Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1995-09-29
1997-08-19
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...
525 98, 525914, 152209R, C08L 906, C08L 5302
Patent
active
056589875
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a rubber composition having excellent low-temperature properties.
BACKGROUND ART
As automobiles have come to have higher performances and have become more diversified, property requirements for tire have changed accordingly and a need has become high for an all-weather tire balanced in properties such as high grip, low fuel consumption, low-temperature properties in winter, and the like. Hence, it is desired to develop a rubber material balanced in such properties.
There were proposed, as such a rubber material, for example, blends of natural rubber (NR) or a polyisoprene rubber (IR) and a styrene-butadiene copolymer rubber (SBR) or a high-cis polybutadiene rubber (CBR). They, however, have inferior wet skid property and, when using a SBR of high styrene content, have low grip at low temperatures and cause cracking of tire tread portion, etc.; thus, they have no satisfactory requirements. There were also proposed blends of a polymer of high glass transition temperature (high Tg) (for example, a SBR of high styrene content) and a polymer of low Tg [for example, a high-cis polybutadiene (CBR)]. They, however, are low in tensile strength property and inferior in balance between wet skid and low-temperature properties. There were also proposed, as a polymer having properties of both a high-Tg polymer and a low-Tg polymer, block polymers composed of said two polymers as block components [e.g. Japanese Patent Publication No. 37415/1974, Japanese Patent Application Kokai (Laid-Open) No. 102912/1982, Japanese Patent Publication No. 21702/1992, Japanese Patent Publication No. 61900/1992, EP 54,440 and U.S. Pat. No. 4,463,133]. The block copolymers certainly have improved low-temperature properties, but are inferior in tensile strength and abrasion property.
DISCLOSURE OF THE INVENTION
The present inventors made an extensive study in order to develop a rubber material balanced in wet skid resistance and low-temperature properties. As a result, the present inventors found out that by blending particular two polymers having poor compatibility with each other (they cause phase separation) and a block copolymer composed of said two polymers as block components, a rubber composition can be obtained which is well balanced between low temperature properties, wet skid, abrasion property and tensile strength property. The finding has led to the completion of the present invention.
According to the present invention, there is provided a rubber composition comprising a copolymer A specified below, a copolymer B specified below and a block copolymer C composed of said copolymer A and said copolymer B as block components, all of the three copolymers being obtained by copolymerization of a conjugated diene and an aromatic vinyl compound using an alkali metal-based catalyst, in which rubber composition the copolymer A has:
(1) an aromatic vinyl compound content of 30% by weight or more,
(2) a 1,2-vinyl content in conjugated diene units, of 45% by weight or more, and
(3) a glass transition temperature of -20.degree. C. or higher,
(a) an aromatic vinyl compound content of 30% by weight or less,
(b) a 1,2-vinyl content in conjugated diene units, of 20% by weight or less, and
(c) a glass transition temperature of -50.degree. C. or lower,
90-50% by weight of a 20-80:80-20 (by weight ratio) mixture (I) of the copolymer A and the copolymer B, and
10-50% by weight of the block copolymer C (II).
Description is made below on the random copolymers A and B and the block copolymer C, all used in the present invention. All of these copolymers can be produced by copolymerizing a conjugated diene and an aromatic vinyl compound using an alkali metal-based catalyst.
The conjugated diene used in the present invention includes 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 1,3-hexadiene, etc. The aromatic vinyl compound includes styrene, .alpha.-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, divinylnaphthalene, etc.
The alkali metal-based ca
REFERENCES:
patent: 4463133 (1984-07-01), Takeuchi et al.
Nakamura Masao
Suzuki Fumitoshi
Tanaka Kiyoshi
Nippon Zeon Co. Ltd.
Warzel Mark L.
LandOfFree
Rubber composition does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Rubber composition, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rubber composition will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1105501