Polyurethane foams and method for making the foam

Abstract

Flexible polyurethane foams are made by reacting a polyether mixture and water with a polyisocyanate. The foams have excellent suite of properties for use in seating applications, as they are supporting, comfortable and resilient foam. A further advantage is these properties can be obtained at isocyanate indices of close to or even greater than 100.

Claims

1. A mixture of polyethers that comprises a) 60 to 80% by weight, based on the weight of the mixture of polyethers, of one or more nominally trifunctional ethylene-oxide capped poly(propylene oxide) polyols having an oxyethylene content of 10 to 25% by weight and a hydroxyl equivalent weight of 1500 to 2500, in which at least 70% of the hydroxyl groups are primary; b) 10 to 30% by weight, based on the weight of the mixture of polyethers, of one or more ethylene-oxide capped poly(propylene oxide) polyols having a nominal functionality of 4 to 8, an oxyethylene content of 10 to 25% by weight and a hydroxyl equivalent weight of 1500 to 2500, wherein at least 70% of the hydroxyl groups are primary hydroxyls; c) 5 to 12% by weight, based on the weight of the mixture of polyethers of one or more polyether polyols having a nominal functionality of at least 3, a molecular weight of at least 4000 and an oxyethylene content of at least 70% by weight; and d) 2 to 10% by weight, based on the weight of the mixture of polyethers, of one or more monofunctional copolymers of propylene oxide and ethylene oxide having an oxyethylene content of 20 to 65% by weight and a molecular weight of 400 to 2000.

2. The mixture of polyethers of claim 1 which comprises 65 to 75% by weight of a), 10 to 20% of b), 5 to 10% of c) and 3 to 6% of d).

3. The mixture of polyethers of claim 2 wherein d) has an oxyethylene content of 40 to 63% by weight.

4. A method for making a polyurethane foam, comprising reacting an aromatic polyisocyanate with at least one crosslinker, water a mixture of polyethers and no more than 2 parts by weight, per 100 parts by weight of the polyol mixture of other isocyanate-reactive compounds in the presence of at least one catalyst and at least one surfactant, wherein the isocyanate index is 85 to 125 and the amount of water is 1.0 to 3.0 parts by weight per 100 parts by weight of the mixture of polyethers to produce a polyurethane foam having a foam density of at least 55 kg/m.sup.3, wherein the mixture of polyethers comprises a) 60 to 80% by weight, based on the weight of the mixture of polyethers, of one or more nominally trifunctional ethylene-oxide capped poly(propylene oxide) polyols having an oxyethylene content of 10 to 25% by weight and a hydroxyl equivalent weight of 1500 to 2500, in which at least 70% of the hydroxyl groups are primary; b) 10 to 30% by weight, based on the weight of the mixture of polyethers, of one or more ethylene-oxide capped poly(propylene oxide) polyols having a nominal functionality of 4 to 8, an oxyethylene content of 10 to 25% by weight and a hydroxyl equivalent weight of 1500 to 2500, wherein at least 70% of the hydroxyl groups are primary hydroxyls; c) 5 to 12% by weight, based on the weight of the mixture of polyethers of one or more polyether polyols having a nominal functionality of at least 3, a molecular weight of at least 4000 and an oxyethylene content of at least 70% by weight; and d) 2 to 10% by weight, based on the weight of the mixture of polyethers, of one or more monofunctional copolymers of propylene oxide and ethylene oxide having an oxyethylene content of 20 to 65% by weight and a molecular weight of 400 to 2000.

5. The method of claim 4 wherein the amount of water is 1.5 to 2.25 parts by weight per 100 parts by weight of the mixture of polyethers.

6. The method of claim 4 wherein the isocyanate index is at least 90.

7. The method of claim 4 wherein the isocyanate index is at least 100.

8. A flexible polyurethane foam made by the method of claim 4.

9. The flexible polyurethane foam of claim 8, which has a resiliency of at least 50% on the ASTM D-3574-11 ball rebound test, a compression force deflection (CFD) at 40% compression of at least 1.0 kPa as measured according to ISO3386-1, and a sag factor of 3.5 or greater.

10. The flexible polyurethane foam of claim 8, which has a resiliency of at least 52% on the ASTM D-3574-11 ball rebound test, a compression force deflection (CFD) at 40% compression of at least 1.8 kPa as measured according to ISO3386-1, a sag factor of 3.6 or greater and an airflow after mechanical crushing of at least 1.25 liters per second.

11. The flexible polyurethane foam of claim 8, which has a sag factor of 3.8 or greater.

12. The mixture of polyethers of claim 1 wherein b) is formed by polymerizing propylene oxide or a mixture of propylene oxide and ethylene oxide onto sorbitol or sucrose to form polyether chains, followed by polymerizing ethylene oxide by itself onto the end of the polyether chains.

13. The method of claim 4 wherein b) is formed by polymerizing propylene oxide or a mixture of propylene oxide and ethylene oxide onto sorbitol or sucrose to form polyether chains, followed by polymerizing ethylene oxide by itself onto the end of the polyether chains.

Description

EXAMPLES 1-4 AND COMPARATIVE SAMPLE A

(1) Polyurethane foams are made from the formulations described in the Table below. The amount of water indicated is total water from all sources.

(2) Polyol 1 is a 2000 equivalent weight ethylene oxide-capped poly(propylene oxide) triol. It has greater than 70% primary hydroxyl groups and an oxyethylene content of about 15% based on the weight of Polyol 1.

(3) Polyol 2 is a mixture of an ethylene oxide-capped poly(propylene oxide) triol and a 1750 equivalent weight ethylene oxide-capped poly(propylene oxide) hexol. It is prepared by propoxylating and then ethoxylating a mixture of glycerin and sorbitol. The triol and hexol each have greater than 70% primary hydroxyl groups and an oxyethylene content of about 15% based on the weight of Polyol 1.

(4) Polyol 3 is a copolymer of ethylene oxide and propylene oxide. It has an oxyethylene content of at least 70%, a nominal hydroxyl functionality of 3 and molecular weight of about 5000.

(5) Polyol 4A is a 750 molecular weight monofunctional block copolymer of about 50% propylene oxide and 50% ethylene oxide.

(6) Polyol 4B is a 500 molecular weight monofunctional block copolymer of about 60% propylene oxide and 40% ethylene oxide.

(7) The polyisocyanate is a polymeric MDI having an isocyanate equivalent weight of about 130.

(8) All ingredients except the isocyanate are stirred together at room temperature using a propeller mixer. The isocyanate is then added. The ingredients are stirred for 10 additional seconds and the resulting mixture poured into a 30×30×25 cm open box, where it cures without added heat. The resulting foam is removed from the box and post-cured at 140° C. for 5 minutes. The foam is cooled to room temperature and manually crushed. The tightness of the foam is evaluated subjectively as the foam is crushed, and rated on a scale of 1-10 with 1 representing a very open foam and 10 representing a very tight foam with many closed cells.

(9) Foam density (ISO845-88), CFD (ISO3386-1) at 25%, 40% and 65% compression, resiliency (ASTM D3574-11), air flow (ISO7231) (on the crushed foam), hysteresis (ISO3386-1) and compression set (ISO1856) at 75% compression and 90% compression are all measured. Sag factor is calculated from the 65% and 25% compression measurements. Results are as indicated in the Table.

(10) TABLE-US-00001 TABLE Example or Comparative Sample A* 1 2 3 4 Ingredient Polyol 1 67.5 65.0 65.0 65.0 62.5 Polyol 2 25.0 22.5 22.5 22.5 22.5 Polyol 3 5.0 7.5 7.5 7.5 10.0 Polyol 4A 0 5.0 5.0 0 5.0 Polyol 4B 0 0 0 3.35 0 Polyol a/b/c/d 75.8/ 72.5/15/ 72.5/15/ 73.7/15.3/ 70/15/ Ratio 16.7/5/0 7.5/5 7.5/5 7.6/3.4 10/5 Blocked Amine 0.14 0.14 0.14 0.14 0.14 Catalyst 33% triethylene 0.23 0.23 0.23 0.23 0.23 diamine solution 85% 2.41 2.41 2.41 2.41 2.41 diethanolamine in water Silicone 1.35 1.35 1.35 1.35 1.35 Surfactant Water 1.88 1.88 1.88 1.88 1.88 Isocyanate 90 90 110 90 90 Index Properties Foam Tightness 5 4 1 3 2 Rating Density, kg/m.sup.3 62 62 59 62 67 25% CFD, kPa 2.6 1.8 2.1 1.8 1.2 40% CFD, kPa 3.5 2.6 3.2 2.6 2.0 65% CFD, kPa 8.6 6.9 9.4 7.1 6.7 Sag factor 3.3 3.8 4.5 4.0 5.5 Hysteresis, % 82 80 77 80 78 Resilience, % 61 54 57 57 50 Air flow, L/s 1.1 1.5 1.5 1.3 1.5 75% 3 4 5 3 4 Compression Set, % 90% 4 4 6 4 7 Compression Set, %

(11) As indicated by the data in Table, the polyether mixture of the invention provides a foam having, at equivalent densities, higher airflow and higher sag factors. 25% CFD values are lower, which is desirable for furniture and bedding applications. The foams of the invention also process more easily, as indicated by the lower tightness ratings. Example 2 is especially notable, as these excellent results are obtained at an isocyanate index greater than 100.