A high temperature resistant hot melt adhesive film and preparation method thereof

Abstract

The present invention discloses a high temperature resistant hot melt adhesive film and a preparation method thereof, and relates to the technical field of fuel cell production. The high temperature resistant hot melt adhesive film comprises a release layer, a hot melt layer I, a toughening layer and a hot melt layer II arranged in sequence, wherein the toughening layer is respectively embedded in the hot melt layer I and the hot melt layer II; the release layer is one of a double-sided matte OPP film, a CPP film or a PP synthetic paper; the toughening layer is a thermoplastic nanofiber film prepared by an electrostatic spinning process. The high temperature resistant hot melt adhesive film of the present invention not only has high bonding strength, good sealing, low compression deformation and excellent stress buffering, but also uses a nanofiber membrane as a toughening layer to not only improve the stiffness of the hot melt adhesive film, but also facilitates product die cutting processing, and the nanofiber membrane impregnated in the hot melt layer can improve the peeling strength of the hot melt adhesive film at high temperature, avoiding the reduction of the bonding strength of the hot melt adhesive film at high temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cell production, and in particular to a high-temperature resistant hot-melt adhesive film and a preparation method thereof. Background Art

[0002] A fuel cell is a power generation device that converts the chemical energy present in fuel and oxidant directly into electrical energy. Fuel cells have the advantages of zero emission, no vibration or noise, good load responsiveness, and high reliability. Fuel cells can generally be divided into alkaline fuel cells, phosphoric acid fuel cells, molten carbon carbonate fuel cells, solid oxide fuel cells, and proton exchange membrane fuel cells. Among them, proton exchange membrane fuel cells have high energy conversion efficiency, can be quickly started at room temperature, have no electrolyzed water loss, and have a long life. They have developed rapidly in recent years and are receiving more and more attention.

[0003] A fuel cell usually includes a membrane electrode and a current collector; the membrane electrode of the fuel cell is the electrochemical reaction site where the reducing agent undergoes oxidation reaction and the oxidant undergoes reduction reaction. The traditional membrane electrode mainly includes a proton exchange membrane located in the middle and a cathode and an anode are integrally provided on both sides thereof, and a gas diffusion layer located on the upper and lower surfaces of the proton exchange membrane. In order to promote the occurrence of electrochemical reactions, a catalyst is generally provided between the cathode, the anode and the proton exchange membrane (usually located at the interface between the proton exchange membrane and the gas diffusion layer); and the current collector is usually also called a bipolar plate, which is responsible for distributing fuel and air to the surfaces of the positive and negative electrodes and the heat dissipation of the stack. It is also responsible for connecting the single cells in series to form a fuel cell stack. It mainly plays the role of separating the oxidant, the reducing agent and the coolant and collecting the current. In actual manufacturing, the fluid transmission channels in the fuel cell stack and the fluid transmission channels and the outside of the stack need to be sealed. The leakage of fluids or the mixing of different fluids in the stack not only causes waste and reduces the performance of the stack, but also may cause safety accidents. Therefore, the sealing technology in the fuel cell stack technology has a huge impact on the safety, life, efficiency and other aspects of the stack. In the prior art fuel cell stack, an embedding groove is usually set at the edge of the graphite or metal plate to be sealed, and a sealing gasket is placed in the embedding groove, or a circle of glue is applied on the edge of the seal by a glue machine, and then cured and pressed to achieve sealing. However, these sealing methods usually face the following technical problems:

[0004] a. Generally there is only a single seal to prevent leakage, and the risk of seal failure is high.

[0005] b. A great deal of pressure needs to be applied to the sealing ring to form a good seal, which results in a large stress in a local area of ​​the plate, which can easily lead to damage or distortion of the plate.

[0006] c. It is necessary to preset grooves on the electrode plate, which increases the thickness requirement of the electrode plate and reduces the power density of the fuel cell stack.

[0007] d. A single sealing ring or sealing rubber line is prone to plastic deformation, and the risk of sealing failure is high.

[0008] Therefore, it is very necessary to seek new sealing technology solutions to effectively improve the sealing performance of fuel cell cells. Summary of the invention

[0009] The first technical problem to be solved by the present invention is: to provide a high temperature resistant hot melt adhesive film with high bonding strength and good sealing performance in view of the deficiencies in the prior art.

[0010] To solve the above-mentioned first technical problem, the technical solution of the present invention is:

[0011] A high temperature resistant hot melt adhesive film, comprising a release layer, a hot melt layer I, a toughening layer and a hot melt layer II arranged in sequence, wherein the toughening layer is embedded in the hot melt layer I and the hot melt layer II respectively;

[0012] The release layer is one of a double-sided matte OPP film, a CPP film or a PP synthetic paper;

[0013] The toughening layer is a thermoplastic nanofiber membrane made by an electrostatic spinning process.

[0014] Preferably, the release layer has a thickness of 25-100 μm.

[0015] Preferably, the toughening layer has a thickness of 5-20 μm.

[0016] The hot melt layer I and the hot melt layer II are both composed of copolyester resin, polybutadiene resin, adhesion promoter, curing agent and diluent solvent in a weight ratio of 100: (1-10): (0.5-5): (1-5): (400-600).

[0017] Preferably, the thickness of the hot-melt layer I and the hot-melt layer II are both 20-50 μm.

[0018] Preferably, the copolyester resin is a low-crystalline copolyester resin, the weight average molecular weight of the copolyester resin is 25,000-45,000, and the softening point is 110-170°C.

[0019] Preferably, the polybutadiene resin is a polybutadiene resin modified with a hydroxyl group, a carboxyl group or an epoxy group.

[0020] Preferably, the curing agent is any one of an epoxy curing agent, an isocyanate curing agent, and a carbodiimide curing agent.

[0021] The second technical problem to be solved by the present invention is: in view of the deficiencies in the prior art, a method for preparing a high-temperature resistant hot-melt adhesive film is provided, wherein the prepared high-temperature resistant hot-melt adhesive film has high bonding strength and good sealing performance.

[0022] To solve the above second technical problem, the technical solution of the present invention is:

[0023] A method for preparing a high temperature resistant hot melt adhesive film comprises the following steps:

[0024] S01. Preparation of copolyester resin glue

[0025] Adding copolyester resin and diluent solvent into a reaction kettle, stirring at a speed of 300-900 r / min, dissolving at 70-85° C. for 1-3 hours, and obtaining copolyester resin glue;

[0026] S02. Preparation of hot melt adhesive layer adhesive

[0027] Add polybutadiene resin, adhesion promoter and curing agent to the copolyester resin glue prepared by S01, maintain the reaction kettle at 55-65℃, rotate at a uniform speed of 300-900r / min, filter through a 200-800 mesh filter or a 1-20um filter element, and then use a scraper coater or a CED coater to coat it on the double-sided matte release layer. After drying completely, heat-bond it with the toughening layer. Use the same method to prepare the hot melt adhesive layer on the other side. After aging, a high temperature resistant hot melt adhesive film is obtained.

[0028] The dilution solvent is any one of acetone, butanone, cyclohexanone, methyl isobutyl ketone, toluene, xylene, and cyclohexane, or a mixed solution of two or more thereof.

[0029] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0030] 1. The hot-melt layer I and the hot-melt layer II are coated on the matte release material to make the adhesive surface matte and free of initial adhesion. When hot-pressing and bonding with the plate or membrane electrode frame, bubbles can be effectively discharged to avoid poor bonding. After high-temperature hot pressing, the bonding strength is improved to achieve a strong bond. At the same time, it has excellent high temperature resistance, hydrolysis resistance and low compression deformation, which simplifies the single-cell manufacturing process and significantly improves efficiency and yield.

[0031] 2. The high temperature resistant hot melt adhesive film of the present invention can not only effectively bond the sealing electrode frame material, but also has excellent bonding properties to the plates with different coatings.

[0032] 3. The high temperature resistant hot melt adhesive film of the present invention not only has high bonding strength, good sealing, low compression deformation and excellent stress buffering, but also uses nanofiber membrane as the toughening layer which can not only improve the stiffness of the hot melt adhesive film and facilitate product die-cutting processing, but also the nanofiber membrane impregnated in the hot melt layer can improve the peel strength of the hot melt adhesive film at high temperature, thereby avoiding the reduction of the bonding strength of the hot melt adhesive film at high temperature.

[0033] 4. The adhesion promoter added in the present invention can utilize the interaction between triazine and metal to generate extremely strong adhesion to further improve the adhesion to the metal plate.

[0034] 5. The hot melt adhesive film prepared by the present invention using hydroxyl, carboxyl or epoxy grafted polybutadiene materials and a curing agent to improve the copolyester resin not only has extremely high bonding strength but also has a high-density interpenetrating cross-linked network structure that can provide temperature resistance and hydrolysis resistance. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the embodiments. Example 1

[0036] 1. Add 100 kg of HCXC-736 copolyester (melting point 125°C) and 400 kg of toluene into a 1T autoclave and dissolve them at 80°C and 500 r / min for 2 hours to obtain a copolyester resin glue solution;

[0037] 2. Add 3kg of Japan Tosoh epoxidized polybutadiene resin JP-100, 0.5kg of Japan Shikoku Chemical adhesion promoter VD-5, and 2.5kg of Wanhua WANNATE® TL-75E isocyanate curing agent to the copolyester resin adhesive in batches, maintain 60℃, 500r / min and stir evenly, then filter with a 400-mesh filter, and then coat 25μm on 50μm double-sided matte OPP with a doctor blade coater. After drying completely, heat-stick it with a 12μm nanofiber membrane and roll it up. Use the same method to prepare the hot-melt adhesive layer on the other side. After aging, the high-temperature resistant hot-melt adhesive film is obtained. Example 2

[0038] 1. Add 100 kg of HCXC-736 copolyester (melting point 125°C), 400 kg of xylene and 50 kg of acetone into a 1T autoclave and dissolve them at 80°C for 2 hours to obtain a copolyester resin glue solution;

[0039] 2. Add 5kg of Japan Tosoh epoxidized polybutadiene resin JP-200, 1kg of Japan Shikoku Chemical adhesion promoter VD-5, and 1kg of Covestro Desmodur L75 A isocyanate curing agent in batches to the polyester resin glue, maintain 60°C and stir evenly, then filter with a 400-mesh filter, and then use a scraper coater to coat a 30μm hot-melt adhesive layer on an 80μm double-sided matte CPP film. After drying completely, heat-stick it with a 5μm nanofiber membrane and roll it up. Use the same method to prepare the hot-melt adhesive layer on the other side. After aging, a high-temperature resistant hot-melt adhesive film is obtained. Example 3

[0040] 1. Add 100 kg of HCXC-736 copolyester (melting point 125°C), 400 kg of cyclohexanone and 200 kg of cyclohexane into a 1T autoclave and dissolve them at 80°C for 2 hours to obtain a copolyester resin glue solution;

[0041] 2. Add 1kg of Evonik maleic anhydride grafted polybutadiene POLYVEST®MA-75, 3kg of Japan Shikoku Chemical adhesion promoter VD-5, and 2kg of Japan Nisshinbo CARBODILITE C-768 polycarbodiimide in batches to the polyester resin glue, maintain 60°C and stir evenly, then filter with a 20μm filter element, and then coat a 20μm hot-melt adhesive layer on 100μm double-sided matte PP synthetic paper with a doctor blade coater. After drying completely, hot-stick it with a 20μm nanofiber membrane and roll it up. Use the same method to prepare the hot-melt adhesive layer on the other side. After aging, a hot-melt adhesive film with nanofiber membrane toughening and reinforcement is obtained. Example 4

[0042] 1. Add 100 kg of HCXC-736 copolyester (melting point 125°C) and 500 kg of a mixed solvent of toluene, xylene and butanone (4.5:4.5:1) into a 1T autoclave and dissolve them at 80°C for 2 hours to obtain a copolyester resin glue solution;

[0043] 2. Add 10kg of Evonik's hydroxyl-terminated polybutadiene POLYVEST® HT, 0.5kg of Japan Shikoku Chemical adhesion promoter VD-5, and 5kg of Japan polyurethane isocyanate curing agent L-75 in batches to the polyester resin glue, maintain 60℃ and stir evenly, then filter with a 10μm filter element, and then use a scraper coater to coat a 50μm hot-melt adhesive layer on a 75μm double-sided matte OPP film. After drying completely, heat-stick it with a 12μm nanofiber membrane and roll it up. Use the same method to prepare the hot-melt adhesive layer on the other side. After aging, a hot-melt adhesive film with nanofiber membrane toughening and reinforcement is obtained. Example 5

[0044] 1. Add 100 kg of HCXC-736 copolyester (melting point 125°C) and 500 kg of a mixed solvent of xylene, toluene and methyl isobutyl ketone (8:1:1) into a 1T autoclave and dissolve them at 80°C for 2 hours to obtain a copolyester resin glue solution;

[0045] 2. Add 3kg of Japan Tosoh epoxidized polybutadiene resin JP-100, 5kg of Japan Shikoku Chemical adhesion promoter VD-5 and 3kg of Nan Ya NPES901 epoxy resin curing agent to the polyester resin glue in batches, maintain 60℃ and stir evenly, then filter with a 20μm filter element, and then use a scraper coater to coat a 25μm hot melt adhesive layer on a 50μm double-sided matte 0PP film. After drying completely, hot-stick it with a 12μm nanofiber membrane and roll it up. Use the same method to prepare the hot melt adhesive layer on the other side. After aging, a hot melt adhesive film with nanofiber membrane toughening and reinforcement is obtained. Comparative Example 1

[0046] Without adding Wanhua WANNATE® TL-75E curing agent, the rest is exactly the same as in Example 1. Comparative Example 2

[0047] The polybutadiene resin JP-100 was not added, and the rest was exactly the same as in Example 1. Comparative Example 3

[0048] The 0.5 kg adhesion promoter VD-5 was not added, and the rest was exactly the same as in Example 1.

[0049] The performance of the high temperature resistant hot melt adhesive film products in the above-mentioned Examples 1-5 and Comparative Examples 1-3 were tested respectively. The specific test items and test methods are shown in Table 1 below, and the test results are shown in Table 2.

[0050] Table 1

[0051]

[0052] Table 2

[0053]

[0054] Among them: 160℃*60s*1Mpa hot pressing is used during the test.

[0055] It can be obtained from the experimental data in the above table that by adding different proportions, a high-temperature resistant hot-melt adhesive film material can be prepared which has excellent bonding strength to the electrode plate and the membrane electrode PEN frame at room temperature and high temperature and has a low drop in peel strength after acid immersion; the present invention can further cross-link and improve the temperature resistance and hydrolysis resistance of the hot-melt adhesive film and reduce compression deformation by cross-linking through the reaction of copolyester resin with polybutadiene resin having functional groups and adhesion promoter and curing agent; the present invention uses thermoplastic nanofiber membrane embedded in the hot-melt adhesive film, which can not only improve the stiffness of the hot-melt adhesive film and facilitate product die-cutting processing, but also the destruction of the nanofiber layers during high-temperature peeling further improves the peel strength at high temperature.

[0056] It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope limited by the appended claims of the application.

Claims

1. A high temperature resistant hot melt adhesive film, characterized in that: It comprises a release layer, a hot-melt layer I, a toughening layer and a hot-melt layer II which are arranged in sequence, wherein the toughening layer is embedded in the hot-melt layer I and the hot-melt layer II respectively; The release layer is one of a double-sided matte OPP film, a CPP film or a PP synthetic paper; The toughening layer is a thermoplastic nanofiber membrane made by an electrospinning process; The hot melt layer I and the hot melt layer II are both composed of copolyester resin, polybutadiene resin, adhesion promoter, curing agent, and diluent solvent in a weight ratio of 100: (1-10): (0.5-5): (1-5): (400-600); The copolyester resin is a low-crystalline copolyester resin, the weight average molecular weight of the copolyester resin is 25000-45000, and the softening point is 110-170°C; The polybutadiene resin is a polybutadiene resin modified with a hydroxyl group, a carboxyl group or an epoxy group; The curing agent is any one of an epoxy curing agent, an isocyanate curing agent, and a carbodiimide curing agent; The adhesion promoter is Japan Shikoku Chemical Adhesion Promoter VD-5; The method for preparing the high temperature resistant hot melt adhesive film comprises the following steps: S01. Preparation of copolyester resin glue Adding copolyester resin and diluent solvent into a reaction kettle, stirring at a speed of 300-900 r / min, dissolving at 70-85° C. for 1-3 hours, and obtaining copolyester resin glue; S02. Preparation of hot melt adhesive layer adhesive Add polybutadiene resin, adhesion promoter and curing agent to the copolyester resin glue prepared by S01, maintain the reactor at 55-65°C and rotate at a uniform speed of 300-900r / min, filter through a 200-800 mesh filter or a 1-20um filter element, and then use a scraper coater or a CED coater to coat it on the double-sided matte release layer. After drying completely, heat-bond it with the toughening layer. Use the same method to prepare the hot melt adhesive layer on the other side. After aging, a high temperature resistant hot melt adhesive film is obtained.

2. A high temperature resistant hot melt adhesive film as claimed in claim 1, characterized in that: The release layer has a thickness of 25-100 μm.

3. The high temperature resistant hot melt adhesive film according to claim 1, characterized in that: The thickness of the toughening layer is 5-20 μm.

4. A high temperature resistant hot melt adhesive film as claimed in claim 1, characterized in that The thickness of the hot-melt layer I and the hot-melt layer II are both 20 to 50 μm.

5. The high temperature resistant hot melt adhesive film according to claim 1, characterized in that: The dilution solvent is any one of acetone, butanone, cyclohexanone, methyl isobutyl ketone, toluene, xylene, and cyclohexane, or a mixed solution of two or more thereof.

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