Abstract

Amino resins have found important uses in leather manufacturing due to their selective filling properties. Conventional amino resins are produced from formaldehyde and result in an increase of formaldehyde content in finished leather greater than the permitted limits. Due to strict legislations and restrictions regarding formaldehyde contents in leather goods there is a growing demand to produce formaldehyde-free leather. In this study formaldehyde-free resins with improved thermal stabilities were prepared using glyoxal as condensing agent and orthanilic acid (o-amino-benzene sulphonic acid) as a sulfonating agent.

The glyoxal to melamine ratio (G/M) was varied from 2-6 and orthanilic acid to melamine ratio (ONA/M) was varied from 0.5-3 to produce aqueous solutions of the melamine resins. The viscosity trend in the series of resins was observed by varying the degree of sulfonation and varying the glyoxal/melamine ratio. Progress of reaction was monitored by FTIR spectrum through functional group region.

Newly synthesised melamine resins (MGONA) were comparatively applied on leather as a retanning agent against a conventional melamine-formaldehyde resin and further evaluated for tear strength, tensile strength and elongation at break. The leather retanned with the optimal resin was further assessed for organoleptic properties and SEM analysis. The thermal stability of the optimised resin was also evaluated comparatively against a conventional resin. The optimised polymeric resin was free from formaldehyde plus having better retanning properties and improved thermal stability.