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Formation of anistripic membrane by the hybrid process with thermally induced phase separation and nonsolvent induced phase separation

通过热诱导相分离和非溶剂诱导相分离混合工艺形成不均匀膜

基本信息

批准号：
09450292
负责人：
TERAMOTO Masaaki
金额：
$ 4.16万
依托单位：
Kyoto Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

Anisotropic membranes were produced by the hybrid process with both thermally induced phase separation and dry process. To induce an anisotropic structure, diluent was evaporated from one side of the polymer-diluent melt-blended, thereby creating a concentration gradient in the nascent membrane prior to quenching and inducing phase separation. The system used to prepare these membranes was isotactic polypropylene (iPP) in diphenyl ether.In the case of no evaporation, nearly isotropic structures were obtained. This indicates that the cooling rates at both surfaces were controlled to be nearly equal. The evaporation process was found to be useful in producing anisotropic structures. The effects of evaporation time and initial polymer concentration on the anisotropic membrane structure were investigated. The pore size at the top surface decreased by increasing evaporation time.The effects of thermal history, such as cooling rate and quench temperature on membrane structure were investigated. When cooled in air, decreasing the quench temperature brought about an increase in the cooling rate, which led to a decrease in the average cell diameter at the bottom surface. The combined use of a thermal gradient and concentration gradient produced pronounced asymmetric structures with a skin layer at the top surface.The evaporation process was analyzed by solving appropriate mass transfer and heat transfer equations. The agreement between the calculated results and the experimental data on the membrane weight loss and the membrane thickness was satisfactory. The anisotropic structures were discussed in detail based on the calculated polymer volume fraction profiles in the membranes.

采用热致相分离和干法相结合的混合工艺制备了各向异性膜。为了诱导各向异性结构，从聚合物-稀释剂熔融共混的一侧蒸发稀释剂，从而在猝灭和诱导相分离之前在新生膜中产生浓度梯度。采用等规聚丙烯(IPP)-二苯醚体系，在不蒸发的情况下，得到了近乎各向同性的结构。这表明，两个表面的冷却速度被控制为几乎相等。蒸发过程被发现在产生各向异性结构中是有用的。考察了蒸发时间和聚合物初始浓度对各向异性膜结构的影响。随着蒸发时间的延长，膜的顶面孔径减小，考察了冷却速度、淬火温度等热历史因素对膜结构的影响。在空气中冷却时，降低淬火温度会增加冷却速度，从而导致底部表面平均泡孔直径的减小。结合使用温度梯度和浓度梯度，在顶面形成了明显的非对称结构，通过求解合适的传质和传热方程，对蒸发过程进行了分析。膜失重和膜厚的计算结果与实验数据吻合较好。根据计算的膜中聚合物体积分数分布，详细讨论了膜的各向异性结构。