Preparation method and device of bipolar membrane

Abstract

The invention discloses a preparation method and device of a bipolar membrane. The preparation method comprises the following steps: 1) treating a base membrane by adopting a plasma surface treatment machine; 2) infiltrating the base membrane into the catalyst solution, and then drying; 3) coating one side of the base membrane with the positive membrane material liquid, and drying; and 4) coating the other side of the base membrane with the anion membrane material liquid, and drying. The surface polarity of the base material is improved through the plasma processor, so that the positive and negative membrane layers of the bipolar membrane are bonded more firmly. By adopting the method, automation is completely realized, the energy consumption is low, the production cost is low, the product quality is stable, the industrial problems that a traditional bipolar membrane is easy to blister, peel and break and the like are effectively solved, the operation efficiency of the bipolar membrane is greatly improved, and the manufacturing cost and the equipment investment cost of the bipolar membrane are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of bipolar membrane production, and in particular relates to a method and a device for preparing a bipolar membrane. Background Art

[0002] Bipolar membranes (BPMs) are special ion exchange membranes composed of anion exchange layers and cation exchange layers. Due to their unique water dissociation properties, bipolar membranes play an irreplaceable role in the fields of chemical industry, environmental protection, energy storage, food processing, etc. In the past 20 years, the commercial market for bipolar membranes has continued to expand, and research on bipolar membranes has also developed rapidly.

[0003] Bipolar membrane is a new type of ion exchange composite membrane, which is usually composed of a cation exchange layer (CEL), an intermediate layer and an anion exchange layer (AEL). The intermediate layer is usually a few nanometers thick, electrically neutral and contains a catalyst. Under the action of a DC electric field, the intermediate layer of the bipolar membrane can dissociate water to produce H + and OH - . Subsequently, the generated H+ and OH- migrate to the cathode and anode respectively, driven by the potential difference between the cathode and anode. At the same time, the water in the solution on both sides of the bipolar membrane will enter the middle layer through AEL and CEL to replenish the water consumption. The working principle of the bipolar membrane is that the bipolar membrane can be specially designed to make the transfer or reaction of different components in the membrane vary greatly, and it has the advantages of simple process, good selectivity, and mild operating conditions. Therefore, it has broad and potential applications in the fields of pollution control, resource recovery, chemical production, etc. In particular, bipolar membrane electrodialysis (BMED) technology has become an irreplaceable process due to its unique advantages in acid-base production and energy conversion.

[0004] At present, commercial bipolar membranes generally have problems such as high resistance, low current efficiency, easy cracking of the anode and cathode membranes, short service life and high energy consumption.

[0005] Chinese patent CN 114432894 A discloses a bipolar membrane preparation process, which requires using DMF solvent to dissolve sulfonated polyethersulfone (SPES) and then scrape it into a film as the positive membrane surface of the bipolar membrane, and coating molybdenum sulfide (MoS 2 ) catalyst, polyethylene (PE) and polyvinylidene fluoride (PVDF) are dissolved in dimethyl sulfoxide (DMSO), coated on the cation membrane surface with the catalyst, dried, and aminated with trimethylamine to finally obtain a bipolar membrane. This invention patent has a complex process, the cation and cathode layers are easy to peel off, and its service life has not been verified. Summary of the invention

[0006] In view of the above problems existing in the prior art, the purpose of the present invention is to provide a method and device for preparing a bipolar membrane. The process can produce bipolar membranes quickly, efficiently, at low cost and continuously, and the prepared bipolar membranes have low resistance, high current efficiency, and the cation and cathode membranes are not easy to crack and have a long service life.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preparing a bipolar membrane comprises the following steps:

[0009] 1) Use plasma surface treatment machine to treat the base film;

[0010] 2) soaking the base film in the catalyst solution and then drying it;

[0011] 3) Coating the cation film liquid on one side of the base film and drying;

[0012] 4) Coat the negative film liquid on the other side of the base film and dry it.

[0013] Preferably, the base film is a polyethylene terephthalate base film.

[0014] The base film ionizes the process gas through the high-frequency electric field generated by the plasma surface treatment machine to generate plasma, which reacts with the surface of the polyethylene terephthalate, so that some molecular bonds on the polyethylene terephthalate surface are broken, polar bonds are generated, and the surface polarity and surface tension of the polyethylene terephthalate are improved. The wettability and adhesion of the polyethylene terephthalate surface are enhanced, so that the catalyst is easier to infiltrate into the polyethylene terephthalate base film, and the positive and negative membrane materials of the bipolar membrane are easier to adhere to the surface of the polyethylene terephthalate base film.

[0015] Preferably, in step 2), after the base film is taken out, excess catalyst solution is squeezed out and then dried.

[0016] Preferably, in step 2), after the base film is taken out, the excess catalyst solution is squeezed out by a squeezing roller. The base film soaked with the catalyst is squeezed out by a squeezing roller to squeeze out the excess catalyst, so as to ensure that there is no catalyst dripping in the subsequent process.

[0017] Preferably, in step 2), the base film is dried at a temperature of 40-80°C, preferably 50-65°C.

[0018] Preferably, the catalyst is an organotin catalyst.

[0019] Preferably, the organotin catalyst is selected from dibutyltin dilaurate, dibutyltin dibutyrate, stannous octoate, dibutyltin diacetate, and dioctyltin oxide; preferably dibutyltin dibutyrate and dioctyltin oxide.

[0020] Preferably, a surfactant is also added to the catalyst solution.

[0021] Preferably, the surfactant is selected from fatty acid glycerides, polysorbate, sodium xylene sulfonate, and polyoxyethylene fatty acid esters; the surfactant enables the organotin catalyst to better and evenly form a catalyst solution with water.

[0022] Preferably, based on 100% of the total mass of the catalyst solution, the mass content of the organotin catalyst is 2-15%, preferably 5-12%, and more preferably the mass content of the surfactant is 0.01-0.15%, preferably 0.05-0.12%.

[0023] Preferably, the cation film liquid comprises sulfonated polyphenylene ether and a solvent, wherein the solvent is preferably DMF.

[0024] Preferably, in step 3), the drying is carried out at a temperature of 50-100°C, preferably 60-80°C.

[0025] Preferably, the anion film liquid comprises aminated polyphenylene ether and a solvent, wherein the solvent is chlorobenzene or DMF.

[0026] Preferably, in step 4), the drying is carried out at a temperature of 60-80°C.

[0027] The present application also provides a bipolar membrane preparation device, comprising a sequentially connected unwinding roller, a plasma surface treatment machine, a catalyst impregnation tank, a first oven, a first coating roller, a second oven, a second coating roller, and a winding roller;

[0028] A base film is placed on the unwinding roller, wherein the base film has a thickness of 60-120 μm and a porosity of 60-90%.

[0029] The catalyst impregnation tank of the present invention is in an inverted trapezoidal shape, a impregnation roller is provided at the bottom of the catalyst impregnation tank, and an extrusion roller is connected to the outlet of the catalyst impregnation tank.

[0030] The pressure of the squeezing roller is 5-12kg / cm2, and the wetting speed of the base film is 0.2-1m / min;

[0031] Preferably, the pressure of the squeezing roller is 7-10 kg / cm2;

[0032] Preferably, the wetting speed of the nonwoven fabric is 0.4-0.8,m / min;

[0033] The coating roller of the present invention can be a transfer coating device, a scraper coating device and a slit coating device, and its coating thickness is 80-140 μm.

[0034] Preferably, the coating device is a transfer coating device;

[0035] Preferably, the coating thickness is 100-120 μm;

[0036] The coating roller 2 described in the present invention can be a transfer coating roller, a scraper coating roller, or a slit coating roller. The coating thickness is 20-50 μm.

[0037] Preferably, the second coating roller is a transfer coating device;

[0038] Preferably, the coating thickness of the second coating roller is 25-40 μm;

[0039] The dried membrane is rolled up by a winding roller to obtain a bipolar membrane, wherein the winding tension of the winding roller is 120-200 N / M and the winding diameter is 10-40 cm.

[0040] Preferably, the tension of the winding roller is 150-180 n / m.

[0041] Preferably, the winding diameter is 15-30 cm.

[0042] Compared with the prior art, the present invention has the following advantages:

[0043] 1. After the base film is treated by a plasma surface treatment machine, the bonding of the cation and positive membranes becomes stronger and less likely to bubble and peel off.

[0044] 2. The catalyst content is increased by impregnating the catalyst with a substrate, thus enhancing the efficiency of the catalyst.

[0045] 3. The double-sided coating process technology of the base film can adjust the coating thickness of the cation and positive membranes, and can maximize the performance of the bipolar membrane.

[0046] The continuous production process of the present invention can realize rapid, efficient, continuous and automated production of bipolar membranes, and the bipolar membranes have good performance, low production cost, stable product quality, and the cation and cathode membranes are not easy to peel off. It effectively solves the current industry problems of low efficiency, short service life, high production cost, unstable product quality, etc. in the bipolar membrane industry, and greatly reduces the production difficulty and equipment investment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A schematic diagram of a device for preparing a bipolar membrane by a double-sided coating method according to Example 1;

[0048] In the figure: 1. Unwinding roller

[0049] 2. Plasma surface treatment machine

[0050] 3. Catalyst impregnation tank

[0051] 4. Oven 1

[0052] 5. Coating roller 1

[0053] 6. Oven 2

[0054] 7. Coating roller 2

[0055] 8. Winding roller DETAILED DESCRIPTION

[0056] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited thereto.

[0057] Catalyst batching, the steps include:

[0058] A certain amount of deionized water is put into a measuring cup, and then dibutyltin dibutyrate is added, and stirred for 10 minutes by a magnetic stirrer, and then dioctyltin oxide is added, and finally sodium xylene sulfonate is added, and stirred for 30 minutes to form a milky water emulsion; wherein the mass fraction of dibutyltin dibutyrate is 10%, the mass fraction of dioctyltin oxide is 5%, and the mass fraction of sodium xylene sulfonate is 0.1%.

[0059] The steps of preparing the cation film liquid include:

[0060] Raw materials: sulfonated polyphenylene ether, DMF, chlorobenzene.

[0061] The preparation process is as follows:

[0062] Take 35 parts by mass of sulfonated polyphenylene ether, put it into a beaker, add 35 parts by mass of DMF, and add 30 parts by mass of chlorobenzene, raise the temperature to 45°C, stir for 30 minutes, and a cationic coating solution can be obtained.

[0063] The steps of preparing the negative membrane liquid include:

[0064] Raw materials: brominated polyphenylene ether, dimethylaminoethanol, DMF

[0065] The preparation process is as follows:

[0066] 50 parts by mass of brominated polyphenylene ether solid was crushed with a crusher, and then dissolved in 30 parts by mass of DMF. The dissolved brominated polyphenylene ether and DMF mixed solution was put into a beaker, and then 20 parts by mass of dimethylaminoethanol was dropped into the mixed solution, and the mixture was placed in a shaker for amination. The amination temperature was 50°C and the time was 55 minutes, and finally the amination solution of polyphenylene ether was obtained.

[0067] The plasma surface treatment machine in the embodiment of the present application is a Shenzhen Hongzhan automatic plasma surface treatment machine.

[0068] Example 1

[0069] A device for preparing bipolar membrane by double-sided coating method, such as Figure 1As shown, it includes an unwinding roller 1 and a plasma surface treatment machine 2, a catalyst impregnation tank 3, an oven 1 4, a coating roller 1 5, an oven 2 6, a coating roller 2 7 and a winding roller 8 which are connected in sequence.

[0070] The length of the unwinding roller is 30cm, the length of the catalyst impregnation tank is 40CM, the bottom width is 10cm, and the pressure of the squeezing roller on the upper part of the catalyst impregnation tank is 8kg / cm2.

[0071] The catalyst drying oven is 3 m long and the oven temperature is 50°C.

[0072] The length of coating roller 1 is 40 cm, and the coating method is transfer coating.

[0073] The length of oven 2 is 5 m, and the oven temperature is set at 60°C.

[0074] The length of the coating roller 2 is 40 cm, and the coating method is transfer coating.

[0075] The length of the winding roller is 40 cm.

[0076] Example 2

[0077] A method for preparing a bipolar membrane, using the device described in Example 1, comprising the following steps:

[0078] 1) The polyethylene terephthalate nonwoven base film from the unwinding roll passes through a plasma surface treatment machine and enters a catalyst impregnation tank to be impregnated with a catalyst solution at a rate of 0.5 m / min. It is then squeezed by an extrusion roller to squeeze out excess catalyst and then enters an oven for drying at a temperature of 52°C.

[0079] 2) After passing through the oven, the base film is coated with the cationic film liquid by a cationic film coating roller, and the coating method is transfer coating. After the coating is completed, the base film enters the polymerization oven for polymerization, and the temperature of the polymerization oven is 55°C.

[0080] 3) After the polymerization of the positive film layer is completed in the polymerization oven, the negative film liquid is coated on the other side of the base film through a negative film coating roller. The coating method is transfer coating. After the negative film layer is coated, it enters the oven again at 55°C for polymerization.

[0081] 4) After the anion film layer is polymerized, it enters the winding roller for winding. After the winding is completed, the bipolar membrane production is completed.

[0082] During the membrane making process, samples were taken for testing at 20 min, 40 min and 60 min after the start of the device operation. A total of three samples were taken to measure the performance indicators of the bipolar membrane. The results are shown in Table 1.

[0083] Table 1 Test results of three samples of Example 2

[0084]

[0085] Comparative Example 1

[0086] The main difference between the device of comparative example 1 and the device of embodiment 1 is that there is no plasma surface treatment machine. A method for preparing a bipolar membrane comprises the following steps:

[0087] 1) The polyethylene terephthalate nonwoven base film from the unwinding roll enters the catalyst impregnation tank and is impregnated with the catalyst solution at a rate of 0.5 m / min. It is then squeezed by an extrusion roller to squeeze out excess catalyst and then enters an oven for drying at a temperature of 52°C.

[0088] 2) After passing through the oven, the base film is coated with the cationic film liquid by a cationic film coating roller, and the coating method is transfer coating. After the coating is completed, the base film enters the polymerization oven for polymerization, and the temperature of the polymerization oven is 55°C.

[0089] 3) After the polymerization of the positive film layer is completed in the polymerization oven, the negative film liquid is coated on the other side of the base film through a negative film coating roller. The coating method is transfer coating. After the negative film layer is coated, it enters the oven again at 55°C for polymerization.

[0090] 4) After the anion film layer is polymerized, it enters the winding roller for winding. After the winding is completed, the bipolar membrane production is completed.

[0091] During the membrane making process, samples were taken for testing at 20 minutes, 40 minutes, and 60 minutes after the start of the device operation. A total of three samples were taken to measure the performance indicators of the bipolar membrane. The results are shown in Table 2.

[0092] Table 2 Comparative Example 1 Sample Performance

[0093]

[0094] Through the data of Example 2 and Comparative Example 1, we found that the bipolar membrane made in the comparative example without plasma treatment had obvious differences in hydrolysis voltage, current efficiency and burst strength compared with Example 2.

[0095] Embodiment 3-5

[0096] The bipolar membrane was prepared by the same method as in Example 2, except that the coating speed and the oven temperature were changed. For details, see Table 3. Samples were taken for testing after 60 minutes. The results are shown in Table 3:

[0097] Table 3 Performance test of samples of Examples 3-5

[0098]

[0099] The process and device for continuously manufacturing bipolar membranes of the present invention realize efficient and stable manufacturing, and solve the problems of low current efficiency, high hydrolysis power supply and low blasting strength of bipolar membranes in other processes.

[0100] Of course, the present invention may have other various embodiments, and those skilled in the art may make various corresponding changes and modifications according to the present invention without departing from the spirit and essence of the present invention. However, these corresponding changes and modifications shall all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a bipolar membrane, characterized in that: The following steps are involved: 1) Use plasma surface treatment machine to treat the base film; 2) soaking the base film in the catalyst solution and then drying it; 3) Coating the cation film liquid on one side of the base film and drying; 4) Coat the negative film liquid on the other side of the base film and dry it.

2. The preparation method according to claim 1, characterized in that: The base film is a polyethylene terephthalate base film.

3. The preparation method according to claim 1 or 2, characterized in that: In step 2), after the base film is taken out, the excess catalyst solution is squeezed out and then dried; Preferably, in step 2), after the base film is taken out, the excess catalyst solution is squeezed out by a squeezing roller. The base film soaked with the catalyst is squeezed out by a squeezing roller to ensure that there is no catalyst dripping in the subsequent process; Preferably, in step 2), the base film is dried at a temperature of 40-80°C, preferably 50-65°C.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The catalyst is an organotin catalyst; Preferably, the organotin catalyst is dibutyltin dilaurate, dibutyltin dibutyrate, stannous octoate, dibutyltin diacetate, or dioctyltin oxide; A surfactant is also added to the catalyst solution; Preferably, the surfactant is fatty acid glyceride, polysorbate, sodium xylene sulfonate, or polyoxyethylene fatty acid ester; Preferably, based on 100% of the total mass of the catalyst solution, the mass content of the organotin catalyst is 2-15%, preferably 5-12%. More preferably, the mass content of the surfactant is 0.01-0.15%, preferably 0.05-0.12%.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The cation film liquid comprises sulfonated polyphenylene ether and a solvent, wherein the solvent is preferably one or more of DMF or chlorobenzene; Preferably, in step 3), drying is performed at a temperature of 50-100°C, preferably 60-80°C; Preferably, the anion film liquid comprises aminated polyphenylene ether and a solvent, wherein the solvent is chlorobenzene or DMF; Preferably, in step 4), the drying is carried out at a temperature of 60-80°C.

6. A device for preparing a bipolar membrane using the preparation method according to any one of claims 1 to 5, characterized in that: It includes an unwinding roller, a plasma surface treatment machine, a catalyst impregnation tank, a first oven, a first coating roller, a second oven, a second coating roller, and a winding roller connected in sequence; A base film is placed on the unwinding roller, wherein the base film has a thickness of 60-120 μm and a porosity of 60-90%.

7. The device according to claim 5 or 6, characterized in that The catalyst impregnation tank is in an inverted trapezoidal shape, a impregnation roller is provided at the bottom of the catalyst impregnation tank, and an extrusion roller is connected to the outlet of the catalyst impregnation tank; Preferably, the pressure of the squeezing roller is 5-12 kg / cm2, and the wetting speed of the base film is 0.2-1 m / min; Preferably, the pressure of the squeezing roller is 7-10 kg / cm2; Preferably, the wetting speed of the nonwoven fabric is 0.4-0.8,m / min; Preferably, the coating roller 1 can be a transfer coating device, a blade coating device and a slit coating device; Preferably, the coating device is a transfer coating device; Preferably, the coating thickness of coating roller 1 is 80-140 μm; Preferably, the coating thickness of the coating roller 1 is 100-120 μm.

8. The device according to any one of claims 5 to 7, characterized in that: The second coating roller can be a transfer coating roller, a scraper coating roller, or a slit coating roller; Preferably, the second coating roller is a transfer coating device; Preferably, the coating thickness of the second coating roller is 20-50 μm, and more preferably, the coating thickness of the second coating roller is 25-40 μm; The dried membrane is rolled up by a winding roller to obtain a bipolar membrane, wherein the winding tension of the winding roller is 120-200 N / M and the winding diameter is 10-40 cm; Preferably, the tension of the winding roller is 150-180n / m; Preferably, the winding diameter is 15-30 cm.

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