Modified polysaccharides having improved absorbent properties and process for the preparation thereof

A method for producing a water-swellable, water-insoluble carboxymethyl cellulose, the method comprising the following steps:

• forming a homogeneous mixture comprising a water-soluble carboxymethyl cellulose, water, and a crosslinking agent selected from the group consisting of organic compounds comprising at least two functional groups capable of reacting with a carboxyl or hydroxyl group of a carboxyalkyl polysaccharide and a metal ion having more than 2 positive charges, wherein the water-soluble carboxyalkyl polysaccharide dissolves into the water;
• recovering said carboxymethyl cellulose and said crosslinking agent from said mixture;
• and
• heat-treating said recovered carboxymethyl cellulose and crosslinking agent at a temperature above about 100.degree. C. for a time effective to crosslink said carboxymethyl cellulose to render said carboxymethyl cellulose water swellable and water insoluble wherein said heat-treated carboxymethyl cellulose has an initial Absorbency Under Load value of at least 17 and retains at least about 50 percent of the initial Absorbency Under Load value after aging for about 60 days at about 24.degree. C. and at least about 30 percent relative humidity.

A method for producing a water-swellable, water-insoluble carboxyalkyl polysaccharide, the method comprising the following steps:

• forming a homogeneous mixture comprising a water-soluble carboxyalkyl polysaccharide and water, wherein the water-soluble carboxyalkyl polysaccharide dissolves into the water;
• recovering said carboxyalkyl polysaccharide from said mixture;
• and
• heat-treating said recovered carboxyalkyl polysaccharide at a temperature between about 200.degree. C. and about 250.degree. C. for an amount of time between about 50 to about 90 seconds, wherein said heat-treating is effective to crosslink said carboxyalkyl polysaccharide to render said carboxyalkyl polysaccharide water swellable and water insoluble, wherein the water-swellable, water-insoluble carboxyalkyl polysaccharide exhibits an initial Absorbency Under Load value of at least 17 and retains at least about 50 percent of the initial Absorbency Under Load value after aging for about 60 days at about 24.degree. C. and at least about 30 percent relative humidity.

A method for producing a water-swellable, water-insoluble carboxyalkyl polysaccharide, the method comprising the following steps:

• forming a homogeneous mixture comprising a water-soluble carboxyalkyl polysaccharide and water, wherein the water-soluble carboxyalkyl polysaccharide dissolves into the water;
• adding to the homogeneous mixture a solution comprising a crosslinking agent, comprising an aluminum ion, dissolved in water;
• and
• recovering said carboxyalkyl polysaccharide and said crosslinking agent from said mixture, wherein the water-swellable, water-insoluble carboxyalkyl polysaccharide exhibits an initial Absorbency Under Load value of at least 8 and retains at least about 50 percent of the initial Absorbency Under Load value after aging for about 60 days at about 24.degree. C. and at least about 30 percent relative humidity.

A method for producing a water-swellable, water-insoluble carboxyalkyl polysaccharide comprising:

• a. preparing a reaction dispersion comprising a solvent and a polysaccharide comprising an original crystalline structure;
• b. adding a carboxyalkylating reagent to the reaction dispersion at conditions effective to allow the carboxyalkylating reagent to react with the polysaccharide to prepare a water-insoluble, water-dispersible carboxyalkyl polysaccharide, wherein the carboxyalkyl polysaccharide comprises an amount of the original crystalline structure of the polysaccharide and a non-crystalline structure;
• c. recovering the water-insoluble, water-dispersible carboxyalkyl polysaccharide from the reaction dispersion;
• d. preparing a mixture comprising the recovered water-insoluble, water-dispersible carboxyalkyl polysaccharide and water, wherein the carboxyalkyl polysaccharide is dispersed in the water and the non-crystalline structure of the carboxyalkyl polysaccharide dissolves into the water;
• and
• e. recovering the carboxyalkyl polysaccharide from the mixture, wherein the carboxyalkyl polysaccharide comprises an amount of the original crystalline structure of the polysaccharide to be effective to result in a water-swellable, water-insoluble carboxyalkyl polysaccharide exhibiting an initial Absorbency Under Load value of at least 17 and retaining at least about 50 percent of the initial Absorbency Under Load value after aging for about 60 days at about 24.degree. C. and at least about 30 percent relative humidity.