Felted hydrophilic ester polyurethane foams
View Patent ↗An ester polyurethane foam is prepared by reacting a mixture of one or more polyester polyols with one or more isocyanates and one or more silicone surfactants in the presence of a blowing agent, such as water, and other additives, such as catalysts. The cured foam is chemically treated in a caustic solution and is then felted (compressed under heat and pressure) to form a hydrophilic ester polyurethane foam having a water absorption rate of at least 30 pounds of water per square foot per minute (1.44 kPa/min). The foam also has greater water holding capacity and wet strength than cellulose.
1. A method far making a hydrophilic ester polyurethane foam, comprising:
(a) forming a polyurethane foam by mixing together the following components:
(i) 100 parts by weight of an ester polyol mixture, wherein at least 5.0 parts by weight of the ester polyol mixture comprises a hydrophilic polyester polyol made from an adipic acid and a polyethylene glycol;
(ii) from 20.0 to 62.0 parts by weight, based on 100 parts polyol, of an isocyanate, wherein the isocyanate index is 120 or less; and
(iii) from 1.0 to 3.0 parts by weight, based on 100 parts polyol, of a silicone stabilizing surfactant;
(b) treating the polyurethane foam in a caustic bath to form the hydrophilic ester polyurethane foam, and
(c) felting the treated foam,
wherein the hydrophilic ester polyurethane foam has a water absorption rate of at least 20 pounds of water per square foot per minute.
2. The method of claim 1 , further comprising from 1.0 to 5.0 parts by weight, based on 100 parts polyol, of a blowing agent as a component.
3. The method of claim 1 , wherein the blowing agent is water.
4. The method of claim 1 , further comprising as a component a catalyst selected from the group consisting of: gel catalysts and gas forming catalysts, and mixtures thereof.
5. The method of claim 1 , further comprising from 0.5 to 2.0 parts of a blow catalyst and from 0 to 0.3 parts of a gel catalyst.
6. The method of claim 1 , further comprising a double cell-forming additive as a component.
7. The method of claim 1 , further comprising an antimicrobial additive as a component.
8. The method of claim 1 , wherein the caustic bath is formed as a solution containing sodium hydroxide.
9. The method of claim 1 , wherein the treated foam is felted by compressing the foam to from one-third to one-eighth of its original thickness.
10. The method of claim 1 , wherein the treated foam is felted by compressing the foam while heating the treated foam to a temperature of from 340 to 380° F. (171 to 193° C.).
11. The method of claim 1 , wherein before felting, the hydrophilic ester polyurethane foam has pore sizes in the range of 70 to 130 pores per linear inch (27.6 to 51 pores per cm).
12. The method of claim 1 , wherein the isocyanate index is 100 or less.
13. The method of claim 1 , wherein the hydrophilic ester polyurethane foam has an instantaneous wet out.
14. A hydrophilic ester polyurethane foam made according to the method of claim 1 .