Resilient tires and wheels – Tires – resilient – Anti-skid devices
Reexamination Certificate
1998-01-29
2001-04-24
Hoke, Veronica P. (Department: 1714)
Resilient tires and wheels
Tires, resilient
Anti-skid devices
C152S905000, C524S099000, C524S262000, C524S426000
Reexamination Certificate
active
06220323
ABSTRACT:
FIELD
The invention relates to a rubber composition containing relatively low levels of carbon black and/or silica reinforcement together with a particulate calcium carbonate and selected modifier(s). The invention particularly relates to a tire with a component thereof, particularly a tire tread.
BACKGROUND
Rubber compositions are typically used for tire treads which may be optimized for various rubber composition properties to promote one or more of three tire properties; namely, traction, rolling resistance and treadwear.
In this regard, typically desirable physical properties for tire tread rubber compositions may include, for example, hysteresis, hardness and modulus. Some properties are normally indicated by their rebound properties, tangent delta (Tan. delta) at 0° C., and abrasion resistance. Hysteresis is conventionally related to Hot Rebound values. Such physical properties are well known to those having skill in the rubber compounding art and, in general, are considered to be somewhat predictive of tire tread performance.
More specifically, it is sometimes desired that a tire have a relatively low rolling resistance to enhance a vehicle's fuel economy. A lower hysteresis, usually evidenced by a higher hot rebound value, of a cured, or vulcanized, rubber composition is predictive of reduced heat build-up for the rubber composition and, therefore, of its utility for a relatively low rolling rubber composition for use as a tire tread.
It is often an accepted practice to reduce particulate reinforcement of a rubber composition to a relatively low level to reduce its hysteresis and thus, a predictive reduction in rolling resistance for a tire tread application. For example, where it might be desired to reduce a tire's rolling resistance by reducing hysteresis increasing hot rebound values of a rubber composition for a tire tread application, particulate reinforcement such as carbon black and/or silica might conventionally be reduced from a somewhat normal range of about 55 to about 80 phr to a reduced amount of such reinforcement in a range of about 30 to about 50, and particularly about 30 to about 45, phr. Such reduction in particulate reinforcement for a tire tread rubber for reduction in a tire's rolling resistance is well known to those having skill in such art.
However, commensurate with rolling resistance of the tire tread composition reduction by reducing reinforcing filler content, with other aspects of the rubber composition being essentially unchanged, the tire tread wear resistance often decreases, as may be evidenced by an increase in the tire's treadwear, and there is usually a degree of loss in tire tread traction. In one aspect, a tire's increase in treadwear can sometimes be predicted or somewhat correlated, reduction in the cured rubber composition's abrasion resistance.
Accordingly, it is desired herein to provide a tire tread rubber composition with reduced hysteresis (increased hot rebound values) while substantially maintaining an acceptable abrasion resistance, and usually an acceptable tire tread traction.
It is desired to provide such rubber composition with low levels of carbon black and/or silica reinforcement.
It is recognized herein that calcium carbonate has sometimes been used as a relatively low cost filler and extender for various polyolefin resins and some elastomers. However, it is believed herein that it has not been used in tire treads with a relatively low carbon black content together with specified modifier(s).
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 DESCRIPTION OF THE INVENTION
In accordance with this invention, a rubber composition is provided, and particularly a tire with a component of such composition, including a tire tread, which comprises (A) 100 parts by weight of elastomer consisting essentially of (1) at least one diene-based elastomer, or (2) a combination of diene-based elastomer and an epoxidized diene-based elastomer, preferably as a cis 1,4-polyisoprene natural rubber, (B) about 15 to about 45, alternatively about 25 to about 40, phr of particulate reinforcement selected from carbon black and/or precipitated silica, said silica having silanol groups on the surface thereof, (C) about 5 to about 50, alternatively about 10 to about 30, phr of particulate calcium carbonate and (D) at least one modifier comprised of at least one of dithiodipropionic acid, nicotinamide and bis-3(trialkoxysilylalkyl) polysulfide having an average of from 2.1 to about 4 sulfur atoms in its polysulfide bridge and where such alkyl groups contain from two to four carbon atoms.
In one aspect of the invention, wherein said elastomers are about (a) 5 to about 30 phr of epoxidized diene-based rubber, preferably epoxidized natural cis 1,4-polyisoprene rubber, containing about 20 to about 50 percent epoxidization and (b) about 95 to about 70 phr of said diene based rubber.
In one aspect, the said particulate reinforcement for the rubber composition may be composed of about 15 to about 30 phr of such carbon black without precipitated silica or about 13 to about 35 phr of precipitated silica and about 2 to about 20 phr of carbon black.
For the purposes of this invention, a significant aspect is the relatively low concentration of carbon black reinforcement in combination with the use of calcium carbonate and modifiers).
The modifier may be dithiodipropionic acid.
The modifier may be nicotinamide.
The modifier may be a bis-3(trialkoxysilylalkyl) polysulfide having from 2 to about 8, with an average of about 2.1 to about 4, sulfur atoms in its polysulfidic bridge. Usually an average of from 2.1 to about 2.5 or from about 3.2 to about 4 sulfur atoms are preferred for the polysulfidic bridge. Usually the trialkoxy groups are selected from trimethoxy and triethoxy groups and the remaining alkyl groups are selected from ethyl, propyl and butyl groups. Thus, such modifier might, for example, be selected from bis-1(trimethoxysilylpropyl) polysulfide and bis-3(triethoxysilylpropyl) polysulfide.
While it is recognized that such modifiers might also sometimes be known as silica couplers having a moiety reactive with silanol groups contained on the surface of the silica and another moiety, usually a polysulfide, interactive with one or more of said diene-based elastomers, in this case it appears that they serve to interact with the calcium carbonates.
Usually the modifier is present as a weight ratio of modifier to calcium carbonate in a range of about 1/100 to about 1/1, alternatively in a range of about 1/50 to about 1/5 or in a more limited range of about 1/20 to about 1/10.
Other forms of silica, including fumed silica which is different from precipitated silica, are not preferred.
Usually the calcium carbonate has a particle size average diameter in a range of about 50 to about 14,000 nanometers (nm).
In practice, the surface of the particulate calcium carbonate can be coated, if desired, to aid in its dispersion in a rubber composition. Such coating may be, for example, in a form of a polyolefinic material, particularly a saturated polyolefinic material.
FURTHER DETAILED DESCRIPTION
It is considered that this invention is particularly applicable where it is desired to endeavor to minimize tire tread rolling resistance and, namely to provide higher hot rebound values for a tire tread elastomer composition, but where it is also desired to substantially retain rubber composition physical properties such as, fo
Sandstrom Paul Harry
Sinsky Mark Samuel
Hoke Veronica P.
The Goodyear Tire & Rubber Company
Young, Jr. Henry C
LandOfFree
Composition and tire with tread containing calcium carbonate does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Composition and tire with tread containing calcium carbonate, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Composition and tire with tread containing calcium carbonate will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2511321