Hot melt adhesive, hydrogen fuel cell packaging hot melt adhesive film based on the hot melt adhesive, and method for preparing the same

Abstract

The application discloses a hot melt adhesive, a hydrogen fuel cell packaging hot melt adhesive film based on the hot melt adhesive and a preparation method of the hydrogen fuel cell packaging hot melt adhesive film, and the hot melt adhesive comprises the following components in parts by weight: 50-80 parts of a main resin, 10-50 parts of a tackifying resin, 2-10 parts of an adhesion modifying resin and 0.05-0.5 parts of an antioxidant; wherein the main resin comprises 80-95% of a main resin A and 5-20% of a main resin B in mass percentage, and the mass percentage of the main resin A and the main resin B is 100%. The hot melt adhesive film prepared from the hot melt adhesive provided by the application has no adhesion at room temperature, so that the placement accuracy can be improved and the rework can be reduced; meanwhile, the hot melt adhesive film has a high softening point and a high shear adhesion failure temperature, can guarantee the adhesion in a high-temperature and high-humidity environment and has excellent weather resistance, and can be well applied to the use environment of a fuel cell.

Description

Technical Field

[0001] This invention relates to the field of hot melt adhesive film technology, and in particular to a hot melt adhesive, a hot melt adhesive film for hydrogen fuel cell encapsulation based on the hot melt adhesive, and a method for preparing the same. Background Technology

[0002] With the technological advancements in hydrogen energy and fuel cells, a greener and more environmentally friendly hydrogen fuel energy revolution has arrived. Hydrogen fuel cells, due to their high energy conversion efficiency (40-60%), environmental friendliness, rapid start-up, and long service life, have become a key clean energy technology for development worldwide. A fuel cell consists of bipolar plates and a membrane electrode assembly (MEA), with the MEA serving as a crucial core component that plays a vital role in the fuel cell's performance, efficiency, lifespan, and cost.

[0003] The commonly referred to membrane electrode assembly (MEA) is a seven-layer MEA, including an anode gas diffusion layer, an anode frame, an anode catalyst layer, a proton exchange membrane, and a cathode catalyst layer, a cathode frame, and a cathode diffusion layer. Currently used proton exchange membranes are increasingly thinner, reducing their thickness from tens of micrometers to around 10 μm. This significantly reduces ohmic polarization, optimizes battery water management, and improves battery performance. Therefore, to protect the ultra-thin electrolyte membrane from damage during the encapsulation and hot-pressing process and to achieve gas and liquid sealing, a hot-melt adhesive film is added to the MEA structure as a protective frame. The seal is then pressed onto this protective frame, rather than onto the ultra-thin electrolyte membrane.

[0004] In fuel cell membrane electrode assembly (MEA) encapsulation technology, the encapsulation material plays a crucial role. Its performance directly affects the encapsulation and sealing effect, which in turn affects the cycle life and normal operation stability of the fuel cell. Existing fuel cell MEA encapsulation materials have shortcomings to varying degrees, including insufficient adhesion, poor temperature resistance, aging resistance, and hydrolysis resistance. Their mechanical properties, sealing performance, and performance stability need further improvement, and they are prone to degradation and migration, which can contaminate other components within the MEA.

[0005] Traditional epoxy resin adhesives, while having good bonding properties, suffer from poor weather resistance and are prone to cracking under high temperature and humidity conditions.

[0006] Patent document CN110444790B discloses a membrane electrode assembly, a preparation method, and a fuel cell single cell. The electrode encapsulation materials used are polyurethane elastomer (TPU), styrene-butadiene rubber (SBR) or ethylene propylene rubber (EPR), polyethersulfone resin (PES) or ethylene-vinyl acetate (EVA). However, these materials still have some defects in terms of adhesion and aging resistance, which need to be further improved.

[0007] Patent document CN114933866A discloses a fuel cell membrane electrode encapsulation material and its preparation method. The electrode encapsulation material adhesive layer uses a mixture of rosin-based hyperbranched epoxy resin, 2-(1-propen-2-yl)benzo[d]oxazole / isocyanoethyl methacrylate / N-(4-cyano-3-trifluoromethylphenyl)methacrylamide / tetrahydrofurfuryl acrylate copolymer, antioxidant, viscosity modifier, hydroxyl-terminated hyperbranched polyester, filler, coupling agent, etc., which are then dispersed in acetone after high-speed mixing and uniform stirring. This mixture is then coated onto the upper surface of a substrate layer to form the adhesive layer. This encapsulation material method suffers from drawbacks such as poor aging resistance, easy cracking, and easy degradation and migration that contaminates the membrane electrode.

[0008] Therefore, it is now necessary to improve existing technologies to provide more reliable solutions. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a hot melt adhesive, a hot melt adhesive film for hydrogen fuel cell encapsulation based on the hot melt adhesive, and a method for preparing the same.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: In the first aspect of the present invention, a hot melt adhesive is provided, which comprises the following components in parts by weight: 50-80 parts of main resin, 10-50 parts of tackifying resin, 2-10 parts of adhesive modifying resin, and 0.05-0.5 parts of antioxidant.

[0011] The main resin comprises 80-95% main resin A and 5-20% main resin B by mass, and the sum of the mass percentages of main resin A and main resin B is 100%.

[0012] Wherein, the main resin A is selected from one or more of the following: polyethylene, polypropylene, polyolefin elastomer, amorphous α-olefin copolymer, copolyester, polyether polyester, copolyamide, styrene-ethylene-butadiene-styrene copolymer, styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer, ethylene-acrylic acid copolymer, ethylene-propylene acetate copolymer, and ethylene-methyl methacrylate copolymer.

[0013] The main resin B is selected from one or more of the following: maleic anhydride modified polyolefin elastomer, acrylic acid modified polyolefin, maleic anhydride modified polyolefin, modified polypropylene, and chlorinated polyolefin.

[0014] Preferably, the main resin A is one or both of polyolefin elastomer and amorphous α-olefin copolymer.

[0015] Preferably, the tackifying resin is one or more of the following: C5 aliphatic petroleum resin, C9 aromatic petroleum resin, aromatic hydrocarbon modified aliphatic resin, rosin, hydrogenated rosin, and terpene resin.

[0016] Preferably, the adhesive-modified resin is one or more selected from the group consisting of: polyolefin resin modified with one or more of maleic anhydride, acrylic acid, hydroxyl and carboxyl groups, and polyolefin wax modified with one or more of maleic anhydride, acrylic acid, hydroxyl and carboxyl groups.

[0017] Preferably, the main resin A is a mixture of polyolefin elastomer and amorphous α-olefin copolymer, the main resin B is maleic anhydride modified polyolefin, the tackifying resin is C5 aliphatic petroleum resin, the adhesive modifying resin is maleic anhydride modified polypropylene wax, and the antioxidant is antioxidant 1010.

[0018] Preferably, the softening point of the main resin A is above 100°C and the shear bond failure temperature is above 100°C; the softening point of the main resin B is above 100°C and the shear bond failure temperature is above 60°C.

[0019] Preferably, the softening point of the tackifying resin is above 100°C, and the softening point of the adhesive modifying resin is above 100°C.

[0020] In a second aspect, the present invention provides a hot melt adhesive film for encapsulating a hydrogen fuel cell, comprising a substrate layer, a hot melt adhesive layer and a release film stacked sequentially, wherein the hot melt adhesive layer is obtained by coating the substrate layer with the hot melt adhesive as described above.

[0021] A third aspect of the present invention provides a method for preparing the hot melt adhesive film for hydrogen fuel cell encapsulation as described above, comprising the following steps:

[0022] S1. Mix 50-80 parts of the main resin, 10-50 parts of the tackifying resin, 2-10 parts of the adhesive modifying resin, and 0.05-0.5 parts of the antioxidant, melt at 150-200°C, and stir evenly to obtain the hot melt adhesive.

[0023] S2. Using a hot melt coating equipment, hot melt adhesive is applied to the surface of the substrate layer to form a hot melt adhesive layer with a thickness of 10 to 200 μm.

[0024] S3. Lay a release film onto the surface of the hot melt adhesive layer;

[0025] S4. Wind up and die-cut to obtain the hot melt adhesive film for hydrogen fuel cell encapsulation.

[0026] Preferably, the softening point of the hot melt adhesive layer is above 100°C, and the shear bond failure temperature is above 100°C.

[0027] The beneficial effects of this invention are:

[0028] The hot melt adhesive prepared by this invention by selecting a main resin with a softening point >100℃ and a shear bond failure temperature >100℃ and other tackifying resins and adhesive modifiers with a softening point greater than 100℃ has excellent water resistance and can maintain excellent adhesion for a long time under high temperature and high humidity conditions during fuel cell applications.

[0029] The hot melt adhesive film prepared by the hot melt adhesive provided by this invention is non-sticky at room temperature, thereby improving placement accuracy and reducing rework; at the same time, it has a high softening point and a high shear bond failure temperature, which can ensure that the adhesion is maintained in high temperature and high humidity environments, and has excellent weather resistance, making it well-suited for the use environment of fuel cells. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0031] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0032] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. For examples where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments whose manufacturers are not specified, they are all commercially available products.

[0033] The present invention provides a hot melt adhesive comprising the following components in parts by weight: 50-80 parts of main resin, 10-50 parts of tackifying resin, 2-10 parts of adhesive modifying resin, and 0.05-0.5 parts of antioxidant.

[0034] The main resin comprises 80-95% main resin A and 5-20% main resin B by mass, and the sum of the mass percentages of main resin A and main resin B is 100%.

[0035] In a preferred embodiment, the main resin A is selected from: polyethylene (PE), polypropylene (PP), polyolefin elastomer (POE), amorphous α-olefin copolymer (APAO), copolyester (PES), polyether polyester, copolyamide (COPA), styrene-ethylene-butadiene-styrene copolymer (SEBS), styrene-isoprene-styrene block copolymer (SIS), styrene-butadiene-styrene block copolymer (SBS), ethylene-acrylic acid copolymer (EAA), ethylene-propylene acetate copolymer (EEA), and ethylene-methyl methacrylate copolymer (EMMA). In a further preferred embodiment, the main resin A is one or both of polyolefin elastomer and amorphous α-olefin copolymer.

[0036] In a preferred embodiment, the main resin B is selected from one or more of the following: maleic anhydride modified polyolefin elastomer (MA-POE), acrylic acid modified polyolefin, maleic anhydride modified polyolefin (MA-APAO), modified polypropylene (MPP), and chlorinated polyolefin (CPP).

[0037] In a preferred embodiment, the tackifying resin is one or more of the following: C5 aliphatic petroleum resin, C9 aromatic petroleum resin, aromatic hydrocarbon modified aliphatic resin, rosin, hydrogenated rosin, and terpene resin.

[0038] In a preferred embodiment, the adhesive-modified resin is one or more selected from the group consisting of: polyolefin resins modified with one or more of maleic anhydride, acrylic acid, hydroxyl and carboxyl groups, and polyolefin waxes modified with one or more of maleic anhydride, acrylic acid, hydroxyl and carboxyl groups.

[0039] In a preferred embodiment, the antioxidant is antioxidant 1010 or antioxidant 168.

[0040] In a preferred embodiment, the softening point of the main resin A is above 100°C, more preferably above 130°C; and the shear bond failure temperature is above 100°C, more preferably above 110°C.

[0041] In a preferred embodiment, the softening point of the main resin B is above 100°C, more preferably above 130°C; and the shear bond failure temperature is above 60°C, more preferably above 80°C.

[0042] In a preferred embodiment, the softening point of the tackifying resin is above 100°C, more preferably above 130°C.

[0043] In a preferred embodiment, the softening point of the adhesive-modified resin is above 100°C, more preferably above 130°C.

[0044] The present invention also provides a hot melt adhesive film for encapsulating hydrogen fuel cells, comprising a substrate layer, a hot melt adhesive layer and a release film stacked sequentially, wherein the hot melt adhesive layer is obtained by coating the substrate layer with the hot melt adhesive as described above.

[0045] In a preferred embodiment, the substrate layer is polyethylene naphthalate (PEN), the release film is PET release film, and the surface of the PET release film is coated with a low-silicone release agent.

[0046] The present invention also provides a method for preparing the hot melt adhesive film for hydrogen fuel cell encapsulation as described above, comprising the following steps:

[0047] S1. Mix 50-80 parts of the main resin, 10-50 parts of the tackifying resin, 2-10 parts of the adhesive modifying resin, and 0.05-0.5 parts of the antioxidant, melt at 150-200°C, and stir evenly to obtain the hot melt adhesive.

[0048] S2. Using a hot melt coating device, hot melt adhesive is applied to the surface of the substrate layer to form a hot melt adhesive layer with a thickness of 10 to 200 μm, wherein the thickness of the hot melt adhesive layer is further preferably 15 to 50 μm.

[0049] S3. Lay a release film onto the surface of the hot melt adhesive layer;

[0050] S4. Wind up and die-cut to obtain the hot melt adhesive film for hydrogen fuel cell encapsulation.

[0051] In a preferred embodiment, the hot melt adhesive layer has no initial tack at room temperature; the softening point of the hot melt adhesive layer is above 100°C, more preferably above 130°C; and the shear bond failure temperature is above 100°C, more preferably above 110°C.

[0052] In the hot melt adhesive of this invention, modification with polar functional groups improves adhesion to the substrate layer, enhances water resistance, and reduces the risk of delamination between the adhesive surface and the substrate layer. Furthermore, since the softening point and shear failure temperature of the hot melt adhesive layer provided by this invention are both above 100°C, it ensures that the encapsulated hot melt adhesive film maintains excellent adhesion in the high-temperature water generated during hydrogen fuel cell operation. Tests showed that after boiling in pure water at 95–100°C for 1000 hours, the encapsulated hot melt adhesive film exhibited no cracking, delamination, bubbles, or exudates, and still maintained excellent adhesion.

[0053] The above is the general concept of the present invention. Based on this, detailed embodiments and comparative examples are provided below to further illustrate the present invention.

[0054] Example 1

[0055] A method for preparing a hot melt adhesive film for hydrogen fuel cell encapsulation includes the following steps:

[0056] S1. Heat the hot melt reactor to 200°C, then add the main resin, tackifying resin, adhesive modifier resin and antioxidant, and stir thoroughly to obtain hot melt adhesive.

[0057] S2. After being vacuum-defoamed and filtered for impurities, the hot melt adhesive is applied to the surface of the PEN substrate layer using a hot melt coating equipment, with a coating thickness of 15μm.

[0058] S3. Lay a PET release film onto the surface of the hot melt adhesive layer;

[0059] S4. Rewind and die-cut to obtain hydrogen fuel cell encapsulation hot melt adhesive film products A1-A4. The specific composition of each product is shown in Table 1 below:

[0060] Table 1: Components and proportions for preparing hot melt adhesive films A1-A4

[0061]

[0062]

[0063] Example 2

[0064] A method for preparing a hot melt adhesive film for hydrogen fuel cell encapsulation includes the following steps:

[0065] S1. Heat the hot melt reactor to 200°C, then add the main resin, tackifying resin, adhesive modifier resin and antioxidant, and stir thoroughly to obtain hot melt adhesive.

[0066] S2. After being vacuum-defoamed and filtered for impurities, the hot melt adhesive is applied to the surface of the PEN substrate layer using a hot melt coating equipment, with a coating thickness of 15μm.

[0067] S3. Lay a PET release film onto the surface of the hot melt adhesive layer;

[0068] S4. Winding and die-cutting yield hydrogen fuel cell encapsulation hot melt adhesive film products B1-B4. The specific composition of each product is shown in Table 2 below:

[0069] Table 2: Components and proportions for preparing hot melt adhesive films B1-B4

[0070]

[0071] Example 3

[0072] A method for preparing a hot melt adhesive film for hydrogen fuel cell encapsulation includes the following steps:

[0073] S1. Heat the hot melt reactor to 200°C, then add the main resin, tackifying resin, adhesive modifier resin and antioxidant, and stir thoroughly to obtain hot melt adhesive.

[0074] S2. After being vacuum-defoamed and filtered for impurities, the hot melt adhesive is applied to the surface of the PEN substrate layer using a hot melt coating equipment, with a coating thickness of 15μm.

[0075] S3. Lay a PET release film onto the surface of the hot melt adhesive layer;

[0076] S4. Winding and die-cutting yield hydrogen fuel cell encapsulation hot melt adhesive film products C1-C4. The specific component allocation of each product is shown in Table 3 below:

[0077] Table 3: Components and proportions for preparing hot melt adhesive films C1-C4

[0078]

[0079]

[0080] Example 4

[0081] A method for preparing a hot melt adhesive film for hydrogen fuel cell encapsulation includes the following steps:

[0082] S1. Heat the hot melt reactor to 200°C, then add the main resin, tackifying resin, adhesive modifier resin and antioxidant, and stir thoroughly to obtain hot melt adhesive.

[0083] S2. After being vacuum-defoamed and filtered for impurities, the hot melt adhesive is applied to the surface of the PEN substrate layer using a hot melt coating equipment, with a coating thickness of 15μm.

[0084] S3. Lay a PET release film onto the surface of the hot melt adhesive layer;

[0085] S4. Rewind and die-cut to obtain hydrogen fuel cell encapsulation hot melt adhesive film products D1 and D2. The specific composition of each product is shown in Table 4 below:

[0086] Table 4: Components and proportions for preparing hot melt adhesive films D1 and D2

[0087]

[0088] Comparative Example 1

[0089] A method for preparing a hot melt adhesive film for hydrogen fuel cell encapsulation includes the following steps:

[0090] S1. Heat the hot melt reactor to 200°C, then add the main resin, tackifying resin, adhesive modifier resin and antioxidant, and stir thoroughly to obtain hot melt adhesive.

[0091] S2. After being vacuum-defoamed and filtered for impurities, the hot melt adhesive is applied to the surface of the PEN substrate layer using a hot melt coating equipment, with a coating thickness of 15μm.

[0092] S3. Lay a PET release film onto the surface of the hot melt adhesive layer;

[0093] S4. Winding and die-cutting yield hydrogen fuel cell encapsulation hot melt adhesive film products E1-E3. The specific component allocation of each product is shown in Table 5 below:

[0094] Table 5: Components and proportions for preparing hot melt adhesive films E1-E3

[0095]

[0096] The following performance tests were conducted, and the test methods were as follows: softening point was performed in accordance with the national standard GB / T 15332-94; shear bond failure temperature was performed in accordance with GB / T 36794-2018; and peel force was performed in accordance with GBT2791-1995.

[0097] The test results are shown in Table 6 below:

[0098] Table 6: Performance test results of hot melt adhesive film after boiling in water at 95℃ for 1000 hours

[0099]

[0100] Because fuel cells inevitably experience various vibrations and compressions during use, the encapsulating membrane is subjected to multiple shear forces. Furthermore, the environment in which they operate is characterized by high temperature and humidity. Therefore, the encapsulating hot melt adhesive membrane needs to have good shear resistance, especially against shear forces under high temperature and humidity conditions. Based on the test results in Table 6:

[0101] The peel test results after boiling in water show that by compounding main resin A (80%–95%) and main resin B (5–20%), the shear failure temperature of the hot melt adhesive membrane can be increased to over 100°C. Furthermore, it retains excellent adhesion after aging for 1000 hours in water, with a peel force decrease of <5%. This ensures that the hot melt adhesive membrane maintains excellent performance in various complex working environments within fuel cells.

[0102] The boiling test results of Example A1 and Comparative Example E1 show that the peel strength of E1 decreased significantly after boiling for 1000 hours. This is mainly due to the weak adhesion of APAO resin alone to the substrate. Adding maleic anhydride-modified polyolefin and APAO compound can significantly enhance the adhesion between the hot melt adhesive film and the substrate, thereby improving its boiling resistance and peel strength after boiling.

[0103] The boiling test results of Example A2 and Comparative Example E2 show that the peel strength of E2 decreased significantly after boiling. This is mainly due to the low cohesive strength of the hot melt adhesive caused by the absence of APAO resin. A2 uses a blend of APAO resin and maleic anhydride-modified polyolefin, which can improve cohesive strength and adhesion to the substrate, thus ensuring that the peel strength remains essentially unchanged after boiling.

[0104] As can be seen from Examples A3 and Comparative Example E3, controlling the ratio of main resin A (80%–95%) to main resin B (5–20%) can regulate the shear failure temperature of the hot melt adhesive to >100°C, thereby ensuring that the hot melt adhesive film has excellent thermal shear resistance and excellent encapsulation effect.

[0105] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A hot melt adhesive, characterized in that, It comprises the following components in parts by weight: 50-80 parts of main resin, 10-50 parts of tackifying resin, 2-10 parts of adhesive modifying resin, and 0.05-0.5 parts of antioxidant; The main resin comprises 80-95% main resin A and 5-20% main resin B by mass, and the sum of the mass percentages of main resin A and main resin B is 100%. The main resin A is a mixture of polyolefin elastomer and amorphous α-olefin copolymer, and the main resin B is maleic anhydride modified polyolefin.

2. The hot melt adhesive according to claim 1, characterized in that, The tackifying resin is one or more of the following: C5 aliphatic petroleum resin, C9 aromatic petroleum resin, aromatic hydrocarbon modified aliphatic resin, rosin, hydrogenated rosin, and terpene resin.

3. The hot melt adhesive according to claim 1, characterized in that, The adhesive-modified resin is a polyolefin wax modified with one or more of maleic anhydride, acrylic acid, and hydroxyl groups.

4. The hot melt adhesive according to claim 1, characterized in that, The tackifying resin is C5 aliphatic petroleum resin, the adhesive modifying resin is maleic anhydride modified polypropylene wax, and the antioxidant is antioxidant 1010.

5. The hot melt adhesive according to claim 1, characterized in that, The softening point of the main resin A is above 100℃, and the shear bond failure temperature is above 100℃; the softening point of the main resin B is above 100℃, and the shear bond failure temperature is above 60℃.

6. The hot melt adhesive according to claim 1, characterized in that, The softening point of the tackifying resin is above 100°C, and the softening point of the adhesive modifying resin is above 100°C.

7. A hot melt adhesive film for encapsulating hydrogen fuel cells, characterized in that, It includes a substrate layer, a hot melt adhesive layer and a release film stacked sequentially, wherein the hot melt adhesive layer is obtained by coating the substrate layer with the hot melt adhesive as described in any one of claims 1-6.

8. A method for preparing a hot melt adhesive film for hydrogen fuel cell encapsulation as described in claim 7, characterized in that, Includes the following steps: S1. Mix 50-80 parts of the main resin, 10-50 parts of the tackifying resin, 2-10 parts of the adhesive modifying resin, and 0.05-0.5 parts of the antioxidant, melt at 150-200°C, and stir evenly to obtain the hot melt adhesive. S2. Using a hot melt coating device, hot melt adhesive is applied to the surface of the substrate layer to form a hot melt adhesive layer with a thickness of 10~200μm. S3. Lay a release film onto the surface of the hot melt adhesive layer; S4. Wind up and die-cut to obtain the hot melt adhesive film for hydrogen fuel cell encapsulation.

9. The method for preparing the hot melt adhesive film for hydrogen fuel cell encapsulation according to claim 8, characterized in that, The softening point of the hot melt adhesive layer is above 100°C, and the shear bond failure temperature is above 100°C.

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