有机硅改性聚丙烯酸酯纳米乳液的聚合稳定性研究

The Stability of Emulsion Polymerization for Organosiloxane Modified Acrylate Nanolatex

摘要: 以甲基丙烯酸甲酯(MMA)和丙烯酸丁酯(BA)为主单体，利用不同乳液聚合工艺合成了有机硅改性聚丙烯酸酯纳米乳液，通过测定聚合过程的凝聚率及单体转化率，考察了聚合工艺、反应温度、乳化剂用量、乙烯基三乙氧基硅烷(A-151)用量、甲基丙烯酸羟基乙基酯(HEMA)用量、甲基丙烯酸(MAA)用量、pH值等因素对反应稳定性的影响。结果表明：采用半连续滴加工艺，温度在80℃~85℃，引发剂、复合乳化剂、有机硅A-151、HEMA、MAA的质量百分含量分别为0.5%、3%、4%、2%、2%时反应过程稳定性较好，凝聚物的质量百分含量低于0.5%，乳液粒径为80 nm左右，固含量40%。提高乳化剂用量有利于改善聚合反应的稳定性；升高温度、增加A-151用量不利于聚合反应过程的稳定；而搅拌速率、pH值和引发剂用量均存在使乳液聚合过程稳定的最佳值。

Abstract: Organosiloxane modified acrylate nanolatex was synthesized by different emulsion polymerization processes with methylmethacrylate (MMA) and butylacrylate (BA) as main monomers. The effects of polymerization methods, reaction temperatures, amounts of initiator, emulsifier, vinyl-triethoxysilane (A151), 2-hydroxyethl methacrylate (HEMA), methyl acrylic acid (MAA) contents and pH on polymerization stability were investigated by measuring coagulation rate and monomer conversion. The results showed that with semi-continuous emulsion polymerization, organosiloxane modified acrylate nanolatex with particle size of about 80 nm and with low coagulation rate of 0.5% as well as solid content of 40 wt% was obtained under the condition of the better reaction stability when temperature at 80˚C - 85˚C, the mass fraction of initiator, emulsifier, A151, HEMA, MAA at 0.5%, 3%, 4%, 2%, 2% respectively. The increase of emulsifier contents can improve the stability of the polymerization process; but the temperature increase and the more dosage of A-151 are not conducive to the reaction stability. The optimal values for the stirring speed, pH and dosage of initiator exist for the stable state in emulsion polymerization.