A acetoacetate(BBA) -terminated dendritic hyperbranched polyester was prepared by trans-esterification of dendritic hyperbranched polyester Boltorn?H20 (B-OH) with tert -Butyl acetoacetate (t - BAA). The modified acrylic resins ( WA) by blending and copolymerizing with BBA were used to prepare BBA - WA and BBA/WA based waterborne coatings. Three kinds of waterborne acrylic coatings were prepared with WA - BBA, WA/BBA and WA respectively. The effect of BBA contents on properties of coating films was investigated. The results showed that with increasing BBA contents, the durability, such as water resistance, alkali resistance, acid resistance and brine resistance, were increased for WA - BBA coating films, but only changed slightly for WA/BBA coating films. The durability of WA - BBA coating films was notably better than that of WA/BBA coating films while that of WA coating film was low. The ' H - NMR, FT - IR, DSC and Tg analyses indicated that in the copolymerization process of acrylic monomer and BBA, a hyperbranched polymer with BBA structure as core was formed by grafting copolymerization of acrylic monomers with the methylene of acetoacetyl group contained in BBA molecule. The BBA structure in BBA - WA coatings can increase the crosslinking degree ( CD) of OH in acrylic resin, resulting in a higher CD, Tg, thermal stability and durability. The performance of UV resistance of the coating films also increased due to the UV absorption of acetoacetyl group.%用树枝状超支化聚酯BoltornTM H20(B-OH)与乙酰乙酸叔丁酯(t- BAA)进行酯交换反应制备了乙酰乙酸封端B-OH(BBA).用BBA对丙烯酸酯树脂(WA)进行了共聚改性和共混改性分别制备了BBA - WA和BBA/WA水性涂料.研究了BBA用量对涂料固化涂膜各项性能的影响.结果表明:随着BBA用量的增加,BBA- WA涂膜的耐水、耐碱、耐酸和耐盐水等耐久性显著提高,而BBA/WA涂膜的耐久性变化不大.3类涂料涂膜的耐久性以BBA - WA最优,WA/BBA次之,WA较差.1H- NMR、FT - IR、DSC和Tg分析表明,BBA的乙酰乙酰基的亚甲基与单体发生了接枝共聚反应形成以BBA结构为核的超支化聚合物.在BBA- WA涂料中,BBA结构可提高丙烯酸树脂所含羟基的交联反应程度,使涂膜具有更高的交联程度、更高的玻璃化转变温度和更好的热稳定性,从而使涂膜具有优良的耐久性.由于BBA结构的乙酰乙酰基具有吸收紫外光作用而使涂膜具有优良的耐紫外光老化性能.
展开▼
