Study On Interaction Between The Chrome-free Metal Tanning Agent And Amino Acids

The free-chrome tanning metal agent is an important new environmental friendly tanning agent, and it has been made significant progress. However, the study of mechanism about free-chrome tanning metal agent is hysteretic, so the mechanism is not very clear. In order to develop new products, and provide theoretical basis and methods, so that these products are better used in industrial production, the study of the interaction mechanism about the free-chrome tanning metal agent reacted with collagen is particularly important.Becauce the structure of leather collagen is complex, there is lots of uncertainty to study directly the interaction between tanning agent and leather collagen. However, we could take amino acids as leather collagen mimics and make them interact with tanning agent, because the amino acid is the basic unit of collagen. Furthermore, we could study the interaction of leather collagen and tanning agent by some analytical testing methods.The thesis studied the interaction between zirconium sulfate (Zr(SO₄)₂.4H₂O) and amino acids, including acidic amino acids, basic amino acids, neutral amino acids, hydroxy amino acids, aromatic amino acids and heterocyclic amino acids, with TLC detection (colored by KMnO₄ solution). and IR, NMR and XRD.In the process of amino acids reacting with zirconium sulfate, the amino acids react completely, on the conditions of molar ratio n(amino acids): n(zirconium sulfate) = 1:2, room temperature or 40℃and 5-6 h with TLC detection. It shows from IR and NMR that at low pH condition (pH≈1.0), zirconium sulfate mainly reacts with carboxyl group (-COOH) of amino acids. Furthermore, the electrovalent coordination bond forms between zirconium ions (Zr⁴⁺) and the carboxyl anion (-COO^-).