Application of temperature-sensitive composite material in preparation of separation membrane, nanofiltration membrane and preparation method

Abstract

The application provides application of a temperature-sensitive composite material in preparation of a separation membrane, a nanofiltration membrane and a preparation method, and particularly relates to the technical field of separation membranes. The temperature-sensitive composite material comprises a temperature-sensitive material and conductive fillers. The mass ratio of the temperature-sensitive material and the conductive fillers is 10-30:1-10. The application utilizes the characteristic that the temperature-sensitive material quickly responds to temperature changes, and the temperature-sensitive material transmits to the outside world through the conductive fillers, so that timely feedback and adjustment of the temperature in the preparation process of the separation membrane are realized, the isotropic separation membrane is prepared, the stability of the performance of the separation membrane is ensured, and the quality of the separation membrane product is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of separation membranes, in particular to application of a temperature-sensitive composite material in preparation of a separation membrane, a nanofiltration membrane and a preparation method. BACKGROUND

[0002] Under the background of resource recycling and sustainable development, membrane technology shows great potential in ecological friendliness. Due to the advantages of low energy consumption, easy operation and scalability of separation membranes, membrane separation technology has developed rapidly in the past few decades, and organic membranes have dominated the separation membrane market due to their good mechanical properties, scalable preparation and relatively low production cost.

[0003] Membrane separation technology has been widely used in various industries, such as circulating water, seawater desalination, purification and clean energy production and gas separation. Among various methods for preparing separation membranes, interfacial polymerization technology is easier to control the size and thickness of the film, and the pore structure of the synthesized film is uniform, which has obvious advantages in application fields such as adsorption, catalysis and energy storage. The most important large-scale application of interfacial polymerization technology is in the preparation of ultra-thin composite membranes, including nanofiltration, reverse osmosis, gas separation, etc.

[0004] Interfacial polymerization technology refers to the irreversible condensation reaction of two high-reactivity monomers dissolved in two mutually insoluble solvents at the interface of the two phases. During the membrane preparation process, although there are temperature control measures at key positions such as water phase tank and platform area, the temperature control equipment can only control the temperature of the polymerization reaction according to the temperature in the equipment, and cannot truly obtain the polymerization temperature of the interfacial polymerization layer. Therefore, the temperature change at the interface caused by water phase volatilization and external environment cannot be accurately fed back to the temperature control equipment, affecting the desalination effect and the performance stability, and the change of the actual water / oil phase monomer concentration on the surface of the base film with the change of the season will cause large fluctuations in product performance. The actual temperature during interfacial polymerization affects the diffusion kinetics speed of water / oil phase, and also affects the initial thermodynamic speed of the reaction, ultimately affecting the crosslinking degree of the condensation reaction, so that the permeation amount and impurity removal rate of the formed interfacial polymerization layer become uncontrollable.

[0005] Therefore, the present application is proposed. SUMMARY

[0006] One of the purposes of the present application is to provide an application of a temperature-sensitive composite material in preparation of a separation membrane, aiming to solve the technical problem of uncontrollable performance of separation membrane products caused by uncontrollable temperature of interfacial polymerization in the preparation process of the separation membrane in the prior art.

[0007] The second purpose of the present application is to provide a nanofiltration membrane.

[0008] The third purpose of the present application is to provide a preparation method of a nanofiltration membrane.

[0009] In order to achieve the above object of the present application, the following technical solutions are adopted:

[0010] The first aspect of the present application provides an application of a temperature-sensitive composite material in preparing a separation membrane, wherein the temperature-sensitive composite material comprises a temperature-sensitive material and a conductive filler.

[0011] Further, the mass ratio of the temperature-sensitive material and the conductive filler is 10-30:1-10.

[0012] Preferably, the temperature-sensitive material comprises at least one of polylactic acid, poly-N-isopropyl acrylamide, polystyrene, polyurethane, acrylonitrile-butadiene-styrene copolymer, polycarbonate, polycaprolactone, polyethylene oxide and polyvinyl chloride.

[0013] Preferably, the conductive filler comprises at least one of polyacetylene and its derivatives, polypyrrole and its derivatives, polythiophene and its derivatives, poly-p-phenylenevinylene and its derivatives and polyaniline and its derivatives.

[0014] Preferably, the particle size of the conductive filler is 5nm-20nm.

[0015] Further, the separation membrane comprises a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, a reverse osmosis membrane, a pervaporation membrane or an ion exchange membrane.

[0016] The second aspect of the present application provides a nanofiltration membrane comprising a porous support layer, a temperature-sensitive modification layer and an interfacial polymerization layer arranged in layers.

[0017] Among the temperature-sensitive modification layer, a temperature-sensitive composite material is included.

[0018] Further, the thickness of the porous support layer is 10-50μm, the average pore size is 10-100nm and the porosity is 20-70%.

[0019] Preferably, the thickness of the temperature-sensitive modification layer is 1-5μm, the average pore size is 5-50nm and the porosity is 10-50%.

[0020] Preferably, the thickness of the interfacial polymerization layer is 10-100nm, the average pore size is 0.5-2nm and the porosity is 10-50%.

[0021] The third aspect of the present application provides a preparation method of a nanofiltration membrane, comprising the following steps:

[0022] A. The temperature-sensitive composite material is made into a slurry, and a slit extrusion quantitative coating process is adopted to coat the porous support layer, and a nanofiltration membrane semi-finished product with a temperature-sensitive modification layer arranged on the porous support layer is obtained by drying in a first oven.

[0023] B. coating a water phase solution on one side surface of the nanofiltration membrane semi-product, removing the excess water phase solution on the surface using a nitrogen air knife, then coating an oil phase solution on the surface of the water phase solution, and placing it in a second oven equipped with an infrared temperature probe; the infrared temperature probe is arranged on the temperature-sensitive modification layer to measure the temperature of the surface of the temperature-sensitive modification layer, and a nanofiltration membrane is obtained after drying.

[0024] Further, the infrared temperature probe is arranged on at least three points, left, middle and right, in the width direction of the temperature-sensitive modification layer.

[0025] Preferably, in step B, the drying temperature is 30-90°C, and the drying time is 40-120s.

[0026] Further, in step A, the slurry comprises the following components in terms of mass percentage: 10-30% of temperature-sensitive material, 1-10% of conductive filler, 1-3% of additive, and the balance is solvent.

[0027] Preferably, the additive comprises at least one of ketones, alcohols, a mixture of polyvinyl alcohol with different molecular weights, and a mixture of polyvinylpyrrolidone with different molecular weights.

[0028] Preferably, the molecular weight of the ketone is 30-98;

[0029] Preferably, the ketone comprises at least one of n-propanone, isopropanone, methyl ketone, butanone, and cyclohexanone.

[0030] Preferably, the molecular weight of the alcohol is 32-60;

[0031] Preferably, the alcohol comprises at least one of methanol, ethanol, isopropanol, and n-propanol.

[0032] Preferably, the solvent comprises at least one of dimethylformamide, dimethylacetamide, and dimethyl sulfoxide.

[0033] Further, in step A, the preparation method of the slurry is to first disperse the conductive filler uniformly in the solvent, then add the temperature-sensitive material and the additive and stir uniformly to obtain.

[0034] Further, in step A, in the slot extrusion quantitative coating process, the coating speed is 2-20 m / min, and the coating amount is 10-500 mL / min.

[0035] Preferably, in step A, the drying temperature is 40-80°C.

[0036] Compared with the prior art, the present application has at least the following beneficial effects:

[0037] The application provides application of the temperature-sensitive composite material in preparation of a separation membrane, utilizes the characteristic that the temperature-sensitive material quickly responds to temperature change, transmits to the outside world through the conductive filler, realizes timely feedback and adjustment of temperature in the preparation process of the separation membrane, is beneficial to preparation of an isotropic separation membrane, guarantees stability of performance of the separation membrane, and improves quality of the separation membrane product.

[0038] The nanofiltration membrane provided by the application is mainly composed of a porous support layer, a temperature-sensitive modification layer and an interfacial polymerization layer, the temperature-sensitive modification layer provides good hydrophilicity to improve permeability of the nanofiltration membrane, and can also make the porous support layer and the interfacial polymerization layer be well "riveted" together, improve the bonding force between the porous support layer and the interfacial polymerization layer, solve the problem that the nanofiltration membrane cannot be back-flushed, and prolong the service life of the nanofiltration membrane. Meanwhile, the temperature-sensitive modification layer provides timely temperature feedback, enhances the controllability of interfacial polymerization, is beneficial to obtaining a nanofiltration membrane with uniform performance, isotropy and better stability. And in production, different degrees of interfacial polymerization layers are prepared through temperature control, are matched with different porous support layers and temperature-sensitive modification layers, different specifications of nanofiltration membranes are obtained, product diversification is realized, different application scenarios are met, and the development of the nanofiltration membrane industry is promoted.

[0039] The preparation method of the nanofiltration membrane provided by the application is simple in process, high in mechanization degree, large in product batch processing capacity, and suitable for industrialized production. DETAILED DESCRIPTION

[0040] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the specific embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0041] Figure 1 SEM image of the surface morphology of the polyethylene microporous membrane used for Example 3;

[0042] Figure 2 SEM image of the surface of the nanofiltration membrane semi-finished product obtained in Example 3;

[0043] Figure 3 SEM image of the cross section of the nanofiltration membrane semi-finished product obtained in Example 3;

[0044] Figure 4 SEM image of the surface of the nanofiltration membrane obtained in Example 3. DETAILED DESCRIPTION

[0045] In order to make the objects, technical solutions and advantages of the present application clearer, the following will be combined with the accompanying drawings of the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application.

[0046] Hereinafter, the terms "include", "have", and their conjugations, used in various embodiments of the present application, are only intended to denote a certain characteristic, number, step, operation, element, component, or a combination of the foregoing, and should not be construed to exclude the existence or possibility of adding one or more other characteristics, numbers, steps, operations, elements, components, or combinations thereof.

[0047] In addition, the terms "first", "second", "third", and the like are only used to distinguish descriptions, and should not be understood as indicating or implying relative importance.

[0048] The first aspect of the present application provides an application of a temperature-sensitive composite material in preparing a separation membrane, wherein the temperature-sensitive composite material comprises a temperature-sensitive material and a conductive filler.

[0049] The application of the temperature-sensitive composite material in preparing a separation membrane provided by the present application utilizes the characteristic that the temperature-sensitive material quickly responds to temperature changes, and transmits to the outside world through the conductive filler, so as to realize timely feedback and adjustment of the temperature in the preparation process of the separation membrane, which is conducive to preparing an isotropic separation membrane, ensures the stability of the performance of the separation membrane, and improves the quality of the separation membrane product.

[0050] Further, the mass ratio of the temperature-sensitive material to the conductive filler is 10-30:1-10. When the mass ratio of the temperature-sensitive material to the conductive filler is less than 10:10, the amount of the conductive filler increases, and the amount of the temperature response substance decreases, so it is difficult to achieve sensitive sensing of the temperature; when the mass ratio of the temperature-sensitive material to the conductive filler is greater than 30:1, the amount of the temperature-sensitive material is too much, and the amount of the conductive filler is insufficient, so it is difficult to accurately and losslessly transmit the temperature change and to realize precise temperature control.

[0051] In some embodiments of the present application, the mass ratio of the temperature-sensitive material to the conductive filler is typically but not limited to 10:1, 10:5, 10:10, 20:1, 20:5, 20:10, 30:1, 30:5, or 30:10.

[0052] Preferably, the temperature-sensitive material comprises at least one of polylactic acid, poly N-isopropyl acrylamide, polystyrene, polyurethane, acrylonitrile-butadiene-styrene copolymer, polycarbonate, polycaprolactone, polyethylene oxide, and polyvinyl chloride.

[0053] Preferably, the conductive filler includes at least one of polyacetylene and its derivatives, polypyrrole and its derivatives, polythiophene and its derivatives, poly-p-phenylenevinylene and its derivatives, and polyaniline and its derivatives.

[0054] Preferably, the conductive filler has a particle size of 5 nm to 20 nm, which is conducive to uniform distribution of the conductive filler, so that the conductive filler forms a conductive network and can respond to changes in external temperature. In some embodiments of the present application, the particle size of the conductive filler is typically, but not limited to, 5 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, or 20 nm.

[0055] Further, the separation membrane includes a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, a reverse osmosis membrane, a pervaporation membrane, or an ion exchange membrane.

[0056] In the microfiltration membrane, a functional skin layer is formed by phase inversion, and the application of the temperature-sensitive composite material in the microfiltration membrane can control the phase inversion speed through the temperature-sensitive material, so as to realize the preparation of functional layers with different pore sizes.

[0057] In the ultrafiltration membrane, a functional skin layer is formed by phase inversion, and the application of the temperature-sensitive composite material in the ultrafiltration membrane can control the phase inversion speed through the temperature-sensitive material, so as to realize the preparation of functional layers with different pore sizes.

[0058] In the nanofiltration membrane, a polyamide separation layer is formed by interfacial polymerization, and the application of the temperature-sensitive composite material in the nanofiltration membrane can control the crosslinking degree of the polyamide separation layer through the temperature-sensitive composite material, so as to realize the preparation of nanofiltration membranes with different separation efficiencies.

[0059] In the reverse osmosis membrane, a polyamide separation layer is formed by interfacial polymerization, and the application of the temperature-sensitive composite material in the reverse osmosis membrane can control the crosslinking degree of the polyamide separation layer through the temperature-sensitive composite material, so as to realize the preparation of reverse osmosis membranes with different desalination rates.

[0060] In the pervaporation membrane, a functional skin layer is formed by phase inversion, and the application of the temperature-sensitive composite material in the pervaporation membrane can control the phase inversion speed through the temperature-sensitive material, so as to improve the uniformity of the pervaporation membrane.

[0061] In the ion exchange membrane, a functional layer is formed by slurry polymerization, and the application of the temperature-sensitive composite material in the ion exchange membrane can control the polymerization speed through the temperature-sensitive material, so as to improve the uniformity of the ion exchange membrane.

[0062] The second aspect of the present application provides a nanofiltration membrane including a porous support layer, a temperature-sensitive modification layer, and an interfacial polymerization layer arranged in layers.

[0063] The temperature-sensitive modification layer includes the temperature-sensitive composite material.

[0064] The nanofiltration membrane provided by the application is mainly composed of a porous support layer, a temperature-sensitive modification layer and an interfacial polymerization layer, the temperature-sensitive modification layer provides good hydrophilicity to improve the permeability of the nanofiltration membrane, and can also make the porous support layer and the interfacial polymerization layer be well "riveted" together, improve the bonding force of the porous support layer and the interfacial polymerization layer, solve the problem that the nanofiltration membrane cannot be back-flushed, and prolong the service life of the nanofiltration membrane. Meanwhile, the temperature-sensitive modification layer provides timely temperature feedback, enhances the controllability of interfacial polymerization, is conducive to obtaining a nanofiltration membrane with uniform performance, isotropy and better stability. And in production, the preparation of the interfacial polymerization layer with different polymerization degrees is realized through temperature control, and different specifications of nanofiltration membranes are obtained by matching different porous support layers and temperature-sensitive modification layers, the diversification of products is realized, different application scenarios are met, and the development of the nanofiltration membrane industry is promoted.

[0065] In some embodiments of the application, the material of the porous support layer is typically but not limited to one of cellulose acetate (CA), polyvinylidene fluoride (PVDF), polysulfone (PSf), polyacrylonitrile (PAN), polypropylene (PP) and polyethylene (PE). Polyethylene as a support layer material obtains a polyethylene base layer with uniform pores, high surface porosity, excellent solvent resistance and mechanical properties.

[0066] The porous support layer is an important component of the nanofiltration membrane, and provides a transmission channel for water and solutes. Moreover, the surface structure (pore size, porosity, roughness, etc.) and physicochemical properties (surface hydrophilicity or hydrophobicity, surface charge, etc.) of the support layer affect the formation process of the interfacial polymerization layer, thereby affecting the performance of the membrane.

[0067] Further, the thickness of the porous support layer is 10-50 μm, the average pore size is 10-100 nm, and the porosity is 20-70%.

[0068] Preferably, the thickness of the temperature-sensitive modification layer is 1-5 μm, the average pore size is 5-50 nm, and the porosity is 10-50%.

[0069] Preferably, the thickness of the interfacial polymerization layer is 10-100 nm, the average pore size is 0.5-2 nm, and the porosity is 10-50%.

[0070] In some embodiments of the present application, the thickness of the porous support layer in the nanofiltration membrane is 10-30 μm, the average pore size is 50-100 nm, and the porosity is 50-70%; the thickness of the temperature-sensitive modification layer is 1-2 μm, the average pore size is 30-50 nm, and the porosity is 30-50%; and the thickness of the interfacial polymerization layer is 10-30 nm, the average pore size is 0.8-1.5 nm, and the porosity is 30-50%. The nanofiltration membrane has good permeability and is suitable for application in seawater / brackish water desalination pretreatment.

[0071] In some embodiments of the present application, the thickness of the porous support layer in the nanofiltration membrane is 10-30 μm, the average pore size is 50-100 nm, and the porosity is 50-70%; the thickness of the temperature-sensitive modification layer is 1-2 μm, the average pore size is 30-50 nm, and the porosity is 30-50%; and the thickness of the interfacial polymerization layer is 10-30 nm, the average pore size is 0.8-1.5 nm, and the porosity is 30-50%. The nanofiltration membrane has good permeability and is suitable for application in seawater / brackish water desalination pretreatment.

[0072] In some embodiments of the present application, the thickness of the porous support layer in the nanofiltration membrane is 10-30 μm, the average pore size is 50-100 nm, and the porosity is 50-70%; the thickness of the temperature-sensitive modification layer is 1-2 μm, the average pore size is 30-50 nm, and the porosity is 30-50%; and the thickness of the interfacial polymerization layer is 10-30 nm, the average pore size is 0.8-1.5 nm, and the porosity is 30-50%. The nanofiltration membrane has good permeability and is suitable for application in seawater / brackish water desalination pretreatment.

[0073] In some embodiments of the present application, the thickness of the porous support layer in the nanofiltration membrane is 10-30 μm, the average pore size is 50-100 nm, and the porosity is 50-70%; the thickness of the temperature-sensitive modification layer is 1-2 μm, the average pore size is 30-50 nm, and the porosity is 30-50%; and the thickness of the interfacial polymerization layer is 10-30 nm, the average pore size is 0.8-1.5 nm, and the porosity is 30-50%. The nanofiltration membrane has good permeability and is suitable for application in seawater / brackish water desalination pretreatment.

[0074] The third aspect of the present application provides a preparation method of a nanofiltration membrane, comprising the following steps:

[0075] A. The temperature-sensitive composite material is made into a slurry, and a slit extrusion quantitative coating process is used to coat the porous support layer to obtain a nanofiltration membrane semi-finished product with a temperature-sensitive modification layer arranged on the porous support layer under a first drying oven.

[0076] B. coating a water phase solution on one side surface of the nanofiltration membrane semi-product, removing the excess water phase solution on the surface using a nitrogen air knife, then coating an oil phase solution on the surface of the water phase solution, and placing it in a second oven equipped with an infrared temperature probe; the infrared temperature probe is arranged on the temperature-sensitive modification layer to measure the temperature of the surface of the temperature-sensitive modification layer, and a nanofiltration membrane is obtained after drying.

[0077] The preparation method of the nanofiltration membrane provided by the application has simple process, high degree of mechanization, large batch processing capacity of products, and is suitable for industrial production.

[0078] The slit extrusion quantitative coating process is to feed a certain flow of slurry from the feeding port of the extrusion head into the internal cavity of the die, and form a stable pressure, and finally the slurry is uniformly sprayed at the outlet of the die slit and coated on the porous support layer.

[0079] Further, the preparation process of the water phase solution is as follows: 1wt.%-2wt.% of piperazine, 2.2wt.%-2.5wt.% of camphor sulfonic acid, and 0.02wt.%-0.05wt.% of polyvinyl alcohol (pre-heated and stirred to dissolve at 70-80℃) are sequentially added to pure water, then stirred at 35℃-45℃ for 1-2 hours, and then left to stand for 1-2 hours to obtain the water phase solution.

[0080] Further, the preparation process of the oil phase solution is as follows: 0.1wt.%-1.0wt.% of trimesoyl chloride is added to a pure n-hexane solution, magnetically stirred at room temperature for 1 hour, and then left to stand for 1 hour to obtain the oil phase solution.

[0081] Further, the infrared temperature probe is arranged on at least three points, left, middle and right, in the width direction of the temperature-sensitive modification layer. When the width of the nanofiltration membrane product is less than 0.5m, at least three infrared temperature probes are arranged equidistantly in the width direction to ensure uniform polymerization degree in all directions. When the width of the nanofiltration membrane product exceeds 0.5m, at least five infrared temperature probes are arranged equidistantly in the width direction to ensure uniform polymerization degree in all directions.

[0082] Preferably, in step B, the drying temperature is 30℃-90℃, and the time is 40s-120s. It should be noted that the drying temperature here is the temperature of the interfacial polymerization reaction, and the temperature set for the second oven may be higher than this temperature.

[0083] In some embodiments of the application, the drying temperature is typically but not limited to 30℃, 40℃, 50℃, 60℃, 70℃, 80℃ or 90℃; and the time is 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s or 120s.

[0084] Further, in step A, the slurry comprises the following components by mass percentage: 10-30% of the temperature-sensitive material, 1-10% of the conductive filler, 1-3% of the additive, and the rest is solvent.

[0085] In some embodiments of the present application, the mass percentage of the temperature-sensitive material in the slurry is typically but not limited to 10%, 15%, 20%, 25%, or 30%; the mass percentage of the conductive filler is typically but not limited to 1%, 3%, 5%, 8%, or 10%; the mass percentage of the additive is typically but not limited to 1%, 2%, or 3%, and the rest is solvent.

[0086] Preferably, the additive comprises at least one of ketones, alcohols, a mixture of polyvinyl alcohol with different molecular weights, and a mixture of polyvinylpyrrolidone with different molecular weights.

[0087] The additive used in the present application is a hydrophilic substance, which is distributed on the surface of the temperature-sensitive modification layer to provide anchor points for the binding of the interfacial polymerization layer. These additives are cross-linked and solidified at the same time as the water phase and oil phase in the interfacial polymerization layer, thereby improving the mechanical strength, resistance, and selective permeability of the nanofiltration membrane.

[0088] Preferably, the molecular weight of the ketone is 30-98;

[0089] Preferably, the ketone comprises at least one of n-propanone, isopropanone, methyl ketone, butanone, and cyclohexanone.

[0090] Preferably, the molecular weight of the alcohol is 32-60;

[0091] Preferably, the alcohol comprises at least one of methanol, ethanol, isopropyl alcohol, and n-propanol.

[0092] Preferably, the solvent comprises at least one of dimethylformamide, dimethylacetamide, and dimethyl sulfoxide.

[0093] Further, in step A, the preparation method of the slurry is to first uniformly disperse the conductive filler in the solvent, and then add the temperature-sensitive material and the additive to stir uniformly.

[0094] Further, in step A, in the slot extrusion and metering coating process, the coating speed is 2-20 m / min, and the coating amount is 10-500 mL / min.

[0095] The coating speed affects the density and production efficiency of the temperature-sensitive modification layer. In actual production, the coating speed and the coating amount are selected according to the thickness, average pore size and porosity of the temperature-sensitive modification layer. In some embodiments of the present application, the coating speed is typically but not limited to 2 m / min, 6 m / min, 10 m / min, 14 m / min, 18 m / min or 20 m / min; and the coating amount is typically but not limited to 10 mL / min, 50 mL / min, 100 mL / min, 200 mL / min, 300 mL / min, 400 mL / min or 500 mL / min.

[0096] Preferably, in step A, the drying temperature is 40-80°C.

[0097] In some embodiments of the present application, the drying temperature is typically but not limited to 40°C, 50°C, 60°C, 70°C or 80°C.

[0098] The present application is further illustrated by specific examples and comparative examples below, but it should be understood that these examples are only for a more detailed illustration and should not be understood as limiting the present application in any form. In the examples and comparative examples of the present application, the raw materials used are not specified, and the conventional conditions or the conditions recommended by the manufacturer are used. The reagents or instruments used are not specified, and are all conventional products that can be purchased on the market.

[0099] Example 1

[0100] This example provides a nanofiltration membrane, specifically comprising the following steps:

[0101] 1. Disperse polypyrrole (Sigma, 30604-81-0) in N,N-dimethylformamide (DMF) and ultrasonic treat at 70°C for 30 min to obtain a polypyrrole solution; then add polylactic acid (BASF, PLA130), polyvinylpyrrolidone (K30) and isopropanol to the polypyrrole solution and stir at 70°C for 120 min to obtain a slurry. In the slurry, the polypyrrole content is 1 wt.%, the polylactic acid content is 10 wt.%, the polyvinylpyrrolidone content is 1 wt.% and the isopropanol content is 5 wt.%.

[0102] 2. Spray the slurry prepared in step 1 on a polyethylene microporous membrane (Jiangsu Houshen New Energy Technology Co., Ltd., 0.2 microns) using a slot die coating process, control the coating speed to be 5 m / min and the coating amount to be 100 mL / min, and dry at a temperature of 60°C to obtain a nanofiltration membrane semi-finished product by solvent evaporation phase inversion.

[0103] 3. Prepare a piperazine aqueous solution with a concentration of 10 g / L as the aqueous phase solution, and prepare a ParG (paraffin mixed solvent) solution of trimesoyl chloride with a concentration of 2 g / L as the oil phase solution. Dip coat the aqueous phase solution on the semi-finished product of the nanofiltration membrane (dipping time is controlled to be 10-30 s), remove the excess aqueous phase solution on the surface using a nitrogen knife, then coat the oil phase solution on the surface, and place it in a second oven equipped with an infrared temperature probe. The infrared temperature probe is S11-5 from Germany Opus, and the detection range is 10-100°C with an accuracy of ±1°C. Three infrared temperature probes are arranged at the left, middle and right points in the width direction of the membrane. The temperature of the second oven is set so that the temperature detected by the infrared temperature probe is controlled at 40°C for 100 s to obtain the nanofiltration membrane.

[0104] Example 2

[0105] This example provides a nanofiltration membrane, which is different from Example 1 in that the polypyrrole content in the slurry of step 1 is 2 wt.%, and the remaining raw materials and methods are the same as those in Example 1, which are not described here again.

[0106] Example 3

[0107] This example provides a nanofiltration membrane, which is different from Example 1 in that the polypyrrole content in the slurry of step 1 is 5 wt.%, and the remaining raw materials and methods are the same as those in Example 1, which are not described here again.

[0108] Example 4

[0109] This example provides a nanofiltration membrane, which is different from Example 1 in that the polypyrrole content in the slurry of step 1 is 10 wt.%, and the remaining raw materials and methods are the same as those in Example 1, which are not described here again.

[0110] Example 5

[0111] This example provides a nanofiltration membrane, which is different from Example 3 in that in step 2, the coating amount is 50 mL / min, and the drying temperature is 60°C, and the remaining raw materials and steps are the same as those in Example 3, which are not described here again.

[0112] Example 6

[0113] This example provides a nanofiltration membrane, which is different from Example 3 in that in step 2, the coating amount is 200 mL / min, and the drying temperature is 60°C, and the remaining raw materials and steps are the same as those in Example 3, which are not described here again.

[0114] Example 7

[0115] This example provides a nanofiltration membrane, which is different from Example 3 in that in step 2, the coating amount is 100 mL / min, and the drying temperature is 40°C, and the remaining raw materials and steps are the same as those in Example 3, which are not described here again.

[0116] Example 8

[0117] This example provides a nanofiltration membrane, different from example 3, in step 3, the temperature detected by the infrared temperature probe is controlled at 50℃, the rest of the raw materials and steps are the same as example 3, and will not be repeated here.

[0118] Example 9

[0119] This example provides a nanofiltration membrane, different from example 3, in step 3, the temperature detected by the infrared temperature probe is controlled at 60℃, the rest of the raw materials and steps are the same as example 3, and will not be repeated here.

[0120] Example 10

[0121] This example provides a nanofiltration membrane, different from example 3, in step 3, the temperature detected by the infrared temperature probe is controlled at 70℃, the rest of the raw materials and steps are the same as example 3, and will not be repeated here.

[0122] Example 11

[0123] This example provides a nanofiltration membrane, different from example 3, in step 3, the temperature detected by the infrared temperature probe is controlled at 80℃, the rest of the raw materials and steps are the same as example 3, and will not be repeated here.

[0124] Example 12

[0125] This example provides a nanofiltration membrane, different from example 3, in step 3, the reaction temperature is directly controlled by the second oven, and the infrared temperature probe is cancelled, the rest of the raw materials and steps are the same as example 3, and will not be repeated here.

[0126] Example 13

[0127] This example provides a nanofiltration membrane, different from example 3, in step 3, the reaction temperature is directly controlled by the second oven, and one infrared temperature probe is set at the midpoint of the width direction of the membrane, the rest of the raw materials and steps are the same as example 3, and will not be repeated here.

[0128] Comparative Example 1

[0129] This comparative example provides a nanofiltration membrane, a piperazine aqueous solution with a concentration of 10g / L is prepared as the water phase solution, and a trimesoyl chloride n-hexane solution with a concentration of 2g / L is prepared as the oil phase solution. The water phase solution is coated on the nanofiltration membrane semi-finished product, and the excess water phase solution on the surface is removed using a nitrogen knife, then the oil phase solution is coated on the surface, and placed in an oven, kept at 40℃ for 100s to obtain a nanofiltration membrane.

[0130] Comparative Example 2

[0131] The comparative example provides a nanofiltration membrane, which is different from the comparative example 1 in that the temperature of the oven is 60°C for 100s, and the rest of the method and raw materials are the same as those of the comparative example 1, which will not be repeated here.

[0132] Test example 1

[0133] The nanofiltration membranes provided by the examples 1-13 and the comparative examples 1-2 are tested for physical properties, including nanofiltration membrane thickness, average pore size and porosity tests, and the results are shown in Table 1 below.

[0134] Table 1 Nanofiltration membrane physical parameter table

[0135]

[0136] As can be seen from Table 1, within a certain range, as the ratio of conductive material to temperature-sensitive material in the modification solution increases, the average pore size and PEG-200 rejection rate of the composite nanofiltration membrane increase, the porosity decreases, and the functional layer thickness does not change significantly; when the ratio of conductive material to temperature-sensitive material is too large, the average pore size becomes larger. The amount of modification solution coating affects the functional layer thickness, average pore size and PEG-200 rejection rate, and a suitable coating amount is required, and 100 mL / min is preferred (as can be seen from comparative examples 3, 5 and 6). Within a certain range, increasing the interfacial polymerization temperature can increase the crosslinking degree, thereby realizing small pore size, high organic rejection and thin desalination layer. Compared with the comparative examples 1 and 2, the nanofiltration membrane obtained by the temperature-sensitive modification process has a small pore size, high organic rejection and thin desalination layer.

[0137] Test example 2

[0138] The surface morphology of the polyethylene microporous membrane used in example 3 is observed by SEM, and the obtained photos are shown in Figure 1 .

[0139] As can be seen from Figure 1 , the surface of the polyethylene microporous membrane presents a tensile crack-like pore, the pore size distribution is 50-200 nm, the bubble point pore size is about 50 nm, and the surface pore size distribution is relatively wide, mainly due to the molding process.

[0140] The surface and cross-section of the nanofiltration membrane semi-finished product obtained in example 3 are observed by SEM, and the obtained photos are shown in Figure 2 and Figure 3 .

[0141] As can be seen from Figure 2 and Figure 3 , the surface of the nanofiltration membrane semi-finished product is smooth, the membrane pores are significantly reduced, and the cross-section shows a clear temperature-sensitive modification layer.

[0142] The surface of the nanofiltration membrane obtained in example 3 is observed by SEM, and the obtained photos are shown inFigure 4 As shown.

[0143] From Figure 4 It can be seen that the nanofiltration membrane surface presents a microvesicle structure function layer, which can effectively increase the specific surface area.

[0144] Test Example 3

[0145] The nanofiltration membranes provided by Examples 1-13 and Comparative Examples 1-2 were subjected to filtration performance detection, and the desalination rate and water production of NaCl solution and MgSO4 solution were tested respectively. The prepared solution was used as the test solution, the pH value of the test solution was adjusted to 7, the membrane cross-flow test device was used, the cross-flow flow rate was 3.5 L / min, and the flux and salt retention rate of the membrane were tested after pre-pressing for 30 min. The concentration of NaCl solution was 500 ppm, the temperature was 25℃, and the test pressure was 60 psi. The concentration of MgSO4 solution was 2000 ppm, the temperature was 25℃, and the test pressure was 70 psi.

[0146] The desalination rate and water production are shown in Table 2.

[0147] Table 2 Desalination rate and water production data table

[0148]

[0149] As can be seen from Table 2, within a certain range, as the ratio of conductive material to temperature-sensitive material in the modification solution increases, the sodium chloride and magnesium sulfate retention rates of the composite nanofiltration membrane increase, and the flux decreases; when the ratio of conductive material to temperature-sensitive material is too large, the retention of the two salts becomes larger instead. The amount of modification solution coating affects the desalination of sodium chloride and magnesium sulfate and the flux, and an appropriate coating amount is required, and in this case, 100 mL / min is preferred (as can be seen from Comparative Examples 3, 5 and 6). Within a certain range, increasing the interfacial polymerization temperature can increase the crosslinking degree, thereby improving the desalination of sodium chloride and magnesium sulfate. Compared with Comparative Examples 1 and 2, the desalination and water production of the nanofiltration membrane caused by the temperature-sensitive modification process in Case 3 are higher.

[0150] Test Example 4

[0151] The nanofiltration membranes provided by Examples 3, Comparative Examples 1-2 and polyethylene microporous membranes were subjected to uniformity detection, and the desalination rate and water production of NaCl solution and MgSO4 solution were tested for the nanofiltration membranes taken from three positions of left, middle and right in the width direction of the nanofiltration membrane during preparation.

[0152] The prepared solution was used as the test solution, the pH value of the test solution was adjusted to 7, the membrane cross-flow test device was used, the cross-flow flow rate was 3.5 L / min, and the flux and salt retention rate of the membrane were tested after pre-pressing for 30 min.

[0153] The concentration of NaCl solution is 500 ppm, the temperature is 25°C, and the test pressure is 60 psi. The concentration of MgSO4 solution is 2000 ppm, the temperature is 25°C, and the test pressure is 70 psi.

[0154] The desalination rate and water production are shown in Table 3 below.

[0155] Table 3 Desalination rate and water production data table

[0156]

[0157] As can be seen from Table 3, the magnesium sulfate and sodium chloride flux and desalination uniformity of the nanofiltration membranes prepared in Comparative Examples 1 and 2 are both ±7 LMH, and the desalination deviation is ±1.0%, which affects the use stability and tolerance. The flux deviation of the nanofiltration membrane prepared in Example 3 using the new temperature-sensitive modification process is ±2 LMH, and the desalination deviation is ±0.2%, which effectively improves the uniformity.

[0158] Test Example 5

[0159] The nanofiltration membranes provided in Example 3, Comparative Examples 1-2 were made into 1812 membrane elements for stability testing. The prepared solution was used as the test liquid, the pH value of the test liquid was adjusted to 7, a cross-flow test device was used, the cross-flow flow rate was 3.5 L / min, and the pre-pressing time was 30 min. The long-term life evaluation was then performed. The concentration of MgSO4 solution was 2000 ppm, the temperature was 25°C, and the test pressure was 70 psi. The long-term operation was performed according to 30% recovery, and the MgSO4 rejection rate and water flux GPD are shown in Table 4 below.

[0160] Table 4 MgSO4 rejection rate and water flux GPD data table

[0161]

[0162] As can be seen from Table 4, the nanofiltration membrane element prepared in Example 3 using the new temperature-sensitive modification process was continuously operated for 30 d, and the water production and desalination rate did not change significantly; the nanofiltration membrane element prepared in Comparative Examples 1 and 2 was continuously operated for 30 d, and the desalination rate decreased by ≥2.0% and the water production decreased by >10%.

[0163] Finally, it should be noted that the above-described embodiments are merely specific embodiments of the present application, which are used to illustrate the technical solutions of the present application, but not to limit the same. The protection scope of the present application is not limited thereto. Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that any person skilled in the art can still modify or easily think of changes to the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to some of the technical features, within the technical scope disclosed by the present application. The modifications, changes or replacements do not cause the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for producing a nanofiltration membrane, characterized by, The method comprises the following steps: A. A temperature-sensitive composite material is made into a slurry, which is coated on a porous support layer by using a slit extrusion quantitative coating process, dried under a first oven to obtain a nanofiltration membrane semi-finished product provided with a temperature-sensitive modification layer on the porous support layer; B. A water phase solution is coated on one side surface of the nanofiltration membrane semi-finished product, the excess water phase solution on the surface is removed by using a nitrogen air knife, then an oil phase solution is coated on the surface of the water phase solution, and then placed in a second oven provided with an infrared temperature probe; the infrared temperature probe is arranged on the temperature-sensitive modification layer and used for measuring the temperature of the surface of the temperature-sensitive modification layer, and a nanofiltration membrane is obtained after drying. The temperature-sensitive composite material comprises a temperature-sensitive material and a conductive filler.

2. The production method according to claim 1, characterized by, The mass ratio of the temperature-sensitive material to the conductive filler is 10-30:1-10.

3. The production method according to claim 1, characterized by, The temperature-sensitive material comprises at least one of polylactic acid, poly-N-isopropyl acrylamide, polystyrene, polyurethane, acrylonitrile-butadiene-styrene copolymer, polycarbonate, polycaprolactone, polyethylene oxide and polyvinyl chloride.

4. The method of claim 1, wherein, The conductive filler comprises at least one of polyacetylene and its derivatives, polypyrrole and its derivatives, polythiophene and its derivatives, poly-p-phenylenevinylene and its derivatives and polyaniline and its derivatives.

5. The preparation method according to claim 1, characterized in that, The particle size of the conductive filler is 5 nm-20 nm.

6. The method of claim 1, wherein, The nanofiltration membrane comprises a porous support layer, a temperature-sensitive modification layer and an interfacial polymerization layer arranged in layers. The temperature-sensitive modification layer comprises a temperature-sensitive composite material.

7. The production method according to claim 6, wherein The thickness of the porous support layer is 10-50 mu m, the average pore size is 10-100 nm, and the porosity is 20%-70%.

8. The preparation method according to claim 6, characterized in that, The thickness of the temperature-sensitive modification layer is 1-5 mu m, the average pore size is 5-50 nm, and the porosity is 10%-50%.

9. The preparation method according to claim 6, characterized in that, The thickness of the interfacial polymerization layer is 10-100 nm, the average pore size is 0.5-2 nm, and the porosity is 10%-50%.

10. The method of claim 1, wherein, The infrared temperature probe is arranged on at least three points, i.e., left, middle and right, in the width direction of the temperature-sensitive modification layer.

11. The method of claim 1, wherein, In step B, the drying temperature is 30-90 DEG C, and the time is 40-120 s.

12. The method of claim 1, wherein, In step A, the slurry comprises the following components in terms of mass percentage: temperature-sensitive material 10%-30%, conductive filler 1%-10%, additive 1%-3%, and the balance is solvent.

13. The method of claim 12, wherein, The additive comprises at least one of ketones, alcohols, a mixture of polyvinyl alcohol with different molecular weights and a mixture of polyvinylpyrrolidone with different molecular weights.

14. The method of claim 13, wherein, The molecular weight of the ketone is 30-98.

15. The preparation method according to claim 13, characterized in that, The ketone comprises at least one of n-propanone, isopropanone, methyl ketone, butanone and cyclohexanone.

16. The method of claim 13, wherein, The molecular weight of the alcohol is 32-60.

17. The method of claim 13, wherein, The alcohol comprises at least one of methanol, ethanol, isopropyl alcohol and n-propanol.

18. The method of claim 12, wherein, The solvent comprises at least one of dimethylformamide, dimethylacetamide and dimethyl sulfoxide.

19. The method of claim 12, wherein, In step A, the preparation method of the slurry is to uniformly disperse the conductive filler in the solvent, then add the temperature-sensitive material and the additive and stir uniformly.

20. The method of any one of claims 1-19, wherein, In step A, the coating speed in the slit extrusion coating process is 2 m / min-20 m / min, and the coating amount is 10 mL / min-500 mL / min.

21. The method of any one of claims 1-19, wherein, In step A, the temperature of drying is 40°C-80°C.

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