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

Abstract

The present disclosure provides the use of a temperature-sensitive composite material in the preparation of a separation membrane, and a nanofiltration membrane and a preparation method, and in particular relates to the technical field of separation membranes. The temperature-sensitive composite material comprises a temperature-sensitive material and a conductive filler, wherein the mass ratio of the temperature-sensitive material to the conductive filler is 10-30 : 1-10. The present disclosure utilizes the characteristic whereby the temperature-sensitive material quickly responds to a temperature change which is transmitted to the outside through the conductive filler, thereby achieving timely feedback and adjustment of the temperature during the preparation process of a separation membrane, facilitating the preparation of an isotropic separation membrane, ensuring the stability of the performance of the separation membrane, and improving the quality of a separation membrane product.

Description

Application of temperature-sensitive composite materials in preparation of separation membranes, nanofiltration membranes and preparation methods

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The present disclosure claims priority to Chinese patent application number “2023108224194” filed with the Patent Office of China on July 5, 2023, entitled “Application of temperature-sensitive composite materials in the preparation of separation membranes, nanofiltration membranes and preparation methods”, the entire contents of which are incorporated by reference into the present disclosure. Technical Field

[0003] The present disclosure relates to the technical field of separation membranes, and in particular to an application of a temperature-sensitive composite material in the preparation of separation membranes, a nanofiltration membrane, and a preparation method thereof. Background Art

[0004] In the context of resource recovery and sustainable development, membrane technology has shown great potential in eco-friendliness. Due to its advantages such as low energy consumption, ease of operation, and scalability, membrane separation technology has developed rapidly over the past few decades. Organic membranes, with their excellent mechanical properties, scalable preparation, and relatively low production costs, dominate the separation membrane market.

[0005] Membrane separation technology has been widely adopted across various industries, including circulating water and seawater desalination and purification, clean energy generation, and gas separation. Among various methods for preparing separation membranes, interfacial polymerization (IP) facilitates the control of membrane size and thickness, and the resulting membranes exhibit a uniform pore structure, offering significant advantages in applications such as adsorption, catalysis, and energy storage. The most important large-scale application of interfacial polymerization is in the preparation of ultrathin composite membranes, such as those used in nanofiltration, reverse osmosis, and gas separation.

[0006] Interfacial polymerization involves two highly reactive monomers dissolved in two immiscible solvents, each undergoing an irreversible polycondensation reaction at the interface between the two phases. During the membrane production process, although temperature control measures are implemented at key locations such as the aqueous phase tank and platform area, these devices can only control the polymerization temperature based on the device's internal setpoint and cannot accurately measure the polymerization temperature of the interfacial polymerization layer. Temperature fluctuations at the interface, caused by factors such as aqueous volatilization and the external environment, cannot be accurately fed back to the temperature control device, impacting both desalination efficiency and performance stability. Furthermore, seasonal variations in the actual aqueous / oil phase monomer concentrations on the base membrane surface can lead to significant fluctuations in product performance. The actual temperature during interfacial polymerization affects the diffusion kinetics of the aqueous / oil phase, as well as the initial thermodynamic rate of the reaction, ultimately affecting the degree of crosslinking in the polycondensation reaction. This can make the permeability of the resulting interfacial polymerization layer and the impurity removal rate uncontrollable.

[0007] Summary of the Invention

[0008] The present disclosure 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.

[0009] Optionally, the mass ratio of the temperature-sensitive material to the conductive filler is 10-30:1-10.

[0010] Optionally, the temperature-sensitive material includes at least one of polylactic acid, poly (N-isopropylacrylamide), polystyrene, polyurethane, acrylonitrile-butadiene-styrene copolymer, polycarbonate, polycaprolactone, polyethylene oxide and polyvinyl chloride.

[0011] Optionally, the conductive filler includes at least one of polyacetylene and its derivatives, polypyrrole and its derivatives, polythiophene and its derivatives, poly(p-phenylene vinylene) and its derivatives, and polyaniline and its derivatives.

[0012] Optionally, the (average) particle size of the conductive filler is 5 nm-20 nm.

[0013] Optionally, 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.

[0014] The present disclosure also provides a nanofiltration membrane, comprising a porous support layer, a temperature-sensitive modification layer, and an interfacial polymerization layer arranged in a stacked manner;

[0015] Wherein, the temperature-sensitive modification layer includes the temperature-sensitive composite material.

[0016] Optionally, the temperature-sensitive composite material includes a temperature-sensitive material and a conductive filler.

[0017] Optionally, the mass ratio of the temperature-sensitive material to the conductive filler is 10-30:1-10.

[0018] Optionally, the temperature-sensitive material includes at least one of polylactic acid, poly (N-isopropylacrylamide), polystyrene, polyurethane, acrylonitrile-butadiene-styrene copolymer, polycarbonate, polycaprolactone, polyethylene oxide and polyvinyl chloride.

[0019] Optionally, the conductive filler includes at least one of polyacetylene and its derivatives, polypyrrole and its derivatives, polythiophene and its derivatives, poly(p-phenylene vinylene) and its derivatives, and polyaniline and its derivatives.

[0020] Optionally, the (average) particle size of the conductive filler is 5 nm-20 nm.

[0021] Optionally, the porous support layer has a thickness of 10 μm-80 μm, an average pore diameter of 10 nm-100 nm, and a porosity of 20%-70%.

[0022] Optionally, the porous support layer has a thickness of 10 μm-50 μm, an average pore diameter of 10 nm-100 nm, and a porosity of 20%-70%.

[0023] Optionally, the temperature-sensitive modification layer has a thickness of 1 μm-5 μm, an average pore diameter of 5 nm-50 nm, and a porosity of 10%-50%.

[0024] Optionally, the interfacial polymer layer has a thickness of 10 nm to 100 nm, an average pore size of 0.5 nm to 2 nm, and a porosity of 10% to 50%.

[0025] The present disclosure also provides a method for preparing a nanofiltration membrane, comprising the following steps:

[0026] A. preparing the temperature-sensitive composite material into a slurry, coating the slurry on the porous support layer by a slot extrusion quantitative coating process, and drying the slurry in a first oven to obtain a semi-finished nanofiltration membrane having a temperature-sensitive modification layer on the porous support layer;

[0027] B. Coating an aqueous solution on one side surface of the nanofiltration membrane semi-finished product, removing excess aqueous solution on the surface with a nitrogen air knife, then coating the oil solution on the surface of the aqueous solution, and then placing it in a second oven equipped with an infrared temperature probe; the infrared temperature probe is set on the temperature-sensitive modification layer to measure the surface temperature of the temperature-sensitive modification layer, and the nanofiltration membrane is obtained after drying.

[0028] Optionally, the infrared temperature probes are at least arranged at the left, middle and right points in the width direction of the temperature-sensitive modification layer.

[0029] Optionally, in step B, the drying temperature is 30° C.-90° C., and the drying time is 40s-120s.

[0030] Optionally, in step A, the slurry includes the following components in percentage by mass:

[0031] Thermosensitive composite material comprises 11%-40%, additives comprise 1%-8%, and the balance is solvent. Optionally, the thermosensitive composite material comprises a thermosensitive material and a conductive filler.

[0032] Optionally, the mass ratio of the temperature-sensitive material to the conductive filler is 10-30:1-10.

[0033] Optionally, in step A, the slurry includes the following components in percentage by mass:

[0034] Thermosensitive material 10%-30%, conductive filler 1%-10%, additive 1%-3%, and the balance is solvent.

[0035] Optionally, the additive includes at least one of ketones, alcohols, a mixture of polyvinyl alcohols of different molecular weights, and a mixture of polyvinyl pyrrolidones of different molecular weights.

[0036] Optionally, the molecular weight of the ketone is 30-98;

[0037] Optionally, the ketones include at least one of n-acetone, isopropyl ketone, methyl ketone, butanone, and cyclohexanone;

[0038] Optionally, the molecular weight of the alcohol is 32-60;

[0039] Optionally, the alcohol includes at least one of methanol, ethanol, isopropanol and n-propanol.

[0040] Optionally, the solvent includes at least one of dimethylformamide, dimethylacetamide and dimethyl sulfoxide.

[0041] Optionally, in step A, the slurry is prepared by firstly dispersing the conductive filler uniformly in the solvent, and then adding the temperature-sensitive material and the additive and stirring them uniformly to obtain the slurry.

[0042] Optionally, in step A, in the slot extrusion quantitative coating process, the coating speed is 2 m / min-20 m / min, and the coating amount is 10 mL / min-500 mL / min.

[0043] Optionally, in step A, the drying temperature is 40°C-80°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the specific embodiments of the present disclosure or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0045] FIG1 is a SEM image of the surface morphology of the polyethylene microporous membrane used in Example 3;

[0046] FIG2 is a SEM image of the surface of the semi-finished nanofiltration membrane obtained in Example 3;

[0047] FIG3 is a cross-sectional SEM image of the semi-finished nanofiltration membrane obtained in Example 3;

[0048] FIG4 is a surface SEM image of the nanofiltration membrane obtained in Example 3. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in combination with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments.

[0050] Hereinafter, the terms "including", "having" and their cognates, which may be used in various embodiments of the present disclosure, are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or the possibility of adding one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0051] Furthermore, the terms “first,” “second,” “third,” etc., are merely used for distinguishing descriptions and are not to be understood as indicating or implying relative importance.

[0052] One embodiment of the present disclosure provides an application of a temperature-sensitive composite material in preparing a separation membrane, wherein the temperature-sensitive composite material includes a temperature-sensitive material and a conductive filler.

[0053] The application of the temperature-sensitive composite material provided by the present disclosure in the preparation of separation membranes utilizes the characteristic of the temperature-sensitive material to quickly respond to temperature changes and transmits it to the outside world through conductive fillers, thereby realizing timely feedback and adjustment of the temperature during the preparation of the separation membrane, which is conducive to the preparation of isotropic separation membranes, ensures the stability of the separation membrane performance, and improves the quality of the separation membrane products.

[0054] In some embodiments, 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 conductive filler increases, the amount of temperature-responsive material decreases, and sensitive temperature response is difficult to achieve. When the mass ratio of the temperature-sensitive material to the conductive filler is greater than 30:1, the amount of temperature-sensitive material is excessive and the amount of conductive filler is insufficient, making it impossible to accurately and losslessly transmit temperature changes and difficult to achieve precise temperature control.

[0055] In some embodiments of the present disclosure, the mass ratio of the temperature-sensitive material to the conductive filler is typically, but not limited to, for example, 15-25:1-10, 15-25:2-8 or 17-20:3-7, such as 10:1, 10:5, 10:10, 15:1, 15:5, 15:10, 20:1, 20:5, 20:10, 25:1, 25:5, 25:10, 30:1, 30:5 or 30:10.

[0056] Optionally, the temperature-sensitive material includes at least one of polylactic acid, poly (N-isopropylacrylamide), polystyrene, polyurethane, acrylonitrile-butadiene-styrene copolymer, polycarbonate, polycaprolactone, polyethylene oxide and polyvinyl chloride.

[0057] Optionally, the conductive filler includes at least one of polyacetylene and its derivatives, polypyrrole and its derivatives, polythiophene and its derivatives, poly(p-phenylene vinylene) and its derivatives, and polyaniline and its derivatives.

[0058] Optionally, the average particle size of the conductive filler is 5 nm to 20 nm. The conductive filler disclosed herein is within the above numerical range, which is conducive to the uniform distribution of the conductive filler, so that it forms a conductive network that can respond to changes in external temperature.

[0059] In some embodiments of the present disclosure, the (average) particle size of the conductive filler is typically, but not limited to, 7 nm to 18 nm, 9 nm to 16 nm, or 10 nm to 14 nm, such as 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, or 20 nm.

[0060] In some embodiments, 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.

[0061] In the microfiltration membrane, including the functional cortex formed by phase transformation, the application of the thermosensitive composite material in the microfiltration membrane can control the phase transformation speed through the thermosensitive material and realize the preparation of functional layers with different pore sizes.

[0062] In the ultrafiltration membrane, including the functional cortex formed by phase transformation, the application of the thermosensitive composite material in the ultrafiltration membrane can control the phase transformation speed through the thermosensitive material and realize the preparation of functional layers with different pore sizes.

[0063] In the nanofiltration membrane, including a polyamide separation layer formed by interfacial polymerization, the temperature-sensitive composite material is applied to the nanofiltration membrane. The cross-linking degree of the polyamide separation layer can be controlled by the temperature-sensitive composite material, thereby realizing the preparation of nanofiltration membranes with different separation efficiencies.

[0064] In the reverse osmosis membrane, including a polyamide separation layer formed by interfacial polymerization, the temperature-sensitive composite material is applied to the reverse osmosis membrane, and the cross-linking degree of the polyamide separation layer can be controlled by the temperature-sensitive composite material to achieve reverse osmosis preparation with different desalination rates.

[0065] The pervaporation membrane includes a functional skin layer formed by phase transformation. Applying the thermosensitive composite material to the pervaporation membrane can control the phase transformation speed through the thermosensitive material and improve the uniformity of the pervaporation membrane.

[0066] The ion exchange membrane includes a functional layer formed by polymerization through a slurry coating method. Applying the temperature-sensitive composite material to the ion exchange membrane can control the polymerization speed through the temperature-sensitive material and improve the uniformity of the ion exchange membrane.

[0067] One embodiment of the present disclosure further provides a nanofiltration membrane, comprising a porous support layer, a temperature-sensitive modification layer, and an interfacial polymerization layer arranged in a stacked manner;

[0068] Wherein, the temperature-sensitive modification layer includes the temperature-sensitive composite material.

[0069] The nanofiltration membrane provided by the present invention 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 "riveted" together well, thereby improving the bonding force between the porous support layer and the interfacial polymerization layer, solving the problem that the nanofiltration membrane cannot be reversely flushed, and extending the service life of the nanofiltration membrane. At the same time, the temperature-sensitive modification layer provides temperature feedback in a timely manner, thereby enhancing the controllability of the interfacial polymerization, and is conducive to obtaining a nanofiltration membrane with uniform performance, isotropy and better stability. In addition, the preparation of interfacial polymerization layers with different polymerization degrees is achieved through temperature control during production, and nanofiltration membranes of different specifications are obtained by coordinating with different porous support layers and temperature-sensitive modification layers, thereby achieving product diversification, meeting different application scenarios, and promoting the development of the nanofiltration membrane industry.

[0070] In some embodiments of the present disclosure, the porous support layer is typically, but not limited to, at least one of cellulose acetate (CA), polyvinylidene fluoride (PVDF), polysulfone (PSf), polyacrylonitrile (PAN), polypropylene (PP), and polyethylene (PE). Polyethylene as the support layer material provides a polyethylene base layer with uniform pores, high surface porosity, excellent solvent resistance, and excellent mechanical properties.

[0071] The porous support layer is an important component of the nanofiltration membrane, providing a transmission channel for water and solutes. In addition, 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.

[0072] Optionally, the porous support layer has a thickness of 10 μm to 80 μm, an average pore size of 10 nm to 100 nm, and a porosity of 20% to 70%. Optionally, the porous support layer has a thickness of 10 μm to 50 μm, an average pore size of 10 nm to 100 nm, and a porosity of 20% to 70%. For example, the porous support layer has a thickness of 10 μm to 30 μm, an average pore size of 30 nm to 50 nm, and a porosity of 30% to 50%. For example, the porous support layer has a thickness of 10 μm to 30 μm, an average pore size of 50 nm to 100 nm, and a porosity of 50% to 70%. For example, the porous support layer has a thickness of 50 μm to 80 μm, an average pore size of 10 nm to 20 nm, and a porosity of 20% to 40%.

[0073] Optionally, the temperature-sensitive modification layer has a thickness of 1 μm to 5 μm, an average pore size of 5 nm to 50 nm, and a porosity of 10% to 50%. For example, the temperature-sensitive modification layer has a thickness of 1 μm to 2 μm, an average pore size of 30 nm to 50 nm, and a porosity of 30% to 50%. For example, the temperature-sensitive modification layer has a thickness of 1 μm to 2 μm, an average pore size of 20 nm to 40 nm, and a porosity of 20% to 40%.

[0074] Optionally, the interfacial polymeric layer has a thickness of 10 nm to 100 nm, an average pore size of 0.5 nm to 2 nm, and a porosity of 10% to 50%. For example, the interfacial polymeric layer has a thickness of 10 nm to 30 nm, an average pore size of 0.8 nm to 1.5 nm, and a porosity of 30% to 50%. For example, the interfacial polymeric layer has a thickness of 10 nm to 30 nm, an average pore size of 0.5 nm to 1.2 nm, and a porosity of 30% to 50%. For example, the interfacial polymeric layer has a thickness of 30 nm to 50 nm, an average pore size of 0.5 nm to 1.0 nm, and a porosity of 20% to 40%. For example, the interfacial polymeric layer has a thickness of 50 nm to 80 nm, an average pore size of 0.5 nm to 1.0 nm, and a porosity of 20% to 40%.

[0075] In some embodiments of the present disclosure, the nanofiltration membrane has a porous support layer with a thickness of 10-30 μm, an average pore size of 50-100 nm, and a porosity of 50%-70%; a temperature-sensitive modification layer with a thickness of 1-2 μm, an average pore size of 30-50 nm, and a porosity of 30-50%; and an interfacial polymer layer with a thickness of 10-30 nm, an average pore size of 0.8-1.5 nm, and a porosity of 30-50%. This nanofiltration membrane exhibits excellent permeability and is suitable for seawater / brackish water desalination pretreatment.

[0076] In other embodiments of the present disclosure, the nanofiltration membrane comprises a porous support layer having a thickness of 10-30 μm, an average pore size of 30-50 nm, and a porosity of 30%-50%; a temperature-sensitive modification layer having a thickness of 1-2 μm, an average pore size of 30-50 nm, and a porosity of 30%-50%; and an interfacial polymer layer having a thickness of 10-30 nm, an average pore size of 0.5-1.2 nm, and a porosity of 30%-50%. This nanofiltration membrane exhibits excellent permeability and a high hardness removal rate, making it suitable for groundwater softening.

[0077] In other embodiments of the present disclosure, the nanofiltration membrane comprises a porous support layer having a thickness of 30-50 μm, an average pore size of 10-30 nm, and a porosity of 20-40%; a temperature-sensitive modification layer having a thickness of 1-2 μm, an average pore size of 30-50 nm, and a porosity of 30-50%; and an interfacial polymer layer having a thickness of 30-50 nm, an average pore size of 0.5-1.0 nm, and a porosity of 20-40%. This nanofiltration membrane, with its thick desalination layer and small pore size, is suitable for decolorizing textile dye wastewater.

[0078] In other embodiments of the present disclosure, the nanofiltration membrane comprises a porous support layer having a thickness of 50-80 μm, an average pore size of 10-20 nm, and a porosity of 20%-40%; a temperature-sensitive modification layer having a thickness of 1-2 μm, an average pore size of 20-40 nm, and a porosity of 20%-40%; and an interfacial polymer layer having a thickness of 50-80 nm, an average pore size of 0.5-1.0 nm, and a porosity of 20%-40%. This nanofiltration membrane has a very thick desalination layer and high multivalent ion retention, making it suitable for use in high-pressure operating environments such as lithium extraction from salt lakes and industrial zero-emission applications.

[0079] One embodiment of the present disclosure provides a method for preparing a nanofiltration membrane, comprising the following steps:

[0080] A. preparing the temperature-sensitive composite material into a slurry, coating the slurry on the porous support layer by a slot extrusion quantitative coating process, and drying the slurry in a first oven to obtain a semi-finished nanofiltration membrane having a temperature-sensitive modification layer on the porous support layer;

[0081] B. Coating an aqueous solution on one side surface of the nanofiltration membrane semi-finished product, removing excess aqueous solution on the surface with a nitrogen air knife, then coating the oil solution on the surface of the aqueous solution, and then placing it in a second oven equipped with an infrared temperature probe; the infrared temperature probe is set on the temperature-sensitive modification layer to measure the surface temperature of the temperature-sensitive modification layer, and the nanofiltration membrane is obtained after drying.

[0082] The preparation method of the nanofiltration membrane provided by the present disclosure has a simple process, a high degree of mechanization, a large product batch processing volume, and is suitable for industrial production.

[0083] The slot extrusion quantitative coating process is to pass a certain flow of slurry from the feed port of the extrusion head into the internal cavity of the die head and form a stable pressure. The slurry is finally evenly sprayed out from the slit outlet of the die head and coated on the porous support layer.

[0084] In some embodiments, the preparation process of the aqueous phase solution is as follows: 1wt.%-2wt.% piperazine, 2.2wt.%-2.5wt.% camphorsulfonic acid, and 0.02wt.%-0.05wt.% polyvinyl alcohol (heated and stirred in advance at 70-80°C to dissolve) are added to pure water in sequence, and then stirred at 35°C-45°C for 1-2 hours, and then allowed to stand for 1-2 hours to obtain an aqueous phase solution.

[0085] In some embodiments, the oil phase solution is prepared as follows: 0.1 wt.%-1.0 wt.% of trimesoyl chloride is added to pure n-hexane solvent, magnetically stirred for 1 hour at room temperature, and then allowed to stand for 1 hour to obtain an oil phase solution.

[0086] In some embodiments, the infrared temperature probes are positioned at least at the left, center, and right points along the width of the temperature-sensitive modified layer. When the nanofiltration membrane product is less than 0.5 m wide, at least three infrared temperature probes are positioned equidistantly across the width to ensure uniform polymerization degree in all directions. When the nanofiltration membrane product is greater than 0.5 m wide, at least five infrared temperature probes are positioned equidistantly across the width to ensure uniform polymerization degree in all directions.

[0087] Optionally, in step B, the drying temperature is 30° C.-90° C. and the drying time is 40 s-120 s. It should be noted that the drying temperature here is the temperature of the interfacial polymerization reaction, and the temperature set in the second oven may be higher than this temperature.

[0088] In some embodiments of the present disclosure, the drying temperature is typically but not limited to 30°C, 40°C, 50°C, 60°C, 70°C, 80°C or 90°C; and the drying time is 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s or 120s.

[0089] In some embodiments, in step A, the slurry includes the following components by mass percentage: 10%-30% of temperature-sensitive material, 1%-10% of conductive filler, 1%-3% of additive, and the balance being solvent.

[0090] In some embodiments of the present disclosure, 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 balance is solvent.

[0091] Optionally, the additive includes at least one of ketones, alcohols, a mixture of polyvinyl alcohols of different molecular weights, and a mixture of polyvinyl pyrrolidones of different molecular weights.

[0092] The additives used in the present invention are hydrophilic substances, which are distributed on the surface of the temperature-sensitive modification layer and provide anchor points for the binding of the interfacial polymerization layer. These additives are cross-linked and coagulated simultaneously with the water phase and oil phase in the interfacial polymerization layer, thereby improving the mechanical strength, tolerance and selective permeability of the nanofiltration membrane.

[0093] Optionally, the molecular weight of the ketone is 30-98;

[0094] Optionally, the ketones include at least one of n-acetone, isopropyl ketone, methyl ketone, butanone, and cyclohexanone;

[0095] Optionally, the molecular weight of the alcohol is 32-60;

[0096] Optionally, the alcohol includes at least one of methanol, ethanol, isopropanol and n-propanol.

[0097] Optionally, the solvent includes at least one of dimethylformamide, dimethylacetamide and dimethyl sulfoxide.

[0098] In some embodiments, in step A, the slurry is prepared by firstly dispersing the conductive filler uniformly in the solvent, and then adding the temperature-sensitive material and the additive and stirring them uniformly to obtain the slurry.

[0099] In some embodiments, in step A, in the slot extrusion quantitative coating process, the coating speed is 2 m / min-20 m / min, and the coating amount is 10 mL / min-500 mL / min.

[0100] The coating speed affects the density and production efficiency of the temperature-sensitive modified layer. In actual production, the coating speed and coating amount are selected according to the thickness, average pore size, and porosity of the temperature-sensitive modified layer. In some embodiments of the present disclosure, 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; 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.

[0101] Optionally, in step A, the drying temperature is 40°C-80°C.

[0102] In some embodiments of the present disclosure, the drying temperature is typically, but not limited to, 40°C, 50°C, 60°C, 70°C, or 80°C.

[0103] The present disclosure provides an application of a temperature-sensitive composite material in the preparation of a separation membrane, thereby solving the technical problem in the prior art of uncontrollable performance of the separation membrane product caused by uncontrollable temperature of interfacial polymerization during the preparation of the separation membrane.

[0104] The application of the temperature-sensitive composite material provided by the present disclosure in the preparation of separation membranes utilizes the characteristic of the temperature-sensitive material to quickly respond to temperature changes and transmits it to the outside world through conductive fillers, thereby realizing timely feedback and adjustment of the temperature during the preparation of the separation membrane, which is conducive to the preparation of isotropic separation membranes, ensures the stability of the separation membrane performance, and improves the quality of the separation membrane products.

[0105] The nanofiltration membrane provided by the present invention 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 "riveted" together well, thereby improving the bonding force between the porous support layer and the interfacial polymerization layer, solving the problem that the nanofiltration membrane cannot be reversely flushed, and extending the service life of the nanofiltration membrane. At the same time, the temperature-sensitive modification layer provides temperature feedback in a timely manner, thereby enhancing the controllability of the interfacial polymerization, and is conducive to obtaining a nanofiltration membrane with uniform performance, isotropy and better stability. In addition, the preparation of interfacial polymerization layers with different polymerization degrees is achieved through temperature control during production, and nanofiltration membranes of different specifications are obtained by coordinating with different porous support layers and temperature-sensitive modification layers, thereby achieving product diversification, meeting different application scenarios, and promoting the development of the nanofiltration membrane industry.

[0106] The preparation method of the nanofiltration membrane provided by the present disclosure has a simple process, a high degree of mechanization, a large product batch processing volume, and is suitable for industrial production.

[0107] The present disclosure is further illustrated below by specific embodiments and comparative examples. However, it should be understood that these embodiments are merely for the purpose of further explanation and should not be construed as limiting the present disclosure in any form. The raw materials used in the embodiments and comparative examples of this disclosure, unless otherwise specified, were prepared under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without manufacturer indication are all commercially available conventional products.

[0108] Example 1

[0109] This embodiment provides a nanofiltration membrane, comprising the following steps:

[0110] 1. Disperse polypyrrole (Sigma, 30604-81-0) in N,N-dimethylformamide (DMF) and ultrasonicate at 70°C for 30 minutes to obtain a polypyrrole solution. Then, add polylactic acid (BASF, PLA130), polyvinylpyrrolidone (K30), and isopropyl alcohol to the polypyrrolidone solution and stir at 70°C for 120 minutes to obtain a slurry. The slurry contains 1 wt.% polypyrrole, 10 wt.% polylactic acid, 1 wt.% polyvinylpyrrolidone, and 5 wt.% isopropyl alcohol.

[0111] 2. The slurry prepared in step 1 was sprayed onto a polyethylene microporous membrane (Jiangsu Housheng New Energy Technology Co., Ltd., 0.2 μm) using a slit extrusion quantitative coating process. The coating speed was controlled to be 5 m / min, the coating amount was 100 mL / min, the drying temperature was 60°C, and the solvent evaporation phase conversion was used to obtain a nanofiltration membrane semi-finished product.

[0112] 3. Prepare a 10g / L piperazine aqueous solution as the aqueous phase solution, and a 2g / L ParG (alkane mixed solvent) solution of trimesoyl chloride as the oil phase solution. Dip-coat the semi-finished nanofiltration membrane with the aqueous phase solution (dip-coating time controlled at 10-30s). Use a nitrogen knife to remove excess aqueous phase solution from the surface. Then, apply the oil phase solution to the surface and place it in a second oven equipped with an infrared temperature probe (the infrared temperature probe is an S11-5 from Optris, Germany, with a detection range of 10°C-100°C and an accuracy of ±1°C). Set three infrared temperature probes at the left, center, and right points along the membrane width. Adjust the temperature of the second oven so that the temperature detected by the infrared temperature probe is controlled at 40°C and maintained for 100s to obtain a nanofiltration membrane.

[0113] Example 2

[0114] This embodiment provides a nanofiltration membrane. The difference from Example 1 is that the polypyrrole content in the slurry in step 1 is 2 wt.%. The remaining raw materials and methods are the same as those in Example 1 and are not described again here.

[0115] Example 3

[0116] This embodiment provides a nanofiltration membrane. The difference from Example 1 is that the polypyrrole content in the slurry in step 1 is 5 wt.%. The remaining raw materials and methods are the same as those in Example 1 and are not described again here.

[0117] Example 4

[0118] This embodiment provides a nanofiltration membrane. The difference from Example 1 is that the polypyrrole content in the slurry in step 1 is 10 wt.%. The remaining raw materials and methods are the same as those in Example 1 and are not described again here.

[0119] Example 5

[0120] This embodiment provides a nanofiltration membrane. The difference from Example 3 is that in step 2, the coating amount is 50 mL / min and the drying temperature is 60° C. The remaining raw materials and steps are the same as those in Example 3 and are not repeated here.

[0121] Example 6

[0122] This embodiment provides a nanofiltration membrane. The difference from Example 3 is that in step 2, the coating amount is 200 mL / min and the drying temperature is 60° C. The remaining raw materials and steps are the same as those in Example 3 and are not repeated here.

[0123] Example 7

[0124] This embodiment provides a nanofiltration membrane. The difference from Example 3 is that in step 2, the coating amount is 100 mL / min and the drying temperature is 40° C. The remaining raw materials and steps are the same as those in Example 3 and are not repeated here.

[0125] Example 8

[0126] This embodiment provides a nanofiltration membrane. The difference from Example 3 is that in step 3, the temperature detected by the infrared temperature probe is controlled at 50° C. The remaining raw materials and steps are the same as those in Example 3 and are not repeated here.

[0127] Example 9

[0128] This embodiment provides a nanofiltration membrane. The difference from Example 3 is that in step 3, the temperature detected by the infrared temperature probe is controlled at 60°C. The remaining raw materials and steps are the same as those in Example 3 and are not repeated here.

[0129] Example 10

[0130] This embodiment provides a nanofiltration membrane. The difference from Example 3 is that in step 3, the temperature detected by the infrared temperature probe is controlled at 70°C. The remaining raw materials and steps are the same as those in Example 3 and are not repeated here.

[0131] Example 11

[0132] This embodiment provides a nanofiltration membrane. The difference from Example 3 is that in step 3, the temperature detected by the infrared temperature probe is controlled at 80°C. The remaining raw materials and steps are the same as those in Example 3 and are not repeated here.

[0133] Example 12

[0134] This embodiment provides a nanofiltration membrane. The difference from Example 3 is that in step 3, the reaction temperature is directly controlled by the second oven, and the infrared temperature probe is eliminated. The remaining raw materials and steps are the same as those in Example 3 and are not repeated here.

[0135] Example 13

[0136] This embodiment provides a nanofiltration membrane. The difference from Example 3 is that in step 3, the reaction temperature is directly controlled by the second oven, and an infrared temperature probe is set at the midpoint of the membrane width direction. The remaining raw materials and steps are the same as those in Example 3 and are not repeated here.

[0137] Comparative Example 1

[0138] This comparative example provides a nanofiltration membrane. A piperazine aqueous solution having a concentration of 10 g / L is prepared as the aqueous phase solution, and a trimesoyl chloride n-hexane solution having a concentration of 2 g / L is prepared as the oil phase solution. The aqueous phase solution is coated on a semi-finished nanofiltration membrane. Excess aqueous phase solution on the surface is removed using a nitrogen knife. The oil phase solution is then coated on the surface, and the membrane is placed in an oven at 40°C for 100 seconds to produce the nanofiltration membrane.

[0139] Comparative Example 2

[0140] This comparative example provides a nanofiltration membrane. The difference from comparative example 1 is that the temperature of the oven is maintained at 60°C for 100 seconds. The remaining methods and raw materials are the same as those in comparative example 1 and will not be repeated here.

[0141] Test Example 1

[0142] Physical properties tests were performed on the nanofiltration membranes provided in Examples 1-13 and Comparative Examples 1-2, including tests on the thickness, average pore size, and porosity of the nanofiltration membranes. The results are shown in Table 1 below.

[0143] Table 1 Physical parameters of nanofiltration membrane

[0144] As can be seen from Table 1, within a certain range, as the ratio of conductive material to thermosensitive material in the modification solution increases, the average pore size and PEG-200 retention rate of the composite nanofiltration membrane increase, the porosity decreases, and the thickness of the functional layer does not change significantly; when the ratio of conductive material to thermosensitive material is too large, the average pore size becomes larger instead. The amount of modification solution applied affects the thickness of the functional layer, the average pore size, and the PEG-200 retention rate, and an appropriate coating amount is required, preferably 100mL / min (see Examples 3, 5, and 6). Within a certain range, as the interfacial polymerization temperature increases, the cross-linking degree can be increased, thereby achieving small pore size and high organic retention, and reducing the thickness of the desalination layer. Compared with Comparative Examples 1 and 2, the nanofiltration membrane using the thermosensitive modification process has a small pore size, high organic retention, and a thin desalination layer.

[0145] Test Example 2

[0146] The surface morphology of the polyethylene microporous membrane (Jiangsu Housheng New Energy Technology Co., Ltd., 0.2 μm) used in Example 3 was subjected to SEM, and the obtained photograph is shown in FIG1 .

[0147] As can be seen from Figure 1, the surface of the polyethylene microporous membrane presents tensile crack-like pores with a pore size distribution of 50-200 nm and a bubble point pore size of about 50 nm. The wide surface pore size distribution is mainly due to its molding process.

[0148] The surface and cross section of the semi-finished nanofiltration membrane obtained in Example 3 were subjected to SEM, and the obtained photographs are shown in Figures 2 and 3 respectively.

[0149] As can be seen from Figures 2 and 3, the surface of the nanofiltration membrane semi-finished product is smooth, the membrane pores are significantly reduced, and an obvious temperature-sensitive modification layer can be seen on the cross section.

[0150] The surface of the nanofiltration membrane obtained in Example 3 was subjected to SEM, and the obtained photograph is shown in FIG4 .

[0151] As can be seen from Figure 4, the surface of the nanofiltration membrane presents a microvesicle structure functional layer, which can effectively increase the specific surface area.

[0152] Test Example 3

[0153] The nanofiltration membranes provided in Examples 1-13 and Comparative Examples 1-2 were tested for filtration performance, 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, and the pH value of the test solution was adjusted to 7. The membrane flux and salt retention rate were tested using a membrane cross-flow test device with a cross-flow rate of 3.5 L / min and a pre-pressure of 30 minutes. The concentration of the NaCl solution was 500 ppm, the temperature was 25°C, and the test pressure was 60 psi. The concentration of the MgSO4 solution was 2000 ppm, the temperature was 25°C, and the test pressure was 70 psi.

[0154] The desalination rate and water production are shown in Table 2 below.

[0155] Table 2 Desalination rate and water production data

[0156] As can be seen from Table 2, within a certain range, as the ratio of conductive material to thermosensitive material in the modification solution increases, the sodium chloride and magnesium sulfate rejection rate of the composite nanofiltration membrane increases, and the flux decreases; when the ratio of conductive material to thermosensitive material is too large, the retention of the two salts becomes larger. The amount of modification solution applied affects the desalination and flux of sodium chloride and magnesium sulfate, and a suitable coating amount is required, preferably 100mL / min (see Examples 3, 5, and 6). Within a certain range, as the interfacial polymerization temperature increases, the degree of cross-linking can be increased, thereby achieving sodium chloride and magnesium sulfate desalination improvement. Compared with Comparative Examples 1 and 2, Case 3 uses a thermosensitive modification process to achieve higher desalination and water production of the nanofiltration membrane.

[0157] Test Example 4

[0158] The nanofiltration membrane and polyethylene microporous membrane provided in Example 3 and Comparative Examples 1-2 were tested for uniformity, and the desalination rate and water production of NaCl solution and MgSO4 solution were tested at the nanofiltration membranes at three positions on the left, middle and right in the width direction during the preparation process.

[0159] The prepared solution was used as the test solution, the pH value of the test solution was adjusted to 7, and the membrane flux and salt retention rate were tested using a membrane cross-flow test device with a cross-flow rate of 3.5 L / min and a pre-pressure of 30 minutes.

[0160] The concentration of the NaCl solution is 500 ppm, the temperature is 25°C, and the test pressure is 60 psi. The concentration of the MgSO4 solution is 2000 ppm, the temperature is 25°C, and the test pressure is 70 psi.

[0161] The desalination rate and water production are shown in Table 3 below.

[0162] Table 3 Desalination rate and water production data

[0163] As can be seen from Table 3, the flux and desalination uniformity of the magnesium sulfate and sodium chloride nanofiltration membranes prepared in Comparative Examples 1 and 2 were improved after the process optimization, but the flux deviation was still ±7LMH and the desalination deviation was ±1.0%, affecting the stability and tolerance of use. The nanofiltration membrane of Example 3, prepared using the new temperature-sensitive modification process, had a flux deviation of ±2LMH and a desalination deviation of ±0.2%, effectively improving uniformity.

[0164] Test Example 5

[0165] Stability testing was conducted on 1812 membrane elements fabricated from the nanofiltration membranes provided in Example 3 and Comparative Examples 1-2. A prepared solution was used as the test solution, with the pH adjusted to 7. Long-term lifespan evaluation was performed using a cross-flow test apparatus with a cross-flow rate of 3.5 L / min and a preload of 30 minutes. The MgSO₄ solution had a concentration of 2000 ppm, a temperature of 25°C, and a test pressure of 70 psi. Long-term operation was performed with a 30% recovery rate, and acid and base cleanings at pH 2 and pH 12 were performed every 5 days. The MgSO₄ retention and water flux (GPD) are shown in Table 4 below.

[0166] Table 4 MgSO4 retention rate and water flow GPD data

[0167] As can be seen from Table 4, the nanofiltration membrane element of Example 3 prepared by the new temperature-sensitive modification process was continuously operated for 30 days without significant changes in water production and salt rejection. After the nanofiltration membrane elements prepared in Comparative Examples 1 and 2 were continuously operated for 30 days, the salt rejection decreased by ≥2.0% and the water production decreased by >10%.

[0168] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present disclosure, which are used to illustrate the technical solutions of the present disclosure, rather than to limit them. The scope of protection of the present disclosure is not limited thereto. Although the present disclosure has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above-described embodiments within the technical scope disclosed in the present disclosure, or replace some of the technical features therein with equivalents. Such modifications, changes, or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure, and should be included in the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection of the claims. Industrial Applicability

[0169] The present disclosure provides an application of a thermosensitive composite material in the preparation of a separation membrane, a nanofiltration membrane and a preparation method. In the application provided by the present disclosure, the characteristic of the thermosensitive material that responds quickly to temperature changes is utilized and transmitted to the outside world through a conductive filler, so as to realize timely feedback and adjustment of the temperature during the preparation of the separation membrane, which is conducive to the preparation of an isotropic separation membrane, ensures the stability of the separation membrane performance, improves the quality of the separation membrane product, and has excellent application value. The present disclosure provides a nanofiltration membrane, which is mainly composed of a porous support layer, a thermosensitive modification layer and an interfacial polymerization layer. The thermosensitive 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 well "riveted" together, thereby improving the bonding force between the porous support layer and the interfacial polymerization layer, solving the problem that the nanofiltration membrane cannot be reversely flushed, and extending the service life of the nanofiltration membrane, and has excellent application value.

Claims

1. Application of a temperature-sensitive composite material in the preparation of a separation membrane, wherein: The temperature-sensitive composite material comprises a temperature-sensitive material and a conductive filler.

2. The use according to claim 1, characterized in that: The mass ratio of the temperature-sensitive material to the conductive filler is 10-30:1-10; Optionally, the temperature-sensitive material includes at least one of polylactic acid, poly-N-isopropylacrylamide, polystyrene, polyurethane, acrylonitrile-butadiene-styrene copolymer, polycarbonate, polycaprolactone, polyethylene oxide and polyvinyl chloride; Optionally, the conductive filler includes at least one of polyacetylene and its derivatives, polypyrrole and its derivatives, polythiophene and its derivatives, poly(p-phenylene vinylene) and its derivatives, and polyaniline and its derivatives; Optionally, the particle size of the conductive filler is 5nm-20nm; Optionally, the average particle size of the conductive material is 5nm-20nm.

3. The use according to claim 1 or 2, characterized in that: 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.

4. A nanofiltration membrane, characterized in that It includes a porous support layer, a temperature-sensitive modification layer and an interface polymerization layer which are stacked; Wherein, the temperature-sensitive modification layer includes a temperature-sensitive composite material.

5. The nanofiltration membrane according to claim 4, wherein The temperature-sensitive composite material comprises a temperature-sensitive material and a conductive filler; Optionally, the mass ratio of the temperature-sensitive material to the conductive filler is 10-30:1-10; Optionally, the temperature-sensitive material includes at least one of polylactic acid, poly-N-isopropylacrylamide, polystyrene, polyurethane, acrylonitrile-butadiene-styrene copolymer, polycarbonate, polycaprolactone, polyethylene oxide and polyvinyl chloride; Optionally, the conductive filler includes at least one of polyacetylene and its derivatives, polypyrrole and its derivatives, polythiophene and its derivatives, poly(p-phenylene vinylene) and its derivatives, and polyaniline and its derivatives; Optionally, the particle size of the conductive filler is 5nm-20nm; Optionally, the average particle size of the conductive filler is 5nm-20nm.

6. The nanofiltration membrane according to claim 4 or 5, characterized in that: The porous support layer has a thickness of 10 μm-80 μm, an average pore diameter of 10 nm-100 nm, and a porosity of 20%-70%.

7. The nanofiltration membrane according to claim 4 or 5, characterized in that: The porous support layer has a thickness of 10 μm-50 μm, an average pore size of 10 nm-100 nm, and a porosity of 20%-70%; Optionally, the temperature-sensitive modification layer has a thickness of 1 μm-5 μm, an average pore size of 5 nm-50 nm, and a porosity of 10%-50%; Optionally, the interfacial polymerization layer has a thickness of 10 nm-100 nm, an average pore size of 0.5 nm-2 nm, and a porosity of 10%-50%.

8. A method for preparing a nanofiltration membrane according to any one of claims 4 to 7, characterized in that: The following steps are involved: A. preparing the temperature-sensitive composite material into a slurry, coating the slurry on the porous support layer by a slot extrusion quantitative coating process, and drying the slurry in a first oven to obtain a nanofiltration membrane semi-finished product having a temperature-sensitive modification layer on the porous support layer; B. Coating an aqueous solution on one side of the surface of the nanofiltration membrane semi-finished product, using a nitrogen air knife to remove excess aqueous solution on the surface, then coating the oil solution on the surface of the aqueous solution, and then placing it in a second oven equipped with an infrared temperature probe; the infrared temperature probe is set on the temperature-sensitive modification layer to measure the surface temperature of the temperature-sensitive modification layer, and the nanofiltration membrane is obtained after drying.

9. The preparation method according to claim 8, characterized in that: The infrared temperature probe is at least arranged at the left, middle and right points in the width direction of the temperature-sensitive modification layer; Optionally, in step B, the drying temperature is 30° C.-90° C., and the drying time is 40s-120s.

10. The preparation method according to claim 8 or 9, characterized in that: In step A, the slurry includes the following components in percentage by mass: Thermosensitive composite material 11%-40%, additive 1%-8%, the balance is solvent; Optionally, the temperature-sensitive composite material comprises a temperature-sensitive material and a conductive filler; Optionally, the mass ratio of the temperature-sensitive material to the conductive filler is 10-30:1-10.

11. The preparation method according to any one of claims 7 to 10, characterized in that: In step A, the slurry includes the following components in percentage by mass: 10%-30% of temperature-sensitive material, 1%-10% of conductive filler, 1%-3% of additive, and the balance is solvent; Optionally, the additive includes at least one of ketones, alcohols, a mixture of polyvinyl alcohols of different molecular weights, and a mixture of polyvinyl pyrrolidones of different molecular weights; Optionally, the molecular weight of the ketone is 30-98; Optionally, the ketones include at least one of n-acetone, isopropyl ketone, methyl ketone, butanone, and cyclohexanone; Optionally, the molecular weight of the alcohol is 32-60; Optionally, the alcohol includes at least one of methanol, ethanol, isopropanol and n-propanol; Optionally, the solvent includes at least one of dimethylformamide, dimethylacetamide and dimethyl sulfoxide.

12. The preparation method according to claim 11, characterized in that: In step A, the slurry is prepared by firstly dispersing the conductive filler evenly in the solvent, and then adding the temperature-sensitive material and the additive and stirring them evenly to obtain the slurry.

13. The preparation method according to any one of claims 7 to 12, characterized in that: In step A, in the slit extrusion quantitative coating process, the coating speed is 2m / min-20m / min, and the coating amount is 10mL / min-500mL / min; Optionally, in step A, the drying temperature is 40°C-80°C.

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