Aging-resistant automobile rubber tube and preparation method thereof

Abstract

The application relates to the field of automobile rubber pipes and provides a preparation method of an anti-aging automobile rubber pipe, which comprises the following steps: S1, first, halloysite nanotubes are dried, a preservative solution is injected under a reduced pressure, and then halloysite loading is obtained through separation and solvent evaporation; S2, the halloysite loading is washed at low temperature, dispersed in an organic solvent, then a blocking agent is added, and reaction is carried out under the protection of an inert gas, and then the blocked halloysite loading is obtained through separation and drying; S3, the blocked halloysite loading is mixed with ethylene-acrylate rubber, a vulcanizing agent and an additive to obtain rubber material; and S4, the rubber material is extruded into a pipe blank, and then vulcanization is carried out to obtain the automobile rubber pipe. The method realizes slow release and uniform dispersion of the preservative by loading the preservative into the halloysite nanotubes under a reduced pressure and combining end sealing treatment of the preservative with a blocking agent, improves the heat aging resistance of the rubber pipe, and prolongs the service life of the rubber pipe.

Description

Technical Field

[0001] This invention relates to the field of automotive rubber hose technology, and more specifically, to an aging-resistant automotive rubber hose and its preparation method. Background Technology

[0002] Automotive rubber hoses, such as coolant hoses and turbocharger hoses, are prone to aging, hardening, and cracking due to long-term exposure to high temperatures, ozone, and oil-water environments. Therefore, their aging resistance is an important indicator for these products.

[0003] Currently, the mainstream technology involves using ethylene-acrylate rubber (AEM) and fluororubber (FKM) in combination with polymeric antioxidants to achieve relatively good aging resistance. Specifically, using AEM as the main component, followed by oxide vulcanization and the addition of grafted polymeric antioxidants can significantly delay thermo-oxidative aging. However, polymeric antioxidants often have large molecular weights, making them difficult to disperse in rubber, prone to local agglomeration, and also leading to a decrease in the hardness of the rubber compound, affecting the pipe's resistance to compression flattening.

[0004] In addition, to reduce costs, existing technologies also use ethylene propylene diene monomer (EPDM) rubber as the main material, and then perform deep modification to improve aging resistance. For example, patent CN108997660A discloses an aging-resistant and swelling-resistant rubber hose for automobiles and its preparation method. It improves aging resistance and other properties by adding biomass ceramics and composite plasticizers. However, its production process is complex, especially the preparation process of its biomass ceramics, which is extremely complex and requires three-stage high-temperature calcination under nitrogen protection. It has high energy consumption and demanding equipment requirements. Summary of the Invention

[0005] To address the aforementioned shortcomings in existing technologies, the core objective of this invention is to solve the technical problems of easy migration and loss of antioxidants and uneven dispersion in existing automotive rubber hoses, as well as the complexity and high energy consumption of existing anti-aging processes. Specifically, the antioxidant solution is first injected into halloysite nanotubes under negative pressure, and then the tube openings are sealed with a silane coupling agent to form a plugging halloysite loading material. Finally, it is mixed and vulcanized with ethylene-acrylate rubber to achieve slow release and uniform dispersion of the antioxidant.

[0006] This invention is achieved through the following technical solution: The first objective of this invention is to provide a method for preparing an aging-resistant automotive rubber hose, comprising the following steps: S1. First, the halloysite nanotubes are dried, and then an antioxidant solution is injected under reduced pressure. After separation and solvent evaporation, the halloysite loaded material is obtained. S2. The halloysite loading is washed at low temperature, then dispersed in an organic solvent, then a blocking agent is added, and reacted under inert gas protection. After separation and drying, the blocking halloysite loading is obtained. S3. The blocking halloysite loading material is mixed with ethylene-acrylate rubber, vulcanizing agent and additives to obtain rubber compound; S4. The rubber compound is extruded into a tube blank, and then vulcanized to obtain an automotive rubber tube.

[0007] In this invention, halloysite nanotubes are first vacuum dried, then an antioxidant solution is introduced, followed by separation and solvent evaporation to load the antioxidant into the halloysite nanotubes. Further low-temperature washing is then performed to remove the antioxidant adhering to the outer wall of the tubes. More importantly, an end-sealing reaction is carried out using a sealing agent under nitrogen or argon protection to obtain a blocked halloysite loading. Finally, the blocked halloysite loading is mixed with ethylene-acrylate rubber, a vulcanizing agent, and additives, and then extruded and vulcanized to obtain an automotive rubber hose.

[0008] Furthermore, in step S1, the antioxidant is preferably antioxidant 1076 or antioxidant 1010. Both are hindered phenolic antioxidants, which have the characteristics of high temperature resistance and low volatility. More importantly, because their molecular size is much smaller than the inner diameter of halloysite nanotubes and they have good solubility in anhydrous ethanol, they are easy to load into halloysite nanotubes.

[0009] Furthermore, the pressure of the pressure reduction condition is 0.02~0.08 MPa, i.e., absolute pressure, in order to facilitate the extraction of the solvent used in the antioxidant solution.

[0010] Further, in step S2, the sealing agent is either bis-(3-triethoxysilylpropyl)-disulfide or bis-(3-trimethoxysilylpropyl)-disulfide. Both sealing agents are specifically preferred silane coupling agents, with one end bearing an ethoxy or methoxy group, enabling them to react with the silanol groups at the halloysite orifice, and the other end bearing a disulfide bond to facilitate subsequent participation in rubber vulcanization.

[0011] Furthermore, the organic solvent is an aqueous ethanol solution; the volume fraction of the aqueous ethanol solution is 93%~97%; wherein, an aqueous ethanol solution with a volume fraction of 95% is selected to provide the trace amount of water required for the reaction between the sealing agent and the silanol groups on the halloysite surface, thereby promoting the hydrolysis of methoxy or ethoxy groups to generate silanol groups, which preferentially adsorb onto the high-energy silanol sites at the halloysite orifice. After heating, the silanol groups condense with the silanol groups at the orifice to form Si-O-Si covalent bonds, and cross-link with each other to form a network that blocks the orifice, ultimately constituting a barrier layer that allows the antioxidant to diffuse slowly; while the disulfide bonds in the middle of the sealing agent participate in cross-linking during subsequent rubber vulcanization, confining the end-sealed portion in the rubber matrix to prevent detachment.

[0012] Further, in step S2, the low-temperature washing is performed by rinsing with anhydrous ethanol or petroleum ether at 5~10℃, with each rinsing amount being 3 times the mass of the halloysite loading material, and rinsing 3 times. After rinsing, the material is immediately filtered to avoid excessive rinsing time or excessive solvent volume, which could lead to the loss of the antioxidant.

[0013] Furthermore, the reaction parameters include: a reaction temperature of 60~100℃ and a reaction time of 4~8h. Even further, after the reaction is complete, the reaction solution is cooled and centrifuged, the precipitate is washed twice with anhydrous ethanol, and then dried under vacuum at 60℃ for 8h.

[0014] Further, in step S3, the vulcanizing agent can be dicumyl peroxide, which is commonly used in the art; the additives include stearic acid, carbon black, and a crosslinking agent. Even further, the crosslinking agent is preferably triallyl isocyanurate or trimethylolpropane trimethacrylate, both of which are multifunctional monomers that form additional crosslinking bonds during peroxide vulcanization, thereby improving heat resistance and compression set resistance.

[0015] Further, based on 100 parts by weight of the ethylene-acrylate rubber, the amounts of the remaining raw materials are as follows: 10-30 parts of the blocking halloysite loading material, 2-5 parts of the vulcanizing agent, 1-4 parts of the crosslinking agent, 1-2 parts of stearic acid, and 40-60 parts of carbon black.

[0016] Further, in step S3, the mixing parameters include: mixing temperature of 45~60℃, mixing time of 10~20min; after mixing, the glue is discharged, the discharge temperature is 35~55℃, and the mixture is repeatedly rolled and passed through 3~5 times.

[0017] Furthermore, in step S4, the vulcanization parameters include: vulcanization temperature of 170~200℃ and vulcanization time of 15~40min.

[0018] The second objective of this invention is to provide an aging-resistant automotive rubber hose prepared by the above-described preparation method, wherein the raw materials, by weight, include 100 parts of ethylene-acrylate rubber, 10-30 parts of a sealing halloysite loading material, and 42-66 parts of the additives. Furthermore, the additives include 2-5 parts of the vulcanizing agent, 1-4 parts of the crosslinking agent, 1-2 parts of stearic acid, and 40-60 parts of carbon black.

[0019] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects: (1) This invention achieves the slow release of antioxidant by loading anti-aging agent into halloysite nanotubes under negative pressure and combining it with end-sealing agent, which effectively improves the heat aging resistance of rubber tubes and extends the service life of rubber tubes.

[0020] (2) The present invention achieves uniform dispersion of antioxidant in rubber matrix by loading antioxidant on halloysite nanotubes and end-sealing it, thus avoiding the problem of antioxidant agglomeration leading to a decrease in hardness.

[0021] (3) The present invention adopts a mild solution reaction and conventional mixing process, without the need for complex high-temperature calcination and multi-stage heat treatment, which reduces production energy consumption and equipment threshold, and is easier to industrialize. Detailed Implementation

[0022] Example 1 This embodiment provides a method for preparing an aging-resistant automotive rubber hose, including the following steps: S1, Preparation of halloysite-supported materials Take 100 g of purified halloysite nanotubes with an aspect ratio of 17~33, place them in a vacuum drying oven, dry them at 100℃ and 0.02 MPa absolute pressure for 12 h, and cool them to room temperature for later use.

[0023] Antioxidant 1076 (i.e., β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester, CAS registration number 2082-79-3) was dissolved in anhydrous ethanol to prepare an antioxidant solution with a mass fraction of 15%.

[0024] The dried halloysite nanotubes were placed in a reaction flask with a vacuum interface, and the vacuum was drawn to an absolute pressure of 0.04 MPa. After maintaining the vacuum for 30 min, the antioxidant solution was slowly injected through a separatory funnel at a liquid-to-solid ratio of 5:1 mL / g. The vacuum valve was then closed, and the mixture was soaked at normal pressure for 5 h.

[0025] After soaking, the solid was separated by vacuum filtration. The filter cake was placed in a fume hood at room temperature for 12 h to evaporate the solvent, and then transferred to a vacuum drying oven at 50 °C for 4 h to obtain halloysite loading.

[0026] S2. Preparation of plugging halloysite loadings Take 100 g of halloysite loaded in step S1 and place it in a Buchner funnel. Wash it with anhydrous ethanol that has been pre-cooled to 8°C. Each wash should use 3 times the mass of halloysite loaded. After washing evenly, filter immediately. Repeat the washing process 3 times.

[0027] The washed solids were dispersed in a 95% ethanol aqueous solution, which was prepared by mixing 95 mL of anhydrous ethanol and 5 mL of deionized water and used immediately; then, the solids were ultrasonically dispersed for 15 min at a solid-liquid ratio of 1:10 (g / mL).

[0028] Under nitrogen protection, bis-(3-triethoxysilylpropyl)-disulfide (CAS registration number 56706-10-6) was added at 12% of the halloysite loading mass, and the mixture was heated to 80°C and refluxed with stirring for 6 h.

[0029] After the reaction was completed, the mixture was cooled to room temperature, centrifuged at 8000 rpm for 10 min, the supernatant was discarded, and the precipitate was washed twice with anhydrous ethanol, each time using 5 times the mass of the solid. The precipitate was then dried in a vacuum drying oven at 60℃ for 8 h to obtain the plugging halloysite loading.

[0030] S3. Preparation of compounded rubber. Weigh the following raw materials in the indicated weight proportions: 100 parts ethylene-acrylate rubber, 20 parts of the blocking halloysite loading material obtained in step S2, 3.5 parts dicumyl peroxide, 2 parts triallyl isocyanurate, 1.5 parts stearic acid, and 50 parts carbon black N330.

[0031] Ethylene-acrylate rubber was put into a mixer and plasticized at 45°C for 1 min; stearic acid, carbon black and blocking halloysite loading were added and mixed for 5 min; dicumyl peroxide and triallyl isocyanurate were added and mixed for a total time of 15 min, during which the mixing temperature was controlled not to exceed 60°C.

[0032] After mixing, the rubber is discharged, and the discharge temperature is controlled at 45℃. The rubber compound is then transferred to the open mill, and the roller temperature is controlled at 50℃. The roller gap is adjusted to 0.5 mm, and the rubber is passed through the mill 4 times. After each pass, the rubber is folded and rolled up. Finally, the roller gap is increased to produce the sheet, thus obtaining the rubber compound.

[0033] S4, Extrusion Molding and Vulcanization The rubber compound obtained in step S3 is fed into a screw extruder. The extruder barrel temperature is set as follows: 50°C for the rear section, 55°C for the middle section, 60°C for the front section, and 65°C for the die head. The extrusion is formed into a tube blank with an inner diameter of 12 mm and a wall thickness of 2 mm.

[0034] The tube blank is placed in a flat vulcanizing machine and vulcanized at 180℃ and 15 MPa pressure for 25 minutes. After vulcanization, it is slowly cooled to room temperature to obtain the aging-resistant automotive rubber hose.

[0035] Example 2 The difference between this embodiment and Embodiment 1 is that in step S1, antioxidant 1010 is used as the antioxidant.

[0036] Example 3 The difference between this embodiment and Example 1 is that in step S2, the sealing agent is bis-(3-trimethoxysilylpropyl)-disulfide, the organic solvent is an aqueous ethanol solution with a volume fraction of 93%, the reaction temperature is controlled at 60°C, and the reaction time is extended to 8 h.

[0037] Example 4 The difference between this embodiment and Embodiment 1 is that, in step S3, by weight: 100 parts of ethylene-acrylate rubber, 10 parts of blocking halloysite loading material, 2 parts of dicumyl peroxide, 1 part of trimethylolpropane trimethacrylate as the crosslinking agent, 1 part of stearic acid, and 40 parts of carbon black N550.

[0038] Example 5 The difference between this embodiment and Embodiment 1 is that, in step S3, by weight: 100 parts of ethylene-acrylate rubber, 30 parts of blocking halloysite loading material, 5 parts of dicumyl peroxide, 4 parts of triallyl isocyanurate as the crosslinking agent, 2 parts of stearic acid, and 60 parts of carbon black N330.

[0039] Comparative Example 1 The difference between this comparative example and Example 1 is that no antioxidant solution is added in step S1.

[0040] Comparative Example 2 The difference between this comparative example and Example 1 is that in step S1, an antioxidant is used directly, and anhydrous ethanol is not used to prepare the solvent.

[0041] Comparative Example 3 The difference between this comparative example and Example 1 is that in step S2, no blocking agent is used and no end-sealing reaction is performed.

[0042] Comparative Example 4 The difference between this comparative example and Example 1 is that: no halloysite nanotubes are added in steps S1 and S2, and no blocking halloysite loading is prepared; in step S3, antioxidant 1076 is directly mixed with ethylene-acrylate rubber, dicumyl peroxide, triallyl isocyanurate, stearic acid, and carbon black N330.

[0043] Test case This experiment tested the rubber tubing samples prepared in Examples 1-5 and Comparative Examples 1-4 with the following performance tests. The average value of three samples was taken for each test. The specific test methods are as follows: (1) Hot air aging performance: Following GB / T3512-2014, the material was aged in a hot air aging chamber at 120℃ for 72 hours. Tensile strength and elongation at break were tested before and after aging, and retention rate was calculated. Retention rate (%) = (value after aging / value before aging) × 100%; among which, tensile strength and elongation at break were determined according to GB / T528-2009, using dumbbell-shaped specimens, and the tensile speed was 500 mm / min.

[0044] (2) Antioxidant migration and precipitation rate: The rubber tube sample was cut into small segments of about 10 mm in length, and 10 g was weighed and placed in 100 mL of n-hexane, and soaked at 40 °C for 72 h. Then, the concentration of antioxidant in the soaking solution was determined by ultraviolet spectrophotometry, and the percentage of the precipitated antioxidant mass to the total antioxidant mass in the rubber tube was calculated, i.e.: Extraction rate = (mass of antioxidant extracted from the soaking solution ÷ total mass of antioxidant in the rubber tube) × 100%.

[0045] (3) Hardness: The Shore hardness was determined according to GB / T 39693.4-2025, and the average value of 3 points was taken. The test results are shown in Table 1 below: Table 1 Test Results of Various Performance Indicators

[0046] Analysis of the data in Table 1 shows that the tensile strength retention rate and elongation at break retention rate of all embodiments were 85-90% and 81-86%, respectively, both significantly higher than the comparative examples. However, the 72-hour antioxidant precipitation rate was 15-22%, far lower than that of comparative examples 2-4. This indicates that the present invention achieves the slow release of antioxidants through the synergistic effect of halloysite loading and end-sealing treatment, significantly improving aging resistance and the service life of the rubber hose. Furthermore, the hardness of the samples in each embodiment after adding antioxidants was in the range of 68-75 Shore A, meaning that while maintaining acceptable hardness, the aging resistance was significantly improved while still meeting the requirements for rubber hose use. Furthermore, the 72-hour precipitation rate of all embodiments was 15%-22%, while that of comparative examples 2-4 was as high as 52%-75%, further demonstrating that halloysite lumen loading and end-sealing layers can significantly inhibit the migration and loss of antioxidants during mixing, vulcanization, and use.

Claims

1. A process for the preparation of an anti-aging automotive rubber tube, characterized by, Includes the following steps: S1. First, the halloysite nanotubes are dried, and then an antioxidant solution is injected under reduced pressure. After separation and solvent evaporation, halloysite loading is obtained. S2. The halloysite loading is washed at low temperature, then dispersed in an organic solvent, then a blocking agent is added, and reacted under inert gas protection. After separation and drying, the blocking halloysite loading is obtained. S3. The blocking halloysite loading material is mixed with ethylene-acrylate rubber, vulcanizing agent and additives to obtain rubber compound; S4. The rubber compound is extruded into a tube blank, and then vulcanized to obtain an automotive rubber tube.

2. The method for preparing the aging-resistant automotive rubber hose according to claim 1, characterized in that, In step S1, the antioxidant is antioxidant 1076 or antioxidant 1010; And / or, the pressure of the pressure reduction condition is 0.02~0.08 MPa.

3. The method of claim 1, wherein the antioxidant is added in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the rubber composition. In step S2, the sealing agent is bis-(3-triethoxysilylpropyl)-disulfide or bis-(3-trimethoxysilylpropyl)-disulfide.

4. The method of claim 1, wherein the antioxidant is added in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the rubber composition. In step S2, the organic solvent is an aqueous ethanol solution; the volume fraction of the aqueous ethanol solution is 93%~97%.

5. The method for preparing the aging-resistant automotive rubber hose according to claim 1, characterized in that, In step S2, the low-temperature washing is performed by rinsing with anhydrous ethanol or petroleum ether at 5~10℃, with each rinsing amount being 3 times the mass of the halloysite loading material, and rinsing is performed 3 times. After rinsing, the material is immediately filtered.

6. The method for preparing the aging-resistant automotive rubber hose according to claim 1, characterized in that, The reaction parameters include: a reaction temperature of 60~100℃ and a reaction time of 4~8h.

7. The method for preparing the aging-resistant automotive rubber hose according to claim 1, characterized in that, In step S3, the additives include stearic acid, carbon black, and crosslinking agent.

8. The method for preparing the aging-resistant automotive rubber hose according to claim 1, characterized in that, In step S3, the mixing parameters include: mixing temperature of 45~60℃, mixing time of 10~20min; after mixing, the glue is discharged at a temperature of 35~55℃, and the mixture is repeatedly rolled and passed through a thin tube 3~5 times.

9. The method for preparing the aging-resistant automotive rubber hose according to claim 1, characterized in that, In step S4, the vulcanization parameters include: vulcanization temperature of 170~200℃ and vulcanization time of 15~40min.

10. An aging-resistant automotive rubber hose prepared by the method according to any one of claims 1 to 9, characterized in that: The raw materials, by weight, include 100 parts of ethylene-acrylate rubber, 10-30 parts of plugging halloysite loading material, 2-5 parts of the vulcanizing agent, and 42-66 parts of the additives.

Images