Amphiphilic polyvinylidene fluoride hollow fiber dry membrane and preparation method thereof

Abstract

The present invention provides an amphiphilic polyvinylidene fluoride hollow fiber dry membrane and a preparation method thereof, and relates to the field of water treatment technology. The preparation method of the amphiphilic polyvinylidene fluoride hollow fiber dry membrane provided by the present invention comprises: forming a polyvinylidene fluoride solution through a mold, and then sequentially undergoing initiation polymerization, non-solvent phase conversion curing and cleaning to prepare an amphiphilic polyvinylidene fluoride hollow fiber dry membrane; wherein the polyvinylidene fluoride solution comprises a hydrophilic monomer, a hydrophobic monomer, an initiator, polyvinylidene fluoride powder, a solvent and an additive. The preparation method has a simple and controllable production process and low manufacturing cost. The prepared amphiphilic polyvinylidene fluoride hollow fiber dry membrane has the advantages of good hydrophilicity, high interception accuracy and permeability, can be dried at high temperature, and abandons the traditional glycerin moisturizing process.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, in particular to an amphiphilic polyvinylidene fluoride hollow fiber dry membrane and a preparation method thereof. Background Art

[0002] Among the many membrane materials, polyvinylidene fluoride (PVDF), as a crystalline polymer membrane material, has excellent mechanical properties, thermal stability, resistance to chemical cleaning, weathering, oxidation, and radiation, and has been widely used in the preparation of microfiltration and ultrafiltration membranes. However, PVDF separation membranes still have the following problems in their application: (1) Its hydrophobic properties make it prone to protein adsorption contamination when treating water-based solutions containing natural organic substances such as biopharmaceuticals, food and beverages, and domestic sewage, thereby increasing cleaning costs and operating expenses; (2) The hydrophobic PVDF membrane has an extremely low surface energy, resulting in a low water flux and high energy consumption of the microporous membrane; (3) Existing membrane preparation and modification methods often lead to a contradiction between flux and retention rate. Improving flux often comes at the expense of reducing retention rate, while increasing retention rate often reduces its flux; (4) It is usually necessary to add a protective liquid to moisturize the membrane, which is not conducive to the storage, transportation, and use of the membrane, and it is easy to breed bacteria, causing secondary pollution.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The first object of the present invention is to provide a method for preparing an amphiphilic polyvinylidene fluoride hollow fiber dry membrane, which has low cost and simple production process.

[0005] A second object of the present invention is to provide an amphiphilic polyvinylidene fluoride hollow fiber dry membrane, which has strong hydrophilicity, high permeation flux and high retention accuracy, and can solve at least one of the above problems.

[0006] In a first aspect, the present invention provides a method for preparing an amphiphilic polyvinylidene fluoride hollow fiber dry membrane, comprising the following steps:

[0007] The polyvinylidene fluoride solution is formed into a mold, and then sequentially subjected to polymerization initiation, non-solvent phase conversion curing and washing to prepare an amphiphilic polyvinylidene fluoride hollow fiber dry membrane;

[0008] The polyvinylidene fluoride solution comprises a hydrophilic monomer, a hydrophobic monomer, an initiator, polyvinylidene fluoride powder, a solvent and additives.

[0009] As a further technical solution, the hydrophilic monomer has an N-vinyl group, including at least one of N-vinylpyrrolidone, N-vinylacetamide, N-vinylimidazole, N-vinylcaprolactam and N-vinylformamide;

[0010] The hydrophobic monomer includes propylene oxide;

[0011] The initiator is a radiation initiator, including a water-soluble peroxodisulfate initiator and a transition metal ion co-initiator;

[0012] The water-soluble peroxodisulfate initiator includes sodium peroxodisulfate, potassium peroxodisulfate or ammonium peroxodisulfate; the transition metal ion co-initiator includes ferric / ferrous, copper / cuprous, tetravalent cerium / trivalent cerium, cobalt / cobaltous, vanadate (V) / vanadate (IV), permanganate and manganese / manganous;

[0013] The solvent is a water-soluble solvent, including at least one of triethyl phosphate, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone;

[0014] The additive is an alcohol or acid additive, including at least one of ethylene glycol, ethylene glycol polymer, glycerol, dicarboxylic acid, and citric acid.

[0015] As a further technical solution, the polyvinylidene fluoride solution comprises 1 to 10 wt.% of the hydrophilic monomer, 1 to 10 wt.% of the hydrophobic monomer, 0.01 to 5 wt.% of the initiator, 10 to 25 wt.% of the polyvinylidene fluoride powder, 25 to 88 wt.% of the solvent, and 1 to 25 wt.% of the additive.

[0016] Preferably, in the polyvinylidene fluoride solution, the content of hydrophilic monomer is 3 wt.%, the content of hydrophobic monomer is 3 wt.%, the content of initiator is 0.6 wt.%, the content of polyvinylidene fluoride powder is 17 wt.%, the content of solvent is 66.4 wt.%, and the content of additives is 10 wt.%.

[0017] As a further technical solution, the mold forming is to form the polyvinylidene fluoride solution through a hollow fiber mold under pressurized conditions.

[0018] As a further technical solution, the mold further includes degassing and filtering before forming.

[0019] As a further technical solution, the initiation of polymerization includes ultraviolet radiation initiation of polymerization, and the radiation time is 5 to 100 seconds.

[0020] As a further technical solution, the non-solvent phase inversion solidification is to immerse the formed article after initiation of polymerization into a coagulation bath;

[0021] Preferably, the coagulation bath contains at least 20 wt.% of an alcohol non-solvent;

[0022] Preferably, the alcohol non-solvent includes at least one of ethylene glycol, ethylene glycol polymers, and glycerol.

[0023] As a further technical solution, the cleaning includes water cleaning;

[0024] Preferably, the cleaning temperature is 40-80°C;

[0025] Preferably, the cleaning further includes drying;

[0026] Preferably, the drying temperature is 40-60°C.

[0027] In a second aspect, the present invention provides an amphiphilic polyvinylidene fluoride hollow fiber dry membrane, which is prepared using the above-mentioned preparation method.

[0028] As a further technical solution, the water content of the amphiphilic polyvinylidene fluoride hollow fiber dry membrane is ≤1wt.%, the static hydrophilic contact angle is ≤40°, the dynamic water contact angle penetration time is ≤15s, the average pore size is ≤100nm, and the pure water permeability is ≥1000LMH / bar.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention modifies PVDF hollow fiber membrane by in-situ polymerization of amphiphilic polymer. Hydrophilic monomer, hydrophobic monomer and PVDF resin are fully miscible. After being triggered, the hydrophilic monomer and the hydrophobic monomer undergo polymerization reaction, and the generated amphiphilic polymer and PVDF molecular chain are entangled with each other to form an interpenetrating network structure. This structure forms a huge number of physical crosslinking points between the two molecules, and the amphiphilic polymer will only be lost after the material ages and the molecular chain breaks, so the hydrophilic effect is more lasting, which is initially manifested as a lower water contact angle and a higher pure water flux. The obtained polyvinylidene fluoride hollow fiber membrane can be dried at high temperature, abandoning the traditional glycerin moisturizing process, reducing the storage and transportation costs of the membrane, and becoming a dry membrane that can be repeatedly wetted and dried. The preparation method has a simple and controllable production process and low manufacturing cost. The prepared amphiphilic polyvinylidene fluoride hollow fiber dry membrane has the advantages of good hydrophilicity, high interception accuracy and high permeability. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1Schematic diagram of the process for preparing the amphiphilic PVDF hollow fiber dry membrane in Example 1;

[0033] Figure 2 is the dynamic water contact angle of the amphiphilic PVDF hollow fiber dry membrane of Example 1;

[0034] Figure 3 This is the pore size distribution of the amphiphilic PVDF hollow fiber dry membrane in Example 1. DETAILED DESCRIPTION

[0035] Below in conjunction with embodiment and example, embodiment of the present invention is described in detail, but those skilled in the art will appreciate that the following embodiment and example are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiment in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise all fall within the scope of protection of the present invention. Unspecified conditions are carried out according to the conditions of normal conditions or manufacturer's recommendations. Reagents used or instruments not specified by the manufacturer are conventional products that can be purchased commercially.

[0036] In a first aspect, the present invention provides a method for preparing an amphiphilic polyvinylidene fluoride hollow fiber dry membrane, comprising the following steps:

[0037] The polyvinylidene fluoride solution is formed into a mold, and then sequentially subjected to polymerization initiation, non-solvent phase conversion curing and washing to prepare an amphiphilic polyvinylidene fluoride hollow fiber dry membrane;

[0038] The polyvinylidene fluoride solution comprises a hydrophilic monomer, a hydrophobic monomer, an initiator, polyvinylidene fluoride powder, a solvent and additives.

[0039] The general amphiphilic polymer blending modification utilizes the hydrophobic interaction between the hydrophobic segments in the amphiphilic polymer and the PVDF molecules, but the intermolecular force is limited. Under the action of long-term running water scouring and molecular chain motion, the amphiphilic polymer gradually loses from the blended modified PVDF hollow fiber membrane, resulting in a decrease in the hydrophilicity of the membrane material. The present invention modifies the PVDF hollow fiber membrane by in-situ polymerization of amphiphilic polymers. The hydrophilic monomer, the hydrophobic monomer and the PVDF resin are fully miscible. After being triggered, the hydrophilic monomer and the hydrophobic monomer undergo polymerization reaction, and the generated amphiphilic polymer and the PVDF molecular chain are entangled with each other to form an interpenetrating network structure. This structure forms a huge number of physical cross-linking points between the two molecules, and the amphiphilic polymer will only be lost after the material ages and the molecular chain breaks, so the hydrophilic effect is more lasting, which is manifested as a lower water contact angle and a higher pure water flux at the beginning. The obtained polyvinylidene fluoride hollow fiber membrane can be dried at high temperature, abandoning the traditional glycerin moisturizing process, reducing the storage and transportation costs of the membrane, and is a dry membrane that can be repeatedly moistened and dried.

[0040] In some preferred embodiments, the hydrophilic monomer has an N-vinyl group, including but not limited to at least one of N-vinyl pyrrolidone, N-vinylacetamide, N-vinylimidazole, N-vinylcaprolactam and N-vinylformamide;

[0041] The hydrophobic monomer includes propylene oxide;

[0042] The initiator is a radiation initiator, including but not limited to a water-soluble peroxodisulfate initiator and a transition metal ion co-initiator;

[0043] The water-soluble peroxodisulfate initiator includes but is not limited to sodium peroxodisulfate, potassium peroxodisulfate or ammonium peroxodisulfate; the transition metal ion co-initiator includes ferric / ferrous, copper / cuprous, tetravalent cerium / trivalent cerium, cobalt / cobaltous, vanadate (V) / vanadate (IV), permanganate and manganese / manganous;

[0044] The solvent is a water-soluble solvent, including but not limited to at least one of triethyl phosphate, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone;

[0045] The additive is an alcohol or acid additive, including but not limited to at least one of ethylene glycol, ethylene glycol polymers, glycerol, dicarboxylic acid, and citric acid.

[0046] In some preferred embodiments, the content of the hydrophilic monomer in the polyvinylidene fluoride solution may be, for example, but not limited to, 1 wt.%, 2 wt.%, 4 wt.%, 6 wt.%, 8 wt.% or 10 wt.%, preferably 3 wt.%;

[0047] The content of the hydrophobic monomer is 1 wt.%, 2 wt.%, 4 wt.%, 6 wt.%, 8 wt.% or 10 wt.%, preferably 3 wt.%;

[0048] The content of the initiator is 0.01 wt.%, 0.02 wt.%, 0.05 wt.%, 0.1 wt.%, 0.2 wt.%, 0.5 wt.%, 1 wt.%, 2 wt.% or 5 wt.%, preferably 0.6 wt.%;

[0049] The content of the polyvinylidene fluoride powder is 10 wt.%, 15 wt.%, 20 wt.% or 25 wt.%, preferably 17 wt.%;

[0050] The content of the solvent is 25 wt.%, 45 wt.%, 65 wt.% or 88 wt.%, preferably 66.4 wt.%;

[0051] The content of the additive is 1 wt.%, 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.% or 25 wt.%, preferably 10 wt.%.

[0052] By further optimizing and adjusting the components and proportions in the polyvinylidene fluoride solution, the reaction is sufficient and the hydrophilic effect is long-lasting.

[0053] In some preferred embodiments, the mold forming is to form the polyvinylidene fluoride solution through a hollow fiber mold under pressurized conditions. The present invention does not impose any specific limitation on the pressure, as long as the polyvinylidene fluoride solution can be formed, for example, it can be carried out at a pressure of 0.2 MPa.

[0054] In some preferred embodiments, the preparation method of the polyvinylidene fluoride solution can be, for example, adding hydrophilic monomer, hydrophobic monomer, initiator, polyvinylidene fluoride powder, solvent, alcohol or acid additives according to the film-forming solution ratio into a dissolving kettle, and heating and stirring to dissolve under a protective atmosphere.

[0055] In some preferred embodiments, the process further includes degassing and filtering before the mold forming.

[0056] The prepared polyvinylidene fluoride solution may contain bubbles and solid impurities. In order to avoid structural defects of the hollow fiber membrane, the polyvinylidene fluoride solution is preferably degassed and filtered before mold forming. The degassed and filtered methods can be used in a manner familiar to those skilled in the art.

[0057] In some preferred embodiments, the initiating polymerization comprises ultraviolet radiation initiating polymerization, and the irradiation time can be, for example, but not limited to, 5s, 10s, 20s, 40s, 60s, 80s or 100s.

[0058] In some preferred embodiments, the non-solvent phase inversion solidification is performed by immersing the formed article after initiation of polymerization into a coagulation bath;

[0059] Preferably, the coagulation bath contains at least 20 wt.% of an alcohol non-solvent;

[0060] Preferably, the alcohol non-solvent includes at least one of ethylene glycol, ethylene glycol polymers, and glycerol.

[0061] In some preferred embodiments, the washing includes washing with water to remove soluble substances such as solvents, alcohols or acids;

[0062] Preferably, the cleaning temperature may be, for example, but not limited to, 40°C, 50°C, 60°C, 70°C or 80°C to accelerate the dissolution of the extractables;

[0063] Preferably, the cleaning further includes drying to remove excess water;

[0064] Preferably, the drying temperature may be, for example, but not limited to, 40°C, 45°C, 50°C, 55°C or 60°C.

[0065] In a second aspect, the present invention provides an amphiphilic polyvinylidene fluoride hollow fiber dry membrane, which is prepared using the above-mentioned preparation method.

[0066] After testing, the amphiphilic polyvinylidene fluoride hollow fiber dry membrane prepared by the above preparation method has a water content of ≤1wt.%, a static hydrophilic contact angle ≤40°, a dynamic water contact angle penetration time ≤15s, an average pore size ≤100nm, and a pure water permeability ≥1000LMH / bar.

[0067] The present invention is further described below by means of specific examples and comparative examples. However, it should be understood that these examples are merely provided for more detailed description and are not to be construed as limiting the present invention in any form.

[0068] Example 1

[0069] A method for manufacturing a polyvinylidene fluoride hollow fiber dry membrane modified by in-situ polymerization of an amphiphilic polymer (amphiphilic polyvinylidene fluoride hollow fiber dry membrane) comprises the following steps:

[0070] (1) Preparation of polyvinylidene fluoride solution: 3 wt.% of hydrophilic monomer N-vinyl pyrrolidone, 3 wt.% of hydrophobic monomer propylene oxide, 0.5 wt.% of ammonium peroxodisulfate and 0.1 wt.% of ferrous sulfate / ferrous sulfate as radiation initiator, 17 wt.% of PVDF powder (Solvay 1015), 66.4 wt.% of solvent N,N-dimethylacetamide, and 10 wt.% of polyethylene glycol 400 were added to a dissolving kettle, and heated to 70°C under nitrogen protection and stirred to dissolve;

[0071] (2) Molding by a mold: the PVDF solution prepared in step (1) is statically degassed and filtered, and then passed through a hollow fiber mold (model Ф54×Ф2.8×Ф2.0×Ф1.75) at a pressure of 0.2 MPa to form a preliminary molded object;

[0072] (3) curing by radiation-induced polymerization and non-solvent phase inversion: the formed article obtained in step (2) was subjected to ultraviolet radiation-induced polymerization for 20 seconds before being immersed in a water bath containing 30% polyethylene glycol 400 to solidify, thereby obtaining a PVDF hollow fiber membrane;

[0073] (4) Removing soluble matter and drying: The PVDF hollow fiber membrane obtained in step (3) is subjected to five stages of extraction in hot water at 60°C to remove soluble matter such as N,N-dimethylacetamide and polyethylene glycol 400, and then dried in hot air at 60°C to obtain a PVDF hollow fiber dry membrane modified by in-situ polymerization of an amphiphilic polymer. The PVDF hollow fiber dry membrane modified by in-situ polymerization of an amphiphilic polymer obtained by the above method is a hollow fiber membrane having an outer diameter of 2.0 mm and a wall thickness of 100 μm.

[0074] Example 2

[0075] A method for manufacturing an amphiphilic polyvinylidene fluoride hollow fiber dry membrane, the experimental process is as follows Figure 1 As shown, the following steps are included:

[0076] (1) Preparation of polyvinylidene fluoride solution: 10 wt.% of a hydrophilic monomer N-vinylacetamide, 10 wt.% of a hydrophobic monomer propylene oxide, 4 wt.% of potassium peroxodisulfate and 1 wt.% of copper sulfate / cuprous sulfate as radiation initiators, 10 wt.% of PVDF powder (Solvay 1015), 64 wt.% of a solvent triethyl phosphate, and 1 wt.% of glycerol were added to a dissolving kettle, and heated to 70°C under nitrogen protection, stirred and dissolved;

[0077] (2) Molding by a mold: the PVDF solution prepared in step (1) is statically degassed and filtered, and then passed through a hollow fiber mold (model Ф54×Ф2.8×Ф2.0×Ф1.75) at a pressure of 0.2 MPa to form a preliminary molded object;

[0078] (3) curing by radiation-induced polymerization and non-solvent phase inversion: the formed article obtained in step (2) was subjected to ultraviolet radiation-induced polymerization for 100 seconds before being solidified in a 20% glycerol water bath to obtain a PVDF hollow fiber membrane;

[0079] (4) Removal of soluble matter and drying: The PVDF hollow fiber membrane obtained in step (3) is subjected to five-stage extraction in hot water at 60°C to remove soluble matter such as triethyl phosphate and propylene glycol, and then dried in hot air at 60°C to obtain a PVDF hollow fiber dry membrane modified by in-situ polymerization of an amphiphilic polymer.

[0080] Example 3

[0081] A method for manufacturing an amphiphilic polyvinylidene fluoride hollow fiber dry membrane comprises the following steps:

[0082] (1) Preparation of polyvinylidene fluoride solution: 2 wt.% of hydrophilic monomer N-vinylcaprolactam, 1 wt.% of hydrophobic monomer propylene oxide, 0.08 wt.% of sodium peroxodisulfate and 0.02 wt.% of cobalt sulfate / cobaltous sulfate as radiation initiators, 25 wt.% of PVDF powder (Solvay 1015), 46.9 wt.% of solvent dimethyl sulfoxide, and 25 wt.% of ethylene glycol were added to a dissolving kettle, and heated to 70°C under nitrogen protection and stirred for dissolution;

[0083] (2) Molding by a mold: the PVDF solution prepared in step (1) is statically degassed and filtered, and then passed through a hollow fiber mold (model Ф54×Ф2.8×Ф2.0×Ф1.75) at a pressure of 0.2 MPa to form a preliminary molded object;

[0084] (3) curing by radiation-induced polymerization and non-solvent phase inversion: the formed article obtained in step (2) was subjected to ultraviolet radiation-induced polymerization for 5 seconds before being immersed in a 60% ethylene glycol water bath for solidification to obtain a PVDF hollow fiber membrane;

[0085] (4) Removal of soluble matter and drying: The PVDF hollow fiber membrane obtained in step (3) is subjected to five-stage extraction in hot water at 60°C to remove soluble matter such as dimethyl sulfoxide and ethylene glycol, and then dried in hot air at 60°C to obtain a PVDF hollow fiber dry membrane modified by in situ polymerization of an amphiphilic polymer.

[0086] Comparative Example 1

[0087] A hollow fiber membrane, the preparation method is as follows:

[0088] (1) Preparation of polyvinylidene fluoride solution: 6 wt.% of amphiphilic polymer PVP-PPO, 17 wt.% of PVDF powder (Solvay 1015), 67 wt.% of solvent N,N-dimethylacetamide, and 10 wt.% of polyethylene glycol 400 were added to a dissolving kettle, heated to 70°C under nitrogen protection, and stirred to dissolve;

[0089] (2) Molding by a mold: the PVDF solution prepared in step (1) is statically degassed and filtered, and then passed through a hollow fiber mold (model Ф54×Ф2.8×Ф2.0×Ф1.75) at a pressure of 0.2 MPa to form a preliminary molded object;

[0090] (3) solidification by non-solvent phase inversion: the formed product obtained in step (2) was allowed to fly in air for 20 seconds before being immersed in a water bath containing 30% polyethylene glycol 400 to solidify, thereby obtaining a PVDF hollow fiber membrane;

[0091] (4) Removing soluble matter and drying: The PVDF hollow fiber membrane obtained in step (3) is subjected to five-stage extraction in hot water at 60°C to remove soluble matter such as solvent N,N-dimethylacetamide and polyethylene glycol 400, and then dried in hot air at 60°C to obtain an amphiphilic polymer blend-modified PVDF hollow fiber dry membrane.

[0092] The amphiphilic polymer blended and modified PVDF hollow fiber dry membrane obtained in this comparative example has an outer diameter of 2.0 mm and a wall thickness of 100 μm.

[0093] Test Example 1

[0094] The properties of the hollow fiber membranes prepared in Example 1 and Comparative Example 1 were measured using the following method:

[0095] (1) Pure water flux (LMH / bar)

[0096] The membrane was fully moistened with water, two hollow membranes with an effective length of 50 cm were folded into a U shape and placed in a hollow mold, or a flat membrane with an effective diameter of 5 cm was placed in a flat mold. The stable permeation flow rate of pure water of the membrane was tested at a pressure of 0.1 MPa and a temperature of 25°C. The flow rate per unit area per unit time was calculated as the pure water flux of the membrane.

[0097] (2) Contact angle measurement

[0098] The film samples were flatly adhered to a glass slide using double-sided tape and vacuum-dried at 40°C for 24 hours. The dynamic and static contact angles of the sample films were measured using a video optical contact angle meter (OCA50AF, Dataphysics, Germany) with a high-speed camera. 3 μl of deionized water was gently applied to the sample film surface, and a video camera captured the dynamic change of the droplet over time. The dynamic contact angle was then fitted using the appropriate software.

[0099] (3) Determination of hydrophilic stability

[0100] Fully moisten the membrane with water, fold two hollow membranes with an effective length of 50 cm into a U shape and install them into a hollow mold, or install a flat membrane with an effective diameter of 5 cm into a flat mold. Run at a constant flow rate of 60LMH pure water flux for 48 hours at 25°C, and take out the membrane sample to test the contact angle.

[0101] (4) Determination of membrane pore size

[0102] The membrane samples were moistened with ethanol or Isopar G liquid, and the pore size distribution and average pore size of the membranes were measured using a capillary flow pore analyzer with a gas-liquid displacement method.

[0103] It has been determined that Figure 2 and Figure 3 As shown, the static hydrophilic contact angle of the hollow fiber membrane provided in Example 1 is 32°, the dynamic water contact angle penetration time of the membrane is 8s, the average pore size of the membrane is 21nm, and the pure water permeability is 1200LMH / bar. After running for 48 hours, the static hydrophilic contact angle is 34°, and the dynamic water contact angle penetration time of the membrane is 8s. The static hydrophilic contact angle of the hollow fiber membrane provided in Comparative Example 1 is 65°, the dynamic water contact angle penetration time of the membrane is 28s, the average pore size of the membrane is 25nm, and the pure water permeability is 980LMH / bar. After running for 48 hours, the static hydrophilic contact angle is 72°, and the dynamic water contact angle penetration time of the membrane is 42s.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an amphiphilic polyvinylidene fluoride hollow fiber dry membrane, characterized in that: The following steps are involved: The polyvinylidene fluoride solution is formed into a mold, and then sequentially subjected to polymerization initiation, non-solvent phase conversion curing and washing to prepare an amphiphilic polyvinylidene fluoride hollow fiber dry membrane; The polyvinylidene fluoride solution comprises a hydrophilic monomer, a hydrophobic monomer, an initiator, polyvinylidene fluoride powder, a solvent and additives; The hydrophilic monomer has an N-vinyl group and includes at least one of N-vinyl pyrrolidone, N-vinylacetamide, N-vinylimidazole, N-vinylcaprolactam and N-vinylformamide; The hydrophobic monomer includes propylene oxide.

2. The preparation method according to claim 1, characterized in that The initiator is a radiation initiator, including a water-soluble peroxodisulfate initiator and a transition metal ion co-initiator; The water-soluble peroxodisulfate initiator includes sodium peroxodisulfate, potassium peroxodisulfate or ammonium peroxodisulfate; the transition metal ion co-initiator includes iron / ferrous iron, copper / cuprous iron, tetravalent cerium / trivalent cerium, cobalt / cobaltous iron, pentavalent vanadate / tetravalent vanadate, permanganate and manganese / manganous iron; The solvent is a water-soluble solvent, including at least one of triethyl phosphate, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone; The additive is an alcohol or acid additive, including at least one of ethylene glycol, polyethylene glycol, glycerol, dicarboxylic acid, and citric acid.

3. The preparation method according to claim 1, wherein In the polyvinylidene fluoride solution, the content of the hydrophilic monomer is 1-10 wt.%, the content of the hydrophobic monomer is 1-10 wt.%, the content of the initiator is 0.01-5 wt.%, the content of the polyvinylidene fluoride powder is 10-25 wt.%, the content of the solvent is 25-88 wt.%, and the content of the additive is 1-25 wt.%.

4. The preparation method according to claim 3, wherein In the polyvinylidene fluoride solution, the content of the hydrophilic monomer is 3 wt.%, the content of the hydrophobic monomer is 3 wt.%, the content of the initiator is 0.6 wt.%, the content of the polyvinylidene fluoride powder is 17 wt.%, the content of the solvent is 66.4 wt.%, and the content of the additive is 10 wt.%.

5. The preparation method according to claim 1, characterized in that The mold forming is to form the polyvinylidene fluoride solution through a hollow fiber mold under pressure.

6. The preparation method according to claim 1, characterized in that Before the mold is formed, degassing and filtering are also included.

7. The preparation method according to claim 1, wherein The initiation of polymerization includes ultraviolet radiation initiation polymerization, and the radiation time is 5 to 100 s.

8. The preparation method according to claim 1, characterized in that The non-solvent phase inversion solidification is to immerse the formed article after initiation of polymerization into a coagulation bath.

9. The preparation method according to claim 8, characterized in that The coagulation bath contains at least 20 wt.% of an alcohol non-solvent; The alcohol non-solvent includes at least one of ethylene glycol, polyethylene glycol, and glycerol.

10. The preparation method according to claim 1, characterized in that The cleaning includes water cleaning.

11. The preparation method according to claim 10, characterized in that: The cleaning temperature is 40-80°C; The cleaning also includes drying; The drying temperature is 40-60°C.

12. An amphiphilic polyvinylidene fluoride hollow fiber dry membrane, characterized in that: The preparation method is described in any one of claims 1 to 11.

13. The amphiphilic polyvinylidene fluoride hollow fiber dry membrane according to claim 12, characterized in that The amphiphilic polyvinylidene fluoride hollow fiber dry membrane has a water content of ≤1wt.%, a static hydrophilic contact angle of ≤40°, a dynamic water contact angle penetration time of ≤15 s, an average pore size of ≤100 nm, and a pure water permeability of ≥1000 LMH / bar.

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