A process for the provision of a plant extract containing condensed tannins and a plant extract with astringent characteristics

摘要

Obtaining a plant extract comprises adding 2-5.8 wt.% water; adding 1.2-2.5 wt.% copolymerization agent comprising acrylic acid, methacrylic acid, and/or their esters; adding 0.1-1.7 wt.% thioglycolic acid; mixing a powdered extract of a plant with 0.5-2 kg per liter of water; mixing 25-60% tannin; raising the temperature to 67-98[deg]C; adding 0.5-4 wt.% sodium bisulfite; raising the temperature; and allowing a reaction time of 4 hours. Obtaining a plant extract containing condensed tannins, with astringent characteristics, modified by copolymerization, to be used in tannage and retanning of skins, comprises adding 2-5.8 wt.% water to a reactor; adding 1.2-2.5 wt.% copolymerization agent comprising acrylic acid, methacrylic acid, and/or their esters, while stirring the mixture; adding 0.1-1.7 wt.% thioglycolic acid while cooling the mixture, allowing to react where there occurs the exothermal reaction and the temperature reaches 95[deg]C, and after the reaction the product obtained from the reaction being left to cool; adjusting the pH to 3.5-7, by adding an alkali to the mixture; mixing a powdered extract of a plant with 0.5-2 kg per liter of water; or alternatively, mixing a solution of 25-60% tannin in liquid form; raising the temperature of the mixture to 67-98[deg]C, to carry out the reaction, for 2-7 hours, preferably for 5 hours; adding 0.5-4 wt.% sodium bisulfite, over the amount of tannin; raising the temperature of the mixture, keeping the reaction system heated at 45-127[deg]C, the pressure at 0.2-7 kgf/cm 2>; and allowing a reaction time of 4 hours.