Study On Vegeatble Tannin Extract And Its Application Performance In Retanning Process

In this paper, the acid and salt resistance ability was studied based on theabsorbance, pH and conductivity difference in different vegtable extract solutions;based on the change in leather area, thickness, shrinkage temperature and tearingstrength, the single and combination retanning performance of9different vegeatbletannin extract were analyzed. Use optical microscope to observe microstructure ofleather, and study the relationship between leather three-dimensional size, yield andtearing strength was also included. The result indicated that:(1) The stability of FS tannin extract solution is related to the time andtemperature, at low temperature it has good solubility, but will not aggregate; at hightemperature it still keep good solubility, and also with high aggregate effect. Threedifferent salts that used will decrease the solubility of FS and ME. Formic acid andacetic acid can inhibit the dissolve of FS, raising reaction temperature will improve thedissolution, but enhance the aggregate effect at he same time. Formic acid has higherreaction degree than acetic acid.(2) Different tannin extract have different properties in single tannin leather.Firstly, the leather thickness, area, Ts, tear strength and vertical and horizontaluniformity were quite different. And the fiber loose degree are also different, in termsof order: CC> GS> FS> ATO> ME> CHA> UNITONE> CHD> LIGHTAN. Thebetter in fiber loose degree, the smaller difference in vertical and horizontal tearstrength. Secondly, retanning lower the tear strength, in terms of order: blue wet>chrome> tannin extract (CC> ATO> GS> FS> CHA> LIGHTAN> UNITON>CHD>ME).(3) For combination tannin extract retanning:â‘ In CC and FS retanning, theleather thickness and width increase, the length decrease, yield increase and tearstrength improved, but the vertical and horizontal difference is not big.â‘¡For thecombination retanning of different tannin extract with chrome, the thickness of leatherincrease, the area change varies. Their Ts are all below those of blue wet, the tearstrength and its vertical and horizontal difference are big, the gap between fibersincreaser, the boundary between papillary and reticular layer comes clear. In terms ofthe order of fiber loose degree: FS> ATO> CC> GS. (4) Chrome combination retanning makes the leather thinner and wider, whereaschrome tannin causes the leather thicker and narrower, but both of them cause theshrink in length and area. Both the yield and difference between vertical and horizontaltear strength of chrome retanning leather are higher than chrome tannin. Chromeretanning has some adjustability for the vertical and horizontal difference of wet blue,however the dosage must be controlled.(5) During wet back process of blue wet, the effect of weight increase and areashrink of formic acid are larger than sodium formate.