Synthesis And Characterization Of Cationic Waterborne Polyurethane With High Solid Content

The aqueous polyurethane (WPU)，usually as a kind of polyurethane emulsion,in which water is used as dispersion medium, is widely applied in various fields. It isnon-toxic, environmentally friendly and difficult to burn. And it has good wettabilityfor hydrophobic polyester and woven acrylic fabrics. Besides, it is not sensitive to thehardness of water and can be used in the acidic condition. So it has wide prospects invarious applications, such as textiles, leather and paper.However, the drying time for the aqueous polyurethane emulsion is often toolong for industrial applications. This problem can be at least partially solved byimproving its solid content. Because of convenient transportation, the higher transportefficiency and the lower transportation costs, research for the WPU with high solidcontent is of interesting significance. Yet reports about WPU with high solid contenthave been focused on the anionic kinds. By far there is almost no report about how toimprove the solid content of cationic waterborne polyurethane.In this experiment, diol and mixed diisocyanate have been used as the startingmonomer, N-methyl diethanolamine have been used as hydrophilic agent. Theexploration of synthesis routes and processes for high solid content of cationicwaterborne polyurethane by adjusting the proportion of the mixture, controlling thedosage of hydrophilic agent, as well as by adjusting the feeding of the manner andsequence. The impact of some factors for the cationic waterborne polyurethaneperformance has also been explored.1. Those factors affecting solid content, breaking elongation, water absorption ofthe cationic waterborne polyurethane are discussed, including the volume ratio ofmix-diisocyanate, the mole ratio of diisocyanate and diols during prepolymerization,the dosage of MDEA, the dosage of TMP, the neutralization degree. 2. One kind of cationic waterborne polyurethane was prepared by thestep-growth polyaddition process of mixed diisocyanates and polyether dibasicalcohol with N-methyl diethanolamine as hydrophilic chain extender. Its solidcontent was46.70%, while synthesized emulsion was showed the bimodal particlesize distribution, the water absorption of its membrane form was as low as3.665%,and the breaking elongation of its membrane form can reach1512.88%, TG analysisshowed that the formed membrane began to degradation at250℃, and becamecompletely weightless at460℃. These results show that the synthesized waterbornepolyurethane not only has high solid content but also shows good mechanicalproperties and comprehensive performance.