Thixotropic silicone gel composition, silicone gel cured product, and electric and electronic parts

Abstract

A silicone gel composition in which a crosslinking agent and a base polymer having a specific molecular structure are selectively used in combination, which contains micropowdered silica having a hydrophobized surface and a specific epoxy-group-containing siloxane oligomer, and which yields a silicone gel cured product having a degree of penetration of 10-100 as specified by JIS K6249 upon curing is liquid at room temperature (23°C±15°C) but spreads little during application and undergoes little change in shape before and after curing, and therefore is suitable for sealing electrical / electronic components such as photocouplers.

Description

Technical Field

[0001] The present invention relates to a thermosetting thixotropic silicone gel composition, a cured product thereof (silicone gel), and an electric and electronic component such as a photocoupler sealed with the silicone gel cured product, which are suitable for sealing electric and electronic components such as photocouplers because they are liquid at room temperature (23 ° C. ± 15 ° C), have small spreadability during application, and have small shape changes before and after curing.

Background Art

[0002] Silicone gel is excellent in properties such as electrical insulation, stability of electrical properties, and flexibility, and is used as a coating material for covering control circuit elements such as ICs and capacitors to protect them from thermal and mechanical damages for potting and sealing of electric and electronic components.

[0003] Since the liquid silicone gel composition used for such purposes is assumed to be injected into a case, it often has high fluidity and is unsuitable for spot potting that covers only a specific element.

[0004] On the other hand, silicone gel compositions having thixotropic properties that enable the above-mentioned spot potting have been studied. In Patent Document 1 (Japanese Patent No. 3073888), an addition-curing type silicone gel composition containing an organopolysiloxane having a 3,3,3-trifluoropropyl group in the molecular chain side chain and hydrophobized silica, and in Patent Document 2 (Japanese Patent Laid-Open No. 9-132718), an alkenyl group-containing organopolysiloxane and an inorganic filler having a specific surface area of 50 to 500 m 2 / g have been proposed as two-component curable silicone gel compositions.

[0005] However, even with these thixotropic silicone gel compositions, although the shape is maintained immediately after applying the composition, spreading occurs during the heat curing process, and as a result, there has been a problem that the cured product is also applied to parts other than the target sealing site.

[0006] In Patent Document 3 (Japanese Patent No. 3746394), an addition-curing silicone gel composition containing a branched organopolysiloxane having an alkenyl group, silica powder, an epoxy compound, and / or a polyhydric alcohol has been proposed. In this composition, a silicone gel composition having a low viscosity of 10 Pa·s or less is disclosed. However, the shape retention during the heat-curing process is insufficient, and when a polyhydric alcohol is used, there is a risk of property changes (curing failure) over time.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] The present invention has been made in view of the above circumstances, and provides a thixotropic silicone gel composition suitable for sealing electrical and electronic components such as photocouplers, which is liquid at room temperature (23°C ± 15°C), has small spreadability during application, and small shape changes before and after curing, a silicone gel cured product obtained by curing the composition, and an electrical and electronic component such as a photocoupler sealed with the silicone gel cured product.

Means for Solving the Problems

[0009] As a result of intensive studies to achieve the above object, the present inventors have found that a silicone gel composition containing a base polymer having a specific molecular structure and a crosslinking agent selectively used in combination, finely divided silica having a hydrophobized surface, and a specific epoxy group-containing siloxane oligomer, and capable of providing a silicone gel cured product having a penetration of 10 to 100 as defined in JIS K6249 upon curing can solve the above problems, and thus the present invention has been completed.

[0010] That is, the present invention provides the following thixotropic silicone gel composition, a cured product thereof (silicone gel), and an electric and electronic component such as a photocoupler sealed with the silicone gel cured product. [1] (A) As a diorganosiloxane unit in the main chain, (C6H5)2SiO 2 / 2 is contained in an amount of 0.1 to 10 mol% in all the diorganosiloxane units in the main chain, and an alkenyl group bonded to a silicon atom is 0.004~0.05 mol / 100 g: 100 parts by mass of a linear or branched organopolysiloxane, (B) The following average compositional formula (1) [Chemical formula] (In the formula, R 1 is the same or different monovalent hydrocarbon group having 1 to 10 carbon atoms and not containing an aliphatic unsaturated bond, a is 0 or 1, b is a positive number of 0.002 to 0.3, and c is a positive number of 0.1 to 0.6.) An organohydrogenpolysiloxane represented by the formula and containing hydrogen atoms bonded to at least three silicon atoms in one molecule: an amount such that the hydrogen atoms bonded to the silicon atoms in the component (B) are 0.3~1.2 mol per 1 mol of the alkenyl group in the component (A), (C) A platinum-based curing catalyst: an effective amount as a catalyst, (D) Organosilazane, organochlorosilane, organoalkoxysilane or organopolysiloxane having only a methyl group as a monovalent hydrocarbon group bonded to a silicon atom, and having a specific surface area (BET adsorption method) of 50 to 500 m 2Fumed silica having a specific surface area of 2 to 30 parts by mass, and (E) The following general formula (2) R 2 X R 3 Y Si(OR 4 ) 4-X-Y (2) (In the formula, R 2 is a monovalent organic group having 2 to 30 carbon atoms and having one or more epoxy groups, R 3 is a monovalent hydrocarbon group having 1 to 20 carbon atoms, and R 4 is a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms. X is 1 or 2, Y is 0 or 1, and X + Y is 1 or 2.) One or more partial (hydrolytic) condensates of organosilane compounds represented by and / or the organosilane compound represented by the above general formula (2) and the following general formula (3) R 5 Z Si(OR 6 ) 4-Z (3) (In the formula, R 5 is a monovalent hydrocarbon group having 1 to 20 carbon atoms, and R 6 is a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms. Z is an integer of 0 to 3.) An epoxy group-containing siloxane oligomer which is a partial co-(hydrolytic) condensate with an organosilane compound represented by: 0.01 to 5 parts by mass A thixotropic silicone gel composition which contains and, when cured, gives a silicone gel cured product having a penetration of 10 to 100 as defined in JIS K6249. [2] The thixotropic silicone gel composition according to [1], wherein the apparent viscosities (25 ° C) are measured at rotational speeds such that the rotation speed ratio is 1:10 by a method conforming to JIS K7117, and the SVI value obtained from the following formula is 2.0 to 10.0. SVI value = (apparent viscosity at the lower rotational speed) / (apparent viscosity at the higher rotational speed) [3] A silicone gel cured product obtained by curing the thixotropic silicone gel composition described in [1] or [2]. [4] An electric / electronic component encapsulated with the silicone gel cured product described in [3]. [5] The electric / electronic component described in [4] which is a photocoupler. [Advantages of the Invention]

[0011] The thixotropic silicone gel composition of the present invention is liquid at room temperature (23°C ± 15°C), has little spreading property during coating, and has little shape change before and after curing. Therefore, it can be used to encapsulate elements and the like in a desired shape, and is useful as a silicone gel composition for encapsulating electric / electronic components such as photocouplers. [Embodiments for Carrying Out the Invention]

[0012] The thixotropic silicone gel composition of the present invention contains the following components (A) to (E) as essential components. In the present invention, the silicone gel cured product (or silicone gel) is a cured product with a low crosslinking density mainly composed of organopolysiloxane, and has a penetration (also referred to as cone penetration) of 10 to 100 as defined in JIS K6249 by the penetration test method (1 / 4 cone) of JIS K2220. This corresponds to a very low hardness (i.e., soft) and low elasticity (low stress property) such that the measured value (rubber hardness value) becomes 0 in the rubber hardness measurement by JIS K6301 and does not show an effective rubber hardness value. In this regard, it is different from the so-called silicone rubber cured product (rubbery elastic body).

[0013] Hereinafter, the present invention will be described in detail.

[0014] [Component (A)] The organopolysiloxane of component (A) is the main agent (base polymer) of the thixotropic silicone gel composition of the present invention, and is a bifunctional diorganosiloxane unit (R2SiO that constitutes the main chain. 2 / 2As the D unit represented by, and R being an unsubstituted or substituted monovalent hydrocarbon group), (C6H5)2SiO 2 / 2 The unit (diphenylsiloxane unit) is contained in 0.1 to 10 mol% of all the diorganosiloxane units in the main chain, and at least one alkenyl group bonded to a silicon atom in one molecule (hereinafter sometimes referred to as "alkenyl group bonded to a silicon atom").) (usually 1 to 20, preferably 2 to 10, more preferably about 2 to 5), a linear or branched (in the repeating structure of the bifunctional diorganosiloxane unit constituting the main chain, a trifunctional organosilsesquioxane unit (RSiO 3 / 2 As the T unit represented by, and R being an unsubstituted or substituted monovalent hydrocarbon group), it has a small amount, for example, 1 to 5, preferably about 1 to 3), an organopolysiloxane (that is, a linear or branched alkenyl group-containing organopolysiloxane that essentially has a specific amount of diphenylsiloxane units in the molecule). In the present invention, the linear organopolysiloxane means an organopolysiloxane composed only of a bifunctional diorganosiloxane unit (D unit) constituting the main chain and a monofunctional triorganosiloxy unit (R3SiO 1 / 2 As the M unit represented by, and R being an unsubstituted or substituted monovalent hydrocarbon group), and the branched organopolysiloxane means a trifunctional organosilsesquioxane unit (T unit) constituting a branch point, a bifunctional diorganosiloxane unit (D unit) constituting the main chain, and a monofunctional triorganosiloxy unit (M unit) constituting the molecular chain end, and means an organopolysiloxane having a branch in the molecule, and may have a cyclic structure in the molecule. Examples of R mentioned here can include a phenyl group, an alkenyl group described later, and an "organic group bonded to a silicon atom" described later.

[0015] The alkenyl group preferably has 2 to 10 carbon atoms. Specifically, examples include vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, isobutenyl group, pentenyl group, hexenyl group, cyclohexenyl group, heptenyl group, etc. Among them, the vinyl group is particularly preferred. The bonding position of the silicon atom-bonded alkenyl group in the organopolysiloxane molecule may be at the molecular chain end, at the non-terminal of the molecular chain (i.e., the side chain of the molecular chain), or both. In component (A), the content of the silicon atom-bonded alkenyl group is preferably 0.001 to 10 mol / 100 g, more preferably 0.002 to 1 mol / 100 g, particularly preferably 0.003 to 0.11 mol / 100 g, and still more preferably 0.004 to 0.05 mol / 100 g.

[0016] In the organopolysiloxane of component (A), the organic group bonded to the silicon atom other than the phenyl group constituting the silicon atom-bonded alkenyl group and the diphenylsiloxane unit (hereinafter also referred to as "silicon atom-bonded organic group") is not particularly limited as long as it does not have an aliphatic unsaturated bond. For example, non-substituted or substituted monovalent hydrocarbon groups having usually 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, excluding aliphatic unsaturated bonds, etc. are included. Examples of this non-substituted or substituted monovalent hydrocarbon group include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group; cycloalkyl groups such as cyclohexyl group; aryl groups (excluding phenyl group) such as tolyl group, xylyl group, naphthyl group; aralkyl groups such as benzyl group, phenethyl group; and halogenated alkyl groups such as chloromethyl group, 3-chloropropyl group, 3,3,3-trifluoropropyl group in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as chlorine atom, fluorine atom, bromine atom, etc. From the viewpoint of simplicity of synthesis, an alkyl group, an aryl group, and a halogenated alkyl group are preferred, a methyl group and a trifluoropropyl group are more preferred, and a methyl group is particularly preferred.

[0017] The organopolysiloxane of component (A) contains (C6H5)2SiO units in the molecule (particularly, in all the diorganopolysiloxane units composed of the repetition of bifunctional diorganosiloxane units constituting the main chain of the molecular chain), usually in an amount of 0.1 to 10 mol%, preferably 0.5 to 8 mol%, particularly preferably 1 to 6 mol%. 2 / 2 When the content of the (C6H5)2SiO unit exceeds the upper limit of the above range, the viscosity of the resulting composition becomes extremely high and the coating workability deteriorates. 2 / 2 When the content of the (C6H5)2SiO unit exceeds the upper limit of the above range, the viscosity of the resulting composition becomes extremely high and the coating workability deteriorates.

[0018] The viscosity of component (A) at 25 °C is preferably 100 to 100,000 mPa·s, particularly preferably 300 to 10,000 mPa·s, because the workability of the composition and the mechanical properties of the cured product (silicone gel cured product) are more excellent. In the present invention, the viscosity can be measured by a rotational viscometer (for example, BL type, BH type, BS type, cone plate type, rheometer, etc.) (hereinafter the same). For the same reason, the number of silicon atoms (or degree of polymerization) in component (A) is usually about 30 to 1,200, preferably 50 to 1,000, more preferably about 80 to 800. In the present invention, the degree of polymerization (or molecular weight) 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 (hereinafter the same).

[0019] Specific examples of such component (A) are as follows. Organopolysiloxanes having triorganosiloxy groups blocked at both ends of the molecular chain, such as dimethylsiloxane-diphenylsiloxane copolymer blocked at both ends with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane-diphenylsiloxane copolymer blocked at both ends with dimethylvinylsiloxy groups, dimethylsiloxane-vinylmethylsiloxane-diphenylsiloxane copolymer blocked at both ends with trimethylsiloxy groups, dimethylsiloxane-diphenylsiloxane copolymer blocked at one end with a trimethylsiloxy group and at the other end with a dimethylvinylsiloxy group, dimethylsiloxane-diphenylsiloxane-methylvinylsiloxane copolymer blocked at one end with a trimethylsiloxy group and at the other end with a dimethylvinylsiloxy group, dimethylsiloxane-diphenylsiloxane copolymer blocked at both ends with methyldivinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane-diphenylsiloxane copolymer blocked at both ends with methyldivinylsiloxy groups, dimethylsiloxane-diphenylsiloxane copolymer blocked at both ends with trivinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane-diphenylsiloxane copolymer blocked at both ends with trivinylsiloxy groups, and branched-chain (linear with partial branching) organopolysiloxanes in which 1 to 5, preferably 1 to 3, more preferably 1 or 2 of the difunctional diorganosiloxane units constituting the main chain in these linear diorganopolysiloxanes are substituted with a branched structure (trifunctional organosilsesquioxane unit), etc.

[0020] (A) The organopolysiloxane of the component may be used alone or in combination of two or more as long as it satisfies the condition that the organopolysiloxane of the component (A) has an average of at least 0.5 silicon atom-bonded alkenyl groups per molecule in one molecule.

[0021] [Component (B)] The organohydrogenpolysiloxane of component (B) used in the present invention is a component that acts as a crosslinking agent (curing agent) in the hydrosilylation addition curing reaction with component (A). Component (B) is represented by the following average composition formula (1) and contains at least 3, preferably 4 to 300, more preferably 5 to 100 hydrogen atoms bonded to silicon atoms (hereinafter also referred to as "silicon atom-bonded hydrogen atoms" (i.e., SiH groups)) in one molecule. It is a linear organohydrogenpolysiloxane (more specifically, a molecular chain both-end triorganosiloxy group-capped organohydrogensiloxane·diorganosiloxane copolymer or a molecular chain both-end diorganohydrogensiloxy group-capped organohydrogensiloxane·diorganosiloxane copolymer), and it must have hydrogen atoms (SiH groups) bonded to silicon atoms in the non-terminal (in the middle of the molecular chain) of the molecular chain. However, it may further have hydrogen atoms (SiH groups) bonded to silicon atoms at the molecular chain terminals.

Chemical formula

[0022] In the above average composition formula (1), R 1is a monovalent hydrocarbon group that does not contain the same or different aliphatic unsaturated bonds, and is preferably an unsubstituted or substituted monovalent hydrocarbon group that does not contain aliphatic unsaturated bonds and usually has 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms. For example, alkyl groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group; cycloalkyl groups such as cyclohexyl group; aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group; aralkyl groups such as benzyl group, phenethyl group; and halogenated alkyl groups such as chloromethyl group, 3-chloropropyl group, 3,3,3-trifluoropropyl group in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as chlorine atom, fluorine atom, bromine atom, etc. are mentioned. Preferably, they are alkyl groups and aryl groups, and more preferably methyl group, phenyl group, etc.

[0023] In the above formula (1), a is 0 or 1. Further, b is 0.002 to 0.3, preferably 0.006 to 0.2, more preferably 0.013 to 0.1, and c is a positive number of 0.1 to 0.6, preferably 0.1 to 0.4. When b is less than 0.002, a silicone gel cured product having a desired penetration cannot be obtained. When b exceeds 0.3, it is not only difficult to obtain a silicone gel cured product with a low elastic modulus and low stress, but also unevenness occurs on the surface of the cured product, resulting in a decrease in the displacement durability of the cured product.

[0024] From the above average composition formula (1), the molecular structure of the component (B) is a molecular chain both ends triorganosiloxy group-blocked organohydrogensiloxane·diorganosiloxane copolymer or a molecular chain both ends diorganohydrogensiloxy group-blocked organohydrogensiloxane·diorganosiloxane copolymer, and can be represented by the following average molecular formula (1').

Chemical formula

[0025] The viscosity of the organohydrogenpolysiloxane of component (B) at 25 °C is preferably in the range of 0.1 to 5,000 mPa·s, more preferably 0.5 to 1,000 mPa·s, particularly preferably 2 to 500 mPa·s, because the workability of the composition and the optical or mechanical properties of the cured product become more excellent. A range that is liquid at room temperature (25 °C) is desirable. When such a viscosity is satisfied, the number of silicon atoms (or degree of polymerization) in one molecule of the organohydrogenpolysiloxane is usually 7 to 1,000, preferably 10 to 330, more preferably about 20 to 150. In addition, in component (B), the content of hydrogen atoms (SiH groups) bonded to the silicon atoms is preferably 0.0005 to 0.008 mol / g, particularly preferably 0.001 to 0.006 mol / g.

[0026] Specific examples of the linear organohydrogenpolysiloxane of component (B) include those represented by the following average composition formula.

Chemical formula

[0027] The organohydrogenpolysiloxane of component (B) may be used alone or in combination of two or more.

[0028] (B) The addition amount of the component is such that the silicon atom-bonded hydrogen atom (SiH group) in the (B) component is 0.01 to 3 moles, preferably 0.05 to 2 moles, more preferably 0.1 to 1.8 moles, still more preferably 0.2 to 1.5 moles, and particularly preferably 0.3 to 1.2 moles, per 1 mole of the silicon atom-bonded alkenyl group in the above (A) component. If the silicon atom-bonded hydrogen atom from this (B) component is less than 0.01 mole per 1 mole of the silicon atom-bonded alkenyl group in the (A) component, a silicone gel cured product having a desired penetration cannot be obtained. If it exceeds 3 moles, the cured product may not exhibit a gel state or the heat resistance may decrease.

[0029] [Component (C)] The (C) component used in the present invention is used as a catalyst for promoting the hydrosilylation addition reaction between the silicon atom-bonded alkenyl group in the (A) component and the silicon atom-bonded hydrogen atom (SiH group) in the (B) component. The (C) component is a platinum-based curing catalyst (platinum or a platinum-based compound), and known ones can be used. Specific examples thereof include platinum black, chloroplatinic acid, alcohol-modified products such as chloroplatinic acid; platinum group metal catalysts such as complexes of chloroplatinic acid with olefins, aldehydes, vinylsiloxanes or acetylene alcohols, etc.

[0030] (C) The compounding amount of the component may be an effective amount as a catalyst and can be appropriately increased or decreased according to the desired curing rate. Usually, it is in the range of 0.1 to 1,000 ppm, preferably 1 to 300 ppm, in terms of the mass of platinum group metal atoms, based on the total amount of the (A) component and the (B) component. If this compounding amount is too large, the heat resistance of the obtained cured product may decrease. If it is too small, the hydrosilylation addition reaction may not proceed sufficiently under predetermined curing conditions and a gel-like cured product may not be obtained.

[0031] [Component (D)] The component (D) used in the present invention is finely divided silica having a specific surface area (BET adsorption method) of 50 to 500 m 2 / g, the surface of which is hydrophobized with an organosilazane, organochlorosilane, organoalkoxysilane or organopolysiloxane having only a methyl group as a monovalent hydrocarbon group bonded to a silicon atom, and is a component for imparting thixotropy to the composition before curing and reducing the spreadability during coating by being used in combination with the component (E) described below. Such finely divided silica exhibits sufficient thixotropy in the composition of the present invention due to the interaction with the component (E) described below. For this purpose, it is necessary to have a specific surface area (BET method) of 50 to 500 m 2 / g, preferably 50 to 400 m 2 / g, and the surface thereof is hydrophobized with an organosilazane, organochlorosilane, organoalkoxysilane or organopolysiloxane having only a methyl group as an organic substituent (monovalent hydrocarbon group) bonded to a silicon atom.

[0032] Specific examples of the surface treatment agent as described above include hexamethyldisilazane; trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane; trimethylalkoxysilane, dimethyldialkoxysilane, methyltrialkoxysilane (where alkoxy groups include methoxy group, ethoxy group, propoxy group, butoxy group, etc.); cyclic or linear polydimethylsiloxane, etc. These may be used alone or in combination of two or more. The dimethylpolysiloxane may be cyclic or linear.

[0033] Examples of the finely divided silica include fumed silica (dry silica), crushed silica, fused silica, crystalline silica (quartz fine powder), precipitated silica (wet silica), colloidal silica, etc. From the viewpoint of the desired specific surface area (or average particle size), fumed silica is preferred.

[0034] The specific surface area (BET adsorption method) of the finely divided silica having a hydrophobized surface is 50 to 500 m 2per g, preferably 50 to 400 m 2 / g. When the specific surface area is less than 50 m 2 / g, it is difficult to impart sufficient thixotropy to the composition, and when it exceeds 500 m 2 / g, the viscosity of the composition becomes too high, and the coating workability is significantly reduced.

[0035] As such hydrophobically treated fine powder silica, commercially available products can be used, and examples thereof include DM-30S (manufactured by Tokuyama Corporation), NSX-200 (manufactured by Nippon Aerosil Co., Ltd.), CAB-O-SIL TS-610 (manufactured by Cabot Corporation, USA), and the like.

[0036] The blending amount of component (D) is in the range of 2 to 30 parts by mass, preferably 3 to 20 parts by mass, more preferably 5 to 15 parts by mass, based on 100 parts by mass of component (A). If the blending amount of component (D) is too small, sufficient thixotropy cannot be imparted to the composition, and the spreadability during coating cannot be controlled. If the blending amount is too large, the viscosity of the composition becomes significantly high, and the coating workability deteriorates.

[0037] [Component (E)] Component (E) acts as a thixotropy-imparting agent for imparting thixotropy to the composition of the present invention and reducing the spreadability during coating, together with component (D) described above, without impairing the fluidity of the composition of the present invention. The following epoxy group-containing siloxane oligomers are used. That is, component (E) used in the present invention is a partially (hydrolytic) condensate obtained by partially (hydrolytic) condensing one or more of the organosilane compounds (epoxy group-modified organoxysilane or hydroxysilane) represented by the following general formula (2), and / or one or more of the organosilane compounds represented by the following general formula (2) and one or more of the organosilane compounds (organoxysilane or hydroxysilane) represented by the following general formula (3) are partially co-(hydrolytic) condensed. It is an epoxy group-containing siloxane oligomer which is a partial co-(hydrolytic) condensate. In the present invention, the "partial (hydrolytic) condensate" means an organosiloxane oligomer having at least two, preferably three or more, residual hydrolyzable groups (residual organooxy groups) and / or residual hydroxy groups, which is formed by partially (hydrolytically) condensing one or more of the organosilane compounds represented by the following general formula (2) (epoxy group-modified organoxysilane or hydroxysilane). The "partial co-(hydrolytic) condensate" means an organosiloxane oligomer having at least two, preferably three or more, residual hydrolyzable groups (residual organooxy groups) and / or residual hydroxy groups, which is formed by partially co-(hydrolytically) condensing one or more of the organosilane compounds represented by the following general formula (2) (epoxy group-modified organoxysilane or hydroxysilane) and one or more of the organosilane compounds represented by the following general formula (3) (organoxysilane or hydroxysilane).

[0038] R 2 X R 3 Y Si(OR 4 ) 4-X-Y (2) (In the formula, R 2 is a monovalent organic group having 2 to 30 carbon atoms and having at least one epoxy group (epoxy group-containing monovalent hydrocarbon group which may contain an ether bond oxygen atom and / or a nitrogen atom), R 3 is a monovalent hydrocarbon group having 1 to 20 carbon atoms, and R 4 is a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms. X is 1 or 2, Y is 0 or 1, and X + Y is 1 or 2.)

[0039] In the above formula (2), R 2is not particularly limited as long as it is a monovalent organic group having 1 or more epoxy groups and 2 to 30 carbon atoms, preferably 3 to 20 carbon atoms, more preferably 6 to 12 carbon atoms. Examples include monovalent hydrocarbon groups containing 1 or more epoxy groups and optionally containing an ether bond oxygen atom and / or a nitrogen atom constituting an amino group. Specifically, for example, 3-glycidoxypropyl group, 2-(3,4-epoxycyclohexyl)ethyl group, 2-(2,3-epoxycyclohexyl)ethyl group, 3-(N-allyl-N-glycidyl)aminopropyl group, 3-(N,N-glycidyl)aminopropyl group, etc. can be mentioned.

[0040] R 3 is a monovalent hydrocarbon group having 1 to 20 carbon atoms. Specific examples of the monovalent hydrocarbon group include alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, α-ethylhexyl group, cycloalkyl groups such as cyclohexyl group, cycloheptyl group, alkenyl groups such as vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, isobutenyl group, pentenyl group, hexenyl group, cyclohexenyl group, octenyl group, aryl groups such as phenyl group, tolyl group, xylyl group, styryl group, and aralkyl groups such as benzyl group, phenylethyl group, phenylpropyl group, etc. Among these, an alkyl group is preferred, and more preferably a methyl group or an ethyl group.

[0041] R 4is a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms. As the monovalent hydrocarbon group, an alkyl group having 1 to 10 carbon atoms is preferable, and an alkoxy-substituted alkyl group substituted with a methoxy group or an ethoxy group may also be used. Specifically, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, cyclohexyl group, cycloheptyl group, octyl group, α-ethylhexyl group, methoxymethyl group, methoxyethyl group, ethoxymethyl group, ethoxyethyl group and the like can be mentioned. Among them, the preferable ones are methyl group and ethyl group.

[0042] X is 1 or 2, Y is 0 or 1, and X + Y is 1 or 2.

[0043] Specific examples of the organosilane compound represented by the general formula (2) include, for example, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 2-(2,3-epoxycyclohexyl)ethyltrimethoxysilane, 2-(2,3-epoxycyclohexyl)ethyltriethoxysilane, 3-(N-allyl-N-glycidyl)aminopropyltrimethoxysilane, 3-(N-allyl-N-glycidyl)aminopropyltriethoxysilane, 3-(N-allyl-N-glycidyl)aminopropylmethyldimethoxysilane, 3-(N,N-glycidyl)aminopropyltrimethoxysilane, 3-(N,N-glycidyl)aminopropyltriethoxysilane, 3-(N,N-glycidyl)aminopropylmethyldimethoxysilane and the like.

[0044] R 5 Z Si(OR 6 ) 4-Z (3) (In the formula, R 5 is a monovalent hydrocarbon group having 1 to 20 carbon atoms, and R 6 is a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms. Z is an integer from 0 to 3.)

[0045] In the above formula (3), R 5 is a monovalent hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms. Specifically, examples include a hydrogen atom, an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a neopentyl group, a hexyl group, an octyl group, a cycloalkyl group such as a cyclohexyl group, an alkenyl group such as a vinyl group, an allyl group, a propenyl group, an aryl group such as a phenyl group, a tolyl group, a xylyl group, a styryl group, and an aralkyl group such as a benzyl group, a phenylethyl group, and a phenylpropyl group. Among these, an alkyl group and an aryl group are preferred, and a methyl group and an ethyl group are more preferred.)

[0046] R 6 is a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and examples thereof are the same as those exemplified for R 4 in the above formula (2). Among these, an alkyl group is preferred, and a methyl group, an ethyl group, and a propyl group are more preferred.) Z is an integer from 0 to 3, preferably an integer from 0 to 2.)

[0047] Specific examples of the organosilane compound represented by the above general formula (3) include, for example, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltripropoxysilane, ethyltributoxysilane, propyltrimethoxysilane, propyltriethoxysilane, propyltripropoxysilane, propyltributoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltripropoxysilane, benzyltrimethoxysilane, benzyltriethoxysilane, p-styryltrimethoxysilane, and also dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldipropoxysilane, dimethyldibutoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diethyldipropoxysilane, diethyldibutoxysilane, dipropyldimethoxysilane, dipropyldiethoxysilane, dipropyldipropoxysilane, dipropyldibutoxysilane, diphenyldihydroxysilane, and also trimethylmethoxysilane, trimethylethoxysilane, trimethylpropoxysilane, trimethylbutoxysilane, triethylmethoxysilane, triethylethoxysilane, triethylpropoxysilane, triethylbutoxysilane, tripropylmethoxysilane, tripropylethoxysilane, tripropylpropoxysilane, tripropylbutoxysilane, triphenylhydroxysilane, and also tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane and the like.

[0048] (E) The method for producing the epoxy group-containing organosiloxane oligomer is not particularly limited. For example, one or more of the organoxysilanes or hydroxysilanes represented by the general formula (2), or one or more of the organoxysilanes or hydroxysilanes represented by the general formula (2) and one or more of the organoxysilanes or hydroxysilanes represented by the general formula (3) are mixed, and an acidic catalyst and a solvent are added as necessary, and it can be obtained by partial (hydrolysis) polycondensation or partial co-(hydrolysis) polycondensation under weakly acidic or weakly alkaline conditions.

[0049] Here, when using one or more organoxysilanes represented by the general formula (2) and one or more organoxysilanes represented by the general formula (3), the usage ratio thereof is such that the molar ratio of one or more organoxysilanes represented by the general formula (2) to one or more organoxysilanes represented by the general formula (3) is 1:10 to 10:1, preferably 1:5 to 5:1.

[0050] Hydrolysis is usually preferably carried out at 5 to 50 °C for 120 minutes or more. The hydrolyzate thus obtained is, if necessary, then subjected to polycondensation. The polycondensation reaction is preferably carried out at 50 to 100 °C for about 60 to 240 minutes.

[0051] The epoxy group-containing siloxane oligomer thus obtained preferably has an epoxy equivalent of 50 to 1,000 g / mol, particularly 100 to 1,000 g / mol. If the epoxy equivalent is less than 50 g / mol, sufficient thixotropy cannot be imparted, and the spreading property during coating may increase. If it exceeds 1,000 g / mol, the thixotropy may become too large and the composition may significantly increase in viscosity.

[0052] In addition, the epoxy group-containing siloxane oligomer preferably has an alkoxy group content of 20 to 70% by mass, particularly 30 to 60% by mass. If the alkoxy group content is less than 20% by mass, the interaction with fine powder silica may decrease, and a sufficient thixotropy imparting effect may not be obtained. If it exceeds 70% by mass, the heat resistance of the cured product may decrease. The epoxy equivalent and the alkoxy group content can be measured by methods defined by JIS K7236 or 1 1H-NMR, 29 means such as 29Si-NMR.

[0053] Furthermore, the epoxy group-containing siloxane oligomer preferably has a viscosity at 25°C of 1 to 300 mPa·s, particularly preferably 5 to 200 mPa·s. If the viscosity at 25°C is less than 1 mPa·s, the miscibility with the composition may decrease, and if it exceeds 300 mPa·s, the viscosity of the composition may become too high.

[0054] In addition, commercially available products may be used for the component (E). Examples of such commercially available products include KR-516, KR-517, X-41-1059A (all manufactured by Shin-Etsu Chemical Co., Ltd.), etc.

[0055] The blending amount of the component (E) is 0.01 to 5 parts by mass, particularly preferably 0.05 to 1 part by mass, based on 100 parts by mass of the component (A). If it is less than 0.01 part by mass, sufficient thixotropy cannot be imparted to the composition, and if it exceeds 5 parts by mass, the viscosity increases and the coating workability significantly deteriorates.

[0056] In the thixotropic silicone gel composition of the present invention, optional components can be blended within a range that does not impair the object of the present invention, in addition to the above components (A) to (E). Examples of such optional components include reaction inhibitors, inorganic fillers, organopolysiloxanes that do not contain silicon atom-bonded hydrogen atoms and silicon atom-bonded alkenyl groups, adhesion-imparting agents such as alkoxyorganosilanes that contribute to improving adhesion or tackiness, heat-resistant additives, flame-retardant additives, pigments, dyes, and the like.

[0057] The reaction inhibitor is a component for suppressing the reaction of the above composition. Specifically, examples thereof include reaction inhibitors such as acetylene-based, amine-based, carboxylic acid ester-based, and phosphite-based reaction inhibitors.

[0058] Examples of the inorganic filler include fine powder silica such as crystalline silica and precipitated silica other than the component (D) above, inorganic hollow fillers (such as silica hollow fillers and titanium oxide hollow fillers), silsesquioxane, fumed titanium dioxide, magnesium oxide, zinc oxide, iron oxide, aluminum hydroxide, magnesium carbonate, calcium carbonate, zinc carbonate, layered mica, diatomaceous earth, glass fiber and other inorganic fillers; fillers obtained by subjecting these fillers to surface hydrophobization treatment with organosilicon compounds such as organoalkoxysilane compounds, organochlorosilane compounds, organosilazane compounds, and low molecular weight siloxane compounds, and the like. Further, silicone rubber powder, silicone resin powder and the like may be blended.

[0059] The thixotropic silicone gel composition of the present invention can be obtained by uniformly mixing the above components (A) to (E) and other optional components in predetermined amounts. At that time, the components to be mixed may be divided into two parts or more parts and mixed as necessary. For example, it is also possible to divide them into a part consisting of a part of the component (A) and the components (C), (D), and (E) and a part consisting of the remaining part of the component (A) and the component (B) and mix them. Here, examples of the mixing means to be used include a homomixer, a paddle mixer, a homodisper, a colloid mill, a vacuum mixing and stirring mixer, and a planetary mixer, but it is not particularly limited as long as it can uniformly mix at least the above components (A) to (E).

[0060] The thixotropic silicone gel composition of the present invention preferably has an SVI value of 2.0 to 10.0, particularly 3.0 to 8.0, which is obtained from the following formula by measuring the apparent viscosity (25°C) at rotation speeds where the rotation speed ratio is 1:10 according to the method conforming to JIS K7117. SVI value = (apparent viscosity at the lower rotation speed) / (apparent viscosity at the higher rotation speed) If the ratio of the apparent viscosities (SVI value) is less than 2.0, sufficient thixotropy cannot be obtained, and the spreadability during coating may increase. If it exceeds 10.0, it may not be possible to apply it in a desired shape.

[0061] Here, as a specific calculation method of the SVI value, which is the ratio of apparent viscosities, in accordance with JIS K7117 for the viscosity of the thixotropic silicone gel composition, the thixotropic silicone gel composition is measured for apparent viscosity at 25 °C by a rheometer (ARES G2 manufactured by TA Instruments) at rotational speeds of 1 s -1 , 10 s -1 respectively, and it can be obtained by the following formula using these apparent viscosities. SVI value = (apparent viscosity at rotational speed of 1 s -1 ) / (apparent viscosity at rotational speed of 10 s -1 )

[0062] In the present invention, the SVI value (ratio of apparent viscosities) of the thixotropic silicone gel composition within the above range can be achieved by appropriately adjusting the blending amounts of fine powder silica ((D) component) and / or epoxy group-containing organosiloxane oligomer ((E) component), etc.

[0063] As the curing conditions of the thixotropic silicone gel composition of the present invention, it can be 23 to 150 °C, particularly 50 to 130 °C for 10 minutes to 8 hours, particularly 30 minutes to 5 hours.

[0064] The silicone gel cured product obtained by curing the thixotropic silicone gel composition of the present invention has a penetration of 10 to 100, preferably 20 to 70, as defined in JIS K6249. If the penetration is less than 10, the adhesion to the sealed substrate may be insufficient, and if it exceeds 100, the strength of the sealing gel itself may be low and cracks may be generated during heat resistance. In the present invention, as a means for setting the penetration of the silicone gel cured product within the above range, the blending ratio of component (A) and component (B) (that is, the molar ratio of the silicon atom-bonded hydrogen atom (SiH group) in component (B) to the silicon atom-bonded alkenyl group in component (A)), etc. can be appropriately adjusted to achieve this.

[0065] In the case of the thixotropic silicone gel composition of the present invention, although it is liquid, it has a small spreading property during application and a small shape change before and after curing. Therefore, it can be sealed in a desired shape for elements and the like, and it is possible to seal only the elements for the purpose of sealing. It is useful as a sealing material for electrical and electronic components that require spot potting such as photocouplers.

[0066] [Electrical and Electronic Components] The electrical and electronic components of the present invention are sealed with a silicone gel cured product obtained by curing the above-described thixotropic silicone gel composition of the present invention. Examples of such electrical and electronic components to be sealed include electrical and electronic components that require spot potting such as photocouplers, printed wiring boards, and the like.

Examples

[0067] Hereinafter, examples and comparative examples will be shown to specifically explain the present invention. However, the present invention is not limited to the following examples. In the following examples, "parts" indicates parts by mass, and the viscosity of each exemplified component is a measured value by a rotational viscometer at 25°C. Me represents a methyl group. The degree of polymerization indicates the number average degree of polymerization in terms of polystyrene in gel permeation chromatography (GPC) analysis using toluene as a developing solvent. The SVI value, spreading property of the silicone gel composition, and heat resistance of the silicone gel cured product were evaluated as follows.

[0068] [SVI Value of Silicone Gel Composition] The viscosity of the silicone gel composition was measured by a method conforming to JIS K7117. That is, the silicone gel composition was measured by a rheometer (ARES G2 manufactured by TA Instruments) at 25°C at rotational speeds (1 s -1 and 10 s -1 ) where the rotational speed ratio is 1:10, and the apparent viscosities were measured respectively. The SVI value was determined by the following formula. SVI value = (apparent viscosity at rotational speed 1 s -1 ) / (apparent viscosity at rotational speed 10 s -1 )

[0069] [Spreading property of silicone gel composition] Collect about 5 g of the silicone gel composition into a 5-ml microsyringe, and slowly discharge 1 g portion at the center of a 50 mm × 50 mm glass plate. After leaving it for 30 minutes in a 25°C atmosphere, measure the diameter of the circularly spread silicone gel composition in two perpendicular directions, namely the vertical direction and the horizontal direction, and obtain the average value. This value was used as an index of the spreading property before curing. The glass plate coated with the above silicone gel composition was cured by heating in an oven at 130°C for 30 minutes. At this time, measure the diameter of the silicone gel cured product obtained in two perpendicular directions, namely the vertical direction and the horizontal direction, and obtain the average value. This value was used as an index of the spreading property during curing.

[0070] [Heat resistance of silicone gel cured product] The silicone gel composition was heated at 130°C for 30 minutes to obtain a cylindrical silicone gel cured product with a size of about 40 mm in diameter and about 20 mm in thickness. Measure the penetration at this time and use this as the value at the initial stage of curing. The penetration was measured by the softening point test method (1 / 4 cone) of JIS K2220 specified in JIS K6249. The silicone gel cured product obtained above was exposed in a 200°C atmosphere for 72 hours, and the penetration of the obtained sample was measured. This was used as the penetration after heat resistance at 200°C.

[0071] Component (A) (A-1) Branched-chain molecular chain terminal dimethylvinylsiloxy group-trimethylsiloxy group-blocked polysiloxane ((C6H5)2SiO with a viscosity of about 1 Pa·s at 25°C represented by the following average molecular formula (4) 2 / 2 Unit: 2 mol% in all diorganopolysiloxane units, alkenyl group content: 0.011 mol / 100 g) [Chemical formula]

[0072] (A-2) A linear polysiloxane blocked at the molecular chain ends with dimethylvinylsiloxy groups and trimethylsiloxy groups, having a viscosity of about 0.7 Pa·s at 25°C, represented by the following average molecular formula (5) ((C6H5)2SiO 2 / 2 Unit: 5 mol% in all diorganopolysiloxane units, alkenyl group content: 0.005 mol / 100 g) [Chemical formula] [Note] The linear polysiloxane blocked at the molecular chain ends with dimethylvinylsiloxy groups and trimethylsiloxy groups, represented by the above average molecular formula (5), is a homogeneous mixture of a linear polysiloxane [5a] blocked at one molecular chain end with a dimethylvinylsiloxy group and at the other molecular chain end with a trimethylsiloxy group, represented by the following average molecular formula (5a), and a linear polysiloxane [5b] blocked at both molecular chain ends with trimethylsiloxy groups, represented by the following average molecular formula (5b), with [5a]:[5b] = 6:4 (molar ratio ≒ mass ratio). [Chemical formula] [Chemical formula]

[0073] (A-3) A branched polysiloxane blocked at the molecular chain ends with dimethylvinylsiloxy groups and trimethylsiloxy groups, having a viscosity of about 0.8 Pa·s at 25°C, represented by the following average molecular formula (6) ((C6H5)2SiO 2 / 2 Unit: 0 mol% in all diorganopolysiloxane units, alkenyl group content: 0.012 mol / 100 g) [Chemical formula] [Note] The branched-chain molecular chain terminal dimethylvinylsiloxy group-trimethylsiloxy group-blocked polysiloxane represented by the above average molecular formula (6) is a homogeneous mixture of a branched-chain polysiloxane [6a] having two molecular chain terminals blocked with dimethylvinylsiloxy groups represented by the following average molecular formula (6a) and a branched-chain polysiloxane [6b] having two molecular chain terminals blocked with trimethylsiloxy groups represented by the following average molecular formula (6b), with [6a]:[6b]=4:6 (molar ratio ≒ mass ratio). [Chemical formula] [Chemical formula]

[0074] (A-4) Branched-chain molecular chain terminal dimethylvinylsiloxy group-trimethylsiloxy group-blocked polysiloxane having a viscosity of about 1 Pa·s at 25°C and represented by the following average molecular formula (7) ((C6H5)2SiO 2 / 2 Unit: 0 mol% in all diorganopolysiloxane units, alkenyl group content: 0.011 mol / 100 g) [Chemical formula]

[0075] (A-5) Molecular chain terminal dimethylvinylsiloxy group-trimethylsiloxy group-blocked linear polysiloxane having a viscosity of about 0.8 Pa·s at 25°C and represented by the following average molecular formula (8) ((C6H5)2SiO 2 / 2 Unit: 0 mol% in all diorganopolysiloxane units, alkenyl group content: 0.004 mol / 100 g) [Chemical formula] [Annotation] The linear polysiloxane blocked at the molecular chain ends with dimethylvinylsiloxy groups and trimethylsiloxy groups, represented by the above average molecular formula (8), is a homogeneous mixture of a linear polysiloxane [8a] in which one end of the molecular chain segment is blocked with a dimethylvinylsiloxy group and the other end of the molecular chain segment is blocked with a trimethylsiloxy group, represented by the following average molecular formula (8a), and a linear polysiloxane [8b] in which both ends of the molecular chain are blocked with trimethylsiloxy groups, represented by the following average molecular formula (8b), with [8a]:[8b]=6:4 (molar ratio ≒ mass ratio). [Chemical formula] [Chemical formula]

[0076] (A-6) A linear polysiloxane blocked at the molecular chain ends with dimethylvinylsiloxy groups and trimethylsiloxy groups, represented by the following average molecular formula (9), having a viscosity at 25°C of about 0.8 Pa·s ((C6H5)2SiO 2 / 2 Unit: 0 mol% in all diorganopolysiloxane units, alkenyl group content: 0.005 mol / 100 g) [Chemical formula] [Annotation] The linear polysiloxane blocked at the molecular chain ends with dimethylvinylsiloxy groups and trimethylsiloxy groups, represented by the above average molecular formula (9), is a homogeneous mixture of a linear polysiloxane [9a] in which one end of the molecular chain segment is blocked with a dimethylvinylsiloxy group and the other end of the molecular chain segment is blocked with a trimethylsiloxy group, represented by the following average molecular formula (9a), and a linear polysiloxane [9b] in which both ends of the molecular chain are blocked with trimethylsiloxy groups, represented by the following average molecular formula (9b), with [9a]:[9b]=6:4 (molar ratio ≒ mass ratio). [Chemical formula] [Chemical formula]

[0077] (B) component (B-1) Methylhydrogenpolysiloxane with a viscosity of 30 mPa·s at 25°C, represented by the following average molecular formula (10) (SiH group content: 0.004 mol / g) [Chemical formula]

[0078] (B-2) Methylhydrogenpolysiloxane with a viscosity of 110 mPa·s at 25°C, represented by the following average molecular formula (11) (SiH group content: 0.006 mol / g) [Chemical formula]

[0079] (B-3) Methylhydrogenpolysiloxane with a viscosity of 20 mPa·s at 25°C, represented by the following average molecular formula (12) (SiH group content: 0.001 mol / g) [Chemical formula]

[0080] (C) component Solution of chloroplatinic acid-vinylsiloxane complex with molecular chain both-end vinyldimethylsiloxy group-blocked dimethylpolysiloxane as solvent (platinum atom content: 1 mass%) [Chemical formula]

[0081] (D) component (D-1) Fumed silica with a BET specific surface area of 300 m 2 / g, surface-treated with dimethyldichlorosilane (product name: DM-30S, manufactured by Tokuyama Corporation) (D-2) Fumed silica with a BET specific surface area of 140 m 2 / g, surface-treated with trimethylchlorosilane (product name: NSX-200, manufactured by Nippon Aerosil Co., Ltd.)

[0082] (E) component (E-1) Epoxy equivalent: 830 g / mol, alkoxy group content: 50 mass%, viscosity at 25 °C: 12 mPa·s epoxy group·alkoxy group-containing siloxane oligomer (trade name: KR-517, manufactured by Shin-Etsu Chemical Co., Ltd.) (E-2) Epoxy equivalent: 350 g / mol, alkoxy group content: 42 mass%, viscosity at 25 °C: 30 mPa·s epoxy group·alkoxy group-containing siloxane oligomer (trade name: X-41-1059A, manufactured by Shin-Etsu Chemical Co., Ltd.) (E-3) 3-Glycidoxypropyltrimethoxysilane (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) (E-4) 8-Glycidyloxyoctyltrimethoxysilane (trade name: KBM-4803, manufactured by Shin-Etsu Chemical Co., Ltd.) (E-5) Methoxy group content: 28 mass%, viscosity at 25 °C: 25 mPa·s methoxy group-containing siloxane oligomer (trade name: KR-500, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0083] [Examples 1 to 4, Comparative Examples 1 to 7] The above components (A) to (E) were blended and mixed as shown in Tables 1 and 2 to prepare silicone gel compositions S1 to S11. The viscosities of these silicone gel compositions were measured using the rheometer described above, and the SVI values were calculated. Also, for these silicone gel compositions, changes in spreadability before and after curing were confirmed by the method described above. Furthermore, for the cured products of these silicone gel compositions, heat resistance was evaluated by the method described above. The above results are shown in Tables 1 and 2.

[0084] The silicone gel compositions of Examples 1 to 4 shown in Table 1 satisfy the requirements of the present invention and are silicone gel compositions having thixotropy. Since there is almost no spreadability during heat curing, they are useful for spot potting of sealing elements. Also, since the change in penetration at 200 °C atmosphere is small and they have good heat resistance, generation of cracks in the sealing resin (cured silicone gel) is suppressed even during high-temperature operation, and they have the characteristic of having a small load on the sealing element.

[0085]

Table 1

[0086]

Table 2

Claims

1. (A) As the diorganosiloxane unit in the main chain, (C 6 H 5 ), 2 SiO 2 / 2 units are contained in an amount of 0.1 to 10 mol% in all the diorganosiloxane units in the main chain, and the alkenyl group bonded to the silicon atom is contained in an amount of 0.004 to 0.05 mol / 100 g: 100 parts by mass, (B)The organohydrogenpolysiloxane represented by the following average composition formula (1) 【Chemical 1】 (wherein R 1 is a monovalent hydrocarbon group having 1 to 10 carbon atoms and containing no aliphatic unsaturated bond, a is 0 or 1, b is a positive number of 0.002 to 0.3, and c is a positive number of 0.1 to 0.6). and containing hydrogen atoms bonded to at least three silicon atoms in one molecule: an amount such that the hydrogen atoms bonded to the silicon atoms in component (B) are 0.3 to 1.2 moles per mole of the alkenyl group in component (A); (C)Platinum-based curing catalyst: an effective amount as a catalyst, (D) Organosilazane, organochlorosilane, organoalkoxysilane, or organopolysiloxane having only a methyl group as a monovalent hydrocarbon group bonded to a silicon atom, and having a specific surface area (BET adsorption method) of 50 to 500 m 2 / g, fine powder silica: 2 to 30 parts by mass, and (E)A partial (hydrolytic) condensate of one or more organosilane compounds represented by the following general formula (2) R 2 X R 3 Y Si(OR 4 ) 4-X-Y (2) (In the formula, R 2 is a monovalent organic group having one or more epoxy groups and having 2 to 30 carbon atoms, and R 3 is a monovalent hydrocarbon group having 1 to 20 carbon atoms, and R 4 is a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms. X is 1 or 2, Y is 0 or 1, and X + Y is 1 or 2.) and / or a partial co-(hydrolytic) condensate of the organosilane compound represented by the above general formula (2) and an organosilane compound represented by the following general formula (3) R 5 Z Si(OR 6 ) 4-Z (3) (wherein, R 5 is a monovalent hydrocarbon group having 1 to 20 carbon atoms, and R 6 is a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms. Z is an integer of 0 to 3.) An epoxy group-containing siloxane oligomer, which is 0.01 to 5 parts by mass A thixotropic silicone gel composition comprising the same and capable of providing a silicone gel cured product having a penetration of 10 to 100 as defined in JIS K6249 upon curing.

2. The thixotropic silicone gel composition according to Claim 1, wherein the apparent viscosities (25 °C) are measured respectively at rotation speeds such that the rotation speed ratio is 1:10 by a method conforming to JIS K7117, and the SVI value obtained from the following formula is 2.0 to 10.

0. SVI value = (apparent viscosity at the lower rotation speed) / (apparent viscosity at the higher rotation speed)

3. A silicone gel cured product obtained by curing the thixotropic silicone gel composition according to Claim 1 or 2.

4. An electric / electronic component sealed with the silicone gel cured product according to Claim 3.

5. The electric / electronic component according to Claim 4, which is a photocoupler.

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