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
2001-12-13
2004-02-24
Harlan, Robert (Department: 1713)
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...
C525S240000, C525S244000
Reexamination Certificate
active
06696516
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a thermoplastic elastomer composition whose rubber products give a vulcanized rubber-like flexibility and rubbery nature as well as low hardness and low compression set and which is excellent in terms of an injection fusibility.
BACKGROUND ART
While a gasket having a sophisticated shape such as an automobile gasket and a building gasket can be made using a vulcanized rubber, its manufacturing process is extremely complicated since a linear part and a curved part to be attached thereto should be produced separately. Accordingly, it becomes a trend that a curved part, whose process tends to be complicated especially, is produced using a thermoplastic elastomer, which allows a labor-saving process and an improved producibility to be achieved, as a substitute of a vulcanized rubber. Among such elastomers, an olefinic thermoplastic elastomer has a combination of several excellent properties such as (1) excellent heat resistance, ozone resistance and weather resistance, (2) a vulcanized rubber-like nature, (3) a moldability almost comparable with that of an olefinic thermoplastic resin such as polyethylenes and polypropylenes, (4) no need of a secondary vulcanizing step required for a vulcanized rubber and (5) a recyclability and the like. Nevertheless, such olefinic thermoplastic elastomer involves an extreme difficulty in obtaining a sufficient adhesion with a vulcanized rubber or a non-vulcanized rubber.
Among the elastomers, one known as a flexible olefinic thermoplastic elastomer employed preferably in the curved part of the gasket employed in an automobile window seal, door seal, trunk seal and the like, and a gasket employed as a building material which should have a rubbery nature especially is one having a high ethylene.&agr;-olefinic copolymeric rubber content. However, this elastomer has a poor fluidity upon melting and is difficult to be molded by an injection molding which is the most widely employed molding process.
In addition, such elastomer is problematic also since it still possesses a resin-like nature and is hard when compared with a vulcanized rubber and thus is poor with regard to a rubbery texture or the like. On the other hand, a method for fusing molded articles of olefinic thermoplastic elastomers with each other is disclosed for example in Japanese Patent Publication No. Sho-61-53933, Japanese Unexamined Patent Publication No. Sho-59-221347 and the like, but it still involves a problem which is experienced as a difficulty in achieving a sufficient adhesion especially when an article to be fused is a molded article made of an olefinic vulcanized rubber or the like.
Also when a molded article which has an especially low hardness and a high flexibility such as an irregularly extruded article of a vulcanized foam rubber is employed as a linear part, it should be fused using a thermoplastic elastomer which has an ultimate rubbery nature in terms of a low hardness, a high flexibility and the like.
This invention is intended to solve the problems described above and its objective is to provide a thermoplastic elastomer which has a low hardness, an excellent flexibility, a satisfactory rubbery nature, an excellent fluidity and injection fusibility upon molding, as well as an excellent strength of the adhesion both to an olefinic vulcanized rubber and an olefinic thermoplastic elastomer composition and also a high strength of adhesion especially to a vulcanized foam rubber.
DISCLOSURE OF THE INVENTION
The thermoplastic elastomer composition of the invention is comprising an ethylene.&agr;-olefinic copolymeric rubber (A) whose intrinsic viscosity [&eegr;] determined at 135° C. in decalin solvent is 3.5 to 6.8 dl/g, a mineral oil-based softener (B), an &agr;-olefinic crystalline polymer (C) whose degree of crystallinity is 50% or higher and an &agr;-olefinic amorphous polymer (D) whose melt viscosity at 190° C. is 50,000 cPs or less and whose degree of crystallinity is less than 50%, and at least a part of a mixture containing 20 to 78% by mass of the (A), 20 to 78% by mass of the (B), 1 to 12% by mass of the (C) and 1 to 12% by mass of the (D), based on 100% by mass of the total of the (A), (B), (C) and (D), is crosslinked.
The “ethylene.&agr;-olefinic copolymeric rubber” described above (hereinafter referred to simply as “copolymeric rubber (A)”) means a copolymeric rubber whose main constituent unit is ethylene and an &agr;-olefin except ethylene. The copolymeric rubber preferably contains 90% by mole or more of ethylene and the &agr;-olefin based on 100% by mole of the entire constituent units. The amount less than 90% by mole is not preferable since it leads to a reduction in the flexibility or the mechanical strength of a molded article made using the thermoplastic elastomer composition of the invention.
The &agr;-olefin described above constituting the copolymeric rubber described above may for example be an &agr;-olefin having 3 to 12 carbon atoms such as propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3-ethyl-1-pentene, 1-octene, 1-decene, 1-undecene (two or more of which may be employed in combination). Among those listed above, propylene and 1-butene are preferred.
Other constituent unit may be a non-conjugated diene. Such non-conjugated diene may for example be 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 1,7-octadiene, 1,9-decadiene, 3,6-dimethyl-1,7-octadiene, 4,5-dimethyl-1,7-octadiene, 5-methyl-1,8-nonadiene, dicyclopentadiene, 5-ethylidene-2-norbornene, 5-vinyl-2-norbornene, 2,5-norbornadiene, and the like, which may be employed alone or in combination of two or more. Among those listed above, dicyclopentadiene and 5-ethylidene-2-norbornene are preferred.
Thus, the copolymeric rubber (A) described above may preferably be used an ethylene.&agr;-olefin binary copolymer, an ethylene.&agr;-olefin non-conjugated diene ternary copolymer, a combination thereof and the like.
The ethylene.&agr;-olefin binary copolymer may for example be ethylene-propylene copolymer (hereinafter abbreviated as EPM), ethylene.&agr;-butene copolymer (hereinafter abbreviated as EBM), ethylene.&agr;-pentene copolymer, ethylene.3-methyl-1-butene copolymer, ethylene.1-hexene copolymer, ethylene.3-methyl-1-pentene copolymer, ethylene.4-methyl-1-pentene copolymer, ethylene.3-ethyl-1-pentene copolymer, ethylene.1-octene copolymer, ethylene.1-decene copolymer, ethylene.1-undecene copolymer and the like. Among those listed above, EPM and EBM are preferred. Any of these copolymers may be employed alone or in combination of two or more.
When EPM and/or EBM is employed as the ethylene.&agr;-olefin binary copolymer described above, ethylene content is preferably 50 to 95% by mole (more preferably 60 to 90% by mole) based on 100% by mole of the entire copolymers.
The ethylene.&agr;-olefin non-conjugated diene ternary copolymer described above is especially ethylene.propylene.dicyclopentadiene ternary copolymer, ethylene.propylene.5-ethylidene-2-norbornene ternary copolymer, ethylene.1-butene.dicyclopentadiene ternary copolymer and ethylene.1-butene.5-ethylidene-2-norbornene ternary copolymer preferred. The ethylene content in such ternary copolymer is preferably 50 to 95% by mole (more preferably 60 to 90% by mole) based on 100% by mole of the total of ethylene unit and propylene unit or 1-butene unit. The dicyclopentadiene or 5-ethylidene-2-norbornene content is preferably 3 to 10% by mole (more preferably 3 to 8% by mole) based on 100% by mole of the total of ethylene unit and propylene or 1-butene unit.
The ethylene contents in the binary copolymer and the ternary copolymer described above less than 50% by mole lead to a reduction in the crosslinking efficiency (especially when using an organic peroxide as a crosslinking agent), resulting in a difficulty in obtaining a satisfactory physical property intended. On the other hand, the ethylene contents exceeding 95% by mole lead to an undesirable reduction in the flexibility of the copolymeric rubber.
In addition to the bin
Kanae Kentarou
Maeda Minoru
Morikawa Akihiko
Nakanishi Hideo
Harlan Robert
JSR Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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