Preparation of reinforced elastomer, elastomer composite,...

Details Preparation of reinforced elastomer, elastomer composite,... Preparation of reinforced elastomer, elastomer composite,...

2000-03-03

2001-11-06

Dawson, Robet (Department: 1712)

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...

C524S266000, C524S268000, C524S858000, C524S860000, C525S100000, C525S015000, C528S018000, C528S034000

Reexamination Certificate

active

06313220

ABSTRACT:

FIELD
This invention relates to the preparation of an elastomer which contains a dispersion of a reinforcing system formed in situ within an elastomer host by the interaction of a telechelic hydroxy and/or alkoxy terminated polysiloxane and a reticulating agent having a moiety comprised of at least two alkoxy groups. The invention further includes a rubber composition of at least two elastomers wherein one of said elastomers is a pre-formed composite of elastomer and the in situ formed reinforcement system. A tire having a component of such rubber composition, particularly a tire tread, is specifically contemplated.
BACKGROUND OF THE INVENTION
Elastomers are conventionally reinforced with particulate reinforcing fillers such as, for example, carbon black and sometimes amorphous silica, usually precipitated silica.
However, it may sometimes be desired to create the silica reinforcement in situ within an elastomer host in order to gain benefits of an enhanced dispersion of silica reinforcement within the elastomer.
Historically, it has heretofore been proposed to use a sol-gel process of creating a dispersion of silica in polysiloxane polymers such as poly(dimethylsiloxane) or (PDMS) elastomer(s) by in-situ formation of silica from a base-catalyzed sol-gel conversion of tetraethylorthosilicate (TEOS). For example see “Precipitation of Silica-Titania Mixed-Oxide Fillers Into Poly(dimethylsiloxane) Networks” by J. Wen and J. Mark;
Rubber Chem and Tech
. (1994), volume 67, No.5, (pages 806-819).
Historically, a process of preparing rubber products has been suggested by mixing the TEOS with a solution of unvulcanized rubber in an organic solvent and subjecting it to a sol-gel condensation reaction to provide a finely powdered silica. For example, see Japanese patent application publication 93/02152.
Historically, a composition has been suggested as comprising a base rubber and globular silica made by a sol-gel method and having an average particle diameter of 10-30 microns and specific surface area of 400-700 square meters per gram. The composition is suggested for use in a flap of a tire. For example, see Japanese patent application publication 6145429.
Historically, a tread rubber composition has been proposed as a composition of a base rubber and spherical silica prepared by a sol-gel transformation. For example, see Japanese patent application publication 6116440 and corresponding Japanese patent publication 2591569.
Historically, an in-situ formation of silica from a sol-gel reaction of TEOS in an organic solution of styrene/butadiene rubber, onto which a bis(3-triethoxysilylpropyl) tetrasulfide has been previously grafted to form triethoxysilyl groups, has been reported. (“The Effect of Bis(3-triethoxysilylpropyl) Tetrasulfide on Silica Reinforcement of Styrene-Butadiene Rubber” by Hashim, et al, in
Rubber Chem
&
Tech.
1998, Volume 71, Pages 289 through 299).
However, it is desired herein to provide an alternative process, and resulting product, of forming a filler reinforcement in situ within an elastomer host.
In the description of this invention, the term “phr” where used herein, and according to conventional practice, refers to “parts of a respective material per 100 parts by weight of rubber, or elastomer”.
In the description of this invention, the terms “rubber” and “elastomer” if used herein, may be used interchangeably, unless otherwise prescribed. The terms “rubber composition”, “compounded rubber” and “rubber compound”, if used herein, are used interchangeably to refer to “rubber which has been blended or mixed with various ingredients and materials” and such terms are well known to those having skill in the rubber mixing or rubber compounding art.
SUMMARY AND PRACTICE OF THE INVENTION
In accordance with this invention, a method is provided for preparing an elastomer/reinforcement system composite, said reinforcement system being formed in situ within an elastomer host, which comprises:
(A) blending in an organic solvent solution of an elastomer host,
(1) at least one telechelic hydroxy and/or alkoxy terminated polysiloxane,
(2) at least one reticulating agent having a moiety which comprises at least two alkoxy groups, and
(3) a catalytic amount of a catalyst to promote a reaction between said polysiloxane and said reticulating agent; allowing a catalyzed reaction to initiate and proceed between said polysiloxane and said reticulating agent within said elastomer host and to thereby form a reinforcement system for said elastomer host; and recovering said resulting composite; or
(B) blending, in an internal rubber mixer,
(1) at least one telechelic hydroxy and/or alkoxy terminated polysiloxane,
(2) at least one reticulating agent having a moiety which comprises at least two alkoxy groups, and
(3) a catalytic amount of a catalyst to promote a reaction between said polysiloxane and said reticulating agent; allowing a catalyzed reaction to initiate and proceed between said polysiloxane and said reticulating agent within said elastomer host and to thereby form a reinforcement system for said elastomer host; and recovering said resulting composite.
In one aspect, the in situ reaction may be conducted without an addition of water to the reaction system.
In the practice of the invention, said elastomer host may be selected from at least one of (1) homopolymers of conjugated dienes, copolymers of conjugated dienes, copolymers of conjugated diene with a vinyl aromatic compound, preferably selected from styrene and alpha-methylstyrene and more preferably styrene, (2) terpolymers of ethylene, propylene and a minor amount (e.g.: about 2 to about 8 weight percent) of a non-conjugated diene, and (3) a copolymer of isobutylene and a minor amount (e.g.: about 2 to about 10 weight percent) of a conjugated diene.
In the practice of this invention, said telechelic hydroxy and/or alkoxy terminated polysiloxane may be represented by the following general Formula (I):
wherein R is the same or different alkyl radical selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, and isobutyl radicals, preferably methyl radicals; wherein X is the same or different radical selected from hydroxyl and OR′ (alkoxy) radicals, preferably hydroxyl radicals, wherein R′ is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, and isobutyl radicals, preferably methyl radicals, and phenoxy radicals, where in R′ is represented as C
6
H
5-m
R″
m
, wherein R″ is a radical selected from methyl ethyl, n-propyl, isopropyl, n-butyl, and isobutyl; wherein m is from zero to five; and wherein n is zero or a number of from 2 to 500, alternatively from 1 to 200.
In the practice of this invention, said reticulating agent having a moiety comprised of at least two alkoxy groups is of at least one of the general formulas (IIA), (IIB), (IIC), (III), (IV) and (V):
M(OR
1
)
x
(R
2
)
y
  (IIA)
(R
1
O)
x
(R
2
)
y
M—O—M′(R
2
)
z
(R
2
)
w
  (IIB)
(R
1
O)
x
(R
2
)
y
M—(CH
2
)
r
—M′(R
2
)
z
(R
1
)
w
  (IIC)
wherein M and M′ are the same or different and are selected from silicon, titanium, zirconium, boron, and aluminum, preferably silicon, where R
1
and R
2
are individually selected from radicals having from 1 to 10 carbon atoms, as alkyl radicals having from one to four carbon atoms, preferably from methyl, ethyl, n-propyl, isopropyl, n-butyl, and isobutyl radicals, and a phenyl radical, wherein R
1
is preferably an ethyl radical and R
2
is preferably a methyl radical, and wherein the sum of each of x+y and w+z integers is equal to 3 or 4 depending upon the valence of the associated M or M′, as the case may be and is, therefore, 4 except when its associated M or M′ is boron or aluminum for which it is 3, and wherein r is from 1 to 15, preferably from 1 to 6;
Z—R
3
—S
j
—R
3
—Z  (III)
wherein j is a number in a range of from 2 to about 8 and the average for j is in a range of (A) about 2 to about 2.6 or (B) about 3.5 to about 4.5;
wherein Z is represented by the following formulas of which is preferably (Z3

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