Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1998-06-26
2000-11-07
Seidleck, James J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524430, 524437, 524492, C08J 510, C08K 520, C08L 5100, C08L 7700
Patent
active
061438197
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FILED
The present invention relates to a composite sheet which is excellent in thermal conductivity, heat resistance, electrical characteristics, chemical resistance, mechanical characteristics and the like, and to a production method therefor. More specifically, the present invention relates to a composite sheet which is useful as an electrical insulation material in areas of rotary machines and transformers. The present invention further relates to an electrical apparatus provided with such a composite sheet.
BACKGROUND ART
Heretofore, a molded material based on a heat-resistant polymer has been used in electrical applications requiring heat resistance. In particular, molded materials based on an aromatic polyamide (hereinafter referred to as "aramide") are advantageous industrial materials with heat resistance, chemical resistance, and flame retarding properties which are attributed to the structure of aramide molecules. Above all, tissue paper (registered trademark: NOMEX) comprising fibrid and fiber of poly(m-phenylene isophthalamide) is widely used as electrical insulating paper with excellent heat resistance.
Recently, in areas of rotary machines and transformers, there has been an increasing demand for compact machines for the purpose of reduction in the number of parts and of space-saving. As means for meeting the demand, electrical insulation materials with high thermal conductivity have been needed which can rapidly dissipate heat generated from rotary parts and coils. Conventional aramide tissue paper, which includes air in the inside, is low in thermal conductivity, and thus does not sufficiently meet the above demand.
Heretofore, as for heat dissipation sheets for heat generating electronic parts such as power transistors, thyristors, and the like, there have been proposed organo-polysiloxane (silicone resin) compositions and molded materials therefrom, based on a silicone resin with superior heat resistance mixed with a filler with good thermal conductivity. Their improvement in thermal conductivity, that could not be achieved by silicone resin alone, has been realized by way of adding a filler.
(1) Japanese Patent Application Laying-open No. 14654/1977 describes an organo-polysiloxane composition comprising organo-polysiloxane, organo-hydrogen-polysiloxane, a silica based filler, a zinc carbonate powder, and a platinum catalyst.
(2) Japanese Patent Application Laying-open No. 155506/1978 describes a heat conductive silicone rubber composition comprising organo-polysiloxane, to which are added boron nitride, a low-molecular weight organo-polysiloxane and a hardener.
(3) Japanese Patent Application Laying-open No. 2349/1981 describes a heat dissipating rubber-like molded material with improved thermal conductivity which comprises poly(di-organosiloxane) which is blended with a filler, an organic peroxide catalyst, and silicone oil, vulcanized, and molded.
As described above, silicone resin compositions and molded materials with electrical insulation properties and thermal conductivity are known in the art. However, silicone resin compositions and molded materials of (1) to (3) have been defective in that low tear strength inherent to silicone resins is not overcome and that large amounts of fillers contained therein rather deteriorate their mechanical strength.
With the aim of solving such problems, a method has been proposed in which silicone resin is reinforced with another material as follows.
(4) Japanese Patent Application Laying-open No. 21446/1983 describes a production method for a heat conductive insulation sheet in which a mixture of an addition polymerization type liquid silicone rubber and a filler for enhancing its thermal conductivity is sheet-coated on a reinforcing fabric or non-woven fabric, and then cross-linked. Here, the fabric or non-woven fabric may comprise one of inorganic fibers such as glass fiber, silica fiber, alumina fiber, or boron nitride fiber, or organic fibers such as those of polyester or fluororesin.
(5) Japanese Patent Application Laying-open
REFERENCES:
patent: 5681612 (1997-10-01), Benedict et al.
patent: 5705258 (1998-01-01), Okami et al.
DuPont Teijin Advanced Papers, Ltd.
Rajguru U. K.
Seidleck James J.
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