Resilient tires and wheels – Tires – resilient – Anti-skid devices
Reexamination Certificate
2001-02-09
2004-07-13
Maki, Steven D. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Anti-skid devices
C152S209160, C152S523000, C152S525000, C152S902000
Reexamination Certificate
active
06761198
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a pneumatic rubber tire having a rubber sidewall of a lug and groove configuration which is designed to be ground contacting. Such sidewall configuration is of a rubber composition comprised of a blend of natural rubber and cis 1,4-polybutadiene rubber which contains specified carbon black reinforcement and silica together with a coupling agent. The tire tread rubber composition differs from the rubber composition of said sidewall lug and groove configuration by being exclusive of silica and coupling agent and carbon black reinforcement exclusive of said specified carbon black.
BACKGROUND OF THE INVENTION
Pneumatic rubber tires are conventionally composed of a toroidal carcass with a circumferential tread and adjoining sidewalls.
The tread is conventionally designed to be ground-contacting and thereby is of a suitable rubber composition for such purpose and also is of a suitable configuration. For example, such a tread may have properties which emphasize good traction and resistance to treadwear. Such tires may have a tread of a lug and grove configuration which is designed to be ground-contacting.
In contrast, the associated sidewalls are conventionally not designed to be ground contacting and, in order to be appropriately supportive of the tread, are conventionally composed of a rubber composition which is not designed for traction and resistance to treadwear but, instead, of a rubber composition which is of low hysteresis to provide low heat buildup and is softer to provide greater flexibility than that of the tread rubber.
As a result, such softer sidewall rubber compositions typically have less resistance to puncturing objects, abrasion and to scuffing against road curbs or other objects.
However, some tires are desired to be utilized under more harsh conditions such as, for example, rough roads or off-the-road service or on specialty vehicles which may be designed to run on low inflation tires where the tire sidewall may come in contact with the ground. Such circumstances may occur, for example, in various mine operations and in logging operations, or where the tire is run over rough terrain at low inflation pressures. Under such conditions, growth of a crack, or cut, in the sidewall and, also, resistance to puncture, are significant considerations.
A significant need for a sidewall rubber composition for such use is a hybrid rubber composition which with suitable resistance to puncture and abrasion typically associated with tread rubber compositions while substantially maintaining flex fatigue and hysteretic properties typically associated with sidewall rubber compositions.
It is appreciated that commercially available tires may sometimes have sidewalls designed to be resistant to cut growth which are comprised of carbon black reinforced elastomer compositions comprised of natural rubber and cis 1,4-polybutadiene rubber.
It is also appreciated that carbon blacks for reinforcement of tire sidewall rubber compositions are conventionally of appreciably larger particle size than carbon blacks usually used for tire treads since resistance to heat buildup rather than abrasion resistance is typically more important for tire sidewalls.
Such carbon black might be exemplified, for example, by having an Iodine value (number) (ASTM D1510) in a range of about 35 to about 85 g/kg instead of a higher iodine value of at least about 105 which would be more representative of a carbon black typically used for a tread rubber composition.
Here, however, it is desired to provide a novel tire with rubber sidewall of a composition comprised of natural rubber and cis 1,4-polybutadiene of which a significant portion is designed to be occasionally ground-contacting and thereby having a resistance to puncture as well as resistance to abrasion more typical of tire tread rubber compositions yet substantially retaining flexibility and low hysteresis usually required for a tire sidewall.
It may be readily thought of to increase the natural rubber content of the sidewall composition in order to increase resistance to tear. However the cis 1,4-polybutadiene content would be correspondingly reduced which would be expected to thereby undesirably reduce its resistance to abrasion and undesirably increase its hysteresis (as would be expected to be evidenced by a reduction in its rebound property).
Accordingly, it is desired herein to provide such a tire sidewall of a rubber composition which contains large particle size carbon black reinforcement common for sidewall compositions and which is composed of natural rubber and cis 1,4-polybutadiene elastomers, also somewhat common to many sidewall compositions but, however, which has enhanced resistance to abrasion and puncturing objects and, also enhanced resistance to tear more common to tire tread rubber compositions.
In the description of this invention, the term “phr” relates to parts by weight of an ingredient per 100 parts by weight of rubber.
The terms “rubber” and “elastomer are used interchangeably.
The term “Tg” relates to a glass transition temperature of an elastomer, normally determined by a differential scanning (DSC) calorimeter with a temperature rise of 10° C. per minute.
Disclosure and Practice of the Invention
In accordance with this invention, a pneumatic rubber tire is provided with a carcass with circumferential rubber tread and associated sidewalls, wherein said tread and a portion of said sidewalls are of a lug and groove configuration designed to be ground-contacting, wherein said lug and groove configuration extends from said tread over at least thirty, alternatively at least fifty, percent of the tire sidewall adjacent to said tread, and alternately at least to a maximum section width of the tire, and wherein
(A) the said lug and groove configured portion of said sidewall is of a rubber composition which comprises, based on 100 parts by weight rubber (phr),
(1) elastomers comprised of
(a) about 40 to about 80, preferably about 45 to about 70, phr of cis 1,4-polyisoprene natural rubber and
(b) about 20 to about 60, preferably about 30 to about 55, phr of cis 1,4-polybutadiene rubber,
(2) about 55 to about 80 phr of reinforcing filler comprised of carbon black and precipitated silica which is comprised of
(a) about 5 to about 40 phr of carbon black having an Iodine value (ASTM D1510) of about 35 to about 85 g/kg and a dibutylphthalate (DBP) value (ASTM D2414) of about 70 to about 130 cm3/100 g and
(b) about 10 to about 70 phr of precipitated silica having a BET surface area of about 125 to about 200 m2/g; wherein the weight ratio of silica to carbon black is in a range of about 0.3/1 to about 3/1, preferably about 0.8/1 to about 1.5/1, and wherein said rubber composition is exclusive of carbon blacks having an Iodine value of greater than 85 g/kg, and
(3) a coupling agent having a moiety reactive with silanol groups on said silica and another moiety interactive with said elastomers, and
(B) wherein the rubber composition of said circumferential tread, other than said rubber composition of said lug and groove configuration of said tire sidewall, is comprised of, based on 100 parts by weight rubber (phr):
(1) at least one diene based elastomer selected from polymers of isoprene and 1,3-butadiene and their mixtures and copolymers of isoprene, 1,3-butadiene and their mixtures with styrene,
(2) about 30 to about 95, alternately about 40 to about 75, phr of carbon black having Iodine value in a range of about 100 to about 145 g/kg and a DBP value in a range of about 110 to about 145 cm3/100 g;
wherein said tread rubber composition is exclusive of silica and coupling agent, and
wherein said tread rubber composition is exclusive of carbon black reinforcement having an Iodine value of about 35 to about 85 g/kg and a dibutylphthalate (DBP) value of about 70 to about 130 cm3/100 g.
Therefore, the circumferential tire tread rubber composition differs significantly from the rubber composition of the lug and groove portion of the tire sidewall.
While the required different rubber compositions for the
Bezilla, Jr. Bernard Matthew
Sandstrom Paul Harry
Zanzig David John
Maki Steven D.
Young, Jr. Henry C.
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