Wet Spinning Process Of Alkali-Soluble Hydroxy Ethyl Cellulose

With the decrease of petroleum resources,cellulose as a biodegradable, renewable,environment friendly and resourceful material,has attracted wide attention. However,the traditional viscose process has its own shortcomings such as,toxic gas(CH₂,H₂S) and heavy metals.These disadvantages are challenging researchers to dedicate themselves exploring new process producing cellulose and its derivatives.In this thesis,we studied a new process to produce Hydroxy Ethyl Cellulose(HEC) fibers.HEC,product of the etherification between cellulose and ethylene oxide,could be divided into water soluble and alkali soluble two types according to different mole degrees of substitution(MS).HEC with low degree MS does not dissolve in water but can dissolve in diluted alkali solution.This alkali soluble HEC has a good processability of making fibers,and is promising to be another vital cellulose fibers.In this paper,the preparation of alkali soluble HEC with gas-solid reaction route, as well as the HEC fiber spinning were studied.Fist,HEC solution in 8wt%NaOH with different mass fractions was prepared.After that,static rheological behavior and dynamic rheological behavior of HEC/NaOH solution were respectively studied by falling-sphere viscosimeter and plate rheometeres.The wet spinning process parameters like mass fraction of H₂SO₄,coagulation bath temperature,coagulation bath time,sprayer extension,water bath temperature and heat treatment were comprehensively investigated.Besides,the structure and thermal properties of HEC fibers were studied too.The results showed that,the hydroxy ethyl cellulose solution prepared in our lab almost having no degradation at the temperature of 50℃,within 8 hours.And this stability of the solution makes it qualified to deaeration and other pretreatments.The calculated static viscous activation energy of the solution was 30 KJ/mol.Dynamic rheological behavior study of HEC/NaOH solution showed that,in the low frequency area,the storage modulus value G′was less than the loss modulus value G″,which appeared to be elastic behavior.With the increase of angular frequency,value G′and value G″were also increased.The elastic behavior was observed when value G″appeared to be higher than value G′.And this behavior was easier to be seen in the HEC/NaOH solution with a higher mass fraction.So the HEC/NaOH solution was a shear thinning non-Newtonian fluid.The dynamic viscosityη′was declined when the angular frequency increased.With the mass fraction of HEC increased from 8%to 9%, the dynamic viscosity was increased dramatically.Furthermore,the impact of temperature to solution viscosity was enlarged with a higher HEC mass fraction.The gel point was appeared within a temperature range from -7.3℃to -7.2℃.When the temperature raised from -6℃,value G′and G″were declined much slower than before, and with value G′declined faster.Gradually,the viscous behavior was became dominated.The optimum spinning process was:mass fraction of HEC 6%,mass fraction of H₂SO₄ 15%,coagulation bath temperature 20℃,coagulation bath time around 10s, sprayer extension 1.33,water bath drawing ratio 1.25,water bath temperature 50℃, dry drawing ratio 1.2 and heat treatment temperature 110℃.The best performance of the acquired alkali soluble HEC fiber was:dry breaking tenacity 2.55 cN/dtex,wet breaking tenacity 1.43 cN/dtex,breaking extension 17.33%and crystallization degree 50.44%.The thermal properties of HEC and HEC fibers studied by DSC-TG,showed a very close result to cellulose,as they all appeared to decompose at the temperature of 300℃.The HEC kinetic parameters of its thermal degradation were obtained respectively by Friedman method and Kissinger method.The results using each method were Ea=151.68 KJ/mol,n=1.01,lnA=16.05 and Ea=158.1 KJ/mol, lnA=23.15. The main innovative points of the dissertation are as follows.1.The dynamic theological behavior of HEC/NaOH solution was analyzed;2.The HEC fiber with good performance was first acquired by wet spinning process;3.The thermal characteristics of HEC and HEC fibers were first investigated by TG-DSC.