CN113198335A - Polyvinylidene fluoride hollow fiber ultrafiltration membrane and preparation method thereof - Google Patents
Polyvinylidene fluoride hollow fiber ultrafiltration membrane and preparation method thereof Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/30—Polyalkenyl halides
- B01D71/32—Polyalkenyl halides containing fluorine atoms
- B01D71/34—Polyvinylidene fluoride
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/08—Hollow fibre membranes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/30—Chemical resistance
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
- Y02A20/131—Reverse-osmosis
Abstract
The invention provides a polyvinylidene fluoride hollow fiber ultrafiltration membrane and a preparation method thereof, wherein the pure water flux of the polyvinylidene fluoride hollow fiber ultrafiltration membrane is more than or equal to 1000L/m2h, the water pressure bubble point is more than or equal to 0.1MPa, the peeling pressure is more than or equal to 0.35MPa, and the surface aperture is less than or equal to 40 nm. The polyvinylidene fluoride hollow fiber ultrafiltration membrane provided by the invention has high flux, small pore diameter and strong pollution resistance, can bear chemical cleaning, aeration and backwashing, and has high application value; the preparation method of the polyvinylidene fluoride hollow fiber ultrafiltration membrane provided by the invention is simple in preparation process and mild in preparation conditions, and the prepared ultrafiltration membrane is good in compactness and large in membrane flux.
Description
Technical Field
The invention relates to the field of separation membranes, in particular to a polyvinylidene fluoride hollow fiber ultrafiltration membrane and a preparation method thereof.
Background
The membrane separation technology is rapidly developed in a short time, is widely applied to various fields of food, medicine, chemical industry, water treatment and the like, generates great economic benefit, and becomes one of the most important means of the current separation subject. With the rapid development of modern industry and the continuous expansion of urban scale, the water consumption and waste water quantity of cities are continuously increased, so that the water quantity of urban water sources is increasingly insufficient, the water environment is gradually deteriorated, and the water resource crisis is gradually severe. Membrane bioreactor (Membrane Bio-Reactor, abbreviated to MBR) is receiving increasing attention from researchers in various countries as a new and efficient sewage treatment technology. MBR membrane is the core component of membrane bioreactor system, and its effect is to realize accurate and efficient solid-liquid separation, and it has fused bioreactor degradation and the high-efficient separation of membrane in an organic whole, has the unique advantage that traditional biochemical treatment technology can't compare: good and stable effluent quality, high treatment efficiency, small occupied space and convenient operation.
The membrane pollution and the high membrane cost are main reasons for restricting the popularization and the application of the MBR membrane bioreactor. Membrane fouling is mainly three: (1) the filter cake layer is mainly formed by that when water permeates through the membrane, part of intercepted activated sludge and colloidal substances are accumulated on the surface of the membrane under the action of filtration pressure difference and permeated water flow to form membrane pollution after being sent away. (2) Soluble organic matter, the main source of which is the metabolite of the microorganism, can form a gel layer on the surface of the membrane, and can also be adsorbed on the surface of micropores in the membrane to block the pore channels, so that the flux of the membrane is reduced. (3) Microbial contamination, and nutrient substances needed by microbes exist in the film surface and micropores in the film, so that the breeding of a large amount of microbes cannot be avoided.
In view of membrane pollution, researchers usually adopt blending modification or surface modification of membrane materials to improve the anti-pollution performance of the membrane, however, in fact, as the hydrophilicity of the membrane materials is improved, the phase separation of the spinning casting solution in the phase inversion process is delayed, the roughness of the membrane surface is increased, the surface pore size of the membrane is increased, and the water flux is increased. Experiments show that when a separation membrane with a larger membrane aperture is selected for solid-liquid separation, the pollution of the membrane is accelerated, the water flux is reduced quickly, and the optimal selection is that the cutting molecular weight of the general separation membrane is one order of magnitude smaller than the size of the pollutant to be separated. Because the molecular weight of the polyvinylidene fluoride resin is high, the viscosity of a spinning casting solution is extremely high, a low-aperture structure cannot be realized by improving the solid content of the resin, and the preparation of the internal support type hollow fiber ultrafiltration membrane with a small surface aperture by using the polyvinylidene fluoride resin is challenging. Some researchers try to perform secondary coating on the surface of the polyvinylidene fluoride hollow fiber ultrafiltration membrane to prepare a composite membrane, so as to modify the pore size of the surface membrane, the composite membrane is easy to damage a coating layer and lose application value after being subjected to back washing in practical application, and the processing technology is complex and has no possibility of commercialization and industrialization. Some researchers change the composition of a membrane material to optimize the pore diameter of the membrane by blending and modifying the polymer, however, in fact, the compatibility of the polyvinylidene fluoride and most of resins after blending and modifying is poor, and if the addition amount of the modified resin is too small, the modification effect cannot be achieved, and a membrane product with stable performance cannot be prepared. However, when the temperature of the coagulation bath is lowered to achieve the preparation of a small pore size on the surface, the separation membrane prepared by this method tends to have too low flux to be practically useful. Therefore, the prior art has the defects that the small aperture and the high flux are a pair of spears, and the two are difficult to be compatible.
How to obtain small pore size and high throughput has become a problem for researchers.
Disclosure of Invention
The invention aims to solve the technical problem of providing a polyvinylidene fluoride hollow fiber ultrafiltration membrane with high flux and small pore diameter and a preparation method thereof.
In order to achieve the purpose, the invention adopts the technical scheme that:
the invention provides a preparation method of a polyvinylidene fluoride hollow fiber ultrafiltration membrane, which is characterized in that polyvinylidene fluoride prepared by an emulsion method and having the number average molecular weight of 50-100 ten thousand is adopted to prepare a spinning membrane casting solution; and then forming a film by using the spinning membrane casting solution to prepare the polyvinylidene fluoride hollow fiber ultrafiltration membrane.
In the prior art, a high-flux hollow fiber membrane is often obtained by increasing the aperture of the membrane, and when the filtration requirement of the membrane is met, the large-aperture hollow fiber membrane is easy to block the pores by particles, so that the membrane is polluted; hollow fiber membranes with small pore sizes tend to have low flux and lose their use value. In order to obtain the hollow fiber membrane with high flux and small aperture, the invention selects polyvinylidene fluoride synthesized by emulsion method to prepare the hollow fiber membrane, polyvinylidene fluoride polymerized by emulsion has more branched chains and cross-linked structures, and is affected by intermolecular entanglement, the formed polyvinylidene fluoride can easily form a plurality of wide finger-shaped aperture structures under microscopic form, the intermolecular spacing is large, which is beneficial to water passing, and under macroscopic form, the prepared hollow fiber membrane is more compact after film forming due to the cross-linking between the polyvinylidene fluoride branched chains, so that the prepared hollow fiber membrane simultaneously satisfies the small aperture and the large flux.
Preferably, the number average molecular weight of the polyvinylidene fluoride is 80 to 100 ten thousand. When the number average molecular weight of the polyvinylidene fluoride is 80-100 ten thousand, the polyvinylidene fluoride has more branched chains and cross-linked structures, the more branched chains and cross-linked structures can increase the molecular distance, and a loose porous structure is formed under a separation skin layer, so that the separation membrane obtains high flux.
Preferably, the viscosity of the spinning membrane casting solution is 16000-25000 mpa.s, and further 17500-25000 mpa.s.
Preferably, the polyvinylidene fluoride hollow fiber ultrafiltration membrane is prepared by treating the spinning membrane casting solution with a coagulating liquid.
Further preferably, the temperature of the solidification liquid is controlled to be 5 to 25 ℃, and further preferably 5 to 15 ℃.
Wherein, through the crystallization shrink of low temperature coagulation bath acceleration membrane material for the surface aperture obviously narrows down, forms the separation cortex compact and thicker, such structure can bear chemical cleaning more in the practical application process, explodes gas and back flush, and is difficult to be blockked up by the filter of large size, thereby possess better antipollution.
Still more preferably, the solidification solution comprises a Dimethylacetamide (DMAC) aqueous solution with a mass content of 30-50%.
Preferably, the preparation method further comprises post-treating the polyvinylidene fluoride hollow fiber ultrafiltration membrane, wherein the post-treating comprises contacting the polyvinylidene fluoride hollow fiber ultrafiltration membrane with a post-treating liquid.
Further preferably, the post-treatment liquid includes a moisture absorbent. Because the membrane material is preserved in the air, the membrane material can the syneresis for inside pore reduces, fills the pore of membrane through the aftertreatment liquid in, avoids the membrane material syneresis, simultaneously, offsets the shrink stress of membrane material, has further increased the stability of membrane material.
Still more preferably, the moisture absorbent comprises a glycerol aqueous solution with the mass content of 10-40%.
Preferably, the spinning casting solution comprises, by mass, 15-20% of polyvinylidene fluoride, 40-70% of a solvent, 5-20% of a hydrophilic non-solvent, 5-15% of a pore-forming agent and 0-5% of a surfactant.
Further preferably, the spinning casting solution comprises, by mass, 15-18% of polyvinylidene fluoride, 57-63% of a solvent, 10-12% of a hydrophilic non-solvent, 10-13% of a pore-forming agent and 0.5-1.5% of a surfactant.
Further preferably, the solvent comprises one or more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, and dimethylsulfoxide.
Further preferably, the hydrophilic non-solvent comprises one or more of glycerol, diethylene glycol, ethyl acetate, ethylene glycol methyl ether, polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600.
Further preferably, the pore former comprises one or more of polyvinylpyrrolidone, vinylpyrrolidone/vinyl acetate copolymer, vinylpyrrolidone/vinylimidazole copolymer.
Even more preferably, the porogen comprises one or more of PVP-K17, PVP-K30, PVP-K60, PVP-K90, PVP-VA 64.
Further preferably, the surfactant comprises one or more of tween series, span series, polyethylene glycol 4000, polyethylene glycol 6000, polyethylene glycol 8000, polyethylene glycol 10000, polyethylene glycol 20000, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, polyoxyethylene polyoxypropylene copolymer, fatty alcohol polyoxypropylene ether, fatty acid polyoxypropylene ether, alkylphenol polyoxypropylene ether and the like.
Preferably, the spinning membrane casting solution is selectively coated on the support layer through spinning, and the polyvinylidene fluoride hollow fiber ultrafiltration membrane is prepared through an air section, a solidification solution, a cleaning solution and a post-treatment solution.
Further preferably, the temperature of the spinning casting solution is controlled to be 60-90 ℃, and further 80-90 ℃.
More preferably, the air section is 0-50 cm, and still more preferably 10-50 cm. By the arrangement of the air section, the spinning membrane casting solution can be cooled and phase-separated in the air after contacting the air; additives with low solubility in the spinning membrane casting solution start to migrate to the air interface of the spinning membrane casting solution through an air section and separate out in a split-phase manner, so that the flux of the membrane is increased to a certain extent; the larger the air space, the better, the longer the dope solution stays in the air space, which increases its viscosity and, in turn, decreases the flux of the resulting membrane.
Further preferably, the temperature of the solidification liquid is controlled to be 5 to 25 ℃, and further preferably 5 to 15 ℃.
More preferably, the solidification solution is an aqueous solution of Dimethylacetamide (DMAC) having a mass content of 30 to 50%.
Further preferably, the residence time in the coagulation liquid is controlled to be 30 to 90 seconds, further 40 to 60 seconds.
Further preferably, the cleaning liquid is water.
Still more preferably, the temperature of the cleaning liquid is controlled to be 5-25 ℃.
More preferably, the post-treatment liquid is a glycerol aqueous solution with the mass content of 10-40%.
Further preferably, the residence time in the post-treatment liquid is controlled to be 12 to 36 hours, and further 22 to 26 hours.
Preferably, the support layer is a support tube.
Further preferably, the support tube is a braided tube.
Still further preferably, the braided tube is a polyester fiber braided tube.
More preferably, the outer diameter of the support tube is 1.5 to 2.5mm, and still more preferably 1.8 to 2.0 mm.
Preferably, the polyvinylidene fluoride hollow fiber ultrafiltration membrane has an outer diameter of 1.8 to 2.7mm, and further 2.0 to 2.2 mm.
Another aspect of the present invention provides a polyvinylidene fluoride hollow fiber ultrafiltration membrane having a surface average pore diameter of 40nm or less and a pure water flux of 1000L/m or more2The water pressure bubble point is greater than or equal to 0.1MPa, and the peeling pressure is greater than or equal to 0.35 MPa.
Preferably, the polyvinylidene fluoride hollow fiber ultrafiltration membrane comprises a support layer and a spinning membrane casting solution which is coated on the support layer and is treated.
Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:
(1) the preparation method of the polyvinylidene fluoride hollow fiber ultrafiltration membrane provided by the invention utilizes the polyvinylidene fluoride synthesized by the emulsion method to prepare the hollow fiber membrane, the preparation method is simple, the preparation condition is mild, and the polyvinylidene fluoride after membrane formation can form a wide finger-shaped pore structure while meeting the compactness of the hollow fiber membrane through more branched chains and cross-linked structures of the polyvinylidene fluoride, thereby being beneficial to the introduction of water;
(2) the polyvinylidene fluoride hollow fiber ultrafiltration membrane provided by the invention has the advantages of high flux, small pore diameter, strong pollution resistance, capability of bearing chemical cleaning, gas explosion and back washing, and high application value.
Detailed Description
The present invention will be further described with reference to the following examples. However, the present invention is not limited to the following examples. The implementation conditions adopted in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not mentioned are conventional conditions in the industry. The technical features of the embodiments of the present invention may be combined with each other as long as they do not conflict with each other.
In the present invention, wt% means a mass fraction unless otherwise specified.
Example 1
Preparing a spinning membrane casting solution: 16 wt% of polyvinylidene fluoride (molecular weight: 90 ten thousand), 60 wt% of N, N-dimethylacetamide, 11 wt% of glycerol, 12 wt% of polyvinylpyrrolidone (PVP-K30) and 801 wt% of Tween.
Wherein the viscosity of the spinning casting solution is 20000mpa.s, and the temperature of the spinning casting solution is 80 ℃.
Preparing an internal support type hollow fiber ultrafiltration membrane: extruding the prepared spinning membrane casting solution from an annular hole of a spinneret plate through a filter and a metering pump, simultaneously, synchronously drawing an inner support tube made of terylene from a central hole of the spinneret plate by a godet wheel, covering the spinning membrane casting solution on a support tube and moving forward under the traction of the godet wheel, converting the spinning membrane casting solution by an air section, a coagulating liquid and a cleaning liquid to form an inner support type hollow fiber membrane wire, and soaking the hollow fiber membrane wire in a glycerol aqueous solution with the mass content of 40% for 24 hours until the hollow fiber membrane wire is fully gelled to prepare the inner support type hollow fiber ultrafiltration membrane.
Wherein the traction speed of the godet wheel is 10/min, the terylene inner supporting tube is a braided tube with higher compactness, and the outer diameter of the braided tube is 1.9 mm; the height of the air section of the phase transition is 50 cm; the solidification solution is a DMAC (dimethylacetamide) aqueous solution with the mass content of 40 +/-10%, the nascent state membrane filaments stay in the solidification solution for 50s, and the temperature of the solidification solution is 15 ℃; the cleaning solution is water, and the temperature of the cleaning solution is 15 ℃.
Testing the performance of the hollow fiber membrane: the outer diameter of the prepared inner support type hollow fiber ultrafiltration membrane is 2.1mm, the dead end test is carried out under the water pressure condition of 0.1MPa, and the first pure water flux is recorded as Qa(ii) a Under the condition of 0.1MPa water pressure, cross-flow operation is carried out for 1h by using a Polystyrene (PS) microsphere particle aqueous solution with the particle size of 40nm, a water sample in the cross-flow operation is taken, and an ultraviolet spectrophotometer is utilized to determine the absorbance of the polystyrene microsphere aqueous solution to be A1Wherein the concentration of the stock solution of the prepared polystyrene microsphere particle aqueous solution is 200ppm (the absorbance of the stock solution of the polystyrene microsphere particle aqueous solution measured by an ultraviolet spectrophotometer is A)0) Performing dead end test under the water pressure of 0.1MPa, and recording the pure water flux of the second time as Qb。
Wherein the flux loss rate is (Q)a-Qb)/QaThe larger the flux loss is, the more the membrane pores are seriously polluted and blocked, and the larger the membrane surface pores are. Wherein the PS microsphere particle retention rate is (A)0-A1)/A0And when the retention rate is more than or equal to 90 percent, the retention pore diameter of the membrane pores is less than or equal to the particle size of the PS microspheres.
The bubble point pressure and the peeling pressure are tested by the following method: taking a 1m long membrane wire, injecting quick-drying glue into one end of the membrane wire, inserting a leak stopping needle into the sealed end, immersing the membrane wire in water, and injecting compressed air into the other end of the membrane wire, wherein when bubbles emerge from the surface of the membrane wire, the gas pressure is the bubble point pressure; and continuously increasing the pressure, and breaking the film yarn coating layer to obtain the stripping pressure.
The test shows that: the finished product of the internal support type polyvinylidene fluoride hollow fiber ultrafiltration membrane prepared by the embodiment has the outer diameter of 2.1mm and the pure water flux of 1200L/m2h, the water pressure bubble point is more than 0.1MPa, the peeling pressure is more than 0.35MPa, and the surface average pore diameter is less than 40 nm.
In examples 2 and 3 and comparative example 1, the temperatures of the coagulating liquid and the cleaning liquid were adjusted, and the other main formulations and process parameters were consistent. Table 1 shows the formulations, process parameters and performance parameters of the spinning dope solutions of examples 1-3 and comparative example 1.
TABLE 1 parameters of examples 1-3 and comparative examples 1-2
As can be seen from Table 1, the temperature adjustment of the coagulating liquid has a large influence on the pure water flux, mainly because the temperature of the coagulating liquid is related to the solidification and crystallization rate of the polymer, and the lower the temperature of the coagulating liquid is, the faster the polymer crystallization and solidification speed is, the denser the surface pores are, the smaller the pore diameter is, the thicker the separation skin layer is and the smaller the pure water flux is.
Examples 4 and 5 and comparative examples 2 and 3, respectively, adjusted the molecular weight of polyvinylidene fluoride and determined its intrinsic viscosity, consistent with other main formulation and process parameters. Table 2 shows the formulations, process parameters and performance parameters of the spinning dope solutions of examples 1,4 to 5 and comparative examples 2 to 3.
TABLE 2 parameters of examples 1, 4-5 and comparative examples 2-3
As can be seen from Table 2, the molecular weight of the polyvinylidene fluoride has a great influence on the viscosity of the spinning casting solution, the larger the molecular weight of the polyvinylidene fluoride is, the larger the viscosity of the spinning casting solution is, in comparative example 3, the spinning has to be slowed down due to the excessively high viscosity of the spinning casting solution, so that the practical production value is not obtained, and the molecular migration rate is slow during crystallization due to the excessively high molecular weight, so that the formed surface pores are large, and the contamination resistance is poor; in comparative example 2, the low molecular weight of polyvinylidene fluoride leads to the low viscosity of the spinning dope solution, because polyvinylidene fluoride has less grafting and branching during the growth of the molecular chain treatment chain in the synthesis process, the molecular structure is mainly a straight chain structure, the molecular gap formed in the crystallization process is small, the pore diameter is small, the flux is low, and the low molecular weight leads to the poor pressure bearing capacity and the short service cycle of the membrane material.
Examples 6 and 7 and comparative examples 4 and 5 respectively adjust the mass content of polyvinylidene fluoride in the spinning dope solution, measure the intrinsic viscosity of the spinning dope solution, and ensure that other main formulas and process parameters are consistent. Table 3 shows the formulations, process parameters and performance parameters of the spinning dope solutions of examples 1,6 to 7 and comparative examples 4 to 5.
TABLE 3 parameters of examples 1,6 to 7 and comparative examples 4 to 5
As can be seen from Table 3, the solid content of polyvinylidene fluoride has a large influence on the viscosity of the spinning dope solution, the higher the solid content of polyvinylidene fluoride is, the higher the viscosity of the spinning dope solution is, and in comparative example 5, the spinning dope solution has to be spun at a reduced speed due to the excessively high viscosity of the spinning dope solution, so that the practical production value is not obtained; in comparison 4, the initial flux of the membrane yarn is higher due to the excessively low viscosity of the spinning casting solution, the membrane material has poor pressure bearing capacity and excessively large surface pore diameter due to the small solid content of the polyvinylidene fluoride, and the flux is easily polluted and blocked by the 40nm polystyrene microsphere particles to cause flux loss.
In example 8 and comparative examples 6 and 7, polyvinylidene fluoride prepared by different synthesis processes is selected respectively, the intrinsic viscosity is measured, and other main formulas and process parameters are consistent. Table 4 shows the formulations, process parameters and performance parameters of the spinning dope solutions of examples 1 and 8 and comparative examples 4 to 5.
TABLE 4 parameters of examples 1,6 to 7 and comparative examples 4 to 5
As can be seen from table 4, the molecular structure of the polyvinylidene fluoride is greatly affected by the synthesis process, and the viscosity of the dope solution for spinning is increased as the molecular weight of the polyvinylidene fluoride is increased and the branched structure is increased. Due to the existence of the branched chain structure, the intermolecular gap is increased in the crystallization process, and a crystalline or semi-crystalline state cannot be formed, so that the formed product has small surface pore diameter and larger flux.
The present invention has been described in detail in order to enable those skilled in the art to understand the invention and to practice it, and it is not intended to limit the scope of the invention, and all equivalent changes and modifications made according to the spirit of the present invention should be covered by the present invention.
Claims (10)
1. A preparation method of a polyvinylidene fluoride hollow fiber ultrafiltration membrane is characterized by comprising the following steps: preparing a spinning membrane casting solution from polyvinylidene fluoride which is prepared by an emulsion method and has the number average molecular weight of 50-100 ten thousand; and then forming a film by using the spinning membrane casting solution to prepare the polyvinylidene fluoride hollow fiber ultrafiltration membrane.
2. The method for preparing a polyvinylidene fluoride hollow fiber ultrafiltration membrane according to claim 1, wherein: the viscosity of the spinning casting solution is 16000-25000 mpa.s.
3. The method for preparing a polyvinylidene fluoride hollow fiber ultrafiltration membrane according to claim 1, wherein: and treating the spinning membrane casting solution with a coagulating liquid to prepare the polyvinylidene fluoride hollow fiber ultrafiltration membrane, wherein the temperature of the coagulating liquid is controlled to be 5-25 ℃.
4. The method for preparing a polyvinylidene fluoride hollow fiber ultrafiltration membrane according to claim 3, wherein: the solidification liquid comprises a dimethylacetamide aqueous solution with the mass content of 30-50%.
5. The method for preparing a polyvinylidene fluoride hollow fiber ultrafiltration membrane according to claim 1, wherein: the preparation method further comprises the step of carrying out post-treatment on the polyvinylidene fluoride hollow fiber ultrafiltration membrane, wherein the post-treatment comprises the step of contacting the polyvinylidene fluoride hollow fiber ultrafiltration membrane with post-treatment liquid, and the post-treatment liquid comprises a moisture absorbent.
6. The method for preparing a polyvinylidene fluoride hollow fiber ultrafiltration membrane according to claim 5, wherein: the moisture absorbent comprises a glycerol aqueous solution with the mass content of 10-40%.
7. The method for preparing a polyvinylidene fluoride hollow fiber ultrafiltration membrane according to any one of claims 1 to 6, wherein: according to the mass percentage, the spinning casting solution comprises 15-20% of polyvinylidene fluoride, 40-70% of solvent, 5-20% of hydrophilic non-solvent, 5-15% of pore-forming agent and 0-5% of surfactant.
8. The method for preparing a polyvinylidene fluoride hollow fiber ultrafiltration membrane according to claim 7, wherein: the solvent comprises one or more of N, N-dimethylformamide, N-dimethylacetamide, N-methyl pyrrolidone and dimethyl sulfoxide;
the hydrophilic non-solvent comprises one or more of glycerol, diethylene glycol, ethyl acetate, ethylene glycol methyl ether, polyethylene glycol 200, polyethylene glycol 400 and polyethylene glycol 600;
the pore-forming agent comprises one or more of polyvinylpyrrolidone, vinylpyrrolidone/vinyl acetate copolymer and vinylpyrrolidone/vinyl imidazole copolymer;
the surfactant comprises one or more of Tween series, span series, polyethylene glycol 4000, polyethylene glycol 6000, polyethylene glycol 8000, polyethylene glycol 10000, polyethylene glycol 20000, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, polyoxyethylene polyoxypropylene copolymer, fatty alcohol polyoxypropylene ether, fatty acid polyoxypropylene ether, alkylphenol polyoxypropylene ether and the like.
9. The method for preparing a polyvinylidene fluoride hollow fiber ultrafiltration membrane according to claim 1, wherein: selectively covering the spinning membrane casting solution on a supporting layer through spinning, and preparing the polyvinylidene fluoride hollow fiber ultrafiltration membrane through an air section, a solidification solution, a cleaning solution and a post-treatment solution; wherein the temperature of the spinning casting solution is controlled to be 60-90 ℃, and the temperature of the solidification solution is controlled to be 5-25 ℃; the air section is 0-50 cm, the coagulating liquid is a dimethylacetamide aqueous solution with the mass content of 30-50%, the cleaning liquid is water, and the post-treatment liquid is a glycerol aqueous solution with the mass content of 10-40%.
10. A polyvinylidene fluoride hollow fiber ultrafiltration membrane produced by the production method according to any one of claims 1 to 9, characterized in that: said polyvinylidene fluorideThe average pore diameter of the surface of the ethylene hollow fiber ultrafiltration membrane is less than or equal to 40nm, and the pure water flux is greater than or equal to 1000L/m2The water pressure bubble point is greater than or equal to 0.1MPa, and the peeling pressure is greater than or equal to 0.35 MPa.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113441018A (en) * | 2021-08-06 | 2021-09-28 | 苏州富淼膜科技有限公司 | Preparation method of polyvinylidene fluoride hollow fiber ultrafiltration membrane |
| CN117065578A (en) * | 2023-10-07 | 2023-11-17 | 沧州市天津工业大学研究院 | Preparation method of woven tube reinforced polyvinylidene fluoride hollow fiber membrane |
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| CN113441018A (en) * | 2021-08-06 | 2021-09-28 | 苏州富淼膜科技有限公司 | Preparation method of polyvinylidene fluoride hollow fiber ultrafiltration membrane |
| CN113441018B (en) * | 2021-08-06 | 2023-08-04 | 苏州富淼膜科技有限公司 | Preparation method of polyvinylidene fluoride hollow fiber ultrafiltration membrane |
| CN117065578A (en) * | 2023-10-07 | 2023-11-17 | 沧州市天津工业大学研究院 | Preparation method of woven tube reinforced polyvinylidene fluoride hollow fiber membrane |
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