ALTERNATIVE LEATHER MANUFACTURING PROCESS - 1.PRE-TANNING WITH A REACTIVE OLIGOMERIC RESIN

Abstract

This paper presents a non-conventional tanning technology, which uses a benzenesulfonate melamine-formaldehyde resin (BSMF) as pre-tanning agent. BSMF tanning alone can produce white leather, which generates chrome-free leather wastes. A BSMF pre-tanning step can be applied prior to a tanning step with lower chrome offer - 1 % Cr2O3, as compared with the conventional chrome tanning technology, which uses around 2 % Cr2O3. Thus, low chrome-content leather can be obtained, having the organoleptic properties and physico-mechanical behavior similar to those obtained through conventional processing, mainly as it regards the hydrothermal stability. The cross-section of leather pre-tanned with the BSMF resin is less compact as the cross-section of the conventionally chrome tanned leather, which proves that BSMF tannage alone cannot provide leather with the performances acquired by the chrome tannage. Physical deposition of the BSMF product in the interfibrillar voids and envelopment of collagen fibers, significantly contribute to the fibrilar matrix consolidation, which is the essential condition for splitting and shaving in the tanyard, before chrome tanning and vegetable retanning steps. A BSMF pre-tanning, followed by a chrome tanning with an offer of 1 % Cr2O3 and mimosa extract retanning results in leather having the compositional and structural characteristics required by the upper leather type standards.

Keywords

• Tanned leather
• melamine-formaldehyde resins
• wet-blue
• wet-white
• clean technology