Absorbents from Saponified Starch‐g‐poly (acrylonitrile‐co‐2‐acrylamido‐2‐methyl‐propanesulfonic acid). Some Practical Considerations

Ceric‐initiated graft polymerizations of monomer systems containing 90–99 mole % acrylonitrile and 1–10 mole % 2‐acrylamido‐2‐methyl‐propanesulfonic acid onto gelatinized starch, followed by alkaline saponification of the polyacrylonitrile (PAN) moiety, were carried out under more practical conditions. Highest absorbencies of both water and 0.9% NaCl were obtained when starch was gelatinized either by stirring in water at 95°C or by jet cooking and when the temperature of the exothermic graft polymerization was not allowed to exceed 30°C. Saponifications should be run at the lowest practical polymer concentration and for a period of time somewhat longer than that required for loss of the red color characteristic of alkali‐treated PAN. Moreover, the alkaline saponificate should not be neutralized prior to methanol precipitation. Increased conversions of monomers to polymer were obtained by adding a second equal portion of ceric ammonium nitrate initiator.