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
2000-07-25
2003-01-14
Medley, Margaret (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...
C524S262000, C524S492000
Reexamination Certificate
active
06506829
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a silica-filled rubber compositions and their use in tires.
BACKGROUND OF THE INVENTION
Recently, there has been a lot of interest in the use of silica reinforcement of rubber for use in tire treads. Use of high reinforcing grades of silica are known to improve the treadwear of the tread rubber. Use of less reinforcing grades of silica are known to improve wet traction and rolling resistance.
SUMMARY OF THE INVENTION
The present invention relates to a rubber composition containing a blend of two different silicas.
DETAILED DESCRIPTION OF THE INVENTION
There is disclosed a rubber composition comprising (A) an elastomer containing olefinic unsaturation and (B) 35 to 110 phr of silica filler, wherein said silica filler is comprised of (i) 10 to 100 phr of a first silica having a pore size distribution maximum of the aggregates in the first silica ranging from greater than 55 to 400 nm as determined by mercury porosimetry and an average specific surface area ranging from 60 to 135 m
2
/g as determined by N
2
adsorption; and (ii) 10 to 100 phr of a second silica having a pore size distribution maximum ranging from 5 to 50 nm as determined by mercury porosimetry and an average specific surface area ranging from 140 to 250 m
2
/g as determined by N
2
adsorption.
In addition, there is disclosed a method of processing a rubber composition which comprises mixing
(i) 100 parts by weight of at least one sulfur vulcanizable elastomer containing olefinic unsaturation; and
(ii) 35 to 110 phr of total silica filler, the improvement comprising (a) initially dispersing in said elastomer from 10 to 100 phr of a high reinforcing grade silica characterized by a pore size distribution maximum ranging from 5 to 50 nm as determined by mercury porosimetry and an average specific surface area ranging from 140 to 250 m
2
/g as determined by N
2
adsorption; and thereafter (b) dispersing in said elastomer from 10 to 100 phr of a low reinforcing grade silica characterized by a pore size distribution maximum ranging from greater than 55 to 400 nm as determined by mercury porosimetry and an average specific surface area ranging from 60 to 135 m
2
/g as determined by N
2
adsorption.
The present invention relates to sulfur vulcanizable 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, 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. The preferred rubber or elastomers are polybutadiene and SBR.
In yet another aspect of the present invention, it is preferred to use a rubber or elastomer containing olefinic unsaturation and an additional functional group reactive with the sulfur containing organosilicon compounds of Formula I described later. Representative functional groups include halogens, such as C1 and Br; alkoxy groups, such as methoxy groups; and pseudohalogens, such as —SCN.
In yet another aspect of the invention, the elastomer containing olefinic unsaturation may be a siloxy-terminated polymer, such as siloxy-terminated styrene-butadiene copolymer, siloxy-terminated isoprene-butadiene copolymer and siloxy-terminated styrene-isoprene-butadiene terpolymer.
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
Agostini Giorgio
Edme Materne Thierry Florent
Frank Uwe Ernst
Visel Friedrich
Zimmer Rene Jean
Delong John D.
Hendricks Bruce J.
Medley Margaret
The Goodyear Tire & Rubber Company
LandOfFree
Rubber composition containing two silicas does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Rubber composition containing two silicas, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rubber composition containing two silicas will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3055234