LOW DENSITY, LOW COMPRESSION SET, LONG RECOVERY TIME POLYURETHANE FOAM

Abstract

Flexible polyurethane foams are characterized in having slow recovery times, low foam densities and very low compression sets. The foams are useful in human comfort applications such as pillows and mattresses.

Claims

1. (canceled).

2. A flexible polyurethane foam characterized by having a) a core foam density of 20 to 33 kg/m.sup.3, b) a 90% compression set of no greater than 10% as measured according to ISO 1856 method A and c) a recovery time of 0.5 to 20 seconds, which foam is a reaction product of a reaction mixture comprising a) an aromatic polyisocyanate having an isocyanate content of 20 to 33% by weight, in an amount to produce an isocyanate index is 50 to 90; and b) polyethers comprising b-1) at least one polyether having a hydroxyl equivalent weight of 500 to 2000, a nominal hydroxyl functionality of 1 to 4 and an oxyethylene content of 40 to 95% by weight, wherein at least 80% of the hydroxyl groups are primary; b-2) at least one homopolymer or copolymer of propylene oxide, the homopolymer or copolymer of propylene oxide having a hydroxyl equivalent weight of 600 to 2000 and a nominal hydroxyl functionality of 1 to 6, and wherein at least 80% of the hydroxyl groups are secondary; and b-3) optionally at least one homopolymer or copolymer of propylene oxide, the homopolymer or copolymer of propylene oxide having a hydroxyl equivalent weight of 80 to 599 and a nominal hydroxyl functionality of 1 to 6, and wherein at least 80% of the hydroxyl groups are secondary, wherein i) the ratio of hydroxyl equivalents provided by component b-1) to the hydroxyl equivalents provided by components b-2) and b-3) is 1 to 2.5, ii) component b-1) constitutes 65 to 85 weight percent of the combined weights of components b)-f); iii) component b-2) constitutes 1 to 30 weight percent of the combined weights of components b)-f), iii) component b-3) constitutes 0 to 20 weight percent to of the combined weights of components b)-f), and iv) the combined weight of components b-1), b-2) and b-3) constitute at least 70% of the combined weight of components b)-f); c) water in an amount of 4.5 to 6.5 weight percent, based on the combined weight of components b)-f), d) at least one catalyst for the reaction of an isocyanate group with an alcohol and/or water and e) at least one silicone foam-stabilizing surfactant, f) 0 to 5 weight percent, based on the combined weights of components b)-f), of isocyanate reactive compounds different than components b), c), d) and e), provided that the reaction mixture contains no more than 5 weight percent, based on the combined weight of components b)-f), of an ethylene oxide-capped polypropylene oxide) polyol having an oxyethylene content of up to 30% based on the weight of the ethylene oxide-capped polypropylene oxide) polyol.

3. The flexible polyurethane foam of claim 2 wherein polyether b-3) constitutes 1 to 15 weight percent of the combined weights of components b)-f).

4. The flexible polyurethane foam of claim 2 wherein water constitutes at least 5 weight percent of the combined weight of components b)-f).

5. The flexible polyurethane foam of claim 2 wherein water constitutes 5.5 to 6 weight percent of the combined weight of components b)-f).

6. The flexible polyurethane foam of claim 2 wherein the reaction mixture contains no more than 5 weight percent of compounds having one or more primary and/or secondary amine groups, based on the combined weight of components b)-f).

7. The flexible polyurethane foam of claim 2 wherein the reaction mixture contains no more than 15 weight percent of a polyether polyol having an oxyethylene content of 50% or greater and in which fewer than 50% of hydroxyl groups are primary, based the combined weight of components b)-f).

8. The flexible polyurethane foam of claim 2 wherein the reaction mixture contains no more than 1 weight percent of polyols having hydroxyl equivalent weights of 79 or less, based the combined weight of components b)-f).

9. The flexible polyurethane foam of claim 2 wherein the reaction mixture contains no more than 5 weight percent, based on the combined weight of components b)-f), of any isocyanate-reactive materials different from components b)-e).

10. The flexible polyurethane foam of claim 2 wherein component a) includes an MDI product that contains up to 50 weight percent of the 2,4′-isomer and up to 5 weight percent of the 2,2′-isomer, the remainder being the 4,4′-isomer, and/or a mixture thereof with PMDI.

11. The flexible polyurethane foam of claim 2 wherein component a) includes a urethane group-containing prepolymer made in the reaction of a polyol with MDI product that contains up to 50 weight percent of the 2,4′-isomer and up to 5 weight percent of the 2,2′-isomer, the remainder being the 4,4′-isomer, and/or a mixture thereof with PMDI.

12. The flexible polyurethane foam claim 2 wherein the isocyanate index is 60 to 90.

13. The flexible polyurethane foam claim 2 which has a core foam density of 20 to 30 kg/m.sup.3.

14. The flexible polyurethane foam of claim 2 which has a core foam density of 20 to 28 kg/m.sup.3.

15. A flexible polyurethane foam characterized by having a) a core foam density of 20 to 33 kg/m.sup.3, b) a 90% compression set of no greater than 10% as measured according to ISO 1856 method A and c) a recovery time of 0.5 to 20 seconds, which foam is a reaction product of a reaction mixture that comprises: a) an aromatic polyisocyanate having an isocyanate content of 20 to 33% by weight, in an amount to produce an isocyanate index is 50 to 90 and b) polyethers comprising i) at least one polyether having a hydroxyl equivalent weight of 500 to 2000, a nominal hydroxyl functionality of 1 to 4 and an oxyethylene content of 40 to 95% by weight, wherein at least 60% of the hydroxyl groups are primary; and ii) at least one homopolymer or copolymer of propylene oxide, the homopolymer or copolymer of propylene oxide having a hydroxyl equivalent weight of 80 to 2000 and a nominal hydroxyl functionality of 1 to 6, and wherein at least 80% of the hydroxyl groups are secondary; wherein polyether ii) is present in an amount such that it is at least partially incompatible with polyether i). c) water in an amount of 4.5 to 6.5 weight percent, based on the combined weight of components b)-f), d) at least one catalyst for the reaction of an isocyanate group with an alcohol and/or water and e) at least one silicone foam-stabilizing surfactant, f) 0 to 25 weight percent, based on the combined weights of components b)-f), of isocyanate-reactive compounds different than components b), c), d) and e), provided that the reaction mixture contains no more than 5 weight percent, based on the combined weight of components b)-f), of ethylene oxide-capped polypropylene oxide) polyols having an oxyethylene content of up to 30% based on the weight of the ethylene oxide-capped polypropylene oxide) polyol.

Description

EXAMPLES 1-2 AND COMPARATIVE SAMPLE A

[0106] These foams are made from the ingredients indicated in Table 1.

TABLE-US-00001 TABLE 1 Parts By Weight Ingredient Comp. A* Ex. 1 Ex. 2 Polyol b-1 67.29 66.82 71.1 Polyol b-2 27.3 27.1 16.8 Polyol b-3a 0 0 6.0 Surfactant A 0.28 0.18 0.2 Surfactant B 0.03 0 0 Catalyst 0.9 0.9 0.9 Water 4.2 5.0 5.0 Prepolymer A 60, 70 index 60, 70 index 60, 70 index Equivalent ratio, 1.62 1.62 1.63 b-1):(b-2) + b-3)) *Comparative.

[0107] Foam core density, recovery time, 90% compression set and 40% compression load deflection are measured for the resulting foams. Results are as indicated in Table 2.

TABLE-US-00002 TABLE 2 Core 90% 40% Density, Recovery compression CLD, Designation kg/m.sup.3 time, s set, % kPa Comp. A* (60 index) 35.4 1-2 5.0 0.33 Comp. A* (70 index) 31.9 1-2 3.9 0.47 Ex. 1 (60 index) 29.7 2.7 4.3 0.31 Ex. 1 (70 index) 28.2 5.4 5.6 0.78 Ex. 2 (60 index) 29.3 2.9 7.7 0.34 Ex. 2 (70 index) 26.5 6.1 6.4 0.81 *Comparative.

[0108] Comparative Sample A shows the effect of using 4.2 parts water and an isocyanate index of 60 or greater. Recovery times and 90% compression sets are good, but foam densities are higher than are wanted.

[0109] Examples 1-2 demonstrate the desired combination of very low density (well below 30 kg/m.sup.3), extremely low compression set and recovery time of greater than 1 second. Little or no loss of load bearing (as indicated by the CLD measurement) is seen in relation to Comparative Sample A.

EXAMPLES 3-6 AND COMPARATIVE SAMPLE B

[0110] These foams are made from the ingredients indicated in Table 3. Foam properties are as indicated in Table 4.

TABLE-US-00003 TABLE 3 Parts by Weight Ingredient Comp. B* Ex. 3 Ex. 4 Ex. 5 Ex. 6 Polyol b-1 76.2 75.6 76.2 76.2 75.1 Polyol b-2 6.0 6.0 6.0 6.0 6.0 Polyol b-3a 12.5 12.5 12.5 12.5 12.3 Surfactant A 0.2 0.2 0.2 0.2 0.2 Surfactant C 0 0 0 0.05 0 Catalyst 0.9 0.9 0.9 0.9 0.9 Water 4.2 5.0 5.0 5.0 5.5 Prepolymer A 66, 70 60, 70 0 60, 70 60, 70 (index) Prepolymer B 0 0 60,70 0 0 (index) Prepolymer C 0 0 0 0 0 (index) Equivalent ratio, 1.63 1.64 1.63 1.63 1.63 b-1):(b-2) + b-3)) *Comparative.

TABLE-US-00004 TABLE 4 Core 90% 40% Density, Recovery compression CLD, Designation kg/m.sup.3 time, s set, % kPa Comp. B* (66 index) 34.2 1-5 6.0 0.54 Comp. B* (70 index) 34.0 1-5 6.0 0.72 Ex. 3 (60 index) 30.5 2.5 8.6 0.44 Ex. 3 (70 index) 28.8 2.5 3.5 0.92 Ex. 4 (60 index) 32.4 1-5 5.8 0.53 Ex. 4 (70 index) 32.8 1-5 7.1 0.85 Ex. 5 (60 index) 30.2 3.1 3.7 0.43 Ex. 5 (70 index) 29.2 3.5 13.8 0.95 Ex. 6 (60 index) 24.8 3.5 6.0 0.42 Ex. 6 (70 index) 24.4 3.5 8.6 0.94 *Comparative.

[0111] Very low compression sets are obtained at foam densities as low as 24.4 kg/m.sup.3, while retaining good viscoelastic character in the foams.

EXAMPLES 7 AND 8 AND COMPARATIVE SAMPLE C

[0112] These foams are made from the ingredients indicated in Table 5. Foam properties are as indicated in Table 6.

TABLE-US-00005 TABLE 5 Ingredient Comp. C* Ex. 7 Ex. 8 Polyol b-1 78.7 77.55 82.15 Polyol b-2 0 1 6 Polyol b-3a 16 15.35 0 Polyol b-3b 0 0 5.8 Surfactant A 0.2 0.2 0.15 Catalyst 0.9 0.9 0.9 Water 4.2 5.0 5.0 Prepolymer A 60 or 70 index 60, 70 index 60, 70 index Equivalent 1.63 1.62 1.63 ratio, b-1):(b-2) + b-3)) *Comparative.

TABLE-US-00006 TABLE 6 Core 90% 40% Density, Recovery compression CLD, Designation kg/m.sup.3 time, s set, % kPa Comp. C* Not moldable even at 4.2 parts water Ex. 7 (60 index) 30.2 2.5 5.0 0.45 Ex. 7 (70 index) 30.1 2.5 5.4 0.96 Ex. 8 (60 index) 30.5 1.4 5.2 0.53 Ex. 8 (70 index) 29.4 1.5 3.4 0.84 *Comparative.

[0113] Very low compression sets are obtained at low isocyanate index and low density in all cases.

Comparative Samples D and E

[0114] These foams are made from the ingredients indicated in Table 7. Foam properties are as indicated in Table 8.

TABLE-US-00007 TABLE 7 Parts By Weight Ingredient Comp. D* Comp. E* Polyol b-1 61.39 67.5 Polyol b-2 14 5.45 Polyol b-3a 0 10.95 Polyol X 10 10 Monol Z 10 0 Surfactant A 0.18 0.2 Surfactant B 0.03 0 Catalyst 0.65 0.9 Water 3.75 5.0 Prepolymer A 65, 70 index 60, 72 index Equivalent ratio, 2.884 1.635 b-1):(b-2) + b-3)) *Comparative.

TABLE-US-00008 TABLE 8 Core 90% 40% Density, Recovery compression CLD, Designation kg/m.sup.3 time, s set, % kPa Comp. D* (65 index) 40 2-3 66% at only 0.7 75% compression Comp. D* (70 index) 40 2-3 68% at only 0.9 75% compression Comp. E* (60 index) 31.2 12.5 85.6 0.45 Comp. E* (72 index) 29.8 8.1 85.9 0.95 *Comparative.

[0115] The presence of the ethylene oxide-capped polypropylene oxide) (Polyol X) is seen to cause compression sets to become very high in these foams, even at high foam densities, at all isocyanate indices evaluated.

EXAMPLES 9 AND 10

[0116] These foams are made from the ingredients indicated in Table 9. Foam properties are as indicated in Table 10.

TABLE-US-00009 TABLE 9 Ingredient Ex. 9 Ex. 10 Polyol b-1 64.1 64.1 Polyol b-2 18.5 18.5 Polyol W 11.3 11.3 Surfactant A 0.2 0.2 Catalyst 0.9 0.9 Water 5.0 5.5 Prepolymer A 60, 70 index 60, 70 index

TABLE-US-00010 TABLE 10 Core 90% 40% Density, Recovery compression CLD, Designation kg/m.sup.3 time, s set, % kPa Ex. 9 (60 index) 31.7 3.6 81.5 0.44 Ex. 9 (70 index) 30.0 3.7 4.8 0.69 Ex. 10 (60 index) 27.3 4.5 76.9 0.35 Ex. 10 (70 index) 25.6 5.6 5.5 0.72

[0117] These examples demonstrate that excellent results can be obtained even when the foam formulation contains a quantity of a component f) material (i.e., Polyol W). Excellent recovery times and good load bearing are obtained in all cases. When Polyol W is present, compression set suffers at the very low isocyanate index of 60, but very low compression sets are obtained when the index is raised to 70.

EXAMPLES 11 AND 12

[0118] These foams are made from the ingredients indicated in Table 11. Foam properties are as indicated in Table 12.

TABLE-US-00011 TABLE 11 Ingredient Ex. 11 Ex. 12 Polyol b-1 74.7 64.1 Polyol b-2 6 18.5 Polyol b-3 12.2 11.3 Surfactant A 0.2 0.2 Catalyst 0.9 0.9 Water 6.0 5.5 Prepolymer A 60, 70 index 60, 70 index

TABLE-US-00012 TABLE 12 Core 90% 40% Density, Recovery compression CLD, Designation kg/m.sup.3 time, s set, % kPa Ex. 11 (60 index) 25.5 4.0 6.2 0.45 Ex. 11 (70 index) 25.0 4.4 8.4 1.03 Ex. 12 (60 index) 22.4 3.3 6.0 0.37 Ex. 12 (70 index) 21.9 2.9 5.5 0.67

[0119] These examples demonstrate the very unusual and unexpected properties obtained in an extremely high (6 part) water formulation. Foam densities are as low as 21.9 kg/m.sup.3, but compression set remains below 10% while good viscoelastic properties are obtained.