The Synthesis Of Polyacrylamide By High-gravity Technology

Polyacrylamide(PAM)is a kind of polymer that is made of Acrylamide(AM)monomer homopolymerization or copolymerization with other functional monomers.It has been widely used in petroleum,water treatment,paper making,medicine and other fields.At present,the technical problems encountered in PAM production include large investment in the production process,backward production technology and low product quality.In this paper,polyacrylamide with different qualities was synthesized in a Rotating Packed Bed(RPB)reactor using the combination of high-gravity technology and free radical polymerization mechanism.The process optimization was carried out with its molecular weight as the optimization index,and the structure of the polymer products was characterized.The main research contents are as follows:(1)PAM with different molecular weights were synthesized in RPB reactor by RPB inversed emulsion polymerization,using cyclohexane as oil phase,span-80 and tween-20 as complex emulsifiers,acrylamide monomer aqueous solution as water phase and ammonium persulfate as initiator.The effects of high-gravity level,temperature,AM monomer concentration,initiator concentration,the oil-water ratio on PAM molecular weight and its distribution were studied.The chemical structure,purity,and AM residues of the polymeric products were characterized by IR,1H NMR,and HPLC.PAM with viscosity average molecular weight of 1.63 million can be synthesized in RPB.Compared with the stirred reactor(STR),the molecular weight distribution of the product prepared by RPB is narrower,the purity was increased from 92.57%to 98.66%,the residual monomer content was decreased from 0.0073%to 0.0028%,and the reaction time was shortened from 8.5 h to 40 min.The production efficiency and product quality were greatly improved.(2)In order to further improve the molecular weight of PAM and improve the stability of the polymerization system,PAM with different molecular weight were continued to be synthesized in RPB reactor by RPB inversed microemulsion polymerization.Using more stable isopar-M as oil phase,span80 and tween-80 as complex emulsifiers,the AM monomer aqueous solution as water phase and replacing the single initiator with a more efficient REDOX initiator system composed of ammonium persulfate and sodium bisulfite as the initiator.The viscosity average molecular weight of PAM was characterized by the viscosity method and the effects of high-gravity level,temperature,AM monomer concentration,initiator concentration and oil-water ratio on the molecular weight of PAM were studied.Under the optimal condition,the viscosity average molecular weight of PAM can reach 3.29 million,the yield is 84%.Compared with the STR process,the reaction time was shortened from 8.5 h to 2 h,and the production efficiency was improved.(3)Poly(acrylamide-sodium alginate)copolymers with different qualities were synthesized by graft copolymerization in RPB reactor by RPB aqueous solution polymerization,using REDOX initiator system composed of ammonium persulfate and sodium bisulfite as the initiator and sodium alginate as graft copolymer.The effects of high-gravity level,reaction temperature,acrylamide concentration and initiator concentration on the viscosity average molecular weight of copolymer were researched.The structure and morphology of the copolymer were characterized by IR and SEM.Under the optimal condition,the viscosity average molecular weight of P(AM-SAG)can reach 2.94 million and the yield is 90.19%.Compared with the STR process,the reaction time is shortened from 9 h to 3 h.The flocculation performance of the copolymer synthesized under the optimal process conditions in RPB and STR reactors was studied,and the flocculation effect of the RPB product was better.