Process for preparing isobutene cyclopentadiene-methylcyclopenta

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...

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526 77, 526237, 526308, 5263487, 526912, C08F23206, C08F 452

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058832076

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BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a process for preparing isobutene-cyclodiene copolymers. More particularly, the present invention relates to a process for preparing isobutene-cyclodiene copolymers having a number-average molecular weight of at least 100,000 and a degree of unsaturation of 1.about.30% by mol, characterized in that polymerization is carried out by reacting isobutene with conjugated cyclic compounds such as cyclopentadiene, methylcyclopentadiene, cyclohexadiene, methylcyclohexadiene, methylenecyclohexene, etc.; or with unconjugated cyclic compounds such as pinene, etc.; or with a mixture thereof, without gel formation even under the reaction condition of high content of cyclodiene.


BACKGROUND ART

Heretofore, the process for producing isobutene-cyclodiene copolymers has been well known. In order to appreciate the commercial utility of the copolymer as a rubber, the copolymer should possess appropriate mechanical strength and strong adhesive strength as well as a high number-average molecular weight and a high degree of unsaturation.
It is known that as the number-average molecular weight of the copolymer increases, the copolymer's tensile strength tends to increase, and as the number of unsaturation bond of the copolymer increases, the copolymer's adhesive strength with respect to another rubber tends to increase. In other words, when the copolymer is vulcanized together with highly unsaturated rubber such as natural rubber etc., the adhesive strength of the copolymer increases as the number of unsaturation bond increases and the crosslinking reaction increases and the similarity in crosslinking behavior will also increase.
Isobutene-isoprene copolymer ("butyl rubber") is well known as a representative example of existing isobutene-diene copolymer. But butyl rubber has less than 2.5 mol % of isoprene content as comonomer, which has double bond; thus, it has low number of crosslinking sites which can bond with other rubber. Also its crosslinking reaction behavior is different from the highly unsaturated rubber. All of the above for example, results in its weak adhesive strength which decreases further when exposed to external shock, vibration etc. As a method of improving adhesive strength of butyl rubber, it has been proposed to incorporate halogen compounds into butyl rubber, such as chorine and bromine which can promote the crosslinking reaction, and to increase isoprene content. But in case of the former, investment on additional equipment is required for halogenation process of the resulting polymer after the production of the polymer. In case of the latter, although improved adhesive strength is obtained, there exists the problem of decreasing gas barrier property, which is one of the most desirable properties of butyl rubber. Moreover, U.S. Pat. Nos. 3,356,661, 3,165,503 and 3,466,268 etc. reported that the higher the content of isoprene, the lower the number-average molecular weight and as a result, the copolymer of little utility value is produced. Also it is known that the structure and quantity of the unsaturated bond influence the resistance of rubber against aging. In case of butyl rubber, the degree of unsaturation is lower than that of natural rubber, so it is somewhat stable against aging, but because the site of unsaturation is in the polymer backbone, this polymer is subject to ozone cleavage, thus the aging of rubber cannot be avoided.
On the other hand, in case of isobutene-cyclodiene copolymer which is similar to butyl rubber, improvement in adhesive strength is obtained as well as excellent gas barrier property even at high degree of unsaturation. Even if the unsaturation bond is attacked and cyclic structure is severed, the copolymer backbone will be highly resistant to ozone attack because the diene compound having cyclic structure is copolymerized and the unsaturation bond does not exist on the backbone. Thus the resistance of rubber against aging is excellent and its improved characteristics makes it an excellent tire material. Even though the abov

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