ICAMS 2016 – 6 th International Conference on Advanced Materials and Systems ISOCYANATE-FUNCTIONALIZED COLLAGEN HYDROLYSATES AS PRETANNING AGENTS FOR ORGANIC WET-WHITE LEATHER VASILICA MAIER 1 , TUDOREL BĂLĂU MÎNDRU 1 , DAN ROȘU 2 , ALEXANDRA IRINA CRUDU 2 , STELIAN SERGIU MAIER 1* 1 “Gheorghe Asachi” Technical University of Iaşi, Romania, Department of Textile and Leather Chemical Engineering, 71 Dimitrie Mangeron Avenue,700500, Iaşi, Romania, E-Mail: smaier@ch.tuiasi.ro 2 Petru Poni" Institute of Macromolecular Chemistry, 41A Grigore Ghica Vodă Alley, 700487, Iași, Romania The present paper aims to synthesize and test a pretanning agent based on isocyanate- functionalized collagen hydrolysates of low molecular mass (0.9 ÷ 3.6 kDa; polypeptides that include 8 to 32 amino acids), obtained starting from hides wet wastes, and used without further purification. Raw colloidal suspension resulted after hydrolysis was centrifuged to separate insoluble particles, and then was repeatedly filtered to retain coarse particulate and fatty maters. The clarified solution was concentrated by vaporization up to 35 % w/v dry matter, mixed with 10 % v/v dimethyl sulfoxide (DMSO), and maturated overnight under efficient mixing, in a hermetically closed reaction vessel, at ambient temperature. Using a solution of diisocyanate in DMSO, the molecular mass of the product was further increased by cross-linking, in parallel with the functionalization in the virtue of a small amount of free isocyanate groups that remain unreacted. The functionalized collagen hydrolysate was characterized by chemical (total nitrogen content, the amount of free carboxyl, amino, and isocyanate groups) and instrumental methods (infrared spectroscopy). The fraction of increased molecular mass after cross-linking was determined by comparative dialysis through membranes with 3.5 and 12 kDa. Pretanning ability of the functionalized hydrolysates was estimated by gelatin precipitation, and tested on sheep pelts. An increase of 6 ºC was measured for the shrinkage temperature. Pretanned pelts were gradually dehydrated (preventing the local drying) and drum-tumbled, and then was treated once again with the same functionalized product, in a short concentrated float. A supplemental increase of shrinkage temperature with 8 ºC was measured. Key words: collagen hydrolysate, functionalization, diisocyanate, pretanning agent. INTRODUCTION Coordinative chromium salts still remain the preferred industrial tanning agents, and the classical vegetable tannins were only partially replaced in retanning recipes. The objective of replacing these “old fashioned” products currently faces to two challenges: (i) the fact that the definitions of the most important leather characteristics and properties were developed in relation with them, and were imposed by their use, and (ii) their technological efficiency and their tanning efficacy / price ratio are unrivalled in comparison with other tanning / retanning products. The race to develop replacing products is imposed nowadays by the ecological constraints, and by the increasing demands of the modern consumer, the “natural” or “organic” terms being enforced by marketers. During the time, different products were tested as organic tanning / retanning agents. Due to their crosslinking potential, small-molecular, oligo- and poly-meric chemical compounds are sporadically used at industrial level, but, excepting some (di)aldehydes, none of them were largely accepted. Functionalized compounds of natural origin represent a current investigated alternative. Protein hydrolysates could support a range of functionalizing reactions to