Preparation And Tanning Properties Of T-Lys/T-Tyr/T-Arg

Based on the reaction characteristics of cyanuric chloride,N,N'-bis-?4,6-dichloro-[1,3,5]-triazin-2-ylamino?-2,6-diaminohexanoic acid?T-Lys?,2-?4,6-dichloro-[1,3,5]-triazin-2-ylamino?-3-[4-?4,6-dichloro-[1,3,5]-triazin-2-yloxy?-phenyl]-propionic acid?T-Tyr?,N,N'-bis-?4,6-dichloro-[1,3,5]-triazin-2-ylamino?-2-amino-5-guanidine-valeric acid were synthesized by reacting two molecules of cyanuric chloride with one molecule of lysine?Lys?,tyrosine?Tyr?,arginine?Arg?,respectively.A three-factor orthogonal test was used to investigate the synthesis conditions.The suitable synthesis conditions for T-Lys are:n?TCT?:n?Lys?=3.0:1.0,KOH is used as an acid binding agent,reaction time is 6h,reaction temperature is 0⁵?,the yield is up to 91%;the suitable synthesis conditions for T-Tyr are:n?TCT?:n?Tyr?=2.5:1.0,NaHCO₃ is used as an acid binding agent,reaction time is 7h,reaction temperature is 0⁵?,yield is up to89%;the suitable synthesis conditions for T-Arg are:n?TCT?:n?Arg?=2.4:1.0,NaOH is used as an acid binding agent,reaction time is 6h,reaction temperature is 0⁵?,and the yield can reach 93%.Fourier transform infrared spectroscopy?FT-IR?and nuclear magnetic resonance?¹H-NMR?were used to confirm the formation of corresponding products.Based on the reaction characteristics of active chlorine groups in T-Lys,T-Tyr and T-Arg structures,delimed and bated sheep skin were tanned with T-Lys,T-Tyr and T-Arg tanning agents.The effects of tanning conditions on the tanning properties were investigated by taking shrinkage temperature and sensory properties of crust leather as indexes.The results show that the optimum tanning conditions for T-Lys tanning agent are as follows:T-Lys liquid dosage is20%,tanning for 2h at 25?as beginning,tanning for 2h at 40?,tanning for 4h at 55?as ending;The optimum tanning conditions of T-Tyr tanning agent are as follows:T-Tyr liquid dosage is 25%,tanning for 2h at 35?as beginning,tanning for 2h at 40?,tanning for 5h at 55?as ending;The optimum tanning conditions for T-Arg tanning agent are as follows:tanning for 2h at 25?as beginning,tanning for 2h at 40?,tanning for 5h at 55?as ending;The liquid ratio of the three tanning processes are all 1,and the pH value at the end of tanning is maintained at 4.5⁵.0.The shrinkage temperatures of the corresponding tanned leather range from 80⁸5?.At the same time,under the optimum conditions,the differences of tanning properties between T-Lys,T-Tyr,T-Arg,TWT,F-90 and T-A chrome-free tanning agents were coMPared and studied.The results show that the moisture and heat resistance of T-Lys,T-Tyr,T-Arg tanned crust leather is similar to that of TWT tanned crust leather and higher than that of F-90 and T-A tanned crust leather;Furthermore,T-Lys,F-90and T-A tanned crust leather show the best performance,with the yellowing resistance reaching grade 5;T-tyr tanning agent has excellent filling properties among the six tanning agents.In order to investigate the retanning performance of T-Lys,T-Tyr,T-Arg,TWT,F-90 and T-A tanning agents with chrome retanning agent and aluminium retanning agent,the retanning properties of chrome retanning agent and aluminium retanning agent on T-Lys,T-Tyr,T-Arg,TWT,F-90 and T-A tanning agents were studied by comparing the shrinkage temperature,physical and mechanical properties,yellowing resistance of crust leather.The results show that:T-lys,T-Tyr,T-Arg,F-90,TWT and T-A tanned leather have the same moisture and heat resistance after chrome retanning,which are close to that of chrome retanned blue wet leather;The yellowing resistance of T-Lys,T-Tyr,T-Arg,TWT,F-90 and T-A tanned crust leather is improved after aluminium retanning;The moisture and thermal stability,physical and mechanical properties of T-lys,T-Tyr,T-Arg tanned leather after aluminium re-tanning are similar to those of F-90 main tanned aluminium retanned leather,slightly lower than TWT tanned aluminium retanned leather and higher thanT-A tanned aluminium retanned leather.In order to further verify the difference of cross-linking degree of collagen fibers between several chrome-free tanning agents and chrome tanning agent,the thermal stability and thermal degradation process parameters of leather fibers tanned by T-Lys,T-Tyr,T-Arg,TWT,F-90 and chrome powder were tested and studied via DSC/TG analysis method.Thermal degradation activation energy of collagen fibers tanned by several tanning agents mentioned above was calculated through the Coats-Redfern and Satava-Sesták method.The results show that the cross-linking stability of T-Lys,T-Tyr,T-Arg with collagen fibers are higher than that of TWT,but lower than that of F-90 and chrome tanning agent,the thermal degradation mechanisms of leather collagen fibers tanned by T-Lys,T-Tyr,T-Arg,F-90,TWT and chrome tanning agent are consistent with G???=[-ln?1-??]⁴function model,the activation energies of thermal degradation are148.590¹50.378 kJ/mol,162.465¹63.432 kJ/mol,158.227¹59.281 kJ/mol,200.790²01.137 kJ/mol,141.050¹43.005 kJ/mol,246.613²49.294 kJ/mol,respectively.The activation energy of T-Lys,T-Tyr,T-Arg and TWT tanned collagen fibers are significantly lower than that of F-90 and chrome tannned collagen fibers,indicating that the cross-linking degree of T-Lys,T-Tyr,T-Arg and TWT tanned collagen fibers are lower than that of F-90 and chrome tanned collagen fibers;The activation energy of leather collagen fibers tanned by T-Tyr is the highest between T-Lys,T-Tyr,T-Arg,indicating that the cross-linking strength of T-Tyr with collagen fibers is relatively higher.The tanning ecology of T-Lys,T-Tyr and T-Arg tanning agents was investigated preliminarily by BOD₅/COD value and environmental iMPact analysis.The data show that the BOD₅/COD values of T-Lys,T-Tyr and T-Arg tanning agents are all higher than 0.45.Meanwhile,the EIA values of T-Lys,T-Tyr and T-Arg tanning wastewater are lower than those of traditional chrome tanning wastewater.The results show that T-Lys,T-Tyr and T-Arg tanning agents have good biodegradability and could greatly reduce the pollution of tanneries.This work is valuable significance for the processing of chromium-free ecological leather.