Corrosion-resistant spraying material applied to railway freight cars and preparation method thereof

Abstract

The application belongs to the technical field of spraying materials, and particularly discloses a kind of corrosion-resistant spraying materials applied to railway freight cars and a preparation method thereof.The corrosion-resistant spraying material applied to railway freight cars provided by the application comprises component A and component B, component A comprises terminal isocyanate-based polyether type prepolymer and diphenylmethane-4,4'-diisocyanate;the terminal isocyanate-based polyether type prepolymer is prepared by reacting polyol compound and diphenylmethane-4,4'-diisocyanate;the polyol compound comprises polypropylene glycol, glycerol type polyether polyol and polyether polyol with a functionality of greater than or equal to 4.5.Component B comprises polyoxypropylene polyether polyol and diethyl toluene diamine.The application provides a corrosion-resistant, impact-resistant and strongly adhesive corrosion-resistant spraying material applied to railway freight cars by reasonably designing material components, which can effectively block corrosive media and protect the car body, and is suitable for complex railway freight transport scenarios.

Description

Technical Field

[0001] This invention belongs to the field of spraying materials technology, specifically relating to a corrosion-resistant spraying material for railway freight cars and its preparation method. Background Technology

[0002] In the existing technology, railway freight cars are mostly open wagons, and water-based paint is often used to coat the car body. However, due to the characteristics of railway freight cars such as large load capacity, mechanized loading and unloading, long transportation distances and large environmental differences, after a period of use, railway freight cars coated with water-based paint often suffer from severe corrosion and damage to the car body, requiring the replacement of some steel plates, thus shortening the service life of railway freight cars.

[0003] Statistics show that after two factory overhaul periods, railway freight cars suffer from severe corrosion in parts such as end plates, upper side plates, side column reinforcement plates, floor, doors, side column connecting irons, and lower side beams. The plate replacement rate is as high as 70% or more, which seriously shortens the service life of railway freight cars.

[0004] Therefore, how to design a railway freight car coating material with excellent corrosion resistance, impact resistance and strong adhesion to block corrosive media, protect the car body and increase the service life of railway freight cars has become a key technical bottleneck in the application of coating materials in the field of railway freight cars. Summary of the Invention

[0005] To address the shortcomings of traditional railway freight car coating materials, this invention provides a corrosion-resistant coating material for railway freight cars with excellent corrosion resistance, impact resistance, and strong adhesion, as well as its preparation method.

[0006] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a corrosion-resistant spraying material for railway freight cars, comprising component A and component B; Component A includes isocyanate-terminated polyether prepolymer and diphenylmethane-4,4'-diisocyanate; The terminal isocyanate-based polyether prepolymer is prepared by reacting a polyol complex with diphenylmethane-4,4'-diisocyanate; wherein the polyol complex includes polypropylene glycol, glycerol-type polyether polyol, and polyether polyol with a functionality ≥ 4.5.

[0007] Component B includes polyoxypropylene polyether polyol and diethyltoluene diamine; The polypropylene glycol provided by this invention, as a flexible segment, primarily offers elasticity, reduces system viscosity, improves processing flowability, and enhances the low-temperature flexibility of the final product. Glyceryl polyether polyol, as the base polyol, provides moderate crosslinking density and mechanical strength. Polyether polyols with a functionality ≥4.5, as high-functionality, high-rigidity segments, achieve complementary performance advantages through the scientific blending of polyether polyols with different functionalities, molecular structures, and segment flexibility in this composite polyol composition.

[0008] The addition of polypropylene glycol effectively reduces the high viscosity of high-functionality polyol systems and improves mixing efficiency with other components such as isocyanates. Glyceryl polyols provide basic strength, polyether polyols with a functionality ≥4.5 impart high hardness and dimensional stability, and polypropylene glycol contributes elasticity, resulting in a final product with both good load-bearing capacity and moderate flexibility. It also provides high crosslinking density, enhances the dimensional stability, load-bearing strength, and heat resistance of the product.

[0009] This invention provides a corrosion-resistant spraying material for railway freight cars, achieved through a rationally designed two-component formulation. This material exhibits excellent corrosion resistance, impact resistance, and strong adhesion. The corrosion-resistant spraying material provided by this invention effectively blocks corrosive media, protects the car body, and extends the service life of railway freight cars, making it suitable for complex railway freight car transportation scenarios.

[0010] Preferably, the preparation method of the isocyanate-terminated polyether prepolymer includes the following steps: Polypropylene glycol, glycerol-type polyether polyol and polyether polyol with a functionality ≥4.5 were dehydrated, mixed evenly, homogenized and degassed, and filtered to obtain a polyol complex. The polyol complex and diphenylmethane-4,4'-diisocyanate were subjected to a prepolymerization reaction to obtain the terminal isocyanate-based polyether prepolymer.

[0011] This invention, by dehydrating the polyol complex, eliminates the interference of moisture on isocyanate, ensuring precise and controllable subsequent prepolymerization reactions, preventing bubble formation, and avoiding abnormal gelation of the system. In this invention, long-chain polypropylene glycol, glycerol-type polyether polyol, and polyether polyol with a functionality ≥4.5 are linked together by diphenylmethane-4,4'-diisocyanate to form a polymer backbone with isocyanate groups at its ends. This provides a precise and calculable chemical reaction point for subsequent chain extension with component B and mixing with free diphenylmethane-4,4'-diisocyanate. The isocyanate-terminated polyether prepolymer prepared by this invention exhibits high crosslinking density, enhanced dimensional stability, load-bearing strength, and heat resistance of the product. In the prepolymerization reaction system, the isocyanate-terminated polyether prepolymer of this invention, together with the free diphenylmethane-4,4'-diisocyanate in component A, constitutes a reaction system capable of low-temperature construction and rapid reaction with amine curing agents to form a high-strength elastomer.

[0012] Preferably, the dehydration treatment temperature is 60~80℃ and the dehydration treatment time is 1~3h.

[0013] Preferably, the dehydration vacuum degree is ≥-0.095MPa.

[0014] More preferably, the moisture content after the dehydration treatment is <0.05%.

[0015] Preferably, the mixing speed is 50~200 rpm.

[0016] Preferably, the mixing temperature is 40~60℃ and the mixing time is 30~90min.

[0017] Preferably, the homogenizing stirring speed is 300~600 rpm and the stirring time is 20~40 min.

[0018] Preferably, the degassing vacuum degree is -0.09 to -0.098 MPa, and the time is 20 to 40 minutes.

[0019] Preferably, the filtration uses a 100-300 mesh filter.

[0020] The polyol complex prepared under the preparation conditions provided in this invention is homogeneous and bubble-free, which can completely eliminate the interference of moisture on diphenylmethane-4,4'-diisocyanate, ensuring precise control of the subsequent prepolymerization reaction and curing process. This is beneficial to improving the reaction efficiency with diphenylmethane-4,4'-diisocyanate, avoiding abnormal gelation of the system, and thus ensuring that the final corrosion-resistant material obtains the designed dense structure, stable storage performance and excellent mechanical properties.

[0021] Preferably, the raw materials for preparing the terminal isocyanate-based polyether prepolymer include the following components in parts by weight: 20-50 parts of polypropylene glycol, 25-60 parts of glycerol-based polyether polyol, 15-40 parts of polyether polyol with a functionality ≥ 4.5, and 50-80 parts of diphenylmethane-4,4'-diisocyanate.

[0022] The mass fraction of raw materials in the terminal isocyanate polyether prepolymer provided by this invention determines the proportion of functional groups in the prepolymerization reaction and the monomer sequence distribution in the prepolymer chain segments, thereby giving the terminal isocyanate polyether prepolymer significant advantages in terms of flexibility and strength.

[0023] Preferably, the temperature of the prepolymerization reaction is 70~85℃, and the reaction time is 2~4h.

[0024] The prepolymerization reaction conditions provided by this invention are more conducive to controlling the reaction rate and avoiding local overheating and non-uniform molecular chain structure caused by excessively fast reaction.

[0025] Preferably, the number-average molecular weight of the polypropylene glycol is 400 to 4000.

[0026] More preferably, the number-average molecular weight of the polypropylene glycol is 1000-3000.

[0027] Preferably, the hydroxyl value of the polypropylene glycol is 28~280 mg KOH / g.

[0028] Preferably, component A comprises 50-70 parts of isocyanate-terminated polyether prepolymer and 25-30 parts of diphenylmethane-4,4'-diisocyanate.

[0029] Preferably, component B comprises 35-65 parts of polyoxypropylene polyether polyol and 25-36 parts of diethyltoluene diamine.

[0030] Preferably, the mass ratio of component A to component B is 1:0.8~1.2.

[0031] In this invention, the isocyanate-terminated polyether prepolymer provides a precise and calculable chemical reaction point for subsequent chain extension with component B and mixing with free diphenylmethane-4,4'-diisocyanate. The free diphenylmethane-4,4'-diisocyanate acts as an active diluent, significantly reducing the overall viscosity of component A, making it easier to mix uniformly with component B. The synergistic design of the internal prepolymer and free diphenylmethane-4,4'-diisocyanate enables the corrosion-resistant material to achieve high strength, high toughness, and high wear resistance. By rationally adjusting the weight ratio of each component, this invention constructs a three-dimensional network structure with excellent cross-linking properties. This structure provides the required cross-linking density, mechanical strength, and corrosion resistance for corrosion-resistant spray coating materials used in railway freight cars, improving processing fluidity and the low-temperature flexibility, wear resistance, dimensional stability, load-bearing strength, and heat resistance of the final product.

[0032] Preferably, component B further includes 0-1 parts of an organometallic catalyst.

[0033] Preferably, the organometallic catalyst is at least one of an organotin catalyst or an organobismuth catalyst.

[0034] More preferably, the organometallic catalyst is an organotin catalyst.

[0035] The present invention preferably uses an organometallic catalyst that can effectively promote the formation of elastomer networks without excessively interfering with the formation of urea bonds.

[0036] Preferably, the glycerol-type polyether polyol has a number-average molecular weight of 300-600 and a hydroxyl value of 280-560 mg KOH / g.

[0037] Preferably, the polyether polyol with a functionality of ≥4.5 has a number average molecular weight of 400-800 and a hydroxyl value of 350-500 mgKOH / g.

[0038] Preferably, the polyoxypropylene polyether polyol has a number-average molecular weight of 400-4000 g / mol, a hydroxyl value of 350-500 mg KOH / g, and a functionality of 2-4.

[0039] Preferably, the polyether polyol with a functionality of ≥4.5 is a polyether polyol with sucrose macromolecules.

[0040] The glycerol-type polyether polyol, the polyether polyol with a functionality of ≥4.5 and the polyoxypropylene polyether polyol provided by this invention have different reactivity, realizing an orderly and controllable curing process of first shaping, then toughening, and then strengthening.

[0041] Secondly, the present invention provides a method for preparing a corrosion-resistant coating material for railway freight cars, comprising the following steps: The isocyanate-terminated polyether prepolymer was mixed with diphenylmethane-4,4'-diisocyanate to obtain component A. Polyoxypropylene polyether polyol and diethyltoluene diamine are mixed evenly to obtain component B; According to the design ratio, components A and B are mixed to obtain a corrosion-resistant coating material for railway freight cars.

[0042] The corrosion-resistant spraying material prepared by this invention for use in railway freight cars is a two-component solvent-free coating. Furthermore, the preparation method of the corrosion-resistant spraying material for use in railway freight cars is simple, and the separate preparation of component A and component B is more conducive to improving the applicability of the spraying process.

[0043] Preferably, in component A, the mixing temperature is 40~50℃ and the mixing time is 1~2h.

[0044] Preferably, in component B, the mixing temperature is 20~30℃, and the mixture is mixed until homogeneous.

[0045] Thirdly, the present invention provides a method for applying a corrosion-resistant coating material to railway freight cars, comprising the following steps: Step 1: Spray a primer / pre-coating material onto the surface of the railway freight car and allow it to dry. Step 2: Spray the corrosion-resistant coating material used for railway freight cars. After drying, check the thickness of the corrosion-resistant coating material used for railway freight cars. If the thickness is ≤2000μm, re-spray the corrosion-resistant coating material used for railway freight cars until the thickness is 2000~2300μm.

[0046] Preferably, the spraying method for corrosion-resistant coating materials applied to railway freight cars is as follows: Figure 1 As shown.

[0047] The corrosion-resistant coating material and spraying method for railway freight cars provided by this invention are more suitable for the inner surfaces of freight cars transporting corrosive materials. It can ensure that the replacement rate of open wagon plates does not exceed 15% during the second maintenance period of railway freight cars, and the 25-year vehicle lifespan can basically reach 100%. In the prior art, paint is sprayed on end plates, upper side plates, side corners or side pillar reinforcement plates, floors, doors, side pillar connecting irons, lower side beams, etc., where corrosion is severe, the plate replacement rate reaches more than 70%, and the 25-year vehicle lifespan does not exceed 20%, which is far lower than that of this invention.

[0048] Preferably, in step one, the thickness of the special primer pre-coating material for spraying is 30~50μm.

[0049] Preferably, in step two, the thickness is the total thickness of the primer and the corrosion-resistant coating material applied to railway freight cars after spraying and drying.

[0050] Preferably, in step one, the special primer pre-coating material is at least one of a two-component epoxy-modified polyurethane primer or a polyurethane-phosphating primer. Preferably, the two-component epoxy-modified polyurethane primer and polyurethane-phosphating primer are provided by Shanghai Huntsman Polyurethane Co., Ltd.

[0051] Preferably, in step one, the drying temperature is 70~80℃, the humidity is 35%~45%, and the time is 1~2 hours.

[0052] Preferably, in step two, the total thickness of the corrosion-resistant coating material applied to railway freight cars is 2000~2300μm.

[0053] Preferably, in step two, the drying temperature is 50~60℃, the humidity is 20%~30%, and the time is 15~30min.

[0054] Preferably, in step two, the total thickness of the corrosion-resistant coating material applied to railway freight cars after touch-up spraying is 2000~2300μm.

[0055] Within the temperature and humidity range provided by this invention, the reaction time is short and the adhesion is high, without changing the existing vehicle painting process.

[0056] Preferably, in step two, the instrument used for spraying corrosion-resistant coating materials applied to railway freight cars is at least one of the following: MIXPAC MS series two-component static mixer, KXH-200L power mixing equipment, or DH-1000L power mixing equipment.

[0057] Preferably, in step two, the instrument used to detect the thickness of the corrosion-resistant coating material applied to railway freight cars is a coating thickness gauge. Attached Figure Description

[0058] Figure 1 This is a flow chart illustrating the spraying process of the corrosion-resistant coating material applied to railway freight cars in an embodiment of the present invention. Figure 2 This is a test diagram of the adhesion performance of a corrosion-resistant spraying material applied to railway freight cars in an embodiment of the present invention; Figure 3 The figures shown are the results of vertical impact test and lateral impact test in the impact resistance test of the corrosion-resistant spraying material applied to railway freight cars in this embodiment of the invention; wherein Figure A is the vertical impact test figure and Figure B is the lateral impact test figure. Figure 4Figure 1 shows the simulated loading test results of the corrosion-resistant spraying material applied to railway freight cars in an embodiment of the present invention; Figure C shows the coal powder residue on the surface of the sample box after unloading coal powder in the 115℃ test box; Figure D shows the coal powder residue on the surface of the sample box after unloading coal powder in the 170℃ test box. Figure 5 This is a diagram showing the simulated unloading test results of the corrosion-resistant spraying material applied to railway freight cars in an embodiment of the present invention. Figure 6 Figure 1 shows the results of a replacement test in the maintenance and inspection of corrosion-resistant sprayed materials applied to railway freight cars in an embodiment of the present invention; Figure E shows the damage to the coating caused by flame cutting, and Figure F shows the damage to the coating caused by plasma cutting. Figure 7 The figures shown are welding test results in the maintenance and inspection of corrosion-resistant spraying materials applied to railway freight cars in this embodiment of the invention; Figure H is a front view of the weld, and Figure I is a back view of the weld. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0060] The polypropylene glycol, glycerol-type polyether polyol, sucrose macromolecular polyether polyol, and polyoxypropylene polyether polyol used in the following examples were purchased from Shanghai Huntsman Polyurethane Co., Ltd.; the two-component epoxy-modified polyurethane primer and polyurethane-phosphating primer were purchased from Shanghai Huntsman Polyurethane Co., Ltd.; the organotin catalyst was purchased from Shandong Xinhe New Materials Co., Ltd., and the organobismuth catalyst was purchased from Shanghai Deyin Chemical Co., Ltd.; all other compounds or related reagents used were commercially available.

[0061] Example 1 This embodiment provides a corrosion-resistant coating material for railway freight cars and its preparation method, the details of which are as follows: I. This embodiment provides a corrosion-resistant spraying material for railway freight cars, which includes component A and component B, with a weight ratio of component A to component B of 1:1.08.

[0062] Component A contains the following components in parts by weight: 70 parts of isocyanate-terminated polyether prepolymer and 30 parts of diphenylmethane-4,4'-diisocyanate; Component B comprises the following components in parts by weight: 65 parts polyoxypropylene polyether polyol, 25 parts diethyltoluene diamine, and 1 part organotin catalyst; The raw material for the terminal isocyanate-based polyether prepolymer in component A contains the following components in parts by weight: 20 parts polypropylene glycol, 60 parts glycerol-based polyether polyol, 15 parts sucrose-based macromolecular polyether polyol, and 80 parts diphenylmethane-4,4'-diisocyanate.

[0063] The glycerol-type polyether polyol has a number-average molecular weight of 450, a hydroxyl value of 450 KOH / g, and a functionality of 3. The polyether polyols with sucrose macromolecules have a number-average molecular weight of 600, a hydroxyl value of 400 mg KOH / g, and a functionality of 5. The polyoxypropylene polyether polyol has a number-average molecular weight of 900 g / mol, a hydroxyl value of 420 mg KOH / g, and a functionality of 3.

[0064] Polypropylene glycol, glycerol-type polyether polyol, and sucrose-based macromolecular polyether polyol were dehydrated at 80°C and a vacuum of -0.095 MPa for 3 hours until the moisture content decreased to 0.05%. 20 parts of the dried polypropylene glycol, 60 parts of the glycerol-type polyether polyol, and 15 parts of the sucrose-based macromolecular polyether polyol were accurately weighed, mixed thoroughly, and transferred to a mixing tank. The mixture was stirred at 200 rpm and 40°C for 90 minutes to obtain a homogeneous and transparent mixed solution. The stirring speed was then increased to 300 rpm and stirred continuously for 40 minutes to ensure complete miscibility of the components. A vacuum of -0.09 MPa was set for 40 minutes to remove air bubbles, followed by filtration through a 300-mesh molecular sieve. The temperature was lowered to 30°C, and the mixture was discharged under nitrogen protection to obtain a pretreated polyol mixture.

[0065] The obtained pretreated polyol mixture was heated to 60°C, and 80 parts of diphenylmethane-4,4'-diisocyanate were added. The mixture was reacted at 70°C for 4 hours to obtain the terminal isocyanate-based polyether prepolymer. After cooling to 40°C, 30 parts of diphenylmethane-4,4'-diisocyanate were added to 70 parts of the terminal isocyanate-based polyether prepolymer, and the reaction was continued for 1 hour to obtain component A.

[0066] Component B was obtained by mixing 65 parts of polyoxypropylene polyether polyol, 25 parts of diethyltoluene diamine and 1 part of organotin catalyst at 20 degrees Celsius.

[0067] II. This embodiment provides a method for applying a corrosion-resistant coating material to railway freight cars, including the following steps: The internal mechanical parts of the railway freight cars were shot-blasted using a centrifugal shot blasting machine to remove rust, achieving a surface cleanliness level no lower than Sa21 / 2 as specified in GB / T8923.1 "Visual Assessment of Surface Cleanliness of Steel Surfaces Before Coating - Part 1: Rust Grades and Treatment Grades of Uncoated Steel Surfaces and Steel Surfaces After Complete Removal of Existing Coatings". Afterwards, the internal surfaces and lower side beams of the railway freight cars were thoroughly cleaned using a vacuum cleaner. A two-component epoxy-modified polyurethane primer with a dry film thickness of 50 μm was then sprayed onto the shot-blasted areas using an air spray gun and dried at 80℃ and 35% humidity for 1 hour.

[0068] Components A and B were mixed at a weight ratio of 1:1.08 and sprayed using a MIXPAC MS series two-component static mixer. The corrosion-resistant coating for railway freight cars was applied sequentially from top to bottom and from center to end, with each subsequent coat covering 50% of the previous coat. The coating was dried for 15 minutes at 60°C and 20% humidity. The total thickness of the corrosion-resistant coating applied to the railway freight cars after drying was 2300 μm.

[0069] After the corrosion-resistant coating material applied to railway freight cars is sprayed, a coating thickness gauge is used to measure the thickness at three points on the side plate, end plate, and bottom plate. An electric spark tester is used to detect any leaks. If a thickness ≤2000μm or a leak is found, the corrosion-resistant coating material applied to the railway freight cars is reapplied immediately. The total thickness of the reapplied corrosion-resistant coating material applied to the railway freight cars is ensured to be 2300μm.

[0070] Example 2 This embodiment provides a corrosion-resistant coating material for railway freight cars and its preparation method, the details of which are as follows: I. This embodiment provides a corrosion-resistant spraying material for railway freight cars, which includes component A and component B, with a weight ratio of component A to component B of 1:1.2.

[0071] Component A contains the following components in parts by weight: 50 parts of isocyanate-terminated polyether prepolymer and 25 parts of diphenylmethane-4,4'-diisocyanate; Component B comprises the following components in parts by weight: 35 parts polyoxypropylene polyether polyol, 36 parts diethyltoluene diamine, and 0.1 parts organic bismuth catalyst; The raw material for the terminal isocyanate-based polyether prepolymer in component A contains the following components in parts by weight: 50 parts polypropylene glycol, 25 parts glycerol-based polyether polyol, 40 parts sucrose-based macromolecular polyether polyol, and 50 parts diphenylmethane-4,4'-diisocyanate.

[0072] The glycerol-type polyether polyol has a number-average molecular weight of 600, a hydroxyl value of 280 KOH / g, and a functionality of 3. The polyether polyol with sucrose macromolecules has a number-average molecular weight of 800, a hydroxyl value of 350 mg KOH / g, and a functionality of 6. The polyoxypropylene polyether polyol has a number-average molecular weight of 4000 g / mol, a hydroxyl value of 350 mg KOH / g, and a functionality of 2.

[0073] Polypropylene glycol, glycerol-type polyether polyol, and sucrose-based macromolecular polyether polyol were dehydrated at 60°C and a vacuum of -0.032 MPa for 1 hour until the moisture content decreased to 0.04%. 50 parts of the dried polypropylene glycol, 25 parts of the glycerol-type polyether polyol, and 40 parts of the sucrose-based macromolecular polyether polyol were accurately weighed, mixed thoroughly, and transferred to a mixing tank. The mixture was stirred at 50 rpm and 60°C for 30 minutes to obtain a homogeneous and transparent mixed solution. The stirring speed was then increased to 600 rpm and stirred continuously for 20 minutes to ensure complete miscibility of the components. A vacuum of -0.098 MPa was set for 20 minutes to remove air bubbles, followed by filtration through a 100-mesh molecular sieve. The temperature was lowered to 20°C, and the mixture was discharged under nitrogen protection to obtain a pretreated polyol mixture.

[0074] The obtained pretreated polyol mixture was heated to 70°C, and 50 parts of diphenylmethane-4,4'-diisocyanate were added. The mixture was reacted at 85°C for 2 hours to obtain the terminal isocyanate-based polyether prepolymer. After cooling to 50°C, 25 parts of diphenylmethane-4,4'-diisocyanate were added to the 50 parts of terminal isocyanate-based polyether prepolymer, and the reaction was continued for 2 hours to obtain component A.

[0075] Component B was obtained by mixing 35 parts of polyoxypropylene polyether polyol, 36 parts of diethyltoluene diamine and 0.1 parts of organic bismuth catalyst at 30 degrees Celsius.

[0076] II. This embodiment provides a method for applying a corrosion-resistant coating material to railway freight cars, including the following steps: The internal mechanical parts of the railway freight cars were shot-blasted using a centrifugal shot blasting machine to remove rust, achieving a surface cleanliness level no lower than Sa21 / 2 as specified in GB / T8923.1 "Visual Assessment of Surface Cleanliness of Steel Surfaces Before Coating - Part 1: Rust Grades and Treatment Grades of Uncoated Steel Surfaces and Steel Surfaces After Complete Removal of Existing Coatings". Afterwards, the internal surfaces and lower side beams of the railway freight cars were thoroughly cleaned using a vacuum cleaner. A polyurethane-phosphating primer was then sprayed onto the shot-blasted areas using an air spray gun, achieving a dry film thickness of 30 μm, and dried at 70℃ and 45% humidity for 2 hours.

[0077] Components A and B were mixed at a weight ratio of 1:1.2 and sprayed using a KXH-200L power mixing equipment. The corrosion-resistant coating for railway freight cars was applied sequentially from top to bottom and from center to end, with each subsequent coat covering 50% of the previous coat. The coating was dried for 30 minutes at 50°C and 30% humidity. The total thickness of the corrosion-resistant coating applied to the railway freight cars after drying was 2000 μm.

[0078] After the corrosion-resistant coating material applied to railway freight cars is sprayed, a coating thickness gauge is used to measure the thickness at three points on the side plate, end plate, and bottom plate. An electric spark tester is used to detect any leaks. If a thickness ≤2000μm or a leak is found, the corrosion-resistant coating material applied to the railway freight cars is promptly reapplied. The total reapplied thickness of the corrosion-resistant coating material applied to railway freight cars is 2000μm.

[0079] Example 3 This embodiment provides a corrosion-resistant coating material for railway freight cars and its preparation method, the details of which are as follows: I. This embodiment provides a corrosion-resistant spraying material for railway freight cars, which includes component A and component B, with a weight ratio of component A to component B of 1:1.1.

[0080] Component A contains the following components in parts by weight: 60 parts of isocyanate-terminated polyether prepolymer and 28 parts of diphenylmethane-4,4'-diisocyanate; Component B comprises the following components in parts by weight: 45 parts polyoxypropylene polyether polyol, 30 parts diethyltoluene diamine, and 0.6 parts organotin catalyst; The raw materials for the terminal isocyanate-based polyether prepolymer in component A include the following components in parts by weight: 40 parts polypropylene glycol, 50 parts glycerol-based polyether polyol, 30 parts sucrose-based macromolecular polyether polyol, and 60 parts diphenylmethane-4,4'-diisocyanate.

[0081] The glycerol-type polyether polyol has a number-average molecular weight of 300, a hydroxyl value of 560 KOH / g, and a functionality of 3. The polyether polyols with sucrose macromolecules have a number-average molecular weight of 400, a hydroxyl value of 500 mg KOH / g, and a functionality of 4.5. The polyoxypropylene polyether polyol has a number-average molecular weight of 400 g / mol, a hydroxyl value of 500 mg KOH / g, and a functionality of 4.

[0082] Polypropylene glycol, glycerol-type polyether polyol, and sucrose-based macromolecular polyether polyol were dehydrated at 60°C and a vacuum of -0.032 MPa for 1 hour until the moisture content decreased to 0.03%. 40 parts of the dried polypropylene glycol, 50 parts of the glycerol-type polyether polyol, and 30 parts of the sucrose-based macromolecular polyether polyol were accurately weighed, mixed thoroughly, and transferred to a mixing tank. The mixture was stirred at 100 rpm and 50°C for 60 minutes to obtain a homogeneous and transparent mixed solution. The stirring speed was then increased to 400 rpm and stirred continuously for 30 minutes to ensure complete miscibility of the components. A vacuum of -0.095 MPa was set for 30 minutes to remove air bubbles, followed by filtration through a 200-mesh molecular sieve. The temperature was lowered to 25°C, and the mixture was discharged under nitrogen protection to obtain a pretreated polyol mixture.

[0083] The obtained pretreated polyol mixture was heated to 65°C, and 60 parts of diphenylmethane-4,4'-diisocyanate were added. The mixture was reacted at 80°C for 3 hours to obtain the terminal isocyanate-based polyether prepolymer. After cooling to 45°C, 28 parts of diphenylmethane-4,4'-diisocyanate were added to the 60 parts of terminal isocyanate-based polyether prepolymer, and the reaction was continued for 1.5 hours to obtain component A.

[0084] Component B was obtained by mixing 45 parts of polyoxypropylene polyether polyol, 30 parts of diethyltoluene diamine and 0.6 parts of organotin catalyst at 25 degrees Celsius.

[0085] II. This embodiment provides a method for applying a corrosion-resistant coating material to railway freight cars, including the following steps: The internal mechanical parts of the railway freight cars were shot-blasted using a centrifugal shot blasting machine to remove rust, achieving a surface cleanliness level no lower than Sa21 / 2 as specified in GB / T8923.1 "Visual Assessment of Surface Cleanliness of Steel Surfaces Before Coating - Part 1: Rust Grades and Treatment Grades of Uncoated Steel Surfaces and Steel Surfaces After Complete Removal of Existing Coatings". Afterwards, the internal surfaces and lower side beams of the railway freight cars were thoroughly cleaned using a vacuum cleaner. A two-component epoxy-modified polyurethane primer was then sprayed onto the shot-blasted areas using an air spray gun, achieving a dry film thickness of 30 μm, and dried at 75℃ and 40% humidity for 2 hours.

[0086] Components A and B were mixed at a weight ratio of 1:1.1 and sprayed using a DH-1000L power mixing equipment. The corrosion-resistant coating for railway freight cars was applied sequentially from top to bottom and from center to end, with each subsequent coat covering 50% of the previous coat. The coating was dried for 20 minutes at 55°C and 25% humidity. The total thickness of the corrosion-resistant coating applied to the railway freight cars after drying was 2100 μm.

[0087] After the corrosion-resistant coating material applied to railway freight cars was sprayed, a coating thickness gauge was used to measure the thickness at three points on the side plate, end plate, and bottom plate. An electric spark tester was used to detect any leaks. If a thickness ≤2000μm or a leak was found, the corrosion-resistant coating material applied to the railway freight cars was promptly reapplied. The total reapplied thickness of the corrosion-resistant coating material applied to the railway freight cars was 2100μm.

[0088] Example of effect The coating effect of the corrosion-resistant coating material for railway freight cars prepared in Example 1 was tested. The coating effect test results of the corrosion-resistant coating materials for railway freight cars in Examples 2 and 3 were the same as those in Example 1.

[0089] 1. Mechanical properties, gelation and surface drying tests of corrosion-resistant spray coating materials applied to railway freight cars. The mechanical properties of the corrosion-resistant coating material applied to railway freight cars were tested in accordance with GB / T23446-2025, and the test results are shown in Table 1.

[0090] The surface drying time is tested according to GB / T23446-2025.

[0091] The gelation time was determined according to GB / T23446-2025.

[0092] Table 1. Statistical table of mechanical properties and gel and surface drying test results of corrosion-resistant spraying materials applied to railway freight cars.

[0093] 2. Testing the coating effect of corrosion-resistant coating materials applied to railway freight cars. This embodiment provides a method for detecting the coating effect of a corrosion-resistant coating material applied to railway freight cars, specifically including the following methods: 2.1 Corrosion Resistance Testing Test specimens and mechanical properties of corrosion-resistant spray coating materials applied to railway freight cars were prepared in accordance with GB / T23446-2025.

[0094] Ten test specimens with a thickness of 2 mm were prepared for corrosion-resistant spraying materials to be used in railway freight cars. Five specimens were taken from each of the two solutions and immersed in 10% hydrochloric acid aqueous solution and 10% sodium hydroxide aqueous solution, respectively. After immersion for 24 hours, tensile strength and elongation at break were tested, and the average value of the test results was recorded.

[0095] The corrosion resistance test results of the corrosion-resistant spraying material applied to railway freight cars are shown in Table 2.

[0096] Table 2. Statistical Table of Corrosion Resistance Test Results of Corrosion-Resistant Spraying Materials Applied to Railway Freight Cars

[0097] The present invention provides a corrosion-resistant spraying material for railway freight cars and a method for testing its spraying effect on railway freight cars. Corrosion resistance tests show that the corrosion-resistant spraying material provided by the present invention maintains good mechanical properties even under extreme conditions such as acids and alkalis, effectively blocking corrosive media and protecting the car body. 2.2. Adhesion performance testing A 2mm thick corrosion-resistant coating material, suitable for railway freight cars, was sprayed onto the inner door of the railway freight car, and its adhesion was then tested in accordance with ISO 4624:2023.

[0098] The adhesion performance test results of corrosion-resistant spraying materials applied to railway freight cars are shown in the figure below. Figure 2 As shown, the area within the rectangle is a surface view of the corrosion-resistant coating material applied to railway freight cars.

[0099] The adhesion performance test results of the corrosion-resistant spraying material applied to railway freight cars are shown in Table 3.

[0100] Table 3. Statistical Table of Adhesion Performance Test Results of Corrosion-Resistant Spray Coatings Applied to Railway Freight Cars

[0101] Figure 2 The results show that the corrosion-resistant spraying material for railway freight cars provided by the present invention is damaged inside the corrosion-resistant spraying material for railway freight cars, and the adhesion test is 5.02 MPa, indicating that its adhesion is strong. The corrosion-resistant spraying material for railway freight cars provided by the present invention has high strength and good adhesion to the surface of railway freight cars.

[0102] 2.3 Impact resistance test Vertical impact test: A 5kg hammer is dropped freely from a height of 1m, 1.5m, and 2m to impact the door panel coated with 2mm of corrosion-resistant material in a vertical direction, and the impact marks are detected. Lateral impact test: Using a sharp object, at a certain angle to the middle door with the sprayed corrosion-resistant material, a lateral impact test is carried out on the door panel with 2mm of sprayed corrosion-resistant material, in accordance with GB / T23446-2009, and the impact marks are detected.

[0103] The results of vertical and lateral impact tests in the impact resistance testing of corrosion-resistant spray coating materials used in railway freight cars are shown in the figure below. Figure 3 As shown, Figure A is a diagram of a vertical impact test, and Figure B is a diagram of a lateral impact test.

[0104] Figures A and B show that the corrosion-resistant coating material for railway freight cars provided by this invention exhibits no surface damage and strong impact resistance after being subjected to vertical and lateral impacts.

[0105] 2.4. High and Low Temperature Performance Testing Six sample blocks, each 30mm x 30mm in size, were prepared. After being coated with a 2mm layer of corrosion-resistant material, three blocks were placed in a high-temperature chamber at 70℃, and the remaining three blocks were placed in a high-temperature chamber at -50℃ for 3.5 days. Tensile and elongation tests were then performed after the initial testing, and the average of the three sample block results was taken as the final result.

[0106] The high and low temperature performance test results of the corrosion-resistant coating material applied to railway freight cars are shown in Table 4.

[0107] Table 4. Statistical Table of High and Low Temperature Performance Test Results of Corrosion-Resistant Spray Coating Materials Applied to Railway Freight Cars

[0108] The data in Table 4 show that the corrosion-resistant coating material for railway freight cars provided by this invention has stable mechanical properties under different environmental temperatures such as extreme cold and extreme heat, and no significant changes have occurred. In practical applications, it will not affect the normal use of railway freight cars under different temperature conditions.

[0109] 2.5. Loading and unloading test Simulated loading test: A 400mm×300mm×300mm sample box was made, and the inner surface was sprayed with a 2mm thick corrosion-resistant coating material used in railway freight cars. After loading coal powder, it was placed in test chambers at 115℃ and 170℃ respectively for 3 hours. After being removed, it was immediately placed on a pressure testing machine. The side and bottom surfaces of the sample box were subjected to the second working condition bulk cargo lateral pressure and vertical total load, i.e., static load + dynamic load + lateral force, according to the requirements of TB / T 3550.2-2019 standard. The pressure was maintained for 30 minutes, and then unloaded to check the coal powder residue on the inner surface of the sample box.

[0110] Simulated unloading test: An excavator with a power of 36.2KW was used to simulate the unloading test of the excavator to check the peeling and scratches at the pressure points of the coating.

[0111] The simulated loading and unloading test results of corrosion-resistant spraying materials applied to railway freight cars are shown in the figure below. Figure 4 As shown; Figure C is a picture of coal powder residue on the surface of the sample box after unloading coal powder in the 115℃ test box; Figure D is a picture of coal powder residue on the surface of the sample box after unloading coal powder in the 170℃ test box.

[0112] The simulated unloading test results of the corrosion-resistant spraying material applied to railway freight cars are shown in the figure below. Figure 5 As shown.

[0113] Figure 4 In the test, sample boxes placed in test chambers at 115℃ and 170℃ respectively, after loading and unloading coal powder under the above test conditions, showed no coal powder adhering to the surface of the sample boxes. The test results indicate that the corrosion-resistant spraying material prepared by this invention for railway freight cars will not soften and adhere to the cargo after the railway freight cars pass through the thawing warehouse in winter.

[0114] Figure 5 In a simulated unloading test using a 36.2KW excavator, the corrosion-resistant coating material applied to railway freight cars showed no peeling or scratches at the contact points. This indicates that the corrosion-resistant coating material provided by this invention has good adhesion and impact resistance, and that high-intensity unloading does not damage the surface of the railway freight car.

[0115] 2.6. Inspection and Testing The replacement and welding methods commonly used in maintenance were employed to conduct maintenance tests on the door panels of railway freight cars coated with corrosion-resistant spray materials.

[0116] Cut-off test: The door panel of the railway freight car, which is coated with corrosion-resistant spray material applied to railway freight cars, is cut using flame cutting and plasma cutting methods to check the damage to the coating at the cut part.

[0117] Welding test: Weld the side of the replacement part that does not have the corrosion-resistant coating material applied to the railway freight car, and then spray the corrosion-resistant coating material applied to the railway freight car. Record the peeling range of the corrosion-resistant coating material applied to the railway freight car.

[0118] The results of the replacement test in the maintenance and inspection of corrosion-resistant spraying materials applied to railway freight cars are as follows: Figure 6 As shown in the figures. Figure E shows the damage to the coating caused by flame cutting, and Figure F shows the damage to the coating caused by plasma cutting.

[0119] The welding test results of corrosion-resistant spray coating materials applied to railway freight cars during maintenance and inspection are shown in the figure below. Figure 7 As shown in the figure. Figure H is the front view of the weld, and Figure I is the back view of the weld.

[0120] Figure 6 and Figure 7 The results show that the door panels of railway freight cars coated with corrosion-resistant materials can be welded normally after flame cutting or plasma cutting, without affecting the normal maintenance of the railway freight cars.

[0121] The flame during the welding process causes a 5cm peeling of the surrounding coating. This small peeling area, high temperature resistance, and strong adhesion effectively protect the substrate.

[0122] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A corrosion-resistant spraying material for railway freight cars, characterized in that, Includes component A and component B: Component A includes isocyanate-terminated polyether prepolymer and diphenylmethane-4,4'-diisocyanate; The terminal isocyanate-based polyether prepolymer is prepared by reacting a polyol complex with diphenylmethane-4,4'-diisocyanate; wherein the polyol complex includes polypropylene glycol, glycerol-type polyether polyol, and polyether polyol with a functionality ≥4.5; Component B includes polyoxypropylene polyether polyol and diethyltoluene diamine.

2. The corrosion-resistant spraying material for railway freight cars as described in claim 1, characterized in that, The preparation method of the terminal isocyanate polyether prepolymer includes the following steps: Polypropylene glycol, glycerol-type polyether polyol and polyether polyol with a functionality ≥4.5 were dehydrated, mixed evenly, homogenized and degassed, and filtered to obtain a polyol complex. The polyol complex and diphenylmethane-4,4'-diisocyanate were subjected to a prepolymerization reaction to obtain the terminal isocyanate-based polyether prepolymer.

3. The corrosion-resistant spraying material for railway freight cars as described in claim 2, characterized in that, The raw materials for preparing the terminal isocyanate-based polyether prepolymer include the following components in parts by weight: 20-50 parts of polypropylene glycol, 25-60 parts of glycerol-type polyether polyol, 15-40 parts of polyether polyol with a functionality ≥ 4.5, and 50-80 parts of diphenylmethane-4,4'-diisocyanate.

4. The corrosion-resistant spraying material for railway freight cars as described in claim 2, characterized in that, The prepolymerization reaction is carried out at a temperature of 70-85°C for 2-4 hours.

5. The corrosion-resistant spraying material for railway freight cars as described in claim 1, characterized in that, Component A comprises 50-70 parts of isocyanate-terminated polyether prepolymer and 25-30 parts of diphenylmethane-4,4'-diisocyanate; Component B comprises 35-65 parts of polyoxypropylene polyether polyol and 25-36 parts of diethyltoluene diamine; The mass ratio of component A to component B is 1:0.8~1.

2.

6. The corrosion-resistant spraying material for railway freight cars as described in claim 5, characterized in that, Component B also includes 0-1 parts of an organometallic catalyst.

7. The corrosion-resistant spraying material for railway freight cars as described in any one of claims 1 to 6, characterized in that, The glycerol-type polyether polyol has a number-average molecular weight of 300-600 and a hydroxyl value of 280-560 mg KOH / g; and / or The polyether polyol with a functionality ≥ 4.5 has a number average molecular weight of 400-800 and a hydroxyl value of 350-500 mg KOH / g; and / or The polyoxypropylene polyether polyol has a number-average molecular weight of 400~4000g / mol, a hydroxyl value of 350~500mg KOH / g, and a functionality of 2~4.

8. The method for preparing the corrosion-resistant spraying material for railway freight cars according to any one of claims 1 to 7, characterized in that, Includes the following steps: The isocyanate-terminated polyether prepolymer was mixed with diphenylmethane-4,4'-diisocyanate to obtain component A. Polyoxypropylene polyether polyol and diethyltoluene diamine are mixed evenly to obtain component B; According to the design ratio, components A and B are mixed to obtain a corrosion-resistant coating material for railway freight cars.

9. The method for applying a corrosion-resistant coating material to railway freight cars according to any one of claims 1 to 7, characterized in that, Includes the following steps: Step 1: Spray a primer / pre-coating material onto the surface of the railway freight car and allow it to dry. Step 2: Spray the corrosion-resistant coating material used for railway freight cars. After drying, check the thickness of the corrosion-resistant coating material used for railway freight cars. If the thickness is ≤2000μm, re-spray the corrosion-resistant coating material used for railway freight cars until the thickness is 2000~2300μm.

10. The method for applying a corrosion-resistant coating material to railway freight cars as described in claim 9, characterized in that, In step one, the thickness of the sprayed primer pre-coating material is 30~50μm; and / or In step one, the primer pre-coating material is at least one of a two-component epoxy-modified polyurethane primer or a polyurethane-phosphating primer; and / or In step two, the total thickness of the corrosion-resistant coating material applied to railway freight cars is 2000~2300μm.

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