Sealing material, tire for a vehicle wheel including the sealing material, and process for producing the tire

A process for producing a tyre for a vehicle wheel, comprising:

• making at least one coating layer of cross-linkable elastomeric material on an outer surface of a toroidal support whose shape is essentially complementary to an inner surface of the tyre;
• making at least one layer consisting of a composition in a circumferentially outer position with respect to the at least one coating, wherein said composition comprises:
• 100 phr of at least one thermally degradable polymer;
• greater than or equal to 50 phr and less than or equal to 150 phr of at least one reinforcing filler;
• greater than or equal to 30 phr and less than or equal to 100 phr of at least one plasticizer;
• and
• greater than or equal to 10 phr of at least one organic peroxide:
• said at least one layer being;
• disposing a carcass structure comprising at least one carcass ply in a circumferentially outer position with respect to the at least one layer consisting of said composition comprising at least one thermally degradable polymer;
• disposing a belt structure in a circumferentially outer position with respect to the carcass structure;
• disposing a tread in a circumferentially outer position with respect to the belt structure;
• disposing at least one pair of sidewalls on the carcass structure in laterally opposite positions;
• subjecting the at least one coating layer, the at least one layer consisting of said composition comprising at least one thermally degradable polymer, the carcass structure, the belt structure, the tread, and the at least one pair of sidewalls to moulding in a cavity formed in a vulcanization mould;
• and
• subjecting the at least one coating layer, the at least one layer consisting of said composition comprising at least one thermally degradable polymer, the carcass structure, the belt structure, the tread, and the at least one pair of sidewalls to cross-linking by heating to a predetermined temperature and for a predetermined period of time;
• wherein, at an end of the cross-linking, said composition comprising at least one thermally degradable polymer comprises the following characteristics:
• a value of a dynamic elastic modulus, measured at a temperature of 80° C., at a frequency of 1 Hz, and with a deformation of 5%, that is at least 60% lower than the value of the dynamic elastic modulus measured at the temperature of 80° C., at the frequency of 1 Hz, and with a deformation of 1%;
• and
• the value of the dynamic elastic modulus, measured at the temperature of 80° C., at the frequency of 1 Hz, and with the deformation of 5%, that is greater than or equal to 0.05 kPa.

A sealing material comprising:

• 100 phr of at least one thermally degradable polymer;
• greater than or equal to 50 phr and less than or equal to 150 phr of at least one reinforcing filler;
• greater than or equal to 30 phr and less than or equal to 100 phr of at least one plasticizer;
• and
• greater than or equal to 10 phr of at least one organic peroxide;
• wherein said sealing material comprises the following characteristics:
• a value of a dynamic elastic modulus, measured at a temperature of 80° C., at a frequency of 1 Hz, and with a deformation of 5%, that is at least 60% lower than a value of the dynamic elastic modulus measured at the temperature of 80° C., at the frequency of 1 Hz, and with a deformation of 1%;
• and
• the value of the dynamic elastic modulus, measured at the temperature of 80° C., at the frequency of 1 Hz, and with the deformation of 5%, that is greater than or equal to 0.05 kPa.