Study On Tanning Mechanism And Tanning Performance Of Q16 Series Organic Tanning Agents

The active ingredients of Q16 series organic tanning agents?abbreviated as Q16?are a kind of derivatives with triazine ring structure,which can be divided into Q16-1,Q16-2 and Q16-3 according to the differences in the major hydrophilic groups,belongs to a class of green and organic leather tanning agents.In this study,we explore the tanning mechanism of Q16 tanning agent,which provide a theoretical basis for the application of tanning agents and the in-depth study of tanning leather properties.Moreover,the theoretical support for the further development,performance research and popularization and application of Q16 tanning agent are established by optimizing the tanning process,comparing the tanning performances of Q16-1,Q16-2,TWT and F-90and exploring the combined tanning performance and biodegradability of Q16-2and chrome powder/aluminum sulfate.The specific research is based on the following aspects:Q16 was used to interact with polyamide and polyvinyl alcohol respectively to simulate the tanning mechanism of the amide bond and hydroxyl groups in Q16 and leather collagen.Then,the binding degree of Q16 to amide bonds/hydroxyl groups was investigated by gravimetric method.The results indicate that the binding degree of Q16 to amide groups/hydroxyl groups in collagens is relatively low,we presumed that they were mainly combined by hydrogen bonds.Then we used Q16 to interact with cow hides powder,deamidation hides powder,deguanidination hides powder,and decarboxylation hides powder,respectively.The binding degree between hides powder and Q16 was studied by gravimetric method,differential scanning calorimetry analysis and thermogravimetric analysis,and the binding degree between Q16 and a mino groups,carboxyl groups and guanidine in collagen was investigated by the regular pattern of thermal stability of hides powder.It shows that Q16 had a higher binding ability to a mino groups and guanidine in collagen,resulting in a large number of covalent bonds to enhance the thermal stability of collagens.This is further confirmed that the binding degree between Q16 and a mino groups/guanidine group is higher than that of carboxyl group in collagen.Q16 was also used to perform experiments on bated sheep skins and deamidation,decarboxylation,and deguanidination sheep skins.The changes in the crystal shape and stability of chemical media were investigated by X-ray diffraction analysis and changes in shrinkage temperature before and after washing with different chemical mediators.The results show that the crystallinity of the skins and deguainidination skins are significantly lower than that of the deamination skins and decarboxylated skins.It is concluded that the binding degree of Q16 between a mino groups and the guanidine groups is much higher than carboxyl groups.The order of the binding methods that the tanning agent contributes to tanning effect on collagen is:covalent bond>electricity bond>hydrogen bond.The bated sheep skins were tanned by Q16,and the effect of different tanning conditions on the shrinkage temperature of the leather were investigated.The results show that the optimized tanning process is:liquid ratio for 50%,time for 360 min,Q16 tanning agent dosage for 8%¹0%,temperature for 50°C.And the dosage of Q16-1/Q16-2 is over 4%and Q16-3 is over 5%in the condition of non-swelling curst.At the same time,Q16-1,Q16-2,TWT and F-90were studied with shrinkage temperature,denaturation temperature,micro-morphology of collagen,grain surface roughness,yellow-resistance level,whiteness and mechanical properties.The results show that as Q16-1,Q16-2,F-90,and TWT have similar binding patterns to active genes on leather collagen fibers,and therefore could form a stable cross-linking network with active groups in collagen,giving collagen fibers good elasticity and toughness.The four tanning agents could obtain crust with white and fine grain,good dispersion of collagen fibers and good hydrothermal stability,dry-thermal stability and yellowing resistance.The combination of Q16-2 with chromium powder/aluminum was studied basedonshrinkagetemperature,mechanicalproperties,collagen micro-morphology,distribution of chromium/aluminum in section,concentration of Cr³⁺/Al³⁺of effluent.The results show that the shrinkage temperature of the crust leather combined with 4%Q16-2 and 5%chromium powder could reach114.7°C.Compared with the crust tanned with 8%chrome powder,the mechanical properties of combined tanning crust are significantly enhanced,and the fiber dispersion is better,the grain is smoother,the distribution of chromium is more uniform in the section and the concentration of Cr³⁺and the COD in the effluent significantly declined.The results indicate that compared with the crust tanned with 8%aluminum sulfate,the mechanical properties and chemical-resistance stability simultaneously are significantly improved and the problem that aluminum tanned crust was not water-resistant is also addressed.What's more,the grain is smoother,the fiber is well dispersed,the distribution of aluminum is more uniform in the section,the concentration of Al³⁺and the COD in the effluent are greatly reduced.The results of BOD₅/COD indicate that Q16 have good biodegradability.The environmental impact assessment of Q16 tanning agent and chrome tanning waste liquid finds that the COD,BOD₅,TS,DS,and SS of Q16 are obviously lower than that of chrome tanning.We conclude that the tanning technology has good ecological by using Q16 and its tanning system in leather manufacture,which has certain guiding significance for the processing of non-chrome tanning eco-leather.