Method for producing polymer particle

Abstract

To provide a method for producing polymer particles that can reduce the generation of fine powder.SOLUTION: A method for producing polymer particles, comprises: a step of obtaining a coagulation liquid by mixing a polymer latex, a coagulant, and an organic solvent poorly soluble in water; and a step of obtaining coagulation slurry by removing the organic solvent from the coagulation liquid. A polymer contained in the polymer latex includes at least one of monomer-derived structural unit represented by the following formula (1) and siloxane-derived structural unit. The dispersion term (δD) of the Hansen solubility parameter of the organic solvent is 10 to 20 MPa1 / 2, the polar term (δP) is 10 MPa1 / 2 or less, and the hydrogen bonding term (δH) is 10 MPa1 / 2 or less. (In formula (1), R1 to R6 are H or alkyl groups with 1 to 4 carbon atoms)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing polymer particles. [Background technology]

[0002] Known methods for recovering a polymer from a polymer latex obtained by emulsion polymerization include a coagulation method in which the polymer latex is coagulated into particles, and a spray drying method. Examples of methods for recovering polymer powder by coagulation include a method in which a polymer latex is mixed with a coagulant (e.g., an inorganic salt such as aluminum chloride or magnesium sulfate, or an acid such as sulfuric acid) to obtain a coagulated liquid, and then the coagulated product is separated, dried, and recovered as a powder (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 225582 [Patent Document 2] Japanese Patent Publication No. 2020-122146 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional recovery methods tend to generate fine powder, which can make recovery of the powder difficult. An object of the present invention is to provide a method for producing polymer particles that can reduce the generation of fine powder. [Means for solving the problem]

[0005] The present invention has the following aspects. [1] A step of mixing a polymer latex, a coagulant, and an organic solvent that is poorly soluble in water to obtain a coagulated liquid; removing the organic solvent from the coagulation liquid to obtain a coagulation slurry; and The polymer contained in the polymer latex contains at least one of a structural unit derived from a monomer represented by the following formula (1) and a structural unit derived from a siloxane: The dispersion term (δD) of the Hansen solubility parameter of the organic solvent is 10 to 20 MPa 1 / 2 and the polarization term (δP) is 10 MPa. 1 / 2 or less, and the hydrogen bond term (δH) is 10 MPa 1 / 2 A method for producing polymer particles, which is as follows:

[0006] [ka]

[0007] In formula (1), R 1 ~R 6 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

[0008] [2] The method for producing polymer particles according to [1] above, wherein the boiling point of the organic solvent is 100°C or lower. [3] The method for producing polymer particles according to [1] or [2] above, wherein the organic solvent contains at least one of hexane and heptane. [4] The method for producing polymer particles according to any one of [1] to [3] above, wherein the proportion of the organic solvent is 2 to 50 parts by mass per 100 parts by mass of the solid content of the polymer latex. [5] R in the formula (1) 1 is a hydrogen atom or a methyl group, and R 2 ~R 6 The method for producing polymer particles according to any one of the above [1] to [4], wherein is a hydrogen atom. [6] The method for producing polymer particles according to any one of [1] to [5] above, wherein the total amount of the structural units derived from the monomer represented by formula (1) and the structural units derived from the siloxane is 10 to 100 mass% relative to the total mass of all structural units constituting the polymer contained in the polymer latex. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a method for producing polymer particles that can reduce the generation of fine powder. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following definitions of terms are used herein: The term "structural unit" refers to a structural unit derived from a monomer, i.e., a structural unit formed by polymerizing a monomer, or a structural unit in which a portion of the structural unit is converted into a different structure by treating the polymer. Methacrylate and acrylate are collectively referred to as "(meth)acrylate", and methacrylic acid and acrylic acid are collectively referred to as "(meth)acrylic acid". A numerical range indicated by "to" means a numerical range that includes the numbers before and after "to" as the lower and upper limits. The numerical ranges of the contents, various physical property values, and property values disclosed in this specification can be arbitrarily combined with the lower and upper limits to form new numerical ranges.

[0011] The method for producing polymer particles of the present invention is a method for obtaining polymer particles by recovering a polymer as powder particles from a polymer latex. An example of the method for producing polymer particles of the present invention will be described below, but the present invention is not limited to the following embodiment. The method for producing polymer particles of the present embodiment includes the following steps: a polymerization step, a coagulation step, a solvent removal step, a separation step, and a drying step. The method may further include a filtration step of filtering the polymer latex between the polymerization step and the coagulation step.

[0012] <Polymerization process> The polymerization step is a step for obtaining a latex containing the polymer (P) (hereinafter also referred to as "polymer latex (L)"). The polymer (P) contained in the polymer latex (L) contains at least one of a structural unit derived from a monomer represented by the following formula (1) (hereinafter also referred to as "structural unit (p1)") and a structural unit derived from siloxane (hereinafter also referred to as "structural unit (p2)"). The polymer (P) may further include a structural unit derived from a (meth)acrylic acid ester monomer (hereinafter, also referred to as "structural unit (p3)"). The polymer (P) may further include a structural unit (p4) other than the structural unit (p1), the structural unit (p2), and the structural unit (p3).

[0013] (Constituent unit (p1)) The structural unit (p1) is a structural unit derived from a monomer represented by the following formula (1) (hereinafter also referred to as "monomer (1)").

[0014] [ka]

[0015] In formula (1), R 1 ~R 6 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

[0016] Examples of the monomer (1) include styrene, α-methylstyrene, p-methylstyrene, pt-butylstyrene, and 2,4-dimethylstyrene. Among these, styrene and α-methylstyrene are preferred from the viewpoint of further enhancing the effect of reducing fine powder. That is, R in formula (1) 1 is a hydrogen atom or a methyl group, and R 2 ~R 6 is more preferably a hydrogen atom. The monomer (1) may be used alone or in combination of two or more thereof, and it is particularly preferable to use styrene and α-methylstyrene in combination.

[0017] (Constituent unit (p2)) The structural unit (p2) is a structural unit derived from siloxane. Siloxanes include organosiloxanes, which are silicon atoms bonded to at least one organic group. Siloxanes are also called "monomer (2)."

[0018] Examples of organosiloxanes include linear organosiloxanes, alkoxysilane compounds, cyclic organosiloxanes, etc. Among these, alkoxysilane compounds and cyclic organosiloxanes are preferred, and cyclic organosiloxanes are more preferred from the viewpoints of high polymerization stability and high polymerization rate. The organosiloxane may be used alone or in combination of two or more kinds.

[0019] The alkoxysilane compound is preferably a bifunctional alkoxysilane compound, and examples thereof include dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, dimethyldipropoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, methylphenyldimethoxysilane, and methylphenyldiethoxysilane. The alkoxysilane compounds may be used alone or in combination of two or more.

[0020] The cyclic organosiloxane is preferably one having a 3- to 7-membered ring, and examples thereof include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, trimethyltriphenylcyclotrisiloxane, tetramethyltetraphenylcyclotetrasiloxane, octaphenylcyclotetrasiloxane, etc. Among these, octamethylcyclotetrasiloxane is preferred because it is easy to control the particle size distribution. The cyclic organosiloxanes may be used alone or in combination of two or more.

[0021] The organosiloxane preferably contains at least one of a cyclic dimethylsiloxane and a bifunctional dialkylsilane compound, from the viewpoint of improving the low-temperature impact resistance of the polymer (P). Cyclic dimethylsiloxane is a cyclic siloxane having two methyl groups on a silicon atom. Specific examples include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclohexasiloxane. The bifunctional dialkylsilane compound is a compound having two alkyl groups among the above-mentioned bifunctional alkoxysilane compounds. Specific examples include dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, and dimethyldipropoxysilane. The cyclic dimethylsiloxane and the bifunctional dialkylsilane compound may each be used alone or in combination of two or more kinds.

[0022] As the siloxane, in addition to the organosiloxane, one or more selected from a siloxane crosslinking agent, a siloxane grafting agent, and a siloxane oligomer having a terminal blocking group may be used in combination.

[0023] By using a siloxane-based crosslinking agent, a polymer (P) having a crosslinked structure can be obtained. The siloxane crosslinking agent is preferably one having a siloxy group, such as trifunctional or tetrafunctional silane crosslinking agents such as trimethoxymethylsilane, triethoxyphenylsilane, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetrabutoxysilane, etc. Among these, tetrafunctional crosslinking agents are preferred, with tetraethoxysilane being more preferred.

[0024] The siloxane-based grafting agent is preferably one having a siloxy group and a functional group polymerizable with a vinyl monomer, and examples thereof include compounds represented by the following formula (2). R 7 SiR 8 n (OR 9 ) 3-n ···(2) (In formula (2), R 7is a group represented by any one of the following formulas (2-1) to (2-4), and R 8 is a methyl group, an ethyl group, a propyl group, or a phenyl group, and R 9 is an organic group in the alkoxy group, and n is a number from 0 to 2. R 9 Examples of the organic group in the alkoxy group include a methyl group, an ethyl group, a propyl group, and a phenyl group.

[0025] CH2=C(R 10 )-COO-(CH2) p - (2-1) CH2=C(R 11 )-C6H4- ···(2-2) CH2=CH- (2-3) HS-(CH2) q - (2-4) (In formula (2-1), R 10 is a hydrogen atom or a methyl group, and p is an integer of 1 to 6. 11 is a hydrogen atom or a methyl group. In formula (2-4), q is an integer of 1 to 6.

[0026] The functional group represented by formula (2-1) includes a methacryloyloxyalkyl group. Examples of siloxanes having a functional group represented by formula (2-1) include β-methacryloyloxyethyldimethoxymethylsilane, γ-methacryloyloxypropylmethoxydimethylsilane, γ-methacryloyloxypropyldimethoxymethylsilane, γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylethoxydiethylsilane, γ-methacryloyloxypropyldiethoxymethylsilane, and δ-methacryloyloxybutyldiethoxymethylsilane. The siloxane-based grafting agent may be used alone or in combination of two or more kinds.

[0027] The siloxane oligomer having a terminal blocking group refers to a siloxane oligomer in which the terminal of the organosiloxane oligomer has an alkyl group or the like, thereby terminating the polymerization of the polyorganosiloxane. Examples of siloxane oligomers having a terminal blocking group include hexamethyldisiloxane, 1,3-bis(3-glycidoxypropyl)tetramethyldisiloxane, 1,3-bis(3-aminopropyl)tetramethyldisiloxane, and siloxane oligomers in which the terminal blocking group is a trimethylsilyl group. The siloxane oligomer having a terminal blocking group may be used alone or in combination of two or more kinds.

[0028] (Constituent unit (p3)) The structural unit (p3) is a structural unit derived from a (meth)acrylic acid ester monomer (hereinafter also referred to as "monomer (3)"). Examples of the monomer (3) include aromatic-containing (meth)acrylic acid ester monomers such as phenyl (meth)acrylate, 4-t-butylphenyl (meth)acrylate, bromophenyl (meth)acrylate, dibromophenyl (meth)acrylate, 2,4,6-tribromophenyl (meth)acrylate, monochlorophenyl (meth)acrylate, dichlorophenyl (meth)acrylate, trichlorophenyl (meth)acrylate, and benzyl (meth)acrylate; alicyclic skeleton-containing (meth)acrylic acid ester monomers such as cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, and isobornyl (meth)acrylate; (meth)acrylic acid alkyl ester monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate; and reactive functional group-containing (meth)acrylic acid ester monomers such as 2-hydroxyethyl (meth)acrylate, glycidyl (meth)acrylate, and 2-methacryloyloxyethyl phthalate. The monomer (3) may be used alone or in combination of two or more kinds.

[0029] (Constituent unit (p4)) The structural unit (p4) is a structural unit other than the structural units (p2), (p1), and (p3). That is, the structural unit (p4) is a structural unit derived from a monomer other than the monomer (1), siloxane, and monomer (3) (hereinafter, also referred to as "other monomers"). The other monomer is not particularly limited as long as it is copolymerizable with one or more selected from monomer (1), siloxane, and monomer (3), and examples thereof include (meth)acrylic acid; polyfunctional monomers such as divinylbenzene, allyl (meth)acrylate, and 1,3-butylene dimethacrylate; vinyl acetate, maleic anhydride, N-phenylmaleimide, and cyclohexylmaleimide. The other monomer is also referred to as "monomer (4)." The other monomers may be used alone or in combination of two or more.

[0030] (percentage of constituent units) The total amount of the structural units (p1) and (p2) relative to the total mass of all structural units constituting the polymer (P) is preferably 100% by mass or less, more preferably 10 to 100% by mass, and even more preferably 30 to 100% by mass. As will be described in more detail below, if the total amount of the structural units (p1) and (p2) is within the above range, the addition of an organic solvent will more easily achieve the effect of lowering the apparent glass transition temperature (hereinafter also referred to as "apparent Tg") of the polymer (P). The content of the structural unit (p3) is preferably 0 to 90 mass%, more preferably 0 to 70 mass%, relative to the total mass of all structural units constituting the polymer (P). When the content of the structural unit (p3) is at least the above lower limit, the heat resistance of the polymer (P) is further improved. When the content of the structural unit (p3) is at most the above upper limit, the apparent Tg of the polymer (P) is more likely to be lowered by adding an organic solvent.

[0031] (Polymerization method) The polymer latex (L) is obtained by polymerizing a monomer component (M) containing at least one of the monomer (1) and siloxane. The monomer component (M) may further contain the monomer (3) or other monomers as required. The polymerization method of the monomer component (M) is not particularly limited, but examples thereof include emulsion polymerization, suspension polymerization, and fine suspension polymerization. Among these, emulsion polymerization is preferred. That is, the polymer latex (L) is preferably obtained by emulsion polymerization.

[0032] The polymer latex (L) can be obtained, for example, by polymerizing the monomer component (M) in the presence of an emulsifier and a polymerization initiator. In this case, the entire amount of the monomer component (M) may be charged into a reaction vessel and polymerization may be initiated, or a portion of the monomer component (M) may be charged into a reaction vessel and polymerization may be initiated, and then the remaining monomer component (M) may be added in one or more batches. Alternatively, a portion of the monomer component (M) may be charged into a reaction vessel and polymerization may be initiated, and then the remaining monomer component (M) may be added dropwise. There are no particular limitations on the method of adding the emulsifier and polymerization initiator to the reaction vessel; they may be added all at once or in batches.

[0033] As the emulsifier, an anionic emulsifier or a nonionic emulsifier is preferred. Examples of anionic emulsifiers include sodium alkylbenzenesulfonate, sodium alkyldiphenyletherdisulfonate, sodium alkylsulfate, sodium polyoxyethylene alkylsulfate, and sodium polyoxyethylene nonylphenylether sulfate. Examples of nonionic emulsifiers include polyoxyethylene alkyl ethers, polyoxyethylene alkylene alkyl ethers, polyoxyethylene distyrenated phenyl ethers, polyoxyethylene tribenzyl phenyl ethers, and polyoxyethylene polyoxypropylene glycols. The emulsifier may be used alone or in combination of two or more kinds.

[0034] The polymerization initiator is not particularly limited, and any known polymerization initiator can be used. Examples thereof include persulfates, peroxides, azo-based initiators, redox-based initiators in which a persulfate is combined with a reducing agent, and redox-based initiators in which an organic peroxide is combined with a reducing agent. The polymerization initiator may be used alone or in combination of two or more kinds.

[0035] Examples of peroxides include inorganic peroxides such as hydrogen peroxide, potassium persulfate, and ammonium persulfate; and organic peroxides such as diisopropylbenzene hydroperoxide, p-menthane hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, succinic acid peroxide, t-butyl peroxyneodecanoate, t-butyl peroxyneoheptanoate, t-butyl peroxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, and t-butylperoxy-2-ethylhexanoate. The peroxides may be used alone or in combination of two or more.

[0036] Examples of the azo initiator include oil-soluble azo initiators such as 2,2'-azobisisobutyronitrile, dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(2-butyronitrile); and water-soluble azo initiators such as 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis[N-(2-carboxymethyl)-2-methylpropionamidine]hydrate, 2,2'-azobis-(N,N'-dimethyleneisobutylamidine) dihydrochloride, and 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride. The azo initiators may be used alone or in combination of two or more.

[0037] When an organic peroxide is combined with a reducing agent to form a redox initiator, it is preferable to use the above organic peroxide in combination with a reducing agent such as sodium formaldehyde sulfoxylate, L-ascorbic acid, fructose, dextrose, sorbose, or inositol, and ferrous sulfate·ethylenediaminetetraacetic acid disodium salt. The reducing agent may be used alone or in combination of two or more kinds.

[0038] The amount of the emulsifier used is preferably 0.05 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, still more preferably 0.5 to 5 parts by mass, and particularly preferably 1 to 2.5 parts by mass, relative to 100 parts by mass of the monomer component (M). The particle size of the polymer (P) can be adjusted to a desired value by adjusting the amount of the emulsifier used. The amount of the polymerization initiator used is not particularly limited, but is preferably 0.01 to 1 part by mass per 100 parts by mass of the monomer component (M), for example. When a peroxide is used as the polymerization initiator, the amount of the peroxide used is not particularly limited, but is preferably, for example, 0.01 to 1 part by mass per 100 parts by mass of the monomer component (M). The amount of the reducing agent used is not particularly limited, but from the viewpoint of outgassing resistance, it is preferably, for example, 0.01 to 1 part by mass per 100 parts by mass of the monomer component (M).

[0039] The polymerization temperature is not particularly limited, but is preferably 30 to 100°C, for example. The polymerization time is not particularly limited, but is preferably, for example, 3 to 30 hours.

[0040] Here, an example of the polymerization method when the monomer component (M) contains an organosiloxane as the siloxane will be shown below. The polymer latex (L) obtained by polymerizing the monomer component (M) containing organosiloxane is also particularly called "polymer latex (LS)", and the polymer (P) contained in the polymer latex (LS) is also particularly called "polyorganosiloxane (PS)" or "polymer (PS)". The polyorganosiloxane (PS) contains a structural unit (p2).

[0041] <<Production method of polyorganosiloxane (PS)>> There are no particular limitations on the method for producing polyorganosiloxane (PS), and for example, the following production method can be used. First, an organosiloxane mixture containing the above-mentioned organosiloxane, optionally a siloxane-based crosslinking agent, optionally a siloxane-based grafting agent, and optionally a siloxane oligomer having a terminal blocking group is emulsified with an emulsifier and water to prepare an emulsion. The organosiloxane mixture is then polymerized at high temperature using an acid catalyst, and the acid is then neutralized with an alkaline substance to obtain a polyorganosiloxane latex (polymer latex (LS)). In the following description of the manufacturing method, an "organosiloxane mixture" is used as the raw material for polymerization, but the same manufacturing process can be applied when "organosiloxane" is used. Furthermore, the organosiloxane mixture may contain one or more monomers selected from the monomer (1), the monomer (3), and other monomers, as needed.

[0042] In this manufacturing method, the method for preparing emulsion can be exemplified by using a homomixer that uses shear force due to high-speed rotation to atomize; a method that uses a homogenizer that uses the jetting force of a high-pressure generator to atomize, etc., and mixing by high-speed stirring. Among these, the method that uses a homogenizer is preferred from the viewpoint that the particle size distribution of polyorganosiloxane latex is narrow.

[0043] Methods for mixing the acid catalyst into the emulsion during polymerization include adding the acid catalyst all at once together with the organosiloxane mixture, emulsifier, and water, and mixing; adding the aqueous acid catalyst solution all at once to the emulsion of the organosiloxane mixture; and adding the emulsion of the organosiloxane mixture dropwise at a constant rate to a hot aqueous acid catalyst solution and mixing. Because this method makes it easier to control the particle size of the polyorganosiloxane, it is preferable to maintain the emulsion of the organosiloxane mixture at a high temperature and then add the aqueous acid catalyst solution all at once thereto.

[0044] The polymerization temperature is preferably 50° C. or higher, and more preferably 70° C. or higher. There is no particular upper limit to the polymerization temperature, but it is preferably, for example, 100° C. or lower. When polymerization is carried out by adding the aqueous acid catalyst solution all at once to the emulsion of the organosiloxane mixture, the polymerization time is usually 2 hours or longer, and preferably 5 hours or longer. Furthermore, since the crosslinking reaction between silanols proceeds at temperatures of 30°C or less, in order to increase the crosslink density of the polyorganosiloxane, after polymerization at a high temperature of 50°C or more, the produced latex can be kept at a temperature of 30°C or less for about 5 to 100 hours.

[0045] The polymerization reaction of the organosiloxane mixture can be terminated by neutralizing the latex to a pH of 6 to 8 with an alkaline substance such as sodium hydroxide, potassium hydroxide, or aqueous ammonia solution.

[0046] The emulsifier used in the above production method is preferably the anionic emulsifier or nonionic emulsifier described above. The amount of emulsifier used is preferably 0.05 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the organosiloxane mixture. The particle size of the polyorganosiloxane latex can be adjusted to a desired value by adjusting the amount of emulsifier used. In particular, when the amount of emulsifier used is equal to or greater than the lower limit, the emulsion stability of the organosiloxane mixture emulsion is sufficient. When the amount of emulsifier used is equal to or less than the upper limit, the amount of emulsifier remaining in the polyorganosiloxane (PS) powder can be sufficiently reduced, thereby suppressing deterioration in the thermal decomposition resistance and surface appearance of the polyorganosiloxane (PS) and resin compositions containing the polyorganosiloxane (PS).

[0047] Examples of acid catalysts used in the polymerization of the organosiloxane mixture include sulfonic acids such as aliphatic sulfonic acid, aliphatic-substituted benzenesulfonic acid, and aliphatic-substituted naphthalenesulfonic acid; and mineral acids such as sulfuric acid, hydrochloric acid, and nitric acid. Among these, mineral acids such as sulfuric acid, hydrochloric acid, and nitric acid are preferred, from the viewpoint of narrowing the particle size distribution of the polyorganosiloxane latex and further reducing the deterioration in thermal decomposition resistance and poor appearance of the molded article caused by the emulsifier component in the polyorganosiloxane latex. The acid catalyst may be used alone or in combination of two or more kinds.

[0048] The amount of the acid catalyst used is preferably 0.005 to 5 parts by mass, more preferably 0.005 to 1.5 parts by mass, per 100 parts by mass of the organosiloxane. When the amount of the acid catalyst used is equal to or greater than the lower limit, the polyorganosiloxane can be polymerized in a short time. When the amount of the acid catalyst used is equal to or less than the upper limit, a molded article having good thermal decomposition resistance and appearance can be obtained using the polyorganosiloxane (PS).

[0049] Polyorganosiloxane (PS) can also be converted into a polyorganosiloxane-containing graft copolymer, for example, as follows. That is, the monomer component (m2) is polymerized in the presence of rubber (G) containing polyorganosiloxane (PS) and vinyl polymer (PV) to obtain a polyorganosiloxane-containing graft copolymer.

[0050] <<Vinyl polymer (PV)>> The vinyl polymer (PV) can be obtained by polymerizing a monomer component (m1) containing one or more monomers selected from the above-mentioned monomer (1), monomer (3) and other monomers. The content of the vinyl polymer (PV) is preferably from 15 to 90 mass % relative to the total mass of the rubber (G), more preferably from 20 to 60 mass %, and even more preferably from 45 to 60 mass %.

[0051] The vinyl polymer (PV) preferably contains a structural unit derived from a crosslinkable monomer. Examples of crosslinkable monomers include allyl methacrylate, triallyl cyanurate, triallyl isocyanurate, divinylbenzene, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexanediol diacrylate, and triallyl trimellitate. The crosslinkable monomer may be used alone or in combination of two or more kinds.

[0052] The content of the crosslinkable monomer is preferably 0.1 to 10 mass%, more preferably 0.1 to 5 mass%, further preferably 0.3 to 5 mass%, and particularly preferably 0.3 to 3 mass%, relative to the total mass of the monomer component (m1). When the content of the crosslinkable monomer is within the above range, the low-temperature impact resistance of the polyorganosiloxane-containing graft copolymer is improved.

[0053] The method for producing the vinyl polymer (PV) is not particularly limited, but it can be produced by, for example, emulsion polymerization, suspension polymerization, or microsuspension polymerization. Among these, emulsion polymerization is preferred. Specific methods for emulsion polymerization are as described above.

[0054] <<Rubber (G)>> The rubber (G) contains polyorganosiloxane (PS) and vinyl polymer (PV). Examples of the rubber (G) include the following rubbers (G1) to (G3). Rubber (G1): A rubber having a multilayer structure in which a polyorganosiloxane (PS) core is covered with a vinyl polymer (PV) shell. Rubber (G2): A rubber having a multilayer structure in which a vinyl polymer (PV) core is covered with a polyorganosiloxane (PS) shell. Rubber (G3): A composite rubber containing polyorganosiloxane (PS) and vinyl polymer (PV).

[0055] The rubber (G) is preferably the rubber (G3) described above. The polyorganosiloxane-containing graft copolymer obtained from the rubber (G3) has good low-temperature impact resistance. Among the rubbers (G3), the rubber (G) is more preferably a composite rubber made of polyorganosiloxane (PS) and a vinyl polymer (PV).

[0056] The content of polyorganosiloxane (PS) is preferably 40 to 80 mass %, more preferably 40 to 55 mass %, based on the total mass of rubber (G). The content of the vinyl polymer (PV) is preferably from 20 to 60 mass %, more preferably from 45 to 60 mass %, based on the total mass of the rubber (G). When the contents of polyorganosiloxane (PS) and vinyl polymer (PV) in the rubber (G) are within the above ranges, the polyorganosiloxane-containing graft copolymer and the resin composition containing the polyorganosiloxane-containing graft copolymer have a good balance of low-temperature impact resistance, pigment colorability, and flame retardancy.

[0057] There are no particular limitations on the method for producing the rubber (G). Examples of the method for producing the rubbers (G1) to (G3) include the following methods. The rubber (G1) can be obtained, for example, by polymerizing the monomer component (m1) in the presence of the polymer latex (LS) to obtain a latex of the rubber (G1). The rubber (G2) can be obtained, for example, by polymerizing an organosiloxane mixture in the presence of a vinyl polymer (PV) latex to obtain a latex of the rubber (G2). The method for obtaining rubber (G3) can be, for example, adding monomer component (m1) to polymer latex (LS), impregnating polyorganosiloxane particles with monomer component (m1), and then polymerizing the monomer component (m1) to obtain rubber (G3) latex (3-1); adding organosiloxane mixture to vinyl polymer (PV) latex, impregnating vinyl polymer (PV) particles with organosiloxane mixture, and then polymerizing organosiloxane to obtain rubber (G3) latex (3-2). Among these, the method for obtaining rubber (G3) is preferably the method (3-2) from the viewpoint of ease of particle size adjustment.

[0058] <<Monomer component (m2)>> A polyorganosiloxane-containing graft copolymer can be obtained by polymerizing the monomer component (m2) in the presence of the above-mentioned rubber (G) and forming a graft portion consisting of a vinyl polymer, which is a polymer of the monomer component (m2), on the rubber (G). The monomer component (m2) preferably contains one or more monomers selected from the above-mentioned monomer (1), siloxane, monomer (3) and other monomers. The monomer component (m2) may contain the above-mentioned crosslinkable monomer. In this case, the content of the crosslinkable monomer in the monomer component (m2) is preferably 0 to 0.005% by mass relative to the total mass of the monomer component (m2).

[0059] The monomer component (m2) preferably contains at least one selected from the group consisting of an aromatic vinyl monomer, an alkyl(meth)acrylate, a vinyl cyanide monomer, and an aryl(meth)acrylate whose ester group is a phenyl group or a substituted phenyl group. From the viewpoint of compatibility when the polyorganosiloxane-containing graft copolymer is used in combination with a thermoplastic resin, the monomer component (m2) more preferably contains an aryl(meth)acrylate whose ester group is a phenyl group or a substituted phenyl group.

[0060] The content of one or more monomers selected from aromatic vinyl monomers, alkyl(meth)acrylates, vinyl cyanide monomers, and aryl(meth)acrylates whose ester group is a phenyl group or a substituted phenyl group in the monomer component (m2) is preferably 5 to 100 mass%, more preferably 20 to 100 mass%, and even more preferably 50 to 100 mass%, based on the total mass of the monomer component (m2).

[0061] The content of rubber (G) in the polyorganosiloxane-containing graft copolymer is preferably 10 to 99 mass% based on the total mass of the polyorganosiloxane-containing graft copolymer. When the content of rubber (G) is equal to or greater than the above lower limit, the low-temperature impact strength of the polyorganosiloxane-containing graft copolymer and the resin composition containing the polyorganosiloxane-containing graft copolymer is increased. When the content of rubber (G) is equal to or less than the above upper limit, the surface appearance of molded articles obtained using the polyorganosiloxane-containing graft copolymer is improved.

[0062] The graft copolymerization method may be, for example, a method in which the monomer component (m2) is added to the latex of the rubber (G) and polymerized in one or multiple stages. In the case of multiple stages, it is preferable to polymerize by dividing the total amount of the monomer component (m2) into portions and adding them successively or continuously in the presence of the latex of the rubber (G). Such a polymerization method has good polymerization stability and can stably produce a latex having a desired particle size and particle size distribution. It is preferred to polymerize the total amount of the monomer component (m2) by dividing it into portions and adding it successively or continuously to the latex of the rubber (G3) obtained by the above-mentioned method (3-1). During polymerization of the graft portion, an emulsifier can be added as needed. Examples of the emulsifier used for polymerization of the graft portion include the same emulsifiers as those used in producing the rubber (G), and anionic emulsifiers and nonionic emulsifiers are preferred. The polymerization initiator used for the polymerization of the graft portion may be the same as the polymerization initiator used when producing the rubber (G), and an azo-based initiator or a redox-based initiator is preferred.

[0063] <Coagulation process> The coagulation step is a step in which the polymer latex (L), the coagulant (C), and the organic solvent (S) are mixed together to obtain a coagulation liquid.

[0064] (Coagulant (C)) By mixing the polymer latex (L) with the coagulant (C), the electrostatic repulsive force of the emulsifier is reduced, and the polymer (P) aggregates due to intermolecular forces. Examples of the coagulant (C) include sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, phosphorous acid, acetic acid, aluminum sulfate, magnesium sulfate, sodium sulfate, sodium nitrate, calcium nitrate, aluminum chloride, calcium chloride, sodium chloride, calcium acetate, sodium acetate, aluminum acetate, etc. Among these, sulfuric acid and calcium acetate are preferred. The coagulant (C) may be used alone or in combination of two or more kinds.

[0065] The coagulant (C) is usually used as an aqueous solution. The concentration of the coagulant aqueous solution is preferably 0.1 to 20% by mass, more preferably 1 to 15% by mass. When the concentration of the coagulant aqueous solution is equal to or higher than the lower limit, the polymer (P) can be stably coagulated and recovered. When the concentration of the coagulant aqueous solution is equal to or lower than the upper limit, the amount of coagulant remaining in the recovered polymer (P) can be reduced. The amount of the aqueous coagulant solution is not particularly limited, but is preferably 10 to 500 parts by mass per 100 parts by mass of the polymer latex (L).

[0066] (Organic solvent (S)) The organic solvent (S) used in the present invention is poorly soluble in water. In the present invention, "slightly soluble in water" refers to an organic liquid whose solubility in water (concentration in a saturated solution) is 5% by mass or less, preferably 2% by mass or less, and more preferably 1% by mass or less at 25° C. In other words, it refers to an organic liquid whose content is 5 g or more, preferably 2 g or more, and more preferably 1 g or more per 100 g of a saturated solution obtained by dissolving the organic liquid in water at 25° C.

[0067] The dispersion term (δD) of the Hansen solubility parameter of organic solvent (S) is 10-20MPa. 1 / 2 and the polarization term (δP) is 10 MPa 1 / 2 and the hydrogen bond term (δH) is 10 MPa or less. 1 / 2 By using an organic solvent (S) whose dispersion term (δD), polarization term (δP), and hydrogen bonding term (δH) of the Hansen solubility parameters are each within the above ranges, the organic solvent (S) is impregnated into at least a part of the polymer (P), the apparent glass transition temperature (apparent Tg) of the polymer (P) is lowered, and the polymers (P) are more likely to fuse together.

[0068] The dispersion term (δD) of the Hansen solubility parameter of organic solvent (S) is 10-20MPa. 1 / 2 and 15 to 20 MPa 1 / 2 is preferable, and 15 to 18 MPa 1 / 2 is more preferred. The polarization term (δP) of the Hansen solubility parameter of the organic solvent (S) is 10 MPa. 1 / 2 or less, 0 to 8 MPa 1 / 2 is preferably 0 to 5 MPa 1 / 2 is more preferred. The hydrogen bond term (δH) of the Hansen solubility parameter of organic solvent (S) is 10 MPa. 1 / 2 or less, 0 to 8 MPa 1 / 2 is preferably 0 to 5 MPa 1 / 2 is more preferred.

[0069] The Hansen solubility parameters for organic solvents (S) are the solubility parameters introduced by Hildebrand, which Hansen divided into three components: dispersion term (δD), polarization term (δP), and hydrogen bonding term (δH), and displayed in three-dimensional space. The dispersion term (δD) indicates the effect of dispersion forces. The polarization term (δP) indicates the effect of dipole-dipole forces. The hydrogen bonding term (δH) indicates the effect of hydrogen bonding forces.

[0070] For Hansen solubility parameter values, literature values may be used, or values calculated using commercially available computer software (such as "COSMO quick" from Dassault Systèmes) may be used. COSMO quick can calculate the Hansen solubility parameter by obtaining surface charge distribution information from the "COSMO Fragment Data Base" (Dassault Systèmes), which has been generated in advance by quantum chemical calculations. The method for calculating the Hansen solubility parameter using COSMO quick is described in the following literature. Christoph Loschen, and Andreas Klamt. COSMO quick: A Novel Interface for Fast σ-Profile Composition and Its Application to COSMO-RS Solvent Screening Using Multiple Reference Solvents: Ind. Eng. Chem. Res. 2012, 51, 14303-14308

[0071] The organic solvent (S) may be used alone or in combination of two or more kinds. When two or more organic solvents (S) are used in combination, the sum of the dispersion terms (δD) of the Hansen solubility parameters of each organic solvent (S) multiplied by the mass fraction must be 10 to 20 MPa. 1 / 2 It is preferable that the pressure is 15 to 20 MPa. 1 / 2 and more preferably 15 to 18 MPa 1 / 2 is. In addition, the sum of the polarization terms (δP) of the Hansen solubility parameters of each organic solvent (S) multiplied by the mass fraction is 10 MPa. 1 / 2 Preferably, the pressure is equal to or less than 0.5MPa, and more preferably, 0 to 8MPa. 1 / 2 and more preferably 0 to 5 MPa. 1 / 2 is. In addition, the sum of the hydrogen bond term (δH) of the Hansen solubility parameter of each organic solvent (S) multiplied by the mass fraction is 10 MPa. 1 / 2Preferably, the pressure is equal to or less than 0.5MPa, and more preferably, 0 to 8MPa. 1 / 2 and more preferably 0 to 5 MPa. 1 / 2 is.

[0072] Furthermore, from the viewpoint of excellent solubility of the organic solvent (S) in the polymer (P), it is preferable that the differences in the dispersion term (δD), polarization term (δP), and hydrogen bond term (δH) of the Hansen solubility parameters between the organic solvent (S) and the monomer (particularly at least one of siloxane and monomer (1)) constituting the polymer (P) are as small as possible. The more excellent the solubility of the organic solvent (S) in the polymer (P), the more likely the apparent Tg of the polymer (P) is to decrease, and the more likely the polymers (P) are to fuse together. Specifically, the absolute value of the difference between the dispersion term (δD) of the Hansen solubility parameter of the organic solvent (S) and the dispersion term (δD) of the Hansen solubility parameter of the siloxane or monomer (1) is 0 to 5 MPa. 1 / 2 Preferably, the pressure is in the range of 0 to 4 MPa. 1 / 2 and more preferably 0 to 3 MPa. 1 / 2 is. The absolute value of the difference between the polarization term (δP) of the Hansen solubility parameter of the organic solvent (S) and the polarization term (δP) of the Hansen solubility parameter of the siloxane or monomer (1) is 0 to 10 MPa. 1 / 2 Preferably, the pressure is in the range of 0 to 9 MPa. 1 / 2 and more preferably 0 to 8 MPa. 1 / 2 is. The absolute value of the difference between the hydrogen bond term (δH) of the Hansen solubility parameter of the organic solvent (S) and the hydrogen bond term (δH) of the Hansen solubility parameter of the siloxane or monomer (1) is 0 to 10 MPa. 1 / 2 Preferably, the pressure is in the range of 0 to 9 MPa. 1 / 2 and more preferably 0 to 8 MPa. 1 / 2 is.

[0073] The boiling point of the organic solvent (S) is preferably 100°C or lower, more preferably 45 to 100°C, even more preferably 50 to 100°C, and particularly preferably 60 to 100°C. When the boiling point of the organic solvent (S) is the above upper limit or lower, the organic solvent (S) can be easily removed in the solvent removal step described below. The less solvent remaining in the solidified slurry, the more the apparent Tg of the polymer (P) that has been lowered returns to the original value, and the less likely the polymer (P) is to block in the separation step described below. In addition, the load during drying can be reduced. In the present invention, the "boiling point" refers to the boiling point of the organic solvent (S) at atmospheric pressure (1.0 x 10 5 This refers to the value in Pa. When two or more organic solvents (S) are used in combination, the boiling points of all the organic solvents (S) are preferably 100°C or lower, more preferably 45 to 100°C, even more preferably 50 to 100°C, and particularly preferably 60 to 100°C.

[0074] Dispersion term (δD) of Hansen solubility parameter is 10-20MPa 1 / 2 and the polarization term (δP) is 10 MPa. 1 / 2 or less, and the hydrogen bond term (δH) is 10 MPa 1 / 2 Examples of the organic solvent (S) include hexane, heptane, cyclohexane, toluene, etc. Among these, hexane, heptane, and cyclohexane are preferred because they have a boiling point of 100° C. or less and are easily removed in the solvent removal step.

[0075] The proportion of the organic solvent (S) in the coagulation step is preferably 2 to 50 parts by mass, more preferably 4 to 30 parts by mass, per 100 parts by mass of the solid content of the polymer latex (L). If the proportion of the organic solvent (S) is equal to or greater than the lower limit, the apparent Tg of the polymer (P) is sufficiently lowered, and the polymers (P) tend to fuse together. If the proportion of the organic solvent (S) is equal to or less than the upper limit, the load of solvent removal can be reduced.

[0076] In addition, in the solidification step, in addition to the organic solvent (S), an organic solvent other than the organic solvent (S) (hereinafter also referred to as "other organic solvent") may be used in combination, as long as the effects of the present invention are not impaired. The other organic solvent is not particularly limited, but a solvent that is compatible with the organic solvent (S) is preferred.

[0077] The proportion of the organic solvent (S) relative to the total mass of the organic solvent (S) and other organic solvents is preferably 50 to 100 mass%, more preferably 80 to 100 mass%, and particularly preferably 100 mass%. That is, it is particularly preferable to use only the organic solvent (S) in the solidification step.

[0078] (Mixing method) The method for mixing the polymer latex (L), the coagulant (C), and the organic solvent (S) is not particularly limited, but an example thereof includes a method in which the polymer latex (L) and the organic solvent (S) are continuously added to an aqueous coagulant solution while stirring the solution, and the mixture is maintained for a certain period of time. The temperature at which the polymer latex (L), the coagulant (C) and the organic solvent (S) are mixed is not particularly limited, but is preferably 30 to 100°C, for example.

[0079] <Solvent removal process> The solvent removal step is a step in which the organic solvent (S) is removed from the coagulation liquid to obtain a coagulation slurry. When other organic solvents are used in combination in the coagulation step, the other organic solvents are also removed from the coagulation liquid in the solvent removal step.

[0080] The organic solvent (S) can be removed, for example, by heating the coagulation liquid. The method for heating the coagulation liquid is not particularly limited, and for example, the coagulation liquid may be heated using a heater or the like, or the coagulation liquid may be heated by blowing steam into the coagulation liquid. The heating temperature and heating time may be appropriately determined depending on the boiling point and amount of the organic solvent (S) used in the solidification step, but for example, the heating temperature is preferably 45 to 100° C., more preferably 60 to 100° C. The heating time is preferably 1 minute to 3 hours, more preferably 5 minutes to 1 hour.

[0081] <Separation process> The separation step is a step in which the solidified slurry obtained in the solvent removal step is separated into a liquid and a solid, thereby obtaining a solid. The method for solid-liquid separation is not particularly limited, but examples thereof include centrifugal filtration, pressure filtration, and suction filtration.

[0082] <Drying process> The drying step is a step in which the solid obtained in the separation step is dried to obtain a powdery polymer (P). In the present invention, the powdery polymer (P) is also referred to as "polymer particles".

[0083] The method for drying the solid is not particularly limited, but examples thereof include reduced pressure (vacuum) drying, ventilation drying, and fluidized bed drying. The drying temperature and drying time may be appropriately determined depending on the polymer particles to be obtained, but for example, the drying temperature is preferably 30 to 150° C. The drying time is preferably 30 minutes to 24 hours.

[0084] The average particle size of the polymer particles thus obtained is preferably from 40 to 1000 μm, more preferably from 100 to 900 μm, and even more preferably from 200 to 800 μm. The average particle size of the polymer particles is the particle size (median size) corresponding to a cumulative 50% in the volume-based particle size distribution measured using a laser diffraction / scattering particle size distribution measuring device, i.e., the volume-average particle size (Dv).

[0085] Prior to the drying step, at least one of a washing step and a dehydration step may be carried out between the separation step and the drying step, if necessary. The washing step is a step of washing the solid obtained in the separation step with a washing liquid such as water. The dehydration step is a step of dehydrating the solid obtained in the separation step or the solid after washing. The method for dehydrating the solid is not particularly limited, but examples thereof include a method of dehydrating using a compression dehydrator, etc. Furthermore, the separation step, washing step, and dehydration step can be carried out simultaneously during centrifugal filtration using a centrifugal dehydrator, etc.

[0086] <Action and effect> According to the method for producing polymer particles of the present invention described above, in the coagulation step, in addition to the coagulant (C), an organic solvent (S) having a specific Hansen solubility parameter and poorly soluble in water is used. As a result, the polymer (P) aggregates due to intermolecular forces, and the apparent Tg of the polymer (P) decreases, causing the polymers (P) to fuse together. This increases the particle size of the polymer (P), thereby suppressing the generation of fine powder (specifically, particles with a particle size of 39 μm or less). In particular, if an organic solvent (S) with a boiling point of 100°C or less is used, the organic solvent (S) can be sufficiently removed in the solvent removal step. Therefore, the apparent Tg of the polymer (P), which was lowered in the coagulation step, increases to about the Tg of the original polymer (P), making the polymer (P) less likely to block during the separation step. Additionally, the load during drying can be reduced. According to the method for producing polymer particles of the present invention, the generation of fine powder can be suppressed, and therefore the powder (polymer particles) can be easily recovered. [Example]

[0087] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following descriptions. In the following, "parts" means "parts by mass" unless otherwise specified, and "%" means "% by mass" unless otherwise specified.

[0088] [Measurement and Evaluation] (1) Measurement of mean particle size (Dv) The polymer particles were dispersed in water, and the volumetric particle size distribution was measured using a laser diffraction / scattering particle size distribution analyzer (manufactured by Horiba, Ltd., product name "LA-960S"), and the particle size corresponding to 50% of the cumulative total was determined as the volumetric average particle size (Dv).

[0089] (2) Measurement of the fine powder ratio The particle size distribution was calculated by accumulating particles with a particle size of 39 μm or less from the volume-based particle size distribution measured in (1).

[0090] (3) Measurement of the amount of solvent remaining in the solidified slurry (based on polymer) The residual solvent amount in the solidified slurry was calculated by dividing the amount of the residual solvent in the solidified slurry measured by gas chromatography under the following measurement conditions by the solid content of the solidified slurry. <<Measurement conditions>> Gas chromatography equipment: Agilent 7890B. ·Capillary column: DB-WAX. Sample: Approximately 0.1 g of the solidified slurry was dissolved in approximately 20 mL of acetone. In Comparative Example 4, approximately 0.3 g of the solidified slurry was dissolved in approximately 20 mL of dimethylformamide. Internal standard: n-butyl acetate. Injection volume: 1 μL. ·Inlet temperature: 180℃. Detector temperature: 200℃. Detector: FID. · Carrier gas: Helium.

[0091] The solid content of the solidified slurry was measured by the following method. First, the mass (W1) of the aluminum dish was measured to the nearest 0.1 mg. Next, about 2 g of the solidified slurry was placed in an aluminum dish, and the mass (W2) was measured to the nearest 0.1 mg. Next, the aluminum dish containing the solidified slurry was placed in a dryer at 110°C and heated for 4 hours, then removed from the dryer and cooled to room temperature in a desiccator, after which the mass (W3) was measured to the nearest 0.1 mg. The solid content of the solidified slurry was calculated using the following formula. Solid content of solidified slurry = (W3-W1) / (W2-W1)

[0092] (4) Calculation of Hansen solubility parameters The dispersion term (δD), polarization term (δP), and hydrogen bond term (δH) of the Hansen solubility parameter were calculated using the computer software "COSMO quick" (Dassault Systèmes) by obtaining surface charge distribution information from the "COSMO Fragment Data Base" (Dassault Systèmes), which had been generated in advance by quantum chemical calculations. The calculation method for the Hansen solubility parameter was based on the following literature. Christoph Loschen, and Andreas Klamt. COSMO quick: A Novel Interface for Fast σ-Profile Composition and Its Application to COSMO-RS Solvent Screening Using Multiple Reference Solvents: Ind. Eng. Chem. Res. 2012, 51, 14303-14308

[0093] [Production of polymer latex (L)] <Production Example 1: Production of polymer latex (LA)> The following emulsifier mixture (1-1) was placed in a separable flask equipped with a thermometer, a nitrogen inlet tube, a condenser and a stirrer, and the mixture was stirred and heated to an internal temperature of 60°C under a nitrogen atmosphere. <<Emulsifier mixture (1-1)>> Sodium alkyldiphenyl ether sulfonate (manufactured by Kao Corporation, trade name "Pelex SS-L"): 3.0 parts Deionized water: 296 parts.

[0094] Next, the following reducing agent mixture (1-1) was placed in the separable flask. <<Reducing agent mixture (1-1)>> · Ferrous sulfate: 0.0001 parts. · Ethylenediaminetetraacetic acid disodium salt: 0.0003 parts. · Sodium formaldehyde sulfoxylate: 0.3 parts. Deionized water: 4.2 parts.

[0095] Next, the following monomer mixture (1-1) was added dropwise to the separable flask over 180 minutes, and then the mixture was maintained for 90 minutes. <<Monomer mixture (1-1)>> · Styrene: 24.0 parts. · α-Methylstyrene: 12.0 parts. · Phenyl methacrylate: 13.5 parts. · Glycidyl methacrylate: 0.5 parts. · t-Butyl hydroperoxide: 0.1 parts.

[0096] Next, the following monomer mixture (1-2) was added dropwise to the separable flask over 90 minutes, and then the temperature was raised to 85°C. <<Monomer mixture (1-2)>> · Phenyl methacrylate: 12.5 parts. ·Methyl methacrylate: 37.5 parts. · 3-mercaptopropionic acid: 1.5 parts. · t-Butyl hydroperoxide: 0.1 parts.

[0097] Next, the following reducing agent mixture (1-2) was added to the separable flask and kept for 90 minutes. <<Reducing agent mixture (1-2)>> · Ferrous sulfate: 0.00005 parts. · Ethylenediaminetetraacetic acid disodium salt: 0.0002 parts. · Sodium formaldehyde sulfoxylate: 0.15 parts. · Deionized water: 2.1 parts.

[0098] Then, the mixture was cooled to 40° C. to obtain a polymer latex (LA) containing polystyrene.

[0099] <Production Example 2: Production of polymer latex (LB)> The following emulsifier mixture (2-1) was placed in a separable flask equipped with a thermometer, a nitrogen inlet tube, a condenser and a stirrer, and the mixture was stirred and heated to an internal temperature of 60°C under a nitrogen atmosphere. <<Emulsifier mixture (2-1)>> - Polyoxyethylene (4.5) lauryl ether sodium acetate (manufactured by Kao Corporation, trade name "Kao Akipo RLM-45NV"): 8.3 parts Deionized water: 221 parts.

[0100] Next, the following reducing agent mixture (2-1) was placed in the separable flask. <<Reducing agent mixture (2-1)>> · Ferrous sulfate: 0.0001 parts. · Ethylenediaminetetraacetic acid disodium salt: 0.0003 parts. · Sodium formaldehyde sulfoxylate: 0.3 parts. Deionized water: 4.2 parts.

[0101] Next, the following monomer mixture (2-1) was added dropwise to the separable flask over 360 minutes, and then the mixture was maintained for 90 minutes. <<Monomer mixture (2-1)>> · Styrene: 60.5 parts. · α-Methylstyrene: 12.0 parts. ·Methyl methacrylate: 22.5 parts. · n-Octyl mercaptan: 0.5 parts. · t-Butyl hydroperoxide: 0.2 parts.

[0102] Next, the following reducing agent mixture (2-2) was charged into the separable flask. <<Reducing agent mixture (2-2)>> · Ferrous sulfate: 0.00003 parts. · Ethylenediaminetetraacetic acid disodium salt: 0.00008 parts. · Sodium formaldehyde sulfoxylate: 0.075 parts. Deionized water: 1.0 parts

[0103] Next, the following monomer mixture (2-2) was added dropwise to the separable flask over 60 minutes, and then the mixture was maintained for 60 minutes. <<Monomer mixture (2-2)>> ·Methyl methacrylate: 5.0 parts. · n-Octyl mercaptan: 0.28 parts. · t-Butyl hydroperoxide: 0.01 parts.

[0104] The temperature was then raised to 80°C and maintained at that temperature for another 60 minutes, and then cooled to 40°C to obtain a polymer latex (LB) containing polystyrene.

[0105] <Production Example 3: Production of polymer latex (LC)> The following monomer mixture (3-1) was placed in a separable flask equipped with a stirrer and stirred to obtain 100 parts of an organosiloxane mixture. <<Monomer mixture (3-1)>> · Tetraethoxysilane: 2.0 parts. ·3-Methacryloyloxypropyldimethoxymethylsilane: 2.0 parts. · Octamethylcyclotetrasiloxane: 96.0 parts.

[0106] Next, the following emulsifier mixture (3-1) was added to the organosiloxane mixture, and the mixture was stirred at 10,000 rpm for 5 minutes using a homomixer, and then passed through a homogenizer twice at a pressure of 20 MPa to obtain a stable premixed emulsion. <<Emulsifier mixture (3-1)>> · Sodium dodecylbenzenesulfonate: 1.0 parts. Deionized water: 150 parts.

[0107] Next, the premixed emulsion was placed in a separable flask equipped with a thermometer and a stirrer, stirred, and heated to an internal temperature of 80°C. Then, the following emulsifier mixture (3-2) was added dropwise to the separable flask over 3 minutes, and the mixture was then maintained for 420 minutes. <<Emulsifier mixture (3-2)>> ·98% sulfuric acid: 0.2 parts. Deionized water: 49.8 parts.

[0108] The mixture was then cooled to 25°C and kept at 25°C for 6 hours. A 5% aqueous solution of sodium hydroxide was then added as a neutralizer until the pH reached 7.0, followed by stirring to obtain a polymer latex (L-C'). The amount of 5% aqueous solution of sodium hydroxide added was 35 parts.

[0109] Next, 67.11 parts of the polymer latex (LC') (20.0 parts in terms of polymer) and 160 parts of deionized water were placed in a separable flask equipped with a thermometer, a nitrogen inlet tube, a condenser and a stirrer, and stirred. Next, the following monomer mixture (3-2) was charged into the separable flask, and then the mixture was stirred at 40° C. for 60 minutes. <<Monomer mixture (3-2)>> · Styrene: 17.25 parts. ·Allyl methacrylate: 0.44 parts. · Cumene hydroperoxide: 0.07 parts.

[0110] Next, the inside temperature was heated to 70° C. under a nitrogen atmosphere, and then the following reducing agent mixture (3-1) was added to the separable flask and kept for 30 minutes. <<Reducing agent mixture (3-1)>> Ferrous sulfate: 0.001 parts. · Ethylenediaminetetraacetic acid disodium salt: 0.003 parts. · Sodium formaldehyde sulfoxylate: 0.24 parts. Deionized water: 10 parts.

[0111] Next, a mixed emulsion prepared by dispersing the following monomer mixture (3-3) and the following emulsifier mixture (3-3) using an ULTRA-TURRAX (registered trademark) T25 (manufactured by IKA) at 10,000 rpm for 2 minutes was added dropwise over 330 minutes and then held for 60 minutes. <<Monomer mixture (3-3)>> · Styrene: 51.75 parts. · Allyl methacrylate: 1.33 parts. · Cumene hydroperoxide: 0.21 parts. <<Emulsifier mixture (3-3)>> Sodium dodecylbenzenesulfonate (manufactured by Kao Corporation, trade name "Neopelex G-15"): 2.53 parts · Deionized water: 26.74 parts.

[0112] Next, the following monomer mixture (3-4) was added dropwise to the separable flask over 60 minutes, and then the mixture was maintained for 60 minutes. <<Monomer mixture (3-4)>> ·Methyl methacrylate: 9.5 parts. ·Butyl acrylate: 0.5 parts. · t-Butyl hydroperoxide: 0.05 parts.

[0113] Then, the mixture was cooled to 40° C. to obtain a polymer latex (LC) containing polyorganosiloxane and polystyrene.

[0114] <Production Example 4: Production of polymer latex (LD)> Into a separable flask equipped with a thermometer, a nitrogen inlet tube, a condenser and a stirrer, 100.67 parts (30.0 parts in terms of polymer) of the polymer latex (LC') obtained in the same manner as in Production Example 3 and 160 parts of deionized water were added and stirred. Next, the following monomer mixture (4-1) was charged into the separable flask, and then the mixture was stirred at 40° C. for 60 minutes. <<Monomer mixture (4-1)>> ·Styrene: 15.00 parts. ·Allyl methacrylate: 0.38 parts. · Cumene hydroperoxide: 0.07 parts.

[0115] Next, the inside temperature was heated to 70° C. under a nitrogen atmosphere, and then the following reducing agent mixture (4-1) was added to the separable flask, and the flask was kept in this state for 30 minutes. <<Reducing agent mixture (4-1)>> Ferrous sulfate: 0.001 parts. · Ethylenediaminetetraacetic acid disodium salt: 0.003 parts. · Sodium formaldehyde sulfoxylate: 0.24 parts. Deionized water: 10 parts.

[0116] Next, a mixed emulsion prepared by dispersing the following monomer mixture (4-2) and the following emulsifier mixture (4-1) using an ULTRA-TURRAX (registered trademark) T25 (manufactured by IKA) at 10,000 rpm for 2 minutes was added dropwise over 330 minutes and then held for 60 minutes. <<Monomer mixture (4-2)>> ·Styrene: 45.00 parts. ·Allyl methacrylate: 1.15 parts. · Cumene hydroperoxide: 0.21 parts. <<Emulsifier mixture (4-1)>> Sodium dodecylbenzenesulfonate (manufactured by Kao Corporation, trade name "Neopelex G-15"): 2.53 parts · Deionized water: 26.74 parts.

[0117] Next, the following monomer mixture (4-3) was added dropwise to the separable flask over 60 minutes, and then the mixture was maintained for 60 minutes. <<Monomer mixture (4-3)>> ·Methyl methacrylate: 9.5 parts. ·Butyl acrylate: 0.5 parts. · t-Butyl hydroperoxide: 0.05 parts.

[0118] Then, the mixture was cooled to 40° C. to obtain a polymer latex (LD) containing polyorganosiloxane and polystyrene.

[0119] [Example 1] A separable flask equipped with a thermometer, steam inlet tube, condenser, and stirrer was charged with an aqueous coagulant solution containing calcium acetate dissolved in water, and the solution was stirred and heated. The polymer latex (LA) obtained in Production Example 1 and heptane as an organic solvent were added dropwise over 15 minutes to coagulate the polymer in the polymer latex (LA), yielding a coagulated liquid. The condenser was then removed, and the coagulated liquid was further heated by blowing steam into the separable flask. The liquid was then held for a while to remove the heptane, and cooled to 40°C to yield a coagulated slurry (A-1). The coagulated slurry (A-1) was thoroughly stirred, and 0.5 g was sampled, and the amount of solvent remaining in the coagulated slurry (A-1) was measured. The coagulated slurry (A-1) was subjected to solid-liquid separation, and the resulting solid was washed, dehydrated, and then dried to obtain polymer particles (a-1). The particle size distribution of the polymer particles (a-1) was measured, the average particle diameter (Dv) was measured, and the fine powder ratio was calculated. The amounts of polymer latex (LA), organic solvent, coagulant, water, and coagulant aqueous solution added, as well as the coagulation temperature, steam stripping temperature, and steam stripping time were as shown in Example 1 in Table 2. Table 1 shows the results of the Hansen solubility parameters of the organic solvents used in Example 1 and the later-described Examples 2 to 10 and Comparative Examples 1 to 4, as well as the monomers (monomer (1) or siloxane) constituting the polymer contained in the polymer latex (L). Table 2 shows the remaining solvent amount, average particle size (Dv), and fine powder ratio.

[0120] The solubility in water at 25° C. of the organic solvents used in Example 1 and any of Examples 2 to 10 and Comparative Examples 1 to 4 described later is as follows. Solubility in hexane: 0.01% by mass or less. Solubility in heptane: 0.01% by mass or less. Ethanol solubility: 50% by mass or more. Acetone solubility: 50% by mass or more.

[0121] [Example 2] The amounts of polymer latex (LB), organic solvent, coagulant, water, and coagulant aqueous solution added, as well as the coagulation temperature, steam stripping temperature, and steam stripping time, were as shown in Example 2 in Table 2. A coagulated slurry (B-1) and polymer particles (b-1) were obtained in the same manner as in Example 1. The results of the amount of residual solvent, average particle diameter (Dv), and fine powder ratio are shown in Table 2.

[0122] [Example 3] The amounts of polymer latex (LB), organic solvent, coagulant, water, and coagulant aqueous solution added, as well as the coagulation temperature, steam stripping temperature, and steam stripping time, were as shown in Example 3 in Table 2. A coagulated slurry (B-2) and polymer particles (b-2) were obtained in the same manner as in Example 1. The results of the amount of residual solvent, average particle size (Dv), and fine powder ratio are shown in Table 2.

[0123] [Example 4] The amounts of polymer latex (LB), organic solvent, coagulant, water, and coagulant aqueous solution added, as well as the coagulation temperature, steam stripping temperature, and steam stripping time, were as shown in Example 4 in Table 2. A coagulated slurry (B-3) and polymer particles (b-3) were obtained in the same manner as in Example 1. The results of the amount of residual solvent, average particle size (Dv), and fine powder ratio are shown in Table 2.

[0124] [Example 5] The amounts of polymer latex (LC), organic solvent, coagulant, water, and coagulant aqueous solution added, as well as the coagulation temperature, steam stripping temperature, and steam stripping time, were as shown in Example 5 in Table 2. A coagulated slurry (C-1) and polymer particles (c-1) were obtained in the same manner as in Example 1. The results of the amount of residual solvent, average particle diameter (Dv), and fine powder ratio are shown in Table 2.

[0125] [Example 6] The amounts of polymer latex (LC), organic solvent, coagulant, water, and coagulant aqueous solution added, as well as the coagulation temperature, steam stripping temperature, and steam stripping time, were as shown in Example 6 in Table 3. A coagulated slurry (C-2) and polymer particles (c-2) were obtained in the same manner as in Example 1. The results of the amount of residual solvent, average particle diameter (Dv), and fine powder ratio are shown in Table 3.

[0126] [Example 7] The amounts of polymer latex (LC), organic solvent, coagulant, water, and coagulant aqueous solution added, as well as the coagulation temperature, steam stripping temperature, and steam stripping time, were as shown in Example 7 in Table 3. A coagulated slurry (C-3) and polymer particles (c-3) were obtained in the same manner as in Example 1. The results of the amount of residual solvent, average particle diameter (Dv), and fine powder ratio are shown in Table 3.

[0127] [Example 8] The amounts of polymer latex (LC), organic solvent, coagulant, water, and coagulant aqueous solution added, as well as the coagulation temperature, steam stripping temperature, and steam stripping time, were as shown in Example 8 in Table 3. A coagulated slurry (C-4) and polymer particles (c-4) were obtained in the same manner as in Example 1. The results of the amount of residual solvent, average particle diameter (Dv), and fine powder ratio are shown in Table 3.

[0128] [Example 9] The amounts of polymer latex (LD), organic solvent, coagulant, water, and coagulant aqueous solution added, as well as the coagulation temperature, steam stripping temperature, and steam stripping time, were as shown in Example 9 in Table 3. A coagulated slurry (D-1) and polymer particles (d-1) were obtained in the same manner as in Example 1. The results of the amount of residual solvent, average particle size (Dv), and fine powder ratio are shown in Table 3.

[0129] [Example 10] The amounts of polymer latex (LD), organic solvent, coagulant, water, and coagulant aqueous solution added, as well as the coagulation temperature, steam stripping temperature, and steam stripping time, were as shown in Example 10 in Table 3. A coagulated slurry (D-2) and polymer particles (d-2) were obtained in the same manner as in Example 1. The results of the amount of residual solvent, average particle size (Dv), and fine powder ratio are shown in Table 3.

[0130] [Comparative Example 1] A coagulated slurry (A-2) was obtained in the same manner as in Example 1, except that heptane was not added, as shown in Comparative Example 1 in Table 4. The results of the amount of residual solvent, the average particle size (Dv), and the fine powder ratio are shown in Table 4.

[0131] Comparative Example 2 A coagulated slurry (C-5) was obtained in the same manner as in Example 5, except that heptane was not added, as shown in Comparative Example 2 in Table 4, and polymer particles (c-5) were also obtained. The results of the amount of residual solvent, the average particle size (Dv), and the fine powder ratio are shown in Table 4.

[0132] Comparative Example 3 A coagulated slurry (D-3) was obtained in the same manner as in Example 9, except that 30 parts of hexane was replaced with 30 parts of ethanol, as shown in Comparative Example 3 in Table 4. The results of the amount of residual solvent, the average particle size (Dv), and the fine powder ratio are shown in Table 4.

[0133] Comparative Example 4 A coagulated slurry (D-4) was obtained in the same manner as in Example 9, except that 30 parts of hexane was changed to 30 parts of acetone, as shown in Comparative Example 4 in Table 4. The results of the amount of residual solvent, the average particle diameter (Dv), and the fine powder ratio are shown in Table 4.

[0134] [Table 1]

[0135] [Table 2]

[0136] [Table 3]

[0137] [Table 4]

[0138] As is clear from the results in Tables 2 and 3, the polymer particles obtained in each Example had a small fine powder ratio of 2% or less, and the amount of residual solvent in the coagulated slurry was small, at 0.9% or less. On the other hand, as is clear from the results in Table 4, the polymer particles obtained in each comparative example had a high fine powder ratio of 38% or more.

Claims

1. a step of mixing a polymer latex, a coagulant, and an organic solvent that is poorly soluble in water to obtain a coagulated liquid; removing the organic solvent from the coagulation liquid to obtain a coagulation slurry; and The polymer contained in the polymer latex contains at least one of a structural unit derived from a monomer represented by the following formula (1) and a structural unit derived from a siloxane: The dispersion term (δD) of the Hansen solubility parameter of the organic solvent is 10 to 20 MPa. １ / ２ and the polarization term (δP) is 10 MPa １ / ２ The hydrogen bond term (δH) is 10 MPa or less. １ / ２ A method for producing polymer particles, which is as follows: 【Chemical 1】 (In formula (1), R １ ~R ６ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

2. The method for producing polymer particles according to claim 1, wherein the boiling point of the organic solvent is 100°C or lower.

3. The method for producing polymer particles according to claim 1 or 2, wherein the organic solvent contains at least one of hexane and heptane.

4. 3. The method for producing polymer particles according to claim 1, wherein the ratio of the organic solvent is 2 to 50 parts by mass per 100 parts by mass of the solid content of the polymer latex.

5. R in the formula (1) １ is a hydrogen atom or a methyl group, and R ２ ~R ６ The method for producing polymer particles according to claim 1 or 2, wherein is a hydrogen atom.

6. 3. The method for producing polymer particles according to claim 1, wherein the total amount of the structural units derived from the monomer represented by formula (1) and the structural units derived from the siloxane is 10 to 100% by mass with respect to the total mass of all structural units constituting the polymer contained in the polymer latex.

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