| China enjoys the largest textile production and export volume in the world and the production of wool textiles plays an important role in promoting the development of the textile industry.There are a series of problems in the pretreatment of traditional wool textiles,such as high energy consumption,serious pollution,and complicated technology;thus,clean and efficient technology is urgently needed.Based on the supercritical CO2 fluid technology,this subject develops a novel and environmentally friendly cleaning technology which can effectively reduce the waste of water resources in the traditional textile industry,the use of toxic and hazardous chemicals and the emission of environmentally hazardous substances.Therefore,it is of great significance to the realization of the clean production of textiles.Firstly,the cleaning process of cashmere fibers was investigated by supercritical CO2 microemulsion system.The effects of AOT,deionized water,ethanol,detergent,system temperature,pressure,treatment duration and other parameters on the cleaning effect of cashmere fibers were explored and the appropriate process conditions were optimized.Additionally,the catalytic degradation of various impurities on the surface of cashmere fibers by biological enzymes(lipase,cellulase,pectinase,protease)in supercritical CO2 fluid was investigated.The effects of lipase,cellulase,pectinase,protease,system pressure,temperature,duration and other parameters on the cleaning effect of cashmere were explored and the process parameters of enzyme catalyzed cashmere scouring in supercritical CO2 fluid were optimized as well.At the same time,the recommended process was utilized to study the effects of washing times on the cleaning effect of cashmere fibers and enzyme-catalyzed velvet under different media.The structure and properties of cashmere fibers treated by enzyme catalysis cleaning in Furthermore,to remove the pigment and residual impurities on the cashmere fibers simultaneously,this subject also explored the enzymatic oxygen onestep cleaning and bleaching process in supercritical CO2 fluid.Finally,the structure and properties of cashmere fibers after enzymatic cleaning and enzymatic oxygen one-step treatment in supercritical CO2 fluid were tested and characterized by scanning electron microscopy(SEM),X-ray powder diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),the rate of moisture regain measurement,strength measurement,Xray energy spectroscopy(EDS),and thermal analysis(TG-DTG).The obtained results show that the significant oil and pigment removal effect of cashmere fibers cleaned by supercritical CO2 microemulsion is achieved.In this system,the recommended working liquid formula and cleaning process are as follows:0.2 g AOT,40mL deionized water,20 mL ethanol,0.4 g detergent,system pressure at 20 MPa,temperature at 60℃,treatment duration of 60 min.Under these recommended conditions,the oil content of cashmere fibers cleaned by supercritical CO2 microemulsion is 0.78%and the whiteness reaches 72.08.The results of enzyme catalytic cleaning in supercritical CO2 fluid show that the impurities removal effect and whiteness improvement of the treated cashmere fibers are significant.In this system,the recommended cleaning process is as follows:lipase dosage is 1.5%～2.5%(o.m.f);cellulase dosage is 5%～9%(o.m.f);pectinase dosage is 2%-4%(o.m.f);protease dosage is 0.5%～1.0%(o.m.f);the system temperature is 40℃～50℃;the pressure is 20 MPa～22 MPa;and the treatment duration is 120 min～150 min.Under these recommended conditions,the whiteness and weight loss rate of the cashmere fibers catalyzed by supercritical CO2 fluid are 77.28 and 34.28%respectively.In addition,the whiteness and impurities removal of cashmere fibers can be further improved by increasing the cleaning times.Finally,it is proved that supercritical CO2 fluid cleaning is more promising than water bath cleaning.The achieved results of one step enzymatic oxygen treatment in supercritical CO2 fluid disclose that the whiteness of cashmere fibers is improved,and the fiber damage is less,which can meet the requirements of industrial production.The recommended process in this system is as follows:pH=8,0.8 g PEG1000,20 mL buffer solution,20 mL hydrogen peroxide,0.5 g laccase,system temperature at 55℃,pressure at 18 MPa and treatment duration of 90 min.Under these recommended conditions,the whiteness and alkali solubility of cashmere fibers by one step enzymatic oxygen bleaching in supercritical CO2 fluid are 83.36 and 15.55%respectively.SEM results show that the surface of cashmere fibers becomes smooth after supercritical CO2 fluid enzymatic cleaning and bleaching treatment and the significant effect of removing impurities is obtained.Particularly,the scale structure is clearly visible and the structure is less damaged.The X-ray powder diffraction pattern(XRD)shows that the crystal size of the cashmere fibers after cleaning as well as the crystallinity is increased.Infrared spectroscopy(FT-IR)shows that there are no obvious changes in the macromolecular functional groups and the main chain of cashmere fibers before and after cleaning and their chemical structure is not significantly affected.The fiber moisture regain measurement results show that the moisture absorption performance of the cashmere fibers before and after cleaning is significantly improved.The results of strength test display that the breaking strength of cashmere fibers decreases slightly after cleaned by supercritical CO2 fluid whereas the wearability is not affected.X-ray energy spectroscopy(EDS)test results show that a good removal effect on metal ions on cashmere fibers by employing supercritical CO2 fluid cleaning technology is observed.The thermal analysis(TG-DTG)test results show that the supercritical CO2 fluid cleaning process has no significant effect on the thermal properties of cashmere fibers.The subjective test results show that the cashmere fiber cleaned by supercritical CO2 fluid has good softness,smoothness,fluffiness,elasticity and luster,which meets the requirements of garment processing. |
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