A release film for flexible proton exchange membrane and a method for manufacturing the same

Abstract

This invention belongs to the field of release material technology, and relates to a release membrane for proton exchange membranes and its preparation method. The release membrane includes a base membrane and a release layer disposed on either side of the base membrane. The coating solution of the release layer comprises the following substances in parts by weight: 5-10 parts polyvinyl alcohol, 5-10 parts polyvinyl chloride, 5-20 parts water-based modified acrylic polymer A, 0.5-5 parts crosslinking agent, 0.5-5 parts wetting agent, and 40-84 parts deionized water. During the preparation of the proton exchange membrane, it exhibits excellent temperature resistance, chemical resistance, and acid and alkali resistance, while also possessing characteristics such as low release force, high residual rate, and low cost. Therefore, it can be widely used in the large-scale industrial production of proton exchange membranes.

Description

Technical Field

[0001] This invention belongs to the field of release material technology, specifically relating to a release membrane for proton exchange membranes and its preparation method. Background Technology

[0002] Proton exchange membranes (PEMs) play a central role in fuel cells and are a key component of the fuel cell stack. They not only isolate hydrogen and oxygen but also conduct protons, making them a crucial material for the efficient conversion of chemical energy into electrical energy. Their performance directly impacts the efficiency, lifespan, and cost of the fuel cell. Therefore, the performance of PEMs is a major focus of industry attention.

[0003] Domestic patent application CN113594521A discloses a method for preparing a proton exchange membrane, including the following preparation process: preparation of the first functional layer: coating the surface of the release membrane with a first proton exchange resin slurry (containing perfluorosulfonic acid resin solution, etc.) to form a first proton exchange layer; reinforcement layer composite: composite the reinforcement mesh layer onto the surface of the first proton exchange layer, and heat-dry it to form a three-layer composite structure of release membrane / first proton exchange layer / reinforcement mesh layer; preparation of the second functional layer: coating the other side of the reinforcement mesh layer with a second proton exchange resin slurry to form a second proton exchange layer; final treatment: after secondary heating and drying, the membrane is wound up to obtain a material composite of proton exchange membrane and release membrane.

[0004] The selection of release membranes for proton exchange membrane coating has a crucial impact on their quality. For example, the high-temperature resistance of the release membrane determines the manufacturing temperature limit of the proton exchange membrane; the release force and residual rate of the release membrane determine the performance stability of the proton exchange membrane.

[0005] Patent application CN118027482A discloses a release film for proton exchange membrane coating and its preparation method, including using a PI film as a substrate, coating its surface with chlorinated polypropylene (CPP) resin, and treating it with electron beam irradiation to finally prepare a release film with high temperature resistance and low release force. However, while PI has good high temperature resistance and mechanical strength, it suffers from poor dimensional stability under high temperature conditions and high cost, which is not conducive to large-scale industrial production. Furthermore, the method uses chlorinated polypropylene (CPP) as the coating release agent, which, due to its inherent limitations, results in a release film with high release force, posing a risk of poor peeling during the peeling process. Therefore, there is a need for improvement in this method. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention provides a release membrane for proton exchange membranes and its preparation method. The release membrane obtained in this application is manufactured using an online stretching process, resulting in a release membrane with excellent temperature resistance, chemical resistance, and acid and alkali resistance. It also features low release force, high residual rate, and low cost. Therefore, it can be widely used in the large-scale industrial production of proton exchange membranes, effectively reducing manufacturing costs.

[0007] To achieve the aforementioned technical objectives, the technical solution adopted in this application is a release membrane for proton exchange membranes, formed by coating with a coating solution, wherein the coating solution comprises the following substances in parts by weight: 5 to 20 parts of polyvinyl alcohol 5 to 10 parts of polyvinyl chloride Water-based modified acrylic polymer A: 5 to 20 parts 0.5 to 5 parts of crosslinking agent Wetting agent 0.5 to 5 parts 40 to 84 parts deionized water; The average molecular weight of the polyvinyl chloride is 500-10000; The water-based modified acrylic polymer A is obtained by copolymerization of the following monomers, which include the following components in parts by weight: 10-20 parts of polymer monomer 3-10 parts of functional monomers 30-60 parts solvent Initiator: 1.5-2.5 parts; The polymer monomer is one or more of dimethyldecylallylammonium chloride, dimethyldodecylallylammonium chloride, dimethyltetradecylallylammonium chloride, dimethylhexadecylallylammonium chloride, dimethyloctadecylallylammonium chloride, and dimethyldocodimethylallylammonium chloride in any weight ratio. The functional monomers are one or more of acrylamide (AM) and acrylic acid (AA) in any weight ratio; The solvent is deionized water; The initiator is one or more of ammonium persulfate (APS), sodium persulfate (NPS), and potassium persulfate (KPS) in any weight ratio.

[0008] As an improved technical solution of this application, the crosslinking agent is one or more of isocyanate and carbodiimide compounds in any weight ratio.

[0009] As an improved technical solution of this application, the wetting agent is one or more of siloxane compounds and alkynyldiol compounds in any weight ratio.

[0010] As an improved technical solution of this application, the dry film thickness of the release film is 10-300nm.

[0011] As an improved technical solution of this application, the water-based modified acrylic polymer A contains a long-chain alkyl structure with side chains, the number of alkyl carbon atoms is n, the value of n is in the range of 4-22, and the average molecular weight is 20000-100000.

[0012] Another objective of this application is to provide a method for preparing a release membrane for a proton exchange membrane, comprising the following steps: Prepare polyester film sheets; Coating liquid to form release film: The coating liquid is uniformly coated on one surface of a longitudinally stretched polyester film to form a release layer. The temperature is set at 20±5℃ during the coating process. Reheating: The polyester film coated with the release layer is preheated again at a temperature of 50±10℃. Lateral stretching: The preheated polyester film coated with release layer is stretched laterally, with a stretching ratio of 4.5 ± 1 times. Heat setting treatment.

[0013] Beneficial effects 1. This invention involves uniformly dispersing water-based modified acrylic acid A, polyvinyl alcohol, and polyvinyl chloride in deionized water using mechanical stirring. With the aid of polyvinyl alcohol, the polyvinyl chloride is fully dissolved. The addition of a wetting agent improves the wettability of the coating solution on the base film, allowing the coating solution to spread rapidly on the surface of the base film and ensuring good appearance under high-speed dynamic conditions. The coating solution and base film undergo simultaneous transverse stretching, and the water-based modified acrylic acid A forms a uniform film on the base film surface. In the presence of a crosslinking agent, the active groups in the base film chemically bond with the molecules of the water-based modified acrylic acid A in the release coating layer. Polyvinyl chloride and water-based modified acrylic acid undergo physical crosslinking. After drying, the water-based modified acrylic acid acts as a peeling agent, while the polyvinyl chloride effectively improves the high-temperature resistance of both the coating and the base film. In other words, the layers are interconnected in spatial structure to form a three-dimensional network structure, which enables good adhesion between the coating layer and the base film. At the same time, the resulting release film has excellent temperature resistance, chemical resistance and acid and alkali resistance, and also has low release force and high residual rate. It effectively overcomes the defects of existing technologies, such as poor dimensional stability of the release layer and base film under high temperature conditions, poor peeling, and high cost, which are not conducive to large-scale industrial production.

[0014] 2. When waterborne acrylic acid is modified to have long-chain alkyl groups in its branches, the modified acrylic acid exhibits the following characteristics: low surface energy, strong intermolecular forces, moderate mechanical strength and flexibility, and strong chemical stability. Therefore, waterborne modified acrylic acid can be used as a release agent in the general sense. Compared with traditional silicone and fluorine release agents, this type of release agent is free from silicone and fluorine pollution and possesses online stretching properties. Polyvinyl chloride itself has high temperature resistance and flame retardancy, but poor water solubility. However, it exhibits better solubility in the presence of polyvinyl alcohol as a co-solvent, thus improving the high-temperature resistance of coatings and base films, and consequently improving the high-temperature processability of proton exchange / release composite membranes.

[0015] 3. This invention employs an online coating method. The coating liquid is characterized by easy dispersion, easy coating, and low VOC. A chemical bonding reaction occurs between the base film and the release coating layer molecules, forming flexible molecular chain segments in the molecular spatial structure. This satisfies the requirements for online stretching and subsequent adhesion. The online coating preparation method greatly promotes industrial production.

[0016] In summary, the release membrane for proton exchange membranes prepared by this method is manufactured using an online synchronous stretching process. The resulting release membrane exhibits excellent temperature resistance, chemical resistance, and acid and alkali resistance, while also possessing characteristics such as low release force and high residual rate. It is suitable for large-scale clean industrial production and effectively reduces the manufacturing cost of proton exchange membranes. Detailed Implementation

[0017] The following description, in conjunction with embodiments, will provide a more detailed account of this application so that those skilled in the art can implement it based on the text of the specification.

[0018] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art related to this invention. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. Furthermore, the terms "and / or" as used herein cover one or more related combinations of the listed items, including any and all possibilities.

[0019] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all materials and reagents used are commercially available.

[0020] This invention discloses a release film for flexible ultrathin glass protective films and its preparation method, comprising a base film and a release layer disposed on either side of the base film surface. The coating solution used for the release layer comprises a dispersion of an aqueous modified acrylic polymer A, a crosslinking agent, a wetting agent, and deionized water. The weight parts of each component in the coating solution for the release layer are as follows: 5 to 20 parts of polyvinyl alcohol 5 to 10 parts of polyvinyl chloride Water-based modified acrylic polymer A: 5 to 20 parts 0.5 to 5 parts of crosslinking agent Wetting agent 0.5 to 5 parts 40 to 84 parts deionized water.

[0021] In this invention, the waterborne modified acrylic polymer A comprises a side chain with a long-chain alkyl structure, the number of alkyl carbon atoms being n, the value of n being 4-12, and the average molecular weight being 20,000-100,000. When the molecular weight is less than 20,000, the physical crosslinking points decrease, and the peeling effect of the coating after film formation is not obvious; when the molecular weight is greater than 100,000, the hydrophobicity of the coating will be significantly improved, and the appearance of the coating will deteriorate.

[0022] Specifically, the water-based modified acrylic polymer A is obtained by copolymerization of the following monomers, which include the following substances in parts by weight: 10-20 parts of polymer monomer 3-10 parts of functional monomers 30-60 parts solvent Initiator 1.5-2.5 parts.

[0023] The polymer monomer is one or more of dimethyldecylallylammonium chloride, dimethyldodecylallylammonium chloride, dimethyltetradecylallylammonium chloride, dimethylhexadecylallylammonium chloride, dimethyloctadecylallylammonium chloride, and dimethyldocodimethylallylammonium chloride in any weight ratio. The functional monomers are one or more of acrylamide (AM) and acrylic acid (AA) in any weight ratio; The solvent is deionized water; The initiator is one or more of ammonium persulfate (APS), sodium persulfate (NPS), and potassium persulfate (KPS) in any weight ratio.

[0024] In this invention, in order to improve the crosslinking density of the release layer, the coating liquid must contain a crosslinking agent. Compounds with multiple functional groups that react with carboxyl groups can be used. Examples have shown that isocyanates and polycarbodiimide crosslinking agents are effective.

[0025] There are no particular limitations on isocyanates and polycarbodiimides used as crosslinking agents, as long as their molecules contain one or more reactive groups that react with a carboxyl group. Examples of isocyanates include: toluene diisocyanate, diphenylmethane diisocyanate, naphthalene 1,5-diisocyanate, terephthalic diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, methylcyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl isocyanate, phenyl isocyanate, cyclohexyl isocyanate, tert-butyl isocyanate, and isophorone diisocyanate. Polycarbodiimides include: polycarbodiimide, carbonyl imidazole, dicyclohexylcarbodiimide, N,N'-diisopropylcarbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, etc.

[0026] In this invention, to effectively improve the spreading effect of the aqueous coating liquid on the base film surface, the wetting agent can be a siloxane compound or an acetylenic diol compound, preferably an acetylenic diol compound. Due to the excellent dynamic wetting and permeability properties of acetylenic diol compounds, they exhibit low surface tension, which can significantly improve the spreading ability of the coating liquid. Furthermore, acetylenic diols are chemically inert and do not participate in the chemical reaction of the coating system, thus avoiding adverse effects on the performance of the coated film. Simultaneously, they also exhibit good acid and alkali resistance and chemical stability, ensuring that they maintain their excellent performance under various application environments. Therefore, acetylenic diol compounds are an important component for optimizing the coating process and improving the quality of the final product. Exemplary acetylenic diol compounds include: 3-butyn-1-ol, (R)-(+)-3-butyn-2-ol, 3,5-dimethyl-3-hydroxy-1-hexyne, butynediol, dimethyloctylenediol, tetramethyldecynediol, butynediol ethoxylates, etc.

[0027] Regarding the base film of this invention, it can be designed as a two-layer or multi-layer structure based on at least a single layer. For the interlayer structure of non-single-layer films, this invention does not particularly limit the form, allowing various forms such as two-layer (A / B), three-layer (A / B / A), or more layer combinations (such as three-layer (A / B / C)) extruded from different resins. When an opening agent is used, this invention preferably uses two two-layer or multi-layer films to balance the winding and smoothness of the final product, ensuring superior performance in practical applications.

[0028] Another important objective of this invention is to provide a method for preparing an online coated release film. The substrate used in this method is primarily based on polyethylene terephthalate (PET). Considering the mechanical properties, heat resistance, and cost of the substrate, polyethylene terephthalate (PET) is preferred as the substrate used in this invention, ensuring good overall performance and stability during application. The online coating method of this invention can effectively improve the stability and production efficiency of the release film during subsequent high-temperature processing, thereby ensuring the high quality and reliability of the coated film.

[0029] Prepare polyester film sheets; Coating liquid to form release film: The coating liquid is uniformly coated on one surface of a longitudinally stretched polyester film to form a release layer. The temperature is set at 20±5℃ during the coating process. Reheating: The polyester film coated with the release layer is preheated again at a temperature of 50±10℃. Lateral stretching: The preheated polyester film coated with release layer is stretched laterally, with a stretching ratio of 4.5 ± 1 times. Heat setting treatment.

[0030] The preparation of online coated release films includes the following steps: 1. Prepare polyester film; (1) First, polyester raw material chips are uniformly fed into a dedicated extrusion system, where they are melted by temperature control and pressure regulation to form a melt for the base film. This process ensures that the polyester is processed in a uniform molten state to improve product consistency and quality.

[0031] (2) The obtained base film melt is extruded through a die and then formed into an amorphous cast polyester sheet on a rotating cooling roller. In this step, the rotation speed and temperature of the cooling roller need to be precisely controlled to ensure the uniform thickness and good surface smoothness of the sheet.

[0032] (3) The cooled polyester sheet is preheated to reach a suitable temperature range for stretching. Then, it is stretched longitudinally to make the sheet reach 3.0 ± 0.5 times its original length in the longitudinal direction, thus obtaining a polyester sheet.

[0033] II. Longitudinal Stretching (4) Apply the pre-prepared release layer coating solution evenly to one surface of the longitudinally stretched polyester film. The temperature during the coating process is set to 20±5℃. This temperature range helps to improve the fluidity and adhesion of the coating solution, ensuring a good bond between the release layer and the film.

[0034] III. Lateral Stretching (5) The polyester film coated with the release layer is preheated again to improve its flexibility, and then transversely stretched with a stretch ratio of 4.5 ± 1 times. This step is crucial and will significantly improve the mechanical strength and final physical properties of the film.

[0035] IV. Heat setting treatment.

[0036] (6) After transverse stretching, the polyester film is heat-set to ensure its shape remains stable and to eliminate internal stress. Finally, after cooling, the resulting release polyester film is wound up to form a high-performance release film. This release film meets application requirements in both structure and performance, providing reliable material support for subsequent industrial production.

[0037] The dry film thickness of the release film is 10-300 nm.

[0038] In summary, the release membrane for proton exchange membranes prepared by the method of this invention employs an online synchronous stretching manufacturing process. The resulting release membrane exhibits excellent temperature resistance, chemical resistance, and acid and alkali resistance, while also possessing low release force, high residual rate, and low cost. Therefore, it can be widely applied to the large-scale industrial production of proton exchange membranes, effectively reducing manufacturing costs.

[0039] The present invention will now be described with reference to specific embodiments, including the following steps, but the present invention is not limited thereto.

[0040] Example 1 Preparation of waterborne modified acrylic polymer A: Dissolve 3 parts acrylic acid (AA) in 30 parts deionized water, add 10 parts dimethyldodecylallylammonium chloride, and transfer the mixture to an insulated reactor in an ice-water bath. Purge with nitrogen for 30 minutes, then add 1.5 parts ammonium persulfate (APS). Set the initiation temperature to 10°C and react for 3.5 hours. Stop the nitrogen supply and insulate the reactor with insulating material until the reaction temperature begins to decrease. Dry the contents of the reactor, grind them into powder, and filter through a sieve to obtain water-based modified acrylic polymer A1.

[0041] Preparation of release coating solution: Take 5g of polyvinyl alcohol, 5g of polyvinyl chloride, 5g of water-based modified acrylic polymer A1 (molecular weight 20000), 0.5g of isocyanate crosslinking agent (hexamethylene diisocyanate, HT-100, Wanhua Chemical), 0.5g of acetylenic diol wetting agent (dimethyloctylenic diol, Superwet-360, Tuyile), and 84g of deionized water, and disperse them evenly using a high-shear emulsifier to prepare a release coating solution.

[0042] A method for preparing release membranes for proton exchange membranes: First, polyester chips are crystallized and dried before being fed into a corresponding extrusion system and melt-extruded at 220°C, then cast onto a rotating cooling roller. The cooled cast film is preheated and longitudinally stretched to a ratio of 2.5. The release coating solution prepared in Example 1 is applied to one or both sides of the longitudinally stretched film at 20°C using one of the following online coating methods: wire rod coating, doctor blade coating, or microgravure roller coating. The film coated with the release coating solution is then heated and dried, transversely stretched 3.5 times, and then heat-set and wound to obtain an online coated release film with a dry coating thickness of 10 nm. Its performance is shown in Table 1.

[0043] Example 2 Ten parts of acrylic acid (AA) were dissolved in 60 parts of deionized water, and 20 parts of dimethyldocosylallylammonium chloride were added. The mixture was transferred to an insulated reactor in an ice-water bath. Nitrogen gas was introduced for 30 minutes, and then 2.5 parts of sodium persulfate (NPS) were added. The initiation temperature was set to 10°C, and the reaction was carried out for 4.5 hours. Nitrogen gas supply was then stopped, and the reactor was insulated until the reaction temperature began to decrease. The contents of the reactor were dried, ground, and filtered through a sieve to obtain water-based modified acrylic polymer A2.

[0044] Preparation of release coating solution: Take 20g of polyvinyl alcohol, 10g of polyvinyl chloride, 20g of water-based modified acrylic resin A2 (molecular weight 100,000), 5g of isocyanate crosslinking agent (hexamethylene diisocyanate, HT-100, Wanhua Chemical), 5g of acetylenic diol wetting agent (3,5-dimethyl-3-hydroxy-1-hexyne, Superwet-660, Tuyile), and 40g of deionized water, disperse them evenly with a high-shear emulsifier to prepare a release coating liquid.

[0045] A method for preparing release membranes for proton exchange membranes: First, polyester chips are crystallized and dried before being fed into a corresponding extrusion system and melt-extruded at 220°C, then cast onto a rotating cooling roller. The cooled cast film is preheated and longitudinally stretched to a ratio of 3.5. The release coating solution prepared in Example 2 is applied to one or both sides of the longitudinally stretched film at 24°C using one of the following online coating methods: wire rod coating, doctor blade coating, or microgravure roller coating. After heating and drying, the film coated with the release coating solution is laterally stretched 5.5 times, then heat-set and wound to obtain an online coated release film with a dry coating thickness of 300 nm. Its performance is shown in Table 1.

[0046] Example 3 Eight parts of acrylic acid (AA) were dissolved in 50 parts of deionized water, and 12 parts of dimethyl docosylallyl ammonium chloride were added. The mixture was transferred to an insulated reactor in an ice-water bath. Nitrogen gas was introduced for 30 minutes, and then 2 parts of sodium persulfate (NPS) were added. The initiation temperature was set to 10°C, and the reaction was carried out for 4.5 hours. Nitrogen gas supply was then stopped, and the reactor was insulated until the reaction temperature began to decrease. The contents of the reactor were dried, ground, and filtered through a sieve to obtain water-based modified acrylic polymer A3.

[0047] Preparation of release coating solution: Take 12.5g of polyvinyl alcohol, 7.5g of polyvinyl chloride, 12.5g of water-based modified acrylic resin A3 (molecular weight 70000), 2.75g of isocyanate crosslinking agent (hexamethylene diisocyanate, HT-100, Wanhua Chemical), 2.75g of acetylenic diol wetting agent (3,5-dimethyl-3-hydroxy-1-hexyne, Superwet-660, Tu Yile), and 62.5g of deionized water, disperse them evenly with a high-shear emulsifier to prepare a release coating solution.

[0048] A method for preparing release membranes for proton exchange membranes: First, polyester chips are crystallized and dried before being fed into a corresponding extrusion system and melt-extruded at 220°C, then cast onto a rotating cooling roller. The cooled cast film is preheated and longitudinally stretched to a ratio of 3.2. The release coating solution prepared in Example 3 is applied to one or both sides of the longitudinally stretched film at 22°C using one of the following online coating methods: wire rod coating, doctor blade coating, or microgravure roller coating. After heating and drying, the film coated with the release coating solution is laterally stretched 4.5 times, then heat-set and wound to obtain an online coated release film with a dry coating thickness of 155 nm. Its performance is shown in Table 1.

[0049] Example 4 Dissolve 6.5 parts of acrylamide (AM) in 45 parts of deionized water, add 15 parts of dimethyldodecylallylammonium chloride, and transfer the mixture to an insulated reactor in an ice-water bath. Purge with nitrogen for 30 minutes, then add 2.0 parts of ammonium persulfate (APS). Set the initiation temperature to 10°C and react for 4 hours. Stop the nitrogen supply and insulate the reactor with insulating material until the reaction temperature begins to decrease. Dry the contents of the reactor, grind them into powder, and filter through a sieve to obtain water-based modified acrylic polymer A4.

[0050] Preparation of release coating solution: Take 15g of polyvinyl alcohol, 7.5g of polyvinyl chloride, 20g of water-based modified acrylic resin A3 (molecular weight 60000), 2.5g of isocyanate crosslinking agent (hexamethylene diisocyanate, HT-100, Wanhua Chemical), 2.5g of acetylenic diol wetting agent (butynediol, Superwet-206, Tuyile), and 52.5g of deionized water, disperse them evenly with a high-shear emulsifier to prepare a release coating solution.

[0051] A method for preparing release membranes for proton exchange membranes: First, polyester chips are crystallized and dried before being fed into a corresponding extrusion system and melt-extruded at 220°C, then cast onto a rotating cooling roller. The cooled cast film is preheated and longitudinally stretched to a length of 3.0. The release coating solution prepared in Example 3 is applied to one or both sides of the longitudinally stretched film at 22°C using one of the following online coating methods: wire rod coating, doctor blade coating, or microgravure roller coating. After heating and drying, the film coated with the release coating solution is laterally stretched 4.5 times, then heat-set and wound to obtain an online coated release film with a dry coating thickness of 150 nm. Its performance is shown in Table 1.

[0052] Comparative Example 1 Except for replacing the amount of water-based modified acrylic polymer A with 4g, all other conditions were the same as in Example 1, and the performance was measured as shown in Table 1.

[0053] Comparative Example 2 Except for replacing the amount of water-based modified acrylic polymer A with 35g, all other conditions were the same as in Example 1, and the performance was measured as shown in Table 1.

[0054] Comparative Example 3 Two parts of acrylic acid (AA) were dissolved in 30 parts of deionized water, and eight parts of dimethyldodecylallylammonium chloride were added. The resulting mixture was transferred to an insulated reactor in an ice-water bath. Nitrogen gas was introduced for 30 minutes, and then 1.5 parts of ammonium persulfate (APS) were added. The initiation temperature was set to 10°C, and the reaction was allowed to proceed for 2.5 minutes. Nitrogen gas supply was then stopped, and the reactor was insulated until the reaction temperature began to decrease. The contents of the reactor were dried, ground, and filtered through a sieve to obtain a water-based modified acrylic polymer A4 (molecular weight 15,000).

[0055] Preparation of release coating solution: Except for replacing the water-based modified acrylic polymer A1 with A4, all other conditions were the same as in Example 2, and the performance was measured as shown in Table 1.

[0056] Comparative Example 4 Dissolve 12 parts of acrylic acid (AA) in 30 parts of deionized water, add 25 parts of dimethyldodecylallylammonium chloride, and transfer the mixture to an insulated reactor in an ice-water bath. After purging with nitrogen for 30 minutes, add 1.5 parts of ammonium persulfate (APS). Set the initiation temperature to 10°C and react for 5.5 minutes. Then, stop the nitrogen supply and insulate the reactor with insulating material until the reaction temperature begins to decrease. Dry and grind the contents of the reactor into a fine powder, and filter through a sieve to obtain water-based modified acrylic polymer A5 (molecular weight 120,000).

[0057] Except for replacing water-based modified acrylic resin A1 with A5, all other conditions were the same as in Example 2, and the performance was measured as shown in Table 1.

[0058] Comparative Example 5 Except for replacing the water-based isocyanate crosslinking agent (Wanhua Chemical HT-100) with the melamine crosslinking agent (Zhanxin CYMEL 303 LF), all other conditions were the same as in Example 3, and the performance was measured as shown in Table 1.

[0059] Comparative Example 6 Except for adjusting the coating thickness to 5nm, all other conditions were the same as in Example 1, and the performance was measured as shown in Table 1.

[0060] Comparative Example 7 Except for adjusting the coating thickness to 350 nm, all other conditions were the same as in Example 1, and the performance was measured as shown in Table 1.

[0061] Comparative Example 8 Except for removing the polyvinyl alcohol raw material and changing the amount of deionized water to 84g, all other conditions were the same as in Example 1, and the performance was measured as shown in Table 1.

[0062] Comparative Example 9 Except for removing the polyvinyl chloride raw material and changing the amount of deionized water to 84g, all other conditions were the same as in Example 1, and the performance was measured as shown in Table 1.

[0063] 1. Coating appearance Shine a strong flashlight at a 45-degree angle on the sample and visually observe for any cloud-like blooming or stripe-like defects. A "0" indicates the absence of cloud-like blooming or stripe-like defects, while a "×" indicates the presence of such defects.

[0064] 2. The average molecular weight in this experiment was determined using gel permeation chromatography (GPC), also known as size exclusion chromatography, a technique for separating molecules based on their size. By measuring the elution volume of compounds of different molecular sizes, the molecular weight distribution of the compounds can be calculated.

[0065] Experimental instrument: Gel chromatograph, model: Waters e2695-2414 RI Detector.

[0066] 3. Release force test The peeling effect was tested using the GB2792-2014 method for testing the release force and residual rate of adhesive tapes. A peeling force of less than or equal to 20gf was marked as good peeling effect (symbol O), and a value greater than 20gf was marked as poor peeling effect (symbol ×). A residual rate of less than 80% was marked as low residual rate (symbol ×), and a value greater than or equal to 80% was marked as high residual rate (symbol O).

[0067] 4. Adhesion (coating and base film) Adhesion (coating and base film): Cut the prepared release film into A4 size. On the release surface, use a 2kg weight to press down the dust-free paper (soaked in anhydrous ethanol) and drag it back and forth 10 times. Observe the release layer peeling off. If the coating does not peel off, it is 0. If the coating peels off, it is ×.

[0068] 5. Film heat shrinkage test The heat shrinkage performance test adopts GB30693-2014 Test Method for Tensile Properties of Plastic Films. If the shrinkage rate in the MD direction is greater than 2%, it is marked as poor dimensional stability under heat (symbol ×). If the shrinkage rate in the MD direction is less than 0.5%, it is marked as good dimensional stability under heat (symbol O).

[0069]

[0070] As can be seen from the test results of Examples 1-4 in Table 1, the release membrane for proton exchange membrane prepared within the technical scope of the present invention not only has excellent temperature resistance, chemical resistance and acid and alkali resistance, but also has the characteristics of low release force, high residual rate and low cost.

[0071] In Comparative Example 1, it can be seen that as the amount of water-based modified acrylic polymer used decreases, the coating appearance of the release film is good, but the release force is poor. In Comparative Example 2, as the amount of water-based modified acrylic polymer used increases, the release force is good, but the coating appearance shows defects such as mottled and uneven coating, which affects the quality of the release film.

[0072] Comparative Examples 3 and 4 show that as the molecular weight of the synthesized waterborne modified acrylic polymer changes, the release force of the prepared release film tends to be poor, affecting the subsequent use effect.

[0073] In Comparative Example 5, the change in the type of crosslinking agent resulted in a poorer adhesion between the coating and the base film, which affected the adhesion and release force of the release membrane, thus causing quality defects in the proton exchange membrane.

[0074] In Comparative Examples 6 and 7, due to the change in coating thickness, the appearance and release force of the release membrane deteriorated to varying degrees, resulting in quality defects in the proton exchange membrane.

[0075] In Comparative Example 8, the lack of a co-solvent reduced the solubility of polyvinyl chloride, resulting in a cloudy coating solution, poor coating appearance, and consequently, defects in the release film quality.

[0076] In Comparative Example 9, the lack of polyvinyl chloride resulted in poor dimensional stability of the release membrane, which in turn affected the subsequent processing of the proton exchange membrane, leading to quality defects in the proton exchange membrane.

[0077] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and practice of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A release membrane for proton exchange membranes, characterized in that, Formed by coating with a coating liquid, wherein the coating liquid comprises the following substances in parts by weight: 5 to 20 parts of polyvinyl alcohol 5 to 10 parts of polyvinyl chloride Water-based modified acrylic polymer A: 5 to 20 parts 0.5 to 5 parts of crosslinking agent Wetting agent 0.5 to 5 parts 40 to 84 parts deionized water; The average molecular weight of the polyvinyl chloride is 500-10000; The water-based modified acrylic polymer A is obtained by copolymerization of the following monomers, which include the following components in parts by weight: 10-20 parts of polymer monomer 3-10 parts of functional monomers 30-60 parts solvent Initiator: 1.5-2.5 parts; The polymer monomer is one or more of the following in any weight ratio: dimethyldecylallylammonium chloride, dimethyldodecylallylammonium chloride, dimethyltetradecylallylammonium chloride, dimethylhexadecylallylammonium chloride, dimethyloctadecylallylammonium chloride, and dimethyldocodimethylallylammonium chloride. The functional monomers are one or more of acrylamide (AM) and acrylic acid (AA) in any weight ratio; The solvent is deionized water; The initiator is one or more of ammonium persulfate (APS), sodium persulfate (NPS), and potassium persulfate (KPS) in any weight ratio.

2. The release membrane for a proton exchange membrane according to claim 1, characterized in that, The crosslinking agent is one or more of isocyanate and carbodiimide compounds in any weight ratio.

3. The release membrane for a proton exchange membrane according to claim 1, characterized in that, The wetting agent is one or more of siloxane compounds and alkynyl diol compounds in any weight ratio.

4. The release membrane for a proton exchange membrane according to claim 1, characterized in that, The dry film thickness of the release film is 10-300 nm.

5. The release membrane for a proton exchange membrane according to claim 1, characterized in that, The waterborne modified acrylic polymer A contains a long-chain alkyl structure with side chains, the number of alkyl carbon atoms being n, the value of n being 4-22, and the average molecular weight being 20,000-100,000.

6. A method for preparing a release membrane for a proton exchange membrane as described in any one of claims 1-5, characterized in that, Includes the following steps: Prepare polyester film sheets; Coating liquid to form release film: The coating liquid is uniformly coated on one surface of a longitudinally stretched polyester film to form a release layer. The temperature is set at 20±5℃ during the coating process. Reheating: The polyester film coated with the release layer is preheated again at a temperature of 50±10℃. Lateral stretching: The preheated polyester film coated with release layer is stretched laterally, with a stretching ratio of 4.5 ± 1 times. Heat setting treatment.

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