Weather-resistant EPDM leather cap for lead-acid storage battery and preparation method of weather-resistant EPDM leather cap

Abstract

The invention discloses a weather-resistant EPDM leather cap for a lead-acid storage battery and a preparation method of the weather-resistant EPDM leather cap, and belongs to the technical field of EPDM materials. The weather-resistant EPDM leather cap for the lead-acid storage battery comprises the following raw materials in parts by weight: 40-45 parts of EPDM raw rubber; 2-3 parts of zinc oxide; 0.6 to 1 part of stearic acid; 12 to 14 parts of white carbon black; 9 to 12 parts of paraffin oil; 1-2 parts of a dispersant; 0.8-1.2 parts of an internal release agent; 1.5 to 2.5 parts of an accelerant; 2-3 parts of a vulcanizing agent; 8-12 parts of a filling agent; 0.7 to 0.9 part of an anti-aging agent; the filling agent is carboxyl-terminated hyperbranched polyester modified nano calcium carbonate. According to the invention, the EPDM raw rubber, the vulcanization system and the reinforcing filling system are adopted, and a synergistic effect is fully exerted by adjusting the ratio of the raw materials, so that the EPDM product has the advantages of good mechanical property and high thermal aging resistance when being used for sealing the lead-acid storage battery, and has excellent weather resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of EPDM materials, in particular to a weather-resistant EPDM cap for lead-acid storage batteries and a preparation method thereof. BACKGROUND

[0002] During the extension of the service life of lead-acid storage batteries, the core failure mode presents a "chain reaction" feature: first, water loss occurs due to long-term use, which leads to abnormal concentration of electrolyte in the battery and a decrease in heat conduction efficiency, thereby triggering thermal runaway; thermal runaway further exacerbates the evaporation of electrolyte and causes the internal temperature of the battery to rise sharply, resulting in the bulging of the shell due to gas expansion, and accelerating the internal corrosion of the plates and separators; ultimately, the electrode structure is damaged, the active material fails, and the battery cannot normally output capacity, completely losing the ability to supply power. In this failure process, the cap (usually referring to the sealing / ventilation assembly of the battery liquid injection port) plays a key "water loss regulating role", through its ventilation performance and sealing balance design, it can moderately discharge a small amount of hydrogen and oxygen generated during the charging process of the battery, while inhibiting the rapid water loss of the electrolyte due to excessive evaporation, delaying the thermal runaway and subsequent failure process caused by water loss, and indirectly extending the service life of the battery.

[0003] EPDM caps are widely used in lead-acid storage batteries to ensure sealing and durability. Patent CN120209465A provides a rubber gasket and a preparation method thereof, which is prepared by using ethylene-propylene-diene rubber (EPDM) as the base material, enhancing with ethylene-vinyl alcohol copolymer (EVOH) containing 29%-48% ethylene, grafting with styrene-ethylene-butylene-styrene block copolymer grafted maleic anhydride compatibilization, supplemented with carbon black and nanoscale calcium carbonate synergistic reinforcement, and then pre-mixed, hot-pressed, vulcanized and acid-aging treated. It has significant technical advantages and practical value in high-end sealing fields such as fuel cells and tunnel engineering. The material prepared by this patent has the potential to be applied to lead-acid storage batteries, but the nanoscale calcium carbonate in it is easy to agglomerate, which will affect its reinforcing function, thereby making it difficult to prepare a high-weather-resistant EPDM cap.

[0004] Therefore, it is necessary to provide a weather-resistant EPDM cap for lead-acid storage batteries. SUMMARY

[0005] The present application provides a weather-resistant EPDM cap for lead-acid storage batteries and a preparation method thereof, which can solve the problem that nanoscale calcium carbonate is easy to agglomerate, which will affect its reinforcing function, thereby making it difficult to prepare a high-weather-resistant EPDM cap.

[0006] The object of the present application can be achieved by the following technical solutions:

[0007] In a first aspect, the application provides a weather-resistant EPDM cap for a lead-acid storage battery, comprising the following raw materials by weight: EPDM raw rubber 40-45 parts; zinc oxide 2-3 parts; stearic acid 0.6-1 part; white carbon black 12-14 parts; paraffin oil 9-12 parts; dispersant 1-2 parts; internal release agent 0.8-1.2 parts; accelerator 1.5-2.5 parts; vulcanizing agent 2-3 parts; filler 8-12 parts; antioxidant 0.7-0.9 parts;

[0008] The filler is carboxyl-terminated hyperbranched polyester modified nano calcium carbonate.

[0009] Further, the vulcanizing agent is sulfur.

[0010] Further, the accelerator is accelerator BZ or accelerator DM.

[0011] Further, the internal release agent is zinc stearate.

[0012] Further, the dispersant is polyethylene glycol.

[0013] Further, the antioxidant is antioxidant MB.

[0014] Further, the preparation method of the filler is:

[0015] S1, weigh itaconic acid and triethanolamine, stir and dissolve in N,N-dimethylformamide, then transfer to a three-necked flask connected with a mechanical stirrer and a condenser tube, under N2 protection, heat to 120℃ and react for 3-4h, then add perfluorohexane acid to the three-necked flask and continue to react for 4h; then evaporate and concentrate the sample using a rotary evaporator, and finally vacuum dry to obtain carboxyl-terminated hyperbranched polyester;

[0016] Wherein, the amount ratio of itaconic acid, triethanolamine, N,N-dimethylformamide and perfluorohexane acid is 1.3g:3g:80mL:7g-8.7g.

[0017] In the above step, the hydroxyl group of triethanolamine reacts with the carboxyl group of itaconic acid to form a polyester intermediate, then perfluorohexane acid is added, its carboxyl group further reacts with the remaining hydroxyl group of the intermediate, and fluorine element is introduced, and finally carboxyl-terminated hyperbranched polyester is obtained.

[0018] S2, add carboxyl-terminated hyperbranched polyester and nano calcium carbonate to DMF, then stir at 75℃ and 6000r / min for 0.5-1.5h, then reduce pressure, filter, dry, grind and sieve to obtain the filler.

[0019] Wherein, the amount ratio of carboxyl-terminated hyperbranched polyester, nano calcium carbonate and DMF is 0.8-2g:15g:100mL.

[0020] In the above step, the carboxyl groups in the carboxyl-terminated hyperbranched polyester react with the nano calcium carbonate in the process of high-speed stirring, so that the carboxyl-terminated hyperbranched polyester is grafted on the surface of the nano calcium carbonate, and the filler is obtained.

[0021] In a second aspect, the application provides a preparation method of a weather-resistant EPDM cap for lead-acid storage batteries, comprising the following steps:

[0022] Step (1), plasticizing: first adjust the roll gap of the mixing equipment to 2±0.2mm, first put in the raw EPDM rubber for plasticizing, after plasticizing for 1-2min, then add zinc oxide, stearic acid, filler, white carbon black, paraffin oil, dispersing agent, internal release agent, antioxidant, accelerator and vulcanizing agent to obtain the rubber compound;

[0023] Step (2), thin pass: after adjusting the roll gap of the mixing equipment to 0.5-1mm, add the rubber compound for thin pass 4-6 times;

[0024] Step (3), sheeting: adjust the roll gap of the mixing equipment to 2±0.2mm, carry out sheeting and cooling to obtain the rubber compound;

[0025] Step (4), storage: after storing the rubber compound for 22-25h, cut the rubber compound into strips according to the requirement;

[0026] Step (5), vulcanization: after putting the rubber strip into the mold, place the rubber strip in the vulcanization equipment for vulcanization.

[0027] Further, in step (5), the specific conditions of vulcanization are: pressure is 18-22Mpa, heating temperature is 160-180℃, and pressure maintaining time is 8-12min.

[0028] The application has the following beneficial effects:

[0029] 1. Because this invention uses EPDM raw rubber, a vulcanization system, and a reinforcing filler system, and fully leverages the synergistic effect by adjusting the proportions of each raw material, EPDM products used in the sealing of lead-acid batteries have advantages such as good mechanical properties and high heat aging resistance, and excellent weather resistance. Specifically, 40-45 parts of EPDM raw rubber form the core matrix, laying the foundation for weather resistance with its ozone resistance and high and low temperature resistance. Sufficient raw rubber ensures the integrity of the matrix to support the mechanical framework; 2-3 parts of zinc oxide and 0.6-1 parts of stearic acid work synergistically to activate 1.5-2.5 parts of accelerator and 2-3 parts of vulcanizing agent, promoting the cross-linking of EPDM into a dense network, reducing molecular chain slippage and improving tensile strength, while avoiding excessive cross-linking and brittleness, thus balancing mechanical properties. 12-14 parts of silica and 8-12 parts of filler are compounded and uniformly dispersed under the action of 1-2 parts of dispersant. Silica and filler play a reinforcing role, and the filler of this invention has good compatibility with the matrix. 9-12 parts of paraffin oil adjust the viscosity and ensure processability, and can also migrate to form a protective film to block oxygen and ozone erosion. 0.7-0.9 parts of antioxidant inhibit free radical aging and delay molecular chain degradation. The two work synergistically to provide strong weather resistance. 0.8-1.2 parts of internal release agent only ensure molding and demolding, and do not affect the main body performance.

[0030] 2. The filler of this invention is a carboxyl-terminated hyperbranched polyester modified nano-calcium carbonate. After modification, the steric hindrance effect significantly improves the dispersibility of the nano-calcium carbonate in the matrix, thus enhancing its reinforcing effect. Furthermore, the carboxyl-terminated hyperbranched polyester of this invention contains carbon-carbon double bonds and fluorinated alkyl chains. The carbon-carbon double bonds have a similar structure to the EPDM matrix, which can improve the compatibility between the filler and the matrix, reduce interfacial defects, and thereby improve the tensile strength and other mechanical properties of the cap. The fluorinated alkyl chains, on the one hand, utilize their extremely low surface energy to further reduce the agglomeration tendency between filler particles, assisting in improving dispersibility; on the other hand, their excellent chemical stability effectively enhances the weather resistance of the EPDM matrix, while also easily migrating to the material surface to form a hidden protective layer, further blocking the erosion of the external environment.

[0031] 3. In the process of preparing the filler, the present invention limits the mass ratio of terminal carboxyl hyperbranched polyester to nano calcium carbonate to a suitable range. Too little will not be able to fully coat the nano calcium carbonate and will easily cause it to agglomerate, thereby reducing the compatibility and dispersibility of the filler with the matrix; too much will form an excessively thick coating layer, which will also affect the dispersibility of nano calcium carbonate and significantly increase the cost. Detailed Implementation

[0032] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0033] The EPDM raw rubber in the application is a copolymer of ethylene, propylene and diene, that is, a raw rubber of ethylene-propylene-diene terpolymer, the Mooney viscosity is 80MU, the ethylene content is 47.7wt%, the ethylene norbornene (ENB) content is 5.3wt%, the volatile matter is 0.2%, and is purchased from Arlanxeo High Performance Elastomers (Changzhou) Co., Ltd.

[0034] Preparation Example 1

[0035] The preparation method of the filler in the present preparation example is as follows:

[0036] S1, 1.3g of itaconic acid and 3g of triethanolamine are weighed and dissolved by stirring in 80mL of N,N-dimethylformamide, then transferred to a three-necked flask connected with a mechanical stirrer and a condenser, and reacted at 120℃ for 3h under N2 protection, then 7g of perfluorohexanedioic acid is added to the three-necked flask and reacted for another 4h; then the sample is concentrated by rotary evaporation, and finally vacuum dried to obtain a carboxyl-terminated hyperbranched polyester;

[0037] S2, 0.8g of the carboxyl-terminated hyperbranched polyester and 15g of nano calcium carbonate are added to 100mL of DMF, then stirred at 75℃ and 6000r / min for 0.5h, then filtered under reduced pressure, dried, ground and sieved to obtain the filler.

[0038] Preparation Example 2

[0039] The preparation method of the filler in the present preparation example is as follows:

[0040] S1, 1.3g of itaconic acid and 3g of triethanolamine are weighed and dissolved by stirring in 80mL of N,N-dimethylformamide, then transferred to a three-necked flask connected with a mechanical stirrer and a condenser, and reacted at 120℃ for 3h under N2 protection, then 7g of perfluorohexanedioic acid is added to the three-necked flask and reacted for another 4h; then the sample is concentrated by rotary evaporation, and finally vacuum dried to obtain a carboxyl-terminated hyperbranched polyester;

[0041] S2, 0.8g of the carboxyl-terminated hyperbranched polyester and 15g of nano calcium carbonate are added to 100mL of DMF, then stirred at 75℃ and 6000r / min for 0.5h, then filtered under reduced pressure, dried, ground and sieved to obtain the filler.

[0042] Preparation Example 3

[0043] The preparation method of the filler in the present preparation example is as follows:

[0044] S1, 1.3 g of itaconic acid and 3 g of triethanolamine were weighed and dissolved by stirring in 80 mL of N,N-dimethylformamide, then transferred into a three-necked flask connected with a mechanical stirrer and a condenser, and reacted at 120°C for 4 h under N2 protection, then 7 g of perfluorohexanedioic acid was added to the three-necked flask and reacted for another 4 h; then the sample was concentrated by rotary evaporation, and finally vacuum dried to obtain a carboxyl-terminated hyperbranched polyester;

[0045] S2, 2 g of the carboxyl-terminated hyperbranched polyester and 15 g of nano calcium carbonate were added to 100 mL of DMF, then stirred at 75°C and 6000 r / min for 1.5 h, then filtered under reduced pressure, dried, ground and sieved to obtain a filler.

[0046] Comparative Example 1

[0047] The difference between this comparative example and Preparation Example 1 is only that the same amount of succinic acid is used to replace perfluorohexanedioic acid, and the specific steps are as follows:

[0048] S1, 1.3 g of itaconic acid and 3 g of triethanolamine were weighed and dissolved by stirring in 80 mL of N,N-dimethylformamide, then transferred into a three-necked flask connected with a mechanical stirrer and a condenser, and reacted at 120°C for 4 h under N2 protection, then 7 g of perfluorohexanedioic acid was added to the three-necked flask and reacted for another 4 h; then the sample was concentrated by rotary evaporation, and finally vacuum dried to obtain a carboxyl-terminated hyperbranched polyester;

[0049] S2, 2 g of the carboxyl-terminated hyperbranched polyester and 15 g of nano calcium carbonate were added to 100 mL of DMF, then stirred at 75°C and 6000 r / min for 1.5 h, then filtered under reduced pressure, dried, ground and sieved to obtain a filler.

[0050] Comparative Example 2

[0051] The difference between this comparative example and Preparation Example 1 is only that the same amount of succinic acid is used to replace perfluorohexanedioic acid, and the same amount of succinic acid is used to replace itaconic acid, and the specific steps are as follows:

[0052] S1, 1.3 g of itaconic acid and 3 g of triethanolamine were weighed and dissolved by stirring in 80 mL of N,N-dimethylformamide, then transferred into a three-necked flask connected with a mechanical stirrer and a condenser, and reacted at 120°C for 4 h under N2 protection, then 7 g of perfluorohexanedioic acid was added to the three-necked flask and reacted for another 4 h; then the sample was concentrated by rotary evaporation, and finally vacuum dried to obtain a carboxyl-terminated hyperbranched polyester;

[0053] S2, 0.8 g carboxyl-terminated hyperbranched polyester and 15 g nano calcium carbonate were added into 100 mL DMF, then stirred at 6000 r / min at 75℃ for 0.5 h, then filtered, dried, ground and sieved under reduced pressure to obtain the filler.

[0054] Comparative Example 3

[0055] The filler in the present comparative example is nano calcium carbonate.

[0056] Comparative Example 4

[0057] The present comparative example is compared with Preparation Example 1, the only difference is that "0.8 g carboxyl-terminated hyperbranched polyester" is replaced by "0.7 g carboxyl-terminated hyperbranched polyester".

[0058] Comparative Example 5

[0059] The present comparative example is compared with Preparation Example 3, the only difference is that "2 g carboxyl-terminated hyperbranched polyester" is replaced by "2.1 g carboxyl-terminated hyperbranched polyester".

[0060] Example 1

[0061] A weather-resistant EPDM cap for lead-acid storage battery comprises the following raw materials by weight: EPDM raw rubber 40 parts; zinc oxide 2 parts; stearic acid 0.6 parts; white carbon black 12 parts; paraffin oil 9 parts; polyethylene glycol 1 part; zinc stearate 0.8 parts; accelerator BZ 1.5 parts; sulfur 2 parts; the filler obtained in Preparation Example 1 8 parts; antioxidant MB 0.7 parts.

[0062] The preparation method of the weather-resistant EPDM cap is as follows:

[0063] Step (1), plasticating: first adjust the roll gap of the mixing equipment to 2 mm, first put in the EPDM raw rubber for plasticating, after plasticating for 1-2 min, then add zinc oxide, stearic acid, filler, white carbon black, paraffin oil, polyethylene glycol, zinc stearate, antioxidant MB, accelerator BZ and sulfur to obtain the rubber compound;

[0064] Step (2), thin passing: after adjusting the roll gap of the mixing equipment to 0.5 mm, add the rubber compound for thin passing 5 times;

[0065] Step (3), sheeting: adjust the roll gap of the mixing equipment to 2 mm, sheeting and cooling to obtain the rubber compound;

[0066] Step (4), standing: after standing the rubber compound for 23 h, cut into strip-shaped sheets according to needs;

[0067] Step (5), vulcanization: after placing the rubber sheets into the mold, place them in the vulcanization equipment for vulcanization, the pressure for vulcanization is 20 MPa, the heating temperature is 170℃, and the pressure is maintained for 10 min.

[0068] Example 2

[0069] A weather resistant EPDM cap for lead acid battery comprises the following raw materials in parts by weight: EPDM raw rubber 42 parts; zinc oxide 2.5 parts; stearic acid 0.8 part; white carbon black 13 parts; paraffin oil 10 parts; polyethylene glycol 1.5 parts; zinc stearate 1 part; accelerator BZ 2 parts; sulphur 2.5 parts; filler obtained from Preparation 1 9 parts; antioxidant MB 0.8 part.

[0070] The weather resistant EPDM cap is prepared according to the method of Example 1.

[0071] Example 3

[0072] A weather resistant EPDM cap for lead acid battery comprises the following raw materials in parts by weight: EPDM raw rubber 43 parts; zinc oxide 2.5 parts; stearic acid 0.8 part; white carbon black 13 parts; paraffin oil 10 parts; polyethylene glycol 1.5 parts; zinc stearate 1 part; accelerator BZ 2 parts; sulphur 2.5 parts; filler obtained from Preparation 2 10 parts; antioxidant MB 0.8 part.

[0073] The weather resistant EPDM cap is prepared according to the method of Example 1.

[0074] Example 4

[0075] A weather resistant EPDM cap for lead acid battery comprises the following raw materials in parts by weight: EPDM raw rubber 44 parts; zinc oxide 2.5 parts; stearic acid 0.8 part; white carbon black 13 parts; paraffin oil 11 parts; polyethylene glycol 1.5 parts; zinc stearate 1 part; accelerator BZ 2 parts; sulphur 2.5 parts; filler obtained from Preparation 3 10 parts; antioxidant MB 0.8 part.

[0076] The weather resistant EPDM cap is prepared according to the method of Example 1.

[0077] Example 5

[0078] A weather resistant EPDM cap for lead acid battery comprises the following raw materials in parts by weight: EPDM raw rubber 45 parts; zinc oxide 3 parts; stearic acid 1 part; white carbon black 14 parts; paraffin oil 12 parts; polyethylene glycol 2 parts; zinc stearate 1.2 parts; accelerator BZ 2.5 parts; sulphur 3 parts; filler obtained from Preparation 3 12 parts; antioxidant MB 0.9 part.

[0079] The weather resistant EPDM cap is prepared according to the method of Example 1.

[0080] Comparative Example 1

[0081] The comparative example is compared with Example 1, the only difference is that the filler obtained from Comparative Example 1 is used to replace the filler obtained from Preparation Example 1.

[0082] Comparative Example 2

[0083] The comparative example is compared with Example 1, the only difference is that the filler obtained from Comparative Example 2 is used to replace the filler obtained from Preparation Example 1.

[0084] Comparative Example 3

[0085] The comparative example is compared with Example 1, the only difference is that the filler obtained from Comparative Example 3 is used to replace the filler obtained from Preparation Example 1.

[0086] Comparative Example 4

[0087] The comparative example is compared with Example 1, the only difference is that the filler obtained from Comparative Example 4 is used to replace the filler obtained from Preparation Example 1.

[0088] Comparative Example 5

[0089] The comparative example is compared with Example 5, the only difference is that the filler obtained from Comparative Example 5 is used to replace the filler obtained from Preparation Example 3.

[0090] The EPDM materials prepared from Example 1-Example 5 and Comparative Example 1-Comparative Example 5 are tested for performance, the hardness is tested according to GB / T 531.1-2008; the tensile strength is tested according to GB / T 528-2009; the change rate of tensile strength of the sample after being treated at 100℃ for 96h is tested according to GB / T 3512-2014, and the results are shown in Table 1:

[0091] Table 1

[0092]

[0093] As can be seen from Table 1, the EPDM materials prepared from Example 1-Example 5 have excellent mechanical properties and weather resistance.

[0094] The effect of Comparative Example 1 is lower than that of Example 1, which shows that the fluorinated alkyl chain can further reduce the agglomeration tendency between the filler particles on the one hand by virtue of its extremely low surface energy, and assist to improve the dispersibility; on the other hand, by virtue of its excellent chemical stability, it can effectively enhance the weather resistance of the EPDM matrix, and at the same time, it can easily migrate to the surface of the material to form a hidden protective layer, further blocking the erosion of the external environment.

[0095] The effect of Comparative Example 2 is lower than that of Example 1, which shows that the carbon-carbon double bond has a similar structure to the EPDM in the matrix, which can improve the compatibility of the filler and the matrix, reduce the interface defects, and thus improve the mechanical properties such as the tensile strength of the skin cap.

[0096] The effect of Comparative Example 3 is lower than that of Example 1, which indicates that the dispersibility of nano calcium carbonate in the matrix can be significantly improved by steric hindrance effect after the carboxyl-terminated hyperbranched polyester modifies the nano calcium carbonate, and the reinforcing effect of the nano calcium carbonate is facilitated.

[0097] The amount of the carboxyl-terminated hyperbranched polyester in Comparative Example 4 is too small, and the amount of the carboxyl-terminated hyperbranched polyester in Comparative Example 5 is too large. As can be seen from Table 1, the performance of Comparative Example 4 is lower than that of Example 1, and the performance of Comparative Example 5 is lower than that of Example 5, which indicates that in the process of preparing the filler, the mass ratio of the carboxyl-terminated hyperbranched polyester to the nano calcium carbonate is limited in a proper range. Too small amount cannot sufficiently coat the nano calcium carbonate, which is easy to cause the agglomeration of the nano calcium carbonate, and thus reduces the compatibility and dispersibility of the filler with the matrix. Too large amount will form a too thick coating layer, which also affects the dispersibility of the nano calcium carbonate, and significantly increases the cost.

[0098] The above only discloses several specific embodiments of the present application, but the embodiments of the present application are not limited thereto, and any changes that can be thought of by those skilled in the art shall fall within the protection scope of the present application.

Claims

1. A weather-resistant EPDM cap for lead-acid batteries, characterized in that, The raw materials include the following parts by weight: 40-45 parts EPDM raw rubber; 2-3 parts zinc oxide; 0.6-1 part stearic acid; 12-14 parts silica; 9-12 parts paraffin oil; 1-2 parts dispersant; 0.8-1.2 parts internal release agent; 1.5-2.5 parts accelerator; 2-3 parts vulcanizing agent; 8-12 parts filler; and 0.7-0.9 parts antioxidant. The filler is terminal carboxyl hyperbranched polyester modified nano-calcium carbonate.

2. The weather-resistant EPDM cap for lead-acid batteries according to claim 1, characterized in that, The vulcanizing agent is sulfur; the accelerator is accelerator BZ or accelerator DM.

3. The weather-resistant EPDM cap for lead-acid batteries according to claim 1, characterized in that, The internal release agent is zinc stearate.

4. The weather-resistant EPDM cap for lead-acid batteries according to claim 1, characterized in that, The dispersant is polyethylene glycol.

5. A weather-resistant EPDM cap for lead-acid batteries according to claim 1, characterized in that, The antioxidant is antioxidant MB.

6. The weather-resistant EPDM cap for lead-acid batteries according to claim 1, characterized in that, The filler is prepared by: S1. Weigh itaconic acid and triethanolamine, place them in N,N-dimethylformamide and stir to dissolve. Then transfer them to a three-necked flask and react for 3-4 hours under N2 protection by heating to 120°C. Then add perfluoroadipic acid to the three-necked flask and continue the reaction for 4 hours. Then evaporate and concentrate, and finally dry under vacuum to obtain carboxyl-terminated hyperbranched polyester. S2. Add carboxyl-terminated hyperbranched polyester and nano-calcium carbonate to DMF, then stir the reaction at 75℃ and 6000r / min for 0.5-1.5h. Afterwards, filter under reduced pressure, dry, grind and sieve to obtain the filler.

7. A weather-resistant EPDM cap for lead-acid batteries according to claim 6, characterized in that, In step S1, the ratio of itaconic acid, triethanolamine, N,N-dimethylformamide, and perfluoroadipic acid is 1.3g:3g:80mL:7g-8.7g.

8. A weather-resistant EPDM cap for lead-acid batteries according to claim 6, characterized in that, In step S2, the ratio of carboxyl-terminated hyperbranched polyester, nano-calcium carbonate, and DMF is 0.8-2g:15g:100mL.

9. A method for preparing a weather-resistant EPDM cap for lead-acid batteries, used to prepare the weather-resistant EPDM cap for lead-acid batteries as described in any one of claims 1-8, characterized in that, Includes the following steps: Step (1), Plasticizing: First, adjust the roller gap of the mixing equipment to 2±0.2mm, put in EPDM raw rubber for plasticizing, plasticize for 1-2 minutes, then add zinc oxide, stearic acid, filler, silica, paraffin oil, dispersant, internal release agent, antioxidant, accelerator and vulcanizing agent to obtain rubber compound; Step (2), thin pass: After adjusting the roller gap of the mixing equipment to 0.5-1mm, add the rubber material and perform thin pass 4-6 times; Step (3), Sheeting: Adjust the roller gap of the mixing equipment to 2±0.2mm, sheet out and cool to obtain the mixed rubber; Step (4), resting: After resting the compounded rubber for 22-25 hours, cut it into strips as needed; Step (5), vulcanization: After placing the film into the mold, place it in the vulcanization equipment for vulcanization.

10. A method for preparing a weather-resistant EPDM cap for a lead-acid battery according to claim 9, characterized in that, In step (5), the specific conditions for vulcanization are: pressure of 18-22 MPa, heating temperature of 160-180℃, and pressure holding for 8-12 minutes.

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