One-component flexible polyurethane foam compositions and methods for their use

Abstract

Foamable one-part polyurethane compositions contain a high functionality quasi-prepolymer and a hydrated salt. The foamable compositions are capable of expanding to 1000% or more of their original volume to form a low density, stable foam. The compositions are particularly useful as foam-in-place thermal or sound insulation materials, especially in vehicle applications.

Description

Claims

1. A one-component foamable polyurethane composition comprising a) an isocyanate-terminated quasi-prepolymer having an isocyanate content of from 15 to 27% by weight, the quasi-prepolymer having an average isocyanate functionality of from 2.6 to 3.5;b) a hydrated salt of an alkali metal or of an alkaline earth metal, which hydrated salt loses at least one mole of water of hydration per mole of salt when exposed to at least one temperature in the range of from 80 to 190° C.; andc) at least one catalyst for the reaction between an isocyanate group and water, wherein the hydrated salt is present in an amount such that at least 0.5 equivalents of water of hydration are provided per equivalent of isocyanate groups in the quasi-prepolymer when the foamable polyurethane composition is heated to at least one temperature in the range of from 80 to 190° C.

2. The foamable polyurethane composition of claim 1 wherein the hydrated salt loses at least two moles of water per mole of salt when exposed to at least one temperature in the range of from 100 to 180° C.

3. The foamable polyurethane composition of claim 2, further comprising d) from 20 to 50% by weight of the composition of a plasticizer, rubber or combination thereof.

4. The foamable polyurethane composition of claim 2, wherein the isocyanate index is from 20 to 200.

5. The foamable polyurethane composition of claim 4 wherein the quasi-prepolymer has an isocyanate content of from 20 to 25% by weight and an average isocyanate functionality of from 3.0 to 3.4.

6. The foamable polyurethane composition of claim 3, wherein the hydrated salt is a borate or perborate salt.

7. The foamable polyurethane composition of claim 6, wherein the catalyst includes at least one tertiary amine compound.

8. The foamable polyurethane composition of claim 7, wherein at least one of the borate or perborate salt and the tertiary amine compound are encapsulated.

9. The foamable polyurethane composition of claim 7 wherein the hydrated salt is sodium borate or sodium perborate.

10. The foamable polyurethane composition of claim 8 wherein the hydrated salt is sodium borate or sodium perborate.

11. The foamable polyurethane composition of claim 3 wherein the hydrated salt is sodium citrate or potassium citrate.

12. A method of making a rigid polyurethane foam, comprising heating a one-component foamable polyurethane composition containing an isocyanate-terminated prepolymer and a hydrated salt of an alkali or alkaline earth metal to a temperature from 80 to 190° C. such that the hydrated salt loses at least one mole of water of hydration per mole of salt and said released water of hydration reacts with isocyanate groups on the isocyanate-terminated prepolymer to expand and cure the composition, wherein a) the isocyanate-terminated quasi-prepolymer has an isocyanate content of from 15 to 27% by weight and an average isocyanate functionality of from 2.6 to 3.5;b) the hydrated salt loses at least one mole of water per mole of salt when exposed to at least one temperature in the range of 80 to 190° C. andc) the composition contains at least one catalyst for the reaction between an isocyanate group and water.

13. The method of claim 12 wherein the hydrated salt loses at least two moles of water per mole of salt when exposed to at least one temperature in the range of from 100 to 180° C.

14. The method of claim 13, further comprising d) from 20 to 50% by weight of a plasticizer, rubber or combination thereof.

15. The method of claim 14, wherein the isocyanate index is from 40 to 200.

16. The method of claim 15 wherein the quasi-prepolymer has an isocyanate content of from 20 to 25% by weight and an average isocyanate functionality of from 3.0 to 3.4.

17. The method of claim 14, wherein the hydrated salt is a borate or perborate salt.

18. The method of claim 17, wherein the catalyst includes at least one tertiary amine compound.

19. The method of claim 18, wherein at least one of the borate or perborate salt and the tertiary amine compound is encapsulated.

20. The method of claim 18 wherein the hydrated salt is sodium borate or sodium perborate.

21. The method of claim 19 wherein the hydrated salt is sodium borate or sodium perborate.

22. The method of claim 14 wherein the hydrated salt is sodium or potassium citrate.

23. The method of claim 11, wherein the polyurethane composition expands by at least 1000%.

24. The method of claim 23, wherein the polyurethane composition expands by at least 2000%.

25. The method of claim 24, wherein the polyurethane composition expands by at least 2500%.

26. A method of reinforcing a cavity in a vehicle, comprising placing the one-component foamable polyurethane composition of claim 1 into the cavity, and then exposing the polyurethane-forming composition to a temperature of from 80 to 190° C. such that the hydrated salt loses at least one water of hydration and the released water of hydration reacts with isocyanate groups on the isocyanate-terminated prepolymer to expand and cure the composition to form a polyurethane foam within and adhered to the cavity.

27. The method of claim 26, wherein the cavity is assembled onto a vehicle or vehicle sub-assembly, said vehicle or vehicle sub-assembly is coated with a thermally-curable coating either before or after the polyurethane composition is placed into said cavity, and the step of exposing the polyurethane composition to a temperature of from 80 to 190° C. is performed simultaneously with thermally curing the coating.