DESCRIPTION
THERMALLY CONDUCTIVE SILICONE GREASE COMPOSITION
Technical Field
[0001] The present invention relates to a thermally conductive silicone grease
composition which is characterized by excellent resistance to heat and reduced oil
bleeding.
Background Art
[0002] In recent years, following an increase in the degree of density and integration
of hybrid ICs and printed circuit boards that carry transistors, ICs, memory elements, and
other electronic components, various thermally conductive silicone grease compositions
comprising an organopolysiloxane and a thermally conductive filler such as an aluminum
oxide powder, zinc oxide powder or the like have been used in order to achieve efficient
heat transfer from such devices (see Japanese Unexamined Patent Application Publications
(hereinafter referred to as "Kokai") Sho 50-105573, Sho 51-55870, and Sho 61-157587).
However, a problem associated with conventional silicone grease compositions is that a
part of the oil bleeds out, and this impairs reliability of the respective electronic devices.
[0003] On the other hand, in order to increase content of a thermally conductive filler
in a thermally conductive silicone grease composition, it was proposed to use a thermally
conductive silicone grease composition comprising an organopolysiloxane, a thermally
conductive filler, and an organohydrogenpolysiloxane having in one molecule at least three
silicon-bonded hydrogen atoms (see Kokai Hei 4-202496). However, such a thermally
conductive silicone grease composition was subject either to oil bleeding or to dripping
from thick coating layers or from vertical surfaces under the effect of heat.
[0004] It is an object of the present invention to provide a thermally conductive silicone
grease composition which is characterized by excellent resistance to heat and reduced oil
bleeding.
Disclosure of Invention
[0005] The above problems are solved by the present invention that provides a
thermally conductive silicone grease composition comprising at least the following
components:
100 parts by mass of an organopolysiloxane (A) represented by the following
general formula:


[wherein R1 designates identical or different univalent hydrocarbon groups; X designates
identical or different univalent hydrocarbon groups or alkoxysilyl-containing groups of the
following general formula:
-R2-SiR1a(OR3)(3-a),
1
(wherein R designates the previously mentioned groups; R2 designates oxygen atoms or
alkylene groups; R3 designates alkyl groups; and "a" is an integer ranging from 0 to 2); and
"m" and "n" are integers equal to or greater than 0, respectively];
400 to 3,500 parts by mass of a thermally conductive filler (B); and
1 to 100 parts by mass of an organopolysiloxane (C) having silicon-bonded
hydrogen atoms on both molecular terminals and in the molecular chains.
[0006] The aforementioned component (A) may have a viscosity ranging from 5 to
100,000 mPa-s at 25 °C.
[0007] The aforementioned component (B) may have an average particle size ranging
from 0.01 to 100 urn. Component (B) may comprise a metal-based powder, metal oxide-
based powder, or a metal nitride-based powder. In particular, this may be a silver
powder, aluminum powder, aluminum oxide powder, zinc oxide powder, or aluminum
nitride powder.
[0008] Aforementioned component (C) may comprise an organopolysiloxane of the
following general formula:

(wherein R4 designates identical or different univalent hydrocarbon groups, which are free
of unsaturated aliphatic bonds; "p" is an integer equal to or greater than 0; and "q" is an
integer equal to or greater than 1).

[0009] The thermally conductive silicone grease composition of the invention may
further contain a silica-based filler (D) in an amount of 1 to 100 parts by mass for 100 parts
by mass of component (A).
[0010] The thermally conductive silicone grease composition of the invention may
further contain a coupling agent (E) in an amount of 0.1 to 10 parts by mass for 100 parts
by mass of component (A).
Effects of Invention
[0011] The thermally conductive silicone grease composition of the invention is
characterized by excellent resistance to heat and reduced oil bleed.
Detailed Description of the Invention
[0012] The organopolysiloxane of component (A) is one of the main components of
the composition and is represented by the following general formula:

[0013] In this formula, R1 may represent identical or different univalent hydrocarbon
groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl,
undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl,
nonadecyl, eicosyl, and other linear alkyl groups; isopropyl, tertiary butyl, isobutyl, 2-
methyl undecyl, 1-hexyl heptyl, and other branched alkyl groups; cyclopentyl, cyclohexyl,
cyclododecyl, and other cyclic alkyl groups; vinyl, allyl, butenyl, pentenyl, hexenyl, and
other alkenyl groups; phenyl, tolyl, xylyl, and other aryl groups; benzyl, phenethyl, 2-
(2,4,6-trimethylphenyl) propyl, and other aralkyl groups; 3,3,3-trifluoropropyl, 3-
chloropropyl, and other halogenated alkyl groups. Preferably, such groups are alkyl,
alkenyl, or aryl groups, and especially preferably, methyl, vinyl, or phenyl.
[0014] In the above formula, X designates identical or different univalent hydrocarbon
groups or alkoxysilyl-containing groups of the following general formula:
-R2-SiR1a(OR3)(3-a)
The univalent hydrocarbon groups designated by X may be the same as aforementioned
groups designated by R1, of which preferable are alkyl, alkenyl, and aryl groups, especially
methyl, vinyl, or phenyl groups. In the alkoxysilyl-containing groups, R1 are the same as

those mentioned above and preferably are alkyl groups, especially methyl groups. R2
designates oxygen atoms or alkylene groups such as ethylene, propylene, butylenes, or
methylethylene groups, of which preferable are ethylene and propylene groups. R3
designates alkyl groups such as methyl, ethyl, propyl, or butyl groups, of which preferable
are methyl and ethyl groups. In the formula, "a" is an integer ranging from 0 to 2, of
which 0 is preferable.
[0015] There are no special limitations on the viscosity of component (A) at 25 °C.
However, the viscosity is preferably within the range from 5 to 100,000 mPa-s, more
preferably, within the range from 5 to 50,000 mPa-s, and most preferably, within the range
from 10 to 50,000 mPa-s. This is due to the tact that when the viscosity at 25 °C is less
than the lower limit of the above-mentioned range, the physical properties of the resultant
compositions tend to markedly decrease, and, on the other hand, when the viscosity
exceeds me upper limit of the above-mentioned range, the handleability of the resultant
compositions tends to decrease.
[0016] Specific examples of aforementioned component (A) are the following: a
diorganopolysiloxane capped at both molecular terminals with trimethylsiloxy groups; a
dimethylpolysiloxane capped at both molecular terminals with dimethylphenylsiloxy
groups; a copolymer of a dimethylsiloxane and a methylphenylsiloxane capped at both
molecular terminals with trimethylsiloxy groups; a copolymer of a dimethylsiloxane and a
methylphenylsiloxane capped at both molecular terminals with dimethylphenylsiloxy
groups; a methyl (3,3,3-trifluoropropyl) polysiloxane capped at both molecular terminals
with trimethylsiloxy groups; a dimethylpolysiloxane capped at both molecular terminals
with dimethylvinylsiloxy groups; a dimethylpolysiloxane capped at both molecular
terminals with methylphenylvinylsiloxy groups; a copolymer of a dimethylsiloxane and a
methylphenylsiloxane capped at both molecular terminals with dimethylvinylsiloxy
groups; a copolymer of a dimethylsiloxane and a methylvinylsiloxane capped at both
molecular terminals with dimethylvinylsiloxy groups; a copolymer of a dimethylsiloxane
and a methylvinylsiloxane capped at both molecular terminals with trimethylsiloxy groups;
a methyl (3,3,3-trifluoropropyl) polysiloxane capped at both molecular terminals with
dimethylvinylsiloxy groups; a dimethylpolysiloxane capped at both molecular terminals
with trimethoxysiloxy groups; a copolymer of a dimethylsiloxane and a
methylphenylsiloxane capped at both molecular terminals with trimethoxysiloxy groups; a
dimethylpolysiloxane capped at both molecular terminals with methyldimethoxysiloxy

groups; a dimethylpolysiloxane capped at both molecular terminals with triethoxysiloxy
groups; a dimethylpolysiloxane capped at both molecular terminals with
trimethoxysilylethyl groups; a dimethylpolysiloxane having one molecular terminal capped
with a trimethylsiloxy group and another one with a trimethoxysilylethyl group; a
dimethylpolysiloxane having one molecular terminal capped with a dimethylvinylsiloxy
group and another one with a trimethoxysilylethyl group; a dimethylpolysiloxane capped at
both molecular terminals with methyldimethoxysilylethyl groups; a copolymer of a
dimethylsiloxane and a methylphenylsiloxane capped at both molecular terminals with
methyldimethoxysilylethyl groups; or combinations of two or more of the above
compounds.
[0017] When component (A) is an alkoxysilyl-containing organopolysiloxane, it
works as a surface-treatment agent for component (B). As a result, handleability of the
obtained composition is not impaired, even though component (B) has high content.
[0018] Component (B) is a thermally conductive filler used for imparting heat-
conductive properties to the composition of the invention. This component can be
exemplified by a metal powder based on the use of gold, silver, copper, aluminum, nickel,
brass, shape-memory alloy, solder, or the like; powdered ceramic, glass, quartz, organic
resin, or the like surface coated with gold, silver, nickel, copper, or a similar metal applied
by a vapor deposition or a metal plating method; aluminum oxide, magnesium oxide,
beryllium oxide, chromium oxide, zinc oxide, titanium oxide, crystalline silica, or similar
metal oxide powders; boron nitride, silicon nitride, aluminum nitride, or a similar
powdered metal nitride; boron carbide, titanium carbide, silicon carbide, or a similar
powdered metal carbide; aluminum hydroxide, magnesium hydroxide, or a similar metal
hydroxide; carbon nanotubes, carbon microfibers, diamond, graphite, or similar carbon-
based powders; or combinations of two or more of the above substances. Most preferable
for component (B) are metal powders, metal oxide powders, or metal nitride powders, in
particular, silver powder, aluminum powder, aluminum oxide powder, zinc oxide powder,
or aluminum nitride powder. When it is required that the composition have electrical
insulating properties, it is recommended to use metal oxide powders or metal nitride
powders, in particular an aluminum oxide powder, zinc oxide powder, or an aluminum
nitride powder.
[0019] There are no special restrictions with regard to the shape of particles of
component (B) which may be spherical, needle-shaped, disk-shaped, rod-like, or irregular

in shape. There are no limitations also concerning the average particle size of component
(B), which is preferably in the range from 0.01 to 100 urn and, more preferably, in the
range from 0.01 to 50 µm.
[0020] In the present composition, the content of component (B) should be in the
range of 400 to 3,500 parts by mass and, most preferably, 400 to 3,000 parts by mass for
100 parts by mass of component (A). This is due to the fact that when the content of
Component (B) is less than the lower limit of the above-mentioned range, the thermal
conductivity of the resultant compositions tends to be insufficient, and, on the other hand,
when it exceeds the upper limit of the above-mentioned range, the viscosity of the resultant
compositions becomes too high and it will impair handleability of the composition.
[0021] The organopolysiloxane of component (C) is used for suppressing oil bleeding
from the composition. This organopolysiloxane has silicon-bonded hydrogen atoms at
molecular terminals and in the chains. Other silicon-bonded groups contained in
component (C) may comprise univalent hydrocarbon groups which are free of unsaturated
aliphatic groups. Examples of these groups are the following: methyl, ethyl, propyl, butyl,
pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl,
hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, and other linear alkyl groups;
isopropyl, tertiary butyl, isobutyL 2-methyl undecyl, 1-hexyl heptyl, and other branched
alkyl groups; cyclopentyl, cyclohexyl, cyclododecyl, and other cyclic alkyl groups; phenyl,
tolyl, xylyl, and other aryl groups; benzyl, phenethyl, 2-(2,4,6-trimethylphenyl) propyl, and
other aralkyl groups; 3,3,3-trifluoropropyl, 3-chloropropyl, and other halogenated alkyl
groups. Preferably, such groups are alkyl or aryl groups, and especially preferably, methyl
or phenyl.
[0022] There are no special limitations on the viscosity of component (C) at 25°C.
However, the viscosity is preferably within the range from 1 to 10,000 mPa-s, more
preferably, within the range from 1 to 1,000 mPa-s, and most preferably, within the range
from 5 to 1,000 mPa-s. This is due to the fact that when the viscosity at 25°C is less than
the lower limit of the above-mentioned range, the physical properties of the resultant
compositions tend to markedly decrease, and, on the other hand, when the viscosity
exceeds the upper limit of the above-mentioned range, the handleability of the resultant
compositions tends to decrease.
[0023] If component (C) has silicon-bonded hydrogen atoms at molecular terminals
and in the chains, no restrictions exist with regard to the molecular structure of this

component which may be a linear, partially-branched linear, or a branched molecular
structure. The linear molecular structure is preferable. Component (C) is represented by the
following general formula:

In this formula, R4 designates identical or different univalent hydrocarbon groups, which
are free of unsaturated aliphatic bonds; "p" is an integer equal to or greater than 0; and "q"
is an integer equal to or greater than 1.
[0024] Component (C) can be exemplified by a methylhydrogenpolysiloxane capped
at both molecular terminals with dimethylhydrogensiloxy groups, a copolymer of a
dimethylsiloxane and a methylhydrogensiloxane capped at both molecular terminals with
dimethylhydrogensiloxy groups, a copolymer of a methylphenylsiloxane and a
methylhydrogensiloxane capped at both molecular terminals with dimethylhydrogensiloxy
groups, and a copolymer of a dimethylsiloxane, a methylphenylsiloxane, and a
methylhydrogensiloxane capped at both molecular terminals with dimethylhydrogensiloxy
groups.
[0025] In the present composition, the content of component (C) should be in the
range of 1 to 100 parts by mass, preferably 1 to 90 parts by mass, and most preferably 1 to
85 parts by mass for 100 parts by mass of component (A). This is due to the fact that
when the content of component (C) is less than the lower limit of the above-mentioned
range, the resultant compositions will be subject to oil bleeding, and, on the other hand,
when it exceeds the upper limit of the above-mentioned range, this will impair heat-
resistant properties of the composition.
[0026] The composition may contain an arbitrary component in the form of a silica-
based filler (D) which may comprise fumed silica, fused silica, precipitated silica, or the
aforementioned silicas which have been surface treated with an organic silicon compound
such as an organoalkoxysilane, organochlorosilane, organosilazane, or the like.
[0027] In the present composition, there are no limitations concerning the content of
component (D), but preferably it should be in the range of 1 to 100 parts by mass and, most

preferably, 1 to 50 parts by mass, and most preferably, 1 to 20 parts by mass for 100 parts
by mass of component (A).
[0028] If necessary, the composition may also contain another arbitrary component in
the form of a coupling agent (E) that can be exemplified by methyltrimethoxysilane,
butyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, 3-
aminopropyltrimethoxysilane, N-(2-ammoemyl)-3-ammopropyltrimethoxysilane, 3-
glyddoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl) emyltrimethoxysilane, 3-
methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, or a similar
silane coupling agent; tetrabutyltitanate, tetraisopropyltitanate, or a similar titanate
coupling agent.
[0029] Although there are no special restrictions with regard to the content of
component (E), it may be recommended to add this component in an amount of 0.1 to 10
parts by mass, preferably 0.1 to 5 parts by mass for 100 parts by mass of component (A).
[0030] Within the limits not contradicting with the objects of the invention, the
composition may contain other arbitrary components such as carbon black, red iron oxide,
or similar pigments, as well as dyes, fluorescent dyes, heat-resistant agents, flame
retarders, plasticizer, or adhesion promoters.
[0031] There are no special restrictions with regard to the method used for the
preparation of the composition. For examples, the following methods are possible:
component (C) can be added to a preliminarily prepared mixture of components (A) and
(B); components (A), (B), and (C) are mixed simultaneously; component (C) can be added
to a preliminarily prepared mixture of components (A), (B), and (E); or component (C) can
be added to a prelirninarily prepared mixture of components (A), (B), and (D). It is
recommended to mix components (A) and (B) under heating conditions, in particular, with
heating at 100 to 200 °C under a reduced pressure. When component (A) is an
alkoxysilane-containing organopolysiloxane, in order to accelerate surface coating of
component (B), the process is carried out either under heating conditions or with an
addition of a catalytic quantity of acidic substances such as acetic acid, phosphoric acid, or
the like, or with an addition of catalytic quantities of basic substances such as
trialkylamine, tertiary ammonium salt, ammonia gas, ammonium carbonate, or the like.
Examples
[0032] The thermally conductive silicone grease composition of the present invention
will be now explained in more details by referring to Practical Examples. Additionally, it

should be noted that the physical characteristics described in the Practical Examples are
represented by values obtained at 25 °C.
[Viscosity]
[0033] Viscosity of the thermally conductive silicone grease composition was
measured by using the rheometer AR550 of TA Instruments, Ltd., having geometry
defined by a 20 mm diameter plate. Viscosity was measured at the shear rate of 10 (1/s).
[Oil Bleeding Characteristics]
[0034] The thermally conductive silicone grease composition was applied in an
amount of about 0.2 cm3 onto a frosted surface of a square (5 cm side) glass plate frosted
one side (the product of Paltec Co., Ltd.), the coating was covered by a square (1.8 cm
side) cover glass (the product of Matsunami Glass Co., Ltd.), and by using a micrometer
(the product of Mitsutoyo Co., Ltd.), the thickness of the coating was adjusted to 300 µm.
The obtained specimen was held for 3 days at 25 °C, and then the oil-bleed characteristics
of the composition were evaluated as a ratio of a diameter of an oil spot bled out from the
thermally conductive silicone grease composition to the initial diameter of the area
occupied by thermally conductive silicone grease composition.
[Thermal Conductivity]
[0035] 0.6 cm3 of the thermally conductive silicone grease composition was
sandwiched between a copper-made test panel having dimensions of 25 x 75 x 1 mm (the
product of Paltec Co., Ltd.) and a cover glass having dimensions of 25 x 75 x 1 mm (the
product of Matsunami Glass Co., Ltd.), and the thickness of the composition layer was
adjusted to 1 mm by spacers. The obtained specimen was arranged vertically and
subjected to a heat-shock test under the following conditions: minus -40 °C/+125 °C/500
cycles. Thermal conductivity was evaluated by observing the presence or absence of the
composition drips.
[Thermal Conductivity]
[0036] Thermal conductivity of the thermally conductive silicone grease composition
was determined as thermal resistance of the composition measured by means of a resin
thermal resistance tester of Hitachi Seisakusho Co., Ltd. at 50 GC using a layer of the
composition having a 1 cm x 1 cm area and thickness of 200 µm and 500 µm.
[Practical Example 1]

[0037] 100 parts by mass of a dimethylpolysiloxane represented by the following
general formula:

(wherein "m" is a value that occurs at viscosity of 2,000 mPa-s) and 2,360 parts by mass of
a spherical aluminum oxide powder having an average particle diameter of 12 urn were
premixed for 30 min. at room temperature and then mixed for another 60 min. under a
reduced pressure and at a temperature of 150 °C. Following this, the product was cooled
to room temperature and mixed with 80 parts by mass of a copolymer of a
methylhydrogensiloxane and a dimethylsiloxane having viscosity of 10 mPa-s and
represented by the following formula:

whereby a thermally conductive silicone grease composition was obtained.
Practical Example 2]
[0038] 100 parts by mass of a dimethylpolysiloxane represented by the following
general formula:

(wherein "m" is a value that occurs at viscosity of 10,000 mPa-s), 1,240 parts by mass of a
spherical aluminum oxide powder having an average particle diameter of 12 um, and 70
parts by mass an irregular-shaped zinc oxide powder having an average particle size of 0.1
µm were premixed for 30 min. at room temperature and then mixed for another 60 min.
under a reduced pressure and at a temperature of 150 °C. Following this, the product was

cooled to room temperature and mixed with 14 parts by mass of a copolymer of a
methylhydrogensiloxane and a dimethylsiloxane having viscosity of 10 mPa-s and
represented by the following formula:

whereby a thermally conductive silicone grease composition was obtained.
[Practical Example 3]
[0039] 100 parts by mass of a dimethylpolysiloxane represented by the following
general formula:

(wherein "p" is a value that occurs at viscosity of 20 mPa-s), 2,560 parts by mass of a
spherical aluminum oxide powder having an average particle diameter of 12 um, 360 parts
by mass of an irregular-shaped zinc oxide powder having an average particle size of 0.1
una, and 7 parts by mass of a memyltrimethoxysilane were premixed for 30 min. at room
temperature and then mixed for another 60 min. under a reduced pressure and at a
temperature of 150 °C. Following this, the product was cooled to room temperature and
mixed with 2.7 parts by mass of a copolymer of a methylhydrogensiloxane and a
dimethylsiloxane having viscosity of 10 mPa-s and represented by the following formula:

whereby a thermally conductive silicone grease composition was obtained.
[Practical Example 4]

[0040] 100 parts by mass of a dimethylpolysiloxane represented by the following
general formula;

(wherein "m" is a value that occurs at viscosity of 900 mPa-s), 500 parts by mass of a
spherical aluminum oxide powder having an average particle diameter of 12 µm, and 10
parts by mass of a fumed silica having BET specific surface area of 200 m2/g and
hydrophobically surface-treated with a hexamethyldisilazane were premixed for 30 min. at
room temperature and then mixed for another 60 min. under a reduced pressure and at a
temperature of 150 °C. Following this, the product was cooled to room temperature and
mixed with 5 parts by mass of a copolymer of a methylhydrogensiloxane and a
dimethylsiloxane having viscosity of 10 mPa-s and represented by the following formula:

whereby a thermally conductive silicone grease composition was obtained.
[Practical Example 5]
[0041] 100 parts by mass of a dimethylpolysiloxane represented by the following
general formula:

(wherein "m" is a value that occurs at viscosity of 2,000 mPa-s), 650 parts by mass of an
irregular aluminum nitride powder having an average particle diameter of 3 urn, 5 parts by
mass of a dimethylpolysiloxane represented by the following formula:


(wherein "p" is a value that occurs at viscosity of 20 mPas), and 5 parts by mass of a
methyltrimethoxysilane were premixed for 30 min. at room temperature and then mixed
for another 60 min. under a reduced pressure and at a temperature of 150 °C. Following
this, the product was cooled to room temperature and mixed with 10 parts by mass of a
copolymer of a methylhydrogensiloxane and a dimethylsiloxane having viscosity of 10
mPa-s and represented by the following formula:

whereby a thermally conductive silicone grease composition was obtained.
[Practical Example 6]
[0042] 100 parts by mass of a dimethylpolysiloxane represented by the following
general formula:

(wherein V is a value that occurs at viscosity of 2,000 mPa-s), 1,250 parts by mass of a
spherical aluminum oxide powder having an average particle diameter of 12 µm, and 3
parts by mass of a dimethylpolysiloxane represented by the following formula:


(wherein "p" is a value that occurs at viscosity of 20 mPa-s), and 3 parts by mass of a
dimethylpolysilane were premixed for 30 min. at room temperature and then mixed for
another 60 min. under a reduced pressure and at a temperature of 150 °C. Following this,
the product was cooled to room temperature and mixed with 7 parts by mass of a
copolymer of a methylhydrogensiloxane and a dimethylsiloxane having viscosity of 10
mPa-s and represented by the following formula:

whereby a thermally conductive silicone grease composition was obtained.
[Comparative Example 1]
[0043] 100 parts by mass of a dimethylpolysiloxane represented by the following
general formula:

(wherein "m" is a value that occurs at viscosity of 2,000 mPa-s), 1,740 parts by mass of a
spherical aluminum oxide powder having an average particle diameter of 12 µm, and 4
parts by mass of a memyltrimethoxysilane were premixed for 30 min. at room temperature
and then mixed for another 60 min. under a reduced pressure and at a temperature of
150 °C. Following this, the product was cooled to room temperature and mixed with 38
parts by mass of a dimethylsiloxane having viscosity of 10 mPa-s and represented by the
following formula:

whereby a thermally conductive silicone grease composition was obtained.

Comparative Example 2]
0044] 100 parts by mass of a dimethylpolysiloxane represented by the following
eneral formula;

(wherein "m" is a value that occurs at viscosity of 2,000 mPa-s) and 1,850 parts by mass of
a spherical aluminum oxide powder having an average particle diameter of 12 µm were
premixed for 30 min. at room temperature and then mixed for another 60 min. under a
reduced pressure and at a temperature of 150 °C. Following this, the product was cooled
to room temperature and mixed with 40 parts by mass of a copolymer of a
methylhydrogensiloxane and a dimethylsiloxane having viscosity of 60 mPa-s and
represented by the following formula:

whereby a thermally conductive silicone grease composition was obtained.
[Comparative Example 3]
[0045] 100 parts by mass of a dimethylpolysiloxane represented by the following
general formula:

(wherein "m" is a value that occurs at viscosity of 10,000 mPa-s) and 550 parts by mass of
a spherical aluminum oxide powder having an average particle diameter of 12 urn were
premixed for 30 min, at room temperature and then mixed for another 60 min. under a

reduced pressure and at a temperature of 150 °C. whereby a thermally conductive silicone
grease composition was obtained.

Industrial Applicability
[0047] Since the thermally conductive silicone grease composition of the invention is
characterized by excellent resistance to heat and reduced oil bleeding, this composition is
suitable for use as a heat-removing medium in electrical and electronic devices.

CLAIMS
1. A thermally conductive silicone grease composition comprising at least the
following components:
100 parts by mass of an organopolysiloxane (A) represented by the following
general formula:

[wherein R1 designates identical or different univalent hydrocarbon groups; X
designates identical or different univalent hydrocarbon groups or alkoxysilyl-
containing groups of the following general formula:
-R2-SiR1a(OR3)(3-a)
(wherein R1 designates the previously mentioned groups; R2 designates oxygen atoms
or alkylene groups; R3 designates alkyl groups; and "a" is an integer ranging from 0 to
2); and "m" and "n" are integers equal to or greater than 0, respectively];
400 to 3,500 parts by mass of a thermally conductive filler (B); and
1 to .100 parts by mass of an organopolysiloxane (C) having silicon-bonded
hydrogen atoms at both molecular terminals and in the molecular chains.
2. The thermally conductive silicone grease composition according to Claim 1,
wherein component (A) has a viscosity ranging from 5 to 100,000 mPa-s at 25 °C.
3. The thermally conductive silicone grease composition according to Claim 1,
wherein component (B) has an average particle size ranging from 0.01 to 100 µm.
4. The thermally conductive silicone grease composition according to Claim 1,
wherein component (B) is a metal-based powder, metal oxide-based powder, or a
metal nitride-based powder.
5. The thermally conductive silicone grease composition according to Claim 1,
wherein component (B) is a silver powder, aluminum powder, aluminum oxide
powder, zinc oxide powder, or an aluminum nitride powder.

6. The thermally conductive silicone grease composition according to Claim 1,
wherein component (C) is an organopolysiloxane of the following general formula;

(wherein R4 designates identical or different univalent hydrocarbon groups, which are
free of unsaturated aliphatic bonds; "p" is an integer equal to or greater than 0; and "q"
is an integer equal to or greater than 1).
7. The thermally conductive silicone grease composition according to Claim 1, further
containing a silica-based filler (D) in an amount of 1 to 100 parts by mass for 100
parts by mass of component (A).
8. The thermally conductive silicone grease composition according to Claim 1, further
containing a coupling agent (E) in an amount of 0.1 to 10 parts by mass for 100 parts
by mass of component (A).

A thermally conductive silicone grease
composition comprising at least the following components:
an organopolysiloxane (A) represented by the following
general formula : [wherein R1 designates identical
or different univalent hydrocarbon groups; X designates
identical or different univalent hydrocarbon groups
or alkoxysilyl-containing groups of the following general
formula: -R2 -SiR1 a (OR3)(3-a) (wherein R1 designates
the previously mentioned groups; R2 designates oxygen
atoms or alkylene groups; R3 designates alkyl groups;
and 'a' is an integer ranging from 0 to 2); and 'm' and 'n' are integers equal to or greater than 0, respectively]; a thermally conductive
filler (6); and an organopolysiloxane (C) having silicon-bonded hydrogen atoms on both molecular terminals and in the molecular
chains; is characterized by excellent resistance to heat and reduced oil bleeding.