Modified acrylic-based superabsorbent polymers. Effect of temperature and initiator concentration

A solution polymerization process was used industrially to produce superabsorbent polymers based on acrylic monomers. Using a simple, small scale laboratory version of the polymerization part of this process which permits contact with air and evaporative losses, the effects of varying the heat input and the initiator concentration were explored. The presence of oxygen resulted in an inhibition period which lengthened the time for completing polymerization and consequently increased evaporative losses of water. The absorbency of the reaction products was highest under conditions which gave short reaction times. Long reaction times resulted in long inhibition periods, runaway polymerization and low absorbency. These, effects were accounted for in terms of oxygen participation in the polymerization and extensive losses of water as the solvent.