Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-02-19
2001-04-24
Lovering, Richard D. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C523S407000, C525S066000, C525S531000
Reexamination Certificate
active
06221961
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a molding resin composition, or more particularly, a molding resin composition suitable for the manufacture of molded articles having sliding properties and friction/wear resistance.
BACKGROUND ART
So-called engineering plastics, such as polyacetal resin, ABS resin, polyamide resin, polyphenylene oxide resin, polyimide resin, thermoplastic polyester resin, polycarbonate resin, epoxy resin, thermosetting unsaturated polyester resin, phenolic resin and the like are extensively used in various industrial fields like the automotive industry and the electronic-electric industries on account of their high melting points or softening points as well as excellent mechanical properties.
Nevertheless, what are required for any resin used for parts having sliding surfaces like gears used in precision machines are a low coefficient of friction, that is, excellent sliding properties, and excellent friction/wear resistance, and in this respect, the aforementioned engineering plastics by themselves cannot be said to inherently possess sufficient sliding properties and friction/wear resistance.
Molded articles impregnated with grease or the like, as a sliding property improving agent, which have been used up to the present give rise to such problems that grease blooms or exudes to the surface with the result that neighboring parts are stained or the sliding properties improving effect does not last long enough.
There is available another method of incorporating a polymer like fluoroplastics or olefin plastics as an additive to improve the sliding properties of the aforementioned engineering plastics. Even though sliding properties of plastics are improved by this separate method, these polymer additives are accompanied by shortcomings associated with molding processibility such that peel-off of the polymer additive occurs in consequence of the phase separation on the surface of the molded article, due to their poor compatibility with said engineering plastics. Hence the mold release properties are inferior, on the top of the fact that fluoroplastics are generally expensive.
DISCLOSURE OF THE INVENTION
It is the primary object of the present invention to provide a molding resin composition capable of improving sliding properties of molded articles by decreasing their coefficients of friction and imparting excellent friction/wear resistance.
The secondary object is to provide a molding resin composition having excellent molding processibility, such as good mold release properties and no mold fouling.
The present invention relates a molding resin composition comprising of a resin (A) and a modified ethylene-&agr;-olefin random copolymer (B), both of which are described in detail hereunder, having the following composition. Namely, it is a molding resin composition comprising:
(A) 100 parts by weight of one kind of resin selected from the group consisting of polyacetal resin, ABS resin polyamide resin, polyphenylene oxide resin, polyimide resin, thermoplastic polyester resin, polycarbonate resin, epoxy resin, thermosetting unsaturated polyester resin and phenolic resin, and
(B) 0.1-15 parts by weight of ethylene-&agr;-olefin random copolymer having polar groups,
wherein (a) the ethylene-&agr;-olefin random copolymer comprises 20-80 mole % of ethylene units and 20-80 mole % of &agr;-olefin units based on its total structural unit, and
wherein the ethylene-&agr;-olefin random copolymer having polar groups has (b) its number average molecular weight (Mn) is 500-10000, and (c) its molecular weight distribution (Mw/Mn) represented by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 1.2-3.
The polar group of the ethylene-&agr;-olefin random copolymer having polar groups is preferably of one kind selected from the group consisting of carboxyl group, carboxylic acid anhydride group, carbonyl group, oxycarbonyl group, formyl group and hydroxyl group.
It is particularly preferable that the ethylene-&agr;-olefin random copolymer having polar groups is an oxidation-modified material (B-1) produced from ethylene-&agr;-olefin random copolymer, above all an oxidation-modified material having an oxygen content of 0.1-20% by weight, an acid value of 0.1-50 mgKOH/g, and a saponification value of 0.1-100 mgKOH/g.
Also, it is preferable that the ethylene-&agr;-olefin random copolymer having polar groups is a graft-modified material (B-2) produced by graft-copolymerizing 0.1-20% by weight of an ethylenic unsaturated monomer having 3-10 carbon atoms with ethylene-&agr;-olefin random copolymer, which has at least one kind of polar group selected from the group consisting of carboxylic acid group, carboxylic acid anhydride group, ester group and hydroxyl group.
BEST MODE FOR CARRYING OUT THE INVENTION
The molding resin composition of the present invention comprises, as described in the foregoing, a specific resin (A) and a small amount of ethylene-&agr;-olefin random copolymer having polar groups (B). The present invention is described specifically as follows.
The resin (A)
The resin (A) is either one of polyacetal resin, ABS resin, polyamide resin, polyphenylene oxide resin, polyimide resin, thermoplastic polyester resin, and polycarbonate resin which are classified as thermoplastic resins and epoxy resin, thermosetting unsaturated polyester resin and phenolic resin which are classified as thermosetting resins.
The resins are by themselves well-known resins as they are described in publications like, for example, “Engineering Plastics, edited by Hiroshi Maki and Rikio Kobayashi and published by Sangyo Tosho Co., Ltd.” and “FRP Design Handbook”, etc. The preferred mode of each said resin is explained as follows.
(1) Polyacetal Resin
Typically, it is the resin obtained by ring-opening polymerizing formalin or trioxane with, if so required, ethylene oxide in the presence of a cationic catalyst. It is preferable in the present invention that said resin, which has polyoxymethylene chain as its backbone chain, is of the copolymer type. This kind of polyacetal resin is commercially available by such trade names as “lupital” manufactured by Mitsubishi Engineering Plastics Co., Ltd., and “Duracon” manufactured by Polyplastics Co., Ltd. and is preferably used in the present invention.
(2) ABS Resin
Typically, it is a high-impact resin obtained by graft-polymerizing acrylonitrile and styrene, etc. with an elastomeric component such as polybutadiene. It is preferable in the present invention that its polybutadiene content is 5-40% by weight and the styrene content-to-acrylonitrile content (styrene/acrylonitrile) ratio by weight is 70/30-80/20. This kind of ABS resin is commercially available by such trade names as “Stylac” manufactured by Asahi Chemical Industry Co., Ltd., “Cycolac” manufactured by Ube-Cycon Co., Ltd., “Toyorac” manufactured by Toray Corporation, etc. and is preferably used in the present invention.
(3) Polyamide Resin
Typically, it is a resin obtained by polycondensation of diamine with dicarboxylic acid, or ring-opening polymerization of caprolactam. It is preferable in the present invention that said kind of resin is a product of polycondensation reaction of aliphatic diamine with aliphatic or aromatic dicarboxylic acid. This kind of resin is commercially available by such trade names as “Leona” manufactured by Asahi Chemical Industries Co., Ltd. and “Zytel” manufactured by DuPont Japan Limited and is preferably used in the present invention.
(4) Polyphenylene Oxide Resin
Typically, it is a resin obtained by causing oxidative coupling reaction of 2,6-dimethyl phenol in the presence of a copper catalyst. Besides this resin, a modified polyphenylene oxide resin produced by blending another resin therewith may be used in the present invention. A modified material produced by blending styrene polymer with polyphenylene oxide resin is preferably used in the present invention. This kind of polyphenylene oxide resin is commercially available by such trade names as “Xyron” manufactured by Asahi Chemical Industries Co.,
Hirano Hideki
Kaneshige Ryosuke
Tanaka Masahide
Birch & Stewart Kolasch & Birch, LLP
Lovering Richard D.
Mitsui Chemicals Inc.
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