Airtight multilayer laminate for a pneumatic object
View Patent ↗A multilayer elastomer laminate that is impermeable to inflation gases, which is capable of adhering to a diene elastomer composition and which can be used in an inflatable article provided with such a diene composition, said laminate comprising at least two superposed elastomer layers (phr signifying parts by weight per hundred parts of elastomer, in each elastomer composition considered): as a gastight first layer, a first elastomer composition comprising more than 50 phr of a copolymer containing polystyrene and polyisobutylene blocks; as an adhesive second layer, a second elastomer composition comprising more than 50 phr of an unsaturated thermoplastic styrene copolymer and optionally a liquid plasticizing agent at a content from 0 to less than 100 phr. This multilayer laminate possesses very good impermeability properties and a reduced hysteresis compared to layers based on butyl rubber, and also a high adhesion to a diene elastomer third layer.
1. An elastomer laminate that is impermeable to inflation gases, said laminate comprising at least two superposed thermoplastic styrene elastomer layers, wherein:
a first gastight layer is a first elastomer composition comprising more than 50 phr of a first copolymer containing polystyrene and polyisobutylene blocks; and
a second adhesive layer is a second elastomer composition comprising more than 50 phr of an unsaturated thermoplastic styrene second copolymer and optionally a liquid plasticizing agent at a content from 0 to less than 100 phr.
2. The laminate according to claim 1 , wherein the first copolymer is chosen from the group consisting of styrene/isobutylene copolymers, styrene/isobutylene/styrene copolymers and mixtures of these copolymers.
3. The laminate according to claim 2 , wherein the first copolymer is a styrene/isobutylene/styrene copolymer.
4. The laminate according to claim 1 , wherein the second copolymer is a copolymer comprising styrene blocks and diene blocks.
5. The laminate according to claim 4 , wherein the diene blocks are isoprene or butadiene blocks.
6. The laminate according to claim 5 , wherein the second copolymer is chosen from the group consisting of styrene/butadiene (SB), styrene/isoprene (SI), styrene/butadiene/butylene (SBB), styrene/butadiene/isoprene (SBI), styrene/butadiene/styrene (SBS), styrene/butadiene/butylene/styrene (SBBS), styrene/isoprene/styrene (SIS) and styrene/butadiene/isoprene/styrene (SBIS) block copolymers and mixtures of these copolymers.
7. The laminate according to claim 1 , wherein the content of first copolymer in the first composition is greater than 70 phr.
8. The laminate according to claim 1 , wherein the content of second copolymer in the second composition is greater than 70 phr.
9. The laminate according to claim 1 , wherein each of the first and second copolymers comprise between 5 and 50% by weight of styrene.
10. The laminate according to claim 1 , wherein the glass transition temperature of each of the first and second copolymers is below −20° C.
11. The laminate according to claim 1 , wherein the number-average molecular weight of each of the first and second copolymers is between 30 000 and 500 000 g/mol.
12. The laminate according to claim 1 , wherein the first gastight layer comprises an extender oil.
13. The laminate according to claim 12 , 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.
14. The laminate according to claim 13 , wherein the extender oil is a polybutene oil.
15. The laminate according to claim 14 , wherein the polybutene oil is a polyisobutylene oil.
16. The laminate according to claim 12 , wherein the number-average molecular weight of the extender oil is between 200 and 25 000 g/mol.
17. The laminate according to claim 12 , wherein the content of extender oil is greater than 5 phr.
18. The laminate according to claim 17 , wherein the content of extender oil is between 5 and 100 phr.
19. The laminate according to claim 1 , wherein the content of liquid plasticizing agent in the second elastomer composition is between 5 and 50 phr.
20. The laminate according to claim 1 , wherein the liquid plasticizing agent of the second elastomer composition is an oil chosen from the group consisting of polyolefin oils, paraffinic oils, naphthenic oils, aromatic oils, mineral oils and mixtures of these oils.
21. The laminate according to claim 1 , wherein the liquid plasticizing agent of the second elastomer composition is a liquid elastomer.
22. The laminate according to claim 1 , wherein the first gastight layer comprises a platy filler.
23. An article comprising a laminate according to claim 1 .
24. The article according to claim 23 , wherein the laminate is placed on the inner wall of the inflatable article.
25. The article according to claim 23 , wherein said article is a pneumatic tire.
26. The article according to claim 23 , wherein said article is an inner tube.