Low density attached polyurethane foams made using a combination of frothing and blowing methods

Abstract

Textiles backed with a polyurethane cushion are produced by applying a layer of frothed polyurethane-forming mixture to a surface of the textile. The mixture contains both water and a physical blowing agent. The layer expands due to the action of the water and the physical blowing agent and cures to form an attached cushion having a density of 176 g/L or less.

Claims

1. A process for making a cushion-backed textile, comprising: a) forming a frothed polyurethane-forming composition having a density of about 250 to 600 grams per liter wherein the polyurethane-forming composition includes one or more polyols including at least one polyol having a hydroxyl equivalent weight of at least 400, 0.25 to 2 parts of water per 100 parts by weight polyol(s) having a hydroxyl equivalent weight of at least 400, 3 to 10 parts by weight of a physical blowing agent having a boiling temperature of −30 to 40° C. per 100 parts by weight polyol(s) having a hydroxyl equivalent weight of at least 400, 100 to 400 parts by weight of a filler per 100 parts by weight polyol(s) having a hydroxyl equivalent weight of at least 400, a foam stabilizing surfactant, at least one polyisocyanate in an amount sufficient to provide an isocyanate index of from 85 to 130 and a polyurethane catalyst in an amount such that the polyurethane-forming composition has a gel time of at least 180 seconds; b) forming the uncured froth into a 0.05 to 0.75 inch (0.127 to 1.9 cm) thick layer across the top surface of a textile having a width of at least 24 inches (61 cm); and c) curing the layer of the frothed composition with its top surface open to the atmosphere such that the frothed composition can freely rise to form a foamed polyurethane cushion having a density of no greater than 176 grams/liter (11 pounds/cubic foot) bonded to the textile.

2. The process of claim 1 wherein the amount of water is 1 to 1.8 parts by weight per 100 parts by weight polyol(s) having a hydroxyl equivalent weight of at least 400.

3. The process of claim 2 wherein the physical blowing agent has a boiling temperature of 10 to 30° C.

4. The process of claim 3 wherein the amount of physical blowing agent is 5 to 8 parts by weight per 100 parts by weight polyol(s) having a hydroxyl equivalent weight of at least 400.

5. The process of claim 3 wherein the foamed polyurethane cushion has a density of 96 to 160 g/L.

6. The process of claim 3, wherein step a) is performed by mixing the polyol(s) and the filler, and combining the mixture of polyol and filler with the polyisocyanate and the physical blowing agent simultaneously with the frothing step by adding the polyisocyanate and physical blowing agent as separate streams into the frothing apparatus.

7. The process of claim 3, wherein the water is added after the frothing step.

8. The process of claim 3, wherein step a) is performed by mixing the polyol(s) and the filler, and then combining the mixture of polyol and filler with the polyisocyanate, and then adding the physical blowing agent and water simultaneously to frothing.

9. The process of claim 3, wherein the catalyst is added after the frothing step.

10. The process of claim 3 wherein step b) is performed by dispensing the frothed polyurethane-forming composition to form a puddle on the substrate, and then passing the puddle under a doctor blade to gauge the layer.

Description

EXAMPLES 1 AND 2 AND COMPARATIVE SAMPLES A AND B

Example 1

(1) A polyol mixture is formed from 48.3 parts of a nominally trifunctional 3000 molecular weight random copolymer of 87% propylene oxide and 13% ethylene oxide; 40 parts of a 4800 molecular weight nominally trifunctional block copolymer of propylene oxide and ethylene oxide, 10 parts of a 2000 molecular weight, nominally difunctional block copolymer of propylene oxide and ethylene oxide, 4 parts diethylene glycol, 1 part castor oil, 1.2 parts of a silicone foam stabilizing surfactant, 1 part of a viscosity depressant and 2 parts of a 1% solution of dibutyl tin sulfide in a polyether polyol and 1.8 parts water. This polyol mixture is blended with 190 parts of a particulate calcium carbonate until the blend reaches a temperature of 120° F. (49° C.). The resulting filled polyol mixture is cooled to about 20° C.

(2) The filled polyol is charged to a 2-inch (5.08 cm) Oakes dispensing/frothing machine. Separately, 43 parts of a polymeric MDI (isocyanate index 90) and 6 parts of HFC-245fa (1,1,1-3,3-pentafluoropropane) are charged to the Oakes machine, where they are combined with the filled polyol mixture and the resulting reaction mixture is frothed to a froth density of 301 g/L. The temperature of the exiting froth is 31° C.

(3) A portion of the froth discharged from the Oakes machine is captured in a container and its temperature is measured until the exothermic heat of reaction raises it temperature to 49° C. The time required to reach this temperature (i.e., the gel time) is 6 minutes and 5 seconds.

(4) Another portion of the froth is discharged onto a non-stick backing material, gauged to a thickness of approximately 7/16 inch to ⅝ inch (1.1 to 1.58 cm), and then cured uncovered in a 140° C. oven. The cured material is removed from the non-stick backing material. Test samples are prepared and density, 25% IFD and 65% IFD are measured, with results as in Table 1. Duplicate test samples are processed for 20,000 cycles in a Hexapod tumble drum tester according to ASTM D 5252, and the 25% IFD and 65% IFD are measured. The loss in IFD, compared to the original samples, is as reported in Table 1. A gain in IFD is reported as a negative loss.

(5) Comparative Sample A is made in the same general manner, with these differences: First, the amount of water is increased to 2.3 parts by weight. The amount of catalyst is increased to 2.3 parts to accommodate the increased amount of water. The HFC-245fa is omitted. Because the viscosity of the composition is higher as a result of omitting the physical blowing agent, the amount of calcium carbonate particles is reduced from 190 parts to only 170 parts.

(6) Comparative Sample C is made in the same way as Comparative Sample A, except the amount of catalyst is reduced to 1.4 parts, and the amount of calcium carbonate particles is 180 parts.

(7) Example 2 is made the same way as Example 1, except the isocyanate index is increased to 100.

(8) For each of Comparative Samples A and B and Example 2, the gel time of the frothed material and the density, 25% IFD and 65 IFD are measured as before. Results are as in Table 1.

(9) TABLE-US-00001 TABLE 1 Designation Ex. 1 Comp. A Comp. B Ex. 2 Water, parts 1.8 2.3 2.3 1.8 HFC 245fa, parts 6.0 0 0 6.0 Catalyst solution, parts 2.0 2.3 1.4 2.0 Filler loading, parts 190 170 180 190 Isocyanate index 90 90 90 100 Froth Density, g/L 301 351 321 307 Gel time, min:sec 6:05 3:50 3:30 5:19 Curing temp, ° C. 140 140 120 140 Cured foam density, g/L 160 183 197 171 25% IFD, kg 2.7 6.0 9.3 3.4 25% ILD loss, % 5 30 44 −1 65% ILD loss, % −22 7 13 −18

(10) Example 1 and Comparative Sample A are direct comparisons. Upon replacing the physical blowing agent with additional water and correspondingly increasing the catalyst level, one obtains a system with a much shorter gel time. The froth density for Comparative Sample A is significantly higher than Example 1. This indicates that Comparative Sample A has a higher viscosity that makes it more difficult to froth. Without a containment layer, the Comparative Sample A material produces a cured density of 183 g/L (or about 15% greater than Example 1). When the physical blowing agent replaces some of the water (as in Example 1), a lower density is obtained, despite the lack of a containment layer.

(11) In Comparative Sample B, the catalyst level and cure temperature each are reduced to try (unsuccessfully) to obtain a slower-curing system. This leads to even higher density in the cured product.

(12) Example 2 shows the effect of increasing the isocyanate index to 100. A slightly greater density is obtained than in Example 1, but the density is still well below that of the Comparative Samples.

(13) The 25% ILD values indicate that the cured cushions of Examples 1 and 2 are much softer than Comparative Samples A and B, which is desirable in a cushioning product.

(14) The 25% ILD loss and 65% ILD loss values indicated that the Example 1 and 2 materials are much more durable than the Comparative Samples. The negative values indicate an increase after durability testing. By contrast, the Comparative Samples show very significant loss in load-bearing on this test, especially at 25% indentation.