Study On Twin-screw Wet Spining Process Of Alkali-solubil Hydroxyethyl Cellulose

Cellulose is one of the re-generable resources among nature polymers.However,its application has been hindered by its insolubility in organic and inorganic solvents due to the existence of large amount of hydrogen bonds,the complicated structure of molecular aggregation,and its high degree of cystalization.Therefore,it is very important to study the synthesis of cellulose and develop a compatible solvent system,as well as it processing techniques.Hydroxyethyl Cellulose(HEC)is the product of cellulose etherified using ethylene oxide.Based on mole degree of substitution(MS),it can be divided into water soluble HEC and alkali soluble HEC.HEC with low MS is insoluble in water but soluble in diluted alkali solution.The alkali soluble HEC has good fiber forming properties and is expected to become another vital cellulose fiber after viscous and lyocell.This paper studied the preparation method of HEC using gas to solid phase reaction suitable for wet spinning technique.In addition,it studied the structure and its relevant properties of the prepared HEC.The prepared HEC has shown good alkali solubility which makes it possible to obtain homogeneous spinning solvent in diluted alkali solution.This paper also developed a spinning process by introducing a twin screw extruder and thermal forming stretcher.In this method,squeezed cellulose pupl was placed into a pressured reactor to react with gas phase ethylene oxide.The results indicate that homogeneous alkali soluble HEC can be obtained when mass ratio is 0.20, squeeze ratio of the alkalized cellulose is 3.20,and etherification time is from 80min to 100min with etherification temperature of 40℃.Using IR,1H-NMR and XRD,the resulting product has characterized with an etherification degree of 0.40 and crystallization degree of 55.21%.A dissolvability of 98.56% was obtained when the resulting HEC was dissolved in 8wt% NaOH solution for 8 hours at 0℃,and this paper has attempted to explain the dissolve mechanism from thermodynamic point of view.Dynamic rheological measurements of the spinning solution shows the HEC spinning solution is a non-Newtonian fluid,with non-Newtonian fluid index n between 0.79 and 0.91,Viscosity flow activation energy between 5.73 and 25.01kJ/mol,and structure viscosity index between 3.29 and 8.31.The coagulant was studied using orthogonal method.The as-spun fibers demonstrated ideal structure and tenacity that benefit further process development when the coagulant was composed of 15wt% sulfuric acid,15wt% sodium sulphate and 70wt% de-ionized water. A spinning process was developed by introducing twin screw extruder and thermal forming stretcher into traditional wet spinning technology,and process parameters were established using orthogonal method.The fiber structures during different stages of the spinning process were also observed and captured using SEM.The resulting HEC fiber has exhibited a breaking tenacity of 1.53 cn/dtex and elongation of 14.65%. The originality of this study has been reflected from the following perspectives;1.Developed a wet spinning compatible preparation method for alkali soluble Hydroxyethyl Cellulose of low degree of etherification synthesizied using gas to solid phase reaction.Ideal parameters to dissolve alkalized HEC were established.2.A coagulant composed of water,sulfuric acid,and sodium sulfate, which has good coagulation properties and controllable coagulation speed was developed for spinning of alkali soluble HEC,using orthogonal analytical method.3.The application of twin screw extruder and thermal forming stretcher in the spinning process makes it possible to spin high solid content,high viscosity alkali soluble HEC.Ideal spinning process parameters were established using orthogonal analytical method.