八甲基环四硅氧烷改性丙烯酸酯乳液的研究

【作者】 陈红梅；

【导师】 马承银；

【作者基本信息】 中南大学 ， 应用化学， 2003， 硕士

【摘要】 本论文以建筑外墙涂料用水溶性有机硅改性丙烯酸树脂为研究背景，研究含羟基聚硅氧烷改性丙烯酸酯乳液聚合。论文以D₄为起始原料，经过阴离子乳液聚合得到含羟基的聚硅氧烷，再将它经自由基聚合键合到丙烯酸酯聚合物中，制备出有机硅丙烯酸酯乳液。本论文的研究工作分为两部分，一是通过D₄阴离子乳液聚合合成含羟基聚硅氧烷的研究，得出合成聚硅氧烷的实验室理想条件。二是在合成聚硅氧烷乳液的基础上，应用硅烷偶联剂MATS与聚硅氧烷协同完成对丙烯酸酯的改性，得出有机硅丙烯酸酯乳液合成的优化条件，并对乳液性能的影响因素进行了分析。 在D₄阴离子乳液聚合制备含羟基聚硅氧烷研究中，主要探讨聚合反应温度、乳化剂体系及用量对聚合反应速率、聚合物分子量以及乳液稳定性的影响，得出较为理想的反应条件是反应温度为80℃，乳化剂DBSA用量为3％-5％，反应6h产物分子量达到6-8万。通过分析和计算得出了该体系的反应级数和表观活化能。从反应过程液层变化和粒径的动态变化角度进行研究，分析得出羟基硅油乳液“漂油”问题的主要原因是大颗粒“过渡层粒子”的存在。 在聚硅氧烷改性丙烯酸酯的乳液合成中，首先研究了反应温度、乳化剂体系及用量、聚硅氧烷等对产物粒径大小及分布、电解质稳定性的影响。得出聚硅氧烷用量在10％左右，反应温度控制在78-82℃，反应过程中逐步补加3％的OS／Ap065复合乳化剂能得到性能较好的乳液。其次研究了硅烷偶联剂MATS对乳液膜性能的影响，MATS用量为聚硅氧烷的5％，涂膜润湿角大于90°，涂膜的憎水性好。以TG、DTG、DTA、IR和SEM等为表征手段，通过对MATS加料方式的研究，得出硅烷偶联剂在聚合反应中的作用机理：MATS相当于是“过渡层”，两边分别连接着聚硅氧烷和丙烯酸酯。更多还原

【Abstract】 The goals for this work are to get a better understanding on the emulsion polymerization of polysiloxane-modified-polyacrylate, which was used as an important composite in civic buildings’ outside-wall-dope. Poly(siloxane/acrylate) was synthesized by emulsion polymerization by using octamethyltetracyclosiloxane (D4), 3-(trimethoxylsilyl)propyl methacrylate (MATS)- BA. MMA and AA as raw materials, potassium peroxydisulfate , OS/AP065 as initiator and emulsifiers respectively. This study was divided into two parts: the first part is about the mechanism of anionic emulsion polymerization of D4 and the optimum conditions were got by experiments. The second part is synthesizing poly(siloxane/acrylate) latex with MATS used as coupling agent and polysiloxane which has been got in the first part. Optimum lab conditions were got by experiments. And also factors that affect the performance of latex mostly were studied.Factors including temperature, catalysts systems and its dosage which affect reaction’s velocity, molecular weight and the latex’s stability are studied in anionic polymerization of D4. Under the optimum conditions ?temperature is 80癈, the dosage of DBSA is 3%-5% ,reaction time is 6h, Molecular weight can reach 60 thousand to 80 thousand. Reaction progression and AEa were calculated. And latex particles formation and its transformation during reaction process were studied. It was found that the existence of large particles called "transition-layer-particles" was the main-cause of the instability of the latex, which led to the appearance of "floating oil".In emulsion polymerization of poly(siloxane/acrylate), factors including temperature, catalysts systems and its dosage, polysiloxane which affect latex’s particles size & distribution and Ca2+-stability arestudied. When polysiloxane’s amount is 10% of acrylate, temperature was controlled between the OS/AP065 was added gradually whose adding amount is 3% of system, latex with good performance can be synthesized. Then membrane’s properties of polymer were studied via different dosage and adding ways of MATS. While the MATS’ amount is 5% of polysiloxane, its hydrophile angle is bigger than 90?It shows that its anti-water property is very good. The role of MATS in this reaction was studied by TG. DTG. DTA. IR and SEM analysis: In this system MATS acted as transition agent reacted with both polysiloxane and acrylate.更多还原