Research On Synthesis Technology Of Polyester Diol From The Vacuum Melting Method

Polyester diol can be synthesized from diacids and diols via esterification, polyesterification and transesterification. It is mainly used for production of thermoplastic polyurethane, polyurethane synthetic leather, polyurethane sole slurry, rigid polyurethane foams and polyurethane products. Using adipic acid, ethylene glycol and diethylene glycol as the main raw material, the polyester diol were prepared from vacuum melting method in this study and the product is mainly expected to used for the water soluble polyurethane production.According to the actual requirements of the industrial production process, this paper researches on the synthesis technology of polyester diol from the vacuum melting method. The influence of the reaction conditions, such as the esterification reaction temperature, catalyst types and dosage, the molar ratio of diol and diacid, the polycondensation and transesterrification reaction temperature, vacuum degree and vacuum transition time in the polycondensation and transesterification period and other factors on the synthesis process of polyester diol were investigated.The optimal conditions of the polyester polyol synthesis from vacuum melting method was determined as follows:the esterification reaction temperature is230℃, the stuff molar ratio of diol and diacid is1.10:1, the catalyst is titanate series2#, the catalyst dosage used is0.20‰(mass fraction of total diacids and diols), the reaction temperature of polycondensation and transesterification is230℃, vacuum degree is0.09MPa and vacuum transition time is1.5h in the polycondensation and transesterification period. Under above conditions, the esterification reaction time and the polycondensation and transesterification reaction time were5.5h and6h respectively. The acid value of the products is<lmgKOH/g, and hydroxyl value is36-40mgKOH/g. Its viscosity can be controlled at24000±1000mPa·s, and the appearance of the product is light yellow transparent viscous liquid.The related factors of the product appearance and color were investigated, and the gel permeation chromatography (GPC), infrared spectroscopy (FTIR), nuclear magnetic resonance analyzer (1H-NMR) and thermogravimetric analysis (TGA) were used to measure the viscosity, structure, molecular weight and thermostability of the prepared products systematically.