Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-07-14
2002-08-27
Jagannathan, Vasu (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S146000, C524S154000, C524S492000, C524S548000, C524S560000, C524S571000, C524S574000, C524S575500, C152S209100
Reexamination Certificate
active
06441070
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a rubber composition containing an elastomer and a trivalent phosphorous compound-silica complex.
BACKGROUND OF THE INVENTION
Organosilicon compounds having ethoxy groups are commonly used in silica-filled natural and synthetic rubber compositions. Unfortunately, during the thermal mixing of such processing compositions, ethanol is released. Whereas use of organosilicon compounds benefits the properties of the silica-filled rubber, it is desired to achieve similar properties without the undesirable evolution of ethanol.
SUMMARY OF THE INVENTION
The present invention relates to the use of a trivalent phosphorous compound-silica complex in a mixture with an elastomer.
DETAILED DESCRIPTION OF THE INVENTION
There is disclosed a method for processing a rubber composition which comprises mixing
(i) 100 parts by weight of at least one elastomer; with
(ii) 1 to 150 phr of a trivalent phosphorous compound-silica complex.
There is also disclosed a rubber composition comprising an intimate mixture of
(i) 100 parts by weight of at least one elastomer; and
(ii) from 1 to 150 phr of a trivalent phosphorous compound-silica complex.
The present invention may be used to process rubbers or elastomers containing olefinic unsaturation. The phrase “rubber or elastomer” 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 containing olefinic unsaturation 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 one aspect the rubber is preferably a mixture of two 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.
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.
In addition to the above elastomers, halogenated copolymers of isobutylene and p-methyl styrene may be used. Typically, such copolymers have a ratio of isobutylene to p-methyl styrene in a range of about 50/1 to 7/1.
In practice, the halogenated copolymer may, for example, first be prepared by copolymerizing isobutylene and p-methyl styrene. Then the copolymer may be halogenated with a halogen, such as with bromine by bromination of the isobutylene/p-methyl styrene copolymer which occurs at the paramethyl position, yielding a benzyl bromide functionality. The degree of bromination can be typically varied from about 0.5 weight percent to about 2.5 weight percent bromine, based on the copolymer of isobutylene and p-methyl styrene. For the tire tread applications, it is considered herein that about 1.5 weight percent to about 2.5 weight percent bromine is preferred.
The following reference provide additional information relating to the preparation of such halogenated copolymers: (i) “A New Isobutylene Copolymer: Non-tire Uses”, D. Kruse and J. V. Fuscon,
Rubber & Plastics News
, Feb. 1, 1993.
Such a halogenated copolymer may, for example, have the following physical characteristics: Mooney viscosity, ML(1+8) at 125° C. in a range of about 35° C. to about 60° and a Tg in a range of about −50° to about −60° C.
Typically, the halogen for such halogenation is bromine. Thus, typically the halogenated copolymer is a brominated copolymer of isobutylene and p-methyl styrene.
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 amount of trivalent phosphorous compound-silica complex that is added to the rubber may vary widely depending on the type of rubber and other compounds presen
Halasa Adel Farhan
Hirst Robert Charles
Zanzig David John
DeLong John D.
Hendricks Bruce J.
Jagannathan Vasu
Shosho Callie E
The Goodyear Tire & Rubber Company
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