Method for producing polymer fine particles, polymer fine particle molded body and method for recycling polymer fine particles

Abstract

The present invention provides a method for recycling polymer fine particles, the method being applicable to various polymers. This method for recycling polymer fine particles comprises (A) a step for dismantling a first polymer fine particle molded body, which has been obtained by molding first polymer fine particles, into second polymer fine particles by applying external stimuli to the first polymer fine particle molded body.

Description

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

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

[0002] In recent years, in order to prevent resource depletion and environmental pollution, active efforts have been made to develop methods for recycling polymers. Polymer recycling methods include a method in which a polymer is purified by dissolving it in a solvent and reused as a polymer (e.g., Patent Documents 1 and 2), and a method in which a polymer is decomposed into monomers and reused (e.g., Patent Documents 3 and 4).

[0003] Patent Document 1 (JP 2009-30017 A) describes a polymer recycling method in which a polymer such as polymethyl methacrylate is dissolved in a liquid containing water and a poor solvent for the polymer, and the polymer precipitate precipitated from the polymer solution is reused.

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

[0005] Patent Document 3 (JP 2006-83145 A) describes a recycling method using foamed polystyrene, which comprises the steps of dissolving recovered foamed polystyrene in a solvent comprising d-limonene to prepare a polystyrene solution, heating the polystyrene solution to vaporize it and separate the polystyrene, regenerating the polystyrene as styrene monomer, and using the regenerated styrene monomer as a raw material to produce 1,1-diarylethane by the Friedel-Crafts reaction.

[0006] Patent Document 4 (JP 2004-196880 A) describes a method for depolymerizing polyethylene terephthalate, in which polyethylene terephthalate is heated and melted to depolymerize it, using an extruder and a reactor provided downstream of the outlet of the extruder to heat, melt, and carry out a depolymerization reaction of the polyethylene terephthalate, and also introducing glycol downstream of the outlet of the extruder and mixing the glycol with the polyethylene terephthalate using a mixer provided between the extruder and the reactor.

[0007] On the other hand, materials formed from polymer fine particles have been proposed as polymer molded bodies (Patent Documents 5 and 6: JP 2021-195521 A and JP 2022-91113 A).

[0008] JP 2009-30017 A JP 2001-302842 A JP 2006-83145 A JP 2004-196880 A JP 2021-195521 A JP 2022-91113 A

[0009] The method of purifying such a polymer by dissolving it in a solvent and reusing it as a polymer, and the method of decomposing the polymer into monomers and reusing them have problems such as limitations on applicable polymers, a complicated purification process, and high production costs.

[0010] An object of the present invention is to provide a method for producing polymer microparticles from a molded body of polymer microparticles by a simple operation. In one embodiment, the polymer microparticles produced from the molded body of polymer microparticles are reused. A further object of the present invention is to provide a polymer microparticle molded body that can be decomposed by a simple operation. A further object of the present invention is to provide a method for recycling polymer microparticles that can be applied to various polymers.

[0011] While prior art methods attempt to reuse polymers by breaking them down into polymer chains or monomers, the present inventors have discovered that by treating polymers in the form of fine particles, it is possible to mold, break down, and reuse a variety of polymers.

[0012] That is, the present invention includes the following aspects: [1] A method for producing polymer microparticles, comprising applying an external stimulus to a molded body of polymer microparticles, thereby decomposing the molded body into polymer microparticles. [2] The method according to [1], wherein the method for applying the external stimulus is to swell the polymer microparticles with a solvent. [3] The solvent is 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 compounds of the formula R １ COOR ２ (In the formula, R １ is hydrogen or an alkyl group having 1 to 3 carbon atoms, and R ２is an alkyl group having 1 to 3 carbon atoms.) The method according to [2], wherein the polymer constituting the polymer microparticles is a (meth)acrylate polymer or a poly(meth)acrylamide polymer. [5] A polymer microparticle molding obtained by molding polymer microparticles, wherein 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, alkoxy group-containing methacrylate, alkoxy group-containing acrylate having 2 or more carbon atoms, (meth)acrylamide, and derivatives thereof. [6] The polymer microparticle molding according to [5], which does not contain a structure derived from a rotaxane. [7] A method for recycling polymer microparticles, the method comprising: (A) applying an external stimulus to a first polymer microparticle molding obtained by molding first polymer microparticles, thereby decomposing the first polymer microparticle molding into second polymer microparticles. [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. [9] The recycling method according to [7] or [8], wherein the rate of change between the average particle size of the first polymer microparticles before molding and the average particle size of the second polymer microparticles after the decomposition is 15% or less.

[10] The recycling method according to any 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.

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

[10] , wherein the method further comprises: (B) a step of molding the second polymer microparticles obtained in step (A) to produce a second polymer microparticle molding.

[12] The recycling method according to

[11] , wherein the molding in 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

[11] or

[12] , further comprising repeating step (A) using the second polymer microparticle molding obtained in step (B) as the first polymer microparticle molding in step (A).

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

[11] , wherein the first polymer microparticle molding further comprises a functionalizing agent.

[15] The method according to

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

[16] A closed-loop recycling method for polymers using polymer microparticles, comprising, in this order: (a) providing a polymer microparticle dispersion containing polymer microparticles and a dispersion medium; (b) molding the polymer microparticle dispersion to obtain a molded product; and (c) adding a solvent as an external stimulus to the molded product to swell the polymer microparticles constituting the molded product, thereby decomposing the molded product into the polymer microparticles.

[17] The method according to

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

[18] The method according to

[16] or

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

[19] The solvent is 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 represented by the formula R. １ COOR ２ (In the formula, R １ is hydrogen or an alkyl group having 1 to 3 carbon atoms, and R ２is an alkyl group having 1 to 3 carbon atoms.) The method according to

[18] , wherein the polymer fine particles in the polymer fine particle dispersion contain at least one ester represented by the formula (I).

[20] The method according to any one of

[16] to

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

[21] The method according to any one of

[16] to

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

[22] The method according to

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

[23] The method according to

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

[24] The method according to any one of

[21] to

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

[25] The method according to

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

[26] The method according to any one of

[16] to

[20] , wherein the dispersion medium is air.

[27] The method according to

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

[0013] According to the present invention, polymer microparticles can be produced from a molded body of polymer microparticles by a simple operation. The polymer microparticles produced from a molded body of polymer microparticles can be reused. According to the present invention, a polymer microparticle molded body that can be decomposed by a simple operation can be provided. Furthermore, according to the present invention, a method for recycling polymer microparticles that can be applied to various polymers can be provided.

[0014] 1 shows AFM images of polymer microparticles (unused polymer microparticles) of Production Example 5 and polymer microparticles after decomposition of Example 10, and a histogram of particle diameters (Krumbine diameter) (nm) of individual polymer microparticles. 1 shows stress-strain curves of polymer microparticle film MA-E (cycle 0) and polymer microparticle film MA-E (cycle 1) produced in Example 10. 1 shows stress-strain curves of blue polymer microparticle film MA-E (cycle 0) and polymer microparticle film MA-E (cycle 1) produced in Example 16.

[0015] The present invention will be described in detail below. One embodiment of the present invention includes a method for producing polymer microparticles from a molded body of polymer microparticles (hereinafter, sometimes simply referred to as a molded body). Another embodiment of the present invention includes a molded body of polymer microparticles. Another embodiment of the present invention includes a method for recycling polymer microparticles. These will be described below.

[0016] <Polymer Particles> First, the polymer particles used in the present invention will be described.

[0017] The type of polymer constituting the polymer microparticles constituting the molded product of the polymer microparticles (hereinafter sometimes referred to as polymer microparticles) used in the present invention is not particularly limited. The polymer constituting the polymer microparticles may be one type or two or more types. Examples of the polymer include natural resins and synthetic polymers. Examples of the natural resin include casein, gelatin, and starch. Examples of the synthetic polymer include acrylic resins, polyolefin resins, polystyrene resins, polyester resins, polyamide resins, polyimide resins, novolac resins, polyurethane resins, polycarbonate resins, cellulose-based resins, polyalkylene glycols, polysiloxanes, polyrotaxanes, and derivatives of these resins.

[0018] Each polymer constituting the polymer microparticles may be a homopolymer made of a single type of monomer, or a copolymer made of multiple types of monomers. In the case of a copolymer, it may be a block copolymer or a random copolymer.

[0019] The weight average molecular weight of the polymer constituting the polymer microparticles is not limited, but the lower limit can usually be 10,000 or more, or 50,000 or more, or 80,000 or more, and the upper limit can usually be 5,000,000 or less, or 4,000,000 or less, or 3,000,000 or less. In this specification, the weight average molecular weight means a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0020] The average particle size of the polymer particles 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.

[0021] In the present disclosure, the average particle size of polymer microparticles is the average value of the particle widths at which the particle height (maximum value - minimum value) of the polymer microparticles is half that of 100 randomly selected polymer microparticles, analyzed using image analysis software from an image obtained using an atomic force microscope.

[0022] The polymer particles used in the present invention may not have a hierarchical structure, or may have a hierarchical structure such as a core-shell structure.

[0023] The shape of the polymer particles used in the present invention is not particularly limited, but may be spherical, ellipsoidal, or rod-like. The polymer particles may also be hollow.

[0024] The polymer microparticles used in the present invention may contain a solvent, or may not contain a solvent. Examples of the solvent contained in the polymer microparticles include the solvent used in producing polymer microparticles and the dispersion medium used in producing polymer microparticle molded bodies, and a specific example is water.

[0025] In one embodiment, the polymer constituting the polymeric particles is a (meth)acrylic polymer or poly(meth)acrylamide, which may or may not have a crosslinked structure.

[0026] The (meth)acrylate used in the production of the (meth)acrylic 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, and isononyl (meth)acrylate. linear or branched alkyl (meth)acrylates such as isodecyl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate; cyclic alkyl (meth)acrylates such as cyclohexyl (meth)acrylate, dicyclohexyl (meth)acrylate, and isobornyl (meth)acrylate; hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate; polyalkylene glycol (meth)acrylates such as alkoxy group-containing (meth)acrylates, 2-(2-methoxyethoxy)ethyl (meth)acrylate, 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; aromatic group-containing (meth)acrylates such as benzyl (meth)acrylate and 9-anthryl (meth)acrylate; N,N-dimethylaminoethyl (meth)acrylate; and N,Examples of the acrylate include amino group-containing (meth)acrylates such as N-diethylaminoethyl (meth)acrylate, alkoxyethyl (meth)acrylates such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate, and 2-cyclohexyloxyethyl (meth)acrylate, aryloxyethyl (meth)acrylates such as phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, and 2-morpholinoethyl (meth)acrylate. Among these, linear or branched alkyl (meth)acrylates, polyalkylene glycol (meth)acrylates, and alkoxyethyl (meth)acrylates are preferred because of their ease of decomposition, with linear or branched alkyl (meth)acrylates in which the alkyl group has 1 to 4 carbon atoms, polyalkylene glycol (meth)acrylates containing diethylene glycol units, and alkoxyethyl (meth)acrylates in which the alkoxy group has 1 to 3 carbon atoms being more preferred, and with methyl (meth)acrylate, 2-(2-methoxyethoxy)ethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, 2-methoxyethyl (meth)acrylate, and 2-ethoxyethyl (meth)acrylate being even more preferred. The (meth)acrylates may be used alone or in any combination of two or more in any ratio.

[0027] In one embodiment, the (meth)acrylic polymer is a homopolymer or copolymer of (meth)acrylate. The (meth)acrylic polymer may also be a copolymer of (meth)acrylate and another monomer. The other monomer is not particularly limited, and specific examples 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 a rotaxane having one polymerizable unsaturated group. The other monomer may be used alone, or two or more types may be used in any ratio and combination.

[0028] The (meth)acrylamide used in producing 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-benzyl acryl(meth)acrylamide, etc. The (meth)acrylamides may be used alone or in any combination and ratio.

[0029] (Method for producing polymer microparticles from monomers) The method for producing the polymer microparticles from a monomer is not particularly limited, and polymer microparticles capable of producing the polymer microparticle molded article used in the present invention can be produced appropriately. In one embodiment, polymer microparticles can be produced by polymerizing a monomer, which is a component of the polymer constituting the polymer microparticles, into fine particles by a standard method and purifying it as necessary. In a specific embodiment, the polymer microparticles can be produced as a polymer microparticle dispersion. Hereinafter, the polymer microparticle dispersion will be described.

[0030] The polymer particle dispersion contains polymer particles and a dispersion medium. The polymer particles used here are the same as those described above.

[0031] The dispersion medium includes a solvent and air. When the dispersion medium is a solvent, the polymer particle dispersion is provided as a dispersion liquid. When the dispersion medium is air, the polymer particle dispersion is provided as a powder.

[0032] In one embodiment, the dispersion medium is an aqueous solvent. In the present disclosure, an aqueous solvent refers to a solvent having a water content of more than 50% by volume. The water content in the dispersion medium may be 80% by volume or more, 90% by volume or more, 95% by volume or more, 99% by volume or more, or 100% by volume. The aqueous solvent may contain water and a water-miscible organic solvent. Examples of water-miscible organic solvents include methanol, ethanol, propanol, N,N-dimethylformamide (DMF), and acetone. The aqueous solvent is preferably water. As the water, distilled water, deionized water, pure water, etc. can be used.

[0033] In this embodiment, the polymer microparticle dispersion is provided as a dispersion of polymer microparticles in an aqueous solvent. The content of the polymer microparticles in the aqueous solvent dispersion is preferably 1% by mass to 50% by mass, and more preferably 3% by mass to 40% by mass. Within this range, the dispersion stability of the polymer microparticles in the aqueous solvent dispersion is good.

[0034] The aqueous solvent dispersion of polymer microparticles may contain a functionalizing agent. The functionalizing agent is not particularly limited as long as it imparts a specific function to the molded article and is soluble or dispersible in the aqueous solvent, and specific examples include pigments, dyes, organic fillers, and inorganic fillers. The size of dispersible functionalizing agents is usually 1 nm to 1 mm. The functionalizing agents may be used alone or in any combination and ratio.

[0035] Examples of pigments include inorganic pigments and organic pigments.

[0036] Examples of inorganic fillers include silica filler and carbon black.

[0037] The content of the functionalizing agent in the aqueous solvent dispersion of polymer fine particles is preferably 0.01% by mass to 20% by mass, and more preferably 0.01% by mass to 5% by mass, in which case the dispersion stability of the functionalizing agent in the aqueous solvent is good.

[0038] The amount of the functionalizing agent used 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, per 100 parts by mass of the polymer microparticles. When the amount is 50 parts by mass or less, the moldability of the polymer microparticles is good.

[0039] The aqueous solvent dispersion of polymer microparticles may contain, as optional components, additives such as a fusing agent, a softening agent, and an interparticle crosslinking agent. By using at least one selected from the group consisting of a fusing agent, a softening agent, and an interparticle crosslinking agent, the moldability of the polymer microparticles can be improved.

[0040] The aqueous solvent dispersion of polymer microparticles may contain unreacted monomers, polymers that are not incorporated into the polymer microparticles, as well as surfactants and polymerization initiators that are optionally used in the method for producing the polymer microparticle dispersion described below.

[0041] In one embodiment, the dispersion medium is air. In this embodiment, the polymer particle dispersion is provided as a powder of polymer particles.

[0042] (Method for Producing Polymer Microparticle Dispersion from Monomer) The method for producing the polymer microparticle dispersion is not particularly limited. For example, a method may be used in which a monomer is polymerized in an aqueous solvent to obtain a dispersion of polymer microparticles in an aqueous solvent, and the dispersion is purified as necessary to obtain the polymer microparticle dispersion.

[0043] Examples of the polymerization method include emulsion polymerization, soap-free emulsion polymerization, suspension polymerization, dispersion polymerization, microemulsion polymerization, miniemulsion polymerization, and microsuspension polymerization. Emulsion polymerization and soap-free emulsion polymerization are preferred from the viewpoint of easy size control of the polymer fine particles.

[0044] When polymerizing the monomer, 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 needed.

[0045] The surfactant is not particularly limited, but includes anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants.

[0046] Examples of anionic surfactants include sodium oleate, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium alkylsulfonate, sodium polyoxyethylene alkyl ether sulfate, and their corresponding potassium salts, calcium salts, alkylnaphthalenesulfonates, and alkylphosphates.

[0047] Examples of cationic surfactants include alkylamine salts such as laurylamine acetate and stearylamine acetate, and quaternary ammonium salts such as lauryltrimethylammonium chloride.

[0048] Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylamines, and glycerin fatty acid esters.

[0049] Examples of amphoteric surfactants include lauryl dimethylamine oxide.

[0050] The surfactant can be appropriately selected depending on the type of monomer used, the polymerization method, etc. When a (meth)acrylic polymer or poly(meth)acrylamide is produced by emulsion polymerization, the surfactant is preferably an anionic surfactant, more preferably sodium dodecylbenzenesulfonate.

[0051] The surfactants may be used alone or in any combination of two or more kinds in any ratio.

[0052] The amount of 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 this range, the size of the resulting polymer fine particles is appropriate.

[0053] When a radical polymerizable monomer is used, it is preferable to use a polymerization initiator. The polymerization initiator is not particularly limited, and examples thereof include persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate, benzoyl peroxide, lauroyl peroxide, o-chlorobenzoyl peroxide, o-methoxybenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, tert-butylperoxy-2-ethylhexanoate, di-tert-butyl peroxide, cumene hydroperoxide, and t-butyl hydroxybenzoate. Examples of the polymerization initiator include organic peroxides such as droperoxide, 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 these, persulfates are preferred, and potassium persulfate is more preferred. The polymerization initiator may be used alone, or two or more types may be used in combination in any ratio and combination.

[0054] 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, per 100 parts by mass of the monomer.

[0055] The crosslinking agent is not particularly limited as long as it is a compound having two or more functional groups reactive with the monomer. When a radical polymerizable monomer is used, examples of the crosslinking agent include 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. Among these, ethylene glycol di(meth)acrylate and 1,6-hexanediol di(meth)acrylate are preferred. Examples of the crosslinking agent include rotaxanes having two or more polymerizable unsaturated groups. A rotaxane is composed of a cyclic molecule, a linear molecule skewered and included in the cyclic molecule, and a bulky terminal group to prevent the cyclic molecule from detaching from the linear molecule. At least one of the cyclic molecule and the linear molecule may have two or more polymerizable unsaturated groups, and preferably both the cyclic molecule and the linear molecule have polymerizable unsaturated groups. A rotaxane having two or more polymerizable unsaturated groups can be obtained, for example, by reacting a rotaxane with a compound having a polymerizable unsaturated group and a functional group reactive with the functional group of the rotaxane. For example, when the functional group of the rotaxane is a hydroxyl group, a compound having an isocyanato group and a polymerizable unsaturated group, such as 2-isocyanatoethyl (meth)acrylate, can be used. Examples of polymerizable unsaturated groups include vinyl groups and (meth)acrylic groups. Examples of rotaxanes having a hydroxyl group include SH2400P and SH1300P (both manufactured by ASM Corporation).

[0056] The crosslinking agents may be used alone or in any combination of two or more kinds in any ratio.

[0057] The amount of the crosslinking agent used is preferably 0.001 to 50 parts by mass, and more preferably 0.001 to 25 parts by mass, per 100 parts by mass of the monomer.

[0058] The inorganic salt is used for the purpose of adjusting the separation (dispersion) stability of the emulsion and polymer microparticles. Specific examples of the inorganic salt include 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. The inorganic salt may be used alone or in any combination and ratio.

[0059] The amount of inorganic salt used is preferably 0.0001 to 10 parts by mass, and more preferably 0.01 to 5 parts by mass, per 100 parts by mass of monomer. When the amount of inorganic salt used is 0.0001 part by mass or more, the separation (dispersion) stability derived from the inorganic salt is easily adjusted. When the amount of inorganic salt used is 10 parts by mass or less, the polymer fine particles do not aggregate, and the size of the resulting polymer fine particles is appropriate.

[0060] The temperature and time of the polymerization reaction can be appropriately selected depending on the monomer, polymerization method, polymerization initiator, etc. For example, when emulsion polymerization or soap-free emulsion polymerization is performed using at least one monomer selected from the group consisting of (meth)acrylate, (meth)acrylamide, and (meth)acrylamide derivatives, the reaction temperature and time are 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.

[0061] In an embodiment in which the dispersion medium is an aqueous solvent, the aqueous solvent dispersion of polymer microparticles obtained by the polymerization reaction may be molded as is to produce a molded product. However, from the viewpoint of improving the quality of the molded product, it is preferable to obtain a polymer microparticle dispersion (aqueous solvent dispersion of polymer microparticles) by performing purification procedures such as centrifugation, filtration, and dialysis, and, if necessary, re-dispersing the polymer microparticles in an aqueous solvent.

[0062] In an embodiment in which the dispersion medium is an aqueous solvent, optional components such as a functionalizing agent and additives can be added to the aqueous solvent dispersion of polymer particles, if necessary.

[0063] In an embodiment in which the dispersion medium is air, the polymer microparticle dispersion obtained by the polymerization reaction is purified by purification procedures such as centrifugation and dialysis as necessary, and then the solvent is removed to obtain a polymer microparticle dispersion (a powder of polymer microparticles).The method for removing the solvent is not particularly limited, but includes freeze-drying.

[0064] (Method for Producing Molded Article of Polymer Particles) A ​​molded article of polymer particles can be produced, for example, by using the polymer particle dispersion.

[0065] A method for producing a molded article using a dispersion of polymer microparticles includes, for example, volatilizing the solvent used as a dispersion medium. Specifically, a molded article of polymer microparticles can be obtained by applying or spraying the dispersion of polymer microparticles onto a substrate or placing it in a mold, and then volatilizing the solvent. The method for volatilizing the solvent is not particularly limited, but a specific example is a method in which the solvent is volatilized under atmospheric pressure or reduced pressure while heating as necessary.

[0066] A method for producing a molded article using a powder of polymer fine particles includes, for example, heat pressing the powder of polymer fine particles. Specifically, the powder of polymer fine particles is placed in a mold, and heated and pressurized to obtain a molded article.

[0067] The temperature during heat pressing can be set appropriately within a range that exceeds the glass transition temperature (Tg) of the polymer constituting the polymer microparticles but does not melt the polymer microparticles. For example, when the polymer microparticles are polymethyl methacrylate, the temperature during heat pressing is preferably 100 to 200°C, more preferably 100 to 150°C.

[0068] The pressure during heat pressing can be set appropriately within a range that does not destroy the polymer particles, and is, for example, 0.2 to 100 MPa, or 0.3 to 50 MPa.

[0069] The obtained polymer microparticle molding may be further annealed. By annealing the polymer microparticle molding, the degree of 0102 alignment of the polymer chains between the polymer microparticles can be increased, i.e., the interface thickness can be increased.

[0070] The annealing temperature and time are not particularly limited, and can be set appropriately depending on the type of polymer constituting the polymer microparticles, 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 varies depending on the temperature, but is usually 1 to 200 hours.

[0071] [Polymer microparticle molding] One embodiment of polymer microparticle molding, that is, polymer microparticle molding made by molding polymer microparticles, is a polymer microparticle molding, wherein 80 mol% or more of the monomer that constitutes polymer is selected from the group consisting of polyalkylene glycol (meth) acrylate, alkoxy group-containing methacrylate, alkoxy group-containing acrylate of carbon number 2 or more, (meth) acrylamide and their derivatives at least one monomer.(These are also referred to as the polymer microparticle molding that is made by specific monomer hereinafter.) At least one monomer that is selected from the group consisting of polyalkylene glycol (meth) acrylate, alkoxy group-containing methacrylate, alkoxy group-containing acrylate of carbon number 2 or more, (meth) acrylamide and their derivatives preferably accounts for more than 90 mol% of the monomer that constitutes polymer, more preferably accounts for more than 95 mol%, and even more preferably accounts for more than 99 mol%. 100 mol % of the monomers constituting the polymer may be at least one monomer selected from the group consisting of polyalkylene glycol (meth)acrylates, alkoxy group-containing methacrylates, alkoxy group-containing acrylates having two or more carbon atoms, (meth)acrylamides, and derivatives thereof.

[0072] In one embodiment, the polymer particle molded product made of a specific monomer is a molded product in which the polymer particles are bonded to each other by entanglement of the polymer chains between the polymer particles. The molded product formed by such characteristics has the characteristics of the polymer itself, such as toughness.

[0073] The polymer microparticle moldings composed of specific monomers are novel moldings that can be easily used to produce polymer microparticles by subjecting the moldings of polymer microparticles of the present invention to the method for producing polymer microparticles, and are preferable in that they can be easily decomposed, recovered, and reused as polymer microparticles compared to polymers obtained by polymerizing each monomer using known general methods.

[0074] Examples of derivatives of the above-mentioned monomers include compounds in which the above-mentioned monomers are substituted with one or more substituents, provided that the substitution does not deviate from the spirit of the present invention. Examples of the substituents in this case include, but are not limited to, a hydroxy group, a thiol group, a carboxy group, a nitro group, a cyano group; a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a sec-butyl group, a pentyl group, an isopentyl group, a neopentyl group, a hexyl group, a heptyl group, an octyl group, a decyl group, or a nonyl group; an alkenyl group such as an ethenyl group, a propenyl group, an allyl group, a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, or an octenyl group; an alkynyl group such as a propargyl group; a cyclopropyl group, ... cycloalkyl groups such as a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a bicyclooctyl group, and a spirooctyl group; alkoxy groups such as a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a sec-butoxy group, and a tert-butoxy group; aryl groups such as a phenyl group, a benzyl group, a tolyl group, a naphthyl group, and an anthracenyl group; aryloxy groups such as a phenyloxy group, a benzyloxy group, and a naphthyloxy group; acyl groups such as an acetyl group, a propionyl group, a benzoyl group, a paramethoxybenzoyl group, and a cinnamoyl group; unsubstituted amino groups, and substituted amino groups such as a dimethylamino group, a benzylamino group, and a triphenylmethylamino group;Furanyl group, thiophenyl group, pyranyl group, pyrrolinyl group, pyrrolyl group, 2,3-dihydro-1H-pyrrolyl group, piperidinyl group, piperazinyl group, homopiperazinyl group, morpholino group, thiomorpholino group, 1,2,4,6-tetrahydropyridyl group, hexahydropyrimidyl group, hexahydropyridazyl group, 1,2,4,6-tetrahydropyridyl group, 1,2,4,6-tetrahydropyridazyl group, 3,4-dihydropyridyl group, imidazolyl group, 4,5-dihydro-1H-imidazolyl group, 2,3-dihydro-1H-imidazolyl group, pyrazolyl group, 4,5-dihydro-1H-pyra Heterocyclic groups such as azolyl group, a 2,3-dihydro-1H-pyrazolyl group, an oxazolyl group, a 4,5-dihydro-1,3-oxazolyl group, a 2,3-dihydro-1,3-oxazolyl group, a 2,5-dihydro-1,3-oxazolyl group, a thiazolyl group, a 4,5-dihydro-1,3-thiazolyl group, a 2,3-dihydro-1,3-thiazolyl group, a 2,5-dihydro-1,3-thiazolyl group, and a carbazolyl group; heterocyclic oxy groups such as a furanyloxy group, a pyrrolyloxy group, an indolyloxy group, and a quinolyloxy group; and groups in which the above groups are substituted with one or more substituents (for example, halogen groups).

[0075] Specific examples of polyalkylene glycol (meth)acrylates 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.

[0076] Specific examples of alkoxy group-containing methacrylates include 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, 2-propoxyethyl methacrylate, and 2-cyclohexyloxyethyl methacrylate.

[0077] Specific examples of alkoxy group-containing acrylates having two or more carbon atoms include 2-ethoxyethyl acrylate, 2-propoxyethyl acrylate, and 2-cyclohexyloxyethyl acrylate.

[0078] Specific examples of (meth)acrylamide and its derivatives include (meth)acrylamide, N-substituted (meth)acrylamides, and N,N-disubstituted (meth)acrylamides. Specific examples of the substituent of the (meth)acrylamide derivative include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, and tert-butyl groups, cyclic alkyl groups such as cyclopropyl groups, aryl groups such as phenyl groups, and benzyl groups. In the case of N,N-disubstituted (meth)acrylamides, the substituents may be bonded to form a ring structure. Specific examples of the (meth)acrylamide derivative 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, acryloylmorpholine, and N-benzylacryl(meth)acrylamide.

[0079] Among these, polyalkylene glycol (meth)acrylates containing diethylene glycol units, alkoxyethyl methacrylates in which the alkoxy group has 1 to 3 carbon atoms, alkoxyethyl acrylates in which the alkoxy group has 2 to 3 carbon atoms, and N-substituted (meth)acrylamides are preferred, as the glass transition temperature (Tg) of the resulting polymer is appropriate and they are easy to mold and decompose, 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.

[0080] Examples of other monomers constituting the polymer include linear or branched alkyl (meth)acrylates, cyclic alkyl (meth)acrylates, methoxy group-containing acrylates, hydroxy group-containing (meth)acrylates, aromatic group-containing (meth)acrylates, amino group-containing (meth)acrylates, aryloxyethyl (meth)acrylates, (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. Among these, linear or branched alkyl (meth)acrylates and methoxy group-containing acrylates are preferred, linear or branched alkyl (meth)acrylates having an alkyl group of 1 to 4 carbon atoms and methoxyethyl acrylate are more preferred, and methyl (meth)acrylate and methoxyethyl acrylate are even more preferred. In one embodiment, the monomers constituting the polymer do not include a rotaxane having one polymerizable unsaturated group.

[0081] The polymer constituting the polymer microparticles composed of a specific monomer may or may not have a crosslinked structure. The crosslinking agent that imparts a crosslinked 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 the monomers that constitute the polymer. Examples of crosslinking agents include 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. Among these, ethylene glycol di(meth)acrylate and 1,6-hexanediol di(meth)acrylate are preferred. The cross-linking agent may also be a rotaxane having two or more polymerizable unsaturated groups, such as vinyl groups and (meth)acrylic groups.

[0082] In one embodiment, the polymer microparticle molded product made of the specific monomer does not contain a structure derived from rotaxane, which is preferable in terms of advantageous production costs.

[0083] The shape of the polymer microparticle molded product made of a specific monomer is not particularly limited. The polymer microparticle molded product may be a coating film formed on a substrate, or may be a free-standing molded product such as a free-standing film. Furthermore, by using an appropriate mold, a molded product of any shape can be obtained. When a sheet-shaped molded product is produced, its thickness is usually 10 nm to 1 cm.

[0084] The polymer particle molding composed of the specific monomer may contain a functionalizing agent. The functionalizing agent is the same as that contained in the polymer particle dispersion. When the polymer particle molding used in the present invention is produced using a polymer particle dispersion containing a functionalizing agent, the function of the functionalizing agent is usually imparted to the molding.

[0085] 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, per 100 parts by mass of the polymer fine particles.

[0086] In one embodiment, a polymer microparticle molded product made from a specific monomer is a molded product in which polymer microparticles are bonded to each other by entanglement of polymer chains between the polymer microparticles. In this case, because the polymer chains penetrate each other at the interface between the polymer microparticles, the interface has a certain thickness (interface thickness). In this embodiment, the interfacial thickness between the polymer microparticles is, for example, 2.5 to 5.0 nm, 2.8 to 4.8 nm, or 3.0 to 4.5 nm. Without being bound by any theory, the density of polymer chains near the surface of the polymer microparticles is lower than that at the center of the microparticles, making the polymer chains more mobile. Therefore, during molding, the polymer chains present on the surfaces of adjacent polymer microparticles become entangled, bonding the polymer microparticles to each other and forming a molded product. Methods for promoting the formation of entanglement of polymer chains include annealing the molded product and adding a small amount of organic solvent to an aqueous solvent dispersion of polymer microparticles, i.e., to an extent that does not dissolve the polymer microparticles. These methods are thought to facilitate the movement of polymer chains on the surface of the polymer microparticles. As the organic solvent, an organic solvent with high affinity for the polymer constituting the polymer microparticles is preferably used. A preferred organic solvent is, for example, N,N-dimethylformamide.

[0087] [Method for Producing Polymer Microparticles from Molded Polymer Microparticles] In one embodiment, the method for producing polymer microparticles comprises applying an external stimulus to the molded polymer microparticles, thereby decomposing the molded polymer microparticles into polymer microparticles. The molded polymer microparticles can be produced by the same method as the method for producing the molded polymer microparticles described above. Note that the molded polymer microparticles that can be used in the method for producing polymer microparticles from the molded polymer microparticles are not limited to the molded polymer microparticles composed of the specific monomers described above. In the molded polymer microparticles, the particulate nature of the raw polymer microparticles is not completely lost. Therefore, the molded polymer microparticles can be decomposed into polymer microparticles by applying an external stimulus.

[0088] An example of a method for applying an external stimulus to a molded product of polymer microparticles is swelling the polymer microparticles that make up the molded product with a solvent. Without being bound by any theory, in a molded product of polymer microparticles, the polymer microparticles are bonded to each other by entanglement of polymer chains on their surfaces while retaining a certain degree of particle character. When a solvent is applied to a molded product of polymer microparticles as an external stimulus, the solvent penetrates between the entangled polymer chains, causing the entanglement of the polymer chains to unravel. As a result, the molded product is decomposed into polymer microparticles.

[0089] The solvent is not particularly limited as long as it can swell the polymer microparticles that make up the molded body. Examples include water, aqueous solvents, and organic solvents. Among these, solvents with high affinity for the polymer that makes up the polymer microparticles are preferably used. The solvents may be used alone or in any combination and ratio.

[0090] Specifically, the solvent can be selected based on, for example, the chemical structure of the polymer constituting the polymer microparticles, the Hansen solubility parameter, and the like.

[0091] The Hansen solubility parameter (HSP value) is calculated by multiplying the solubility parameter (SP value) proposed by Hildebrand by the dispersion term (δ Ｄ ), polar term (δ Ｐ ), and the hydrogen bond term (δ Ｈ) and expressed in three-dimensional space. The Hansen solubility parameter (HSP value) expresses solubility as a three-dimensional vector, and generally, those with similar vectors have high solubility. The distance Ra between the HSP value of the polymer and the HSP value of the solvent is calculated by the following formula: Ra = (4(δ Ｄ２ -δ Ｄ１ ) ２ + (δ Ｐ２ -δ Ｐ１ ) ２ + (δ Ｈ２ -δ Ｈ１ ) ２ ) １／２ δ Ｄ１ : dispersion term of the solvent, δ Ｄ２ : dispersion term of polymer, δ Ｐ１ : polarity term of the solvent, δ Ｐ２ : polar term of the polymer, δ Ｈ２ : Hydrogen bond term of the solvent, δ Ｈ１ : Hydrogen bond term of polymer A small distance Ra indicates similar intermolecular interactions and is an index of the ease of swelling of the polymer. The HSP value can be determined, for example, from the presence or absence of solubility or swelling in a solvent with a known HSP value. The HSP value can also be estimated from the structural formula, and can be calculated, for example, using software (HSPiP ver. 4.1.07).

[0092] 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 amines represented by the formula R １ COOR ２ (In the formula, R １ is hydrogen or an alkyl group having 1 to 3 carbon atoms, and R ２ is an alkyl group having 1 to 3 carbon atoms.

[0093] Examples of alcohols having 2 to 6 carbon atoms include ethanol, propanol, butanol, and pentanol.

[0094] Examples of ketones having 3 to 5 carbon atoms include acetone and ethyl methyl ketone.

[0095] Examples of aromatic hydrocarbons having 6 to 10 carbon atoms include benzene, toluene, and xylene.

[0096] Formula R １ COOR ２ (In the formula, R １ is hydrogen or an alkyl group having 1 to 3 carbon atoms, and R ２ is an alkyl group having 1 to 3 carbon atoms. Examples of the ester represented by the formula (I) include methyl acetate, ethyl acetate, propyl acetate, methyl butyrate, and ethyl butyrate.

[0097] When the polymer microparticles are (meth)acrylic polymer microparticles or poly(meth)acrylamide microparticles, the solvent is preferably 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 amines represented by the formula R １ COOR ２ (In the formula, R １ is hydrogen or an alkyl group having 1 to 3 carbon atoms, and 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, an alcohol having 2 to 5 carbon atoms, acetone, ethyl methyl ketone, and an aromatic hydrocarbon having 6 to 10 carbon atoms, and even more preferably at least one selected from N,N-dimethylformamide, an alcohol having 2 to 5 carbon atoms, acetone, and toluene.

[0098] The solvent is selected from 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 amines having the formula R １ COOR ２ (In the formula, R １ is hydrogen or an alkyl group having 1 to 3 carbon atoms, and R ２is an alkyl group having 1 to 3 carbon atoms. When the solvent contains at least one selected from the group consisting of esters represented by the formula (I), the solvent contains these solvents in a total amount 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.

[0099] [Method for Recycling Polymer Microparticles] In one embodiment, the method for recycling polymer microparticles includes the step of (A) applying an external stimulus to a first polymer microparticle molded body obtained by molding the first polymer microparticles, thereby decomposing the first polymer microparticle molded body into second polymer microparticles. The second polymer microparticles obtained in step (A) can be reused.

[0100] The first polymer microparticles can be the polymer microparticles used in the present invention. The external stimulus can be applied to the first polymer microparticle molding by the same method as that for applying the external stimulus in the method for producing polymer microparticles from the polymer microparticle molding.

[0101] The first polymer microparticle molding can be produced by the same method as the method for producing the polymer microparticle molding. Note that the moldings that can be used in the method for recycling polymer microparticles are not limited to the polymer microparticle moldings composed of the specific monomer.

[0102] The average particle size of the first polymer fine particles 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.

[0103] The rate of change (%) between the average particle size of the first polymer microparticles before molding and the average particle size of the second polymer microparticles after decomposition (difference between the average particle size (nm) of the first polymer microparticles and the average particle size (nm) of the second polymer microparticles / average particle size (nm) of the first polymer microparticles x 100) is preferably 15% or less, more preferably 10% or less, even more preferably 8% or less, and even more preferably 5% or less. In one embodiment of the method for recycling polymer microparticles, molding and decomposition of a molded body are carried out by the reversible formation and dissolution of polymer chain entanglements between polymer microparticles, so the quality of the polymer microparticles does not substantially change. In other words, the second polymer microparticles have properties similar to those of the first polymer microparticles.

[0104] The ratio of the total mass of the second polymer microparticles obtained after decomposition to the total mass of the first polymer microparticles used in molding the first polymer microparticle molding is preferably 0.95 or more, more preferably 0.97 or more, and even more preferably 0.99 or more.In one embodiment of the method for recycling polymer microparticles, molding and decomposition of the molding are carried out by the formation and dissolution of reversible entanglement of polymer chains between polymer microparticles, so the quality of the polymer microparticles does not change substantially, and a high recovery rate can be obtained.In addition, as described below, when the first polymer microparticle molding 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 in molding the first polymer microparticle molding is not particularly limited, but is preferably 0.70 or more.This is because a step of separating the second polymer microparticles and the functionalizing agent may be performed.

[0105] The method for recycling polymer microparticles in one embodiment further includes a step (B) of molding the second polymer microparticles obtained in the step (A) to produce a second polymer microparticle molded article.

[0106] The molding in step (B) can be carried out, for example, using a second polymer microparticle dispersion in which the second polymer microparticles are dispersed in a dispersion medium. Specifically, it can be carried out by the same method as the above-mentioned method for producing a molded article from polymer microparticles.

[0107] In an embodiment in which the dispersion medium is a solvent, optional components such as functionalizing agents and additives can be added to the second polymer particle dispersion, if necessary.

[0108] In step (A), when the first polymer microparticle molding is decomposed into second polymer microparticles by swelling the polymer microparticles with a solvent, a dispersion of second polymer microparticles is obtained.In this case, the obtained dispersion of second polymer microparticles may be molded as it is to produce a second polymer microparticle molding, but from the viewpoint of improving the quality of the molding, it is preferable to perform purification operations such as centrifugation, filtration, and dialysis, and if necessary, re-disperse the second polymer microparticles in a solvent to obtain a second polymer microparticle dispersion.In an embodiment in which the dispersion medium is air, the dispersion of second polymer microparticles obtained in step (A) is purified by purification operations such as centrifugation and dialysis as necessary, and then the solvent is removed to obtain a second polymer microparticle dispersion.The method of removing the solvent is not particularly limited, but freeze-drying can be mentioned.

[0109] In one embodiment, the second polymer particle molding is also a molding in which the polymer particles are bonded to each other by entanglement of the polymer chains between the polymer particles. As described above, the thickness of the interface between the polymer particles is, for example, 2.5 to 5.0 nm, 2.8 to 4.8 nm, or 3.0 to 4.5 nm.

[0110] The step (B) may also include a step of annealing the second polymer particle molding.

[0111] The shape of the second polymer microparticle molding is not particularly limited. The second polymer microparticle molding may be a coating film formed on a substrate, or may be a free-standing molding such as a free-standing film.

[0112] In one embodiment, step (B) does not include a step of dissolving or melting the second polymeric microparticles.

[0113] In one embodiment, the method for recycling polymer microparticles further comprises using the second polymer microparticle molding obtained in the step (B) as the first polymer microparticle molding in the step (A) and carrying out the step (A) again. In this way, by repeating the steps (A) and (B), the polymer microparticles can be used repeatedly.

[0114] The first polymer microparticle molding may contain the functionalizing agent. When the first polymer microparticle molding contains a functionalizing agent, the method for recycling polymer microparticles may further include a step of separating the second polymer microparticles and the functionalizing agent after step (A). The method for separating the second polymer microparticles and the functionalizing agent is not particularly limited and can be carried out using a known method. Specific examples include centrifugation, filtration, dialysis, etc. By carrying out the above separation step, the second polymer microparticles and the functionalizing agent can be recovered and reused separately. Generally, it is difficult to separate and recover a polymer from a molding containing a functionalizing agent, but in the method for recycling polymer microparticles, the particulate nature of the polymer microparticles is maintained to a certain extent in the molding, so the polymer microparticles and the functionalizing agent can be separated by simple operations such as centrifugation and dialysis.

[0115] [Closed-loop recycling method for polymer microparticles] A more specific embodiment of the above-mentioned method for recycling polymer microparticles of the present invention (sometimes referred to as a "closed-loop recycling method") will now be described. However, this embodiment is merely one 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.

[0116] In one embodiment, a closed-loop recycling method for polymers includes, in this order: (a) providing a polymer microparticle dispersion containing polymer microparticles and a dispersion medium; (b) molding the polymer microparticle dispersion to obtain a molded body; and (c) adding a solvent as an external stimulus to the molded body to swell the polymer microparticles constituting the molded body and decompose the molded body into polymer microparticles. Generally, polymer molding is performed by dissolving raw materials such as pellets in an appropriate solvent or by heating and melting the raw materials. In other words, the shape of the raw materials does not remain in the molded body. On the other hand, a closed-loop recycling method for polymers using polymer microparticles of this embodiment includes molding a polymer microparticle dispersion containing polymer microparticles to obtain a molded body composed of polymer microparticles. In the molded body composed of polymer microparticles, the particulate nature of the raw polymer microparticles is not completely lost. Therefore, the molded body can be decomposed into polymer microparticles by the simple operation of adding a solvent as an external stimulus, and the polymer microparticles can be recycled.

[0117] <(a) Step of Providing a Polymer Particle Dispersion Containing Polymer Particles and a Dispersion Medium> This step is the same as the method for producing a polymer particle dispersion from a monomer.

[0118] <(b) Step of Molding Polymer Particle Dispersion to Obtain Molded Article> This step is the same as the method for producing a molded article of polymer particles using the polymer particle dispersion.

[0119] (c) Step of adding a solvent as an external stimulus to a molded body to swell the polymer microparticles constituting the molded body and decomposing the molded body into polymer microparticles: This step is the same as the method for producing the polymer microparticles from the molded body of polymer microparticles, i.e., the step of applying an external stimulus to the first polymer microparticle molded body to decompose the first polymer microparticle molded body into second polymer microparticles.

[0120] <(d) Step of Separating Polymer Particles and Functionalizing Agent> In an embodiment in which the polymer particle dispersion (aqueous solvent dispersion of polymer particles) contains a functionalizing agent, a step (d) of separating the polymer particles and the functionalizing agent may be further carried out after step (c). The method for separating the polymer particles and the functionalizing agent is not particularly limited and can be carried out using a known method. Specific examples include centrifugation, filtration, dialysis, etc. By carrying out step (d), the polymer particles and the functionalizing agent can be recovered and reused separately. Generally, it is difficult to separate and recover a polymer from a molded product containing a functionalizing agent. However, in a closed-loop polymer recycling method using polymer particles, the particulate nature of the polymer particles is maintained to a certain extent in the molded product, so the polymer particles and the functionalizing agent can be separated by simple operations such as centrifugation and dialysis.

[0121] The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to these examples.

[0122] (1) Evaluation Method (Average Particle Diameter of Polymer Microparticles) Measurement Method for the Average Particle Diameter (nm) of Polymer Microparticles Atomic Force Microscope: AFM5200S manufactured by Hitachi High-Tech Science Corporation Image Analysis Software: NanoNavi II (NanoNavi Station, Version 5.60A, manufactured by SII NanoTechnology, Inc.) Measurement Sample Preparation Method: 100 μL of a 0.1% by mass aqueous dispersion of polymer microparticles was mixed with 100 μL of ethanol. This mixture (200 μL) was placed on the surface of approximately 20 mL of water in a glass Petri dish. After 1 minute, a glass substrate (18 mm long, 18 mm wide, Matsunami Glass Industry Co., Ltd.) washed with detergent and deionized water was brought into contact with the water surface and then slowly lifted vertically from the water surface. The glass substrate was dried at room temperature (25°C) to obtain a measurement sample. From the atomic force microscope images, the particle width when the particle height (maximum value - minimum value) of the polymer microparticles was half was analyzed using image analysis software, and the average value of the values ​​obtained by arbitrarily selecting 100 polymer microparticles was calculated.

[0123] (Shape of polymer microparticles and average Krumbein diameter) Method for measuring the shape of polymer microparticles and Krumbein diameter (maximum length in a fixed direction of a projected particle image) Atomic force microscope: AFM5200S manufactured by Hitachi High-Tech Science Corporation Image analysis software: Image J (1.53 k, Wayne Rasband, National Institutes of Health, USA) The average value of the values ​​obtained by randomly selecting 100 polymer microparticles was determined as the average Krumbein diameter. The measurement sample was obtained in the same manner as for the average particle size of the polymer microparticles described above.

[0124] (Mean hydrodynamic diameter of polymer microparticles) The mean hydrodynamic diameter of polymer microparticles (D ｈ ) (nm) was evaluated by DLS measurement using a Zetasizer Nano S (Malvern Instruments). Measurement sample preparation method: A 0.01% by mass aqueous dispersion of polymer microparticles was used. Data was averaged over 30 measurements using intensity autocorrelation with an acquisition time of 30 seconds. Scattering intensity was detected over a total scattering angle of 173°. The hydrodynamic diameter of the polymer microparticles in water was calculated using the Stokes-Einstein equation. Each sample was evaluated three times using the above procedure, and the average value of the obtained hydrodynamic diameters was determined as the average hydrodynamic diameter.

[0125] (Tensile Properties) Using a test piece punching machine (Kobunshi Keiki Co., Ltd.), three test pieces (Type 4 dumbbell shape as defined in ISO 37) were cut out from the polymer microparticle film or the polyMA bulk film. The thickness of each obtained test piece was measured at three points using a digital micrometer (MCD130-25D, Niigata Seiki Co., Ltd.), and the average value was determined as the test piece thickness. A tensile test (STB-1225L, A&D Co., Ltd.) was carried out on the three test pieces using a 50 N load cell, and stress-strain curves were obtained. The breaking strength (MPa) and breaking energy (MJ / m ３ The average values ​​were determined as the breaking strength and breaking energy of the polymer particle film or poly-MA bulk film. The tensile test was performed at a temperature of 26±0.5°C and a pulling speed of 1000 mm / min. The results are shown in Table 3 and Figures 2 and 3.

[0126] (2) Raw Materials The raw materials used in the Examples and Comparative Examples are as follows.

[0127] Monomers used in producing polymer microparticles include 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 (MEO ２ MA, Aldrich), 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.) were used.

[0128] [Production Example 1] Production of polymer particle aqueous dispersion MA-A 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 resulting solution and 34.4 parts by mass of methyl acrylate were placed in a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and inert gas inlet, and heated and stirred at 70 ° C. for 30 minutes under a nitrogen gas atmosphere. To this solution, 0.0540 parts by mass of potassium persulfate (Fujifilm Wako Pure Chemical Industries, Ltd.) (2 mM) dissolved in 5 mL of water was added, and the mixture was heated and stirred at 70 ° C. for 1 day under a nitrogen gas atmosphere and cooled to room temperature to obtain polymer particle aqueous dispersion MA-A.

[0129] [Production Example 2] Production of polymer particle aqueous dispersion MA-B 600 parts by mass of water and 51.6 parts by mass of methyl acrylate were placed in a four-neck flask equipped with a stirrer, a reflux condenser, a thermometer, and an inert gas inlet, and heated and stirred for 30 minutes at 70°C under a nitrogen gas atmosphere. To this solution, 0.0540 parts by mass of potassium persulfate (2 mM) dissolved in 5 mL of water was added, and the mixture was heated and stirred at 70°C for 1 day under a nitrogen gas atmosphere and cooled to room temperature to obtain polymer particle aqueous dispersion MA-B.

[0130] [Production Example 3] Production of polymer particle aqueous dispersion MA-C 600 parts by weight of water, 51.6 parts by weight of methyl acrylate, 0.15 parts by weight of 1,6-hexanediol dimethacrylate (FUJIFILM Wako Pure Chemical Industries, Ltd.), and 0.18 parts by weight 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 for 30 minutes at 70 ° C. under a nitrogen gas atmosphere. To this solution, 0.1080 parts by weight of potassium persulfate (2 mM) dissolved in 10 mL of water was added, and the mixture was heated and stirred at 70 ° C. for 1 day under a nitrogen gas atmosphere and cooled to room temperature to obtain a polymer particle aqueous dispersion MA-C.

[0131] [Production Example 4] Production of polymer particle aqueous dispersion MA-D 1.39 parts by mass of sodium dodecylbenzenesulfonate as a surfactant was dissolved in 200 parts by mass of water. The resulting 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-neck flask equipped with a stirrer, reflux condenser, thermometer, and inert gas inlet, and heated and stirred at 70 °C for 30 minutes under a nitrogen gas atmosphere. 0.0540 parts by mass of potassium persulfate (2 mM) dissolved in 5 mL of water was added to this solution, and the mixture was heated and stirred at 70 °C for 1 day under a nitrogen gas atmosphere and cooled to room temperature to obtain polymer particle aqueous dispersion MA-D.

[0132] [Production Examples 5 to 8] Polymer particle aqueous dispersions (polymer particle aqueous dispersions MA-E, F, G, and polymer particle aqueous dispersion MEO) were prepared in the same manner as in Production Example 4, except that the compositions shown in Table 1 were used. ２ MA) was obtained.

[0133] [Production Examples 9 to 13] Aqueous polymer particle dispersions (polymer particle aqueous dispersions MEMA, EEMA, MEA, DEGA, and NIPAm, respectively) were obtained in the same manner as in Production Example 3, except that the compositions shown in Table 1 were used. These aqueous polymer particle dispersions were placed in a mold and dried to produce polymer particle membranes.

[0134] [Production Example 14] A polymer particle aqueous dispersion MMA was obtained in the same manner as in Production Example 2, except that the composition shown in Table 1 was used. The polymer particle aqueous dispersion MMA was placed in a mold and dried to produce a polymer particle film.

[0135] [Production Example 15] Preparation of Blue Pigment Dispersion A three-neck flask was charged with 90 parts by mass of an aqueous sodium hydroxide solution (sodium hydroxide concentration: 50 mM), and 10 parts by mass of MF-5460 Blue (product name) (blue pigment defined by C.I.: PB-28, Dainichiseika Color & Chemicals Mfg. Co., Ltd.) was added, followed by shaking and mixing to obtain a blue pigment aqueous dispersion. The absence of precipitate in the aqueous dispersion was confirmed by visual inspection. [Production Example 16] Preparation of Red Pigment Dispersion A three-neck flask was charged with 90 parts by mass of an aqueous sodium hydroxide solution (sodium hydroxide concentration: 50 mM), and 10 parts by mass of MF-5160 Brown (product name) (red pigment defined by C.I.: PR-101, Dainichiseika Color & Chemicals Mfg. Co., Ltd.) was added. This mixture was subjected to ultrasonic treatment at 375 W for 10 minutes in an ice bath using an ultrasonic homogenizer (VCX-750, Ieda Trading Co., Ltd.), to obtain a red pigment aqueous dispersion. It was visually confirmed that no precipitate was present in the aqueous dispersion.

[0136] Example 1 Production and Decomposition of Molded Body of Poly-MA Particles (Production of Polymer Particle Film MA-A) The aqueous dispersion of polymer particles MA-A obtained in Production Example 1 was poured into a silicone rubber mold (length 3.5 cm, width 3.5 cm, depth 1 mm) at a concentration of 48 mg (polymer particles) / cm ２ The mixture was placed in a low-temperature incubator (LTI-2100, Tokyo Rikakikai Co., Ltd.) and dried at 25° C. for 24 hours to obtain a polymer particle film MA-A.

[0137] (Decomposition of polymer particle film MA-A) In a three-necked flask equipped with a stirrer, 0.5 parts by mass of polymer particle film MA-A was immersed in 94 parts by mass of N,N-dimethylformamide (FUJIFILM Wako Pure Chemical Industries, Ltd.), and the mixture was stirred at room temperature (25° C.) for 24 hours. Decomposition of the polymer particle film MA-A was confirmed visually.

[0138] [Examples 2 to 7, and 14] Production and decomposition of molded bodies of poly MA microparticles Production and decomposition of polymer microparticle films (polymer microparticle films MA-A, MA-B, MA-C, and MA-G) were carried out in the same manner as in Example 1, except that the polymer microparticle aqueous dispersions and the solvents used for decomposition of the polymer microparticle films were as shown in Table 2. In Examples 2 to 7, and 14, it was visually confirmed that the polymer microparticle films (polymer microparticle films MA-A, MA-B, MA-C, and MA-G) had decomposed.

[0139] [Example 8] Production and decomposition of molded body of polymer MA microparticles (Production of polymer microparticle film MA-D) A polymer microparticle film MA-D was obtained in the same manner as in Example 1, except that the polymer microparticle aqueous dispersion MA-D was used instead of the polymer microparticle aqueous dispersion MA-A.

[0140] (Decomposition of polymer particle membrane MA-D) In ​​a three-neck flask equipped with a stirrer, 0.5 parts by mass of polymer particle membrane MA-D was immersed in 84 parts by mass of an 80% by volume aqueous solution of ethanol (Fujifilm Wako Pure Chemical Industries, Ltd.) and stirred at room temperature (25°C) for 24 hours to obtain a polyMA particle dispersion. This dispersion was concentrated using a rotary evaporator to obtain an aqueous polyMA particle dispersion. The average hydrodynamic diameter of the polyMA particle was determined using the obtained aqueous polyMA particle dispersion.

[0141] Example 9: Production and decomposition of molded body of poly MA fine particles (Production of polymer fine particle film MA-D) A polymer fine particle film MA-D was obtained in the same manner as in Example 8.

[0142] (Decomposition of polymer particle membrane MA-D) In ​​a three-necked flask equipped with a stirrer, 0.5 parts by mass of polymer particle 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 particle dispersion. This dispersion was purified in deionized water using a dialysis membrane to obtain an aqueous polyMA particle dispersion. The average hydrodynamic diameter of the polyMA particle was determined using the obtained aqueous polyMA particle dispersion.

[0143] Example 10 Recycling of Poly MA Particles (Production of Polymer Particle Film MA-E (Cycle 0)) A polymer particle film MA-E (Cycle 0) was obtained in the same manner as in Example 1, except that the polymer particle aqueous dispersion MA-E was used instead of the polymer particle aqueous dispersion MA-A. The tensile properties of the obtained polymer particle film MA-E (Cycle 0) were evaluated. The results are shown in Table 3 and FIG. 2.

[0144] (Decomposition of polymer particle membrane MA-E (cycle 0)) The polymer particle membrane MA-E (cycle 0) was decomposed using the same procedure as in Example 1. The obtained polyMA particle dispersion was purified in deionized water using a dialysis membrane to obtain an aqueous dispersion of polyMA particles. The average particle size of the polyMA particles was determined using the obtained aqueous dispersion of polyMA particles. In addition, the Krumbine diameter of the polyMA particles was also measured. The results are shown in Figure 1 as polymer particles after decomposition.

[0145] A portion of the resulting aqueous dispersion of polyMA microparticles was purified by centrifugation. 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. This 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 in producing the polymer microparticle film MA-E (cycle 0). The results are shown in Table 2.

[0146] (Production of polymer particle film MA-E (cycle 1)) A polymer particle film MA-E (cycle 1) was produced in the same manner as in Example 1, except that the polymer particle aqueous dispersion MA-A obtained in Production Example 1 was replaced with a polymer MA particle aqueous dispersion obtained by decomposing the polymer particle film MA-E (cycle 0). The tensile properties of the resulting polymer particle film MA-E (cycle 1) were evaluated. The results are shown in Table 3 and FIG. 2.

[0147] Example 11: Production and decomposition of molded body of polyMA microparticles Production and decomposition of polymer microparticle membrane MA-E were carried out in the same manner as in Example 1, except that the solvents used for the polymer microparticle aqueous dispersion and the decomposition of the polymer microparticle membrane were as shown in Table 2. The obtained polyMA microparticle dispersion was concentrated using a rotary evaporator to obtain an aqueous polyMA microparticle dispersion. The average particle size of the polyMA microparticles was determined using the obtained aqueous polyMA microparticle dispersion.

[0148] A portion of the resulting aqueous dispersion of polyMA microparticles was purified by centrifugation. 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. This 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 in producing the polymer microparticle film MA-E. The results are shown in Table 2.

[0149] Example 12: Production and decomposition of molded body of polyMA microparticles Production and decomposition of polymer microparticle membrane MA-F were carried out in the same manner as in Example 1, except that the solvents used for the polymer microparticle aqueous dispersion and the decomposition of the polymer microparticle membrane were as shown in Table 2. The obtained polyMA microparticle dispersion was concentrated using a rotary evaporator to obtain an aqueous polyMA microparticle dispersion. The average hydrodynamic diameter of the polyMA microparticles was determined using the obtained aqueous polyMA microparticle dispersion.

[0150] Example 13: Production and decomposition of molded bodies of polyMA microparticles. Polymer microparticle membrane MA-F was produced and decomposed in the same manner as in Example 1, except that the solvents used for the aqueous polymer microparticle dispersion and the decomposition of the polymer microparticle membrane were as shown in Table 2. The resulting polyMA microparticle dispersion was purified in deionized water using a dialysis membrane to obtain an aqueous polyMA microparticle dispersion. The average hydrodynamic diameter of the polyMA microparticles was determined using the resulting aqueous polyMA microparticle dispersion.

[0151] [Example 15] PolyMEO ２ Production and decomposition of MA particle moldings (polymer particle membrane MEO ２ Preparation of MA) Aqueous dispersion of polymer particles MEO obtained in Preparation Example 8 ２MA was placed in a silicone rubber mold (3.5 cm long, 3.5 cm wide, 1 mm deep) at 48 mg (polymer fine particles) / cm ２ The mixture was placed in a low-temperature incubator (LTI-2100, Tokyo Rikakikai Co., Ltd.) and dried at 25°C for 24 hours to form a polymer particle film MEO. ２ I got an MA.

[0152] (Polymer particle film MEO ２ Decomposition of MA) In a three-neck flask equipped with a stirrer, the polymer particle membrane MEO was dissolved in deionized water. ２ The MA was immersed in the solution and stirred at 10°C for 24 hours to form a polymer particle aqueous dispersion MEO. ２ MA was obtained. The obtained polyMEO ２ Using MA fine particle aqueous dispersion, polyMEO ２ The average culmbein diameter of the MA microparticles was determined.

[0153] Example 16 Recycling of PolyMA Microparticles (Production of Blue Polymer Microparticle Film MA-E (Cycle 0)) In a three-neck flask equipped with a stirrer, the polymer microparticle aqueous dispersion MA-E obtained in Production Example 5 and the blue pigment aqueous dispersion obtained in Production Example 15 were mixed. The resulting mixture (MF-5460 Blue: 10% by mass) was poured into a silicone rubber mold (length 3.5 cm, width 3.5 cm, depth 1 mm) at a concentration of 48 mg (polymer microparticles) / cm. ２ The mixture was placed in a low-temperature incubator (LTI-2100, Tokyo Rikakikai Co., Ltd.) at 25°C for 24 hours to obtain a blue polymer particle film MA-E (cycle 0). The tensile properties of the obtained blue polymer particle film MA-E (cycle 0) were evaluated. The results are shown in Table 3 and FIG. 3.

[0154] (Decomposition of blue polymer particle film MA-E (Cycle 0)) In a three-neck flask equipped with a stirrer, 0.5 parts by mass of blue polymer particle film MA-E (Cycle 0) was immersed in 84 parts by mass of an 80% by volume aqueous solution of ethanol, and the mixture was stirred at room temperature (25°C) for 24 hours to obtain a polyMA particle dispersion containing a blue pigment. This dispersion was concentrated using a rotary evaporator to obtain an aqueous polyMA particle dispersion containing a blue pigment.

[0155] (Separation of PolyMA Microparticles and Blue Pigment) The resulting aqueous dispersion of polyMA microparticles containing the blue pigment was centrifuged to recover the supernatant, yielding a polyMA microparticle dispersion. The average hydrodynamic diameter of the polyMA microparticles was determined using the resulting dispersion. The residue was then redispersed in deionized water to obtain a blue pigment dispersion.

[0156] A portion of the resulting 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. This 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 in producing the blue polymer microparticle film MA-E (cycle 0). The results are shown in Table 2.

[0157] (Production of Polymer Particle Film MA-E (Cycle 1)) A polymer particle film MA-E (Cycle 1) was produced in the same manner as in Example 1, except that the polymer particle aqueous dispersion MA-A obtained in Production Example 1 was replaced with a polymer MA particle dispersion obtained by separating the polymer particle from the blue pigment. The tensile properties of the resulting polymer particle film MA-E (Cycle 1) were evaluated. The results are shown in Table 3 and FIG. 3.

[0158] [Example 17] Production and decomposition of molded body of poly MA microparticles (Production of red polymer microparticle film MA-E) A red polymer microparticle film MA-E was obtained in the same manner as in Example 16, except that the red pigment aqueous dispersion obtained in Production Example 16 was used instead of the blue pigment aqueous dispersion obtained in Production Example 15.

[0159] (Decomposition of Red Polymer Particle Film MA-E) A red pigment-containing aqueous dispersion of polymer MA particles was obtained in the same manner as in Example 16, except that the red polymer particle film MA-E was used instead of the blue polymer particle film MA-E.

[0160] (Separation of PolyMA Microparticles and Red Pigment) The resulting aqueous dispersion of polyMA microparticles containing the red pigment was centrifuged to recover the supernatant, yielding a polyMA microparticle dispersion. The average hydrodynamic diameter of the polyMA microparticles was determined using the resulting dispersion. The residue was then redispersed in deionized water to obtain a red pigment dispersion.

[0161] A portion of the resulting 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. This 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 in producing the red polymer microparticle film MA-E. The results are shown in Table 2.

[0162] Example 18: Production of Molded Articles of PolyMMA Microparticles (Production of Polymer Microparticle Film MMA) The polymer microparticle aqueous dispersion MMA obtained in Production Example 14 was freeze-dried to obtain a powder of polymer microparticle MMA. 0.80 g of the obtained powder was placed in a mold (Type 4 dumbbell shape as defined in ISO 37) and heat-pressed (small heat press HC300-01) for 2 hours at 120°C and 20 MPa (memory pressure) to obtain a polymer microparticle film MMA. The obtained polymer microparticle film MMA was a molded article formed without the use of any other material to bond the polymer microparticles together, and it is believed that it can be decomposed into polyMMA microparticles by the application of an external stimulus. More specifically, it is believed that the addition of an appropriate solvent as an external stimulus swells the polyMMA microparticles that make up the molded article, allowing the molded article to be decomposed into polyMMA microparticles.

[0163] Reference Example 1 (Production of PolyMA Bulk Membrane) A mixture of 3.44 parts by mass (40 mmol) of methyl acrylate (Fujifilm Wako Pure Chemical Industries, Ltd.), 0.01 parts by mass (0.04 mmol) of 1,6-hexanediol dimethacrylate, and 0.034 parts by mass of Irgacure™ 500 (Ciba Specialty Chemicals Co., Ltd.) was poured into a mold prepared by laminating a release sheet (PET25G, Lintec Corporation) and a glass plate, in that order, on both sides of a silicone rubber frame. The mixture was then photopolymerized by irradiating one of the glass plates with ultraviolet light for 20 minutes using an ultra-high pressure UV lamp (USH-250SC2, Ushio Inc.). The resulting photopolymer was purified by swelling it in dichloromethane and then deswelling it in methanol, a process repeated twice. The purified photopolymerized material was dried at 25°C for 24 hours, and then dried for 12 hours at 25°C under reduced pressure using a freeze dryer (FDU-1200, Tokyo Rikakikai Co., Ltd.) to obtain a polyMA bulk membrane. The tensile properties of the resulting polyMA bulk membrane were evaluated. The results are shown in Table 3.

[0164]

[0165]

[0166]

[0167]

[0168] Evaluation of the tensile properties of the polymer particle film MA-E (cycle 0) produced in Example 10 and the polyMA bulk film produced in Reference Example 1 showed that, when compared at the same crosslinking degree, the polymer particle film had higher breaking strength than the bulk film. The evaluation of the tensile properties of Examples 10 and 16 showed that, even after undergoing the molding and decomposition steps, a polymer particle film (cycle 1) could be produced that had tensile properties equivalent to those of a polymer particle film (cycle 0) produced from unused polymer particles. Examples 16 and 17 showed that it was possible to separate and recover pigment and polymer particles from a pigment-containing polymer particle film.

[0169] By using polymer fine particles, it is possible to provide a polymer recycling method that is applicable to a variety of polymers.

Claims

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

2. The method of claim 1 , wherein the method of applying the external stimulus is swelling the polymer microparticles with a solvent.

3. The solvent is 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 aryl groups represented by the formula R １ COOR ２ (In the formula, R １ is hydrogen or an alkyl group having 1 to 3 carbon atoms; R ２ and R 1 is an alkyl group having 1 to 3 carbon atoms.

4. The method according to any one of claims 1 to 3, wherein the polymer constituting the polymeric fine particles is a (meth)acrylate-based polymer or a poly(meth)acrylamide-based polymer.

5. A polymer microparticle molding obtained by molding polymer microparticles, A polymer microparticle molding, wherein 80 mol % or more of the monomers constituting the polymer are at least one monomer selected from the group consisting of polyalkylene glycol (meth)acrylates, alkoxy group-containing methacrylates, alkoxy group-containing acrylates having two or more carbon atoms, (meth)acrylamides, and derivatives thereof.

6. The polymer microparticle molding according to claim 5, which does not contain a structure derived from a rotaxane.

7. 1. A method for recycling polymeric microparticles, the method comprising: (A) A step of applying an external stimulus to a first polymer microparticle molding obtained by molding first polymer microparticles, thereby decomposing the first polymer microparticle molding into second polymer microparticles. The method includes:

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

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

10. 9. The recycling method according to claim 7, wherein a ratio of a total mass of the second polymer particles obtained after the decomposition to a total mass of the first polymer particles used in the molding is 0.95 or more.

11. The method further comprises: (B) A step of producing a second polymer particle molded product by molding the second polymer particle obtained in the step (A). The recycling method according to claim 7 or 8, comprising:

12. The recycling method according to claim 11, wherein the molding in the step (B) is carried out using a second polymer fine particle dispersion in which the second polymer fine particles are dispersed in a dispersion medium.

13. The recycling method according to claim 11, further comprising: performing step (A) again using the second polymer microparticle molding obtained in step (B) as the first polymer microparticle molding in step (A).

14. The recycling method according to claim 9, wherein the first polymeric particulate molding further comprises a functionalizing agent.

15. 15. The method of claim 14, further comprising the step of separating the second polymeric particulate and the functionalizing agent.