Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
1998-03-10
2001-04-24
Ball, Michael W. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S565000, C524S495000, C524S496000
Reexamination Certificate
active
06220326
ABSTRACT:
FIELD
This invention relates to a tire having a carcass ply component with a rubber composition having a low carbon black content where the carbon black is of a defined structure and particle size.
BACKGROUND OF THE INVENTION
Pneumatic rubber tires are conventionally prepared with a rubber tread and supporting carcass. The carcass is conventionally composed of one or more rubberized cord reinforced plies. Such construction is well known to those having skill in such art.
Here, it is desired to provide such rubber composition which contains a relatively small amount of carbon black reinforcement on the order of about 15 to about 35 phr and in the absence, or at least substantial absence, of silica and accompanying silica coupling agent.
It is recognized that in U.S. Pat. No. 5,396,940 a carcass ply rubber composition has been disclosed which is composed of 5-95 phr of epoxidized natural rubber, 5-85 phr of silica, a silica coupler, carbon black which can be a carbon black such as N299, which can also contain 95-5 phr of other rubbers including natural rubber and cis 1,4-polybutadiene rubber.
In the description of this invention, the term “phr” where used means “parts of material by weight per 100 parts by weight of rubber”.
SUMMARY AND PRACTICE OF THE INVENTION
In accordance with this invention a tire comprised of a tread and supporting carcass wherein said carcass contains at least one ply comprised of a cord reinforced rubber composition and wherein said carcass ply rubber composition is comprised of, based on 100 phr of rubber, (A) about 60 to about 90 phr of natural cis 1,4-polyisoprene rubber and about 10 to about 40 phr of cis 1,4-polybutadiene rubber, (B) about 15 to about 35, alternatively about 20 to about 30, phr of carbon black having a D B P value in a range of about 110 to about 135 cm
3
/100 g and an Iodine adsorption value in a range of about 90 to about 120 g/kg, and (C) about 2 to about 8 phr of rosin acid.
In practice, the rubber composition for the carcass ply is often referred to as a ply coat.
Conventionally, the carcass ply component of the tire is a cord reinforced element of the tire carcass. Often two or more carcass ply components are used in a tire carcass. The carcass ply component itself is conventionally a multiple cord reinforced component where the cords are embedded in a rubber composition which is usually referred to as a ply coat. The ply coat rubber composition is conventionally applied by calendering the rubber onto the multiplicity of cords as they pass over, around and through relatively large, heated, rotating, metal cylindrical rolls. Such carcass ply component of a tire, as well as the calendering method of applying the rubber composition ply coat, are well known to those having skill in such art.
The importance of using a relatively low level of carbon black reinforcement for the ply coat, is to endeavor to achieve a high rebound value and relatively low hysteresis for the rubber composition which is intended, ultimately, to enhance (reduce) the tire's rolling resistance. Because a relatively small amount of carbon black reinforcement is to be used, it was decided to try a higher than normal structured (higher reinforcing) carbon black than what might be used for a carcass ply rubber, more of the type of rubber which might be used for a tire tread rubber composition.
The importance of using natural rubber for the ply coat is to endeavor to obtain a relatively high shear strength, low hysteresis and good processability during the calendering of the ply coat onto the cord reinforcement.
It is desired to use cis 1,4-polybutadiene rubber as an elastomer in the ply coat rubber composition to contribute to a relatively low hysteresis and improved compound aging.
The importance of using rosin acid for the ply coat rubber composition is to endeavor to achieve good cured adhesion to the ply cords while maintaining good, original and aged tack. Various rosin acids can be used, particularly natural occurring rosin acids, although they might be refined somewhat. Representative of such rosin acids are, for example, wood rosin, tall oil rosin and gum rosin. Such rosin acids and their use in rubber compositions are well known to those having skill in such art.
In a practice of this invention, it is preferred that the rosin acid is utilized in place of more conventional phenolic resin which are more commonly used for enhancing tack for a rubber composition. This is because, for the purposes of this invention, it is considered herein that such the phenolic resins would provide the necessary building tack but have been observed to cause a reduction in cord adhesion.
For the practice of this invention, it is intended to not use silica reinforcement, at least not any substantial amount of silica, (10 phr or 5 phr or less and preferably zero amount) since it is desired, for this invention, that the amount of reinforcing filler, including the specified carbon black, be kept relatively low. Therefore, a greater reinforcing effect of the carbon black, particularly a relatively high structure carbon black is desired to offset the use of a relatively small amount of carbon black.
It is also intended to not use epoxidized natural rubber for the ply coat rubber composition because it is envisioned that such rubber would tend to cause an unwanted higher hysteresis for the ply coat rubber composition.
Accordingly, for the practice of this invention, it is preferred that the carcass ply rubber composition is exclusive of any appreciable amount, particularly of any amount of (1) epoxidized natural rubber, (2) phenolic, particularly synthetic phenolic, tackifiers, (3) silica, (4) silica coupler and/or (5) additional carbon black having a D B P value of less than 100 cm
3
/100 g and Iodine No. value of less than 90 g/kg.
If desired, up to about 10, such as about 5 to about 10, phr of additional rubber may be included in the ply coat rubber composition selected from at least one of medium vinyl polybutadiene rubber (40-60 percent vinyl), styrene-butadiene rubber, styrene-isoprene rubber and styrene-isoprene-butadiene rubber.
The D B P and Iodine value characterizations of carbon black are well known and a reference to such values relating to carbon black and ASTM methods of their determination may be found in
The Vanderbilt Rubber Handbook,
13
th
edition (1990), pages 416-419.
In general, the D B P value tends to relate to what is known as the structure of the carbon black. Relatively high structure carbon blacks are typically used for reinforcing tire tread rubber compositions such as those having a D B P (dibutylphthalate) value in a range of about 100 to about 160 cm
3
/100 g. Carcass ply rubber compositions usually use a lower structure carbon black reinforcement such as those having a D B P value in a range of about 80 to about 100 cm
3
/100 g.
Significantly, for the purposes of this invention a relatively low level of carbon black is used for the carcass ply rubber composition in order to endeavor to achieve higher rebound and reduced hysteresis. Therefore, it is envisioned herein that a higher structure carbon black with a D B P value in a range of about 110 to about 135 cm
3
/100 g be used in order to provide enough reinforcement.
Further, it is desired to use a carbon black reinforcement with a finer particle size than what may normally be used for a carcass ply rubber composition as indicated by the carbon black's Iodine No. value which, in turn, is a surface area indicator.
Significantly, carbon blacks used for carcass ply reinforcement are usually of a relatively large particle size characterized by having an Iodine No. value in a range of about 30 to about 60 g/kg, whereas smaller carbon blacks are often used for tread rubber usually having a Iodine No. value in a range of about 80 to about 140 g/kg.
For this invention, it is envisioned that a smaller than typical carcass ply carbon black be used with an Iodine Number value in a range of about 90 to about 120 g/kg.
In practice, cords of various compositions may be used for the carcass ply such
Blok Edward John
Hahn Bruce Raymond
Sandstrom Paul Harry
Ball Michael W.
Musser Barbara J.
The Goodyear Tire & Rubber Company
Young, Jr. Henry C
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