Large-scale fabrication technique for PIM-1 asymmetric membranes doped with low-molecular-weight polyethylene glycol for gas separation

A fabrication technique for PIM-1 asymmetric membranes doped with polyethylene glycol for gas separation, comprising the following steps:

• 1) adding polyethylene glycol into a PIM-1 casting solution for phase inversion, and controlling the additive amount of polyethylene glycol within a concentration range of 0.1-4.0 wt %, wherein polyethylene glycol molecular weight is between 400 and 1500 Dalton, and one of the molecular chain end groups is hydroxyl group;
• and then, forming a plate-like PIM-1 asymmetric membrane structure through dry/wet phase inversion, with a dense layer on one side and a porous support layer on the other side;
• 2) moving the PIM-1 asymmetric membrane structure formed in the first step into a nonsolvent coagulation environment constituted with water for a retention time of 2-6 hours, so that the solvent for membrane casting is removed from the PIM-1 asymmetric membrane structure;
• transferring the PIM-1 asymmetric membrane structure from the nonsolvent coagulation environment to an atmospheric environment, and simultaneously spraying an aqueous solution of polyethylene glycol which has a concentration range of 2.0-5.0 wt % on the surface on the side of porous support layer, wherein polyethylene glycol molecular weight is between 400 and 1500 Dalton;
• keeping the dihedral angle between gravitational direction and transmembrane direction larger than 60 degrees for the PIM-1 asymmetric membrane structure during spraying process, so that the adhesion amount of polyethylene glycol solution on the PIM-1 asymmetric membrane structure is controlled by gravity;
• 3) transferring the PIM-1 asymmetric membrane structure which has been sprayed with polyethylene glycol solution on one side to an oven with directional water evaporation ability, wherein the PIM-1 asymmetric membrane structure is outspreaded;
• making the side of the dense layer of the PIM-1 asymmetric membrane structure enter the oven environment specified with sub-atmospheric pressure and heating functions;
• controlling the vacuum degree and temperature to be respectively in the ranges of 0-20 kPa and 40-80° C. to promote water evaporation on the side of the dense layer;
• making the side of the porous support layer enter the oven environment specified with humidification and cooling functions;
• controlling relative humidity and temperature to be respectively in the ranges of 80-100% and 20-35° C. to inhibit water evaporation on the side of the porous support layer;
• through directional water evaporation and the resultant capillary action, realizing the directional migration and enrichment of polyethylene glycol from the porous support layer to the dense layer in the PIM-1 asymmetric membrane structure;
• 4) after directional migration and enrichment with polyethylene glycol, transferring the PIM-1 asymmetric membrane structure into a vacuum oven for dehydration;
• controlling the vacuum degree and temperature to be within the ranges of 0-80 kPa and 60-120° C. respectively, and the dehydration time to be not less than 8.0 hours;
• through conducting dehydration, inhibiting the migration of polyethylene glycol, accomplishing the large-scale fabrication of a PIM-1 asymmetric membrane with polyethylene glycol controllably doped in the dense layer for gas separation.