A method for preparing a hydrophilic pvdf membrane with drug resistance

Abstract

The application belongs to the technical field of polymer membrane separation, and relates to a preparation method of a hydrophilic PVDF membrane with drug resistance. The hydrophilic polymer is first blended with PVDF to form a film through wet phase inversion, and an organic metal chelate is grafted onto the hydrophilic polymer through post-processing to achieve hydrophilicity. The hydrophilicity and drug resistance of the PVDF membrane are improved, and the hydrophilic micro-ultrafiltration membrane with drug resistance is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polymer membrane separation, and particularly relates to a preparation method of a hydrophilic PVDF membrane with drug resistance. BACKGROUND

[0002] The PVDF membrane is widely used in the field of membrane separation due to its excellent mechanical strength, chemical stability and thermal stability, and aging resistance. At present, the PVDF membrane faces the problems of membrane pollution, flux decline, separation performance weakening, cleaning or membrane replacement cost increase, and membrane service life reduction in the water separation process due to the hydrophobicity of the PVDF material itself.

[0003] The current mainstream hydrophilic modification methods can bring good hydrophilicity to the PVDF membrane, but few patent documents mention the tolerance of the hydrophilic agent to the drug (acid, alkali and oxidant). In the industrial membrane water treatment process, the use of the drug is very common, especially the use of NaClO. As a strong oxidant, NaClO shows electrophilicity. NaClO attacks from strong to weak according to the electron density of the hydrophilic functional group, causing the gradual degradation of the hydrophilic functional group, and thus the PVDF membrane loses hydrophilicity.

[0004] The Chinese patent with the authorized announcement number CN108993174B "ePTFE hydrophilic membrane resistant to sodium hypochlorite and preparation method and application thereof" can form a cross-linked hydrophilic layer mechanically entangled on the fibril and node structure of the ePTFE membrane surface through the cross-linking action of the hydrophilic polymer and the bridging agent, which can effectively improve the hydrophilicity of the ePTFE membrane. The hydrophilic organic metal chelate attached to the surface of the ePTFE membrane after hydrophilic modification will induce sodium hypochlorite to preferentially attack the hydrophilic organic metal chelate, so that the ePTFE membrane can long keep hydrophilicity, prolong the service life of the filtration membrane, and the preparation method is simple and can realize industrialized continuous production. The preparation method improves the NaClO resistance of the ePTFE membrane, but is limited to the ePTFE membrane prepared by the stretching method and cannot be applied to the PVDF membrane. SUMMARY

[0005] In order to solve the problem of poor cleaning ability of the hydrophilic agent and the drug resistance in the prior art, the application provides a preparation method of a hydrophilic PVDF membrane with drug resistance. The hydrophilic polymer is first blended with the PVDF to form a film by wet phase inversion, and the organic metal chelate is reacted and grafted onto the hydrophilic polymer through post-treatment to achieve hydrophilicity. The hydrophilicity and drug resistance of the PVDF membrane are improved, and a hydrophilic micro-ultrafiltration membrane with drug resistance is obtained.

[0006] The specific technical scheme of the application is as follows:

[0007] The application provides a preparation method of a hydrophilic PVDF membrane with drug resistance, comprising the following steps:

[0008] The PVDF and the hydrophilic polymer are dissolved by a solvent to prepare a casting solution, and the casting solution is stirred and defoamed to form a gel film, and then the hollow fiber membrane is obtained by casting, and then the hollow fiber membrane is soaked in a solution containing an organic metal chelate to obtain the hydrophilic PVDF membrane with drug resistance.

[0009] In the application, a blending method is used, and the PVDF and the hydrophilic polymer are blended in the casting solution, and then the PVDF and the hydrophilic polymer are separated and formed into a film. In the post-treatment process of the membrane, the PVDF membrane is reacted with the organic metal chelate, so that the organic metal chelate is attached to the surface of the PVDF hydrophilic membrane. The hydrophilic organic metal chelate can induce the oxidant such as NaClO to attack the high electron density part preferentially, so as to inhibit the decomposition of the skeleton and the breaking of the chemical bond in the hydrophilic polymer, and finally the PVDF membrane can keep hydrophilic for a long time, and the service life of the filter membrane is prolonged.

[0010] Preferably, the organic metal chelate is one or more of a carboxylic acid type chelate, a lactic acid chelate and an alkanolamine chelate.

[0011] More preferably, the organic metal chelate is an aminocarboxylic acid chelate and / or a hydroxycarboxylic acid chelate.

[0012] The organic metal chelate is attached to the surface of the PVDF hydrophilic membrane, and the surface potential of the aminocarboxylic acid chelate and / or the hydroxycarboxylic acid chelate changes with the change of the acid-base environment of the environment:

[0013] In an acidic environment, the middle part segment of the aminocarboxylic acid chelate and / or the hydroxycarboxylic acid chelate is electrically neutral, the outer segment is protonated, and the whole chelate is positively charged, so that the PVDF membrane has the effect of keeping hydrophilic for a long time in an acidic environment.

[0014] In an alkaline environment, the middle part segment of the aminocarboxylic acid chelate and / or the hydroxycarboxylic acid chelate is negatively charged, and the outer segment is positively charged. The middle segment and the outer segment have electrostatic interaction, so that the PVDF membrane has the effect of keeping hydrophilic for a long time in an alkaline environment.

[0015] Further, the organic metal chelate is sodium ethylenediaminetetramethylene phosphonate.

[0016] By using the above technical solution, the hydrophilic and drug-resistant property of the PVDF membrane is significantly improved after the surface treatment of the organic metal chelate; compared with using different concentrations of organic metal chelates to treat the PVDF membrane, the results show that the concentration of 5-8wt% is the best; compared with using different types of organic metal chelates to treat the PVDF membrane, the results show that the drug-resistant effect obtained by selecting amino carboxylic acid and / or hydroxyl carboxylic acid chelate as the organic metal chelate to treat the PVDF membrane is better. Based on the experimental and theoretical research, the team of the present application found that the drug-resistant effect obtained by selecting ethylenediamine tetramethylene phosphonic acid sodium as the organic metal chelate to treat the PVDF membrane is the best, and the reason is that the chelate and the PVDF membrane can form a new texture of grafting network or crosslinking network through hydrogen bond or complexation.

[0017] Preferably, the mass fraction of the organic metal chelate in the solution containing the organic metal chelate is 5-8%.

[0018] When the mass fraction of the organic metal chelate aqueous solution is greater than 8wt%, the hydrophilic effect of the prepared PVDF membrane is poor. Based on the experimental and theoretical research, the team of the present application found that when the mass fraction of the organic metal chelate aqueous solution is controlled to be 5-8wt%, the formation of by-products can be reduced, the purity of the product is improved, and the PVDF membrane treated by this method has better hydrophilic resistance. When the mass fraction of the organic metal chelate aqueous solution is greater than 8wt%, by-products are produced; the reason is that the organic metal chelate is attached to the surface of the PVDF hydrophilic membrane, the surface potential of the amino carboxylic acid and / or hydroxyl carboxylic acid chelate is too high, the hydrophilic organic metal chelate is decarboxylated or intermolecular condensation occurs, and a side reaction is generated to produce impurities.

[0019] Preferably, the temperature of the soaking is 50-90℃.

[0020] More preferably, the temperature of the soaking is 80-90℃.

[0021] In order to further improve the drug resistance, the PVDF film formed by gel phase separation needs to be soaked in a solution containing an organic metal chelate for post-processing, and the PVDF film is soaked in a hydrophilic organic metal chelate aqueous solution for 5-60 min and then taken out and drained. The temperature of the hydrophilic organic metal chelate aqueous solution is 50-90℃. Based on experiments and theoretical research, the team of the present application found that when the temperature of the hydrophilic organic metal chelate aqueous solution is higher than 90℃, by-products are produced. It is speculated that different post-processing temperatures have an effect on the organic metal chelate grafting reaction, and when the temperature is too high, the hydrophilic organic metal chelate is decarboxylated or intermolecular condensation occurs, resulting in a side reaction and the generation of impurities. Based on this, the temperature of the hydrophilic organic metal chelate aqueous solution is controlled at 80-90℃, which can reduce the formation of by-products and improve the purity of the product. The PVDF film obtained by this method has better hydrophilic resistance.

[0022] As a preferred, the hydrophilic polymer is one or several of polymethyl methacrylate, polyvinyl alcohol, polyvinyl butyral, vinyl acetate-maleic anhydride copolymer, polyacrylic acid and diethanolamine.

[0023] More preferably, the hydrophilic polymer is polyvinyl butyral.

[0024] The hydrophilic polymer and PVDF are blended to form a film by wet phase inversion. The aforementioned hydrophilic polymer containing amine groups, carboxyl groups or hydroxyl groups can be distributed on the surface of the PVDF film pores by blending, thereby improving the hydrophilic performance of PVDF. Based on experiments and theoretical research, the team of the present application found that polyvinyl butyral is the best choice as a hydrophilic polymer for blending with PVDF to improve the hydrophilic performance of PVDF, and the reason is that polyvinyl butyral can be loaded inside the pores of the PVDF film, resulting in a new structure and improving the hydrophilic performance.

[0025] As a preferred, the casting solution includes the following components by weight:

[0026] PVDF 10-30 parts;

[0027] Hydrophilic polymer 0.1-10 parts;

[0028] Solvent 50-80 parts.

[0029] More preferably, the casting solution includes the following components by weight:

[0030] PVDF 15-25 parts;

[0031] Hydrophilic polymer 0.5-5 parts;

[0032] Solvent 50-70 parts.

[0033] The casting solution further comprises an additive. The additive is one or more of polyoxyethylene, polyethylene glycol, water, ethanol, ethylene glycol, diethylene glycol and ethylene glycol monomethyl ether, and the weight of the additive is 0.5-20 parts. The molecular weight of the polyoxyethylene is 1x10 4 ~1x10 6 ; the molecular weight of the polyethylene glycol is 2x10 2 ~2x10 4 . In the casting solution, the solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone, and the molecular weight of the PVDF is 400,000-1,000,000, and more preferably, the molecular weight of the PVDF is 500,000-800,000.

[0034] Preferably, the gel forms a film, specifically, the casting solution is gelled and solidified in a coagulation liquid to form a hollow fiber membrane.

[0035] The gel forms a film, i.e. the casting solution is cast on a glass plate to form a flat film, or is extruded through a cannula spinneret, the inner cavity is formed by a core liquid, and then the casting solution is gelled and solidified in a coagulation liquid to form a hollow fiber membrane. The temperature of the coagulation bath is 20-80°C. The coagulation bath or the core liquid is preferably a combination of a solvent and a non-solvent.

[0036] Preferably, the temperature of the dissolution is 25-100°C.

[0037] The PVDF and the hydrophilic polymer are dissolved in the solvent and stirred until uniform. After the stirring is completed, a defoaming operation is performed. The PVDF and the hydrophilic polymer are fully mixed with the solvent, the temperature of the stirring is 25-100°C, and the time of the stirring is 4-48 hours.

[0038] Preferably, the temperature of the casting solution is 20-80°C.

[0039] Compared with the prior art, the present application has the following beneficial effects:

[0040] (1) The present application provides a preparation method of a hydrophilic PVDF membrane with drug resistance, which is simple in process and can realize industrialized continuous production.

[0041] (2) The present application first blends the hydrophilic polymer with the PVDF to form a film by wet phase inversion, and then grafts the organic metal chelate onto the hydrophilic polymer by post-processing to achieve hydrophilicity. The hydrophilicity and drug resistance of the PVDF membrane are improved, and a hydrophilic micro-ultrafiltration membrane with drug resistance is obtained.

[0042] (3) The present application provides a hydrophilic PVDF membrane with drug resistance, which is permanently hydrophilic and has strong resistance to drugs, and is especially suitable for industrial membrane water treatment process to resist strong acids, strong bases and oxidizing agents.

[0043] (4) By using the hydrophilic PVDF membrane with drug resistance of the present application, the problem of membrane pollution caused by the hydrophobicity of PVDF material itself in the water separation process is solved, not only the flux is improved, but also the separation performance is enhanced, thereby reducing the cleaning or replacing membrane cost, and greatly prolonging the service life of the membrane. DETAILED DESCRIPTION

[0044] The present application will be further described below in combination with examples.

[0045] General examples

[0046] A preparation method of a hydrophilic PVDF membrane with drug resistance, comprising the following steps:

[0047] Dissolve PVDF and hydrophilic polymer with a solvent to prepare a casting solution, gel into a membrane after stirring and defoaming, obtain a hollow fiber membrane, and then immerse it in a solution containing an organic metal chelate to obtain a hydrophilic PVDF membrane with drug resistance.

[0048] As a preferred, the organic metal chelate is one or several of carboxylic acid type chelate, lactic acid chelate and alkanolamine chelate.

[0049] More preferably, the organic metal chelate is amino carboxylic acid and / or hydroxyl carboxylic acid chelate.

[0050] Further, the organic metal chelate is sodium ethylenediaminetetramethylene phosphonate.

[0051] As a preferred, the temperature of the immersion is 50-90℃.

[0052] More preferably, the temperature of the immersion is 80-90℃.

[0053] As a preferred, the hydrophilic polymer is one or several of polymethyl methacrylate, polyvinyl alcohol, polyvinyl butyral, vinyl acetate-maleic anhydride copolymer, polyacrylic acid and diethanolamine.

[0054] More preferably, the hydrophilic polymer is polyvinyl butyral.

[0055] As a preferred, the casting solution includes the following components by weight:

[0056] PVDF 10-30 parts;

[0057] Hydrophilic polymer 0.1-10 parts;

[0058] Solvent 50-80 parts.

[0059] More preferably, the casting solution comprises, by weight parts:

[0060] PVDF 15-25 parts;

[0061] Hydrophilic polymer 0.5-5 parts;

[0062] Solvent 50-70 parts.

[0063] As preferred, the gel forms a membrane, specifically the casting solution is gelled and solidified in a coagulation liquid to form a hollow fiber membrane.

[0064] As preferred, the temperature of the dissolution is 25-100°C.

[0065] As preferred, the temperature of the casting solution is 20-80°C.

[0066] Example 1

[0067] A hydrophilic PVDF membrane with drug resistance is prepared using the formulation shown in Table 1, specifically:

[0068] 320g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 100g of hydrophilic polymer (polyvinyl butyral), 100g of polyethylene glycol, 300g of ethylene glycol monomethyl ether, 1080g of dimethylformamide are uniformly mixed at 80°C, dissolved with stirring, degassed, coated on a polyester hollow braided cord with an outer diameter of 1.85-1.9mm at 80°C, gelled and solidified by a 70°C, 40% concentration dimethylformamide coagulation bath for 10-60s, then collected by a yarn collector to form a reinforced PVDF hollow fiber membrane with an outer diameter of 2.05mm, and then the hollow fiber membrane is immersed in an 80°C, 5wt% hydrophilic organic metal chelate (disodium ethylenediaminetetraacetate) aqueous solution for 30min, then taken out and drained.

[0069] Example 2

[0070] A hydrophilic PVDF membrane with drug resistance is prepared using the formulation shown in Table 1, specifically:

[0071] 320g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 100g of hydrophilic polymer (polyvinyl butyral), 100g of polyethylene glycol, 300g of ethylene glycol monomethyl ether, and 1080g of dimethylformamide were uniformly mixed at 80℃, stirred to dissolve, and degassed. The mixture was then coated onto a polyester hollow braided rope with an outer diameter of 1.85-1.9mm at 80℃. The rope was then gelled and cured in a 40% dimethylformamide coagulation bath at 70℃ for 10-60 seconds. After being wound up by a winding wheel, a 2.05mm outer diameter reinforced PVDF hollow fiber membrane was obtained. The hollow fiber membrane was then immersed in an aqueous solution of a 5wt% hydrophilic organometallic chelate (sodium gluconate) at 80℃ for 30 minutes and then drained.

[0072] Example 3

[0073] A hydrophilic PVDF membrane with chemical resistance was prepared using the formulation shown in Table 1, specifically as follows:

[0074] 320g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 100g of hydrophilic polymer (polyvinyl butyral), 100g of polyethylene glycol, 300g of ethylene glycol monomethyl ether, and 1080g of dimethylformamide were uniformly mixed at 80℃, stirred to dissolve, and degassed. The mixture was then coated onto a polyester hollow braided rope with an outer diameter of 1.85-1.9mm at 80℃. The rope was then gelled and cured in a 40% dimethylformamide coagulation bath at 70℃ for 10-60 seconds. After being wound up by a winding wheel, a 2.05mm outer diameter reinforced PVDF hollow fiber membrane was obtained. The hollow fiber membrane was then immersed in a 5wt% aqueous solution of a hydrophilic organometallic chelate (sodium ethylenediaminetetramethylphosphonate) at 80℃ for 30 minutes, and then drained.

[0075] Example 4

[0076] A hydrophilic PVDF membrane with chemical resistance was prepared using the formulation shown in Table 1, specifically as follows:

[0077] 320g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 100g of hydrophilic polymer (polyvinyl butyral), 100g of polyethylene glycol, 300g of ethylene glycol monomethyl ether, and 1080g of dimethylformamide were uniformly mixed at 80℃, stirred to dissolve, and degassed. The mixture was then coated onto a polyester hollow braided rope with an outer diameter of 1.85-1.9mm at 80℃. The rope was then gelled and cured in a 40% dimethylformamide coagulation bath at 70℃ for 10-60 seconds. After being wound up by a winding wheel, a 2.05mm outer diameter reinforced PVDF hollow fiber membrane was obtained. The hollow fiber membrane was then immersed in an aqueous solution of a 2wt% hydrophilic organometallic chelate (sodium ethylenediaminetetramethylphosphonate) at 80℃ for 30 minutes, and then drained.

[0078] Example 5

[0079] A hydrophilic PVDF membrane with drug resistance was prepared using the formulation shown in Table 1, specifically:

[0080] 320g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 100g of hydrophilic polymer (polyvinyl butyral), 100g of polyethylene glycol, 300g of ethylene glycol monomethyl ether, and 1080g of dimethylformamide were uniformly mixed at 80°C, dissolved with stirring, degassed, coated on a polyester hollow braided cord with an outer diameter of 1.85-1.9mm at 80°C, and gelled and solidified into shape in a 70°C dimethylformamide coagulation bath with a concentration of 40% for 10-60s, and then wound on a take-up reel to produce an inner-lining-reinforced PVDF hollow fiber membrane with an outer diameter of 2.05mm. Subsequently, the hollow fiber membrane was immersed in a 60°C aqueous solution of a hydrophilic organometallic chelate (sodium ethylenediaminetetra(methylene phosphonate)) with a concentration of 5wt% for 30min, and then removed and drained.

[0081] Example 6

[0082] A hydrophilic PVDF membrane with drug resistance was prepared using the formulation shown in Table 1, specifically:

[0083] 320g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 100g of hydrophilic polymer (polyvinyl butyral), 100g of polyethylene glycol, 300g of ethylene glycol monomethyl ether, and 1080g of dimethylformamide were uniformly mixed at 80°C, dissolved with stirring, degassed, coated on a polyester hollow braided cord with an outer diameter of 1.85-1.9mm at 80°C, and gelled and solidified into shape in a 70°C dimethylformamide coagulation bath with a concentration of 40% for 10-60s, and then wound on a take-up reel to produce an inner-lining-reinforced PVDF hollow fiber membrane with an outer diameter of 2.05mm. Subsequently, the hollow fiber membrane was immersed in a 60°C aqueous solution of a hydrophilic organometallic chelate (sodium ethylenediaminetetra(methylene phosphonate)) with a concentration of 5wt% for 30min, and then removed and drained.

[0084] Example 7

[0085] A hydrophilic PVDF membrane with drug resistance was prepared using the formulation shown in Table 1, specifically:

[0086] 320g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 100g of hydrophilic polymer (polyvinyl butyral), 100g of polyethylene glycol, 300g of ethylene glycol monomethyl ether, and 1080g of dimethylformamide were uniformly mixed at 80℃, stirred to dissolve, and degassed. The mixture was then coated onto a polyester hollow braided rope with an outer diameter of 1.85-1.9mm at 80℃. The rope was then gelled and cured in a 40% dimethylformamide coagulation bath at 70℃ for 10-60 seconds. After being wound up by a winding wheel, a 2.05mm outer diameter reinforced PVDF hollow fiber membrane was obtained. The hollow fiber membrane was then immersed in a 5wt% aqueous solution of a hydrophilic organometallic chelate (sodium ethylenediaminetetramethylphosphonate) at 90℃ for 30 minutes, and then drained.

[0087] Example 8

[0088] A hydrophilic PVDF membrane with chemical resistance was prepared using the formulation shown in Table 1, specifically as follows:

[0089] 320g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 100g of hydrophilic polymer (polyvinyl butyral), 100g of polyethylene glycol, 300g of ethylene glycol monomethyl ether, and 1080g of dimethylformamide were uniformly mixed at 80℃, stirred to dissolve, and degassed. The mixture was then coated onto a polyester hollow braided rope with an outer diameter of 1.85-1.9mm at 80℃. The rope was then gelled and cured in a 40% dimethylformamide coagulation bath at 70℃ for 10-60 seconds. After being wound up by a winding wheel, a 2.05mm outer diameter reinforced PVDF hollow fiber membrane was obtained. The hollow fiber membrane was then immersed in a 50℃ aqueous solution of a hydrophilic organometallic chelate (sodium ethylenediaminetetramethylphosphonate) at a concentration of 5wt% for 30 minutes before being removed and drained.

[0090] Example 9

[0091] A hydrophilic PVDF membrane with chemical resistance was prepared using the formulation shown in Table 1, specifically as follows:

[0092] 320g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 100g of hydrophilic polymer (polyvinyl butyral), 100g of polyethylene glycol, 300g of ethylene glycol monomethyl ether, and 1080g of dimethylformamide were uniformly mixed at 80℃, stirred to dissolve, and degassed. The mixture was then coated onto a polyester hollow braided rope with an outer diameter of 1.85-1.9mm at 80℃. The rope was then gelled and cured in a 40% dimethylformamide coagulation bath at 70℃ for 10-60 seconds. After being wound up by a winding wheel, a 2.05mm outer diameter reinforced PVDF hollow fiber membrane was obtained. The hollow fiber membrane was then immersed in a 5wt% aqueous solution of a hydrophilic organometallic chelate (sodium ethylenediaminetetramethylphosphonate) at 120℃ for 30 minutes and then drained.

[0093] Example 10

[0094] A hydrophilic PVDF membrane with drug resistance was prepared using the formulation shown in Table 1, specifically:

[0095] 320g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 100g of hydrophilic polymer (polyvinyl butyral), 100g of polyethylene glycol, 300g of ethylene glycol monomethyl ether, 1180g of dimethylformamide were uniformly mixed at 80°C, dissolved with stirring, degassed, coated on a polyester hollow braided rope with an outer diameter of 1.85-1.9mm at 80°C, and gelled and solidified into a shape by passing through a 70°C dimethylformamide coagulation bath with a concentration of 40% for 10-60s, and then wound on a take-up reel to produce an inner-lining-reinforced PVDF hollow fiber membrane with an outer diameter of 2.05mm. Subsequently, the hollow fiber membrane was immersed in an 80°C aqueous solution of a hydrophilic organometallic chelate (sodium ethylenediaminetetramethylene phosphonate) with a concentration of 10wt% for 30min, and then taken out and drained.

[0096] Table 1 Membrane preparation formulation

[0097]

[0098] Comparative Example 1

[0099] A hydrophilic PVDF membrane with drug resistance was prepared using the formulation shown in Table 1, specifically:

[0100] 320g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 100g of hydrophilic polymer (polyvinyl butyral), 100g of polyethylene glycol, 300g of ethylene glycol monomethyl ether, 1180g of dimethylformamide were uniformly mixed at 80°C, dissolved with stirring, degassed, coated on a polyester hollow braided rope with an outer diameter of 1.85-1.9mm at 80°C, and gelled and solidified into a shape by passing through a 70°C dimethylformamide coagulation bath with a concentration of 40% for 10-60s, and then wound on a take-up reel to produce an inner-lining-reinforced PVDF hollow fiber membrane with an outer diameter of 2.05mm. Subsequently, the hollow fiber membrane was immersed in an 80°C aqueous solution of a hydrophilic organometallic chelate (sodium ethylenediaminetetramethylene phosphonate) with a concentration of 10wt% for 30min, and then taken out and drained.

[0101] Comparative Example 2

[0102] A hydrophilic PVDF membrane with drug resistance was prepared using the formulation shown in Table 1, specifically:

[0103] 320g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 100g of a hydrophilic polymer (polyacrylate), 100g of polyethylene glycol, 300g of ethylene glycol monomethyl ether, and 1180g of dimethylformamide were uniformly mixed at 80°C, dissolved by stirring, degassed, coated on a polyester hollow braided cord with an outer diameter of 1.85-1.9mm at 80°C, gelled and solidified by a 70°C dimethylformamide coagulation bath with a concentration of 40% for 10-60s, and then taken up by a take-up wheel to produce an inner-lining reinforced PVDF hollow fiber membrane with an outer diameter of 2.05mm.

[0104] Comparative Example 3

[0105] A hydrophilic PVDF membrane with a drug resistance was prepared using the formulation shown in Table 1, specifically:

[0106] 320g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 100g of a hydrophilic polymer (polyacrylate), 100g of polyethylene glycol, 300g of ethylene glycol monomethyl ether, and 1180g of dimethylformamide were uniformly mixed at 80°C, dissolved by stirring, degassed, coated on a polyester hollow braided cord with an outer diameter of 1.85-1.9mm at 80°C, gelled and solidified by a 70°C dimethylformamide coagulation bath with a concentration of 40% for 10-60s, and then taken up by a take-up wheel to produce an inner-lining reinforced PVDF hollow fiber membrane with an outer diameter of 2.05mm.

[0107] Comparative Example 4

[0108] A hydrophilic PVDF membrane with a drug resistance was prepared using the formulation shown in Table 1, specifically:

[0109] 320g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 100g of a hydrophilic polymer (polyacrylate), 100g of polyethylene glycol, 300g of ethylene glycol monomethyl ether, and 1180g of dimethylformamide were uniformly mixed at 80°C, dissolved by stirring, degassed, coated on a polyester hollow braided cord with an outer diameter of 1.85-1.9mm at 80°C, gelled and solidified by a 70°C dimethylformamide coagulation bath with a concentration of 40% for 10-60s, and then taken up by a take-up wheel to produce an inner-lining reinforced PVDF hollow fiber membrane with an outer diameter of 2.05mm.

[0110] Comparative Example 5

[0111] A hydrophilic PVDF membrane with a drug resistance was prepared using the formulation shown in Table 1, specifically:

[0112] The 320g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 100g of hydrophilic polymer (vinyl acetate-maleic anhydride copolymer), 100g of polyethylene glycol, 300g of ethylene glycol monomethyl ether, 1180g of dimethylformamide were uniformly mixed at 80°C, dissolved by stirring, degassed, coated on a polyester hollow braided cord with an outer diameter of 1.85-1.9mm at 80°C, gelled and solidified into shape by a dimethylformamide coagulation bath with a concentration of 40% at 70°C for 10-60s, and then taken up by a take-up wheel to produce an inner-lining reinforced PVDF hollow fiber membrane with an outer diameter of 2.05mm.

[0113] Comparative Example 6

[0114] A hydrophilic PVDF membrane with drug resistance was prepared using the formulation shown in Table 1, specifically:

[0115] The 320g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 100g of hydrophilic polymer (vinyl acetate-maleic anhydride copolymer), 100g of polyethylene glycol, 300g of ethylene glycol monomethyl ether, 1180g of dimethylformamide were uniformly mixed at 80°C, dissolved by stirring, degassed, coated on a polyester hollow braided cord with an outer diameter of 1.85-1.9mm at 80°C, gelled and solidified into shape by a dimethylformamide coagulation bath with a concentration of 40% at 70°C for 10-60s, and then taken up by a take-up wheel to produce an inner-lining reinforced PVDF hollow fiber membrane with an outer diameter of 2.05mm.

[0116] Comparative Example 7

[0117] A hydrophilic PVDF membrane with drug resistance was prepared using the formulation shown in Table 1, specifically:

[0118] The 320g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 100g of hydrophilic polymer (vinyl acetate-maleic anhydride copolymer), 100g of polyethylene glycol, 300g of ethylene glycol monomethyl ether, 1180g of dimethylformamide were uniformly mixed at 80°C, dissolved by stirring, degassed, coated on a polyester hollow braided cord with an outer diameter of 1.85-1.9mm at 80°C, gelled and solidified into shape by a dimethylformamide coagulation bath with a concentration of 40% at 70°C for 10-60s, and then taken up by a take-up wheel to produce an inner-lining reinforced PVDF hollow fiber membrane with an outer diameter of 2.05mm.

[0119] Comparative Example 8

[0120] A hydrophilic PVDF membrane with drug resistance was prepared using the formulation shown in Table 1, specifically:

[0121] 600g of polyvinylidene fluoride resin with a weight average molecular weight of 600,000, 200g of hydrophilic polymer (diethanolamine), 100g of polyethylene glycol, 100g of ethylene glycol monomethyl ether, 1000g of dimethylformamide were uniformly mixed at 80°C, dissolved by stirring, degassed, coated on a polyester hollow braided rope with an outer diameter of 1.85-1.9mm at 80°C, and gelled and solidified into a shape by a dimethylformamide concentration of 40% at 70°C for 10-60s, and then wound by a yarn take-up wheel to obtain an inner lining reinforced PVDF hollow fiber membrane with an outer diameter of 2.05mm.

[0122] Test Example

[0123] The hydrophilic PVDF membranes with drug resistance prepared in each example and comparative example were subjected to hydrophilicity test and drug resistance test: the hydrophilic PVDF membranes were respectively placed in a solution of pH = 1, pH = 12 and 2000ppm NaClO and continuously soaked for more than 30 days, and samples were taken every 3 days for hydrophilicity determination, mainly including water contact angle and wetting time. The change of hydrophilicity at different times was compared, wherein the qualified standard of contact angle was ≤90°, and the qualified standard of wetting time was ≤120s, and the results are shown in Table 2.

[0124] Table 2 Performance test results of all comparative examples and examples

[0125]

[0126]

[0127] Wherein, “O” represents that both the contact angle and the wetting time meet the standard, and “X” represents that one or neither of the contact angle and the wetting time meets the standard.

[0128] From the above table, it can be seen that:

[0129] Compared with examples 1-2, example 3 uses ethylenediaminetetramethylene phosphonic acid sodium as an organic metal chelate for treatment, and the PVDF membrane prepared has the best drug resistance effect. Based on experimental and theoretical research, the team found that compared with using different types of organic metal chelates to treat PVDF membranes, the results showed that the drug resistance effect of using aminocarboxylic acid and / or hydroxycarboxylic acid chelate as an organic metal chelate to treat PVDF membranes was better, and it was speculated that the reason was that the chelate of ethylenediaminetetramethylene phosphonic acid sodium could form a new texture of graft network or crosslinking network with PVDF membrane through hydrogen bonding or complexation.

[0130] Compared with Example 3 and Examples 6-8, the temperature of the hydrophilic organometallic chelate aqueous solution in Example 9 is greater than 90℃, and the hydrophilic effect of the PVDF membrane prepared is poor. Based on experimental and theoretical research, the present team found that when the temperature of the hydrophilic organometallic chelate aqueous solution is controlled at 80-90℃, the formation of by-products can be reduced, the purity of the product is improved, and the PVDF membrane obtained by this method has better hydrophilic resistance. When the temperature of the hydrophilic organometallic chelate aqueous solution is greater than 90℃, by-products are produced; it is speculated that the reason is that different post-treatment temperatures have an effect on the grafting reaction of the organometallic chelate: when the temperature is too high, the hydrophilic organometallic chelate decarboxylates or intermolecular condensation occurs, a side reaction is produced, and impurities are generated.

[0131] Compared with Examples 3-5, the mass fraction of the organometallic chelate aqueous solution in Example 10 is greater than 8wt%, and the hydrophilic effect of the PVDF membrane prepared is poor. Based on experimental and theoretical research, the present team found that when the mass fraction of the hydrophilic organometallic chelate aqueous solution is controlled at 5-8wt%, the formation of by-products can be reduced, the purity of the product is improved, and the PVDF membrane obtained by this method has better hydrophilic resistance. When the mass fraction of the hydrophilic organometallic chelate aqueous solution is greater than 8wt%, by-products are produced; it is speculated that the reason is that the organometallic chelate is attached to the surface of the PVDF hydrophilic membrane, the surface potential of the amino carboxylic acid chelate and / or the hydroxy carboxylic acid chelate is too high, the hydrophilic organometallic chelate decarboxylates or intermolecular condensation occurs, a side reaction is produced, and impurities are generated.

[0132] Compared with Comparative Examples 1-6, it can be known that:

[0133] The hydrophilic PVDF membrane obtained by blending the hydrophilic polymer has been endowed with hydrophilicity;

[0134] The hydrophilic PVDF membrane obtained by blending the hydrophilic polymer gradually loses under the treatment of the medicament and is difficult to permanently maintain hydrophilicity;

[0135] Comparative Example 3 selects polyvinyl butyral as the hydrophilic polymer for blending with PVDF to improve the hydrophilic performance of PVDF, and the effect is the best. Based on experimental and theoretical research, the present team found that the aforementioned hydrophilic polymer containing amine groups, carboxyl groups or hydroxyl groups can be distributed on the surface of the PVDF membrane hole by blending to improve the hydrophilic performance of PVDF;

[0136] After the surface treatment of the organometallic chelate in Examples 1-10, the hydrophilic resistance of the PVDF membrane is significantly improved.

[0137] The raw materials and equipment used in the present application are all common raw materials and equipment in the field unless otherwise specified; the methods used in the present application are all conventional methods in the field unless otherwise specified.

[0138] The above is only the preferred embodiment of the present application, and does not limit the present application. Any simple modification, change and equivalent transformation of the above embodiment according to the technical essence of the present application still belongs to the protection scope of the technical solution of the present application.

Claims

1. A method for producing a hydrophilic PVDF membrane having a drug resistance, characterized by, The method comprises the following steps: The PVDF and the hydrophilic polymer are dissolved with a solvent to prepare a casting solution, and the casting solution is stirred and defoamed to form a gel film, so as to obtain a hollow fiber membrane; and the hollow fiber membrane is soaked in a solution containing sodium ethylenediaminetetra (methylenephosphonate), so as to obtain a hydrophilic PVDF membrane with drug resistance; and the mass fraction of the sodium ethylenediaminetetra (methylenephosphonate) in the solution is 5-8%.

2. The method of claim 1, wherein The mass fraction of the sodium ethylenediaminetetra (methylenephosphonate) in the solution is 5%.

3. The preparation method according to claim 1, characterized in that, The temperature of the soaking is 50-90 DEG C.

4. The preparation method according to claim 3, characterized in that, The temperature of the soaking is 80-90 DEG C.

5. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. The hydrophilic polymer is one or more of polyvinyl alcohol, polyvinyl butyral, vinyl acetate-maleic anhydride copolymer and polyacrylic acid.

6. The preparation method according to claim 5, characterized in that, The hydrophilic polymer is polyvinyl butyral.

7. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. The casting solution comprises the following components by weight: PVDF 10-30 parts; hydrophilic polymer 0.1-10 parts; solvent 50-80 parts.

8. The preparation method according to claim 7, characterized in that, The casting solution comprises the following components by weight: PVDF 15-25 parts; hydrophilic polymer 0.5-5 parts; solvent 50-70 parts.

9. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. The gel film forming specifically comprises gel solidification of the casting solution in a coagulation solution to form a hollow fiber membrane.

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