EPOXIDIZED POLYISOPRENE TIRE TREAD
The present invention relates to a tire tread comprising a rubber composition which improves the compromise between wear and durability of the tire, especially a tire intended to run off-road. The composition comprises: from more than 50 to 100 phr of a polyisoprene matrix, the polyisoprene matrix containing an epoxidized polyisoprene having a molar degree of epoxidation ranging from 5% to less than 50%, a carbon black and a silica, the weight of carbon black being greater than 50% of the total weight of carbon black and silica, from 0 to less than 2 phr of a coupling agent, and a crosslinking system. The epoxidized polyisoprene is an epoxidized natural rubber or an epoxidized synthetic polyisoprene having a molar content of 1,4-cis bonds of at least 90% before epoxidation, or a mixture thereof, and, if the epoxidized polyisoprene is an epoxidized polyisoprene having a molar degree of epoxidation of from 5% to 25%, the rubber composition contains more than 50 phr of epoxidized polyisoprene.
1 .- 28 . (canceled)
29 . A tire tread comprising a rubber composition comprising:
from more than 50 to 100 phr of a polyisoprene matrix, the polyisoprene matrix containing an epoxidized polyisoprene having a molar degree of epoxidation ranging from 5% to less than 50%;
a carbon black and a silica, the weight of carbon black being greater than 50% of the total weight of carbon black and silica;
from 0 to less than 2 phr of a coupling agent; and
a crosslinking system,
wherein the epoxidized polyisoprene is an epoxidized natural rubber or an epoxidized synthetic polyisoprene having a molar content of 1,4-cis bonds of at least 90% before epoxidation, or a mixture thereof, and
wherein, if the epoxidized polyisoprene is an epoxidized polyisoprene having a molar degree of epoxidation of from 5% to 25%, the rubber composition contains more than 50 phr of epoxidized polyisoprene.
30 . The tire tread according to claim 29 , wherein the content of the coupling agent is from 0 to less than 1 phr.
31 . The tire tread according to claim 30 , wherein the content of the coupling agent is from 0 to less than 0.5 phr.
32 . The tire tread according to claim 31 , wherein the content of the coupling agent is equal to 0 phr.
33 . The tire tread according to claim 29 , wherein the content of carbon black is from 30 to 90 phr.
34 . The tire tread according to claim 33 , wherein the content of carbon black is from 30 to 70 phr.
35 . The tire tread according to claim 34 , wherein the content of carbon black is from 35 to 60 phr.
36 . The tire tread according to claim 29 , wherein the content of silica is greater than 0 phr and less than or equal to 35 phr.
37 . The tire tread according to claim 36 , wherein the content of silica is from 2 to 35 phr.
38 . The tire tread according to claim 29 , wherein the carbon black has a BET specific surface area of at least 90 m 2 /g.
39 . The tire tread according to claim 38 , wherein the carbon black has a BET specific surface area of at least 100 m 2 /g.
40 . The tire tread according to claim 29 , wherein the composition comprises a covering agent for the silica.
41 . The tire tread according to claim 40 , wherein the covering agent is a polyethylene glycol.
42 . The tire tread according to claim 29 , wherein the crosslinking system is a vulcanization system.
43 . The tire tread according to claim 29 , wherein the epoxidized polyisoprene is an epoxidized natural rubber.
44 . The tire tread according to claim 29 , wherein the epoxidized polyisoprene is an epoxidized polyisoprene having a molar degree of epoxidation of from 5% to 35%.
45 . The tire tread according to claim 44 , wherein the epoxidized polyisoprene is an epoxidized polyisoprene having a molar degree of epoxidation of from 5% to 30%.
46 . The tire tread according to claim 45 , wherein the epoxidized polyisoprene is an epoxidized polyisoprene having a molar degree of epoxidation of from 5% to 25%.
47 . The tire tread according to claim 29 , wherein the epoxidized polyisoprene is an epoxidized polyisoprene having a molar degree of epoxidation of from 5% to 40%.
48 . The tire tread according to claim 47 , wherein the epoxidized polyisoprene is an epoxidized polyisoprene having a molar degree of epoxidation of from 10% to 35%.
49 . The tire tread according to claim 29 , wherein the content of the polyisoprene matrix is greater than 80 phr.
50 . The tire tread according to claim 29 , wherein the content of epoxidized polyisoprene is greater than 80 phr.
51 . The tire tread according to claim 50 , wherein the content of epoxidized polyisoprene is equal to 100 phr.
52 . The tire tread according to claim 29 , wherein the polyisoprene matrix contains a polyisoprene having a molar content of 1,4-cis bonds of at least 90%.
53 . The tire tread according to claim 52 , wherein the polyisoprene matrix is a mixture of the polyisoprene having a molar content of 1,4-cis bonds of at least 90% and the epoxidized polyisoprene.
54 . The tire tread according to claim 52 , wherein the polyisoprene having a molar content of 1,4-cis bonds of at least 90% is natural rubber.
55 . The tire tread according to claim 29 further comprising another diene elastomer.
56 . The tire tread according to claim 55 , wherein the another diene elastomer is an essentially unsaturated diene elastomer selected from the group consisting of polybutadienes, butadiene copolymers, isoprene copolymers and mixtures thereof.
57 . The tire tread according to claim 29 , wherein the content of the polyisoprene matrix is equal to 100 phr.
58 . A process for preparing the tire tread according to claim 29 comprising the steps of:
adding the carbon black, the silica and, if present, the coupling agent to the polyisoprene matrix during a first non-productive step by kneading thermomechanically until a maximum temperature of between 110° C. and 200° C. is reached;
cooling the mixture to a temperature of less than 110° C.;
subsequently incorporating the crosslinking system;
kneading the mixture up to a maximum temperature of less than 110° C. in order to obtain the rubber composition; and
calendaring or extruding the rubber composition into the tire tread.
59 . A tire comprising a tire tread according to claim 29 .
60 . The tire according to claim 59 , wherein the tire is intended to bear heavy loads.
61 . The tire according to claim 60 , wherein the tire is intended to runoff-road.
62 . The tire according to claim 61 , wherein the tire is a tire for a civil engineering vehicle.
63 . A process for preparing the tire according to claim 59 comprising the steps of:
adding the carbon black, the silica and, if present, the coupling agent to the polyisoprene matrix during a first non-productive step by kneading thermomechanically until a maximum temperature of between 110° C. and 200° C. is reached;
cooling the mixture to a temperature of less than 110° C.;
subsequently incorporating the crosslinking system;
kneading up to a maximum temperature of less than 110° C. in order to obtain the rubber composition; and
calendering or extruding the rubber composition into the tire tread.