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
2000-09-14
2002-10-01
Michl, Paul R. (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...
Reexamination Certificate
active
06458882
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a conjugated diene-based rubber composition reinforced with particulate silica-based reinforcement together with tetrathiodipropionic acid as a non-silane containing coupling agent to aid in the reinforcement of the rubber composition with a particulate silica-based material and 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.
Such coupling agents might also be sometimes referred to as being adhesive agents insofar as use thereof to enhance reinforcement of various elastomer compositions with various silica-based materials such as, for example, aggregates of precipitated silica.
Historically, such coupling agents are conventionally 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 byproduct.
For various purposes, it may be desired to reduce or substantially, 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.
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-based elastomer,
(B) about 25 to about 100, optionally about 35 to about 90, phr of particulate reinforcing filler comprised of about 25 to about 100, alternately about 10 to about 70, phr of synthetic amorphous silica aggregates and, correspondingly, from zero to about 75, alternately about 10 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) a coupling agent as tetrathiodipropionic acid;
wherein said tetrathiodipropionic acid is mixed with said elastomer(s), according to one or more of the following:
(1) mixing said tetrathiodipropionic acid with said elastomer(s) and said particulate reinforcement, preferably in an internal rubber mixer,
(2) mixing said tetrathiodipropionic acid with said elastomer(s) and said particulate reinforcement, preferably in an internal rubber mixer, wherein said tetrathiodipropionic acid has been pre-reacted with said carbon black to form a carbon black composite thereof,
(3) mixing said tetrathiodipropionic acid with said elastomer(s) and said particulate reinforcement, preferably in an internal rubber mixer, wherein said tetrathiodipropionic acid has been pre-reacted with said silica treated carbon black to form a silica treated carbon black composite thereof,
(4) mixing said tetrathiodipropionic acid with said elastomer(s) and said particulate reinforcement, preferably in an internal rubber mixer, wherein said tetrathiodipropionic acid has been pre-reacted with
(a) a synthetic precipitated silica or
(b) an aqueous dispersion of colloidal silica particles from which a precipitated silica is recovered to form a silica composite thereof,
(5) mixing said tetrathiodipropionic acid with said elastomer(s) and said particulate reinforcement, preferably in an internal rubber mixer, according to any of said steps (1), (2), (3) or (4) 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 (I):
X
n
—Si—R
4−n
(I)
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,
(6) mixing said tetrathiodipropionic acid with said elastomer(s) and an alkylsilane of the said Formula (I) with said elastomer(s) and particulate reinforcement, preferably in an internal rubber mixer, and
(7) mixing said tetrathiodipropionic acid and said alkylsilane of Formula (I) with said elastomer(s) and said particulate reinforcement, preferably in an internal rubber mixer, wherein said tetrathiodipropionic acid and said alkylsilane of Formula (I) have all been pre-reacted with
(a) a synthetic precipitated silica or
(b) an aqueous dispersion of colloidal silica particles from a which a precipitated silica is recovered to form a silica composite thereof
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.
A significant aspect of this invention for the use of tetrathiodipropionic acid as a coupling agent is that the reaction, and therefore the coupling, of the terminal hydroxyl functional group of tetrathiodipropionic acid with the hydroxyl groups on the surface of the silica and/or surface of the silica of the silica treated carbon black (e.g. silanol groups) results in a formation of water instead of an alcohol.
In addition, it is contemplated that the non-silane coupler of this invention can be used in combination with a reduced amount of an alkoxysilane polysulfide coupling agent (e.g. a bis(3-ethoxysilylpropyl) disulfide or tetrasulfide) to reduce an evolution of an alcohol byproduct during the reaction thereof with hydroxyl groups (e.g. silanol groups) on the surface of a silica in the manufacture of rubber products.
The silica treated carbon black relates to carbon black which co
Pyle Kevin James
Sandstrom Paul Harry
Smith Richard Robinson
Wideman Lawson Gibson
Michl Paul R.
The Goodyear Tire & Rubber Company
Young, Jr. Henry C.
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