A homogeneous membrane and a preparation method thereof

Abstract

The present invention belongs to the technical field of ion exchange membranes, and specifically relates to a homogeneous membrane and a preparation method thereof, and a preparation method of a homogeneous cation membrane, including: sulfonation modification of a mesh cloth to obtain a cation membrane mesh cloth; laying the cation membrane mesh cloth flat on a PET film, uniformly coating a cation membrane slurry on the mesh cloth and the PET film, separating the PET film after drying to obtain a homogeneous cation membrane; wherein, the cation membrane slurry is a partially sulfonated polystyrene and a dehydrating agent completely dissolved in a good solvent. A preparation method of a homogeneous anion membrane, including: chloromethylation modification of a mesh cloth to obtain an anion membrane mesh cloth; laying the anion membrane mesh cloth flat on a PET film, uniformly coating an anion membrane slurry on the mesh cloth and the PET film, separating the PET film after drying to obtain a homogeneous anion membrane; wherein, the anion membrane slurry is a partially chloromethylated polystyrene, a toughening polymer, a double bond-containing mono-tertiary amine, a non-double bond-containing mono-tertiary amine, and an initiator completely dissolved in a good solvent. The homogeneous membrane of the present invention has high strength, low permeability, good dimensional stability, and a longer service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of ion exchange membranes, and particularly relates to a homogeneous membrane and a preparation method thereof. Background Art

[0002] Homogeneous membranes are mainly divided into homogeneous cation exchange membranes and homogeneous anion exchange membranes. Homogeneous cation exchange membranes contain acidic groups and are polymer membranes with selective permeability to cations; homogeneous anion exchange membranes contain basic groups and are polymer membranes with selective permeability to anions.

[0003] Currently, there are mainly two types of homogeneous membranes on the market. One type is the impregnated type, which uses an impregnable thin film or porous thin film, made into a base film through impregnation polymerization, and then sulfonated and aminated. Such membranes generally have poor dimensional stability during use, relatively low strength, and a high permeability due to dimensional changes after long-term use. The other type uses a high-strength mesh as a support, and a polymerizable monomer and the mesh are together formed into a polymer membrane, which has high strength and good dimensional stability, but there will be gaps between the support and the resin, and the permeability is also relatively high.

[0004] Therefore, there is an urgent need in the art to develop a homogeneous ion exchange membrane with high strength, good dimensional stability, low permeability, and long service life, which is beneficial to preparing high-purity products and effectively reducing operating costs. Summary of the Invention

[0005] Based on the above-mentioned drawbacks and deficiencies existing in the prior art, one of the purposes of the present invention is to at least solve one or more of the above problems existing in the prior art. In other words, one of the purposes of the present invention is to provide a homogeneous membrane and a preparation method thereof that meet one or more of the foregoing requirements.

[0006] In order to achieve the above-mentioned invention purpose, the present invention adopts the following technical solutions:

[0007] A preparation method of a homogeneous membrane, comprising the following steps:

[0008] (1) Sulfonation modification of the mesh to obtain a cationic membrane mesh;

[0009] (2) Lay the cationic membrane mesh flat on a PET film, evenly coat the cationic membrane slurry on the mesh and the PET film, and separate the PET film after drying to obtain a homogeneous cationic membrane;

[0010] Wherein, the cationic membrane slurry is partially sulfonated polystyrene and a dehydrating agent completely dissolved in a good solvent.

[0011] As a preferred scheme, the dehydrating agent is selected from at least one of acidic montmorillonite, phosphotungstic acid silica, and phosphorus pentoxide;

[0012] The good solvent is selected from at least one of dichloroethane, N,N-dimethylformamide, dimethylacetamide, and dimethyl sulfoxide.

[0013] As a preferred embodiment, in the step (2), the drying process includes: first drying at 60-90 °C for 2-10 hours, and then drying at 90-150 °C for 2-10 hours;

[0014] The preparation process of the partially sulfonated polystyrene includes:

[0015] Adding the sulfonation solution to the polystyrene solution for sulfonation reaction, the sulfonation reaction temperature is 30-90 °C, and the reaction time is 0.5-10 hours;

[0016] Adding the material liquid after the sulfonation reaction is completed to an ice-water mixture, and the precipitated solid is filtered, washed, and dried to obtain the partially sulfonated polystyrene.

[0017] As a preferred embodiment, the step (1) specifically includes the following steps:

[0018] (11) Preparing an impregnating solution with styrene, divinylbenzene, and an initiator, heating to 30-70 °C, completely immersing the mesh cloth in the impregnating solution, taking out the mesh cloth after soaking for 5-120 minutes, removing the excess impregnating solution, and laying it flat between two PET films, and sealing the edges of the PET films with tape;

[0019] (12) Putting the PET film and the mesh cloth into a hot water tank for polymerization reaction, taking out from the hot water tank after the polymerization reaction is completed, and separating the mesh cloth from the PET film;

[0020] Among them, the hot water temperature of the hot water tank is 65-90 °C, and the reaction time is 1-15 hours;

[0021] (13) Placing the separated mesh cloth in the sulfonation solution of the sulfonation reaction tank for sulfonation reaction, and washing and drying the mesh cloth after the sulfonation reaction is completed;

[0022] Among them, the temperature of the sulfonation reaction is 30-90 °C, and the reaction time is 0.3-10 hours.

[0023] As a preferred embodiment, the mesh cloth is a woven cloth, a non-woven cloth or a porous film, and the material is low-density polyethylene LDPE, high-density polyethylene HDPE, polyvinyl chloride PVC, polyphenylene sulfide PPS or polyether ether ketone PEEK.

[0024] As a preferred embodiment, in the step (11), the impregnating solution is heated to 40-60 °C, and the soaking time is 10-60 minutes;

[0025] In the step (12), the hot water temperature of the hot water tank is 65-80 °C, and the reaction time is 3-10 hours;

[0026] In step (13), the temperature of the sulfonation reaction is 30 - 80 °C, and the reaction time is 0.3 - 4 hours.

[0027] The present invention also provides a method for preparing a homogeneous membrane, comprising the following steps:

[0028] (a) Chloromethylation modification of the mesh cloth to obtain an anion membrane mesh cloth;

[0029] (b) Lay the anion membrane mesh cloth flat on a PET film, evenly coat the anion membrane slurry on the mesh cloth and the PET film, dry it and then separate the PET film to obtain a homogeneous anion membrane;

[0030] Among them, the anion membrane slurry is that partially chloromethylated polystyrene, a toughening polymer, a double-bond-containing secondary amine, a non-double-bond-containing secondary amine, and an initiator are completely dissolved in a good solvent.

[0031] As a preferred scheme, step (a) specifically comprises the following steps:

[0032] (a1) Prepare an impregnating solution with styrene, divinylbenzene, and an initiator, heat it to 30 - 70 °C, then completely immerse the mesh cloth in the impregnating solution, take out the mesh cloth after soaking for 5 - 120 minutes, remove the excess impregnating solution, and lay it flat between two PET films, and seal the edges of the PET films with tape;

[0033] (a2) Put the PET film and the mesh cloth together into a hot water tank for polymerization reaction, take them out from the hot water tank after the polymerization reaction is completed, and separate the mesh cloth from the PET film;

[0034] Among them, the hot water temperature of the hot water tank is 65 - 90 °C, and the reaction time is 1 - 15 hours;

[0035] (a3) Place the separated mesh cloth in chloromethyl ether in a chloromethylation reaction tank for chloromethylation reaction, the reaction temperature is 20 - 60 °C, the reaction time is 0.1 - 20 hours, wash and dry the mesh cloth after the chloromethylation reaction is completed, then soak it in a double-bond-containing mono-tertiary amine solution at a temperature of 20 - 60 °C for 0.1 - 10 hours, take it out after soaking, remove the excess double-bond-containing mono-tertiary amine solution on the membrane surface, and then dry it at 40 - 90 °C for 2 - 10 hours.

[0036] As a preferred scheme, the preparation process of the partially chloromethylated polystyrene includes:

[0037] Add chloromethyl ether to the polystyrene solution for chloromethylation reaction, the reaction temperature is 20 - 60 °C, the reaction time is 1 - 20 hours, to obtain a liquid material after the chloromethylation is completed;

[0038] The liquid material after chloromethylation is added to methanol. The precipitated solid is filtered, washed, and dried to obtain partially chloromethylated polystyrene.

[0039] As a preferred embodiment, in the step (b), the double bond-containing mono-tertiary amine is selected from at least one of N,N-dimethylallylamine, N,N,2-trimethylallylamine, and 3-(dimethylamino)acrylonitrile;

[0040] The double bond-free mono-tertiary amine is selected from at least one of triethanolamine, triethylamine, dodecyldimethyltertiary amine, and dioctylmethyltertiary amine;

[0041] The drying temperature is 60-110°C, and the time is 2-10 hours.

[0042] The present invention also provides a homogeneous membrane, which is a homogeneous cation membrane prepared by the preparation method described in any one of the above schemes or a homogeneous anion membrane prepared by the preparation method described in any one of the above schemes.

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] (1) The mesh cloth of the homogeneous membrane of the present invention is functionally modified, and there are chemical bonds connected to both the cation and anion layer resins, with a tight combination and low permeability;

[0045] (2) The present invention adopts a unique cross-linking method of cross-linking after film formation, with more controllable film formation and higher product yield;

[0046] (3) Compared with the existing impregnated homogeneous membrane, the homogeneous membrane of the present invention has high strength, good dimensional stability, and longer service life; and enhances the bonding force between the mesh cloth support material and the cation and anion layer resins, effectively reducing the leakage and penetration formed by the solute directly passing through the gap between the resin and the mesh cloth, improving the product quality, and being beneficial to energy consumption reduction. Specific Embodiments

[0047] The preparation method of the homogeneous membrane provided by the present invention will be further described below.

[0048] The homogeneous membrane of the present invention is divided into two types: homogeneous cation membrane and homogeneous anion membrane.

[0049] The preparation method of the homogeneous cation membrane of the present invention includes the following processes:

[0050] The mesh cloth is hydrophilically improved by impregnation, polymerization, re-sulfonation or direct sulfonation to prepare a cation membrane mesh cloth;

[0051] Using polystyrene as a raw material, partially sulfonated polystyrene is prepared by partial sulfonation, purified and dissolved in a solvent, and a dehydrating agent is added, and after dissolution, it is formulated into a cation membrane slurry;

[0052] Lay the positive film mesh cloth on the PET film, evenly coat the positive film slurry on the positive film mesh cloth and the PET film, separate the PET film after drying to obtain the positive film.

[0053] The preparation method of the homogeneous negative film of the present invention includes the following process:

[0054] Carry out chloromethyl modification on the mesh cloth in the form of impregnation, polymerization, chloromethylation or direct chloromethylation, then soak it in a solution of double bond mono-tertiary amine for a certain time, take it out and dry it to obtain the negative film mesh cloth;

[0055] Use polystyrene as the raw material, carry out partial chloromethylation, after purification, dissolve it with a toughening polymer in a solvent, and then add a certain amount of double bond-containing mono-tertiary amine, non-double bond-containing mono-tertiary amine and initiator after dissolution, mix evenly and prepare the negative film slurry;

[0056] Lay the negative film mesh cloth on the PET film, evenly coat the negative film slurry on the negative film mesh cloth and the PET film, separate the PET film after drying to obtain the negative film.

[0057] The homogeneous positive film and homogeneous negative film prepared by the present invention have high mechanical strength, stable product size and low permeability.

[0058] Specifically, the preparation methods of the homogeneous positive film and homogeneous negative film of the present invention include the following steps:

[0059] 1. Preparation of modified mesh cloth;

[0060] a) Material selection: Select a mesh cloth prepared from a material capable of impregnating styrene or directly sulfonating or chloromethylating. The form of the mesh cloth can be woven cloth, non-woven cloth, porous film, and its materials include but are not limited to low-density polyethylene LDPE, high-density polyethylene HDPE, polyvinyl chloride PVC, polyphenylene sulfide PPS, polyether ether ketone PEEK, bisphenol A polysulfone PSU, polyethersulfone PES, etc.;

[0061] b) Impregnation: Prepare an impregnating solution with styrene, divinylbenzene and an initiator, heat it to 30-70 °C, then completely immerse the mesh cloth in the impregnating solution to ensure full contact between the mesh cloth and the impregnating solution, and take out the mesh cloth after soaking for 5-120 minutes, remove the excess impregnating solution, and lay it flat between two PET films, and seal the PET edges with tape;

[0062] Among them, the weight ratio of styrene, divinylbenzene, and initiator is 1:0.01 - 0.4:0.001 - 0.1; the initiator is mainly a type of substance that can form free radicals, selected from organic peroxides such as lauroyl peroxide, tert-butyl peroxy laurate, tert-butyl peroxy isobutyrate, benzoyl peroxide BPO, di-tert-butyl peroxide, etc., and at least one of azo organic compounds such as azobisisobutyronitrile AIBN, azobis(2,4-dimethylvaleronitrile) ABVN, dimethyl 2,2'-azobis(2-methylpropionate) AIBME;

[0063] c) Polymerization: Put the PET film and the mesh cloth into a hot water tank together for polymerization reaction. The hot water temperature is 65 - 90°C, and the reaction time is 1 - 15 hours;

[0064] d) Stripping: Take out the mesh cloth after polymerization from the hot water tank, separate the mesh cloth from the PET film, and the mesh cloth is used for subsequent reactions;

[0065] e) Preparation of sulfonation solution: The sulfonation solution is a reagent that can introduce sulfonic acid groups onto the benzene ring, such as 90 - 98wt% sulfuric acid, chlorosulfonic acid, a mixed solution of chlorosulfonic acid and sulfuric acid with a weight ratio of 1:0.1 - 9, a mixed solution of acetic anhydride and sulfuric acid with a weight ratio of 1:0.1 - 1, etc.;

[0066] f) Sulfonation: First, add the sulfonation solution into the sulfonation reaction tank, and then place the mesh cloth from step d) in the sulfonation reaction tank for sulfonation reaction. The reaction temperature is 30 - 90°C, and the reaction time is 0.3 - 10 hours. After sulfonation, the mesh cloth is first rinsed in a low-concentration acid, then washed with water and dried for standby; thus, the preparation of the cationic membrane mesh cloth is completed.

[0067] g) Chloromethylation: Place the mesh cloth from step d) in the chloromethylation reaction tank, and then inject chloromethyl ether for chloromethylation reaction. The reaction temperature is 20 - 60°C, and the reaction time is 0.1 - 20 hours. After the reaction is completed, it is washed with water and dried, and then soaked in a solution of double-bonded mono-tertiary amine at a temperature of 20 - 60°C for 0.2 - 10 hours. After completion, it is taken out, the excess solution of double-bonded mono-tertiary amine on the membrane surface is removed, and then dried at 40 - 90°C for 2 - 10 hours; thus, the preparation of the anionic membrane mesh cloth is completed.

[0068] 2. Preparation of partially sulfonated polystyrene;

[0069] h) Preparation of polystyrene solution: In a reaction kettle with stirring, first inject a certain amount of good solvents for polystyrene, such as dichloroethane DCE, N,N-dimethylformamide DMF, dimethylacetamide DMAC, dimethyl sulfoxide DMSO, etc. After starting the stirring, add an appropriate amount of polystyrene, and stir until the polystyrene is completely dissolved for standby;

[0070] i) Sulfonation: In a reaction kettle equipped with a stirrer, first take a part of the polystyrene solution prepared in step h) and add it to the reaction kettle. After starting the stirrer, start heating up. After reaching the set temperature, slowly add a certain amount of the sulfonation solution prepared in step e) to the reaction kettle. The sulfonation reaction temperature is 30 - 90 °C, and the reaction time is 0.5 - 10 hours;

[0071] j) Partially sulfonated polystyrene: In a reaction kettle equipped with a stirrer, add an appropriate amount of ice - water mixture. After starting the stirrer, slowly pour the material liquid after the sulfonation in step i) into it. The precipitated solid is filtered and washed multiple times, and then dried for standby; Thus, partially sulfonated polystyrene is prepared.

[0072] 3. Preparation of partially chloromethylated polystyrene;

[0073] k) Chloromethylation: In a reaction kettle equipped with a stirrer, first take a part of the polystyrene solution prepared in step h) and add it to the reaction kettle. After starting the stirrer, start heating up. After reaching the set temperature, slowly add a certain amount of chloromethyl ether to the reaction kettle. The chloromethylation reaction temperature is 20 - 60 °C, and the reaction time is 1 - 20 hours;

[0074] l) Partially chloromethylated polystyrene: In a reaction kettle equipped with a stirrer, add an appropriate amount of methanol. After starting the stirrer, slowly pour the material liquid after the chloromethylation in step k) into it. The precipitated solid is filtered and washed multiple times, and then dried for standby; Thus, partially chloromethylated polystyrene is prepared;

[0075] 4. Preparation of homogeneous cation - exchange membrane;

[0076] m) Preparation of cation - exchange membrane slurry: In a reaction kettle equipped with a stirrer, first inject a certain amount of good solvent for sulfonated polystyrene, such as DCE, DMF, DMAC, DMSO, etc. After starting the stirrer, first add an appropriate amount of the partially sulfonated polystyrene prepared in step j), and then add a dehydrating agent. After complete dissolution, prepare a cation - exchange membrane slurry;

[0077] Among them, the dehydrating agent is mainly a kind of auxiliary agent that can catalyze the dehydration reaction, including acidic montmorillonite, phosphotungstic acid silica, phosphorus pentoxide, etc.; The weight ratio of the partially sulfonated polystyrene to the dehydrating agent in the cation - exchange membrane slurry is 1:0.005 - 0.3;

[0078] n) Coating of cation - exchange membrane: Lay the cation - exchange membrane mesh prepared in step f) flat on the PET film, and then evenly coat the cation - exchange membrane slurry prepared in step m) on the cation - exchange membrane mesh and the PET film. Then bake at 60 - 90 °C for 2 - 10 hours, and then bake at 90 - 150 °C for 2 - 10 hours. After complete drying, separate the cation - exchange membrane from the PET film; Thus, the preparation of the homogeneous cation - exchange membrane is completed.

[0079] 5. Preparation of homogeneous anion - exchange membrane;

[0080] o) Preparation of chloromethylated polystyrene slurry: In a reaction kettle with stirring, first inject a certain amount of good solvents for chloromethylated polystyrene, such as DCE, DMF, DMAC, DMSO, etc. After starting the stirring, first add a part of the chloromethylated polystyrene from step l), then add an appropriate amount of toughening polymers, which can be one or more mixtures of polymers such as ether bond-containing polymers, amides, lipids, rubber-like polymers, etc. Then add a certain amount of initiator, double-bond-containing mono-tertiary amine, and non-double-bond-containing mono-tertiary amine. After complete dissolution, prepare an anion membrane slurry;

[0081] The above double-bond-containing mono-tertiary amine is selected from at least one of N,N-dimethylallylamine, N,N,2-trimethylallylamine, 3-(dimethylamine)acrylonitrile;

[0082] The above non-double-bond-containing mono-tertiary amine is selected from at least one of triethanolamine, triethylamine, dodecyldimethyltertiary amine, dioctyldimethyltertiary amine;

[0083] p) Anion membrane coating: Lay the anion membrane mesh cloth from step g) flat on the PET film, then evenly coat the anion membrane slurry from step o) on the anion membrane mesh cloth and the PET film. Then, dry at 60 - 110 °C for 2 - 10 hours. After complete drying, separate the anion membrane from the PET film; Thus, the preparation of the homogeneous anion membrane is completed.

[0084] In one embodiment, in the above step b), the impregnation temperature is 40 - 60 °C and the time is 10 - 60 minutes;

[0085] In one embodiment, in the above step c), the polymerization temperature is 65 - 80 °C and the time is 3 - 10 hours;

[0086] In one embodiment, in the above step f), the sulfonation reaction temperature is 30 - 80 °C and the reaction time is 0.3 - 4 hours;

[0087] In one embodiment, in the above step g), the chloromethylation reaction temperature is 20 - 50 °C and the reaction time is 0.1 - 8 hours; the soaking temperature of the dried membrane sheet is 30 - 50 °C and the soaking time is 0.5 - 6 hours; the drying temperature after soaking is 40 - 80 °C and the drying time is 4 - 8 hours;

[0088] In one embodiment, in the above step i), the sulfonation reaction temperature is 40 - 80 °C and the reaction time is 2 - 8 hours;

[0089] In one embodiment, in the above step k), the chloromethylation reaction temperature is 30 - 50 °C and the reaction time is 2 - 8 hours;

[0090] In one embodiment, in the above step n), the drying temperature of the first stage is 70 - 80 °C, the drying time is 4 - 8 hours, the drying temperature of the second stage is 100 - 140 °C, and the drying time is 4 - 8 hours;

[0091] In one embodiment, in the above step p), the drying temperature is 70 - 90 °C, and the drying time is 4 - 8 hours;

[0092] The homogeneous membrane of the present invention and its preparation method are further described below through specific examples:

[0093] Example 1:

[0094] The preparation method of the homogeneous cationic membrane in this example includes the following steps:

[0095] Step 1: Take 1000 g of styrene, 140 g of divinylbenzene, and 1 g of azobisisobutyronitrile, stir and mix evenly at room temperature to prepare an impregnating solution; take a HDPE woven mesh cloth with a thickness of about 0.1 mm, completely immerse it in the impregnating solution, after heating to 55 °C, keep the temperature for impregnation for 15 minutes; after the impregnation is completed, take out the mesh cloth, remove the impregnating solution attached to the surface, lay it flat between two PET films, seal the edges of the PET films with tape, then put it into a hot water bath at 80 °C, take it out after keeping the temperature for 5 hours, separate the mesh cloth from the PET films, soak the obtained mesh cloth in 98% concentrated sulfuric acid, react at 80 °C for 3 hours, wash it with clear water and dry it to obtain a cationic membrane mesh cloth;

[0096] Step 2: Inject 250 mL of DCE into a 500 mL three-necked flask, start stirring, add 10 g of polystyrene, heat it to 50 °C in a constant temperature water bath, after complete dissolution, slowly drop 98% concentrated sulfuric acid into it, control the dropping time to add 8 mL of concentrated sulfuric acid in about 45 minutes, keep the temperature for reaction for 5 hours, then pour the reaction solution into ice water to precipitate, filter and wash it several times and dry it for standby;

[0097] Step 3: Take 5 g of the partially sulfonated polystyrene prepared in Step 2, dissolve it in 45 mL of DMAC, after complete dissolution, add 0.5 g of phosphorus pentoxide, after complete dissolution, prepare a cationic membrane slurry for standby;

[0098] Step 4: Lay a PET film flat on a glass plate, then lay the cationic membrane mesh cloth obtained in Step 1 flat on the PET film and fix it. Then evenly coat the cationic membrane slurry on the mesh cloth and the PET film, and then put it into an oven for drying. The drying temperature of the first stage is set at 70 °C, the drying time is 5 hours, the drying temperature of the second stage is set at 120 °C, and the drying time is 7 hours; after drying, separate the membrane sheet from the PET film to obtain a homogeneous cationic membrane.

[0099] Example 2:

[0100] The preparation method of the homogeneous anion membrane of this embodiment includes the following steps:

[0101] Step 1: Take 1000 g of styrene, 140 g of divinylbenzene, and 1 g of azobisisobutyronitrile, stir and mix evenly at room temperature to prepare an impregnating solution; take a HDPE woven mesh cloth with a thickness of about 0.1 mm, completely immerse it in the impregnating solution, heat it to 55 °C, and keep it for impregnation for 15 minutes; after the impregnation is completed, take out the mesh cloth, remove the attached impregnating solution on the surface, lay it flat between two PET films, then seal the edges of the PET films with tape, and then put it into a hot water bath at 80 °C, take it out after keeping it for 5 hours, separate the mesh cloth from the PET film, soak the obtained mesh cloth in chloromethyl methyl ether solution, react at 35 °C for 3 hours, wash it with clean water and dry it, then soak it in N,N-dimethylallylamine solution, the temperature is 20 - 60 °C, the time is 0.2 - 10 hours, take it out after completion, remove the excess N,N-dimethylallylamine solution on the membrane surface, and then dry it at 40 - 90 °C for 2 - 10 hours; thus, the preparation of the anion membrane mesh cloth is completed;

[0102] Step 2: Inject 250 mL of DCE into a 500 mL three-necked flask, start stirring, add 10 g of polystyrene and 0.2 g of SnCl 4 , heat it to 35 °C in a constant temperature water bath, after complete dissolution, slowly dropwise add chloromethyl methyl ether to it, control the dropping time to finish adding 30 mL of chloromethyl methyl ether in about 65 minutes, keep the reaction for 4 hours, then pour the reaction solution into methanol to precipitate, filter and wash it repeatedly and then dry it for standby;

[0103] Step 3: Take 5 g of the partially chloromethylated polystyrene prepared in Step 2 and 1 g of polyethersulfone, dissolve them in 54 mL of DMAC, after complete dissolution, add 1.1 mL of N,N-dimethylallylamine, 1.64 g of triethanolamine, and 0.012 g of BPO and mix and dissolve them to prepare an anion membrane slurry for standby;

[0104] Step 4: Lay a PET film flat on a glass plate, then lay the anion membrane mesh cloth obtained in Step 1 flat on the PET film and fix it, then evenly coat the anion membrane slurry on the mesh cloth and the PET film, after completion, put it into an oven for drying, the drying temperature is 70 - 90 °C, the drying time is 4 - 8 hours, take it out after drying, separate the membrane sheet from the PET film to obtain a homogeneous anion membrane.

[0105] Example 3:

[0106] The preparation method of the homogeneous cation membrane of this embodiment is different from that of Example 1 in that: Step 1 is different;

[0107] Specifically, in step 1, a PPS mesh cloth with a thickness of 0.1 mm is selected, and the PPS mesh cloth is directly immersed in 93% sulfuric acid. After reacting for 20 minutes at 30 °C, the mesh cloth is taken out, washed with clean water to remove the residual acid, and then dried for standby;

[0108] Other steps are the same as those in Example 1.

[0109] Example 4:

[0110] The preparation method of the homogeneous anion membrane in this example is different from that in Example 2 in that: step 1 is different;

[0111] Specifically, in step 1, a PPS mesh cloth with a thickness of 0.1 mm is selected, and the PPS mesh cloth is directly immersed in chloromethyl ether. After reacting for 8 minutes at 20 °C, the mesh cloth is taken out, washed with clean water to remove the residues, and then dried for standby;

[0112] Other steps are the same as those in Example 2.

[0113] Comparative Example 1:

[0114] The preparation method of the homogeneous cation membrane in this comparative example is different from that in Example 1 in that: step 1 is different;

[0115] Specifically, the mesh cloth is not hydrophilically modified in step 1, but is directly used for film making;

[0116] Other steps are the same as those in Example 1.

[0117] Comparative Example 2:

[0118] The preparation method of the homogeneous cation membrane in this comparative example is different from that in Example 1 in that: step 1 is different;

[0119] Specifically, after the mesh cloth is impregnated, it is not sulfonated with sulfuric acid and is directly used for film making;

[0120] Other steps are the same as those in Example 1.

[0121] Comparative Example 3:

[0122] The preparation method of the homogeneous anion membrane in this comparative example is different from that in Example 2 in that: step 1 is different;

[0123] Specifically, the mesh cloth is not hydrophilically modified in step 1, but is directly used for film making;

[0124] Other steps are the same as those in Example 2.

[0125] The homogeneous membranes of the above Examples 1-4 and Comparative Examples 1-3 were respectively tested, and the test results are shown in Table 1.

[0126] Table 1 Test Results of Homogeneous Membranes

[0127] ;

[0128] Among them, the method for testing the permeation amount of the homogeneous membrane is as follows:

[0129] Apparatus: Two hollow cubes with a side length of 8 cm and a wall thickness of 1.2 cm, one side of which is not closed and there is a small hole with a diameter of 5 mm on one side; Place the non-closed sides of the two hollow cubes facing each other, ensure that the side with the small hole faces upward, then place a gasket for sealing on each side of the 8*8 cm membrane to be tested, place it between the hollow cubes, and finally lock the apparatus with an external screw to ensure good sealing and no liquid leakage.

[0130] Testing method: Place the above apparatus in a water bath at 25 °C, place a small magnetic stirrer at the bottom of the apparatus and at the center of the cube respectively, and place a magnetic stir bar in each of the two cube containers. Then pour 100 mL of preheated 4 mol / L sodium chloride solution and 100 mL of pure water into the two containers respectively, start stirring, stop stirring after 1 hour, suck out all the solution on the pure water side, and then suck out all the solution after rinsing 3 times with pure water. All are injected into a 250 mL volumetric flask for volume fixation, and then take 100 mL to test the chloride ion concentration to determine the amount of NaCl in the 250 mL solution.

[0131] The permeation amount of the present invention is characterized by the solute permeability coefficient, and its calculation formula is as follows:

[0132] ;

[0133] ;

[0134] Among them: σ is the solute permeability coefficient, with the unit mmol / (m 2 ·h·mol / L); q is the total amount of sodium chloride permeated into pure water, with the unit mmol; A is the effective area of the test membrane, with the unit m 2 , generally 0.00314 m 2 ; Δ C is the concentration difference, with the unit mol / L, that is, the initial concentration of the permeate is used as the concentration difference, which is 4 mol / L here; t is the test duration, with the unit h, usually 1 h; c Ag is the concentration of the silver nitrate standard solution, with the unit mol / L; V is the amount of the silver nitrate standard solution consumed during titration, with the unit mL.

[0135] The diaphragms of the above Examples 1-4 and Comparative Examples 1-3 were tested, and the tensile fracture strength was ≥ 40 MPa and the bursting strength was ≥ 1.0 MPa. Compared with the tensile fracture strength (≤ 10 MPa) and bursting strength (≤ 0.5 MPa) of the diaphragm without non-woven fabric support developed by ourselves, there has been a great improvement, which also correspondingly improves the service adaptability and lifespan of the membrane.

[0136] As can be seen from Table 1, as long as the present invention is implemented under appropriate conditions, the osmotic energy of the homogeneous membrane can be effectively reduced, which is beneficial to the preparation of high-purity products and effectively reduces energy consumption and operating costs.

[0137] In view of the large number of embodiments of the present invention, the raw materials and dosages involved can be selected according to actual needs within the limited range. The experimental data of each embodiment are huge and numerous, and it is not suitable to list them one by one here. However, the contents to be verified and the final conclusions obtained in each embodiment are similar. Therefore, the verification contents of each embodiment will not be described one by one here.

[0138] The above description only details the preferred embodiments and principles of the present invention. For those of ordinary skill in the art, based on the idea provided by the present invention, there will be changes in the specific implementation manners, and these changes should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a homogeneous membrane, characterized in that: The following steps are involved: (1) Sulfonation modification of the mesh to obtain a cationic membrane mesh; (2) Laying the cationic membrane mesh on the PET film, evenly coating the cationic membrane slurry on the mesh and the PET film, and separating the PET film after drying to obtain a homogeneous cationic membrane; The cation membrane slurry is partially sulfonated polystyrene, and the dehydrating agent is completely dissolved in a good solvent.

2. The preparation method according to claim 1, characterized in that: The dehydrating agent is phosphorus pentoxide; The good solvent is selected from at least one of N,N-dimethylformamide, dimethylacetamide and dimethyl sulfoxide.

3. The preparation method according to claim 1, characterized in that: In step (2), the drying process includes: first drying at 60-90°C for 2-10 hours, and then drying at 90-150°C for 2-10 hours; The preparation process of partially sulfonated polystyrene includes: The sulfonation liquid is added into the polystyrene solution to carry out the sulfonation reaction, the sulfonation reaction temperature is 30-90°C, and the reaction time is 0.5-10 hours; The feed liquid after the sulfonation reaction is completed is added into an ice-water mixture, and the precipitated solid is filtered, washed and dried to obtain partially sulfonated polystyrene.

4. The preparation method according to claim 1, characterized in that: The step (1) specifically includes the following steps: (11) Prepare an impregnation liquid with styrene, divinylbenzene and initiator, heat it to 30-70°C, completely immerse the mesh in the impregnation liquid, and take out the mesh after soaking for 5-120 minutes. After removing the excess impregnation liquid, lay it flat between two PET films, and seal the edges of the PET films with tape; (12) placing the PET film and the mesh together in a hot water tank for polymerization reaction, taking them out from the hot water tank after the polymerization reaction is completed, and separating the mesh from the PET film; The hot water temperature of the hot water tank is 65-90°C, and the reaction time is 1-15 hours; (13) The separated mesh is placed in the sulfonation liquid of the sulfonation reaction tank for sulfonation reaction. After the sulfonation reaction is completed, the mesh is washed and dried; The temperature of the sulfonation reaction is 30-90° C., and the reaction time is 0.3-10 hours.

5. The preparation method according to claim 1 or 4, characterized in that: The mesh cloth is a woven cloth, a non-woven cloth or a porous film, and is made of low-density polyethylene LDPE, high-density polyethylene HDPE, polyvinyl chloride PVC, polyphenylene sulfide PPS or polyetheretherketone PEEK.

6. A method for preparing a homogeneous membrane, characterized in that: The following steps are involved: (a) Chloromethylation modification of the mesh to obtain a cationic membrane mesh; (b) laying the anion membrane mesh on the PET film, evenly coating the anion membrane slurry on the mesh and the PET film, and separating the PET film after drying to obtain a homogeneous anion membrane; The anion membrane slurry is partially chloromethylated polystyrene, toughening polymer, double-bond-containing monotertiary amine, double-bond-free monotertiary amine, and initiator completely dissolved in a good solvent; The step (a) specifically comprises the following steps: (a1) preparing an impregnation liquid with styrene, divinylbenzene and initiator, heating it to 30-70°C, and then completely immersing the mesh in the impregnation liquid. After immersing for 5-120 minutes, the mesh is taken out, and after removing the excess impregnation liquid, it is laid flat between two PET films, and the edges of the PET films are sealed with tape; (a2) placing the PET film and the mesh together in a hot water tank for polymerization reaction, taking them out from the hot water tank after the polymerization reaction is completed, and separating the mesh from the PET film; The hot water temperature of the hot water tank is 65-90°C, and the reaction time is 1-15 hours; (a3) The separated mesh is placed in chloromethyl ether in a chloromethylation reaction tank for chloromethylation reaction at a reaction temperature of 20-60°C for a reaction time of 0.1-20 hours. After the chloromethylation reaction is completed, the mesh is washed and dried, and then immersed in a double-bond monotertiary amine solution at a temperature of 20-60°C for a time of 0.1-10 hours. After the immersion is completed, the mesh is taken out to remove excess double-bond monotertiary amine solution on the surface of the membrane, and then dried at 40-90°C for 2-10 hours.

7. The preparation method according to claim 6, characterized in that: The preparation process of the partially chloromethylated polystyrene comprises: Adding chloromethyl ether to a polystyrene solution for chloromethylation reaction at a reaction temperature of 20-60° C. for a reaction time of 1-20 hours to obtain a chloromethylation-completed feed solution; The chloromethylated feed liquid is added into methanol, and the precipitated solid is filtered, washed and dried to obtain partially chloromethylated polystyrene.

8. The preparation method according to claim 6, characterized in that: In the step (b), the double-bond-containing monotertiary amine is selected from at least one of N,N-dimethylallylamine, N,N,2-trimethylallylamine, and 3-(dimethylamino)acrylonitrile; The monotertiary amine without double bonds is selected from at least one of triethanolamine, triethylamine, dodecyldimethyl tertiary amine and dioctylmethyl tertiary amine; The drying temperature is 60-110°C and the drying time is 2-10 hours.

9. A homogeneous membrane, characterized in that The homogeneous membrane is a homogeneous cation membrane prepared by the preparation method according to any one of claims 1 to 5 or a homogeneous anion membrane prepared by the preparation method according to any one of claims 6 to 8.