Homogeneous ion exchange membrane prepared from reclaimed materials and preparation method of homogeneous ion exchange membrane

Abstract

The invention belongs to the technical field of polymer functional membranes, and particularly relates to a homogeneous ion exchange membrane prepared from reclaimed materials and a preparation method of the homogeneous ion exchange membrane. The preparation method of the homogeneous ion exchange membrane prepared from the reclaimed materials comprises the following steps: treating the reclaimed materials, then carrying out melt extrusion granulation, measuring the related performance of the reclaimed materials, supplementing resin powder, and then carrying out melt extrusion; and then, carrying out melt casting to prepare a homogeneous mixed acid-based membrane, embedding the reinforced matrix material into the homogeneous mixed acid-based membrane, and finally, soaking to obtain the homogeneous ion exchange membrane. According to the homogeneous ion exchange membrane prepared from the reclaimed materials, the rim charge in the preparation process of a chlor-alkali ion exchange membrane composite membrane is used as a raw material, and the prepared homogeneous ion exchange membrane has good impurity tolerance and impurity blocking capacity, can operate in a complex environment, has good mechanical strength, and can be used for preparing the homogeneous ion exchange membrane. The raw material cost is low; the invention further provides a preparation method, and the preparation process is simple.

Description

Technical Field

[0001] This invention belongs to the field of polymer functional membrane technology, specifically relating to a homogeneous ion exchange membrane prepared from recycled materials and its preparation method. Background Technology

[0002] Ion exchange membranes are polymer membrane materials with selective ion permeation capabilities. Their core characteristic is that they can allow ions with specific charges to pass through under the drive of an electric field or concentration gradient, while preventing the large-scale permeation of ions with opposite charges, neutral molecules, or solvents (such as water molecules). They are key materials in membrane separation technology, electrochemical engineering, and other fields, and are widely used in chlor-alkali industry, fuel cells, water treatment, energy storage, and other scenarios.

[0003] Currently, the chlor-alkali ion exchange membranes on the market are mainly composite ion exchange membranes, whose structure consists of three key parts: a sulfonic acid resin layer responsible for conducting sodium ions on the anode side, a carboxylic acid resin layer blocking hydroxide ions on the cathode side, and a matrix reinforcement material providing mechanical support. In practical applications, the specifications and dimensions of the electrolyzers prepared by different companies are different. The membranes produced in production need to be cut before use. In addition, the normal production process will also cut long strips of edge material on both sides of the membrane. Since it is impossible to effectively recycle the perfluorosulfonic acid resin and perfluorocarboxylic acid resin separately, and the recycling cost is high, the edge material generated by the above-mentioned cutting is treated as waste membrane in production. The disposal methods for waste ion exchange membranes are mostly landfill and centralized incineration, which causes great waste of resources and environmental pollution.

[0004] CN1884352A discloses a method for preparing perfluorosulfonic acid resin solution using waste ion exchange membranes from the chlor-alkali industry. First, the waste membrane containing perfluorosulfonic acid resin and perfluorocarboxylic acid resin is swollen using a low-grade alcohol, and then processed into resin particles using an emulsifier. Subsequently, in an autoclave, using a specific ratio of alcohol / water mixture as a good solvent, the particles are dissolved under high temperature, high pressure, and nitrogen protection. Solid-liquid separation yields the perfluorosulfonic acid resin solution and solid perfluorocarboxylic acid resin. This process achieves the recovery of perfluorosulfonic acid resin, producing a product with high purity, extremely low impurity content, strong repeatability, and stable control of solution viscosity, concentration, and other indicators. However, this method has certain drawbacks. First, it cannot effectively recover perfluorocarboxylic acid resin, only obtaining a semi-dissolved layered or flocculent solid perfluorocarboxylic acid resin. Second, the recovered perfluorosulfonic acid resin solution dissolves in an alcohol-water solution and requires further processing before it can be used for new membrane preparation. Finally, the recovery process uses high temperature and high pressure, making operation difficult and energy-intensive. These factors restrict the industrialization and application of this method.

[0005] In summary, compared to waste ion exchange membranes, the scrap generated during the production process has only undergone preliminary processing and has not been electrolyzed, so there are no electrolytic impurities. Therefore, if this scrap can be effectively utilized, production costs can be reduced and expenses can be saved. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned problems by providing a homogeneous ion exchange membrane prepared from recycled materials. Using scrap materials from the chlor-alkali ion exchange membrane preparation process as raw materials, a homogeneous ion exchange membrane is finally prepared through regranulation and resin ratio adjustment. When applied to the complex field of electrodialysis, it exhibits good impurity tolerance and impurity blocking capabilities. Furthermore, the homogeneous ion exchange membrane itself possesses good mechanical strength, ensuring operational safety and service life. This invention also provides a simple preparation method.

[0007] The method for preparing a homogeneous ion exchange membrane using recycled materials according to the present invention includes the following steps: (1) Soak, clean, dry and cut the recycled material into sheet-like mixed acid resin granules. The prepared sheet-like mixed acid resin granules are melt-extruded and granulated under a protective gas atmosphere and then further cut. (2) Determine the ratio and ion exchange capacity (IEC) of perfluorosulfonic acid resin and perfluorocarboxylic acid resin in the mixed acid material, and add perfluorosulfonic acid resin powder and perfluorocarboxylic acid resin powder to it. After mixing evenly, repeat the melt extrusion granulation step, cool down and roll up to obtain mixed acid resin granules. (3) A homogeneous mixed acid-based film was prepared by melt casting of mixed acid resin; (4) The reinforcing matrix material is embedded into the heated and softened homogeneous mixed acid matrix membrane to obtain the reinforced homogeneous membrane; (5) Immerse the enhanced homogeneous membrane from step (4) in a mixed solvent and maintain the temperature at 40-80℃ to obtain a homogeneous ion exchange membrane.

[0008] The recycled material is a chlor-alkali ion exchange membrane composite membrane, which is prepared from perfluorosulfonic acid resin and perfluorocarboxylic acid resin, preferably products of Shandong Dongyue Polymer Materials Co., Ltd.; before soaking, the unembedded reinforcing matrix material in the recycled material needs to be removed.

[0009] In step (1), the solvent used for soaking and cleaning is one of methanol, ethanol, or propylene glycol, with ethanol being preferred, and the soaking and cleaning time is 18-24 hours.

[0010] The protective gas includes one or more of nitrogen, argon, and helium, with nitrogen being preferred.

[0011] The perfluorosulfonic acid resin powder is obtained by in-situ polymerization of tetrafluoroethylene and perfluoro3,6-dioxa-4-methyl-7-octenesulfonyl fluoride, with an ion exchange capacity of 0.8-1.2 mmol / g; the perfluorocarboxylic acid resin powder is obtained by copolymerization of perfluoro4,7-dioxa-5-methyl-8-nonenoate methyl ester, with an ion exchange capacity of 0.8-1.2 mmol / g.

[0012] In step (1), the width of the flake-shaped mixed acid resin granules is 0.5cm-1.5cm and the length is 1.5cm-2.5cm.

[0013] The method for determining the ratio of perfluorosulfonic acid resin and perfluorocarboxylic acid resin in step (2) is as follows: the prepared granules are placed in a hydrothermal reactor, and ethanol and water with a volume ratio of 1:1 are added. The mixture is then heated in an oil bath at 260°C for 1 hour to obtain a perfluorosulfonic acid resin solution and a perfluorocarboxylic acid resin solid. The weight and IEC are then measured.

[0014] In step (2), the mass ratio of perfluorosulfonic acid resin to perfluorocarboxylic acid resin in the mixed acid resin granules is 4:(1-1.5).

[0015] In step (3), the melt casting temperature is 270-350℃, and the thickness of the homogeneous mixed acid base film is 140-200μm; in step (4), the heating softening temperature is 100-150℃.

[0016] The reinforcing matrix material is woven from one or more of polytetrafluoroethylene, polyethylene terephthalate, polyvinylidene fluoride, polyimide, polyphenylene sulfone amide, polybenzimidazole, polyisophthaloylm-phenylenediamine, and polyamide-imide. Preferably, the reinforcing matrix material is woven from polytetrafluoroethylene filaments, which are monofilaments with an elastic modulus of 7 N / Tex and a breaking elongation of 5.0%. The filaments are woven on a water-jet loom at a weaving density of 20 threads / inch and a weaving tension of 800 N. The structure of the reinforcing mesh is plain weave.

[0017] The mixed solvent is composed of an organic solvent and an aqueous solution of an alkali metal hydroxide. The concentrations of both the organic solvent and the alkali metal hydroxide in the mixed solvent are 15-30 wt.%. The organic solvent is one of N,N-dimethylformamide, dimethyl sulfoxide, toluene, trichloroethylene, carbon tetrachloride, and isopropanol. The alkali metal hydroxide is one of potassium hydroxide and sodium hydroxide. Preferably, the organic solvent is one of N,N-dimethylformamide and dimethyl sulfoxide.

[0018] The homogeneous ion exchange membrane prepared from recycled materials is obtained by the above-described preparation method.

[0019] This invention eliminates the need for complex processes to separate perfluorosulfonic acid resin and perfluorocarboxylic acid resin. Instead, it obtains mixed acid granules through recycling and regranulation, which are used to prepare homogeneous mixed acid ion exchange membranes. These membranes possess tolerance not found in single-layer or composite membranes, exhibiting better barrier properties against waste acid and alkali solutions containing numerous impurities or organic solvents. Furthermore, the uniform mixing of the two resins results in enhanced mechanical strength, making them suitable for recovering precious metals, wastewater recycling, and the desalination and purification of metal salts.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention recycles the edge material of the chlor-alkali ion composite membrane and limits the ion exchange capacity and ratio of the perfluorosulfonic acid resin and the perfluorocarboxylic acid resin to prepare a mixed acid homogeneous ion exchange membrane. The mixed acid homogeneous ion exchange membrane has good impurity tolerance and impurity blocking ability and can operate stably in complex environments.

[0021] (2) The mixed acid homogenized membrane prepared by the present invention has higher mechanical strength than single perfluorosulfonic acid membrane, perfluorocarboxylic acid membrane, and perfluorosulfonic acid-perfluorocarboxylic acid composite membrane, and can better adapt to complex environments and is safer and more reliable.

[0022] (3) The method for preparing the mixed acid homogenized membrane described in this invention is simple and more suitable for large-scale industrial production applications. Detailed Implementation

[0023] The present invention will be further described below with reference to the embodiments and comparative examples. Unless otherwise specified, the raw materials used in the embodiments and comparative examples are all conventional commercially available raw materials, and the process methods used in the embodiments and comparative examples are all conventional methods in the art unless otherwise specified.

[0024] The raw materials used in the examples and comparative examples are described below: The recycled materials are all edge materials generated by Shandong Dongyue Polymer Materials Co., Ltd. during the production of chlor-alkali ion exchange membrane composite membranes. The chlor-alkali ion exchange membrane composite membranes are made of perfluorosulfonic acid resin and perfluorocarboxylic acid resin. Before soaking, the non-embedded reinforcing matrix material in the recycled materials has been removed. The reinforcing matrix material is woven from polytetrafluoroethylene (PTFE) filaments. The PTFE filaments are monofilaments with an elastic modulus of 7 N / Tex and a breaking elongation of 5.0%. They are woven on a water-jet loom with a weaving density of 20 filaments / inch and a weaving tension of 800 N. The reinforcing mesh has a plain weave structure.

[0025] The method for preparing the homogeneous ion exchange membrane using recycled materials includes the following steps: (1) Place the recycled material in an ethanol solution and soak for 18-24 hours. Then dry and cut it into sheet-like mixed acid resin granules with a width of 0.5cm-1.5cm and a length of 1.5cm-2.5cm. Melt and extrude the prepared sheet-like mixed acid resin granules under a protective gas atmosphere and cut them further. (2) The proportion and ion exchange capacity (IEC) of perfluorosulfonic acid resin and perfluorocarboxylic acid resin in the mixed acid material were determined, and perfluorosulfonic acid resin powder and perfluorocarboxylic acid resin powder were added to it so that the mass ratio of perfluorosulfonic acid resin to perfluorocarboxylic acid resin in the mixed acid resin granules was 4:(1-1.5). After mixing evenly, the melt extrusion granulation step was repeated again, and the mixture was cooled and rolled up to obtain mixed acid resin granules. The ion exchange capacity of perfluorosulfonic acid resin powder was 0.8-1.2 mmol / g, and the ion exchange capacity of perfluorocarboxylic acid resin powder was 0.8-1.2 mmol / g. (3) At a temperature of 270-350℃, the mixed acid resin granules are melt-cast to prepare a homogeneous mixed acid base film with a thickness of 140-200μm; (4) The reinforcing matrix material is embedded into the heated and softened homogeneous mixed acid base film to obtain the reinforced homogeneous film. The heating and softening temperature is 100-150℃. (5) Immerse the enhanced homogeneous membrane from step (4) in a mixed solvent and maintain the temperature at 40-80℃ to obtain a homogeneous ion exchange membrane; wherein the mixed solvent is composed of an organic solvent and an aqueous solution of an alkali metal hydroxide, and the concentrations of the organic solvent and the alkali metal hydroxide in the mixed solvent are both 15-30 wt.%, the organic solvent is one of N,N-dimethylformamide and dimethyl sulfoxide; the alkali metal hydroxide is one of potassium hydroxide and sodium hydroxide.

[0026] Example 1 The method for preparing the homogeneous ion exchange membrane using recycled materials includes the following steps: (1) The recycled material was placed in an ethanol solution and soaked for 20 hours. Then it was dried and cut into sheet-like mixed acid resin granules with a width of 0.5 cm and a length of 1.5 cm. The prepared sheet-like mixed acid resin granules were melt-extruded and granulated under a nitrogen atmosphere and then further cut. (2) The proportion and ion exchange capacity (IEC) of perfluorosulfonic acid resin and perfluorocarboxylic acid resin in the mixed acid material were determined, and perfluorosulfonic acid resin powder and perfluorocarboxylic acid resin powder were added to it so that the mass ratio of perfluorosulfonic acid resin to perfluorocarboxylic acid resin in the mixed acid resin granules was 4:1.25. After mixing evenly, the melt extrusion granulation step was repeated again, and the mixture was cooled and rolled up to obtain mixed acid resin granules. The ion exchange capacity of perfluorosulfonic acid resin powder was 0.8 mmol / g, and the ion exchange capacity of perfluorocarboxylic acid resin powder was 0.8 mmol / g. (3) At a temperature of 270℃, a homogeneous mixed acid base film with a thickness of 140μm was prepared by melt casting of mixed acid resin granules. (4) The reinforcing matrix material is embedded into the heated and softened homogeneous mixed acid matrix film to obtain the reinforced homogeneous film. The heating and softening temperature is 100℃. (5) Immerse the enhanced homogeneous membrane from step (4) in a mixed solvent, maintain the temperature at 80°C, and transform for 80 min to obtain a homogeneous ion exchange membrane; wherein the mixed solvent is composed of dimethyl sulfoxide and NaOH aqueous solution, and the concentrations of dimethyl sulfoxide and NaOH in the mixed solvent are both 15 wt.%.

[0027] Example 2 The method for preparing the homogeneous ion exchange membrane using recycled materials includes the following steps: (1) The recycled material was placed in an ethanol solution and soaked for 18 hours. Then it was dried and cut into sheet-like mixed acid resin granules with a width of 1 cm and a length of 2 cm. The prepared sheet-like mixed acid resin granules were melt-extruded and granulated under a nitrogen atmosphere and then further cut. (2) The proportion and ion exchange capacity (IEC) of perfluorosulfonic acid resin and perfluorocarboxylic acid resin in the mixed acid material were determined, and perfluorosulfonic acid resin powder and perfluorocarboxylic acid resin powder were added to it so that the mass ratio of perfluorosulfonic acid resin to perfluorocarboxylic acid resin in the mixed acid resin granules was 4:1.5. After mixing evenly, the melt extrusion granulation step was repeated again, and the mixture was cooled and rolled up to obtain mixed acid resin granules. The ion exchange capacity of perfluorosulfonic acid resin powder was 1.0 mmol / g, and the ion exchange capacity of perfluorocarboxylic acid resin powder was 1.0 mmol / g. (3) At a temperature of 350℃, the mixed acid resin granules were melt-cast to prepare a homogeneous mixed acid base film with a thickness of 170μm; (4) The reinforcing matrix material is embedded into the heated and softened homogeneous mixed acid matrix film to obtain the reinforced homogeneous film. The heating and softening temperature is 130℃. (5) Immerse the enhanced homogeneous membrane from step (4) in a mixed solvent, maintain the temperature at 60°C, and transform for 80 min to obtain a homogeneous ion exchange membrane; wherein the mixed solvent is composed of N,N-dimethylformamide and KOH aqueous solution, and the concentrations of N,N-dimethylformamide and KOH in the mixed solvent are both 15 wt.%.

[0028] Example 3 The method for preparing the homogeneous ion exchange membrane using recycled materials includes the following steps: (1) The recycled material was placed in an ethanol solution and soaked for 24 hours. Then it was dried and cut into sheet-like mixed acid resin granules with a width of 1.5 cm and a length of 2.5 cm. The prepared sheet-like mixed acid resin granules were melt-extruded and granulated under a nitrogen atmosphere and then further cut. (2) The proportion and ion exchange capacity (IEC) of perfluorosulfonic acid resin and perfluorocarboxylic acid resin in the mixed acid material were determined, and perfluorosulfonic acid resin powder and perfluorocarboxylic acid resin powder were added to it so that the mass ratio of perfluorosulfonic acid resin to perfluorocarboxylic acid resin in the mixed acid resin granules was 4:1.2. After mixing evenly, the melt extrusion granulation step was repeated again, and the mixture was cooled and rolled up to obtain mixed acid resin granules; wherein, the ion exchange capacity of perfluorosulfonic acid resin powder was 1.2 mmol / g, and the ion exchange capacity of perfluorocarboxylic acid resin powder was 0.9 mmol / g. (3) At a temperature of 300℃, the mixed acid resin granules were melt-cast to prepare a homogeneous mixed acid base film with a thickness of 170μm; (4) The reinforcing matrix material is embedded into the heated and softened homogeneous mixed acid matrix film to obtain the reinforced homogeneous film. The heating and softening temperature is 140℃. (5) Immerse the enhanced homogeneous membrane from step (4) in a mixed solvent, maintain the temperature at 40°C, and transform for 80 min to obtain a homogeneous ion exchange membrane; wherein the mixed solvent is composed of dimethyl sulfoxide and NaOH aqueous solution, and the concentrations of dimethyl sulfoxide and NaOH in the mixed solvent are both 20 wt.%.

[0029] Example 4 The method for preparing the homogeneous ion exchange membrane using recycled materials includes the following steps: (1) The recycled material was placed in an ethanol solution and soaked for 20 hours. Then it was dried and cut into sheet-like mixed acid resin granules with a width of 1 cm and a length of 2 cm. The prepared sheet-like mixed acid resin granules were melt-extruded and granulated under a nitrogen atmosphere and then further cut. (2) The proportion and ion exchange capacity (IEC) of perfluorosulfonic acid resin and perfluorocarboxylic acid resin in the mixed acid material were determined, and perfluorosulfonic acid resin powder and perfluorocarboxylic acid resin powder were added to it so that the mass ratio of perfluorosulfonic acid resin to perfluorocarboxylic acid resin in the mixed acid resin granules was 4:1. After mixing evenly, the melt extrusion granulation step was repeated again, and the mixture was cooled and rolled up to obtain mixed acid resin granules. The ion exchange capacity of perfluorosulfonic acid resin powder was 0.8 mmol / g, and the ion exchange capacity of perfluorocarboxylic acid resin powder was 1.2 mmol / g. (3) At a temperature of 270℃, the mixed acid resin granules were melt-cast to prepare a homogeneous mixed acid base film with a thickness of 200μm; (4) The reinforcing matrix material is embedded into the heated and softened homogeneous mixed acid matrix film to obtain the reinforced homogeneous film. The heating and softening temperature is 150℃. (5) Immerse the enhanced homogeneous membrane from step (4) in a mixed solvent, maintain the temperature at 50°C, and transform for 80 min to obtain a homogeneous ion exchange membrane; wherein the mixed solvent is composed of dimethyl sulfoxide and NaOH aqueous solution, and the concentrations of dimethyl sulfoxide and NaOH in the mixed solvent are both 30 wt.%.

[0030] Comparative Example 1 The method for preparing the homogeneous ion exchange membrane using recycled materials includes the following steps: (1) The recycled material was placed in an ethanol solution and soaked for 20 hours. Then it was dried and cut into sheet-like mixed acid resin granules with a width of 0.5 cm and a length of 1.5 cm. The prepared sheet-like mixed acid resin granules were melt-extruded and granulated under a nitrogen atmosphere and then further cut. (2) At a temperature of 270℃, the mixed acid material obtained in step (1) was melt-cast to prepare a homogeneous mixed acid base film with a thickness of 140μm; (4) The reinforcing matrix material is embedded into the heated and softened homogeneous mixed acid matrix film to obtain the reinforced homogeneous film. The heating and softening temperature is 100℃. (5) Immerse the enhanced homogenized membrane from step (4) in a mixed solvent, maintain the temperature at 80°C, and transform for 80 min to obtain an ion exchange membrane; wherein the mixed solvent is composed of dimethyl sulfoxide and NaOH aqueous solution, and the concentrations of dimethyl sulfoxide and NaOH in the mixed solvent are both 15 wt.

[0031] Comparative Example 2 The method for preparing the homogeneous ion exchange membrane using recycled materials includes the following steps: (1) The recycled material was placed in an ethanol solution and soaked for 20 hours. Then it was dried and cut into sheet-like mixed acid resin granules with a width of 0.5 cm and a length of 1.5 cm. The prepared sheet-like mixed acid resin granules were melt-extruded and granulated in the air and then further cut. (2) The proportion and ion exchange capacity (IEC) of perfluorosulfonic acid resin and perfluorocarboxylic acid resin in the mixed acid material were determined, and perfluorosulfonic acid resin powder and perfluorocarboxylic acid resin powder were added to it so that the mass ratio of perfluorosulfonic acid resin to perfluorocarboxylic acid resin in the mixed acid resin granules was 4:1.25. After mixing evenly, the melt extrusion granulation step was repeated again, and the mixture was cooled and rolled up to obtain mixed acid resin granules. The ion exchange capacity of perfluorosulfonic acid resin powder was 0.8 mmol / g, and the ion exchange capacity of perfluorocarboxylic acid resin powder was 0.8 mmol / g. (3) At a temperature of 270℃, a homogeneous mixed acid base film with a thickness of 140μm was prepared by melt casting of mixed acid resin granules. (4) The reinforcing matrix material is embedded into the heated and softened homogeneous mixed acid matrix film to obtain the reinforced homogeneous film. The heating and softening temperature is 100℃. (5) Immerse the enhanced homogeneous membrane from step (4) in a mixed solvent, maintain the temperature at 80°C, and transform for 80 min to obtain a homogeneous ion exchange membrane; wherein the mixed solvent is composed of dimethyl sulfoxide and NaOH aqueous solution, and the concentrations of dimethyl sulfoxide and NaOH in the mixed solvent are both 15 wt.%.

[0032] Comparative Example 3 The method for preparing the homogeneous ion exchange membrane using recycled materials includes the following steps: (1) The recycled material was placed in an ethanol solution, soaked for 20 hours, dried, melt-extruded and granulated under a nitrogen atmosphere, and then further cut. (2) The proportion and ion exchange capacity (IEC) of perfluorosulfonic acid resin and perfluorocarboxylic acid resin in the mixed acid material were determined, and perfluorosulfonic acid resin powder and perfluorocarboxylic acid resin powder were added to it so that the mass ratio of perfluorosulfonic acid resin to perfluorocarboxylic acid resin in the mixed acid resin granules was 4:1.5. After mixing evenly, the melt extrusion granulation step was repeated again, and the mixture was cooled and rolled up to obtain mixed acid resin granules. The ion exchange capacity of perfluorosulfonic acid resin powder was 0.8 mmol / g, and the ion exchange capacity of perfluorocarboxylic acid resin powder was 1.2 mmol / g. (3) At a temperature of 230°C, a homogeneous mixed acid base film with a thickness of 200 μm was prepared by melt casting of mixed acid resin granules. (4) The reinforcing matrix material is embedded into the heated and softened homogeneous mixed acid matrix film to obtain the reinforced homogeneous film. The heating and softening temperature is 150℃. (5) Immerse the enhanced homogeneous membrane from step (4) in a mixed solvent, maintain the temperature at 80°C, and transform for 80 min to obtain a homogeneous ion exchange membrane; wherein the mixed solvent is composed of dimethyl sulfoxide and NaOH aqueous solution, and the concentrations of dimethyl sulfoxide and NaOH in the mixed solvent are both 15 wt.%.

[0033] The ion exchange membranes prepared in the examples and comparative examples were subjected to performance tests, as shown in Table 1. The sheet resistance of the homogeneous ion exchange membrane was tested according to the standard SJ / T10171.5 method; the burst strength of the homogeneous ion exchange membrane was tested according to the standard GT / B 454-2020 method; the transverse tensile strength and longitudinal tensile strength of the homogeneous ion exchange membrane were tested according to the standard GT / B 1040.1-2006 method; and the transverse breaking strength and longitudinal breaking strength of the homogeneous ion exchange membrane were tested according to the standard GT / B 16578.2-2009 method.

[0034] The impurity tolerance performance of the ion exchange membranes in the examples and comparative examples was tested, and the results are shown in Table 2. The test process was as follows: the prepared homogeneous ion exchange membrane was placed in a diffusion transdermal tester for diffusion testing with sodium chloride aqueous solution. 200 g / L sodium chloride aqueous solution and 0.01 wt% calcium chloride, magnesium chloride, ferric chloride, barium chloride and potassium iodide were supplied to the anode chamber, and pure water was supplied to the cathode chamber. The test was conducted for 2 hours to obtain the conductivity. The pure water after electrolysis in the cathode chamber was then tested by ICP-OES to obtain the ion concentration.

[0035] Table 1 Performance test data for examples and comparative examples

[0036] Table 2. Performance Test Tables of Products Obtained from Examples and Comparative Examples

[0037] Comparing the results in Tables 1 and 2, Comparative Example 1, unlike Example 1, did not involve re-blending the resin granules, and all other conditions remained the same. However, due to differences in the ratio of fluorosulfonic acid resin to perfluorocarboxylic acid resin in different batches of recycled materials (chlor-alkali ion exchange membrane composite membrane), the recycled material was extremely unstable in the finished product. Furthermore, the melt processing conditions of perfluorosulfonic acid resin and perfluorocarboxylic acid resin differed significantly, making it impossible to obtain a stable and uniform mixed acid membrane using a fixed processing method. The product was a non-uniform ion exchange membrane, making further testing impossible. Comparative Example 2, unlike Example 1, involved direct granulation in air without the use of nitrogen. Under the same protective atmosphere and other conditions, since the perfluorosulfonic acid resin has already been processed into a film at high temperature once, remelting will cause oxidation of the main chain and destruction of the sulfonate groups in the side chain. The destruction of functional groups will greatly reduce the performance of the recycled material, significantly reduce mechanical properties, and make it impossible to maintain a certain strength, which will seriously affect the service life and effectiveness. Compared with Example 1, Comparative Example 3 did not perform orderly cutting of the recycled edge material, which resulted in uneven membrane size during feeding, gas trapped in the feed port, and air trapped in the extruded granules. Ultimately, this resulted in the presence of tiny air bubbles in the membrane mass during the preparation of the ion exchange membrane, which reduced the mechanical strength of the membrane. In summary, optimizing the resin granules and readjusting the ratio of perfluorosulfonic acid resin to perfluorocarboxylic acid resin within their composition is crucial. Different ratios and different IECs result in significant differences in resin processing technology, and the film-forming properties of perfluorosulfonic acid resin and perfluorocarboxylic acid resin also differ markedly. Even if a mixed acid solid can be obtained, a stable film-forming product cannot be achieved. Secondly, the protective atmosphere determines the stability of resin performance and prevents damage caused by repeated processing, while the cutting of the film material avoids the introduction of air bubbles into the ion exchange membrane and improves mechanical strength.

Claims

1. A method for producing a homogeneous ion exchange membrane using a recycled material, characterized by, The method comprises the following steps: (1) soaking and cleaning the recycled material, drying, cutting into sheet-shaped mixed acid resin particles, melting and extruding the prepared sheet-shaped mixed acid resin particles under a protective gas atmosphere, and further cutting; (2) determining the ratio of perfluorosulfonic acid resin and perfluorocarboxylic acid resin and ion exchange capacity in the mixed acid material, adding perfluorosulfonic acid resin powder and perfluorocarboxylic acid resin powder thereto, mixing uniformly, repeating the melting and extruding step again, cooling and winding to obtain mixed acid resin particles; (3) preparing a homogeneous mixed acid base film by melt casting the mixed acid resin; (4) embedding a reinforcing matrix material into the softened homogeneous mixed acid base film to obtain a reinforced homogeneous film; (5) soaking the reinforced homogeneous film in step (4) in a mixed solvent at a temperature of 40-80℃ to obtain a homogeneous ion exchange membrane.

2. The method for producing a homogeneous ion exchange membrane using a recycled material according to claim 1, characterized by, The recycled material is a chlor-alkali ion exchange membrane composite film prepared from perfluorosulfonic acid resin and perfluorocarboxylic acid resin. Before soaking, the reinforcing matrix material not embedded therein needs to be peeled off.

3. The method for producing a homogeneous ion exchange membrane using a recycled material according to claim 1, characterized by, The protective gas atmosphere comprises one or more of nitrogen, argon and helium.

4. The method for producing a homogeneous ion exchange membrane using a recycled material according to claim 1, characterized by, The perfluorosulfonic acid resin powder is obtained by in-situ polymerization of tetrafluoroethylene and perfluoro-3,6-dioxa-4-methyl-7-octene sulfonic acid fluoride, and has an ion exchange capacity of 0.8-1.2 mmol / g; the perfluorocarboxylic acid resin powder is obtained by copolymerization of perfluoro-4,7-dioxa-5-methyl-8-nonene acid methyl ester, and has an ion exchange capacity of 0.8-1.2 mmol / g.

5. The method for preparing a homogeneous ion exchange membrane using recycled materials according to claim 1, characterized in that, In step (1), the sheet-shaped mixed acid resin particles have a width of 0.5-1.5 cm and a length of 1.5-2.5 cm.

6. The method for preparing a homogeneous ion exchange membrane using recycled materials according to claim 1, characterized in that, In step (2), the mass ratio of perfluorosulfonic acid resin to perfluorocarboxylic acid resin in the mixed acid resin is 4: (1-1.5).

7. The method for preparing a homogeneous ion exchange membrane using recycled materials according to claim 1, characterized in that, In step (3), the melt casting temperature is 270-350℃, and the homogeneous mixed acid base film obtained has a thickness of 140-200 μm; in step (4), the heating softening temperature is 100-150℃.

8. The method for producing a homogeneous ion exchange membrane with recycled materials according to claim 1, characterized by, The reinforcing matrix material is woven from one or more of polytetrafluoroethylene, polyethylene terephthalate, polyvinylidene fluoride, polyimide, polyphenylsulfone amide, polybenzimidazole, poly-m-phenylene isophthalamide and polyamide-imide.

9. The method for preparing a homogeneous ion exchange membrane using recycled materials according to claim 1, characterized in that, The mixed solvent is composed of an organic solvent and an aqueous alkali metal hydroxide solution, and the concentration of the organic solvent and the aqueous alkali metal hydroxide in the mixed solvent is 15-30 wt.%, the organic solvent is one of N,N-dimethylformamide, dimethyl sulfoxide, toluene, trichloroethylene, carbon tetrachloride and isopropyl alcohol, and the alkali metal hydroxide is one of potassium hydroxide and sodium hydroxide.

10. A homogeneous ion exchange membrane prepared from recycled material, which is prepared by the method of any one of claims 1-9.

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