Pneumatic Object Provided with a Gas-Tight Layer Comprising a Thermoplastic Elastomer and Expanded Thermoplastic Microspheres
An inflatable article provided with an elastomer layer impermeable to the inflation gas, such as air, said layer comprising at least, as major elastomer, a thermoplastic polystirene/polyisobutylene block copolymer, such as an SIBS (stirene/isobutylene/stirene) copolymer, and expanded thermoplastic microspheres with a preferential content between 1 and 30 phr. Preferably, this copolymer comprises between 5% and 50% stirene by weight, its number-average molecular weight is between 30 000 and 500 000 g/mol and its Tg is below −20° C. Optionally, the gastight elastomer layer also contains, as plasticizer, an extender oil, especially a polybutene oil, with a preferential content between 5 and 100 phr. This gastight layer not only has excellent impermeability properties, but also a density and a hysteresis that are both reduced compared with layers based on butyl rubber. The inflatable article can be a pneumatic tire for a motor vehicle.
1 . An inflatable article equipped with an elastomer layer impermeable to inflation gases, characterized in that said elastomer layer comprises at least, as major elastomer, a thermoplastic polystirene/polyisobutylene block copolymer and expanded thermoplastic microspheres.
2 . The inflatable article according to claim 1 , wherein the thermoplastic copolymer is chosen from the group consisting of stirene/isobutylene copolymers, stirene/isobutylene/stirene copolymers and mixtures of these copolymers.
3 . The inflatable article according to claim 1 , wherein the thermoplastic copolymer comprises between 5 and 50% by weight of stirene.
4 . The inflatable article according to claim 1 , wherein the glass transition temperature of the thermoplastic copolymer is less than −20° C.
5 . The inflatable article according to claim 1 , wherein the number-average molecular weight of the thermoplastic copolymer is between 30 000 and 500 000 g/mol.
6 . The inflatable article according to claim 1 , wherein the gastight layer comprises an extender oil for the thermoplastic copolymer.
7 . The inflatable article according to claim 6 , wherein the extender oil is chosen from the group consisting of polyolefin oils, paraffinic oils, naphthenic oils, aromatic oils, mineral oils, and mixtures of these oils.
8 . The inflatable article according to claim 7 , wherein the extender oil is chosen from the group consisting of polybutene oils.
9 . The inflatable article according to claim 8 , wherein the extender oil is a polyisobutylene oil.
10 . The inflatable article according to claim 6 , wherein the number-average molecular weight of the extender oil is between 200 and 25 000 g/mol.
11 . The inflatable article according to claim 10 , wherein the content of extender oil is greater than 5 phr.
12 . The inflatable article according to claim 11 , wherein the content of extender oil is between 5 and 100 phr.
13 . The inflatable article according to claim 1 , wherein the gastight layer comprises a platy filler.
14 . The inflatable article according to claim 1 , wherein the content of expanded thermoplastic microspheres is between 0.1 and 30 phr.
15 . The inflatable article according to claim 14 , wherein the content of expanded thermoplastic microspheres is between 0.5 and 10 phr.
16 . The inflatable article according to claim 1 , wherein the density of the gastight elastomer layer is less than 1.0 g/cm 3 .
17 . The inflatable article according to claim 1 , wherein the density of the gastight layer is less than 0.9 g/cm 3 .
18 . The inflatable article according to claim 1 , wherein the gastight layer has a thickness greater than 0.05 mm.
19 . The inflatable article according to claim 18 , wherein the gastight layer has a thickness between 0.1 and 10 mm.
20 . The inflatable article according to claim 1 , wherein the gastight layer is placed on the inner wall of the inflatable article.
21 . The inflatable article according to claim 1 , wherein said article is made of rubber.
22 . The inflatable article according to claim 21 , wherein said rubber article is a pneumatic tire.
23 . The inflatable article according to claim 21 , wherein said inflatable article is an inner tube.
24 . (canceled)