Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-05-08
2002-05-21
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S049000, C524S492000, C524S495000
Reexamination Certificate
active
06391945
ABSTRACT:
FIELD
The present invention relates to a rubber composition containing a combination of starch, modified starch and/or starch/plasticizer composite together with selected methylene donor and/or methylene acceptor compounds. The invention also relates to tires having at least one component comprised of such rubber composition. Such tire component can be, for example, its circumferential tread or other component of the tire.
BACKGROUND
Starch, modified starch and starch/plasticizer composites have sometimes been used in various compositions which might have included elastomer formulations, for various purposes which might have included tire components such as tire treads.
Such materials might be used alone or in conjunction with silica and/or carbon black reinforcing fillers or also with other fillers such as, for example, recycled, or ground, vulcanized rubber particles, short fibers, kaolin clay, mica, talc, titanium oxide and limestone. Such short fibers can be, for example, fibers of cellulose, aramid, nylon, polyester and carbon composition.
U.S. Pat. Nos. 5,403,923, 5,258,430, and 4,900,361 disclose the preparation and use of various starch compositions and U.S. Pat. No. 5,672,639 relates to use of starch/plasticizer composites in rubber compositions including as a tire component such as a tire tread.
However, use of starch-based fillers, in general, may present some limitations as reinforcement for various elastomers where resistance to abrasion and tear properties for elastomer composition are significantly desirable properties.
Accordingly, it is desired to enhance the use of starch-based materials in elastomer compositions.
Historically, starch may typically be represented as a carbohydrate polymer having repeating units of amylose (anhydroglucopyranose units joined by glucosidic bonds) and amylopectin, a branched chain structure, as is well known to those having skill in such art. Often, starch is composed of about 25 percent amylose and about 75 percent amylopectin. [
The Condensed Chemical Dictionary, Ninth Edition
(1977, revised by G. G. Hawley, published by Van Nostrand Reinhold Company, page 813]. Starch can be, reportedly, a reserve polysaccharide in plants such as, for example, corn, potatoes, rice and wheat as typical commercial sources.
Starch by itself typically has a softening point of about 200° C. or above and, therefore, usually is thought of as having a somewhat limited use in many rubber products, primarily because rubber compositions are normally processed by preliminarily blending rubber with various ingredients at temperatures in a range of about 140° C. to about 170° C., usually at least about 160° C., and sometimes up to 180° C. which is not a high enough temperature to cause the starch (with softening temperature of at least about 200° C.) to effectively melt and efficiently blend with the rubber composition. As a result, the starch particles tend to remain in individual domains, or granules, within the rubber composition rather than as a more homogeneous blend.
Accordingly, starch is sometimes modified with a plasticizer of lower softening point to create a starch/plasticizer composite for use in rubber compositions.
The term “phr” as used herein, and according to conventional practice, refers to “parts of a respective material per 100 parts by weight of rubber, or elastomer”.
In the description of this invention, the terms “rubber” and “elastomer” where used herein, may be used interchangeably, unless otherwise prescribed. The terms “rubber composition”, “compounded rubber” and “rubber compound”, where used herein, are used interchangeably to refer to “rubber which has been blended or mixed with various ingredients and materials” and such terms are well known to those having skill in the rubber mixing or rubber compounding art.
The term “carbon black” as used herein means “carbon blacks having properties typically used in the reinforcement of elastomers, particularly sulfur curable elastomers”.
The term “silica” as used herein can relate to precipitated or fumed silica and typically relates to precipitated silica, including an aluminosilicate, which is well known to those having skill in such art.
A reference to an elastomer's Tg refers to its glass transition temperature, which can conveniently be determined by a differential scanning calorimeter at a heating rate of 10° C. per minute.
SUMMARY AND PRACTICE OF THE INVENTION
In accordance with one aspect of this invention, a rubber composition is provided which comprises (A) 100 parts by weight of at least one diene-based elastomer, (B) about 0.1 to about 120, alternatively about 25 to about 90, phr of at least one elastomer reinforcing filler composed of (1) about 0.1 to about 120, alternatively about 5 to about 70, phr of at least one starch-based material selected from at least one of starch, starch/plasticizer composite and modified starch, and (2) zero to about 90, alternatively about 20 to about 85, phr of (a) carbon black or silica, namely an amorphous silica or (b) carbon black and silica, namely an amorphous silica; and, optionally, at least one additional inorganic reinforcing or non-reinforcing filler, (C) optionally a coupler for said starch-based material and silica, if silica is used, where said coupler has a moiety reactive with the surface of said starch composite and the surface of said silica, as the case may be, and a moiety interactive with the said elastomer, and (D) a methylene acceptor and/or methylene donor exclusive of hexamethylene tetramine.
Preferably, said modified starch is selected from at least one of hydroxyethylated starch, oxidized starch and acid modified starch.
In practice, said starch is typically composed of amylose units and amylopectin units in a ratio of about 15/85 to about 35/65, alternatively about 20/80 to about 30/70, and has a softening point according to ASTM No. D1228 in a range of about 180° C. to about 220° C.; and the starch/plasticizer has a softening point in a range of about 110° C. to about 170° C. according to ASTM No. D1228.
In the practice of this invention it is preferred that the methylene donor compound contains an —CH
2
OX group wherein X is an alkyl radical having from one to 8 carbon atoms, preferably selected from methyl, ethyl, propyl and octyl radicals and is exclusive of hexamethylene tetramine. For example, see U.S. Pat. No. 5,886,074.
Representative of such methylene donor compounds, exclusive of hexamethylene tetramine are, for example, hexamethoxymethylmelamine, hexaethoxymethylmelamine and ethoxymethylpyridinium chloride; and N-methylol derivatives of melamine such as, for example N,N′,N″-trimethylolmelamine, N-methylolmelamine and N′,N″-dimethhylolmelamine.
Representative of methylene acceptor compounds are, for example, phenolic cashew nut oil resins, resorcinol monobenzoate and polyhydric phenoxy resin, preferably phenolic cashew nut oil resin. for example, see U.S. Pat. Nos. 5,206,289 and 4,605,696.
Such phenolic cashew nut oil resins may be available, for example, as SP6700 from the Schnectady company.
Phenolic resins are conventionally produced by an acid condensation of phenol, or a mixture of phenols, with an aldehyde, usually formaldehyde. Such phenolic resins might be referred to as two-stage resins and are conventionally known as novolacs. This technology is understood to be well known to those having skill in such art. The Schenectady resin SP6700 is a two-stage phenolic resin from a condensation of a phenol and aldehyde, (a novolac), in which the phenolic component is a mixture of phenol and liquid cashew nut oil which might sometimes be referred to as “CSL”. The CSL might be described as a mixture of primarily monophenols substituted in the meta position with C15 hydrocarbon chains.
A significant feature of this invention is that it has been observed that hexamethylene tetramine, a well known methylene donor, did not work satisfactorily for use in this invention where the starch-based materials are utilized either by itself or in combination with the preferred methyl
Rajguru U. K
Seidleck James J.
The Goodyear Tire & Rubber Company
Young, Jr. Henry C.
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