Superabsorbent materials having high, controlled gel-bed friction angles and composites made from the same

Abstract

The present invention relates to water swellable, water insoluble superabsorbent materials having controlled variable gel-bed friction angles. Controlling the gel-bed friction angle of the superabsorbent materials may allow control of the swelling of the material, the absorbency of the material, and/or the absorbency, resiliency, and porosity of the absorbent composite containing the superabsorbent material. The present invention relates to treatments for superabsorbent materials to manipulate friction angle and new superabsorbent materials having the desired friction angle characteristics. The present invention also relates to absorbent composites employing superabsorbent materials having the desired friction angle characteristics.

We claim:  
     
         1 . A superabsorbent material, comprising: 
 a water swellable, water insoluble superabsorbent material; and,    the superabsorbent material having a first gel-bed friction angle at a superabsorbent material swelling level of about 5.0 grams of 0.9 weight percent sodium chloride solution/gram of the superabsorbent material and gel-bed friction angles, at superabsorbent material swelling levels greater than about 5.0 grams of 0.9 weight percent sodium chloride solution/gram of the superabsorbent material, substantially equal to or greater than the first gel-bed friction angle,    wherein the first gel-bed friction angle is about 30 degrees or greater.    
     
     
         2 . The superabsorbent material of  claim 1 , wherein the first gel-bed friction angle is about 38 degrees or greater.  
     
     
         3 . The superabsorbent material of  claim 1 , wherein the water swellable, water insoluble superabsorbent material is selected from the group consisting essentially of natural materials, modified natural materials, synthetic materials, and combinations thereof.  
     
     
         4 . The superabsorbent material of  claim 3 , wherein the water swellable, water insoluble superabsorbent material is selected from the group consisting essentially of silica gels, agar, pectin, guar gum, alkali metal salts of polyacrylic acids, polyacrylamides, polyvinyl alcohols, ethylene maleic anhydride copolymers, polyvinyl ethers, hydroxypropylcelluloses, polyvinyl morpholinones, polymers and copolymers of vinyl sulfonic acid, polyacrylates, polyacrylamides, polyvinyl pyridine, acrylonitrile grafted starch, acrylic acid grafted starch, isobutylene maleic anhydride copolymers, and combinations thereof.  
     
     
         5 . The superabsorbent material of  claim 3 , wherein the water swellable, water insoluble superabsorbent material is selected from the group consisting essentially of silica gels, agar, pectin, guar gum, alkali metal salts of polyacrylic acids, polyacrylamides, polyvinyl alcohols, ethylene maleic anhydride copolymers, polyvinyl ethers, hydroxypropylcelluloses, polyvinyl morpholinones, polymers and copolymers of vinyl sulfonic acid, polyacrylates, polyacrylamides, polyvinyl pyridine, acrylonitrile grafted starch, acrylic acid grafted starch, isobutylene maleic anhydride copolymers, polyamines, and combinations thereof.  
     
     
         6 . The superabsorbent material of  claim 1 , further comprising a friction angle increasing additive in combination with the superabsorbent material.  
     
     
         7 . The superabsorbent material of  claim 6 , wherein the friction angle increasing additive is selected from the group consisting of chitosan, sodium silicate, sodium aluminate, alumino silicates, and combinations thereof.  
     
     
         8 . The superabsorbent material of  claim 1 , further comprising a structure selected from the group consisting of particles, fibers, flakes, spheres, and combinations thereof.  
     
     
         9 . An absorbent composite, comprising: 
 a plurality of wettable fibers; and,    a water swellable, water insoluble superabsorbent material in combination with the wettable fibers and having a first gel-bed friction angle at a superabsorbent material swelling level of about 5.0 grams of 0.9 weight percent sodium chloride solution/gram of the superabsorbent material and gel-bed friction angles, at superabsorbent material swelling levels greater than about 5.0 grams of 0.9 weight percent sodium chloride solution/gram of the superabsorbent material, substantially equal to or greater than the first gel-bed friction angle,    wherein the first gel-bed friction angle is about 30 degrees or greater.    
     
     
         10 . The absorbent composite of  claim 9 , wherein the first gel-bed friction angle is about 38 degrees or greater.  
     
     
         11 . The absorbent composite of  claim 9 , wherein the water swellable, water insoluble superabsorbent material is selected from the group consisting essentially of natural materials, modified natural materials, synthetic materials, and combinations thereof.  
     
     
         12 . The absorbent composite of  claim 11 , wherein the water swellable, water insoluble superabsorbent material is selected from the group consisting essentially of silica gels, agar, pectin, guar gum, alkali metal salts of polyacrylic acids, polyacrylamides, polyvinyl alcohols, ethylene maleic anhydride copolymers, polyvinyl ethers, hydroxypropylcelluloses, polyvinyl morpholinones, polymers and copolymers of vinyl sulfonic acid, polyacrylates, polyacrylamides, polyvinyl pyridine, acrylonitrile grafted starch, acrylic acid grafted starch, isobutylene maleic anhydride copolymers, and combinations thereof.  
     
     
         13 . The absorbent composite of  claim 11 , wherein the water swellable, water insoluble superabsorbent material is selected from the group consisting essentially of silica gels, agar, pectin, guar gum, alkali metal salts of polyacrylic acids, polyacrylamides, polyvinyl alcohols, ethylene maleic anhydride copolymers, polyvinyl ethers, hydroxypropylcelluloses, polyvinyl morpholinones, polymers and copolymers of vinyl sulfonic acid, polyacrylates, polyacrylamides, polyvinyl pyridine, acrylonitrile grafted starch, acrylic acid grafted starch, isobutylene maleic anhydride copolymers, polyamines, and combinations thereof.  
     
     
         14 . The absorbent composite of  claim 9 , further comprising a friction angle increasing additive in combination with the superabsorbent material.  
     
     
         15 . The absorbent composite of  claim 14 , wherein the friction angle increasing additive is selected from the group consisting of chitosan, sodium silicate, sodium aluminate, alumino silicates, and combinations thereof.  
     
     
         16 . The absorbent composite of  claim 9 , wherein the superabsorbent material further comprises a structure selected from the group consisting of particles, fibers, flakes, spheres, and combinations thereof.  
     
     
         17 . The absorbent composite of  claim 9 , further comprising a friction angle increasing additive in combination with the wettable fibers.  
     
     
         18 . The absorbent composite of  claim 17 , wherein the friction angle increasing additive is selected from the group consisting of chitosan, sodium silicate, sodium aluminate, alumino silicates, and combinations thereof.