Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1998-01-09
1999-09-14
Nutter, Nathan M.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524212, 524227, 524230, 524231, 428411, 264241, 264259, 2642711, 26427211, 264279, 2642791, C08L 5900, C08K 520, B29C 4500, B29C 4514
Patent
active
059524103
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of The Invention
The present invention relates to a polyacetal resin composition and an insert molded article comprising the same. More particularly, the present invention is concerned with a polyacetal resin composition having high mechanical strength retentivity, which comprises a polyacetal resin having a specific, relatively low melting temperature, a specific bisamide in a specific amount and a specific monoamide in a specific amount, and is also concerned with an insert molded article comprising the same.
The polyacetal resin composition of the present invention has excellent weatherability, specifically resistance to cooling-heating cycles (hereinafter, frequently referred to simply as "cooling-heating cycle resistance"), i.e., mechanical strength retentivity during cooling-heating cycles. For example, in the polyacetal resin composition of the present invention, not only the occurrence of whitening, crazing or cracking but also the lowering in impact resistance can be suppressed even after the polyacetal resin composition experiences repeated cooling-heating cycles.
The polyacetal resin composition of the present invention exhibits excellent cooling-heating cycle resistance with respect to the mechanical strength and, therefore, can be advantageously used in various applications where repeated heating-cooling cycles are necessarily experienced and where, hence, use of conventional polyacetal resins has been restricted. Therefore, the polyacetal resin composition of the present invention can be advantageously used as material for parts in various industrial fields. Also, an insert molded article comprising the above-mentioned polyacetal resin composition and a shaped part unified with the resin composition by insert molding, exhibits excellent cooling-heating cycle resistance with respect to the mechanical strength, so that, even after the insert molded article experiences repeated cooling-heating cycles, it does not suffer either appearance deterioration, such as whitening due to fine crazing, or a lowering in impact resistance. Thus, the insert molded article of the present invention can be used for a prolonged period of time, without suffering crazing or cracking.
BACKGROUND ART
Insert molding methods which have conventionally been used for producing insert molded articles, in which a resin (plastic) segment is unified with a metallic segment (i.e., insert), can be roughly classified into the following two modes: (1) a mode in which, for the purpose of reinforcing a resin molded article, insert molding is conducted so as to embed a metallic segment, such as a shaft, nut or sleeve, in a resin article; and (2) a mode in which, for the purpose of avoiding cumbersome operations in producing a metal-resin composite article, which operations involve separately and then assembling the separately produced parts, molding is conducted so as to produce a metal-resin composite article (other than a metal-embedded article) by a one-time molding operation (in which article a resin part, such as a pin or a bushing, and a metallic part or substrate are combined in a unified form) (this second mode is also frequently called "outsert molding") (see for example, Unexamined Japanese Patent Application Laid-Open Specification No. 7-124997)!. The above-mentioned insert molding has been widely used for manufacturing parts of various electrical appliances and automobiles.
Conventionally, as a thermoplastic resin to be used in the insert molding, a polyacetal resin has been advantageously used since the polyacetal resin has excellent mechanical strength, electrical characteristics, chemical resistance and sliding properties.
However, insert molded articles produced using a conventional polyacetal resin have serious disadvantages. For example, when insert molded articles are used as parts of electrical appliances, parts of automobiles or the like, which parts frequently experience repeated cooling-heating cycles during use thereof, the resin segments of the insert molded articles a
REFERENCES:
patent: 4382994 (1983-05-01), Matsumi
Ariyasu Hideyuki
Nagahara Hajime
Yokoyama Hiroshi
Asahi Kasei Kogyo Kabushiki Kaisha
Nutter Nathan M.
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