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
2000-11-03
2001-12-04
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C528S271000, C528S295500, C528S302000, C528S303000, C525S055000, C525S064000, C525S065000, C525S069000, C525S166000, C525S167500, C525S191000, C525S195000, C525S222000, C525S240000, C525S445000, C524S081000, C524S115000, C524S177000, C524S179000, C524S380000, C524S464000
Reexamination Certificate
active
06326435
ABSTRACT:
TECHNICAL FIELD
This invention relates to a thermoplastic resin composition which comprises a thermoplastic polyester resin, a specific modified polyolefinic polymer and an ester compound and is useful in providing a sliding member having excellent abrasion/wear resistance, a process for producing the same, and to a shaped article made therefrom.
BACKGROUND ART
Owing to their excellent mechanical and electrical properties as well as other physical and chemical properties and good processability, crystalline thermoplastic polyester resins (e.g., polyalkylene terephthalate resins) have been used extensively as engineering plastics in the production of automotive parts, electric or electronic device parts, and others. Although these crystalline thermoplastic polyester resins can be shaped into a variety of articles singly, depending on the field of use, various reinforcing agents or additives are added thereto to improve their properties, particularly mechanical properties.
However, there is a tendency in such fields toward ever-better properties or characteristics. For example, further improvement in sliding characteristics or dimensional accuracy has been desired. For instance, driving mechanisms for video tape recorders, tape recorders, and printers capable of providing further improved sound or picture quality have been desired. In these operation mechanisms, the dimensional accuracy of the sliding members (e.g., gears) as main driving members is one of the important subjects of further investigation, for their dimensional accuracy is directly and deeply related to the quality of sound reproduction or printing. Further, their initial dimensional accuracy is desired to be maintained even through a long-term service. Materials that show excellent abrasion/wear resistance against gears and shafts (e.g., metal shafts) also have been desired.
From the viewpoint of safety, members constituting the operation mechanisms of printers and facsimiles also are required to be flame-retardant. Until now, resin materials having flame retardancy, sliding characteristics, and molding accuracy all at high levels have no yet been found, and generally, grease is put on a conventional inflammable material or an flammable material such as polyacetal is used. However, a toner for printing is caught by grease and clings to a gear, hindering the driving stability of the gear and remarkably accelerating the wear of the gear. In addition, so that the material of the gear itself is poor in wear resistance against a gear of the same material and in sliding characteristics against metal, if the gear ran out of grease, the performance of the gear will be lowered largely.
Conventionally, a sliding member (e.g., a gear) is made from a material blended with a fluorine-containing resin. However, its reduced gear accuracy due to the anisotropy of the fluorine-containing resin or poor accuracy as a result of mold deposit due to the separation of the fluorine-containing resin from the polyester resin, and the wear of the gear against a member of metal or of the same material have not yet been improved to satisfactory levels, and therefore, materials with improved wear resistance have been desired.
Japanese Patent Application Laid-Open No. 9369/1993 (JP-5-9369A) discloses a resin composition comprised of a polyester-series resin and a polyolefinic resin dispersed therein in a specific state thereby to improve the sliding characteristics and molding processability. However, the combination of a polyester-series resin and a polyolefinic resin does not improve the dimensional accuracy and sliding characteristics largely. Japanese Patent Application Laid-Open No. 35050/1991 (JP-3-35050A) discloses a resin composition comprising, in order to improve the moldability and inhibit the occurrence of surface delamination phenomenon, a thermoplastic polyester resin; an ethylene-&agr;-olefin co-polymer grafted with an unsaturated carboxylic acid, or an ethylene-unsaturated carboxylic acid ester copolymer; and a bisoxazoline compound. This literature says that the resin composition may comprise a fatty acid ester of a polyhydric alcohol. However, it cannot be said that such resin composition and a shaped article made therefrom always have improved moldability or sliding characteristics. Japanese Patent Application Laid-Open No.150022/1995 (JP-7-150022A) discloses a polyester resin having good sliding characteristics, the resin comprising a crystalline thermoplastic polyester resin, an olefinic polymer comprised of an olefinic polymer fragment and a vinyl-series polymer fragment, and a fatty acid ester obtained from a fatty acid having 12 or more carbon atoms. However, the moldability and sliding characteristics of these resin compositions are still unsatisfactory.
Thus, an object of the present invention is to provide a polyester resin composition with largely improved dimensional accuracy and sliding characteristics, a process for producing the same, a shaped article formed from the same, a resin composition with improved sliding characteristics, and a process for improving sliding characteristics.
Another object of the present invention is to provide a polyester resin composition having good flame retardancy as well as good dimensional accuracy and sliding characteristics, and a shaped article formed therefrom.
DISCLOSURE OF INVENTION
The inventors of the present invention made extensive and intensive studies to solve the problems mentioned above, and finally found that a composition which is not only excellent in moldability but shows excellent sliding characteristics can be obtained from the combination of a thermoplastic polyester resin, a specific modified polyolefinic copolymer, and an aliphatic ester having a specific molecular weight. The present invention was accomplished based on the above findings.
That is, the polyester resin composition of the present invention comprises: (A) a thermoplastic polyester resin, (B) an olefinic polymer modified with at least one member selected from the group consisting of an unsaturated carboxylic acid and its derivatives, and (C) an aliphatic ester having a molecular weight of 400 to 1,000. The thermoplastic polyester resin (A) may be a polyalkylene arylate-series resin (particularly, polybutylene terephthalate-series resin). The modified olefinic polymer (B) may be an olefinic polymer modified (in particular, grafted) with an unsaturated carboxylic acid or a derivative thereof (e.g., maleic anhydride, (meth)acrylic acid). In the modified olefinic polymer(B), the degree of modification by the unsaturated carboxylic acid or its derivative may be about 0.1 to 5% by weight. The olefinic polymer may be a homo- or copolymer of an olefinic monomer (e.g., ethylene, propylene), or a co-polymer of the olefinic monomer with an &agr;, &bgr;-unsaturated carboxylic acid ester (e.g., (meth)acrylic acid C
1-4
alkyl ester). The aliphatic ester (C) may be an ester of a straight chain C
10-30
fatty acid with an alcohol typified by a straight chain C
8-30
aliphatic alcohol, a C
2-20
alkylene diol, a C
3-8
alkane triol and a C
4-8
alkane tetraol. The content of the modified olefinic polymer (B) per 100 parts by weight of the thermoplastic polyester resin (A) is about 0.5 to 18 parts by weight, and the content of the aliphatic ester (C) is about 0.2 to 8 parts by weight. The ratio of the modified olefinic polymer (B) to the aliphatic ester (C) is about 95/5 to 30/70. The polyester resin composition of the present invention may comprise (D) a flame retardant, (E) a flame retardant auxiliary (particularly, an inorganic flame retardant auxiliary), and others. The content of the flame retardant (D) per 100 parts by weight of the thermoplastic polyester resin (A) is about 0.5 to 25 parts by weight, and that of the inorganic flame retardant auxiliary (E) is about 0.1 to 20 parts by weight.
In the present invention, the components (A), (B), and (C) mentioned above are mixed together to produce a polyester resin composition. In the process, a flame retardant (D) or an inorganic flame retardant auxiliary (
Kobayashi Kazuhito
Takayama Katsunori
Acquah Samuel A.
Nixon & Vanderhye P.C.
Polyplastics Co. Ltd.
LandOfFree
Polyester resin composition does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polyester resin composition, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polyester resin composition will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2581871