Composite fire-retardant coating, and preparation method and application method thereof

Abstract

The application provides a composite fire-retardant coating, a preparation method and an application method thereof. The composite fire-retardant coating comprises an intumescent fire-retardant coating and a ceramic fire-retardant coating. The intumescent fire-retardant coating is coated on a substrate, dried to form an intumescent fire-retardant coating layer. The ceramic fire-retardant coating is coated on the intumescent fire-retardant coating layer, dried to form a ceramic fire-retardant coating layer. The intumescent fire-retardant coating layer is foamed and expanded under high-temperature combustion to lift the ceramic fire-retardant coating layer on the surface. Meanwhile, the ceramic fire-retardant coating layer is sintered at a higher temperature to realize thorough ceramization, thereby achieving better fireproof performance. The loose and porous structure of the ceramic fire-retardant coating layer is conducive to reducing heat conduction. Further heating of the ceramic fire-retardant coating layer will rapidly generate a very dense ceramic structure to directly isolate the flame and avoid erosion of the intumescent layer. Meanwhile, the ceramic fire-retardant coating layer has the characteristic of slow heat conduction, which further coordinates the intumescent layer to achieve the purpose of protecting the body.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flame-retardant coating, in particular to a composite flame-retardant coating, a preparation method and an application method thereof. BACKGROUND

[0002] In modern society, the frequent occurrence of fire accidents poses a serious threat to people's life and property safety. According to statistics, a large number of fire accidents are caused by the flammability of materials, so passive fire protection is a viable option that can reduce fire damage or delay the inevitable fire damage to give time to save human lives or rescue assets. Among passive fire protection measures, intumescent flame-retardant coating (IFRCs) is the most common and effective protection measure. It has the advantages of simple production process, maintaining the integrity of the inherent properties of the substrate, and being easy to apply to various materials. In addition, intumescent coating can protect steel structures from corrosion during its service life. IFRCs form a thick protective carbonized layer, creating an effective thermal barrier insulation layer between the flame and the substrate.

[0003] Although there are many products of intumescent flame-retardant / fire-resistant coatings, the existing flame-retardant coatings still have certain limitations in terms of high-temperature resistance. On the one hand, single-component flame-retardant coatings cannot meet the requirements of high-temperature resistance and flame retardance at the same time; on the other hand, the existing composite flame-retardant coatings still need to be improved in terms of flame-retardant effect and stability at high temperatures. In order to solve this problem, researchers are constantly exploring new coating formulations and preparation processes. High-temperature-resistant composite flame-retardant coatings, as a new type of functional material, have the characteristics of maintaining stability and preventing flame spread in high-temperature environments. The technical core lies in building a composite system composed of an organic intumescent layer and inorganic ceramic materials. The organic intumescent layer foams under the action of high temperature to form a loose and expanded structure, which plays a role in insulating heat; the inorganic ceramic materials can form a dense protective film at high temperatures, further insulating the flame and reducing energy transfer.

[0004] However, the existing preparation methods of high-temperature-resistant composite flame-retardant coatings have the following problems: first, compatibility problem, the poor compatibility of different components leads to uneven internal structure of the coating, affecting the performance of the coating. Second, multi-component synergistic fireproof performance, the thermal decomposition temperature mismatch of multi-component flame-retardant components, and the durability problem of materials cause the failure of the flame-retardant process during the fireproof process. Third, the porosity or structural damage of the coating, the coating surface may form a porous structure or crack at high temperatures, which directly reduces its heat insulation and flame retardant performance. Based on the above problems, the applicability of fire-retardant coatings is limited, especially for materials with high surface treatment requirements.

[0005] Based on the defects of the existing high-temperature-resistant composite flame-retardant coatings, it is necessary to improve them. SUMMARY

[0006] In view of this, the present invention proposes a composite flame retardant coating and a preparation method and an application method thereof, in order to solve or partially solve the problems existing in the prior art.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a composite flame retardant coating, wherein the composite flame retardant coating comprises an intumescent flame retardant coating and a ceramic flame retardant coating;

[0009] The method for preparing the intumescent flame-retardant coating comprises the following steps:

[0010] Phytic acid and dicyandiamide are dissolved in DMF and subjected to solvent thermal reaction to obtain amidine phosphate polymers;

[0011] dissolving an amidine phosphate polymer in a polyvinyl alcohol aqueous solution, adding ammonium polyphosphate, and performing a hydrothermal reaction to obtain an intumescent flame retardant coating;

[0012] The preparation method of the ceramic flame retardant coating comprises:

[0013] Boric acid, aluminum oxide and silicon oxide are mixed, ground and calcined to obtain a composite material;

[0014] The composite material is added to the silicone resin to obtain a ceramic flame retardant coating.

[0015] Preferably, in the step of dissolving phytic acid and dicyandiamide in DMF and performing a solvothermal reaction, the solvothermal reaction temperature is 100-200° C. and the reaction time is 3-15 h.

[0016] Preferably, in the step of dissolving the amidine phosphate polymer in a polyvinyl alcohol aqueous solution, adding ammonium polyphosphate, and performing a hydrothermal reaction, the hydrothermal reaction temperature is 80-150° C. and the time is 2-10 hours.

[0017] Preferably, the mass volume ratio of the phytic acid, dicyandiamide, polyvinyl alcohol aqueous solution to DMF is 500g:(150-200)g:(2500-3000)g:(1-1.5)L;

[0018] The mass concentration of the polyvinyl alcohol aqueous solution is 10-15%.

[0019] Preferably, after grinding the boric acid, aluminum oxide and silicon oxide, in the calcination step, the calcination temperature is 300-500° C. and the time is 3-10 hours.

[0020] Preferably, boric acid, aluminum oxide and silicon oxide are mixed and ground to a particle size of ≤1 μm;

[0021] And / or, the mass-volume ratio of the boric acid, aluminum oxide, silicon oxide and silicone resin is 100g:(300-1200)g:(800-1500)g:(1-1.5)L.

[0022] And / or, the silicone resin is a hydroxyl-containing silicone resin or an amino-containing silicone resin.

[0023] In a second aspect, the present application further provides a composite flame-retardant coating prepared by the preparation method.

[0024] In a third aspect, the present application further provides the composite flame-retardant coating prepared by the preparation method or the application of the composite flame-retardant coating in preparing a flame-retardant product.

[0025] In a fourth aspect, the present application further provides an application method of the composite flame-retardant coating, comprising the following steps:

[0026] applying the intumescent flame-retardant coating to the substrate and drying to form an intumescent flame-retardant coating layer;

[0027] applying the ceramic flame-retardant coating to the intumescent flame-retardant coating layer and drying to form a ceramic flame-retardant coating layer.

[0028] Preferably, the material of the substrate is any one of steel, wood and polymer material.

[0029] If the material of the substrate is steel, the thickness ratio of the intumescent flame-retardant coating layer and the ceramic flame-retardant coating layer is (2-5):1.

[0030] If the material of the substrate is wood, the thickness ratio of the intumescent flame-retardant coating layer and the ceramic flame-retardant coating layer is (1-3):2.

[0031] If the material of the substrate is polymer material, the thickness ratio of the intumescent flame-retardant coating layer and the ceramic flame-retardant coating layer is (1-1.5):1.

[0032] The composite flame-retardant coating, the preparation method and the application method thereof have the following beneficial effects compared with the prior art:

[0033] 1. The preparation method of the composite fire-retardant coating of the present application, which comprises intumescent fire-retardant coating and ceramic fire-retardant coating; wherein, for the preparation of the intumescent fire-retardant coating, organic phytic acid and dicyandiamide are used to generate polymerization reaction at high temperature and high pressure to form three-dimensional amidine phosphate polymer, and ammonium polyphosphate is coated, and finally the coated components are grafted into polyvinyl alcohol system; here, polyvinyl alcohol serves as green binder on one hand, which is bonded to the surface of the protected substrate, and on the other hand, it also serves as carbon source (polyhydric alcohol) in the intumescent fire-retardant coating; for the preparation of the ceramic fire-retardant coating, boric acid is directly coated onto the surface of silicon oxide and aluminum oxide at high temperature, which is to reduce the ceramization temperature and play the role of cosolvent; the boric acid coated composite is grafted into silicone resin system, which can also achieve stable storage of the coating product and long-term stability and no migration after the coating is dried; finally, the two coatings are further crosslinked by boric acid and polyvinyl alcohol to achieve good effects of interface stability and no peeling; therefore, the present application solves the problems existing in most products on the market, and innovatively combines two excellent fireproof mechanisms, which has high practical significance and application value.

[0034] 2. The present application coats the intumescent fire-retardant coating onto the substrate, dries, forms the intumescent fire-retardant coating layer; coats the ceramic fire-retardant coating onto the intumescent fire-retardant coating layer, dries, forms the ceramic fire-retardant coating layer; uses the intumescent fire-retardant coating to foam and expand at high temperature combustion, "lifts up" the surface ceramic fire-retardant coating layer, and at the same time, the ceramic fire-retardant coating layer sintering at higher temperature realizes careful ceramization, thereby realizing better fireproof performance; in terms of fireproof performance, the intumescent fire-retardant coating layer preferentially generates catalytic carbonization and expansion reaction, rapidly "lifts up" the ceramic fire-retardant coating layer, and the porous structure in the ceramic fire-retardant coating layer is beneficial to reducing heat conduction; further heating the ceramic fire-retardant coating layer will rapidly generate reaction to form very dense ceramic structure, directly insulates the flame to avoid its erosion to the intumescent layer, and at the same time, the ceramic fire-retardant coating layer also has the characteristics of slow heat conduction, further coordinates the intumescent layer to realize the purpose of protecting the body; wherein, boric acid has very many functions in the system, on one hand, it maintains the stability of the coating, and on the other hand, it reduces the ceramization temperature and plays the role of cosolvent. Therefore, the present application has high practical significance and application value. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0036] Figure 1A scanning electron microscope (SEM) of the organically coated ammonium polyphosphate prepared in Example 1;

[0037] Figure 2 A scanning electron microscope (SEM) of the borate adsorbed silica and alumina prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0039] In the description of the present application, it should be understood that the orientation or position relationship indicated by terms such as "upper" is based on the orientation or position relationship shown in the drawings, or the orientation or position relationship commonly used when the product of the present application is used, or the orientation or position relationship commonly understood by those skilled in the art, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0040] The sequence of the following embodiments is not limited as the preferred sequence of the embodiments. In addition, in the description of the present application, the term "comprising" means "including but not limited to". Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is only for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the described range has been specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated in this text, it refers to any cited number (fraction or integer) within the indicated range.

[0041] The embodiment of the present application provides a preparation method of a composite flame-retardant coating, and the composite flame-retardant coating comprises an intumescent flame-retardant coating and a ceramic flame-retardant coating.

[0042] The preparation method of the intumescent flame-retardant coating comprises the following steps:

[0043] S11, dissolving phytic acid and dicyandiamide in DMF to perform a solvothermal reaction to obtain amidine phosphate polymer;

[0044] S12, dissolve the amidine phosphate polymer into the polyvinyl alcohol aqueous solution, add ammonium polyphosphate, and perform hydrothermal reaction to obtain the intumescent flame-retardant coating;

[0045] The preparation method of the ceramic flame-retardant coating comprises the following steps:

[0046] S21, mix boric acid, aluminum oxide and silicon oxide, grind, and calcine to obtain a composite material;

[0047] S22, add the composite material into silicone resin to obtain the ceramic flame-retardant coating.

[0048] The preparation method of the composite flame-retardant coating aims to solve the problems of poor temperature resistance, poor coating stability and low coordination flame-retardant efficiency of the conventional intumescent flame-retardant coating. 18 O 24 P6) and dicyandiamide (chemical formula C2H4N4) at high temperature and high pressure to form a three-dimensional amidine phosphate polymer, and the ammonium polyphosphate is coated, and finally the coated component is grafted into a polyvinyl alcohol system; here, the polyvinyl alcohol serves as a green binder on one hand, and is bonded to the surface of the protected base material, and on the other hand, can also serve as a carbon source (polyhydric alcohol) in the intumescent flame-retardant coating; for the preparation of the ceramic flame-retardant coating, boric acid is directly coated onto the surface of silicon oxide and aluminum oxide at high temperature, which serves as a dissolving aid to reduce the ceramization temperature; the composite material coated with boric acid is grafted into an organic silicone resin system, which can also achieve stable storage of the coating product and long-term stability and no migration of the coating after drying; finally, the two coatings are further crosslinked by boric acid and polyvinyl alcohol to achieve good effects of interface stability and no peeling. Therefore, the present application solves the problems of most products on the market, and innovatively combines two excellent fireproof mechanisms, which has high practical significance and application value.

[0049] In some embodiments, in the step of dissolving the phytic acid and the dicyandiamide in DMF (N,N-dimethylformamide) and performing solvothermal reaction, the temperature of the solvothermal reaction is 100-200 DEG C, and the time is 3-15 h.

[0050] Specifically, the phytic acid and the dicyandiamide are dissolved in DMF to perform solvothermal reaction, the material is cooled and distilled at low pressure to separate DMF and the amidine phosphate polymer, and the amidine phosphate polymer is obtained.

[0051] In some embodiments, in the step of dissolving the amidine phosphate polymer into the polyvinyl alcohol aqueous solution, adding ammonium polyphosphate, and performing hydrothermal reaction, the temperature of the hydrothermal reaction is 80-150 DEG C, and the time is 2-10 h.

[0052] Specifically, the amidine phosphate polymer is dispersed into a polyvinyl alcohol aqueous solution, heated to dissolve, and then ammonium polyphosphate is added to further react under high temperature and high pressure through hydrothermal treatment to form a uniform dispersion, thereby obtaining the intumescent flame-retardant coating.

[0053] In some embodiments, the mass-volume ratio of phytic acid, dicyandiamide, polyvinyl alcohol aqueous solution and DMF is 500g:(150-200)g:(2500-3000)g:(1-1.5)L.

[0054] The mass concentration of the polyvinyl alcohol aqueous solution is 10-15%.

[0055] In some embodiments, after the boric acid, aluminum oxide and silicon oxide are ground, the calcination temperature in the calcination step is 300-500℃, and the time is 3-10h.

[0056] Specifically, the boric acid, aluminum oxide and silicon oxide are dispersed and ground in a sand mill, and then high-temperature calcination treatment is performed to form a boric acid-coated aluminum oxide and silicon oxide composite material; the composite material is crushed and added to a silicone resin, and stirring is performed until the composite material is uniformly dispersed, thereby obtaining the ceramic flame-retardant coating.

[0057] In some embodiments, the boric acid, aluminum oxide and silicon oxide are mixed and ground to a particle size of ≤1μm.

[0058] In some embodiments, the mass-volume ratio of boric acid, aluminum oxide, silicon oxide and silicone resin is 100g:(300-1200)g:(800-1500)g:(1-1.5)L.

[0059] In some embodiments, the silicone resin is a hydroxyl-containing silicone resin or an amino-containing silicone resin.

[0060] In some embodiments, the boric acid, aluminum oxide and silicon oxide are dispersed in water, and are cyclically ground by a high-speed sand mill until the final particle size is ≤1μm, thereby obtaining a mixture; after the mixture is dried, high-temperature calcination treatment is performed to form a boric acid-coated aluminum oxide and silicon oxide composite material; and the mass ratio of boric acid to water is 1:(1-2).

[0061] Based on the same inventive concept, the application further provides a composite flame-retardant coating prepared by the above preparation method.

[0062] Based on the same inventive concept, the application further provides an application of the composite flame-retardant coating prepared by the above preparation method or the above composite flame-retardant coating in the preparation of a flame-retardant product.

[0063] Based on the same inventive concept, the application further provides an application method of the above composite flame-retardant coating, which comprises the following steps:

[0064] The intumescent fire-retardant coating is applied to the substrate and dried to form an intumescent fire-retardant coating layer;

[0065] The ceramic fire-retardant coating is applied to the intumescent fire-retardant coating layer and dried to form a ceramic fire-retardant coating layer.

[0066] Specifically, when the ceramic fire-retardant coating is applied to the intumescent fire-retardant coating layer and dried, the boric acid in the ceramic fire-retardant coating and the polyvinyl alcohol in the intumescent fire-retardant coating layer further crosslink.

[0067] In some embodiments, the material of the substrate is any one of steel, wood, and polymer material.

[0068] If the material of the substrate is steel, the thickness ratio of the intumescent fire-retardant coating layer to the ceramic fire-retardant coating layer is (2-5):1.

[0069] If the material of the substrate is wood, the thickness ratio of the intumescent fire-retardant coating layer to the ceramic fire-retardant coating layer is (1-3):2.

[0070] If the material of the substrate is polymer material, the thickness ratio of the intumescent fire-retardant coating layer to the ceramic fire-retardant coating layer is (1-1.5):1.

[0071] The intumescent fire-retardant coating is applied to the substrate and dried to form an intumescent fire-retardant coating layer; the ceramic fire-retardant coating is applied to the intumescent fire-retardant coating layer and dried to form a ceramic fire-retardant coating layer; the intumescent fire-retardant coating layer is foamed and expanded under high-temperature combustion to “lift” the ceramic fire-retardant coating layer on the surface, and the ceramic fire-retardant coating layer is sintered at a higher temperature to achieve thorough ceramicization, thereby achieving better fireproof performance.

[0072] The composite fire-retardant coating prepared by the application is coated on a substrate to form an intumescent fire-retardant coating and a ceramic fire-retardant coating, which not only has the advantages of the intumescent coating in isolating flame and energy transmission, but also has the heat insulation and flame penetration isolation ability of the ceramic fire-retardant coating, achieving the goal of 1+1>2. The specific principle is that the cross-linking reaction of phytic acid and dicyandiamide coats ammonium polyphosphate, realizing the disadvantages of uneven dispersion of inorganic fire retardant and easy migration in the later period; at the same time, the grafting reaction of excess phosphate and polyvinyl alcohol can reduce the acidity of the system and corrode the protected body; on the other hand, the organic coated ammonium polyphosphate can also be firmly limited in the system by polyvinyl alcohol, which fundamentally solves the dispersion and stability of inorganic fire retardants in organic systems. In addition, boric acid can be adsorbed to the surface of alumina and silica at high temperature and then dispersed into the silicone resin, and the cross-linking reaction between boric acid and the hydroxyl or amino groups in the silicone increases the viscosity of the system and improves the stability of the liquid system, and the high hardness and strength of the outer surface after the coating is dried can also protect the inner intumescent layer from being damaged, and finally the intumescent fire-retardant coating and the ceramic fire-retardant coating are still combined by chemical bonding, that is, the cross-linking polymerization reaction between boric acid and polyvinyl alcohol makes the two coatings more closely and stably combined.

[0073] In terms of fireproof performance, the intumescent fire-retardant coating preferentially undergoes catalytic carbonization and intumescent reaction, rapidly "lifting" the ceramic fire-retardant coating, and the loose and porous structure of the ceramic fire-retardant coating is beneficial to reducing heat conduction; further heating of the ceramic fire-retardant coating will rapidly react to generate a very dense ceramic structure, directly isolating the flame and avoiding its erosion of the intumescent layer, and the ceramic fire-retardant coating also has the characteristic of slow heat conduction, further coordinating the intumescent layer to achieve the purpose of protecting the body; among them, boric acid plays a very important role in the system, on the one hand, it maintains the stability of the coating, and on the other hand, it reduces the ceramization temperature and plays the role of a cosolvent. Therefore, the application has high practical significance and application value.

[0074] The composite fire-retardant coating formed by the composite fire-retardant coating prepared by the application has the advantages of improving the uniform dispersion and stability of the fire-retardant components in the binder system, and reasonably designing the thermal decomposition and synergistic effect between different fireproof components, realizing a solid ceramic oxide layer on the outer surface to isolate the erosion of the flame, and a loose intumescent structure inside to delay heat transmission, and achieving the purpose of efficient fireproofing.

[0075] The following further illustrates the composite fire-retardant coating, its preparation method and application method of the application with specific examples. This part further illustrates the content of the application in combination with specific examples, but should not be understood as a limitation of the application. If not specifically stated, the technical means used in the examples is the conventional means familiar to those skilled in the art. Unless specifically stated, the reagents, methods and equipment used in the application are conventional reagents, methods and equipment in the art.

[0076] The organic silicone resin used in the following examples is a hydroxyl-containing organic silicone resin, and the specific model is Dow Corning RSN 6018 model organic silicone resin. Example 1

[0077] The embodiment of the present application provides a preparation method of a composite flame-retardant coating, and the composite flame-retardant coating comprises an intumescent flame-retardant coating and a ceramic flame-retardant coating.

[0078] The preparation method of the intumescent flame-retardant coating comprises the following steps.

[0079] S11, 500g of phytic acid and 150g of dicyandiamide are dissolved in 1L of N,N-dimethylformamide (DMF), and polymerization reaction is carried out at 180℃ for 5h, and then the mixture is cooled and distilled at low pressure to separate DMF and amidine phosphate polymer, so as to obtain the amidine phosphate polymer;

[0080] S12, the amidine phosphate polymer in S11 is dispersed into 3000g of polyvinyl alcohol aqueous solution (the mass concentration of the polyvinyl alcohol aqueous solution is 10%), and the amidine phosphate polymer is dissolved by heating to 80℃, then 2000g of ammonium polyphosphate is added, and the temperature is raised to 120℃ again, and reaction is carried out at 120℃ for 3h, and finally the temperature is lowered to room temperature (25℃), so as to form a uniform dispersion liquid, and the intumescent flame-retardant coating is obtained.

[0081] The preparation method of the ceramic flame-retardant coating comprises the following steps.

[0082] S21, 100g of boric acid, 500g of aluminum oxide and 1500g of silicon oxide are dispersed into 100mL of water, and the mixture is ground by a high-speed sand mill to a particle size of less than or equal to 500nm, so as to obtain a mixture.

[0083] The mixture is dried at 100℃ for 12h;

[0084] The dried mixture is calcined at 350℃ for 5h to obtain a boric acid-coated aluminum oxide and silicon oxide composite material.

[0085] S22, the composite material in S21 is crushed and added into 1L of an organic silicone resin, and stirring is carried out until the mixture is uniformly dispersed, so as to obtain the ceramic flame-retardant coating; the organic silicone resin is a hydroxyl-containing organic silicone resin, and the specific model is Dow Corning RSN 6018 model organic silicone resin.

[0086] The embodiment also provides an application method of the composite flame-retardant coating, and the application method comprises the following steps.

[0087] S31, the intumescent flame-retardant coating prepared in Example 1 is coated on the surface of wood (the thickness is 5mm), and drying is carried out at room temperature (25℃) for 24h to obtain an intumescent flame-retardant coating with a thickness of 2mm.

[0088] S32, the ceramic flame retardant coating prepared in Example 1 is coated on the intumescent flame retardant coating, and dried at room temperature (25℃) for 24h to obtain a ceramic flame retardant coating with a thickness of 2mm.

[0089] Example 2

[0090] The embodiment of the present application provides a preparation method of a composite flame retardant coating, the composite flame retardant coating comprising an intumescent flame retardant coating and a ceramic flame retardant coating.

[0091] The preparation method of the intumescent flame retardant coating comprises the following steps:

[0092] S11, 500g of phytic acid and 150g of dicyandiamide are dissolved in 1L of N,N-dimethylformamide (DMF), and polymerization reaction is carried out at 180℃ for 5h, and the mixture is cooled and discharged and subjected to low-pressure distillation to separate DMF and amidine phosphate polymer, thereby obtaining the amidine phosphate polymer;

[0093] S12, the amidine phosphate polymer in S11 is dispersed into 3000g of polyvinyl alcohol aqueous solution (the mass concentration of the polyvinyl alcohol aqueous solution is 10%), and the mixture is heated to 80℃ to dissolve the amidine phosphate polymer, 2000g of ammonium polyphosphate is added, the mixture is heated to 120℃ again, and the mixture is reacted at 120℃ for 3h, and finally the mixture is cooled to room temperature (25℃) to form a uniform dispersion, thereby obtaining the intumescent flame retardant coating;

[0094] The preparation method of the ceramic flame retardant coating comprises:

[0095] S21, 100g of boric acid, 1000g of aluminum oxide and 1000g of silicon oxide are dispersed into 100mL of water, and the mixture is subjected to cyclic grinding by a high-speed sand mill until the particle size of each material is ≤500nm, thereby obtaining a mixture;

[0096] The mixture is dried at 100℃ for 12h;

[0097] The dried mixture is calcined at 400℃ for 5h to obtain a boric acid-coated aluminum oxide and silicon oxide composite material;

[0098] S22, the composite material in S21 is crushed and added into 1L of silicone resin, and the mixture is stirred until the mixture is uniformly dispersed, thereby obtaining the ceramic flame retardant coating; the silicone resin is a hydroxyl-containing silicone resin, and the specific model is Dow Corning RSN 6018 type silicone resin.

[0099] The embodiment also provides an application method of the composite flame retardant coating, comprising the following steps:

[0100] S31, the intumescent flame retardant coating prepared in Example 2 is coated on the surface of steel material (thickness of 5 mm), dried at room temperature (25℃) for 24 h to obtain an intumescent flame retardant coating with a thickness of 3 mm;

[0101] S32, the ceramic flame retardant coating prepared in Example 2 is coated on the intumescent flame retardant coating, dried at room temperature (25℃) for 24 h to obtain a ceramic flame retardant coating with a thickness of 1 mm.

[0102] Example 3

[0103] The embodiment of the present application provides a preparation method of a composite flame retardant coating, the composite flame retardant coating comprising an intumescent flame retardant coating and a ceramic flame retardant coating;

[0104] The preparation method of the intumescent flame retardant coating comprises the following steps:

[0105] S11, 500 g of phytic acid and 200 g of dicyandiamide are dissolved in 1 L of N,N-dimethylformamide (DMF), and polymerization reaction is carried out at 150℃ for 5 h, and the mixture is cooled and discharged and subjected to low-pressure distillation to separate DMF and amidine phosphate polymer, thereby obtaining the amidine phosphate polymer;

[0106] S12, the amidine phosphate polymer in S11 is dispersed into 2500 g of polyvinyl alcohol aqueous solution (the mass concentration of the polyvinyl alcohol aqueous solution is 10%), and the mixture is heated to 80℃ to dissolve the amidine phosphate polymer, then 1500 g of ammonium polyphosphate is added, and the mixture is heated to 120℃ again and reacted at 120℃ for 3 h, and finally cooled to room temperature (25℃) to form a uniform dispersion, thereby obtaining the intumescent flame retardant coating;

[0107] The preparation method of the ceramic flame retardant coating comprises:

[0108] S21, 100 g of boric acid, 300 g of aluminum oxide and 1000 g of silicon oxide are dispersed into 100 mL of water, and the mixture is subjected to cyclic grinding by a high-speed sand mill until the particle size of each material is ≤500 nm, thereby obtaining a mixture;

[0109] The mixture is dried at 100℃ for 12 h;

[0110] The dried mixture is calcined at 400℃ for 5 h to obtain a boric acid-coated aluminum oxide and silicon oxide composite material;

[0111] S22, the composite material in S21 is crushed and added into 1 L of silicone resin, and the mixture is stirred until the mixture is uniformly dispersed, thereby obtaining the ceramic flame retardant coating; the silicone resin is a hydroxyl-containing silicone resin, and the specific model is Dow Corning RSN 6018 type silicone resin.

[0112] The embodiment also provides an application method of the composite fire-retardant coating.

[0113] S31, the intumescent fire-retardant coating prepared in Example 3 is coated on the surface of a polymer (specifically, a PP (polypropylene) substrate with a thickness of 5 mm), and dried at room temperature (25°C) for 24 h to obtain an intumescent fire-retardant coating layer with a thickness of 2 mm;

[0114] S32, the ceramic fire-retardant coating prepared in Example 3 is coated on the intumescent fire-retardant coating layer, and dried at room temperature (25°C) for 24 h to obtain a ceramic fire-retardant coating layer with a thickness of 2 mm.

[0115] Comparative Example 1

[0116] The comparative example provides a preparation method of an intumescent fire-retardant coating, including the following steps:

[0117] S11, 500 g of phytic acid and 150 g of dicyandiamide are dissolved in 1 L of N,N-dimethylformamide (DMF), and polymerized at 180°C for 5 h, and then the material is discharged after cooling and low-pressure distillation to separate DMF and amidine phosphate polymer, to obtain the amidine phosphate polymer;

[0118] S12, the amidine phosphate polymer in S11 is dispersed into 3000 g of a polyvinyl alcohol aqueous solution (with a mass concentration of 10%), heated to 80°C to dissolve the amidine phosphate polymer, and then 2000 g of ammonium polyphosphate is added, and heated to 120°C again, and reacted at 120°C for 3 h, and finally cooled to room temperature (25°C) to form a uniform dispersion, to obtain the intumescent fire-retardant coating;

[0119] The comparative example also provides an application method of the intumescent fire-retardant coating, including the following steps:

[0120] The intumescent fire-retardant coating prepared in Comparative Example 1 is coated on the surface of a steel material (with a thickness of 5 mm), and dried at room temperature (25°C) for 24 h to obtain an intumescent fire-retardant coating layer with a thickness of 4 mm.

[0121] Comparative Example 2

[0122] The comparative example provides a preparation method of a ceramic fire-retardant coating, including the following steps:

[0123] S11, 100 g of boric acid and 1000 g of aluminum oxide and 1000 g of silicon oxide are dispersed into 100 mL of water, and circularly ground by a high-speed sand mill until the particle size of each material is ≤500 nm to obtain a mixture;

[0124] The mixture is dried at 100°C for 12 h;

[0125] The mixture after drying is calcined at 400℃ for 5h to obtain borate-coated alumina and silica composite material;

[0126] S12, the composite material after crushing in S11 is added to 1L silicone resin, and stirring is carried out until uniform dispersion is obtained, to obtain a ceramic flame-retardant coating; the silicone resin is a hydroxyl-containing silicone resin, and the specific model is Dow Corning RSN 6018 model silicone resin.

[0127] The present comparative example also provides an application method of the above-mentioned ceramic flame-retardant coating, comprising the following steps:

[0128] The ceramic flame-retardant coating prepared in Comparative Example 2 is dried on the surface of a steel material (thickness of 5mm) at room temperature (25℃) for 24h to obtain a ceramic flame-retardant coating layer with a thickness of 4mm.

[0129] Performance test

[0130] Figure 1 The scanning electron microscope (SEM) of the organic-coated ammonium polyphosphate prepared in Example 1 is shown in the figure.

[0131] As can be seen from the figure, Figure 1 the size of the organic-coated ammonium polyphosphate is 300-500nm, and the distribution is very uniform.

[0132] Figure 2 The scanning electron microscope (SEM) of the borate-adsorbed silica and alumina prepared in Example 1 of the present application is shown in the figure.

[0133] As can be seen from the figure, Figure 2 the borate-coated and silica and alumina particle size distribution is uniform, and the surface is very smooth, and the fireproof coating formed thereby has a smooth surface and can quickly form a ceramic fireproof layer under high-temperature combustion.

[0134] The coating layers formed after the different substrates prepared in Examples 1-3 are coated with the composite flame-retardant coating are tested in a propane flame for 10min, and the intumescent flame-retardant coating and ceramic flame-retardant coating formed by the intumescent flame-retardant coating and ceramic flame-retardant coating in Comparative Examples 1-2 are tested in a propane flame for 10min; and pure steel, pure wood and pure PP (polypropylene) with a thickness of 5mm are used as substrates, and no flame-retardant coating is coated (i.e. the coating thickness is 0mm), and the test is carried out in a propane flame for 10min; the test results are shown in Table 1 below.

[0135] Table 1- Fire resistance test of coating layers formed after different examples are coated with composite flame-retardant coating

[0136]

[0137]

[0138] The total thickness of the coating in Table 1 refers to the sum of the thickness of all the coatings on the substrate; the total thickness of the coating after expansion refers to the total thickness of the coating after the coating is expanded at the time of testing; the temperature of the back surface of the substrate refers to the temperature of the end surface of the substrate that does not form a coating.

[0139] As can be seen from Table 1, the composite fire-retardant coating prepared by the present application has excellent fireproof performance and can be applied to steel, wood and plastic products, and all of them exhibit excellent fireproof performance during the fire resistance test.

[0140] The above description is merely preferred embodiments of the present application but not to confine the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a composite flame retardant coating, characterized in that: The composite flame retardant coating comprises an intumescent flame retardant coating and a ceramic flame retardant coating; The method for preparing the intumescent flame-retardant coating comprises the following steps: Phytic acid and dicyandiamide are dissolved in DMF and subjected to solvent thermal reaction to obtain amidine phosphate polymers; dissolving an amidine phosphate polymer in a polyvinyl alcohol aqueous solution, adding ammonium polyphosphate, and performing a hydrothermal reaction to obtain an intumescent flame retardant coating; The preparation method of the ceramic flame retardant coating comprises: Boric acid, aluminum oxide and silicon oxide are mixed, ground and calcined to obtain a composite material; The composite material is added to the silicone resin to obtain a ceramic flame retardant coating.

2. The method for preparing the composite flame retardant coating according to claim 1, wherein: In the step of dissolving phytic acid and dicyandiamide in DMF and performing a solvothermal reaction, the temperature of the solvothermal reaction is 100-200° C. and the time is 3-15 hours.

3. The method for preparing the composite flame retardant coating according to claim 1, wherein: In the step of dissolving the amidine phosphate polymer into a polyvinyl alcohol aqueous solution, adding ammonium polyphosphate, and performing a hydrothermal reaction, the hydrothermal reaction temperature is 80-150° C. and the time is 2-10 hours.

4. The method for preparing the composite flame retardant coating according to claim 1, wherein: The mass volume ratio of the phytic acid, dicyandiamide, polyvinyl alcohol aqueous solution and DMF is 500g: (150-200)g: (2500-3000)g: (1-1.5)L; The mass concentration of the polyvinyl alcohol aqueous solution is 10-15%.

5. The method for preparing the composite flame retardant coating according to claim 1, wherein: After grinding boric acid, aluminum oxide and silicon oxide, in the calcination step, the calcination temperature is 300-500° C. and the time is 3-10 hours.

6. The method for preparing the composite flame retardant coating according to claim 1, wherein: Boric acid, aluminum oxide, and silicon oxide are mixed and ground to a particle size of ≤1 μm; And / or, the mass volume ratio of the boric acid, aluminum oxide, silicon oxide and silicone resin is 100g:(300-1200)g:(800-1500)g:(1-1.5)L; And / or, the organic silicone resin is an organic silicone resin containing hydroxyl groups or an organic silicone resin containing amino groups.

7. A composite flame retardant coating, characterized in that: The preparation method is as described in any one of claims 1 to 6.

8. Use of the composite flame retardant coating prepared by the preparation method according to any one of claims 1 to 6 or the composite flame retardant coating according to claim 7 in the preparation of flame retardant products.

9. A method for applying the composite flame retardant coating according to claim 7, characterized in that: The following steps are involved: applying the intumescent flame retardant coating onto a substrate and drying the coating to form an intumescent flame retardant coating; The ceramic flame retardant coating is applied onto the intumescent flame retardant coating and dried to form a ceramic flame retardant coating.

10. The application method according to claim 9, characterized in that: The material of the substrate is any one of steel, wood, and polymer materials; If the substrate is made of steel, the thickness ratio of the intumescent flame retardant coating to the ceramic flame retardant coating is (2-5):1; If the substrate is made of wood, the thickness ratio of the intumescent flame retardant coating to the ceramic flame retardant coating is (1-3):2; If the material of the substrate is a polymer material, the thickness ratio of the intumescent flame retardant coating to the ceramic flame retardant coating is (1-1.5):1.

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