Compounded surface treated carboxyalkylated starch polycrylate composites

A method of making a composite saponified polyacrylamide:carboxyalkyl starch particle comprising the sequential steps of:

• a) blending a polymerized saponified polyacrylamide hydrogel with an aqueous solution of a carboxymethyl starch to form a gelatinous admixture wherein the carboxymethyl starch comprises at least greater than 20% and the saponified polyacrylamide is 20 to less than 90% of the weight of the blend excluding the aqueous solution and any soluble components thereof;
• b) drying the gelatinous admixture to a moisture content of less than 10% forming a dried composite powder;
• c) grinding the dried composite powder to form composite particles of a size of 20-100 mesh;
• d) contacting a surface of the dried composite particles with a first solution containing a C2-C4 polyol and with a non-crosslinking mineral acid forming an acidic polyol coated composite material;
• e) contacting the surface-coated composite particles with a second solution comprising a trivalent metal salt;
• f) heating the acidic dual-coated composite material at a temperature of 100-190° C. for a time sufficient to crosslink to form ester or amide crosslinks between the C2-C4 polyol and at least one of the carboxymethyl starch and the saponified polyacrylamide on the surface of the particle, forming a surface crosslinked composite particle.

A composite superabsorbent particle comprising

• a) a carboxyalkylated starch content ranging from greater than 20% to 80% wt/wt of the particle;
• b) a synthetic polycarboxylate polymer ranging from 80% to 20% wt/wt of the particle;
• c) a surface region comprising ester linkages between at least one of the carboxyalkylated starch, a C2-C4 polyol and the polycarboxylate polymer, and ionic cross links with a trivalent metal ion;
• d) a core region, wherein the surface region of the particle has a higher concentration of the ester linkages and ionic cross links with the trivalent metal than the core region;
• and
• e) wherein the particle exhibits a FSC of at least 40 g/g, a CRC of at least 25 g/g, an AUL of at least 15 g/g under a load of 0.7 psi, and a SFR of at least 50 ml/min. with 0.9% saline.