Curable liquid silicone gel composition and cured product thereof

Abstract

Provided is a curable liquid silicone gel composition that gives a cured silicone gel product with a low modulus of elasticity and a low coefficient of linear expansion. [Solution] (A) a linear or branched diorganopolysiloxane having, per molecule, at least one alkenyl group bonded to a silicon atom and at least 20 mol% of phenyl groups bonded to silicon atoms; (B) a linear or branched organohydrogenpolysiloxane having at least two hydrogen atoms bonded to silicon atoms in one molecule; (C) Platinum catalyst and (D) Hollow inorganic filler: 10 to 60 mass% of the total mass of component (A) and component (B) A curable liquid silicone gel composition comprising:

Description

[Technical Field]

[0001] The present invention relates to a hollow inorganic filler-containing curable liquid silicone gel composition that provides a cured silicone gel product with a low linear expansion coefficient, and to the cured product thereof. [Background technology]

[0002] In recent years, power modules, primarily consisting of insulated gate bipolar transistors (IGBTs), have become widely used in power conversion equipment. The inside of the power module case is filled with a low-elasticity silicone gel to insulate and protect the surface of the ceramic insulating substrate and the power semiconductor chips on the substrate.

[0003] The filled silicone gel comes into contact with various substrates (such as copper or polyimide), and if the difference in linear expansion coefficient between the silicone gel and the substrate is large, thermomechanical stress occurs, which can result in voids or peeling. Therefore, a silicone gel composition with a low linear expansion coefficient is desired.

[0004] It is generally known that silicone resins have a higher linear expansion coefficient than organic resins, but as a silicone material with a low linear expansion coefficient, for example, a new silicone resin is disclosed in Patent Document 1. However, the silicone resin described in Patent Document 1 has a problem in that it has a high elastic modulus.

[0005] It is known that the linear expansion coefficient can be reduced by blending an inorganic filler such as inorganic glass into a silicone composition, and Patent Document 2 proposes a polysiloxane composition containing inorganic particles, but this composition also has a high hardness and does not achieve both a low elastic modulus and a low linear expansion coefficient.

[0006] Patent Document 3 proposes a curable silicone composition that has a small linear expansion coefficient and excellent hot melt properties, but like the silicone resin described in Patent Document 1 and the polysiloxane composition described in Patent Document 2, it is a material with high hardness. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 4805578 [Patent Document 2] Patent No. 5856060 [Patent Document 3] International Publication No. 2023 / 032734 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, an object of the present invention is to provide a curable liquid silicone gel composition that provides a cured silicone gel product with a low modulus of elasticity and a low coefficient of linear expansion, and to provide a cured product thereof. [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, they discovered that by adding a hollow inorganic filler to a silicone composition that uses a linear or branched diorganopolysiloxane that has at least one alkenyl group bonded to a silicon atom and at least 20 mol % phenyl groups per molecule, it is possible to obtain a cured silicone gel with a low elastic modulus and a low linear expansion coefficient, which led to the completion of the present invention.

[0010] Therefore, the present invention provides a hollow inorganic filler-containing curable liquid silicone gel composition, as shown below, which gives a cured silicone gel product with a low modulus of elasticity and a low coefficient of linear expansion, and a cured product thereof.

[0011] [1] (A) a linear or branched diorganopolysiloxane having, per molecule, at least one silicon-bonded alkenyl group and at least 20 mol % of silicon-bonded phenyl groups; (B) a linear or branched organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule: an amount such that there are 0.5 to 4 moles of silicon-bonded hydrogen atoms in component (B) per mole of alkenyl groups in component (A); (C) platinum catalyst: an amount such that the platinum atom content in component (C) is 0.1 to 1,000 ppm by mass relative to the total mass of component (A) and component (B); and (D) A curable liquid silicone gel composition containing a hollow inorganic filler in an amount of 10 to 60% by mass of the total mass of components (A) and (B). [2] The curable liquid silicone gel composition according to [1], wherein the hollow inorganic filler of component (D) is spherical. [3] The curable liquid silicone gel composition according to [1] or [2], wherein the hollow inorganic filler of component (D) has a specific gravity of 0.1 to 1.3. [4] The curable liquid silicone gel composition according to any one of [1] to [3], further having a linear expansion coefficient of 200 ppm / °C or less after curing. [5] A cured product of the curable liquid silicone gel composition according to any one of [1] to [4]. [Effects of the Invention]

[0012] The curable liquid silicone gel composition of the present invention uses, as component (A), a linear or branched diorganopolysiloxane having at least one silicon-bonded alkenyl group per molecule and at least 20 mol% of silicon-bonded phenyl groups per molecule, and also contains, as component (D), a hollow inorganic filler, thereby providing a cured silicone gel product with a low linear expansion coefficient. By using a linear or branched diorganopolysiloxane containing not only alkenyl groups but also at least 20 mol% phenyl groups as component (A), the π-π interactions of the phenyl groups can be utilized to produce a cured silicone gel with a lower linear expansion coefficient than when using a diorganopolysiloxane with less than 20 mol% phenyl groups bonded to silicon atoms. Furthermore, by including a hollow inorganic filler as component (D), the proportion of silicone component per volume can be reduced, resulting in a cured silicone gel with a low linear expansion coefficient. Using a hollow inorganic filler with a lower specific gravity than a solid inorganic filler can suppress increases in elastic modulus and also suppress filler separation in the curable liquid silicone gel composition. DETAILED DESCRIPTION OF THE INVENTION

[0013] The curable liquid silicone gel composition of the present invention contains the following components (A) to (D) as essential components. In the present invention, the term "curable liquid silicone gel composition" refers to a composition that cures to produce a cured silicone gel. A cured silicone gel (or silicone gel) refers to a cured product with a low crosslink density, primarily composed of organopolysiloxane, having a consistency (hereinafter referred to as "penetration") measured by JIS K2220 (1 / 4 cone) of 10 to 100. This corresponds to a rubber hardness measurement according to JIS K6301 that yields a measured value (rubber hardness value) of 0, meaning that the hardness is so low (i.e., soft) and elastic that it does not exhibit a valid rubber hardness value. In this respect, it is distinct from so-called cured silicone rubber (rubber-like elastomer). The penetration of the cured product is preferably 100 or less, more preferably 10 to 100.

[0014] In the present invention, the coefficient of linear expansion (CTE) was measured using an optical thermal expansion measuring device (TA Instruments, DIL806). This device measures the thermal expansion of a sample placed horizontally in a furnace by evaluating the width of the sample's shadow in a parallel beam of light. External contact forces acting on the sample are completely eliminated, making it suitable for measuring soft or fragile samples such as cured silicone gels. The coefficient of linear expansion of the cured product is preferably 200 ppm / °C or less, and more preferably 80 to 180 ppm / °C.

[0015] The present invention will be described in detail below.

[0016] [Curable liquid silicone gel composition] The curable liquid silicone gel composition of the present invention is a blend of the components (A) to (D) described below, and, if necessary, other components.

[0017] [(A) Diorganopolysiloxane having alkenyl groups and phenyl groups] The diorganopolysiloxane containing alkenyl and phenyl groups of component (A) is a linear or branched diorganopolysiloxane having at least one silicon-bonded alkenyl group and at least 20 mol% silicon-bonded phenyl groups per molecule, and serves as the base polymer of the curable liquid silicone gel composition of the present invention (hereinafter also referred to as the composition of the present invention). Typically, the main chain is essentially composed of repeating diorganosiloxane units, and both molecular chain terminals are blocked with triorganosiloxy groups, resulting in a linear main chain diorganopolysiloxane. This may also be a branched diorganopolysiloxane containing a branched structure in part of the siloxane structure that makes up the molecular chain. Phenyl groups may be present not only in the main chain but also at the terminals.

[0018] The alkenyl- and phenyl-containing diorganopolysiloxane of component (A) has at least one (typically 1 to 50), preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 or 2 alkenyl groups bonded to silicon atoms per molecule. Examples of alkenyl groups include vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, and cyclohexenyl, which typically have 2 to 8 carbon atoms. The alkenyl groups may be bonded to silicon atoms at the molecular chain terminals or non-terminal (intermediate) silicon atoms in the molecular chain. Preferably, the alkenyl groups are bonded to silicon atoms at at least (both) molecular chain terminals. In this case, the alkenyl groups may be present only at (both) molecular chain terminals, or at (both) molecular chain terminals and non-terminal (intermediate) molecular chains. The amount of phenyl groups bonded to silicon atoms in component (A) is 20 mol % to 100 mol %, preferably 25 to 50 mol %, and more preferably 25 to 35 mol % of all substituents bonded to silicon atoms (non-terminal) forming the main chain. The phenyl groups may be bonded to silicon atoms at the molecular chain terminals or non-terminal (mid-molecular chain) silicon atoms.

[0019] An example of such a diorganopolysiloxane having an alkenyl group and a phenyl group is a linear diorganopolysiloxane represented by the following general formula (1). [ka] (wherein X is an alkenyl group, and at least one X is contained in one molecule. R 1 R is independently an unsubstituted or substituted monovalent hydrocarbon group that does not contain an aliphatic unsaturated bond. 2 is a phenyl group, and is contained in one molecule at least 20 mol%. n, m, l, and p are numbers of 0 or more, and a and b are numbers of 0 to 3 independently for each silicon atom to which they are bonded, but at least one of a and m at both ends is a number of 1 or more.

[0020] In the above formula (1), examples of the alkenyl group for X include those having 2 to 8 carbon atoms, such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, and cyclohexenyl groups, and among these, lower alkenyl groups such as vinyl and allyl are preferred. In the linear diorganopolysiloxane represented by formula (1) above, the alkenyl group X may be bonded to a silicon atom at a molecular chain terminal, or may be bonded to a silicon atom at a non-terminal location (in the middle of the molecular chain). It is preferable for the alkenyl group to be bonded to a silicon atom at at least one of the molecular chain terminals, and it is particularly preferable for the alkenyl group to be only at one of the molecular chain terminals (at least one of the "a"s at both terminals is a number greater than or equal to 1, and m is 0).

[0021] In the above formula (1), R 1 Examples of the unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond include those having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, and more preferably 1 to 6 carbon atoms. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl; and hydrogen atoms bonded to carbon atoms of these groups. Examples of such groups include groups in which some or all of the atoms are substituted with halogen atoms such as fluorine, chlorine or bromine, or with a cyano group, such as a chloromethyl group, a 2-bromoethyl group, a 3-chloropropyl group, a 3,3,3-trifluoropropyl group, a chlorophenyl group, a fluorophenyl group, a cyanoethyl group, and a 3,3,4,4,5,5,6,6,6-nonafluorohexyl group. Preferred are unsubstituted groups having 1 to 3 carbon atoms such as a methyl group, an ethyl group, a propyl group, a chloromethyl group, a bromoethyl group, a 3,3,3-trifluoropropyl group, or a cyanoethyl group, and more preferred is a methyl group.

[0022] In the above formula (1), n ​​is a number of 0 or more, preferably a number of 10 to 1,000, and more preferably a number of 20 to 500; m is a number of 0 or more, preferably a number of 0 to 40, and more preferably a number of 0 to 20; l is a number of 0 or more, preferably a number of 0 to 1,000, and more preferably a number of 0 to 500; and p is a number of 0 or more, preferably a number of 0 to 1,000, and more preferably a number of 1 to 500. Furthermore, n, m, l, and p must be numbers that satisfy the condition 0.2≦(l+2p) / {2(n+m+l+p)}. In this case, the units in parentheses enclosed by n, m, l, and p may be arranged randomly. In the above formula (1), a and b are numbers of 0 to 3, preferably 0 or 1, for each silicon atom to which they are bonded.

[0023] Furthermore, the diorganopolysiloxane having an alkenyl group and a phenyl group may be, for example, a diorganopolysiloxane having a monofunctional siloxy unit (X a R 1 b R 2 (3-a-b) SiO 1 / 2 unit) and bifunctional siloxane unit ((R 1 )2SiO 2 / 2 Units, (R 1 )(X)SiO 2 / 2 Units, (R 1 )(R 2 )SiO 2 / 2 Units, (R 2 )2SiO 2 / 2 In addition to the trifunctional siloxane unit (i.e., (R 1 )SiO 3 / 2 , (X)SiO 3 / 2 , (R 2 )SiO 3 / 2 Examples of suitable diorganosiloxanes include branched diorganopolysiloxanes having a small amount of silsesquioxane units represented by the following formula (1) in the molecule.

[0024] Furthermore, it is preferable that such diorganopolysiloxanes having alkenyl groups and phenyl groups have a viscosity at 23°C of 10 to 50,000 mPa·s, and particularly 100 to 10,000 mPa·s. If the viscosity is less than 10 mPa·s, the viscosity of the resulting curable liquid silicone gel composition will be low, making it difficult to work with, and the resulting cured silicone gel may be too hard. If the viscosity exceeds 50,000 mPa·s, the viscosity of the resulting curable liquid silicone gel composition will be high, making it difficult to work with. In the present invention, the number of repeating diorganosiloxane units (or degree of polymerization) in one molecule can usually be determined as the polystyrene-equivalent number average molecular weight (or number average degree of polymerization) in gel permeation chromatography (GPC) analysis using toluene or the like as a developing solvent. The viscosity is usually a value measured at 23°C using a rotational viscometer (e.g., BL type, BH type, BS type, cone-plate type, rheometer, etc.) (the same applies hereinafter).

[0025] The diorganopolysiloxane containing alkenyl groups and phenyl groups of the component (A) may be used alone, or two or more different types may be used in combination. In the curable liquid silicone gel composition, the blending ratio of the diorganopolysiloxane containing alkenyl groups and phenyl groups as component (A) is preferably 60 to 90 mass %, and more preferably 68 to 83 mass %.

[0026] [(B) Organohydrogenpolysiloxane] The organohydrogenpolysiloxane (B) crosslinking agent is a linear or branched (branched or three-dimensional network structure (resin structure)) organohydrogenpolysiloxane having two or more (usually 2 to 200), preferably 2 to 100 hydrogen atoms bonded to silicon atoms (SiH groups) per molecule.

[0027] The organohydrogenpolysiloxane may be an organohydrogenpolysiloxane represented by the following average composition formula (2). [Chemical formula] (In the formula, R 3 is an unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond, or a phenyl group, and c and d are numbers such that 0.001 ≦ c ≦ 1.2, 0.8 ≦ d ≦ 2, and 0.8 < c + d ≦ 3, preferably numbers such that 0.05 ≦ c ≦ 1, 1.2 ≦ d ≦ 2, and 1.5 ≦ c + d ≦ 2.7.)

[0028] In the above formula (2), examples of the unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond of R 3 are the same as those exemplified as R 1 in the general formula (1), and include, for example, those having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 7 carbon atoms, and particularly preferably lower alkyl groups having 1 to 3 carbon atoms such as a methyl group, a phenyl group, and a 3,3,3-trifluoropropyl group.

[0029] As the component (B), those having 2 to 300 silicon atoms, particularly 3 to 150 silicon atoms, and especially 3 to 100 silicon atoms and being liquid at room temperature are preferably used. The hydrogen atoms bonded to the silicon atoms may be located at either the molecular chain ends or in the middle (non-terminal) of the molecular chain, or may be located at both.

[0030] Examples of such organohydrogenpolysiloxanes include 1,1,3,3-tetramethyldisiloxane, 1,1,3,3,5,5-hexamethyltrisiloxane, tris(dimethylhydrogensiloxy)methylsilane, tris(dimethylhydrogensiloxy)phenylsilane, methylhydrogenpolysiloxanes capped at both molecular chain ends with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymers capped at both molecular chain ends with trimethylsiloxy groups, diphenylsiloxane-methylhydrogensiloxane copolymers capped at both molecular chain ends with trimethylsiloxy groups, methylphenylsiloxane-methylhydrogensiloxane copolymers capped at both molecular chain ends with trimethylsiloxy groups, and dimethylsiloxane-diphenylsiloxane copolymers capped at both molecular chain ends with trimethylsiloxy groups. dimethylsiloxane-methylhydrogensiloxane copolymer, dimethylpolysiloxane end-blocked with dimethylhydrogensiloxy groups, methylhydrogenpolysiloxane end-blocked with dimethylhydrogensiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymer end-blocked with dimethylhydrogensiloxy groups, diphenylsiloxane-methylhydrogensiloxane copolymer end-blocked with dimethylhydrogensiloxy groups, methylphenylsiloxane-methylhydrogensiloxane copolymer end-blocked with dimethylhydrogensiloxy groups, dimethylsiloxane-diphenylsiloxane-methylhydrogensiloxane copolymer end-blocked with dimethylhydrogensiloxy groups, dimethylhydrogensiloxy unit and SiO 4 / 2 Examples of such silicone resins include silicone resins having a three-dimensional network structure consisting of units and which may optionally contain trimethylsiloxy units, dimethylsiloxane units, methylhydrogensiloxane units, hydrogensilsesquioxane units, and / or methylsilsesquioxane units, and compounds in which some or all of the methyl groups in the above-mentioned exemplary compounds have been substituted with other alkyl groups or phenyl groups.

[0031] The kinematic viscosity of the organohydrogenpolysiloxane crosslinking agent at 23°C is preferably 1 to 1,000 mm 2 / s, more preferably 1 to 200 mm 2 / s range. 2 If the viscosity is less than 1,000 mm / s, the viscosity of the aerobically curable liquid silicone composition will be low, which may result in poor workability. 2 If the kinematic viscosity exceeds 1 / s, the viscosity of the resulting aerobically curable liquid silicone composition will also increase, which may result in poor workability. Note that in the present invention, the kinematic viscosity can be measured using a Cannon-Fenske viscometer.

[0032] The linear or branched organohydrogenpolysiloxane can be obtained by a known method, for example, by using a compound represented by the following general formula: 2 SiHCl2 and R 2 2SiHCl (where R 2 is the same as above.) or by (co)hydrolytic condensation of the chlorosilane with a compound represented by the following general formula: R 2 3SiCl and R 2 2SiCl2 (wherein, R 2 are the same as above.) and at least one chlorosilane selected from the group consisting of chlorosilanes ...

[0033] From the viewpoint of curing to give a silicone gel cured product, the amount of organohydrogenpolysiloxane (B) blended is such that the number of hydrogen atoms bonded to silicon atoms (i.e., SiH groups) in the organohydrogenpolysiloxane (B) is 0.5 to 4 moles, and preferably 0.8 to 2.5 moles, per mole of alkenyl groups in the alkenyl-containing diorganopolysiloxane (A).

[0034] The organohydrogenpolysiloxane of component (B) may be used alone or in combination of two or more different compounds.

[0035] [(C) Platinum catalyst] The platinum catalyst of component (C) is a catalyst comprising platinum or a platinum compound that has been conventionally used to promote hydrosilylation addition reactions, such as simple platinum (including platinum black); platinum chlorides such as HPtCl·xHO, HPtCl·xHO, NaHPtCl·xHO, KHPtCl·xHO, NaPtCl·xHO, KPtCl·xHO, PtCl·xHO, PtCl, and NaHPtCl·xHO (wherein x is a number from 0 to 6, preferably 0 or 6); chloroplatinic acid and chloroplatinic acid salts; alcohol-modified chloroplatinic acid (see U.S. Pat. No. 3,220,972); complexes of chloroplatinic acid with olefins (see U.S. Pat. Nos. 3,159,601, 3,159,662, and 3,775,452); complexes of platinum chloride, chloroplatinic acid, or chloroplatinic acid salts with siloxanes having vinyl groups, particularly cyclic siloxanes having vinyl groups; and complexes of platinum with alcohols or siloxanes having vinyl groups.

[0036] The amount of component (C) to be blended is 0.1 to 1,000 ppm, preferably 1 to 300 ppm, calculated as platinum atom mass relative to the total mass of components (A) and (B). The amount of component (C) to be blended is an effective amount as a catalyst, and need only be an amount that can promote the reaction between components (A) and (B), and can be adjusted appropriately depending on the desired curing rate. Within the above range, more efficient catalytic action can be expected.

[0037] [(D) Hollow inorganic filler] The hollow inorganic filler of component (D) acts as a filler that imparts low elasticity (silicone gel-like) and a low coefficient of linear expansion to the cured product obtained from the curable liquid silicone gel composition of the present invention. By filling the composition with hollow inorganic fillers, the proportion of silicone material per volume can be reduced, resulting in a cured silicone gel with a low linear expansion coefficient. By using hollow inorganic fillers with a lower specific gravity than solid inorganic fillers, it is possible to suppress an increase in the elastic modulus and also to suppress separation of the filler in the curable liquid silicone gel composition.

[0038] In the present invention, the average particle size of the hollow inorganic filler is not particularly limited, but is preferably 200 μm or less. If it exceeds 200 μm, the hollow inorganic filler may be destroyed by pressure during blending or molding. The lower limit of the average particle size is preferably 5 μm. The average particle size in the present invention is the volume average particle size D 50 (i.e., the particle size or median size when the cumulative volume is 50%).

[0039] In the present invention, the shape of the hollow inorganic filler is not particularly limited, but a spherical shape is preferred. Furthermore, the specific gravity of the hollow inorganic filler is not particularly limited, but from the viewpoint of suppressing separation of the hollow inorganic filler, it is preferable that the specific gravity is close to the specific gravity of the composition before adding the hollow inorganic filler, preferably 0.1 to 1.3, more preferably in the range of 0.9 to 1.1.

[0040] In the present invention, the type of hollow inorganic filler is not particularly limited, but glass, silica, carbon, alumina, zirconia, shirasu, etc. are preferred. Specific examples of component (D) include glass balloons, silica balloons, carbon balloons, alumina balloons, zirconia balloons, shirasu balloons, etc. Among these, glass balloons are preferred because they are easily available.

[0041] The blending amount of component (D) is 10 to 60% by mass, preferably 20 to 45% by mass, of the total mass of components (A) and (B). If the blending amount is less than 10% by mass, the linear expansion coefficient of the cured product may not decrease, whereas if it exceeds 60% by mass, the viscosity may increase, which may decrease workability. The component (D) may be used alone or in combination of two or more.

[0042] [Other ingredients] In addition to the above components (A) to (D), the curable liquid silicone gel composition of the present invention may contain known additives to the extent that the object of the present invention is not impaired. Such additives include, for example, (E) a reaction inhibitor. The (E) reaction inhibitor may be any one that can suppress the curing reaction at room temperature and inhibit the catalytic activity of component (C) in order to extend the shelf life and pot life, and may be appropriately selected from known reaction inhibitors. Specific examples of the (E) reaction inhibitor include acetylene compounds having a hydroxyl group such as 1-ethynyl-1-cyclohexanol and 3-butyn-1-ol, various nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds. Among these, acetylene compounds having a hydroxyl group that are not corrosive to metals are preferred. The reaction inhibitor may be diluted with an organic solvent such as toluene, xylene, or isopropyl alcohol to improve dispersibility in the silicone composition.

[0043] Other additives include heat resistance aids, adhesion promoters, pigment pastes, dispersants (wetters), and the like.

[0044] [Method for producing a curable liquid silicone gel composition] The method for producing the curable liquid silicone gel composition of the present invention is not particularly limited and may be any conventional method. That is, the curable liquid silicone gel composition of the present invention can be obtained by mixing components (A) to (D) and other components that are used as needed.

[0045] [Method for curing the curable liquid silicone gel composition] The method for curing the curable liquid silicone gel composition of the present invention includes the step of curing the above-mentioned curable liquid silicone gel composition of the present invention at room temperature or under heat. When the composition is cured at room temperature (23°C), the curing time is preferably 24 to 168 hours, and more preferably 24 to 72 hours. When the composition is cured under heat, the curing conditions are preferably 30 to 180°C, and more preferably 60 to 160°C, for 0.1 to 3 hours, and more preferably 0.5 to 1 hour.

[0046] The cured silicone gel product obtained from the curable liquid silicone gel composition of the present invention thus obtained has a low elastic modulus and a low coefficient of linear expansion, making it suitable not only as a sealant for electronic components and pressure sensors, but also for in-vehicle components, aircraft, home appliances, etc. [Example]

[0047] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following examples, the viscosity of component (A) was measured at 23°C using a rotational viscometer (manufactured by Toki Sangyo Co., Ltd., TVB-10 type viscometer, rotor TM3, rotation speed 60 rpm). The kinematic viscosity of component (B) was measured at 23°C using a Canon-Fenske viscometer (manufactured by Shibata Scientific Co., Ltd., viscometer Canon-Fenske SO No. 150). "Room temperature" is 23°C.

[0048] [Comparative Examples 1 and 2] The components were uniformly mixed in a polycup at room temperature in the amounts shown in Table 1. The components were added in the following order while mixing: (A) diorganopolysiloxane having alkenyl groups and phenyl groups, (C) platinum catalyst, (E) reaction inhibitor, and (B) organohydrogenpolysiloxane.

[0049] [Examples 1, 2, and 3] At room temperature, the components were uniformly mixed in a polycup in the amounts shown in Table 1. The components were added in the following order while mixing: (A) diorganopolysiloxane having alkenyl groups and phenyl groups, (C) platinum catalyst, (E) reaction inhibitor, (D) hollow inorganic filler, and (B) organohydrogenpolysiloxane. The blending amount of the hollow inorganic filler (D) in Example 1 was 11 mass % of the total mass of the components (A) and (B), in Example 2 it was 25 mass %, and in Example 3 it was 43 mass %. The details of each component are as follows:

[0050] (A) Diorganopolysiloxane having alkenyl groups and phenyl groups (A-1) A linear diorganopolysiloxane having vinyl and phenyl groups (3 mol%), which is represented by the following average formula (3) and has a viscosity of 1,000 mPa·s at 23°C: [ka]

[0051] (A-2) A linear diorganopolysiloxane having vinyl and phenyl groups (25 mol%), which is represented by the following average formula (4) and has a viscosity of 1,500 mPa·s at 23°C: [ka]

[0052] (B) Organohydrogenpolysiloxane (B-1) The viscosity at 23°C represented by the following average formula (5) is 20 mm 2 / s is a linear methylhydrogenpolysiloxane [ka]

[0053] (B-2) The viscosity at 23°C represented by the following average formula (6) is 100 mm 2 / s branched methylhydrogenpolysiloxane [ka]

[0054] (B-3) Viscosity at 23 ° C. represented by the following average formula (7) is 3 mm 2 / s is a linear methylhydrogenpolysiloxane [ka]

[0055] (C) Platinum catalyst Platinum-divinyltetramethyldisiloxane complex / toluene solution (platinum atomic content 0.5% by mass)

[0056] (D) Hollow inorganic filler Sphericel 110P8 manufactured by Potters Barotini Co., Ltd. (Spherical hollow glass beads) Average particle size: 12 μm, specific gravity: 1.10

[0057] (E) Reaction inhibitor 3-Methyltridec-1-yn-3-ol

[0058] The cured product appearance, penetration, and CTE of the prepared curable liquid silicone gel compositions were evaluated as follows. The results of each evaluation are shown in Table 1.

[0059] [Appearance of cured product] The prepared curable liquid silicone gel compositions were heated at 150°C for 1 hour to obtain cured products, and the appearance of the cured products was then evaluated visually. Each comparative example was colorless and transparent, while each example, which contained a hollow inorganic filler, was white and opaque.

[0060] [Penetration] The hardness (penetration) of the cured product of the prepared curable liquid silicone gel composition was evaluated as follows. The hardness of the cured product was determined by pouring the prepared curable liquid silicone gel composition obtained above into a glass petri dish and heating it at 150°C for 1 hour, and measuring the penetration as specified in JIS K 6249 (1 / 4 cone consistency according to JIS K 2220) of the resulting cured product.

[0061] Coefficient of Linear Expansion (CTE) The linear expansion coefficient of the cured product obtained by heating the prepared curable liquid silicone gel composition at 150°C for 1 hour was measured using an optical thermal expansion measuring device (DIL806, manufactured by TA Instruments). The oven temperature was in the range of -100°C to 200°C.

[0062] [Table 1]

[0063] From the above results, it was confirmed that the curable liquid silicone gel composition of the present invention provides a cured silicone gel product with a low modulus of elasticity and a low coefficient of linear expansion.

Claims

1. (A) a linear or branched diorganopolysiloxane having, per molecule, at least one silicon-bonded alkenyl group and at least 20 mol % silicon-bonded phenyl groups; (B) a linear or branched organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule: in an amount such that there are 0.5 to 4 moles of silicon-bonded hydrogen atoms in component (B) per mole of alkenyl groups in component (A); (C) platinum catalyst: an amount equivalent to 0.1 to 1,000 ppm by mass of platinum atoms in component (C) relative to the total mass of component (A) and component (B); and (D) Hollow inorganic filler: 10 to 60% by mass of the total mass of component (A) and component (B) A curable liquid silicone gel composition comprising:

2. 2. The curable liquid silicone gel composition according to claim 1, wherein the hollow inorganic filler of component (D) is spherical.

3. 2. The curable liquid silicone gel composition according to claim 1, wherein the hollow inorganic filler of component (D) has a specific gravity of 0.1 to 1.

3.

4. 2. The curable liquid silicone gel composition according to claim 1, further having a coefficient of linear expansion after curing of 200 ppm / °C or less.

5. A cured product of the curable liquid silicone gel composition according to any one of claims 1 to 4.

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