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
2000-04-04
2003-06-03
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
Reexamination Certificate
active
06573324
ABSTRACT:
FIELD
The invention relates to a tire having at least one component comprised of a rubber composition which contains pre-hydrophobated precipitated silica aggregates. Such tire component may be, for example although not limited to, a tire tread, sidewall and/or sidewall insert. Such pre-hydrophobated precipitated silica aggregates are contemplated as being prepared, for example, by treatment of a colloidal silica with a combination of both an organomercaptosilane and an alkylsilane.
BACKGROUND OF THE INVENTION
Tires may be prepared with a rubber component which contains a precipitated silica which is hydrophobated in situ within the elastomer host by addition of both an, organomercaptosilane and an alkyl silane. For example, see U.S. Pat. No. 4,474,908.
Tires may also be prepared with a rubber component in which both an organosilyl polysulfide and an alkylsilane are individually added to a silica-containing rubber composition to treat the amorphous silica in-situ within the rubber host with both (1) a hydrophobating agent (the alkylsilane) and (2) a silica coupler (the organosilyl polysulfide compound). For example, see U.S. Pat. No. 5,780,538.
In practice, it is recognized that precipitated silica aggregates are typically hydrophilic (water attracting) in nature and, in order to aid in dispersing the silica aggregates in various rubber compositions, it is sometimes desired to make the silica aggregates more hydrophobic (water repelling) in nature and therefore more compatible with the rubber. Accordingly, and as described in the aforesaid U.S. Pat. Nos. 4,474,908 and 5,780,538, a hydrophobating agent may be added to a rubber composition in addition to the precipitated silica to combine with the silica in-situ within the rubber host to make the silica more hydrophobic in nature.
However, it is considered herein, for tire tread applications where enhanced properties such as, for abrasion resistance, are often sought, and particularly where a good homogeneous dispersion in the rubber host is often sought, that an in-situ modification of the amorphous silica within a viscous rubber host on a hit and miss basis, under relatively harsh high sheer and high temperature conditions is a relatively inefficient procedure of modifying the amorphous silica for use in rubber compositions which are intended to be silica reinforced, particularly where both an organosilane and alkyl silane are used which would compete within the rubber composition for reaction sites on the silica surface.
Accordingly, it is proposed herein to provide a tire having a component comprised of a rubber composition which contains particulate pre-hydrophobated precipitated silica aggregates where the silica aggregates are added to, or mixed with, the rubber composition in a pre-hydrophobated form instead of more inefficiently subsequently hydrophobating the silica aggregates in situ within the elastomer host.
Historically, according to U.S. Pat. Nos. 5,708,069 and 5,789,514 a silica gel may be derived by hydrophobating a silica hydrogel with both an organomercaptosilane and alkyl silane and drying the product. The resulting hydrophobated silica gel may be blended with natural rubber and/or synthetic rubber. This invention is intended to be exclusive of recovered silica gels and is intended to be limited to precipitated silica aggregates.
Also, historically, according to U.S. Pat. No. 5,750,610, an organosilicatemodified silica gel may be hydrophobated with both an organomercaptosilane and alkyl silane and the dried treated organosilicate-modified silica gel blended with natural rubber and/or synthetic rubber. This invention is intended to be exclusive of such modified silica gels.
A general description of silica gel and precipitated silica may be found, for example, in the
Encyclopedia of Chemical Technology
, Fourth Edition (1997), Volume 21, Kirk-Othmer, silica gel is described in Pages 1020 through 1023 as a “. . . coherent, rigid, continuous three-dimensional network of spherical particles of colloidal silica.” Precipitated silica is described on pages 1023 through 1026 as being “. . . composed of aggregates (or secondary particles) of ultimate (or primary) particles of colloidal-size silica that have not become linked in a massive gel network during the preparation process.” “Particulate silica powders have a more open structure with higher pore volume than do dried pulverized gels . . . ”.
The pre-hydrophobated precipitated silica aggregates for this invention are intended to be exclusive of silica gels of a three dimensional network of spherical particles as referenced in the above Encyclopedia of Chemical Technology.
A further descriptive discussion of silica gels and precipitated silicas may be found, for example, in U.S. Pat. No. 5,094,829 which, as such reference, is intended to be incorporated here in its entirety.
The proposal for this invention for a tire with a component of a rubber composition which contains pre-hydrophobated precipitated silica aggregates of elementary silica particles instead of precipitated silica aggregates which are hydrophobated in situ within the elastomer host with individually added hydrophobating compounds, by treatment of a colloidal silica by both an organomercaptosilane and an alkylsilane, is considered herein to be novel and a departure from past practice.
In the description of this invention, the term “phr” relates to parts by weight for a material or ingredient per 100 parts by weight elastomer(s)”. The terms “rubber” and “elastomer” are used interchangeably unless otherwise indicated. The terms “cure” and “vulcanize” are used interchangeably unless otherwise indicated.
SUMMARY AND PRACTICE OF THE INVENTION
In accordance with this invention, a tire is provided which contains at least one component comprised of a rubber composition comprised of, based on 100 parts by weight (phr) of diene-based elastomer,
(A) 100 phr of at least one hydrocarbon conjugated diene-based elastomer,
(B) about 10 to about 120, alternately about 40 to about 100, phr of reinforcing filler comprised of
(i) particulate, pre-hydrophobated precipitated silica aggregates, and optionally
(ii) about 2 to about 100, alternately about 2 to about 50, phr of at least one additional reinforcing filler selected from at least one of carbon black and an additional synthetic amorphous silica, wherein said pre-hydrophobated precipitated silica aggregates are pre-hydrophobated by treating silica in anaqueous colloidal form thereof with both an organomercaptosilane and an alkylsilane in a weight ratio of said organomercaptosilane to said alkylsilane in a range of from 10/90 to 90/10;
wherein said alkylsilane is of the general Formula (I)
X
n
—Si—R
4−n
(I)
wherein R is an alkyl radical having from one to 18, preferably from one to 8, carbon atoms such as, for example, methyl, ethyl, isopropyl, n-butyl and octadecyl radicals, n is a value of from 1 to 3 and X is a radical selected from halogen, namely chlorine or bromine, preferably a chlorine radical, and alkoxy radicals, preferably an alkoxy radical as (R
1
O)—, wherein R
1
is an alkyl radical having from one to 3 carbon atoms such as, for example, methyl, ethyl and isopropyl radicals, preferably from methyl and ethyl radicals, and where said organomercaptosilane is of the general formula (II):
(X)
n
(R
2
O)
3−n
—Si—R
3
—SH (II)
wherein X is a radical selected from halogen, namely chlorine or bromine, preferably a chlorine radical, and alkyl radicals having from one to 16, preferably from one to 4, carbon atoms, preferably selected from methyl, ethyl, n-propyl and n-butyl radicals; wherein R
2
is an alkyl radical having from one to 16, preferably from one to 4 carbon atoms, preferably selected from methyl and ethyl radicals and R
3
is an alkylene radical having from one to 16, preferably from one to 4, carbon atoms, preferably a propylene radical; n is a value from zero to 3, preferably zero.
The hydrophobated precipitated silica aggregates might be recovered, for example, from said treated colloidal silica, for
Cohen Martin Paul
Magnus Fredrick Lewis
Smith Richard Robinson
Cain Edward J.
The Goodyear Tire & Rubber Company
Young, Jr. Henry C.
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