Superabsorbent surface-treated carboxylated polysaccharides and process for producing same

Abstract

Surface-treated carboxyalkylated polysaccharides comprising a biobased content of at least 82% are described herein. The surface-treated carboxyalkylated polysaccharides comprise a CRC of at least 18 g/g, a FSC of at least 26 g/g, and an AUL at 0.7 psi of at least 14 g/g. Processes for the manufacture of surface-treated carboxyalkylated polysaccharides are also described herein.

1 - 70 . (canceled) 
     
     
         71 . A superabsorbent material comprising: a particle formed of a carboxyalkylated starch having a pH in a range from about 5.0 to about 10, said particle having an interior and a surface, each of which exhibiting a differentiated functionality; said interior is absorbent; said surface is treated with a non-crosslinking acid, such that penetration depth of said non-crosslinking acid is limited to said surface; and said carboxyalkylated starch has a homogeneous carboxyalkylated substitution pattern. 
     
     
         72 . The superabsorbent material according to  claim 71 , wherein said carboxyalkylated starch exhibits an ester linkage as characterized by the presence of an ester shoulder or ester band as determined by ATR-IR spectroscopy. 
     
     
         73 . The superabsorbent material according to  claim 71 , wherein said non-crosslinking acid is selected from the group consisting of organic monovalent acids and inorganic monovalent acids. 
     
     
         74 . The superabsorbent material according to  claim 73 , wherein said non-crosslinking acid is at least: hydrochloric acid, stearic acid, and citric acid. 
     
     
         75 . The superabsorbent material according to claim  1 , wherein said carboxyalkylated starch exhibits a substitution degree ranging from 0.2 to 1.0. 
     
     
         76 . The superabsorbent material according to claim  5 , wherein said carboxyalkylated starch exhibits a substitution degree ranging from 0.4 to 0.7. 
     
     
         77 . The superabsorbent material according to claim  1 , wherein said carboxalkylated starch is carboxyalkylated in an aqueous alkaline medium. 
     
     
         78 . A superabsorbent material comprising: a particle formed of a carboxyalkylated polysaccharide having a pH in a range from about 5.0 to about 10, said particle having an interior and a surface, each exhibiting a differentiated functionality; said interior is absorbent; said surface is treated with a non-crosslinking acid, such that penetration depth of said non-crosslinking acid is limited to said surface, said non-crosslinking acid induces ester linkages between polysaccharide strands at said particle surface, which imparts said particle with a sufficient structural rigidity to enable said particle to maintain a discrete particle shape when contacted with a salt solution, and said carboxyalkylated polysaccharide particle has a greater absorbance under load (AUL) of said salt solution at 0.7 psi than a comparative particle formed of the carboxyalkylated polysaccharide having a surface that is not treated with the non-crosslinking acid. 
     
     
         79 . A hygiene article comprising an absorbent member, said absorbent member includes from 15% to 80% of a carboxylated polysaccharide particle, said carboxylated polysaccharide particle having an external surface treated with a non-crosslinking acid, such that penetration depth of said non-crosslinking acid is limited to said surface, and said carboxylated polysaccharide particle having a homogeneous carboxyalkylated substitution pattern. 
     
     
         80 . The hygiene article according to  claim 79 , wherein said hygiene article is characterized by properties selected from the group consisting of: a third acquisition rate of at least 0.22 ml/sec; a third rewet of at most 4.0 grams; an averaged acquisition rate of at least 0.12 ml/sec., and a total rewet of at most 6.0 grams. 
     
     
         81 . The hygiene article according to  claim 79 , wherein said hygiene article is at least one of the following: diapers, incontinence articles, feminine hygiene products, sanitary napkins, absorbent dressings, absorbent paper products, textile products, printing products, air-laids, household articles, food pads, animal litter products, and sealing materials. 
     
     
         82 . A process of making a carboxyalkylated polysaccharide particle, comprising: treating a glass-like polysaccharide particle with a non-crosslinking acid, such that penetration depth of said non-crosslinking acid is limited to a surface of said glass-like polysaccharide particle, such that said non-crosslinking acid generates ester linkages between polysaccharide strands at said particle surface, which imparts said particle with a sufficient structural rigidity to enable said particle to maintain a discrete particle shape when contacted with a salt solution. 
     
     
         83 . The process of  claim 82 , wherein said glass-like polysaccharide particle is internally cross-linked prior to carboxyalkylating. 
     
     
         84 . The process of  claim 82 , wherein said glass-like polysaccharide particle is carboxyalkylated in an alkaline medium. 
     
     
         85 . The process of  claim 84 , wherein said alkaline medium is either: a dry alkali medium, an aqueous alkaline hydrophilic organic solvent, or aqueous alkaline solution. 
     
     
         86 . The process of  claim 82 , wherein said carboxyalkylated polysaccharide is carboxyalkylated in a reactive extrusion. 
     
     
         87 . The process of  claim 86 , wherein said carboxyalkylated polysaccharide is carboxyalkylated in an extrusion with a water content ranging from 15% to 30%. 
     
     
         88 . The process of  claim 86 , wherein carboxyalkylated polysaccharide is carboxyalkylated in a reactive extrusion exhibiting at least of 60% efficiency. 
     
     
         89 . The process of  claim 86 , wherein said reactive extrusion involves using a twin screw extruder.