Pneumatic Tire Having a Top Area with a Water Barrier Layer
A radial tire ( 1 ) for motor vehicle, comprising: a crown ( 2 ) surmounted by a tread ( 3 ) provided with at least one radially outer part ( 3 a ) intended to come into contact with the road; two inextensible beads ( 4 ), two sidewalls ( 5 ) connecting the beads ( 4 ) to the tread ( 3 ), a carcass reinforcement ( 6 ) passing into the two sidewalls ( 5 ) and anchored in the beads ( 4 ); the crown ( 2 ) being reinforced by a crown reinforcement or belt ( 7 ) placed circumferentially between the carcass reinforcement ( 6 ) and the tread ( 3 ); a radially inner elastomer layer ( 3 b , 8 ) known as a “underlayer”, having a formulation different from the formulation of the radially outer elastomer layer ( 3 a ), this underlayer being placed between the radially outer layer ( 3 a ) of the tread ( 3 ) and the belt ( 7 ), wherein said underlayer comprises 50 to 100 phr of a copolymer based on stirene and on butadiene, preferably an SBR having in particular a Tg above −40° C., a reinforcing filler and between 10 and 150 phr of a platy filler. This elastomer underlayer has excellent water-barrier properties, giving the tire and its belt improved protection against the risks of water penetration through the tread.
1 . A radial tire for a motor vehicle, comprising:
a crown surmounted by a tread provided with at least one radially outer part intended to come into contact with the road;
two inextensible beads, two sidewalls connecting the beads to the tread, a carcass reinforcement passing into the two sidewalls and anchored in the beads;
the crown being reinforced by a crown reinforcement or belt placed circumferentially between the carcass reinforcement and the tread;
a radially inner elastomer layer named “underlayer” underlayer, having a formulation different from the formulation of the radially outer elastomer layer, this underlayer being placed between the radially outer layer of the tread and the belt,
wherein said underlayer comprises 50 to 100 phr of a copolymer based on stirene and on butadiene, a reinforcing filler and between 10 and 150 phr of a platy filler.
2 . The tire according to claim 1 , wherein said copolymer is chosen from the group consisting of stirene-butadiene copolymers, stirene-butadiene-isoprene copolymers and blends of such copolymers.
3 . The tire according to claim 2 , wherein said copolymer is a stirene-butadiene copolymer.
4 . The tire according to claim 1 , wherein said copolymer has a glass transition temperature which is above −40° C.
5 . The tire according to claim 4 , wherein the glass transition temperature of said copolymer is above −35° C.
6 . The tire according to claim 5 , wherein the glass transition temperature of said copolymer is between −30° C. and 0° C.
7 . The tire according to claim 1 , wherein said copolymer based on stirene and on butadiene is used as a blend with a second diene elastomer, different from said copolymer based on stirene and on butadiene.
8 . The tire according to claim 7 , wherein the second diene elastomer is chosen from the group consisting of natural rubbers, synthetic polyisoprenes, polybutadienes, isoprene copolymers and blends of these elastomers.
9 . The tire according to claim 8 , wherein the second diene elastomer is an isoprene elastomer.
10 . The tire according to claim 9 , wherein the isoprene elastomer is natural rubber.
11 . The tire according to claim 1 , wherein the content of said copolymer in the underlayer is within a range from 50 to 90 phr.
12 . The tire according to claim 11 , wherein the content of said copolymer in the underlayer is within a range from 60 to 85 phr.
13 . The tire according to claim 1 , wherein the content of second diene elastomer in the underlayer is within a range from 10 to 50 phr.
14 . The tire according to claim 13 , wherein the content of second diene elastomer in the underlayer is within a range from 15 to 40 phr.
15 . The tire according to claim 1 , wherein the content of reinforcing filler in the underlayer is greater than 20 phr.
16 . The tire according to claim 15 , wherein the content of reinforcing filler is within a range from 30 to 70 phr.
17 . The tire according to claim 1 , wherein the reinforcing filler comprises silica or carbon black or a mixture of silica and carbon black.
18 . The tire according to claim 1 , wherein the content of platy filler in the underlayer is between 20 and 100 phr.
19 . The tire according to claim 18 , wherein the content of platy filler is within a range from 25 to 80 phr.
20 . The tire according to claim 1 , wherein the platy filler is chosen from the group consisting of graphites, talcs, micas and mixtures of such fillers.
21 . The tire according to claim 20 , wherein the platy filler comprises graphite particles.
22 . The tire according to claim 1 , wherein the underlayer additionally comprises a hydrocarbon plasticizing resin.
23 . The tire according to claim 1 , wherein the underlayer has a thickness between 0.1 and 2 mm.
24 . The tire according to claim 23 , wherein the underlayer has a thickness within a range from 0.2 to 1.5 mm.
25 . The tire according to claim 1 , wherein the underlayer constitutes the base of a tread of cap-base construction.
26 . The tire according to claim 1 , wherein the underlayer is external to the tread, placed between the tread and the belt.
27 . (canceled)