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
2001-12-21
2004-04-27
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...
C524S432000, C524S433000, C524S444000, C524S451000, C524S492000, C524S571000, C524S572000
Reexamination Certificate
active
06727307
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a rubber composition, and more particularly to a rubber composition having excellent fracture properties and wear resistance by using a polar group-containing diene polymer which is obtained through an emulsion polymerization and has an enhanced interaction with an inorganic filler such as aluminum hydroxide or the like.
2. Description of Related Art
Heretofore, carbon black is frequently used as a filler for the reinforcement of a rubber composition. Because, carbon black can provide a high reinforcing property and an excellent wear resistance as compared with other fillers.
On the other hand, it is attempted to reduce a hysteresis loss property of rubber in a tire, and hence a rolling resistance of the tire, for saving a fuel consumption of a vehicle accompanied with a social demand for recent energy-saving. In this case, it is considered to decrease an amount of carbon black filled or to use carbon black having a larger particle size. In any case, however, it is known that the lowering of the reinforcing property, wear resistance or gripping property on a wet road surface is irremissible.
Furthermore, silica is known as a filler simultaneously establishing the low hysteresis loss property, reinforcing property, wear resistance and gripping property on a wet road surface, which is proposed, for example, in JP-A-3-25243 1, JP-A-6-248116, JP-A-7-70369, JP-A-7-188466, JP-A-7-196850, JP-A-8-225684, JP-A-8-245838, JP-A-8-337687 and so on.
However, silica has a drawback that the running performances on a dry road surface are poor as compared with those of a carbon black having approximately the same specific surface area because a storage modulus of a rubber composition compounded with silica is small. In order to enhance the storage modulus, therefore, it is known to increase an amount of silica filled or a specific surface area of silica. In this case, however, it is a problem to lower the low hysteresis loss property inherent to the use of silica
And also, it is known to be effective to heighten a glass transition temperature (Tg) of rubber or tan &dgr; at 0° C. as means for improving the gripping property on the wet road surface. However, as the Tg of rubber heightens, performances at lower temperatures degrade and the rolling resistance increases and hence there is caused a problem of degrading the low fuel consumption.
In order to solve these problems, there are disclosed various techniques, for example, (1) a rubber composition for a tire tread improving a gripping property on a wet road surface with a special silica and a devised milling (EP0501227B), (2) a rubber composition for a tire tread holding a low hysteresis loss property and an improved wet skid performance without degrading a processability and a wear resistance (JP-A-7-149950), (3) a rubber composition for a tire tread improving a gripping property on a wet road surface or a semi-wet road surface at lower and higher temperature zones and a processability (JP-A-8-59893), (4) a rubber composition for a tire tread improving a gripping property on a wet road surface or a semi-wet road surface at lower and higher temperature zones without degrading a wear resistance (JP-A-8-59894) and the like.
However, the rubber composition of the above item (1) has a problem in the processability (workability), and the rubber composition of the above item (2) can not be said to be sufficient in the wear resistance. And also, the rubber compositions of the above items (3) and (4) have a problem that a quantity of a reinforcing filler compounded is too large.
On the other hand, inorganic fillers are known as a reinforcing filler for rubber (JP-A-8-59893, JP-A-8-59894, JP-A-9-151276, JP-A-1 1-334310, JP-A-2000-80204 and so on). When a tire tread is formed by using a rubber composition containing such an inorganic filler, wet performances such as a gripping property on a wet road surface and the like are good and a low fuel consumption is attained, but fracture properties and wear resistance are poor. Therefore, an amount of the inorganic filler used is naturally critical, and also the effect by adding a silane coupling agent is not sufficiently obtained.
In order to obtain a rubber composition having a low hysteresis loss property, there are developed many techniques of enhancing a dispersibility of a filler used in a rubber composition. Among them, a method of modifying a living end of a diene polymer obtained by an anionic polymerization using an organic lithium compound with a functional group having an interaction with a filler becomes most generic.
For instance, a rubber composition containing silica as a reinforcing filler and a rubber component obtained by modifying a living end of a diene polymer obtained through an anionic polymerization with a silicon compound having an alkoxyl group is disclosed in JP-B-6-57767, JP-A-7-233216, JP-A-9-87426 and the like. Even in such a rubber composition, however, all of the wet performances, low fuel consumption property and wear resistance can not be always satisfied sufficiently under the present circumstances.
SUMMARY OF THE INVENTION
Under the above situation, the invention is to solve the aforementioned problems of the conventional techniques and to provide a rubber composition simultaneously establishing the wet performances, low fuel consumption property, fracture properties, wear resistance and the like by using a diene polymer having a polar group in its molecule as a rubber component, and an inorganic filler.
The inventors have made various studies in order to achieve the above object and aimed at good wet performances and low fuel consumption developed, by an inorganic filler such as aluminum hydroxide or the like, and found that the above object can be achieved with a rubber composition using an inorganic filler such as aluminum hydroxide or the like and, if necessary, carbon black or silica as a reinforcing filler, and a specified polar group-containing diene polymer having an interaction enhanced to such a reinforcing filler as a rubber component and as a result, the invention has been accomplished.
According to the invention, there is the provision of a rubber composition comprising a diene polymer synthesized through an emulsion polymerization and having a polar group in its molecule as a rubber component, and an inorganic filler represented by the following formula (1)
mM.xSiO
y
.zH
2
O (1)
wherein M is a metal selected from the group consisting of aluminum, magnesium, titanium and calcium, an oxide or a hydroxide of such a metal or a hydrate thereof, m is an integer of 1 to 5, x is an integer of 0 to 10, y is an integer of 2 to 5 and z is an integer of 0 to 10.
In a preferable embodiment of the invention, the polar group is at least one selected from the group consisting of hydroxyl group, alkoxysilyl group, epoxy group, carboxyl group, carbonyl group, oxycarbonyl group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, imino group, amino group, nitrile group, ammonium group, imido group, amido group, hydrazo group, azo group, diazo group, oxygen-containing heterocyclic group, nitrogen-containing, heterocyclic group and sulfur-containing heterocyclic group.
In another preferable embodiment of the invention, the diene polymer having a polar group in its molecule is at least one of a polybutaeine based polymer, which is obtained by polymerizing mainly butadiene, and a butadiene-aromatic vinyl compound copolymer, which is obtained by polymerizing mainly butadione and an aromatic vinyl compound.
In the other preferable embodiment of the invention, the polar group is introduced as a polar group containing monomer.
In a further preferable embodiment of the invention, the polar group-containing monomer is at least one selected from the group consisting of vinylpyridine, acrylonitrile, acrylic acid, methacrylic acid, acrylic acid ester and methacrylic acid ester
In a still further preferable embodiment of the invention, the inorganic filler represented by
Kondo Hajime
Konno Tomohisa
Tadaki Toshihiro
Udagawa Yoshiyuki
Yanagisawa Kazuhiro
Bridgestone Corporation
Hu Henry S.
Sughrue & Mion, PLLC
Wu David W.
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