A method for preparing a hydrogen barrier negative film by a roll-to-roll impregnation process

Abstract

This invention discloses a method for preparing a hydrogen-barrier anion exchange membrane using a roller-type impregnation method. In a continuous fabrication production line, a porous mesh is drawn into a membrane solution tank, where the membrane solution impregnates the mesh. After impregnation, protective films are applied to both the top and bottom sides of the mesh. Following film application, the mesh is drawn into a pre-heating oven for heat treatment. After leaving the pre-heating oven, the protective films are peeled off. The mesh is then drawn into a post-heating oven for post-treatment. After post-treatment, the mesh is drawn into an acid bath for acid washing. After acid washing, the mesh is drawn out of the acid bath, thus obtaining the hydrogen-barrier anion exchange membrane. The hydrogen-barrier anion exchange membrane obtained by this invention has a water content of approximately 10-20%, and its surface resistivity measured in 0.5M hydrochloric acid is approximately 2-6 ohm·cm. 2 The migration number can reach 0.98; when assembled into an electrodialysis device, hydrochloric acid can be concentrated from 1 mol / L to 3 mol / L, and the current efficiency of the concentration process is over 50%.

Description

Technical Field

[0001] This invention relates to a method for preparing hydrogen-barrier anion membranes using a roller-type impregnation method, which are suitable for inorganic acid electrodialysis concentration processes. Background Technology

[0002] Membranes are widely used in human production and daily life for separating substances. Ion exchange membranes, due to their advantages of high selectivity and high separation efficiency, are widely used in many fields such as purification and separation of substances.

[0003] Electrodialysis technology is used for the desalination or concentration of saline solutions. An electrodialysis unit consists of alternating anion exchange membranes, desalination chambers, cation exchange membranes, and concentration chambers. Under the influence of an electric field, anions in the desalination chamber migrate towards the positive electrode, pass through the anion exchange membrane into the concentration chamber, and are blocked by the cation exchange membrane. Conversely, cations in the desalination chamber migrate towards the negative electrode, pass through the cation exchange membrane into the concentration chamber, and are blocked by the anion exchange membrane. This results in a decrease in salt concentration in the desalination chamber and an increase in salt concentration in the concentration chamber. Inorganic acids can also be concentrated by electrodialysis; however, hydrogen ions easily migrate through the anion exchange membrane, leading to a lower degree of acid concentration and low current efficiency. Therefore, there is an urgent need in the field of electrodialysis for concentrating dilute acids to develop hydrogen-blocking anion exchange membranes that can limit hydrogen ion leakage.

[0004] Hydrogen ions exhibit a unique transport mechanism in the membrane substrate and solution, namely, their migration is carried or mediated by water molecules. Therefore, reducing the water content of the anion exchange membrane is a crucial approach to achieving acid blocking. Furthermore, according to the principle of pore size sieving, ion permeation is inhibited as membrane density increases. Thus, improving membrane density and reducing membrane water content are fundamental principles for preparing hydrogen-blocking anion exchange membranes. Current methods for increasing membrane density mainly include forming a high-density cross-linked layer on the membrane and creating non-charged regions in the membrane substrate; methods for reducing membrane water content mainly include introducing hydrophobic groups and introducing weak base groups such as pyridine to reduce hydration. Japanese Patent JP 43-10060 utilizes compounds with epoxy and amine groups to form a high-density cross-linked layer on a conventional anion exchange membrane. This high-density cross-linked layer can inhibit hydrogen ion permeation, achieving acid blocking to a certain extent. In the paper (JPolymSciPolymPhysEd1989, 27, 2229-2241), a copolymer membrane composed of 4-vinylpyridine, styrene, and divinylbenzene was reacted with long-chain alkyl bromides (octyl bromide, dodecyl bromide, or hexadecyl bromide), and hydrophobic groups were introduced through quaternization, which reduced the water content of the membrane and increased the fixed ion concentration, successfully preparing anion exchange membranes with certain acid-blocking properties. However, the experiment also found that although the acid diffusion coefficient was significantly reduced, the membrane resistance increased to a certain extent. In the literature (JMembrSci,1993,84,259-269), a rigid and dense polypyrrole with secondary amine groups was introduced and combined with a commercial anion exchange membrane to form a composite membrane, exhibiting significant acid-blocking performance. This study found that due to the formation of a polypyrrole layer on the membrane surface, the hydrochloric acid permeation coefficient was significantly reduced, and the current efficiency was also improved.

[0005] Although the performance of hydrogen barrier membranes has indeed been improved in the literature, the current efficiency of acid recovery is still not very high. Therefore, it is necessary to develop a high-performance hydrogen barrier anion exchange membrane that can achieve electrodialysis concentration of dilute acid to high-concentration acid at high current efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide a high-performance hydrogen-barrier anion exchange membrane that can be prepared by a roller-type impregnation method, exhibiting low resistance and high mobility, and capable of electrodialysis concentration of dilute acid to concentrated acid at high current efficiency.

[0007] To achieve the above-mentioned objective, the present invention provides a method for preparing hydrogen barrier anion membranes using a roller-type impregnation method, comprising the following steps:

[0008] In a continuous fabrication production line, a porous mesh is drawn into a membrane solution tank, where the membrane solution impregnates the porous mesh. After impregnation, protective films are applied to both the top and bottom sides of the porous mesh. After the films are applied, the porous mesh is drawn into a preheating oven for heat treatment. After the porous mesh leaves the preheating oven, the protective films are peeled off. After peeling off the protective films, the porous mesh is drawn into a postheating oven for post-treatment. After post-treatment, the porous mesh is drawn into an acid bath for acid washing. After acid washing, the porous mesh is drawn out of the acid bath, thus obtaining a hydrogen barrier anion membrane.

[0009] The membrane solution is composed of a functional monomer containing amine groups and carbon-carbon double bonds, a crosslinking agent containing two carbon-carbon double bonds, and a free radical initiator.

[0010] The functional monomer is selected from one or a mixture of two or more of the following in any mass ratio: 4-vinylbenzylamine, N-4-vinylbenzyl-N,N-dimethylamine, N-2-vinylbenzyl-N,N-dimethylamine, 6-[4-(4-vinylphenyl)methoxyphenyl]-1,3,5-triazine-2,4-diamine, 1-[(4-vinylphenyl)methyl]-1H-benzimidazole, 9-(4-vinylbenzyl)-9H-carbazole, and 1-[(4-vinylphenyl)methyl]-4-methylpiperidine; the crosslinking agent is selected from 1,3-bis(1 A mixture of one or more of the following in any mass ratio: (-methylvinyl)benzene, 4,4-divinyl-P-diphenyl, N,N-vinylbisacrylamide, 2,5-divinylbenzene-1,4-diamine, 5,5-divinyl-2,2-bipyridine, and 1,4-bis(4-methylstyryl)benzene; the free radical initiator is azobisisobutyronitrile or benzoyl peroxide; the mass ratio of the functional monomer to the crosslinking agent is 50-90:10-50, and the free radical initiator accounts for 0.2-5% of the sum of the mass of the functional monomer and the crosslinking agent.

[0011] The acid solution is hydrochloric acid, sulfuric acid, or nitric acid, and the hydrogen ion concentration of the acid solution is 0.1-4 mol / L.

[0012] The internal temperature of the front and rear ovens is controlled between 60℃ and 120℃.

[0013] The porous mesh is made of materials including but not limited to polyolefin, fluorinated polyolefin, polyester or polyacrylic acid; the thickness of the porous mesh is 40μm-180μm, the porosity is 30%-70%, and the average pore size is 0.05μm-2μm.

[0014] The method also includes the step of drawing the porous mesh into a water washing tank after acid washing for water washing, and the hydrogen barrier anion membrane is obtained after water washing.

[0015] The continuous fabric production equipment for implementing the method of the present invention includes a frame, on which, from front to back, are sequentially connected a rotatable mesh unwinding roller, a membrane liquid tank, a front drying oven, a rear drying oven, an acid tank, and a rotatable hydrogen-barrier anion membrane take-up roller; a front upper impregnation guide roller and a rear upper impregnation guide roller, rotatably connected to the frame or the tank wall, are respectively provided on the front and rear sides of the top of the membrane liquid tank; a front lower impregnation guide roller and a rear lower impregnation guide roller, rotatably connected to the tank wall, are respectively provided on the front and rear sides of the bottom of the membrane liquid tank; an upper protective film unwinding roller, a lower protective film unwinding roller, a front upper film applying roller, a front lower film applying roller, a rear upper film applying roller, a rear lower film applying roller, an upper protective film take-up roller, a lower protective film take-up roller, and a steering roller are rotatably connected to the frame; the upper protective film unwinding roller and the lower protective film unwinding roller are located above and below the rear of the membrane liquid tank, respectively; the front upper film applying roller and the front lower film applying roller are located at the front... The front upper and lower film-applying rollers are positioned opposite each other at the front of the oven inlet; the rear upper and lower film-applying rollers are positioned opposite each other at the rear of the oven outlet; the upper and lower protective film winding rollers are located above and below the rear of the front oven, respectively; the deflector roller is located behind the rear oven outlet; the top of the acid tank has a front upper pickling guide roller and a rear upper pickling guide roller rotatably connected to the frame or the acid tank wall on the front and rear sides, respectively; the bottom of the acid tank has a front lower pickling guide roller and a rear lower pickling guide roller rotatably connected to the acid tank wall on the front and rear sides, respectively; the upper and lower protective film winding rollers are driven by a protective film winding power device connected to the frame, and the hydrogen-barrier anion film winding roller is driven by an anion film winding power device connected to the frame; heating devices are installed inside the front and rear ovens.

[0016] The continuous fabric production equipment has a washing tank between the acid tank and the hydrogen barrier anion film take-up roller. The top front and rear sides of the washing tank are respectively provided with a front upper washing guide roller and a rear upper washing guide roller, which are rotatably connected to the frame or the washing tank wall. The bottom front and rear sides of the washing tank are respectively provided with a front lower washing guide roller and a rear lower washing guide roller, which are rotatably connected to the washing tank wall.

[0017] The heating device is an electric heating device or heating coil inside the oven; the heating coil is connected to an external heat source supply device, and the heat source is hot air, hot water or hot oil.

[0018] In addition to being rotatably connected to the frame, the front upper film-applying roller, the front lower film-applying roller, the rear upper film-applying roller, and the rear lower film-applying roller can also move up and down on the frame.

[0019] In the above process, the membrane liquid fills the pores of the porous mesh. Under the protection of the protective film, the membrane liquid undergoes a polymerization reaction in the front oven. After the protective film is peeled off, it enters the rear oven for further heat treatment, which can make the polymerization reaction complete and volatilize the residual functional monomers or crosslinking agents. Subsequently, in the acid bath, the amine groups of the polymer react with the acid to form ammonium salts, thus obtaining a hydrogen barrier anion membrane.

[0020] The membrane solution is composed of one or more functional monomers containing amine groups, one or more crosslinking agents, and a free radical initiator. Under heating conditions, the free radical initiator initiates the polymerization reaction, and the monomers and crosslinking agents undergo free radical polymerization to obtain polymer chains. Because the membrane solution is distributed in the pores of the mesh, the polymerized functional polymer chains are intertwined with the polymer chains of the mesh, ensuring the stability of the functional polymer chains. The membrane solution does not contain organic solvents, resulting in a denser membrane after polymerization.

[0021] The hydrogen-barrier anion exchange membrane obtained by the method described in this invention has a water content of approximately 10-20%, and its surface resistivity measured in 0.5M hydrochloric acid is approximately 2-6 ohm·cm. 2 The migration number can reach over 0.96 in 0.5M / 0.1M hydrochloric acid; when assembled into an electrodialysis device to concentrate hydrochloric acid from 1 mol / L to 3 mol / L, the current efficiency of the concentration process is over 50%.

[0022] The method described in this invention is implemented using a continuous fabric production device, which enables continuous production. Attached Figure Description

[0023] Figure 1 This is a structural diagram of a continuous fabric feeding production equipment.

[0024] Figure 2 This is a schematic diagram of a production equipment with a different continuous fabric feeding structure. Detailed Implementation

[0025] The following embodiments further illustrate the technical solution of the present invention. These embodiments are only used to demonstrate the technical concept and feasibility of the present invention in detail, and are not intended to limit the scope of protection of the present invention. Equivalent substitutions and modifications made using the technical concept of the present invention are still within the scope of protection of the present invention.

[0026] The method described in this invention is implemented on a continuous fabric feeding production device. A continuous fabric feeding production device with the following structure is described below. Figure 1The continuous fabric production equipment includes a frame (omitted in the figure), on which, from front to back, are connected a rotatable mesh unwinding roller 1, a membrane liquid tank 2, a front drying oven 3, a rear drying oven 4, an acid liquid tank 5, and a rotatable hydrogen-barrier anion membrane take-up roller 6. The top front and rear sides of the membrane liquid tank 2 are respectively provided with a front upper impregnation guide roller 7 and a rear upper impregnation guide roller 8 rotatably connected to the frame or the tank wall of the membrane liquid tank 2. The bottom front and rear sides of the membrane liquid tank 2 are respectively provided with a front lower impregnation guide roller 9 and a rear lower impregnation guide roller 10 rotatably connected to the tank wall of the membrane liquid tank 2. The frame is rotatably connected to an upper protective film unwinding roller 11, a lower protective film unwinding roller 12, a front upper film applying roller 13, a front lower film applying roller 14, a rear upper film applying roller 15, a rear lower film applying roller 16, an upper protective film take-up roller 17, a lower protective film take-up roller 18, and a guide roller 19. The upper protective film unwinding roller 11 and the lower protective film unwinding roller 12 are located above and below the rear of the film liquid tank 2, respectively. The front upper film-applying roller 13 and the front lower film-applying roller 14 are located in front of the inlet of the front oven 3 and are arranged vertically opposite each other, with the front upper film-applying roller 13 and the front lower film-applying roller 14 being closer to the inlet of the front oven 3 than the upper protective film unwinding roller 11 and the lower protective film unwinding roller 12; the rear upper film-applying roller 15 and the rear lower film-applying roller 16 are located behind the outlet of the front oven 3 and are arranged vertically opposite each other; the front upper film-applying roller 13 and the front lower film-applying roller 16 are arranged vertically opposite each other. 4. The upper rear film-applying roller 15 and the lower rear film-applying roller 16 are not only rotatably connected to the frame, but also vertically movable. These four film-applying rollers are rotatably connected to their respective roller seats (omitted in the figure). The roller seats are slidably connected to the frame. Adjusting the vertical position of the roller seats allows for appropriate gaps between the upper front film-applying roller 13 and the lower front film-applying roller 14, as well as between the upper rear film-applying roller 15 and the lower rear film-applying roller 16, to accommodate film application to porous mesh fabrics of different thicknesses. The upper protective film take-up roller 17 and the lower protective film take-up roller 18 are located above and below the rear of the front oven 3, respectively; the upper and lower protective film take-up rollers 17 and 18 are further away from the outlet of the front oven 3 than the upper rear film-applying roller 15 and the lower rear film-applying roller 16. The deflector roller 19 is located behind the outlet of the rear oven 4. The top front and rear sides of the acid tank 5 are respectively provided with a front upper pickling guide roller 20 and a rear upper pickling guide roller 21 rotatably connected to the frame or the tank wall of the acid tank 5. The bottom front and rear sides of the acid tank 5 are respectively provided with a front lower pickling guide roller 22 and a rear lower pickling guide roller 23 rotatably connected to the tank wall of the acid tank 5. The upper protective film winding roller 17 and the lower protective film winding roller 18 are driven by a protective film winding power unit (omitted in the figure) connected to the frame. There can be two sets of protective film winding power units, one to drive the upper protective film winding roller 17 and the other to drive the lower protective film winding roller 18. The protective film winding power unit can be a motor or a combination of a motor and a gearbox. The protective film winding power unit and the protective film winding roller can be directly connected or connected by existing transmission chains such as gears, chains and sprockets, belts and pulleys.The hydrogen-barrier anion film take-up roller 6 is driven by anion film take-up power unit (omitted in the figure) connected to the frame. The anion film take-up power unit can be a motor or a combination of a motor and a gearbox. The anion film take-up power unit and the hydrogen-barrier anion film take-up roller 6 can be directly connected or connected by existing transmission chains such as gears, chains and sprockets, belts and pulleys. Heating devices (omitted in the figure) are respectively installed in the front drying oven 3 and the rear drying oven 4. The heating devices can be electric heating devices installed in the drying oven or heating coils installed in the drying oven. The heating coils are connected to an external heat source supply device, and the heat source can be hot air, hot water, hot oil, etc.

[0027] Another type of continuous fabric production equipment (refer to) Figure 2 , Figure 2 The continuous fabric feeding production equipment shown is in Figure 1 Based on the continuous fabric production equipment shown, a washing tank 24 is added between the acid tank 5 and the hydrogen barrier anion film take-up roller 6. The front upper washing guide roller 25 and the rear upper washing guide roller 26 are respectively rotatably connected to the frame or the tank wall of the washing tank 24 on the front and rear sides of the top of the washing tank 24. The front lower washing guide roller 27 and the rear lower washing guide roller 28 are respectively rotatably connected to the tank wall of the washing tank 24 on the front and rear sides of the bottom of the washing tank 24.

[0028] Figure 1 The operation of the continuous fabric feeding production equipment shown is as follows. (Refer to...) Figure 1The multi-hole mesh fabric 29, in roll form, is mounted onto the mesh unwinding roller 1 via its core tube, and the core tube is fixedly connected to the mesh unwinding roller 1. The upper protective film roll 30 and the lower protective film roll 31 are mounted onto the upper protective film unwinding roller 11 and the lower protective film unwinding roller 12 respectively via their respective core tubes, and the core tubes are fixedly connected to the protective film unwinding rollers. Core tubes are then mounted and fixed onto the upper protective film take-up roller 17, the lower protective film take-up roller 18, and the hydrogen-barrier anion film take-up roller 6 respectively. The perforated mesh is sequentially passed around the front upper immersion guide roller 7, the front lower immersion guide roller 9, the rear lower immersion guide roller 10, and the rear upper immersion guide roller 8. Then, the perforated mesh is sequentially passed between the front upper film-applying roller 13 and the front lower film-applying roller 14, between the front oven 3, the rear upper film-applying roller 15 and the rear lower film-applying roller 16, and the rear oven 4. It is then sequentially passed around the turning roller 19, the front upper pickling guide roller 20, the front lower pickling guide roller 22, the rear lower pickling guide roller 23, and the rear upper pickling guide roller 21, finally achieving pre-winding on the hydrogen-barrier anion film take-up roller 6. The protective film on the upper protective film unwinding roller 11 and the lower protective film unwinding roller 12 is sequentially passed between the front upper film-applying roller 13 and the front lower film-applying roller 14, between the front oven 3, the rear upper film-applying roller 15, and the rear lower film-applying roller 16, and then pre-wound onto the upper protective film take-up roller 17 and the lower protective film take-up roller 18, respectively. Add the membrane solution to the membrane solution tank 2 and the acid solution to the acid solution tank 5. Turn on the heating device, the protective membrane winding power device, and the anion membrane winding power device. At this time, the production of hydrogen barrier anion membrane can be carried out.

[0029] Figure 2 The operation of the continuous fabric feeding production equipment shown is the same as described above. Figure 1 The operation of the continuous fabric feeding production equipment shown is basically the same, but because... Figure 2 The continuous fabric production equipment shown has an added washing tank 24. The porous mesh needs to pass around the upper rear acid washing guide roller 21 and then pass around the upper front washing guide roller 25, the lower front washing guide roller 27, the lower rear washing guide roller 28, and the upper rear washing guide roller 26 in sequence before finally being pre-wound on the hydrogen barrier anion film take-up roller 6.

[0030] The following examples are in Figure 1 This is achieved on the continuous fabric feeding production equipment shown. Example 1

[0031] Reference Figure 1 According to the above Figure 1The production preparation for the continuous fabric feeding equipment is as follows: Membrane solution is added to membrane solution tank 2, and acid solution is added to acid solution tank 5. Upon startup, the hydrogen-barrier anion membrane take-up roller 6, upper protective film take-up roller 17, and lower protective film take-up roller 18 begin to rotate. Under the traction of the hydrogen-barrier anion membrane take-up roller 6, the perforated mesh fabric on the unwinding roller 1 begins to feed. After passing through membrane solution tank 2, the perforated mesh fabric is fully wetted by the membrane solution. After passing between the upper front film-applying roller 13 and the lower front film-applying roller 14, a protective film is applied to the upper and lower surfaces of the wetted perforated mesh fabric (the protective film's movement is powered by the upper protective film take-up roller 17 and the lower protective film take-up roller 18). The perforated mesh fabric with the protective film applied... After the mesh fabric passes between the front drying oven 3, the upper rear film-applying roller 15, and the lower rear film-applying roller 16, the protective films on the upper and lower surfaces of the porous mesh fabric are wound onto the upper and lower protective film winding rollers 17 and 18, respectively, under the action of the upper and lower protective film winding rollers 17 and 18. This achieves the peeling of the protective film from the porous mesh fabric. After the protective film is peeled off, the porous mesh fabric passes through the rear drying oven 4 and enters the pickling tank for pickling. After pickling, a hydrogen-barrier anion membrane is obtained, which is finally wound onto the hydrogen-barrier anion membrane winding roller 6. During the process of the porous mesh fabric passing through the front drying oven, heat treatment is carried out to cause the film liquid on it to undergo a polymerization reaction. After the protective film is peeled off, further heat treatment is carried out during the process of passing through the rear drying oven, which can ensure that the polymerization reaction is complete and that residual functional monomers or crosslinking agents are volatilized. The temperature in the front drying oven is 100°C. o C, the temperature inside the post-drying oven is 80°C. o C. During the production process, the fabric feeding speed should be controlled so that the heat treatment time in the pre-drying oven is not less than 30 minutes.

[0032] The membrane solution of this embodiment is composed of 4-vinylbenzylamine, N-4-vinylbenzyl-N,N-dimethylamine, 2,5-divinylbenzene-1,4-diamine, 5,5-divinyl-2,2-bipyridine and azobisisobutyronitrile, mixed uniformly in a mass ratio of 387:468:116:151:6.

[0033] The acid used in this embodiment is hydrochloric acid, with a hydrogen ion concentration of 1 mol / L. The porous mesh used in this embodiment is made of polypropylene, with a thickness of 85 micrometers, a porosity of 48%, and an average pore size of 0.15 micrometers. Example 2

[0034] The production steps in this embodiment are basically the same as those in Embodiment 1, except that the membrane solution, acid solution, heat treatment time, heat treatment temperature, and porous mesh are different.

[0035] The membrane solution in this embodiment is prepared by uniformly mixing 4-vinylbenzylamine, N-4-vinylbenzyl-N,N-dimethylamine, 1,3-bis(1-methylvinyl)benzene and azobisisobutyronitrile in a mass ratio of 387:350:312:11.

[0036] In this embodiment, the temperature inside the front oven is 110°C. o C, the temperature inside the post-drying oven is 65°C. o C. The pre-baking oven heat treatment time is 25 minutes, the acid solution is sulfuric acid, and the hydrogen ion concentration is 0.5 mol / L. The porous mesh used in this embodiment is made of polyethylene, with a thickness of 45 micrometers, a porosity of 42%, and an average pore size of 0.25 micrometers. Example 3

[0037] The production steps in this embodiment are basically the same as those in Embodiment 1, except that the membrane solution, acid solution, heat treatment time, heat treatment temperature, and porous mesh are different.

[0038] The membrane solution in this embodiment is prepared by uniformly mixing 6-[4-(4-vinylphenyl)methoxyphenyl]-1,3,5-triazine-2,4-diamine, 1-[(4-vinylphenyl)methyl]-1H-benzimidazole, 2,5-divinylphenyl-1,4-diamine, 5,5-divinyl-2,2-bipyridine, and azobisisobutyronitrile in a mass ratio of 387:774:252:252:16.

[0039] In this embodiment, the temperature inside the pre-drying oven is 80°C. o C, the temperature inside the post-drying oven is 100°C. o C. The pre-baking oven heat treatment time is 40 minutes, the acid solution is nitric acid, and the hydrogen ion concentration is 3.2 mol / L. The porous mesh used in this embodiment is made of polyvinylidene fluoride, with a thickness of 50 micrometers, a porosity of 38%, and an average pore size of 0.3 micrometers. Example 4

[0040] The production steps in this embodiment are basically the same as those in Embodiment 1, except that the membrane solution, acid solution, heat treatment time, heat treatment temperature, and porous mesh are different.

[0041] The membrane solution of this embodiment is prepared by uniformly mixing 6-[4-(4-vinylphenyl)methoxyphenyl]-1,3,5-triazine-2,4-diamine, 1-[(4-vinylphenyl)methyl]-1H-benzimidazole, 2,5-divinylphenyl-1,4-diamine, 5,5-divinyl-2,2-bipyridine and benzoyl peroxide in a mass ratio of 387:232:100:44:8.

[0042] In this embodiment, the temperature inside the front oven is 100°C. o C, the temperature inside the post-drying oven is 60°C. oC. The pre-baking oven heat treatment time is 50 minutes, the acid solution is hydrochloric acid, and the hydrogen ion concentration is 0.2 mol / L. The porous mesh used in this embodiment is made of polytetrafluoroethylene, with a thickness of 42 micrometers, a porosity of 72%, and a pore size of 0.45 micrometers. Example 5

[0043] The production steps in this embodiment are basically the same as those in Embodiment 1, except that the membrane solution, acid solution, heat treatment time, heat treatment temperature, and porous mesh are different.

[0044] The membrane solution in this embodiment is prepared by uniformly mixing N-4-vinylbenzyl-N,N-dimethylamine, 1,3-bis(1-methylvinyl)benzene and azobisisobutyronitrile in a mass ratio of 387:124:10.

[0045] In this embodiment, the temperature inside the pre-drying oven is 90°C. o C, the temperature inside the post-drying oven is 70°C. o C. The pre-baking oven heat treatment time is 30 minutes, the acid solution is hydrochloric acid, and the hydrogen ion concentration is 1.0 mol / L. The porous mesh used in this embodiment is made of polypropylene, with a thickness of 100 micrometers, a porosity of 48%, and an average pore size of 0.10 micrometers.

[0046] Two important parameters characterizing the performance of ion exchange membranes, membrane resistance and mobility number, can be measured using a membrane potential testing device similar to Figure 3.17 in Heiner Strathmann's book, *Ion-exchange membrane separation processes* (ISBN: 978-0-444-50236-0). The device consists of metal electrodes at both ends, with the ion exchange membrane placed in the middle. Ag / AgCl reference electrodes are placed near the membrane on both sides. The effective membrane area S of the ion exchange membrane is 7 cm². 2 .

[0047] When measuring membrane resistance, a 0.5 mol / L hydrochloric acid solution is injected into the apparatus, and a 50 mA DC current I is applied through the metal electrode. The potential difference E2 between the two reference electrodes without a membrane sample and the potential difference E1 between the two reference electrodes with a membrane sample are measured. The formula for calculating the membrane resistance R is as follows:

[0048] ;

[0049] When measuring the transport number, the solutions on both sides of the membrane sample were 0.1 mol / L and 0.5 mol / L hydrochloric acid solutions, respectively. No current was applied, and the potential difference E1 between the two reference electrodes was measured. The formula for calculating the membrane transport number t is as follows:

[0050] ;

[0051] ;

[0052] Where E2 is the standard potential difference, R is the gas constant (8.314 J / K / mol), T is the absolute temperature of the solution, F is the Faraday constant (96480 C / mol), and a1 / a2 refers to the activity ratio of the solutions on both sides of the membrane.

[0053] The method for measuring moisture content is as follows: After soaking the membrane sample in 0.5 M NaCl solution for 4 hours, rinse the membrane surface with distilled water, then gently wipe the surface moisture with filter paper, and quickly place it in a pre-weighed weighing bottle or weighing dish to obtain the wet weight of the membrane; then place the membrane sample in an 80℃ oven for more than 8 hours, take it out and place it in a desiccator to cool to room temperature, and weigh it again to obtain the dry weight of the membrane; the membrane moisture content refers to the ratio of the weight of water contained in the membrane in the wet state to the weight of the membrane in the dry state.

[0054] Samples of the hydrogen-barrier anion membranes prepared in Examples 1-5 were taken and immersed in 0.5 mol / L hydrochloric acid solution for more than 0.5 hours. The membrane resistance, migration number and water content were measured according to the above method. The samples were compared with the hydrogen-barrier anion membrane ACM produced by ASTOM Corporation of Japan and the general anion membrane AMX. The test results are shown in Table 1.

[0055]

[0056] As shown in the table above, the membrane resistance of the commercial hydrogen barrier anion exchange membrane (ACM) in hydrochloric acid solution is 3.6 ohm·cm. 2 The migration number (selectivity) is 0.98; the film resistivity of commercially available anion exchange membrane AMX is 3.3 ohm·cm. 2 However, its migration number is only 0.902, far lower than that of the hydrogen-blocking anion exchange membrane (ACM). The membrane resistivity of the membranes prepared in the examples is between 2.4 and 4.3 ohm·cm. 2 The migration number ranges from 0.968 to 0.986. The membrane resistivity of the membranes prepared in the examples is within the industrial application range, and the migration number is much higher than that of the general-purpose anion exchange membrane AMX, and very close to that of the hydrogen barrier anion exchange membrane ACM. This indicates that the membrane prepared in this invention is a hydrogen barrier anion exchange membrane, and its performance is close to that of the commercially available hydrogen barrier anion exchange membrane ACM. In addition, the water content of the hydrogen barrier anion exchange membrane ACM is 12%, the water content of the general-purpose anion exchange membrane AMX is 26%, and the water content of the hydrogen barrier anion exchange membrane prepared in the examples is between 14% and 20%. The hydrogen barrier anion exchange membrane prepared in the examples of this invention has a low water content.

[0057] The hydrogen-barrier anion exchange membrane prepared in Example 1 was used in the electrodialysis acid concentration process at 400 mA / cm². 2The constant current density membrane, operating at 25°C for 3 hours, can concentrate hydrochloric acid from 3% to 12%, with a current efficiency of 51% during the acid concentration process. In contrast, using a general-purpose anion exchange membrane (AMX), hydrochloric acid can only be concentrated to a maximum of 8.5%, with a current efficiency of 38%. The hydrogen-barrier anion exchange membrane prepared in this invention is suitable for electrodialysis acid concentration processes, and can improve the degree of acid concentration and the current efficiency of the electrodialysis process.

[0058] The above embodiments 1-5, through Figure 1 The continuous fabric production equipment shown does not mean that... Figure 2 The continuous fabric production equipment shown cannot realize this invention. Figure 2 The continuous fabric production equipment shown is a replacement Figure 1 The continuous fabric production equipment shown is used to implement Examples 1-5, and can still achieve the purpose of the invention and obtain the expected technical effect.

Claims

1. A method for preparing hydrogen barrier anion membranes using a roller-type impregnation method, characterized in that... Includes the following steps: In a continuous fabrication production line, a porous mesh is drawn into a membrane solution tank, where the membrane solution impregnates the porous mesh. After impregnation, protective films are applied to both the top and bottom sides of the porous mesh. After the films are applied, the porous mesh is drawn into a preheating oven for heat treatment. After the porous mesh leaves the preheating oven, the protective films are peeled off. After peeling off the protective films, the porous mesh is drawn into a postheating oven for post-treatment. After post-treatment, the porous mesh is drawn into an acid bath for acid washing. After acid washing, the porous mesh is drawn out of the acid bath, thus obtaining a hydrogen barrier anion membrane. The membrane solution is composed of a functional monomer containing an amine group and a carbon-carbon double bond, a crosslinking agent containing two carbon-carbon double bonds, and a free radical initiator; The functional monomer is selected from one or a mixture of two or more of the following in any mass ratio: 4-vinylbenzylamine, N-4-vinylbenzyl-N,N-dimethylamine, N-2-vinylbenzyl-N,N-dimethylamine, 6-[4-(4-vinylphenyl)methoxyphenyl]-1,3,5-triazine-2,4-diamine, 1-[(4-vinylphenyl)methyl]-1H-benzimidazole, 9-(4-vinylbenzyl)-9H-carbazole, and 1-[(4-vinylphenyl)methyl]-4-methylpiperidine; the crosslinking agent is selected from 1,3-bis(1 A mixture of one or more of the following in any mass ratio: (-methylvinyl)benzene, 4,4-divinyl-p-diphenyl, N,N-vinylbisacrylamide, 2,5-divinylbenzene-1,4-diamine, 5,5-divinyl-2,2-bipyridine, and 1,4-bis(4-methylstyryl)benzene; the free radical initiator is azobisisobutyronitrile or benzoyl peroxide; the mass ratio of the functional monomer to the crosslinking agent is 50-90:10-50, and the free radical initiator accounts for 0.2-5% of the sum of the mass of the functional monomer and the crosslinking agent.

2. The method for preparing hydrogen barrier anion membrane by roller impregnation as described in claim 1, characterized in that: The acid solution is hydrochloric acid, sulfuric acid, or nitric acid, and the hydrogen ion concentration of the acid solution is 0.1-4 mol / L.

3. The method for preparing hydrogen barrier anion membrane by roller impregnation as described in claim 1, characterized in that: The internal temperature of the front and rear ovens is controlled between 60℃ and 120℃; the heat treatment time in the front oven is not less than 20 minutes.

4. The method for preparing hydrogen barrier anion membrane by roller impregnation as described in claim 1, characterized in that: The porous mesh is made of polyolefin, fluorinated polyolefin, polyester or polyacrylic acid; the thickness of the porous mesh is 40μm-180μm, the porosity is 30%-70%, and the average pore size is 0.05μm-2μm.

5. The method for preparing hydrogen barrier anion membrane by roller impregnation as described in claim 1, characterized in that: The method also includes the step of drawing the porous mesh into a water washing tank after acid washing for water washing, and the hydrogen barrier anion membrane is obtained after water washing.

6. The method for preparing hydrogen barrier anion membrane by roller impregnation as described in claim 1, characterized in that: The continuous fabric production equipment includes a frame, on which, from front to back, are connected a rotatable mesh unwinding roller, a membrane solution tank, a front drying oven, a rear drying oven, an acid solution tank, and a rotatable hydrogen-barrier anion membrane take-up roller. The top of the membrane solution tank has a front upper immersion guide roller and a rear upper immersion guide roller rotatably connected to the frame or the tank wall, respectively. The bottom of the membrane solution tank has a front lower immersion guide roller and a rear lower immersion guide roller rotatably connected to the tank wall, respectively. The frame is rotatably connected to an upper protective film unwinding roller, a lower protective film unwinding roller, a front upper film applying roller, a front lower film applying roller, a rear upper film applying roller, a rear lower film applying roller, an upper protective film take-up roller, a lower protective film take-up roller, and a steering roller. The upper and lower protective film unwinding rollers are located above and below the rear of the membrane solution tank, respectively. The front upper and lower film applying rollers are located at the entrance of the front drying oven. The front upper and lower film-applying rollers are positioned opposite each other at the front of the oven; the rear upper and lower film-applying rollers are located behind the outlet of the front oven and are also positioned opposite each other at the rear; the upper and lower protective film winding rollers are located above and below the rear of the front oven, respectively; the steering roller is located behind the outlet of the rear oven; the top of the acid tank has a front upper pickling guide roller and a rear upper pickling guide roller rotatably connected to the frame or the tank wall, respectively; the bottom of the acid tank has a front lower pickling guide roller and a rear lower pickling guide roller rotatably connected to the tank wall, respectively; the upper and lower protective film winding rollers are driven by a protective film winding power device connected to the frame, and the hydrogen-blocking anion film winding roller is driven by an anion film winding power device connected to the frame; heating devices are installed inside the front and rear ovens.

7. The method for preparing hydrogen barrier anion membrane by roller impregnation as described in claim 6, characterized in that: The continuous fabric production equipment has a washing tank between the acid tank and the hydrogen barrier anion film take-up roller. The top front and rear sides of the washing tank are respectively provided with a front upper washing guide roller and a rear upper washing guide roller, which are rotatably connected to the frame or the washing tank wall. The bottom front and rear sides of the washing tank are respectively provided with a front lower washing guide roller and a rear lower washing guide roller, which are rotatably connected to the washing tank wall.

8. The method for preparing hydrogen-barrier anion membranes by roller impregnation as described in claim 6 or 7, characterized in that: The heating device is an electric heating device or heating coil inside the oven; the heating coil is connected to an external heat source supply device, and the heat source is hot air, hot water or hot oil.

9. The method for preparing hydrogen-barrier anion membranes by roller impregnation as described in claim 6 or 7, characterized in that: In addition to being rotatably connected to the frame, the front upper film-applying roller, the front lower film-applying roller, the rear upper film-applying roller, and the rear lower film-applying roller can also move up and down on the frame.

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