Production method of crosslinked block copolymer

Abstract

To provide a production method of a novel crosslinked block copolymer capable of producing polymer particles of which the particles are hardly collapsed.SOLUTION: A production method of a crosslinked block copolymer contains obtaining a block copolymer from two or more kinds of polymerizable monomers (first polymerization) and obtaining a crosslinked block copolymer by adding one or more kinds of polymerizable monomers out of the two or more kinds of the polymerizable monomers and a poly functional monomer to the block copolymer (second polymerization). The second polymerization preferably contains crosslinking the block copolymers to each other.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a crosslinked block copolymer. [Background technology]

[0002] Conventionally, thermoplastic resin compositions in which a rubber component is blended with a thermoplastic resin such as acrylonitrile or styrene have been applied to various fields because of their excellent heat resistance, oil resistance, etc. Known examples of such thermoplastic resin compositions include acrylonitrile-butadiene-styrene copolymers (ABS resins), acrylonitrile-styrene-(meth)acrylic acid ester copolymers (ASA resins), acrylonitrile-ethylene-propylene-styrene copolymers (AES resins), and acrylonitrile-chlorinated polyethylene-styrene copolymers (ACS resins).

[0003] As a method for producing a rubber component (polymer particles) that can be blended with a thermoplastic resin, for example, Patent Documents 1 and 2 propose a method for producing an aqueous dispersion of particles containing a polymer by RAFT polymerization. However, when the polymer particles produced by such a method are melt-kneaded with the above-mentioned thermoplastic resin, the polymer particles may crumble, making it difficult to exhibit the desired physical properties. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-168260 A [Patent Document 2] Patent Publication No. 2022-015395 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, an object of the present invention is to provide a novel method for producing a cross-linked block copolymer, which can produce polymer particles that are resistant to crumbling. [Means for solving the problem]

[0006] In view of the above circumstances, the present inventors conducted intensive research and found that the above problems can be solved by a method for producing a cross-linked block copolymer, the method including obtaining a block copolymer from two or more types of polymerizable monomers (first polymerization), and adding one or more types of polymerizable monomers selected from the two or more types of polymerizable monomers and a polyfunctional monomer to the block copolymer to obtain a cross-linked block copolymer (second polymerization). Effect of the Invention

[0007] According to the present invention, there is provided a novel method for producing a crosslinked block copolymer, which can produce polymer particles that are resistant to crumbling. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of the present disclosure will be described in detail, but the scope of the present disclosure is not limited to the embodiment described here, and various modifications can be made within the scope of the present disclosure. Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. In addition, when multiple upper and lower limit values ​​are described for a specific parameter, any upper and lower limit values ​​among these upper and lower limit values ​​can be combined to form a suitable numerical range. In addition, the lower and / or upper limit values ​​of the numerical range described in this disclosure are numerical values ​​within the numerical range and may be replaced with numerical values ​​shown in the examples. The expression "X to Y" indicating a numerical range means "X or more and Y or less". When a specific description described for one embodiment is also applicable to other embodiments, the description may be omitted in other embodiments.

[0009] The configurations and combinations thereof in each embodiment are merely examples, and addition, omission, substitution, and other modifications of the configurations are possible as appropriate without departing from the spirit of the present disclosure. The present disclosure is not limited to the embodiments. Each feature disclosed herein may be combined with any other feature disclosed herein.

[0010] [Method of manufacturing cross-linked block copolymer] The present embodiment relates to a method for producing a cross-linked block copolymer, which includes obtaining a block copolymer from two or more types of polymerizable monomers (first polymerization), and adding one or more types of polymerizable monomers among the two or more types of polymerizable monomers and a polyfunctional monomer to the block copolymer to obtain a cross-linked block copolymer (second polymerization).

[0011] <First Polymerization> The production method according to the present embodiment includes a first polymerization step of obtaining a block copolymer from two or more polymerizable monomers. After preparing a block copolymer in the first polymerization step, the block copolymer is reacted with one or more polymerizable monomers and a polyfunctional monomer added in the first polymerization step to prepare a crosslinked block copolymer of interest.

[0012] (Block Copolymer) The block copolymer obtained in the first polymerization is a polymer of two or more kinds of polymerizable monomers, and is a copolymer having two or more blocks. In a preferred embodiment, the block copolymer includes a block (A) containing a polymerizable monomer (m1), a block (B) containing a polymerizable monomer (m2) that is the same as or different from the polymerizable monomer (m1), and a block (C) containing a polymerizable monomer (m3) that is different from the polymerizable monomers (m1) and (m2).

[0013] When the polymerizable monomer (m2) is the same monomer as the polymerizable monomer (m1), the block (B) is substantially composed of the same monomer units as the block (A). In this case, the block copolymer is prepared as a diblock copolymer containing the block (A) (or block (B)) and the block (C). On the other hand, when the polymerizable monomer (m2) is a monomer different from the polymerizable monomer (m1), the block copolymer is a triblock copolymer containing at least the blocks (A), (B) and (C). In addition, when the block copolymer is prepared from the above-mentioned polymerizable monomers (m1), (m2) and (m3), it is preferable that the one or more polymerizable monomers added together with the polyfunctional monomer in the second polymerization include the polymerizable monomer (m3).

[0014] [Polymerizable monomer] The polymerizable monomer for constituting the block copolymer is not particularly limited as long as it is a monomer having one or more polymerizable functional groups. When the finally obtained crosslinked block copolymer is melt-kneaded with a thermoplastic resin, it is preferable to contain two or more polymerizable monomers selected from an aromatic vinyl compound, vinyl cyanide, and a (meth)acrylic acid ester. In this specification, the term "(meth)acrylic acid ester" includes one or both of an acrylic acid ester and a methacrylic acid ester.

[0015] Aromatic vinyl compounds Examples of aromatic vinyl compounds include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, β-methylstyrene, 2,6-dimethylstyrene, 2,4-dimethylstyrene, α-methyl-o-methylstyrene, α-methyl-m-methylstyrene, α-methyl-p-methylstyrene, β-methyl-o-methylstyrene, β-methyl-m-methylstyrene, β-methyl-p-methylstyrene, 2,4,6-trimethylstyrene, α-methyl-2,6-dimethylstyrene, α-methyl-2,4-dimethylstyrene, β-methyl-2,6-dimethylstyrene, β-methyl-2,4-dimethylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,6-dichlorostyrene, 2,4-dichlorostyrene, α-chloro-o-chlorostyrene, α-chlorostyrene, Examples of the aromatic vinyl compounds include chloro-m-chlorostyrene, α-chloro-p-chlorostyrene, β-chloro-o-chlorostyrene, β-chloro-m-chlorostyrene, β-chloro-p-chlorostyrene, 2,4,6-trichlorostyrene, α-chloro-2,6-dichlorostyrene, α-chloro-2,4-dichlorostyrene, β-chloro-2,6-dichlorostyrene, β-chloro-2,4-dichlorostyrene, ot-butylstyrene, mt-butylstyrene, pt-butylstyrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-chloromethylstyrene, m-chloromethylstyrene, p-chloromethylstyrene, o-bromomethylstyrene, m-bromomethylstyrene, p-bromomethylstyrene, styrene derivatives substituted with silyl groups, indene, vinylnaphthalene, vinylanthracene, etc. These aromatic vinyl compounds may be used alone or in combination of two or more. Among these, from the viewpoint of the balance between production costs and physical properties, styrene, α-methylstyrene, p-methylstyrene, and mixtures thereof are preferred, and styrene is more preferred.

[0016] Vinyl cyanide Examples of vinyl cyanides include acrylonitrile, methacrylonitrile, and ethacrylonitrile. These vinyl cyanides may be used alone or in combination of two or more. Among these, it is preferable to use acrylonitrile from the viewpoint of the balance between production cost and physical properties.

[0017] (Meth)acrylic acid esters Examples of (meth)acrylic acid esters include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, amyl methacrylate, isoamyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, lauryl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, phenyl methacrylate, etc. Also included are methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, amyl acrylate, isoamyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, lauryl acrylate, stearyl acrylate, cyclohexyl acrylate, benzyl acrylate, phenyl acrylate, etc. These (meth)acrylic acid esters may be used alone or in combination of two or more. Among these, from the viewpoint of the balance between production cost and physical properties, (meth)acrylic acid alkyl esters having an alkyl group with 1 to 4 carbon atoms are preferred, and n-butyl acrylate is more preferred.

[0018] Other polymerizable monomers The polymerizable monomer may contain a monomer (other monomer) other than the above-mentioned aromatic vinyl compound, vinyl cyanide, and (meth)acrylic acid ester. When the polymerizable monomer contains two or more selected from the above-mentioned aromatic vinyl compound, vinyl cyanide, and (meth)acrylic acid ester, the other monomer is preferably a monomer that does not inhibit the effects of the present invention and is copolymerizable therewith. In one embodiment, examples of the other monomer include maleic anhydride, N-substituted maleimide, acrylic acid, methacrylic acid, acrylamide, and methacrylamide. The other monomer may contain one or more selected from these.

[0019] <Polymerizable monomer (m1)> In one embodiment, the polymerizable monomer (m1) preferably includes one or more polymerizable monomers selected from an aromatic vinyl compound and a vinyl cyanide, more preferably includes an aromatic vinyl compound, and further preferably includes styrene.

[0020] <Polymerizable monomer (m2)> The polymerizable monomer (m2) may be the same monomer as the above-mentioned polymerizable monomer (m1), or may be a different monomer. Here, "the polymerizable monomer (m2) may be the same monomer as the polymerizable monomer (m1)" means that the polymerizable monomer (m1) and the polymerizable monomer (m2) may be the same compound (for example, the polymerizable monomer (m1) and the polymerizable monomer (m2) may both be styrene). On the other hand, "the polymerizable monomer (m2) may be a monomer different from the polymerizable monomer (m1)" means that the polymerizable monomer (m1) and the polymerizable monomer (m2) "may be different compounds". In this case, the polymerizable monomer (m1) and the polymerizable monomer (m2) may be the same type of compound (e.g., aromatic vinyl compound) but different compounds (e.g., the polymerizable monomer (m1) may be styrene and the polymerizable monomer (m2) may be α-methylstyrene). In addition, the polymerizable monomer (m1) and the polymerizable monomer (m2) may be different types of compounds (e.g., the polymerizable monomer (m1) may be an aromatic vinyl compound (e.g., styrene) and the polymerizable monomer (m2) may be a vinyl cyanide compound (e.g., acrylonitrile), or the polymerizable monomer (m1) may be an aromatic vinyl compound or a vinyl cyanide compound and the polymerizable monomer (m2) may be a compound other than an aromatic vinyl compound and a vinyl cyanide compound). The polymerizable monomer (m2) may be a mixture of a plurality of monomers, or may be a mixture of an aromatic vinyl compound or a vinyl cyanide compound with another monomer.

[0021] In one embodiment, the polymerizable monomer (m2) preferably contains the same monomer as the polymerizable monomer (m1), more preferably contains an aromatic vinyl compound, and further preferably contains styrene.

[0022] In one embodiment, the polymerizable monomer (m2) may include aromatic vinyl compounds and vinyl cyanides, and may include styrene and acrylonitrile. In one embodiment, when the polymerizable monomer (m2) is a mixture of an aromatic vinyl compound and a vinyl cyanide, the proportion of the aromatic vinyl compound to the total mass of the mixture is preferably 60 to 95 mass%, more preferably 70 to 90 mass%, and the proportion of the vinyl cyanide to the total mass is preferably 5 to 40 mass%, more preferably 10 to 30 mass%.

[0023] <Polymerizable monomer (m3)> The polymerizable monomer (m3) is preferably a monomer different from the polymerizable monomers (m1) and (m2). When the polymerizable monomers (m1) and (m2) each contain one or more selected from an aromatic vinyl compound and a vinyl cyanide, the polymerizable monomer (m3) preferably contains a (meth)acrylic acid ester, more preferably contains a (meth)acrylic acid alkyl ester having an alkyl group with 1 to 4 carbon atoms, and further preferably contains n-butyl acrylate.

[0024] (Polymerization method) In the first polymerization, the method for preparing the block copolymer is not particularly limited, but examples thereof include the following methods. (I) A method in which polymers having reactive functional groups at their termini are synthesized in advance, and these polymers are reacted to obtain a block copolymer having reactive functional groups at its termini. (II) A method for obtaining a block copolymer by living radical polymerization. Of the above methods (I) and (II), method (II) is preferred from the viewpoint of ease of control over the structure of the finally obtained crosslinked block copolymer.

[0025] Examples of living radical polymerization methods include the NMP method (nitroxide-mediated radical polymerization method), the ATRP method (atom transfer radical polymerization method), the TERP method (radical polymerization method using an organotellurium compound), the RAFT polymerization method (reversible addition-fragmentation chain transfer polymerization method), etc. Among these, the RAFT polymerization method is preferred because it can be polymerized under mild conditions and can be used with various monomers.

[0026] In the RAFT polymerization method, a polymerizable monomer is polymerized in the presence of a RAFT agent (reversible addition-fragmentation chain transfer agent). The polymerization method in the RAFT polymerization method is not particularly limited, but examples thereof include solution polymerization, suspension polymerization, emulsion polymerization, and mini-emulsion polymerization. Among these, emulsion polymerization and mini-emulsion polymerization are preferred from the viewpoints of being capable of polymerization in water, the safety of the working environment, and excellent productivity. Hereinafter, one aspect of the manufacturing method according to this embodiment when implemented by the RAFT polymerization method will be described.

[0027] The first polymerization preferably includes reacting a polymerizable monomer (m1) with a RAFT agent to obtain a polymer (P1) of the polymerizable monomer (m1) having an active end derived from the RAFT agent (step (i)), reacting the polymer (P1) with a polymerizable monomer (m2) that is the same as or different from the polymerizable monomer (m1) to obtain a polymer (P2) of the polymerizable monomers (m1) and (m2) (step (ii)), and reacting the polymer (P2) with a polymerizable monomer (m3) that is different from the polymerizable monomers (m1) and (m2) to obtain a block copolymer (step (iii)). Hereinafter, the details of steps (i) to (iii) will be described.

[0028] [Step (i)] The first polymerization preferably includes step (i) of reacting a polymerizable monomer (m1) with a RAFT agent to obtain a polymer (P1) of the polymerizable monomer (m1) having an active end derived from the RAFT agent. More preferably, in step (i), a polymerization initiator is added to a mixed solution containing the polymerizable monomer (m1), the RAFT agent, water, and an emulsifier to obtain an aqueous dispersion (W1) containing seed particles (S1) having an active end derived from the RAFT agent and consisting of the polymer (P1) of the polymerizable monomer (m1).

[0029] The water used in step (i) is preferably pure water, and its addition amount is preferably in the range of 100 to 400% by mass based on the total mass of the polymerizable monomer (m1).

[0030] The polymer (P1) is a polymer constituting the aforementioned block (A). The polymer (P1) has a block (polymer chain) composed of units derived from the polymerizable monomer (m1) and an active end derived from the RAFT agent. Note that the polymer (P1) may contain unreacted polymerizable monomer (m1), an emulsifier, a polymerization initiator, etc., which will be described later.

[0031] <RAFT agent> The RAFT agent used in step (i) is a compound that causes RAFT polymerization, and is generally a compound having a structure shown in formula 1 below (e.g., a thiocarbonylthio compound such as dithiobenzoate, trithiocarbamate, dithiocarbamate, xanthate, etc.).

[0032] [ka]

[0033] In formula 1, Z is a functional group that controls the reactivity of the C=S bond and affects the rate of addition and cleavage of radicals, and R is a homolytic leaving group that restarts the polymerization reaction and is favorable for the propagating radical.

[0034] The substituents Z and R in formula 1 must be appropriately selected depending on the monomer to be used, and there are many references providing guidance therefor, such as those shown in the following documents: Keddie, DJ, Moad, G., Rizzardo, E., Thang, SH: Macromolecules, 45, 5321 (2012).

[0035] In one embodiment, the RAFT agent represented by formula 1 is not particularly limited, and a general compound can be used. For example, dithiocarbamates, dithioesters, trithiocarbamates, etc. can be mentioned. Specifically, the RAFT agent represented by formula 1 includes benzyl 1-pyrrole carbodithioate (trivial name: benzyl 1-pyrrole dithiocarbamate), benzyl phenyl carbodithioate, 1-benzyl-N,N-dimethyl-4-aminodithiobenzoate, 1-benzyl-4-methoxydithiobenzoate, 1-phenylethyl imidazole carbodithioate (trivial name: 1-phenylethyl imidazole dithiocarbamate), benzyl-1-(2-phenylethyl imidazole dithiocarbamate), benzyl phenyl carbodithioate, 1-benzyl-N,N-dimethyl-4-aminodithiobenzoate, 1-benzyl-4-methoxydithiobenzoate, 1-phenylethyl imidazole carbodithioate (trivial name: 1-phenylethyl imidazole dithiocarbamate), benzyl 1-(2-phenylethyl imidazole dithiocarbamate), benzyl phenyl carbodithioate, ... -pyrrolidinone)carbodithioate) (common name: benzyl-1-(2-pyrrolidinone)dithiocarbamate), benzyl phthalimidyl carbodithioate, (common name: benzyl phthalimidyl dithiocarbamate), 2-cyanoprop-2-yl-1-pyrrole carbodithioate, (common name: 2-cyanoprop-2-yl-1-pyrrole dithiocarbamate), 2-cyanobut-2-yl-1-pyrrole carbodithioate, (common name: 2-cyano Nobut-2-yl-1-pyrrole dithiocarbamate), benzyl-1-imidazole carbodithioate, (common name benzyl-1-imidazole dithiocarbamate), 2-cyanoprop-2-yl-N,N-dimethyldithiocarbamate, benzyl-N,N-diethyldithiocarbamate, cyanomethyl-1-(2-pyrrolidone)dithiocarbamate, 2-(ethoxycarbonylbenzyl)prop-2-yl-N,N-diethyldithiocarbamate , 1-phenylethyl dithiobenzoate, 2-phenylprop-2-yl dithiobenzoate, 1-acetate-1-yl-ethyl dithiobenzoate, 1-(4-methoxyphenyl)ethyl dithiobenzoate, benzyl dithioacetate, ethoxycarbonylmethyl dithioacetate, 2-(ethoxycarbonyl)prop-2-yl dithiobenzoate, 2-cyanoprop-2-yl dithiobenzoate, tert-butyl dithiobenzoate, 2,4,4-Trimethylpent-2-yldithiobenzoate, 2-(4-chlorophenyl)-prop-2-yldithiobenzoate, 3-vinylbenzyldithiobenzoate, 4-vinylbenzyldithiobenzoate, benzyldiethoxyphosphinyldithioformate, tert-butyltrithioperbenzoate, 2-phenylprop-2-yl-4-chlorodithiobenzoate, Na Phthalene-1-carboxylic acid-1-methyl-1-phenyl-ethyl ester, 4-cyano-4-methyl-4-thiobenzylsulfanyl butyric acid, dibenzyl tetrathioterephthalate, carboxymethyl dithiobenzoate, poly(ethylene oxide) with dithiobenzoate end groups, poly(ethylene oxide) with 4-cyano-4-methyl-4-thiobenzylsulfanyl butyric acid end groups, 2-[(2-phenylethanethioyl)sulfanyl]propanoic acid, 2-[(2-phenylethanethioyl)sulfanyl]succinic acid, potassium 3,5-dimethyl-1H-pyrazole-1-carbodithioate, cyanomethyl-3,5-dimethyl-1H-pyrazole-1-carbodithioate, Cyanomethyl-N-methyl-N-phenyldithiocarbamate, benzyl-4-chlorodithiobenzoate, phenylmethyl-4-chlorodithiobenzoate, 4-nitrobenzyl-4-chlorodithiobenzoate, phenylprop-2-yl-4-chlorodithiobenzoate, 1-cyano-1-methylethyl-4-chlorodithiobenzoate, 3-chloro-2-butenyl-4-chlorodithiobenzoate, 2-chloro-2-butenyl dithiobenzoate, benzyl dithioacetate, 3-chloro-2-butenyl-1H-pyrrole-1-dithiocarboxylic acid, 2-cyanobutan-2-yl 4-chloro-3,5-dimethyl-1H-pyrazole-1-carbodithioate.

[0036] Examples of trithiocarbamates include 2-cyano-2-propyldodecyltrithiocarbonate, dibenzyltrithiocarbonate, butylbenzyltrithiocarbonate, 2-[[(butylthio)thioxomethyl]thio]propionic acid, 2-[[(dodecylthio)thioxomethyl]thio]propionic acid, 2-[[(butylthio)thioxomethyl]thio]succinic acid, 2-[[(dodecylthio)thioxomethyl]thio]succinic acid, 2-[[(dodecylthio)thioxomethyl]thio]-2-methylpropionic acid, 2,2'- Examples of trithiocarbonates include [carbonothioylbis(thio)]bis[2-methylpropionic acid], 2-amino-1-methyl-2-oxoethyl butyl trithiocarbonate, benzyl 2-[(2-hydroxyethyl)amino]-1-methyl-2-oxoethyl trithiocarbonate, 3-[[[(tert-butyl)thio]thioxomethyl]thio]propionic acid, cyanomethyl dodecyl trithiocarbonate, diethylaminobenzyl trithiocarbonate, and dibutylaminobenzyl trithiocarbonate. Among these, butylbenzyl trithiocarbonate is preferred from the viewpoint of easy control of the molecular weight.

[0037] <Emulsifier> The emulsifier is not particularly limited, and examples thereof include anionic surfactants, nonionic surfactants, and amphoteric surfactants. More specifically, examples of the emulsifier include anionic surfactants such as sulfate esters of higher alcohols (e.g., alcohols having 6 to 30 carbon atoms), alkylbenzenesulfonates, fatty acid sulfonates, phosphate salts (e.g., ammonium monoglyceride phosphate), fatty acid salts (e.g., dipotassium alkenylsuccinate), and amino acid derivative salts; nonionic surfactants such as alkyl esters, alkyl ethers, and alkylphenyl ethers of polyethylene glycol; and amphoteric surfactants having carboxylates, sulfates, sulfonates, and phosphate salts in the anion portion and amine salts, quaternary ammonium salts, in the cation portion. These emulsifiers may be used alone or in combination of two or more. Among these, in consideration of emulsion stability and ease of handling, the emulsifier is preferably anionic surfactants, more preferably alkylbenzenesulfonates, and even more preferably sodium dodecylbenzenesulfonate.

[0038] From the viewpoint of efficiently carrying out the polymerization reaction, the concentration of the emulsifier is preferably 1 to 10% by mass relative to the total amount (100% by mass) of all polymerizable monomers used in steps (i) to (iii).

[0039] <Polymerization initiator> Examples of the polymerization initiator include persulfates, sodium persulfate, hydrogen peroxide, tert-butyl hydroperoxide, and azo compounds. Among these, azo compounds are preferred from the viewpoint of suppressing side reactions derived from the initiator. The amount of the polymerization initiator is preferably 10 to 50 mol% based on the amount of the RAFT agent used.

[0040] <Azo compounds> Examples of azo compounds include 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 1-[(1-cyano-1-methylethyl)azo]formamide, 4,4'-azobis(4-cyanovaleric acid), dimethyl 2,2'-azobis(2 -methylpropionate), dimethyl 1,1'-azobis(1-cyclohexanecarboxylate), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2'-azobis(N-cyclohexyl-2-methylpropionamide), 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis(2,4,4-trimethylpentane), etc. These may be used alone or in combination of two or more.

[0041] <Polymerization conditions> The polymerization temperature in step (i) may be 10 to 100° C. or 20 to 80° C. Step (i) is preferably carried out until the monomer conversion rate reaches 70 to 100%, more preferably 80 to 100%.

[0042] <Seed particles (S1)> The polymer (P1) obtained in step (i) is obtained in a state of being dispersed in the aqueous dispersion (W1). In a preferred embodiment, the polymer (P1) is a seed particle (S1) having an average particle size of 50 to 500 nm. The average particle size of the seed particle (S1) can be easily controlled by adjusting the degree of polymerization of the polymerizable monomer (m1), the content of the emulsifier, the polymerization temperature, the polymerization time, and the like. By preparing the polymer (P1) as the seed particle (S1) having the above-mentioned average particle size, it becomes easy to control the average particle size of the crosslinked block copolymer finally obtained within a desired range. In this specification, the average particle size refers to the average particle size measured by dynamic light scattering and calculated by photon correlation spectroscopy.

[0043] In one embodiment, the seed particles (S1) are preferably polymers containing one or more monomer units selected from an aromatic vinyl compound unit and a vinyl cyanide unit, more preferably polymers containing an aromatic vinyl compound unit, and even more preferably polymers containing a styrene unit. In a particularly preferred embodiment, the seed particles (S1) are polystyrene particles having an average particle size of 50 to 500 nm.

[0044] [Step (ii)] In the first polymerization, after the above-mentioned step (i), it is preferable to carry out step (ii) of reacting the polymer (P1) with a polymerizable monomer (m2) that is the same as or different from the polymerizable monomer (m1) to obtain a polymer (P2) of the polymerizable monomers (m1) and (m2). More preferably, step (ii) is to add a polymerizable monomer (m2) that is the same as or different from the polymerizable monomer (m1) to the aqueous dispersion (W1) to react the active terminal of the seed particle (S1) with the polymerizable monomer (m2) to obtain an aqueous dispersion (W2) containing seed particles (S2) having the active terminal and consisting of a polymer (P2) of the polymerizable monomers (m1) and (m2).

[0045] More specifically, it is preferable to add a polymerizable monomer (m2) to an aqueous dispersion (W1) containing seed particles (S1), absorb the polymerizable monomer (m1) into the seed particles (S1), and then heat the mixture to a polymerization initiation temperature to react the active end of the seed particles (S1) with the polymerizable monomer (m2). This makes it possible to obtain an aqueous dispersion (W2) containing seed particles (S2) consisting of a polymer (P2) of the seed particles (S1) and the polymerizable monomer (m2). The polymerizable monomer (m2) may be added all at once or may be added dropwise continuously or intermittently. From the viewpoint of the stability of the reaction system, it is preferable to add dropwise continuously or intermittently.

[0046] <Polymerization conditions> The polymerization temperature in step (ii) may be 10 to 100° C. or 20 to 80° C. Step (ii) is preferably carried out until the monomer conversion reaches 70 to 100%, more preferably 80 to 100%.

[0047] The polymer (P2) obtained in the step (ii) includes a block (A) containing a polymerizable monomer (m1) and a block (B) containing a polymerizable monomer (m2). In one embodiment, the ratio of the polymer (P2) to the total mass of the finally obtained crosslinked block copolymer is preferably 10% by mass or more, more preferably 30% by mass or more. The upper limit may be 60% by mass or less, 55% by mass or less, or 50% by mass or less. That is, the ratio of the polymer (P2) to the total mass of the finally obtained crosslinked block copolymer may be 10 to 60% by mass, 20 to 55% by mass, or 30 to 50% by mass. By making the polymer (P2) within the above-mentioned range, a crosslinked block copolymer having a desired average particle size can be easily obtained.

[0048] In one embodiment, when the polymerizable monomer (m2) is the same as the polymerizable monomer (m1), the proportion of the polymerizable monomer (m2) relative to the total amount (100 mass%) of the polymerizable monomers (m1) and (m2) in the polymer (P2) is preferably 40 to 90 mass%, more preferably 50 to 80 mass%, and even more preferably 60 to 80 mass%. After preparing the seed particles (S1) in step (i), a monomer the same as the polymerizable monomer (m1) is further reacted in the above-mentioned ratio, whereby a crosslinked block copolymer having a desired average particle size is more easily obtained.

[0049] <Seed particles (S2)> The polymer (P2) is also obtained in a state of being dispersed in the aqueous dispersion (W2). When the polymer (P1) having the active terminal of the above-mentioned formula 1 is reacted with the polymerizable monomer (m2), it is preferable that the obtained polymer (P2) also has the active terminal represented by formula 1.

[0050] In a preferred embodiment, the polymer (P2) is a seed particle (S2) having an average particle size of 70 to 800 nm. If the average particle size of the seed particle (S2) is within the above range, a crosslinked block copolymer having a desired average particle size is more easily obtained. The average particle size of the seed particle (S2) is easily controlled by adjusting the amount of monomer added, polymerization conditions such as polymerization temperature and time, etc.

[0051] In a more preferred embodiment, the seed particles (S2) are preferably polymers containing one or more monomer units selected from an aromatic vinyl compound unit and a vinyl cyanide compound, more preferably polymers containing an aromatic vinyl compound unit, and even more preferably polymers containing a styrene unit. In a particularly preferred embodiment, the seed particles (S2) may be polystyrene particles or acrylonitrile-styrene copolymer particles having an average particle size of 70 to 800 nm. The seed particles (S2) may contain unreacted monomers, emulsifiers, polymerization initiators, etc.

[0052] [Step (iii)] In the first polymerization, after the step (ii), it is preferable to carry out a step (iii) of reacting the polymer (P2) with a polymerizable monomer (m3) different from the polymerizable monomers (m1) and (m2) to obtain a block copolymer. More preferably, the step (iii) is to add a polymerizable monomer (m3) different from the polymerizable monomers (m1) and (m2) to the aqueous dispersion (W2) to react the active terminal of the seed particle (S2) with the polymerizable monomer (m3) to obtain a seed particle (S3) made of a block copolymer.

[0053] More specifically, it is preferable to add the polymerizable monomer (m3) to the aqueous dispersion (W2) containing the seed particles (S2), absorb the polymerizable monomer (m3) into the seed particles (S2), and then heat the mixture to a polymerization initiation temperature to react the active end of the seed particles (S2) with the polymerizable monomer (m3). As a result, the polymerizable monomer (m3) absorbed in the seed particles (S2) is copolymerized with the seed particles (S2) (the above-mentioned polymer (P2)), and the seed particles (S3) made of a block copolymer can be obtained. The seed particles (S3) are obtained in a state of being dispersed in the aqueous dispersion (W3). The polymerizable monomer (m3) may be added all at once, or may be added dropwise continuously or intermittently. From the viewpoint of the stability of the reaction system, it is preferable to add dropwise continuously or intermittently.

[0054] <Polymerization conditions> The polymerization temperature in step (iii) may be 10 to 100° C. or 20 to 80° C. Step (iii) is preferably carried out until the monomer conversion rate reaches 70 to 100%, more preferably 80 to 100%.

[0055] <Seed particles (S3)> Seed particles (S3) made of a block copolymer are also obtained in a dispersed state in the aqueous dispersion (W3). When the polymer (P2) having the active terminal derived from the RAFT agent described above is reacted with the polymerizable monomer (m3), the resulting seed particles (S3) also have the active terminal derived from the RAFT agent.

[0056] In a preferred embodiment, the seed particles (S3) have an average particle size of 90 to 1000 nm. The seed particles (S3) may contain trace components such as unreacted monomers, emulsifiers, and polymerization initiators.

[0057] <Second Polymerization> After the first polymerization is carried out by the above-mentioned method, the second polymerization is carried out successively. The second polymerization is to obtain a crosslinked block copolymer by adding one or more polymerizable monomers selected from the above-mentioned two or more polymerizable monomers and a polyfunctional monomer to the block copolymer obtained by the first polymerization.

[0058] In one embodiment, it is preferable that one or more polymerizable monomers added in the second polymerization include a polymerizable monomer constituting at least one end block of the block copolymer. Here, when the seed particle (S3) is prepared by the above-mentioned RAFT polymerization method, the seed particle (S3) includes a block (A) containing a polymerizable monomer (m1), a block (B) containing a polymerizable monomer (m2) that is the same as or different from the polymerizable monomer (m1), and a block (C) containing a polymerizable monomer (m3) different from the polymerizable monomers (m1) and (m2), and the polymerizable monomer constituting the end block is preferably the block (C). That is, the polymerizable monomer added in the second polymerization is preferably a polymerizable monomer (m3), more preferably contains a (meth)acrylic acid ester, even more preferably contains a (meth)acrylic acid ester having an alkyl group with 1 to 4 carbon atoms, and particularly preferably contains n-butyl acrylate.

[0059] The manufacturing method according to the present embodiment is characterized in that the polymerizable monomer constituting a specific block is added separately to the first polymerization and the second polymerization, and a polyfunctional monomer is blended in the second polymerization. The inventors of the present application have found that by adding the specific polymerizable monomer separately to the first polymerization and the second polymerization in this manner, it becomes easier to control the crosslinking position by the polyfunctional monomer, which makes it easier to develop a microphase separation structure and to maintain the particle shape of the polymer particles. In a preferred embodiment, the ratio of the polymerizable monomer (m3) added in the second polymerization may be 10 to 90 mass% or 25 to 75 mass% with respect to the total amount (100 mass%) of the polymerizable monomer (m3) used in the first polymerization and the second polymerization.

[0060] In the second polymerization, a polymerizable monomer and a polyfunctional monomer are added and reacted with the block copolymer, so that the block copolymers are crosslinked to form stronger polymer particles (crosslinked block copolymers). Here, "crosslinking block copolymers" includes crosslinking two or more blocks (including the same blocks) selected from blocks (A), (B), and (C) contained in one block copolymer, as well as crosslinking one or more blocks contained in one block copolymer with one or more blocks contained in the other block copolymer among the two or more block copolymers. In a preferred embodiment, the second polymerization may include crosslinking one or more blocks contained in one block copolymer with one or more blocks contained in the other block copolymer among the two or more block copolymers, or may include crosslinking a block (C) of one block copolymer with a block (C) of the other block copolymer. This makes it easier for the resulting crosslinked block copolymer to become a stronger polymer particle, and makes it easier to maintain the particle shape during melt kneading.

[0061] (Polyfunctional Monomer) The polyfunctional monomer added in the second polymerization is not particularly limited as long as it is a monomer having two or more polymerizable functional groups. Examples of the "polymerizable functional group" include an ethylenically unsaturated group, an oxiranyl group, an oxetanyl group, and an N-alkoxymethylamino group. Among these, the polyfunctional monomer is preferably a compound having two or more ethylenically unsaturated groups, and more preferably a compound having a (meth)acryloyl group or an aromatic polyene. In this specification, the "(meth)acryloyl group" includes one or both of an acryloyl group and a methacryloyl group. The polyfunctional monomer may be used alone or in combination of two or more types.

[0062] Specific examples of the compound having two or more (meth)acryloyl groups include polyfunctional (meth)acrylic acid esters obtained by reacting an aliphatic polyhydroxy compound with (meth)acrylic acid; caprolactone-modified polyfunctional (meth)acrylic acid esters; alkylene oxide-modified polyfunctional (meth)acrylic acid esters; polyfunctional urethane (meth)acrylic acid esters obtained by reacting a (meth)acrylic acid ester having a hydroxyl group with a polyfunctional isocyanate; and polyfunctional (meth)acrylic acid esters having a carboxyl group obtained by reacting a (meth)acrylic acid ester having a hydroxyl group with an acid anhydride. Among these, polyfunctional (meth)acrylic acid esters obtained by reacting an aliphatic polyhydroxy compound with (meth)acrylic acid are preferred, and bifunctional (meth)acrylic acid esters are more preferred.

[0063] Specific examples of bifunctional (meth)acrylic acid esters (excluding those having a hydroxyl group) include diol diacrylates such as 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, and 1,10-decanediol diacrylate; ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, and polypropylene glycol diacrylate. Examples of the diacrylate include glycol diacrylates such as chol diacrylate, neopentyl glycol diacrylate, diacrylates of diols obtained by adding at least one of ethylene oxide and propylene oxide to neopentyl glycol, and caprolactone-modified hydroxypivalic acid neopentyl glycol diacrylate; diacrylates of EO adducts of bisphenol A, diacrylates of PO adducts of bisphenol A, tricyclodecane dimethanol diacrylate, hydrogenated dicyclopentadienyl diacrylate, and diacrylates having a cyclic structure such as cyclohexyl diacrylate. These may be used alone or in combination of two or more. Of these, it is preferable to include 1,9-nonanediol diacrylate.

[0064] The aromatic polyene is preferably an aromatic polyene having 10 to 30 carbon atoms, two or more double bonds (vinyl groups), and one or more aromatic groups. More specifically, examples of the aromatic polyene include o-divinylbenzene, p-divinylbenzene, m-divinylbenzene, 1,4-divinylnaphthalene, 3,4-divinylnaphthalene, 2,6-divinylnaphthalene, 1,2-divinyl-3,4-dimethylbenzene, and 1,3-divinyl-4,5,8-tributylnaphthalene, and is preferably at least one selected from o-divinylbenzene, p-divinylbenzene, and m-divinylbenzene.

[0065] The amount of the polyfunctional monomer added is preferably 10 mass % or less, more preferably 0.5 to 8 mass %, further preferably 1 to 5 mass %, particularly preferably 1 to 3 mass %, based on the total mass of the resulting crosslinked block copolymer.

[0066] In a preferred embodiment, the second polymerization preferably includes adding a polymerizable monomer (m3) and a polyfunctional monomer containing a (meth)acrylic acid ester having two or more functional groups to the block copolymer, and crosslinking the block copolymers with the polyfunctional monomer. The method of adding the polyfunctional monomer may be to add the polyfunctional monomer by blending it into the polymerizable monomer (m3), or to add it directly into the aqueous dispersion (W3) containing the seed particles (S3). From the viewpoint of maintaining the particle shape during melt kneading, it is preferable to blend it into the polymerizable monomer (m3).

[0067] After the second polymerization, the resulting block copolymer may contain an active end derived from the RART agent, for example, an active end represented by the above formula 1. Therefore, after the second polymerization, the active end may be treated (step (iv)). Various techniques are known for step (iv). These techniques can be suitably used in the present disclosure. Suitable techniques include those described in, for example, Chong et al, macromolecules 2007, 40, 4446-4455; Chong et al, Aust. J. Chem. 2006, 59, 755-762; Postmaetal, macromolecules 2005, 38, 5371-5374; Moadetal, polymer International 60, no. 1, 2011, 9-25; and Wilcocketal, Polym. Chem., 2010, 1, 149-157.

[0068] After the polymerization reaction is stopped, it is preferable to remove the unreacted monomer by a known method such as vacuum distillation. After removing the unreacted monomer, the crosslinked block copolymer can be recovered by, for example, <1> A method in which the aqueous dispersion is poured into hot water in which a coagulant has been dissolved, and the crosslinked block copolymer is recovered by coagulating it into a slurry state (wet method); <2> Examples of the method include a method in which an aqueous dispersion of the crosslinked block copolymer is sprayed in a heated atmosphere to semi-directly recover the crosslinked block copolymer (spray drying method).

[0069] <1> Examples of the coagulant in the above step include, but are not limited to, inorganic acids such as sulfuric acid, hydrochloric acid, phosphoric acid, and nitric acid, and metal salts such as calcium chloride, calcium acetate, aluminum sulfate, and magnesium sulfate.

[0070] Examples of methods for obtaining a dry cross-linked block copolymer from a cross-linked block copolymer in a slurry state include <1-1> a ​​method in which the emulsifier residue and the coagulant residue remaining in the slurry are dissolved into water by washing, and then the slurry is dehydrated using a centrifugal dehydrator or a press dehydrator, and further dried using a flash dryer or the like; and <1-2> a method in which the slurry is simultaneously dehydrated and dried using a squeeze dehydrator, extruder, or the like.

[0071] According to the above-mentioned production method, a crosslinked block copolymer can be produced as the polymer particles. Such polymer particles are strong particles that do not easily crumble during melt kneading.

[0072] [Crosslinked block copolymer] The crosslinked block copolymer obtained by the production method of this embodiment has two or more blocks. When the above-mentioned polymerizable monomers (m1) to (m3) are used, the crosslinked block copolymer obtained at least includes a block (A) containing the polymerizable monomer (m1), a block (B) containing a polymerizable monomer (m2) that is the same as or different from the polymerizable monomer (m1), and a block (C) containing a polymerizable monomer (m3) different from the polymerizable monomers (m1) and (m2).

[0073] <Block (A)> The block (A) is a block containing a polymerizable monomer (m1), and in a preferred embodiment, the block (A) contains an aromatic vinyl compound unit. In a more preferred embodiment, the block (A) is a block consisting of an aromatic vinyl compound unit, and may be a polystyrene block. Each block constituting the crosslinked block copolymer may contain a trace component that is inevitably mixed in, such as the polymerization terminal of an initiator.

[0074] In one embodiment, the proportion of the block (A) relative to all blocks (100% by mass) constituting the crosslinked block copolymer may be 1 to 36% by mass, or 10 to 30% by mass.

[0075] In one embodiment, the weight average molecular weight (hereinafter referred to as "Mw") of the block (A) is preferably 10,000 to 80,000, and more preferably 10,000 to 50,000. The Mw (and the number average molecular weight (hereinafter referred to as "Mn")) of the seed particle (S1) can be measured under the following conditions using GPC (for example, product name "HLC-8320" manufactured by Tosoh Corporation). <Measurement conditions> Column: 3 TSKgel GMHHR-H in series Temperature: 40℃ Detection: Differential refractive index Solvent: THF Calibration curve: Prepared using standard polystyrene (PS).

[0076] <Block (B)> The block (B) is a block containing a polymerizable monomer (m2), and in one embodiment, the block (B) is composed of the same monomer units as the block (A). In one embodiment, the block (B) may be a block composed of aromatic vinyl compound units, or may be a polystyrene block. In a preferred embodiment, the block (B) may be a block composed of aromatic vinyl compound units and vinyl cyanide units, or may be a poly(styrene / acrylonitrile) block.

[0077] In one embodiment, the proportion of the block (B) relative to all blocks (100% by mass) constituting the crosslinked block copolymer may be 4 to 54% by mass, or may be 20 to 40% by mass.

[0078] In one embodiment, the Mw of the block (B) is preferably 10,000 to 100,000. The total Mw of the block (A) and the block (B) (the Mw of the diblock copolymer) may be 20,000 to 180,000 or 20,000 to 100,000.

[0079] <Block (C)> The block (C) is a block containing the polymerizable monomer (m3), and in a preferred embodiment, the block (C) contains a (meth)acrylic acid ester unit. In a more preferred embodiment, the block (C) is a block consisting of a (meth)acrylic acid ester unit, and may be a polybutyl acrylate block.

[0080] In one embodiment, the proportion of the block (C) relative to all blocks (100% by mass) constituting the crosslinked block copolymer may be 40 to 90% by mass, or 45 to 70% by mass.

[0081] In one embodiment, the Mw of the block (C) is preferably 12,000 to 180,000.

[0082] (Average particle size) In one embodiment, the average particle size of the crosslinked block copolymer may be 50 to 1000 nm, or 100 to 500 nm. The average particle size is measured by a dynamic light scattering method (for example, product name "ELSZ-2000ZS" manufactured by Otsuka Electronics Co., Ltd.).

[0083] (Molecular weight of cross-linked block copolymer) The production method according to the present embodiment makes it easy to obtain a crosslinked block copolymer having a narrow Mw / Mn (weight average molecular weight / number average molecular weight) and a high molecular weight. In one embodiment, the Mw of the crosslinked block copolymer is preferably equal to or greater than a critical molecular weight (hereinafter, sometimes referred to as "Mc"). If the Mw of the crosslinked block copolymer is equal to or greater than Mc, the crosslinked block copolymer is more likely to exhibit sufficient physical properties for practical use. Here, the "critical molecular weight" is a molecular weight corresponding to the molecular chain length required for entanglement of molecules in an undiluted polymer. When the molecular weight of the polymer exceeds Mc, the viscosity increases rapidly. Mc varies depending on the type and composition of the polymer (for example, the monomer composition of each block forming a block copolymer). Mc is shown in many documents. For example, but not limited to, it has been reported that the Mc of acrylonitrile-styrene copolymer is 24,000, the Mc of polystyrene is 31,200, and the Mc of polymethyl methacrylate is 27,500.

[0084] As a method for measuring Mc of the crosslinked block copolymer according to the present embodiment, a conventionally known method can be adopted. For example, a method for experimentally deriving Mc by determining the point (critical point) where the slope of a logarithmic graph (horizontal axis: log(Mw), vertical axis: log(viscosity)) showing the relationship between Mw and viscosity of the crosslinked block copolymer changes from 1.0 to 3.4 (for example, a method described in JP-A-2010-506002, etc.), or a method for confirming whether a rubber-like plateau appears when measuring the storage modulus by viscoelasticity measurement, etc. can be adopted. Note that the Mw and Mn of the crosslinked block copolymer can be values ​​measured under the above-mentioned conditions. In addition, the crosslinked block copolymer finally obtained may not dissolve in a solvent, and in that case, the Mw of the crosslinked block copolymer finally obtained may be determined to be equal to or greater than Mc by measuring the Mc by the above-mentioned viscoelasticity measurement or by confirming that the Mw of the block copolymer obtained after the first polymerization is equal to or greater than Mc.

[0085] [Application] The crosslinked block copolymer obtained by the production method according to the present embodiment is a strong particle that does not easily collapse during melt kneading. Such a crosslinked block copolymer can be used, for example, by blending it into a thermoplastic resin as a novel rubber component. A resin composition in which the crosslinked block copolymer according to the present embodiment is dispersed in a thermoplastic resin that is a matrix resin is also included in one aspect of the present disclosure. Such a resin composition can be produced by mixing the crosslinked block copolymer obtained by the production method according to the present embodiment with a thermoplastic resin. As the thermoplastic resin, for example, a styrene-based resin can be used. EXAMPLES

[0086] The present invention will be described in more detail below with reference to examples. Note that the examples described below are representative examples of the present invention, and the present invention is not limited to the following examples.

[0087] [Example 1] (First Polymerization) Synthesis of Block Copolymer ·Process (i) 9 parts by mass of sodium dodecylbenzenesulfonate and 2 parts by mass of sodium hydrogen carbonate were dissolved in 220 parts by mass of deionized water that had been substituted with nitrogen, and the solution was placed in a polymerization vessel equipped with a stirrer. Then, while stirring the liquid in the polymerization vessel, 1.3 parts by mass of butylbenzyltrithiocarbonate (RAFT agent) was dissolved in 100 parts by mass of styrene (polymerizable monomer (m1)) in advance, and the internal temperature was set to 80°C. Then, 2.5 parts by mass of a 20% by mass aqueous solution of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride was added as a polymerization initiator to carry out polymerization, and an aqueous dispersion (W1) containing seed particles (S1) made of polystyrene and having active terminals derived from the RAFT agent was obtained. The seed particles (S1) were polymer (P1) constituting the block (A). The polymer (P1) had an Mw of 17,700, an Mn of 15,400, and a molecular weight distribution (Mw / Mn) of 1.1, as measured by the methods described below.

[0088] ·Process (ii) To the obtained aqueous dispersion (W1), 161 parts by mass of styrene (polymerizable monomer (m2)), 137 parts by mass of deionized water, and 21 parts by mass of sodium dodecylbenzenesulfonate were added under stirring, and polymerization was carried out at an internal temperature of 80°C to obtain an aqueous dispersion (W2) containing seed particles (S2) made of polystyrene. The seed particles (S2) were polymers (P2) made of blocks (A) (polystyrene blocks) and (B) (polystyrene blocks), and the Mw, Mn, and molecular weight distribution (Mw / Mn) of the polymer (P2), measured by the method described below, were 41,300, 31,800, and 1.3, respectively. At this time, it was confirmed that the Mw of the polymer (P2) was equal to or greater than the Mc (31,200) of polystyrene.

[0089] ·Process (iii) To the obtained aqueous dispersion (W2), 144 parts by mass of n-butyl acrylate (polymerizable monomer (m3)), 345 parts by mass of deionized water, and 0.7 parts by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) were added with stirring, and polymerization was carried out at an internal temperature of 80°C to obtain an aqueous dispersion (W3) containing seed particles (S3) consisting of a block copolymer of styrene and n-butyl acrylate. The seed particles (S3) were a block copolymer consisting of block (A) (polystyrene block), block (B) (polystyrene block), and block (C) (polybutyl acrylate block).

[0090] (Second Polymerization) Synthesis of Crosslinked Block Copolymer After the first polymerization, 144 parts by mass of n-butyl acrylate (polymerizable monomer (m3)), 14 parts by mass of 1,9-nonanediol diacrylate (multifunctional monomer), 95 parts by mass of deionized water, and 4 parts by mass of sodium dodecylbenzenesulfonate were continuously added to the aqueous dispersion (W3) to obtain an aqueous dispersion containing polymer particles made of a crosslinked block copolymer. The average particle size and particle shape retention of the obtained polymer particles of the crosslinked block copolymer were evaluated under the following conditions.

[0091] (Measurement of average particle size) The average particle size of the crosslinked block copolymer was measured by dynamic light scattering using an "ELSZ-2000ZS" manufactured by Otsuka Electronics Co., Ltd., and calculated by cumulant analysis. The measurement conditions were a temperature of 25°C, an accumulation of 25 times, and the refractive index of water (1.333) was used as the refractive index of the dispersion solvent.

[0092] (Measurement of Mw and Mn) Mw and Mn were measured using GPC (manufactured by Tosoh Corporation, product name "HLC-8320") under the following conditions. Column: 3 TSKgel GMHHR-H in series Temperature: 40℃ Detection: Differential refractive index Solvent: THF Calibration curve: Prepared using standard polystyrene (PS).

[0093] (Evaluation of particle shape retention) Polymer particles were collected from the obtained aqueous dispersion of the crosslinked block copolymer. Then, the polymer particles were blended into a matrix resin (polystyrene resin (PS resin) (manufactured by Toyo Styrene Co., Ltd., product name "G200C")) in a ratio such that the ratio of the matrix resin was 70% by mass, and melt-kneaded using a small kneading device (manufactured by Toyo Seiki Seisakusho Co., Ltd., product name "Labo Plastomill (registered trademark)") under the conditions of cylinder temperature: 220°C, rotation speed: 100 rpm, and kneading time: 5 minutes. After preparing a test piece from the obtained melt-kneaded resin, the test piece was stained with ruthenium tetroxide and observed with a transmission electron microscope (TEM). The state of the polymer particles in the test piece was observed and evaluated according to the following evaluation criteria. <Evaluation criteria> Pass: The polymer particles did not collapse and maintained their original particle shape. Failed: The polymer particles were disintegrated and could not maintain the original particle shape.

[0094] [Examples 2 to 3 and Comparative Example 1] In Examples 2 to 3 and Comparative Example 1, block copolymers were obtained and evaluated in the same manner as in Example 1, except that the blending ratio was changed as shown in Table 1. In Example 3, the internal temperature in the first polymerization step was set to 70° C., and an acrylonitrile-styrene copolymer (AS resin, manufactured by Denka Co., Ltd., product name "AS-C-800") was used as the matrix resin in the evaluation of particle shape retention. In Example 3, the seed particle (S1) made of polystyrene (polymer (P1) made of block (A)) had an Mw of 17,700, an Mn of 15,400, and a molecular weight distribution (Mw / Mn) of 1.1. The seed particle (S1) and the seed particle (S2) copolymerized with acrylonitrile and styrene (polymer (P2) made of block (A) (polystyrene block) and block (B) (acrylonitrile-styrene block)) had an Mw of 38,400, an Mn of 33,900, and a molecular weight distribution (Mw / Mn) of 1.1. It was confirmed that the Mw of the polymer (P2) was equal to or greater than the Mc (24,000) of the acrylonitrile-styrene copolymer.

[0095] [Table 1]

[0096] The abbreviations in Table 1 have the following meanings. St: styrene AN: Acrylonitrile nBA: n-butyl acrylate NDDA: 1,9-nonanediol diacrylate

[0097] As shown in Table 1, the crosslinked block copolymer obtained by the production method according to this embodiment maintained its particle shape even when it was blended into a matrix resin and melt-kneaded. On the other hand, the block copolymer of Comparative Example 1, in which no multifunctional monomer was added in the second polymerization, collapsed during melt-kneading and could not maintain its shape. From the above results, it was found that the production method according to this embodiment can produce polymer particles that are less likely to collapse.

[0098] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of the present disclosure are set forth below. [1] Obtaining a block copolymer from two or more polymerizable monomers (first polymerization); and adding one or more polymerizable monomers selected from the two or more polymerizable monomers and a polyfunctional monomer to the block copolymer to obtain a crosslinked block copolymer (second polymerization). [2] The method for producing a crosslinked block copolymer according to [1], wherein the second polymerization includes crosslinking the block copolymers to each other. [3] The method for producing a crosslinked block copolymer according to [1] or [2], wherein the polymerizable monomer added in the second polymerization contains a polymerizable monomer constituting at least one end block of the block copolymer. [4] The first polymerization comprises obtaining the block copolymer comprising a block (A) containing a polymerizable monomer (m1), a block (B) containing a polymerizable monomer (m2) that is the same as or different from the polymerizable monomer (m1), and a block (C) containing a polymerizable monomer (m3) that is different from the polymerizable monomers (m1) and (m2), The method for producing a crosslinked block copolymer according to any one of [1] to [3], wherein the polymerizable monomer added in the second polymerization contains the polymerizable monomer (m3). [5] the first polymerization reacting a polymerizable monomer (m1) with a RAFT agent to obtain a polymer (P1) of the polymerizable monomer (m1) having an active terminal derived from the RAFT agent; reacting the polymer (P1) with a polymerizable monomer (m2) which is the same as or different from the polymerizable monomer (m1) to obtain a polymer (P2) of the polymerizable monomers (m1) and (m2); and reacting the polymer (P2) with a polymerizable monomer (m3) different from the polymerizable monomers (m1) and (m2) to obtain the block copolymer. [6] The first polymerization adding a polymerization initiator to a mixed liquid containing a polymerizable monomer (m1), a RAFT agent, water, and an emulsifier to obtain an aqueous dispersion (W1) containing seed particles (S1) having active ends derived from the RAFT agent and consisting of a polymer (P1) of the polymerizable monomer (m1); adding a polymerizable monomer (m2) that is the same as or different from the polymerizable monomer (m1) to the aqueous dispersion (W1) to react the active terminal of the seed particle (S1) with the polymerizable monomer (m2) to obtain an aqueous dispersion (W2) containing a seed particle (S2) having the active terminal and consisting of a polymer (P2) of the polymerizable monomers (m1) and (m2); and adding a polymerizable monomer (m3) different from the polymerizable monomers (m1) and (m2) to the aqueous dispersion (W2) to react the active terminal of the seed particle (S2) with the polymerizable monomer (m3), thereby obtaining a seed particle (S3) made of the block copolymer. [7] The method for producing a crosslinked block copolymer according to any one of [4] to [6], wherein the second polymerization comprises adding the polymerizable monomer (m3) and the polyfunctional monomer containing a di- or higher functional (meth)acrylic acid ester to the block copolymer, and crosslinking the block copolymers with the polyfunctional monomer. [8] The method for producing a crosslinked block copolymer according to any one of [4] to [7], wherein the polymerizable monomer (m1) contains an aromatic vinyl compound. [9] The method for producing a crosslinked block copolymer according to any one of [4] to [8], wherein the polymerizable monomer (m2) comprises at least one selected from vinyl cyanide and an aromatic vinyl compound.

[10] The method for producing a crosslinked block copolymer according to any one of [4] to [9], wherein the polymerizable monomer (m3) contains a (meth)acrylic acid ester.

Claims

1. Obtaining a block copolymer from two or more polymerizable monomers (first polymerization); and adding one or more polymerizable monomers selected from the two or more polymerizable monomers and a polyfunctional monomer to the block copolymer to obtain a crosslinked block copolymer (second polymerization).

2. The method for producing a crosslinked block copolymer according to claim 1 , wherein the second polymerization comprises crosslinking the block copolymers to each other.

3. 3. The method for producing a crosslinked block copolymer according to claim 1, wherein the polymerizable monomer added in the second polymerization includes a polymerizable monomer constituting at least one end block of the block copolymer.

4. the first polymerization comprises obtaining the block copolymer comprising a block (A) containing a polymerizable monomer (m1), a block (B) containing a polymerizable monomer (m2) that is the same as or different from the polymerizable monomer (m1), and a block (C) containing a polymerizable monomer (m3) that is different from the polymerizable monomers (m1) and (m2); The method for producing a crosslinked block copolymer according to claim 1 or 2, wherein the polymerizable monomer added in the second polymerization includes the polymerizable monomer (m3).

5. The first polymerization reacting a polymerizable monomer (m1) with a RAFT agent to obtain a polymer (P1) of the polymerizable monomer (m1) having an active terminal derived from the RAFT agent; reacting the polymer (P1) with a polymerizable monomer (m2) which is the same as or different from the polymerizable monomer (m1) to obtain a polymer (P2) of the polymerizable monomers (m1) and (m2); and reacting the polymer (P2) with a polymerizable monomer (m3) different from the polymerizable monomers (m1) and (m2) to obtain the block copolymer.

6. The first polymerization adding a polymerization initiator to a mixed liquid containing a polymerizable monomer (m1), a RAFT agent, water, and an emulsifier to obtain an aqueous dispersion (W1) containing seed particles (S1) having active ends derived from the RAFT agent and consisting of a polymer (P1) of the polymerizable monomer (m1); adding a polymerizable monomer (m2) that is the same as or different from the polymerizable monomer (m1) to the aqueous dispersion (W1) to react the active terminal of the seed particle (S1) with the polymerizable monomer (m2) to obtain an aqueous dispersion (W2) containing a seed particle (S2) having the active terminal and consisting of a polymer (P2) of the polymerizable monomers (m1) and (m2); 3. The method for producing a crosslinked block copolymer according to claim 1, further comprising: adding a polymerizable monomer (m3) different from the polymerizable monomers (m1) and (m2) to the aqueous dispersion (W2) to react the active terminal of the seed particle (S2) with the polymerizable monomer (m3), thereby obtaining a seed particle (S3) made of the block copolymer.

7. The method for producing a crosslinked block copolymer according to claim 4, wherein the second polymerization comprises adding the polymerizable monomer (m3) and the polyfunctional monomer containing a di- or higher functional (meth)acrylic acid ester to the block copolymer, and crosslinking the block copolymers with the polyfunctional monomer.

8. The method for producing a crosslinked block copolymer according to claim 4 , wherein the polymerizable monomer (m1) comprises an aromatic vinyl compound.

9. The method for producing a crosslinked block copolymer according to claim 4, wherein the polymerizable monomer (m2) comprises at least one selected from the group consisting of vinyl cyanide and aromatic vinyl compounds.

10. The method for producing a crosslinked block copolymer according to claim 4 , wherein the polymerizable monomer (m3) includes a (meth)acrylic acid ester.

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