Single-sheet type bipolar membrane and preparation method thereof

Abstract

A monolithic bipolar membrane and a preparation method thereof relate to functional polymer membrane materials. The monolithic bipolar membrane includes a cation exchange layer and an anion exchange layer. Preparation method 1: basement membrane pre-irradiation; simultaneous grafting on both sides; sulfonation; quaternization. Preparation method two: basement membrane pre-irradiation; double-sided step-by-step grafting; sulfonation; quaternization. The preparation of bipolar membranes by radiation grafting technology not only saves the film-forming process in the traditional bipolar membrane preparation process, but also does not need to add initiators and catalysts during the grafting process, and the prepared bipolar membranes are very uniform and pure. The steps are simple, and the thermal stability and chemical stability of the film are better. Even if it is used for a long time, there will be no problems such as bubbling and cracking in the middle interface layer that are easy to occur during the use of composite bipolar membranes. Good mechanical properties, thermal stability and chemical stability. Avoid the use of strong carcinogenic reagents such as chloromethyl ether, and reduce the harm to the human body and the environment.

Description

technical field [0001] The invention relates to a functional polymer membrane material, in particular to a monolithic bipolar membrane and a preparation method thereof. Background technique [0002] Bipolar membrane is a special ion exchange membrane, which is composed of anion exchange layer and cation exchange layer, and has a wide range of applications in pollution control, resource recovery, life science, environmental science, energy and many other fields. At present, there are mainly two types of bipolar membranes: composite type and monolithic type. The preparation methods mainly include: 1) hot pressing forming method of anion and cation exchange membrane layers; 2) adhesive forming method of anion and cation exchange membrane layers; 3) one 4) The method of introducing anion and cation exchange groups on both sides of the base film respectively; 5) The method of electrodeposition forming of one film layer on the other film layer. [0003] Radiation grafting technol...

AI Technical Summary

Problems solved by technology

The disadvantages of this preparation method mainly include: 1) because the polymer base film is introduced into polystyrene through the method of soaking and polymerizing for many times, the operation steps are very complicated and the reproducibility is low; 2) the chloromethylation process of this method Chloromethyl ether and other strong carcinogenic chemicals are used in the drug, causing great harm to the environment and human body

Chinese patents CN201010281997.4 and CN201510260096.X have been improved on this basis, wherein Chinese patent CN201010281997.4 adopts a binary blended alloy film of polyethylene and ethylene and octene copolymer elastomer or polyethylene and ethylene and octene The ternary blended alloy film of ethylene copolymer elastomer and polyisobutylene rubber is used as the base film, the crystallinity of the base film is reduced, and a base film with a higher impregnation rate can be obtained after soaking for several hours at a temperature from room temperature to 40 °C , followed by sulfonation, chloromethylation and quaternization on both sides of the membrane to prepare a monolithic bipolar membrane. This method reduces operating steps to a certain extent and can obtain a substrate with a higher impregnation rate. Membrane, so that the final bipolar membrane has a higher ion exchange capacity, but the chloromethylation process still needs to use strong carcinogenic chemicals such as chloromethyl ether, and the bipolar membrane obtained by this method has a chemical Stability and mechanical properties still need to be improved

Chinese patent CN201510260096.X uses polyolefin films as the base film, adopts the method of co-irradiation grafting, grafts styrene on the base film, and then sulfonates, chloromethylates and quaternizes on both sides of the film respectively , to obtain a monolithic bipolar membrane. The bipolar membrane prepared by this method has high mechanical strength and can withstand higher temperatures, and the grafting rate of the membrane can be controlled by controlling the irradiation dose, and then the membrane can be controlled. However, on the one hand, co-irradiation grafting will cause a large amount of monomers to self-polymerize, resulting in waste of monomers; on the other hand, the chloromethylation process still inevitably uses strong carcinogenic chemicals such as chloromethyl ether

This method also has several obvious disadvantages: First, by sandwiching the basement membrane with blotting paper for grafting, compared with directly soaking the basement membrane in the monomer solution, under the same reaction conditions, not only the grafting rate is higher low, and its grafting uniformity is also worse; the second is because the porous material is used as the base membrane, the phenomenon of mutual penetration of the grafted monomers on both sides is difficult to avoid, and the middle interface layer of the bipolar membrane is not clear; the third is The method of co-radiation grafting will cause a large amount of monomers to self-polymerize, and the utilization rate of monomers is very low, which is not suitable for industrial production; Fourth, in order to achieve the required grafting rate, it is usually necessary to clean the grafted membrane and re- Grafting (similar to the above-mentioned U.S. patent for soaking the monomer solution multiple times and polymerizing) increases the number of synthesis steps; the fifth is that under the influence of the grafted monomers, the bipolar membrane made in the paper, whether it is its positive or negative side, its The chemical stability and thermal stability of functional groups with ion exchange capacity are not high, thus greatly limiting their scope of use

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