逆向热致相分离法制备聚醚砜微孔膜及成膜机理研究

Microporous polyethersulfone (PES) membranes are prepared by reverse thermally induced phase separation (R-TIPS) method in which the membrane-forming system that is employed featured a low critical solution temperature (LCST), soluble at room temerature and consisted of PES, solvent and non-solvent. The membrane-forming temperature is lower enough to overcome the formation of dense skin layer. The phase separation is induced by rapid heat transfer. Thus the macrovoid in membrane cross section is suppressed and membrane strength is improved. The preparation of PES microporous membrane via R-TIPS method was studied. The thermodynamic phase diagrams of membrane-forming system are obtained by the measurement of cloud point and theoretical calculation. The membrane-forming kinetics was analyzed by dynamic observation technique. The effects of casting solution composition and membrane formation process on the morphologies and performances are studied in order to achieve controls of membrane structure and properties, and the PES microporous membrane of excellent performances was prepared. The membrane-forming system composition of R-TIPS method is simple and needs less control of process parameters, low energy consumption, less pollution, low cost, easy to realize industrialization.

本项目利用室温可溶的低临界共溶温度聚醚砜（PES）/溶剂/非溶剂体系为铸膜液，采用逆向热致相分离法（R-TIPS）制备PES微孔膜；成膜温度低，可克服致密皮层的形成；以升温诱导迅速的热交换产生相分离，抑制膜断面产生大孔穴和改善膜强度。主要研究：采用R-TIPS法制备PES微孔膜；通过浊点测试和理论计算获得完整的成膜体系热力学相图；采用动态观测技术分析R-TIPS法的成膜动力学；研究铸膜液的组成及成膜工艺等对膜形态和性能的影响，实现对膜结构和性能的调控，制备出综合性能优异的PES微孔膜。RTIPS法成膜体系组成简单、需控制的工艺参数少、能耗低、污染少、成本低，易于实现工业化。

针对传统制膜方法（NIPS和TIPS）的不足，提出了一种新的成膜技术逆向热致相分离法(RTIPS)。该技术以具有低临界共溶温度(LCST)的聚合物溶液作为成膜体系，基于聚合物溶液低温相容、高温分相的基本原理，以升温诱导相分离，将NIPS 法温和的成膜温度和TIPS法迅速热交换诱导相分离的成膜机理相结合，其成膜体系的组成和工艺简单，能耗低，污染少，成本低，易于实现工业化。主要成果包括：（1）以三元低临界共溶温度体系PES/溶剂/非溶剂为铸膜液，采用RTIPS 技术成功制备了PES 微孔膜；根据Hansen溶解度参数理论，通过实验测定和理论计算实现了热力学相图相分离温度的预测，建立了相分离温度的理论计算方法；重点研究了PES的分子量及浓度、溶剂/非溶剂的种类及配比、成膜工艺等对成膜动力学、膜结构和性能的影响，同时辅以PES微孔膜的亲水改性，实现了膜结构的调控。与传统制膜方法所得膜进行性能对比发现，RTIPS法所制膜具有相对高的孔隙率、纯水通量、截留率和力学性能，且平均有效孔径小。（2）还对RTIPS法制备聚砜（PSf）微孔膜进行了研究，发现了聚砜/溶剂/非溶剂体系也存在LCST。以PSf/溶剂/非溶剂三元体系为基础，辅以自合成的亲水性聚合物超支化聚酯（HBPE），对HBPE的含量和平均分子量对PSf中空纤维膜的结构和性能的影响进行了系统的研究。研究结果表明，当成膜温度高于相分离温度时，成膜的主要推动力为热传导，抑制了皮层结构的生成，由RTIPS法所制备的膜为海绵状结构，膜的纯水通量、孔隙率、平均孔径及断裂强度随成膜温度的升高增大。