Continuous process for solution polymerization of acrylamide

Claim 1

A continuous polymerization process for producing a continuous, substantially homogeneous stream of a solid, non-tacky polymer which comprises the steps of: (a) forming a concentrated aqueous monomer solution at a temperature of from 23° to 40° C. to form a single phase solution said monomers being: (i) a mixture consisting essentially of an alkali metal salt of acrylic acid, a hydroxyalkyl acrylate and acrylamide, in proportions of from 5 to 62 mole%, from 2.1 to 40 mole% and from 31 to 91 mole%, respectively; or (ii) a mixture consisting essentially of (a) a (meth)acrylamidoalkylsulfonic acid or alkali metal salt thereof and (b) (meth)acrylamide or N-alkyl(meth)acrylamide, in proportions of from 8 to 70 mole% and from 30 to 92 mole %, respectively; or (iii) mixture (ii), further containing from 0.2 to 4.4 moles of a quaternary ammonium salt cross-linking agent; (b) heating a continuous stream of the monomer solution of step (a) to a polymerization initiation temperature of from 60° to 80° C. for mixture (i) or from 55° to 65° C. for mixture (ii) or (iii), by passage through an indirect heat exchanger at a rate such that the residence time of the solution in the heat exchanger is not longer than 0.5 minute; (c) immediately and continuously thereafter depositing the heated stream of monomer solution as a continuous, substantially uniform layer on a moving surface; (d) substantially simultaneously with step (c), continuously and substantially uniformly applying to the moving surface of catalytically effective amount of an aqueous solution of a polymerization initiator for the monomers, thereby continuously forming a substantially uniform reaction mixture of the heated monomer solution and the initiator on the moving surface said moving surface and said reaction mixture being unheated or heated only sufficiently to keep the temperature of the polymerizing mixture on the moving surface from falling substantially below said polymerization initiation temperature until polymerization is substantially complete; whereby the monomers exothermically and substantially homogeneously polymerize and a portion of the water therein evaporates to form a continuous stream of a substantially homogeneous solid, non-tacky polymer; and (e) recovering the resultant solid, non-tacky polymer.