Tire, the inner wall of which has a layer of specific polyurethane foam
The inner wall of a pneumatic tyre, in the vulcanized state, is provided with a layer of polyurethane foam, characterized in that the polyurethane is based on a diphenylmethane diisocyanate (MDI), in particular 4,4′-diphenylmethane diisocyanate, and on a polyol having an ethylene oxide content of greater than 50% (% by weight). This specific polyurethane formulation makes it possible to obtain a light foam that efficiently absorbs noise; it has the advantages of being simple and inexpensive and of being easy to process by direct casting of the reactants in the pneumatic tyre of the invention.
1. A pneumatic tire, in a vulcanized state, an inner wall of which is provided with a layer of polyurethane foam,
wherein the polyurethane foam is based on a diphenylmethane diisocyanate and on a randomly polymerized polyol having an ethylene oxide content of greater than 50% by weight of the polyol and a propylene oxide content from 10% to 50% by weight of the polyol, and
wherein a molar ratio of diphenylmethane diisocyanate/randomly polymerized polyol is between 2 and 10.
2. The pneumatic tire according to claim 1 , wherein the diphenylmethane diisocyanate is the only diisocyanate compound present.
3. The pneumatic tire according to claim 1 , wherein the diphenylmethane diisocyanate is 4,4′-diphenylmethane diisocyanate.
4. The pneumatic tire according to claim 1 , wherein the randomly polymerized polyol having an ethylene oxide content of greater than 50% by weight of the polyol is the only polyol present.
5. The pneumatic tire according to claim 1 , wherein the ethylene oxide content of the polyol is greater than 70%.
6. The pneumatic tire according to claim 1 , wherein the molar ratio of diphenylmethane diisocyanate/randomly polymerized polyol is between 3 and 6.
7. The pneumatic tire according to claim 1 , wherein the polyurethane foam has an apparent core density, measured according to the ISO 845 standard, between 0.020 and 0.070 g/cm 3 .
8. The pneumatic tire according to claim 7 , wherein the polyurethane foam has an apparent core density, measured according to the ISO 845 standard, in a range from 0.030 to 0.060 g/cm 3 .
9. The pneumatic tire according to claim 1 , wherein the polyurethane foam has a stress/strain characteristic in compression, measured according to the ISO 3386-1 standard at 50% volume compression, between 2 and 11 kPa.
10. The pneumatic tire according to claim 1 , wherein the polyurethane foam has a compression set, measured according to the ISO 1856 standard method A at 90% compression and at a temperature of 70° C., less than 25%.
11. The pneumatic tire according to claim 9 , wherein the polyurethane foam has a compression set, measured according to the ISO 1856 standard method A at 90% compression and at a temperature of 70° C., less than 15%.
12. The pneumatic tire according to claim 1 , wherein the polyurethane foam has an air flow resistivity, measured according to the ISO 4638 standard, greater than 10 000 Pa·s·m −2 .
13. The pneumatic tire according to claim 12 , wherein the polyurethane foam has an air flow resistivity, measured according to the ISO 4638 standard, greater than 20 000 Pa·s·m −2 .
14. The pneumatic tire according to claim 1 , wherein a thickness of the layer of polyurethane foam is between 5 and 100 mm.
15. The pneumatic tire according to claim 14 , wherein the thickness of the layer of polyurethane foam is between 10 and 50 mm.
16. The pneumatic tire according to claim 1 further comprising another diisocyanate compound, wherein the diphenylmethane diisocyanate represents more than 50% of the total weight of diisocyanate compounds present.
17. The pneumatic tire according to claim 1 further comprising another polyol, wherein the randomly polymerized polyol, having an ethylene oxide content of greater than 50% by weight of the polyol and a propylene oxide content from 10% to 50% by weight of the polyol, represents more than 50% of the total weight of polyols.