Application of Y-shaped Polyurethane and Polyacrylic Acid as a Complex Retanning Agent in Aldehyde-tanned Goat Leather

Abstract

A kind of Y-shaped amphiphilic block polyurethane copolymers(PUGs) with different molecular weights were successfullysynthesized to be used as retanning agent combined withpolyacrylic acid (PAA) for modified glutaraldehyde tannedgoatskin. The structures of resulting products were characterizedby FTIR, and the molecular weights of products were measuredwith GPC. The application performances were investigated bymeasuring the organoleptic and physical mechanical propertiesof resulting leathers according to the alone or combined use ofPUG and PAA, the molecular weight of PUG, and the offerpercentage of retanning agent. The best performance was foundin the leather retanned by PUG750 and PAA complex retanningagent at the total offer percentage of 4 wt%. Finally, the freeformaldehyde contents in the leathers retanned with 4 wt%PUG750 and PAA at different pH conditions were analyzed withacetyl acetone colorimetric method. The mechanical propertiesas well as the fibers morphologies of the experimental andcontrol groups were also investigated. The results demonstratedthat when the pH value at the later stage of retanning processwas controlled at 4.0 or 3.0, the free formaldehyde content wassignificantly reduced by 20.3% or 38% respectively; and thephysical mechanical properties of leathers were also veryexcellent to meet the performance requirements of goatskingarment leathers. According to these results, the method forusing PUG and PAA as a complex retanning agent might be agood choice in chrome-free tanning process.