Environment-friendly wear-resistant coating for railway and preparation method thereof

Abstract

The invention discloses an environment-friendly wear-resistant coating for railways and a preparation method thereof, and belongs to the technical field of coating preparation, the environment-friendly wear-resistant coating for railways comprises the following raw materials by mass: 45-60% of epoxy-organosilicon hybrid resin, 2-5% of modified nanocellulose, 8-10% of a water-based curing agent, and the balance of a solvent. Aiming at the technical problems of insufficient wear resistance, poor dynamic fatigue resistance, high VOCs (volatile organic compounds) content and the like of a railway facility coating in high mechanical stress, extreme climate and chemical corrosion environments, the epoxy-organic silicon hybrid resin and the modified nano cellulose are subjected to molecular design, interface enhancement and synergistic coupling of the epoxy-organic silicon hybrid resin and the modified nano cellulose; the wear-resistant coating provided by the invention is environment-friendly and excellent in performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of coating preparation, and particularly relates to an environmentally friendly wear-resistant coating for railways and a preparation method thereof. Background Art

[0002] Railway facilities (such as tracks, bridges, carriage connectors, etc.) are long-term exposed to high mechanical stress, extreme climate and chemical corrosion environments, and have extremely high requirements for the wear resistance, weather resistance and environmental friendliness of the surface coating. Existing railway coatings mostly adopt solvent-based epoxy resin or polyurethane systems. Although they have certain wear resistance, they contain a large amount of volatile organic compounds (VOCs), which do not meet environmental protection regulations; at the same time, the wear resistance of traditional coatings depends on high-hardness fillers (such as silicon carbide), resulting in high brittleness of the coating and easy cracking and peeling under dynamic loads.

[0003] Currently, in order to reduce the content of VOCs in waterborne environmentally friendly coatings, low cross-linking density acrylic resins or polyurethane dispersions are usually used, but their molecular chain flexibility is too high to balance wear resistance and anti-fatigue performance under dynamic loads. Specifically, in the high-frequency vibration scenario of railway facilities, microcracks are generated in the coating due to repeated deformation, accelerating wear and corrosion penetration, resulting in a significant reduction in service life.

[0004] The maintenance cost of railway facilities is high and it affects operation safety. There is an urgent need for a coating with high wear resistance, dynamic anti-fatigue performance and environmental protection characteristics. If the coating can achieve a rigid-flexible mechanical property through molecular structure design while maintaining low VOCs, it will significantly improve the durability of railway facilities and reduce environmental pollution. Summary of the Invention

[0005] The purpose of the present invention is to provide an environmentally friendly wear-resistant coating for railways and a preparation method thereof to solve the problems in the background art.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] An environmentally friendly wear-resistant coating for railways, comprising the following raw materials in mass percentage:

[0008]

[0009] The balance is solvent.

[0010] Further, the epoxy-organosilicon hybrid resin is prepared by the following steps:

[0011] A1. Under a nitrogen atmosphere, stir and mix phenyltrimethoxysilane, tetramethyldisiloxane, and isopropanol, then dropwise add a 0.1 mol / L hydrochloric acid aqueous solution thereto, then raise the temperature to 55-60 °C, stir constantly for 3-6 h, then adjust the pH of the system to neutral, and then perform vacuum distillation to obtain an organosilicon prepolymer;

[0012] A2. Mix bisphenol A epoxy resin with the above-mentioned organosilicon prepolymer, then add isopropanol thereto. After stirring, add triphenylphosphine thereto, and then raise the temperature to 80 - 100 °C. After reacting for 4 - 5 h, an epoxy resin graft-modified organosilicon prepolymer is obtained.

[0013] A3. Dissolve dopamine hydrochloride in deionized water, and then add it to the above-mentioned epoxy resin graft-modified organosilicon prepolymer. Adjust the pH of the system to 9.5 - 10.0. After completion, raise the temperature of the system to 70 - 80 °C, and then stir it at a constant temperature for 6 - 8 h. After completion, carry out vacuum distillation to obtain an epoxy-organosilicon hybrid resin.

[0014] Further, the dosage ratio of phenyltrimethoxysilane, tetramethyldisiloxane, isopropanol, 0.1 mol / L hydrochloric acid aqueous solution, bisphenol A epoxy resin, isopropanol, triphenylphosphine, dopamine hydrochloride, and deionized water is 115 - 125 g: 75 - 85 g: 100 mL: 50 mL: 500 g: 100 - 150 mL: 0.5 - 1.0 g: 22 - 25 g: 250 mL.

[0015] Further, the epoxy equivalent of the bisphenol A epoxy resin in A2 is 210 - 240 g / eq, and the viscosity is 2500 MPa·s.

[0016] Further, the modified nanocellulose is prepared by the following steps:

[0017] B1. Stir and disperse microcrystalline cellulose in a 64% sulfuric acid solution by mass, control the temperature at 45 - 50 °C, and react at a constant temperature for 1 - 2 h. Then add deionized water thereto, and then collect the precipitate by centrifugation and wash the precipitate with pure water until it is neutral to obtain a nanocellulose gel.

[0018] B2. Mix the nanocellulose gel with a 5% NaOH solution by mass. Raise the temperature of the system to 50 - 60 °C and stir for 50 - 60 min. Then wash it by centrifugation until it is neutral and freeze-dry it to obtain nanocellulose powder.

[0019] B3. Disperse the nanocellulose powder in anhydrous ethanol, then perform ultrasonic treatment, and then add hexamethylene diisocyanate and dibutyltin dilaurate thereto. Under nitrogen protection, raise the temperature to 70 - 75 °C and stir and react at a constant temperature for 6 - 8 h. After completion, immediately cool it in an ice bath to 5 - 10 °C, then add deionized water thereto, collect the precipitate by centrifugation, wash the precipitate three times with ethanol and acetone respectively, collect the precipitate, and after vacuum drying the precipitate, obtain the modified nanocellulose.

[0020] Further, the dosage ratio of the microcrystalline cellulose, 64% sulfuric acid solution by mass, and deionized water in B1 is 100 g: 500 mL: 2000 mL.

[0021] Further, the dosage ratio of the nanocellulose gel described in B2 to the NaOH solution with a mass fraction of 5% is 50 g: 500 mL.

[0022] Further, the dosage ratio of the nanocellulose powder, anhydrous ethanol, hexamethylene diisocyanate, dibutyltin dilaurate, and deionized water described in B3 is 20 g: 500 mL: 18 - 20 g: 0.3 - 0.5 g: 100 mL.

[0023] Further, the aqueous curing agent is Curing agent of type XTJ - 506 or Huntsman EDR - 176.

[0024] Further, the solvent is compounded from deionized water and propylene glycol monomethyl ether acetate according to a volume ratio of 3: 1 - 2.

[0025] Further, the preparation method of the environmentally friendly wear - resistant coating for railways includes the following steps:

[0026] Weigh each raw material according to mass percentage, stir the epoxy - organosilicon hybrid resin and the modified nanocellulose into the solvent, stir at a high speed of 2000 rpm for 20 - 30 min, then stir and add the aqueous curing agent thereto, stir at a low speed of 800 rpm for 20 - 30 min to obtain a slurry, then transfer the slurry to a vacuum degassing machine, evacuate to - 0.095 MPa and maintain for 25 - 30 min, and assist with ultrasonic degassing. After completion, an environmentally friendly wear - resistant coating for railways is obtained.

[0027] Advantages of the present invention:

[0028] Aiming at the technical problems of insufficient wear resistance, poor dynamic fatigue resistance, and high VOCs content faced by railway facility coatings in high mechanical stress, extreme climate, and chemical corrosion environments, through the molecular design of epoxy - organosilicon hybrid resin, the interface enhancement of modified nanocellulose, and the synergistic coupling of the two, the present invention provides a wear - resistant coating with both environmental protection and excellent performance. The specific advantages are as follows:

[0029] (1) Excellent wear resistance: Due to the rigid - flexible structure of the epoxy - organosilicon hybrid resin in the present invention (the organosilicon chain segment provides flexibility and the epoxy resin gives rigidity), the coating can effectively disperse stress under dynamic loads and avoid brittle cracking. The nano - scale reinforcement effect of the modified nanocellulose further inhibits crack propagation, further reducing the Taber wear index. The interpenetrating network structure formed by the synergistic effect of the two significantly extends the service life of the coating in the high - frequency vibration environment of railways.

[0030] (2) Excellent adhesion and corrosion resistance: Catechol groups in the epoxy-organosilicon hybrid resin of the present invention form strong coordination bonds with the metal substrate, and the modified nanocellulose is covalently connected to the epoxy-organosilicon hybrid resin through urethane bonds, constructing a dual interface protection mechanism of "chemical anchoring + physical enhancement". After salt spray testing, the adhesion still remains at level 0, indicating that the coating can maintain excellent interface stability under extremely humid and salt-corroded environments. In addition, the hydrophobic modification of nanocellulose effectively blocks moisture penetration and further delays the corrosion process.

[0031] (3) Synergistic optimization of environmental friendliness and performance: The present invention uses a waterborne curing agent and a low-VOCs solvent (a mixture of deionized water and propylene glycol methyl ether acetate), with the VOCs content as low as below 40 g / L, meeting strict environmental protection regulations. The high crosslinking density of the epoxy-organosilicon hybrid resin and the high-efficiency strengthening effect of nanocellulose reduce the dependence on high-hardness fillers and avoid the problems of increased VOCs and coating embrittlement caused by traditional fillers, achieving a balance between environmental friendliness and mechanical properties.

[0032] (4) Significant improvement in dynamic fatigue resistance: Traditional coatings are difficult to adapt to the dynamic loads of railway facilities due to excessive molecular chain flexibility (such as acrylic resins) or excessive rigidity (such as silicon carbide-filled systems). Through the dynamic reversibility of the Si-O-C bond in the epoxy-organosilicon hybrid resin and the stress dispersion effect of nanocellulose in the present invention, the coating maintains structural integrity during repeated deformation, and the adhesion after salt spray does not decay, completely solving the problem of accelerated wear caused by microcracks.

[0033] In summary, the technical solution provided by the present invention not only overcomes the technical bottlenecks of traditional coatings in terms of environmental friendliness, wear resistance, corrosion resistance, etc., but also realizes the synergistic optimization of multiple performance indicators, providing a long-term and environmentally friendly surface protection solution for railway facilities, with broad market application prospects. Detailed implementation manners

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0035] Example 1

[0036] Preparation of epoxy-organosilicon hybrid resin:

[0037] A1. Synthesis of organosilicon prepolymer:

[0038] (1) Reactor pretreatment: The reactor is purged with nitrogen three times to ensure an oxygen-free environment.

[0039] (2) Feeding and mixing: Add phenyltrimethoxysilane (115 g), tetramethyldisiloxane (75 g), and isopropanol (100 mL) into the reactor, and stir at a stirring rate of 300 rpm for 10 min.

[0040] (3) Hydrolysis and condensation: Then, add 0.1 mol / L hydrochloric acid aqueous solution (50 mL) dropwise into the reactor. Heat the reactor to 55 °C and stir at a constant temperature for 3 h to generate a phenyl-containing silicone prepolymer.

[0041] (4) Termination of reaction: Add sodium bicarbonate into the reactor to neutralize until pH = 7.0, and remove the solvent by vacuum distillation (80 °C, -0.08 MPa) to obtain a transparent viscous organosilicon prepolymer.

[0042] A2. Epoxy resin graft modification:

[0043] (1) Premixing: Mix bisphenol A epoxy resin (500 g, E-44, epoxy equivalent 210 - 240 g / eq, viscosity 2500 MPa·s) with the organosilicon prepolymer, and then stir and add isopropanol (100 mL) into it. Stir for 20 min to obtain a mixture after completion.

[0044] (2) Graft reaction: Then, add triphenylphosphine (0.5 g) into the mixture. Heat the system to 80 °C and react for 4 h. During the reaction, the main chain of the epoxy resin is connected to the silicone prepolymer through the Si - O - C bond. After completion, an epoxy resin graft-modified organosilicon prepolymer is obtained.

[0045] A3. Introduction of catechol groups:

[0046] (1) Functionalization modification: Dissolve dopamine hydrochloride (22 g) in deionized water (250 mL), then add it into the above epoxy resin graft-modified organosilicon prepolymer, and then add sodium hydroxide to adjust the pH to 9.5.

[0047] (2) Graft reaction: After adjusting the pH, heat the system to 70 °C and stir at a constant temperature for 6 h. During the reaction, the catechol groups in dopamine hydrochloride are grafted to the ends of the epoxy resin graft-modified organosilicon prepolymer through Michael addition reaction.

[0048] (3) Purification: After stirring, remove the solvent by vacuum distillation (70 °C, -0.095 MPa) to obtain a light yellow viscous liquid, which is the epoxy - organosilicon hybrid resin.

[0049] Example 2

[0050] Preparation of epoxy - organosilicon hybrid resin:

[0051] A1. Synthesis of organosilicon prepolymer:

[0052] (1) Reactor pretreatment: Replace the gas in the reactor with nitrogen three times to ensure an oxygen-free environment.

[0053] (2) Feeding and mixing: Add phenyltrimethoxysilane (120 g), tetramethyldisiloxane (82 g), and isopropyl alcohol (100 mL) into the reactor, and stir at a stirring rate of 300 rpm for 30 min.

[0054] (3) Hydrolysis and condensation: Then, add 0.1 mol / L hydrochloric acid aqueous solution (50 mL) dropwise into the reactor. Heat the reactor to 55 °C and stir at a constant temperature for 6 h to generate a phenyl-containing silicone prepolymer.

[0055] (4) Terminate the reaction: Add sodium bicarbonate into the reactor to neutralize until pH = 7.0, and remove the solvent by vacuum distillation (80 °C, -0.08 MPa) to obtain a transparent viscous organosilicon prepolymer.

[0056] A2. Epoxy resin graft modification:

[0057] (1) Premixing: Mix bisphenol A epoxy resin (500 g, E-44, epoxy equivalent 210 - 240 g / eq, viscosity 2500 MPa·s) with the organosilicon prepolymer, and then stir and add isopropyl alcohol (120 mL) into it. Stir for 30 min to obtain a mixture.

[0058] (2) Graft reaction: Then, add triphenylphosphine (1.0 g) into the mixture. Heat the system to 80 °C and react for 5 h. During the reaction, the main chain of the epoxy resin is connected to the silicone prepolymer through Si-O-C bonds. After completion, an epoxy resin graft-modified organosilicon prepolymer is obtained.

[0059] A3. Introduction of catechol groups:

[0060] (1) Functionalization modification: Dissolve dopamine hydrochloride (24 g) in deionized water (250 mL), then add it into the above epoxy resin graft-modified organosilicon prepolymer, and then add sodium hydroxide to adjust the pH to 9.5.

[0061] (2) Graft reaction: After adjusting the pH, heat the system to 70 °C and stir at a constant temperature for 8 h. During the reaction, the catechol groups in dopamine hydrochloride are grafted to the end of the epoxy resin graft-modified organosilicon prepolymer through Michael addition reaction.

[0062] (3) Purification: After stirring, remove the solvent by vacuum distillation (72 °C, -0.095 MPa) to obtain a light yellow viscous liquid, which is the epoxy-silicon hybrid resin.

[0063] Example 3

[0064] Preparation of epoxy - organosilicon hybrid resin:

[0065] A1. Synthesis of organosilicon prepolymer:

[0066] (1) Reactor pretreatment: Replace the air in the reactor with nitrogen three times to ensure an oxygen - free environment.

[0067] (2) Feeding and mixing: Add phenyltrimethoxysilane (125 g), tetramethyldisiloxane (85 g), and isopropyl alcohol (100 mL) into the reactor, and stir at a stirring rate of 300 rpm for 30 min.

[0068] (3) Hydrolysis and condensation: Then, add 0.1 mol / L hydrochloric acid aqueous solution (50 mL) dropwise into the reactor. Heat the reactor to 60 °C and stir at a constant temperature for 6 h to form a phenyl - containing siloxane prepolymer.

[0069] (4) Terminate the reaction: Add sodium bicarbonate into the reactor to neutralize until pH = 7.0, and remove the solvent by vacuum distillation (80 °C, - 0.08 MPa) to obtain a transparent viscous organosilicon prepolymer.

[0070] A2. Epoxy resin graft modification:

[0071] (1) Premixing: Mix bisphenol A epoxy resin (500 g, E - 44, epoxy equivalent 210 - 240 g / eq, viscosity 2500 MPa·s) with the organosilicon prepolymer, and then stir - add isopropyl alcohol (150 mL) into it and stir for 30 min. After completion, a mixture is obtained.

[0072] (2) Graft reaction: Then add triphenylphosphine (1.0 g) into the mixture. Heat the system to 100 °C and react for 5 h. During the reaction, the main chain of the epoxy resin is connected to the siloxane prepolymer through the Si - O - C bond. After completion, an epoxy resin - graft - modified organosilicon prepolymer is obtained.

[0073] A3. Introduction of catechol groups:

[0074] (1) Functional modification: Dissolve dopamine hydrochloride (25 g) in deionized water (250 mL), then add it into the above - mentioned epoxy resin - graft - modified organosilicon prepolymer, and then add sodium hydroxide to adjust the pH to 10.0.

[0075] (2) Graft reaction: After the pH adjustment is completed, heat the system to 80 °C and stir at a constant temperature for 8 h. During the reaction, the catechol groups in dopamine hydrochloride are grafted to the end of the epoxy resin - graft - modified organosilicon prepolymer through Michael addition reaction.

[0076] (3) Purification: After stirring, the solvent was removed by vacuum distillation (75 °C, -0.095 MPa) to obtain a pale yellow viscous liquid, which is the epoxy-silicone hybrid resin.

[0077] Test Example 1

[0078] The epoxy-silicone hybrid resins prepared in Examples 1 to 3 were subjected to performance tests. The performance test process is as follows, and the test results are shown in Table 1:

[0079] 1. Epoxy equivalent test (hydrochloric acid-acetone method):

[0080] Experimental group: Weigh 0.5 g of the epoxy-silicone hybrid resin, dissolve it in 20 mL of acetone, then add 25 mL of 0.2 mol / L hydrochloric acid-acetone solution to it, shake well and let it stand for 30 min, and titrate with 0.1 mol / L NaOH standard solution until the phenolphthalein indicator turns pink.

[0081] Blank control: Without adding the epoxy-silicone hybrid resin, repeat the above steps.

[0082] Calculation: Epoxy equivalent = [1000×m] / [(V0 - V)×c];

[0083] Where, m is the mass (g) of the epoxy-silicone hybrid resin; V0 and V are the consumption volumes (mL) of the NaOH standard solution in the experimental group and the blank control respectively; c is the concentration of NaOH (mol / L).

[0084] 2. Viscosity test (rotational viscometer method):

[0085] The epoxy-silicone hybrid resin was equilibrated in a 25 °C constant temperature water bath for 30 min, the rotor speed was set at 20 rpm, the viscometer (Brookfield DV2T viscometer) was started, and the value was recorded after the reading was stable. Repeat 3 times and take the average value, with the error controlled within ±3%.

[0086] Table 1 Test Results

[0087] Project Example 1 Example 2 Example 3 Epoxy equivalent 220 g / eq 227 g / eq 225 g / eq Viscosity (25°C) 2700 mPa·s 2800 mPa·s 2850 mPa·s

[0088] Example 4

[0089] Preparation of modified nanocellulose:

[0090] B1. Preparation of nanocellulose suspension (acid hydrolysis method):

[0091] (1) Acid hydrolysis reaction: 100 g of microcrystalline cellulose (MCC, purity ≥ 99.9%) was dispersed in 500 mL of sulfuric acid solution with a mass fraction of 64%. Mechanical stirring (500 rpm) was carried out while controlling the temperature at 45 °C for 1 h to dissociate cellulose fibers into nanoscale fibers. After completion, an acid hydrolysis mixture was obtained.

[0092] (2) Termination and purification: 2000 mL of deionized water was added to the acid hydrolysis mixture to terminate the reaction. The precipitate was separated and collected by centrifugation (8000 rpm, 15 min), and the precipitate was washed with pure water until it was neutral to obtain nanocellulose gel.

[0093] B2. Surface activation of nanocellulose:

[0094] 50 g of nanocellulose gel was mixed with 500 mL of NaOH solution with a mass fraction of 5%. Stirring was carried out at 50 °C for 50 min to enhance the activity of surface hydroxyl groups. After completion, it was centrifuged and washed until it was neutral, and then freeze-dried (-50 °C, 24 h) to obtain nanocellulose powder.

[0095] B3. Graft modification with urethane groups:

[0096] (1) Grafting reaction: 20 g of nanocellulose powder was dispersed in 500 mL of anhydrous ethanol. Ultrasonic treatment (40 kHz, 30 min) was carried out until it was uniformly suspended to form a suspension. Then, hexamethylene diisocyanate (18 g) and dibutyltin dilaurate (0.3 g) were added to the suspension. Under nitrogen protection, the temperature was raised to 70 °C, and constant stirring (300 rpm) was carried out for 6 h. The isocyanate group (-NCO) of hexamethylene diisocyanate reacted with the surface hydroxyl group (-OH) of nanocellulose to form a urethane bond (-NH-CO-O-).

[0097] (2) Termination and purification: After the reaction was completed, it was immediately cooled to 5 °C in an ice bath. Then, 100 mL of deionized water was added to terminate the reaction. The precipitate was collected by centrifugation (10000 rpm, 20 min), and the precipitate was washed three times with ethanol and acetone respectively to remove unreacted HDI. The precipitate was collected and placed in a vacuum dryer (50 °C, 24 h). After completion, white powdery modified nanocellulose was obtained.

[0098] Example 5

[0099] Preparation of modified nanocellulose:

[0100] B1. Preparation of nanocellulose suspension (acid hydrolysis method):

[0101] (1) Acid hydrolysis reaction: 100 g of microcrystalline cellulose (MCC, purity ≥ 99.9%) was dispersed in 500 mL of sulfuric acid solution with a mass fraction of 64%. Mechanical stirring (500 rpm) was carried out while controlling the temperature at 45 °C for 2 h to dissociate the cellulose fibers into nanoscale fibers. After completion, an acid hydrolysis mixture was obtained.

[0102] (2) Termination and purification: 2000 mL of deionized water was added to the acid hydrolysis mixture to terminate the reaction. The precipitate was separated and collected by centrifugation (8000 rpm, 15 min), and the precipitate was washed with pure water until it was neutral to obtain nanocellulose gel.

[0103] B2. Surface activation of nanocellulose:

[0104] 50 g of nanocellulose gel was mixed with 500 mL of NaOH solution with a mass fraction of 5%. Stirring was carried out at 55 °C for 60 min to enhance the activity of surface hydroxyl groups. After completion, it was centrifuged and washed until it was neutral, and then freeze-dried (-50 °C, 24 h) to obtain nanocellulose powder.

[0105] B3. Graft modification with urethane groups:

[0106] (1) Grafting reaction: 20 g of nanocellulose powder was dispersed in 500 mL of anhydrous ethanol. Ultrasonic treatment (40 kHz, 30 min) was carried out until it was uniformly suspended to form a suspension. Then, hexamethylene diisocyanate (20 g) and dibutyltin dilaurate (0.5 g) were added to the suspension. Under nitrogen protection, the temperature was raised to 70 °C, and constant stirring (300 rpm) was carried out for 8 h. The isocyanate group (-NCO) of hexamethylene diisocyanate reacted with the surface hydroxyl group (-OH) of nanocellulose to form a urethane bond (-NH-CO-O-).

[0107] (2) Termination and purification: After the reaction was completed, it was immediately cooled to 5 °C in an ice bath. Then, 100 mL of deionized water was added to terminate the reaction. The precipitate was collected by centrifugation (10000 rpm, 20 min), and the precipitate was washed three times with ethanol and acetone respectively to remove the unreacted HDI. The precipitate was collected and placed in a vacuum dryer (50 °C, 24 h). After completion, white powdery modified nanocellulose was obtained.

[0108] Example 6

[0109] Preparation of modified nanocellulose:

[0110] B1. Preparation of nanocellulose suspension (acid hydrolysis method):

[0111] (1) Acid hydrolysis reaction: 100 g of microcrystalline cellulose (MCC, purity ≥ 99.9%) was dispersed in 500 mL of sulfuric acid solution with a mass fraction of 64%, mechanically stirred (500 rpm), the temperature was controlled at 50 °C, and the reaction was carried out for 2 h to dissociate cellulose fibers into nanoscale fibers. After completion, an acid hydrolysis mixture was obtained.

[0112] (2) Termination and purification: Then, 2000 mL of deionized water was added to the acid hydrolysis mixture to terminate the reaction. The precipitate was separated and collected by centrifugation (8000 rpm, 15 min), and the precipitate was washed with pure water until it was neutral to obtain nanocellulose gel.

[0113] B2. Surface activation of nanocellulose:

[0114] 50 g of nanocellulose gel was mixed with 500 mL of NaOH solution with a mass fraction of 5%, stirred at 60 °C for 60 min to enhance the activity of surface hydroxyl groups. After completion, it was centrifuged and washed until neutral, and freeze-dried (-50 °C, 24 h) to obtain nanocellulose powder.

[0115] B3. Graft modification with urethane groups:

[0116] (1) Grafting reaction: 20 g of nanocellulose powder was dispersed in 500 mL of anhydrous ethanol, ultrasonically treated (40 kHz, 30 min) until uniformly suspended to form a suspension. Then, hexamethylene diisocyanate (20 g) and dibutyltin dilaurate (0.5 g) were added to the suspension. Under nitrogen protection, the temperature was raised to 75 °C, and it was stirred at a constant temperature (300 rpm) for 8 h. The isocyanate groups (-NCO) of methylene diisocyanate reacted with the surface hydroxyl groups (-OH) of nanocellulose to form urethane bonds (-NH-CO-O-).

[0117] (2) Termination and purification: After the reaction was completed, it was immediately cooled to 10 °C in an ice bath, then 100 mL of deionized water was added to terminate the reaction. The precipitate was collected by centrifugation (10000 rpm, 20 min), and the precipitate was washed three times with ethanol and acetone respectively to remove unreacted HDI. The precipitate was collected and placed in vacuum drying (50 °C, 24 h). After completion, white powdery modified nanocellulose was obtained.

[0118] Example 7

[0119] Preparation of environmentally friendly wear-resistant coating for railways:

[0120] First, the environmentally friendly wear-resistant coating for railways includes the following raw materials in mass percentage:

[0121]

[0122] The balance is solvent;

[0123] Among them, the solvent is a compound of deionized water and propylene glycol methyl ether acetate in a volume ratio of 3:1.

[0124] Then, a preparation method of the environmentally friendly wear-resistant coating for railways includes the following steps:

[0125] Weigh each raw material according to the above mass percentages, stir the epoxy-silicone hybrid resin prepared in Example 1 and the modified nanocellulose prepared in Example 4 into the solvent, stir at a high speed of 2000 rpm for 20 min, and then stir and add XTJ-506 type curing agent, stir at a low speed of 800 rpm for 20 min to obtain a slurry, then transfer the slurry to a vacuum degassing machine, evacuate to -0.095 MPa and maintain for 25 min, and assist with ultrasonic degassing (40 kHz, 5 min). After completion, the environmentally friendly wear-resistant coating for railways is obtained.

[0126] Example 8

[0127] Prepare the environmentally friendly wear-resistant coating for railways:

[0128] First, the environmentally friendly wear-resistant coating for railways includes the following raw materials in mass percentages:

[0129]

[0130] The balance is the solvent;

[0131] Among them, the solvent is a compound of deionized water and propylene glycol methyl ether acetate in a volume ratio of 3:2.

[0132] Then, a preparation method of the environmentally friendly wear-resistant coating for railways includes the following steps:

[0133] Weigh each raw material according to the above mass percentages, stir the epoxy-silicone hybrid resin prepared in Example 2 and the modified nanocellulose prepared in Example 5 into the solvent, stir at a high speed of 2000 rpm for 30 min, and then stir and add Huntsman EDR-176 type curing agent, stir at a low speed of 800 rpm for 30 min to obtain a slurry, then transfer the slurry to a vacuum degassing machine, evacuate to -0.095 MPa and maintain for 30 min, and assist with ultrasonic degassing (40 kHz, 5 min). After completion, the environmentally friendly wear-resistant coating for railways is obtained.

[0134] Example 9

[0135] Prepare the environmentally friendly wear-resistant coating for railways:

[0136] First, the environmentally friendly wear-resistant coating for railways includes the following raw materials in mass percentages:

[0137] Epoxy-organosilicon hybrid resin prepared in Example 3: 60%;

[0138] Modified nanocellulose prepared in Example 6: 2%;

[0139] Huntsman EDR-176 curing agent: 8%;

[0140] The balance is solvent;

[0141] Among them, the solvent is prepared by compounding deionized water and propylene glycol methyl ether acetate according to a volume ratio of 3:2.

[0142] Then, a preparation method of the environmentally friendly wear-resistant coating for railways includes the following steps:

[0143] Weigh each raw material according to the above mass percentages, stir the epoxy-organosilicon hybrid resin prepared in Example 3 and the modified nanocellulose prepared in Example 6 into the solvent, stir at a high speed of 2000 rpm for 30 min, then stir and add the Huntsman EDR-176 curing agent thereto, stir at a low speed of 800 rpm for 30 min to obtain a slurry, then transfer the slurry to a vacuum degassing machine, evacuate to -0.095 MPa and maintain for 30 min, and assist with ultrasonic degassing (40 kHz, 5 min). After completion, the environmentally friendly wear-resistant coating for railways is obtained.

[0144] Comparative Example 1

[0145] Comparative Example 1 is the control group of Example 8. Replace the epoxy-organosilicon hybrid resin prepared in Example 2 in the raw materials of Example 8 with bisphenol A epoxy resin, and keep the other raw materials, raw material dosages and preparation methods the same as those in Example 8. Finally, the environmentally friendly wear-resistant coating for railways is obtained.

[0146] Comparative Example 2

[0147] Comparative Example 2 is the control group of Example 8. Replace the modified nanocellulose prepared in Example 5 in the raw materials of Example 8 with the nanocellulose powder prepared by B2 in Example 5, and keep the other raw materials, raw material dosages and preparation methods the same as those in Example 8. Finally, the environmentally friendly wear-resistant coating for railways is obtained.

[0148] Comparative Example 3

[0149] Comparative Example 3 is the control group of Example 8. Remove the modified nanocellulose prepared in Example 5 in the raw materials of Example 8, and keep the other raw materials, raw material dosages and preparation methods the same as those in Example 8. Finally, the environmentally friendly wear-resistant coating for railways is obtained.

[0150] Performance tests were conducted on the environmentally friendly wear-resistant coatings for railways (hereinafter referred to as coatings) prepared in Examples 7 to 9 and Comparative Examples 1 to 3. The performance test process is as follows, and the test results are shown in Table 2:

[0151] Sample preparation: Coat the coating on a steel plate (100×100×1 mm), cure at 80 °C for 2 h, the thickness of the dry film coating is 100 ± 5 μm, and place it at room temperature for 24 h after curing.

[0152] 1. Taber abrasion index (Taber Abrasion, unit: mg):

[0153] (1) Test standard: GB / T 1768;

[0154] (2) Test conditions: Instrument: Taber Abraser 5135 type; Grinding wheel: CS-10 rubber wheel; Load: 1000 g / wheel; Rotation speed: 60 rpm; Number of rotations: 1000 rotations.

[0155] (3) Operation process: Fix the sample on the turntable, let the grinding wheel contact the surface, start the instrument, pause every 250 rotations, clean the grinding debris with a soft brush, and after the test is completed, weigh the mass loss of the sample with an electronic balance (accuracy 0.1 mg).

[0156] (5) Calculation: Taber abrasion index = [mass loss (mg)] × 1000 / number of rotations.

[0157] 2. Adhesion (cross-cut method, grade 0 - 5):

[0158] (1) Test standard: GB / T 9286;

[0159] (2) Steps: Cross-cut tool: multi-edge cutting knife (6 edges, knife spacing 2 mm, tip angle 30°); Cross-cut area: 25×25 mm, forming 11×11 squares.

[0160] (3) Operation process: Cut vertically and uniformly through the dry film coating on the surface of the sample to the steel plate, clean the debris with a soft brush, paste 3M 600-grade tape, press it firmly and quickly peel it off at a 60° angle, observe the area of the squares that fall off, and then classify according to the test results specified in the standard.

[0161] 3. Adhesion after salt spray:

[0162] (1) Steps: Salt spray test: Salt solution: 5% NaCl, pH = 7.2 (25 °C); Test chamber temperature: 35 °C, deposition rate 2 mL / h·80 cm 2 ; Test time: 480 h (20 days).

[0163] (2) Post-treatment: Take out the samples, gently rinse them with deionized water, and dry them at room temperature for 24 h.

[0164] (3) Test the adhesion according to the cross-cut method described above.

[0165] 4. VOCs content (g / L):

[0166] (1) Test standard: GB 30981-2020 (Paints and varnishes);

[0167] (2) Procedure: Take 10 g of the coating, add 200 mL of deionized water, stir and let it stand for stratification; take the upper clear liquid and filter it through a 0.45 μm filter membrane.

[0168] (3) Test process: Test instrument: Gas chromatograph (GC-FID), DB-5 capillary column (30 m × 0.32 mm × 0.25 μm); Test conditions: Injection port 250 °C, detector 300 °C, column temperature program 40 °C (5 min) → 10 °C / min → 280 °C (10 min); Determine the content of VOCs.

[0169] Note: VOCs < 50 g / L meets the environmental protection requirements.

[0170] Table 2 Test results

[0171] Project Example 7 Example 8 Example 9 Comparative Example 1 Comparative Example 2 Comparative Example 3 Taber abrasion index (mg) 45 38 40 162 87 95 Adhesion (cross-cut method) Grade 0 Grade 0 Grade 0 Grade 3 Grade 0 Grade 1 Adhesion after salt spray Grade 0 Grade 0 Grade 0 Grade 4 Grade 2 Grade 3 VOCs content (g / L) 35 32 33 30 34 35

[0172] It can be seen from Table 1 that:

[0173] (1) Taber abrasion index (mg): Example 8 (38 mg) is significantly better than Comparative Example 1 (162 mg), Comparative Example 2 (87 mg) and Comparative Example 3 (95 mg), and the analysis is as follows:

[0174] a. Comparative Example 1 (without epoxy-silicone hybrid resin): The abrasion resistance drops sharply, indicating that the epoxy-silicone hybrid resin effectively disperses the dynamic load stress through its rigid-flexible molecular structure (the silicone chain segment imparts flexibility and the epoxy resin provides rigidity), avoiding brittle cracking of the coating.

[0175] b. Comparative Example 2 (unmodified nanocellulose): The abrasion resistance is inferior to that of Example 8, indicating that the urethane groups on the surface of the modified nanocellulose enhance the interfacial bonding force with the epoxy-silicone hybrid resin, and improve the scratch resistance of the coating through nano-dispersion and physical cross-linking.

[0176] c. Comparative Example 3 (without nanocellulose): The abrasion resistance deteriorates further, indicating that the modified nanocellulose and the epoxy-silicone hybrid resin may form an interpenetrating network, and its nano-scale reinforcement effect inhibits crack propagation, and synergistically improves the abrasion resistance with the epoxy-silicone hybrid resin.

[0177] (2) Adhesion (cross - cut method) and adhesion after salt spray: The initial adhesion and adhesion after salt spray of Example 8 are both grade 0 (the highest grade), while significant deterioration occurs in Comparative Example 1 (grade 3 / 4), Comparative Example 2 (grade 0 / 2), and Comparative Example 3 (grade 1 / 3). The analysis is as follows:

[0178] a. Comparative Example 1 (without epoxy - silicone hybrid resin): Ordinary epoxy resin lacks the flexibility of silicone segments and the strong adhesion of catechol groups, resulting in insufficient chemical bonding between the coating and the metal substrate, and the interface is easily corroded and damaged in a salt spray environment.

[0179] b. Comparative Example 2 (unmodified nanocellulose): The surface hydroxyl groups of unmodified nanocellulose have low activity and poor compatibility with epoxy - silicone hybrid resin. In a salt spray environment, moisture easily penetrates to the interface, weakening the adhesion.

[0180] c. Comparative Example 3 (without nanocellulose): Lack of the physical strengthening effect of nanocellulose, stress concentration occurs inside the coating, and it is more likely to peel off after salt spray corrosion.

[0181] d. Synergistic effect: The catechol groups of epoxy - silicone hybrid resin form coordination bonds with the metal substrate, while modified nanocellulose is covalently connected to epoxy - silicone hybrid resin through urethane bonds. The two jointly construct a dual - interface protection mechanism of "chemical anchoring + physical strengthening", significantly improving the corrosion resistance and metal adhesion of the finally prepared environmentally friendly wear - resistant coating for railways.

[0182] (3) VOCs content (g / L): Example 8 (32 g / L) and Comparative Examples 1 - 3 (30 - 35 g / L) all meet the environmental protection standard (<50 g / L), indicating that VOCs control mainly depends on the compound design of water - based curing agents and solvents.

[0183] (4) Summary:

[0184] a. Epoxy - silicone hybrid resin: Improves fatigue resistance under dynamic loads through the rigid - flexible balance of molecular chains, and its functional groups (catechol) enhance metal - interface adhesion.

[0185] b. Modified nanocellulose: Inhibits crack propagation through nano - reinforcement and interface cross - linking, and forms an interpenetrating network structure with epoxy - silicone hybrid resin.

[0186] c. Synergistic effect: The chemical stability of epoxy - silicone hybrid resin and the physical strengthening effect of nanocellulose are coupled with each other. While reducing VOCs, it realizes the comprehensive improvement of wear resistance, adhesion and salt - spray resistance, breaking through the bottleneck of the performance fragmentation of traditional coatings.

[0187] It should be noted that, in this document, terms such as "including", "comprising", or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device that includes a series of elements not only includes those elements, but also includes other elements that are not explicitly listed, or further includes elements that are inherent to such a process, method, article, or device.

[0188] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An environmentally friendly and wear-resistant coating for railways, characterized in that, It includes raw materials with the following mass percentages: Epoxy-silicone hybrid resin: 45% - 60%; Modified nano-cellulose: 2% - 5%; Waterborne curing agent: 8% - 10%; The balance is solvent.

2. An environmentally friendly wear-resistant coating for railways according to claim 1, characterized in that, The epoxy-silicone hybrid resin is prepared by the following steps: A1. Under a nitrogen atmosphere, stir and mix phenyltrimethoxysilane, tetramethyldisiloxane, and isopropanol, then dropwise add 0.1 mol / L hydrochloric acid aqueous solution thereto, then raise the temperature to 55 - 60 °C, stir at a constant temperature for 3 - 6 h, then adjust the pH of the system to neutral, and then perform vacuum distillation to obtain an organosilicon prepolymer; A2. Mix bisphenol A epoxy resin with the above-mentioned organosilicon prepolymer, then add isopropanol thereto, stir, then add triphenylphosphine thereto, then raise the temperature to 80 - 100 °C, and react for 4 - 5 h to obtain an epoxy resin graft-modified organosilicon prepolymer; A3. Dissolve dopamine hydrochloride in deionized water, then add it to the above-mentioned epoxy resin graft-modified organosilicon prepolymer, adjust the pH of the system to 9.5 - 10.0, after completion, raise the temperature of the system to 70 - 80 °C, then stir at a constant temperature for 6 - 8 h, after completion, perform vacuum distillation again to obtain an epoxy-silicone hybrid resin.

3. An environment-friendly wear-resistant coating for railways according to claim 2, characterized in that, The dosage ratios of phenyltrimethoxysilane, tetramethyldisiloxane, isopropanol, 0.1 mol / L hydrochloric acid aqueous solution, bisphenol A epoxy resin, isopropanol, triphenylphosphine, dopamine hydrochloride, and deionized water are 115 - 125 g: 75 - 85 g: 100 mL: 50 mL: 500 g: 100 - 150 mL: 0.5 - 1.0 g: 22 - 25 g: 250 mL.

4. An environmentally friendly wear-resistant coating for railways according to claim 1, characterized in that, The modified nano-cellulose is prepared by the following steps: B1. Stir and disperse microcrystalline cellulose in a 64% sulfuric acid solution by mass fraction, control the temperature at 45 - 50 °C, react at a constant temperature for 1 - 2 h, then add deionized water thereto, and then collect the precipitate by centrifugation and wash the precipitate with pure water until it is neutral to obtain nano-cellulose gel; B2. Mix the nano-cellulose gel with a 5% NaOH solution by mass fraction, raise the temperature of the system to 50 - 60 °C and stir for 50 - 60 min, then wash by centrifugation until it is neutral and freeze-dry to obtain nano-cellulose powder; B3. Disperse the nano-cellulose powder in anhydrous ethanol, then perform ultrasonic treatment, then add hexamethylene diisocyanate and dibutyltin dilaurate thereto, raise the temperature to 70 - 75 °C under nitrogen protection, stir and react at a constant temperature for 6 - 8 h, after completion, immediately cool it in an ice bath to 5 - 10 °C, then add deionized water thereto, collect the precipitate by centrifugation, then wash the precipitate three times with ethanol and acetone respectively, collect the precipitate, and after the precipitate is vacuum-dried, obtain modified nano-cellulose.

5. An environmentally friendly wear-resistant coating for railways according to claim 4, characterized in that, The dosage ratios of microcrystalline cellulose, 64% sulfuric acid solution by mass fraction, and deionized water in B1 are 100 g: 500 mL: 2000 mL.

6. An environmentally friendly wear-resistant coating for railways according to claim 4, characterized in that, The dosage ratios of nano-cellulose gel and 5% NaOH solution by mass fraction in B2 are 50 g: 500 mL.

7. An environment-friendly wear-resistant coating for railways according to claim 4, characterized in that, The dosage ratio of the nanocellulose powder, absolute ethanol, hexamethylene diisocyanate, dibutyltin dilaurate, and deionized water described in B3 is 20 g: 500 mL: 18 - 20 g: 0.3 - 0.5 g: 100 mL.

8. An environmentally friendly wear-resistant coating for railways according to claim 1, characterized in that, The aqueous curing agent is Curing agent of type XTJ-506 or Huntsman EDR-176.

9. The environmentally friendly wear-resistant coating for railways according to claim 1, characterized in that, The solvent is prepared by compounding deionized water and propylene glycol methyl ether acetate according to a volume ratio of 3:1 - 2.

10. The preparation method of an environmentally friendly wear-resistant coating for railways according to any one of claims 1 to 9, characterized in that, It includes the following steps: Weigh each raw material according to the mass percentage, stir epoxy - organosilicon hybrid resin and modified nanocellulose into the solvent, stir at a high speed of 2000 rpm for 20 - 30 min, then stir and add a water - borne curing agent thereto, stir at a low speed of 800 rpm for 20 - 30 min to obtain a slurry. Then transfer the slurry to a vacuum degassing machine, evacuate to - 0.095 MPa and maintain for 25 - 30 min, and assist with ultrasonic degassing. After completion, an environmentally friendly wear - resistant coating for railways is obtained.

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