Preparation And Application Of Polyethersulfone Hollow Fiber Ultrafiltration Membranes Modified By Segmented Polyetherurathane In Component Separation Of Chinese Drug Danshen

In this dissertation, diisocyanate terminated polyetherurathane (OCN-PEU-NCO) was synthesized with 4,4'-diphenylmethane diisocyanate (MDI), 1,4-butane diol (BDO) and hydrophilic polyethylene glycols (PEG) of different molecular weights. And the PEU of different chain structures was introduced into the chain of polyethersulfone (PES) with different molecular weights through block copolymerization. The effects of reaction temperature, reaction concentration and different types of solvent on the block copolymerization were investigated. Thus the optimal synthesizing technology conditions were determined. The structure of the obtained products was characterized with FTIR spectrum and DSC chart.Phase diagrams of the ternary and the quaternary PEU-PES membrane-forming systems were obtained by cloudpoint titration method. The influences of molecular weight of polyethersulfone, the solvent and the nonsolvent on the phase diagram of the ternary system, polymer/solvent/nonsolvent, were studied. As for the quaternary system, polymer/solvent/nonsolvent/pore-forming additive, the roles of different types of pore-forming additives and their use levels were particularly discussed. As a result of these experiments, some useful ideas on choosing the conditions for PEU-PES hollow fibre membrane preparation and spinning technology were suggested.Membrane-forming solution were prepared, using the PEU-PES segmented copolymers as membrane spinning material, dimethylsulfoxide (DMSO), dimethyl-formamide (DMF), dimethylacetamide (DMAC) as solvents, polyethylene glycols(PEG) and polyvinylpyrrolidone(PVP) as pore-forming additives (PFA). Hollow fiber membranes were spun by dry-jet wet spinning method, using water as nonsolvent. The effects of molecular weight of polyethersulfone, solvent and pore-forming additive on the structure and performance of the hollow fibre membrane were researched. The results obtained show that most of the PEU-PES hollow fiber membranes have asymmetric figure-type structure, which has the outer and inner double skin layers. The pure water fluxes (PWF) and the rejection rate of BSA of modified hollow fibre membranes(PEU-PES) are improved, compared with the unmodified polyethersulfone membrane materials.The self-made hollow fiber ultrafilter was applicated to the component separation of Chinese drug Danshen. The measurement of high performance of liquid chromatography (HPLC) indicated that the loss of the main effective component protocatechuic aldehyde was 10.8-18.9%, which was smaller than that of the traditional water-alcohol-precipitation method. And the results of examining the impurities in the filtrate were also better.By the means of contact angle and fouling rate testing, it showed that the hydrophiliciry of the modified membranes was enhanced, and the function of fouling resistance was also improved, in comparison with the unmodified membrane.