Flame laminable hydrophilic ester polyurethane foams

Abstract

A hydrophilic ester polyurethane foam is flame laminated to a substrate using a thin sacrificial layer, preferably a sacrificial foam layer. The sacrificial layer in the resulting laminate structure has a thickness of 1.5 mm or less, and preferably is substantially burnt away. The resulting laminate exhibits good bond strength along its length and width without loss of liquid wicking and absorptive properties.

1 . A method for flame bonding a hydrophilic ester polyurethane foam to a substrate to form a laminate structure, comprising: 
 providing a sacrificial sheet with a face surface and a reverse surface;    heating at least the face surface of the sacrificial sheet;    contacting the heated face surface of the sacrificial sheet with a surface of a sheet of hydrophilic ester polyurethane foam; and    contacting the reverse surface of the sacrificial sheet with a surface of the substrate; wherein the hydrophilic ester polyurethane foam is bonded to the substrate to form a resulting laminate structure in which the sacrificial sheet has a thickness of no more than about 1.5 mm.    
     
     
         2 . The method of  claim 1 , wherein the sacrificial sheet is a foam that has a starting thickness of no more than about one millimeter.  
     
     
         3 . The method of  claim 2 , wherein the sacrificial foam sheet has a starting thickness of from about 0.5 to 1 mm.  
     
     
         4 . The method of  claim 1 , wherein the sacrificial sheet is substantially consumed by the flame bonding.  
     
     
         5 . The method of  claim 1 , wherein the sacrificial sheet is a nonhydrophilic ester polyurethane foam.  
     
     
         6 . The method of  claim 5 , wherein the sacrificial foam sheet has a pore size from 3 to 200 ppi.  
     
     
         7 . The method of  claim 5 , wherein the sacrificial foam sheet has a pore size from 70 ppi to 200 ppi.  
     
     
         8 . The method of  claim 5 , wherein the nonhydrophilic ester polyurethane foam has a density of 90 lb/ft 3  or less.  
     
     
         9 . The method of  claim 1 , wherein the heating step comprises the steps of pre-bonding the face surface of the sacrificial sheet to a surface of the hydrophilic foam sheet and then heating the reverse surface of the sacrificial sheet.  
     
     
         10 . The method of  claim 1 , further comprising concurrently heating the reverse surface of the sacrificial sheet.  
     
     
         11 . The method of  claim 1 , wherein the heating causes the face surface and the reverse surface of the sacrificial sheet to soften for in situ bonding.  
     
     
         12 . The method of  claim 1 , wherein the substrate comprises a material selected from the group consisting of: a melamine or melamine-formaldehyde foam, a polyether polyurethane foam, a polyester polyurethane foam, a polymeric nonwoven, a textile fabric, an ethylene vinyl acetate (EVA) sheet or film, a polyolefin sheet or film, an acrylic sheet or film, a polyvinylchloride (PVC) sheet or film, a reticulated foam, a fleece, a cellulose sheet, a metallic sheet, a wood, pulp or pulp and fiber composite, a combination of polymers, and a polyester/polyamide/rayon fabric.  
     
     
         13 . A laminate structure made according to the method of  claim 1 .  
     
     
         14 . The laminate structure of  claim 13 , wherein the hydrophilic ester polyurethane foam is bonded to the substrate without an auxiliary adhesive.  
     
     
         15 . An absorbent article made according to the method of  claim 1 .  
     
     
         16 . A laminate structure, comprising: 
 a hydrophilic ester polyurethane foam sheet bonded to a substrate by flame bonding, wherein said flame bonding includes providing a sacrificial sheet with a face surface and a reverse surface, heating at least the face surface of the sacrificial sheet, contacting the heated face surface of the sacrificial sheet with a surface of a sheet of hydrophilic ester polyurethane foam; and contacting the reverse surface of the sacrificial sheet with a surface of the substrate; and further wherein the sacrificial sheet has a thickness of no more than about 1.5 mm in the laminate structure.    
     
     
         17 . The laminate structure of  claim 16 , wherein the sacrificial sheet is a foam that has a starting thickness of no more than about one millimeter.  
     
     
         18 . The laminate structure of  claim 17 , wherein the sacrificial foam sheet has a starting thickness of from about 0.5 to 1 mm.  
     
     
         19 . The laminate structure of  claim 17 , wherein the sacrificial foam sheet is a nonhydrophilic ester polyurethane foam with a density of 90 lb/ft 3  or less.  
     
     
         20 . The laminate structure of  claim 16 , wherein the sacrificial sheet is substantially consumed by the flame bonding.  
     
     
         21 . The laminate structure of  claim 16 , wherein the sacrificial sheet is a nonhydrophilic ester polyurethane foam.  
     
     
         22 . The laminate structure of  claim 16 , wherein the substrate comprises a material selected from the group consisting of: a melamine or melamine-formaldehyde foam, a polyether polyurethane foam, a polyester polyurethane foam, a polymeric nonwoven, a textile fabric, an ethylene vinyl acetate (EVA) sheet or film, a polyolefin sheet or film, an acrylic sheet or film, a polyvinylchloride (PVC) sheet or film, a reticulated foam, a fleece, a cellulose sheet, a metallic sheet, a wood, pulp or pulp and fiber composite, a combination of polymers, and a polyester/polyamide/rayon fabric.  
     
     
         23 . The laminate structure of  claim 16 , wherein the hydrophilic ester polyurethane foam is bonded to the substrate with a bond strength of at least about 7 oz/inch [76.6 N/m].  
     
     
         24 . The laminate structure of  claim 16 , wherein the hydrophilic ester polyurethane foam is bonded to the substrate without auxiliary adhesives.  
     
     
         25 . An absorbent article comprising the laminate structure of  claim 16.