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
1999-10-06
2002-03-26
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...
C524S493000, C524S496000, C526S335000, C526S340000
Reexamination Certificate
active
06362272
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an oil extended rubber and rubber composition. More particularly, the present invention relates to an oil extended rubber which can produce vulcanized products exhibiting well-balanced improved properties such as wet skid properties, low hysteresis loss properties, abrasion resistance, and breaking strength, 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 low wet skid resistance.
On the other hand, a rubber composition comprising silica or a mixture of silica and carbon black as a reinforcing agent (filler) has been proposed recently as a rubber material exhibiting low rolling resistance and good wet skid resistance. However, tire treads with such a reinforcing agent incorporated therein 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 rubber compositions comprising polymers in which functional groups exhibiting affinity with silica have been introduced have been proposed to improve tensile strength and abrasion resistance of vulcanized products made from rubber compositions containing such a reinforcing agent. For example, Japanese Patent Publication No. 36957/1974 discloses a method of manufacturing polymers by reacting silicon tetrahalide, trihalosilane, or the like. Japanese Patent Publication No. 5071/1977 discloses a method of manufacturing polymers which are modified with a halogenated silane compound. Moreover, Japanese Patent Application Laid-open No. 188501/1989 discloses a diene-type rubber with an alkyl silyl group introduced therein, and Japanese Patent Application Laid-open No. 230286/1993 discloses a diene-type rubber with a halogenated silyl group introduced. Japanese Patent Applications Laid-open No. 101344/1989, No. 22940/1989, and No. 71687/1997 disclose diene-type rubbers with an amino group introduced therein, as polymers for use with an addition of silica. These polymers with amino groups introduced are known as effective modified polymers for the addition not only of silica, but also of carbon black. Examples of such polymers 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 Applications Laid-open No. 279515/1994, No. 199923/1994, and 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 dialkyl amino benzophenone compound (Japanese Patent Applications Laid-open No. 162604/1983 and No. 189203/1983). Improvement in the properties are attempted by using these modified polymers as polymer components in the composition to which such a reinforcing agent has been incorporated.
However, a rubber composition comprising a polymer in which functional groups having affinity with silica are introduced tends to exhibit impaired processability. Poor processability not only increases the cost, but also impairs blending characteristics of components, such as insufficient dispersion of reinforcing agents and the like, which results in worsening of properties.
The present invention has been completed in view of this situation. Specifically, an object of the present invention is to provide an oil extended rubber and a composition comprising the oil extended rubber, which can produce vulcanized products exhibiting well-balanced improved properties such as wet skid properties, low hysteresis loss properties, abrasion resistance, and breaking strength, and is useful as a tread material for low fuel consumption tires, large tires, and high performance tires, in the case where either carbon black or silica, or both, is used or in the case where a carbon-silica dual-phase-filler is used.
As a result of extensive studies, the present inventors have found that the above object can be achieved by an oil extended rubber comprising an amino group-containing copolymer rubber of a conjugated diolefin and an aromatic vinyl compound containing a specific amount of bonded amino groups and extensible oil at a specific proportion.
SUMMARY OF THE INVENTION
Specifically, the present invention provides the following oil extended rubber and rubber composition.
[1] An oil extended rubber comprising 100 parts by weight of (A) an amino group-containing copolymer rubber of a conjugated diolefin and an aromatic vinyl compound which contains bonded amino groups in the amount of 0.002-0.20 mmol/g polymer, and 10-100 parts by weight of (B) an extensible oil.
[2] The oil extended rubber of [1] above, wherein at least 40 wt % of the copolymer rubber of a conjugated diolefin and an aromatic vinyl compound (A) is a polymer modified by a compound selected from the group consisting of alkoxysilanes represented by the following formula (1), halogen-containing silicon compounds, ketone compounds, and tin compounds:
X
n
Si(OR)
m
R′
4−(m+n)
(1)
wherein X is a halogen atom, R is a hydrocarbon group having 1-20 carbon atoms, R′ is an alkyl group, aryl group, vinyl group, or alkyl halide group having 1-20 carbon atoms, m is an integer of 1-4, and n is an integer of 0-2, provided that m+n is 2-4.]
[3] The oil extended rubber of [1] or [2] above, wherein said copolymer rubber of a conjugated diolefin and an aromatic vinyl compound contains 40 wt % or more of a single chain aromatic vinyl compound unit consisting of an independently linked aromatic vinyl compound and less than 10 wt % of a long chain aromatic vinyl compound unit comprising 8 or more linked molecules of aromatic vinyl compound.
[4] The oil extended rubber described in any one of [1] to [3] above, wherein the Mooney viscosity (ML 1+4, 100° C.) of the copolymer rubber of a conjugated diolefin and an aromatic vinyl compound (A) is from 80 to 200.
[5] The oil extended rubber of any one of [1] to [4] above, wherein the molecular weight distribution of the copolymer rubber of a conjugated diolefin and an aromatic vinyl compound (A) represented by the ratio of the weight average molecular weight (Mw) and the number average molecular weight (Mn) (Mw/Mn) is from 1.3 to 3.0.
[6] The oil extended rubber described in any one of [1] to [5] above, wherein said extensible oil (B) is at least one oil selected from aromatic-type mineral oil having a viscosity gravity constant (V.G.C. value) of 0.900-1.049 (aromatic oil) and an alicyclic-type mineral oil having a viscosity gravity co
Akema Hiroshi
Kobayashi Naokazu
Tadaki Toshihiro
Harlan R.
JSR Corporation
Wu David W.
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