Polyamide membrane with multi-layer composite structure as well as preparation method and device of polyamide membrane

Abstract

The invention provides a multi-layer composite structure polyamide membrane and a preparation method and device, and the preparation method comprises the following steps: A) a porous base membrane is driven by a coating machine to be coated with a water phase solution of a polyamine monomer, after liquid drops on the membrane surface are blown away, only a water phase layer in a hole is left, and then the porous base membrane moves to a slit coating head; b) coating an organic phase solution containing a first multi-element acyl chloride monomer through the first layer of slits; c) within the time interval of 1-60 seconds, coating an organic phase solution containing a second multi-element acyl chloride monomer through a second layer of slit; d) within the time interval of 1-60 seconds, coating the third layer of slit with an organic phase solution of an acyl chloride monomer containing a special functional group; and E) curing the film belt subjected to the coating procedure to obtain the polyamide film with the multi-layer composite structure. The preparation method provided by the invention can be used for preparing the composite polyamide reverse osmosis membrane with a multi-layer composite structure and multiple materials, so that function division and performance optimization are realized, the comprehensive performance of the membrane is improved, and the cost is reduced by more than 30%.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of membrane separation technology, and particularly relates to a multilayer composite structure polyamide membrane, a preparation method and device thereof. BACKGROUND

[0002] The core of the composite separation membrane (Thin-Film Composite, TFC) is to form an ultra-thin polyamide separation layer on the microporous base membrane through interfacial polymerization. The traditional TFC membrane usually adopts the dip coating method (such as patent US4277344A), that is:

[0003] Step 1: immerse the porous base membrane (such as a polysulfone ultrafiltration membrane) in an aqueous phase (such as a m-phenylenediamine MPDA solution);

[0004] Step 2: after removing the excess aqueous phase on the surface, immerse it in an organic phase (such as a hydrocarbon solution of trimesoyl chloride TMC) to form a polyamide layer;

[0005] Step 3: after heat curing, the finished membrane is obtained.

[0006] The method has the following main problems:

[0007] Uncontrollable reaction: the dip coating method leads to random monomer diffusion and uneven crosslinking degree (Journal of Membrane Science, 2018, 555: 429-437);

[0008] Single function: it is difficult to introduce multiple functional groups (such as carboxyl, sulfonic acid group, etc.) through traditional single interfacial polymerization;

[0009] Solvent residue: excessive use of organic phase leads to environmental pollution (Desalination, 2020, 496: 114702).

[0010] In recent years, slot coating (Slot Die Coating) has been tried for composite membrane preparation (such as CN110585815A), which has the following advantages:

[0011] Precise control: through slot extrusion of monomer solution, waste is reduced;

[0012] Continuous production: suitable for roll-to-roll (Roll-to-Roll) process.

[0013] However, there are still the following limitations:

[0014] Single-layer coating limitation: the existing technology only realizes single organic phase coating (such as only TMC solution), and cannot build a gradient crosslinking structure;

[0015] Insufficient timing control: the interval time between coating is fixed, and it is difficult to control the interfacial polymerization kinetics;

[0016] Functional defect: unable to integrate multiple functional layers such as hydrophilic / hydrophobic / charge modification in a single membrane. SUMMARY

[0017] The present application aims to provide a multi-layer composite structure polyamide membrane, a preparation method and device thereof, the preparation method in the present application can realize control of multi-layer reaction, has high process flexibility, realizes functional partition and performance optimization.

[0018] The present application provides a preparation method of a multi-layer composite structure polyamide membrane, comprising the following steps:

[0019] A) the porous base membrane is driven to coat a water phase solution of polyamine monomers by a coating machine, after blowing off the liquid drops on the membrane surface, only the water phase layer in the holes is left, and then the membrane strip is transported to the slit coating head;

[0020] B) the first layer of slit coating is used to coat an organic phase solution containing the first polyacyl chloride monomer;

[0021] C) within a time interval of 1-60 seconds, the second layer of slit coating is used to coat an organic phase solution containing the second polyacyl chloride monomer;

[0022] D) within a time interval of 1-60 seconds, the third layer of slit coating is used to coat an organic phase solution containing the acyl chloride monomer with special functional groups;

[0023] E) the membrane strip after the above coating process is subjected to post-treatment and solidification to obtain a multi-layer composite structure polyamide membrane.

[0024] Preferably, the porous base membrane is a polysulfone ultrafiltration membrane.

[0025] Preferably, the polyamine monomer in step A) is m-phenylenediamine.

[0026] Preferably, the first polyacyl chloride monomer is trimesoyl chloride, and the concentration of the organic phase solution containing the first polyacyl chloride monomer is 0.01-1.0 wt%.

[0027] Preferably, the second polyacyl chloride monomer is biphenyl tetracarboxylic acid chloride, and the concentration of the organic phase solution containing the second polyacyl chloride monomer is 0.01-1.0 wt%.

[0028] Preferably, the acyl chloride monomer containing special functional groups is isonicotinic acid chloride, and the concentration of the organic phase solution containing the acyl chloride monomer with special functional groups is 0.01-1.0 wt%.

[0029] Preferably, the solidification in step E) is thermal solidification and / or ultraviolet irradiation solidification.

[0030] The present application provides a multi-layer composite structure polyamide membrane, which is prepared according to the preparation method described above.

[0031] The application provides a multi-layer timing coating device, which comprises a base film unwinding device, a polyamine aqueous solution coating device, a film surface drop removing device, a multi-layer independent slot coating device, a curing device and a winding device.

[0032] Preferably, the polyamine aqueous solution coating device is a round roller coating device or a slot coating device.

[0033] The application provides a preparation method of a multi-layer composite structure polyamide membrane, which comprises the following steps: A) a porous base film is driven by a coating machine to coat a polyamine monomer aqueous solution, and only the water phase layer in the holes is left after the film surface drops are blown off, and then the film strip is transported to a slot coating head; B) a first slot coating head is used to coat an organic phase solution containing a first polyacyl chloride monomer; C) within a time interval of 1-60 seconds, a second slot coating head is used to coat an organic phase solution containing a second polyacyl chloride monomer; D) within a time interval of 1-60 seconds, a third slot coating head is used to coat an organic phase solution containing an acyl chloride monomer with a special functional group; and E) the film strip after the above coating process is subjected to post-treatment and curing to obtain a multi-layer composite structure polyamide membrane. The application provides a multi-layer timing coating device and process, a plurality of organic phases (polyacyl chloride solutions) are coated in stages, a plurality of organic phase solutions are coated in sequence within a time interval of 1-60 seconds, polyamine diffusion through the previous layer of polyamide is fully utilized, and a polyacyl chloride in the next layer is immediately subjected to a polymerization reaction, a composite polyamide reverse osmosis membrane with a multi-layer composite structure and a plurality of materials is prepared, different material polyamide layers are respectively optimized in terms of permeability, selectivity and nuclear electrical property, functional partition and performance optimization are realized, and the comprehensive performance of the membrane is improved. The process in the application is suitable for continuous production in a roll-to-roll mode, and the cost is reduced by more than 30%. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only the embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of the provided drawings.

[0035] Figure 1 The structural schematic diagram of the multi-layer timing coating device used in an embodiment of the present application;

[0036] Figure 2 The structural schematic diagram of the multi-layer timing coating device used in another embodiment of the present application;

[0037] Figure 3 The process flow diagram of the preparation of the multi-layer composite structure polyamide membrane. DETAILED DESCRIPTION

[0038] The present application provides a preparation method of a multilayer composite structure polyamide membrane, comprising the following steps:

[0039] Step 1: a porous base membrane (such as a polysulfone ultrafiltration membrane) is driven by a coating machine to coat a water phase solution of a polyamine monomer (such as m-phenylenediamine, MPDA), after blowing off the liquid drops on the membrane surface, only the water phase layer in the pores is left, and then the water phase layer in the pores is driven to a slot coating head;

[0040] Step 2: a first layer of slot coating is performed to coat an organic phase solution containing a first polyacyl chloride monomer (such as trimesoyl chloride, TMC) (the solvent is isomeric alkane ISOPAR G, and the concentration is 0.01-1.0wt%);

[0041] Step 3: within a time interval of 1-60 seconds, a second layer of slot coating is performed to coat an organic phase solution containing a second polyacyl chloride monomer (such as biphenyltetracarboxylic acid chloride, BETC) (the solvent is isomeric alkane ISOPAR G or cyclohexane, and the concentration is 0.01-1.0wt%);

[0042] Step 4: within a time interval of 1-60 seconds, a third layer of slot coating is performed to coat an organic phase solution containing a special functional group acyl chloride monomer (such as isonicotinic acid chloride, PCC) (the solvent is toluene, and the concentration is 0.01-1.0wt%);

[0043] Step 5: the membrane strip after the above coating procedure is subjected to post-treatment (such as heat curing and ultraviolet radiation curing), to obtain a multilayer composite structure polyamide membrane.

[0044] The present application also provides a multilayer composite structure polyamide membrane, which is prepared according to the preparation method described above.

[0045] The present application provides a layer time sequence coating device, which comprises a base membrane unwinding device, a polyamine water phase solution coating device, a membrane surface liquid drop removing device, a multilayer independent slot coating device, a curing device and a winding device.

[0046] The coating head of the multilayer independent slot coating device is provided with a plurality of independent slots (the width of each slot is 0.02-0.2mm), and the slot spacing is adjustable (1-500mm); each slot is equipped with an independent metering pump and a temperature control system (20-40℃), to realize time sequence coating; and the coating speed is adjustable (0.5-50.0m / min).

[0047] The application provides a preparation method of a multilayer composite structure polyamide membrane, comprising the following steps: A) a porous base film is driven to coat a water phase solution of polyamine monomers by a coating machine, after liquid drops on the film surface are blown off, only the water phase layer in the holes is left, and then the film strip is transported to a slit coating head; B) an organic phase solution containing a first polyacyl chloride monomer is coated by a first layer of slit coating; C) within a time interval of 1-60 seconds, an organic phase solution containing a second polyacyl chloride monomer is coated by a second layer of slit coating; D) within a time interval of 1-60 seconds, an organic phase solution containing an acyl chloride monomer with a special functional group is coated by a third layer of slit coating; E) the film strip after the coating process is treated and solidified to obtain a multilayer composite structure polyamide membrane. The application provides a multilayer time sequence coating device and process, a plurality of organic phases (polyacyl chloride solutions) are coated in stages, a plurality of organic phase solutions are coated in sequence within a time interval of 1-60 seconds, after the polyamine diffuses through the previous layer of polyamide membrane, the polyacyl chloride in the next layer immediately undergoes a polymerization reaction, a composite polyamide reverse osmosis membrane with a multilayer composite structure and a plurality of materials is prepared, the polyamide layers with different materials are respectively optimized in terms of permeability, selectivity and nuclear electrical properties, functional partition and performance optimization are realized, and the comprehensive performance of the membrane is improved. The process in the application is suitable for continuous production in a roll-to-roll mode, and the cost is reduced by more than 30%

[0048] In order to further illustrate the application, the application provides a multilayer composite structure polyamide membrane, a preparation method and device thereof, which are described in detail below in combination with examples, but should not be understood as limiting the protection scope of the application.

[0049] Example 1

[0050] Coating speed: 6.0 m / min

[0051] The polysulfone ultrafiltration membrane with a molecular weight cut-off of 100 KDa is used as the base film.

[0052] The water phase monomer for immersion coating: the concentration of m-phenylenediamine (MPDA) is 2.0%;

[0053] The first layer of organic phase solution: the concentration of trimesoyl chloride (TMC) is 0.1 wt%, and the solvent is Isopar G;

[0054] The second layer of organic phase solution: the concentration of isophthaloyl chloride (IPC) is 0.1 wt%, and the solvent is cyclohexane;

[0055] The distance interval between the first layer and the second layer of coating heads is 10 cm, and the coating time interval is 1 second.

[0056] The coated film enters a 90℃ oven for heat treatment for 5 minutes.

[0057] Performance: water flux 45 L / m 2• h, NaCl rejection 99.84%, zeta potential -24 mV, membrane negatively charged;

[0058] (Test conditions: 2000 ppm NaCl, 25°C, 1.55 MPa, pH 7.0.)

[0059] Example 2

[0060] Coating speed: 6.0 m / min;

[0061] The base membrane was a polysulfone ultrafiltration membrane with a molecular weight cut-off of 100 KDa;

[0062] The water phase monomer for dip coating: m-phenylenediamine (MPDA) concentration 2.0%;

[0063] The first layer of organic phase solution: TMC concentration 0.1 wt%, solvent Isopar G

[0064] The second layer of organic phase solution: terephthaloyl chloride (TPC) concentration 0.1 wt%, solvent toluene;

[0065] The distance between the first and second coating heads was 10 cm, and the coating time interval was 1 second;

[0066] The coated membrane was introduced into an oven at 90°C for heat treatment for 5 minutes;

[0067] Performance: water flux 55 L / m 2 • h, NaCl rejection 99.78%, zeta potential -19 mV, membrane negatively charged;

[0068] (Test conditions: 2000 ppm NaCl, 25°C, 1.55 MPa, pH 7.0.)

[0069] Example 3

[0070] Coating speed: 6.0 m / min;

[0071] The base membrane was a polysulfone ultrafiltration membrane with a molecular weight cut-off of 100 KDa;

[0072] The water phase monomer for dip coating: m-phenylenediamine (MPDA) concentration 2.0%;

[0073] The first layer of organic phase solution: TMC concentration 0.05 wt%, solvent Isopar G;

[0074] The second layer of organic phase solution: biphenyl tetracarboxylic chloride (BETC) concentration 0.05 wt%, solvent Isopar G;

[0075] The distance between the first and second coating heads was 10 cm, and the coating time interval was 1 second;

[0076] The coated membrane was heat treated in an oven at 90 °C for 5 minutes;

[0077] Performance: water flux 46 L / m 2 • h, NaCl desalination rate 99.88%, zeta potential -35 mV, membrane negatively charged;

[0078] (Test conditions: 2000 ppm NaCl, 25 °C, 1.55 MPa, pH 7.0.)

[0079] Example 4

[0080] Coating speed: 6.0 m / min;

[0081] The polysulfone ultrafiltration membrane with a molecular weight cut-off of 100 KDa was used as the base membrane;

[0082] The water phase monomer for dip coating: m-phenylenediamine (MPDA) concentration 2.0%;

[0083] The first layer of organic phase solution: TMC concentration 0.05 wt%, solvent Isopar G;

[0084] The second layer of organic phase solution: biphenyl tetracarboxylic chloride (BETC) concentration 0.05 wt%, solvent Isopar G;

[0085] The third layer of organic phase solution: isophthaloyl chloride (IPC) concentration 0.1 wt%, solvent cyclohexane;

[0086] The distance between the first, second and third coating heads was 10 cm, and the coating time was 1 second;

[0087] The coated membrane was heat treated in an oven at 90 °C for 5 minutes;

[0088] Performance: water flux 36 L / m 2 • h, NaCl desalination rate 99.92%, zeta potential -31 mV, membrane negatively charged;

[0089] (Test conditions: 2000 ppm NaCl, 25 °C, 1.55 MPa, pH 7.0.)

[0090] Example 5

[0091] Coating speed: 6.0 m / min;

[0092] The polysulfone ultrafiltration membrane with a molecular weight cut-off of 100 KDa was used as the base membrane;

[0093] The water phase monomer for dip coating: m-phenylenediamine (MPDA) concentration 2.0%;

[0094] First layer organic phase solution: TMC concentration 0.05wt%, solvent Isopar G;

[0095] Second layer organic phase solution: Biphenyl tetracarboxylic chloride (BETC) concentration 0.05wt%, solvent Isopar G;

[0096] Third layer organic phase solution: Picolinoyl chloride (PCC) concentration 0.1wt%, solvent Toluene;

[0097] The distance between the first layer, second layer, and third layer coating heads is each spaced 10 cm, and the coating time is each spaced 1 second;

[0098] The coated film enters a 90°C oven for heat treatment for 5 minutes;

[0099] Performance: water flux 55 L / m 2 • h, NaCl desalination rate 99.52%, zeta potential 6 mV, membrane positive electric property;

[0100] (Test conditions: 2000 ppm NaCl, 25°C, 1.55 MPa, pH 7.0.)

[0101] Example 6

[0102] Coating speed: 6.0 m / min;

[0103] The polysulfone ultrafiltration membrane with a molecular weight cut-off of 100 KDa is used as the base film;

[0104] Immersion coating aqueous phase monomer: m-phenylenediamine (MPDA) concentration 2.0%;

[0105] First layer organic phase solution: TMC concentration 0.05wt%, solvent Isopar G;

[0106] Second layer organic phase solution: Biphenyl tetracarboxylic chloride (BETC) concentration 0.05wt%, solvent Isopar G;

[0107] Third layer organic phase solution: Picolinoyl chloride (PCC) concentration 0.06wt%, solvent Toluene;

[0108] The distance between the first layer, second layer, and third layer coating heads is each spaced 10 cm, and the coating time is each spaced 1 second;

[0109] The coated film enters a 90°C oven for heat treatment for 5 minutes;

[0110] Performance: water flux 58 L / m 2 • h, NaCl desalination rate 99.64%, zeta potential 0 mV, membrane electrically neutral;

[0111] (Test condition: 2000 ppm NaCl, 25 °C, 1.55 MPa, pH 7.0.)

[0112] Example 7

[0113] Coating speed: 6.0 m / min;

[0114] The base membrane is a polysulfone ultrafiltration membrane with a molecular weight cut-off of 100 KDa;

[0115] The water-phase monomer for dip coating is m-phenylenediamine (MPDA) with a concentration of 2.0%;

[0116] The first layer of organic-phase solution is TMC with a concentration of 0.1 wt%, and the solvent is Isopar G;

[0117] The second layer of organic-phase solution is isonicotinic acid chloride (PCC) with a concentration of 0.04 wt%, and the solvent is toluene;

[0118] The distance between the first and second layers is 10 cm, and the coating time is 1 second;

[0119] The coated membrane enters a 90 °C oven for heat treatment for 5 minutes;

[0120] Performance: water flux 65 L / m 2 NaCl desalination rate 99.68%, zeta potential 0 mV, and the membrane is electrically neutral;

[0121] (Test condition: 2000 ppm NaCl, 25 °C, 1.55 MPa, pH 7.0.)

[0122] Example 8

[0123] Coating speed: 6.0 m / min;

[0124] The base membrane is a polysulfone ultrafiltration membrane with a molecular weight cut-off of 100 KDa;

[0125] The water-phase monomer for dip coating is piperazine (PIP) with a concentration of 1.0%;

[0126] The first layer of organic-phase solution is TMC with a concentration of 0.1 wt%, and the solvent is Isopar G;

[0127] The second layer of organic-phase solution is 4-(chlorosulfonyl)benzoyl chloride (CSBC) with a concentration of 0.6 wt%, and the solvent is toluene;

[0128] The distance between the first and second layers is 10 cm, and the coating time is 1 second;

[0129] The coated membrane enters a 90 °C oven for heat treatment for 5 minutes;

[0130] Performance: water flux 58 L / m 2 • h, Na2SO4 rejection 99.92%, MgCl2 rejection 38%, zeta potential -62 mV, membrane is electronegative;

[0131] (Test condition: 2000 ppm Na2SO4 or 2000 ppm MgCl2, 25°C, 0.7 MPa)

[0132] Example 9

[0133] Coating speed: 6.0 m / min;

[0134] The base membrane is a polysulfone ultrafiltration membrane with a molecular weight cut-off of 100 KDa;

[0135] The water phase monomer for dip coating is piperazine (PIP) with a concentration of 1.0%;

[0136] The first layer of organic phase solution is TMC with a concentration of 0.1 wt%, and the solvent is Isopar G;

[0137] The second layer of organic phase solution is picolinoyl chloride (PCC) with a concentration of 0.6 wt%, and the solvent is toluene;

[0138] The distance between the first layer and the second layer coating heads is 10 cm, and the coating time is 1 second;

[0139] The coated membrane enters a 90°C oven for heat treatment for 5 minutes;

[0140] Performance: water flux 47 L / m 2 • h, Na2SO4 rejection 29.4%, MgCl2 rejection 98.9%, zeta potential 28 mV, membrane is electropositive;

[0141] (Test condition: 2000 ppm Na2SO4 or 2000 ppm MgCl2, 25°C, 0.7 MPa)

[0142] Example 10

[0143] Coating speed: 3.0 m / min;

[0144] The base membrane is a polysulfone ultrafiltration membrane with a molecular weight cut-off of 100 KDa;

[0145] The water phase monomer for dip coating is piperazine (PIP) with a concentration of 1.0%;

[0146] The first layer of organic phase solution is TMC with a concentration of 0.1 wt%, and the solvent is Isopar G;

[0147] Second layer organic phase solution: isonicotinic acid chloride (PCC) concentration 0.6 wt%, solvent toluene;

[0148] The distance between the first and second layer coating heads was 10 cm apart, and the coating time was 2 seconds apart.

[0149] The coated membrane was then heat treated in a 90 °C oven for 5 minutes.

[0150] Performance: water flux 44 L / m 2 • h, Na2SO4 rejection 32.4%, MgCl2 rejection 99.9%, zeta potential 19 mV, membrane positively charged;

[0151] (Test conditions: 2000 ppm Na2SO4 or 2000 ppm MgCl2, 25 °C, 0.7 MPa)

[0152] Example 12

[0153] Coating speed: 6.0 m / min;

[0154] The base membrane was a polysulfone ultrafiltration membrane with a molecular weight cut-off of 100 KDa;

[0155] Immersion coated aqueous phase monomer: m-phenylenediamine (MPDA) concentration 2.0%;

[0156] First layer organic phase solution: TMC concentration 0.1 wt%, solvent Isopar G;

[0157] Second layer organic phase solution: TMC concentration 0.3 wt%, solvent Isopar G;

[0158] The distance between the first and second layer coating heads was 10 cm apart, and the coating time was 1 second apart.

[0159] The coated membrane was then heat treated in a 90 °C oven for 5 minutes.

[0160] Performance: water flux 36 L / m 2 • h, NaCl desalination 99.89%, boron rejection 98%, zeta potential -28 mV, membrane negatively charged;

[0161] (Test conditions: 32800 ppm NaCl, 25 °C, 5.55 MPa, pH 8.0; seawater desalination conditions)

[0162] Comparative Example 1 (single layer coating - aqueous phase MPDA - organic phase TMC):

[0163] The parameters were the same as Example 1, but only a single layer of TMC organic phase solution was coated using a slot die, with no second and third layers of organic phase.

[0164] Coating speed: 6.0 m / min;

[0165] The base membrane was a polysulfone ultrafiltration membrane with a molecular weight cut-off of 100 KDa;

[0166] The water phase monomer for dip coating: m-phenylenediamine (MPDA) concentration 2.0%;

[0167] The organic phase solution: trimesoyl chloride (TMC) concentration 0.1 wt%, solvent Isopar G;

[0168] The coated membrane was heat treated in an oven at 90 °C for 5 minutes;

[0169] Performance: water flux 56 L / m 2 ·h, NaCl desalination rate 99.34%, zeta potential -33 mV, membrane negatively charged;

[0170] (Test conditions: 2000 ppm NaCl, 25 °C, 1.55 MPa, pH 7.0.)

[0171] (If changed to seawater desalination condition test: water flux 66 L / m 2 ·h, NaCl desalination rate 99.23%, boron removal rate 68%, zeta potential -19 mV,

[0172] Comparative Example 2 (single layer coating - water phase MPDA - organic phase IPC):

[0173] The parameters were the same as Example 1, but only a single layer of the slit coated TMC organic phase solution was used, without a second and third layer of organic phase.

[0174] Coating speed: 6.0 m / min;

[0175] The base membrane was a polysulfone ultrafiltration membrane with a molecular weight cut-off of 100 KDa;

[0176] The water phase monomer for dip coating: m-phenylenediamine (MPDA) concentration 2.0%;

[0177] The first layer of organic phase solution: isophthaloyl chloride (IPC) concentration 0.1 wt%, solvent cyclohexane;

[0178] The coated membrane was heat treated in an oven at 90 °C for 5 minutes;

[0179] Performance: water flux 145 L / m 2 ·h, NaCl desalination rate 5.6%, zeta potential -4 mV, membrane negatively charged;

[0180] (Test conditions: 2000 ppm NaCl, 25 °C, 1.55 MPa, pH 7.0.)

[0181] Comparative Example 3 (single layer coating - aqueous PIP - organic TMC):

[0182] Coating speed: 6.0 m / min;

[0183] The base membrane was a polysulfone ultrafiltration membrane with a molecular weight cut-off of 100 KDa;

[0184] The aqueous monomer for dip coating was piperazine (PIP) at a concentration of 1.0%;

[0185] The first layer of organic solution was TMC at a concentration of 0.1 wt% in Isopar G;

[0186] The coated membrane was heat treated in an oven at 90 °C for 5 minutes;

[0187] Performance: water flux 40 L / m 2 • h, Na2S04rejection 97.2%, MgCl2rejection 46%, zeta potential -24 mV, membrane electronegative;

[0188] (Test conditions: 2000 ppm Na2S04or 2000 ppm MgCl2, 25 °C, 0.7 MPa)

[0189] Comparative Example 4 (single layer coating - aqueous PIP - organic TMC):

[0190] Coating speed: 6.0 m / min;

[0191] The base membrane was a polysulfone ultrafiltration membrane with a molecular weight cut-off of 100 KDa;

[0192] The aqueous monomer for dip coating was piperazine (PIP) at a concentration of 1.0%;

[0193] The first layer of organic solution was isonicotinic acid chloride (PCC) at a concentration of 0.6 wt% in toluene;

[0194] The coated membrane was heat treated in an oven at 90 °C for 5 minutes;

[0195] Performance: water flux 607 L / m 2 • h, Na2S04rejection 0%, MgCl2rejection 1.8%, zeta potential 46 mV, membrane electropositive;

[0196] (Test conditions: 2000 ppm Na2S04or 2000 ppm MgCl2, 25 °C, 0.7 MPa)

[0197] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. A method for preparing a multi-layer composite structure polyamide film, comprising the following steps: A) The porous base membrane is driven by a coating machine to coat the aqueous solution of polyamine monomers. After the droplets on the membrane surface are blown off, only the aqueous phase layer in the pores remains, and then it moves to the slit coating head; B) coating an organic phase solution containing a first polyacyl chloride monomer through a first slit; C) coating an organic phase solution containing a second polyacyl chloride monomer through a second slit at intervals of 1 to 60 seconds; D) coating an organic phase solution of an acyl chloride monomer containing a specific functional group through the third slit at intervals of 1 to 60 seconds; E) The film strip having undergone the above coating process is cured to obtain a multi-layer composite structure polyamide film.

2. The method for preparing a multi-layer composite structure polyamide film according to claim 1, characterized in that: The porous base membrane is a polysulfone ultrafiltration membrane.

3. The method for preparing a multi-layer composite structure polyamide film according to claim 1, characterized in that: The polyamine monomer in step A) is m-phenylenediamine.

4. The method for preparing a multi-layer composite structure polyamide film according to claim 1, characterized in that: The first polyacyl chloride monomer is trimesoyl chloride, and the concentration of the organic phase solution containing the first polyacyl chloride monomer is 0.01-1.0 wt %.

5. The method for preparing a multi-layer composite structure polyamide membrane according to claim 1, characterized in that: The second polyacyl chloride monomer is biphenyltetracarboxylic acid chloride, and the concentration of the organic phase solution containing the second polyacyl chloride monomer is 0.01-1.0 wt %.

6. The method for preparing a multi-layer composite structure polyamide membrane according to claim 1, characterized in that: The acyl chloride monomer containing a special functional group is isonicotinic acid chloride, and the concentration of the organic phase solution of the acyl chloride monomer containing a special functional group is 0.01-1.0 wt %.

7. The method for preparing a multi-layer composite structure polyamide membrane according to claim 1, characterized in that: The curing in step E) is thermal curing and / or ultraviolet radiation curing.

8. A multi-layer composite structure polyamide membrane prepared according to the preparation method according to any one of claims 1 to 7.

9. A multi-layer sequential coating device, comprising a base film unwinding device, a polyamine aqueous solution coating device, a film surface droplet removal device, a multi-layer independent slit coating device, a curing device and a winding device.

10. The multi-layer sequential coating device according to claim 9, characterized in that: The polyamine aqueous solution coating device is a round roller coating device or a slit coating device.

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