Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-08-29
2004-03-09
Rabago, Roberto (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S338000, C526S342000, C526S347000, C526S340000, C526S340100, C524S565000, C524S566000, C524S575000, C524S543000, C524S556000, C524S850000, C524S853000
Reexamination Certificate
active
06703470
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a conjugated diene-based rubber capable of being converted into a vulcanized rubber having a low rolling resistance, an excellent wet skid property sufficient wearing resistance, tensile strength and the like when incorporating an inorganic filler such as silica as a reinforcing agent, and also to an oil extended rubber containing such rubber and an extending oil. The present invention also relates to a rubber composition comprising a conjugated diene-based rubber or an oil extended rubber described above and an inorganic filler and having an excellent processability. This rubber composition gives a vulcanized rubber which is useful especially as a tire tread.
DESCRIPTION OF THE PRIOR ART
In response to recent demand for low gas mileage of automobile, rubber material such as a conjugated diene-based rubber or the like capable of giving a rubber composition for a tire which has low rolling resistance, excellent wearing resistance and destruction characteristics and whose wet skid resistance, which is a representative index of a driving stability, is high is desired.
Tire rolling resistance can be reduced by lowering hysteresis loss of vulcanized rubber. The hysteresis loss can be evaluated based on various properties. For example, compositions preferably have high impact resilience at 50-80° C., a low tan &dgr; at 50-80° C. or low Goodrich heat release. Compositions with low hysteresis loss include natural rubber, isoprene rubber, butadiene rubber and the like, but these are also associated with the problem of low wet skid resistance.
In recent years, there have been proposed methods of using inorganic filler such as silica and the like to serve as reinforcing agent, or combining inorganic filler with carbon black. Tire treads employing inorganic filler or both inorganic filler and carbon black have low rolling resistance and excellent driving stability, represented by, for example, the wet skid resistance. However, they exhibit a problem of poor wearing resistance, tensile strength and the like for the vulcanized rubber. The cause is believed to be the fact that the affinity of inorganic filler for the conjugated diene-based rubber is lower than that of carbon black, such that a sufficient reinforcing effect cannot be achieved.
In order to increase the affinity between the silica as an inorganic filler and the conjugated diene-based rubber, it has been attempted to use conjugated diene-based rubbers introduced therein functional group with affinity for inorganic filler. For example, there have been proposed a conjugated diene-based rubber introduced a hydroxyl group therein (WO96/23027), a conjugated diene-based rubber introduced an alkoxysilyl group therein (Japanese Patent laid-open publication No. HEI-9-208623) and a conjugated diene-based rubber introduced an alkoxysilyl group and an amino and/or a hydroxyl group therein (Japanese Patent laid-open publication No. HEI-9-208633). However, most conjugated diene-based rubbers with such an introduced functional group exhibit strong interaction with an inorganic filler when the inorganic filler is combined therewith, and this creates such problems as impaired dispersion of the inorganic filler, greater heat release during processing, poor processability and the like.
SUMMARY OF THE INVENTION
The present invention solves the problems associated with prior arts described above and is intended to provide a conjugated diene-based rubber and an oil extended rubber, each of which is capable of being converted into a vulcanized rubber having a low rolling resistance, an excellent wet skid property and sufficient wearing resistance, tensile strength, and the like. Another aspect of the invention is intended to provide a rubber composition capable of being converted into a vulcanized rubber which has an excellent processability and is useful as a tire tread of an automobile or the like.
A rubber composition for a tire tread and the like usually contains a reinforcing agent for the purpose of improving tensile strength and wearing resistance, but silica and similar substances do not easily disperse uniformly because of their tendency to aggregate. When using a rubber composition in which the reinforcing agent is not uniformly dispersed, the desired effect of including the reinforcing agent cannot be achieved, while the processability is also notably impaired. For this reason, it has generally been attempted to improve the dispersion properties by also including a silane coupling agent when using a silica as an inorganic filler.
It was discovered that by using a conjugated diene-based rubber having a certain composition in which an unsaturated nitrile monomer unit is contained in a molecular chain a sufficient improvement in the wearing resistance, the tensile strength, and the like as well as the processability can be achieved even with a reduced amount of a silane coupling agent or rather without any silane coupling agent.
The present invention is based on the findings described above and can be described as follows.
1. A conjugated diene-based rubber being characterized in having a repeating unit comprising {circle around (1)} 1 to 30% by mass of an olefinically unsaturated nitrile monomer unit, {circle around (2)} 10 to 50% by mass of an aromatic vinyl monomer unit {circle around (3)} 19.9 to 88.9% by mass of a conjugated diene monomer unit and {circle around (4)} 0.1 to 10% by mass of a monomer unit having one polymerizable unsaturated group and at least one functional group selected from the group consisting of an amino group, a hydroxy group, an epoxy group, a carboxyl group and an alkoxysilyl group [where the total of {circle around (1)}, {circle around (2)}, {circle around (3)} and {circle around (4)} is 100% by mass], and whose Mooney viscosity [ML
1+4
(100° C.)] is 20 to 200.
2. A conjugated diene-based rubber according to 1 above wherein, the glass transition point of the above-mentioned conjugated diene-based rubber is −60 to 0° C., and the difference between the extrapolated temperatures of the initiation and the termination of the above-mentioned glass transition is 20° C. or less.
3. A conjugated diene-base rubber according to 2 above wherein,
a monomer forming the above-mentioned olefinically unsaturated nitrile monomer unit is at least one selected from the group consisting of acrylonitrile and methacrylonitrile;
a monomer forming the above-mentioned aromatic vinyl monomer unit is at least one selected from the group consisting of styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, &agr;-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene and tert-butoxystyrene;
a monomer forming the above-mentioned conjugated diene monomer unit is at least one selected from the group consisting of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene and chloroprene.
4. An oil extended rubber being characterized in comprising 100 parts by mass of a conjugated diene-based rubber which has a repeating unit comprising {circle around (1)} 1 to 30% by mass of an olefinically unsaturated nitrile monomer unit, {circle around (2)} 10 to 50% by mass of an aromatic vinyl monomer unit {circle around (3)} 19.9 to 88.9% by mass of a conjugated diene monomer unit and {circle around (4)} 0.1 to 10% by mass of a monomer unit having one polymerizable unsaturated group and at least one functional group selected from the group consisting of an amino group, a hydroxy group, an epoxy group, a carboxyl group and an alkoxysilyl group [where the total of {circle around (1)}, {circle around (2)}, {circle around (3)} and {circle around (4)} is 100% by mass], and whose Mooney viscosity [ML
1+4
(100° C.)] is 40 to 200, and 10 to 60 parts by mass of an extending oil.
5. An oil extended rubber according to 4 above wherein, the transition point of the above-mentioned conjugated diene-based rubber is −60 to 0° C., and the difference between the extrapolated temperatures of the initiation and the termination of the ab
Konno Tomohisa
Tadaki Toshihiro
Udagawa Yoshiyuki
JSR Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Rabago Roberto
LandOfFree
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