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
2001-02-01
2003-06-17
Cain, Edward J. (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...
C524S493000, C152S209500
Reexamination Certificate
active
06579930
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to tires and vehicular tracks having minimal-marking rubber treads and particularly to skid steering, fixed axle, tire/wheel or track assemblies where said tire or vehicular track has a minimal-marking tread. In particular, such rubber tread has a surface intended to be ground-contacting which is also intended to be minimal-marking and having suitable physical properties for a tire tread.
BACKGROUND OF THE INVENTION
Tires and vehicular tracks are typically provided with rubber treads which contain carbon black reinforcement and also contain rubber staining amine-based antidegradants and sometimes rubber staining aromatic rubber processing oils.
However, sometimes tires and vehicular tracks are provided for vehicles which are intended to be driven over surfaces other than black-colored asphalt pavement, such as for example concrete, for which it is desired that their treads do not leave colored marks, especially black marks, on the surface when the vehicle itself is driven over the surface.
Particular tire treads marking problems are considered herein to be often evident for vehicles which control their direction of travel by what is known as “skid-steering”. For such skid-steering phenomenon, the vehicular front wheel, or track, is mounted on a fixed axle which is not allowed to pivot to enable the vehicle to change its direction of travel. In such case, the vehicle is turned by causing one wheel, or track as the case may be, to turn faster, or slower, than its opposite wheel, or track, on the other side of the vehicle. Thus the tread “slides” over the surface with a typical abrading away of a portion of the tread on the surface over which the tread skids.
Accordingly, the treads of such vehicular tires or tracks, as the case may be, which “skid-steer” have a relatively high rate of tread wear and incidence of marking of the surface over which the tread skids, even if the vehicle is a relatively slow moving vehicle.
For example, medium to small vehicles which rely upon skid steering to control their direction of travel may be used to haul rocks and dirt, as well as individuals over various paved road surfaces which may be of rough or smooth non-black colored surfaces (e.g. concrete) where it is desired that the treads to not excessively mark the surfaces with cosmetically unacceptable marks. Such paved surfaces may be, for example, a factory floor or a garage for parking the vehicle as well as a driveway associated with such garage.
Accordingly, it is desired to provide a tire and vehicular track with rubber treads that do not easily leave marks on a non-black substrate, or ground yet still has acceptable physical properties for a tread.
Vehicular tracks, as contemplated herein, are conventionally endless rubber tracks, usually positioned over at least two fixed axle vehicular wheels, normally a drive wheel for engaging an inner surface of the rubber track and driving the track and at least one vehicular driven wheel to aid in guiding the contorted path of the rubber track as it moves around the vehicular wheels to propel the associated vehicle over the ground.
The outer surface of the rubber track, namely its tread, is intended to be ground contacting and typically contains a plurality of raised rubber lugs designed to contact, or engage, the ground.
While it may be readily thought of to provide such a tread without, or with only a minimal amount of carbon black, and with an alternate reinforcing filler such as, for example, amorphous silica, there are other factors to take into consideration for the rubber composition to be resistant to marking of a non-black substrate and to also have appropriate physical properties.
For example, such treads preferably have a balance between good traction and resistance to wear.
It is recognized that it is well known to use various materials, and amounts of various individual materials, for tire treads such as, for example, carbon black reinforcement, amorphous silica (e.g. precipitated silica) reinforcement, rubber processing oil and antidegradants (particularly antioxidants), as well as individual elastomers, for example, cis 1,4-polyisoprene natural and synthetic rubber, cis 1,4-polybutadiene rubber and styrenelbutadiene copolymer rubber.
Indeed for tire and vehicular track treads intended to be non-marking for non-black substrates, it is considered herein that particular considerations should be made. For such purpose, this invention is primarily based upon the use of known materials used in what is considered herein to be novel, material-specific combinations for a tire tread.
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.
In the description of this invention, the term “phr” refers to parts of a respective material per 100 parts by weight of rubber, or elastomer. The terms “rubber” and “elastomer” may be used interchangeably unless otherwise indicate. The terms “cure” and “vulcanize” may be used interchangeably unless otherwise indicated.
SUMMARY AND PRACTICE OF THE INVENTION
In accordance with this invention, a minimal-marking tread intended to be ground-contacting for a tire or vehicular track wherein said tread is of a rubber composition which comprises, based upon 100 parts by weight rubber (phr),
(A) 100 parts by weight of at least one conjugated diene-based elastomer,
(B) about 35 to about 100, alternately about 40 to about 90, phr of particulate filler comprised of aggregate of synthetic amorphous silica and from about zero to about 7, alternately from one to about 5, and preferably zero, phr of carbon black,
(C) about 2 to about 5 phr of a phenolic-based antidegradant to the exclusion of an amine-based antidegradant,
(D) about five to about 15 of a paraffinic rubber processing oil which contains less than about 14 weight percent aromatic compound(s) to the exclusion of rubber processing oil containing greater than 15 weight percent of aromatic compounds and
(E) at least one coupling agent having a moiety reactive with hydroxyl groups contained on the surface of the said amorphous silica (e.g. silanol groups) and another moiety interactive with at least one of said diene-based elastomers.
Therefore, for the purposes of this invention, the tire, or track, tread rubber compositions do not necessarily have to be devoid of carbon black, and therefore may be of a black color, however, they are to contain only a minimal amount of carbon black, if any amount of carbon black at all. Accordingly, for many applications, it may be desired that the tread rubber compositions do not contain carbon black and are therefore reinforced with silica as described above. With such treads required to contain a relatively quantitative amount of silica and a minimal, if any, amount of carbon black, it is considered herein that it remains to be a challenge to provide such tread rubber compositions which have suitable physical properties for a tire or track tread.
In one aspect of the invention, said tread rubber is desired to be prepared by a sequential mixing process in at least one internal rubber mixer, which comprises, based upon parts by weight per 100 parts by weight rubber (phr)
(A) mixing in at least two sequential preparatory blending steps in at least one internal rubber mixer to a temperature in a range of about 100° C. to about 180° C. a blend of ingredients comprised of, based on 100 parts by weight rubber (phr)
(1) 100 parts by weight of at least one conjugated diene-based elastomer,
(2) about 35 to about 100, alternately about 40 to about 90, phr of particulate filler comprised of aggregates of synthetic amorphous silica having hydroxyl groups on its surface and from about zero to about
Herberger, Sr. James Robert
Lukich Lewis Timothy
Cain Edward J.
Lee Katarzyna W.
The Goodyear Tire & Rubber Company
Young, Jr. Henry C.
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