Polyurea elastomeric topcoat and method of making and use thereof

Abstract

This invention belongs to the field of elastic topcoat technology, specifically relating to a polyurea elastic topcoat, its preparation method, and its application. The polyurea elastic topcoat raw materials include a paint and a curing agent. The polyurea elastic topcoat of this invention comprises a ternary blend resin system formed by polyurea resin, hyperbranched hydroxyl polyester resin, and organosilicon resin, combined with wear-resistant fillers, reinforcing fillers, wetting and dispersing agents, leveling agents, UV absorbers, light stabilizers, matting agents, and diluents to form the paint. The elastic topcoat obtained by mixing and curing the paint with a flexible aliphatic isocyanate prepolymer has advantages such as good stone impact resistance, good elasticity, strong stress release capability, high elongation, impact resistance, wear resistance, water resistance, moisture resistance, acid and alkali resistance, salt spray resistance, and good weather resistance.

Description

Technical Field

[0001] This invention belongs to the field of elastic topcoat technology, specifically relating to a polyurea elastic topcoat, its preparation method, and its application. Background Technology

[0002] Elastic topcoat is a type of coating with elastic properties, typically formulated with synthetic resin emulsion as a base, along with pigments, fillers, and additives. Its elasticity primarily comes from its unique resin emulsion and additive system, allowing the coating to deform to a certain extent without cracking under external forces. Due to its high elasticity, water resistance, and weather resistance, it is widely used in building exteriors, wind turbine blade surfaces, and rail transit axles.

[0003] Currently, the coatings used on rail transit vehicle axles consist of an epoxy primer and an acrylic polyurethane topcoat system. Due to the low elasticity of this system, it exhibits poor stress release under high-frequency vibration, leading to quality problems such as coating cracking and paint peeling after a period of operation, resulting in a short service life. Furthermore, the strict requirements of the spraying application site mean that recoating increases construction costs. Summary of the Invention

[0004] This invention proposes a polyurea elastic topcoat, its preparation method, and its application, to solve at least one aspect of the above-mentioned technical problems.

[0005] This invention is achieved through the following technical solution:

[0006] In a first aspect, the present invention provides a polyurea elastic topcoat, the raw materials of which include paint and curing agent;

[0007] The paint is composed of the following components in parts by weight:

[0008]

[0009] The curing agent comprises 75 to 85 parts by weight of an aliphatic isocyanate prepolymer.

[0010] In some possible implementations, the polyurea resin is an aspartic polyurea resin.

[0011] In some possible implementations, the wear-resistant filler is one or more of nano-silicon carbide and nanocrystalline carbon powder.

[0012] In some possible implementations, the reinforcing filler is one or more of carbon black, nano-silica, calcium carbonate, ceramic fiber, and carbon fiber.

[0013] In some possible implementations, the adjuvant comprises the following components in weight fractions:

[0014] 1 to 2 parts wetting and dispersing agent, 0.2 to 0.5 parts leveling agent, 0.8 to 1.2 parts ultraviolet absorber, 1 to 1.5 parts light stabilizer, 0 to 3 parts matting agent, 0 to 17 parts pigment and 10 to 15 parts diluent.

[0015] In some possible implementations, the curing agent further includes 15 to 25 parts by weight of xylene.

[0016] In some possible implementations, the pigment is in the form of 13 to 17 parts by weight.

[0017] In some possible implementations, the diluent is a mixture of PMA and DBE.

[0018] In a second aspect, the present invention provides a method for preparing the polyurea elastic topcoat provided in the first aspect of the present invention, comprising the following steps:

[0019] The polyurea elastic topcoat is obtained by spraying and curing a coating containing the paint and the curing agent.

[0020] The mass ratio of the paint to the curing agent is 100:(75-100).

[0021] In some possible implementations, the viscosity of the spray coating is 40s-60s (Ford Cup 6).

[0022] In some possible implementations, the spraying step includes a spraying pressure of 0.4 MPa to 0.6 MPa, a spray width of 10 cm to 12 cm, a spraying distance of 15 cm to 30 cm, an overlap range of 1 / 2 to 1 / 3, a spraying angle of 90° ± 1°, and a nozzle diameter of 0.6 mm to 1.0 mm.

[0023] In some possible implementations, the steps for preparing the paint include:

[0024] The mixture containing resin slurry, the wear-resistant filler, and the reinforcing filler is ground and then filtered to obtain the paint.

[0025] The resin slurry contains polyurea resin, hyperbranched hydroxyl polyester resin, silicone resin, and additives.

[0026] In the grinding step, the average particle size of the mixture after grinding is less than 30 μm.

[0027] In some possible implementations, in the step of preparing the paint, the grinding step involves grinding the mixture until the average particle size is 20 μm to 30 μm.

[0028] In some possible implementations, the steps for preparing the resin slurry include:

[0029] The polyurea resin, the hyperbranched hydroxyl polyester resin, the silicone resin and the additives are mixed and treated to obtain a pre-dispersed slurry;

[0030] The pre-dispersed slurry is ground to an average particle size of less than 10 μm and filtered to obtain the resin slurry.

[0031] Thirdly, the present invention provides an application of the polyurea elastic topcoat provided in the first aspect of the present invention on a rail transit vehicle axle.

[0032] The polyurea elastic topcoat and its preparation method of the present invention have at least the following beneficial technical effects compared with the prior art:

[0033] (1) The polyurea elastic topcoat of the present invention comprises a ternary blended resin system of polyurea resin, hyperbranched hydroxyl polyester resin and organosilicon resin, and a paint material formed by combining wear-resistant filler, reinforcing filler, wetting and dispersing agent, leveling agent, ultraviolet absorber, light stabilizer, matting agent and diluent. The elastic topcoat obtained by mixing and curing the paint material with a flexible aliphatic isocyanate prepolymer has the advantages of good stone impact resistance, good elasticity, strong stress release ability, high elongation, impact resistance, wear resistance, water resistance, moisture resistance, acid and alkali resistance, salt spray resistance and good weather resistance.

[0034] (2) The polyurea elastic topcoat of the present invention has good elasticity and weather resistance. The paint film obtained by the cross-linking and curing of the amino group in the polyurea resin and the isocyanate group in the curing agent has good elasticity and weather resistance.

[0035] (3) The polyurea elastic topcoat of the present invention has an interpenetrating network structure obtained by the interaction and reaction of its components, which balances the elasticity and rigidity of the paint film and has a high degree of density. As a result, the polyurea elastic topcoat has good elasticity, wear resistance and weather resistance, which can fully meet the relevant requirements of rail transit coatings for axle paints. In addition, the high elasticity can greatly increase the service life of the polyurea elastic topcoat.

[0036] (4) The preparation method of the polyurea elastic topcoat of the present invention, in the step of preparing the paint, firstly, the raw materials including polyurea resin, hyperbranched hydroxyl polyester resin, organosilicon resin, wetting and dispersing agent, leveling agent, ultraviolet absorber, light stabilizer, matting agent and diluent are made into a resin slurry with a particle size of less than 10 μm, and then mixed and ground with wear-resistant filler and reinforcing filler, with a larger grinding particle size; this sequential grinding method not only maintains the performance of each component in the resin slurry, but also maintains the performance of the wear-resistant filler and reinforcing filler themselves (wear resistance of wear-resistant filler and mechanical properties of reinforcing filler); thus, the elastic topcoat made has the advantages of good stone crushing resistance, good elasticity, strong stress release ability, high elongation, impact resistance, wear resistance, water resistance, moisture resistance, acid and alkali resistance, salt spray resistance and good weather resistance. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this application clearer, the following description and illustration are provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0038] Obviously, the following description is merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios without any inventive effort. Furthermore, it is understood that although the effort involved in such development may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0039] However, there may be instances where unnecessary detailed descriptions are omitted. For example, detailed descriptions of well-known matters or repetitive descriptions of essentially the same structure may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to enable those skilled in the art to fully understand this application and is not intended to limit the subject matter of the claims.

[0040] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions, and all technical features and optional technical features of this application can be combined to form new technical solutions.

[0041] The term "coating" refers to polyurea elastic topcoat.

[0042] The viscosity data of the spray coatings involved in this application were all obtained when the temperature of the spray coating was around 25°C.

[0043] For rail transit axles that operate in harsh environments (high-frequency washing and friction, wind and sand impact, etc.), the performance requirements for coatings are even more stringent. However, existing hydroxyl acrylic resin / aliphatic isocyanate systems are sensitive to temperature and humidity, and are prone to cracking, paint peeling, and other problems when exposed to harsh environments, resulting in a short service life.

[0044] Aspartic polyurea is the third generation of polyurea, following aromatic and aliphatic polyurea. Aspartic polyurea is an elastomer containing urea bonds, formed by the reaction of secondary amine groups on polyaspartic ester resin with isocyanate. It possesses excellent properties such as high elasticity, water resistance, corrosion resistance, wear resistance, and impact resistance. Compared to hydroxyl acrylic resin / aliphatic isocyanate systems, aspartic polyurea is less sensitive to temperature and humidity, does not contain organotin drying agents, and is free of heavy metals, exhibiting better environmental friendliness.

[0045] To balance the requirements of coating lifespan and environmental protection, this invention provides a polyurea elastic topcoat and its preparation method. The polyurea elastic topcoat has advantages such as good stone impact resistance, good elasticity, strong stress release capability, high elongation, impact resistance, wear resistance, water resistance, moisture resistance, acid and alkali resistance, salt spray resistance, and good weather resistance.

[0046] The following is a detailed description of a polyurea elastic topcoat and its preparation method according to an embodiment of the present invention.

[0047] Polyurea Elastic Topcoat

[0048] The first aspect of this invention provides a polyurea elastic topcoat, the raw materials of which include paint and curing agent;

[0049] The paint is composed of the following components in parts by weight:

[0050]

[0051] The curing agent comprises 75 to 85 parts by weight of an aliphatic isocyanate prepolymer.

[0052] An embodiment of the present invention provides a polyurea elastic topcoat, comprising a ternary blend resin system of polyurea resin, hyperbranched hydroxyl polyester resin, and silicone resin, combined with wear-resistant filler, reinforcing filler, wetting and dispersing agent, leveling agent, ultraviolet absorber, light stabilizer, matting agent, and diluent to form the paint material. The elastic topcoat obtained by mixing and curing the paint material with a flexible aliphatic isocyanate prepolymer has advantages such as good stone chip resistance, good elasticity, strong stress release capability, high elongation, impact resistance, wear resistance, water resistance, moisture resistance, acid and alkali resistance, salt spray resistance, and good weather resistance.

[0053] In the examples, the polyurea resin is 35 to 40 parts by weight, which can be typical but not limiting, such as 35, 38, or 40 parts by weight, or any range between two weights. In this case, the amino groups in the polyurea resin react with the isocyanate groups in the curing agent to crosslink and cure into a film. The coating film formed by the combination of aspartic polyurea resin and aliphatic elastic curing agent has good elasticity and excellent weather resistance.

[0054] In the embodiments, the hyperbranched hydroxyl polyester resin is 10 to 15 parts by weight, which can be typical but not limiting weights such as 10 parts, 14 parts, or 10 parts, or any range between two weights. In this case, the hydroxyl groups in the hyperbranched hydroxyl polyester resin react with the isocyanate groups in the curing agent to crosslink and cure into a film. The hyperbranched polyester has high bond energy, good thermal and chemical stability, thereby enhancing the film's chemical resistance, scrub resistance, and abrasion resistance. Furthermore, the hyperbranched hydroxyl polyester has a small molecular weight. Compared with ordinary hydroxyl acrylic resin, the hyperbranched hydroxyl polyester resin has a high solids content, good flexibility and mechanical properties, and can effectively reduce the pressure on the film when subjected to external forces such as scrubbing and friction.

[0055] In the embodiments, the silicone resin is 3 to 5 parts by weight, which can be a typical but non-limiting number of parts by weight, such as 3, 4, or 5 parts, or any range between two parts by weight. In this case, the silicone resin has a certain degree of miscibility with polyurea resin and hyperbranched hydroxyl polyester resin. At the same time, the silicone resin has a smooth surface and good slip properties, which can reduce the coefficient of friction. It also has a good defoaming effect on the coating system, so no additional defoamer needs to be added.

[0056] In the embodiments, the abrasion-resistant filler is 5 to 7.5 parts by weight, which can be a typical but non-limiting number of parts by weight such as 5 parts, 6 parts, or 7.5 parts, or any range between two parts by weight. In this case, the abrasion-resistant filler can improve the abrasion resistance, stone chip resistance, and hardness of the polyurea elastic topcoat.

[0057] In the embodiments, the reinforcing filler is 5 to 8 parts by weight, which can be a typical but not limiting number of parts by weight, such as 5 parts or 8 parts, or any range between two parts by weight. In this case, the reinforcing filler can improve the tear resistance and tensile strength of the elastic paint film, while reducing the gloss of the paint film and increasing the interlayer adhesion of the paint film.

[0058] In the embodiments, the additive is present in parts by weight of 14.5 to 23.2 parts, and can be a typical but non-limiting part by weight such as 15.5 parts, 16 parts, or 20 parts, or any range between two parts by weight. In this case, the additive can improve the solution stability of the paint, reduce the coefficient of friction of the polyurea elastic topcoat under stress, and improve the service life of the polyurea elastic topcoat.

[0059] In the examples, the aliphatic isocyanate prepolymer is present in a weight ratio of 75 to 85 parts, which can be a typical but not limiting weight ratio such as 75 parts, 80 parts, or 85 parts, or any range between two weight ratios. In this case, the amino groups in the polyurea resin react with the isocyanate groups in the curing agent to crosslink and cure into a film.

[0060] In some embodiments, the polyurea resin is aspartic polyurea resin. In this case, aspartic polyurea resin has a faster curing speed than hydroxyl polyurethane, but when used in conjunction with a flexible curing agent, the curing time is extended to more than 45 minutes, which is longer than the curing time of ordinary two-component polyurea (5 minutes to 30 minutes). This provides a longer working time for spraying, meeting the time requirements for paint used in rail transit vehicle axle coating. At the same time, no additional drying agent needs to be added, and it is not sensitive to humidity and temperature, and has the characteristics of being environmentally friendly and having low requirements for the construction environment. Furthermore, aspartic polyurea resin has high solids content, thick coating in one application, and dense film after film formation, which can effectively block the intrusion of small molecules such as water vapor and oxygen. The paint film has excellent elasticity, tensile and impact strength, flexibility, wear resistance, weather resistance, and corrosion resistance.

[0061] In some embodiments, the wear-resistant filler is one or more of nano-silicon carbide and nanocrystalline carbon powder. In this case, the wear-resistant filler still has extremely high hardness despite its extremely fine particle size, which can significantly improve the wear resistance of the paint film, thereby improving the paint film's resistance to stone impact and wind and sand.

[0062] In some embodiments, the reinforcing filler is one or more of carbon black, nano-silica, calcium carbonate, ceramic fiber, and carbon fiber. In this case, the reinforcing filler gives the paint film better adhesion and mechanical properties, and improves its impact resistance.

[0063] In some embodiments, the adjuvant comprises the following components by weight fraction:

[0064] 1 to 2 parts wetting and dispersing agent, 0.2 to 0.5 parts leveling agent, 0.8 to 1.2 parts ultraviolet absorber, 1 to 1.5 parts light stabilizer, 0 to 3 parts matting agent, 0 to 17 parts pigment and 10 to 15 parts first diluent.

[0065] Among the above-mentioned additives, wetting and dispersing agents have excellent wetting and dispersing properties for other organic and inorganic components, and also have good dispersion properties for matting agents and anti-hardening sedimentation effects; leveling agents give the polyurea elastic topcoat film good slip properties after film formation, and can reduce the coefficient of friction of the film under stress; the synergistic effect of ultraviolet absorbers and light stabilizers can effectively convert high-energy ultraviolet light energy into kinetic energy, and then into heat energy, thereby protecting the chemical bonds of the film from damage and extending the life of the film; matting agents reduce the gloss of the film surface, forming a matte or matte effect; and thinners reduce the viscosity of the paint.

[0066] In some specific embodiments, the wetting and dispersing agent is BYK163 from BYK GmbH, Germany. In this case, the wetting and dispersing agent is a high-molecular block deflocculating wetting and dispersing agent, which has good wetting and dispersing properties for organic and inorganic pigments and fillers. At the same time, it has a neutral pH value and does not affect the drying and curing time of the coating. Acidic and alkaline dispersing aids often have a drying effect on polyurea elastic topcoats, which can cause defects in the paint film during storage and application.

[0067] In some specific embodiments, the leveling agent is BYK333 from BYK GmbH, Germany. In this case, the leveling agent is a well-compatible silicone leveling agent, which provides good slip properties after the paint film is formed and can reduce the coefficient of friction of the paint film under stress.

[0068] In some specific embodiments, the ultraviolet absorber is RIASORB UV-1130 from Tianjin Lianlong Company.

[0069] In some specific embodiments, the light stabilizer is RIASORB UV-292 from Tianjin Lianlong Company.

[0070] In some specific embodiments, the matting agent is present in parts by weight of 1.5 to 3 parts.

[0071] In some specific embodiments, the matting agent is OK-520 from Evonik GmbH, Germany.

[0072] In some embodiments, the pigment is present in parts by weight of 13 to 17 parts. In exemplary cases, it can be typical but not limiting parts by weight such as 13 parts, 15 parts, or 17 parts, or any range between two parts by weight. It should be noted that the color of the pigment can be selected as needed. For example, the pigment color can be DuPont titanium dioxide R706 for white and Degussa FW200 for black.

[0073] In some specific embodiments, the first diluent is a mixture of PMA and DBE. In some specific embodiments, the mass ratio of PMA to DBE is (1-1.2):1. In this case, the diluent has the advantages of strong polarity and strong dissolving ability, and it does not contain benzene solvents, making it highly environmentally friendly. At the same time, the high flash points of PMA and DBE solvents better meet the safety requirements of the production line.

[0074] PMA: Propylene Glycol Methyl Ether Acetate.

[0075] DBE: Abbreviation for high-boiling-point solvent mixed dicarboxylic acid ester (DuPont calls it DBE), which is a mixture of dicarboxylic acid esters composed of dimethyl succinate, dimethyl glutarate and dimethyl adipate, with a distillation range of 195℃~225℃.

[0076] In some embodiments, the curing agent is Desmodur E 30700 from Bayer AG, Germany. In this case, the curing agent provides good elasticity, elongation, tensile strength, etc., for the elastic topcoat for rail vehicle axles while ensuring non-yellowing and weather resistance.

[0077] In some embodiments, the curing agent further includes 15 to 25 parts by weight of xylene, which, in exemplary cases, can be typical but not limiting parts by weight such as 15, 20, or 25, or any range between two parts by weight.

[0078] In some embodiments, the thickness of the polyurea elastic topcoat is 100μm to 130μm. In this case, the polyurea elastic topcoat can adapt to operation under harsh climatic conditions such as wind and sand damage at various high altitudes, ultraviolet radiation damage, coastal salt spray, humid corrosion, and acid and alkaline environments. It can also withstand cleaning with a wide range of pH cleaning agents without significant changes to the paint film over a long period of time.

[0079] [A method for preparing a polyurea elastic topcoat]

[0080] A second aspect of this invention provides a method for preparing a polyurea elastic topcoat, comprising the following steps:

[0081] S1. The coating material containing paint and hardener is sprayed and then cured to obtain the polyurea elastic topcoat;

[0082] The mass ratio of paint to hardener is 100:(75-100).

[0083] An embodiment of the present invention provides a method for preparing a polyurea elastic topcoat, wherein in the step of preparing the paint,

[0084] In some embodiments, the step of preparing the paint in step S1 above includes:

[0085] S11. Grind and filter the mixture containing resin slurry, wear-resistant filler and reinforcing filler to obtain paint;

[0086] The resin slurry contains polyurea resin, hyperbranched hydroxyl polyester resin, silicone resin, and additives.

[0087] The average particle size of the mixture after grinding is below 30μm.

[0088] The above-mentioned steps for preparing the paint first involve preparing a resin slurry from polyurea resin, hyperbranched hydroxyl polyester resin, silicone resin, and additives, and then mixing and grinding it with wear-resistant fillers and reinforcing fillers. This sequential grinding method preserves the properties of each component in the resin slurry, as well as the properties of the wear-resistant fillers and reinforcing fillers themselves (wear resistance of the wear-resistant fillers and mechanical properties of the reinforcing fillers). As a result, the elastic topcoat produced has advantages such as good stone chip resistance, good elasticity, strong stress release ability, high elongation, impact resistance, wear resistance, water resistance, moisture resistance, acid and alkali resistance, salt spray resistance, and good weather resistance.

[0089] In some embodiments, the step of preparing the resin slurry in step S11 above includes:

[0090] S1101. A pre-dispersed slurry is obtained by mixing polyurea resin, hyperbranched hydroxyl polyester resin, silicone resin and additives.

[0091] S1102. Grind the pre-dispersed slurry to an average particle size of less than 10 μm, filter, and obtain resin slurry.

[0092] The above steps prepare polyurea resin, hyperbranched hydroxyl polyester resin, silicone resin and additives into a resin slurry with a particle size of less than 10μm. The ultrafine particles of polyurea resin, hyperbranched hydroxyl polyester resin, silicone resin and additives can improve the elasticity, stress release ability, elongation, impact resistance, water resistance, moisture resistance, acid and alkali resistance, salt spray resistance and weather resistance of polyurea elastic topcoat.

[0093] In some embodiments, in step S1101 above, the mixing process involves mixing polyurea resin, hyperbranched hydroxyl polyester resin, silicone resin, and additives at a speed of 500 rpm to 800 rpm, and then dispersing the mixture at a speed of 1000 rpm to 1200 rpm for 5 to 8 minutes to obtain a pre-dispersed slurry. It should be noted that the speed, time, etc., in the mixing process can be adjusted according to actual conditions, as long as the polyurea resin, hyperbranched hydroxyl polyester resin, silicone resin, and additives are mixed evenly, and are not limited to the scope defined in the embodiments of the present invention.

[0094] In some embodiments, in step S1102 above, the filter screen used for filtration is 180 mesh. It should be noted that the mesh size of the filter screen can be selected according to the actual situation, as long as it can achieve the purpose of filtering and removing impurities and large particles in the pre-dispersed slurry, and is not limited to the scope defined in the embodiments of the present invention.

[0095] In some embodiments, in step S11 above, the step of preparing the mixture is as follows: the resin slurry, wear-resistant filler, and reinforcing filler are mixed at a speed of 300 rpm to 500 rpm, and then dispersed at a speed of 800 rpm to 1000 rpm for 5 min to 8 min to obtain the mixture. It should be noted that the speed, time, etc. in preparing the mixture can be adjusted according to the actual situation, as long as the resin slurry, wear-resistant filler, and reinforcing filler are mixed evenly, and are not limited to the scope defined in the embodiments of the present invention.

[0096] In some embodiments, in step S11 above, the average particle size of the mixture after grinding is 20 μm to 30 μm.

[0097] In some embodiments, the filter used in step S11 is a 120-mesh screen. It should be noted that the mesh size of the filter can be selected according to actual conditions, as long as it achieves the purpose of filtering and removing impurities and large particles from the mixture, and is not limited to the scope defined in the embodiments of the present invention.

[0098] In some embodiments, the step of preparing the curing agent in step S1 above includes:

[0099] The aliphatic isocyanate prepolymer and xylene were mixed at a rotation speed of 500 rpm to 800 rpm and then dispersed at a rotation speed of 1000 rpm to 1200 rpm for 5 min to 8 min to obtain the curing agent. It should be noted that the rotation speed, time, etc., in the curing agent preparation step can be adjusted according to actual conditions, as long as the aliphatic isocyanate prepolymer and xylene are mixed evenly, and are not limited to the scope specified in the embodiments of this invention. Furthermore, if the curing agent only contains the aliphatic isocyanate prepolymer, this preparation is unnecessary.

[0100] In some embodiments, in step S1 above, the viscosity of the sprayed coating is 40s to 60s (tested using a Forecast cup 6). In this case, it exhibits good storage stability; low viscosity makes it prone to sedimentation, while high viscosity makes it difficult to disperse by stirring.

[0101] In some embodiments, the spray coating material further includes a second thinner in step S1 described above. In this case, the thinner is used to adjust the viscosity of the spray coating material to 22s to 24s (tested using a Forco 4 cup) for subsequent spraying.

[0102] In some specific embodiments, the components of the second diluent are the same as those of the first diluent, which is a mixture of PMA and DBE, with a mass ratio of PMA to DBE of (1 to 1.2):1.

[0103] In some embodiments, in step S1 above, the spraying step includes a spraying pressure of 0.4 MPa to 0.6 MPa, a spray width of 10 cm to 12 cm, a spraying distance of 15 cm to 30 cm, an overlap range of 1 / 2 to 1 / 3, a spraying angle of 90° ± 1°, and a nozzle diameter of 0.6 mm to 1.0 mm.

[0104] Pressure refers to the pressure supplied by the spray gun, which determines the degree of paint atomization and the spraying effect.

[0105] Spray width refers to the width of the paint spread on the work surface when the spray gun is used for spraying.

[0106] Spraying distance refers to the distance between the spray gun nozzle and the object being sprayed.

[0107] Overlap range refers to the overlapping portion between two adjacent sprays during each spraying process.

[0108] Spraying angle refers to the angle between the spray gun nozzle and the object being sprayed.

[0109] Nozzle diameter refers to the diameter of the nozzle exit point of the spray gun.

[0110] In some embodiments, the spraying time in step S1 is 45 minutes or more. In this case, it can meet the requirements of small-batch spraying of rail transit components (such as axles, roof covers, etc.) and also meet the requirements of pipeline spraying, with a smooth and flat paint film appearance.

[0111] In some embodiments, in step S1 above, the curing temperature is 20°C to 25°C and the curing time is 12h to 16h.

[0112] In some embodiments, a method for preparing a polyurea elastic topcoat is provided, comprising the following steps:

[0113] S10. Preparation of paint:

[0114] ① Preparation of resin slurry: At a speed of 500 rpm to 800 rpm, aspartic polyurea resin, hyperbranched hydroxyl polyester resin, organosilicon resin, wetting and dispersing agent, leveling agent, ultraviolet absorber, light stabilizer, matting agent and diluent are mixed and dispersed at a speed of 1000 rpm to 1200 rpm for 5 min to 8 min to obtain a pre-dispersed slurry; the pre-dispersed slurry is ground to an average particle size of less than 10 μm and filtered through a 180 mesh screen to obtain the resin slurry.

[0115] ② Mix the resin slurry, wear-resistant filler and reinforcing filler at a speed of 300 rpm to 500 rpm, and disperse at a speed of 800 rpm to 1000 rpm for 5 min to 8 min to obtain a mixture; grind the mixture to an average particle size of 20 μm to 30 μm, filter it through a 120 mesh screen to obtain the paint.

[0116] (2) Preparation of curing agent: The aliphatic isocyanate prepolymer and xylene are mixed at a speed of 500 rpm to 800 rpm and dispersed at a speed of 1000 rpm to 1200 rpm for 5 min to 8 min to obtain the curing agent.

[0117] (3) Mix the paint, hardener and thinner into a spray coating and then spray it;

[0118] The mass ratio of paint to hardener is 100:(75-100);

[0119] The diluent is a mixture of PMA and DBE in a volume ratio of 1:1;

[0120] The viscosity of the spray coating is 40s to 60s (Ford Cup 6);

[0121] The spraying pressure is 0.4MPa~0.6MPa, the spray width is 10cm~12cm, the spraying distance is 15cm~30cm, the overlap range is 1 / 2~1 / 3, the spraying angle is 90°±1°, and the nozzle diameter is 0.6mm~1.0mm.

[0122] (4) Curing at a temperature of 20℃~25℃ for 12h~16h yields polyurea elastic topcoat.

[0123] The following description, in conjunction with specific embodiments, provides further details.

[0124] In the following specific embodiments, the aspartic polyurea resin is NH2886 produced by Covestro; the hyperbranched hydroxyl polyester resin is HPE 1170B produced by BASF; the silicone resin is SH9611 produced by Hubei Longsheng Sihai New Materials Co., Ltd.; the wear-resistant filler is GCF1200# produced by Shandong Jinmeng New Materials Co., Ltd.; the reinforcing filler is HB-152 produced by Hubei Huifu Nanomaterials Co., Ltd.; the wetting and dispersing agent and the leveling agent are BYK163 and BYK333 produced by BYK GmbH, Germany, respectively; the UV absorber and the light stabilizer are RIASORB@UV-1130 and RIASORB@UV-292 produced by Tianjin Lianlong Co., Ltd., respectively; the matting agent is OK-520 produced by Evonik GmbH, Germany; the curing agent is Desmodur@E 30700 produced by Bayer AG, Germany; and the solvent is xylene, PMA (propylene glycol methyl ether acetate), and DBE (diester mixture) produced by Jiangsu Sanmu Chemical Co., Ltd. The pigment is DuPont titanium dioxide R706.

[0125] Example 1

[0126] Example 1 provides a polyurea elastic topcoat, the raw materials of which consist of paint and curing agent; the components and weight parts of the paint and curing agent are shown in Table 1 below.

[0127] The diluent is a mixture of PMA and DBE, with a mass ratio of PMA to DBE of 1:1.

[0128] Example 1 also provides a method for preparing the polyurea elastic topcoat provided in this example, the steps of which are as follows:

[0129] (1) Preparation of paint:

[0130] ① Preparation of resin slurry: At a speed of 700 rpm, aspartic polyurea resin, hyperbranched hydroxyl polyester resin, silicone resin, BYK163, BYK333, RIASORB UV-1130, RIASORB UV-292, OK-520, titanium dioxide R706 and the first diluent are mixed and dispersed at a speed of 1100 rpm for 7 min to obtain a pre-dispersed slurry; the pre-dispersed slurry is ground to an average particle size of less than 10 μm and filtered through a 180-mesh filter to obtain the resin slurry.

[0131] ② At a speed of 400 rpm, the resin slurry, wear-resistant filler and reinforcing filler are mixed and dispersed at a speed of 900 rpm for 8 minutes to obtain a mixture; the mixture is ground to an average particle size of 20 μm to 30 μm and filtered through a 120-mesh filter to obtain a paint.

[0132] (2) Preparation of curing agent: The aliphatic isocyanate prepolymer and xylene were mixed at a speed of 700 rpm and dispersed at a speed of 1200 rpm for 6 min to obtain the curing agent.

[0133] (3) Mix the paint, hardener and second thinner into a spray coating and then spray it.

[0134] The mass ratio of paint to hardener is 100:80.

[0135] The second diluent is a mixture of PMA and DBE in a mass ratio of 1:1;

[0136] The viscosity of the spray coating is 55s (Ford Cup 6);

[0137] The spraying pressure is 0.5MPa, the spray width is 11cm, the spraying distance is 20cm, the overlap is 1 / 3, the spraying angle is 90°±1°, and the nozzle diameter is 0.8mm.

[0138] (4) Curing at 22℃ for 15 hours yields polyurea elastic topcoat.

[0139] Example 2

[0140] Example 2 provides a polyurea elastic topcoat, the raw materials of which consist of paint and curing agent; the components and weight parts of the paint and curing agent are shown in Table 1 below.

[0141] The first diluent is a mixture of PMA and DBE, with a mass ratio of PMA to DBE of 1:1.

[0142] Example 2 also provides a method for preparing the polyurea elastic topcoat provided in this example, the steps of which are basically the same as those in Example 1.

[0143] Example 3

[0144] Example 3 provides a polyurea elastic topcoat, the raw materials of which consist of paint and curing agent; the components and weight parts of the paint and curing agent are shown in Table 1 below.

[0145] The diluent is a mixture of PMA and DBE, with a mass ratio of PMA to DBE of 1:1.

[0146] Example 3 also provides a method for preparing the polyurea elastic topcoat provided in this example, the steps of which are basically the same as those in Example 1.

[0147] Example 4

[0148] Example 4 provides a polyurea elastic topcoat with the same composition as in Example 1.

[0149] Example 4 also provides a method for preparing the polyurea elastic topcoat provided in this example. The steps are basically the same as those in Example 1, except that:

[0150] In step (3), the viscosity of the spray coating is 40s;

[0151] The spraying pressure is 0.4MPa, the spray width is 10cm, the spraying distance is 30cm, the overlap is 1 / 3, the spraying angle is 90°±1°, and the nozzle diameter is 0.6mm.

[0152] The curing temperature in step (4) is 25℃ and the curing time is 16h to obtain polyurea elastic topcoat.

[0153] Example 5

[0154] Example 5 provides a polyurea elastic topcoat with the same composition as in Example 1.

[0155] Example 5 also provides a method for preparing the polyurea elastic topcoat provided in this example. The steps are basically the same as those in Example 1, except that:

[0156] In step (3), the viscosity of the spray coating is 60s;

[0157] The spraying pressure is 0.6MPa, the spray width is 12cm, the spraying distance is 15cm, the overlap is 1 / 2, the spraying angle is 90°±1°, and the nozzle diameter is 1mm.

[0158] The curing temperature in step (4) is 20℃ and the curing time is 12h to obtain polyurea elastic topcoat.

[0159] Example 6

[0160] Example 6 provides a polyurea elastic topcoat with the same composition as in Example 1.

[0161] Example 6 also provides a method for preparing the polyurea elastic topcoat provided in this example. The steps are basically the same as those in Example 1, except that:

[0162] In step (3), the viscosity of the spray coating is 50s;

[0163] The spraying pressure is 0.45MPa, the spray width is 12cm, the spraying distance is 18cm, the overlap is 1 / 3, the spraying angle is 90°±1°, and the nozzle diameter is 0.7mm.

[0164] The curing temperature in step (4) is 23℃ and the curing time is 15h, resulting in polyurea elastic topcoat.

[0165] Comparative Example 1

[0166] Comparative Example 1 provides a polyurea elastic topcoat, the composition of which is shown in Table 1 below.

[0167] Comparative Example 1 also provides a method for preparing the polyurea elastic topcoat provided in this embodiment, the steps of which are basically the same as those in Example 1.

[0168] Comparative Example 2

[0169] Comparative Example 2 provides a polyurea elastic topcoat, the composition of which is shown in Table 1 below.

[0170] Comparative Example 2 also provides a method for preparing the polyurea elastic topcoat provided in this embodiment, the steps of which are basically the same as those in Example 1.

[0171] Comparative Example 3

[0172] Comparative Example 3 provides a polyurea elastic topcoat with the same composition as Example 1, as shown in Table 1 below.

[0173] Comparative Example 3 also provides a method for preparing the polyurea elastic topcoat provided in this embodiment. The steps are basically the same as those in Example 1, except that:

[0174] In step (1) when preparing the paint, aspartic polyurea resin, hyperbranched hydroxyl polyester resin, silicone resin, wear-resistant filler, reinforcing filler, BYK163, BYK333, RIASORB UV-1130, RIASORB UV-292, OK-520, titanium dioxide R706 and the first diluent are mixed and ground until the average particle size is below 10μm to obtain the paint.

[0175] Comparative Example 4

[0176] Comparative Example 4 provides a polyurea elastic topcoat with the same composition as Example 1, as shown in Table 1 below.

[0177] Comparative Example 4 also provides a method for preparing the polyurea elastic topcoat provided in this embodiment. The steps are basically the same as those in Example 1, except that:

[0178] In step (1) when preparing the paint, aspartic polyurea resin, hyperbranched hydroxyl polyester resin, silicone resin, wear-resistant filler, reinforcing filler, BYK163, BYK333, RIASORB UV-1130, RIASORB UV-292, OK-520, titanium dioxide R706 and the first diluent are mixed and ground until the average particle size is 20μm to 30μm to obtain the paint.

[0179] To verify the advancement of the polyurea elastic topcoat and its preparation method provided in the embodiments of this application, polyurea elastic topcoats prepared according to the polyurea elastic topcoat and its preparation method provided in the embodiments and comparative examples were tested according to the corresponding standards. The test standards and results are shown in Table 2 below. Among them, the performance results of abrasion resistance, salt spray resistance, stone chip resistance and impact resistance of the embodiments and comparative examples are shown in Table 3 below.

[0180] Table 1

[0181]

[0182] Note: In Table 1 above, "*" indicates that the weight of the corresponding component is the same as in Example 1;

[0183] "-" indicates that the component is not used.

[0184] Table 2

[0185]

[0186]

[0187] Table 3

[0188]

[0189] From Tables 2 and 3 above, at least the following conclusions can be drawn:

[0190] (1) A polyurea elastic topcoat according to an embodiment of the present invention, wherein polyurea resin, hyperbranched hydroxyl polyester resin and organosilicon resin form a ternary blend resin system, and the paint is formed by combining wear-resistant filler, reinforcing filler, wetting and dispersing agent, leveling agent, ultraviolet absorber, light stabilizer, matting agent and diluent. The elastic topcoat obtained by mixing and curing the paint with a flexible aliphatic isocyanate prepolymer has the advantages of good stone impact resistance, good elasticity, strong stress release ability, high elongation, impact resistance, wear resistance, water resistance, moisture resistance, acid and alkali resistance, salt spray resistance and good weather resistance.

[0191] (2) A polyurea elastic topcoat according to an embodiment of the present invention, wherein the paint film obtained by the cross-linking and curing of the amino group in the polyurea resin and the isocyanate group in the curing agent has good elasticity and weather resistance.

[0192] (3) In an embodiment of the present invention, a polyurea elastic topcoat is obtained by the interaction and reaction of the components to form an interpenetrating network structure, which balances the elasticity and rigidity of the paint film and has a high degree of density. As a result, the polyurea elastic topcoat has good elasticity, wear resistance, and weather resistance, and can fully meet the relevant requirements for axle paints in rail transit coatings. In addition, the high elasticity can greatly increase the service life of the polyurea elastic topcoat.

[0193] (4) A method for preparing a polyurea elastic topcoat according to an embodiment of the present invention, wherein in the step of preparing the paint, the raw materials of polyurea resin, hyperbranched hydroxyl polyester resin, organosilicon resin, wetting and dispersing agent, leveling agent, ultraviolet absorber, light stabilizer, matting agent and diluent are first made into a resin slurry with a particle size of less than 10 μm, and then mixed and ground with wear-resistant filler and reinforcing filler, with a larger grinding particle size; this sequential grinding method maintains the performance of each component in the resin slurry, as well as the performance of the wear-resistant filler and reinforcing filler themselves (wear resistance of wear-resistant filler and mechanical properties of reinforcing filler); thereby making the prepared elastic topcoat have the advantages of good stone crushing resistance, good elasticity, strong stress release ability, high elongation, impact resistance, wear resistance, water resistance, moisture resistance, acid and alkali resistance, salt spray resistance and good weather resistance.

[0194] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A polyurea elastic topcoat, characterized in that, The raw materials include paint and hardener; The paint is composed of the following components in parts by weight: 35-40 parts polyurea resin, 10-15 parts hyperbranched hydroxyl polyester resin, 3-5 parts silicone resin, 5-7.5 parts wear-resistant filler, 5-8 parts reinforcing filler, 14.5-40.2 parts additives; The curing agent comprises 75 to 85 parts by weight of aliphatic isocyanate prepolymer and 15 to 25 parts by weight of xylene; The polyurea resin is aspartic polyurea resin; The thickness of the polyurea elastic topcoat is 100μm~130μm; The hyperbranched hydroxyl polyester resin is HPE 1170B manufactured by BASF. The wear-resistant filler is one or more of nano-silicon carbide and nanocrystalline carbon powder; The reinforcing filler is one or more of carbon black, nano silica, calcium carbonate, ceramic fiber, and carbon fiber; The additives comprise the following components in parts by weight: 1 to 2 parts wetting and dispersing agent, 0.2 to 0.5 parts leveling agent, 0.8 to 1.2 parts ultraviolet absorber, 1 to 1.5 parts light stabilizer, 1.5 to 3 parts matting agent, 13 to 17 parts pigment, and 10 to 15 parts diluent; The diluent is a mixture of PMA and DBE, with a mass ratio of PMA to DBE of 1 to 1.2:

1.

2. A method for preparing a polyurea elastic topcoat as described in claim 1, characterized in that, Includes the following steps: The polyurea elastic topcoat is obtained by spraying and curing a coating containing the paint and the curing agent. The mass ratio of the paint to the curing agent is 100:(75~100).

3. The method for preparing polyurea elastic topcoat according to claim 2, characterized in that, The viscosity of the spray coating is 40s~60s.

4. The method for preparing polyurea elastic topcoat according to claim 3, characterized in that, In the spraying step, the spraying pressure is 0.4MPa~0.6MPa, the spray width is 10cm~12cm, the spraying distance is 15cm~30cm, the overlap range is 1 / 2~1 / 3, the spraying angle is 90°±1°, and the nozzle diameter is 0.6mm~1.0mm.

5. The method for preparing polyurea elastic topcoat according to any one of claims 2 to 4, characterized in that, The steps for preparing the paint include: The mixture containing resin slurry, the wear-resistant filler, and the reinforcing filler is ground and then filtered to obtain the paint. The resin slurry contains polyurea resin, hyperbranched hydroxyl polyester resin, silicone resin, and additives. In the grinding step, the average particle size of the mixture after grinding is less than 30 μm.

6. The method for preparing polyurea elastic topcoat according to claim 5, characterized in that, In the step of preparing the paint, the grinding step involves grinding until the average particle size of the mixture is 20μm~30μm.

7. The method for preparing polyurea elastic topcoat according to claim 6, characterized in that, The steps for preparing the resin slurry include: The polyurea resin, the hyperbranched hydroxyl polyester resin, the silicone resin and the additives are mixed and treated to obtain a pre-dispersed slurry; The pre-dispersed slurry is ground to an average particle size of less than 10 μm and filtered to obtain the resin slurry.

8. The application of the polyurea elastic topcoat as described in claim 1 on a rail vehicle axle.

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