A polyimide nanofiltration membrane prepared based on synergistic imidization and method thereof

Abstract

The invention discloses a polyimide nanofiltration membrane prepared on the basis of synergic imidization and a method thereof. The method comprises the following steps: carrying out chemical imidization to implement synthesis of partial polyimide, forming a membrane, and carrying out hot imidization to rearrange the pore structure. The two imidization synergic processes are carried out to obtain the nanofiltration membrane. The method disclosed by the invention is simple and easy to implement, and does not relate to grafting and other complex reactions. The prepared polyimide nanofiltration membrane has the advantages of higher strength, higher solvent resistance and higher nanofiltration separating capacity. The membrane pores are in an asymmetric structure, and the membrane pore canals are developed, thereby solving the problem that the high-performance nanofiltration membrane can not be prepared by the single imidization process. The prepared polyimide nanofiltration membrane can be reused.

Description

technical field [0001] The invention relates to a preparation method of a polyimide nanofiltration membrane, in particular to a polyimide nanofiltration membrane prepared by synergistic imidization and a method thereof. Background technique [0002] Polyimide (abbreviated as PI) is a kind of functional high temperature resistant polymer. Polyimide has outstanding heat resistance and superior mechanical properties, and also has excellent thermal stability, radiation resistance and dielectric properties. , oxidation stability and chemical resistance. It is widely used in heat-resistant materials and aerospace equipment, and other aspects include electronic packaging materials for electronic information, high-tech industries, viscose, engineering plastics, and photoresists. However, while polyimide material has its excellent performance, it also has obvious deficiencies, which are mainly manifested as not melting under ordinary heating and insoluble in common organic solvents,...

AI Technical Summary

Problems solved by technology

[0005] Two kinds of insoluble polyimide and soluble polyimide can be prepared by the above-mentioned imidization method. The performance of polyimide, especially the solubility, is closely related to the molecular structure of the monomer. The conventional aromatic diamine monomer ( Such as ODA, PMDA, PDA) generally have a symmetrical structure and no substituted side groups, so that the corresponding polyimide is often insoluble, which brings great difficulties to its processing and molding, especially difficult to prepare a comprehensive Separation membrane with excellent performance

In order to improve the processing performance of polyimide, flexible structural units, side groups or side chains are often introduced into the monomer through molecular design to destroy the repeat regularity and symmetry of the molecular chain and improve its solubility. Many reports involve the preparation of soluble polyimide, but the effect of the invention is only that the prepared material has solubility, and does not involve the preparation of nanofiltration membranes, but nanofiltration membranes are prepared from soluble polyimide polymers Often involves complex craftsmanship or creative labor

[0006] The method for preparing polyimide nanofiltration membrane includes two types of common schemes, one is by means of polyamic acid prepolymer and thermal imidization, but the polyimide nanofiltration membrane prepared by this scheme has the following disadvantages: (1) A single thermal imidization process involves high-temperature reactions, which will lead to negative effects such as brittleness and rupture of the film, which is obviously detrimental to the mechanical properties of the film, affecting the practical performance of the film, and the reusability of the film is also limited. (2) A single chemical imidization method is not suitable for this scheme, because in the chemical imidization process, it is necessary to add imidization reagent to the uniform polyamic acid solution and mix well, obviously, in this scheme , since the polyamic acid prepolymer has already formed a film, it does not meet the conditions for uniform mixing

[0007] The second is to use soluble polyimide as the membrane material to prepare polyimide nanofiltration membranes by means of grafting and cross-linking. However, this scheme involves reactions such as grafting and cross-linking, and there are many modifiers. complex process, etc., and is different from the strategy for preparing nanofiltration membranes based on imidization involved in the present invention

[0008] In addition, with the help of a single chemical imidization, although polyimide polymers with excellent comprehensive properties can be prepared, this single method is difficult to prepare polyimide nanofiltration membranes, because polyimide nanofiltration membranes In addition to requiring an imidized structure in terms of molecular structure, there are also higher requirements for pore structure

Images