JP2704732B2 - Curable liquid organopolysiloxane composition - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a curable liquid organopolysiloxane composition which forms a cured product having excellent thermal conductivity.
A curable liquid organopolysiloxane composition that has a relatively low viscosity despite the large amount of alumina powder, does not settle and separates the alumina powder during holding, and cures to form a cured product with excellent thermal conductivity. About things.

2. Description of the Related Art In recent years, in electronic devices, a method of transmitting and dissipating heat has become important as electronic components on which heat-generating elements are mounted have become smaller, denser, and more sophisticated.

Conventionally, a curable liquid organopolysiloxane composition containing a metal oxide powder such as alumina powder as a heat conductive medium having good heat resistance and adhesion between such a heat generating element and a metal chassis such as a radiation fin. Cured products have been frequently used. For example, JP-B-36-8334, JP-B-61-857, JP-A-57-191902, JP-A-58-191902
JP-A-21446 and JP-A-58-219259 describe such curable liquid organopolysiloxane compositions.

Problems to be Solved by the Invention However, in order to increase the thermal conductivity of these cured products, a large amount of alumina powder must be blended with these curable liquid organopolysiloxane compositions. However, there is a problem that the fluidity of the cured product decreases, and the flexibility of the obtained cured product is lost, resulting in a decrease in workability and adhesion. Further, the curable liquid organopolysiloxane composition obtained by blending a large amount of alumina powder having a large average particle size has a problem that the alumina powder sediments and undergoes phase separation when stored. Also,
When an attempt is made to mix a large amount of alumina powder having a small average particle size with the curable liquid organopolysiloxane composition, the viscosity of the resulting composition increases remarkably, and there is a problem that it is difficult to mix this in an amount. .

An object of the present invention is to solve the problems of the prior art, and despite containing a large amount of alumina powder, the viscosity is relatively small, and there is no sedimentation and separation of this alumina powder during storage, and it is hardened. It is intended to provide a curable liquid organopolysiloxane composition which forms a cured product having excellent thermal conductivity.

Means of Solving the Problems and Action The purpose of the present invention is to provide (a) a curable liquid organopolysiloxane and (b) a curing agent as main components, and (c) an average particle size of 0.1 to 5%.
μm amorphous alumina powder (20 to 60% by weight of the whole composition) and (d) spherical alumina powder with an average particle size of 5 to 50 μm (65 to 25% of the whole composition).
At least one of the components (c) and (d) is treated with a silane-based surface treating agent, and the total amount of the components (c) and (d) is 70 to 90% by weight of the composition. (C) a curable liquid organopolysiloxane composition, and (a ′) a curable liquid organopolysiloxane having two or more silanol groups or silicon-bonded hydrolyzable groups in one molecule; ') A curing agent as a main ingredient, (c')
Amorphous alumina powder having an average particle size of 0.1 to 5 μm (20 to 60% by weight of the whole composition) and (d ′) spherical alumina powder having an average particle size of 5 to 50 μm (65 to 25% by weight of the whole composition) Wherein the total amount of the components (c ') and (d') is 70 to 90% by weight of the whole composition. This is achieved by a curable liquid organopolysiloxane composition which is cured by a condensation reaction.

 First, the former composition will be described in detail.

The curable liquid organopolysiloxane of the component (a)
An organopolysiloxane that is liquid at room temperature and undergoes a crosslinking reaction by the action of the curing agent (b) to cure. The curing mechanism of this composition may be any of a hydrosilylation reaction curing type, a condensation reaction curing type, a radical reaction curing type with an organic peroxide, and particularly preferably a hydrosilylation reaction curing type or a condensation reaction curing type. When the composition is a hydrosilylation reaction-curable type, the component (a) is an organopolysiloxane having two or more alkenyl groups in one molecule, and when the composition is a condensation reaction-curable type. Means that component (a) is 1
When the composition is an organopolysiloxane having two or more silanol groups or silicon-bonded hydrolyzable groups in the molecule, and when the composition is a radical reaction-curable type, the component (a) is contained in one molecule. Arganopolysiloxane having two or more alkyl groups or alkenyl groups.

The molecular structure of the component (a) may be any of linear, branched, network, and light three-dimensional structures, and may be any of a homopolymer and a copolymer. It may be a mixture of polymers.

The viscosity of the component (a) is not particularly limited as long as it is liquid at ordinary temperature, but from the viewpoint of workability, the viscosity at 25 ° C.
Those having 100 to 20,000 cst are preferred.

The silicon-bonded organic groups in the component (a) include alkyl groups such as methyl, ethyl, propyl, butyl, and octyl; vinyl, allyl,
Alkenyl groups such as hexenyl group; cycloalkyl groups such as cyclopentyl group and cyclohexyl group; aryl groups such as phenyl group, tolyl group and xylyl group; aralkyl groups such as benzyl group and phenylethyl group; hydrogen atoms of these hydrocarbon groups Is partially substituted with a halogen atom, a cyano group, or the like. In particular, it is preferred that 50 mol% or more of all the silicon-bonded organic groups in the component (a) are methyl groups.

As the organopolysiloxane having two or more alkenyl groups in one molecule of the component (a), examples of the organopolysiloxane include simethylpolysiloxane and dimethylsiloxane in which both ends of a molecular chain are blocked with a vinyldimethylsiloxy group or a vinylmethylphenylsiloxy group.・ Methylphenylsiloxane copolymer, dimethylsiloxane ・ Methylvinylsiloxane copolymer or methyl (3,3,3-trifluoropropyl)
Polysiloxane, dimethylsiloxane / methylvinylsiloxane copolymer or dimethylsiloxane / methylvinylsiloxane / methylphenylsiloxane copolymer in which both molecular chain terminals are blocked with a trimethylsiloxy group, dimethylphenylsiloxy group or hydroxydimethylsiloxy group, or (CH ₃ ) ₃ SiO _1/2 unit and (CH ₃ ) ₂ (CH ₂ =
CH) Copolymers consisting of SiO _1/2 units and SiO _4/2 units are exemplified.

In the component (a), the organopolysiloxane having two or more silal groups or silicon-bonded hydrolyzable groups in one molecule includes dimethylpolysiloxane in which both ends of the molecular chain are blocked with hydroxydimethylsiloxy groups. , Methylphenylpolysiloxane, dimethylsiloxane / methylphenylsiloxane copolymer, methyl (3,
3,3-trifluoropropyl) polysiloxane or [HO (C
H ₃ ) ₂ ] Copolymers consisting of SiO _1/2 units and (CH ₃ ) ₃ SiO _1/2 units and SiO _4/2 units, and further, the silal groups of these organopolysiloxanes are replaced with methoxy, ethoxy, acetoxy groups And an organopolysiloxane substituted with a silicon-bonded hydrolyzable group such as methylethylketoxime group.

In the component (a), as an organopolysiloxane having an alkyl group or two or more alkyl groups in one molecule, both ends of the molecular chain are blocked with a trimethylsiloxy group, a dimethylphenylsiloxy group or a dimethylhexylsiloxy group. Examples are dimethylpolysiloxane, methylphenylpolysiloxane, dimethylsiloxane-methylphenylsiloxane copolymer or dimethylsiloxane-methyl (3,3,3-trifluoropropyl) siloxane copolymer.

As the curing agent of the component (b), when the composition is a hydrosilylation reaction-curable type, an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms in one molecule and a platinum-based catalyst are used. When the composition is a condensation-curable type, a crosslinking agent such as a silane or siloxane oligomer having three or more silicon-bonded hydrolyzable groups in one molecule and a metal salt of an organic acid;
When the composition is a curing catalyst such as a titanate ester, and when the composition is a radical reaction-curable type with an organic peroxide, examples thereof include organic peroxides commonly used for thermal vulcanization of silicone rubber. Is done.

This organohydrogenpolysiloxane is also preferably liquid at room temperature, and its molecular structure is linear, branched or cyclic, and the silicon-bonded organic group is exemplified by the aforementioned component (a). Organic groups other than alkenyl groups among the organic groups described above are exemplified. When the number of alkenyl groups of component (a) is two in one molecule, three or more silicon-bonded hydrogen atoms are required in one molecule, When the number of alkenyl groups in the component (a) is 3 or more per molecule, two or more alkenyl groups are required per molecule.

Examples of the platinum-based catalyst include platinum fine powder, chloroplatinic acid,
Examples are complexes of chloroplatinic acid with β-diketones, olefins or alkenylsiloxanes.

Examples of the silane or siloxane oligomer containing three or more silicon-bonded hydrolyzable groups in one molecule include methyltrimethoxysilane, vinyltriethoxysilane, tyltri (methylethylketoxime) silane, vinyltriacetoxysilane, and the like. Ethyl orthosilicate is exemplified.

Examples of the organic acid metal salt include tin dioctylate, dilaurate dilaurate, and dipropyltin dioctoate. Examples of the titanate include tetra (n-butyl) titanate, tetra (i-propyl) titanate, and dipropoxy titanium bis ( Acetoacetate).

Examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, 2,5-dimethylbis (2,5-t-butylperoxy) hexane, di-t-
Butyl peroxide and t-butyl perbenzoate are exemplified.

The amorphous alumina powder of the component (c) is a component for imparting thermal conductivity to a cured product of the composition, and has an average particle size of 0.1 to 5 μm. The alumina powder is mainly α-alumina powder obtained by a crushing method, and its oil absorption is usually 15 ml / gr or more. In this composition,
If the amount of component (c) is too large, the viscosity of the resulting composition will be too high, and if it is too low, the alumina powder will sediment and undergo phase separation when the resulting composition is stored for a long period of time. Therefore, the amount of the component (c) is set to 20 to 60% by weight of the whole component.

The spherical alumina powder of the component (d) is a component for imparting thermal conductivity to the cured product of the composition together with the component (c), and has an average particle size of 5 to 50 μm. This alumina powder is an α-alumina powder obtained mainly by a high temperature spraying method or a hydrothermal treatment of alumina hydrate. The term “spherical” as used herein means not only a true sphere but also a shape approximating a true sphere, that is, 90% or more of all particles have a shape factor of 1.0 to 1.0.
Refers to those in the range of 1.4. In addition, the shape factor referred to here is calculated from the average value of the ratio of the major axis to the minor axis orthogonal to 200 particles determined by the microscope magnification method of JIS R 6002. Therefore, if only perfect spherical particles are used, the shape factor is 1.0, and the shape factor becomes more non-spherical as the shape factor deviates from 1.0. In this composition, if the amount of the component (d) is too large, the alumina powder will precipitate when the obtained composition is stored for a long period of time, resulting in intense phase separation, and the resulting cured product will have large performance variations. Also, if this is too small, the thermal conductivity of the cured product will not increase,
The amount of the component (d) is 65 to 25% by weight of the whole composition.

In this composition, at least one of the component (c) and the component (d) is methyltrimethoxysilane, vinyltrimethoxysilane, dimethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane. It is necessary to perform a surface treatment with a silane-based surface treatment agent such as silane or hexamethyldisilazane. Examples of the surface treatment method include a method of blending alumina powder previously treated with these silane-based surface treatment agents, and a method of treating alumina powder blended in component (a) with these silane-based surface treatment agents. These methods may be used in combination.

In addition, in this composition, if the total amount of the components (c) and (d) is too small, the thermal conductivity of the obtained cured product will be small, and if it is too large, the viscosity of the obtained composition will be low. (C)
The total amount of the component and the component (d) is 70 to 90% by weight of the whole composition.

This composition is produced by using the above-mentioned components (a) and (b) as main ingredients, and uniformly kneading predetermined amounts of the components (c) and (d) with a mixer. The composition may optionally contain an adhesion promoter such as a silane coupling agent or a derivative thereof; a filler such as fumed silica, precipitated silica, diatomaceous earth, quartz fine powder, calcium carbonate, or carbon black; Heat resistant agents such as iron and cerium oxide; fumed titanium dioxide, zinc carbonate,
Flame retardants such as aluminum hydroxide; pigments; hydrosilation reaction retarders such as alkyne alcohols, alkynes and benzotriazole; non-reactive silicone oils; organic solvents and the like may be added.

 Subsequently, the latter composition will be described in detail.

The curable liquid organopolysiloxane of the component (a ') is liquid at normal temperature and is cured by a condensation reaction caused by the action of the curing agent of the component (b'). An organopolysiloxane having two or more decomposable groups.

The molecular structure of the component (a ') is linear, branched,
It may be any of a network-like or light three-dimensional structure, may be a homopolymer or a copolymer, or may be a mixture of two or more polymers.

The viscosity of the component (a ') is not particularly limited as long as it is liquid at ordinary temperature.
Those having 0 to 20,000 cst are preferred.

The silicon-bonded organic group in the component (a ′) includes a methyl group, an ethyl group, a propyl group, a butyl group,
Alkyl group such as octyl group; alkenyl group such as vinyl group, allyl group and hexenyl group; cycloalkyl group such as cyclopentyl group and cyclohexyl group; aryl group such as phenyl group, tolyl group and xylyl group; benzyl group and phenylethyl An aralkyl group such as a group; and a group in which a hydrogen atom of these hydrocarbon groups is partially substituted with a halogen atom, a cyano group, or the like. In particular, it is preferable that 50 mol% or more of all the silicon-bonded organic groups in the component (a ′) are methyl groups.

Examples of such a component (a ') include dimethylpolysiloxane, methylphenylpolysiloxane, dimethylsiloxane-methylphenylsiloxane copolymer, and dimethyl (3,3,3-triphenyl) having both molecular chains terminated with hydroxydimethylsiloxy groups. Fluoropropyl) polysiloxane or [HO (CH ₃ ) ₂ ] SiO _1/2 unit and (CH ₃ ) ₃ SiO _1/2 unit and S
copolymers comprising iO _4/2 units, and organopolysiloxanes in which the silanol groups of these organopolysiloxanes are substituted with silicon-bonded hydrolyzable groups such as methoxy, ethoxy, acetoxy, and methylethylketoxime groups. Is exemplified.

As the curing agent of the component (b '), a crosslinking agent such as a silane or siloxane oligomer having three or more silicon-bonded hydrolyzable groups in one molecule and a curing catalyst such as an organic acid metal salt or titanate ester. Is exemplified.

Examples of the silane or siloxane oligomer containing three or more silicon-bonded hydrolyzable groups in one molecule include methyltrimethoxysilane, vinyltriethoxysilane, methyltri (methylethylketoxime) silane,
Examples thereof include vinyltriacetoxysilane and ethyl orthosilicate.

The organic acid metal salts include tin dioctylate,
Examples thereof include dibutyltin dilaurate and dipropyltin dioctoate. Examples of the titanate include tetra (n-butyl) titanate, tetra (i-propyl) titanate, and dipropoxytitanium bis (acetoacetate).

The amorphous alumina powder of the component (c ') is a component for imparting thermal conductivity to a cured product of the composition, and has an average particle size of 0.1 to 5 [mu] m. The alumina powder is mainly α-alumina powder obtained by a crushing method, and its oil absorption is usually 15 ml / gr or more. This alumina powder is a silane-based surface treatment agent such as methyltrimethoxysilane, vinyltrimethoxysilane, dimethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, and hexamethyldisilazane. Or a surface treatment with a titanium-based surface treating agent such as tetra (i-propyl) titanate or tri (n-butoxy) monostearyl titanate. In this composition, if the amount of the component (c ') is too large, the viscosity of the obtained composition is increased. If the amount is too small, the alumina powder precipitates when the obtained composition is stored for a long period of time. Phase separation easily occurs, so that the amount of component (c ′) is
20-60% by weight.

The spherical alumina powder of the component (d ') is a component for imparting thermal conductivity to the cured product of the composition together with the component (c'), and has an average particle diameter of 5 to 50 [mu] m. This alumina powder is an α-alumina powder obtained mainly by a high temperature spraying method or a hydrothermal treatment of alumina hydrate. This alumina powder may be surface-treated with the aforementioned silane-based surface treatment agent or titanium-based surface treatment agent. In this composition, if the amount of the component (d ') is too large, the alumina powder will precipitate when the obtained composition is stored for a long period of time, resulting in intense phase separation, and the resulting cured product will have uneven performance. If the amount is too small, the thermal conductivity of the cured product does not increase, so that the amount of the component (d ') is 65 to 25% by weight of the whole composition.

In this composition, the component (c ′) and the component (d ′)
If the total amount of the components is too small, the thermal conductivity of the obtained cured product will be small, and if it is too large, the viscosity of the obtained composition will be large and the fluidity will be poor,
The total amount of the components (c ') and (d') is 70 to 90% by weight of the whole composition.

This composition is produced by using the above-mentioned components (a ') and (b') as main components and uniformly kneading predetermined amounts of the components (c ') and (d') with a mixer. . This composition may contain, if necessary, an adhesion promoter such as a silane coupling agent or a derivative thereof; a filler such as fumed silica, precipitated silica, diatomaceous earth, quartz fine powder, calcium carbonate, or carbon black; Heat-resistant agents such as iron and cerium oxide; fumed titanium dioxide;
Flame retardants such as zinc carbonate and aluminum hydroxide; pigments; non-reactive silicone oils; organic solvents and the like may be added.

Such a curable liquid organ polysiloxane composition of the present invention can be cured by means of leaving at room temperature, heating, high frequency irradiation, electron beam irradiation, etc., depending on the curing mechanism, and the resulting cured product is a rubber. , Gel, hard resin, etc. Such a curable liquid organopolysiloxane composition of the present invention can be used as a potting agent, an adhesive, a coating material, a sealing material, or the like that requires thermal conductivity.

Examples Examples of the present invention and comparative examples will be described. In the Examples and Comparative Examples, “parts” means “parts by weight”, and the storage stability, the viscosity of the composition, and the thermal conductivity of the cured product are measured values at 25 ° C.

Leaving stability, the composition in which all components other than the curing catalyst were uniformly kneaded was placed in a cylindrical glass container and left for 148 hours, and sedimentation separation occurred when the alumina powder settled and separated from the liquid organopolysiloxane. It was determined.

The viscosity of the composition was measured with a B-type viscometer manufactured by Tokyo Keiki Co., Ltd.

The thermal conductivity of the cured product was measured by a hot wire method according to JIS R 2616. Shot manufactured by Showa Denko KK as a measuring device
herm QTM was used.

Examples 1 and 2 In a double planetary mixer, dimethylpolysiloxane having a dimethylvinyliciloxy group at both ends blocked (viscosity of 2,
000cps) 100 parts, methylhydrogenpolysiloxane with a trimethylsiloxy group at both ends (viscosity 5cps) 3.2
Part, 3% by weight of methyltrimethoxysilane was added in a V-blender, mixed at room temperature for 1 hour, and then mixed at 160 ° C. for 2 hours in a nitrogen gas stream to obtain an average particle size which was surface-treated. Amorphous alumina powder obtained by a crushing method of 3 μm and spherical alumina powder having an average particle diameter of 20 μm and a shape factor of 1.1 were each added so as to have a weight percentage shown in Table 1, and kneaded until uniform. The storage stability was examined.

Next, as a curing catalyst, an ethanol solution of chloroplatinic acid was added in an amount of 10 ppm by weight of platinum metal in the whole composition in a weight unit, and the mixture was kneaded until the mixture became uniform. A curable liquid organopolysiloxane composition was prepared. The viscosity of this composition was measured. Then, the composition was 3 mm deep and 5.0 mm wide.
The silicone rubber was molded by injecting the mixture into a mold having a depth of 5.0 cm and a depth of 5.0 cm, and curing by leaving it in a hot-air circulation oven at 150 ° C. for 30 minutes.

The silicone rubber was taken out of the mold and the thermal conductivity was measured. Table 1 shows the results of these measurements.

Comparative Examples 1 and 2 In a double planetary mixer, dimethylpolysiloxane having a dimethylvinylsiloxy group at both ends blocked (viscosity 2,2)
000cps) 100 parts, methylhydrogenpolysiloxane with a trimethylsiloxy group at both ends (viscosity 5cps) 3.2
Parts, an amorphous alumina powder obtained by a crushing method having an average particle diameter of 3 μm, and a spherical alumina powder having an average particle diameter of 20 μm and a shape factor of 1.1 were each added so as to have a weight% shown in Table 1, and these were uniformly mixed. The mixture was kneaded until it became stable, and then the storage stability was examined.

Next, as a curing catalyst, an ethanol solution of chloroplatinic acid is added in an amount such that the platinum metal becomes 10 ppm by weight in the whole composition, and the mixture is kneaded until uniform, whereby the curability of the hydroxylation reaction curing type is increased. A liquid organopolysiloxane composition was prepared. The viscosity of this composition was measured. Then, a depth of 3 mm and a width of 5.0
The silicone rubber was molded by injecting the mixture into a mold having a depth of 5.0 cm and a depth of 5.0 cm, and curing by leaving it in a hot-air circulation oven at 150 ° C. for 30 minutes.

The silicone rubber was taken out of the mold and the thermal conductivity was measured. Table 1 shows the results of these measurements.

Examples 3 to 5 In a double planetary mixer, dimethylpolysiloxane having a dimethylvinylsiloxy group at both ends blocked (viscosity 2,2)
000cps) 100 parts, methylhydrogenpolysiloxane with a trimethylsiloxy group at both ends (viscosity 5cps) 3.2
Part, 3% by weight of methyltrimethoxysilane was added in a V-bunder, mixed at room temperature for 1 hour, and then mixed at 160 ° C. for 2 hours in a nitrogen gas stream to obtain an average particle size which was surface-treated. Amorphous alumina powder obtained by a crushing method of 3 μm and spherical alumina powder having an average particle diameter of 30 μm and a shape factor of 1.1 were each added so as to have a weight percentage shown in Table 2, and these were kneaded until uniform. Was examined for storage stability.

Next, an ethanol solution of chloroplatinic acid is added as a curing catalyst in an amount such that platinum metal becomes 10 ppm by weight in the entire composition, and the mixture is kneaded until uniform, and the mixture is kneaded with a hydroxylation reaction-curable liquid. An organopolysiloxane composition was prepared. The viscosity of this composition was measured. Then, the composition is 3 mm deep, 5.0 cm wide, and
It was poured into a 5.0 cm mold and left in a hot air circulating oven at 150 ° C. for 30 minutes to cure it to form a silicone rubber.

The silicone rubber was taken out of the mold and the thermal conductivity was measured. Table 2 shows the measurement results.

Comparative Examples 3 and 4 In a double planetary mixer, dimethylpolysiloxane having a dimethylvinylsiloxy group at both ends blocked (viscosity of 2,
000cps) 100 parts, methylhydrogenpolysiloxane with a trimethylsiloxy group at both ends (viscosity 5cps) 3.2
Parts, an amorphous alumina powder obtained by a crushing method having an average particle diameter of 3 μm, and a spherical alumina powder having an average particle diameter of 30 μm and a shape factor of 1.1 were each added so as to have a weight% shown in Table 2, and these were uniformly mixed. The mixture was kneaded until it became stable, and then the storage stability was examined.

Next, an ethanol solution of chloroplatinic acid is added as a curing catalyst in an amount such that platinum metal becomes 10 ppm by weight in the entire composition, and the mixture is kneaded until uniform, and the mixture is kneaded with a hydroxylation reaction-curable liquid. An organopolysiloxane composition was prepared. The viscosity of this composition was measured. Then, the composition is 3 mm deep, 5.0 cm wide, and
It was poured into a 5.0 cm mold and left in a hot air circulating oven at 150 ° C. for 30 minutes to cure it to form a silicone rubber.

The silicone rubber was taken out of the mold and the thermal conductivity was measured. Table 2 shows the measurement results.

Example 6 Dimethoxy end-blocked dimethylpolysiloxane (viscosity 7,000 cps) 110 in a double planetary mixer
Parts, 3.0 parts of methyltrimethoxysilane, and 3% by weight of methyltrimethoxysilane in a V-blender, and mixed at room temperature for 1 hour.
227 parts of an amorphous alumina powder having an average particle diameter of 3 μm and a spherical alumina powder having an average particle diameter of 10 μm and a shape factor of 1.1, which have been surface-treated by mixing for 2 hours, are homogenized. When kneaded until kneading, the storage stability was examined, and there was no sedimentation and separation of the alumina powder.

Next, 3.5 parts of tetra (n-butyl) titanate as a curing catalyst and 8.5 parts of methyltrimethoxysilane are added and mixed until uniform, to prepare a condensation-curable curable liquid organopolysiloxane composition. did. The viscosity of this composition was measured and found to be 110,000 cps. This composition is poured into a mold having a depth of 3 mm, a width of 5.0 cm and a depth of 5.0 cm,
The silicone rubber was molded by leaving it at room temperature for one week to cure it.

The silicone rubber was taken out of the mold and the thermal conductivity was measured and found to be 1.1 W / K, M.

Curing of the Invention The curable liquid organopolysiloxane composition of the present invention, despite containing a large amount of alumina powder, has a relatively small viscosity, and does not cause sedimentation and separation of these alumina powders during storage. To form a cured product having excellent thermal conductivity.

Claims (3)

(57) [Claims] 1. A composition comprising (a) a curable liquid organopolysiloxane and (b) a curing agent as main components, and (c) an average particle size of 0.1 to 5 μm.
m of amorphous alumina powder (20 to 60% by weight of the whole composition) and (d) spherical alumina powder of average particle size of 5 to 50 μm (65 to 25% by weight of the whole composition).
At least one of the component (c) and the component (d) is treated with a silane-based surface treatment agent, and the total amount of the component (c) and the component (d) is 70 to 90% by weight of the whole composition. (4) A curable liquid organopolysiloxane composition. (2) Component (a) contains two alkenyl groups in one molecule.
(B) component is an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms in one molecule and a platinum-based catalyst, and is cured by a hydrosilylation reaction.
The curable liquid organopolysiloxane composition according to claim 1. 3. A curable liquid organopolysiloxane having two or more silanol groups or silicon-bonded hydrolyzable groups in one molecule of (a ') a curable liquid organopolysiloxane and (b') a curing agent,
(C ′) amorphous alumina powder having an average particle size of 0.1 to 5 μm (20 to 60% by weight of the total composition) and (d ′) average particle size of 5
球状 50 μm spherical alumina powder (65 to 25% by weight of the total composition). However, the total amount of the components (c ′) and (d ′) is 70 to 90% by weight of the total composition. is there. (4) A curable liquid organopolysiloxane composition which is cured by a condensation reaction.