Polyurethane foams for comfort applications

Abstract

Flexible polyurethane foams are made by reacting a hydrophilic quasi-prepolymer, water and a polymer polyol in the presence of a silicone surfactant and an ethylene oxide/higher alkylene oxide block copolymer. The foams exhibit desirably low densities and compression sets, and have good thermal and moisture-wicking properties. The foams are useful in bedding and other comfort applications in which they are exposed to body heat and bear at least a portion of the weight of the user. The thermal and moisture wicking properties contribute to perceived comfort for the user.

Claims

1. A flexible polyurethane foam comprising a reaction product of a reaction mixture that comprises a) an isocyanate-functional quasi-prepolymer, which isocyanate-functional quasi-prepolymer is a reaction product of at least one hydroxyl-terminated polymer of ethylene oxide with an excess of an organic polyisocyanate that includes at least 80 weight-% diphenylmethane diisocyanate of which diphenylmethane diisocyanate at least 50 weight-% is 4,4′-diphenylmethane diisocyanate, wherein the isocyanate-functional quasi-prepolymer has an isocyanate content of 5 to 15% by weight and contains 30 to 70 weight percent of oxyethylene units, based on the weight of the isocyanate-functional quasi-prepolymer, b) water, c) at least one polymer polyol comprising polymer particles dispersed in at least one base polyol, d) at least one silicone surfactant and e) at least one ethylene oxide/higher alkylene oxide block copolymer, wherein i) the quasi-prepolymer constitutes 50 to 75% of the combined weights of components a-e; ii) water constitutes 15-41% of the combined weights of components a-e; iii) the at least one polymer polyol constitutes 8 to 20% of the combined weights of components a-e and the polymer particles constitute 0.5 to 8% of the combined weights of components a-e; iv) the at least one silicone surfactant constitutes 0.5 to 3% of the combined weights of components a-e and v) the at least one ethylene oxide/higher alkylene oxide block copolymer constitutes 0.5 to 3% of the combined weights of components a-e.

2. The flexible polyurethane foam of claim 1 wherein the at least one polymer polyol constitutes 9 to 15% of the combined weights of components a-e and the polymer particles constitute 1.5 to 6% of the combined weights of components a-e.

3. The flexible polyurethane foam of claim 2 wherein the polymer particles are particles of a copolymer of styrene and acrylonitrile.

4. The flexible polyurethane foam of claim 1 wherein the reaction mixture contains no more than 5 parts per million by weight of metals and no more than 100 parts per million of amine compounds.

5. The flexible polyurethane foam of claim 1 wherein the silicone surfactant contains 25 to 70% by weight polysiloxane, 10 to 75% by weight polymerized ethylene oxide and 0 to 10% by weight polymerized propylene oxide, based on the weight of the silicone surfactant.

6. The flexible polyurethane foam of claim 1 wherein the ethylene oxide/higher alkylene oxide block copolymer contains 40 to 90% oxyethylene units and has a number average molecular weight of 1,500 to 12,000.

7. A method of making a flexible polyurethane foam, comprising A. forming a reaction mixture by mixing at least the following components a-e: a) an isocyanate-functional quasi-prepolymer, which isocyanate-functional quasi-prepolymer is a reaction product of at least one hydroxyl-terminated polymer of ethylene oxide with an excess of an organic polyisocyanate that includes at least 80 weight-% diphenylmethane diisocyanate of which diphenylmethane diisocyanate at least 50 weight-% is 4,4′-diphenylmethane diisocyanate, wherein the isocyanate-functional quasi-prep olymer has an isocyanate content of 5 to 15% by weight and contains 30 to 70 weight percent of oxyethylene units, based on the weight of the isocyanate-functional quasi-prepolymer, b) water, c) at least one polymer polyol comprising polymer particles dispersed in at least one base polyol, d) at least one silicone surfactant and e) at least one ethylene oxide/higher alkylene oxide block copolymer, and B. subjecting the reaction mixture formed in step A. to conditions at which the isocyanate-functional quasi-prepolymer and one or more of components b-e react to form the flexible polyurethane foam, wherein i) the quasi-prepolymer constitutes 50 to 75% of the combined weights of components a-e; ii) water constitutes 15-41% of the combined weights of components a-e; iii) the at least one polymer polyol constitutes 8 to 20% of the combined weights of components a-e and the polymer particles constitute 0.5 to 8% of the combined weights of components a-e; iv) the at least one silicone surfactant constitutes 0.5 to 3% of the combined weights of components a-e; and v) the at least one ethylene oxide/higher alkylene oxide block copolymer constitutes 0.5 to 3% of the combined weights of components a-e).

8. The method of claim 7 wherein the at least one polymer polyol constitutes 9 to 15% of the combined weights of components a-e and the polymer particles constitute 1.5 to 6% of the combined weights of components a-e.

9. The method of claim 8 wherein the polymer particles are particles of a copolymer of styrene and acrylonitrile.

10. The method of claim 7 wherein the reaction mixture contains no more than 5 parts per million by weight of metals and no more than 100 parts per million of amine compounds.

11. The method of claim 7 wherein the silicone surfactant contains 25 to 70% by weight polysiloxane, 10 to 75% by weight polymerized ethylene oxide and 0 to 10% by weight polymerized propylene oxide, based on the weight of the silicone surfactant.

12. The method of claim 7 wherein the ethylene oxide/higher alkylene oxide block copolymer contains 40 to 90% oxyethylene units and has a number average molecular weight of 1,500 to 12,000.

13. The method of claim 7 wherein after step B. the foam is dried to a constant weight.

14. A cushion comprising a flexible polyurethane foam of claim 1.

15. The cushion of claim 14, which is a pillow, mattress topper, mattress, comforter, furniture seat or back, automotive seat or back; quilt or article of insulated clothing.

16. The cushion of claim 14, wherein the flexible polyurethane foam, when dried to a constant weight, has a density of 48 to 80 kg/m.sup.3 and a compression set of 40% or less.

17. The cushion of claim 14, wherein the flexible polyurethane foam, when dried to a constant weight, has a density of 48 to 64 kg/m.sup.3 and a compression set of 15% or less.

18. The cushion of any of claim 14 wherein the flexible polyurethane foam, when dried to a constant weight, exhibits a specific heat of at least 1.5 J/g.Math.° K, a thermal conductivity of at least 0.05 W/m.Math.° K, a water uptake of 300% to 700% and a moisture wicking time of 5 seconds or less, preferably 4 seconds or less.

Description

EXAMPLES 1-2 AND COMPARATIVE SAMPLES A-F

(1) A. Quasi-Prepolymer Formation

(2) Quasi-Prepolymers A-C are made in the following general manner, from ingredients as indicated in Table 1. The polyol(s) are dried to a moisture content of less than 250 ppm by heating them to 100° C. overnight with stirring under nitrogen. A trace of benzoyl chloride is added to the dried polyols and stirred in. The polyisocyanate(s) are separately heated to 50° C. and combined with the polyol(s). No urethane catalyst is added to the resulting reaction mixture, which contains no more than 1 part per million by weight of metals and no more than 100 parts per million of amine compounds. The reaction mixture is heated at 75° C. under nitrogen until a constant isocyanate content is obtained. The quasi-prepolymer is then cooled to room temperature and stored under nitrogen.

(3) The NCO content is measured according to ASTM D5155. The oxyethylene content of the quasi-prepolymer is calculated from those of the starting materials. The 4,4′-content of the starting polyisocyanate(s) is calculated from those of the starting isocyanates. The resulting values are as reported in Table 1.

(4) Polyol A is a 1000 molecular weight, nominally difunctional homopolymer of ethylene oxide. It contains 100% oxyethylene groups. Polyol A is commercially available as Carbowax™ 1000 polyol from The Dow Chemical Company.

(5) Polyol B is a copolymer of ethylene oxide and propylene oxide having a nominal hydroxyl functionality of 2 and a number average molecular weight of approximately 2,400 g/mole. It contains 64% oxyethylene groups. Polyol B is commercially available as UCON™ PCL-270 polyol from The Dow Chemical Company.

(6) Polyol C is a copolymer of ethylene oxide and propylene oxide having a nominal hydroxyl functionality of 3 and a number average molecular weight of approximately 5,000 g/mole. It contains 75% oxyethylene groups. Polyol C is commercially available as VORANOL™ CP-1421 polyol from The Dow Chemical Company.

(7) Polyol D is a homopolymer of propylene oxide. It has a nominal hydroxyl functionality of 2 and a number average molecular weight of about 2000 g/mole.

(8) Isocyanate A is a mixture of 98% 4,4′-MDI and 2% 2,4′-MDI. It has an isocyanate content of 33.5%. Isocyanate A is available from The Dow Chemical Company as ISONATE™ 125M polyisocyanate.

(9) Isocyanate B is a mixture of 50% 4,4′-MDI and 50% 2,4′-MDI. It has an isocyanate content of 33.5%. Isocyanate B is available from The Dow Chemical Company as ISONATE™ 50 O,P polyisocyanate.

(10) TABLE-US-00001 TABLE 1 Parts by Weight QP-A QP-B QP-C Ingredient Polyol A 52 0 0 Polyol B 13 7.2 0 Polyol C 0 65.1 0 Polyol D 0 0 68.9 Isocyanate A 21 16.6 12.4 Isocyanate B 14 11.1 18.7 Properties NCO Content, % 7 7 7 Oxyethylene 62 48 0 content 4,4′-MDI 80% 80% 69% isomer content
B. Preparation of Polyurethane Foams

(11) Polyurethane foams are made by separately reacting the foregoing quasi-prepolymers with an aqueous phase. The aqueous phase contains ingredients as set forth in Table 2. In each case, the various ingredients of the aqueous phase are first combined and the resulting aqueous phase is mixed with the quasi-prepolymer in a high-speed laboratory mixer at room temperature. The reaction mixture is poured into an open mold and allowed to rise and cure without application of heat.

(12) The silicone surfactant is a silicone/ethylene oxide block copolymer containing about 70% by weight polymerized ethylene oxide. It is sold as Silwet® L-7605 by Momentive.

(13) The ethylene oxide/propylene oxide block copolymer is a triblock copolymer having an internal polypropylene oxide) block of 1750 g/mol and which contains 80% by weight terminal poly(ethylene oxide) blocks. It has a nominal functionality of 2 hydroxyl groups per molecule.

(14) The polymer polyol is a dispersion of 20% by weight styrene-acrylonitrile particles in a base polyol. The base polyol is a block copolymer of propylene oxide and ethylene oxide which has an average hydroxyl number of about 36, has a nominal functionality of 3 and contains 20% by weight oxyethylene units. The particle size is generally between 300 nm and 10 μm.

(15) TABLE-US-00002 TABLE 2 Designation Ex. 1 Ex. 2 A* B* C* D* E* F* Aqueous Phase Ingredient Parts by Weight Water 25 25 49 26.5 26.5 27.4 12 25 Silicone 1.5 1.5 1 1.5 0 1.5 1.5 1.5 Surfactant EO/PO Block 1.5 1.5 0 0 1.5 1.5 1.5 1.5 Copolymer Polymer 9.5 9.5 0 9.5 9.5 7.1 22.5 9.5 Polyol Total Aqueous 37.5 37.5 50 37.5 37.5 37.5 37.5 37.5 Phase Weight Prepolymer/ A/62.5 B/62.5 A/50 A/62.5 A/62.5 A/62.5 A/62.5 C/62.5 Amount Polymer 1.9 1.9 0 1.9 1.9 1.4 5.5 1.9 Particles, % *Comparative

(16) After curing, the foams are cured overnight under ambient conditions. The skins are removed and the foams are aged for 24 hours under ambient conditions before testing. The foams are evaluated for density and airflow according to ASTM D3574. Other specimens (except Comp. Sample A) are dried to constant weight, and compression set, moisture wicking, thermal conductivity and specific heat according to the test methods described above. Results are as indicated in Table 3.

(17) TABLE-US-00003 TABLE 3 Property Moisture Thermal Specific Sample Density, Compression Wicking, Airflow, Conductivity, Heat, Designation kg/m.sup.3 set, % s l/s W/m-K J/g*° C. 1 59.2 10 4 1.9 0.0409 2.01 2 73.6 34.3 4 0.76 0.0400 2.09 A* 108.8 ND ND 0.61** 0.0950**  3.0** B* 75.2 47.4 4 1.22 0.0410 1.93 C* 104.0 85 4 0.71 0.0469 1.92 D* 86.4 88 4 0.61 0.0421 2.11 E* 61.6 83 4 2.7 0.0488 2.05 F* Does not form stable foam *Comparative. **Measured on undried foam samples.

(18) Comparative Sample A corresponds to Example 1 of WO 2016/069537. This foam is made without the polymer polyol and using a silicone surfactant but not the ethylene oxide/propylene block copolymer. That foam has generally good properties but the density of about 109 kg/m.sup.3 is higher than is wanted.

(19) Comparative Sample B shows the effect of introducing a copolymer polyol into an aqueous phase that contains a silicone surfactant but no ethylene oxide/propylene oxide block copolymer. These modifications permit density to be reduced to about 75 kg/.sup.3, but compression set is high at over 47%.

(20) In Comparative Sample C, the silicone surfactant of Comparative Sample B is replaced with the ethylene oxide/propylene oxide block copolymer. Foam density, airflow and compression set all suffer significantly.

(21) Example 2 is the same as Comparative Samples B and C, except the silicone surfactant and the ethylene oxide/propylene oxide block copolymer are both present in the aqueous phase. Density is decreased to below 60 kg/m.sup.3, and compression set is reduced dramatically, to 10%. At the same time, good moisture wicking is preserved and high airflows are achieved.

(22) Example 1 demonstrates the effect of using a quasi-prepolymer having a somewhat lower oxyethylene content. Density is significantly lower than any of Comparative Samples A-C, and compression set is reduced substantially. Moisture wicking is preserved. Example 1 represents a significant improvement over Comparative Samples A-C.

(23) Comparative Samples D and E show the effect of varying the amount of the polymer polyol. Too little polymer polyol (D) or too much polymer polyol (E) results in a dramatic and undesirable increase in compression set. Too little polymer polyol also leads to a substantial density increase.

(24) Comparative Sample F demonstrates the need for the quasi-prepolymer to contain oxyethylene groups. Without the hydrophilic nature imparted by oxyethylene groups, the quasi-prepolymer is unable even to form a stable foam.