JP2013203938A - Resin particle, method for producing the same and method for manufacturing porous resin molded product using the resin particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide resin particles that hardly dissolve in a vinyl monomer, readily dissolve in an organic solvent and are excellent in monodispersity, and a method for producing the same.SOLUTION: Resin particles comprise a non-crosslinked polymer, have a mass-average molecular weight of 200,000-600,000 and have a coefficient of variation of the particle size of ≤15%, wherein the non-crosslinked polymer comprises 80-95 mass% structural unit derived from an alkyl (meth)acrylate wherein an alkyl group has 3 or less carbons (first monomer) and 5-20 mass% structural unit derived from an alkyl (meth)acrylate wherein an alkyl group has 4-12 carbons (second monomer). A method for producing the resin particles comprises steps of: producing seed particles by carrying out emulsion polymerization of the first monomer in the presence of a prescribed amount of a chain transfer agent; allowing the seed particles to absorb the first monomer and subsequently polymerizing the same in the presence of a prescribed amount of the chain transfer agent so as to enlarge the seed particles; and allowing the seed particles to absorb a non-crosslinkable monomer mixture comprising 80-95 mass% of the first monomer and 5-20 mass% of the second monomer and subsequently polymerizing the same in the presence of a water-soluble polymerization inhibitor.

Description

  The present invention relates to a resin particle and a method for producing the same, and more particularly to a monodispersed resin particle (property having a particle size distribution close to monodisperse) suitable as a pore former and a method for producing the same. Moreover, this invention relates also to the manufacturing method which manufactures a porous resin molding using the said resin particle as a pore making material.

  Resin particles include, for example, paint additives (matting agents, design imparting agents for imparting fine irregularities to the coating surface, etc.), ink additives (matting agents, etc.), adhesives, etc. Main component or additive, additive for artificial marble (low shrinkage agent, etc.), paper treatment agent, packing material for cosmetics (packing material for improving slipperiness), column packing material for chromatography, electrostatic charge It is used in applications such as toner additives used for image development, anti-blocking agents for films, and light diffusing agents for light diffusers (such as light diffusing films).

  Further, by imparting monodispersity to the resin particles, various physical properties (optical properties and uniformity) of the resin particles can be improved. As one method for producing monodisperse resin particles, a seed polymerization method is generally known. The seed polymerization method is a method in which a resin particle (referred to as “seed particle”) prepared in advance is absorbed with a monomer (usually used in the state of an emulsion) and polymerized in an aqueous medium. is there.

  Patent Document 1 describes a method for producing resin particles of about 0.1 to 500 μm by seed polymerization. For example, in Example 9 of Patent Document 1, 1.4 parts by mass of monodisperse polymethyl methacrylate particles having a number average particle size of 0.12 μm are used as seed particles (seed particles), and 100 parts by mass of 2-ethylhexyl acrylate is added. It is described that a dispersion containing monodisperse polymethyl methacrylate particles is brought into contact with a dispersion and then polymerized to obtain monodisperse polymer particles having a number average particle diameter of 0.51 μm and a standard deviation value of 3%. ing.

  On the other hand, conventionally, various methods for producing a porous resin molded body are known. For example, Patent Document 2 discloses that a granular material obtained by soaking carboxylated polyoxyethylene alkyl ether sodium at a high concentration in the vicinity of the surface of 100 parts by mass of an olefin polymer granular material is added at room temperature by a press molding machine. A method for producing a porous olefin-based polymer sintered body that is sintered in a sintering furnace after being pressed is described.

  However, in the above method, the shape and diameter of the pores (voids) in the obtained porous olefin polymer sintered body depend on the pressing conditions of the press molding machine and the sintering conditions of the sintering furnace, and are desired. There was a problem that a porous olefin-based polymer sintered body having a pore shape and a pore diameter of 5 mm could not be obtained.

  Various methods for producing porous ceramic molded bodies are also known. For example, Patent Document 3 describes a method for producing a porous ceramic structure by firing a molded body containing ceramic particles and resin particles that serve as a pore-forming agent, and burning the resin particles. . In this method, when a resin is used as a base material instead of ceramics, not only the resin particles used as a pore-forming agent but also the resin used as the base material disappears when fired. Therefore, it is impossible to divert such a method for producing a porous ceramic structure to the production of a porous resin molded body.

  In addition, as another method for producing a porous resin molded body, a step of filling a plurality of resin particles as a pore-forming agent into a mold, and heating the mold to fuse the resin particles together. From the polymer of the vinyl monomer by adding the vinyl monomer and the polymerization initiator into the mold, and polymerizing the vinyl monomer. And a method of removing the resin particles from the resin molded body by dissolving the resin particles in an organic solvent (hereinafter referred to as “resin dissolution removal method porosity”). Has been proposed "."

  In this method, a porous olefin-based resin molded article having a desired pore shape and pore diameter is obtained by using resin particles having a desired pore shape and particle diameter corresponding to the pore diameter as a pore-forming agent. There is an advantage that can be obtained. In this method, it is possible to form a porous structure with a material (resin) that is relatively weak against heat.

Japanese Examined Patent Publication No. 6-74285 Japanese Patent Laid-Open No. 7-300538 JP 2007-45686 A

  However, in the method for producing a porous resin molded article of the above resin dissolution removal method, part of the resin particles are dissolved in the vinyl monomer before the polymerization of the vinyl monomer, and the particle shape cannot be maintained. There is a problem that the function as a pore-forming agent may be lost. In that case, if a part of the resin particles loses the function as a pore-forming agent, a good porous resin molded product having a desired pore shape and pore diameter cannot be obtained. Moreover, in the manufacturing method of the porous resin molding of the said resin dissolution removal system, since resin particle | grains do not fully melt | dissolve in an organic solvent, there exists a problem that resin particle | grains cannot fully be removed. If the resin particles cannot be sufficiently removed, a good porous resin molded product having a desired pore shape and pore diameter cannot be obtained. According to the study by the present inventor, it has been found that these problems are because the mass average molecular weight is out of a predetermined range (200,000 to 600,000).

  Since the resin particles of Patent Document 1 described above have a mass average molecular weight that is not adjusted within the predetermined range, the above-described problems can be avoided when used in the method for producing a resin-removed porous resin molded body. I can't. Moreover, although the resin particle of patent document 1 mentioned above does not describe the mass average molecular weight, the proportion of 2-ethylhexyl acrylate in the total monomers used for the production of the resin particles is as high as 98.6 parts by mass. Since it is high, it is estimated that the mass average molecular weight is smaller than a predetermined range (200,000 to 600,000).

  The present invention has been made in view of the above-described conventional problems, and its purpose is to be hardly soluble in a vinyl monomer used in a method for producing a resin-removable porous resin molded body, while a resin. An object of the present invention is to provide resin particles that are easily dissolved in an organic solvent used in a method for manufacturing a porous resin molded article of a dissolution removal method and the like and excellent in monodispersibility, and a method for manufacturing the resin particles. Another object of the present invention is to provide a method for producing a porous resin molded body that can obtain a porous resin molded body having a desired pore shape and pore diameter and having a uniform pore diameter. .

  In order to solve the above problems, the resin particles of the present invention have a structural unit of 80 to 95% by mass derived from alkyl (meth) acrylate having an alkyl group having 3 or less carbon atoms, and the alkyl group has a carbon number of It consists of a non-crosslinked polymer containing 5 to 20% by mass of a structural unit derived from an alkyl (meth) acrylate that is 4 or more and 12 or less, has a mass average molecular weight in the range of 200,000 to 600,000, and has a particle size of The coefficient of variation is 15% or less.

  The resin particles are made of a non-crosslinked polymer. The resin particles have a mass average molecular weight of 600,000 or less. In addition to the structural unit derived from an alkyl (meth) acrylate having 3 or less carbon atoms in the alkyl group, the resin particle has an alkyl (meth) acrylate having 4 to 12 carbon atoms in the alkyl group. Since 5 mass% or more of the structural unit derived from is contained, the mass average molecular weight is suppressed to be moderately low. Due to these synergistic effects, the resin particles are easily dissolved in an organic solvent used in a method for producing a porous resin molded body by dissolving and removing resin particles. It is suitable as a resin particle (resin particle for pore-forming agent) used as a pore-forming agent in a production method or the like.

  Furthermore, the resin particles have a mass average molecular weight of 200,000 or more. Moreover, since the content rate of the structural unit derived from the alkyl group (meth) acrylate whose carbon number of an alkyl group is 4 or more and 12 or less is 20 mass% or less, the said resin particle is not too low in a mass average molecular weight. It is adjusted to an appropriate range. Due to these synergistic effects, the resin particles are difficult to dissolve in the vinyl-based monomer used in the method for producing a resin-dissolved removal type porous resin molded article, and the resin-dissolved removal-type porous resin molded article. It is suitable as a resin particle (resin particle for pore-forming agent) used as a pore-forming agent in a production method or the like.

  In addition, the resin particles have a coefficient of variation in particle diameter of 15% or less. In addition to the structural unit derived from an alkyl (meth) acrylate having 3 or less carbon atoms in the alkyl group, the resin particles have 4 to 12 carbon atoms in the alkyl group having lower water solubility ( Since the structural unit derived from alkyl (meth) acrylate contains 5% by mass or more, when producing resin particles by the seed polymerization method, by suppressing the absorption rate of the monomer to the seed particles, The simultaneous absorption of the monomer and the coalescence of the seed particles swollen by absorbing the monomer can be suppressed, and as a result, the generation of coarse particles can be suppressed. Further, since the resin particles have a content of structural units derived from alkyl (meth) acrylate having an alkyl group with 4 or more and 12 or less carbon atoms, the resin particles are produced by seed polymerization. In this case, the monomer can be sufficiently absorbed by the seed particles, and the monomer can be prevented from being independently polymerized at a position away from the seed particles to generate fine particles. Due to these synergistic effects, the resin particles are excellent in monodispersity, and are used as a pore-forming agent in a method for producing a resin-removable porous resin molding (resin particles for pore-forming agent). ).

  In the present specification, “(meth) acryl” means acryl or methacryl. In the present specification, the “mass average molecular weight” is a polystyrene-reduced mass average molecular weight measured using gel permeation chromatography, for example, measured by the measurement method described in the “Example” section below. It shall mean the weight average molecular weight determined. In this specification, “particle diameter coefficient of variation” means the standard deviation in the volume-based particle size distribution (particle size distribution) measured by the Coulter method divided by the arithmetic average diameter in the volume-based particle size distribution. For example, the coefficient of variation of the particle diameter measured by the measurement method described in the section of [Example] in the latter part.

  In order to solve the above-mentioned problem, the method for producing resin particles of the present invention comprises an alkyl (meth) acrylate having an alkyl group having 3 or less carbon atoms, based on 100 parts by mass of the alkyl (meth) acrylate. Including a seed particle production step of producing seed particles comprising a non-crosslinked polymer by emulsion polymerization in the presence of 0.5 to 3 parts by mass of a chain transfer agent, and after the seed particle production step, After the seed particles absorb the alkyl (meth) acrylate having 3 or less carbon atoms, the chain transfer agent is 0.5 to 3 parts by mass with respect to 100 parts by mass of the absorbed alkyl (meth) acrylate. The seed particles are enlarged by polymerizing the alkyl (meth) acrylate in the presence of, and at least one seed particle enlargement step to obtain enlarged seed particles made of a non-crosslinked polymer, and Previous After the seed particle enlargement step, the alkyl group has 80 to 95% by mass of an alkyl (meth) acrylate monomer having 3 or less carbon atoms, and the alkyl group has 4 to 12 carbon atoms (meth). The non-crosslinkable monomer mixture containing 5 to 20% by mass of alkyl acrylate is absorbed in the enlarged seed particles, and then the non-crosslinkable monomer mixture is present in the presence of a water-soluble polymerization inhibitor. It is characterized by including a resin particle production step of producing a non-crosslinked resin particle by polymerizing.

  According to the above method, non-crosslinked resin particles can be obtained. Moreover, according to the said method, in addition to the alkyl (meth) acrylate whose carbon number of an alkyl group is 3 or less, the said non-crosslinkable monomer mixture has 4 or more and 12 or less carbon atoms of an alkyl group. Since the alkyl (meth) acrylate is contained in an amount of 5% by mass or more, the mass average molecular weight of the resin particles is kept low. Moreover, according to the said method, 0.5 mass part or more with respect to 100 mass parts of alkyl (meth) acrylates whose carbon number of an alkyl group is 3 or less in both a seed particle manufacturing process and a seed particle enlargement process. Since the polymerization is carried out in the presence of the chain transfer agent, the mass average molecular weight of the resin particles is moderately low. Due to these synergistic effects, the resin particles obtained by the above method are easily dissolved in an organic solvent used in a method for producing a porous resin molded body by dissolving and removing resin particles, and the resin dissolution and removal method is porous. It is suitable as a resin particle (resin particle for pore-forming agent) used as a pore-forming agent in a method for producing a resin molded body.

  Furthermore, according to the above method, since the content of alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms in the non-crosslinkable monomer mixture is 20% by mass or less, the mass average The molecular weight is adjusted to an appropriate range without being too low. Moreover, according to the said method, in both a seed particle manufacturing process and a seed particle enlargement process, the amount of chain transfer agents used is 100 parts by mass of alkyl (meth) acrylate having 3 or less carbon atoms in the alkyl group. Therefore, the mass average molecular weight is adjusted to an appropriate range without being too low. Due to these synergistic effects, the resin particles obtained by the above method are difficult to dissolve in the vinyl monomer used in the method for producing a resin-removed / removable porous resin molded article, and the resin-dissolved / removable porous It is suitable as a resin particle (resin particle for pore-forming agent) used as a pore-forming agent in a method for producing a resin molded body.

  In addition, according to the above method, the non-crosslinkable monomer mixture has an alkyl group having a carbon number of 3 or less and an alkyl group having a lower water solubility, in addition to the alkyl (meth) acrylate. Since it contains 5% by mass or more of alkyl (meth) acrylate that is 4 or more and 12 or less, in the resin particle production process, by suppressing the absorption rate of the monomer to the seed particles, It is possible to suppress the simultaneous generation of absorption and coalescence of the seed particles swollen by absorbing the monomer, and as a result, the generation of coarse particles can be suppressed. Further, according to the above method, since the content of alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms in the non-crosslinkable monomer mixture is 20% by mass or less, seed particles It is possible to sufficiently absorb the non-crosslinkable monomer mixture and to polymerize the non-crosslinkable monomer mixture independently at a position away from the seed particles to form fine particles. Further, according to the above method, since the polymerization of the non-crosslinkable monomer mixture is performed in the presence of a water-soluble polymerization inhibitor, the non-crosslinkable monomer mixture is uniquely polymerized in the aqueous phase. Can be suppressed. Therefore, the generation of fine particles due to polymerization of the non-crosslinkable monomer mixture can be suppressed, and the polymer of the non-crosslinkable monomer mixture connects the resin particles (primary particles) to form secondary particles. It can also be suppressed. Due to these synergistic effects, the resin particles obtained by the above method have excellent monodispersibility, and are used as a pore-forming agent in a method for producing a resin-removed porous resin molded body (pore-forming (Resin particles for agent).

  The method for producing a porous resin molded body of the present invention comprises a step of filling a plurality of resin particles of the present invention as a pore-forming agent in a mold and heating the mold to fuse the resin particles together. Attaching the resin particles to each other and adding a vinyl monomer and a polymerization initiator that do not dissolve the resin particles in the mold, and polymerizing the vinyl monomer, A step of obtaining a resin molded body comprising the vinyl monomer polymer, and dissolving the resin particles in an organic solvent which dissolves the resin particles but does not dissolve the vinyl monomer polymer. And a step of removing the resin particles from the resin molded body.

  According to the above method, since the resin particles of the present invention that are easily dissolved in an organic solvent are used as a pore-forming agent, the resin particles can be sufficiently removed by dissolution in an organic solvent, and a desired pore shape and pore diameter can be obtained. It is possible to obtain a good porous resin molded body having the same. In addition, according to the above method, since the resin particles of the present invention that are difficult to dissolve in the vinyl monomer are used as a pore-forming agent, a part of the resin particles are vinyl monomer before polymerization of the vinyl monomer. Thus, it is possible to avoid the problem that the particle shape cannot be maintained due to dissolution in the resin, and a good porous resin molded article having a desired pore shape and pore diameter can be obtained. Furthermore, according to the above method, since the resin particles of the present invention excellent in monodispersibility are used as a pore-forming agent, a porous resin molded product having a uniform pore diameter can be obtained.

  As described above, according to the present invention, it is difficult to dissolve in a vinyl-based monomer used in a method for producing a resin-dissolved removal type porous resin molded body, while a resin-dissolved removal type porous resin molded body. It is possible to provide resin particles that are easily soluble in an organic solvent used in the production method and the like and excellent in monodispersibility, and a production method thereof. Therefore, the resin particles and the production method thereof according to the present invention are resin particles (resin particles for pore-forming agent) used as a pore-forming agent in a method for producing a resin-removable porous resin molded body and the production method thereof. Is preferred.

  In addition, as described above, according to the present invention, there is provided a method for producing a porous resin molded body capable of obtaining a porous resin molded body having a desired pore shape and pore diameter and having a uniform pore diameter. Can be provided.

  The present invention will be described in detail below.

[Resin particles]
The resin particles of the present invention have a structural unit of 80 to 95% by mass derived from an alkyl (meth) acrylate having an alkyl group with 3 or less carbon atoms, and an alkyl group with 4 to 12 carbon atoms (meth). It consists of a non-crosslinked polymer containing 5 to 20% by mass of a structural unit derived from an alkyl acrylate, has a mass average molecular weight in the range of 200,000 to 600,000, and a coefficient of variation in particle diameter of 15% or less. Since the resin particles of the present invention are non-crosslinked particles, they are easily dissolved in an organic solvent used in the method for producing a porous resin molded article by dissolving and removing the resin particles.

  In addition to the structural unit derived from an alkyl (meth) acrylate having 3 or less carbon atoms in the alkyl group, the resin particles of the present invention have an alkyl (meth) acrylate having 4 to 12 carbon atoms in the alkyl group. Compared to resin particles consisting only of structural units derived from alkyl (meth) acrylate having 3 or less carbon atoms in the alkyl group because it contains derived structural units (particularly resin particles by seed polymerization method). The mass average molecular weight is kept low). In addition to the structural unit derived from alkyl (meth) acrylate having 3 or less carbon atoms in the alkyl group having relatively high water solubility, the resin particles of the present invention can also be obtained from carbon having an alkyl group having relatively low water solubility. Since it contains a structural unit derived from an alkyl (meth) acrylate having a number of 4 or more and 12 or less, the alkyl group consists only of a structural unit derived from an alkyl (meth) acrylate having a carbon number of 3 or less. Compared to resin particles, the rate of monomer absorption into seed particles can be suppressed during production by seed polymerization. In addition, the resin particle which consists only of the structural unit derived from the alkyl (meth) acrylate whose carbon number of an alkyl group is 3 or less is a seed particle, when manufacturing the resin particle of comparatively large particle diameter by a seed polymerization method. The absorption rate of the monomer to the particle is too high, so the absorption of the monomer into the seed particles and the coalescence of the seed particles swollen by absorbing the monomer occur simultaneously, increasing the coarse particles As a result, the monodispersity of the resulting resin particles becomes poor. As a result, it becomes difficult to produce the resin particles of the present invention having a coefficient of variation in particle diameter of 15% or less.

  Examples of the alkyl (meth) acrylate having 4 to 12 carbon atoms in the alkyl group include, for example, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, and n-acrylate. An acrylic acid ester having an alkyl group having 4 to 12 carbon atoms, such as dodecyl (lauryl acrylate); n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, Examples thereof include methacrylic acid esters having 4 to 12 carbon atoms in the alkyl group, such as n-octyl methacrylate and n-dodecyl methacrylate (lauryl methacrylate). These compounds may be used alone or in combination of two or more.

  The alkyl (meth) acrylate having 4 to 12 carbon atoms in the alkyl group is more preferably an alkyl (meth) acrylate having 4 to 10 carbon atoms in the alkyl group. Thereby, when manufacturing resin particles by a seed polymerization method or the like, aggregation of resin particles can be further suppressed by further suppressing an increase in the viscosity of the reaction solution. Therefore, it is possible to realize resin particles having further excellent monodispersibility. In the case of using an alkyl (meth) acrylate having a carbon number of 13 or more (for example, 18) instead of an alkyl (meth) acrylate having 4 to 12 carbon atoms in the alkyl group, When the resin particles are produced by the seed polymerization method, the viscosity of the reaction liquid is increased and the resin particles are aggregated, so that the monodispersity of the obtained resin particles is deteriorated. Therefore, the resin particles of the present invention having a particle diameter variation coefficient of 15% or less are difficult to produce.

  In the non-crosslinked polymer constituting the resin particle of the present invention, the content of the structural unit derived from the alkyl (meth) acrylate having an alkyl group with 4 or more and 12 or less carbon atoms is in the range of 5 to 20% by mass. It is.

  When the content of the structural unit derived from the alkyl (meth) acrylate having 4 to 12 carbon atoms in the non-crosslinked polymer constituting the resin particle of the present invention is less than 5% by mass, the alkyl group Since the effect of suppressing the mass average molecular weight of the resin particles by the structural unit derived from the alkyl (meth) acrylate having 4 to 12 carbon atoms is insufficient, the mass average molecular weight of the resin particles is increased. Therefore, the resin particles of the present invention having a mass average molecular weight of 600,000 or less are difficult to produce. Further, in the non-crosslinked polymer constituting the resin particle of the present invention, when the content of the structural unit derived from alkyl (meth) acrylate having 4 to 12 carbon atoms in the alkyl group is less than 5% by mass, When producing resin particles by the seed polymerization method, the absorption rate of the monomer into the seed particles is too high, so the absorption of the monomer into the seed particles and the seed particles swollen by absorbing the monomer The coalescence between them occurs at the same time, coarse particles frequently occur, and the monodispersity of the resulting resin particles becomes worse. As a result, it becomes difficult to produce the resin particles of the present invention having a particle diameter variation coefficient of 15% or less.

  On the other hand, in the non-crosslinked polymer constituting the resin particles of the present invention, when the content of structural units derived from alkyl (meth) acrylate having an alkyl group with 4 or more and 12 or less carbon atoms is greater than 20% by mass, The mass average molecular weight of the resin particles becomes too small. Therefore, the resin particles of the present invention having a mass average molecular weight of 200,000 or more are difficult to produce. Further, in the non-crosslinked polymer constituting the resin particle of the present invention, when the content of the structural unit derived from the alkyl (meth) acrylate having 4 to 12 carbon atoms in the alkyl group is more than 20% by mass, When resin particles are produced by the seed polymerization method, the monomers are not absorbed well into the seed particles, and the monomers are polymerized independently (in an aqueous medium) at a position away from the seed particles (as desired). Resin particle having a particle size significantly smaller than the particle size of the resin particle), and the monodispersibility of the resulting resin particle is deteriorated. As a result, it becomes difficult to produce the resin particles of the present invention having a particle diameter variation coefficient of 15% or less.

  In the non-crosslinked polymer constituting the resin particle of the present invention, the content of the structural unit derived from the alkyl (meth) acrylate having an alkyl group with 4 or more and 12 or less carbon atoms is in the range of 5 to 10% by mass. It is more preferable that Thus, when resin particles are produced by the seed polymerization method, the generation of coarse particles and fine particles can be further suppressed, so that resin particles having further excellent monodispersibility can be realized.

  Examples of the alkyl (meth) acrylate having 3 or less carbon atoms in the alkyl group include alkyl groups having 1 to 3 carbon atoms such as methyl acrylate, ethyl acrylate, n-propyl acrylate, and the like. And methacrylic acid esters in which the alkyl group has 1 to 3 carbon atoms, such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, and the like. These compounds may be used alone or in combination of two or more.

  In the non-crosslinked polymer constituting the resin particle of the present invention, the content of the structural unit derived from alkyl (meth) acrylate having 3 or less carbon atoms in the alkyl group is in the range of 80 to 95% by mass. . In the non-crosslinked polymer constituting the resin particle of the present invention, the content of the structural unit derived from the alkyl (meth) acrylate having 3 or less carbon atoms in the alkyl group is in the range of 90 to 95% by mass. It is more preferable. Thus, when resin particles are produced by the seed polymerization method, the generation of coarse particles and fine particles can be further suppressed, so that resin particles having further excellent monodispersibility can be realized.

  The non-crosslinked polymer constituting the resin particle of the present invention has a structural unit derived from an alkyl (meth) acrylate having an alkyl group having 3 or less carbon atoms, and an alkyl group having 4 to 12 carbon atoms ( It may consist of only structural units derived from (meth) alkyl acrylate, and includes structural units derived from other non-crosslinkable (monofunctional) vinyl monomers in addition to these structural units. Also good.

  The other non-crosslinkable vinyl monomer is not particularly limited as long as it is a compound having one ethylenically unsaturated bond other than alkyl (meth) acrylate. Examples of the other non-crosslinkable vinyl monomers include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and fumaric acid; 2-chloroethyl acrylate, phenyl acrylate, and acrylic acid. Acrylic esters other than alkyl acrylates such as 2- (dimethylamino) ethyl, 2- (diethylamino) ethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate; phenyl methacrylate, methacrylic acid Methacrylic acid esters other than alkyl methacrylates such as 2- (dimethylamino) ethyl, 2- (diethylamino) ethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate; methyl α-chloroacrylate Α-haloacrylic acid esthetics such as Styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexyl Styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, p-methoxy styrene, p-phenyl styrene, p-chloro styrene, 3,4-dichloro Aromatic vinyl compounds such as styrene and vinyl naphthalene; vinyl carboxylates such as vinyl acetate, vinyl propionate and vinyl butyrate; acrylic acid derivatives other than acrylic esters such as acrylonitrile and acrylamide; methacrylonitrile, methacrylamide and the like Methacrylic acid derivatives other than methacrylic acid esters Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N -N-vinyl compounds such as vinylpyrrolidone (N-vinylamine, N-vinylamide, etc.) and the like. These compounds may be used alone or in combination of two or more.

  The other non-crosslinkable vinyl monomer may be contained in the non-crosslinked polymer constituting the resin particle of the present invention within a range of 15% by mass or less.

  The structural unit derived from each monomer contained in the resin particle of the present invention is identified and quantified by gas chromatography, liquid chromatography, infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR). This can be confirmed by using a known analysis method such as. In addition, the content (mass%) of the structural unit derived from each monomer in the resin particle of the present invention is the amount of each monomer (alkyl group) in all the monomers used in the production of the resin particle of the present invention. Content of alkyl (meth) acrylate having 3 or less carbon atoms, alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms, and other non-crosslinkable vinyl monomers) ( Mass%).

  The mass average molecular weight of the resin particles is in the range of 200,000 to 600,000. Resin particles having a mass average molecular weight outside the range of 200,000 to 600,000 are porous having a desired pore shape and pore diameter when used as a pore-forming agent in a method for producing a resin-removed porous resin molding. A good porous resin molded product having a porous structure cannot be obtained. That is, resin particles having a mass average molecular weight of less than 200,000 are used as a pore-forming agent in a resin dissolution removal method for producing a porous resin molded body. Before the material is formed, some of the resin particles dissolve in the vinyl monomer and cannot retain the shape of the particles. As a result, a porous structure having a desired pore shape and pore diameter is obtained. It is not possible to obtain a good porous resin molded product having On the other hand, resin particles having a mass average molecular weight exceeding 600,000 are not sufficiently dissolved in an organic solvent when used as a pore-forming agent in a method for producing a resin-removable porous resin molded body. The resin particles cannot be sufficiently removed after the formation of the (base material), and as a result, a good porous resin molded article having a porous structure having a desired pore shape and pore diameter cannot be obtained. The mass average molecular weight of the resin particles is more preferably in the range of 300,000 to 500,000. Thereby, when resin particles are used as a pore-forming agent in a method for producing a resin-removed porous resin molded body, a porous resin molded body having an even better porous structure can be obtained.

  The volume average particle diameter of the resin particles is preferably in the range of 15 μm to 60 μm, more preferably in the range of 20 μm to 50 μm, and still more preferably in the range of 30 μm to 40 μm. Resin particles having a volume average particle diameter in the range of 15 μm to 60 μm are suitable as resin particles for a pore-forming agent used in the method for producing a resin-removed porous resin molded body. When the resin particles having a volume average particle diameter of less than 15 μm are used as a pore-forming agent in the method for producing a resin-removable porous resin molded body, the resulting porous resin molded body has fewer voids and is good. Since a porous resin molded product having a porous structure cannot be obtained, it is not preferable. On the other hand, resin particles with a volume average particle diameter exceeding 60 μm have too many voids in the resulting porous resin molded article when used as a pore-forming agent in a method for producing a resin-removed porous resin molded article. This is not preferable because the strength of the porous resin molding is reduced. Further, when the volume average particle diameter of general resin particles is 15 μm or more, the coefficient of variation of the particle diameter when manufactured by the seed polymerization method exceeds 15%. On the other hand, the resin particles of the present invention have a structural unit of 5 to 20 mass derived from alkyl (meth) acrylate having an alkyl group with 4 or more and 12 or less carbon atoms, even if the volume average particle diameter is 15 μm or more. %, The coefficient of variation of the particle diameter when manufactured by the seed polymerization method is 15% or less. Therefore, the resin particles of the present invention can be easily produced using the seed polymerization method even if the volume average particle diameter is 15 μm or more. In the present specification, the “volume average particle diameter” of the resin particles refers to the arithmetic average diameter in the volume-based particle diameter distribution measured by the Coulter method, for example, the measurement method described in the “Example” section below. It means the volume average particle diameter measured in (1).

  The coefficient of variation of the particle diameter of the resin particles is 15% or less. When the coefficient of variation of the particle diameter of the resin particles exceeds 15%, a porous resin molded body having a uniform pore diameter is obtained when used as a pore-forming agent in a method for producing a resin-removed porous resin molded body. I can't. Moreover, when the variation coefficient of the particle diameter of the resin particles exceeds 15%, characteristics such as light diffusibility of the resin particles become non-uniform. The coefficient of variation of the particle diameter of the resin particles is more preferably 12% or less. Thereby, when the resin particles are used as a pore-forming agent in the method for producing a resin-removed porous resin molded body, a porous resin molded body having a more uniform pore diameter can be obtained. Characteristics such as light diffusibility of the resin particles can be made more uniform.

[Production method of resin particles]
In the method for producing resin particles of the present invention, an alkyl (meth) acrylate having an alkyl group having 3 or less carbon atoms is linked in an amount of 0.5 to 3 parts by mass with respect to 100 parts by mass of the alkyl (meth) acrylate. Including a seed particle manufacturing step of manufacturing seed particles made of a non-crosslinked polymer by emulsion polymerization in the presence of a transfer agent, and after the seed particle manufacturing step, the carbon number of the alkyl group is 3 or less (meta ) After the alkyl acrylate is absorbed by the seed particles, the (meth) acrylic compound in the presence of 0.5 to 3 parts by mass of a chain transfer agent with respect to 100 parts by mass of the absorbed alkyl (meth) acrylate. The seed particles are enlarged by polymerizing an acid acid, and include at least one seed particle enlargement step to obtain enlarged seed particles made of a non-crosslinked polymer, and after the seed particle enlargement step, A 80 to 95% by mass of an alkyl (meth) acrylate monomer having 3 or less carbon atoms in the kill group and 5 to 20% by mass of alkyl (meth) acrylate having 4 to 12 carbon atoms in the alkyl group. The non-crosslinkable (monofunctional) monomer mixture containing the above is absorbed into the enlarged seed particles, and then the non-crosslinkable monomer mixture is polymerized in the presence of a water-soluble polymerization inhibitor. And a resin particle production process for producing non-crosslinked resin particles.

[Seed particle manufacturing process]
In the seed particle production step, seed particles made of a non-crosslinked polymer are produced by emulsion polymerization of an alkyl (meth) acrylate having 3 or less carbon atoms in the alkyl group. Examples of and preferred compounds of alkyl (meth) acrylate (hereinafter referred to as “short-chain (meth) acrylate”) having 3 or less carbon atoms in the alkyl group used in each step of the production method of the present invention The compound is as described in the section [Resin Particles].

  In the seed particle manufacturing step, short chain alkyl (meth) acrylate is emulsion-polymerized in the presence of a chain transfer agent (molecular weight modifier). By performing emulsion polymerization in the presence of the chain transfer agent, the mass average molecular weight of the seed particles can be kept low. Thereby, in the seed particle enlargement step, the monomer (short chain alkyl (meth) acrylate or non-crosslinkable monomer mixture) can be rapidly absorbed in the seed particle, so that the monomer is the seed particle. It can suppress producing | generating a microparticle by polymerizing uniquely in the position away from (in aqueous medium). As a result, resin particles with improved monodispersity can be obtained. Moreover, the mass average molecular weight of the resin particle finally obtained can be restrained low by restraining the mass average molecular weight of a seed particle low.

  Examples of the chain transfer agent include n-octyl mercaptan (1-octanethiol), n-dodecyl mercaptan (lauryl mercaptan), tert-dodecyl mercaptan, 2-hydroxyethyl mercaptan, n-octadecyl mercaptan (stearyl mercaptan), and alkylene. Examples include mercaptans such as dithiol and thiocyanuric acid; styrene dimers such as α-methylstyrene dimer; terpenes such as γ-terpinene and dipentene; and halogenated hydrocarbons such as chloroform and carbon tetrachloride. Of these chain transfer agents, mercaptans and styrene dimers are preferred, and mercaptans are more preferred. These chain transfer agents may be used alone or in combination of two or more.

  The amount of the chain transfer agent used is in the range of 0.5 to 3 parts by mass with respect to 100 parts by mass of the short-chain alkyl (meth) acrylate. When the amount of the chain transfer agent used is less than 0.5 parts by mass with respect to 100 parts by mass of the short-chain alkyl (meth) acrylate, the mass average molecular weight of the seed particles is sufficiently low (for example, 50,000 or less). ) Can not be suppressed. As a result, in the seed particle enlargement process, the seed particles cannot absorb the monomer sufficiently quickly, and the monomers are independently polymerized (in an aqueous medium) at a position away from the seed particles. The generation of microparticles cannot be sufficiently suppressed. As a result, resin particles excellent in monodispersity (for example, the coefficient of variation is 15% or less) cannot be obtained. Further, since the mass average molecular weight of the seed particles cannot be sufficiently reduced (for example, 50,000 or less), the mass average molecular weight of the finally obtained resin particles is sufficiently reduced (for example, 600,000 or less). I can't. As a result, when the resin particles finally obtained are used as a pore-forming agent in a method for producing a resin-removable porous resin molded body, the resin particles are not sufficiently dissolved in an organic solvent. The resin particles cannot be sufficiently removed after the formation of).

  On the other hand, when the amount of the chain transfer agent used exceeds 3 parts by mass with respect to 100 parts by mass of the short chain alkyl (meth) acrylate, the mass average molecular weight of the seed particles becomes too low (for example, less than 5,000). Therefore, the mass average molecular weight of the finally obtained resin particles becomes too low (for example, less than 200,000). As a result, when the resin particles finally obtained are used as a pore-forming agent in the method of manufacturing a resin-removable porous resin molded body, the resin molded body (base material) is formed by polymerization of a vinyl monomer. Before being formed, some of the resin particles are dissolved in the vinyl monomer, so that the particle shape cannot be maintained, and the function as a pore-forming agent is lost.

  The method for emulsion polymerization of the short-chain alkyl (meth) acrylate may be a soap-free polymerization method (emulsion polymerization method not using a surfactant), or an emulsion polymerization method (emulsion polymerization method using a surfactant). However, it is easy to obtain seed particles having good monodispersity, and it is easy to obtain seed particles having a volume average particle diameter of 0.25 μm to 1.0 μm. It is preferable that

  In the seed particle production step, the short chain alkyl (meth) acrylate is usually polymerized by dispersing it in an aqueous medium. The aqueous medium is not particularly limited, and examples thereof include water and a mixed medium of water and a water-soluble organic medium (lower alcohol (alcohol having 5 or less carbon atoms) such as methanol and ethanol). The amount of the aqueous medium used is usually in the range of 100 to 1000 parts by mass with respect to 100 parts by mass of the short-chain alkyl (meth) acrylate in order to stabilize the seed particles.

  The polymerization temperature of the short-chain alkyl (meth) acrylate is preferably in the range of 30 to 100 ° C. The time for maintaining this polymerization temperature is preferably within the range of 0.1 to 20 hours. By the polymerization in the aqueous medium, a dispersion liquid in which the seed particles are dispersed in the aqueous medium is obtained. If necessary, the dispersion may be centrifuged to remove the aqueous medium, washed with water and an organic solvent, and then dried to isolate seed particles.

  In the polymerization of the short-chain alkyl (meth) acrylate, a polymerization initiator is usually added to the short-chain alkyl (meth) acrylate. Examples of the polymerization initiator include peroxides such as benzoyl peroxide, lauroyl peroxide, tert-butyl peroxyisobutyrate; 2,2′-azobisisobutyronitrile, 2,2′-azobis (2 , 4-dimethylvaleronitrile), 2,2-azobis- (2-methylpropionate) and the like; and peroxides such as potassium persulfate and ammonium persulfate. These polymerization initiators may be used alone or in combination of two or more.

  The amount of the polymerization initiator used is preferably in the range of 0.01 to 10 parts by mass, and in the range of 0.01 to 5 parts by mass with respect to 100 parts by mass of the short chain alkyl (meth) acrylate. More preferably, it is within. When the usage-amount of the said polymerization initiator is less than 0.01 mass part with respect to 100 mass parts of said short chain (meth) acrylates, a polymerization initiator does not fulfill | perform a polymerization start function easily. Moreover, when the usage-amount of the said polymerization initiator exceeds 10 mass parts with respect to 100 mass parts of said short chain (meth) acrylates, since it is uneconomical in cost, it is not preferable.

  The seed particles obtained in the seed particle manufacturing step preferably have a volume average particle diameter in the range of 0.25 μm to 1.0 μm. If the volume average particle diameter of the seed particles is smaller than 0.25 μm, more steps are required to enlarge the seed particles to the desired size (enlarged) seed particles used in the resin particle manufacturing process. Therefore, it is not preferable. When the volume average particle diameter of the seed particles is larger than 1.0 μm, it is difficult to produce the seed particles by emulsion polymerization. In the present specification, “volume average particle diameter of seed particles” means the arithmetic average diameter in the volume-based particle diameter distribution measured by the laser diffraction scattering method, for example, measured by the measurement method described in the section of Examples. It shall mean the volume average particle diameter made.

  The seed particles obtained in the seed particle manufacturing step preferably have a mass average molecular weight in the range of 5,000 to 50,000. When the mass average molecular weight of the seed particles is less than 5,000, the step of causing the seed particles to absorb the short chain alkyl (meth) acrylate (swelling step) or the short chain alkyl (meth) acrylate in the seed particle enlargement step In the step of polymerization (polymerization step), particle coalescence occurs, and the monodispersibility of the finally obtained resin particles is lowered, which is not preferable. When the mass average molecular weight of the seed particles is larger than 50,000, it is not preferable because the seed particles cannot rapidly absorb the short-chain alkyl (meth) acrylate (monomer) in the seed particle enlargement step.

[Seed particle enlargement process]
The seed particle enlargement step is performed at least once after the seed particle production step. By performing the seed particle enlargement step at least once, it is possible to obtain resin particles having a relatively large particle size (for example, a volume average particle size of 15 μm or more). By increasing the number of executions of the seed particle manufacturing process, the particle diameter of the obtained resin particles can be further increased.

  In the seed particle enlargement step, after the short-chain alkyl (meth) acrylate is absorbed by the seed particles, the seed particles are enlarged by polymerizing the absorbed alkyl (meth) acrylate, Enlarged seed particles made of a crosslinked polymer are obtained.

  In the seed particle enlargement step, the amount of the short-chain alkyl (meth) acrylate absorbed by the seed particles is in the range of 1,000 to 25,000 parts by mass with respect to 100 parts by mass of the seed particles. It is preferable. When the amount of the short chain alkyl (meth) acrylate absorbed in the seed particles is less than 1,000 parts by mass with respect to 100 parts by mass of the seed particles, the increase in the particle diameter due to enlargement becomes small. The number of executions of the seed particle enlargement process necessary for obtaining resin particles having a desired particle diameter increases, and production efficiency may deteriorate. On the other hand, when the amount of the short chain alkyl (meth) acrylate absorbed by the seed particles exceeds 25,000 parts by mass with respect to 100 parts by mass of the seed particles, the short chain (meth) acrylate is converted into seed particles. The short chain alkyl (meth) acrylate may be polymerized independently (in an aqueous medium) to form microparticles at a position away from the seed particles. The monodispersity of the particles may deteriorate. If the monodispersity of the enlarged seed particles deteriorates, the monodispersity of the finally obtained resin particles also deteriorates.

  In the seed particle enlargement step, the short chain alkyl (meth) acrylate is usually absorbed in the aqueous medium and the short chain alkyl (meth) acrylate is polymerized. In the seed particle enlargement step, an aqueous emulsion in which oil droplets in which the short chain alkyl (meth) acrylate is absorbed in seed particles is dispersed in an aqueous medium is usually prepared, and the short chain (meta) ) Polymerize alkyl acrylate. The aqueous emulsion can be produced, for example, by treating a mixed solution of the short-chain alkyl (meth) acrylate and an aqueous medium with a fine emulsifier such as a homogenizer, an ultrasonic processor, or a nanomizer. The short-chain alkyl (meth) acrylate may be added after the seed particles are added to the aqueous medium, or the seed particles may be added to a mixed solution of the short-chain alkyl (meth) acrylate and the aqueous medium. Good. In addition, when a dispersion liquid in which seed particles are dispersed in an aqueous medium is obtained in the seed particle manufacturing process, the dispersion liquid can be used as it is in the seed particle enlargement process. Examples of the aqueous medium that can be used and the normal amount of the aqueous medium used are the same as those described in the section of [Seed particle production process].

  Absorption of the short-chain alkyl (meth) acrylate into the seed particles can usually be performed by stirring the aqueous emulsion after addition of the seed particles at room temperature (about 20 ° C.) for 1 to 12 hours. Moreover, you may accelerate | stimulate absorption of the said short chain (meth) acrylate to the said seed particle by heating an aqueous emulsion to about 30-50 degreeC.

  The polymerization reaction is preferably carried out by raising the temperature after the short-chain alkyl (meth) acrylate is completely absorbed by the seed particles. The polymerization of the short chain alkyl (meth) acrylate in the aqueous medium is preferably performed while stirring the aqueous emulsion in which the short chain alkyl (meth) acrylate is dispersed as spherical droplets. The stirring may be performed loosely enough to prevent, for example, floating of spherical droplets and sedimentation of particles after polymerization.

  In the seed particle enlargement step, 0.5 to 3 parts by mass of a chain transfer agent of 0.5 to 3 parts by mass with respect to 100 parts by mass of the short chain (meth) acrylate is absorbed by the short chain alkyl (meth) acrylate absorbed by the seed particles. Polymerizes in the presence. Thereby, while being able to adjust the mass average molecular weight of the resin particle finally obtained within a predetermined range (for example, within a range of 200,000 to 600,000), it is possible to keep the mass average molecular weight of the seed particles after enlargement low. The swelling ratio of the seed particles can be increased in the resin particle production process. Examples of the chain transfer agent that can be used and the amount of the chain transfer agent used are the same as those described in the section of [Seed particle production process].

  The short chain alkyl (meth) acrylate polymerization method may be a soap-free polymerization method (emulsion polymerization method not using a surfactant), or an emulsion polymerization method using a surfactant (containing a surfactant). A method of polymerizing with an aqueous medium), a soap-free polymerization method is preferred. That is, it is preferable.

  The surfactant is not particularly limited, and any of an anionic surfactant, a nonionic surfactant, a cationic surfactant, and a zwitterionic surfactant can be used.

  Examples of the anionic surfactant include fatty acid oils such as sodium oleate and castor oil potassium; alkyl sulfate salts such as sodium lauryl sulfate and ammonium lauryl sulfate; alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate; alkylnaphthalene Sulfonates; alkane sulfonates; dialkyl sulfosuccinates such as sodium dioctyl sulfosuccinate; phosphate esters such as sodium polyoxyethylene alkylphenyl ether sodium phosphate and sodium polyoxyalkylene aryl ether; formalin condensation of naphthalene sulfonate Polyoxyethylene alkylphenyl ether sulfate salt; polyoxyethylene alkylsulfuric acid ester salt; and the like.

  Examples of the nonionic surfactant include polyoxyethylene alkyl ethers such as polyoxyethylene tridecyl ether, polyoxyethylene alkyl phenyl ethers, polyoxyethylene styrenated phenyl ethers, and alkylene groups having 3 or more carbon atoms. Polyoxyalkylene alkyl ethers such as polyoxyalkylene tridecyl ether, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate, polyoxyethylene alkylamines, glycerin fatty acid esters, oxy Examples include ethylene-oxypropylene block polymers.

  Examples of the cationic surfactant include alkylamine salts such as laurylamine acetate and stearylamine acetate; quaternary ammonium salts such as lauryltrimethylammonium chloride.

  Examples of the zwitterionic surfactant include lauryl dimethylamine oxide and phosphate ester or phosphite ester surfactants.

  Of these surfactants, it is preferable to use at least one of an anionic surfactant and a nonionic surfactant. These surfactants may be used alone or in combination of two or more.

  It is preferable that the usage-amount of surfactant in the said polymerization reaction exists in the range of 0.01-5 mass parts with respect to 100 mass of said short chain (meth) acrylates. When the amount of the surfactant used is less than 0.01 parts by mass with respect to 100 parts by mass of the short chain alkyl (meth) acrylate, it is difficult to maintain the polymerization stability, which is not preferable. Moreover, when the usage-amount of the said surfactant exceeds 5 mass parts with respect to 100 mass parts of said short chain alkyl (meth) acrylates, the said short chain (meth) acrylate alkyl is in the position away from the seed particle ( It is not preferable because the polymer particles are uniquely polymerized (in an aqueous medium) to produce fine particles, and the resulting resin particles have poor monodispersibility.

  In the polymerization reaction, a dispersion stabilizer can be used as necessary. The dispersion stabilizer is not particularly limited, and examples thereof include water-soluble polymers such as polyvinyl alcohol and polyvinyl pyrrolidone; poorly water-soluble inorganic salts such as tertiary calcium phosphate, calcium carbonate, and magnesium pyrophosphate. It is done. These dispersion stabilizers may be used alone or in combination of two or more.

  Also in the polymerization reaction, a polymerization initiator is usually added to the short-chain alkyl (meth) acrylate. Examples of the polymerization initiator that can be used in the polymerization reaction and the preferred amount of the polymerization initiator used are the same as those described in the section of [Seed Particle Production Step]. However, when the surfactant concentration in the reaction liquid (emulsion liquid) is higher than the critical micelle concentration, the polymerization initiator is an oil-soluble polymerization initiator such as benzoyl peroxide or 2,2′-azobisisobutyronitrile. Is preferably used. When the surfactant concentration of the reaction liquid (emulsion liquid) is equal to or higher than the critical micelle concentration, when a water-soluble polymerization initiator such as potassium persulfate is used as the polymerization initiator, the monomer is positioned away from the seed particles. This is not preferable because it may polymerize uniquely (in an aqueous medium) to produce fine particles, and the resulting resin particles may be poorly monodispersed.

  The preferred range of the polymerization temperature and the time for maintaining the polymerization temperature in the seed particle enlargement step is the same as described in the section of [Seed particle production step].

  The enlarged seed particles obtained in at least one seed particle enlargement step preferably have a mass average molecular weight in the range of 5000 to 50000. When the mass average molecular weight of the seed particles is smaller than 5000, the step of absorbing the non-crosslinkable monomer mixture into the enlarged seed particles (swelling step) or polymerizing the non-crosslinkable monomer mixture in the resin particle production process Since coalescence of particles occurs in the process (polymerization process) and the monodispersity of the finally obtained resin particles is lowered, it is not preferable. When the mass average molecular weight of the seed particles is larger than 50000, it is not preferable because the enlarged seed particles cannot quickly absorb the non-crosslinkable monomer mixture in the resin particle manufacturing process.

[Resin particle manufacturing process]
In the resin particle manufacturing step, after the seed particle enlargement step, the non-crosslinkable monomer mixture is absorbed into the enlarged seed particles, and then the non-crosslinkable monomer mixture is polymerized to be non-polymerized. Crosslinked resin particles are produced.

  The non-crosslinkable monomer mixture is a mixture of a plurality of types of compounds having one ethylenically unsaturated bond (non-crosslinkable monomer), and the alkyl group has 4 to 12 carbon atoms. It contains 5 to 20% by mass of a certain alkyl (meth) acrylate and 80 to 95% by mass of a short-chain (meth) acrylate monomer. Since the non-crosslinkable monomer mixture contains an alkyl (meth) acrylate having 4 to 12 carbon atoms in addition to the short-chain alkyl (meth) acrylate, the carbon of the alkyl group The mass average molecular weight of the resulting resin particles can be kept low compared to the case where the number is only 3 (alkyl) (meth) acrylates. In addition to the short-chain alkyl (meth) acrylate having a relatively high water solubility, the non-crosslinkable monomer mixture has an alkyl group having a relatively low water solubility of 4 to 12 carbon atoms (meta ) Since alkyl acrylate is contained, the absorption rate of the non-crosslinkable monomer mixture into the seed particles can be suppressed as compared with the case of consisting of only a short-chain (meth) acrylate.

  Examples of compounds that can be used as alkyl (meth) acrylates in which the alkyl group has 4 or more and 12 or less carbon atoms and preferred compounds are as described in the section of [Resin Particles].

  The content of alkyl (meth) acrylate having 4 to 12 carbon atoms in the alkyl group in the non-crosslinkable monomer mixture is in the range of 5 to 20% by mass.

  In the non-crosslinkable monomer mixture, when the content of alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms is less than 5% by mass, the alkyl group has 4 to 12 carbon atoms. Since the effect of suppressing the mass average molecular weight of the resin particles by a certain alkyl (meth) acrylate becomes insufficient, the mass average molecular weight of the obtained resin particles becomes too large (for example, more than 600,000). As a result, when the obtained resin particles are used as a pore-forming agent in a method for producing a resin-removable porous resin molding, the resin particles are not sufficiently dissolved in an organic solvent. The resin particles cannot be sufficiently removed, and as a result, a good porous resin molded product having a porous structure with a desired pore shape and pore diameter cannot be obtained. In addition, when the content of alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms in the non-crosslinkable monomer mixture is less than 5% by mass, the non-crosslinkable single amount to the seed particles Since the absorption rate of the body mixture is too high, absorption of the non-crosslinkable monomer mixture into the seed particles and coalescence of the swollen seed particles absorbed by the non-crosslinkable monomer mixture occur simultaneously. Coarse particles frequently occur and the resulting resin particles have poor monodispersity (for example, the coefficient of variation of the particle diameter exceeds 15%).

  On the other hand, when the content of alkyl (meth) acrylate having 4 to 12 carbon atoms in the non-crosslinkable monomer mixture is more than 20% by mass, the resin particles obtained have a mass average molecular weight. It becomes too small (for example, less than 200,000). As a result, when the resin particles obtained are used as a pore-forming agent in a method for producing a resin-removable porous resin molded body, before the resin molded body (base material) is formed by polymerization of a vinyl monomer. As a result, a part of the resin particles are dissolved in the vinyl-based monomer and the shape of the particles cannot be maintained, and as a result, a good porous resin having a porous structure having a desired pore shape and pore diameter. A molded body cannot be obtained. In addition, when the content of alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms in the non-crosslinkable monomer mixture is more than 20% by mass, the monomer is absorbed well into the seed particles. However, the monomer is independently polymerized at a position away from the seed particles (in an aqueous medium) to produce microparticles, and the monodispersity of the resulting resin particles is deteriorated (for example, the coefficient of variation in particle diameter is Over 15%).

  In the non-crosslinkable monomer mixture, the content of alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms is more preferably within a range of 5 to 10% by mass. Thereby, since generation | occurrence | production of a coarse particle and a microparticle can further be suppressed, the resin particle which has the further outstanding monodispersibility is realizable.

  Content of the short chain alkyl (meth) acrylate in the said non-crosslinkable monomer mixture exists in the range of 80-95 mass%. In the non-crosslinked polymer constituting the resin particles of the present invention, the content of alkyl (meth) acrylate having 3 or less carbon atoms in the alkyl group is more preferably in the range of 90 to 95% by mass. Thereby, since generation | occurrence | production of a coarse particle and a microparticle can further be suppressed, the resin particle which has the further outstanding monodispersibility is realizable. The non-crosslinkable monomer mixture may consist of only a short-chain alkyl (meth) acrylate and an alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms. And other non-crosslinkable (monofunctional) vinyl monomers may be contained within a range of 15% by mass or less. Examples of the compound that can be used as the other non-crosslinkable vinyl monomer are as described in the section of [Resin particles].

  In the resin particle production process, the amount of the non-crosslinkable monomer mixture absorbed in the seed particles is within a range of 4,000 to 22,000 parts by mass with respect to 100 parts by mass of the enlarged seed particles. Preferably there is. When the amount of the non-crosslinkable monomer mixture to be absorbed by the seed particles is less than 4,000 parts by mass with respect to 100 parts by mass of the enlarged seed particles, the increase in the particle diameter due to enlargement becomes small. Therefore, the particle diameter of the resin particles obtained becomes small. For this reason, the number of implementations of the seed particle enlargement process necessary for obtaining resin particles having a desired particle diameter increases, and production efficiency may deteriorate. On the other hand, when the amount of the non-crosslinkable monomer mixture absorbed by the seed particles exceeds 22,000 parts by mass with respect to 100 parts by mass of the enlarged seed particles, the non-crosslinkable monomer mixture is The resin is not completely absorbed by the enlarged seed particles, and the non-crosslinkable monomer mixture may be polymerized uniquely (in an aqueous medium) at a position away from the seed particles to form microparticles. The monodispersity of the particles may deteriorate.

  In the resin particle production process, the non-crosslinkable monomer mixture is polymerized in the presence of the water-soluble polymerization inhibitor. Thereby, it can suppress that the non-crosslinkable monomer mixture which exists in a trace amount in a water phase superpose | polymerizes uniquely. Therefore, the generation of fine particles due to polymerization of the non-crosslinkable monomer mixture can be suppressed, and the polymer of the non-crosslinkable monomer mixture connects the resin particles (primary particles) to form secondary particles. It can also be suppressed. As a result, the monodispersity of the resin particles obtained can be improved (for example, the coefficient of variation of the particle diameter can be made 15% or less).

  Examples of the water-soluble polymerization inhibitor include nitrites, sulfites, hydroquinones, ascorbic acids, water-soluble vitamin Bs, citric acid, and polyphenols. Examples of the nitrites include alkali nitrites such as sodium nitrite and potassium nitrite; alkaline earth nitrites such as magnesium nitrite; ammonium nitrite and the like. Among these, nitrites are preferable because the effect of suppressing the polymerization of the non-crosslinkable monomer mixture in the aqueous phase is remarkable. Among the nitrites, sodium nitrite is most preferable in terms of solubility, dissociation property in water, and the like. These water-soluble polymerization inhibitors may be used alone or in combination of two or more.

  The amount of the water-soluble polymerization inhibitor used is preferably in the range of 0.03 to 0.3 parts by mass with respect to 100 parts by mass of the non-crosslinkable monomer mixture. When the amount of the polymerization inhibitor used is less than 0.03 parts by mass with respect to 100 parts by mass of the non-crosslinkable monomer mixture, generation of fine particles in the aqueous phase by the water-soluble polymerization inhibitor Insufficient effect may be insufficient, and the monodispersity of the resulting resin particles may not be sufficiently improved. Further, when the amount of the polymerization inhibitor used exceeds 0.3 parts by mass with respect to 100 parts by mass of the non-crosslinkable monomer mixture, the progress of the polymerization of the non-crosslinkable monomer mixture is inhibited. This is not preferable because there is a possibility.

In the resin particle production process, the method of absorbing the non-crosslinkable monomer mixture into the seed particles, the temperature rise during the polymerization, the stirring during the polymerization, the polymerization temperature, the time for maintaining the polymerization temperature, the polymerization method, etc. This is the same as described in the section of the seed particle enlargement step. Also in the resin particle production step, it is usually preferable to use an aqueous medium and a polymerization initiator and use a surfactant, as in the seed particle enlargement step, and if necessary, use a dispersion stabilizer. use. Examples of usable aqueous media and normal amounts of aqueous media used, examples of usable polymerization initiators and used polymerization initiators, examples of usable surfactants and used amounts of surfactants, dispersion stability The amount of the agent used is the same as that described in the section of [Seed particle enlargement step].
[Method for producing porous resin molding]
The method for producing a porous resin molded body of the present invention comprises a step of filling a plurality of resin particles of the present invention as pore formers into a mold and heating the mold to fuse the resin particles together. A step of attaching the resin particles to each other and adding a vinyl monomer and a polymerization initiator that do not dissolve the resin particles in the mold, and polymerizing the vinyl monomer, A step of obtaining a resin molded body comprising a polymer of the vinyl monomer, and dissolving the resin particles in an organic solvent which dissolves the resin particles but does not dissolve the vinyl monomer polymer. And a step of removing the resin particles from the resin molded body.

  Examples of the material of the mold include metals such as steel; ceramics; resins such as polyetheretherketone (PEEK) and the like.

  The heating temperature of the mold in the step of connecting the resin particles is not particularly limited as long as the resin particles can be partially fused to connect the resin particles. It is preferable to be within the range of 150 to 200 ° C. When the heating temperature of the mold is less than 150 ° C., the resin particles are not fused with each other, and the resin particles may not be connected. On the other hand, when the heating temperature of the mold exceeds 200 ° C., the entire resin particles are melted and the shape of the particles cannot be maintained, and as a result, a porous structure may not be formed.

  The vinyl monomer is not particularly limited as long as it is a compound that does not dissolve resin particles, does not dissolve in an organic solvent when polymerized, and has an ethylenically unsaturated bond. Examples of the vinyl monomers include non-crosslinkable (meth) acrylic acid esters such as 2-hydroxyethyl methacrylate and methyl methacrylate; and cross-links such as tetraethylene glycol dimethacrylate and poly (ε-caprolactone) dimethacrylate. (Functional) (meth) acrylic acid ester; fluorine-containing non-crosslinkable vinyl monomer constituting water-soluble fluororesin (for example, “Teflon (registered trademark) AF”); vinyl alcohol and the like. These vinyl monomers may be used alone or in combination of two or more.

  When the porous resin molding of the present invention is used as a biocompatible material such as a biological carrier for culturing cells and microorganisms, 2-hydroxyethyl methacrylate, tetraethylene glycol dimethacrylate, poly (ε-caprolactone) Hydrophilic vinyl monomers such as dimethacrylate, water-soluble fluororesin (for example, “Teflon (registered trademark) AF”) and other hydrophilic vinyl monomers such as vinyl alcohol are used as the vinyl monomers. It is preferable. The vinyl monomer is a non-crosslinkable vinyl monomer having one ethylenically unsaturated bond (non-crosslinkable (meth) acrylic acid ester, fluorine-containing non-crosslinkable vinyl monomer, Vinyl alcohol and the like) and a crosslinkable vinyl monomer having two or more ethylenically unsaturated bonds (crosslinkable (meth) acrylic acid ester and the like). Thereby, the polymer of the vinyl monomer becomes a cross-linked polymer, and it can be avoided that the polymer of the vinyl monomer is dissolved in the organic solvent.

  As the polymerization initiator, various polymerization initiators described as being used in the method for producing resin particles can be used, and the preferred range of the amount of the polymerization initiator used is also the polymerization used in the method for producing resin particles. Similar to the initiator.

  Water and a polyhydric alcohol such as ethylene glycol may be added to the vinyl monomer. Thereby, the resin molding in the state of hydrogel can be obtained by polymerization of the vinyl monomer, and the porous resin molding in the state of hydrogel can be finally obtained.

  The method for polymerizing the vinyl monomer is not particularly limited, and examples thereof include an emulsion polymerization method, a suspension polymerization method, a solution polymerization method, and a bulk polymerization method.

  The polymerization of the vinyl monomer may be performed in the presence of an antioxidant such as disodium disulfite.

  As the organic solvent, at least one of a ketone organic solvent having a boiling point of 80 ° C. or lower and an acetate ester organic solvent having a boiling point of 80 ° C. or lower has high resin particle solubility (easy to dissolve resin particles), In addition, it is preferable from the viewpoint that the residual degree in the resin molding is low, and among them, at least one of acetone, methyl ethyl ketone, ethyl acetate and the like is preferable.

  Examples of the method for removing the resin particles from the resin molding by dissolving the resin particles in the organic solvent include a method of Soxhlet extraction of the resin molding in the organic solvent.

  The organic solvent used for removing the resin particles may be removed by a cleaning treatment using an organic solvent different from the organic solvent used for removing the resin particles, if necessary. An example of the organic solvent used for the cleaning treatment is acetone. Moreover, you may remove the organic solvent used for the removal of the resin particle, and the organic solvent used for the washing process by Soxhlet extraction in water as needed.

  As described above, a porous resin molded product can be produced. The porous resin molded body produced by the above method has a plurality of pores having a substantially uniform diameter, and has a good porous structure in which almost all pores are connected. In addition, when the step of connecting the resin particles is omitted from the manufacturing method, the resin particles are in contact with each other when the vinyl monomer is polymerized depending on the filling state of the resin particles. And a portion where the resin particles are not in contact with each other. As a result, the obtained porous resin molding has a non-uniform porous structure in which a portion where pores are connected and a portion where pores are not connected are mixed.

  Hereinafter, although an example and a comparative example explain the present invention, the present invention is not limited to this.

[Method for measuring mass average molecular weight of resin particles]
The measurement of the mass average molecular weight of the resin particles in the following Examples and Comparative Examples was performed as follows using gel permeation chromatography (GPC). The measured mass average molecular weight is a polystyrene (PS) conversion mass average molecular weight. The measuring method is as follows. First, 50 mg of resin particles were dissolved in 10 ml of tetrahydrofuran (THF). The resulting solution was filtered using a 0.45 μm non-aqueous chromatographic disk. The obtained filtrate was analyzed by GPC, and PS-converted mass average molecular weight was measured. GPC measurement conditions were as follows.

GPC apparatus: trade name “Gel Permeation Chromatograph HLC-8020” manufactured by Tosoh Corporation
Column: Two trade names “TSKgel GMH XL-L” (diameter 7.8 mm × length 30 cm) manufactured by Tosoh Corporation Column temperature: 40 ° C.
Effluent: Tetrahydrofuran (THF)
Outflow rate: 1 ml / min Outflow temperature: 40 ° C
Detection: RI (differential refractive index detector)
Injection volume: 100 μl
Standard polystyrene for calibration curve for calculating PS-converted mass average molecular weight: trade name “shodex” (mass average molecular weight: 1030000) manufactured by Showa Denko KK and standard polystyrene for calibration curve (mass average molecular weight: manufactured by Tosoh Corporation) 5480000, 3840000, 355000, 102000, 37900, 9100, 2630, 870)
[Method for measuring volume average particle diameter of seed particles]
The volume average particle diameter of seed particles (polymethyl methacrylate particles) in the following examples and comparative examples was measured as follows.

  First, 0.1 g of seed particles and 10 ml of a 0.1% by mass nonionic surfactant aqueous solution are put into a test tube and mixed for 2 seconds with a touch mixer (trade name “TOUCMIXER MT-31”, manufactured by Yamato Scientific Co., Ltd.). did. Thereafter, the seed particles in the test tube are preliminarily dispersed in the above aqueous solution over 10 minutes using a commercially available ultrasonic cleaner (trade name “ULTRA SONIC CLEANER VS-150”, manufactured by Vervocrea). Got. While irradiating the obtained dispersion with ultrasonic waves, the volume average particle diameter (arithmetic average diameter in the volume-based particle diameter distribution) of the seed particles contained in the obtained dispersion is measured by a laser diffraction scattering system particle size distribution measuring apparatus. (Model number “LS230”, manufactured by Beckman Coulter, Inc.). The optical model used for calculation of the volume average particle diameter in the laser diffraction / scattering particle size distribution analyzer was adjusted to the refractive index of the seed particles produced.

[Method for measuring volume average particle diameter of resin particles and coefficient of variation of particle diameter]
The volume average particle diameter and the coefficient of variation of the particle diameter of the resin particles in the following examples and comparative examples were measured as follows.

  For the volume average particle diameter of the resin particles and the coefficient of variation of the particle diameter, an aperture having a size (diameter) of X μm adapted to the particle diameter of the particles to be measured is used according to Reference MANUARY FOR THE COULTER MULTISIZER published by Coulter Electronics Limited. The Coulter type precision particle size distribution measuring device (trade name “Coulter Multisizer III”, manufactured by Beckman Coulter, Inc.) was calibrated and measured with the above Coulter type precision particle size distribution measuring device.

  The aperture size X μm is 20 μm for resin particles having an average particle diameter of less than 1 μm, 50 μm for resin particles having an average particle diameter of 1 μm or more and less than 10 μm, and for resin particles having an average particle diameter of 10 μm or more and less than 30 μm. The average particle size is 280 μm for resin particles having an average particle size of 30 μm or more and less than 90 μm, and 400 μm for resin particles having an average particle size of more than 90 μm.

  Specifically, 0.1 g of resin particles are preliminarily placed in 10 ml of a 0.1% by mass nonionic surfactant aqueous solution using a touch mixer (trade name “TOUCMIXER MT-31”, manufactured by Yamato Scientific Co., Ltd.) and ultrasonic waves. Dispersion was performed to obtain a dispersion. Next, this dispersion is dropped with a dropper while gently stirring in a beaker filled with a measurement electrolyte (“ISOTON (registered trademark) II”, manufactured by Beckman Coulter, Inc.) provided in the measurement apparatus main body. Then, the reading of the densitometer on the measuring apparatus main body screen was adjusted to around 10%. Next, the aperture size X μm is set in the measuring apparatus main body, and the current (aperture current), gain (gain), and polarity (polarity of the inner electrode) are set to predetermined conditions according to the aperture size, and the volume average particle The standard deviation of the particle size distribution on the size and volume basis was measured. During the measurement, the beaker was gently agitated to the extent that no bubbles were introduced, and the measurement was completed when 100,000 resin particles were measured. The arithmetic average diameter (arithmetic average diameter in volume% mode) in the volume-based particle diameter distribution was calculated as the volume average particle diameter of the resin particles.

  The coefficient of variation (CV) of the particle diameter of the resin particles was calculated from the standard deviation (σ) and the volume average particle diameter (D) by the following formula.

CV (%) = (σ / D) × 100
[Example 1]
[Seed particle manufacturing process]
First, 3000 g of ion-exchanged water as an aqueous medium was added to the reaction vessel. Next, 10 g of 1-octanethiol as a chain transfer agent (2 parts by mass with respect to 100 parts by mass of methyl methacrylate) is dissolved in 500 g of methyl methacrylate (MMA) as the short chain alkyl (meth) acrylate, A methyl methacrylate solution of 1-octanethiol was obtained. Next, the methyl methacrylate solution of 1-octanethiol was added to the ion exchange water in the reaction vessel. Further, 2.6 g of potassium persulfate as a polymerization initiator was dissolved in 100 g of ion-exchanged water as an aqueous medium to obtain a potassium persulfate aqueous solution. While stirring the ion-exchanged water in the reaction vessel and the methyl methacrylate solution of 1-octanethiol in a nitrogen stream, the temperature is raised to 55 ° C., and the aqueous potassium persulfate solution is charged into the reaction vessel at 55 ° C. By stirring for 12 hours, polymerization of methyl methacrylate was performed to obtain a dispersion of polymethyl methacrylate particles (solid content: 14.3% by mass) as seed particles. The polymethyl methacrylate particles contained in the obtained dispersion had a volume average particle diameter of 0.7 μm and a mass average molecular weight of 13,000.

[First seed particle enlargement process]
Next, 550 g of methyl methacrylate (MMA) as a short chain alkyl (meth) acrylate, 5.5 g of 2,2′-azobisisobutyronitrile as a polymerization initiator, and 1- Octanethiol 5.5 g (1 part by mass with respect to 100 parts by mass of methyl methacrylate) was dissolved to obtain a monomer mixture. Moreover, 5.5 g of sodium dodecylbenzenesulfonate as a surfactant was dissolved in 2194.5 g of ion-exchanged water as an aqueous medium to obtain 2200 g of a sodium dodecylbenzenesulfonate aqueous solution. The monomer mixture is mixed with 2200 g of the aqueous sodium dodecylbenzenesulfonate solution, and the mixture is put into a high-speed emulsifier / disperser (trade name “TK homomixer MARK II 2.5 type”, manufactured by Primix Co., Ltd.). The emulsion was processed by an emulsifier / disperser at a rotational speed of 8000 rpm for 10 minutes to obtain an emulsion.

  In this emulsion, 390 g of polymethyl methacrylate dispersion (solid content: 14.3% by mass) as seed particles having a volume average particle diameter of 0.7 μm obtained in the seed particle production step (polymethyl methacrylate particles) Content of 55.8 g) was added and stirred at room temperature for 3 hours to obtain a dispersion in which polymethyl methacrylate particles were dispersed in the emulsion. When the dispersion at that time was observed with an optical microscope, it was confirmed that the methyl methacrylate in the emulsion was completely absorbed by the polymethyl methacrylate particles. In this example, the amount of methyl methacrylate absorbed by the polymethyl methacrylate particles is 986 parts by mass with respect to 100 parts by mass of the polymethyl methacrylate particles.

  To this dispersion, 1100 g of a 3.6 mass% aqueous solution of polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “GOHSENOL (registered trademark) GH-17”) as a dispersion stabilizer was added to obtain a reaction solution. . Thereafter, the reaction liquid was heated at 55 ° C. for 6 hours to polymerize methyl methacrylate, and then heated at 80 ° C. for 1.5 hours to polymerize methyl methacrylate, and the seed particles were enlarged. A dispersion of polymethyl methacrylate particles (solid content: 14.3% by mass) was obtained. The polymethyl methacrylate particles contained in the obtained dispersion had a volume average particle diameter of 1.50 μm and a mass average molecular weight of 23,000.

[Second seed particle enlargement process]
Furthermore, 500 g of methyl methacrylate (MMA) as a short-chain alkyl (meth) acrylate, 5 g of 2,2′-azobisisobutyronitrile as a polymerization initiator, and 5 g of 1-octanethiol as a chain transfer agent (1 part by mass with respect to 100 parts by mass of methyl methacrylate) was dissolved to obtain a monomer mixture. Further, 5 g of sodium dodecylbenzenesulfonate as a surfactant was dissolved in 995 g of ion-exchanged water as an aqueous medium to obtain 1000 g of a sodium dodecylbenzenesulfonate aqueous solution. The above monomer mixture is mixed with 1000 g of the above sodium dodecylbenzenesulfonate aqueous solution, and put into a high-speed emulsifier / disperser (trade name “TK homomixer MARK II 2.5 type”, manufactured by Primix Co., Ltd.). The emulsion was processed by an emulsifier / disperser at a rotational speed of 8000 rpm for 10 minutes to obtain an emulsion.

  In this emulsion, 36 g of polymethyl methacrylate particle dispersion (solid content: 14.3% by mass) as seed particles having a volume average particle diameter of 1.50 μm obtained in the first seed particle enlargement step (polyester) The content of methyl methacrylate particles (5.1 g) was added, and the mixture was stirred at room temperature for 3 hours to obtain a dispersion in which polymethyl methacrylate particles were dispersed in the emulsion. When the dispersion at that time was observed with an optical microscope, it was confirmed that the methyl methacrylate in the emulsion was completely absorbed by the polymethyl methacrylate particles. In this example, the amount of methyl methacrylate absorbed by the polymethyl methacrylate particles is 9713 parts by mass with respect to 100 parts by mass of the polymethyl methacrylate particles.

  To this dispersion was added 2000 g of a 1.5 mass% aqueous solution of polyvinyl alcohol (manufactured by Kuraray Co., Ltd., trade name “Kuraray (registered trademark) Poval PVA-217E”) as a dispersion stabilizer to obtain a reaction solution. Thereafter, the reaction solution is heated at 65 ° C. for 4 hours, and then the reaction solution is heated at 80 ° C. for 2 hours to polymerize methyl methacrylate, and a dispersion of polymethyl methacrylate particles as seed particles enlarged. (Solid content 14.3 mass%) was obtained. The polymethyl methacrylate particles contained in the obtained dispersion had a volume average particle diameter of 7.64 μm and a mass average molecular weight of 28,000.

[Resin particle manufacturing process]
First, 620 g of methyl methacrylate (MMA) as short-chain alkyl (meth) acrylate (89.9% by mass with respect to a mixture of non-crosslinkable monomer mixture methyl methacrylate and isobutyl methacrylate) , 70 g of isobutyl methacrylate (IBMA) as alkyl (meth) acrylate having an alkyl group with 4 or more and 12 or less carbon atoms (for a mixture of non-crosslinkable monomer mixture methyl methacrylate and isobutyl methacrylate) 89.9% by mass), 3.4 g of 2,2′-azoisobutyronitrile and 2.7 g of tert-butylperoxy-2-ethylhexanoate as polymerization initiators were dissolved in each other, and A monomer mixture was obtained. Further, 6 g of sodium dodecylbenzenesulfonate as a surfactant was dissolved in 1144 g of ion-exchanged water to obtain 1150 g of a sodium dodecylbenzenesulfonate aqueous solution.

  Next, the above monomer mixture was mixed with 1150 g of a sodium dodecylbenzenesulfonate aqueous solution, and put into a high-speed emulsification / dispersing machine (trade name “TK homomixer MARK II 2.5 type”, manufactured by Primix Co., Ltd.) The emulsion was processed by the high-speed emulsification / dispersing machine at a rotation speed of 8000 rpm for 10 minutes.

  In this emulsion, 40 g of a dispersion of polymethyl methacrylate particles (solid content: 14.3% by mass) as seed particles having a volume average particle diameter of 7.64 μm obtained in the second seed particle enlargement step is obtained. The content of methyl methacrylate particles (5.7 g) was added, and the mixture was stirred at 30 ° C. for 8 hours to allow the polymethyl methacrylate particles to absorb the monomer mixture. Thereby, the dispersion liquid of the state which the polymethyl methacrylate particle | grains which absorbed the monomer mixture disperse | distributed in the emulsion was obtained. In this example, the total amount of methyl methacrylate and isobutyl methacrylate absorbed by the polymethyl methacrylate particles is 12063 parts by mass with respect to 100 parts by mass of the polymethyl methacrylate particles.

  To this dispersion, 2000 g of 3% by weight aqueous solution of polyvinyl alcohol (trade name “Kuraray (registered trademark) Poval PVA-217E” manufactured by Kuraray Co., Ltd.) as a dispersion stabilizer and 0.7 g of sodium nitrite (methyl methacrylate) And 0.1 parts by mass with respect to 100 parts by mass of the total amount of isobutyl methacrylate) to obtain a reaction solution. Thereafter, the reaction liquid is heated at 60 ° C. for 4 hours with stirring, and then the reaction liquid is heated at 100 ° C. for 1.5 hours with stirring, thereby polymerizing methyl methacrylate and isobutyl methacrylate, Obtained.

  When the volume-based particle size distribution of the obtained resin particles was measured by the method described above, the obtained resin particles had a volume average particle size of 36.9 μm and a variation coefficient of the volume-based particle size of 7. 0%. The obtained resin particles had a mass average molecular weight of about 390,000. In this example, the proportion of methyl methacrylate in all monomers used for the production of the resin particles (equal to the content of structural units derived from methyl methacrylate in the resin particles) is 90.7% by mass. The ratio of isobutyl methacrylate in all monomers used for the production of resin particles (equal to the content of structural units derived from isobutyl methacrylate in the resin particles) is 9.3% by mass.

[Example 2]
[Seed particle manufacturing process]
In the same manner as in Example 1, a dispersion of polymethyl methacrylate particles having a volume average particle diameter of 0.7 μm and a mass average molecular weight of 13,000 (solid content: 14.3 mass%) as seed particles is obtained. It was.

[First seed particle enlargement process]
In the same manner as in Example 1, a dispersion of polymethyl methacrylate particles having a volume average particle diameter of 1.50 μm and a mass average molecular weight of 23,000 as solid seed particles (a solid content of 14.3% by mass) )

[Second seed particle enlargement process]
Furthermore, the amount of polymethyl methacrylate particle dispersion (solid content 14.3 mass%) having a volume average particle size of 1.50 μm was changed from 36 g to 55 g (content of polymethyl methacrylate particles 7.9 g). Except that, in the same manner as in Example 1, a dispersion of polymethyl methacrylate particles (solid content: 14.3% by mass) was obtained as enlarged seed particles. In this example, the amount of methyl methacrylate absorbed by the polymethyl methacrylate particles is 6357 parts by mass with respect to 100 parts by mass of the polymethyl methacrylate particles.

  The polymethyl methacrylate particles contained in the obtained dispersion had a volume average particle size of 6.17 μm and a mass average molecular weight of 23,000.

[Resin particle manufacturing process]
In the second seed particle enlargement step of this example, instead of 40 g of the dispersion of polymethyl methacrylate particles having a volume average particle diameter of 7.64 μm obtained in the second seed particle enlargement step of Example 1. Resin particles in the same manner as in Example 1 except that 77 g of a dispersion of polymethyl methacrylate particles having a volume average particle diameter of 6.17 μm (content of polymethyl methacrylate particles 11.0 g) was used. Got. In this example, the amount of methyl methacrylate and isobutyl methacrylate absorbed by the polymethyl methacrylate particles is 6266 parts by mass with respect to 100 parts by mass of the polymethyl methacrylate particles.

  When the volume-based particle size distribution of the obtained resin particles was measured by the method described above, the obtained resin particles had a volume average particle size of 27.3 μm and a variation coefficient of the volume-based particle size of 8. 0%. The obtained resin particles had a mass average molecular weight of about 440,000. In this example, the proportion of methyl methacrylate in all monomers used for the production of resin particles (corresponding to the content of structural units derived from methyl methacrylate in the resin particles) is 91.5% by mass. The ratio of isobutyl methacrylate in the total monomers used for the production of the resin particles (corresponding to the content of structural units derived from isobutyl methacrylate in the resin particles) is 8.5% by mass.

Example 3
[Seed particle manufacturing process]
In the same manner as in Example 1, a dispersion of polymethyl methacrylate particles having a volume average particle diameter of 0.7 μm and a mass average molecular weight of 13,000 (solid content: 14.3 mass%) as seed particles is obtained. It was.

[First seed particle enlargement process]
Next, the amount of polymethyl methacrylate particle dispersion having a volume average particle diameter of 0.7 μm (solid content: 14.3% by mass) was added from 390 g to 33.8 g (content of polymethyl methacrylate particles: 4.8 g). In the same manner as in Example 1 except that it was changed to), a dispersion of polymethyl methacrylate particles (solid content: 14.3% by mass) was obtained as enlarged seed particles. In this example, the amount of methyl methacrylate absorbed by the polymethyl methacrylate particles is 11379 parts by mass with respect to 100 parts by mass of the polymethyl methacrylate particles.

  The polymethyl methacrylate particles contained in the obtained dispersion had a volume average particle size of 3.30 μm and a mass average molecular weight of 23,000.

[Second seed particle enlargement process]
Further, the first seed particle enlargement of the present example was replaced with 36 g of a dispersion of polymethyl methacrylate particles having a volume average particle diameter of 1.50 μm obtained in the first seed particle enlargement step of Example 1. In the same manner as in Example 1, except that 74 g of polymethyl methacrylate particle dispersion (volume content of 10.6 g of polymethyl methacrylate particles) having a volume average particle size of 3.30 μm obtained in the step was used. A dispersion of polymethyl methacrylate particles (solid content: 14.3% by mass) was obtained as enlarged seed particles. In this example, the amount of methyl methacrylate absorbed by the polymethyl methacrylate particles is 4725 parts by mass with respect to 100 parts by mass of the polymethyl methacrylate particles.

  The polymethyl methacrylate particles contained in the obtained dispersion had a volume average particle diameter of 11.3 μm and a mass average molecular weight of 24,000.

[Resin particle manufacturing process]
In the second seed particle enlargement step of this example, instead of 40 g of the dispersion of polymethyl methacrylate particles having a volume average particle diameter of 7.64 μm obtained in the second seed particle enlargement step of Example 1. Resin particles were obtained in the same manner as in Example 1 except that 57 g of a dispersion of polymethyl methacrylate particles having a volume average particle diameter of 11.3 μm (content of polymethyl methacrylate particles 8.2 g) was used. Got. In this example, the amount of methyl methacrylate and isobutyl methacrylate absorbed by the polymethyl methacrylate particles is 8465 parts by mass with respect to 100 parts by mass of the polymethyl methacrylate particles.

  When the volume-based particle size distribution of the obtained resin particles was measured by the method described above, the obtained resin particles had a volume average particle size of 53.3 μm and a variation coefficient of the volume-based particle size of 10. It was 6%. The obtained resin particles had a mass average molecular weight of about 400,000. In this example, the proportion of methyl methacrylate in all monomers used for the production of resin particles (corresponding to the content of structural units derived from methyl methacrylate in the resin particles) was 91.0% by mass. The ratio of isobutyl methacrylate in the total amount of monomers used for the production of the resin particles (corresponding to the content of structural units derived from isobutyl methacrylate in the resin particles) is 9.0% by mass.

Example 4
[Seed particle manufacturing process, first seed particle enlargement process, second seed particle enlargement process]
In the same manner as in Example 1, seed particles were produced and enlarged.

[Resin particle manufacturing process]
Polymerization was carried out under the same conditions as in Example 1 except that 610 g of methyl methacrylate and 70 g of 2-ethylhexyl acrylate were used in place of 620 g of methyl methacrylate and 70 g of isobutyl methacrylate as the non-crosslinkable monomer mixture. Particles were obtained.

  When the volume-based particle size distribution of the obtained resin particles was measured by the method described above, the obtained resin particles had a volume average particle size of 33.4 μm and a variation coefficient of the volume-based particle size of 11. It was 8%. The obtained resin particles had a mass average molecular weight of about 290,000.

[Comparative Example 1]
In the resin particle production process of Example 1, polymethacrylic acid was obtained in the same manner as in Example 1 except that only 680 g of methyl methacrylate was used instead of 620 g of methyl methacrylate and 70 g of isobutyl methacrylate as the non-crosslinkable monomer. 100 mass% resin particles of methyl acid were obtained.

  When the volume-based particle size distribution of the obtained resin particles was measured by the method described above, the obtained resin particles had a volume average particle size of 32.8 μm and a variation coefficient of the volume-based particle size of 20. It was 9%. Therefore, the resin particles obtained in this comparative example were inferior in monodispersibility compared with the resin particles obtained in Example 1. Moreover, the mass average molecular weight of the obtained resin particles was about 840,000.

[Comparative Example 2]
In the resin particle production process of Example 1, only 646 g of methyl methacrylate was used instead of 620 g of methyl methacrylate and 70 g of isobutyl methacrylate as the non-crosslinkable monomer, and 34 g of ethylene glycol dimethacrylate was used as the crosslinkable monomer. Except that, resin particles made of methyl methacrylate-ethylene glycol dimethacrylate copolymer (crosslinked polymer) were obtained in the same manner as Example 1.

  When the volume-based particle size distribution of the obtained resin particles was measured by the method described above, the obtained resin particles had a volume average particle size of 35.0 μm and a volume-based particle size variation coefficient of 10. 2%.

[Comparative Example 3]
[Seed particle manufacturing process, first seed particle enlargement process, second seed particle enlargement process]
In the same manner as in Example 1, seed particles were produced and enlarged.

[Resin particle manufacturing process]
Example 1 except that 620 g of isostearyl acrylate (89.9% by mass with respect to the mixture of methyl methacrylate and isobutyl methacrylate as a non-crosslinkable monomer mixture) was used instead of 620 g of methyl methacrylate Attempts were made to prepare resin particles in the same manner as in Example 1, but aggregation was severe and monodisperse resin particles could not be obtained.

[Example 5 (manufacturing example of porous resin molding)]
The resin particles (plural) obtained in Example 1 were filled into a polyether ether ketone (PEEK) mold having a length of 5 cm, a width of 3 cm, and a depth of 1 cm as a mold. Heat treatment was performed for 20 hours so that the temperature was 190 ° C. Thereby, the surface parts of the resin particles were fused and the resin particles were connected.

  Next, 7.0 ml of 2-hydroxyethyl methacrylate as a vinyl monomer that does not dissolve the resin particles, 2.0 ml of ethylene glycol as a polyhydric alcohol, and resin particles are added to the porous template obtained by this fusion. 0.3 ml of tetramethylene glycol dimethacrylate as a vinyl monomer that does not dissolve, 0.7 ml of ammonium persulfate (0.4 g / ml) as a polymerization initiator, disodium disulfite (0.15 g / ml) as an antioxidant ml) A monomer mixture consisting of 0.7 ml and deionized water 1.4 ml is infiltrated into the above mold and polymerized 2-hydroxyethyl methacrylate and tetramethylene glycol dimethacrylate at 70 ° C. for 12 hours. I let you. Thereby, the resin molding which consists of a copolymer of 2-hydroxyethyl methacrylate (HEMA) and tetraethylene glycol dimethacrylate containing the resin particle obtained in Example 1 was obtained.

  Next, the obtained resin molding was subjected to an immersion treatment at room temperature for 4 hours in acetone as an organic solvent that dissolves the resin particles but does not dissolve the vinyl monomer polymer. The target porous resin molded product was obtained by dissolving and removing the resin particles obtained in 1.

Comparative Example 4 (Production Example of Porous Resin Molded Body (Resin Molded Body Using Resin Particles of Comparative Example 1))
Instead of the resin particles obtained in Example 1, an attempt was made to produce a resin molded article under the same conditions as in Example 5 except that the resin particles obtained in Comparative Example 1 were used. However, resin particles remained in the resin molded body, and the intended porous resin molded body was not obtained.

[Comparative Example 5 (Production Example of Porous Resin Molded Body (Resin Molded Body Using Resin Particles of Comparative Example 2)])
Instead of the resin particles obtained in Example 1, an attempt was made to produce a resin molded article under the same conditions as in Example 5 except that the resin particles obtained in Comparative Example 2 were used. However, some resin particles remain in the resin molded body, and the intended porous resin molded body was not obtained.

  The resin particles of the present invention can be suitably used as resin particles (resin particles for pore-forming agent) used as a pore-forming agent in a method for producing a resin-removable porous resin molding. In addition, the resin particles of the present invention can be obtained by preparing a molded body obtained by mixing a heat-resistant material such as ceramics with resin particles serving as a pore-forming agent, and then heating the molded body at a high temperature to burn out the resin particles. It can also be used as resin particles (pore-forming agent) used in a method for producing a porous molded body. Furthermore, the resin particles of the present invention can be used as a light diffusing agent, an antiblocking agent, a cosmetic additive, and the like.

  In addition, the porous resin molded body of the present invention includes, for example, a biocompatible material such as a biological carrier for culturing cells and microorganisms, a filter used for capturing particles of a certain size, microorganisms, and the like (for example, diesel Diesel particulate filter (DPF) that traps and reduces particulate matter in engine exhaust gas, porous molded body that traps or dissipates gas and liquid at a constant rate (eg, gradually releases drug) Capsules).

Claims (5)

80 to 95 mass% of structural units derived from alkyl (meth) acrylate having 3 or less carbon atoms in the alkyl group and structures derived from alkyl (meth) acrylate having 4 to 12 carbon atoms in the alkyl group It consists of a non-crosslinked polymer containing 5 to 20% by mass of units,
The weight average molecular weight is in the range of 200,000 to 600,000,
Resin particles having a coefficient of variation of particle diameter of 15% or less. The resin particle according to claim 1,
Resin particles having a volume average particle diameter in the range of 15 to 60 μm. Emulsion polymerization of alkyl (meth) acrylate having an alkyl group having 3 or less carbon atoms in the presence of 0.5 to 3 parts by mass of a chain transfer agent with respect to 100 parts by mass of the alkyl (meth) acrylate. Including a seed particle production step of producing seed particles made of a non-crosslinked polymer,
After the seed particle production step, after the alkyl (meth) acrylate having an alkyl group having 3 or less carbon atoms is absorbed by the seed particle, the absorbed alkyl (meth) acrylate is 100 parts by mass. Seed particles that enlarge the seed particles by polymerizing the alkyl (meth) acrylate in the presence of 0.5 to 3 parts by mass of a chain transfer agent to obtain enlarged seed particles made of a non-crosslinked polymer. Including at least one enlargement process, and
After the seed particle enlargement step, the alkyl group has 80 to 95% by mass of an alkyl (meth) acrylate monomer having 3 or less carbon atoms, and the alkyl group has 4 to 12 carbon atoms (meta ) After absorbing a non-crosslinkable monomer mixture containing 5 to 20% by mass of an alkyl acrylate into the enlarged seed particles, the non-crosslinkable monomer is present in the presence of a water-soluble polymerization inhibitor. A method for producing resin particles, comprising a resin particle production step of producing a non-crosslinked resin particle by polymerizing a mixture. It is a manufacturing method of the resin particle according to claim 3,
In the seed particle manufacturing step, a seed particle having a mass average molecular weight in the range of 5,000 to 50,000 and a volume average particle diameter in the range of 0.25 μm to 1.0 μm is manufactured.
In the seed particle enlargement step, 1,000 to 25,000 parts by mass of the alkyl (meth) acrylate is absorbed with respect to 100 parts by mass of the seed particles,
In the resin particle production step, 4,000 to 22,000 parts by mass of the non-crosslinkable monomer mixture is absorbed with respect to 100 parts by mass of the enlarged seed particles. . Filling a plurality of resin particles according to claim 1 or 2 in a mold;
Heating the mold and fusing the resin particles together to connect the resin particles;
A resin molding comprising a polymer of the vinyl monomer by adding a vinyl monomer that does not dissolve the resin particles and a polymerization initiator into the mold and polymerizing the vinyl monomer. Obtaining a body;
A step of removing the resin particles from the resin molding by dissolving the resin particles in an organic solvent that dissolves the resin particles but does not dissolve the polymer of the vinyl monomer. A method for producing a porous resin molded article.