PRODUCTION OF SYNTHETHIC TANNINS FROM DIFFERENT STARTING MATERIALS AND THEIR EFFECTS ON LEATHER
Project no. 1349 · Status: Kapanmış · 2017
Summary
Synthetic tannins have been used for many years in leather production especially to fill the loose parts of leathers and to increase the performance of vegetable tannins. Due to the increase in demand for chrome-free leathers in recent years, the use of syntans in tanning has also increased significantly. Most of the resins used by Turkish Leather Industry are imported from abroad and there are only a few of local companies capable of producing these resins. Moreover, these companies are able to make their production with the help of imported know-how technology and they have difficulties in R&D for new products for market. Synthetic tannins are prepared mostly from phenol and naphthol derivatives via their condensation with formaldehyde. The present project shows the attempts of synthesis of synthetic tanning agents based on different starting materials of phenol, urea, salicylic acid, resorcinol, dihydroxydiphenyl sulfone via condensation with formaldehyde. After many trials, best results were obtained from phenol-formaldehyde, phenol-urea-formaldehyde and dihydroxydiphenyl sulfone-formaldehyde systems. It was shown that the experiments with other starting materials need further investigations and more detailed studies for controlled reactions to obtain usable resins. The successful resins obtained from reactions were used for the tanning of pickled sheep skins and all the applications resulted in shrinkage temperatures over 70 °C for leathers. Moreover, leathers tanned with the produced syntans gave very White and/or light grey colors with a good filling effect and plain grain structure. The project let the researchers to gain significant experience and knowledge on synthetic tanning production which can be transferred to Industry as well as to prepare further studies and more advanced projects.