A PVDF hollow fiber membrane and its preparation method and production device

Abstract

The present invention relates to a PVDF hollow fiber membrane and a preparation method and a production device thereof; the preparation method consists of a filter membrane preparation part and a filter membrane hydrophilic modification part. In the hydrophilic modification section, a hydrophilic substance is coated on the membrane surface by a special coating head, and then the hydrophilic substance is evenly coated on the membrane surface by a coating device, and a hydrophilic filter membrane is prepared after a cross-linking bath. The present invention has the following advantages: 1. It realizes industrialized continuous preparation of hydrophilic filter membranes; 2. It is simple and controllable to coat and modify the modified substance on the membrane surface; 3. The equipment is easy to operate and has high production efficiency.

Description

Technical Field

[0001] The invention relates to a hydrophilic organic filter membrane, in particular to a process equipment for preparing a hydrophilic polyvinylidene fluoride (PVDF) filter membrane. Background Art

[0002] As an emerging technology, membrane separation technology has been widely used. Among many membrane materials, PVDF is widely used in membrane processes such as ultrafiltration and microfiltration because of its good mechanical strength and chemical resistance. It is one of the most widely used membrane materials on the market. However, PVDF itself is hydrophobic. When used in the solid-liquid separation process, it is very easy to be contaminated by organic substances (sugars, proteins, etc.) in the filtrate, resulting in a decrease in water flux and an increase in the maintenance cleaning frequency. In order to make PVDF materials better play its excellent performance in the field of water treatment, it is of great significance to prepare hydrophilic PVDF filter membranes. Hydrophilic PVDF filter membranes are mainly prepared by two methods: membrane body modification and membrane surface modification. Membrane body modification is mainly achieved through blending and copolymerization. Membrane surface modification mainly includes surface coating modification, surface chemical modification, low-temperature plasma modification, and surface photoinitiated grafting modification. At the same time, membrane surface modification has the advantages of convenient operation, controllable process, and easy implementation, and has been applied in actual processes.

[0003] Patent CN103861466A provides a method for preparing a hydrophilic separation membrane, in which a hydrophilic substance is introduced into the surface of a base membrane support layer after hydroxylation treatment through a chemical reaction on the membrane surface to form a hydrophilic separation layer. Patent CN108043248A discloses a method, a preparation device and an application of a PVA-PVDF hollow fiber ultrafiltration membrane, which is mainly characterized by narrow slit coating. A layer of PVA solution is first controllably coated on the PVDF hollow fiber base membrane, and the PVA is further promoted to spread and adhere evenly on the surface. However, firstly, it is necessary to provide a PVDF base membrane, and then modify it on the basis of the base membrane, which cannot be continuous in actual production. Secondly, due to the low viscosity of the PVA solution, whether it can be uniformly coated on the surface of the PVDF base membrane through a narrow slit for hydrophilic modification remains to be verified. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the conventional coating and cross-linking of the surface of the hollow fiber membrane with a modifier easily leads to low performance stability of the prepared hollow fiber membrane, and different regions on the membrane filament and different membrane filaments are prone to inconsistent modification effects. The present invention provides an improved method for manufacturing a PVDF hollow fiber membrane, wherein a modifier coating and uniform coating device is used to improve the product uniformity of the prepared hollow fiber membrane.

[0005] The technical solution is:

[0006] A production device for a PVDF hollow fiber membrane, comprising:

[0007] A film casting liquid tank, used for adding PVDF film casting liquid into the spinneret;

[0008] A coagulation bath tank, used for receiving the hollow fiber base membrane obtained from the spinneret and completing the phase conversion under the coagulation bath condition;

[0009] A rinsing tank, used for rinsing the hollow fiber membrane treated in the coagulation bath;

[0010] The first annular air knife is used to purge the hollow fiber membrane obtained in the rinsing tank;

[0011] A hydrophilic agent coating device is used to coat the hollow fiber membrane obtained in the first annular air knife with a hydrophilic agent; a coating tube is provided inside the hydrophilic agent coating device, fine holes are distributed around the coating tube, and a hydrophilic agent inlet hole is also provided on the hydrophilic agent coating device, and the hydrophilic agent inlet hole is connected to the fine holes;

[0012] The hydrophilic agent coating device is used to perform a hydrophilic agent scraping treatment on the hollow fiber membrane obtained in the hydrophilic agent coating device; the hydrophilic agent coating device is cylindrical, and coated fibers are evenly distributed on the inner wall, and the free ends of the coated fibers form a membrane fiber channel inside the hydrophilic agent coating device;

[0013] A channel is used to receive the hollow fiber membrane obtained from the hydrophilic agent coating device and keep the hollow fiber membrane under set temperature and humidity conditions for a set time;

[0014] The second annular air knife is used to purge the hollow fiber membrane obtained in the tunnel;

[0015] A cross-linking bath, used for immersing the hollow fiber membrane obtained in the second annular air knife with a cross-linking agent and subjecting it to a cross-linking reaction treatment;

[0016] The third annular air knife is used to purge the hollow fiber membrane obtained in the cross-linking bath.

[0017] In one embodiment, the spinneret includes an internal channel and an external channel, and the casting liquid tank is connected to the external channel; the production device also includes a core liquid tank, which is connected to the internal channel and is used to add core liquid to the spinneret.

[0018] In one embodiment, the interior of the spinneret includes an internal channel and an external channel, the internal channel is used to feed the braided tube, and the film casting liquid tank is used to be connected to the external channel.

[0019] In one embodiment, the hydrophilic agent coating device is further provided with a hydrophilic agent overflow hole for discharging excess hydrophilic agent in the coating tube.

[0020] In one embodiment, a collecting wheel is further included to pull the hollow fiber membrane during the production process.

[0021] In one embodiment, the invention further comprises a hydrophilic agent storage tank connected to the hydrophilic agent inlet hole.

[0022] In one embodiment, the hydrophilic agent storage tank is connected to the hydrophilic agent inlet hole via a metering pump.

[0023] In one embodiment, a temperature and humidity controller is further included to control the temperature and humidity of the corridor.

[0024] In one embodiment, the structure of the first annular wind knife, the second annular wind knife, and the third annular wind knife is: the whole is annular, the inside of the wind knife is connected to the air source, and an annular oblique opening is provided on the outside of the wind knife, and the oblique opening is connected to the air source, and the opening angle of the oblique opening is toward the central axis of the wind knife.

[0025] In one embodiment, the opening angle of the oblique opening is 10-80° with respect to the central axis.

[0026] In one embodiment, the diameter of the hollow fiber membrane is 0.5-3 mm, and the inner diameters of the first annular air knife, the second annular air knife, and the third annular air knife are 0.1-5 mm larger than the outer diameter of the hollow fiber membrane.

[0027] In one embodiment, the diameter of the pores is 0.1-1 mm, a circle of pores is arranged every 5-8 mm along the axis of the coating tube, and the number of pores is 20-50.

[0028] A method for preparing a PVDF hollow fiber membrane comprises the following steps:

[0029] Step 1, providing a PVDF hollow fiber base membrane, sending the base membrane into the inner channel of the annular air knife, and using the annular air knife to blow away excess solution on the surface of the hollow fiber base membrane;

[0030] Step 2, applying the modifier evenly on the surface of the hollow fiber base membrane obtained in step 1 by using a coating head, and evenly applying the modifier by using a coating head;

[0031] Step 3: Send the hollow fiber membrane obtained in step 2 into the channel, allow the modifier to penetrate into the hollow fiber membrane, send the hollow fiber membrane into the inner channel of the annular air knife, and use the annular air knife to blow away the excess solution on the surface of the hollow fiber membrane;

[0032] In the fourth step, the hollow fiber membrane obtained in the third step is immersed in a cross-linking agent to allow the modifier and the cross-linking agent to undergo a cross-linking reaction, and the hollow fiber membrane is sent into the internal channel of the annular air knife, and then the excess solution on the surface of the hollow fiber base membrane is blown away by the annular air knife to obtain a PVDF hollow fiber membrane.

[0033] In one embodiment, the modifier is a 0.05-0.5wt% aqueous solution of polyvinyl alcohol; the cross-linking agent is an aqueous solution containing 2-6wt% glutaraldehyde, 1-3wt% sulfuric acid, 1-3wt% glacial acetic acid, and 5-15wt% methanol.

[0034] In one embodiment, the temperature in the tunnel is 20-60° C., and the humidity is 30-70% RH.

[0035] In one embodiment, the cross-linking reaction temperature is 40-70°C.

[0036] Beneficial Effects

[0037] The present invention has the following advantages and effects: it provides a continuous production and preparation of hydrophilic PVDF filter membrane, and the equipment consists of a filter membrane preparation part and a filter membrane hydrophilic modification part. In the hydrophilic modification section, a hydrophilic substance is coated on the membrane surface by a special coating head, and then the hydrophilic substance is evenly coated on the membrane surface by a coating device, and a hydrophilic filter membrane is prepared after a cross-linking bath. Different types of membrane filaments can be prepared by the filter membrane preparation equipment, which improves the application field of the preparation equipment. For example, the preparation fields of hollow fiber membranes, flat membranes, and lined membranes. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a production equipment flow chart;

[0039] Figure 2 It is a stereoscopic diagram of a hydrophilic agent coating device;

[0040] Figure 3 This is the front view of the hydrophilic agent coating equipment;

[0041] Figure 4 is a side view of a hydrophilic agent coating device;

[0042] Figure 5 This is a stereoscopic picture of the hydrophilic agent coating equipment

[0043] Figure 6 This is the front view of the hydrophilic agent coating equipment;

[0044] Figure 7 This is a side view of the hydrophilic agent coating equipment;

[0045] Figure 8 Schematic diagram of annular wind knife;

[0046] Fig. 9 This is a photo of the annular wind knife;

[0047] Fig.10 This is the electron microscope photo of the cross section of the original PVDF filter membrane;

[0048] Fig.11 This is an electron micrograph of the cross section of a PVA / PVDF composite membrane, with the surface being a hydrophilic modified substance;

[0049] Fig.12 This is an electron micrograph of the cross section of a PVP / PVDF composite membrane, with the surface being a hydrophilic modified substance;

[0050] Fig.13 Contact angle characterization results

[0051] Fig.14 The pore size distribution characterization results

[0052] 1. Core liquid tank; 2. Film casting liquid tank; 3. Spinneret; 4. Coagulation bath; 5. Rinsing tank; 6-1. Hydrophilic agent coating equipment; 6-2. Corridor; 6-3. Temperature and humidity controller; 6-4. Hydrophilic agent storage tank; 6-5. Metering pump; 6-6. Hydrophilic agent coating equipment; 7. Cross-linking bath; 8. Wire collection wheel; 9. Braided tube; 101. First annular air knife; 102. Second annular air knife; 103. Third annular air knife; 11. Oblique opening; 12. Membrane filament; 13. Coating tube; 14. Fine pores; 15. Hydrophilic agent inlet hole; 16. Hydrophilic agent overflow hole. DETAILED DESCRIPTION

[0053] The purpose of the present invention is to provide a hydrophilic polyvinylidene fluoride membrane preparation process equipment. Through the preparation device provided by the present invention, the separation membrane prepared not only has a good hydrophilic type, but also has a relatively simple preparation process and strong reliability. At the same time, continuous production from PVDF ultrafiltration membrane base membrane to modified hydrophilic membrane can be achieved. In addition, if the PVDF material is replaced with polyethersulfone, polysulfone and other materials, the equipment provided by this invention can also be used for preparation. In addition, the filter membrane preparation method provided in the present invention is mainly a dry-jet-wet spinning method. If the filter membrane preparation method is changed to a melt-spinning method, it can also be coupled with the modification section provided by the present invention, which will not be described in detail in the present invention.

[0054] Figure 1 It provides hollow fiber membrane and liner-reinforced hollow fiber membrane hydrophilic preparation equipment, which is a complete set of continuous production lines.

[0055] In the production process, it is first necessary to manufacture a hollow fiber base membrane. The manufacturing equipment of the base membrane includes a core liquid tank 1 for storing core liquid. The core liquid tank 1 is connected to the internal channel of the spinneret 3 through a metering pump. It also includes a casting liquid tank 2 for storing casting liquid. The casting liquid tank 2 is connected to the external channel of the spinneret 3 through a metering pump. In the process of manufacturing the base membrane, the core liquid and the casting liquid are pressed into the internal and external channels of the spinneret 3 at the same time, and the extruded membrane filaments then enter the coagulation bath 4, and the hollow fiber membrane filaments are obtained after phase conversion.

[0056] In another embodiment, lined membrane yarns can be produced, wherein a braided tube 9 (no longer a core liquid) is fed into the internal channel of the spinneret 3, and hollow fiber membrane yarns with a textile tube 9 inside and a polymer layer outside can be obtained, which have higher physical strength.

[0057] After the base membrane is obtained, the excess solution in the hollow fiber membrane is washed by the elution tank 5. The surface of the base membrane is hydrophilized by the hydrophilic modification manufacturing equipment. An improvement of the present invention is that the base membrane obtained in the elution tank 5 is firstly purged by using the first air knife 101. The structure of the air knife is as follows: Figure 8 and Fig. 9 As shown, the wind knife is annular in shape as a whole, the inside of the wind knife is connected to the air source, and a ring-shaped oblique opening 11 is provided on the outside of the wind knife, and the oblique opening 11 is connected to the air source, and the opening angle of the oblique opening 11 is toward the central axis of the wind knife. The obtained base film is passed through the middle of the wind knife and purged into the inside through the air source. After the purging treatment, the retained cleaning liquid and the like can be removed, effectively avoiding the influence on the effect of the subsequent coating of the hydrophilic agent.

[0058] The main components for preparing hydrophilic membranes are Figure 2-4 The hydrophilic agent coating device 6-1 is shown. A coating tube 13 is set in the hydrophilic agent coating device 6-1. The coating tube 13 is provided with fine holes 14 with a hole diameter of 0.1~1mm every 5-8mm along the axial direction. The number of fine holes is 20-50, and the fine holes are evenly distributed along the radial direction of the coating tube 13. When the membrane filament 12 passes through the coating tube 13, the hydrophilic agent is pumped into the coating tube 13 by a metering pump, and the hydrophilic agent is sprayed on the surface of the membrane filament 12 through the fine holes 14 on the coating tube 13. The amount of hydrophilic agent coating can be determined by the metering pump and the spinning speed. The hydrophilic modifier contacts the membrane filament in the coating head. The coating tube is cylindrical in the middle, and the two ends are two truncated cone structures. The purpose of the truncated cone structure is to keep the pipe filled with water, and at the same time, remove the excess hydrophilic agent on the surface of the membrane filament. The diameter of the holes at both ends of the coating tube is in the range of 1.5-3.0mm. The hydrophilic agent coating device 6-1 is provided with a hydrophilic agent inlet hole 15 and a hydrophilic agent overflow hole 16, and the hydrophilic agent inlet hole 15 is connected to the hydrophilic agent storage tank 6-4 through a metering pump 6-5. Excess hydrophilic agent flows out from the lower port of the device to the hydrophilic agent storage tank, and a Y-type filter is provided in front of the storage tank.

[0059] Next, the device is provided with a hydrophilic agent coating device 6-6, the structure of which is as follows: Figure 5 , Figure 6 , Figure 7 As shown, the main body of the hydrophilic agent coating device 6-6 is cylindrical, and coated fibers are evenly distributed on the inner wall, and the free ends of the coated fibers form a membrane thread channel inside the hydrophilic agent coating device 6-6; the membrane thread obtained from the hydrophilic agent coating device 6-1 enters the hydrophilic agent coating device 6-6, and the coated fibers brush the hydrophilic modifier on the surface. The principle is similar to that of a brush. The coated membrane thread passes through the device, and the hydrophilic agent on the surface of the membrane thread is evenly coated, and the excess hydrophilic substance is further wiped off. The brush embedded in the coating device is mainly made of wool, polyester, nylon, etc.

[0060] The membrane filaments obtained from the hydrophilic agent coating device 6-6 are sent to the subsequent channel 6-2, and the hydrophilic agent further penetrates into the membrane filaments. The length of the equipment channel is 1-2 meters. There is no guide wheel in the front 2 / 3 of the channel, and a guide wheel is set in the back 1 / 3. The staying distance of the membrane filaments in the channel can be set. The channel uses electric heating to provide heat source, and is equipped with a temperature and humidity control system to adjust the process parameters suitable for the penetration between the hydrophilic agent and the membrane filaments.

[0061] After passing through the channel 6-2, the membrane filaments are passed through the second annular air knife 102, which has the same structure as the first annular air knife 102, to continue processing the membrane filaments; then they enter the cross-linking bath 7, which is filled with a cross-linking agent. The hydrophilic agent reacts with the components in the cross-linking bath, and the cross-linked membrane filaments have permanent hydrophilicity; the membrane filaments after the cross-linking reaction are passed through the third annular air knife 103 to sweep away excess cross-linking agent on the surface, so that the properties of the obtained hollow fiber membrane can be made more stable, and finally the filaments are collected to preserve the pores and dried for testing.

[0062] The operation flow of the above device is as follows:

[0063] The main process is as follows: prepare PVDF membrane casting solution in a certain proportion, and pass it through a spinneret, scraper or coating head to prepare PVDF filter membrane. The prepared filter membrane forms hollow fiber membrane, flat membrane, and lined reinforced braided tube membrane. The prepared filter membrane passes through a coagulation bath and a rinsing bath in turn to form a membrane, and then enters the coating head after the excess water on the membrane surface is blown away by an annular air knife. In the coating head, the hydrophilic modifier is accurately coated on the surface of the filter membrane through a metering pump and then passes through a coating device, which is used to evenly coat the modifier on the surface of the membrane wire. The membrane wire enters the channel. Then the membrane wire passes through an annular air knife to blow away the excess liquid and enters the cross-linking bath for cross-linking reaction. After the reaction, the excess liquid is blown away and the wire collection device is used. The self-made hydrophilic agent coating equipment is designed. The internal coating tube is provided with 0.1~1mm pores every 5-8mm. The membrane filament passes through the coating tube. The metering pump quantitatively delivers the hydrophilic agent to the internal channel of the coating equipment. The internal channel and the coating tube form a ring structure. The hydrophilic agent enters the coating tube from the internal channel and is sprayed onto the membrane filament to modify the surface of the base membrane and the pores. The hydrophilic agent coating equipment is a ring structure. A circle of brushes (made of nylon, wool, etc.) is embedded inside the ring of the equipment to evenly coat the hydrophilic agent on the base membrane. After the coating, there is a layer of solution on the surface of the membrane filament. A temperature and humidity controller is provided inside the channel to control the drying speed of the hydrophilic agent and the base membrane in the channel when the modified filter membrane passes through the channel. The coagulation bath, the rinsing bath, and the cross-linking bath are respectively provided with heating devices, which adopt electric heating and the heating temperature is 0~100℃.

[0064] Example 1

[0065] 1) Preparation of casting solution: Weigh 12% by mass of PVDF, 12% of PVP-K90, and 76% of DMAC, stir in a stirred kettle for 4 hours in a water bath at 80°C, and perform vacuum degassing to obtain PVDF casting solution;

[0066] 2) Prepare a hydrophilic modifier and place it in the 6-4 storage tank. The preparation method of the hydrophilic agent is as follows: dissolve a certain amount of polyvinyl alcohol (PVA) powder in water, heat the water to 60-80°C and dissolve it to prepare a PVA solution with a PVA mass fraction of 0.1%. PVA uses PVA205 (with an alcoholysis degree of 88-89%).

[0067] 3) The casting liquid and the core liquid are squeezed into the spinneret 3 by a metering pump, and the primary membrane fibers are prepared in a coagulation bath 4 and a rinsing bath 5;

[0068] 4) The membrane filaments are pulled by the rollers through the hydrophilic agent coating head 6-1. The hydrophilic agent is pumped into the head by the metering pump 6-5. The hydrophilic agent contacts the membrane filaments in the coating head. The membrane filaments are hydrophilically modified more efficiently under the forced convection of the hydrophilic agent. After passing through the coating head, the membrane filaments enter the coating equipment.

[0069] 5) The membrane fibers pass through a channel with a length of 2 meters, a temperature of 50°C, and a humidity of 40%. The hydrophilic agent in the membrane fibers penetrates into the membrane fibers in the channel environment;

[0070] 6) After passing through the air knife, the membrane filaments enter the cross-linking bath, and the cross-linking bath temperature is 60°C. The composition of the cross-linking bath is glutaraldehyde, sulfuric acid, glacial acetic acid, methanol, with a ratio of 4%, 2%, 2%, 10%, and the rest is water. The membrane filaments stay in the cross-linking bath for 5 minutes;

[0071] 7) After the membrane fibers have passed through the cross-linking bath, the excess components are blown off by an air knife, and the fibers are collected and soaked in a glycerol aqueous solution for dry storage.

[0072] Example 2

[0073] 1) The preparation of primary membrane filaments is the same as in Example 1, and the prepared membrane filaments enter the hydrophilic modification part;

[0074] 2) Prepare the hydrophilic modifier and place it in the 6-4 storage tank. The preparation method of the hydrophilic agent is: PVP k30 and water, PVP accounts for 30, and the heating temperature of the hydrophilic agent is 80℃;

[0075] 3) The composition of the cross-linking bath is 0.5% potassium persulfate solution, and the temperature of the cross-linking bath is 80°C;

[0076] 4) After the membrane fibers have passed through the cross-linking bath, the excess components are blown off by air knives, and the fibers are collected and soaked in a glycerol aqueous solution for dry storage.

[0077] Example 3

[0078] This example is a method for preparing a hollow fiber membrane with a lined braided tube;

[0079] 1) Figure 1 In the production equipment flow chart, 9 represents the schematic diagram of the preparation of the lined braided tube membrane filament. In the coating head, the casting liquid is coated on the braided tube to prepare the lined braided tube membrane filament, and then the steps described in Example 1 are followed to prepare the hydrophilic membrane filament. This type of membrane filament is mostly prepared into a curtain-type component for use in membrane bioreactors and submerged ultrafiltration. The hydrophilic filter membrane can slow down membrane contamination and extend the maintenance cleaning cycle during use.

[0080] The contact angle test was carried out on the prepared membrane surface. Figure 8 As shown, it shows that the prepared membrane filaments have good hydrophilic properties. At the same time, a scanning electron microscope was used to observe the cross section of the prepared membrane filaments.

[0081] Comparative Example 1

[0082] The difference from Example 1 is that after the hollow fiber base membrane is rinsed, no annular air knife is used for blowing treatment.

[0083] Comparative Example 2

[0084] The difference from Example 1 is that after the treatment in the tunnel, no annular air knife is used for blowing treatment.

[0085] Six batches of hollow fiber membranes prepared in Example 1, Comparative Example 1 and Comparative Example 2 were randomly selected, and six segments of membrane fibers were randomly selected from one batch of products for performance characterization. The results are as follows:

[0086] Performance data of 6 batches of products

[0087]

[0088] It can be seen from the above table that the PVDF hydrophilic modified membrane prepared according to the present method uses an annular air knife to process each step. Compared with Control Example 1, the water on the surface of the membrane fiber can be eliminated by air knife treatment after rinsing. When the modifier is applied, the coating amount is more stable, so that the PVDF hydrophilic modified membrane obtained in the subsequent cross-linking process has more stable membrane performance in multiple batches of preparation, and the relative standard deviation is less than 5%; relative to Control Example 2, the annular air knife treatment before the subsequent addition of the cross-linking agent reduces the deviation of the tensile strength and molecular weight cutoff performance in multiple batches of preparation experiments. Similarly, the pore size distribution of the hollow fiber membrane prepared in the above Example 1 and Control Examples 1 and 2 is as follows: Fig.14 As shown, it can be seen that the pore size distribution of the hollow fiber membranes obtained in Control Examples 1 and 2 is wider because they have not been treated with annular air knife. Therefore, the pore size distribution of the hydrophilic hollow fiber membrane prepared by the annular air knife treatment can be reduced.

Claims

1. A production device for PVDF hollow fiber membrane, characterized in that: include: A film casting liquid tank (2), used for adding PVDF film casting liquid to the spinneret (3); A coagulation bath tank (4) is used to receive the hollow fiber base membrane obtained from the spinneret (3) and complete the phase conversion under the coagulation bath conditions; A rinsing tank (5) is used to rinse the hollow fiber membrane obtained by treatment in the coagulation bath tank (4); A first annular air knife (101) is used to perform a purge treatment on the hollow fiber membrane obtained in the rinsing tank (5); A hydrophilic agent coating device (6-1) is used to coat the hollow fiber membrane obtained in the first annular air knife (101) with a hydrophilic agent; a coating tube (13) is provided inside the hydrophilic agent coating device (6-1), fine holes (14) are distributed around the coating tube (13), and a hydrophilic agent inlet hole (15) is also provided on the hydrophilic agent coating device (6-1), and the hydrophilic agent inlet hole (15) is connected to the fine holes (14); The hydrophilic agent coating device (6-6) is used to perform a hydrophilic agent scraping treatment on the hollow fiber membrane obtained in the hydrophilic agent coating device (6-1); the hydrophilic agent coating device (6-6) is cylindrical, and coated fibers are evenly distributed on the inner wall, and the free ends of the coated fibers form a membrane fiber channel inside the hydrophilic agent coating device (6-6); The channel (6-2) is used to receive the hollow fiber membrane obtained in the hydrophilic agent coating device (6-6) and keep the hollow fiber membrane under set temperature and humidity conditions for a set time; A second annular air knife (102) is used to purge the hollow fiber membrane obtained in the channel (6-2); A cross-linking bath (7) for immersing the hollow fiber membrane obtained in the second annular air knife (102) in a cross-linking agent and subjecting it to a cross-linking reaction treatment; A third annular air knife (103) is used to purge the hollow fiber membrane obtained in the cross-linking bath (7); The spinneret (3) includes an internal channel and an external channel, and the casting liquid tank (2) is connected to the external channel; the production device also includes a core liquid tank (1), which is connected to the internal channel and is used to add core liquid to the spinneret (3); or the interior of the spinneret (3) includes an internal channel and an external channel, the internal channel is used to supply the braided tube (9), and the casting liquid tank (2) is used to be connected to the external channel; The hydrophilic agent coating device (6-1) is also provided with a hydrophilic agent overflow hole (16) for discharging excess hydrophilic agent in the coating tube (13).

2. The production device of PVDF hollow fiber membrane according to claim 1, characterized in that: It also includes a collecting wheel (8) for pulling the hollow fiber membrane during the production process; It also includes a hydrophilic agent storage tank (6-4) connected to the hydrophilic agent inlet hole (15); The hydrophilic agent storage tank (6-4) is connected to the hydrophilic agent inlet hole (15) via a metering pump (6-5).

3. The production device of PVDF hollow fiber membrane according to claim 1, characterized in that: It also includes a temperature and humidity controller (6-3) for controlling the temperature and humidity of the corridor (6-2); The structures of the first annular wind knife (101), the second annular wind knife (102), and the third annular wind knife (103) are as follows: the wind knife is annular in shape as a whole, the inside of the wind knife is connected to the air source, an annular oblique opening (11) is provided on the outside of the wind knife, and the oblique opening (11) is connected to the air source, and the opening angle of the oblique opening (11) is oriented toward the central axis of the wind knife; The opening angle of the oblique opening (11) is 10-80° with respect to the central axis; The diameter of the hollow fiber membrane is 0.5-3 mm, and the inner diameters of the first annular air knife (101), the second annular air knife (102), and the third annular air knife (103) are 0.1-5 mm larger than the outer diameter of the hollow fiber membrane.

4. The production device of PVDF hollow fiber membrane according to claim 1, characterized in that: The diameter of the fine holes (14) is 0.1-1 mm, and a circle of fine holes (14) is arranged every 5-8 mm along the axis of the coating tube (13), and the number of the fine holes (14) is 20-50.

5. A method for preparing a PVDF hollow fiber membrane, characterized in that: The PVDF hollow fiber membrane is prepared by using the production device of any one of claims 1 to 4, comprising the following steps: Step 1, providing a PVDF hollow fiber base membrane, sending the base membrane into the inner channel of the annular air knife, and using the annular air knife to blow away excess solution on the surface of the hollow fiber base membrane; Step 2, applying the modifier evenly on the surface of the hollow fiber base membrane obtained in step 1 by using a coating head, and evenly applying the modifier by using a coating head; Step 3: Send the hollow fiber membrane obtained in step 2 into the channel, allow the modifier to penetrate into the hollow fiber membrane, send the hollow fiber membrane into the inner channel of the annular air knife, and use the annular air knife to blow away the excess solution on the surface of the hollow fiber membrane; In the fourth step, the hollow fiber membrane obtained in the third step is immersed in a cross-linking agent to allow the modifier and the cross-linking agent to undergo a cross-linking reaction, and the hollow fiber membrane is sent into the internal channel of the annular air knife, and then the excess solution on the surface of the hollow fiber base membrane is blown away by the annular air knife to obtain a PVDF hollow fiber membrane.

6. The method for preparing a PVDF hollow fiber membrane according to claim 5, characterized in that: The modifier is a 0.05-0.5wt% polyvinyl alcohol aqueous solution; the cross-linking agent is an aqueous solution containing 2-6wt% glutaraldehyde, 1-3wt% sulfuric acid, 1-3wt% glacial acetic acid, and 5-15wt% methanol.

7. The method for preparing a PVDF hollow fiber membrane according to claim 5, characterized in that: The temperature in the tunnel is 20-60°C, the humidity is 30-70%RH; the cross-linking reaction temperature is 40-70°C.

8. Use of the PVDF hollow fiber membrane production device according to claim 1 in preparing hydrophilic PVDF hollow fiber membranes.

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