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
2000-03-10
2002-09-10
Wu, David W. (Department: 1713)
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...
C524S773000, C524S599000, C524S925000
Reexamination Certificate
active
06448318
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of processing rubber compositions containing soya fatty acids, sunflower fatty acids and mixtures thereof and the rubber compositions made therefrom.
BACKGROUND OF THE INVENTION
Processing aids are commonly used in both natural and synthetic rubber compositions. Representative examples of processing aids include petroleum and naphthenic oils. Such processing aids are used during the mixing, permitting incorporation of fillers and other ingredients rapidly with lower power consumption.
U.S. Pat. Nos. 4,870,135 and 4,895,911 relate to a method for enhancing the cure of a sulfur vulcanizable elastomer which comprises adding to the elastomer a mixture of tall oil fatty acids comprising
(a) from 28 to 55 percent by weight of oleic acid;
(b) from 25 to 40 percent by weight of linoleic acid;
(c) from 4 to 20 percent by weight conjugated linoleic acid; and
(d) from 0 to 8 percent by weight rosin acids.
SUMMARY OF THE INVENTION
The present invention relates to the thermomechanically mixing of a rubber composition containing a fatty acid selected from the group consisting of soya fatty acid, sunflower fatty acid and mixtures thereof.
DETAILED DESCRIPTION OF THE INVENTION
There is disclosed a method for processing a rubber composition which comprises thermomechanically mixing at a rubber temperature in a range of from 140° C. to 190° C. for a mixing time of from 4 minutes to 20 minutes,
(i) 100 parts by weight of at least one uncured elastomer containing olefinic unsaturation selected from the group consisting of natural rubber and conjugated diene homopolymers and copolymers and from copolymers of at least one conjugated diene and aromatic vinyl compound; with
(ii) 1 to 25 phr of a fatty acid selected from the group consisting of soya fatty acid, sunflower fatty acids and mixtures thereof.
There is also disclosed a rubber composition which is produced by the sulfur vulcanization of a rubber composition which had been previously thermomechanically mixed with 1 to 25 phr of a fatty acid selected from the group consisting of soya fatty acids, sunflower fatty acids and mixtures thereof.
The present invention may be used to process uncured 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 polymerizes 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 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/lisoprene/butadiene rubber, emulsion and solution polymerization derived styrenel/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.
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 parts by weight of rubber, or elastomer.”
The fatty acids for use in the present invention include soya fatty acids, sunflower fatty acids and mixtures thereof. Preferably, the fatty acid is soya fatty acids. The fatty acids are predominately 18 carbon straight chain fatty acids including linoleic acid and oleic acid. The representative weight percentages of the fatty acids may be determined according to ASTM D-803-65. The amount of linoleic acid generally ranges from 50 to 68 percent by weight. Preferably the amount of linoleic acid is approximately 51 to 52 percent. The amount of oleic acid generally ranges from 19 to 30 percent by weight. Preferably, the level of oleic acid is around 29 p
DeLong John D.
Harlan R.
Hendricks Bruce J.
The Goodyear Tire & Rubber Company
Wu David W.
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