Polymer hollow fiber membrane, method for producing the same, and use thereof

Abstract

The application discloses a kind of polymer hollow fiber membrane and its preparation method and application, and the raw material of preparation polymer hollow fiber membrane includes solid polymer resin, phase separation aid, structure regulator and processing aid.The application carries out innovative design to film-forming formula and thermally induced phase separation extrusion spinning process, by full solid component compounding, combined with full water-soluble membrane structure adjustment, can be prepared to obtain polymer hollow fiber membrane with surface separation layer pore structure and internal double continuous pore structure, its pore size distribution is narrow, small molecule dissolution rate is low in use process, with excellent anti-burst pressure, anti-tensile fracture force, tensile elongation and separation performance, especially suitable for medical, food and other life health and diet health industry.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high molecular separation membrane materials, in particular to a polymer hollow fiber membrane and a preparation method and application thereof. BACKGROUND

[0002] In addition to being widely used in traditional water treatment, membrane separation technology is also increasingly used in material separation processes in the pharmaceutical, food and other industries. Since the 1980s, a large number of non-solvent induced phase separation membrane preparation methods have been disclosed, but the membrane materials prepared by such methods generally have uneven pore size distribution and poor strength, and such methods require finding a suitable solvent for dissolving the polymer, and the range of available polymers for membrane preparation is narrow.

[0003] Thermally induced phase separation membrane preparation technology is based on the principle of high-temperature blending of a polymer and a diluent and low-temperature phase separation. By lowering the temperature, the polymer and the diluent are phase separated, and then the diluent is removed by extraction to obtain a microporous membrane structure. This method not only improves the strength of the polymer microporous membrane, but also expands the range of available polymers for membrane preparation. For example, Chinese patent CN101569837A discloses a method for preparing a polyvinylidene fluoride microporous membrane by thermally induced phase separation; patent CN106268356A discloses a method for preparing an ultra-high molecular weight polyethylene composite hollow fiber membrane by thermally induced phase separation; and patent CN102228805A discloses a method for preparing an ethylene-chlorotrifluoroethylene copolymer porous membrane by thermally induced phase separation. The thermally induced phase separation method expands the selection of membrane polymer resins from traditional solvent-dissolved polymers to melt-processed polymers, but most of the currently disclosed thermally induced phase separation membrane preparation methods are based on oil-soluble organic ester diluent systems, which are prone to lead to the growth of polymer spherocrystals during the temperature reduction and phase separation process, resulting in a decrease in the mechanical properties of the prepared membrane material. At the same time, oil-soluble organic ester diluents often need to be extracted with solvents such as ethanol and n-hexane, and are difficult to extract and clean completely, resulting in significant residual diluent, which greatly limits their application in the life and health and diet and health industries.

[0004] In recent years, researchers have successively explored water-soluble diluent systems for preparing polymer microporous membranes by thermal phase separation method. For example, patent CN103252173A discloses a method for preparing a polyvinylidene fluoride microporous membrane by thermal phase separation, which uses water-soluble diluent caprolactam to prepare the polyvinylidene fluoride microporous membrane. Patent CN110935335A discloses a high-hydrophilic polymer hybrid membrane and a preparation method thereof, which discloses water-soluble diluent gamma-butyrolactone. Patent CN110721598A discloses water-soluble diluents ethylene carbonate and propylene carbonate. However, compared with oil-soluble diluents, the water-soluble diluents have less selectivity, and the thermal phase separation membrane preparation technology of most of the disclosed water-soluble diluent systems has unsatisfactory structural regularity of the prepared membrane material, and has problems such as poor separation performance, which is difficult to meet the actual application requirements. In addition, whether based on oil-soluble diluents or water-soluble diluents, most of the disclosed technologies need to add a large amount of liquid components, which makes the polymer hollow fiber membrane processing difficult, requires high equipment, and the liquid components are easy to form volatile steam in the high-temperature processing process, which is not very friendly to human health. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is a green thermal phase separation method for preparing a polymer hollow fiber membrane, which solves the problems of the prior art, such as difficult processing, poor environmental protection, poor mechanical properties and separation performance of the prepared polymer hollow fiber membrane.

[0006] To solve the above technical problems, the first aspect of the present application provides a preparation method of a polymer hollow fiber membrane, comprising the following steps:

[0007] S1, uniformly mixing a polymer resin, a phase separation aid, a structure adjusting agent and a processing aid to obtain a mixture, wherein the mass percentage of the polymer resin is 20%-35%, the mass percentage of the phase separation aid is 30%-45%, the mass percentage of the structure adjusting agent is 25%-40%, and the mass percentage of the processing aid is 1%-5%, and the components of the mixture are solid powders or solid particles at room temperature;

[0008] S2, extruding the mixture obtained in step S1 through a double-screw extruder and supporting with a core liquid to form a hollow fiber;

[0009] S3, placing the hollow fiber obtained in step S2 in a gel bath for solidification to obtain a polymer hollow fiber membrane precursor;

[0010] S4, washing the polymer hollow fiber membrane precursor obtained in step S4 to remove the water-soluble part to obtain a polymer hollow fiber membrane.

[0011] The application innovatively designs the film forming formula and the thermally induced phase separation extrusion spinning process, and through the full solid component compounding and the full water-soluble membrane structure adjustment, a polymer hollow fiber membrane with a surface separation layer pore structure and an internal double continuous pore structure can be prepared.

[0012] Further, in the step S1, the polymer resin is selected from one or more of polyvinylidene fluoride, polyvinyl chloride, polyether sulfone, polysulfone, polyvinyl alcohol, polyacrylonitrile, ethylene-chlorotrifluoroethylene copolymer, poly-4-methyl-1-pentene, polypropylene, polyethylene, and ethylene-propylene copolymer. The mass percentage of the polymer resin in the preparation process is 20%-35%, preferably 20%-30%. It can be understood that when the mass fraction of the polymer is less than 20%, the porosity of the obtained hollow fiber membrane is high, but the mechanical properties of the membrane are relatively weak; when the mass fraction of the polymer is higher than 35%, the porosity of the obtained polymer hollow fiber membrane is lower, and the separation performance is decreased.

[0013] Further, in the step S1, the structure adjusting agent is selected from one or more of polyethylene glycol, polyoxyethylene, polyvinylpyrrolidone, and polyoxyethylene-polyoxypropylene copolymer. The structure adjusting agent is a water-soluble polymer, and the introduction of the structure adjusting agent can adjust the hydrophilicity of the polymer hollow fiber membrane.

[0014] Further, in the step S1, the phase separation aid is a blend of caprolactam and a solid plasticizer, and the mass ratio of caprolactam to the solid plasticizer is 5:1-10:1. The solid plasticizer used in the application is more environmentally friendly and safe than the liquid plasticizer, and the solid plasticizer does not produce plasticizer vapor at high temperature. The use of solid components is beneficial to material mixing and extrusion processing.

[0015] Further, in the step S1, the processing aid is a blend of an antioxidant and a lubricant, and the mass ratio of the antioxidant to the lubricant is 1:1-10:1. The antioxidant is selected from one or both of antioxidant 1010 and antioxidant 264, and the lubricant is selected from one or more of stearic acid, stearic acid amide, stearic acid ester, and oleic acid amide. The application preferably uses non-toxic antioxidant and lubricant, which is helpful for producing polymer hollow fiber membranes suitable for medical, food and other high industry standard use. For some polymer resins, such as polyvinyl chloride, additional heat stabilizers are required for processing, which are not described in the application.

[0016] Further, in the step S2, the core liquid during extrusion is a mixed liquid of oligomeric ethylene glycol and polar solvent, wherein the volume ratio of oligomeric ethylene glycol to polar solvent is 10:0-2:8, and in the step S3, the gel bath is a mixed liquid of water and polar solvent or oligomeric ethylene glycol in any ratio, the oligomeric ethylene glycol is selected from one or more of polyethylene glycol, ethylene glycol, diethylene glycol and triethylene glycol, and the polar solvent is selected from one or more of dimethylformamide, dimethylacetamide, triethyl phosphate, trimethyl phosphate, methylpyrrolidone and dimethyl sulfoxide. It can be understood that, in order to further adjust and control the film structure, an appropriate amount of caprolactam can be added to the core liquid and / or the gel bath, which is not described herein.

[0017] Further, the preparation method further comprises a step S5 of subjecting the polymer hollow fiber membrane obtained in the step S4 to restretching and heat setting. The restretching and heat setting process can improve the separation performance of the polymer hollow fiber membrane.

[0018] Further, in the step S3, the gel bath temperature is 0-25℃, in the step S5, the restretching environment is a water bath environment, the water bath temperature is 50-90℃, the stretching ratio is 0-1.5 times, the heat setting environment is a hot air environment, the setting temperature is 50-70℃, and the setting time is 3-10 seconds.

[0019] The second aspect of the present application provides a polymer hollow fiber membrane prepared by the above preparation method, wherein the polymer hollow fiber membrane has a double-layer structure, including a separation pore layer and a double-continuous pore layer, the thickness of the polymer hollow fiber membrane is 100-300 microns, and the thickness of the separation pore layer is 1-20 microns.

[0020] The polymer hollow fiber membrane prepared by the present application has a narrow pore size distribution, low small molecule dissolution rate during use, excellent anti-burst pressure, anti-tensile fracture force, tensile elongation rate and separation performance, and is particularly suitable for application in the life and health and diet health industries such as medicine and food.

[0021] The third aspect of the present application provides the application of the above-mentioned polytetrafluoroethylene hollow fiber composite catalytic membrane in a material separation assembly in the medicine and food industries.

[0022] In summary, compared with the prior art, the present application has the following beneficial effects:

[0023] 1) The present application starts from the design of the membrane-forming component, avoids the complex, difficult and harmful to the environment and the body membrane preparation process and membrane cleaning process caused by the large amount of use of oil-soluble organic ester diluent and liquid additive components in the traditional thermal phase process, and makes the thermal phase membrane preparation process more green and safe, and the production process more safe, and the prepared hollow fiber membrane material has only a very low diluent and small molecule residual amount.

[0024] 2) Unlike the traditional thermal phase process which requires a high proportion of diluent addition, the present application reduces the amount of diluent by the composite design of phase separation aid and processing aid, and improves the processability of the thermal phase preparation process of the polymer resin.

[0025] 3) Unlike the traditional thermal phase separation process, the present application is based on the design of the whole water-soluble thermal phase structure adjustment component. During the instantaneous phase separation process of the membrane filament from the spinneret into the gel bath, based on the thermal phase-liquid phase double phase separation mechanism of the membrane surface interface, the thermal phase-liquid phase double phase separation process occurs simultaneously in the micro area near the membrane surface interface to form a controllable and adjustable membrane separation pore layer, and the thermal phase separation process occurs only in the deep membrane internal area to form a high-strength, high-continuous pore structure layer, realizing the preparation of a polymer hollow fiber membrane with a typical surface interface separation pore layer structure and an internal double-continuous pore layer structure. Thus, the present application realizes the independent design of the thermal phase polymer hollow fiber membrane separation pore layer and the support internal channel empty layer, which is beneficial to the controllable design and preparation of a membrane material with more abundant membrane structure, membrane separation function and higher separation precision.

[0026] 4) The polymer hollow fiber membrane prepared by the present application has excellent anti-burst pressure, anti-tensile fracture force, tensile elongation and separation performance, narrow pore size distribution and low small molecule leaching rate during use, and is not only suitable for traditional water treatment application fields, but especially suitable for application and promotion in the medical, food and other life and health and diet health industries. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The cross-section panoramic electron micrograph of the polyvinylidene fluoride hollow fiber membrane prepared for Comparative Example 1.

[0028] Figure 2 The electron micrograph of the cross-section near the outer surface of the polyvinylidene fluoride hollow fiber membrane prepared for Comparative Example 1.

[0029] Figure 3 The electron micrograph of the cross-section near the center of the polyvinylidene fluoride hollow fiber membrane prepared for Comparative Example 1.

[0030] Figure 4 The electron micrograph of the outer surface of the polyvinylidene fluoride hollow fiber membrane prepared for Comparative Example 1.

[0031] Figure 5 Cross-sectional panoramic electron micrograph of a polyvinylidene fluoride hollow fiber membrane prepared in Example 1.

[0032] Figure 6 Electron micrograph of a cross-section of a polyvinylidene fluoride hollow fiber membrane prepared in Example 1 near the outer surface.

[0033] Figure 7 Electron micrograph of a cross-section of a polyvinylidene fluoride hollow fiber membrane prepared in Example 1 near the center.

[0034] Figure 8 Electron micrograph of the outer surface of a polyvinylidene fluoride hollow fiber membrane prepared in Example 1.

[0035] Figure 9 Cross-sectional panoramic electron micrograph of a polyvinylidene fluoride hollow fiber membrane prepared in Example 2.

[0036] Figure 10 Electron micrograph of a cross-section of a polyvinylidene fluoride hollow fiber membrane prepared in Example 2 near the outer surface.

[0037] Figure 11 Electron micrograph of the outer surface of a polyvinylidene fluoride hollow fiber membrane prepared in Example 2.

[0038] Figure 12 Electron micrograph of a cross-section of an ethylene-propylene copolymer hollow fiber membrane prepared in Example 7 near the center.

[0039] Figure 13 Electron micrograph of a cross-section of an ethylene-propylene copolymer hollow fiber membrane prepared in Example 7 near the outer surface. DETAILED DESCRIPTION

[0040] In order to make the above objects, features and advantages of the present application more clear and comprehensible, specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0041] It should be understood that the terms used in the present application are merely used to describe particular embodiments and are not intended to limit the present application. In addition, for numerical ranges in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is specifically disclosed. Each smaller range within a stated range and within any other stated range, as well as intermediate values of stated values and intermediate values of stated ranges are also included in the present application. The upper limit and the lower limit of these smaller ranges can be included or excluded independently from the range.

[0042] Many modifications and variations to the illustrative embodiments described herein will be apparent to those of ordinary skill in the art from this specification, which is to be regarded in an illustrative manner. Other embodiments will be apparent to those of ordinary skill in the art from consideration of the specification and practice of the subject matter disclosed herein. The specification and examples given herein are illustrative only and not intended to be limiting.

[0043] Comparative Example 1

[0044] Step 1): 25% PVDF and 75% Caprolactam were added into a high speed mixer and blended evenly.

[0045] Step 2): The temperature of each section of the twin-screw extruder was set to 155-165°C, and the rotation speed of the twin-screw was set to 250 rpm. The solid mixture powder blended evenly was added into the twin-screw extruder through a feeder, and hollow fibers were prepared by extruding through a hollow fiber spinneret. The supporting liquid was a blended solution of diethylene glycol and triethyl phosphate with a volume ratio of 8:2.

[0046] Step 3): The hollow fibers were introduced into a gel bath for solidification, and the air gap was 10 cm. The gel bath was a mixed solution of 60% triethyl phosphate and water with a volume ratio of 6:4, and the temperature was 15°C.

[0047] Step 4): The solidified hollow fibers were transferred into water at 25°C, and soaked for 48 hours for cleaning. The water was replaced 4 times during the soaking, and polyvinylidene fluoride hollow fiber membranes were obtained.

[0048] The prepared polyvinylidene fluoride hollow fiber membranes were used for pure water flux test, and the result was that the pure water flux of the hollow fiber membranes was about 25 L / m 2 ·h·bar, and the flux was very low.

[0049] The mechanical properties of the polyvinylidene fluoride hollow fiber membranes were tested by tensile test, and the average tensile breaking force was 2.9 N, and the average elongation at break was 90%.

[0050] The hydrophilicity of the polyvinylidene fluoride hollow fiber membranes was tested by contact angle, and the initial water droplet contact angle was 97 degrees.

[0051] Through pore size analyzer analysis, the average pore size of the polyvinylidene fluoride hollow fiber membranes was 21 nm.

[0052] As shown in FIGS. Figure 1 and Figure 2 are cross-sectional panoramic electron microscope photos and enlarged electron microscope photos of the prepared polyvinylidene fluoride hollow fiber membranes, and it can be seen that there is a dense layer with a relatively thick thickness near the outer surface of the membrane, and the thickness is about 15 microns-25 microns, and there is also a dense layer with a thicker thickness near the inner surface of the membrane, and the thickness is 50 microns-60 microns. Figure 3As shown in Fig. 3, which is a cross-sectional SEM photograph of the prepared polyvinylidene fluoride hollow fiber membrane, it can be seen that the membrane surface is very dense. Figure 4 As shown in Fig. 3, which is a cross-sectional SEM photograph of the prepared polyvinylidene fluoride hollow fiber membrane, it can be seen that the membrane surface is very dense.

[0053] As shown in Fig. 3, which is a cross-sectional SEM photograph of the prepared polyvinylidene fluoride hollow fiber membrane, it can be seen that the membrane surface is very dense.

[0054] Example 1

[0055] Step 1): 25% by mass of polyvinylidene fluoride, 32.8% of caprolactam, 5% of solid plasticizer (brand YH1800), 30% of polyethylene glycol 10000, 6% of polyvinylpyrrolidone K15, 1% of antioxidant 1010 and 0.2% of ethylene bis-stearamide were added into a high-speed mixer and blended uniformly;

[0056] Step 2): the temperature of each section of the twin-screw extruder was set to 155-165°C, and the rotation speed of the twin-screw was 250 rpm. The uniformly blended solid mixture powder was added into the twin-screw extruder through a feeder, and hollow fibers were prepared by extrusion through a hollow fiber spinneret. The supporting liquid was a blended solution of diethylene glycol and triethyl phosphate at a volume ratio of 8:2.

[0057] Step 3): the hollow fibers were introduced into a gel bath for solidification, and the air gap was 10 cm. The gel bath was a mixed solution of 60% triethyl phosphate and water at a volume ratio of 6:4, and the temperature was 15°C.

[0058] Step 4): the solidified hollow fibers were transferred into water at 25°C, and were soaked and cleaned for 48 hours, during which the water was replaced 4 times, to obtain polyvinylidene fluoride hollow fiber membranes.

[0059] The prepared polyvinylidene fluoride hollow fiber membranes were used for pure water flux test, and the result was that the pure water flux of the hollow fiber membranes was about 380 L / m 2 ·h·bar.

[0060] As shown in Fig. 3, which is a cross-sectional SEM photograph of the prepared polyvinylidene fluoride hollow fiber membrane, it can be seen that the membrane surface is very dense. Figure 5 and Figure 6 As shown in Fig. 4, which is a cross-sectional panoramic SEM photograph of the prepared polyvinylidene fluoride hollow fiber membrane and a magnified SEM photograph of the region close to the outer surface of the membrane, it can be seen that there is a layer of separation pores with smaller pore size close to the outer surface of the membrane, and the thickness is about 5-10 microns. Below the separation pore layer, the structure layer extending to the inner surface of the membrane is relatively uniform and is a bicontinuous pore structure layer without dense and defective regions. Figure 7 As shown in Fig. 3, which is a cross-sectional SEM photograph of the prepared polyvinylidene fluoride hollow fiber membrane, it can be seen that the membrane surface is very dense.Figure 8 As shown, this is an electron microscope image of the prepared polyvinylidene fluoride hollow fiber membrane, which shows that a large number of pore structures are uniformly distributed on the surface of the membrane.

[0061] Tensile testing revealed that the average tensile breaking force of the polyvinylidene fluoride hollow fiber membrane prepared in this embodiment was 5.7 N, and the average elongation at break was 270%.

[0062] The initial water droplet contact angle of the polyvinylidene fluoride hollow fiber membrane prepared in this embodiment was measured to be 67 degrees through contact angle testing.

[0063] Analysis using a pore size analyzer revealed that the average pore size of the polyvinylidene fluoride hollow fiber membrane prepared in this embodiment was 61 nm.

[0064] The prepared polyvinylidene fluoride hollow fiber membrane was used for bovine serum albumin solution retention test, and the results showed that the hollow fiber membrane had a retention rate of more than 95% for bovine serum albumin.

[0065] Example 2

[0066] The polyvinylidene fluoride hollow fiber membrane prepared in Example 1 was stretched by 0.7 times in a 60°C hot water bath, and then set in a 60°C hot oven for 5 seconds to obtain a re-stretched polyvinylidene fluoride hollow fiber membrane.

[0067] The polyvinylidene fluoride hollow fiber membrane obtained in this embodiment was used for pure water flux testing, and the result was: the pure water flux of the hollow fiber membrane was approximately 1190 L / m³. 2 ·h·bar.

[0068] like Figure 9 and Figure 10 As shown, it is a panoramic electron microscope (EM) image of the cross-section of the prepared restretched polyvinylidene fluoride hollow fiber membrane and a magnified EEM image near the outer surface. It can be seen that a layer of smaller pores exists near the outer surface of the membrane, while below this layer extending towards the inner surface of the membrane, there is a relatively uniform double-continuous pore structure layer. Figure 11 As shown, it is a surface electron microscope image of the polyvinylidene fluoride hollow fiber membrane after the restretching treatment. It can be seen that a large number of pore structures are uniformly distributed on the surface of the membrane.

[0069] Tensile testing revealed that the average tensile breaking force of the polyvinylidene fluoride hollow fiber membrane prepared in this embodiment was 6.8 N, and the average elongation at break was 110%.

[0070] The initial water droplet contact angle of the polyvinylidene fluoride hollow fiber membrane prepared in this embodiment was measured to be 63 degrees through contact angle testing.

[0071] The average pore size of the polyvinylidene fluoride hollow fiber membrane prepared in this example was measured to be 103 nm by a pore size analyzer.

[0072] The polyvinylidene fluoride hollow fiber membrane obtained in this example was used for bovine serum albumin solution rejection test, and the result was that the rejection rate of the hollow fiber membrane to bovine serum albumin reached more than 90%.

[0073] Example 3

[0074] Step 1): 30% by mass of polyvinyl chloride, 30% of caprolactam, 6% of solid plasticizer (brand S1105S), 21.6% of polyethylene glycol 20000, 8% of polyoxyethylene-polyoxypropylene copolymer F127, 1% of antioxidant 1010, 1% of antioxidant 264, 0.4% of oleic acid amide and 2% of calcium stearate were added to a high-speed mixer and uniformly blended.

[0075] Step 2): The temperature of each section of the twin-screw extruder was set to 150-155°C, and the rotation speed of the twin-screw was 200 rpm. The uniformly blended solid mixture powder was fed into the twin-screw extruder through a feeder, and hollow fibers were prepared by extrusion through a hollow fiber spinneret. The supporting liquid was a blended solution of triethylene glycol and dimethylacetamide at a volume ratio of 5:5.

[0076] Step 3): The hollow fibers were introduced into a gel bath for solidification, with an air gap of 5 cm. The gel bath was a mixed solution of dimethylacetamide and water at a volume ratio of 5:5, and the temperature was 10°C.

[0077] Step 4): The solidified hollow fibers were transferred to water at 50°C, soaked and washed for 50 hours, and the water was replaced 4 times during the period, to obtain polyvinyl chloride hollow fiber membranes.

[0078] The obtained polyvinyl chloride hollow fiber membranes were used for pure water flux test, and the result was that the pure water flux of the hollow fiber membranes was about 200 L / m 2 ·h·bar.

[0079] By tensile test, the average tensile breaking force of the polyvinyl chloride hollow fiber membrane prepared in this example was measured to be 5.1 N, and the average elongation at break was 180%.

[0080] By contact angle test, the initial water droplet contact angle of the polyvinyl chloride hollow fiber membrane prepared in this example was measured to be 73 degrees.

[0081] By pore size analyzer analysis, the average pore size of the polyvinyl chloride hollow fiber membrane prepared in this example was measured to be 53 nm.

[0082] The obtained polyvinyl chloride hollow fiber membrane was used for bovine serum albumin solution rejection test, and the result was that the rejection rate of the hollow fiber membrane to bovine serum albumin reached more than 97%.

[0083] Example 4

[0084] The polyvinyl chloride hollow fiber membrane prepared in Example 3 was stretched by 0.3 times in a hot water bath at 50°C, and then was set in a hot oven at 70°C for 3 seconds to obtain a restretching treated polyvinyl chloride hollow fiber membrane.

[0085] The obtained polyvinyl chloride hollow fiber membrane was used for pure water flux test, and the result was that the pure water flux of the hollow fiber membrane was about 490 L / m 2 ·h·bar.

[0086] Through the tensile test, it was measured that the average tensile breaking force of the polyvinyl chloride hollow fiber membrane prepared in this embodiment was 5.7 N, and the average elongation at break was 130%.

[0087] Through the contact angle test, it was measured that the initial water droplet contact angle of the polyvinyl chloride hollow fiber membrane prepared in this embodiment was 72 degrees.

[0088] Through the pore size analyzer analysis, it was measured that the average pore size of the polyvinyl chloride hollow fiber membrane prepared in this embodiment was 59 nm.

[0089] The obtained restretching treated polyvinyl chloride hollow fiber membrane was used for bovine serum albumin solution rejection test, and the result was that the rejection rate of the hollow fiber membrane to bovine serum albumin reached more than 97%.

[0090] Example 5

[0091] Step 1): 20% by mass of ethylene-propylene copolymer, 40% of caprolactam, 4% of solid plasticizer (brand E5), 34% of polyoxyethylene 200,000, 1% of antioxidant 264, and 1% of stearic acid amide were added into a high-speed mixer and uniformly blended.

[0092] Step 2): The temperature of each section of the double screw extruder was set to 170-180°C, and the rotation speed of the double screw was 200 rpm. The uniformly blended solid mixture powder was added into the double screw extruder through a feeder, and hollow fibers were prepared by extrusion through a hollow fiber spinneret. The supporting core liquid was pure polyethylene glycol 200.

[0093] Step 3): The hollow fibers were introduced into a gel bath for solidification, and the air gap was 20 cm. The gel bath was a mixed solution of polyethylene glycol 200 and water in a volume ratio of 7:3, and the temperature was 25°C.

[0094] Step 4): The solidified hollow fiber was transferred to water at 80°C and soaked for 30 hours, with water changed 4 times, to obtain the ethylene-propylene copolymer hollow fiber membrane.

[0095] The obtained ethylene-propylene copolymer hollow fiber membrane was used for pure water flux test, and the result was that the pure water flux of the hollow fiber membrane was about 300 L / m 2 ·h·bar.

[0096] Through tensile test, it was measured that the average tensile breaking force of the ethylene-propylene copolymer hollow fiber membrane prepared in this embodiment was 4.3 N, and the average elongation at break was 370%.

[0097] Through contact angle test, it was measured that the initial water droplet contact angle of the ethylene-propylene copolymer hollow fiber membrane prepared in this embodiment was 77 degrees.

[0098] Through pore size analyzer analysis, it was measured that the average pore size of the ethylene-propylene copolymer hollow fiber membrane prepared in this embodiment was 83 nm.

[0099] The obtained ethylene-propylene copolymer hollow fiber membrane was used for bovine serum albumin solution rejection test, and the result was that the rejection rate of the hollow fiber membrane to bovine serum albumin reached more than 96%.

[0100] Example 6

[0101] The ethylene-propylene copolymer hollow fiber membrane prepared in Example 5 was stretched by 1.5 times in a hot water bath at 90°C, and then was set in a hot oven at 50°C for 10 seconds to obtain a re-stretched ethylene-propylene copolymer hollow fiber membrane.

[0102] The obtained re-stretched ethylene-propylene copolymer hollow fiber membrane was used for pure water flux test, and the result was that the pure water flux of the hollow fiber membrane was about 1190 L / m 2 ·h·bar.

[0103] Through tensile test, it was measured that the average tensile breaking force of the ethylene-propylene copolymer hollow fiber membrane prepared in this embodiment was 6.7 N, and the average elongation at break was 150%.

[0104] Through contact angle test, it was measured that the initial water droplet contact angle of the ethylene-propylene copolymer hollow fiber membrane prepared in this embodiment was 77 degrees.

[0105] Through pore size analyzer analysis, it was measured that the average pore size of the ethylene-propylene copolymer hollow fiber membrane prepared in this embodiment was 120 nm.

[0106] The obtained ethylene-propylene copolymer hollow fiber membrane after restretching was used for bovine serum albumin solution retention test. The results showed that the hollow fiber membrane had a retention rate of more than 86% for bovine serum albumin.

[0107] Example 7

[0108] Referring to Example 5, keeping other parameters unchanged, the gel bath was replaced with water, and the temperature was set to 0°C. An ethylene-propylene copolymer hollow fiber membrane was thus obtained.

[0109] like Figure 12 As shown, this is a magnified electron microscope image of the prepared ethylene-propylene copolymer hollow fiber membrane near the center of the cross section, which shows that it exhibits a uniform double continuous pore structure. Figure 13 A magnified electron microscope image of the area near the outer surface reveals a dense separation layer of a certain thickness, ranging from 10 to 20 micrometers. This is because, although the coagulation bath is pure water, which is miscible with caprolactam and polyethylene oxide in the membrane components, the long air path causes polymer enrichment due to surface cooling after the hollow fibers leave the spinneret. Subsequently, the fibers enter 0°C water, causing the polymer enriched on the membrane surface to solidify rapidly, preventing the exchange between the gel bath and the water-soluble components on the surface, thus forming a uniform dense membrane layer on the membrane surface. Meanwhile, a thermo-induced phase separation process, primarily liquid-liquid phase separation, still occurs inside the fibers, resulting in a bicontinuous pore structure. Because this ethylene-propylene copolymer hollow fiber membrane has a dense layer of a certain thickness on its surface, oxygen and carbon dioxide permeation tests were conducted. The results showed that its oxygen and carbon dioxide permeation ratio is close to 1, making it suitable for use in artificial lungs.

[0110] Example 8

[0111] Step 1): Add 28% polyethersulfone, 40% caprolactam, 4% solid plasticizer (brand name YH1800), 2% solid plasticizer (brand name S1105S), 18% polyethylene glycol 6000, 8% polyvinylpyrrolidone K30, 0.6% antioxidant 1010, 0.2% stearic acid and 0.2% oleamide to a high-speed mixer and mix evenly.

[0112] Step 2): Set the temperature of each section of the twin-screw extruder to 145℃-165℃ and the twin-screw speed to 200 rpm. Feed the uniformly mixed solid powder into the twin-screw extruder via a feeder, and extrude it through a hollow fiber spinneret to form hollow fibers. The core fluid is a blend of polyethylene glycol 400 and dimethyl sulfoxide in a volume ratio of 7:3.

[0113] Step 3): Introduce the hollow fibers into the gel bath for curing, with an air gap of 30 cm. The gel bath is a mixed solution of dimethyl sulfoxide, water, and caprolactam in a mass ratio of 3:6:1, at a temperature of 15°C.

[0114] Step 4): Transfer the cured hollow fiber to water at 25°C and soak and clean it for 48 hours, changing the water 4 times during the process, to obtain a polyethersulfone hollow fiber membrane.

[0115] The prepared polyethersulfone hollow fiber membrane was used for pure water flux testing, and the results showed that the pure water flux of the hollow fiber membrane was approximately 870 L / m³. 2 ·h·bar.

[0116] Tensile testing revealed that the average tensile breaking force of the polyethersulfone hollow fiber membrane prepared in this embodiment was 5.2 N, and the average elongation at break was 200%.

[0117] The initial water droplet contact angle of the polyvinylidene fluoride hollow fiber membrane prepared in this embodiment was measured to be 61 degrees through contact angle testing.

[0118] Analysis using a pore size analyzer revealed that the average pore size of the polyvinylidene fluoride hollow fiber membrane prepared in this embodiment was 130 nm.

[0119] The prepared polyethersulfone hollow fiber membrane was used for bovine serum albumin solution retention test, and the results showed that the hollow fiber membrane had a retention rate of more than 90% for bovine serum albumin.

[0120] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the scope of protection of this invention.

Claims

1. A method for preparing a polymer hollow fiber membrane, characterized in that, Includes the following steps: S1. The polymer resin, phase separation agent, structure modifier and processing aid are mixed evenly to obtain a mixture, wherein the polymer resin has a mass percentage of 20%-35%, the phase separation agent has a mass percentage of 30%-45%, the structure modifier has a mass percentage of 25%-40%, and the processing aid has a mass percentage of 1%-5%. The components of the mixture are solid powders or solid particles at room temperature. S2. The mixture obtained in step S1 is extruded and core liquid supported by a twin-screw extruder to form hollow fibers; S3. Place the hollow fibers obtained in step S2 in a gel bath and solidify them to obtain a polymer hollow fiber membrane precursor. S4. Clean the polymer hollow fiber membrane precursor obtained in step S3 to remove the water-soluble part and obtain the polymer hollow fiber membrane. In step S1, the phase separation aid is a blend of caprolactam and solid plasticizer, wherein the mass ratio of caprolactam to solid plasticizer is 5:1-10:

1.

2. The method for preparing the polymer hollow fiber membrane according to claim 1, characterized in that, In step S1, the polymer resin is selected from one or more of polyvinylidene fluoride, polyvinyl chloride, polyethersulfone, polysulfone, polyvinyl alcohol, polyacrylonitrile, ethylene-chlorotrifluoroethylene copolymer, poly4-methyl-1-pentene, polypropylene, polyethylene, and ethylene-propylene copolymer.

3. The method for preparing the polymer hollow fiber membrane according to claim 1, characterized in that, In step S1, the structure modifier is selected from one or more of polyethylene glycol, polyoxyethylene, polyvinylpyrrolidone, and polyoxyethylene-polyoxypropylene copolymer.

4. The method for preparing the polymer hollow fiber membrane according to claim 1, characterized in that, In step S1, the processing aid is a blend of antioxidant and lubricant, wherein the mass ratio of antioxidant to lubricant is 1:1-10:1, the antioxidant is selected from one or two of antioxidant 1010 and antioxidant 264, and the lubricant is selected from one or more of stearic acid, stearamide, stearate, and oleamide.

5. The method for preparing the polymer hollow fiber membrane according to claim 1, characterized in that, In step S2, the core liquid during extrusion is a mixture of oligoethylene glycol and a polar solvent. In step S3, the gel bath is a mixture of water and any ratio of a polar solvent or oligoethylene glycol. The oligoethylene glycol is selected from one or more of polyethylene glycol, ethylene glycol, diethylene glycol, and triethylene glycol. The polar solvent is selected from one or more of dimethylformamide, dimethylacetamide, triethyl phosphate, trimethyl phosphate, methylpyrrolidone, and dimethyl sulfoxide.

6. The method for preparing the polymer hollow fiber membrane according to any one of claims 1-5, characterized in that, It also includes step S5, which involves re-stretching and heat-setting the polymer hollow fiber membrane obtained in step S4.

7. The method for preparing the polymer hollow fiber membrane according to claim 6, characterized in that, In step S3, the gel bath temperature is 0-25℃. In step S5, the re-stretching environment is a water bath environment with a water bath temperature of 50-90℃ and a stretching ratio of 0-1.5 times. The heat setting environment is a hot air environment with a setting temperature of 50-70℃ and a setting time of 3-10 seconds.

8. A polymer hollow fiber membrane, characterized in that, The polymer hollow fiber membrane, prepared by any one of the preparation methods described in claims 1-7, has a bilayer structure, including a separation pore layer and a dual continuous pore layer, wherein the thickness of the polymer hollow fiber membrane is 100 micrometers to 300 micrometers, and the thickness of the separation pore layer is 1 micrometer to 20 micrometers.

9. An application of the polymer hollow fiber membrane as described in claim 8, characterized in that, The polymer hollow fiber membrane is used for material separation in the pharmaceutical and food industries.

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