Silicone rubber particles and aqueous dispersion of silicone rubber particles

Abstract

[Problem] The purpose of the present invention is to provide silicone rubber particles having high strength and elongation and a small amount of agglomerated particles, and to provide an aqueous dispersion of silicone rubber particles. [Solution] Silicone rubber particles which are spherical and have a volume average particle diameter of 0.5 [mu] m to 50 [mu] m, and which are a product of an addition reaction of a curable liquid silicone composition comprising the following components (A-1), (A-2), and (A-3). (A-1) a diorganopolysiloxane having two or more alkenyl groups in one molecule, wherein the amount of alkenyl groups is from 0.0025 mol / 100 g to 0.034 mol / 100 g; (A-2) an organopolysiloxane resin which contains R13SiO1 / 2 units and SiO4 / 2 units, in which the molar ratio of the R13SiO1 / 2 units to the SiO4 / 2 units is 0.60-1.7, and the amount of alkenyl groups is 0.001 mol / 100 g or more (in the formula, R1 groups independently represent a substituted or unsubstituted monovalent hydrocarbon group having 1-30 carbon atoms and not having an alkenyl group, or an alkenyl group having 2-8 carbon atoms, and at least one of all R1 groups is an alkenyl group); and (A-3) an organohydrogenpolysiloxane having two or more silicon atom-bonded hydrogen atoms (referred to as SiH groups) in each molecule and having an amount of 0.030 mol / 100 g to 1.30 mol / 100 g, the amount of the component (A-2) being 1.0 parts by mass to 65 parts by mass with respect to a total of 100 parts by mass of the component (A-1), the component (A-2), and the component (A-3).

Description

Technical Field

[0001] The present invention relates to silicone rubber particles having high strength and elongation and an aqueous dispersion of the silicone rubber particles. Background Art

[0002] Silicone rubber particles are used for applications such as stress relaxants for resins, light diffusers for resins, feel enhancers for cosmetics, matting agents for paints or coatings, feel enhancers, and slip enhancers.

[0003] Generally, silicone rubber particles do not contain fillers such as silica, so the rubber has low strength and small elongation. When used in paints or coating agents, the silicone rubber particles may be broken due to the load of friction on the coating film.

[0004] Patent Document 1 proposes a high-strength silicone rubber particle containing silicon dioxide. The particle can be produced by mixing silicon dioxide in a curable liquid silicone composition, dispersing (emulsifying) the mixture in water containing a surfactant, and subjecting the mixture to a curing reaction. In the method, the stability of the obtained emulsion is poor, and sometimes some particles aggregate. In addition, it is difficult to increase the content of silicon dioxide in the particles, thereby making it difficult to form rubber particles with higher strength.

[0005] Patent Document 2 proposes silicone rubber particles containing an organosiloxane resin using diorganopolysiloxane having alkenyl groups, an organopolysiloxane resin, and an organohydrogenpolysiloxane having silicon-bonded hydrogen as raw materials. However, the silicone rubber particles described in Patent Document 2 have low rubber strength and elongation.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Laid-Open No. 4-168117

[0009] Patent Document 2: Japanese Patent Application Publication No. 2000-204258

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide silicone rubber particles and an aqueous dispersion of silicone rubber particles having high strength and elongation and a small amount of aggregated particles. Summary of the invention

[0011] Technical means of solving problems

[0012] The present inventors have conducted intensive studies to achieve the above object and have found that the above object can be achieved by using a specific amount of an organopolysiloxane having an alkenyl group in silicone rubber particles containing an organopolysiloxane resin, which is made of a diorganopolysiloxane having an alkenyl group, an organopolysiloxane resin having an alkenyl group, and an organohydrogenpolysiloxane having silicon-bonded hydrogen, thereby completing the present invention.

[0013] That is, the present invention provides the following silicone rubber particles and an aqueous dispersion of silicone rubber particles.

[0014] A silicone rubber particle is an addition reaction product of a curable liquid silicone composition comprising the following components (A-1), (A-2) and (A-3), and has a volume average particle diameter of 0.5 μm to 50 μm and is spherical.

[0015] (A-1) a diorganopolysiloxane having two or more alkenyl groups in one molecule and an alkenyl group amount of 0.0025 mol / 100 g to 0.034 mol / 100 g;

[0016] (A-2) contains R 1 3 SiO 1 / 2 Unit and SiO 4 / 2 Unit, R 1 3 SiO 1 / 2 Unit relative to SiO 4 / 2 An organopolysiloxane resin having a molar ratio of units of 0.60 to 1.7 and an alkenyl content of 0.001 mol / 100 g or more,

[0017] (In the formula, R 1 are independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 30 carbon atoms or an alkenyl group having 2 to 8 carbon atoms, and all R 1 at least one of which is alkenyl); and

[0018] (A-3) an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms (referred to as SiH groups) in one molecule and having an SiH group content of 0.030 mol / 100 g to 1.30 mol / 100 g,

[0019] The amount of the component (A-2) is 1.0 to 65 parts by mass based on 100 parts by mass of the total of the components (A-1), (A-2) and (A-3).

[0020] Furthermore, the present invention provides the above-mentioned silicone rubber particles, wherein the above-mentioned silicone rubber particles contain the following silicone rubber: for a rubber sheet with a thickness of 1 mm subjected to a heat treatment at 150° C. for 30 minutes, the elongation at break of a dumbbell-shaped No. 3 test piece according to the test method specified in Japanese Industrial Standard (JIS) K 6251 is 20% or more, and the tensile strength at break according to the test method specified in JIS K 6251 is 1.0 MPa or more.

[0021] Furthermore, the present invention provides an aqueous dispersion of the silicone rubber particles, wherein the aqueous dispersion of the silicone rubber particles comprises:

[0022] (A) 100 parts by mass of the silicone rubber particles according to claim 1 or 2

[0023] (B) surfactant: 0.05 to 20 parts by mass, and

[0024] (C) Water: 20 to 2,000 parts by mass.

[0025] Effects of the Invention

[0026] The silicone rubber particles of the present invention have high rubber strength and elongation. The silicone particles and the aqueous dispersion containing the silicone particles are effectively used as a paint or coating agent that is subject to friction. DETAILED DESCRIPTION

[0027] Hereinafter, the present invention will be described in detail.

[0028] [Silicone rubber particles]

[0029] The particle shape of the silicone rubber particles (A) of the present invention is spherical. In this specification, the so-called "spherical" means that the particle shape is not only a sphere, but also a deformed sphere whose average length of the longest axis / length of the shortest axis (aspect ratio) is usually 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 using an optical microscope, an electron microscope, etc. In addition, it can be measured by a particle shape analysis device using a dynamic image analysis method.

[0030] The volume average particle size of the particles is 0.5 μm to 50 μm, preferably 1.0 μm to 30 μm, and more preferably 2.0 μm to 20 μm. The volume average particle size is measured by a Coulter counter method (electrical resistance method).

[0031] The silicone rubber of the silicone rubber particles (A) is an addition reaction product of a curable liquid silicone composition comprising (A-1) a diorganopolysiloxane having two or more alkenyl groups in one molecule, (A-2) an organopolysiloxane resin having alkenyl groups, and (A-3) an organohydrogenpolysiloxane having two or more SiH groups in one molecule.

[0032] The diorganopolysiloxane having two or more alkenyl groups in one molecule of the component (A-1) is represented by the following average composition formula (1).

[0033] R 2 a R 3 b SiO (4-a-b) / 2 (1)

[0034] In the formula, R 2 are independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 30 carbon atoms and not having an alkenyl group, R 3 Each is independently an alkenyl group having 2 to 8 carbon atoms, and a and b are positive numbers satisfying 0<a<3, 0<b≦3, and 0.1≦a+b≦3.

[0035] The diorganopolysiloxane represented by the average composition formula (1) may be used alone or in combination of two or more.

[0036] R 2 It is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 30 carbon atoms, preferably a monovalent hydrocarbon group having 1 to 22 carbon atoms, and more preferably a monovalent hydrocarbon group having 1 to 18 carbon atoms.

[0037] As R 2 , for example, alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, decyl, undecyl, dodecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl, docosyl, tricosyl, tetracosyl, triacontyl, etc.; aryl groups such as phenyl, tolyl, naphthyl, etc.; aralkyl groups such as benzyl, phenethyl, etc.; cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl, etc.; and hydrocarbon groups in which a part or all of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with atoms such as halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, iodine atoms) and / or substituents such as acryloyloxy, methacryloyloxy, amino, epoxy, glycidyloxy, carboxyl, etc. Preferably, all R 2 50 mol % or more of the groups are methyl groups.

[0038] R 3 Examples thereof include a vinyl group, an allyl group, a propenyl group, a butenyl group, a pentenyl group, a hexenyl group, and an octenyl group. A vinyl group, an allyl group, and a hexenyl group are preferred, and a vinyl group is more preferred.

[0039] a and b are preferably positive numbers satisfying 0<a≦2.295, 0.005≦b≦2.3, and 0.5≦a+b≦2.3.

[0040] The silicone rubber particles of the present invention are characterized in that the alkenyl content of the component (A-1) is 0.0025 mol / 100 g to 0.034 mol / 100 g. If it is more than 0.034 mol / 100 g, the strength or elongation of the silicone rubber obtained becomes low. If it is less than 0.0025 mol / 100 g, it becomes a structure with a high degree of polymerization, so the viscosity becomes high, and the viscosity of the curable liquid silicone containing the components (A-2) and (A-3) becomes high, and the emulsification described later becomes difficult. It is preferably 0.0030 mol / 100 g to 0.027 mol / 100 g, and more preferably 0.0035 mol / 100 g to 0.020 mol / 100 g.

[0041] The viscosity of the component (A-1) at 25°C is preferably 100,000 mm 2 / s or less, more preferably 50,000 mm 2 / s or less. If the viscosity is higher than 100,000mm 2 / s, the viscosity of the curable liquid silicone containing the components (A-2) and (A-3) becomes high, and the emulsification described later becomes difficult. The lower limit of the viscosity is not particularly limited, but is less than about 150 mm 2 / s, it is difficult for the olefin content to be less than 0.033 mol / 100 g, so as long as 150 mm 2 / s or above, especially 300mm 2 / s or more.

[0042] The structure of component (A-1) may be any of linear, cyclic and branched, and is particularly preferably linear or branched with fewer branch units. The bonding site of the alkenyl group is not particularly limited, and may be bonded to a silicon atom at any of the side chain and the terminal of the molecule.

[0043] Examples of the linear structure include a structure represented by the following general formula (2).

[0044] [Chemistry 1]

[0045]

[0046] In the formula, R 2 , R 3As described above, c is a positive number of 10 to 1,500, preferably a positive number of 30 to 1000, more preferably a positive number of 50 to 800, and even more preferably a positive number of 80 to 800, d is a positive number of 0 or less, and e is 0, 1, 2 or 3, wherein d and e are numbers satisfying d+2×e≧2.

[0047] Examples of the branched structure include: 2 SiO 3 / 2 The structure represented by the following general formula (3) is branched by units.

[0048] [Chemistry 2]

[0049]

[0050] In the formula, R 2 , R 3 As described above, f is a positive number of 10 to 1,500, preferably a positive number of 30 to 1000, more preferably a positive number of 50 to 800, and even more preferably a positive number of 80 to 800, g is a positive number of 0 or less, h is a positive number of 1 to 10, and i is 0, 1, 2 or 3, wherein g and i are numbers satisfying g+i≧1.

[0051] As SiO 4 / 2 An example of a structure branched by a unit of the present invention is the structure represented by the following general formula (4).

[0052] [Chemistry 3]

[0053]

[0054] In the formula, R 2 , R 3 As described above, j is a positive number of 10 to 1,500, preferably a positive number of 30 to 1000, more preferably a positive number of 50 to 800, and even more preferably a positive number of 80 to 800, k is a positive number of 0 or less than 50, l is a positive number of 1 to 5, and m is 0, 1, 2 or 3, wherein k and m are numbers satisfying k+m≧1.

[0055] (A-2) component contains R 1 3 SiO 1 / 2 Unit and SiO 4 / 2 It is an organopolysiloxane resin having alkenyl groups and having 1, 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 3

[0056] In the formula, R 1 Each of R is independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 30 carbon atoms or an alkenyl group having 2 to 8 carbon atoms. 1At least one of the organopolysiloxane resins may be used alone, or two or more may be used in combination.

[0057] The monovalent hydrocarbon group not having an alkenyl group has a carbon number of 1 to 30, preferably 1 to 20, and more preferably 1 to 10. Examples of the monovalent hydrocarbon group not having an alkenyl group include R 2 The exemplified groups are preferably all R 1 50 mol % or more of the groups are methyl groups.

[0058] Examples of the alkenyl group having 2 to 8 carbon atoms include vinyl, allyl, propenyl, butenyl, pentenyl and hexenyl. Preferred are vinyl and allyl, and more preferred are vinyl.

[0059] In organopolysiloxane resin, R 1 3 SiO 1 / 2 unit (hereinafter referred to as M unit) and SiO 4 / 2 The molar ratio of the unit (hereinafter referred to as Q unit), that is, [mole of M unit] / [mole of Q unit] is 0.60 to 1.7, preferably 0.65 to 1.3, and more preferably 0.70 to 1.1.

[0060] The component (A-2) may contain (R 4 O)SiO 3 / 2 Unit. In the formula, R 4 are independently a hydrogen atom or an unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms. (R 4 O)SiO 3 / 2 The unit is derived from the raw material. 4 O groups undergo condensation reaction, but sometimes unreacted R 4 O-based.

[0061] Examples of the unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms include methyl, ethyl, propyl, butyl, pentyl, and hexyl. 4 O)SiO 3 / 2 Unit (called Q 3 The content of unit) is preferably (R 4 O)SiO 3 / 2 Unit and SiO 4 / 2 The molar ratio of the unit [(R 4 O)SiO 3 / 2 mole of unit] / [SiO 4 / 2 The amount of [Q 3[mol of Q units] / [mol of Q units] is preferably 0 to 0.50, more preferably 0.01 to 0.40, and still more preferably 0.02 to 0.30.

[0062] The component (A-2) may contain R within a range that does not impair the property of forming a solid at 25° C. and the solubility in the components (A-1) and (A-3) in the production of the silicone rubber particles (A) described below. 5 SiO 3 / 2 Unit and / or R 6 2 SiO 2 / 2 Unit. In the formula, R 5 and R 6 R is independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 30 carbon atoms. 5 SiO 3 / 2 Unit (called T unit) and R 6 2 Si 2 / 2 The content of the unit (referred to as D unit) is preferably such that [moles of T units and D units] / [moles of Q units] is 0.3 or less.

[0063] The alkenyl amount of component (A-2) is 0.001 mol / 100 g or more. If it is less than 0.001 mol / 100 g, the strength or elongation of the silicone rubber becomes low. It is preferably 0.005 mol / 100 g or more, and more preferably 0.01 mol / 100 g or more. There is no particular limit on the upper limit, but if it is more than 2.0 mol / 100 g, the molar ratio [mole of M unit] / [mole of Q unit] cannot be less than 1.7, so it only needs to be 0.8 mol / 100 g or less, especially 0.50 mol / 100 g or less. The polystyrene-equivalent weight average molecular weight of component (A-2) by gel permeation chromatography is preferably 1,000 to 10,000, and more preferably 2,000 to 8,000.

[0064] The organohydrogenpolysiloxane having two or more SiH groups in one molecule of the component (A-3) is preferably represented by the following average composition formula (5).

[0065] R 7 n H o SiO (4-n-0) / 2 (5)

[0066] In the formula, R 7Each is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 30 carbon atoms and not having an alkenyl group. n and o are numbers satisfying 0<n<3, 0<o≦3, and 0.1≦n+o≦3.

[0067] One type of the organohydrogenpolysiloxane represented by the average composition formula (5) may be used alone, or two or more types may be used in combination.

[0068] R 7 The number of carbon atoms in R is 1 to 30, preferably 1 to 22, and more preferably 1 to 18. 7 Can be listed as R 2 The exemplary monovalent hydrocarbon groups are preferably R 7 More than 80 mol % of the groups are methyl groups, more preferably more than 95 mol % are methyl groups.

[0069] It is preferable that n and o are positive numbers satisfying 0<n≦2.295, 0.005≦o≦2.3, and 0.5≦n+o≦2.3.

[0070] The amount of SiH groups in component (A-3) is 0.030 mol / 100 g to 1.30 mol / 100 g. If it is less than 0.030 mol / 100 g, the strength or elongation of the silicone rubber will be reduced. If it is more than 1.30 mol / 100 g, there is a risk of agglomeration of dispersed particles in the aqueous dispersion of silicone rubber particles described later. It is preferably 0.050 mol / 100 g to 1.10 mol / 100 g, and more preferably 0.10 mol / 100 g to 0.90 mol / 100 g.

[0071] The viscosity of the component (A-3) at 25°C is preferably 100,000 mm 2 / s or less, more preferably 10,000 mm 2 / s or less. If the viscosity is 100,000mm 2 / s or less, silicone microparticles with a narrow particle size distribution can be obtained particularly easily by the production method described later. The lower limit of the viscosity is not particularly limited as long as it is 0.4 mm 2 / s or above, especially 2mm 2 / s or more.

[0072] In addition, the structure of the component (A-3) may be any of linear, cyclic, and branched, and is particularly preferably linear or branched. In addition, the bonding site of the hydrogen atom bonded to the silicon atom is not particularly limited, and may be bonded to the silicon atom of any of the side chain and the terminal of the molecule.

[0073] Examples of the linear structure include a structure represented by the following general formula (6).

[0074] [Chemistry 4]

[0075]

[0076] In the formula, R 7 As described above, p is a positive number of 1,500 or less, preferably 1 to 1000, more preferably 5 to 500, and even more preferably 10 to 100, q is a positive number of 0 or 300 or less, preferably 1 to 100, and more preferably 5 to 60, and r is 0, 1, 2 or 3, wherein q and r are numbers satisfying q+2×r≧2.

[0077] Examples of the branched structure include: 7 SiO 3 / 2 The structure represented by the following general formula (7) is branched by units.

[0078] [Chemistry 5]

[0079]

[0080] In the formula, R 7 As described above, s is a positive number of 1,500 or less, preferably 1 to 1000, more preferably 5 to 500, and even more preferably 10 to 100, t is a positive number of 0 or 300 or less, preferably 1 to 100, and more preferably 5 to 60, u is a positive number of 1 to 10, and v is 0, 1, 2 or 3, wherein t and v are numbers satisfying t+v≧1.

[0081] As SiO 4 / 2 An example of a structure in which a unit is branched is the structure represented by the following general formula (8).

[0082] [Chemistry 6]

[0083]

[0084] In the formula, R 7 As described above, w is a positive number of 1,500 or less, preferably 1 to 1000, more preferably 5 to 500, and even more preferably 10 to 100, x is a positive number of 0 or 300 or less, preferably 1 to 100, and more preferably 5 to 60, y is a positive number of 1 to 5, and z is 0, 1, 2 or 3, wherein x and z are numbers satisfying x+z≧1.

[0085] In addition, there can be mentioned a structure represented by the following unit formula (9) having two or more hydrogen atoms bonded to a silicon atom per molecule.

[0086] [R 7 3 SiO 1 / 2 ] a1 [H(R 7 ) 2 SiO1 / 2 ] b1 [SiO 4 / 2 ] c1

[0087] [(OR 8 )SiO 3 / 2 ] d1 (9)

[0088] In the formula, R 7 Same as above, R 8 is a hydrogen atom or an unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms, a1 is 0 or a positive number, b1 is a positive number, c1 is a positive number, and d1 is 0 or a positive number. The upper limit of a1, b1, c1, and d1 is 20, respectively.

[0089] A curable liquid silicone composition is prepared by mixing and dissolving a diorganopolysiloxane (A-1) having two or more alkenyl groups in one molecule, an organopolysiloxane resin (A-2) having alkenyl groups, and an organohydrogenpolysiloxane (A-3) having two or more SiH groups in one molecule.

[0090] The curable liquid silicone composition is a composition in which the component (A-2) is set to 1.0 to 65 parts by mass relative to the total amount of the components (A-1), (A-2) and (A-3) of 100 parts by mass. If the component (A-2) is less than 1.0 parts by mass, the elongation or strength of the silicone rubber decreases. If it is more than 65 parts by mass, the viscosity of the liquid silicone composition increases, and the emulsification described later becomes difficult. It is preferably 2.0 to 55 parts by mass, and more preferably 4.0 to 45 parts by mass.

[0091] The curable liquid silicone composition preferably has a composition in which the number ratio of SiH groups in component (A-3) is 0.9 to 3.0 relative to the total amount of alkenyl groups in component (A-1) and alkenyl groups in component (A-2). If the number ratio of SiH groups in component (A-3) is less than 0.9, the elongation or strength of the silicone rubber decreases. If it is higher than 3.0, there is a risk of agglomeration of dispersed particles in the aqueous dispersion of silicone rubber particles described later. More preferably, it is in the range of 1.0 to 2.3.

[0092] The silicone rubber of the silicone rubber particles (A) is an addition reaction product of the curable liquid silicone composition. It is preferred to use a catalyst in the addition reaction. The catalyst for the addition reaction can be a platinum group metal catalyst used in a hydrosilylation reaction. For example, platinum group metal monomers such as platinum (including platinum black), rhodium, and palladium; 2 PtCl 4 ·XH 2 O, H 2 PtCl 6 ·XH2 O、NaHPtCl 6 ·XH 2 O、KHPtCl 6 ·XH 2 O、Na 2 PtCl 6 ·XH 2 O.K 2 PtCl 4 ·XH 2 O、PtCl 4 ·XH 2 O、PtCl 2 、Na 2 HPtCl 4 ·XH 2 O (wherein, X is an integer of 0 to 6, preferably 0 or 6) and other platinum chloride, chloroplatinic acid and chloroplatinate; alcohol-modified chloroplatinic acid; complexes of platinum chloride, chloroplatinic acid and olefins; complexes of chloroplatinic acid and vinyl siloxane; complexes of platinum and vinyl siloxane; catalysts in which platinum group metals such as platinum black and palladium are supported on carriers such as alumina, silica, and carbon; rhodium-olefin complexes; chlorotris(triphenylphosphine)rhodium (Wilkinson catalyst), etc. One may be used alone or two or more may be used in combination.

[0093] The amount of the platinum group metal catalyst to be added is an effective amount as an addition reaction catalyst, and is an amount such that the amount of the platinum group metal in the platinum group metal catalyst relative to the total amount of the components (A-1), (A-2) and (A-3) is generally about 0.1 ppm to 500 ppm, preferably about 0.5 ppm to 200 ppm, and more preferably about 1 ppm to 100 ppm. The curing conditions for the addition reaction of the curable liquid silicone composition are not particularly limited, but are preferably at a temperature of 1°C to 100°C for 1 hour or more. The temperature is preferably 10°C to 100°C.

[0094] The silicone rubber of the silicone rubber particles (A) preferably has an elongation at break of 20% or more and a tensile strength at break of 1.0 MPa or more. The elongation at break and the tensile strength at break refer to the values ​​measured by the test method specified in JIS K 6251:2017 for a dumbbell-shaped No. 3 test piece with a thickness of 1 mm that has been heat treated at 150°C for 30 minutes. More preferably, the elongation at break is 50% or more and the tensile strength at break is 2.0 MPa or more. There is no particular limit to the upper limit of the elongation at break, as long as it is 1000% or less, especially 500% or less. There is no particular limit to the upper limit of the tensile strength at break, as long as it is 20 MPa or less, especially 10 MPa or less.

[0095] The silicone rubber type A durometer hardness of the silicone rubber particles (A) is preferably in the range of 20 to 95. The hardness is a value measured by the test method specified in JIS K 6253:2012 on a test piece treated at 150°C for 30 minutes.

[0096] Silicone rubber may also contain silicone oil, organic silane, inorganic powder, organic powder, antioxidant and the like.

[0097] [Aqueous dispersion of silicone rubber particles]

[0098] The aqueous dispersion of silicone rubber particles of the present invention is a composition containing (A) silicone rubber particles, (B) a surfactant, and (C) water.

[0099] The surfactant (B) functions as a dispersant for the silicone rubber particles and, as described later, also functions as an emulsifier for the curable liquid silicone composition in the production of an aqueous dispersion of silicone rubber particles.

[0100] The surfactant (B) is not particularly limited and can be a nonionic surfactant, anionic surfactant, cationic surfactant or two ionic surfactants. A nonionic surfactant or anionic surfactant is preferred. These can be used alone or in combination of two or more.

[0101] Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyethylene glycol fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, glycerol fatty acid esters, polyoxyethylene glycerol fatty acid esters, polyglycerol 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, and polyoxyethylene polyoxypropylene modified organopolysiloxanes.

[0102] Preferred are polyoxyethylene alkyl ethers or polyoxyethylene polyoxypropylene alkyl ethers having a hydrophilic-lipophilic balance (HLB) value of 12.0 to 19.0. More preferred are polyoxyethylene alkyl ethers or polyoxyethylene polyoxypropylene alkyl ethers having an alkyl group with a carbon number of 10 to 18. In addition, the HLB value is more preferably 13.0 to 18.0.

[0103] In addition, the HLB value here is a value calculated by Griffin's formula represented by the following formula.

[0104] HLB = [molecular weight of the polyoxyethylene part and the alcohol part / molecular weight of the surfactant] × 20

[0105] When two or more nonionic surfactants having different HLB values ​​are used in combination, the HLB value is a weighted average value.

[0106] Examples of the anionic surfactant include alkyl sulfate ester salts such as sodium lauryl sulfate, polyoxyethylene alkyl ether sulfate ester salts, polyoxyethylene alkylphenyl ether sulfate ester salts, sulfate ester salts of fatty acid alkylolamides, alkylbenzene sulfonates, polyoxyethylene alkylphenyl ether sulfonates, α-olefin sulfonates, α-sulfofatty acid ester salts, alkylnaphthalene sulfonates, alkyldiphenyl ether disulfonates, alkane sulfonates, N-acyltaurates, dialkyl sulfosuccinates, monoalkyl sulfosuccinates, polyoxyethylene alkyl ether sulfosuccinates, fatty acid salts, polyoxyethylene alkyl ether carboxylates, N-acylamino acid salts, monoalkyl phosphate ester salts, dialkyl phosphate ester salts, polyoxyethylene alkyl ether phosphate ester salts, and the like.

[0107] Preferred are alkyl sulfates having an alkyl group with 10 to 18 carbon atoms, polyoxyethylene alkyl ether sulfates, sulfates of fatty acid alkylolamides, alkylbenzene sulfonates, α-sulfofatty acid esters, alkane sulfonates, N-acyltaurates, polyoxyethylene alkyl ether sulfosuccinates, polyoxyethylene alkyl ether carboxylates, N-acylamino acid salts, monoalkyl phosphates, dialkyl phosphates, polyoxyethylene alkyl ether phosphates, α-olefin sulfonates having an olefin with 10 to 18 carbon atoms, alkylnaphthalene sulfonates having an alkyl group with 1 to 14 carbon atoms, and alkyldiphenylether disulfonates having an alkyl group with 6 to 14 carbon atoms.

[0108] Examples of the cationic surfactant include alkyltrimethylammonium salts, dialkyldimethylammonium salts, polyoxyethylene alkyldimethylammonium salts, dimeroxyethylene alkylmethylammonium salts, trimeroxyethylene alkylammonium salts, alkylbenzyldimethylammonium salts, alkylpyridinium salts, monoalkylamine salts, and monoalkylamideamine salts.

[0109] Examples of the amphoteric surfactant include alkyl dimethyl amine oxide, alkyl dimethyl carboxy betaine, alkyl amidopropyl dimethyl carboxy betaine, alkyl hydroxysulfobetaine, and alkyl carboxymethyl hydroxyethyl imidazolinium betaine.

[0110] The amount of component (B) is 0.05 to 20 parts by mass relative to 100 parts by mass of silicone rubber particles (A). If it is less than 0.05 parts by mass, the emulsification of the curable liquid silicone composition described later cannot be performed, and there is a risk of reduced stability of the aqueous dispersion. Even if it is more than 20 parts by mass, the water dispersibility of the silicone rubber particles will not be improved, and there is a risk of damaging the properties of the formulated coating material. It is preferably 0.10 to 10 parts by mass, and more preferably 0.20 to 2 parts by mass.

[0111] Water (C) is a dispersion medium for the silicone rubber particles (A). The amount of the component (C) is 20 to 2,000 parts by mass, preferably 40 to 1,000 parts by mass, based on 100 parts by mass of the silicone rubber particles (A).

[0112] The aqueous dispersion of silicone rubber particles may be appropriately formulated with an antiseptic, a thickener, a pH adjuster, a defoaming agent, and the like, as required.

[0113] [Aqueous dispersion of silicone rubber particles and method for producing silicone rubber particles]

[0114] The aqueous dispersion of silicone rubber particles can be produced by a known method. For example, the following method can be cited: a surfactant (B) and water (C) are added to a curable liquid silicone composition comprising component (A-1), component (A-2) and component (A-3), emulsified to form an emulsion, and then a platinum group metal catalyst is added to perform an addition reaction.

[0115] For emulsification, a general emulsifying and dispersing machine can be used, and examples thereof include: a high-speed rotating centrifugal radial agitator such as a homodisper; a high-speed rotating shearing agitator such as a homomixer; a high-pressure jet emulsifying and dispersing machine such as a homogenizer; a colloid mill; an ultrasonic emulsifying machine, etc. As long as emulsification can be achieved and the desired particle size can be formed, the stirring speed, time, etc. are not particularly limited.

[0116] After the emulsion is prepared, a platinum group metal catalyst is added. However, if the dispersibility in water is poor, it is preferably added to the emulsion in a state dissolved in a surfactant. Examples of the surfactant include the surfactants described above, and nonionic surfactants are particularly preferred. A method of pre-blending a platinum group metal catalyst in a curable liquid silicone composition is also possible, but in such a case, it is necessary to adjust the temperature, adjust the amount of the catalyst, or blend a reaction regulator, so that the reaction does not proceed until the emulsification is completed.

[0117] The addition reaction can be carried out at room temperature (1° C. to 30° C.), but in order to accelerate the reaction speed or increase the reaction rate, it can also be carried out under heating at less than 100° C. The addition reaction time is appropriately selected.

[0118] The silicone rubber particles can be obtained by removing water (C) from the water dispersion of the silicone rubber particles obtained in the above process.

[0119] The removal of water (C) can be carried out, for example, by heating the aqueous dispersion under normal pressure or under reduced pressure to volatilize it. For example, there can be mentioned: a method of removing the dispersion by standing it under heating, a method of removing it while stirring the dispersion under heating to make it flow, a method of spraying the dispersion in a hot air flow like a spray dryer to disperse it, a method of using a flowing heat medium, etc. In addition, as a pretreatment for the above operation, after the particles are further agglomerated by adding inorganic salts, they can be concentrated by filtration separation such as pressure filtration, centrifugal separation, decantation, etc., and the concentrate can also be washed with water or alcohol as needed.

[0120] When silicone oil, organosilane, inorganic powder, organic powder, antioxidant, etc. are contained in the silicone rubber particles, these may be dissolved or dispersed in the curable liquid silicone composition.

[0121] The water dispersion of silicone rubber particles or silicone rubber particles of the present invention can be used, for example, in a coating or coating agent. It is desirable that after applying the coating or coating agent containing the silicone rubber particles on a substrate, the coating or coating agent is heat-treated at a temperature of 100°C to 300°C for 1 minute to 3 hours. The heat treatment increases the addition reaction rate, and the elongation and strength of the silicone rubber are increased. In addition, the silicone rubber particles can be heat-treated at a temperature of 100°C to 300°C for 1 minute to 3 hours before being mixed in a coating or coating agent.

[0122] Example

[0123] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[0124] In addition, in the examples, the dynamic viscosity is a value measured at 25°C using a capillary viscometer.

[0125] The following polysiloxane was prepared.

[0126] (A-1)-1: represented by formula (10), vinyl content of 0.00627 mol / 100 g, dynamic viscosity of 5,060 mm 2 / s vinyl-containing dimethyl polysiloxane

[0127] [Chemistry 7]

[0128]

[0129] (A-1)-2: represented by formula (11), vinyl content of 0.00369 mol / 100 g, dynamic viscosity of 30,500 mm 2 / s vinyl-containing dimethyl polysiloxane

[0130] [Chemistry 8]

[0131]

[0132] (A-1)-3: represented by formula (12), vinyl content of 0.0179 mol / 100 g, dynamic viscosity of 386 mm 2 / s vinyl-containing dimethyl polysiloxane

[0133] [Chemistry 9]

[0134]

[0135] (A-1)-4: A dissolver of (A-1)-1 and (A-1)-3 mixed in a mass ratio of 40:60, with a vinyl content of 0.0132 mol / 100 g and a dynamic viscosity of 1080 mm 2 / s vinyl-containing dimethyl polysiloxane

[0136] (A-1)-5: represented by formula (13), vinyl content of 0.120 mol / 100 g, dynamic viscosity of 23 mm 2 / s vinyl-containing dimethyl polysiloxane (for comparative example)

[0137] [Chemistry 10]

[0138]

[0139] (A-1)-6: represented by formula (14), vinyl content of 0.0348 mol / 100 g, dynamic viscosity of 125 mm 2 / s vinyl-containing dimethyl polysiloxane (for comparative example)

[0140] [Chemistry 11]

[0141]

[0142] (A-1)-7: represented by formula (15), vinyl content of 0.0433 mol / 100 g, dynamic viscosity of 378 mm 2 / s vinyl-containing dimethyl polysiloxane (for comparative example)

[0143] [Chemistry 12]

[0144]

[0145] (A-2)-1: Contains (CH 3 ) 3 SiO 1 / 2 Unit, (CH 3 ) 2 (CH=CH 2 )SiO 1 / 2 Unit, SiO 4 / 2 Unit, (OH)SiO 3 / 2 Unit, and (OCH 3 )SiO 3 / 2 units, and a vinyl-containing methyl polysiloxane resin having the following molar ratios

[0146] Molar ratio ([(CH 3 ) 3 SiO 1 / 2 ]+[(CH 3 ) 2 (CH=CH 2 )SiO 1 / 2 ]) / [SiO 4 / 2 ] is 0.83;

[0147] Molar ratio [(CH 3 ) 3 SiO 1 / 2 ] / [SiO 4 / 2 ] is 0.71;

[0148] Molar ratio [(CH 3 ) 2 (CH=CH 2 )SiO 1 / 2 ] / [SiO 4 / 2 ] is 0.12;

[0149] Molar ratio ([HOSiO 3 / 2 ]+[CH 3 OSiO 3 / 2 ] / [SiO 4 / 2 ]) is 0.088;

[0150] Molar ratio [HOSiO 3 / 2 ] / [SiO 4 / 2 ] is 0.041;

[0151] Molar ratio [CH 3 OSiO 3 / 2 ] / [SiO 4 / 2 ] is 0.047,

[0152] The vinyl content was 0.089 mol / 100 g and the weight average molecular weight was 4,100.

[0153] (A-2)-2: Contains (CH 3 ) 3 SiO 1 / 2 Unit, (CH=CH 2 ) 3 SiO 1 / 2 Unit, SiO 4 / 2 Unit, HOSiO 3 / 2 Unit, and C 2 H 5 OSiO 3 / 2 units, and a vinyl-containing methyl polysiloxane resin having the following molar ratios

[0154] Molar ratio ([(CH 3 ) 3 SiO 1 / 2 ]+[(CH=CH 2 ) 3 SiO 1 / 2 ]) / [SiO 4 / 2 ] is 1.01;

[0155] Molar ratio [(CH 3 ) 3 SiO 1 / 2 ] / [SiO 4 / 2 ] is 0.90;

[0156] Molar ratio [(CH=CH 2 ) 3 SiO 1 / 2 ] / [SiO 4 / 2 ] is 0.11;

[0157] Molar ratio ([HOSiO 3 / 2 ]+[C 2 H 5 OSiO 3 / 2 ] / [SiO 4 / 2 ]) is 0.10;

[0158] Molar ratio [HOSiO 3 / 2 ] / [SiO 4 / 2 ] is 0.050;

[0159] Molar ratio [C 2 H 5 OsSiO 3 / 2 ] / [SiO 4 / 2 ] is 0.050,

[0160] The vinyl content was 0.23 mol / 100 g and the weight average molecular weight was 5,730.

[0161] (A-3)-1: represented by formula (16), SiH group content is 0.418 mol / 100 g, dynamic viscosity is 27 mm 2 / s methyl hydrogen polysiloxane

[0162] [Chemistry 13]

[0163]

[0164] (A-3)-2: represented by formula (17), SiH group content is 0.744 mol / 100 g, dynamic viscosity is 117 mm 2 / s methyl hydrogen polysiloxane

[0165] [Chemistry 14]

[0166]

[0167] (A-3)-3: represented by formula (18), SiH group content is 0.137 mol / 100 g, dynamic viscosity is 37 mm 2 / s methyl hydrogen polysiloxane

[0168] [Chemistry 15]

[0169]

[0170] (A-3)-4: represented by formula (19), SiH group content is 0.427 mol / 100 g, dynamic viscosity is 48 mm 2 / s methyl hydrogen polysiloxane

[0171] [Chemistry 16]

[0172]

[0173] [Example 1]

[0174] A vinyl-containing dimethylpolysiloxane (A-1)-1, a vinyl-containing methylpolysiloxane resin (A-2)-1 and a methylhydrogenpolysiloxane (A-3)-1 were mixed and dissolved at a mass ratio of 63.0:27.0:10.0 to prepare a curable liquid silicone composition. The ratio of the number of SiH groups in the methylhydrogenpolysiloxane to the total amount of the vinyl groups in the vinyl-containing dimethylpolysiloxane and the vinyl groups in the vinyl-containing methylpolysiloxane resin was 1.49.

[0175] 500.0 g of a curable liquid silicone composition, 2.0 g of polyoxyethylene tridecyl ether (ethylene oxide addition mole number = 15 mol) and 80.0 g of water were placed in a 1-liter glass beaker, and stirred at 6,000 rpm using a homogenizer. As a result, it became an oil-in-water type, and thickening was confirmed. Stirring was continued for 15 minutes. Next, 415.6 g of water was added while stirring at 2,000 rpm to obtain a uniform white emulsion. The emulsion was transferred to a 1-liter glass flask with a stirring device using an anchor-type stirring blade, and after adjusting the temperature to 15°C to 20°C, a mixed solution of 1.2 g of an isododecane solution of a platinum-vinyl-containing disiloxane complex (platinum content 0.5%) and 1.2 g of polyoxyethylene lauryl ether (ethylene oxide addition mole number = 9 mol) was added under stirring. The mixture was stirred at the above temperature for 6 hours to cure the curable liquid silicone by an addition reaction, thereby obtaining an aqueous dispersion of silicone rubber particles.

[0176] The total amount of polyoxyethylene tridecyl ether and polyoxyethylene lauryl ether was 0.64 parts by mass based on 100 parts by mass of the obtained silicone rubber particles.

[0177] The silicone rubber particles were spherical when observed under an optical microscope, and the volume average particle size was measured using a particle size distribution measuring apparatus "Coulter Multisizer 3" (trade name, manufactured by Beckman Coulter Co., Ltd.) to find that it was 6.7 μm.

[0178] The obtained water dispersion of silicone rubber particles was evaporated and removed using a spray dryer at an inlet temperature of 150° C. and an outlet temperature of 80° C. to obtain silicone rubber particles. The obtained silicone rubber particles were then heated in a thermostatic bath at 150° C. for 30 minutes.

[0179] The obtained silicone rubber particles were non-sticky particles, and their shapes were spherical when observed under an electron microscope.

[0180] The tensile strength at break and the elongation at break of the silicone rubber of the silicone rubber particles were measured as follows.

[0181] 0.24 parts by mass of an isododecane solution of a platinum-vinyl disiloxane complex (0.5% platinum content) and 0.05 parts by mass of 1,1-dimethylpropoxytrimethylsilane (reaction regulator) were mixed with 100 parts by mass of a curable liquid silicone composition prepared with the same composition as in Example 1, and poured into a polypropylene tray so as to have a thickness of about 1 mm. After being left at 25° C. for 24 hours, the cured silicone was peeled off the tray and heated in a thermostatic bath at 150° C. for 30 minutes to obtain a non-sticky silicone rubber sheet.

[0182] The silicone rubber sheet was cut into a dumbbell No. 3 test piece of the shape and size specified in JIS K6251: 2017, and the tensile strength at break and the elongation at break were measured according to the method specified in JIS K6251: 2017. The tensile strength at break was 6.5 MPa, and the elongation at break was 101%.

[0183] The hardness of the silicone rubber of the silicone rubber particles was measured as follows.

[0184] 0.24 parts by mass of an isododecane solution of a platinum-vinyl disiloxane complex (0.5% platinum content) and 0.05 parts by mass of 1,1-dimethylpropoxytrimethylsilane (reaction regulator) were mixed with 100 parts by mass of a curable liquid silicone composition prepared with the same composition as in Example 1, and poured into an aluminum petri dish so as to have a thickness of 10 mm. After being left at 25°C for 24 hours, it was heated in a thermostatic bath at 150°C for 30 minutes to obtain a non-sticky silicone rubber. The hardness of the silicone rubber was measured using a type A durometer specified in JIS K6253, and the result was 58.

[0185] [Example 2 to Example 11] [Comparative Example 1 to Comparative Example 10]

[0186] In the composition described in Table 1 or Table 2, Example 1 was repeated except that a curable liquid silicone composition prepared by mixing and dissolving a vinyl-containing dimethylpolysiloxane, a vinyl-containing methylpolysiloxane resin (some compositions not used) and a methylhydrogenpolysiloxane was used to obtain an aqueous dispersion of silicone rubber particles.

[0187] Table 1 or Table 2 shows the volume average particle size of silicone rubber particles, the shape of silicone rubber particles, the tensile strength at break of silicone rubber, the elongation at break of silicone rubber, and the hardness of silicone rubber measured in the same manner as in Example 1.

[0188] [Table 1]

[0189]

[0190] [Table 2]

[0191]

[0192] [Example 12]

[0193] A vinyl-containing dimethylpolysiloxane (A-1)-4, a vinyl-containing methylpolysiloxane resin (A-2)-1, and a methylhydrogenpolysiloxane (A-3)-1 were mixed and dissolved at a mass ratio of 62.0:26.6:11.4 to prepare a curable liquid silicone composition. The composition is the same as that of the curable liquid silicone composition of Example 11.

[0194] The obtained silicone rubber had a tensile strength at break of 3.0 MPa, an elongation at break of 75%, and a hardness of 61 as measured by a type A durometer.

[0195] 500.0 g of the curable liquid silicone composition, 1.0 g of polyoxyethylene tridecyl ether (ethylene oxide addition mole number = 15 mol) and 100.0 g of water were placed in a 1-liter glass beaker, and stirred at 6,000 rpm using a homogenizer. As a result, it became an oil-in-water type, and thickening was confirmed. Stirring was continued for 15 minutes. Next, 396.6 g of water was added while stirring at 2,000 rpm to obtain a uniform white emulsion. The emulsion was transferred to a 1-liter glass flask equipped with a stirring device using an anchor-type stirring blade, and after adjusting the temperature to 15°C to 20°C, a mixed solution of 1.2 g of an isododecane solution of a platinum-vinyl-containing disiloxane complex (platinum content 0.5%) and 1.2 g of polyoxyethylene lauryl ether (ethylene oxide addition mole number = 9 mol) was added under stirring. Stirring was performed at the temperature for 6 hours to obtain an aqueous dispersion of silicone rubber particles.

[0196] The shape of the silicone rubber particles observed under an optical microscope was spherical. The volume average particle size was measured using a particle size distribution measuring device "Coulter Particle Counter (Multisizer) 3" (trade name, manufactured by Beckman Coulter (Co., Ltd.)), and the result was 11 μm. The obtained silicone rubber particles were evaporated and removed by spray dryer under the conditions of an inlet temperature of 150°C and an outlet temperature of 80°C to obtain silicone rubber particles. Furthermore, the obtained silicone rubber particles were heated in a constant temperature bath at 150°C for 30 minutes. The obtained silicone rubber particles were non-sticky particles, and the shape was spherical when observed under an electron microscope.

[0197] [Example 13]

[0198] Into a 1-liter glass beaker, 500.0 g of the same curable liquid silicone composition as in Example 12, 6.0 g of polyoxyethylene tridecyl ether (ethylene oxide addition mole number = 15 moles), and 40.0 g of water were placed, and stirred at 6,000 rpm using a homogenizer. As a result, an oil-in-water type was obtained, and thickening was confirmed. Next, the mixer was changed to a disperser, and stirred at 4,000 rpm for 15 minutes. The mixer was changed to a homogenizer again, and 451.6 g of water was added while stirring at 2,000 rpm, resulting in a uniform white emulsion. The emulsion was transferred to a 1-liter glass flask equipped with a stirring device using an anchor-type stirring blade, and after adjusting the temperature to 15° C. to 20° C., a mixed solution of 1.2 g of an isododecane solution of a platinum-vinyl disiloxane complex (platinum content 0.5%) and 1.2 g of polyoxyethylene lauryl ether (ethylene oxide addition mole number = 9 mol) was added under stirring. Stirring was performed at the temperature for 6 hours to obtain an aqueous dispersion of silicone rubber particles.

[0199] The silicone rubber particles were spherical when observed under an optical microscope. The volume average particle size was measured using a particle size distribution measuring device "Coulter Particle Counter (Multisizer) 3" (trade name, manufactured by Beckman Coulter (Co., Ltd.)), and the result was 1.9 μm. For the obtained water dispersion of silicone rubber particles, a spray dryer was used to volatilize and remove water under the conditions of an inlet temperature of 150°C and an outlet temperature of 80°C to obtain silicone rubber particles. Furthermore, the obtained silicone rubber particles were heated in a constant temperature bath at 150°C for 30 minutes. The obtained silicone rubber particles were non-sticky particles, and were spherical when observed under an electron microscope.

[0200] [Example 14]

[0201] 500.0 g of the same curable liquid silicone composition as in Example 12, 5.7 g of a 35% sodium pentylnaphthalenesulfonate aqueous solution (sodium pentylnaphthalenesulfonate amount = about 2.0 g) and 76.0 g of water were placed in a 1-liter glass beaker and stirred at 6,000 rpm using a homomixer. As a result, an oil-in-water type was obtained and thickening was confirmed. Next, the mixer was changed to a disperser and stirred at 4,000 rpm for 15 minutes. The mixer was changed to a homomixer again, and 415.9 g of water was added while stirring at 2,000 rpm to obtain a uniform white emulsion. The emulsion was transferred to a 1-liter glass flask equipped with a stirring device using an anchor-type stirring blade, and after adjusting the temperature to 15° C. to 20° C., a mixed solution of 1.2 g of an isododecane solution of a platinum-vinyl disiloxane complex (platinum content 0.5%) and 1.2 g of polyoxyethylene lauryl ether (ethylene oxide addition mole number = 9 mol) was added under stirring. Stirring was performed at the temperature for 6 hours to obtain an aqueous dispersion of silicone rubber particles.

[0202] The silicone rubber particles were spherical when observed under an optical microscope. The volume average particle size was measured using a particle size distribution measuring device "Coulter Particle Counter (Multisizer) 3" (trade name, manufactured by Beckman Coulter (Co., Ltd.)), and the result was 6.4 μm. For the obtained water dispersion of silicone rubber particles, a spray dryer was used to volatilize and remove water under the conditions of an inlet temperature of 150°C and an outlet temperature of 80°C to obtain silicone rubber particles. Furthermore, the obtained silicone rubber particles were heated in a constant temperature bath at 150°C for 30 minutes. The obtained silicone rubber particles were non-sticky particles, and were spherical when observed under an electron microscope.

Claims

1. A silicone rubber particle, which is an addition reaction product of a curable liquid silicone composition comprising the following components (A-1), (A-2) and (A-3), and has a volume average particle size of 0.5 μm to 50 μm and is spherical. (A-1) a diorganopolysiloxane having two or more alkenyl groups in one molecule and an alkenyl group amount of 0.0025 mol / 100 g to 0.034 mol / 100 g; (A-2) contains R 1 3SiO 1 / 2 Unit and SiO 4 / 2 Unit, R 1 3SiO 1 / 2 Unit relative to SiO 4 / 2 An organopolysiloxane resin having a molar ratio of units of 0.60 to 1.7 and an alkenyl content of 0.001 mol / 100 g or more, (In the formula, R 1 are independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 30 carbon atoms or an alkenyl group having 2 to 8 carbon atoms, and all R 1 at least one of which is alkenyl); and (A-3) an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms (referred to as SiH groups) in one molecule and having an SiH group content of 0.030 mol / 100 g to 1.30 mol / 100 g, The amount of the component (A-2) is 1.0 to 65 parts by mass based on 100 parts by mass of the total of the components (A-1), (A-2) and (A-3).

2. The silicone rubber particles according to claim 1, wherein the silicone rubber particles comprise a silicone rubber having an elongation at break of 20% or more for a dumbbell-shaped No. 3 test piece according to the test method specified in Japanese Industrial Standard K 6251, and a tensile strength at break of 1.0 MPa or more according to the test method specified in Japanese Industrial Standard K 6251, for a rubber sheet having a thickness of 1 mm subjected to a heat treatment at 150° C. for 30 minutes.

3. An aqueous dispersion of silicone rubber particles, which is the aqueous dispersion of silicone rubber particles as claimed in claim 1 or 2, comprising: (A) 100 parts by mass of the silicone rubber particles according to claim 1 or 2 (B) surfactant: 0.05 to 20 parts by mass, and (C) Water: 20 to 2,000 parts by mass.

Images