Novel polyurethane reactive hot melt adhesives based on polycarbonate polyols derived from CO2 for the footwear industry

Since raw materials used in polyurethane adhesives come from fossil resources, there is a trend towards renewable alternatives to petroleum. In this sense, the use of carbon dioxide as a feedstock for the chemical industry is an interesting alternative to oil because CO2 is inexpensive and abundant in the atmosphere. A new generation of CO2-based polymers has been recently developed, specifically, polyols, essential components for polyurethane synthesis.This work focused on the synthesis of reactive polyurethane hot melt adhesives (HMPUR) containing polycarbonate polyols derived from CO2 and 4,4′-diphenylmethane diisocyanate (MDI). The sustainable polyurethane adhesives derived from carbon dioxide were characterised by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Finally, the adhesion properties were measured from a T-peel test on leather/polyurethane adhesive/SBR rubber joints, in order to establish the amount of CO2-based polycarbonate polyol that could be added to reactive polyurethane hot melt adhesives satisfactorily to meet the quality requirements of footwear joints.All percentages of CO2-based polyol added to polyurethane adhesives meet successfully the quality requirements of footwear, being comparable to conventional adhesives used currently in shoe joints both in terms of green and final strength, and after high temperature/humidity conditions and hydrolysis tests. Therefore, this new generation of sustainable polyurethane adhesives could replace the adhesives commonly used in shoe joints.