Cabot Corporation

Trevor Alan Brown

Meng-Jiao Wang

Ralph E Dickinson

Novel methods of making elastomer compositions irclude the use of certain modifying agents and mechanical working prior to incorporation of a vulcanization system in a first or other early stage of a multi-stage process particulate filler, such as carbon black, and sulfur cross-linking agent are substantially dispersed into sulfur crosslinkable hydrocarbon elastomer. The particulate filler and sulfur crosslinking agent can be pre-mixed together as a pre-blend prior to being added to the elastomer. A substantially unvulcanized, processable elastomer is produced by the multi-stage process, involving further mechanical working of the initial masterbatch. A curative additive comprising accelerator, and optionally additional sulfur crosslinking agent, can be added and dispersed in the elastomer to produce a vulcanizable composition. In accordance with another aspect, extender oil is added to the elastomer subsequent to addition and substantial dispersion of the filler and sulfur crosslinking agent into the elastomer in the aforesaid early stage of the multi-stage process. Significant improvement in performance characteristics is achieved, especially by preferred embodiments, including good abrasion resistance and low hysteresis measured, for example, as tan delta-max at 70&deg; C. The present invention further relates to novel unvulcanized, processable elastomer compositions comprising certain treated carbon black particulate filler and certain pre-vulcanization modifier in an amount effective to substantially increase bound rubber content in a substantially unvulcanized processable elastomer product of a non-productive thermo-mechanical working of the elastomer composition.

Elastomer compositions and methods

Novel elastomeric compositions are disclosed, incorporating silicon-treated carbon black and pre-vulcanization modifier selected from non-silane polysulfidic organo-compounds. The silicon-treated carbon black particulate filler differs chemically and in its performance characteristics from simple mixtures of silica and carbon black fillers. The pre-vulcanization modifier is effective to substantially increase bound rubber content in the product of a non-productive thermomechanical working of a base composition incorporating the silicon-treated carbon black particulate filler and SBR or other such unsaturated elastomer. The thermal working takes place at a maximum temperature sufficient to vulcanize the unsaturated elastomer if it were in the presence of a suitable vulcanization system. The non-vulcanized rubber masterbatch produced by such thermal working, having substantially increased bound rubber content, can be admixed with a vulcanization system in a thermomechanical finishing step carried out at a maximum temperature less than the vulcanization temperature. The resulting composition can be vulcanized by thermomechanical working at or above the vulcanization temperature. The resulting elastomeric compositions in accordance with preferred embodiments are found to have improved performance characteristics, including hysterisis balance of low temperature traction and high temperature rolling resistance.

Elastomers compositions with dual phase aggregates and pre-vulcanization modifier

In a multi-stage process for producing a substantially unvulcanized elastomer composition, a masterbatch is produced by thermomechanical working in a first or other early stage of the multi-stage process. The masterbatch comprises sulfur crosslinkable hydrocarbon elastomer in which is substantially dispersed, particulate fillers, for example carbon black or silicon-treated carbon black, modified carbon black and/or silica and sulfur crosslinking agent effective to crosslink the hydrocarbon elastomer and selected from sulfur donors and sulfur. The filler and sulfur crosslinking agent can be mixed together as a pre-blend prior to being added to the elastomer. The substantially unvulcanized elastomer is then produced in one or more later stages of the multi-stage process, involving further theromechanical working of the masterbatch. A curative additive comprising accelerator, and optionally additional sulfur crosslinking agent, is added and dispersed in the elastomer in the last stage of the multistage process. In accordance with another aspect, oil is added to the elastomer subsequent to addition and substantial dispersion of the filler and sulfur crosslinking agent. The substantially unvulcanized elastomer composition can be cured or vulcanized to form tire tread and other commercial products. Significant improvement in performance characteristics is achieved by preferred embodiments, including good abrasion resistance and low hysteresis measured, for example, as tan .delta..sub.max at 70.degree. C.

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Groton, MA, United States of America

Trevor Alan Brown