Aqueous dispersion of silica-containing silicone rubber particles, silica-containing silicone rubber particles, and methods for producing the same

Abstract

To provide a silicone rubber particle having high strength and a water dispersion thereof.SOLUTION: The present invention provides the following water dispersion of silica-containing silicone rubber particles, and silica-containing silicone rubber particles. The silicone rubber particles contain 1 to 50 pts.mass of hydrophobized silica (A-2) per 100 pts.mass of silicone rubber (A-1), and the silicone rubber particles have a volume average particle diameter of 0.5 to 100 μm and spherical shape. The hydrophobized silica (A-2) is hydrophobized with at least one selected from a triorganosilyl group, a diorganosilyl group, a monoorganosilyl group, and a polydiorganosiloxy group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to high-strength silicone rubber particles, and more particularly to an aqueous dispersion of silica-containing silicone rubber particles, silica-containing silicone rubber particles, and methods for producing the same. [Background technology]

[0002] Silicone rubber particles are used as stress relief agents for resins, light diffusing agents for resins, texture improvers for cosmetics, matting agents for paints and coatings, texture improvers, and slip improvers, etc. When used in paints and coatings, silicone rubber that does not contain fillers such as silica has low strength, and therefore, when the coating film is subjected to friction, the silicone rubber particles contained therein may break.

[0003] Patent Document 1 proposes high-strength silicone rubber particles containing silica. They are produced by mixing silica into a curable liquid silicone composition, dispersing (emulsifying) the mixture in water containing a surfactant, and then subjecting it to a curing reaction. The silica used here is wet silica that has been hydrophobized with a liquid organopolysiloxane. As noted in Patent Document 1, if silica that has not been hydrophobized is used, during the emulsification process of the curable liquid silicone composition containing silica, the silica migrates from the silicone composition to the aqueous phase, which serves as the dispersion medium, and silica-containing silicone rubber particles cannot be obtained. In the case of hydrophobic treatment using organopolysiloxane, the siloxane does not chemically modify the silica surface, but rather physically adsorbs to it, and during the process of emulsifying a curable liquid silicone composition containing silica, some of the incorporated silica may migrate into the aqueous phase. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 4-168117 Summary of the Invention [Problem to be solved by the invention]

[0005] When wet silica is hydrophobized with silane or silazane, the silyl groups are chemically modified to produce sufficiently hydrophobic silica. However, curable liquid silicone compositions containing silica hydrophobized with silane or silazane cannot be emulsified with surfactants typically used to emulsify curable liquid silicones.

[0006] The present invention has been made in view of the above circumstances, and has as its object to provide silicone rubber particles having high strength and an aqueous dispersion thereof. [Means for solving the problem]

[0007] As a result of extensive research into achieving the above object, the present inventors discovered that by using a low HLB nonionic surfactant in a method for producing silicone rubber particles containing silica that has been hydrophobized with silane or silazane, it is possible to effectively emulsify a curable liquid silicone composition containing silica, thereby providing silicone rubber particles containing silica within the silicone rubber particles, which led to the completion of the present invention.The silicone rubber particles have high strength due to the inclusion of silica within the silicone rubber particles.

[0008] That is, the present invention provides the following aqueous dispersion of silica-containing silicone rubber particles and silica-containing silicone rubber particles. The silicone rubber particles comprise 1 to 50 parts by mass of (A-2) hydrophobized silica per 100 parts by mass of (A-1) silicone rubber, the silicone rubber particles having a volume average particle size of 0.5 to 100 μm and being spherical, and the (A-2) hydrophobized silica has been hydrophobized with at least one group selected from the group consisting of a triorganosilyl group, a diorganosilyl group, a monoorganosilyl group, and a polydiorganosiloxy group.

[0009] The present invention further provides the above-mentioned silicone rubber particles, wherein the (A-1) silicone rubber is an addition reaction cured product of (a) an organopolysiloxane having alkenyl groups and (b) an organohydrogenpolysiloxane having silicon-bonded hydrogen atoms. The present invention further provides the above-mentioned silicone rubber particles, wherein the (A-1) silicone rubber is a cured product obtained by a condensation reaction between (c) an organopolysiloxane having a hydroxyl group or a hydrolyzable group bonded to a silicon atom and (d) a silane having a hydrolyzable group bonded to a silicon atom. The present invention further provides the above-mentioned silicone rubber particles, wherein the (A-1) silicone rubber is a radical reaction cured product of (e) an organopolysiloxane having a radical polymerization reactive group.

[0010] The present invention further provides a method for producing silicone rubber particles containing hydrophobically treated silica, the method comprising the steps of: (i) mixing 100 parts by mass of at least one curable organosilicon compound selected from organopolysiloxanes and silanes with 1 to 50 parts by mass of (A-2) hydrophobized silica; (ii) adding 0.1 to 20 parts by mass of (B) a nonionic surfactant having an HLB of 1.0 to 12.0, 5 to 2,000 parts by mass of (C) water, and optionally 0.05 to 5 parts by mass of (D) a water-soluble polymer to the mixture obtained in (i) and emulsifying the mixture to obtain an oil-in-water emulsion; (iii) curing the curable organosilicon compound in the oil-in-water emulsion to obtain an aqueous dispersion of silicone rubber particles; and (iv) removing water from the aqueous dispersion obtained in step (iii) to obtain silicone rubber particles; The present invention provides a method for producing silicone rubber particles, characterized in that the silicone rubber particles have a volume average particle size of 0.5 to 100 μm and are spherical, and the hydrophobized silica is hydrophobized with at least one group selected from a triorganosilyl group, a diorganosilyl group, a monoorganosilyl group, and a polydiorganosiloxy group.

[0011] The present invention further provides a method for producing an aqueous dispersion of silicone rubber particles containing hydrophobized silica, the method comprising the steps of: (i) mixing 100 parts by mass of at least one curable organosilicon compound selected from organopolysiloxanes and silanes with 1 to 50 parts by mass of (A-2) hydrophobized silica; (ii) adding 0.1 to 20 parts by mass of (B) a nonionic surfactant having an HLB of 1.0 to 12.0, 5 to 2,000 parts by mass of (C) water, and optionally 0.05 to 5 parts by mass of (D) a water-soluble polymer to the mixture obtained in (i) and emulsifying the mixture to obtain an oil-in-water emulsion; and (iii) curing the curable organosilicon compound in the oil-in-water emulsion to obtain an aqueous dispersion of silicone rubber particles; The silicone rubber particles have a volume average particle size of 0.5 to 100 μm and are spherical, and the hydrophobized silica is hydrophobized with at least one group selected from a triorganosilyl group, a diorganosilyl group, a monoorganosilyl group, and a polydiorganosiloxy group. A method for producing the aqueous dispersion is provided. [Effects of the Invention]

[0012] The silicone rubber particles of the present invention have high mechanical strength due to the silica contained within the particles, and therefore aqueous dispersions of these silicone rubber particles are useful in paints and coatings that are subject to friction. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below.

[0014] (A) Silica-containing silicone rubber particles Component (A) is a particle containing (A-2) hydrophobized silica in (A-1) silicone rubber. The amount of hydrophobized silica (A-2) in the particle is in the range of 1 to 50 parts by mass, preferably 3 to 35 parts by mass, and more preferably 5 to 30 parts by mass, per 100 parts by mass of (A-1) silicone rubber. If the amount of hydrophobized silica is less than the above lower limit, the improvement in mechanical strength will be low. If the amount of hydrophobized silica is more than the above upper limit, the mixture of the curable liquid silicone and hydrophobized silica described below will have no fluidity, making it difficult to emulsify.

[0015] The particle shape is spherical. In this specification, "spherical" means that the particle shape is not only a perfect sphere but also a deformed sphere in which the average aspect ratio (length of the longest axis / length of the shortest axis) is usually in the range of 1.0 to 4.0, preferably 1.0 to 2.0, more preferably 1.0 to 1.6, and even more preferably 1.0 to 1.4. The particle shape can be confirmed by observing the particles with an optical microscope, an electron microscope, or the like. It can also be measured using a particle shape analyzer using dynamic image analysis. The volume average particle size of the particles is 0.5 to 100 μm, preferably 1 to 40 μm, and more preferably 2 to 20 μm. The volume average particle size is measured by the Coulter counter method (electrical resistance method).

[0016] The silicone rubber particles are preferably non-sticky, and their rubber hardness, measured using a Type A durometer as specified in JIS K6253, is preferably in the range of 5 to 95, more preferably 20 to 85. The rubber hardness is a value measured by preparing a test piece having the shape and dimensions specified in JIS K6253 using the particle composition.

[0017] The mechanical strength of the silicone rubber is preferably 0.5 to 10 MPa, more preferably 0.8 to 5 MPa, in terms of tensile strength at break, measured according to the method specified in JIS K 6251. The elongation at break is preferably in the range of 5 to 1000%, more preferably 10 to 500%. The tensile strength at break and elongation at break refer to values ​​measured using a 1 mm thick sheet prepared with the particle composition and having the shape and dimensions of a dumbbell-shaped No. 3 test piece specified in JIS K 6251.

[0018] The silicone rubber particles may contain non-functional silicone oil, inorganic powder (excluding silica), organic powder, antioxidant, and the like.

[0019] (A-1) Silicone rubber is a compound represented by the formula -(R 1 2SiO 2 / 2 ) f Preferably, the cured product comprises a linear organosiloxane block represented by the formula: 1 is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 30 carbon atoms, preferably 1 to 22 carbon atoms, more preferably 1 to 18. f is a positive integer of 5 to 5,000, preferably 10 to 2,000, more preferably 20 to 1,000.

[0020] R 1Examples of the alkyl group include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, decyl, undecyl, dodecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl, henicosyl, docosyl, tricosyl, tetracosyl, and triacontyl; aryl groups such as phenyl, tolyl, and naphthyl; benzyl, phenethyl, and the like. groups; alkenyl groups such as vinyl and allyl groups; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl groups; and hydrocarbon groups in which some or all of the hydrogen atoms bonded to carbon atoms of these groups have been substituted with atoms such as halogen atoms (fluorine, chlorine, bromine, and iodine atoms) and / or substituents such as acryloyloxy, methacryloyloxy, amino, epoxy, glycidoxy, and carboxyl groups. 1 Preferably, 50 mol % or more of the groups are methyl groups.

[0021] The silicone rubber is preferably a cured product of a curable liquid silicone composition. Examples of curable liquid silicone compositions include addition reaction, condensation reaction, and radical reaction curing types. The curable liquid silicone composition contains at least one curable organosilicon compound selected from organopolysiloxanes and silanes having a reactive group for the curing reaction, and preferably a curing catalyst. The curable organosilicon compound may be an organosilicon compound having both reactive groups in one molecule, or may be a combination of an organosilicon compound having one reactive group and another organosilicon compound having a reactive group that reacts with the reactive group.

[0022] One aspect of the present invention is a curable liquid silicone composition that provides a silicone rubber, wherein the curable organosilicon compounds are (a) an organopolysiloxane having alkenyl groups and (b) an organohydrogenpolysiloxane having silicon-bonded hydrogen atoms. Another aspect is a curable liquid silicone composition that gives a silicone rubber, wherein the curable organosilicon compound is (c) an organopolysiloxane having a hydroxyl group or a hydrolyzable group bonded to a silicon atom and (d) a silane having a hydrolyzable group bonded to a silicon atom. Another aspect is a curable liquid silicone composition that gives a silicone rubber, wherein the curable organosilicon compound is (e) an organopolysiloxane having a radically polymerizable group.

[0023] One aspect of the (A-1) silicone rubber of the present invention is preferably an addition reaction cured product of (a) an organopolysiloxane having an alkenyl group and (b) an organohydrogenpolysiloxane having a silicon-bonded hydrogen atom. The curable liquid silicone composition that gives the addition reaction cured product contains (a) an organopolysiloxane having an alkenyl group and (b) an organohydrogenpolysiloxane having a silicon-bonded hydrogen atom, and preferably further contains a catalyst for the addition reaction. This will be described in detail below.

[0024] (a) The organopolysiloxane having an alkenyl group is preferably represented by the following average composition formula (2) and preferably has at least two alkenyl groups in one molecule. R 2 g R 3 h SiO (4-g-h) / 2 (2) In the formula, R 2 is, independently of each other, an unsubstituted or substituted monovalent hydrocarbon group having 1 to 30 carbon atoms and no alkenyl group, and R 3 is, independently of each other, an alkenyl group having 2 to 6 carbon atoms, and g and h are positive numbers satisfying 0 < g < 3, 0 < h ≦ 3, and 0.1 ≦ g + h ≦ 3.

[0025] R 2 is a monovalent hydrocarbon group having 1 to 30 carbon atoms, preferably a monovalent hydrocarbon group having 1 to 22 carbon atoms, more preferably a monovalent hydrocarbon group having 1 to 18 carbon atoms. As R 2 , R 1Among the monovalent hydrocarbon groups exemplified for this purpose, monovalent hydrocarbon groups excluding alkenyl groups are mentioned, and it is preferable that 50 mol% or more is a methyl group.

[0026] R 3 Examples include vinyl group, allyl group, propenyl group, butenyl group, pentenyl group, hexenyl group, and preferably a vinyl group.

[0027] g and h are preferably positive numbers satisfying 0 < g ≦ 2.295, 0.005 ≦ h ≦ 2.3, and 0.5 ≦ g + h ≦ 2.3.

[0028] The organopolysiloxane having an alkenyl group preferably has 2 to 500 alkenyl groups in one molecule. The amount of alkenyl group is preferably 5.4×10 -4 ~1.1 mol / 100 g. The degree of polymerization of the organopolysiloxane is preferably 2 to 5,000, more preferably 10 to 2,000, and even more preferably 20 to 1,000.

[0029] (Component (a) preferably has a viscosity of 0.7 to 100,000 mm 2 / s at 25°C, more preferably 2 to 10,000 mm 2 / s. Even more preferably 5 to 1,000 mm 2 / s, and even more preferably 10 to 500 mm 2 / s. The structure of component (a) may be linear, cyclic, or branched, but linear or branched is preferred. Also, the bonding position of the alkenyl group is not particularly limited and may be bonded to any silicon atom in the side chain and terminal of the molecule.

[0030] Examples of the linear organopolysiloxane include those represented by the following general formula (3).

Chemical formula

[0031] Examples of branched organopolysiloxanes include R 2 SiO 3 / 2 Examples of the branched units are those represented by the following general formula (4). [ka] In the formula, R 2 and R 3 is as defined above, l is a positive number, m is 0 or a positive number, n is a positive number, and o is 0, 1, 2, or 3, provided that m and o are numbers that satisfy m+o≧1.

[0032] SiO 4 / 2 Examples of organopolysiloxanes having a structure branched by units include those represented by the following general formula (5). [ka] In the formula, R 2 and R 3 is as defined above, p is a positive number, q is 0 or a positive number, r is a positive number, and s is 0, 1, 2, or 3, provided that q and s are numbers that satisfy q+s≧1.

[0033] Further examples include organopolysiloxanes represented by the following unit formula (6) and having two or more alkenyl groups per molecule. [R 2 3SiO 1 / 2 ] t [R 3 (R 2 )2SiO 1 / 2 ] u [SiO 4 / 2 ] v [(OR 4 )SiO 3 / 2 ] W (6) In the formula, R 2 and R 3 are as described above, R 4 is a hydrogen atom or an unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms, t is 0 or a positive number, u is a positive number, v is a positive number, and w is 0 or a positive number.

[0034] (b) The organohydrogenpolysiloxane having a silicon atom-bonded hydrogen atom is preferably represented by the following average composition formula (7) and has at least 2 hydrogen atoms bonded to silicon atoms (referred to as SiH groups) in one molecule. R 5 x H y O (4-x-y) / 2 (7) In the formula, R 5 are, independently of each other, unsubstituted or substituted monovalent hydrocarbon groups having no alkenyl group and having 1 to 30 carbon atoms, and x and y are positive numbers satisfying 0 < x < 3, 0 < y ≤ 3, and 0.1 ≤ x + y ≤ 3.

[0035] R 5 is a monovalent hydrocarbon group having 1 to 30 carbon atoms, preferably a monovalent hydrocarbon group having 1 to 22 carbon atoms, more preferably a monovalent hydrocarbon group having 1 to 18 carbon atoms. For R 5 Examples include the monovalent hydrocarbon groups excluding the alkenyl group among the monovalent hydrocarbon groups exemplified for R 1 , and preferably 50 mol% or more is a methyl group.

[0036] x and y are preferably positive numbers satisfying 0 < x ≤ 2.295, 0.005 ≤ y ≤ 2.3, and 0.5 ≤ x + y ≤ 2.3.

[0037] The number of SiH groups in one molecule is preferably 2 to 500. The amount of SiH groups is preferably 5.3×10 -4 ~1.7 mol / 100 g. The degree of polymerization is preferably 2 to 5,000, more preferably 10 to 2,000, and still more preferably 20 to 1,000.

[0038] The viscosity of component (b) at 25°C is 0.4 to 100,000 mm 2 / s is preferable, and 2 to 10,000 mm 2 / s. More preferably, it is 5 to 1,000 mm 2 / s, more preferably 10 to 500 mm 2 / s. The structure of component (b) may be linear, cyclic, or branched, but linear or branched is preferred. There are no particular restrictions on the bonding position of the hydrogen atom bonded to the silicon atom, and the hydrogen atom may be bonded to either a side chain or terminal silicon atom of the molecule.

[0039] An example of the organopolysiloxane having a linear structure is one represented by the following general formula (8). [ka] In the formula, R 5 is as described above, z is a positive number, a1 is 0 or a positive number, and b1 is 0, 1, 2, or 3, provided that a1 and b1 are numbers that satisfy a1+2×b1≧2.

[0040] Examples of organopolysiloxanes having a branched structure include R 5 SiO 3 / 2 Examples include those represented by the following general formula (9) which are branched by units. [ka] In the formula, R 5 are as described above, c1 is a positive number, d1 is 0 or a positive number, e1 is a positive number, and f1 is 0, 1, 2, or 3, provided that d1 and f1 are numbers that satisfy d1+f1≧1.

[0041] SiO 4 / 2 An example of the organopolysiloxane branched by units is one represented by the following general formula (10). [ka] In the formula, R5 is the same as above, g1 is a positive number, h1 is 0 or a positive number, i1 is a positive number, and j1 is 0, 1, 2, or 3, provided that h1 and j1 are numbers that satisfy h1+j1≧1.

[0042] Further examples include organopolysiloxanes represented by the following unit formula (11) and having two or more SiH groups per molecule. [R 5 3SiO 1 / 2 ] k1 [H(R 5 )2SiO 1 / 2 ] l1 [SiO 4 / 2 ] m1 [(OR 6 )SiO 3 / 2 ] n1 (11) In the formula, R 5 is as described above, and R 6 is a hydrogen atom or an unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms, k1 is 0 or a positive number, l1 is a positive number, m1 is a positive number, and n1 is 0 or a positive number.

[0043] As described above, component (a) is an organopolysiloxane having at least two alkenyl groups per molecule, and component (b) is an organohydrogenpolysiloxane having at least two SiH groups per molecule, but it is preferable that the composition excludes a combination of (a) having only two alkenyl groups and (b) having only two SiH groups. That is, more preferably, when component (a) has two alkenyl groups, at least one component (b) has three or more SiH groups, and when component (b) has two SiH groups, at least one component (a) has three or more alkenyl groups.

[0044] The amount of component (b) relative to component (a) is such that the ratio of the number of SiH groups in component (b) to one alkenyl group in component (a) is 0.5 to 2, preferably 0.7 to 1.5, and more preferably 0.8 to 1.3.

[0045] Examples of the catalyst for the addition reaction include platinum group metal catalysts used in hydrosilylation reactions, such as platinum group metals such as platinum (including platinum black), rhodium, and palladium; H2PtCl4·XH2O, H2PtCl6·XH2O, NaHPtCl6·XH2O, KHPtCl6·XH2O, Na2PtCl6·XH2O, K2PtCl4·XH2O, Examples of suitable platinum chlorides include PtCl4·XH2O, PtCl2, and Na2HPtCl4·XH2O (wherein X is an integer of 0 to 6, preferably 0 or 6), as well as chloroplatinic acid and chloroplatinic acid salts; alcohol-modified chloroplatinic acid; platinum chloride, complexes of chloroplatinic acid with olefins, complexes of chloroplatinic acid with vinyl group-containing siloxanes, and complexes of platinum with vinyl group-containing siloxanes; platinum black, platinum group metals such as palladium supported on supports such as alumina, silica, and carbon; rhodium-olefin complexes; and chlorotris(triphenylphosphine)rhodium (Wilkinson's catalyst).

[0046] The platinum group metal catalyst may be added in an amount effective as a hydrosilylation reaction catalyst, for example, such that the amount of platinum group metal in the platinum group metal catalyst component relative to the total amount of components (a) and (b) is preferably 0.1 to 500 ppm, more preferably 1 to 100 ppm, by mass.

[0047] Another embodiment of the silicone rubber (A-1) of the present invention is preferably a condensation reaction cured product of (c) an organopolysiloxane having silicon-bonded hydroxyl groups or hydrolyzable groups and (d) a silane having silicon-bonded hydrolyzable groups. The curable liquid silicone composition that gives this condensation reaction cured product contains (c) an organopolysiloxane having silicon-bonded hydroxyl groups or hydrolyzable groups and (d) a silane having silicon-bonded hydrolyzable groups, and preferably further contains a condensation reaction catalyst. This will be explained in detail below.

[0048] (c) The organopolysiloxane having a hydroxyl group or a hydrolyzable group bonded to a silicon atom is preferably represented by the following average composition formula (12) and has at least two hydroxyl groups or hydrolyzable groups bonded to a silicon atom in one molecule. R 7 o1 R 8 p1 SiO (4-o1-p1) / 2 (12) In the formula, R 7 is, independently of one another, an unsubstituted or substituted monovalent hydrocarbon group having 1 to 30 carbon atoms, and R 8 is, independently of one another, a hydroxyl group or a hydrolyzable group bonded to a silicon atom, and o1 and p1 are positive numbers satisfying 0 < o1 < 3, 0 < p1 ≤ 3, and 0.1 ≤ o1 + p1 ≤ 3.

[0049] R 7 is a monovalent hydrocarbon group having 1 to 30 carbon atoms, preferably a monovalent hydrocarbon group having 1 to 22 carbon atoms, more preferably a monovalent hydrocarbon group having 1 to 18 carbon atoms. Examples of R 7 include the monovalent hydrocarbon groups exemplified for the above R 1 , and preferably 50 mol% or more is a methyl group.

[0050] R 8 is, independently of one another, a hydroxyl group or a hydrolyzable group bonded to a silicon atom. Examples of the hydrolyzable group include alkoxy groups such as methoxy group, ethoxy group, and propoxy group; oxime groups such as methyl ethyl ketoxime and dimethyl ketoxime groups; acetoxy group and aminoxy group, and preferably an alkoxy group. R 8 is preferably a hydroxyl group bonded to a silicon atom.

[0051] o1 and p1 are preferably positive numbers satisfying 0 < o1 ≤ 2.295, 0.005 ≤ p1 ≤ 2.3, and 0.5 ≤ o1 + p1 ≤ 2.3.

[0052] The viscosity at 25°C of the component (c) is preferably 1 to 100,000 mm 2 / s, more preferably 2 to 10,000 mm 2 / s. More preferably, it is 10 to 1,000 mm 2 / s. The structure of component (c) may be linear, cyclic, or branched, but linear or branched with few branching units is preferred. There are no particular restrictions on the bonding site of the hydroxyl group or hydrolyzable group bonded to the silicon atom, and the hydroxyl group or hydrolyzable group may be bonded to either the side chain or terminal silicon atom of the molecule.

[0053] R 8 is a hydroxyl group and has a linear structure, for example, a compound represented by the following general formula (13): [ka] In the formula, R 7 is as described above, q1 is a positive number, r1 is 0 or a positive number, and s1 is 0, 1, 2, or 3, provided that r1 and s1 are numbers that satisfy r1+2×s1≧2.

[0054] R 8 is a hydroxyl group, and examples of organopolysiloxanes having a branched structure include those having R 7 SiO 3 / 2 Examples of compounds include compounds represented by the following general formula (14) which are branched by the unit: [ka] In the formula, R 7 are as described above, t1 is a positive number, u1 is 0 or a positive number, v1 is a positive number, and w1 is 0, 1, 2, or 3, provided that u1 and w1 are numbers that satisfy u1+w1≧1.

[0055] SiO 4 / 2 Examples of organopolysiloxanes branched by the above units include compounds represented by the following general formula (15). [ka] In the formula, R 7are as described above, x1 is a positive number, y1 is 0 or a positive number, z1 is a positive number, and a2 is 0, 1, 2, or 3, provided that y1 and a2 are numbers that satisfy y1+a2≧1.

[0056] Component (d) is a silane having at least three silicon-bonded hydrolyzable groups per molecule. Examples of silicon-bonded hydrolyzable groups include alkoxy groups such as methoxy, ethoxy, and propoxy; oxime groups such as methyl ethyl ketoxime and dimethyl ketoxime; and acetoxy groups, with alkoxy groups being preferred.

[0057] Silanes in which the hydrolyzable group is alkoxy are represented by the following formulas (16) and (17), and may also be partial hydrolysis condensates thereof. R 9 Si(OR 10 )3(16) Si(OR 11 )4(17) In the formula, R 9 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and R 10 and R 11 is an unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms.

[0058] R 9 Examples of the alkyl group include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, decyl, undecyl, dodecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, and icosyl; aryl groups such as phenyl, tolyl, and naphthyl; aralkyl groups such as benzyl and phenethyl; alkenyl groups such as vinyl and allyl; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl; and hydrocarbon groups in which some or all of the hydrogen atoms bonded to carbon atoms of these groups have been substituted with atoms such as halogen atoms (fluorine, chlorine, bromine, and iodine) and / or substituents such as acryloyloxy, methacryloyloxy, epoxy, glycidoxy, and carboxyl.

[0059] R 10 and R 11 is a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, or a hexyl group, and is preferably a methyl group or an ethyl group.

[0060] The amount of component (d) relative to component (c) is an amount such that the ratio of the number of hydrolyzable groups bonded to silicon atoms in component (d) to one hydroxyl group or hydrolyzable group bonded to silicon atoms in component (c) is 0.8 or more, and preferably 1.0 or more. Component (d) is a crosslinking agent for component (c). However, components (d) can undergo a condensation reaction with each other. Therefore, the ratio of the number of hydrolyzable groups bonded to silicon atoms in component (d) to one hydroxyl group or hydrolyzable group bonded to a silicon atom in component (c) may be in large excess. The upper limit of the amount of component (d) is preferably 50 parts by mass or less, and more preferably 30 parts by mass or less, of component (d) per 100 parts by mass of component (c).

[0061] Examples of condensation reaction catalysts include organic tin compounds such as dibutyltin dilaurate, dioctyltin diversatate, dioctyltin dilaurate, tin octenoate, and tin laurate; organic titanium compounds such as titanium acetylacetonate, titanium tetraacetylacetonate, and titanium octanedioleate; acidic compounds such as hydrochloric acid, sulfuric acid, and dodecylbenzenesulfonic acid; and alkaline compounds such as ammonia and sodium hydroxide. The amount of the condensation reaction catalyst to be added may be an effective amount as a condensation reaction catalyst, preferably 0.001 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, per 100 parts by mass of the total amount of components (d) and (c).

[0062] Another embodiment of the silicone rubber (A-1) of the present invention is preferably a radical reaction cured product of (e) an organopolysiloxane having a radical polymerization reactive group. The curable liquid silicone composition that provides this radical reaction cured product contains (e) an organopolysiloxane having a radical polymerization reactive group, and preferably contains a radical generator.

[0063] (e) The organopolysiloxane having a radical polymerization reactive group is preferably represented by the following average composition formula (18) and has at least one radical polymerization reactive group in one molecule. R 12 b2 R 13 c2 SiO (4-b2-c2) / 2 (18) In the formula, R 12 is, independently of each other, an unsubstituted or substituted monovalent hydrocarbon group having 1 to 30 carbon atoms and not having a radical polymerization reactive group, and R 13 is, independently of each other, a hydrocarbon group having a radical polymerization reactive group with 2 to 10 carbon atoms, and b2 and c2 are positive numbers satisfying 0 < b2 < 3, 0 < c2 ≤ 3, and 0.1 ≤ b2 + c2 ≤ 3.

[0064] R 12 is a monovalent hydrocarbon group having 1 to 30 carbon atoms, preferably a monovalent hydrocarbon group having 1 to 22 carbon atoms, more preferably a monovalent hydrocarbon group having 1 to 18 carbon atoms. R 12 is, among the monovalent hydrocarbon groups exemplified for R 1 above, a monovalent hydrocarbon group excluding an alkenyl group and a hydrocarbon group substituted with a substituent of an acryloyloxy group or a methacryloyloxy group. It is preferable that 50 mol% or more of R 12 is a methyl group.

[0065] R 13 Examples of the radical polymerization reactive group of R

[0066] include an acryloyl group, a methacryloyl group, an acrylamide group, a vinyl group, an allyl group, an isoprenyl group, and a styryl group, etc., and preferably an acryloyl group and a methacryloyl group.

[0067] (e) The viscosity of the component at 25 °C is 1 to 100,000 mm 2 / s is preferable, and 2 to 10,000 mm 2 / s. More preferably, it is 5 to 1,000 mm 2 / s, more preferably 10 to 500 mm 2 The structure of component (e) may be linear, cyclic, or branched, but linear or branched with few branching units is preferred. The bonding site of the radical polymerization reactive group is not particularly limited, and it may be bonded to either a silicon atom in the side chain or at the terminal of the molecule.

[0068] An example of the organopolysiloxane having a linear structure and a methacryloyl group as the radical polymerization reactive group is one represented by the following general formula (19). [ka] In the formula, R 12 is the same as above, and R 14 is expressed by the following equation (20). [ka] d2 is a positive number, e2 is 0 or a positive number, f2 is 0, 1, 2 or 3, and g2 is 0, 1, 2 or 3, provided that any one of e2, f2 and g2 is 1 or greater.

[0069] R 13 The radical polymerization reactive group in the compound is a methacryloyl group, and examples of compounds having a branched structure include R 12 SiO 3 / 2 Examples of compounds include compounds represented by the following general formula (21) which are branched by the unit: [ka] In the formula, R 12 is as described above, and R 14 is represented by the above formula (20), h2 is a positive number, i2 is 0 or a positive number, j2 is a positive number, and k2 is 0, 1, 2, or 3, provided that either i2 or k2 is 1 or more.

[0070] SiO4 / 2 An example of the organopolysiloxane branched by units is one represented by the following general formula (22). [ka] In the formula, R 12 is as described above, and R 14 is represented by the above formula (20), l2 is a positive number, m2 is 0 or a positive number, n2 is a positive number, and o2 is 0, 1, 2, or 3, provided that either m2 or o2 is 1 or more.

[0071] Examples of the radical generator include organic peroxides, inorganic peroxides, azo initiators, redox initiators which combine an oxidizing agent and a reducing agent, photopolymerization initiators, etc. Among these, redox initiators and photopolymerization initiators are preferred.

[0072] As the redox initiator, a redox initiator in which ferrous sulfate, sodium pyrophosphate, glucose, and hydroperoxide are combined, or a redox initiator in which ferrous sulfate, ethylenediaminetetraacetic acid disodium salt, Rongalite, and hydroperoxide are combined, is particularly preferred.

[0073] Examples of photopolymerization initiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propan-1-one, phenylglyoxylic acid methyl ester, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide.

[0074] Examples of silica in (A-2) hydrophobized silica include wet silica such as precipitated silica, and dry silica such as silica xerogel and fumed silica. All of these silicas are hydrophilic silica. Hydrophobized silica is obtained by subjecting these silicas to hydrophobization treatment.

[0075] The hydrophobicity of silica is preferably achieved by modifying the hydrophilic groups of hydrophilic silica with triorganosilyl groups, diorganosilyl groups, monoorganosilyl groups, or polydiorganosiloxy groups.More preferably, the modifying groups are trimethylsilyl groups, dimethylsilyl groups, and monomethylsilyl groups.These hydrophobicity treatments can be carried out by conventionally known methods, that is, by treating with organosilicon compounds such as organochlorosilanes, organoalkoxysilanes, organodisilazanes, partial hydrolysis condensates of organochlorosilanes, partial hydrolysis condensates of organoalkoxysilanes, organopolysiloxanes, and organohydrogenpolysiloxanes.The organosilicon compounds are preferably silanes or silazanes containing methyl groups. More particularly, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, trimethylalkoxysilane, dimethyldialkoxysilane, methyltrialkoxysilane, hexamethyldisilazane, and 1,3-divinyl-1,1,3,3-tetramethyldisilazane.

[0076] The hydrophobicity treatment is preferably carried out to a state where the silica does not disperse in water under stirring. That is, the hydrophobicity is preferably greater than 0, more preferably greater than 5, and even more preferably greater than 40. If the hydrophobicity is low, during the emulsification process of the curable liquid silicone composition containing silica (described below), the silica will migrate from the silicone composition to the aqueous phase, which serves as the dispersion medium, making it impossible to obtain silicone rubber particles containing silica. There is no particular upper limit to the hydrophobicity, but the hydrophobicity is preferably 80 or less, more preferably 70 or less. The hydrophobicity is also called methanol wettability and is the methanol concentration (volume %) at which the powder disperses completely in an aqueous methanol solution under stirring. The higher the value, the higher the hydrophobicity.

[0077] (A-2) Hydrophobic treated silica is a fine powder with a specific surface area of ​​100 m2 by BET method. 2 / g or more is preferred, and more preferably 100 to 500m 2 / g, more preferably 150 to 400m 2 / g.

[0078] The present invention further provides an aqueous dispersion of silicone rubber particles, comprising 100 parts by mass of the above-mentioned (A) silicone rubber particles, 0.1 to 20 parts by mass of (B) a nonionic surfactant having an HLB of 1.0 to 12.0, and 5 to 2,000 parts by mass of (C) water.

[0079] (B) Nonionic surfactant The (B) nonionic surfactant functions as a dispersant for the (A) silicone rubber particles and also as an emulsifier for the mixture of organopolysiloxane, silane, and hydrophobized silica in the production of the (A) silicone rubber particle aqueous dispersion, which will be described later.

[0080] Component (B) has an HLB value of 1.0 to 12.0, preferably 3.0 to 11.5, more preferably 6.0 to 11.0, and even more preferably 6.5 to 10.5. If the HLB value exceeds 12.0, the dispersion stability of the silicone rubber particles (A) decreases. Furthermore, emulsification may not be possible during the emulsification process of the mixture of organopolysiloxane, silane, and hydrophobized silica, or the silicone rubber particles obtained by curing the organopolysiloxane and silane may aggregate. When two or more nonionic surfactants are used in combination, the average HLB value should be in the range of 1.0 to 12.0, preferably 3.0 to 11.5, more preferably 6.0 to 11.0, and even more preferably 6.5 to 10.5. A nonionic surfactant with an HLB value of greater than 12.0 may also be included. In this case, the HLB value should be 15.0 or less, preferably 13.0 or less, and even more preferably 12.5 or less. The HLB value in the present invention is calculated by the following formula: HLB = [molecular weight of polyoxyethylene portion and alcohol portion / molecular weight of surfactant] x 20 When two or more nonionic surfactants with different HLB values ​​are used in combination, the HLB value is a weighted average value.

[0081] Examples of nonionic surfactants having the above HLB include polyoxyethylene alkyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyethylene glycol fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbit fatty acid esters, glycerin fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyglycerin fatty acid esters, propylene glycol fatty acid esters, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, polyoxyethylene hydrogenated castor oil fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene fatty acid amides, polyoxyethylene-modified organopolysiloxanes, polyoxyethylene polyoxypropylene-modified organopolysiloxanes, etc. These can be used alone or in appropriate combinations of two or more.

[0082] The amount of (B) nonionic surfactant is 0.1 to 20 parts by mass, preferably 1 to 18 parts by mass, and more preferably 3 to 15 parts by mass, per 100 parts by mass of (A) silicone rubber particles. If the amount of nonionic surfactant is less than the above lower limit, the dispersion stability of the (A) silicone rubber particles decreases. Furthermore, during the emulsification process of the curable liquid silicone composition containing silica, emulsification may fail or the resulting silicone rubber particles may aggregate. Furthermore, if the amount of nonionic surfactant is greater than the above upper limit, the water dispersion performance of the (A) silicone rubber particles will not be improved, and in applications such as paints and coating agents, the physical properties of the coating film may be reduced.

[0083] (D) Water-soluble polymer The aqueous dispersion of the present invention may further contain a water-soluble polymer (D). The water-soluble polymer (D) functions as an aid to the dispersibility and emulsification of component (B), and also increases the viscosity of the aqueous dispersion, thereby inhibiting the settling of the silicone rubber particles (A).

[0084] Examples of component (D) include natural water-soluble polymers such as gum arabic, tragacanth gum, galactan, guar gum, carob gum, karaya gum, carrageenan, pectin, agar, quince seed, algae colloid (cassow extract), starch (rice, corn, potato, wheat), and plant-based polymers such as glycyrrhizic acid; microbial polymers such as xanthan gum, dextran, succinoglucan, and pullulan; and animal-based polymers such as collagen, casein, albumin, and gelatin; starch-based polymers such as carboxymethyl starch and methylhydroxypropyl starch; methylcellulose, nitrocellulose, ethylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, sodium cellulose sulfate, and hydroxypropylcellulose. Examples include semi-synthetic water-soluble polymers such as cellulose-based polymers such as cellulose, sodium carboxymethylcellulose (CMC), crystalline cellulose, and cellulose powder; alginate-based polymers such as sodium alginate and propylene glycol alginate; vinyl-based polymers such as polyvinyl alcohol, polyvinyl methyl ether, polyvinylpyrrolidone, carboxyvinyl polymer, and alkyl-modified carboxyvinyl polymer; polyoxyethylene-based polymers such as polyethylene glycol 1500, 4000, and 6000; polyoxyethylene-polyoxypropylene copolymer-based polymers; acrylic polymers such as sodium polyacrylate, polyethyl acrylate, and polyacrylamide; polyethyleneimine; and synthetic water-soluble polymers such as cationic polymers.

[0085] The amount of (D) water-soluble polymer is 0 to 5 parts by mass, preferably 0.05 to 5 parts by mass, more preferably 0.05 to 3 parts by mass, and even more preferably 0.1 to 1.5 parts by mass, per 100 parts by mass of component (A). If the amount is more than the upper limit, the viscosity of the dispersion becomes too high, making it difficult to handle.

[0086] (C)Water Water is a dispersion medium for the silicone rubber particles. The amount of water in the aqueous dispersion is 5 to 2,000 parts by mass, and preferably 10 to 100 parts by mass, per 100 parts by mass of the (A) silicone rubber particles.

[0087] In addition to the above components (A) to (D), various additives can be blended into the aqueous dispersion of silica-containing silicone rubber particles of the present invention, as needed. Examples include preservatives, pH adjusters, antioxidants, colorants, etc. Anionic surfactants, cationic surfactants, and amphoteric surfactants are preferably not blended in the production method described below, as they may not be able to be emulsified, may produce aggregates during the curing reaction, or may destroy the emulsion.

[0088] [Method for producing aqueous dispersion of silica-containing silicone rubber particles] The aqueous dispersion of silica-containing silicone rubber particles of the present invention is produced by a method comprising the following steps (i) to (iii). (i) mixing 100 parts by mass of at least one curable organosilicon compound selected from organopolysiloxanes and silanes with 1 to 50 parts by mass of (A-2) hydrophobized silica; (ii) adding 0.1 to 20 parts by mass of (B) a nonionic surfactant having an HLB of 1.0 to 12.0, 5 to 2,000 parts by mass of (C) water, and optionally 0.05 to 5 parts by mass of (D) a water-soluble polymer to the mixture obtained in (i) and emulsifying the mixture to obtain an oil-in-water emulsion; and (iii) A step of curing the curable organosilicon compound in the oil-in-water emulsion to obtain an aqueous dispersion of silicone rubber particles.

[0089] To mix the organopolysiloxane and silane with the hydrophobic treated silica, kneaders such as a gate mixer, kneader, pressure kneader, twin-screw kneader or intensive mixer, or stirrers such as a homodisper or homomixer can be used.

[0090] The mixing may be carried out at room temperature (e.g., 1 to 30°C), but may also be carried out under heating at a temperature of less than 200°C. The above-mentioned organosilicon compound for hydrophobizing the silica or an alkaline catalyst for the hydrophobizing treatment may also be added. When an alkaline catalyst is added, a neutralizing agent may be added after the mixing treatment to carry out a neutralization reaction, if necessary.

[0091] (A-2) Colloidal silica, in which silica is dispersed in water, cannot be used in place of hydrophobized silica. Because the dispersion medium is water, such colloidal silica does not mix with organopolysiloxane and silane. Furthermore, even if the above colloidal silica is added in the process of emulsifying organopolysiloxane and silane, the silica is hydrophilic and therefore does not enter the organopolysiloxane and silane.

[0092] The nonionic surfactant (B) used for emulsification has an HLB of 1.0 to 12.0, preferably 3.0 to 11.5, more preferably 6.0 to 11.0, and even more preferably 6.5 to 10.5. It is preferable not to use anionic surfactants, cationic surfactants, or amphoteric surfactants during emulsification. Emulsification can be carried out using a general emulsifying / dispersing machine. Examples of such machines include a high-speed rotation centrifugal radial mixer such as a Homodisper; a high-speed rotation shear mixer such as a Homomixer; a high-pressure jet emulsifying / dispersing machine such as a homogenizer; a colloid mill; and an ultrasonic emulsifier.

[0093] The curing catalyst and radical generator may be mixed with the organopolysiloxane and silane in advance in the above step (i), or may be added after the oil-in-water emulsion is obtained in the above step (ii). When the silicone rubber particles contain other components such as non-functional silicone oil, inorganic powder (excluding silica), organic powder, and antioxidants, they are preferably mixed with the organopolysiloxane and silane in step (i). The amounts of these components may be adjusted as appropriate within a range that does not impair the properties of the silicone rubber particles of the present invention.

[0094] In the method of blending a curing catalyst or radical generator after preparing an emulsion (step (ii) above), if the curing catalyst or radical generator has poor water dispersibility, it is preferable to add it to the emulsion in a state dissolved in a surfactant or to add it in the form of an emulsion with a surfactant. The surfactant used here is preferably nonionic and, more preferably, has a high HLB. The HLB and amount of the nonionic surfactant used in emulsifying the mixture of organopolysiloxane, silane, and hydrophobized silica must be set so that the average HLB of the surfactant is in the range of 1.0 to 12.0. The average HLB is preferably in the range of 3.0 to 11.5, more preferably 6.0 to 11.0, and even more preferably 6.5 to 10.5. If the average HLB is greater than 12.0, the silicone may aggregate or the emulsion may break down during the curing reaction. When a nonionic surfactant having an HLB of more than 12.0 is used, its HLB is preferably 15.0 or less, more preferably 13.0 or less, and even more preferably 12.5 or less.

[0095] In the above step (iii), when curing is performed by an addition reaction or a condensation reaction, the reaction may be carried out at room temperature (1 to 30°C), but if the reaction does not go to completion, it may be carried out under heating at less than 100°C.

[0096] In the above step (iii), when curing is performed by a radical reaction, heating at less than 100°C is sufficient if a redox initiator is used, and irradiation with light such as ultraviolet light is sufficient if a photopolymerization initiator is used.

[0097] [Method of manufacturing silica-containing silicone rubber particles] The silica-containing silicone rubber particles of the present invention can be obtained by removing water from the aqueous dispersion of silica-containing silicone rubber particles obtained in the above step (step (iv)).

[0098] The removal of water can be carried out, for example, by heating the aqueous dispersion under normal pressure or reduced pressure to volatilize it. More specifically, examples include a method in which the dispersion is left standing under heating to remove the water, a method in which the dispersion is removed while being stirred and fluidized under heating, a method in which the dispersion is sprayed and dispersed in a hot air current as in a spray dryer, and a method using a fluidized heat medium. As a pretreatment for this operation, the particles may be agglomerated by adding an inorganic salt or the like, and then concentrated by a method such as filtration separation by pressure filtration, centrifugation, decantation, or the like, and if necessary, the concentrate may be washed with water, alcohol, or the like. [Example]

[0099] EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the examples, the kinematic viscosity is a value measured at 25°C using a capillary viscometer, and "%" representing concentration and content indicates "% by mass".

[0100] [Example 1] The kinematic viscosity shown by the following average formula (23) is 55 mm 2 / s vinyl group-containing dimethylpolysiloxane 186 g (a-1), kinematic viscosity represented by the following average formula (24) 30 mm 2 / s methylhydrogenpolysiloxane 30g (b-1, blending amount of 1.14 SiH groups per vinyl group), [ka] [ka] and hydrophobic silica (A-2-1, specific surface area by BET method: 300 m) prepared by treating dry silica with hexamethyldisilazane. 2 24 g (11.1 parts by mass per 100 parts by mass of the resulting silicone rubber) of 100% propylene glycol acrylate (0.15 g, hydrophobicity 60) were placed in a 1-liter glass beaker and mixed by stirring at 2,000 rpm using a homomixer. Next, the mixture was treated with Sannonik SS-30 (B-1, product name, manufactured by Sanyo Chemical Industries, Ltd., polyoxyethylene alkyl (C 12 H 25 ~C 14 H 29 A mixture of 20 g of cellulose ether (HLB=8.0) and 3 g of Cellogen WS-C (D-1, trade name, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., sodium carboxymethylcellulose) (1.3 parts by weight per 100 parts by weight of the resulting silicone rubber particles) was added to 300 g of water and stirred at 6,000 rpm using a homomixer. The mixture became oil-in-water and thickened. Stirring was continued for another 15 minutes. Next, while stirring at 2,000 rpm, 436 g of water (307 parts by weight of water per 100 parts by weight of the resulting silicone rubber particles) was added, resulting in a uniform white oil-in-water emulsion. This emulsion was transferred to a 1-liter glass flask equipped with an anchor-type stirring blade stirrer, and the temperature was adjusted to 20-25°C. After that, a mixed solution of 0.5 g of an isododecane solution of a platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) and 1.0 g of Finesurf TD-70 (B-2, trade name, manufactured by Aoki Oil & Fat Industries Co., Ltd., polyoxyethylene tridecyl ether, HLB=12.0) was added with stirring, and the mixture was stirred at the same temperature for 5 hours to obtain an aqueous dispersion of silica-containing silicone rubber particles. The average HLB of the nonionic surfactant (B) in the aqueous dispersion is 8.2. The amount of the nonionic surfactant is 8.8 parts by mass per 100 parts by mass of the silicone rubber particles.

[0101] When the aqueous dispersion was filtered through a 100 mesh screen, the amount of silica-containing silicone rubber particles retained (ie, the amount of agglomerates) was less than 1.0% of the total amount filtered.

[0102] The shape of the silica-containing silicone rubber particles in the aqueous dispersion was observed under an optical microscope and was found to be spherical, and the volume average particle size was measured using a particle size distribution analyzer "Multisizer 3" (trade name, manufactured by Beckman Coulter, Inc.) and was found to be 6 μm.

[0103] The hardness of the silica-containing silicone rubber constituting the silica-containing silicone rubber particles was measured as follows. The same vinyl group-containing dimethylpolysiloxane (a-1), methylhydrogenpolysiloxane (b-1), hydrophobic treated silica (A-2-1), and an isododecane solution of platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) were mixed in the above-mentioned ratio and poured into an aluminum petri dish to a thickness of 10 mm. After leaving it at 25°C for 24 hours, it was heated in a thermostatic chamber at 50°C for 1 hour to obtain a non-sticky silica-containing silicone rubber. The hardness of this silicone rubber was measured using a Type A durometer specified in JIS K6253 and was found to be 62.

[0104] The tensile strength at break and elongation at break of the silica-containing silicone rubber that constitutes the silica-containing silicone rubber particles were measured as follows. The same vinyl group-containing dimethylpolysiloxane (a-1), methylhydrogenpolysiloxane (b-1), hydrophobic treated silica (A-2-1), and an isododecane solution of platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) were mixed in the above-mentioned ratio and poured into a polypropylene tray to a thickness of approximately 1 mm. After leaving the sheet at 25°C for 24 hours, it was heated in a constant temperature bath at 50°C for 1 hour to obtain a non-sticky silica-containing silicone rubber sheet. This silicone rubber sheet was cut to the shape and dimensions of a dumbbell-shaped No. 3 test piece specified in JIS K6251, and the tensile strength at break and elongation at break were measured according to the methods specified in JIS K6251, finding values ​​of 1.4 MPa and 52%, respectively.

[0105] [Examples 2 to 8] In Example 1, the nonionic surfactant (Sanonic SS-30) used to emulsify the mixture of vinyl group-containing dimethylpolysiloxane (a-1), methylhydrogenpolysiloxane (b-1), and hydrophobic treated silica (A-2-1) was replaced with the nonionic surfactant shown in Table 1, and the steps of Example 1 were repeated to obtain an aqueous dispersion of silica-containing silicone rubber particles.

[0106] The resulting aqueous dispersion of silicone rubber particles was evaluated in the same manner as in Example 1. The average HLB of the nonionic surfactant (B) in the aqueous dispersion is shown in Table 1, and the amount of silica-containing silicone rubber particles retained when the aqueous dispersion was filtered through a 100-mesh screen (i.e., the amount of aggregates) is shown in Table 4. Table 4 also shows the results of observing the shape of the silica-containing silicone rubber particles in the aqueous dispersion and the results of measuring the volume average particle size.

[0107] [Examples 9 to 10] In Example 1, the 30 g of water-soluble polymer (Cellogen WS-C) used to emulsify the mixture of vinyl group-containing dimethylpolysiloxane (a-1), methylhydrogenpolysiloxane (b-1), and hydrophobic treated silica (A-2-1) was replaced with the water-soluble polymer and amount shown in Table 1, and the steps of Example 1 were repeated to obtain an aqueous dispersion of silica-containing silicone rubber particles. In the table, D-2 is hydroxypropyl methylcellulose (Metolose 60SH-10000, manufactured by Shin-Etsu Chemical Co., Ltd.).

[0108] The resulting aqueous dispersion of silicone rubber particles was evaluated in the same manner as in Example 1. The average HLB of the nonionic surfactant (B) in the aqueous dispersion is shown in Table 1, and the amount of silica-containing silicone rubber particles retained when the dispersion was filtered through a 100-mesh screen is shown in Table 4. Table 4 also shows the results of observing the shape of the silica-containing silicone rubber particles and the results of measuring the volume-average particle size.

[0109] [Example 11] The kinematic viscosity shown by the average formula (23) is 55 mm 2 / s, 165 g (a-1) of a vinyl group-containing dimethylpolysiloxane having a kinematic viscosity of 30 mm 2 27 g of methylhydrogenpolysiloxane (b-1, blending amount of 1.15 SiH groups per vinyl group) with 27 g of methylhydrogenpolysiloxane (b-1, blending amount of 1.15 SiH groups per vinyl group) and hydrophobic treated silica (A-2-1, specific surface area by BET method 300 m) prepared by treating dry silica with hexamethyldisilazane. 2 48 g (25.0 parts by mass per 100 parts by mass of the resulting silicone rubber) of 10.5 g of silicone rubber (H2O3 / g, hydrophobicity 60) was charged into a gate mixer and mixed until uniform. The resulting mixture was treated with Sannonik SS-30 (B-1, product name, manufactured by Sanyo Chemical Industries, Ltd., polyoxyethylene alkyl (C 12 H 25 ~C 14 H 29 A mixture of 20 g of cellulose ether (HLB=8.0) and 3 g of Cellogen WS-C (D-1, trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., sodium carboxymethylcellulose) (1.3 parts by weight per 100 parts by weight of the resulting silicone rubber particles) and 600 g of water was placed in a 1-liter glass beaker and stirred at 6,000 rpm using a homomixer. The mixture became oil-in-water and thickened. Stirring was continued for another 15 minutes. Next, while stirring at 2,000 rpm, 136 g of water (307 parts by weight of water per 100 parts by weight of the resulting silicone rubber particles) was added, resulting in a uniform white oil-in-water emulsion. This emulsion was transferred to a 1-liter glass flask equipped with an anchor-type impeller stirrer and adjusted to 20-25°C. After adjusting the temperature, a mixture of 0.5 g of an isododecane solution of a platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) and 1.0 g of Finesurf TD-70 (B-2, product name, manufactured by Aoki Oil & Fat Industries Co., Ltd., polyoxyethylene tridecyl ether, HLB=12.0) was added with stirring and stirred for 5 hours at the same temperature to obtain an aqueous dispersion of silica-containing silicone rubber particles. The average HLB of the nonionic surfactant (B) in the aqueous dispersion was 8.2. The amount of nonionic surfactant was 8.8 parts by weight per 100 parts by weight of silicone rubber particles.

[0110] When the aqueous dispersion was filtered through a 100 mesh screen, the amount of silica-containing silicone rubber particles retained (ie, the amount of agglomerates) was less than 1.0% by weight of the total amount filtered. The shape of the silica-containing silicone rubber particles in the aqueous dispersion was observed under an optical microscope and was found to be spherical, and the volume average particle size was measured using a particle size distribution analyzer "Multisizer 3" (trade name, manufactured by Beckman Coulter, Inc.) and was found to be 3 μm.

[0111] The hardness of the silica-containing silicone rubber constituting the silica-containing silicone rubber particles was measured as follows. The same vinyl group-containing dimethylpolysiloxane (a-1), methylhydrogenpolysiloxane (b-1), hydrophobic treated silica (A-2-1), and an isododecane solution of platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) were mixed in the above-mentioned ratio and poured into an aluminum petri dish to a thickness of 10 mm. After leaving it at 25°C for 24 hours, it was heated in a thermostatic chamber at 50°C for 1 hour to obtain a non-sticky silica-containing silicone rubber. The hardness of this silicone rubber was measured using a Type A durometer specified in JIS K6253 and was found to be 71.

[0112] The tensile strength at break and elongation at break of the silica-containing silicone rubber that constitutes the silica-containing silicone rubber particles were measured as follows. The same vinyl group-containing dimethylpolysiloxane (a-1), methylhydrogenpolysiloxane (b-1), hydrophobic treated silica (A-2-1), and an isododecane solution of platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) were mixed in the above-mentioned ratio and poured into a polypropylene tray to a thickness of approximately 1 mm. After leaving the sheet at 25°C for 24 hours, it was heated in a constant temperature bath at 50°C for 1 hour to obtain a non-sticky silica-containing silicone rubber sheet. This silicone rubber sheet was cut to the shape and dimensions of a dumbbell-shaped No. 3 test piece specified in JIS K6251, and the tensile strength at break and elongation at break were measured according to the methods specified in JIS K6251, finding values ​​of 1.9 MPa and 54%, respectively.

[0113] [Example 12] The kinematic viscosity shown by the average formula (23) is 55 mm 2 / s, 196 g (a-1) of a vinyl group-containing dimethylpolysiloxane having a kinematic viscosity of 30 mm 2 32 g of methylhydrogenpolysiloxane (b-1, blending amount of 1.15 SiH groups per vinyl group) with 1,3-divinyl-1,1,3,3-tetramethyldisilazane (A-2-2, specific surface area by BET method 300 m) was used. 2 12 g (5.3 parts by mass per 100 parts by mass of the resulting silicone rubber) of 100% propylene glycol acrylate (1.0 g / g, hydrophobicity 55) were placed in a 1-liter glass beaker and mixed by stirring at 2,000 rpm using a homomixer. Next, Sannonik SS-30 (B-1, product name, manufactured by Sanyo Chemical Industries, Ltd., polyoxyethylene alkyl (C 12 H 25 ~C 14 H 29A mixture of 20 g of cellulose ether (HLB=8.0) and 3 g of Cellogen WS-C (D-1, trade name, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., sodium carboxymethylcellulose) (1.3 parts by weight per 100 parts by weight of the resulting silicone rubber particles) was added to 300 g of water and stirred at 6,000 rpm using a homomixer. The mixture became oil-in-water and thickened. Stirring was continued for another 15 minutes. Next, while stirring at 2,000 rpm, 436 g of water (307 parts by weight of water per 100 parts by weight of the resulting silicone rubber particles) was added, resulting in a uniform white oil-in-water emulsion. This emulsion was transferred to a 1-liter glass flask equipped with an anchor-type impeller stirrer and adjusted to 20-25°C. After adjusting the temperature, a mixture of 0.5 g of an isododecane solution of platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) and 1.0 g of Finesurf TD-70 (B-2, product name, manufactured by Aoki Oil & Fat Industries Co., Ltd., polyoxyethylene tridecyl ether, HLB=12.0) was added and stirred at the same temperature for 5 hours to obtain an aqueous dispersion of silica-containing silicone rubber particles. The average HLB value of the nonionic surfactant in the aqueous dispersion was 8.2. The amount of nonionic surfactant was 8.8 parts by weight per 100 parts by weight of silicone rubber particles.

[0114] When the aqueous dispersion was filtered through a 100 mesh screen, the amount of silica-containing silicone rubber particles retained (ie, the amount of agglomerates) was less than 1.0% by weight of the total amount filtered. The shape of the silica-containing silicone rubber particles in the aqueous dispersion was observed under an optical microscope and was found to be spherical. The volume average particle size was measured using a particle size distribution analyzer "Multisizer 3" (trade name, manufactured by Beckman Coulter, Inc.) and was found to be 7 μm.

[0115] The hardness of the silica-containing silicone rubber constituting the silica-containing silicone rubber particles was measured as follows. The same vinyl group-containing dimethylpolysiloxane (a-1), methylhydrogenpolysiloxane (b-1), hydrophobic treated silica (A-2-2), and an isododecane solution of platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) were mixed in the above-mentioned ratio and poured into an aluminum petri dish to a thickness of 10 mm. After leaving it at 25°C for 24 hours, it was heated in a thermostatic chamber at 50°C for 1 hour to obtain a non-sticky silica-containing silicone rubber. The hardness of this silicone rubber was measured using a Type A durometer specified in JIS K6253 and was found to be 57.

[0116] The tensile strength at break and elongation at break of the silica-containing silicone rubber that constitutes the silica-containing silicone rubber particles were measured as follows. The same vinyl group-containing dimethylpolysiloxane (a-1), methylhydrogenpolysiloxane (b-1), hydrophobic treated silica (A-2-2), and an isododecane solution of platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) were mixed in the above-mentioned ratio and poured into a polypropylene tray to a thickness of approximately 1 mm. After leaving the sheet at 25°C for 24 hours, it was heated in a constant temperature bath at 50°C for 1 hour to obtain a non-sticky silica-containing silicone rubber sheet. This silicone rubber sheet was cut to the shape and dimensions of a dumbbell-shaped No. 3 test piece specified in JIS K6251, and the tensile strength at break and elongation at break were measured according to the methods specified in JIS K6251, finding values ​​of 1.2 MPa and 48%, respectively.

[0117] [Example 13] The kinematic viscosity is 690 mm, as shown by the average formula (25) below. 2 / s hydroxyl group-containing dimethylpolysiloxane 205g (c-1), [ka] 11 g of phenyltriethoxysilane (d-1, a blending amount that gives 6.7 ethoxy groups per hydroxyl group) and hydrophobic treated silica (A-2-1, specific surface area by BET method 300 m) prepared by treating dry silica with hexamethyldisilazane were used. 2 24 g (11.4 parts by mass per 100 parts by mass of the resulting silicone rubber) of 100% propylene glycol acrylate (w / g, hydrophobicity 60) was charged into a gate mixer and mixed until uniform. The resulting mixture was treated with Sannonik SS-30 (B-1, product name, manufactured by Sanyo Chemical Industries, Ltd., polyoxyethylene alkyl (C 12 H 25 ~C 14 H 29 A mixture of 20 g of cellulose ether (HLB=8.0) and 3 g of Cellogen WS-C (D-1, product name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., sodium carboxymethylcellulose) (1.4 parts by weight per 100 parts by weight of the resulting silicone rubber particles) and 600 g of water was placed in a 1-liter glass beaker and stirred at 6,000 rpm using a homomixer. The mixture became oil-in-water and thickened, and stirring was continued for another 15 minutes. Next, while stirring at 2,000 rpm, 135 g of water (312 parts by weight of water total per 100 parts by weight of the resulting silicone rubber particles) was added, resulting in a uniform white oil-in-water emulsion. This emulsion was transferred to a 1-liter glass flask equipped with an anchor-type impeller stirrer and adjusted to 20-25°C. A mixed solution of 1.0 g of dioctyltin dilaurate and 1.0 g of Finesurf TD-70 (D-2, product name, manufactured by Aoki Oil & Fat Industries Co., Ltd., polyoxyethylene tridecyl ether, HLB=12.0) was then added, and the mixture was stirred at the same temperature for 24 hours to obtain an aqueous dispersion of silica-containing silicone rubber particles. The average HLB value of the nonionic surfactant in the aqueous dispersion was 8.2. The amount of nonionic surfactant was 10.0 parts by weight per 100 parts by weight of silicone rubber particles.

[0118] When the aqueous dispersion was filtered through a 100 mesh screen, the amount of silica-containing silicone rubber particles retained (ie, the amount of agglomerates) was less than 1.0% by weight of the total amount filtered. The shape of the silica-containing silicone rubber particles in the aqueous dispersion was observed under an optical microscope and was found to be spherical, and the volume average particle size was measured using a particle size distribution analyzer "Multisizer 3" (trade name, manufactured by Beckman Coulter, Inc.) and was found to be 4 μm.

[0119] The hardness of the silica-containing silicone rubber constituting the silica-containing silicone rubber particles was measured as follows. The same hydroxyl-containing dimethylpolysiloxane (c-1), phenyltriethoxysilane (d-1), hydrophobic treated silica (A-2-1), and dioctyltin dilaurate as above were mixed in the ratios described above and poured into an aluminum petri dish to a thickness of 10 mm. After leaving at 25°C for 48 hours, it was heated in a thermostatic chamber at 50°C for 1 hour to obtain a non-sticky silica-containing silicone rubber. The hardness of this silicone rubber was measured using a Type A durometer specified in JIS K6253 and found to be 40.

[0120] The tensile strength at break and elongation at break of the silica-containing silicone rubber that constitutes the silica-containing silicone rubber particles were measured as follows. The same hydroxyl group-containing dimethylpolysiloxane (c-1), phenyltriethoxysilane (d-1), hydrophobic treated silica (A-2-1), and dioctyltin dilaurate as above were mixed in the above-mentioned ratio and poured into a polypropylene tray to a thickness of approximately 1 mm. After leaving the sheet at 25°C for 48 hours, it was heated in a constant temperature bath at 50°C for 1 hour to obtain a non-sticky silica-containing silicone rubber sheet. This silicone rubber sheet was cut to the shape and dimensions of a dumbbell-shaped No. 3 test piece specified in JIS K6251, and the tensile strength at break and elongation at break were measured according to the methods specified in JIS K6251, finding values ​​of 1.2 MPa and 190%, respectively.

[0121] [Example 14] The kinematic viscosity shown by the following average formula (26) is 180 mm 2 / s 216 g (e-1) of methacryloyl group-containing dimethylpolysiloxane, [ka] Hydrophobic treated silica (A-2-3, specific surface area by BET method: 200 m) prepared by treating dry silica with dimethyldichlorosilane 2 24 g (11.1 parts by mass per 100 parts by mass of the resulting silicone rubber) of 2-hydroxy-2-methyl-1-phenyl-propan-1-one (1 / g, hydrophobicity 48) was placed in a gate mixer and mixed until uniform. The resulting mixture was treated with Sannonik SS-30 (B-1, product name, manufactured by Sanyo Chemical Industries, Ltd., polyoxyethylene alkyl (C 12 H 25 ~C 14 H 29 A mixture of 20 g of cellulose ether (HLB=8.0) (8.3 parts by weight per 100 parts by weight of the resulting silicone rubber particles) and 3 g of Cellogen WS-C (D-1, trade name, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., sodium carboxymethylcellulose) (1.3 parts by weight per 100 parts by weight of the resulting silicone rubber particles) and 600 g of water (C) was placed in a 1-liter glass beaker and stirred at 6,000 rpm using a homomixer. The mixture became oil-in-water and thickened. Stirring was continued for another 15 minutes. Next, while stirring at 2,000 rpm, 135 g of water (306 parts by weight per 100 parts by weight of the resulting silicone rubber particles) was added, resulting in a uniform white oil-in-water emulsion. This emulsion was transferred to a 1-liter glass flask equipped with an anchor-type stirring blade stirrer, and after adjusting the temperature to 20-25°C, the probe of an LED light source for photochemical reactions (356 nm wavelength, 507 mW) was inserted into the emulsion and irradiation began. Irradiation was continued while stirring at the same temperature for 4 hours, yielding an aqueous dispersion of silica-containing silicone rubber particles.

[0122] When the aqueous dispersion was filtered through a 100 mesh screen, the amount of silica-containing silicone rubber particles retained (ie, the amount of agglomerates) was less than 1.0% by weight of the total amount filtered. The shape of the silica-containing silicone rubber particles in the aqueous dispersion was observed under an optical microscope and was found to be spherical, and the volume average particle size was measured using a particle size distribution analyzer "Multisizer 3" (trade name, manufactured by Beckman Coulter, Inc.) and was found to be 4 μm.

[0123] The hardness of the silica-containing silicone rubber constituting the silica-containing silicone rubber particles was measured as follows. The same methacryloyl group-containing dimethylpolysiloxane (e-1), hydrophobized silica (A-2-3), and 2-hydroxy-2-methyl-1-phenyl-propan-1-one as above were mixed in the ratios described above and poured into an aluminum dish to a thickness of 10 mm. Irradiation was performed for 5 minutes with a UV-LED irradiator (wavelength 365 nm, 154 mW) under a nitrogen atmosphere to obtain a non-sticky silica-containing silicone rubber. The hardness of this silicone rubber was measured using a Type A durometer specified in JIS K6253, and was found to be 48.

[0124] The tensile strength at break and elongation at break of the silica-containing silicone rubber that constitutes the silica-containing silicone rubber particles were measured as follows. The same methacryloyl group-containing dimethylpolysiloxane (e-1), hydrophobized silica (A-2-3), and 2-hydroxy-2-methyl-1-phenyl-propan-1-one as above were mixed in the ratios described above and poured into a polypropylene tray to a thickness of approximately 1 mm. Under a nitrogen atmosphere, the mixture was irradiated with a UV-LED irradiator (365 nm wavelength, 154 mW) for 5 minutes to produce a non-sticky silica-containing silicone rubber sheet. This silicone rubber sheet was cut to the shape and dimensions of a dumbbell-shaped No. 3 test piece specified in JIS K6251. The tensile strength and elongation at break were measured according to the methods specified in JIS K6251 and found to be 1.5 MPa and 190%, respectively.

[0125] [Comparative Example 1] The kinematic viscosity shown by the average formula (23) is 55 mm 2186 g of vinyl group-containing dimethylpolysiloxane (a-1) having a kinematic viscosity of 30 mm / s, represented by the average formula (24) above 2 30 g of methylhydrogenpolysiloxane (b-1, blending amount of 1.14 SiH groups per vinyl group) with 1000 kJ / s (A-2-1, specific surface area of ​​300 m2 measured by BET method) and hydrophobic treated silica (A-2-1, specific surface area of ​​300 m2 measured by BET method) prepared by treating dry silica with hexamethyldisilazane. 2 24 g (11.1 parts by mass per 100 parts by mass of the resulting silicone rubber) of 100% propylene glycol acrylate (1.2 g, hydrophobicity 60) were placed in a 1-liter glass beaker and mixed by stirring at 2,000 rpm using a homomixer. Next, the mixture was treated with Sannonik SS-70 (B-10, product name, manufactured by Sanyo Chemical Industries, Ltd., polyoxyethylene alkyl (C 12 H 25 ~C 14 H 29 A mixture of 20 g of ether (HLB=12.1) and 3 g of Cellogen WS-C (D-1, trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., sodium carboxymethylcellulose) and 300 g of water (C) was added and stirred at 6,000 rpm using a homomixer. The mixture became oil-in-water and thickened. Stirring was continued for an additional 15 minutes. Next, 436 g of water was added while stirring at 2,000 rpm, resulting in a uniform white oil-in-water emulsion. This emulsion was transferred to a 1-liter glass flask equipped with an anchor-type stirring blade stirrer, and the temperature was adjusted to 20-25°C. Then, with stirring, a mixed solution of 0.5 g of an isododecane solution of a platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) and 1.0 g of Finesurf TD-70 (B-2, trade name, manufactured by Aoki Oil & Fat Industries Co., Ltd., polyoxyethylene tridecyl ether, HLB=12.0) was added. Stirring was continued at the same temperature, and after a while, the emulsion particles began to aggregate and the emulsion was destroyed.

[0126] Comparative Example 2 The kinematic viscosity shown by the average formula (23) is 55 mm 2 / s, 186 g (a-1) of a vinyl group-containing dimethylpolysiloxane having a kinematic viscosity of 30 mm2 30 g of methylhydrogenpolysiloxane (b-1, blending amount of 1.14 SiH groups per vinyl group) with 1000 kJ / s (A-2-1, specific surface area of ​​300 m2 measured by BET method) and hydrophobic silica (A-2-1, specific surface area of ​​300 m2 measured by BET method) prepared by treating dry silica with hexamethyldisilazane. 2 24 g (11.1 parts by mass per 100 parts by mass of the resulting silicone rubber) of 100% propylene glycol acrylate (1.2 g, hydrophobicity 60) were placed in a 1-liter glass beaker and mixed by stirring at 2,000 rpm using a homomixer. Next, to the mixture was added a mixture of 22 g of Tergitol TMN-6 <90% aqueous solution> (B-11, trade name, manufactured by Dow Chemical Japan, Ltd., 90% aqueous solution of polyoxyethylene trimethyl nonyl ether, HLB=13.1) and 3 g of Cellogen WS-C (D-1, trade name, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., sodium carboxymethyl cellulose), and 298 g of water, and the mixture was stirred at 6,000 rpm using a homomixer. However, the mixture of polysiloxane and hydrophobic treated silica did not disperse at all in the water and could not be emulsified.

[0127] Comparative Example 3 The kinematic viscosity shown by the average formula (23) is 55 mm 2 / s, 186 g (a-1) of a vinyl group-containing dimethylpolysiloxane having a kinematic viscosity of 30 mm 2 30 g of methylhydrogenpolysiloxane (b-1, blending amount of 1.14 SiH groups per vinyl group) with 1000 kJ / s (A-2-1, specific surface area of ​​300 m2 measured by BET method) and hydrophobic silica (A-2-1, specific surface area of ​​300 m2 measured by BET method) prepared by treating dry silica with hexamethyldisilazane. 2 24 g (11.1 parts by mass per 100 parts by mass of the resulting silicone rubber) of 100% propylene glycol acrylate (1.2 g, hydrophobicity 60) were placed in a 1-liter glass beaker and mixed by stirring at 2,000 rpm using a homomixer. Next, a mixture of 20 g of Emulgen 123P (B-12, trade name, manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB=16.9) and 3 g of Cellogen WS-C (D-1, trade name, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., sodium carboxymethylcellulose) and 300 g of water was added to the mixture, and the mixture was stirred at 6,000 rpm using a homomixer. However, the mixture of polysiloxane and hydrophobic treated silica did not disperse at all in the water and could not be emulsified.

[0128] Comparative Example 4 The kinematic viscosity shown by the average formula (23) is 55 mm 2 / s, 186 g (a-1) of a vinyl group-containing dimethylpolysiloxane having a kinematic viscosity of 30 mm 2 30 g of methylhydrogenpolysiloxane (b-1, blending amount of 1.14 SiH groups per vinyl group) with 1000 kJ / s (A-2-1, specific surface area of ​​300 m2 measured by BET method) and hydrophobic silica (A-2-1, specific surface area of ​​300 m2 measured by BET method) prepared by treating dry silica with hexamethyldisilazane. 2 24 g (11.1 parts by mass per 100 parts by mass of the resulting silicone rubber) of 100% propylene glycol acrylate (1.2 g, hydrophobicity 60) were placed in a 1-liter glass beaker and mixed by stirring at 2,000 rpm using a homomixer. Next, 20 g of Nikkol SLS (B-13, trade name, manufactured by Nikko Chemicals Co., Ltd., anionic surfactant, sodium lauryl sulfate) and 300 g of water (C) were added, and the mixture was stirred at 6,000 rpm using a homomixer. However, the mixture of polysiloxane and hydrophobic treated silica did not disperse in the water at all, and emulsification was not possible.

[0129] Comparative Example 5 The kinematic viscosity shown by the average formula (23) is 55 mm 2 / s, 186 g (a-1) of a vinyl group-containing dimethylpolysiloxane having a kinematic viscosity of 30 mm 2 30 g of methylhydrogenpolysiloxane (b-1, blending amount of 1.14 SiH groups per vinyl group) with 1000 kJ / s (A-2-1, specific surface area of ​​300 m2 measured by BET method) and hydrophobic silica (A-2-1, specific surface area of ​​300 m2 measured by BET method) prepared by treating dry silica with hexamethyldisilazane.2 24 g (11.1 parts by mass per 100 parts by mass of the resulting silicone rubber) of 100% propylene glycol acrylate (1.2 g, hydrophobicity 60) were placed in a 1-liter glass beaker and mixed by stirring at 2,000 rpm using a homomixer. Next, 67 g of Nissan Cation BB (B-14, trade name, manufactured by NOF Corporation, cationic surfactant, 30% aqueous solution of dodecyltrimethylammonium chloride) and 253 g of water were added, and the mixture was stirred at 6,000 rpm using a homomixer. However, the mixture of polysiloxane and hydrophobic treated silica did not disperse at all in the water, and emulsification was not possible.

[0130] Comparative Example 6 The kinematic viscosity shown by the average formula (23) is 55 mm 2 / s, 186 g (a-1) of a vinyl group-containing dimethylpolysiloxane having a kinematic viscosity of 30 mm 2 30 g of methylhydrogenpolysiloxane (b-1, blending amount of 1.14 SiH groups per vinyl group) with 1000 kJ / s (A-2-1, specific surface area of ​​300 m2 measured by BET method) and hydrophobic silica (A-2-1, specific surface area of ​​300 m2 measured by BET method) prepared by treating dry silica with hexamethyldisilazane. 2 24 g (11.1 parts by mass per 100 parts by mass of the resulting silicone rubber) of polysiloxane (Hydrophobicity 60) was placed in a 1-liter glass beaker and stirred at 2,000 rpm using a homomixer. Next, 65 g of Amphitol 20BS (B-15, product name, manufactured by Kao Corporation, amphoteric surfactant, 31% aqueous solution of lauryl dimethylaminoacetate betaine) and 255 g of water (C) were added and stirred at 6,000 rpm using a homomixer. The mixture of polysiloxane and hydrophobic-treated silica did not disperse at all in the water and could not be emulsified.

[0131] [Table 1]

[0132] [Table 2]

[0133] [Table 3]

[0134] [Table 4] *In Comparative Examples 2 to 6, the mixture of organopolysiloxane and hydrophobic treated silica did not disperse in water and did not emulsify.

[0135] [Example 15] The water dispersion of silica-containing silicone rubber particles obtained in Example 1 was volatilized using a spray dryer at an inlet temperature of 150°C and an outlet temperature of 80°C to obtain silica-containing silicone rubber particles. The silica-containing silicone rubber particles obtained were not sticky, and when observed under an electron microscope, they were found to be spherical. No silica was observed, which suggests that silica is present within the silicone rubber particles.

[0136] [Example 16] The water dispersion of silica-containing silicone rubber particles obtained in Example 13 was subjected to evaporation and removal of water using a spray dryer at an inlet temperature of 150°C and an outlet temperature of 80°C, yielding silica-containing silicone rubber particles. The silica-containing silicone rubber particles obtained were not sticky, and when observed under an electron microscope, they were found to be spherical. No silica was observed, which suggests that silica is present within the silicone rubber particles.

[0137] [Example 17] The water dispersion of silica-containing silicone rubber particles obtained in Example 14 was volatilized using a spray dryer at an inlet temperature of 150°C and an outlet temperature of 80°C to remove water, yielding silica-containing silicone rubber particles. The silica-containing silicone rubber particles obtained were not sticky, and when observed under an electron microscope, they were found to be spherical. No silica was observed, which suggests that silica is present within the silicone rubber particles.

[0138] As described above, the present invention uses a low HLB nonionic surfactant in the method for producing silicone rubber particles containing hydrophobized silica, which enables a mixture of organopolysiloxane and hydrophobized silica to be emulsified well in water.The silicone rubber particles of the present invention contain silica within the particles, allowing them to have high strength.

[0139] The silicone rubber particles of the present invention have high mechanical strength, and aqueous dispersions of said silicone rubber particles are useful for paints and coating agents that are subject to friction.

Claims

1. (A-1) silicone rubber particles containing 1 to 50 parts by mass of hydrophobized silica (A-2) per 100 parts by mass of silicone rubber, the silicone rubber particles having a volume average particle size of 0.5 to 100 μm and being spherical; The silicone rubber particles (A-2) are characterized in that the hydrophobized silica is hydrophobized with at least one group selected from a triorganosilyl group, a diorganosilyl group, and a monoorganosilyl group, or a partial hydrolysis condensate of an organochlorosilane, a partial hydrolysis condensate of an organoalkoxysilane, an organopolysiloxane, and an organohydrogenpolysiloxane, and has a degree of hydrophobicity of 40 or more as indicated by methanol wettability, the degree of hydrophobicity being expressed as the methanol concentration (volume %) at which the powder is completely dispersed in an aqueous methanol solution under stirring.

2. 2. The silicone rubber particles according to claim 1, wherein the silicone rubber (A-1) is a cured product obtained by an addition reaction between (a) an organopolysiloxane having alkenyl groups and (b) an organohydrogenpolysiloxane having silicon-bonded hydrogen atoms.

3. 2. The silicone rubber particles according to claim 1, wherein the silicone rubber (A-1) is a cured product obtained by a condensation reaction between (c) an organopolysiloxane having a hydroxyl group or a hydrolyzable group bonded to a silicon atom and (d) a silane having a hydrolyzable group bonded to a silicon atom.

4. 2. The silicone rubber particles according to claim 1, wherein the silicone rubber (A-1) is a radical reaction cured product of an organopolysiloxane (e) having a radical polymerization reactive group.

5. The silicone rubber particles according to any one of claims 1 to 4, wherein the hydrophobized silica is obtained by hydrophobizing hydrophilic silica with at least one silane or silazane selected from trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, trimethylalkoxysilane, dimethyldialkoxysilane, methyltrialkoxysilane, hexamethyldisilazane, and 1,3-divinyl-1,1,3,3-tetramethyldisilazane.

6. 5. The silicone rubber particles according to claim 1, wherein the silicone rubber particles have a tensile strength at break of 0.5 to 10 MPa as measured by the method specified in JIS K6251.

7. (A) (A-1) 100 parts by mass of silicone rubber particles (A-2) containing 1 to 50 parts by mass of hydrophobic treated silica per 100 parts by mass of silicone rubber; (B) a nonionic surfactant having an HLB of 1.0 to 12.0: 0.1 to 20 parts by mass, and (C) Water: 5 to 2,000 parts by mass An aqueous dispersion of silicone rubber particles comprising: the silicone rubber particles have a volume average particle size of 0.5 to 100 μm and are spherical; the hydrophobized silica is hydrophobized with at least one group selected from a triorganosilyl group, a diorganosilyl group, and a monoorganosilyl group, or a partial hydrolysis condensate of an organochlorosilane, a partial hydrolysis condensate of an organoalkoxysilane, an organopolysiloxane, and an organohydrogenpolysiloxane; and has a hydrophobicity degree of 40 or more as indicated by methanol wettability, the hydrophobicity degree being represented by the methanol concentration (volume %) at which the powder is completely dispersed in an aqueous methanol solution under stirring; The aqueous dispersion.

8. 8. The aqueous dispersion according to claim 7, wherein the silicone rubber is a cured product obtained by an addition reaction between (a) an organopolysiloxane having alkenyl groups and (b) an organohydrogenpolysiloxane having silicon-bonded hydrogen atoms.

9. 8. The aqueous dispersion according to claim 7, wherein the silicone rubber is a cured product obtained by a condensation reaction between (c) an organopolysiloxane having a hydroxyl group or a hydrolyzable group bonded to a silicon atom and (d) a silane having a hydrolyzable group bonded to a silicon atom.

10. 8. The aqueous dispersion according to claim 7, wherein the silicone rubber is a radical reaction cured product of (e) an organopolysiloxane having a radical polymerization reactive group.

11. The aqueous dispersion according to any one of claims 7 to 10, further comprising (D) a water-soluble polymer in an amount of 0.05 to 5 parts by mass per 100 parts by mass of the silicone rubber particles.

12. The aqueous dispersion according to any one of claims 7 to 10, wherein the hydrophobized silica is hydrophilic silica that has been hydrophobized with at least one silane or silazane selected from trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, trimethylalkoxysilane, dimethyldialkoxysilane, methyltrialkoxysilane, hexamethyldisilazane, and 1,3-divinyl-1,1,3,3-tetramethyldisilazane.

13. A method for producing silicone rubber particles containing hydrophobized silica, comprising the steps of: (i) mixing 100 parts by mass of at least one curable organosilicon compound selected from organopolysiloxanes and silanes with 1 to 50 parts by mass of (A-2) hydrophobized silica; (ii) adding 0.1 to 20 parts by mass of (B) a nonionic surfactant having an HLB of 1.0 to 12.0, 5 to 2,000 parts by mass of (C) water, and optionally 0.05 to 5 parts by mass of (D) a water-soluble polymer to the mixture obtained in (i) and emulsifying the mixture to obtain an oil-in-water emulsion; (iii) curing the curable organosilicon compound in the oil-in-water emulsion to obtain an aqueous dispersion of silicone rubber particles; and (iv) removing water from the aqueous dispersion obtained in step (iii) to obtain silicone rubber particles; the silicone rubber particles have a volume average particle size of 0.5 to 100 μm and are spherical; the hydrophobized silica is hydrophobized with at least one group selected from a triorganosilyl group, a diorganosilyl group, and a monoorganosilyl group, or a partial hydrolysis condensate of an organochlorosilane, a partial hydrolysis condensate of an organoalkoxysilane, an organopolysiloxane, and an organohydrogenpolysiloxane; and has a hydrophobicity degree of 40 or more as indicated by methanol wettability, the hydrophobicity degree being represented by the methanol concentration (volume %) at which the powder is completely dispersed in an aqueous methanol solution under stirring; The manufacturing method.

14. A method for producing an aqueous dispersion of silicone rubber particles containing hydrophobized silica, comprising the steps of: (i) mixing 100 parts by mass of at least one curable organosilicon compound selected from organopolysiloxanes and silanes with 1 to 50 parts by mass of (A-2) hydrophobized silica; (ii) adding 0.1 to 20 parts by mass of (B) a nonionic surfactant having an HLB of 1.0 to 12.0, 5 to 2,000 parts by mass of (C) water, and optionally 0.05 to 5 parts by mass of (D) a water-soluble polymer to the mixture obtained in (i) and emulsifying the mixture to obtain an oil-in-water emulsion; and (iii) curing the curable organosilicon compound in the oil-in-water emulsion to obtain an aqueous dispersion of silicone rubber particles; the silicone rubber particles have a volume average particle size of 0.5 to 100 μm and are spherical; the hydrophobized silica is hydrophobized with at least one group selected from a triorganosilyl group, a diorganosilyl group, and a monoorganosilyl group, or a partial hydrolysis condensate of an organochlorosilane, a partial hydrolysis condensate of an organoalkoxysilane, an organopolysiloxane, and an organohydrogenpolysiloxane; and has a hydrophobicity degree of 40 or more as indicated by methanol wettability, the hydrophobicity degree being represented by the methanol concentration (volume %) at which the powder is completely dispersed in an aqueous methanol solution under stirring; The manufacturing method.

15. The method according to claim 13 or 14, wherein the hydrophobized silica is obtained by hydrophobizing hydrophilic silica with at least one silane or silazane selected from trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, trimethylalkoxysilane, dimethyldialkoxysilane, methyltrialkoxysilane, hexamethyldisilazane, and 1,3-divinyl-1,1,3,3-tetramethyldisilazane.

16. 15. The method according to claim 13, wherein the curable organosilicon compound is (a) an organopolysiloxane having alkenyl groups and (b) an organohydrogenpolysiloxane having silicon-bonded hydrogen atoms.

17. 15. The method according to claim 13, wherein the curable organosilicon compound is (c) an organopolysiloxane having a hydroxyl group or a hydrolyzable group bonded to a silicon atom, and (d) a silane having a hydrolyzable group bonded to a silicon atom.

18. 15. The method according to claim 13, wherein the curable organosilicon compound is (e) an organopolysiloxane having a radical polymerization reactive group.

Images