阅读说明：本技术 二氧化硅被覆粒子及其制造方法 (Silica-coated particle and method for producing same ) 是由 井口良范 于 2020-04-06 设计创作，主要内容包括：提供在树脂和液体物中的分散性良好、具有可与树脂反应的官能团、滑动性良好、具有拒水性的二氧化硅被覆粒子及其制造方法。二氧化硅被覆粒子,是(A)固体粒子的表面被(B)二氧化硅被覆、(B)二氧化硅的表面的羟基的一部分或全部与(C)选自有机烷氧基硅烷、其水解物和有机硅氮烷中的1种以上反应的二氧化硅被覆粒子,相对于(A)固体粒子100质量份,(B)二氧化硅为0.5～100质量份。(Provided are silica-coated particles which have good dispersibility in resins and liquid materials, have functional groups reactive with resins, have good sliding properties, and have water repellency, and a method for producing the same. The silica-coated particle is a silica-coated particle in which (A) the surface of a solid particle is coated with (B) silica, and (B) 1 or more species selected from organoalkoxysilanes, hydrolysates thereof, and organosilazanes are reacted with a part or all of hydroxyl groups on the surface of the silica, and the amount of (B) silica is 0.5 to 100 parts by mass per 100 parts by mass of (A) the solid particle.)

1. The silica-coated particle is a silica-coated particle in which (A) the surface of a solid particle is coated with (B) silica, and a part or all of hydroxyl groups on the surface of the (B) silica is reacted with (C) 1 or more selected from the group consisting of organoalkoxysilane, a hydrolysate thereof, and organosilazane, wherein the amount of (B) silica is 0.5 to 100 parts by mass per 100 parts by mass of the (A) solid particle.

2. The silica-coated particle according to claim 1, wherein the silica (B) is a hydrolysis/condensation product of the tetraalkoxysilane (D).

3. The silica-coated particle according to claim 1 or 2, wherein (a) the solid particle is an inorganic particle.

4. The silica-coated particle according to claim 1 or 2, wherein (a) the solid particle is an organic particle.

5. The silica-coated particle according to any one of claims 1 to 4, wherein the organoalkoxysilane of the component (C) is selected from the group consisting of R¹Si(OR²)₃An organotrialkoxysilane represented by R³ ₂Si(OR⁴)₂Diorganodialkoxysilane represented by the formula (CH)₃)₃SiOR⁵A group in the formula (I), wherein R is¹、R³Is a C1-20 organic radical, R²、R⁴、R⁵The organic silazane is unsubstituted C1-6 alkyl radical and is Composed of (CH)₃)₃SiNHSi(CH₃)₃Hexamethyldisilazane.

6. A method for producing the silica-coated particle according to any one of claims 1 to 5, comprising the following steps (i) to (iv):

(i) a step for preparing a liquid containing (A) solid particles, (E) a basic substance, (F) at least one selected from the group consisting of cationic surfactants and cationic water-soluble polymer compounds, and (G) water;

(ii) (ii) adding (D) tetraalkoxysilane to the liquid obtained in step (i) to hydrolyze and condense the tetraalkoxysilane, thereby coating the surface of the solid particles (a) with silica (B) to obtain a dispersion of silica-coated particles;

(iii) (iii) adding (E) an alkaline substance and, if necessary, (F) at least one selected from the group consisting of a cationic surfactant and a cationic water-soluble polymer compound to the dispersion of silica-coated particles obtained in step (ii) to obtain an additionally added dispersion;

(iv) (iv) adding (C) 1 or more species selected from the group consisting of organoalkoxysilane, a hydrolysate thereof, and organosilazane to the additionally added dispersion obtained in step (iii), and reacting (B) a part or all of the hydroxyl groups on the surface of the silica with (C) 1 or more species selected from the group consisting of organoalkoxysilane, a hydrolysate thereof, and organosilazane.

Technical Field

The present invention relates to silica particles having a solid particle surface coated with silica and a method for producing the same.

Background

Metal powder, inorganic powder such as titanium oxide, zinc oxide, mica, talc, and barium sulfate, and organic resin powder are generally used for resins, paints, and cosmetic materials. The surface of these particles may be coated with silica for the purpose of non-aggregation, fluidity, dispersibility, photocatalytic activity suppression, alkali resistance and acidity resistance, improvement in touch, improvement in light diffusion, and the like.

As a method for coating the surface of the solid particles with silica, there is a method in which the solid particles and silica particles are mixed in a dry manner by using an apparatus such as a ball mill or a mixer (hybridizer), and further an impact force is applied to the mixture to coat the surface (patent document 1: japanese patent laid-open No. 6-32725); a method of removing water from a liquid comprising an aqueous dispersion of solid particles and a silica sol to coat the particles (patent document 2: Japanese patent application laid-open No. 4-348143). Further, there are a method of depositing a silica component on the surface of solid particles in a silicic acid solution in which solid particles are dispersed (patent document 3: Japanese patent application laid-open No. 2002-87817), and a method of hydrolyzing tetraalkoxysilane in an organic solvent in which solid particles are dispersed to form silica on the surface of solid particles (patent document 4: Japanese patent application laid-open No. 11-193354).

However, these silica-coated particles are not sufficiently dispersible in a particulate resin or a liquid material. In addition, the silanol groups on the surface of silica may increase the aggregation property as compared with particles not coated with silica. Further, since the adhesion to the resin is poor in the blending into the resin, there is a problem that the particles fall off from the cut surface when the resin is cut.

In cosmetics, the feeling of slipperiness (slipping) is insufficient. Silica-coated particles are hydrophilic, and water repellency is sometimes required in cosmetics.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 6-32725

Patent document 2: japanese laid-open patent publication No. 4-348143

Patent document 3: japanese patent laid-open publication No. 2002-87817

Patent document 4: japanese laid-open patent publication No. 11-193354

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide silica-coated particles which have good dispersibility in resins and liquid materials, have functional groups reactive with resins, have good sliding properties, and have water repellency, and a method for producing the same.

Means for solving the problems

The present inventors have intensively studied to achieve the above object and, as a result, have found that: in the silica coating, the above problems can be solved by reacting a part or all of the hydroxyl groups on the silica surface with (C) 1 or more species selected from the group consisting of organoalkoxysilane, a hydrolysate thereof, and organosilazane, and the present invention has been completed.

Accordingly, the present invention provides the following silica-coated particles and a method for producing the same.

[1] The silica-coated particle is a silica-coated particle in which (A) the surface of a solid particle is coated with (B) silica, and a part or all of hydroxyl groups on the surface of the (B) silica is reacted with (C) 1 or more selected from the group consisting of organoalkoxysilane, a hydrolysate thereof, and organosilazane, wherein the amount of (B) silica is 0.5 to 100 parts by mass per 100 parts by mass of the (A) solid particle.

[2] [1] the silica-coated particle according to claim 1, wherein the silica (B) is a hydrolysis/condensation product of the tetraalkoxysilane (D).

[3] The silica-coated particle according to [1] or [2], wherein the solid particles (A) are inorganic particles.

[4] The silica-coated particle according to [1] or [2], wherein the solid particles (A) are organic particles.

[5].[1]～[4]The silica-coated particle according to any one of the above items, wherein the organoalkoxysilane as the component (C) is selected from the group consisting of R¹Si(OR²)₃An organotrialkoxysilane represented by R³ ₂Si(OR⁴)₂Diorganodialkoxysilane represented by the formula (CH)₃)₃SiOR⁵A group in the formula (I), wherein R is¹、R³Is a C1-20 organic radical, R²、R⁴、R⁵The organic silazane is unsubstituted C1-6 alkyl radical and is Composed of (CH)₃)₃SiNHSi(CH₃)₃Hexamethyldisilazane.

[6] A method for producing the silica-coated particle according to any one of [1] to [5], which comprises the following steps (i) to (iv):

(i) a step for preparing a liquid containing (A) solid particles, (E) a basic substance, (F) at least one selected from the group consisting of cationic surfactants and cationic water-soluble polymer compounds, and (G) water;

(ii) (ii) adding (D) tetraalkoxysilane to the liquid obtained in step (i) to hydrolyze and condense the tetraalkoxysilane, thereby coating the surface of the solid particles (a) with silica (B) to obtain a dispersion of silica-coated particles;

(iii) (iii) adding (E) an alkaline substance and, if necessary, (F) at least one selected from the group consisting of a cationic surfactant and a cationic water-soluble polymer compound to the dispersion of silica-coated particles obtained in step (ii) to obtain an additionally added dispersion;

(iv) (iv) adding (C) 1 or more species selected from the group consisting of organoalkoxysilane, a hydrolysate thereof, and organosilazane to the additionally added dispersion obtained in step (iii), and reacting (B) a part or all of the hydroxyl groups on the surface of the silica with (C) 1 or more species selected from the group consisting of organoalkoxysilane, a hydrolysate thereof, and organosilazane.

Effects of the invention

According to the production method of the present invention, silica-coated particles having good dispersibility in resins and liquid materials, having functional groups reactive with resins, good sliding properties, and water repellency, and a production method thereof can be provided.

Detailed Description

The present invention will be described in detail below.

[ (A) component ]

(A) The solid particles are particles that serve as the core of the silica-coated particles of the present invention, and 1 type of the solid particles can be used alone or 2 or more types can be used in combination as appropriate. The solid particles may be inorganic particles or organic particles, and may have any geometric form such as spherical, polyhedral, spindle, needle-like, plate-like, or nonporous or porous forms. The volume average particle diameter (MV value) is preferably 0.01 to 100 μm, more preferably 0.1 to 50 μm. The volume average particle diameter is measured by appropriately selecting from a microscopic method, a light scattering method, a laser diffraction method, a liquid phase sedimentation method, a resistance method, and the like, depending on the particle diameter. For example, in the case of 0.01 μm or more and less than 1 μm, the measurement can be performed by a light scattering method, and in the case of 1 μm or more and 100 μm or less, the measurement can be performed by a resistance method.

Examples of the inorganic particles include particles of iron oxide, nickel oxide, chromium oxide, zinc oxide, titanium oxide, zirconium oxide, zinc oxide, cerium oxide, magnesium oxide, barium sulfate, calcium sulfate, magnesium sulfate, calcium carbonate, magnesium carbonate, talc, mica, kaolin, sericite, aluminum silicate, magnesium silicate, aluminum magnesium silicate, calcium silicate, barium silicate, strontium silicate, metal tungstate, hydroxyapatite, vermiculite, sepiolite, bentonite, montmorillonite, hectorite, zeolite, ceramic, calcium hydrogen phosphate, aluminum oxide, aluminum hydroxide, boron nitride, glass, and the like.

Examples of the organic particles include particles of polymethyl methacrylate such as polyamide, polyacrylic acid-acrylate, polyester, polyethylene, polypropylene, polystyrene, styrene-acrylic acid copolymer, divinylbenzene-styrene copolymer, polyurethane, vinyl resin, urea resin, melamine resin, benzoguanamine, polymethylbenzoguanamine, tetrafluoroethylene, and polymethyl methacrylate, cellulose, silk, nylon, phenol resin, epoxy resin, polycarbonate, polybutadiene rubber, acrylic rubber, polyurethane rubber, silicone rubber, and fluororubber.

[ (B) component ]

(B) The silica coats the surface of the solid particles (a) serving as the core. The silicon dioxide is made of SiO₂The structure of the unit is not particularly limited in the production method, and is preferably obtained by a hydrolysis-condensation reaction of (D) tetraalkoxysilane as in the production method described later. The tetraalkoxysilane (D) is composed of Si (OR)⁶)₄And (4) showing. In the formula⁶Is an alkyl group. The alkyl group is preferably an alkyl group having 1 to 6 carbon atoms. Specifically, methyl, ethyl, propyl, butyl, pentyl, hexyl and the like are mentioned, and methyl and ethyl are more preferable from the viewpoint of reactivity. Namely, tetramethoxysilane and tetraethoxysilane are more preferable, and tetramethoxysilane is further preferable.

[ (C) ingredient ]

(C) The component (A) is at least 1 selected from the group consisting of organoalkoxysilane, hydrolysate thereof and organosilazane, and 1 can be used alone or 2 or more can be used in combination as appropriate.

The organoalkoxysilane is not particularly limited, and for example, the organoalkoxysilane may be represented by R¹Si(OR²)₃An organotrialkoxysilane represented by R³ ₂Si(OR⁴)₂Diorganodialkoxysilane represented by the formula (CH)₃)₃SiOR⁵Trimethylalkoxysilane (in the formula, R)¹、R³Is a C1-20 organic radical, R²、R⁴、R⁵Is an unsubstituted C1-6 alkyl group. ) Etc., and 1 kind can be used alone or 2 or more kinds can be used in combination as appropriate.

R¹、R³Is a C1-20 organic group, preferably an unsubstituted or substituted C1-10 organic group. Examples thereof include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, and eicosyl; cycloalkyl groups such as cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl(ii) a Aryl groups such as phenyl, tolyl, and naphthyl; aralkyl groups such as benzyl, phenethyl, and β -phenylpropyl; alkenyl groups such as vinyl and allyl; and hydrocarbon groups in which some or all of the hydrogen atoms bonded to carbon atoms of these groups are substituted with atoms such as halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, iodine atoms) and/or substituents such as acryloyloxy groups, methacryloyloxy groups, epoxy groups, glycidyloxy groups, amino groups, mercapto groups, carboxyl groups, alkylenediol groups, polyoxyalkylene groups, aminoalcohol groups, phosphorylcholine groups, etc.

R²、R⁴、R⁵The hydrocarbon group is an unsubstituted C1-6 hydrocarbon group, and specifically includes methyl, ethyl, propyl, butyl, pentyl and hexyl groups, and preferably a methyl group from the viewpoint of reactivity.

The hydrolyzate may be represented by the formula R¹Si(OH)₃、R³ ₂Si(OH)₂、(CH₃)₃SiOH, etc.

The organosilicon nitrogen alkane is not particularly limited, but is preferably represented by (CH)₃)₃SiNHSi(CH₃)₃Hexamethyldisilazane.

[ silica-coated particles ]

The silica-coated particle of the present invention is a silica-coated particle in which the surface of (a) a solid particle serving as a core is coated with (B) silica, and (B) 1 or more species selected from organoalkoxysilanes, hydrolysates thereof, and organosilazanes are reacted with a part or all of hydroxyl groups on the surface of the silica.

The amount of (B) silica is 0.5 to 100 parts by mass, preferably 1 to 50 parts by mass, and more preferably 3 to 20 parts by mass, per 100 parts by mass of (A) solid particles. When the amount of (B) silica is less than 0.5 part by mass, the properties such as non-aggregability, fluidity, dispersibility, photocatalytic activity suppression, alkali/acid resistance, improvement in touch, and light diffusibility are not exhibited, and when it exceeds 100 parts by mass, the properties of (A) solid particles are hardly exhibited.

The shape of the coated silica may be a film or a granular form. The coating condition of the silica may be a part or the whole of the surface of the solid particles (a), and is preferably a condition in which the entire particle surface of the solid particles (a) is coated substantially without any gaps. The state of coating can be confirmed, for example, by an electron microscope.

The silica-coated particles may have any geometric form such as a spherical form, a polyhedral form, a spindle form, a needle form, a plate form, and the like, and may be nonporous or porous. The volume average particle diameter is preferably 0.01 to 100 μm, more preferably 0.1 to 50 μm.

The silica-coated particle of the present invention is a silica-coated particle in which (B) a part or all of hydroxyl groups on the surface of silica are reacted with (C) 1 or more selected from organoalkoxysilane, a hydrolysate thereof, and organosilazane. The condensation reaction of the component (C) with not all the hydroxyl groups on the surface of the silica (B) may be carried out, and the hydroxyl groups may remain.

The amount of the component (C) may be an amount capable of reacting with hydroxyl groups on the surface of the coated silica (B), and the amount required may be varied depending on the specific surface area, dispersibility, water repellency and other properties of the particles, and the required degree of the reactive functional groups, and is preferably 0.01 to 20 parts by mass, more preferably 0.05 to 10 parts by mass, based on 100 parts by mass of the total of the solid particles (a) and the silica (B).

[ Process for producing silica-coated particles ]

The method for producing the silica-coated particles of the present invention includes, for example, a production method including the following steps.

(i) A step for preparing a liquid containing (A) solid particles, (E) a basic substance, (F) at least one selected from the group consisting of cationic surfactants and cationic water-soluble polymer compounds, and (G) water;

(ii) (ii) adding (D) tetraalkoxysilane to the liquid obtained in step (i) to hydrolyze and condense the tetraalkoxysilane, thereby coating the surface of the solid particles (a) with silica (B) to obtain a dispersion of silica-coated particles;

(iii) (iii) adding (E) an alkaline substance and, if necessary, (F) at least one selected from the group consisting of a cationic surfactant and a cationic water-soluble polymer compound to the dispersion of silica-coated particles obtained in step (ii) to obtain an additionally added dispersion;

(iv) (iv) adding (C) 1 or more species selected from the group consisting of organoalkoxysilane, a hydrolysate thereof, and organosilazane to the additionally added dispersion obtained in step (iii), and reacting (B) a part or all of the hydroxyl groups on the surface of the silica with (C) 1 or more species selected from the group consisting of organoalkoxysilane, a hydrolysate thereof, and organosilazane.

The step (i) is a step of preparing a liquid containing (a) solid particles, (E) a basic substance, (F) at least one selected from a cationic surfactant and a cationic water-soluble polymer compound, and (G) water. The liquid containing the components (a), (E), (F) and (G) in the step (i) is prepared by mixing these components. For the (a) solid particles, a product prepared as an aqueous dispersion of the (a) component can be used. (E) The alkaline substance may be added after mixing the components (A), (F) and (G).

[ (E) ingredient ]

(E) The basic substance functions as a catalyst for the hydrolysis and condensation reaction of the tetraalkoxysilane (D) in the step (ii). The alkaline substance can be used alone 1, or more than 2.

The basic substance is not particularly limited, and for example, an alkali metal hydroxide such as potassium hydroxide, sodium hydroxide, or lithium hydroxide; alkaline earth metal hydroxides such as calcium hydroxide and barium hydroxide; alkali metal carbonates such as potassium carbonate and sodium carbonate; ammonia; tetraalkylammonium hydroxides such as tetramethylammonium hydroxide and tetraethylammonium hydroxide; amines such as monomethylamine, monoethylamine, monopropylamine, monobutylamine, monopentylamine, dimethylamine, diethylamine, trimethylamine, triethanolamine and ethylenediamine. Among these, ammonia is preferred from the viewpoint that it is volatilized and can be easily removed from the powder of the obtained silica-coated particles. As ammonia, a commercially available aqueous ammonia solution can be used.

The amount of the component (E) to be added is preferably an amount such that the pH of the liquid containing the components (A), (E), (F) and (G) in the step (i) at 25 ℃ is 9.0 to 12.0, more preferably 9.5 to 11.0. When a basic substance is added in an amount such that the pH is 9.0 to 12.0, (D) the hydrolysis/condensation reaction of tetraalkoxysilane proceeds and (A) the coating of silica on the surface of the solid particles becomes more sufficient.

[ (F) ingredient ]

(F) 1 or more species selected from the group consisting of cationic surfactants and cationic water-soluble polymer compounds can be used alone or in combination of 2 or more species. (F) The component (A) has the effect of promoting the condensation reaction of the hydrolyzed tetraalkoxysilane to produce silica. Further, the produced silica may have an action of adsorbing on the surface of the solid particles (a). In addition, the particles may also function as a dispersant for the solid particles (a).

Examples of the cationic surfactant include alkyltrimethylammonium salts, dialkyldimethylammonium salts, polyoxyethylene alkyldimethylammonium salts, polyoxyethylene alkylmethylammonium salts, polyoxyethylene alkylammonium salts, alkylbenzyldimethylammonium salts, alkylpyridinium salts, monoalkylamine salts, and monoalkylamide amine salts.

Examples of the cationic water-soluble polymer compound include polymers of dimethyldiallylammonium chloride, polymers of vinylimidazoline, polymers of methylvinylimidazolium chloride, polymers of ethyltrimethylammonium chloride acrylate, ethyltrimethylammonium chloride methacrylate, acrylamidopropyltrimethylammonium chloride, methacrylamidopropyltrimethylammonium chloride, epichlorohydrin/dimethylamine polymers, polymers of ethyleneimine, quaternary products of ethyleneimine polymers, polymers of allylamine hydrochloride, polylysine, cationic starch, cationized cellulose, chitosan, and derivatives thereof obtained by copolymerizing monomers having nonionic or anionic groups among these.

The amount of the component (F) to be added is preferably 0.01 to 2 parts by mass, more preferably 0.02 to 1 part by mass, based on 100 parts by mass of water in the liquid containing the components (A), (E), (F) and (G). If the amount is less than 0.01 part by mass, there is a possibility that silica is not coated on the surface of the solid particles of (A); when the amount exceeds 2 parts by mass, silica not coated on the surface of the solid particles (a) may be formed.

[ (G) ingredient ]

(G) The component (c) is water, and purified water or the like can be suitably used. The amount of water is preferably 1 to 50% by mass, more preferably 5 to 30% by mass, of the solid particles (A) in the liquid containing the components (A), (E), (F) and (G).

The dispersant for the solid particles (a) may be a nonionic surfactant, an amphoteric surfactant, or a nonionic water-soluble polymer compound. These can be used alone in 1 or more than 2 kinds of appropriate combination. Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyethylene glycol fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyglycerol fatty acid esters, propylene glycol fatty acid esters, polyoxyethylene castor oils, polyoxyethylene hardened castor oil fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene fatty acid amides, polyoxyethylene-modified organopolysiloxanes, and polyoxyethylene polyoxypropylene-modified organopolysiloxanes. Examples of the zwitterionic surfactant include alkyldimethylamine oxide, alkyldimethylcarboxybetaine, alkylamidopropyldimethylcarboxybetaine, alkylhydroxysulfobetaine, and alkylcarboxymethylhydroxyethylimidazolium betaine. Examples of the nonionic water-soluble polymer compound include guar gum, starch, xanthan gum, methyl cellulose, ethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol, polyvinyl methyl ether, polyvinyl pyrrolidone, polyethylene glycol, a polyoxyethylene-polyoxypropylene copolymer polymer compound, polyethyl acrylate, and polyacrylamide.

The step (ii) is a step of adding (D) tetraalkoxysilane to the liquid obtained in the step (i) to hydrolyze and condense the tetraalkoxysilane, thereby coating the surface of the solid particles (a) with silica (B) to obtain a dispersion of silica-coated particles. (D) The condensate of the tetraalkoxysilane is (B) silica, and the produced (B) silica adheres to the surface of the (a) solid particles, whereby the surface of the (a) solid particles is coated with the (B) silica. Tetraalkoxysilane (D) As described above, a product of partial or complete hydrolysis of alkoxy groups can be used. Further, a partially condensed product may be used.

The amount of the component (D) is preferably in the range of 0.5 to 100 parts by mass, more preferably 1 to 50 parts by mass, relative to 100 parts by mass of the solid particles (a).

(D) The addition of the components is carried out under stirring using a conventional stirrer such as a propeller blade, a flat blade, or an anchor-type stirring blade. (D) The ingredients may be added at once, preferably over a period of time. The dropping time is preferably in the range of 1 minute to 6 hours, more preferably 10 minutes to 3 hours. The temperature at this time is preferably 0 to 60 ℃, more preferably 0 to 40 ℃. The surface of the solid particles (A) can be coated with the silica (B) at a temperature of 0 to 60 ℃. After the addition of the component (D), the stirring was continued until the hydrolysis/condensation reaction of the component (D) was completed. The confirmation of the obtained coated particles can be accomplished by observation of the particle surface with an electron microscope, elemental analysis of the particle surface, a test of hydrophilicity, or the like.

The step (iii) is a step of adding (E) a basic substance and, if necessary, 1 or more selected from the group consisting of a cationic surfactant and a cationic water-soluble polymer compound to the dispersion of the silica-coated particles obtained in the step (ii) to obtain an additionally added dispersion.

(E) Component (iii) functions as a reaction catalyst in step (iv) for reacting hydroxyl groups on the surface of silica with 1 or more kinds selected from organoalkoxysilane, a hydrolysate thereof, and organosilazane. Since the hydrolysis/condensation reaction does not proceed sufficiently in the amount added in step (i), the addition is performed in step (iii). Further, 1 or more species selected from the group consisting of cationic surfactants and cationic water-soluble polymer compounds are additionally added as required.

The amount of the component (E) added in the step (iii) is preferably 5 times or more, more preferably 10 to 300 times the amount of the component (E) added in the step (i). When the component (F) is added, the amount of the component (F) added is preferably 0.01 to 2 parts by mass, and more preferably 0.02 to 1 part by mass, based on 100 parts by mass of water in the liquid containing the components (a), (E), (F), and (G).

The step (iv) is a step of adding (C) 1 or more species selected from the group consisting of organoalkoxysilane, a hydrolysate thereof, and organosilazane to the dispersion additionally added in the step (iii) to react (B) a part or all of the hydroxyl groups on the surface of silica with (C) 1 or more species selected from the group consisting of organoalkoxysilane, a hydrolysate thereof, and organosilazane. (C) The ingredients are as described above.

(C) The amount of the component (c) added may be an amount that can react with the hydroxyl groups on the surface of the coated silica (B), and may be an amount that can react with a part of the hydroxyl groups on the surface of the coated silica (B) as long as the desired characteristics are obtained.

(C) The addition of the components is carried out under stirring using a conventional stirrer such as a propeller blade, a flat blade, or an anchor-type stirring blade.

(C) The ingredients may be added over a period of time or may be added at once. The temperature at this time is preferably 0 to 60 ℃, more preferably 0 to 40 ℃. Stirring was continued after the addition of component (C) until the reaction of component (C) was completed. In order to complete the condensation reaction, the stirring may be carried out under heating at about 40 to 100 ℃.

After the reaction of component (C), water is removed from the resulting aqueous dispersion of particles of the present invention. The removal of water can be carried out, for example, by heating the aqueous dispersion under normal pressure or reduced pressure, and specifically, a method of removing water by leaving the dispersion under heating; a method of removing water while stirring and flowing the dispersion under heating; a method of spraying and dispersing the dispersion in a hot air stream as in a spray dryer; a method of flowing a heat medium, and the like. As a pretreatment for this operation, the dispersion may be concentrated by a method such as dehydration by heating, filtration, centrifugation, or decantation, and the dispersion may be washed with water or alcohol as necessary.

When the product obtained by removing water from the aqueous dispersion is aggregated, it is crushed by a pulverizer such as a jet mill, a ball mill, or a hammer mill.

Whether or not the component (C) is condensed with the hydroxyl groups on the surface of the silica-coated solid particles is judged by a water repellency test, for example, a state of floating on water or alcohol water when the component (C) is put into water or alcohol water, when the organic group of the component (C) is hydrophobic. When the organic group of component (C) is hydrophilic, it can be judged by an experiment or the like of a change in hydrophilicity.

The obtained silica-coated particles can be used for resins, paints, cosmetic materials, and the like. In particular, since they have the characteristics of non-aggregability and dispersibility, they are suitable for particles having high aggregability and poor dispersibility.

Examples

The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the examples. In the composition, "%" is not particularly specified, and "part(s)" is mass%, "part(s)" is (are) part(s) by mass.

[ example 1]

120g of titanium oxide particles (trade name: タイペーク PFC-407, manufactured by Shigaku industries Co., Ltd.), 1.3g of a 40% aqueous solution of a dimethyldiallylammonium chloride polymer (trade name: ME polymer H40W, manufactured by Toho chemical industries Co., Ltd., average molecular weight: 24 ten thousand) and 1040g of water were charged in a 2-liter glass beaker, and stirred at 6000rpm for 10 minutes using a homomixer. Next, the mixture was passed through a homogenizer under a pressure of 100MPa to obtain an aqueous dispersion of titanium oxide particles.

The volume average particle diameter of the titanium oxide particle-containing aqueous dispersion was measured to be 340nm by using a dynamic light scattering particle size distribution measuring apparatus (manufactured by N4Plus, ベックマン & コールター Co.).

968g of the obtained aqueous dispersion of titanium oxide particles was transferred to a 2-liter glass flask equipped with a stirrer using an anchor-type stirring blade, and 1.6g of 2.9% aqueous ammonia was added thereto. The pH of the liquid at this time was 10.5. After the temperature was adjusted to 5 to 10 ℃, 14.5g of tetramethoxysilane (the amount of silica after hydrolysis/condensation reaction was 5.7 parts per 100 parts of titanium oxide particles) was added dropwise over 15 minutes, and the liquid temperature therebetween was kept at 5 to 10 ℃, followed by stirring for 1 hour to obtain an aqueous dispersion of silica-coated titanium oxide particles.

Next, 10g of 29% aqueous ammonia was added, and 6.0g of trimethylsilanol was added. The liquid temperature is kept at 5-10 ℃, stirred for 30 minutes, heated to 70-75 ℃, and stirred for 1 hour under the state of keeping the temperature.

The resulting liquid was dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirrer using an anchor-type stirring blade, 1000g of 50% methanol water was added thereto, and the mixture was stirred for 30 minutes and then dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade, 1000g of water was added, and after stirring for 30 minutes, the mixture was dehydrated using a pressure filter, and the same operation was repeated again. The obtained dehydrated product was dried at a temperature of 105 ℃ in a hot air flow dryer, and the dried product was crushed with a jet mill to obtain particles.

The volume average particle diameter of the obtained particles was measured by a dynamic light scattering particle size distribution measuring apparatus (manufactured by N4Plus, ベックマン & コールター Co., Ltd.) to 350 nm.

The obtained particles were put into water and stirred, and as a result, the particles were not dispersed in water but floated on water. Further, 40 vol% methanol water was poured and stirred, and as a result, the particles were not dispersed in the methanol water but floated on the methanol water. From the results, it was found that the trimethylsilanol reacted with the hydroxyl group on the surface of the silica-coated titanium oxide particle by condensation.

[ example 2]

An aqueous dispersion of titanium oxide particles was obtained in the same manner as in example 1. 968g of the obtained aqueous dispersion of titanium oxide particles was transferred to a 2-liter glass flask equipped with a stirrer using an anchor-type stirring blade, and 1.6g of 2.9% aqueous ammonia was added thereto. The pH of the liquid at this time was 10.5. After the temperature was adjusted to 5 to 10 ℃, 14.5g of tetramethoxysilane (the amount of silica after hydrolysis/condensation reaction was 5.7 parts per 100 parts of titanium oxide particles) was added dropwise over 15 minutes, and the liquid temperature therebetween was kept at 5 to 10 ℃, followed by stirring for 1 hour to obtain an aqueous dispersion of silica-coated titanium oxide particles.

Next, 10g of 29% aqueous ammonia was added, and 5.4g of hexamethyldisilazane was added. The liquid temperature is kept at 5-10 ℃, stirred for 30 minutes, heated to 70-75 ℃, and stirred for 1 hour under the state of keeping the temperature.

The resulting liquid was dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirrer using an anchor-type stirring blade, 1000g of 50% methanol water was added thereto, and the mixture was stirred for 30 minutes and then dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade, 1000g of water was added, and after stirring for 30 minutes, the mixture was dehydrated using a pressure filter, and the same operation was repeated again. The obtained dehydrated product was dried at a temperature of 105 ℃ in a hot air flow dryer, and the dried product was crushed with a jet mill to obtain particles.

The volume average particle diameter of the obtained particles was measured by a dynamic light scattering particle size distribution measuring apparatus (manufactured by N4Plus, ベックマン & コールター Co., Ltd.) to 350 nm. The obtained particles were put into water and stirred, and as a result, the particles were not dispersed in water but floated on water. Further, 40 vol% methanol water was poured and stirred, and as a result, the particles were not dispersed in the methanol water but floated on the methanol water. From the results, it was found that hexamethyldisilazane reacts with hydroxyl groups on the surfaces of the silica-coated titanium oxide particles to form trimethylsilylated particles.

Comparative example 1

An aqueous dispersion of titanium oxide particles was obtained in the same manner as in example 1. 968g of the obtained aqueous dispersion of titanium oxide particles was transferred to a 2-liter glass flask equipped with a stirrer using an anchor-type stirring blade, and 1.6g of 2.9% aqueous ammonia was added thereto. The pH of the liquid at this time was 10.5. After the temperature was adjusted to 5 to 10 ℃, 14.5g of tetramethoxysilane (the amount of silica after hydrolysis/condensation reaction was 5.7 parts per 100 parts of titanium oxide particles) was added dropwise over 15 minutes, and the liquid temperature therebetween was kept at 5 to 10 ℃, and further stirring was performed for 1 hour. Then, the mixture was heated to 70 to 75 ℃ and stirred for 1 hour while maintaining the temperature, thereby obtaining an aqueous dispersion of silica-coated titanium oxide particles.

The resulting liquid was dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirrer using an anchor-type stirring blade, 1000g of 50% methanol water was added thereto, and the mixture was stirred for 30 minutes and then dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade, 1000g of water was added, and after stirring for 30 minutes, the mixture was dehydrated using a pressure filter, and the same operation was repeated again. The obtained dehydrated product was dried at a temperature of 105 ℃ in a hot air flow dryer, and the dried product was crushed with a jet mill to obtain particles.

The volume average particle diameter of the obtained particles was measured by using a resistance-method particle size distribution measuring apparatus (manufactured by マルチサイザー 3, ベックマン & コールター Co., Ltd.) to be 3.5. mu.m. From the results, it was found that the particles were disintegrated by a pulverizer, but the aggregation was too strong and the particles were not primary particles. The obtained particles were put into water and stirred, and as a result, the particles were dispersed in water and were hydrophilic.

[ example 3]

150g of spherical polymethyl methacrylate particles (trade name: アートパール J-7P, manufactured by Kokusho Kogyo Co., Ltd.) having a volume average particle diameter of 6 μm, 1.5g of 2.9% aqueous ammonia, and 5g of a 30% aqueous solution of dodecyltrimethylammonium chloride (trade name: カチオン BB, manufactured by Nizhi Kogyo Co., Ltd.) were placed in a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade. The pH of the liquid at this time was 10.1. After the temperature was adjusted to 5 to 10 ℃, 24.3g of tetramethoxysilane (6.4 parts of silica after hydrolysis/condensation reaction per 100 parts of the spherical polymethylmethacrylate particles) was added dropwise over 20 minutes, and the mixture was stirred for 1 hour while maintaining the liquid temperature at 5 to 10 ℃ to obtain an aqueous dispersion of silica-coated polymethylmethacrylate particles.

Next, 3g of a 30% hexadecyltrimethylammonium chloride aqueous solution (trade name: コータミン 60W, manufactured by Kao corporation) and 10g of 29% aqueous ammonia were added, and then 2.1g of phenyltrimethoxysilane was added. The liquid temperature is kept at 5-10 ℃, stirred for 30 minutes, heated to 70-75 ℃, and stirred for 1 hour under the state of keeping the temperature.

The resulting liquid was dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirrer using an anchor-type stirring blade, 1000g of 50% methanol water was added thereto, and the mixture was stirred for 30 minutes and then dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade, 1000g of water was added, and after stirring for 30 minutes, the mixture was dehydrated using a pressure filter, and the same operation was repeated again. The obtained dehydrated product was dried at a temperature of 105 ℃ in a hot air flow dryer, and the dried product was crushed with a jet mill to obtain particles.

The volume average particle diameter of the obtained particles was measured to be 6 μm using a resistance-method particle size distribution measuring apparatus (manufactured by strain マルチサイザー 3, ベックマン, コールター).

The obtained particles were put into water and stirred, and as a result, the particles were not dispersed in water but floated on water. Further, 10 vol% of methanol water was poured and stirred, and as a result, the particles were not dispersed in methanol water but floated on methanol water. From these results, it was found that phenyltrimethoxysilane reacted with hydroxyl groups on the surface of the silica-coated polymethyl methacrylate particles by hydrolysis and condensation.

Comparative example 2

150g of spherical polymethyl methacrylate particles (trade name: アートパール J-7P, manufactured by Kokusho Kogyo Co., Ltd.) having a volume average particle diameter of 6 μm, 1.5g of 2.9% aqueous ammonia, and 5g of a 30% aqueous solution of dodecyltrimethylammonium chloride (trade name: カチオン BB, manufactured by Nizhi Kogyo Co., Ltd.) were placed in a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade. The pH of the liquid at this time was 10.1. After the temperature was adjusted to 5 to 10 ℃, 24.3g of tetramethoxysilane (6.4 parts of silica after hydrolysis/condensation reaction per 100 parts of polymethyl methacrylate spherical particles) was added dropwise over 20 minutes, and the liquid temperature therebetween was kept at 5 to 10 ℃, and further stirred for 1 hour. Then, the mixture was heated to 70 to 75 ℃ and stirred for 1 hour while maintaining the temperature, thereby obtaining an aqueous dispersion of silica-coated polymethyl methacrylate particles.

The resulting liquid was dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirrer using an anchor-type stirring blade, 1000g of 50% methanol water was added thereto, and the mixture was stirred for 30 minutes and then dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade, 1000g of water was added, and after stirring for 30 minutes, the mixture was dehydrated using a pressure filter, and the same operation was repeated again. The obtained dehydrated product was dried at a temperature of 105 ℃ in a hot air flow dryer, and the dried product was crushed with a jet mill to obtain particles.

The volume average particle diameter of the obtained particles was measured to be 6 μm using a resistance-method particle size distribution measuring apparatus (manufactured by strain マルチサイザー 3, ベックマン, コールター). The obtained particles were put into water and stirred, and as a result, the particles were dispersed in water and were hydrophilic.

Comparative example 3

150g of spherical polymethyl methacrylate particles (trade name: アートパール J-7P, manufactured by Kokusho Kogyo Co., Ltd.) having a volume average particle diameter of 6 μm, 1.5g of 2.9% aqueous ammonia, and 5g of a 30% aqueous solution of dodecyltrimethylammonium chloride (trade name: カチオン BB, manufactured by Nizhi Kogyo Co., Ltd.) were placed in a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade. The pH of the liquid at this time was 10.1. After the temperature was adjusted to 5 to 10 ℃, 24.3g of tetramethoxysilane (6.4 parts of silica after hydrolysis/condensation reaction per 100 parts of the spherical polymethylmethacrylate particles) was added dropwise over 20 minutes, and the mixture was stirred for 1 hour while maintaining the liquid temperature at 5 to 10 ℃ to obtain an aqueous dispersion of silica-coated polymethylmethacrylate particles.

Next, 3g of a 30% aqueous solution of cetyltrimethylammonium chloride (trade name: コータミン 60W, manufactured by Kao corporation) was added, and 2.1g of phenyltrimethoxysilane was added. Ammonia was not added additionally at the time of adding phenyltrimethoxysilane. The liquid temperature is kept at 5-10 ℃, stirred for 30 minutes, heated to 70-75 ℃, and stirred for 1 hour under the state of keeping the temperature.

The resulting liquid was dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirrer using an anchor-type stirring blade, 1000g of 50% methanol water was added thereto, and the mixture was stirred for 30 minutes and then dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade, 1000g of water was added, and after stirring for 30 minutes, the mixture was dehydrated using a pressure filter, and the same operation was repeated again. The obtained dehydrated product was dried at a temperature of 105 ℃ in a hot air flow dryer, and the dried product was crushed with a jet mill to obtain particles.

The volume average particle diameter of the obtained particles was measured to be 6 μm using a resistance-method particle size distribution measuring apparatus (manufactured by strain マルチサイザー 3, ベックマン, コールター).

The obtained particles were put into water and stirred, and as a result, the particles were dispersed in water and were hydrophilic. From the results, it was found that phenyltrimethoxysilane did not cause hydrolysis/condensation reaction with the hydroxyl groups on the surface of the silica-coated polymethyl methacrylate particles.

[ example 4]

A kinematic viscosity of 8.4mm represented by the following average formula (1)²139g of methyl vinyl polysiloxane per s and a kinematic viscosity of 12mm represented by the following average formula (2)²61 g/s of methylhydrogenpolysiloxane were charged into a glass beaker having a capacity of 1 liter and dissolved with stirring at 2000rpm using a homomixer. Next, 0.8g of polyoxyethylene lauryl ether (ethylene oxide addition mole number: 9 moles) and 50g of water were added, and stirred at 6000rpm using a homomixer to form an oil-in-water type, thereby confirming thickening, and further, stirring was continued for 15 minutes. Next, 747g of water was added thereto while stirring at 2000rpm, to obtain a white emulsion. Next, the mixture was introduced into a homogenizer under a pressure of 40MPa to refine the emulsion particles. The obtained emulsion was transferred to a glass flask having a capacity of 1 liter and equipped with a stirring device using an anchor-type stirring blade, the temperature was adjusted to 15 to 20 ℃, and then a mixed solution of 0.5g of an isododecane solution (platinum content: 0.5%) of a platinum-vinyl-containing disiloxane complex and 1g of polyoxyethylene lauryl ether (ethylene oxide addition mole number: 9 moles) was added under stirring, and stirred at the same temperature for 12 hours to obtain an aqueous dispersion of silicone rubber particles. In the following formulae, the bonding order of the siloxane units is not limited to the following bonding order.

[ solution 1]

The shape of the silicone rubber particles in the obtained aqueous dispersion was observed by an optical microscope to be spherical, and the volume average particle diameter was measured to be 2 μm by using a resistance method particle size distribution measuring apparatus (manufactured by マルチサイザー 3, ベックマン, コールター).

750g of the obtained aqueous dispersion of silicone rubber particles was transferred to a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade, and 200g of water, 1.5g of 2.9% aqueous ammonia, and 5g of a 30% aqueous solution of dodecyltrimethylammonium chloride (trade name: カチオン BB, manufactured by Nichikoku corporation) were added. The pH of the liquid at this time was 10.2. After the temperature was adjusted to 5 to 10 ℃, 29.1g of tetramethoxysilane (the amount of silica after hydrolysis/condensation reaction was 7.7 parts per 100 parts of silicone rubber particles) was added dropwise over 25 minutes, and the liquid temperature therebetween was kept at 5 to 10 ℃, followed by stirring for 1 hour to obtain an aqueous dispersion of silica-coated silicone rubber particles.

Next, 3g of a 30% hexadecyltrimethylammonium chloride aqueous solution (trade name: コータミン 60W, manufactured by Kao corporation) and 10g of 29% aqueous ammonia were added, and 1.8g of trimethylmethoxysilane was added. The liquid temperature is kept at 5-10 ℃, stirred for 30 minutes, heated to 70-75 ℃, and stirred for 1 hour under the state of keeping the temperature.

The resulting liquid was dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirrer using an anchor-type stirring blade, 1000g of 50% methanol water was added thereto, and the mixture was stirred for 30 minutes and then dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade, 1000g of water was added, and after stirring for 30 minutes, the mixture was dehydrated using a pressure filter, and the same operation was repeated again. The obtained dehydrated product was dried at a temperature of 80 ℃ in a hot air flow dryer, and the dried product was crushed with a jet mill to obtain particles.

The volume average particle diameter of the obtained particles was measured to be 2 μm using a resistance-method particle size distribution measuring apparatus (manufactured by strain マルチサイザー 3, ベックマン, コールター).

The obtained particles were put into water and stirred, and as a result, the particles were not dispersed in water but floated on water. Further, 35 vol% methanol water was poured and stirred, and as a result, the particles were not dispersed in the methanol water but floated on the methanol water. From the results, it was found that the trimethylmethoxysilane and the hydroxyl group on the surface of the silica-coated silicone rubber particle underwent hydrolysis and condensation reaction.

[ example 5]

An aqueous dispersion of silicone rubber particles was obtained in the same manner as in example 4. 750g of the obtained aqueous dispersion of silicone rubber particles was transferred to a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade, and 199g of water, 1.5g of 2.9% aqueous ammonia, and 5g of a 30% aqueous solution of dodecyltrimethylammonium chloride (trade name: カチオン BB, manufactured by Nichikoku corporation) were added. The pH of the liquid at this time was 10.2. After the temperature was adjusted to 5 to 10 ℃, 29.1g of tetramethoxysilane (the amount of silica after hydrolysis/condensation reaction was 7.7 parts per 100 parts of silicone rubber particles) was added dropwise over 25 minutes, and the liquid temperature therebetween was kept at 5 to 10 ℃, followed by stirring for 1 hour to obtain an aqueous dispersion of silica-coated silicone rubber particles.

Next, 3g of a 30% hexadecyltrimethylammonium chloride aqueous solution (trade name: コータミン 60W, manufactured by Kao corporation) and 10g of 29% aqueous ammonia were added, and then 2.1g of phenyltrimethoxysilane was added. The liquid temperature is kept at 5-10 ℃, stirred for 30 minutes, heated to 70-75 ℃, and stirred for 1 hour under the state of keeping the temperature.

The resulting liquid was dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirrer using an anchor-type stirring blade, 1000g of 50% methanol water was added thereto, and the mixture was stirred for 30 minutes and then dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade, 1000g of water was added, and after stirring for 30 minutes, the mixture was dehydrated using a pressure filter, and the same operation was repeated again. The obtained dehydrated product was dried at a temperature of 80 ℃ in a hot air flow dryer, and the dried product was crushed with a jet mill to obtain particles.

The volume average particle diameter of the obtained particles was measured to be 2 μm using a resistance-method particle size distribution measuring apparatus (manufactured by strain マルチサイザー 3, ベックマン, コールター).

The obtained particles were put into water and stirred, and as a result, the particles were not dispersed in water but floated on water. Further, 10 vol% of methanol water was poured and stirred, and as a result, the particles were not dispersed in methanol water but floated on methanol water. From these results, it was found that phenyltrimethoxysilane caused hydrolysis and condensation reaction with hydroxyl groups on the surface of the silica-coated silicone rubber particles.

[ example 6]

An aqueous dispersion of silicone rubber particles was obtained in the same manner as in example 4. 750g of the obtained aqueous dispersion of silicone rubber particles was transferred to a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade, and 199g of water, 1.5g of 2.9% aqueous ammonia, and 5g of a 30% aqueous solution of dodecyltrimethylammonium chloride (trade name: カチオン BB, manufactured by Nichikoku corporation) were added. The pH of the liquid at this time was 10.2. After the temperature was adjusted to 5 to 10 ℃, 29.1g of tetramethoxysilane (the amount of silica after hydrolysis/condensation reaction was 7.7 parts per 100 parts of silicone rubber particles) was added dropwise over 25 minutes, and the liquid temperature therebetween was kept at 5 to 10 ℃, followed by stirring for 1 hour to obtain an aqueous dispersion of silica-coated silicone rubber particles.

Next, 3g of a 30% aqueous solution of cetyltrimethylammonium chloride (trade name: コータミン 60W, manufactured by Kao corporation) and 10g of 29% aqueous ammonia were added, and 1.9g of 3-methacryloxypropyltrimethoxysilane was added. The liquid temperature is kept at 5-10 ℃, stirred for 30 minutes, heated to 70-75 ℃, and stirred for 1 hour under the state of keeping the temperature.

The resulting liquid was dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirrer using an anchor-type stirring blade, 1000g of 50% methanol water was added thereto, and the mixture was stirred for 30 minutes and then dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade, 1000g of water was added, and after stirring for 30 minutes, the mixture was dehydrated using a pressure filter, and the same operation was repeated again. The obtained dehydrated product was dried at a temperature of 80 ℃ in a hot air flow dryer, and the dried product was crushed with a jet mill to obtain particles.

The volume average particle diameter of the obtained particles was measured to be 2 μm using a resistance-method particle size distribution measuring apparatus (manufactured by strain マルチサイザー 3, ベックマン, コールター).

The obtained particles were put into water and stirred, and as a result, the particles were not dispersed in water but floated on water. Further, 10 vol% of methanol water was poured and stirred, and as a result, the particles were not dispersed in methanol water but floated on methanol water. From these results, it was found that 3-methacryloxypropyltrimethoxysilane reacted with hydroxyl groups on the surface of the silica-coated silicone rubber particles by hydrolysis and condensation.

Comparative example 4

An aqueous dispersion of silicone rubber particles was obtained in the same manner as in example 4. 750g of the obtained aqueous dispersion of silicone rubber particles was transferred to a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade, and 200g of water, 1.5g of 2.9% aqueous ammonia, and 5g of a 30% aqueous solution of dodecyltrimethylammonium chloride (trade name: カチオン BB, manufactured by Nichikoku corporation) were added. The pH of the liquid at this time was 10.2. After the temperature was adjusted to 5 to 10 ℃, 29.1g of tetramethoxysilane (the amount of silica after hydrolysis/condensation reaction was 7.7 parts per 100 parts of silicone rubber particles) was added dropwise over 25 minutes, and the liquid temperature therebetween was kept at 5 to 10 ℃, followed by stirring for 1 hour. Then, the mixture was heated to 70 to 75 ℃ and stirred for 1 hour while maintaining the temperature, thereby obtaining an aqueous dispersion of silica-coated silicone rubber particles.

The resulting liquid was dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirrer using an anchor-type stirring blade, 1000g of 50% methanol water was added thereto, and the mixture was stirred for 30 minutes and then dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade, 1000g of water was added, and after stirring for 30 minutes, the mixture was dehydrated using a pressure filter, and the same operation was repeated again. The obtained dehydrated product was dried at a temperature of 80 ℃ in a hot air flow dryer, and the dried product was crushed with a jet mill to obtain particles.

The volume average particle diameter of the obtained particles was measured to be 2 μm using a resistance-method particle size distribution measuring apparatus (manufactured by strain マルチサイザー 3, ベックマン, コールター).

The obtained particles were put into water and stirred, and as a result, the particles were dispersed in water and were hydrophilic.

Comparative example 5

An aqueous dispersion of silicone rubber particles was obtained in the same manner as in example 4. 750g of the obtained aqueous dispersion of silicone rubber particles was transferred to a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade, and 200g of water, 1.5g of 2.9% aqueous ammonia, and 5g of a 30% aqueous solution of dodecyltrimethylammonium chloride (trade name: カチオン BB, manufactured by Nichikoku corporation) were added. The pH of the liquid at this time was 10.2. After the temperature was adjusted to 5 to 10 ℃, 29.1g of tetramethoxysilane (the amount of silica after hydrolysis/condensation reaction was 7.7 parts per 100 parts of silicone rubber particles) was added dropwise over 25 minutes, and the liquid temperature therebetween was kept at 5 to 10 ℃, followed by stirring for 1 hour to obtain an aqueous dispersion of silica-coated silicone rubber particles.

Next, 3g of a 30% aqueous solution of cetyltrimethylammonium chloride (trade name: コータミン 60W, manufactured by Kao corporation) was added, and 1.8g of trimethylmethoxysilane was added. When trimethylmethoxysilane was added, ammonia was not additionally added. The liquid temperature is kept at 5-10 ℃, stirred for 30 minutes, heated to 70-75 ℃, and stirred for 1 hour under the state of keeping the temperature.

The resulting liquid was dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirrer using an anchor-type stirring blade, 1000g of 50% methanol water was added thereto, and the mixture was stirred for 30 minutes and then dehydrated using a pressure filter. The dehydrated product was transferred to a 2-liter glass flask equipped with a stirring device using an anchor-type stirring blade, 1000g of water was added, and after stirring for 30 minutes, the mixture was dehydrated using a pressure filter, and the same operation was repeated again. The obtained dehydrated product was dried at a temperature of 80 ℃ in a hot air flow dryer, and the dried product was crushed with a jet mill to obtain particles.

The volume average particle diameter of the obtained particles was measured to be 2 μm using a resistance-method particle size distribution measuring apparatus (manufactured by strain マルチサイザー 3, ベックマン, コールター).

The obtained particles were put into water and stirred, and as a result, the particles were dispersed in water and were hydrophilic. From the results, it was found that the trimethylmethoxysilane did not undergo hydrolysis/condensation reaction with the hydroxyl groups on the surface of the silica-coated silicone rubber particles.

[ compounding viscosity of liquid epoxy resin ]

In a glass bottle, 70g of a liquid epoxy resin (trade name: ZX-1059, manufactured by Nippon iron chemical Co., Ltd.) and 8g of silica-coated silicone rubber particles shown in Table 1 were weighed and stirred with a spatula so that the silica-coated silicone rubber particles were uniformly dispersed. The viscosity of the dispersion at 25 ℃ was measured using a rotational viscometer, and the results are shown in table 1.

[ Table 1]

Silica-coated silicone rubber particles	Viscosity (mPa. s)
		Not in cooperation with	2,020
Silicon dioxide-coated silicone rubber particles of comparative example 3	5,450
		Silica-coated silicone rubber particles of example 5	3,900

The viscosity of the liquid epoxy resin containing the silica-coated silicone rubber particles was lower in the resin of the particles of example 5 in which the hydroxyl groups on the silica surface were reacted with phenyltrimethoxysilane than in the particles of comparative example 3 in which the silica surface was not treated. From this, it was found that the particles of example 5 in which the hydroxyl groups on the silica surface were reacted with phenyltrimethoxysilane had good dispersibility and wettability with respect to the epoxy resin.