Rubber containing aramid pulp reinforcement

A process for building a tire containing one or more aramid-reinforced components including a tread, said process comprising:

• (a) forming a premix consisting essentially of fibrillated aramid fibers and one or more particulate reinforcing agents selected from the group consisting of carbon black, silicon, clay and mixtures thereof, said premix containing the entire quantity of aramid fibers desired in said composite and sufficient quantity of reinforcing agent to cause partitioning of said aramid fibers and thereby promote subsequent compounding of said aramid fibers with elastomer, said aramid fibers being composed of
• (1) a trunk portion having a length in the range of about 0.2 to about 5 millimeters, a diameter in the range of about 0.005 to about 0.02 millimeters and an aspect ratio greater than about 100, and
• (2) a plurality of fibrils extending outwardly from said trunk and having diameters substantially smaller than the diameter of the trunk from which they extend, said fibers having a surface area in the range of about 4 to about 20 square meters per gram,
• (b) mixing said premix with a vulcanizable elastomeric matric material, additional amounts of said one or more particulate reinforcing agents, and additional tire compounding ingredients in the absence of a solvent to form an unvulcanized elastomer composite, the quantity of said aramid fibers no exceeding 5 parts by weight per 100 of elastomer, and
• (c) forming the resulting unvulcanized elastomer composite or one or more portions thereof into one or more tire components, including a tread, in which aramid reinforcement is desired,
• (d) assembling said components into an uncured tire, and
• (e) curing the tire.

In a pneumatic tire comprising a plurality of components including a tire tread, a pair of sidewalls, a cord reinforced carcass, a pair of beads and one or more additional elastomeric structural reinforcing components, the improvement wherein at least one of said components comprises aramid fiber-reinforced vulcanized elastomeric composite comprising a matrix of cured elastomer, a reinforcing amount of a particulate reinforcing agent selected from the group consisting of carbon black, silica, clay and mixtures thereof, and an effective reinforcing amount not exceeding 5 parts by weight per 100 of elastomer, of short, discontinuous, fibrillated aramid fibers dispersed therein, said fibers being composed of (a) a trunk portion having a length in the range of about 0.2 to about 5 millimeters, a diameter in the range of about 0.005 to about 0.02 millimeters and an aspect ratio greater than about 100, and (b) a plurality of fibrils extending outwardly from said trunk and having diameters substantially smaller than the diameter of the trunk from which they extend, said fibers having a surface area in the range of about 4 to about 20 square meters per gram, said composite being prepared by a process which comprises (1) forming a premix consisting essentially of all of said aramid fibers with at least a portion and less than all of said particulate reinforcing agent or mixture thereof, the quantity of said reinforcing agent or mixture thereof being sufficient to cause partitioning of said aramid fibers and thereby promote subsequent compounding of said aramid fibers with elastomer, (2) mixing said premix with a vulcanizable elastomer, the remaining portion of said reinforcing agent or mixture thereof, and additional tire compounding ingredients and (3) curing the tire.