A flame-retardant polyurea protective coating, its preparation method and application

Abstract

This application provides a flame-retardant polyurea protective coating, its preparation method, and its application, belonging to the technical field of polyurea protective coatings. The coating is prepared by mixing component A and component B in a 1:1 volume ratio. Component A is a prepolymer obtained by reacting a reactive flame retardant, solvent, MDI, and polyol. The reactive flame retardant includes at least one of melamine, cyanuric acid, and trihydroxyethyl isocyanurate. Component B includes a polyol, an amine chain extender, an antioxidant, a catalyst, and additives. This application embeds a reactive flame retardant into the isocyanate prepolymer main chain using a block copolymerization method, fixing the triazine nitrogen-containing heterocycle on the main chain and forming a three-dimensional network structure with the isocyanate groups. This improves the crosslinking density of the system, thereby enhancing both the flame retardancy and mechanical properties of the polyurea coating.

Description

Technical Field

[0001] This application relates to the field of polyurea protective coating technology, specifically to a flame-retardant polyurea protective coating, its preparation method, and its application. Background Technology

[0002] Polyurea coatings are a new type of solvent-free, pollution-free green coating developed abroad to meet environmental protection requirements, following high-solids coatings, water-based coatings, radiation-cured coatings, and powder coatings. Compared with traditional environmentally friendly coatings, polyurea coatings have the following advantages: ① Rapid curing, can be sprayed onto any curved, inclined, and vertical surface without sagging; ② Insensitive to moisture and humidity, unaffected by ambient temperature and humidity during construction; ③ 100% solids content, free of any volatile organic compounds (VOCs), environmentally friendly; ④ Can be sprayed or poured at a 1:1 volume ratio, achieving the designed thickness in a single application, overcoming the drawbacks of previous multi-layer construction; ⑤ Excellent theoretical properties... Chemical properties, such as tensile strength, elongation, tear strength, flexibility, abrasion resistance, aging resistance, and corrosion resistance; ⑥ It has good thermal stability, can be used for a long time at 120℃, and can withstand short-term thermal shock at 150℃; ⑦ The coating color is adjustable; ⑧ The formulation system is arbitrarily adjustable, and the feel ranges from soft rubber (Shore A20) to hard elastomer (Shore D75); ⑨ It has good original reproduction, and the coating is continuous, dense, seamless, and free of pinholes, making it beautiful and practical; ⑩ It uses complete sets of equipment, making construction convenient and highly efficient.

[0003] Commonly used polyurea coatings have high resin content and poor flame retardant properties. In fields such as explosion-proof polyurea products for new energy batteries and military explosion-proof polyurea products, polyurea coatings are often required to have a certain degree of flame retardant properties in addition to high physicochemical properties. However, currently, in the formulation of polyurea coatings, in order to achieve a certain flame retardant effect after curing, a large amount of flame retardant is often added, which leads to a sharp drop in the strength of the polyurea coating. Summary of the Invention

[0004] In view of the technical problems existing in the background art, this application provides a flame-retardant polyurea protective coating, its preparation method and application, aiming to solve the technical problem that adding flame retardants to polyurea coatings leads to a decrease in the strength of the polyurea coating.

[0005] Firstly, it is prepared by mixing component A and component B in a volume ratio of 1:1. Component A is a prepolymer obtained by reacting reactive flame retardant, solvent, MDI and polyol. The reactive flame retardant includes at least one of melamine, cyanuric acid and trihydroxyethyl isocyanurate. Component B includes polyol, amine chain extender, antioxidant, catalyst and auxiliaries.

[0006] In the existing technology, reactive flame retardants are used as additive flame retardants. When they are directly added to polyurea coatings, they will block the resin crosslinking of components A and B of the polyurea coating during the polymerization process, resulting in a sharp decline in the tensile strength, tear strength and other mechanical properties of the polyurea coating.

[0007] In this embodiment, the reactive flame retardant, after being dissolved in a solvent, can react with diphenylmethane diisocyanate (MDI) to fix the reactive flame retardant onto the main chain of the prepolymer synthesized from MDI and polyol. The reactive flame retardant includes melamine, cyanuric acid, and trihydroxyethyl isocyanurate. The reaction mechanism of these three with MDI is as follows:

[0008] Melamine has three amino groups. When melamine is added directly to MDI, it does not react with MDI. However, when melamine is dissolved in a solvent and then added to MDI, the three amino groups of melamine can react with MDI to form polyurea. When melamine solution and polyol are added dropwise to MDI at the same time, the polyol reacts with MDI to form isocyanate prepolymer. Melamine reacts with MDI at the same time, fixing the triazine nitrogen-containing heterocycle of melamine on the main chain of the isocyanate prepolymer. Since melamine contains three amino groups, it can form a three-dimensional network structure with isocyanate groups, which increases the crosslinking density of the system and enhances the mechanical properties of the coating.

[0009] When cyanuric acid is dissolved in a solvent, the three hydroxyl groups in cyanuric acid react with MDI to form polyurethane. When melamine solution and polyol are added dropwise to MDI at the same time, the polyol reacts with MDI to form isocyanate prepolymer. Cyanuric acid reacts with MDI at the same time, fixing the triazine nitrogen-containing heterocycle of cyanuric acid on the main chain of isocyanate prepolymer. Cyanuric acid contains three hydroxyl groups, which can form a three-dimensional network structure with isocyanate groups.

[0010] When trihydroxyethyl isocyanurate is dissolved in a solvent, it reacts with MDI. The isocyanate groups of MDI can react with the hydroxyl groups of trihydroxyethyl isocyanurate to form urethane bonds (-NHCOO-), which fix the triazine nitrogen-containing heterocycle of trihydroxyethyl isocyanurate on the main chain of the isocyanate prepolymer. Since trihydroxyethyl isocyanurate contains three hydroxyl groups, a cross-linked network structure is constructed, resulting in a three-dimensional polyurethane structure.

[0011] A prepolymer was synthesized by reacting a reactive flame retardant, diphenylmethane diisocyanate (MDI), and a polyol. The triazine nitrogen-containing heterocycle of the reactive flame retardant was fixed on the main chain of the prepolymer and formed a three-dimensional network structure with the isocyanate group. This improved the crosslinking density of the system, thereby enhancing both the flame retardancy of the polyurea coating and the crosslinking density of the system, thus strengthening the mechanical properties of the coating.

[0012] The reactive flame retardant, MDI, and polyol in component A react to generate a triazine-containing nitrogen-containing heterocyclic isocyanate-based prepolymer. Component B contains an amine chain extender. In the preparation of the flame-retardant polyurea coating, components A and B are mixed at a volume ratio of 1:1 and heated. The isocyanate (R-NCO) in component A reacts with the amino group (R'-NH2) of the amine chain extender in component B to generate a polymer material with urea bonds (RNHCONHR'). After curing, a polyurea coating is obtained. The polyol in component B can play a role in plasticizing and crosslinking.

[0013] Preferably, the solvent includes at least one of pyridine, dimethylformamide dimethyl sulfoxide, and N,N-dimethylpyrrolidone.

[0014] Preferably, by mass parts, component A includes 25-45 parts of polyol, 5-20 parts of reactive flame retardant, and 40-50 parts of MDI.

[0015] In this embodiment, the coating exhibits the best flame retardant and mechanical properties when the reactive flame retardant content in component A is 10% to 15%. If the reactive flame retardant content is too high, the viscosity of component A increases, which is not conducive to construction. If the content is too low, the flame retardant effect is poor.

[0016] Preferably, by mass, component B comprises 55-65 parts of polyol, 15-30 parts of amine chain extender, 0.1-0.5 parts of antioxidant, 0.05-0.2 parts of catalyst, and 4.6-7.6 parts of additives, including 1-2 parts of coupling agent, 0.05-0.15 parts of defoamer, 0.1-0.3 parts of leveling agent, 3-5 parts of dehydrating agent, and 0.2-0.4 parts of dispersant.

[0017] Preferably, the coupling agent includes at least one of silane coupling agents, titanate coupling agents, aluminate coupling agents, bimetallic coupling agents, phosphate coupling agents, and borate coupling agents.

[0018] The defoamer includes at least one of BYK-066N, BYK-054, and BYK-057.

[0019] The leveling agent includes at least one of BYK-306, BYK-307, and BYK-310.

[0020] The dispersant includes at least one of BYK-161, BYK-163, BYK-164, and BYK-170.

[0021] Preferably, the polyol includes at least two of the following: polyether diol, polyester diol, polyether triol, polytetrahydrofuran diol, conventional polyester polyol, polycaprolactone polyol, and polycarbonate diol.

[0022] Preferably, the polyol includes at least two of TEP-330N, PPG4000, PPG2000, PPG1000, MN3050, MN1000, MN700, MN500, PTMG-1000, PTMG-2000, PCL-1200, PCL-2044, PCL-2053, PCL-3057, PCL-2200A, and PCL-2200C.

[0023] Preferably, the catalyst includes at least one of stannous octoate, dibutyltin dilaurate and dibutyltin oxide, bismuth neodecanoate, bismuth laurate, bismuth isooctanoate, bismuth naphthenate, and oxazolidinone.

[0024] Preferably, the amine chain extender includes at least one of diethyltoluenediamine, dimethylthiotoluenediamine, 4,4'-bis-sec-butylaminodiphenylmethane, and 3,3'-dichloro-4,4'-diaminodiphenylmethane.

[0025] Secondly, embodiments of this application provide a method for preparing a flame-retardant polyurea protective coating, comprising the following steps:

[0026] The reactive flame retardant and solvent are mixed and stirred until the reactive flame retardant is completely dissolved to obtain a reactive flame retardant solution. The polyol is dehydrated in a reaction vessel at 70-80°C under vacuum for 2-3 hours, then the vacuum is removed and the temperature is lowered to below 70°C to obtain the dehydrated polyol. A calculated amount of liquid MDI is added to another reaction vessel and the temperature is raised to 40-60°C. The reactive flame retardant solution and the dehydrated polyol are added to the liquid MDI, the temperature is raised to 70-80°C, and the reaction is carried out for 2-3 hours. After the reaction is completed, the solvent is removed and the mixture is filtered to obtain component A.

[0027] The polyol and auxiliaries were stirred at high speed until homogeneous. Then, amine chain extenders, antioxidants, and catalysts were added and stirred until homogeneous. After dehydration, component B was obtained.

[0028] Preferably, a reactive flame retardant solution and a dehydrated polyol are added dropwise to the MDI simultaneously within 1 to 2 hours.

[0029] Thirdly, this application provides an application of a flame-retardant polyurea protective coating, comprising the following steps: adding 5-10 parts of propylene carbonate (PC) solvent to component A and component B respectively, so that the viscosity of component A and component B is less than 2000 mPa·s, and the viscosity difference between component A and component B is not more than 50 mPa·s; using a polyurea-specific spraying machine to mix the diluted component A and component B evenly at a volume ratio of 1:1 and then spraying; and placing it at room temperature for curing to obtain a flame-retardant polyurea protective coating.

[0030] The advantages of this application, which differ from existing technical solutions, include:

[0031] This application involves simultaneously adding a reactive flame retardant solution and a polyol dropwise into MDI. The polyol reacts with MDI to generate an isocyanate prepolymer. Simultaneously, the reactive flame retardant is embedded into the isocyanate prepolymer backbone using a block copolymerization method. This fixes the triazine nitrogen-containing heterocycle of the reactive flame retardant onto the backbone, forming a three-dimensional network structure with the isocyanate groups. This improves the crosslinking density of the system, enhancing both the flame retardancy and mechanical properties of the polyurea coating. With the addition of 10%–20% reactive flame retardant, the coating achieves an oxygen index of 26–32, a tensile strength of 19 MPa, and a tear strength of 78 KN / m. The high-performance flame-retardant polyurea coating prepared using this method meets user requirements for flame retardant performance while also exhibiting improved mechanical properties, demonstrating promising application prospects.

[0032] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Detailed Implementation

[0033] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion.

[0035] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0036] Currently, when formulating polyurea coatings, in order to achieve a certain flame retardant effect after curing, a large amount of flame retardant is often added, which leads to a sharp drop in the strength of the polyurea coating.

[0037] To address the technical problem of reduced strength of polyurea coatings due to the addition of flame retardants, this application provides a flame-retardant polyurea protective coating, comprising component A and component B. Component A is a prepolymer obtained by reacting a reactive flame retardant, MDI, and a polyol. The reactive flame retardant includes at least one of melamine, cyanuric acid, and trihydroxyethyl isocyanurate. Component B includes a polyol, an amine chain extender, an antioxidant, a catalyst, and an additive. The volume ratio of component A to component B is 1:1.

[0038] Furthermore, in some embodiments, component A includes 25-45 parts of polyol, 5-20 parts of reactive flame retardant, and 40-50 parts of MDI.

[0039] Furthermore, in some embodiments, component B includes 55-65 parts of polyol, 15-30 parts of amine chain extender, 0.1-0.5 parts of antioxidant, 0.05-0.2 parts of catalyst, and 4.6-7.6 parts of additives. The additives include 1-2 parts of coupling agent, 0.05-0.15 parts of defoamer, 0.1-0.3 parts of leveling agent, 3-5 parts of dehydrating agent, and 0.2-0.4 parts of dispersant.

[0040] In this embodiment, the coupling agent includes at least one of silane coupling agents, titanate coupling agents, aluminate coupling agents, bimetallic coupling agents, phosphate coupling agents, and borate coupling agents.

[0041] The defoamer includes at least one of BYK-066N, BYK-054, and BYK-057.

[0042] The leveling agent includes at least one of BYK-306, BYK-307, and BYK-310.

[0043] The dispersant includes at least one of BYK-161, BYK-163, BYK-164, and BYK-170.

[0044] Furthermore, in some embodiments, the polyol includes at least two of polyether diols, polyester diols, polyether triols, polytetrahydrofuran diols, conventional polyester polyols, polycaprolactone polyols, and polycarbonate diols.

[0045] In this embodiment, the polyol includes at least two of the following: TEP-330N, PPG4000, PPG2000, PPG1000, MN3050, MN1000, MN700, MN500, PTMG-1000, PTMG-2000, PCL-1200, PCL-2044, PCL-2053, PCL-3057, PCL-2200A, and PCL-2200C.

[0046] Furthermore, in some embodiments, the catalyst includes at least one selected from stannous octoate, dibutyltin dilaurate and dibutyltin oxide, bismuth neodecanoate, bismuth laurate, bismuth isooctanoate, bismuth naphthenate, and oxazolidinone.

[0047] Furthermore, in some embodiments, the amine chain extender includes at least one of diethyltoluenediamine, dimethylthiotoluenediamine, 4,4'-bis-sec-butylaminodiphenylmethane, and 3,3'-dichloro-4,4'-diaminodiphenylmethane.

[0048] Secondly, embodiments of this application provide a method for preparing a flame-retardant polyurea protective coating, comprising the following steps:

[0049] The reactive flame retardant and solvent are mixed and stirred until the reactive flame retardant is completely dissolved to obtain a reactive flame retardant solution. The polyol is dehydrated in a reaction vessel at 70-80°C under vacuum for 2-3 hours, then the vacuum is removed and the temperature is lowered to below 70°C to obtain the dehydrated polyol. A calculated amount of liquid MDI is added to another reaction vessel, and the temperature is raised to 40-60°C. The reactive flame retardant solution and the dehydrated polyol are added to the liquid MDI, and the temperature is raised to 70-80°C for 2-3 hours. The temperature is then raised to 100°C, and the solvent is removed under vacuum. The vacuum is removed, the temperature is lowered to below 60°C, and the mixture is filtered to obtain component A.

[0050] The polyol and auxiliaries were stirred at high speed until homogeneous. Then, amine chain extenders, antioxidants, and catalysts were added and stirred until homogeneous. The mixture was dehydrated at 105°C under vacuum for 2 hours. After removing the vacuum and cooling to room temperature, component B was obtained.

[0051] Furthermore, in some embodiments, a fully reactive flame retardant solution and a dehydrated polyol are simultaneously added to the MDI within 1 to 2 hours.

[0052] Thirdly, this application provides an application of a flame-retardant polyurea protective coating, comprising the following steps: adding PC solvent to component A and component B respectively, so that the viscosity of component A and component B is less than 2000 mPa·s, and the viscosity difference between component A and component B is not more than 50 mPa·s; using a polyurea-specific spraying machine to mix the diluted component A and component B evenly at a volume ratio of 1:1 and then spraying; and placing it at room temperature for curing for 7 days to obtain a flame-retardant polyurea protective coating.

[0053] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0054] I. Preparation Method

[0055] Example 1

[0056] Example 1 provides a reactive high-performance flame-retardant polyurea coating. The preparation method of the reactive high-performance flame-retardant polyurea coating includes the following steps:

[0057] (1) Add 20 parts of reactive flame retardant melamine and 20 parts of N,N-dimethylpyrrolidone (NMP) to a dispersion tank and stir until the melamine is completely dissolved; add 27 parts of polyol PPG2000 to a reaction vessel and dehydrate it under vacuum at 70~80℃ for 2~3h, then remove the vacuum and cool it down to below 70℃ for later use; add 53 parts of liquid MDI to another reaction vessel and heat it to 40~60℃, and simultaneously add the reactive flame retardant solution and the dehydrated polyol PPG2000 to the reaction vessel within 1~2h, heat it up to 70~80℃ and react for 2~3h; then heat it up to 100℃ and remove NMP under vacuum; remove the vacuum and cool it down to below 60℃, and test the NCO content to be 15.88%, then filter and package.

[0058] (2) Mix 42 parts of polyol PPG2000, 20 parts of polyol MN700, 0.4 parts of UV stabilizer UV-24, 0.3 parts of dispersant BYK-163, 0.2 parts of leveling agent BYK-306, 0.1 parts of defoamer BYK-054, 1 part of coupling agent KH-560, 4 parts of molecular sieve A4, 1 part of bentonite BP127, 1.9 parts of black paste, and 8.6 parts of white paste at high speed until homogeneous. Then add 20 parts of E-100 amine chain extender, 0.4 parts of antioxidant 245, and 0.1 parts of T18 catalyst and mix until homogeneous. Dehydrate under vacuum at 105℃ for 2 hours, then remove the vacuum and cool to room temperature before packaging.

[0059] (3) Add 5-10 parts of PC solvent to adjust the viscosity of components A and B. At a working temperature of 65℃, the viscosity of component A is 98mPa·s and that of component B is 89mPa·s. Use a polyurea-specific spraying machine to transport components A and B separately through heated pipes at a volume ratio of 1:1 to the spray gun mixing chamber. Mix them evenly by instant collision under high temperature and high pressure. After passing through the nozzle, atomize and spray the test sample and sample piece. Place them at room temperature for curing for 7 days.

[0060] Example 2

[0061] The only difference between the reactive high-performance flame-retardant polyurea coating in this embodiment and that in Example 1 is the amount of raw material added in component A. All other steps are the same. The preparation method of component A includes the following steps:

[0062] Add 15 parts of reactive flame retardant melamine and 20 parts of NMP to a dispersion tank and stir until the melamine is completely dissolved. Add 31 parts of polyol PPG2000 to a reaction vessel and dehydrate under vacuum at 70-80°C for 2-3 hours. Then remove the vacuum and cool to below 70°C for later use. Add 54 parts of liquid MDI to another reaction vessel and heat to 40-60°C. Simultaneously add the reactive flame retardant solution and the dehydrated polyol PPG2000 to the reaction vessel over 1-2 hours. Heat to 70-80°C and react for 2-3 hours. Then heat to 100°C and remove NMP under vacuum. Remove the vacuum, cool to below 60°C, and test the NCO content to be 16.02%. Filter and package.

[0063] Example 3

[0064] The only difference between the reactive high-performance flame-retardant polyurea coating in this embodiment and that in Example 1 is the amount of raw material added in component A. All other steps are the same. The preparation method of component A includes the following steps:

[0065] Add 10 parts of reactive flame retardant melamine and 20 parts of NMP to a dispersion tank and stir until the melamine is completely dissolved. Add 36 parts of polyol PPG2000 to a reaction vessel and dehydrate under vacuum at 70-80°C for 2-3 hours. Then remove the vacuum and cool to below 70°C for later use. Add 54 parts of liquid MDI to another reaction vessel and heat to 40-60°C. Simultaneously add the reactive flame retardant solution and the dehydrated polyol PPG2000 to the reaction vessel over 1-2 hours. Heat to 70-80°C and react for 2-3 hours. Then heat to 100°C and remove NMP under vacuum. Remove the vacuum, cool to below 60°C, and test the NCO content to be 15.64%. Filter and package.

[0066] Example 4

[0067] The only difference between the reactive high-performance flame-retardant polyurea coating in this embodiment and that in Example 1 is the type and amount of raw materials for component A. All other steps are the same. The preparation method of component A includes the following steps:

[0068] Add 15 parts of reactive flame retardant cyanuric acid and 20 parts of NMP to a dispersion tank and stir until the melamine is completely dissolved. Add 31 parts of polyol PPG2000 to a reaction vessel and dehydrate under vacuum at 70-80°C for 2-3 hours. Then remove the vacuum and cool to below 70°C for later use. Add 54 parts of liquid MDI to another reaction vessel and heat to 40-60°C. Simultaneously add the completed reactive flame retardant solution and the dehydrated polyol PPG2000 to this reaction vessel over 1-2 hours. Heat to 70-80°C and react for 2-3 hours. Then heat to 100°C and remove NMP under vacuum. Remove the vacuum, cool to below 60°C, and test the NCO content. The result is 15.92%. Filter and package.

[0069] Example 5

[0070] The only difference between the reactive high-performance flame-retardant polyurea coating in this embodiment and that in Example 1 is the type and amount of raw materials for component A. All other steps are the same. The preparation method of component A includes the following steps:

[0071] Add 15 parts of reactive flame retardant trihydroxyethyl isocyanate and 20 parts of NMP to a dispersion tank and stir until melamine is completely dissolved. Add 31 parts of polyol PPG2000 to a reaction vessel and dehydrate under vacuum at 70-80°C for 2-3 hours. Then remove the vacuum and cool to below 70°C for later use. Add 54 parts of liquid MDI to another reaction vessel and heat to 40-60°C. Simultaneously add the reactive flame retardant solution and the dehydrated polyol PPG2000 to the reaction vessel over 1-2 hours. Heat to 70-80°C and react for 2-3 hours. Then heat to 100°C and remove NMP under vacuum. Remove the vacuum, cool to below 60°C, and test the NCO content to be 15.76%. Filter and package.

[0072] Comparative Example 1

[0073] Comparative Example 1 provides a reactive high-performance flame-retardant polyurea coating, which differs from Example 1 in that no flame retardant is added. The preparation method of the reactive high-performance flame-retardant polyurea coating in Comparative Example 1 includes the following steps:

[0074] (1) Add 48 parts of polyol PPG2000 to the reactor and dehydrate it under vacuum at 70~80℃ for 2~3h. Then remove the vacuum and cool it down to below 70℃ for later use. Add 52 parts of liquid MDI to another reactor and heat it to 40~60℃. Add the dehydrated polyol PPG2000 dropwise over 1~2h and heat it to 70~80℃ for 2~3h. Remove the vacuum and cool it down to below 60℃. The NCO content is 15.68%. Filter and package.

[0075] (2) Mix 42 parts of polyol PPG2000, 20 parts of polyol MN700, 0.4 parts of UV stabilizer UV-24, 0.3 parts of dispersant BYK-163, 0.2 parts of leveling agent BYK-306, 0.1 parts of defoamer BYK-054, 1 part of coupling agent KH-560, 4 parts of molecular sieve A4, 1 part of bentonite BP127, 1.9 parts of black paste, and 8.6 parts of white paste at high speed until homogeneous. Then add 20 parts of E-100 amine chain extender, 0.4 parts of antioxidant 245, and 0.1 parts of T18 catalyst and mix until homogeneous. Dehydrate under vacuum at 105℃ for 2 hours, then remove the vacuum and cool to room temperature before packaging.

[0076] (3) Add 5-10 parts of PC solvent to adjust the viscosity of components A and B. At a working temperature of 65℃, the viscosity of component A is 98mPa·s and that of component B is 89mPa·s. Use a polyurea-specific spraying machine to transport components A and B separately through heated pipes at a volume ratio of 1:1 to the spray gun mixing chamber. Mix them evenly by instant collision under high temperature and high pressure. After passing through the nozzle, atomize and spray the test sample and sample piece. Place them at room temperature for curing for 7 days.

[0077] Comparative Example 2

[0078] Compared with Example 1, the only difference in this comparative example is that the reactive flame retardant in step (1) is added directly without being dissolved:

[0079] (1) Add 48 parts of polyol PPG2000 to a reaction vessel and dehydrate it under vacuum at 70~80℃ for 2~3h. Then remove the vacuum and cool it down to below 70℃ for later use. Add 52 parts of liquid MDI to another reaction vessel and heat it to 40~60℃. Add the dehydrated polyol PPG2000 dropwise over 1~2h and heat it to 70~80℃ for 2~3h. Remove the vacuum and cool it down to below 60℃. Then add 20 parts of melamine and disperse it evenly. The NCO content is 15.73%. Filter and package.

[0080] Comparative Example 3

[0081] Compared with Example 1, the only difference is that 20 parts of the reactive flame retardant melamine are added directly to step (2) without being dissolved. The preparation method of the reactive high-performance flame-retardant polyurea coating in Comparative Example 3 includes the following steps:

[0082] (1) Add 48 parts of polyol PPG2000 to the reactor and dehydrate it under vacuum at 70~80℃ for 2~3h. Then remove the vacuum and cool it down to below 70℃ for later use. Add 52 parts of liquid MDI to another reactor and heat it to 40~60℃. Add the dehydrated polyol PPG2000 dropwise over 1~2h and heat it to 70~80℃ for 2~3h. Remove the vacuum and cool it down to below 60℃. The NCO content is 15.85%. Filter and package.

[0083] (2) Mix 42 parts of polyol PPG2000, 20 parts of polyol MN700, 20 parts of melamine, 0.4 parts of UV stabilizer UV-24, 0.3 parts of dispersant BYK-163, 0.2 parts of leveling agent BYK-306, 0.1 parts of defoamer BYK-054, 1 part of coupling agent KH-560, 4 parts of molecular sieve A4, 1 part of bentonite BP127, 1.9 parts of black paste, and 8.6 parts of white paste at high speed until homogeneous. Then add 20 parts of E-100 amine chain extender, 0.4 parts of antioxidant 245, and 0.1 parts of T18 catalyst and mix until homogeneous. Dehydrate under vacuum at 105℃ for 2 hours, then remove the vacuum and cool to room temperature before packaging.

[0084] (3) Add 5-10 parts of PC solvent to adjust the viscosity of components A and B. At a working temperature of 65℃, the viscosity of component A is 98mPa·s and that of component B is 89mPa·s. Use a polyurea-specific spraying machine to transport components A and B separately through heated pipes at a volume ratio of 1:1 to the spray gun mixing chamber. Mix them evenly by instant collision under high temperature and high pressure. After passing through the nozzle, atomize and spray the test sample and sample piece. Place them at room temperature for curing for 7 days.

[0085] Comparative Example 4

[0086] Compared with Example 1, the only difference is that step (1) is:

[0087] (1) Add 5 parts of reactive flame retardant melamine and 20 parts of NMP to a dispersion tank and stir until the melamine is completely dissolved; add 41 parts of polyol PPG2000 to a reaction vessel and dehydrate under vacuum at 70~80℃ for 2~3h, then remove the vacuum and cool down to below 70℃ for later use; add 54 parts of liquid MDI to another reaction vessel and heat to 40~60℃, and simultaneously add the reactive flame retardant solution and the dehydrated polyol PPG2000 to the reaction vessel within 1~2h, heat to 70~80℃ and react for 2~3h; then heat to 100℃ and remove NMP under vacuum; remove the vacuum, cool down to below 60℃, and test the NCO content to be 15.91%, then filter and package.

[0088] Comparative Example 5

[0089] Compared with Example 1, the only difference is that step (1) is:

[0090] (1) Add 30 parts of reactive flame retardant cyanuric acid and 20 parts of NMP to a dispersion tank and stir until the melamine is completely dissolved; add 16 parts of polyol PPG2000 to a reaction vessel and dehydrate under vacuum at 70~80℃ for 2~3h, then remove the vacuum and cool down to below 70℃ for later use; add 54 parts of liquid MDI to another reaction vessel and heat to 40~60℃, and simultaneously add the reactive flame retardant solution and dehydrated polyol PPG2000 to the reaction vessel within 1~2h, heat to 70~80℃ and react for 2~3h; then heat to 100℃ and remove NMP under vacuum; remove the vacuum, cool down to below 60℃, and test the NCO content to be 15.74%, then filter and package.

[0091] II. Testing Methods

[0092] 1. Adhesion test method: GB / T 5210 Paint and varnish pull-off adhesion test.

[0093] 2. Test methods for tensile strength and elongation at break: GB / T 528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber.

[0094] 3. Tear strength test method: GB / T 529-2008 Determination of tear strength of vulcanized rubber or thermoplastic rubber (trouser-shaped, right-angled and crescent-shaped specimens).

[0095] 4. Oxygen index test method: GB / T 2406.2-2009 Oxygen index method for determining combustion behavior of plastics.

[0096] 5. Shore hardness (SHD) testing method: The test is performed using a Shore hardness tester.

[0097] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0098] Polyurea coatings were prepared according to the methods described in Examples 1-5 and Comparative Examples 1-5. The adhesion of the polyurea coatings, tensile strength, tear strength, elongation at break, and flame retardant properties of the polyurea samples were tested at room temperature. The test data are shown in Table 1 below:

[0099] Table 1. Performance test data of polyurea coatings in each embodiment and comparative example.

[0100]

[0101] The reactive flame retardant added in Examples 1-3 and Comparative Examples 4-5 was melamine. As can be seen from Table 1 above, in Examples 1-3, the amount of melamine added was 10-20 parts, accounting for 10%-20% of component A. Within this percentage range, as the amount of melamine added increased, the tensile strength, tear strength, and flame retardant oxygen index of the polyurea sample gradually increased, while the elongation at break gradually decreased. The flame retardant properties of the coating could reach an oxygen index of 24-32, the tensile strength increased from 16 MPa to 19 MPa, and the tear strength increased from 75 KN / m to 78 KN / m. The polyurea samples prepared in Examples 1-3 had good flame retardant and mechanical properties. In Comparative Example 4, the amount of melamine added was 5 parts, accounting for 5% of component A. As shown in Table 1, the tensile strength, tear strength, and flame retardant oxygen index of the polyurea sample prepared in Comparative Example 4 were significantly reduced, with an oxygen index of 15.4, indicating that the coating was flammable. This shows that the amount of flame retardant added was too low and could not achieve the desired flame retardant effect. In Comparative Example 5, the amount of melamine added accounted for 30% of component A. As shown in Table 1, the elongation at break in Comparative Example 5 was significantly reduced, the Shore hardness (SHD) increased, and the amount of reactive flame retardant added was too high, resulting in increased viscosity of component A, which is not conducive to construction. This indicates that the amount of reactive flame retardant added should be 10-20 parts.

[0102] In Examples 4 and 5, cyanuric acid and trihydroxyethyl isocyanate were used as reactive flame retardants, respectively, and the resulting polyurea coatings showed good flame retardant and mechanical properties.

[0103] In Comparative Example 1, no flame retardant was added, resulting in a polyurea coating with an oxygen index of 14, which is less than 21, classifying it as a flammable material. In Comparative Example 2, melamine was added directly to component A without being dissolved in a solvent, resulting in a polyurea coating with an oxygen index of 18, which is less than 21, classifying it as a flammable material. Furthermore, its tensile strength, tear strength, and adhesion were significantly lower than in Examples 1-5. In Comparative Example 3, melamine was added directly to component A without being dissolved in a solvent, resulting in a polyurea coating with an oxygen index of 17.6, which is less than 21, classifying it as a flammable material. Furthermore, its tensile strength, tear strength, and adhesion were significantly lower than in Examples 1-5. Therefore, it can be concluded that adding reactive flame retardants directly to polyurea coatings without dissolving them does not achieve the desired flame retardant performance and leads to a decrease in the mechanical properties of the polyurea coating.

[0104] 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 flame-retardant polyurea protective coating, characterized in that, The mixture is prepared by mixing component A and component B in a volume ratio of 1:

1. Component A is a prepolymer obtained by reacting a reactive flame retardant, a solvent, MDI, and a polyol. The reactive flame retardant includes at least one of melamine, cyanuric acid, and trihydroxyethyl isocyanurate. Component B includes a polyol, an amine chain extender, an antioxidant, a catalyst, and an additive. Component A contains 25-45 parts of polyol, 10-20 parts of reactive flame retardant, and 40-50 parts of MDI. The preparation method of the flame-retardant polyurea protective coating includes the following steps: The reactive flame retardant and solvent are mixed and stirred until the reactive flame retardant is completely dissolved to obtain a reactive flame retardant solution. The polyol is dehydrated in a reaction vessel at 70-80°C under vacuum for 2-3 hours, then the vacuum is removed and the temperature is lowered to below 70°C to obtain the dehydrated polyol. A calculated amount of liquid MDI is added to another reaction vessel and the temperature is raised to 40-60°C. The reactive flame retardant solution and the dehydrated polyol are added to the liquid MDI, the temperature is raised to 70-80°C, and the reaction is carried out for 2-3 hours. After the reaction is completed, the solvent is removed and the mixture is filtered to obtain component A. The polyol and auxiliaries were stirred at high speed until homogeneous. Then, amine chain extenders, antioxidants, and catalysts were added and stirred until homogeneous. After dehydration, component B was obtained.

2. The flame-retardant polyurea protective coating according to claim 1, characterized in that, The solvent includes at least one of pyridine, dimethylformamide, dimethyl sulfoxide, and N,N-dimethylpyrrolidone.

3. The flame-retardant polyurea protective coating according to claim 1, characterized in that, By mass, component B comprises 55-65 parts of polyol, 15-30 parts of amine chain extender, 0.1-0.5 parts of antioxidant, 0.05-0.2 parts of catalyst, and 4.6-7.6 parts of additives, wherein the additives include 1-2 parts of coupling agent, 0.05-0.15 parts of defoamer, 0.1-0.3 parts of leveling agent, 3-5 parts of dehydrating agent, and 0.2-0.4 parts of dispersant.

4. The flame-retardant polyurea protective coating according to claim 1, characterized in that, The polyols include at least two of polyether diols, polyester diols, and polyether triols.

5. The flame-retardant polyurea protective coating according to claim 1, characterized in that, The catalyst includes at least one of stannous octoate, dibutyltin dilaurate, dibutyltin oxide, bismuth neodecanoate, bismuth laurate, bismuth isooctanoate, bismuth naphthenate, and oxazolidinone.

6. The flame-retardant polyurea protective coating according to claim 1, characterized in that, The amine chain extender includes at least one of diethyltoluenediamine, dimethylthiotoluenediamine, 4,4'-bis(sec-butylamino)diphenylmethane, and 3,3'-dichloro-4,4'-diaminodiphenylmethane.

7. The flame-retardant polyurea protective coating according to claim 1, characterized in that, Within 1-2 hours, a reactive flame retardant solution and a dehydrated polyol are simultaneously added dropwise to the MDI.

8. The application of a flame-retardant polyurea protective coating according to any one of claims 1 to 7, characterized in that, The process includes the following steps: adding 5-10 parts of PC solvent to component A and component B respectively, so that the viscosity of component A and component B is less than 2000 mPa·s and the viscosity difference between component A and component B does not exceed 50 mPa·s; mixing the diluted component A and component B evenly at a volume ratio of 1:1 and then spraying the mixture, and curing it at room temperature to obtain a flame-retardant polyurea protective coating.

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