Room-temperature curable organopolysiloxane coating composition and article

Abstract

To provide a room-temperature curable organopolysiloxane coating composition that can yield a cured product (silicone rubber) having excellent insulation and light transmittance properties, which are not achievable by conventional room-temperature curable (RTV) silicone rubber compositions, and that, owing to its superior thixotropy when diluted with a solvent, offers enhanced coating workability as well as superior shape retention and resistance to sagging when applied to a substrate.SOLUTION: A room-temperature curable organopolysiloxane coating composition comprises: (A) a linear diorganopolysiloxane, (B) a hydrolyzable organosilane compound and / or a partial hydrolysis-condensation product thereof, (C) a curing catalyst, (D) silica having an apparent specific gravity of 100-200 g / l, and (E) an organic solvent.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a room-temperature-curable organopolysiloxane coating composition (room-temperature-curable silicone rubber coating composition) that is excellent in transparency and in thixotropy of a solvent-containing composition, and to an article coated with a cured product of the coating composition, and in particular to a room-temperature-curable organopolysiloxane coating composition (photocoupler sealant) that is suitable as a sealant for photocouplers, and to a photocoupler sealed with a cured product of the sealant. [Background technology]

[0002] Room temperature curable (RTV) silicone rubber compositions that crosslink with atmospheric moisture at room temperature (23°C ± 10°C) are easy to handle and have excellent weather resistance and electrical properties (electrical insulation), and are therefore used in a variety of fields, such as sealing materials for building materials and adhesives in the electrical and electronic fields. In particular, alcohol-free room temperature curable organopolysiloxane compositions are characterized by having no unpleasant odor and not corroding metals, and are preferably used in the electrical and electronic fields. A typical room temperature curable organopolysiloxane composition contains a diorganopolysiloxane (base polymer) having a silanol group (a hydroxyl group bonded to a silicon atom) or an alkoxysilyl group at the molecular chain end, a curing agent, and a curing catalyst, and various fillers are added as necessary to impart tensile strength and the like. In particular, silica is added as an inorganic filler to colorless room temperature curable organopolysiloxane compositions to impart tensile strength and thixotropy (Patent Document 1).

[0003] These silicone oil components (such as the liquid diorganopolysiloxane component that is the base polymer and the nonfunctional diorganopolysiloxane component that serves as a flexibility imparting agent) are generally silicone oils that have methyl groups on their side chains. Therefore, when silica is mixed with these, the optical transparency of the mixture decreases due to the difference in refractive index, and even a colorless room-temperature curable organopolysiloxane composition becomes translucent.

[0004] Furthermore, in order to lower the viscosity of alcohol-free room-temperature curable organopolysiloxane compositions and improve their workability as coatings, they are often diluted with a solvent. However, the viscosity is reduced by dilution with a solvent, which increases flowability and makes it impossible to maintain its shape in the uncured state.

[0005] In particular, in the field of optoelectronics, which relates to elements that can operate via light without physical contact, photocouplers (photoisolators) have become increasingly important in recent years. These photocouplers consist of a light-emitting element such as an LED and a light-receiving element that are insulated from each other, in which the light-emitting element converts the input electrical signal into light, and the light-receiving element converts the light back into an electrical signal and transmits it to the output circuit. However, the sealant that protects photocouplers from the loads and influences of the external environment must not only be transparent and insulating, but also easy to work with when applied and be able to retain its shape in an uncured state (thixotropy). Techniques for maintaining the shape of a composition are described in Patent Documents 1 to 5, but there is no description of the shape retention of a composition that contains a solvent. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2015-113377 A [Patent Document 2] Japanese Patent Application Publication No. 56-853 [Patent Document 3] Japanese Patent Application Publication No. 62-135560 [Patent Document 4] Japanese Patent Application Publication No. 2-41361 [Patent Document 5] JP 2015-21019 A Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, an object of the present invention is to provide a room-temperature-curable organopolysiloxane coating composition which gives a cured product (silicone rubber) with excellent insulating properties and light transmittance that could not be achieved with conventional room-temperature-curable (RTV) silicone rubber compositions, and which, due to the excellent thixotropy of a solvent-containing composition, has excellent workability during application, shape retention when applied to a substrate, and anti-sagging properties, as well as articles and the like coated with a cured product of said coating composition. [Means for solving the problem]

[0008] As a result of intensive research conducted by the present inventors in order to achieve the above-mentioned object, they discovered that the above-mentioned object can be achieved by using a room temperature vulcanizable (RTV) silicone rubber composition containing an organopolysiloxane having an aromatic group as a side chain of the molecule (i.e., a monovalent substituent bonded to a silicon atom in the diorganosiloxane repeating unit constituting the main chain) as a main agent, silica having an apparent specific gravity of 100 to 200 g / L as a filler, and a specific amount of an organic solvent such as an aromatic solvent as a solvent, and a cured product thereof, as a coating agent, which led to the completion of the present invention. That is, the present invention provides the following room temperature curable organopolysiloxane coating composition and articles coated with a cured product of said coating composition.

[0009] [1] (A) 100 parts by mass of an organopolysiloxane represented by the following general formula (1) and / or (2): [ka] (In formula (1), Ar is independently an aromatic group; R 1 are independently an unsubstituted or halogen-substituted aliphatic monovalent hydrocarbon group having 1 to 10 carbon atoms. n and m are each a number from 1 to 1000, n / (m+n) is 0.02 or more and less than 1, and the arrangement of the siloxane units to which n and m are attached is arbitrary. X is independently an oxygen atom or an alkylene group having 1 to 4 carbon atoms, R 2are independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms, and a is independently 0 or 1 for each silicon atom to which it is bonded. [ka] (In formula (2), Ar is independently an aromatic group; R 1 are independently an unsubstituted or halogen-substituted aliphatic monovalent hydrocarbon group having 1 to 10 carbon atoms. n and m are each a number from 1 to 1000, n / (m+n) is 0.02 or more and less than 1, and the arrangement of the siloxane units to which n and m are attached is arbitrary. (B) a hydrolyzable organosilane compound represented by the following general formula (3) and / or a partial hydrolysis condensate thereof: 0.1 to 30 parts by mass, [ka] (In formula (3), R 3 are independently monovalent hydrocarbon groups selected from alkyl groups having 1 to 12 carbon atoms, vinyl groups, and phenyl groups; R 4 are independently an alkyl group, an alkenyl group, or an acyl group, and b is an integer of 2 to 4. (C) Curing catalyst: 0.01 to 20 parts by mass, (D) Silica having an apparent specific gravity of 100 to 200 g / l: 1 to 300 parts by mass, and (E) Organic solvent: 20 to 60% by mass based on the total mass of the composition A room temperature curable organopolysiloxane coating composition comprising: [2] The room-temperature-curable organopolysiloxane coating composition according to [1], wherein the organic solvent of component (E) is an aromatic organic solvent. [3] The room-temperature-curable organopolysiloxane coating composition according to [1] or [2], wherein some or all of the aromatic groups represented by Ar in general formula (1) and formula (2) are phenyl groups. [4] The room-temperature-curable organopolysiloxane coating composition according to any one of [1] to [3], which has a thixotropic ratio of 5.0 or more. [5] The room-temperature-curable organopolysiloxane coating composition according to any one of [1] to [4], which gives a cured product having a light transmittance of 75% or more at a wavelength of 400 nm and a thickness of 0.4 mm. [6] An article coated with a cured product of the room-temperature-curable organopolysiloxane coating composition according to any one of [1] to [5]. [7] A photocoupler sealant comprising the room-temperature-curable organopolysiloxane coating composition according to any one of [1] to [5]. [8] A photocoupler encapsulated with a cured product of the photocoupler encapsulant according to [7]. Effect of the Invention

[0010] According to the present invention, it is possible to provide a room-temperature-curable organopolysiloxane coating composition which gives a cured product having excellent light transmittance in addition to the insulating properties inherent to silicone rubber, and which has an excellent thixotropic ratio when used in a solvent-containing composition, and which therefore has excellent workability during application and excellent shape retention and sagging prevention properties when applied to a substrate, as well as an article such as a photocoupler sealed with a cured product of the coating composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in detail below.

[0012] [Component (A)] The component (A) of the room temperature curable organopolysiloxane coating composition (room temperature curable organopolysiloxane coating composition) used as the coating agent of the present invention is a linear diorganopolysiloxane represented by the following general formula (1) and / or (2), which acts as the main agent (base polymer) in the room temperature curable organopolysiloxane composition. The organopolysiloxane is preferably liquid at room temperature (23°C ± 10°C). [ka] (In formula (1), Ar is independently an aromatic group; R 1 are independently an unsubstituted or halogen-substituted aliphatic monovalent hydrocarbon group having 1 to 10 carbon atoms. n and m are each a number from 1 to 1000, n / (m+n) is 0.02 or more and less than 1, and the arrangement of the siloxane units to which n and m are attached is arbitrary. X is independently an oxygen atom or an alkylene group having 1 to 4 carbon atoms, R 2 are independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms, and a is independently 0 or 1 for each silicon atom to which it is bonded. [ka] (In formula (2), Ar is independently an aromatic group; R 1 are independently an unsubstituted or halogen-substituted aliphatic monovalent hydrocarbon group having 1 to 10 carbon atoms. n and m are each a number from 1 to 1000, n / (m+n) is 0.02 or more and less than 1, and the arrangement of the siloxane units to which n and m are attached is arbitrary.

[0013] In formulas (1) and (2), the aromatic group represented by Ar includes aromatic hydrocarbon groups such as a phenyl group, a biphenyl group, and a naphthyl group, and aromatic groups having a heteroatom (O, S, N) such as a furanyl group, and the aromatic group may further have a substituent such as a halogen atom (e.g., a chlorine atom, a bromine atom, a fluorine atom).Ar is preferably an unsubstituted aromatic hydrocarbon group, and particularly preferably a phenyl group.

[0014] In formulas (1) and (2), R1 is an unsubstituted or halogen-substituted aliphatic monovalent hydrocarbon group having 1 to 10 carbon atoms, such as alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, and decyl; cycloalkyl groups such as cyclohexyl; alkenyl groups such as vinyl, allyl, propenyl, and isopropenyl; and groups in which the hydrogen atoms of these groups are partially substituted with halogen atoms, such as 3,3,3-trifluoropropyl. Of these, lower alkyl groups such as methyl and ethyl are particularly preferred. In the formulas (1) and (2), the R 1 may be the same group or different groups.

[0015] Additionally, m and n in formulas (1) and (2) are each numbers from 1 to 1000, and are particularly preferably numbers that result in a viscosity of the diorganopolysiloxane at 23° C. in the range of 25 to 500,000 mPa s, and preferably in the range of 500 to 100,000 mPa s. In the present invention, the viscosity can be measured, for example, with a rotational viscometer (for example, BL type, BH type, BS type, cone-plate type, rheometer, etc.) (the same applies hereinafter). In the above formulas (1) and (2), the difunctional diorganosiloxane unit (R 1 )2SiO 2 / 2 The value of m, which indicates the number of repetitions (or degree of polymerization) of (a) is a number equal to or greater than 1, and is preferably a number from 10 to 1,000, more preferably a number from 25 to 600, and further preferably a number from 50 to 500. In the present invention, the degree of polymerization can be determined, for example, as the number average degree of polymerization (or number average molecular weight) in terms of polystyrene in gel permeation chromatography (GPC) analysis using toluene or the like as a developing solvent. In the above formulas (1) and (2), the diorganosiloxane unit ((ArSiO 2 / 2The value of n, which indicates the number of repetitions (or degree of polymerization) of (a) is 1 or more, and is preferably a number from 5 to 800, more preferably a number from 6 to 100, and further preferably a number from about 7 to 50. In the above formulas (1) and (2), n / (m+n) is 0.02 or more and less than 1 (preferably 0.02 to 0.9), more preferably 0.03 to 0.6, and even more preferably 0.03 to 0.3.

[0016] In addition, R in formula (1) 2 is a monovalent hydrocarbon group having 1 to 6 carbon atoms, examples of which include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, and hexyl; cycloalkyl groups such as cyclohexyl; alkenyl groups such as vinyl, allyl, propenyl, and isopropenyl; and phenyl groups, with a methyl group being particularly preferred.

[0017] X in formula (1) is an alkylene group having 2 to 4 carbon atoms or an oxygen atom, and examples of the alkylene group include an ethylene group (-CH2CH2-), a propylene group (trimethylene group; -CH2CH2CH2-, a methylethylene group; -CH(CH3)CH2-), a tetramethylene group (-CH2CH2CH2CH2-), etc. X is preferably an ethylene group (-CH2CH2-), a trimethylene group (-CH2CH2CH2-) or an oxygen atom.

[0018] In formula (1), a is independently 0 or 1 for each silicon atom to which it is bonded, and 0 is particularly preferred. The component (A) may be used alone or in combination of two or more types.

[0019] [(B) Component] The component (B) functions as a curing agent (crosslinking agent) in the room temperature curable organopolysiloxane coating composition of the present invention, and is a hydrolyzable organosilane compound and / or a partial hydrolysis condensate thereof (i.e., an organosiloxane oligomer obtained by partially hydrolyzing and condensing the hydrolyzable organosilane compound and having an average of 2 or more, preferably 3 or more, residual hydrolyzable groups in the molecule) represented by the following general formula (3), which has two or more (2 or more, preferably 3 or 4) alkoxy groups, alkenyloxy groups, and / or acyloxy groups as hydrolyzable groups bonded to silicon atoms in one molecule, and in the case where a residual group bonded to a silicon atom is present, the residual group is a monovalent hydrocarbon group selected from an alkyl group, a vinyl group, and a phenyl group having 1 to 12 carbon atoms. [ka] (In formula (3), R 3 are independently a monovalent hydrocarbon group selected from an alkyl group having 1 to 12 carbon atoms (preferably an alkyl group having 1 to 10 carbon atoms), a vinyl group, and a phenyl group; R 4 are independently an alkyl group, an alkenyl group, or an acyl group, and b is an integer of 2 to 4.

[0020] R in Equation (3) 3 Examples of the alkyl group having 1 to 12 carbon atoms in the formula (I) include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group. Among these, an alkyl group having 1 to 10 carbon atoms is preferred, and a methyl group, an ethyl group, a propyl group, and a decyl group are more preferred.

[0021] OR in Equation (3) 4That is, the hydrolyzable group possessed by the hydrolyzable organosilane compound of component (B) and its partial hydrolysates is an alkoxy group, an alkenyloxy group, or an acyloxy group. Examples of the alkoxy group, alkenyloxy group, or acyloxy group include alkoxy groups having 1 to 4 carbon atoms, such as methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, isobutoxy group, sec-butoxy group, and tert-butoxy group; alkenyloxy groups having 2 to 4 carbon atoms, such as vinyloxy group, allyloxy group, propenyloxy group, and isopropenyloxy group; and acyloxy groups having 2 to 4 carbon atoms, such as acetoxy group and propionoxy group. Of these, methoxy and ethoxy groups are preferred.

[0022] In the formula (3), b is an integer of 2 to 4, preferably 3 or 4, and more preferably 3.

[0023] In addition, the component (B) is a compound represented by the general formula (3) having a hydrolyzable group OR 4 Residual groups R bonded to silicon atoms other than 3 If the remaining group R 3 However, in that it is an unsubstituted monovalent hydrocarbon group that does not contain a functional group containing a heteroatom such as an oxygen atom, a nitrogen atom, or a sulfur atom, it is clearly distinguished from carbon functional hydrolyzable organosilane compounds (CF silane compounds) such as so-called silane coupling agents that are usually formulated as adhesion promoters, etc.

[0024] Specific examples of component (B) include alkoxysilanes such as methyltrimethoxysilane, dimethyldimethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, decyltrimethoxysilane, tetramethoxysilane, and tetraethoxysilane; acetoxysilanes such as methyltriisopropenyloxysilane, dimethyldiisopropenyloxysilane, vinyltriisopropenyloxysilane, phenyltriisopropenyloxysilane, methyltriacetoxysilane, dimethyldiacetoxysilane, vinyltriacetoxysilane, phenyltriacetoxysilane, methyltripionoxysilane, decyltriacetoxysilane, tetraacetoxysilane, and tetrapropionoxysilane; and partial hydrolysis condensates of these silanes. The component (B) may be used alone or in combination of two or more types.

[0025] The amount of the (B) component is 0.1 to 30 parts by mass, preferably 0.5 to 20 parts by mass, and particularly preferably 1 to 15 parts by mass, per 100 parts by mass of the (A) component. If the amount is less than 0.1 parts by mass, sufficient crosslinking (curing) is not obtained, and it is difficult to obtain a composition that gives a cured product (silicone rubber) with the desired rubber elasticity. If the amount is more than 30 parts by mass, the mechanical properties of the obtained cured product (silicone rubber) tend to deteriorate.

[0026] [(C) component] Component (C) is a curing catalyst that acts as a curing agent (crosslinking agent) for promoting crosslinking and curing by hydrolysis and condensation reaction between the hydrolyzable silyl groups at both molecular chain terminals in component (A) and the hydrolyzable organosilane compound and / or its partial hydrolysis condensate in component (B) in the room temperature curable organopolysiloxane coating composition of the present invention. Examples of this curing catalyst include (C-1) a non-metallic organic catalyst and / or (C-2) a metallic catalyst.

[0027] There are no particular limitations on the non-metallic organic catalyst (C-1), but any of the known curing accelerators for condensation curing organopolysiloxane compositions can be used. Examples of the catalyst include phosphazene-containing compounds such as N,N,N',N',N'',N''-hexamethyl-N'''-(trimethylsilylmethyl)-phosphorimidic triamide; amine compounds or salts thereof such as hexylamine and dodecylamine phosphate; quaternary ammonium salts such as benzyltriethylammonium acetate; dialkylhydroxylamines such as dimethylhydroxylamine and diethylhydroxylamine; silanes and siloxanes containing guanidyl groups such as N,N,N',N'-tetramethylguanidylpropyltrimethoxysilane, N,N,N',N'-tetramethylguanidylpropylmethyldimethoxysilane, and N,N,N',N'-tetramethylguanidylpropyltris(trimethylsiloxy)silane; and silanes and siloxanes containing amino groups such as γ-aminopropyltrimethoxysilane and γ-(β-aminoethyl)aminopropyltrimethoxysilane. The nonmetallic organic catalyst may be used alone or in combination of two or more.

[0028] The metal catalyst (C-2) is not particularly limited, but any known catalyst may be used as a curing catalyst for condensation curing organopolysiloxane compositions. For example, alkyl tin ester compounds such as dibutyltin diacetate, dibutyltin dilaurate, dibutyltin dioctoate, dioctyltin dilaurate, dioctyltin dineodecanoate, and di-n-butyl-dimethoxytin; titanate esters or titanium chelate compounds such as tetraisopropoxytitanium, tetra-n-butoxytitanium, tetrakis(2-ethylhexoxy)titanium, dipropoxybis(acetylacetonato)titanium, diisopropoxytitanium bis(ethylacetoacetate), and titanium isopropoxyoctylene glycol; zinc naphthenate, zinc stearate, and zinc-2-ethyloctoate; and aluminum isopropoxytitanium chelate compounds such as titanium stearate, zinc stearate, and aluminum isopropoxytitanium chelate. Examples of suitable catalysts include aluminum alcoholate compounds such as aluminum diisopropylate and aluminum secondary butylate; aluminum chelate compounds such as aluminum alkyl acetate diisopropylate and aluminum bisethylacetoacetate monoacetylacetonate; organometallic compounds such as bismuth neodecanoate (III), bismuth 2-ethylhexanoate (III), bismuth citrate (III), bismuth octylate, iron 2-ethylhexoate, cobalt 2-ethylhexoate, manganese 2-ethylhexoate, and cobalt naphthenate; and alkali metal salts of lower fatty acids such as potassium acetate, sodium acetate, and lithium oxalate. Metal catalysts may be used alone or in combination of two or more.

[0029] The amount of the curing catalyst for component (C) may be a so-called catalytic amount, and specifically, the amount of component (C) is 0.01 to 20 parts by mass, preferably 0.05 to 10 parts by mass, and more preferably 0.05 to 5 parts by mass, per 100 parts by mass of component (A). If the amount of component (C) is less than 0.01 parts by mass, good curability cannot be obtained, resulting in a slow curing speed. If the amount exceeds 20 parts by mass, the curing speed of the composition is too fast, which may shorten the workable time after application of the composition or deteriorate the mechanical properties of the resulting rubber.

[0030] [(D) component] The component (D) is silica as an inorganic filler that improves the thixotropy of the room temperature curable organopolysiloxane coating composition of the present invention when diluted with a solvent, and improves the physical properties of the silicone rubber cured product obtained by curing the room temperature curable organopolysiloxane composition, such as mechanical strength. For example, pulverized silica, fused silica, fumed silica, wet silica (precipitated silica), crystalline silica (fine quartz powder), etc. can be used alone or in combination of two or more kinds. These silicas may be untreated or may be surface-treated with a known treatment agent. Among these, fumed silica and wet silica are particularly preferred.

[0031] The apparent specific gravity of the silica of component (D) may be 100 to 200 g / l, preferably 120 to 200 g / l, and more preferably 130 to 200 g / l. If the apparent specific gravity is less than 100, it is difficult to achieve both the desired thixotropic ratio and transparency of the cured product. If it exceeds 200 g / l, it is difficult to obtain a cured product having rubber strength and rubber elasticity.

[0032] The specific surface area (BET method) of the silica in component (D) is 30 to 300 m 2 / g is preferable, and 40 to 250m 2 / g is more preferable, and 45 to 230m 2 / g is particularly preferred. 2 If it is less than 300 m / g, the transparency of the cured product will decrease, making it difficult to obtain the desired transparency, or it may be difficult to obtain a cured product having rubber strength and rubber elasticity. 2 If it exceeds 1 / g, the viscosity of the composition will increase significantly, resulting in poor workability and making it difficult to prepare a room-temperature curable organopolysiloxane composition.

[0033] The amount of component (D) is 1 to 300 parts by mass, preferably 5 to 80 parts by mass, and particularly preferably 10 to 40 parts by mass, per 100 parts by mass of component (A). If the amount is less than 1 part by mass, it may be difficult to obtain a cured product having rubber strength and rubber elasticity. If the amount is more than 300 parts by mass, it may be difficult to knead with component (A), and it may be difficult to prepare a room temperature curable organopolysiloxane composition.

[0034] [(E) component] Component (E) is an organic solvent for lowering the viscosity of the room temperature curable organopolysiloxane coating composition of the present invention to improve workability, and examples thereof include aromatic organic solvents, halogenated hydrocarbon organic solvents, and aliphatic hydrocarbon organic solvents. Of these, aromatic organic solvents are preferred, and toluene and xylene are more preferred.

[0035] The amount of the organic solvent (E) is 20 to 60% by mass, preferably 25 to 55% by mass, and more preferably 35 to 50% by mass, based on the total mass of the coating composition of the present invention. If the amount of the organic solvent is less than 20% by mass, it is not possible to obtain a room-temperature curable organopolysiloxane coating composition having an excellent thixotropy with a thixotropy ratio of 5.0 or more, whereas if the amount is more than 60% by mass, the viscosity becomes high and workability decreases.

[0036] [Other ingredients] In addition, in the present invention, when the room temperature curable organopolysiloxane coating composition of the present invention requires adhesion, an adhesion promoter may be added as an optional component other than the above components. As the adhesion promoter, a known silane coupling agent is preferably used.

[0037] Examples of the silane coupling agent include silane compounds having an alkoxysilyl group or an alkenoxysilyl group as a hydrolyzable group, and examples thereof include vinyltris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltriisopropenoxysilane, and γ-glycidoxypropylmethyldiisopropenoxysilane.

[0038] When a silane coupling agent is used, the amount is preferably 0.1 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, and particularly preferably 0.1 to 5 parts by mass, per 100 parts by mass of component (A). If the amount is less than 0.1 parts by mass, sufficient adhesion may not be obtained, whereas if the amount is more than 20 parts by mass, good mechanical properties may not be obtained, and the cost may be disadvantageous.

[0039] In addition to the above components, known additives may be added as optional components to the room temperature curable organopolysiloxane coating composition of the present invention, as necessary, within the range that does not impair the object of the present invention. For example, non-reactive phenyl silicone oil as a plasticizer, triphenylsiloxy ((C6H5)3SiO 2 as a crosslink density improver, 1 / 2 ) units and SiO2 units.

[0040] Furthermore, non-reactive phenyl silicone oil and fluoro silicone oil may be added as bleeding oils as necessary, provided that the object of the present invention is not impaired.

[0041] The room-temperature-curable organopolysiloxane coating composition of the present invention can be prepared, for example, by uniformly mixing the above-mentioned components (A) to (E) and, if necessary, other optional components in a conventional manner using a known mixer such as a planetary mixer or a Shinagawa mixer in a state that is protected from moisture (in a dry atmosphere or under reduced pressure). Furthermore, the room temperature curable organopolysiloxane coating composition of the present invention preferably has a viscosity at 23° C. of 1 to 10 Pa·s, and more preferably 1.5 to 9.5 Pa·s. When the room temperature curable organopolysiloxane coating composition of the present invention has a viscosity (23° C.) of 10 Pa·s or less, the workability during application is good.

[0042] The room temperature curable organopolysiloxane coating composition of the present invention crosslinks and cures, for example, when left in the air at room temperature (23°C ± 10°C), as a result of hydrolysis and condensation reactions caused by moisture (water) in the air. The molding method, curing conditions, etc. may be any known method and condition suited to the type of composition. For example, the composition can be cured by leaving it in the air at 23°C / 50% RH for several hours to several days (e.g., 6 hours to 7 days).

[0043] Furthermore, the cured product (thickness: 0.4 mm) of the room temperature curable organopolysiloxane coating composition of the present invention has a light transmittance of 75% or more at a wavelength of 400 nm. The room-temperature-curable organopolysiloxane coating composition of the present invention is excellent not only in light transmission (transparency) and insulating properties, but also in thixotropy when diluted with a solvent, and therefore can be suitably used as a coating agent, particularly as a photocoupler sealant.

[0044] The thixotropic ratio (α) of the composition of the present invention was defined as η1 / η2, where η1 is the viscosity measured at 23°C with a B-type rotational viscometer at a rotor speed of 0.6 rpm, and η2 is the viscosity measured at 23°C with a rotor speed of 12 rpm. The thixotropy ratio of the composition of the present invention is 5.0 or more, preferably in the range of 5.0 to 15.0, more preferably in the range of 5.5 to 11.0, and particularly preferably in the range of 6.0 to 10.0. When the room-temperature-curable organopolysiloxane coating composition of the present invention has a thixotropy ratio of 5.0 or more, the composition exhibits good shape retention and anti-sagging properties when applied to a substrate. EXAMPLES

[0045] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following examples, the viscosity is a value measured by a rotational viscometer at 23°C.

[0046] [Example 1] A polysiloxane (R 1 = methyl group, m = about 200, n = about 20, Ar = phenyl group, same below) and 82 parts by mass of fumed silica (apparent specific gravity 160 g / l, BET specific surface area 45 m 2 After mixing 20 parts by mass of 100% ethylhexyl ether (1 / g, manufactured by Nippon Aerosil Co., Ltd.) for 30 minutes, 8 parts by mass of vinyltrimethoxysilane was added and stirred under normal pressure for 15 minutes, 0.1 parts by mass of dioctyltin dilaurate was added and stirred under normal pressure for 5 minutes, and then mixed under reduced pressure for 15 minutes. After that, 73.4 parts by mass of xylene (an amount equivalent to 40% by mass relative to the total mass of the composition) was added and mixed for 15 minutes under reduced pressure holding conditions of 0.8 MPa, and composition 1 was obtained.

[0047] [Example 2] The fumed silica described in Example 1 (apparent specific gravity 160 g / l, BET specific surface area 45 m 2 / g, Nippon Aerosil Co., Ltd.) 20 parts by mass was replaced with fumed silica (apparent specific gravity 140 g / l, BET specific surface area 150 m 2 Composition 2 was obtained in the same manner as in Example 1, except that 20 parts by mass of 1,2-dichlorophenyl ether (1 / g, manufactured by Nippon Aerosil Co., Ltd.) was used.

[0048] [Example 3] The fumed silica described in Example 1 (apparent specific gravity 160 g / l, BET specific surface area 45 m 2 / g, Nippon Aerosil Co., Ltd.) 20 parts by mass was replaced with fumed silica (apparent specific gravity 200 g / l, BET specific surface area 150 m 2 Composition 3 was obtained in the same manner as in Example 1, except that 20 parts by mass of 1,2-dichlorophenyl ether (1 / g, manufactured by Nippon Aerosil Co., Ltd.) was used.

[0049] [Example 4] Composition 4 was obtained in the same manner as in Example 1, except that xylene was replaced with toluene.

[0050] [Example 5] The polysiloxane described in Example 1 was converted to a polysiloxane having both ends of the molecular chain capped with trimethoxysilyl groups, phenyl groups and methyl groups on the side chains, and a viscosity of 20 Pa s at 23°C (in general formula (1), R 1 =R 2 Composition 5 was obtained in the same manner as in Example 1, except that X=methyl group, X=O, a=0, m=about 200, n=about 20, Ar=corresponding to a phenyl group, the same applies below).

[0051] [Example 6] The polysiloxane described in Example 1 was converted to a polysiloxane having both ends of the molecular chain capped with hydroxyl groups, phenyl groups and methyl groups on the side chains, and a viscosity of 4 Pa ​​s at 23°C (in general formula (1), R 1 =R 2 = methyl group, X = C2H4, a = 0, m = about 70, n = about 30, Ar = phenyl group, same below), fumed silica (apparent specific gravity 160g / l, BET specific surface area 45m 2 Composition 6 was obtained in the same manner as in Example 1, except that 30 parts by mass of 1,2-dichlorophenyl ether (1 / g, manufactured by Nippon Aerosil Co., Ltd.) was used instead.

[0052] [Example 7] The polysiloxane described in Example 6 was converted to a polysiloxane having both ends of the molecular chain capped with hydroxyl groups, phenyl groups and methyl groups on the side chains, and a viscosity of 5 Pa s at 23°C (in general formula (1), R 1 =R2 = methyl group, X = C2H4, a = 0, m = about 370, n = about 20, Ar = phenyl group, the same applies below) was used to obtain composition 7 in the same manner as in Example 1.

[0053] [Example 8] Composition 8 was obtained in the same manner as in Example 1, except that 73.4 parts by mass of xylene (40% by mass relative to the total amount) described in Example 1 was replaced with 110.1 parts by mass of xylene (50% by mass relative to the total mass of the composition).

[0054] [Example 9] Composition 9 was obtained in the same manner as in Example 1, except that 73.4 parts by mass of xylene (40% by mass relative to the total amount) described in Example 1 was replaced with 55.1 parts by mass of xylene (30% by mass relative to the total mass of the composition).

[0055] [Comparative Example 1] The polysiloxane described in Example 1 was converted to a polysiloxane having both molecular chain ends blocked with hydroxyl groups, methyl groups on the side chains, and a viscosity of 20 Pa s at 23°C (in general formula (2), R 1 Composition 10 was obtained in the same manner as in Example 1, except that the formula (I) was replaced with the formula (I): m = methyl group, m = about 620, n = 0; the same applies below.

[0056] [Comparative Example 2] The polysiloxane described in Example 1 was converted to a polysiloxane having both molecular chain ends capped with trimethoxysilyl groups, methyl groups on the side chains, and a viscosity of 20 Pa s at 23°C (in general formula (1), R 1 =R 2 Composition 11 was obtained in the same manner as in Example 1, except that X=methyl group, X=O, a=0, m=approximately 620, and n=0 (the same applies below).

[0057] [Comparative Example 3] The fumed silica described in Example 1 (apparent specific gravity 160 g / l, BET specific surface area 45 m 2 / g, Nippon Aerosil Co., Ltd.) 20 parts by mass was replaced with fumed silica (apparent specific gravity 40 g / l, BET specific surface area 45 m 2 Composition 12 was obtained in the same manner as in Example 1, except that 10 parts by mass of 1,2-dichlorophenyl ether (1 / g, manufactured by Nippon Aerosil Co., Ltd.) was used.

[0058] [Comparative Example 4] The fumed silica described in Example 1 (apparent specific gravity 160 g / l, BET specific surface area 45 m 2 / g, Nippon Aerosil Co., Ltd.) 20 parts by mass was replaced with fumed silica (apparent specific gravity 50 g / l, BET specific surface area 120 m 2 Composition 13 was obtained in the same manner as in Example 1, except that 20 parts by mass of 1,2-dichlorophenyl ether (1 / g, manufactured by Shin-Etsu Chemical Co., Ltd.) was used.

[0059] [Comparative Example 5] Composition 14 was obtained in the same manner as in Example 1, except that 73.4 parts by mass of xylene (40% by mass relative to the total amount) described in Example 1 was replaced with 18.4 parts by mass of xylene (10% by mass relative to the total mass of the composition).

[0060] The prepared compositions 1 to 14 were used to measure the following properties.

[0061] [viscosity] The viscosity of each of the prepared compositions 1 to 14 was measured at 23° C. with a B-type rotational viscometer (Model TVB-10, manufactured by Toki Sangyo Co., Ltd.) at a rotor speed of 12 rpm. The results are shown in Table 1.

[0062] [Thixotropy] The thixotropic ratio α of each of the prepared compositions 1 to 14 was defined as η1 / η2. Here, η1 is the viscosity measured at 23°C with a B-type rotational viscometer (Model TVB-10, manufactured by Toki Sangyo Co., Ltd.) at a rotor speed of 0.6 rpm, and η2 is the viscosity measured at 23°C with a rotor speed of 12 rpm. The values ​​of the thixotropic ratio α calculated from η1 / η2 are shown in Table 1.

[0063] [Light transparency] Each of the prepared compositions 1 to 14 was applied onto a Teflon (registered trademark) sheet at 23°C, and cured by exposure to an environment of 23°C / 50% RH for 7 days to prepare a silicone rubber sheet (silicone rubber cured product) having a thickness of 0.4 mm. The light transmittance (wavelength: 400 nm) (%) of the silicone rubber sheet was measured using a spectrophotometer U-4100 (manufactured by Hitachi High-Tech Science Co., Ltd.). The results are shown in Table 1. In addition, when each of the prepared compositions 1 to 14 was applied onto a Teflon (registered trademark) sheet, the workability during application, shape retention when applied to a substrate, and anti-sagging properties of each of the prepared compositions 1 to 14 were evaluated. <Workability during application> Viscosity of 10 Pa·s or less was evaluated as good, and viscosity of more than 10 Pa·s was evaluated as poor. <Shape retention and sagging prevention when applied to substrate> A thixotropic ratio of 5.0 or more was evaluated as good, and a thixotropic ratio of less than 5.0 was evaluated as poor.

[0064] [Table 1]

[0065] The compositions of Examples 1 to 9 had a viscosity (23°C) of 10 Pa s or less, a thixotropic ratio of 5.0 or more, and showed good workability during application, shape retention when applied to a substrate, and anti-sagging properties. In addition, the cured products of the compositions of Examples 1 to 9 showed a light transmittance of 75% or more. The composition of Comparative Example 5 had a viscosity (23° C.) of more than 10 Pa s. The compositions of Comparative Examples 2 and 4 had a thixotropic ratio of less than 5.0. Furthermore, the light transmittance of the cured products of the compositions of Comparative Examples 1 to 3 was less than 75%. Comparison of Examples 1 to 9 with Comparative Examples 1 to 5 reveals that the cured product obtained from the room temperature curable organopolysiloxane coating composition of the coating agent of the present invention has excellent light transmittance (transparency) in addition to the insulating properties inherent to silicone rubber, and is therefore suitable for use as a coating agent, particularly as a sealing material for photocouplers.

Claims

1. (A) 100 parts by mass of an organopolysiloxane represented by the following general formula (1) and / or (2): 【Chemistry 1】 In formula (1), Ar is independently an aromatic group, and R 1 are independently an unsubstituted or halogen-substituted aliphatic monovalent hydrocarbon group having 1 to 10 carbon atoms. n and m are each a number from 1 to 1000, n / (m+n) is 0.02 or more and less than 1, and the arrangement of the siloxane units to which n and m are attached is arbitrary. X is independently an oxygen atom or an alkylene group having 1 to 4 carbon atoms, R 2 are independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms, and a is independently 0 or 1 for each silicon atom to which it is bonded. 【Chemistry 2】 In formula (2), Ar is independently an aromatic group, and R 1 are independently an unsubstituted or halogen-substituted aliphatic monovalent hydrocarbon group having 1 to 10 carbon atoms. n and m are each a number from 1 to 1000, n / (m+n) is 0.02 or more and less than 1, and the arrangement of the siloxane units to which n and m are attached is arbitrary. (B) a hydrolyzable organosilane compound represented by the following general formula (3) and / or a partial hydrolysis condensate thereof: 0.1 to 30 parts by mass, 【Chemistry 3】 (In formula (3), R 3 are independently monovalent hydrocarbon groups selected from alkyl groups having 1 to 12 carbon atoms, vinyl groups, and phenyl groups; R 4 are independently an alkyl group, an alkenyl group, or an acyl group, and b is an integer from 2 to 4. (C) Curing catalyst: 0.01 to 20 parts by mass, (D) silica having an apparent specific gravity of 100 to 200 g / l: 1 to 300 parts by mass, and (E) Organic solvent: 20 to 60% by mass based on the total mass of the composition A room temperature curable organopolysiloxane coating composition comprising:

2. 2. The room temperature curable organopolysiloxane coating composition according to claim 1, wherein the organic solvent of component (E) is an aromatic organic solvent.

3. 2. The room temperature curable organopolysiloxane coating composition according to claim 1, wherein some or all of the aromatic groups represented by Ar in formulas (1) and (2) are phenyl groups.

4. 2. The room temperature curable organopolysiloxane coating composition according to claim 1, which has a thixotropic ratio of 5.0 or more.

5. 2. The room temperature curable organopolysiloxane coating composition according to claim 1, which gives a cured product having a light transmittance of at least 75% at a wavelength of 400 nm and a thickness of 0.4 mm.

6. 2. An article coated with the cured product of the room temperature curable organopolysiloxane coating composition of claim 1.

7. A photocoupler sealant comprising the room temperature curable organopolysiloxane coating composition according to claim 1.

8. A photocoupler sealed with a cured product of the photocoupler sealant according to claim 7.

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