Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-02-23
2001-01-09
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S215000, C524S492000, C524S495000, C524S571000, C524S572000, C524S575000, C152S209120, C152S450000
Reexamination Certificate
active
06172137
ABSTRACT:
FIELD
This invention relates to a rubber composition composed of at least one elastomer and carbon black reinforcement therefor. Electrical conductivity adjustment of a rubber composition is contemplated. The invention also relates to a tire having a component thereof such as, for example, a tread.
BACKGROUND
Tires are typically prepared of treads of elastomer based rubber compositions which are conventionally carbon black reinforced. Sometimes tire tread rubber compositions may also be reinforced with silica by utilizing a combination of individual silica and carbon black particles. Typically the silica is a precipitated silica.
Often coupling agents are used with precipitated silica to assist in its reinforcement of elastomers with which the silica is mixed. Utilization of silica couplers for such purpose is well known to those skilled in such art.
It is appreciated that electrical conductivity of a rubber composition is reduced when silica replaces a portion of more conventional carbon black for reinforcing rubber compositions
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 rubber composition is provided which is comprised of
(A) 100 parts by weight of at least one diene-based elastomer selected from homopolymers of conjugated dienes, copolymers of conjugated dienes and copolymers of conjugated dienes with vinyl aromatic compounds such as styrene and alpha-methylstyrene;
(B) about 30 to about 110, alternatively about 30 to about 90, phr of reinforcing filler composed of (i) a carbon black composite containing integral silica on the surface thereof or (ii) about 20 to about 70, or even up to about 90, phr of said carbon black composite and at least one of (a) about 10 to about 80 phr of classical rubber reinforcing carbon black and (b) about 10 to about 80 phr of precipitated silica; wherein said carbon black composite is composed of carbon black having integral silica domains on the surface thereof; wherein said silica domains of said carbon black composite and said precipitated silica contain silanol groups on the surface thereof; wherein said carbon black of said carbon black composite and said classical carbon black contain hydroxyl groups on the surface thereof; and wherein the silicon to carbon ratio of said carbon black composite is in a range of about 0.1/1 to about 0.9/1.
(C) at least one coupling agent having a moiety reactive with the said silanol groups and said hydroxyl groups and another moiety interactive with at least one of said diene-based elastomers.
In one aspect of the invention, it is desired that the rubber composition is prepared by (a) thermomechanically working and mixing, in at least two sequential mixing steps, a mixture comprised of the said diene-based elastomer, carbon black composite, and optionally the said classical carbon black and/or precipitated silica, all in the absence of curatives cure accelerators (i) to a maximum temperature in a range of about 160° C. to about 180° C. and for a duration of time, upon reaching said maximum temperature, in a range of about 1 to about 10 minutes at a temperature within about 5° C. to about 100° C. of said maximum temperature or (ii) to a maximum temperature in a range of about 155° C. to about 165° C. and for a duration of time upon reaching said maximum temperature, in a range of about four to about twenty minutes at a temperature within about 5° C. to about 10° C. of said maximum temperature, followed by (b) a final thermomechanical mixing step in which sulfur curatives and cure accelerators are mixed with said mixture for about one to about four minutes to a temperature of about 90° C. to about 120° C.; whereas the rubber mixture is cooled to a temperature below about 40° C. between each of the aforesaid mixing stages.
Depending somewhat upon the rotor speed of the mixer, the fill factor and the rubber composition itself, the time to reach the maximum temperature may range from about 2 to about 5 minutes. The term “file factor” is believed to be well known to those having skill in such art as the portion of the volume of the internal mixer occupied by the rubber composition itself. Other parameters being equal, a rubber composition having a higher oil content will usually take a longer time to reach the maximum temperature.
In practice, an internal rubber mixer is preferred for the individual mixing steps.
In a further aspect of the invention, a tire is provided having a component of the rubber composition of this invention. Such tire components may include, for example, tread, wire coat, sidewall and chafer, although other tire components might also be composed of the rubber composition.
Preferably, a tire is provided having a tread composed of the rubber composition of this invention.
An interesting feature of this invention is an ability to adjust the electrical conductivity of a rubber composition by selecting the ratio of carbon black to silica in the carbon black composite used in this invention. This feature may become significant where traction enhanced by use of silica reinforcement is desired but, conversely, it is desired to minimize the electrical conductivity reduction effect of the silica. Here, a method of modifying the volume resistivity of the rubber composition and, thus, the tire component such as a tire tread of this invention comprises providing the rubber composition having an electrical volume resistivity from about 1000 ohm.cm to about at least 10 meg.ohm.cm and possibly even to 10 to the twelfth power or more ohm.cm by (i) selectively modifying the carbon black composite by selectively preparing it (modifying it) to have a silicon to carbon ratio in the aforesaid range of about 0.1/1 to about 0.9/1 and (ii) adjusting the content of said carbon black composite in the rubber composition within the aforesaid ranges. Usually an electrical resistivity in a range of about 1000 to about 10 meg ohm.cm is desired, although in some cases a higher electrical resistivity may have to be used if greater friction (eg tire tread traction) is desired for the rubber composition.
The carbon black composite for use in this invention may be prepared by (i) cofuming carbon black with silica at an elevated temperature in a manner to provide a composite of carbon black with integral discrete silica entities, or domains, primarily on the outer surface of the carbon or by (ii) coprecipitating carbon black and silica such as, for example, from a dispersion of carbon black in sodium silicate, to provide integral silica entities, or domains, on the outer surface of the carbon black
It is contemplated that the silica entities, or domains, on the surface of the carbon black of the carbon black composite are integral with the carbon black in a sense of being an actual part of the carbon black composite as compared to simple mixtures of carbon black and silica.
In the practice of this invention, it is to be appreciated that the carbon black conventionally has substituents on its surface such as, for example, hydroxyl groups as well as carboxyl, phenyl and quinone groups, which are generally considered to be reactive groups although for convenience, the hydroxyl groups are usually referred to in the description of this invention It is also to be appreciated that the silica conventionally has silanol groups on its surface. Both of such hydroxyl groups and such silanol groups are intended to be conventionally reactive with the aforesai
Agostini Giorgio
Edme Materne Thierry Florent
Teskin Fred
The Goodyear Tire & Rubber Company
Young, Jr. Henry C
LandOfFree
Rubber composition and tire having tread thereof 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 and tire having tread thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rubber composition and tire having tread thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2480414