Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-06-15
2002-06-18
Jagannathan, Vasu (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C524S252000, C524S495000, C152S209100
Reexamination Certificate
active
06407180
ABSTRACT:
FIELD
The invention relates to ground sulfur pre-vulcanized rubber (e.g. recycled cured rubber) which is blended with a pre-formed composite of carbon black and tris(2-aminoethyl) amine following which it is sulfur vulcanized. The invention also relates to articles of manufacture, including tires, which have at least one component as a rubber composition comprised of such treated recycled particulate rubber.
BACKGROUND OF THE INVENTION
Various articles, including tires and industrial products have at least one component as a sulfur vulcanized rubber, particularly of various diene-based rubbers. It is sometimes desired to re-use, or recycle, the vulcanized rubber of one or more of such components.
The vulcanized rubber desired to be recycled may be in a form of a manufactured article such as a pneumatic tire, industrial conveyor or power transmissions belt, hose and the like. Scrap pneumatic tires are especially large source of such vulcanized rubber.
The scrap vulcanized rubber may be prepared for re-use by being either by physically grinding it down to relatively small sizes and reclaimed by reducing its chemical character by various processes in which the rubber is conventionally de-vulcanized.
Alternatively, the scrapped vulcanized rubber may be reclaimed by grinding it down to extremely small particles and mixing it as a compounding ingredient, usually as a filler, with other rubbers and rubber compounding ingredients to form a rubber composition followed by sulfur vulcanizing the resultant rubber composition. In this case, the recycled rubber remains vulcanized but is in a form of a fine, particulate rubber.
In this description, the terms “recycle” and “recycled rubber” are used somewhat interchangeably and are intended to relate to vulcanized and sulfur pre-vulcanized rubber compositions unless otherwise designated.
Generally, such recycled, rubber, unlike conventional pre-vulcanized rubber compositions, is a complex mixture of largely unknown diene-based elastomers of compounding ingredients, possibly bits of textile fiber, and the like.
It has been observed that, after adding sulfur and accelerator to recycle rubber, followed by its revulcanization, the resulting physical properties, such as tensile and elongation, are usually lower than the corresponding properties of the original vulcanized rubber from which it was derived.
A process of improving properties of ground recycled sulfur pre-vulcanized rubber through use of a tris (2-aminoethyl) amine has been disclosed in EP 0972792 application published on or about Jan. 19, 2000.
However, it is considered herein that it may be beneficial to utilize such tris amine as a pre-formed composite of the tris amine in a dissociated form on the surface of a rubber reinforcing carbon black to thereby form a strong amine bond to the highly dispersible carbon black prior to blending the composite with one or more sulfur pre-vulcanized elastomers.
In the description of this invention, the term “phr” relates to parts by weight in a rubber composition of an ingredient therein per 100 parts of elastomer. The terms “rubber” and “elastomer” may be used interchangeably unless otherwise indicated. The terms “rubber composition” and “compound” may be use interchangeably unless otherwise indicated. The terms “vulcanize” and “cure” may also be used interchangeably unless otherwise indicated.
SUMMARY OF THE INVENTION
The present invention relates to a process for improving the properties of ground recycled sulfur vulcanized rubber.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with this invention, a process for preparation of sulfur vulcanized rubber composition comprising:
(A) homogeneously blending a pre-formed composite of carbon black and tris(2-aminoethyl) amine, with a particulate, sulfur pre-vulcanized rubber composition, wherein said pre-formed composite has a weight ratio of said amine to carbon black in a range of about 0.1 to about 12, and in an amount of said amine to provide from about 0.18 to about 10, alternatively about 1 to about 5, phr of said tris(2-aminoethyl) amine in said particulate sulfur pre-vulcanized rubber composition, and wherein said particulate sulfur pre-vulcanized rubber composition is of a particle size of less than 420 microns, to form a treated vulcanized rubber composition thereof;
(B) mixing about one to about 40 parts by weight of said treated pre-vulcanized rubber composition with 100 parts by weight of at least one unvulcanized rubber to form a rubber composition blend comprised of said unvulcanized rubber and said treated pre-vulcanized rubber.
(C) heating said rubber composition blend for a time sufficient and at a suitable temperature to vulcanize the unvulcanized rubber composition contained therein.
In further accordance with this invention a rubber composition prepared by the method of this invention is also provided.
In additional accordance with this invention, an article of manufacture which contains at least one component comprised of such rubber composition is provided.
In additional accordance with this invention, a tire which contains at least one component comprised of such rubber composition is provided. Such tire component may be, for example, a tire tread.
In practice, said particulate, sulfur pre-vulcanized rubber composition should have a maximum particle size of about 420 microns (40 mesh). Any particles greater than this are considered herein to render it impractical for subsequent mixing with the treated vulcanized rubber/unvulcanized rubber. In general, the individual sulfur pre-vulcanized rubber particles should preferably have a maximum particle size of about 250 microns (60 mesh) and preferably less than about 177 microns (80 mesh). Preferably, the individual particle size ranges from about 250 microns (60 mesh) to about 74 microns (200 mesh).
It is a significant aspect of this invention that the tris (2-aminoethyl) amine is provided as a pre-formed composite of a dissociated form of the amine with a particulate rubber reinforcing carbon black.
The use of such composite is particularly beneficial in order to reduce volatility of the amine, which therefore is considered herein to facilitate a blending of more highly dispersed and dissociated form of the tris (2-aminoethyl) amine with a sulfur pre-vulcanized rubber.
The use of the tris amine as a component of the pre-formed carbon black composite is considered herein to be beneficial by providing the tris amine as being bound in a highly dispersed form on the carbon black and to thereby enhance a relatively strong and efficient interaction with the particulate, sulfur-vulcanized rubber with which it is blended.
Use of a composite blending procedure with the recycle rubber is considered herein to be particularly advantageous as an alternative to use of a volatile organic solvent carrier for the tris (2-aminoethyl) amine for other various reasons, such as, for example, safety and environmental considerations.
Representative of various particulate carbon blacks for preparation of the composite are, for example, conventional rubber reinforcing carbon blacks with ASTM numbered designations ranging from N110 to N991.
The composite of carbon black and tris (2-aminoethyl) amine may be suitably prepared by highly dispersing the amine onto the surface of the carbon black to thereby maximize the interaction of the amine with the surface of the carbon black.
The dispersing of the tris amine onto the carbon black surface may be accomplished by, for example, by use of a volatile organic solvent which can readily be removed by evaporation, or by spraying or atomizing the tris amine onto the surface of the carbon black.
In the practice of this invention, the amine/carbon black composite is dispersed in the particulate sulfur pre-vulcanized rubber in a manner that the tris (2-aminoethyl) amine itself is dispersed in the pre-vulcanized rubber in an amount ranging from 0.18 to 10.0 phr of the amine. Preferably, the level of tris (2-aminoethyl) amine that is dispersed ranges from 0.36 to 5.0 phr, based upon the pre-vulcanized rubber.
For the
Balogh George Frank
Sandstrom Paul Harry
Wideman Lawson Gibson
Jagannathan Vasu
Shosho Callie E.
The Goodyear Tire & Rubber Company
Young, Jr. Henry C.
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