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
2001-02-01
2003-02-25
Cain, Edward J. (Department: 1714)
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...
C524S493000, C524S495000, C524S496000, C524S128000, C524S127000, C152S209500
Reexamination Certificate
active
06525128
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a rubber composition comprised of a halogenated (e.g. brominated) copolymer of isobutylene and p-methyl styrene elastomer reinforced with synthetic particulate silica-based reinforcement together with an organo phosphite to aid in enhancing the silica reinforcement of the halogenated isobutylene copolymer elastomer. Preferably, the rubber composition is comprised of a combination of a brominated copolymer of isobutylene and p-methyl styrene and at least one diene-based elastomer. The invention further relates to an article of manufacture, including a tire, having at least one component comprised of such rubber composition
BACKGROUND FOR THE INVENTION
Rubber compositions based upon sulfur curable diene derived elastomers which contain carbon-to-carbon double bond unsaturation in their elastomer backbone are usually reinforced with carbon black. However, they are sometimes reinforced with a combination of carbon black and synthetic silica particles. In some cases, it might be desired to use only silica reinforcement in the absence of carbon black.
A coupling agent is often used for such silica-containing rubber compositions to aid in enabling the silica to reinforce the rubber composition. Widely used coupling agents for such purpose are comprised of a moiety (e.g. an alkoxysilane moiety) which is reactive with hydroxyl groups (e.g. silanol groups) on the surface of the silica and another moiety (e.g. a polysulfide moiety) which is interactive with unsaturated elastomers which contain carbon-to-carbon double bonds in their elastomer backbone. Such silica coupling agent activity is believed to be well known to those skilled in such art.
However, saturated elastomers, which inherently do not have carbon-to-carbon double bond in their backbone, such as halogenated (e.g. brominated) copolymers of isobutylene and p-methyl styrene elastomers inherently do not respond to sulfur bonding or crosslinking in the manner of unsaturated diene-based elastomers.
Accordingly, coupling agents for the silica which rely upon an interaction with diene-based elastomers which contain carbon-to-carbon double bonds unsaturation in their backbone, namely polysulfide based couplers such as, for example bis(3-alkoxysilylalkyl) polysulfides, are considered herein to have limited value for coupling the silica to the elastomer, even when the rubber composition contains a diene hydrocarbon based elastomer, wherein the rubber composition has an appreciable amount of an elastomeric brominated copolymer of isobutylene and p-methyl styrene.
In practice, the aforesaid saturated halogenated copolymer elastomer might be prepared, for example, by first copolymerizing isobutylene and p-methyl styrene. Usually a ratio of isobutylene to p-methyl styrene in a range of about 50/1 to about 7/1 is used. The resulting copolymer is then halogenated with a halogen such as bromine which occurs at the paramethyl position, yielding a benzyl bromide functionality. The degree of bromination can typically be varied from about 0.5 to about 2.5, usually preferably about 1.5 to about 2.5, weight percent, based upon the copolymer of isobutylene and p-methyl styrene.
The following reference provides additional information relating to the preparation of such halogenated copolymers: “A New Isobutylene Copolymer; Non-tire Uses” by D. Kruse and J. Fusco,
Rubber & Plastics News
, Feb. 1, 1993.
Such brominated copolymer of isobutylene and p-methyl styrene may, for example, have an unvulcanized physical property such as a Mooney viscosity value (ML(1+8)) at 125° C. in a range of about 35 to about 60 and a Tg in a range of about −50° C. to about −60° C.
It is to be appreciated that such halogenated (e.g. brominated) copolymer elastomer has a completely saturated backbone as being devoid of carbon-to-carbon double bond unsaturation and therefore is uniquely useful for a rubber composition where stability of various of its physical properties desired when the rubber composition is exposed to atmospheric conditions which conventionally attack unsaturated diene-based elastomers and particularly influences of oxidation and ozone attack.
However, the utility for such halogenated saturated elastomers is limited because, as hereinbefore discussed, because of its lack of carbon-to-carbon double bonds, it is not considered as being reactive with sulfur and is therefore not ordinarily considered as being sulfur curable in a sense of diene hydrocarbon-based elastomers.
Historically, some organo phosphites have previously been recognized as being reactive with alkyl halides. For example, see
Introduction to Organic Chemistry
, 2
nd
Edition, by A. Steitwieser, Jr., and C. H Heathcock, Page 829, which refers to a Arbuzov-Michaelis reaction of a phosphite with an alkyl halide.
It is contemplated herein to apply such indicated alkyl halide activity of organo phosphites for enhancing the utilization of silica reinforcement of rubber compositions which contain a halogenated copolymer of isobutylene and p-methyl styrene.
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 rubber composition comprises, based upon parts by weight of ingredient per 100 parts by weight elastomer(s), phr:
(A) 100 phr of elastomer comprised of
(1) about 5 to about 100, alternately about 10 to about 50, phr of a halogenated copolymer of isobutylene and p-methyl styrene, wherein said halogen is selected from bromine or chlorine, preferably bromine,
(2) from zero to about 95, alternately about 50 to about 90, phr of at least one diene-based elastomer and
(B) about 10 to about 100, optionally about 15 to about 90, phr of particulate reinforcing filler comprised of
(1) from zero to about 100, alternately about 10 to about 85, phr of synthetic amorphous silica aggregates and, correspondingly,
(2) 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) 0.5 to 25, preferably 1 to 15, phr of an organo phosphite as a coupling agent selected from at least one of organo diphosphites selected from diisodecyl pentearythritol diphosphite, distearyl pentaerythritol diphosphite and pentearythritol diphosphite and organo monophosphites selected from the general formulas:
((OR)
2
—P—O—R′)
2
—R″ (II)
wherein each R radical is independently selected from alkyl radicals and phenyl radicals and alkyl substituted phenyl radicals; wherein said R alkyl radicals have from 1 to 18 carbon atoms, preferably from 1 through 4 or from 4 through 12, carbon atoms, and preferably selected from methyl, ethyl, propyl radicals, from propyl, butyl, octyl and ethylhexyl radicals or from phenyl radicals; wherein said alkyl radicals for said alkyl substituted phenyl radicals have from 3 to 9 carbon atoms, wherein R′ is a phenyl radical; and wherein R″ is selected from alkyl radicals having from 2 to 8 carbon atoms preferably selected from ethyl, propyl and butyl radicals;
wherein said organo phosphite is preferably selected from the organo phosphites of said formula (I);
wherein said organo phosphite is provided by one or more of the following:
(1) by mixing said organo phosphite with said elastomer(s) and said particulate reinforcing filler preferably in an internal rubber mixer,
(2) by pre-reacting said halogenated copolymer of isobutylene and p-methyl styrene with said organo phosphite prior to blending said reinforcing filler therewith,
(3)
Cain Edward J.
Lee Katarzyna W
The Goodyear Tire & Rubber Company
Young, Jr. Henry C.
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