Anionic Polyacrylamide Particles Prepared By Aqueous Dispersion Polymerization

In recent years,polymeric particle profile control technology has attracted much attention in improving oil recovery.This technology relies on the delayed swelling property of different size particles to block the formation pore to achieve the purpose of deep profile control.Aqueous dispersion polymerization has been widely concerned by researchers as a low cost,environmentally friendly and mild way to prepare micron sized polymeric particles.The dispersion copolymerization of acrylamide(AM)and sodium 2-acryla mido-2-methylpropanesulfonate(AMPSNa)in aqueous ammonium sulfate(AS)s olution was performed comparatively with poly(2-acrylamido-2-methyl-propanes ulfonate)(PAMPSNa)and the macro-RAFT agent sodium poly(2-acrylamido-2-methylpropanesulfonate)trithiocarbonate(PAMPSNa-TTC)as stabilizers.First,the effects of stirring,ammonium sulfate concentration,dispersant concentration,monomer concentration,polymerization temperature and chain transfer agent concentration on the molecular weight,particle size and stability of dispersion in PAMPSNa stabilized dispersion polymerization system were studied.In the system,the mechanical stirring has a great influence on the dispersion particle size and chain transfer agent has a significant effect on PAMPSNa stability efficiency.Experiments showed that dispersions with solid content of 12 ~ 16 wt%,average particle size of 1.91 ~ 4.81 ?m and molecular weight of 158.4 ~ 442.9ml/g have been prepared.Second,macro-RAFT agents PAMPSNa-TTC with different molecular weight were prepared by RAFT solution polymerization in deionized water using S,S?-bis(?,??-dimethyl-???-acetic acid)trithiocarbonate(BDMAT)as the RAFT agent and were used as the stabilizers to prepare water in water(W/W)dispersions.By analyzing the change of the transmittance,polymer molecular weight,particle size of the dispersion during the dispersion polymerization process and simulating the phase separation point,the process of phase separation,particle formation,growth,and stability of dispersion polymerization were studied.The effects of the stabilizer's molecular weight and concentration,AM/AMPSNa mass feed ratio,monomer concentration,AS concentration,and polymerization temperature were systematically investigated regarding particle size,molecular weight,apparent viscosity,and dispersion stability.The results showed that stable dispersions with high solid content(20 wt%),high molecular weight([?] = 1299 ml/g),and micron-sized particles(0.96 ~ 2.90 ?m)were obtained.Mechanical stirring has no obvious influence on the dispersion particle size in this dispersion polymerization system.Based on the comparison of the two dispersion systems and previous experimental phenomena,a new mechanism for the formation and stability of water based dispersed polymer particles was proposed.Finally,the feasibilities of preparing crosslinked polyacrylamide W/W dispersion by pre-crosslinking,seed crosslinking and post crosslinking method were explored.The experimental results showed that crosslinking W/W dispersions with good fluidity and high crosslinked could be prepared by post crosslinking method with urotropine-resorcinol,glyoxal(GO)and hexamethylolmelamine(HMM)as the crosslinker,and the swelling behaviors of crosslinked particles in water were studied.