Single-component epoxy adhesive for protection of nickel-hydrogen battery and preparation method thereof

Abstract

The present application relates to the technical fields of epoxy adhesive, in particular to a single-component epoxy adhesive for nickel-hydrogen battery protection and a preparation method thereof, which comprises at least, by weight: 18-26 parts of elastic epoxy organosilicon copolymer, 10-15 parts of polyacrylate modified epoxy resin, 2-3 parts of latent cationic curing agent, 1-2 parts of functional filler, 1-2 parts of silane coupling agent, 5-8 parts of active diluent, and 50-55 parts of nanoparticle dispersion. By optimizing the product formula system, the bonding strength, environmental durability, production process and functionality of the product are effectively balanced, and the practical application requirements of nickel-hydrogen battery protection are met.

Description

A single-component epoxy adhesive for protecting nickel-metal hydride batteries and its preparation method Technical Field

[0001] This invention relates to the field of epoxy adhesive technology, specifically to a single-component epoxy adhesive for the protection of nickel-metal hydride batteries and its preparation method. Background Technology

[0002] Nickel-metal hydride (NiMH) batteries are high-performance rechargeable batteries. Compared to traditional nickel-cadmium (NiCd) batteries, they offer advantages such as high energy density, no memory effect, and environmental friendliness, making them widely used in consumer electronics, power tools, hybrid vehicles, and energy storage. However, NiMH batteries also possess some inherent characteristics and risks during operation, making effective physical protection and secure fixing crucial. Currently, adhesives are primarily used to firmly bond and encapsulate the battery cells, battery management system, thermal management components, and structural parts together. As one of the key auxiliary materials for ensuring the safe, stable, and long-life operation of NiMH batteries, its development and performance assurance are of paramount importance.

[0003] Chinese patent application (publication number CN103074022A) discloses a thermally conductive electronic potting compound containing modified fillers. This is achieved by using modified fillers and rare-earth-doped nano-silicon carbide in the electronic potting compound, combined with diluents and coupling agents, to improve the product's thermal conductivity and insulation. Currently available polyurethane-modified epoxy resin-dicyandiamide epoxy adhesives, while possessing certain advantages in adhesion, suffer from high viscosity, slow curing speed, and insufficient chemical resistance, failing to meet the practical application requirements of nickel-metal hydride batteries. Chinese patent application (authorization announcement number CN115820169B) discloses an adhesive, tape, its preparation method, and an electrochemical device. This invention solves the problem of adhesive failure under high temperature and high humidity environments by using an improved adhesive in lithium-ion power batteries, combined with supramolecular compounds and other additives. However, existing adhesives still cannot meet the comprehensive application requirements of nickel-metal hydride battery protection in terms of adhesive strength, environmental durability, manufacturing processes, and functionality. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a single-component epoxy adhesive for protecting nickel-metal hydride batteries. By optimizing the product formulation system, it effectively balances the product's adhesive strength, environmental durability, manufacturing process, and functionality, thus meeting the practical application requirements for protecting nickel-metal hydride batteries.

[0005] One aspect of this invention provides a single-component epoxy adhesive for the protection of nickel-metal hydride batteries, comprising, by weight, at least: 18-26 parts of an elastic epoxy silicone copolymer, 10-15 parts of a polyacrylate-modified epoxy resin, 2-3 parts of a latent cationic curing agent, 1-2 parts of a functional filler, 1-2 parts of a silane coupling agent, 5-8 parts of an active diluent, and 50-55 parts of a nanoparticle dispersion.

[0006] In one embodiment, the elastic epoxy silicone copolymer has a silicone content of 30-50 wt%, an epoxy equivalent of 700-900 g / eq, and a dynamic viscosity of 30,000-55,000 centipoise at 25°C.

[0007] In one embodiment, the elastic epoxy silicone copolymer has a silicone content of 40 wt%, an epoxy equivalent of 850 g / eq, a dynamic viscosity of 45,000 centipoise at 25°C, and is designated Albiflex® 297, sourced from Evonik Industries.

[0008] In one embodiment, the latent cationic curing agent is a hexafluoroantimonate-based epoxy curing agent.

[0009] In one embodiment, the hexafluoroantimonate-based epoxy curing agent is designated K-PURECXC-1612 and is sourced from King Industries.

[0010] In one embodiment, the raw materials for preparing the polyacrylate-modified epoxy resin, by weight, include at least: 100 parts of polyacrylate resin, 200-250 parts of solvent, 20-25 parts of epoxy resin, 1-1.5 parts of triphenylphosphine, and 0.01-0.02 parts of hydroquinone.

[0011] In one embodiment, the raw materials for preparing the polyacrylate resin, by weight, include at least: 100-120 parts of an acrylic acid mixture solution, 10.5-12 parts of an initiator solution, and 10-15 parts of ethyl acetate.

[0012] In one embodiment, the acrylic acid mixture solution comprises acrylic acid, methacrylic acid, butyl acrylate, 2-fluoroacrylic acid, ethyl methacrylate and ethyl acetate in a mass ratio of (10-15):(5-10):(20-30):(20-30):(5-10):(25-30).

[0013] In one embodiment, the initiator solution comprises lauroyl peroxide and ethyl acetate in a mass ratio of (0.5-1):10.

[0014] In one embodiment, the method for preparing the polyacrylate resin includes the following steps: adding ethyl acetate to a reaction vessel, adding an acrylic acid mixture solution, heating to 70-75°C, adding an initiator solution dropwise, and performing a polymerization reaction for 7-8 hours; after the polymerization reaction is completed, heating to 90-100°C and vacuum treating for 1-1.5 hours to obtain the polyacrylate resin.

[0015] In one embodiment, the solvent is ethyl acetate.

[0016] In one embodiment, the epoxy resin is of type HiREM-1 and is sourced from Shikoku Chemical Industry Co., Ltd.

[0017] In one embodiment, the preparation method of the polyacrylate-modified epoxy resin includes the following steps: adding polyacrylate resin to a solvent and stirring to dissolve it; adding epoxy resin, triphenylphosphine and hydroquinone; controlling the reaction temperature at 85-90℃ and the reaction time at 2-3 hours; determining the acid value according to GB2895-82 method; terminating the reaction when the acid value drops below 1 mg KOH / g; and removing the solvent under vacuum at 95-100℃ to obtain the polyacrylate-modified epoxy resin.

[0018] This invention effectively improves the curing speed of the product while reducing its viscosity by using an elastic epoxy silicone copolymer in combination with a latent cationic curing agent and an active diluent, thus meeting the requirements of the spraying process. However, the product's curing shrinkage rate increases, its storage modulus decreases, and its glass transition temperature decreases. To address these issues, this invention initially introduces a core-shell rubber toughening agent. Although this improves the product's curing shrinkage rate, storage modulus, and glass transition temperature to some extent, it increases the product's water absorption rate, reduces its bond strength, and decreases its chemical resistance, failing to meet the practical application requirements of nickel-metal hydride batteries. Especially since nickel-metal hydride batteries use strongly alkaline electrolytes (such as KOH solution), the adhesive must be able to resist the erosion of the alkaline environment for a long time and must not swell, soften, hydrolyze, or chemically degrade. Furthermore, nickel metal is an inert material, making chemical bonding difficult, and its relatively smooth surface makes effective physical bonding in surface areas challenging. In addition, the surface layer of nickel reacts with moisture, and over time, moisture penetrates into the inner layer of the adhesive, causing a gradual decrease in adhesive strength. Further research in this invention revealed that by introducing a self-prepared polyacrylate-modified epoxy resin in combination with epoxy resin-containing nano-silica and elastic epoxy silicone copolymer, and by controlling the amount of addition, under the condition of the presence of a specific hexafluoroantimonate-based epoxy curing agent and silane coupling agent, the provided product exhibits excellent adhesion to inert nickel while also possessing excellent chemical resistance and impact resistance (mechanical and temperature difference), meeting the requirements of practical spraying processes and medium-temperature ultra-fast curing.

[0019] In one embodiment, the functional filler includes at least carbon black.

[0020] In one embodiment, the carbon black has a particle diameter of 20-30 nm and a nitrogen-attached specific surface area of ​​90-110 m². 2 / g.

[0021] In one embodiment, the carbon black has a particle diameter of 29 nm and a nitrogen-attached specific surface area of ​​92 m². 2 / g, model number is Mitsubishi carbon black MA-11.

[0022] In one embodiment, the silane coupling agent comprises at least an epoxy silane coupling agent.

[0023] In one embodiment, the epoxy silane coupling agent is designated Silquest A-187 and is sourced from Momentive Performance Materials Inc.

[0024] In one embodiment, the active diluent is selected from at least one of 1,4-butanediol diglycidyl ether or resorcinol diglycidyl ether.

[0025] In one embodiment, the nanoparticle dispersion is epoxy resin-containing nano-silica.

[0026] In one embodiment, the epoxy-containing nano-silica is designated NANOPOX® E 601 and is sourced from Evonik Industries.

[0027] Another aspect of the present invention provides a method for preparing a single-component epoxy adhesive for the protection of nickel-metal hydride batteries, comprising at least the following steps: adding an elastic epoxy silicone copolymer, a polyacrylate-modified epoxy resin, a latent cationic curing agent, and a nanoparticle dispersion into a reaction vessel, heating to 50-60°C, stirring for 1.5-2 hours until the latent cationic curing agent dissolves, cooling to 20-25°C, adding an active diluent, a functional filler, and a silane coupling agent, stirring and mixing, then dispersing through a three-roll mill, and finally degassing and encapsulating.

[0028] The single-component epoxy adhesive provided by this invention is easy to use, requires no on-site mixing, and avoids the limitations of uneven mixing, air bubbles, and operation time associated with two-component adhesives. It is very suitable for automated dispensing and large-scale production lines.

[0029] The single-component epoxy adhesive provided by this invention exhibits excellent storage stability, maintaining its performance for several months during transportation and storage at low temperatures. After assembly, it can be rapidly cured through a standardized heating process, improving production efficiency.

[0030] Beneficial effects

[0031] 1. This invention provides a single-component epoxy adhesive for the protection of nickel-metal hydride batteries. By optimizing the product formulation system, it effectively balances the product's adhesive strength, environmental durability, manufacturing process, and functionality, thereby meeting the practical application requirements for the protection of nickel-metal hydride batteries.

[0032] 2. This invention effectively improves the curing speed of the product while reducing its viscosity by using an elastic epoxy silicone copolymer in combination with a latent cationic curing agent and an active diluent, thus enabling the provided product to meet the requirements of the spraying process.

[0033] 3. In this invention, by introducing a self-prepared polyacrylate-modified epoxy resin in combination with epoxy resin-containing nano-silica and elastic epoxy silicone copolymer and controlling the amount of addition, under the condition of the presence of a specific hexafluoroantimonate-based epoxy curing agent and silane coupling agent, the provided product has excellent adhesion to inert metal nickel while also having excellent chemical resistance and impact resistance (mechanical and temperature difference), meeting the requirements of actual spraying processes and medium-temperature ultra-fast curing.

[0034] 4. The single-component epoxy adhesive provided by this invention is easy to use, requires no on-site mixing, and avoids the limitations of uneven mixing, air bubbles, and operation time associated with two-component adhesives. It is very suitable for automated dispensing and large-scale production lines.

[0035] 5. The single-component epoxy adhesive provided by this invention has good storage stability, maintaining its performance for several months during transportation and storage at low temperatures. After assembly, it can be rapidly cured through a standardized heating process, improving production efficiency. Attached Figure Description

[0036] Figure 1 is a comparison of the chemical resistance test results of the products in Examples 1 and 2. In the figure, a - the solution condition of Example 1 after the chemical resistance test, b - the adhesion condition of Example 2 after the chemical resistance test, and c - the adhesion condition of Example 1 after the chemical resistance test.

[0037] Figure 2 is a comparison of the chemical resistance test results of Comparative Examples 1, 3 and the control example. In the figure, a - the solution condition of Comparative Example 1 after the chemical resistance test, b - the solution condition of the control example after the chemical resistance test, c - the adhesion condition of Comparative Example 1 after the chemical resistance test, d - the adhesion condition of the control example after the chemical resistance test, and e - the adhesion condition of Comparative Example 3 after the chemical resistance test. Detailed Implementation

[0038] The information on raw materials used in the various embodiments and comparative examples of this invention is shown in Table 1.

[0039] Table 1

[0040]

[0041] The raw materials for preparing the polyacrylate-modified epoxy resin include at least: 100 parts polyacrylate resin, 250 parts solvent, 20 parts epoxy resin, 1 part triphenylphosphine, and 0.01 parts hydroquinone.

[0042] The raw materials for preparing the polyacrylate resin, by weight, include: 100 parts of acrylic acid mixture solution, 10.5 parts of initiator solution, and 10 parts of ethyl acetate.

[0043] The acrylic acid mixture solution comprises acrylic acid, methacrylic acid, butyl acrylate, 2-fluoroacrylic acid, ethyl methacrylate, and ethyl acetate in a mass ratio of 15:5:30:20:5:25.

[0044] The initiator solution comprises lauroyl peroxide and ethyl acetate in a mass ratio of 0.5:10.

[0045] The preparation method of the polyacrylate resin includes the following steps: adding ethyl acetate to a reaction vessel, adding an acrylic acid mixture solution, heating to 70°C, adding an initiator solution dropwise, and performing a polymerization reaction for 7 hours; after the polymerization reaction is completed, heating to 90°C and vacuum treating for 1 hour to obtain the polyacrylate resin.

[0046] The solvent is ethyl acetate.

[0047] The epoxy resin is of type HiREM-1 and is sourced from Shikoku Chemical Industry Co., Ltd.

[0048] The preparation method of the polyacrylate-modified epoxy resin includes the following steps: adding polyacrylate resin to a solvent and stirring to dissolve it; adding epoxy resin, triphenylphosphine and hydroquinone; controlling the reaction temperature at 85°C and the reaction time at 3 hours; determining the acid value according to GB2895-82 method; terminating the reaction when the acid value drops below 1 mg KOH / g; and removing the solvent under vacuum at 95°C to obtain the polyacrylate-modified epoxy resin.

[0049] Examples 1-3, Comparative Examples 1-5

[0050] Examples 1-3 and Comparative Examples 1-5 of the present invention provide a single-component epoxy adhesive for the protection of nickel-metal hydride batteries. The formulation by weight is shown in Table 2.

[0051] Table 2

[0052]

[0053] Examples 1-3 and Comparative Examples 1-5 of the present invention provide a method for preparing a single-component epoxy adhesive for the protection of nickel-metal hydride batteries, comprising the following steps: adding an elastic epoxy silicone copolymer, a polyacrylate-modified epoxy resin, a latent cationic curing agent, and a nanoparticle dispersion into a reaction vessel, heating to 50°C, stirring for 2 hours until the latent cationic curing agent dissolves, cooling to 20°C, adding an active diluent, a functional filler, and a silane coupling agent, stirring and mixing, then dispersing through a three-roll mill, and degassing and encapsulating.

[0054] Comparison Example

[0055] The comparative example of the present invention provides a polyurethane-modified epoxy resin-dicyandiamide combined epoxy adhesive, the formulation of which is shown in Table 3 by weight.

[0056] Table 3

[0057]

[0058] Performance testing

[0059] The following performance tests were performed on each embodiment, comparative example, and control example of this application, and the results are shown in Table 4.

[0060] 1. Viscosity and thixotropy:

[0061] Viscosity: Viscosity was measured using an Anton Paar Physica MCR302 rheometer at 23°C with a 200 μm gap using a standard measuring cone PP20, and determined at a shear rate of 10 / s.

[0062] Thixotropy: TI = viscosity at 6 rpm / viscosity at 60 rpm. Viscosity was tested using a Brookfield rotational viscometer.

[0063] 2. Curing shrinkage rate: (corresponding to low warpage): Refer to ISO-3521-1997 to calculate the curing shrinkage rate of the cured sample. The formula for calculating the curing shrinkage rate is: Curing shrinkage rate = (specific gravity of the cured resin - specific gravity of the resin liquid before curing) × 100% / specific gravity of the cured resin.

[0064] 3. Coefficient of thermal expansion (corresponding to low warpage): The linear coefficient of thermal expansion (CTE1α1 below Tg and CTE1α2 above Tg) of the cured sample was calculated by the TMA method under the condition of heating from 30°C to 260°C at a heating rate of 5°C / min using a thermal analysis instrument (model TMA, manufactured by TA).

[0065] 4. Storage Modulus: The storage modulus of the cured sample was tested using dynamic thermomechanical analysis (DMA). The DMA mold was a cuboid of 12mm × 35mm × 3mm (thickness). The prepared adhesive was injected into the prepared mold. Then, the adhesive was placed in an oven and cured according to the curing conditions in Table 4. Finally, the cured sample was polished to a smooth finish. The DMA was performed using a heating rate of 5℃ / min and an oscillation frequency of 1Hz, with a temperature range of 0℃ to 260℃, to test its storage modulus.

[0066] 5. Glass transition temperature (Tg): Based on static thermomechanical analysis using a thermal analysis instrument (model TMA450, manufactured by TA).

[0067] 6. Fracture toughness (K1c): The adhesive is injected into the mold to prepare a specimen with a length of 35mm × width of 7mm × thickness of 3mm. The specimen is then tested using an electronic universal testing machine (Shimadzu AGX-10kNVD). A crack is introduced in the middle of the specimen during preparation using a blade. The heating rate is 5℃ / min, and the temperature range is 0℃ to 260℃.

[0068] 7. Water absorption rate: Refer to ASTM D570IS062, the test conditions are 25℃ for 24 hours.

[0069] 8. Adhesive strength: Tested according to GB / T7124-2008 standard. Apply adhesive to a sample on a nickel sheet, then attach another nickel sheet to it, and cure according to the curing conditions in Table 4. After curing, test with a universal testing machine to obtain the adhesive strength.

[0070] 9. The curing rate determined by DSC is calculated as follows: (heat release of completely uncured resin ΔH - heat release of the test sample ΔH) / heat release of completely uncured resin ΔH × 100%, in accordance with QJ 2508-1993.

[0071] 10. Chemical resistance: First, spray a 100-micron thick epoxy adhesive onto the surface of the nickel sheet and cure it according to the curing conditions in Table 4. Then, immerse it in a 30wt% potassium hydroxide aqueous solution at 60℃ for 1000 hours and observe whether the surface swells, wrinkles / falls off and whether the potassium hydroxide aqueous solution changes color. See Figures 1 and 2 for the test results of Examples 1 and 2, Comparative Examples 1 and 3 and Control Examples.

[0072] Table 4

[0073]

[0074] As shown in Table 4, the products provided in Examples 1-3 have better overall performance than those provided in Comparative Examples 1-5 and the control examples, and can meet the actual application requirements of nickel-metal hydride batteries.

Claims

1. A single-component epoxy adhesive for protecting nickel-metal hydride batteries, characterized in that, By weight, the raw materials include at least: 18-26 parts of elastic epoxy silicone copolymer, 10-15 parts of polyacrylate-modified epoxy resin, 2-3 parts of latent cationic curing agent, 1-2 parts of functional filler, 1-2 parts of silane coupling agent, 5-8 parts of reactive diluent, and 50-55 parts of nanoparticle dispersion; the latent cationic curing agent is a hexafluoroantimonate-based epoxy curing agent, model K-PURECXC-1612; by weight, the raw materials for preparing the polyacrylate-modified epoxy resin include at least: 100 parts of polyacrylate resin, 200-250 parts of solvent, 20-25 parts of epoxy resin, and 1 part of triphenylphosphine. -1.5 parts, hydroquinone 0.01-0.02 parts; by weight, the raw materials for preparing the polyacrylate resin include at least: 100-120 parts of acrylic acid mixture solution, 10.5-12 parts of initiator solution, and 10-15 parts of ethyl acetate; the acrylic acid mixture solution includes acrylic acid, methacrylic acid, butyl acrylate, 2-fluoroacrylic acid, ethyl methacrylate ethoxylate and ethyl acetate in a mass ratio of (10-15):(5-10):(20-30):(20-30):(5-10):(25-30); the nanoparticle dispersion is nano-silica containing epoxy resin.

2. The single-component epoxy adhesive for protecting nickel-metal hydride batteries according to claim 1, characterized in that, The elastic epoxy silicone copolymer has a silicone content of 30-50 wt%, an epoxy equivalent of 700-900 g / eq, and a dynamic viscosity of 30,000-55,000 centipoise at 25°C.

3. The single-component epoxy adhesive for protecting nickel-metal hydride batteries according to claim 1, characterized in that, The functional filler includes at least carbon black.

4. The single-component epoxy adhesive for protecting nickel-metal hydride batteries according to claim 1, characterized in that, The silane coupling agent includes at least an epoxy silane coupling agent.

5. The single-component epoxy adhesive for protecting nickel-metal hydride batteries according to claim 1, characterized in that, The active diluent is selected from at least one of 1,4-butanediol diglycidyl ether or resorcinol diglycidyl ether.

6. A method for preparing a single-component epoxy adhesive for protecting nickel-metal hydride batteries according to any one of claims 1-5, characterized in that, The process includes at least the following steps: adding the elastic epoxy silicone copolymer, polyacrylate-modified epoxy resin, latent cationic curing agent, and nanoparticle dispersion into a reaction vessel, heating to 50-60℃, stirring for 1.5-2 hours until the latent cationic curing agent dissolves, cooling to 20-25℃, adding the reactive diluent, functional filler, and silane coupling agent, stirring and mixing, then dispersing through a three-roll mill, and finally degassing and encapsulating.

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