Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1998-01-02
2000-08-29
Warzel, Mark L.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525240, 525194, 525197, 525198, C08L 2304
Patent
active
061110213
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a rubber composition comprising an ethylene/.alpha.-olefin
onconjugated polyene copolymer rubber (EPDM) and a polyolefin resin that is a thermoplastic resin, and also relates to a process for preparing of the composition. More particularly, the invention relates to a raw rubber composition by the use of which a slightly microdispersible polyolefin resin can be readily microdispersed by a rubber kneading machine when the composition is kneaded with compounding ingredients such as reinforcing agents, fillers, softeners, vulcanizing agents and vulcanization accelerators, and also relates to a process for preparing the composition.
BACKGROUND OF THE INVENTION
Because of excellent weathering resistance, ozone resistance and heat resistance of ethylene/.alpha.-olefin
onconjugated polyene copolymer rubbers, they have been broadly used for automobile parts, building materials, electrical wires and industrial parts. In such uses, the ethylene/.alpha.-olefin
onconjugated polyene copolymer rubbers are conventionally kneaded, like other rubbers, with various compounding ingredients such as reinforcing agents (e.g., carbon black), fillers (e.g., talc, clay), softeners, vulcanization accelerators and vulcanizing agents by means of batch type kneading machines such as Banbury mixer or roll, or each kind of extruders to prepare compounded rubbers.
In the preparation of products of the ethylene/.alpha.-olefin
onconjugated polyene copolymer rubbers, polymers each of which has different molecular weight and molecular weight distribution are combined with various compounding ingredients to adjust balance between processability and product property.
The compounded rubbers are generally designed to have their respective compositions according to the hardness of the resulting rubber products. In order to obtain a certain harness, carbon black, talc, clay, silica, calcium carbonate, etc. are used in consideration of balance between cost and product property. The reinforcing agents and the fillers mentioned above exert effects of increasing a product hardness in greater or lesser degrees, but they have nature of decreasing processability of the resulting compounded rubbers because of a rise in the viscosity of the compounded rubbers. Additionally, the reinforcing agents and the fillers also have nature of decreasing extensibility that is an important property of the rubber products.
Other than the reinforcing agents and fillers having such nature as mentioned above, there are known polyolefin resins (e.g., polyethylene) which are used as fillers exerting an effect of increasing a product hardness to almost the same degrees as those carbon black and exhibit an effect of decreasing a viscosity of the compounded rubbers thereby to improve the processability. Polyethylene is practically used in compounding with rubbers.
On the other hand, with respect to polypropylene if the amount thereof is not more than 50 parts by weight based on 100 parts by weight of the total amount of EPDM and polypropylene, the resulting compounded rubber takes a "sea-island structure" wherein the EPDM phase is like a sea and the polypropylene phase is like an island. That is, polypropylene is not blended with EPDM, unlike polyethylene, and therefore polypropylene cannot be usually used as a reinforcing agent for vulcanized rubbers.
Even if a polypropylene/EPDM blend, wherein polypropylene having a mean particle diameter of not more than 2 .mu.m is microdispersed, is prepared by a process comprising the step of melt blending EPDM with polypropylene at a temperature of not lower than the melting point of polypropylene, when employing a step of roll processing, by means of a conventional kneading machine such as a Banbury mixer, which comprises adding carbon black, an oil and a filler to the polypropylene/EPDM blend to prepare a compounded rubber and then adding a vulcanization accelerator and a vulcanizing agent to the compounded rubber with cooling the compounded rubber, as the compounded rubber
REFERENCES:
patent: 4311628 (1982-01-01), Abdou-Sabet et al.
patent: 5869563 (1999-02-01), Kawasaki et al.
Abstract of Jap. Laid-Open Pat. Appln. Publication No. 06-128491 (May 10, 1994).
Abstracts of Jap. Laid-Open Pat. Appln. Publication No. 58-42633 (Mar. 12, 1983).
Abstracts of Jap. Laid-Open Pat. Appln. Publication No. 60-40141 (Mar. 2, 1985).
Hosomi Yasuhiro
Ishii Yuji
Kawasaki Masaaki
Koda Taku
Maejima Yoshio
Mitsui Chemicals Inc
Warzel Mark L.
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