Studies On The Dechroming Of Wet Blue And The Preparation And Characterization Of Threadlike Collagen Fibers

The technical conditions of dechroming and the preparation of the threadlike collagen fiber were studied. The structure and properties of the threadlike collagen fiber were characterized.The changes of the rate of weight gain and thickening of wet-blue, the pH value of the solution and the amount of dechroming were studied to analyze the mechanisms of soaking with enzymes. The results showed that soaking with enzymes could improve the rate of wet back . NM enzyme mainly acted on the polar groups of side chain of the collagenic carboxylic group and advanced absorbing water because of the high-hydrophilic property of the polar groups. MS enzyme mainly acted on the non-polar groups of side chain of the collagenic carboxylic group and promoted the swelling of collagen fiber. The hydrogen bond and electrovalent bond were destroyed in soaking with enzymes, and some fixed chrome complexes were dechromed.The solubilization of urea to Ca(OH)2 and its application effects in liming were studied. According to the research of the dechroming property of phosphoric acid, lactic acid and mixed acids, the effects of dechroming temperature, time and the offer of acids on the quantity of dechroming and collagen hydrolysis were studied to explore the dechroming mechanisms of each acid. The results showed that urea could solubilize Ca(OH)2 and when the content of urea was 7%, the solubilization effect was the best. Urea could buffer the pH value of the liming solution. When the content of urea was 15%, the buffer action effect was best. It bulked the collagen fiber and restrained the swelling of collagen fiber itself. The quantity of dechroming and the collagen hydrolisis increased with increasing temperature, the offer of lactic acids and dechroming reaction time. The primary and secondary effects of dechroming with H+ and acid group in acids were reflected by the change of pH value. It indicated that main dechroming by the acid group when pH drops and by H+ when pH rises. The regular pattern of phosphoric acid was similar to that of lactic acid. According to the research of the system of mixed acids, effect of acid A on hydrolysis reaction of collagen was weaker than that of acid B, and the ratio of acid A and acid B had great influence on the amount of hydrolyzed collagen. The pH value of the system of mixed acids was much more stable than the system of single acid and it had some buffer action. Its effect of dechroming was better and the amount of hydrolyzed collagen fiber was less, especially when the ratio of acid A and acid B was 1:1 and the state of swelling of collagen fiber was better.The collagen fiber was prepared based on the dechroming method by the mixed acids and loosen the collagen fiber of wet-blue. The microstructure, degree of crystallinity and dry heat property of prepared fiber were characterized. The effects of dechroming time, fatliquoring time and the amount of fatliquoring agents on the performances of the collagen fiber prepared finally were studied by orthogonal test to determine the best process conditions and explore the primary and secondary order of each factor. The results showed that when the ratio of acid A and acid B was 1:1 (volume ratio) ,the dechroming time was 12 hours, the fatliquoring time was 1 hours and the percent of fatliquoring agents was 15%, the prepared fiber loosened well. The structure shape remained good, the degree of crystallinity was 53.4%, and the dry heat shrinkage temperature was 230℃.