Study On Synthesis Process Of Polyester Polyol And Its Application In Waterborne Polyurethane Plastic Coatings

In the paper, hexanediol(HDO) was used as the main material, together with phthalic anhydride(PA) and adipic acid(AA) to synthesize two kinds of polyester polyols, the relative molecular weight of which ranged from 1000 to 2000, the acid value of which was less than 1mgKOH/g, under the protection of N2. According to the polyester polyols’s reaction theory, polymerization realation degree and materials proportion,we determine the specific method to synthesize polyester polyol. Measuring the acid value,hydroxyl value, viscosity, moisture and the relative molecular weight of the product.Characterizing the construction of the production by using infrared spectrum and gel chromatography. The relative molecular weight, acid value and hydroxyl value were considering as the most important factors that determining the practical application. The mole ratio of hydroxyl to carboxyl groups, reaction time, the highest reaction temperature, catalyst, catalyst dosage and degree of vaccum in late stage were studied to know their effects on the reaction. The synthesis process and formula design were optimized by using the control variable method. The best synthesis way to produce poly phthalic anhydride- hexanediol ester was: alkanol acid molar ratio I:13:1, reaction time 9h, the highest reaction temperature 220℃, catalyst monobutyl tin oxide, catalyst dosage 0.03wt% and degree of vaccum in late stage 0.085MPa.In addition, sulfonate-based adipic acid polyester polyol was synthesized by two-step method of transesterification-alkyd polycondensation, using dimethyl-5-sulfophthalate sodium salt (SIPM), HDO, PA and AA as raw materials, the waterborne polyurethane(WPU) was prepared with the polyester polyol synthesized in the experiment as soft segment, toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI) as hard segment, dimethylol propionic acid (DMPA) as chain extender, triethylamine (TEA) as neutralizing agent, through prepolymers way, and plastic coating was prepared on the ABS board by spraying coating. The structure of the sulfonated polyester poyol was characterized by ATR and GPC. The mole ratio of HDO to SIPM in transesterification-alkyd polycondensation stage, the impact of the amount of SIPM,and the mole ratio of hydroxyl to carboxyl on the properties of the sulfonated polyester polyol was investigated, and the performances of the WPU were also tested. The results showed that the translucent WPU emulsion synthesized by sulfonated polyester polyol which was obtained under the condition of w(SIPM) = 0.16mol/kg (based on the weight of polyester polyol), first cast of HDO, the mole ratio of HDO to SIPM 7: 1 and the mole ratio of hydroxyl to carboxyl groups 1.13:1 had high solid content (46wt%), low viscosity (25℃,102mPa.s), and finer average particle size(60nm).Continuously adjusting the process plan, ABS plastic coating prepared by the WPU achieve the thickness of 10-15pm, can be self-dry or 50 ℃ and 70 ℃ baking 30min to test the performance of low temperature. The coating has a gloss of more than 92, the appearance was smooth and bright, drying time 20min, hardness HB, adhesion to 0 degree, which were in line with industry standards, has good application prospects.