Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-12-19
2004-02-03
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C526S173000, C526S335000, C526S337000, C526S340000, C526S347000, C525S241000, C525S331900, C525S332800, C525S342000, C525S365000, C525S367000
Reexamination Certificate
active
06686420
ABSTRACT:
BACKGROUND OF THE INVENTION
It is highly desirable for tires to have good wet skid resistance, low rolling resistance and good wear characteristics. It has traditionally been very difficult to improve a tire's wear characteristics without sacrificing its wet skid resistance and traction characteristics. These properties depend, to a great extent, on the dynamic viscoelastic properties of the rubbers utilized in making the tire.
In order to reduce the rolling resistance and to improve the treadwear characteristics of tires, rubbers having a high rebound have traditionally been utilized in making tire tread rubber compounds. On the other hand, in order to increase the wet skid resistance of a tire, rubbers which undergo a large energy loss have generally been utilized in the tire's tread. In order to balance these two viscoelastically inconsistent properties, mixtures of various types of synthetic and natural rubber are normally utilized in tire treads. For instance, various mixtures of styrene-butadiene rubber and polybutadiene rubber are commonly used as a rubbery material for automobile tire treads.
U.S. Pat. No. 6,103,842 and U.S. application Ser. No. 10/124,006 disclose processes and catalyst systems for the copolymerization of 1,3-butadiene monomer and styrene monomer into a styrene-butadiene or styrene-isoprene-butadiene copolymer having a high trans-1,4-polybutadiene content and having a random distribution of repeat units which are derived from styrene. It is also therein disclosed that styrene-isoprene-butadiene rubber made utilizing the catalyst system and techniques therein may be used in the preparation of tire tread rubber compounds which exhibit improved wear characteristics. What is not disclosed is that superior wear characteristics may be obtained using a low styrene content in the high trans random SIBR.
SUMMARY OF THE INVENTION
The current invention is directed to a pneumatic tire having at least one component comprising a high trans solution styrene-isoprene-butadiene rubber (HTSEBR) with a random distribution of repeat units which are derived from styrene. The invention is based on the highly surprising and unexpected discovery that a desirable balance of properties may be realized by using a HTSIBR with a low styrene content.
It is then an object of the present invention to provide a pneumatic tire having at least one component comprising a vulcanizable rubber composition, wherein the vulcanizable rubber composition comprises, based on 100 parts by weight of elastomer (phr), from about 30 to 100 phr of high trans random SIBR, and from about zero to about 70 phr of at least one additional elastomer, wherein the high trans random SIBR comprises from about 3 to about 30 percent by weight of styrene.
DESCRIPTION OF THE INVENTION
The pneumatic tire of the present invention has at least one component comprising a high trans solution styrene-isoprene-butadiene rubber HTSIBR. By HTSIBR, it is meant an SIBR produced by a solution method and having a percentage of trans-1,4-butadiene conformation in the polybutadiene segments of the polymer of greater than 60 percent by weight. Alternatively, suitable HTSIBR may have a percentage of trans-1,4-butadiene conformation in the polybutadiene segments of the polymer of greater than 70 percent by weight. Suitable HTSIBR may contain from about 3 to about 30 percent by weight of styrene. Alternatively, suitable HTSIBR may contain from about 3 to about 20 percent by weight of styrene. Alternatively, suitable HTSIBR may contain from about 3 to about 10 percent by weight of styrene.
Suitable HTSIBR may be made by any of the suitable solution polymerization methods as are known in the art. In one embodiment, suitable HTSIBR may be made using the methods of U.S. Pat. No. 6,103,842. In another embodiment, suitable HTSIBR may be made using the methods of U.S. application Ser. No. 10/124,006. Styrene-isoprene-butadiene rubbers so made may contain from about 2 weight percent to about 50 weight percent styrene, from about 2 to about 20 percent by weight of isoprene, and from about 50 weight percent to about 98 weight percent 1,3-butadiene. However, in some cases, the amount of styrene included will be as low as about 1 weight percent. In one embodiment of the present invention, suitable styrene-isoprene-butadiene rubber so made will contain from about 3 weight percent to about 30 weight percent styrene, from about 2 to about 20 percent by weight of isoprene, and from about 70 weight percent to about 97 weight percent 1,3-butadiene. In another embodiment, suitable styrene-isoprene-butadiene rubber will contain from about 3 weight percent to about 20 weight percent styrene, from about 2 to about 20 percent by weight of isoprene, and from about 80 weight percent to about 97 weight percent 1,3-butadiene. In another embodiment, suitable styrene-isoprene-butadiene rubber will contain from about 3 weight percent to about 10 weight percent styrene, from about 2 to about 20 percent by weight of isoprene, and from about 90 weight percent to about 97 weight percent 1,3-butadiene. These styrene-isoprene-butadiene rubbers typically have a melting point which is within the range of about below 44° C. Higher styrene content HTSIBR may exhibit no melting point.
The styrene-isoprene-butadiene rubber will typically have a glass transition temperature in a range of from about −90° C. to about −70° C.; alternatively from about −85° C. to about −75° C.
In suitable styrene-isoprene-butadiene rubbers containing less than about 30 weight percent bound styrene, the distribution of repeat units derived from styrene, isoprene and butadiene is essentially random. The term “random”, as used herein, means that less than 10 percent of the total quantity of repeat units derived from styrene are in blocks containing more than five styrene repeat units. In other words, more than 90 percent of the repeat units derived from styrene are in blocks containing five or fewer repeat units. About 20% of the repeat units derived from styrene will be in blocks containing only one styrene repeat unit. Such blocks containing one styrene repeat unit are bound on both sides by repeat units which are derived from 1,3-butadiene.
In suitable styrene-isoprene-butadiene rubbers containing less than about 20 weight percent bound styrene, less than 4 percent of the total quantity of repeat units derived from styrene are in blocks containing five or more styrene repeat units. In other words, more than 96 percent of the repeat units derived from styrene are in blocks containing less than five repeat units. In such styrene-isoprene-butadiene rubbers, over 25 percent of repeat units derived from styrene will be in blocks containing only one styrene repeat unit, over 60 percent of the repeat units derived from styrene will be in blocks containing less than 3 repeat units and over 90 percent of the repeat units derived from styrene will be in blocks containing 4 or fewer repeat units.
In suitable styrene-isoprene-butadiene rubbers containing less than about 10 weight percent bound styrene, less than 1 percent of the total quantity of repeat units derived from styrene are in blocks containing 5 or more styrene repeat units. In other words, more than 99 percent of the repeat units derived from styrene are in blocks containing 4 or less repeat units. In such styrene-isoprene-butadiene rubbers, at least about 50 percent of repeat units derived from styrene will be in blocks containing only one styrene repeat unit and over about 85 percent of the repeat units derived from styrene will be in blocks containing less than 3 repeat units.
Suitable styrene-isoprene-butadiene copolymers also have a consistent composition throughout their polymer chains. In other words, the styrene content of the polymer will be the same from the beginning to the end of the polymer chain. No segments of at least 100 repeat units within the polymer will have a styrene content which differs from the total styrene content of the polymer by more than 10 percent. Such styrene-isoprene-butadiene c
Halasa Adel Farhan
Verthe John Joseph Andre
Zanzig David John
Zuppo, III John Robert
DeLong John D.
Pezzuto Helen L.
The Goodyear Tire & Rubber Company
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