Elastomeric compositions and their applications
The present disclosure relates to self-sealing silicone sealant and/or gel compositions cured via a condensation cure chemistry and to their use subsequent to cure as puncture-resistant layers in any type of “inflatable” article, i.e. articles which take their functional shape after inflation with a suitable gas such as air. The present disclosure also relates to silicone materials, e.g. elastomers and/or gels obtained subsequent to curing said compositions designed to function as self-sealing tire puncture material, i.e. to seal puncture holes in the tread region of tires if/when punctured by a foreign body.
1. A multi-part self-sealing moisture curing silicone sealant composition comprising:
(i) at least one condensation curable silyl terminated polymer having at least one, optionally at least 2 hydroxyl functional groups per molecule;
(ii) a cross-linker selected from the group consisting of;
silanes having at least 2 hydrolysable groups, optionally at least 3 hydrolysable groups per molecule, and/or
silyl functional molecules having at least 2 silyl groups, each silyl group containing at least one hydrolysable group;
(iii) a condensation catalyst selected from the group consisting of titanates and/or zirconates; and
(iv) a filler;
wherein polymer (i), cross-linker (ii) and condensation catalyst (iii) are not stored together in a single part; and
wherein the molar ratio of total silicon-bonded hydroxyl groups to total hydrolysable groups is between 0.5:1 and 2:1 using a silane containing cross-linker (ii) or 0.5:1 to 10:1 using a silyl functional molecule containing cross-linker (ii) and the molar ratio of condensation catalyst (iii) M-OR functions to the sum of moisture present in the composition, as determined in accordance with ISO 787-2:1981, and total silicon-bonded hydroxyl groups is between 0.01:1 and 0.6:1, where M is titanium or zirconium and R is an aliphatic hydrocarbon group.
2. The multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1 , wherein the viscosity of the polymer (i) and the cross-linker (ii) when mixed at 23° C. is at least 40,000 mPa·s.
3. The multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1 , wherein the filler (iv) is selected from the group consisting of fumed and precipitated silicas, calcium carbonate, carbon black, hollow glass beads and/or carbon nanotubes.
4. The multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 3 , wherein the filler (iv) is multiwall carbon nanotubes and/or is carbon black.
5. The multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1 , wherein the molar ratio of total silicon-bonded hydroxyl groups to total hydrolysable groups is between 1:1 and 2:1.
6. The multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1 , wherein the composition is stored in two parts, a base part comprising polymer (i) and filler (iv), and a curing part comprising cross-linker (ii) and condensation catalyst (iii).
7. The multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1 , wherein polymer (i) has at least 2 hydroxyl functional groups per molecule.
8. The multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1 , wherein cross-linker (ii) is selected from the group consisting of silanes having at least 3 hydrolysable groups per molecule.
9. The multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1 , wherein the filler (iv) contains moisture.
10. The multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1 , wherein the condensation catalyst (iii) comprises a titanate.
11. The multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 10 , wherein the titanate is of the general formula Ti[OR] 4 where R is an aliphatic hydrocarbon group.
12. A moisture cured self-sealing silicone sealant for an inflatable article comprising the condensation reaction product of the multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1 .
13. A self-sealing inflatable article comprising the moisture cured self-sealing silicone sealant in accordance with claim 12 .
14. The self-sealing inflatable article in accordance with claim 13 which is in the form of a tire.
15. The self-sealing inflatable article in accordance with claim 14 comprising:
a) a tire body that is made of flexible and airtight material and is adapted to be assembled with a rim; and
b) the moisture cured self-sealing silicone sealant adapted to seal a puncture in the tire body.
16. The self-sealing inflatable article in accordance with claim 13 having a puncture-resistant layer, wherein the puncture-resistant layer is a layer of the moisture cured self-sealing silicone sealant.
17. The self-sealing inflatable article according to claim 16 , wherein the puncture-resistant layer has a thickness of greater than 0.3 mm.
18. The self-sealing inflatable article according to claim 17 , wherein the puncture-resistant layer has a thickness of between 0.5 mm and 10 mm.
19. The self-sealing inflatable article according to claim 16 , wherein the puncture-resistant layer is positioned on an internal wall of the inflatable article.
20. A self-sealing tire comprising the condensation reaction product of the multi-part self-sealing moisture curing silicone sealant composition in accordance with claim 1 .