Method for producing polymer microparticles and dispersion stabilizer

Abstract

Provided is a production method by which polymer fine particles having excellent polymerization stability and a small particle diameter (for example, the average particle diameter is at most 0.20 μm) can be obtained. The production method comprises a step for producing polymer fine particles by polymerizing one or more second vinyl monomers, in the presence of a first polymer having a polymer chain of one or more first vinyl monomers and a unit of living radical polymerization activity, through dispersion polymerization using living radical polymerization based on the living radical polymerization activity. The unit of living radical polymerization activity can be used as an active unit in living radical polymerization through an exchange chain mechanism or a bond-dissociation mechanism.

Description

Technical Field

[0001] This specification relates to a method for producing polymer microparticles and the like.

[0002] (Cross-reference to related applications) This application is a related application of Japanese Patent Application No. 2019-207465, which was filed on November 15, 2019. This application claims the priority based on this application and incorporates all the contents described in this application.

Background Art

[0003] Polymer microparticles are used in a wide range of fields, such as electric and electronic materials such as conductive microparticles, spacers (for LCD cells, touch panel seal parts, etc.), modifiers for resin films, thickeners (for paints, cosmetics, etc.). Conventional methods for producing polymer microparticles with a size of less than micron size include emulsion polymerization method, suspension polymerization method, precipitation polymerization method, and dispersion polymerization method.

[0004] The emulsion polymerization method is a technique in which a solvent, a polymerizable monomer hardly soluble in the solvent, and an emulsifier (surfactant) are mixed, and polymerization is carried out using a polymerization initiator soluble in the solvent to obtain nano-order polymer microparticles. However, since it is necessary to use a large amount of a low-molecular-weight emulsifier, there are concerns about adverse effects (turbidity, water resistance, etc.) on the final product. The suspension polymerization method is a technique in which droplets are formed by mechanically stirring a polymerizable monomer in water in the presence of a dispersion stabilizer, and polymerization is carried out using an appropriate oil-soluble polymerization initiator to obtain polymer particles. The precipitation polymerization method is a technique for obtaining polymer particles in a system in which the polymerizable monomer is dissolved in a solvent but the resulting polymer is insoluble in the solvent and precipitates. Here, in the suspension polymerization method, polymer particles with a particle diameter of several tens of micrometers or more are generally obtained, and in the precipitation polymerization method, polymer particles with a diameter of several micrometers to several hundreds of micrometers are generally obtained. However, these methods are polymerization methods that cannot be applied to applications that require a smaller particle diameter.

[0005] In contrast, the dispersion polymerization method is a method of performing precipitation polymerization in the presence of a dispersion stabilizer. The particle size of the generated fine particles can be controlled by the types and addition amounts of the polymerizable monomer, solvent, and dispersion stabilizer, and the fine particles have the characteristic of having a narrow particle size distribution.

[0006] As methods for producing polymer fine particles by dispersion polymerization, various methods are known. In Patent Document 1, as a method for forming fine particles of acrylamide and its derivatives, p-styrenesulfonic acid and its salts, (meth)acrylic acid and their salts, etc., as homopolymers of these monomers or copolymers of these monomers, or copolymers with other monomers, a water-miscible organic solvent such as ethanol is used as the solvent for polymerization, and a polymer soluble in a water-miscible organic solvent or a mixed solvent with water is present in advance during polymerization, and the above monomers are polymerized to produce hydrophilic polymer fine particles. The range of the average particle size of the polymer fine particles specifically disclosed in the examples is 0.34 to 2.40 μm.

[0007] In Patent Document 2, a method for producing polymer fine particles is disclosed by polymerizing acrylamide or an acrylate neutralized product alone or as a mixture in a mixed solvent of water and a water-miscible organic solvent in the presence of polyvinylpyrrolidone or a polyvinylpyrrolidone copolymer having a weight average molecular weight of 10,000 or more. The range of the average particle size of the polymer fine particles specifically disclosed in the examples is 0.7 to 1.30 μm.

[0008] Patent Document 3 discloses a method for producing monodisperse polymer fine particles by polymerizing one or more vinyl monomers that are soluble in an alcoholic medium but the resulting polymer is insoluble or hardly soluble in the alcoholic medium in the presence of a polymer (dispersion stabilizer) obtained by polymerizing specific monomers in the alcoholic medium. The range of the average particle diameter of the polymer fine particles specifically disclosed in the examples is 0.19 to 9.0 μm. More specifically, in this dispersion polymerization method, when acrylamide is used as the vinyl monomer, polymer fine particles with average particle diameters of 0.19 μm and 0.20 μm can be obtained, and when ammonium acrylate is used as the vinyl monomer, polymer fine particles with an average particle diameter of 0.21 μm can be obtained.

[0009] Patent Document 4 discloses that a raw material monomer containing a monomer having two or more unsaturated double bonds and an unsaturated monomer having a hydrophilic functional group or an active hydrogen group is subjected to solution polymerization, preferably dispersion polymerization or precipitation polymerization similar thereto, using a polymerization initiator in a medium in which the raw material monomer is soluble but the resulting polymer is insoluble, so that crosslinked polymer fine particles having a narrow particle size distribution and a relatively uniform particle diameter can be efficiently obtained without using seed particles. Further, at this time, by adding an organic compound having 5 or more carbon atoms and a melting point of 80 °C or lower to the reaction system, the dispersibility of the particles is improved, the particle size distribution can be controlled more uniformly, and monodisperse polymer fine particles can be efficiently obtained. The range of the average particle diameter of the polymer fine particles specifically disclosed in the examples is 2.5 μm to 5.2 μm.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

[0011] However, in the dispersion polymerization methods described in Patent Documents 1, 2, and 4, polymer fine particles with a small particle size (e.g., 0.20 μm or less) could not be produced. Further, according to Patent Document 3, when ammonium acrylate was used as a monomer, the particle size was 0.21 μm.

[0012] In addition, according to the present inventors, when other vinyl monomers other than the vinyl polymers specifically disclosed in Patent Document 3 were used, problems such as a decrease in the dispersibility of the fine particles and aggregation during the polymerization reaction occurred, and the polymerization stability was sometimes a problem. There was also a problem with the degree of freedom in the selection of vinyl monomers.

[0013] This specification provides a production method capable of obtaining polymer fine particles having excellent polymerization stability and a small particle size (e.g., an average particle size of 0.20 μm or less), and a dispersion stabilizer therefor.

[0014] The present inventors focused on, for example, a polymer having a polymerizable group used as a dispersion stabilizer. Then, by using a polymer having a specific living radical polymerization active unit as a dispersion stabilizer and performing dispersion polymerization using living radical polymerization utilizing the specific living radical polymerization activity, they obtained the finding that secondary aggregation and the like during the polymerization step can be suppressed and polymer fine particles with a small particle size can be stably obtained. According to this specification, the following means are provided based on such findings.

[0015] [1] A step of producing polymer fine particles by polymerizing one or more second vinyl monomers by dispersion polymerization using living radical polymerization based on the living radical polymerization activity in the presence of a polymerization chain of one or more first vinyl monomers and a first polymer having a living radical polymerization active unit. comprising A method wherein the living radical polymerization active unit is an active unit in living radical polymerization by an exchange chain mechanism or a bond-dissociation mechanism. [2] The method according to [1], wherein the living radical polymerization active unit is living radical polymerization by the exchange chain mechanism. [3] The method according to [1] or [2], wherein the living radical polymerization active unit is an active unit in living radical polymerization by a reversible addition-fragmentation chain transfer polymerization method or an iodine transfer polymerization method. [4] The method according to any one of [1] to [3], characterized in that the molecular weight distribution of the first polymer is 2.0 or less. [5] In the production process of the polymer fine particles, 0.3 parts by mass or more and 50 parts by mass or less of the first polymer are used with respect to 100 parts by mass of the one or more second vinyl monomers. The method according to any one of [1] to [4]. [6] In the production process of the polymer fine particles, 0.3 parts by mass or more and 20 parts by mass or less of the first polymer are used with respect to 100 parts by mass of the one or more second vinyl monomers. The method according to [5]. [7] The method according to any one of [1] to [6], wherein the one or more second vinyl monomers contain acrylic acid or a salt thereof, and the polymerization solvent in the production process of the polymer fine particles contains acetonitrile. [8] The method according to [7], wherein the one or more first vinyl monomers include two or more styrenes selected from the group consisting of styrenes, (meth)acrylonitrile compounds, maleimide compounds, unsaturated acid anhydrides, and unsaturated carboxylic acid compounds. [9] The method according to any one of [1] to [8], wherein the one or more second vinyl monomers contain 50% by mass or more and 100% by mass or less of acrylic acid based on the total mass.

[10] The method according to [9], wherein the one or more first vinyl monomers contain 20% by mass or more of styrenes based on the total mass.

[11] The one or more first vinyl monomers contain styrenes in an amount of 20% by mass or more of their total mass, and the one or more second vinyl monomers contain acrylic acid or its salt in an amount of 50% by mass or more and 100% by mass or less of their total mass. The first polymer has a living radical polymerization active unit by reversible addition-fragmentation chain transfer polymerization. The method according to [1], wherein 0.3 part by mass or more and 20 parts by mass or less of the first polymer is used with respect to 100 parts by mass of the one or more second vinyl monomers.

[12] A dispersion stabilizer for use in the production of polymer fine particles, comprising a polymer having a polymerization chain of one or more first vinyl monomers and a living polymerization active unit provided in at least a part of the polymerization chain.

Embodiments for Carrying Out the Invention

[0016] The disclosure of this specification relates to a method for producing polymer fine particles, a dispersion stabilizer, and the like. According to the method for producing polymer fine particles disclosed in this specification, in the presence of a first polymer having a polymerization chain containing units derived from a first vinyl monomer (hereinafter also referred to as the first polymerization chain) and a living polymerization active unit, a second vinyl monomer is polymerized, so that the second vinyl monomer is polymerized with the first polymerization chain as a base point, and its polymerization chain (hereinafter also referred to as the second polymerization chain) is extended from the living polymerization active unit. The extension of the second polymerization chain forms the nucleus of the polymer fine particles, and then, by the extension of the second polymerization chain and the interaction between the second polymerization chains, particles are formed and the particle size of the particles increases.

[0017] The first polymer to the second polymerization chain are polymerized by living radical polymerization based on the active units in living radical polymerization by an exchange chain mechanism or a bond-dissociation mechanism. Generally, the molecular weight distribution is narrow, and when the polymer fine particles grow, it acts to stabilize the dispersion of the polymer fine particles. Further, due to the above-described living polymerization activity derived from the first polymer, polymer fine particles having a first polymerization chain and a second polymerization chain and excellent in the uniformity of the molecular weights of these polymerization chains and the entire polymerization chain can be obtained.

[0018] By selecting the types of the first polymer chain and the second polymer chain, etc., polymer microparticles having the first polymer chain of the first polymer on the surface layer of the polymer microparticles and having the second polymer chain as a core can be produced.

[0019] In the production process of the polymer microparticles, at the start of polymerization, a homogeneous solution in which all monomers, initiators, etc. are dissolved in a medium, and in the dispersion polymerization method in which the polymer generated by the start of polymerization precipitates and aggregates to form particles and becomes a heterogeneous solution, the above method can be applied. At this time, these polymer chains are organized such that the first polymer chain is arranged on the surface layer side of the polymer microparticles and the second polymer chain is arranged inside the polymer microparticles, and the polymer microparticles are generated and grown. Since the first polymer or the first polymer chain functions as an excellent dispersion stabilizer and the dispersion stability of the polymer microparticles is ensured in the polymer microparticle production process, polymer microparticles having an average particle diameter of 0.2 μm or less can be easily obtained.

[0020] Hereinafter, representative and non-limiting specific examples of the present disclosure will be described in detail. This detailed description is merely intended to show those skilled in the art the details for carrying out preferred examples of the present disclosure, and is not intended to limit the scope of the present disclosure. Further, the additional features and inventions disclosed below can be used separately or together with other features and inventions in order to provide a further improved "method for producing polymer microparticles and dispersion stabilizer".

[0021] Also, the combinations of features and steps disclosed in the following detailed description are not essential for carrying out the present disclosure in the broadest sense, and are described only for explaining representative specific examples of the present disclosure in particular. Further, the various features of the above and below representative specific examples, as well as the various features described in the independent and dependent claims, do not have to be combined as in the specific examples described herein or in the order listed when providing additional and useful embodiments of the present disclosure.

[0022] All features described in this specification and / or claims are intended to be disclosed individually and independently of each other, as limitations on the initial disclosure and the claimed subject matter, apart from the configurations of the features described in the examples and / or claims. Further, all descriptions of numerical ranges and groups or collections are made with the intention of disclosing intermediate configurations as limitations on the initial disclosure and the claimed subject matter.

[0023] Hereinafter, various embodiments disclosed in this specification will be described in detail. In this specification, "(meth)acryl" means acrylic and / or methacrylic, and "(meth)acrylate" means acrylate and / or methacrylate. Also, "(meth)acryloyl group" means acryloyl group and / or methacryloyl group.

[0024] (Method for producing polymer microparticles) The method for producing polymer microparticles disclosed in this specification (hereinafter, also simply referred to as this production method) can include a step of polymerizing one or more second vinyl monomers (hereinafter, also simply referred to as the second monomer) in the presence of a first polymer chain containing monomer units derived from one or more first vinyl monomers (hereinafter, also simply referred to as the first monomer) and a first polymer having a living polymerization active unit to produce polymer microparticles.

[0025] (First polymer) In this method, a first polymer can be used. The first polymer can include a first polymer chain containing units derived from one or more first monomers and a living polymerization active unit. The first monomer can vary depending on the function and use of the polymer microparticles to be obtained, and various vinyl monomers can be used without particular limitation.

[0026] (First Polymer Chain) The first polymer chain is obtained by polymerizing a monomer composition containing a first monomer. Examples of the first monomer include styrenes, (meth)acrylonitrile compounds, maleimide compounds, unsaturated acid anhydrides, and unsaturated carboxylic acid compounds. One or more of these can be used in combination.

[0027] Styrenes include styrene and its derivatives. Specific compounds include styrene, α-methylstyrene, β-methylstyrene, vinylxylene, vinylnaphthalene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, p-n-butylstyrene, p-isobutylstyrene, p-t-butylstyrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-chloromethylstyrene, p-chloromethylstyrene, o-chlorostyrene, p-chlorostyrene, o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, divinylbenzene, etc. One or more of these can be used. Among these, from the viewpoint of polymerizability, styrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene are preferred.

[0028] Examples of the (meth)acrylonitrile compound include (meth)acrylonitrile, α-methylacrylonitrile, etc. For example, acrylonitrile is used.

[0029] Examples of maleimide compounds include maleimide and N-substituted maleimide compounds. Specific examples of N-substituted maleimide compounds include N-alkyl-substituted maleimide compounds such as N-methylmaleimide, N-ethylmaleimide, N-n-propylmaleimide, N-isopropylmaleimide, N-n-butylmaleimide, N-isobutylmaleimide, N-tert-butylmaleimide, N-pentylmaleimide, N-hexylmaleimide, N-heptylmaleimide, N-octylmaleimide, N-laurylmaleimide, N-stearylmaleimide; N-cycloalkyl-substituted maleimide compounds such as N-cyclopentylmaleimide, N-cyclohexylmaleimide; N-aryl-substituted maleimide compounds such as N-phenylmaleimide, N-(4-hydroxyphenyl)maleimide, N-(4-acetylphenyl)maleimide, N-(4-methoxyphenyl)maleimide, N-(4-ethoxyphenyl)maleimide, N-(4-chlorophenyl)maleimide, N-(4-bromophenyl)maleimide, and N-aralkyl-substituted maleimide compounds such as N-benzylmaleimide. One or more of these can be used. For example, N-phenylmaleimide is used.

[0030] Examples of unsaturated acid anhydrides include maleic anhydride, itaconic anhydride, citraconic anhydride, etc. One or more of these can be used.

[0031] Examples of unsaturated carboxylic acid compounds include (meth)acrylic acid, cinnamic acid, crotonic acid, and unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, and monoalkyl esters of unsaturated dicarboxylic acids. One or more of these can be used.

[0032] As the first monomer, among these, for example, it is preferable to contain at least styrenes. This is because styrenes are easy to undergo living polymerization and can impart appropriate hydrophobicity and affinity for organic solvents. The first polymer chain can be imparted with hydrophobicity or affinity for organic solvents. By doing so, for example, when producing polymer fine particles by dispersion polymerization in a polar organic solvent, the first polymer tends to be present on the surface layer of the polymer fine particles, and the dispersion stability of the polymer fine particles is improved.

[0033] Styrenes are, for example, 20% by mass or more of the total mass of the first monomer (the first monomer unit of the first polymer chain) for polymerizing the first polymer chain. When it is 20% by mass or more, living polymerization becomes easy, and appropriate hydrophobicity and affinity for organic solvents can be imparted. Also, for example, it is 30% by mass or more, also for example, 35% by mass or more, also for example, 40% by mass or more, also for example, 50% by mass or more, also for example, 60% by mass or more, also for example, 65% by mass or more, also for example, 70% by mass or more, also for example, 75% by mass or more. Further, styrenes are 100% by mass or less of the total mass, also for example, 95% by mass or less, also for example, 90% by mass or less, also for example, 85% by mass or less, also for example, 80% by mass or less, also for example, 75% by mass or less. As the range with respect to the total mass of styrenes, the above-mentioned lower limit and upper limit can be set by appropriately combining them. For example, it is 20% by mass or more and 95% by mass or less, also for example, 30% by mass or more and 75% by mass or less, also for example, 35% by mass or more and 85% by mass or less.

[0034] (Meta)acrylonitrile compounds, maleimide compounds, acid anhydrides, and unsaturated carboxylic acid compounds can each be used alone, or it is preferable to use one or more of these four types in combination with styrenes. This is because all of these four types can maintain, adjust, or impart hydrophobicity or organic solvent affinity to the first polymer chain. Among them, one or more of (meta)acrylonitrile compounds such as acrylonitrile, maleimide compounds such as N-phenylmaleimide, and acid anhydrides are preferable, and combinations such as styrene and acrylonitrile, styrene and N-phenylmaleimide are suitable. In addition, unsaturated carboxylic acid compounds are preferable in that they can easily change the polarity of the first polymer.

[0035] When used in combination with styrenes, the total amount of these one or more first monomers other than styrenes is, for example, 20% by mass or more of the total mass of the first monomers (the first monomer units of the first polymer chain) for polymerizing the first polymer chain. Also, for example, 25% by mass or more, also for example, 30% by mass or more, also for example, 35% by mass or more, also for example, 40% by mass or more, also for example, 50% by mass or more, also for example, 60% by mass or more. Further, the (meta)acrylonitrile compound is 80% by mass or less of the total mass, also for example, 75% by mass or less, also for example, 70% by mass or less, also for example, 65% by mass or less, also for example, 60% by mass or less, also for example, 55% by mass or less, also for example, 50% by mass or less. The total amount of these one or more first monomers other than styrenes can be set by appropriately combining the above-mentioned lower and upper limits. For example, it is 20% by mass or more and 65% by mass or less, also for example, 25% by mass or more and 50% by mass or less.

[0036] The first polymer chain may be a polymer chain consisting only of the above-described first monomer, but if necessary, other vinyl monomers other than the above can be used as the first monomer. For example, known vinyl monomers such as (meth)acrylic acid esters such as alkyl (meth)acrylate can be used. Such other monomers are, for example, 10% by mass or less, for example, 5% by mass or less, for example, 3% by mass or less, for example, 1% by mass or less, and for example, 0.5% by mass or less of the total mass of the monomers constituting the first polymer chain.

[0037] In addition to the above-described first polymer chain, the first polymer may include a polymer chain as another block. Examples of the vinyl monomer constituting such a polymer chain include (meth)acrylic acid, known alkyl (meth)acrylate esters, and known hydroxyalkyl (meth)acrylate esters. Such vinyl monomers may be the second monomers described later. Such other polymer chains may be added, for example, in another synthesis step after the formation of the first polymer chain. By being provided so as to be directly linked to the living radical active unit described later and linked to the first polymer chain, a part of the monomer common to the second monomer used for the polymer fine particles can be provided in the first polymer in advance.

[0038] (Living radical polymerization active unit) The first polymer can include a living radical polymerization active unit. Living radical polymerization generally consists only of an initiation reaction and a growth reaction in the polymerization process, without accompanying side reactions that deactivate the growth end such as a chain transfer reaction or a termination reaction, and the growth end always maintains the growth activity (living radical polymerization activity) based on radical species during polymerization. The living radical polymerization active unit is the growth active unit in living radical polymerization. Also, the living radical polymerization active unit is a unit derived from a controller of the living radical polymerization method.

[0039] Although various living radical polymerizations are known from their reaction mechanisms, the living radical polymerization active units can be the active units in living radical polymerization by an exchange chain mechanism or a bond-dissociation mechanism. With these living radical polymerizations, it is possible to easily obtain a first polymer with a narrow molecular weight distribution, and in the dispersion polymerization of polymer fine particles, various monomers can be selected for the solubility of the first polymer in the polymerization solvent and the function as a dispersion stabilizer.

[0040] Examples of living radical polymerization by an exchange chain mechanism include reversible addition-fragmentation chain transfer polymerization (RAFT method), iodine transfer polymerization method, polymerization method using an organic tellurium compound (TERP method), polymerization method using an organic antimony compound (SBRP method), polymerization method using an organic bismuth compound (BIRP method), and the like. Living radical polymerization by an exchange chain mechanism is preferable in that the average particle diameter of the polymer fine particles can be reduced. Among these, the RAFT method and the iodine transfer polymerization method are preferable in that the molecular weight distribution of the first polymer can be narrowed. Furthermore, the RAFT method is preferably used.

[0041] Examples of living radical polymerization by a bond-dissociation mechanism include, for example, the nitroxide radical method (NMP method). Living radical polymerization by a bond-dissociation mechanism is preferable in that the average particle diameter of the polymer fine particles can be reduced. Among these, the NMP method is preferable in that the molecular weight distribution of the first polymer can be narrowed.

[0042] The polymerization conditions for these various living radical polymerizations are well-known to those skilled in the art, and if necessary, the synthesis of the first polymer by the RAFT method, iodine transfer polymerization method, and NMP method will be exemplified. In the living radical polymerization process, there are various processes such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. However, considering that it is the polymerization basis in the production of polymer fine particles and functions as a dispersion stabilizer, solution polymerization can be used, for example, in the production of the first polymer.

[0043] The first polymer can be synthesized by the RAFT method using, for example, a RAFT agent. The RAFT method is a living radical polymerization method suitable for obtaining a first polymer having a molecular weight distribution of 2.0 or less. As the RAFT agent, which is a living radical polymerization controller in the RAFT method, known RAFT agents can be used without particular limitation. For example, dithioester compounds, xanthate compounds, trithiocarbonate compounds, dithiocarbamate compounds, and the like can be mentioned. The RAFT agent may be monofunctional with one active site, or a polyfunctional agent having two or more active sites can also be used. A polyfunctional RAFT agent having two or more active sites causes the polymerization chain to extend in two or more directions. From the viewpoint of producing polymer particles, it may be preferable to use a bifunctional or trifunctional or higher RAFT agent.

[0044] The substituents in the RAFT agent can be appropriately determined in consideration of the first monomer and the second monomer. Also, the amount of the RAFT agent used is appropriately adjusted according to the target Mn, but it can be used, for example, in an amount of 0.1 part by mass or more and 10 parts by mass or less, or for example, 0.5 part by mass or more and 5 parts by mass or less, or for example, 1 part by mass or more and 4 parts by mass or less, or for example, 1 part by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the first monomer.

[0045] As the RAFT agent, various known RAFT agents such as dithioester compounds, xanthate compounds, trithiocarbonate compounds, and dithiocarbamate compounds can be used. More specifically, for example, dibenzyl trithiocarbonate, dithiobenzoate·2-cyano-2-propyl benzodithioate, 2-phenyl-2-propyl benzodithioate, trithiocarbonate, 2-cyano-2-propyl dodecyl trithiocarbonate, methyl 2-(dodecylthiocarbonothioylthio)-2-methylpropanoate, distyryl trithiocarbonate, dicumyl trithiocarbonate, dithiocarbamate, cyanomethyl N-methyl-N-phenyldithiocarbamate, and the like can be mentioned.

[0046] As the radical polymerization initiator (radical generator) used in the polymerization by the RAFT method, known radical polymerization initiators such as azo compounds, organic peroxides, and persulfates can be used. However, azo compounds are preferred because they are easy to handle in terms of safety and less likely to cause side reactions during radical polymerization. Specific examples of the above azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), dimethyl-2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile), and the like. One or more of the above radical polymerization initiators can be used.

[0047] The usage ratio of such a radical polymerization initiator is not particularly limited. However, from the viewpoint of obtaining a polymer with a narrower molecular weight distribution, although the usage ratio of the radical polymerization initiator is not particularly limited, for example, it can be used in an amount of 0.005% by mass or more and 2% by mass or less, for example, 0.005% by mass or more and 1% by mass or less, or for example, 0.005% by mass or more and 0.5% by mass or less based on 100 parts by mass of the total mass of the first monomer.

[0048] In the RAFT method, it may be carried out in the presence of a chain transfer agent as necessary. One or more known chain transfer agents can be used.

[0049] In addition, in the RAFT method, known polymerization solvents can be used, including nitrile solvents, aromatic solvents, ketone solvents, ester solvents, orthoester solvents, dimethylformamide, dimethyl sulfoxide, alcohols, water, and the like. Specific examples of nitrile solvents include acetonitrile, isobutyronitrile, and benzonitrile. Specific examples of aromatic solvents include benzene, toluene, xylene, and anisole. Specific examples of ketone solvents include acetone, methyl ethyl ketone, and methyl isobutyl ketone. Specific examples of ester solvents include methyl acetate, ethyl acetate, propyl acetate, and butyl acetate. Specific examples of orthoester solvents include trimethyl orthoformate, triethyl orthoformate, tri(n-propyl) orthoformate, tri(isopropyl) orthoformate, trimethyl orthoacetate, triethyl orthoacetate, triethyl orthopropionate, trimethyl ortho-n-butyrate, and trimethyl orthoisobutyrate. Preferably, nitrile solvents such as acetonitrile and / or aromatic solvents such as anisole can be used.

[0050] When polymerizing the first polymer by living radical polymerization, the concentration of the first monomer is not particularly limited with respect to the total mass of the polymerization solvent and the first monomer. For example, it can be 10% by mass or more and 80% by mass or less, or for example, 15% by mass or more and 70% by mass or less, 20% by mass or more and 70% by mass or less, and so on.

[0051] The reaction temperature during the polymerization reaction by the RAFT method is preferably 40°C or higher and 100°C or lower, more preferably 45°C or higher and 90°C or lower, and even more preferably 50°C or higher and 80°C or lower. If the reaction temperature is 40°C or higher, the polymerization reaction can proceed smoothly. On the other hand, if the reaction temperature is 100°C or lower, side reactions can be suppressed and the restrictions on initiators and solvents that can be used are relaxed.

[0052] The first polymer can also be synthesized by the iodine transfer polymerization method using, for example, a controller for the iodine transfer polymerization method. The controller in the iodine transfer polymerization method can be a known controller without particular limitation. For example, methyl iodide, methylene iodide, iodoform, carbon tetraiodide, 1-phenylethyl iodide, benzyl iodide, methyl 2-iodoisobutyrate, ethyl 2-iodoisobutyrate, ethyl 2-iodo-2-phenylacetate, ethylene glycol bis(2-iodo-2-phenylacetate), ethylene glycol bis(2-iodoisobutyrate), etc. can be mentioned.

[0053] The amount of the controller for the iodine transfer reaction is appropriately adjusted according to the target Mn. For example, it can be used in an amount of 0.1 part by mass or more and 10 parts by mass or less, for example, 0.5 part by mass or more and 5 parts by mass or less, for example, 1 part by mass or more and 4 parts by mass or less with respect to 100 parts by mass of the first monomer. For example, it can be used in an amount of 0.1 part by mass or more and 10 parts by mass or less, for example, 0.5 part by mass or more and 5 parts by mass or less, for example, 1 part by mass or more and 4 parts by mass or less with respect to 100 parts by mass of the first monomer.

[0054] As the radical polymerization initiator (radical generator) used in the polymerization by the iodine transfer polymerization method, known radical polymerization initiators such as azo compounds, organic peroxides, and persulfates can be used in the same manner and in the same amount as in the RAFT method. Regarding the reaction temperature, polymerization solvent, and first monomer concentration in the iodine transfer polymerization method, they can be appropriately selected and applied from the same manner as in the RAFT method.

[0055] The first polymer can also be synthesized by the NMP method using, for example, a controller for the NMP method. The controller in the NMP method can be a known controller without particular limitation. For example, 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO), N-tert-butyl-N-[1-diethylphosphono-(2,2-dimethylpropyl)] nitroxide (DEPN), 2,2,5-trimethyl-4-phenyl-3-azahexane-3-nitroxide (TIPNO), N-tert-butyl-N-(1-tert-butyl-2-ethylsulfinyl)propyl-N-oxyl (BESN), etc. can be mentioned.

[0056] The amount of the controller used by the NMP method is appropriately adjusted according to the target Mn. For example, it can be used in an amount of 0.1 part by mass or more and 10 parts by mass or less, for example, 0.5 part by mass or more and 5 parts by mass or less, or for example, 1 part by mass or more and 4 parts by mass or less with respect to 100 parts by mass of the first monomer. For example, it can be used in an amount of 0.1 part by mass or more and 10 parts by mass or less, for example, 0.5 part by mass or more and 5 parts by mass or less, or for example, 1 part by mass or more and 4 parts by mass or less with respect to 100 parts by mass of the first monomer.

[0057] As the radical polymerization initiator (radical generator) used during the polymerization by the NMP method, known radical polymerization initiators such as azo compounds, organic peroxides, and persulfates can be used in the same manner and in the same amount as in the RAFT method. Regarding the reaction temperature, polymerization solvent, and first monomer concentration in the NMP method, they can be appropriately selected and applied from the same manner as in the RAFT method.

[0058] By synthesizing a first polymer through a predetermined living radical polymerization, a first polymer chain containing a first monomer and a first polymer having a living polymerization active unit can be obtained. The first polymer can also include two or more types of first polymer chains. For example, after performing living radical polymerization or the like using one or more first monomers of a certain composition, living radical polymerization or the like is performed using one or more first monomers of another composition, whereby a first polymer having a first polymer chain (block) having units derived from first monomers of different compositions can be obtained.

[0059] According to the predetermined living radical polymerization, a first polymer with controlled number average molecular weight (Mn) and weight average molecular weight (Mw) can be obtained. The Mn of the first polymer is not particularly limited, but for example, it is 3,000 or more, and for example, 5,000 or more, and for example, 7,000 or more, and for example, 8,000 or more, and for example, 10,000 or more. Also, the same Mn is 50,000 or less, and for example, 30,000 or less, and for example, 25,000 or less, and for example, 20,000 or less, and for example, 15,000 or less, and for example, 14,000 or less, and for example, 12,000 or less. As the range of Mn, the above-mentioned lower limit and upper limit can be appropriately combined and set. For example, it is 5,000 or more and 25,000 or less, and for example, 10,000 or more and 25,000 or less, and for example, 10,000 or more and 15,000 or less, and for example, 10,000 or more and 14,000 or less.

[0060] The Mw of the first polymer is not particularly limited. For example, it is 5,000 or more, and for example, 7,000 or more, and for example, 9,000 or more, and for example, 10,000 or more, and for example, 13,000 or more, and for example, 15,000 or more. Also, the same Mw is 60,000 or less, and for example, 55,000 or less, and for example, 50,000 or less, and for example, 45,000 or less, and for example, 40,000 or less, and for example, 36,000 or less, and for example, 35,000 or less, and for example, 30,000 or less, and for example, 25,000 or less. As the range of Mw, the above-mentioned lower limit and upper limit can be appropriately combined and set. For example, it is 1,000 or more and 40,000 or less, and for example, 10,000 or more and 35,000 or less, and for example, 10,000 or more and 30,000 or less, and for example, 15,000 or more and 25,000 or less.

[0061] Incidentally, both the Mw and Mn of the first polymer can be measured by gel permeation chromatography using polystyrene as a standard substance. As the details of the chromatography conditions, the conditions disclosed in the following examples can be adopted.

[0062] The molecular weight distribution (Mw / Mn) of the first polymer is not particularly limited. For example, it is 2.5 or less, and for example, 2.4 or less, and for example, 2.3 or less, and for example, 2.0 or less, and for example, 1.6 or less, and for example, 1.5 or less, and for example, 1.4 or less, and for example, 1.3 or less. Also, the molecular weight distribution is, for example, 1.1 or more, and for example, 1.2 or more, and for example, 1.3 or more, and for example, 1.4 or more, and for example, 1.5 or more. As the range of the molecular weight distribution, the above-mentioned lower limit and upper limit can be appropriately combined and set. For example, it can be 1.1 or more and 2.5 or less, and for example, 1.1 or more and 2.4 or less, and for example, 1.1 or more and 2.3 or less, and for example, 1.1 or more and 2.0 or less, etc.

[0063] The narrower the molecular weight distribution, the more likely the average particle size of the resulting polymer microparticles is to be small. To obtain polymer microparticles with an average particle size of 0.2 μm or less, it is preferable that the molecular weight distribution is 2.4 or less. To obtain polymer microparticles with a smaller average particle size, it is preferable that it is 1.7 or less, more preferably 1.6 or less, and even more preferably 1.4 or less.

[0064] The first polymer can include a first polymer chain and a living polymerization active unit. Typically, when a monofunctional regulator is used, the living polymerization active unit is provided at the end of the first polymer chain. When a bifunctional or higher-functional regulator is used, the living polymerization active unit branches in two or more directions, and each branch has a first polymer chain. In any case, when there is another polymer chain, this other polymer chain is directly bonded to the living polymerization active unit, and the first polymer chain is bonded to the distal end of the other polymer chain so that the first polymer chain is provided on the more distal side with respect to the living polymerization active unit.

[0065] (Production of Polymer Microparticles) In this method, in the presence of a first polymer, one or more second monomers can be subjected to dispersion polymerization to produce polymer microparticles. In this method, the first polymer can be used as a basis for the polymerization of the second monomer during the production of the polymer microparticles and as a dispersion stabilizer in the polymerization solvent of the polymer microparticles. By doing so, polymerization stability, that is, aggregation of the polymer microparticles during the polymerization process can be suppressed, generation of coarse aggregated particles can be suppressed, and polymer microparticles with a small average particle size and a narrow particle size distribution can be obtained.

[0066] (Second vinyl monomer) The second vinyl monomer is not particularly limited, and can be appropriately selected from known vinyl monomers according to the use of the polymer fine particles or the like. For example, in order to effectively exert the function as a dispersion stabilizer on the first polymer, make it present on the surface side of the polymer fine particles, and make the second polymer chain present on the core side as the main component of the polymer fine particles, the second monomer can be a vinyl monomer having a hydrophilic group. Considering this viewpoint, examples of the second monomer include vinyl monomers containing a carboxyl group, vinyl monomers containing a hydroxy group, and the like.

[0067] Examples of the vinyl monomer containing a carboxy group include unsaturated carboxylic acids such as (meth)acrylic acid and crotonic acid, unsaturated dicarboxylic acids such as itaconic acid, maleic acid, and fumaric acid, and monoalkyl esters of unsaturated dicarboxylic acids. Among them, (meth)acrylic acid is preferred.

[0068] (Meth)acrylic acid may be in the form of a salt. Here, (meth)acrylic acid (salt) includes (meth)acrylic acid and (meth)acrylate salts. The salt in the (meth)acrylate salt is an alkali metal salt, an alkaline earth metal salt, an ammonium salt, or an organic amine salt. Specifically, alkali metal salts such as sodium salt, lithium salt, potassium salt, rubidium salt, and cesium salt; alkaline earth metal salts such as magnesium salt, calcium salt, strontium salt, and barium salt; examples of the organic amine salt include alkanolamine salts such as monoethanolamine salt, diethanolamine salt, and triethanolamine salt, alkylamine salts such as monoethylamine salt, diethylamine salt, and triethylamine salt, and salts of organic amines such as polyamines such as ethylenediamine salt and triethylenediamine salt.

[0069] Examples of the hydroxy group-containing vinyl monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and mono(meth)acrylic acid esters of polyalkylene glycols such as polyethylene glycol and polypropylene glycol. These compounds may be used alone or in combination of two or more.

[0070] Such second monomers can be used alone or in combination of two or more. The carboxyl group-containing vinyl monomer can be, for example, 40% by mass or more, and can be, for example, 50% by mass or more, and can be, for example, 60% by mass or more, and can be, for example, 70% by mass or more, and can be, for example, 80% by mass or more, and can be, for example, 90% by mass or more, and can be, for example, 95% by mass or more, and can be, for example, 100% by mass, based on the total mass of the second monomer. The range of use of the carboxyl group-containing vinyl monomer with respect to the total mass of the second monomer can be set by appropriately combining the above-mentioned lower and upper limits. For example, it is 60% by mass or more and 100% by mass or less, and can be, for example, 80% by mass or more and 100% by mass or less, and can be, for example, 90% by mass or more and 100% by mass or less.

[0071] Also, with respect to the total mass of the second monomer, the hydroxy group-containing vinyl monomer is, for example, 5% by mass or more, and for example, 10% by mass or more, for example, 20% by mass or more, and for example, 30% by mass or more, and for example, 40% by mass or more. Also, it is 50% by mass or less, and for example, 40% by mass or less, and for example, 30% by mass or less, and for example, 20% by mass or less, and for example, 10% by mass or less, and for example, 5% by mass or less. The range of use of the hydroxy group-containing vinyl monomer with respect to the total mass of the second monomer can be set by appropriately combining the above-described respective lower and upper limits. For example, it is 0% by mass or more and 40% by mass or less, and for example, 0% by mass or more and 20% by mass or less, and for example, 0% by mass or more and 10% by mass or less.

[0072] As the second monomer, other vinyl monomers can be included as long as the intended function of the second polymer chain in the polymer fine particles is not impaired. Such vinyl monomers are not particularly limited, and examples thereof include (meth)acrylic acid alkyl esters, (meth)acrylic acid alkoxyalkyl esters, and the like. Such second monomers can be contained, for example, in an amount of 20% by mass or less, for example, 10% by mass or less, for example, 5% by mass or less, for example, 3% by mass or less, and for example, 1% by mass or less with respect to the total mass of the second monomer.

[0073] Examples of the (meth)acrylic acid alkyl ester include linear or branched alkyl ester compounds of (meth)acrylic acid such as methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, and dodecyl (meth)acrylate; and aliphatic cyclic ester compounds of (meth)acrylic acid such as cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentanyl (meth)acrylate.

[0074] Examples of the (meth)acrylic acid alkoxyalkyl ester include methoxymethyl (meth)acrylate, ethoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 3-propoxypropyl (meth)acrylate, 3-butoxypropyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 3-ethoxybutyl (meth)acrylate, 3-propoxybutyl (meth)acrylate, and 3-butoxybutyl (meth)acrylate.

[0075] In the process for producing the polymer fine particles, a crosslinked structure can be introduced into the second polymer chain.

[0076] The method for introducing the crosslinked structure is not particularly limited, and examples of the mode include the following methods. 1) Copolymerization of a crosslinkable monomer 2) Utilize chain transfer to the polymer chain during radical polymerization 3) After synthesizing a polymer having reactive functional groups, a crosslinking agent is added for post-crosslinking as necessary Among these, the method by copolymerization of a crosslinkable monomer is preferable because of its simple operation and easy control of the degree of crosslinking.

[0077] Examples of the crosslinkable monomer include polyfunctional polymerizable monomers having two or more polymerizable unsaturated groups, and monomers having a self-crosslinkable crosslinkable functional group such as a hydrolyzable silyl group. The above polyfunctional polymerizable monomers are compounds having two or more polymerizable functional groups such as (meth)acryloyl groups and alkenyl groups in the molecule, and examples include polyfunctional (meth)acrylate compounds, polyfunctional alkenyl compounds, and compounds having both (meth)acryloyl groups and alkenyl groups. These compounds may be used alone or in combination of two or more. Among these, polyfunctional alkenyl compounds are preferable in terms of easily obtaining a uniform crosslinked structure, and polyfunctional allyl ether compounds having a plurality of allyl ether groups in the molecule are particularly preferable.

[0078] Examples of the polyfunctional (meth)acrylate compounds include di(meth)acrylates of divalent alcohols such as ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate; tri(meth)acrylates and tetra(meth)acrylates of polyvalent alcohols having trivalent or higher valences such as trimethylolpropane tri(meth)acrylate, tri(meth)acrylate of a trimethylolpropane ethylene oxide modified product, glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate, i.e., poly(meth)acrylates; bisamides such as methylenebisacrylamide and hydroxyethylenebisacrylamide.

[0079] Examples of the polyfunctional alkenyl compound include polyfunctional allyl ether compounds such as trimethylolpropane diallyl ether, trimethylolpropane triallyl ether, pentaerythritol diallyl ether, pentaerythritol triallyl ether, tetraallyloxyethane, and polyallyl sucrose; polyfunctional allyl compounds such as diallyl phthalate; and polyfunctional vinyl compounds such as divinylbenzene, etc.

[0080] Examples of the compound having both a (meth)acryloyl group and an alkenyl group include allyl (meth)acrylate, isopropenyl (meth)acrylate, butenyl (meth)acrylate, pentenyl (meth)acrylate, 2-(2-vinyloxyethoxy)ethyl (meth)acrylate, etc.

[0081] Specific examples of the monomer having the self-crosslinkable crosslinkable functional group include vinyl monomers containing a hydrolyzable silyl group, N-methylol(meth)acrylamide, N-methoxyalkyl(meth)acrylamide, etc. These compounds can be used alone or in combination of two or more.

[0082] The vinyl monomer containing a hydrolyzable silyl group is not particularly limited as long as it is a vinyl monomer having at least one hydrolyzable silyl group. For example, vinyl silanes such as vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, and vinyldimethylmethoxysilane; silyl group-containing acrylic acid esters such as trimethoxysilylpropyl acrylate, triethoxysilylpropyl acrylate, and methyldimethoxysilylpropyl acrylate; silyl group-containing methacrylic acid esters such as trimethoxysilylpropyl methacrylate, triethoxysilylpropyl methacrylate, methyldimethoxysilylpropyl methacrylate, and dimethylmethoxysilylpropyl methacrylate; silyl group-containing vinyl ethers such as trimethoxysilylpropyl vinyl ether; silyl group-containing vinyl esters such as vinyl trimethoxysilylundecanoate, etc. can be mentioned.

[0083] The amount of the crosslinkable monomer used is, for example, 0.1% by mass or more and 5% by mass or less, and for example, 0.5% by mass or more and 3% by mass or less, based on the total mass of monomers other than the crosslinkable monomer (non-crosslinkable monomers). Further, the amount of the crosslinkable monomer used is, for example, 0.01 mol% or more and 2 mol% or less, and also for example, 0.03 mol% or more and 2 mol% or less, and also for example, 0.5 mol% or more and 1 mol% or less, based on the total molar amount of the non-crosslinkable monomers.

[0084] In the production of the polymer microparticles, since the first polymer has a living polymerization active unit, by adding an appropriate radical polymerization initiator (radical generator), the second monomer is polymerized with respect to the living polymerization active unit. As the radical polymerization initiator, it can be appropriately selected from various embodiments described for the RAFT agent. The usage ratio of the radical polymerization initiator is not particularly limited, but from the viewpoint of obtaining a polymer with a narrower molecular weight distribution, for example, 0.01% by mass or more and 5% by mass or less, and also for example, 0.02% by mass or more and 3% by mass or less, and also for example, 0.03% by mass or more and 3% by mass or less can be used with respect to 100 parts by mass of the total mass of the second monomer.

[0085] In the production of the polymer microparticles, by adopting the dispersion polymerization method, polymer microparticles with a small average particle diameter can be easily obtained. The polymerization solvent used in the production of the polymer microparticles can be appropriately set according to the polymerization method adopted and the types of the first monomer, the second monomer, etc. When adopting the dispersion polymerization method, for example, various solvents used in the synthesis of the first polymer can be appropriately used. For example, nitrile solvents such as acetonitrile can be used.

[0086] By using the polymerization solvent at the time of synthesis of the first polymer, the first polymer can be dissolved, and since it is a good solvent that easily dissolves the first polymer chain and the controller of living radical polymerization, the first polymer chain is present on the surface layer side of the polymer microparticles, and the second polymer chain side composed of acrylic acid or the like that becomes the extended end can be polymerized while being organized to exist inside the polymer microparticles. Therefore, it becomes easy to form a microparticle structure excellent in dispersion stability.

[0087] When determining the polymerization solvent during the production of polymer microparticles, further considering dispersion polymerization, it is necessary to take into account that it should be a poor solvent in which the second monomer or the like dissolves but the polymer microparticles containing its polymer chains do not dissolve.

[0088] For example, as the polymerization solvent during the production of polymer microparticles, there are nitrile solvents such as acetonitrile, alcohol solvents such as methanol and t-butyl alcohol, ketone solvents such as acetone, furan solvents such as tetrahydrofuran, ether solvents such as tetrahydrofuran, and in addition, benzene, ethyl acetate, dichloroethane, n-hexane, cyclohexane, n-heptane, etc. These can be used alone or in combination of two or more. Furthermore, they can also be used as a mixed solvent with a highly polar solvent such as water. When the polymerization solvent of the polymer microparticles contains a highly polar solvent such as water, (meth)acrylic acid can be quickly neutralized in the polymerization step. The usage amount of the highly polar solvent is preferably 0.05 to 10.0% by mass, more preferably 0.1 to 5.0% by mass, and even more preferably 0.1 to 1.0% by mass based on the total mass of the medium. If the proportion of the highly polar solvent is 0.05% by mass or more, the effect on the above neutralization reaction can be recognized, and if it is 10.0% by mass or less, no adverse effect on the polymerization reaction is observed.

[0089] The concentration of the second monomer in the polymerization solvent is not particularly limited and can be set as appropriate. For example, it can be 5% by mass or more and 30% by mass or less, and for another example, it can be 10% by mass or more and 20% by mass or less.

[0090] The reaction temperature during the polymerization reaction when producing polymer microparticles is not particularly limited. For example, it is 40°C or higher and 100°C or lower. For another example, it is 45°C or higher and 90°C or lower, and for another example, it is 50°C or higher and 80°C or lower. If the reaction temperature is 40°C or higher, the polymerization reaction can proceed smoothly. On the other hand, if the reaction temperature is 100°C or lower, side reactions can be suppressed and the restrictions on initiators and solvents that can be used are relaxed.

[0091] Although the second monomer will be described in detail later, in producing polymer fine particles by polymerizing the second monomer in the presence of the first polymer, in order for the first polymer to function as a dispersion stabilizer, for example, the first polymer can be used in an amount of 0.3 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the total mass of the second monomer. By using it within such a range, it is possible to produce polymer fine particles mainly containing the second monomer while making the first polymer function as a dispersion stabilizer. Further, when the amount of the first polymer is less than 0.3 parts by mass, it is difficult to obtain a sufficient dispersion stabilizing effect, and the average particle diameter of the polymer fine particles tends to exceed 0.2 μm. Even when the amount exceeds 50 parts by mass, the functionality as a dispersion stabilizer is difficult to improve, and the effect of reducing the average particle diameter of the polymer fine particles also becomes small.

[0092] The first polymer can be used, for example, in an amount of 0.5 parts by mass or more, and for example, 1 part by mass or more with respect to 100 parts by mass of the total mass of the second monomer. Further, the first polymer can be used, for example, in an amount of 50 parts by mass or less, for example, 40 parts by mass or less, for example, 30 parts by mass or less, and for example, 20 parts by mass or less. The range of the amount of the first polymer used with respect to 100 parts by mass of the total mass of the second monomer can be set by appropriately combining the above upper and lower limits. For example, it is 0.3 parts by mass or more and 30 parts by mass or less, for example, 0.3 parts by mass or more and 20 parts by mass or less, for example, 0.5 parts by mass or more and 20 parts by mass or less, and for example, 1 part by mass or more and 20 parts by mass or less.

[0093] By the above method, polymer microparticles can be produced. According to this method, polymer microparticles having an average particle diameter of 0.2 μm or less can be easily obtained. Also, since it has excellent polymerization stability, the generation of aggregates during the polymerization process can be suppressed, and the generation of coarse particles can be suppressed. In this specification, the average particle diameter of the polymer microparticles can be obtained by measuring the particle diameters of the polymer microparticles observed under a microscope using image analysis software or the like and obtaining the average values thereof. The average value of the particle diameters of 400 particles in the image observed with a field emission scanning electron microscope can be taken as the average particle diameter of the microparticles. More specifically, the following method can be adopted. Using a field emission scanning electron microscope (FE-SEM, JSM-6330F manufactured by JEOL Ltd.) or a microscope having the same resolution as the electron microscope, a plurality of photographed images in which 50 to 100 particles can be observed per sheet are acquired. For the obtained images, use image analysis software "WinROOF" manufactured by Mitani Corporation or software that can count the number of particles and particle diameters with the same accuracy and accuracy as the software, and count until the total number of particles reaches 200. Measure the particle diameter (equivalent circle diameter) for 200 particles. Further, this operation is similarly performed for another photographed image to measure the particle diameters for 200 particles. The average value of these total 400 particle diameters can be taken as the average particle diameter. Also, particles having a particle diameter of 2 times or more the average particle diameter thus obtained are regarded as coarse particles, and the number of coarse particles among 100 particles can be counted to obtain the number of coarse particles.

[0094] In particular, polymer microparticles with residual aggregates in the polymerization stability test disclosed in the examples can be obtained, for example, at 200 ppm or less, or for example, 150 ppm or less, or for example, 100 ppm or less, or for example, 60 ppm or less, or for example, 40 ppm or less, or for example, 20 ppm or less, or for example, 10 ppm or less.

[0095] Also, polymer microparticles with 2 or fewer coarse particles per 100 particles, or for example, 1 or fewer coarse particles, disclosed in the examples can be obtained.

[0096] As described above, the first polymer disclosed in this specification is useful as a dispersion stabilizer for the production of polymer microparticles. By using the first polymer as a dispersion stabilizer to produce polymer microparticles, a polymerization base point of polymer microparticles that can be dissolved with a uniform number average molecular weight in a polymerization solvent is provided, and self-organization of the first polymer chain and the second polymer chain suitable for particle nuclei and particle growth by the second monomer in the polymerization solvent is promoted, so that polymer microparticles with a small average particle diameter can be easily produced while maintaining good polymerization stability.

Examples

[0097] Hereinafter, examples as specific examples will be described to more specifically explain the disclosure of this specification. The following examples are for explaining the disclosure of this specification and do not limit its scope. In the following examples, unless otherwise specified, % represents mass %, and parts represent parts by mass.

[0098] (Method for measuring the molecular weight of the polymer) In the following examples, the molecular weight of the polymer was measured by gel permeation chromatography (GPC). That is, the number average molecular weight (Mn) and weight average molecular weight (Mw) in terms of polystyrene were obtained by THF-based GPC. In addition, the molecular weight distribution (Mw / Mn) was calculated from the obtained values. Note that GPC was performed under the following conditions.

[0099] Column: 4 columns of TSKgel SuperMultipore HZ-M manufactured by Tosoh Solvent: Tetrahydrofuran Temperature: 40°C Detector: RI Flow rate: 600 μL / min

[0100] (Synthesis of a polymer having living polymerization activity) (Polymer 1: P(St / PhMI)) Into a 1 L flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, 2.0 parts of a RAFT agent (dibenzyl trithiocarbonate: hereinafter also referred to as "DBTTC"), 0.014 part of 2,2'-azobis(2-methylbutyronitrile) (manufactured by Nippon Fine Chemical Co., Ltd., trade name "ABN-E": hereinafter also referred to as "ABN-E"), 38 parts of styrene (hereinafter also referred to as "St"), 62 parts of N-phenylmaleimide (hereinafter also referred to as "PhMI"), and 222 parts of acetonitrile were charged. After thorough degassing by nitrogen bubbling, polymerization was initiated in a constant temperature bath at 70 °C. After 4 hours, it was cooled to room temperature to stop the reaction. The above polymerization solution was purified by reprecipitation from methanol / water = 90 / 10 (vol%) and vacuum dried to obtain Polymer 1. As a result of analysis by gas chromatography, the reaction rates of the obtained Polymer 1 were 75% for St and 75% for PhMI. The molecular weight of Polymer 1 was Mn 10,200, Mw 15,300, and Mw / Mn was 1.51. Note that St and PhMI correspond to the first monomers. The composition and molecular weight distribution of the polymer are shown in Table 1 (the same applies hereinafter).

[0101] (Polymer 2: P(St / AN)) Into a 1 L flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, 2.0 parts of a RAFT agent (DBTTC), 0.41 part of ABN-E, 75 parts of St, 25 parts of acrylonitrile (hereinafter also referred to as "AN"), and 67 parts of anisole were charged. After thorough degassing by nitrogen bubbling, polymerization was initiated in a constant temperature bath at 80 °C. After 4 hours, it was cooled to room temperature to stop the reaction. The above polymerization solution was purified by reprecipitation from methanol / water = 90 / 10 (vol%) and vacuum dried to obtain Polymer 2. As a result of analysis by gas chromatography, the reaction rates of Polymer 2 were 73% for St and 72% for AN. The molecular weight of Polymer 2 was Mn 11,900, Mw 15,500, and Mw / Mn was 1.30. Note that St and AN correspond to the first monomers.

[0102] (Polymer 3: P(St / maleic anhydride)) Into a 1 L flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, 2.0 parts of a RAFT agent (DBTTC), 0.070 part of ABN-E, 52 parts of St, 48 parts of maleic anhydride, and 207 parts of acetonitrile were charged, thoroughly degassed by nitrogen bubbling, and polymerization was initiated in a constant temperature bath at 70 °C. After 4 hours, It was cooled to room temperature to stop the reaction. The above polymerization solution was purified by reprecipitation from toluene and vacuum dried to obtain Polymer 3. As a result of analysis by gas chromatography, the reaction rates of the obtained Polymer 3 were 71% for St and 71% for maleic anhydride. The molecular weight of Polymer 3 was Mn 13,800, Mw 22,200, and Mw / Mn was 1.61. Note that St and maleic anhydride correspond to the first monomer.

[0103] (Polymer 4: P(St / PhMI)) Into a 1 L flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, 3.24 parts of 1-phenylethyl iodide (1-PEI), 0.019 part of ABN-E, 38 parts of St, 62 parts of PhMI, and 221 parts of acetonitrile were charged, thoroughly degassed by nitrogen bubbling, and polymerization was initiated in a constant temperature bath at 70 °C. After 4 hours, it was cooled to room temperature to stop the reaction. The above polymerization solution was purified by reprecipitation from methanol / water = 90 / 10 (vol%) and vacuum dried to obtain Polymer 4. As a result of analysis by gas chromatography, the reaction rates of Polymer 4 were 74% for St and 74% for PhMI. The molecular weight of Polymer 4 was Mn 13,100, Mw 31,100, and Mw / Mn was 2.37. Note that St and PhMI correspond to the first monomer.

[0104] (Polymer 5: P(St / AN)-b-PAA) Into a 1 L flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 70 parts of Polymer 2, 0.019 part of ABN-E, 100 parts of acrylic acid (hereinafter also referred to as "AA"), and 255 parts of acetonitrile were charged, thoroughly degassed by nitrogen bubbling, and polymerization was initiated in a constant temperature bath at 70 °C. After 4 hours, it was cooled to room temperature and the reaction was stopped. The above polymerization solution was purified by reprecipitation from hexane and vacuum dried to obtain Polymer 5. As a result of analysis by gas chromatography, the reaction rate of AA was 74%. The molecular weights after methyl esterification of Polymer 5 were Mn 24,800, Mw 35,500, and Mw / Mn was 1.43. Note that St and AN correspond to the first monomer.

[0105] (Synthesis of Polymer without Living Polymerization Activity) (Polymer 1': P(St / AN)) Into a 1 L flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 1.0 part of a RAFT agent (DBTTC), 0.38 part of ABN-E, 75 parts of St, 25 parts of AN, and 66 parts of anisole were charged, thoroughly degassed by nitrogen bubbling, and polymerization was initiated in a constant temperature bath at 80 °C. After 4 hours, a part of the polymerization solution was sampled, and the monomer reaction rates obtained by measurement by gas chromatography were 73% for St and 72% for AN. Next, after cooling the reaction solution to 40 °C, 4.14 parts of n-propylamine thoroughly degassed by nitrogen bubbling was charged, and the decomposition reaction of the RAFT group was carried out. After another 4 hours, 9.04 parts of methyl acrylate (MA) thoroughly degassed by nitrogen bubbling was charged, and the terminal inactivation reaction was carried out at 40 °C for 4 hours. The above polymerization solution was purified by reprecipitation from methanol / water = 90 / 10 (vol%) and vacuum dried to obtain Polymer 1'. The molecular weights of Polymer 1' were Mn 11,200, Mw 15,100, and Mw / Mn was 1.35.

[0106] Here, for Polymer 1', according to the following measurement method, as a result of calculating the decomposition rate of the RAFT group (thiocarbonylthio group), since it was 100%, it was confirmed that Polymer 1' does not have living polymerization activity.

[0107] (Measurement Method for Decomposition Rate of Thiocarbonylthio Group) After dissolving 1.5 g of the polymer in 15 g of acetone, it was cast into a disposable tray made of polypropylene (100 mm × 70 mm × 13 mm, manufactured by AS ONE), allowed to air-dry at room temperature for 16 hours, and then dried at 70 °C and 4.5 Torr for 16 hours to prepare a sheet-like sample. Next, using the obtained sheet-like sample, fluorescence X-ray analysis was performed under the following measurement conditions to quantify the sulfur content (%) in the sample. Using the obtained sulfur content, the decomposition rate (%) of the thiocarbonylthio group by n-propylamine was calculated according to the following formula. The results are shown in Table 1. Decomposition rate of thiocarbonylthio group = {(B - A) / B} × {N / (N - 1)} × 100 B: Sulfur content (%) in the sample before the reaction with n-propylamine A: Sulfur content (%) in the sample after the reaction with n-propylamine N: Number of sulfur atoms in one molecule of the thiocarbonylthio group ○ Measurement conditions Measuring instrument: ZSX PrimusII manufactured by Rigaku Corporation X-ray: Rh (50 kV, 50 mA) Measured elements: C~U (C, N, O, S measured at a fixed angle) Analysis diameter: 20 mm Analysis: Semi-quantitative analysis of the detected elements by the fundamental parameter method (FP method)

[0108]

Table 1

[0109] <Production example of polymer microparticles> (Example 1) In Example 1, polymer microparticles were produced using Polymer 1. For the polymerization, a reactor equipped with a stirring blade, a thermometer, a reflux condenser, and a nitrogen inlet tube was used. 567 parts of acetonitrile, 2.20 parts of ion-exchanged water, 100.0 parts of AA, 0.90 part of trimethylolpropane diallyl ether (manufactured by Daiso Co., Ltd., trade name "Neoallyl T-20"), 1.0 part of Polymer 1, and triethylamine corresponding to 1.0 mol% with respect to the above AA were charged into the reactor. After thoroughly purging the inside of the reactor with nitrogen, it was heated to raise the internal temperature to 55°C. After confirming that the internal temperature had stabilized at 55°C, 0.040 part of 2,2'-azobis(2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd., trade name "V-65") was added as a polymerization initiator. At this point, the reaction solution became cloudy, so this point was taken as the polymerization start point. The polymerization reaction was continued while adjusting the external temperature (water bath temperature) to maintain the internal temperature at 55°C. When 6 hours had elapsed from the polymerization start point, the internal temperature was raised to 65°C. The internal temperature was maintained at 65°C, and when 12 hours had elapsed from the reaction start point, the reaction rate of AA was 97%, and a reaction solution of a slurry-like polymer in which the particles were dispersed in the medium was obtained. The obtained reaction solution was centrifuged to precipitate the polymer microparticles, and then the supernatant was removed. Thereafter, the precipitate was redispersed in acetonitrile having the same mass as the polymerization reaction solution, and then the washing operation of precipitating the polymer microparticles by centrifugation and removing the supernatant was repeated twice. The precipitate was recovered and dried at 80°C for 3 hours under reduced pressure conditions to remove volatile components, thereby obtaining the polymer microparticles described in Example 1.

[0110] (Examples 2 to 12, Comparative Examples 1 and 2) Except that the charging was changed as shown in Table 2, the same operations as in Example 1 were performed to obtain polymer microparticles.

[0111] (Evaluation of Polymerization Stability) The reaction solutions of the slurry-like polymers obtained in each Example and Comparative Example were filtered through a 200-mesh polyester net (mesh opening: 114 μm), and for the aggregates remaining on the polyester net, the mass after drying was measured, and the amount of aggregates with respect to the total charged amount was measured. The results are shown in Table 2.

[0112] <Measurement of Average Particle Diameter and Number of Coarse Particles> Regarding the polymer fine particles obtained in each example and comparative example, using a field emission scanning electron microscope (FE-SEM, JSM-6330F manufactured by JEOL Ltd.), a plurality of photographed images in which 50 to 100 particles can be observed per sheet were acquired. For the obtained images, using the image analysis software "WinROOF" manufactured by Mitani Shoko Co., Ltd., counting was performed until the total number of particles reached 200, and the particle diameters (equivalent circle diameters) of 200 particles were measured. This operation was also performed for 200 particles for another photographed image to measure the particle diameters. The average value of the total 400 particle diameters was taken as the average particle diameter. Also, particles having a particle diameter of 2 times or more the average particle diameter thus obtained were defined as coarse particles, and the number of coarse particles among 100 particles was counted. The results are shown in Table 2.

[0113]

Table 2

[0114] As shown in Table 2, in Examples 1 to 12, Polymers 1 to 3 and 5 having active units in living radical polymerization by an exchange chain mechanism obtained using RAFT polymerization, and Polymer 4 having active units in living radical polymerization by a bond-dissociation mechanism obtained using iodine transfer polymerization were used. As a result, the polymerization stability during the polymerization of the polymer fine particles was excellent, the number of coarse particles was small, and the average particle diameter of the obtained polymer fine particles was 0.20 μm or less. On the other hand, Comparative Example 1 in which such a dispersion stabilizer was not used and Comparative Example 2 in which a polymer having no living polymerization activity was used as the dispersion stabilizer were inferior in polymerization stability, so the number of coarse particles was large, and the average particle diameter of the obtained polymer fine particles exceeded 0.50 μm.

[0115] Further, from Table 2, it was found that the narrower the molecular weight distribution of Polymers 1 to 5 (dispersion stabilizers) having a predetermined living radical polymerization active unit, the smaller the average particle diameter of the polymer fine particles. Also, from the results of Examples 2 to 6, it was found that when the amount of the polymer (dispersion stabilizer) having a living polymerization active unit used was large, the average particle diameter of the polymer fine particles became smaller.

Claims

1. In the presence of a polymer chain of one or more first vinyl monomers and a first polymer having a living radical polymerization active unit, one or more second vinyl monomers are polymerized by dispersion polymerization based on the living radical polymerization activity of the first polymer and using the first polymer as a dispersion stabilizer, comprising a step of producing polymer fine particles, wherein the living radical polymerization active unit is an active unit in living radical polymerization by an exchange chain mechanism or a bond-dissociation mechanism (excluding the polymerization method using an organic tellurium compound (TERP method)).

2. The method according to claim 1, wherein the living radical polymerization active unit is living radical polymerization by the exchange chain mechanism.

3. The method according to claim 1 or 2, wherein the living radical polymerization active unit is an active unit in living radical polymerization by reversible addition-fragmentation chain transfer polymerization or iodine transfer polymerization.

4. The method according to any one of claims 1 to 3, characterized in that the molecular weight distribution of the first polymer is 2.0 or less.

5. In the step of producing the polymer fine particles, 0.3 parts by mass or more and 50 parts by mass or less of the first polymer are used with respect to 100 parts by mass of the one or more second vinyl monomers. The method according to any one of claims 1 to 4.

6. In the step of producing the polymer fine particles, 0.3 parts by mass or more and 20 parts by mass or less of the first polymer are used with respect to 100 parts by mass of the one or more second vinyl monomers. The method according to claim 5.

7. The method according to any one of claims 1 to 6, wherein the one or more second vinyl monomers contain acrylic acid or a salt thereof, and the polymerization solvent in the step of producing the polymer fine particles contains acetonitrile.

8. The method according to claim 7, wherein the one or more first vinyl monomers include two or more styrenes selected from the group consisting of styrenes, (meth)acrylonitrile compounds, maleimide compounds, unsaturated acid anhydrides, and unsaturated carboxylic acid compounds.

9. The method according to any one of claims 1 to 8, wherein the one or more second vinyl monomers contain 50% by mass or more and 100% by mass or less of acrylic acid based on the total mass thereof.

10. The method according to claim 9, wherein the one or more first vinyl monomers contain styrenes in an amount of 20% by mass or more of their total mass.

11. The one or more first vinyl monomers contain styrenes in an amount of 20% by mass or more of their total mass, and the one or more second vinyl monomers contain acrylic acid or a salt thereof in an amount of 50% by mass or more and 100% by mass or less of their total mass. The first polymer is provided with living radical polymerization active units by reversible addition-fragmentation chain transfer polymerization. The method according to claim 1, wherein 0.3 part by mass or more and 20 parts by mass or less of the first polymer is used with respect to 100 parts by mass of the one or more second vinyl monomers.

12. A dispersion stabilizer for producing polymer fine particles by polymerizing one or more second vinyl monomers by dispersion polymerization based on the living radical polymerization activity of the polymer and using the polymer as a dispersion stabilizer, the polymer comprising a polymerization chain of one or more first vinyl monomers and a living polymerization active unit provided in at least a part of the polymerization chain (excluding the polymerization active unit of the polymerization method using an organic tellurium compound (TERP method)).

Images