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
2001-01-08
2003-03-18
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, C524S495000, C524S496000, C524S261000, C524S424000, C525S349000
Reexamination Certificate
active
06534584
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a conjugated diene-based rubber composition reinforced with silica-based reinforcement together with a composite of carbon black supported non-silane coupling agent as 1-thioglycerol(3-mercapto-1,2-propanediol) and exclusive of 2,2′-benzothiazyl disulfide. The invention includes an article of manufacture, including a tire, having at least one component comprised of such rubber composition.
BACKGROUND FOR THE INVENTION
For various applications utilizing rubber compositions, carbon black and/or synthetic amorphous silica-based materials are conventionally used as particulate reinforcing fillers for the elastomer(s) of the rubber composition(s).
Often a coupling agent is used together with the silica in order to couple, or otherwise enhance, its elastomer reinforcement effect for the elastomer(s) and such use of a coupling agent is well known to those having skill in such art.
Historically, such coupling agents may be, for example, silane-based compounds which have one moiety (a silane-based moiety such as, for example, an alkoxysilane moiety) which is reactive with hydroxyl groups (e.g. silanol groups) on the surface of a synthetic amorphous silica and having another moiety (e.g. a polysulfide bridge) which becomes interactive with a conjugated diene-based elastomer.
For example, bis-(3-trialkoxysilylpropyl) polysulfides having an average of from 2 to 4 connecting sulfur atoms in their polysulfidic bridge are often used as a coupling agent (or adhesive) to enhance coupling of synthetic amorphous silicas, such as aggregates of precipitated silica, to various conjugated diene-based elastomers. Use of such coupling agents is well known to those having skill in such art.
However, use of silane-containing coupling agents, or adhesives, which rely upon a reaction between the silane and hydroxyl groups (e.g. silanol groups) on the surface of a synthetic amorphous silica typically releases an alcohol as a by-product of such reaction. For example, a reaction of a bis-(3-triethoxysilylpropyl) tetrasulfide coupling agent with silanol groups on the surface of a silica material releases ethanol as a by-product.
For various purposes, it may be desired to reduce or substantially eliminate, or even entirely eliminate such alcohol evolution created by an in situ reaction of said reactants, with an associated alcohol formation, within an elastomer host during the mixing of a rubber composition which contains such reactants.
It has heretofore been suggested to utilize, as a combination of materials for use as a non-silane coupling agent, a combination of 1-thioglycerol(3-mercapto-1,2-propanediol) and 2,2′-benzothiazyl disulfide including such combination where at least one of said materials is provided as being deposited on carbon black.
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 one aspect of this invention, a rubber composition is provided which comprises
(A) 100 parts by weight of at least one diene hydrocarbon based elastomer,
(B) about 25 to about 100, optionally about 35 to about 90, phr of particulate reinforcing filler comprised of about zero to about 100, alternately about 10 to about 70, phr of synthetic amorphous silica aggregates and, correspondingly, from zero to about 75, alternately about 5 to about 60, phr of at least one of carbon black and silica treated carbon black having domains of silica on its surface, wherein said silica aggregates and said silica domains on the surface of said treated carbon black contain hydroxyl groups (e.g. silanol groups) on their surface; and
(C) about 0.5 to about 10, preferably about 1 to about 7, phr of a coupling agent as 1-thioglycerol(3-mercapto-1,2-propanediol), exclusive of 2,2′-benzothiazyl disulfide, provided as a composite of carbon black and said 1-thioglycerol(3-mercapto-1,2-propanediol), in a weight ratio of said thioglycerol material to carbon black in a range of from about 1:10 to about 1:1;
wherein said coupling agent composite is mixed with said elastomer(s), according to one or more of the following:
(1) mixing said 1-thioglycerol(3-mercapto-1,2-propanediol)/carbon black composite and said particulate reinforcement in an internal rubber mixer;
(2) mixing said 1-thioglycerol(3-mercapto-1,2-propanediol)/carbon black composite with said elastomer(s) and said particulate reinforcement in an internal rubber mixer, wherein said particulate reinforcement includes at least one of said synthetic precipitated silica aggregates and said silica treated carbon black which has been pre-hydrophobated prior to mixing with said elastomers with an alkylsilane of the general formula (II):
X
n
—Si—R
4-n
(II)
wherein X is a radical selected from alkoxy radicals having from 1 through 3 carbon atoms, preferably selected from methoxy and ethoxy radicals, and from halogen radicals selected from at least one of chlorine and bromine radicals, preferably a chlorine radical; R is an alkyl radical having from 1 to 18 carbon atoms, preferably from 1 through 4 carbon atoms and more preferably selected from methyl and ethyl groups; and n is an integer of 1 through 3,
(3) mixing said 1-thioglycerol(3-mercapto-1,2-propanediol)/carbon black composite with said elastomer(s) and an alkylsilane of the said formula (II) with said elastomer(s) and particulate reinforcement in an internal rubber mixer, and
In further accordance with this invention, an article of manufacture is provided which contains at least one component comprised of the rubber composition of this invention.
In additional accordance with this invention, a tire is provided which contains at least one component comprised of the rubber composition of this invention.
In further accordance with this invention, a tire is provided having a tread comprised of the rubber composition of this invention.
Accordingly, the synthetic amorphous silica may be selected from aggregates of precipitated silica, which is intended to include precipitated aluminosilicates as a co-precipitated silica and aluminum, and from fumed (pyrogenically formed) silica, whereas the silica is preferably a precipitated silica.
Such precipitated silica is, in general, well known to those having skill in such art. For example, such precipitated silica may be precipitated by controlled addition of an acid such as, for example, hydrochloric acid or sulfuric acid, to a basic solution (e.g. sodium hydroxide) of a silicate, for example, sodium silicate, usually in the presence of an electrolyte, for example, sodium sulfate. Primary, colloidal silica particles typically form during such process which quickly coalesce to form aggregates of such primary particles and which are then recovered as precipitates by filtering, washing the resulting filter cake with water or an aqueous solution, and drying the recovered precipitated silica. Such method of preparing precipitated silica, and variations thereof, are well known to those having skill in such art.
The carbon black with domains of exposed silica on its surface may be, for example, carbon black prepared by treatment of carbon black by reaction of an alkyl silane (e.g. an alkoxy silane) with carbon black or by co-fuming carbon black and silica at an elevated temperature. For example, see U.S. Pat. Nos. 5,679,728 and 6,028,137.
In practice, as hereinbefore discussed, the said 1-thioglycerol(3-mercapto-1,2-propanediol)/carbon black composite, exclusive of 2,2′-benzothiazyl disulfide, is provided as being supported on a carbon black carrier, as a composite of said thioglycerol and carbon black, in order to promote an improved dispersion of the material thioglycerol coupling agent in the rubber composition. The thioglyce
Pyle Kevin James
Sandstrom Paul Harry
Smith Richard Robinson
Wideman Lawson Gibson
Hu Henry S.
The Goodyear Tire & Rubber Company
Wu David W.
Young, Jr. Henry C.
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