Anti-aging air conditioner rubber hose and preparation process thereof

Abstract

The invention belongs to the technical field of air conditioner rubber hoses, and particularly relates to an anti-aging air conditioner rubber hose and a preparation process thereof. The air conditioner rubber tube comprises an outer rubber layer, wherein the outer rubber layer comprises the following components in parts by weight: 50-60 parts of ethylene propylene diene monomer; 40 to 50 parts of natural rubber; 10 to 15 parts of carbon black; 8 to 10 parts of modified halloysite nanotubes; 6-8 parts of modified grafted polypropylene fiber; 3-5 parts of zinc oxide; 2-3 parts of stearic acid; 1-2 parts of a lubricant; 2-3 parts of a vulcanizing agent; 1-2 parts of an accelerant; the modified grafted polypropylene fibers and the modified halloysite nanotubes are added into the components of the outer rubber layer, so that the mechanical property of the outer rubber layer is improved, the flame retardant property of the outer rubber layer is enhanced, and particularly, the hot air aging resistance and ozone aging resistance of the outer rubber layer are greatly improved; the anti-aging outer rubber layer provided by the invention is suitable for preparing an anti-aging air conditioner rubber tube.

Description

Technical Field

[0001] This invention belongs to the field of air conditioning hose technology, specifically relating to an aging-resistant air conditioning hose and its preparation process. Background Technology

[0002] Air conditioning hoses are crucial flexible conduits connecting core components such as compressors, condensers, and evaporators in automotive, residential, and industrial refrigeration systems. They primarily handle the circulation and transport of refrigerant, and their performance directly impacts the system's cooling efficiency, sealing, and durability. Air conditioning hoses typically consist of an inner rubber layer, a braided layer (reinforcing layer), and an outer rubber layer. The inner rubber layer, in direct contact with the refrigerant, requires excellent resistance to media, density, and temperature resistance, and is often made of materials such as nitrile rubber, natural rubber, or synthetic rubber. The braided layer withstands internal pressure and external forces, improving the hose's strength and pressure resistance; it is usually made of multi-layered fibers (such as polyester or aramid fibers) or steel wire braiding. The outer rubber layer protects the inner layer from external damage and UV aging, preventing environmental influences. It typically uses wear-resistant and aging-resistant rubber materials (such as EPDM rubber or acrylic rubber). The aging resistance of the outer rubber layer is critical, directly affecting the service life and performance stability of the air conditioning hose.

[0003] Patent application CN202111085750.X discloses an automotive air conditioning hose for conveying R134a refrigerant, composed of the following components: EPDM rubber, EPDM latex, silane coupling agent KH560, graphene, zinc oxide, stearic acid, antioxidant, polyethylene glycol PEG6000, coumarone resin, carbon black N660, calcium powder, paraffin oil, sulfur, accelerator, and scorching inhibitor CTP. Based on a traditional air conditioning hose rubber formulation, it incorporates special materials capable of blocking small molecule gases and is manufactured using a special processing method, achieving excellent barrier properties against R134a refrigerant. However, the air conditioning hose exhibits poor aging resistance. Patent application CN202311164405.4... The application discloses a middle rubber layer material for an air conditioning hose, a preparation method thereof, and the air conditioning hose itself. The middle rubber layer material comprises the following components: 100 parts chlorinated butyl rubber, 20-40 parts natural rubber, 30-50 parts reinforcing agent, 8-20 parts tackifying resin, 2-6 parts plasticizer, 5-10 parts vulcanizing agent, and 3-5 parts vulcanization accelerator. The tackifying resin is a terpene-modified phenolic resin, which can give the middle rubber layer excellent adhesion and mechanical properties, and good adhesion to the barrier layer, giving the air conditioning hose low permeability to water and refrigerant. The reinforcing agents include carbon black, silica, and organomontmorillonite, which can improve the heat aging resistance and low compression set of the middle rubber layer to a certain extent, but still cannot make the middle rubber layer achieve high aging resistance. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing an aging-resistant air conditioning hose and its manufacturing process. The air conditioning hose includes an outer rubber layer. By adding modified grafted polypropylene fibers and modified halloysite nanotubes to the components of the outer rubber layer, the mechanical properties of the outer rubber layer are improved, the flame retardant properties of the outer rubber layer are enhanced, and in particular, the heat resistance and ozone resistance of the outer rubber layer are greatly improved. The aging-resistant outer rubber layer provided by this invention is suitable for preparing aging-resistant air conditioning hoses.

[0005] The technical solution adopted by the present invention to achieve the above objectives is as follows: An aging-resistant air conditioning hose, comprising an outer rubber layer; the outer rubber layer comprises the following components in parts by weight: 50-60 parts EPDM rubber; 40-50 parts natural rubber; 10-15 parts carbon black; 8-10 parts modified halloysite nanotubes; 6-8 parts modified grafted polypropylene fiber; 3-5 parts zinc oxide; 2-3 parts stearic acid; 1-2 parts lubricant; 2-3 parts vulcanizing agent; and 1-2 parts accelerator.

[0006] Furthermore, the lubricant is polyethylene wax or ethyl silicone oil.

[0007] Furthermore, the vulcanizing agent is sulfur; the accelerator is accelerator DM.

[0008] Furthermore, the air conditioning hose also includes an inner rubber layer and a reinforcing layer; the inner rubber layer includes chlorinated butyl rubber or brominated butyl rubber; the reinforcing layer is woven from polyester fiber or aramid fiber.

[0009] Furthermore, the modified grafted polypropylene fiber is prepared by adding 4-allyl catechol and benzoyl peroxide to xylene, stirring until uniform, immersing the polypropylene fiber in the mixture, heating to 100-110℃, and reacting for 3-4 hours to obtain the modified grafted polypropylene fiber.

[0010] Furthermore, the mass ratio of the polypropylene fiber, 4-allyl catechol, benzoyl peroxide, and xylene is 1:0.3-0.4:0.02-0.03:15-20.

[0011] Furthermore, the method for preparing the modified halloysite nanotubes is as follows: Step S1: Add aminated halloysite nanotubes to N,N-dimethylformamide and disperse evenly. First, add 5-chlorobenzotriazole and triethylamine, heat to 65-70℃, and stir for 5-6 hours. Then add 3-chloropropene and sodium hydroxide, heat to 80-85℃, and continue stirring for 4-5 hours to obtain alkenylated halloysite nanotubes. Step S2: Add alkenylated halloysite nanotubes to N,N-dimethylformamide, disperse evenly, then add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, heat to 90-95℃, stir for 8-9 hours to obtain modified halloysite nanotubes.

[0012] Further, the preparation method of the aminated halloysite nanotubes in step S1 is as follows: add halloysite nanotubes to toluene, disperse them evenly, then add 3-aminopropyltriethoxysilane, heat to 110℃, and reflux for 5-6 hours to obtain aminated halloysite nanotubes.

[0013] Furthermore, the mass ratio of halloysite nanotubes, 3-aminopropyltriethoxysilane, and toluene is 1:0.9-1:20-25.

[0014] Further, the mass ratio of the aminated halloysite nanotubes, 5-chlorobenzotriazole, triethylamine, 3-chloropropene, sodium hydroxide, and N,N-dimethylformamide in step S1 is 1:0.5-0.6:0.4-0.5:0.3-0.35:0.2-0.25:20-25.

[0015] Further, in step S2, the mass ratio of the alkenylated halloysite nanotubes, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and N,N-dimethylformamide is 1:0.7-0.8:20-25.

[0016] The present invention also provides a preparation process for an aging-resistant air conditioning hose, comprising the following steps: according to the mass ratio, EPDM rubber and natural rubber are added to a mixer and mixed at 90-100℃ for 5-10 minutes; then carbon black, modified halloysite nanotubes, modified grafted polypropylene fibers, zinc oxide, stearic acid, and lubricant are added and mixed for another 10-15 minutes; then vulcanizing agent and accelerator are added and mixed at 160-170℃ for 20-25 minutes to obtain an outer rubber layer, which is then processed into an air conditioning hose.

[0017] The present invention has the following beneficial effects: To improve the aging resistance of polypropylene fibers, this invention involves a free radical reaction between polypropylene fibers and 4-allyl catechol under the action of benzoyl peroxide as an initiator. This grafts catechol groups with aging-resistant properties onto the polypropylene fibers, resulting in modified grafted polypropylene fibers with improved aging resistance. This invention incorporates the modified grafted polypropylene fibers into the outer adhesive layer, thereby enhancing the outer adhesive layer's resistance to heat aging and ozone aging. Furthermore, this invention uses halloysite nanotubes as raw materials, sequentially reacting them with 3-aminopropyltriethoxysilane... Modified halloysite nanotubes were obtained by reacting alkanes, 5-chlorobenzotriazole, 3-chloropropene, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). The surface of the modified halloysite nanotubes was incorporating benzotriazole groups with anti-aging properties and DOPO groups with flame-retardant properties. These groups synergistically interact with the catechol groups in the modified grafted polypropylene fiber molecules to further improve the heat aging resistance and ozone aging resistance of the outer adhesive layer, while also enhancing the flame-retardant properties of the outer adhesive layer.

[0018] This invention improves the mechanical properties and enhances the flame retardant properties of the outer adhesive layer by adding modified grafted polypropylene fibers and modified halloysite nanotubes to the components of the outer adhesive layer. In particular, it greatly improves the resistance to heat air aging and ozone aging of the outer adhesive layer. The aging-resistant outer adhesive layer provided by this invention is suitable for preparing aging-resistant air conditioning hoses. Detailed Implementation

[0019] 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, and not all embodiments. The technical features designed in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. 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.

[0020] In the technical solution of this invention, all chemical reagents used are commercially available. Specifically, the EPDM rubber is Kumho KEP-330 from South Korea, the natural rubber is 20# standard rubber, the carbon black CAS number is 1333-86-4, the halloysite nanotubes are purchased from Angxing New Carbon Materials Changzhou Co., Ltd., the polypropylene fiber has a diameter of 10-20μm and a length of 3-5mm, the zinc oxide CAS number is 1314-13-2, the stearic acid CAS number is 57-11-4, the polyethylene wax CAS number is 9002-88-4, the ethyl silicone oil CAS number is 63148-61-8, the sulfur CAS number is 7704-34-9, and the accelerator is DM. CAS No. 120-78-5, 4-allyl catechol CAS No. 1126-61-0, benzoyl peroxide CAS No. 94-36-0, 3-aminopropyltriethoxysilane CAS No. 919-30-2, 5-chlorobenzotriazole CAS No. 94-97-3, triethylamine CAS No. 121-44-8, 3-chloropropene CAS No. 107-05-1, sodium hydroxide CAS No. 1310-73-2, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) CAS No. 35948-25-5, toluene CAS No. 108-88-3, xylene CAS No. 1330-20-7, acetone CAS No. 67-64-1, N,N-dimethylformamide CAS No. 68-12-2, ethanol CAS No. 64-17-5.

[0021] Example 1 An aging-resistant air conditioning hose, comprising an outer rubber layer; the outer rubber layer comprises the following components by weight: 60 parts EPDM rubber; 50 parts natural rubber; 13 parts carbon black; 10 parts modified halloysite nanotubes; 8 parts modified grafted polypropylene fiber; 4 parts zinc oxide; 3 parts stearic acid; 2 parts lubricant; 3 parts vulcanizing agent; 2 parts accelerator; wherein the lubricant is polyethylene wax; the vulcanizing agent is sulfur; and the accelerator is DM accelerator.

[0022] The modified grafted polypropylene fiber is prepared by adding 4-allyl catechol and benzoyl peroxide to xylene, stirring until uniform, immersing the polypropylene fiber in the mixture, heating to 110℃, reacting for 3 hours, filtering, washing the product sequentially with xylene and acetone, and drying in a vacuum drying oven at 50℃ for 6 hours to obtain the modified grafted polypropylene fiber; wherein the mass ratio of polypropylene fiber, 4-allyl catechol, benzoyl peroxide, and xylene is 1:0.4:0.03:20.

[0023] The preparation method of modified halloysite nanotubes is as follows: Step S1: Aminated halloysite nanotubes are added to N,N-dimethylformamide and dispersed evenly. First, 5-chlorobenzotriazole and triethylamine are added, the temperature is raised to 70°C, and the reaction is stirred for 6 hours. Then, 3-chloropropene and sodium hydroxide are added, the temperature is raised to 80°C, and the reaction is stirred for another 5 hours. After the reaction is complete, the mixture is filtered, and the product is washed successively with ethanol and water. It is then dried in a vacuum drying oven at 50°C for 6 hours to obtain alkenylated halloysite nanotubes. The mass ratio of aminated halloysite nanotubes, 5-chlorobenzotriazole, triethylamine, 3-chloropropene, sodium hydroxide, and N,N-dimethylformamide is 1:0.6:0.5:0.35:0.25:25. Step S2: Add alkenylated halloysite nanotubes to N,N-dimethylformamide and disperse evenly. Then add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, heat to 95℃, and stir for 8 hours. After the reaction is complete, filter and wash the product with ethanol. Place it in a vacuum drying oven and dry at 50℃ for 6 hours to obtain modified halloysite nanotubes. The mass ratio of alkenylated halloysite nanotubes, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and N,N-dimethylformamide is 1:0.8:25.

[0024] The preparation method of aminated halloysite nanotubes is as follows: Halloysite nanotubes are added to toluene and dispersed evenly. Then, 3-aminopropyltriethoxysilane is added, and the mixture is heated to 110℃ and refluxed for 6 hours. After the reaction is completed, the mixture is filtered, and the product is washed successively with toluene and ethanol. The product is then dried in a vacuum drying oven at 50℃ for 6 hours to obtain aminated halloysite nanotubes. The mass ratio of halloysite nanotubes, 3-aminopropyltriethoxysilane, and toluene is 1:1:25.

[0025] A process for preparing an aging-resistant air conditioning hose includes the following steps: EPDM rubber and natural rubber are added to a mixer according to the mass ratio, and mixed at 100°C for 5 minutes. Then carbon black, modified halloysite nanotubes, modified grafted polypropylene fibers, zinc oxide, stearic acid, and lubricant are added, and mixing continues for 15 minutes. Then vulcanizing agent and accelerator are added, and mixing is carried out at 170°C for 20 minutes to obtain an outer rubber layer, which is then processed into an air conditioning hose.

[0026] Example 2 An aging-resistant air conditioning hose, comprising an outer rubber layer; the outer rubber layer comprises the following components by weight: 50 parts EPDM rubber; 45 parts natural rubber; 15 parts carbon black; 8 parts modified halloysite nanotubes; 6 parts modified grafted polypropylene fiber; 5 parts zinc oxide; 2 parts stearic acid; 1.5 parts lubricant; 2 parts vulcanizing agent; 1 part accelerator; wherein the lubricant is ethyl silicone oil; the vulcanizing agent is sulfur; and the accelerator is accelerator DM.

[0027] The modified grafted polypropylene fiber is prepared by adding 4-allyl catechol and benzoyl peroxide to xylene, stirring until uniform, immersing the polypropylene fiber in the mixture, heating to 100℃, reacting for 4 hours, filtering, washing the product sequentially with xylene and acetone, and drying in a vacuum drying oven at 50℃ for 6 hours to obtain the modified grafted polypropylene fiber; wherein the mass ratio of polypropylene fiber, 4-allyl catechol, benzoyl peroxide, and xylene is 1:0.35:0.025:18.

[0028] The preparation method of modified halloysite nanotubes is as follows: Step S1: Aminated halloysite nanotubes are added to N,N-dimethylformamide and dispersed evenly. First, 5-chlorobenzotriazole and triethylamine are added, the temperature is raised to 65°C, and the reaction is stirred for 5 hours. Then, 3-chloropropene and sodium hydroxide are added, the temperature is raised to 85°C, and the reaction is stirred for another 4 hours. After the reaction is complete, the mixture is filtered, and the product is washed successively with ethanol and water. It is then dried in a vacuum drying oven at 50°C for 6 hours to obtain alkenylated halloysite nanotubes. The mass ratio of aminated halloysite nanotubes, 5-chlorobenzotriazole, triethylamine, 3-chloropropene, sodium hydroxide, and N,N-dimethylformamide is 1:0.5:0.4:0.3:0.2:20. Step S2: Add alkenylated halloysite nanotubes to N,N-dimethylformamide and disperse evenly. Then add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, heat to 90℃, and stir for 9 hours. After the reaction is complete, filter and wash the product with ethanol. Place it in a vacuum drying oven and dry at 50℃ for 6 hours to obtain modified halloysite nanotubes. The mass ratio of alkenylated halloysite nanotubes, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and N,N-dimethylformamide is 1:0.7:20.

[0029] The preparation method of aminated halloysite nanotubes is as follows: Halloysite nanotubes are added to toluene and dispersed evenly. Then, 3-aminopropyltriethoxysilane is added, and the mixture is heated to 110℃ and refluxed for 5.5 h. After the reaction is complete, the mixture is filtered, and the product is washed successively with toluene and ethanol. The product is then dried in a vacuum drying oven at 50℃ for 6 h to obtain aminated halloysite nanotubes. The mass ratio of halloysite nanotubes, 3-aminopropyltriethoxysilane, and toluene is 1:0.9:20.

[0030] A process for preparing an aging-resistant air conditioning hose includes the following steps: EPDM rubber and natural rubber are added to a mixer according to the mass ratio, and mixed at 95°C for 8 minutes. Then carbon black, modified halloysite nanotubes, modified grafted polypropylene fibers, zinc oxide, stearic acid, and lubricant are added, and mixing continues for 12 minutes. Then vulcanizing agent and accelerator are added, and mixing is carried out at 165°C for 23 minutes to obtain an outer rubber layer, which is then processed into an air conditioning hose.

[0031] Example 3 An aging-resistant air conditioning hose, comprising an outer rubber layer; the outer rubber layer comprises the following components by weight: 55 parts EPDM rubber; 40 parts natural rubber; 10 parts carbon black; 9 parts modified halloysite nanotubes; 7 parts modified grafted polypropylene fiber; 3 parts zinc oxide; 2.5 parts stearic acid; 1 part lubricant; 2.5 parts vulcanizing agent; 1.5 parts accelerator; wherein the lubricant is polyethylene wax; the vulcanizing agent is sulfur; and the accelerator is DM accelerator.

[0032] The modified grafted polypropylene fiber is prepared as follows: 4-allyl catechol and benzoyl peroxide are added to xylene and stirred evenly. Then, the polypropylene fiber is immersed in the mixture, heated to 105℃, reacted for 3.5h, filtered, and the product is washed successively with xylene and acetone. It is then dried in a vacuum drying oven at 50℃ for 6h to obtain the modified grafted polypropylene fiber. The mass ratio of polypropylene fiber, 4-allyl catechol, benzoyl peroxide, and xylene is 1:0.3:0.02:15.

[0033] The preparation method of modified halloysite nanotubes is as follows: Step S1: Aminated halloysite nanotubes were added to N,N-dimethylformamide and dispersed evenly. First, 5-chlorobenzotriazole and triethylamine were added, the temperature was raised to 68°C, and the reaction was stirred for 5.5 h. Then, 3-chloropropene and sodium hydroxide were added, the temperature was raised to 82°C, and the reaction was stirred for another 4.5 h. After the reaction was completed, the mixture was filtered, and the product was washed successively with ethanol and water. It was then dried in a vacuum drying oven at 50°C for 6 h to obtain alkenylated halloysite nanotubes. The mass ratio of aminated halloysite nanotubes, 5-chlorobenzotriazole, triethylamine, 3-chloropropene, sodium hydroxide, and N,N-dimethylformamide was 1:0.55:0.45:0.33:0.22:23. Step S2: Add alkenylated halloysite nanotubes to N,N-dimethylformamide and disperse evenly. Then add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, heat to 93℃, and stir for 8.5 h. After the reaction is complete, filter, wash the product with ethanol, and dry it in a vacuum drying oven at 50℃ for 6 h to obtain modified halloysite nanotubes. The mass ratio of alkenylated halloysite nanotubes, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and N,N-dimethylformamide is 1:0.75:22.

[0034] The preparation method of aminated halloysite nanotubes is as follows: Halloysite nanotubes are added to toluene and dispersed evenly. Then, 3-aminopropyltriethoxysilane is added, and the mixture is heated to 110℃ and refluxed for 5 hours. After the reaction is completed, the mixture is filtered, and the product is washed successively with toluene and ethanol. The product is then dried in a vacuum drying oven at 50℃ for 6 hours to obtain aminated halloysite nanotubes. The mass ratio of halloysite nanotubes, 3-aminopropyltriethoxysilane, and toluene is 1:0.95:22.

[0035] A process for preparing an aging-resistant air conditioning hose includes the following steps: EPDM rubber and natural rubber are added to a mixer according to the mass ratio, and mixed at 90°C for 10 minutes. Then carbon black, modified halloysite nanotubes, modified grafted polypropylene fibers, zinc oxide, stearic acid, and lubricant are added, and mixing continues for 10 minutes. Then vulcanizing agent and accelerator are added, and mixing is carried out at 160°C for 25 minutes to obtain an outer rubber layer, which is then processed into an air conditioning hose.

[0036] Example 4 An aging-resistant air conditioning hose, comprising an outer rubber layer; the outer rubber layer comprises the following components by weight: 60 parts EPDM rubber; 40 parts natural rubber; 12 parts carbon black; 8 parts modified halloysite nanotubes; 8 parts modified grafted polypropylene fiber; 4 parts zinc oxide; 3 parts stearic acid; 1 part lubricant; 2.5 parts vulcanizing agent; and 1 part accelerator; wherein the lubricant is ethyl silicone oil; the vulcanizing agent is sulfur; and the accelerator is accelerator DM.

[0037] The modified grafted polypropylene fiber is prepared as follows: 4-allyl catechol and benzoyl peroxide are added to xylene and stirred evenly. Then, the polypropylene fiber is immersed in the mixture, heated to 110℃, reacted for 4 hours, filtered, and the product is washed successively with xylene and acetone. It is then placed in a vacuum drying oven and dried at 50℃ for 6 hours to obtain the modified grafted polypropylene fiber. The mass ratio of polypropylene fiber, 4-allyl catechol, benzoyl peroxide, and xylene is 1:0.4:0.02:20.

[0038] The preparation method of modified halloysite nanotubes is as follows: Step S1 is the same as step S1 in Example 1; Step S2 is the same as step S2 in Example 2.

[0039] The preparation method of the aminated halloysite nanotubes is the same as that in Example 3.

[0040] A process for preparing an aging-resistant air conditioning hose includes the following steps: EPDM rubber and natural rubber are added to a mixer according to the mass ratio, and mixed at 90°C for 8 minutes. Then carbon black, modified halloysite nanotubes, modified grafted polypropylene fibers, zinc oxide, stearic acid, and lubricant are added, and mixing continues for 15 minutes. Then vulcanizing agent and accelerator are added, and mixing is carried out at 170°C for 25 minutes to obtain an outer rubber layer, which is then processed into an air conditioning hose.

[0041] Comparative Example 1 Compared with Example 1, in Comparative Example 1, the modified grafted polypropylene fibers in the outer adhesive layer component were replaced with polypropylene fibers.

[0042] An aging-resistant air conditioning hose, comprising an outer rubber layer; the outer rubber layer comprises the following components by weight: 60 parts EPDM rubber; 50 parts natural rubber; 13 parts carbon black; 10 parts modified halloysite nanotubes; 8 parts polypropylene fiber; 4 parts zinc oxide; 3 parts stearic acid; 2 parts lubricant; 3 parts vulcanizing agent; 2 parts accelerator; wherein the lubricant is polyethylene wax; the vulcanizing agent is sulfur; and the accelerator is DM accelerator.

[0043] The preparation methods for aminated halloysite nanotubes and modified halloysite nanotubes are the same as in Example 1.

[0044] The preparation process of an aging-resistant air conditioning hose is the same as that in Example 1.

[0045] Comparative Example 2 Compared with Example 1, in Comparative Example 1, the modified halloysite nanotubes in the outer adhesive layer component were replaced with halloysite nanotubes.

[0046] An aging-resistant air conditioning hose, comprising an outer rubber layer; the outer rubber layer comprises the following components by weight: 60 parts EPDM rubber; 50 parts natural rubber; 13 parts carbon black; 10 parts halloysite nanotubes; 8 parts modified grafted polypropylene fiber; 4 parts zinc oxide; 3 parts stearic acid; 2 parts lubricant; 3 parts vulcanizing agent; 2 parts accelerator; wherein the lubricant is polyethylene wax; the vulcanizing agent is sulfur; and the accelerator is accelerator DM.

[0047] The preparation method of the modified grafted polypropylene fiber is the same as that in Example 1.

[0048] The preparation process of an aging-resistant air conditioning hose is the same as that in Example 1.

[0049] Comparative Example 3 Compared with Example 1, in Comparative Example 1, the modified grafted polypropylene fiber in the outer adhesive layer component was replaced with polypropylene fiber, and the modified halloysite nanotubes were replaced with halloysite nanotubes.

[0050] An aging-resistant air conditioning hose, comprising an outer rubber layer; the outer rubber layer comprises the following components by weight: 60 parts EPDM rubber; 50 parts natural rubber; 13 parts carbon black; 10 parts halloysite nanotubes; 8 parts polypropylene fiber; 4 parts zinc oxide; 3 parts stearic acid; 2 parts lubricant; 3 parts vulcanizing agent; 2 parts accelerator; wherein the lubricant is polyethylene wax; the vulcanizing agent is sulfur; and the accelerator is DM accelerator.

[0051] The preparation process of an aging-resistant air conditioning hose is the same as that in Example 1.

[0052] Performance testing The outer adhesive layers prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to performance tests. Tensile strength and elongation at break were tested according to GB / T 528-2009 standard at a tensile speed of 500 mm / min; compression set was tested according to GB / T 7759.1-2015 at 100℃ for 72 hours; hot air aging was tested according to GB / T 3512-2014 at 150℃ for 48 hours; ozone aging was tested according to GB / T 30313-2013 at 100 pphm at 40℃ for 20% for 70 hours; and limiting oxygen index was tested according to GB / T 2406-2009. The test results are shown in Table 1 below.

[0053] Table 1 Performance Test Results As shown in Table 1, the outer adhesive layers prepared in Examples 1 to 4 of the present invention have good mechanical properties, resistance to hot air aging, resistance to ozone aging, and flame retardant properties. Compared with Comparative Examples 1 to 3, the addition of modified grafted polypropylene fibers and modified halloysite nanotubes to the outer adhesive layer components in Example 1 of the present invention helps to improve the mechanical properties of the outer adhesive layer. The modified grafted polypropylene fibers have catechol groups with anti-aging properties grafted into their molecules, which improves the resistance to hot air aging and ozone aging of the outer adhesive layer. The modified halloysite nanotubes also have benzotriazole groups with anti-aging properties and DOPO groups with flame retardant properties introduced into their surface. These groups work synergistically with the catechol groups in the modified grafted polypropylene fibers to further improve the resistance to hot air aging and ozone aging of the outer adhesive layer, while also enhancing the flame retardant properties of the outer adhesive layer.

[0054] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0055] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An aging-resistant air conditioning hose, characterized in that, The air conditioning hose includes an outer rubber layer; the outer rubber layer comprises the following components by weight: 50-60 parts EPDM rubber; 40-50 parts natural rubber; 10-15 parts carbon black; 8-10 parts modified halloysite nanotubes; 6-8 parts modified grafted polypropylene fiber; 3-5 parts zinc oxide; 2-3 parts stearic acid; 1-2 parts lubricant; 2-3 parts vulcanizing agent; and 1-2 parts accelerator. The modified halloysite nanotubes are prepared by: Step S1: Add aminated halloysite nanotubes to N,N-dimethylformamide and disperse evenly. First, add 5-chlorobenzotriazole and triethylamine, heat to 65-70℃, and stir for 5-6 hours. Then add 3-chloropropene and sodium hydroxide, heat to 80-85℃, and continue stirring for 4-5 hours to obtain alkenylated halloysite nanotubes. Step S2: Add alkenylated halloysite nanotubes to N,N-dimethylformamide, disperse evenly, then add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, heat to 90-95℃, stir for 8-9 hours to obtain modified halloysite nanotubes.

2. The aging-resistant air conditioning hose according to claim 1, characterized in that, The modified grafted polypropylene fiber is prepared by adding 4-allyl catechol and benzoyl peroxide to xylene, stirring until uniform, immersing the polypropylene fiber in the mixture, heating to 100-110℃, and reacting for 3-4 hours to obtain the modified grafted polypropylene fiber.

3. The aging-resistant air conditioning hose according to claim 2, characterized in that, The mass ratio of the polypropylene fiber, 4-allyl catechol, benzoyl peroxide, and xylene is 1:0.3-0.4:0.02-0.03:15-20.

4. The aging-resistant air conditioning hose according to claim 1, characterized in that, The preparation method of the aminated halloysite nanotubes in step S1 is as follows: Halloysite nanotubes are added to toluene and dispersed evenly, then 3-aminopropyltriethoxysilane is added, the temperature is raised to 110℃, and the reaction is refluxed for 5-6 hours to obtain aminated halloysite nanotubes.

5. The aging-resistant air conditioning hose according to claim 4, characterized in that, The mass ratio of halloysite nanotubes, 3-aminopropyltriethoxysilane, and toluene is 1:0.9-1:20-25.

6. The aging-resistant air conditioning hose according to claim 1, characterized in that, The mass ratio of the aminated halloysite nanotubes, 5-chlorobenzotriazole, triethylamine, 3-chloropropene, sodium hydroxide, and N,N-dimethylformamide in step S1 is 1:0.5-0.6:0.4-0.5:0.3-0.35:0.2-0.25:20-25.

7. The aging-resistant air conditioning hose according to claim 1, characterized in that, The mass ratio of the alkenylated halloysite nanotubes, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and N,N-dimethylformamide in step S2 is 1:0.7-0.8:20-25.

8. The aging-resistant air conditioning hose according to claim 1, characterized in that, The lubricant is polyethylene wax or ethyl silicone oil.

9. The aging-resistant air conditioning hose according to claim 1, characterized in that, The vulcanizing agent is sulfur; the accelerator is accelerator DM.

10. A manufacturing process for an aging-resistant air conditioning hose as described in any one of claims 1-9, characterized in that, The process includes the following steps: According to the mass ratio, EPDM rubber and natural rubber are added to a mixer and mixed at 90-100℃ for 5-10 minutes. Then, carbon black, modified halloysite nanotubes, modified grafted polypropylene fibers, zinc oxide, stearic acid, and lubricant are added and mixed for another 10-15 minutes. Finally, vulcanizing agent and accelerator are added and mixed at 160-170℃ for 20-25 minutes to obtain the outer rubber layer, which is then processed into air conditioning hoses.

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