Study On Component Separation Of Waste Polyester Cotton Blended Fabric And Reuse Of Cellulose Material

With the vigorous development of textile and garment industry and the improvement of people's awareness of green environmental protection,the recycling of waste fabrics has gradually become a hot topic.Among them,the recycling method of waste polyester cotton blended fabrics,which accounts for more than 80%of the total waste fabrics,has naturally attracted the attention of many researchers.However,there are two components of polyester fiber and cellulose fiber in waste polyester cotton blended fabric.The morphology,structure and characteristics of the two components are different,and the main properties will be reduced due to mutual doping.Therefore,in the recycling process of waste polyester cotton blended fabric,appropriate methods must be taken to separate the two components and reuse them respectively.In this paper,the degradation effects of concentrated phosphoric acid(85%)method and phosphoric acid hydrothermal method on cellulose fiber were studied,and their separation effects on polyester cotton components were studied.In addition,cellulose xanthate and cellulose nanocrystals were prepared from the recovered cellulose materials,and their applications in the adsorption of methylene blue dye wastewater and BTCA crease resistant finishing of cotton fabric were studied respectively.The main conclusions are as follows:(1)Cellulose fiber was degraded by concentrated phosphoric acid method.The degradation process was as follows:phosphoric acid concentration 85%,50?and 3.5 h.At this time,the recovery rate of cellulose was 95.00%,the degree of polymerization was 104.59,the recovered product was small-size irregular granular type II cellulose powder,the chemical structure had no change compared with the original cellulose,the crystal structure changed into type II cellulose,and the crystallinity decreased.(2)Cellulose fiber was degraded by phosphoric acid hydrothermal method.The degradation process was as follows:phosphoric acid concentration 4%,140?,3h,150?,2h.At this time,the recovery of cellulose was 92.91%and 93.20%,the degree of polymerization was 138.80 and134.98,and the degradation products were 30?80?m.The crystallinity of irregular short rod type I cellulose powder increased to 70.81%and 65.69%respectively,resulting in the improvement of its thermal stability and the corresponding increase of the maximum thermal degradation temperature to about 340-350?.Compared with phosphoric acid degradation method,phosphoric acid hydrothermal method has less acid demand and no change in product crystal form,so it is more suitable for polyester cotton separation.(3)The process conditions are as follows:the concentration of phosphoric acid is 4%,140?and 3h,the recovery rate of polyester fiber is 96.63%,the appearance is still smooth and uniform solid circular fiber,and the chemical structure and crystal structure have no change,only a little decrease in crystallinity and loss of thermal stability.(4)Cellulose xanthate was prepared by NaOH-CS₂system with cellulose powder recovered from separation.The preparation process was as follows:NaOH concentration of 10%,CS₂dosage of 0.9ml,alkalization temperature of 25?,alkalization time of 1h,esterification temperature of 30?,esterification time of 2.5h and Mg SO₄dosage of 8 ml.At this time,the average particle size of cellulose xanthate is 50.79?m yellow powder.The optimum adsorption conditions were as follows:cellulose xanthate dosage 0.12 g,initial dye concentration 100 mg/L,temperature 40?,time 60 min,solid-liquid ratio 3:1250.At this time,the removal rate of methylene blue dye was 99.12%.The adsorbent was desorbed and regenerated by HCl-NaOH system.The optimum regeneration process was as follows:HCl concentration 1.2 mol/L,temperature 50?,time 45 min,solid-liquid ratio 1:100.After four adsorption desorption cycles,the removal rate of methylene blue dye was 96.50%,the residual solution was diluted 40 times,and the absorbance was 0.014.It was close to colorless state and met the recyclable requirements.(5)Cellulose nanocrystals were prepared by using the separated and recovered cellulose powder through hydrochloric acid hydrothermal system.The CNC preparation process conditions were as follows:HCl concentration 6 mol/L,hydrothermal temperature 90?,hydrothermal time 3h,solid-liquid ratio 1:60.The yield of CNC is 90.12%.The apparent morphology is rod like nanocrystalline particles with a certain length diameter ratio.The average particle size is 274.9 nm,the crystallinity is increased to 87.37%,and the maximum degradation temperature is also increased to 350?.After BTCA/CNC/CS anti wrinkle finishing,the fabric WRA is 228.3°,the lifting rate is 76.98%,and the strength retention rate is 70.66%.(6)Cotton fabric was finished with BTCA/CNC/CS composite system.The finishing process was as follows:BTCA concentration of 70g/L,CNC concentration of 2 g/L and CS concentration of 3g/L.the process flow was:two dipping and two rolling(dipping time of 3min,liquid carrying rate of 90%,bath ratio of 1:20)?pre drying(80?,5min)?baking(160?,3min).After finishing,the TSR of the fabric was 55.04%,the WRA was 251.3°,and the WRA improvement rate was80.79%.CNC is evenly distributed on the fiber surface without obvious agglomeration,and forms a network membrane coating structure with BTCA and CS,which improves the properties of the finished fiber.