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
1999-09-16
2001-07-03
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...
C524S495000
Reexamination Certificate
active
06255379
ABSTRACT:
FIELD
The invention relates to composites of rubber compositions reinforced with short, discontinuous fibers together with an anchoring agent. Preferably, the rubber composition is exclusive of amorphous silica. The invention also relates to articles, including industrial products and tires which have at least one component thereof. The invention particularly relates to industrial rubber belts having at least one component of such rubber composite and to tires having at least one component of such rubber composite.
BACKGROUND
It is sometimes desired to reinforce various rubber compositions with short, discontinuous fibers for various purposes. For example, see U.S. Pat. No. 4,871,004.
Use of only a very minor amount (e.g. from 4 to 8 phr) of short fibers in a rubber composition formulation typically substantially increases the viscosity (e.g. Mooney viscosity) of the uncured rubber composition to an extent which may make the rubber composition more difficult to mix in an internal rubber mixer and otherwise process. It is believed that such phenomenon is well known to those having skill in such art.
Where it is desired to provide a durable cured rubber composition as a component in various articles such as, for example, a component of an industrial belt or as an insert in a tire sidewall to stiffen the sidewall, it might seem logical to contemplate the use short fibers as reinforcement for such rubber composition.
Silica rich rubber compositions conventionally shrink somewhat upon sulfur vulcanization. It has been previously suggested, in the case of silica reinforced tire treads which contain at least 30 phr of silica which is accompanied by a silica coupling agent (see U.S. Pat. No. 5,852,097), to add about 2 to about 10 phr of short fibers to alleviate, or at least reduce such shrinkage. Apparently, the chemical reaction between the silica coupling agent and silica is necessarily expected to continue in order that the silica in the silica rich rubber composition fulfills its use as a reinforcing filler which is coupled to the elastomer(s) of the tire tread rubber composition.
Significantly, while it has been observed herein that addition of small amounts of short fiber reinforcement in a silica-free, carbon black reinforced rubber composition does increase its uncured viscosity so that processing of the uncured rubber has to be taken into consideration, one or more physical properties of the cured rubber composition may be degraded.
For example, it has heretofore been observed that although a 300 percent modulus of such a carbon black reinforced cured rubber composition may increase upon addition of a short fiber, the ultimate tensile strength of the cured rubber composition has been reduced. The reduction in tensile strength of a rubber composition may be a serious matter where such cured rubber composition is relied for its durability during service conditions for the rubber composition.
While such phenomenon may not be fully understood, it is believed that it is due, at least in part, to a very small degree of relative mobility of the short fibers within the cured rubber composition as compared to particulate carbon black reinforcement during service conditions during which the rubber composition may be subject to extensive dynamic flexing even though such flexing may only involve relative short extensions, or deformations, of the rubber composition itself.
Accordingly, it has been contemplated herein to add an anchoring agent to a substantially silica-free, carbon black reinforced rubber composition to provide some degree of anchoring at least a portion of short fibers contained in a rubber composition and thereby prevent, or at least retard, their small relative movement within the rubber composition during service conditions.
While various anchoring agents may be considered, use of coupling agents sometime used for coupling amorphous silica to various diene-based rubber compositions are considered herein. While such silica coupling agents typically chemically react with the surface of the silica to couple the silica to an elastomer by having a moiety which is chemically reactive with hydroxyl groups on the surface of the silica (e.g. silanol groups) and another moiety which is interactive with a diene-based elastomer of the rubber composition itself.
In the description of this invention, the term “phr” means parts by weight of a specified ingredient per 100 parts by weight of elastomer.
Also, in the description of this invention, the terms “rubber” and “elastomer” are used interchangeably, unless otherwise noted.
The terms “vulcanized” and “cured” are also used interchangeably unless otherwise noted.
SUMMARY AND PRACTICE OF THE INVENTION
In accordance with this invention, a rubber composition, substantially exclusive of silica, particularly amorphous silica, preferably less than 12 phr and more preferably exclusive of such silica, and is comprised of, based upon 100 phr of elastomer, (A) 100 phr of at least one diene-based elastomer selected from homopolymers and copolymers of conjugated diene and copolymers of at least one conjugated diene with a vinyl aromatic compound selected from styrene and alpha-methylstyrene, preferably styrene, (B) about 0.5 to about 10, preferably about 0.5 to about 4, phr of short, discrete organic fibers, (B) from about 35 to about 85 phr of reinforcing carbon black and (C) an anchoring agent for said fibers having a moiety reactive with at least one of hydroxyl groups and alkoxy groups and another moiety interactive with at least one of said diene-based elastomers.
In further accordance with this invention, such rubber composition is sulfur vulcanized. Such sulfur vulcanization is conventionally vulcanizing said rubber composition in a suitable mold to a temperature in a range of about 140° C. to about 190° C. for a sufficient period of time for the rubber composition to vulcanize, usually from about 12 to about 25 minutes.
In practice, such anchoring agent may, for example and not intended to be limiting, be comprised of the general formula (I) or (II):
(OR)
3
—Si—R′—S
n
—R′—Si—(OR)
3
(I)
(OR)
3
—Si—R′—X (II)
wherein R is an alkyl group selected from at least one of methyl and ethyl groups, R′ is an alkyl group selected from ethyl, propyl and butyl groups and n is a value of from 2 to 6 with an average of from 2 to 2.6 or from 3.5 to 4, and X is a radical selected from at least one of mercapto, methacrylate and epoxide, vinyl, amino, thiocyanato, ureido, isocyanato radicals.
Representative examples of an anchoring agent of formula (I) are, for example bis-(3-trialkoxysilyl) tetrasulfide with an average of from about 2 to 2.5 or 3.5 to 4 connecting sulfur atoms in its polysulfidic bridge.
For example, such anchoring agent may be a bis-(3-triethoxysilyl) polysulfide.
Representative examples of an anchoring agent of formula (II) are, for example, 3-mercapto propyl triethoxysilane, 2-mercapto ethyl triethoxysilane and 4-mercapto butyl triethoxysilane; and (3-glycidoxypropyl)triethoxysilane.
While various of such anchoring agents might have also been proposed for use as silica coupling agents for silica rich rubber compositions, including for example tire treads of such rubber compositions, it has been preferred to refer to such materials as “anchoring agents” herein because, as hereinbefore discussed, first, the rubber composition of this invention is not intended to be a silica rich rubber composition and secondly, the mechanism of the interaction of the anchoring agent, in the absence of the silica, is not entirely clear insofar as its anchoring effect may be based upon a creation of a stabilizing siloxane compound by an in-situ chemical interaction with itself which may or may not involve a significant physical and/or chemical in-situ interaction with the short fibers itself.
It has been observed herein that a particular significance of providing a rubber composition which contains a short fiber reinforcement in combination with an anchoring agent can be an improvement of the cured rubber co
Edme Materne Thierry Florent
Hahn Bruce Raymond
Cain Edward J.
The Goodyear Tire & Rubber Company
Young, Jr. Henry C
LandOfFree
Rubber containing short fiber reinforcement with anchoring... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Rubber containing short fiber reinforcement with anchoring..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rubber containing short fiber reinforcement with anchoring... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2448136