Abstract

Amino resins used in the leather retanning process are condensation products of formaldehyde which makes such resins objectionable due to environmental hazards. Due to the carcinogenic effects of formaldehyde, there is a growing demand to produce formaldehyde-free leather. This work involves the synthesis of formaldehyde free melamine resins for producing environment friendly leather with improved retanning properties and thermal stability. A series of resins was produced by condensation of glyoxal and melamine at varied mole ratios. Stability and water solubility was achieved by sulfonation with aniline 2,5 disulfonic acid at varied degrees of sulfonation. Resins were evaluated to measure the viscosity trends in series.

Synthesised resins were studied for their comparative retanning properties in comparison with a commercial melamine resin as control. Mechanical properties like tensile strengths tear strengths, and elongation at break were measured and found to be improved. Similarly, the organoleptic properties were also evaluated and found to be better than for the control. Retanned pieces of leather were examined by SEM and tested for free formaldehyde content. The optimal resin was subjected to analysis by FTIR, TGAand molecular weight determination. Effluents collected from retanning baths were tested for pollution load efficiency. The results of the study confirmed that the prepared resins were supportive in producing formaldehyde-free leather with improved mechanical and organoleptic properties. The thermal stability of the resulting resins and pollution load efficiency was also found to be improved.