Hydrophilic ester polyurethane foams
An ester polyurethane foam is prepared by reacting one or a mixture of hydrophilic polyester polyols with one or more isocyanates and a cell opening surfactant. The cured foam does not require post-foaming processing to achieve a water absorption rate of at least 20 pounds of water per square foot per minute, preferably at least 25 pounds of water per square foot per minute. The foam may be bonded to a substrate to form an absorbent article, such as a sponge, mop head, or a medical or industrial wipe.
1 . A method for making a hydrophilic polyester polyurethane foam, comprising:
(a) forming a polyurethane foam by mixing together the following components:
(i) 100 parts by weight of a polyol or mixture of polyols, wherein at least about 40 parts by weight of such polyol or mixture of polyols comprises a hydrophilic polyester polyol with an hydroxyl number of 40 to 100;
(ii) at least about 30 parts by weight, based on 100 parts polyol, of an isocyanate, wherein the isocyanate index is from 60 to 110; and
(iii) up to about 3.0 parts by weight, based on 100 parts polyol, of a cell opening surfactant;
wherein the hydrophilic polyester 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 , wherein the polyol or mixture of polyols comprises at least about 70 parts by weight of a hydrophilic polyester polyol with an hydroxyl number of 40 to 100.
3 . The method of claim 2 , wherein the hydrophilic polyester polyol made from an adipic acid and a polyethylene glycol.
4 . The method of claim 1 wherein 100 parts of the polyol or mixture of polyols comprises a single polyol that is a hydrophilic polyester polyol with an hydroxyl number of 40 to 100.
5 . The method of claim 1 , wherein the isocyanate is selected from the group consisting of toluene diisocyanates, methylene diisocyanates, and mixtures of such isocyanates.
6 . The method of claim 1 , wherein the cell opening surfactant is a silicone surfactant.
7 . 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.
8 . The method of claim 7 , wherein the blowing agent is water.
9 . The method of claim 1 , further comprising a catalyst selected from the group consisting of: gel catalysts and gas forming catalysts, and mixtures thereof.
10 . 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.
11 . The method of claim 1 , wherein the hydrophilic polyester polyurethane foam has pore sizes in the range of 60 to 130 pores per linear inch.
12 . The method of claim 1 , wherein the isocyanate index is about 70 to 90.
13 . The method of claim 1 , wherein the hydrophilic polyester polyurethane foam has a water absorption rate of at least 25 pounds of water per square foot per minute.
14 . The method of claim 1 , wherein the hydrophilic polyester polyurethane foam has such water absorption rate without a chemical reticulation step.
15 . The method of claim 1 , wherein the hydrophilic polyester polyurethane foam is flame laminatable to a substrate to achieve a bond strength of at least about 8 ounces.
16 . A hydrophilic polyester polyurethane foam made according to the method of claim 1 .
17 . An absorbent article incorporating the hydrophilic polyester polyurethane foam of claim 16 .
18 . A method for making an absorbent article, comprising:
(a) forming a hydrophilic polyurethane foam by mixing together the following components:
(i) 100 parts by weight of a polyol or mixture of polyols, wherein at least about 40 parts by weight of such polyol or mixture of polyols comprises a hydrophilic polyester polyol with an hydroxyl number of 40 to 100;
(ii) at least about 30 parts by weight, based on 100 parts polyol, of an isocyanate, wherein the isocyanate index is from 60 to 110; and
(iii) up to about 3.0 parts by weight, based on 100 parts polyol, of a cell opening surfactant;
wherein the hydrophilic polyester polyurethane foam has a water absorption rate of at least 20 pounds of water per square foot per minute; and
(b) laminating the hydrophilic polyester polyurethane foam to a substrate.
19 . The absorbent article of claim 18 , wherein the laminating step is by flame lamination.
20 . The absorbent article of claim 18 , wherein the hydrophilic polyester polyurethane foam has such water absorption rate without a chemical reticulation step.
21 . The absorbent article of claim 18 , wherein the hydrophilic polyester polyurethane foam has a water absorption rate of at least 25 pounds of water per square foot per minute.