Method for producing polymer microparticles, molded body of polymer microparticles, and method for recycling polymer microparticles

Abstract

Provided is a method for recycling polymer microparticles that can be applied to a plurality of polymers. A method for recycling polymer microparticles, which comprises: (A) a step for decomposing a first polymer microparticle molded body into second polymer microparticles by applying an external stimulus to the first polymer microparticle molded body obtained by molding the first polymer microparticles;

Description

Technical Field

[0001] The present invention relates to a method for producing polymer microparticles, a polymer microparticle molded body, and a method for recycling polymer microparticles. Background Art

[0002] In recent years, from the viewpoint of suppressing resource depletion and environmental pollution, the development of polymer recycling methods has been actively carried out. As polymer recycling methods, there are the following methods: a method of refining a polymer by dissolving it in a solvent and recycling it in the form of a polymer (for example, Patent Documents 1 and 2); and a method of decomposing a polymer into monomers and recycling them (for example, Patent Documents 3 and 4).

[0003] Patent Document 1 (Japanese Patent Application Laid-Open No. 2009-30017) describes a method for recycling a polymer, wherein a polymer such as polymethyl methacrylate is dissolved in a liquid containing water and a poor solvent for the polymer, and a polymer precipitate precipitated from the polymer solution is recycled.

[0004] Patent Document 2 (Japanese Patent Application Laid-Open No. 2001-302842) describes a method for treating waste expanded polystyrene, wherein the waste expanded polystyrene is dissolved in limonene, and the limonene is evaporated and separated from the limonene solution to recover the polystyrene.

[0005] Patent document 3 (Japanese Patent Publication No. 2006-83145) describes a recycling method using expanded polystyrene, which includes: a step of dissolving the recovered expanded polystyrene in a solvent containing d-limonene to prepare a polystyrene solution; a step of heating and gasifying the polystyrene solution to separate the polystyrene; a step of regenerating the polystyrene in the form of styrene monomer; and a step of using the regenerated styrene monomer as a raw material to generate 1,1-diarylethane by Friedel-Crafts reaction.

[0006] Patent document 4 (Japanese Patent Application Laid-Open No. 2004-196880) describes a method for depolymerizing polyethylene terephthalate, wherein, when polyethylene terephthalate is heated and melted for depolymerization, an extruder and a reactor provided at the outlet of the extruder are used to carry out heating, melting and depolymerization reactions of the polyethylene terephthalate, and a diol is added at and after the outlet of the extruder, and a stirrer provided between the extruder and the reactor is used to mix the diol and the polyethylene terephthalate.

[0007] On the other hand, as a polymer molded product, a material obtained by molding polymer microparticles has been proposed (Patent Documents 5 and 6: Japanese Patent Application Publication Nos. 2021-195521 and 2022-91113).

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2009-30017

[0011] Patent Document 2: Japanese Patent Application Publication No. 2001-302842

[0012] Patent Document 3: Japanese Patent Application Publication No. 2006-83145

[0013] Patent Document 4: Japanese Patent Application Publication No. 2004-196880

[0014] Patent Document 5: Japanese Patent Application Publication No. 2021-195521

[0015] Patent Document 6: Japanese Patent Application Publication No. 2022-91113 Summary of the invention

[0016] Problem that the invention aims to solve

[0017] The above-mentioned methods of dissolving a polymer in a solvent to purify it and then reusing it as a polymer and the methods of decomposing a polymer into monomers and reusing it have the following problems: limited applicable polymers; complicated purification process; high production cost, etc.

[0018] The object of the present invention is to provide a method for producing polymer particles from a polymer particle molded body by a simple operation. In one embodiment, the polymer particles produced from the polymer particle molded body are provided for recycling. Furthermore, the object of the present invention is to provide a polymer particle molded body that can be decomposed by a simple operation. Furthermore, the object of the present invention is to provide a method for recycling polymer particles that can be applied to a variety of polymers.

[0019] Solutions for solving problems

[0020] Conventional methods attempt to reuse polymers by decomposing them into polymer chains or monomers. On the other hand, the present inventors have found that by treating polymers in the form of microparticles, various polymers can be molded and decomposed for reuse.

[0021] That is, the present invention includes the following aspects.

[0022] [1] A method for producing polymer microparticles, comprising:

[0023] By applying an external stimulus to the molded body of polymer microparticles, the molded body is decomposed into polymer microparticles.

[0024] [2] The method according to [1], wherein the external stimulus is applied by swelling the polymer microparticles with a solvent.

[0025] [3] The method according to [2], wherein the solvent comprises an alcohol selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, an alcohol having 2 to 6 carbon atoms, a ketone having 3 to 5 carbon atoms, an aromatic hydrocarbon having 6 to 10 carbon atoms, and a compound of formula R 1 COOR 2 (Where R 1 is hydrogen or an alkyl group having 1 to 3 carbon atoms, R 2 At least one selected from the group consisting of esters represented by an alkyl group having 1 to 3 carbon atoms.

[0026] [4] The method according to any one of [1] to [4], wherein the polymer constituting the polymer microparticles is a (meth)acrylate polymer or a poly(meth)acrylamide polymer.

[0027] [5] A polymer microparticle molded product obtained by molding polymer microparticles,

[0028] At least 80 mol% of the monomers constituting the polymer are at least one monomer selected from the group consisting of polyalkylene glycol (meth)acrylates, methacrylates containing an alkoxy group, acrylates containing an alkoxy group having 2 or more carbon atoms, (meth)acrylamide, and derivatives thereof.

[0029] [6] The polymer microparticle molded body according to [5], which does not contain a structure derived from rotaxane.

[0030] [7] A method for recycling polymer microparticles, wherein the method comprises:

[0031] (A) A step of applying an external stimulus to a first polymer microparticle molded body obtained by molding first polymer microparticles, thereby decomposing the first polymer microparticle molded body into second polymer microparticles.

[0032] [8] The recycling method according to [7], wherein the average particle size of the first polymer microparticles before molding is 50 nm to 5 μm.

[0033] [9] The recycling method according to [7] or [8], wherein the change rate between the average particle size of the first polymer microparticles before molding and the average particle size of the second polymer microparticles after decomposition is 15% or less.

[0034]

[10] The recycling method according to any one of [7] to [9], wherein the ratio of the total mass of the second polymer microparticles obtained after the decomposition to the total mass of the first polymer microparticles used in the molding is 0.95 or more.

[0035]

[11] The recycling method according to any one of [7] to

[10] , wherein the method further comprises:

[0036] (B) A step of molding the second polymer microparticles obtained in the step (A) to produce a second polymer microparticle molded body.

[0037]

[12] The recycling method according to

[11] , wherein the molding in the step (B) is performed using a second polymer microparticle dispersion in which the second polymer microparticles are dispersed in a dispersion medium.

[0038]

[13] The recycling method according to

[11] or

[12] , wherein the method further comprises: using the second polymer microparticle molded body obtained by the above step (B) as the first polymer microparticle molded body of the above step (A), and performing the above step (A) again.

[0039]

[14] The recycling method according to any one of [9] to

[11] , wherein the first polymer microparticle molded body further contains a functionalizing agent.

[0040]

[15] The method according to

[14] , further comprising the step of separating the second polymer microparticles from the functionalizing agent.

[0041]

[16] A closed-loop recycling method for polymers using polymer microparticles, comprising:

[0042] (a) providing a polymer microparticle dispersion comprising polymer microparticles and a dispersion medium;

[0043] (b) forming the polymer microparticle dispersion to obtain a formed body; and

[0044] (c) a step of adding a solvent to the molded body as an external stimulus to swell the polymer microparticles constituting the molded body, thereby decomposing the molded body into the polymer microparticles.

[0045]

[17] The method according to

[16] , wherein the average particle size of the polymer microparticles is 50 nm to 5 μm.

[0046]

[18] The method according to

[16] or

[17] , wherein the polymer microparticles are (meth)acrylic acid polymer microparticles or poly(meth)acrylamide microparticles.

[0047]

[19] The method according to

[18] , wherein the solvent comprises an alcohol selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, an alcohol having 2 to 6 carbon atoms, a ketone having 3 to 5 carbon atoms, an aromatic hydrocarbon having 6 to 10 carbon atoms, and a compound of formula R 1 COOR 2 (Where R 1 is hydrogen or an alkyl group having 1 to 3 carbon atoms, R 2 At least one selected from the group consisting of esters represented by an alkyl group having 1 to 3 carbon atoms.

[0048]

[20] The method according to any one of

[16] to

[19] , wherein the change rate between the average particle size of the polymer particles in the polymer particle dispersion and the average particle size of the polymer particles obtained in the step (c) is 15% or less.

[0049]

[21] The method according to any one of

[16] to

[10] , wherein the dispersion medium is an aqueous solvent.

[0050]

[22] The method according to

[21] , wherein the step (b) is a step of volatilizing the aqueous solvent to obtain a molded body.

[0051]

[23] The method according to

[22] , wherein the step (b) includes a step of annealing the molded body.

[0052]

[24] The method according to any one of

[21] to

[23] , wherein the polymer microparticle dispersion further contains a functionalizing agent.

[0053]

[25] The method according to

[24] , further comprising, after the step (c), a step (d) of separating the polymer microparticles from the functionalizing agent.

[0054]

[26] The method according to any one of

[16] to

[20] , wherein the dispersion medium is air.

[0055]

[27] The method according to

[26] , wherein the step (b) is a step of hot-pressing the polymer microparticle dispersion to obtain a molded body.

[0056] Effects of the Invention

[0057] According to the present invention, polymer particles can be produced from a polymer particle molded body by a simple operation. The polymer particles produced from the polymer particle molded body can be reused. According to the present invention, a polymer particle molded body that can be decomposed by a simple operation can be provided. Furthermore, according to the present invention, a method for recycling polymer particles that can be applied to a variety of polymers can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is an AFM image of the polymer fine particles of Production Example 5 (unused polymer fine particles) and the decomposed polymer fine particles of Example 10, and a histogram of the particle size (Krumbin particle size) (nm) of each polymer fine particle.

[0059] Figure 2 These are stress-strain curves of the polymer fine particle membrane MA-E (cycle 0) and the polymer fine particle membrane MA-E (cycle 1) produced in Example 10.

[0060] Figure 3 3 and 4 are stress-strain curves of the blue polymer fine particle film MA-E (cycle 0) and the polymer fine particle film MA-E (cycle 1) produced in Example 16. DETAILED DESCRIPTION

[0061] The present invention is described in detail below. As one embodiment of the present invention, a method for producing polymer particles from a molded body of polymer particles (hereinafter sometimes referred to as a molded body) is included. In addition, as another embodiment, a molded body of polymer particles is included. In addition, as another embodiment, a method for recycling polymer particles is included. These are described below.

[0062] 〈Polymer Microparticles〉

[0063] First, the polymer microparticles used in the present invention will be described.

[0064] The type of polymer constituting the polymer particles of the molded body constituting the polymer particles used in the present invention (hereinafter sometimes referred to as polymer particles) is not particularly limited. The polymer constituting the polymer particles may be one kind or two or more kinds. As polymers, natural resins and synthetic polymers may be listed. As natural resins, casein, gelatin and starch may be listed. As synthetic polymers, for example, acrylic resins, polyolefin resins, polystyrene resins, polyester resins, polyamide resins, polyimide resins, novolac resins, polyurethane resins, polycarbonate resins, cellulose resins, polyalkylene glycols, polysiloxanes, polyrotaxanes and derivatives of these resins may be listed.

[0065] Each polymer constituting the polymer microparticles may be a homopolymer formed from one monomer or a copolymer formed from a plurality of monomers. In the case of a copolymer, it may be a block copolymer or a random copolymer.

[0066] The weight average molecular weight of the polymer constituting the polymer microparticles is not limited, and the lower limit can be generally set to 10,000 or more, 50,000 or more, or 80,000 or more, and the upper limit can be generally set to 5,000,000 or less, 4,000,000 or less, or 3,000,000 or less. In this specification, the weight average molecular weight refers to the standard polystyrene conversion value measured by gel permeation chromatography (GPC).

[0067] The average particle size of the polymer microparticles used in the present invention is not particularly limited, but is preferably 50 nm to 5 μm, more preferably 60 nm to 1500 nm, and even more preferably 70 nm to 1200 nm.

[0068] In the present application, the average particle size of polymer microparticles refers to the average value of the values ​​obtained by analyzing the particle width when the particle height (maximum value - minimum value) of the polymer microparticles reaches half of the particle height (maximum value - minimum value) of the polymer microparticles using image analysis software based on the image obtained using an atomic force microscope, and selecting 100 arbitrary polymer microparticles.

[0069] The polymer microparticles used in the present invention may not have a hierarchical structure, or may have a hierarchical structure such as a core-shell structure.

[0070] The shape of the polymer microparticles used in the present invention is not particularly limited, and may be spherical, ellipsoidal or rod-shaped. The polymer microparticles may be hollow.

[0071] The polymer particles used in the present invention may or may not contain a solvent. Examples of the solvent contained in the polymer particles include solvents used in producing polymer particles and dispersion media used in producing polymer particle molded bodies, and specific examples include water.

[0072] In one embodiment, the polymer constituting the polymer microparticles is a (meth)acrylic acid polymer or poly(meth)acrylamide. These polymers may or may not have a cross-linked structure.

[0073] The (meth)acrylic acid ester used for producing the (meth)acrylic acid polymer is not particularly limited, and specific examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, and (meth)acrylic acid. Straight chain alkyl or branched chain alkyl (meth)acrylates such as stearyl acetate, cyclohexyl (meth)acrylate, dicyclohexyl (meth)acrylate and isobornyl (meth)acrylate and other cyclic alkyl (meth)acrylates, hydroxyl-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate and 2-hydroxybutyl (meth)acrylate, 2-(2-methoxyethoxy)ethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, butoxydiethylene glycol (meth)acrylate, methoxy Polyalkylene glycol (meth)acrylates such as dipropylene glycol (meth)acrylate, methoxytripropylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, poly(ethylene glycol-tetramethylene glycol) (meth)acrylate, poly(propylene glycol-tetramethylene glycol) (meth)acrylate, polyethylene glycol-polypropylene glycol (meth)acrylate; (meth)acrylates containing aromatic groups such as benzyl (meth)acrylate and 9-anthracene (meth)acrylate; (meth)acrylates containing amino groups such as acrylates, N,N-dimethylaminoethyl (meth)acrylate and N,N-diethylaminoethyl (meth)acrylate; (meth)acrylate alkoxyethyls such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate and 2-cyclohexyloxyethyl (meth)acrylate; (meth)acrylate aryloxyethyls such as phenoxyethyl (meth)acrylate; tetrahydrofurfuryl (meth)acrylate, 2-morpholinylethyl (meth)acrylate, etc. Among them, from the aspect of easy decomposition, linear alkyl or branched alkyl (meth)acrylate, polyalkylene glycol (meth)acrylate and alkoxyethyl (meth)acrylate are preferred, and linear alkyl or branched alkyl (meth)acrylate having 1 to 4 carbon atoms in the alkyl group, polyalkylene glycol (meth)acrylate containing diethylene glycol units and alkoxyethyl (meth)acrylate having 1 to 3 carbon atoms in the alkoxy group are more preferred, and methyl (meth)acrylate, 2-(2-methoxyethoxy)ethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, 2-methoxyethyl (meth)acrylate and 2-ethoxyethyl (meth)acrylate are further preferred. The (meth)acrylate may be used alone or in combination of two or more in any ratio and combination.

[0074] In one embodiment, the (meth)acrylic acid polymer is a homopolymer or copolymer of (meth)acrylate. The (meth)acrylic acid polymer can be a copolymer of (meth)acrylate and other monomers. Other monomers are not particularly limited, and specific examples thereof include (meth)acrylamide, (meth)acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, acrylonitrile, styrene, p-methylstyrene, α-methylstyrene, vinyl acetate, vinyl chloride, and rotaxanes having one polymerizable unsaturated group. Other monomers can be used alone or in any ratio and combination.

[0075] The (meth)acrylamide used to produce the poly(meth)acrylamide is not particularly limited, and specific examples thereof include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-tert-butyl(meth)acrylamide, and N-benzylacryloyl(meth)acrylamide, etc. (Meth)acrylamide may be used alone or in combination of two or more in any ratio and combination.

[0076] (Method for producing polymer microparticles from monomers)

[0077] The method for producing the aforementioned polymer particles from monomers is not particularly limited, and polymer particles capable of producing the polymer particle molded body used in the present invention can be appropriately produced. As one mode, polymer particles can be produced by polymerizing the constituent components of the polymer constituting the polymer particles, i.e., monomers, into particles by conventional methods and purifying them as needed. As a specific mode, polymer particles can be produced in the form of a polymer particle dispersion. The following is an explanation of the polymer particle dispersion.

[0078] The polymer microparticle dispersion comprises polymer microparticles and a dispersion medium. The polymer microparticles used here are the same as those described above.

[0079] Examples of the dispersion medium include solvents and air. When the dispersion medium is a solvent, the polymer microparticle dispersion is provided in the form of a dispersion liquid. When the dispersion medium is air, the polymer microparticle dispersion is provided in the form of a powder.

[0080] In one embodiment, the dispersion medium is an aqueous solvent. In the present application, an aqueous solvent refers to a solvent in which the content of water exceeds 50% by volume. The content of water in the dispersion medium can be set to more than 80% by volume, more than 90% by volume, more than 95% by volume, more than 99% by volume or 100% by volume. The aqueous solvent can include water and a water-miscible organic solvent. As a water-miscible organic solvent, for example, methanol, ethanol, propanol, N,N-dimethylformamide (DMF) and acetone can be listed. The aqueous solvent is preferably water. As water, distilled water, deionized water and pure water etc. can be used.

[0081] In the present embodiment, the polymer microparticle dispersion is provided in the form of an aqueous solvent dispersion of polymer microparticles. The content of the polymer microparticles in the aqueous solvent dispersion is preferably 1% to 50% by mass, more preferably 3% to 40% by mass. If it is within the above range, the dispersion stability of the polymer microparticles in the aqueous solvent dispersion is good.

[0082] The aqueous solvent dispersion of polymer particles may contain a functionalizing agent. The functionalizing agent is not particularly limited as long as it imparts a specific function to the molded body and can be dissolved or dispersed in an aqueous solvent. Specific examples thereof include pigments, dyes, organic fillers, and inorganic fillers. The size of the functionalizing agent that can be dispersed is usually 1 nm to 1 mm. The functionalizing agent may be used alone or in any ratio and combination of two or more.

[0083] Examples of the pigment include inorganic pigments and organic pigments.

[0084] Examples of the inorganic filler include silica fillers and carbon black.

[0085] The content of the functionalizing agent in the aqueous solvent dispersion of the polymer microparticles is preferably 0.01% to 20% by mass, more preferably 0.01% to 5% by mass. Within the above range, the dispersion stability of the functionalizing agent in the aqueous solvent is good.

[0086] The amount of the functionalizing agent used is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and further preferably 30 parts by mass or less, based on 100 parts by mass of the polymer microparticles. When it is 50 parts by mass or less, the moldability of the polymer microparticles is good.

[0087] The aqueous solvent dispersion of polymer microparticles may contain additives such as a fusing agent, a softening agent, and an interparticle crosslinking agent as optional components. The use of at least one selected from the group consisting of a fusing agent, a softening agent, and an interparticle crosslinking agent can improve the moldability of the polymer microparticles.

[0088] The aqueous solvent dispersion of polymer microparticles may contain unreacted monomers and polymers that have not been incorporated into polymer microparticles, as well as a surfactant and a polymerization initiator that are optionally used in the method for producing a polymer microparticle dispersion described below.

[0089] In one embodiment, the dispersion medium is air. In this embodiment, the polymer microparticle dispersion is provided in the form of polymer microparticle powder.

[0090] (Method for producing polymer microparticle dispersion from monomers)

[0091] The method for producing the polymer microparticle dispersion is not particularly limited, but an example thereof includes a method in which a monomer is polymerized in an aqueous solvent to obtain an aqueous solvent dispersion of polymer microparticles, and a purification operation is performed as necessary to obtain a polymer microparticle dispersion.

[0092] Examples of the polymerization method include emulsion polymerization, soap-free emulsion polymerization, suspension polymerization, dispersion polymerization, microemulsion polymerization, miniemulsion polymerization, and microsuspension polymerization. From the viewpoint of easy control of the size of polymer particles, emulsion polymerization and soap-free emulsion polymerization are preferred.

[0093] When the monomers are polymerized, at least one selected from the group consisting of a surfactant, a polymerization initiator, a crosslinking agent and an inorganic salt may be used as necessary.

[0094] The surfactant is not particularly limited, and examples thereof include anionic surfactants, cationic surfactants, nonionic surfactants, and two-sided surfactants.

[0095] Examples of the anionic surfactant include sodium oleate, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium alkyl sulfonates, sodium polyoxyethylene alkyl ether sulfates, and their corresponding potassium salts, calcium salts, alkylnaphthalenesulfonates, and alkyl phosphates.

[0096] Examples of the cationic surfactant include alkylamine salts such as laurylamine acetate and stearylamine acetate, and quaternary ammonium salts such as lauryltrimethylammonium chloride.

[0097] Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylamines, and glycerol fatty acid esters.

[0098] Examples of the amphoteric surfactant include lauryl dimethyl amine oxide and the like.

[0099] The surfactant can be appropriately selected according to the type of monomer used, the polymerization method, etc. When the (meth)acrylic acid polymer or poly(meth)acrylamide is produced by emulsion polymerization, the surfactant is preferably an anionic surfactant, and more preferably sodium dodecylbenzenesulfonate.

[0100] The surfactant may be used alone or in combination of two or more in any ratio and combination.

[0101] The amount of the surfactant used is preferably 0.0001 to 10 parts by mass, more preferably 0.001 to 8 parts by mass, and even more preferably 0.01 to 5 parts by mass relative to 100 parts by mass of the monomer. Within the above range, the size of the obtained polymer microparticles is appropriate.

[0102] When a radical polymerizable monomer is used, a polymerization initiator is preferably used. The polymerization initiator is not particularly limited, and examples thereof include persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate; organic peroxides such as benzoyl peroxide, lauroyl peroxide, o-chlorobenzoyl peroxide, o-methoxybenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, tert-butyl peroxy-2-ethylhexanoate, di-tert-butyl peroxide, isopropylbenzene hydroperoxide, and tert-butyl hydroperoxide; and azo compounds such as 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis(2-methylpropionamidine), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine], 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], and 4,4'-azobis(4-cyanovaleric acid). Among them, persulfate is preferred, and potassium persulfate is more preferred. The polymerization initiator may be used alone or in combination of two or more in any ratio and combination.

[0103] The amount of the polymerization initiator used is preferably 0.05 to 15 parts by mass, more preferably 0.5 to 12 parts by mass or more, based on 100 parts by mass of the monomer.

[0104] As long as the cross-linking agent is a compound having more than two reactive functional groups for the monomer, there is no particular limitation. In the case of using a free radical polymerizable monomer, as a cross-linking agent, for example, ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, nonanediol di(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-cyclohexanediol di(meth)acrylate and dicyclopentenyloxyethyl (meth)acrylate can be listed. Among them, ethylene glycol di(meth)acrylate and 1,6-hexanediol di(meth)acrylate are preferred. As a cross-linking agent, a rotaxane having more than two polymerizable unsaturated groups can also be listed. Rotaxane is composed of a cyclic molecule, a linear molecule encapsulated by a cyclic molecule in a punctured shape, and a bulky terminal group for preventing the cyclic molecule from being separated from the linear molecule. At least one of the cyclic molecule and the linear molecule may have more than two polymerizable unsaturated groups, and preferably both the cyclic molecule and the linear molecule have polymerizable unsaturated groups. Rotaxanes having more than two polymerizable unsaturated groups can be obtained by, for example, reacting a compound having a functional group and a polymerizable unsaturated group that are reactive for the functional group possessed by the rotaxane with the rotaxane. For example, when the functional group possessed by the rotaxane is a hydroxyl group, a compound having an isocyanate group and a polymerizable unsaturated group, such as (methyl) 2-isocyanatoethyl acrylate, can be used. As polymerizable unsaturated groups, vinyl and (methyl) acryloyl groups can be listed. As a rotaxane having a hydroxyl group, SH2400P and SH1300P (ASM Company) can be used.

[0105] The cross-linking agent may be used alone or in combination of two or more kinds in any ratio and combination.

[0106] The amount of the cross-linking agent used is preferably 0.001 to 50 parts by mass, more preferably 0.001 to 25 parts by mass, based on 100 parts by mass of the monomer.

[0107] Inorganic salts are used for the purpose of regulating the separation (dispersion) stability of the emulsion and the polymer particles. As specific examples of inorganic salts, sodium chloride, sodium bromide, sodium iodide, sodium carbonate, sodium sulfate, sodium thiosulfate, sodium dihydrogen phosphate, sodium nitrate, sodium perchlorate, sodium thiocyanate, potassium chloride, potassium bromide, potassium iodide, potassium carbonate, potassium sulfate, potassium thiosulfate, potassium dihydrogen phosphate, potassium nitrate, potassium perchlorate, potassium thiocyanate and magnesium sulfate can be listed. Inorganic salts can be used alone or in any ratio and combination.

[0108] The amount of the inorganic salt is preferably 0.0001 to 10 parts by mass, more preferably 0.01 to 5 parts by mass relative to 100 parts by mass of the monomer. If the amount of the inorganic salt is 0.0001 parts by mass or more, it is easy to adjust the separation (dispersion) stability derived from the inorganic salt. If the amount of the inorganic salt is 10 parts by mass or less, the polymer particles will not aggregate, and the size of the resulting polymer particles is appropriate.

[0109] The temperature and time of the polymerization reaction can be appropriately selected according to the monomers used, the polymerization method, the polymerization initiator, etc. For example, when at least one selected from the group consisting of (meth)acrylates, (meth)acrylamide, and (meth)acrylamide derivatives is used as a monomer, the reaction temperature and time when emulsion polymerization or soap-free emulsion polymerization is preferably in the range of 25 to 90° C. and 5 to 36 hours, and more preferably in the range of 60 to 80° C. and 10 to 24 hours.

[0110] In an embodiment where the dispersion medium is an aqueous solvent, the aqueous solvent dispersion of polymer microparticles obtained by the polymerization reaction can be directly molded to produce a molded body. From the viewpoint of improving the quality of the molded body, it is preferred to perform purification operations such as centrifugation, filtration and dialysis, and then redisperse the polymer microparticles in an aqueous solvent as needed to obtain a polymer microparticle dispersion (aqueous solvent dispersion of polymer microparticles).

[0111] In the embodiment where the dispersion medium is an aqueous solvent, optional components such as a functionalizing agent and additives may be added to the aqueous solvent dispersion of the polymer microparticles as necessary.

[0112] In the embodiment where the dispersion medium is air, the polymer microparticle dispersion obtained by the polymerization reaction is purified by purification operations such as centrifugation and dialysis as needed, and then the solvent is removed to obtain a polymer microparticle dispersion (powder of polymer microparticles). The method for removing the solvent is not particularly limited, and freeze drying can be cited.

[0113] (Method for producing a molded product of polymer microparticles)

[0114] The polymer microparticle molded article can be produced using, for example, the above-mentioned polymer microparticle dispersion.

[0115] As a method for producing a molded body using a dispersion of polymer particles, for example, a method of volatilizing a solvent as a dispersion medium can be cited. Specifically, a dispersion of polymer particles is applied or sprayed on a substrate, or is placed in a mold frame, and then the solvent is volatilized, thereby obtaining a molded body of polymer particles. The method of volatilizing the solvent is not particularly limited, and specifically, a method of volatilizing the solvent under atmospheric pressure or reduced pressure by heating as needed can be cited.

[0116] Examples of methods for producing a molded body using a powder of polymer particles include a method of hot pressing the powder of polymer particles. Specifically, the powder of polymer particles is placed in a mold frame and heated and pressed to obtain a molded body.

[0117] The temperature during hot pressing can be appropriately set within a range that exceeds the glass transition temperature (Tg) of the polymer constituting the polymer microparticles and does not melt the polymer microparticles. For example, when the polymer microparticles are polymethyl methacrylate, the temperature during hot pressing is preferably 100 to 200°C, more preferably 100 to 150°C.

[0118] The pressure during hot pressing can be appropriately set within a range that does not damage the polymer microparticles. The pressure during hot pressing is, for example, 0.2 to 100 MPa or 0.3 to 50 MPa.

[0119] The obtained polymer microparticle molded body may be further annealed. The polymer microparticle molded body may be annealed to increase the 0102 degree of the polymer chains between the polymer microparticles, that is, to increase the interface thickness.

[0120] The temperature and time of annealing are not particularly limited and can be appropriately set according to the type of polymer constituting the polymer microparticles and the glass transition temperature (Tg), etc. For example, when the polymer constituting the polymer microparticles is polymethyl acrylate, the preferred temperature is 25 to 200°C, when the polymer constituting the polymer microparticles is polymethyl methacrylate, the preferred temperature is 100 to 200°C, and when the polymer constituting the polymer microparticles is poly(N-isopropylacrylamide), the preferred temperature is 33 to 200°C. The annealing time also varies depending on the temperature, but is generally 1 to 200 hours.

[0121] [Polymer microparticle molded body]

[0122] The polymer microparticle molded body of one embodiment, that is, the polymer microparticle molded body formed by molding polymer microparticles is a polymer microparticle molded body in which 80 mol% or more of the monomers constituting the polymer are at least one monomer selected from the group consisting of polyalkylene glycol (meth) acrylate, methacrylate containing an alkoxy group, acrylate containing an alkoxy group having 2 or more carbon atoms, (meth) acrylamide, and their derivatives (hereinafter, they are also referred to as polymer microparticle molded bodies composed of specific monomers). At least one monomer selected from the group consisting of polyalkylene glycol (meth) acrylate, methacrylate containing an alkoxy group, acrylate containing an alkoxy group having 2 or more carbon atoms, (meth) acrylamide, and their derivatives preferably accounts for 90 mol% or more of the monomers constituting the polymer, more preferably 95 mol% or more, and further preferably 99 mol% or more. 100 mol% of the monomers constituting the polymer can be at least one monomer selected from the group consisting of polyalkylene glycol (meth) acrylate, methacrylate containing an alkoxy group, acrylate containing an alkoxy group having 2 or more carbon atoms, (meth) acrylamide, and their derivatives.

[0123] In one embodiment, the polymer microparticle molded body composed of a specific monomer is a molded body in which polymer microparticles are bound to each other by mutual entanglement of polymer chains between polymer microparticles. Based on this characteristic, the molded body has the characteristics of the polymer itself, such as toughness.

[0124] The polymer microparticle molded body composed of specific monomers is a novel molded body that can easily produce polymer microparticles by applying the method for producing polymer microparticles from the polymer microparticle molded body of the present invention. They are preferred in that polymers obtained by polymerizing each monomer by a known general method can be easily decomposed, recovered, and reused in the form of polymer microparticles.

[0125] As examples of derivatives of the above-mentioned monomers, compounds in which the above-mentioned monomers are substituted with one or more substituents can be listed as long as they do not violate the main purpose of the present invention. Examples of substituents in this case are not limited, and include hydroxyl, thiol, carboxyl, nitro, cyano; halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms; alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, pentyl, isopentyl, neopentyl, hexyl, heptyl, octyl, decyl, and nonyl; alkenyl groups such as vinyl, propenyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, and octenyl; alkynyl groups such as propargyl; cyclopropyl, cyclobutyl, cyclopentyl, and cyclopentyl; Cycloalkyl groups such as pentyl, cyclohexyl, cycloheptyl, bicyclooctyl, and spirooctyl; alkoxy groups such as methoxy, ethoxy, propoxy, butoxy, sec-butoxy, and tert-butoxy; aryl groups such as phenyl, benzyl, tolyl, naphthyl, and anthracenyl; aryloxy groups such as phenoxy, benzyloxy, and naphthyloxy; acyl groups such as acetyl, propionyl, benzoyl, p-methoxybenzoyl, and cinnamoyl; unsubstituted amino groups, and substituted amino groups such as dimethylamino, benzylamino, and triphenylmethylamino; furyl, thienyl, pyranyl, pyrrolinyl, pyrrolyl, 2,3-dihydro-1H-pyrrolyl, piperidinyl, piperazinyl, homopiperazinyl, morpholinyl, thiomorpholinyl, 1,2,4,6-tetrahydropyridinyl, hexahydropyrimidinyl, hexahydropyridazinyl, 1,2,4,6-tetrahydropyridinyl, 1,2,4,6-tetrahydropyridinyl, 3,4-dihydropyridinyl, imidazolyl, 4,5-dihydro-1H-imidazolyl, 2,3-dihydro-1H-imidazolyl, pyrazolyl, 4,5-dihydro-1H-pyrazolyl, 2,3-dihydro-1H-pyrazolyl, Heterocyclic groups such as oxazolyl, 4,5-dihydro-1,3-oxazolyl, 2,3-dihydro-1,3-oxazolyl, 2,5-dihydro-1,3-oxazolyl, thiazolyl, 4,5-dihydro-1,3-thiazolyl, 2,3-dihydro-1,3-thiazolyl, 2,5-dihydro-1,3-thiazolyl, and carbazolyl; heterocyclic oxy groups such as furanyloxy, pyrrolyloxy, indolyloxy, and quinolyloxy; groups obtained by replacing the above groups with one or more substituents (for example, halogen groups); and the like.

[0126] Specific examples of the polyalkylene glycol (meth)acrylate include ethoxydiethylene glycol (meth)acrylate, butoxydiethylene glycol (meth)acrylate, methoxydipropylene glycol (meth)acrylate, methoxytripropylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, poly(ethylene glycol-tetramethylene glycol) (meth)acrylate, poly(propylene glycol-tetramethylene glycol) (meth)acrylate, and polyethylene glycol-polypropylene glycol (meth)acrylate.

[0127] Specific examples of the methacrylate containing an alkoxy group include 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, 2-propoxyethyl methacrylate, and 2-cyclohexyloxyethyl methacrylate.

[0128] Specific examples of the acrylic acid ester containing an alkoxy group having 2 or more carbon atoms include 2-ethoxyethyl acrylate, 2-propoxyethyl acrylate, and 2-cyclohexyloxyethyl acrylate.

[0129] Specific examples of (meth)acrylamide and its derivatives include (meth)acrylamide, N-substituted (meth)acrylamide, and N,N-disubstituted (meth)acrylamide. Specific examples of substituents of (meth)acrylamide derivatives include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, and tert-butyl; cyclic alkyl groups such as cyclopropyl; aryl groups such as phenyl; benzyl, etc. In N,N-disubstituted (meth)acrylamide, the substituents may be combined to form a ring structure. Specific examples of (meth)acrylamide derivatives include N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N-n-propyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-tert-butyl (meth)acrylamide, N-cyclopropyl (meth)acrylamide, acryloyl morpholine, and N-benzylacryloyl (meth)acrylamide.

[0130] Among them, polyalkylene glycol (meth)acrylates containing diethylene glycol units, alkoxyethyl methacrylates having 1 to 3 carbon atoms in the alkoxy group, alkoxyethyl acrylates having 2 to 3 carbon atoms in the alkoxy group, and N-substituted (meth)acrylamide are preferred, and 2-(2-methoxyethoxy)ethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, 2-methoxyethyl methacrylate, 2-ethoxyethyl (meth)acrylate, and N-isopropyl (meth)acrylamide are more preferred, since the glass transition temperature (Tg) of the obtained polymer is appropriate and molding and decomposition are easy.

[0131] As other monomers constituting the polymer, for example, linear alkyl or branched alkyl (meth) acrylate, (meth) cyclic alkyl ester, methoxy-containing acrylate, hydroxy-containing (meth) acrylate, aromatic group-containing (meth) acrylate, amino-containing (meth) acrylate, (meth) aryloxyethyl (meth) acrylate, (meth) acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, acrylonitrile, styrene, p-methylstyrene, α-methylstyrene, vinyl acetate, vinyl chloride, and a rotaxane having one polymerizable unsaturated group can be cited. Among them, linear alkyl or branched alkyl (meth) acrylate and methoxy-containing acrylate are preferred, and linear alkyl or branched alkyl (meth) acrylate having 1 to 4 carbon atoms in the alkyl group and methoxyethyl acrylate are more preferred, and methyl (meth) acrylate and methoxyethyl acrylate are further preferred. In one embodiment, the monomer constituting the polymer does not include a rotaxane having one polymerizable unsaturated group.

[0132] The polymer constituting the polymer microparticles composed of a specific monomer may or may not have a cross-linked structure. The cross-linking agent that imparts a cross-linked structure to the polymer is not particularly limited as long as it is a compound having two or more functional groups that are reactive with respect to the monomer constituting the polymer. As a cross-linking agent, for example, ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, nonanediol di(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-cyclohexanediol di(meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate, etc., can be cited. Among them, ethylene glycol di(meth)acrylate and 1,6-hexanediol di(meth)acrylate are preferred. As a cross-linking agent, a rotaxane having two or more polymerizable unsaturated groups can also be cited. Examples of the polymerizable unsaturated group include a vinyl group and a (meth)acryloyl group.

[0133] In one embodiment, the polymer microparticle molded body composed of the specific monomer does not include a structure derived from rotaxane. Not including a structure derived from rotaxane is advantageous in terms of production cost and is preferred from this viewpoint.

[0134] The shape of the polymer microparticle molded body composed of a specific monomer is not particularly limited. The polymer microparticle molded body may be a coating film formed on a substrate, or may be a self-supporting molded body such as a self-supporting film. In addition, by using an appropriate mold frame, a molded body of any shape can be obtained. In the case of manufacturing a sheet-like molded body, the thickness thereof is usually 10 nm to 1 cm.

[0135] The polymer microparticle molded body composed of the specific monomer may contain a functionalizing agent. The functionalizing agent is the same as the functionalizing agent contained in the aforementioned polymer microparticle dispersion. When the polymer microparticle molded body used in the present invention is produced using a polymer microparticle dispersion containing a functionalizing agent, the function of the functionalizing agent is usually imparted to the aforementioned molded body.

[0136] The content of the functionalizing agent in the molded article is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less, based on 100 parts by mass of the polymer fine particles.

[0137] In one embodiment, the polymer microparticle molded body composed of a specific monomer is a molded body obtained by bonding polymer microparticles to each other through the mutual entanglement of polymer chains between polymer microparticles. In this case, at the interface between polymer microparticles, polymer chains invade each other, so the interface has a certain degree of thickness (interface thickness). In the present embodiment, the thickness of the interface between polymer microparticles is, for example, 2.5 to 5.0 nm, 2.8 to 4.8 nm, or 3.0 to 4.5 nm. Although not bound by any theory, near the surface of the polymer microparticles, the density of polymer chains is low compared to the center of the microparticles, and the polymer chains are easy to move. Therefore, during the molding process, the polymer microparticles are bonded to each other by the mutual entanglement of polymer chains respectively existing on the surfaces of adjacent polymer microparticles to form a molded body. As a means of promoting the mutual entanglement of polymer chains, it can be listed as: annealing the molded body; and adding a small amount of organic solvent to the aqueous solvent dispersion of polymer microparticles, that is, not dissolving the polymer microparticles to this extent. It can be considered that: by these means, the polymer chains on the surface of the polymer microparticles can be easily moved. As an organic solvent, it is preferred to use an organic solvent with high affinity for the polymer constituting the polymer microparticles. Preferred examples of organic solvents include N,N-dimethylformamide.

[0138] [Method for producing polymer microparticles from a molded product of polymer microparticles]

[0139] A method for producing polymer microparticles according to one embodiment includes: applying an external stimulus to a molded body of polymer microparticles, thereby decomposing the molded body into polymer microparticles. The molded body of polymer microparticles can be produced by the same method as the method for producing the molded body of polymer microparticles described above. It should be noted that the molded body that can be used in the method for producing polymer microparticles from the molded body of polymer microparticles is not limited to the aforementioned polymer microparticle molded body composed of a specific monomer. In the molded body of polymer microparticles, the granularity of the polymer microparticles as a raw material is not completely lost. Therefore, by applying an external stimulus, the molded body can be decomposed into polymer microparticles.

[0140] As a method of applying an external stimulus to a molded body of polymer particles, for example, a method of using a solvent to swell the polymer particles constituting the molded body can be cited. Although not bound by any theory, in a molded body of polymer particles, the polymer particles are bound to each other by the mutual entanglement of polymer chains on their surfaces while maintaining a certain degree of granularity. If a solvent is added to the molded body of polymer particles as an external stimulus, the solvent enters between the mutually entangled polymer chains, and the mutual entanglement of the polymer chains is loosened. As a result, the molded body is decomposed into polymer particles.

[0141] The solvent is not particularly limited as long as it is a solvent that can swell the polymer particles constituting the molded body. As examples, water, aqueous solvents and organic solvents can be cited. Among them, it is preferred to use a solvent with high affinity for the polymer constituting the polymer particles. The solvent can be used alone or in any ratio and combination. Two or more solvents can be used in combination.

[0142] Specifically, the solvent can be selected based on, for example, the chemical structure and Hansen solubility parameter of the polymer constituting the polymer microparticles.

[0143] The Hansen Solubility Parameter (HSP value) is a parameter that represents the solubility parameter (SP value) proposed by Hildebrand in three components: dispersion term (δD), polar term (δP), and hydrogen bonding term (δH) in three-dimensional space. The Hansen Solubility Parameter (HSP value) represents solubility using a three-dimensional vector. Generally speaking, substances with similar vectors have high solubility. The distance Ra between the HSP value of a polymer and the HSP value of a solvent is calculated using the following formula.

[0144] Ra=(4(δ D2 -δ D1 ) 2 +(δ P2 -δ P1 ) 2 +(δ H2 -δ H1 ) 2 ) 1 / 2

[0145] δ D1 : Dispersion term of solvent, δ D2 : Dispersion term of polymer, δ P1 : The polarity term of the solvent, δ P2 : Polar term of polymer, δ H2 : Hydrogen bonding term of solvent, δ H1 : Hydrogen bonding term of polymer

[0146] A small distance Ra indicates similar interactions between molecules, and serves as an indicator of the ease of swelling of the polymer. The HSP value can be obtained, for example, by whether it is dissolved or swollen relative to a solvent with a known HSP value. The HSP value can also be calculated based on the structural formula, for example, using software (HSPiP ver.4.1.07).

[0147] Examples of the solvent include N,N-dimethylformamide, N,N-dimethylacetamide, alcohols having 2 to 6 carbon atoms, ketones having 3 to 5 carbon atoms, aromatic hydrocarbons having 6 to 10 carbon atoms, and compounds of the formula R 1 COOR 2 (Where R 1 is hydrogen or an alkyl group having 1 to 3 carbon atoms, R 2 At least one selected from the group consisting of esters represented by an alkyl group having 1 to 3 carbon atoms.

[0148] Examples of the alcohol having 2 to 6 carbon atoms include ethanol, propanol, butanol, and pentanol.

[0149] Examples of the ketone having 3 to 5 carbon atoms include acetone and methyl ethyl ketone.

[0150] Examples of the aromatic hydrocarbon having 6 to 10 carbon atoms include benzene, toluene, and xylene.

[0151] As the formula R 1 COOR 2 (Where R 1 is hydrogen or an alkyl group having 1 to 3 carbon atoms, R 2 The ester represented by (i) an alkyl group having 1 to 3 carbon atoms includes, for example, methyl acetate, ethyl acetate, propyl acetate, methyl butyrate and ethyl butyrate.

[0152] When the polymer particles are (meth)acrylic acid polymer particles or poly(meth)acrylamide particles, the solvent preferably contains an alcohol selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, an alcohol having 2 to 6 carbon atoms, a ketone having 3 to 5 carbon atoms, an aromatic hydrocarbon having 6 to 10 carbon atoms, and a compound of formula R 1 COOR 2 (Where R 1 is hydrogen or an alkyl group having 1 to 3 carbon atoms, R 2 is an alkyl group having 1 to 3 carbon atoms), more preferably at least one selected from the group consisting of N,N-dimethylformamide, alcohols having 2 to 5 carbon atoms, acetone, methyl ethyl ketone and aromatic hydrocarbons having 6 to 10 carbon atoms, and further preferably at least one selected from the group consisting of N,N-dimethylformamide, alcohols having 2 to 5 carbon atoms, acetone and toluene.

[0153] The solvent comprises a solvent selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, alcohols having 2 to 6 carbon atoms, ketones having 3 to 5 carbon atoms, aromatic hydrocarbons having 6 to 10 carbon atoms, and a hydrocarbon of formula R 1 COOR 2 (Where R 1 is hydrogen or an alkyl group having 1 to 3 carbon atoms, R 2 When the solvent is at least one of the group consisting of esters represented by alkyl having 1 to 3 carbon atoms), the solvent contains a total of, for example, 50 to 100 mass %, 60 to 95 mass %, or 70 to 90 mass %. The solvent may further contain at least one selected from the group consisting of water and other organic solvents.

[0154] [Method for recycling polymer microparticles]

[0155] A method for recycling polymer particles according to one embodiment includes: (A) applying an external stimulus to a first polymer particle molded body obtained by molding first polymer particles, thereby decomposing the first polymer particle molded body into second polymer particles. The second polymer particles obtained in step (A) can be recycled.

[0156] As the first polymer microparticles, the polymer microparticles used in the present invention can be used. Regarding the application of external stimulus to the first polymer microparticle molded body, the same method as the method of applying external stimulus in the method of producing polymer microparticles from the above polymer microparticle molded body can be used.

[0157] The first polymer microparticle molded body can be produced by the same method as the method for producing the aforementioned polymer microparticle molded body. It should be noted that the molded body that can be used by the method of recycling polymer microparticles is not limited to the aforementioned polymer microparticle molded body composed of the specific monomer.

[0158] The average particle size of the first polymer microparticles before molding is preferably 50 nm to 5 μm, more preferably 60 nm to 1500 nm, and even more preferably 70 nm to 1200 nm.

[0159] The rate of change of the average particle size of the first polymer particles before molding and the average particle size of the second polymer particles after decomposition (the difference between the average particle size (nm) of the first polymer particles and the average particle size (nm) of the second polymer particles / the average particle size (nm) of the first polymer particles × 100) (%) is preferably 15% or less, more preferably 10% or less, further preferably 8% or less, and further preferably 5% or less. In the method for recycling polymer particles of one embodiment, since the molding and decomposition of the molded body are performed by reversibly forming and eliminating the mutual entanglement of polymer chains between the polymer particles, the quality of the polymer particles does not substantially change. That is, the second polymer particles have the same properties as the first polymer particles.

[0160] The ratio of the total mass of the second polymer particles obtained after decomposition to the total mass of the first polymer particles used when forming the first polymer particle-molded body is preferably 0.95 or more, more preferably 0.97 or more, and even more preferably 0.99 or more. In the method for recycling polymer particles of one embodiment, since the molding and decomposition of the molded body are performed by reversibly forming and eliminating the mutual entanglement of polymer chains between polymer particles, the quality of the polymer particles does not substantially change, and a high recovery rate can be obtained.

[0161] Furthermore, as described above, when the first polymer microparticle molded body contains the functionalizing agent, the ratio of the total mass of the second polymer microparticles obtained after decomposition to the total mass of the first polymer microparticles used to mold the first polymer microparticle molded body is not particularly limited, but is preferably 0.70 or more. This is because a step of separating the second polymer microparticles from the functionalizing agent may be performed.

[0162] The method for recycling polymer microparticles according to one embodiment further includes: (B) forming the second polymer microparticles obtained in the above step (A) to produce a second polymer microparticle formed body.

[0163] The molding in step (B) can be performed using, for example, a second polymer microparticle dispersion in which second polymer microparticles are dispersed in a dispersion medium. Specifically, the molding can be performed by the same method as the above-mentioned method for producing a molded body of polymer microparticles.

[0164] In the embodiment where the dispersion medium is a solvent, optional components such as a functionalizing agent and additives may be added to the second polymer microparticle dispersion as necessary.

[0165] In the step (A), when the first polymer particle molded body is decomposed into the second polymer particles by swelling the polymer particles with a solvent, a dispersion of the second polymer particles can be obtained. In this case, the dispersion of the obtained second polymer particles can be directly molded to produce the second polymer particle molded body. From the viewpoint of improving the quality of the molded body, it is preferred that the second polymer particles are redispersed in the solvent as needed by performing purification operations such as centrifugation, filtration and dialysis to obtain a second polymer particle dispersion. In an embodiment in which the dispersion medium is air, the dispersion of the second polymer particles obtained by the step (A) is purified by purification operations such as centrifugation and dialysis as needed, and then the solvent is removed to obtain a second polymer particle dispersion. The method for removing the solvent is not particularly limited, and freeze drying can be cited.

[0166] In one embodiment, the second polymer particle molded body is also a molded body in which polymer particles are bonded to each other by entanglement of polymer chains between polymer particles. As described above, the thickness of the interface between polymer particles is, for example, 2.5 to 5.0 nm, 2.8 to 4.8 nm, or 3.0 to 4.5 nm.

[0167] In addition, the step (B) may include a step of annealing the second polymer microparticle molded body.

[0168] The shape of the second polymer microparticle molded body is not particularly limited. The second polymer microparticle molded body may be a coating film formed on a substrate, or may be a self-supporting molded body such as a self-supporting film.

[0169] In one embodiment, the step (B) does not include a step of dissolving or melting the second polymer microparticles.

[0170] The method for recycling polymer microparticles according to one embodiment further comprises: using the second polymer microparticle molded body obtained by the above step (B) as the first polymer microparticle molded body of the above step (A), and performing the above step (A) again. In this way, by repeating steps (A) and (B), the polymer microparticles can be repeatedly used.

[0171] The first polymer microparticle molded body may contain the aforementioned functionalizing agent. In the case where the first polymer microparticle molded body contains a functionalizing agent, the method for recycling the polymer microparticles may further include a step of separating the second polymer microparticles from the functionalizing agent after step (A). The method for separating the second polymer microparticles from the functionalizing agent is not particularly limited, and can be implemented using a known method. As specific examples, centrifugation, filtration, and dialysis can be cited. By implementing the above-mentioned separation step, the second polymer microparticles and the functionalizing agent can be recovered separately and reused separately. In general, it is difficult to separate and recover the polymer from a molded body containing a functionalizing agent, but in the method for recycling polymer microparticles, the molded body retains a certain degree of granularity of the polymer microparticles, and therefore, the polymer microparticles and the functionalizing agent can be separated by simple operations such as centrifugation and dialysis.

[0172] [Closed-loop recycling method for polymer microparticles]

[0173] A more specific embodiment of the method for recycling polymer microparticles of the present invention (sometimes referred to as a "closed-loop recycling method") is described below. However, this embodiment is only an example of the method for recycling polymer microparticles of the present invention, and the method for recycling polymer microparticles of the present invention is not limited to this embodiment in any sense.

[0174] A closed-loop recycling method for a polymer according to one embodiment includes, in sequence: (a) providing a polymer particle dispersion containing polymer particles and a dispersion medium; (b) molding the polymer particle dispersion to obtain a molded body; and (c) adding a solvent to the molded body as an external stimulus, thereby causing the polymer particles constituting the molded body to swell and decomposing the molded body into polymer particles. Generally speaking, the molding of a polymer is carried out in a state where a raw material such as a pellet is dissolved in an appropriate solvent or the raw material is heated and melted. That is, the shape of the raw material does not remain in the molded body. On the other hand, the closed-loop recycling method for a polymer using polymer particles according to the present embodiment includes molding a polymer particle dispersion containing polymer particles to obtain a molded body composed of polymer particles. In the molded body composed of polymer particles, the granularity of the polymer particles as the raw material is not completely lost. Therefore, by the simple operation of adding a solvent as an external stimulus, the molded body can be decomposed into polymer particles and the polymer particles can be reused.

[0175] <(a) Providing a polymer microparticle dispersion comprising polymer microparticles and a dispersion medium>

[0176] This is the same process as the method for producing a polymer microparticle dispersion from the above-mentioned monomers.

[0177] <(b) Step of molding the polymer microparticle dispersion to obtain a molded body>

[0178] This is the same process as the method for producing the aforementioned polymer fine particle shaped body using the aforementioned polymer fine particle dispersion.

[0179] <(c) a step of adding a solvent to the molded body as an external stimulus to cause the polymer microparticles constituting the molded body to swell and decompose the molded body into polymer microparticles>

[0180] This is the same process as the method for producing the polymer microparticles from the polymer microparticle molded body, that is, the same process as the process of decomposing the first polymer microparticle molded body into the second polymer microparticles by applying an external stimulus to the first polymer microparticle molded body.

[0181] <(d) Step of separating polymer microparticles from functionalizing agent>

[0182] In an embodiment in which the polymer particle dispersion (aqueous solvent dispersion of polymer particles) includes a functionalizing agent, after step (c), a step (d) of separating the polymer particles from the functionalizing agent can be further implemented. The method for separating the polymer particles from the functionalizing agent is not particularly limited, and can be implemented using a known method. As a specific example, centrifugation, filtration, and dialysis can be listed. By implementing step (d), the polymer particles and the functionalizing agent can be recovered separately and reused separately. In general, it is difficult to separate and recover the polymer from the molded body containing the functionalizing agent, but in the closed-loop recycling method of the polymer using polymer particles, the molded body retains a certain degree of granularity of the polymer particles, and therefore, the polymer particles and the functionalizing agent can be separated by simple operations such as centrifugation and dialysis.

[0183] Example

[0184] Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0185] (1) Evaluation method

[0186] (Average particle size of polymer microparticles)

[0187] Method for determining the average particle size (nm) of polymer microparticles

[0188] Atomic force microscope: AFM5200S manufactured by Hitachi High-Tech

[0189] Image analysis software: NanoNaviII manufactured by SII Nano Technology (NanoNavi Station, Version: 5.60A)

[0190] The sample preparation method is as follows: 100 μL of the polymer microparticle aqueous dispersion (0.1% by mass) is mixed with 100 μL of ethanol. The mixture (200 μL) is placed on the surface of about 20 mL of water contained in a glass watch glass. After 1 minute, a glass substrate (18 mm in length and 18 mm in width, Matsunami Glass Industries) cleaned with a cleaning agent and deionized water is brought into contact with the surface of the water and then slowly lifted vertically relative to the surface of the water. The glass substrate is dried at room temperature (25°C) to obtain a sample for measurement.

[0191] From the images captured by the atomic force microscope, the particle width of the polymer microparticles when the particle height (maximum value - minimum value) reaches half was analyzed using image analysis software, and 100 arbitrary polymer microparticles were selected and the average of the obtained values ​​was calculated.

[0192] (Polymer Microparticle Shape and Average Krumbin Particle Size)

[0193] Method for determining the shape and Krumbin diameter of polymer microparticles (maximum length in a specified direction of the projected particle image)

[0194] Atomic force microscope: AFM5200S manufactured by Hitachi High-Tech

[0195] Image analysis software: Image J (1.53k, Wayne Rasband, National Institutes of Health)

[0196] 100 arbitrary polymer microparticles are selected, and the average of the obtained values ​​is determined as the average Krumbin particle size. The measurement sample is obtained by the same method as the average particle size of the above polymer microparticles.

[0197] (Average hydrodynamic diameter of polymer particles)

[0198] The average hydrodynamic diameter of the polymer particles (D h ) (nm) was evaluated by DLS measurement using a Zetasizer Nano S (Malvern Instruments).

[0199] Measurement sample preparation method: A 0.01 mass % aqueous dispersion of polymer microparticles was used.

[0200] The data were averaged for 30 measurements using intensity autocorrelation with an acquisition time of 30 seconds. The scattering intensity was detected at a total scattering angle of 173°. The hydrodynamic diameter of the polymer microparticles in water was calculated using the Stokes-Einstein formula. Following the above steps, each sample was evaluated three times, and the average of the obtained hydrodynamic diameters was determined as the average hydrodynamic diameter.

[0201] (Tensile properties)

[0202] Use a test piece punching machine (Kanomoto Keiki Co., Ltd.) to punch out three test pieces (Type 4 dumbbell shape specified in ISO 37) from the polymer microparticle film or polyMA bulk film. Use a digital micrometer (MCD130-25D, Niigata Seiki Co., Ltd.) to measure the thickness of the test piece at three points, and determine the average value as the test piece thickness. For these three test pieces, use a 50N force sensor to perform a tensile test (STB-1225L, A&D Co., Ltd.) to obtain a stress-strain curve. Calculate the breaking strength (MPa) and breaking energy (MJ / m 3 ), and the average value was determined as the breaking strength and breaking energy of the polymer microparticle film or the polyMA bulk film. The tensile test conditions were set at a temperature of 26±0.5°C and a tensile speed of 1000 mm / min. The results are shown in Table 3 and Figure 2 and Figure 3 .

[0203] (2) Raw materials

[0204] The raw materials used in Examples and Comparative Examples are as follows.

[0205] As monomers used in the production of polymer microparticles, methyl acrylate (MA, Fujifilm Wako Pure Chemical Industries, Ltd.), 2-methoxyethyl methacrylate (MEMA, Tokyo Chemical Industry Co., Ltd.), 2-ethoxyethyl methacrylate (EEMA, Tokyo Chemical Industry Co., Ltd.), 2-methoxyethyl acrylate (MEA, Fujifilm Wako Pure Chemical Industries, Ltd.), 2-(2-methoxyethoxy)ethyl methacrylate (MEO2MA, Aldrich Co., Ltd.), ethoxydiethylene glycol acrylate (DEGA, Tokyo Chemical Industry Co., Ltd.), methyl methacrylate (MMA, Fujifilm Wako Pure Chemical Industries, Ltd.) and N-isopropylacrylamide (NIPAm, Fujifilm Wako Pure Chemical Industries, Ltd.) are used.

[0206] [Manufacturing Example 1] Manufacture of polymer microparticle aqueous dispersion MA-A

[0207] 0.11 parts by mass of sodium dodecylbenzenesulfonate (Tokyo Chemical Industry Co., Ltd.) as a surfactant was dissolved in 200 parts by mass of water. The obtained solution and 34.4 parts by mass of methyl acrylate were put into a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer and an inert gas inlet, and heated and stirred at 70°C for 30 minutes under a nitrogen atmosphere. 0.0540 parts by mass of potassium persulfate (Fujifilm Wako Pure Chemical Industries, Ltd.) (2 mM) dissolved in 5 mL of water was added to the solution, heated and stirred at 70°C for 1 day under a nitrogen atmosphere, and cooled to room temperature, thereby obtaining a polymer microparticle aqueous dispersion MA-A.

[0208] [Manufacturing Example 2] Manufacture of polymer microparticle aqueous dispersion MA-B

[0209] 600 parts by mass of water and 51.6 parts by mass of methyl acrylate were placed in a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and an inert gas inlet, and heated and stirred at 70° C. for 30 minutes under a nitrogen atmosphere. 0.0540 parts by mass of potassium persulfate (2 mM) dissolved in 5 mL of water was added to the solution, heated and stirred at 70° C. for 1 day under a nitrogen atmosphere, and cooled to room temperature, thereby obtaining a polymer microparticle aqueous dispersion MA-B.

[0210] [Manufacturing Example 3] Manufacture of polymer microparticle aqueous dispersion MA-C

[0211] 600 parts by mass of water, 51.6 parts by mass of methyl acrylate, 0.15 parts by mass of 1,6-hexanediol dimethacrylate (Fujifilm Wako Pure Chemical Industries, Ltd.) and 0.18 parts by mass of sodium chloride (Fujifilm Wako Pure Chemical Industries, Ltd.) were placed in a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer and an inert gas inlet, and heated and stirred at 70° C. for 30 minutes under a nitrogen atmosphere. 0.1080 parts by mass of potassium persulfate (2 mM) dissolved in 10 mL of water was added to the solution, heated and stirred at 70° C. for 1 day under a nitrogen atmosphere, and cooled to room temperature to obtain a polymer microparticle aqueous dispersion MA-C.

[0212] [Manufacturing Example 4] Manufacture of polymer microparticle aqueous dispersion MA-D

[0213] 1.39 parts by mass of sodium dodecylbenzenesulfonate as a surfactant was dissolved in 200 parts by mass of water. The obtained solution, 34.4 parts by mass of methyl acrylate and 0.1 parts by mass of 1,6-hexanediol dimethacrylate were placed in a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer and an inert gas inlet, and heated and stirred at 70°C for 30 minutes under a nitrogen atmosphere. 0.0540 parts by mass of potassium persulfate (2 mM) dissolved in 5 mL of water was added to the solution, heated and stirred at 70°C for 1 day under a nitrogen atmosphere, and cooled to room temperature, thereby obtaining a polymer microparticle aqueous dispersion MA-D.

[0214] [Production Examples 5 to 8]

[0215] Aqueous polymer particle dispersions (polymer particle dispersions MA-E, F, and G, and polymer particle dispersion MEO2MA, respectively) were obtained by the same method as in Production Example 4 except that the compositions shown in Table 1 were used.

[0216] [Production Examples 9 to 13]

[0217] Polymer microparticle aqueous dispersions (polymer microparticle aqueous dispersions MEMA, EEMA, MEA, DEGA, and NIPAm) were obtained by the same method as in Production Example 3 except that the compositions described in Table 1 were used. These polymer microparticle aqueous dispersions were placed in a mold and dried to produce a polymer microparticle film.

[0218] [Production Example 14]

[0219] A polymer microparticle aqueous dispersion MMA was obtained by the same method as in Production Example 2 except that the composition described in Table 1 was used. The polymer microparticle aqueous dispersion MMA is poured into a mold and dried, thereby producing a polymer microparticle film.

[0220] [Manufacturing Example 15] Preparation of blue pigment dispersion

[0221] In a three-necked flask, 90 parts by mass of an aqueous sodium hydroxide solution (sodium hydroxide concentration: 50 mM) were added, 10 parts by mass of MF-5460Blue (product name) (blue pigment specified in CI: PB-28, Dainichi Seika Industries) were added, and the mixture was shaken to obtain a blue pigment aqueous dispersion. No sediment was observed in the aqueous dispersion.

[0222] [Manufacturing Example 16] Preparation of red pigment dispersion

[0223] 90 parts by mass of sodium hydroxide aqueous solution (sodium hydroxide concentration: 50 mM) were added to a three-necked flask, and 10 parts by mass of MF-5160Brown (product name) (red pigment specified in CI: PR-101, Dainichi Seika Industries Co., Ltd.) were added. Ultrasonic homogenizer (VCX-750, Jiatian Trading Co., Ltd.) was used to treat the mixed solution with ultrasound at 375 W for 10 minutes in an ice bath to obtain a red pigment aqueous dispersion. No sediment was observed in the aqueous dispersion.

[0224] [Example 1] Production and Decomposition of PolyMA Microparticle Molded Body

[0225] (Manufacturing of polymer microparticle membrane MA-A)

[0226] The polymer microparticle aqueous dispersion MA-A obtained in Preparation Example 1 was diluted to 48 mg (polymer microparticles) / cm 2 The resulting mixture was placed in a silicone rubber mold (3.5 cm in length, 3.5 cm in width, 1 mm in depth) and dried in a cryostat (LTI-2100, Tokyo Rikaki Co., Ltd.) at 25°C for 24 hours to obtain a polymer microparticle membrane MA-A.

[0227] (Decomposition of polymer microparticle membrane MA-A)

[0228] In a three-necked flask equipped with a stirrer, 0.5 parts by mass of polymer microparticle membrane MA-A was immersed in 94 parts by mass of N,N-dimethylformamide (Fujifilm Wako Pure Chemical Industries, Ltd.) and stirred at room temperature (25° C.) for 24 hours. Decomposition of the polymer microparticle membrane MA-A was visually confirmed.

[0229] [Examples 2 to 7 and 14] Production and Decomposition of Molded PolyMA Microparticles

[0230] The polymer particle films (polymer particle films MA-A, MA-B, MA-C and MA-G) were produced and decomposed in the same manner as in Example 1, except that the solvents used for decomposition of the polymer particle aqueous dispersion and the polymer particle film were as shown in Table 2. For Examples 2 to 7 and 14, it was visually confirmed that the polymer particle films (polymer particle films MA-A, MA-B, MA-C and MA-G) were decomposed.

[0231] [Example 8] Production and Decomposition of PolyMA Microparticle Molded Body

[0232] (Manufacturing of polymer microparticle membrane MA-D)

[0233] A polymer fine particle membrane MA-D was obtained by the same procedure as in Example 1 except that the polymer fine particle aqueous dispersion MA-D was used instead of the polymer fine particle aqueous dispersion MA-A.

[0234] (Decomposition of polymer microparticle membrane MA-D)

[0235] In a three-necked flask equipped with a stirrer, 0.5 parts by mass of polymer microparticle membrane MA-D was immersed in 84 parts by mass of ethanol (Fujifilm Wako Pure Chemical Industries, Ltd.) 80% by volume aqueous solution, and stirred at room temperature (25°C) for 24 hours to obtain a polyMA microparticle dispersion. The dispersion was concentrated using a rotary evaporator to obtain a polyMA microparticle aqueous dispersion. The obtained polyMA microparticle aqueous dispersion was used to determine the average hydrodynamic diameter of the polyMA microparticles.

[0236] [Example 9] Production and Decomposition of Molded PolyMA Microparticles

[0237] (Manufacturing of polymer microparticle membrane MA-D)

[0238] According to the same procedure as in Example 8, a polymer microparticle membrane MA-D was obtained.

[0239] (Decomposition of polymer microparticle membrane MA-D)

[0240] In a three-necked flask equipped with a stirrer, 0.5 parts by mass of polymer microparticle membrane MA-D was immersed in 94 parts by mass of N,N-dimethylformamide and stirred at room temperature (25°C) for 24 hours to obtain a polyMA microparticle dispersion. The dispersion was purified using a dialysis membrane in deionized water to obtain a polyMA microparticle aqueous dispersion. The obtained polyMA microparticle aqueous dispersion was used to determine the average hydrodynamic diameter of the polyMA microparticles.

[0241] [Example 10] Recycling of polyMA microparticles

[0242] (Production of polymer microparticle membrane MA-E (cycle 0))

[0243] The same procedure as in Example 1 was followed except that the polymer microparticle aqueous dispersion MA-E was used instead of the polymer microparticle aqueous dispersion MA-A to obtain a polymer microparticle membrane MA-E (cycle 0). The tensile properties of the obtained polymer microparticle membrane MA-E (cycle 0) were evaluated. The results are shown in Tables 3 and 4. Figure 2 .

[0244] (Decomposition of polymer microparticle membrane MA-E (cycle 0))

[0245] The polymer microparticle membrane MA-E (cycle 0) was decomposed in the same manner as in Example 1. The obtained polyMA microparticle dispersion was purified using a dialysis membrane in deionized water to obtain a polyMA microparticle aqueous dispersion. The obtained polyMA microparticle aqueous dispersion was used to determine the average particle size of the polyMA microparticles. In addition, the Krumbin particle size of the polyMA microparticles was also measured. The results are shown as the polymer microparticles after decomposition. Figure 1 .

[0246] A portion of the obtained polyMA microparticle aqueous dispersion was purified by centrifugal separation. The mass of the polyMA microparticles contained in the purified dispersion was measured, and the total mass of the polyMA microparticles obtained after decomposition was calculated. Using this total mass, the ratio of the total mass of the polyMA microparticles obtained after decomposition to the total mass of the polyMA microparticles used to produce the polymer microparticle membrane MA-E (cycle 0) was calculated. The results are shown in Table 2.

[0247] (Production of polymer microparticle membrane MA-E (cycle 1))

[0248] A polymer microparticle membrane MA-E (cycle 1) was obtained by the same procedure as in Example 1 except that the polymer microparticle aqueous dispersion obtained by decomposing the polymer microparticle membrane MA-E (cycle 0) was used instead of the polymer microparticle aqueous dispersion MA-A obtained in Production Example 1. The tensile properties of the obtained polymer microparticle membrane MA-E (cycle 1) were evaluated. The results are shown in Tables 3 and 4. Figure 2 .

[0249] [Example 11] Production and Decomposition of PolyMA Microparticle Molded Body

[0250] The polymer microparticle film MA-E was produced and decomposed in the same manner as in Example 1 except that the solvents used for decomposition of the polymer microparticle aqueous dispersion and the polymer microparticle film were set as described in Table 2. The obtained polyMA microparticle dispersion was concentrated using a rotary evaporator to obtain a polyMA microparticle aqueous dispersion. The obtained polyMA microparticle aqueous dispersion was used to determine the average particle size of the polyMA microparticles.

[0251] A portion of the obtained polyMA microparticle aqueous dispersion was purified by centrifugal separation. The mass of the polyMA microparticles contained in the purified dispersion was measured, and the total mass of the polyMA microparticles obtained after decomposition was calculated. Using this total mass, the ratio of the total mass of the polyMA microparticles obtained after decomposition to the total mass of the polyMA microparticles used to produce the polymer microparticle membrane MA-E was calculated. The results are shown in Table 2.

[0252] [Example 12] Production and Decomposition of PolyMA Microparticle Molded Body

[0253] The polymer particle film MA-F was produced and decomposed in the same manner as in Example 1 except that the solvents used for decomposition of the polymer particle aqueous dispersion and the polymer particle film were set as described in Table 2. The obtained polyMA particle dispersion was concentrated using a rotary evaporator to obtain a polyMA particle aqueous dispersion. The average hydrodynamic diameter of the polyMA particles was determined using the obtained polyMA particle aqueous dispersion.

[0254] [Example 13] Production and Decomposition of Molded PolyMA Microparticles

[0255] The polymer microparticle membrane MA-F was produced and decomposed in the same manner as in Example 1 except that the solvents used for decomposition of the polymer microparticle aqueous dispersion and the polymer microparticle membrane were set as described in Table 2. The obtained polyMA microparticle dispersion was purified using a dialysis membrane in deionized water to obtain a polyMA microparticle aqueous dispersion. The average hydrodynamic diameter of the polyMA microparticles was determined using the obtained polyMA microparticle aqueous dispersion.

[0256] [Example 15] Production and Decomposition of Molded PolyMEO2MA Microparticles

[0257] (Manufacturing of polymer microparticle membrane MEO2MA)

[0258] The polymer microparticle aqueous dispersion MEO2MA obtained in Preparation Example 8 was diluted to 48 mg (polymer microparticles) / cm 2 The resulting mixture was placed in a silicone rubber mold (3.5 cm in length, 3.5 cm in width, 1 mm in depth) and dried in a cryostat (LTI-2100, Tokyo Rikki Co., Ltd.) at 25°C for 24 hours to obtain a polymer microparticle membrane MEO2MA.

[0259] (Decomposition of polymer microparticle membrane MEO2MA)

[0260] In a three-necked flask equipped with a stirrer, the polymer microparticle membrane MEO2MA was immersed in deionized water and stirred at 10°C for 24 hours to obtain a polymer microparticle aqueous dispersion MEO2MA. The average Krumbin particle size of the polymer MEO2MA microparticles was determined using the obtained polymer MEO2MA microparticle aqueous dispersion.

[0261] [Example 16] Recycling of polyMA microparticles

[0262] (Production of Blue Polymer Microparticle Membrane MA-E (Cycle 0))

[0263] In a three-necked flask equipped with a stirrer, the polymer microparticle aqueous dispersion MA-E obtained in Preparation Example 5 and the blue pigment aqueous dispersion obtained in Preparation Example 15 were mixed. The resulting mixed solution (MF-5460 Blue: 10% by mass) was stirred at a concentration of 48 mg (polymer microparticles) / cm 2 The obtained blue polymer microparticle film MA-E (cycle 0) was used to evaluate the tensile properties. The results are shown in Tables 3 and 4. Figure 3 .

[0264] (Decomposition of blue polymer microparticle film MA-E (cycle 0))

[0265] In a three-necked flask equipped with a stirrer, 0.5 parts by mass of blue polymer microparticle membrane MA-E (cycle 0) was immersed in 84 parts by mass of 80% by volume ethanol aqueous solution, and stirred at room temperature (25° C.) for 24 hours to obtain a polyMA microparticle dispersion containing a blue pigment. The dispersion was concentrated using a rotary evaporator to obtain a polyMA microparticle aqueous dispersion containing a blue pigment.

[0266] (Separation of polyMA particles and blue pigment)

[0267] The obtained polyMA microparticle aqueous dispersion containing blue pigment was centrifuged and the supernatant was recovered to obtain a polyMA microparticle dispersion. The obtained polyMA microparticle dispersion was used to determine the average hydrodynamic diameter of the polyMA microparticles. On the other hand, the residue was redispersed in deionized water to obtain a blue pigment dispersion.

[0268] A portion of the obtained polyMA microparticle dispersion was used to measure the mass of the polyMA microparticles contained in the dispersion, and the total mass of the polyMA microparticles obtained after decomposition was calculated. Using this total mass, the ratio of the total mass of the polyMA microparticles obtained after decomposition to the total mass of the polyMA microparticles used to produce the blue polymer microparticle film MA-E (cycle 0) was calculated. The results are shown in Table 2.

[0269] (Production of polymer microparticle membrane MA-E (cycle 1))

[0270] The same procedure as in Example 1 was followed except that the polymer fine particle dispersion obtained by separation from the blue pigment was used instead of the polymer fine particle aqueous dispersion MA-A obtained in Production Example 1 to obtain a polymer fine particle film MA-E (cycle 1). The tensile properties of the obtained polymer fine particle film MA-E (cycle 1) were evaluated. The results are shown in Tables 3 and 4. Figure 3 .

[0271] [Example 17] Production and Decomposition of Molded PolyMA Microparticles

[0272] (Manufacturing of Red Polymer Microparticle Film MA-E)

[0273] A red polymer microparticle film MA-E was obtained by the same procedure as in Example 16 except that the red pigment aqueous dispersion obtained in Preparation Example 16 was used instead of the blue pigment aqueous dispersion obtained in Preparation Example 15.

[0274] (Decomposition of red polymer microparticle film MA-E)

[0275] A polyMA fine particle aqueous dispersion containing a red pigment was obtained by following the same procedure as in Example 16 except that the red polymer fine particle membrane MA-E was used instead of the blue polymer fine particle membrane MA-E.

[0276] (Separation of polyMA particles and red pigment)

[0277] The obtained polyMA microparticle aqueous dispersion containing red pigment was centrifuged and the supernatant was recovered to obtain a polyMA microparticle dispersion. The obtained polyMA microparticle dispersion was used to determine the average hydrodynamic diameter of the polyMA microparticles. On the other hand, the residue was redispersed in deionized water to obtain a red pigment dispersion.

[0278] A portion of the obtained polyMA microparticle dispersion was used to measure the mass of the polyMA microparticles contained in the dispersion, and the total mass of the polyMA microparticles obtained after decomposition was calculated. The total mass was used to calculate the ratio of the total mass of the polyMA microparticles obtained after decomposition to the total mass of the polyMA microparticles used to produce the red polymer microparticle film MA-E. The results are shown in Table 2.

[0279] [Example 18] Production of a Molded Body of PolyMMA Microparticles

[0280] (Manufacturing of polymer microparticle membrane MMA)

[0281] The polymer microparticle aqueous dispersion MMA obtained in Preparation Example 14 was freeze-dried to obtain a powder of polymer microparticle MMA. 0.80 g of the obtained powder was put into a mold (a dumbbell shape of Type 4 specified in ISO 37), and hot pressed for 2 hours at 120° C. and 20 MPa (storage pressure) (small hot press HC300-01) to obtain a polymer microparticle film MMA. It can be considered that the obtained polymer microparticle film MMA is a molded body formed without using other materials that bind polymer microparticles to each other, and can be decomposed into poly MMA microparticles by applying external stimulation. More specifically, it can be considered that by adding an appropriate solvent as an external stimulus, the poly MMA microparticles constituting the molded body are swollen, and the molded body can be decomposed into poly MMA microparticles.

[0282] [Reference Example 1]

[0283] (Manufacturing of PolyMA Bulk Film)

[0284] A mixture of 3.44 parts by mass (40 mmol) of methyl acrylate (Fujifilm Wako Pure Chemicals), 0.01 parts by mass (0.04 mmol) of 1,6-hexanediol dimethacrylate, and 0.034 parts by mass of Irgacure (trademark) 500 (Ciba Specialty Chemicals) was injected into a mold made by laminating a release sheet (PET25G, LINTEC) and a glass plate on both sides of a silicone rubber frame. Next, a photopolymerization reaction was performed by irradiating the surface of a glass plate with ultraviolet light for 20 minutes using an ultrahigh pressure UV lamp (USH-250SC2, Ushio). The photopolymer was swelled in dichloromethane and then deswelled in methanol twice, thereby refining the photopolymer. The purified photopolymer was dried at 25°C for 24 hours, and then dried at 25°C for 12 hours under reduced pressure using a freeze dryer (FDU-1200, Tokyo Rika Instruments Co., Ltd.) to obtain a polyMA bulk film. The obtained polyMA bulk film was used to evaluate tensile properties. The results are shown in Table 3.

[0285] [Table 1-1]

[0286]

[0287] [Table 1-2]

[0288]

[0289] [Table 2]

[0290]

[0291] [Table 3]

[0292] Table 3

[0293]

[0294] The evaluation of the tensile properties of the polymer microparticle film MA-E (cycle 0) produced in Example 10 and the polymer MA bulk film produced in Reference Example 1 showed that, when compared at the same degree of crosslinking, the polymer microparticle film had a higher breaking strength than the bulk film. The evaluation of the tensile properties of Examples 10 and 16 showed that, even after the steps of molding and decomposition, a polymer microparticle film (cycle 1) having the same tensile properties as a polymer microparticle film (cycle 0) produced from unused polymer microparticles could be produced. Examples 16 and 17 showed that the pigment and the polymer microparticles could be separated and recovered from the polymer microparticle film containing the pigment.

[0295] Industrial Applicability

[0296] By using polymer microparticles, a polymer recycling method that can be applied to a variety of polymers can be provided.

Claims

1. A method for producing polymer microparticles, comprising: By applying an external stimulus to the molded body of polymer microparticles, the molded body is decomposed into polymer microparticles.

2. The method according to claim 1, wherein: The external stimulus is applied by swelling the polymer microparticles with a solvent.

3. The method according to claim 2, wherein: The solvent comprises a solvent selected from N,N-dimethylformamide, N,N-dimethylacetamide, alcohols with 2 to 6 carbon atoms, ketones with 3 to 5 carbon atoms, aromatic hydrocarbons with 6 to 10 carbon atoms, and a hydrocarbon of formula R 1 COOR 2 At least one of the group consisting of esters shown, Formula R 1 COOR 2 In, R 1 is hydrogen or an alkyl group having 1 to 3 carbon atoms, R 2 It is an alkyl group having 1 to 3 carbon atoms.

4. The method according to any one of claims 1 to 4, wherein: The polymer constituting the polymer fine particles is a (meth)acrylate polymer or a poly(meth)acrylamide polymer.

5. A polymer microparticle molded body, which is obtained by molding polymer microparticles, At least 80 mol % of the monomers constituting the polymer are at least one monomer selected from the group consisting of polyalkylene glycol (meth)acrylates, methacrylates containing an alkoxy group, acrylates containing an alkoxy group having 2 or more carbon atoms, (meth)acrylamide, and derivatives thereof. The polymer microparticle molded body according to claim 5 , which does not contain a structure derived from rotaxane.

7. A method for recycling polymer microparticles, wherein: The method comprises: (A) A step of applying an external stimulus to a first polymer microparticle molded body obtained by molding first polymer microparticles, thereby decomposing the first polymer microparticle molded body into second polymer microparticles.

8. The recycling method according to claim 7, wherein: The average particle size of the first polymer particles before molding is 50 nm to 5 μm.

9. The recycling method according to claim 7 or 8, wherein: The change rate between the average particle size of the first polymer microparticles before molding and the average particle size of the second polymer microparticles after decomposition is 15% or less.

10. The recycling method according to any one of claims 7 to 9, wherein: The ratio of the total mass of the second polymer microparticles obtained after the decomposition to the total mass of the first polymer microparticles used in the molding is 0.95 or more.

11. The recycling method according to any one of claims 7 to 10, wherein: The method further comprises: (B) A step of molding the second polymer microparticles obtained in the step (A) to produce a second polymer microparticle molded body.

12. The recycling method according to claim 11, wherein: The molding in the step (B) is performed using a second polymer microparticle dispersion in which the second polymer microparticles are dispersed in a dispersion medium.

13. The recycling method according to claim 11 or 12, wherein: The method further includes performing the step (A) again using the second polymer microparticle molded body obtained in the step (B) as the first polymer microparticle molded body in the step (A).

14. The recycling method according to any one of claims 9 to 11, wherein: The first polymer microparticle shaped body further comprises a functionalizing agent. 15 . The method according to claim 14 , further comprising the step of separating the second polymer microparticles from the functionalizing agent.

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