Application Research Of Zirconium Tanning Technology On Leather

Because of the irreversible damage to the environment by chrome tanning and the shortage of chromium resources in China,the development of non-chromium leather tanning agents is imminent.Commonly used non-chromium metal tanning agents are Zr,Al,and Rare-earth metal etc.These tanning agents have their own defects compared to chrome tanning when be used alone.Now we adopt multi-metal joint tanning to achieve the effect of complementing each other.The main contents of this paper:(1)Since the precipitation point of zirconium tanning agent is low,the requirement of leather tanning is not met,and the coordination polymer inhibitor agent P15 is added to increase the precipitation point pH of zirconium tanning agent.The coordination polymer inhibitor agent P15 contains small molecules of organic acids,its structure is stable,and it can exist in strong acid and alkali high concentration salt solution stably.ZR(SO4)2 precipitation point increases with increasing P15 dosage.When the dosage ratio is 1:1,the pH can reach 12.34.In order to prevent the leather detanning,to add the multi-metal complexing agent S75 is a hyperbranched polymer containing lots of carboxyls which is flocculation at pH<1 and is stable at pH>1.Due to its special structure,it can work with leather collagen and tanning agent to form a system of "tanning agent-collagen-S75",which increases the stability of binding and prevents detanning,zirconium tanning agent precipitation point reduce with increasing S75 dosage.When the dosage ratio is 1:2,the pH can reach 1.5,below the precipitation point of zirconium tanning agent is 1.76.The combination of P15 and S75 can increase the pH of the tanned skin liquid in the early stage of tanning,avoid premature precipitation,reduce the amount of basifying agent and enhance the combination of tanning agent and leather in the later stage.(2)In comparison with the T-3 tanning process,the optimum dosage and optimum ratio of zirconium aluminum rare earth tanning agent are confirmed by using shrinkage temperature and hand feeling.Range of shrinkage temperature is decrease with total tanning agent dosage increasing,total tanning agent dosage is confirmed in the end.The dosage of total tanning agent is unchanged,the dosage of zirconium tanning agent is continuously reduced,the dosage of aluminum tanning agent is increased,and the shrinkage temperature is first increased and then decreased.Decreasing rate of zirconium tanning agent suitably,leatherwear hand feeling can increase.Zirconium aluminum rare earth tanning agent are confirmed final,it was 4:3:3 and 4:3.5:2.5.Based on the optimum dosage and ratio,the effects of basification pH,heating temperature and heating time on shrinkage temperature were studied.It is found that the two tanning processes are consistent basically.With the increase of basification pH,the shrinkage temperature first increases and then decreases,and the optimum basification pH is 4.With the increase of heating temperature,the shrinkage temperature first increases and then decreases,and the optimum heating temperature is 38?.With the increase of heating time,the shrinkage temperature first increases and then unchanged,and the optimum heating time is 5h.(3)Changing the dosage of P15 and explore the effect of its dosage on the procedural shrinkage temperature and the zirconium content of the procedural waste liquid.With the increase dosage of P15,shrinkage temperature has difference in the beginning.In the first 5h of the beginning,with increase dosage of P15,the range of shrinkage temperature is reduce,shrinkage temperature is basically unchanged at the end of the tanning.With increase dosage of P15,zirconium content of the procedural waste liquid is increased at the end of the tanning.On this basis,the leather samples were washed with water,10%salt solution,pH=2.5 acid solution and pH=9 alkali solution,and the shrinkage temperature after washing and the zirconium content of the leather were measured,and the shrinkage temperature and the zirconium content of the leather were found to decrease.The lowest shrinkage temperature and zirconium content were measured in water or alkaline solution,and the highest shrinkage temperature and zirconium content were measure in the acid solution.This means that the leather is the most resistant to water and the least resistant to acid solution.(4)Traditional chrome tanning,T-3 tanning,zirconium tanning,zirconium tanning+T-3 retanning process were compared the shrinkage temperature of four leather sample,leather tanning agent content and resistance to elution in water,10%salt solution,pH 2.5 acid solution,pH=9 alkali solution.It is found that the chrome tanning leather has the highest shrinkage temperature,the T-3 tanning leather has the lowest shrinkage temperature,and the zirconium tanning has a higher shrinkage temperature than the zirconium tanning+T-3 retanning,but total samples can reach above 95oC.In four processes,the chrome tanning is that the tanning agent content of the loose part is higher than the tight part,and the other three kinds of zirconium tanning processes are the loose parts of the tanning agent content lower than the tight part.Washing in the four solutions,using the post-elution shrinkage temperature and the leather tanning agent content as evaluation criterion,it was found that the four processes were the most resistant to water washing and the least resistant to acid solution.