Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1997-05-22
1999-05-11
Henderson, Christopher
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525236, 525274, C08L9/00
Patent
active
059028564
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a diene rubber having superior processability when unvulcanized and giving a vulcanized rubber improved in abrasion resistance, resiliency and low-temperature properties; as well as to a rubber composition comprising such a diene rubber.
BACKGROUND ART
In recent years, the lower fuel consumption requirement for automobiles became stricter from the standpoints of energy saving, environmental protection, etc. In this connection, a rubber material for tires, of small rolling friction and superior abrasion resistance is required strongly.
It is known that in diene rubbers such as polybutadiene (BR), styrene-butadiene copolymer rubber (SBR) and the like, their abrasion resistance and resilience can be improved by making larger the molecular weight. Diene rubbers of larger molecular weight are improved in these properties; however, they have drawbacks such as lower processability when unvulcanized, increased hardness at low temperatures and the like, making difficult their practical use in many cases. Hence, there were proposed methods of adding, as a processability improver, a liquid BR, a liquid SBR or the like all having a molecular weight of 50,000 or less (e.g. JP-A-4-277537, JP-A-6-65418 and JP-A-6-65419). With these methods, however, addition of a large amount of a liquid rubber reduces the superior abrasion resistance and resilience inherently possessed by high-molecular polymers, and the other drawback of high-molecular polymers, i.e. the low-temperature hardness is not improved noticeably.
Meanwhile, JP-A-61-271338 disclosed a rubber composition comprising a branched polymer and a modified polymer, obtained by subjecting a diene polymer containing active lithium in the molecule, obtained by anionic polymerization using n-butyllithium, to tin coupling of required level and then modifying the remaining active lithium with a particular cyclic urea compound. In this rubber composition, however, the branched polymer has a low weight-average molecular weight not higher than 600,000; therefore, the rubber composition is insufficient in resiliency, abrasion resistance, etc. and, moreover, is not fully satisfactory in processability, low-temperature hardness, etc.
DISCLOSURE OF THE INVENTION
In view of the above situation, the present inventors made a study. As a result, the present inventors found out that a diene rubber obtained by mixing a modified polymer having a particular molecular weight, obtained using a particular modifier such as N-methyl-.epsilon.-caprolactam or the like, with a diene high-molecular polymer having a weight-average molecular weight of 800,000 or more has superior processability when unvulcanized and gives a vulcanized rubber of improved resiliency, abrasion resistance and low-temperature properties; that the diene rubber can be highly balanced in abrasion resistance, resiliency, processability and low-temperature hardness by making large the ratio of the molecular weight of the high-molecular polymer to the molecular weight of the modified polymer; that the diene rubber superior in the above-mentioned properties can be easily obtained by mixing the modified polymer and the high-molecular polymer in a solution state; and that a rubber composition obtained by adding a small amount of the diene rubber to other diene rubber such as natural rubber or the like gives a vulcanized rubber sufficiently improved in properties such as resiliency, abrasion resistance, low-temperature hardness and the like.
According to the present invention, there is provided a diene rubber (iii) comprising: 150,000-500,000, obtained by reacting a diene polymer having a bound active metal in the molecule, with a modifier having a functional group represented by the general formula --C(.dbd.M)-- (wherein M is an oxygen atom or a sulfur atom), and of 800,000 or more.
According to the present invention, there is further provided a process for producing a diene rubber (iii), which comprises mixing: 150,000-500,000, obtained by subjecting a conjugated diene or a
REFERENCES:
patent: 5017636 (1991-05-01), Hattori
patent: 5552490 (1996-09-01), Zanzig
Nakamura Masao
Suzuki Fumitoshi
Tomisawa Manabu
Henderson Christopher
Nippon Zeon Co. Ltd.
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