Tires are conventionally composed of various components, such as for example treads, which are rubber compositions which contain various fillers such as, for example, carbon black reinforcement which is the most widely used reinforcing particulate material for various rubber products. Such rubber reinforcing carbon black is in a form of aggregates of primary carbon particles formed by, for example, of controlled deposition from a gaseous phase to form a soot. Such rubber reinforcing carbon black is well known to those having skill in the art and is reported, for example, The Vanderbilt Rubber Handbook, (1978) Pages 408 through 428, which includes various ASTM designations for various rubber reinforcing carbon blacks.
Rubber reinforcing carbon blacks, in a form of aggregates of very small primary carbon particles of a highly disturbed graphitic structure, differ significantly from other crystalline forms of carbonaceous materials such as, for example those of a cubic (diamond, both natural and synthetic) crystalline structure. Such crystalline carbonaceous materials are conventionally of an ordered crystalline structure. The crystalline structure is conventionally evidenced by X-ray reflection analysis or detection. Imperfections in X-ray reflections are indicative of a disturbed crystalline structure which, in the case of large disturbances, a crystalline structure cannot normally be detected, and may be conventionally referred to as being roentgen-amorphous, so that therefore the absence of appropriate X-ray reflections is indicative of the significant presence of the amorphous form of carbon. Accordingly, such crystalline carbonaceous materials having significantly less than a perfectly ordered crystalline structure are referred to herein as being composed of a combination of disturbed crystalline phases and amorphous carbon phases.
Carbonaceous materials in a form containing diamond material may be reportedly prepared by, for example, heating carbon to a very high temperature and pressure or by a detonation process. For example, see U.S. Pat. Nos. 5,353,708, 5,861,349 and 5,916,955 as well as U.S. Pat. No. 4,273,561 showing an alternate process.
Other carbonaceous materials are reported as being formed by various detonation/combustion processes which contain synthetic diamonds as well as other carbon microstructures. For example, see U.S. Pat. Nos. 5,443,861, 5,985,451 and 5,482,695.
For example, according to U.S. Pat. No. 5,861,349, a carbonaceous diamond-containing material may be prepared by a controlled detonation process which may be comprised of about 50 to about 90 weight percent diamond cubic crystal structure phase and about 10 to about 30 weight percent amorphous carbon phase. Reportedly, from 10 to 20 percent of the surface of the material may contain methyl, nitrile and hydroxyl groups as well as functional oxycarbonic groups of the general formula: O═R where R represents ═COH, ═COOH, ═CO, and ═C6H4O or any of their combination and from 1 to 2 percent of the surface consists of carbon atoms with non-compensated links. (Reference: A. L. Vereschagin et al. “Properties of Ultrafine Diamond Clusters from Detonation Synthesis” in Diamond and Related Materials, Volume 3 (1933), Pages 160 through 162.)
As hereinbefore mentioned, carbonaceous materials of a disturbed crystalline cubic, diamond-like, structure may reportedly be prepared, for example, by detonating a carbon containing, oxygen-deficient explosive in closed volume in a gaseous medium inert toward carbon to form a material of a diamond-like cubic crystalline phase and an amorphous carbon phase. The disturbed structured carbon material reportedly may have functional groups on its surface, as hereinbefore discussed, which may include, for example, one or more of methyl, carboxyl, quinone, lactone ether and aldehyde functional groups.
Thus, such disturbed cubic crystalline/graphitic structured carbon composite materials, usually referred to herein as a composite of a “disturbed crystalline/amorphous carbon material” because of its included amorphous carbon content, are of an entirely different structure than more conventional aggregates of primary carbon black particles used as rubber reinforcing carbon blacks and reportedly may contain more extensive functional groups on their surfaces to further differentiate them from such rubber reinforcing carbon blacks.
Further examples of carbon materials comprised of disturbed cubic/graphitic structure are reported by M. D. Sokolova, O. A. Andrianova and S. N. Popov at the Sixth Russian Scientific and Practical Konference of Rubber Tires, Moscow, 1998, having a particle size of about 4 to 6 nanometers and aggregates thereof of a particle size of about 20 to 30 nanometers and a BET surface area via Argon absorption of about 250 to 350 m2/g.
The BET method of measuring surface area is described in the Journal of the American Chemical Society, Volume 60, (1930), Page 304.
Use of synthetic, explosive-formed, diamond material for use with rubbers has been discussed by A. P. Voznayokovskii, et al, in “Prospects of Using Technical-grade Diamond Carbon Synthesized by Explosion for the Reinforcement of Polyisoprene Rubbers” in Kauchuk i Rezina, No. 6 (1996), Page 27, with an English translation reportedly appearing in International Polymer Science and Technology, Volume 24, No.6, (1997), Page T/6, and as “Study of Reaction of Rubbers with Industrial Diamond Carbon Produced by Explosion Synthesis” in International Polymer Science and Technology, Volume 5, No.6, (1998), PageT/7, or by O. A. Adrianova, et al., in “Potential for Improving the Quality of Rubber Sealing Materials Used in the Conditions of the Far North” as reported in International Polymer Science and Technology, Volume 25, No. 6, (1998), Pages 24 through 27.
U.S. Pat. Nos. 6,608,318 and 5,935,715, mention the use of diamond powder in rubber for a radiation protection composition or as part of a quartz in a layer on rubber, respectively, although the nature of the diamond powder is not entirely specified.
However, this invention is directed to avoiding the sole use of a composite of a disturbed crystalline/amorphous phased carbonaceous material as a reinforcing filler additive for a rubber composition for a tire component and particularly a tire tread having a running surface intended to be ground-contacting.
Indeed, this invention is directed to a tire having a component, particularly a tread, of a rubber composition which contains a reinforcing filler as a combination of a composite of disturbed crystalline/amorphous phased carbonaceous particulate material together with rubber reinforcing carbon black aggregates (aggregates of primary graphitic carbon particles) or together with a combination of rubber reinforcing carbon black aggregates and synthetic amorphous silica aggregates (aggregates of primary silica particles), particularly in a form of synthetic amorphous precipitated silica aggregates, and wherein said filler also optionally contains a starch/plasticizer composite and/or short fibers.
As hereinbefore discussed, evidence of crystalline structure (e.g. cubic diamond and hexagonal grapitic crystalline structured phases) and amorphous carbon phases contained in the disturbed crystalline/amorphous phased carbonaceous filler for use in this invention can be discerned by X-ray diffraction. By X-ray diffraction analysis, crystalline faces of the crystalline structured regions, or phases, of the carbonaceous material can be detected and distinguished from graphitic or disturbed graphitic phases. Amorphous non-crystalline regions, or phases, of the carbonaceous material are not responsive to and are therefore not readily detectable by the X-ray diffraction method. However, the width of the X-ray scattered signal reportedly can show that the crystalline disorder or microstress (referred to in the aforesaid “Properties of Ultrafine Diamond Clusters for Detonation Synthesis” by A. L. Vereschagin, et al.) is excessive for a regular, undisturbed crystalline structure thereby indicating the significant presence of the respective phases within the disturbed, or irregular, crystalline structure of the carbonaceous material.
For the purposes of this invention, although it is envisioned herein that the disturbed crystalline/amorphous phased carbonaceous filler contains a cubic (diamond) crystalline structure, it may also typically contain a significant amount, or content, of an hexagonal (graphitic) crystalline structure as well as an amorphous carbon. Thus, it is envisioned herein that the disturbed crystalline/amorphous phased carbonaceous filler is a composite, rather than a simple blend, which may be composed of a combination of such disturbed cubic (diamond) crystalline structure and such disturbed hexagonal (graphitic) crystalline structure or composed of such disturbed cubic (diamond) crystalline structure and may also have a significant amorphous carbon content.
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 elastomer”. In the description of this invention, the terms “rubber” and “elastomer” can be used interchangeably, unless otherwise indicated The terms “rubber composition”, “compounded rubber” and “rubber compound” can be 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.