Composite separation membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of membrane separation, and discloses a composite separation membrane and a preparation method and application thereof, and the composite separation membrane sequentially comprises a reinforcing layer, a supporting layer and a separation layer; wherein the supporting layer is cross-linked polyimide or cross-linked polyetherimide, and the separating layer is cross-linked polyamide; the contact angle between the supporting layer and water is 55-70 degrees, and the composite separation membrane can give consideration to both high flux and high retention rate.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, and more specifically, to a composite separation membrane, its preparation method, and its application. Background Technology

[0002] Membrane separation technology, as an advanced separation and purification technique, has become an effective means to solve problems such as resource scarcity and environmental pollution due to its high efficiency, energy saving, and environmental friendliness. Membrane separation processes have unparalleled advantages over traditional separation methods such as evaporation, distillation, and extraction, and have been widely used in modern chemical, environmental protection, biomedicine, and food industries. In recent years, with the increasing awareness of low-carbon and environmental protection, numerous experts and scholars have conducted extensive and in-depth research on the preparation of separation membrane materials, membrane separation technology, and the application of membrane separation technology. These efforts have not only greatly promoted the rapid development of membrane science but also provided a powerful impetus for its innovative progress.

[0003] Composite membranes are composed of two or more membrane materials with different properties. They combine the advantages of different membrane materials, resulting in higher separation efficiency, better stability, and lower cost. For example, commercially available nanofiltration and reverse osmosis membranes are typically thin-film composite membranes formed by interfacial polymerization of a thin polyamide layer onto a porous support layer. Traditionally, the polyamide layer was considered the decisive factor in membrane separation performance. However, recent studies have shown that the porous support layer not only regulates the transport pathways of solvents and solutes through the membrane but also determines the formation of the polyamide film, thus affecting the performance of the composite membrane.

[0004] An ideal porous support layer should possess high porosity, suitable pore size, high channel connectivity, and a smooth surface. Increasing the porosity of the support layer can generally increase the flux of the composite membrane. High-porosity support layers can be easily obtained by reducing the polymer solids content of the casting solution and increasing the amount of pore-forming agent added, but the pore size may also be too large, leading to a decrease in separation performance. Furthermore, adding inorganic nanoparticles to the support layer increases the channels between the nanoparticles and the polymer, but the effect is limited because nanoparticles themselves do not have sieving capabilities and there is the problem of inorganic particle agglomeration. While MOFs and COFs materials can both increase pore size and provide separation capabilities, they suffer from problems such as complex preparation and high cost.

[0005] In summary, improving the porosity of the support layer and optimizing its pore structure remain key challenges in preparing high-throughput, high-precision composite separation membranes. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem that existing composite separation membranes cannot achieve both high throughput and high separation accuracy, and to provide a composite separation membrane, its preparation method and application, which can achieve both high throughput and high rejection rate.

[0007] To achieve the above objectives, the first aspect of the present invention provides a composite separation membrane, wherein the composite separation membrane comprises, in sequence, a reinforcing layer, a supporting layer, and a separation layer;

[0008] The support layer is cross-linked polyimide or cross-linked polyetherimide, and the separation layer is cross-linked polyamide;

[0009] The contact angle between the support layer and water is 55-70°.

[0010] A second aspect of the present invention provides a method for preparing a composite separation membrane, wherein the method includes:

[0011] (1) Dissolve polyimide or polyetherimide to obtain casting solution, load the casting solution onto the reinforcing layer, and perform phase transformation to obtain the support layer substrate-I;

[0012] (2) The support layer substrate-I is brought into first contact with an alcohol solution of a crosslinking agent to obtain support layer substrate-II;

[0013] (3) The support layer substrate-II is sequentially immersed in the first solvent and the second solvent to obtain the support layer substrate-III;

[0014] (4) After the support layer substrate-III is brought into a second contact with the polyamine solution, and then into a third contact with the polyacryl chloride solution, heat treatment is performed to obtain a composite separation membrane;

[0015] The polyamine is selected from at least one of phenylenediamine, piperazine, polyethyleneimine, and polyethylene polyamine;

[0016] In step (3), the Hansen solubility parameter S1 of the first solvent is 18-30 (MPa). 0.5 The Hansen solubility parameter S2 of the second solvent is 15-50 (MPa). 0.5 And the absolute value of the difference between the polarity vectors of the first solvent and the second solvent |Δδ P |≥2(MPa) 0.5 .

[0017] A third aspect of the present invention provides a composite separation membrane prepared by the above-described preparation method.

[0018] A fourth aspect of the present invention provides an application of the above-described composite separation membrane in the field of separation.

[0019] Through the above technical solutions, the composite separation membrane, its preparation method, and its application provided by the present invention have the following beneficial effects.

[0020] The composite separation membrane of the present invention comprises, in sequence, a reinforcing layer, a support layer of cross-linked polyimide or cross-linked polyetherimide, and a cross-linked polyamide separation layer; wherein, when the contact angle between the support layer and water meets a specific range, the obtained composite separation membrane can simultaneously achieve high throughput and high retention rate.

[0021] This invention involves preparing a cross-linked polyimide layer or a cross-linked polyetherimide layer on the reinforcing layer, and then immersing it in a first solvent and a second solvent in sequence. The cross-linked polymer layer swells in the first solvent and then undergoes "annealing" in the second solvent, which changes the arrangement of the polymer chains and causes changes in the pore structure and hydrophilicity / hydrophobicity of the support layer, resulting in a composite separation membrane with high flux and retention rate. Detailed Implementation

[0022] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0023] The first aspect of the present invention provides a composite separation membrane, wherein the composite separation membrane comprises, in sequence, a reinforcing layer, a supporting layer and a separation layer;

[0024] The support layer is cross-linked polyimide or cross-linked polyetherimide, and the separation layer is cross-linked polyamide;

[0025] The contact angle between the support layer and water is 55-70°.

[0026] In this invention, the composite separation membrane sequentially comprises a reinforcing layer, a support layer of cross-linked polyimide or cross-linked polyetherimide, and a cross-linked polyamide separation layer; wherein, when the contact angle between the support layer and water meets a specific range, the obtained composite separation membrane can simultaneously achieve high throughput and high retention rate.

[0027] In this invention, both the support layer and the separation layer in the composite separation membrane are cross-linked structures, which gives the composite separation membrane good solvent resistance and makes it suitable for the field of organic solvent separation.

[0028] Furthermore, the contact angle between the support layer and water is 60-70°.

[0029] According to the present invention, the porosity of the support layer is 60-80%.

[0030] According to the present invention, the average pore size of the support layer is 5-20 nm.

[0031] In this invention, when the porosity and / or average pore size of the support layer meet the above range, it indicates that the support layer has a porous structure, which makes the thickness of the subsequently formed cross-linked polyamide separation layer thinner and the average pore size smaller, so that the composite separation membrane has the advantages of both high throughput and high retention rate.

[0032] Furthermore, the porosity of the support layer is 65-75%.

[0033] Furthermore, the average pore size of the support layer is 8-15 nm.

[0034] According to the present invention, the thickness of the support layer is 30-60 μm.

[0035] In this invention, when the thickness of the support layer meets the above-mentioned range, the composite separation membrane not only has good mechanical strength, but also has the advantages of high throughput and high rejection rate.

[0036] Furthermore, the thickness of the support layer is 40-55 μm.

[0037] According to the present invention, the average pore size of the separation layer is 0.15-0.5 nm.

[0038] According to the present invention, the thickness of the separation layer is 20-120 nm.

[0039] In this invention, when the average pore size and / or thickness of the separation layer meets the above-mentioned range, the obtained composite separation membrane has the advantages of both high throughput and high rejection rate.

[0040] Furthermore, the average pore size of the separation layer is 0.2-0.3 nm.

[0041] Furthermore, the thickness of the separation layer is 60-90 nm.

[0042] According to the present invention, the thickness of the composite separation membrane is 100-200 μm.

[0043] In this invention, when the thickness of the composite separation membrane meets the above-mentioned range, the composite separation membrane not only has good mechanical strength, but also has the advantages of high throughput and high rejection rate.

[0044] Furthermore, the thickness of the composite separation membrane is 120-160 μm.

[0045] According to the present invention, the thickness of the reinforcing layer is 60-200 μm.

[0046] Furthermore, the thickness of the reinforcing layer is 80-120 μm.

[0047] In this invention, the reinforcing layer is a polypropylene nonwoven fabric and / or a polyester nonwoven fabric.

[0048] According to the present invention, the crosslinked polyamide comprises structural unit A provided by a polyamine and structural unit B provided by a polyacrylamide compound.

[0049] According to the present invention, based on the total mass of the crosslinked polyamide, the content of structural unit A is 35-85 wt%, and the content of structural unit B is 15-65 wt%.

[0050] In this invention, when the content of each structural unit in the crosslinked polyamide meets the above-mentioned range, the composite separation membrane has a high retention rate.

[0051] Furthermore, based on the total mass of the crosslinked polyamide, the content of structural unit A is 40-50 wt%, and the content of structural unit B is 50-60 wt%.

[0052] According to the present invention, the polyacrylamide chloride compound is selected from at least one of pyromellitic chloride, isophthaloyl chloride and terephthaloyl chloride.

[0053] According to the present invention, the polyamine is selected from at least one of phenylenediamine, piperazine, polyethyleneimine, and polyethylene polyamine.

[0054] In this invention, when the polyacrylamide compound and the polyamine are selected from the above categories, the composite separation membrane has a higher degree of crosslinking, thereby having a higher retention rate.

[0055] In this invention, the weight-average molecular weight of the polyethyleneimine is 10,000-70,000 g / mol.

[0056] In this invention, the polyethyleneimine may be branched polyethyleneimine.

[0057] In this invention, the phenylenediamine is selected from m-phenylenediamine and / or p-phenylenediamine.

[0058] In this invention, the polyethylene polyamine has the structure shown in Formula I;

[0059] Where n≥5.

[0060] In this invention, the polyethylene polyamine is selected from at least one of hexaethylene heptaamine, heptaethylene octaamine, and octaethylene nonaamine.

[0061] In this invention, the polyethylene polyamine can be any one selected from hexaethylene heptaamine, heptaethylene octaamine, and octaethylene nonaamine, or a mixture of any two or more of them.

[0062] Furthermore, n is preferably 5-7.

[0063] According to a preferred embodiment of the present invention, the polyacrylamide compound is pyromellitic trimethylolpropionate chloride; and the polyamine is piperazine.

[0064] According to another preferred embodiment of the present invention, the polyacrylamide compound is isophthaloyl chloride; the polyamine is polyethylene polyamine and polyethyleneimine.

[0065] According to the present invention, the toluene flux of the composite separation membrane is ≥2 L / (m³). 2 ·h·bar).

[0066] According to the present invention, the ethyl acetate flux of the composite separation membrane is ≥0.3 L / (m²). 2 ·h·bar).

[0067] According to the present invention, the composite separation membrane has a retention rate of ≥90% for Sudan III.

[0068] A second aspect of the present invention provides a method for preparing a composite separation membrane, wherein the method includes:

[0069] (1) Dissolve polyimide or polyetherimide to obtain casting solution, load the casting solution onto the reinforcing layer, and perform phase transformation to obtain the support layer substrate-I;

[0070] (2) The support layer substrate-I is brought into first contact with an alcohol solution of a crosslinking agent to obtain support layer substrate-II;

[0071] (3) The support layer substrate-II is sequentially immersed in the first solvent and the second solvent to obtain the support layer substrate-III;

[0072] (4) After the support layer substrate-III is brought into a second contact with the polyamine solution, and then into a third contact with the polyacryl chloride solution, heat treatment is performed to obtain a composite separation membrane;

[0073] The polyamine is selected from at least one of phenylenediamine, piperazine, polyethyleneimine, and polyethylene polyamine;

[0074] In step (3), the Hansen solubility parameter S1 of the first solvent is 18-30 (MPa). 0.5 The Hansen solubility parameter S2 of the second solvent is 15-50 (MPa). 0.5 And the absolute value of the difference between the polarity vectors of the first solvent and the second solvent |Δδ P |≥2(MPa) 0.5 .

[0075] In this invention, after preparing a cross-linked polyimide layer or a cross-linked polyetherimide layer on the reinforcing layer, the cross-linked polymer layer is soaked in a first solvent and a second solvent in sequence. The cross-linked polymer layer is swollen in the first solvent and then undergoes "annealing" in the second solvent, which changes the arrangement of the polymer chains and causes changes in the pore structure and hydrophilicity / hydrophobicity of the support layer, resulting in a composite separation membrane with high flux and retention rate.

[0076] Furthermore, in step (3), the Hansen solubility parameter S1 of the first solvent is 20-25 (MPa). 0.5 .

[0077] Furthermore, the Hansen solubility parameter S2 of the second solvent is 15-45 (MPa). 0.5 .

[0078] Furthermore, 4 (MPa) 0.5 ≤|Δδ P ≤15 (MPa) 0.5 .

[0079] According to the present invention, the first solvent is selected from at least one of N,N-dimethylformamide, N-methylpyrrolidone, N,N-dimethylacetamide, dimethyl sulfoxide, PolarClean, tetrahydrofuran, dioxane, acetonitrile, and acetone, preferably selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide; the second solvent is selected from at least one of water, methanol, ethanol, isopropanol, ethyl acetate, toluene, xylene, acetone, butanone, cyclohexanone, n-hexane, chloroform, and diethyl ether, preferably selected from at least one of methanol, ethanol, isopropanol, ethyl acetate, toluene, xylene, acetone, butanone, cyclohexanone, n-hexane, chloroform, and diethyl ether.

[0080] According to a preferred embodiment of the present invention, the first solvent is N,N-dimethylformamide and / or N,N-dimethylformamide; the second solvent is at least one of toluene, acetone and cyclohexanone.

[0081] According to the present invention, the solid content of the casting solution is 15-28 wt%.

[0082] Furthermore, the solid content of the casting solution is 18-25 wt%.

[0083] In this invention, the solvent for dissolving polyimide or polyetherimide is selected from at least one of N,N-dimethylformamide, N-methylpyrrolidone, N,N-dimethylacetamide, dimethyl sulfoxide, PolarClean, tetrahydrofuran, dioxane, acetonitrile, and acetone.

[0084] According to the present invention, the ratio of the volume of the casting solution to the area of ​​the reinforcing layer is 0.004-0.02 mL / cm². 2 .

[0085] Furthermore, the ratio of the volume of the casting solution to the area of ​​the reinforcing layer is 0.006-0.015 mL / cm². 2 .

[0086] In this invention, in step (1), the phase transformation is carried out in a coagulation bath.

[0087] In this invention, there are no special limitations on the solvent used for phase transformation; it can be a poor solvent for polyimide or polyetherimide. For example, the solvent used for phase transformation can be deionized water.

[0088] According to the present invention, in step (2), the crosslinking agent is selected from at least one of 1,2-ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,6-hexanediamine, p-phenylenediamine, diethylenetriamine, triethylenetetramine, polyethylenepolyamine and polyethyleneimine.

[0089] According to the present invention, the concentration of the alcohol solution of the crosslinking agent is 2-20 wt%.

[0090] Furthermore, the concentration of the alcohol solution of the crosslinking agent is 5-10 wt%.

[0091] In this invention, there are no special limitations on the temperature and time of the first contact. For example, the temperature of the first contact is 20-40°C and the time of the first contact is 0.5-24h.

[0092] According to the present invention, the volume ratio of the alcohol solution of the crosslinking agent to the area of ​​the support layer substrate-I is 0.025-0.125 mL / cm². 2 .

[0093] Furthermore, the volume ratio of the alcohol solution of the crosslinking agent to the area of ​​the support layer substrate-I is 0.05-0.1 mL / cm². 2 .

[0094] According to the present invention, the volume ratio of the first solvent to the area of ​​the support layer substrate-II is 0.025-0.125 mL / cm². 2 .

[0095] Furthermore, the volume ratio of the first solvent to the area of ​​the support layer substrate-II is 0.05-0.1 mL / cm². 2 .

[0096] According to the present invention, the volume ratio of the second solvent to the area of ​​the support layer substrate-II is 0.025-0.125 mL / cm². 2.

[0097] Furthermore, the volume ratio of the second solvent to the area of ​​the support layer substrate-II is 0.05-0.125 mL / cm². 2 .

[0098] According to the present invention, the support layer substrate-II is immersed in the first solvent at a temperature of 0-60°C for a time of 0.5-24h.

[0099] According to the present invention, the support layer substrate-II is immersed in the second solvent at a temperature of 0-60°C for a time of 0.5-24h.

[0100] In this invention, when the conditions for immersing the support layer substrate-II in the first solvent or the second solvent meet the above-mentioned range, the support layer substrate is brought into full contact with the first solvent or the second solvent, so that the support layer has a special pore structure and appropriate hydrophilic and hydrophobic properties, and the resulting composite separation membrane has high flux and retention rate.

[0101] Furthermore, the support layer substrate-II is immersed in the first solvent at a temperature of 20-40°C for 1-8 hours.

[0102] According to the present invention, the support layer substrate-II is immersed in the second solvent at a temperature of 20-40°C for a time of 8-24 hours.

[0103] According to the present invention, in step (4), the mass ratio of the polyamine to the volume of the solvent in the polyamine solution is 0.1-10 g / 100 mL.

[0104] Furthermore, in the polyamine solution, the mass ratio of the polyamine to the volume of the solvent is 0.2-2 g / 100 mL.

[0105] In this invention, the solvent for the polyamine solution is water.

[0106] According to the present invention, the volume ratio of the polyamine solution to the area of ​​the support layer substrate-III is 0.025-0.125 mL / cm². 2 .

[0107] Furthermore, the volume ratio of the polyamine solution to the area of ​​the support layer substrate-III is 0.05-0.1 mL / cm². 2 .

[0108] According to the present invention, the temperature of the second contact is 20-50°C and the time is 10-300s.

[0109] According to the present invention, in step (4), the mass ratio of the polyacrylamide chloride to the volume of the solvent in the polyacrylamide chloride solution is 0.01-1 g / 100 mL.

[0110] Further, in step (4), the mass ratio of the polyacrylamide chloride to the volume of the solvent in the polyacrylamide chloride solution is 0.05-0.5 g / 100 mL.

[0111] According to the present invention, the polyacryl chloride in the polyacryl chloride solution is selected from at least one of pyromellitic chloride, isophthalic chloride and terephthalic chloride.

[0112] In this invention, the solvent in the polyacrylamide chloride solution is selected from at least one of n-hexane, n-heptane, and isoalkanes. For example, the isoalkanes are selected from at least one of Isopar E, Isopar G, and Isopar H.

[0113] According to the present invention, the volume ratio of the polyacrylamide chloride solution to the area of ​​the support layer substrate-III is 0.025-0.125 mL / cm². 2 .

[0114] Furthermore, the volume ratio of the polyacrylamide chloride solution to the area of ​​the support layer substrate-III is 0.05-0.1 mL / cm². 2 .

[0115] According to the present invention, the temperature of the third contact is 20-50°C and the time is 10-300s.

[0116] According to the present invention, the conditions for the heat treatment include: a temperature of 50-80°C and a time of 1-10 min.

[0117] In this invention, when the heat treatment conditions meet the above range, the degree of crosslinking of the polyamide obtained by the reaction of polyamine and polyacrylamide chloride can be improved, which is beneficial to obtaining a composite separation membrane with high throughput and high rejection rate.

[0118] A third aspect of the present invention provides a composite separation membrane prepared by the above-described preparation method.

[0119] A fourth aspect of the present invention provides an application of the above-described composite separation membrane in the field of separation.

[0120] Furthermore, the composite separation membrane is used in the field of organic solvent separation.

[0121] The present invention will be described in detail below through embodiments.

[0122] In the following embodiments, the porosity (ε) of the support layer was calculated by gravimetric method. First, the support layer (i.e., support layer substrate-III) immersed in deionized water was removed and its surface was dried. The weight w was measured, and the area and thickness of the support layer were measured. Then, it was vacuum dried at 60°C to constant weight, and the weight w1 after drying was recorded. The porosity was calculated using the following formula:

[0123]

[0124] Where w and w1 are the weights (g) of the support layer before and after drying, respectively, and A is the area (cm²) of the support layer. 2 h is the thickness of the support layer (cm), and ρ is the density of water under the test conditions (g / cm³). 3 ).

[0125] The average pore size of the support layer was measured using an ultrafiltration membrane pore size analyzer (PSMA-10, Nanjing Gaoqian Functional Materials Technology Co., Ltd.).

[0126] The contact angle between the support layer and water was measured using a contact angle measuring instrument.

[0127] The thickness of the reinforcing layer, the support layer, and the composite separation membrane is measured by a thickness gauge.

[0128] The thickness of the separation layer was observed using a scanning electron microscope.

[0129] The average pore size of the separation layer was determined using the PEG solute transfer method, the detailed steps of which are as follows:

[0130] (1) Test the retention rate of composite separation membrane for PEG of different molecular sizes;

[0131] (2) Linear fitting of PEG size and retention rate in log-probability coordinate system, the PEG size corresponding to 50% retention rate is the average pore size of the separation layer.

[0132] The rejection rate of Sudan III by the composite separation membrane was measured by dead-end filtration. The specific test conditions were 25℃ temperature, 1.5MPa pressure, and 500rpm stirring speed. The rejection rate R was calculated according to Formula 1.

[0133]

[0134] c1 and c0 are the concentrations of Sudan III dye in the permeate (i.e., the solution after passing through the composite separation membrane) and the retention solution (i.e., the Sudan III ethyl acetate solution retained by the composite separation membrane), respectively; the concentration of the Sudan III ethyl acetate solution is calculated by an ultraviolet-visible spectrophotometer at a wavelength of 505 nm using an absorbance-concentration curve.

[0135] The toluene flux and ethyl acetate flux of the composite separation membrane are obtained by recording the volume of permeate passing through the composite separation membrane over a certain period of time and calculating it according to Formula 2.

[0136]

[0137] In the formula, V is the volume of permeate, in liters (L); A is the effective area of ​​the membrane, in m². 2 t represents time in hours (h); P represents test pressure in bars.

[0138] Content of structural unit A and structural unit B: The content of polyamine in the polyamine solution after membrane immersion is tested by liquid chromatography or gas chromatography (liquid chromatography is used for high molecular weight polyamines, and gas chromatography is used for low molecular weight polyamines). The content of polyacrylamide in the polyacrylamide solution after membrane immersion is tested by gas chromatography. The content of structural unit A and structural unit B in polyamide is calculated.

[0139] Polyimide, purchased from Evonik, brand name P84.

[0140] Polyetherimide, purchased from SABIC Innovative Plastics (China) Co., Ltd., brand name Ultem 1000.

[0141] Branched polyethyleneimine (weight average molecular weight 25,000 g / mol), pyromellitic acid chloride, and isophthaloyl chloride were purchased from Bailingwei Technology Co., Ltd.

[0142] Piperazine, polyethylene polyamine (molecular weight 275 g / mol), and other reagents were purchased from Beijing Innocare Technology Co., Ltd.

[0143] The thickness of the polypropylene nonwoven fabric is 100μm.

[0144] The Hansen solubility parameter for N,N-dimethylformamide is 24.8 (MPa). 0.5 ;δ P It is 13.7 (MPa) 0.5 ;

[0145] The Hansen solubility parameter for N-methylpyrrolidone is 23 MPa. 0.5 ;δ P It is 12.3 (MPa) 0.5 ;

[0146] The Hansen solubility parameter for water is 47.8 (MPa). 0.5 ;δ P It is 16.0 (MPa) 0.5 ;

[0147] The Hansen solubility parameter for isopropanol is 23.6 (MPa).0.5 ;δ P It is 6.1 (MPa) 0.5 ;

[0148] The Hansen solubility parameter for toluene is 18.2 (MPa). 0.5 ;δ P It is 1.43 (MPa) 0.5 ;

[0149] The Hansen solubility parameter for acetone is 19.9 (MPa). 0.5 ;δ P It is 10.4 (MPa) 0.5 ;

[0150] The Hansen solubility parameter for cyclohexanone is 19.6 (MPa). 0.5 ;δ P It is 5.1 (MPa) 0.5 ;

[0151] The Hansen solubility parameter for diethylene glycol monomethyl ether is 22.0 (MPa). 0.5 ;δ P It is 12.6 (MPa) 0.5 ;

[0152] The Hansen solubility parameter for hexane is 14.9 (MPa). 0.5 ;δ P =0 (MPa) 0.5 .

[0153] Example 1

[0154] S1. Dissolve 22g of polyetherimide in 78g of N,N-dimethylacetamide to obtain a casting solution (the solid content of the casting solution is 22wt%). Then, use a doctor blade to scrape the casting solution onto a polypropylene nonwoven fabric, and immerse it in a deionized water coagulation bath to complete the phase transformation, obtaining the support layer substrate-I; wherein, the volume ratio of the casting solution to the area of ​​the reinforcing layer is 0.008mL / cm². 2 ;

[0155] S2. The support layer substrate-I is immersed in a 5 wt% 1,6-hexanediamine methanol solution at 25°C for 4 hours to obtain the support layer substrate-II; the volume ratio of the crosslinking agent alcohol solution to the area of ​​the support layer substrate-I is 0.1 mL / cm². 2 ;

[0156] S3. Immerse the support layer substrate-II in N,N-dimethylformamide at 25°C for 1 hour, and then immerse it in deionized water at 25°C for 24 hours to obtain the support layer substrate-III; the volume ratio of the first solvent to the area of ​​the support layer substrate-II is 0.05 mL / cm². 2 The volume ratio of the second solvent to the area of ​​the support layer substrate-II is 0.125 mL / cm². 2 ;

[0157] S4. Immerse the substrate-III of the support layer in a solution (25°C) consisting of 0.5 g piperazine and 100 g deionized water for 30 s, then remove the excess aqueous phase, and then immerse it in a solution (25°C) consisting of 0.1 g trimesoyl chloride and 100 mL hexane for 30 s to obtain the initial separation membrane; the volume ratio of the polyamine solution to the area of ​​the substrate-III of the support layer is 0.125 mL / cm². 2 The volume ratio of the polyacrylamide chloride solution to the area of ​​the support layer substrate-III is 0.1 mL / cm². 2 ;

[0158] S5. The initial separation membrane was heated at 70°C for 5 minutes to obtain the composite separation membrane M1. The test results are shown in Table 1 and Table 2.

[0159] Example 2

[0160] The method of Example 1 was followed, except that in step S3, deionized water was replaced with toluene. The composite separation membrane M2 was obtained, and the test results are shown in Tables 1 and 2.

[0161] Example 3

[0162] The method of Example 1 was followed, except that in step S3, deionized water was replaced with acetone. The composite separation membrane M3 was obtained, and the test results are shown in Tables 1 and 2.

[0163] Example 4

[0164] The method of Example 1 was followed, except that in step S2, 1,6-hexanediamine was replaced with triethylenetetramine; and in step S3, N,N-dimethylformamide was replaced with N-methylpyrrolidone. The composite separation membrane M4 was obtained, and the test results are shown in Tables 1 and 2.

[0165] Example 5

[0166] S1. Dissolve 20g of polyimide in 80g of N,N-dimethylformamide to obtain a casting solution (the solid content of the casting solution is 20wt%). Then, use a doctor blade to scrape the casting solution onto a polypropylene nonwoven fabric, and immerse it in a deionized water coagulation bath to complete the phase inversion, obtaining the support layer substrate-I; wherein, the volume ratio of the casting solution to the area of ​​the reinforcing layer is 0.01mL / cm². 2;

[0167] S2. Immerse the support layer substrate-I in a 5 wt% p-phenylenediamine methanol solution at 25°C for 1 hour to obtain the support layer substrate-II; the volume ratio of the crosslinking agent alcohol solution to the area of ​​the support layer substrate-I is 0.05 mL / cm². 2 ;

[0168] S3. Immerse the support layer substrate-II in N,N-dimethylformamide at 25°C for 1 hour, and then immerse it in isopropanol at 25°C for 24 hours to obtain the support layer substrate-III; the volume ratio of the first solvent to the area of ​​the support layer substrate-II is 0.1 mL / cm². 2 The volume ratio of the second solvent to the area of ​​the support layer substrate-II is 0.125 mL / cm². 2 ;

[0169] S4. Immerse the support layer substrate-III in a solution (25℃) consisting of 0.3g polyethylene polyamine, 0.2g branched polyethyleneimine, and 100g water for 30s. Then remove the excess aqueous phase and immerse it in a solution (25℃) consisting of 0.1g isophthaloyl chloride and 100mL hexane for 1min to obtain the initial separation membrane. The ratio of the volume of the polyamine solution to the area of ​​the support layer substrate-III is 0.125mL / cm². 2 The volume ratio of the polyacrylamide chloride solution to the area of ​​the support layer substrate-III is 0.1 mL / cm². 2 ;

[0170] S5. The initial separation membrane was heated at 70°C for 5 minutes to obtain the composite separation membrane M5. The test results are shown in Table 1 and Table 2.

[0171] Example 6

[0172] Following the method of Example 5, except that in step S3, isopropanol was replaced with cyclohexanone. The composite separation membrane M6 was obtained, and the test results are shown in Tables 1 and 2.

[0173] Example 7

[0174] The method of Example 5 was followed, except that in step S3, N,N-dimethylformamide was replaced with acetone and isopropanol was replaced with hexane. The composite separation membrane M7 was obtained, and the test results are shown in Tables 1 and 2.

[0175] Comparative Example 1

[0176] S1. Dissolve 22g of polyetherimide in 78g of N,N-dimethylacetamide to obtain a casting solution (the solid content of the casting solution is 22wt%). Then, use a doctor blade to scrape the casting solution onto a polypropylene nonwoven fabric, and immerse it in a deionized water coagulation bath to complete the phase transformation, obtaining the support layer substrate-I; wherein, the volume ratio of the casting solution to the area of ​​the reinforcing layer is 0.008mL / cm². 2 ;

[0177] S2. The support layer substrate-I was immersed in a solution of 0.5 g piperazine and 100 g deionized water (25°C) for 30 s, then the excess aqueous phase was removed, and then immersed in a solution of 0.1 g trimesoyl chloride and 100 mL hexane (25°C) for 30 s to obtain the initial separation membrane; the ratio of the volume of the polyamine solution to the area of ​​the support layer substrate-III was 0.125 mL / cm². 2 The volume ratio of the polyacrylamide chloride solution to the area of ​​the support layer substrate-III is 0.1 mL / cm². 2 ;

[0178] S3. The initial separation membrane was heated at 70°C for 5 minutes to obtain the composite separation membrane D1. The test results are shown in Table 1 and Table 2.

[0179] Comparative Example 2

[0180] S1. Dissolve 22g of polyetherimide in 78g of N,N-dimethylacetamide to obtain a casting solution (the solid content of the casting solution is 22wt%). Then, use a doctor blade to scrape the casting solution onto a polypropylene nonwoven fabric, and immerse it in a deionized water coagulation bath to complete the phase transformation, obtaining the support layer substrate-I; wherein, the volume ratio of the casting solution to the area of ​​the reinforcing layer is 0.008mL / cm². 2 ;

[0181] S2. The support layer substrate-I is immersed in a 5 wt% 1,6-hexanediamine methanol solution at 25°C for 4 hours to obtain the support layer substrate-II; the volume ratio of the crosslinking agent alcohol solution to the area of ​​the support layer substrate-I is 0.1 mL / cm². 2 ;

[0182] S3. The support layer substrate-III was immersed in a solution (25°C) consisting of 0.5 g piperazine and 100 g deionized water for 30 s, then the excess aqueous phase was removed, and then immersed in a solution (25°C) consisting of 0.1 g trimesoyl chloride and 100 mL hexane for 30 s to obtain the initial separation membrane; the ratio of the volume of the polyamine solution to the area of ​​the support layer substrate-III was 0.125 mL / cm². 2 The volume ratio of the polyacrylamide chloride solution to the area of ​​the support layer substrate-III is 0.1 mL / cm². 2 ;

[0183] S4. The initial separation membrane was heated at 70°C for 5 minutes to obtain the composite separation membrane D2. The test results are shown in Table 1 and Table 2.

[0184] Comparative Example 3

[0185] Composite separation membrane D3 was prepared according to the method in Example 1, except that in Example 3, the support layer substrate-II was immersed in N-methylpyrrolidone at 25°C for 1 hour, and then immersed in ethylene glycol monomethyl ether at 25°C for 24 hours to obtain support layer substrate-III. The test results of composite separation membrane D3 are shown in Tables 1 and 2.

[0186] Table 1

[0187]

[0188]

[0189] Continued from Table 1

[0190] serial number Structural unit A (wt%) Structural unit B (wt%) Example 1 38.5 61.5 Example 2 42.6 57.4 Example 3 40.8 59.2 Example 4 39.3 60.7 Example 5 36.2 63.8 Example 6 41.6 58.4 Example 7 38.9 61.1 Comparative Example 1 53.7 46.3 Comparative Example 2 48.2 51.8 Comparative Example 3 51.5 48.5

[0191] Table 2

[0192]

[0193] As can be seen from the results in Tables 1 and 2, the porosity, pore size and contact angle of the composite separation membrane support layer described in this invention can all be adjusted by soaking in the first solvent and the second solvent, so that the final composite separation membrane has the advantages of both high throughput and high rejection rate.

[0194] As can be seen from the comparison of Examples 1-4 and Comparative Example 2 in Table 1, the porosity of the support layer increased and the average pore size decreased after soaking in the first solvent and the second solvent. This is mainly because the polymer in the support layer swells in the first solvent and then undergoes "annealing" in the second solvent, causing the polymer chains to rearrange.

[0195] I93706BHY

[0196] This alters the hydrophilicity and pore structure of the support layer. A comparison of Examples 1-7 and Comparative Examples 1-2 shows that the separation layer of the composite separation membrane described in this invention has the advantages of being thinner and having a smaller average pore size than traditional composite separation membranes.

[0197] As can be seen from the comparison of Example 1 with Comparative Examples 1 and 2 in Table 2, the composite separation membrane of the present invention has a higher flux and retention rate than the traditional composite separation membrane.

[0198] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A composite separation membrane, characterized in that, The composite separation membrane comprises, in sequence, a reinforcing layer, a supporting layer, and a separation layer; The support layer is cross-linked polyimide or cross-linked polyetherimide, and the separation layer is cross-linked polyamide; The contact angle between the support layer and water is 55-70°.

2. The composite separation membrane according to claim 1, wherein, The contact angle between the support layer and water is 60-70°; Preferably, the porosity of the support layer is 60-80%, more preferably 65-75%; Preferably, the average pore size of the support layer is 5-20 nm, and more preferably 8-15 nm; Preferably, the thickness of the support layer is 30-60 μm, and more preferably 40-55 μm.

3. The composite separation membrane according to claim 1 or 2, wherein, The average pore size of the separation layer is 0.15-0.5 nm, preferably 0.2-0.3 nm; Preferably, the thickness of the separation layer is 20-120 nm, and more preferably 60-90 nm; Preferably, the thickness of the composite separation membrane is 100-200 μm, and more preferably 120-160 μm; Preferably, the thickness of the reinforcing layer is 60-200 μm, and more preferably 80-120 μm.

4. The composite separation membrane according to any one of claims 1-3, wherein, The crosslinked polyamide includes structural unit A provided by a polyamine and structural unit B provided by a polyacrylamide compound; Preferably, based on the total mass of the crosslinked polyamide, the content of structural unit A is 35-85 wt%, preferably 40-50 wt%; and the content of structural unit B is 15-65 wt%, preferably 50-60 wt%. Preferably, the polyacrylamide chloride compound is selected from at least one of pyromellitic methyl methacrylate, isophthaloyl chloride, and terephthaloyl chloride; Preferably, the polyamine is selected from at least one of phenylenediamine, piperazine, polyethyleneimine, and polyethylene polyamine.

5. The composite separation membrane according to any one of claims 1-4, wherein, The toluene flux of the composite separation membrane is ≥2 L / (m³). 2 ·h·bar); Preferably, the ethyl acetate flux of the composite separation membrane is ≥0.3 L / (m²). 2 ·h·bar); Preferably, the composite separation membrane has a rejection rate of ≥90% for Sudan III.

6. A method for preparing a composite separation membrane, characterized in that, The method includes: (1) Dissolve polyimide or polyetherimide to obtain casting solution, load the casting solution onto the reinforcing layer, and perform phase transformation to obtain the support layer substrate-I; (2) The support layer substrate-I is brought into first contact with an alcohol solution of a crosslinking agent to obtain support layer substrate-II; (3) The support layer substrate-II is sequentially immersed in the first solvent and the second solvent to obtain the support layer substrate-III; (4) After the support layer substrate-III is brought into a second contact with the polyamine solution, and then into a third contact with the polyacryl chloride solution, heat treatment is performed to obtain a composite separation membrane; The polyamine is selected from at least one of phenylenediamine, piperazine, polyethyleneimine, and polyethylene polyamine; In step (3), the Hansen solubility parameter S1 of the first solvent is 18-30 (MPa). 0.5 The Hansen solubility parameter S2 of the second solvent is 15-50 (MPa). 0.5 And the absolute value of the difference between the polarity vectors of the first solvent and the second solvent |Δδ P |≥2(MPa) 0.5 .

7. The preparation method according to claim 6, wherein, In step (1), the solid content of the casting solution is 15-28 wt%, preferably 18-25 wt%. Preferably, the volume ratio of the casting solution to the area of ​​the reinforcing layer is 0.004-0.02 mL / cm². 2 Preferably, it is 0.006-0.015 mL / cm 2 .

8. The preparation method according to claim 6 or 7, wherein, In step (2), the crosslinking agent is selected from at least one of 1,2-ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,6-hexanediamine, p-phenylenediamine, diethylenetriamine, triethylenetetramine, polyethylenepolyamine and polyethyleneimine; Preferably, the concentration of the alcohol solution of the crosslinking agent is 2-20 wt%. Preferably, the temperature of the first contact is 20-40℃, and the contact time is 0.5-24h; Preferably, the volume ratio of the alcohol solution of the crosslinking agent to the area of ​​the support layer substrate-I is 0.025-0.125 mL / cm². 2 Preferably, the concentration is 0.05-0.1 mL / cm³. 2 .

9. The preparation method according to any one of claims 6-8, wherein, In step (3), the Hansen solubility parameter S1 of the first solvent is 20-25 (MPa). 0.5 ; Preferably, the Hansen solubility parameter S2 of the second solvent is 15-45 (MPa). 0.5 ; Preferably, 4 (MPa) 0.5 ≤|Δδ P ≤15 (MPa) 0.5 ; Preferably, the first solvent is selected from at least one of N,N-dimethylformamide, N-methylpyrrolidone, N,N-dimethylacetamide, dimethyl sulfoxide, PolarClean, tetrahydrofuran, dioxane, acetonitrile, and acetone, and more preferably from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide; the second solvent is selected from at least one of water, methanol, ethanol, isopropanol, ethyl acetate, toluene, xylene, acetone, butanone, cyclohexanone, n-hexane, chloroform, and diethyl ether, and more preferably from at least one of methanol, ethanol, isopropanol, ethyl acetate, toluene, xylene, acetone, butanone, cyclohexanone, n-hexane, chloroform, and diethyl ether. Preferably, the volume ratio of the first solvent to the area of ​​the support layer substrate-II is 0.025-0.125 mL / cm². 2 ; Preferably, the volume ratio of the second solvent to the area of ​​the support layer substrate-II is 0.025-0.125 mL / cm². 2 ; Preferably, the support layer substrate-II is immersed in the first solvent at a temperature of 0-60°C, preferably 20-40°C, for a time of 0.5-24h, preferably 1-8h; Preferably, the support layer substrate-II is immersed in the second solvent at a temperature of 0-60°C, more preferably 20-40°C, for a time of 0.5-24h, more preferably 8-24h.

10. The preparation method according to any one of claims 6-9, wherein, In step (4), the mass ratio of the polyamine to the volume of the solvent in the polyamine solution is 0.1-10 g / 100 mL, preferably 0.2-2 g / 100 mL; Preferably, the volume ratio of the polyamine solution to the area of ​​the support layer substrate-III is 0.025-0.125 mL / cm². 2 Preferably, the concentration is 0.05-0.1 mL / cm³. 2 ; Preferably, the temperature of the second contact is 20-50°C, and the time is 10-300 seconds.

11. The preparation method according to any one of claims 6-10, wherein, In step (4), the mass ratio of the polyacrylamide chloride to the volume of the solvent in the polyacrylamide chloride solution is 0.01-1 g / 100 mL, preferably 0.05-0.5 g / 100 mL; Preferably, the polyacryl chloride in the polyacryl chloride solution is selected from at least one of pyromellitic methyl methacrylate chloride, isophthaloyl chloride, and terephthaloyl chloride; Preferably, the volume ratio of the polyacrylamide chloride solution to the area of ​​the support layer substrate-III is 0.025-0.125 mL / cm². 2 Preferably, the concentration is 0.05-0.1 mL / cm³. 2 ; Preferably, the temperature of the third contact is 20-50℃, and the time is 10-300s; Preferably, the heat treatment conditions include: a temperature of 50-80°C and a time of 1-10 minutes.

12. A composite separation membrane prepared by the preparation method according to any one of claims 6-11.

13. The application of the composite separation membrane according to any one of claims 1-5 and 12 in the field of separation.

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