环氧丙烯酸酯无皂核-壳乳液的合成及其性能

Synthesis of soap-free core–shell epoxy acrylate emulsion and its properties

首先以可聚合单体苯乙烯溶解环氧树脂E-44,并与丙烯酸进行酯化反应制备环氧丙烯酸酯。研究了反应温度、催化剂三乙胺用量、环氧树脂与丙烯酸的摩尔比以及阻聚剂对苯二酚用量对酯化反应的影响。然后以环氧丙烯酸酯为核单体,以丙烯酸丁酯为壳单体,采用半连续种子乳液聚合法合成了环氧丙烯酸酯无皂核-壳乳液。考察了引发剂(由摩尔比为1∶1的过硫酸铵和亚硫酸氢钠组成)用量、功能单体丙烯酸用量及聚合温度对乳液性能的影响。用红外光谱仪、核磁共振仪和透射电镜对产物进行了表征。制备环氧丙烯酸酯的最优条件为:催化剂2.0%(相对于环氧树脂与丙烯酸的质量),阻聚剂0.5%(相对于体系总质量),环氧树脂与丙烯酸的摩尔比为1.00∶1.05,在100°C下反应2.5 h。当引发剂用量为1.0%,功能单体用量为1.0%时,在70°C下反应所得环氧丙烯酸酯无皂核-壳乳液呈黄色,凝胶率为0.45%,固含量为33.40%,稳定性较好,其胶膜的水接触角为69.22°,浸泡在常温蒸馏水中5.5 d不发白或起泡,附着力1级,铅笔硬度2H。采用上述方法制备乳液不仅减少了作为环氧树脂分散介质的有机溶剂的用量,而且提高了环氧树脂与丙烯酸的接枝率,单体转化率达到了96.40%。

An epoxy acrylate was prepared by esterification of epoxy resin E-44, which was dissolved by styrene（also a polymerizable monomer）, with acrylic acid. The effects of the reaction temperature, the amount of triethylamine（as a catalyst）, the molar ratio of epoxy resin to acrylic acid, and the amount of hydroquinone（as an inhibitor） on the esterification reaction were studied. A soap-free core–shell epoxy acrylate emulsion was then synthesized by semi-continuous seeded emulsion polymerization using the epoxy acrylate as core monomer and butyl acrylate as shell monomer. The effects of the dosage of initiator comprising ammonium persulfate and sodium bisulfite at a molar ratio of 1：1, the amount of acrylic acid（as a functional monomer）, and the polymerization temperature on the properties of emulsion were examined. The products were characterized by infrared spectroscopy, nuclear magnetic resonance spectroscopy, and transmission electron microscopy. The optimal process conditions for preparing the epoxy acrylate were obtained as follows： catalyst 2.0%（with respect to the total mass of epoxy resin and acrylic acid）, inhibitor 0.5%（with respect to the total mass of raw materials）, molar ratio of epoxy resin to acrylic acid 1.00：1.05, reaction temperature 100 °C, and reaction time 2.5 h. The soap-free core–shell epoxy acrylate emulsion prepared with initiator 1.0% and functional monomer 1.0% at 70 °C is yellow and stable, and has a gel content of 0.45% and a solid content of 33.40%. The latex film obtained therefrom has a water contact angle of 69.22°, 1-grade adhesion, and pencil hardness of 2 H. No whitening or blistering was observed on it after being immersed in distilled water at normal temperature within 5.5 days. Using the presented method to synthesize emulsion not only reduces the usage of organic solvent, which is commonly used as a dispersion medium for epoxy resin, but also improves the grafting percentage of epoxy resin by acrylic acid, as shown by the conversion rate of monomers being up to 96.40%.