CN113882087A - Polyimide porous membrane with light absorption property, preparation method thereof and method for dehydrating and concentrating aprotic polar solvent - Google Patents

Polyimide porous membrane with light absorption property, preparation method thereof and method for dehydrating and concentrating aprotic polar solvent Download PDF

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CN113882087A
CN113882087A CN202010617516.6A CN202010617516A CN113882087A CN 113882087 A CN113882087 A CN 113882087A CN 202010617516 A CN202010617516 A CN 202010617516A CN 113882087 A CN113882087 A CN 113882087A
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porous membrane
polyimide porous
membrane
dianhydride
polyimide
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张培斌
崔晶
刘京妮
孙旭阳
陈雪
张宏
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China Petroleum and Chemical Corp
Sinopec Shanghai Research Institute of Petrochemical Technology
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China Petroleum and Chemical Corp
Sinopec Shanghai Research Institute of Petrochemical Technology
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    • C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
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    • C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • C08G73/1085—Polyimides with diamino moieties or tetracarboxylic segments containing heterocyclic moieties
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    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
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Abstract

The invention relates to a polyimide porous membrane with light absorption property, a preparation method thereof and a method for dehydrating and concentrating an aprotic polar solvent. The polyimide porous membrane absorbs part of visible light and ultraviolet light and converts the visible light and the ultraviolet light into heat, and the cut-off wavelength of the whole light absorption area is 370-520 nm. The invention utilizes the light absorption characteristic of the polyimide porous membrane to convert solar energy into heat energy, and further evaporates water in a membrane distillation mode to achieve the purpose of concentrating the aprotic polar solvent. The invention better solves the problem of energy supply in the traditional solvent separation process, and can be used for separating the green aprotic polar solvent from water.

Description

Polyimide porous membrane with light absorption property, preparation method thereof and method for dehydrating and concentrating aprotic polar solvent
Technical Field
The invention relates to the field of membrane separation, in particular to a polyimide porous membrane with light absorption property, a preparation method thereof and a method for dehydrating and concentrating an aprotic polar solvent.
Background
The membrane distillation technology is a membrane separation process driven by transmembrane vapor pressure difference caused by temperature difference, compared with the traditional thermal distillation technology, the required heat supply requirement is lower, the separation can be realized at the temperature far lower than the boiling point of a substance to be separated, the required operation heat source can be provided by solar energy, terrestrial heat, industrial waste heat or waste heat, and the membrane distillation device has low operation pressure and simple equipment, and is expected to become a cheap and efficient separation technology.
The separation membrane required in the membrane distillation process is generally a porous separation membrane which cannot be infiltrated by the components of the separation liquid, only the gaseous phase of the component to be separated can permeate through the two sides of the membrane through diffusion, and capillary condensation does not occur in the process. In the whole separation process, after the separated liquid is heated to a specified temperature, the effective utilization part of energy only exists in the change of the liquid-gas intermolecular phase state generated on the contact side of the liquid and the membrane, and the heat of the solution body is dissipated to the surrounding environment or the transmembrane side through heat conduction, radiation and diffusion, so that the energy waste is caused, and the utilization rate of the energy cannot be further improved.
Disclosure of Invention
In order to improve the utilization rate of energy in the membrane distillation process and further improve and optimize the performance of a membrane material, the invention provides a polyimide porous membrane with light absorption property, a preparation method thereof and an application method in dehydration and concentration of an aprotic polar solvent. The polyimide porous membrane with light absorption performance can absorb sunlight and convert the sunlight into heat, and the energy is transferred only at a contact interface by a separation liquid, the energy dissipation of the separation liquid can be effectively reduced by the delocalized heating mode, the photothermal is converted into sensible heat and latent heat which are directly converted into a solution at the interface, the heat utilization rate is improved, and the effect of a separation barrier is achieved.
The polyimide porous membrane has good solvent resistance, can stably run in the separation process of the aprotic polar solvent and water, and provides a new method for realizing green separation of the aprotic polar solvent and the water by developing and applying the materials.
An object of the present invention is to provide a polyimide porous film having light absorption properties, which absorbs a part of visible light and ultraviolet light and converts them into heat, and has a cutoff wavelength of 370 to 520nm in the entire light absorption region.
The polyimide porous membrane is prepared from diamine monomer with ionization potential less than 7.25eV and dianhydride monomer with electron affinity greater than 1.9 eV.
Wherein the diamine monomer is selected from aromatic biphenyl structure or diamine with hydrogen bond donor-acceptor structure, preferably at least one of p-phenylenediamine, 4' -biphenyldiamine, 2- (diaminophenyl) benzimidazole-5 amine, 2- (4-aminophenyl) -5-aminobenzoxazole, 3' -diaminobenzidine and 4,4' -diaminobenzanilide;
the dianhydride monomer is at least one selected from pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, 4' - (acetylene-1, 2-diyl) diphthalic anhydride, 2,3,6, 7-naphthalene tetracarboxylic dianhydride, 3, 6-difluoro pyromellitic dianhydride and 3, 6-bis-trifluoromethyl pyromellitic dianhydride.
The surface of the polyimide porous membrane is a hydrophobic modified layer modified by a low-surface-energy modifier.
The surface energy of the modifier with low surface energy is less than 20mN/m, and the modifier is preferably at least one of long-chain alkane, fluorine-containing alkane and silicon-containing alkane, more preferably at least one of amino or mercapto long-chain alkane, fluorine-containing alkane and silicon-containing alkane, and most preferably at least one of dodecyl mercaptan, gamma-methacryloxypropyl trimethoxy silane, 1H,2H, 2H-perfluorodecyl amine, polydimethylsiloxane and dodecyl trimethoxy silane.
The thickness of the polyimide porous membrane is 20-200 mu m, the porosity is 40-85%, and the pore size distribution is 0.1-1 mu m; preferably, the porous membrane has a thickness of 50 to 100 μm, a porosity of 50 to 80%, and a pore size distribution of 0.2 to 0.9 μm.
Another object of the present invention is to provide a method for preparing the polyimide porous membrane, comprising the steps of: the preparation method comprises the steps of polymerizing components including diamine monomers and dianhydride monomers, forming a film, performing thermal imidization to obtain the polyimide porous film, and then performing hydrophobic surface modification on the porous film by adopting a low-surface-energy modifier.
Preferably, the preparation method comprises the steps of:
(1) reacting a diamine monomer and a dianhydride monomer to prepare a polyamic acid precursor solution;
(2) obtaining a polyamic acid porous membrane by the precursor solution through an electrostatic spinning or phase separation method;
(3) performing thermal imidization on the polyamic acid porous membrane to obtain a polyimide porous membrane;
(4) and soaking the polyimide porous membrane in the modifier to perform hydrophobic surface modification.
In the technical scheme, the polyimide system with the light absorption characteristic in the step (1) is subjected to electron correlation properties of dianhydride and diamine monomers through quantum chemistry calculation, wherein conformation geometry optimization of dianhydride and diamine is optimized by B3LYP/6-311G (x), electron affinity of dianhydride is calculated by a functional group and a group of w97B/aug-cc-pvtz, ionization potential of diamine is calculated by a functional group and a group of M062x/pvtz, and a combination with strong charge transfer capacity is selected for polymerization to obtain a precursor solution.
The dianhydride monomer is selected from monomers with high electron affinity of more than 1.9eV, and is preferably one or more of pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, 4' - (acetylene-1, 2-diyl) diphthalic anhydride, 2,3,6, 7-naphthalene tetracarboxylic dianhydride, 3, 6-difluoro pyromellitic dianhydride and 3, 6-bis-trifluoromethyl pyromellitic dianhydride.
Wherein the diamine monomer is selected from monomer with small ionization potential, the ionization potential is less than 7.25eV, and monomer with certain rigid structure base is selected, such as aromatic biphenyl structure or diamine with hydrogen bond donor-acceptor structure, preferably one or more of p-phenylenediamine, 4' -biphenyldiamine, 2- (diaminophenyl) benzimidazole-5 amine, 2- (4-aminophenyl) -5-aminobenzoxazole, 3' -diaminobenzidine, and 4,4' -diaminobenzanilide.
In the technical scheme, the molar ratio of anhydride to amine in the polymerization reaction of the dianhydride monomer and the diamine monomer in the step (1) is 0.90-1.10, wherein the preferable molar ratio is 0.95-1.05.
The reaction solvent is a common aprotic polar solvent, and is not limited to dimethylformamide, dimethylacetamide, vinylpyrrolidone, and the like. Wherein the mass ratio of the total mass of the monomers to the solvent is (10: 90) - (20: 80), preferably (12: 88) - (18: 82).
The polyamic acid solution is obtained by polymerization in an inert gas atmosphere, the reaction temperature is 5-50 ℃, the solid content is 10-20%, and the preferred molar ratio of the dianhydride monomer to the diamine monomer is (0.95-1.05): 1.
In the above technical solution, in the step (2), the polyimide porous membrane is prepared by electrospinning or phase separation of the polyamic acid precursor solution, and preferably by needle electrospinning or non-solvent induced phase separation.
The porous film has a thickness of 20-200 μm, a porosity of 40-85%, and a pore size distribution of 0.1-1 μm, wherein the preferable film thickness is 50-100 μm, the porosity is 50-80%, and the pore size distribution is 0.2-0.9 μm.
In the above technical scheme, the porous film in step (3) is imidized by a thermal imidization method to obtain a polyimide porous film having a light absorption characteristic, the ultraviolet-visible light absorption cutoff wavelength of the polyimide porous film is greater than 370nm, and the film can absorb part of visible light and infrared light and convert the visible light and infrared light into heat under the illumination condition.
In the step (3), the temperature of thermal imidization is 300-350 ℃.
In the technical scheme, the porous membrane is subjected to hydrophobic modification in the step (4) so as not to be soaked by the aprotic polar solvent and water, a foundation is provided for the heating, vaporization and diffusion of liquid in the subsequent membrane distillation experiment process, and the separation of components is realized by gas molecules of different solvents through the diffusion rate, so that the aim of dehydration and concentration of the aprotic polar solvent is fulfilled.
In the technical scheme, the porous membrane is subjected to hydrophobic modification, modified molecules with low surface energy are selected, and modification is realized by carrying out nucleophilic reaction on polyimide through carried active groups. The surface energy of the low surface energy modifier is less than 20mN/m, and long-chain alkane, fluorine-containing alkane, silicon-containing alkane and the like are preferred; the modified molecule has active groups with certain alkalinity and nucleophilic groups, preferably amino or sulfhydryl groups, more preferably at least one of amino or sulfhydryl long-chain alkane, fluorine-containing alkane and silicon-containing alkane, and most preferably at least one of dodecyl mercaptan, gamma-methacryloxypropyl trimethoxysilane, 1H,2H, 2H-perfluorodecyl amine, polydimethylsiloxane and dodecyl trimethoxysilane.
In the step (4), the concentration of the modifier is 0.5-15 wt%, preferably 1-10 wt%; the soaking time is 0.2-2 h, preferably 0.5-1.5 h.
The invention also provides a polyimide porous membrane with light absorption property obtained by the preparation method.
The fourth purpose of the invention is to provide a method for dehydrating and concentrating the aprotic polar solvent, which comprises the steps of placing the polyimide porous membrane or the polyimide porous membrane obtained by the preparation method in an aprotic polar solvent aqueous solution to be concentrated, and distilling by light irradiation.
In the technical scheme, the aprotic polar solvent comprises N, N-dimethylformamide, N-dimethylacetamide, N-vinyl pyrrolidone, dimethyl sulfoxide and the like, the solvent has strong interaction with water and can be infinitely dissolved and dissolved, and the conventional method is difficult to realize high-efficiency separation.
The mass ratio of the aprotic solvent to the water is (10: 90) - (90: 10), wherein the preferable condition of high water content has more remarkable separation flux, and the mass ratio of the aprotic solvent to the water is (20: 80) - (50: 50).
In the above technical solution, the distillation process comprises the following steps: after absorbing heat, the components to be separated are vaporized at one side of the membrane, and are diffused to the other side at different rates through the membrane holes, and finally the concentration of the substances at the feeding side is changed, so that the purpose of concentration is realized. The membrane module form for distillation comprises direct contact membrane distillation, air gap membrane distillation, purge air gap membrane distillation, vacuum membrane distillation and the like, wherein air gap membrane distillation, purge air gap membrane distillation or a combination mode of the two is preferred.
According to a preferred embodiment of the present invention, the method for applying the polyimide porous membrane to the dehydration and concentration of an aprotic polar solvent comprises the following steps:
(1) through quantum chemical calculation, selecting a diamine monomer with lower ionization potential to react with a dianhydride monomer with higher electron affinity to prepare a precursor solution polyamic acid of polyimide with light absorption;
(2) electrostatic spinning the precursor solution or adding a pore-forming agent to obtain a polyamic acid porous membrane by a non-solvent induced phase separation method;
(3) performing thermal imidization on the porous membrane to obtain a polyimide porous membrane;
(4) soaking the porous membrane in a hydrophobic modifier in a dip-coating mode to obtain hydrophobic polyimide, and finally performing heat treatment to obtain the hydrophobic modified polyimide porous membrane;
(5) the porous membrane is placed in the aprotic polar solvent aqueous solution to be concentrated, solar energy is converted into heat energy by utilizing the light absorption characteristic of the polyimide porous membrane, and water is further evaporated in a membrane distillation mode, so that the purpose of concentrating the aprotic polar solvent is achieved.
In the technical scheme, the heat required by solvent molecules in the green separation process is obtained through solar illumination, extra energy is not required to be provided, the problem of energy supply in the traditional solvent separation process is well solved, the porous membrane plays a role of a separation barrier, energy conversion is realized, good economic benefits are achieved, the high energy consumption required in the traditional aprotic polar solvent dehydration separation process is solved, and the green and environment-friendly separation process is provided.
The invention mainly aims at the defects of high energy consumption and low efficiency in the separation of an aprotic polar solvent and a polar solvent, and provides a polyimide porous membrane with light absorption and an application method thereof in dehydration and concentration of the aprotic polar solvent. The polyimide porous membrane with the light absorption characteristic is prepared by reacting a diamine monomer with lower ionization potential and a monomer with a certain rigid structure base with a dianhydride monomer with higher electron affinity, and the conversion from light energy to heat energy is realized through the charge transfer of polyimide; the porous membrane is subjected to hydrophobic modification and then used in a membrane distillation process, and the energy of photothermal conversion is transferred on the contact side of a separation liquid and a membrane and undergoes phase change, so that transmembrane diffusion is further performed, and green separation of an aprotic polar solvent and water is realized.
The invention is further illustrated by the following examples.
Drawings
FIG. 1 is a UV-VIS absorption spectrum of the porous film of examples 1-3. The figure is a uv-vis absorption spectrum of a mean film of the same thickness, with the region to the left of the cut-off being the almost fully absorbed region and the region to the right of the cut-off being the partially absorbed region.
Detailed Description
While the present invention will be described in detail with reference to the following examples, it should be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the present invention.
The starting materials used in the embodiments of the present invention are commercially available.
The test equipment and test conditions used in the present invention are:
porosity and average pore diameter of porous film: and testing the relevant data of the membrane pores by using a mercury intrusion instrument, and counting the average pore size distribution and the porosity of the membrane.
Film thickness: the thickness of the porous membrane was measured using a membrane thickness gauge Millimar C1216M. The average thickness and standard deviation of the sample are obtained by measuring 10 different points in the transverse and longitudinal directions of the same film sample.
Testing the light absorption property of the film: the film samples were tested using an ultraviolet-visible spectrophotometer with an integrating sphere. In order to ensure the comparison of ultraviolet light absorption characteristics between the nanofiber membrane and the microporous membrane under different thicknesses, a homogeneous membrane with the same thickness is prepared by blade coating, the ultraviolet-visible light absorption characteristics of the homogeneous membrane are measured, and the influence of the membrane thickness and the pore passage size on the light absorption characteristics is reduced.
Membrane distillation test: and (3) adopting an air gap membrane distillation assembly form, placing the modified polyimide porous membrane on an interface of the liquid to be separated, using 1 solar intensity xenon lamp light source to replace a natural light source for irradiation, and continuously counting evaporation weight reduction and concentration change of the liquid to obtain separation related data.
Testing the wettability of the film: measured by a contact angle tester. And selecting water and diiodomethane as a test solution, measuring to obtain a contact angle, and then calculating to obtain the surface energy of the modified membrane.
Example 1
1. Geometric conformations of dianhydride and diamine are optimized through gaussian 16 software, and electric energy is further calculated to obtain the electron affinity of the dianhydride and the ionization potential of the diamine, wherein the conformational geometric optimization of the dianhydride and the diamine is optimized by B3LYP/6-311G (. + -), the electron affinity of the dianhydride is calculated by using a functional group and a base group of w97B/aug-cc-pvtz, and the ionization potential of the diamine is calculated by using the functional group and the base group of M062 x/pvtz.
2. The electron affinity of pyromellitic dianhydride (PMDA) was calculated to be 2.31eV, and the ionization potential of 2- (diaminophenyl) benzimidazole-5 amine (BIA) was calculated to be 7.0 eV. 14.72g of PMDA and 15.28g of BIA were dissolved in 170.0g of N, N-dimethylformamide (the mass ratio of the monomer to the solvent was 15:85), and the resulting solution was subjected to polymerization reaction at 40 ℃ under a nitrogen atmosphere for 4 hours while stirring to obtain a polyamic acid solution. And (3) spinning the polyamic acid solution on release paper through needle type electrostatic spinning to obtain a polyamic acid film, wherein the thickness of the film is 100 mu m.
3. The polyimide film is taken down from the substrate and put into a hot oven, and then imidized by heat treatment at 350 ℃ to obtain the polyimide film, wherein the porosity of the polyimide film is 75 percent, and the average pore size is 0.88 mu m. The ultraviolet absorption cutoff wavelength of the ultraviolet-visible light scan of the polyimide film was 520 nm.
4. Soaking the polyimide film in an ethanol solution containing 1 wt% of dodecyl mercaptan for 1h, cleaning with ethanol after reaction, and drying to obtain the hydrophobic modified porous membrane, wherein the pure water contact angle of the membrane surface is greater than 120 degrees.
5. Preparing a mixed solution with the mass ratio of N, N-dimethylacetamide to water being 20:80, placing a polyimide porous membrane on the surface of the solution to enable the polyimide porous membrane to float, placing the solution on an electronic balance to continuously count the mass change of the solution, then placing a xenon lamp light source right above the membrane, adjusting a proper distance to enable the illumination intensity received by the position of the membrane to be 1 sun, so as to simulate natural illumination conditions, and adopting a nitrogen gas to sweep the surface of the membrane to form a sweeping air gap membrane distillation assembly.
6. The final evaporation rate of the porous membrane under 1 solar illumination intensity is 0.45kg/m2h, collecting evaporated liquor, wherein the mass ratio of water to N, N-dimethylacetamide is 92:8, and concentrating the original solution after a certain time.
Example 2
1. The dianhydride diamine corresponding parameters were calculated with reference to example 1.
2. The electron affinity of the benzophenone tetracarboxylic dianhydride is calculated to be 2.03eV, and the ionization potential of the p-phenylenediamine is calculated to be 7.20 eV. 22.52g of benzophenonetetracarboxylic dianhydride and 7.48g of p-phenylenediamine were dissolved in 170.0g of N, N-dimethylacetamide (the mass ratio of the monomer to the solvent was 15:85), and the mixture was subjected to polymerization reaction at 25 ℃ under a nitrogen atmosphere and stirred for 6 hours to obtain a polyamic acid solution after the reaction. And (3) spinning the polyamic acid solution on release paper through needle type electrostatic spinning to obtain a polyamic acid film, wherein the thickness of the film is 80 microns.
3. The polyamic acid film was taken off from the glass substrate, placed in a thermal oven, and then imidized by heat treatment at a temperature of 330 ℃ by programming to obtain a polyimide film having a porosity of 70% and an average pore size of 1.0 μm. The ultraviolet absorption cutoff wavelength of the ultraviolet-visible light scan of the polyimide film was 450 nm.
4. The hydrophobic modification was performed with reference to example 1 to obtain a hydrophobic modified porous membrane having a pure water contact angle of 125 ° on the membrane surface.
5. A membrane distillation separation test was conducted with reference to example 1.
6. The final evaporation rate of the porous membrane under 1 sun illumination intensity is 0.32kg/m2h, collecting evaporated liquid, wherein the mass ratio of water to N, N-dimethylacetamide is 90: 10.
Example 3
1. The dianhydride diamine corresponding parameters were calculated with reference to example 1.
2. The electron affinity of 4,4' - (acetylene-1, 2-diyl) diphthalic anhydride was calculated to be 1.92eV, and the ionization potential of 2- (4-aminophenyl) -5-aminobenzoxazole was calculated to be 7.25 eV. 14.05g of 4,4' - (acetylene-1, 2-diyl) diphthalic anhydride and 9.95g of 2- (4-aminophenyl) -5-aminobenzoxazole were dissolved in 176.0g of vinylpyrrolidone (mass ratio of monomer to solvent: 12:88), and the mixture was stirred for 6 hours for polymerization reaction at 40 ℃ under a nitrogen atmosphere, whereby a polyamic acid solution was obtained after the completion of the reaction. And (3) spinning the polyamic acid solution onto release paper through needle type electrostatic spinning to obtain a polyamic acid film, wherein the thickness of the film is 60 mu m.
3. Taking the polyimide film off the substrate, putting the polyimide film into a hot oven, and performing imidization by programmed heating to 350 ℃ for heat treatment to obtain the polyimide film, wherein the porosity of the polyimide film is 75 percent, and the average pore size is 0.88 mu m. The ultraviolet absorption cutoff wavelength of the ultraviolet-visible light scan of the polyimide film was 370 nm.
4. Soaking the polyimide film in an ethanol solution containing 1 wt% of dodecyl mercaptan for 1h, cleaning with ethanol after reaction, and drying to obtain the hydrophobic modified porous membrane, wherein the pure water contact angle of the membrane surface is greater than 120 degrees.
5. A membrane distillation separation test was conducted with reference to example 1.
6. The porous membrane is finally provided inThe evaporation rate is 0.20kg/m under 1 sunlight illumination intensity2h, collecting evaporated liquid, wherein the mass ratio of water to N, N-dimethylacetamide is 88: 12.
Example 4
1. The dianhydride diamine corresponding parameters were calculated with reference to example 1.
2. The ionization potential of 4,4 '-biphenyldiamine was calculated to be 7.04eV, and the ionization potential of 4,4' -diaminobenzanilide was calculated to be 7.20 eV. 15.44g of pyromellitic dianhydride, 6.52g of 4,4 '-biphenyldiamine and 8.04g of 4,4' -diaminobenzenecarboxanilide (wherein the molar ratio of dianhydride monomer to diamine monomer is 2:1:1, respectively, and the mass ratio of monomer to solvent is 15:85) were subjected to polymerization reaction at 25 ℃ under a nitrogen atmosphere and stirred for 4 hours to obtain a polyamic acid solution after the reaction. And (3) spinning the polyamic acid solution on release paper through needle type electrostatic spinning to obtain a polyamic acid film, wherein the thickness of the film is 80 microns.
3. Taking the polyimide film off the substrate, putting the polyimide film into a hot oven, and performing imidization by programmed heating to 350 ℃ for heat treatment to obtain the polyimide film, wherein the porosity of the polyimide film is 85 percent, and the average pore size is 0.80 mu m. The ultraviolet absorption cutoff wavelength of the ultraviolet-visible light scan of the polyimide film was 460 nm.
4. The hydrophobic property-imparting modification of the porous membrane was performed with reference to example 1.
5. A membrane distillation separation test was conducted with reference to example 1.
6. The final evaporation rate of the porous membrane under 1 solar illumination intensity is 0.35kg/m2h, collecting evaporated liquid, wherein the mass ratio of water to N, N-dimethylacetamide is 91: 9.
Example 5
1. The dianhydride diamine corresponding parameters were calculated with reference to example 1.
2. 7.47g of pyromellitic dianhydride, 11.04g of benzophenone tetracarboxylic dianhydride, 3.70g of p-phenylenediamine and 7.79g of 4,4' -diaminobenzanilide are dissolved in N, N-dimethylformamide (wherein the molar ratio of dianhydride monomer to diamine monomer is 1:1:1:1, and the mass ratio of monomer to solvent is 15:85), and the mixture is subjected to polymerization reaction at 25 ℃ for 4 hours under a nitrogen atmosphere and stirred to obtain a polyamic acid solution after the reaction is finished. And (3) spinning the polyamic acid solution on release paper through needle type electrostatic spinning to obtain a polyamic acid film, wherein the thickness of the film is 80 microns.
3. Taking the polyimide film off the substrate, putting the polyimide film into a hot oven, and performing imidization by programmed heating to 350 ℃ for heat treatment to obtain the polyimide film, wherein the porosity of the polyimide film is 80%, and the average pore size is 0.90 mu m. The ultraviolet absorption cutoff wavelength of the ultraviolet-visible light scanning of the polyimide film was 480 nm.
4. The hydrophobic property-imparting modification of the porous membrane was performed with reference to example 1.
5. A membrane distillation separation test was conducted with reference to example 1.
6. The final evaporation rate of the porous membrane under 1 solar illumination intensity is 0.38kg/m2h, collecting evaporated liquid, wherein the mass ratio of water to N, N-dimethylacetamide is 92: 8.
Example 6
1. The dianhydride diamine corresponding parameters were calculated with reference to example 1.
2. The electron affinity of the benzophenone tetracarboxylic dianhydride is calculated to be 2.03eV, and the ionization potential of the p-phenylenediamine is calculated to be 7.20 eV. 22.52g of benzophenonetetracarboxylic dianhydride and 7.48g of p-phenylenediamine were dissolved in 170.0g of N, N-dimethylacetamide (the mass ratio of the monomer to the solvent was 15:85), and the mixture was subjected to polymerization reaction at 25 ℃ under a nitrogen atmosphere and stirred for 6 hours to obtain a polyamic acid solution after the reaction. Adding 6g of polyethylene glycol-400 into the polyamic acid solution, stirring uniformly, then carrying out blade coating on the polyamic acid solution by a scraper, then placing the liquid film in a non-solvent water bath, carrying out a non-solvent induced phase separation process to obtain a polyamic acid film, wherein the thickness of the polyamic acid film is 150 mu m, and soaking the polyamic acid film in water for more than 12h to remove N, N-dimethylformamide and polyethylene glycol additives.
3. The polyamic acid film was taken off from the glass substrate, placed in a hot oven, and then imidized by heat treatment at a temperature of 330 ℃ by programming to obtain a polyimide film having a porosity of 40% and an average pore size of 1.0 μm. The ultraviolet absorption cutoff wavelength of the ultraviolet-visible light scan of the polyimide film was 450 nm.
4. The hydrophobic property-imparting modification of the porous membrane was performed with reference to example 1.
5. A membrane distillation separation test was conducted with reference to example 1.
6. The final evaporation rate of the porous membrane under 1 sun illumination intensity is 0.18kg/m2h, collecting evaporated liquid, wherein the mass ratio of water to N, N-dimethylacetamide is 85: 15.
Example 7
1. The dianhydride diamine corresponding parameters were calculated with reference to example 1.
2. The polymerization was carried out in accordance with example 1 to obtain a polyamic acid solution and form a polyamic acid film.
3. A polyimide film was obtained by imidization in accordance with example 1.
4. Soaking a polyimide film in a mixed solution containing 10 wt% of gamma-methacryloxypropyltrimethoxysilane ethanol and water, wherein the mass ratio of the ethanol to the water is 1:1, adjusting the pH of the solution to 9.0 by using ammonia water, reacting for 0.5h, cleaning and drying by using ethanol after the reaction to obtain a hydrophobic modified porous membrane, and the contact angle of pure water on the surface of the membrane is larger than 130 degrees.
5. A membrane distillation separation test was conducted with reference to example 1.
6. The final evaporation rate of the porous membrane under 1 solar illumination intensity is 0.35kg/m2h, collecting evaporated liquid, wherein the mass ratio of water to N, N-dimethylacetamide is 94: 6.
Example 8
1. The dianhydride diamine corresponding parameters were calculated with reference to example 1.
2. The polymerization was carried out in accordance with example 1 to obtain a polyamic acid solution and form a polyamic acid film.
3. A polyimide film was obtained by imidization in accordance with example 1.
4. Soaking the polyimide film in 5 wt% of 1H,1H,2H, 2H-perfluorodecylamine ethanol solution for 4H, cleaning with ethanol after reaction, and drying to obtain the hydrophobic modified porous membrane, wherein the pure water contact angle of the membrane surface is greater than 135 degrees.
5. A membrane distillation separation test was conducted with reference to example 1.
6. The final evaporation rate of the porous membrane under 1 solar illumination intensity is 0.30kg/m2h, collecting water and N, N in evaporated liquidThe mass ratio of dimethylacetamide to dimethylacetamide is 95: 5.
Example 9
1. The dianhydride diamine corresponding parameters were calculated with reference to example 1.
2. The polymerization was carried out in accordance with example 1 to obtain a polyamic acid solution and form a polyamic acid film.
3. A polyimide film was obtained by imidization in accordance with example 1.
4. The polyimide film was hydrophobically modified with reference to example 1.
5. Membrane distillation experiment an experiment was carried out with reference to example 1, in which the concentration mass ratio of the raw material liquid was changed to 50: 50 parts of N, N-dimethylformamide is mixed with the aqueous solution.
6. The final evaporation rate of the porous membrane under 1 sun illumination intensity is 0.69kg/m2h, collecting evaporated liquid, wherein the mass ratio of water to N, N-dimethylacetamide is 84: 16.
example 10
1. The dianhydride diamine corresponding parameters were calculated with reference to example 1.
2. The polymerization was carried out in accordance with example 1 to obtain a polyamic acid solution and form a polyamic acid film.
3. A polyimide film was obtained by imidization in accordance with example 1.
4. The polyimide film was hydrophobically modified with reference to example 1.
5. Membrane distillation experiment an experiment was performed with reference to example 1, in which the membrane distillation process was changed to an air gap type process.
6. The final evaporation rate of the porous membrane under 1 sun illumination intensity is 0.18kg/m2h, collecting evaporated liquid, wherein the mass ratio of water to N, N-dimethylacetamide is 88: 12.
comparative example 1
1. The corresponding dianhydride and diamine parameters were calculated with reference to example 1.
2. The ionization potential of 4,4' -diaminodiphenyl ether is calculated to be 7.18eV, which accords with the selection of diamine with low ionization potential. 15.57g of pyromellitic dianhydride and 14.43g of 4,4' -diaminodiphenyl ether were dissolved in 170g N, and the solution was reacted and polymerized for 4 hours to obtain a polyamic acid solution, and after the reaction was completed, the polyamic acid solution was obtained. And (3) spinning the polyamic acid solution on release paper through needle type electrostatic spinning to obtain a polyamic acid film, wherein the thickness of the film is 100 mu m.
3. A polyimide film was obtained by imidization in accordance with example 1.
4. The polyimide film was hydrophobically modified with reference to example 1.
5. The film distillation test was conducted in reference to example 1, and it was found that the polyimide film was partially impregnated with the solvent, and the swelling and breakage thereof became gradually worse and the evaporation performance was decreased to disappear.
Comparative example 2
1. The corresponding dianhydride and diamine parameters were calculated with reference to example 1.
2. The combination of dianhydride with low electron affinity and diamine with high ionization potential is obtained by calculation, wherein the electron affinity of hydrogenated pyromellitic dianhydride is 0.13eV, 4,4 '-diamino-2, 2' -bistrifluoromethylbiphenyl is 7.95eV, 12.35g of hydrogenated pyromellitic dianhydride and 17.65g of 4,4 '-diamino-2, 2' -bistrifluoromethylbiphenyl are dissolved in 170g N, and N-dimethylformamide solution is reacted and polymerized for 4h to obtain polyamic acid solution. And (3) spinning the polyamic acid solution on release paper through needle type electrostatic spinning to obtain a polyamic acid film, wherein the thickness of the film is 100 mu m.
3. The imidization was carried out in accordance with example 1 to obtain a polyimide film having an ultraviolet absorption cutoff wavelength of 290nm, i.e., a low absorption of visible light.
4. The polyimide film was hydrophobically modified with reference to example 1.
5. A membrane distillation separation test was conducted with reference to example 1.
6. The final evaporation rate of the porous membrane under 1 solar illumination intensity is 0.08kg/m2h, collecting evaporation liquid, wherein the mass ratio of water to N, N-dimethylacetamide is 82: 18.
The invention utilizes the light absorption characteristic of the polyimide porous membrane to convert solar energy into heat energy, and further evaporates water in a membrane distillation mode to achieve the purpose of concentrating the aprotic polar solvent. The technical scheme of the invention better solves the problem of energy supply in the traditional solvent separation process, and can be used for separating the green aprotic polar solvent from water.

Claims (16)

1. A polyimide porous membrane having light absorption properties, which absorbs part of visible light and ultraviolet light and converts them into heat, and the cutoff wavelength of the entire light absorption region is 370-520 nm.
2. The polyimide porous film according to claim 1, wherein:
the polyimide porous membrane is prepared from diamine monomer with ionization potential less than 7.25eV and dianhydride monomer with electron affinity greater than 1.9 eV.
3. The polyimide porous film according to claim 2, wherein:
the diamine monomer is selected from aromatic biphenyl structure or diamine with hydrogen bond donor-acceptor structure, preferably at least one of p-phenylenediamine, 4' -biphenyldiamine, 2- (diaminophenyl) benzimidazole-5 amine, 2- (4-aminophenyl) -5-aminobenzoxazole, 3' -diaminobenzidine and 4,4' -diaminobenzanilide;
the dianhydride monomer is at least one selected from pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, 4' - (acetylene-1, 2-diyl) diphthalic anhydride, 2,3,6, 7-naphthalene tetracarboxylic dianhydride, 3, 6-difluoro pyromellitic dianhydride and 3, 6-bis-trifluoromethyl pyromellitic dianhydride.
4. The polyimide porous film according to any one of claims 1 to 3, wherein:
the surface of the polyimide porous membrane is a hydrophobic modified layer modified by a low-surface-energy modifier.
5. The polyimide porous film according to claim 4, wherein:
the surface energy of the modifier with low surface energy is less than 20mN/m, and the modifier is preferably at least one of long-chain alkane, fluorine-containing alkane and silicon-containing alkane, more preferably at least one of amino or mercapto long-chain alkane, fluorine-containing alkane and silicon-containing alkane, and most preferably at least one of dodecyl mercaptan, gamma-methacryloxypropyl trimethoxy silane, 1H,2H, 2H-perfluorodecyl amine, polydimethylsiloxane and dodecyl trimethoxy silane.
6. The polyimide porous film according to claim 1, wherein:
the porous membrane has a thickness of 20-200 μm, a porosity of 40-85% and a pore diameter of 0.1-1 μm; preferably, the porous membrane has a thickness of 50 to 100 μm, a porosity of 50 to 80%, and a pore diameter of 0.2 to 0.9 μm.
7. A method for producing a polyimide porous film according to any one of claims 1 to 6, comprising the steps of: the preparation method comprises the steps of polymerizing components including diamine monomers and dianhydride monomers, forming a film, performing thermal imidization to obtain the polyimide porous film, and then performing surface modification on the porous film by using a low-surface-energy modifier.
8. The method for producing a polyimide porous membrane according to claim 7, characterized in that:
the diamine monomer is selected from aromatic biphenyl structure or diamine with hydrogen bond donor-acceptor structure, preferably at least one of p-phenylenediamine, 4' -biphenyldiamine, 2- (diaminophenyl) benzimidazole-5 amine, 2- (4-aminophenyl) -5-aminobenzoxazole, 3' -diaminobenzidine and 4,4' -diaminobenzanilide; and/or the presence of a gas in the gas,
the dianhydride monomer is selected from at least one of pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, 4' - (acetylene-1, 2-diyl) diphthalic anhydride, 2,3,6, 7-naphthalene tetracarboxylic dianhydride, 3, 6-difluoro pyromellitic dianhydride and 3, 6-bis-trifluoromethyl pyromellitic dianhydride; and/or the presence of a gas in the gas,
the modifier with low surface energy is at least one of long-chain alkane, fluorine-containing alkane and silicon-containing alkane, preferably at least one of amino or mercapto long-chain alkane, fluorine-containing alkane and silicon-containing alkane, and more preferably at least one of dodecyl mercaptan, gamma-methacryloxypropyl trimethoxy silane, 1H,2H, 2H-perfluorodecyl amine, polydimethylsiloxane and dodecyl trimethoxy silane.
9. The method for producing a polyimide porous membrane according to claim 7 or 8, characterized by comprising:
(1) reacting a diamine monomer and a dianhydride monomer to prepare a polyamic acid precursor solution;
(2) obtaining a polyamic acid porous membrane by electrostatic spinning or phase separation method of the polyamic acid precursor solution;
(3) performing thermal imidization on the polyamic acid porous membrane to obtain a polyimide porous membrane;
(4) and soaking the polyimide porous membrane in a modifier solution to perform surface modification.
10. The method for producing a polyimide porous membrane according to claim 9, characterized in that:
in the step (1), the molar ratio of anhydride/amine of the dianhydride monomer to the diamine monomer is 0.90-1.10, preferably 0.95-1.05; and/or the presence of a gas in the gas,
the reaction solvent is an aprotic polar solvent, preferably at least one of dimethylformamide, dimethylacetamide and vinylpyrrolidone, wherein the mass ratio of the total mass of the monomers to the solvent is (10: 90) to (20: 80), preferably (12: 88) to (18: 82).
11. The method for producing a polyimide porous membrane according to claim 9, characterized in that:
in the step (3), the temperature of thermal imidization is 300-350 ℃.
12. The method for producing a polyimide porous membrane according to claim 9, characterized in that:
in the step (4), the concentration of the modifier is 0.5-15 wt%, preferably 1-10 wt%;
the soaking time is 0.2-2 h, preferably 0.5-1.5 h.
13. A polyimide porous membrane obtained by the production method according to any one of claims 7 to 12.
14. A method for dehydration concentration of an aprotic polar solvent, which comprises placing the polyimide porous membrane described in any one of claims 1 to 6 or the polyimide porous membrane described in claim 13 in an aqueous solution of an aprotic polar solvent to be concentrated, and distilling by light irradiation.
15. The method of claim 14, wherein:
the aprotic polar solvent is at least one of N, N-dimethylformamide, N-dimethylacetamide, N-vinyl pyrrolidone and dimethyl sulfoxide; and/or the presence of a gas in the gas,
the mass ratio of the aprotic polar solvent to water is (10: 90) to (90: 10), preferably (20: 80) to (50: 50).
16. The method of claim 14, wherein:
the membrane module form of distillation comprises at least one of contact membrane distillation, air gap membrane purging distillation and vacuum membrane distillation, and preferably air gap membrane distillation and/or air gap membrane purging distillation.
CN202010617516.6A 2020-07-01 2020-07-01 Polyimide porous membrane with light absorption property, preparation method thereof and method for dehydrating and concentrating aprotic polar solvent Pending CN113882087A (en)

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Citations (4)

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JPH10239841A (en) * 1997-02-28 1998-09-11 Toray Ind Inc Photosensitive polyimide precursor composition
CN104014259A (en) * 2014-05-27 2014-09-03 中国科学院过程工程研究所 Preparation method of hydrophobic separating membrane
CN105273189A (en) * 2015-10-29 2016-01-27 阜新泓扬光电材料有限公司 Transparent polyimide film having ultraviolet obstruction function as well as preparation and application thereof
CN110387040A (en) * 2019-07-17 2019-10-29 中国科学院上海硅酸盐研究所 A kind of black polyamide film

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10239841A (en) * 1997-02-28 1998-09-11 Toray Ind Inc Photosensitive polyimide precursor composition
CN104014259A (en) * 2014-05-27 2014-09-03 中国科学院过程工程研究所 Preparation method of hydrophobic separating membrane
CN105273189A (en) * 2015-10-29 2016-01-27 阜新泓扬光电材料有限公司 Transparent polyimide film having ultraviolet obstruction function as well as preparation and application thereof
WO2017071643A1 (en) * 2015-10-29 2017-05-04 武汉依麦德新材料科技有限责任公司 Transparent polyimide film with ultraviolet (uv) blocking function, preparation and use thereof
CN110387040A (en) * 2019-07-17 2019-10-29 中国科学院上海硅酸盐研究所 A kind of black polyamide film

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