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
1999-09-22
2002-07-30
Mulcahy, Peter D. (Department: 1713)
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...
C524S444000
Reexamination Certificate
active
06426378
ABSTRACT:
FIELD
The invention relates to the preparation of a partially vulcanized, pre-shaped rubber composition and use thereof as a component of an article of manufacture. In practice, the partially vulcanized rubber composition is adhered to an unvulcanized rubber substrate to form a composite thereof and the resulting composite vulcanized to create an article of manufacture. Such pre-vulcanized rubber composition is a composite comprised of at least one diene-based elastomer, amorphous silica, coupling agent and liquid diene-based polymer. Such partially vulcanized, pre-shaped rubber composition may be a component of a tire such as, for example, an apex, sidewall insert or tread. It may also be a component of an industrial rubber product such as, for example, a component of a conveyor belt, power transmission belt or a hose.
BACKGROUND
Various articles of manufacture are sometimes produced by forming an assembly of a plurality of components of unvulcanized rubber compositions and vulcanizing the resulting assembly, at an elevated pressure and temperature in a suitable mold to form a vulcanized rubber product.
Conventionally, the unvulcanized rubber composition tends to flow somewhat within the mold during the vulcanization process. While the mold may confine the overall volume of the assembly, various unvulcanized rubber components of assembly tend to flow somewhat and to, therefore, become somewhat distorted.
Accordingly, one or more components of an assembly may be partially pre-vulcanized, or pre-cured, in order to enhance their dimensional stability during the vulcanization process. For example, it has been proposed to pre-vulcanize a tire's apex prior to building it into an assembly of unvulcanized tire components and then vulcanizing the resulting in a suitable mold under conditions of elevated temperature and pressure to create a resulting vulcanized tire. It is believed that such suggested practice is well known to those having skill in such art.
Upon vulcanization of the assembly of components, good adhesion and co-adhesion between the various components at their individual interfaces is desired, and is usually required, for stability of the resulting product under working conditions. Such philosophy of adhesion between the individual vulcanized rubber components of manufactured articles is well known to those having skill in such art.
For example, as hereinbefore discussed, a rubber tire may be prepared by assembling various unvulcanized rubber-based components and building an assembly of such components, followed by sulfur vulcanizing the resulting assembly in a suitable mold at an elevated temperature to form the tire as an article of manufacture.
As a further example, rubber tires are sometimes re-treaded by applying a partially pre-cured rubber tread to an already cured rubber carcass, with an uncured adhesive rubber composition gum strip therebetween for enhanced adhesion purposes and the resulting assembly vulcanized to form the re-treaded tire.
Adhesion of the various vulcanized rubber-based components to each other is usually of significant importance for the above resulting tires as would be understood by those having skill in such art.
As hereinbefore discussed, for some applications it may be desired for an individual rubber-based component to have sufficient dimensional stability that it does not appreciably deform during the building, shaping and molding of an assembly of rubber-based components in the preparation of an article of manufacture.
Accordingly, for many of the above component assembly purposes, it is desired that a rubber-based component be partially pre-vulcanized and pre-shaped, prior to its assembly with other unvulcanized rubber components yet still exhibit good adhesion to each other at their interfaces upon vulcanization of the assembly to form an article of manufacture.
However, it is to be appreciated that such good vulcanized adhesion between rubber-based components may be significantly reduced where one rubber-based component has been partially pre-vulcanized prior to assembly with at least one unvulcanized rubber-based component and the resulting assembly then vulcanized.
It is hypothesized that such reduction of vulcanized adhesion may be due, for example, to a possible reduction in cross-linking between the interfaces of the associated components during the vulcanization of the assembly. Also, there may be a reduced mobility of various constituents of the partially pre-vulcanized component which may logically lead to reduced interfacial adhesion to other associated rubber-based components after vulcanization of the assembly unless an intermediate adhesive layer (cement layer) is applied to at least one interfacial surface prior to assembling the respective components in order to achieve adequate adhesion after vulcanization.
It is believed that occurrence of such phenomenon of reduced vulcanized adhesion between such components is well known to those having skill in such art.
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 OF PRACTICE OF THE INVENTION
In accordance with this invention, a partially sulfur pre-vulcanized rubber composition is provided which is comprised of, based on 100 parts by weight of elastomer, (A) at least one solid 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, (B) about 3 to about 15, alternatively about 3 to about 10, phr of liquid conjugated diene polymer having a molecular weight in a range of about 1,000 to about 40,000, alternatively about 4,000 to about 20,000, (C) from about 45 to about 65 phr of reinforcing filler selected from amorphous silica, aluminosilicate which is preferably an amorphous aluminosilicate, and modified carbon black; wherein said amorphous silica, aluminosilicate and modified carbon black have hydroxyl groups (e.g.: silanol groups) on the surface thereof and, wherein said reinforcing filler contains from about 60 to about 100, preferably about 80 to about 100, weight percent of at least one of said amorphous silica and aluminosilicate and (D) a coupling agent having a moiety reactive with said hydroxyl groups (e.g.: silanol groups) on the surface of the said amorphous silica, aluminosilicate and modified carbon black, as the case may be, and another moiety interactive with at least one of said diene-based elastomers; wherein said rubber composition is pre-sulfur vulcanized to about 20 to about 60 percent of its T
90
vulcanization state.
In further accordance with this invention, such rubber composition is pre-shaped and partially sulfur pre-vulcanized by positioning said rubber composition in a suitable enclosed mold cavity and heating the rubber composition 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 to about 20 to about 60, preferably about 20 to about 50, percent of its T
90
vulcanization state according to ASTM D5289.
Representative of said liquid conjugated diene-based polymers are, for example, liquid cis 1,4-polyisoprene polymers, liquid cis 1,4-polybutadiene polymers and liquid styrene/butadiene copolymer polymers.
Preferably, said liquid polymer is a cis 1,4-polyisoprene polymer. Such polymer may be a depolymerized cis 1,4-polyisoprene elastomer.
Alternatively, said liquid conjugated diene-based polymers may be end functionalized with hydroxyl, mercapto and/or epoxy moieties and, thus, have an enhanced reactivity potential.
In practice, it is preferred that the resulting interfacial adhesion between said vulcanized components is at least 15 N/mm.
Such interfacial adhesion may be determined by an adhesion m
Gerard Denis Jean René
Henoumont Marc Jules Alexis
Lickes Jean-Paul
Mulcahy Peter D.
The Goodyear Tire & Rubber Company
Young, Jr. Henry C.
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