Silicone rubber particles and aqueous dispersions of silicone rubber particles

Abstract

To provide silicone rubber particles and a water dispersion which have high strength and elongation and have a small amount of aggregated particles.SOLUTION: Silicone rubber particles are an addition reaction product of a curable liquid silicone composition containing following three components, have a volume average particle diameter of 0.5 to 50 μm, and are spherical. (A-1) Diorganopolysiloxane having two or more alkenyl groups in one molecule, (A-2) an organopolysiloxane resin containing an R13SiO1 / 2 unit and an SiO4 / 2 unit, wherein R1 is each independently a monovalent group having no alkenyl group or having an alkenyl group, and at least one of all the R1 is an alkenyl group, and (A-3) organohydrogenpolysiloxane having two or more silicon atom-bonded hydrogen atoms in one molecule, wherein an amount of the component (A-2) with respect to 100 pts.mass of the total of the component (A-1), the component (A-2) and the component (A-3) is 1.0 to 65 pts.mass.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to silicone rubber particles with high strength and elongation, and to aqueous dispersions of said silicone rubber particles. [Background technology]

[0002] Silicone rubber particles are used in applications such as stress relievers for resins, light diffusers for resins, texture enhancers for cosmetics, matting agents, texture enhancers, and lubricity enhancers for paints and coatings. Generally, silicone rubber particles do not contain fillers such as silica, resulting in low rubber strength and limited elongation. In applications such as paints and coatings, the silicone rubber particles may break down under the load of friction applied to the coating.

[0003] Patent Document 1 proposes high-strength silicone rubber particles containing silica. These particles are produced by mixing silica with a curable liquid silicone composition, dispersing (emulsifying) the mixture in water containing a surfactant, and then curing it. However, this method results in an emulsion with poor stability, and some particles may aggregate. Furthermore, it is difficult to increase the silica content in the particles, making it challenging to produce rubber particles with higher strength. Patent Document 2 proposes silicone rubber particles containing organosiloxane resin, using diorganopolysiloxane having alkenyl groups, organopolysiloxane resin, and organohydrogenpolysiloxane having silicon atom-bonded hydrogen as raw materials. However, the silicone rubber particles described in Patent Document 2 have low rubber strength and elongation. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 4-168117 [Patent Document 2] Japanese Patent Publication No. 2000-204258

[0005] The present invention has been made in view of the above circumstances, and aims to provide silicone rubber particles and aqueous dispersions of silicone rubber particles that have high strength and elongation and a small amount of aggregated particles. [Overview of the project] [Means for solving the problem]

[0006] As a result of diligent research to achieve the above objective, the inventors have discovered that the above objective can be achieved by using a specific amount of organopolysiloxane having an alkenyl group in silicone rubber particles containing organopolysiloxane resin, which are made from diorganopolysiloxane having an alkenyl group, organopolysiloxane resin having an alkenyl group, and organohydrogenpolysiloxane having silicon atom-bonded hydrogen, and have thus completed the present invention.

[0007] In other words, the present invention provides the following silicone rubber particles and aqueous dispersions of silicone rubber particles. Silicone rubber particles are spherical, having a volume average particle size of 0.5 to 50 μm, and are the addition reaction product of a curable liquid silicone composition containing the following components (A-1), (A-2), and (A-3). (A-1) Diorganopolysiloxane having two or more alkenyl groups in one molecule, with an alkenyl group content of 0.0025 to 0.034 mol / 100g, (A-2)R 1 3SiO 1 / 2 Units and SiO 4 / 2 It contains units, SiO 4 / 2 R for units 1 3SiO 1 / 2 Organopolysiloxane resins having a molar ratio of 0.60 to 1.7 and an alkenyl group content of 0.001 mol / 100g or more, (In the above formula, R 1 These are independently substituted or unsubstituted monovalent hydrocarbon groups having 1 to 30 carbon atoms that do not have an alkenyl group, or alkenyl groups having 2 to 6 carbon atoms, and all R 1(At least one of them is an alkenyl group), and (A-3) Organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms (referred to as SiH groups) in one molecule, with a SiH group content of 0.030 to 1.30 mol / 100g The amount of component (A-2) is 1.0 to 65 parts by mass relative to 100 parts by mass of the total of components (A-1), (A-2), and (A-3).

[0008] Furthermore, the present invention provides silicone rubber particles in which the silicone rubber particles are made of silicone rubber having a 1 mm thick rubber sheet heat-treated at 150°C for 30 minutes, and a dumbbell-shaped test piece of type 3 that has an elongation of 20% or more at break according to the test method specified in JIS K 6251, and a tensile strength at break of 1.0 MPa or more according to the test method specified in JIS K 6251.

[0009] Furthermore, the present invention, (A) Silicone rubber particles according to claim 1 or 2: 100 parts by mass (B) Surfactant: 0.05 to 20 parts by mass, and (C) Water: 20~2,000 parts by mass The present invention provides an aqueous dispersion of the silicone rubber particles, including the above. [Effects of the Invention]

[0010] The silicone rubber particles of the present invention have high rubber strength and elongation. The silicone particles and aqueous dispersions containing the silicone particles are useful for paints and coatings that are subjected to friction. [Modes for carrying out the invention]

[0011] The present invention will be described in detail below. [Silicone rubber particles] The shape of the silicone rubber particles (A) of the present invention is spherical. In this specification, "spherical" means that the shape of the particles is not only a perfect sphere, but also an average aspect ratio of the length of the longest axis / the length of the shortest axis (aspect ratio) 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, and it can also be a deformed sphere. The shape of the particles can be confirmed by observing the particles with an optical microscope, an electron microscope, etc. It can also be measured by a particle shape analyzer using the dynamic image analysis method. The volume average particle diameter of the particles is 0.5 to 50 μm, preferably 1.0 to 30 μm, more preferably 2.0 to 20 μm. The volume average particle diameter is measured by the Coulter counter method (electrical resistance method).

[0012] The silicone rubber of the silicone rubber particles (A) is an addition reaction product of a curable liquid silicone composition containing (A-1) a diorganopolysiloxane having two or more alkenyl groups in one molecule, (A-2) an organopolysiloxane resin having an alkenyl group, and (A-3) an organohydrogenpolysiloxane having two or more SiH groups in one molecule.

[0013] The diorganopolysiloxane having two or more alkenyl groups in one molecule of the component (A-1) has the following average composition formula (1) R 2 a R 3 b SiO (4-a-b) / 2 (1) shown by. In the formula, R 2 are each independently a monovalent hydrocarbon group having 1 to 30 carbon atoms which is unsubstituted or substituted and does not have an alkenyl group, and R 3 are each 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. One kind of the diorganopolysiloxane represented by the average composition formula (1) may be used alone or two or more kinds may be used in combination.

[0014] R 2is a monovalent hydrocarbon group having 1 to 30 carbon atoms, which is unsubstituted or substituted, preferably a monovalent hydrocarbon group having 1 to 22 carbon atoms, more preferably 1 to 18 carbon atoms. R 2 Examples of the group include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, decyl group, undecyl group, dodecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group, henicicosyl group, docosyl group, tricosyl group, tetracosyl group, triacontyl group; aryl groups such as phenyl group, tolyl group, naphthyl group; aralkyl groups such as benzyl group, phenethyl group; cycloalkyl groups such as cyclopentyl group, cyclohexyl group, cycloheptyl group; and hydrocarbon groups in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with atoms such as halogen atoms (fluorine atom, chlorine atom, bromine atom, iodine atom) and / or substituents such as acryloyloxy group, methacryloyloxy group, amino group, epoxy group, glycidoxy group, carboxyl group. In all R 2 It is preferable that 50 mol% or more thereof is a methyl group. R 3 Examples of the group include vinyl group, allyl group, propenyl group, butenyl group, pentenyl group, hexenyl group, octenyl group, preferably vinyl group, allyl group and hexenyl group, more preferably vinyl group. a and b are preferably positive numbers satisfying 0 < a ≦ 2.295, 0.005 ≦ b ≦ 2.3, and 0.5 ≦ a + b ≦ 2.3.

[0015] The silicone rubber particles of the present invention are characterized in that the amount of alkenyl groups in component (A-1) is 0.0025 to 0.034 mol / 100g. If the amount is greater than 0.034 mol / 100g, the strength and elongation of the resulting silicone rubber will be lower. If the amount is less than 0.0025 mol / 100g, a structure with a high degree of polymerization will be formed, resulting in high viscosity, and the viscosity of the curable liquid silicone consisting of components (A-2) and (A-3) will be high, making emulsification as described later difficult. Preferably, the amount is 0.0030 to 0.027 mol / 100g, more preferably 0.0035 to 0.020 mol / 100g.

[0016] The viscosity of component (A-1) at 25°C is 100,000 mm². 2 A value of less than / s is preferable, and more preferably 50,000 mm 2 The viscosity is less than / s. 2 If the viscosity is higher than / s, the viscosity of the curable liquid silicone consisting of components (A-2) and (A-3) will increase, making emulsification, as described later, difficult. There is no particular lower limit to the viscosity, but it is approximately 150 mm. 2 At a degree of polymerization lower than / s, the amount of alkenyl is unlikely to fall below 0.033 mol / 100g, therefore, 150 mm 2 Anything above / s is fine, especially 300mm 2 It is / s or greater. Furthermore, the structure of component (A-1) may be linear, cyclic, or branched, but linear or branched with fewer branching units is particularly preferred. The bonding site of the alkenyl group is not particularly limited and may be bonded to any silicon atom in the side chain or terminal of the molecule.

[0017] Examples of linear structures include those represented by the following general formula (2). [ka] In the formula, R 2 , R 3The same applies as described above, where c is a positive number between 10 and 1,500, preferably between 30 and 1,000, more preferably between 50 and 800, and even more preferably between 80 and 800; d is 0 or a positive number less than or equal to 50; and e is 0, 1, 2, or 3, provided that d and e satisfy d + 2 × e ≥ 2.

[0018] Examples of branched structures include R 2 SiO 3 / 2 Examples include those represented by the following general formula (3), which are branched depending on the unit. [ka] In the formula, R 2 , R 3 The same applies as described above, where f is a positive number between 10 and 1,500, preferably between 30 and 1,000, more preferably between 50 and 800, and even more preferably between 80 and 800; g is a positive number of 0 or less than or equal to 50; h is a positive number between 1 and 10; and i is 0, 1, 2, or 3, provided that g and i satisfy g+i≧1.

[0019] SiO 4 / 2 An example of a structure that branches according to its units is the one represented by the following general formula (4). [ka] In the formula, R 2 , R 3 The same applies as described above, where j is a positive number between 10 and 1,500, preferably between 30 and 1,000, more preferably between 50 and 800, and even more preferably between 80 and 800; k is a positive number of 0 or less than or equal to 50; l is a positive number between 1 and 5; and m is 0, 1, 2, or 3, provided that k and m satisfy k+m≧1.

[0020] (A-2) component is R 1 3SiO 1 / 2 Units and SiO 4 / 2 It is an organopolysiloxane resin containing alkenyl groups with units. It is in a solid state at 25°C. In the formula, R 1These are, independently of each other, substituted or unsubstituted monovalent hydrocarbon groups with 1 to 30 carbon atoms or alkenyl groups with 2 to 8 carbon atoms that do not contain an alkenyl group. Total R 1 At least one of these groups is an alkenyl group. One type of organopolysiloxane resin may be used alone, or two or more types may be used in combination.

[0021] The monovalent hydrocarbon group that does not have an alkenyl group has 1 to 30 carbon atoms, preferably 1 to 20, and more preferably 1 to 10. The monovalent hydrocarbon group that does not have an alkenyl group is R 2 The bases exemplified for this purpose are listed, and the total R 1 It is preferable that 50 mol% or more of the material consists of methyl groups.

[0022] Alkenyl groups having 2 to 8 carbon atoms include vinyl, allyl, propenyl, butenyl, pentenyl, and hexenyl groups, with vinyl and allyl groups being preferred, and vinyl groups being more preferred.

[0023] In organopolysiloxane resins, R 1 3SiO 1 / 2 Units (hereinafter referred to as M units) and SiO 4 / 2 The molar ratio of the unit (hereinafter referred to as Q unit), i.e., [moles of M unit] / [moles of Q unit], is 0.60 to 1.7. Preferably, it is 0.65 to 1.3, and more preferably 0.70 to 1.1.

[0024] (A-2) Component is (R 4 O)SiO 3 / 2 It may contain units. In the formula, R 4 These are, independently of each other, 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 condense together, but R groups do not react. 4 O groups may remain in the organopolysiloxane resin. Examples of unsubstituted monovalent hydrocarbon groups with 1 to 6 carbon atoms include the methyl group, ethyl group, propyl group, butyl group, pentyl group, and hexyl group. (R 4 O)SiO 3 / 2 The content of the unit (called Q3 unit) is (R 4 O)SiO 3 / 2 Units and SiO 4 / 2 Molar ratio of units [(R 4 O)SiO 3 / 2 [Mole as a unit] / [SiO 4 / 2 A quantity such that the moles per unit are less than 0.50 is preferred. That is, [moles per unit Q3] / [moles per unit Q] is preferably 0 to 0.50, more preferably 0.01 to 0.40, and even more preferably 0.02 to 0.30.

[0025] Component (A-2) is solid at 25°C and does not impair the properties of solubility in components (A-1) and (A-3) in the production of the silicone rubber particles (A) described below, R 5 SiO 3 / 2 Units and / or R 6 2SiO 2 / 2 It is also possible to include units. In the formula, R 5 and R 6 These are independently substituted or unsubstituted monovalent hydrocarbon groups having 1 to 30 carbon atoms. 5 SiO 3 / 2 Units (called T units) and R 6 2Si 2 / 2 The amount of unit (referred to as D unit) is preferably such that the ratio of [moles of T unit and D unit] / [moles of Q unit] is 0.3 or less.

[0026] (A-2) component has an alkenyl group content of 0.001 mol / 100 g or more. If it is less than 0.001 mol / 100 g, the strength and elongation of the silicone rubber will be low. Preferably, it is 0.005 mol / 100 g or more, more preferably 0.01 mol / 100 g or more. The upper limit is not particularly limited, but if it is more than 2.0 mol / 100 g, the molar ratio [moles of M unit] / [moles of Q unit] cannot be 1.7 or less, so it may be 0.8 mol / 100 g or less, particularly 0.50 mol / 100 g or less. The polystyrene-reduced weight average molecular weight of the (A-2) component by gel permeation chromatography is preferably 1,000 to 10,000, more preferably 2,000 to 8,000.

[0027] (A-3) component, the organohydrogenpolysiloxane having two or more SiH groups in one molecule, has the following average composition formula (5) R 7 n H o SiO (4-n-0) / 2 (5) shown by. In the formula, R 7 are, independently of each other, unsubstituted or substituted monovalent hydrocarbon groups having no alkenyl group and having 1 to 30 carbon atoms. n and o are numbers satisfying 0 < n < 3, 0 < o ≤ 3 and 0.1 ≤ n + o ≤ 3. One kind of the organohydrogenpolysiloxane represented by the average composition formula (5) may be used alone or two or more kinds may be used in combination.

[0028] R 7 has 1 to 30 carbon atoms, preferably 1 to 22, more preferably 1 to 18. R 7 is the monovalent hydrocarbon group exemplified for R 2 , and preferably 80 mol% or more of R 7 is a methyl group, more preferably 95% or more is a methyl group. n and o are preferably positive numbers satisfying 0 < n ≤ 2.295, 0.005 ≤ o ≤ 2.3 and 0.5 ≤ n + o ≤ 2.3.

[0029] The SiH group content of component (A-3) is 0.030 to 1.30 mol / 100g. If it is less than 0.030 mol / 100g, the strength and elongation of the silicone rubber will be reduced. If it is more than 1.30 mol / 100g, there is a risk of aggregation of dispersed particles in the aqueous dispersion of silicone rubber particles described later. Preferably, it is 0.050 to 1.10 mol / 100g, and more preferably, 0.10 to 0.90 mol / 100g.

[0030] The viscosity of component (A-3) at 25°C is 100,000 mm². 2 A value of less than or equal to / s is preferred, and more preferably 10,000 mm 2 The viscosity is less than / s. 2 When the viscosity is less than or equal to / s, it is particularly easy to obtain silicone fine particles with a narrow particle size distribution by the manufacturing method described later. The lower limit of viscosity is not particularly limited, but 0.4 mm 2 Anything above / s is fine, especially 2mm 2 It is / s or greater. Furthermore, the structure of component (A-3) may be linear, cyclic, or branched, but linear or branched is particularly preferred. Also, the bonding sites of the hydrogen atoms bonded to the silicon atoms are not particularly limited and may be bonded to any silicon atom in the side chains or terminals of the molecule.

[0031] Examples of linear structures include those represented by the following general formula (6). [ka] In the formula, R 7 As described above, p is a positive number less than or equal to 1,500, preferably between 1 and 1,000, more preferably between 5 and 500, and even more preferably between 10 and 100; q is 0 or a positive number less than or equal to 300, preferably between 1 and 100, more preferably between 5 and 60; and r is 0, 1, 2, or 3, provided that q and r satisfy q + 2 × r ≥ 2.

[0032] Examples of branched structures include R 7 SiO 3 / 2Examples include those represented by the following general formula (7) and branched by units of [Chemical formula] In the formula, R 7 is as described above, s is a positive number of 1,500 or less, preferably 1 to 1,000, more preferably 5 to 500, still more preferably 10 to 100, t is 0 or a positive number of 300 or less, preferably 1 to 100, more preferably 5 to 60, u is a positive number of 1 to 10, v is 0, 1, 2 or 3, provided that t and v satisfy t + v ≥ 1.

[0033] SiO 4 / 2 Examples of the structure branched by units of [Chemical formula] In the formula, R 7 is as described above, w is a positive number of 1,500 or less, preferably 1 to 1,000, more preferably 5 to 500, still more preferably 10 to 100, x is 0 or a positive number of 300 or less, preferably 1 to 100, more preferably 5 to 60, y is a positive number of 1 to 5, z is 0, 1, 2 or 3, provided that x and z satisfy x + z ≥ 1.

[0034] Moreover, examples include those represented by the following unit formula (9) and having hydrogen atoms bonded to two or more silicon atoms per molecule. [R 7 3SiO 1 / 2 a1 [H(R 7 )2SiO 1 / 2 b1 [SiO 4 / 2 c1 [(OR 8 )SiO 3 / 2 d1 (9) In the formula, R 7 is the same as above, R 8 ​​​​is a hydrogen atom or an unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms, where 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 for a1, b1, c1, and d1 is 20 each.

[0035] A curable liquid silicone composition is obtained by mixing and dissolving components of 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.

[0036] The curable liquid silicone composition has a composition in which component (A-2) is present in an amount of 1.0 to 65 parts by mass per 100 parts by mass of the total amount of components (A-1), (A-2), and (A-3). If the amount of component (A-2) is less than 1.0 part by mass, the elongation and strength of the silicone rubber will be low. If the amount is greater than 65 parts by mass, the viscosity of the liquid silicone composition will be high, making emulsification as described later difficult. Preferably, it is 2.0 to 55 parts by mass, more preferably 4.0 to 45 parts by mass.

[0037] The curable liquid silicone composition is preferably composed such that the number ratio of SiH groups in component (A-3) to the total amount of alkenyl groups in component (A-1) and component (A-2) is 0.9 to 3.0. If the number ratio of SiH groups in component (A-3) is less than 0.9, the elongation and strength of the silicone rubber will be low. If it is higher than 3.0, there is a risk of aggregation 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.

[0038] The silicone rubber of the silicone rubber particles (A) is an addition reaction product of the above-mentioned curable liquid silicone composition. It is preferable to use a catalyst for the addition reaction. Examples of catalysts for the addition reaction include platinum group metal catalysts used in hydrosilylation reactions. For example, elemental platinum group metals such as platinum (including platinum black), rhodium, and palladium; platinum chloride, platinum chlorinated acid, and platinum chloride such as H2PtCl4·XH2O, H2PtCl6·XH2O, NaHPtCl6·XH2O, KHPtCl6·XH2O, Na2PtCl6·XH2O, K2PtCl4·XH2O, PtCl4·XH2O, PtCl2, and Na2HPtCl4·XH2O (wherein X is an integer from 0 to 6, preferably 0 or 6). Examples include salts; alcohol-modified chloroplatinic acid; platinum chloride; complexes of chloroplatinic acid and olefins; complexes of chloroplatinic acid and vinyl group-containing siloxanes; complexes of platinum and vinyl group-containing siloxanes; platinum group metals such as platinum black and palladium supported on carriers such as alumina, silica, and carbon; rhodium-olefin complexes; and chlorotris(triphenylphosphine)rhodium (Wilkinson catalyst). These can be used individually or in combination of two or more.

[0039] The amount of platinum group metal catalyst blended should be an effective amount as an addition reaction catalyst, such that the amount of platinum group metal in the platinum group metal catalyst is typically about 0.1 to 500 ppm, preferably about 0.5 to 200 ppm, and more preferably about 1 to 100 ppm, on a mass basis, relative to the total amount of components (A-1), (A-2), and (A-3). The addition reaction curing conditions for the curable liquid silicone composition are not particularly limited, but are preferably at a temperature of 1 to 100°C for 1 hour or more. The temperature is preferably 10°C to 100°C.

[0040] 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 tensile strength at break refer to the values ​​measured using the test method specified in JIS K 6251:2017 for a 1 mm thick dumbbell-shaped test piece (Type 3) 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 upper limit to the elongation at break, but it should be 1000% or less, and especially 500% or less. There is no particular upper limit to the tensile strength at break, but it should be 20 MPa or less, and especially 10 MPa or less.

[0041] The silicone rubber of the silicone rubber particles (A) preferably has a Type A durometer hardness in the range of 20 to 95. Hardness refers to the value measured by the test method specified in JIS K 6253:2012 on a test piece treated at 150°C for 30 minutes. More preferably, it is in the range of 40 to 85.

[0042] The silicone rubber may contain silicone oil, organosilane, inorganic powder, organic powder, and antioxidants, etc.

[0043] [Aqueous dispersion of silicone rubber particles] The aqueous dispersion of silicone rubber particles of the present invention has a composition comprising (A) silicone rubber particles, (B) a surfactant, and (C) water.

[0044] Surfactant (B) functions as a dispersant for silicone rubber particles. Furthermore, as will be described later, it also functions as an emulsifier for the curable liquid silicone composition in the production of an aqueous dispersion of silicone rubber particles.

[0045] The surfactant (B) is not particularly limited and may be a nonionic surfactant, anionic surfactant, cationic surfactant, or amphoteric surfactant. Preferably, it is a nonionic surfactant or anionic surfactant. These can be used individually or in appropriate combinations of two or more.

[0046] Examples of nonionic surfactants 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, 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, and polyoxyethylene polyoxypropylene-modified organopolysiloxanes. Preferably, the HLB value is 12.0 to 19.0 and the HLB value is 13.0 to 18.0. More preferably, the HLB value is 13.0 to 18.0. The HLB value here is calculated using the following formula: HLB = [Molecular weight of polyoxyethylene portion and alcohol portion / Molecular weight of surfactant] × 20 This value is calculated using the Griffin formula shown. When using two or more nonionic surfactants with different HLB values ​​in combination, the above HLB value is a weighted average.

[0047] Examples of anionic surfactants include alkyl sulfate esters such as sodium lauryl sulfate, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkylphenyl ether sulfate, sulfate esters of fatty acid alkylolamides, alkylbenzene sulfonates, polyoxyethylene alkylphenyl ether sulfonates, α-olefin sulfonates, α-sulfo fatty acid esters, alkylnaphthalene sulfonates, alkyldiphenyl ether disulfonates, alkanesulfonates, N-acyl taurates, dialkyl sulfosuccinates, monoalkyl sulfosuccinates, polyoxyethylene alkyl ether sulfosuccinates, fatty acid salts, polyoxyethylene alkyl ether carboxylates, N-acyl amino acid salts, monoalkyl phosphate salts, dialkyl phosphate salts, and polyoxyethylene alkyl ether phosphate salts. Preferably, alkyl sulfate esters with 10 to 18 C1 of the alkyl group, polyoxyethylene alkyl ether sulfate esters, sulfate esters of fatty acid alkylolamides, alkylbenzene sulfonates, α-sulfo fatty acid esters, alkane sulfonates, N-acyl taurates, polyoxyethylene alkyl ether sulfosuccinates, polyoxyethylene alkyl ether carboxylates, N-acyl amino acid salts, monoalkyl phosphate esters, dialkyl phosphate esters, polyoxyethylene alkyl ether phosphate esters, α-olefin sulfonates with 10 to 18 C1 of the olefin, alkylnaphthalene sulfonates with 1 to 14 C1 of the alkyl group, and alkyldiphenyl ether disulfonates with 6 to 14 C1 of the alkyl group.

[0048] Examples of cationic surfactants include alkyltrimethylammonium salts, dialkyldimethylammonium salts, polyoxyethylenealkyldimethylammonium salts, dipolyoxyethylenealkylmethylammonium salts, tripolyoxyethylenealkylammonium salts, alkylbenzyldimethylammonium salts, alkylpyridium salts, monoalkylamine salts, and monoalkylamidoamine salts. Examples of amphoteric surfactants include alkyldimethylamine oxide, alkyldimethylcarboxybetaine, alkylamidopropyldimethylcarboxybetaine, alkylhydroxysulfobetaine, and alkylcarboxymethylhydroxyethylimidazolinium betaine.

[0049] The amount of component (B) is 0.05 to 20 parts by mass per 100 parts by mass of silicone rubber particles (A). If the amount is less than 0.05 parts by mass, the curable liquid silicone composition described later will not be able to be emulsified, and the stability of the aqueous dispersion may decrease. If the amount is more than 20 parts by mass, it will not improve the aqueous dispersion performance of the silicone rubber particles and may impair the properties of the paint or other materials that are blended with it. Preferably, it is 0.10 to 10 parts by mass, more preferably 0.20 to 2 parts by mass.

[0050] Water (C) is the dispersion medium for the silicone rubber particles (A). The amount of component (C) is 20 to 2,000 parts by mass, preferably 40 to 1,000 parts by mass, per 100 parts by mass of silicone rubber particles (A).

[0051] The aqueous dispersion of silicone rubber particles may contain preservatives, thickeners, pH adjusters, defoamers, and other additives as needed.

[0052] [Aqueous dispersion of silicone rubber particles and method for producing silicone rubber particles] Aqueous dispersions of silicone rubber particles can be produced by known methods. For example, a method can be used in which a surfactant (B) and water (C) are added to a curable liquid silicone composition consisting of components (A-1), (A-2), and (A-3), emulsification is performed to form an emulsion, and then a platinum group metal catalyst is added to carry out an addition reaction.

[0053] To perform emulsification, a general emulsifying and dispersing machine can be used, such as a high-speed rotating centrifugal radiation type stirrer like a homodisper, a high-speed rotating shear type stirrer like a homomixer, a high-pressure jet type emulsifying and dispersing machine like a homogenizer, a colloid mill, or an ultrasonic emulsifier. As long as emulsification can be achieved and the desired particle size can be obtained, the stirring speed, time, etc., are not particularly limited.

[0054] After preparing the emulsion, a platinum group metal catalyst is added. However, if the catalyst has poor dispersibility in water, it is preferable to add it to the emulsion in a state where it is dissolved in a surfactant. Examples of surfactants include those listed above, with nonionic surfactants being particularly preferred. Alternatively, the platinum group metal catalyst may be incorporated into the curable liquid silicone composition beforehand. In this case, it is necessary to control the temperature, adjust the amount of catalyst, or add reaction regulators to prevent the reaction from proceeding before emulsification is complete.

[0055] The addition reaction may be carried out at room temperature (1-30°C), but it may also be carried out under heating below 100°C to increase the reaction rate or improve the reaction efficiency. The addition reaction time should be selected as appropriate.

[0056] Silicone rubber particles can be obtained by removing water (C) from the aqueous dispersion of silicone rubber particles obtained in the above step.

[0057] Water (C) can be removed, for example, by heating the aqueous dispersion under normal or reduced pressure to volatilize it. Examples include removing water by letting the dispersion stand under heating, removing water while stirring and flowing the dispersion under heating, spraying and dispersing the dispersion in a hot air stream like a spray dryer, and using a fluid heat transfer medium. As a pretreatment for this operation, the particles may be aggregated by adding inorganic salts, and then concentrated by methods such as filtration separation by pressure filtration, centrifugation, or decantation. If necessary, the concentrate may be washed with water or alcohol.

[0058] When silicone rubber particles contain silicone oil, organosilane, inorganic powder, organic powder, and antioxidants, these can be dissolved or dispersed in a curable liquid silicone composition.

[0059] The aqueous dispersion of silicone rubber particles or silicone rubber particles of the present invention are used, for example, by being incorporated into paints and coatings. It is desirable to apply the paint or coating containing the silicone rubber particles to a substrate and then heat-treat it at a temperature of 100 to 300°C for 1 minute to 3 hours. Heat treatment improves the addition reaction rate and increases the elongation and strength of the silicone rubber. Alternatively, the silicone rubber particles may be heat-treated at a temperature of 100 to 300°C for 1 minute to 3 hours before being incorporated into paints or coatings. [Examples]

[0060] 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 this example, the kinematic viscosity was measured using a capillary viscometer at 25°C.

[0061] The following polysiloxanes were prepared. (A-1)-1: As shown in formula (10), the vinyl group content is 0.00627 mol / 100g and the kinematic viscosity is 5,060 mmHg. 2 / s vinyl group-containing dimethylpolysiloxane [ka]

[0062] (A-1)-2: As shown in formula (11), the vinyl group content is 0.00369 mol / 100g and the kinematic viscosity is 30,500 mmHg. 2 / s vinyl group-containing dimethylpolysiloxane [ka]

[0063] (A-1)-3: As shown in formula (12), the vinyl group content is 0.0179 mol / 100g and the kinematic viscosity is 386 mmHg. 2 / s vinyl group-containing dimethylpolysiloxane [ka]

[0064] (A-1)-4: This is a solution obtained by mixing (A-1)-1 and (A-1)-3 in a mass ratio of 40:60, with a vinyl group content of 0.0132 mol / 100g and a kinematic viscosity of 1080 mmHg. 2 / s vinyl group-containing dimethylpolysiloxane

[0065] (A-1)-5: As shown in formula (13), the vinyl group content is 0.120 mol / 100 g and the kinematic viscosity is 23 mmHg. 2 Dimethylpolysiloxane containing vinyl groups of / s (for comparative example) [ka]

[0066] (A-1)-6: Formulated by equation (14), with a vinyl group content of 0.0348 mol / 100g and a kinematic viscosity of 125 mmHg. 2 Dimethylpolysiloxane containing vinyl groups of / s (for comparative example) [ka]

[0067] (A-1)-7: As shown in formula (15), the vinyl group content is 0.0433 mol / 100g and the kinematic viscosity is 378 mmHg. 2 Dimethylpolysiloxane containing vinyl groups of / s (for comparative example) [ka]

[0068] (A-2)-1:(CH3)3SiO 1 / 2 Unit: (CH3)2(CH=CH2)SiO 1 / 2 Unit, SiO4 / 2 Unit: (OH)SiO 3 / 2 Units, and (OCH3)SiO 3 / 2 A vinyl group-containing methylpolysiloxane resin consisting of units and having the following molar ratios. Molar ratio ([(CH3)3SiO 1 / 2 ]+[(CH3)2(CH=CH2)SiO1 / 2 ]) / [SiO 4 / 2 ] is 0.83, Molar ratio [(CH3)3SiO 1 / 2 ] / [SiO 4 / 2 ] is 0.71, Molar ratio [(CH3)2(CH=CH2)SiO 1 / 2 ] / [SiO 4 / 2 ] is 0.1 2, Molar ratio ([HOSiO 3 / 2 ]+[CH3OSiO 3 / 2 ] / [SiO 4 / 2 ]) is 0.088, Molar ratio [HOSiO 3 / 2 ] / [SiO 4 / 2 ] is 0.041, Molar ratio [CH3OSiO 3 / 2 ] / [SiO 4 / 2 ] is 0.047, The vinyl group content is 0.089 mol / 100g, and the weight-average molecular weight is 4,100.

[0069] (A-2)-2:(CH3)3SiO 1 / 2 Unit: (CH=CH2)3SiO 1 / 2 Unit, SiO 4 / 2 Unit, HOSiO 3 / 2 Units, and C2H5OSiO 3 / 2 A vinyl group-containing methylpolysiloxane resin consisting of units and having the following molar ratios. Molar ratio ([(CH3)3SiO 1 / 2 ]+[(CH=CH2)3SiO 1 / 2 ]) / [SiO 4 / 2 ] is 1.01, Molar ratio [(CH3)3SiO 1 / 2 ] / [SiO 4 / 2 ] is 0.90, Molar ratio [(CH=CH2)3SiO1 / 2 ] / [SiO 4 / 2 ] is 0.11, Molar ratio ([HOSiO 3 / 2 ]+[C2H5OSiO 3 / 2 ] / [SiO 4 / 2 ]) is 0.10, Molar ratio [HOSiO 3 / 2 ] / [SiO 4 / 2 ] is 0.050, Molar ratio [C2H5OsSiO 3 / 2 ] / [SiO 4 / 2 ] is 0.050, The vinyl group content is 0.23 mol / 100g, and the weight-average molecular weight is 5,730.

[0070] (A-3)-1: As shown in formula (16), the SiH group content is 0.418 mol / 100g and the kinematic viscosity is 27 mmHg. 2 / s methylhydrogenpolysiloxane [ka]

[0071] (A-3)-2: As shown in formula (17), the SiH group content is 0.744 mol / 100g and the kinematic viscosity is 117 mmHg. 2 / s methylhydrogenpolysiloxane [ka]

[0072] (A-3)-3: As shown in formula (18), the SiH group content is 0.137 mol / 100g and the kinematic viscosity is 37 mmHg. 2 / s methylhydrogenpolysiloxane [ka]

[0073] (A-3)-4: As shown in formula (19), the SiH group content is 0.427 mol / 100g and the kinematic viscosity is 48 mmHg. 2 / s methylhydrogenpolysiloxane [ka]

[0074] [Example 1] A curable liquid silicone composition was prepared by mixing and dissolving vinyl group-containing dimethylpolysiloxane (A-1)-1, vinyl group-containing methylpolysiloxane resin (A-2)-1, and methylhydrogenpolysiloxane (A-3)-1 in a mass ratio of 63.0:27.0:10.0. The number ratio of SiH groups in methylhydrogenpolysiloxane to the total amount of vinyl groups in vinyl group-containing dimethylpolysiloxane and vinyl group-containing methylpolysiloxane resin is 1.49.

[0075] In a 1-liter glass beaker, 500.0 g of a curable liquid silicone composition, 2.0 g of polyoxyethylene tridecyl ether (15 moles of ethylene oxide added), and 80.0 g of water were charged 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, 415.6 g of water was added, and a uniform white emulsion was obtained. This emulsion was transferred to a 1-liter glass flask equipped with an anchor-shaped stirring device, and after adjusting the temperature to 15-20°C, a mixed solution of 1.2 g of isododecane solution of a platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) and 1.2 g of polyoxyethylene lauryl ether (9 moles of ethylene oxide added) was added under stirring. The mixture was stirred at the same temperature for 6 hours to cure the curable liquid silicone by addition reaction, obtaining an aqueous dispersion of silicone rubber particles. Furthermore, the total amount of polyoxyethylene tridecyl ether and polyoxyethylene lauryl ether is 0.64 parts by mass per 100 parts by mass of the resulting silicone rubber particles.

[0076] When the shape of these silicone rubber particles was observed using an optical microscope, they were found to be spherical, and the volume-average particle size was measured using a particle size distribution analyzer, "Multisizer 3" (product name, manufactured by Beckman Coulter, Inc.), and found to be 6.7 μm.

[0077] The resulting aqueous dispersion of silicone rubber particles was subjected to water evaporation using a spray dryer under 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.

[0078] The obtained silicone rubber particles were non-sticky, and their shape, as observed with an electron microscope, was found to be spherical.

[0079] The tensile strength and elongation at break of the silicone rubber particles were measured as follows. To 100 parts by mass of a curable liquid silicone composition prepared with the same composition as in Example 1 above, 0.24 parts by mass of an isododecane solution of a platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) and 0.05 parts by mass of 1,1-dimethylpropynyloxytrimethylsilane (reaction modifier) ​​were mixed, and the mixture was poured into a polypropylene tray to a thickness of approximately 1 mm. After being left at 25°C for 24 hours, the cured silicone was peeled off the tray and heated in a constant temperature bath at 150°C for 30 minutes to obtain a non-sticky silicone rubber sheet. This silicone rubber sheet was cut to the shape and dimensions of a dumbbell-shaped test specimen (Type 3) as specified in JIS K6251:2017, and the tensile strength and 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%.

[0080] The hardness of the silicone rubber particles was measured as follows. To 100 parts by mass of a curable liquid silicone composition prepared with the same composition as in Example 1 above, 0.24 parts by mass of an isododecane solution of a platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) and 0.05 parts by mass of 1,1-dimethylpropynyloxytrimethylsilane (reaction modifier) ​​were mixed, and the mixture was poured into an aluminum petri dish to a thickness of 10 mm. After being left at 25°C for 24 hours, it was heated in a constant temperature bath at 150°C for 30 minutes to obtain a non-sticky silicone rubber. The hardness of this silicone rubber was measured using a Type A durometer specified in JIS K6253 and was found to be 58.

[0081] [Examples 2-11][Comparative Examples 1-10] A curable liquid silicone composition was obtained by mixing and dissolving vinyl group-containing dimethylpolysiloxane, vinyl group-containing methylpolysiloxane resin (some compositions do not use this component), and methylhydrogenpolysiloxane in the composition described in Table 1 or 2, except that Example 1 was repeated to obtain an aqueous dispersion of silicone rubber particles. Table 1 or 2 shows the volume-average particle size, shape of the silicone rubber particles, tensile strength at break, elongation at break, and hardness of the silicone rubber, all measured in the same manner as in Example 1.

[0082] [Table 1]

[0083] [Table 2]

[0084] [Example 12] A curable liquid silicone composition was prepared by mixing and dissolving vinyl group-containing dimethylpolysiloxane (A-1)-4, vinyl group-containing methylpolysiloxane resin (A-2)-1, and methylhydrogenpolysiloxane (A-3)-1 in a mass ratio of 62.0:26.6:11.4. This composition is the same as the curable liquid silicone composition of Example 11. The obtained silicone rubber had a tensile strength of 3.0 MPa at break, an elongation of 75% at break, and a hardness of 61 on a Type A durometer.

[0085] 500.0 g of the above-mentioned curable liquid silicone composition, 1.0 g of polyoxyethylene tridecyl ether (ethylene oxide added = 15 moles), and 100.0 g of water were charged into 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, 396.6 g of water was added while stirring at 2,000 rpm, and a uniform white emulsion was obtained. This emulsion was transferred to a 1-liter glass flask equipped with an anchor-shaped stirring device, and after adjusting the temperature to 15-20°C, a mixed solution of 1.2 g of isododecane solution of a platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) and 1.2 g of polyoxyethylene lauryl ether (ethylene oxide added = 9 moles) was added under stirring. The mixture was stirred at the same temperature for 6 hours to obtain an aqueous dispersion of silicone rubber particles.

[0086] Regarding the aqueous dispersion of silicone rubber particles, the shape of the silicone rubber particles was observed using an optical microscope and found to be spherical. The volume-average particle size was measured using a particle size distribution analyzer "Multisizer 3" (product name, manufactured by Beckman Coulter, Inc.) and found to be 11 μm. The obtained aqueous dispersion of silicone rubber particles was subjected to volatilization removal using a spray dryer under 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 and their shape was observed using an electron microscope and found to be spherical.

[0087] [Example 13] In 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 (15 moles of ethylene oxide added), and 40.0 g of water were charged and stirred at 6,000 rpm using a homomixer. This resulted in an oil-in-water mixture and increased viscosity. Next, the mixer was changed to a disperser and stirred at 4,000 rpm for 15 minutes. The mixer was again changed to a homomixer and 451.6 g of water was added while stirring at 2,000 rpm, resulting in a uniform white emulsion. This emulsion was transferred to a 1-liter glass flask equipped with an anchor-shaped stirring device, and after being heated to 15-20°C, a mixed solution of 1.2 g of isododecane solution of a platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) and 1.2 g of polyoxyethylene lauryl ether (9 moles of ethylene oxide added) was added under stirring. The mixture was stirred at the same temperature for 6 hours to obtain an aqueous dispersion of silicone rubber particles.

[0088] Observation of the shape of these silicone rubber particles using an optical microscope revealed them to be spherical, and the volume-average particle size was measured using a particle size distribution analyzer "Multisizer 3" (product name, manufactured by Beckman Coulter, Inc.) and found to be 1.9 μm. The resulting aqueous dispersion of silicone rubber particles was subjected to evaporation using a spray dryer under 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, and observation of their shape using an electron microscope revealed them to be spherical.

[0089] [Example 14] In a 1-liter glass beaker, 500.0 g of the same curable liquid silicone composition as in Example 12, 5.7 g of 35% sodium pentylnaphthalenesulfonate aqueous solution (sodium pentylnaphthalenesulfonate amount = approximately 2.0 g), and 76.0 g of water were placed and stirred at 6,000 rpm using a homomixer. This resulted in an oil-in-water mixture and increased viscosity. Next, the mixer was changed to a disperser and stirred at 4,000 rpm for 15 minutes. The mixer was then changed back to a homomixer and 415.9 g of water was added while stirring at 2,000 rpm, resulting in a uniform white emulsion. This emulsion was transferred to a 1-liter glass flask equipped with an anchor-shaped stirring device, and after adjusting the temperature to 15-20°C, a mixed solution of 1.2 g of isododecane solution of a platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) and 1.2 g of polyoxyethylene lauryl ether (ethylene oxide addition moles = 9 moles) was added under stirring. The mixture was stirred at the same temperature for 6 hours to obtain an aqueous dispersion of silicone rubber particles.

[0090] Observation of the shape of these silicone rubber particles using an optical microscope revealed them to be spherical, and the volume-average particle size was measured using a particle size distribution analyzer "Multisizer 3" (product name, manufactured by Beckman Coulter, Inc.) and found to be 6.4 μm. The resulting aqueous dispersion of silicone rubber particles was subjected to evaporation using a spray dryer under 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, and observation of their shape using an electron microscope revealed them to be spherical.

Claims

1. Silicone rubber particles are spherical, having a volume average particle size of 0.5 to 50 μm, and are the addition reaction product of a curable liquid silicone composition containing the following components (A-1), (A-2), and (A-3). (A-1) A diorganopolysiloxane having two or more alkenyl groups in one molecule, with an alkenyl group content of 0.0025 to 0.034 mol / 100g. (A-2)R １ ３ SiO １／２ Units and SiO ４／２ It contains units, SiO ４／２ R for units １ ３ SiO １／２ Organopolysiloxane resin having a molar ratio of 0.60 to 1.7 units and an alkenyl group content of 0.001 mol / 100g or more, (where each of the above Rs １ is, independently of one another, a monovalent hydrocarbon group having 1 to 30 carbon atoms and not having an alkenyl group, which may be substituted or unsubstituted, or an alkenyl group having 2 to 8 carbon atoms, and at least one of all the Rs １ is an alkenyl group), and (A-3) Organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms (referred to as SiH groups) in one molecule, with an SiH group content of 0.030 to 1.30 mol / 100g The amount of component (A-2) is 1.0 to 65 parts by mass relative to 100 parts by mass of the total of components (A-1), (A-2), and (A-3).

2. The silicone rubber particles according to claim 1, wherein the silicone rubber particles consist of silicone rubber having a 1 mm thick rubber sheet heat-treated at 150°C for 30 minutes, and exhibiting an elongation of 20% or more at break of a dumbbell-shaped test piece (Type 3) according to the test method specified in JIS K 6251, and a tensile strength of 1.0 MPa or more at break according to the test method specified in JIS K 6251.

3. (A) Silicone rubber particles according to claim 1 or 2: 100 parts by mass (B) Surfactant: 0.05 to 20 parts by mass, and (C) Water: 20 to 2,000 parts by mass An aqueous dispersion of the silicone rubber particles, including the aforementioned.

Images