Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-11-04
2002-02-05
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S865000, C524S484000, C524S490000, C524S491000, C524S492000, C526S279000, C526S340000, C526S347000, C525S332900, C525S332800, C525S333100
Reexamination Certificate
active
06344518
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a conjugated diolefin copolymer rubber and a rubber composition. More particularly, the present invention relates to a conjugated diolefin copolymer rubber which exhibits superior processability (such as easiness in mixing by a mixer such as Banbury, easiness in winding the sheets made from the rubber composition by a roller mill, excellent smoothness of the surface of the sheets, tidy edge of the sheets, etc.) and which can produce vulcanized products exhibiting well-balanced improved properties such as wet skid properties, low hysteresis loss properties, abrasion resistance, breaking strength, and superior processability, irrespective of the types and combinations of fillers to be added, and is useful as a tread material for low fuel consumption tires, large tires, and high performance tires.
2. Description of the Background Art
Development of a conjugated diolefin-type rubber material for use in tires exhibiting reduced rolling resistance, high abrasion resistance, excellent breaking strength, as well as superior operational stability performance typified by superior wet skid properties is desired to respond to recent demand for vehicles with a low fuel consumption.
Rolling resistance can generally be reduced by decreasing the hysteresis loss of vulcanized rubber. Impact resilience at 50-80° C., tan &dgr; at 50-80° C., and small Goodrich heat generation, and the like are used as an index of evaluation of the hysteresis loss of vulcanized rubber materials. Specifically, rubber materials with a large impact resilience at 50-80° C., a small tan &dgr; at 50-80° C., and a small Goodrich heat generation are preferable.
Natural rubbers, polyisoprene rubber, or polybutadiene rubber, and so on are known as rubber materials with low hysteresis loss. A problem with these rubber materials is their poor wet skid resistance.
As a method for decreasing the hysteresis loss without impairing wet skid resistance in the polymerization of styrene-butadiene copolymers of various structures using an organic alkali metal initiator in a hydrocarbon solvent, various methods for modifying the polymer terminals by introducing functional groups have been proposed. Examples of such polymers include styrene-butadiene copolymers obtained by modifying or coupling the polymer terminals with a tin compound (Japanese Patent Application Laid-open No. 55912/1982), styrene-butadiene copolymers obtained by modifying the polymer terminals with an isocyanate compound (Japanese Patent Application Laid-open No. 141741/1986) or a lactam compound (Japanese Patent Application Laid-open No. 43402/1986), and the like.
The polymers thus obtained by modifying the terminals are made into rubber compositions by incorporating carbon black as a reinforcing agent and vulcanized, to produce vulcanized rubber which exhibits a decreased hysteresis loss, superior abrasion resistance, and excellent failure characteristics, without impairing wet skid resistance. More recently, tires made from a rubber composition containing silica which can improve both rolling resistance and wet skid resistance are accepting wider popularity. Because a rubber composition containing silica has a problem of inferior processability and electrical resistance, rubber compositions containing a mixture of silica and carbon black are usually used.
However, such a silica-containing rubber composition has a problem that the vulcanized products exhibit low tensile strength and abrasion resistance. Moreover, a silica-containing composition exhibits inferior processability as compared with a carbon black-containing composition, resulting in an increased processing cost.
Various silica-containing rubber compositions comprising polymers in which functional groups exhibiting affinity with silica are introduced to the terminals have been proposed to improve tensile strength and abrasion resistance of vulcanized products made from the silica-containing composition (such polymers may be hereinafter called “modified polymers”). For example, Japanese Patent Publication No. 36957/1974 discloses a method of preparing polymers by reacting silicon tetrahalide, or trihalosilane, or the like; Japanese Patent Publication No.5071/1977 discloses a method of producing polymers modified with a halogenated silane compound; Japanese Patent Application Laid-open No.188501/1989 discloses diene-type rubber in which a halogenated silyl group is introduced; and Japanese Patent Application Laid-open No. 230286/1997 discloses diene-type rubber in which an alkyl silyl group is introduced.
Although the properties of silica-containing rubber compositions disclosed by these patents have been improved to some extent by the use of modified polymers, tensile strength and abrasion resistance of vulcanized rubbers made from such rubber compositions are not necessarily satisfied. Moreover, the effect of lowering a hysteresis loss was not necessarily satisfactory in the composition using a mixture of silica and carbon black, particularly when the proportion of carbon black is increased. As mentioned above, a silica-containing composition exhibits inferior processability as compared with a carbon black-containing composition. This tendency is conspicuous when the modified polymer is used.
Conventional modified polymers used for silica-containing compositions are broadly grouped into those suitable for use with carbon black and those suitable for use with silica. The necessity for selecting optimum combinations of the types of filler as reinforcing agents and rubber copolymers in accordance with the application of the ultimate rubber product posed a problem associated with complicated and difficult tasks in the manufacture of the rubber product, because if one of the components is altered, the other component must also be altered. Moreover, when a mixture of silica and carbon black is used, the effect of the reinforcing agent varies according to the proportion of silica and carbon black, irrespective of the types of modified polymers. Deciding the proportion according to the application of the product was also a difficult and complicated task.
To overcome such complexity and difficulty, polymers in which amino groups are introduced have been proposed as effective modified polymers for use with silica or carbon black. Examples of such polymers for use with carbon black include (1) polymers obtained by introducing an amino group at the initial chain end of the polymer using a lithium amide initiator (Japanese Patent Application Laid-open No.38209/1984, Japanese Patent Publication No. 1298/1993, Japanese Patent Application Laid-open No. 279515/1994, Japanese Patent Application Laid-open No. 199923/1994, and Japanese Patent Application Laid-open No. 53616/1995) and (2) various styrene-butadiene copolymers of different structures polymerized using an organolithium initiator, of which the terminals are modified with a nitrogen-containing compound such as a urea compound (Japanese Patent Application Laid-open No. 27338/1986) or a dialkylamino benzophenone compound (Japanese Patent Applications Laid-open No. 162604/1983 and No. 189203/1983).
As the modified polymers used with silica, diene-type rubbers with an alkyl silyl group introduced therein have been proposed (Japanese Patent Applications Laid-open No. 101344/1989, No. 22940/1989, and No. 71687/1997).
A certain degree of improvement in the properties has been achieved by the modified polymers disclosed by these patent applications in both the compositions containing silica and the compositions containing carbon black.
However, disclosure in these patent applications relates to the methods for introducing amino groups into polymers for the most part and there are no specific descriptions on the relationship between the structure of the modified polymers and various properties. The disclosure in these patent applications thus was not necessarily satisfactory.
The present invention has been completed in view of this situation. Specifically, an object of the present inven
Akema Hiroshi
Kobayashi Naokazu
Tadaki Toshihiro
Harlan R.
JSR Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Wu David W.
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