Single-component waterway epoxy adhesive as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of adhesive preparation, and particularly relates to a single-component waterway epoxy adhesive as well as a preparation method and application thereof. The single-component epoxy adhesive for the waterway comprises the following components in parts by weight: 20-40 parts of epoxy resin, 40-60 parts of modified epoxy resin, 10-30 parts of a toughening composition, 0.1-2 parts of a defoaming agent, 10-50 parts of filler, 0.1-10 parts of a thixotropic agent and 10-30 parts of a latent curing agent. The adhesive disclosed by the invention is resistant to damp heat, cooling liquid and acid, has the advantages of good toughness, good manufacturability and the like, and can meet the adhesive requirements of the bipolar plate of the hydrogen fuel cell.

Description

Technical Field

[0001] The invention belongs to the technical field of adhesive preparation, and specifically relates to a one-component waterway epoxy adhesive and a preparation method and application thereof. Background Art

[0002] Hydrogen fuel cells have shown broad application prospects and market potential due to their clean and pollution-free characteristics and high energy conversion efficiency. As one of the important components of fuel cells, bipolar plates not only have the functions of conducting electricity and heat, but also need to support the membrane electrode and distribute the reaction gas. In order to ensure good sealing and bonding between bipolar plates, adhesives are usually required. However, adhesives used in hydrogen fuel cells often face complex working conditions such as high temperature, high humidity, and coolant erosion. Therefore, adhesives are required to have excellent resistance to moisture and heat, coolant and acid, and must also meet the requirements of long battery life and high stability.

[0003] However, at present, fuel cell bipolar plate adhesives still have the following problems: First, ordinary epoxy resin adhesives have poor resistance to moisture, heat, coolant and acid when working in hydrogen fuel cell stacks, and are difficult to cope with high temperature, high humidity, coolant erosion and acidic environments, resulting in insufficient service life and stability; second, special epoxy resins that are resistant to chemical media are generally solid or semi-solid at room temperature. When various components are added to improve resistance to moisture, heat, coolant and acid, the viscosity of the adhesive increases significantly, resulting in poor operability and difficulty in achieving uniform mixing and efficient construction.

[0004] Patent CN116426234A uses one or two of o-cresol epoxy resin and silicone modified epoxy resin as solvent-resistant epoxy resins, and one or two of dicyclopentadiene epoxy resin and polyol resin as hydrophobic epoxy resins to improve the solvent resistance and water resistance of the adhesive. However, the softening point of the solvent-resistant epoxy resin CYDCN-200 used in the embodiment of the patent is 60-75°C, and its preparation method only preheats and mixes the hydrophobic epoxy resin and the toughening resin, ignoring the raw material state of the solvent-resistant o-cresol epoxy resin CYDCN-200. It is difficult to fully melt and mix with other components at room temperature, resulting in limited performance of the adhesive.

[0005] Therefore, there is an urgent need to develop a one-component water-path epoxy adhesive for bonding fuel cell bipolar plates to solve the problems of insufficient moisture and heat resistance, coolant resistance and acid resistance, as well as poor operability of adhesives in the prior art, so as to meet the use requirements of hydrogen fuel cells under complex working conditions. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a one-component waterway epoxy adhesive and a preparation method and application thereof. The adhesive of the present invention is resistant to moisture and heat, coolant, and acid, and has the advantages of good toughness and good processability, and can meet the adhesive requirements of hydrogen fuel cell bipolar plates.

[0007] The technical solution adopted by the present invention to solve the above problems is as follows:

[0008] A one-component waterway epoxy adhesive comprises the following components by weight: 20-40 parts of epoxy resin, 40-60 parts of modified epoxy resin, 10-30 parts of toughening composition, 0.1-2 parts of defoaming agent, 10-50 parts of filler, 0.1-10 parts of thixotropic agent and 10-30 parts of latent curing agent.

[0009] Preferably, the epoxy resin is bisphenol A epoxy resin.

[0010] Furthermore, the modified epoxy resin comprises the following raw materials in parts by weight: 50 to 70 parts of low-viscosity epoxy resin, 5 to 10 parts of modified cashew nut shell oil, and 30 to 50 parts of chemical-resistant epoxy resin.

[0011] Furthermore, the low-viscosity epoxy resin is at least one of a low-viscosity bisphenol A epoxy resin and a low-viscosity bisphenol F epoxy resin.

[0012] Preferably, the viscosity of the low-viscosity epoxy resin is in the range of 3000 to 5500 mPa.s.

[0013] Furthermore, the chemical-resistant epoxy resin is at least one of phenolic epoxy resin, dicyclopentadiene epoxy resin, biphenyl epoxy resin, and naphthalene epoxy resin.

[0014] Furthermore, the preparation method of the modified epoxy resin comprises the following steps:

[0015] (1) Weigh 50-70 parts of low-viscosity epoxy resin, 5-10 parts of modified cashew nut shell oil, and 30-50 parts of chemical-resistant epoxy resin;

[0016] (2) heating the temperature to 120-130°C, stirring at a speed of 200-300 r / min for 1-2 hours, and then stirring at a speed of 800-1000 r / min for 2-3 hours;

[0017] (3) Stop heating, continue stirring for 1 to 2 hours, then stop stirring and filter, cool to room temperature to obtain a modified epoxy resin.

[0018] Furthermore, the toughening composition is a core-shell rubber particle dispersion; in the core-shell rubber particle dispersion, the core polymer of the core-shell rubber particles is one or a mixture of butadiene rubber, butadiene styrene rubber and silicone rubber; the shell polymer of the core-shell rubber particles is one or both of an acrylate polymer or an epoxy resin.

[0019] Preferably, the defoaming agent is at least one of BYK-A530, BYK-A550, Deqian Defom6800, Shanghai Tiger Additives Tech-49202, Tech-330, and Tech-386N produced by German BYK Chemical.

[0020] Furthermore, the filler is one or more of hydrophobically modified silica powder, modified mica powder, modified glass flakes, and vinyl modified glass fiber.

[0021] Furthermore, the thixotropic agent is one or a mixture of hydrophobically treated and untreated fumed silica, and treated and untreated bentonite.

[0022] Preferably, the thixotropic agent is hydrophobically treated fumed silica.

[0023] The present invention also provides a method for preparing the above-mentioned one-component waterway epoxy adhesive, comprising the following steps:

[0024] S1. According to the formula, the epoxy resin, modified epoxy resin, toughening composition and defoaming agent are first added to the reactor and mixed;

[0025] S2. Add filler and thixotropic agent to the reactor and mix according to the formula;

[0026] S3. Cooling water is passed through the reactor to control the temperature of the mixture within 20 to 35 ° C, and then the latent curing agent is added to the reactor to mix;

[0027] S4. After the mixing is completed, filtering and centrifugal degassing are performed to obtain a single-component water-based epoxy adhesive.

[0028] Preferably, in step S1, the mixing revolution speed is 30 Hz, the dispersion speed is 20 Hz, and the time is 30 to 60 minutes.

[0029] Preferably, in step S2, the mixing revolution speed is 30 Hz, the dispersion speed is 20 Hz, and the time is 90 to 120 min.

[0030] Preferably, in step S3, the mixing revolution speed is 20 Hz, the dispersion speed is 15 Hz, and the time is 90 to 120 min.

[0031] More preferably, the mixing is vacuum mixing.

[0032] Preferably, in step S4, the filtration is performed using a filter screen of 150 to 200 meshes and through a press.

[0033] The present invention also provides the use of the single-component waterway epoxy adhesive as described above in the preparation of graphite bipolar plates for hydrogen fuel cells.

[0034] The present invention has the following beneficial effects:

[0035] The one-component water-path epoxy adhesive of the present invention has excellent moisture and heat resistance, and can remain stable for a long time in a high temperature and high humidity environment, ensuring the reliable operation of the hydrogen fuel cell; secondly, the adhesive of the present invention has a strong tolerance to the coolant, and can resist the chemical corrosion therein, which is beneficial to prolonging the service life of the battery; in addition, the adhesive can still remain stable in an acidic environment, ensuring the normal operation of the battery under various working conditions. After curing, the adhesive of the present invention has high peel strength and shear strength, ensuring close bonding and sealing between the bipolar plates, and improving the stability of the overall structure. The adhesive of the present invention exhibits excellent durability and stability under a variety of complex working conditions, can significantly prolong the service life of hydrogen fuel cells, and meet the requirements of hydrogen fuel cell bipolar plates for long life and high reliability of adhesives. DETAILED DESCRIPTION

[0036] The specific technical solutions adopted by the present invention to solve the above problems are as follows:

[0037] A one-component waterway epoxy adhesive comprises the following components by weight: 20-40 parts of epoxy resin, 40-60 parts of modified epoxy resin, 10-30 parts of toughening composition, 0.1-2 parts of defoaming agent, 10-50 parts of filler, 0.1-10 parts of thixotropic agent and 10-30 parts of latent curing agent.

[0038] In certain preferred embodiments of the present invention, the epoxy resin is a bisphenol A epoxy resin. For example, the bisphenol A epoxy resin may be NPEL-128, but the present invention is not limited thereto.

[0039] In some specific embodiments of the present invention, the modified epoxy resin comprises the following raw materials in parts by weight: 50-70 parts of low-viscosity epoxy resin, 5-10 parts of modified cashew nut shell oil, and 30-50 parts of chemical-resistant epoxy resin.

[0040] In some specific embodiments of the present invention, the low-viscosity epoxy resin is at least one of a low-viscosity bisphenol A epoxy resin and a low-viscosity bisphenol F epoxy resin.

[0041] In certain preferred embodiments of the present invention, the viscosity of the low-viscosity epoxy resin ranges from 3000 to 5500 mPa.s.

[0042] For example, the low-viscosity bisphenol A epoxy resin may be Yangnong YN1821 or Xinzhengxing JY6121; the bisphenol F epoxy resin may be EPON Resin 862 or NPEF-170; but the present invention is not limited thereto.

[0043] In the modified epoxy resin, the cashew nut shell oil modified substance has a unique long carbon chain structure, which can provide higher flexibility and impact resistance; and it contains an aromatic ring structure, has good chemical resistance and heat resistance, and helps to improve the water resistance, bending strength, impact toughness and high and low temperature resistance of the epoxy resin composition. Exemplarily, the cashew nut shell oil modified substance includes but is not limited to Cardolite NC-513, Ultra Lite 513, NC-514 (S), Atu K-513, Huntsman Araldite DY-CNO / US.

[0044] In some specific embodiments of the present invention, the chemical-resistant epoxy resin is at least one of a phenolic epoxy resin, a dicyclopentadiene epoxy resin, a biphenyl epoxy resin, and a naphthalene epoxy resin.

[0045] For example, the phenolic epoxy resin may be DOW DEN438, Huntsman 8250, Changchun CNE202; the dicyclopentadiene type epoxy resin can be selected from Changchun DNE260, DIC HP-7200L, HP-7200, HP-7200H; the biphenyl type epoxy resin can be selected from Mitsubishi YX4000, YX4000K; the naphthalene type epoxy resin can be selected from DICHP-4032, HP-4032D.

[0046] In the above technical scheme, the modified epoxy resin uses a chemical medium resistant epoxy resin containing a multi-ring molecular structural unit (such as dicyclopentadiene, biphenyl and naphthalene, etc.), which can effectively improve the heat resistance, hygroscopicity and coolant acid resistance of the adhesive; but most of these structural resins are in a solid or semi-solid state at room temperature, and the use of low-viscosity bisphenol A type epoxy resin or low-viscosity bisphenol F type epoxy resin and chemical medium resistant epoxy resin by heating and melting can achieve a viscosity reduction effect. This process does not require the use of organic solvents, and will not produce the problem of high organic volatile content and serious environmental pollution.

[0047] In some specific embodiments of the present invention, the method for preparing the modified epoxy resin comprises the following steps:

[0048] (1) Weigh 50-70 parts of low-viscosity epoxy resin, 5-10 parts of modified cashew nut shell oil, and 30-50 parts of chemical-resistant epoxy resin;

[0049] (2) heating the temperature to 120-130°C, then stirring at a speed of 200-300 r / min for 1-2 hours, and then stirring at a speed of 800-1000 r / min for 2-3 hours;

[0050] (3) Stop heating, continue stirring for 1 to 2 hours, then stop stirring and filter, cool to room temperature to obtain a modified epoxy resin.

[0051] In some specific embodiments of the present invention, the toughening composition is a core-shell rubber particle dispersion; in the core-shell rubber particle dispersion, the core polymer of the core-shell rubber particles is one or a mixture of butadiene rubber, butadiene styrene rubber and silicone rubber; the shell polymer of the core-shell rubber particles is one or both of an acrylate polymer or an epoxy resin.

[0052] For example, the toughening composition includes, but is not limited to, the MX series products of Kaneka Chemical, such as the trade names MX-125, MX-153, and MX-154; the core-shell rubber particles and epoxy resin dispersions thereof such as PARALOID EXL 2600 of Rohm & Haas. The selected core-shell rubber can improve the brittleness of the epoxy resin, improve the bonding strength of the adhesive, the high and low temperature alternation resistance, and the impact resistance.

[0053] In certain preferred embodiments of the present invention, the defoaming agent is at least one of BYK-A530, BYK-A550, Deqian Defom 6800, Shanghai Tiger Additives Tech-49202, Tech-330, and Tech-386N produced by German BYK Chemicals.

[0054] In some specific embodiments of the present invention, the filler is one or more of hydrophobically modified silica powder, modified mica powder, modified glass flakes, and vinyl modified glass fiber.

[0055] In certain preferred embodiments of the present invention, the filler is hydrophobically modified silica powder.

[0056] Illustratively, the hydrophobically modified silicon micropowder includes, but is not limited to, the modified silicon micropowder of Foshan Huaya Nanotechnology Co., Ltd., the modified silicon micropowder of Guangzhou Xiyi Chemical Co., Ltd., and the like.

[0057] In some specific embodiments of the present invention, the thixotropic agent is one or a mixture of hydrophobically treated and untreated fumed silica, and treated and untreated bentonite.

[0058] In certain preferred embodiments of the present invention, the thixotropic agent is hydrophobically treated fumed silica.

[0059] Exemplarily, the treated hydrophobic fumed silica includes but is not limited to R202, R 805, R972, etc.

[0060] For example, the latent curing agent includes but is not limited to NOVACURE HX-3722 from ASAHI KASEI of Japan or Fuji Chemical Co., Ltd. of Japan, Fuji FXR-1020, FXR-1081 or Ajinomoto PN-23, MY-24, PN-H, MY-25, etc. These commercial products can be used alone or in combination of two or more.

[0061] The present invention also provides a method for preparing the above-mentioned one-component waterway epoxy adhesive, comprising the following steps:

[0062] S1. According to the formula, the epoxy resin, modified epoxy resin, toughening composition and defoaming agent are first added to the reactor and mixed;

[0063] S2. Add filler and thixotropic agent to the reactor and mix according to the formula;

[0064] S3. Cooling water is passed through the reactor to control the temperature of the mixture within 20 to 35 ° C, and then the latent curing agent is added to the reactor to mix;

[0065] S4. After the mixing is completed, filtering and centrifugal degassing are performed to obtain a single-component water-based epoxy adhesive.

[0066] In certain preferred embodiments of the present invention, in step S1, the mixing revolution speed is 30 Hz, the dispersion speed is 20 Hz, and the time is 30 to 60 min.

[0067] In certain preferred embodiments of the present invention, in step S2, the mixing revolution speed is 30 Hz, the dispersion speed is 20 Hz, and the time is 90 to 120 min.

[0068] In certain preferred embodiments of the present invention, in step S3, the mixing revolution speed is 20 Hz, the dispersion speed is 15 Hz, and the time is 90 to 120 min.

[0069] In some more preferred embodiments of the present invention, the mixing is vacuum mixing.

[0070] In certain preferred embodiments of the present invention, in step S4, the filtration is performed using a 150-200 mesh filter and a press.

[0071] The present invention also provides the use of the single-component waterway epoxy adhesive as described above in the preparation of graphite bipolar plates for hydrogen fuel cells.

[0072] In order to make the technical problems, technical solutions and technical advantages to be solved by the present invention clearer, the following will be described in detail with reference to specific examples, but the protection scope of the present invention is not limited to the following specific embodiments, and the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, and are not limitations of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0073] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0074] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0075] Preparation Example 1: Preparation of modified epoxy resin 1

[0076] (1) Weigh 60 parts of low-viscosity bisphenol A epoxy resin YN1821, 10 parts of cashew nut shell oil modified material UltraLite513, and 40 parts of dicyclopentadiene epoxy resin DNE260;

[0077] (2) The temperature was heated to 130°C, and then stirred at 240 r / min for 2 h, and then stirred at 1000 r / min for 2 h;

[0078] (3) Stop heating, continue stirring for 2 h, then stop stirring and filter, cool to room temperature to obtain modified epoxy resin 1.

[0079] Preparation Example 2: Preparation of modified epoxy resin 2

[0080] (1) Weigh 60 parts of bisphenol F epoxy resin NPEF-170, 8 parts of cashew nut shell oil modified material NC-513, 10 parts of novolac epoxy resin CNE202, and 30 parts of biphenyl epoxy resin YX4000;

[0081] (2) The temperature was heated to 130°C, and then stirred at 240 r / min for 2 h, and then stirred at 1000 r / min for 2 h;

[0082] (3) Stop heating, continue stirring for 2 h, then stop stirring and filter, cool to room temperature to obtain a modified epoxy resin.

[0083] Preparation Example 3: Preparation of modified epoxy resin 3

[0084] (1) Weigh low viscosity bisphenol A epoxy resin JY6121, 5 parts of cashew nut shell oil modified material NC-514S, 30 parts of phenolic epoxy resin DEN438, and 10 parts of naphthalene epoxy resin HP-4032;

[0085] (2) The temperature was heated to 120°C, and then stirred at 240 r / min for 2 h, and then stirred at 1000 r / min for 2 h;

[0086] (3) Stop heating, continue stirring for 2 h, then stop stirring and filter, cool to room temperature to obtain a modified epoxy resin.

[0087] Table 1 is a table of component contents of the adhesives of Examples 1 to 4 and Comparative Examples 1 to 3, unit: parts by weight.

[0088]

[0089] The steps for preparing the one-component waterway epoxy adhesive in Examples 1 to 4 are as follows:

[0090] S1. According to the formula in Table 1, epoxy resin, modified epoxy resin, toughening composition and defoaming agent are first added to a reaction kettle and mixed under vacuum, with an orbital speed of 30 Hz, a dispersion speed of 20 Hz and a time of 60 min;

[0091] S2. Add filler and thixotropic agent into the reactor according to the formula in Table 1 and mix them under vacuum. The revolution speed is 30 Hz, the dispersion speed is 20 Hz, and the time is 120 min.

[0092] S3. Cooling water is introduced into the reactor to control the temperature of the mixed material in the reactor within 20-35°C. According to the formula in Table 1, the latent curing agent is added to the reactor and vacuum mixed. The revolution speed is 20 Hz, the dispersion speed is 15 Hz, and the time is 120 min.

[0093] S4. After the mixing is completed, a 150-mesh filter is used and the filter is filtered and packaged through a press, and centrifugal degassing is performed to obtain a single-component water-based epoxy adhesive.

[0094] Comparative Example 1 The steps for preparing the epoxy adhesive are as follows:

[0095] S1. According to the formula in Table 1, epoxy resin, toughening composition and defoaming agent are first added to the reaction kettle and vacuum mixed at an orbital speed of 30 Hz, a dispersion speed of 20 Hz and a time of 60 min;

[0096] S2. Add filler and thixotropic agent into the reactor according to the formula in Table 1 and mix them under vacuum. The revolution speed is 30 Hz, the dispersion speed is 20 Hz, and the time is 120 min.

[0097] S3. Cooling water is introduced into the reactor to control the temperature of the mixed material in the reactor within 20-35°C. According to the formula in Table 1, the latent curing agent is added to the reactor and vacuum mixed. The revolution speed is 20 Hz, the dispersion speed is 15 Hz, and the time is 120 min.

[0098] S4. After the mixing is completed, a 150-mesh filter is used and the mixture is filtered, packaged, and centrifuged for degassing to obtain an epoxy adhesive.

[0099] Comparative Example 2 The steps for preparing the epoxy adhesive are as follows:

[0100] S1. According to the formula in Table 1, epoxy resin, high temperature resistant epoxy resin, toughening composition and defoaming agent are first added to a reaction kettle and mixed by vacuuming, with a revolution speed of 30 Hz, a dispersion speed of 20 Hz and a time of 60 min;

[0101] S2. Add filler and thixotropic agent into the reactor according to the formula in Table 1 and mix them under vacuum. The revolution speed is 30 Hz, the dispersion speed is 20 Hz, and the time is 120 min.

[0102] S3. Cooling water is introduced into the reactor to control the temperature of the mixed material in the reactor within 20-35°C. According to the formula in Table 1, the latent curing agent is added to the reactor and vacuum mixed. The revolution speed is 20 Hz, the dispersion speed is 15 Hz, and the time is 120 min.

[0103] S4. After the mixing is completed, a 150-mesh filter is used and the mixture is filtered, packaged, and centrifuged for degassing to obtain a high-temperature resistant epoxy adhesive.

[0104] Comparative Example 3 The steps for preparing the epoxy adhesive are as follows:

[0105] S1. Add epoxy resin and chemical resistant resin into a mixing barrel according to the formula ratio (4:1), set the heating temperature to 130°C, stir at a stirring speed of 240r / min for 2 hours, increase the speed to 1000r / min and stir for 2 hours. Turn off the heating and continue stirring for 2 hours. Stop the machine for filtering and cool to room temperature to obtain a premix;

[0106] S2. Add the premix obtained in step S1, the toughening composition and the defoaming agent into a reaction kettle according to the formula in Table 1 and mix them under vacuum at an orbital speed of 30 Hz and a dispersion speed of 20 Hz for 60 min.

[0107] S3. Add filler and thixotropic agent into the reactor according to the formula in Table 1 and mix them under vacuum. The revolution speed is 30 Hz, the dispersion speed is 20 Hz, and the time is 120 min.

[0108] S4. Cooling water is introduced into the reactor to control the temperature of the mixed material in the reactor within 20-35°C. According to the formula in Table 1, the latent curing agent is added to the reactor and vacuum mixed. The revolution speed is 20 Hz, the dispersion speed is 15 Hz, and the time is 120 min.

[0109] S5. After the mixing is completed, a 150-mesh filter is used and the material is filtered, packaged, and centrifuged for degassing to obtain an epoxy adhesive with high viscosity and resistance to chemical media.

[0110] The adhesives prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were tested for performance, and the specific method is as follows:

[0111] 1. Adhesion test:

[0112] The tensile shear strength test was used for evaluation.

[0113] Use 45# steel as the substrate (the reason why graphite plate is not used as the substrate is that all graphite plate bonding is substrate damage, and the bonding strength of each formula cannot be well compared). Polish and clean the surface of the 45# steel substrate to ensure that there is no oil stain and other impurities on the surface. Apply the adhesive to the surface of the 45# steel substrate with a thickness of 0.2mm and a size of 25mm*12.5mm. Curing at 120℃ for 30min, obtain the tensile shear strength test piece. According to GB / T 7124-2008 standard, the tensile shear strength test is carried out on a tensile testing machine.

[0114] Evaluation criteria: If the tensile shear strength of the adhesive is above 14 MPa, it is defined as very good adhesion; if the tensile shear strength of the adhesive is between 10 and 14 MPa, it is defined as good adhesion; if the tensile shear strength of the adhesive is less than 10 MPa, it is defined as fair adhesion.

[0115] 2. Moisture and heat resistance:

[0116] The evaluation was conducted using the change in tensile shear strength before and after high temperature and high humidity aging and the rate of mass change before and after hot water immersion.

[0117] 2.1. High temperature and high humidity test

[0118] Prepare the test piece according to the above tensile shear strength test method, and use a programmable constant temperature and humidity test machine for aging. Put the test piece into a high temperature and high humidity box set to double 85, take it out after 7 days, cool it to room temperature, and use a tensile test machine for testing.

[0119] If the tensile shear strength is above 10MPa, the test is defined as passed and the adhesive has good resistance to moisture and heat.

[0120] 2.2 Hot water immersion test

[0121] Use a mold to cure 5 small discs, each with a mass of 2.6 to 2.7 g. Place them in a 120°C oven for 30 minutes, mark them with a marker, and place them in a 50°C oven for 24 hours. Cool to room temperature, weigh the mass before immersion with an analytical balance with a sensitivity of 0.1 mg, and record the data. Place the small discs in 90°C water for 7 and 30 days, take them out, wipe off the surface moisture, and weigh the mass after immersion with an analytical balance.

[0122] The mass change rate is calculated according to the following formula: mass change rate (%) = (mass before immersion - mass after immersion) / mass before immersion × 100%. If the mass change rate is ≤ 3%, the adhesive is defined as having good moisture and heat resistance.

[0123] 3. Coolant resistance:

[0124] The mass change rate before and after immersion in high-temperature coolant was used for evaluation.

[0125] Use a mold to solidify 5 small discs, each with a mass of 2.6 to 2.7 g. Place them in a 120°C oven for 30 minutes, mark them with a marker, and place them in a 50°C oven for 24 hours. Cool to room temperature, weigh the mass before immersion with an analytical balance with a sensitivity of 0.1 mg, and record the data. Place the small disc in a 90°C coolant (ethylene glycol: water = 1:1) and soak for 7 days and 30 days. After taking them out, simply wipe the surface solution and weigh the mass after immersion with an analytical balance.

[0126] The mass change rate is calculated according to the following formula: mass change rate (%) = (mass before immersion - mass after immersion) / mass before immersion × 100%. If the mass change rate is ≤ 3%, the adhesive is defined as having good coolant resistance.

[0127] 4. Acid resistance:

[0128] The mass change rate before and after immersion in high-temperature acid solution was used for evaluation.

[0129] Test method for high temperature acid solution resistance: Use a mold to cure 5 small discs, each with a mass of 2.6 to 2.7 g, place them in a 120°C oven for 30 minutes, mark them with a marker, and place them in a 50°C oven for 24 hours. Cool to room temperature, weigh the mass before immersion with an analytical balance with a sensitivity of 0.1 mg, and record the data. Place the small disc in a 10% sulfuric acid solution at 90°C, soak for 7 days and 30 days, take it out, simply wipe the surface solution, and weigh the mass after immersion with an analytical balance.

[0130] The mass change rate is calculated according to the following formula: mass change rate (%) = (mass before immersion - mass after immersion) / mass before immersion × 100%. If the mass change rate is ≤ 3%, the adhesive is defined as having good acid resistance.

[0131] 5. Operability:

[0132] The evaluation was performed using the Brookfield viscometer test.

[0133] If the viscosity at 20 revolutions is ≤56000mPa.s, it is defined as OK and suitable for screen printing process; if the viscosity at 20 revolutions is greater than 56000mPa.s, it is defined as NG and not suitable for screen printing process.

[0134] The results of the above performance tests are shown in Table 2.

[0135] Table 2: Performance test results of adhesives prepared in Examples and Comparative Examples

[0136]

[0137] It can be seen from the above table that the tensile shear strength of the adhesives prepared in Examples 1 to 4 of the present invention are all above 14 MPa, having excellent bonding strength, and the average mass change rates when immersed in hot water, high-temperature coolant solution, and high-temperature acid solution are all ≤3%, indicating that the one-component adhesive of the present invention has good resistance to moisture and heat, resistance to coolant, and resistance to acid.

[0138] The adhesives prepared in Comparative Examples 1 to 2 have very good tensile shear strength before aging, but the tensile shear strength after high temperature and high humidity aging is less than 10 MPa. The high temperature resistant epoxy resin AG-80 is a tetraglycidylamine type epoxy resin. Although it is a high temperature resistant resin, it has poor moisture resistance. Even in the high temperature resistant coolant immersion test, the mass change rate is much higher than that of Comparative Example 1.

[0139] The adhesive prepared in Comparative Example 3 has good coolant resistance and acid resistance, but its high viscosity leads to poor wettability to the substrate, which affects the bonding strength. In addition, its viscosity is 271200 mPa.s, which is much greater than 56000 mPa.s and is not suitable for screen printing sizing process.

[0140] Compared with conventional epoxy resin adhesives, the one-component waterway epoxy adhesive of the present invention has better resistance to moisture and heat, resistance to coolant, resistance to acid, etc. If the adhesive strip needs better formability, the content of the thixotropic agent can be appropriately increased on the basis of the embodiment.

[0141] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0142] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0143] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A one-component waterway epoxy adhesive, characterized in that: The invention comprises the following components by weight: 20-40 parts of epoxy resin, 40-60 parts of modified epoxy resin, 10-30 parts of toughening composition, 0.1-2 parts of defoaming agent, 10-50 parts of filler, 0.1-10 parts of thixotropic agent and 10-30 parts of latent curing agent.

2. The one-component waterway epoxy adhesive according to claim 1, characterized in that: The modified epoxy resin comprises the following raw materials in parts by weight: 50-70 parts of low-viscosity epoxy resin, 5-10 parts of cashew nut shell oil modified material, and 30-50 parts of chemical medium resistant epoxy resin.

3. The one-component waterway epoxy adhesive according to claim 2, characterized in that: The viscosity of the low-viscosity epoxy resin ranges from 3000 to 5500 mPa.s.

4. The one-component waterway epoxy adhesive according to claim 2, characterized in that: The chemical medium resistant epoxy resin is at least one of phenolic epoxy resin, dicyclopentadiene epoxy resin, biphenyl epoxy resin and naphthalene epoxy resin.

5. The one-component waterway epoxy adhesive according to claim 1, characterized in that: The preparation method of the modified epoxy resin comprises the following steps: (1) Weigh 50-70 parts of low-viscosity epoxy resin, 5-10 parts of modified cashew nut shell oil, and 30-50 parts of chemical-resistant epoxy resin; (2) heating the temperature to 120-130°C, then stirring at a speed of 200-300 r / min for 1-2 hours, and then stirring at a speed of 800-1000 r / min for 2-3 hours; (3) Stop heating, continue stirring for 1 to 2 hours, then stop stirring and filter, cool to room temperature to obtain a modified epoxy resin.

6. The one-component waterway epoxy adhesive according to claim 1, characterized in that: The toughening composition is a core-shell rubber particle dispersion; in the core-shell rubber particle dispersion, the core polymer of the core-shell rubber particles is one or a mixture of butadiene rubber, butadiene styrene rubber and silicone rubber; the shell polymer of the core-shell rubber particles is one or both of acrylate polymer and epoxy resin.

7. The one-component waterway epoxy adhesive according to claim 1, characterized in that: The filler is one or more of hydrophobically modified silica powder, modified mica powder, modified glass flakes, and vinyl modified glass fiber.

8. The one-component waterway epoxy adhesive according to claim 1, characterized in that: The thixotropic agent is one or a mixture of hydrophobically treated and untreated fumed silica, and treated and untreated bentonite.

9. A method for preparing the one-component waterway epoxy adhesive according to any one of claims 1 to 7, characterized in that: The steps include: S1. First, epoxy resin, modified epoxy resin, toughening composition and defoaming agent are added to the reaction kettle and mixed according to the formula; S2. Add filler and thixotropic agent to the reactor and mix according to the formula; S3. Cooling water is passed through the reactor to control the temperature of the mixture within 20 to 35 ° C, and then the latent curing agent is added to the reactor to mix; S4. After the mixing is completed, filtering and centrifugal degassing are performed to obtain a single-component water-based epoxy adhesive.

10. Use of the one-component waterway epoxy adhesive according to any one of claims 1 to 7 in the preparation of graphite bipolar plates for hydrogen fuel cells.

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