水性聚氨酯链段序列分布对乳液固含及性能的影响

Influence of segment sequence distribution of water-borne PU on the solid content and performance

通过改变预聚加料顺序,采用"拼接软段"的方法,合成了一系列总体成分相同而链段分布不同的水性聚氨酯乳液。着重研究了乳化过程相反转完成时乳液的固含变化,进而对乳液的黏度、粒径、分子量以及乳液表干速度进行测试,藉此分析链段分布对乳液粒子结构和性质的影响。结果表明,适度地改变软硬段在聚氨酯主链上的相对分布,能有效提升水性聚氨酯乳液的固体含量,其机理是增加软硬段平均长度,使它们更容易各自聚集,因此乳化时乳液粒径增大,而且羧基更多迁移到粒子的壳层,使得粒子内部水分较少,表干速度大大加快。

We have synthesized a series of water-borne PU latexes with the same total composition and different chain segment distribution by the method of ＂splicing soft segment＂ and changing the adding order of materials in prepolymerization. This paper studies the change of solid content when phase inversion is completed in the process of emulsification, then tests the viscosity, particle size, molecular weight and touch-dry speed of latex, and then analyzes the influence of segment distribution o11 the structure and performance of latex. It is showed that changing the distribution of sofa segment and hard segment in the main chain of PU in some degree can efficiently improve the solid content of water-borne PU latex. The mechanism is that increasing the average length of soft segment and hard segment makes them aggregate easily, so the particle size of emulsion becomes larger and more carboxyl migrates to the shell of particles, causing water content in particle decrease and touch-dry speed increases greatly.