Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-04-17
2003-09-30
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S176000, C526S180000, C526S187000, C526S188000, C526S189000, C526S335000, C526S340000, C526S340200
Reexamination Certificate
active
06627715
ABSTRACT:
BACKGROUND OF THE INVENTION
It is highly desirable for tires to have good wet skid resistance, low rolling resistance, tear strength, and good wear characteristics. It has traditionally been very difficult to improve the wear characteristics of a tire without sacrificing 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 that undergo a large energy loss have generally been utilized in the tread of the tire. 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.
It is conventionally believed to be desirable for styrene-butadiene rubber that is utilized in tire tread compounds to have a high level of vinyl content (1,2-microstructure). It is also generally desirable for the repeat units which are derived from styrene to be randomly distributed throughout the polymer chains of the rubber. To achieve these objectives, styrene-butadiene rubbers are often synthesized by solution polymerization that is conducted in the presence of one or more modifying agents. Such modifying agents are well known in the art and are generally ethers, tertiary amines, chelating ethers or chelating amines. Tetrahydrofuran, tetramethylethylene diamine (TMEDA) and diethyl ether are some representative examples of modifying agents which are commonly utilized.
U.S. Pat. No. 5,284,927 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) a tripiperidino phosphine oxide, (b) an alkali metal alkoxide and (c) an organolithium compound.
U.S. Pat. No. 5,534,592 discloses a process for preparing high vinyl polybutadiene rubber which comprises polymerizing 1,3-butadiene monomer with a lithium initiator at a temperature which is within the range of about 5° C. to about 100° C. in the presence of a sodium alkoxide and a polar modifier, wherein the molar ratio of the sodium alkoxide to the polar modifier is within the range of about 0.1:1 to about 10:1; and wherein the molar ratio of the sodium alkoxide to the lithium initiator is within the range of about 0.01:1 to about 20:1.
U.S. Pat. No. 5,100,965 discloses a process for synthesizing a high trans polymer which comprises adding (a) at least one organolithium initiator, (b) an organoaluminum compound, (c) a group IIa metal alkoxide and (d) a lithium alkoxide to a polymerization medium which is comprised of an organic solvent and at least one conjugated diene monomer.
U.S. Pat. No. 5,100,965 further discloses that high trans polymers can be utilized to improve the characteristics of tire tread rubber compounds. By utilizing high trans polymers in tire tread rubber compounds, tires having improved wear characteristics, tear resistance and low temperature performance can be made. Such high trans polymers include, trans-1,4-polybutadiene, trans styrene-isoprene-butadiene terpolymers, isoprene-butadiene copolymers and trans-styrene-butadiene copolymers.
U.S. Pat. No. 6,103,842 discloses a catalyst system for synthesizing a highly random styrene-butadiene rubber having a high trans content by solution polymerization. The styrene-butadiene rubber made by the process of U.S. Pat. No. 6,103,842 can be utilized in tire tread rubbers that exhibit improved wear characteristics. The catalyst system disclosed by U.S. Pat. No. 6,103,842 consists essentially of (a) an organolithium compound, (b) a group IIa metal alkoxide and (c) a lithium alkoxide. U.S. Pat. No. 6,103,842 further discloses a process for synthesizing a random styrene-butadiene rubber having a low vinyl content by a process which comprises copolymerizing styrene and 1,3-butadiene under isothermal conditions in an organic solvent in the presence of a catalyst system which consists essentially of (a) an organolithium compound, (b) a group IIa metal alkoxide and (c) a lithium alkoxide.
U.S. Pat. No. 4,996,273 discloses a highly active anionic polymerization catalyst containing an organolithium compound, a barium, strontium or calcium compound, and a trialkylaluminum compound containing at least 13 carbon atoms per molecule. These catalyst systems are reported to produce butadiene polymers having a high 1,4-trans-dienyl content.
SUMMARY OF THE INVENTION
This invention is based upon the unexpected discovery that a group IIa metal containing catalyst system that is comprised of a) an organolithium compound, (b) a group IIa metal salt selected from the group consisting of group IIa metal salts of amino alcohols and group IIa metal salts of glycol ethers, and (c) an organoaluminum compound, will catalyze the polymerization of conjugated diolefin monomers, such as 1,3-butadiene and isoprene, into rubbery polymers having a high trans microstructure content. The group IIa metal containing catalyst systems of this invention can also be used to copolymerize one or more conjugated diolefin monomers with vinyl aromatic monomers into copolymer rubbers, such as styrene-butadiene rubber. High trans-1,4-polybutadiene rubber and styrene-butadiene rubber that is synthesized using the catalyst system of this invention is highly useful in the preparation of tire tread rubber compounds which exhibit improved wear and tear characteristics, such as tread compounds that contain high levels of silica.
The subject invention more specifically discloses a catalyst system which is comprised of (a) an organolithium compound, (b) a group IIa metal salt selected from the group consisting of group IIa metal salts of amino glycols and group IIa metal salts of glycol ethers, and (c) an organometallic compound selected from the group consisting of organoaluminum compound that contain less than 13 carbon atoms and organomagnesium compounds.
The subject invention also reveals process for synthesizing rubbery polymers having a high trans microstructure by a process that comprises polymerizing a conjugated diolefin monomer in an organic solvent in the presence of a catalyst system that is comprised of (a) an organolithium compound, (b) a group IIa metal salt selected from the group consisting of group IIa metal salts of amino glycols and group IIa metal salts of glycol ethers, and (c) an organometallic compound selected from the group consisting of organoaluminum compounds and organomagnesium compounds.
The present invention further discloses a catalyst system that is comprised of (a) an organolithium compound, (b) a group IIa metal salt selected from the group consisting of group IIa metal salts of amino glycols and group IIa metal salts of glycol ethers, wherein the group IIa metal is selected from the group consisting of beryllium and magnesium, and (c) an organometallic compound selected from the group consisting of organoaluminum compounds and organomagnesium compounds.
The present invention also discloses a catalyst system that is comprised of (a) an organolithium compound, (b) a group IIa metal salt of an amino glycols, and (c) an organometallic compound selected from the group consisting of organoaluminum compounds and organomagnesium compounds.
The subject invention further discloses a catalyst system that is comprised of (a) an organolithium compound, (b) a group IIa metal salt selected from the group consisting of group IIa metal salts of amino glycols and group IIa metal
Austin Laurie Elizabeth
Halasa Adel Farhan
Hsu Wen-Liang
Jasiunas Chad Aaron
Zuppo, III John Robert
Rockhill Alvin T.
Teskin Fred
The Goodyear Tire & Rubber Company
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