Polymerization process, apparatus mid polymer

Abstract

A process for producing a substantially dry polymer particle powder. A mixture of polymerization reagents is formed from a mixture of at least one monomer source and a solvent selected from the group consisting essentially of water and organic solvents and an initiator source. The mixture of polymerization reagents is sprayed into a heated, controlled atmosphere, forming droplets of the mixture which are allowed to fall through the heated, controlled atmosphere for a sufficient period of time to obtain a desired degree of polymerization. The solvent is continuously evacuated from the atmosphere during the polymerization process.

We claim:  
     
         1 . A water absorbing, small particle size, substantially dry, crosslinked polymer comprising the reaction product of a monomer selected from the group consisting of acrylic acid, methacrylic acid, and salts of acrylic and methacrylic acid, acrylamide, methacrylamide, salts of acrylic acid and methacrylic acid, esters of acrylic and methacrylic acid, and mixtures thereof, the reaction occurring in the presence of water or an organic solvent, a crosslinker and an initiator, the polymer having a substantially smooth surface, a water content of less than about 2 percent by weight and a particle size of less than about 50 microns.  
     
     
         2 . The water absorbing, small particle size, substantially dry, crosslinked polymer of  claim 1  wherein the initiator is selected from the group consisting of peroxygen compounds, peroxides, substituted nitrites and azo compounds.  
     
     
         3 . The water absorbing, small particle size, substantially dry, crosslinked polymer of  claim 1  wherein the crosslinker is selected from the group consisting of polyvinyls, polyesters of unsaturated carboxylic acids, bisacrylamides, carbamyl esters, esters of acrylic or methacrylic acid, oxides, hydroxides and weak acid salts.  
     
     
         4 . The water absorbing, small particle size, substantially dry, crosslinked polymer of  claim 1  wherein the monomer is a ethylenically unsaturated monomeric acid.  
     
     
         5 . A small particle size, substantially dry, water absorbing crosslinked polymer comprising the reaction product of acrylic acid monomer in the presence of water or an organic solvent, a crosslinker and an initiator, the polymer having a substantially smooth and spherical surface, a water content of less than about 2 percent by weight and a particle size of less than about 50 microns.  
     
     
         6 . A small particle size, substantially dry, water absorbing crosslinked polymer comprising the reaction product of acrylic acid monomer in the presence of water, a crosslinker and an initiator, the polymer having a substantially irregular shape, a water content of less than about 2 percent by weight and a particle size of less than about 50 microns.  
     
     
         7 . The small particle size, substantially dry, water absorbing crosslinked polymer of  claim 6  wherein the substantially irregular shape is flake-like.  
     
     
         8 . A small particle size, substantially dry, water absorbing crosslinked polymer consisting essentially of acrylic acid or methacrylic acid residues, the polymer having a substantially smooth and spherical shape, a water content of less than about 2 percent by weight and a particle size of less than about 50 microns.