Preparation device of ultrafiltration membrane with low molecular weight cutoff

Abstract

The utility model discloses a preparation device of a low molecular weight cutoff ultrafiltration membrane, and belongs to the technical field of ultrafiltration membrane preparation. The inner cavity wall of the gel tank (pure water) is respectively connected with a guide roller and an unwinding device, the guide roller, a coating support roller and a winding device are respectively connected with a base material, and the periphery of the coating support roller is respectively provided with a scraper edge coated with an upper-layer membrane casting solution, a scraper edge coated with a lower-layer membrane casting solution, an upper-layer membrane casting solution storage tank and a lower-layer membrane casting solution storage tank; the knife edge of the scraper coated with the upper-layer membrane casting liquid is placed at the lower part of the upper-layer membrane casting liquid storage tank, and the knife edge of the scraper coated with the lower-layer membrane casting liquid is placed at the lower part of the lower-layer membrane casting liquid storage tank. The device is reasonable and practical in structure, simple in whole equipment and small in occupied area. The upper layer casting film liquid storage tank, the lower layer casting film liquid storage tank and the two scraper edges are adopted, two different casting film liquids can be coated at the same time, a double-layer film is obtained, the thickness of the upper layer casting film liquid and the thickness of the lower layer casting film liquid are controlled by controlling the thickness of feeler gauges on the two sides of the scraper edges, and therefore the structure and performance of the obtained double-layer film are regulated and controlled.

Description

TECHNICAL FIELD

[0001] The utility model belongs to ultrafiltration membrane preparation technical field relates to a kind of preparation device of low molecular weight cut-off ultrafiltration membrane. BACKGROUND

[0002] At present, the ultrafiltration membrane with molecular weight cut-off ≤5000 is less studied in China, and the products used in experiments and production mainly rely on import. The devices reported for preparing low molecular weight cut-off ultrafiltration membrane mostly use single casting solution and prepare finished membrane by non-solvent induced phase inversion method.

[0003] Patent application CN103816810A reports a kind of low molecular weight cut-off spiral ultrafiltration membrane preparation and its product, single casting solution is coated on polyester non-woven fabric, and low molecular weight cut-off ultrafiltration membrane is obtained by phase inversion. Patent application CN106268365A discloses a kind of flat plate separation membrane and its preparation method, single casting solution is coated on one surface of non-woven fabric using coating machine, and the device has only one casting solution storage tank and single coating port. In order to improve the retention effect of low molecular substances by ultrafiltration membrane, crosslinking reaction is usually carried out on the membrane surface to reduce the pore size of the membrane surface, and the base membrane is mostly prepared by the above-mentioned scraping / coating machine, which can only scrape / coat single casting solution, and the temperature stability of the casting solution cannot be controlled.

[0004] The existing devices have the following disadvantages: (1) there is only one casting solution storage tank and single coating port, and the scraping / coating of two or more different casting solutions cannot be carried out simultaneously, so that the double-layer membrane cannot be obtained, and the regulation of membrane structure and performance has certain limitations. (2) single casting solution is used, and non-solvent induced phase separation method is mostly used for casting, which cannot meet the application scenarios of combining multiple methods for membrane preparation, thereby limiting the further regulation of membrane structure and performance. (3) the casting solution storage tank mostly used cannot be temperature-controlled, and when high material temperature experiment is carried out, the temperature stability of the casting solution cannot be controlled, which causes poor consistency and repeatability of membrane performance. SUMMARY

[0005] The utility model provides a kind of preparation device of low molecular weight cut-off ultrafiltration membrane according to prior art problems.

[0006] A kind of low molecular weight cut-off ultrafiltration membrane device, the inner cavity wall of gel tank (pure water) is connected with guide roller respectively, unwinding device, guide roller, coating support roller and winding device are connected with base material respectively, the periphery of coating support roller has scraper blade edge of coating upper layer casting solution, scraper blade edge of coating lower layer casting solution, upper layer casting solution storage tank and lower layer casting solution storage tank respectively, scraper blade edge of coating upper layer casting solution is placed in the lower part of upper layer casting solution storage tank, and scraper blade edge of coating lower layer casting solution is placed in the lower part of lower layer casting solution storage tank.

[0007] The advantages of this invention are: the device has a reasonable and practical structure, simple overall equipment, and small footprint. It employs two casting solution storage tanks (upper and lower) and two doctor blades, allowing simultaneous coating with two different casting solutions to obtain a double-layer membrane. The thickness of the upper and lower casting solutions is controlled by adjusting the thickness of the feeler gauges on both sides of the doctor blades, thereby regulating the structure and performance of the resulting double-layer membrane. The two casting solution storage tanks can use two different casting solution systems, combining thermally induced phase separation and non-solvent-induced phase separation methods to further improve the performance of ultrafiltration membranes and expand their application scenarios. Furthermore, the device can separately control the temperature of the upper and lower casting solution storage tanks, meeting the different temperature requirements of the upper and lower casting solutions while ensuring temperature stability, thus guaranteeing consistent and repeatable membrane performance.

[0008] This invention uses two different casting solutions to prepare a double-layer ultrafiltration membrane. The prepared ultrafiltration membrane maintains a high rejection rate while having a relatively high flux. Moreover, the preparation and post-treatment processes are simple and save water resources. Attached Figure Description

[0009] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. As shown in the figures:

[0010] Figure 1 This is a schematic diagram of the device of this utility model.

[0011] Figure 2 This is a schematic diagram showing the position of the casting liquid during the coating process of this utility model.

[0012] Figure 3 This is a field emission scanning electron microscope image of the ultrafiltration membrane surface of this invention.

[0013] Figure 4 This is a field emission scanning electron microscope image of the cross-section of the ultrafiltration membrane of this invention. Detailed Implementation

[0014] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0015] Example 1: As shown in Figure 1 , Figure 2 , Figure 3 and Figure 4 A preparation device for a low molecular weight cut-off ultrafiltration membrane includes an unwinding device 1, a base material 2, a guide roller 3, a coating support roller 4, a doctor blade knife edge 5 for coating an upper layer of casting solution, a doctor blade knife edge 6 for coating a lower layer of casting solution, an upper layer casting solution storage tank 7, a lower layer casting solution storage tank 8, a gel tank (pure water) 9, a cleaning tank (pure water) 10, a winding device 11, and the inner cavity wall of the gel tank (pure water) 9 is connected to the guide roller 3, the unwinding device 1, the guide roller 3, the coating support roller 4, and the winding device 11 are connected to the base material 2, respectively. The coating support roller 4 has the doctor blade knife edge 5 for coating the upper layer of casting solution, the doctor blade knife edge 6 for coating the lower layer of casting solution, the upper layer casting solution storage tank 7, and the lower layer casting solution storage tank 8 around its periphery. The doctor blade knife edge 5 for coating the upper layer of casting solution is placed at the lower part of the upper layer casting solution storage tank 7, and the doctor blade knife edge 6 for coating the lower layer of casting solution is placed at the lower part of the lower layer casting solution storage tank 8. The unwinding device 1, the guide roller 3, the coating support roller 4, and the winding device 11 are connected to the machine frame, respectively.

[0016] A preparation method for a low molecular weight cut-off ultrafiltration membrane includes the following steps: first, press the doctor blade knife edge on the base material, and pad a certain thickness of feeler gauge on both sides of the doctor blade knife edge 5 for coating the upper layer of casting solution and the doctor blade knife edge 6 for coating the lower layer of casting solution, and press tightly. Then, start the doctor blade knife edge control system, the unwinding device 1 starts to work, the base material 2 passes through the guide roller 3 and enters the surface of the coating support roller 4, the lower layer of casting solution is poured into the lower layer casting solution storage tank 8 first, so that the lower layer of casting solution is coated on the base material, then the upper layer of casting solution is poured into the upper layer casting solution storage tank 7, so that the upper layer of casting solution is coated on the lower layer of casting solution, the casting solution together with the base material passes through the dry section, enters the gel tank (pure water) 9 to undergo phase separation, then passes through three guide rollers 3 and enters the cleaning tank (pure water) 10 for cleaning, and after cleaning in the cleaning tank, the finished product is collected on the winding device 11.

[0017] A preparation method for a low molecular weight cut-off ultrafiltration membrane also includes the following steps:

[0018] Step one: dissolve the polymer in the solvent, uniformly stir at 70-100°C for 8-10h, after complete dissolution, stop stirring, keep warm, and stand for 6-8h to remove bubbles, to obtain a clear and transparent upper layer of casting solution, and use the same method to prepare the lower layer of casting solution;

[0019] Step two: install the substrate on the film doctor machine, put a certain thickness of the feeler gauge on both sides of the doctor blade, turn on the film doctor machine control system, pour the lower casting solution on the side of the doctor blade close to the substrate unwinding, evenly coat the lower casting solution on the substrate, then pour the upper casting solution on the other side of the doctor blade, evenly coat the upper casting solution on the lower casting solution, then pass through the dry section, enter the coagulation bath, and after washing with pure water, the finished membrane is obtained.

[0020] In step one, the polymer includes a polysulfone substance, a mixture of the polysulfone substance and a sulfonated polysulfone substance, wherein the polysulfone substance includes one of polysulfone and polyethersulfone, and the sulfonated polysulfone substance includes one of sulfonated polysulfone and sulfonated polyphenylsulfone; in step one, the mass fraction of the polymer is 20-35 parts.

[0021] The sulfonation degree of the sulfonated polysulfone substance is 10-30%; the mass ratio of the polysulfone substance to the sulfonated polysulfone substance is 3:1-5:1.

[0022] In step one, the solvent includes one or a mixture of several of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, caprolactam, dimethyl sulfoxide, butyrolactone, and triethyl phosphate; in step one, the mass fraction of the solvent is 65-80 parts.

[0023] In step one, the upper casting solution and the lower casting solution are different in composition, wherein the polymer content of the upper casting solution is greater than that of the lower casting solution.

[0024] In step two, the substrate is one of polyolefin non-woven fabric and polyester non-woven fabric.

[0025] In step two, the doctor blade coating is single-layer doctor blade double-layer coating, double-layer doctor blade double-layer coating, or coating head coating.

[0026] In step two, the dry section temperature is 10-25℃, and the humidity is 0-30%.

[0027] In step two, the coagulation bath is pure water, and the temperature is 5-15℃.

[0028] The ultrafiltration membrane has a double-layer structure, wherein the upper layer is a sponge pore structure, and the lower layer is a finger-like pore structure.

[0029] Example 2: The ultrafiltration membrane is composed of a very thin skin layer for separation and a thicker sponge pore or finger-like pore layer for support, and the cut-off molecular weight of the membrane is several hundred to several million.

[0030] Double-layer ultrafiltration membrane: refers to an ultrafiltration membrane prepared by using two casting solutions to coat the upper and lower layers of the casting solution on the substrate at the same time, one of which is coated on the substrate (referred to as the lower casting solution), and the other is coated on the casting solution (referred to as the upper casting solution).

[0031] As Figure 1 , Figure 2 , Figure 3 and Figure 4 indicate, a preparation method of a low molecular weight cut-off ultrafiltration membrane, which adopts a combination of a thermally induced phase separation method and a non-solvent induced phase separation method for membrane preparation, effectively balances the relationship between the ultrafiltration membrane flux and the rejection rate, and provides high rejection to low molecular weight substances while considering relatively high flux. Two casting solutions are used for double-layer simultaneous coating, the casting solutions are coated on the substrate, and after passing through the dry section, phase separation occurs in the coagulation bath, and the finished membrane is obtained after cleaning, the process is simple, and the obtained membrane is an integrated structure, and there is no risk of separation layer falling off. The coagulation bath used in the casting process is pure water, which is beneficial to recycling and post-processing of the ultrafiltration membrane.

[0032] Example 3: A preparation method of a low molecular weight cut-off ultrafiltration membrane, comprising the following steps:

[0033] Step 1: Prepare the upper casting solution and the lower casting solution respectively, the upper casting solution is composed of 25.8 parts of polyether sulfone, 5.2 parts of sulfonated polysulfone and 69 parts of N,N-dimethylacetamide, and the lower casting solution is composed of 22 parts of polyether sulfone, 7.8 parts of triethyl phosphate and 70.2 parts of N,N-dimethylacetamide, the polymers are dissolved in the solvent, mixed uniformly, stirred at 100℃ for 10h, after complete dissolution, stop stirring, keep warm, and stand for 8h to remove bubbles, and two kinds of uniform and clear casting solutions are obtained.

[0034] Step 2: Install the substrate on the film doctor machine, pad a certain thickness of feeler gauge on the knife edges of the double-layer doctor blade, open the film doctor machine control system, control the vehicle speed to be 10m / min, pour the lower casting solution on the side of the doctor blade close to the substrate, at this time the lower casting solution contacts the substrate, then pour the upper casting solution on the other side of the doctor blade, at this time the upper casting solution contacts the lower casting solution, then pass through the dry section, enter the pure water coagulation bath for phase separation, and the finished membrane is obtained after pure water cleaning. The casting solution is uniformly coated on the substrate by using the doctor blade, and the thickness of the upper and lower casting solutions is controlled by controlling the thickness of the feeler gauge on the two knife edges of the doctor blade.

[0035] The membrane layer thickness of the ultrafiltration membrane obtained by the utility model is 40-70μm, the membrane structure is as shown in Figure 3 and Figure 4 , the surface is a dense skin layer, the upper layer of the section is a sponge pore structure, and the lower layer is a finger-shaped pore structure. The pure water flux of the ultrafiltration membrane is 40-60L / m 2 / h, the rejection rate to PEG2000 is 97.2%, and the rejection rate to PEG5000 is 99.3%.

[0036] The utility model mainly protects the device and simple deformation mode of double -deck coating cast film, and the film prepared has double -deck structure, and the upper layer is sponge hole structure, and the lower layer is finger hole structure. Two kinds of cast film liquid are used, and the membrane is prepared by combining the thermotropic phase separation method and the non - solvent induced phase separation method, and the structure - activity relationship of the ultrafiltration membrane can be effectively adjusted. The equipment form includes but is not limited to doctor blade coating, coating head coating, the coating film form includes but is not limited to double -deck coating, multilayer coating (more than double -deck).

[0037] The above merely describes the preferred embodiments of the utility model and is not intended to limit the utility model, and any modification, equivalent replacement and improvement, etc. made within the spirit and principle of the utility model should be included in the protection scope of the utility model.

Claims

1. An apparatus for producing a low molecular weight cut-off ultrafiltration membrane, characterized by comprising: The inner cavity wall of the gel tank is connected with the guide roller respectively, the unwinding device, the guide roller, the coating support roller and the winding device are connected with the base material respectively, the periphery of the coating support roller is provided with the scraper blade edge for coating the upper casting fluid, the scraper blade edge for coating the lower casting fluid, the upper casting fluid storage tank and the lower casting fluid storage tank respectively, the scraper blade edge for coating the upper casting fluid is placed at the lower part of the upper casting fluid storage tank, and the scraper blade edge for coating the lower casting fluid is placed at the lower part of the lower casting fluid storage tank.

2. The apparatus for producing a low molecular weight cut-off ultrafiltration membrane according to claim 1, wherein The unwinding device, the guide roller, the coating support roller and the winding device are connected with the rack respectively.

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