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...
Reexamination Certificate
2001-05-03
2003-05-27
Dawson, Robert (Department: 1712)
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...
C524S266000, C524S445000, C524S449000, C524S451000, C525S100000, C525S105000, C525S431000, C525S436000
Reexamination Certificate
active
06569931
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a thermoplastic elastomer composition, more particularly, to a thermoplastic elastomer composition with excellent surface lubricity and resistance to damage, as well as to a method of manufacturing of the above composition and to articles molded therefrom.
BACKGROUND OF THE INVENTION
Thermoplastic resins are light in weight and possess various useful properties, such as excellent resistance to corrosion, and therefore find application in manufacturing internal and external automotive parts and external parts of domestic electrical appliances. However thermoplastic resins, especially thermoplastic resin elastomers, typically have poor surface lubricity and resistance to abrasive wear. Furthermore, surfaces of articles molded from these resins are prone to damage. It has been proposed to solve the above problems by preparing a composition from a thermoplastic resin elastomer in combination with a polyorganosiloxane. For example, in Japanese Patent Publication Hei 6-509378 it is proposed to prepare a polymer composition by combining a block copolymer of propylene, random ethylene, and propylene with a plate-like inorganic filler and a polyorganosiloxane oil. However, articles molded from such a composition have insufficient surface lubrication properties and resistance to damage, and therefore are not always satisfactory for use.
It is an object of the present invention to provide a thermoplastic elastomer composition with excellent damage-resistant and surface lubricity. Another object is to provide a method of manufacturing the above composition. Still another object is to provide articles molded from the aforementioned thermoplastic elastomer composition.
SUMMARY OF THE INVENTION
A thermoplastic elastomer composition, method for preparation, and articles formed therefrom. The thermoplastic elastomer composition comprises (A) a thermoplastic elastomer, (B) a thermoplastic resin which has a Rockwell hardness (R scale) exceeding 80 at 25° C., (C) a polydiorganosiloxane which has a Williams plasticity exceeding 100 at 25° C.; and (D) an inorganic filler.
DESCRIPTION OF THE INVENTION
A first embodiment of the present invention is a thermoplastic elastomer composition comprising (A) a thermoplastic elastomer, (B) a thermoplastic resin which has a Rockwell hardness (R scale) exceeding 80 at 25° C., (C) a polydiorganosiloxane which has a Williams plasticity exceeding 100 at 25° C.; and (D) an inorganic filler. A second embodiment of the present invention is a method of manufacture of the thermoplastic elastomer composition comprising the steps of mixing components (B) and (C) with heating thereby preparing a thermoplastic resin composition; adding the thermoplastic resin composition and component (D) to component (A), and mixing with heating. A third of embodiment of the present invention is an article formed from the aforementioned thermoplastic elastomer composition.
Component (A) is a thermoplastic elastomer and is a main component of the present composition. At room temperature this thermoplastic elastomer behaves as a rubber-like elastomer, while under elevated temperatures it represents a plastically-deformable organic resin (see “Practical Encyclopedia on Plastics (Jitsuy Purastiku Jiten], issued on May 1, 1993, Investigative Committee of Industrial Companies (Kabushiki kaisha sangy), pp. 180-207”). The following are examples of the aforementioned thermoplastic elastomers: polystyrene-type thermoplastic elastomer, polyolefin-type thermoplastic elastomer, polyvinylchloride-type thermoplastic elastomer, polyester-type thermoplastic elastomer, polyurethane-type thermoplastic elastomer, polyamide-type thermoplastic elastomer, and fluoropolymer-type thermoplastic elastomer. Most preferable among the above are polyolefin-type thermoplastic elastomer, polystyrene-type thermoplastic elastomer, and polyester-type thermoplastic elastomer, especially the polyolefin-type thermoplastic elastomer. The polyolefin-type thermoplastic elastomer can be represented by a hard-phase elastomer such as polyethylene or polypropylene, and a polymer-copolymer thermoplastic elastomer or a polymer-blend type thermoplastic elastomer having both a hard phase and a soft-phase, such as EPDM (ethylene-propylene-diene monomer), EPR ethylene-propylene rubber, or butyl rubber. The aforementioned polyolefin-type thermoplastic elastomers are commercially produced, e.g., by Mitsui Chemical Co., Ltd. under trademarks Mirastomer™ and Goodmer™. Polystyrene-type thermoplastic elastomers may be represented by a hard-phase form, such as polystyrene, or a block-copolymer type thermoplastic elastomer having both a hard phase and a soft phase, such as a polybutadiene, polyisobutylene, or a hydrogenated polybutadiene. The aforementioned polystyrene-type thermoplastic elastomers are commercially produced, for example, by Asahi Chemical Industries Co., Ltd. under trademarks Tuftek™, Tufprene™, Sorprene™, and Asaprene™. Polyester-type thermoplastic elastomers may be represented by a hard phase, such as polyester, or by a block-copolymer type thermoplastic elastomer having a soft phase, such as polyether or polyester. These polystyrene -type thermoplastic elastomers are commercially produced, for example, by Toray-DuPont Co., Ltd. under the trademark Hytrel™. Component (A) of the present composition can be represented by one of the above elastomers or by a mixture of two or more elastomers. It is recommended that component (A) have a Rockwell hardness (R scale) less than 70 at 25° C. Component (A) should have a Shore D hardness (ASTM D2240) below 60, and preferably below 50.
Component (B) is a thermoplastic resin with a Rockwell hardness (R scale) above 80 at 25° C. This component is finely dispersed in component (A). Component (B) protects the thermoplastic elastomer from loss of softness, increases its surface hardness, and thus improves resistance of the surface to damage. There are no special limitations with regard to the type of component (B), provided it has a Rockwell hardness (R scale) above 80 at 25° C. Component (B) can be a thermoplastic resin insoluble in component (A) but uniformly dispersible in component (A) at a predetermined dimension. The following are examples of compounds suitable for use as component (B): a polypropylene resin, propylene-ethylene copolymer, or a similar polyolefin-type resin; Nylon 6, Nylon 66, Nylon 11, Nylon 12, Nylon 46, or a similar polyamide resin; a polyethylene terephthalate, polybutylene terephthalate, or a similar polyester resin; an aromatic polycarbonate resin; a polyamide resin, polyphenylene sulfide resin, polyallylate resin, polyamidoimide resin, polyetherimide resin, polyetheretherketone resin, polyimide resin, and liquid-crystal polyester resin. Among the above, most preferable are a polypropylene resin, propylene-ethylene copolymer, or similar polyolefin resins; Nylon 6, Nylon 66, Nylon 12, Nylon 11, Nylon 46, or similar polyamide resins; polyethylene terephthalate, polybutylene terephthalate, or similar polyester resins; and an aromatic polycarbonate resin.
Component (B) is used in an amount of 0.1 to 25 parts by weight based on 100 parts by weight of component (A).
The polydiorganosiloxane which is component (C) of the present composition is a component for imparting the properties of moldability and resistance to damage. At room temperature, component (C) is in a state of rubber gum. Component (C) should have a Williams plasticity above 100, preferably above 120, and even above 150. In the context of the present invention, Williams plasticity means plasticity measured by the method specified by JIS K6249: 1997 (Method for Testing Non-Cured and Cured Silicone Rubber). More specifically, 4.2 g of polyorganopolysiloxane are first prepared in the form of a cylindrical specimen. This specimen is then placed between cellophane papers and is placed into a parallel-plate plastometer equipped with a dial gage (product of Ueshima Co, Williams plastometer). After holding for 2 min. under a 5 kg load, the thickness of the s
Furukawa Haruhiko
Lupton Kevin Edward
Morita Yoshitsugu
Romenesko David Joseph
Dawson Robert
Dow Corning Corporation
Zimmer Marc S
Zombeck Alan
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