Synthesis And Application Of Waterborne Polyurethane With Sulfonic/Carboxylic Groups For ABS Plastic Coatings

High solid content, low viscosity and excellent performance waterborne polyurethane with sulfonic/carboxylic groups (WPU) was suitable for ABS plastic prime coating prefilming resin, which had a captivating development potential. As a new water-based material, WPU had not only ecological characteristic of non-toxic, but also economic advantages of simple progress and low cost. At present, domestic coating enterprises are adjusting the structure of products. Solvent-based products are being replaced gradually by high functional water-based products, which will be the new trend in the development of engineering coating industry.In this paper, a new type of environmental protection and practical waterborne polyurethane was obtained by self-created sulfonated adipic acid polyester polyol, and then used in the process of ABS plastic coating. The paper mainly includes three parts as follows:Firstly, two-step method was adopted in this chapter to synthesize sulfonated adipic acid polyester polyol with different sulfonate contents. Influences of the mole ratio of HDO to SIPM in first step, total mole ratio of hydroxyl to carboxyl groups,polymerization temperature and time, catalysts on the properties of sulfonated adipic acid polyester polyol were investigated. The results indicated that the sulfonated adipate acid polyester polyol with low acid value (0.96 mgKOH/g ) and proper hydroxyl value(56.63 mgKOH/g) can be obtained using dimethyl-5-sulfophthalate (SIPM), hexane-diol (HDO) and adipic acid (AA) as initial materials, whose optimal synthesizing conditions were n(HDO):n(SIPM)=7:1, mole ratio of hydroxyl to carboxyl groups 1.13:7, polymerization temperature 200?220?, polymerization time 2h, monobutyltin oxide as catalyst. The synthesized product can be adapted for the sequel synthesis of WPU.In the second part, a kind of WPU with high solid content (50 wt%) and low viscosity (95mPa.s, 25 ? ) applied to ABS plastic prime coatings was prepared succesfuly using sulfonated adipate acid polyester polyols, polymethylene polyphenyl isocyanate (PM-200) and hexamethylene diisocyanate (HDI) as main materials,sulfonic/carboxylic as complex hydrophilic groups, epoxy resin (E-44) as cross-linking agent, and small molecule diamine as chain extender. Some factors that influenced the comprehensive properties of WPU emulsion and film were discussed, such as sulfonate contents in soft segment, hard segment structure, n(NCO)/n(OH), amount of DMPA,introduction of epoxy resin E-44 and types of small molecule chain extender. The chemical structures and thermodynamic properties of the WPU were characterized by FTIR and TGA. The results indicated that the WPU film showed excellent mechanical properties (tensile strength 33.8 MPa, elongation at break 585%), low water absorption(8.7 wt%), superior adhesion to ABS substrate (0 grade), proper hardness (pencil HB?1H),good flexibility (2mm) and high gloss (95.3%,60°) under the conditions of w(S03-Na+)=0.22mol/kg,w(DMPA)=1 .9%, n(PM-200)/n(HDI)=1/6, w(E-44)=2.0%,R=1.4. Furthermore, the WPU coatings could be dried completely within 30 minutes at 60 ?.Additives were also discussed in the last part of this thesis for improving coating performance before using WPU on coating progress. We selected 4?6 wt% DPNB as coalescing agent, 0.3 wt% Glide 410 as wetting agent, 0.25 wt% content WELLMIX 2165 as defoamer agent and 0.3 wt% WELLMIX 3731 as flatting agent, respectively.Application test results showed that main coating parameters can reach or approach to the levels of solvent-type PU, and the quality of the WPU-based coating can meet the requirements of cooperative company's application quality standards.