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
1999-10-12
2001-12-04
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...
C524S492000, C524S493000, C524S495000, C524S496000, C152S209100, C152S450000, C152S525000
Reexamination Certificate
active
06326424
ABSTRACT:
BACKGROUND OF THE INVENTION
It is desirable for a tire to exhibit good traction characteristics on wet and dry pavements, and for the tire to provide good treadwear and low rolling resistance. In order to reduce she rolling resistance of a tire, rubbers having a high rebound can be utilized in making the tires' treads. Tires made with such rubbers undergo less energy loss during rolling. The traditional problem associated with this approach is that the tire's wet traction and wet skid resistance characteristics are compromised. This is because good rolling resistance which favors low energy loss and good traction characteristics which favor high energy loss are viscoelastically inconsistent properties.
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. To further improve traction characteristics, silica is also commonly included in the tread rubber as a filler. However, such blends are not totally satisfactory for all purposes.
U.S. Pat. No. 4,843,120 discloses that tires having improved performance characteristics can be prepared by utilizing rubbery polymers having multiple glass transition temperatures as the tread rubber. These rubbery polymers having multiple glass transition temperatures exhibit a first glass transition temperature which is within the range of about −100° C. to −20° C. and exhibit a second glass transition temperature which is within the range of about −50° C. to 0° C. According to U.S. Pat. No. 4,843,120, these polymers are made by polymerizing at least one conjugated diolefin monomer in a first reaction zone at a temperature and under conditions sufficient to produce a first polymeric segment having a glass transition temperature which is between −110° C. and −20° C. and subsequently continuing said polymerization in a second reaction zone at a temperature and under conditions sufficient to produce a second polymeric segment having a glass transition temperature which is between −20° C. and 20° C. Such polymerizations are normally catalyzed with an organolithium catalyst and are normally carried out in an inert organic solvent.
U.S. Pat. No. 5,137,998 discloses a process for preparing a rubbery terpolymer of styrene, isoprene and butadiene having multiple glass transition temperatures and having an excellent combination of properties for use in making tire treads which comprises terpolymerizing styrene, isoprene and 1,3-butadiene in an organic solvent at a temperature of no more than about 40° C. in the presence of (a) at least one member selected from the group consisting of tripiperidino phosphine oxide and alkali metal alkoxides and (b) an organolithium compound.
U.S. Pat. No. 5,047,483 discloses a pneumatic tire having an outer circumferential tread where said tread is a sulfur-cured rubber composition comprised of, based on 100 parts by weight rubber (phr), (A) about 10 to about 90 parts by weight of a styrene, isoprene, butadiene terpolymer rubber (SIBR), and (B) about 70 to about 30 weight percent of at least one of cis 1,4-polyisoprene rubber and cis 1,4-polybutadiene rubber wherein said SIBR rubber is comprised of (1) about 10 to about 35 weight percent bound styrene, (2) about 30 to about 50 weight percent bound isoprene and (3) about 30 to about 40 weight percent bound butadiene and is characterized by having a single glass transition temperature (Tg) which is in the range of about −10° C. to about −40° C. and, further, the said bound butadiene structure contains about 30 to about 40 percent 1,2-vinyl units, the said bound isoprene structure contains about 10 to about 30 percent 3,4-units and the sum of the percent 1,2-vinyl units of the bound butadiene and the percent 3,4-units of the bound isoprene is in the range of about 40 to about 70 percent.
U.S. Pat. No. 5,272,220 discloses a styrene-isoprene-butadiene rubber which is particularly valuable for use in making truck tire treads which exhibit improved rolling resistance and tread wear characteristics, said rubber being comprised of repeat units which are derived from about 5 weight percent to about 20 weight percent styrene, from about 7 weight percent to about 35 weight percent isoprene and from about 55 weight percent to about 88 weight percent 1,3-butadiene, wherein the repeat units derived from styrene, isoprene and 1,3-butadiene are in essentially random order, wherein from about 25 percent to about 40 percent of the repeat units derived from the 1,3-butadiene are of the cis-microstructure, wherein from about 40 percent to about 60 percent of the repeat units derived from the 1,3-butadiene are of the trans-microstructure, wherein from about 5 percent to about 25 percent of the repeat units derived from the 1,3-butadiene are of the vinyl-microstructure, wherein from about 75 percent to about 90 percent of the repeat units derived from the isoprene are of the 1,4-microstructure, wherein from about 10 percent to about 25 percent of the repeat units derived from the isoprene are of the 3,4-microstructure, wherein the rubber has a glass transition temperature which is within the range of about −90° C. to about −70° C., wherein the rubber has a number average molecular weight which is within the range of about 150,000 to about 400,000, wherein the rubber has a weight average molecular weight of about 300,000 to about 800,000 and wherein the rubber has an inhomogeneity which is within the range of about 0.5 to about 1.5.
U.S. Pat. No. 5,231,153 and U.S. Pat. No. 5,336,739 disclose that alkyl tetrahydrofurfuryl ether compounds, having the structural formula:
wherein n is an integer from 5 to about 10, can be used as modifiers in the synthesis of polydiene rubbers, such as isoprene-butadiene rubbers. These patents specifically disclose the synthesis of isoprene-butadiene copolymers having high glass transition temperatures of −30° C., −32° C., −37° C. and −39° C. Some specific examples of alkyl tetrahydrofurfuryl ethers which are reported to be useful as modifiers include hexyltetrahydrofurfuryl ether, heptyltetrahydrofurfuryl ether, octyltetrahydrofurfuryl ether and nonyltetrahydrofurfuryl ether. Hexyltetrahydrofurfuryl ether reported to be highly preferred because its utilization does not result in the creation of obnoxious odors and its employment results in fast polymerization rates and the high vinyl contents.
SUMMARY OF THE INVENTION
It has been unexpectedly determined that isoprene-butadiene rubber having a high glass transition temperature within the range of about −40° C. to about −25° C. (high Tg IBR) can be loaded with silica as a filler and utilized in manufacturing tire treads that have outstanding performance characteristics. For instance, such tire treads offer lower hysteresis at high temperatures (improved rolling resistance) and higher hysteresis at low temperatures (improved wet traction characteristics). By utilizing high Tg IBR in tire tread compounds, the maximum benefits of silica compounding can be realized without the need for solution or emulsion styrene-butadiene rubber (SBR) in the tread rubber formulations.
The tire tread rubber formulations of this invention will normally contain about 60 phr (parts per 100 parts of rubber) to about 100 phr of the high Tg IBR. In other words, the tread rubber will normally contain at least 20 phr of the high Tg IBR and can contain up to 100 phr of the high Tg IBR. The tread compound will also contain 40 phr to 150 phr of a filler with the proviso that at least about 20 phr of silica is included in the filler. The tire tread compound will also contain a silica coupling agent.
This invention more specifically discloses a tire tread rubber composition which is comprised of (1) at least about 20 phr of an isoprene-butadiene rubber having a glass transition temper
Halasa Adel Farhan
Hsu Wen-Liang
Louis Olivier
Harlan R.
Rockhill Alvin T.
The Goodyear Tire & Rubber Company
Wu David W.
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