Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-01-08
2001-07-03
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C525S193000, C525S285000
Reexamination Certificate
active
06255372
ABSTRACT:
TECHNICAL FIELD
This invention relates to improved rubber compositions. More particularly, this invention is directed toward rubber vulcanizates that demonstrate improved tear strength. Specifically, the rubber compositions and vulcanizates of this invention include polypropylene and maleic anhydride as additives to achieve the desired properties. The preferred embodiments of this invention are directed toward vulcanizable compositions of matter that are useful for fabricating tires.
BACKGROUND OF THE INVENTION
Off road or heavy truck tires are often subjected to rough road conditions that produce repetitive, localized high pressure pounding on the tire. These stresses can cause fatigue fracture and lead to crack formation and growth. This degradation of the tire has also been referred to as chipping or chunking of the tread surface or base material.
In an attempt to prevent this degradation, it is known to add reinforcements such as carbon black, silicas, silica/silanes or short fibers. Silica has been found advantageous due to its ability to deflect and suppress cut prolongation, while silanes have been added to bind the silica to unsaturated elastomers. The fibers that have been added include nylon and aramid fibers.
It is also known that the addition of polyolefins to rubber compositions can provide several beneficial properties. For example, low molecular weight, high density polyethylene, and high molecular weight, low density polyethylene, are known to improve the tear strength of polybutadiene or natural rubber vulcanizates. In the tire art, it has also been found that polyethylene increases the green, tear strength of carcass compounds and permits easy extrusion in calendering without scorch. Polypropylene likewise increases the green strength of butyl rubber. Polypropylene has also been effective in raising the static and dynamic modulus of rubber, as well as its tear strength.
Although the addition of polyolefins to rubber compositions is known to provide several beneficial effects, the addition of polyolefin to tire recipes has, heretofore, had a deleterious affect on the mechanical and wear properties of tires, as well as handling and ride comfortability of the tire.
Accordingly, there remains a need in the art to improve the tear strength of rubber vulcanizates, especially those deriving from tire compositions, without sacrificing the other properties of vulcanizates, tire components, or tires.
SUMMARY OF INVENTION
It is therefore an object of the present invention to provide a tire component having increased tear strength, where the tire component is less susceptible to chipping and chunking, without substantially impacting the mechanical and wear properties of the tire component.
It is another object of the present invention to provide a tire component having increased tear strength, where the tire component is less susceptible to chipping or chunking, without substantially impacting the hysteresis properties of the tire component.
It is yet another object of the present invention to provide a vulcanizate having increased tear strength, where the vulcanizate is less susceptible to chipping and chunking, without substantially impacting the mechanical and wear properties of the vulcanizate.
It is still another object of the present invention to provide a vulcanizate having increased tear strength, where the vulcanizate is less susceptible to chipping or chunking, without substantially impacting the hysteresis properties of the vulcanizate.
It is also an object of the present invention to provide vulcanizable compositions of matter that will give rise to a cured product having increased tear strength, where the cured product is less susceptible to chipping and chunking, without substantially impacting the mechanical and wear properties of the cured product.
It is another object of the present invention to provide vulcanizable compositions of matter that will give rise to a cured product having increased tear strength, where the cured product is less susceptible to chipping or chunking, without substantially effecting the hysteresis properties of the cured product.
It is yet another object of the present invention to provide a tire having increased tear strength without substantially impacting the mechanical and wear properties of the tire at high temperatures.
It is still yet another object of the present invention to provide a vulcanizate having increased tear strength without substantially impacting the mechanical and wear properties of the vulcanizate after heat aging.
At least one or more of the foregoing objects, together with the advantages thereof over the known art relating to tire components and compositions for making the same, which shall become apparent from the specification that follows, are accomplished by the invention as hereinafter described and claimed.
In general the present invention provides a tire having improved tear strength including at least one component comprising a vulcanized elastomer; from about 5 to about 50 parts by weight polypropylene per one hundred parts by weight elastomer; and from about 0.05 to about 2.0 parts by weight of an anhydride compatibilizing agent per one hundred parts by weight elastomer.
The present invention also provides a vulcanizable composition of matter comprising an elastomer; up to about 50 parts by weight polypropylene per one hundred parts by weight elastomer; at least 0.05 parts by weight of an anhydride compatibilizing agent per one hundred parts by weight elastomer; and up to about 100 parts by weight of a reinforcing filler per one hundred parts by weight elastomer.
The present invention further provides a vulcanizate prepared by a process comprising the steps of preparing a vulcanizable composition of matter including an elastomer; from about 5 to about 50 parts by weight polypropylene per one hundred parts by weight elastomer; from about 0.05 to about 2.0 parts by weight of an anhydride compatibilizing agent per one hundred parts by weight elastomer; and from about 1 to about 100 parts by weight of a reinforcing filler; and vulcanizing the composition of matter with at least one vulcanizing agent.
PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION
It has now been found that the tear strength of rubber vulcanizates can be improved without a corresponding deleterious decrease in the other mechanical properties of the vulcanizates. This result is achieved by the addition of polypropylene and an anhydride compatibilizing agent to a vulcanizable composition of matter. Accordingly, the present invention is directed toward rubber compositions that include polypropylene and an anhydride compatibilizing agent, as well as vulcanizates prepared from these compositions. The preferred embodiments of this invention are directed toward rubber compositions that are useful for fabricating tire components, as well as rubber vulcanizates that are useful as tire components. The practice of the present invention is especially useful in base stock recipes, but inasmuch as the increase in tear strength does not deleteriously impact the wear, mechanical, and hysteresis properties of the rubber, the practice of the present invention may also be applied to the tread and side wall stocks of tires. Furthermore, it should be understood that the practice of the present invention is believed to be especially advantageous for off-road or heavy-duty truck tires, although it is believed that the practice of the present invention will improve other tires such as passenger tires.
In general, the improved vulcanizates of this invention are prepared from rubber compositions that include at least one rubber, at least one type of polypropylene,and an anhydride compatibilizing agent. In general, the composition should include up to about 50 parts by weight polypropylene per one hundred parts by weight rubber and at least about 0.05 parts by weight anhydride compatibilizing agent per one hundred parts by weight rubber. More specifically, the rubber compositions include from about 5 to about 50 parts by weight polypropylene, per one hun
Lin Chen-Chy
Tatsuro Hamada
Bridgestone Corporation
Choi Ling-Siu
Hall Daniel N.
Hornickel John N.
Reginelli Arthur M.
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