Synthesis And Application Of Dye-retanning Agent

In order to improve the amount of dyes bonded into the polymers, that is, making the molecule of the dyes being macromolecule, the feasibility of two kinds of synthetic method were studied. One is by chemical modifying to prepare dye-retanning agent of suspended side chain; the other is addition polymerization to prepare dye-retanning agent of bonded main chain. Both products were applied to leather retanning process to investigate their dyeing and retanning effect.The results show that the dye-retanning agent of suspended side chain could be prepared by grafting the dyes on the polyacrylamide skeleton, which was synthesized by aqueous copolymerization. The optimum synthesis conditions are as follows, at preparing polyacrylamide step, hydrophobic monomer should be 20% in whole polymer chains; the viscosity of the polyacrylamide should be controlled between 1000 and 1500 mPa?S. At grafting step, dye KN-B (active dye) should be 20% of the polyacrylamide skeleton, other conditions are temperature 80℃, pH value 7.5-8.5, time 8 hours. The largest conversion of the KN-B is 85.9%, and the amount of the dyes is 17.2% of polymer skeleton.The anthraquinone type dyes containing double carbon bonds were prepared by two-step method. The highest yield rate is 77.0%. Then the dye-retanning agents were prepared by addition polymerization between the dye monomer and the acrylic monomer. In the products, the conversion of dyes monomer is 80.2%,there are 10.03% of polymerized anthraquinone dye monomers in polymer skeletons. The optimum reaction conditions are: emulsifying agent 0.5%, temperature 75℃, pH value 5-6.Both type of dye-retanning agents were applied to leather retanning process. The results showed that both of them not only have common retanning properties of acrylic resins, but also have good dyeing properties.