Fine resin particles and production method therefor

Abstract

To provide fine resin particles that have solvent resistance sufficient to withstand a heating step after solvent dispersion, that generate few bubbles during dispersion, and have high dispersibility in a solvent.SOLUTION: The present invention provides fine resin particles obtained by polymerizing a vinyl monomer, the fine resin particles having a gel fraction of 93% or more, a solvent resistance index of 50 or less, a volume average particle diameter of 10 to 1000 nm, and a residual surfactant level of 0.01 to 1 pt.mass relative to 100 pts.mass of the resin fine particles.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to resin fine particles and a method for producing the same. [Background technology]

[0002] Methods for producing resin microparticles include suspension polymerization, seed polymerization, emulsion polymerization, soap-free polymerization, and dispersion polymerization. In particular, emulsion polymerization is suitable for producing resin microparticles with a microparticle size such as submicron, and the resulting microparticles are used in a wide range of applications, such as antiblocking agents for light diffusion plates and various film membranes, various film modifiers, spacers between microparts of various electronic devices, pore-forming agents for various battery components, and core particles for conductive microparticles that are responsible for electrical connections. In particular, when used in the optical field, it is necessary to consider the effects on optical properties such as haze and light transmittance, so resin microparticles obtained by polymerizing (meth)acrylic monomers or styrene monomers as the particle composition have been preferably used. In this case, there are methods such as dispersing particles in a solvent and using them, and methods of directly kneading them with resin raw materials. In general, crosslinked microparticles are highly resistant to solvents and heat, and are preferably used. Patent Document 1 and the like are examples of the production of crosslinked microparticles. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3742154 [Patent Document 2] Patent No. 6258740 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even among crosslinked fine particles, depending on the degree of crosslinking, the solvent resistance is low, and when a heating process or the like is added after dispersion in a solvent, the particles swell, resulting in problems such as not obtaining the desired particle size when used. In addition, Patent Document 2 describes particles obtained by a production method that maintains solvent resistance and has good productivity, but in all cases a non-reactive surfactant is used during emulsion polymerization. If the particles obtained by the method described in Patent Document 2 are used as is after drying, free residual surfactant will remain in the solvent or resin, and foaming will occur during dispersion, which will cause particle aggregation, precipitation, and particle detachment from the substrate. In addition, although it is possible to remove it by washing, etc., this leads to an increase in the number of steps, which is undesirable in terms of production. The present invention has been made in consideration of the above-mentioned problems, and aims to provide resin microparticles that have solvent resistance sufficient to withstand the heating process after solvent dispersion, generate little air bubbles during dispersion, and have excellent dispersibility in a solvent, as well as a method for producing the same. [Means for solving the problem]

[0005] As a result of extensive investigations, the present inventors have found that the above-mentioned problems can be solved by using specific resin fine particles. [1] Resin particles obtained by polymerizing a vinyl monomer, the resin particles having a gel fraction of 93% or more and a solvent resistance index of 50 or less. [2] Resin microparticles obtained by polymerizing a vinyl monomer, characterized in that the vinyl monomer contains a reactive surfactant having a polyoxyalkylene chain in its molecule and contains a hydroxyl group derived from a polymerization initiator at the end of the vinyl polymerization chain of the resin microparticles. [3] Resin microparticles according to [2], characterized in that they have a gel fraction of 93% or more and a solvent resistance index of 50 or less. [4] The resin fine particles according to any one of [1] to [3], having a volume average particle diameter of 10 to 1,000 nm. [5] The resin fine particles according to any one of [1] to [4], characterized in that the coefficient of variation of the volume average particle diameter is 25% or less. [6] The resin fine particles according to any one of [1] to [5], wherein the amount of residual surfactant is 0.01 to 1 part by mass per 100 parts by mass of the resin fine particles. [7] The resin fine particles according to any one of [1] to [6], wherein the vinyl monomer comprises a monofunctional (meth)acrylic monomer and / or a monofunctional aromatic vinyl monomer. [8] The resin fine particles according to any one of [1] to [7], wherein the vinyl monomer comprises a polyfunctional (meth)acrylic monomer and / or a polyfunctional aromatic vinyl monomer. [9] A method for producing resin microparticles, comprising: a first polymerization step of polymerizing a monomer emulsion containing a vinyl-based monomer, an aqueous medium, and a reactive surfactant having a polyoxyalkylene chain in its molecule using a water-soluble polymerization initiator to obtain seed particles; and a second polymerization step of absorbing the monomer emulsion containing the vinyl-based monomer, the aqueous medium, and the reactive surfactant having a polyoxyalkylene chain in its molecule into the seed particles and then polymerizing the monomer emulsion.

[10] The method for producing resin microparticles according to [9], characterized in that the vinyl monomer comprises one or more selected from the group consisting of monofunctional (meth)acrylic monomers, monofunctional aromatic vinyl monomers, polyfunctional (meth)acrylic monomers and polyfunctional aromatic vinyl monomers.

[11] The method for producing resin microparticles according to [9] or

[10] , further comprising a spray drying step of spray-drying the resin microparticles obtained in the second polymerization step under conditions of an inlet temperature of 80 to 220°C and an outlet temperature of 50 to 100°C to obtain aggregates.

[12] The method for producing resin microparticles according to

[11] , further comprising a crushing step of crushing the aggregates to disperse the resin microparticles.

[13] The method for producing resin fine particles according to any one of [9] to

[12] , comprising a classifying step of classifying the resin fine particles.

[14] The resin fine particles according to any one of [1] to [8], which are used as an antiblocking agent for a resin film.

[15] The resin fine particles according to any one of [1] to [8], which are used as an additive for a light diffusion plate.

[16] The resin fine particles according to any one of [1] to [8], which are used as a spacer in an electronic device. Effect of the Invention

[0006] The present invention provides resin fine particles which have solvent resistance sufficient to withstand a heating step after dispersion in a solvent, generate little bubbles during dispersion, and have excellent dispersibility in a solvent, as well as a method for producing the same. The resin particles of the present invention are difficult to swell even when heated in a solvent-dispersed state, and have a small particle size variation. In addition, since the amount of free surfactant is small, a washing step is not required, and productivity is excellent. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] The present invention will be described in detail below. [Resin fine particles] The resin microparticles of the present invention are resin microparticles obtained by polymerizing a vinyl monomer, and are characterized in that they have a gel fraction of 93% or more and a solvent resistance index of 50 or less. Also, they are resin microparticles obtained by polymerizing a vinyl monomer, and are characterized in that the vinyl monomer contains a monofunctional vinyl monomer, a polyfunctional vinyl monomer, and a reactive surfactant having a polyoxyalkylene chain in the molecule, and contains a hydroxyl group at the end of the vinyl polymer chain of the resin microparticles.

[0008] <Vinyl monomer> The resin fine particles of the present invention are obtained by polymerizing a vinyl monomer. The vinyl monomer in the present invention is at least one selected from monofunctional vinyl monomers having one vinyl group in one molecule and polyfunctional vinyl monomers having two or more vinyl groups in one molecule. Examples of the monofunctional vinyl monomer include a monofunctional (meth)acrylic monomer, a monofunctional aromatic vinyl monomer, and the like. Examples of the polyfunctional vinyl monomer include a polyfunctional (meth)acrylic monomer and a polyfunctional aromatic vinyl monomer. In this specification, "(meth)acrylic" refers to acrylic or methacrylic, and "(meth)acrylate" refers to acrylate or methacrylate.

[0009] Examples of monofunctional (meth)acrylic monomers include methyl (meth)acrylate (methyl methacrylate, methyl acrylate), ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, Examples of such esters include (meth)acrylic acid alkyl esters having 1 to 20 carbon atoms in the alkyl group bonded to the ester, such as isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate, as well as (meth)acrylic acid esters having an alicyclic structure in the ester moiety, such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate. Among these, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, and decyl (meth)acrylate are preferred for general purpose, and cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate are preferred for applications requiring heat resistance. These alkyl (meth)acrylate esters may be used alone or in combination of two or more.

[0010] Examples of monofunctional aromatic vinyl monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, t-butylstyrene, vinylnaphthalene, styrenesulfonic acid, styrenesulfonate salts (sodium styrenesulfonate, ammonium styrenesulfonate, etc.), vinylbenzoic acid, and hydroxystyrene. Among these, styrene, α-methylstyrene, and sodium styrenesulfonate are preferred. These monofunctional aromatic vinyl monomers may be used alone or in combination of two or more.

[0011] Examples of the polyfunctional (meth)acrylic monomer include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, decaethylene glycol di(meth)acrylate, pentadecaethylene glycol di(meth)acrylate, pentacontahexaethylene glycol di(meth)acrylate, 1,3-butylene di(meth)acrylate, allyl (meth)acrylate (allyl methacrylate, allyl acrylate), trimethylolpropane tri(meth)acrylate, and pentaerythritol tetraacrylate. Among these, ethylene glycol di(meth)acrylate (ethylene glycol dimethacrylate) and allyl (meth)acrylate (allyl methacrylate) are preferred. These polyfunctional (meth)acrylic monomers may be used alone or in combination of two or more.

[0012] Examples of polyfunctional aromatic vinyl monomers include divinylbenzene, divinylnaphthalene, etc. These polyfunctional aromatic vinyl monomers may be used alone or in combination of two or more.

[0013] The mass ratio of the monofunctional vinyl monomer to the polyfunctional vinyl monomer in the vinyl monomer (monofunctional vinyl monomer / polyfunctional vinyl monomer) can be preferably 1 / 30 to 30 / 1, more preferably 1 / 20 to 20 / 1, and even more preferably 1 / 10 to 10 / 1. The content of the monofunctional (meth)acrylic monomer in the vinyl monomer can be set to preferably 2 to 95% by mass, more preferably 5 to 90% by mass, and further preferably 10 to 85% by mass. The content of the monofunctional aromatic vinyl monomer in the vinyl monomer can be preferably 0 to 25% by mass, more preferably 0 to 20% by mass, and further preferably 0 to 18% by mass. The mass ratio of the monofunctional aromatic vinyl monomer to the monofunctional (meth)acrylic monomer in the monofunctional vinyl monomer, expressed as monofunctional aromatic vinyl monomer / monofunctional (meth)acrylic monomer, can be preferably 0 to 1, more preferably 0 to 0.5, and even more preferably 0 to 0.25. The content of the polyfunctional (meth)acrylic monomer in the vinyl monomer can be set to preferably 0.4 to 98% by mass, more preferably 0.5 to 95% by mass, and further preferably 0.5 to 91% by mass. The content of the polyfunctional aromatic vinyl monomer in the vinyl monomer can be preferably 0 to 30% by mass, more preferably 0 to 20% by mass, and further preferably 0 to 15% by mass. The mass ratio of the polyfunctional aromatic vinyl monomer to the polyfunctional (meth)acrylic monomer in the polyfunctional vinyl monomer can be preferably 0 to 33, more preferably 0 to 30, and even more preferably 0 to 28, in terms of polyfunctional aromatic vinyl monomer / polyfunctional (meth)acrylic monomer. For example, the monofunctional vinyl monomer / polyfunctional vinyl monomer ratio can be 2 / 1 to 8 / 1, the content of the monofunctional (meth)acrylic monomer in the vinyl monomer can be 60 to 85 mass%, the content of the monofunctional aromatic vinyl monomer in the vinyl monomer can be 1 to 18 mass%, the monofunctional aromatic vinyl monomer / monofunctional (meth)acrylic monomer can be 0.005 to 0.25, the content of the polyfunctional (meth)acrylic monomer in the vinyl monomer can be 0.3 to 30 mass%, the content of the polyfunctional aromatic vinyl monomer in the vinyl monomer can be 0 to 8 mass%, and the polyfunctional aromatic vinyl monomer / polyfunctional (meth)acrylic monomer can be 0 to 30. Furthermore, for example, the monofunctional vinyl monomer / polyfunctional vinyl monomer ratio can be 1 / 20 to 4 / 1, the content of the monofunctional (meth)acrylic monomer in the vinyl monomer can be 5 to 15 mass%, the content of the monofunctional aromatic vinyl monomer in the vinyl monomer can be 0 to 5 mass%, the monofunctional aromatic vinyl monomer / monofunctional (meth)acrylic monomer can be 0 to 0.05, the content of the polyfunctional (meth)acrylic monomer in the vinyl monomer can be 85 to 98 mass%, the content of the polyfunctional aromatic vinyl monomer in the vinyl monomer can be 0 to 5 mass%, and the polyfunctional aromatic vinyl monomer / polyfunctional (meth)acrylic monomer can be 0 to 5.

[0014] In addition to the above-mentioned monomers, the vinyl monomer may also be an unsaturated carboxylic acid monomer such as (meth)acrylic acid, a hydroxyalkyl (meth)acrylate monomer such as hydroxyethyl (meth)acrylate, a (meth)acrylamide monomer, a (meth)acrylonitrile monomer, a halogenated vinyl monomer such as vinyl chloride, a vinyl carboxylate monomer such as vinyl acetate, an olefin monomer such as ethylene, an unsaturated imide monomer, or vinyl alcohol.

[0015] <Gel fraction> The resin fine particles of the present invention may have a gel fraction of 93% or more, preferably 95% or more, and more preferably 96% or more. The gel fraction of the resin fine particles of the present invention means the proportion of crosslinked portions that are present in the resin fine particles and that exhibit solvent insolubility. When the gel fraction is 93% or more, the resin particles can be stably dispersed in an organic solvent such as toluene, and the resin particles do not dissolve even when heated thereafter.

[0016] <Solvent resistance index> The resin fine particles of the present invention may have a solvent resistance index of not more than 50, preferably not more than 25, and more preferably not more than 10. The lower limit of the solvent resistance index is not particularly limited. The solvent resistance index of the resin fine particles in the present invention is obtained by the following measurement method. -Method of measuring solvent resistance index- 1 part by mass of resin particles and 50 parts by mass of toluene are placed in a 100 mL plastic container with a lid, and stirred for 3 minutes with a degassing mixer (Thinky Corporation, Rotating / Revolving Mixer (Atmospheric Pressure Type) AR-100 (Product Name: Awatori Rentaro AR-100 (THINKYMIXER (Non Vacuum) AR-100))). The "volume average particle size of the resin particles" is measured with a dynamic light scattering concentrated nanoparticle size distribution measuring device (CORDOUAN Corporation, "VASCO"). The obtained resin particle toluene dispersion is then placed in a glass flask with a reflux tube, refluxed at 130°C for 24 hours, and cooled. The "volume average particle size of the resin particles after heating" of the obtained resin particle toluene dispersion after heating is measured with the particle size distribution measuring device, and the solvent resistance index is calculated according to the following formula. Solvent resistance index (%) = 100 × (volume average particle diameter of resin particles after heating (nm) - volume average particle diameter of resin particles (nm)) / volume average particle diameter of resin particles (nm)

[0017] <Reactive surfactant> The resin fine particles of the present invention may be those obtained by polymerizing a vinyl monomer containing a reactive surfactant having a polyoxyalkylene chain in the molecule.

[0018] The reactive surfactant having a polyoxyalkylene chain in the molecule is a surfactant having a double bond that can be copolymerized with the monomer in the polymerization system and a polyoxyalkylene chain that is a polymer of oxyalkylene in the molecule.By using such a reactive surfactant, the surfactant does not separate from the surface of the resin fine particle, and the mechanical stability of the resin fine particle can be improved.In addition, even if the amount of the surfactant used is reduced, polymerization can be performed without impairing polymerization stability. Examples of monomers constituting the polyoxyalkylene chain include oxyalkylenes such as ethylene oxide, propylene oxide, and butylene oxide. The reactive surfactants having a polyoxyalkylene chain may be used alone or in combination of two or more kinds.

[0019] Examples of the reactive surfactant include polyoxyethylene-1-(allyloxymethyl) alkyl ether sulfate ammonium salt (Aqualon KH1025 manufactured by Daiichi Kogyo Seiyaku Co., Ltd., etc.), polyoxyethylene nonylpropenyl ether sulfate salt (Aqualon HS1025, Aqualon BC-10 manufactured by Daiichi Kogyo Seiyaku Co., Ltd., etc.), polyoxyethylene allyl glycidyl nonylphenyl ether sulfate salt (ADEKA ADEKA REASOAP SE, etc.), sodium alkyl allyl sulfosuccinate (Eleminol JS-2 manufactured by Sanyo Chemical Industries, Ltd., etc.), and methacrylic acid polyoxyalkylene sulfate salt (Sanyo Chemical Industries, Ltd., etc.). anionic reactive emulsifiers having reactive groups such as propenyl groups, allyl groups, isopropenyl groups, acrylate groups, methacrylate groups, etc., such as "Eleminol RS-30" manufactured by Yokasei Kogyo Co., Ltd.), bis(polyoxyethylene polycyclic phenyl ether) methacrylate sulfate salts ("Anthox MS-60" manufactured by Nippon Nyukazai Co., Ltd.), ethylene glycol methacrylate sulfate salts ("Anthox MS-2N" and "Anthox MS-NH4" manufactured by Nippon Nyukazai Co., Ltd.), and those having other structures ("Latemul" manufactured by Kao Corporation, "New Frontier" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., "RA-1823" and "RA-2320" manufactured by Nippon Nyukazai Co., Ltd., etc.);

[0020] Polyoxyethylene nonylpropenyl ether (Dai-Ichi Kogyo Seiyaku's "Aqualon RN", etc.), polyoxyethylene allyl glycidyl nonylphenyl ether (ADEKA's "ADEKA REASOAP NE", etc.), polyoxyalkylene glycol monoacrylate (NOF Corp.'s "Blenmer AET", "Blenmer APT", etc.), lauroxy polyethylene glycol monoacrylate (NOF Corp.'s "Blenmer ALE", etc.), lauroxy polyethylene glycol monomethacrylate (NOF Corp.'s "Blenmer PLE", etc.), stearoxy polyethylene glycol monomethacrylate (NOF Corp.'s "Blenmer PSE", etc.), stearoxy polyethylene glycol-polypropylene glycol monoacrylate (NOF Corp.'s "Blenmer ASEP", etc.), ", etc.), allyloxypolyalkylene glycol monomethacrylate (NOF Corporation's "BLEMMER PNEP", "BLEMMER PNPE", etc.), nonylphenoxypolyoxyalkylene glycol monoacrylate (NOF Corporation's "BLEMMER 43ANEP-500", "BLEMMER 70ANEP-550", etc.), polyethylene glycol-polypropylene glycol polyethylene glycol dimethacrylate (NOF Corporation's "BLEMMER 80PDC", etc.), polyethylene glycol polypropylene glycol-polyethylene glycol diacrylate (NOF Corporation's "BLEMMER 30ADC", etc.). The amount of the reactive surfactant used is preferably in the range of 0.1 to 20 parts by mass, more preferably 0.3 to 15 parts by mass, and further preferably 0.5 to 10 parts by mass, based on 100 parts by mass of the vinyl monomer.

[0021] <Hydroxyl group at the end of vinyl polymer chain> The resin fine particles of the present invention may contain a hydroxyl group derived from the polymerization initiator at the end of the vinyl polymer chain. Such resin particles can be obtained by using a polymerization initiator containing a hydroxyl group when polymerizing a vinyl monomer. Preferred examples of the polymerization initiator containing a hydroxyl group include azo-based polymerization initiators containing a hydroxyl group. Examples of the azo polymerization initiator containing a hydroxyl group include 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] (trade name "VA-086"), 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide} (trade name "VA-080"), 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)ethyl]propionamide} (trade name "VA-082"), and 2,2'-azobis{2-methyl-N-[2-(1-hydroxybutyl)]-propionamide} (trade name "VA-085") (all manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). These azo polymerization initiators containing a hydroxyl group may be used alone or in combination of two or more. The amount of the polymerization initiator used is preferably in the range of 0.1 to 2 parts by mass, more preferably 0.2 to 1 part by mass, and further preferably 0.3 to 0.8 part by mass, based on 100 parts by mass of the vinyl monomer.

[0022] <Physical properties of resin particles> (Volume average particle size and its coefficient of variation) The volume average particle diameter of the resin fine particles of the present invention is not particularly limited and is appropriately set depending on the purpose and application, and is preferably in the range of 10 to 1000 nm, more preferably 30 to 750 nm, and further preferably 50 to 500 nm. The coefficient of variation of the volume average particle diameter of the resin fine particles of the present invention is not particularly limited, but is preferably in the range of 25% or less, more preferably 23% or less, and further preferably 21% or less. The coefficient of variation (CV value) of the volume average particle diameter of the resin fine particles is calculated by the following formula. Coefficient of variation of volume average particle diameter of resin microparticles = [(Standard deviation of volume-based particle size distribution of resin microparticles) / (Volume average particle diameter of resin microparticles)] x 100

[0023] (Residual surfactant amount) The amount of the residual surfactant relative to 100 parts by mass of the resin microparticles of the present invention is not particularly limited and is appropriately set according to the purpose and use. It is preferably in the range of 0.01 to 1 part by mass, more preferably 0.03 to 0.7 parts by mass, and even more preferably 0.05 to 0.5 parts by mass. When a surfactant is used during polymerization, if the amount of the residual surfactant is less than 0.01 part by mass, the process becomes complicated and it may be disadvantageous in terms of cost, etc. If the amount of the residual surfactant is 1 part by mass or more, there is a risk of foaming occurring when the resin microparticles are dispersed in a medium. The amount of the remaining surfactant in the present invention can be determined, for example, as follows. The resin particles were extracted with a solvent and measured using a liquid chromatograph linear ion trap mass spectrometer (LC / MS / MS device). As the LC / MS / MS device, "UHPLC ACCELA" manufactured by Thermo Fisher Scientific and "Linear Ion Trap LC / MSn LXQ" manufactured by Thermo Fisher Scientific can be used. The surfactant content is measured by the following method. Approximately 0.01 g of resin microparticles were precisely weighed into a centrifuge tube, the extraction liquid was poured in, and the resin microparticles and the extraction liquid were thoroughly mixed. After ultrasonic extraction, the mixture was mixed again and centrifuged, and the resulting supernatant was filtered to prepare the test liquid. The concentration of the surfactant in this test solution was measured using an LC / MS / MS device, and the content was calculated from the peak area value on the obtained chromatogram using a calibration curve prepared in advance.The surfactant content in the resin microparticles was then calculated using the following formula from the measured surfactant concentration in the test solution, the weight of the resin microparticles used as a sample (sample weight), and the amount of the extracted solution. Surfactant content = surfactant concentration in test solution x volume of extract ÷ sample weight The method for creating the calibration curve is as follows. After preparing an intermediate standard solution (methanol solution) of the surfactant at approximately 1000 ppm, it was further diluted stepwise with methanol to prepare standard solutions for creating a calibration curve at 20 ppm, 10 ppm, 5 ppm, and 2.5 ppm. The standard solutions for creating a calibration curve at each concentration were measured under the following conditions, and the peak area values ​​on the chromatogram of the monitor ion m / z = 730 to 830 were obtained. Each concentration and the area value were plotted to obtain an approximation curve (quadratic curve) by the least squares method, and this was used as the calibration curve for quantification.

[0024] (Solvent dispersibility) The solvent dispersibility of the resin microparticles of the present invention is evaluated as good when the solvent resistance index is not more than 50. A solvent resistance index of not more than 50 means that the change in the volume average particle diameter of the resin microparticles after heating is small, and that the resin microparticles are not swollen and are dispersed in the solvent without agglomeration. (number average particle size) The number average particle diameter of the resin fine particles of the present invention is not particularly limited and is appropriately set depending on the purpose and application, and is preferably in the range of 10 to 1000 nm, more preferably 30 to 750 nm, and further preferably 50 to 350 nm.

[0025] (Monodispersity) The monodispersity of the resin fine particles of the present invention is not particularly limited and is appropriately set depending on the purpose and application, and is preferably in the range of 1.2 or less, more preferably 1.15 or less, and further preferably 1.12 or less. The monodispersity is calculated from the following formula. Monodispersity=(volume average particle diameter of resin particles) / (number average particle diameter of resin particles)

[0026] <Other ingredients> The resin microparticles of the present invention may contain additives such as plasticizers, anti-binding agents, bubble regulators, crosslinking agents, fillers, lubricants, colorants, adhesion promoters, spreading agents, antioxidants, flame retardants and flame retardant assistants, within the range that does not impair the effects of the present invention.

[0027] [Method of manufacturing resin particles] The resin fine particles can be produced by polymerizing a vinyl monomer in the presence of a polymerization initiator and a surfactant (emulsifier) ​​as necessary.

[0028] <Polymerization initiator> The polymerization initiator used in the polymerization of the resin microparticles of the present invention is not particularly limited, but it is preferable to use a thermally decomposable water-soluble polymerization initiator. Examples of the thermally decomposable water-soluble polymerization initiator include persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] (trade name "VA-086"), 2,2'-azobis[2-(2-imidazolin-2-yl)propane] (trade name "VA-061"), 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (trade name "VA-044"), and the like. "), 2,2'-azobis[2-(2-imidazolin-2-yl)propane]disulfate dihydrate (trade name "VA-046B"), 2,2'-azobis(2-methylpropionamidine) dihydrochloride (trade name "V-50"), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate (trade name "VA-057"), 4,4'-azobis(4-cyanovaleric acid) (trade name "V-501"), 2,2'-azobis{2- 2,2'-Azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide} (trade name "VA-080"), 2,2'-Azobis{2-methyl-N-[1,1-bis(hydroxymethyl)ethyl]propionamide} (trade name "VA-082"), 2,2'-Azobis{2-methyl-N-[2-(1-hydroxybutyl)]-propionamide} (trade name "VA-085"), 2,2'-Azobis(2-amidinopropane)dihydrochloride Examples of the azo compounds include azo compounds such as 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane}dihydrochloride, 2,2'-azobis(1-imino-1-pyrrolidino-2-ethylpropane)dihydrochloride, 2,2'-azobis(1-imino-1-pyrrolidino-2-methylpropane)dihydrochloride, and 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}. In particular, water-soluble azo polymerization initiators are preferred because they have little effect on the pH of the slurry after polymerization, and further, from the viewpoint of improving the dispersibility of the resin fine particles, those that have a hydroxyl group in the molecule and can introduce a hydroxyl group derived from the polymerization initiator to the end of the vinyl polymerization chain of the resin fine particles are preferred.

[0029] In the present invention, a polymerization initiator other than the water-soluble polymerization initiator can also be used. Examples of such polymerization initiators include cumene hydroperoxide, di-tert-butyl peroxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, dimethylbis(tert-butylperoxy)hexane, dimethylbis(tert-butylperoxy)hexyne-3, bis(tert-butylperoxyisopropyl)benzene, bis(tert-butylperoxy)trimethylcyclohexane, butyl-bis(tert-butylperoxy)valerate, 2-ethylhexyl ether, butyl-bis(tert-butylperoxy)valerate ... Organic peroxides such as tert-butyl diethylhexane peroxyate, dibenzoyl peroxide, paramenthane hydroperoxide and tert-butyl peroxybenzoate; 2,2'-azobisisobutyronitrile (2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2-isopropylbutyronitrile), 2,2'-azobis(2,3-dimethylbutyronitrile), 2,2'-azobis(2,4-dimethylbutyronitrile), 2,2'-azobis(2-methylcapronitrile), 2 ,2'-Azobis(2,3,3-trimethylbutyronitrile), 2,2'-Azobis(2,4,4-trimethylvaleronitrile), 2,2'-Azobis(2,4-dimethylvaleronitrile), 2,2'-Azobis(2,4-dimethyl-4-ethoxyvaleronitrile), 2,2'-Azobis(2,4-dimethyl-4-n-butoxyvaleronitrile), 2,2'-Azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-Azobis[N-(2-propenyl)-2-methylpropionamide], 2,2'- Examples of the azo compounds include azobis(N-butyl-2-methylpropionamide), 2,2'-azobis(N-cyclohexyl-2-methylpropionamide), 1,1'-azobis(1-acetoxy-1-phenylethane), 1,1'-azobis(cyclohexane-1-carbonitrile), dimethyl-2,2'-azobis(2-methylpropionate), dimethyl-2,2'-azobisisobutyrate, dimethyl-2,2'-azobis(2-methylpropionate), and 2-(carbamoylazo)isobutyronitrile.

[0030] Furthermore, a redox initiator obtained by combining the above-mentioned persulfates and organic peroxides as a polymerization initiator with a reducing agent such as sodium sulfoxylate formaldehyde, sodium hydrogen sulfite, ammonium hydrogen sulfite, sodium thiosulfate, ammonium thiosulfate, hydrogen peroxide, sodium hydroxymethanesulfinate, L-ascorbic acid and its salts, cuprous salts, and ferrous salts may be used as the polymerization initiator. These polymerization initiators may be used alone or in combination of two or more. These polymerization initiators are preferably used in an amount of 0.1 to 2 parts by mass, more preferably 0.2 to 1 part by mass, and even more preferably 0.3 to 0.8 parts by mass, based on 100 parts by mass of the vinyl monomer.

[0031] <Surfactant> The surfactant for producing the resin fine particles of the present invention is not particularly limited, but it is preferable to use a reactive surfactant. Examples of anionic reactive surfactants include JS-20 and RS-3000 of ELEMINOL (registered trademark) manufactured by Sanyo Chemical Industries, Ltd., KH-10, KH-1025, KH-05, HS-10, HS-1025, BC-0515, BC-10, BC-1025, BC-20, BC-2020, AR-1025, and AR-2025 of AQUALON (registered trademark) manufactured by Daiichi Kogyo Seiyaku Co., Ltd., S-120, S-180A, S-180, and PD-104 of LATEMUL (registered trademark) manufactured by Kao Corporation, and SR-1025 and SE-10N of ADEKA ADEKA REASOAP (registered trademark). Examples of nonionic reactive surfactants include alkyl ether surfactants (commercially available products include ADEKA ADEKA REASOAP ER-10, ER-20, ER-30, and ER-40, and Kao LATEMURU PD-420, PD-430, and PD-450); alkyl phenyl ether surfactants or alkyl phenyl ester surfactants (commercially available products include Aqualon RN-10, RN-20, RN-30, RN-50, AN-10, AN-20, AN-30, and AN-5065, and ADEKA ADEKA REASOAP NE-10, NE-20, NE-30, and NE-40, and (meth)acrylate sulfate surfactants (commercially available products include Nippon Nyukazai RMA-564, RMA-568, and RMA-1114, and the like). Among these reactive surfactants, those having a polyoxyalkylene chain in the molecule are preferred from the viewpoints of particle dispersibility, dispersion stability, and the like.

[0032] In the present invention, a surfactant other than a reactive surfactant can also be used. As such a surfactant, any of anionic surfactants, cationic surfactants, amphoteric surfactants and nonionic surfactants can be used.

[0033] Examples of anionic surfactants include sodium oleate; fatty acid soaps such as castor oil potassium soap; alkyl sulfate ester salts such as sodium lauryl sulfate and ammonium lauryl sulfate; alkyl benzene sulfonates such as sodium dodecylbenzene sulfonate; alkyl naphthalene sulfonates; alkanesulfonates; dialkyl sulfosuccinates; alkyl phosphate ester salts; naphthalenesulfonate-formaldehyde condensates; polyoxyethylene alkyl phenyl ether sulfate ester salts; and polyoxyethylene alkyl sulfate ester salts.

[0034] Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxysorbitan fatty acid esters, polyoxyethylene alkylamines, glycerin fatty acid esters, and oxyethylene-oxypropylene block polymers.

[0035] Examples of the cationic surfactant include alkylamine salts such as laurylamine acetate and stearylamine acetate; and quaternary ammonium salts such as lauryltrimethylammonium chloride. Examples of the zwitterionic surfactant include lauryl dimethylamine oxide, phosphate surfactants, and phosphite surfactants.

[0036] These surfactants may be used alone or in combination of two or more. The type of surfactant is appropriately selected and the amount used is appropriately adjusted in consideration of the particle size of the resulting resin microparticles and the dispersion stability of the polymerizable monomer during polymerization.

[0037] The amount of the surfactant used is preferably in the range of 0.3 to 20 parts by mass, more preferably 0.5 to 15 parts by mass, and further preferably 0.7 to 10 parts by mass, based on 100 parts by mass of the vinyl monomer.

[0038] <medium> The medium used during polymerization may be either an aqueous medium or a non-aqueous medium. In the present invention, it is preferable to use an aqueous medium. Examples of the aqueous medium include water (e.g., ion-exchanged water) and a mixed solvent of water and a water-soluble solvent (e.g., a lower alcohol such as ethanol).

[0039] <Dispersant> When an aqueous medium is used during polymerization, a dispersant may be used to stabilize the dispersibility of the droplets and seed particles of the vinyl monomer. Examples of such dispersants include organic dispersants such as partially saponified polyvinyl alcohol, polyacrylates, polyvinylpyrrolidone, carboxymethylcellulose, and methylcellulose; and inorganic dispersants such as magnesium pyrophosphate, calcium pyrophosphate, calcium phosphate, calcium carbonate, magnesium phosphate, magnesium carbonate, and magnesium oxide. When an inorganic dispersant is used, it is preferable to use a surfactant in combination.

[0040] <Polymerization method> In producing the resin microparticles, the polymerization method of the vinyl monomer is not particularly limited as long as it is a known polymerization method. If necessary, a polymerization initiator or a surfactant (emulsifier) ​​is used. For example, seed polymerization, emulsion polymerization, suspension polymerization, etc. are included.

[0041] Seed polymerization is a method in which resin fine particles made of a polymer of a vinyl monomer are used as seed particles, the seed particles are made to absorb the vinyl monomer in an aqueous medium, and the vinyl monomer is polymerized within the seed particles. In this method, by growing the seed particles, resin fine particles having a particle size larger than that of the original seed particles can be obtained. Emulsion polymerization is a polymerization method in which an aqueous medium, a vinyl monomer that is difficult to dissolve in the medium, and a surfactant (emulsifier) ​​are mixed, and a polymerization initiator that is soluble in the aqueous medium is added to the mixture to carry out polymerization. Emulsion polymerization is characterized by the small variation in particle size of the resulting resin microparticles. Suspension polymerization is a polymerization method in which a vinyl monomer and an aqueous medium are mechanically stirred to suspend the vinyl monomer in the aqueous medium and polymerize it. Suspension polymerization is characterized by its ability to produce resin fine particles that are small and relatively uniform in particle size. In the present invention, seed polymerization is most preferred.

[0042] (Seed polymerization) The polymerization method of the vinyl monomer to obtain the seed particles used in the seed polymerization is not particularly limited, but dispersion polymerization, emulsion polymerization, soap-free emulsion polymerization (emulsion polymerization without using a surfactant as an emulsifier), seed polymerization, suspension polymerization, etc. can be used. In order to obtain resin microparticles with a substantially uniform particle size by seed polymerization, it is necessary to first use seed particles with a substantially uniform particle size and grow these seed particles substantially uniformly. The seed particles with a substantially uniform particle size as the raw material can be produced by polymerization using a polymerization method such as soap-free emulsion polymerization (emulsion polymerization without using a surfactant), polymerization using a reactive surfactant, and dispersion polymerization of the vinyl monomer. The reactive surfactant is not particularly limited, but it is preferable to use a reactive surfactant having a polyoxyalkylene chain in the molecule. Therefore, as a polymerization method for polymerizing the vinyl monomer to obtain the seed particles, emulsion polymerization, soap-free emulsion polymerization, seed polymerization, and dispersion polymerization are preferable.

[0043] In the polymerization for obtaining the seed particles, a polymerization initiator is used as necessary. The polymerization initiator may be any of the above-mentioned polymerization initiators. The amount of the polymerization initiator used is preferably within a range of 0.1 to 2 parts by mass per 100 parts by mass of the vinyl monomer used to obtain the seed particles. The weight average molecular weight of the obtained seed particles can be adjusted by the amount of the polymerization initiator used.

[0044] In the polymerization for obtaining seed particles, a molecular weight regulator may be used to adjust the weight average molecular weight of the obtained seed particles. As the molecular weight regulator, for example, mercaptans such as n-octyl mercaptan and tert-dodecyl mercaptan, α-methylstyrene dimer, terpenes such as γ-terpinene and dipentene, halogenated hydrocarbons such as chloroform and carbon tetrachloride, etc. can be used. The weight average molecular weight of the obtained seed particles can be adjusted by adjusting the amount of the molecular weight regulator used. The volume average particle size of the seed particles can be adjusted appropriately according to the average particle size of the resin fine particles. It is preferably in the range of 1 to 300 nm, and the average mass is 1 to 100 mg / 100 particles. The shape of the seed particles may be a perfect sphere, an elliptical sphere (egg shape), etc.

[0045] In the seed polymerization, seed particles are first added to an emulsion containing a vinyl monomer and an aqueous medium. The emulsion can be prepared by a known method. For example, an emulsion can be obtained by adding a vinyl monomer to an aqueous medium and dispersing the mixture with a microemulsifier such as a homogenizer, an ultrasonic processor, or a Nanomizer (registered trademark).

[0046] In the seed polymerization, it is preferable to use 0.3 to 15 parts by mass of a surfactant per 100 parts by mass of a vinyl monomer. The above-mentioned surfactants can be used as the surfactant. If the amount of the surfactant used is less than the above range, the polymerization stability may be reduced. If the amount of the surfactant used is more than the above range, it is uneconomical in terms of cost.

[0047] The seed particles may be added to the emulsion as they are, or may be added to the emulsion in a form dispersed in an aqueous medium. After the seed particles are added to the emulsion, the vinyl monomer is absorbed into the seed particles. This absorption can usually be carried out by stirring the emulsion at room temperature (about 25°C) for 1 to 12 hours. In addition, in order to promote the absorption of the vinyl monomer into the seed particles, the emulsion may be heated to about 30 to 50°C.

[0048] The seed particles swell by absorbing the vinyl monomer. The mixing ratio of the vinyl monomer to the seed particles is preferably within the range of 1 to 100 parts by mass, more preferably within the range of 5 to 50 parts by mass, of the vinyl monomer per part by mass of the seed particles. If the mixing ratio of the vinyl monomer is smaller than the above range, the increase in particle size due to polymerization is small, and the production efficiency decreases. On the other hand, if the mixing ratio of the vinyl monomer is larger than the above range, the vinyl monomer is not completely absorbed into the seed particles, and may be independently emulsion-polymerized in the aqueous medium, resulting in the production of resin microparticles with an abnormal particle size that is not intended. The end of the absorption of the vinyl monomer into the seed particles can be determined by confirming the increase in particle size by observation with an optical microscope.

[0049] Next, the vinyl monomer absorbed in the seed particles is polymerized to obtain a resin fine particle dispersion liquid. The resin fine particle dispersion liquid may be obtained by repeating the process of absorbing the vinyl monomer in the seed particles and polymerizing it several times.

[0050] When polymerizing the vinyl monomer absorbed in the seed particles, a polymerization initiator may be added as necessary. After mixing the polymerization initiator with the vinyl monomer, the resulting mixture may be dispersed in an aqueous medium, or the polymerization initiator and the vinyl monomer may be separately dispersed in an aqueous medium and then mixed. It is preferable that the particle size of the droplets of the vinyl monomer present in the resulting emulsion is smaller than the particle size of the seed particles, since the vinyl monomer is efficiently absorbed by the seed particles.

[0051] As the polymerization initiator, the above-mentioned polymerization initiators can be used. The polymerization initiator is preferably used in an amount of 0 to 3 parts by mass relative to 100 parts by mass of the vinyl monomer.

[0052] The polymerization temperature for the seed polymerization can be appropriately selected depending on the type of vinyl monomer and the type of polymerization initiator used as necessary, and is, for example, 25 to 110°C, and preferably 50 to 100°C. The polymerization time for the seed polymerization can be appropriately selected depending on the type of vinyl monomer and the type of polymerization initiator used as necessary, and is, for example, 1 to 12 hours. The seed polymerization may be carried out under an atmosphere of a gas inert to the polymerization (eg, nitrogen). In the seed polymerization, it is preferable to carry out the polymerization at an elevated temperature after the vinyl monomer and the polymerization initiator, which is used if necessary, are completely absorbed into the seed particles.

[0053] In the seed polymerization, in order to improve the dispersion stability of the resin particles, the above-mentioned dispersant may be added to the polymerization reaction system as a dispersion stabilizer. Among these dispersion stabilizers, polyvinyl alcohol and polyvinylpyrrolidone are preferred. The amount of the dispersion stabilizer added is preferably within the range of 1 to 10 parts by mass per 100 parts by mass of the vinyl monomer.

[0054] In order to suppress the generation of emulsion polymerization products (resin fine particles having too small a particle size) in the aqueous medium during the polymerization reaction, a water-soluble polymerization inhibitor such as nitrites such as sodium nitrite, sulfites, hydroquinones, ascorbic acids, water-soluble vitamin B, citric acid, polyphenols, etc. may be added to the aqueous medium. The amount of the polymerization inhibitor added is, for example, within the range of 0.002 to 0.2 parts by mass relative to 100 parts by mass of the vinyl monomer.

[0055] A preferred embodiment of the method for producing resin microparticles of the present invention includes a method for producing resin microparticles, which comprises a first polymerization step in which a monomer emulsion containing a vinyl-based monomer, an aqueous medium, and a reactive surfactant having a polyoxyalkylene chain in its molecule is polymerized using a water-soluble polymerization initiator to obtain seed particles, and a second polymerization step in which the monomer emulsion containing a vinyl-based monomer, an aqueous medium, and a reactive surfactant having a polyoxyalkylene chain in its molecule is absorbed into the seed particles and then polymerized. Another preferred embodiment of the method for producing resin microparticles of the present invention is a method for producing resin microparticles, which includes a first seed particle polymerization step in which a monomer emulsion consisting of a vinyl monomer, ion-exchanged water, and a surfactant such as a reactive surfactant having a polyoxyalkylene chain in its molecule is polymerized using a water-soluble polymerization initiator in the same nitrogen-substituted polymerization vessel, and a second polymerization step in which a monomer emulsion consisting of a vinyl monomer, ion-exchanged water, and a surfactant such as a reactive surfactant having a polyoxyalkylene chain in its molecule is divided or dropped into the seed particles to be absorbed and polymerized.

[0056] <Drying, crushing and classification of resin particles> After the polymerization is completed, the resin microparticles are converted into a cake containing the aqueous medium (water-containing cake) by a method such as suction filtration, centrifugation, or pressure separation, and then optionally washed with water and / or a solvent, dried, and optionally crushed and classified to be isolated as a dry powder. The drying method is not particularly limited, but may be a spray drying method using a spray dryer, a freeze drying method, or a drying method in which the mixture is adhered to a heated rotating drum such as a drum dryer. In the present invention, it is preferable to use a spray drying step in which the resin fine particles obtained in the second polymerization step are spray-dried to obtain an aggregate under conditions of an inlet temperature of 80 to 220° C. and an outlet temperature of 50 to 100° C. The obtained aggregate has good handleability. In the present invention, it is preferable to include a crushing step of crushing the obtained aggregates to disperse the resin fine particles. The resin fine particles dispersed by crushing have good dispersibility in a solvent. In the present invention, it is preferable to include a classification step of classifying the resin fine particles. For example, it is preferable to include at least one of a classification step of classifying the resin fine particles obtained in the second polymerization step and a classification step of classifying the resin fine particles obtained in the crushing step. The classification can be performed by a known means.

[0057] [Applications of resin particles] The resin fine particles of the present invention can be used for various applications, such as additives for light diffusion plates, antiblocking agents for various film membranes, various film modifiers, spacers between minute parts of various electronic devices, pore-forming agents for various battery components, and core particles of conductive fine particles that perform electrical connection. The resin fine particles of the present invention can maintain the intended particle size without swelling even when a heating step is added after dispersing them in a solvent when used. EXAMPLES

[0058] The present invention will be specifically described below with reference to examples and comparative examples. However, the following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples. In the examples and comparative examples, the obtained resin fine particles were evaluated as follows.

[0059] <Gel fraction> The resin particles were collected and precisely weighed to determine the weight (W 1 After measuring the weight of the insoluble matter (W g), the resin particles were immersed in 100 parts by mass of toluene, stirred under reflux at 130° C. for 24 hours, and then cooled. The obtained resin particle dispersion was centrifuged at 18,000 rpm for 30 minutes in a centrifuge, the supernatant was removed, and the resin particles were dried in a vacuum dryer at 60° C. for 12 hours. 2 g) is measured. 2 / W 1 Calculate the gel fraction of the resin particles using the formula: x 100.

[0060] <Solvent resistance index> 1 part by mass of resin fine particles and 50 parts by mass of toluene are placed in a 100 mL plastic container with a lid, and stirred for 3 minutes with a degassing mixer (Thinky Corporation, Rotating / Revolving Mixer (Atmospheric Pressure Type) AR-100 (Product Name: Awatori Rentaro AR-100) (THINKYMIXER (Non Vacuum) AR-100)). The "volume average particle size of the resin fine particle toluene dispersion" is measured using a dynamic light scattering concentrated nanoparticle size distribution measuring device (CORDOUAN Corporation, "VASCO"). The obtained resin fine particle toluene dispersion is then placed in a glass flask with a reflux tube, refluxed at 130°C for 24 hours, and cooled. The "volume average particle size of the resin fine particle toluene dispersion after heating" is measured for the obtained resin fine particle toluene dispersion after heating with the particle size distribution measuring device, and the solvent resistance index is calculated according to the following formula. Solvent resistance index (%) = 100 × (volume average particle diameter of resin particles after heating (nm) - volume average particle diameter of resin particles (nm)) / volume average particle diameter of resin particles (nm)

[0061] <Solvent resistance> Based on the gel fraction and the solvent resistance index, the solvent resistance was evaluated according to the following criteria. ◎: Gel fraction is 93% or more, solvent resistance index is 10 or less ○: Gel fraction is 93% or more, solvent resistance index is more than 10 and less than 25 △: Gel fraction is 93% or more, solvent resistance index is more than 25 and less than 50 ×: Gel fraction is less than 93%, solvent resistance index is more than 50

[0062] <Solvent dispersibility> Based on the results of the above-mentioned solvent resistance index, the dispersibility in a solvent was evaluated according to the following criteria. ○: Solvent resistance index is 50 or less ×: Solvent resistance index exceeds 50

[0063] <Volume average particle size, number average particle size> The volume average particle size and number average particle size of the resin microparticles were measured using a laser diffraction scattering type particle size distribution analyzer (model number "LS230", manufactured by Beckman Coulter, Inc.). Specifically, 0.1 g of the resin microparticle water dispersion (20% solid content) and 20 ml of 2 mass% anionic surfactant solution were placed in a test tube. Then, the mixture was dispersed for 5 minutes using a test tube mixer (manufactured by AS ONE Corporation, "Test Tube Mixer TRIO HM-1N") and an ultrasonic cleaner (manufactured by AS ONE Corporation, "ULTRASONIC CLEANER VS-150") to obtain a dispersion. The volume average particle size and number average particle size of the resin microparticles in the dispersion were measured using a laser diffraction scattering type particle size distribution analyzer while irradiating the dispersion with ultrasonic waves. The measurement conditions for the laser diffraction scattering type particle size distribution analyzer are as follows. medium = water Refractive index of medium = 1.333 Refractive index of solid = Refractive index of resin particles PIDS relative concentration: 40-55% The optical model used in the measurement was adjusted to the refractive index of the resin microparticles produced. When one type of monomer was used to produce the resin microparticles, the refractive index of the homopolymer of that monomer was used as the refractive index of the resin microparticles. When multiple types of monomers were used to produce the resin microparticles, the average value obtained by weighting the refractive index of the homopolymer of each monomer by the amount of each monomer used was used as the refractive index of the resin microparticles. From the measurement results, a volumetric particle size distribution of the resin fine particles was obtained, and the arithmetic mean of the volumetric particle size distribution was taken as the volumetric average particle diameter of the resin fine particles.

[0064] <Residual surfactant amount> The content of the surfactant in the resin fine particles was measured by extracting the resin fine particles with a solvent and using a liquid chromatograph linear ion trap mass spectrometer (LC / MS / MS device). In addition, to measure the surfactant content in the resin microparticles in the examples and comparative examples described below, LC / MS / MS devices used were "UHPLC ACCELA" manufactured by Thermo Fisher Scientific and "Linear Ion TrapLC / MSn LXQ" manufactured by Thermo Fisher Scientific. In addition, the resin microparticles in the examples and comparative examples described below use Aqualon AR-1025 (purity 25%, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and AN-5065 (purity 65%, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) as surfactants, and the surfactant content in the resin microparticles in the examples and comparative examples was measured by the method described below. Approximately 0.01 g of resin particles as a sample was precisely weighed into a centrifuge tube, and 5 mL of methanol as an extraction solution was poured into the tube using a whole pipette to thoroughly mix the resin particles and the extraction solution. After ultrasonic extraction for 15 minutes, the mixture was thoroughly mixed again and centrifuged at 3,500 rpm for 60 minutes. The supernatant thus obtained was filtered through a GL Chromatodisk non-aqueous 0.20 μm filter (GL Sciences) to prepare the test solution.

[0065] The concentrations of the surfactants AR-1025 and AN-5065 in the test solution were measured using an LC / MS / MS device. The surfactant content (μg / g) in the resin microparticles was calculated from the measured surfactant concentration (μg / mL) in the test solution, the weight of the resin microparticles used as the sample (sample weight (g)), and the amount of the extract (extract volume (mL)) using the following calculation formula. The amount of the extract was 5 mL. Surfactant content (μg / g) = Surfactant concentration in test solution (μg / mL) × volume of extraction solution (mL) ÷ sample weight (g) The surfactant concentration was calculated using a calibration curve prepared in advance from the peak area values ​​on the obtained chromatogram using an LC / MS / MS device. The method for creating the calibration curve is as follows. After preparing an intermediate standard solution (methanol solution) of the surfactant at approximately 1000 ppm, it was further diluted stepwise with methanol to prepare standard solutions for creating a calibration curve at 20 ppm, 10 ppm, 5 ppm, and 2.5 ppm. The standard solutions for creating a calibration curve at each concentration were measured under the following conditions, and the peak area values ​​on the chromatogram of the monitor ion m / z = 730 to 830 were obtained. Each concentration and the area value were plotted to obtain an approximation curve (quadratic curve) by the least squares method, and this was used as the calibration curve for quantification. The LC measurement conditions are as follows. Measurement device: UHPLC ACCELA (Thermo Fisher Scientific) Column: Hypersil GOLD C18 1.9 μm (inner diameter 2.1 mm, length 100 mm) (Thermo Fisher Scientific) Column temperature: 40℃ Mobile phase: (A: 10 mM ammonium acetate / B: acetonitrile) Mobile phase conditions: 0min=B concentration 70% 0→0.5min=B concentration 70%→80% 0.5→1.5min=B concentration 80% 1.5→1.6min=B concentration 80%→70% 1.6→4min=B concentration 70% Flow rate: 0.3mL / min Pump temperature: Room temperature (25℃) Injection volume: 2μL Measurement time: 4 min The MS measurement conditions are as follows. Measurement equipment: Linear Ion Trap LC / MSn LXQ (Thermo Fisher Scientific) (Manufacturer) Ionization: (ESI / positive) Sheath Gas: 45arb Auxiliary Gas: 0arb Sweep Gas: 0arb Spray Voltage: 4.0kV Capillary Temp: 350℃ Capillary voltage: 25V Tube lens voltage: 100V MonitoringMass(m / z):AR-1025(SIM=730~830), AN-5065(SIM=730~830)

[0066] <Monodispersity> The monodispersity of the resin particles was calculated by the following formula. Monodispersity=(volume average particle diameter of resin particles) / (number average particle diameter of resin particles)

[0067] <Foaming test> 80 ml of ion-exchanged water was poured into a 200 ml beaker with a stirrer placed at the bottom. 0.8 g of resin particles from each Example and Comparative Example was floated on the water surface and stirred at 300 rpm for 30 minutes. The foamability in the ion-exchanged water was evaluated according to the following criteria. No foaming: After the foaming test, no foaming was observed on the liquid surface. Foaming: After the foaming test, foaming was observed on the liquid surface.

[0068] [Example 1] In a polymerization vessel equipped with a stirrer, a thermometer, and a cooling mechanism, 320 parts by mass of ion-exchanged water and 0.08 parts by mass of reactive surfactant Aqualon AR-1025 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were mixed. In another vessel, 3.8 parts by mass of methyl methacrylate and 0.2 parts by mass of ethylene glycol dimethacrylate were thoroughly mixed and charged into the polymerization vessel, and the mixture was stirred for 10 minutes at 8000 rpm with a TK homomixer (manufactured by Primix Corporation) to obtain a monomer mixture. After purging the polymerization vessel with nitrogen for 5 minutes, the temperature was raised to 75°C, and when the temperature reached 75°C, 10 parts by mass of water-soluble polymerization initiator VA-086 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) dissolved in ion-exchanged water was charged and reacted for 1 hour to obtain a slurry (1). Next, in a container separate from the one used above, 36 parts by mass of ion-exchanged water, 0.3 parts by mass of Aqualon AR-1025 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and 0.03 parts by mass of reactive surfactant Aqualon AN-5065 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were mixed to obtain a surfactant solution. In another container, 22 parts by mass of methyl methacrylate, 6 parts by mass of styrene, and 8 parts by mass of ethylene glycol dimethacrylate were thoroughly mixed and added to the surfactant solution, and the mixture was stirred at 8000 rpm for 10 minutes with a TK homomixer (manufactured by Primix Corporation) to obtain a monomer mixture (2). The monomer mixture (2) was added in eight portions over a period of two hours to the slurry (1) held at 75° C. in the polymerization vessel, and then the mixture was aged for one hour, heated to 100° C. and held for three hours, and then cooled to prepare a slurry containing fine resin particles. The slurry containing resin particles was passed through a 400 Mesh nylon net to classify the resin particles, thereby obtaining a classified resin particle slurry. The classified resin particle slurry was spray-dried using a spray dryer (manufactured by Sakamoto Giken Co., Ltd., machine name: spray dryer, model: atomizer take-up method, model number: TRS-3WK) under the following device conditions to obtain an aggregate of resin particles.

[0069] <Spray dryer equipment conditions> Slurry supply rate containing resin particles: 25mL / min Atomizer rotation speed: 12000 rpm Air volume: 2m 3 / min Inlet temperature (temperature of the slurry inlet containing resin fine particles, which is provided in the spray dryer and through which the slurry containing resin fine particles is sprayed and introduced): 150°C Outlet temperature (the temperature of the powder outlet from which the vinyl resin fine particles are discharged from the spray dryer): 70°C

[0070] The resulting aggregate of resin particles was subjected to a crushing treatment using a current jet mill (manufactured by Nisshin Engineering, product name: CJ-10, crushing air pressure: 0.5 MPa), to obtain the target resin particles. The volume average particle diameter of the obtained resin microparticles was 212 nm, and the coefficient of variation was 19.3%. In addition, when evaluation was performed according to the method for measuring the solvent resistance index, the volume average particle diameter of the toluene dispersion was 215 nm, the volume average particle diameter of the toluene dispersion after heating was 228 nm, and the solvent resistance index was 6. The amount of residual surfactant in the obtained resin microparticles was measured to be 0.1 mass %. The gel fraction of the obtained resin microparticles was measured to be 96%, confirming that the resin microparticles had solvent resistance. In addition, when a foaming test was performed on the obtained resin microparticles, no foaming was observed.

[0071] [Examples 2 to 6, Comparative Examples 1 and 2] Resin microparticles were obtained in the same manner as in Example 1, except that the production conditions for the resin microparticles were as shown in Table 1. Various physical properties of the obtained resin microparticles are also shown in Table 1.

[0072] [Table 1]

[0073] The names of compounds and their abbreviations used in the examples and comparative examples are as follows: AR-1025: Anionic reactive surfactant with polyoxyalkylene chain in the molecule MMA: Methyl methacrylate EGDMA: Ethylene glycol dimethacrylate VA-086: Water-soluble azo polymerization initiator (2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide]) AN-5065: A nonionic reactive surfactant with a polyoxyalkylene chain in the molecule. St: styrene DVB: Divinylbenzene

Claims

1. Resin fine particles obtained by polymerizing a vinyl monomer, The gel fraction is 93% or more and the solvent resistance index is 50 or less, The solvent resistance index is calculated according to the following formula: Solvent resistance index (%)=100×(volume average particle diameter of resin fine particles after heating (nm)−volume average particle diameter of resin fine particles (nm)) / volume average particle diameter of resin fine particles (nm) This is obtained by The volume average particle diameter (nm) of the resin microparticles after heating is the volume average particle diameter (nm) of the resin microparticles after refluxing in toluene at 130° C. for 24 hours, The volume average particle size is 10 to 1000 nm, The amount of the residual surfactant is 0.01 to 1 part by mass per 100 parts by mass of the resin fine particles.

1. A resin microparticle comprising:

2. 2. The resin fine particles according to claim 1, wherein the coefficient of variation of the volume average particle diameter is 25% or less.

3. 3. The resin fine particles according to claim 1, wherein the vinyl monomer comprises a monofunctional (meth)acrylic monomer and / or a monofunctional aromatic vinyl monomer.

4. 4. The resin fine particles according to claim 1, wherein the vinyl monomer comprises a polyfunctional (meth)acrylic monomer and / or a polyfunctional aromatic vinyl monomer.

5. 5. The resin fine particles according to claim 1, which are used as an antiblocking agent for a resin film.

6. 5. The resin fine particles according to claim 1, which are used as an additive for a light diffusion plate.

7. 5. The resin fine particles according to claim 1, which are used as spacers in electronic devices.

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