Production process for highly water absorbable polymer

DETAILED DESCRIPTION OF THE INVENTION In accordance with one embodiment of the present invention a cross-linked polyacrylate resin is prepared by aqueous solution polymerization while dehydrating or drying the reaction product during polymerization by utilizing the exothermic heat from the polymerization and cross-linking reactions for drying.
It has been found that acrylic acid neutralized in the range of 70 to 100 mole percent will polymerize rapidly with acrylamide and cross-link rapidly with a polyvinyl monomer cross-linking agent to drive away excess water leaving a solid water absorbing resin having a desired degree of polymerization as well as new and unexpected water absorbing capacity.
One or more polymerization catalysts or initiators can be added to the aqueous monomer mixture to aid in polymerization.
Acrylic acid neutralized 70-100 mole percent is mixed with a water-miscible or water-soluble polyvinyl monomer in an aqueous solution at a temperature of about 20.
degree.
to 100.
degree.
C.
The solution is subjected to a polymerization reaction and a cross-linking reaction by the addition of a polymerization initiator.
The polymerization reaction proceeds sufficiently within a very short period of time and if the monomer concentration is at least 70 percent by weight of the aqueous monomer mixture, the heat or the polymerization and cross-linking reactions will evaporate water rapidly from the reaction system to form a dry solid (less than 15 percent by weight water) water absorbing resin without the need for any subsequent drying step.
The solid can be easily pulverized into a powder suitable for any desired use.
Further, according to one embodiment of the invention, when the monomer concentration is at least 70 percent by weight of the polymerization mixture, the polymerization reaction and evaporation of water can be completed very rapidly, usually within several minutes, without external heating.
The process can be practiced very efficiently with greatly reduced consumption of heat energy while achieving a desired degree of polymerization very suitable for a commercial operation