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
2001-06-29
2003-12-09
Yoon, Tae H. (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, C524S526000, C523S215000, C525S332600
Reexamination Certificate
active
06660791
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to articles of manufacture, such as for example, tires and industrial products, which have at least one component comprised of a rubber composition which contains particles of pre-sulfur vulcanized rubber (e.g. ground recycled rubber) and high purity trithiodipropionic acid, wherein said trithiodipropionic acid is preferably provided as particles of a carbon black composite comprised of carbon black and said high purity trithiodipropionic acid. Said high purity trithiodipropionic acid is comprised of polythiodipropionic acids containing at least 80 weight percent trithiodipropionic acid based upon said polythiodipropionic acids.
BACKGROUND OF THE INVENTION
Various manufactured articles, including for example, various tires and industrial products, have at least one component comprised of a sulfur vulcanized rubber. It is sometimes desired to blend relatively small amounts of particles of pre-vulcanized rubber with a rubber composition for one or more of such components followed by vulcanizing said rubber composition in a suitable mold. Said pre-vulcanized rubber is in a form of ground, recycled pre-vulcanized rubber obtained from, for example, various tires and industrial products. Scrap pneumatic tires may, for example, be used as a source of such pre-vulcanized rubber.
In practice, scrap vulcanized rubber may be prepared for recycling, for example, by depolymerizing it or otherwise changing its chemical character by various processes.
However, for the purposes of this invention, the scrap vulcanized rubber (the pre-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 pre-vulcanized rubber remains vulcanized but is in a form of a fine, particulate pre-vulcanized rubber.
For the description of this invention, the terms “recycle” and “recycled rubber” are used somewhat interchangeably and are intended to relate to sulfur pre-vulcanized rubber compositions which have been ground into small particles unless otherwise designated.
Generally, such particulate recycled sulfur pre-vulcanized rubber is a complex mixture of largely unknown diene-based elastomers and various rubber compounding ingredients, and may contain a small quantity of textile fiber, and the like.
It has been observed that, after adding sulfur and accelerator to recycled sulfur pre-vulcanized 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, for example, of improving properties of ground recycled sulfur vulcanized rubber through use of a tris (2-aminoethyl) amine has been disclosed as U.S. Pat. No. 6,077,874. U.S. Pat. No. 5,883,139 discloses the use of tetrathiodipropionic acid (which may be referred to herein as S4) to improve properties of rubber compositions which contain particles of ground recycle, sulfur cured diene-based rubber while the use of dithiodipropionic acid (S2) is not seen to improve the properties of rubber compositions which contain particles of ground recycle, sulfur cured diene-based rubber. Therefore, it is considered herein that it would not be obvious to one having skill in such art to successfully use a high purity trithiodipropionic acid (S3) to improve the properties of rubber compositions which contain particles of ground recycle sulfur cured, diene-based rubber.
For the purposes of this invention, such high purity trithiodipropionic acid (S3) is a blend of polythiodipropionic acids which contains at least 80, and preferably a range of from 80 to about 90, weight percent 3,3′-trithiodipropionic acid weight of such acid, based upon said polythiodipropionic acids, with the remainder comprised of other polythiodipropionic acids which are primarily said S4 and S2.
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 and particularly improving sulfur curable diene-based rubber compositions which contain particulate pre-sulfur vulcanized diene-based rubber.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with this invention, a process of preparing sulfur vulcanizable rubber composition which comprises:
A. preparing a pre-blend by homogeneously blending
1. particles of a sulfur vulcanized, diene-based rubber composition, together with
2. high purity trithiodipropionic acid and particles of carbon black; or
3. particles of a carbon black composite comprised of carbon black and high purity trithiodipropionic acid, having a weight ratio of said high purity trithiodipropionic acid to carbon black in a range of from about 1/10 to about 10/1;
wherein said high purity trithiodipropionic acid having the general Formula (I):
HO
2
CCH
2
CH
2
—S
n
—CH
2
CH
2
CO
2
H (I)
wherein n is a value of from 2 to about 5 and wherein at least 80 percent, and preferably from about 80 to about 90 percent, of n is 3,
wherein about 0.18 to about 10, alternately from 1 to about 5, parts by weight of trithiodipropionic acid is thereby provided per 100 parts by weight of diene-based rubber contained in said sulfur vulcanizable rubber composition, and wherein said particles of sulfur vulcanized rubber composition is of a particle size of less than 420 microns;
(B) mixing about one to about 40, alternately about 15 to about 20, parts by weight of said pre-blend with 100 parts by weight of at least one unvulcanized hydrocarbon diene-based, sulfur vulcanizable rubber to form a rubber composition comprised of said unvulcanized rubber and said pre-blend.
Accordingly, in practice, the high purity trithiodipropionic acid may be added directly to the particulate pre-vulcanized rubber or as said carbon black composite.
In further accordance with this invention, a rubber composition is provided which is comprised of said pre-blend and said unvulcanized rubber.
In additional accordance with this invention, sulfur (referred to herein as free sulfur) is blended with said rubber composition in an amount in a range of about 1 to about 5 parts by weight thereof per 100 parts by weight of said unvulcanized diene-based rubber (usually together with conventional sulfur cure accelerators and other conventional rubber compounding ingredients in conventional amounts) to form a free sulfur-containing rubber composition.
In further accordance with this invention, said free sulfur-containing rubber composition is sulfur vulcanized in a suitable mold under conditions of elevated temperature (e.g. in a range of about 140° C. to about 180° C.) and pressure to form a sulfur vulcanized article of manufacture.
In further accordance with this invention a sulfur vulcanized, pre-vulcanized rubber-containing, rubber composition is provided.
In additional accordance with this invention, an article of manufacture is provided which contains at least one component of a said sulfur vulcanized, pre-vulcanized rubber-containing, rubber composition.
In further accordance with this invention, a tire is provided which contains at least one component of a rubber composition comprised of said sulfur vulcanized, pre-vulcanized rubber-containing, rubber composition.
In additional accordance with this invention, a tire is provided having a tread of a rubber composition which is comprised of said sulfur vulcanized, pre-vulcanized rubber-conta
Balogh George Frank
Wideman Lawson Gibson
The Goodyear Tire & Rubber Company
Yoon Tae H.
Young, Jr. Henry C.
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