Rubber composition containing solid magnetizable particles of greater stiffness than the rubbery compounds

A process for preparing a rubber composition, wherein the rubber composition comprises about 100 parts by weight of at least one sulfur vulcanizable elastomer selected from conjugated diene homopolymers and copolymers, 50 to 250 phr solid magnetizable ferrite particles, 2 to 8 organosilane polysulfide bonding the elastomer and the ferrite particles, accelerator(s), and sulfur, comprising at least three mixing stages of:

• 1) preparing a first master batch by mixing all of the at least one elastomer, half of the ferrite particles and all of the organosilane polysulfide,
• 2) preparing a second master batch by mixing the first master batch with all remaining ingredients, including the other half of the ferrite particles, and not including the accelerators and sulfur,
• 3) completing the rubber composition by mixing the second batch with the accelerators and sulfur.