these structures become impurities in performing chemical recycling, which is not preferable. In this regard, the methacrylic resin according to this embodiment has a large proportion of structural units derived from methyl methacrylate, and it is expected that the monomer recovered as cracked oil has a high yield and exhibits good chemical recyclability.

[0036] (Method for producing methacrylic resin) The method for producing a methacrylic resin according to this embodiment includes, for example, a polymerization step of polymerizing a monomer mixture having a methyl methacrylate content of 98% by mass or more at 100°C or lower in the presence of a non-nitrile-based azo polymerization initiator (hereinafter, also simply referred to as "polymerization initiator") and a chain transfer agent until 90% or more of the resulting methacrylic resin is produced. Here, "until 90% or more of the resulting methacrylic resin is produced" means "at least until the conversion rate reaches 90%" when the polymerization reaction is carried out to a conversion rate of 100%. For example, when the polymerization reaction is terminated at a conversion rate of 50%, it means "at least until the conversion rate reaches 45%". After 90% or more of the resulting methacrylic resin is produced, the polymerization temperature may be raised to a temperature exceeding 100°C for the purpose of reducing the residual monomer component and deactivating the residual polymerization initiator. As a method for producing methacrylic resin, a conventionally known polymerization method can be adopted. For example, a radical polymerization method such as a continuous bulk polymerization method, a solution polymerization method, an emulsion polymerization method, a soap-free emulsion polymerization method, or a suspension polymerization method can be adopted. Among them, from the viewpoints of the degree of freedom in the structural design of methacrylic resin, the simplicity of polymerization, productivity, etc., a production method that performs aqueous polymerization is preferable, the suspension polymerization method and the emulsion polymerization method are more preferable, and the suspension polymerization method is even more preferable.

[0037] In addition, when the methacrylic resin according to the present embodiment is produced by aqueous polymerization, it is also advantageous from the viewpoint of impurities in the resin. For example, in the anionic solution polymerization method, since an organometallic compound is used as a polymerization initiator, metal ions derived from the organometallic compound remain in the resin at about several hundred mass ppm. On the other hand, in aqueous polymerization, since an organometallic compound is not used as a polymerization initiator, the total residual metal ions in the resin can be made 100 mass ppm or less. When performing aqueous polymerization, preferably, the content of Al in the resin is 1 mass ppm or less, and the content of Li is 1 mass ppm or less. Further, in aqueous polymerization, a step of removing residual metal ions is not required, so it is excellent in economy. Furthermore, in aqueous polymerization, since organic solvents such as aliphatic hydrocarbons and alicyclic hydrocarbons used in the anionic solution polymerization method are not used, it is also excellent in terms of the environment.

[0038] (Suspension polymerization method) In the suspension polymerization method, a methacrylic resin is synthesized in an aqueous suspension obtained by mixing water, a monomer mixture, a dispersant, a polymerization initiator, a chain transfer agent, and optionally other additives. The order of mixing each component is not particularly limited. For example, each component may be mixed simultaneously to prepare an aqueous suspension. Alternatively, after mixing water, a polymerization initiator, and optionally other additives to prepare an aqueous solution, a monomer mixture and a chain transfer agent may be added, and subsequently a dispersant may be 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.

[0039] As the monomer mixture, those having a methyl methacrylate content of 98% by mass or more, preferably 99% by mass or more, more preferably 100% by mass are used.

[0040] Examples of the dispersant include hardly water-soluble inorganic salts such as tricalcium phosphate, magnesium pyrophosphate, hydroxyapatite, and kaolin; water-soluble polymers such as polyvinyl alcohol, methylcellulose, polyacrylamide, and polyvinylpyrrolidone; and the like. When using a hardly water-soluble inorganic salt as the dispersant, it is effective to use a surfactant such as sodium α-olefin sulfonate or sodium dodecylbenzenesulfonate in combination. These dispersants may be added during the polymerization as necessary.

[0041] Examples of the non-nitrile polymerization initiator include the non-nitrile azo polymerization initiator represented by the above formula (2). Among the non-nitrile azo polymerization initiators represented by the above formula (2), at least one selected from dimethyl 2,2'-azobis(isobutyrate) and methyl 1,1'-azobis(cyclohexanecarboxylate) is preferable from the viewpoints of half-life temperature, cost, etc.

[0042] In general, examples of the polymerization initiator used in the radical polymerization method include azo polymerization initiators and peroxide polymerization initiators. It is known that the free radicals generated from the polymerization initiator cause a hydrogen abstraction reaction in addition to the addition reaction to the monomer when there is a substance that easily gives hydrogen. In this regard, since the azo polymerization initiator generates only alkyl radicals, its hydrogen abstraction ability is lower than that of the peroxide polymerization initiator. Here, when the hydrogen abstraction ability of the polymerization initiator is high, for example, when methyl methacrylate is used as the monomer, hydrogen is abstracted from the α-methyl group of methyl methacrylate or the methyl group of the ester by the free radicals generated from the polymerization initiator, and polymerization proceeds from the radicals on the newly generated α-methyl group or the methyl group of the ester, and as a result, a polymer with a double bond derived from the monomer structure remaining at the end is likely to be generated. Therefore, when using a polymerization initiator with a high hydrogen abstraction ability, the resulting methacrylic resin tends to have insufficient thermal stability. Therefore, an azo polymerization initiator is more suitable than a peroxide polymerization initiator in order to obtain a methacrylic resin with high thermal stability.

[0043] The hydrogen abstraction ability of the polymerization initiator can be measured, for example, by a radical trapping method using α-methylstyrene dimer (i.e., α-methylstyrene dimer trapping method).

[0044] The amount of the polymerization initiator used is preferably 0.1 part by mass or less, more preferably 0.05 part by mass or less, and even more preferably 0.04 part by mass or less, based on 100 parts by mass of the total amount of the monomer mixture. The lower limit of the amount of the polymerization initiator used is not particularly limited, but from the viewpoint of the polymerization rate, it is preferably 0.001 part by mass or more based on 100 parts by mass of the total amount of the monomer mixture.

[0045] Examples of the chain transfer agent include primary alkyl mercaptan-based chain transfer agents such as n-butyl mercaptan, n-octyl mercaptan, n-hexadecyl mercaptan, n-dodecyl mercaptan, and n-tetradecyl mercaptan; secondary alkyl mercaptan-based chain transfer agents such as s-butyl mercaptan and s-dodecyl mercaptan; tertiary alkyl mercaptan-based chain transfer agents such as t-dodecyl mercaptan and t-tetradecyl mercaptan; thiodiglycolic acid esters such as 2-ethylhexyl thiodiglycolate, ethylene glycol dithiodiglycolate, trimethylolpropane tris(thiodiglycolate), and pentaerythritol tetrakis(thiodiglycolate); thiophenol, tetraethylthiuram disulfide, pentaphenylethane, acrolein, methacrolein, allyl alcohol, carbon tetrachloride, ethylene bromide, styrene oligomer (such as α-methylstyrene dimer), and terpinolene. These chain transfer agents may be used alone or in combination of two or more.

[0046] Among these chain transfer agents, alkyl mercaptan-based chain transfer agents and thiodiglycolic acid esters are preferred from the viewpoints of handleability, stability, and thermal stability of the resulting methacrylic resin. As the alkyl mercaptan-based chain transfer agent, n-octyl mercaptan is more preferred, and as the thiodiglycolic acid ester, 2-ethylhexyl thiodiglycolate is more preferred.

[0047] 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 it is preferably 0.45 mol% or less based on the total amount of the monomer mixture.

[0048] By setting the amount of the chain transfer agent to the above-mentioned amount, a methacrylic resin containing a structure derived from the chain transfer agent can be obtained. The structure derived from the chain transfer agent is, for example, a structure generated by the reaction of a growing radical with hydrogen of an alkyl mercaptan-based chain transfer agent or thioglycolic acid ester (that is, a saturated bond terminal structure), or a resin structure generated by the reaction of a sulfur radical generated by the extraction of hydrogen by an alkyl mercaptan-based chain transfer agent or thioglycolic acid ester with a monomer (that is, a resin structure containing sulfur). In the methacrylic resin according to the present embodiment, the amount of sulfur contained in the resin, that is, the amount of bonded sulfur atoms, is preferably 0.05 mol% or more, more preferably 0.10 mol% or more, from the viewpoint of the thermal stability of the resin. Here, the amount of bonded sulfur atoms is the amount relative to the structural unit derived from the monomer in the methacrylic resin.

[0049] In order to reduce the ratio of the terminal double bonds of the obtained methacrylic resin and improve the thermal stability, the ratio of the total mol amount of the chain transfer agent to the total mol amount of the polymerization initiator is set to 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 even more 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, but it is preferably 50 or less, for example.

[0050] When synthesizing the methacrylic resin, the polymerization temperature is set to 100°C or lower, preferably 20 - 100°C, more preferably 30 - 95°C, even more preferably 50 - 90°C, and particularly preferably 60 - 85°C, from the viewpoints of controlling the syndiotacticity of the resulting methacrylic resin and productivity. After completing the main reaction in the first-stage polymerization, in order to reduce the residual monomer, the temperature may be raised to a higher temperature than the first stage to carry out post-polymerization.

[0051] In addition, in order to initiate polymerization with a small amount of polymerization initiator, it is preferable to carry out the polymerization reaction with a low dissolved oxygen content. The dissolved oxygen content in the raw materials for polymerization is preferably 10 ppm or less, more preferably 5 ppm or less, even more preferably 4 ppm or less, and particularly preferably 2 ppm or less. By setting the dissolved oxygen content within such a range, the polymerization reaction proceeds smoothly, and the coloring of the molded body of the methacrylic resin tends to be suppressed. As a method for removing the dissolved oxygen in the raw materials for polymerization, for example, before raising the temperature to a predetermined polymerization temperature, during the temperature rise, and continuously after the temperature rise, an inert gas such as nitrogen gas is fed into the reaction vessel. In order to remove the dissolved oxygen from the raw materials added during the polymerization, it is also preferable to separately aerate an inert gas through these raw materials.

[0052] Also, in order to make the polymerization reaction proceed smoothly, when the monomer mixture contains a polymerization inhibitor, it is preferable to remove the polymerization inhibitor by distillation, alkali extraction, or using an adsorbent such as alumina, silica gel, molecular sieve, activated carbon, ion exchange resin, zeolite, acid clay, etc.

[0053] The suspension containing the methacrylic resin obtained by suspension polymerization may be subjected to washing operations such as acid washing, water washing, and alkali washing in order to remove the dispersant. The number of times of performing these washing operations may be selected as an optimal number considering the working efficiency and the removal efficiency of the dispersant, and it may be once or multiple times.

[0054] As a method for separating methacrylic resin from a suspension containing methacrylic resin, a conventionally known dehydration method can be adopted. Examples of the dehydration method include a method using a centrifuge, a method of sucking and removing water on a porous belt or a filtration membrane, and the like.

[0055] The water-containing methacrylic resin obtained through the above dehydration can be dried and recovered by a conventionally known method. Examples of the drying method include hot air drying in which hot air is sent into a tank from a hot air blower, a blow heater, etc.; vacuum drying in which the system is depressurized and then heated as necessary; barrel drying in which the obtained methacrylic resin is rotated in a container to remove moisture; spin drying in which drying is performed using centrifugal force; and the like. These drying methods may be carried out alone or in combination of two or more.

[0056] (Emulsion polymerization method) In the emulsion polymerization method, methacrylic resin is synthesized in an emulsion obtained by mixing water, a monomer mixture, an emulsifier, a polymerization initiator, a chain transfer agent, and optionally other additives.

[0057] As the monomer mixture, those having a methyl methacrylate content of 98% by mass or more, preferably 99% by mass or more, more preferably 100% by mass are used.

[0058] Examples of the emulsifier include anionic surfactants such as alkyl sulfonates, alkylbenzene sulfonates, dialkyl sulfosuccinates, α-olefin sulfonates, naphthalene sulfonate-formaldehyde condensates, alkyl naphthalene sulfonates, N-methyl-N-acyl taurine salts, phosphate esters (such as polyoxyethylene alkyl ether phosphates); nonionic surfactants; and the like. Examples of the above salts include lithium salts, sodium salts, potassium salts, calcium salts, magnesium salts, and the like. These emulsifiers may be used alone or in combination of two or more. Note that the emulsifier used in emulsion polymerization may remain in the final methacrylic resin.

[0059] When the pH of the emulsion deviates from neutrality and becomes acidic or basic, an appropriate pH adjuster can be used to prevent hydrolysis of methyl methacrylate, which is a monomer, and structural units derived from methyl methacrylate in the methacrylic resin obtained by polymerization. Examples of the pH adjuster to be used 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, disodium hydrogen phosphate - citric acid, and the like.

[0060] Examples of the polymerization initiator and the chain transfer agent include the same ones as those in the suspension polymerization method described above.

[0061] In order to reduce the proportion of terminal double bonds in the obtained methacrylic resin and improve the thermal stability, the ratio of the total mol amount of the chain transfer agent to the total mol amount of the polymerization initiator is set to 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 even more 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, but for example, it is preferably 50 or less.

[0062] The latex of the methacrylic resin obtained by emulsion polymerization is subjected to heat drying or spray drying, or is coagulated by adding a water-soluble electrolyte such as a salt or an acid, and further heat-treated, and then the resin component is separated from the aqueous phase and dried by a known method such as this to obtain a solid or powdery methacrylic resin. The above-mentioned salt is not particularly limited, but a divalent salt is preferred. Specifically, calcium salts such as calcium chloride and calcium acetate; magnesium salts such as magnesium chloride and magnesium sulfate; and the like can be mentioned. Among these salts, magnesium salts such as magnesium chloride and magnesium sulfate are preferred. Additives generally added, such as an antioxidant and an ultraviolet absorber, may be added during coagulation.

[0063] Before the above-mentioned coagulation operation, it is preferable to filter the latex with a filter, mesh, etc. to remove fine polymerization scales. Thereby, when the methacrylic resin is made into a molded body, fish eyes, foreign substances, etc. caused by fine polymerization scales can be reduced.

[0064] In this embodiment, the form of the methacrylic resin obtained by aqueous polymerization may be powder, granules, or a powder-granule mixture containing both powder and granules. Regarding the powder, granules, and primary particles constituting the powder-granule mixture, suspension polymerization is suitable when producing primary particles with an average particle diameter of about 10 to 1,000 μm, and emulsion polymerization is suitable when producing primary particles with an average particle diameter of about 50 to 500 nm. Aggregates, which are aggregates of the above primary particles, may be included in the powder, granules, and powder-granule mixture.

[0065] After the polymerization is completed, if necessary, volatile components such as residual monomers, residual oligomers, and chain transfer agents in the methacrylic resin may be removed. The removal method is not particularly limited, but heat devolatilization is preferable. Examples of the devolatilization method include treatment with 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. Since the twin-screw gives greater shear energy to the resin and has a greater degree of surface renewal compared to a single-screw, devolatilization can be carried out efficiently. The cylinder heating temperature of the extruder is preferably 150 to 270 °C, more preferably 160 to 260 °C, and even more preferably 180 to 250 °C. By setting the cylinder heating temperature to 270 °C or lower, thermal decomposition of the methacrylic resin can be suppressed.

[0066] (Crosslinked particles) By using a methacrylic resin composition containing crosslinked particles, a resin film excellent in transparency, color tone, and further excellent in mechanical strength such as flex resistance can be obtained. As the crosslinked particles, acrylic crosslinked particles are preferable. The acrylic crosslinked particles will be described below.

[0067] The acrylic crosslinked particles can be widely used, such as hard or soft acrylic crosslinked particles, without particular limitation, and can be either single-layer or multi-layer. As the hard acrylic crosslinked particles, methacrylic acid esters such as methyl methacrylate and polyfunctional monomers having two or more non-conjugated double bonds can be used as raw materials, and acrylic rubber particles with excellent thermal stability can also be used. As the acrylic rubber particles, core-shell type elastomers having a core layer made of a rubbery polymer and a shell layer made of a glassy polymer (also referred to as a hard polymer) are preferred.

[0068] The acrylic crosslinked particles can be formed, for example, by a graft copolymer called a multi-layer structure polymer, so-called core-shell type polymer. The multi-layer 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).

[0069] In the acrylic crosslinked particles, the average particle diameter of the core layer can be 125 to 400 nm. If the average particle diameter of the core layer is 125 nm or more, the strength of the produced resin film can be excellent. Also, if it is 400 nm or less, the produced resin film is excellent in transparency, appearance, optical properties, etc. The average particle diameter of the core layer is preferably 130 to 380 nm, and particularly preferably 200 to 260 nm. The average particle diameter of the core layer of the acrylic crosslinked particles in the present invention is calculated by measuring the light scattering at a wavelength of 546 nm using a spectrophotometer in the state of the polymer latex of the core layer before polymerizing the shell layer.

[0070] 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 (I) polymerization step to the (II) polymerization step corresponds to the core layer, and the polymer layer formed after the (III) polymerization step corresponds to the shell layer.

[0071] (I) Polymerization step (I) In the polymerization stage, it is preferable to polymerize a monomer mixture (a) composed of 40 to 100% by mass of a methacrylic acid ester (a-1) and 60 to 0% by mass of another monomer (a-2) having a double bond copolymerizable therewith, and 0.01 to 10 parts by mass of a polyfunctional monomer and 0.1 to 4.0 parts by mass of a chain transfer agent with respect to 100 parts by mass in total of the above (a-1) and (a-2) to obtain a rigid polymer (I).

[0072] As the other monomer having a copolymerizable double bond (hereinafter sometimes referred to as "copolymerizable monomer"), an alkyl acrylate having 1 to 12 carbon atoms in the alkyl group and / or an aromatic vinyl monomer is preferable.

[0073] The monomer mixture (a) preferably consists of 40 to 100% by mass of a methacrylic acid ester, 0 to 35% by mass of an acrylic acid ester, 0 to 10% by mass of an aromatic vinyl monomer, and 0 to 15% by mass of another monomer having a copolymerizable double bond, and particularly preferably consists of 51 to 96.8% by mass of a methacrylic acid ester, 3.1 to 29% by mass of an acrylic acid ester, 0.1 to 10% by mass of an aromatic vinyl monomer, and 0 to 10% by mass of another monomer having a copolymerizable double bond. Within this range, dipping depolymerization during high-temperature molding is suppressed to enhance thermal stability, and the resulting acrylic crosslinked particles can be blended into a methacrylic resin composition without impairing the optical properties such as the transparency and color tone of the methacrylic resin.

[0074] Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, isobornyl methacrylate, phenyl methacrylate, benzyl methacrylate and the like. Among these, alkyl methacrylates having an alkyl group with 1 to 4 carbon atoms are preferred, for example, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate and t-butyl methacrylate. These may be used alone or in combination of two or more, and methyl methacrylate is particularly preferred.

[0075] The other monomer having a copolymerizable double bond is 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 an alkyl group with 1 to 12 carbon atoms, aromatic vinyl monomers, and copolymerizable monomers other than (meth)acrylic acid esters and aromatic vinyl monomers. As the other monomer having a copolymerizable double bond, an acrylic acid alkyl ester having an alkyl group with 1 to 12 carbon atoms and / or an aromatic vinyl monomer is preferred.

[0076] (I) The amount of the polyfunctional monomer used in the polymerization stage 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 with respect to the total 100 parts by mass of (a-1) and (a-2). When the amount of the polyfunctional monomer used is 0.01 part by mass or more, the transparency of the resulting film is improved, and when it is 10 parts by mass or less, excellent mechanical properties can be imparted to the film.

[0077] As the polyfunctional monomer, any monomer known as a crosslinking agent or a crosslinkable monomer can be used. As the crosslinkable monomer, it is more preferable to use allyl methacrylate alone or a combination of allyl methacrylate and other polyfunctional monomers.

[0078] In the present invention, in the (I) polymerization stage, in the presence of a chain transfer agent, it is preferable to polymerize the monomer mixture (a) and the mixture of the polyfunctional monomer to obtain a hard polymer (I).

[0079] The chain transfer agent used in the (I) polymerization stage is not particularly limited, and a chain transfer agent known in the art can be used. These can be used alone or in combination of two or more.

[0080] When the chain transfer agent contains a sulfur component, the thermal stability of the acrylic crosslinked particles is improved. Therefore, an alkyl mercaptan-based chain transfer agent and thiophenol are preferable, and an alkyl mercaptan-based chain transfer agent is more preferable. Among them, n-octyl mercaptan and n-dodecyl mercaptan are preferable, and n-octyl mercaptan is particularly preferable.

[0081] The hard polymer (I) obtained in the (I) polymerization stage in the acrylic crosslinked particles preferably has an alkylthio group derived from an alkyl mercaptan-based chain transfer agent, and more preferably has a primary and / or secondary alkylthio group derived from a primary and / or secondary alkyl mercaptan-based chain transfer agent. The alkylthio group refers to a structure represented by RS- (R is an alkyl group) in the chemical formula, and the primary and / or secondary alkylthio group means that R is a primary and / or secondary alkyl group.

[0082] (II) Polymerization stage (II) In the polymerization stage, it is preferable to polymerize a monomer mixture (b) consisting of 60 to 100% by mass of an acrylate (b-1) and 0 to 40% by mass of another monomer (b-2) having a copolymerizable double bond, and 0.1 to 5 parts by mass of a polyfunctional monomer and 0 to 2.0 parts by mass of a chain transfer agent with respect to 100 parts by mass in total of the above (b-1) and (b-2) to obtain a soft polymer (II).

[0083] As the other monomer having a copolymerizable double bond, it is preferably at least one selected from the group consisting of a methacrylate and other monomers having a copolymerizable double bond.

[0084] As the acrylate, an alkyl acrylate having 1 to 12 carbon atoms in the alkyl group is preferable, and examples thereof include ethyl acrylate, n-butyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate and the like. These acrylates may be used alone or in combination of two or more. As the alkyl acrylate, n-butyl acrylate is preferable, and a combination of n-butyl acrylate and ethyl acrylate or a combination of n-butyl acrylate and 2-ethylhexyl acrylate is also preferable. In particular, the acrylate used in the (II) polymerization stage preferably has a content ratio of n-butyl acrylate of 50 to 100% by mass, and particularly preferably 80 to 100% by mass.

[0085] Regarding the methacrylate, other monomers having a copolymerizable double bond, polyfunctional monomers and chain transfer agents used in the (II) polymerization stage, those described in the above (I) polymerization stage can be mentioned. In the (II) polymerization stage, a chain transfer agent may or may not be used, but it is preferable not to use it.

[0086] (III) Polymerization stage (III) In the polymerization stage, it is preferable to polymerize a monomer mixture (c) consisting of 60 to 100% by mass of a methacrylate (c-1) and 40 to 0% by mass of another monomer (c-2) having a copolymerizable double bond, and 0 to 10 parts by mass of a polyfunctional monomer and 0 to 6 parts by mass of a chain transfer agent with respect to 100 parts by mass in total of the above (c-1) and (c-2) to obtain a hard polymer (III).

[0087] (III) In order to lower the glass transition temperature of the hard polymer (III) formed in the polymerization stage, the monomer mixture (c) preferably contains an acrylate. 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 in the monomer mixture (c).

[0088] The acrylic crosslinked particles have a structure in which the hard polymer (III) is graft-bonded to the hard polymer (I) and / or the soft polymer (II). All of the hard polymer (III) may be graft-bonded to the hard polymer (I) and / or the soft polymer (II), or a part of the hard polymer (III) is graft-bonded to the hard polymer (I) and / or the soft polymer (II), but the remainder may exist as a polymer component (free polymer) that is not graft-bonded to either the hard polymer (I) or the soft polymer (II). The polymer component that is not graft-bonded is also considered to constitute a part of the acrylic crosslinked particles.

[0089] (III) Examples of the methacrylate, other monomer having a copolymerizable double bond, polyfunctional monomer, and chain transfer agent used in the polymerization stage include the same ones as described in the above (I) polymerization stage. In the (III) polymerization stage, a polyfunctional monomer and / or a chain transfer agent may or may not be used, but it is preferable not to use them.

[0090] (IV) Polymerization stage (IV) In the polymerization stage, it is preferable to polymerize a monomer mixture (d) composed of 40 to 100% by mass of a methacrylate (d-1), 0 to 60% by mass of an acrylate (d-2), and 0 to 5% by mass of another monomer (d-3) having a copolymerizable double bond, and 0 to 10 parts by mass of a polyfunctional monomer and 0 to 6 parts by mass of a chain transfer agent with respect to 100 parts by mass in total of the above (d-1), (d-2) and (d-3) to obtain a hard polymer (IV).

[0091] In order to lower the glass transition temperature of the hard polymer (IV) formed in the (IV) polymerization stage, the amount of the acrylate (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.

[0092] Examples of the methacrylate, acrylate, other monomer having a copolymerizable double bond, polyfunctional monomer and chain transfer agent used in the (IV) polymerization stage are the same as those described in the above (I) to (III). In the (IV) polymerization stage, a polyfunctional monomer and / or a chain transfer agent may or may not be used, but it is preferable not to use them.

[0093] In the preferred embodiment of the acrylic crosslinked particles, the hard polymer (IV) may have a structure in which it is graft-bonded to the hard polymer (I) and / or the soft polymer (II) and / or the hard polymer (III). All 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), or a part of the hard polymer (IV) is graft-bonded to the hard polymer (I) and / or the soft polymer (II) and / or the hard polymer (III), but the remainder may exist as a polymer component that is not graft-bonded to any of the hard polymer (I), the soft polymer (II) and the hard polymer (III). The polymer component that is not graft-bonded is also considered to constitute a part of the acrylic crosslinked particles.

[0094] The acrylic crosslinked particles can be produced by ordinary emulsion polymerization using a known emulsifier.

[0095] 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 lower. The polymerization initiator is not particularly limited as long as it is a polymerization initiator having a 10-hour half-life temperature of 100°C or lower, but the 10-hour half-life temperature of the polymerization initiator is preferably 100°C or lower, more preferably 80°C or lower, and particularly preferably 75°C or lower. Further, it is preferably a persulfate, and examples thereof include potassium persulfate, sodium persulfate, ammonium persulfate, and the like. Among them, potassium persulfate is particularly preferable.

[0096] The polymerization initiator is preferably used during the polymerization in the polymerization stage, and more preferably used during the polymerization in the polymerization stage using a chain transfer agent. Further, it is particularly preferable to carry out polymerization using the polymerization initiator in all polymerization stages of the acrylic crosslinked particles.

[0097] The total amount of the polymerization initiator used is preferably 0.01 to 1.0 part by mass, and particularly preferably 0.01 to 0.2 part by mass, based on 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 a three-stage polymerization process of (I) to (III), when each monomer mixture in each of the polymerization stages of (I) to (III) is 100 parts by mass, the amount of the polymerization initiator used in each stage is preferably 0.01 to 1.85 parts by mass in the (I) polymerization stage, 0.01 to 0.6 parts by mass in the (II) polymerization stage, and 0.01 to 0.90 parts by mass in the (III) polymerization stage, and particularly preferably 0.01 to 0.2 parts by mass in the (I) polymerization stage, 0.01 to 0.4 parts by mass in the (II) polymerization stage, and 0.01 to 0.2 parts by mass in the (III) polymerization stage. Further, the amount of the polymerization initiator used in the (I) polymerization stage is preferably more than 1% by mass and 29% by mass or less based on the total amount of the polymerization initiator used.

[0098] In the present invention, the core layer of the acrylic crosslinked particles refers to a crosslinked structure polymer obtained by carrying out polymerization up to the polymerization stage (II) (therefore, the outermost layer of the core layer is a soft polymer formed by the polymerization stage (II)), and the shell layer refers to a hard polymer obtained by carrying out polymerization after the polymerization stage (II).

[0099] The latex for acrylic crosslinked particles thus obtained is coagulated by spray drying or by adding a water-soluble electrolyte such as a salt or an acid, and then, after heat treatment, the resin component is separated from the aqueous phase and appropriately washed and dried by a known method such as this, solid or powdery acrylic crosslinked particles are obtained.

[0100] In the present application, "soft" means that the glass transition temperature of the polymer is less than 10°C. From the viewpoint of enhancing the impact resistance improvement effect such as crack resistance, the glass transition temperature of the soft polymer is preferably less than 0°C, and more preferably less than -20°C. In addition, in the present application, "hard" means that the glass transition temperature of the polymer is 10°C or higher.

[0101] The hard polymer (the polymer formed by the polymerization stage (III) or (IV)) constituting the shell layer of the acrylic crosslinked particles (when the shell layer is multilayered, the layer with the highest glass transition temperature among the multilayer) preferably has a glass transition temperature of 10°C or higher and 92°C or lower.

[0102] In the present application, the glass transition temperatures of the "soft" and "hard" polymers shall be the values calculated using Fox's formula using the values described in Polymer Handbook [Polymer Hand Book (J. Brandrup, Interscience 1989)] (for example, polymethyl methacrylate is 105°C, and polybutyl acrylate is -54°C).

[0103] According to a preferred embodiment of the present invention, (I) the polymer (I) obtained in the polymerization stage is a hard polymer, (II) the polymer (II) obtained in the polymerization stage is a soft polymer, and (III) the polymer (III) obtained in the polymerization stage is a hard polymer. Further, (IV) the polymer (IV) obtained in the polymerization stage is a hard polymer. The acrylic crosslinked particles having such a configuration have a well-balanced appearance, transparency, weather resistance, gloss, processability, thermal stability, etc. when blended with various thermoplastic acrylic resins. Thereby, it is possible to provide a film excellent in thermal stability, weather resistance, gloss, processability, etc. without impairing the excellent color tone, appearance, and transparency peculiar to the blended thermoplastic acrylic resin.

[0104] (Methacrylic resin composition) The methacrylic resin composition according to the present embodiment contains the methacrylic resin according to the present embodiment described above and acrylic crosslinked particles. In the resin composition according to the present embodiment, the blending ratio of the methacrylic resin and the acrylic crosslinked particles varies depending on the use of the molded article, etc., but the mass ratio of the methacrylic resin and 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 and the acrylic crosslinked particles is preferably 95:5 to 65:35, and more preferably 90:10 to 60:40. When the blending amount of the methacrylic resin is 65 parts by mass or more with respect to a total of 100 parts by mass of the blending amounts of both the methacrylic resin and the acrylic crosslinked particles, the characteristics of the methacrylic resin can be sufficiently exhibited, and when it is 95 parts by mass or less, the mechanical strength of the methacrylic resin can be sufficiently improved.

[0105] The 5% weight loss temperature (Td5) of the methacrylic resin composition is 334°C or higher, more preferably 335°C or higher, still more preferably 336°C or higher, and particularly preferably 337°C or higher. If the 5% weight loss temperature (Td5) of the methacrylic resin composition is 334°C or higher, it can be said that the methacrylic resin composition and the resin film formed from the methacrylic resin composition are excellent in thermal decomposition resistance. The 5% weight loss temperature (Td5) can be measured using a thermogravimetric analyzer (STA7200, manufactured by Hitachi High-Tech Science Corporation).

[0106] Regarding the retention thermal stability of the methacrylic resin composition, it is preferable that the thermal weight loss rate when exposed to 280°C for 15 minutes in a nitrogen gas atmosphere is less than 1.0%. The retention thermal stability can be evaluated using a thermogravimetric analyzer (STA7200, manufactured by Hitachi High-Tech Science Corporation).

[0107] From the viewpoint of further improving the light resistance of the obtained molded article, the methacrylic resin composition according to this embodiment preferably contains an ultraviolet absorber. The ultraviolet absorber is not particularly limited, and ultraviolet absorbers conventionally blended in various resins can be used. Examples of the ultraviolet absorber include benzotriazole compounds, triazine compounds, oxalic acid anilide compounds, cyanoacrylate compounds, salicylate compounds, benzophenone compounds, and the like. Among these, triazine compounds are preferable from the viewpoint of the light resistance of the methacrylic resin composition.

[0108] Examples of triazine compounds include 2,4-diphenyl-6-(2-hydroxyphenyl-4-hexyloxyphenyl)-1,3,5-triazine, 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-(octyloxy)phenol, 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]phenol, 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]phenol, 2,4,6-tris(2-hydroxy-4-alkoxy-3-methylphenyl)-1,3,5-triazine, and the like. The alkoxy group in 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, and the like.

[0109] Among these triazine compounds, 2-(4,6-diphenyl-1,3,5-triazin-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-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]phenol is available as Adeka Stab LA-46 (manufactured by ADEKA Corporation). 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine is available as Adeka Stab LA-F70 (manufactured by ADEKA Corporation). These ultraviolet absorbers may be used alone or in combination of two or more.

[0110] When the methacrylic resin composition according to this embodiment contains an ultraviolet absorber, the amount used is not uniform depending on the type of ultraviolet absorber, usage conditions, etc., but is preferably 0.1 to 5 parts by mass, and more preferably 0.2 to 3 parts by mass with respect to 100 parts by mass of the methacrylic resin. When the amount of the ultraviolet absorber used is 0.1 part by mass or more, the ultraviolet absorption effect can be improved. Further, when the amount of the ultraviolet absorber used is 5 parts by mass or less, coloring of the obtained molded body can be suppressed, and deterioration of transparency due to an increase in haze of the molded body can be suppressed.

[0111] The methacrylic resin composition according to this embodiment may further contain known additives such as a light stabilizer, a heat stabilizer, a matting agent, a light diffusing agent, a colorant, a dye, a pigment, an antistatic agent, a heat ray reflecting material, a lubricant, a plasticizer, a stabilizer, a flame retardant, a release agent, a polymer processing aid, an antioxidant, a filler, etc., and a resin other than the methacrylic resin. Examples of the resin other than the methacrylic resin include styrene resins such as acrylonitrile styrene resin and styrene maleic anhydride resin; polycarbonate resin; polyvinyl acetal resin; cellulose acylate resin; fluorine-based resins such as polyvinylidene fluoride and polyalkyl (meth)acrylate resin; silicone-based resins; polyolefin-based resins; polyethylene terephthalate resin; polybutylene terephthalate resin; and the like.

[0112] In addition, the methacrylic resin composition according to this embodiment may contain inorganic fine particles having birefringence described in Japanese Patent No. 3648201, Japanese Patent No. 4336586, etc., and low molecular weight compounds having birefringence and a molecular weight of 5,000 or less (preferably 1,000 or less) described in Japanese Patent No. 3696649 in order to adjust the orientation birefringence of the molded body.

[0113] The form of the methacrylic resin composition according to this embodiment is not particularly limited, and it may be a powder, a granule, a powder and granule mixture containing both powder and granule, or a pellet.

[0114] (Molded body) The methacrylic resin composition according to this embodiment can be formed into a molded article by a known molding method. Examples of the molding method include melt molding methods such as the T-die method (lamination method, coextrusion method, etc.), inflation method (coextrusion method, etc.), compression molding method, blow molding method, calender molding method, vacuum molding method, injection molding method (insert method, two-color method, press method, core-back method, sandwich method, etc.); solution casting method; and the like.

[0115] (Resin film) The resin film according to this embodiment is produced, for example, by a melt extrusion method using the methacrylic resin composition according to the above-described embodiment. When producing a resin film by the melt extrusion method, first, the methacrylic resin composition according to this embodiment is pre-dried, then supplied to an extruder, heated and melted, and supplied to a T-die. Next, the methacrylic resin composition supplied to the T-die is extruded as a sheet-like molten resin and cooled and solidified using a cooling roll or the like to obtain a resin film.

[0116] The thickness of the resin film according to this embodiment is preferably, for example, 500 μm or less, more preferably 300 μm or less, and even more preferably 200 μm or less. Also, the thickness of the resin film according to this embodiment is preferably, for example, 10 μm or more, more preferably 30 μm or more, even more preferably 50 μm or more, and particularly preferably 60 μm or more. If the thickness of the resin film is within the above range, there is an advantage that when vacuum molding is carried out using the resin film, it is difficult to deform and breakage at the deep drawing part is less likely to occur. Furthermore, there is also an advantage that a resin film with uniform optical properties and good transparency can be produced.

[0117] The total light transmittance of the resin film according to this embodiment is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more. If the total light transmittance is within the above range, due to high transparency, it can be suitably used for optical applications where light transmittance is required.

[0118] The glass transition temperature of the resin film according to this embodiment is preferably 120°C or higher, more preferably higher than 120°C, even more preferably 121°C or higher, and particularly preferably 122°C or higher. If the glass transition temperature is within the above range, the heat resistance of the resin film will be sufficient.

[0119] The haze of the resin film according to this embodiment is preferably 2.0% or less, more preferably 1.5% or less, even more preferably 1.3% or less, and particularly preferably 1.0% or less. Also, the internal haze of the resin film is preferably 1.5% or less, more preferably 1.0% or less, even more preferably 0.5% or less, and particularly preferably 0.4% or less. If the haze and the internal haze are within the above ranges, due to the high transparency, it can be suitably used for optical applications where light transmittance is required. Note that the haze consists of the haze inside the film and the haze on the film surface (outside), and they are respectively expressed as internal haze and external haze.

[0120] The yellowness index YI (Yellow Index) of the resin film according to this embodiment is preferably 1.2 or less, more preferably 1.0 or less. If the YI is within the above range, due to the high transparency, it can be suitably used for optical applications where light transmittance is required.

[0121] The resin film according to this embodiment preferably contains an ultraviolet absorber from the viewpoint of further improving the light resistance. The ultraviolet absorber is intended to improve the light resistance by absorbing ultraviolet light with a wavelength of 400 nm or less. The resin film according to this embodiment preferably has a transmittance at a wavelength of 380 nm 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%.

[0122] When the proportion of crosslinked particles in the methacrylic resin composition used for manufacturing the resin film according to this embodiment increases, the mechanical strength such as the flex resistance of the resin film tends to improve. Specifically, when the proportion of the crosslinked particles in 100 parts by mass in total of the methacrylic resin and the crosslinked particles in the methacrylic resin composition is 10 parts by mass or more, a resin film excellent in mechanical strength such as flex resistance can be obtained.

[0123] The resin film according to this embodiment can be suitably used as an optical film such as a polarizer protective film. When the resin film according to this embodiment is used as a polarizer protective film, it is preferably small in optical anisotropy. In particular, it is preferably small not only in the in-plane direction (length direction, width direction) optical anisotropy of the resin film but also in the optical anisotropy in the thickness direction. That is, it is preferably small in both the absolute value of the in-plane retardation and the absolute value of the thickness direction retardation. For example, when the measurement wavelength is 590 nm, the absolute value of the in-plane retardation is preferably 20 nm or less, more preferably 15 nm or less. Also, the absolute value of the thickness direction retardation is preferably 50 nm or less, more preferably 20 nm or less, and even more preferably 15 nm or less.

[0124] Retardation is an index value calculated based on birefringence. The in-plane retardation (Re) and the thickness direction retardation (Rth) can be calculated by the following formulas respectively. In an ideal resin film that is completely optically isotropic in the three-dimensional direction, both the in-plane retardation Re and the thickness direction retardation Rth become 0.

[0125] Re = (nx - ny) × d Rth = 〔(nx + ny) / 2 - nz〕× d In the above formulas, nx, ny, and nz represent the refractive indices in the respective axial directions when the stretching direction in the plane (the 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. Also, d represents the thickness of the resin film, and nx - ny represents the orientation birefringence. Note that the MD direction of the film is the X-axis, but in the case of a stretched film, the stretching direction is the X-axis.

[0126] The resin film according to this embodiment preferably has a value of orientation birefringence of -5.0×10 -4 ~5.0×10 -4 ; more preferably -4.0×10 -4 ~4.0×10 -4 ; even more preferably -3.8×10 -4 ~3.8×10 -4 . If the orientation birefringence is within the above range, birefringence during molding process is less likely to occur, and stable optical properties tend to be obtained.

[0127] (Stretching) The resin film according to this embodiment may be further stretched. By stretching the resin film, the mechanical strength and film thickness accuracy of the resin film can be improved.

[0128] When stretching the resin film according to this embodiment, an unstretched resin film is first formed from the methacrylic resin composition according to this embodiment, and then uniaxial stretching or biaxial stretching is performed. Thereby, a stretched film (uniaxially stretched film or biaxially stretched film) can be manufactured.

[0129] The stretching 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. Although it also depends on the stretching temperature, the stretching ratio is generally preferably selected in the range of 1.1 to 5 times, more preferably selected in the range of 1.3 to 4 times, and even more preferably selected in the range of 1.5 to 3 times. If the stretching ratio is within the above range, the mechanical properties such as the elongation rate, tear propagation strength, and fatigue resistance to rubbing of the film tend to be significantly improved.

[0130] (Applications) The resin film according to this embodiment can be used for various applications such as transportation equipment, solar cell members, civil engineering and construction members, daily sundries, electric and electronic equipment, optical members, medical supplies, etc. In particular, since the resin film according to this embodiment is excellent in heat resistance and optical properties, it can be suitably used for optical applications. Examples of optical applications include front panels (cover windows) of various display devices, diffusion plates, polarizer protection films, polarizing plate protection films, retardation films, light diffusion films, optically isotropic films, and the like.

[0131] Among these, the resin film according to this embodiment can be suitably used as a polarizer protection film or a front panel (cover window) of a display device. When the resin film according to this embodiment is used as the front panel (cover window) of various display devices, a functional coating film layer such as a primer layer or a hard coat layer may be formed on at least one main surface of the resin film as necessary. Further, when the resin film according to this embodiment is used as a polarizer protection film, the resin film according to this embodiment is bonded to a polarizer to form a polarizing plate. The polarizer is not particularly limited, and any conventionally known polarizer can be used. This polarizing plate is used, for example, in display devices such as liquid crystal display devices and organic EL display devices.

Examples

[0132] Hereinafter, the present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited to the following examples. The measurement methods of various physical properties described in the examples and comparative examples are as follows.

[0133] (1) Polymerization conversion rate (conversion rate) The polymerization conversion rate was determined from the ratio of the weight of the solid content remaining after drying to the weight of the charged monomer by the gravimetric method. The weight of the solid content was determined by drying the resin beads in an oven heated to 150 °C for 30 min. Conversion rate (%) = (weight of solid content / weight of charged monomer) × 100

[0134] (2) Average particle diameter of crosslinked particles The average particle diameter was measured in the latex state. Using a U-5100 type Recio beam spectrophotometer manufactured by Hitachi High-Technologies Corporation as the measuring device, it was determined using light scattering at a wavelength of 546 nm.

[0135] (3) Syndiotacticity (rr) of triad display For methacrylic resin 1 The 1H-NMR spectrum was measured using a nuclear magnetic resonance apparatus (manufactured by Bruker, AVANCEIII 400 MHz) in a deuterated chloroform solution at 22 °C under the condition of 16 integration times. From the spectrum, the area (X) in the region of 0.60 to 0.95 ppm and the area (Y) in the region of 0.60 to 1.25 ppm were measured when tetramethylsilane (TMS) was set to 0 ppm, and then the syndiotacticity (rr) of the triad display was calculated by the formula: (X / Y) × 100.

[0136] (4) Average molecular weight, molecular weight distribution The weight average molecular weight (Mw), number average molecular weight (Mn) of the methacrylic resin, and the ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight, which is an index of the molecular weight distribution, were calculated by the standard polystyrene conversion method using gel permeation chromatography (GPC). Specifically, using a sample solution prepared by dissolving 4 mg of methacrylic resin in 2 mL of chloroform, analysis was performed using the following apparatus and conditions. Measuring instrument: HLC-8220GPC (Tosoh) Detector: RI detector Solvent: Chloroform Guard column: KF-G 4A (manufactured by Resonac Co., Ltd.) Analysis column: A series connection of KF-806M and KF-806L manufactured by Resonac Co., Ltd. Flow rate: 1 mL / min Measurement temperature: 40 °C Standard substance: Standard polystyrene (Tosoh)

[0137] (5) Amount of terminal double bonds As a pretreatment, methacrylic resin was dissolved in methylene chloride, and the solution was dropped into methanol to precipitate and purify the resin. The precipitated resin was collected by suction filtration and dried, and the dried product was subjected to analysis. A solution was prepared by dissolving 20 mg of the dried methacrylic resin in 0.6 - 0.7 mL of deuterated chloroform, and 1 1H-NMR measurement was performed using a nuclear magnetic resonance apparatus (manufactured by Bruker, AVANCE NEO 700 MHz). The measurement temperature was 20 °C, the number of integrations was 8,192 times, and using the Excitation Sculpting (ES) method, which is a kind of solvent suppression method, measurement was performed 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 was 7.26 ppm). From the obtained 1 1H-NMR spectrum, the total area (X) of the peaks (5.47 - 5.53 ppm and 6.21 ppm) derived from the terminal double bond part of the methacrylic resin and the area (Y) of the peak (0.5 - 1.25 ppm) derived from the α-methyl group of the methacrylic resin were measured. Then, the ratio of the amount of terminal double bonds in the methacrylic resin was calculated by the formula: [(3×X) / (2×Y)]×100.

[0138] (6) Glass transition temperature (Tg) The glass transition temperature of the methacrylic resin composition pellets was measured by the following method. Using a differential scanning calorimeter (DSC; manufactured by Hitachi High-Tech Science Corporation, DSC7000X), first, under a nitrogen flow rate of 40 mL / min, the first heating was performed from 40 °C to 160 °C at a heating rate of 10 °C / min. After cooling to 40 °C, DSC measurement was performed under the condition of the second heating from 40 °C to 160 °C at a heating rate of 10 °C / min. Then, from the DSC curve measured during the second heating, the midpoint glass transition temperature (the temperature at the point where a straight line equidistant in the vertical axis direction from both a straight line obtained by extrapolating the baseline before the inflection point to the high temperature side and a straight line obtained by extrapolating the baseline after the inflection point to the low temperature side, and the curve of the stepwise change part of the glass transition intersects) was read.

[0139] (7) 5% weight loss temperature (Td5) The 5% weight loss temperature (Td5) of the methacrylic resin composition pellets and the crosslinked particle powder was measured using a thermogravimetric analyzer (STA7200, manufactured by Hitachi High-Tech Science Corporation). First, under a nitrogen flow of 200 mL / min, the first temperature increase was carried out from 40°C to 190°C at a heating rate of 10°C / min. After that, it was cooled to 40°C, and then the second temperature increase was carried out from 40°C to 500°C at a heating rate of 10°C / min. The temperature at which the weight of the sample decreased to 95% of the weight at the start of the second temperature increase, as determined from the thermogravimetric (TG) curve measured during the second temperature increase, was defined as the 5% weight loss temperature (Td5).

[0140] (8) Retention heat stability The retention heat stability of the methacrylic resin composition pellets was evaluated using a thermogravimetric analyzer (STA7200, manufactured by Hitachi High-Tech Science Corporation). First, under a nitrogen flow of 200 mL / min, the temperature was increased from 40°C to 190°C at a heating rate of 10°C / min and heat-treated under the condition of holding at 190°C for 2.0 - 2.5 minutes. Then, after cooling to 40°C, the temperature was increased from 40°C to 280°C at a heating rate of 10°C / min, and the mass change was recorded under the condition of holding at 280°C for 30 minutes. Let the mass when the sample temperature reached 280°C be X0 and the mass when held at 280°C for 15 minutes be X 15 and the retention heat stability was evaluated from the mass reduction rate calculated by the formula: [(X0 - X 15 ) / X0] × 100.

[0141] (9) Total light transmittance The total light transmittance of the stretched resin film was measured in accordance with JIS K7361-1 using a haze meter (HZ-V3, manufactured by Suga Test Instruments Co., Ltd.).

[0142] (10) Haze, internal haze The haze of the stretched resin film was measured in accordance with JIS K7136 using a haze meter (HZ-V3, manufactured by Suga Test Instruments Co., Ltd.). Also, the value obtained by performing the same measurement with both sides of the resin film sandwiched between glycerin and then glass in that order was defined as the internal haze. The obtained results were converted to the equivalent of a film thickness of 40 μm.

[0143] (11) Yellowness Index (YI) The Yellowness Index (YI) of the stretched resin film was measured in accordance with JIS K7373 using a spectrophotometer (SC-P, manufactured by Suga Test Instruments Co., Ltd.). The obtained results were converted to the equivalent of a film thickness of 40 μm.

[0144] (12) b* value The b* value of the stretched resin film was measured in accordance with JIS Z8781-4 using a spectrophotometer (SC-P, manufactured by Suga Test Instruments Co., Ltd.).

[0145] (13) Light transmittance at a wavelength of 380 nm 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).

[0146] (14) Coefficient of static friction Measurement was carried out in accordance with 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 weight thread with double-sided tape. When the thread was moved at a speed of 100 mm / min via a pulley, the load was read by a load cell to calculate the coefficient of static friction. The measurement was performed 5 times by replacing the film, and the average value was calculated.

[0147] (15) MIT flex resistance test The stretched resin film was cut into strips with a width of 15 mm and used as test pieces. Using an MIT flex fatigue tester model D manufactured by Toyo Seiki Seisaku-sho, Ltd., the test was carried out at a test load of 1.96 N, a speed of 175 cycles / min, a curvature radius R of the bending clamp of 0.38 mm, and a bending angle of 135° to the left and right. The number of reciprocating bends at which the test piece broke was determined. Five measurements were performed for both the MD direction and the TD direction, and the arithmetic mean value was taken as the MIT reciprocating bend number.

[0148] (Production of methacrylic resin (resin A)) Into a 4-liter glass reactor equipped with an H-type stirring blade mixer, 150 parts by mass of deionized water, 0.20 parts by mass of tricalcium phosphate as a dispersant, 0.0075 parts by mass of sodium α-olefin sulfonate, and 0.30 parts by mass of sodium chloride were charged. While stirring at 250 rpm 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 (manufactured by Fujifilm Wako Pure Chemical Corporation, V-601) as a polymerization initiator were added into the reactor. Then, the temperature of the liquid in the reactor was raised to 70 °C to initiate polymerization. After 2 hours from the start of polymerization, 0.10 parts by mass of tricalcium phosphate was added to the reaction solution. An exothermic peak associated with the gel effect was observed at 4 hours and 20 minutes from the start of polymerization. Heating was started at 7 hours from the start of polymerization, and the temperature of the liquid in the reactor was raised to 95 °C. The conversion rate at 7 hours from the start of polymerization was 93%. Two hours after reaching 95 °C, the reactor was cooled to room temperature to terminate the polymerization. The conversion rate at the end of polymerization was 99%. The methacrylic resin bead dispersion obtained by the above polymerization was washed with 1 N hydrochloric acid in an amount 0.1 times the weight ratio based on the amount of the charged monomer, followed by acid washing and water washing to remove the dispersant and the like, and further dehydrated and dried to obtain bead-shaped methacrylic resin (resin A).

[0149] (Production of acrylic crosslinked particles (1)) 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 phosphate, 0.5 parts by mass of boric acid, and 0.05 parts by mass of sodium carbonate were charged. After thoroughly replacing the inside of the polymerization machine with nitrogen gas, the internal temperature was set to 80°C, and 26% of (I) shown in Table 1 was added to the polymerization machine all at once. Then, 0.06 parts by mass of sodium formaldehyde sulfoxylate, 0.006 parts by mass of disodium ethylenediaminetetraacetate, 0.001 parts by mass of ferrous sulfate, and 0.02 parts by mass of t-butyl hydroperoxide were added. Fifteen minutes later, 0.03 parts by mass of t-butyl hydroperoxide was added, and polymerization was continued for another 15 minutes. Next, 0.01 parts by mass of sodium hydroxide was added as a 2% aqueous solution, 0.09 parts by mass of polyoxyethylene lauryl ether phosphate was added, and the remaining 74% of (I) was continuously added over 60 minutes. Thirty minutes after the addition was completed, 0.07 parts by mass of t-butyl hydroperoxide was added, and polymerization was continued for another 30 minutes to obtain a polymer of (I). Thereafter, 0.03 parts by mass of sodium hydroxide was added as a 2% aqueous solution, 0.08 parts by mass of potassium persulfate was added as 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 potassium persulfate was added as a 2% aqueous solution, and polymerization was continued for 120 minutes to obtain a polymer of (II). The average particle diameter was 225 nm. Thereafter, 0.02 parts by mass of potassium persulfate was added as a 2% aqueous solution, (III-1) shown in Table 1 was continuously added over 45 minutes, and polymerization was continued for another 30 minutes. Thereafter, (III-2) shown in Table 1 was continuously added over 25 minutes, and polymerization was continued for another 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.

[0150] (Production of Acrylic Crosslinked Particles (2)) An 8 L polymerization apparatus equipped with a stirrer was charged with 180 parts by mass of deionized water, 0.003 parts by mass of polyoxyethylene lauryl ether phosphate, 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. After thoroughly replacing the inside of the polymerization machine with nitrogen gas, the internal temperature was set to 80°C, 0.03 parts by mass of potassium persulfate was put in as a 2% aqueous solution, and then (I) shown in Table 1 was continuously added over 81 minutes. Polymerization was further continued for 60 minutes to obtain a polymer of (I). Thereafter, 0.03 parts by mass of sodium hydroxide was added as a 2% aqueous solution, 0.08 parts by mass of potassium persulfate was added as 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 as a 2% aqueous solution, and polymerization was continued for 120 minutes to obtain a polymer of (II). The average particle diameter was 224 nm. Thereafter, 0.02 parts by mass of potassium persulfate was added as a 2% aqueous solution, (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 salting out, coagulated with 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.

[0151]

Table 1

[0152] <Example 1> A mixture of 90 parts by mass of a methacrylic resin (resin A) and 10 parts by mass of acrylic crosslinked particles (1) was extruded at a resin temperature of 255°C using a meshing type co-rotating twin-screw extruder with a diameter of 15 mm (manufactured by Technovel Corporation, KZW15TWIN-45MG, L / D = 45). The resin that came out as a strand from the die provided at the exit of the extruder was cooled in a water tank and then pelletized with a pelletizer to obtain resin composition pellets. After drying the obtained resin composition pellets at 90 °C for 4 hours, they were extruded at a resin temperature of 240 °C using a meshing co-rotating twin-screw extruder with a diameter of 15 mm equipped with a T-die at the extruder outlet (manufactured by Technovel Corporation, KZW15TWIN-45MG, L / D = 45). The sheet-like molten resin extruded from the T-die was cooled with 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 surface B, and the other surface was defined as surface A. From the obtained resin film, small pieces of 100 mm × 100 mm were cut out so that two sides were parallel to the extrusion direction. The small pieces were set in a pantograph-type biaxial stretching device and simultaneously biaxially stretched at 135 °C by 2 times in the direction parallel to the extrusion direction and 2 times in the perpendicular direction. The stretching speed in each direction was 100 mm / min. Then, it was taken out at room temperature and rapidly cooled to obtain a stretched film with a thickness of 38 μm. The physical properties of the resin composition pellets and the stretched film are shown in Table 2.

[0153] <Examples 2 and 3> Except that 80 parts by mass of methacrylic resin (resin A) and 20 parts by mass of acrylic crosslinked particles (1), and 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, resin composition pellets and stretched films were obtained in the same manner as in Example 1. The thicknesses of the stretched films were 36 μm and 39 μm, respectively. Each physical property is shown in Table 2.

[0154] <Example 4> 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) in Example 1, resin composition pellets and a stretched film with a thickness of 39 μm were obtained in the same manner as in Example 1. Each physical property is shown in Table 2.

[0155] <Example 5> In Example 1, instead of 90 parts by mass of methacrylic resin (Resin A) and 10 parts by mass of acrylic crosslinked particles (1), 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 (Adekastab LA-F70 manufactured by ADEKA Corporation) were used. Resin composition pellets and a stretched film with a thickness of 40 μm were obtained in the same manner as in Example 1. The physical properties are shown in Table 2.

[0156] <Example 6> In Example 1, instead of 90 parts by mass of methacrylic resin (Resin A) and 10 parts by mass of acrylic crosslinked particles (1), 99.9 parts by mass of methacrylic resin (Resin A) and 0.1 parts by mass of acrylic crosslinked particles (2) were used. Resin composition pellets and a stretched film with a thickness of 40 μm were obtained in the same manner as in Example 1. The physical properties are shown in Table 2.

[0157] <Example 7> In Example 1, instead of 90 parts by mass of methacrylic resin (Resin A) and 10 parts by mass of acrylic crosslinked particles (1), 99 parts by mass of methacrylic resin (Resin A) and 1 part by mass of acrylic crosslinked particles (2) were used. Resin composition pellets and a stretched film with a thickness of 38 μm were obtained in the same manner as in Example 1. The physical properties are shown in Table 2.

[0158] <Example 8> In Example 1, instead of 90 parts by mass of methacrylic resin (Resin A) and 10 parts by mass of acrylic crosslinked particles (1), 95 parts by mass of methacrylic resin (Resin A) and 5 parts by mass of acrylic crosslinked particles (2) were used. Resin composition pellets and a stretched film with a thickness of 41 μm were obtained in the same manner as in Example 1. The physical properties are shown in Table 2.

[0159] <Comparative Example 1> In Example 1, instead of 90 parts by mass of methacrylic resin (Resin A) and 10 parts by mass of acrylic crosslinked particles (1), 100 parts by mass of methacrylic resin (Resin A) were used. Resin composition pellets and a stretched film with a thickness of 39 μm were obtained in the same manner as in Example 1. The physical properties are shown in Table 2. Compared with Examples 1 to 8, the thermal decomposition resistance (Td5, residence heat stability) of the resin composition pellets was low, and the static friction coefficient of the stretched film was also high. Further, compared with Examples 1 to 5, the MIT reciprocal bending number of the stretched film was low and the bending resistance was poor.

[0160] <Comparative Example 2> 100 parts by mass of pellets of methacrylic resin (Resin B) (Parapet HR-S, manufactured by Kuraray Co., Ltd.) were dried at 90°C for 4 hours, and then extruded at a resin temperature of 240°C using a meshing type co-rotating twin-screw extruder with a diameter of 15 mm equipped with a T-die at the extruder outlet (KZW15TWIN-45MG, L / D = 45, manufactured by Technovel Corporation). The sheet-like molten resin extruded from the T-die was cooled with a cooling roll to obtain a resin film having a width of 130 mm and a thickness of 160 μm. From the obtained resin film, a 100 mm × 100 mm small piece was cut out so that both sides were parallel to the extrusion direction. The small piece was set in a pantograph type biaxial stretching device and simultaneously biaxially stretched at 135°C by 2 times in the direction parallel to the extrusion direction and 2 times in the perpendicular direction. The stretching speed in each direction was 100 mm / min. Then, it was taken out at room temperature and rapidly cooled to obtain a stretched film having a thickness of 37 μm. The physical properties of the resin pellets and the stretched film are shown in Table 2. Compared with Examples 1 to 8, the thermal decomposition resistance (Td5, residence heat stability) of the resin composition pellets was low, the heat resistance (glass transition temperature) was also insufficient, and the static friction coefficient of the stretched film was also high. Further, compared with Examples 1 to 5, the MIT reciprocal bending number of the stretched film was low and the bending resistance was poor.

[0161] <Comparative Example 3> In Example 1, instead of 90 parts by mass of methacrylic resin (Resin A) and 10 parts by mass of acrylic crosslinked particles (1), 80 parts by mass of methacrylic resin (Resin B) pellets and 20 parts by mass of acrylic crosslinked particles (1) were used. Resin composition pellets and a stretched film with a thickness of 39 μm were obtained in the same manner as in Example 1. The physical properties are shown in Table 2. Compared with Examples 1 to 8, the heat decomposition resistance (retention heat stability) of the resin composition pellets was low, the glass transition temperature was low and the heat resistance was insufficient, and the static friction coefficient of the stretched film was high.

[0162]

Table 2

[0163] From the above results, the methacrylic resin composition defined by the present invention is excellent in that it has high heat decomposition resistance and is less likely to undergo thermal decomposition during molding with an extruder. Also, since the glass transition temperature is high, during film formation with an extruder, cooling and solidification with a casting roll is fast and the processability is excellent. Further, it was a surprising result that Td5 of the resin composition pellets obtained by combining a methacrylic resin and acrylic crosslinked particles was higher than Td5 of either the methacrylic resin alone or the acrylic crosslinked particles alone. Also, the resin film produced from the methacrylic resin composition maintains the excellent optical properties (transparency, color tone) of the methacrylic resin, is excellent in heat resistance, and has a relatively low static friction coefficient, so wrinkles and creases due to contact between the films are less likely to occur when winding up as a roll, and the roll winding property (slip property) is good, making it useful as an optical film. Also, when the proportion of acrylic crosslinked particles in the methacrylic resin composition increases, the bending resistance of the resin film produced from the methacrylic resin composition is improved, and a resin film excellent in mechanical strength is obtained. Also, as shown in Example 5, it is possible to impart even more excellent light resistance by adding an ultraviolet absorber. Also, since the content of methyl methacrylate in the methacrylic resin composition defined by the present invention can be made very high, it is suggested that 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 a methacrylic resin and crosslinked particles, The methacrylic resin has a glass transition temperature of 120° C. or higher and a triad syndiotacticity of 55% or higher but lower than 65%, The 5% weight loss temperature of the methacrylic resin composition is 334°C or higher.

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

3. 3. The methacrylic resin composition according to claim 1, which has a thermal weight loss rate of less than 1.0% when exposed to 280° C. for 15 minutes in a nitrogen gas atmosphere.

4. The methacrylic resin composition according to claim 1 or 2, wherein the crosslinked particles are acrylic crosslinked particles.

5. The methacrylic resin composition according to claim 4, wherein the acrylic crosslinked particles are a core-shell type polymer.

6. The methacrylic resin composition according to claim 4, wherein the acrylic crosslinked particles are acrylic rubber particles.

7. 7. The methacrylic resin composition according to claim 6, wherein the acrylic rubber particles are a core-shell type elastomer having a core layer made of a rubber-like polymer and a shell layer made of a glassy polymer.

8. The methacrylic resin composition according to claim 1 or 2, wherein the mass ratio of the methacrylic resin to the crosslinked 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 molecular weight distribution (Mw / Mn) of the methacrylic resin exceeds 1.

5.

11. The methacrylic resin composition according to claim 1 or 2, further comprising an ultraviolet absorber.

12. An optical film comprising the methacrylic resin composition according to claim 1 or 2.

13. The optical film of claim 12 , wherein the optical film is a polarizer protection film.

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