Patent ID: 7591974

Claim:
A method of producing a superabsorbent polymer product for use in agricultural applications, comprising: graft polymerizing a monomer onto a starch in the presence of an initiator to form a starch graft copolymer, the starch graft copolymer forming a polymerization dough; feeding the polymerization dough into a heated extruder comprising an extrusion screw at a pressure of between 25 psi and 40 psi, the polymerization dough having a viscosity of between 2.5 million centipoise and 0.5 million centipoise when introduced to the heated extruder; operating the extrusion screw at a speed of between about 20 rpm to about 150 rpm; reducing the moisture content of the polymerization dough by drying the polymerization dough in the heated extruder, wherein the heated portions of the extruder heat the polymerization dough at a temperature of between 50° C. and 160° C.; cooling the polymerization dough in such a manner to allow moisture to be drawn to the outer surface of the polymerization dough after exiting the heated extruder; and drying the polymerization dough a second time after cooling the polymerization dough.