共聚聚酰亚胺膜材料的合成及其气体渗透性能研究

以2,2′-双(3,4-二羧基苯基)六氟丙烷二酐(6FDA)作为二酐单体,1,3-苯二胺(mPDA)和2,6-二氨基甲苯(2,6-DAT)为二胺单体,采用溶液共缩聚方法合成了一系列新型共聚聚酰亚胺(6FDA-2,6-DAT/mPDA),该类聚合物均能溶于DMF、DMAc、NMP等极性非质子溶剂中,具有较好的成膜性.测试了H2、N2、O2、CH4、CO25种气体在6FDA-2,6-DAT/mPDA共聚聚酰亚胺致密膜中的渗透性能.结果显示,该系列共聚物具有优异的分离性能.在35℃,0.2 MPa下,H2/N2、O2/N2、CO2/CH4的分离性能均接近或突破Robeson上限.

SYNTHESIS,CHARACTERIZATION,AND GAS PERMEATION PROPERTIES OF COPOLYIMIDES

The goal of this work is to explore new polyimide materials that exhibit both a high permeability and a high selectivity for specific gases.Copolyimides offer the possibility of preparing membranes with gas permeabilities and selectivities not obtainable with homopolyimides.A series novel fluorinated copolyimides were synthesized with various diamine compositions by chemical imidization in a two-pot procedure.Polyamic acids were prepared by stoichiometric addition of solid dianhydride in portion wise to the diamine(s).The gas permeation behavior of 2,2′-bis(3,4′-dicarboxyphenyl) hexafluoropropane dianhydride(6FDA)-2,6-diamine toluene(DAT)/1,3-phenylenediamine(mPDA) polyimides were investigated.The physical properties of the copolyimides were characterized by IR,DSC,and TGA.Glass transition temperature increased with increase in DAT content.All the copolyimides were soluble in most of the common solvents.The gas permeabilities coefficients decreased with increasing mPDA content;however,the permselectivity of gas pairs such as H_2/N_2,O_2/N_2,and CO_2/CH_4 was enhanced with the incorporation of mPDA moiety.The permeability coefficients of H_2,O_2,N_2,CO_2 and CH_4 were found to decrease with the increasing order of kinetic diameters of the penetrant gases.6FDA-2,6-DAT/mPDA(3∶1) copolyimide and 6FDA-2,6-DAT polyimide had high separation properties for H_2/N_2,O_2/N_2,CO_2/CH_4.The H_2,O_2 and CO_2 permeabilities were 64.99 Barrer,5.22 Barrer,23.87 Barrer and 81.96 Barrer,8.83 Barrer,39.59 Barrer respectively at 35℃ and 0.2 MPa(1 Barrer=7.5×10~(-14) cm~3(STP)·cm·cm~(-2)·s~(-1)·Pa~(-1));and the ideal selectivities of H_2/N_2,O_2/N_2 and CO_2/CH_4 were 69.61,6.09,63.92 and 53.45,5.76,57.41,respectively.Moreover,all of the copolyimides studied in this work exhibited performance near,lying on or above the existing upper bound trade-off line between permselectivity and permeability.It may be utilized as commercial gas separation membrane material.