Low-density, open-cell, soft, flexible, thermoplastic, absorbent foam and method of making foam

Abstract

A soft, flexible, low-density, open-cell, thermoplastic, absorbent foam formed from a foam polymer formula including a balanced amount of a plasticizing agent and a surfactant in combination with a base resin. Thermoplastic elastomers can be added to the foam polymer formula to improve softness, flexibility, elasticity, and resiliency of the resulting foam. The surfactant may be either a single surfactant or a multi-surfactant system. The foam possesses a number of qualities, such as softness and strength, which render the foam particularly suitable for use in a variety of personal care products, medical products, and the like.

1 . A thermoplastic absorbent foam, comprising: 
 a base resin;    a surfactant; and    a plasticizing agent;    the foam having an open cell content of about 50% or greater, a density of about 0.10 grams/cm 3  or less, a saturated capacity of about 3 grams/gram or greater measured under a load of 3.45 KPa, and a bending modulus of less than about 6000 KPa at 1 mm deflection.    
     
     
         2 . The foam of  claim 1 , wherein the base resin comprises at least one of the group consisting of polystyrene, styrene copolymers, polyolefins, polyesters, and combinations thereof.  
     
     
         3 . The foam of  claim 1 , further comprising between about 10% and about 50% thermoplastic elastomer, by weight, of the foam.  
     
     
         4 . The foam of  claim 3 , wherein the thermoplastic elastomer comprises at least one of the group consisting of styrenic block copolymers including diblock and triblock copolymers which may include styrene-isoprene-styrene (SIS), styrene-butadiene-styrene (SBS), styrene-isoprene-butadiene-styrene (SIBS), styrene-ethylene/butylene-styrene (SEBS), styrene-ethylene/propylene-styrene (SEPS); polyolefin-based thermoplastic elastomers including random block copolymers including ethylene α-olefin copolymers; block copolymers including hydrogenated butadiene-isoprene-butadiene block copolymers; stereoblock polypropylenes; graft copolymers, including ethylene-propylene-diene terpolymer (EPDM), ethylene-propylene random copolymers (EPM) and ethylene propylene rubbers (EPR); blends of thermoplastic elastomers with dynamic vulcanized elastomer-thermoplastic blends; thermoplastic polyether ester elastomers; ionomeric thermoplastic elastomers; polyamide thermoplastic elastomers; thermoplastic polyurethanes; and combinations thereof.  
     
     
         5 . The foam of  claim 1 , wherein the surfactant comprises an anionic surfactant.  
     
     
         6 . The foam of  claim 1 , wherein the surfactant comprises a multi-component surfactant system  
     
     
         7 . The foam of  claim 1 , wherein the plasticizing agent comprises at least one of the group consisting of polyethylene; ethylene vinyl acetate; mineral oil, palm oil, waxes, naphthalene oil, paraffin oil, acetyl tributyl citrate; acetyl triethyl citrate; p-tert-butylphenyl salicylate; butyl stearate; butylphthalyl butyl glycolate; dibutyl sebacate; di-(2-ethylhexyl) phthalate; diethyl phthalate; diisobutyl adipate; diisooctyl phthalate; diphenyl-2-ethylhexyl phosphate; epoxidized soybean oil; ethylphthalyl ethyl glycolate; glycerol monooleate; monoisopropyl citrate; mono-, di-, and tristearyl citrate; triacetin (glycerol triacetate); triethyl citrate; 3-(2-xenoyl)-1,2-epoxypropane; and combinations thereof.  
     
     
         8 . The foam of  claim 1 , wherein the plasticizing agent comprises a thermoplastic elastomer.  
     
     
         9 . The foam of  claim 1 , wherein the foam has a fluid intake flux of about 0.15 ml/sec/cm 2  or greater upon the first insult, about 0.15 ml/sec/cm 2  or greater upon the second insult, and about 0.15 ml/sec/cm 2  or greater upon the third insult.  
     
     
         10 . The foam of  claim 1 , wherein the foam has a cross-direction trap tear strength of about 200 grams or greater and a machine-direction trap tear strength of about 400 grams or greater.  
     
     
         11 . The foam of  claim 1 , wherein the foam has a peak load edge compression of about 1000 grams or less.  
     
     
         12 . The foam of  claim 1 , wherein the foam has a compression resistance of about 20% compression set or less.  
     
     
         13 . The foam of  claim 1 , wherein the foam has a vertical wicking height of about 5 cm or greater.  
     
     
         14 . The foam of  claim 1 , wherein the bending modulus is less than about 4000 KPa at 1 mm deflection.  
     
     
         15 . The foam of  claim 1 , wherein the bending modulus is less than about 2000 KPa at 1 mm deflection.  
     
     
         16 . An absorbent article comprising the foam of  claim 1 .  
     
     
         17 . The absorbent article of  claim 16 , wherein the article is selected from the group consisting of personal care articles, household/industrial articles and health/medical articles.  
     
     
         18 . A roll product comprising a foam sheet wound into a roll, wherein the foam sheet comprises the foam of  claim 1 .  
     
     
         19 . A thermoplastic absorbent foam, comprising: 
 about 45 to about 90% by weight of a base resin;    about 10 to about 55% by weight of a thermoplastic elastomer; and    about 0.05 to about 10% by weight of a surfactant;    wherein the foam has an open cell content of about 50% or greater, a fluid intake flux of about 0.15 ml/sec/cm 2  or greater, and a bending modulus of less than about 6000 KPa at 1 mm deflection.    
     
     
         20 . The foam of  claim 19 , further comprising about 0.5% to about 10% by weight of an additional plasticizing agent.  
     
     
         21 . The foam of  claim 19 , wherein the thermoplastic elastomer comprises a styrenic block copolymer including at least one of the group consisting of styrene-isoprene-styrene (SIS), styrene- butadiene-styrene (SBS), styrene-isoprene-butadiene-styrene (SIBS), styrene-ethylene/butylene-styrene (SEBS), styrene-ethylene/propylene-styrene (SEPS), and combinations thereof.  
     
     
         22 . The foam of  claim 21 , wherein the thermoplastic elastomer has a diblock content between about 50% and about 80% of a total weight of the thermoplastic elastomer.  
     
     
         23 . The foam of  claim 19 , wherein the bending modulus is less than about 4000 KPa at 1 mm deflection.  
     
     
         24 . The foam of  claim 19 , wherein the bending modulus is less than about 2000 KPa at 1 mm deflection.  
     
     
         25 . The foam of  claim 19 , comprising a vertical wicking fluid flux at zero height of at least about 5 g/sec/m 2 .  
     
     
         26 . The foam of  claim 19 , comprising a functional capacity greater than about 0.2 cc/gram.  
     
     
         27 . The foam of  claim 19 , comprising a compression resistance of about 20% compression set or less.  
     
     
         28 . The foam of  claim 19 , comprising a density of less than about 0.07 g/cm 3 .  
     
     
         29 . The foam of  claim 19 , comprising a density of about 0.02 g/cm 3  to about 0.10 g/cm 3 .  
     
     
         30 . The foam of  claim 19 , comprising a saturated capacity of about 3 g/g to about 9 g/g, as measured under a 3.45 KPa loading.  
     
     
         31 . The foam of  claim 19 , comprising a wet tensile loss of less than about 10% in a machine direction and in a cross direction.  
     
     
         32 . The foam of  claim 19 , comprising a static coefficient of friction of about 0.4 to about 1.0.  
     
     
         33 . An absorbent article comprising the foam of  claim 19 .  
     
     
         34 . The absorbent article of  claim 33 , wherein the article is selected from the group consisting of personal care articles, household/industrial articles and health/medical articles.  
     
     
         35 . A roll product comprising a foam sheet wound into a roll, wherein the foam sheet comprises the foam of  claim 19 .  
     
     
         36 . A thermoplastic absorbent foam, comprising: between about 40% and about 80% by weight of a polystyrene base resin and between about 20% and about 60% by weight of a styrene block copolymer thermoplastic elastomer, wherein the absorbent foam has an open cell content of about 50% or greater, a bending modulus less than about 6000 KPa at 1 mm deflection, and a density of about 0.10 grams/cm 3  or less.  
     
     
         37 . An absorbent article comprising the foam of  claim 36 .  
     
     
         38 . The absorbent article of  claim 37 , wherein the article is selected from the group consisting of personal care articles, household/industrial articles, and health/medical articles.  
     
     
         39 . A roll product comprising a foam sheet wound onto a roll, wherein the foam sheet comprises the foam of  claim 36.