A method for preparing a bonded bipolar membrane

Abstract

The present application discloses a method for preparing an adhesive bipolar membrane, which belongs to the technical field of bipolar membrane preparation. The bipolar membrane is obtained by bonding an anion membrane and a cation membrane with an adhesive. The adhesive contains a flexible component, a rigid component and a catalyst. The flexible component is a flexible polymer containing an ionized group and can conduct ion migration. The rigid component includes an organic monomer and a cross-linking agent. Under the action of a redox initiator, the organic monomer and the cross-linking agent undergo a polymerization reaction to promote the bonding of the anion membrane and the cation membrane. The catalyst promotes the water dissociation ability of the bipolar membrane and reduces the transmembrane voltage of the bipolar membrane. According to the different materials of the anion membrane and the cation membrane, the ratio of the flexible component, the rigid component and the catalyst component in the adhesive can be flexibly adjusted. The preparation process of the present application is simple, the adhesive has universal applicability, and has broad application prospects.

Description

Technical Field

[0001] The present application belongs to the technical field of bipolar membrane preparation, and in particular, relates to a method for preparing a bonded bipolar membrane. Background Art

[0002] The bipolar membrane is a special ion exchange membrane, which is composed of a positive membrane layer and a negative membrane layer. Under the action of a DC electric field, water can be dissociated into H + and OH - , thereby converting salt into acid and base; the bipolar membrane structure includes an anion membrane layer, a cation membrane layer and an intermediate layer; the preparation methods of bipolar membranes mainly include bonding method, hot pressing method, casting method, electrodeposition method, etc. Among them, the bonding method is to use adhesive to coat one side of the anion and cation exchange membranes respectively, and then tightly bond them, remove the internal bubbles and excess adhesive, and dry them to obtain a bipolar membrane. The advantage of this method is that it can make full use of the existing mature anion exchange membrane (anion membrane) and cation exchange membrane (cation membrane) as the anion and cation layers, and the preparation process is simple; US Patent US4670125A uses a molecular weight of 10 4 -10 6 Polyvinylamine is used as a binder to bond the anion membrane and the cation membrane to obtain a bipolar membrane, which is then installed in an electrodialysis device and powered on to strengthen the bonding between the two membrane layers. Polyvinylamine contains amino groups and has ion conductivity, which can increase the resistance of the bipolar membrane without excessively increasing the resistance of the bipolar membrane. However, polyvinylamine itself is soluble in water and has insufficient bonding strength. The prepared bipolar membrane adopts a subsequent power-on step to enhance the bonding between the anion and cation membrane layers. Summary of the invention

[0003] The purpose of the present application is to provide a method for preparing an adhesive bipolar membrane to solve the technical problems of low stability, poor adhesion and poor functionality of bipolar membrane adhesives in the prior art.

[0004] To achieve the above object, the technical solution adopted in the present application is: to provide a method for preparing a bonded bipolar membrane, which specifically comprises the following steps:

[0005] (I) Preparation of adhesive:

[0006] (a) Preparation of a flexible component polymer solution: blending a functional monomer, a comonomer, an organic solvent, isopropanol and a free radical initiator, and performing a polymerization reaction to obtain a flexible component polymer solution;

[0007] (b) Preparation of a rigid component monomer solution: blending an acrylic monomer with a cross-linking agent to prepare a rigid component monomer solution;

[0008] (c) Preparation of catalyst dispersion: dispersing the catalyst in an organic solvent to obtain a catalyst dispersion;

[0009] (d) preparing the adhesive reduction solution: mixing the flexible component polymer solution, the catalyst dispersion and the reducing agent component of the redox initiator in proportion to obtain the adhesive reduction solution;

[0010] (e) Preparation of the adhesive oxidation liquid: mixing the rigid component monomer solution and the oxidant component of the redox initiator in proportion to obtain the adhesive oxidation liquid;

[0011] The adhesive reducing liquid and the adhesive oxidizing liquid are mixed in proportion to obtain an adhesive;

[0012] (ii) Preparation of bonded bipolar membrane: The adhesive is coated on one side of the anion membrane and the cation membrane respectively, the two membranes are tightly attached and the excess adhesive is squeezed out. After the adhesive is solidified, the membrane is heated to obtain a bonded bipolar membrane.

[0013] In one embodiment,

[0014] The organic solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide or N-methyl-2-pyrrolidone.

[0015] In one embodiment,

[0016] Step (I) (a) The functional monomer is 1-propyl-4-vinylpyridinium bromide or 1-vinyl-3-propylimidazolium bromide; the comonomer is styrene or p-methylstyrene, and the molar ratio of the comonomer to the functional monomer is 3-7: 7-3; the mass of isopropanol accounts for 10-30% of the mass of the functional monomer; the free radical initiator is one of azobisisobutyronitrile, azobisisoheptanenitrile or dibenzoyl peroxide, and the molar number of the free radical initiator accounts for 0.5-4% of the sum of the molar numbers of the functional monomer and the comonomer; preferably, the functional monomer is 1-vinyl-3-propylimidazolium bromide, the comonomer is p-methylstyrene, the molar ratio of the comonomer to the functional monomer is 3-4: 6-7, the mass of isopropanol accounts for 20% of the mass of the functional monomer, and the free radical initiator is azobisisobutyronitrile, and preferably, the molar number of the free radical initiator accounts for 1% of the sum of the molar numbers of the functional monomer and the comonomer;

[0017] Furthermore, the functional monomer is an organic ammonium salt containing a carbon-carbon double bond, which undergoes a solution polymerization reaction with the comonomer under the action of a free radical initiator to obtain a flexible component polymer solution; the ammonium group of the flexible component polymer can conduct ions, so that the subsequently obtained adhesive can conduct ions, which helps to reduce the water dissociation voltage of the bipolar membrane; the comonomer does not contain a hydrophilic group, so that the flexible component polymer contains both a hydrophilic component and a hydrophobic component, and the hydrophobic component makes the flexible component polymer insoluble in water, which helps to avoid possible loss of the flexible component polymer during the use of the bipolar membrane and helps to improve the adhesion of the adhesive; the comonomer and the functional monomer should maintain an appropriate ratio. If the ratio of the functional monomer is too high, the flexible component polymer will be too hydrophilic or soluble in water. If the ratio of the comonomer is too high, the flexible component polymer will contain insufficient ammonium groups, resulting in insufficient ion conduction ability.

[0018] In one embodiment,

[0019] The polymerization reaction temperature in step (a) is 80-110°C and the reaction time is 4-24 h; preferably, the polymerization reaction temperature is 90°C and the reaction time is 16 h.

[0020] In one embodiment,

[0021] Step (i) (b) the acrylic monomer is one of methacrylic acid, methyl methacrylate, acrylic acid or methyl acrylate; the crosslinking agent is ethylene glycol dimethacrylate or polyethylene glycol dimethacrylate; the mass ratio of the crosslinking agent to the acrylic monomer is 3-7:7-3; preferably, the acrylic monomer is methacrylic acid, the crosslinking agent is ethylene glycol dimethacrylate, and the mass ratio of the crosslinking agent to the acrylic monomer is 5:5;

[0022] Furthermore, the crosslinking agent and acrylic monomer should maintain a suitable ratio. If the crosslinking agent ratio is insufficient, the degree of crosslinking after subsequent polymerization will be insufficient, affecting the adhesion between membrane layers. If the crosslinking agent ratio is too high, the rigid component after subsequent polymerization will be easily brittle and cracked, affecting the performance of the bipolar membrane.

[0023] In one embodiment,

[0024] In step (i) (c), the catalyst component is one of polyvinyl alcohol, polyethyleneimine, titanic acid, nano titanium oxide or nano zinc oxide; the concentration of the catalyst dispersion is 1-20 wt%; preferably, the catalyst component is nano zinc oxide, and the concentration of the catalyst dispersion is 1 wt%.

[0025] In one embodiment,

[0026] The reducing agent component of the redox initiator in step (i) (d) is one of tetramethylthiourea, N,N-dimethylaniline, triethylamine or N-methyldiethanolamine; the catalyst dispersion accounts for 1-10% of the mass of the flexible component polymer solution; the reducing agent component accounts for 1-5% of the mass of the flexible component polymer solution; preferably, the reducing agent component of the redox initiator is tetramethylthiourea, the catalyst dispersion accounts for 6.7% of the mass of the flexible component polymer solution, and the reducing agent component accounts for 3.3% of the mass of the flexible component polymer solution.

[0027] In one embodiment,

[0028] In step (i) (e), the oxidant component of the redox initiator is one of cumene hydroperoxide, hydrogen peroxide or dibenzoyl peroxide; the oxidant component accounts for 10-40% of the mass of the rigid component monomer solution; preferably, the oxidant component of the redox initiator is cumene hydroperoxide, and the oxidant component accounts for 36.7% of the mass of the rigid component monomer solution.

[0029] In one embodiment,

[0030] In step (i) (e), the adhesive reducing solution and the adhesive oxidizing solution are mixed in a mass ratio of 4-12:1. Preferably, the adhesive reducing solution and the adhesive oxidizing solution are mixed in a mass ratio of 8.25:1.

[0031] In one embodiment,

[0032] Step (ii) The film is heated at a temperature of 60-100°C, preferably 80°C;

[0033] Furthermore, the adhesive reducing solution and the adhesive oxidizing solution need to be used immediately after mixing, because the oxidant component and the reducing agent component react after mixing to form free radicals, and the free radicals trigger the polymerization reaction of the acrylic monomer and the crosslinking agent in the rigid component monomer solution, thereby promoting the bonding of the positive and negative film layers; in the process of bonding the two film layers, it is necessary to squeeze out the excess adhesive so that the two film layers fit tightly together, and rolling the film layers with a roller can help the two film layers fit tightly together, or two flat plates can be used to press the two film layers together to make the two film layers fit tightly together; in the process of bonding the two film layers, it is necessary to remove the bubbles between the film layers, and the film layers can be bonded in a negative pressure environment to remove the bubbles; curing the two film layers can be carried out at room temperature or in an environment with an increased temperature, such as 40-100°C, which helps the rapid curing of the adhesive; the cured adhesive may also contain an organic solvent, and the film sheet can be placed in an oven and heated to volatilize the organic solvent, and the oven temperature is 60-100°C; in order to enhance the bonding strength between the film layers, one side of the negative film and the positive film can also be polished to make the surface rough.

[0034] The present application provides a method for preparing an adhesive bipolar membrane, wherein an anion membrane and a cation membrane are bonded by an adhesive to obtain a bipolar membrane; the adhesive contains a flexible component, a rigid component and a catalyst, the flexible component polymer has an ion conducting property, so that the adhesive has low resistance; the rigid component cross-linked structure polymer is formed during the curing process of the adhesive, so that the adhesive has high efficient bonding force; the catalyst promotes water dissociation, so that the bipolar membrane has a low transmembrane voltage; the preparation process is simple, and the adhesive has universal applicability. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clear, the present application is further described in detail. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0036] Both the electrodialysis anion membrane and the electrodialysis cation membrane are produced by Shandong Tianwei Membrane Technology Co., Ltd.

[0037] Example 1

[0038] (I) Preparation of adhesive:

[0039] (a) Preparation of a flexible component polymer solution: 19.2 g of 1-vinyl-3-propyl imidazole bromide, 19.2 g of p-methylstyrene, 21.8 g of N,N-dimethylformamide, 3.84 g of isopropanol and 0.29 g of azobisisobutyronitrile were mixed into a uniform solution, and the mixture was polymerized at 90 °C for 16 h to obtain a flexible component polymer solution.

[0040] (b) Preparation of rigid component monomer solution: weigh 1.5 g of methacrylic acid and 1.5 g of ethylene glycol dimethacrylate and stir and mix them evenly to prepare a rigid component monomer solution;

[0041] (c) Preparation of catalyst dispersion: weigh 0.02 g of nano zinc oxide and 2.0 g of N,N-dimethylformamide, mix and stir for 30 min to obtain a catalyst dispersion;

[0042] (d) Preparation of adhesive reduction solution: 30.0 g of the flexible component polymer solution, 2 g of the catalyst dispersion and 1.0 g of tetramethylthiourea were mixed and stirred to obtain an adhesive reduction solution;

[0043] (e) Preparation of adhesive oxidation liquid: Add 1.1 g of cumene hydroperoxide to 3.0 g of the rigid component monomer solution and mix and stir evenly to obtain an adhesive oxidation liquid;

[0044] 33 g of the adhesive reduction solution and 4.0 g of the adhesive oxidation solution were quickly mixed to obtain an adhesive;

[0045] (II) Preparation of bonded bipolar membrane:

[0046] One side surface of the electrodialysis anion membrane and the electrodialysis cation membrane was polished with sandpaper to make the surface rough; the adhesive was coated on the rough surface of the electrodialysis anion membrane and the electrodialysis cation membrane respectively, the two membranes were attached, and two flat plates were pressed together to squeeze out the excess adhesive, and placed in a 60 ℃ oven for 2 h; the two flat plates were removed, and the membrane was placed in an 80 ℃ oven for 4 h; the membrane was immersed in water to obtain a bonded bipolar membrane.

[0047] Example 2

[0048] (I) Preparation of adhesive:

[0049] (a) Preparation of the flexible component polymer solution: 19.2 g of 1-propyl-4-vinylpyridinium bromide, 28.8 g of styrene, 27.2 g of N-methyl-2-pyrrolidone, 4.8 g of isopropanol and 0.35 g of azobisisobutyronitrile were mixed into a uniform solution, and the mixture was polymerized at 80 °C for 16 h to obtain a flexible component polymer solution.

[0050] (b) Preparation of rigid component monomer solution: weigh 2.0 g of methyl methacrylate and 2.0 g of ethylene glycol dimethacrylate and stir and mix them evenly to prepare a rigid component monomer solution;

[0051] (c) Preparation of catalyst dispersion: weigh 0.02 g of nano-titanium oxide and 2.0 g of N-methyl-2-pyrrolidone, mix and stir for 30 min to obtain a catalyst dispersion;

[0052] (d) Preparation of adhesive reduction solution: 30.0 g of the flexible component polymer solution, 2 g of the catalyst dispersion and 1.0 g of N,N-dimethylaniline were mixed and stirred to obtain an adhesive reduction solution;

[0053] (e) Preparation of adhesive oxidation liquid: Add 1.1 g of cumene hydroperoxide to 4.0 g of the rigid component monomer solution and mix and stir evenly to obtain an adhesive oxidation liquid;

[0054] 33 g of the adhesive reduction solution and 5.1 g of the adhesive oxidation solution were quickly mixed to obtain an adhesive;

[0055] (II) Preparation of bonded bipolar membrane:

[0056] One side surface of the electrodialysis anion membrane and the electrodialysis cation membrane was polished with sandpaper to make the surface rough; the adhesive was coated on the rough surface of the electrodialysis anion membrane and the electrodialysis cation membrane respectively, the two membranes were attached, and two flat plates were pressed together to squeeze out excess adhesive, and placed in a 60 ℃ oven for 2 h; the two flat plates were removed, and the membrane was placed in an 80 ℃ oven for 4 h; the membrane was immersed in water to obtain a bonded bipolar membrane.

[0057] Example 3

[0058] The present embodiment is different from the embodiment 1 in that in step (i) (a), the functional monomer is 1-propyl-4-vinylpyridinium bromide, the organic solvent is N,N-dimethylacetamide, and the free radical initiator is azobisisoheptanenitrile; in step (i) (c), the organic solvent is N,N-dimethylacetamide, and the remaining operations are the same.

[0059] Example 4

[0060] The difference between this embodiment and embodiment 3 is that the free radical initiator is dibenzoyl peroxide, and the other operations are the same.

[0061] Example 5

[0062] The difference between this embodiment and embodiment 1 is that in step (i) (a), the molar ratio of p-methylstyrene to 1-vinyl-3-propylimidazolium bromide is 3:7, and the remaining operations are the same.

[0063] Example 6

[0064] The difference between this embodiment and embodiment 1 is that in step (i) (a), the molar ratio of p-methylstyrene to 1-vinyl-3-propyl imidazole bromide is 4:6, and the remaining operations are the same.

[0065] Example 7

[0066] The difference between this embodiment and embodiment 1 is that in step (i) (a), the molar ratio of p-methylstyrene to 1-vinyl-3-propyl imidazole bromide is 7:3, and the remaining operations are the same.

[0067] Example 8

[0068] The difference between this embodiment and embodiment 1 is that in step (i) (a), the mass of isopropanol accounts for 10% of the mass of 1-vinyl-3-propyl imidazole bromide, and the remaining operations are the same.

[0069] Example 9

[0070] The difference between this embodiment and embodiment 1 is that in step (i) (a), the mass of isopropanol accounts for 30% of the mass of 1-vinyl-3-propyl imidazole bromide, and the remaining operations are the same.

[0071] Example 10

[0072] The difference between this embodiment and embodiment 1 is that in step (i) (a), the polymerization reaction temperature is 100° C. and the reaction time is 20 h, and the other operations are the same.

[0073] Embodiment 11

[0074] The difference between this embodiment and embodiment 1 is that in step (i) (a), the polymerization reaction temperature is 110° C. and the reaction time is 4 h, and the remaining operations are the same.

[0075] Example 12

[0076] The difference between this embodiment and embodiment 1 is that in step (i) (a), the polymerization reaction temperature is 110° C. and the reaction time is 24 h. The other operations are the same.

[0077] Example 13

[0078] The difference between this embodiment and embodiment 1 is that in step (i) (a), the molar number of azobisisobutyronitrile accounts for 0.5% of the sum of the molar numbers of 1-vinyl-3-propylimidazolium bromide and p-methylstyrene, and the remaining operations are the same.

[0079] Embodiment 14

[0080] This embodiment is different from embodiment 1 in that in step (i) (a), the molar number of azobisisobutyronitrile accounts for 2.5% of the sum of the molar numbers of 1-vinyl-3-propylimidazolium bromide and p-methylstyrene, and the remaining operations are the same.

[0081] Embodiment 15

[0082] This embodiment is different from embodiment 1 in that in step (i) (a), the molar number of azobisisobutyronitrile accounts for 4% of the sum of the molar numbers of 1-vinyl-3-propylimidazolium bromide and p-methylstyrene, and the remaining operations are the same.

[0083] Example 16

[0084] The difference between this embodiment and embodiment 1 is that in step (i) (b), the acrylic monomer is acrylic acid, and the cross-linking agent is polyethylene glycol dimethacrylate, and the remaining operations are the same.

[0085] Embodiment 17

[0086] The difference between this embodiment and embodiment 13 is that acrylic acid is replaced with methyl acrylate, and the remaining operations are the same.

[0087] Embodiment 18

[0088] The difference between this embodiment and embodiment 1 is that in step (i) (b), the mass ratio of ethylene glycol dimethacrylate to methacrylic acid is 3:7, and the remaining operations are the same.

[0089] Embodiment 19

[0090] The difference between this embodiment and embodiment 1 is that in step (i) (b), the mass ratio of ethylene glycol dimethacrylate to methacrylic acid is 7:3, and the remaining operations are the same.

[0091] Embodiment 20

[0092] The difference between this embodiment and embodiment 1 is that in step (i) (c), the catalyst component is polyvinyl alcohol, and the rest of the operations are the same.

[0093] Embodiment 21

[0094] The difference between this embodiment and embodiment 1 is that in step (i) (c), the catalyst component is polyethyleneimine, and the rest of the operations are the same.

[0095] Embodiment 22

[0096] The difference between this embodiment and embodiment 1 is that in step (i) (c), the concentration of the catalyst dispersion is 10 wt %, and the rest of the operations are the same.

[0097] Embodiment 23

[0098] The difference between this embodiment and embodiment 1 is that in step (i) (c), the concentration of the catalyst dispersion is 20 wt %, and the other operations are the same.

[0099] Embodiment 24

[0100] This embodiment is different from Embodiment 1 in that in step (i) (d), the reducing agent component of the redox initiator is triethylamine, and in step (i) (e), the oxidizing agent component of the redox initiator is hydrogen peroxide, and the remaining operations are the same.

[0101] Embodiment 25

[0102] This embodiment is different from Embodiment 1 in that in step (i) (d), the reducing agent component of the redox initiator is N-methyldiethanolamine, and in step (i) (e), the oxidizing agent component of the redox initiator is dibenzoyl peroxide, and the remaining operations are the same.

[0103] Embodiment 26

[0104] The difference between this embodiment and embodiment 1 is that in step (i) (d), the catalyst dispersion accounts for 1% by weight of the flexible component polymer solution, and the tetramethylthiourea accounts for 1% by weight of the flexible component polymer solution. The remaining operations are the same.

[0105] Embodiment 27

[0106] The difference between this embodiment and embodiment 1 is that in step (i) (d), the catalyst dispersion accounts for 10% of the mass of the flexible component polymer solution, and the tetramethylthiourea accounts for 5% of the mass of the flexible component polymer solution. The remaining operations are the same.

[0107] Embodiment 28

[0108] The difference between this embodiment and embodiment 1 is that in step (i) (e), cumene hydroperoxide accounts for 10% of the mass of the rigid component monomer solution, and the remaining operations are the same.

[0109] Embodiment 29

[0110] The difference between this embodiment and embodiment 1 is that in step (i) (e), cumene hydroperoxide accounts for 25% of the mass of the rigid component monomer solution, and the remaining operations are the same.

[0111] Embodiment 30

[0112] The difference between this embodiment and embodiment 1 is that in step (i) (e), cumene hydroperoxide accounts for 40% of the mass of the rigid component monomer solution, and the remaining operations are the same.

[0113] Embodiment 31

[0114] The difference between this embodiment and embodiment 1 is that in step (i) (e), the mass ratio of the mixture of the adhesive reducing solution and the adhesive oxidizing solution is 4:1, and the remaining operations are the same.

[0115] Embodiment 32

[0116] The difference between this embodiment and embodiment 1 is that in step (i) (e), the mass ratio of the mixture of the adhesive reducing solution and the adhesive oxidizing solution is 12:1, and the remaining operations are the same.

[0117] Embodiment 33

[0118] The difference between this embodiment and embodiment 1 is that in step (ii), after removing the two flat plates, the membrane is placed in a 60° C. oven for 4 h, and the remaining operations are the same.

[0119] Embodiment 34

[0120] The difference between this embodiment and embodiment 1 is that in step (ii), after removing the two flat plates, the membrane is placed in a 100° C. oven for 4 h, and the remaining operations are the same.

[0121] Comparative Example 1 (without rigid component)

[0122] This comparative example is different from Example 1 in that step (i) (b) is omitted, and the adhesive oxidation solution in step (i) (e) does not contain the rigid component monomer solution but only contains 1.1 g of cumene hydroperoxide, and the remaining operations are the same.

[0123] Comparative Example 2 (without flexible component)

[0124] This comparative example is different from Example 1 in that step (i) (a) is omitted, and the adhesive reduction solution in step (i) (d) does not contain the flexible component polymer solution but only contains 2 g of the catalyst dispersion and 1.0 g of tetramethylthiourea, and the remaining operations are the same.

[0125] Comparative Example 3 (without catalyst)

[0126] This comparative example is different from Example 1 in that step (i) (c) is omitted, and the binder reduction solution in step (i) (d) does not contain a catalyst dispersion but only contains 30.0 g of a flexible component polymer solution and 1.0 g of tetramethylthiourea, and the remaining operations are the same.

[0127] Test of bipolar membrane transmembrane voltage: The transmembrane voltage of the prepared bipolar membrane is tested according to the industry standard HG / T 6093-2022 "Bipolar Membrane" "5.7 Transmembrane Voltage". This indicator characterizes the water dissociation performance of the bipolar membrane. At a current density of 100 mA / cm 2 The lower bipolar membrane transmembrane voltage test data are shown in Table 1.

[0128] Table 1 Bipolar membrane transmembrane voltage test results

[0129]

[0130] From the data in Table 1, it can be seen that the transmembrane voltage of Examples 1 and 2 is 2.0-2.5 V, and the transmembrane voltage of the comparative example is higher than 5 V. The water dissociation performance of the bipolar membrane prepared by the method of Examples 1-2 is significantly better than that of Comparative Examples 1-3.

[0131] The present application provides a method for preparing an adhesive bipolar membrane, which comprises preparing an adhesive containing a flexible component, a rigid component and a catalyst, and using the adhesive to bond an anion membrane and a cation membrane to obtain a bipolar membrane; the method has a simple preparation process, and the adhesive has universal applicability, and can be applied to preparing bipolar membranes from most types of anion membranes and cation membranes; the flexible component of the adhesive is a flexible polymer containing an ionizing group, which is prepared by copolymerizing an organic ammonium salt functional monomer containing a carbon-carbon double bond with a styrene or p-methylstyrene comonomer; the amine group enables the adhesive to conduct ions, which helps to reduce the water dissociation voltage of the bipolar membrane; the comonomer makes the polymer insoluble in water, thereby ensuring the stability and adhesion of the adhesive; the rigid component of the adhesive is an acrylic monomer, which reacts with a crosslinking agent in an oxidative reaction. The cross-linked structure polymer is obtained by polymerization reaction under the action of a reducing initiator. The formation of the rigid component is synchronized with the curing of the adhesive. When the monomer and the cross-linking agent are coated on one side of the anion membrane and the cation membrane, they partially penetrate into the interior of the membrane layer, undergo polymerization reaction, and form a cross-linked structure, which promotes the close adhesion of the membrane layer. The flexible component polymer solution and the rigid component monomer solution should be kept in an appropriate ratio. The catalyst promotes the water dissociation of the bipolar membrane to produce acid and base. The catalyst is blended with the remaining components. During the curing process of the adhesive, the catalyst is also fixed between the anion membrane and the cation membrane. The catalyst also reduces the water dissociation voltage of the bipolar membrane. According to the different materials of the anion membrane and the cation membrane, the ratio of the flexible component, the rigid component and the catalyst component in the adhesive can be flexibly adjusted to prepare a bonded bipolar membrane.

[0132] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0133] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a bonded bipolar membrane, characterized in that: The specific steps include: (I) Preparation of adhesive: (a) Preparation of a flexible component polymer solution: blending a functional monomer, a comonomer, an organic solvent, isopropanol and a free radical initiator, and performing a polymerization reaction to obtain a flexible component polymer solution; (b) Preparation of a rigid component monomer solution: blending an acrylic monomer with a cross-linking agent to prepare a rigid component monomer solution; (c) Preparation of catalyst dispersion: dispersing the catalyst in an organic solvent to obtain a catalyst dispersion; (d) preparing the adhesive reduction solution: mixing the flexible component polymer solution, the catalyst dispersion and the reducing agent component of the redox initiator in proportion to obtain the adhesive reduction solution; (e) Preparation of adhesive oxidation liquid: mixing the rigid component monomer solution and the oxidant component of the redox initiator in proportion to obtain an adhesive oxidation liquid; The adhesive reducing liquid and the adhesive oxidizing liquid are mixed in proportion to obtain an adhesive; (ii) preparing a bonded bipolar membrane: coating the adhesive on one side of the anion membrane and the cation membrane respectively, closely attaching the two membranes and squeezing out excess adhesive, and after the adhesive is cured, heating the membrane to obtain a bonded bipolar membrane; Step (i) (a) The functional monomer is 1-propyl-4-vinylpyridinium bromide or 1-vinyl-3-propylimidazolium bromide; the comonomer is styrene or p-methylstyrene, and the molar ratio of the comonomer to the functional monomer is 3-7:7-3; the mass of the isopropanol accounts for 10-30% of the mass of the functional monomer; the free radical initiator is one of azobisisobutyronitrile, azobisisoheptanenitrile or dibenzoyl peroxide, and the molar number of the free radical initiator accounts for 0.5-4% of the sum of the molar numbers of the functional monomer and the comonomer; (b) the acrylic monomer is one of methacrylic acid, methyl methacrylate, acrylic acid or methyl acrylate; the cross-linking agent is ethylene glycol dimethacrylate or polyethylene glycol dimethacrylate; the mass ratio of the cross-linking agent to the acrylic monomer is 3-7:7-3; (c) the catalyst component is one of polyvinyl alcohol, polyethyleneimine, metatitanic acid, nano titanium oxide or nano zinc oxide; the concentration of the catalyst dispersion is 1-20 wt%; (e) The mass ratio of the adhesive reducing solution to the adhesive oxidizing solution is 4-12:

1.

2. The method for preparing a bonded bipolar membrane according to claim 1, characterized in that: The organic solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide or N-methyl-2-pyrrolidone.

3. The method for preparing a bonded bipolar membrane according to claim 1, characterized in that: The temperature of the polymerization reaction in step (a) is 80-110 o C, time is 4-24 h.

4. The method for preparing a bonded bipolar membrane according to claim 1, characterized in that: In step (i) (d), the reducing agent component of the redox initiator is one of tetramethylthiourea, N,N-dimethylaniline, triethylamine or N-methyldiethanolamine; the catalyst dispersion accounts for 1-10% of the mass of the flexible component polymer solution; and the reducing agent component accounts for 1-5% of the mass of the flexible component polymer solution.

5. The method for preparing a bonded bipolar membrane according to claim 1, characterized in that: The oxidant component of the redox initiator in step (i) (e) is one of cumene hydroperoxide, hydrogen peroxide or dibenzoyl peroxide; the oxidant component accounts for 10-40% of the mass of the rigid component monomer solution.

6. The method for preparing a bonded bipolar membrane according to claim 1, characterized in that: Step (ii) The temperature of the membrane heating is 60-100 o C.

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