Pneumatic Object Provided with Gas-Tight Layer Comprising Two Thermoplastic Elastomers
Inflatable article equipped with an elastomer layer impermeable to the inflation gases comprising at least: as first thermoplastic stirene elastomer, at least 50 phr of a copolymer containing polystirene and polyisobutylene blocks, in particular SIBS; as second thermoplastic stirene elastomer, at most 50 phr of a thermoplastic stirene copolymer of unsaturated type, in particular SIS; and optionally an extender oil, in particular polybutene, at a content preferably between 5 and 100 phr. This gastight elastomer layer has very good impermeability properties and a lower hysteresis compared to layers based on butyl rubber. The inflatable article can be, in particular, an inner tube or a pneumatic tire for a motor vehicle.
1 . An inflatable article equipped with an elastomer layer impermeable to inflation gases, wherein said elastomer layer comprises:
as first thermoplastic stirene elastomer, at least 50 phr of a copolymer containing polystirene and polyisobutylene blocks; and
as second thermoplastic stirene elastomer, at most 50 phr of an unsaturated thermoplastic stirene copolymer.
2 . The inflatable article according to claim 1 , wherein the first elastomer 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 2 , wherein the first elastomer is a stirene/isobutylene/stirene copolymer.
4 . The inflatable article according to claim 1 , wherein the content of first thermoplastic stirene elastomer is at least 70 phr.
5 . The inflatable article according to claim 1 , wherein the content of second thermoplastic stirene elastomer is at most 30 phr.
6 . The inflatable article according to claim 5 , wherein the content of second thermoplastic stirene elastomer is within a range from 1 to 30 phr.
7 . The inflatable article according to claim 6 , wherein the content of second thermoplastic stirene elastomer is within a range from 2 to 25 phr.
8 . The inflatable article according to claim 1 , wherein the second thermoplastic stirene elastomer is a copolymer comprising stirene blocks and diene blocks.
9 . The inflatable article according to claim 8 , wherein the diene blocks are isoprene or butadiene blocks.
10 . The inflatable article according to claim 9 , wherein the second stirene elastomer is chosen from the group consisting of stirene/butadiene (SB), stirene/isoprene (SI), stirene/butadiene/butylene (SBB), stirene/butadiene/isoprene (SBI), stirene/butadiene/stirene (SBS), stirene/butadiene/butylene/stirene (SBBS), stirene/isoprene/stirene (SIS) and stirene/butadiene/isoprene/stirene (SBIS) block copolymers and blends of these copolymers.
11 . The inflatable article according to claim 1 , wherein each thermoplastic stirene elastomer comprises between 5 and 50% by weight of stirene.
12 . The inflatable article according to claim 1 , wherein the glass transition temperature of each thermoplastic stirene elastomer is less than −20° C.
13 . The inflatable article according to claim 1 , wherein the number-average molecular weight of the first thermoplastic stirene elastomer is between 30 000 and 500 000 g/mol.
14 . The inflatable article according to claim 1 , wherein the number-average molecular weight of the second thermoplastic stirene elastomer is between 3000 and 500 000 g/mol.
15 . The inflatable article according to claim 1 , wherein the airtight layer comprises an extender oil.
16 . The inflatable article according to claim 15 , 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.
17 . The inflatable article according to claim 16 , wherein the extender oil is chosen from the group consisting of polybutene oils.
18 . The inflatable article according to claim 17 , wherein the extender oil is a polyisobutylene oil.
19 . The inflatable article according to claim 15 , wherein the number-average molecular weight of the extender oil is between 200 and 25 000 g/mol.
20 . The inflatable article according to claim 15 , wherein the content of extender oil is greater than 5 phr.
21 . The inflatable article according to claim 20 , wherein the content of extender oil is between 5 and 100 phr.
22 . The inflatable article according to claim 1 , wherein the airtight elastomer layer comprises a platy filler.
23 . The inflatable article according to claim 1 , wherein the elastomer layer has a thickness greater than 0.05 mm.
24 . The inflatable article according to claim 23 , wherein the elastomer layer has a thickness between 0.1 and 10 mm.
25 . The inflatable article according to claim 1 , wherein the elastomer layer is placed on the inner wall of the inflatable article.
26 . The inflatable article according to claim 1 , wherein said inflatable article is a pneumatic tire.
27 . The inflatable article according to claim 1 , wherein said inflatable article is an inner tube.