Addition-curing silicone coating agent and rubber article

Abstract

To provide an addition-curable silicone coating agent which gives a coating film having abrasion resistance and a low coefficient of dynamic friction.SOLUTION: The addition-curable silicone coating agent contains: (A) 100 pts.mass of an alkenyl group-containing silicone resin, an organopolysiloxane having an alkenyl group content of 0.0014 mol / 100 g or more and an average degree of polymerization of 50 or more and less than 1,000, and an organopolysiloxane having an alkenyl group content of 0.00034 mol / 100 g or more and an average degree of polymerization of 1,000 or more; (B) an organohydrogensiloxane in such an amount that the content of hydrosilyl groups thereof is 0.1-20 mol per mol of the total amount of alkenyl groups of the component (A); (C) 0.1-1,000 ppm of an addition reaction catalyst in terms of platinum group metal atoms; (D) 1.5-130 pts.mass of a silicone powder having an average particle diameter of 0.1-50 μm and an organopolysiloxane having an average degree of polymerization of 1,000 or more and having no alkenyl group; (E) 0-30 pts.mass of a diluent having a boiling point of 100°C or higher and 250°C or lower; and (F) 0-10 pts.mass of a diluent having a boiling point lower than 100°C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an addition-curing silicone coating and to rubber articles coated with said silicone coating. [Background technology]

[0002] Silicone rubber has excellent weather resistance, electrical properties, low compression set, heat resistance, cold resistance, and other properties, and is therefore widely used in a variety of fields, including electrical equipment, automobiles, construction, medicine, and food. Examples of uses include rubber contact materials used as rubber contacts in remote controllers, computer terminals, musical instruments, etc.; construction gasket materials; various roll materials such as copier rolls, developing rolls, and transfer rolls; vibration-proof rubber materials for audio equipment, etc.; and packing materials for compact discs used in computers.

[0003] O-rings for motion, such as those used on rotating shafts, are required to have high abrasion resistance and a low coefficient of dynamic friction, and to provide these, silicone coating agents that provide a silicone rubber coating film are used.

[0004] For example, Patent Document 1 discloses a method for obtaining a silicone material with a low coefficient of friction by combining a polysiloxane having an alkenyl group with a high-viscosity polysiloxane not having an alkenyl group. However, because the average particle size of the filler is 0.1 μm or less, the lubricity is insufficient.

[0005] Patent Document 2 discloses an addition-cure type silicone rubber composition that uses three types of polysiloxanes in fixed ratios: two types of polysiloxanes with different alkenyl group amounts and average degrees of polymerization, and a polysiloxane with no alkenyl groups at all. However, this invention relates to a silicone rubber with high elongation and high tear strength, and does not mention smoothness.

[0006] Furthermore, Patent Document 3 discloses a low-friction silicone rubber coating composition containing an organic solvent, but the organic solvent volatilizes during curing, which is undesirable from the standpoint of safety and the environment. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-195939 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-082309 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-098319 Summary of the Invention [Problem to be solved by the invention]

[0008] In order to solve the above problems, an object of the present invention is to provide an addition-curable silicone coating agent that can provide a silicone rubber coating film that has excellent abrasion resistance and a low coefficient of dynamic friction, and to provide a rubber article coated with the silicone coating agent. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides: (A) 100 parts by mass of alkenyl group-containing organopolysiloxanes represented by the following (A-1) to (A-3): (A-1) Alkenyl group-containing silicone resin represented by the following formula (1): 10 to 80 parts by mass (R 1 3SiO 1 / 2 ) a (R 1 2SiO 2 / 2 ) b (R 1 SiO 3 / 2 ) c (SiO 4 / 2 ) d (1) (In the formula (1), R 1is a monovalent hydrocarbon group independently selected from an alkyl group having 1 to 10 carbon atoms and an alkenyl group having 2 to 10 carbon atoms, has an average of 2.5 or more alkenyl groups in one molecule, and a to d are 0 < a ≤ 0.7, 0 ≤ b ≤ 0.2, 0 ≤ c ≤ 0.2, 0 < d ≤ 0.7, provided that 0.8 ≤ a + d ≤ 1 and a + b + c + d = 1.) (A-2) An alkenyl group-containing organopolysiloxane that is liquid at 25°C, contains an alkenyl group bonded to two or more silicon atoms in one molecule, has an alkenyl group content of 0.0014 mol / 100 g or more, and an average degree of polymerization of 50 or more and less than 1,000: 10 to 80 parts by mass (A-3) A rubbery alkenyl group-containing organopolysiloxane that is liquid at 25°C, contains an alkenyl group bonded to two or more silicon atoms in one molecule, has an alkenyl group content of 0.00034 mol / 100 g or more, and an average degree of polymerization of 1,000 or more: 1 to 20 parts by mass (B) An organohydrogensiloxane having two or more hydrosilyl groups in one molecule: an amount such that the hydrosilyl groups of the component (B) are 0.1 to 20 mol with respect to 1 mol of the total amount of alkenyl groups contained in the component (A) (C) An addition reaction catalyst: an amount to be 0.1 to 1,000 ppm in terms of platinum group metal atoms (D) A lubricity-imparting agent composed of the following components (D-1) and (D-2): 1.5 to 130 parts by mass (D-1) A silicone powder having an average particle size of 0.1 to 50 μm: 1 to 100 parts by mass (D-2) An organopolysiloxane that is rubbery at 25°C, has an average degree of polymerization of 1,000 or more, and does not have an alkenyl group: 0.5 to 30 parts by mass (E) A diluent having a boiling point of 100°C or higher and 250°C or lower under a pressure of 1013 hPa: 0 to 30 parts by mass (F) A diluent having a boiling point of less than 100°C under a pressure of 1013 hPa: 0 to 10 parts by mass Provided is an addition-curing type silicone coating agent containing the above components.)

[0010] Such an addition-curing silicone coating agent can provide a silicone rubber coating film that has excellent abrasion resistance and a low coefficient of dynamic friction.

[0011] The component (E) is preferably a linear dimethylpolysiloxane.

[0012] By using such an addition-curing silicone coating agent, it is possible to obtain a coating film with even greater abrasion resistance.

[0013] The present invention also provides a rubber article, which is coated with the addition-curable silicone coating agent described above.

[0014] Such a rubber article can have high abrasion resistance and a low dynamic friction coefficient. [Effects of the Invention]

[0015] The addition-curing silicone coating agent of the present invention can provide a silicone rubber coating film that has excellent abrasion resistance and a low coefficient of dynamic friction. DETAILED DESCRIPTION OF THE INVENTION

[0016] As described above, there has been a demand for a silicone coating agent that can produce a silicone rubber coating film that has excellent abrasion resistance and a low coefficient of dynamic friction.

[0017] As a result of extensive research into achieving the above-mentioned object, the present inventors discovered that the above-mentioned object can be achieved by an addition-curable silicone coating agent comprising an alkenyl group-containing silicone resin, an alkenyl group-containing organopolysiloxane that is liquid and rubber-like at 25°C, an organohydrogenpolysiloxane, silicone powder, an alkenyl group-free organopolysiloxane, a diluent, and a hydrosilylation reaction catalyst, and thus completed the present invention.

[0018] That is, the present invention is (A) Alkenyl group-containing organopolysiloxane represented by the following (A-1) to (A-3): 100 parts by mass (A-1) Alkenyl group-containing silicone resin represented by the following formula (1): 10 to 80 parts by mass (R 1 3SiO 1 / 2 ) a (R 1 2SiO 2 / 2 ) b (R 1 SiO 3 / 2 ) c (SiO 4 / 2 ) d (1) (In the above formula (1), R 1 is independently a monovalent hydrocarbon group selected from an alkyl group having 1 to 10 carbon atoms and an alkenyl group having 2 to 10 carbon atoms, has an average of 2.5 or more alkenyl groups in one molecule, and a to d are 0 < a ≦ 0.7, 0 ≦ b ≦ 0.2, 0 ≦ c ≦ 0.2, 0 < d ≦ 0.7, provided that 0.8 ≦ a + d ≦ 1 and a + b + c + d = 1.) (A-2) An alkenyl group-containing organopolysiloxane that contains an alkenyl group bonded to two or more silicon atoms in one molecule, has an alkenyl group content of 0.0014 mol / 100 g or more, and has an average degree of polymerization of 50 or more and less than 1,000 and is liquid at 25°C: 10 to 80 parts by mass (A-3) An alkenyl group-containing organopolysiloxane that contains an alkenyl group bonded to two or more silicon atoms in one molecule, has an alkenyl group content of 0.00034 mol / 100 g or more, and has an average degree of polymerization of 1,000 or more and is rubbery at 25°C: 1 to 20 parts by mass (B) Organohydrogensiloxane having two or more hydrosilyl groups in one molecule: an amount such that the hydrosilyl group of the component (B) is 0.1 to 20 mol with respect to 1 mol of the total amount of the alkenyl groups contained in the component (A) (C) Addition reaction catalyst: an amount that becomes 0.1 to 1,000 ppm in terms of platinum group metal atoms (D) A lubricity-imparting agent composed of the following component (D-1) and component (D-2): 1.5 to 130 parts by mass (D-1) Silicone powder having an average particle size of 0.1 to 50 μm: 1 to 100 parts by mass (D-2) Organopolysiloxane having an average degree of polymerization of 1,000 or more and having a crude rubber-like consistency at 25°C and containing no alkenyl groups: 0.5 to 30 parts by mass (E) Diluent having a boiling point of 100°C or higher and 250°C or lower under a pressure of 1013 hPa: 0 to 30 parts by mass (F) Diluent having a boiling point of less than 100°C under a pressure of 1013 hPa: 0 to 10 parts by mass The addition-curing silicone coating agent comprises:

[0019] The present invention will be described in detail below, but the present invention is not limited thereto.

[0020] <Addition-curing silicone coating agent> The present invention is an addition-curable silicone coating agent containing the following components (A) to (E):

[0021] [(A) Alkenyl Group-Containing Organopolysiloxane] Component (A) is an alkenyl group-containing organopolysiloxane in which the total amount of components (A-1) to (A-3) below is blended is 100 parts by mass.

[0022] (A-1) Alkenyl group-containing silicone resin Component (A-1) is an alkenyl group-containing organopolysiloxane, R 1 3SiO 1 / 2 Unit (M unit), R 1 2SiO 2 / 2 Unit (D unit), R 1 SiO 3 / 2 Units (T units) and SiO 4 / 2 The silicone resin is composed of structural units selected from units (Q units), and the silicone resin is represented by the following formula (1). (R 1 3SiO 1 / 2 ) a (R 1 2SiO 2 / 2 ) b (R1 SiO 3 / 2 ) c (SiO 4 / 2 ) d (1)

[0023] In formula (1), R 1 is independently a monovalent hydrocarbon group selected from an alkyl group having 1 to 10 carbon atoms and an alkenyl group having 2 to 10 carbon atoms. Specifically, examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a cyclohexyl group, and the like. Examples of the alkenyl group include a vinyl group, an allyl group, a butenyl group, a pentenyl group, a hexenyl group, a cyclohexenyl group, and the like. On average, 2.5 or more, preferably 2.5 to 5, R 1 in one molecule is an alkenyl group. When the average number of alkenyl groups in one molecule is less than 2.5, the cured product becomes sticky and difficult to handle.

[0024] Also, from the perspective of compatibility with other components, for the (A-1) component, the vinyl group is preferred as the alkenyl group, and preferably 80 mol% or more of R 1 is a methyl group. If the compatibility of each component is good, the transparency of the cured product of the addition-curable silicone rubber composition does not decrease. Also, a satisfies 0 < a ≦ 0.7, preferably 0.3 < a < 0.7, b satisfies 0 ≦ b ≦ 0.2, preferably 0 ≦ b ≦ 0.1, c satisfies 0 ≦ c ≦ 0.2, preferably 0 ≦ c ≦ 0.1, d satisfies 0 < d ≦ 0.7, preferably 0.3 < d < 0.7, and is a number such that 0.8 ≦ a + d ≦ 1 and a + b + c + d = 1.

[0025] In the silicone resin (formula (1)) of component (A-1) above, of the four structural units, M and Q units are essential. To improve the hardness of the rubber coating film of an addition-curable silicone coating agent, the proportion of these two structural units to all structural units must be 80 mol % or more (0.8≦a+d≦1.0), preferably 90 mol % or more (0.9≦a+d≦1.0), and more preferably 100 mol % (a+d=1.0). It should be noted that D and T units may or may not be present.

[0026] If the molar ratio of M units to Q units (a / d) is 0.5 or higher, the compatibility of component (A-1) with other components will not deteriorate, and if it is 1.5 or lower, there is no risk of the hardness of the cured film of the addition-curable silicone coating agent decreasing. Therefore, the molar ratio of M units to Q units (a / d) is preferably in the range of 0.5 to 1.5, and more preferably in the range of 0.7 to 1.2.

[0027] The alkenyl group content (alkenyl group amount) of the component (A-1) is preferably 0.06 to 0.15 mol / 100g, more preferably 0.07 to 0.15 mol / 100g. If the alkenyl group content is 0.06 mol / 100g or more, abrasion resistance is ensured, and if it is 0.15 mol / 100g or less, a rubber with a low dynamic friction coefficient can be obtained. In the present invention, the alkenyl group content is 29 The value is measured by Si-NMR.

[0028] [ 29 Si-NMR measurement conditions] Measurement equipment: ECX500II (JEOL RESONANCE) 29 Si nuclear measurement frequency: 99.325MHz Accumulation count: 5,000 Sample concentration: 20% by mass (solvent: chloroform-d) Temperature: 25℃

[0029] Specific examples of the silicone resin of component (A-1) include a copolymer of a vinyldimethylsiloxy group and a Q unit, a copolymer of a vinyldimethylsiloxy group, a trimethylsiloxy group and a Q unit, a copolymer of a vinyldimethylsiloxy group, a dimethylsiloxane and a Q unit, a copolymer of a trimethylsiloxy group, a vinylmethylsiloxane and a Q unit, etc. These may be used alone or in combination of two or more.

[0030] (A-2) Alkenyl group-containing organopolysiloxane that is liquid at 25°C The organopolysiloxane of component (A-2) of the present invention contains two or more alkenyl groups bonded to silicon atoms per molecule, and has an alkenyl group content of 0.0014 mol / 100 g or more, an average degree of polymerization of 50 or more but less than 1,000, and is liquid at 25°C (i.e., exhibits self-flowing properties at 25°C).

[0031] Here, the alkenyl group preferably has 2 to 8 carbon atoms, and more preferably has 2 to 6 carbon atoms. Examples of alkenyl include vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl, and octenyl groups. Of these, vinyl is preferred.

[0032] Examples of the substituent other than the alkenyl group include alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 10 carbon atoms, and aralkyl groups having 7 to 10 carbon atoms. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; and aralkyl groups such as benzyl, phenylethyl, and phenylpropyl. These groups may also be used in which some or all of the hydrogen atoms have been substituted with halogen atoms. It is preferable that 90 mol% or more of all substituents, particularly all groups other than alkenyl groups, are methyl groups.

[0033] Examples of the alkenyl group-containing organopolysiloxane include dimethylpolysiloxanes both ends of which are capped with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers both ends of which are capped with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers both ends of which are capped with trimethylsiloxy groups, dimethylpolysiloxanes both ends of which are capped with trivinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers both ends of which are capped with trivinylsiloxy groups, etc. These may be used alone or in combination of two or more.

[0034] As component (A-2), linear organopolysiloxanes containing alkenyl groups are preferred because they can be used in combination with one or more different molecular structures (for example, the types and ratios of triorganosiloxy groups at the molecular chain terminals and substituents on diorganosiloxane units in the main chain) and degrees of polymerization.

[0035] The content of silicon-bonded alkenyl groups in the entire component (A-2) is at least 0.0014 mol / 100g, preferably 0.0014 to 0.03 mol / 100g, and more preferably 0.0020 to 0.02 mol / 100g. The alkenyl groups may be bonded to silicon atoms at the molecular chain terminals, or to silicon atoms along the molecular chain (non-terminal), or both, but it is preferable that they be bonded to silicon atoms at at least both molecular chain terminals.

[0036] The organopolysiloxane of component (A-2) has an average degree of polymerization of at least 50 but less than 1,000, and is a fluid liquid at 25° C. Liquid (A-2) also functions as a solvent to dissolve (A-1) and (A-3), which will be described later, and not only broadens the range of organic solvents that can be used, but also enables the creation of compositions in which reduced amounts are used.

[0037] The average degree of polymerization (or molecular weight) in the present invention can usually be determined by calculation from the weight-average degree of polymerization (or weight-average molecular weight) in terms of polystyrene measured by gel permeation chromatography (GPC) analysis using toluene as a developing solvent.

[0038] [Measurement conditions] Developing solvent: toluene Flow rate: 1mL / min Detector: Refractive index detector (RI) Column: KF-805L x 2 (Shodex) Column temperature: 25℃ Sample injection volume: 30 μL (0.2% by mass toluene solution)

[0039] (A-3) Alkenyl group-containing organopolysiloxane that is in the form of a raw rubber at 25°C The organopolysiloxane of component (A-3) of the present invention contains, per molecule, two or more alkenyl groups bonded to silicon atoms, the alkenyl group content is 0.00034 mol / 100 g or more, the average degree of polymerization is 1,000 or more, and the organopolysiloxane is in a raw rubber state at 25°C (i.e., it does not exhibit self-flowability at 25°C).

[0040] Here, the alkenyl group preferably has 2 to 8 carbon atoms, and more preferably 2 to 6 carbon atoms. Examples of alkenyl include vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl, and octenyl groups. Of these, vinyl is preferred. Examples of substituents other than the alkenyl group include alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 10 carbon atoms, and aralkyl groups having 7 to 10 carbon atoms. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl groups; aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups; and aralkyl groups such as benzyl, phenylethyl, and phenylpropyl groups. Furthermore, some or all of the hydrogen atoms of these groups may be substituted with halogen atoms. It is preferred that 90 mol % or more of all the substituents, particularly all groups other than alkenyl groups, are methyl groups.

[0041] Examples of the alkenyl group-containing organopolysiloxane include dimethylpolysiloxanes both ends of which are capped with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers both ends of which are capped with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers both ends of which are capped with trimethylsiloxy groups, dimethylpolysiloxanes both ends of which are capped with trivinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers both ends of which are capped with trivinylsiloxy groups, etc. These may be used alone or in combination of two or more.

[0042] The structure of the organopolysiloxane of component (A-3) that is in a rubber-like state at 25°C is preferably such that both molecular chain terminals are blocked with triorganosiloxy groups and the main chain has a linear structure consisting of repeating diorganosiloxane units, although it may also have a partially branched structure, cyclic structure, etc. Furthermore, one or more types of organopolysiloxanes with different structures or degrees of polymerization can be used in combination.

[0043] The organopolysiloxane of component (A-3) is in a raw rubber state at 25°C and has an average degree of polymerization of at least 1,000, preferably from 1,000 to 30,000, and more preferably from 2,000 to 20,000. If the average degree of polymerization is less than 1,000, it will not provide a low dynamic friction coefficient, and the resulting silicone rubber will not have sufficient mechanical strength.

[0044] The content of silicon-bonded alkenyl groups in the entire component (A-3) is at least 0.00034 mol / 100g, preferably 0.00034 to 0.2 mol / 100g, and more preferably 0.00034 to 0.15 mol / 100g.

[0045] The total amount of components (A-1), (A-2), and (A-3) blended is 100 parts by mass, with 10 to 80 parts by mass of component (A-1), 10 to 80 parts by mass of component (A-2), and 1 to 20 parts by mass of component (A-3). The blending ratio of each component preferably satisfies [(A-1) + (A-2)] > (A-3). Within this ratio range, a cured silicone rubber product with a low coefficient of dynamic friction is easily obtained.

[0046] [(B) Organohydrogenpolysiloxane] Component (B) is one or a mixture of two or more organohydrogenpolysiloxanes each having two or more hydrosilyl groups (hereinafter sometimes abbreviated as SiH groups) per molecule, preferably 3 to 200, more preferably 3 to 100, and even more preferably 4 to 50. The SiH groups in the molecule undergo a hydrosilylation addition reaction with the alkenyl groups bonded to silicon atoms in component (A) to crosslink, thereby acting as a curing agent for curing the composition.

[0047] Here, examples of the substituent on the organohydrogenpolysiloxane include the same groups as those exemplified as groups other than alkenyl groups for component (A) above. Examples include alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 10 carbon atoms, and aralkyl groups having 7 to 10 carbon atoms. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; and aralkyl groups such as benzyl, phenylethyl, and phenylpropyl. Methyl and other alkyl groups, or phenyl groups, are preferred.

[0048] The hydrosilyl group (SiH group) content of the organohydrogenpolysiloxane of component (B) is preferably 0.0030 to 0.030 mol / g, and more preferably 0.0040 to 0.025 mol / g. In the present invention, the hydrosilyl group content is 29The values were measured by Si-NMR.

[0049] The molecular structure of the organohydrogenpolysiloxane of component (B) may be linear, cyclic, branched, or three-dimensional network, and those that are liquid at 25° C. are preferably used. The hydrogen atoms bonded to silicon atoms may be bonded to silicon atoms at either the terminals of the molecular chain or non-terminals (in the middle of the molecular chain), or may be bonded to both.

[0050] Examples of the organohydrogenpolysiloxane of component (B) include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, methylhydrogensiloxane cyclic polymer, methylhydrogensiloxane-dimethylsiloxane cyclic copolymer, tris(dimethylhydrogensiloxy)methylsilane, tris(dimethylhydrogensiloxy)phenylsilane, methylhydrogenpolysiloxane capped at both ends with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymer capped at both ends with trimethylsiloxy groups, methylhydrogenpolysiloxane capped at both ends with dimethylhydrogensiloxy groups, dimethylpolysiloxane capped at both ends with dimethylhydrogensiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymer capped at both ends with dimethylhydrogensiloxy groups, methylhydrogensiloxane-methylhydrogensiloxane copolymer capped at both ends with trimethylsiloxy groups, Diphenylsiloxane copolymer, methylhydrogensiloxane-methylphenylsiloxane copolymer both ends capped with trimethylsiloxy groups, methylhydrogensiloxane-diphenylsiloxane-dimethylsiloxane copolymer both ends capped with trimethylsiloxy groups, methylhydrogensiloxane-methylphenylsiloxane-dimethylsiloxane copolymer both ends capped with trimethylsiloxy groups, methylhydrogensiloxane-diphenylsiloxane copolymer both ends capped with dimethylhydrogensiloxy groups, methylhydrogensiloxane-methylphenylsiloxane copolymer both ends capped with dimethylhydrogensiloxy groups, methylhydrogensiloxane-diphenylsiloxane-dimethylsiloxane copolymer both ends capped with dimethylhydrogensiloxy groups, methylhydrogensiloxane-methylphenylsiloxane-dimethylsiloxane copolymer both ends capped with dimethylhydrogensiloxy groups, (CH3)2HSiO 1 / 2 Units and SiO 4 / 2 A copolymer consisting of (CH3)2HSiO units 1 / 2 Units and (CH3)3SiO 1 / 2 Units and SiO 4 / 2 A copolymer consisting of (CH3)2HSiO units 1 / 2 Units and SiO 4 / 2Units and (C6H5)3SiO 1 / 2 and copolymers consisting of these units, and compounds in which some or all of the methyl groups have been substituted with other unsubstituted alkyl groups, trifluoropropyl groups, phenyl groups, etc.

[0051] The amount of organohydrogenpolysiloxane (B) blended is 0.2 to 20 parts by mass, preferably 0.3 to 15 parts by mass, per 100 parts by mass of the total of component (A). If the amount of component (B) blended is 0.2 part by mass or more, crosslinking is sufficient and the rubber is not sticky, and if it is 20 parts by mass or less, no foaming is observed in the molded product (cured silicone rubber product) and it is easy to release from the mold.

[0052] Furthermore, the molar ratio of SiH groups in component (B) to the total alkenyl groups bonded to silicon atoms in component (A) (SiH groups / alkenyl groups) is in the range of 0.1 to 20, preferably 0.8 to 10.0, and more preferably 1.0 to 5.0, and can be incorporated in an amount such that this ratio is in the range of 0.1 to 20. If this ratio is less than 0.1, crosslinking may be insufficient, resulting in a sticky rubber, while if it is more than 20, foaming may be observed in the molded product, and it may be difficult to release from the mold.

[0053] [(C) Addition reaction catalyst] The addition reaction catalyst for component (C) is not particularly limited as long as it is suitable for hydrosilylation addition reactions, and examples include platinum-based catalysts such as platinum black, platinic chloride, chloroplatinic acid, reaction products of chloroplatinic acid with monohydric alcohols, complexes of chloroplatinic acid with olefins, platinum bisacetoacetate, etc., palladium-based catalysts, and rhodium-based catalysts.

[0054] The amount of the addition reaction catalyst component (C) blended is 0.1 to 1,000 ppm, and particularly preferably 0.5 to 1,000 ppm, of platinum group metal (by mass) per 100 parts by mass of component (A).

[0055] If the amount of component (C) is less than 0.1 ppm per 100 parts by mass of component (A), curing will be slow to proceed, while if it is more than 1,000 ppm, the cured product may become discolored.

[0056] [(D) Slippage-imparting agent] Component (D) of the present invention is a slip-imparting agent composed of the following components (D-1) and (D-2), and is blended to impart slip (surface lubricity) to the silicone coating agent of the present invention. Component (D) is blended in an amount of 1.5 to 130 parts by mass per 100 parts by mass of component (A).

[0057] (D-1) Silicone powder with an average particle size of 0.1 to 50 μm The silicone powder of component (D-1) is added for the purpose of increasing the surface roughness by partially appearing on the surface during curing, thereby reducing the effective contact area and the surface coefficient of friction. For this purpose, the average particle size must be 0.1 to 50 μm, preferably 0.2 to 40 μm, more preferably 0.5 to 30 μm, and even more preferably 1 to 25 μm.

[0058] The average particle size can be determined, for example, as the cumulative mass average diameter D50 (or median diameter) in particle size measurement by laser light diffraction. If the average particle size is smaller than 0.1 μm, it will be difficult for the particle to appear on the surface during solvent evaporation and curing, and if it is larger than 50 μm, the surface roughness will be too great, significantly impairing the appearance of the substrate.

[0059] The silicone powder used in the present invention may be, for example, a powder obtained by blending silicone oil with an inorganic support, a powder obtained by three-dimensionally crosslinking silicone oil with a silicone resin, or a powder obtained by powdering silicone rubber. Component (D-1) may be used alone or in combination of two or more types.

[0060] The amount of silicone powder (D-1) blended is 1 to 100 parts by mass, preferably 1 to 80 parts by mass, and more preferably 1 to 60 parts by mass per 100 parts by mass of component (A).

[0061] If the amount of component (D-1) is less than 1 part by mass, the amount of silicone powder that migrates to and appears on the surface will be small, the surface roughness will not increase, and low friction performance will not be achieved. If the amount is more than 100 parts by mass, processability will deteriorate and the surface roughness will become too great, significantly impairing the appearance of the substrate.

[0062] (D-2) An organopolysiloxane that has an average degree of polymerization of 1,000 or more, does not contain alkenyl groups, and is in the form of a raw rubber at 25°C. The organopolysiloxane of component (D-2) of the present invention is an organopolysiloxane that does not contain alkenyl groups in the molecule and is in the form of a crude rubber at 25° C. The incorporation of component (D-2) has the effect of producing a silicone rubber cured coating with a lower dynamic friction coefficient than a cured coating obtained from component (A) alone.

[0063] The substituents here are the same as those exemplified for component (A-3) above, excluding alkenyl groups, and include alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 10 carbon atoms, and aralkyl groups having 7 to 10 carbon atoms. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; and aralkyl groups such as benzyl, phenylethyl, and phenylpropyl. These groups may also be used in which some or all of the hydrogen atoms have been substituted with halogen atoms. Preferably, 90 mol% or more of all the substituents are methyl groups.

[0064] The structure of the organopolysiloxane of component (D-2), similar to that of component (A-3), is preferably such that both molecular chain terminals are blocked with triorganosiloxy groups and the main chain has a linear structure consisting of repeating diorganosiloxane units, although it may also have a partially branched structure, cyclic structure, etc.

[0065] The organopolysiloxane of component (D-2) is in a raw rubber state at 25° C. and has an average degree of polymerization of at least 1,000, preferably from 1,000 to 30,000, and more preferably from 2,000 to 20,000. If the average degree of polymerization is less than 1,000, a low dynamic friction coefficient will not be achieved.

[0066] The amount of component (D-2), an organopolysiloxane that is in a rubber-like state at 25°C, blended is 0.5 to 30 parts by mass, preferably 1 to 25 parts by mass, and more preferably 2 to 20 parts by mass, based on 100 parts by mass of the total of component (A). If component (D-2) is less than 0.5 part by mass, slippage is not imparted, and even if more than 30 parts by mass is used, further slippage is not imparted.

[0067] [(E) Diluent having a boiling point of 100°C or higher and 250°C or lower] The diluent (E) acts as a solvent for the silicone coating agent of the present invention. Its boiling point at 1013 hPa is between 100°C and 250°C, preferably between 200°C and 250°C. A boiling point above 250°C is undesirable because the diluent will not volatilize during heat curing and will remain.

[0068] The diluent used as component (E) is not particularly limited as long as it dissolves the silicone components of the silicone coating agent of the present invention (i.e., components (A), (B), and (D-2)) and is within the above-mentioned boiling point range. Examples include aliphatic hydrocarbon solvents such as n-octane and n-decane, aromatic hydrocarbon solvents such as toluene and xylene, ketone solvents such as methyl isobutyl ketone, ether solvents such as ethyl cellosolve, butyl cellosolve, and ethylene glycol diethyl ether, cyclic dimethylpolysiloxanes such as octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane, and linear dimethylpolysiloxanes such as hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, and dodecamethylpentasiloxane. Among these, linear dimethylpolysiloxanes are preferred, and those having a kinematic viscosity of 2 mm at 25°C measured using a Canon-Fenske viscometer according to JIS Z8803:2011 are preferred. 2 Linear dimethylpolysiloxanes having a viscosity of 1 / s or less are preferred.

[0069] The amount of diluent (E) blended is 0 to 30 parts by mass, preferably 1 to 30 parts by mass, and more preferably 1 to 15 parts by mass, per 100 parts by mass of organopolysiloxane (A). If the amount of component (E) blended is more than 30 parts by mass, processability may be impaired.

[0070] [(F) Diluent having a boiling point of less than 100°C] The diluent (F), which also functions as a solvent for the silicone coating agent of the present invention, has a boiling point under a pressure of 1013 hPa of less than 100°C, preferably 60°C or higher but lower than 100°C, and more preferably 80°C or higher but lower than 100°C.

[0071] The diluent used as component (F) is not particularly limited as long as it dissolves the silicone components of the silicone coating agent of the present invention (i.e., components (A), (B), and (D-2)) and has a boiling point within the above range. For example, n-heptane can be used.

[0072] The amount of diluent (F) blended is 0 to 10 parts by mass, and preferably 1 to 10 parts by mass, per 100 parts by mass of organopolysiloxane (A). If the amount of component (E) blended is more than 10 parts by mass, a large amount of diluent will volatilize before curing, which may cause peeling on the coating film surface.

[0073] Both components (E) and (F) may be blended, or only one of them may be blended in an amount not exceeding the upper limit above, or neither may be blended.

[0074] If necessary, a diluent having a boiling point outside the above range may be added.

[0075] [Other ingredients] Other components that may be blended as necessary include fillers such as quartz powder, diatomaceous earth, calcium carbonate, and aluminum oxide; conductive agents such as carbon black, conductive zinc oxide, and metal powder; hydrosilylation reaction inhibitors such as nitrogen-containing compounds, acetylene compounds, phosphorus compounds, nitrile compounds, carboxylates, tin compounds, mercury compounds, and sulfur compounds; heat-resistant agents such as iron oxide, titanium oxide, and cerium oxide; internal release agents such as dimethyl silicone oil; dispersants; adhesion-imparting agents; and thixotropy-imparting agents.

[0076] [Method of preparing coating agent] The addition-curable silicone coating agent of the present invention can be obtained by mixing the components that make up the coating agent in a known mixer such as a kneader, Banbury mixer, or two-roll mill.

[0077] When a composition containing the above components (A) to (E) is used as the silicone coating agent, it is preferable to first mix the organopolysiloxane of component (A), the solvent of component (E), and the slip-imparting agent of component (D) to obtain a mixture, and then add the curing agents of components (B) and (C) to the mixture.

[0078] Furthermore, when the coating agent containing the above components (A) to (E) further contains other components, it is preferable to first mix the organopolysiloxane of component (A), the solvent of component (E), the slippage-imparting agent of component (D), and the other components to obtain a mixture, and then add the curing agents of components (B) and (C) to the mixture.

[0079] Furthermore, in the present invention, the addition-curable silicone coating agent of the present invention may be prepared by adding component (C) to a primary composition obtained by mixing components (A), (B), (D), and (E).

[0080] [Method for forming low-friction silicone rubber coating film] The method for forming a low-friction silicone rubber coating film involves applying the addition-curing silicone coating agent to the surface of a substrate and then heating the coating agent to harden it and form a silicone rubber coating film on the surface of the substrate.

[0081] The coating method for the substrate surface can be any known method such as coating, spraying, or dipping. The amount of silicone rubber coating film formed after coating, heating, and curing on the substrate surface is usually 0.3 to 100 g / m 2 , especially 0.6 to 50 g / m 2 , especially 1 to 10 g / m 2 The degree is preferable.

[0082] Silicone coating amount: 0.3g / m 2 If the coating amount is more than 100g / m, the effect of reducing the dynamic friction coefficient is fully realized. 2 In the following cases, the amount of coating is not excessive, so the effect of reducing the dynamic friction coefficient does not saturate, and it is economical.

[0083] The thickness of the silicone rubber coating film formed by the coating amount within the above range generally corresponds to about 0.3 to 100 μm, particularly about 0.6 to 50 μm, and especially about 1 to 10 μm.

[0084] The heating temperature after coating on the substrate surface is usually 120 to 250° C., preferably 150 to 200° C., and the heating time is usually 1 to 60 minutes, preferably 5 to 20 minutes.

[0085] The substrate to which the silicone coating agent is applied is not particularly limited as long as the coating film adheres to it, but examples include molded articles made from materials selected from the group consisting of thermoplastic resins, thermosetting resins, rubber, metals, and glass.

[0086] The low-friction silicone rubber coating film thus formed has a dynamic friction coefficient of 0.35 or less, particularly 0.32 or less, and is also highly wear-resistant. For example, by forming the above-mentioned silicone rubber coating film on the surface of an O-ring, an O-ring suitable for dynamic use can be obtained that has high wear resistance and a low dynamic friction coefficient. [Example]

[0087] EXAMPLES The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0088] The components of the silicone coating agent used to form the silicone rubber coating film are as follows:

[0089] <Component (A)> (A-1): A silicone resin copolymer of vinyldimethylsiloxy and trimethylsiloxy groups and Q units, with an average of four vinyl groups per molecule and a number-average molecular weight of 3,000 (alkenyl group content: 0.085 mol / 100 g, molar ratio of constituent units: M:D:T:Q = 43:0:0:57, M / Q = 0.75). (A-2): Dimethylpolysiloxane oil with an average degree of polymerization of 450 and both ends capped with dimethylvinylsiloxy groups (alkenyl group content: 0.006 mol / 100 g) (A-3): Organopolysiloxane gum with both ends capped with dimethylvinylsiloxy groups, methylvinylsiloxy groups in the side chains with an alkenyl group content of 0.0064 mol / 100 g, and an average degree of polymerization of approximately 8,000 (total alkenyl group content: 0.00674 mol / 100 g).

[0090] <(B) component> (B): Organohydrogenpolysiloxane (SiH group amount: 0.0212 mol / g, manufactured by Shin-Etsu Chemical Co., Ltd.) with an average of 48 methylhydrogensiloxy groups, both ends of which are blocked with trimethylsilyl groups.

[0091] <(C) component> (C): Platinum catalyst (chloroplatinic acid neutralized with sodium bicarbonate (manufactured by Shin-Etsu Chemical Co., Ltd.), containing 1% by mass of platinum in terms of metal mass)

[0092] <(D) component> (D-1): Silicone powder with an average particle size of 2 μm (D-2): Dimethylpolysiloxane raw rubber consisting of 100 mol% dimethylsiloxy units and having an average degree of polymerization of 8,000

[0093] <(E) component> (E): Silicone oil (boiling point 229°C, product name: KF-96L-2cs, manufactured by Shin-Etsu Chemical Co., Ltd.) which is a linear dimethylpolysiloxane with three dimethylsiloxy units and both ends blocked with trimethylsilyl groups.

[0094] <Component (F)> (F): N-heptane (boiling point 98.42°C)

[0095] [Preparation of silicone coating agent and formation of silicone rubber coating film] Components (A), (B), (D), (E), and (F) were mixed in the amounts shown in Tables 1 and 2 to obtain primary compositions, to which was added a platinum catalyst (C) in an amount of 67 ppm, calculated as platinum metal mass relative to component (A). These compositions were used to prepare the silicone coating agents of Examples 1 to 5 and Comparative Examples 1 to 11. These compositions were applied to the surface of a silicone rubber sheet substrate using a coater, and then heated at 120°C for 30 minutes to cure the composition, forming a silicone rubber coating film approximately 10 μm thick on the surface of the silicone rubber sheet. The details of Examples 1 to 5 and Comparative Examples 1 to 12 are as follows:

[0096] Example 1 A silicone coating agent prepared according to the composition of Example 1 in Table 1 was used.

[0097] Example 2 A silicone coating agent prepared according to the composition of Example 2 in Table 1 was used.

[0098] Example 3 A silicone coating agent prepared according to the composition of Example 3 in Table 1 was used.

[0099] Example 4 The silicone coating agent prepared according to the composition of Example 4 in Table 1 was used.

[0100] Example 5 The silicone coating agent prepared according to the composition of Example 5 in Table 1 was used.

[0101] (Comparative Example 1) A silicone coating agent was used which was the same as that of Example 1 but did not contain component (D).

[0102] (Comparative Example 2) A silicone coating agent was used which was the same as that of Example 1 but which did not contain component (D-2).

[0103] (Comparative Example 3) A silicone coating agent was used which was the same as that of Example 1 but which did not contain the component (D-1).

[0104] Comparative Example 4 (D-3) was used instead of the component (D-1) in Example 1, and the BET specific surface area was 200 m 2 A silicone coating agent containing 48 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) was used.

[0105] (Comparative Example 5) The component (A) in Example 1 was replaced with 100 parts by mass of the component (A-3) alone, and the component (D-1) was added to produce a cellulose ester having a BET specific surface area of 200 m 2 A silicone coating agent containing 48 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) was used.

[0106] (Comparative Example 6) The component (E) in Comparative Example 5 was changed from silicone oil, and a silicone coating agent using 400 parts by mass of N-heptane (boiling point 98.42°C) as the component (F) was used.

[0107] (Comparative Example 7) A silicone coating agent was used in which the component (A) of Comparative Example 5 was replaced with 97.5 parts by mass of (A-4) dimethylpolysiloxane gum (alkenyl group content: 0.00034 mol / 100 g) with an average degree of polymerization of 8,000 and both ends blocked with dimethylvinylsiloxy groups, and 2.5 parts by mass of the component (A-2).

[0108] (Comparative Example 8) The component (E) in Comparative Example 7 was changed from silicone oil, and a silicone coating agent using 400 parts by mass of N-heptane (boiling point 98.42°C) as the component (F) was used.

[0109] (Comparative Example 9) A silicone coating agent was used in which the amount of component (E) in Example 2 was changed from 9 parts by mass to 50 parts by mass.

[0110] (Comparative Example 10) A silicone coating agent was used in which the amount of component (F) in Example 5 was changed from 9 parts by mass to 30 parts by mass.

[0111] (Comparative Example 11) A silicone coating agent was used in which the 9 parts by mass of component (E) in Comparative Example 5 was changed to 9 parts by mass of component (F).

[0112] (Comparative Example 12) The evaluation was carried out without applying any silicone coating agent to the silicone rubber sheet substrate (blank).

[0113] [Conditions for creating silicone rubber sheet substrate] Materials: KE-871C-U / KE-951KU = 1 / 1 (mass ratio) (both manufactured by Shin-Etsu Chemical Co., Ltd.) Size: 175 x 150 mm, thickness: 2 mm Curing conditions: 165°C x 10 minutes press cure, then 200°C x 4 hours post cure

[0114] [Evaluation method] The resulting surface-treated silicone sheet was tested, measured, and evaluated for the following properties. The results are shown in Tables 1 and 2.

[0115] Dynamic friction coefficient: The dynamic friction coefficient of the sheet was measured using a TYPE14FW product manufactured by HEIDEN Co., Ltd. The load was set to 100 g, and the rubbing agent: SUS ball with a diameter of 10 mm was used.

[0116] Wear resistance: After measuring the dynamic friction coefficient, the coating surface was evaluated based on the presence or absence of peeling or dents. The evaluation criteria were as follows: ○: No peeling or dents ×: Peeling and dents

[0117] [Table 1] *The amount of component (C) is calculated by mass ratio relative to component (A).

[0118] [Table 2] *The amount of component (C) is calculated by mass ratio relative to component (A).

[0119] In Examples 1 to 5, it was confirmed that the addition-curing coating agent of the present invention forms a good coating film on the surface of the substrate, and provides a coating film that combines low friction and abrasion resistance.

[0120] In Comparative Examples 1 to 3, the coefficient of dynamic friction was higher than in Examples 1 to 5 because the composition lacked either or both of the component (D-1) and the component (D-2) in the component (D).

[0121] In Comparative Example 4, fumed silica was used instead of silicone powder, so the contribution to slipperiness was small, and the dynamic friction coefficient was higher than in Examples 1-5.

[0122] In Comparative Examples 5, 7, and 11, component (A) was either raw rubber alone or mainly raw rubber, so the viscosity of the coating agent was too high and it could not be applied to the substrate.

[0123] In Comparative Examples 6 and 8, the absence of component (A-1) resulted in poor abrasion resistance, and because a large amount of n-heptane, which has a low boiling point, was used as the diluent instead of dimethylpolysiloxane, the diluent evaporated before curing, and peeling was confirmed on the coating film surface after measuring the dynamic friction coefficient.

[0124] In Comparative Example 9, a large amount of diluent (component (E)) was used, which resulted in a decrease in curability and poor processability.

[0125] In Comparative Example 10, a large amount of the diluent (component (F)) was used, and therefore a large amount of the diluent evaporated before curing, and peeling was confirmed on the surface of the coating film after measuring the dynamic friction coefficient.

[0126] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. (A) 100 parts by mass of alkenyl group-containing organopolysiloxanes represented by the following (A-1) to (A-3): (A-1) Alkenyl group-containing silicone resin represented by the following formula (1): 10 to 80 parts by mass (R １ ３ SiO １／２ ) ａ (R １ ２ SiO ２／２ ) ｂ (R １ SiO ３／２ ) ｃ (SiO ４／２ ) ｄ (1) (In the formula (1), R １ are independently monovalent hydrocarbon groups selected from alkyl groups having 1 to 10 carbon atoms and alkenyl groups having 2 to 10 carbon atoms, containing an average of 2.5 or more alkenyl groups per molecule, and a to d are numbers such that 0<a≦0.7, 0≦b≦0.2, 0≦c≦0.2, and 0<d≦0.7, with the proviso that 0.8≦a+d≦1 and a+b+c+d=1. (A-2) 10 to 80 parts by mass of an alkenyl-containing organopolysiloxane that is liquid at 25°C and contains two or more alkenyl groups bonded to silicon atoms per molecule, has an alkenyl group content of 0.0014 mol / 100 g or more, and has an average degree of polymerization of 50 or more but less than 1,000. (A-3) Alkenyl-containing organopolysiloxane that is in the form of a crude rubber at 25°C and contains two or more alkenyl groups bonded to silicon atoms per molecule, has an alkenyl group content of 0.00034 mol / 100 g or more, and has an average degree of polymerization of 1,000 or more: 1 to 20 parts by mass (B) an organohydrogensiloxane having two or more hydrosilyl groups per molecule: an amount such that the hydrosilyl groups in component (B) are 0.1 to 20 moles per mole of the total number of alkenyl groups in component (A) (C) Addition reaction catalyst: an amount equivalent to 0.1 to 1,000 ppm in terms of platinum group metal atoms (D) A slip-imparting agent consisting of the following components (D-1) and (D-2): 3 to 80 parts by mass (D-1) Silicone powder having an average particle size of 0.1 to 50 μm: 1 to 60 parts by mass (D-2) Organopolysiloxane having an average degree of polymerization of 1,000 or more and having no alkenyl groups, which is in a raw rubber form at 25°C: 2 to 20 parts by mass (E) Diluent having a boiling point of 100°C or higher and 250°C or lower under a pressure of 1013 hPa: 0 to 30 parts by mass (F) Diluent having a boiling point of less than 100°C under a pressure of 1013 hPa: 0 to 10 parts by mass An addition-curing silicone coating agent comprising:

2. 2. The addition-curable silicone coating agent according to claim 1, wherein component (E) is a linear dimethylpolysiloxane.

3. A rubber article, characterized in that the rubber article is coated with the addition-curing silicone coating agent according to claim 1 or 2.

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