Room temperature curable silicone coating composition and article

Abstract

A room-temperature-curable silicone coating composition comprising (A) an organopolysiloxane resin of a three-dimensional net structure which has an R3SiO1 / 2 / SiO4 / 2 molar ratio of 0.5-1.5, contains a given amount of silanol groups, and has a molecular weight of 2,000-10,000, (B) a silane compound having three or more hydrolyzable groups in the molecule and / or a product of partial hydrolytic condensation of the silane compound, (C) a linear diorganopolysiloxane in which both ends of the molecular chain have been blocked with silanol groups, and (D) a moisture-curing initiator comprising an oligomer of an organotitanium compound, the room-temperature-curable silicone coating composition giving a cured object having a durometer A hardness of 50 or greater. This composition can be an alcohol elimination type room-temperature-curable silicone coating composition which can be easily produced at low cost, has excellent long-term storage stability, and gives high-hardness cured objects (coating films), the cured coating films combining transparency with heat resistance.

Description

[Technical field]

[0001] The present invention relates to a room-temperature curable silicone coating composition that gives a cured product / coating film with a high hardness, with a hardness (Duro A hardness) of 50 or more as measured with a Type A durometer specified in JIS K 6249, and in particular to a room-temperature curable silicone coating composition containing an organopolysiloxane resin with a three-dimensional network structure that is suitable for use as a coating agent (conformal coating agent) for electric / electronic components and their substrates, a sealant for liquid crystal display elements, etc. In particular, the present invention relates to an alcohol-free, room-temperature curable silicone coating composition that is characterized by being easy to produce at low cost, capable of forming a coating film with high hardness, and which provides a cured coating film with high transparency and excellent heat resistance. [Background technology]

[0002] Room temperature vulcanizable (RTV) silicone rubber compositions, which can be crosslinked and cured by atmospheric moisture at room temperature (23°C ± 15°C) to give silicone elastomers (cured silicone rubber products), are easy to handle and have excellent weather resistance and electrical properties, 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, in the electrical and electronic fields, alcohol-free RTV silicone rubber compositions tend to be used because of their suitability for adhesion and coating to the adherends (resin-based) used. The same is true for coating agents for liquid crystal peripherals and power circuit boards, for which demand has been rapidly increasing in recent years, and alcohol-free RTV silicone rubber compositions are used. However, although this coating agent satisfies its main purpose of insulating and moisture-proofing electrical and electronic circuits, it has been insufficient in terms of hardness improvement as a conformal coating agent intended to protect wiring and the like due to the finer circuit patterns. To date, the following technologies have been disclosed for silicone rubber intended to protect circuit patterns and the like and to provide moisture protection.

[0003] Japanese Patent Laid-Open Publication No. 2004-143331 (Patent Document 1) discloses a room-temperature curable organopolysiloxane composition that gives a cured product / coating film that is highly transparent and has high strength. However, (CH3)3SiO 1 / 2 Units and SiO 4 / 2 It consists of the unit (CH3)3SiO 1 / 2 Unit / SiO 4 / 2 The problem is that the reaction time is long because an organopolysiloxane with a molar ratio of 0.74 and a silicon-bonded hydroxyl group content of 1.62% by mass and a dimethylpolysiloxane blocked at both ends with silanol groups are condensed with aqueous ammonia at 20° C. for 12 hours. Even if an ammonia removal step is added by heating, the odor of ammonia remains in the composition, which may cause problems in practical use.

[0004] Japanese Patent Application Laid-Open No. 2002-327115 (Patent Document 2) discloses a room temperature curable organopolysiloxane composition having excellent moisture resistance. (CH3)3SiO 1 / 2 Units and SiO 4 / 2 It consists of the unit (CH3)3SiO 1 / 2 Unit / SiO 4 / 2 An organopolysiloxane having a unit (molar ratio) of 0.74 and silanol groups at both ends of the molecular chain is dissolved in toluene to form a resinous copolymer, and a room temperature curable organopolysiloxane composition is prepared by heating. The problem is that the manufacturing is not easy due to the heating process.

[0005] Japanese Patent Application Laid-Open No. 2007-99955 (Patent Document 3) also discloses a method for producing a room temperature curable organopolysiloxane composition that gives a high strength cured product and coating film. (CH3)3SiO 1 / 2 Units and SiO 4 / 2 It consists of the unit (CH3)3SiO 1 / 2 Unit / SiO 4 / 2An organopolysiloxane having a molar ratio of 0.75 and a content of hydroxyl groups bonded to silicon atoms of 1.1% by mass and a dimethylpolysiloxane having both ends blocked with silanol groups are subjected to a condensation reaction with tetramethylguanidine at room temperature for 1 hour. The production time is shorter than that of JP-A-2002-327115 (Patent Document 2), but since a highly polar amine compound is used, it has poor compatibility with the organosiloxane composition and does not crosslink directly with the organopolysiloxane, which causes a problem of the amine compound seeping out of the composition.

[0006] Japanese Patent No. 6319168 (Patent Document 4) discloses a method for producing a room temperature curable organosiloxane composition, which is characterized by its simple production and short tact time, and 1 / 2 Units and SiO 4 / 2A method has been disclosed in which an organopolysiloxane resin having a three-dimensional network structure composed of units and an organosilane compound having an average of two or more hydrolyzable groups bonded to silicon atoms per molecule are condensed using an amino group-containing organosilane as a catalyst to introduce hydrolyzable groups into the organopolysiloxane resin having a three-dimensional network structure in advance, and then the organopolysiloxane resin is condensed with a linear diorganopolysiloxane having both ends of the molecular chain blocked with silanol groups in the presence of a catalyst to produce a condensation reaction product (cured silicone rubber).However, in the case of a dealcohol type, this composition contains alkoxytitanium (single unit) as a condensation catalyst, which is easily hydrolyzed by moisture in the air, so the composition itself may turn white.In addition, compositions containing condensation catalysts such as general alkoxytitanium (single unit) have problems such as yellowing during long-term storage. In addition, Japanese Patent No. 6319168 (Patent Document 4) discloses a method for producing a room temperature curable composition of an acetone-free type, which contains vinyltriisopropenoxysilane as a crosslinking agent and tetramethylguanidylpropyltrimethoxysilane as a condensation catalyst, but the silane is expensive, and condensation catalysts such as tetramethylguanidylpropyltrimethoxysilane are strongly basic, so they react with flux components used in electric and electronic components and their substrates to generate conductive salts, which may lead to a decrease in electrical performance. Furthermore, these compositions have problems such as low transparency and low heat resistance of the obtained cured product. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2004-143331 A [Patent Document 2] JP 2002-327115 A [Patent Document 3] JP 2007-99955 A [Patent Document 4] Patent No. 6319168 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in view of the above circumstances, and has as its object to provide an alcohol-free, room-temperature-curable silicone coating composition which can be used as a coating agent for the electrical and electronic fields (particularly peripherals of liquid crystal displays and power circuit boards), which is easy to produce at low cost, contains an organopolysiloxane resin with a three-dimensional network structure, has excellent long-term storage stability, is both transparent and heat resistant, and gives a cured product (coating film) with high hardness, and also provides an article coated with the cured product of said composition. [Means for solving the problem]

[0009] As a result of intensive research conducted by the present inventors in order to achieve the above-mentioned object, it has been found that a room-temperature curable silicone coating composition containing as a main agent (A) an organopolysiloxane resin having a three-dimensional network structure of a specific molecular weight and specific molecular structure and having a specific amount of silanol groups, as a crosslinking agent (B) a hydrolyzable (organo)silane compound and / or a partial hydrolysis condensate thereof having three or more hydrolyzable groups in one molecule, as a flexibility-imparting agent (C) a linear diorganopolysiloxane having both molecular chain terminals blocked with silanol groups, and as a curing catalyst (D) a specific amount of a moisture curing initiator consisting of an oligomer of an organotitanium compound, is easy to produce and inexpensive, and furthermore, satisfies the requirements of JIS K The present inventors have found that a room-temperature curable silicone coating composition can be used suitably as a conformal coating material, which gives a cured product (coating film) with a high hardness of 50 or more as measured by a type A durometer specified in JIS K 6249, and which has both transparency and heat resistance and does not discolor even when stored for a long period of time (excellent long-term storage stability), and has thus completed the present invention.

[0010] That is, the present invention provides the following room temperature curable silicone coating composition and an article coated with the cured product of said composition. [1] The following components (A) to (D) (A)R3SiO1 / 2 units (wherein R independently represents an unsubstituted or substituted monovalent hydrocarbon group or hydroxyl group having 1 to 6 carbon atoms) and SiO 4 / 2 Contains the unit SiO 4 / 2 R3SiO for units 1 / 2 The molar ratio of the units is 0.5 to 1.5, and RSiO 2 / 2 Units and RSiO 3 / 2 The unit (wherein R is as defined above) is SiO 4 / 2 100 parts by mass of an organopolysiloxane resin having a three-dimensional network structure and a molecular weight of 2,000 to 10,000, which may contain 0 to 1 molar ratio of each of the above units and has 0.005 to 0.15 mol / 100 g of hydroxy groups (silanol groups) bonded to silicon atoms, (B) a hydrolyzable (organo)silane compound having three or more hydrolyzable groups per molecule and / or a partial hydrolysis condensate thereof: an amount such that the molar ratio of component (B) to the silanol groups in component (A) is 0.2 to 2; (C) a linear diorganopolysiloxane having both molecular chain terminals blocked with silanol groups: 10 to 100 parts by mass, (D) Moisture curing initiator consisting of an oligomer of an organic titanium compound: 0.1 to 5 parts by mass and giving a cured product having a hardness of 50 or more as measured by a Type A durometer specified in JIS K 6249. [2] The room-temperature-curable silicone coating composition according to [1], wherein the content of hydroxy groups (silanol groups) bonded to silicon atoms in component (A) is 0.11 to 0.15 mol / 100 g. [3] The room-temperature-curable silicone coating composition according to [1] or [2], wherein component (D) is an oligomer of a titanate compound and / or an oligomer of a titanium chelate compound. [4] (D) component is an oligomer of tetra-n-propoxytitanium, an oligomer of tetraisopropoxytitanium, an oligomer of tetra-n-butoxytitanium, an oligomer of tetraisobutoxytitanium, an oligomer of tetra-sec-butoxytitanium, an oligomer of tetrakis(2-ethylhexoxy)titanium, an oligomer of titanium isopropoxyoctylene glycol, an oligomer of diisopropoxybis(acetylacetonato)titanium, or an oligomer of diisopropoxybis(ethylacetonato)titanium. [1] or [ 2] 2. The room temperature curable silicone coating composition according to claim 1 . [5] It can be left in a 250°C environment for 5 minutes to give a cured product that does not produce bubbles. [1] or [ 2] 2. The room temperature curable silicone coating composition according to claim 1 . [6] It gives a cured product with a thickness of 1 mm that has a light transmittance of 70% or more in the wavelength range of 450 to 800 nm. [1] or [ 2] 2. The room temperature curable silicone coating composition according to claim 1 . [7] For coating electrical and electronic components and / or their substrates.[1] or [ 2] 2. The room temperature curable silicone coating composition according to claim 1 . [8] [1] or [ 2] 2. An article coated with a cured product of the room temperature curable silicone coating composition according to claim 1. Effect of the Invention

[0011] According to the present invention, it is possible to provide a room-temperature curable silicone coating composition which is easy to produce, inexpensive, and has excellent long-term storage stability, and which further gives a cured product (coating film) with a high hardness of at least 50 as measured with a Type A durometer specified in JIS K 6249, and which gives a cured film that is both transparent and heat resistant. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will be described in detail below.

[0013] The room temperature curable silicone coating composition of the present invention contains the following component (A) (base), component (B) (crosslinking agent), component (C) (flexibility imparting agent), and component (D) (curing catalyst), and gives a cured product having a hardness of 50 or more as measured with a Type A durometer specified in JIS K 6249 (hereinafter sometimes referred to as Duro A hardness).

[0014] [Component (A)] First, in the room temperature curable silicone coating composition of the present invention, the component (A) used as the main component (base polymer) is RSiO 1 / 2 units (wherein R independently represents an unsubstituted or substituted monovalent hydrocarbon group or hydroxyl group having 1 to 6 carbon atoms) and SiO 4 / 2 Contains the unit SiO 4 / 2 R3SiO for units 1 / 2 The molar ratio of the units is 0.5 to 1.5, and further RSiO 2 / 2 Units and RSiO 3 / 2 The unit (wherein R is as defined above) is SiO 4 / 2 The organopolysiloxane resin may contain 0 to 1 molar ratio of each of these units, has 0.005 to 0.15 mol / 100 g of hydroxy groups (silanol groups) bonded to silicon atoms, and has a three-dimensional network structure with a molecular weight of 2,000 to 10,000.

[0015] The R represents an unsubstituted or substituted monovalent hydrocarbon group or hydroxy group having 1 to 6 carbon atoms, and examples of the monovalent hydrocarbon group of R 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 and allyl groups, and phenyl groups, as well as chloromethyl groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms or the like. As these R, methyl, ethyl, propyl, and phenyl groups are preferred, and methyl and phenyl groups are particularly preferred.

[0016] In the component (A), SiO 4 / 2 R3SiO for units 1 / 2 The molar ratio of the units is in the range of 0.5 to 1.5, preferably 0.6 to 1.3, and particularly preferably 0.65 to 1.2. If this molar ratio is less than 0.5, the reinforcing properties of the cured product will be insufficient, and if it exceeds 1.5, the hardness of the cured product will be insufficient.

[0017] The organopolysiloxane resin having a three-dimensional network structure of component (A) is, for example, RSiO 1 / 2 Units and SiO 4 / 2 It is preferable that the unit consists only of SiO 4 / 2 R2SiO for units 2 / 2 Molar ratio of units, SiO 4 / 2 RSiO for units 3 / 2 The molar ratio of each unit may be in the range of 0 to 1, and more preferably each of the molar ratios is 0.8 or less (0 to 0.8).

[0018] The silanol groups contained in the organopolysiloxane resin having a three-dimensional network structure of the component (A) must be 0.005 to 0.15 mol / 100g (i.e., 0.085 to 2.5 mass% in terms of the OH amount of hydroxyl groups bonded to silicon atoms), preferably 0.01 to 0.13 mol / 100g (0.17 to 2.2 mass%), and more preferably 0.02 to 0.12 mol / 100g (0.3 to 2.0 mass%). If the silanol groups are present in an amount greater than 0.15 mol / 100g, the rubber properties (especially hardness) will be high, and cracks may occur in the composition. If the silanol groups are present in an amount less than 0.005 mol / 100g, the condensation reaction between the components (A) and (C) may not proceed sufficiently, and the desired properties may not be obtained.

[0019] The three-dimensional network-structured organopolysiloxane resin of component (A) has a molecular weight of about 2,000 to 10,000, preferably about 2,500 to 8,000. If the molecular weight is too small, the cured product (silicone rubber cured product) obtained by curing the organopolysiloxane composition will have poor rubber elasticity and will be easily cracked, and if the molecular weight is too large, it will be difficult to prepare a uniform organopolysiloxane composition. This molecular weight (or degree of polymerization) can usually be determined as the number average molecular weight (or number average degree of polymerization) converted into polystyrene in gel permeation chromatography (GPC) analysis using toluene, tetrahydrofuran (THF), or the like as a developing solvent.

[0020] The organopolysiloxane resin having a three-dimensional network structure of component (A) is obtained by cohydrolyzing and condensing, in an organic solvent, a monofunctional triorganosilane having one hydrolyzable group together with a tetrafunctional silane having four hydrolyzable groups, or further together with a trifunctional silane having three hydrolyzable groups and / or a difunctional silane having two hydrolyzable groups, and is a known material that is substantially free of volatile components (copolymer).

[0021] The organic solvent used in the cohydrolysis reaction must be capable of dissolving the organopolysiloxane resin, which is component (A). Typical organic solvents include aromatic solvents such as toluene and xylene, halogenated solvents such as chloroform and dichloromethane, and hydrocarbon solvents such as cyclohexane, ethylcyclohexane, and isoparaffin.

[0022] [(B) Component] The component (B) is a hydrolyzable (organo)silane compound having three or more hydrolyzable groups in one molecule and / or a partial hydrolysis condensate thereof (a siloxane oligomer having three or more residual hydrolyzable groups in the molecule produced by partial hydrolysis and condensation of the silane compound), which functions as a crosslinking agent (curing agent) that crosslinks the above component (A) with the component (C) described below. Preferred examples of the (organo)silane compound include monosilane compounds, disilane compounds in which monosilanes are linked to each other via alkylene groups or alkenylene groups, and trisilane compounds, which are represented by the following general formulas (1) to (6).

[0023] R 1 Si(OR 2 )3(1) Si(OR 2 )4(2) R 1 (OR 2 )2Si-X-Si(OR 2 )2R 1 (3) (OR 2 )3Si-X-Si(OR 2 )3(4) R 1 (OR 2 )2Si-X-SiR 1 2-X-Si(OR 2 )2R 1 (5) (OR 2 )3Si-X-SiR 1 2-X-Si(OR 2 )3(6)

[0024] In the above formula, R 1represents alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, hexyl, and decyl; alkenyl groups such as vinyl (ethenyl), allyl, propenyl, isopropenyl, butenyl, pentenyl, and hexenyl; aryl groups such as phenyl, tolyl, xylyl, and α- and β-naphthyl; aralkyl groups such as benzyl, 2-phenylethyl, and 3-phenylpropyl; and groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as F, Cl, and Br, or cyano groups, for example, unsubstituted or substituted monovalent hydrocarbon groups having 1 to 10 carbon atoms such as 3-chloropropyl, 3,3,3-trifluoropropyl, and 2-cyanoethyl. Among these, it is preferable that aliphatic unsaturated hydrocarbon groups such as alkenyl groups are excluded, and alkyl groups such as methyl and ethyl groups are more preferable, with methyl being particularly preferable.

[0025] Hydrolyzable group (OR 2 Examples of the alkyl group include alkoxy groups having 1 to 4 carbon atoms, particularly 1 or 2 carbon atoms, such as a methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, isobutoxy group, and tert-butoxy group; alkoxyalkoxy groups having 2 to 4 carbon atoms, such as a methoxyethoxy group, ethoxyethoxy group, and methoxypropoxy group; ketoxime groups having 3 to 7 carbon atoms, such as a dimethylketoxime group, an ethylmethylketoxime group, and a diethylketoxime group; alkenyloxy groups having 2 to 6 carbon atoms, such as a vinyloxy group, a propenyloxy group, an isopropenyloxy group, and a 1-ethyl-2-methylvinyloxy group; acyloxy groups having 2 to 8 carbon atoms, such as an acetoxy group, an octanoyloxy group, and a benzoyloxy group; and dialkylaminooxy groups having 2 to 6 carbon atoms, such as a dimethylaminooxy group and a diethylaminooxy group. Among these, an alkoxy group or an isopropenoxy group is preferred, and an alkoxy group is particularly preferred.

[0026] X is an alkylene group having 2 to 6 carbon atoms, such as an ethylene group, a propylene group (a trimethylene group, a methylethylene group), a butylene group (a tetramethylene group, a methylpropylene group), or a hexamethylene group; or an alkenylene group having 2 to 4 carbon atoms, such as a vinylene group, a propenylene group, a 1-butenylene group, or a 2-butenylene group.

[0027] Specific examples of the component (B) include trialkoxysilanes such as methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-butyltrimethoxysilane, n-butyltriethoxysilane, isobutyltrimethoxysilane, n-hexyltrimethoxysilane, and n-decyltrimethoxysilane; tetramethoxysilane, tetraethoxysilane, bis[2-(dimethoxy(methyl)silyl)ethenyl]dimethylsilane, and bis[2-(diethoxy(methyl)silyl)ethenyl]dimethylsilane. Examples of the silanes include hexaalkoxysilanes such as tetraalkoxysilane, 1,2-bis(trimethoxysilyl)ethane, 1,2-bis(triethoxysilyl)ethane, 1,6-bis(trimethoxysilyl)hexane, 1,6-bis(triethoxysilyl)hexane, bis[2-(trimethoxysilyl)ethenyl]dimethylsilane, and bis[2-(triethoxysilyl)ethenyl]dimethylsilane; isopropenoxy group-containing silanes such as methyltriisopropenoxysilane, ethyltriisopropenoxysilane, vinyltriisopropenoxysilane, and phenyltriisopropenoxysilane; acetoxysilanes such as methyltriacetoxysilane, ethyltriacetoxysilane, and vinyltriacetoxysilane, and the like, and partial hydrolysis and condensation products thereof.

[0028] The hydrolyzable (organo)silane compound of component (B) is represented by the following general formula (7), which has R at the α-position as a substituent bonded to a silicon atom. 4Also included are hydrolyzable organosilane compounds having a methylene group (for example, an organooxymethyl group such as an alkoxymethyl group) which has an organooxy group represented by O- (for example, an alkoxy group).

[0029] [ka] (In the formula, R 3 are independently unsubstituted or substituted monovalent hydrocarbon groups having 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms; R 4 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms, Y is a hydrolyzable group, and m is 0 or 1.

[0030] Here, in the above formula (7), R 3 Examples of the unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms, represented by the following formula (1) include alkyl groups such as 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, and a dodecyl group; cycloalkyl groups such as a cyclopentyl group and a cyclohexyl group; a vinyl group, an allyl group, a propene group, Examples of such groups include alkenyl groups such as nyl, isopropenyl, butenyl, pentenyl, and hexenyl; aryl groups such as phenyl, tolyl, xylyl, and α- and β-naphthyl; aralkyl groups such as benzyl, 2-phenylethyl, and 3-phenylpropyl; and groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as F, Cl, and Br or cyano groups, such as 3-chloropropyl, 3,3,3-trifluoropropyl, and 2-cyanoethyl. Among these, those excluding aliphatic unsaturated hydrocarbon groups such as alkenyl groups are preferred, alkyl groups such as methyl and ethyl groups are more preferred, and methyl groups are particularly preferred.

[0031] Next, in the above formula (7), R 4 Examples of the unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms, represented by the following formula (1): alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, and dodecyl groups; cycloalkyl groups such as cyclopentyl and cyclohexyl groups; alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, pentenyl, and hexenyl groups; phenyl Examples of such groups include aryl groups such as a tolyl group, a xylyl group, and an α- or β-naphthyl group; aralkyl groups such as a benzyl group, a 2-phenylethyl group, and a 3-phenylpropyl group; groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as F, Cl, and Br, or with a cyano group, such as a 3-chloropropyl group, a 3,3,3-trifluoropropyl group, and a 2-cyanoethyl group; and alkyl groups in which some of the hydrogen atoms of these groups are substituted with lower alkoxy groups such as a methoxy group and an ethoxy group, such as a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, and an ethoxyethyl group. Among these, lower alkyl groups having 1 to 4 carbon atoms such as a methyl group and an ethyl group are preferred.

[0032] In the above formula (7), Y is a hydrolyzable group, and examples thereof include alkoxy groups having 1 to 4 carbon atoms, such as a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, and a tert-butoxy group; alkoxyalkoxy groups having 2 to 4 carbon atoms, such as a methoxyethoxy group, an ethoxyethoxy group, and a methoxypropoxy group; acyloxy groups having 2 to 8 carbon atoms, such as an acetoxy group, an octanoyloxy group, and a benzoyloxy group; vinyloxy groups, propenyloxy groups, isopropenyloxy groups, 1-ethyl-2-methyloxy groups, and the like. Examples of such groups include alkenyloxy groups having 2 to 6 carbon atoms, such as an alkylvinyloxy group; ketoxime groups having 3 to 7 carbon atoms, such as a dimethylketoxime group, a methylethylketoxime group, a diethylketoxime group, and the like; amino groups having 2 to 6 carbon atoms, such as a dimethylamino group, a diethylamino group, a butylamino group, a cyclohexylamino group, and the like; aminoxy groups having 2 to 6 carbon atoms, such as a dimethylaminooxy group, a diethylaminooxy group, and the like; and amide groups having 3 to 8 carbon atoms, such as an N-methylacetamide group, an N-ethylacetamide group, an N-methylbenzamide group, and the like. Among these, alkoxy groups are preferred, and methoxy and ethoxy groups are particularly preferred. m is 0 or 1, and is preferably 0.

[0033] Specific examples of the hydrolyzable organosilane compound represented by the above formula (7) containing an organooxymethyl group such as an alkoxymethyl group bonded to a silicon atom in the molecule, and partial hydrolysis condensates thereof include methoxymethyltrimethoxysilane, ethoxymethyltriethoxysilane, methoxymethyl(methyl)dimethoxysilane, ethoxymethyl(methyl)diethoxysilane, methoxymethyl(ethyl)dimethoxysilane, ethoxymethyl(ethyl)diethoxysilane, methoxymethyl(hexyl)dimethoxysilane, ethoxymethyl(hexyl)diethoxysilane, methoxymethyl(octyl)dimethoxysilane, ethoxymethyl(octyl)diethoxysilane, methoxymethyl(phenyl)dimethoxysilane, ethoxymethyl(phenyl)diethoxysilane, and partial hydrolysis condensates thereof.

[0034] For example, the structural formulae of the above specific examples, methoxymethyltrimethoxysilane and ethoxymethyltriethoxysilane, are as follows: Of these, ethoxymethyltriethoxysilane is particularly preferred. [ka]

[0035] In the room temperature curable silicone coating composition of the present invention, the hydrolyzable (organo)silane compound having three or more hydrolyzable groups per molecule of component (B) and / or its partial hydrolysis condensate acts as a crosslinking agent (curing agent) that bonds component (A) with component (C) described below, and the amount of component (B) blended is an amount such that the molar ratio of component (B) to the silanol groups in component (A) is 0.2 to 2, and preferably an amount of 0.4 to 2. If the amount of component (B) is too small, sufficient rubber properties may not be obtained even when the composition is cured, or storage stability may be impaired, while if the amount is too large, rapid curing properties may be impaired or it may be economically disadvantageous.

[0036] The amount of component (B) blended is preferably an amount such that the molar ratio of component (B) to the sum of the amounts of silanol groups in components (A) and (C) is 0.3 to 1, and more preferably an amount such that the molar ratio is 0.4 to 1.0. If the molar ratio of component (B) to the sum of the amounts of silanol groups in components (A) and (C) is less than 0.3, good storage stability cannot be obtained, while if it exceeds 1, the curing time becomes long and it is also disadvantageous in terms of cost.

[0037] The hydrolyzable (organo)silane compound of component (B) does not have a monovalent hydrocarbon group substituted with a functional group (excluding organooxy groups) having a heteroatom such as nitrogen, oxygen or sulfur in the molecule, and is therefore clearly distinguishable from the silane coupling agent, which is an optional component and will be described later.

[0038] [(C) component] Component (C) is a necessary component for linking the organopolysiloxane resins of the three-dimensional network structure together by mixing with components (A) and (B) and undergoing a condensation reaction with these components. The addition of component (C) makes it possible to impart flexibility to the cured product (cured coating) of the room temperature curable silicone coating composition of the present invention. Specifically, component (C) is a linear diorganopolysiloxane in which both ends of the molecular chain are blocked with silanol groups (or hydroxydiorganosiloxy groups), and is preferably represented by the following general formula (8). [ka] (In the formula, R 5 are independently an unsubstituted or alkoxy-substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and n is an integer of 10 or greater.

[0039] In the above formula (8), R 5 Examples of the unsubstituted or alkoxy-substituted monovalent hydrocarbon group having 1 to 10 carbon atoms 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 and allyl; aryl groups such as phenyl and naphthyl; and alkoxy-substituted monovalent hydrocarbon groups in which some or all of the hydrogen atoms of these groups have been substituted with alkoxy groups, such as alkoxy-substituted alkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl. Of these, a methyl group is preferred.

[0040] The viscosity of component (C) is preferably a fluid (liquid) exhibiting a viscosity of 10,000 mPa·s or less (usually 30 to 10,000 mPa·s), preferably 50 to 8,000 mPa·s, and particularly preferably about 100 to 6,000 mPa·s at 23°C, and usually corresponds to the number of repeating units n (degree of polymerization) in the above formula (8) of about 10 to 1,000, preferably 30 to 500, and more preferably about 50 to 400. The viscosity can usually be measured using a rotational viscometer (for example, BL type, BH type, BS type, cone-plate type, etc.) (the same applies hereinafter).

[0041] The amount of component (C) is 10 to 100 parts by mass, preferably 10 to 80 parts by mass, per 100 parts by mass of component (A). If the amount of component (C) is too small, the composition will cure but will have too high a hardness and good rubber properties will not be obtained. If the amount of component (C) is too large, it may not be mixed uniformly with component (A).

[0042] [(D) component] Component (D) is a moisture curing initiator consisting of an oligomer of an organotitanium compound (a polymer (condensation) product of an organotitanium compound with a low degree of polymerization), and functions as a catalyst to promote moisture curing of the room-temperature-curable silicone coating composition of the present invention by atmospheric moisture (water) at room temperature (23°C±15°C). One type of organotitanium compound oligomer may be used alone, or two or more types may be used as a mixture.

[0043] Here, the component (D) is preferably an oligomer of a titanate compound and / or an oligomer of a titanium chelate compound. Specific examples of the (D) component include oligomers of organic titanium compounds, such as oligomers of titanate compounds such as tetra-n-propoxytitanium oligomers, tetraisopropoxytitanium oligomers, tetra-n-butoxytitanium (also known as tetra-n-butyltitanate) oligomers, tetraisobutoxytitanium oligomers, tetra-sec-butoxytitanium oligomers, tetra-tert-butoxytitanium oligomers, tetrakis(2-ethylhexoxy)titanium oligomers, and titanium isopropoxyoctylene glycol oligomers, and oligomers of titanium chelate compounds such as diisopropoxybis(acetylacetonato)titanium oligomers and diisopropoxybis(ethylacetonato)titanium oligomers. Among these, from the viewpoints of the environment and toxicity to the human body and the long-term color resistance of the room temperature curable silicone coating composition of the present invention, oligomers of titanic acid butyl ester compounds such as tetra-n-butoxytitanium oligomers and tetra-tert-butoxytitanium oligomers are particularly preferred. As the oligomer of titanic acid butyl ester compounds, for example, Tyzor BTP (manufactured by Dorf Ketal) can be used.

[0044] The oligomer of the organic titanium compound has a structure in which the above-mentioned titanate ester or titanium chelate compound is condensed, and is preferably a dimer to 50-mer, more preferably a dimer to 20-mer, of these organic titanium compounds. Such an oligomer of an organic titanium compound can be obtained by reacting the organic titanium compound with water in an alcohol solution to cause condensation.

[0045] The amount of the (D) component is 0.1 to 5 parts by mass, preferably 0.1 to 4 parts by mass, and particularly preferably 0.5 to 3 parts by mass, based on 100 parts by mass of the (A) component. If the amount is less than 0.1 parts by mass, sufficient crosslinking is not obtained, and the intended cured product is not obtained. If the amount is more than 5 parts by mass, there are disadvantages such as being disadvantageous in terms of cost and a decrease in the curing speed.

[0046] [Other ingredients] In addition, in addition to the above-mentioned components, the room temperature curable silicone coating composition of the present invention may contain fillers and various additives as necessary within the scope of the present invention.As fillers, pulverized silica, fumed silica, calcium carbonate, zinc carbonate, aluminum hydroxide, aluminum oxide hydroxide, alumina, magnesium oxide, wet silica, etc. are included.As additives, known additives, such as polyethers as wetters and thixotropy improvers, plasticizers, non-reactive dimethyl silicone oils, etc. are included.

[0047] Furthermore, if necessary, colorants such as pigments and dyes, fluorescent whitening agents, antifungal agents, antibacterial agents, and surface modifiers such as non-reactive phenyl silicone oils, fluorosilicone oils, and organic liquids incompatible with silicones as bleed oils may also be added.

[0048] Also, a silane coupling agent (a functional group-containing hydrolyzable organosilane compound having a monovalent hydrocarbon group substituted with a functional group having a heteroatom such as nitrogen, oxygen or sulfur in the molecule, a so-called carbon functional silane compound other than component (B)) may be blended to impart adhesiveness. Examples of such a component include silane compounds having an alkoxysilyl group or an alkenoxysilyl group as a hydrolyzable group, such as γ-methacryloxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β-(aminoethyl)γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, 3-(N-aminomethylbenzylamino)propyl Examples of the silane coupling agent include N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine, N,N-bis[3-(trimethoxysilyl)propyl]amine, γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltriisopropenoxysilane, γ-glycidoxypropylmethyldiisopropenoxysilane, a reaction product of (meth)acrylic silane and aminosilane, a reaction product of epoxy silane and aminosilane, a reaction product of aminosilane and halogenated alkyl group-containing silane, etc. In particular, it is preferable to use a silane coupling agent containing at least one amino group in the molecule.

[0049] When a silane coupling agent is used, the amount is 0.1 to 20 parts by mass, 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 part by mass, sufficient adhesion cannot be obtained, and if the amount is more than 20 parts by mass, not only is it cost-prohibitive, but good curability may not be achieved.

[0050] The room temperature curable silicone coating composition of the present invention can be produced by mixing the above-mentioned components in a conventional manner and stored in a moisture-free atmosphere. When left at room temperature (23°C±15°C), it will usually cure in 5 minutes to 1 week in the presence of moisture in the air. It is preferable that the component (A) is prepared by blending the organopolysiloxane resin having the three-dimensional network structure as a solution having a solid content of 40 to 70 mass % using a specific organic solvent (for example, an aromatic solvent such as toluene or xylene, a halogen-based solvent such as chloroform or dichloromethane, or a hydrocarbon solvent such as cyclohexane, ethylcyclohexane, or isoparaffin).

[0051] The viscosity of the room temperature curable silicone coating composition of the present invention at 23°C is preferably 10 to 5,000 mPa·s, and more preferably 20 to 3,000 mPa·s.

[0052] The room temperature curable silicone coating composition of the present invention is particularly characterized by its ease of production, low cost, ability to form a coating film with high hardness, and the fact that the cured coating film has high transparency and excellent heat resistance and does not discolor over the long term.

[0053] The room temperature curable silicone coating composition of the present invention is characterized by containing the components (A) to (D) specified as above, and giving a cured product having a hardness of 50 or more, preferably 50 to 90, measured by a type A durometer specified in JIS K 6249. If the Duro A hardness of the obtained cured product is less than 50, it is not suitable as a conformal coating agent for protecting wiring and the like accompanying fine circuit patterns. In addition, in order to obtain a cured product having a Duro A hardness of 50 or more in the room temperature curable silicone coating composition of the present invention, the composition containing the above-mentioned components (A) to (D) in the specific blending ratio described above can be condensed and cured by moisture in the air at room temperature according to a conventional method (for example, by leaving it for 7 days in an environment of 23°C / 50% RH until the thickness becomes 3 mm).

[0054] In addition, the cured product of the room temperature curable silicone coating composition of the present invention is preferably one that does not generate bubbles when left in a 250°C environment for 5 minutes, and preferably one that has a light transmittance of 70% or more in the wavelength range of 450 to 800 nm when the cured product is 1 mm thick. In order to obtain these cured products, a composition containing the above-mentioned components (A) to (D) in the above-mentioned specific blending ratio is condensed and cured by moisture in the air at room temperature according to a conventional method (for example, by leaving it for 7 days in a 23°C / 50% RH environment until the thickness becomes 3 mm). The light transmittance in the above-mentioned specific wavelength region can usually be measured by a spectrophotometer.

[0055] Furthermore, it is preferred that the room-temperature-curable silicone coating composition of the present invention has excellent long-term storage stability, such that the color of the composition does not change even when stored for a long period of time (for example, about 4 months) at room temperature (23°C±15°C) in a sealed state protected from moisture.

[0056] The room-temperature-curable silicone coating composition of the present invention is suitable as a conformal coating material, and is particularly suitable as a coating agent for electric and electronic parts and / or their substrates, a sealant for liquid crystal display elements, and the like. Furthermore, according to the present invention, it is possible to provide an article coated with a cured product of the room temperature curable silicone coating composition of the present invention. Examples of articles to which the present invention can be applied include liquid crystal peripherals, power circuit boards, and water-repellent coated substrates for vehicles. EXAMPLES

[0057] Examples and comparative examples are provided below to specifically explain the present invention, but the present invention is not limited to the following examples. In the following examples, Me is a methyl group, the viscosity is a value measured by a rotational viscometer at 23° C., and the molecular weight is the number average molecular weight in terms of polystyrene measured by GPC analysis using toluene as a developing solvent.

[0058] [Example 1] (A) Me3SiO as component 1 / 2 Units, and SiO 4 / 2 It consists of the unit SiO 4 / 2 Me3SiO for units 1 / 2 The mixture consisted of 92 parts by mass of a three-dimensional network methylpolysiloxane resin having a unit molar ratio of 0.68, a molecular weight of approximately 3,500, a silanol group content of 0.11 mol / 100 g (1.87% by mass), and dissolved in IsoparE (manufactured by Exxon Mobil, boiling point 115 to 140°C, the same applies below) to a solid content of 60% by mass, 10 parts by mass of tetraethoxysilane as component (B) (an amount such that the molar ratio of component (B) to the silanol groups in component (A) was 0.79), 35 parts by mass of dimethylpolysiloxane as component (C) whose molecular chain was blocked at both ends with hydroxydimethylsilyl groups, had a viscosity of 5,000 mPa s at 23°C, and had a degree of polymerization of approximately 389, and tetra-n-butoxytitanium oligomer Tyzor BTP (Dorf Composition 1 was obtained by mixing 1 part by mass of γ-aminopropyltriethoxysilane (manufactured by Ketal Corporation) and 1.6 parts by mass of γ-aminopropyltriethoxysilane at room temperature (23° C.) for 30 minutes.

[0059] [Example 2] (A) Me3SiO as component 1 / 2 Units, and SiO 4 / 2 It consists of the unit SiO 4 / 2 Me3SiO for units 1 / 2Composition 2 was obtained by mixing 92 parts by mass of a three-dimensional network methylpolysiloxane resin having a unit molar ratio of 0.68, a molecular weight of approximately 3,500, a silanol group content of 0.11 mol / 100 g (1.87% by mass), and dissolved in Isopar E to a solid content of 60% by mass, 10 parts by mass of tetraethoxysilane as component (B) (an amount such that the molar ratio of component (B) to the silanol groups in component (A) is 0.79), 35 parts by mass of a dimethylpolysiloxane as component (C) whose molecular chain ends are blocked with hydroxydimethylsilyl groups, has a viscosity at 23°C of 5,000 mPa s, and has a degree of polymerization of approximately 389, 1 part by mass of a tetra-n-butoxytitanium oligomer Tyzor BTP (manufactured by Dorf Ketal) as component (D), and 0.8 parts by mass of γ-aminopropyltriethoxysilane for 30 minutes at room temperature (23°C).

[0060] [Example 3] (A) Me3SiO as component 1 / 2 Units, and SiO 4 / 2 It consists of the unit SiO 4 / 2 Me3SiO for units 1 / 2 Composition 3 was obtained by mixing 92 parts by mass of a three-dimensional network methylpolysiloxane resin having a unit molar ratio of 0.68, a molecular weight of approximately 3,500, and a silanol group content of 0.11 mol / 100 g (1.87% by mass) dissolved in Isopar E to a solid content of 60% by mass, 10 parts by mass of methyltrimethoxysilane as component (B) (an amount such that the molar ratio of component (B) to the silanol groups in component (A) is 1.21), 40 parts by mass of a dimethylpolysiloxane as component (C) whose molecular chain ends are blocked with hydroxydimethylsilyl groups, has a viscosity of 700 mPa s at 23°C, and has a degree of polymerization of approximately 270, and 1 part by mass of a tetra-n-butoxytitanium oligomer Tyzor BTP (manufactured by Dorf Ketal) as component (D) for 30 minutes at room temperature (23°C).

[0061] [Example 4] (A) Me3SiO as component 1 / 2 Units, and SiO 4 / 2 It consists of the unit SiO 4 / 2Me3SiO for units 1 / 2 The mixture consisted of 92 parts by mass of a three-dimensional network methylpolysiloxane resin having a unit molar ratio of 0.68, a molecular weight of approximately 3,500, a silanol group content of 0.11 mol / 100 g (1.87% by mass), and dissolved in Isopar E to a solid content of 60% by mass; 10 parts by mass of (ethoxymethyl)triethoxysilane as component (B) (an amount such that the molar ratio of component (B) to the silanol groups in component (A) was 0.74); 35 parts by mass of a dimethylpolysiloxane having both ends of the molecular chain blocked with hydroxydimethylsilyl groups, a viscosity at 23°C of 5,000 mPa s, and a degree of polymerization of approximately 389 as component (C); and Tyzor BTP (Dorf) oligomer of tetra-n-butoxytitanium as component (D). Composition 4 was obtained by mixing 1 part by mass of γ-aminopropyltriethoxysilane (manufactured by Ketal) and 1 part by mass of γ-aminopropyltriethoxysilane at room temperature (23° C.) for 30 minutes.

[0062] [Comparative Example 1] (A) Me3SiO as component 1 / 2 Units, and SiO 4 / 2 It consists of the unit SiO 4 / 2 Me3SiO for units 1 / 2 Composition 5 was obtained by mixing 92 parts by mass of a three-dimensional network methylpolysiloxane resin having a unit molar ratio of 0.68, a molecular weight of approximately 3,500, a silanol group content of 0.11 mol / 100 g (1.87% by mass), and dissolved in Isopar E to a solid content of 60% by mass, 10 parts by mass of tetraethoxysilane as component (B) (an amount such that the molar ratio of component (B) to the silanol groups in component (A) is 0.79), 35 parts by mass of dimethylpolysiloxane as component (C) whose molecular chain ends are blocked with hydroxydimethylsilyl groups, has a viscosity of 5,000 mPa s at 23 °C, and has a degree of polymerization of approximately 389, 1 part by mass of tetra-n-butyl titanate (single substance), and 1.6 parts by mass of γ-aminopropyltriethoxysilane for 30 minutes at room temperature (23 °C).

[0063] [Comparative Example 2] (A) Me3SiO as component 1 / 2 Units, and SiO 4 / 2It consists of the unit SiO 4 / 2 Me3SiO for units 1 / 2 Composition 6 was obtained by mixing 92 parts by mass of a three-dimensional network methylpolysiloxane resin having a unit molar ratio of 0.68, a molecular weight of approximately 3,500, a silanol group content of 0.11 mol / 100 g (1.87% by mass), and dissolved in Isopar E to a solid content of 60% by mass, 10 parts by mass of tetraethoxysilane as component (B) (an amount such that the molar ratio of component (B) to the silanol groups in component (A) is 0.79), 35 parts by mass of dimethylpolysiloxane as component (C) whose molecular chain ends are blocked with hydroxydimethylsilyl groups, has a viscosity at 23°C of 5,000 mPa s, and has a degree of polymerization of approximately 389, 1 part by mass of tetra-n-octyl titanate (single unit), and 1.6 parts by mass of γ-aminopropyltriethoxysilane for 30 minutes at room temperature (23°C).

[0064] [Comparative Example 3] (A) Me3SiO as component 1 / 2 Units, and SiO 4 / 2 It consists of the unit SiO 4 / 2 Me3SiO for units 1 / 2 Composition 7 was obtained by mixing 92 parts by mass of a three-dimensional network methylpolysiloxane resin having a unit molar ratio of 0.68, a molecular weight of approximately 3,500, a silanol group content of 0.11 mol / 100 g (1.87% by mass), and dissolved in Isopar E to a solid content of 60% by mass, 10 parts by mass of tetraethoxysilane as component (B) (an amount such that the molar ratio of component (B) to the silanol groups in component (A) was 0.79), 35 parts by mass of a dimethylpolysiloxane as component (C) whose molecular chain ends are blocked with hydroxydimethylsilyl groups, has a viscosity at 23°C of 5,000 mPa s, and has a degree of polymerization of approximately 389, and 1.6 parts by mass of γ-aminopropyltriethoxysilane for 30 minutes.

[0065] [Comparative Example 4] (A) Me3SiO as component 1 / 2 Units, and SiO 4 / 2 It consists of the unit SiO 4 / 2 Me3SiO for units 1 / 2Composition 8 was obtained by mixing 92 parts by mass of a three-dimensional network methylpolysiloxane resin having a unit molar ratio of 0.68, a molecular weight of approximately 3,500, a silanol group content of 0.11 mol / 100 g (1.87% by mass), and dissolved in Isopar E to a solid content of 60% by mass, 8 parts by mass of (ethoxymethyl)triethoxysilane as component (B) (an amount such that the molar ratio of component (B) to the silanol groups in component (A) is 0.74), 30 parts by mass of a dimethylpolysiloxane having both molecular chain ends blocked with hydroxydimethylsilyl groups, a viscosity at 23°C of 5,000 mPa s, and a degree of polymerization of approximately 389 as component (C) at room temperature (23°C), 0.8 parts by mass of γ-aminopropyltriethoxysilane, and 0.1 parts by mass of γ-(N,N'-dimethylguanidyl)propyltrimethoxysilane for 30 minutes.

[0066] The following properties were confirmed using the prepared compositions 1 to 8.

[0067] Appearance, viscosity and initial hardening The appearance of the prepared compositions 1 to 8 was visually confirmed, and the viscosity was measured under a 23°C / 50% RH environment. The prepared compositions 1 to 8 were left to stand for 7 days under a 23°C / 50% RH environment to harden to a thickness of 3 mm, and the hardness (Duro A hardness) was measured using a type A durometer specified in JIS K 6249.

[0068] ·Heat resistance The prepared compositions 1 to 8 were placed on an aluminum plate of 50 mm x 50 mm x 5 mm thickness and left to cure for 7 days under a 23°C / 50% RH environment until the thickness reached 5 mm. Then, the test specimens of the cured compositions 1 to 8 were left in an oven at 250°C for 5 minutes, and the presence or absence of bubbles in the cured rubber was confirmed. The results were as follows: (Judgment criteria) ○: No air bubbles were found in the test specimen (good heat resistance) ×: Air bubbles were generated in the test specimen (poor heat resistance)

[0069] ·Light transmittance The prepared compositions 1 to 8 were left to harden for 7 days in an environment of 23°C / 50% RH to a thickness of 1 mm, and then the light transmittance (%) of the cured product in the thickness direction was measured at wavelengths of 450 nm, 600 nm, and 800 nm using a spectrophotometer U-3310 manufactured by Hitachi High-Tech Science.

[0070] ·Long-term storage stability The prepared compositions 1 to 8 were placed in a sealable transparent bottle and left in a sealed state in an environment of 23° C. / 50% RH for 4 months, and the color change of the composition was confirmed. The results are shown in the table below.

[0071] [Table 1]

[0072] [Table 2]

[0073] As a result of the above, in Examples 1 to 4 (Compositions 1 to 4), good cured products with Duro A hardness of 50 or more were obtained, the heat resistance was good, the light transmittance at wavelengths of 450 nm, 600 nm, and 800 nm was all 70% or more, and no color change was observed even when stored for a long period of time, so the products were stable. In contrast, in Comparative Examples 1 and 2 (Compositions 5 and 6), good cured products were obtained and the heat resistance was also good, but yellowing was confirmed during long-term storage. In Comparative Example 3 (Composition 7), no cured product was obtained even when left in a 23°C / 50% RH environment, and it was impossible to measure hardness, heat resistance, and light transmittance. In Comparative Example 4 (Composition 8), by blending (ethoxymethyl)triethoxysilane, which has excellent fast curing properties, as component (B), a cured product was obtained without blending component (D) or by blending a basic condensation catalyst instead of component (D). However, in the evaluation of heat resistance, many bubbles were generated in the cured product, resulting in poor heat resistance.

Claims

1. The following components (A) to (D): (A) R 3 SiO 1 / 2 units (wherein R independently represents an unsubstituted or substituted monovalent hydrocarbon group or hydroxyl group having 1 to 6 carbon atoms) and SiO 4 / 2 Contains units, SiO 4 / 2 R for units 3 SiO 1 / 2 The molar ratio of units is 0.5 to 1.5, and further R 2 SiO 2 / 2 Units and RSiO 3 / 2 The units (wherein R is as defined above) are 4 / 2 100 parts by mass of an organopolysiloxane resin having a three-dimensional network structure and a molecular weight of 2,000 to 10,000, which may contain 0 to 1 molar ratio of each of these units and has 0.005 to 0.15 mol / 100 g of hydroxy groups (silanol groups) bonded to silicon atoms, (B) a hydrolyzable (organo)silane compound having three or more hydrolyzable groups per molecule and / or a partial hydrolysis condensate thereof: in an amount such that the molar ratio of component (B) to the silanol groups in component (A) is 0.2 to 2; (C) a linear diorganopolysiloxane having both molecular chain terminals blocked with silanol groups: 10 to 100 parts by mass, (D) Moisture curing initiator consisting of an oligomer of an organic titanium compound: 0.1 to 5 parts by mass and a mixture of the above compounds, which gives a cured product having a hardness of 50 or more as measured by a Type A durometer specified in JIS K 6249.

2. 2. The room-temperature-curable silicone coating composition according to claim 1, wherein the content of hydroxy groups (silanol groups) bonded to silicon atoms in component (A) is 0.11 to 0.15 mol / 100 g.

3. 3. The room-temperature-curable silicone coating composition according to claim 1, wherein component (D) is an oligomer of a titanate compound and / or an oligomer of a titanium chelate compound.

4. 3. The room-temperature-curable silicone coating composition according to claim 1 or 2, wherein component (D) is a tetra-n-propoxytitanium oligomer, a tetraisopropoxytitanium oligomer, a tetra-n-butoxytitanium oligomer, a tetraisobutoxytitanium oligomer, a tetra-sec-butoxytitanium oligomer, a tetrakis(2-ethylhexoxy)titanium oligomer, a titanium isopropoxyoctylene glycol oligomer, a diisopropoxybis(acetylacetonato)titanium oligomer, or a diisopropoxybis(ethylacetonato)titanium oligomer.

5. 3. The room temperature curable silicone coating composition according to claim 1, which gives a bubble-free cured product when left in a 250°C environment for 5 minutes.

6. 3. A room temperature curable silicone coating composition according to claim 1 or 2, which gives a cured product having a thickness of 1 mm and a light transmittance of 70% or more in the wavelength region of 450 to 800 nm.

7. 3. The room temperature curable silicone coating composition according to claim 1, which is used for coating electric or electronic parts and / or substrates thereof.

8. 3. An article coated with a cured product of the room temperature curable silicone coating composition according to claim 1 or 2.

Images