Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
2000-06-07
2002-06-18
Short, Patricia A. (Department: 1712)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C524S306000, C524S311000, C525S177000
Reexamination Certificate
active
06405775
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a tire having a tread of a rubber composition which contains a low molecular weight polyester plasticizer. Representative of various low molecular weight polyesters are, for example, polyester sebacate, triethylene glycol caprate-caprylate, triethylene glycol diheptanoate, triethylene glycol dipelargonate, triethylene glycol dipelargonate and triethylene glycol di-2-ethylhexoate.
BACKGROUND OF THE INVENTION
High performance tires typically have rubber treads for which their surfaces intended to be ground-contacting are also intended to exhibit relatively high traction characteristics.
Accordingly, it is conventionally desired that the tread rubber composition of such high performance tire be relatively soft as evidenced by a relatively low hardness value, and/or to provide relatively high traction for the tread rubber as being predictive by a relatively higher hysteresis for the rubber composition as evidenced by higher tan delta and J″ physical properties.
In the description of this invention, the term “phr” is used to designate parts by weight of a material per 100 parts by weight of elastomer. In the further description, the terms “rubber” and “elastomer” may be used interchangeably unless otherwise mentioned. The terms “vulcanized” and “cured” may be used interchangeably, as well as “unvulcanized” or “uncured”, unless otherwise indicated.
SUMMARY AND PRACTICE OF THE INVENTION
In accordance with this invention, a tire having a tread of a rubber composition comprised of, based upon 100 parts by weight of conjugated diene-based elastomer (phr),
(A) 100 phr of at least one diene-based elastomer, and
(B) about 1 to about 20, alternatively about 2 to about 15, phr of low molecular weight polyester selected from at least one of polyester sebacate having a molecular weight in a range of about 1000 to about 3000 so long as it has a melting point below 0° C., triethylene glycol caprate-caprylate having molecular weight of about 430 formula weight, triethylene glycol diheptanoate having a molecular weight of about 388 formula weight, triethylene glycol dipelargonate having a molecular weight of about 420 formula weight and triethylene glycol di-2-ethylhexoate having a molecular weight of about 374 formula weight, preferably the polyester sebacate and the triethylene glycol caprate-caprylate.
Representative of said polyester sebacate is, for example, as PLASTHALL P-1070 from CP Hall. (melt point of about −22° C.)
Representative of said triethylene glycol caprate-caprylate is, for example, PLASTHALL 4141 from C P Hall (melt point of about −5° C.).
Representative of said triethylene glycol diheptanoate is, for example, TegMeR 703 from C P Hall.
Representative of said triethylene glycol dipelargonate is, for example, TegMeR 903 from C P Hall.
Representative of said triethylene glycol di-2-ethylhexoate is, for example as TegMeR 803 from C P Hall Company.
The above molecular weights and indicated freeze (melt) points are values reported by the C P Hall Company.
A significant characteristic of the various triethylene glycol materials recited for use in this invention is that they have molecular weights being preferably below 750.
In practice, various conjugated diene-based elastomers may be used for the tire tread such as, for example, homopolymers and copolymers of monomers selected from isoprene and 1,3-butadiene and copolymers of at least one diene selected from isoprene and 1,3-butadiene and a vinyl aromatic compound selected from styrene and alphamethyl styrene, preferably styrene.
Representative of such conjugated diene-based elastomers are, for example, cis 1,4-polyisoprene (natural and synthetic), cis 1,4-polybutadiene, styrene/butadiene copolymers (aqueous emulsion polymerization prepared and organic solvent solution polymerization prepared), medium vinyl polybutadiene having a vinyl 1,2-content in a range of about 15 to about 90 percent, isoprene/butadiene copolymers, styrene/isoprene/butadiene terpolymers, styrene/isoprene copolymers and 3,4-polyisoprene.
A significant aspect of this invention appears to be, although the mechanism may not be entirely understood, that use of the low molecular weight polyester sebacate in a conjugated diene-based elastomer composition intended for use as a high performance tire tread has been observed to increase both a rubber composition's 300 percent modulus and its hysteresis.
A significant aspect of this invention appears to be, although the mechanism may not be entirely understood, that use of the low molecular weight triethylene glycol caprate-caprylate in a conjugated diene-based elastomer composition intended for use as a high performance tire tread has been observed to reduce the room temperature hardness and RPA G′ 1% while maintaining the hysteretic properties and sometimes increasing the Strebler adhesion. As used herein the term “RPA” means rubber processing analyzer analytical equipment as produced by the Monsanto Company, and referred to as “RPA 2000”. The term “RPA G′ 1 percent” refers to the dynamic storage modulus “G′” at a one (1) percent strain (elongation) as determined by the RPA 2000 analytical equipment.
It is readily understood by those having skill in the art that the rubber composition would be compounded by methods generally known in the rubber compounding art, such as mixing the various sulfur-vulcanizable constituent rubbers with various commonly used additive materials such as, for example, curing aids, such as sulfur, activators, retarders and accelerators, plasticizers additives, such as oils and resins, fillers, pigments, fatty acid, zinc oxide, waxes, antioxidants and antiozonants and reinforcing materials such as, for example, carbon black, silica and clay. As known to those skilled in the art, depending on the intended use of the sulfur vulcanizable and sulfur vulcanized material (rubbers), the additives mentioned above are selected and commonly used in conventional amounts.
Typical amounts of processing oils, if used, comprise about 1 to about 50 phr. Such processing oils can include, for example, aromatic, napthenic, and/or paraffinic processing oils. Typical amounts of antioxidants comprise about 0.5 to about 5 phr. Representative antioxidants may be, for example, diphenyl-p-phenylenediamine and others, such as, for example, those disclosed in
The Vanderbilt Rubber Handbook
(1978), Pages 344 through 346. Typical amounts of antiozonants comprise about 0 to 5 phr. Typical amounts of fatty acids, if used, which can include stearic acid comprise about 0.5 to about 3 phr. Typical amounts of zinc oxide comprise about 1 to about 10 phr. Typical amounts of waxes comprise about 0 to about 5 phr. Often microcrystalline waxes are used. The vulcanization is conducted in the presence of a sulfur vulcanizing agent. Examples of suitable sulfur vulcanizing agents include elemental sulfur (free sulfur) or sulfur donating vulcanizing agents, for example, an amine disulfide, polymeric polysulfide or sulfur olefin adducts. Preferably, the sulfur vulcanizing agent is elemental sulfur. As known to those skilled in the art, sulfur vulcanizing agents are used in an amount ranging from about 0.5 to about 4 phr, or even, in some circumstances, up to about 8 phr.
Accelerators are used to control the time and/or temperature required for vulcanization and to improve the properties of the vulcanizate. In one embodiment, a single accelerator system may be used, i.e., primary accelerator. Conventionally and preferably, a primary accelerator(s) is used in total amounts ranging from about 0.5 to about 4, preferably about 0.8 to about 1.5, phr. In another embodiment, combinations of a primary and a secondary accelerator might be used with the secondary accelerator being used in smaller amounts (of about 0.05 to about 3 phr) in order to activate and to improve the properties of the vulcanizate. Combinations of these accelerators might be expected to produce a synergistic effect on the final properties and are somewhat better than those produced by use o
Fantozzi Justin Joseph
Maly Neil Arthur
Short Patricia A.
The Goodyear Tire & Rubber Company
Young, Jr. Henry C.
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