coating agent

Abstract

To provide a coating agent which enables formation of a coating film excellent in surface smoothness and wear resistance even against high-load friction.SOLUTION: A coating agent contains silicone rubber particles which are an addition reaction product of a curable liquid silicone composition containing (A) a resin having film formability, and (B) following components (B-1), (B-2) and (B-3), and water. A ratio of the (A) to the (B) is 85:15 to 25:75 in a mass ratio. (B-1) Diorganopolysiloxane having two or more alkenyl groups in one molecule, (B-2) organopolysiloxane resin containing an R13SiO1 / 2 unit and an SiO4 / 2 unit, in which a molar ratio of SiO4 / 2 unit to R13SiO1 / 2 is 0.60 to 1.7, wherein R1 is independently a monovalent hydrocarbon group or an alkenyl group, and at least one of all the R1 is an alkenyl group, and (B-3) organohydrogenpolysiloxane having two or more SiH groups in one molecule.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a coating agent, and more particularly to an aqueous coating agent for rubber materials that provides a cured film having excellent abrasion resistance and surface smoothness to a substrate made of a rubber material. [Background technology]

[0002] Conventionally, in order to impart surface smoothness, abrasion resistance, water repellency, stain resistance, and anti-sticking properties to various types of rubber, the surface has been coated with an aqueous silicone-based composition or an aqueous urethane-based composition and then cured.

[0003] In order to improve surface smoothness and abrasion resistance, Patent Document 1 proposes blending spherical silicone rubber particles into a film-forming aqueous silicone composition. The light-scattering properties of the particles can also impart a matte finish to the coating film. However, the abrasion resistance against friction under load is insufficient. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-49955

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a coating agent, particularly an aqueous coating agent for rubber, which forms a coating film that has excellent surface smoothness and abrasion resistance even under high load friction. Summary of the Invention [Means for solving the problem]

[0006] As a result of extensive research to achieve the above object, the inventors of the present invention have hypothesized that the silicone rubber particles in the coating film are being destroyed by the load, and have discovered that the above object can be achieved by blending silicone rubber particles with high rubber strength and great elongation into the coating agent, thereby completing the present invention. Specifically, the inventors discovered that the above-mentioned problems can be solved by blending silicone rubber particles, which are an addition reaction product of a silicone composition obtained by further blending an organopolysiloxane resin having alkenyl groups into a composition made from raw materials of a diorganopolysiloxane having alkenyl groups and an organohydrogenpolysiloxane having silicon-bonded hydrogen, into a coating agent containing a film-forming resin.

[0007] That is, the present invention provides the following coating agent. (A) a resin having film-forming properties; (B) Silicone rubber particles that are the addition reaction product of a curable liquid silicone composition containing the following components (B-1), (B-2), and (B-3): (B-1) a diorganopolysiloxane having two or more alkenyl groups per molecule; (B-2)R 1 3SiO 1 / 2 Units and SiO 4 / 2 Contains SiO units 4 / R for 2 units 1 3SiO 1 / 2 An organopolysiloxane resin having a molar ratio of units of 0.60 to 1.7 (wherein R 1 are each independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 30 carbon atoms without an alkenyl group, or an alkenyl group having 2 to 6 carbon atoms, and all R 1 at least one of which is an alkenyl group, and (B-3) Organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms (referred to as SiH groups) per molecule the amount of the component (B-2) is 1.0 to 65 parts by mass per 100 parts by mass of the total of the components (B-1), (B-2), and (B-3); and a coating agent containing water, wherein the mass ratio of the component (A) to the component (B) is 85:15 to 25:75.

[0008] Furthermore, the present invention provides a coating agent further having at least one characteristic selected from the following [1] to [9]. [1] The coating agent as described above, wherein (B-1) the diorganopolysiloxane has an alkenyl group content of 0.0025 to 0.034 mol / 100 g, (B-2) the organopolysiloxane resin has an alkenyl group content of 0.001 mol / 100 g or more, and (B-3) the organohydrogenpolysiloxane has an SiH group content of 0.030 to 1.30 mol / 100 g. [2] The coating agent, wherein the amount of (A) the film-forming resin is 0.5 to 59 parts by mass, the amount of (B) the silicone rubber particles is 0.3 to 52 parts by mass, and the amount of water is 30 to 98 parts by mass, per 100 parts by mass of the coating agent. [3] The coating agent as described above, wherein the silicone rubber particles are spherical and have a volume average particle size of 0.5 to 50 μm. [4] The coating agent as described above, which contains an emulsion of the resin having film-forming properties. [5] The coating agent as described above, wherein the film-forming resin is at least one selected from the group consisting of urethane resin, vinyl chloride resin, acrylic resin, silicone-acrylic copolymer resin, silicone-urethane copolymer resin, styrene-butadiene-acrylonitrile resin, polyester resin, amide resin, and silicone rubber. [6] The coating agent as described above, wherein the resin having film-forming properties is at least one selected from the group consisting of urethane resin, silicone rubber, and silicone-urethane copolymer resin. [7] The coating agent as described above, which contains an aqueous dispersion of the silicone rubber particles, and the amount of the silicone rubber particles relative to the mass of the aqueous dispersion is 5 to 70 mass %. [8] The coating agent, wherein the silicone rubber particles are silicone rubber having a dumbbell-shaped No. 3 test piece of a 1 mm thick rubber sheet heat-treated at 150°C for 30 minutes, an elongation at break of 15% or more when measured in accordance with JIS K 6251:2017, and a tensile strength at break of 0.9 MPa or more when measured in accordance with JIS K 6251:2017. [9] The coating agent is a coating agent for rubber materials. [Effects of the Invention]

[0009] The coating agent of the present invention can form a film that has excellent surface smoothness and abrasion resistance even under high-load friction. Therefore, the aqueous coating agent for rubber of the present invention can be used to improve the slipperiness, abrasion resistance, and stain resistance of rubber rollers, and to prevent sticking of O-rings, packings, gaskets, etc., and is particularly useful for improving the abrasion resistance, sliding properties, and prevention of squeaking noises of weatherstrip rubber used in car doors and around trucks. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below.

[0011] [Component (A)] Component (A) of the present invention is an emulsion of a film-forming resin, which is a resin that can form a solid film by volatilizing the water in the emulsion or by heat treatment.

[0012] The solid content of the emulsion of the resin (A) is not particularly limited, but is preferably 5 to 80% by mass, more preferably 20 to 60% by mass, based on the mass of the emulsion. The dispersion medium for the emulsion is preferably water.

[0013] The emulsion of the resin (A) may contain an anionic surfactant or a nonionic surfactant. If the resin is self-emulsifying, it may not contain a surfactant.

[0014] In order for the emulsion of the resin (A) to have film-forming ability, the volume average particle size of the resin is preferably small. Specifically, it is 5 to 1000 nm, more preferably 50 to 500 nm, and even more preferably 100 to 400 nm. In the present invention, the volume average particle size of the resin is measured using a laser diffraction / scattering particle size analyzer.

[0015] The coating formed from the above resin emulsion preferably has an elongation at break of 50% or more and a tensile strength at break of 1.0 MPa or more. If the elongation at break is low, the coating will crack when the coated base rubber is deformed. More preferably, it is 100% or more, and even more preferably 200% or more. If the tensile strength at break is low, the abrasion resistance of the coating film will decrease. It is more preferably 1.5 MPa or more, and even more preferably 2.0 MPa or more. In the present invention, the elongation at break and the tensile strength at break refer to values ​​measured using a 1 mm thick dumbbell-shaped No. 3 test piece that has been heat-treated at 150°C after volatilization of water, according to the test method specified in JIS K 6251.

[0016] The film-forming resin emulsion may be any conventionally known film-forming resin. Examples include emulsions of urethane resin, vinyl chloride resin, acrylic resin, silicone-acrylic copolymer resin, silicone-urethane copolymer resin, styrene-butadiene-acrylonitrile resin, polyester resin, amide resin, and silicone rubber. Urethane resin emulsion, silicone rubber emulsion, and silicone-urethane copolymer resin are preferred. Emulsions of two or more different resins may also be used in combination.

[0017] [(B) Component] Component (B) of the present invention is an aqueous dispersion of silicone rubber particles. Component (B) does not have film-forming ability.

[0018] The particle shape of the aqueous dispersion (B) of silicone rubber particles is preferably spherical. In this specification, "spherical" means that the particle shape is not only a perfect sphere, but also a deformed sphere in which the average aspect ratio (length of the longest axis / length of the shortest axis) is typically in the range of 1.0 to 4.0, preferably 1.0 to 2.0, more preferably 1.0 to 1.6, and even more preferably 1.0 to 1.4. The particle shape can be confirmed by observing the particles with an optical microscope, electron microscope, or the like. It can also be measured using a particle shape analyzer that employs dynamic image analysis.

[0019] The volume average particle size of the particles is preferably 0.5 to 50 μm. If the particle size is small, the resulting coating will have poor surface smoothness, while if the particle size is large, the abrasion resistance may be poor. The volume average particle size is preferably 1.0 to 30 μm, more preferably 1.5 to 20 μm, and even more preferably 1.9 to 15 μm. In the present invention, the volume average particle size of the silicone rubber particles is measured by the Coulter counter method (electrical resistance method).

[0020] The silicone rubber of the silicone rubber particles is an addition reaction product of a curable liquid silicone composition containing (B-1) a diorganopolysiloxane having two or more alkenyl groups per molecule, (B-2) an organopolysiloxane resin having alkenyl groups, and (B-3) an organohydrogenpolysiloxane having two or more SiH groups per molecule.

[0021] The diorganopolysiloxane having two or more alkenyl groups per molecule of component (B-1) is represented by the following average composition formula (1): R 2 a R 3 b SiO (4-a-b) / 2 (1) In the formula, R 2 are each independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 30 carbon atoms and not containing an alkenyl group, and R 3are, independently of each other, alkenyl groups 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.

[0022] R 2 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, more preferably 1 to 18 carbon atoms. R 2 Examples 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, etc. It is preferable that 50 mol% or more of all R 2 is a methyl group. R 3 Examples 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.

[0023] In the silicone rubber particles, the amount of alkenyl groups in component (B-1) is preferably 0.0025 to 0.034 mol / 100 g. If it is more than 0.034 mol / 100 g, the strength and elongation of the silicone rubber may be reduced. If it is less than 0.0025 mol / 100 g, a structure with a high degree of polymerization is formed, resulting in a high viscosity. This increases the viscosity of the curable liquid silicone composed of components (B-2) and (B-3), which may make the emulsification described below difficult. A more preferred amount is 0.0030 to 0.027 mol / 100 g, and even more preferably 0.0035 to 0.020 mol / 100 g.

[0024] The viscosity of component (B-1) at 25°C is 100,000 mm 2 / s or less is preferable, and 50,000 mm 2 / s or less. Viscosity is 100,000mm 2 If the viscosity is higher than 1 / s, the viscosity of the curable liquid silicone composed of components (B-2) and (B-3) will be too high, which may make the emulsification described below difficult. 2 At a degree of polymerization lower than 130mm / s, the alkenyl content is unlikely to be 0.034 mol / 100g or less. 2 / s or more is sufficient, especially 200mm 2 / s or more. The structure of component (B-1) may be linear, cyclic, or branched, with linear or branched structures with few branching units being particularly preferred. There are no particular restrictions on the bonding site of the alkenyl group, and it may be bonded to either a silicon atom in the side chain or at the terminal of the molecule.

[0025] An example of a linear structure is one represented by the following general formula (2). [ka] In the formula, R 2 , R 3is the same as above, c is a positive number of 10 to 1,500, preferably a positive number of 30 to 1,200, more preferably a positive number of 50 to 950, and even more preferably a positive number of 80 to 800, d is 0 or a positive number of 50 or less, and e is 0, 1, 2, or 3, with the proviso that d and e are numbers that satisfy d+2×e≧2.

[0026] Examples of branched structures include R 2 SiO 3 / 2 Examples of the branched units include those represented by the following general formula (3). [ka] In the formula, R 2 , R 3 is the same as above, f is a positive number of 10 to 1,500 or less, preferably a positive number of 30 to 1,200, more preferably a positive number of 50 to 950, and even more preferably a positive number of 80 to 800, g is 0 or a positive number of 50 or less, h is a positive number of 1 to 10, and i is 0, 1, 2, or 3, with the proviso that g and i are numbers that satisfy g+i≧1.

[0027] SiO 4 / 2 An example of a structure branched by the unit is one represented by the following general formula (4). [ka] In the formula, R 2 , R 3 is the same as above, j is a positive number of 10 to 1,500 or less, preferably a positive number of 30 to 1,200, more preferably a positive number of 50 to 950, and even more preferably a positive number of 80 to 800, k is 0 or a positive number of 50 or less, l is a positive number of 1 to 5, and m is 0, 1, 2, or 3, with the proviso that k and m are numbers that satisfy k+m≧1.

[0028] The component (B-2) is R 1 SiO 1 / 2 Units and SiO 4 / 2 It is an organopolysiloxane resin with alkenyl groups containing units. It is in a solid state at 25°C. In the formula, R 1are each independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 30 carbon atoms that does not contain an alkenyl group, or an alkenyl group having 2 to 8 carbon atoms. 1 At least one of the groups is an alkenyl group. One organopolysiloxane resin may be used alone, or two or more may be used in combination.

[0029] The monovalent hydrocarbon group not having an alkenyl group has 1 to 30 carbon atoms, preferably 1 to 20, and more preferably 1 to 10. The monovalent hydrocarbon group not having an alkenyl group is, for example, R 2 The groups exemplified for R 2 Preferably, 50 mol % or more of the groups are methyl groups.

[0030] Examples of the alkenyl group having 2 to 8 carbon atoms include a vinyl group, an allyl group, a propenyl group, a butenyl group, a pentenyl group, and a hexenyl group, and preferably a vinyl group and an allyl group, and more preferably a vinyl group.

[0031] In organopolysiloxane resins, R 1 3SiO 1 / 2 Unit (hereinafter referred to as M unit) and SiO 4 / 2 The molar ratio of units (hereinafter referred to as Q units) (i.e., [moles of M units] / [moles of Q units]) is 0.60 to 1.7, preferably 0.65 to 1.3, and more preferably 0.70 to 1.1.

[0032] The component (B-2) contains (R 4 O)SiO 3 / 2 In the formula, R 4 are each independently a hydrogen atom or an unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms. (R 4 O)SiO 3 / 2 The units are derived from the raw material. 4 O groups undergo condensation reaction, but R groups do not react. 4O groups may remain in the organopolysiloxane resin. Examples of unsubstituted monovalent hydrocarbon groups having 1 to 6 carbon atoms include methyl, ethyl, propyl, butyl, pentyl, and hexyl groups. (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 The unit of mole ratio [(R 4 O)SiO 3 / 2 units in moles] / [SiO 4 / 2 In other words, [moles of Q3 units] / [moles of Q units] is preferably 0 to 0.50, more preferably 0.01 to 0.40, and even more preferably 0.02 to 0.30.

[0033] The component (B-2) is preferably a silicone rubber having a R content of 1.0 to 1.5% by weight, within a range that does not impair its ability to remain solid at 25°C and its solubility in the components (B-1) and (B-3) in the production of silicone rubber particles (A), which will be described later. 5 SiO 3 / 2 Units and / or R 6 2SiO 2 / 2 It is also possible to include units in the formula: 5 and R 6 are each independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 30 carbon atoms. 5 SiO 3 / 2 Units (called T units) and R 6 2Si 2 / 2 The content of units (referred to as D units) is preferably an amount such that [moles of T units and QD units] / [moles of Q units] is 0.3 or less.

[0034] (B-2) The amount of alkenyl groups is preferably 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. More preferably, it is 0.005 mol / 100 g or more, and even 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 [mol of M unit] / [mol of Q unit] cannot be 1.7 or less, so it may be 0.8 mol / 100 g or less, and particularly 0.50 mol / 100 g or less.

[0035] (B-2) The polystyrene-reduced weight average molecular weight of the component (B-2) by gel permeation chromatography is preferably from 1,000 to 10,000, and more preferably from 2,000 to 8,000.

[0036] (B-3) The organohydrogenpolysiloxane having two or more SiH groups in one molecule of the component (B-3) has the following average composition formula (5) R 7 n H o SiO (4-n-0) / 2 (5) It is represented by. In the formula, R 7 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. 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.

[0037] R 7 has 1 to 30 carbon atoms, preferably 1 to 22, and 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, and 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.

[0038] The amount of SiH groups in component (B-3) is preferably 0.030 to 1.30 mol / 100 g. If it is less than 0.030 mol / 100 g, the strength and elongation of the silicone rubber will be reduced. If it is more than 1.30 mol / 100 g, there is a risk of dispersed particles coagulating in the aqueous dispersion of silicone rubber particles described below. A more preferred amount is 0.050 to 1.10 mol / 100 g, and even more preferred is 0.10 to 0.90 mol / 100 g.

[0039] The viscosity of component (B-3) at 25°C is 100,000 mm 2 / s or less is preferable, and 10,000 mm 2 / s or less. Viscosity is 100,000mm 2 When the viscosity is less than 0.4 mm / s, it is particularly easy to obtain silicone microparticles with a narrow particle size distribution by the manufacturing method described below. 2 / s or more is sufficient, especially 2 mm 2 / s or more. The structure of component (B-3) may be linear, cyclic, or branched, with linear or branched being particularly preferred. There are no particular restrictions on the bonding position of the hydrogen atom bonded to the silicon atom, and the hydrogen atom may be bonded to either a side chain or terminal silicon atom of the molecule.

[0040] An example of a linear structure is one represented by the following general formula (6). [ka] In the formula, R 7 is as described above, p is a positive number of 1,500 or less, preferably 1 to 1,000, more preferably 5 to 500, and even more preferably 10 to 100, q is 0 or a positive number of 300 or less, preferably 1 to 100, and more preferably 2 to 60, and r is 0, 1, 2, or 3, with the proviso that q and r are numbers that satisfy q+2×r≧2.

[0041] Examples of branched structures include R 7 SiO3 / 2 Examples of the branched units are those represented by the following general formula (7). [ka] 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, and even more preferably 10 to 100, t is 0 or a positive number of 300 or less, preferably 1 to 100, and more preferably 2 to 60, u is a positive number of 1 to 10, and v is 0, 1, 2, or 3, with the proviso that t and v are numbers that satisfy t+v≧1.

[0042] SiO 4 / 2 An example of a structure branched by the unit is one represented by the following general formula (8). [ka] 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, and even more preferably 10 to 100, x is 0 or a positive number of 300 or less, preferably 1 to 100, and more preferably 2 to 60, y is a positive number of 1 to 5, and z is 0, 1, 2, or 3, with the proviso that x and z are numbers that satisfy x+z≧1.

[0043] Further examples include those represented by the following unit formula (9) and having two or more hydrogen atoms bonded to silicon atoms per molecule. [R 7 3SiO 1 / 2 ] a1 [H(R 7 )2SiO 1 / 2 ] b1 [SiO 4 / 2 ] c1 [R 8 OSiO 3 / 2 ] d1 (9) In the formula, R 7 is the same as above, and R 8represents 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 each of a1, b1, c1, and d1 is a number satisfying 20.

[0044] A curable liquid silicone composition is obtained by mixing and dissolving a diorganopolysiloxane (B-1) having two or more alkenyl groups per molecule, an organopolysiloxane resin (B-2) having alkenyl groups, and an organohydrogenpolysiloxane (B-3) having two or more SiH groups per molecule.

[0045] The curable liquid silicone composition has a composition in which the (B-2) component is 1.0 to 65 parts by mass per 100 parts by mass of the total of the (B-1), (B-2), and (B-3) components. If the (B-2) component is less than 1.0 part by mass, the elongation and strength of the silicone rubber will be reduced. If the (B-2) component is more than 65 parts by mass, the viscosity of the liquid silicone composition will increase, making the emulsification described below difficult. The amount is preferably 2.0 to 55 parts by mass, and more preferably 4.0 to 45 parts by mass.

[0046] The curable liquid silicone composition preferably has a composition in which the ratio of the number of SiH groups in component (B-3) to the total number of alkenyl groups in component (B-1) and component (B-2) is 0.9 to 3.0. If the ratio of the number of SiH groups in component (B-3) is less than 0.9, the elongation and strength of the silicone rubber will be reduced. 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 below. A more preferred range is 1.0 to 2.3.

[0047] The silicone rubber of the silicone rubber particles is an addition reaction product of the curable liquid silicone composition. A catalyst is preferably used for the addition reaction. Examples of catalysts for the addition reaction include platinum group metal catalysts used in hydrosilylation reactions. Examples include platinum group metals such as platinum (including platinum black), rhodium, and palladium; platinum chlorides such as HPtCl·XHO, HPtCl·XHO, NaHPtCl·XHO, KHPtCl·XHO, NaPtCl·XHO, KPtCl·XHO, PtCl·XHO, PtCl, and NaHPtCl·XHO (wherein X is an integer of 0 to 6, preferably 0 or 6); chloroplatinic acid; and platinum chlorides such as chloroplatinic acid. Examples of such catalysts include acid 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 black, platinum group metals such as palladium supported on a support such as alumina, silica, or carbon, rhodium-olefin complexes, and chlorotris(triphenylphosphine)rhodium (Wilkinson's catalyst). These catalysts may be used alone or in combination of two or more.

[0048] The amount of platinum group metal catalyst to be added may be an amount effective as an addition reaction catalyst, and is an amount such that the amount of platinum group metal in the platinum group metal catalyst relative to the total amount of components (B-1), (B-2), and (B-3), converted to mass, is typically about 0.1 to 500 ppm, preferably about 0.5 to 200 ppm, and more preferably about 1 to 100 ppm. 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 longer. The temperature is preferably 10 to 100°C.

[0049] The silicone rubber of the silicone rubber particles preferably has an elongation at break of 15% or more and a tensile strength at break of 0.9 MPa or more. The elongation at break and tensile strength at break are values ​​measured using a 1 mm thick dumbbell-shaped No. 3 test piece heat-treated at 150°C for 30 minutes, according to the test method specified in JIS K 6251:2017. Low elongation and tensile strength result in poor abrasion resistance of the resulting coating. More preferably, the elongation at break is 20% or more, and the tensile strength at break is 1.0 MPa or more. The upper limit of the elongation at break is not particularly limited, but it should be 1000% or less, particularly 500% or less. The upper limit of the tensile strength at break is not particularly limited, but it should be 20 MPa or less, particularly 10 MPa or less.

[0050] The silicone rubber of the silicone rubber particles preferably has a Type A durometer hardness in the range of 20 to 95. The hardness is measured using a test piece heat-treated at 150°C for 30 minutes according to the test method specified in JIS K 6253:2012. If the hardness is low, the resulting coating will have poor surface smoothness, while if the hardness is high, the abrasion resistance will be poor. A range of 40 to 85 is more preferable.

[0051] The silicone rubber may contain silicone oil, organosilane, inorganic powder, organic powder, antioxidant, and the like.

[0052] The aqueous dispersion (B) of silicone rubber particles of the present invention is a composition containing, in addition to silicone rubber particles, a surfactant and water. The surfactant functions as a dispersant for the silicone rubber particles. As described below, it also functions as an emulsifier for the curable liquid silicone composition in the production of the aqueous dispersion of silicone rubber particles.

[0053] The surfactant is not particularly limited and may be a nonionic surfactant, an anionic surfactant, a cationic surfactant, or an amphoteric surfactant. Preferably, it is a nonionic surfactant or an anionic surfactant. These may be used alone or in appropriate combination of two or more.

[0054] 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, polyoxyethylene sorbit fatty acid esters, glycerin fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyglycerin fatty acid esters, propylene glycol fatty acid esters, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, polyoxyethylene hydrogenated castor oil fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene fatty acid amides, polyoxyethylene-modified organopolysiloxanes, and polyoxyethylene polyoxypropylene-modified organopolysiloxanes. Preferably, it is a polyoxyethylene alkyl ether or polyoxyethylene polyoxypropylene alkyl ether having an HLB value of 12.0 to 19.0, and more preferably a polyoxyethylene alkyl ether or polyoxyethylene polyoxypropylene alkyl ether having an alkyl group with 10 to 18 carbon atoms. The HLB value is more preferably 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] x 20 When two or more nonionic surfactants with different HLB values ​​are used in combination, the HLB value is a weighted average value.

[0055] Examples of anionic surfactants include alkyl sulfate salts such as sodium lauryl sulfate, polyoxyethylene alkyl ether sulfate salts, polyoxyethylene alkylphenyl ether sulfate salts, sulfate salts of fatty acid alkylolamides, alkylbenzenesulfonates, polyoxyethylene alkylphenyl ether sulfonates, α-olefinsulfonates, α-sulfofatty acid ester salts, alkylnaphthalenesulfonates, alkyldiphenylether disulfonates, alkanesulfonates, N-acyltaurate salts, dialkylsulfosuccinates, monoalkylsulfosuccinates, polyoxyethylene alkyl ether sulfosuccinates, fatty acid salts, polyoxyethylene alkyl ether carboxylate salts, N-acylamino acid salts, monoalkyl phosphate salts, dialkyl phosphate salts, polyoxyethylene alkyl ether phosphate salts, and the like. Preferred are alkyl sulfates in which the alkyl group has 10 to 18 carbon atoms, polyoxyethylene alkyl ether sulfates, sulfates of fatty acid alkylolamides, alkylbenzenesulfonates, α-sulfofatty acid ester salts, alkanesulfonates, N-acyltaurates, polyoxyethylene alkyl ether sulfosuccinates, polyoxyethylene alkyl ether carboxylates, N-acylamino acid salts, monoalkyl phosphate salts, dialkyl phosphate salts, polyoxyethylene alkyl ether phosphate salts, α-olefin sulfonates in which the olefin has 10 to 18 carbon atoms, alkylnaphthalenesulfonates in which the alkyl group has 1 to 14 carbon atoms, and alkyldiphenylether disulfonates in which the alkyl group has 6 to 14 carbon atoms.

[0056] Examples of the cationic surfactant include alkyltrimethylammonium salts, dialkyldimethylammonium salts, polyoxyethylenealkyldimethylammonium salts, dipolyoxyethylenealkylmethylammonium salts, tripolyoxyethylenealkylammonium salts, alkylbenzyldimethylammonium salts, alkylpyridium salts, monoalkylamine salts, and monoalkylamidoamine salts. Examples of the amphoteric surfactant include alkyldimethylamine oxide, alkyldimethylcarboxybetaine, alkylamidopropyldimethylcarboxybetaine, alkylhydroxysulfobetaine, and alkylcarboxymethylhydroxyethylimidazolinium betaine.

[0057] The amount of surfactant is 0.05 to 20 parts by mass per 100 parts by mass of silicone rubber particles. If it is less than 0.05 parts by mass, the curable liquid silicone composition described below cannot be emulsified, and the stability of the aqueous dispersion may decrease. If it is more than 20 parts by mass, the water dispersion performance of the silicone rubber particles will not be improved and the properties of materials such as paints that are blended with it may be impaired. The amount is preferably 0.10 to 10 parts by mass, and more preferably 0.20 to 2 parts by mass.

[0058] The amount of water in the aqueous dispersion (B) of silicone rubber particles of the present invention is 20 to 2,000 parts by mass, preferably 40 to 1,000% by mass, per 100 parts by mass of silicone rubber particles, and preferably 5 to 70% by mass of silicone rubber particles relative to the mass of the aqueous dispersion.

[0059] [Method for producing aqueous dispersion of silicone rubber particles (B)] The aqueous dispersion of silicone rubber particles (B) can be produced by known methods, such as adding a surfactant and water to a curable liquid silicone composition consisting of components (B-1), (B-2), and (B-3), emulsifying the composition to form an emulsion, and then adding a platinum group metal catalyst to carry out an addition reaction.

[0060] For emulsification, a general emulsifying disperser may be used, and examples thereof include a high-speed rotation centrifugal radiation type agitator such as a Homodisper, a high-speed rotation shear type agitator such as a Homomixer, a high-pressure jet type emulsifying disperser such as a homogenizer, a colloid mill, an ultrasonic emulsifier, etc. The stirring speed, time, etc. are not particularly limited as long as emulsification is possible and the desired particle size can be obtained.

[0061] After the emulsion is prepared, a platinum group metal catalyst is added, but if the dispersibility in water is poor, it is preferable to add it to the emulsion in a state dissolved in a surfactant. Examples of surfactants include those mentioned above, and nonionic surfactants are particularly preferred. A method in which a platinum group metal catalyst is previously blended into the curable liquid silicone composition may also be used, but in this case, it is necessary to prevent the reaction from proceeding before the emulsification is completed by adjusting the temperature, adjusting the amount of catalyst, or blending a reaction modifier, etc.

[0062] The addition reaction may be carried out at room temperature (1 to 30°C), but in order to increase the reaction rate or the reaction ratio, it may be carried out under heating at a temperature of less than 100°C. The addition reaction time is appropriately selected.

[0063] When silicone rubber particles contain silicone oil, organosilane, inorganic powder, organic powder, antioxidant, etc., these may be dissolved or dispersed in the curable liquid silicone composition.

[0064] In the present invention, the above-mentioned water dispersion of silicone rubber particles or silicone rubber particles are incorporated into a coating agent for use. After applying the coating agent containing the silicone rubber particles to a substrate, it is desirable to 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. Furthermore, the silicone rubber particles may be heat-treated in advance at a temperature of 100 to 300°C for 1 minute to 3 hours before being incorporated into a paint, coating agent, or the like.

[0065] [Coating agent] The coating agent of the present invention is a composition containing the above-mentioned film-forming resin, the above-mentioned silicone rubber particles, and water. More specifically, it can be obtained by mixing an emulsion of the film-forming resin with an aqueous dispersion of silicone rubber particles. Mixing can be carried out using a conventional mixer equipped with paddle-type, anchor-type, or other stirring blades.

[0066] The mass ratio of the film-forming solids in component (A) to the silicone rubber particles in component (B) is in the range of 85:15 to 25:75. A low ratio of component (B) results in a coating with poor surface smoothness and abrasion resistance, while a high ratio of component (B) results in poor abrasion resistance. The ratio is preferably 80:20 to 30:70. The amount of component (A) in the coating agent is 0.5 to 59 mass%, preferably 1.2 to 50 mass%, and more preferably 2.5 to 42 mass%, in terms of the resin content. The amount of component (B) in the coating agent is 0.3 to 52 mass%, preferably 0.7 to 44 mass%, and more preferably 1.5 to 37 mass%, in terms of the silicone rubber content.

[0067] Water may be added to adjust the amounts of components in the coating agent. The coating agent of the present invention is aqueous, and the amount of water in the coating agent is 30 to 98% by mass, preferably 40 to 95% by mass, and more preferably 50 to 90% by mass. Various organic or inorganic pigments, adhesion improvers such as wax emulsions, silicone oil emulsions, wetting improvers, and chlorinated polyolefin emulsions, preservatives, thickeners, pH adjusters, and antifoaming agents may be added to the coating agent as needed, within the range that does not impair the effects of the present invention.

[0068] The coating agent of the present invention is suitable for application to a substrate made of a rubber material. Examples of rubber materials include, but are not limited to, natural rubber, ethylene-propylene-diene rubber (EPDM), styrene-butadiene rubber (SBR), chloroprene rubber, isoprene-isobutylene rubber, and nitrile rubber. The substrate may be in any form, including porous and hard.

[0069] Methods for applying the coating agent to the substrate include, for example, brush coating, spray coating, roll coating, flow coating, dip coating, bar coating, etc. It is preferable to apply the agent so that the thickness of the cured film is in the range of 1 to 40 μm, and particularly 2 to 20 μm.

[0070] After applying the coating agent to the substrate, it is recommended to heat treat it at a temperature of 100 to 300°C. This promotes the polymerization reaction and fusion of the resin components in component (A), resulting in a strong coating film. It also improves the addition reaction rate of the silicone rubber particles in component (B), increasing the hardness, elongation, and strength of the silicone rubber. This in turn improves surface smoothness and abrasion resistance. [Example]

[0071] EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the examples, the kinematic viscosity is a value measured at 25°C using a capillary viscometer.

[0072] The following film-forming resin emulsion of component (A) was prepared. (A)-1: Adeka Bontiter HUX-564 Urethane emulsion, solid content = 40%, volume average particle size = 320 nm, Made by ADEKA Corporation (A)-2: Charine RU-911 Urethane silicone emulsion, solid content = 36%, volume average particle size = 260 nm, manufactured by Nissin Chemical Industry Co., Ltd. (A)-3:KM-9749 Silicone rubber emulsion, solid content = 43%, volume average particle size = 190 nm, Shin-Etsu Chemical Co., Ltd.

[0073] The film properties of component (A) were measured as follows. The resin emulsion was poured into a polypropylene tray in an amount that would result in a thickness of approximately 1 mm after drying, and dried for 48 hours at 25°C. The dried product was peeled off from the tray and heated in a hot air circulating thermostatic chamber at 105°C for 60 minutes to obtain a sheet. The elongation at break and tensile strength at break of the dumbbell-shaped No. 3 test pieces were tested according to the method specified in JIS K 6251:2017. Six sheets were stacked and the rubber hardness was measured using a Type A durometer tester according to the method specified in JIS K 6251:2017. The results are shown in Table 1.

[0074] [Table 1]

[0075] [Preparation of an aqueous dispersion of silicone rubber particles (B)] The following polysiloxanes were prepared: (B-1)-1: Represented by formula (10), vinyl group amount is 0.00627 mol / 100 g, kinematic viscosity is 5,060 mm 2 / s vinyl group-containing dimethylpolysiloxane [ka]

[0076] (B-1)-2: Represented by formula (11), vinyl group amount is 0.00369 mol / 100 g, kinematic viscosity is 30,500 mm 2 / s vinyl group-containing dimethylpolysiloxane [ka]

[0077] (B-1)-3: Represented by formula (12), vinyl group amount is 0.0179 mol / 100 g, kinematic viscosity is 386 mm 2 / s vinyl group-containing dimethylpolysiloxane [ka]

[0078] (B-1)-4: A solution of (A-1)-1 and (A-1)-3 mixed in a mass ratio of 40:60, with a vinyl group content of 0.0132 mol / 100 g and a kinematic viscosity of 1080 mm 2 / s vinyl group-containing dimethylpolysiloxane

[0079] (B-1)-5: Represented by formula (13), vinyl group amount is 0.0348 mol / 100 g, kinematic viscosity is 125 mm 2 / s vinyl group-containing dimethylpolysiloxane [ka]

[0080] (B-1)-6: Represented by formula (14), vinyl group amount is 0.120 mol / 100 g, kinematic viscosity is 23 mm 2 / s vinyl group-containing dimethylpolysiloxane [ka]

[0081] (B-1)-7: Represented by formula (15), vinyl group amount is 0.180 mol / 100 g, kinematic viscosity is 10 mm 2 / s vinyl group-containing dimethylpolysiloxane [ka]

[0082] (B-2)-1:(CH3)3SiO 1 / 2 Units: (CH3)2(CH=CH2)SiO 1 / 2 Units, SiO 4 / 2 Units, HOSiO 3 / 2 units, and CH3OSiO 3 / 2 A vinyl group-containing methylpolysiloxane resin consisting of units and having the following molar ratio: 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)SiO1 / 2 ] / [SiO 4 / 2 ] is 0.1 2, Molar ratio ([HOSiO 3 / 2 ]+[CH3OSiO 3 / 2 ] / [SiO 4 / 2 ])but 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 amount is 0.089 mol / 100 g, and the weight average molecular weight is 4,100.

[0083] (B-2)-2:(CH3)3SiO 1 / 2 Units: (CH=CH2)3SiO 1 / 2 Units, SiO 4 / 2 Units, HOSiO 3 / 2 units, and C2H5OSiO 3 / 2 A vinyl group-containing methylpolysiloxane resin consisting of units having the following molar ratio: 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)3SiO 1 / 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 [C2H5OSiO 3 / 2 ] / [SiO 4 / 2 ] is 0.050, The vinyl group amount is 0.23 mol / 100 g, and the weight average molecular weight is 5,730.

[0084] (B-3)-1: Represented by formula (16), the amount of SiH groups is 0.418 mol / 100 g, the kinematic viscosity is 27 mm 2 / s methylhydrogenpolysiloxane [ka]

[0085] (B-3)-2: Represented by formula (17), the amount of SiH groups is 0.744 mol / 100 g, the kinematic viscosity is 117 mm 2 / s methylhydrogenpolysiloxane [ka]

[0086] (B-3)-3: Represented by formula (18), the amount of SiH groups is 0.137 mol / 100 g, the kinematic viscosity is 37 mm 2 / s methylhydrogenpolysiloxane [ka]

[0087] [Production of component (B)-1] A curable liquid silicone composition was prepared by mixing and dissolving a vinyl-containing dimethylpolysiloxane (B-1)-1, a vinyl-containing methylpolysiloxane resin (B-2)-1, and a methylhydrogenpolysiloxane (B-3)-1 in a mass ratio of 63.0:27.0:10.0. The ratio of the number of SiH groups in the methylhydrogenpolysiloxane to the total number of vinyl groups in the vinyl-containing dimethylpolysiloxane and the vinyl-containing methylpolysiloxane resin was 1.49.

[0088] A 1-liter glass beaker was charged with 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. The mixture was stirred at 6,000 rpm using a homomixer, resulting in an oil-in-water emulsion with increased viscosity. Stirring was continued for another 15 minutes. Next, 415.6 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-type impeller stirrer. The temperature was adjusted to 15-20°C, and then a mixed solution of 1.2 g of an isododecane solution of a platinum-vinyl group-containing disiloxane complex (0.5% platinum content) and 1.2 g of polyoxyethylene lauryl ether (9 moles of ethylene oxide added) was added with stirring. The mixture was stirred at the same temperature for 6 hours, and the curable liquid silicone was cured by an addition reaction to obtain an aqueous dispersion of silicone rubber particles (B)-1. The total amount of polyoxyethylene tridecyl ether and polyoxyethylene lauryl ether was 0.64 parts by mass per 100 parts by mass of the resulting silicone rubber particles.

[0089] When the shape of this silicone rubber particle (B)-1 was observed under an optical microscope, it was found to be spherical, and when the volume average particle size was measured using a particle size distribution measuring device "Multisizer 3" (trade name, manufactured by Beckman Coulter, Inc.), it was found to be 6.7 μm.

[0090] Approximately 2 g of the resulting aqueous dispersion of silicone rubber particles was placed in an aluminum petri dish and heated in a hot air circulating thermostatic chamber at 150°C for 30 minutes to volatilize the water and further promote the addition reaction. The resulting dried product was a non-sticky granular product, and its shape was found to be spherical when observed under an electron microscope.

[0091] The tensile strength at break and elongation at break of the silicone rubber particles were measured as follows. 100 parts by weight of a curable liquid silicone composition prepared with the same composition as in Example 1 above was mixed with 0.24 parts by weight of an isododecane solution of a platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) and 0.05 parts by weight of 1,1-dimethylpropynyloxytrimethylsilane (reaction modifier), and the mixture was poured into a polypropylene tray to a thickness of approximately 1 mm. After leaving the mixture at 25°C for 24 hours, the cured silicone was peeled from 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 No. 3 test piece specified in JIS K6251:2017. The tensile strength at break and elongation at break were measured according to the method specified in JIS K6251:2017 and found to be 6.5 MPa and 101%, respectively.

[0092] The hardness of the silicone rubber particles was measured as follows. 100 parts by weight of a curable liquid silicone composition prepared with the same composition as in Example 1 above was mixed with 0.24 parts by weight of an isododecane solution of a platinum-vinyl group-containing disiloxane complex (platinum content 0.5%) and 0.05 parts by weight of 1,1-dimethylpropynyloxytrimethylsilane (reaction modifier), and the mixture was poured into an aluminum dish to a thickness of 10 mm. After leaving the mixture at 25°C for 24 hours, it was heated in a thermostatic chamber 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 found to be 58.

[0093] [Production of Components (B)-2 to (B)-12] An aqueous dispersion of silicone rubber particles was obtained in the same manner as for component (B)-1, except that a curable liquid silicone composition prepared by mixing and dissolving the vinyl group-containing dimethylpolysiloxane, vinyl group-containing methylpolysiloxane resin, and methylhydrogenpolysiloxane shown in Table 2 was used. Table 2 shows the volume average particle size of the silicone rubber particles, the shape of the silicone rubber particles, the tensile strength at break of the silicone rubber, the elongation at break of the silicone rubber, and the hardness of the silicone rubber, all measured in the same manner as for component (B)-1.

[0094] [Table 2]

[0095] [Production of component (B)-13] A curable liquid silicone composition was prepared by mixing and dissolving vinyl-containing dimethylpolysiloxane (B-1)-4, vinyl-containing methylpolysiloxane resin (B-2)-1, and methylhydrogenpolysiloxane (B-3)-1 in a mass ratio of 62.0:26.6:11.4. This composition is the same as the curable liquid silicone composition for silicone rubber particles (B)-12. The tensile strength at break was 3.0 MPa, the elongation at break was 75%, and the rubber hardness (Type A durometer) was 61.

[0096] A 1-liter glass beaker was charged with 500.0 g of curable liquid silicone composition, 1.0 g of polyoxyethylene tridecyl ether (15 moles of ethylene oxide added), and 100.0 g of water. The mixture was stirred at 6,000 rpm using a homomixer, resulting in an oil-in-water emulsion with increased viscosity. Stirring was continued for another 15 minutes. Next, 396.6 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-type impeller stirrer. The temperature was adjusted to 15-20°C, and then a mixed solution of 1.2 g of an isododecane solution of a platinum-vinyl group-containing disiloxane complex (0.5% platinum content) and 1.2 g of polyoxyethylene lauryl ether (9 moles of ethylene oxide added) was added with stirring. Stirring was continued at the same temperature for 6 hours to obtain an aqueous dispersion of silicone rubber particles.

[0097] When the shape of these silicone rubber particles was observed under an optical microscope, it was found to be spherical, and when the volume average particle size was measured using a particle size distribution measuring device "Multisizer 3" (trade name, manufactured by Beckman Coulter, Inc.), it was found to be 11 μm.

[0098] Approximately 2 g of the resulting aqueous dispersion of silicone rubber particles was placed in an aluminum petri dish and heated in a hot air circulating thermostatic chamber at 150°C for 30 minutes to volatilize the water and further promote the addition reaction. The resulting dried product was a non-sticky granular product, and its shape was found to be spherical when observed under an electron microscope.

[0099] [Production of component (B)-14] A 1-liter glass beaker was charged with 500.0 g of the same curable liquid silicone composition used in the preparation of silicone rubber particles (B)-13, 6.0 g of polyoxyethylene tridecyl ether (ethylene oxide addition moles = 15 moles), and 40.0 g of water. The mixture was stirred at 6,000 rpm using a homomixer, resulting in an oil-in-water emulsion and increased viscosity. The mixer was then changed to a disperser and stirred at 4,000 rpm for 15 minutes. The mixer was then changed again 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-type stirring blade stirrer, and after adjusting the temperature to 15-20°C, a mixed solution of 1.2 g of an 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 while stirring. Stirring was continued at the same temperature for 6 hours to obtain an aqueous dispersion of silicone rubber particles.

[0100] When the shape of these silicone rubber particles was observed under an optical microscope, they were found to be spherical, and when the volume average particle size was measured using a particle size distribution analyzer "Multisizer 3" (trade name, manufactured by Beckman Coulter, Inc.), it was found to be 1.9 μm.

[0101] Approximately 2 g of the resulting aqueous dispersion of silicone rubber particles was placed in an aluminum petri dish and heated in a hot air circulating thermostatic chamber at 150°C for 30 minutes to volatilize the water and further promote the addition reaction. The resulting dried product was a non-sticky granular product, and its shape was found to be spherical when observed under an electron microscope.

[0102] [Production of component (B)-15] A 1-liter glass beaker was charged with 500.0 g of the same curable liquid silicone composition used in the preparation of silicone rubber particles (B)-13, 4.0 g of polyoxyethylene tridecyl ether (15 moles of ethylene oxide added), and 80.0 g of water. The mixture was stirred at 6,000 rpm using a homomixer, resulting in an oil-in-water emulsion with increased viscosity. Stirring was continued for another 15 minutes. Next, 413.6 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-type impeller stirrer. The temperature was adjusted to 15-20°C, and then a mixed solution of 1.2 g of an isododecane solution of a platinum-vinyl group-containing disiloxane complex (0.5% platinum content) and 1.2 g of polyoxyethylene lauryl ether (9 moles of ethylene oxide added) was added with stirring. The mixture was stirred at the same temperature for 6 hours to obtain an aqueous dispersion of silicone rubber particles.

[0103] When the shape of these silicone rubber particles was observed under an optical microscope, it was found to be spherical, and when the volume average particle size was measured using a particle size distribution measuring device "Multisizer 3" (trade name, manufactured by Beckman Coulter, Inc.), it was found to be 4.5 μm.

[0104] Approximately 2 g of the resulting aqueous dispersion of silicone rubber particles was placed in an aluminum petri dish and heated in a hot air circulating thermostatic chamber at 150°C for 30 minutes to volatilize the water and further promote the addition reaction. The resulting dried product was a non-sticky granular product, and its shape was found to be spherical when observed under an electron microscope.

[0105] [Production of component (B)-16] A 1-liter glass beaker was charged with 500.0 g of the same curable liquid silicone composition used in the preparation of silicone rubber particles (B)-13, 1.3 g of polyoxyethylene tridecyl ether (15 moles of ethylene oxide added), and 80.0 g of water. The mixture was stirred at 6,000 rpm using a homomixer, resulting in an oil-in-water emulsion with increased viscosity. Stirring was continued for another 15 minutes. Next, 416.3 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-type impeller stirrer. The temperature was adjusted to 15-20°C, and then a mixed solution of 1.2 g of an 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 with stirring. Stirring was continued at the same temperature for 6 hours to obtain an aqueous dispersion of silicone rubber particles.

[0106] When the shape of these silicone rubber particles was observed under an optical microscope, it was found to be spherical, and when the volume average particle size was measured using a particle size distribution measuring device "Multisizer 3" (trade name, manufactured by Beckman Coulter, Inc.), it was found to be 8.7 μm.

[0107] Approximately 2 g of the resulting aqueous dispersion of silicone rubber particles was placed in an aluminum petri dish and heated in a hot air circulating thermostatic chamber at 150°C for 30 minutes to volatilize the water and further promote the addition reaction. The resulting dried product was a non-sticky granular product, and its shape was found to be spherical when observed under an electron microscope.

[0108] [Production of component (B)-17] A 1-liter glass beaker was charged with 500.0 g of the same curable liquid silicone composition used in the preparation of silicone rubber particles (B)-13, 5.7 g of a 35% aqueous solution of sodium pentyl naphthalene sulfonate (approximately 2.0 g of sodium pentyl naphthalene sulfonate), and 76.0 g of water. The mixture was stirred at 6,000 rpm using a homomixer, resulting in an oil-in-water emulsion and increased viscosity. The mixer was then changed to a disperser and stirred at 4,000 rpm for 15 minutes. The mixer was then changed again 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-type stirring blade stirrer, and after adjusting the temperature to 15-20°C, a mixed solution of 1.2 g of an 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 while stirring. Stirring was continued at the same temperature for 6 hours to obtain an aqueous dispersion of silicone rubber particles.

[0109] When the shape of these silicone rubber particles was observed under an optical microscope, it was found to be spherical, and when the volume average particle size was measured using a particle size distribution measuring device "Multisizer 3" (trade name, manufactured by Beckman Coulter, Inc.), it was found to be 6.4 μm.

[0110] Approximately 2 g of the resulting aqueous dispersion of silicone rubber particles was placed in an aluminum dish and heated in a hot air circulating thermostatic chamber at 150°C for 30 minutes to volatilize and remove the water and further promote the addition reaction. The dried product obtained was a non-sticky granular product, and its shape was found to be spherical when observed under an electron microscope.

[0111] [Production of Comparative Silicone Rubber Particles] An aqueous dispersion of silicone rubber particles was obtained in the same manner as for component (B)-1, except for using a curable liquid silicone composition prepared by mixing and dissolving the vinyl group-containing dimethylpolysiloxane and methylhydrogenpolysiloxane shown in Table 3. Table 3 shows the volume average particle size of the silicone rubber particles, the shape of the silicone rubber particles, the tensile strength at break of the silicone rubber, the elongation at break of the silicone rubber, and the hardness of the silicone rubber, all of which were measured in the same manner as for component (B)-1.

[0112] [Table 3]

[0113] [Examples 1 to 16, Comparative Examples 1 to 4] An aqueous coating agent was prepared by mixing the emulsion of the above-mentioned (A) film-forming resin ((A)-1 or (A)-2), an aqueous dispersion containing 50% by mass of silicone rubber particles, the addition reaction product of the above-mentioned (B) curable liquid silicone composition, and water in the amounts shown in Tables 4, 5, and 6. The resulting aqueous coating agent was applied with a brush to one side of an EPDM rubber sheet (2 mm thick) and heated for 5 minutes in a hot-air circulating thermostatic chamber at 150°C to form a cured film. The surface smoothness and abrasion resistance of the cured film were evaluated according to the following evaluation methods. The results are shown in Tables 4, 5, and 6.

[0114] [Surface smoothness test] The coefficient of dynamic friction against glass was measured using a friction and wear tester "Tribogear Type: 40" (product name, manufactured by Shinto Chemical Co., Ltd.). A glass plate was fixed to the table, and a 50 mm x 50 mm EPDM rubber sheet was attached to the indenter with double-sided tape. The coefficient of dynamic friction was measured when the indenter was moved back and forth under the following conditions: load: 500 g, movement speed: 1,000 mm / min, movement distance: 80 mm. The lower the coefficient of dynamic friction, the higher the surface smoothness.

[0115] [Wear resistance test] A wear test was carried out using a friction and wear tester "Tribogear Type: 40" (trade name, manufactured by Shinto Chemical Co., Ltd.) with a stainless steel ball and a load of 300 g. An EPDM rubber sheet measuring 25mm x 150mm was fixed to the table, and the indenter was a stainless steel ball with a diameter of 10mm. The indenter was moved back and forth under the following conditions: load: 300g, movement speed: 6,000mm / min, movement distance: 50mm. Observations were made at the following numbers of reciprocations: 1, 10, 50, 100, 500, 1000, 1500, and 2000, and the test was continued until scraping of the coating was observed. The results were recorded as the number of reciprocations at which scraping of the coating was observed.

[0116] [Table 4]

[0117] [Table 5]

[0118] [Table 6]

[0119] As shown in Tables 4 and 5 above, the coating agent of the present invention can form a coating film that is excellent in surface smoothness and abrasion resistance.

[0120] [Examples 17 to 30, Comparative Examples 5 to 8] An aqueous coating agent was prepared by mixing an emulsion of the above-mentioned (A) film-forming resin ((A)-3), an aqueous dispersion containing 50% by weight of silicone rubber particles, the addition reaction product of the above-mentioned (B) curable liquid silicone composition, and water in the amounts shown in Tables 7, 8, and 9. The resulting aqueous coating agent was applied with a brush to one side of an EPDM rubber sheet (2 mm thick) and heated for 5 minutes in a hot-air circulating thermostatic chamber at 150°C to form a cured film. The surface smoothness and abrasion resistance of this cured film were evaluated according to the following evaluation methods. The results are shown in Tables 7, 8, and 9.

[0121] [Surface smoothness test] The coefficient of dynamic friction against glass was measured using a friction and wear tester "Tribogear TYPE: 40" (trade name, manufactured by Shinto Chemical Co., Ltd.). A glass plate was fixed to the table, and a 50mm x 50mm EPDM rubber sheet was attached to the indenter with double-sided tape. The coefficient of dynamic friction was measured when the indenter was moved back and forth under the following conditions: load: 500g, moving speed: 1,000mm / min, moving distance: 80mm. The lower the coefficient of dynamic friction, the higher the surface smoothness.

[0122] [Wear resistance test] A wear test was carried out using a friction and wear tester "Tribogear Type: 40" (trade name, manufactured by Shinto Chemical Co., Ltd.) with a stainless steel ball and a load of 1,000 g. An EPDM rubber sheet measuring 25mm x 150mm was fixed to the table, and the indenter was a 10mm diameter stainless steel ball. The indenter was moved back and forth under the following conditions: load: 1,000g, movement speed: 6,000mm / min, movement distance: 50mm. Observations were made at 100, 500, 1,000, 1,500, 2,000, 2,500, 3,000, 3,500, and 4,000 repetitions, and the test was continued until scraping of the coating was observed. The results were recorded as the number of repetitions at which scraping of the coating was observed.

[0123] [Table 7]

[0124] [Table 8]

[0125] [Table 9]

[0126] As shown in Tables 7 and 8 above, the coating agent of the present invention can form a coating film that is excellent in surface smoothness and abrasion resistance even under high load friction. [Industrial Applicability]

[0127] The coating agent of the present invention can be used to improve the slipperiness, abrasion resistance, and stain resistance of rubber rollers, and to prevent sticking of O-rings, packings, gaskets, etc., and is particularly useful for improving the abrasion resistance, sliding properties, and prevention of squeaking noises of weatherstrip rubber used in car doors and around trucks.

Claims

1. (A) a resin having film-forming properties; (B) Silicone rubber particles that are an addition reaction product of a curable liquid silicone composition containing the following components (B-1), (B-2), and (B-3): (B-1) a diorganopolysiloxane having two or more alkenyl groups per molecule; (B-2) R １ ３ SiO １／２ Units and SiO ４／２ Contains units, SiO ４／ ２ R for units １ ３ SiO １／２ An organopolysiloxane resin having a molar ratio of units of 0.60 to 1.7 (wherein R １ are each independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 30 carbon atoms without an alkenyl group, or an alkenyl group having 2 to 6 carbon atoms, and all R １ at least one of which is an alkenyl group, and (B-3) Organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms (referred to as SiH groups) per molecule the amount of the component (B-2) is 1.0 to 65 parts by mass per 100 parts by mass of the total of the components (B-1), (B-2), and (B-3); and a coating agent containing water, wherein the mass ratio of the component (A) to the component (B) is 85:15 to 25:

75.

2. 2. The coating agent according to claim 1, wherein the diorganopolysiloxane (B-1) has an alkenyl group content of 0.0025 to 0.034 mol / 100 g, the organopolysiloxane resin (B-2) has an alkenyl group content of 0.001 mol / 100 g or more, and the organohydrogenpolysiloxane (B-3) has an SiH group content of 0.030 to 1.30 mol / 100 g.

3. 2. The coating agent according to claim 1, wherein the amount of (A) the film-forming resin is 0.5 to 59 parts by mass, the amount of (B) the silicone rubber particles is 0.3 to 52 parts by mass, and the amount of water is 30 to 98 parts by mass, per 100 parts by mass of the coating agent.

4. 2. The coating agent according to claim 1, wherein the silicone rubber particles are spherical and have a volume average particle size of 0.5 to 50 μm.

5. The coating agent according to claim 1 , comprising an emulsion of said film-forming resin.

6. 2. The coating agent according to claim 1, wherein the film-forming resin is at least one selected from the group consisting of urethane resin, vinyl chloride resin, acrylic resin, silicone-acrylic copolymer resin, silicone-urethane copolymer resin, styrene-butadiene-acrylonitrile resin, polyester resin, amide resin, and silicone rubber.

7. 7. The coating agent according to claim 6, wherein the film-forming resin is at least one selected from the group consisting of urethane resin, silicone rubber, and silicone-urethane copolymer resin.

8. 2. The coating agent according to claim 1, comprising an aqueous dispersion of silicone rubber particles, wherein the amount of the silicone rubber particles relative to the mass of the aqueous dispersion is 5 to 70% by mass.

9. The coating agent according to any one of claims 1 to 8, wherein the silicone rubber particles comprise a silicone rubber having a dumbbell-shaped No. 3 test piece having an elongation at break of 15% or more, measured in accordance with JIS K 6251:2017, on a 1 mm thick rubber sheet heat-treated at 150°C for 30 minutes, and a tensile strength at break of 0.9 MPa or more, measured in accordance with JIS K 6251:2017.

10. The coating agent according to any one of claims 1 to 8, which is a coating agent for rubber materials.

Images