Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1998-04-01
2000-01-11
Marquis, Melvyn I.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C08F 800
Patent
active
060137290
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a novel postcurable, moisture-curable elastomer, a process for producing the same, and a molded elastomer composition having rubber elasticity as obtained after postcuring of said elastomer.
The moisture-curable elastomer of the present invention has good moldability and workability and gives, after postcuring, molded elastomers comparable in rubber elasticity and oil resistance to vulcanized rubbers over a wide temperature range.
BACKGROUND ART
In recent years, thermoplastic elastomers have been used as elastomers having rubber elasticity, requiring no curing, and having excellent moldability and workability like thermoplastic resins, in the fields of automotive parts, household electrical appliance parts, electric wire coverings, medical device parts, miscellaneous goods, footwear and so forth. As such thermoplastic elastomers, Japanese Kokai Tokkyo Koho S61-34050, for instance, describes thermoplastic elastomers containing a vinyl aromatic compound block (hard segment) and a conjugated diene compound block (soft segment) alternately in the copolymer chain. In the case of these thermoplastic elastomers, products meeting various specifications, ranging from those rich in flexibility to rigid ones, can be produced by varying the proportions of the two segments appropriately. However, those thermoplastic elastomer compositions containing the soft segment in large proportions are low in tensile strength, heat resistance, flowability and oil resistance and therefore cannot be used in a broad range of applications.
Further, compositions resulting from melt-kneading a monoolefin copolymer rubber and a polyolefin resin together with an organic peroxide as a rubber auxiliary crosslinking agent to thereby effect partial crosslinking are described in Japanese Patent Publication S53-21021, for instance.
Such thermoplastic elastomers in which the monoolefin copolymer rubber has been only partially crosslinked are not satisfactory enough in oil resistance, form recovery at high temperature, and other properties, and hence cannot be used in a sufficiently wide range of applications. The radicals formed from the organic peroxide used for crosslinking cause polymer chain cleavage, hence a reduction in mechanical strength.
Furthermore, it is described in Japanese Patent Publication S58-415138 that the monoolefin copolymer rubber alone is preferentially crosslinked using a heat-reactive alkilphenol resin as the crosslinking agent to thereby overcome the drawbacks mentioned above. Thus, there are described thermoplastic elastomers obtained by crosslinking the EPDM rubber component of a thermoplastic resin preferentially using a phenolic curing agent. The thermoplastic elastomers obtained by such a procedure in which the rubber component has been completely crosslinked show improved oil resistance and form recovery at high temperature but the improvements attainable are not satisfactory enough when compared with cured rubbers.
In U.S. Pat. No. 4,803,244, there are described thermoplastic elastomers obtained by crosslinking the rubber component comprising a monoolefin copolymer using an organosiloxane. However, the matrix components of the thermoplastic elastomers described there are polypropylene, polyethylene, ethylene-.alpha.-olefin copolymers and the like, hence the elastomer compositions show a low rate of recovery after compression. Even when a monoolefin copolymer having relatively good compatibility with the matrix components is used as the rubber component in said elastomer compositions, the dispersion of the rubber component is insufficient because of the poor compatibility of the crystalline fraction of the matrix. In particular, the state of dispersion worsens as the proportion of rubber increases, failing to give physical properties necessary for automotive parts, such as weather strips and dust boots, for which rubber elasticity is particularly needed.
U.S. Pat. Nos. 4,970,263 and 4,500,688 also describe thermoplastic resin compositions in which the rubber com
REFERENCES:
patent: 4500688 (1985-02-01), Arkles
patent: 4558094 (1985-12-01), Deguchi et al.
patent: 4803244 (1989-02-01), Umpleby
patent: 4970263 (1990-11-01), Arkles et al.
patent: 5597867 (1997-01-01), Tsujimoto et al.
Iwasa Tsuyoshi
Tsujimoto Motoyoshi
Marquis Melvyn I.
Milstead Mark W.
Sumitomo Bakelite Co. Ltd.
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