Method for producing methacrylic polymer particles, method for producing methacrylic block copolymer particles, methacrylic polymer particles, methacrylic resin composition, and resin molded article

Abstract

To provide a method for producing methacrylic polymer particles, by which the methacrylic polymer particles excellent in polymerization stability and having a well-controlled molecular weight distribution can be obtained at a low cost and a low environmental load in a recovery process of a post-step after polymerization.SOLUTION: A polymerization step (1) of producing methacrylic polymer particles by subjecting a monomer mixture containing 50 to 100 parts by weight of a methacrylic acid ester monomer and optionally 0 to 50 parts by weight of another copolymerizable monomer per 100 parts by weight of the monomer mixture to living radical polymerization in an aqueous medium by reversible addition-fragmentation chain transfer polymerization (RAFT) using a RAFT agent, wherein the methacrylic polymer particles have a volume-average particle diameter of 100 μm or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing methacrylic polymer particles, a method for producing methacrylic block copolymer particles, methacrylic polymer particles, a methacrylic resin composition, and a resin molded article. [Background technology]

[0002] In general, acrylic resins have excellent properties such as high transparency, high weather resistance, high hardness, and easy processability. Therefore, they are used in a wide range of applications, such as automotive parts, building materials, electrical and electronic products, furniture, vehicles, and decorations, and are widely available in powder or pellet form. Conventional methods for producing acrylic resins in powder form include suspension polymerization, emulsion polymerization, precipitation polymerization, and dispersion polymerization.

[0003] Suspension polymerization is a method in which a solvent and a monomer that is insoluble in the solvent are stirred in the presence of a dispersion stabilizer to form droplets, and then polymerized using a polymerization initiator that is insoluble in the solvent to obtain polymer particles on the order of microns. This method is characterized by the fact that it produces polymers with a high degree of polymerization and that the polymer particles can be easily isolated and recovered. However, compared to emulsion polymerization, which will be described later, the large oil droplet size of suspension polymerization makes it prone to agglomeration due to collisions between oil droplets during the polymerization reaction, making it difficult to control the particle size. Emulsion polymerization is a method for obtaining nano-sized polymer particles by polymerizing solvent-insoluble monomers with a polymerization initiator that dissolves in the solvent in the presence of an emulsifier. Because the polymerization proceeds within the micelles of the emulsifier, the polymerization is relatively stable, allowing nano-sized polymer particles to be obtained. However, emulsion polymerization requires a large amount of salting-out agent when recovering the polymer particles, which raises concerns about environmental impacts and increased production costs. Precipitation polymerization is a method for obtaining polymer particles by precipitating a polymer without dissolving it in a solvent, while a monomer dissolves in the solvent. However, this method has the limitation that it can only be performed with certain combinations of solvent and monomer. Dispersion polymerization is a method of obtaining polymer particles with smaller and narrower particle size distribution by carrying out precipitation polymerization in the presence of a dispersion stabilizer, but there is a concern that the use of a large amount of dispersion stabilizer may deteriorate the color tone of the product.

[0004] Conventionally, the above-mentioned polymerization methods for obtaining polymer particles have generally been carried out in aqueous media. These polymerizations are heterogeneous systems in which droplets or micelles formed in the aqueous medium act as microreactors in which polymerization proceeds to produce polymers. Advantages of this method include the ease of removing the polymer particles by filtration, the ease of removing polymerization heat, and the high conversion of polymers. However, compared with homogeneous solution polymerization, the difficulty of controlling the reaction conditions and the lack of uniformity and stability of the polymerization system mean that there are few examples of industrial use of living radical polymerization in aqueous media.

[0005] Living radical polymerization is a method for obtaining polymers with uniform chain length by controlling the termination reaction in conventional radical polymerization using dormant species (dormant species) added to the terminal of a growing radical. Common living radical polymerization methods include atom transfer radical polymerization (ATRP), nitroxide-mediated polymerization (NMP), and reversible addition-fragmentation chain transfer polymerization (RAFT). Among these, RAFT is the most commonly used method because it can be easily performed by simply adding a RAFT agent as a chain transfer agent to the conventional radical polymerization reaction system. By appropriately selecting the type of RAFT agent, it can be applied to a variety of monomers and solvents.

[0006] As an example of living radical polymerization of an acrylic resin in an aqueous medium, Patent Document 1 discloses a method for producing a methacrylic resin by radical copolymerizing raw materials containing an acrylic acid ester and a methacrylic acid ester in the presence of a RAFT agent.

[0007] Patent Document 2 discloses a method for producing polymer microparticles by dispersing one or more second vinyl monomers in the presence of a first polymer having polymer chains of one or more first vinyl monomers and living radical polymerization active units, using living radical polymerization based on the living radical polymerization activity, and the living radical polymerization active units are active units in living radical polymerization via an exchange chain mechanism or a bond-dissociation mechanism.

[0008] Patent document 3 discloses a method for the suspension polymerization of (meth)acrylic and / or styrenic monomers to obtain beads of a composition comprising at least one block copolymer. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-128712 [Patent Document 2] International Publication No. 2021 / 095739 [Patent Document 3] International Publication No. 2022 / 123185 Summary of the Invention [Problem to be solved by the invention]

[0010] In the method disclosed in Patent Document 1, the particle size is estimated to be on the nano-order, but a large amount of salting-out agent is used to aggregate and recover polymer fine particles from emulsion polymerization latex, which raises concerns about the impact on the color tone of the product and the increased cost of the recovery process. Furthermore, when handled as polymer particles, the small particle size increases the tendency for the particles to scatter, which may make them difficult to handle. The method disclosed in Patent Document 2 produces polymer particles on the order of several hundred nanometers, but the large amount of organic solvent component raises concerns about increased costs and environmental impacts associated with post-processing such as recovery. The method disclosed in Patent Document 3 uses the NMP method for living radical polymerization, which requires the polymerization reaction to be carried out at a temperature exceeding 100°C, which places restrictions on equipment. In addition, there is room for improvement in the molecular weight distribution when the resulting block copolymer is produced.

[0011] Therefore, an object of the present invention is to provide a method for producing methacrylic polymer particles, which allows for a post-polymerization recovery process to be performed at low cost and with little environmental impact, and which provides methacrylic polymer particles having excellent polymerization stability and a well-controlled molecular weight distribution. Another object of the present invention is to provide a method for producing methacrylic block copolymer particles, which allows for a post-polymerization recovery process to be performed at low cost and with little environmental impact, and which provides methacrylic block copolymer particles having excellent polymerization stability and a well-controlled molecular weight distribution. Another object of the present invention is to provide methacrylic polymer particles that have excellent polymerization stability, large particle size, and a well-controlled molecular weight distribution, and a methacrylic resin composition and a resin molded article that contain the methacrylic polymer particles. [Means for solving the problem]

[0012] As a result of intensive research conducted by the present inventors to achieve this object, they have found that by blending a RAFT agent with a monomer mixture containing a methacrylic acid ester monomer and the like and polymerizing the mixture in an aqueous medium by reversible addition-fragmentation chain transfer polymerization (RAFT) to produce polymer particles, the post-polymerization recovery process can be performed at low cost and with little environmental impact, and methacrylic polymer particles with excellent polymerization stability and well-controlled molecular weight distribution can be obtained.

[0013] [1] A method for producing methacrylic polymer particles by polymerizing a monomer mixture, comprising: The method includes a polymerization step (1) of producing methacrylic polymer particles by living radical polymerization of a monomer mixture containing 50 to 100 parts by weight of a methacrylic acid ester monomer and, optionally, 0 to 50 parts by weight of other copolymerizable monomers, per 100 parts by weight of the monomer mixture, in an aqueous medium by reversible addition-fragmentation chain transfer polymerization (RAFT) using a RAFT agent; The method for producing methacrylic polymer particles, wherein the methacrylic polymer particles have a volume average particle size of 100 μm or more.

[0014] [2] The number average molecular weight (Mn) of the methacrylic polymer particles is 10,000 to 200,000; The method for producing methacrylic polymer particles according to [1], characterized in that the molecular weight distribution (Mw / Mn) is 1.0 to 1.9.

[0015] [3] The method for producing methacrylic polymer particles according to [1] or [2], wherein the RAFT agent has a trithiocarbonate structure.

[0016] [4] A polymerization step (2) of producing methacrylic block copolymer particles by multi-stage polymerization of a slurry containing methacrylic polymer particles produced by the method according to any one of [1] to [3], wherein a monomer copolymerizable with the methacrylic acid ester monomer is added to the slurry, and the multi-stage polymerization is carried out; A method for producing methacrylic block copolymer particles, characterized in that the molar ratio (b / a) of the number of moles (b) of the copolymerizable monomer in the polymerization step (2) to the number of moles (a) of the monomer mixture in the polymerization step (1) is 0.5 to 15.

[0017] [5] The method for producing methacrylic block copolymer particles according to [4], characterized in that the copolymerizable monomer is added directly to the slurry without recovering or purifying the methacrylic polymer particles produced in the polymerization step (1) and then polymerization is carried out in the polymerization step (2).

[0018] [6] The method for producing methacrylic block copolymer particles according to [4] or [5], wherein the molecular weight distribution (Mw / Mn) of the methacrylic block copolymer particles is 1.0 to 1.9.

[0019] [7] 50 to 100% by weight of structural units derived from methacrylic acid ester monomers, and optionally 0 to 50% by weight of structural units derived from other copolymerizable monomers; at least a portion of the polymer end structures are end structures derived from the RAFT agent; Methacrylic polymer particles having a volume average particle size of 100 μm or more.

[0020] [8] A methacrylic resin composition containing the methacrylic polymer particles according to [7] and an additional thermoplastic resin.

[0021] [9] The methacrylic resin composition according to [8], wherein the additional thermoplastic resin is a methacrylic resin.

[0022]

[10] A resin molded product obtained by molding the methacrylic polymer particles according to [7].

[0023]

[11] A resin molded product obtained by molding the methacrylic resin composition according to [8] or [9]. [Effects of the Invention]

[0024] According to the method for producing methacrylic polymer particles of the present invention, the post-polymerization recovery process is low cost and has a low environmental impact, and methacrylic polymer particles having excellent polymerization stability and a well-controlled molecular weight distribution can be obtained. Furthermore, according to the method for producing methacrylic block copolymer particles of the present invention, the recovery process after polymerization is low cost and has a low environmental impact, and methacrylic block copolymer particles having excellent polymerization stability and a well-controlled molecular weight distribution can be obtained. Furthermore, the present invention can provide methacrylic polymer particles that have excellent polymerization stability, large particle size, and a well-controlled molecular weight distribution, as well as a methacrylic resin composition and a resin molded article that contain the methacrylic polymer particles. DETAILED DESCRIPTION OF THE INVENTION

[0025] The method for producing methacrylic polymer particles, the method for producing methacrylic block copolymer particles, the methacrylic polymer particles, the methacrylic resin composition, and the resin molded article of the present invention will be described in detail below.

[0026] <Method for producing methacrylic polymer particles> The method for producing methacrylic polymer particles of this embodiment includes a polymerization step (1) of producing methacrylic polymer particles (hereinafter sometimes simply referred to as "polymer particles") by living radical polymerization of a monomer mixture containing 50 to 100 parts by weight of a methacrylic acid ester monomer and, optionally, 0 to 50 parts by weight of other copolymerizable monomers, per 100 parts by weight of the monomer mixture, by reversible addition-fragmentation chain transfer polymerization (RAFT method) using a RAFT agent in an aqueous medium; The methacrylic polymer particles are characterized in that the volume average particle size is 100 μm or more. The above-described method for producing methacrylic polymer particles allows for a post-polymerization recovery process at low cost and with low environmental impact, and produces methacrylic polymer particles with excellent polymerization stability and a well-controlled molecular weight distribution. More specifically, the volume-average particle diameter of the produced methacrylic polymer particles is 100 μm or more, which is larger than that of particles produced by emulsion polymerization or the like, and therefore the recovery process can be performed easily, resulting in low cost and low environmental impact.

[0027] The volume average particle diameter of the methacrylic polymer particles produced by the method for producing methacrylic heavy particles of this embodiment is 100 μm or more. The volume average particle diameter of the methacrylic polymer particles is preferably 100 to 1000 μm, more preferably 100 to 700 μm, and most preferably 100 to 500 μm. When the volume average particle diameter of the methacrylic polymer particles is 100 μm or more, the operation in the recovery process becomes simple, and when the volume average particle diameter is 1000 μm or less, polymerization stability tends to be improved. The volume average particle size can be measured using the laser scattering method of a Beckman Coulter LS13320.

[0028] Examples of methacrylic acid ester monomers include methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, isononyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, phenoxyethyl methacrylate, norbornyl methacrylate, isobornyl methacrylate, and 4-t-butylcyclohexyl methacrylate, as well as derivatives thereof. The above methacrylic acid ester monomers may be used alone or in combination of two or more types as necessary.

[0029] In the method for producing methacrylic polymer particles of this embodiment, the amount of the methacrylic acid ester monomer in the monomer mixture is 50 to 100 parts by weight, preferably 70 parts by weight or more, and more preferably 80 parts by weight or more, per 100 parts by weight of the monomer mixture. When the amount of the methacrylic acid ester monomer is 50 parts by weight or more per 100 parts by weight of the monomer mixture, the color tone of the resulting polymer particles is excellent, which is preferable.

[0030] Examples of copolymerizable other monomers include acrylic esters and derivatives thereof, such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, phenoxyethyl acrylate, norbornyl acrylate, isobornyl acrylate, and 4-t-butylcyclohexyl acrylate; unsaturated carboxylic acids and derivatives thereof, such as methacrylic acid, acrylic acid, and maleic acid; acid anhydrides and derivatives thereof, such as maleic anhydride; aromatic vinyl compounds and derivatives thereof, such as styrene and α-methylstyrene; and maleimides and derivatives thereof, such as N-cyclohexylmaleimide and N-phenylmaleimide. These may be used alone, or two or more may be used as necessary.

[0031] In the monomer mixture, the amount of other copolymerizable monomers is 0 to 50 parts by weight, preferably 30 parts by weight or less, more preferably 20 parts by weight or less, in 100 parts by weight of the monomer mixture.

[0032] In the method for producing methacrylic polymer particles of this embodiment, a polymerization initiator and a RAFT agent as a chain transfer agent are added in addition to the monomer mixture.

[0033] The polymerization initiator is not particularly limited, and examples thereof include organic peroxides such as diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauryl peroxide, dilauroyl peroxide, t-butylperoxy 2-ethylhexanoate, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, and 1,1-bis(t-butylperoxy)cyclohexane; azo initiators such as 2,2-azobis(isobutyronitrile) and 2,2-azobis(isobutyrate)dimethyl; and water-soluble initiators such as potassium persulfate, sodium persulfate, and ammonium persulfate. These initiators may be used alone or in combination. These radical initiators may also be combined with an appropriate reducing agent to form a redox initiator. Among these polymerization initiators, it is preferable to use azo initiators, which are less susceptible to side reactions during polymerization. The amount of the polymerization initiator is preferably 1 / 2 to 1 / 10 of the number of moles of the RAFT agent added as a chain transfer agent (described later), more preferably 1 / 3 to 1 / 6, and most preferably 1 / 4 to 1 / 5 of the number of moles of the RAFT agent.

[0034] The RAFT agent used as a chain transfer agent preferably has a thiocarbonylthio structure (represented by the following general formula (1)). [ka] (In general formula (1), Z represents an organic group which may have one or more heteroatoms selected from the group consisting of oxygen atoms, nitrogen atoms, and sulfur atoms; R represents an organic group which may have one or more heteroatoms selected from the group consisting of oxygen atoms, nitrogen atoms, and sulfur atoms. In the general formula (1), R is a substituent that cleaves to generate radicals and reacts with the monomer to promote polymerization. An appropriate substituent is selected for the monomer used. For example, R can be a nitrile group, aromatic group, or carbonyl group. In the general formula (1), Z is a substituent that affects the stability of the intermediate radical. The type of RAFT agent varies depending on the Z substituent. For example, Z can be an aromatic group such as an aryl group or a thioalkyl group. If Z is an aromatic group such as an aryl group, the agent will be a dithiobenzoate type, and if Z is a thioalkyl group, the agent will be a trithiocarbonate type. Guidelines for selecting R and Z in the general formula (1) can be found on the websites of manufacturers selling RAFT agents, such as in the organic information magazine "Wako Organic Square No. 56." R and Z can be selected by referring to such literature.

[0035] Examples of the RAFT agent include dithiobenzoate-type RAFT agents such as 4-cyano-4-[(thiobenzoyl)sulfanyl]pentanoic acid and 2-cyanopropan-2-yl benzodithioate; trithiocarbonate-type RAFT agents such as 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid, 2-cyano-2-propyldodecyltrithiocarbonate, S,S-dibenzyltrithiocarbonate and trithiocarbonate = bis[4-(allyloxycarbonyl)benzyl]; and dithiocarbamate-type RAFT agents such as 4-chloro-3,5-dimethylpyrazole-1-carbodithioate 2'-cyanonobutan-2'-yl and cyanomethyl N-methyl-N-phenyldithiocarbamate. From the viewpoint of reactivity with methacrylic acid ester monomers and hydrolysis resistance of the RAFT agent, the RAFT agent is preferably a trithiocarbonate-type RAFT agent (represented by the following general formula (2)). The amount of these RAFT agents is adjusted depending on the number average molecular weight (Mn) (hereinafter sometimes referred to as "Mn") of the target methacrylic polymer particles, and it is preferable to add them in an amount in the range of, for example, 1 mole per 100 to 2000 moles of methacrylic acid ester monomer. [ka] (In general formula (2), R is the same as in general formula (1), R' represents an organic group which may have one or more heteroatoms selected from the group consisting of oxygen atoms, nitrogen atoms, and sulfur atoms. In the above general formula (2), R and R' may be the same substituent. When R and R' are the same substituent, the RAFT agent has symmetric reactivity and is reactive at both ends.

[0036] In addition, in the method for producing methacrylic polymer particles, a chain transfer agent generally used in radical polymerization may be used in combination for the purpose of controlling the molecular weight distribution within a desired range. Examples of chain transfer agents include compounds having a mercapto group, α-methylstyrene dimer, and terpinolene. Among these, compounds having a mercapto group are preferred as chain transfer agents. Examples of compounds having a mercapto group include alkyl mercaptans such as n-octyl mercaptan, 1-dodecyl mercaptan, and t-dodecyl mercaptan, as well as 2-mercaptoethanol, aromatic mercaptans, thioglycolic acid esters, 3-mercaptopropionic acid, and β-mercaptopropionic acid esters. These may be used alone, or two or more types may be used as necessary.

[0037] The method for producing methacrylic polymer particles according to the present embodiment is not particularly limited as long as it is carried out in an aqueous medium. For example, in methods such as suspension polymerization, emulsion polymerization, precipitation polymerization, dispersion polymerization, microemulsion polymerization, and soap-free emulsion polymerization, methacrylic polymer particles having properties such as number average molecular weight (Mn) that satisfy desired ranges can be produced by adjusting the polymerization temperature and polymerization time. From the viewpoints of process simplicity, low environmental impact, and excellent color tone of the polymer, it is preferable to use suspension polymerization as the polymerization method.

[0038] In the suspension polymerization method, the ratio of the amount of water charged as a solvent to the amount of monomer charged is preferably 1.0 to 10.0, more preferably 1.0 to 5.0, and most preferably 1.0 to 3.0. When the ratio of the amount of water charged as a solvent to the amount of monomer charged is 1.0 or more, the heat of polymerization can be efficiently removed, and when it is 10.0 or less, it is preferable from the viewpoint of product yield and cost per batch.

[0039] In the method for producing methacrylic polymer particles of this embodiment, a dispersion stabilizer may be used to improve polymerization stability. The type of dispersion stabilizer used is not particularly limited, and examples include inorganic particles such as calcium phosphate, calcium carbonate, and aluminum hydroxide; surfactants such as dodecylbenzenesulfonic acid and sodium lauryl sulfate; and water-soluble polymers such as polyethylene glycol, polyvinylpyrrolidone, and modified cellulose. These dispersion stabilizers may be used alone or in combination. Among these, inorganic particles are preferred as dispersion stabilizers because they are not modified during polymerization and are inexpensively available. The amount of dispersion stabilizer used is adjusted appropriately depending on the particle size of the target polymer, but is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 2 parts by weight, and most preferably 0.5 to 1.5 parts by weight per 100 parts by weight of the monomer mixture.

[0040] In the method for producing methacrylic polymer particles of this embodiment, the polymerization temperature is adjusted appropriately depending on the molecular weight of the target polymer, and may be 50 to 100° C., preferably 60 to 90° C., and more preferably 70 to 80° C. A polymerization temperature of 50° C. or higher can increase the polymerization rate, and a polymerization temperature of 100° C. or lower does not have equipment limitations.

[0041] In the method for producing methacrylic polymer particles according to this embodiment, the polymerization time is also appropriately adjusted depending on the molecular weight of the target methacrylic polymer particles. The polymerization time is, for example, 30 to 480 minutes, preferably 30 to 300 minutes, and more preferably 60 to 180 minutes. By setting the polymerization time to 30 minutes or more, the monomer conversion rate can be sufficiently increased, and by setting it to 480 minutes or less, there is an advantage in terms of production costs.

[0042] The methacrylic polymer particles produced by the method for producing methacrylic polymer particles of this embodiment preferably have a number average molecular weight of 10,000 to 200,000, more preferably 50,000 to 150,000, and even more preferably 80,000 to 120,000. Having an Mn of 10,000 or more improves polymerization stability during polymerization, while having an Mn of 200,000 or less improves the processability of the methacrylic polymer particles. Mn is a value obtained by converting a chromatogram measured by gel permeation chromatography (GPC) into the molecular weight of standard PMMA.

[0043] The methacrylic polymer particles produced by the method for producing methacrylic polymer particles of this embodiment preferably have a ratio of weight-average molecular weight (hereinafter sometimes referred to as "Mw") to number-average molecular weight (Mw / Mn: hereinafter sometimes referred to as "molecular weight distribution") of 1.0 to 1.9, more preferably 1.0 to 1.5, and even more preferably 1.0 to 1.3. Polymers polymerized by living radical polymerization are characterized by a narrow molecular weight distribution, and a smaller Mw / Mn value indicates a more highly controlled polymerization. Mw is a value obtained by converting a chromatogram measured by gel permeation chromatography (GPC) into the molecular weight of standard PMMA.

[0044] <Method for producing methacrylic block copolymer particles> The method for producing methacrylic block copolymer particles (hereinafter, sometimes simply referred to as "block copolymer particles") of this embodiment includes a polymerization step (2) in which a monomer copolymerizable with a methacrylic acid ester monomer is added to a slurry containing methacrylic polymer particles produced by the method for producing methacrylic polymer particles of this embodiment, and a multi-stage polymerization is performed to produce methacrylic block copolymer particles, The molar ratio (b / a) of the number of moles (b) of the copolymerizable monomer in the polymerization step (2) to the number of moles (a) of the monomer mixture in the polymerization step (1) is 0.5 to 15. According to the above-described method for producing methacrylic block copolymer particles, the post-polymerization recovery process is low cost and has a low environmental impact, and methacrylic block copolymer particles having excellent polymerization stability and a well-controlled molecular weight distribution can be obtained.

[0045] In the above-described method for producing methacrylic block copolymer particles, the methacrylic polymer particles obtained by the method for producing methacrylic polymer particles of this embodiment are used as a macro RAFT agent, and a monomer copolymerizable with the methacrylic acid ester monomer (hereinafter sometimes simply referred to as a "copolymerizable monomer") is added to produce block copolymer particles having any polymer structure. The block copolymer particles are block copolymer particles consisting of at least two or more polymer blocks, and some of the polymer blocks may have a continuous gradient orientation of the composition.

[0046] Examples of methods for producing block copolymer particles include a method in which polymer particles (macro RAFT agent) having RAFT agent terminals polymerized in polymerization step (1) are recovered and purified, and then the macro RAFT agent and a polymerizable monomer are newly mixed in polymerization step (2) to perform multi-stage polymerization; and a method in which a second new monomer (a monomer copolymerizable with the methacrylic acid ester monomer) is added directly to the system obtained by polymerizing the macro RAFT agent in polymerization step (1) to perform multi-stage polymerization in one pod. Among these methods, the method of obtaining block copolymer particles by multi-stage polymerization in one pod is preferred in terms of the complexity and production cost of the production process. That is, it is preferable to perform polymerization in polymerization step (2) by directly adding a monomer copolymerizable with the methacrylic acid ester monomer to the slurry of the methacrylic polymer particles produced in polymerization step (1) without recovering and purifying them.

[0047] In the method for producing methacrylic block copolymer particles of this embodiment, a block copolymer can be obtained by adding a monomer copolymerizable with the methacrylic acid ester monomer (hereinafter, sometimes simply referred to as "copolymerizable monomer") to the polymer particles polymerized in the polymerization step (polymerization step (1)) of the methacrylic polymer particles. Examples of the monomer copolymerizable with the methacrylic acid ester monomer include methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, isononyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, phenoxyethyl methacrylate, norbornyl methacrylate, isobornyl methacrylate, and 4-t-butylcyclohexyl methacrylate, and derivatives thereof; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, and t-butyl acrylate; Examples of copolymerizable monomers include acrylic esters and derivatives thereof, such as 2-ethylhexyl acrylate, isononyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, phenoxyethyl acrylate, norbornyl acrylate, isobornyl acrylate, and 4-t-butylcyclohexyl acrylate; unsaturated carboxylic acids and derivatives thereof, such as methacrylic acid, acrylic acid, and maleic acid; acid anhydrides and derivatives thereof, such as maleic anhydride; aromatic vinyl compounds and derivatives thereof, such as styrene and α-methylstyrene; and maleimides and derivatives thereof, such as N-cyclohexylmaleimide and N-phenylmaleimide. The copolymerizable monomers may be used alone or in combination of two or more, if necessary.

[0048] The amount of the monomer copolymerizable with the methacrylic acid ester monomer used is adjusted appropriately depending on the molecular weight of the target polymer, but for example, the molar ratio (b / a) of the number of moles (a) of the monomer mixture added in polymerization step (1) to the number of moles (b) of the copolymerizable monomer added in polymerization step (2) is preferably in the range of 0.5 to 15. The molar ratio (b / a) is more preferably 1 to 10, and even more preferably 1 to 5. A molar ratio (b / a) of 0.5 or more increases the polymerization stability in polymerization step (2), while a molar ratio (b / a) of 15 or less makes it possible to obtain block copolymer particles that do not impair the polymer properties of polymerization step (1).

[0049] The method for producing methacrylic block copolymer particles according to this embodiment may further include a polymerization step (3). By including this additional polymerization step, methacrylic block copolymer particles having three polymer blocks can be produced. When producing block copolymer particles having three polymer blocks, the molar ratio (c / (a+b)) of the number of moles (c) of the monomer copolymerizable with the methacrylic acid ester monomer newly added in the polymerization step (3) to the sum of the number of moles (a) of the monomer mixture in the polymerization step (1) and the number of moles (b) of the monomer in the polymerization step (2) is preferably in the range of 0.5 to 15, more preferably 1 to 10, and even more preferably 1 to 5. A molar ratio (c / (a+b)) of 0.5 or more increases the polymerization stability in the polymerization step (3), while a molar ratio of 15 or less allows for the production of block copolymer particles that do not impair the polymer properties of the polymerization step (2). The methacrylate ester monomer in the polymerization step (3) is the same as that in the polymerization step (2). Furthermore, although the polymerization step (3) has been described in this embodiment, an additional polymerization step (for example, polymerization step (4)) may be included as necessary.

[0050] During the production of the methacrylic block copolymer particles of this embodiment, a polymerization initiator may be added as a radical source. The polymerization initiator is not particularly limited, and examples thereof include organic peroxides such as diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauryl peroxide, dilauroyl peroxide, t-butylperoxy 2-ethylhexanoate, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, and 1,1-bis(t-butylperoxy)cyclohexane; azo initiators such as 2,2-azobis(isobutyronitrile) and 2,2-azobis(isobutyrate) dimethyl; and water-soluble initiators such as potassium persulfate, sodium persulfate, and ammonium persulfate. These initiators may be used alone or in combination. Furthermore, these polymerization initiators may be combined with an appropriate reducing agent to form a redox initiator. Among the above polymerization initiators, it is preferable to use an azo initiator, which is less susceptible to side reactions during polymerization. In the polymerization step (2), the amount of the polymerization initiator is preferably 1 / 2 to 1 / 10 of the number of moles of the macro RAFT agent (methacrylic polymer particles) polymerized in the polymerization step (1), more preferably 1 / 3 to 1 / 6, and most preferably 1 / 4 to 1 / 5 of the number of moles of the macro RAFT agent (methacrylic polymer particles).

[0051] The ratio of the weight-average molecular weight (hereinafter sometimes referred to as "Mw") to the number-average molecular weight (Mw / Mn; hereinafter this value may be referred to as "molecular weight distribution") of the methacrylic block copolymer particles obtained by the method for producing methacrylic block copolymer particles of this embodiment is preferably 1.0 to 1.9, more preferably 1.0 to 1.5, and even more preferably 1.0 to 1.3. Copolymers polymerized by living radical polymerization are characterized by a narrow molecular weight distribution, and a smaller Mw / Mn value indicates a more highly controlled polymerization. Note that Mn and Mw are values ​​obtained by converting a chromatogram measured by gel permeation chromatography (GPC) into the molecular weight of standard PMMA.

[0052] <Methacrylic polymer particles> The methacrylic polymer particles of the present embodiment contain 50 to 100% by weight of structural units derived from methacrylic acid ester monomers, and optionally 0 to 50% by weight of structural units derived from other copolymerizable monomers, at least a portion of the polymer end structures are end structures derived from the RAFT agent; It is characterized by having a volume average particle size of 100 μm or more.

[0053] In the methacrylic polymer particles, the amount of the structural units derived from the methacrylic acid ester monomer is 50% by weight or more, preferably 70% by weight or more, and more preferably 80% by weight or more. When the structural units derived from the methacrylic acid ester monomer are 50% by weight or more, the color tone of the resulting polymer particles is excellent, which is preferable.

[0054] In the methacrylic polymer particles, the amount of structural units derived from other copolymerizable monomers is 50% by weight or less, preferably 30% by weight or less, and more preferably 20% by weight or less.

[0055] In the methacrylic polymer particles of this embodiment, at least a part of the polymer end structures is an end structure derived from a RAFT agent. The end structure derived from a RAFT agent is preferably an end structure derived from a RAFT agent having a thiocarbonylthio structure, and more preferably an end structure derived from a trithiocarbonate-type RAFT agent. The end structure derived from a RAFT agent is 1 This can be confirmed by H-NMR.

[0056] When a RAFT agent having a thiocarbonylthio structure represented by the following general formula (1) is used as the terminal structure derived from the RAFT agent, the terminal structure derived from the RAFT agent will be the following general formula (3) or *-R (where R is the same as in general formula (1), and * represents a bond). [ka] [ka] (In general formula (3), Z is the same as in general formula (1), and * represents a bond.)

[0057] The polymerization initiator is not particularly limited, and examples thereof include organic peroxides such as diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauryl peroxide, dilauroyl peroxide, t-butylperoxy 2-ethylhexanoate, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, and 1,1-bis(t-butylperoxy)cyclohexane; azo initiators such as 2,2-azobis(isobutyronitrile) and 2,2-azobis(isobutyrate) dimethyl; and water-soluble initiators such as potassium persulfate, sodium persulfate, and ammonium persulfate. These initiators may be used alone or in combination. These radical initiators may also be combined with an appropriate reducing agent to form a redox initiator. It is preferable to use an azo initiator as the polymerization initiator, as it is less susceptible to side reactions during polymerization. The number of moles of these polymerization initiators is preferably 1 / 2 to 1 / 10, more preferably 1 / 3 to 1 / 6, and most preferably 1 / 4 to 1 / 5, of the number of moles of the RAFT agent added as a chain transfer agent.

[0058] The RAFT agent used as a chain transfer agent preferably has a thiocarbonylthio structure. Examples of the RAFT agent include dithiobenzoate-type RAFT agents such as 4-cyano-4-[(thiobenzoyl)sulfanyl]pentanoic acid and 2-cyanopropan-2-yl benzodithioate; trithiocarbonate-type RAFT agents such as 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid, 2-cyano-2-propyldodecyltrithiocarbonate, S,S-dibenzyltrithiocarbonate, and trithiocarbonate = bis[4-(allyloxycarbonyl)benzyl]; and dithiocarbamate-type RAFT agents such as 2'-cyanonobutan-2'-yl 4-chloro-3,5-dimethylpyrazole-1-carbodithioate and cyanomethyl N-methyl-N-phenyldithiocarbamate. From the viewpoint of reactivity with methacrylic acid ester monomers and the hydrolysis resistance of the RAFT agent, the RAFT agent is preferably a trithiocarbonate-type RAFT agent.

[0059] In the methacrylic polymer particles of this embodiment, the amount of RAFT agent is adjusted depending on the number-average molecular weight (Mn) of the target methacrylic polymer particles, but it is preferably added in an amount within a range of, for example, 1 mol per 100 to 2000 mols of methacrylic acid ester monomer. For example, from the perspective of increasing the molecular weight of the resulting polymer and increasing its strength, the amount of RAFT agent is preferably 1.0 mol to 3.0 mol, more preferably 1.0 mol to 2.0 mol, and even more preferably 1.0 mol to 1.5 mol, per 1000 mol of methacrylic acid ester monomer.

[0060] The methacrylic polymer particles of this embodiment preferably have an Mn of 10,000 to 200,000, more preferably 50,000 to 150,000, and even more preferably 10,000 to 120,000. Having an Mn of 10,000 or more improves polymerization stability during polymerization, while having an Mn of 200,000 or less improves the processability of the methacrylic polymer particles. Mn is a value obtained by converting a chromatogram measured by gel permeation chromatography (GPC) into the molecular weight of standard PMMA.

[0061] The ratio of the weight-average molecular weight (hereinafter sometimes referred to as "Mw") to the number-average molecular weight (Mw / Mn: hereinafter sometimes referred to as "molecular weight distribution") of the methacrylic polymer particles of this embodiment is preferably 1.0 to 1.9, more preferably 1.0 to 1.5, and even more preferably 1.0 to 1.3. Polymers polymerized by living radical polymerization are characterized by a narrow molecular weight distribution, and a smaller Mw / Mn value indicates a more highly controlled polymerization. Mw is a value obtained by converting a chromatogram measured by gel permeation chromatography (GPC) into the molecular weight of standard PMMA.

[0062] The volume average particle diameter of the methacrylic heavy particles of this embodiment is 100 μm or more. The volume average particle diameter of the methacrylic polymer particles is preferably 100 to 1000 μm, more preferably 100 to 700 μm, and most preferably 100 to 500 μm. When the volume average particle diameter of the methacrylic polymer particles is 100 μm or more, the environmental load can be reduced, and when it is 1000 μm or less, polymerization stability tends to be improved. The volume average particle size of the methacrylic polymer particles can be measured using a laser scattering method with a Beckman Coulter LS13320.

[0063] The value obtained by dividing the standard deviation of the volume-average particle diameter of the methacrylic heavy particle of this embodiment by the average value (hereinafter, sometimes referred to as "CV value") is preferably 10 to 200. The CV value is more preferably 10 to 100, and most preferably 10 to 50. A smaller CV value indicates higher monodispersity of the volume-average particle diameter and better polymerization stability. Furthermore, a smaller CV value is preferable because it can suppress quality deterioration due to clogging in piping, torque fluctuations during molding, etc.

[0064] The glass transition temperature of the methacrylic polymer particles of this embodiment is preferably 80°C or higher, more preferably 100°C or higher, and even more preferably 110°C or higher. The glass transition temperature can be controlled by adjusting the molecular weight, syndiotacticity (rr), and polymer composition ratio. When the glass transition temperature of the methacrylic polymer particles is 80°C or higher, the heat resistance of a resin composition obtained using the methacrylic polymer particles of this embodiment is improved. The glass transition temperature can be measured using a differential scanning calorimeter in accordance with JIS-K7121.

[0065] Although not particularly limited, the methacrylic polymer particles of this embodiment preferably have a melt mass flow rate of 0.1 to 30 g / 10 min, more preferably 0.5 to 20 g / 10 min, and even more preferably 1.0 to 10 g / 10 min, measured at 230°C under a load of 3.8 kg in accordance with JIS K 7210. When the melt mass flow rate is within this range, the methacrylic polymer particles have good moldability, and a molded product with excellent appearance can be obtained.

[0066] The methacrylic polymer particles of the present embodiment may contain additives such as antioxidants, heat deterioration inhibitors, ultraviolet absorbers, light stabilizers, lubricants, and mold release agents, as long as the additives do not impair the properties of the resin contained in the methacrylic polymer particles.

[0067] The antioxidant is effective in preventing oxidative degradation of the resin by itself in the presence of oxygen. Examples of the antioxidant include phosphorus-based antioxidants, hindered phenol-based antioxidants, and thioether-based antioxidants. These may be used alone or in combination of two or more. Among these, from the viewpoint of the effect of preventing degradation of optical properties due to coloring, phosphorus-based antioxidants and hindered phenol-based antioxidants are preferred, and a combination of a phosphorus-based antioxidant and a hindered phenol-based antioxidant is more preferred. When a phosphorus-based antioxidant and a hindered phenol-based antioxidant are used in combination, the mass ratio of the phosphorus-based antioxidant to the hindered phenol-based antioxidant (phosphorus-based antioxidant / hindered phenol-based antioxidant) is preferably 0.2 / 1 to 2 / 1, and more preferably 0.5 / 1 to 1 / 1.

[0068] Examples of phosphorus-based antioxidants include 2,2-methylenebis(4,6-di-tert-octyl phosphite) (manufactured by ADEKA Corporation; trade name: Adeka STAB HP-10), tris(2,4-di-tert-butylphenyl) phosphite (manufactured by BASF Corporation; trade name: IRGAFOS168), 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane (manufactured by ADEKA Corporation; trade name: Adeka STAB PEP-36), and tris(2,4-di-tert-butylphenyl) phosphite (manufactured by ADEKA Corporation; trade name: Adeka STAB 2112).

[0069] Preferred examples of the hindered phenol antioxidant include pentaerythrityl tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (manufactured by BASF; trade name IRGANOX 1010), octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (manufactured by BASF; trade name IRGANOX 1076), and 3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5,5]undecane (manufactured by ADEKA; trade name AO-80).

[0070] The thermal degradation inhibitor can prevent thermal degradation of resins by capturing polymer radicals generated when the resin is exposed to high heat in a substantially oxygen-free state. Preferred examples of the thermal degradation inhibitor include 2-t-butyl-6-(3-tert-butyl-5-methyl-hydroxybenzyl)-4-methylphenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd.; trade name "Sumilizer GM") and 2,4-di-t-amyl-6-(3,5-di-tert-amyl-2-hydroxy-α-methylbenzyl)phenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd.; trade name "Sumilizer GS").

[0071] An ultraviolet absorber is a compound capable of absorbing ultraviolet light, and is said to have the function of converting light energy into heat energy. Examples of ultraviolet absorbers include benzophenones, benzotriazoles, triazines, benzoates, salicylates, cyanoacrylates, oxalic acid anilides, malonic acid esters, and formamidines. Among these, ultraviolet absorbers include benzotriazoles, triazines, or compounds having a maximum molar absorption coefficient εmax of 100 dm at a wavelength of 380 to 450 nm. 3 mol -1 cm -1 The following ultraviolet absorbers are preferred: The content of the ultraviolet absorber depends on the molar extinction coefficient of the ultraviolet absorber and the wavelength to be absorbed, but is generally preferably 0.01 to 10 mass%, more preferably 0.1 to 5 mass%, and even more preferably 0.2 to 2 mass%. If the content of the ultraviolet absorber is high, long-term deterioration is suppressed, but bleed-out occurs during molding and use. On the other hand, if the content of the ultraviolet absorber is too low, the desired ultraviolet absorption is not achieved, so the content of the ultraviolet absorber is preferably 0.01 to 10 mass%.

[0072] Light stabilizers are compounds that are said to have the function of capturing radicals generated mainly by oxidation due to light. Suitable light stabilizers include hindered amines such as compounds having a 2,2,6,6-tetraalkylpiperidine skeleton.

[0073] Examples of lubricants include stearic acid, behenic acid, stearamidic acid, methylene bisstearamide, hydroxystearic acid triglyceride, paraffin wax, ketone wax, octyl alcohol, and hydrogenated oil.

[0074] The mold release agent is a compound that functions to facilitate the release of a molded article from a mold. Examples of the mold release agent include higher alcohols such as cetyl alcohol and stearyl alcohol; and higher fatty acid esters of glycerin such as stearic acid monoglyceride and stearic acid diglyceride. In this embodiment, it is preferable to use a combination of a higher alcohol and a glycerin fatty acid monoester as the mold release agent. When a combination of a higher alcohol and a glycerin fatty acid monoester is used, the mass ratio of the higher alcohol to the glycerin fatty acid monoester (higher alcohol / glycerin fatty acid monoester) is preferably in the range of 2.5 / 1 to 3.5 / 1, and more preferably in the range of 2.8 / 1 to 3.2 / 1.

[0075] The additives may be used singly or in combination of two or more. The total amount of the additives is preferably 5 parts by weight or less, more preferably 3 parts by weight or less, and even more preferably 1 part by weight or less, based on 100 parts by weight of the methacrylic polymer particles, from the viewpoint of suppressing defects in the appearance of the resulting polymer particles and molded articles.

[0076] The methacrylic polymer particles of this embodiment may be mixed with other thermoplastic resins to adjust the resin properties to the desired range. Examples of such thermoplastic resins include polypropylene resins, polyethylene resins, polystyrene resins, ABS resins, methacrylic resins, AS resins, BAAS resins, MBS resins, AAS resins, biodegradable resins, polycarbonate resins, polyalkylene arylate resins, polyamide resins, polyphenylene ether resins, polyphenylene sulfide resins, and phenolic resins. These thermoplastic resins may be used alone or in combination of two or more. From the viewpoint of resin compatibility, it is preferable to mix the methacrylic polymer particles with a methacrylic resin. While the mixing method is not particularly limited, melt-kneading is preferred due to its simple process. Mixing and kneading can be performed using known mixing or kneading devices such as a kneader-ruder, a single-screw or twin-screw extruder, a mixing roll, or a Banbury mixer. Among these, a twin-screw extruder is preferred. In order to obtain the desired properties, additives such as antioxidants, heat deterioration inhibitors, ultraviolet absorbers, light stabilizers, lubricants, and mold release agents may be added during mixing and kneading.

[0077] The methacrylic polymer particles of this embodiment can be used for applications such as adhesives, thickeners, resin modifiers, resin compatibilizers, etc. By using the methacrylic polymer particles of this embodiment for these applications, it is possible to impart properties such as increased viscosity stability, improved strength, and improved compatibility due to the arbitrarily controlled polymer structure.

[0078] <Methacrylic block copolymer particles> The methacrylic block copolymer particles of this embodiment can be obtained by adding a monomer copolymerizable with the methacrylic acid ester monomer to the methacrylic polymer particles of this embodiment and polymerizing the mixture. The glass transition temperature of the methacrylic block copolymer particles of this embodiment is preferably 80°C or higher, more preferably 100°C or higher, and even more preferably 110°C or higher. The glass transition temperature can be controlled by adjusting the molecular weight, syndiotacticity (rr), and polymer composition ratio. When the glass transition temperature of the methacrylic polymer particles is 80°C or higher, the heat resistance of a resin composition obtained using the methacrylic polymer particles of this embodiment is improved.

[0079] Although not particularly limited, the methacrylic block copolymer particles of this embodiment preferably have a melt mass flow rate of 0.1 to 30 g / 10 min, more preferably 0.5 to 20 g / 10 min, and even more preferably 1.0 to 10 g / 10 min, measured at 230°C under a load of 3.8 kg in accordance with JIS K 7210. When the melt mass flow rate is within this range, the methacrylic block copolymer particles have good moldability, and a molded product with excellent appearance can be obtained.

[0080] The methacrylic block copolymer particles of this embodiment may contain additives such as antioxidants, heat deterioration inhibitors, ultraviolet absorbers, light stabilizers, lubricants, and mold release agents, within the range that does not impair the properties of the resin contained in the methacrylic block copolymer particles. The explanation of these additives is the same as the explanation of the additives for the methacrylic polymer particles.

[0081] The methacrylic block copolymer particles of this embodiment may be mixed with other thermoplastic resins to adjust the resin properties to the desired range. Examples of such thermoplastic resins include polypropylene resins, polyethylene resins, polystyrene resins, ABS resins, methacrylic resins, AS resins, BAAS resins, MBS resins, AAS resins, biodegradable resins, polycarbonate resins, polyalkylene arylate resins, polyamide resins, polyphenylene ether resins, polyphenylene sulfide resins, and phenolic resins. These thermoplastic resins may be used alone or in combination. From the viewpoint of resin compatibility, mixing with a methacrylic resin is preferred. While the mixing method is not particularly limited, melt-kneading is preferred due to its simple process. Mixing and kneading can be performed using known mixing or kneading devices, such as a kneader-ruder, a single-screw or twin-screw extruder, a mixing roll, or a Banbury mixer. Among these, a twin-screw extruder is preferred. In order to obtain the desired properties, additives such as antioxidants, heat deterioration inhibitors, ultraviolet absorbers, light stabilizers, lubricants, and mold release agents may be added during mixing and kneading.

[0082] The methacrylic block copolymer of this embodiment can be used, for example, as an adhesive, a thickener, a resin modifier, a resin compatibilizer, etc. By using the methacrylic block copolymer particles of this embodiment for these applications, it is possible to impart properties such as increased viscosity stability, improved strength, and improved compatibility due to the arbitrarily controlled polymer structure.

[0083] <Methacrylic resin composition> The methacrylic resin composition of the present embodiment contains the methacrylic polymer particles of the present embodiment and an additional thermoplastic resin.

[0084] Examples of such additional thermoplastic resins include polypropylene resins, polyethylene resins, polystyrene resins, ABS resins, methacrylic resins, AS resins, BAAS resins, MBS resins, AAS resins, biodegradable resins, polycarbonate resins, polyalkylene arylate resins, polyamide resins, polyphenylene ether resins, polyphenylene sulfide resins, and phenolic resins. These thermoplastic resins may be used alone or in combination. From the viewpoint of resin compatibility, methacrylic resins are preferred as additional thermoplastic resins. While the mixing method is not particularly limited, melt-kneading is preferred due to its simple process. Mixing and kneading can be carried out using known mixing or kneading devices such as a kneader-ruder, a single-screw or twin-screw extruder, a mixing roll, or a Banbury mixer. Of these, a twin-screw extruder is preferred. In order to obtain the desired properties, additives such as antioxidants, heat deterioration inhibitors, ultraviolet absorbers, light stabilizers, lubricants, and mold release agents may be added during mixing and kneading.

[0085] The methacrylic resin composition of the present embodiment may contain methacrylic block copolymer particles instead of methacrylic polymer particles, or may contain methacrylic polymer particles and methacrylic block copolymer particles.

[0086] <Resin molded body> The resin molded article of this embodiment is a resin molded article obtained by molding the methacrylic resin composition of this embodiment, or may be a resin molded article obtained by molding a resin composition containing the methacrylic block copolymer particles of this embodiment. The resin molded article of this embodiment is also preferably a resin molded article obtained by molding the methacrylic polymer particles of this embodiment.

[0087] The resin molded article of this embodiment can be produced by a known molding method, such as a melt molding method such as a T-die method (lamination method, co-extrusion method, etc.), an inflation method (co-extrusion method, etc.), a compression molding method, a blow molding method, a calendar molding method, a vacuum molding method, or an injection molding method (insert method, two-color method, press method, core-back method, sandwich method, etc.), or a solution casting method.

[0088] The resin molded article of this embodiment preferably has a light transmittance of 80% or more, more preferably 85% or more, and particularly preferably 90% or more at a thickness of 3.0 mm. The haze at a thickness of 3.0 mm is preferably 3.0% or less, more preferably 2.0% or less, and even more preferably 1.5% or less. Having the light transmittance and haze within the above ranges results in a molded article with excellent transparency and visibility. The light transmittance and haze can be measured, for example, using a spectrophotometer / haze meter COH7700 (manufactured by Nippon Denshoku Industries Co., Ltd.) under the conditions specified in JIS K 7136 (ISO 14782) and JIS K 7136-1 (ISO 13468-1).

[0089] Examples of uses of the resin molded article of this embodiment include exterior materials and electrical / electronic components for personal computers, laptop computers, game machines (such as home game machines, commercial game machines, pachinko machines, and slot machines), display devices (such as CRTs, LCDs, plasma displays, projectors, and organic electroluminescence displays), mice, printers, copiers, scanners, and fax machines (including all-in-one devices), and switch molded articles such as keyboard keys and various switches. Furthermore, the resin molded article of this embodiment is useful in a wide range of other applications, and further uses of the resin molded article include electrical / electronic devices such as personal digital assistants (so-called PDAs), mobile phones, portable books (such as dictionaries), portable televisions, drives for recording media (such as CDs, MDs, DVDs, next-generation high-density discs, and hard disks), readers for recording media (such as IC cards, SmartMedia cards, and Memory Sticks), optical cameras, digital cameras, parabolic antennas, power tools, VTRs, irons, hair dryers, rice cookers, microwave ovens, audio equipment, lighting equipment, refrigerators, air conditioners, air purifiers, negative ion generators, and typewriters. The resin molded article of the present invention can be applied to various parts such as these exterior materials. The resin molded article of this embodiment is also suitable for various miscellaneous goods such as various containers, covers, writing implement bodies, and decorative items. Furthermore, applications of the resin molded article of this embodiment include vehicle parts such as lamp sockets, lamp reflectors, lamp housings, instrument panels, center console panels, deflector parts, car navigation parts, car audiovisual parts, and automobile computer parts. [Example]

[0090] The present invention will be explained below by way of specific examples and comparative examples, but is not limited to these.

[0091] [Raw materials] The raw materials used in the examples and comparative examples described later are shown below. [monomer] Methyl methacrylate (MMA) Asahi Kasei Corporation (contains 2.5 ppm of 2,4-dimethyl-6-t-butylphenol manufactured by Chugai Boeki Co., Ltd. as a polymerization inhibitor) Methyl acrylate (MA): Mitsubishi Chemical Corporation n-Butyl acrylate (BA): Nippon Shokubai Co., Ltd. Styrene (St): manufactured by Asahi Kasei Corporation [Polymerization initiator] 2,2-Azobis(isobutyrate) dimethyl: Fujifilm Wako Pure Chemical Industries, Ltd. Potassium persulfate: Fujifilm Wako Pure Chemical Industries, Ltd. Nitroxide-terminated butyl acrylate polymer: FLEXIBLOC D2 (registered trademark), manufactured by Arkema Co., Ltd. [Chain transfer agent] 4-Cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid: Fujifilm Wako Pure Chemical Industries, Ltd., trithiocarbonate type 2-Cyano-2-propyldodecyl trithiocarbonate: Fujifilm Wako Pure Chemical Industries, Ltd., trithiocarbonate type n-Octyl mercaptan: Arkema Co., Ltd. [others] - Tricalcium phosphate: Manufactured by Nippon Chemical Industry Co., Ltd., used as a suspending agent. Calcium carbonate: Manufactured by Shiraishi Kogyo Co., Ltd., used as a suspending agent. Sodium lauryl sulfate: Manufactured by Wako Pure Chemical Industries, Ltd., used as a suspension aid.

[0092] The methods for measuring the properties of the methacrylic polymer particles and the methacrylic block copolymer particles will be described below.

[0093] <1. Number average molecular weight (Mn)> The number average molecular weight (Mn) and weight average molecular weight (Mw) of the methacrylic polymer particles and methacrylic block copolymer particles were measured using the following apparatus and conditions. Measurement equipment: Tosoh Corporation, gel permeation chromatography (HLC-8320GPC) Measurement conditions: Columns: One TSKguardcolumn SuperH-H, two TSKgel SuperHM-M, and one TSKgel SuperH2500 connected in series. With this column, high molecular weights elute early, and low molecular weights elute late. The developing solvent was tetrahydrofuran, the flow rate was 0.6 mL / min, and 0.1 g / L of 2,6-di-t-butyl-4-methylphenol (BHT) was added as an internal standard. Detector: RI (differential refractive index) detector Detection sensitivity: 3.0 mV / min Column temperature: 40℃ Sample: 0.02 g of methacrylic polymer or methacrylic block copolymer in 20 mL of tetrahydrofuran solution Injection volume: 10μL Standard sample for calibration curve: The following ten types of polymethyl methacrylate (PMMA Calibration Kit MM-10, manufactured by Polymer Laboratories) with known monodisperse weight peak molecular weights and different molecular weights were used. Weight peak molecular weight (Mp) Standard sample 1 1,916,000 Standard sample 2 625,500 Standard sample 3 298,900 Standard sample 4 138,600 Standard sample 5 60,150 Standard sample 6 27,600 Standard sample 7 10,290 Standard sample 8 5,000 Standard sample 9 2,810 Standard sample 10,850 Under the above conditions, the RI detection intensity was measured against the elution time of the methacrylic polymer. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the methacrylic resin were determined based on the area in the GPC elution curve and the calibration curve of the third-order approximation equation. The results are shown in Table 1. The molecular weight distribution (Mw / Mn) was calculated from the number average molecular weight (Mn) and weight average molecular weight (Mw). In this specification, a molecular weight distribution (Mw / Mn) of less than 1.90 is considered to be well-controlled, and preferably 1.50 or less.

[0094] <2. Volume average particle diameter of methacrylic polymer particles> The volume average particle size (μm) of the methacrylic polymer particles was measured using the laser scattering method of a Beckman Coulter LS13320.

[0095] <3. Polymerization stability> The polymerization stability during the production of methacrylic polymer particles and methacrylic block copolymer particles was observed during polymerization and judged according to the following criteria. A: No agglomeration occurs due to aggregation of droplets or polymer particles during the polymerization reaction. B: During the polymerization reaction, some agglomeration occurred due to aggregation of droplets and polymer particles. C: During the polymerization reaction, droplets and polymer particles aggregated and became agglomerates.

[0096] <Production of methacrylic polymer particles and methacrylic block copolymer particles> The method for producing the methacrylic polymer particles and the methacrylic block copolymer particles will be described below.

[0097] Example 1 Into a container equipped with a stirrer, 0.1 kg of ion-exchanged water, 3.25 g of tribasic calcium phosphate, 1.95 g of calcium carbonate, and 0.020 g of sodium lauryl sulfate were placed to obtain a mixed solution (a). Next, 45 g of ion-exchanged water was added to a 100 mL reactor and heated to 80 ° C. Mixture (a), 24.3 g of methyl methacrylate, 0.7 g of methyl acrylate, 0.10 g of 2,2-azobis(isobutyrate)dimethyl, and 0.70 g of 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid were added. Then, suspension polymerization was carried out while maintaining the temperature at approximately 80 ° C. under stirring. After an exothermic peak was observed, the mixture was aged at 95 ° C. for 60 minutes to essentially complete the polymerization reaction. The mixture was then cooled to 50 ° C., and 20% by weight of sulfuric acid was added to dissolve the suspending agent. The slurry was then sieved through a 1.68 mm mesh to remove aggregates. The resulting polymer particles were washed, dehydrated, and dried to obtain methacrylic polymer particles. The resulting methacrylic polymer particles had a number average molecular weight of 14,500 and a molecular weight distribution (Mw / Mn) of 1.12, and a volume average particle size of 430 μm.

[0098] Example 2 A container equipped with a stirrer was charged with 0.1 kg of ion-exchanged water, 3.25 g of tribasic calcium phosphate, 1.95 g of calcium carbonate, and 0.020 g of sodium lauryl sulfate to obtain a mixed solution (a). Next, a 100 mL reactor was charged with 45 g of ion-exchanged water and heated to 80°C, and then mixed solution (a), 32.9 g of methyl methacrylate, 0.02 g of dimethyl 2,2-azobis(isobutyrate), and 1.30 g of 2-cyano-2-propyldodecyl trithiocarbonate were charged. Thereafter, suspension polymerization was carried out while maintaining the temperature at about 80°C under stirring, and after observing an exothermic peak, the temperature was raised to 92°C at a rate of 1°C / min and aged for 60 minutes to essentially complete the polymerization reaction. Subsequently, the mixture was cooled to 50°C, and 20% by mass of sulfuric acid was added to dissolve the suspending agent. The slurry was then sieved through a 1.68 mm mesh to remove aggregates, and the resulting methacrylic polymer particles were washed, dehydrated, and dried to obtain methacrylic polymer particles. The resulting methacrylic polymer particles had a number average molecular weight of 71,100, a molecular weight distribution (Mw / Mn) of 1.32, and a volume average particle size of 442 μm.

[0099] Examples 3 to 5 Methacrylic polymer particles were produced and evaluated in the same manner as in Example 1, except that the monomers, initiators, and chain transfer agents in the amounts shown in "Polymerization step (1)" in Table 1 were used. The results are shown in Table 1.

[0100] Example 6 <Polymerization process (1)> A vessel equipped with a stirrer was charged with 0.1 kg of ion-exchanged water, 3.25 g of tribasic calcium phosphate, 1.95 g of calcium carbonate, and 0.020 g of sodium lauryl sulfate to obtain a mixed solution (a). Next, a 100 mL reactor was charged with 45 g of ion-exchanged water and heated to 80°C, and mixed solution (a), 1.58 g of methyl methacrylate, 0.05 g of methyl acrylate, 0.076 g of dimethyl 2,2-azobis(isobutyrate), and 0.046 g of 2-cyano-2-propyldodecyl trithiocarbonate were then charged. The mixture was then stirred at approximately 80°C for 1.0 hour to carry out suspension polymerization, essentially completing the reaction of polymerization step (1). A portion of the slurry obtained in polymerization step (1) was collected, washed, dehydrated, and dried to obtain methacrylic polymer particles. The resulting methacrylic polymer particles had a number average molecular weight of 13,400 and a molecular weight distribution (Mw / Mn) of 1.21, and a volume average particle size of 236 μm. <Polymerization process (2)> Next, 32.0 g of methyl methacrylate and 0.077 g of dimethyl 2,2-azobis(isobutyrate) were added to the polymerization reaction solution produced in polymerization step (2). The ratio (b / a) of the number of moles of the newly added monomer (b) to the number of moles of the monomer mixture (a) added in polymerization step (1) was 13.6. Subsequently, suspension polymerization was carried out by maintaining the temperature at approximately 80°C for 5.0 hours under stirring, and the reaction in polymerization step (2) was essentially completed. The slurry was cooled to 50°C, and 20% by weight sulfuric acid was added to dissolve the suspending agent. The slurry was then sieved through a 1.68 mm mesh to remove aggregates. The resulting copolymer particles were washed, dehydrated, and dried to obtain methacrylic block copolymer particles. The number-average molecular weight of the resulting methacrylic block copolymer particles was 206,000, and the molecular weight distribution (Mw / Mn) was 1.44. The volume average particle size of the resulting methacrylic block copolymer particles was 473 μm.

[0101] (Examples 7 and 8) Methacrylic block copolymer particles were produced and evaluated in the same manner as in Example 6, except that the monomers, initiators, and chain transfer agents were used in the amounts shown in "Polymerization step (1)" and "Polymerization step (2)" in Table 1. The results are shown in Table 1.

[0102] Example 9 <Polymerization process (1)> A vessel equipped with a stirrer was charged with 0.1 kg of ion-exchanged water, 3.25 g of tribasic calcium phosphate, 1.95 g of calcium carbonate, and 0.020 g of sodium lauryl sulfate to obtain a mixed solution (a). Next, 45 g of ion-exchanged water was charged into a 100 mL reactor, and the temperature was raised to 80°C. Then, mixed solution (a), 13.67 g of methyl methacrylate, 0.032 g of dimethyl 2,2-azobis(isobutyrate), and 0.22 g of 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid were charged. Then, the mixture was stirred at approximately 80°C for 1.0 hour to carry out suspension polymerization, and the reaction in polymerization step (1) was essentially completed. A portion of the slurry obtained in polymerization step (1) was collected, washed, dehydrated, and dried to obtain methacrylic polymer particles. The resulting methacrylic polymer particles had a number average molecular weight of 17,700 and a molecular weight distribution (Mw / Mn) of 1.14, and a volume average particle size of 235 μm. <Polymerization process (2)> Next, 8.67 g of butyl acrylate and 0.032 g of dimethyl 2,2-azobis(isobutyrate) were added to the polymerization reaction solution produced in the polymerization step (1). The ratio (b / a) of the number of moles (b) of the newly added monomer to the number of moles (a) of the monomer mixture added in the polymerization step (1) was 0.4. Thereafter, suspension polymerization was carried out while maintaining the temperature at approximately 80°C for 1.0 hour with stirring, and the reaction in the polymerization step (2) was essentially completed. <Third polymerization step> Next, 13.68 g of methyl methacrylate and 0.022 g of dimethyl 2,2-azobis(isobutyrate) were added to the polymerization reaction solution produced in polymerization step (2). The ratio (c / (a+b)) of the number of moles of the newly added monomer (c) to the sum of the number of moles of the monomers added in polymerization steps (1) and (2) (a+b) was 0.7. Subsequently, suspension polymerization was carried out by maintaining the temperature at approximately 80°C for 5.0 hours under stirring, and the reaction in polymerization step (3) was essentially completed. The slurry was cooled to 50°C, and 20% by weight sulfuric acid was added to dissolve the suspending agent. The polymerization reaction solution was then sieved through a 1.68 mm mesh to remove aggregates. The resulting copolymer particles were washed, dehydrated, and dried to obtain methacrylic block copolymer particles. The resulting methacrylic block copolymer particles had a number-average molecular weight of 54,800 and a molecular weight distribution (Mw / Mn) of 1.33. The volume average particle size of the resulting methacrylic block copolymer particles was 449 μm.

[0103] (Comparative Examples 1, 2, and 4) Methacrylic polymer particles were produced and evaluated in the same manner as in Example 1, except that the monomers, initiators, and chain transfer agents in the amounts shown in "Polymerization step (1)" in Table 1 were used. The results are shown in Table 1.

[0104] (Comparative Example 3) Methacrylic polymer particles were produced and evaluated in the same manner as in Example 6, except that emulsion polymerization was performed instead of suspension polymerization, using the monomers, initiators, and chain transfer agents in the amounts shown in "Polymerization step (1)" and "Polymerization step (2)" in Table 1. The results are shown in Table 1.

[0105] [Table 1]

[0106] In Comparative Example 1, when a general chain transfer agent that is not a RAFT agent having a thiocarbonylthio skeleton was used, there was no problem with polymerization stability, but the Mw / Mn was 2.0, indicating that the molecular weight distribution could not be controlled. Furthermore, when the chain transfer agent used in Comparative Example 1 was used, it was mechanically difficult to control the molecular weight distribution to a narrower value. In Comparative Example 2, the proportion of methacrylic acid ester monomer in the monomer mixture was lower than 50 wt%, resulting in poor polymerization stability, agglomeration, and failure to obtain polymer particles. In Comparative Example 3, in which the molar ratio (b / a) of the monomer mixture added in polymerization step (2) was 0.5 to 15, there was no problem with polymerization stability, but the volume average particle diameter was less than 100 μm, on the nano-order, making it difficult to mold using a commonly used extruder and molding machine alone. Furthermore, the small volume average particle diameter is expected to result in high recovery costs. In Comparative Example 4, a nitroxide-terminated polybutyl acrylate polymer was used as the initiator in the polymerization step (1) and polymerization was carried out by the NMP method, but the reaction did not proceed well and polymer particles were not obtained.

[0107] As shown in Table 1, by carrying out polymerization of methacrylic acid ester monomers in an aqueous medium using a RAFT agent as a chain transfer agent, it is possible to produce methacrylic polymer particles with excellent polymerization stability, large particle size, and well-controlled molecular weight distribution. Furthermore, when producing a block copolymer, if the ratio (b / a) of the number of moles (a) of the monomer mixture added in polymerization step (1) to the number of moles (b) of the monomer mixture newly added in polymerization step (2) is within a certain range, it is possible to produce methacrylic block copolymer particles with excellent polymerization stability, large particle size, and well-controlled molecular weight distribution. [Industrial Applicability]

[0108] According to the method for producing methacrylic polymer particles of the present invention, the post-polymerization recovery process is low cost and has little environmental impact, and methacrylic polymer particles having excellent polymerization stability and a well-controlled molecular weight distribution can be obtained.Furthermore, according to the method for producing methacrylic block copolymer particles of the present invention, the post-polymerization recovery process is low cost and has little environmental impact, and methacrylic block copolymer particles having excellent polymerization stability and a well-controlled molecular weight distribution can be obtained. Furthermore, the present invention can provide methacrylic polymer particles which have a low-cost, environmentally friendly post-polymerization recovery process, excellent polymerization stability, and a well-controlled molecular weight distribution, as well as a methacrylic resin composition and a resin molded article which contain the methacrylic polymer particles.

Claims

1. A method for producing methacrylic polymer particles by polymerizing a monomer mixture, comprising: The method includes a polymerization step (1) of producing methacrylic polymer particles by living radical polymerization of a monomer mixture containing 50 to 100 parts by weight of a methacrylic acid ester monomer and, optionally, 0 to 50 parts by weight of another copolymerizable monomer, per 100 parts by weight of the monomer mixture, in an aqueous medium by a reversible addition-fragmentation chain transfer polymerization method (RAFT method) using a RAFT agent; The method for producing methacrylic polymer particles, wherein the methacrylic polymer particles have a volume average particle size of 100 μm or more.

2. the number average molecular weight (Mn) of the methacrylic polymer particles is 10,000 to 200,000; 2. The method for producing methacrylic polymer particles according to claim 1, wherein the molecular weight distribution (Mw / Mn) is 1.0 to 1.

9.

3. 3. The method for producing methacrylic polymer particles according to claim 1, wherein the RAFT agent has a trithiocarbonate structure.

4. a polymerization step (2) of producing methacrylic block copolymer particles by multistage polymerization of a monomer copolymerizable with the methacrylic acid ester monomer to a slurry containing the methacrylic polymer particles produced by the method according to claim 1 or 2, A method for producing methacrylic block copolymer particles, characterized in that a molar ratio (b / a) of the number of moles (b) of the copolymerizable monomer in the polymerization step (2) to the number of moles (a) of the monomer mixture in the polymerization step (1) is 0.5 to 15.

5. 5. The method for producing methacrylic block copolymer particles according to claim 4, wherein the copolymerizable monomer is directly added to a slurry of the methacrylic polymer particles produced in the polymerization step (1) without recovering or purifying the methacrylic polymer particles, and then polymerization is carried out in the polymerization step (2).

6. 6. The method for producing methacrylic block copolymer particles according to claim 5, wherein the molecular weight distribution (Mw / Mn) of the methacrylic block copolymer particles is 1.0 to 1.

9.

7. Contains 50 to 100% by weight of structural units derived from methacrylic acid ester monomers, and optionally 0 to 50% by weight of structural units derived from other copolymerizable monomers; at least a portion of the polymer end structures are end structures derived from the RAFT agent; Methacrylic polymer particles having a volume average particle size of 100 μm or more.

8. A methacrylic resin composition comprising the methacrylic polymer particles according to claim 7 and an additional thermoplastic resin.

9. The methacrylic resin composition according to claim 8, wherein the additional thermoplastic resin is a methacrylic resin.

10. A resin molded article obtained by molding the methacrylic polymer particles according to claim 7.

11. A resin molded article obtained by molding the methacrylic resin composition according to claim 8.

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