Preparation And Properties Of Novel Waterborne Polyurethane With High Solid Content Adhesive For Footwear Application

China is the largest footwear producing country in the world, so there is a huge shoeadhesive market in it. Developing environmental friendly waterborne polyurethane (WPU)adhesive with high performance is the target of research about shoe adhesive.In this paper, a new type of waterborne polyurethane adhesive was prepared with IPDI(isophorone the ketone diisocyanate), PCL1000(Polycaprolactone polyol), and DMPA [2,2,-dual-(hydroxymethyl) propionic acid] as main raw material, and the mixture of water and asmall amount of MEK (methyl ethyl ketone) as dispersion medium. This polyurethaneadhesive had special water in oil microstructure, which was different from the traditionalwaterborne polyurethane emulsion, and the solid content of prepared polyurethane adhesivewas very high. When TEA was used as neutralizer, EDA (ethylene diamine) or EG (ethyleneglycol) used as small molecular extender, the solid content of prepared waterbornepolyurethane adhesive (WPU) was about60wt%. Further study showed that WPU got the bestcomprehensive properties when the content of DMPA was about5wt%, neutralization degreewas90%, molar ratio of-NCO/-OH was1.6, and EDA was used as small molecular extender.When HEMA (hydroxyethyl methacrylate) was used as blocking agent, TEA was used asneutralizer, the solid content of prepared waterborne polyurethane adhesive (WPUA) was ashigh as65wt%. Further work showed that the content of DMPA and neutralization degree hadnearly no influences on the adhesion properties, while the molar ratio of-NCO and-OHinfluence the adhesion properties significantly. When the molar ratio of-NCO/-OH was about1.6, APS (ammonium persulfate,0.3wt%) and SPS (sodium pyrosulfite,0.15wt%) were usedas initiator, the obtained adhesive had the best comprehensive properties.The analysis of microstructure of debonding interface showed that WPU adhesive hadgood infiltration function and adhesion property on PVC leather, PU leather, and cow leather.The debonding failure was attributed to the breakage of adhesive and base material. WPUAadhesive had good adhesion property on caw leather, for the debonding failure was occurredby the breakage of cow leather. However, the adhesion property of WPUA on PU leather andPVC leather was not so good, because the debonding failure was occurred between theadhesive and based material. WPU and WUPA combining adhesive had better comprehensive properties than WPU adhesive and WUPA adhesive. The thermal analysis showed that WPUadhesive, WPUA adhesive, and WPU/WPUA adhesive had good stability below150℃，which met the requirement of footwear producing process.When the temperature is in therange of-15-50℃, WPU adhesive can ensure the normal use.This research explored the application potential of experimental WPU adhesive in thereal footwear producing line. The result showed that the WPU adhesive with50wt%of solidconcentration and24-26wt%of organic solvent had appropriate adhesion property andprocessing property, which were closed to the commercial PU adhesive. However, thepreliminary adhesion property should be improved further.