Low density attached polyurethane foams made by containment of blowing agents during foam processing
View Patent ↗Polyurethane cushions are formed on the surface of a textile such as carpet. The polyurethane is made in the reaction of a polyurethane forming composition that is frothed, and contains water as a blowing agent. The polyurethane forming composition is cured between the substrate and a containment layer, both of which prevent the blowing gasses from escaping during the curing process. The process allows low density attached cushions to be formed controllably.
1. A process for preparing a polyurethane cushion attached to a substrate, comprising:
a) forming a frothed polyurethane-forming composition having a density of about 300 to 600 grams per liter and a gel time of at least 180 seconds, the polyurethane-forming composition including at least one polyol, 0.5 to 3.0 parts of water per 100 parts by weight polyol, and at least one polyisocyanate in an amount sufficient to provide an isocyanate index of 85 to 130;
b) forming a layer of the frothed composition between a substrate and a containment layer prior to any significant expansion of the polyurethane-forming composition due to the reaction of the water with polyisocyanate groups, by (i) dispensing the polyurethane-forming composition onto the substrate and forming it into a layer and then laying the containment layer atop the layer of the polyurethane-forming composition or (ii) dispensing the polyurethane-forming composition onto the containment layer and forming the composition into a layer and then laying the substrate atop the layer of the polyurethane-forming composition, wherein the substrate and the containment layer each comprises a physical barrier to the release of gases from the frothed composition and further wherein the containment layer is an impervious material or a semi-permeable material having small openings or voids that become plugged or filled when the material is brought into contact with the polyurethane-forming composition and
c) curing the frothed composition whereby the water reacts with isocyanate groups in the polyurethane-forming composition, generating carbon dioxide gas which expands the composition between the substrate and the containment layer to form a foamed polyurethane cushion having a density of no greater than 10 pounds/cubic foot bonded to both the substrate and containment layer.
2. The process of claim 1 , wherein step a) includes the step of
a1) forming a mixture containing at least one polyol, at least one polyisocyanate, the water and at least one filler material and then
a2) frothing the mixture from step a1).
3. The process of claim 2 , wherein the catalyst is blended into the frothed mixture after step a2).
4. The process of claim 1 , wherein step a) includes the step of
a1) forming a mixture containing at least one polyol, at least one polyisocyanate and at least one filler material, then
a2) frothing the mixture from step a1) and
a3) adding the water to the mixture during step a2).
5. The process of claim 1 , wherein the substrate is a textile.
6. The process of claim 5 , wherein the textile is a woven or tufted carpet.
7. The process of claim 1 , wherein the polyurethane-forming composition contains from 30 to 70% by weight of a particulate filler.
8. The process of claim 7 , wherein the foamed polyurethane cushion has a density of from 4 to 10 pounds/cubic foot.
9. The process of claim 1 in which water is incorporated into the mixture in the form of a blend in a polyol in which the water is soluble to the extent of at least 30% by weight at 22° C.
10. The process of claim 2 wherein in step a1) water is added to the mixture in the form of a blend in a polyol in which the water is soluble to the extent of at least 30% by weight at 22° C.
11. The process of claim 4 wherein in step a3) water is added to the polyurethane-forming composition in the form of a blend in a polyol in which the water is soluble to the extent of at least 30% by weight at 22° C.
12. The process of claim 1 , wherein step a) includes the steps of
a1) forming a frothed mixture containing at least one polyol, at least one polyisocyanate and at least one filler material but no more than 0.1 part of water per 100 parts by weight of polyol; and
a2) blending water or a mixture of water and additional polyol into the frothed mixture of step a1).
13. The process of claim 12 , further comprising, before, during or after step a2) but after step a1), blending at least one catalyst into the frothed mixture.
14. The process of claim 13 , wherein the catalyst is blended into the frothed mixture after step a2).
15. The process of claim 12 , wherein the substrate is a textile.
16. The process of claim 15 , wherein the textile is a woven or tufted carpet.
17. The process of claim 13 , wherein the polyurethane-forming composition contains from 30 to 70% by weight of a particulate filler.
18. The process of claim 17 , wherein the foamed polyurethane cushion has a density of from 4 to 10 pounds/cubic foot.
19. The process of claim 12 wherein water is added to the frothed mixture in step a2) in the form of a blend in a polyol in which the water is soluble to the extent of at least 30% by weight at 22° C.
20. The process of claim 1 , wherein the frothed polyurethane-forming composition includes from 0.6 to 1.5 parts of water per 100 parts by weight polyol.