Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-02-27
2003-09-23
Mulcahy, Peter D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S262000, C524S264000
Reexamination Certificate
active
06624214
ABSTRACT:
BACKGROUND OF THE INVENTION
Nanomaterials are particles having a size of from 1 to 30 nanometers in diameter. Use of nanomaterials have been known in rubber. For example, in U.S. Pat. 4,644,988, there is disclosed a tire tread compound containing a styrene-butadiene copolymer rubber reinforced with a high structure carbon black designated as N103 and a particle size smaller than 20 nanometers. In addition, it is known from U.S. Pat. 4,474,908 that siliceous fillers having an ultimate particle size in the range of from 15 to 30 nanometers have been used in rubber. One advantage in using such nanomaterials in rubber is to improve the treadwear. Unfortunately, upon mixing nanomaterials in a rubber composition, such nanomaterials tend to reagglomerate and, therefore, increase the individual particle sizes which result in decreasing the benefits for which they are added. In addition, with increasing levels of nanomaterials in place of larger particles (>100 nanometers in diameter), the rubber becomes more hysteretic.
Precipitated spherical organosilicon particles having a core and a shell are disclosed in F. Bauman, et al., Adv. Materials, 1997, 9, No. 12, Pages 955 through 958. These particles are described as being soluble organosilicon micronetworks with spatially confined reaction sites.
SUMMARY OF THE INVENTION
The present invention relates to rubber compositions containing precipitated organosilicon particles having a core and shell.
DETAILED DESCRIPTION OF THE INVENTION
There is disclosed a rubber composition comprising:
(a) 100 parts by weight of at least one rubber containing olefinic unsaturation; and
(b) 1 to 150 phr of precipitated organosilicon particles having a core and a shell,
wherein the core is obtained by the condensation of at least one monomer of the formula:
R
1
—Si(OR
2
)
3
I
where R
1
is selected from the group consisting of hydrogen, methyl, ethyl, vinyl, alkoxy having from 1 to 4 carbon atoms, and phenyl; R
2
is selected from the group consisting of alkyls having from 1 to 4 carbon atoms and phenyl; and wherein said condensation of said monomer is in the presence of a surfactant; and
wherein the shell is obtained by the subsequent addition to the core of a monomer of the formula
R
3
—Si(OR
2
)
3
II
where R
3
is selected from the group consisting of
—CH═CH
2
, —CH
2
—CH═CH
2
,
&Parenopenst;CH
2
)
n
—SH and mixtures thereof; and
n is an integer of from 2 to 8.
The present invention may be used with rubbers or elastomers containing olefinic unsaturation. The phrase “rubber or elastomer containing olefinic unsaturation” is intended to include both natural rubber and its various raw and reclaim forms as well as various synthetic rubbers. In the description of this invention, the terms “rubber” and “elastomer” may be used interchangeably, unless otherwise prescribed. The terms “rubber composition”, “compounded rubber” and “rubber compound” 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. Representative synthetic polymers are the homopolymerization products of butadiene and its homologues and derivatives, for example, methylbutadiene, dimethylbutadiene and pentadiene as well as copolymers such as those formed from butadiene or its homologues or derivatives with other unsaturated monomers. Among the latter are acetylenes, for example, vinyl acetylene; olefins, for example, isobutylene, which copolymerizes with isoprene to form butyl rubber; vinyl compounds, for example, acrylic acid, acrylonitrile (which polymerize with butadiene to form NBR), methacrylic acid and styrene, the latter compound polymerizing with butadiene to form SBR, as well as vinyl esters and various unsaturated aldehydes, ketones and ethers, e.g., acrolein, methyl isopropenyl ketone and vinylethyl ether. Specific examples of synthetic rubbers include neoprene (polychloroprene), polybutadiene (including cis-1,4-polybutadiene), polyisoprene (including cis-1,4-polyisoprene), butyl rubber, halobutyl rubber such as chlorobutyl rubber or bromobutyl rubber, styrene/isoprene/butadiene rubber, copolymers of 1,3-butadiene or isoprene with monomers such as styrene, acrylonitrile and methyl methacrylate, as well as ethylene/propylene terpolymers, also known as ethylene/propylene/diene monomer (EPDM), and in particular, ethylene/propylene/dicyclopentadiene terpolymers. Additional examples of rubbers which may be used include silicon-coupled and tin-coupled star-branched polymers. The preferred rubber or elastomers are polybutadiene and SBR.
In one aspect the rubber is preferably of at least two of diene based rubbers. For example, a combination of two or more rubbers is preferred such as cis 1,4-polyisoprene rubber (natural or synthetic, although natural is preferred), 3,4-polyisoprene rubber, styrene/isoprene/butadiene rubber, emulsion and solution polymerization derived styrene/butadiene rubbers, cis 1,4-polybutadiene rubbers and emulsion polymerization prepared butadiene/acrylonitrile copolymers.
In one aspect of this invention, an emulsion polymerization derived styrene/butadiene (E-SBR) might be used having a relatively conventional styrene content of about 20 to about 28 percent bound styrene or, for some applications, an E-SBR having a medium to relatively high bound styrene content, namely, a bound styrene content of about 30 to about 45 percent.
The relatively high styrene content of about 30 to about 45 for the E-SBR can be considered beneficial for a purpose of enhancing traction, or skid resistance, of the tire tread. The presence of the E-SBR itself is considered beneficial for a purpose of enhancing processability of the uncured elastomer composition mixture, especially in comparison to a utilization of a solution polymerization prepared SBR (S-SBR).
By emulsion polymerization prepared E-SBR, it is meant that styrene and 1,3-butadiene are copolymerized as an aqueous emulsion. Such are well known to those skilled in such art. The bound styrene content can vary, for example, from about 5 to about 50 percent. In one aspect, the E-SBR may also contain acrylonitrile to form a terpolymer rubber, as E-SBAR, in amounts, for example, of about 2 to about 30 weight percent bound acrylonitrile in the terpolymer.
Emulsion polymerization prepared styrene/butadiene/acrylonitrile copolymer rubbers containing about 2 to about 40 weight percent bound acrylonitrile in the copolymer are also contemplated as diene based rubbers for use in this invention.
The solution polymerization prepared SBR (S-SBR) typically has a bound styrene content in a range of about 5 to about 50, preferably about 9 to about 36, percent. The S-SBR can be conveniently prepared, for example, by organo lithium catalyzation in the presence of an organic hydrocarbon solvent.
A purpose of using S-SBR is for improved tire rolling resistance as a result of lower hysteresis when it is used in a tire tread composition.
The 3,4-polyisoprene rubber (3,4-PI) is considered beneficial for a purpose of enhancing the tire's traction when it is used in a tire tread composition. The 3,4-PI and use thereof is more fully described in U.S. Pat. No. 5,087,668 which is incorporated herein by reference. The Tg refers to the glass transition temperature which can conveniently be determined by a differential scanning calorimeter at a heating rate of 10° C. per minute.
The cis 1,4-polybutadiene rubber (BR) is considered to be beneficial for a purpose of enhancing the tire tread's wear, or treadwear. Such BR can be prepared, for example, by organic solution polymerization of 1,3-butadiene. The BR may be conveniently characterized, for example, by having at least a 90 percent cis 1,4-content.
The cis 1,4-polyisoprene and cis 1,4-polyisoprene natural rubber are well known to those having skill in the rubber art.
The term “phr” as used herein, and according to conventional practice, refers to “parts by weight of a respective material per 100 p
Frank Uwe Ernst
Lauer Wolfgang
Visel Friedrich
Weydert Marc
Zimmer Rene Jean
DeLong John D.
Hendricks Bruce J.
Mulcahy Peter D.
The Goodyear Tire & Rubber Company
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