Preparation Of Starch Dissolved In Medium And Low Warm Water And Its Application In Sizing And Desizing Of Deimn Yarn

Textile and garment industry is a major pillar industry in China.The textile and garment industry accounts for nearly 10%of China’s GDP,and the compound growth rate of per capita clothing consumption in the past five years is almost 20%.Denim clothing is the most important branch of the clothing industry,and the annual sales volume of denim clothing in the world has exceeded 5billion pieces.The number of denim garments produced in China has exceeded 25%of the world’s denim garments.Denim has gradually become the most popular clothing category due to its low price,diverse styles,durable and practical features.Denim fabric is dyed before weaving,but dyeing will cause certain damage to the denim yarn.Therefore,sizing the denim yarn before weaving is critical to resist the mechanical effects of the warp yarn,such as tension,elongation and friction,and improve the weaving efficiency.With the national slogan of"carbon neutral"and"carbon peak",higher requirements are submitted for the textile industry.Starch,as renewable,biodegradable and cheap polysaccharide material,is widely used in yarn sizing,papermaking and wastewater treatment.However,traditional starch as a slurry needs to be boiled at high temperature（≥95℃）,and the slurry film is hard and brittle,can not resist the repeated friction of weaving.Denim yarn sizing requires that the sizing material can be sizing under medium and low temperature conditions（≤65℃）,has good adhesion to indigo and can effectively cover hair,so it needs to choose the appropriate sizing material.In this paper,the corn starch as raw material,supplemented by acid hydrolysis pretreatment,acid hydrolysis starch（HS）,and then in the ethanol-base mixed system with n-2,3-epoxy-propyl trimethyl ammonium chloride（GTA）etherification reaction,the preparation of cold water-soluble,flexible,strong adhesion of low temperature soluble starch slurry（HS-g-GTA）,the specific research is as follows:（1）Preparation and process optimization of medium and low temperature water soluble starch slurryCorn starch was retreated with hydrochloric acid and etherified with GTA in ethanol-base system.A series of HS-g-GTA slurry with different substitution degrees were prepared by controlling the molar ratio of glucose unit（AGU）between GTA and starch.The water solubility,surface morphology and zeta potential of HS-g-GTA were studied.The influence of temperature,time and reagent dosage on the viscosity,solubility and degree of substitution of the slurry was further discussed.The results showed that GTA was successfully theorized with the hydroxyl group on the glucose ring of starch,and the solubility of HS-g-GTA slurry reached 98%,zeta potential reached20 m V,and the degree of substitution reached 0.2.The optimum process of acidolysis is as follows:reaction temperature 60℃,reaction time 2 h,acid dosage 0.5 mol/L,ammonium persulfate dosage5%（the proportion of starch dry base）,the optimum process of iteration reaction is Na OH mass fraction 3%,n _GTA∶n _AGU=0.3,reaction time 2.5 h,V _ethanol∶V _water=5:1.The reaction temperature is 65℃.（2）Study on the properties of medium and low temperature quaternary ammonium starch slurry slurry filmIn order to further explore sizing performance of HS-g-GTA grout,this chapter explores the sizing film performance of a series of substituent grout prepared.The relationship between grout temperature,mass fraction,degree of substitution and viscosity,as well as the stability and light transmittance of grout at different temperatures was studied.The surface morphology,hydrophilicity and mechanical properties of serious film with different degrees of substitution were investigated.The results show that with the increase of slurry substitution,the transparency stability of the slurry is improved,and the surface smoothness,hydrophilicity and mechanistic properties of the slurry are improved.The stability of HS-g-GTA slurry under medium and low temperature can reach 90%,the maximum specific adhesion of the slurry can reach more than 1000c N/%^-1,and the breaking strength of the slurry with the size of 120 mm×20 mm×0.2 mm can reach more than 100N.（3）Sizing and desizing practice of denim yarn based on HS-g-GTA sizingIn the first two chapters,the properties of the sizing,the properties of the sizing film are explored.The results show that the viscosity stability of the sizing HS-g-GTA sizing and the hydrophilic wear resistance of the sizing film meets the requirements of the sizing of denim yarn.In this chapter,the denim yarn is sizing with HS-g-GTA slurry and the sizing wastewater is treated.The hairiness,wear resistance,hydrophilicity and yarn breaking and elongation properties of the yarn after sizing are analyzed.Sizing wastewater can be simulated by kaolin and indigo solution under weak alkaline condition.The results show that after sizing,the breaking strength increases by 40.07%,the elongation at break increases by 11.82%,the feather index decreases by 90%,the wear resistance times increases by about 4 times,the desizing effect is excellent,and the wastewater removal rate can reach 80%.