| Leather tanning agent is an important chemical used in leather industry.The quality of leather mainly depends on the quality of leather chemicals,especially tanning agent.At present,the production of leather tanning agent is mainly chrome,which can give the leather soft plump,moisture resistance,high thermal stability,but the environmental pollution caused by chrome tanning agent can not be ignored.Therefore,it is imperative to develop new chrome free tanning agent to reduce or replace chrome tanning agen t.The use of aluminum salts tanning has a long history.The characteristics of aluminum tanning is color white,smooth and plump,soft,wear resistance and good extensibility.But the aluminum ions in solution will form outer orbital complexes with small s ize,and weak collagen binding force,so the shrinkage temperature of aluminum tanning is not high,and detanning occurre s easily in water,which makes the application of aluminum tanning agent limited.The aluminum ions in the aluminum tanning agent have t he tendency of strong coordination reaction with the organic compounds containing hydroxyl,amino and carboxyl groups to improve the tanning property.In this thesis,we proposed the coordination of acrylamide with aluminum ions,then graft copolymerization of starch with free radical polymerization,a chrome free tanning agent was prepared with the advantages of starch,vinyl tanning agent and aluminum tanning agent.The main research work was as follows:The starch was degraded by Na OH and hydrogen peroxi de at a certain temperature to make oxidized starch containing carboxyl in structure with the short molecular chain,decreased hot paste viscosity,easier gelatinization,high solubility,low viscosity,small cold coagulation.Then adjust the p H value with citric acid,the starch modified acrylamide and aluminum complex tanning agent was prepared by copolymerization of aluminum s ulfate and acrylamide with hydrogen peroxide as initiator.The structure of the product was characterized by Fourier transform infrared spectroscopy(TF-IR),X-ray diffraction(XRD),thermogravimetric analysis(TGA)and scanning electron microscopy(SEM),t he results showed that the coordination of acrylamide and aluminum ion occurred,and the copolymerization of co mplex and starch was successful.Through single factor experiments,the effects of Na OH dosage,degradation temperature,degradation time,the dosage of aluminum sulfate and acrylamide on the properties of the product were discussed.The optimal synthesis conditions were obtained as follows : Starch 10 g,water 35 ml,Na OH dosage 0.2 g,aluminum sulfate dosage 4 g,the amount of acrylamide is 10 g,the degradation temperature is 80 ?,degradation time is 80 min.In this paper,the starch modified acrylamide and the aluminum complex tanning agent synthesized in the optimum conditions were used in the tanning,retanning and fatliquoring dyeing process,through the shrinkage temperature,thickening rate and uniformit y of leather dyeing with fat,degree of shading and fullness after tanning and retanning to determine the optimal dosage is 6 %(with the weight of wet blue).It is measured that the maximum s hrinkage temperature is 110.8 ?,the thickening rate of 6.7 %,the breaking elongation is 121.8 %,tensile strength is 9.45 MPa,tear strength is 40.41 N·mm-1,softness is 6.62,water vapor permeability is 3482 g·(m2·24h)-1 after tanning andretanning with the best dosage.Based on the analysis of the micro morphology of the leather,it is concluded that the tanning agent is easy to penetrate into the skin structure,and it has a certain cross-linking effect between the skin collagen forming a three-dimensional network support structure.According to the combination of tanning and chrome chromium content in liquor,it is concluded that the tanning agent can improve the absorption rate of chrome leather,the chromium content in l iquor decrease to 0.58 g/L,the leather of chromium absorption rate is above 87.65 %,while in the conventional chrome tanning process,the chrome content in the waste water is 2~4 g/L,leather of chromium absorption rate is only 60 %~ 70 % leaving about 1/3 of chromium in wastewater.It can be seen that the tanning agent can greatly reduce the chromium content in the waste liquid and the pollution to the environment improving the absorption rate of leather to chromium powder.Through the analysis of the performance of the leather after retanning using the tanning agent and the results of structural analysis,it is founded that the tanning agent has good filling performance and can effectively improve the fullness of the leather and the stability of heat and moisture,making the leather surface color uniform and pure. |
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