Low density flexible resilient absorbent open-cell thermoplastic foam
View Patent ↗A low density, flexible, resilient, absorbent open-cell thermoplastic foam includes a combination of thermoplastic elastomer, ethylene ionomer, stiff polymer, and surfactant selected to provide various advantageous properties. The foam is useful in personal care absorbent articles, medical absorbent articles, absorbent wiping articles, and a variety of other applications.
1. An open-cell, absorbent thermoplastic foam, including at least 75% by weight of a foam formula mixture which comprises:
A) about 5 to about 70 parts by weight of a thermoplastic styrene block copolymer elastomer;
B) about 5 to about 70 parts by weight of an ethylene ionomer;
C) about 15 to about 60 parts by weight of a stiff polymer selected from the group consisting of polystyrene, high impact polystyrene, and combinations thereof; and
D) about 0.5 to about 5 parts by weight of a surfactant selected from the group consisting of ethoxylated dimethylsilicone surfactants, polyoxyethylene copolymer surfactants, block copolymers of ethylene oxide and propylene oxide, organic sulfonates, alkylpolyglycosides, polyolefin glycol derivatives, and combinations thereof;
wherein the thermoplastic foam has an open-cell content of at least about 70% and a vertical wicking height of at least about 4.5 cm.
2. The thermoplastic foam of claim 1 , wherein the thermoplastic styrene block copolymer elastomer comprises a styrene block copolymer elastomer selected from the group consisting of styrene diblock copolymers, styrene triblock copolymers, styrene tetrablock copolymers and combinations thereof.
3. The thermoplastic foam of claim 1 , wherein the ethylene ionomer comprises a thermoplastic ionomer having the following formula:
where M is sodium, potassium, lithium, magnesium, zinc or strontium,
R is hydrogen or an alkyl group having 1 to 6 carbon atoms,
m and n are integers, and
the ratio of m/n is about 10 to about 100.
4. The thermoplastic foam of claim 1 , where the ionomer has a percent neutralization of about 5% to about 100%.
5. The thermoplastic foam of claim 1 , wherein the ionomer has a percent neutralization of about 8% to about 85%.
6. The thermoplastic foam of claim 1 , wherein the surfactant comprises a compound selected from the group consisting of ethoxylated dimethylsiloxanes.
7. The thermoplastic foam of claim 1 , wherein the surfactant comprises a compound selected from the group consisting of polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, and combinations thereof.
8. The thermoplastic foam of claim 1 , wherein the surfactant comprises a compound selected from the group consisting of alkyl sulfonates, aryl sulfonates, alkylaryl sulfonates, ether sulfonates, and combinations thereof.
9. The thermoplastic foam of claim 1 , wherein the surfactant comprises an alkyl sulfonate.
10. The thermoplastic foam of claim 1 , wherein the surfactant comprises an alkyl polyglycoside.
11. An absorbent article comprising the thermoplastic foam of claim 1 .
12. A low density, open-cell, absorbent thermoplastic foam, including at least 75% by weight of a foam formula mixture which comprises:
A) 10 to about 50 parts by weight thermoplastic styrene block copolymer elastomer;
B) 10 to about 50 parts by weight ethylene ionomer;
C) about 25 to about 60 parts by weight stiff polymer selected from the group consisting of polystyrene, high impact polystyrene, and combinations thereof; and
D) about 0.5 to about 5 parts by weight of a surfactant selected from the group consisting of ethoxylated dimethylsilicone surfactants, polyoxyethylene copolymer surfactants, block copolymers of ethylene oxide and propylene oxide, organic sulfonates, alkylpolyglycosides, polyolefin glycol derivatives, and combinations thereof;
wherein the thermoplastic foam has a density of about 60 kg/m 3 to about 160 kg/m 3 , a vertical wicking height of at least about 4.5 cm, and an open-cell content of at least about 70%.
13. The thermoplastic foam of claim 12 , wherein the foam formula mixture comprises:
A) about 20 to about 40 parts by weight of the thermoplastic styrene block copolymer elastomer;
B) about 15 to about 40 parts by weight of the ethylene ionomer;
C) about 35 to about 60 parts by weight of the stiff polymer; and
D) about 2 to about 4 parts by weight of the surfactant.
14. The thermoplastic foam of claim 12 , wherein the ethylene ionomer comprises a partially neutralized polymer selected from the group consisting of partially neutralized ethylene acrylic acid, partially neutralized ethylene alkyl acrylic acids, partially neutralized ethylene alkyl acrylates, and combinations thereof.
15. The thermoplastic foam of claim 12 , wherein the surfactant comprises an alkyl sulfonate.
16. The thermoplastic foam of claim 12 , wherein the thermoplastic styrene block copolymer elastomer is selected from the group consisting of styrene diblock copolymers, styrene triblock copolymers, styrene tetrablock copolymers and combinations thereof.
17. The thermoplastic foam of claim 12 , wherein the foam has a density of about 125 kg/m 3 or less.
18. The thermoplastic foam of claim 12 , wherein the foam has a buckling pressure of about 250 kPa or less.
19. The thermoplastic foam of claim 18 , wherein the buckling pressure is about 100 kPa or less.
20. The thermoplastic foam of claim 12 , wherein the foam has a fluid intake rating of about 5 to 9.
21. The thermoplastic foam of claim 20 , wherein the fluid intake rating is about 7 to 9.
22. An absorbent article comprising the thermoplastic foam of claim 12 .
23. A low density, open-cell thermoplastic foam including at least 75% by weight of a foam formula mixture, the foam formula mixture comprising:
A) about 5 to about 70 parts by weight of a thermoplastic elastomer selected from the group consisting of styrene block copolymer elastomers and combinations thereof;
B) about 5 to about 70 parts by weight of an ethylene ionomer;
C) about 15 to about 60 parts by weight of a stiff polymer selected from the group consisting of polystyrene, high impact polystyrene, and combinations thereof; and
D) about 0.5 to about 5 parts by weight of a surfactant selected from the group consisting of ethoxylated dimethylsilicone surfactants, polyoxyethylene copolymer surfactants, block copolymers of ethylene oxide and propylene oxide, organic sulfonates, alkylpolyglycosides, polyolefin glycol derivatives, and combinations thereof;
wherein the thermoplastic foam has a fluid intake rating of about 5 to 9, a density of about 125 kg/m 3 or less, and an open-cell content of at least about 70%.
24. An absorbent article comprising the thermoplastic foam of claim 23 .