CN101254417A - Cross-linked hyperbranched polymer composite nanofiltration membrane and preparation method thereof - Google Patents

Abstract

The invention discloses a cross-linked hyperbranched polymer composite nanofiltration membrane and a preparation method thereof. The cross-linked hyperbranched polymer composite nanofiltration membrane is an ultrafiltration membrane as the base membrane, with a cross-linked hyperbranched polymer as the selective layer, through the interface between the hyperbranched polymer and polyacids, polyacid chlorides, polyanhydrides, and polyamines. Made by polymerization; the interfacial polymerization uses a mixed solution of water and ethanol as the water phase, and n-hexane, n-heptane or n-octane as the organic phase. Because the hyperbranched polymer has a nearly spherical structure, there are many nanopores inside the molecule, which makes the selective layer of the cross-linked hyperbranched polymer composite nanofiltration membrane loose, so that the nanofiltration membrane can maintain a high density under low operating pressure. flux and retention. The nanofiltration membrane can be used in medicine, food, environmental protection and other fields; the composite nanofiltration membrane is suitable for the separation and concentration of high-valent ions and low-valent ions, neutral particles, drugs, food additives, etc.

Description

Cross-linked hyperbranched polymer composite nanofiltration membrane and preparation method thereof

technical field

The invention relates to a nanofiltration membrane material and its preparation technology, and specifically provides a cross-linked hyperbranched polymer composite nanofiltration membrane and a preparation method thereof.

Background technique

Nanofiltration membrane (NF) is a new type of separation membrane developed at home and abroad in recent years. Its separation characteristics are between reverse osmosis and ultrafiltration. processing has been widely used. Foreign membranes and membrane components have been commercialized in the 1980s and have entered the stage of industrial application. my country's nanofiltration membrane research began in the early 1990s. The Water Treatment Center of the State Oceanic Administration, Tsinghua University, Fudan University, Dalian University of Technology, Beijing University of Chemical Technology and other units have carried out a lot of research work and achieved good results, but most of them are in the laboratory. stage.

The separation of inorganic salts by nanofiltration membranes is affected by chemical potential and potential gradient, and the interception of neutral uncharged substances (such as glucose, maltose, etc.) is mainly caused by the molecular sieving effect of the nanopores of the membrane, but its exact The mass transfer mechanism is still unclear.

In order to obtain high-flux nanofiltration membranes, composite membranes are usually prepared. Methods include coating method, interfacial polymerization and in-situ polymerization method. Recently, some scholars have used polyelectrolyte layer-by-layer self-assembly to prepare nanofiltration membranes.

The interfacial polymerization method is currently the most effective method for preparing nanofiltration membranes in the world, and it is also the method with the most varieties and the largest output of industrialized NF membranes. Interfacial polymerization is the use of two highly reactive monomers to polymerize at the interface of two immiscible solvents to form a thin layer on the porous support. In order to obtain better membrane performance, post-treatment processes such as hydrolysis charging, ion radiation or heat treatment are generally required. The advantages of the interfacial polymerization method are: the reaction is self-inhibiting; by changing the monomer concentration of the two solutions, the performance of the selective film layer can be well regulated. The key to this method is the selection and preparation of the base film, the adjustment of the distribution coefficient and diffusion rate of the two types of reactants in the two phases, and the optimization of the interface condensation conditions to rationalize the looseness of the surface layer and make it as thin as possible. The surface chemical structure and surface morphology of the composite nanofiltration membrane also have a great influence on the performance of the membrane.

Generally, the use of charged membranes can have a higher removal rate for charged particles, so nanofiltration membranes are generally charged membranes. The charged membrane can be charged as a whole or as a surface layer. The former mainly uses charged materials to directly form a film, while the latter forms a film first and then charges through surface chemical treatment or impregnation. Pama Mukherjee et al. use ion implantation to increase the charge on the surface of nanofiltration membranes.

At present, the materials of commercial nanofiltration membranes are mainly polyamide (PA), polyvinyl alcohol (PVA), sulfonated polysulfone (SPS), sulfonated polyethersulfone (SPES), cellulose acetate (CA), etc., most of which contain negative charge. The operating pressure is mostly 0.6-1MPa, the removal rate of monovalent ions is greater than 60%, and the removal rate of divalent ions is greater than 90%. Combined with the current situation of nanofiltration membranes in my country, there are two main problems that need to be solved at present: one is to further reduce the operating pressure through the control of selective layer structure; the other is to reduce the membrane fouling phenomenon of nanofiltration membranes. This starts with the preparation of nanofiltration membranes, and reasonably adjusts the porosity of the surface layer to form a large number of surface pores with nanometer scale (10 ^-9 m).

Dendritic branched molecules are a new type of polymer with a unique topology, which can be divided into two categories: Dendriemrs and hyperbranched polymers. The former is an ideal monodisperse branched macromolecule with regular highly branched Three-dimensional structure and regular spherical shape, the degree of branching is approximately equal to 1; the latter structure is between Dendrimers and linear polymers, neither has the regular structure of Dendrimers nor the chain entanglement of linear molecules. Compared with linear polymers, dendritic branched molecules have the characteristics of highly branched structure, high density of surface functional groups, good chemical stability, simple and easy surface functionalization, and easy film formation. Therefore, people have carried out a lot of research work in the fields of drug sustained release, biomedicine, information materials, superabsorbent materials, nonlinear optical materials, nanomaterials, paints, photosensitive materials, conductive materials, biofilms, etc. Big breakthrough. The applicant once used dendritic poly(amide-amine) (PAMAM) to embed nano-copper particles with a particle size of about 4nm and uniform dispersion, and used hyperbranched poly(amine-ester) instead of PAMAM molecules to embed nano-copper particles. Nano-copper particles with a particle size of about 10nm and uniform dispersion can be prepared. At present, the application of dendritic branched molecules in separation membranes is a new research direction. Chung et al. used dendritic poly(amide-amine) (PAMAM) as a supporting liquid membrane to improve the gas separation coefficient of CO ₂ ; Kovvali et al. used PAMAM to do The cross-linking agent cross-links the terminal anhydride of linear polyimide to promote the permeation of _CO2 , etc.

Recently, Li Lianchao from Tsinghua University and others prepared nanofiltration membranes through the interfacial polymerization reaction of dendritic poly(amide-amine) (PAMAM) and trimesoyl chloride, and the effect was good. The applicant's research group has used different generations of PAMAM to prepare composite nanofiltration membranes through interfacial polymerization. When using this membrane to treat 1g/l MgSO ₄ , the desalination rate is as high as 94%, and the water flux is high. However, the synthesis of PAMAM molecules is complicated, separation and purification are difficult, and it is difficult to achieve large-scale production. At present, domestic research on the functional application of hyperbranched polymers is mainly focused on: preparation of catalysts, preparation of nano-metal particles, gas separation membranes, self-assembled membranes, etc., and the use of hyperbranched polymers to prepare nanofiltration composite membranes has not yet been found. reports.

Contents of the invention

The purpose of the invention is to overcome the deficiencies in the prior art, a kind of preparation method of the composite nanofiltration membrane containing cross-linked hyperbranched polymer is provided:

The cross-linked hyperbranched polymer composite nanofiltration membrane uses a porous polymer ultrafiltration membrane as a base membrane and a cross-linked hyperbranched polymer as a selective layer.

The polymer ultrafiltration membrane is polyvinylidene fluoride, polyether sulfone, polysulfone, polyacrylonitrile, polyether sulfone ketone or polyvinyl chloride ultrafiltration membrane.

Described hyperbranched polymer is: molecular weight 1000 to 100,000, terminal group is the hyperbranched poly(amide-amine) of hydroxyl, amino or carboxyl group, hyperbranched poly(amine-ester), hyperbranched poly(propylene-imine) ), hyperbranched polyester or hyperbranched polyacrylic acid.

The preparation method of cross-linked hyperbranched polymer composite nanofiltration membrane comprises the following steps:

1) Immerse the polymer ultrafiltration membrane in the mixed solution of ethanol and water for 10s-1h;

2) Dissolving the hyperbranched polymer in a mixed solution of ethanol and water to prepare an aqueous phase solution, the concentration of the hyperbranched polymer is: 1×10 ^-3 ~ 4×10 ^-2 mol/l;

3) In an air environment with a temperature of 10-40° C. and a relative humidity of 40-90%, soak the polymer ultrafiltration membrane soaked in step 1) into the aqueous phase solution prepared in step 2), The soaking time is 10s~10h, take out the polymer ultrafiltration membrane and dry in the shade;

4) Dissolving the cross-linking agent in the solvent to prepare a cross-linking agent solution with a concentration of 4×10 ^-3 to 8×10 ^-2 , immersing the shade-dried polymer film obtained in step 3) into the cross-linking agent solution, and reacting 10s～10h;

5) The polymer membrane is taken out from the cross-linking agent solution, and placed in an oven at 20-120° C. for 5 min-1 h to obtain a cross-linked hyperbranched polymer composite nanofiltration membrane.

The cross-linked cross-linking agent is: glutaraldehyde, terephthalaldehyde, 3,3', 4,4'-benzophenone tetracarboxylic dianhydride, succinic anhydride, pyromellitic anhydride, butyl Diacid, adipic acid, pyromellitic acid, terephthalic acid, 1,4-butanediamine, ethylenediamine, hexamethylenediamine, 1,4-butanediol, ethylene glycol, diethylene glycol ether , 1,3-propanediol, 1,6-hexanediol, trimesoyl chloride, terephthaloyl chloride, benzyl dichloride or polyethylene glycol with a molecular weight of 200-2000 dihydroxyl end groups. A mixed solution of ethanol and water, wherein the volume percentage of water is: 1% to 80%. The immersion time of the polymer ultrafiltration membrane in the aqueous phase solution is 20s-8h. The solvent of the crosslinking agent is n-hexane, n-heptane or n-octane.

The beneficial effect that the present invention has:

1) The hyperbranched polymer has a nearly spherical structure, and there are many nanopores inside the molecule, which makes the selective layer of the cross-linked hyperbranched polymer composite nanofiltration membrane looser, so that the nanofiltration membrane can operate at a lower operating pressure. Maintain high flux and high retention;

2) The hyperbranched polymer has a large number of terminal groups, and the type of terminal group of the hyperbranched polymer can be easily adjusted by modifying the terminal group to prepare nanofiltration membranes with different charges;

3) The hyperbranched polymer has a large number of terminal groups, which can easily adjust the hydrophilicity and hydrophobicity of the nanofiltration membrane by adjusting the degree of crosslinking, and adjust the applicable water medium of the nanofiltration membrane;

4) The ultrafiltration membrane is pretreated in a mixed solution of ethanol and water, so that the hyperbranched polymer is more easily adsorbed on the surface of the ultrafiltration membrane, so that the selective layer is more easily compounded on the surface of the ultrafiltration membrane;

5) The hyperbranched polymer has been produced industrially, and the material is simple and easy to obtain, which makes it easier to realize the industrialization of the cross-linked hyperbranched polymer composite nanofiltration membrane.

Detailed ways

The preparation method of the composite nanofiltration membrane containing cross-linked hyperbranched polymer described in the present invention has three core steps in the preparation process, which are as follows:

(1) Preparation of aqueous phase solution: dissolve the hyperbranched polymer in ethanol, stir at 10-60°C for 10min-2h to dissolve; then slowly add water to the solution, and then continue at 20-60°C Stir for 10min to 2h to form an aqueous phase solution.

Hyperbranched molecules are: hyperbranched poly(amide-amine), hyperbranched poly(amine-ester), hyperbranched poly(propylene-imine), hyperbranched poly(propylene-imine) with a molecular weight of 1,000 to 100,000 and terminal groups of hydroxyl, amino or carboxyl groups polyester or hyperbranched polyacrylic acid.

(2) Preparation of organic phase solution: dissolve the cross-linking agent molecules in an organic solvent, stir at 10-60° C. for 10 min-2 h to dissolve, and form an organic phase solution.

The crosslinking agent is: dialdehyde, acid anhydride, polybasic acid, diamine or diol that can react with the hydroxyl group, amino group or carboxyl end group of the hyperbranched polymer to make the hyperbranched molecule form a crosslink; wherein the dialdehyde is : glutaraldehyde (GA) or terephthalaldehyde (DBA); acid anhydride: 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), succinic anhydride or pyromellitic anhydride (PMDA); polybasic acid: succinic acid (BDAC), pyromellitic acid (BTA) or terephthalic acid; diamine: 1,4-butanediamine (BDAA), ethylenediamine, or hexamethylenediamine Amines; diols are: 1,4-butanediol (BDAH), ethylene glycol, diethylene glycol ether, 1,3-propanediol, 1,6-hexanediol, trimesoyl chloride, terephthalate Formyl chloride, benzyl dichloride or double-end hydroxyl polyethylene glycol with a molecular weight of 200-2000.

The organic solvent is: n-hexane, n-heptane or n-octane.

(3) Post-treatment: take the polymer membrane out of the crosslinking agent solution, place it in an oven at 20-120° C. for 5 min-1 h, and obtain a hyperbranched polymer composite nanofiltration membrane.

The synthesis method of the hyperbranched molecule is not limited, it can be synthesized by a step-by-step method, or by a one-step method or a quasi-one-step method. Since the molecular weight in this invention is above 1000, hyperbranched molecules can also be called hyperbranched polymer molecules or hyperbranched polymers.

In the crosslinking reaction of the hyperbranched molecule, the chemical amount of the reactive group of the crosslinking agent is equivalent to 5-50% of the chemical equivalent of the terminal group in the hyperbranched molecule. Generally, the type of crosslinking agent depends on the chemical structure of the end group of the hyperbranched molecule and the required crosslinking chains, such as: amino groups react with polyacids, polyacid chlorides or anhydrides to form amide crosslinks, hydroxyl groups react with polyacids, polybasic Acid chlorides or anhydrides react to form ester crosslinks, and hydroxyl groups react with binary aldehydes to form acetal and hemiacetal crosslinks; the amount of crosslinking agent depends on the selection of the degree of crosslinking of hyperbranched molecules. The degree of crosslinking is small, and the amount of crosslinking agent is small; the temperature and time of crosslinking reaction depend on the type of crosslinking reaction, and the crosslinking reaction of carboxyl group, amino group and hydroxyl group needs higher temperature and longer time; The reaction requires slightly lower temperature and shorter time; the reaction of carboxyl, hydroxyl or amino with acid chloride requires lower temperature and shorter time.

The present invention is described in detail below with examples, but the examples do not constitute a limitation to the present invention.

The hyperbranched molecules in the examples were synthesized by the inventor, and the types and synthesis process of the hyperbranched molecules are shown in the patent (ZL 200410067256.0).

The ultrafiltration base membranes in the examples are all purchased commercial products.

Example 1:

Soak the purchased polysulfone ultrafiltration base membrane in a mixed solution of ethanol and water with a volume ratio of 3:2 for 20 minutes; then immerse the polysulfone ultrafiltration membrane in 4.6×10 ^-3 mol/l In the aqueous phase solution, take it out after 40 minutes, and dry it naturally; then soak the film in a 5.8×10 ^-3 mol/l n-hexane solution of trimesoyl chloride, take it out after 20 minutes; then place the film in an oven at 60°C Keep in the medium for 20min to obtain hyperbranched polyester composite nanofiltration membrane. Tested with 1g/l Na ₂ SO ₄ under the pressure of 0.3Mpa, the water flux of the membrane is 79.1l/m ² h, and the removal rate of Na ₂ SO ₄ is 80.4%. Tested with 1g/l Na ₂ SO ₄ under the pressure of 0.6Mpa, the water flux of the membrane is 115.4l/m ² h, and the removal rate of Na ₂ SO ₄ is 85.6%.

Example 2:

Soak the purchased polysulfone ultrafiltration base membrane in the mixed solution of ethanol and water with a volume ratio of 3:2 for 10 minutes; then immerse the polysulfone ultrafiltration membrane in 4.6×10 ^-3 mol/l In the aqueous phase solution, take it out after 50 minutes, and dry it naturally; then soak the film in 8.3×10 ^-3 mol/l n-hexane solution of trimesoyl chloride, take it out after 10 minutes; then put the film in an oven at 90°C Keep in the medium for 10min to obtain hyperbranched polyester composite nanofiltration membrane. Tested with 1g/l Na ₂ SO ₄ under the pressure of 0.3Mpa, the water flux of the membrane is 38.9l/m ² h, and the removal rate of Na ₂ SO ₄ is 86.4%. Tested with 1g/l Na ₂ SO ₄ under the pressure of 0.6Mpa, the water flux of the membrane is 56.1l/m ² h, and the removal rate of Na ₂ SO ₄ is 90.2%.

Example 3:

Soak the purchased polysulfone ultrafiltration base membrane in the mixed solution of ethanol and water with a volume ratio of 3:2 for 50 minutes; then immerse the polysulfone ultrafiltration membrane in 4.6×10 ^-3 mol/l In the aqueous phase solution, take it out after 20 minutes, and dry it naturally; then soak the film in a 6.7×10 ^-3 mol/l n-hexane solution of trimesoyl chloride, take it out after 30 seconds; then place the film in an oven at 40°C Keep in the medium for 50min to obtain hyperbranched polyester composite nanofiltration membrane. Tested with 1g/l Na ₂ SO ₄ under the pressure of 0.3Mpa, the water flux of the membrane is 57.5l/m ² h, and the removal rate of Na ₂ SO ₄ is 85.3%. Tested with 1g/l Na ₂ SO ₄ under the pressure of 0.6Mpa, the water flux of the membrane is 96.5l/m ² h, and the removal rate of Na ₂ SO ₄ is 89.8%.

Example 4:

Soak the purchased polysulfone ultrafiltration base membrane in a mixed solution of ethanol and water with a volume ratio of 3:2 for 30 seconds; then immerse the polysulfone ultrafiltration membrane in 8.9×10 ^-3 mol/l In the aqueous phase solution, take it out after 30s, and dry it naturally; then soak the film in a 1.3×10 ^-2 mol/l n-hexane solution of trimesoyl chloride, take it out after 20s; then place the film in an oven at 100°C Keep in the medium for 5min to obtain hyperbranched polyester composite nanofiltration membrane. Tested with 1g/l Na ₂ SO ₄ under the pressure of 0.3Mpa, the water flux of the membrane is 30.5l/m ² h, and the removal rate of Na ₂ SO ₄ is 89.7%. Tested with 1g/l Na ₂ SO ₄ under the pressure of 0.6Mpa, the water flux of the membrane is 41.3l/m ² h, and the removal rate of Na ₂ SO ₄ is 91.3%.

Example 5:

Soak the purchased polysulfone ultrafiltration base membrane in a mixed solution of ethanol and water with a volume ratio of 3:2 for 20 seconds; then immerse the polysulfone ultrafiltration membrane in 8.9×10 ^-3 mol/l In the water phase solution, take it out after 10s, and dry it naturally; then soak the film in a 2.4×10 ^-2 mol/l n-hexane solution of terephthaloyl chloride, take it out after 5 minutes; then place the film in a 70°C Keep it in the oven for 10 minutes to obtain a hyperbranched polyester composite nanofiltration membrane. Tested with 1g/l Na ₂ SO ₄ under the pressure of 0.3Mpa, the water flux of the membrane is 8-20l/m ² h, and the removal rate of Na ₂ SO ₄ is 94.3%. Tested with 1g/l Na ₂ SO ₄ under the pressure of 0.6Mpa, the water flux of the membrane is 10.3-30l/m ² h, and the removal rate of Na ₂ SO ₄ is 96.8%.

Embodiment 6:

Soak the purchased polysulfone ultrafiltration base membrane in a mixed solution of ethanol and water with a volume ratio of 3:2 for 1 hour; then immerse the polysulfone ultrafiltration membrane in 1.5×10 ^-3 mol/l In the aqueous phase solution, take it out after 1.5h, and dry it naturally; then soak the film in a 4.5×10 ^-3 mol/l n-hexane solution of pyromellitic anhydride, take it out after 2 hours; then place the film at 120°C kept in the oven for 5min to obtain a hyperbranched polyester composite nanofiltration membrane. Tested with 1g/l Na ₂ SO ₄ under the pressure of 0.3Mpa, the water flux of the membrane is 24l/m ² h, and the removal rate of Na ₂ SO ₄ is 80.4%. Tested with 1g/l Na ₂ SO ₄ under the pressure of 0.6Mpa, the water flux of the membrane is 45.4l/m ² h, and the removal rate of Na ₂ SO ₄ is 86.6%.

Embodiment 7:

Soak the purchased polysulfone ultrafiltration base membrane in a mixed solution of ethanol and water with a volume ratio of 3:2 for 20 minutes; then immerse the polysulfone ultrafiltration membrane in 4.6×10 ^-3 mol/l aqueous phase solution, take it out after 3h, and dry it naturally; then soak the film in 4.6×10 ^-3 mol/l n-hexane solution of trimesoyl chloride, take it out after 40min; then place the film in Keep it in an oven at 80° C. for 10 minutes to obtain a hyperbranched polyester composite nanofiltration membrane. The water flux of _the membrane is 69.41/m ² h and the removal rate of Na ₂ SO ₄ is 81.4% under the _pressure of 0.3Mpa. Tested with 1g/l Na ₂ SO ₄ under the pressure of 0.6Mpa, the water flux of the membrane is 75.4l/m ² h, and the removal rate of Na ₂ SO ₄ is 86.6%.

Embodiment 8:

Soak the purchased polysulfone ultrafiltration base membrane in a mixed solution of ethanol and water with a volume ratio of 3:2 for 20 minutes; then immerse the polysulfone ultrafiltration membrane in a 4.6×10 ^-3 mol/l water phase solution, take it out after 40min, and dry it naturally; then soak the membrane in 5.8×10 ^-2 mol/l n-hexane solution of succinic anhydride, take it out after 15min; then place the membrane Keep it in an oven at 30° C. for 1 hour to obtain a hyperbranched polyester composite nanofiltration membrane. Tested with 1g/l Na ₂ SO ₄ under the pressure of 0.3Mpa, the water flux of the membrane is 60l/m ² h, and the removal rate of Na ₂ SO ₄ is 70.4%. The water flux of _the membrane is 85.41/m ² h, and the removal rate of Na ₂ SO ₄ is 82.6% under the _pressure of 0.6Mpa.

Claims (8)

1. A crosslinked hyperbranched polymer composite nanofiltration membrane, characterized in that it is a base membrane with a porous polymer ultrafiltration membrane and a crosslinked hyperbranched polymer as a selective layer. 2. a kind of cross-linked hyperbranched polymer composite nanofiltration membrane according to claim 1, is characterized in that described polymer ultrafiltration membrane is polyvinylidene fluoride, polyether sulfone, polysulfone, polyacrylonitrile, Polyether sulfone ketone or polyvinyl chloride ultrafiltration membrane. 3. a kind of cross-linked hyperbranched polymer composite nanofiltration membrane according to claim 1, is characterized in that described hyperbranched polymer is: molecular weight 1000 to 100,000, terminal group is the hyperbranched of hydroxyl, amino or carboxyl hyperbranched poly(amide-amine), hyperbranched poly(amine-ester), hyperbranched poly(propylene-imine), hyperbranched polyester or hyperbranched polyacrylic acid. 4, a kind of preparation method of cross-linked hyperbranched polymer composite nanofiltration membrane as claimed in claim 1, is characterized in that comprising the following steps: 1) Immerse the polymer ultrafiltration membrane in the mixed solution of ethanol and water for 10s-1h; 2) Dissolving the hyperbranched polymer in a mixed solution of ethanol and water to prepare an aqueous phase solution, the concentration of the hyperbranched polymer is: 1×10 ^-3 ~ 4×10 ^-2 mol/l; 3) In an air environment with a temperature of 10-40° C. and a relative humidity of 40-90%, soak the polymer ultrafiltration membrane soaked in step 1) into the aqueous phase solution prepared in step 2), The soaking time is 10s~10h, take out the polymer ultrafiltration membrane and dry in the shade; 4) Dissolving the cross-linking agent in the solvent to prepare a cross-linking agent solution with a concentration of 4×10 ^-3 to 8×10 ^-2 , immersing the shade-dried polymer film obtained in step 3) into the cross-linking agent solution, and reacting 10s～10h; 5) The polymer membrane is taken out from the cross-linking agent solution, and placed in an oven at 20-120° C. for 5 min-1 h to obtain a cross-linked hyperbranched polymer composite nanofiltration membrane. 5. a kind of cross-linked hyperbranched polymer composite nanofiltration membrane according to claim 4, is characterized in that the cross-linking agent of described cross-linking is: glutaraldehyde, terephthalaldehyde, 3,3 ', 4,4'-Benzophenone tetracarboxylic dianhydride, succinic anhydride, pyromellitic anhydride, succinic acid, adipic acid, pyromellitic acid, terephthalic acid, 1,4-butylene diamine, Ethylenediamine, Hexamethylenediamine, 1,4-Butanediol, Ethylene Glycol, Diethylene Glycol Ether, 1,3-Propanediol, 1,6-Hexanediol, Trimesoyl Chloride, Terephthaloyl Chloride , dichlorobenzyl or polyethylene glycol with a molecular weight of 200-2000. 6. The method for preparing a cross-linked hyperbranched polymer composite nanofiltration membrane according to claim 4, characterized in that the mixed solution of ethanol and water has a water volume percentage of 1% to 80%. 7. The preparation method of the cross-linked hyperbranched polymer composite nanofiltration membrane according to claim 4, characterized in that the immersion time of the polymer ultrafiltration membrane in the aqueous phase solution is 20s-8h. 8. The method for preparing a cross-linked hyperbranched polymer composite nanofiltration membrane according to claim 4, wherein the solvent of the cross-linking agent is n-hexane, n-heptane or n-octane.