Synthesis And Mechanism Of High Solid-content Styrene-acrylate Microlatex For Wood-paints

Acrylate latexes have being used widely in the buildings interior \exterior paints industry. But they are seldom seen in decorative wood-coatings industry because of failure to meet wood-coating needs such as low film-formation temperature, high hardness, gloss and transparency, good handle and excellent water resistance. It is necessary to synthesis latex with ultra fine particle size, and to minimize the emulsifiers' amount for high water-resistance and maximize solid-content for plumy. However, most of conventional latexes have a particle diameter of several hundred nanometers, and up to now, micro-latexes prepared by micro-emulsion polymerization usually have low ratio of polymer to emulsifier (the best ratio reported was 8:1). Hence, we have developed the following studies:All-acrylate micro-latex was successfully synthesized first by conventional emulsion polymerization with emulsifier content 1~2% (based on the total latex), monomer 50%( based on the total latex), particle size 35.6nm, polydispersity of particle size 0.133, weight-average molecular weight 1.2×10~6, polydispersity of molecular weight 6.2, low film formation temperature, gloss 87 and excellent impact-resistance properties. In our experiments, influences of polymerization technology and technical conditions which include the type and level of emulsifier, concentration and addition sequence of initiator, electrolyte concentration, polymerization temperature and agitation intensity and so on, on particle size and performances of latex were studied. Polymerization technology is stable for easily scaling up, which is a new synthesis method for polymer microlatexes.Then the all-acrylate micro-latex was successfully synthesized by micro-emulsion polymerization with emulsifiers content 2.5%, monomer 40%, particle size 34.3nm, polydispersity of particle size 0.176, molecular weight 1.22× 10~6, polydispersity 12.153, low film formation temperature, gloss 87 and excellent physical properties. Influences of polymerization technology and technical conditions including emulsifier level, amount of electrolyte, polymerization temperature and agitation intensity on particle size and performances of latex were studied. Besides the ratio of polymer to emulsifier can be successfully leveled up to 15:1, and the polymerization mechanism was also discussed. The polymerization processed in Winsor I -like system in which the upper monomer had the function of monomer reservoir, which should be continuously and slowly run with mild stirring to provide the micro-emulsion monomer so that the growth of polymer particles could keep.