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
1999-09-10
2001-06-26
Wu, David W. (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...
C525S326100, C525S331900, C525S332900, C525S333100, C525S333200, C525S333300, C152S209100, C152S209500
Reexamination Certificate
active
06251992
ABSTRACT:
FIELD
This invention relates to a rubber composition comprised of a combination of cis 1,4-polyisoprene rubber and at least one liquid hydroxyl terminated polyalkylene polymer and to such a composition being sulfur cured. The rubber composition can also contain an additional diene-based elastomer. The rubber composition contains reinforcement as carbon black or as carbon black and/or silica together with a coupling agent. The invention also relates to a tire having a tread of such rubber composition.
BACKGROUND
Tires are sometimes prepared with treads of rubber compositions comprised of diene-based elastomers which contain reinforcement as carbon black or as silica in combination with a coupling agent to aid in coupling the silica to diene-based elastomers.
A coupling agent for such purpose usually has a moiety which is reactive with hydroxyl groups on the silica (e.g.: silanol groups) and another moiety which is interactive with diene-based elastomers. Such philosophy is well known to those having skill in such art.
Representative of such coupling agents are, for example, bis-(3-alkoxysilanealkyl) polysulfides which contain from two to eight sulfur atoms in their polysulfide bridges, with an average of from 3.5 to 4.5 for a tetrasulfide material and an average of about 2 to about 2.6 for a disulfide material. For such coupling agent, the alkoxysilane is available to react with the silanol groups on the silica.
In the description of this invention, the term “phr” as used herein, and according to conventional practice, refers to “parts of a respective material per 100 parts by weight of rubber elastomer”. In the description of this invention, the terms “rubber” and “elastomer” can be used interchangeably, unless otherwise distinguished. The terms “rubber composition”, “compounded rubber” and “rubber compound” can be used interchangeably to refer to “rubber which has been blended or mixed with various ingredients and materials” and the terms “cure” and “vulcanize” may also be used interchangeably herein, unless otherwise noted and such terms are well known to those having skill in the rubber mixing or rubber compounding art.
PRACTICE AND SUMMARY OF THE INVENTION
This invention relates to a rubber composition comprised of at least one diene-based elastomer, composed primarily of cis 1,4-polyisoprene rubber, and at least one liquid hydroxyl terminated polyalkylene polymer, together with reinforcement as carbon black or as carbon black and/or silica together with a coupling agent; wherein said coupling agent is designed to have a moiety to react with the hydroxyl groups contained on the surface of the liquid polymer as well as hydroxyl groups on the surface of the silica and another moiety to interact with the diene-based rubber.
In accordance with this invention, a rubber composition is provided which is comprised of, based upon 100 parts by weight of its rubber component (phr), (A) 100 parts by weight (phr) of at least one diene-based elastomer comprised of (i) about 55 to about 100, alternatively about 75 to about 100 or about 90 to about 100, phr of cis 1,4-polyisoprene rubber and (ii) from zero to 45, alternatively about zero to about 25 or about 0 to about 10, phr of at least one other diene-based rubber selected from homopolymers and copolymers of conjugated diene and copolymers of at least one conjugated diene with a vinyl aromatic compound selected from styrene and alpha-methylstyrene, preferably styrene, (B) about one to about 50, alternatively about 2 to about 25 or about 2 to about 10, phr of a liquid hydroxyl terminated polyalkylene polymer; wherein the alkylene mer unit for said polyalkylene is selected from at least one of alkylene hydrocarbons containing from 2 to 5, alternatively from 2 to 4, carbon atoms, and wherein said polyalkylene polymer is (i) mono hydroxyl terminated with a primary hydroxyl group or (ii) di-hydroxyl terminated with primary hydroxyl groups, (C) about 20 to about 100, alternatively from about 35 to about 90, phr of particulate reinforcing filler as (1) carbon black or (2) carbon black and silica-based reinforcement; wherein said silica-based reinforcement is selected from at least one of amorphous silica, aluminosilicate and carbon black which contains silicon on its surface; wherein said silica-based reinforcement contains hydroxyl groups on its surface, together with a coupling agent for said silica-based reinforcement; wherein said coupling agent contains a moiety which is reactive with hydroxyl groups on the surface of said silica-based reinforcement and with hydroxyl groups of said hydroxyl terminated polyalkylene polymer groups and another moiety interactive with said elastomer(s).
In practice, it is preferred that said reinforcement is comprised of carbon black and silica-based reinforcement together with a coupling agent; wherein the weight ratio of said silica-based reinforcement to carbon black reinforcement is in a range of from 1/10 to 10/1.
In practice, the polyalkylene component for said polyalkylene of said hydroxyl terminated polyalkylene is derived by hydrogenating a polymer, prepared by organic solution polymerization, of at least one of isoprene and 1,3-butadiene, thereby yielding a hydroxyl terminated polyalkylene comprised of at least one of ethylene, propylene and butylene units.
Alternatively, such polyalkylene component may be a partially hydrogenated polymer of isoprene and/or 1,3-butadiene.
Preferably the polyalkylene component is a hydrogenated, or partially hydrogenated, polymer of isoprene or of 1,3-butadiene.
It is contemplated that the total hydrogenation of the polymer of isoprene and/or 1,3-butadiene provides a polymer having a saturated polyalkylene structure or a combination of saturated and unsaturated structure when partially hydrogenated.
In practice, it is preferred that said liquid hydroxyl terminated polyalkylene is mono-hydroxyl terminated or di-hydroxyl terminated with primary hydroxyl group(s); wherein for said di-hydroxyl terminated polyalkylene polymer, said hydroxyl terminal groups are primary hydroxyl groups.
In practice, said liquid hydroxyl terminated polyalkylene polymer preferably may have an equivalent weight range from about 250 to about 70,000, more preferably about 500 to about 7,000, so long as it is liquid at room temperature, or at about 23° C., namely that it is readily pourable at such temperature.
An example of suitable liquid hydroxyl terminated polyalkylene polymers are those available from Shell Chemical, namely, Kraton L-1203 for a mono-hydroxyl terminated polymer and Kraton L-2203 for a di-hydroxyl terminated polymer.
In practice, the cis 1,4-polyisoprene rubber may be natural rubber or synthetic rubber. Usually the natural rubber is preferred.
In the practice of this invention, various additional diene-based elastomers, or rubbers, may be used in combination with the cis 1,4-polyisoprene rubber. It is considered that the additional elastomer, as a diene-based elastomer, is a sulfur curable, (e.g.: vulcanizable), elastomer. The additional elastomers utilized in accordance with this invention may be derived from the polymerization of conjugated diene monomers which typically contain from 4 to 12 carbon atoms and preferably contain from 4 to about 8 carbon atoms. Representative examples of such conjugated diene monomers are preferably 1,3-butadiene and/or isoprene. The elastomer can also be a copolymer of such dienes with a vinyl aromatic monomers such as, for example, styrene and alpha-methylstyrene, preferably styrene.
Such additional elastomers may be selected from, for example, cis 1,4-polybutadiene, styrene-butadiene copolymers(SBR), isoprene/butadiene copolymers, styrene/isoprene copolymers, high vinyl polybutadiene having a vinyl 1,2- content in a range of about 40 to about 90 percent, 3,4-polyisoprene, trans 1,4-polybutadiene and styrene/isoprene/butadiene terpolymers.
Preferably, such additional elastomers are selected from cis 1,4-polybutadiene, butadiene/styrene copolymers, styrene/isoprene/butadiene terpolymers, isoprene/styrene copolymers and isoprene/butadiene cop
Harlan R.
The Goodyear Tire & Rubber Company
Wu David W.
Young, Jr. Henry C
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