A sealing compound for dry batteries and a method for preparing the same

Abstract

The application provides a sealing glue for dry batteries and a preparation method thereof, and the preparation raw materials include the following components in parts by weight: asphalt 30-40 parts, ethylene-propylene-diene rubber 12-20 parts, polyvinyl chloride 6-10 parts, epoxy grafted ethylene-propylene-diene rubber-chlorinated polyethylene blend 8-12 parts, epoxidized natural rubber 3-5 parts, modified nano calcium carbonate 6-10 parts, hydrophobic fumed nano silicon dioxide 2-4 parts, dioctyl adipate 4-6 parts, calcium-zinc composite heat stabilizer 1-2 parts, silane coupling agent 0.5-1.5 parts, vulcanization system 2.0-3.5 parts. The sealing glue for dry batteries provided by the application is compounded by asphalt, ethylene-propylene-diene rubber, polyvinyl chloride and the like, and has good sealing property, adhesion, weather resistance, low-temperature toughness, and can effectively prevent metal pole corrosion.

Description

Technical Field

[0001] This invention relates to the field of battery sealing materials technology, specifically to a sealing adhesive for dry batteries and its preparation method. Background Technology

[0002] Dry cell batteries are widely used portable chemical power sources, and the sealing adhesive is a key functional material that ensures the battery's sealing performance, storage life, and safety during use. Its main function is to seal the gap between the battery casing and the terminals, preventing electrolyte leakage and the intrusion of external moisture and oxygen, thus determining the battery's electrical performance stability and lifespan. Traditional dry cell battery sealing adhesives mostly use asphalt, single resins, or general-purpose rubber as the main base material. The manufacturing process is relatively simple and the cost is low, which can meet basic sealing requirements under normal use conditions.

[0003] However, existing sealing adhesives generally suffer from poor interfacial compatibility of multiphase components and insufficient bonding force with the metal electrode interface. At the same time, they are prone to decreased thermal stability, low-temperature brittleness, or high-temperature flow under alternating high and low temperature environments. They are difficult to balance sealing performance, weather resistance, mechanical strength, and processing stability. After long-term use, they are prone to problems such as battery leakage and electrode corrosion caused by interface debonding and adhesive layer failure. They are unable to meet the comprehensive performance requirements of sealing adhesives for high-performance dry batteries. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a sealing adhesive for dry batteries and its preparation method.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a sealing adhesive for dry batteries, which, by weight, comprises the following raw materials: 30-40 parts asphalt, 12-20 parts EPDM rubber, 6-10 parts polyvinyl chloride, 8-12 parts epoxy-grafted EPDM rubber-chlorinated polyethylene blend, 3-5 parts epoxidized natural rubber, 6-10 parts modified nano-calcium carbonate, 2-4 parts hydrophobic fumed nano-silica, 4-6 parts dioctyl adipate, 1-2 parts calcium-zinc composite heat stabilizer, 0.5-1.5 parts silane coupling agent, and 2.0-3.5 parts vulcanization system.

[0007] Using the above technical solutions, asphalt can provide basic sealing and adhesion performance; EPDM rubber can improve the weather resistance, elasticity, and low-temperature performance of the sealing adhesive; polyvinyl chloride can enhance the rigidity and chemical corrosion resistance of the material; epoxy-grafted EPDM rubber-chlorinated polyethylene blends can improve the interfacial compatibility between components and strengthen the interfacial bonding strength of the multiphase system; epoxidized natural rubber can further improve the compatibility between components; modified nano-calcium carbonate can enhance the interfacial adhesion between the sealing adhesive and the metal surface and reduce the damage to the interface caused by thermal shock under high and low temperature alternating environments; hydrophobic gas-phase nano-carbon dioxide... Silicon can form a three-dimensional network structure in the system, improving the thixotropic properties and high-temperature anti-flow properties of the system; dioctyl adipate can improve the low-temperature flexibility of the material; calcium-zinc composite heat stabilizers can inhibit the release of hydrogen chloride during the processing of polyvinyl chloride, reduce corrosion of metal electrodes, and inhibit the autocatalytic degradation of the material; silane coupling agents can enable the filler and organic matrix to form a stable interfacial bond and chemical bond, further strengthening the interfacial bond; the vulcanization system can enable the EPDM rubber phase to undergo a cross-linking reaction, forming a stable thermoplastic vulcanizate structure, ensuring the stability of the material during processing and use.

[0008] Preferably, the raw materials for preparing the epoxy-grafted EPDM-chlorinated polyethylene blend, by weight, include: 90-100 parts of EPDM, 50-60 parts of chlorinated polyethylene, 8-12 parts of glycidyl methacrylate, 0.8-1.5 parts of dicumyl peroxide, and 2-4 parts of epoxidized soybean oil.

[0009] Using the above technical solutions, EPDM rubber can provide good elasticity and weather resistance; chlorinated polyethylene has good compatibility with polyvinyl chloride due to their similar structure, improving the interfacial bonding ability between the blend and the polar component; glycidyl methacrylate can be grafted onto the EPDM rubber molecular chain under the action of an initiator, introducing epoxy groups and providing active sites for subsequent chemical reactions with the hydroxyl groups on the filler surface; dicumyl peroxide, as an initiator, can initiate the free radical graft polymerization of glycidyl methacrylate on the EPDM rubber molecular chain; epoxidized soybean oil can absorb and neutralize the hydrogen chloride that may be released during the processing of chlorinated polyethylene, stabilizing the reaction system and inhibiting the high-temperature thermal degradation of chlorinated polyethylene.

[0010] Preferably, the preparation method of the epoxy-grafted EPDM rubber-chlorinated polyethylene blend includes the following steps:

[0011] 1) Add EPDM rubber and chlorinated polyethylene to a mixer and plasticize for 2-3 minutes at a rotor speed of 50-70 r / min and a temperature of 60-80℃ to obtain a premix.

[0012] 2) Add glycidyl methacrylate, dicumyl peroxide and epoxidized soybean oil to the premix, heat to 120~130℃, adjust the rotor speed to 60~80r / min, and react for 15~25min under nitrogen protection.

[0013] 3) Cool the reaction product obtained in step 2) to 45~55℃, then transfer it to an open rubber mixing mill and pass it through a thin mill 3~5 times under the conditions of a roll gap of 0.5~1mm and a roll temperature of 40~50℃; granulate the material after thin passing, and control the particle size to 2~3mm to obtain the epoxy-grafted EPDM rubber-chlorinated polyethylene blend.

[0014] Using the above technical solution, EPDM rubber and chlorinated polyethylene can be plasticized under specific conditions to achieve preliminary uniform blending, providing a foundation for subsequent grafting reactions. Adding glycidyl methacrylate, dicumyl peroxide, and epoxidized soybean oil to the premix and reacting it under nitrogen protection allows glycidyl methacrylate to be grafted onto the EPDM rubber molecular chain under the action of dicumyl peroxide. Epoxidized soybean oil can stabilize the reaction system and reduce the thermal degradation of chlorinated polyethylene. Cooling, thinning, and granulating the reaction products can make the materials more uniformly mixed, facilitating further uniform integration of the components during the subsequent preparation of the sealing adhesive.

[0015] Preferably, the raw materials for preparing the modified nano-calcium carbonate, by weight, include: 90-100 parts of nano-calcium carbonate, 3-5 parts of stearic acid, 2-3 parts of dopamine hydrochloride, and 500-600 parts of tris(hydroxymethyl)aminomethane hydrochloride buffer solution; the concentration of the tris(hydroxymethyl)aminomethane hydrochloride buffer solution is 0.1-0.5 mol / L, and the pH is 8.0-8.5.

[0016] Using the above technical solution, nano-calcium carbonate provides a basic carrier for subsequent modification treatment; stearic acid can be coated on the surface of nano-calcium carbonate to form a modified layer; dopamine hydrochloride can undergo self-polymerization under suitable conditions to form a polydopamine layer and deposit on the surface of nano-calcium carbonate; a tris(hydroxymethyl)aminomethane hydrochloride buffer solution with a concentration of 0.1~0.5 mol / L and a pH of 8.0~8.5 can provide a weakly alkaline reaction environment required for the self-polymerization of dopamine hydrochloride, ensuring that the self-polymerization reaction proceeds stably and fully.

[0017] Preferably, the preparation method of the modified nano-calcium carbonate includes the following steps:

[0018] (1) Add nano-calcium carbonate to a high-speed mixer and stir and dry for 25-30 min at 100-110℃ and rotor speed of 1000-1200 r / min; mix stearic acid and anhydrous ethanol at a mass ratio of 1:1-2, heat to 70-80℃ to dissolve, and then spray the mixture evenly into nano-calcium carbonate through a spraying device. Continue stirring for 15-20 min under the above conditions to obtain stearic acid modified nano-calcium carbonate;

[0019] (2) Stearic acid modified nano-calcium carbonate was added to tris(hydroxymethyl)aminomethane hydrochloride buffer solution and ultrasonically dispersed for 20-30 min under ultrasonic power of 400-500 W and frequency of 30-40 kHz. Dopamine hydrochloride was added and stirred at 200-300 r / min at 25-30℃ for 18-24 h.

[0020] (3) After the reaction is completed, the reaction product is centrifuged, washed, dried, ground and passed through a 200-240 mesh sieve to obtain the modified nano calcium carbonate.

[0021] Using the above technical solution, by stirring, drying, and coating nano-calcium carbonate with stearic acid, stearic acid can be uniformly adsorbed onto the surface of nano-calcium carbonate, achieving preliminary modification of nano-calcium carbonate. Ultrasonic dispersion of stearic acid-modified nano-calcium carbonate in tris(hydroxymethyl)aminomethane hydrochloride buffer solution allows for uniform dispersion into a suspension. Adding dopamine hydrochloride followed by stirring allows dopamine hydrochloride to self-polymerize, forming a polydopamine layer that deposits on the surface of the stearic acid-modified nano-calcium carbonate. Centrifugation, washing, drying, grinding, and sieving of the reaction product removes impurities and controls the particle size of the modified nano-calcium carbonate.

[0022] Preferably, in step (3), the centrifugation, washing and drying steps are as follows: centrifuge at a speed of 5000~6000r / min for 10~15min, wash with deionized water 3~4 times and anhydrous ethanol 1~2 times in sequence, place the obtained filter cake in a vacuum drying oven, and dry it to constant weight under the conditions of vacuum degree -0.09~-0.095MPa and temperature 50~60℃.

[0023] By using the above technical solution, centrifugation of the reaction product can separate the solid product from the liquid system; washing with deionized water and anhydrous ethanol in sequence can remove unreacted raw materials and impurities adhering to the surface of the solid product; and drying the obtained filter cake in a vacuum drying oven to constant weight can remove moisture and residual solvent from the filter cake, thereby obtaining a dry solid product.

[0024] Preferably, the asphalt is No. 50 or No. 70 asphalt; the degree of polymerization of the polyvinyl chloride is 1500-2000, and the K value is 75-80; the degree of epoxidation of the epoxidized natural rubber is 25-40 mol%; and the specific surface area of ​​the hydrophobic fumed silica nanoparticles is 150-200 m² / g. 2 / g.

[0025] Using the above technical solutions, No. 50 or No. 70 asphalt can provide basic sealing and adhesion, while also possessing certain acid and alkali resistance; polyvinyl chloride with a degree of polymerization of 1500~2000 and a K value of 75~80 can provide the required rigidity and chemical corrosion resistance of the material, ensuring that it maintains high cohesive strength after plasticization; epoxidized natural rubber with an epoxidation degree of 25~40 mol% can improve the compatibility of the multiphase system through the interaction between its epoxy groups and the hydroxyl groups on the filler surface; and a specific surface area of ​​150~200 m² / g is required. 2 / g of hydrophobic fumed silica nanoparticles can form a three-dimensional thixotropic network in the system, enhancing the thixotropic properties of the system and improving the high-temperature flow resistance and cohesive strength of the material.

[0026] Preferably, the calcium-zinc composite heat stabilizer has a calcium-zinc molar ratio of 2.0~2.5:1; the silane coupling agent is KH-550 or KH-560; and the vulcanization system is composed of sulfur, accelerator TMTD, zinc oxide and stearic acid in a mass ratio of 1:0.4:1.5:0.8.

[0027] Using the above technical solutions, a calcium-zinc composite heat stabilizer with a calcium-zinc molar ratio of 2.0~2.5:1 can capture the hydrogen chloride released by the decomposition of polyvinyl chloride (PVC), preventing it from corroding the metal electrode or catalyzing the degradation of polymers. Furthermore, at this ratio, the zinc ion concentration is low, causing no significant interference to the vulcanization system. KH-550 or KH-560 type silane coupling agents can form hydrogen bonds, coordination bonds, or covalent bonds with the catechol groups or amino groups in the polydopamine layer on the surface of modified nano-calcium carbonate, achieving interfacial chemical bonding between the filler and the organic matrix and strengthening the interfacial bond. A vulcanization system composed of sulfur, accelerator TMTD, zinc oxide, and stearic acid in a mass ratio of 1:0.4:1.5:0.8 can initiate a cross-linking reaction in the EPDM rubber phase, forming a stable thermoplastic vulcanizate structure. It also exhibits weak degradation of PVC, ensuring the stability of PVC during dynamic vulcanization.

[0028] This invention also provides a method for preparing a sealing adhesive for dry batteries, comprising the following steps:

[0029] S1. Put EPDM rubber, polyvinyl chloride, and epoxy-grafted EPDM rubber-chlorinated polyethylene blend into an internal mixer and mix for 15-20 minutes at 130-140℃ and rotor speed of 60-80 r / min to obtain premixed masterbatch.

[0030] S2. Add preheated and melted asphalt and epoxidized natural rubber to the premixed masterbatch obtained in step S1, adjust the temperature to 120-130°C, rotate the rotor at 50-60 r / min, and continue mixing for 8-10 min to obtain the blend.

[0031] S3. Add dioctyl adipate and calcium-zinc composite heat stabilizer to the blend obtained in step S2, and control the temperature at 110~120℃ for 5~8 minutes.

[0032] S4. Cool the mixture obtained in step S3 to 100~110℃, add modified nano calcium carbonate, hydrophobic fumed nano silica and silane coupling agent, adjust the rotor speed to 80~90 r / min, and mix for 12~15 min.

[0033] S5. Cool the mixture obtained in step S4 to 90~110℃, add it to the vulcanization system, adjust the rotor speed to 40~50r / min, and mix until the torque reaches 1.5~2.0 times the initial torque. After discharge, pass it through an open rubber mixing mill 2~3 times with a roller gap of 1~2mm and a roller temperature of 40~50℃. After pressing or granulating, cool it to 25~30℃ to obtain the sealing adhesive for dry batteries.

[0034] Using the above technical solution, EPDM rubber, polyvinyl chloride, and epoxy-grafted EPDM rubber-chlorinated polyethylene blends are first fully fused to form a premixed masterbatch, ensuring uniform dispersion of each polymer component. Further mixing with asphalt and epoxidized natural rubber improves the compatibility of the multiphase system. The addition of dioctyl adipate and calcium-zinc composite heat stabilizer enhances material flexibility and reduces PVC degradation. The mixing of modified nano-calcium carbonate, hydrophobic fumed silica, and silane coupling agents achieves uniform filler dispersion and strengthens interfacial bonding. The addition of the vulcanization system triggers cross-linking of the EPDM phase to form a thermoplastic vulcanizate structure. Finally, through subsequent thin-pass processing, sheeting or granulation, and cooling, a stable sealing adhesive for dry batteries is obtained.

[0035] Preferably, in step S5, the time for mixing until the torque reaches 1.5 to 2.0 times the initial torque is 5 to 8 minutes.

[0036] Using the above technical solution, mixing for 5-8 minutes until the torque reaches 1.5-2.0 times the initial torque ensures that the vulcanization system fully initiates the crosslinking reaction of the EPDM rubber phase, so that the EPDM rubber phase forms a stable thermoplastic vulcanizate structure. This mixing time can ensure that the crosslinking reaction is sufficient and not excessive, so that the sealing adhesive for dry batteries forms a stable micro-phase state, ensuring the stability of the material's mechanical properties and sealing performance.

[0037] The beneficial effects of this invention are as follows:

[0038] Asphalt provides basic sealing and adhesion properties; EPDM rubber enhances the weather resistance, elasticity, and low-temperature performance of sealing adhesives; PVC strengthens the rigidity and chemical resistance of materials; epoxy-grafted EPDM-chlorinated polyethylene blends improve the interfacial compatibility between components and strengthen the interfacial bonding strength of multiphase systems; epoxidized natural rubber further enhances the compatibility between components; modified nano-calcium carbonate strengthens the interfacial adhesion between sealing adhesives and metal surfaces, reducing the damage to the interface caused by thermal shock under alternating high and low temperatures; hydrophobic fumed silica can contribute to the system's... The process involves forming a three-dimensional network structure to improve the thixotropic properties and high-temperature anti-flow properties of the system; dioctyl adipate can improve the low-temperature flexibility of the material; calcium-zinc composite heat stabilizer can inhibit the release of hydrogen chloride during the processing of polyvinyl chloride, reduce corrosion of metal electrodes, and inhibit the autocatalytic degradation of the material; silane coupling agent can enable the filler and organic matrix to form a stable interfacial bond and chemical bond, further strengthening the interfacial bond; the vulcanization system can enable the EPDM rubber phase to undergo a cross-linking reaction to form a stable thermoplastic vulcanizate structure, ensuring the stability of the material during processing and use. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] The specific information on the raw materials used in the embodiments of the present invention is shown in Table 1.

[0041] Table 1

[0042]

[0043] Example 1:

[0044] This embodiment provides a sealing adhesive for dry batteries. By weight, its raw materials include: 30 parts asphalt, 12 parts EPDM rubber, 6 parts polyvinyl chloride, 8 parts epoxy-grafted EPDM rubber-chlorinated polyethylene blend, 3 parts epoxidized natural rubber with an epoxidation degree of 25 mol%, 6 parts modified nano-calcium carbonate, and a specific surface area of ​​150 m² / g. 2The mixture consists of 2 parts of hydrophobic fumed silica, 4 parts of dioctyl adipate, 1 part of calcium-zinc composite heat stabilizer, 0.5 parts of silane coupling agent, and 2 parts of vulcanization system. The asphalt is No. 50 asphalt; the degree of polymerization of polyvinyl chloride is 1500, and the K value is 75. The calcium-zinc composite heat stabilizer has a calcium-zinc molar ratio of 2:1; the silane coupling agent is KH-550; the vulcanization system is composed of sulfur, accelerator TMTD, zinc oxide, and stearic acid in a mass ratio of 1:0.4:1.5:0.8.

[0045] The raw materials for preparing the epoxy-grafted EPDM-chlorinated polyethylene blend, by weight, include: 90 parts EPDM, 50 parts chlorinated polyethylene, 8 parts glycidyl methacrylate, 0.8 parts dicumyl peroxide, and 2 parts epoxidized soybean oil.

[0046] The preparation method of epoxy-grafted EPDM rubber-chlorinated polyethylene blend includes the following steps:

[0047] 1) Add EPDM rubber and chlorinated polyethylene to a mixer and plasticize for 2 minutes at a rotor speed of 50 r / min and a temperature of 60℃ to obtain a premix;

[0048] 2) Add glycidyl methacrylate, dicumyl peroxide and epoxidized soybean oil to the premix, heat to 120°C, adjust the rotor speed to 60 r / min, and react for 15 min under nitrogen protection.

[0049] 3) Cool the reaction product obtained in step 2) to 45°C, then transfer it to an open rubber mixing mill and pass it through a thin mill 3 times under the conditions of 0.5 mm roll gap and 40°C roll temperature; granulate the material after thin passing and control the particle size to 2 mm to obtain an epoxy-grafted EPDM rubber-chlorinated polyethylene blend.

[0050] The raw materials for preparing modified nano-calcium carbonate, by weight, include: 90 parts nano-calcium carbonate, 3 parts stearic acid, 2 parts dopamine hydrochloride, and 500 parts tris(hydroxymethyl)aminomethane hydrochloride buffer solution; the concentration of the tris(hydroxymethyl)aminomethane hydrochloride buffer solution is 0.1 mol / L, and the pH is 8.0.

[0051] The preparation method of modified nano-calcium carbonate includes the following steps:

[0052] (1) Add nano-calcium carbonate to a high-speed mixer and stir and dry for 25 min at 100°C and 1000 r / min rotor speed; mix stearic acid and anhydrous ethanol at a mass ratio of 1:1, heat to 70°C to dissolve, and then spray the mixture evenly into nano-calcium carbonate through a spraying device. Continue stirring for 15 min under the above conditions to obtain stearic acid modified nano-calcium carbonate.

[0053] (2) Stearic acid modified nano-calcium carbonate was added to tris(hydroxymethyl)aminomethane hydrochloride buffer and ultrasonically dispersed for 20 min under ultrasonic power of 400 W and frequency of 30 kHz. Dopamine hydrochloride was added and stirred at 200 r / min for 18 h at 25 °C.

[0054] (3) After the reaction is completed, the reaction product is centrifuged at 5000 r / min for 10 min, washed with deionized water 3 times and anhydrous ethanol once, and the resulting filter cake is placed in a vacuum drying oven and dried to constant weight under vacuum of -0.09 MPa and temperature of 50℃. After grinding, it is passed through a 200-mesh sieve to obtain modified nano calcium carbonate.

[0055] This embodiment also provides a method for preparing sealing adhesive for dry batteries, including the following steps:

[0056] S1. Ethylene propylene diene monomer (EPDM), polyvinyl chloride (PVC), and epoxy-grafted EPDM-chlorinated polyethylene (CPE) blend are put into an internal mixer and mixed for 15 minutes at 130°C and a rotor speed of 60 r / min to obtain a premixed masterbatch.

[0057] S2. Add preheated and melted asphalt and epoxidized natural rubber to the premixed masterbatch obtained in step S1, adjust the temperature to 120°C, rotate the rotor at 50 r / min, and continue mixing for 8 min to obtain the blend.

[0058] S3. Add dioctyl adipate and calcium-zinc composite heat stabilizer to the blend obtained in step S2, and mix at 110°C for 5 minutes.

[0059] S4. Cool the mixture obtained in step S3 to 100°C, add modified nano-calcium carbonate, hydrophobic fumed nano-silica and silane coupling agent, adjust the rotor speed to 80 r / min, and mix for 12 min.

[0060] S5. Cool the mixture obtained in step S4 to 90°C, add it to the vulcanization system, adjust the rotor speed to 40 r / min, mix for 5 min until the torque reaches 1.5 times the initial torque, after discharge, pass it through an open rubber mixing mill twice with a roller gap of 1 mm and a roller temperature of 40°C, and after pressing, cool it to 25°C to obtain the sealing adhesive for dry batteries.

[0061] Example 2:

[0062] This embodiment provides a sealing adhesive for dry batteries. By weight, its raw materials include: 40 parts asphalt, 20 parts EPDM rubber, 10 parts polyvinyl chloride, 12 parts epoxy-grafted EPDM rubber-chlorinated polyethylene blend, 5 parts epoxidized natural rubber with an epoxidation degree of 40 mol%, 10 parts modified nano-calcium carbonate, and a specific surface area of ​​200 m².2 The composition includes 4 parts of hydrophobic fumed silica, 6 parts of dioctyl adipate, 2 parts of calcium-zinc composite heat stabilizer, 1.5 parts of silane coupling agent, and 3.5 parts of vulcanization system. The asphalt is No. 70 asphalt; the degree of polymerization of polyvinyl chloride is 2000, and the K value is 80. The calcium-zinc composite heat stabilizer has a calcium-zinc molar ratio of 2.5:1; the silane coupling agent is KH-560; the vulcanization system is composed of sulfur, accelerator TMTD, zinc oxide, and stearic acid in a mass ratio of 1:0.4:1.5:0.8.

[0063] The raw materials for preparing the epoxy-grafted EPDM-chlorinated polyethylene blend, by weight, include: 100 parts EPDM, 60 parts chlorinated polyethylene, 12 parts glycidyl methacrylate, 1.5 parts dicumyl peroxide, and 4 parts epoxidized soybean oil.

[0064] The preparation method of epoxy-grafted EPDM rubber-chlorinated polyethylene blend includes the following steps:

[0065] 1) Add EPDM rubber and chlorinated polyethylene to a mixer and plasticize for 3 minutes at a rotor speed of 70 r / min and a temperature of 80℃ to obtain a premix.

[0066] 2) Add glycidyl methacrylate, dicumyl peroxide and epoxidized soybean oil to the premix, heat to 130℃, adjust the rotor speed to 80r / min, and react for 25min under nitrogen protection.

[0067] 3) Cool the reaction product obtained in step 2) to 55°C, then transfer it to an open rubber mixing mill and pass it through 5 times at a roller gap of 1 mm and a roller temperature of 50°C; granulate the material after passing through the mill and control the particle size to 3 mm to obtain an epoxy-grafted EPDM rubber-chlorinated polyethylene blend.

[0068] The raw materials for preparing modified nano-calcium carbonate, by weight, include: 100 parts nano-calcium carbonate, 5 parts stearic acid, 3 parts dopamine hydrochloride, and 600 parts tris(hydroxymethyl)aminomethane hydrochloride buffer solution; the concentration of the tris(hydroxymethyl)aminomethane hydrochloride buffer solution is 0.5 mol / L, and the pH is 8.5.

[0069] The preparation method of modified nano-calcium carbonate includes the following steps:

[0070] (1) Add nano-calcium carbonate to a high-speed mixer and stir and dry for 30 min at 110°C and 1200 r / min rotor speed; mix stearic acid and anhydrous ethanol at a mass ratio of 1:2, heat to 80°C to dissolve, and then spray the mixture evenly into nano-calcium carbonate through a spraying device. Continue stirring for 20 min under the above conditions to obtain stearic acid modified nano-calcium carbonate.

[0071] (2) Stearic acid modified nano-calcium carbonate was added to tris(hydroxymethyl)aminomethane hydrochloride buffer and ultrasonically dispersed for 30 min under ultrasonic power of 500 W and frequency of 40 kHz. Dopamine hydrochloride was added and stirred at 300 r / min for 24 h at 30 °C.

[0072] (3) After the reaction is completed, the reaction product is centrifuged at 6000 r / min for 15 min, washed with deionized water 4 times and anhydrous ethanol 2 times in sequence, and the resulting filter cake is placed in a vacuum drying oven and dried to constant weight under vacuum of -0.095 MPa and temperature of 60℃. After grinding, it is passed through a 240 mesh sieve to obtain modified nano calcium carbonate.

[0073] This embodiment also provides a method for preparing sealing adhesive for dry batteries, including the following steps:

[0074] S1. Ethylene propylene diene monomer (EPDM), polyvinyl chloride (PVC), and epoxy-grafted EPDM-chlorinated polyethylene (CPE) blend are fed into an internal mixer and mixed for 20 minutes at 140°C and a rotor speed of 80 r / min to obtain a premixed masterbatch.

[0075] S2. Add preheated and melted asphalt and epoxidized natural rubber to the premixed masterbatch obtained in step S1, adjust the temperature to 130°C, rotate the rotor at 60 r / min, and continue mixing for 10 min to obtain the blend.

[0076] S3. Add dioctyl adipate and calcium-zinc composite heat stabilizer to the blend obtained in step S2, and mix at 120°C for 8 minutes.

[0077] S4. Cool the mixture obtained in step S3 to 110°C, add modified nano-calcium carbonate, hydrophobic fumed nano-silica and silane coupling agent, adjust the rotor speed to 90 r / min, and mix for 15 min.

[0078] S5. Cool the mixture obtained in step S4 to 110°C, add it to the vulcanization system, adjust the rotor speed to 50 r / min, mix for 8 minutes until the torque reaches 2.0 times the initial torque, and after discharge, pass it through an open rubber mixing mill 3 times with a roller gap of 2 mm and a roller temperature of 50°C. After granulation, cool it to 30°C to obtain the sealing adhesive for dry batteries.

[0079] Example 3:

[0080] This embodiment provides a sealing adhesive for dry batteries. By weight, its raw materials include: 35 parts asphalt, 15 parts EPDM rubber, 8 parts polyvinyl chloride, 10 parts epoxy-grafted EPDM rubber-chlorinated polyethylene blend, 4 parts epoxidized natural rubber with an epoxidation degree of 30 mol%, 8 parts modified nano-calcium carbonate, and a specific surface area of ​​200 m².2 The composition consists of 3 parts hydrophobic fumed silica, 5 parts dioctyl adipate, 2 parts calcium-zinc composite heat stabilizer, 1 part silane coupling agent, and 2.8 parts vulcanization system. The asphalt is No. 70 asphalt; the degree of polymerization of polyvinyl chloride is 1800, and the K value is 78. The calcium-zinc composite heat stabilizer has a calcium-zinc molar ratio of 2.5:1; the silane coupling agent is KH-550; the vulcanization system is composed of sulfur, accelerator TMTD, zinc oxide, and stearic acid in a mass ratio of 1:0.4:1.5:0.8.

[0081] The raw materials for preparing the epoxy-grafted EPDM-chlorinated polyethylene blend, by weight, include: 95 parts EPDM, 55 parts chlorinated polyethylene, 10 parts glycidyl methacrylate, 1 part dicumyl peroxide, and 3 parts epoxidized soybean oil.

[0082] The preparation method of epoxy-grafted EPDM rubber-chlorinated polyethylene blend includes the following steps:

[0083] 1) Add EPDM rubber and chlorinated polyethylene to a mixer and plasticize for 2.5 min at a rotor speed of 60 r / min and a temperature of 70℃ to obtain a premix;

[0084] 2) Add glycidyl methacrylate, dicumyl peroxide and epoxidized soybean oil to the premix, heat to 125°C, adjust the rotor speed to 70 r / min, and react for 20 min under nitrogen protection.

[0085] 3) Cool the reaction product obtained in step 2) to 50°C, then transfer it to an open rubber mixing mill and pass it through a thin mill 4 times under the conditions of 0.8 mm roll gap and 45°C roll temperature; granulate the material after thin passing and control the particle size to 2.5 mm to obtain an epoxy-grafted EPDM rubber-chlorinated polyethylene blend.

[0086] The raw materials for preparing modified nano-calcium carbonate, by weight, include: 95 parts nano-calcium carbonate, 4 parts stearic acid, 2.5 parts dopamine hydrochloride, and 550 parts tris(hydroxymethyl)aminomethane hydrochloride buffer solution; the concentration of the tris(hydroxymethyl)aminomethane hydrochloride buffer solution is 0.3 mol / L, and the pH is 8.2.

[0087] The preparation method of modified nano-calcium carbonate includes the following steps:

[0088] (1) Add nano-calcium carbonate to a high-speed mixer and stir and dry for 28 min at 105℃ and rotor speed of 1100 r / min; mix stearic acid and anhydrous ethanol at a mass ratio of 1:1.5, heat to 75℃ to dissolve, and then spray the mixture evenly into nano-calcium carbonate through a spraying device. Continue stirring for 18 min under the above conditions to obtain stearic acid modified nano-calcium carbonate.

[0089] (2) Stearic acid modified nano-calcium carbonate was added to tris(hydroxymethyl)aminomethane hydrochloride buffer and ultrasonically dispersed for 25 min at an ultrasonic power of 450 W and a frequency of 35 kHz. Dopamine hydrochloride was added and stirred at 250 r / min for 21 h at 28 °C.

[0090] (3) After the reaction is completed, the reaction product is centrifuged at 5500 r / min for 12 min, washed with deionized water 4 times and anhydrous ethanol 2 times in sequence, and the resulting filter cake is placed in a vacuum drying oven and dried to constant weight under vacuum of -0.092 MPa and temperature of 55℃. After grinding, it is passed through a 220 mesh sieve to obtain modified nano calcium carbonate.

[0091] This embodiment also provides a method for preparing sealing adhesive for dry batteries, including the following steps:

[0092] S1. Ethylene propylene diene monomer (EPDM), polyvinyl chloride (PVC), and epoxy-grafted EPDM-chlorinated polyethylene (EPDM) blend are put into an internal mixer and mixed for 18 minutes at 135°C and a rotor speed of 70 r / min to obtain a premixed masterbatch.

[0093] S2. Add preheated and melted asphalt and epoxidized natural rubber to the premixed masterbatch obtained in step S1, adjust the temperature to 125°C, rotate the rotor at 55 r / min, and continue mixing for 9 min to obtain the blend.

[0094] S3. Add dioctyl adipate and calcium-zinc composite heat stabilizer to the blend obtained in step S2, and mix at 115°C for 7 minutes.

[0095] S4. Cool the mixture obtained in step S3 to 105°C, add modified nano-calcium carbonate, hydrophobic fumed nano-silica and silane coupling agent, adjust the rotor speed to 85 r / min, and mix for 14 min.

[0096] S5. Cool the mixture obtained in step S4 to 95°C, add it to the vulcanization system, adjust the rotor speed to 45 r / min, mix for 7 min until the torque reaches 2.0 times the initial torque, after discharge, pass it through an open rubber mixing mill 3 times with a roller gap of 1.5 mm and a roller temperature of 45°C, after granulation, cool it to 28°C to obtain the sealing adhesive for dry batteries.

[0097] Comparative Example 1:

[0098] A sealing adhesive for dry batteries and its preparation method are disclosed, which differ from Example 3 only in that: no epoxy-grafted EPDM-chlorinated polyethylene blend is added.

[0099] Comparative Example 2:

[0100] A sealing adhesive for dry batteries and its preparation method are disclosed. The only difference between this adhesive and Example 3 is that modified nano-calcium carbonate is not added, but is replaced by ordinary nano-calcium carbonate in equal amounts.

[0101] Comparative Example 3:

[0102] A sealing adhesive for dry batteries and its preparation method are disclosed, which differ from Example 3 only in that epoxidized natural rubber is not added.

[0103] Comparative Example 4:

[0104] A sealing adhesive for dry batteries and its preparation method are disclosed, which differ from Example 3 only in that hydrophobic fumed silica is not added.

[0105] Comparative Example 5:

[0106] A sealing adhesive for dry batteries and its preparation method are disclosed, which differ from Example 3 only in that the silane coupling agent KH-550 is not added.

[0107] Comparative Example 6:

[0108] A sealing adhesive for dry batteries and its preparation method are disclosed. The only difference between this method and Example 3 is that no vulcanization system is added and dynamic vulcanization is not performed during the preparation process (i.e., no vulcanization system is added in step S5, and the material is discharged directly).

[0109] Comparative Example 7:

[0110] A sealing adhesive for dry batteries and its preparation method differ from Example 3 only in that: in the preparation process of modified nano-calcium carbonate, only stearic acid modification is performed, and polydopamine coating is not performed (i.e. step (2) is cancelled).

[0111] Comparative Example 8:

[0112] A sealing adhesive for dry batteries and its preparation method differ from Example 3 only in that: in step S2, all polymer components (asphalt, epoxidized natural rubber, dioctyl adipate, calcium-zinc composite heat stabilizer, modified nano-calcium carbonate, hydrophobic fumed nano-silica, silane coupling agent and vulcanization system) are added at once, without segmented mixing.

[0113] The sealing adhesives obtained in Examples 1-3 and Comparative Examples 1-8 were tested for tensile strength and elongation at break, peel strength, low-temperature adhesion, high-temperature anti-flow, alkali resistance, and thermal cycling sealing performance. The testing methods for each performance are as follows:

[0114] (a) Determination of tensile strength and elongation at break

[0115] The tensile stress-strain properties of vulcanized rubber or thermoplastic rubber were determined according to GB / T 528-2009 standard. The sealing rubber was pressed into 2mm thick test pieces on a flat vulcanizing machine and allowed to fully cure for 7 days under standard laboratory conditions (temperature 23℃±2℃, relative humidity 50%±5%). The cured pieces were then cut into type I specimens using a dumbbell-shaped cutter. The tests were conducted using a universal testing machine at a tensile speed of 500mm / min, with at least 5 specimens per group, and the arithmetic mean was taken.

[0116] (ii) Peel strength test

[0117] The test was conducted according to GB / T 2790-1995, "Test Method for T-Peel Strength of Adhesives - Flexible Materials to Flexible Materials". The sealing adhesive was hot-pressed between a nickel-plated steel sheet (50mm×150mm×0.5mm) and a polypropylene sheet (50mm×150mm×0.5mm), with a bonding area of ​​25mm×150mm. The curing conditions were the same as in (I). A universal testing machine was used for the T-peel test at a peel speed of 100mm / min. At least five samples were used in each group, and the arithmetic mean was taken.

[0118] (III) Low-temperature adhesion test

[0119] The determination was performed according to Appendix A of SH / T 0421-92 "Battery Sealing Agents". The sealing adhesive was applied to a pre-polished steel sheet (50mm × 25mm × 2mm), with a coating area of ​​10mm × 10mm. The curing conditions were the same as in (I). The sample was placed in a low-temperature chamber and kept at -30℃ ± 1℃ for 1 hour. Immediately after removal, the adhesion was checked, and the adhesion rate (%) was recorded. Adhesion rate = (number of samples that did not detach / total number of samples) × 100%, with no fewer than 10 samples per group.

[0120] (iv) High-temperature resistance to flow determination

[0121] Inject the sealing adhesive into a metal ring with an inner diameter of 10 mm and a height of 10 mm. The curing conditions are the same as in (I). After demolding, a cylindrical sample with a diameter of 10 mm × 10 mm is formed. Place the sample vertically in an oven at 100℃ ± 2℃ and leave it for 24 hours. After that, take it out and measure the maximum length (mm) of the sample after it has flowed out using a vernier caliper. There should be no less than 5 samples in each group, and the arithmetic mean is taken.

[0122] (v) Alkali resistance test (liquid absorption rate)

[0123] The test was conducted according to GB / T 1690-2010, "Test Method for Liquid Resistance of Vulcanized Rubber or Thermoplastic Rubber". The sealing rubber was prepared into square test pieces of 20mm × 20mm × 2mm and weighed under standard laboratory conditions (W0, accurate to 0.1mg). The test pieces were completely immersed in a 30% potassium hydroxide solution and placed in a constant temperature incubator at 30℃ ± 1℃ for 15 days. After removal, the surface moisture was quickly blotted dry with filter paper, and the samples were immediately weighed (W1, accurate to 0.1mg). The liquid absorption rate was calculated using the following formula:

[0124] Liquid absorption rate (%) = [(W1-W0) / W0] × 100%

[0125] Each group should contain no fewer than 5 samples, and the arithmetic mean should be taken.

[0126] (vi) Thermal cycling sealing performance test

[0127] The sealing adhesive was used to simulate the sealing structure of AA-type alkaline batteries (n=30 samples per test group), and the curing conditions were the same as in (I). The samples were placed in a high and low temperature alternating test chamber and subjected to 20 thermal cycles from -20℃ to 80℃, maintaining each temperature point for 4 hours, with a transition time ≤1 minute. After the cycles, the samples were inspected for cracks and an airtightness test was performed at 0.3 MPa pressure. The number of leaking samples was recorded, and the leakage rate (%) was calculated. Leakage rate = (number of leaking samples / total number of samples) × 100%.

[0128] The results are shown in Tables 2 and 3.

[0129] Table 2 Results of Mechanical and Adhesive Properties Tests

[0130] Group Tensile strength (MPa) Elongation at break (%) Peel strength (N / cm) Low temperature adhesion (-30℃, %) Example 1 11.0 400 11.3 92 Example 2 11.5 410 12.0 94 Example 3 11.8 415 12.3 95 Comparative Example 1 9.0 335 8.2 81 Comparative Example 2 9.8 360 9.0 86 Comparative Example 3 9.7 350 8.5 82 Comparative Example 4 10.2 375 10.0 89 Comparative Example 5 9.9 340 8.2 83 Comparative Example 6 9.2 430 10.5 90 Comparative Example 7 10.5 385 10.2 85 Comparative Example 8 9.5 335 8.0 77

[0131] Table 3. Test results of heat resistance, media resistance and overall sealing performance

[0132] Group High-temperature flow resistance (100℃, mm) Alkali resistance (liquid absorption rate %) Thermal cycling sealing performance (leakage rate %) Example 1 1.1 1.55 1.0 Example 2 0.9 1.35 0.5 Example 3 0.8 1.25 0.3 Comparative Example 1 2.0 2.65 2.8 Comparative Example 2 1.5 2.15 1.5 Comparative Example 3 1.6 2.25 2.0 Comparative Example 4 2.6 2.35 2.2 Comparative Example 5 1.7 2.45 2.3 Comparative Example 6 3.3 2.30 3.5 Comparative Example 7 1.2 1.75 1.0 Comparative Example 8 2.0 2.75 2.8

[0133] Using Example 3 as the control group, the performance differences and causes of Comparative Examples 1-8 are analyzed as follows:

[0134] Comparative Example 1 (Epoxy-grafted EPDM-chlorinated polyethylene blend): Tensile strength decreased from 11.8 MPa to 9.0 MPa (a decrease of 23.7%), elongation at break decreased from 415% to 335% (a decrease of 19.3%), peel strength decreased from 12.3 N / cm to 8.2 N / cm (a decrease of 33.3%), low-temperature adhesion decreased from 95% to 81% (a decrease of 14.7%), high-temperature anti-flow properties increased from 0.8 mm to 2.0 mm (an increase of 150.0%), alkali resistance (liquid absorption rate) increased from 1.25% to 2.65% (an increase of 112.0%), and thermal cycling sealing performance (air leakage rate) increased from 0.3% to 2.8% (an increase of 833.3%). The comparative example lacks the reactive compatibilizer, epoxy-grafted EPDM-chlorinated polyethylene blend, which significantly reduces the interfacial compatibility between EPDM and PVC and asphalt, preventing the formation of a "molecular bridge" structure. This weakens the interfacial bonding force and reduces stress transfer efficiency, resulting in a significant deterioration in mechanical and adhesive properties. Simultaneously, the increased interfacial defects allow for easier electrolyte penetration, leading to a substantial decrease in alkali resistance and thermal cycling sealing.

[0135] Comparative Example 2 (using ordinary nano-calcium carbonate instead of modified nano-calcium carbonate): Tensile strength decreased from 11.8 MPa to 9.8 MPa (a decrease of 16.9%), elongation at break decreased from 415% to 360% (a decrease of 13.3%), peel strength decreased from 12.3 N / cm to 9.0 N / cm (a decrease of 26.8%), low-temperature adhesion decreased from 95% to 86% (a decrease of 9.5%), high-temperature anti-flow properties increased from 0.8 mm to 1.5 mm (an increase of 87.5%), alkali resistance (liquid absorption rate) increased from 1.25% to 2.15% (an increase of 72.0%), and thermal cycling sealing performance (air leakage rate) increased from 0.3% to 1.5% (an increase of 400.0%). Ordinary nano-calcium carbonate lacks the interfacial reinforcement effect of polydopamine and the thermal buffering effect of stearic acid, resulting in weak interfacial bonding with the matrix. During thermal cycling, interfacial defects are easily generated, leading to a comprehensive decline in mechanical properties, adhesive properties, and media resistance.

[0136] Comparative Example 3 (natural rubber without epoxidation): Tensile strength decreased from 11.8 MPa to 9.7 MPa (a decrease of 17.8%), elongation at break decreased from 415% to 350% (a decrease of 15.7%), peel strength decreased from 12.3 N / cm to 8.5 N / cm (a decrease of 30.9%), low-temperature adhesion decreased from 95% to 82% (a decrease of 13.7%), high-temperature anti-flow increased from 0.8 mm to 1.6 mm (an increase of 100.0%), alkali resistance (liquid absorption rate) increased from 1.25% to 2.25% (an increase of 80.0%), and thermal cycling sealing performance (air leakage rate) increased from 0.3% to 2.0% (an increase of 566.7%). Epoxidized natural rubber, as an auxiliary compatibilizer, can interact with the hydroxyl groups on the filler surface. Its absence leads to obstruction of interfacial stress transmission and a decrease in mechanical and sealing properties, but the decrease is less than the effect of the absence of the main compatibilizer. This indicates that the epoxy-grafted EPDM-chlorinated polyethylene blend plays a dominant role in the compatibilization system.

[0137] Comparative Example 4 (without hydrophobic fumed silica): Peel strength decreased from 12.3 N / cm to 10.0 N / cm (a decrease of 18.7%), high-temperature anti-flow properties increased from 0.8 mm to 2.6 mm (an increase of 225.0%), alkali resistance (liquid absorption rate) increased from 1.25% to 2.35% (an increase of 88.0%), and thermal cycling sealing performance (leakage rate) increased from 0.3% to 2.2% (an increase of 633.3%). Hydrophobic fumed silica can form a three-dimensional thixotropic network in the system. Without it, this network structure cannot form, and the adhesive lacks the constraint of a physically entangled network at high temperatures, significantly deteriorating its anti-flow properties. Simultaneously, the absence of nano-silica also weakens the physical barrier effect on electrolyte ions, leading to a decrease in alkali resistance and thermal cycling sealing performance.

[0138] Comparative Example 5 (without silane coupling agent KH-550): Tensile strength decreased from 11.8 MPa to 9.9 MPa (a decrease of 16.1%), elongation at break decreased from 415% to 340% (a decrease of 18.1%), peel strength decreased from 12.3 N / cm to 8.2 N / cm (a decrease of 33.3%), low-temperature adhesion decreased from 95% to 83% (a decrease of 12.6%), high-temperature anti-flow increased from 0.8 mm to 1.7 mm (an increase of 112.5%), alkali resistance (liquid absorption rate) increased from 1.25% to 2.45% (an increase of 96.0%), and thermal cycling sealing (air leakage rate) increased from 0.3% to 2.3% (an increase of 666.7%). Silane coupling agents are key components for achieving chemical bonding between fillers and organic matrices. Without them, the polydopamine layer on the surface of modified nano-calcium carbonate cannot form an effective chemical bond with the matrix, resulting in a significant decrease in interfacial bonding strength and a comprehensive deterioration in mechanical properties, adhesive properties, and barrier properties.

[0139] Comparative Example 6 (without dynamic vulcanization): Tensile strength decreased from 11.8 MPa to 9.2 MPa (a decrease of 22.0%), peel strength decreased from 12.3 N / cm to 10.5 N / cm (a decrease of 14.6%), low-temperature adhesion decreased from 95% to 90% (a decrease of 5.3%), high-temperature anti-flow properties increased from 0.8 mm to 3.3 mm (an increase of 312.5%), alkali resistance (liquid absorption rate) increased from 1.25% to 2.30% (an increase of 84.0%), and thermal cycling sealing performance (air leakage rate) increased from 0.3% to 3.5% (an increase of 1066.7%). Without dynamic vulcanization, the EPDM rubber phase does not form a cross-linked network, and the molecular chains are prone to slippage under stress. Although the elongation at break increases slightly, the tensile strength decreases significantly. At the same time, the lack of a thermoplastic vulcanizate structure results in extremely poor creep resistance at high temperatures, severely deteriorated anti-flow properties, and the absence of a cross-linked network reduces the material's cohesive strength, makes it easier for electrolyte to penetrate, and significantly reduces alkali resistance and thermal cycling sealing.

[0140] Comparative Example 7 (modified nano-calcium carbonate modified with stearic acid only): tensile strength decreased from 11.8 MPa to 10.5 MPa (a decrease of 11.0%), elongation at break decreased from 415% to 385% (a decrease of 7.2%), peel strength decreased from 12.3 N / cm to 10.2 N / cm (a decrease of 17.1%), low-temperature adhesion decreased from 95% to 85% (a decrease of 10.5%), high-temperature anti-flow increased from 0.8 mm to 1.2 mm (an increase of 50.0%), alkali resistance (liquid absorption rate) increased from 1.25% to 1.75% (an increase of 40.0%), and thermal cycling sealing performance (air leakage rate) increased from 0.3% to 1.0% (an increase of 233.3%). Although stearic acid modification provides some thermal buffering, the lack of strong interfacial chemical bonding between the polydopamine shell and the matrix and metal surface results in insufficient interfacial bonding between the filler and the matrix, leading to a significant reduction in peel strength and low-temperature adhesion compared to Example 3. Microcracks are easily generated at the interface during thermal cycling, resulting in decreased sealing performance.

[0141] Comparative Example 8 (all remaining components added at once in step S2): Tensile strength decreased from 11.8 MPa to 9.5 MPa (a decrease of 19.5%), elongation at break decreased from 415% to 335% (a decrease of 19.3%), peel strength decreased from 12.3 N / cm to 8.0 N / cm (a decrease of 35.0%), low-temperature adhesion decreased from 95% to 77% (a decrease of 18.9%), high-temperature anti-flow increased from 0.8 mm to 2.0 mm (an increase of 150.0%), alkali resistance (liquid absorption rate) increased from 1.25% to 2.75% (an increase of 120.0%), and thermal cycling sealing (air leakage rate) increased from 0.3% to 2.8% (an increase of 833.3%). The lack of a segmented mixing process leads to uneven dispersion of components, insufficient plasticization of PVC, and the inability of the interfacial reaction between compatibilizer, filler, and matrix to proceed in an orderly manner, resulting in an unstable phase structure. Consequently, all properties are significantly reduced, especially peel strength and low-temperature adhesion. This indicates that a segmented mixing process is crucial for forming a stable multiphase system and ensuring uniform dispersion of components.

[0142] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sealing adhesive for dry cell batteries, characterized in that, The raw materials for its preparation, by weight, include: 30-40 parts asphalt, 12-20 parts EPDM rubber, 6-10 parts polyvinyl chloride, 8-12 parts epoxy-grafted EPDM rubber-chlorinated polyethylene blend, 3-5 parts epoxidized natural rubber, 6-10 parts modified nano-calcium carbonate, 2-4 parts hydrophobic fumed nano-silica, 4-6 parts dioctyl adipate, 1-2 parts calcium-zinc composite heat stabilizer, 0.5-1.5 parts silane coupling agent, and 2.0-3.5 parts vulcanization system.

2. The sealing adhesive for dry batteries according to claim 1, characterized in that, The raw materials for preparing the epoxy-grafted EPDM-chlorinated polyethylene blend, by weight, include: 90-100 parts of EPDM, 50-60 parts of chlorinated polyethylene, 8-12 parts of glycidyl methacrylate, 0.8-1.5 parts of dicumyl peroxide, and 2-4 parts of epoxidized soybean oil.

3. The sealing adhesive for dry batteries according to claim 2, characterized in that, The preparation method of the epoxy-grafted EPDM rubber-chlorinated polyethylene blend includes the following steps: 1) Add EPDM rubber and chlorinated polyethylene to a mixer and plasticize for 2-3 minutes at a rotor speed of 50-70 r / min and a temperature of 60-80℃ to obtain a premix. 2) Add glycidyl methacrylate, dicumyl peroxide and epoxidized soybean oil to the premix, heat to 120~130℃, adjust the rotor speed to 60~80r / min, and react for 15~25min under nitrogen protection. 3) Cool the reaction product obtained in step 2) to 45~55℃, then transfer it to an open rubber mixing mill and pass it through a thin mill 3~5 times under the conditions of a roll gap of 0.5~1mm and a roll temperature of 40~50℃; granulate the material after thin passing, and control the particle size to 2~3mm to obtain the epoxy-grafted EPDM rubber-chlorinated polyethylene blend.

4. The sealing adhesive for dry batteries according to claim 1, characterized in that, The raw materials for preparing the modified nano-calcium carbonate, by weight, include: 90-100 parts of nano-calcium carbonate, 3-5 parts of stearic acid, 2-3 parts of dopamine hydrochloride, and 500-600 parts of tris(hydroxymethyl)aminomethane hydrochloride buffer solution; the concentration of the tris(hydroxymethyl)aminomethane hydrochloride buffer solution is 0.1-0.5 mol / L, and the pH is 8.0-8.

5.

5. The sealing adhesive for dry batteries according to claim 4, characterized in that, The preparation method of the modified nano-calcium carbonate includes the following steps: (1) Add nano-calcium carbonate to a high-speed mixer and stir and dry for 25-30 min at 100-110℃ and rotor speed of 1000-1200 r / min; mix stearic acid and anhydrous ethanol at a mass ratio of 1:1-2, heat to 70-80℃ to dissolve, and then spray the mixture evenly into nano-calcium carbonate through a spraying device. Continue stirring for 15-20 min under the above conditions to obtain stearic acid modified nano-calcium carbonate; (2) Stearic acid modified nano-calcium carbonate was added to tris(hydroxymethyl)aminomethane hydrochloride buffer solution and ultrasonically dispersed for 20-30 min under ultrasonic power of 400-500 W and frequency of 30-40 kHz. Dopamine hydrochloride was added and stirred at 200-300 r / min at 25-30℃ for 18-24 h. (3) After the reaction is completed, the reaction product is centrifuged, washed, dried, ground and passed through a 200-240 mesh sieve to obtain the modified nano calcium carbonate.

6. The sealing adhesive for dry batteries according to claim 5, characterized in that, In step (3), the centrifugation, washing and drying steps are as follows: centrifuge at a speed of 5000~6000r / min for 10~15min, wash with deionized water 3~4 times and anhydrous ethanol 1~2 times in sequence, place the obtained filter cake in a vacuum drying oven and dry it to constant weight under the conditions of vacuum degree -0.09~-0.095MPa and temperature 50~60℃.

7. The sealing adhesive for dry batteries according to claim 1, characterized in that, The asphalt is No. 50 or No. 70 asphalt; the degree of polymerization of the polyvinyl chloride is 1500-2000, and the K value is 75-80; the degree of epoxidation of the epoxidized natural rubber is 25-40 mol%; and the specific surface area of ​​the hydrophobic fumed silica nanofiber is 150-200 m² / g. 2 / g.

8. The sealing adhesive for dry batteries according to claim 1, characterized in that, The calcium-zinc composite heat stabilizer has a calcium-zinc molar ratio of 2.0~2.5:1; the silane coupling agent is KH-550 or KH-560.

9. A method for preparing a sealing adhesive for dry batteries according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Put EPDM rubber, polyvinyl chloride, and epoxy-grafted EPDM rubber-chlorinated polyethylene blend into an internal mixer and mix for 15-20 minutes at 130-140℃ and rotor speed of 60-80 r / min to obtain premixed masterbatch. S2. Add preheated and melted asphalt and epoxidized natural rubber to the premixed masterbatch obtained in step S1, adjust the temperature to 120-130°C, rotate the rotor at 50-60 r / min, and continue mixing for 8-10 min to obtain the blend. S3. Add dioctyl adipate and calcium-zinc composite heat stabilizer to the blend obtained in step S2, and control the temperature at 110~120℃ for 5~8 minutes. S4. Cool the mixture obtained in step S3 to 100~110℃, add modified nano calcium carbonate, hydrophobic fumed nano silica and silane coupling agent, adjust the rotor speed to 80~90 r / min, and mix for 12~15 min. S5. Cool the mixture obtained in step S4 to 90~110℃, add it to the vulcanization system, adjust the rotor speed to 40~50r / min, and mix until the torque reaches 1.5~2.0 times the initial torque. After discharge, pass it through an open rubber mixing mill 2~3 times with a roller gap of 1~2mm and a roller temperature of 40~50℃. After pressing or granulating, cool it to 25~30℃ to obtain the sealing adhesive for dry batteries.

10. The method for preparing the sealing adhesive for dry batteries according to claim 9, characterized in that, In step S5, the time for mixing until the torque reaches 1.5 to 2.0 times the initial torque is 5 to 8 minutes.

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