Preparation Of Micro-latex And Living/Controlled Microemulsion Polymerization

With the development of society and the increasing consciousness in environmental protection, micro-latexes are getting more and more important. The application of micro-latexes will be broadened if the molecular weight is controlled and the molecular weight distribution is narrow. In this thesis, polyacrylate micro-latex and poly(styrene-acrylate) micro-latex with higher solid content and low emulsifier content were prepared by emulsion polymerization followed with ammonification and micronization or by microemulsion polymerization directly. Meanwhile, the initiator-catalyst-ligand system of atom transfer radical polymerization (ATRP) was introduced into microemulsion. The controllability and the kinetics of styrene polymerization in microemulsions with AIBN/CuCl₂/bpy were investigated.Polyacrylate latex was synthesized by two-stage monomer dropping method in emulsion system, and then the micro-latex with 32% polymer, 1.2% emulsifier, 220cP viscosity and small particle size (63nm) was prepared under shearing in the presence of ammonia. When the pre-added monomers were less than 30%, the polymerization could proceed stably. The micronization effect was found best when ammonification with 4ml ammonia and shearing 5min. The performance of micro-latex membrane was affected by the monomer ratio, the amount of ammonia and shearing time.Poly(styrene-acrylate) micro-latex with 0.6% emulsifier content, 27% solid content and number average particle diameter about 40nm was prepared by stirring the normal latex, which was synthesized in conventional emulsion polymerization, in the presence of ammonia. Ammonification temperature was important and 60℃was optimal. The hardness and adhesion of micro-latex membrane increased when combining acrylic acid with hydroxyethyl methacrylate. The content of emulsifier also affected the performance of micro-latex and its membrane.Several kinds of improved microemulsion polymerization technology were compared, and the polyacrylate micro-latex with 33.4% polymer content, 38.4% solid content and number average particle diameter 64.7nm was prepared by continuously feeding of monomer during polymerization. On the basis of optimal polymerization conditions, the amount of initiator affected the particle size of micro-latex only slightly.