Search

CN-121972005-A - Preparation method of polyimide organic solvent nanofiltration membrane

CN121972005ACN 121972005 ACN121972005 ACN 121972005ACN-121972005-A

Abstract

The invention relates to the technical field of nanofiltration of organic solvents, in particular to a preparation method of a polyimide organic solvent nanofiltration membrane. The preparation method comprises the steps of preparing polyamide acid resin slurry as casting solution, enabling the casting solution to be solidified on non-woven fabrics to form a film, immersing the obtained film in deionized water, immersing the obtained film in imidizing agent to react to generate polyimide, immersing the obtained film in deionized water, immersing the polyimide film in solution containing cross-linking agent, and washing to obtain the polyimide organic solvent nanofiltration membrane. The organic solvent nanofiltration membrane has higher flux and interception performance in polar organic solvents, has long-term stability in common organic solvents such as alcohols, ketones, esters, hydrocarbons and the like, has long-term stability in strong polar aprotic solvents such as DMF, DMAc, NMP, DMSO and the like, and has potential application value in the fields of chemical industry, pharmacy, food and the like.

Inventors

  • FAN HUAZHONG
  • WANG ZHILIANG
  • YANG TAO
  • WU ZONGCE
  • JIN YAN

Assignees

  • 沃顿科技股份有限公司

Dates

Publication Date
20260505
Application Date
20260227

Claims (10)

  1. 1. The preparation method of the polyimide organic solvent nanofiltration membrane is characterized by comprising the following steps of: (1) The polyamide acid resin solution is coated on non-woven fabrics in a scraping way, and then is immediately immersed into a coagulating bath for curing to form a film, wherein the scraping speed is 100-300 mm/s, and the coagulating bath is a mixed bath of water and DMAc; (2) Placing the solidified polyamide acid film into an imidization reagent for soaking to obtain a polyimide film, wherein the soaking temperature is 0-100 oC, and the soaking time is 2-10 minutes; (3) And (3) soaking the polyimide film in a solution containing a cross-linking agent to obtain the polyimide organic solvent nanofiltration membrane, wherein the concentration of the cross-linking agent is 1-20 wt%, the cross-linking reaction temperature is 20-60 oC, and the cross-linking reaction time is 3-20 minutes.
  2. 2. The method for preparing a polyimide organic solvent nanofiltration membrane as claimed in claim 1, wherein the polyamic acid resin solution is obtained by copolymerization of diamine monomer and dianhydride monomer in a polar solvent; the diamine monomer is selected from one or more of p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, 1, 3-cyclohexanediamine, 4' -diaminodiphenyl methane, 4' -diaminodiphenyl ether, 3,4' -diaminodiphenyl ether, 4' -diaminodiphenyl sulfone, 2' -bis [4- (4-aminophenoxyphenyl) ] propane, diphenyl diamine, 4' -diaminodiphenyl sulfide and 4-phenyl-2, 6-bis (4-aminophenyl) pyridine; the dianhydride monomer is selected from one or more of pyromellitic dianhydride, 3', 4' -biphenyl tetracarboxylic dianhydride, 3', 4' -diphenyl ether tetracarboxylic dianhydride, 3', 4' -benzophenone tetracarboxylic dianhydride, bisphenol A dianhydride and bisphenol F dianhydride, preferably, the diamine monomer is 4,4' -diamino diphenyl methane, and the dianhydride monomer is pyromellitic dianhydride; the polar solvent is one or more of DMF, DMAc, NMP, DMSO.
  3. 3. The method for preparing a polyimide organic solvent nanofiltration membrane according to claim 1, wherein the concentration of the polyamic acid is 10-30 wt%, and the viscosity of the polyamic acid is 5000-25000 cp.
  4. 4. The method for preparing a polyimide organic solvent nanofiltration membrane as claimed in claim 2, wherein the viscosity of the polyamic acid is 15000-20000 cp.
  5. 5. The method for preparing a polyimide organic solvent nanofiltration membrane according to claim 2, wherein the concentration of water in the coagulation bath is 70-99 wt%, the temperature of the coagulation bath is 0-30 oC, and the coagulation time is 10-30 minutes.
  6. 6. The preparation method of the polyimide organic solvent nanofiltration membrane as claimed in claim 1, wherein the imidizing agent consists of a dehydrating agent and an accelerator according to the molar ratio of the dehydrating agent to the accelerator=9:1-5:5, wherein the dehydrating agent is one or more selected from trifluoroacetic anhydride, acetic anhydride, propionic anhydride, aromatic monocarboxylic acid anhydride and acetyl chloride, and the accelerator is one or more selected from pyridine, p-pyrroline, lutidine, collidine, quinoline, isoquinoline, triethylamine and N, N-dimethylethanolamine.
  7. 7. The preparation method of the polyimide organic solvent nanofiltration membrane as claimed in claim 1, wherein the dehydrating agent is acetic anhydride or propionic anhydride, the promoter is pyridine or triethylamine, and the molar ratio of the dehydrating agent to the promoter is 8:2.
  8. 8. The method for preparing a polyimide organic solvent nanofiltration membrane as claimed in claim 1, wherein the soaking temperature is 30-60 oC ℃ in the step (2).
  9. 9. The method for preparing the polyimide organic solvent nanofiltration membrane according to claim 1, wherein the cross-linking agent is selected from one or more of ethylenediamine, 1, 2-propylenediamine, 1, 3-propylenediamine, 1, 4-butylenediamine, 1, 5-pentylenediamine, 1, 6-hexamethylenediamine, 1, 8-octylenediamine, 1, 9-nonylenediamine, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, m-xylylenediamine, p-xylylenediamine, furandiamine, 1, 5-naphthylenediamine, 2, 6-naphthylenediamine, anthracene-2, 6-diamine and diethylenetriamine, and the solvent of the cross-linking agent solution is one or more of water, methanol, ethanol and isopropanol.
  10. 10. The method for preparing a polyimide organic solvent nanofiltration membrane according to claim 1 or 8, wherein the crosslinking agent is 1, 6-hexamethylenediamine or p-xylylenediamine.

Description

Preparation method of polyimide organic solvent nanofiltration membrane Technical Field The invention relates to the technical field of nanofiltration of organic solvents, in particular to a preparation method of a polyimide organic solvent nanofiltration membrane. Background Organic solvent nanofiltration (Organic Solvent Nanofiltration, OSN), also known as solvent resistant nanofiltration (Solvent Resistant Nanofiltration, SRNF), enables efficient screening of small molecular compounds with molecular weights of 200-1000 Da in organic solvents. Compared with the traditional operations such as distillation, adsorption, extraction and the like, the OSN has the advantages of (1) low energy consumption requirement, (2) low solid waste generation (compared with solid waste generated by silica gel and adsorbents for chromatographic analysis), (3) mild operation conditions without extreme temperature and pressure, (4) clear amplification process path, easy realization of large-scale expansion, (5) strong stability in severe chemical environment, flexible operation in wide pH value, temperature and solvent selection range, and (6) convenient switching between low boiling point and boiling point solvents. The organic solvent nanofiltration membrane is the core of OSN, and an ideal OSN membrane should be able to maintain good chemical, thermal and mechanical stability over a wide range of organic solvents while exhibiting excellent solvent permeation flux and solute rejection. The current commercialized OSN film is mainly divided into two major categories of ceramic film and polymer film, wherein the ceramic film has high mechanical strength, good chemical and thermal stability, no swelling in organic solvent, high pressure resistance, easy cleaning and the like. However, ceramic membranes are brittle, difficult to process and form, and expensive, which are not conducive to scale-up production and application. In contrast, polymer films have the advantages of good flexibility, easy processing and forming, low price and the like, and are more interesting OSN film materials. The polymer materials currently available for preparing OSN membranes mainly comprise Polyimide (PI), polyacrylonitrile (PAN), polyetheretherketone ((PEEK), polydimethylsiloxane (PDMS), polyamide (PA), polyvinyl alcohol (PVA), sulfonated Polysulfone (SPS), sulfonated Polyethersulfone (SPES), cellulose Acetate (CA) and derivatives thereof, etc., wherein PI is one of the most studied membrane materials in OSN fields due to its various structures, excellent mechanical properties and good solvent resistance, PI is classified into soluble PI (e.g., P84, matrimid) and insoluble PI (e.g., PMDA-based PI, BTDA-based PI, etc.), PI-based OSN membranes currently commercialized are all prepared from soluble PI, such as PuraMem membrane and MetMem membrane of DuPont, which are proposed by Evonik-MET, but only few enterprises in the united states can produce soluble PI at present, so raw materials are very expensive and raw material sources are limited. Compared with soluble PI, most PI is insoluble, the variety of the PI is tens, and the PI is more widely available and cheaper. Limited by poor solubility, insoluble PI is typically first prepared as a soluble polyamic acid, phase converted to a film, and then imidized. Cao Bing and Li Yuan et al, take Kapton as the most commonly used insoluble PI as an example, spin the polyamic acid hollow fiber, and then chemically imidize to prepare a hollow fiber membrane for OSN, wherein the molecular weight cut-off of the membrane in DMF is about 800 Da, the flux can reach 2.51 L.m-2.h-1.bar-1（Journal of Membrane Science, 2017, 544, 1-11; Applied Surface Science, 2019, 473, 1038-1048）., but the method is complex to operate, and a pore-forming agent and a double coagulating bath are required, so that the difficulty of practical production is increased. Furthermore, as a glassy polymer, OSN films made by Kapton lack resistance to swelling and long-term stability in use. The patent with publication number CN 104817707A discloses a preparation method of a high-flux polyimide nanofiltration membrane, which comprises the steps of changing the structure of the polyamide acid membrane by carrying out polyamide acid crystallization or doping inorganic nano particles at low temperature, and then gradually heating to 350 oC to cause the polyamide acid membrane to carry out thermal imidization, thus finally obtaining the polyimide nanofiltration membrane with high flux and high retention rate. However, this method is cumbersome to operate and takes at least several hours, and in addition, poor compatibility between the inorganic nanoparticles and the organic polymer solution makes it difficult to obtain a uniform nanofiltration membrane. In addition, patent publication numbers CN 115505123B, CN 106883431B, CN 113019136A and the like disclose methods for forming polyimide films by imidizing polyamide acid, but polyimide films obtained