Abstract

Synthetic tanning agents are indispensable for making any type of leather article. There is a challenge for syntans to be processed without formaldehyde to meet strict regulations in the leather goods and chemicals arena. In the present study, formaldehyde-free melamine-based retanning has been developed using glyoxal as a condensing agent and sodium sulfamate as a sulfonating agent. Sulfonated glyoxylated melamine-based resins were prepared using different mole ratios of melamine, sodium sulfamate and glyoxal.

The sodium sulfamate to melamine mole ratio (SS/M) was varied from 0.5 to 3.0 and glyoxal to melamine mole ratio (G/M) was varied from 2 to 6. Fluidity and gelling behaviour of resinous solutions were evaluated with the increasing trend of sulfonation and with increasing mole ratio of glyoxal to melamine.

Stabilized resins were applied comparatively as retanning agents on chrome-tanned goatskins against a conventional formaldehyde based melamine resin. Comparative tear strengths, tensile strengths, elongation at break and scanning electron micrographs of glyoxylated melamine and formaldehyde-based melamine-retanned leathers were studied and better performance was found in glyoxylated melamine-tanned leathers. The resin with optimum performance was structurally elucidated by FTIR.