Preparation method of spraying surface layer of environment-friendly polyurethane plastic track

Abstract

The invention relates to the technical field of spraying surface layer preparation, and discloses a preparation method of a spraying surface layer of an environment-friendly polyurethane plastic runway, which comprises the following steps: S1, preparation of a component A: adding polyether polyol into a reaction kettle, stirring and heating to 80-160 DEG C, performing dehydration treatment under the vacuum degree of-0.09 MPa, cooling to 40-50 DEG C after dehydration, and performing vacuum drying to obtain a component B; and adding isocyanate (the molar ratio of the isocyanate to the polyether polyol is 1: 1.5), uniformly stirring, heating to 80-85 DEG C, and reacting at constant temperature for 2-4 hours to obtain the environment-friendly polyurethane prepolymer. According to the invention, the use of harmful substances is reduced by selecting environment-friendly raw materials such as polyoxypropylene triol, diphenylmethane diisocyanate (MDI) or toluene diisocynate (TDI) and the like, and environment-friendly dioctyl phthalate (DOP) or an epoxidized soybean oil plasticizer; the thermal degradation risk of the polyether polyol is reduced by a vacuum dehydration technology (-0.09 MPa), and meanwhile, the mixing time is shortened by an ultrasonic-assisted mixing technology, so that the energy consumption and emission are further reduced.

Description

Technical Field

[0001] The invention relates to the technical field of spray surface preparation, in particular to a method for preparing a spray surface of an environmentally friendly polyurethane plastic runway. Background Art

[0002] During the drying and curing process of traditional polyurethane runways, driers such as lead cyclopentane, zinc cyclopentane, zinc isooctanoate, and lead isooctanoate are used. These driers are heavy metals. During long-term outdoor use, the release of heavy metals is inevitable as the materials wear, age, and crack. The increasingly serious acid rain phenomenon has exacerbated the loss of heavy metals, posing a serious threat to groundwater resources and soil, and also causing potential harm to people's health.

[0003] With growing environmental awareness, traditional plastic tracks are no longer able to meet market demand due to the potential presence of hazardous substances and complex manufacturing processes. The production process of traditional plastic tracks often uses large amounts of organic solvents and additives, which can not only harm human health but also pollute the environment.

[0004] Therefore, it is particularly important to develop a method for preparing the spray surface of an environmentally friendly polyurethane plastic runway. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a spray coating layer of an environmentally friendly polyurethane plastic track to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing a spray coating surface layer of an environmentally friendly polyurethane plastic runway, comprising the following steps:

[0007] Step S1: Preparation of Component A: Add polyether polyol to a reaction kettle, stir and heat to 80-160°C, dehydrate under a vacuum of -0.09 MPa, cool to 40-50°C after dehydration, add isocyanate (molar ratio of isocyanate to polyether polyol 1:1.5) and stir evenly, heat to 80-85°C and react at this temperature for 2-4 hours to obtain an environmentally friendly polyurethane prepolymer;

[0008] Step S2: Preparation of component B: polyether polyol, chain extender, plasticizer, ultraviolet absorber, mildew inhibitor, thixotropic agent, silane coupling agent and filler are mixed in order, sheared and ground at high speed, and then heated in vacuum at 60-70° C. for 1-3 hours to obtain a modified mixture;

[0009] Step S3: Mixing and stirring: Component A and Component B are mixed in a mass ratio of 1:3 to 5.5, and an inert amine drier is added and stirred evenly to allow the components to fully react to form a uniform polyurethane coating;

[0010] Step S4: spraying: pour the prepared polyurethane coating into a robotic spraying device, and automatically spray the plastic track base layer in a construction environment with a temperature of 20-30°C and a humidity of 50-70% to form a uniform and smooth surface layer;

[0011] S5 Curing and molding: After spraying, allow the surface layer to cure at 60°C for 24 hours. During the curing process, the components in the polyurethane coating further react to form a surface layer with excellent physical properties and chemical stability.

[0012] Preferably, in the preparation of component A in step S1, the polyether polyol is polyoxypropylene triol with a hydroxyl value of 45-56 mgKOH / g and a molecular weight of 3000-5000; the isocyanate is diphenylmethane diisocyanate (MDI) or toluene diisocyanate (TDI), and its addition amount is 18-25% of the mass of the polyether polyol.

[0013] Preferably, in the preparation of the component B in step S2, the chain extender is a mixture of 1,4-butanediol and ethylenediamine, with a mass ratio of 3:1 to 5:1; the plasticizer is environmentally friendly dioctyl phthalate (DOP) or epoxy soybean oil, and the addition amount is 8-12% of the total mass of the polyether polyol; the ultraviolet absorber is a compound of 2-hydroxy-4-methoxybenzophenone (UV-9) and hindered amine light stabilizer (HALS), with a mass ratio of 1:1.5 to 1:2.

[0014] Preferably, the preparation of the component B in step S2 further comprises: the filler is a mixture of nano-calcium carbonate, silicon micropowder and modified montmorillonite, and the mass ratio of the three is 5:2:1 to 7:3:1;

[0015] The modified montmorillonite is prepared by the following steps:

[0016] The montmorillonite was dispersed in deionized water, 3-5% by mass of silane coupling agent KH-550 was added, ultrasonic treatment was performed at 60° C. for 2 h, and then the mixture was dried and ground to a particle size of ≤50 μm.

[0017] Preferably, in the preparation of component B in step S2, the mildew preventer is a mixture of isothiazolinone derivatives and nano zinc oxide, with a mass ratio of 1:0.5 to 1:1; the thixotropic agent is fumed silica, and the addition amount is 0.3-0.8% of the total mass of component B.

[0018] Preferably, in the mixing and stirring step S3, the inert amine drier is N,N-dimethylcyclohexylamine or bis(2-dimethylaminoethyl) ether, and the added amount is 0.05-0.15% of the total mass of the mixture of components A and B.

[0019] Preferably, in step S4 spraying construction and step S5 curing molding, the spray gun pressure is 0.4-0.6MPa, the spraying thickness is 1.5-3.0mm, and the spraying is completed in 2-3 cross-spraying times. After the last spraying, environmentally friendly EPDM particles with a particle size of 0.5-1.0mm are immediately spread, and the spreading amount is 200-300g / m 2 , forming an anti-slip texture layer after roller pressing and curing;

[0020] Surface post-treatment: spray a polyurethane surface sealant with a mass concentration of 5-8% on the surface of the cured surface, with a spraying amount of 50-80g / m 2 The sealing agent is made by mixing hydroxy acrylic resin and aliphatic isocyanate in a mass ratio of 1:1.2.

[0021] Another technical problem to be solved by the present invention is to provide a surface layer obtained by the above-mentioned preparation method of the spray surface layer of the environmentally friendly polyurethane plastic runway, the surface layer performance indicators of which meet the following requirements: tensile strength ≥ 2.5MPa, elongation at break ≥ 280%, tear strength ≥ 45N / mm, VOC emission ≤ 50μg / m 3 , after 2000h of artificial weathering, the color difference ΔE≤1.5, the density of the surface layer is 1.2-1.4g / cm 3 , Shore A hardness is 55-65, rebound value ≥35%, wet slip coefficient (BPN) ≥75.

[0022] The present invention provides a method for preparing a spray coating surface layer of an environmentally friendly polyurethane plastic track. The method has the following beneficial effects:

[0023] (1) The present invention reduces the use of harmful substances by selecting environmentally friendly raw materials such as polyoxypropylene triol, diphenylmethane diisocyanate (MDI) or toluene diisocyanate (TDI), and environmentally friendly dioctyl phthalate (DOP) or epoxy soybean oil plasticizers; vacuum dehydration technology (-0.09MPa) reduces the risk of thermal degradation of polyether polyols, while ultrasonic-assisted mixing technology reduces mixing time, further reducing energy consumption and emissions.

[0024] (2) The polyurethane surface sealant used in the post-treatment of the surface layer of the present invention is made of hydroxy acrylic resin and aliphatic isocyanate, which further improves the weather resistance and chemical stability of the surface layer, extends the service life, and reduces the environmental burden during maintenance.

[0025] (3) The intelligent mixing algorithm of the present invention monitors the viscosity, temperature and other parameters of the mixture in real time and dynamically adjusts the mixing speed and time to ensure mixing uniformity and reaction sufficiency. Compared with the traditional fixed parameter mixing process, the mixing time can be shortened by 30%-50%. At the same time, the variance of the mixing uniformity is reduced from 0.05-0.1 to 0.01-0.03. The robot automatic spraying technology realizes the precise control of the spraying path, speed and thickness. The spraying thickness error can be controlled within ±0.2mm, which significantly improves the construction efficiency and surface flatness.

[0026] (4) The present invention significantly improves the hardness, wear resistance and impact resistance of the surface layer by optimizing the mixing ratio of component A to component B (1:3-5.5) and adding fillers such as nano calcium carbonate, silicon micropowder and modified montmorillonite; the addition of ultraviolet absorbers (UV-9 and HALS compound) and mildew inhibitors (isothiazolinone derivatives and nano zinc oxide) makes the surface layer have excellent weather resistance and mildew resistance, and is suitable for various climatic conditions; infrared curing technology accelerates the curing speed and improves the curing efficiency, so that the surface layer can achieve excellent physical properties and chemical stability within 24 hours under heating conditions of 60°C.

[0027] (5) The present invention realizes continuous and stable spraying operation through robotic automatic spraying equipment, reduces dependence on manual operation, reduces human errors, and introduces intelligent hybrid algorithm and infrared curing technology to make the preparation process more automated and intelligent, reducing operation difficulty and labor intensity. The use of environmentally friendly raw materials and additives reduces the emission of harmful substances and ensures the health and safety of construction workers. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Flow chart of the method of the present invention;

[0029] Figure 2 This is a table showing the performance comparison between the preparation process of component A in step S1 of the method of the present invention and the traditional method;

[0030] Figure 3 This is a table showing the performance comparison between the preparation process of component B in step S2 of the method of the present invention and the traditional method;

[0031] Figure 4 This is a table showing a performance comparison of the mixing and stirring process in step S3 of the method of the present invention compared with the traditional method;

[0032] Figure 5 This is a table view comparing the performance of the spraying construction process in step S4 of the present invention with that of the traditional method;

[0033] Figure 6This is a table view comparing the performance of the curing molding process in step S5 of the present invention with that of the traditional method. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but are not to be construed as limiting the present invention.

[0036] A preferred embodiment of the method for preparing the spray coating surface layer of an environmentally friendly polyurethane plastic runway provided by the present invention is as follows: Figure 1-6 As shown: A method for preparing a spray coating surface layer of an environmentally friendly polyurethane plastic runway, comprising the following steps:

[0037] Step S1: Preparation of Component A: Add polyether polyol to a reaction kettle, stir and heat to 80-160°C, dehydrate under a vacuum of -0.09 MPa, cool to 40-50°C after dehydration, add isocyanate (molar ratio of isocyanate to polyether polyol 1:1.5) and stir evenly, heat to 80-85°C and react at this temperature for 2-4 hours to obtain an environmentally friendly polyurethane prepolymer;

[0038] Furthermore, in the preparation of component A in step S1, the polyether polyol is polyoxypropylene triol, having a hydroxyl value of 45-56 mgKOH / g and a molecular weight of 3000-5000; the isocyanate is diphenylmethane diisocyanate (MDI) or toluene diisocyanate (TDI), and the addition amount thereof is 18-25% of the mass of the polyether polyol;

[0039] During the vacuum dehydration process, the boiling point of water can be significantly reduced by reducing the system pressure (i.e. increasing the vacuum degree). Where P is the vapor pressure of water, ΔH vap is the heat of vaporization of water (i.e., the amount of heat absorbed by water when it changes from liquid to gas), R is the gas constant (for water vapor, its value is approximately 8.314 J / (mol\cdotpK)), T is the absolute temperature (in Kelvin), and C is a constant related to the properties of the substance; when the pressure P decreases, in order to maintain the balance of the equation, the temperature T must also decrease (because ΔH vap and R are constants, while ln(P) is related to This means that at lower pressures, water can boil and evaporate at lower temperatures, speeding up the dehydration process.

[0040] By maintaining a vacuum degree of -0.09MPa, the boiling point of water can be effectively lowered, allowing the water in the polyether polyol to evaporate at a lower temperature while preventing thermal degradation of the polyether polyol due to high temperature. This not only improves dehydration efficiency but also ensures the quality of the final product.

[0041] Step S2: Preparation of Component B: Mixing polyether polyol, chain extender, plasticizer, ultraviolet absorber, mildew inhibitor, thixotropic agent, silane coupling agent, and filler in order, shearing and grinding at high speed, and heating under vacuum at 60-70° C. for 1-3 hours to obtain a modified mixture; ultrasonic-assisted mixing technology is used in the process to add ultrasonic vibration during the mixing process to improve mixing uniformity and reduce mixing time;

[0042] Furthermore, in the preparation of component B in step S2, the chain extender is a mixture of 1,4-butanediol and ethylenediamine in a mass ratio of 3:1 to 5:1; the plasticizer is environmentally friendly dioctyl phthalate (DOP) or epoxy soybean oil, and the addition amount is 8-12% of the total mass of the polyether polyol; the ultraviolet absorber is a compound of 2-hydroxy-4-methoxybenzophenone (UV-9) and hindered amine light stabilizer (HALS) in a mass ratio of 1:1.5 to 1:2;

[0043] Furthermore, the preparation of the component B in step S2 further includes: the filler is a mixture of nano-calcium carbonate, silicon micropowder and modified montmorillonite, and the mass ratio of the three is 5:2:1 to 7:3:1;

[0044] Modified montmorillonite is prepared by the following steps:

[0045] Disperse montmorillonite in deionized water, add 3-5% by mass of silane coupling agent KH-550, ultrasonically treat at 60°C for 2h, dry and grind to a particle size of ≤50μm;

[0046] Furthermore, in the preparation of component B in step S2, the mildew-proof agent is a mixture of an isothiazolinone derivative and nano zinc oxide, with a mass ratio of 1:0.5 to 1:1; the thixotropic agent is fumed silica, and the addition amount is 0.3-0.8% of the total mass of component B;

[0047] Step S3: Mixing and stirring: Component A and Component B are mixed in a mass ratio of 1:3 to 5.5, and an inert amine drier is added and stirred evenly to allow the components to fully react to form a uniform polyurethane coating;

[0048] Furthermore, in step S3, the inert amine drier is N,N-dimethylcyclohexylamine or bis(2-dimethylaminoethyl) ether, and the amount added is 0.05-0.15% of the total mass of the mixture of components A and B;

[0049] Furthermore, in step S3, during the mixing and stirring, an intelligent mixing algorithm is introduced to dynamically adjust the mixing speed and time according to real-time monitoring parameters such as the viscosity and temperature of the mixture to ensure mixing uniformity and reaction sufficiency;

[0050] The logic of the intelligent hybrid algorithm is as follows:

[0051] 1. Parameter initialization

[0052] Set the initial mixing speed v0 (eg, 100 rpm) and the initial mixing time t0 (eg, 5 min).

[0053] Set the target viscosity range [η min ,η max ] (such as 1000≤η≤2000mPa·s) and the maximum allowable temperature T max (e.g. 60°C).

[0054] 2. Real-time monitoring and judgment

[0055] Viscosity monitoring: The viscosity of the mixture is measured in real time using a viscometer.

[0056] Temperature monitoring: The mixture temperature T is measured in real time through a temperature sensor.

[0057] Judgment logic:

[0058] If η<η min And T <T max : The viscosity of the mixture is insufficient and further mixing is required.

[0059] If η min ≤η≤η max And T <T max : The viscosity of the mixture meets the standard, but the mixing efficiency can be optimized.

[0060] If η>η max or T ≥ T max : The viscosity of the mixture is too high or the temperature is close to the limit, so the mixing intensity needs to be reduced.

[0061] 3. Dynamically adjust strategies

[0062] Strategy 1: When viscosity is insufficient

[0063] Maintain the current mixing speed v, but extend the mixing time Δt (eg Δt = 1 min).

[0064] If η still does not meet the standard after multiple extensions, gradually increase the mixing speed (e.g., increase by 10 rpm each time).

[0065] Strategy 2: When viscosity meets the target but can be optimized

[0066] The mixing speed Δv was reduced (eg Δv = 20 rpm) while the mixing time was maintained or slightly shortened.

[0067] Monitor changes in η and T to ensure mixing uniformity is not affected.

[0068] Strategy 3: When viscosity is too high or temperature is close to the limit

[0069] Immediately reduce the mixing speed Δv (eg Δv=30 rpm).

[0070] If T≥T max , then suspend mixing, start the cooling system, and resume mixing after the temperature drops to a safe range.

[0071] 4. Termination Conditions

[0072] When the mixing time reaches the preset maximum value t max (e.g. 30 min) or the viscosity of the mixture is stabilized at [η min ,η max ] range, terminate the mixing process;

[0073] According to the deviation between the actual viscosity and the target viscosity, the mixing speed is dynamically adjusted to approach the optimal mixing state. The mixing speed adjustment formula is:

[0074] v new =v old -Δv·sin(η-η target ), where v new is the adjusted mixing speed, v old is the mixing speed before adjustment, Δv is the speed adjustment step (such as 20 rpm), η target is the target viscosity (e.g. (η min +η max ) / 2), sin() is a sign function, if η>η target , then returns -1, otherwise returns 1;

[0075] When the viscosity is insufficient, the mixing time is dynamically extended according to the size of the viscosity gap to ensure mixing uniformity. The mixing time extension formula is used:

[0076] Among them, t new is the extended mixing time, t old is the original mixing time, Δt is the time step for each extension (such as 1 min), ηstep is the viscosity adjustment step size (e.g. 100 mPa·s), floor() is the rounding down function;

[0077] Set a safety threshold lower than the maximum allowable temperature. When the temperature approaches the threshold, take speed reduction or cooling measures in advance to prevent the temperature from exceeding the limit. Use the temperature safety control formula:

[0078] T safe =T max -ΔT buffer , where T safe is the safety temperature threshold (T max -5℃), ΔT buffer is the temperature buffer value (e.g. 5°C);

[0079] Step S4: spraying: pour the prepared polyurethane coating into a robotic spraying device, and automatically spray the plastic track base layer in a construction environment with a temperature of 20-30°C and a humidity of 50-70% to form a uniform and smooth surface layer;

[0080] Step S5: Curing and forming: After spraying is completed, the surface layer is cured at 60°C for 24 hours. During the curing process, infrared curing technology is introduced to heat the surface layer with infrared rays to accelerate the curing speed and improve the curing efficiency. The components in the polyurethane coating further react to form a surface layer with excellent physical properties and chemical stability.

[0081] The propagation of infrared rays in the surface layer follows the Beer-Lambert law: I(x) = I0·e -αx , where I(x) is the infrared intensity at depth x (W / m 2 ), I0 is the infrared incident intensity on the surface (W / m 2 ), α is the infrared absorption coefficient of the surface material (m -1 ), x is the infrared penetration depth (m);

[0082] Among them, the surface temperature distribution is controlled by the heat conduction equation: Where ρ is the surface density (kg / m 3 ), c is the specific heat capacity (J / (kg·K)), k is the thermal conductivity (W / (m·K)), Q rad is the heat source term generated by infrared radiation (W / m 3 ) Infrared heating rapidly raises the surface temperature of the surface layer (up to 80-100°C), and through heat conduction, the internal temperature gradient drives the curing reaction. Experiments have shown that infrared curing can improve the internal temperature uniformity of the surface layer by 40% (the standard deviation is reduced from ±5°C to ±3°C);

[0083] Among them, the curing reaction rate follows the Arrhenius equation; Among them, α is the degree of curing (0-1), A is the pre-factor (s -1 ), Ea is the activation energy (J / mol), R is the gas constant (8.314 J / (mol·K)), T is the absolute temperature (K), and n is the reaction order; infrared heating increases the temperature T and significantly increases the reaction rate constant

[0084] The heat exchange between the surface and the environment follows: conv =h·(T surf -T amb ), where q conv is the convective heat transfer rate (W / m 2 ), h is the convection heat transfer coefficient (10-20W / (m 2 ·K)), T surf is the surface temperature of the surface layer (℃), T amb is the ambient temperature (℃); during the infrared curing process, by controlling the ambient temperature (such as T amb =25℃) and ventilation conditions can adjust the surface cooling rate. Experiments have shown that forced convection can shorten the curing time by 20%-30%;

[0085] Among them, the curing efficiency η can be evaluated by the following formula:

[0086] t conv is the traditional hot air curing time (h), t IR Infrared curing time (h). Infrared curing can shorten the curing time from 48h of traditional process to 24h, improving efficiency by 100%;

[0087] Through the synergistic effect of the above formula, infrared curing technology shortens the curing time of the surface layer by 50%, while improving the uniformity of curing (the standard deviation of the curing degree is reduced from ±0.05 to ±0.02), ensuring that the surface layer has excellent physical properties (such as a Shore hardness of 65A) and chemical stability (acid and alkali resistance is improved by 30%).

[0088] Furthermore, in step S4 spraying construction and step S5 curing molding, the spray gun pressure is 0.4-0.6MPa, the spraying thickness is 1.5-3.0mm, and it is completed in 2-3 cross-spraying. After the last spraying, environmentally friendly EPDM rubber particles with a particle size of 0.5-1.0mm are immediately spread, and the spreading amount is 200-300g / m 2 , forming an anti-slip texture layer after roller pressing and curing;

[0089] Surface post-treatment: spray a polyurethane surface sealant with a mass concentration of 5-8% on the surface of the cured surface, with a spraying amount of 50-80g / m 2The sealing agent is made by mixing hydroxy acrylic resin and aliphatic isocyanate in a mass ratio of 1:1.2.

[0090] Another technical problem to be solved by the present invention is to provide a method for preparing a spray-coated surface layer of an environmentally friendly polyurethane plastic runway, wherein the surface layer has the following performance indicators: tensile strength ≥ 2.5 MPa, elongation at break ≥ 280%, tear strength ≥ 45 N / mm, VOC emission ≤ 50 μg / m 3 , after 2000h of artificial weathering, the color difference ΔE≤1.5, the density of the surface layer is 1.2-1.4g / cm 3 , Shore A hardness is 55-65, rebound value ≥35%, wet slip coefficient (BPN) ≥75.

[0091] In summary, the present invention provides a method for preparing a spray surface layer of an environmentally friendly polyurethane plastic track. By selecting environmentally friendly raw materials, introducing advanced technologies such as vacuum dehydration, ultrasonic-assisted mixing, intelligent mixing algorithms, robotic automatic spraying, and infrared curing, the environmental performance, preparation efficiency, comprehensive performance, and construction convenience of the surface layer are significantly improved. This method not only optimizes the preparation process of traditional polyurethane plastic tracks, but also ensures the stability and consistency of the surface quality through precise parameter control and the application of advanced equipment. At the same time, the use of environmentally friendly raw materials and additives, as well as the provision of a waste treatment system, further reduces the impact on the environment and meets the requirements of sustainable development.

[0092] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0093] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a spray coating surface layer of an environmentally friendly polyurethane plastic runway, characterized in that: The following steps are involved: Step S1: Preparation of Component A: Add polyether polyol to a reaction kettle, stir and heat to 80-160°C, dehydrate under a vacuum of -0.09 MPa, cool to 40-50°C after dehydration, add isocyanate and stir evenly, heat to 80-85°C and react at this temperature for 2-4 hours to obtain an environmentally friendly polyurethane prepolymer; Step S2: Preparation of component B: polyether polyol, chain extender, plasticizer, ultraviolet absorber, mildew inhibitor, thixotropic agent, silane coupling agent and filler are mixed in order, sheared and ground at high speed, and then heated in vacuum at 60-70° C. for 1-3 hours to obtain a modified mixture; Step S3: Mixing and stirring: Component A and Component B are mixed in a mass ratio of 1:3 to 5.5, and an inert amine drier is added and stirred evenly to allow the components to fully react to form a uniform polyurethane coating; Step S4: spraying: pour the prepared polyurethane coating into a robotic spraying device, and automatically spray the plastic track base layer in a construction environment with a temperature of 20-30°C and a humidity of 50-70% to form a uniform and smooth surface layer; Step S5: Curing and forming: After spraying, the surface layer is cured at 60°C for 24 hours. During the curing process, the components in the polyurethane coating further react to form a surface layer with excellent physical properties and chemical stability.

2. The method for preparing the spray coating surface layer of an environmentally friendly polyurethane plastic runway according to claim 1, characterized in that: In the preparation of component A in step S1, the polyether polyol is polyoxypropylene triol with a hydroxyl value of 45-56 mgKOH / g and a molecular weight of 3000-5000; the isocyanate is diphenylmethane diisocyanate (MDI) or toluene diisocyanate (TDI), and its addition amount is 18-25% of the mass of the polyether polyol.

3. The method for preparing the spray coating surface layer of an environmentally friendly polyurethane plastic runway according to claim 1, characterized in that: In the preparation of the second component of step S2, the chain extender is a mixture of 1,4-butanediol and ethylenediamine, with a mass ratio of 3:1 to 5:1; the plasticizer is environmentally friendly dioctyl phthalate (DOP) or epoxy soybean oil, and the addition amount is 8-12% of the total mass of the polyether polyol; the ultraviolet absorber is a compound of 2-hydroxy-4-methoxybenzophenone (UV-9) and hindered amine light stabilizer (HALS), with a mass ratio of 1:1.5 to 1:

2.

4. The method for preparing a spray coating surface layer of an environmentally friendly polyurethane plastic runway according to claim 1, characterized in that: The preparation of the component B in step S2 further includes: the filler is a mixture of nano-calcium carbonate, silicon micropowder and modified montmorillonite, and the mass ratio of the three is 5:2:1 to 7:3:1; The modified montmorillonite is prepared by the following steps: The montmorillonite was dispersed in deionized water, 3-5% by mass of silane coupling agent KH-550 was added, ultrasonic treatment was performed at 60° C. for 2 h, and then the mixture was dried and ground to a particle size of ≤50 μm.

5. The method for preparing the spray coating surface layer of an environmentally friendly polyurethane plastic runway according to claim 1, characterized in that: In the preparation of component B in step S2, the mildew-proof agent is a mixture of isothiazolinone derivatives and nano zinc oxide, with a mass ratio of 1:0.5 to 1:1; the thixotropic agent is fumed silica, and the addition amount is 0.3-0.8% of the total mass of component B.

6. The method for preparing the spray coating surface layer of an environmentally friendly polyurethane plastic runway according to claim 1, characterized in that: In the mixing and stirring step S3, the inert amine drier is N,N-dimethylcyclohexylamine or bis(2-dimethylaminoethyl) ether, and the added amount is 0.05-0.15% of the total mass of the mixture of components A and B.

7. The method for preparing the spray coating surface layer of an environmentally friendly polyurethane plastic track according to claim 1, characterized in that: In step S4 spraying construction and step S5 curing molding, the spray gun pressure is 0.4-0.6MPa, the spray thickness is 1.5-3.0mm, and it is completed in 2-3 cross sprayings. After the last spraying, immediately spread the environmentally friendly EPDM rubber particles with a particle size of 0.5-1.0mm, and the spreading amount is 200-300g / m 2 , forming an anti-slip texture layer after roller pressing and curing; Surface post-treatment: spray a polyurethane surface sealant with a mass concentration of 5-8% on the surface of the cured surface, with a spraying amount of 50-80g / m 2 The sealing agent is made by mixing hydroxy acrylic resin and aliphatic isocyanate in a mass ratio of 1:1.

2.

8. A surface layer obtained by the method for preparing the spraying surface layer of the environmentally friendly polyurethane plastic track according to claims 1-7, characterized in that: The surface performance indicators meet the following requirements: tensile strength ≥ 2.5MPa, elongation at break ≥ 280%, tear strength ≥ 45N / mm, VOC emission ≤ 50μg / m 3 , after 2000h of artificial weathering, the color difference ΔE≤1.5, the density of the surface layer is 1.2-1.4g / cm 3 , Shore A hardness is 55-65, rebound value ≥35%, wet slip coefficient (BPN) ≥75.

Images