可再分散苯丙乳胶粉的制备与表征

Preparation of re-dispersible styrene-acrylate polymer powders and its performance representation

采用半连续种子乳液聚合法,以苯乙烯、丙烯酸丁酯、甲基丙烯酸、甲基丙烯酸甲酯等为主要原料合成了苯丙乳液,并用喷雾干燥法制备了可再分散苯丙乳胶粉。探讨了乳胶粒结构形态、硬单体与软单体配比(St/BA)、喷雾干燥温度对制备可再分散苯丙乳胶粉干燥温度、成膜性、颗粒形态的影响及苯丙乳胶粉改性干混砂浆的结构。结果表明,核壳结构苯丙乳液有利于喷雾干燥;当St/BA为15/61时,苯丙乳胶粉在0℃下成膜表面光滑,均匀致密;干燥温度升高,可再分散乳胶粉含水率降低,再分散液粒径减小,成膜性提高。但温度过高(>160℃)或过低(≤100℃)均会使乳胶粒子在干燥过程中形成粒径较大的聚合物颗粒,导致粉体滤渣含量增加,对于苯丙乳液来说,适当的喷雾干燥温度为120～140℃。红外光谱分析表明,在100～160℃下的干燥没有明显改变乳胶粒子的分子结构。SEM分析表明,聚合物乳胶粉在干混砂浆基体中形成了连续的互穿网状膜。

A kind of styrene-acrylate emulsion was synthesized by semi-continuous Seed emulsion polymerization method. The main monomers were styrene,butyl acrylate,methacrylic acid and methyl methacrylate. And styrene-acrylate re-dispersible powders were prepared by spray drying. The influences of the structure of latex particles,drying temperatures and different ratio of soft and hard monomers （St/BA） on the spray drying temperatures,film-forming ability and particle size of styrene-acrylate-dispersible powders were investigated. And the structure of dry-mixed mortar powder was modified by styrene-acrylic polymer powers. The results showed that core-shell styrene-acrylic emulsion was benefit for spray drying. When the St/BA was 15/61,the film with smooth surface and dense could be easily formed under 0 ℃.With the drying temperature increasing,the water content and particle size of the re-dispersible polymer powders were decreased while film-forming ability were improved. A higher （〉160 ℃） or a lower （≤100 ℃） temperature led to formation of bigger polymer particles which increased the filter residue content. It was found that the appropriate temperatures for spray drying of styrene-acrylate emulsion were 120-140 ℃. The FTIR showed that the molecular structures of the polymer after drying were not obviously changed while the temperature was at 100-160 ℃. The SEM showed that polymer powders generated an interpenetrating network of polymer film in the dry-mixed mortar.