Room temperature curable organopolysiloxane coating compositions and articles

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 exhibits excellent transparency and thixotropy of compositions containing a solvent, and articles coated with the cured product of the coating composition, and more particularly to a room-temperature curable organopolysiloxane coating composition (photocoupler sealant) that is suitable as a sealant for photocouplers, and photocouplers sealed with the cured product of the sealant. [Background technology]

[0002] Room temperature curable (RTV) silicone rubber compositions, which crosslink at room temperature (23°C ± 10°C) due to atmospheric moisture, are easy to handle and have excellent weather resistance and electrical properties (electrical insulation). Therefore, they are used in various fields, such as sealing materials for building materials and adhesives in the electrical and electronic fields. In particular, de-alcoholized room temperature curable organopolysiloxane compositions are characterized by their lack of unpleasant odor and non-corrosive properties to metals, making them suitable for use in the electrical and electronic fields. General room temperature curable organopolysiloxane compositions contain a diorganopolysiloxane (base polymer) having silanol groups (hydroxyl groups bonded to silicon atoms) or alkoxysilyl groups at the molecular chain ends, a curing agent, and a curing catalyst. Various fillers are added as needed to impart tensile strength and other properties. In particular, in colorless room temperature curable organopolysiloxane compositions, silica is added as an inorganic filler to impart tensile strength and thixotropy (Patent Document 1).

[0003] These silicone oil components (such as the liquid diorganopolysiloxane component that serves as the base polymer and the non-functional diorganopolysiloxane component that serves as a flexibility imparter) are generally silicone oils with methyl groups in their side chains. When silica is mixed with these, the difference in refractive index reduces the light transmittance of the mixture, making even a colorless, room-temperature curable organopolysiloxane composition semi-transparent.

[0004] In addition, in order to reduce the viscosity of a de-alcohol type room temperature curable organopolysiloxane composition and improve the workability as a coating, dilution with a solvent is often performed. However, when the viscosity is reduced by solvent dilution, the fluidity increases and the composition cannot maintain its shape in the uncured state.

[0005] Particularly, in the field of optoelectronics related to elements that can operate via light without physical contact, a photocoupler (photo isolator) composed of a light emitting element such as an LED and a light receiving element that are insulated from each other, where the light emitting element converts an input electrical signal into light and the light receiving element converts the light back into an electrical signal and transmits it to the output side circuit, has been increasing in importance in recent years. However, for a sealant for protecting the photocoupler from loads and influences from the external environment, not only transparency and insulation but also workability during coating and shape retention (thixotropy) in the uncured state are required. Techniques for maintaining the shape of the composition are described in Patent Documents 1 to 5, but there is no description regarding the shape retention of a composition containing a solvent.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0007] Therefore, the present invention provides a room temperature curable organopolysiloxane coating composition that gives a cured product (silicone rubber) excellent in insulating properties and light transmittance, which could not be achieved with conventional room temperature curable (RTV) silicone rubber compositions, and is excellent in thixotropy of the composition containing a solvent, and thus is excellent in workability during coating, shape retention when coated on a substrate, and sag prevention, and an article coated with a cured product of the coating composition, etc.

Means for Solving the Problems

[0008] As a result of intensive studies to achieve the above object, the present inventors have found that by applying a room temperature curable (RTV) silicone rubber composition containing, as a main agent, an organopolysiloxane having an aromatic group as a side chain of a molecule (that is, a monovalent substituent bonded to a silicon atom in a diorganosiloxane repeating unit constituting the main chain), 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, the above object can be achieved, and thus the present invention has been completed. That is, the present invention provides the following room temperature curable organopolysiloxane coating composition and an article coated with a cured product of the coating composition, etc.

[0009] [1] (A) 100 parts by mass of an organopolysiloxane represented by the following general formula (1) and / or (2): [Chemical Formula] (In formula (1), Ar is independently an aromatic group, and R 1 is 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, and R 2(where a is 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, and R 1 is independently an unsubstituted or halogen-substituted aliphatic monovalent hydrocarbon group having 1 to 10 carbon atoms. n and m are each numbers from 1 to 1000, n / (m+n) is between 0.02 and less than 1, and the sequence of siloxane units to which n and m are attached is arbitrary. (B) Hydrolyzable organosilane compounds represented by the following general formula (3) and / or partially hydrolyzed condensates thereof: 0.1 to 30 parts by mass, [ka] (In formula (3), R 3 R is a monovalent hydrocarbon group independently selected from alkyl groups having 1 to 12 carbon atoms, vinyl groups, and phenyl groups. 4 (where b is independently an alkyl group, an alkenyl group, or an acyl group, and b is an integer between 2 and 4.) (C) Curing catalyst: 0.01~20 parts by mass, (D) Silica with an apparent specific gravity of 100-200 g / l: 1-300 parts by mass, (E) Organic solvent: an amount equivalent to 20-60% by mass of the total mass of the composition A room-temperature curable organopolysiloxane coating composition containing the following: [2] The room-temperature curable organopolysiloxane coating composition according to [1], wherein the organic solvent of component (E) is an aromatic organic solvent. [3] A room-temperature curable organopolysiloxane coating composition according to [1] or [2], wherein some or all of the aromatic groups represented by Ar in general formulas (1) and (2) are phenyl groups. [4] A room-temperature curable organopolysiloxane coating composition according to any one of [1] to [3], wherein the thixotropy ratio is 5.0 or higher. [5] A 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 a room-temperature curable organopolysiloxane coating composition described in any of [1] to [5]. [7] A photocoupler encapsulant comprising a room-temperature curable organopolysiloxane coating composition as described in any of [1] to [5]. [8] A photocoupler sealed with a cured product of the photocoupler sealant described in [7]. [Effects of the Invention]

[0010] According to the present invention, in addition to the inherent insulating properties of silicone rubber, it provides a cured product with excellent light transmittance, and the solvent-containing composition has an excellent thixotropy ratio, thus providing a room-temperature curable organopolysiloxane coating composition with excellent workability during application, shape retention and sagging prevention when applied to a substrate, and articles such as photocouplers sealed with the cured product of the coating composition. [Modes for carrying out the invention]

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

[0012] [(A) component] Component (A) of the room-temperature curable organopolysiloxane coating composition used as a coating agent of the present invention is a linear diorganopolysiloxane represented by the following general formulas (1) and / or (2), which acts as the main component (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, and R 1 is independently an unsubstituted or halogen-substituted aliphatic monovalent hydrocarbon group having 1 to 10 carbon atoms. n and m are each numbers from 1 to 1000, n / (m+n) is between 0.02 and less than 1, and the sequence of 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, and R 2 (where a is 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, and R 1 is independently an unsubstituted or halogen-substituted aliphatic monovalent hydrocarbon group having 1 to 10 carbon atoms. n and m are each numbers from 1 to 1000, n / (m+n) is between 0.02 and less than 1, and the sequence of 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 phenyl groups, biphenyl groups, and naphthyl groups, and aromatic groups having heteroatoms (O, S, N) such as furanyl groups. Furthermore, the aromatic group may have substituents such as halogen atoms (e.g., chlorine atoms, bromine atoms, fluorine atoms). Ar is preferably an unsubstituted aromatic hydrocarbon group, and particularly preferably a phenyl group.

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

[0015] Further, m and n in formulas (1) and (2) are each a number from 1 to 1000, and particularly, the viscosity of the diorganopolysiloxane at 23 °C is preferably a number in the range of 25 to 500,000 mPa·s, more preferably in the range of 500 to 100,000 mPa·s. In the present invention, the viscosity can be measured by, for example, a rotational viscometer (e.g., BL type, BH type, BS type, cone plate type, rheometer, etc.) (hereinafter, the same). In the above formulas (1) and (2), the value of m indicating the repetition number (or degree of polymerization) of the difunctional diorganosiloxane unit ((R 1 )2SiO 2 / 2 ) is a number of 1 or more, preferably a number from 10 to 1,000, more preferably a number from 25 to 600, and still more 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 difunctional diorganosiloxane unit ((Ar2SiO 2 / 2The value of n, which indicates the number of repetitions (or degree of polymerization) of the compound, is a number of 1 or more, preferably a number between 5 and 800, more preferably a number between 6 and 100, and even more preferably a number between 7 and 50. Furthermore, in formulas (1) and (2) above, 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] Also, R in equation (1) 2 The carbon group is a monovalent hydrocarbon group having 1 to 6 carbon atoms, and examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, and hexyl groups; cycloalkyl groups such as cyclohexyl groups; alkenyl groups such as vinyl, allyl, propenyl, and isopropenyl groups; and phenyl groups, but the methyl group is particularly preferred.

[0017] In formula (1), X is an alkylene group having 2 to 4 carbon atoms or an oxygen atom. Examples of alkylene groups include ethylene group (-CH2CH2-), propylene group (trimethylene group;-CH2CH2CH2-, methylethylene group;-CH(CH3)CH2-), tetramethylene group (-CH2CH2CH2CH2-), etc. Preferably, X is 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, with 0 being particularly preferred. (A) Component may be used alone or in combination of two or more components.

[0019] [(B) Component] Component (B) acts 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 partially hydrolyzed condensate thereof (i.e., an organosiloxane oligomer obtained by partially hydrolyzing and condensing the hydrolyzable organosilane compound, having an average of 2 or more, preferably 3 or more, residual hydrolyzable groups in the molecule) represented by the following general formula (3), wherein one molecule has 2 or more (2 or more, preferably 3 or 4) hydrolyzable groups bonded to a silicon atom, such as an alkoxy group, an alkenyloxy group, and / or an acyloxy group, and if there is a residual group bonded to a silicon atom, the residual group is a monovalent hydrocarbon group selected from an alkyl group having 1 to 12 carbon atoms, a vinyl group, and a phenyl group). [ka] (In formula (3), R 3 R is 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. 4 (where b is independently an alkyl group, an alkenyl group, or an acyl group, and b is an integer between 2 and 4.)

[0020] R in equation (3) 3 Examples of C1-C12 alkyl groups in this context include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl, and dodecyl groups. Of these, C1-C10 alkyl groups are preferred, with methyl, ethyl, propyl, and decyl groups being more preferred.

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

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

[0023] Note that component (B) is a hydrolyzable group OR in general formula (3). 4 Other than the remaining group R that bonds to the silicon atom 3 If it has the remaining base R 3 However, it is clearly distinguishable from carbon functional hydrolyzable organosilane compounds (CF silane compounds), such as so-called silane coupling agents that are usually incorporated as adhesion promoters, in that it is an unsubstituted monovalent hydrocarbon group that does not contain functional groups containing heteroatoms such as oxygen, nitrogen, or sulfur atoms.

[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, methyltripropionoxysilane, decyltriacetoxysilane, tetraacetoxysilane, and tetrapropionoxysilane; and partially hydrolyzed condensates of these silanes. (B) Component may be used alone or in combination of two or more components.

[0025] The amount of component (B) is in the range of 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 component (A). If the amount is less than 0.1 parts by mass, sufficient crosslinking (curing) cannot be obtained, and it is difficult to obtain a composition that gives a cured product (silicone rubber) with the desired rubber elasticity. If the amount exceeds 30 parts by mass, the resulting cured product (silicone rubber) tends to have reduced mechanical properties.

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

[0027] (C-1) The non-metallic organic catalyst is not particularly limited, but one known as a curing accelerator for condensation-curing type organopolysiloxane composition can be used. Examples include phosphazene-containing compounds such as N,N,N',N',N'',N''-hexamethyl-N'''-(trimethylsilylmethyl)-phosphorimidictriamide; 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 a guanidyl group 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 an amino group such as γ-aminopropyltrimethoxysilane and γ-(β-aminoethyl)aminopropyltrimethoxysilane. Furthermore, nonmetallic organic catalysts may be used individually or in combination of two or more.

[0028] (C-2) The metal catalyst is not particularly limited, but known catalysts can be used as curing catalysts for condensation-curing organopolysiloxane compositions. For example, alkyltin 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(acetylacetonate)titanium, diisopropoxytitanium bis(ethylacetoacetate), and titanium isopropoxyoctylene glycol; zinc naphthenate, zinc stearate, zinc-2-ethyloctoate; and aluminum Examples include alcoholic aluminum compounds such as sopropylates and aluminum secondary butyrates; aluminum chelate compounds such as aluminum alkyl acetate diisopropylate and aluminum bisethylacetoacetate monoacetylacetonate; organometallic compounds such as bismuth(III) neodecanoate, bismuth(III) 2-ethylhexanoate, bismuth(III) citrate, bismuth octoate, iron-2-ethylhexoate, cobalt-2-ethylhexoate, manganese-2-ethylhexoate, and cobalt naphthenate; and alkali metal lower fatty acid salts such as potassium acetate, sodium acetate, and lithium oxalate. Metal catalysts may be used individually or in combination of two or more.

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

[0030] [(D) component] Component (D) is silica, an inorganic filler used in the room-temperature curable organopolysiloxane coating composition of the present invention, to improve thixotropy during solvent dilution and to improve physical properties such as mechanical strength of the cured silicone rubber obtained by curing the room-temperature curable organopolysiloxane composition. Examples include crushed silica, fused silica, fumed silica, wet silica (sed silica), and crystalline silica (quartz fine powder), which may be used alone or in combination of two or more types. These silicas may be untreated or surface-treated with known treatment agents. Among these, fumed silica and wet silica are particularly preferred.

[0031] The apparent specific gravity of silica in component (D) should 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 thixotropy ratio and the transparency of the cured product. If it exceeds 200 g / l, it is difficult to obtain a cured product with rubber strength and rubber elasticity.

[0032] The specific surface area (BET method) of silica in component (D) is 30-300 m². 2 / g is preferred, 40-250m 2 / g is more preferable, 45-230m 2 / g is particularly preferred. Specific surface area of ​​30m² 2 If the amount is less than / g, the transparency of the cured product will decrease, making it difficult to obtain the desired transparency, and it may also be difficult to obtain a cured product with rubber strength and elasticity. Also, 300m 2 If the concentration exceeds / g, the viscosity of the composition increases significantly, resulting in poor workability, which may make it difficult to prepare room-temperature curable organopolysiloxane compositions.

[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 with rubber strength and rubber elasticity. If the amount exceeds 300 parts by mass, it may be difficult to knead with component (A), making it difficult to prepare a room-temperature curable organopolysiloxane composition.

[0034] [(E) component] Component (E) is an organic solvent used to reduce viscosity and improve workability in the room-temperature curable organopolysiloxane coating composition of the present invention. Examples include aromatic organic solvents, halogenated hydrocarbon organic solvents, and aliphatic hydrocarbon organic solvents. Among these, aromatic organic solvents are preferred, and toluene and xylene are more preferred.

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

[0036] [Other ingredients] Furthermore, in addition to the above-mentioned components, the present invention may optionally include an adhesion promoter as an optional component if adhesion is required in the room-temperature curable organopolysiloxane coating composition of the present invention. Known silane coupling agents are preferably used as adhesion promoters.

[0037] Examples of silane coupling agents include silane compounds having an alkoxysilyl group or an alkenoxysilyl group as a hydrolyzable group, such as 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 incorporated, 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, and if the amount exceeds 20 parts by mass, good mechanical properties may not be obtained, or it may be unfavorable in terms of cost.

[0039] In addition to the components mentioned above, the room-temperature curable organopolysiloxane coating composition of the present invention may optionally contain known additives, to the extent that they do not impair the objectives of the present invention. For example, non-reactive phenyl silicone oil as a plasticizer, and triphenylsiloxy((C6H5)3SiO2) as a crosslinking density improver. 1 / 2 Examples include three-dimensional network polysiloxanes consisting of ) units and SiO2 units.

[0040] Furthermore, if necessary, non-reactive phenyl silicone oil and fluorosilicone oil may be added as bleed oils, to the extent that they do not impair the objectives of the present invention.

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

[0042] The room-temperature curable organopolysiloxane coating composition of the present invention undergoes hydrolysis and condensation reactions due to humidity (moisture) in the atmosphere when left at room temperature (23°C ± 10°C), resulting in crosslinking and curing. However, known methods and conditions can be used for molding and curing depending on the type of composition. For example, it can be cured by leaving it in the atmosphere at 23°C / 50%RH for several hours to several days (e.g., 6 hours to 7 days).

[0043] Furthermore, the light transmittance of the cured product (thickness: 0.4 mm) of the room-temperature curable organopolysiloxane coating composition of the present invention at a wavelength of 400 nm is 75% or more. The room-temperature curable organopolysiloxane coating composition of the present invention exhibits excellent light transmittance (transparency), insulating properties, and thixotropy when diluted with a solvent, making it particularly suitable for use as a coating agent for photocoupler encapsulants and the like.

[0044] The thixotropy ratio (α) of the composition of the present invention is defined as η1 / η2. Here, η1 is the viscosity measured at 23°C with a rotational speed of 0.6 rpm using a type B rotational viscometer, and η2 is the viscosity measured at 23°C with a rotor rotational speed of 12 rpm. The thixotropy of the composition of the present invention is 5.0 or higher, 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. If the thixotropy of the room-temperature curable organopolysiloxane coating composition of the present invention is 5.0 or higher, the shape retention and anti-sagging properties when applied to a substrate are good. [Examples]

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

[0046] [Example 1] A polysiloxane (general formula (2)) having hydroxyl groups at both ends of the molecular chain and phenyl and methyl groups in the side chain, with a viscosity of 20 Pa·s at 23°C, R 1 82 parts by mass of methyl group (m=approximately 200, n=approximately 20, Ar=corresponding to a phenyl group, the same applies below) and fuzzy silica (apparent specific gravity 160 g / l, BET specific surface area 45 m²). 2 After mixing 20 parts by mass of (manufactured by Nippon Aerosil Co., Ltd.) for 30 minutes, 8 parts by mass of vinyltrimethoxysilane were added and stirred under atmospheric pressure for 15 minutes, then 0.1 parts by mass of dioctyl tin dilaurate were added and stirred under atmospheric pressure for 5 minutes, then mixed under reduced pressure for 15 minutes, and finally 73.4 parts by mass of xylene (an amount equivalent to 40% by mass of the total mass of the composition) were added and mixed under reduced pressure of 0.8 MPa for 15 minutes to obtain composition 1.

[0047] [Example 2] Atomized silica described in Example 1 (apparent specific gravity 160 g / l, BET specific surface area 45 m²) 2 (manufactured by Nippon Aerosil Co., Ltd.) 20 parts by mass are replaced with atomized silica (apparent specific gravity 140 g / l, BET specific surface area 150 m²) 2 Composition 2 was obtained in the same manner as in Example 1, except that 20 parts by mass of (manufactured by Nippon Aerosil Co., Ltd.) were used.

[0048] [Example 3] Atomized silica described in Example 1 (apparent specific gravity 160 g / l, BET specific surface area 45 m²) 2 (Manufactured by Nippon Aerosil Co., Ltd.) 20 parts by mass are replaced with atomized silica (apparent specific gravity 200 g / l, BET specific surface area 150 m²) 2 Composition 3 was obtained in the same manner as in Example 1, except that 20 parts by mass of (manufactured by Nippon Aerosil Co., Ltd.) were used.

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

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

[0051] [Example 6] The polysiloxane described in Example 1 is a polysiloxane (in general formula (1), R) having hydroxyl groups at both ends of the molecular chain and phenyl and methyl groups in the side chain, with a viscosity of 4 Pa·s at 23°C. 1 =R 2 Instead of a methyl group (X=C2H4, a=0, m=approximately 70, n=approximately 30, Ar=corresponding to a phenyl group, the same applies below), fumarole silica (apparent specific gravity 160 g / l, BET specific surface area 45 m²) is used. 2 Composition 6 was obtained in the same manner as in Example 1, except that 30 parts by mass of ( / g, manufactured by Nippon Aerosil Co., Ltd.) was replaced.

[0052] [Example 7] The polysiloxane described in Example 6 is a polysiloxane (in general formula (1), R) having hydroxyl groups at both ends of the molecular chain and phenyl and methyl groups in the side chain, with a viscosity of 5 Pa·s at 23°C. 1 =R2 Composition 7 was obtained in the same manner as in Example 1, except that it was replaced with (=methyl group, X=C2H4, a=0, m=approximately 370, n=approximately 20, Ar=corresponding to a phenyl group, the same applies hereinafter).

[0053] [Example 8] Composition 8 was obtained in the same manner as in Example 1, except that 73.4 parts by mass of xylene (an amount representing 40% by mass of the total amount) described in Example 1 was replaced with 110.1 parts by mass of xylene (an amount representing 50% by mass of 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 (an amount representing 40% by mass of the total amount) described in Example 1 was replaced with 55.1 parts by mass of xylene (an amount representing 30% by mass of the total mass of the composition).

[0055] [Comparative Example 1] The polysiloxane described in Example 1 is a polysiloxane (in general formula (2), R) in which both ends of the molecular chain are sealed with hydroxyl groups and the side chain has a methyl group, and has a viscosity of 20 Pa·s at 23°C. 1 Composition 10 was obtained in the same manner as in Example 1, except that it was replaced with a methyl group (where m=approximately 620 and n=0, the same applies hereafter).

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

[0057] [Comparative Example 3] Atomized silica described in Example 1 (apparent specific gravity 160 g / l, BET specific surface area 45 m²) 2(manufactured by Nippon Aerosil Co., Ltd.) 20 parts by mass are replaced with atomized silica (apparent specific gravity 40 g / l, BET specific surface area 45 m²). 2 Composition 12 was obtained in the same manner as in Example 1, except that 10 parts by mass of (manufactured by Nippon Aerosil Co., Ltd.) was used.

[0058] [Comparative Example 4] Atomized silica described in Example 1 (apparent specific gravity 160 g / l, BET specific surface area 45 m²) 2 (Manufactured by Nippon Aerosil Co., Ltd.) 20 parts by mass are replaced with atomized silica (apparent specific gravity 50 g / l, BET specific surface area 120 m²) 2 Composition 13 was obtained in the same manner as in Example 1, except that 20 parts by mass of (manufactured by Shin-Etsu Chemical Co., Ltd.) were 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 (an amount representing 40% by mass of the total amount) described in Example 1 was replaced with 18.4 parts by mass of xylene (an amount representing 10% by mass of the total mass of the composition).

[0060] The following properties were measured using the prepared compositions 1 to 14.

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

[0062] [Chikiso ratio] The thixotropic ratio α for each of the prepared compositions 1 to 14 was defined as η1 / η2. Here, η1 is the viscosity measured at 23°C with a rotor speed of 0.6 rpm using a Type B rotational viscometer (Toki Sangyo Co., Ltd.: Model TVB-10), 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 to a Teflon® sheet at 23°C and cured by exposure to a 23°C / 50%RH environment for 7 days to produce a 0.4 mm thick silicone rubber sheet (cured silicone rubber product). The light transmittance (wavelength: 400 nm) (%) of the silicone rubber sheet was measured using a spectrophotometer U-4100 (manufactured by Hitachi High-Tech Science Corporation). The results are shown in Table 1. Furthermore, when each of the prepared compositions 1 to 14 was applied to a Teflon® sheet, the workability during application, as well as the shape retention and sagging prevention properties when applied to the substrate, were evaluated. <Workability during application> A viscosity of 10 Pa·s or less was evaluated as good, and a viscosity exceeding 10 Pa·s was evaluated as poor. <Shape retention and sagging prevention when applied to a substrate> A thixotropic ratio of 5.0 or higher 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 (at 23°C) of 10 Pa·s or less, a thixotropic ratio of 5.0 or higher, and exhibited good workability during application, as well as good shape retention and sagging prevention when applied to a substrate. Furthermore, the light transmittance of the cured products of the compositions of Examples 1 to 9 was 75% or higher. The composition of Comparative Example 5 had a viscosity (at 23°C) greater 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%. A comparison of Examples 1-9 and Comparative Examples 1-5 shows that the cured product obtained from the room-temperature curable organopolysiloxane coating composition according to the present invention exhibits excellent light transmittance (transparency) in addition to the inherent insulating properties of silicone rubber, making it suitable for use as a coating agent, particularly as a sealing material for photocouplers.

Claims

1. (A) Organopolysiloxane represented by the following general formula (1) and / or (2): 100 parts by mass, 【Chemistry 1】 (In formula (1), Ar is independently an aromatic group, R 1 is independently an unsubstituted or halogen-substituted aliphatic monovalent hydrocarbon group having 1 to 10 carbon atoms. n and m are each numbers from 1 to 1000, n / (m+n) is 0.02 or more and less than 1, and the sequence of 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, and R 2 (where a is 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 (These are independently unsubstituted or halogen-substituted aliphatic monovalent hydrocarbon groups having 1 to 10 carbon atoms. n and m are each numbers from 1 to 1000, with n / (m+n) being between 0.02 and less than 1, and the sequence of siloxane units to which n and m are attached is arbitrary.) (B) Hydrolyzable organosilane compounds represented by the following general formula (3) and / or partially hydrolyzed condensates thereof: 0.1 to 30 parts by mass, 【Transformation 3】 (In formula (3), R 3 R is a monovalent hydrocarbon group independently selected from alkyl groups having 1 to 12 carbon atoms, vinyl groups, and phenyl groups. 4 (where b is 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 with an apparent specific gravity of 100 to 200 g / l: 1 to 300 parts by mass, (E) Organic solvent: in an amount of 20 to 60% by mass relative to the total mass of the composition A room-temperature curable organopolysiloxane coating composition containing the following:

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

4. The room-temperature curable organopolysiloxane coating composition according to claim 1, wherein the thixotropy ratio is 5.0 or higher.

5. The room-temperature curable organopolysiloxane coating composition according to claim 1, 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 described in claim 1.

7. A photocoupler encapsulant comprising the room-temperature curable organopolysiloxane coating composition described in claim 1.

8. A photocoupler sealed with a cured product of the photocoupler sealant described in claim 7.

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