新型聚醯胺複合膜應用於醇類脫水-­膜製備與鑑定

本研究以無螺旋結構的4,4'-((丙烷-2,2-二基雙(4,1-亞苯基))雙氧基)二苯胺(4,4'-((propane-2,2-diylbis(4,1-phenylene))bis(oxy))dianiline, PPDA)和4,4'-((亞甲基雙(4,1-亞苯基))雙氧基)二苯胺(4,4'-((methylenebis(4,1-phenylene))bis(oxy))dianiline, MPDA)、具螺旋結構的6,6'-雙(4-氨基苯甲氧基)-4,4,4', 4', 7,7'-六甲基-2,2'-螺旋二色滿(6,6’-bis(4-aminopheoxy)-4,4,4’,4’,7,7’-hexamethyl-2,2’-spirobichroman, SBC)三種化學結構相異之高立體障礙二胺單體，與醯氯單體均苯三甲醯氯(trimesoyl chloride, TMC), 在聚醚醯亞胺(polyetherimide, PEI)非對稱基材膜表面進行界面聚合反應，製備一系列聚醯胺複合薄膜(PA/PEI composite membrane)，應用於異丙醇水溶液之滲透蒸發分離程序。研究中利用全反射式傅立葉轉換紅外線光譜儀與X射線光電子能譜儀鑑定聚合層化學結構與組成變化、掃描式電子顯微鏡與原子力顯微鏡分析基材膜與PA/PEI複合膜表面與截面之結構形貌變化、水接觸角儀檢測薄膜表面親疏水性，期望與滲透蒸發分離效能有密切之關聯性。研究發現基材膜表面孔隙度與對單體之親和性，影響聚合之反應性與聚醯胺選擇層之微結構變化。和其他高分子(PSf、PES)基材膜相比，PEI基材膜表面具有最大之孔隙度，在聚合過程中，使單體溶液擴散速度較其他基材膜快速，進而吸附更多單體於膜內。此外，PEI基材膜與單體之間有強氫鍵作用力，也會使單體較容易吸附於膜內，有利於聚合成較完整之選擇層。研究發現不同化學結構單體之立體障礙會影響聚合時反應程度與聚醯胺選擇層結構變化，進而影響滲透蒸發效能。化學結構相異之聚醯胺複合薄膜具有不同的自由體積變化，滲透蒸發效能之通量排序，依序為SBC-TMC＞PPDA-TMC＞MPDA-TMC。以PPDA為單體可獲致較佳的分離效能，擁有較高PSI值。研究中同時探討單體濃度與聚合條件對PA/PEI複合膜滲透蒸發效能之影響。PA/PEI複合膜於25OC進行70 wt% IPA水溶液滲透蒸發測試顯示，隨著PPDA單體濃度增加，透過通量先上升後下降，而透過端水濃度則先上升後下降。透過通量隨著TMC濃度上升，先下降後上升；透過端水濃度則先上升後下降。隨著基材膜浸漬胺單體溶液時間增加，透過端水濃度先上升後持平，而透過通量則為下降趨勢。當聚合時間上升時，透過端水濃度先上升後持平，而透過通量先下降後持平。隨著聚合溫度上升，透過端水濃度先上升後持平，而透過通量則為下降的趨勢。根據以上複合膜效能之比較，此聚醯胺複合薄膜25℃下分離70 wt%異丙醇水溶液具有最理想分離效能製備條件為：PEI基材膜浸漬於0.75 wt% PPDA單體溶液中45分鐘，而後在50℃下與0.25 wt% TMC有機溶液接觸1小時進行聚合反應，其透過通量為705.546.7 g/m2h，透過端水濃度高於99.8 wt%。

關鍵字

滲透蒸發；醇類脫水；界面聚合；二胺單體；聚醚醯亞胺

並列摘要

In this study, polyamide (PA) thin film composite (TFC) membrane was fabricated by the interfacial polymerization between diamine and trimesoyl chloride (TMC) onto polyetherimide (PEI) support. Three novel diamines were used in the preparation of PA/PEI TFC membrane, namely 4,4'-((propane-2,2-diylbis(4,1-phenylene))bis(oxy))dianiline(PPDA), 4,4'-((methylene bis(4,1-phenylene))bis(oxy))dianiline (MPDA), which two without spiro structure and 6,6’-bis(4-aminopheoxy)-4,4,4’,4’,7,7’-hexamethyl-2,2’-spirobichroman (SBC), which monomer with spiro structure, Chemical structure and composition were validated using Attenuated total reflectance–Fourier transform infrared (ATR-FTIR) and x-ray photoelectron spectroscopy (XPS) analysis, the monomer without spiro structure have higher crosslink degree due to less steric hindrance. According to field emission scanning electron microscope (FESEM) images, PPDA-TMC/PEI and MPDA-TMC/PEI had a thin and smooth PA layer. However, due to the sterically hindrance structure, SBC-TMC PA did not form well on the top of PEI support. Compared with PEI support, the novel PA TFC membrane had more hydrophilic surface. At 25°C, the pervaporation performance of 70 wt% aqueous isopropanol solution through the prepared PA TFC membranes increased in the following order: SBC-TMC/PEI < MPDA-TMC/PEI < PPDA-TMC/PEI. At the optimal interfacial polymerization condition between MPDA and TMC: monomer immersion time 45 min and reaction time 1 hr, PPDA-TMC/PEI TFC membrane can exhibit high separation flux of 705 (g/m2 h) with a desirable separation factor of 15694, due to the dialkyl group which in the middle of structure create pathway to enhance the performance. Therefore, PPDA-TMC/PEI TFC membrane is a promising membrane for dehydration of alcohol solution.