高聚合物含量丙烯酸酯超微胶乳的制备

通过对一次加料法、单体预乳化法及单体两段滴加法制备超微胶乳的比较,发现单体两段滴加法的反应过程相当稳定.单体两段滴加法中,当预加单体量小于30%时,聚合过程稳定,氨化剪切后超微胶乳透光率约65%;当聚合物含量超过34%时,超微胶乳体系呈凝胶状.对胶乳的氨化剪切过程进行优化,发现加氨量有一最佳值,此时超微胶乳既保持较高的透光率 (～65%),又具有较低的粘度 (～220cp).最后,通过"单体两段滴加法乳液聚合 氨化剪切"制备了聚合物含量约为32%、乳化剂含量约为1.2%、数均粒径约为63nm、粒径分布为1.17的丙烯酸酯超微胶乳.

PREPARATION OF POLYACRYLATE MICRO-LATEXES WITH HIGH POLYMER CONTENT

The polymerization was found quite stable by using two-stage monomer dropping method to prepare polyacrylate micro-latexes compared to the batch feeding and monomer pre-emulsification method. When the pre-adding fraction of monomer was less than 30%, the polymerization could be carried out stably and a final micro-latex with 65% transparency was obtained. When the fraction of polyacrylate in micro-latex prepared was over 34%, the micro-latexes appeared gelatiniform. Latex shearing with ammonia was investigated. It was found that a micro-latex with both better transparency (~65%) and lower viscosity (~220cp) could be obtained when adding appropriate amount of ammonia during shearing. As a result, a micro-latex with small particles size (~63nm) and narrow size distribution (1.17) was prepared by combining emulsion polymerization with two-stage monomer dropping and latex shearing in the presence of ammonia, which contained 32% polymer and only 1.2% emulsifier.