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The synthesis aqueous polyurethane multi strong hydrophilic dimethylol propionic acid as a crosslinking agent, the dispersion is polymerized to form a linear polymer, the poor water resistance of the film. Present, by raising the degree of crosslinking to increase the water resistance of the aqueous polyurethane is the most studied is more effective, easy to implement measures. This thesis is introduced in the polyurethane during the synthesis of hyperbranched polymers, thereby increasing the degree of crosslinking of the polyurethane, and thus to improve their water resistance. Firstly, with the anhydride-modified hyperbranched polyester Boltorn H20, and then the modified H20 was added to the the early polymerization system of isophorone diisocyanate (IPDI) and a polyether diol obtained in the initial polymerization reaction, was then added and triethylamine agent reaction, and finally add water emulsified hyperbranched waterborne polyurethane emulsion. The results show that when the succinic anhydride (SA) as H20 modifier in acetone in the reaction reaches the end point of the time required in 1,4 - dioxane, the reaction time is much longer, and subsequent tests showed that the preparation of succinic anhydride The obtained emulsion stability is poor. Selection of 1,4 - dioxane as a solvent, maleic anhydride (MA) as H20 modifier, infrared detection reaction can be achieved by the end point of the reaction 2h. When H20 modified different number of terminal hydroxyl groups at different times required for the reaction, IR and NMR tests showed that H20 has been successfully modified to a part of the terminal carboxyl group. So considering selection of maleic anhydride as modifier, 1,4 - dioxane as solvent, the modified terminal hydroxyl number is 2, and the reaction 2h, to obtain a modified product H20-2mA. The paper discusses the two early poly mole ratio of isocyanate group / hydroxyl group (NCO / OH), 5:1 and 2:1, respectively, the results show that the molar ratio of early poly system early poly isocyanate group content (NCO%) the rate of change of the impact is not very significant. The influence of temperature and catalyst on the rate of change of the early poly system NCO% is relatively large. The higher the temperature, early polyethylene faster the reaction rate. Add a small amount of the catalyst dibutyltin dilaurate (DBTDL), early poly system NCO% dropped markedly accelerated. Early poly optimal reaction conditions without adding any catalyst, the reaction temperature is 80 ° C, the the early poly molar ratio of 2:1, the beginning of the polymerization reaction 4h. Add H20-2MA prepolymerization was carried out, the reaction endpoint is reached with the infrared detector need 7h. The carboxyl group content, the type of polyether diol, and the degree and emulsifying conditions and other factors will affect the hyperbranched particle size and storage stability of the aqueous polyurethane emulsion. Carboxyl group content is increased to 2.05% can be obtained by a uniform and stable and suitable particle size of the emulsion. Polyethylene glycol 2000 (PEG2000) as polyether diols obtained emulsion is rendered slightly yellow, while using PTHF2000 as polyether diols, the obtained is a stable milky emulsion. Which degree of 0.7-1.0, and the smaller particle size of the emulsion can be stabilized. When the temperature is 30 ℃, easy to get a uniform emulsion; the prepolymer temperature is too low, the body viscosity, the stirring difficult or even gel difficult emulsification. The final choice PTHF2000 as polyether diol, a carboxyl group content of 2.05% and the neutralization degree of 1.0, the emulsifying temperature of 30-35 ° C, the particle diameter of the aqueous polyurethane emulsion prepared hyperbranched 0.082 UM, can be stably stored for 6 months or more. The optimized conditions for preparation of hyperbranched waterborne polyurethane film's initial thermal decomposition temperature of 260 ° C, the water absorption of 7.14%. Compared with the literature, prepared herein the hyperbranched water resistance and heat stability of the aqueous polyurethane increased.
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