Hot-melt adhesive, its preparation method and fuel cell membrane electrode

Abstract

The present invention relates to the technical field of adhesives, and particularly relates to a hot melt adhesive, a preparation method thereof, and a fuel cell membrane electrode. The hot melt adhesive includes a first adhesive layer and a second adhesive layer; the first adhesive layer includes a polyester resin, a styrene-based thermoplastic elastomer, a graft-type toughening agent, an epoxy-based chain extender, and a first organic solvent; the second adhesive layer includes an ethylene-methyl acrylate copolymer, a copolyester hot melt adhesive, an ethylene-methyl acrylate-glycidyl methacrylate terpolymer, an epoxy ring-opening accelerator, and a second organic solvent. The hot melt adhesive of the present invention has a two-layer structure, can achieve good adhesion to PEN and PFSA, does not foam or crack after being immersed in a sulfuric acid aqueous solution at 95°C and pH = 2 for more than 2000 h, and can maintain good adhesion performance, and has no crystal points when forming a film.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and particularly to a hot melt adhesive, a preparation method thereof, and a fuel cell membrane electrode assembly. Background Art

[0002] The membrane electrode assembly (MEA) is the site for multiphase mass transfer and electrochemical reactions in fuel cells, determining the overall performance, durability, production efficiency, and cost control of fuel cells. It is mainly integrally prepared from a catalyst, a proton exchange membrane (PEM), a gas diffusion layer, and a frame. The proton exchange membrane (PEM) is one of the cores of the MEA component. It has extremely high proton conductivity, good chemical stability, strong hydrophilicity, and can also provide support for the catalyst coating. Currently, perfluorosulfonic acid proton membranes (PFSA) have been widely used due to their good thermal stability, chemical stability, high mechanical strength, and high industrialization level.

[0003] To prevent gas leakage, improve the stability and durability of fuel cells, optimize performance, and prevent chemical corrosion, the encapsulation of fuel cell membrane electrodes is very crucial. In the structure of the membrane electrode, the border membrane plays the following roles: supporting the membrane electrode to keep it stiff, encapsulating, and sealing. Materials that can be used for the border membrane include polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), polyetherimide (PEI), polyimide (PI), polypropylene (PP), polyethylene terephthalate (PET), etc. Among them, PEN is the most commonly used, with the characteristics of high durability, high heat resistance, and high cost performance. To achieve good encapsulation of fuel cell membrane electrodes, it is necessary to bond the border membrane and the proton exchange membrane, that is, bond PEN and PFSA.

[0004] Currently, most use acrylate adhesives to achieve the bonding of PEN and PFSA. For example, the acrylate adhesives disclosed in Chinese patent applications with publication numbers CN115181533A and CN116525871A have good adhesiveness to PEN and PFSA. However, due to problems such as monomer residue, toxicity, cost, heat resistance, and weather resistance, their large-scale use is restricted. In the Chinese patent application with publication number CN116814183A, a hydrolysis-resistant hot melt adhesive layer is prepared by uniformly mixing a polyester resin, an epoxy resin, an organic solvent, an anti-hydrolysis agent, a leveling agent, and a cross-linking agent. It has good adhesion to PEN and PFSA and excellent hydrolysis resistance. However, this preparation method is not easy to control the reaction rate, and a large number of crystal points will be brought during film formation, making it impossible to be practically applied in combination with the membrane electrode process. Moreover, this adhesive is brittle, and the embrittled adhesive is prone to cracking or peeling under external force, seriously affecting its use effect.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The object of the present invention is to provide a hot melt adhesive, a preparation method thereof and a fuel cell membrane electrode. The hot melt adhesive of the present invention can achieve good adhesion to PEN and PFSA, does not foam or crack after being soaked in a sulfuric acid aqueous solution at 95°C and pH = 2 for more than 2000 h, can maintain good adhesion performance, and has no crystal points when forming a film.

[0007] To achieve the above object of the present invention, the present invention provides a hot melt adhesive in the first aspect, which includes a first adhesive layer and a second adhesive layer arranged in a laminated manner;

[0008] The first adhesive layer includes the following components by weight: 50 - 80 parts of polyester resin, 10 - 40 parts of styrene-based thermoplastic elastomer, 5 - 20 parts of graft-type toughening agent, 0.1 - 1.5 parts of epoxy-based chain extender, and 100 - 200 parts of a first organic solvent; the melt index of the polyester resin at 160°C / 2.16 kg ≥ 30 g / 10 min;

[0009] The second adhesive layer includes the following components by weight: 40 - 60 parts of ethylene-methyl acrylate copolymer, 20 - 40 parts of copolyester hot melt adhesive, 10 - 30 parts of ethylene-methyl acrylate-glycidyl methacrylate terpolymer, 0.1 - 2 parts of epoxy ring-opening accelerator, and 100 - 200 parts of a second organic solvent; in the ethylene-methyl acrylate-glycidyl methacrylate terpolymer, the content of GMA is 3 wt% - 6 wt%.

[0010] In a specific embodiment of the present invention, the styrene-based thermoplastic elastomer includes at least one of styrene-butadiene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, and hydrogenated styrene-isoprene-styrene block copolymer.

[0011] In a specific embodiment of the present invention, the graft unit of the graft-type toughening agent is maleic anhydride and / or glycidyl methacrylate. Further, the graft-type toughening agent is at least one of SEBS grafted with maleic anhydride and / or glycidyl methacrylate.

[0012] In a specific embodiment of the present invention, in the graft-type toughening agent, the grafting rate of the graft unit ≥ 0.5%.

[0013] In a specific embodiment of the present invention, in the epoxy-based chain extender, the epoxy equivalent is 200 - 600 g / mol.

[0014] In a specific embodiment of the present invention, the first organic solvent includes methyl ethyl ketone and ethyl acetate. Further, in the first organic solvent, the mass ratio of methyl ethyl ketone to ethyl acetate is (1 to 3):1.

[0015] In a specific embodiment of the present invention, in the ethylene-methyl acrylate copolymer, the content of methyl acrylate is ≥20 wt%.

[0016] In a specific embodiment of the present invention, the melting point of the copolyester hot melt adhesive is ≥110 °C.

[0017] In a specific embodiment of the present invention, the epoxy ring-opening accelerator includes at least one of 2,4,6-tris(dimethylaminomethyl)phenol, N,N-dimethylbenzylamine, and 1-benzyl-2-methylimidazole.

[0018] In a specific embodiment of the present invention, the second organic solvent includes ethyl acetate and acetone. Further, in the second solvent, the mass ratio of ethyl acetate to acetone is (1 to 5):1.

[0019] In a specific embodiment of the present invention, the thickness of the hot melt adhesive is 10 to 25 μm. Further, the thicknesses of both the first adhesive layer and the second adhesive layer are ≥5 μm.

[0020] The second aspect of the present invention provides a method for preparing the hot melt adhesive of the first aspect of the present invention, including the following steps:

[0021] (a) Mix the components of the first adhesive layer evenly, coat and then dry to obtain the first adhesive layer;

[0022] (b) Mix the components of the second adhesive layer evenly, coat on the surface of the first adhesive layer, and dry to obtain the hot melt adhesive.

[0023] The third aspect of the present invention provides a fuel cell membrane electrode, including the hot melt adhesive of the first aspect of the present invention.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) The hot melt adhesive of the present invention has a two-layer structure. The first adhesive layer can be used to connect PEN, and the second adhesive layer can be used to connect PFSA, so as to connect PEN and PFSA through the hot melt adhesive of the present invention. The hot melt adhesive has a strong adhesive effect between PEN, PFSA and the two adhesive layers of the hot melt adhesive. It does not bubble or crack after being soaked in a sulfuric acid aqueous solution at 95 °C and pH = 2 for more than 2000 h, and still maintains good adhesive performance;

[0026] (2) The preparation process of the hot melt adhesive of the present invention is simple, there are no crystal points when coated into a film, and it can be continuously produced, and it can be applied to the field of fuel cell membrane electrode encapsulation. Detailed implementation manners

[0027] The technical solutions of the present invention will be clearly and completely described below in conjunction with the detailed implementation manners. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0028] The hot melt adhesive includes a first adhesive layer and a second adhesive layer arranged in a stacked manner;

[0029] The first adhesive layer includes the following components by weight: 50 - 80 parts of polyester resin, 10 - 40 parts of styrene-based thermoplastic elastomer, 5 - 20 parts of graft toughening agent, 0.1 - 1.5 parts of epoxy chain extender, and 100 - 200 parts of the first organic solvent; the melt index of the polyester resin at 160 °C / 2.16 kg ≥ 30 g / 10 min;

[0030] The second adhesive layer includes the following components by weight: 40 - 60 parts of ethylene-methyl acrylate copolymer, 20 - 40 parts of copolyester hot melt adhesive, 10 - 30 parts of ethylene-methyl acrylate-glycidyl methacrylate terpolymer, 0.1 - 2 parts of epoxy ring-opening accelerator, and 100 - 200 parts of the second organic solvent; in the ethylene-methyl acrylate-glycidyl methacrylate terpolymer, the content of GMA is 3 wt% - 6 wt%.

[0031] The hot melt adhesive of the present invention has a two-layer structure. The first adhesive layer can be used to connect PEN, and the second adhesive layer can be used to connect PFSA, so as to connect PEN and PFSA through the hot melt adhesive of the present invention. The hot melt adhesive has a strong adhesive effect between PEN, PFSA and the two adhesive layers of the hot melt adhesive. It does not bubble or crack after being soaked in a sulfuric acid aqueous solution at 95 °C and pH = 2 for more than 2000 h, and still maintains good adhesive performance.

[0032] The first adhesive layer can be used to bond PEN. The polyester resin in the first adhesive layer has a similar chemical structure to PEN and has good adhesiveness to PEN. However, it has been found that the surface energy of the PEN film material is low and its rigidity is strong, and the wettability of ordinary polyester resin to the PEN film material is poor. In the present invention, a polyester resin with a melt index ≥ 30 g / 10 min (160 °C / 2.16 kg) is used as the main material to improve its wettability to the PEN film material. For example, the melt index of the polyester resin can be 30 g / 10 min, 40 g / 10 min, 50 g / 10 min, 60 g / 10 min, 70 g / 10 min, 80 g / 10 min or a range composed of any two of them, thereby ensuring the wettability and adhesive strength of the first adhesive layer to PEN.

[0033] Introducing a styrene-based thermoplastic elastomer into the first adhesive layer can, on the one hand, improve the flexibility of the polyester resin, and on the other hand, when preparing the coating, such as coating the first adhesive layer on a PEN substrate, the introduction of the styrene-based thermoplastic elastomer can increase the initial adhesion of the first adhesive layer to PEN.

[0034] Introducing an appropriate amount of graft-type toughening agent into the first adhesive layer helps to improve the compatibility between the polyester resin and the styrene-based thermoplastic elastomer. The introduction of an epoxy-based chain extender can further form chemical bonding in the first adhesive layer to achieve chain extension, and can prevent the polyester resin from hydrolyzing or thermally degrading under long-term acid boiling conditions to restore and improve mechanical properties and thermal properties, etc. The first organic solvent is used to dissolve the remaining components in the first adhesive layer to ensure the coating processability.

[0035] In different embodiments, by weight, the amounts of each component in the first adhesive layer can be as follows:

[0036] The amount of the polyester resin can be 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts or a range composed of any two of them; the amount of the styrene-based thermoplastic elastomer can be 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts or a range composed of any two of them; the amount of the graft-type toughening agent can be 5 parts, 8 parts, 10 parts, 12 parts, 15 parts, 18 parts, 20 parts or a range composed of any two of them; the amount of the epoxy-based chain extender can be 0.1 part, 0.3 part, 0.5 part, 0.8 part, 1 part, 1.2 part, 1.5 part or a range composed of any two of them; the amount of the first organic solvent can be 100 parts, 120 parts, 150 parts, 180 parts, 200 parts or a range composed of any two of them.

[0037] The second adhesive layer can be used to connect PFSA. The ethylene-methyl acrylate copolymer in the second adhesive layer has good initial adhesion strength to PFSA. Therefore, the ethylene-methyl acrylate copolymer is used as the main material for bonding PFSA. An appropriate amount of copolyester hot melt adhesive is introduced to increase the adhesion strength between the first adhesive layer and the second adhesive layer. It is found that when the amount of copolyester hot melt adhesive is too small, the adhesion effect between the second adhesive layer and the first adhesive layer is significantly affected. When the amount of copolyester hot melt adhesive is too large, the adhesion between the second adhesive layer and PFSA will be affected. In the present invention, an appropriate amount of copolyester hot melt adhesive is introduced into the second adhesive layer to balance and ensure the adhesion performance of the second adhesive layer to the first adhesive layer and PFSA. The ethylene-methyl acrylate-glycidyl methacrylate terpolymer can improve the compatibility of the ethylene-methyl acrylate copolymer and the copolyester hot melt adhesive, as well as the flexibility of the second adhesive layer. The epoxy ring-opening promoter can promote the epoxy group opening of the ethylene-methyl acrylate-glycidyl methacrylate terpolymer in the second adhesive layer. The second organic solvent is used to dissolve the remaining components in the second adhesive layer to ensure the coating processability. In the present invention, the content of GMA in the ethylene-methyl acrylate-glycidyl methacrylate terpolymer is further regulated to be 3wt% - 6wt%. For example, it can be 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%, 6wt% or the range composed of any two of them. This helps to avoid the problem of film-forming crystal points on the basis of fully improving the compatibility of the second adhesive layer.

[0038] In a specific embodiment of the present invention, the styrenic thermoplastic elastomer includes at least one of styrene-butadiene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, and hydrogenated styrene-isoprene-styrene block copolymer. Further preferably, it includes at least one of hydrogenated styrene-butadiene-styrene block copolymer and hydrogenated styrene-isoprene-styrene block copolymer, which helps to further improve the long-term acid boiling resistance effect.

[0039] In a specific embodiment of the present invention, the grafting unit of the graft toughening agent is maleic anhydride and / or glycidyl methacrylate. Further, the graft toughening agent is at least one of SEBS grafted with maleic anhydride and / or glycidyl methacrylate.

[0040] In a specific embodiment of the present invention, in the graft toughening agent, the grafting rate of the grafting unit ≥ 0.5%. For example, it can be 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2% or the range composed of any two of them.

[0041] In the specific embodiments of the present invention, in the epoxy chain extender, the epoxy equivalent is 200 to 600 g / mol, for example, it can be 200 g / mol, 250 g / mol, 300 g / mol, 350 g / mol, 400 g / mol, 450 g / mol, 500 g / mol, 550 g / mol, 600 g / mol or the range composed of any two of them, so as to achieve appropriate chain extension to balance and ensure strength, toughness, acid boiling resistance performance, etc. Further, the epoxy chain extender includes at least one of the epoxy chain extender ADR-4400 of BASF or the epoxy chain extender ADR-4468 of BASF.

[0042] In the specific embodiments of the present invention, the first organic solvent includes methyl ethyl ketone and ethyl acetate. Further, in the first organic solvent, the mass ratio of methyl ethyl ketone to ethyl acetate is (1 to 3):1, for example, it can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1 or the range composed of any two of them. It is found that when the first organic solvent is a compound of methyl ethyl ketone and ethyl acetate, on the one hand, it can have a high solubility in the other components used in the first adhesive layer; on the other hand, it has a moderate boiling point, and drying can be ensured at an appropriate drying temperature, which is conducive to avoiding the generation of crystal points; moreover, this solvent is convenient for post-treatment.

[0043] In the specific embodiments of the present invention, in the ethylene-methyl acrylate copolymer, the content of methyl acrylate ≥ 20 wt%, for example, it can be 20 wt%, 22 wt%, 25 wt%, 28 wt%, 30 wt% or the range composed of any two of them, which helps to ensure the initial adhesive strength to PFSA and the adhesive strength to the first adhesive layer.

[0044] In the specific embodiments of the present invention, the melting point of the copolyester hot melt adhesive ≥ 110 °C, for example, it can be 110 °C, 120 °C, 130 °C, 140 °C, 150 °C or the range composed of any two of them.

[0045] In the specific embodiments of the present invention, the epoxy ring-opening promoter includes at least one of 2,4,6-tris(dimethylaminomethyl)phenol, N,N-dimethylbenzylamine, and 1-benzyl-2-methylimidazole. The inventors of the present invention found in the research that in order to further match the film appearance and adhesiveness, for example, the epoxy ring-opening promoter basically does not undergo ring-opening reaction during the film-forming process, but undergoes ring-opening reaction during the subsequent hot pressing and lamination of PEN and PFSA and the long-term acid boiling process. At this time, the epoxy groups in the second adhesive layer will undergo chemical reactions with the various functional groups in the first adhesive layer, greatly increasing the adhesive reliability between the first adhesive layer and the second adhesive layer, and at the same time increasing the adhesive durability between the second adhesive layer and PFSA. The present invention has experimentally found that the above epoxy ring-opening promoters can achieve the above-mentioned expected effects.

[0046] In a specific embodiment of the present invention, the second organic solvent includes ethyl acetate and acetone. Further, in the second solvent, the mass ratio of ethyl acetate to acetone is (1-5):1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1 or the range composed of any two of them. It is found that when the second organic solvent is a mixture of ethyl acetate and acetone, on the one hand, it has a high solubility in the other components used in the second adhesive layer; on the other hand, it has a moderate boiling point, and drying can be ensured at an appropriate drying temperature, which is beneficial to avoiding the generation of crystal points; furthermore, this solvent is convenient for post-treatment.

[0047] In a specific embodiment of the present invention, the thickness of the hot melt adhesive is 10-25 μm, for example, it can be 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 25 μm or the range composed of any two of them. Further, the thicknesses of the first adhesive layer and the second adhesive layer are both ≥5 μm, for example, they can each independently be 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm or the range composed of any two of them.

[0048] The second aspect of the present invention provides a preparation method of the hot melt adhesive of the first aspect of the present invention, including the following steps:

[0049] (a) Mix the components of the first adhesive layer evenly, coat and dry to obtain the first adhesive layer;

[0050] (b) Mix the components of the second adhesive layer evenly, coat on the surface of the first adhesive layer and dry to obtain the hot melt adhesive.

[0051] In a specific embodiment of the present invention, in step (a), mixing evenly includes: mixing the polyester resin, styrene-based thermoplastic elastomer, graft-type toughening agent, epoxy-based chain extender, and the first organic solvent according to the ratio, and stirring at 400-1000 r / min until all components are dissolved.

[0052] In a specific embodiment of the present invention, in step (b), mixing evenly includes: mixing the ethylene-methyl acrylate copolymer, copolyester hot melt adhesive, ethylene-methyl acrylate-glycidyl methacrylate terpolymer, epoxy ring-opening promoter, and the second organic solvent according to the ratio, and stirring at 400-1000 r / min until all components are dissolved.

[0053] In a specific embodiment of the present invention, in step (a), coating includes: coating the mixed material on a PEN substrate. Further, the thickness of the PEN substrate can be 5-30 μm, but is not limited thereto.

[0054] In a specific embodiment of the present invention, in step (a), the drying includes: drying treatment at 90 - 110°C. The drying duration of step (a) is adjusted conventionally according to the volatilization of the first organic solvent in the coated layer until the first organic solvent is completely dried.

[0055] In a specific embodiment of the present invention, in step (b), the drying includes: drying treatment at 80 - 90°C. The drying duration of step (b) is adjusted conventionally according to the volatilization of the second organic solvent in the coated layer until the second organic solvent is completely dried.

[0056] The third aspect of the present invention provides a fuel cell membrane electrode, including the hot melt adhesive of the first aspect of the present invention.

[0057] In a specific embodiment of the present invention, the fuel cell membrane electrode includes a PFSA membrane and a PEN border membrane, and the PFSA membrane and the PEN border membrane are bonded by the hot melt adhesive of the present invention; the first adhesive layer of the hot melt adhesive of the present invention is bonded to the PEN border membrane, and the second adhesive layer is bonded to the PFSA membrane.

[0058] The hot melt adhesive of the present invention can be used for the encapsulation of fuel cell membrane electrodes. For example, it can be used to bond the PEN border membrane and the PFSA membrane of fuel cell membrane electrodes to achieve good encapsulation of fuel cell membrane electrodes.

[0059] Example 1

[0060] This example provides a hot melt adhesive, including a first adhesive layer and a second adhesive layer arranged in a stacked manner. The thickness of the first adhesive layer is 10 μm, and the thickness of the second adhesive layer is 10 μm.

[0061] By weight, the raw materials used in the first adhesive layer include: 60 parts of polyester resin, 30 parts of styrene-based thermoplastic elastomer, 10 parts of graft-type toughening agent, 0.5 part of epoxy chain extender, and 150 parts of the first organic solvent. Among them, the melt index (160°C / 2.16 kg) of the polyester resin is 65 g / 10 min (grade 3120H, manufacturer: Guangdong Shuntian New Materials Co., Ltd.); the styrene-based thermoplastic elastomer is hydrogenated styrene-butadiene-styrene block copolymer (SEBS) (grade: Kraton G1641 of the United States); the graft-type toughening agent is maleic anhydride grafted SEBS (grade: Kraton FG1901 of the United States, maleic anhydride grafting rate is 1.7%); the epoxy chain extender is BASF ADR-4468 of Germany; the first organic solvent is a mixture of methyl ethyl ketone and ethyl acetate with a mass ratio of 2:1.

[0062] By weight parts, the raw materials used in the second adhesive layer include: 50 parts of ethylene-methyl acrylate copolymer, 30 parts of copolyester hot melt adhesive, 20 parts of ethylene-methyl acrylate-glycidyl methacrylate terpolymer, 0.5 part of epoxy ring-opening accelerator, and 150 parts of a second organic solvent. Among them, the methyl acrylate content of the ethylene-methyl acrylate copolymer is 25 wt% (grade: Dow AC 1125 of the United States); the melting point of the copolyester hot melt adhesive is 130 °C (grade: HT-5130, manufacturer: Wenzhou Huate Hot Melt Adhesive Co., Ltd.); the GMA content of the ethylene-methyl acrylate-glycidyl methacrylate terpolymer is 6 wt% (grade: Sumitomo BF-7M of Japan); the epoxy ring-opening accelerator is 2,4,6-tris(dimethylaminomethyl)phenol; the second organic solvent is a mixture of ethyl acetate and acetone with a mass ratio of 2:1.

[0063] The preparation method of the hot melt adhesive in this embodiment includes the following steps:

[0064] (1) Stir the raw materials of the first adhesive layer at a stirring speed of 600 r / min at room temperature until the materials are dissolved and mixed evenly to obtain a first adhesive layer mixture;

[0065] (2) Coat the first adhesive layer mixture obtained in step (1) on the surface of a 25-μm-thick PEN substrate, and then place it in an oven at a temperature of 100 °C. After the organic solvent is dried, a PEN-first adhesive layer composite structure is obtained, and the thickness of the first adhesive layer is 10 μm;

[0066] (3) Stir the raw materials of the second adhesive layer at a stirring speed of 800 r / min at room temperature until the materials are dissolved and mixed evenly to obtain a second adhesive layer mixture;

[0067] (4) Coat the second adhesive layer mixture obtained in step (3) on the surface of the first adhesive layer of the composite structure obtained in step (2), and then place it in an oven at a temperature of 80 °C. After the organic solvent is dried, a PEN-first adhesive layer-second adhesive layer composite structure is obtained, and the thickness of the second adhesive layer is 10 μm.

[0068] Example 2

[0069] This embodiment provides a hot melt adhesive, including a first adhesive layer and a second adhesive layer arranged in a stacked manner. The thickness of the first adhesive layer is 8 μm, and the thickness of the second adhesive layer is 7 μm.

[0070] By weight parts, the raw materials used for the first adhesive layer include: 70 parts of polyester resin, 25 parts of styrenic thermoplastic elastomer, 5 parts of graft toughening agent, 0.8 part of epoxy chain extender, and 120 parts of the first organic solvent. Among them, the melt index (160 °C / 2.16 kg) of the polyester resin is 45 g / 10 min (grade 3150H, manufacturer: Guangdong Shuntian New Materials Co., Ltd.); the styrenic thermoplastic elastomer is hydrogenated styrene-isoprene-styrene block copolymer (SEPS) (grade: Baling Petrochemical YH-4053); the graft toughening agent is maleic anhydride grafted SEBS (grade: Formosa Plastics 7126 in Taiwan Province of China, maleic anhydride grafting rate is 1.6%); the epoxy chain extender is BASF ADR-4400 from Germany; the first organic solvent is a mixture of methyl ethyl ketone and ethyl acetate with a mass ratio of 3:1.

[0071] By weight parts, the raw materials used for the second adhesive layer include: 40 parts of ethylene-methyl acrylate copolymer, 35 parts of copolyester hot melt adhesive, 15 parts of ethylene-methyl acrylate-glycidyl methacrylate terpolymer, 0.3 part of epoxy ring-opening accelerator, and 180 parts of the second organic solvent. Among them, the methyl acrylate content of the ethylene-methyl acrylate copolymer is 29 wt% (grade: SK 29MA03T); the melting point of the copolyester hot melt adhesive is 126 °C (grade: Toyobo GM-913); the GMA content of the ethylene-methyl acrylate-glycidyl methacrylate terpolymer is 3 wt% (grade: Sumitomo BF-7L from Japan); the epoxy ring-opening accelerator is 1-benzyl-2-methylimidazole; the second organic solvent is a mixture of ethyl acetate and acetone with a mass ratio of 5:1.

[0072] The preparation method of the hot melt adhesive in this embodiment includes the following steps:

[0073] (1) Stir the raw materials of the first adhesive layer at a stirring speed of 500 r / min at room temperature until the materials are dissolved and mixed evenly to obtain the first adhesive layer mixture;

[0074] (2) Coat the first adhesive layer mixture prepared in step (1) on the surface of a 25-μm-thick PEN substrate, and then place it in an oven at a temperature of 90 °C. After the organic solvent is dried, a PEN-first adhesive layer composite structure is obtained, and the thickness of the first adhesive layer is 8 μm;

[0075] (3) Stir the raw materials of the second adhesive layer at a stirring speed of 600 r / min at room temperature until the materials are dissolved and mixed evenly to obtain the second adhesive layer mixture;

[0076] (4) Coating the second adhesive layer mixture prepared in step (3) on the surface of the first adhesive layer of the composite structure obtained in step (2), and then placing it in an oven at a temperature of 85 °C. After the organic solvent is dried, a PEN-first adhesive layer-second adhesive layer composite structure is obtained, and the thickness of the second adhesive layer is 7 μm.

[0077] Example 3

[0078] This example provides a hot melt adhesive, including a first adhesive layer and a second adhesive layer arranged in a stacked manner. The thickness of the first adhesive layer is 9 μm, and the thickness of the second adhesive layer is 12 μm.

[0079] By weight, the raw materials used for the first adhesive layer include: 50 parts of polyester resin, 35 parts of styrene-based thermoplastic elastomer, 15 parts of graft toughening agent, 1 part of epoxy chain extender, and 100 parts of the first organic solvent. Among them, the melt index (160 °C / 2.16 kg) of the polyester resin is 37 g / 10 min (grade SK EH100); the styrene-based thermoplastic elastomer is a hydrogenated styrene-butadiene-styrene block copolymer (SEBS) (grade Kraton G1651 from the United States); the graft toughening agent is maleic anhydride grafted SEBS (grade Kraton RP6670 from the United States, with a maleic anhydride grafting rate of 1.1%); the epoxy chain extender is BASF ADR-4468 from Germany; the first organic solvent is a mixture of methyl ethyl ketone and ethyl acetate with a mass ratio of 1:1.

[0080] By weight, the raw materials used for the second adhesive layer include: 45 parts of ethylene-methyl acrylate copolymer, 25 parts of copolyester hot melt adhesive, 30 parts of ethylene-methyl acrylate-glycidyl methacrylate terpolymer, 0.8 part of epoxy ring-opening accelerator, and 120 parts of the second organic solvent. Among them, the methyl acrylate content of the ethylene-methyl acrylate copolymer is 21.5 wt% (grade ExxonMobil TC120); the melting point of the copolyester hot melt adhesive is 112 °C (grade Toyobo GM-900); the GMA content of the ethylene-methyl acrylate-glycidyl methacrylate terpolymer is 6 wt% (grade Sumitomo BF-7M from Japan); the epoxy ring-opening accelerator is N,N-dimethylbenzylamine; the second organic solvent is a mixture of ethyl acetate and acetone with a mass ratio of 3:1.

[0081] The preparation method of the hot melt adhesive in this example includes the following steps:

[0082] (1) Stirring the raw materials of the first adhesive layer at a stirring speed of 700 r / min at room temperature until the materials are dissolved and mixed evenly to obtain the first adhesive layer mixture;

[0083] (2) Coat the first adhesive layer mixture prepared in step (1) on the surface of a 25-μm-thick PEN substrate, and then place it in an oven at 95 °C. After the organic solvent is dried, a PEN-first adhesive layer composite structure is obtained, and the thickness of the first adhesive layer is 9 μm;

[0084] (3) Stir the raw materials of the second adhesive layer at a stirring speed of 1000 r / min at room temperature until the materials are dissolved and mixed evenly to obtain the second adhesive layer mixture;

[0085] (4) Coat the second adhesive layer mixture prepared in step (3) on the surface of the first adhesive layer of the composite structure obtained in step (2), and then place it in an oven at 90 °C. After the organic solvent is dried, a PEN-first adhesive layer-second adhesive layer composite structure is obtained, and the thickness of the second adhesive layer is 12 μm.

[0086] Example 4

[0087] This example provides a hot melt adhesive, which includes a first adhesive layer and a second adhesive layer arranged in a laminated manner. The thickness of the first adhesive layer is 6 μm, and the thickness of the second adhesive layer is 8 μm.

[0088] By weight, the raw materials used in the first adhesive layer include: 65 parts of polyester resin, 20 parts of styrene-based thermoplastic elastomer, 15 parts of graft-type toughening agent, 1.2 parts of epoxy chain extender, and 140 parts of the first organic solvent. Among them, the melt index (160 °C / 2.16 kg) of the polyester resin is 65 g / 10 min (grade 3120H, manufacturer: Guangdong Shuntian New Materials Co., Ltd.); the styrene-based thermoplastic elastomer is hydrogenated styrene-isoprene-styrene block copolymer (SEPS) (grade Baling Petrochemical YH-4051); the graft-type toughening agent is glycidyl methacrylate grafted SEBS (manufacturer: Wuxi Zhiyuan Chemical Co., Ltd., the grafting rate of glycidyl methacrylate is 1.5%); the epoxy chain extender is BASF ADR-4400 from Germany; the first organic solvent is a mixture of methyl ethyl ketone and ethyl acetate with a mass ratio of 5:2.

[0089] By weight parts, the raw materials used in the second adhesive layer include: 55 parts of ethylene-methyl acrylate copolymer, 20 parts of copolyester hot melt adhesive, 25 parts of ethylene-methyl acrylate-glycidyl methacrylate terpolymer, 1.2 parts of epoxy ring-opening accelerator, and 100 parts of a second organic solvent. Among them, the methyl acrylate content of the ethylene-methyl acrylate copolymer is 30 wt% (grade: Dow AC 1330 of the United States); the melting point of the copolyester hot melt adhesive is 125 °C (grade: Toyobo 30P); the GMA content of the ethylene-methyl acrylate-glycidyl methacrylate terpolymer is 3 wt% (grade: Sumitomo BF-7L of Japan); the epoxy ring-opening accelerator is 2,4,6-tris(dimethylaminomethyl)phenol; the second organic solvent is a mixture of ethyl acetate and acetone with a mass ratio of 1:1.

[0090] The preparation method of the hot melt adhesive in this example includes the following steps:

[0091] (1) Stir the raw materials of the first adhesive layer at a stirring speed of 800 r / min at room temperature until the materials are dissolved and mixed evenly to obtain a first adhesive layer mixture;

[0092] (2) Coat the first adhesive layer mixture prepared in step (1) on the surface of a 25-μm-thick PEN substrate, and then place it in an oven at a temperature of 105 °C. After the organic solvent is dried, a PEN-first adhesive layer composite structure is obtained, and the thickness of the first adhesive layer is 6 μm;

[0093] (3) Stir the raw materials of the second adhesive layer at a stirring speed of 500 r / min at room temperature until the materials are dissolved and mixed evenly to obtain a second adhesive layer mixture;

[0094] (4) Coat the second adhesive layer mixture prepared in step (3) on the surface of the first adhesive layer of the composite structure obtained in step (2), and then place it in an oven at a temperature of 80 °C. After the organic solvent is dried, a PEN-first adhesive layer-second adhesive layer composite structure is obtained, and the thickness of the second adhesive layer is 8 μm.

[0095] Example 5

[0096] This example provides a hot melt adhesive, including a first adhesive layer and a second adhesive layer arranged in a laminated manner. The thickness of the first adhesive layer is 12 μm, and the thickness of the second adhesive layer is 6 μm.

[0097] By weight parts, the raw materials used in the first adhesive layer include: 80 parts of polyester resin, 10 parts of styrene-based thermoplastic elastomer, 10 parts of graft-type toughening agent, 0.3 parts of epoxy chain extender, and 180 parts of the first organic solvent. Among them, the melt index (160 °C / 2.16 kg) of the polyester resin is 45 g / 10 min (grade 3150H, manufacturer: Guangdong Shuntian New Materials Co., Ltd.); the styrene-based thermoplastic elastomer is hydrogenated styrene-butadiene-styrene block copolymer (SEBS) (grade: Kraton G1642 of the United States); the graft-type toughening agent is maleic anhydride-grafted SEBS (grade: Formosa Plastics 7131 of Taiwan Province of China, maleic anhydride grafting rate is 1.3%); the epoxy chain extender is BASF ADR-4468 of Germany; the first organic solvent is a mixture of methyl ethyl ketone and ethyl acetate with a mass ratio of 7:2.

[0098] By weight parts, the raw materials used in the second adhesive layer include: 60 parts of ethylene-methyl acrylate copolymer, 25 parts of copolyester hot melt adhesive, 15 parts of ethylene-methyl acrylate-glycidyl methacrylate terpolymer, 1.5 parts of epoxy ring-opening accelerator, and 200 parts of the second organic solvent. Among them, the methyl acrylate content of the ethylene-methyl acrylate copolymer is 24 wt% (grade: Dow AC 1224 of the United States); the melting point of the copolyester hot melt adhesive is 122 °C (grade: SK EH400); the GMA content of the ethylene-methyl acrylate-glycidyl methacrylate terpolymer is 6 wt% (grade: Sumitomo BF-7M of Japan); the epoxy ring-opening accelerator is 1-benzyl-2-methylimidazole; the second organic solvent is a mixture of ethyl acetate and acetone with a mass ratio of 4:1.

[0099] The preparation method of the hot melt adhesive in this embodiment includes the following steps:

[0100] (1) Stir the raw materials of the first adhesive layer at a stirring speed of 900 r / min at room temperature until the materials are dissolved and mixed evenly to obtain the first adhesive layer mixture;

[0101] (2) Coat the first adhesive layer mixture prepared in step (1) on the surface of a 25-μm-thick PEN substrate, and then place it in an oven at a temperature of 110 °C. After the organic solvent is dried, a PEN-first adhesive layer composite structure is obtained, and the thickness of the first adhesive layer is 12 μm;

[0102] (3) Stir the raw materials of the second adhesive layer at a stirring speed of 700 r / min at room temperature until the materials are dissolved and mixed evenly to obtain the second adhesive layer mixture;

[0103] (4) Coat the second adhesive layer mixture prepared in step (3) on the surface of the first adhesive layer of the composite structure obtained in step (2), and then place it in an oven at a temperature of 85 °C. After the organic solvent is dried, a PEN-first adhesive layer-second adhesive layer composite structure is obtained, and the thickness of the second adhesive layer is 6 μm.

[0104] Example 6

[0105] This example provides a hot melt adhesive, including a first adhesive layer and a second adhesive layer arranged in a laminated manner. The thickness of the first adhesive layer is 7 μm, and the thickness of the second adhesive layer is 15 μm.

[0106] By weight, the raw materials used in the first adhesive layer include: 55 parts of polyester resin, 25 parts of styrene-based thermoplastic elastomer, 20 parts of graft toughening agent, 0.6 part of epoxy chain extender, and 200 parts of the first organic solvent. Among them, the melt index (160 °C / 2.16 kg) of the polyester resin is 37 g / 10 min (grade SK EH100); the styrene-based thermoplastic elastomer is a hydrogenated styrene-isoprene-styrene block copolymer (SEPS) (grade Baleng Petrochemical YH-4052); the graft toughening agent is glycidyl methacrylate grafted SEBS (manufacturer: Wuxi Zhiyuan Chemical Co., Ltd., the grafting rate of glycidyl methacrylate is 1.5%); the epoxy chain extender is BASF ADR-4400 from Germany; the first organic solvent is a mixture of methyl ethyl ketone and ethyl acetate with a mass ratio of 7:3.

[0107] By weight, the raw materials used in the second adhesive layer include: 52 parts of ethylene-methyl acrylate copolymer, 26 parts of copolyester hot melt adhesive, 22 parts of ethylene-methyl acrylate-glycidyl methacrylate terpolymer, 1.8 parts of epoxy ring-opening accelerator, and 140 parts of the second organic solvent. Among them, the methyl acrylate content of the ethylene-methyl acrylate copolymer is 24 wt% (grade Dow AC 1224 from the United States); the melting point of the copolyester hot melt adhesive is 143 °C (grade Toyobo GM-400); the GMA content of the ethylene-methyl acrylate-glycidyl methacrylate terpolymer is 3 wt% (grade Sumitomo BF-7L from Japan); the epoxy ring-opening accelerator is N,N-dimethylbenzylamine; the second organic solvent is a mixture of ethyl acetate and acetone with a mass ratio of 5:2.

[0108] The preparation method of the hot melt adhesive in this example includes the following steps:

[0109] (1) Stir the raw materials of the first adhesive layer at a stirring speed of 1000 r / min at room temperature until the materials are dissolved and mixed evenly to obtain the first adhesive layer mixture;

[0110] (2) Coat the first adhesive layer mixture prepared in step (1) on the surface of a 25-μm-thick PEN substrate, and then place it in an oven at 95°C. After the organic solvent is dried, a PEN-first adhesive layer composite structure is obtained, and the thickness of the first adhesive layer is 7 μm;

[0111] (3) Stir the raw materials of the second adhesive layer at a stirring speed of 900 r / min at room temperature until the materials are dissolved and mixed evenly to obtain a second adhesive layer mixture;

[0112] (4) Coat the second adhesive layer mixture prepared in step (3) on the surface of the first adhesive layer of the composite structure obtained in step (2), and then place it in an oven at 90°C. After the organic solvent is dried, a PEN-first adhesive layer-second adhesive layer composite structure is obtained, and the thickness of the second adhesive layer is 15 μm.

[0113] Comparative Example 1

[0114] Comparative Example 1 refers to the hot melt adhesive and its preparation method in Example 1, the difference is that: the raw materials used in the first adhesive layer do not include styrene-based thermoplastic elastomer and graft-type toughening agent, and the rest are the same as those in Example 1.

[0115] By weight, the raw materials used in the first adhesive layer of Comparative Example 1 include: 100 parts of polyester resin, 0.5 part of epoxy chain extender, and 150 parts of the first organic solvent.

[0116] Comparative Example 2

[0117] Comparative Example 2 refers to the hot melt adhesive and its preparation method in Example 1, the difference is that: the raw materials used in the first adhesive layer do not include graft-type toughening agent, and the rest are the same as those in Example 1.

[0118] By weight, the raw materials used in the first adhesive layer of Comparative Example 2 include: 70 parts of polyester resin, 30 parts of styrene-based thermoplastic elastomer, 0.5 part of epoxy chain extender, and 150 parts of the first organic solvent.

[0119] Comparative Example 3

[0120] Comparative Example 3 refers to the hot melt adhesive and its preparation method in Example 1, the difference is that: the raw materials used in the first adhesive layer do not include epoxy chain extender, and the rest are the same as those in Example 1.

[0121] By weight, the raw materials used in the first adhesive layer of Comparative Example 3 include: 60 parts of polyester resin, 30 parts of styrene-based thermoplastic elastomer, 10 parts of graft-type toughening agent, and 150 parts of the first organic solvent.

[0122] Comparative Example 4

[0123] Comparative Example 4 refers to the hot melt adhesive and its preparation method in Example 1, with the difference that: the raw materials used in the second adhesive layer do not include copolyester hot melt adhesive, ethylene-methyl acrylate-glycidyl methacrylate terpolymer, and epoxy ring-opening promoter, and the rest are the same as those in Example 1.

[0124] By weight, the raw materials used in the second adhesive layer of Comparative Example 4 include: 100 parts of ethylene-methyl acrylate copolymer and 150 parts of a second organic solvent.

[0125] Comparative Example 5

[0126] Comparative Example 5 refers to the hot melt adhesive and its preparation method in Example 1, with the difference that: the raw materials used in the second adhesive layer do not include copolyester hot melt adhesive, and the rest are the same as those in Example 1.

[0127] By weight, the raw materials used in the second adhesive layer of Comparative Example 5 include: 80 parts of ethylene-methyl acrylate copolymer, 20 parts of ethylene-methyl acrylate-glycidyl methacrylate terpolymer, 0.5 part of epoxy ring-opening promoter, and 150 parts of a second organic solvent.

[0128] Comparative Example 6

[0129] Comparative Example 6 refers to the hot melt adhesive and its preparation method in Example 1, with the difference that: the raw materials used in the second adhesive layer do not include ethylene-methyl acrylate-glycidyl methacrylate terpolymer, and the rest are the same as those in Example 1.

[0130] By weight, the raw materials used in the second adhesive layer of Comparative Example 6 include: 70 parts of ethylene-methyl acrylate copolymer, 30 parts of copolyester hot melt adhesive, 0.5 part of epoxy ring-opening promoter, and 150 parts of a second organic solvent.

[0131] Comparative Example 7

[0132] Comparative Example 7 refers to the hot melt adhesive and its preparation method in Example 1, with the difference that: the type of ethylene-methyl acrylate-glycidyl methacrylate terpolymer used in the second adhesive layer is different, and the rest are the same as those in Example 1.

[0133] The GMA content of the ethylene-methyl acrylate-glycidyl methacrylate terpolymer used in the second adhesive layer of Comparative Example 7 is 8 wt% (grade: Arkema AX 8900 from France).

[0134] Comparative Example 8

[0135] Comparative Example 8 refers to the hot melt adhesive and its preparation method in Example 1, with the difference that: the raw materials used in the second adhesive layer do not include epoxy ring-opening promoter, and the rest are the same as those in Example 1.

[0136] By weight parts, the raw materials used in the second adhesive layer of Comparative Example 8 include: 50 parts of ethylene-methyl acrylate copolymer, 30 parts of copolyester hot melt adhesive, 20 parts of ethylene-methyl acrylate-glycidyl methacrylate terpolymer, and 150 parts of a second organic solvent.

[0137] Comparative Example 9

[0138] Comparative Example 9 refers to the hot melt adhesive and its preparation method in Example 1, the difference being that the type of polyester resin used in the first adhesive layer is different, and the rest is the same as in Example 1.

[0139] The melt index (160 °C / 2.16 kg) of the polyester resin used in the first adhesive layer of Comparative Example 9 is 15 g / 10 min (grade: HT-5120-C, manufacturer: Wenzhou Huate Hot Melt Adhesive Co., Ltd.).

[0140] Experimental Example

[0141] The hot melt adhesives obtained in each example and comparative example were respectively made into the following composite structure specimens:

[0142] PEN / hot melt adhesive / hot melt adhesive / PEN (PEN / first adhesive layer / second adhesive layer / second adhesive layer / first adhesive layer / PEN), PEN / hot melt adhesive / PFSA (PEN / first adhesive layer / second adhesive layer / PFSA), PEN / hot melt adhesive / PFSA / hot melt adhesive / PEN (PEN / first adhesive layer / second adhesive layer / PFSA / second adhesive layer / first adhesive layer / PEN); wherein, the thickness of PEN is 25 μm, and the thickness of PFSA is 15 μm; the composite structure specimens were prepared by laminating at a lamination temperature of 135 °C and a lamination pressure of 0.6 MPa for 10 s.

[0143] The composite structure specimens of PEN / hot melt adhesive / hot melt adhesive / PEN and PEN / hot melt adhesive / PFSA both had peeling openings, and their initial peeling strength and peeling strength after acid boiling for 2000 h were investigated;

[0144] The composite structure specimen of PEN / hot melt adhesive / PFSA / hot melt adhesive / PEN had no peeling opening and was a sealed structure, and the presence of bubbles and cracking after acid boiling for 2000 h was investigated.

[0145] Specifically, the initial peeling strength refers to: the peeling strength measured after cooling the prepared composite structure specimen to room temperature;

[0146] The peeling strength after acid boiling for 2000 h refers to: after cooling the prepared composite structure specimen to room temperature, immersing it in a sulfuric acid aqueous solution at 95 °C and pH = 2 for 2000 h, taking it out, drying the acid solution, and cooling it to room temperature before measuring the peeling strength;

[0147] Whether there are bubbles or cracks after acid boiling for 2000 h means that after cooling the prepared composite structure sample to room temperature, it is immersed in a sulfuric acid aqueous solution at 95 °C and pH = 2 for 2000 h, then taken out, the acid solution is wiped dry, cooled to room temperature, and the appearance of the sample is observed in a well-lit place to detect whether there are bubbles, and the sample is bent and folded in half to detect whether it cracks;

[0148] Whether there are crystal points in the film formation means that the PEN / hot melt adhesive composite structures prepared in different examples and comparative examples are placed under a lamp to detect the number of crystal points. If there are no crystal points with a diameter greater than 1 mm and the number of crystal points with a diameter between 0.5 and 1 mm is less than 5 per square meter, it means that the film formation has no crystal points, otherwise it means that the film formation has crystal points.

[0149] The test results of each item are shown in Table 1. Among them, the test method for the peel strength refers to GB / T GB8808-88 "Test Method for Peel of Flexible Composite Plastic Materials".

[0150] Table 1 Test Results of Each Example and Comparative Example

[0151]

[0152] From the test results of Example 1 and Comparative Examples 1-9, it can be seen that the styrene-based thermoplastic elastomer improves the flexibility of the polyester resin and does not affect its bonding effect on PEN; the graft-type toughening agent improves the compatibility of the polyester resin and the styrene-based thermoplastic elastomer, preventing phase separation from occurring after long-term acid boiling and deteriorating its performance; the epoxy-based chain extender is used to restore and improve the mechanical properties and thermal properties of the polyester resin under long-term acid boiling; an appropriate amount of copolyester hot melt adhesive effectively improves the bonding strength between the second adhesive layer and the first adhesive layer; the ethylene-methyl acrylate-glycidyl methacrylate terpolymer and the epoxy ring-opening promoter greatly improve the acid boiling resistance of the second adhesive layer to the first adhesive layer and the second adhesive layer to PFSA.

[0153] From the test results of Examples 1-6, it can be seen that the hot melt adhesive with a two-layer structure of the present invention can achieve good bonding between PEN and PFSA, and does not bubble or crack after being immersed in a sulfuric acid aqueous solution at 95 °C and pH = 2 for more than 2000 h, and still maintains good bonding performance. Moreover, the preparation process of the hot melt adhesive of the present invention is simple, the film formed by solution coating on the PEN substrate has no crystal points, and it can be continuously produced, and can be applied in the field of fuel cell membrane electrode encapsulation.

[0154] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. Hot melt adhesive, characterized in that: comprising a first adhesive layer and a second adhesive layer stacked; The first adhesive layer comprises the following components by weight: 50-80 parts of polyester resin, 10-40 parts of styrene thermoplastic elastomer, 5-20 parts of grafted toughening agent, 0.1-1.5 parts of epoxy chain extender and 100-200 parts of first organic solvent; the polyester resin has a 160°C / 2.16kg melt index of ≥30g / 10min; The second adhesive layer comprises the following components by weight: 40-60 parts of ethylene-methyl acrylate copolymer, 20-40 parts of copolyester hot melt adhesive, 10-30 parts of ethylene-methyl acrylate-glycidyl methacrylate terpolymer, 0.1-2 parts of epoxy ring-opening accelerator and 100-200 parts of second organic solvent; in the ethylene-methyl acrylate-glycidyl methacrylate terpolymer, the content of GMA is 3wt%-6wt%; The grafted toughening agent is at least one of SEBS grafted with maleic anhydride and / or glycidyl methacrylate.

2. The hot melt adhesive according to claim 1, characterized in that: The styrene-based thermoplastic elastomer includes at least one of a styrene-butadiene-styrene block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer, a styrene-isoprene-styrene block copolymer, and a hydrogenated styrene-isoprene-styrene block copolymer.

3. The hot melt adhesive according to claim 1, characterized in that: In the grafted toughening agent, the grafting rate of the grafted unit is ≥0.5%.

4. The hot melt adhesive according to claim 1, characterized in that: In the epoxy chain extender, the epoxy equivalent is 200 to 600 g / mol.

5. The hot melt adhesive according to claim 1, characterized in that: Having at least one of the following characteristics: (1) The first organic solvent includes butanone and ethyl acetate; (2) In the ethylene-methyl acrylate copolymer, the content of methyl acrylate is ≥ 20wt%.

6. The hot melt adhesive according to claim 1, characterized in that: The epoxy ring-opening accelerator includes at least one of 2,4,6-tris(dimethylaminomethyl)phenol, N,N-dimethylbenzylamine and 1-benzyl-2-methylimidazole.

7. The hot melt adhesive according to claim 1, characterized in that: Having at least one of the following characteristics: (1) The melting point of the copolyester hot melt adhesive is ≥110°C; (2) The second organic solvent includes ethyl acetate and acetone.

8. The hot melt adhesive according to claim 1, characterized in that: The thickness of the hot melt adhesive is 10 to 25 μm; The thickness of the first adhesive layer and the second adhesive layer are both ≥5 μm.

9. The method for preparing the hot melt adhesive according to any one of claims 1 to 8, characterized in that: The steps include: (a) uniformly mixing the components of the first adhesive layer, applying and drying to obtain the first adhesive layer; (b) The components of the second adhesive layer are mixed evenly, coated on the surface of the first adhesive layer, and dried to obtain a hot melt adhesive.

10. A fuel cell membrane electrode, characterized in that: The invention comprises the hot melt adhesive according to any one of claims 1 to 8 or the hot melt adhesive prepared by the preparation method according to claim 9.

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