Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-08-18
2002-09-24
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
Reexamination Certificate
active
06455613
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a tire having a least one component comprised of a rubber composition which contains aggregates of fumed silica reinforcement. Such tire component may be a tire tread.
BACKGROUND OF THE INVENTION
Tires are conventionally prepared with components of various rubber compositions which contain particulate reinforcement in form of carbon black and/or amorphous silica.
While the amorphous silica reinforcement for such tire component rubber compositions are conventionally in a form of precipitated silica, it is to be appreciated that silica such as pyrogenic, or fumed, silica has sometimes also been suggested for such purpose.
As reported in the
Handbook of Fillers for Plastics
by H. S. Katz, et al (1987), published by Van Nostrand Reinhold Company, Pages 174 through 177, fumed silicas are fluffy white powders of an amorphous structure which may be produced, for example, by hydrolysis of silicon tetrachloride in a flame of hydrogen and oxygen at a temperature of, for example, about 1100° C. or 1800° C. in which molten spheres of fumed silica are formed (primary particles) which collide and fuse with one another to form three-dimensional, somewhat branched, chain-like particles (secondary particles) which may be referred to as aggregates.
Fumed silicas can be modified according to the above publication by reaction with silanol groups or by altering the flame process. Commercially available fumed silicas, according to the publication, may be divided into three groups, namely hydrophilic fumed silicas, hydrophobic fumed silicas and mixed oxide fumed silicas. The exemplary hydrophobic silica is created by reacting a hydrophilic silica with an organosilane such as, for example, dimethylchlorosilane.
Fumed silicas typically have smaller bulk densities (uncompacted) than precipitated silicas. For example, fumed silicas reported in the above publication in 1987 had associated bulk densities (uncompacted) ranging, for example, from 37 to 130 g/l. For example, representative Aerosol fumed silicas from Degussa in are reported as having bulk densities ranging from 50 or 130 g/l. Representative Cab-O-Sil fumed silicas from Cabot are reported as having bulk densities of 37 and 72 g/l. Representative HDK fumed silicas from Wacker are reported as having a bulk density of 60 g/l.
In the
Encyclopedia of Chemical Technology Third Edition
, Vol. 20 (1982) by Kirk-Othmer, Page 768, it is reported that a bulk density of pyrogenic silica may range from 30 to 1200 g/l and that a bulk density of precipitated silica may range from 30 to 3000 g/l.
In the description of the invention, the term “phr” relates to parts by weight of a particular ingredient per 100 parts by weight of rubber contained in a rubber composition.
The terms “rubber” and “elastomer” are used interchangeably unless otherwise indicated, and the terms “cure” and “vulcanize” may be used interchangeably unless otherwise indicated.
SUMMARY OF THE INVENTION
The invention relates to a tire having at least one component comprised of a rubber composition which contains aggregates of fumed silica reinforcement.
In accordance with this invention, a tire is provided having at least one component of a rubber composition comprised of, based upon 100 parts by weight of elastomer (phr),
A. 100 phr of at least one diene hydrocarbon based elastomer,
B. about 35 to about 100 phr of particulate reinforcement comprised of about 35 to about 100, alternately about 35 to 90, phr of a branched, fumed amorphous silica and from zero to about 65, alternately about 10 to about 65, phr of at least one additional particulate reinforcement selected from of carbon black, synthetic amorphous silica and silica treated carbon black, wherein said fumed silica aggregates contain hydroxyl groups (e.g. silanol groups) on their surface; wherein prior to mixing with said elastomer(s), said fumed silica aggregates have a pour density in a range of from about 40 to about 60 g/l and a specific density in a range of from about 3.8 to about 5 g/cm
3
; and wherein said filmed silica aggregates are
(1) blended with said elastomer(s) together with a silica coupler having a moiety reactive with said hydroxyl groups on the surface of said fumed silica and another moiety interactive with at least one of said diene-based elastomers, preferably an organosulfur silane of the general formula (I)
[X
m
(R
2
O)
3−m
Si—R
3
]
2
S
2
(I)
wherein X is a halogen radical, preferably a chlorine radical, R
2
is an alkyl radical having from 1 to 3 carbon atoms, preferably selected from methyl and ethyl groups; R
3
is an alkylene radical having from 1 to 18 carbon atoms, preferably from 2 through 4 carbon atoms; m is zero or an integer of from 1 through 3, preferably zero or an integer of 1 or 2; and z is an integer of from 2 to 8, preferably an average of 2 to about 2.6 or from about 3.5 to about 4, or
(2) pre-treated with an alkylsilane of the general formula (II) and thereafter blended with said elastomer(s) and said silica coupler:
X
n
—Si—R
4−n
(II)
wherein R is an alkyl radical having from 1 to 18 carbon atoms, preferably from 1 through 4 carbon atoms; n is an integer of from 1 through 3; X is a radical selected from the group consisting of halogens, preferably chlorine, and alkoxy radicals having from 1 through 3 carbon atoms, preferably selected from methyloxy and ethyl radicals; or
(3) pre-treated with at least one material prior to blending with said elastomer(s) selected from at least one of
a. hexamethyldisilazane;
b. an organosulfur silane of said general formula (I);
c. an organosulfur silane of the general formula (III)
(X)m(R
2
O)
3−m
Si—R
3
—SH (III)
wherein X is a halogen radical, preferably a chlorine radical; R
2
is an alkyl radical having from 1 to 18 carbon atoms, preferably selected from methyl and ethyl groups; R
3
is an alkylene radical having from 1 to 18 carbon atoms, preferably from 2 through 4 carbon atoms; m is zero or an integer of from 1 through 3, preferably zero or an integer of 1 or 2; and z is an integer of from 2 to 8, preferably an average of 2 to about 2.6 or from about 3.5 to about 4; and optionally in addition to the above materials.
d. an alkylsilane selected from said general formula (II).
In one aspect of the invention, said fumed silica is pre-treated with a combination of:
A. a material of the general formula (I) and of the general formula (II), and
B. a material of the general formula (II) and of the general formula (III),
In the practice of this invention, where said fumed silica is pre-treated with at least one material of the general formula (I) or (III), preferably said pre-treated fumed silica is blended with said elastomer(s) in the absence of said silica coupler unless an amorphous precipitated silica, silica treated carbon black or fumed silica which has not been so pre-treated is added to said elastomer(s) and where it is desired to blend a silica coupler with said elastomer on behalf of said un-pretreated silica materials.
A significant consideration of use of the specified branched fumed silica for reinforcement of a rubber tire component is its inherent substantial absence of water (about 0.1 to about 1.5 weight percent water), prior to mixing with the elastomer(s) as compared to a conventional synthetic amorphous precipitated silica (containing about 3.5 to about 8 percent water). This is considered herein to be significant because the relative lack of coordinated water on the surface of silica makes the silica surface more accessible to surface treatment, including said pre-treatment specified by this invention.
The fumed silica contemplated for use in tire components for the present invention is characterized by a relatively visibly branched, less than spherical, structure as opposed to fumed silica which has a relatively visibly more spherically oriented, although still somewhat branched structure. Apparently as a result of the more visibly branched structure, the fumed silica for the tire components of the prese
Weydert Marc
Zimmer Rene Jean
Michl Paul R.
The Goodyear Tire & Rubber Company
Young, Jr. Henry C.
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