High-strength anti-aging rubber water return hose and preparation method thereof

Abstract

The invention relates to the field of rubber, in particular to a high-strength anti-aging rubber water return hose and a preparation method thereof.The high-strength anti-aging rubber water return hose is sequentially composed of an inner rubber layer, a reinforcing layer and an outer rubber layer from inside to outside; ePDM and epoxidized silicone rubber are compounded according to the mass ratio of 2: 1 to serve as base rubber, the epoxidized silicone rubber with the epoxy group content of 10%-15% is introduced, a complex cross-linked network is constructed, and the machinability, aging resistance and mechanical strength of the rubber are improved; the preparation method comprises the following steps: adding dopamine into an alcohol-water solution formed by mixing Zn and Ti, preparing polydopamine-coated Zn-Ti hydrotalcite by utilizing a hydrothermal reaction one-pot method, and modifying the polydopamine-coated Zn-Ti hydrotalcite by sequentially using phosphorus oxychloride and branched polysiloxane to obtain composite hydrotalcite; one or more of cyclohexane dicarboxylate, benzene polycarboxylic acid ester and epoxy environment-friendly plasticizers are compounded to serve as the environment-friendly plasticizer.

Description

Technical Field

[0001] This invention relates to the field of rubber technology, specifically to a high-strength, aging-resistant rubber return hose and its preparation method. Background Technology

[0002] Rubber return hoses are important connecting components in automotive cooling systems and industrial equipment heat exchange. Traditional hoses mostly use EPDM rubber as the main material. Although they have good heat and ozone resistance, they still suffer from problems such as rubber layer hardening, cracking, and peeling from the reinforcing layer when used under high-temperature conditions for a long time, which seriously affects the service life of the components.

[0003] Current technologies primarily improve rubber performance by adding antioxidants and reinforcing fibers, but these methods suffer from several problems: common antioxidants are prone to migration and precipitation, and the rubber matrix exhibits poor interfacial compatibility with inorganic reinforcing materials such as fibers and metal wires. With increasing awareness of environmental protection, the use of traditional phthalate plasticizers, heavy metal activators, and harmful accelerators is strictly limited. Furthermore, with rising industrial safety standards, higher requirements are placed on the flame retardancy of rubber hoses. Bromine-based and chlorine-based flame retardants are restricted due to environmental concerns, while the flame retardancy of inorganic fillers often requires high filler volumes, thus affecting the material's processability, mechanical properties, and long-term heat resistance. Summary of the Invention

[0004] The purpose of this invention is to provide a high-strength, aging-resistant rubber return hose and its preparation method, so as to solve the problems in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A high-strength, aging-resistant rubber return hose, consisting of an inner rubber layer, a reinforcing layer, and an outer rubber layer from the inside out; The inner and outer rubber layers have the same composition, and the raw materials are: base rubber, environmentally friendly plasticizer, composite hydrotalcite, activator, antioxidant, vulcanizing agent, and accelerator; the base rubber is a compound of EPDM rubber and epoxidized silicone rubber in a mass ratio of 2:1.

[0006] Furthermore, the reinforcing layer is obtained by weaving or winding one or more of basalt fiber, stainless steel wire, aluminum alloy wire, aramid wire, nylon wire, and polyester wire onto the surface of the inner adhesive layer.

[0007] Furthermore, the environmentally friendly plasticizer is one or more of the following: cyclohexane dicarboxylic acid esters, benzene polycarboxylic acid esters, and epoxy environmentally friendly plasticizers.

[0008] Furthermore, the activator is one or more of zinc oxide, stearic acid, and silica adsorbing zinc 2-ethylhexanoate; the vulcanizing agent is one or more of sulfur, hexamethylenediamine carbamate, and peroxide vulcanizing agents; and the accelerator is an environmentally friendly accelerator.

[0009] Furthermore, the vulcanizing agent is obtained by compounding sulfur and BIPB in a mass ratio of 1:2.

[0010] Furthermore, by mass, the raw material composition of the inner and outer adhesive layers is as follows: 100 parts base adhesive, 4-9 parts environmentally friendly plasticizer, 5-8 parts composite hydrotalcite, 1-3 parts activator, 1-2 parts antioxidant, 1-3 parts vulcanizing agent, and 1-2 parts accelerator.

[0011] Furthermore, the epoxy content in epoxidized silicone rubber is 10-15%.

[0012] Furthermore, the preparation of epoxy silicone rubber includes the following steps: Under a nitrogen atmosphere, octamethylcyclotetrasiloxane and tetramethyltetravinylcyclotetrasiloxane are mixed, heated to 78-80℃ and held for 5-7 minutes, the nitrogen is turned off, a vacuum is drawn to a negative pressure of -0.09MPa and held for 2 hours, the oil bath is heated to 110-113℃, an alkaline rubber catalyst and hexadecyl heptasiloxane are added, the temperature is held for 3 hours, the temperature is raised to 160-163℃, and nitrogen is purged for 3 hours to obtain methyl vinyl silicone rubber; Methyl vinyl silicone rubber and chlorobenzene were mixed and stirred in an oil bath at 55°C for 8 hours. Then, m-chloroperoxybenzoic acid was added and stirred for 38-40 hours. Ethanol was added and the mixture was dried under vacuum to obtain epoxidized silicone rubber.

[0013] Furthermore, the preparation of the alkaline gel catalyst includes the following steps: Under a nitrogen atmosphere, octamethylcyclotetrasiloxane and tetramethylammonium hydroxide are mixed and kept in an oil bath at 78-80℃ for 5-8 minutes. The nitrogen atmosphere is then turned off and a vacuum is drawn to a negative pressure of -0.09MPa and kept at that temperature for 2 hours. Nitrogen gas is then introduced and the oil bath is heated to 118-120℃ and kept at that temperature for 4 hours to obtain the alkaline gel catalyst, which is then stored in the dark.

[0014] Furthermore, the preparation of composite hydrotalcite includes the following steps: (1) Mix anhydrous zinc acetate, ethanol and deionized water, add titanium tetrachloride and dopamine hydrochloride, adjust the pH to 7.9-8.1, transfer to a reaction vessel, heat to 118-120℃ and keep warm for 23-24h, centrifuge, wash and dry to obtain polydopamine-coated Zn-Ti hydrotalcite. (2) Polydopamine-coated hydrotalcite, phosphorus oxychloride and tetrahydrofuran are mixed, triethanolamine is added, and the mixture is sonicated at 18-25℃ for 0.5-1h. A mixture of branched polysiloxane and tetrahydrofuran is added, and the mixture is kept at 18-25℃ for 23-24h. The mixture is washed and dried under reduced pressure to obtain composite hydrotalcite.

[0015] Furthermore, the mass ratio of polydopamine-coated hydrotalcite, phosphorus oxychloride, and branched polysiloxane is 0.5:0.4:1.

[0016] Furthermore, the preparation of branched polysiloxanes includes the following steps: Phenyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, methanol, and tetrahydrofuran were mixed and heated to 55°C for 10-15 minutes. A hydrochloric acid aqueous solution with a pH of 1-3 was added, and the mixture was kept at this temperature for 4-5 hours. The pH was adjusted to neutral, and the mixture was rotary evaporated to obtain branched polysiloxane.

[0017] Furthermore, the molar ratio of phenyltrimethoxysilane to γ-glycidoxypropyltrimethoxysilane is 1:1.

[0018] Furthermore, a method for preparing a high-strength, aging-resistant rubber return hose includes the following steps: S1: Put the base rubber into the internal mixer, then add the environmentally friendly plasticizer, composite hydrotalcite, activator and antioxidant in sequence, mix, discharge the rubber to form a rubber compound, transfer it to the open mill, press it into sheets, cool it, add vulcanizing agent and accelerator, filter it, discharge the sheets, let it stand, vulcanize it to obtain the rubber layer material. S2: Extruding rubber material onto the mold core as the inner rubber layer, cooling and then weaving or winding the reinforcing layer onto the inner rubber layer, heat treating, and then extruding rubber material onto the reinforcing layer as the outer rubber layer, resulting in a high-strength, aging-resistant rubber return hose.

[0019] Furthermore, the surface temperature of the inner adhesive layer after heat treatment is 95-105℃.

[0020] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a high-strength, aging-resistant rubber return hose and its preparation method. Through formula and process optimization, an environmentally friendly, highly flame-retardant, high-strength, and aging-resistant rubber return hose is prepared.

[0021] In this invention, EPDM rubber and epoxidized silicone rubber are compounded in a mass ratio of 2:1 as the base rubber. By introducing epoxidized silicone rubber with an epoxy group content of 10-15%, a complex cross-linking network is constructed to improve the processability, aging resistance and mechanical strength of the rubber, thereby extending the service life of the return water hose.

[0022] Based on the optimization requirements of flame retardancy and aging resistance of return hoses, this invention selects environmentally friendly halogen-free Zn-Ti hydrotalcite as both a flame retardant and an aging resistant agent. To address the issues of low flame retardancy efficiency and poor bonding with the base adhesive when added alone, dopamine is added to an alcohol-water mixture of Zn and Ti. Polydopamine-coated Zn-Ti hydrotalcite is prepared using a one-pot hydrothermal reaction. The polydopamine-coated Zn-Ti hydrotalcite is then modified sequentially with phosphorus oxychloride and branched polysiloxanes. The branched polysiloxanes are phenyltrimethoxysilane and γ-glycidyl etheroxypropyltrimethoxysilane prepared by controlled molar ratio hydrolysis. By grafting nitrogen, phosphorus, and silicon elements, the flame retardancy of the hydrotalcite is significantly enhanced. At the same time, the introduction of multiple active sites significantly improves the bonding strength between the hydrotalcite and the base adhesive, achieving a simultaneous improvement in mechanical strength, aging resistance, and flame retardancy.

[0023] This invention uses one or more of the following environmentally friendly plasticizers as a compound: cyclohexane dicarboxylic acid esters, benzene polycarboxylic acid esters, and epoxy plasticizers. Compared with traditional plasticizers such as phthalates, which have reproductive toxicity and are prone to migration and precipitation, this invention improves environmental safety while increasing the bonding strength with the base rubber and composite hydrotalcite, and increasing the complexity of the crosslinking network, thereby extending the service life of the rubber return hose. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0026] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0027] Example 1: A method for preparing a high-strength, aging-resistant rubber return hose, comprising the following steps: S1: Put the base rubber into the internal mixer, then add the environmentally friendly plasticizer, composite hydrotalcite, activator and antioxidant in sequence, mix, discharge the rubber to form a rubber compound, transfer it to the open mill, press it into sheets, cool it, add vulcanizing agent and accelerator, filter it, discharge the sheets, let it stand, vulcanize it to obtain the rubber layer material. S2: Extrude the rubber material on the mold core as the inner rubber layer, and after cooling, weave or wrap the reinforcing layer on the inner rubber layer, heat treat it, and then extrude the rubber material on the reinforcing layer as the outer rubber layer to obtain a high-strength and aging-resistant rubber return hose. By weight, the raw material composition of the inner and outer rubber layers is as follows: 100 parts base rubber, 4 parts environmentally friendly plasticizer, 5 parts composite hydrotalcite, 1 part activator, 1 part antioxidant, 1 part vulcanizing agent, and 1 part accelerator. The base rubber is a compound of EPDM rubber and epoxidized silicone rubber in a mass ratio of 2:1; the epoxy content of the epoxidized silicone rubber is 10%. The reinforcing layer is obtained by winding a single layer of stainless steel wire around the surface of the inner adhesive layer; The environmentally friendly plasticizer is a compound of cyclohexane dicarboxylic acid ester plasticizer and epoxidized soybean oil in a mass ratio of 1:1. The activator is obtained by compounding stearic acid and zinc 2-ethylhexanoate with silica in a mass ratio of 2:1; the vulcanizing agent is obtained by compounding sulfur and BIPB vulcanizing agent in a mass ratio of 1:2; the accelerator is an environmentally friendly accelerator. The preparation of the composite hydrotalcite includes the following steps: (1) Mix 0.73 g anhydrous zinc acetate, 80 mL ethanol and 80 mL deionized water, add 0.22 mL titanium tetrachloride, add 0.3 g dopamine hydrochloride, add ammonium carbonate to adjust the pH to 7.9, transfer to a reaction vessel, heat to 118 °C and keep warm for 24 h, centrifuge, wash and dry to obtain polydopamine-coated Zn-Ti hydrotalcite; (2) Mix 0.5g polydopamine-coated hydrotalcite, 0.4g phosphorus oxychloride, and 50mL tetrahydrofuran, add 1g triethanolamine, sonicate at 18℃ for 1h, add 1g branched polysiloxane and 40mL tetrahydrofuran mixture, keep warm at 18℃ for 24h, wash, and dry under reduced pressure to obtain composite hydrotalcite; The preparation of the branched polysiloxane includes the following steps: 0.1 mol phenyltrimethoxysilane, 0.1 mol γ-glycidoxypropyltrimethoxysilane, 25 mL methanol, and 20 mL tetrahydrofuran were mixed and heated to 55 °C for 10 min. 30 mL of hydrochloric acid aqueous solution with pH 2 was added within 20 min, and the mixture was kept at this temperature for 4 h. The pH was adjusted to neutral, and the mixture was rotary evaporated to obtain branched polysiloxane.

[0028] Example 2: A method for preparing a high-strength, aging-resistant rubber return hose, comprising the following steps: S1: Put the base rubber into the internal mixer, then add the environmentally friendly plasticizer, composite hydrotalcite, activator and antioxidant in sequence, mix, discharge the rubber to form a rubber compound, transfer it to the open mill, press it into sheets, cool it, add vulcanizing agent and accelerator, filter it, discharge the sheets, let it stand, vulcanize it to obtain the rubber layer material. S2: Extrude the rubber material on the mold core as the inner rubber layer, and after cooling, weave or wrap the reinforcing layer on the inner rubber layer, heat treat it, and then extrude the rubber material on the reinforcing layer as the outer rubber layer to obtain a high-strength and aging-resistant rubber return hose. By weight, the raw material composition of the inner and outer rubber layers is as follows: 100 parts base rubber, 6 parts environmentally friendly plasticizer, 6 parts composite hydrotalcite, 2 parts activator, 1.5 parts antioxidant, 2 parts vulcanizing agent, and 1.5 parts accelerator. The base rubber is a compound of EPDM rubber and epoxidized silicone rubber in a mass ratio of 2:1; the epoxy content of the epoxidized silicone rubber is 10%. The reinforcing layer is obtained by winding stainless steel wire around the surface of the inner adhesive layer; The environmentally friendly plasticizer is a compound of cyclohexane dicarboxylic acid ester plasticizer and epoxidized soybean oil in a mass ratio of 1:1. The activator is obtained by compounding stearic acid and zinc 2-ethylhexanoate with silica in a mass ratio of 2:1; the vulcanizing agent is obtained by compounding sulfur and BIPB vulcanizing agent in a mass ratio of 1:2; the accelerator is an environmentally friendly accelerator. The preparation of the composite hydrotalcite includes the following steps: (1) Mix 0.73 g anhydrous zinc acetate, 80 mL ethanol and 80 mL deionized water, add 0.22 mL titanium tetrachloride, add 0.3 g dopamine hydrochloride, add ammonium carbonate to adjust the pH to 8, transfer to a reaction vessel, heat to 119 °C and keep warm for 23.5 h, centrifuge, wash and dry to obtain polydopamine-coated Zn-Ti hydrotalcite; (2) Mix 0.5g polydopamine-coated hydrotalcite, 0.4g phosphorus oxychloride, and 50mL tetrahydrofuran, add 1g triethanolamine, sonicate at 20℃ for 0.6h, add 1g branched polysiloxane and 40mL tetrahydrofuran mixture, keep warm at 20℃ for 23.5h, wash, and dry under reduced pressure to obtain composite hydrotalcite; The preparation of the branched polysiloxane includes the following steps: 0.1 mol phenyltrimethoxysilane, 0.1 mol γ-glycidoxypropyltrimethoxysilane, 25 mL methanol, and 20 mL tetrahydrofuran were mixed and heated to 55 °C for 12 min. 30 mL of hydrochloric acid aqueous solution with pH 2 was added within 20 min, and the mixture was kept at this temperature for 4.5 h. The pH was adjusted to neutral, and the mixture was rotary evaporated to obtain branched polysiloxane.

[0029] Example 3: A method for preparing a high-strength, aging-resistant rubber return hose, comprising the following steps: S1: Put the base rubber into the internal mixer, then add the environmentally friendly plasticizer, composite hydrotalcite, activator and antioxidant in sequence, mix, discharge the rubber to form a rubber compound, transfer it to the open mill, press it into sheets, cool it, add vulcanizing agent and accelerator, filter it, discharge the sheets, let it stand, vulcanize it to obtain the rubber layer material. S2: Extrude the rubber material on the mold core as the inner rubber layer, and after cooling, weave or wrap the reinforcing layer on the inner rubber layer, heat treat it, and then extrude the rubber material on the reinforcing layer as the outer rubber layer to obtain a high-strength and aging-resistant rubber return hose. By weight, the raw material composition of the inner and outer rubber layers is as follows: 100 parts base rubber, 9 parts environmentally friendly plasticizer, 8 parts composite hydrotalcite, 3 parts activator, 2 parts antioxidant, 3 parts vulcanizing agent, and 2 parts accelerator. The base rubber is a compound of EPDM rubber and epoxidized silicone rubber in a mass ratio of 2:1; the epoxy content of the epoxidized silicone rubber is 15%. The reinforcing layer is obtained by winding stainless steel wire around the surface of the inner adhesive layer; The environmentally friendly plasticizer is a compound of cyclohexane dicarboxylic acid ester plasticizer and epoxidized soybean oil in a mass ratio of 1:1. The activator is obtained by compounding stearic acid and zinc 2-ethylhexanoate with silica in a mass ratio of 2:1; the vulcanizing agent is obtained by compounding sulfur and BIPB vulcanizing agent in a mass ratio of 1:2; the accelerator is an environmentally friendly accelerator. The preparation of the composite hydrotalcite includes the following steps: (1) Mix 0.73 g anhydrous zinc acetate, 80 mL ethanol and 80 mL deionized water, add 0.22 mL titanium tetrachloride, add 0.3 g dopamine hydrochloride, add ammonium carbonate to adjust the pH to 8.1, transfer to a reaction vessel, heat to 120 °C and keep warm for 23 h, centrifuge, wash and dry to obtain polydopamine-coated Zn-Ti hydrotalcite; (2) Mix 0.5g polydopamine-coated hydrotalcite, 0.4g phosphorus oxychloride, and 50mL tetrahydrofuran, add 1g triethanolamine, sonicate at 25℃ for 0.5h, add 1g branched polysiloxane and 40mL tetrahydrofuran mixture, keep warm at 25℃ for 23h, wash, and dry under reduced pressure to obtain composite hydrotalcite; The preparation of the branched polysiloxane includes the following steps: 0.1 mol phenyltrimethoxysilane, 0.1 mol γ-glycidoxypropyltrimethoxysilane, 25 mL methanol, and 20 mL tetrahydrofuran were mixed and heated to 55 °C for 15 min. 30 mL of hydrochloric acid aqueous solution with pH 2 was added within 20 min, and the mixture was kept at this temperature for 5 h. The pH was adjusted to neutral, and the mixture was rotary evaporated to obtain branched polysiloxane.

[0030] Comparative Example 1: Example 3 served as the control group, with no branched polysiloxane added and other processes proceeding normally.

[0031] Comparative Example 2: Using Example 3 as the control group, Zn-Ti hydrotalcite coated with polydopamine was used to replace the composite hydrotalcite, while other processes were normal.

[0032] Comparative Example 3: Using Example 3 as the control group, the epoxy silicone rubber with an epoxy content of 5% (octamethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane, hexadecylheptasiloxane, and alkaline gel catalyst in a molar ratio of 95:5:0.015:0.06) replaced the epoxy silicone rubber with an epoxy content of 15%, and other processes were normal.

[0033] The preparation of epoxy silicone rubber with an epoxy content of 10% includes the following steps: Under a nitrogen atmosphere, octamethylcyclotetrasiloxane and tetramethyltetravinylcyclotetrasiloxane were mixed, heated to 80°C and held for 5 minutes. The nitrogen atmosphere was then turned off, and the mixture was evacuated to a negative pressure of -0.09 MPa and held for 2 hours. The mixture was then heated to 113°C in an oil bath, and an alkaline gel catalyst and hexadecyl heptasiloxane were added. The mixture was held for 3 hours, then heated to 163°C and purged with nitrogen for 3 hours to obtain methyl vinyl silicone rubber. The molar ratio of octamethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane, hexamethylheptasiloxane, and alkaline gel catalyst is 90:10:0.015:0.06. 4g of methyl vinyl silicone rubber and 96mL of chlorobenzene were mixed and stirred in an oil bath at 55°C for 8 hours. Then, 1.19g of m-chloroperoxybenzoic acid was added and stirred for 40 hours. Finally, 192mL of ethanol was added and the mixture was dried under vacuum to obtain epoxidized silicone rubber. The preparation of epoxy silicone rubber with an epoxy content of 15% includes the following steps: Under a nitrogen atmosphere, octamethylcyclotetrasiloxane and tetramethyltetravinylcyclotetrasiloxane were mixed, heated to 80°C and held for 5 minutes. The nitrogen atmosphere was then turned off, and the mixture was evacuated to a negative pressure of -0.09 MPa and held for 2 hours. The mixture was then heated to 113°C in an oil bath, and an alkaline gel catalyst and hexadecyl heptasiloxane were added. The mixture was held for 3 hours, then heated to 163°C and purged with nitrogen for 3 hours to obtain methyl vinyl silicone rubber. The molar ratio of octamethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane, hexamethylheptasiloxane, and alkaline gel catalyst is 85:15:0.015:0.06. 4g of methyl vinyl silicone rubber and 96mL of chlorobenzene were mixed and stirred in an oil bath at 55°C for 8 hours. Then, 1.77g of m-chloroperoxybenzoic acid was added and stirred for 40 hours. Finally, 192mL of ethanol was added and the mixture was dried under vacuum to obtain epoxidized silicone rubber.

[0034] The preparation of alkaline gel catalysts includes the following steps: Under a nitrogen atmosphere, 20 g of octamethylcyclotetrasiloxane and 0.4 g of tetramethylammonium hydroxide were mixed, kept in an oil bath at 80 °C for 5 min, the nitrogen was turned off and the vacuum was pumped to a negative pressure of -0.09 MPa and kept for 2 h, then nitrogen was introduced, and the oil bath was heated to 120 °C and kept for 4 h to obtain an alkali gel catalyst with a mass fraction of 2%, which was stored away from light.

[0035] In the examples and comparative examples, the surface temperature of the inner rubber layer after heat treatment was 95 °C.

[0036] Raw material sources (for demonstration only): Ethylene propylene diene monomer EPDM4770R: Dow; octamethylcyclotetrasiloxane (556-67-2, 99%), tetramethyltetravinylcyclotetrasiloxane (2554-06-5, 99%), stainless steel wire (AISI304, 0.5 mm), phenyltrimethoxysilane (2996-92-1, 98%), γ-glycidoxypropyltrimethoxysilane (2530-83-8, 97%), cyclohexanedicarboxylate plasticizer (diisononyl cyclohexane-1,2-dicarboxylate, 99%), sulfur S-80, vulcanizing agent BIPB (2212-81-9, 99%), epoxy soybean oil (epoxy value 6.6, viscosity 350-450, 99%): purchased commercially; zinc 2-ethylhexanoate adsorbed on silica (silica mass fraction 33%, the balance is zinc 2-ethylhexanoate): Schill + Seilacher GmbH; antioxidant BLE, environmental promoter TMTM: Karnos.

[0037] Performance testing: The inner rubber layers prepared in the examples and comparative examples were subjected to performance testing: Tensile strength: Tested according to GB / T528-2009. A sample with a thickness of 2 mm was cut into a Type 1 dumbbell-shaped specimen, and the tensile speed was 500 mm / min. The test was carried out at 25 °C; Flame retardancy: UL-94 vertical burning rating test was carried out. The sample size was 125 mm in length, 13 mm in width and 3 mm in thickness; Thermal aging: Kept at 150 °C for 720 h, and then the tensile strength of the rubber was tested again, which was characterized by the tensile strength retention rate; Resistance to ozone aging: The sample size was 100 mm in length, 10 mm in width and 2 mm in thickness. Test was carried out using Method A according to GB / T7762-2014. When kept at an ozone concentration of 100×10 -8 Kept for 72 h at 25 °C, and if there were no phenomena such as cracking and fissuring, it was qualified, otherwise it was unqualified. The test results are shown in Table 1; Table 1

[0038] This invention provides a high-strength, aging-resistant rubber return hose and its preparation method. By optimizing the formula and process, an environmentally friendly, highly flame-retardant, high-strength, and aging-resistant rubber return hose is prepared. In Table 1, / indicates that it was not tested.

[0039] Comparing Example 3 with Comparative Examples 1 and 2, this invention optimizes the flame retardancy and aging resistance of the return hose based on the requirements of flame retardancy and aging resistance. Environmentally friendly halogen-free Zn-Ti hydrotalcite is selected as both a flame retardant and an aging resistant agent. To address the issues of low flame retardancy efficiency and poor bonding with the base adhesive when added alone, dopamine is added to a Zn and Ti mixed alcohol-water solution precursor. Polydopamine-coated Zn-Ti hydrotalcite is prepared using a one-pot hydrothermal reaction. The polydopamine-coated Zn-Ti hydrotalcite is then modified sequentially with phosphorus oxychloride and branched polysiloxane. The branched polysiloxane is prepared by controlling the molar ratio of phenyltrimethoxysilane and γ-glycidyl etheroxypropyltrimethoxysilane through hydrolysis. By grafting nitrogen, phosphorus, and silicon elements, the flame retardancy of the hydrotalcite is significantly enhanced. At the same time, the introduction of multiple active sites significantly improves the bonding strength between the hydrotalcite and the base adhesive, achieving a simultaneous improvement in mechanical strength, aging resistance, and flame retardancy.

[0040] Comparing Example 3 with Comparative Example 3, EPDM rubber has advantages such as low price, ozone resistance, and excellent chemical resistance, but poor high and low temperature resistance; silicone rubber has excellent high and low temperature stability and heat resistance, but has low mechanical strength, poor oil resistance, and high cost; In this invention, EPDM rubber and epoxy silicone rubber are compounded in a mass ratio of 2:1 as the base rubber. By introducing epoxy silicone rubber with an epoxy group content of 10-15%, a complex cross-linking network is constructed to improve the processability, aging resistance, and mechanical strength of the rubber, thereby extending the service life of the return water hose.

[0041] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the present invention's specification under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A high-strength, aging-resistant rubber return hose, characterized in that, From the inside out, it consists of an inner adhesive layer, a reinforcing layer, and an outer adhesive layer; The raw material composition of the inner and outer rubber layers is: base rubber, environmentally friendly plasticizer, composite hydrotalcite, activator, antioxidant, vulcanizing agent, and accelerator; the base rubber is obtained by compounding EPDM rubber and epoxidized silicone rubber in a mass ratio of 2:

1.

2. The high-strength, aging-resistant rubber return hose according to claim 1, characterized in that, The reinforcing layer is obtained by weaving or winding one or more of basalt fiber, stainless steel wire, aluminum alloy wire, aramid wire, nylon wire, and polyester wire onto the surface of the inner adhesive layer.

3. The high-strength, aging-resistant rubber return hose according to claim 1, characterized in that, The environmentally friendly plasticizer is one or more of the following: cyclohexane dicarboxylic acid esters, benzene polycarboxylic acid esters, and epoxy environmentally friendly plasticizers; the activator is one or more of the following: zinc oxide, stearic acid, and silica adsorbing zinc 2-ethylhexanoate; the vulcanizing agent is one or more of the following: sulfur, hexamethylenediamine carbamate, and peroxide vulcanizing agents; and the accelerator is an environmentally friendly accelerator.

4. The high-strength, aging-resistant rubber return hose according to claim 1, characterized in that, By weight, the raw material composition of the inner and outer adhesive layers is as follows: 100 parts base adhesive, 4-9 parts environmentally friendly plasticizer, 5-8 parts composite hydrotalcite, 1-3 parts activator, 1-2 parts antioxidant, 1-3 parts vulcanizing agent, and 1-2 parts accelerator.

5. The high-strength, aging-resistant rubber return hose according to claim 1, characterized in that, The epoxy content in the epoxidized silicone rubber is 10-15%.

6. The high-strength, aging-resistant rubber return hose according to claim 1, characterized in that, The preparation of the composite hydrotalcite includes the following steps: (1) Mix anhydrous zinc acetate, ethanol and deionized water, add titanium tetrachloride, add dopamine hydrochloride, add carbamide to adjust the pH to 7.9-8.1, transfer to a reaction vessel, heat to 118-120℃ and keep warm for 23-24h, centrifuge, wash and dry to obtain polydopamine-coated Zn-Ti hydrotalcite. (2) Polydopamine-coated hydrotalcite, phosphorus oxychloride and tetrahydrofuran are mixed, triethanolamine is added, and the mixture is sonicated at 18-25℃ for 0.5-1h. A mixture of branched polysiloxane and tetrahydrofuran is added, and the mixture is kept at 18-25℃ for 23-24h. The mixture is washed and dried under reduced pressure to obtain composite hydrotalcite.

7. A high-strength, aging-resistant rubber return hose according to claim 6, characterized in that, The mass ratio of polydopamine-coated hydrotalcite, phosphorus oxychloride, and branched polysiloxane is 0.5:0.4:

1.

8. A high-strength, aging-resistant rubber return hose according to claim 6, characterized in that, The preparation of the branched polysiloxane includes the following steps: Phenyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, methanol, and tetrahydrofuran were mixed, heated to 55°C and kept at that temperature for 10-15 minutes. Hydrochloric acid aqueous solution was added, and the mixture was kept at that temperature for another 4-5 hours. The pH was adjusted to neutral, and the mixture was rotary evaporated to obtain branched polysiloxane.

9. A high-strength, aging-resistant rubber return hose according to claim 8, characterized in that, The molar ratio of phenyltrimethoxysilane to γ-glycidoxypropyltrimethoxysilane is 1:

1.

10. A method for preparing a high-strength, aging-resistant rubber return hose according to any one of claims 1-9, characterized in that, Includes the following steps: S1: Put the base rubber into the internal mixer, then add the environmentally friendly plasticizer, composite hydrotalcite, activator and antioxidant in sequence, mix, discharge the rubber to form a rubber compound, transfer it to the open mill, press it into sheets, cool it, add vulcanizing agent and accelerator, filter it, discharge the sheets, let it stand, vulcanize it to obtain the rubber layer material. S2: Extruding rubber material onto the mold core as the inner rubber layer, cooling and then weaving or winding the reinforcing layer onto the inner rubber layer, heat treating, and then extruding rubber material onto the reinforcing layer as the outer rubber layer, resulting in a high-strength, aging-resistant rubber return hose.

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