Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1997-09-10
1998-10-20
Acquah, Samuel A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525100, 525185, 525471, 525472, 525474, 525521, 525540, C08L 5300
Patent
active
058247424
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a polyacetal resin composition, specifically to a resin composition materially comprising a polyacetal resin, a polymer composition based on an olefinic polymer having glycidyl-group-containing pendent chains and a dimethyl siloxane polymer; and this resin composition containing, in addition, carbon black. The invention also relates to a molded article, obtained by molding these resin compositions, having excellent resistance to heat aging and grease resistance, and no loss in physical properties in molded sections, along with improved abrasion resistance characteristics.
DESCRIPTION OF THE RELATED ART
Polyacetal resins, which are plastic materials with excellent repeated fatigue characteristics and wear resistance and well balanced mechanical properties, are used in a broad area, such as in automobiles and electrical and electronic parts, and the like. However, polyacetal resin, in general, tends to oxidatively degrade at high temperatures with mechanical properties decreasing too rapidly to be maintained when subjected to repeated usage at the high temperatures of 90.degree.-120.degree. C.
Many proposals have been made for improving resistance to heat aging (long term heat stability) which, for example, includes methods of adding antioxidants and heat stabilizers, such as polyamides and polydicarboimide as disclosed in U.S. Pat. Nos. 4,098,843 and 4,845,161. Japanese Patent Laid Open H4-345649 discloses a polyacetal resin composition with improved resistance to heat aging and grease resistance (long term oil resistance) comprising a polyacetal resin and a compound having epoxy, nitrile groups and/or oxazolyl groups as functional groups.
The present inventors developed and proposed (Japanese Patent Application Publication H6-111711), an improved polyacetal resin composition which has resistance to heat aging and grease resistance and has welded sections with no decrease in physical properties, which materially comprises a polyacetal resin, an olefinic type polymer having glycidyl-group-containing pendent chains, and a styrene polymer having an oxazolyl-group-containing pendent chains.
Much improvement has been made on polyacetal resins as described above. Molded articles using these improved polyacetal resin compositions, such as molded gears, switches, rollers, switch mechanism parts, cams, and the like, which are subjected to high loads, sometimes in their service suffer from problems of wear or squeaking problems, for which further improvement has been required on wear resistance, or the like, friction characteristics.
It is an objective of this invention to provide a polyacetal resin composition which has excellent resistance to heat aging and grease resistance and has welded sections with no decrease in physical properties, along with further improved friction characteristics of the polyacetal resin.
SUMMARY OF THE INVENTION
This invention relates to a polyacetal resin composition having per 100 parts by weight of a polyacetal resin, 2-7 parts by weight of a polymer composition based on an olefinic polymer having glycidyl-group-containing pendant chains and 0.5-2.5 parts by weight of a dimethyl siloxane polymer of a plasticity of at least one, as well as molding articles made from the resin composition.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic diagram for the reciprocating friction wear tester used in the friction characteristic evaluation test.
DETAILED DESCRIPTION
The means for solving the problems in the prior art are as follows.
The present inventors discovered that the addition of a dimethyl siloxane polymer to a polyacetal resin composition materially comprising a polyacetal resin, an olefin type polymer having glycidyl containing pendent chains, and a styrene polymer having oxazolyl-group-containing pendent chains, considerably improves wear resistance, and that an additional incorporation of carbon black substantially decreases the wear rate.
The present invention is a polyester resin composition comprising per
REFERENCES:
Interantional Search Report Jul. 11, 1996.
Acquah Samuel A.
E. I. Du Pont de Nemours and Company
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