自乳化聚酯树脂汽车中涂漆的合成及性能研究

Synthesis of self-emulsifying polyester for automotive primer surfacer and the performance of cured film

用逐步聚合法合成了聚酯树脂,用苯偏三酸酐(TMA)在聚酯分子链末端引入羧基以赋予其自乳化性能。讨论了原料,合成工艺条件,TMA用量对聚酯树脂及其水分散体性能的影响。采用GPC分析了封端前后的聚酯树脂的相对分子质量及其分布,以FTIR检测了聚酯树脂及其固化漆膜的结构与变化。结果表明,氮气保护下,当酯化、缩聚反应温度均为240℃,反应时间均为2h并保持反应体系的压力低于2kPa时,可获得高分子质量低酸值的聚酯树脂,在酸值(KOH)>15mg/g的封端树脂中加入三乙胺中和后可获得水分散性优良、储存稳定性高和表观粘度低的水分散体。用酸值(KOH)在10～20mg/g的封端聚酯树脂与六甲醇醚化的三聚氰胺甲醛树脂配制成水性涂料,其固化漆膜具有优良的综合性能,适于用作汽车中涂漆。

The self- emulsifying polyester was synthesized by step - reaction polymerization and end capped by trimellitic anhydride（TMA）. The effects of raw materials , process conditions and the amounts of TMA on the the properties of polyester resin and the water- dispersion were also investigated. The polyester resin and cured film were characterized by FTIR and GPC. The results indicated that the high molecular polyester resin with low acid value could be obtained when the easterification and polycondensation reactions were carried out at 240 ℃ for 2 hours under the protection of nitrogen atmosphere and a reduced pressure 2 kPa respetively. The water- dispersion with good dispersity, excellent stability and low - viscosity was prepared by adding triethylamine to the end capped resin with acid value 〉 15 mg KOH/g. The polyester resin having an acid value between 10 to 20 mg KOH/g was mixed with hexakis（methoymethyl）melamine（HMMM） to give a waterborne coating which cured film had excellent performance and was suitable for automotive primer surface.