Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-01-12
2001-05-08
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S111000, C524S506000
Reexamination Certificate
active
06228908
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a polymer and a composition using said polymer. More particularly, the present invention relates to a novel functionalized polymer having excellent fracture properties, good abrasion resistance, excellent processability and a novel elastomeric composition for a tire tread using the functionalized polymer wherein the tire tread formed from the composition displays an highly balanced wet traction, rolling resistance ice and snow traction, and fracture property like wear performance.
BACKGROUND OF THE INVENTION
As tires for higher performance are being developed, a rubber having superior fracture properties, good abrasion resistance and low hysteresis loss (low rolling resistance) is desired as the rubber for the tire tread for such tires.
For decreasing the hysteresis loss, cis-1,4-polybutadiene rubber and the like are used. However, the polybutadiene rubber and the like do not have good fracture properties even though they have good abrasion resistance. As a rubber having a remarkably lower hysteresis loss, a solution polymerized butadiene-styrene rubber having the tin-carbon bond in the molecular chain has been developed. However, this rubber does not always have a good balance between wet grip and low rolling resistance.
An elastomeric composition for a tread in which carbon black alone is used as the filler for the rubber described above can realize the desired balance between various properties and performances to some degree. However, simultaneous improvement of wet grip and low rolling resistance to a higher degree has come to be required more urgently in recent years and it is difficult for the rubber described above to satisfy this requirement. In order to solve this problem, there have been disclosed elastomeric compositions in which white carbon such as silica is used alone or in combination with carbon black as the filler. The use of silica in tire tread compositions sometimes improves the balance between wet traction and traction in ice and snow. However, it has been known that diene polymers have low affinity with white carbon such as silica and it is difficult to obtain a homogeneously dispersed rubber composition by milling. To improve this drawback, a large amount of an expensive silane coupling agent is mixed together in many cases. However, since the use of these silane coupling agents in a rubber formulation generates a substantial amount of ethanol in a Banbury mixer, the coupled rubbery mixture may contain undesirable large bubbles that may form blisters or surface defects in the resultant formed articles. Silane coupling agent which is widely used in the rubber industry for this purpose contains free sulfur groups which are undesirable if present in a rubber formulation processed at high mixing temperatures because “scorching” of the rubber may occur. Scorching reduces the processability of the rubber or renders the rubber unusable.
In order to overcome many of these deficiencies the use of an elastomer having a functionality that interacts with silica was proposed. An example of such elastomeric composition is an elastomeric composition containing a polymer modified with an alkoxysilane compound at the end and a silica filler, as displayed in Japanese Patent Publication Showa 52(1977)-5071, Japanese Patent Application Laid-Open Nos. Showa 56(1981)-104906, Showa 62(987)-50346 and Showa 62(1987)-22/908. With these technologies, the physical properties of tires containing the silane modified rubbers, silica and other ingredients could be improved while reducing the necessary amount of the expensive additive Si-69. However, due to the reaction occurring between the silica filler and the hydrocarboxysilanes functionality of the polymers, Mooney viscosities of the resultant compounds were usually too high, thereby creating problems in mixing, in roll milling and in extruding processes. A countermeasure to the high Mooney viscosity was to reduce the molecular weight of the base diene polymer, however this solution created additional problems at the synthetic rubber plant where polymers are made on an industrial scale. These polymers could not be processed by drying to a final rubber bale because of the low molecular weight (Gum Mooney) of the hydrocarboxysilane terminated polymers. Also the raw, low molecular weight diene polymers were susceptible to “cold flow” during storage.
SUMMARY OF THE INVENTION
Thus, the object of the current invention is to provide a polymer composition having a workable molecular weight at synthesis in the polymer plant (e.g. no “hot flow” and “cold flow”), good processability during mixing and the extrusion (tubing) process at the tire plant, satisfying various required properties with a good balance and which is advantageous for practical use.
The present invention displays diene polymers or copolymers formed from a mixture of:
(a) from about 10 to about 70 percent by weight of a diene polymer or copolymer of a diene monomer and a vinyl aromatic hydrocarbon monomer containing carbon-tin bonds in the main polymer or copolymer chain; and
(b) from about 90 to about 30 percent by weight of a diene polymer or copolymer of a diene monomer and a vinyl aromatic hydrocarbon monomer containing terminals, formed by reacting living diene polymer or copolymer chains having organoalkali or organoalkaline earth metal terminals with a hydrocarboxysilane compound, such as an alkoxysilane compound, aryloxysilane compound and aralkyloxysilane compound or mixtures thereof.
The diene polymers or copolymers are prepared by a method referred to as primary partial coupling which involves first coupling a portion of the living diene polymer or copolymer chains obtained by anionic polymerization with a tin halide coupling agent and then terminating the remaining living polymer or copolymer chains with a hydrocarboxysilane compound, such as a alkoxysilane compound, aryloxysilane compound and/or aralkyloxysilane compound.
Elastomer compositions of the invention may contain: (a) from 20 to 100 percent by weight of said diene polymers or copolymers and (b) from 0 to 80 percent by weight of a rubber selected from the group consisting of natural rubber, polybutadiene rubber, styrene-butadiene rubber and mixtures thereof.
Accordingly, an object of the present invention is to provide a novel functionalized polymer having improved balance between raw polymer viscosity and mixed compound viscosity, useful in tire tread compositions having highly balanced wet traction, rolling resistance, traction in ice and snow, and fracture properties in the cured and white carbon reinforced states. To this end, the functionalized polymer of the present invention comprises a diene-type polymer having a portion of the diene-type polymer tin-coupled and having a portion of the diene-type polymer having terminal hydrocarboxysilane groups.
The elastomeric composition of the present invention comprises a rubber material containing a functionalized polymer in an amount of 10 or more parts by weight in 100 parts by weight of the rubber material, and a filler of 10 to 100 parts by weight based on 100 parts by weight of the rubber material, wherein the filler contains a white carbon, and the functionalized polymer comprises a diene-type polymer having a portion of the diene-type polymer tin-coupled and having a portion of the diene-type polymer having a hydrocarboxysilane group, such as an alkoxysilane group, an aryloxysilane group, or an aralkyloxysilane group.
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patent: 4482657 (1
Cole William M.
Graves Daniel F.
Hergenrother William L.
Lawson David F.
Oziomek James
Arndt Barbara E.
Bridgestone Corporation
Hornickel John H.
Moore Margaret G.
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