Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2003-01-16
2004-10-05
Egwim, Kelechi C. (Department: 1713)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C152S151000, C524S300000, C524S432000, C524S571000, C524S575000, C524S575500
Reexamination Certificate
active
06800126
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to preparation and use of a rubber/carbon black composite comprised of at least one elastomer which contains a dispersion therein of carbon black aggregates. Such carbon black is formed by preparing a pre-blend comprised of uncompacted carbon black aggregates and oil and/or aqueous latex of, preferably, a low molecular weight diene-based elastomer particles, followed by blending said pre-blend with an aqueous emulsion of diene-based elastomer particles and/or with an organic solution of a diene-based elastomer, and/or with solid diene-based elastomers, and recovery therefrom of a solid rubber/carbon black composite comprised of said diene-based elastomer, (which may include butyl rubber, EPDM rubber and thermoplastic polymers), which contains a dispersion therein of said carbon black aggregates having an apparent density significantly lower than the specific gravity of said carbon black aggregates and significantly lower than compacted carbon black aggregates. Such carbon black aggregates may be optionally in a form of silica treated carbon black which contains silica domains on its surface. A rubber composition is further provided which is comprised of said rubber/carbon black composite. An article of manufacture is also provided, such as a tire, having at least component comprised of said rubber/carbon black composite or said rubber composition.
This invention relates to preparation of a rubber/carbon black composite comprised of at least one elastomer which contains a dispersion therein of carbon black aggregates. Such carbon black is formed by preparing a oil/carbon black aggregate premix composite and blending said premix composite with either with an aqueous emulsion of diene-based elastomer particles or with an organic solution of a diene-based elastomer and recovery thereof to form a solid rubber/carbon black composite comprised of said diene-based elastomer which contains a dispersion therein of said carbon black aggregates having a low apparent density. Such carbon black aggregates may be optionally in a form of silica treated carbon black which contains silica domains on its surface. A rubber composition is further provided which is comprised of said rubber/carbon black composite. An article of manufacture is also provided, such as a tire, having at least component comprised of said rubber/carbon black composite or said rubber composition.
BACKGROUND OF THE INVENTION
Carbon black for reinforcement of various rubber compositions is conventionally used in a form of compacted carbon aggregates, usually in a form of pellets of compacted carbon black aggregates.
The carbon black aggregates themselves are composed of aggregated primary carbon black particles of colloidal dimensions and high surface area by deposited from a carbon black vapor phase at very high temperatures. Such carbon black aggregates have very low apparent densities as compared to their specific gravity.
However in general commercial practice, the fine particles of carbon black aggregates are dusty in nature and are more easily processible by being compacted, for example compacted into pellets, for mixing with rubber compositions in order to reduce the presence of the dusty carbon black particulate aggregates in a rubber product manufacturing environment. Such pellets of compacted carbon black have an apparent density more nearly approximating the specific gravity of the carbon black.
Upon mixing with rubber compositions under high shear mixing conditions, the compacted carbon black pellets break down to granules of compacted carbon black aggregates of which only a minority, if any, are present in an uncompacted carbon black aggregate form.
However, it is considered herein that use of carbon black aggregates in their relatively low apparent density form, rather than granulated compacted carbon black aggregates with a substantial higher apparent density, is more desirable to promote or enhance reinforcement of elastomers.
Historically various carbon black/elastomer pre-blends, or masterbatches, have also been prepared and used for blending with additional elastomers. Such masterbatches have been prepared, for example, by:
(A) first masterbatching various rubber latices with carbon black, usually in a compacted (e.g. pelletized) form, under low shear and temperatures followed by
(B) blending the masterbatch with additional elastomer(s) and compounding ingredients under high shear and temperature conditions.
For example, see U.S. Pat. Nos. 3,294,733; 3,298,984; 3,317,458; 3,345,324; 3,491,052; 3,767,605 and 3,923,707.
U.S. Pat. No. 3,317,458, for example, relates to masterbatching a combination of carbon black and silica with a rubber latex.
Various rubber compositions have also heretofore been prepared by mixing an aqueous slurry of carbon black with an organic solvent solution of elastomer(s). For example see U.S. Pat. No. 3,350,342.
U.S. Pat. No. 3,304,281, for example, relates to mixing together a solution of one polymer with a latex of another polymer and then coagulating the rubber crumb from the resulting mixture. Such process is said to be useful in incorporating an oil and/or carbon black into the polymer. For example according to the patent disclosure, the oil can be introduced as an aqueous emulsion and the oil emulsion mixed with the latex prior to contact with the solution. Alternatively, all three components can be mixed simultaneously. Alternatively, an aqueous slurry of such carbon black can be added to the solution-latex mixture or it can be mixed with the latex prior to mixing with the solution.
U.S. Pat. No. 3,491,052 for example, relates to mixing an elastomer in an aqueous latex form with a solution of an elastomer which has been dissolved in a water immiscible organic solvent to form a pseudo-emulsion and recovering the mixed elastomers by adding a latex coagulating agent at a temperature sufficient to vaporize the solvent. Alternatively a rubber pigment (e.g. carbon black) may be dispersed in the pseudo-emulsion prior to coagulation.
U.S. Pat. No. 3,533,988, for example, relates to blending a hydrocarbon solution of rubber with an aqueous suspension of a rubber reinforcing agent, such as carbon black. In its background discussion, it relates that, theretofore, in order to avoid a disagreeableness of handling dry, dusty carbon black with raw rubber on mixing rolls, a method was developed for producing masterbatch by dispersing carbon black directly into a rubber solution produced by monomer polymerization in the presence of a solvent. It further relates that, theretofore, another method was to disperse carbon black in a hydrocarbon and mix the dispersion with the rubber solution.
In the description of this invention, the term “phr” relates to parts by weight of an ingredient per 100 parts by weight of rubber.
The terms “rubber” and “elastomer” are used interchangeably unless otherwise specified.
The term “Tg” relates to a glass transition temperature of an elastomer, normally determined by a differential scanning (DSC) calorimeter with a temperature rise of 10° C. per minute.
DISCLOSURE AND PRACTICE OF THE INVENTION
In accordance with this invention, a process of preparing a rubber composition is provided which comprises:
(A) blending non-compacted carbon black aggregates with rubber processing oil to form a pre-formed oil/carbon black aggregate composite comprised of said oil and said carbon black aggregates,
wherein said rubber processing oil is selected from rubber processing oils comprised of aromatic, paraffinic and/or naphthenic containing rubber processing oils,
wherein said rubber processing oil is in a form of:
(1) neat oil, or
(2) emulsified oil comprised of:
(a) water, surfactant and particles of emulsified oil, or
(b) aqueous latex of particles of diene-based elastomer(s) and particles of emulsified oil, followed by:
(B) blending said pre-formed oil/carbon black aggregate composite with
(1) an aqueous emulsion of diene-based elastomer particles, and/or
(2) an organic solvent solution of at least one diene-based elastomer, and/
Gujarathi Ramesh
Magnus Fredrick Lewis
Egwim Kelechi C.
The Goodyear Tire & Rubber Company
Young, Jr. Henry C.
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