Synthesis And Application Of Thermally Activated Waterborne Polyurethane Adhesives

This invention of stable aqueous dispersions of polyurethane andpolyure thane-polyurea was completely new materials, which had out-standing performanceas adhesive. Thermally activated WPU adhesives had economic advantages of conv enientsizing and low costing not only, but also inherited the nontoxic,nonflamm ableand environmental friendly specialty of WPU materials, which had a captiv ating development and application foreground.In the foreign patent,theinvention i s mainly related to a process for the preparationwithwater-solublecopolymer whic hhad sulfonate monomers in it, while the raw material is hard to get; Moreover, it had large organic solvents in hydro-polyurethane emulsion synthesized with ac etone method, so we had to pay more expense on the removal of volatile organ ic compounds.Synthesis a form of thermally activated WPU adhesives with envir onmental friendlyspecialty,which was suitable for the hot-calendar process ofsynt hetic leather is our focus.A sort of thermally activated waterborne polyurethane adhesive had been synt hesized with mixed diisocyanates HDI-TDI,crystalline polyester diol PBA and w ater-soluble sulfonate chain extender A-50, which was suitable for the hot-calend ar process of synthetic leather. Mainly discuss the influences of soft & hard seg ment, content of DMPA, amine chain extenders on the comprehensive properties of adhesive. By means of FT-IR and DSC, its chemical structure and melting temperature had been characterized. The results indicated that the emulsion had an excellent peel strength (37N·25mm-1), a low activation temperature (55℃). Furthermore, the film exhibited well performance at water-resistance (<6.8%) an d heat-resistance (110℃),which could be melted quickly on the circumstance o f 100℃ and had a stable performance after cooled.The present invention further related to adhesive promoter according to the pr eparation and using process of coatings on flexible or rigid substrates and in pa rticular to their use as adhesives.Finally, we selected 0.4% content ofLW44 asthi ckener,0.3%content of BYK-378 as wetting agent,0.15%content of BYK-093 as defoamerand 4%content of SiO2 as filler.The application results showed that the peel strength could reach 37N·25m2-1 with a low activation temperature (55℃) and an appropriate open time (60s).Expect for constant temperature and const ant humidityinspecting result, other items all reached or exceeded levels ofsolve nt-type PU, which could substitute solvent-based polyurethane and meet the requ irements of cooperative enterprise.