Melamine Glyoxal Resin as a Retanning Agent-Preparation and Application

Amino resins have played an important role in the manufacture of leather due to their outstanding filling and dyeing properties. However, a traditionally prepared amino resin usually contains free formaldehyde, which is strictly restricted in leather products. With increasing awareness of potential health problems with formaldehyde, there is a growing demand for formaldehyde-free leathers in the global leather market. In this study, a formaldehyde-free amino resin was synthesized by using glyoxal as condensing agent, and its retanning properties were investigated. It was found that the glyoxal can be used to replace formaldehyde to synthesize an amino resin, and the optimal reaction conditions were that the molar ratio of melamine to glyoxal was 1:6, reaction temperature was 333K and reaction time was 3 hours. Retanning experiments with the prepared amino resin indicated that its retanning properties, including fullness, softness, general appearance of the leather and mechanical strength, are better or equal to those that of a traditionally prepared amino resin.