Electric vehicle cooling water pipe and preparation method thereof

Abstract

The present invention relates to the field of rubber materials, and specifically to an electric vehicle cooling water pipe and a preparation method thereof. In the present invention, a flame retardant is synthesized using 2,4,6-trichloro-1,3,5-triazine as the nitrogen source, eugenol as the carbon source, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide as the phosphorus source, and it is added to ethylene propylene diene monomer rubber together with carbon black, light calcium carbonate, paraffin oil, zinc oxide, stearic acid, and polyethylene glycol as the inner layer compound; in addition, the present invention also modifies the RFL dipping solution, and adds the aramid short fiber composite, carbon black, light calcium carbonate, paraffin oil, zinc oxide, stearic acid, stearic acid, and flame retardant obtained by treating the modified RFL dipping solution to ethylene propylene diene monomer rubber to obtain the outer layer compound; the inner layer compound and the outer layer compound are subjected to mixing, extrusion, and vulcanization to obtain an electric vehicle cooling water pipe with a double-layer structure.

Description

Technical Field

[0001] The present invention relates to the technical field of rubber materials, and particularly to an electric vehicle cooling water pipe and a preparation method thereof. Background Art

[0002] The cooling water pipe of a new energy pure electric vehicle (BEV) is one of the key components in the vehicle thermal management system, responsible for transporting the coolant to maintain the battery pack, motor, and other key electronic components within an appropriate temperature range, ensuring the stability of the power battery system.

[0003] Automobile cooling pipelines need to have properties such as resistance to high and low temperatures, pressure, media, durability, and sealing. Traditional internal combustion engine vehicle rubber water pipes usually adopt a three-layer structure, namely, an inner rubber layer of ethylene propylene diene monomer rubber, an intermediate fiber reinforcement layer, and an outer rubber layer of ethylene propylene diene monomer rubber, which can meet the usage requirements of the cooling water pipe for BEV models. However, its production process is complex, costly, and heavy. The operating temperature and pressure of the cooling water pipe for BEV models are lower than those of traditional fuel vehicles, and due to range anxiety, more stringent requirements are put forward for lightweight. Therefore, developing a cooling water pipe that meets the operating conditions of electric vehicles has become an urgent need in the industry. Summary of the Invention

[0004] The purpose of the present invention is to provide an electric vehicle cooling water pipe and a preparation method thereof to solve the problems raised in the above background art.

[0005] To solve the above technical problems, the present invention provides the following technical solutions: An electric vehicle cooling water pipe and a preparation method thereof, including the following steps:

[0006] Step 1:

[0007] S11: Weigh eugenol and triethylamine, disperse them in anhydrous ethanol, and stir evenly to obtain a mixed solution A; disperse 2,4,6-trichloro-1,3,5-triazine in anhydrous ethanol, and stir evenly to obtain a mixed solution B; heat the mixed solution B to 60 - 70 °C and then add it to the mixed solution A, controlling the addition speed so that the mixed solution B is added within 30 - 60 minutes; carry out a reflux reaction for 8 - 10 hours, perform suction filtration, rotary evaporation, wash the substrate with ethanol, filter, dry, recrystallize with ethyl acetate, filter again, and dry to obtain tris(eugenol) grafted triazine;

[0008] S12: Disperse 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in toluene, heat it to 85 - 95 °C, and after all of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is dissolved, add tris(eugenol) grafted triazine, continue to heat to 100 - 105 °C, react for 8 - 10 hours, then cool and perform suction filtration, wash the substrate with tetrahydrofuran, perform suction filtration, and vacuum dry to obtain a flame retardant;

[0009] Step 2:

[0010] S21: Place the aramid short fibers in deionized water and ultrasonically disperse them for 30 - 60 min to obtain an aramid short fiber dispersion; disperse the epoxy resin in deionized water, stir for 30 - 60 min, then add the blocked isocyanate and stir to obtain a pretreatment solution; add the aramid short fiber dispersion to the pretreatment solution and stir to obtain a pretreated aramid short fiber dispersion; filter and dry to obtain pretreated aramid short fibers;

[0011] S22: Dissolve resorcinol in deionized water, add formaldehyde, react for 6 - 8 h using sodium hydroxide as a catalyst, then add dilute hydrochloric acid to adjust the pH value of the system to 7, add methacryloyl chloride and triethylamine, and react at 40 - 50 °C for 5 - 6 h to obtain a modified phenolic resin adhesive solution with a solid content of 6 - 8%;

[0012] S23: Mix the butadiene - pyridine latex and the modified phenolic resin adhesive solution according to a dry weight ratio of (15 - 20):100, add ammonia water to adjust the pH value to 8 - 9, and stir and cure for 20 - 24 h to obtain an RFL dipping solution;

[0013] S24: Put the pretreated short fibers into the RFL dipping solution, stir for 20 - 30 min and then let it stand, filter using a flocculent filter cloth, and dry in an oven at 100 - 105 °C for 2 - 3 h to obtain aramid short fiber composites;

[0014] Step 3:

[0015] S31: Conduct two - stage mixing on the inner layer rubber compound and the outer layer rubber compound respectively to obtain an inner layer mixed rubber compound and an outer layer mixed rubber compound;

[0016] S32: Set the head temperature to 75 ± 2 °C, the temperature of the second barrel section to 65 ± 2 °C, the temperature of the first barrel section to 60 ± 2 °C, and the feeding port temperature to 50 ± 2 °C. Extrude the inner layer mixed rubber compound and the outer layer mixed rubber compound, and vulcanize at 160 ± 5 °C and a pressure of 0.55 - 0.65 MPa for 20 - 30 min to obtain an electric vehicle cooling water pipe with an inner rubber layer thickness of 0.5 - 0.6 mm and an outer rubber layer thickness of 2 - 2.5 mm.

[0017] Furthermore, in S11, the molar ratio of eugenol, triethylamine, and 2,4,6 - trichloro - 1,3,5 - triazine is (3.05 - 3.1):3:1.

[0018] Furthermore, in S12, the molar ratio of 9,10 - dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide to tris - eugenol - grafted triazine is 1:1.

[0019] Furthermore, in S21, in the pretreated aramid staple fiber dispersion, the weight ratio of aramid staple fiber, epoxy resin, and blocked isocyanate is (7-10): (1-2): (3-5).

[0020] Furthermore, in S22, the molar ratio of resorcinol, formaldehyde and methacryloyl chloride is 1:(1.5~2):(0.3~0.5); the molar ratio of methacryloyl chloride to triethylamine is 1:1; and the molar ratio of sodium hydroxide to m-diphenol is (8~10):100.

[0021] Furthermore, in S31, the contents of each component in the inner layer rubber are, by weight, 100 parts of EPDM rubber, 80-100 parts of carbon black, 15-30 parts of light calcium carbonate, 50-60 parts of paraffin oil, 3-5 parts of zinc oxide, 1.5-2.5 parts of stearic acid, 2-4 parts of polyethylene glycol, 4-6 parts of vulcanizing agent, and 15-20 parts of flame retardant; the contents of each component in the outer layer rubber are, by weight, 100 parts of EPDM rubber, 80-100 parts of carbon black, 15-30 parts of light calcium carbonate, 50-60 parts of paraffin oil, 3-5 parts of zinc oxide, 1.5-2.5 parts of stearic acid, 2-4 parts of polyethylene glycol, 4-6 parts of vulcanizing agent, 15-20 parts of flame retardant, and 30-40 parts of aramid staple fiber composite.

[0022] Furthermore, in S31, the specific conditions of the two mixings are as follows: the conditions for the first mixing are: the air pressure of the upper push pin is 0.5±0.1MPa, the glue feeding temperature is 55±5℃, the mixing speed is 30±5phr, the mixing is 5~8min, and the glue discharge temperature is 140±5℃; at a roller spacing of 1.2±0.2mm, thin pass 3 times, the time is 5~8min; the conditions for the second mixing are: the air pressure of the upper push pin is 0.5±0.1MPa, the glue feeding temperature is 55±5℃, the mixing speed is 20±5phr, the mixing is 3~4min, and the glue discharge temperature is 90±5℃; at a roller spacing of 1.2±0.2mm, thin pass 3 times, the time is 5~8min.

[0023] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: the present invention provides a method for preparing a cooling water pipe for an electric vehicle having a double-layer structure, wherein the inner layer is an EPDM rubber layer, providing good sealing, heat resistance and medium resistance, and the outer layer is a short fiber reinforced EPDM rubber layer, providing excellent mechanical properties and pressure resistance. Compared with the conventional three-layer structured ordinary rubber hose reinforced with filament fibers, the present invention omits the middle fiber reinforcement layer, simplifies the production process, improves production efficiency, reduces material costs, and reduces the overall wall thickness of the product by 30% compared with the conventional three-layer structure pipe, thereby achieving lightweight.

[0024] In order to improve the performance of rubber materials, the present invention synthesizes an efficient flame retardant using 2,4,6-trichloro-1,3,5-triazine as the nitrogen source, eugenol as the carbon source, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide as the phosphorus source, and the synthesis is carried out by a two-step method. The synthesized flame retardant is added to the rubber material, which can produce a synergistic effect with inorganic fillers such as calcium carbonate, jointly improve the flame retardant effect of the rubber matrix, enhance the safety of the rubber material during storage, transportation, and use, and avoid serious losses caused by large-scale fires. Since the flame retardant prepared by the present invention contains two unsaturated double bonds, during the vulcanization process using organic peroxides as vulcanizing agents, a co-crosslinking effect similar to that of triallyl isocyanurate can be produced, shortening the vulcanization time of the rubber and improving the strength and performance of the rubber.

[0025] When preparing the outer rubber compound, the present invention also adds an aramid short fiber composite. The present invention pretreats the aramid short fibers with epoxy resin; mixes resorcinol-formaldehyde resin and butadiene-acrylonitrile latex to obtain an RFL dipping solution, and then adds the pretreated aramid short fibers to the RFL dipping solution to obtain an aramid short fiber composite. After treatment with the RFL dipping solution, the adhesion effect between the aramid short fiber composite and the rubber matrix is improved. The present invention also modifies the resorcinol-formaldehyde resin by introducing carbon-carbon double bonds into the side chain of the resorcinol-formaldehyde resin; during vulcanization, the flame retardant can further promote the crosslinking between the aramid short fiber composite and the rubber matrix, thereby improving the bonding effect between the two.

[0026] In addition, it should be noted that when preparing the flame retardant, the dosage of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide needs to be controlled. In the present invention, the reaction product of 2,4,6-trichloro-1,3,5-triazine and eugenol, tris(eugenol)-grafted triazine, contains three carbon-carbon double bonds, all of which can react with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. Through continuous experiments, it is found that when and only when 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide reacts with one carbon-carbon double bond on tris(eugenol)-grafted triazine and two carbon-carbon double bonds are retained, that is, when the two react in a molar ratio of 1:1, the obtained flame retardant has both a co-crosslinking effect and flame retardant properties. Detailed Embodiments

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] Materials and sources used in the present invention: Ethylene propylene diene monomer rubber comes from Arlanxeo High Performance Elastomers (Changzhou) Co., Ltd., with the grade of Keltan ® 8550C; Aramid short fibers come from Yantai Taihe New Materials Co., Ltd., with a length of 3 mm and the grade of Taipulong Taparan ® Short fibers; The vulcanizing agent is dicumyl peroxide, from Shanghai Gaojiao Petrochemical Co., Ltd.; Polyethylene glycol is polyethylene glycol 400, from Nanjing Xinhua Yuan Chemical Co., Ltd.; Light calcium carbonate comes from Shijiazhuang Yitian Mineral Products Co., Ltd., with a particle size of 800 mesh; Carbon black comes from Kasong Chemical Industry, with the model of N550; Epoxy resin is epoxy resin E51, from Hebei Linyuan Fine Chemical Co., Ltd.; Paraffin oil is paraffin oil 300, from Hebei Shengkang Chemical Co., Ltd.; Pyridine-butadiene latex comes from Zhejiang Tianchen Rubber Industry Co., Ltd., with the grade of TC-P601; Blocked isocyanate comes from Covestro Polymer Co., Ltd., with the grade of IMPRAFIX2794.

[0029] Example 1: An electric vehicle cooling water pipe and its preparation method, including the following steps:

[0030] Step 1:

[0031] S11: Weigh eugenol and triethylamine and disperse them in anhydrous ethanol, stir evenly to obtain mixed solution A; Disperse 2,4,6-trichloro-1,3,5-triazine in anhydrous ethanol, stir evenly to obtain mixed solution B; After heating mixed solution B to 60 °C, add it to mixed solution A, control the addition speed so that mixed solution B is added within 30 min; Carry out reflux reaction for 8 h, filter by suction, rotary evaporate, wash the substrate with ethanol, filter, dry, recrystallize with ethyl acetate, filter again, and dry to obtain tris-eugenol grafted triazine; Among them, the molar ratio of eugenol, triethylamine, and 2,4,6-trichloro-1,3,5-triazine is 3.05:3:1;

[0032] S12: Disperse 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in toluene, heat it to 85 °C, after 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is completely dissolved, add tris-eugenol grafted triazine, continue to heat to 100 °C, react for 8 h, then cool and filter by suction, wash the substrate with tetrahydrofuran, filter by suction, and vacuum dry to obtain the flame retardant; Among them, the molar ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to tris-eugenol grafted triazine is 1:1;

[0033] Step 2:

[0034] S21: Place the aramid short fibers in deionized water and ultrasonically disperse them for 30 min to obtain an aramid short fiber dispersion. Disperse the epoxy resin in deionized water, stir for 30 min, then add the blocked isocyanate and stir to obtain a pretreatment solution. Add the aramid short fiber dispersion to the pretreatment solution and stir to obtain a pretreated aramid short fiber dispersion. Filter and dry to obtain pretreated aramid short fibers. In the pretreated aramid short fiber dispersion, the weight ratio of aramid short fibers, epoxy resin, and blocked isocyanate is 7:1:3;

[0035] S22: Dissolve resorcinol in deionized water, add formaldehyde, react for 6 h using sodium hydroxide as a catalyst, then add dilute hydrochloric acid to adjust the pH value of the system to 7. Add methacryloyl chloride and triethylamine and react at 40 °C for 5 h to obtain a modified phenolic resin adhesive solution with a solid content of 6%. Among them, the molar ratio of resorcinol, formaldehyde, and methacryloyl chloride is 1:2:0.3; the molar ratio of methacryloyl chloride to triethylamine is 1:1; the molar ratio of sodium hydroxide to resorcinol is 8:100;

[0036] S23: Mix the butadiene-acrylonitrile latex and the modified phenolic resin adhesive solution according to a dry weight ratio of 18:100, add ammonia water to adjust the pH value to 8, and stir and cure for 20 h to obtain an RFL dipping solution;

[0037] S24: Put the pretreated short fibers into the RFL dipping solution, stir for 20 min and then let it stand, filter using a flocculated rubber cloth, and dry in an oven at 100 °C for 2 h to obtain an aramid short fiber composite;

[0038] Step 3:

[0039] S31: Mix 100 kg of ethylene propylene diene monomer rubber, 80 kg of carbon black, 15 kg of light calcium carbonate, 50 kg of paraffin oil, 4 kg of zinc oxide, 2 kg of stearic acid, 3 kg of polyethylene glycol, 4 kg of vulcanizing agent, and 20 kg of flame retardant to obtain an inner layer compound. Mix 100 kg of ethylene propylene diene monomer rubber, 80 kg of carbon black, 15 kg of light calcium carbonate, 50 kg of paraffin oil, 4 kg of zinc oxide, 2 kg of stearic acid, 3 kg of polyethylene glycol, 4 kg of vulcanizing agent, 20 kg of flame retardant, and 35 kg of aramid short fiber composite to obtain an outer layer compound. Conduct two-stage mixing on the inner layer compound and the outer layer compound respectively to obtain an inner layer mixed compound and an outer layer mixed compound. Among them, the conditions for the first-stage mixing are: the air pressure of the upper plug is 0.5 MPa, the feeding temperature is 55 °C, the mixing speed is 30 phr, mix for 5 min, and the discharging temperature is 140 °C; under a roll gap of 1.2 mm, thin pass 3 times, with a time of 5 min. The conditions for the second-stage mixing are: the air pressure of the upper plug is 0.6 MPa, the feeding temperature is 60 °C, the mixing speed is 25 phr, mix for 4 min, and the discharging temperature is 90 °C; under a roll gap of 1.2 mm, thin pass 3 times, with a time of 5 min;

[0040] S32: Set the head temperature to 75 °C, the temperature of the second barrel section to 65 °C, the temperature of the first barrel section to 60 °C, and the feeder temperature to 50 °C. Extrude the inner and outer compounded rubber materials, and vulcanize them at 160 °C and a pressure of 0.6 MPa for 30 min to obtain an electric vehicle cooling water pipe with an inner rubber layer thickness of 0.5 mm and an outer rubber layer thickness of 2 mm.

[0041] Example 2: An electric vehicle cooling water pipe and its preparation method, comprising the following steps:

[0042] Step 1:

[0043] S11: Weigh eugenol and triethylamine, disperse them in anhydrous ethanol, and stir evenly to obtain a mixed solution A; disperse 2,4,6-trichloro-1,3,5-triazine in anhydrous ethanol, and stir evenly to obtain a mixed solution B; heat the mixed solution B to 65 °C and then add it to the mixed solution A, controlling the addition rate so that the mixed solution B is added within 45 min; reflux and react for 9 h, filter by suction, rotary evaporate, wash the substrate with ethanol, filter, dry, recrystallize with ethyl acetate, filter again, and dry to obtain tris(eugenol)-grafted triazine; wherein, the molar ratio of eugenol, triethylamine, and 2,4,6-trichloro-1,3,5-triazine is 3.05:3:1;

[0044] S12: Disperse 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in toluene, heat it to 90 °C, and after all of the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is dissolved, add tris(eugenol)-grafted triazine, continue to heat to 105 °C, react for 9 h, then cool and filter by suction, wash the substrate with tetrahydrofuran, filter by suction, and dry under vacuum to obtain a flame retardant; wherein, the molar ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to tris(eugenol)-grafted triazine is 1:1;

[0045] Step 2:

[0046] S21: Place the aramid short fibers in deionized water and ultrasonically disperse them for 45 min to obtain an aramid short fiber dispersion; disperse epoxy resin in deionized water, stir for 45 min, then add a blocked isocyanate and stir to obtain a pretreatment solution; add the aramid short fiber dispersion to the pretreatment solution and stir to obtain a pretreated aramid short fiber dispersion; filter and dry to obtain pretreated aramid short fibers; in the pretreated aramid short fiber dispersion, the weight ratio of aramid short fibers, epoxy resin, and blocked isocyanate is 7:1:3;

[0047] S22: Dissolve resorcinol in deionized water, add formaldehyde, react for 7 h using sodium hydroxide as a catalyst, then add dilute hydrochloric acid to adjust the pH value of the system to 7. Add methacryloyl chloride and triethylamine, and react at 45 °C for 5.5 h to obtain a modified phenolic resin adhesive solution with a solid content of 6%. Among them, the molar ratio of resorcinol, formaldehyde, and methacryloyl chloride is 1:2:0.3; the molar ratio of methacryloyl chloride to triethylamine is 1:1; the molar ratio of sodium hydroxide to resorcinol is 8:100;

[0048] S23: Mix butadiene-acrylonitrile latex and the modified phenolic resin adhesive solution according to a dry weight ratio of 18:100, add ammonia water to adjust the pH value to 8.5, and stir and cure for 22 h to obtain an RFL dipping solution;

[0049] S24: Put the pretreated short fibers into the RFL dipping solution, stir for 25 min and then let it stand, filter using flocculent filter cloth, and dry in an oven at 105 °C for 2.5 h to obtain aramid short fiber composites;

[0050] Step 3:

[0051] S31: Mix 100 kg of ethylene propylene diene monomer rubber, 80 kg of carbon black, 15 kg of light calcium carbonate, 50 kg of paraffin oil, 4 kg of zinc oxide, 2 kg of stearic acid, 3 kg of polyethylene glycol, 4 kg of vulcanizing agent, and 20 kg of flame retardant to obtain an inner layer compound; mix 100 kg of ethylene propylene diene monomer rubber, 80 kg of carbon black, 15 kg of light calcium carbonate, 50 kg of paraffin oil, 4 kg of zinc oxide, 2 kg of stearic acid, 3 kg of polyethylene glycol, 4 kg of vulcanizing agent, 20 kg of flame retardant, and 35 kg of aramid short fiber composites to obtain an outer layer compound; conduct two-stage mixing on the inner layer compound and the outer layer compound respectively to obtain an inner layer mixed compound and an outer layer mixed compound. Among them, the conditions for the first-stage mixing are: the air pressure of the upper plug is 0.5 MPa, the feeding temperature is 55 °C, the mixing speed is 30 phr, mix for 5 min, and the discharging temperature is 140 °C; under a roll gap of 1.2 mm, thin pass 3 times, with a time of 5 min; the conditions for the second-stage mixing are: the air pressure of the upper plug is 0.6 MPa, the feeding temperature is 60 °C, the mixing speed is 25 phr, mix for 4 min, and the discharging temperature is 90 °C; under a roll gap of 1.2 mm, thin pass 3 times, with a time of 5 min;

[0052] S32: Set the head temperature to 75 °C, the temperature of the second section of the barrel to 65 °C, the temperature of the first section of the barrel to 60 °C, and the feeding port temperature to 50 °C. Extrude the inner layer mixed compound and the outer layer mixed compound, and vulcanize at 160 °C and a pressure of 0.6 MPa for 30 min to obtain an electric vehicle cooling water pipe with an inner rubber layer thickness of 0.5 mm and an outer rubber layer thickness of 2 mm.

[0053] Example 3: An electric vehicle cooling water pipe and its preparation method, including the following steps:

[0054] Step 1:

[0055] S11: Weigh eugenol and triethylamine and disperse them in absolute ethanol, stir evenly to obtain mixed solution A; disperse 2,4,6-trichloro-1,3,5-triazine in absolute ethanol, stir evenly to obtain mixed solution B; heat mixed solution B to 70 °C and then add it to mixed solution A, control the addition rate so that mixed solution B is added within 60 min; carry out reflux reaction for 10 h, filter by suction, rotary evaporate, wash the substrate with ethanol, filter, dry, recrystallize with ethyl acetate, filter again, dry to obtain tris-eugenol grafted triazine; among them, the molar ratio of eugenol, triethylamine, and 2,4,6-trichloro-1,3,5-triazine is 3.05:3:1;

[0056] S12: Disperse 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in toluene, heat to 95 °C, after 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is completely dissolved, add tris-eugenol grafted triazine, continue to heat to 105 °C, after reacting for 10 h, cool and filter by suction, wash the substrate with tetrahydrofuran, filter by suction, vacuum dry to obtain the flame retardant; among them, the molar ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to tris-eugenol grafted triazine is 1:1;

[0057] Step 2:

[0058] S21: Take aramid short fibers and place them in deionized water, ultrasonically disperse for 60 min to obtain an aramid short fiber dispersion; disperse epoxy resin in deionized water, stir for 60 min, then add blocked isocyanate and stir to obtain a pretreatment solution; add the aramid short fiber dispersion to the pretreatment solution and stir to obtain a pretreated aramid short fiber dispersion; filter and dry to obtain pretreated aramid short fibers; in the pretreated aramid short fiber dispersion, the weight ratio of aramid short fibers, epoxy resin, and blocked isocyanate is 7:1:3;

[0059] S22: Dissolve resorcinol in deionized water, add formaldehyde, react for 8 h with sodium hydroxide as a catalyst, then add dilute hydrochloric acid to adjust the pH value of the system to 7, add methacryloyl chloride and triethylamine, react at 50 °C for 6 h to obtain a modified phenolic resin adhesive solution with a solid content of 6%; among them, the molar ratio of resorcinol, formaldehyde, and methacryloyl chloride is 1:2:0.3; the molar ratio of methacryloyl chloride to triethylamine is 1:1; the molar ratio of sodium hydroxide to resorcinol is 8:100;

[0060] S23: Mix butadiene-acrylonitrile latex and the modified phenolic resin adhesive solution according to the dry weight ratio of 18:100, add ammonia water to adjust the pH value to 9, stir and cure for 24 h to obtain the RFL dipping solution;

[0061] S24: Put the pretreated short fibers into the RFL dipping solution, stir for 30 min and then let stand. Filter using flocculation filter cloth and dry in an oven at 105 °C for 3 h to obtain aramid short fiber composites;

[0062] Step 3:

[0063] S31: Mix 100 kg of ethylene propylene diene monomer rubber, 80 kg of carbon black, 15 kg of light calcium carbonate, 50 kg of paraffin oil, 4 kg of zinc oxide, 2 kg of stearic acid, 3 kg of polyethylene glycol, 4 kg of vulcanizing agent, and 20 kg of flame retardant to obtain the inner layer compound; Mix 100 kg of ethylene propylene diene monomer rubber, 80 kg of carbon black, 15 kg of light calcium carbonate, 50 kg of paraffin oil, 4 kg of zinc oxide, 2 kg of stearic acid, 3 kg of polyethylene glycol, 4 kg of vulcanizing agent, 20 kg of flame retardant, and 35 kg of aramid short fiber composites to obtain the outer layer compound; Conduct two-stage mixing on the inner layer compound and the outer layer compound respectively to obtain the inner layer mixed compound and the outer layer mixed compound; Among them, the conditions for the first-stage mixing are: the air pressure of the upper plug is 0.5 MPa, the feeding temperature is 55 °C, the mixing speed is 30 phr, mix for 5 min, and the discharging temperature is 140 °C; Under the roll gap of 1.2 mm, thin pass 3 times, and the time is 5 min; The conditions for the second-stage mixing are: the air pressure of the upper plug is 0.6 MPa, the feeding temperature is 60 °C, the mixing speed is 25 phr, mix for 4 min, and the discharging temperature is 90 °C; Under the roll gap of 1.2 mm, thin pass 3 times, and the time is 5 min;

[0064] S32: Set the head temperature to 75 °C, the temperature of the second barrel section to 65 °C, the temperature of the first barrel section to 60 °C, and the feeding port temperature to 50 °C. Extrude the inner layer mixed compound and the outer layer mixed compound, and vulcanize at 160 °C and a pressure of 0.6 MPa for 30 min to obtain an electric vehicle cooling water pipe with an inner rubber layer thickness of 0.5 mm and an outer rubber layer thickness of 2 mm.

[0065] Comparative Example 1: Do not add aramid short fiber composites, and the other parameters are the same as in Example 1.

[0066] Comparative Example 2: Do not add flame retardant, and the other parameters are the same as in Example 2.

[0067] Comparative Example 3: In step S12, react 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with tris(eugenol)grafted triazine in a molar ratio of 2:1, and the other parameters are the same as in Example 3.

[0068] Experiment: According to the methods in Examples 1 to 3 and Comparative Examples 1 to 3, prepare electric vehicle cooling water pipes with an inner diameter of 8 mm for testing. The experimental results are shown in the following table. Among them, the testing method is:

[0069] Flame retardancy test: The vertical burning grade was tested using a UL94 horizontal and vertical burning tester.

[0070] Mechanical property test: Referring to GB / T 528-2019, the tensile strength and elongation at break of the rubber material were tested.

[0071] Outer diameter change rate and burst pressure test: Referring to the standard GB / T5563-2013, the pressure resistance expansion and pressure resistance burst performance of the product were tested.

[0072] Pressure pulse test: According to the following requirements: Select TL774 coolant, at a test pressure of 1 bar, a medium temperature of 110 °C, an ambient temperature of 75 °C, a frequency of 1 Hz, and run for 250,000 times to observe whether there is any rupture.

[0073]

[0074] Conclusion: The production method of the cooling pipe provided by this patent can realize the production of the cooling pipe and meet the usage condition requirements of the cooling water pipe for pure electric vehicles.

[0075] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a cooling water pipe for an electric vehicle, characterized in that: The following steps are involved: Step 1: by weight, 100 parts of EPDM rubber, 80-100 parts of carbon black, 10-20 parts of light calcium carbonate, 40-50 parts of paraffin oil, 3-5 parts of zinc oxide, 1.5-2.5 parts of stearic acid, 2-4 parts of polyethylene glycol, 4-6 parts of vulcanizing agent, and 15-20 parts of flame retardant are mixed to obtain an inner layer rubber; 100 parts of EPDM rubber, 80-100 parts of carbon black, 10-20 parts of light calcium carbonate, 40-50 parts of paraffin oil, 3-5 parts of zinc oxide, 1.5-2.5 parts of stearic acid, 2-4 parts of polyethylene glycol, 4-6 parts of vulcanizing agent, 15-20 parts of flame retardant, and 30-40 parts of aramid staple fiber composite are mixed to obtain an outer layer rubber; the inner layer rubber and the outer layer rubber are mixed twice to obtain an inner layer mixed rubber and an outer layer mixed rubber respectively; Step 2: Set the die temperature to 75±2℃, the barrel 2 section temperature to 65±2℃, the barrel 1 section temperature to 60±2℃, and the feed port temperature to 50±2℃, extrude the inner layer mixed rubber compound and the outer layer mixed rubber compound to obtain a double-layer composite tube embryo, vulcanize at 160±5℃ and a pressure of 0.55~0.65MPa for 20~30min, and obtain an electric vehicle cooling water pipe with an inner rubber layer thickness of 0.5~0.6mm and an outer rubber layer thickness of 2~2.5mm; In step 1, the preparation method of the flame retardant is: S1: Weigh eugenol and triethylamine, disperse them in anhydrous ethanol, and stir them to obtain a mixed solution A; disperse 2,4,6-trichloro-1,3,5-triazine in anhydrous ethanol, and stir them to obtain a mixed solution B; heat the mixed solution B to 60-70°C and add it to the mixed solution A, and control the adding speed so that the mixed solution B is added within 30-60 minutes; reflux for 8-10 hours, filter and rotary evaporate, wash the substrate with ethanol, filter, dry, recrystallize with ethyl acetate, filter again, and dry to obtain trieugenol grafted triazine; S2: Disperse 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in toluene, raise the temperature to 85-95°C, add trieugenol grafted triazine after all 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is dissolved, continue to raise the temperature to 100-105°C, react for 8-10 hours, cool, filter, wash the substrate with tetrahydrofuran, filter, and vacuum dry to obtain a flame retardant; The method for preparing the aramid staple fiber composite comprises the following steps: a. Place aramid staple fibers in deionized water and ultrasonically disperse for 30 to 60 minutes to obtain aramid staple fiber dispersion; disperse epoxy resin in deionized water and stir for 30 to 60 minutes, then add blocked isocyanate and stir to obtain a pretreatment solution; add the aramid staple fiber dispersion to the pretreatment solution and stir to obtain a pretreated aramid staple fiber dispersion; filter and dry to obtain the pretreated aramid staple fibers; b. Dissolve resorcinol in deionized water, add formaldehyde, react for 6-8 hours with sodium hydroxide as a catalyst, add dilute hydrochloric acid to adjust the pH value of the system to 7, add methacryloyl chloride and triethylamine, react for 5-6 hours at 40-50°C, and obtain a modified phenolic resin glue with a solid content of 6-8%; c. Mix the butylpyridine latex and the modified phenolic resin glue, add ammonia water to adjust the pH value to 8-9, stir and mature for 20-24 hours to obtain the RFL dipping solution; d. Place the pretreated short fibers into the RFL dipping solution, stir for 20 to 30 minutes, let stand, filter using a floc filter cloth, and dry in an oven at 100 to 105° C. for 2 to 3 hours to obtain an aramid short fiber composite.

2. The method for preparing a cooling water pipe for an electric vehicle according to claim 1, characterized in that: In step 1, the mixing conditions for the two times are as follows: the conditions for the first mixing are: the air pressure of the upper ejector is 0.5±0.1MPa, the glue inlet temperature is 55±5°C, the mixing speed is 30±5rpm, the mixing is 5~8min, and the glue discharge temperature is 140±5°C; at a roller spacing of 1.2±0.2mm, the thin pass is performed 3 times for 5~8min; the conditions for the second mixing are: the air pressure of the upper ejector is 0.5±0.1MPa, the glue inlet temperature is 55±5°C, the mixing speed is 20±5rpm, the mixing is 3~4min, and the glue discharge temperature is 90±5°C; at a roller spacing of 1.2±0.2mm, the thin pass is performed 3 times for 5~8min.

3. The method for preparing a cooling water pipe for an electric vehicle according to claim 1, characterized in that: In S1, the molar ratio of eugenol, triethylamine, and 2,4,6-trichloro-1,3,5-triazine is (3.05-3.1):3:

1.

4. The method for preparing a cooling water pipe for an electric vehicle according to claim 1, characterized in that: In S2, the molar ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to trieugenol-grafted triazine is 1:

1.

5. The method for preparing a cooling water pipe for an electric vehicle according to claim 1, characterized in that: In a, in the pretreated aramid staple fiber dispersion, the weight ratio of aramid staple fiber, epoxy resin and blocked isocyanate is (7-10): (1-2): (3-5); the aramid staple fiber has a length of 0.1 mm-3 mm and an aspect ratio of 100-200.

6. The method for preparing a cooling water pipe for an electric vehicle according to claim 1, characterized in that: In b, the molar ratio of resorcinol, formaldehyde and methacryloyl chloride is 1:(1.5~2):(0.3~0.5); the molar ratio of methacryloyl chloride to triethylamine is 1:1; and the molar ratio of sodium hydroxide to m-diphenol is (8~10):

100.

7. The method for preparing a cooling water pipe for an electric vehicle according to claim 1, characterized in that: In c, the butylpyrrolidone latex and the modified phenolic resin glue are mixed in a dry weight ratio of (15-20):

100.

8. An electric vehicle cooling water pipe prepared according to the preparation method according to any one of claims 1 to 7.

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