Cesium and rubidium derivatives as catalysts for polyurethane foams
A method of making flexible polyurethane foams mixes a polyol (a hydroxyl group containing compound) with a cesium and/or rubidium fluoride catalyst, and reacts such mixture with at least one isocyanate. The cesium and/or rubidium fluoride may be used as the sole catalyst, replacing the blowing and gelling catalysts, such as amines, and metallic catalysts, such as a tin catalyst. Or, the cesium and/or rubidium fluoride may be used as a catalyst promoter in combination with traditional amine blowing and gelling catalysts and tin catalysts. The resulting flexible polyurethane foams exhibit increased thermal conductivity and lower levels of volatile organic compound emissions.
1. A method of making a flexible polyurethane foam, comprising:
(a) preparing a mixture comprising at least one hydroxyl group-containing compound and a catalyst selected from the group consisting of cesium fluoride, rubidium fluoride and mixtures thereof, wherein the catalyst is present in an amount from 0.1 to 0.5 pph by weight based on parts of polyol; and
(b) reacting the mixture with at least one isocyanate.
2. The method according to claim 1 , wherein the at least one hydroxyl group-containing compound is selected from the group consisting of a monool, a diol, a triol, a tetraol, a pentaol, a hexaol, a heptaol, and combinations thereof.
3. The method according to claim 1 , wherein the catalyst is introduced to the mixture a) as a solution with water.
4. The method according to claim 1 , wherein the reacting step is performed in the absence of an amine-containing or an ammonium-containing compound.
5. The method according to claim 1 , wherein the reacting step is performed in the absence of a tin-containing compound.
6. The method according to claim 1 , wherein the reacting step is performed in the absence of an amine-containing or an ammonium-containing compound, and in the absence of a tin-containing compound.
7. The method according to claim 1 , wherein the reacting step a) is carried out in the presence of at least one additional catalyst selected from the group consisting of an amine-containing compound, an ammonium-containing compound, and a tin-containing compound.
8. The method according to claim 7 , wherein the amine-containing compound is present in an amount from 0.05 to 0.25 pph by weight based on parts of polyol.
9. The method according to claim 7 , wherein the tin-containing compound is present in an amount from 0.03 to 0.1 pph by weight based on parts of polyol.
10. The method according to claim 1 , wherein the mixture a) further comprises at least one additive.
11. The method according to claim 10 , wherein the additive is selected from the group consisting of a surfactant, a cross-linker, a blowing agent, a performance additive, and mixtures thereof.
12. The method according to claim 11 , wherein the mixture consists essentially of the at least one polyol, the catalyst selected from the group consisting of cesium fluoride and rubidium fluoride and mixtures thereof, and the at least one additive.
13. The method according to claim 12 , wherein the polyol comprises a polyether polyol.
14. A flexible polyurethane foam prepared by the method of claim 1 .
15. The flexible polyurethane foam according to claim 14 , wherein the polyurethane foam exhibits thermal conductivity of about 0.05 to 0.2 W/mK.
16. The flexible polyurethane foam according to claim 14 , wherein the polyurethane foam exhibits lower volatile organic compound (VOC) emissions than a control polyurethane foam prepared without using the cesium fluoride or rubidium fluoride as catalyst.
17. A flexible polyurethane foam prepared by the method of claim 12 .
18. The flexible polyurethane foam of claim 17 , wherein the at least one polyol is a polyether polyol.
19. A polyurethane foam-forming composition, comprising:
at least one hydroxyl group-containing compound;
a catalyst selected from the group consisting of cesium fluoride, rubidium fluoride and mixtures thereof, and
at least one isocyanate.
20. The polyurethane foam-forming composition of claim 19 , further comprising at least one additional catalyst selected from the group consisting of an amine-containing compound, an ammonium-containing compound, and a tin-containing compound.