用乙醇调节水溶性聚酯乳液的黏度及其机理分析

Adjustment of viscosity of water-soluble polyester emulsion by ethanol and the mechanism analysis

在质量分数为30.0%的水溶性聚酯乳液中,添加少量乙醇溶剂代替水可极大降低乳液的黏度。随着乙醇含量的增加,乳液黏度先减小后增加;乙醇质量分数为1.0%~9.0%时水溶性聚酯乳液黏度较低,超过9.0%时黏度急剧增加。用激光粒径分析仪测定了乳液粒径和界面电位。结果表明：添加少量乙醇引起水溶性聚酯乳液黏度降低的原因是由于乙醇共溶剂不利于聚酯高分子链中磺酸基的离子化,Zeta电位下降,且使乳液胶粒溶胀,导致其粒径增加;当乙醇质量分数超过9.0%后,水溶性聚酯乳液粒径快速增加,聚酯乳液胶粒扩散层重叠,导致体系黏度急剧增加。

Adding a small amount of ethanol solvent instead of water in a water-soluble polyester emulsion containing 30% solid by mass could decrease viscosity of the emulsion significantly. The viscosity of the emulsion decreased first and increased then with the rise in ethanol content. The viscosity of the water-soluble polyester emulsion was low when the mass percentage of ethanol was 1.0%-9.0%, while the viscosity increased rapidly as the ethanol content was more than 9.0%. The emulsion particle size and interface potential were measured by laser particle size analyzer. The data analysis showed that the reduction in the viscosity of the water-soluble polyester emulsion after the addition of a small amount of ethanol was due to an unfavorable effect of ethanol co-solvent on the ionization of sulfonic acid group in the polyester polymer chain. Consequently, Zeta potentials decreased and the swelling of the particles of the emulsion resulted in the enlargement of the emulsion particle diameter. The particle diameter of the water-souluble polyester emulsion grew rapidly which may cause overlapping of diffusion layers between polyester particles in the emulsion, leading to sharp increases of the system viscosity when the mass percentage of ethanol exceeded 9.0% in the emulsion.