The Dissolution Of Cellulose In Ionic Liquids And Fiber Processing

Ionic liquids（ILs）are a class of compounds composed of organic cations and organic or inorganic anions.Broadly speaking,such organic compounds which melt at or below 100℃are considered ionic liquids. Because of its extremely low volatility,good thermal stability and it is easy to be recycled,some of the RTILs are promising environment-friendly solvents in a range of science and technology applications such as media for organic and inorganic reactions,materials processing,electrochemistry and chemical separation.The main content of this dissertation includes synthesis and characterization of ionic liquids,physical properties of aqueous solution of ionic liquids,dissolution of cellulose in ionic liquids,rheological behavior of cellulose/ionic liquids concentrated solutions and cellulose fiber processing of cellulose/water/ionic liquids system.Firstly,ionic liquids based on imidazolium,1-butyl-3-methylimidazolium chlorides（[BMIM]Cl）,1-ethyl-3-methylimidazolium bromides（[EMIM]Br）,1-butyl-3-methylimidazolium bromides（[BMIM]Br）,1-butyl-3-methylimidazolium tetrafluoroborate（[BMIM]BF₄）,1-allyl-3-methylimidazolium chlorides（[AMIM]Cl）was synthesized.They were characterized by FTIR,H¹-NMR and elementary analysis.The results show that the ionic liquids synthesized are object products.Secondly,physical properties of aqueous solutions of ionic liquids were studied.The measurements of densityρ,refractive index△n, viscosityη,specific conductanceκand surface tensionγwere made over the whole concentration range.The equivalent conductivity∧_m, ionization degree a were calculated.Comparing with the ideal solution, strong and weak electrolyte solution,the aqueous solution of ionic liquids showed a typical aggregation behavior.The experiment of laser light scattering proved this structure further more.The data and evolution of the solution will support the chemical engineering process such as recycle of ionic liquids.Thirdly,the solubility of different kinds of polymers in ionic liquids we synthesized was studied.According to the result,cellulose/ionic liquid [AMIM]Cl and[BMIM]Cl were chose to studied further.The solubility and the dissolution rate of cellulose in two ionic liquids were investigated. The results showed that the solubility and dissolution rate of cellulose in [AMIM]Cl was higher than in[BMIM]Cl.The solubility of cellulose in ionic liquids decreased with the increase of degree of polymerization （DP）.The crystalline structure,chemical structure and DP were characterized by X-Ray diffraction,FT-IR spectroscopy,¹³C-NMR spectroscopy and viscosity method.It was shown that ionic liquids are direct solvents for cellulose.The crystalline form of cellulose transforms from celluloseⅠto celluloseⅡafter regeneration from ionic liquids.The DP of cellulose decreased with increase of dissolution time and temperature.Fourthly,the steady and dynamic rheological behaviors were investigated.The cellulose/ILs solutions act as non-Newtonian fluids at high shear rate.With increasing concentration of the solution the apparent viscosity of solution increases at low shear rate while the viscosity of high concentration solutions was lower than that of low concentration at high shear rate.The viscosity increased with the increase of the DP of cellulose and decrease with the increase of temperature.The higher activation energy E_ηof cellulose/ionic liquids solution indicated that the shear viscosity of solution is more sensitive to temperature.The elasticity of cellulose solutions increased with increasing concentration and DP of cellulose while decreased with increasing temperature.The correlation of dynamic and steady flow viscosity revealed that the Cox-Merz rule did not fit these cellulose solutions at high shear rate.Lastly,the spinning experiment was conducted with the cellulose pulp as raw material,ionic liquids[BMIM]Cl as solvent and water as coagulation bath.The cellulose fiber was obtained by dry-jet wet-spinning technology.The structure and properties of the cellulose fiber were characterized.It is shown that the cross section of the fiber is circle and uniform.The tensile strength is 1.83 cN/dtex and the elongation at break is 6.17%.