Preparation Of Polyurethane As Paper Agent And Studies On Paper-Based Polyurethane

Preparation and application of polyurethane was investigated in this thesis. The synthesis of rosin-based polyurethane sizing agent and determination method of acid value of rosin was also explored in the thesis. At first, pre-polymer was prepared with rosin and toluene-2, 4-diisocyanate (TDI), then methyl diethanolamine was added as chain extender. Furthermore, solution of sodium bisulfite was used to block the free–NCO groups in the pre-polymer compound to obtained cationic emulsion of rosin-based polyurethane pre-polymer. The pre-polymer was used as sizing agent in wet end. Its sizing property in different environment was also researched.Pre-polymer of cationic rosin-based polyurethane was prepared with rosin and TDI, epichlorohydrin and methyl diethanolamine. The pre-polymer was blocked with sodium bisulfite and used in wet end. Results showed that this kind of cationic rosin sizing agent had good sizing properties.Another kind of pre-polymer of polyurethane was also prepared with soluble pre-gelatinization starch and TDI. Similarly, imidazole was used as blocking agent. The main factors as blocking temperature on polyurethane emulsionation were investigated. The obtained pre-polymer emulsion was used in wet end. As a result, this pre-polymer improved physical strength of paper significantly.Effect of characteristics phenolic hydroxyl group of lignin on paper-based polyurethane from different pulps was investigated. Effect of different phenolic hydroxyl on polyurethane reaction was researched as well.The characteristics of sodium bicarbonate in blocking polyurethane pre-polymer were investigated. Following results were obtained.(1) Reaction temperature should be lower than 5℃. At low temperature, there was little second reaction, which could improve blocking effect.(2) When sodium bicarbonate was chosen as blocking agent, value of NaHCO3/NCO should be above 1.1. Sodium carbonate was used as accelerant compound. It could improve the reaction efficiency. Furthermore, it could improve the value of HCO3- and possibility of reaction between–NCO and HCO3-. The results proved that side reaction was reduced.