INNER TUBE FOR A PNEUMATIC TYRE BASED ON A THERMOPLASTIC ELASTOMER
Inner tube for a pneumatic tyre, notably for a bicycle, characterized in that it has an elastomeric gastight layer consisting of an elastomeric composition comprising at least one styrene/isobutylene/styrene thermoplastic elastomer (called “SIBS”) and in that it includes a self-sealing material disposed inside the cavity formed by the airtight elastomeric layer.
1 . An inner tube for a pneumatic tire comprising:
an airtight elastomeric layer formed of an elastomeric composition that includes at least one styrene/isobutylene/styrene thermoplastic elastomer (SIBS elastomer); and
a self-sealing material disposed inside a cavity formed by the airtight elastomeric layer,
wherein the self-sealing material is formed of a layer of a second composition that includes, as a major elastomer, a thermoplastic styrene elastomer (TPS elastomer) and an oil for extending the TPS elastomer in an amount greater than 200 phr.
2 . The inner tube according to claim 1 , wherein a thickness of the airtight elastomeric layer lies between 0.3 and 2.5 mm.
3 . The inner tube according to claim 2 , wherein the thickness of the airtight elastomeric layer lies between 0.4 and 0.9 mm.
4 . The inner tube according to claim 2 , wherein the thickness of the airtight elastomeric layer lies between 1.2 and 2.5 mm.
5 . The inner tube according to claim 1 , wherein the pneumatic tire has a substantially circular axial section.
6 . The inner tube according to claim 1 , wherein the at least one SIBS elastomer includes between 5 and 50% by mass of styrene.
7 . The inner tube according to claim 1 , wherein a glass transition temperature (Tg) of the SIBS elastomer is below −20° C.
8 . The inner tube according to claim 1 , wherein a number-average molecular mass (Mn) of the SIBS elastomer lies between 30 000 and 500 000 g/mol.
9 . The inner tube according to claim 1 , wherein the elastomeric composition of the airtight elastomeric layer includes an extending oil.
10 . The inner tube according to claim 9 , wherein the extending oil is chosen from a group that includes polyolefinic oils, paraffinic oils, naphthenic oils, aromatic oils, mineral oils, and mixtures of these oils.
11 . The inner tube according to claim 9 , wherein the extending oil is chosen from a group that includes polybutenes.
12 . The inner tube according to claim 9 , wherein the extending oil is a polyisobutylene oil.
13 . The inner tube according to claim 9 , wherein a number-average molecular mass (Mn) of the extending oil lies between 200 and 25 000 g/mol.
14 . The inner tube according to claim 9 , wherein an amount of the extending oil is greater than 5 phr (phr signifying parts by weight per hundred parts of elastomer).
15 . The inner tube according to claim 1 , wherein the self-sealing material is a viscous liquid.
16 . The inner tube according to claim 15 , wherein the self-sealing material includes at least one constituent chosen from a group that includes glycol, fibres, vulcanized rubber particles, particles of cellular material, and mixtures thereof.
17 . The inner tube according to claim 1 , wherein the self-sealing material includes a non-aqueous fluid matrix.
18 . The inner tube according to claim 15 , wherein the self-sealing material has a viscosity of less than 60 centipoise at 20° C.
19 . A method for producing an inner tube comprising steps of:
forming a tube using a gastight elastomeric composition that includes at least one styrene/isobutylene/styrene thermoplastic elastomer (SIBS elastomer);
attaching an inflating valve to the tube;
introducing a predetermined quantity of self-sealing material into a cavity of the tube; and
forming an overlapping end weld.
20 . The method according to claim 19 , wherein the forming of the tube is by extrusion or extrusion/blow moulding.
21 . The method according to claim 19 , wherein the forming of the tube is by injection moulding.
22 . (canceled)
23 . The inner tube according to claim 1 , wherein the amount of the oil for extending the TPS elastomer is less than 1200 phr.
24 . The inner tube according to claim 1 , wherein the TPS elastomer is chosen from a group that includes styrene/butadiene/styrene copolymers, styrene/isoprene/styrene copolymers, styrene/isoprene/butadiene/styrene copolymers, styrene/ethylene/butylene/styrene (SEBS) copolymers, styrene/ethylene/propylene/styrene (SEPS) copolymers, styrene/ethylene/ethylene/propylene/styrene block copolymers, and mixtures of these copolymers.
25 . The inner tube according to claim 24 , wherein the TPS elastomer is chosen from a group that includes SEBS copolymers, SEPS copolymers, and mixtures of these copolymers.
26 . The inner tube according to claim 1 , wherein the TPS elastomer includes between 5 and 50% by mass of styrene.
27 . The inner tube according to claim 1 , wherein a glass transition temperature (Tg) of the TPS elastomer is below −20° C.
28 . The inner tube according to claim 1 , wherein a number-average molecular mass (Mn) of the TPS elastomer lies between 50 000 and 500 000 g/mol.
29 . The inner tube according to claim 1 , wherein the oil for extending the TPS elastomer is chosen from a group that includes polyolefinic oils, paraffinic oils, naphthenic oils, aromatic oils, mineral oils, and mixtures of these oils.
30 . The inner tube according to claim 1 , wherein the oil for extending the TPS elastomer is chosen from a group that includes polybutenes, paraffinic oils, and mixtures thereof.
31 . The inner tube according to claim 1 , wherein the oil for extending the TPS elastomer is a polyisobutylene oil.
32 . The inner tube according to claim 1 , wherein a number-average molecular mass (Mn) of the oil for extending the TPS elastomer lies between 200 and 30 000 g/mol.
33 . The inner tube according to claim 1 , wherein the amount of the oil for extending the TPS elastomer lies between 300 and 700 phr.
34 . The inner tube according to claim 1 , wherein a thickness of the airtight elastomeric layer lies between 0.3 mm and 2.5 mm.
35 . The inner tube according to claim 1 , wherein the self-sealing material is disposed on part of an inner wall of the airtight elastomeric layer on a side with a largest diameter of the inner wall.
36 . The inner tube according to claim 1 , wherein the self-sealing material is disposed on part of an inner wall of the airtight elastomeric layer at least from one equator to another passing on a side with largest diameter of the inner wall.
37 . The inner tube according to claim 1 , wherein the self-sealing material is disposed on an entire inner wall of the airtight elastomeric layer.
38 . A method for producing an inner tube comprising steps of:
forming a tube by coextruding:
a first elastomeric composition including at least one styrene/isobutylene/styrene thermoplastic elastomer (SIBS), and
a second elastomeric composition including a thermoplastic styrene elastomer (TPS), which is identical to or different from SIBS, and an oil for extending the TPS in an amount greater than 200 phr; and
closing an inner cavity of the tube.
39 . The method according to claim 38 , wherein the inner cavity of the tube is closed by welding two ends of the tube.
40 . The method according to claim 38 , wherein the inner cavity of the tube is closed by making an overlap end weld.
41 . The method according to claim 38 , further comprising a step of attaching an inflating valve to the tube before the inner cavity of the tube is closed.
42 . The inner tube according to claim 1 , wherein a glass transition temperature (Tg) of the TPS elastomer is below −40° C.
43 . The inner tube according to claim 9 , wherein an amount of the extending oil is greater than 5 and less than 100 phr (phr signifying parts by weight per hundred parts of elastomer).