Tire anti-aging coating and preparation method thereof

Abstract

The invention relates to the technical field of anti-aging coatings, in particular to a tire anti-aging coating and a preparation method thereof. According to the invention, the problems of poor adhesive force and poor aging resistance of a tire coating are solved; through the synergistic effect of the epoxy polysiloxane and the waterborne polyurethane-acrylate copolymer emulsion, multi-stage bonding of a tire / coating interface is realized, and the added fluorosilicone block copolymer can further form a protective barrier; by preparing modified nano silicon dioxide, active groups grafted by a silane coupling agent on the surface capture free radicals, and an oxidation chain reaction is blocked; n, N '-diphenyl-p-phenylenediamine released by the polyurea microcapsules can remove free radicals generated by oxidation in the coating, and the N, N'-diphenyl-p-phenylenediamine is matched with the compound light stabilizer to form a dynamic defense chain; a flexible long chain of the polycaprolactone polyol inhibits crack propagation through free volume filling, and the four components synergistically improve ultraviolet resistance, ozone resistance and oxidation corrosion resistance; and through a staged low temperature-medium temperature-high temperature gradient curing strategy, the adhesive force of the coating is improved.

Description

Technical Field

[0001] The invention relates to the technical field of anti-aging coatings, in particular to a tire anti-aging coating and a preparation method thereof. Background Art

[0002] Tires are essential components of vehicles, and their performance directly impacts driving safety and service life. Over long-term use, tires are subject to a variety of environmental factors, including ozone, ultraviolet rays, and oxidation. This can lead to rubber aging, cracking, hardening, and loss of elasticity, severely impacting tire performance and safety. To address the issue of tire aging, existing technologies often employ methods of coating the tire surface. However, current anti-aging coatings present numerous technical problems. On the one hand, the coating lacks sufficient adhesion to the tire rubber substrate. Under the influence of frequent tire deformation, friction, and the external environment, the coating is prone to peeling and flaking, significantly reducing its anti-aging effect. On the other hand, the coating's aging resistance needs to be improved. Ingredients such as anti-aging agents in traditional coatings are depleted in a short period of time, making them unable to effectively resist ultraviolet rays and oxidation over the long term. Furthermore, the coating is susceptible to wear and tear during tire rolling, making it difficult to meet the protection requirements for long-term tire use. Therefore, developing a tire anti-aging coating with excellent adhesion and aging resistance is of great practical significance.

[0003] Therefore, a tire anti-aging coating and a preparation method thereof are proposed. Summary of the Invention

[0004] The purpose of the present invention is to provide a tire anti-aging coating and a preparation method thereof. Through the synergistic effect of epoxy polysiloxane and water-based polyurethane-acrylate copolymer emulsion, multi-level bonding is achieved at the tire / coating interface, and the fluorosilicone block copolymer can further form a protective barrier; by preparing modified nano-silica, the active groups grafted by the silane coupling agent on the surface capture free radicals and block the oxidation chain reaction; N,N'-diphenyl-p-phenylenediamine released by polyurea microcapsules can remove free radicals generated by oxidation inside the coating, and cooperate with the compounded light stabilizer to form a dynamic defense chain; the flexible long chain of polycaprolactone polyol inhibits crack propagation by filling the free volume, and the four synergistically enhance the resistance to ultraviolet, ozone and oxidative corrosion; and the coating adhesion is improved through a staged low-temperature-medium-temperature-high-temperature gradient curing strategy.

[0005] To achieve the above object, the present invention provides the following technical solutions: It should be noted that all parts in the present invention are parts by mass.

[0006] On one hand, the present invention provides a method for preparing a tire anti-aging coating. The preparation method is as follows: 40-60 parts of an aqueous polyurethane-acrylate copolymer emulsion, 5-10 parts of an epoxy polysiloxane, 6 parts of a crosslinking agent, and 12-18 parts of a polycaprolactone polyol are added to a reactor, and the mixture is stirred and mixed uniformly at 40° C., 3 / 4 of a light stabilizer and 2 parts of an antioxidant are added for free radical emulsion copolymerization, and the mixture is reacted at 80° C. for 3 hours; the temperature is lowered to 40° C., and 5 parts of an ethanol dispersion of polyurea microcapsules and 1 / 4 of a light stabilizer, an isopropanol suspension of modified nano-silica, and 6 parts of a fluorosilicone block copolymer are added in sequence, and the mixture is stirred for 75 minutes; 3 parts of a film-forming aid and 1 part of a defoaming agent are added, and the mixture is stirred and mixed at room temperature for 20 minutes to obtain a uniform coating emulsion; the coating emulsion is sprayed on a tire surface for gradient curing to obtain a tire anti-aging coating; the wet film thickness is 15-25 μm; Polyurea microcapsules are made from N,N'-diphenyl-p-phenylenediamine, isophorone diisocyanate, and polyvinyl alcohol; Modified nano-silica is obtained by modifying nano-silica with a silane coupling agent; The fluorosilicone block copolymer is prepared from perfluoroalkylethyl acrylate, polydimethylsiloxane and azobisisobutyronitrile.

[0007] Preferably, the antioxidant is prepared by compounding pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and dilauryl thiodipropionate in a mass ratio of 3:2.

[0008] Preferably, the preparation method of polyurea microcapsules is as follows: 5 parts of polyvinyl alcohol are added to 300 parts of deionized water, the temperature is raised to 80°C, and the mixture is stirred at 400 rpm for 1.5 hours to obtain an aqueous phase; at room temperature, 20 parts of isophorone diisocyanate are slowly added to 100 parts of toluene, and the mixture is stirred at 300 rpm for 30 minutes to obtain an oil phase; the oil phase is dripped into the aqueous phase while stirring at 1800 rpm for 25-35 minutes to form an emulsion with an oil phase droplet size of 0.5-3 μm; 10 parts of N, N'-diphenyl-p-phenylenediamine are added to 60 parts of ethanol, stirred at 50°C and 300 rpm for 40 minutes to obtain an N,N'-diphenyl-p-phenylenediamine solution; the N,N'-diphenyl-p-phenylenediamine solution was dropped into the emulsion at a rate of 5 mL / min, and stirring was maintained at 1200 rpm during the dropwise addition; after the dropwise addition, the temperature was raised to 50°C and stirring was continued for 2-3 hours; the reaction product was centrifuged at 5000 rpm for 10 minutes, the supernatant was removed, and the obtained precipitate was washed three times with deionized water, and then vacuum dried at 60°C for 12 hours to obtain polyurea microcapsules with a particle size of 0.5-2 μm.

[0009] Preferably, the modified nano-silica preparation method is as follows: 10 parts of deionized water and 0.5 parts of glacial acetic acid are added to 100 parts of anhydrous ethanol, stirred evenly, and the pH of the solution is adjusted; 10 parts of nano-silica are added, ultrasonically dispersed at 300W for 30 minutes, 2 parts of silane coupling agent KH560 are added, and stirred at 60°C for 3-5 hours; after the reaction is completed, the product is centrifuged at 8000 rpm for 15 minutes, the supernatant is removed, and the product is washed with anhydrous ethanol three times, and then vacuum dried to obtain the modified nano-silica.

[0010] Preferably, the preparation method of the fluorosilicone block copolymer is as follows: 15 parts of perfluoroalkylethyl acrylate, 8-12 parts of polydimethylsiloxane and 0.3 parts of azobisisobutyronitrile are added to 100 parts of toluene, and stirred at 40°C for 30 minutes to form a reaction solution; the reaction solution is transferred to a three-necked flask, nitrogen is introduced to exclude air, and polymerization is carried out at 80°C for 5-7 hours. After the reaction is completed, the reaction product is poured into methanol for precipitation, centrifuged at 6000 rpm for 10 minutes, the precipitate is collected, washed with methanol 3 times, and then vacuum dried at 60°C for 12 hours to obtain a fluorosilicone block copolymer.

[0011] Preferably, the light stabilizer is prepared by compounding bis(2,2,6,6-tetramethylpiperidinyl) sebacate and ultraviolet absorber UV-329 in a mass ratio of 2:1.

[0012] Preferably, the gradient curing is to pre-cure with hot air at 60°C for 7-15 minutes to form a preliminary cross-linking network; then heat cure at 90°C for 18-28 minutes to activate the epoxy groups and deep cross-link with the resin matrix; and finally infrared radiation cure at 110-125°C for 5 minutes to strengthen the chemical bonding between the silicone and rubber interface.

[0013] Another aspect of the present invention provides an anti-aging coating for tires. The raw materials used in the production of the anti-aging coating include aqueous polyurethane-acrylate copolymer emulsion, epoxy polysiloxane, a crosslinking agent, polycaprolactone polyol, a light stabilizer, an antioxidant, polyurea microcapsules and modified nano-silica; the anti-aging coating is prepared by any of the above preparation methods.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention achieves multi-stage bonding at the tire / coating interface through the synergistic effect of epoxy polysiloxane and an aqueous polyurethane-acrylate copolymer emulsion: the siloxane groups in the polysiloxane condense with the hydroxyl groups on the rubber surface to form -Si-O-Si- covalent bonds, enhancing substrate wettability; the epoxy groups undergo a ring-opening reaction with the carboxyl groups of the resin matrix, forming a dense cross-linked network. Simultaneously, the fluorocarbon segments in the fluorosilicone block copolymer are targeted and enriched on the coating surface to form a hydrophobic barrier, while the siloxane segments are embedded in the rubber micropores to form a dynamic stress buffer. This design significantly improves the adhesion stability of the coating and prevents peeling failure through the triple mechanism of epoxy-carboxyl bonding, siloxane penetration, and fluorocarbon barrier.

[0015] 2. The light-oxygen synergistic barrier system of the present invention with modified nano-silica as the skeleton realizes multi-level protection: the nanoparticles are evenly dispersed to form a physical maze barrier, extending the diffusion path of oxygen molecules; the active groups grafted by the silane coupling agent on the surface capture free radicals and block the oxidation chain reaction; the N,N'-diphenyl-p-phenylenediamine released by the polyurea microcapsules can scavenge the free radicals generated by oxidation inside the coating, and cooperates with the compound light stabilizer to form a dynamic defense chain - the ultraviolet absorber converts high-energy photons into thermal energy, and the hindered amine substances quench excited oxygen; the flexible long chain of the polycaprolactone polyol fills the free volume to inhibit the expansion of microcracks in the coating, and finally forms a gradient protection network, which synergistically improves the resistance to ultraviolet and thermal oxidative aging.

[0016] 3. The present invention uses a phased low-temperature-medium-temperature-high-temperature gradient curing strategy to simultaneously regulate the coating microstructure and interfacial reaction: 60°C pre-curing stabilizes the self-assembly of the emulsion particles to form a continuous elastic film; 90°C activates the epoxy crosslinker to deeply crosslink with the resin matrix, enhancing the density of the three-dimensional network; 120°C infrared radiation promotes dehydration condensation between the siloxane groups and the rubber substrate, simultaneously driving the migration of the fluorosilicone block copolymer to the interface. This process avoids the microporous defects caused by high-temperature rapid curing, ensuring that the nano-silica is oriented and arranged into a dense stacking structure; at the same time, the thermoplastic properties of the polycaprolactone polyol give the coating the ability to slide under stress, dissipating mechanical energy through elastic deformation, reducing the risk of brittle peeling of the coating under dynamic conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a graph showing the aging resistance test results of Example 2, Examples 5-6, and Comparative Examples 4-9 of the present invention. DETAILED DESCRIPTION

[0018] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0019] Please refer to Figure 1 The present application provides a tire anti-aging coating and a preparation method thereof, and the technical solutions are as follows: The substance information involved in the present application is as follows: Poly (caprolactone) polyol CAS: 27102-04-1; Tetra [beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid] pentaerythritol ester CAS: 6683-19-8; Dilauryl thiodipropionate CAS: 123-28-4; N, N'-diphenyl-p-phenylenediamine CAS: 74-31-7; Polyvinyl alcohol CAS: 9002-89-5; Isophorone diisocyanate CAS: 4098-71-9; Silane coupling agent KH560 CAS: 2530-83-8; Perfluoroalkylethyl acrylate CAS: 65605-70-1; Polydimethylsiloxane CAS: 9016-00-6; Azobisisobutyronitrile CAS: 78-67-1; Propylene glycol phenyl ether CAS: 6180-61-6; Epoxy silicone oil purchased from Shandong Dayi Chemical Co., Ltd.; Hydrogenated bisphenol A type epoxy resin purchased from Tiancheng Chemical (Jiangsu) Co., Ltd.; Nano-silicon dioxide purchased from Shanghai Yinan Chemical Technology Co., Ltd.; Bis (2, 2, 6, 6-tetramethylpiperidyl) sebacate purchased from Yantai Geryin Chemical Co., Ltd.; Ultraviolet absorber UV-329 purchased from Shandong Yinghuan Information Technology Service Co., Ltd.; Defoaming agent BYK-024 purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.; Water-based polyurethane-acrylate copolymer emulsion is prepared according to the method in “Preparation and Performance Research of Water-based Polyurethane-acrylate Copolymer Emulsion”.

[0020] Example 1 40 parts of waterborne polyurethane-acrylate copolymer emulsion, 5 parts of epoxy polysiloxane (epoxy silicone oil), 6 parts of crosslinking agent hydrogenated bisphenol A epoxy resin, and 12 parts of polycaprolactone polyol were added to the reactor and stirred at 40°C for 40 minutes. 3 / 4 parts by weight of light stabilizer and 2 parts of antioxidant were added for free radical emulsion copolymerization. The reaction was carried out at 80°C for 3 hours. The temperature was lowered to 40°C, and 5 parts of polyurea microcapsules and 1 / 4 part by weight of ethanol dispersion of light stabilizer, isopropanol suspension of modified nano-silica (8 parts of modified nano-silica dispersed in 40 parts of isopropanol solution) and 6 parts of fluorosilicone block copolymer were added in sequence. The stirring speed was 500 rpm for 75 minutes. 3 parts of film-forming aid propylene glycol phenyl ether and 1 part of defoamer BYK-024 were added and stirred at room temperature for 20 minutes at a stirring speed of 200 rpm. m, to obtain a uniform coating emulsion; the coating emulsion is sprayed on the tire surface for gradient curing: first, pre-curing with hot air at 60°C for 7 minutes to initially evaporate the solvent and form a preliminary cross-linking network; then, heat curing at 90°C for 18 minutes to activate the epoxy groups and deeply cross-link with the resin matrix to form a covalent cross-linking structure; finally, infrared radiation curing at 110°C for 5 minutes strengthens the chemical bonding at the interface between the siloxane and the rubber, while promoting the diffusion of the fluorosilicone material into the interface layer, thereby obtaining a tire anti-aging coating; the light stabilizer is prepared by compounding bis(2,2,6,6-tetramethylpiperidinyl)sebacate and benzotriazole UV absorber UV-329 in a mass ratio of 2:1, and the ethanol dispersion of the light stabilizer is prepared by dispersing 4 parts of the light stabilizer in 20 parts of ethanol solution; the antioxidant is prepared by compounding pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and dilauryl thiodipropionate in a mass ratio of 3:2.

[0021] The preparation method of polyurea microcapsules is as follows: 5 parts of polyvinyl alcohol are added to 300 parts of deionized water, heated to 80°C, and stirred at 400 rpm for 1.5 hours to obtain an aqueous phase; at room temperature, 20 parts of isophorone diisocyanate are slowly added to 100 parts of toluene, and stirred at 300 rpm for 30 minutes to obtain an oil phase; the oil phase is dropped into the aqueous phase while stirring at 1800 rpm, and the dropping time is controlled within 25-35 minutes to form an emulsion; 10 parts of N, N'-diphenyl-p-phenylenediamine are added to 60 parts of ethanol, heated to 50°C, and stirred at 400 rpm for 1.5 hours to obtain an oil phase; The mixture was stirred at 300 rpm for 40 minutes to obtain an N,N'-diphenyl-p-phenylenediamine solution; the N,N'-diphenyl-p-phenylenediamine solution was added dropwise to the emulsion at a rate of 5 mL / min, and stirring was maintained at 1200 rpm during the addition; after the addition was completed, the mixture was heated to 50°C and stirred for 2-3 hours; the reaction product was centrifuged at 5000 rpm for 10 minutes, the supernatant was removed, and the obtained precipitate was washed three times with deionized water, and then vacuum dried at 60°C for 12 hours to obtain polyurea microcapsules with a particle size of 0.5-2 μm.

[0022] The preparation method of modified nano-silica is as follows: 10 parts of deionized water and 0.5 parts of glacial acetic acid are added to 100 parts of anhydrous ethanol, stirred evenly, and the pH of the solution is adjusted to 4-5; 10 parts of nano-silica are added, ultrasonically dispersed at 300W for 30 minutes, 2 parts of silane coupling agent KH560 are added, and stirred for reaction at 60°C for 3 hours to allow the KH560 molecules to react with hydroxyl groups on the surface of the nano-silica; after the reaction is completed, the product is centrifuged at 8000 rpm for 15 minutes, the supernatant is removed, and the resulting precipitate is washed three times with anhydrous ethanol and then vacuum-dried at 80°C for 10 hours to obtain modified nano-silica.

[0023] The preparation method of the fluorosilicone block copolymer is as follows: 15 parts of perfluoroalkylethyl acrylate, 8 parts of polydimethylsiloxane and 0.3 parts of azobisisobutyronitrile are added to 100 parts of toluene, and stirred at 40°C for 30 minutes to form a reaction solution; the reaction solution is transferred to a three-necked flask with a condenser, nitrogen is introduced to exclude air, and polymerization is carried out at 80°C for 5 hours. The initiator azobisisobutyronitrile decomposes to generate free radicals, which initiate a block copolymerization reaction between perfluoroalkylethyl acrylate and polydimethylsiloxane; after the reaction is completed, the reaction product is poured into methanol for precipitation, centrifuged at 6000 rpm for 10 minutes, the precipitate is collected, washed with methanol three times, and then vacuum-dried at 60°C for 12 hours to obtain a fluorosilicone block copolymer.

[0024] Examples 2-4 Refer to the preparation method and parameter conditions of Example 1, the specific differences are shown in Table 1.

[0025] Comparative Example 1 The preparation method and parameter conditions are the same as those in Example 1, except that epoxy silicone oil is not added.

[0026] Comparative Example 2 The preparation method and parameter conditions were similar to those of Example 1, except that the fluorine-silicon block copolymer was not added.

[0027] Comparative Example 3 The preparation method and parameter conditions are similar to those of Example 1, except that the fluorosilicone block copolymer is not added, and instead the raw materials perfluoroalkyl ethyl acrylate and polydimethylsiloxane are directly added to the coating.

[0028] Experimental Example 1 Adhesion Test Adhesion was tested according to ASTM D3359-02; the results are shown in Table 1.

[0029] Table 1 Adhesion test of Examples 1-4 and Comparative Examples 1-3

[0030] As can be seen from Table 1, in Examples 1-4, the adhesion of the coatings obtained is greatly improved, and the adhesion is all 4B. The siloxane groups in the polysiloxane condense with the hydroxyl groups on the rubber surface to form -Si-O-Si- covalent bonds, enhancing the substrate wettability; the epoxy groups react with the carboxyl groups of the resin matrix to form a dense cross-linked network; at the same time, the fluorocarbon segments in the fluorosilicone block copolymer are directionally enriched on the coating surface to form a hydrophobic barrier, while the siloxane segments are embedded in the rubber micropores to form a dynamic stress buffer layer. This design significantly improves the adhesion stability of the coating and avoids peeling failure through the triple mechanism of epoxy-carboxyl bonding, siloxane penetration and fluorocarbon barrier. In Comparative Example 1, epoxy silicone oil was not added, and the cross-linking effect between the epoxy groups and the resin matrix was lacking. The coating and the tire surface were only bonded by physical adsorption, and the adhesion was significantly reduced. In addition, the overall cross-linking network was incomplete, the mechanical strength of the coating was insufficient, and it was easy to peel off due to external force. In Comparative Example 2, without the addition of a fluorosilicone block copolymer, the coating solution struggled to spread evenly across the tire surface, resulting in localized defects and uneven adhesion. Block copolymerization stabilizes the chemical bonds between the fluorocarbon and siloxane segments, forming a molecularly compatible copolymer that simultaneously leverages the low surface energy of the fluorocarbon groups and the interfacial bonding capabilities of the siloxanes. In Comparative Example 3, without the addition of a fluorosilicone block copolymer, perfluoroalkylethylacrylate and polydimethylsiloxane were added directly to the coating. This easily led to phase separation due to polarity differences, resulting in an uneven internal coating structure and weakened overall adhesion. Furthermore, unpolymerized monomers struggled to effectively crosslink with the resin matrix or rubber surface, existing only as low-molecular-weight additives that were prone to migration or volatilization, leading to decreased long-term adhesion. Furthermore, lacking the chemical bonding of the block structure, the fluorocarbon and siloxane segments were unable to synergistically enhance interfacial forces, making the coating susceptible to peeling from the rubber surface.

[0031] Example 5

[0032] The preparation method and parameter conditions were the same as those in Example 2, except that when preparing polyurea microcapsules, the oil phase was added dropwise to the aqueous phase for 30 minutes, the N,N'-diphenyl-p-phenylenediamine solution was added dropwise to the emulsion, and the temperature was raised to 50°C and stirred for 2.5 hours; when preparing modified nano-silica, a silane coupling agent was added and the reaction was stirred for 4 hours; and the amount of polycaprolactone polyol used was 15 parts.

[0033] Example 6

[0034] The preparation method and parameter conditions were the same as those in Example 2, except that when preparing polyurea microcapsules, the oil phase was added dropwise to the aqueous phase for 35 minutes, the N,N'-diphenyl-p-phenylenediamine solution was added dropwise to the emulsion, and the temperature was raised to 50°C and stirred for 3 hours; when preparing modified nano-silica, a silane coupling agent was added and the reaction was stirred for 5 hours; and the amount of polycaprolactone polyol used was 18 parts.

[0035] Comparative Example 4 The preparation method and parameters of Example 1 were referred to, except that no polycaprolactone polyol was added.

[0036] Comparative Example 5 The preparation method and parameters of Example 1 were referred to, except that no polyurea microcapsule was added.

[0037] Comparative Example 6 The preparation method and parameters of Example 1 were referred to, except that no nano-silica was modified.

[0038] Comparative Example 7 The preparation method and parameters of Example 1 were referred to, except that no nano-silica was added.

[0039] Comparative Example 8 The preparation method and parameters of Example 1 were referred to, except that only bis(2,2,6,6-tetramethylpiperidyl) sebacate was used as a light stabilizer.

[0040] Comparative Example 9 The preparation method and parameters of Example 1 were referred to, except that only benzotriazole ultraviolet absorber UV-329 was used as a light stabilizer.

[0041] Experimental Example 2: Aging Resistance Test The change rates of tensile strength before and after ultraviolet aging and thermal oxygen aging (200℃, 48h) were tested according to the standards of GB / T 3512-2001 “Vulcanized Rubber or Thermoplastic Rubber Heating Aging and Heat Resistance Test” and GB / T 16585-1996 “Vulcanized Rubber Artificial Climate Aging Fluorescent Ultraviolet Lamp Test Method”. The tensile strength was tested according to the standard of GB / T 1040.1-2006. The results are shown in Table 2 and Figure 1

[0042] Table 2: Aging Resistance Test of Example 2, Examples 5-6 and Comparative Examples 4-9

[0043] From Table 2 and Figure 1 ​It can be seen that in Examples 2 and 5-6, the tensile strength of the coatings prepared only decreased by 5.5%-5.8% under UV aging and by 4.8%-5.0% under thermal oxidative aging, demonstrating excellent anti-aging properties. The uniformly dispersed nano-silica particles form a physical maze barrier, extending the diffusion path of oxygen molecules; the active groups grafted by the surface silane coupling agent capture free radicals, blocking the oxidation chain reaction; the N,N'-diphenyl-p-phenylenediamine released by the polyurea microcapsules scavenges free radicals generated by oxidation within the coating, and in combination with the compounded light stabilizer, forms a dynamic defense chain: the UV absorber converts high-energy photons into heat, and the hindered amines quench excited oxygen; the flexible long chains of the polycaprolactone polyols fill the free volume, inhibiting the propagation of microcracks in the coating, ultimately forming a gradient protection network that synergistically enhances resistance to UV, ozone, and oxidative corrosion. Polycaprolactone polyol acts as a flexible segment to provide coating flexibility, improve internal stress distribution, enhance entanglement between molecular chains, and improve crack resistance. In Comparative Example 4, polycaprolactone polyol was not added, and the rigidity of the coating cross-linked network increased, while the flexibility decreased. Microcracks were easily generated when subjected to long-term aging factors such as ultraviolet rays, thermal oxygen, etc. In Comparative Example 5, polyurea microcapsules were not added, and the microdamage generated during the aging process of the coating could not be repaired, accelerating structural damage. In Comparative Example 6, nanosilica was not modified, and the surface hydroxyl groups were easily agglomerated, resulting in uneven dispersion and internal defects in the coating, reducing the ultraviolet shielding efficiency. Nanosilica acts as an inorganic filler to physically shield ultraviolet light, while adsorbing free radicals through a high specific surface area to inhibit oxidation reactions. In Comparative Example 7, nanosilica was not added, and the coating lacked a physical ultraviolet shielding layer, accelerating the light aging reaction and exacerbating the breakage of polymer chains. In Comparative Example 8, only bis(2,2,6,6-tetramethylpiperidinyl) sebacate was used as a light stabilizer, which failed to effectively absorb UV light energy and relied solely on free radical capture, resulting in insufficient protection under high-dose UV. In Comparative Example 9, only the benzotriazole UV absorber UV-329 was used as a light stabilizer. This absorber only absorbed UV light and was unable to inhibit the free radicals generated during the aging process. After long-term aging, the absorber itself would fail due to photodegradation, and the accumulation of free radicals would lead to oxidative breakage of the polymer chain, resulting in a rapid decline in the mechanical properties of the coating.

[0044] Examples 7-8 Referring to the preparation method and parameter conditions of Example 5, the specific differences are shown in Table 3.

[0045] Comparative Example 10 The preparation method and parameter conditions are the same as those in Example 5, except that hot air pre-curing is not performed during curing.

[0046] Comparative Example 11 The preparation method and parameter conditions are the same as those in Example 5, except that no heat curing is performed during curing.

[0047] Comparative Example 12 The preparation method and parameter conditions are similar to those of Example 5, except that infrared radiation curing is not performed during curing.

[0048] Experimental Example 3 Adhesion Test The adhesion test was performed according to the method of Experimental Example 1; the results are shown in Table 3.

[0049] Table 3 Adhesion test of Example 5, Examples 7-8 and Comparative Examples 10-12

[0050] As can be seen from Table 3, in Example 5 and Examples 7-8, the best adhesion of the coating can reach 5B. Through the staged low-temperature-medium-temperature-high-temperature gradient curing strategy, the 60°C pre-curing stabilizes the self-assembly of the emulsion particles to form a continuous elastic film; the 90°C activates the epoxy crosslinker to deeply crosslink with the resin matrix, enhancing the density of the three-dimensional network; the 120°C infrared radiation promotes the dehydration condensation of the siloxane groups and the rubber substrate, and simultaneously drives the fluorosilicone block copolymer to migrate to the interface. This process avoids the microporous defects caused by high-temperature rapid curing, ensuring that the nano-silica is oriented and arranged into a dense stacking structure; at the same time, the thermoplastic properties of the polycaprolactone polyol give the coating the ability to slide under stress, dissipating mechanical energy through elastic deformation, reducing the risk of brittle peeling of the coating under dynamic conditions. In Comparative Example 10, hot air pre-curing was not performed, and the solvent was not fully volatilized. During the subsequent high-temperature curing, the coating is prone to bubbles or cracks due to the rapid volatilization of the solvent, resulting in loose bonding between the coating and the substrate interface; the starting point of chemical crosslinking is insufficient, and the final crosslinking density is reduced. In Comparative Example 11, thermal curing was not performed, and the chemical reaction between the epoxy groups and the resin was not activated, resulting in a lack of covalent crosslinking. The coating relied primarily on physical adsorption, resulting in insufficient cohesive strength and easy overall flaking. In Comparative Example 12, infrared radiation curing was not performed, and deep chemical bonding between the silicone and rubber interface was not achieved. The interfacial transition layer was weak, and the coating and substrate were bonded only through chemical crosslinking during pre-curing and thermal curing.

[0051] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a tire anti-aging coating, characterized in that: The preparation method is as follows: adding waterborne polyurethane-acrylate copolymer emulsion, epoxy polysiloxane, crosslinking agent and polycaprolactone polyol into a reaction kettle and stirring, adding part of light stabilizer and antioxidant to react; after cooling, adding polyurea microcapsules, remaining light stabilizer, modified nano-silicon dioxide and fluorosilicone block copolymer in sequence and stirring; adding film-forming agent and defoaming agent and stirring to obtain a coating emulsion; Spraying the coating emulsion on the tire surface and performing gradient curing to obtain the tire anti-aging coating; The polyurea microcapsules are prepared from N,N'-diphenyl-p-phenylenediamine, isophorone diisocyanate and polyvinyl alcohol; The modified nano-silica is obtained by modifying nano-silica with a silane coupling agent; The fluorosilicone block copolymer is prepared from perfluoroalkylethyl acrylate, polydimethylsiloxane and azobisisobutyronitrile.

2. The method for preparing a tire anti-aging coating according to claim 1, characterized in that: The antioxidant is obtained by compounding pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and dilauryl thiodipropionate.

3. The method for preparing a tire anti-aging coating according to claim 1, wherein: The preparation method of the polyurea microcapsules is as follows: adding the polyvinyl alcohol to deionized water, heating and stirring to obtain an aqueous phase; adding the isophorone diisocyanate to toluene, stirring to obtain an oil phase; dropping the oil phase into the aqueous phase to form an emulsion; adding the N,N'-diphenyl-p-phenylenediamine to ethanol to obtain an N,N'-diphenyl-p-phenylenediamine solution; dropping the N,N'-diphenyl-p-phenylenediamine solution into the emulsion, heating and continuing to stir to obtain the polyurea microcapsules.

4. The method for preparing a tire anti-aging coating according to claim 1, wherein: The preparation method of modified nano-silica is as follows: adding deionized water and glacial acetic acid to anhydrous ethanol and stirring evenly, adjusting the pH of the solution; adding the nano-silica and ultrasonically dispersing it, adding the silane coupling agent and stirring to react, thereby obtaining the modified nano-silica.

5. The method for preparing a tire anti-aging coating according to claim 1, characterized in that: The preparation method of the fluorosilicone block copolymer is as follows: the perfluoroalkylethyl acrylate, the polydimethylsiloxane and the azobisisobutyronitrile are added to toluene and stirred to form a reaction solution; the reaction solution is transferred to a three-necked flask, nitrogen is introduced to exclude air, and a polymerization reaction is carried out; after the reaction is completed, the reaction product is poured into methanol for precipitation, and the precipitate is collected to obtain the fluorosilicone block copolymer.

6. The method for preparing a tire anti-aging coating according to claim 1, characterized in that: The light stabilizer is obtained by compounding bis(2,2,6,6-tetramethylpiperidinyl)sebacate and ultraviolet absorber UV-329.

7. The method for preparing a tire anti-aging coating according to claim 1, characterized in that: The gradient curing is to first perform hot air pre-curing to form a preliminary cross-linking network; then perform heat curing after heating to activate the epoxy groups and deep cross-linking with the resin matrix; and finally perform infrared radiation curing to strengthen the chemical bonding between the silicone and rubber interface.

8. A tire anti-aging coating, characterized by: The raw materials for preparing the anti-aging coating include aqueous polyurethane-acrylate copolymer emulsion, epoxy polysiloxane, crosslinking agent, polycaprolactone polyol, light stabilizer, antioxidant, polyurea microcapsule and modified nano-silica; the anti-aging coating is prepared by the preparation method according to any one of claims 1 to 7.

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