Silicone grease composition

Details Silicone grease composition Silicone grease composition

1999-12-02

2001-07-03

McAvoy, Ellen M. (Department: 1764)

Solid anti-friction devices, materials therefor, lubricant or se

Lubricants or separants for moving solid surfaces and...

Inorganic compound

C508S155000, C508S161000, C508S208000

Reexamination Certificate

active

06255257

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a silicone grease composition having excellent thermal conductivity.
BACKGROUND OF THE INVENTION
Most of electronic parts generate heat during the operation, and so the heat removal therefrom is required for making them function properly. As to heat-reducing materials applicable to electronic parts, there are high expectations for aluminum nitride because of its high thermal conductivity and electric insulation. The aluminum nitride can be used in various forms, e.g., as a molding and a powder for the filler of grease or rubber.
For achieving high thermal conductivity by the use of aluminum nitride powder as the filler of grease or rubber, it is necessary to raise the filling rate of the aluminum nitride powder. In the case of grease, therefore, the use of a wetter or the art of using as a base oil a modified oil having good wettability has so far been proposed as a solution for raising the filling rate. However, both proposals have failed in achieving satisfactorily high filling rate of aluminum nitride to result in being unsuccessful at obtaining high thermal conductivity.
SUMMARY OF THE INVENTION
As a result of our intensive study of the problem of raising thermal conductivity by increasing the filling rate of aluminum nitride in silicone grease, it has been found that a very good result can be obtained when the filler used is a mixture of two kinds of aluminum nitride powders differing in average particle size, thereby achieving the present invention.
Therefore, an object of the invention is to provide a silicone grease composition having especially high thermal conductivity.
The aforementioned object of the invention is attained with a silicone grease composition comprising the following components (A) to (C):
(A) 50 to 95 weight % of a mixture of an aluminum nitride powder &agr; having an average particle size of 0.5 to 5 &mgr;m and an aluminum nitride powder &bgr; having an average particle size of 6 to 20 &mgr;m, wherein the aluminum nitride powders &agr; and &bgr; are mixed so that the &agr;/(&agr;+&bgr;) ratio is from 0.1 to 0.9 by weight and the average particle size after mixing is from 1 to 10 &mgr;m,
(B) 5 to 15 weight % of organopolysiloxanes having a viscosity of from 50 to 50,000 cs at 25° C. and represented by formula R
1
a
SiO
(4−a)/2
, wherein R
1
represents at least one group selected from saturated or unsaturated univalent hydrocarbon groups containing 1 to 18 carbon atoms and
1.8≦a≦2.2,
and
(C) 0 to 35 weight % of at least one inorganic compound powder having an average particle size of 0.5 to 100 &mgr;m selected from the group consisting of zinc oxide, alumina, boron nitride and silicon carbide powders.


REFERENCES:
patent: 4265775 (1981-05-01), Aakalu et al.
patent: 5100568 (1992-03-01), Takahashi et al.
patent: 5227081 (1993-07-01), Sawa et al.
patent: 5981641 (1999-11-01), Takahashi et al.
patent: 6015777 (2000-01-01), Lostritto, Jr. et al.
patent: 6114429 (2000-09-01), Yamada et al.

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