A flame-retardant and fire-proof coating and its preparation method

Abstract

The present invention relates to the technical field of coatings, and discloses a flame retardant and fireproof coating and a preparation method thereof. The flame retardant and fireproof coating of the present invention includes 100 parts by weight of epoxy resin, 3-12 parts by weight of polyphosphate-indole flame retardant, 6.8-11.5 parts by weight of curing agent, etc.; polyphosphate-indole flame retardant is used as an intumescent flame retardant, which can effectively improve the carbonization and mass residual rate of epoxy resin coating cured product. When burning, it promotes the dehydration of polyaromatic hydrocarbon fused ring structure and epoxy resin matrix to form an intumescent carbon layer, significantly reduces the peak heat release rate, total heat release and total smoke release, and shows excellent flame retardant properties. Polyphosphate-indole flame retardant contains a flexible aliphatic long chain, has a good toughening effect on epoxy resin, and significantly improves the impact strength and toughness of the cured product.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, in particular to a flame retardant and fireproof coating and a preparation method thereof. Background Art

[0002] Epoxy resin coatings offer a wide range of applications due to their high corrosion resistance, excellent insulation properties, and high mechanical strength. However, traditional epoxy resin coatings suffer from poor flame retardancy and toughness, limiting their practical application in flame retardancy and fire protection. Flame retardants, such as phosphorus-containing flame retardants, intumescent flame retardants, and brominated flame retardants, are typically added to epoxy resin coatings.

[0003] Intumescent flame retardants combine acid, carbon, and gas sources, resulting in high char-forming and flame-retardant properties. Commonly used epoxy resin toughening agents include polyethers, silicones, and substances containing flexible aliphatic long chains. Patent CN113292852B discloses a resin composition containing a phosphophenyl bisphenol polymer, its preparation method, and applications. By reacting phenylphosphonyl dichloride or phenyl dichlorophosphate with tetramethylbisphenol, a phosphophenyl bisphenol polymer flame retardant is produced. This improves the epoxy resin's glass transition temperature and flame retardancy, but the patent does not address the epoxy resin's poor toughness, such as impact strength. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention solves the problem of poor flame retardancy and toughness of epoxy resin coatings.

[0005] The invention provides a flame retardant and fireproof coating, comprising 100 parts by weight of epoxy resin, 3-12 parts by weight of polyphosphate-indole flame retardant, 6.8-11.5 parts by weight of curing agent, 0.5-1 part by weight of defoaming agent, 0.3-0.6 part by weight of leveling agent and 0.2-0.4 part by weight of wetting agent.

[0006] The preparation method of the flame retardant and fireproof coating comprises the following steps: adding epoxy resin, polyphosphate-indole flame retardant, curing agent, defoaming agent, leveling agent and wetting agent into n-butanol solvent, stirring and mixing, and obtaining the flame retardant and fireproof coating.

[0007] Preferably, the curing agent is ethylenediamine, diethylenetriamine or triethylenetetramine.

[0008] Preferably, the preparation method of the polyphosphate-indole flame retardant is:

[0009] (1) Add 6,12-diphenol-5,11-dihydroindole[3,2-b]carbazole and benzyltriethylammonium chloride to dimethyl sulfoxide, and add sodium hydroxide aqueous solution and 1-bromoalkane (structural formula Br-C n H 2n+1), stirring at 20-30°C for 6-10h, adding water to dilute, precipitating the precipitate, filtering, washing with water, and recrystallizing the product from a mixed solution of N,N-dimethylformamide and chloroform to obtain a diphenolylalkyl indole intermediate.

[0010] .

[0011] (2) Add phenyl dichlorophosphate, diphenolyl alkyl indole intermediate, and triethylamine to N,N-dimethylformamide, stir and react at 30-50°C for 12-18 hours, then add diphenolyl alkyl indole intermediate, continue stirring and react for 0.5-1 hour, pour the solution into water to precipitate the precipitate, filter it, wash it with water and ethanol in turn, and dry it to obtain a polyphosphate-indole flame retardant. The reaction formula is:

[0012] .

[0013] Preferably, the molar ratio of 6,12-diphenol-5,11-dihydroindole[3,2-b]carbazole, benzyltriethylammonium chloride, sodium hydroxide, and 1-bromoalkane in (1) is 1:(0.008-0.01):(10-12):(2.4-2.8).

[0014] Preferably, the molecular formula of 1-bromoalkane in (1) is Br-C n H 2n+1 , n is any integer between 10 and 16.

[0015] Preferably, the molar ratio of phenyl dichlorophosphate, diphenolylalkyl indole intermediate, and triethylamine in (2) is 1:(1.04-1.08):(2.1-2.2).

[0016] The beneficial technical effects of the present invention are as follows: the present invention conducts a phosphate polymerization reaction on a diphenol-based alkyl indole intermediate and phenyl dichlorophosphate to obtain a polyphosphate-indole flame retardant, which contains a phosphate and an indole nitrogen-containing heterocycle as an acid source and a gas source, and also contains a polyaromatic hydrocarbon fused ring structure as a carbon source to form an intumescent flame retardant, which can effectively improve the carbonization and mass residual rate of the epoxy resin coating cured product. During combustion, the polyaromatic hydrocarbon fused ring structure and the epoxy resin matrix are promoted to dehydrate to form an intumescent carbon layer, which can inhibit the contact between oxygen and the epoxy resin matrix, prevent heat conduction, inhibit the combustion reaction process, and simultaneously play a role in inhibiting smoke emission, significantly reducing the peak heat release rate, the total heat release and the total smoke release, and showing excellent flame retardant properties.

[0017] The terminal hydroxyl groups of the polyphosphate-indole flame retardant of the present invention react with the epoxy groups of the epoxy resin during a high-temperature thermal curing reaction, thereby grafting the flame retardant into the epoxy resin curing system, thereby improving the interfacial bonding strength between the flame retardant and the epoxy resin and having less influence on the mechanical properties of the epoxy resin cured product. At the same time, the flame retardant contains flexible long aliphatic chains, which have a good toughening effect on the epoxy resin and significantly improve the impact strength and toughness of the cured product. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described 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.

[0019] To 2 mL of acetonitrile were added 0.234 g (2 mmol) of indole, 0.244 g (2 mmol) of p-hydroxybenzaldehyde, 0.0228 g of catalyst N,2-dibromo-6-chloro-3,4-dihydro-2H-benzo[e][1,2,4]thiadiazine-7-sulfonamide-1,1-dioxide (DCDBTSD, structural formula ), react at 50°C for 20 minutes, filter and dry, and the product is recrystallized in a mixed solution of N,N-dimethylformamide and chloroform to obtain 6,12-diphenol-5,11-dihydroindole[3,2-b]carbazole. The structural formula is .

[0020] Example 1

[0021] (1) Add 5 mmol of 6,12-diphenol-5,11-dihydroindole[3,2-b]carbazole and 0.04 mmol of benzyltriethylammonium chloride to 80 mL of dimethyl sulfoxide. Add 6 mL of an aqueous solution containing 56 mmol of sodium hydroxide and 12 mmol of 1-bromotetradecane in a nitrogen atmosphere. Stir and react at 20°C for 10 hours. Add water to dilute the mixture, filter the precipitate, wash with water, and recrystallize the product in a mixed solution of N,N-dimethylformamide and chloroform in a volume ratio of 1:1 to obtain a diphenol-alkyl indole intermediate. The structural formula is: .

[0022] (2) Add 10 mmol of phenyl dichlorophosphate, 10 mmol of diphenolylalkylindole intermediate, and 22 mmol of triethylamine to 100 mL of N,N-dimethylformamide, and stir the mixture at 50°C for 12 h. Then add 0.8 mmol of diphenolylalkylindole intermediate and continue stirring the mixture for 0.5 h. Pour the solution into water to precipitate the precipitate. After filtering, wash the precipitate with water and ethanol in turn, and dry it to obtain a polyphosphate-indole flame retardant.

[0023] (3) Add 100 g of epoxy resin E44, 3 g of polyphosphate-indole flame retardant, 9.8 g of curing agent diethylenetriamine, 0.5 g of defoaming agent BYK-A530, 0.4 g of leveling agent TEGO-2300, and 0.4 g of wetting agent TEGOWet270 to 130 mL of n-butanol solvent, stir and mix to obtain a flame retardant and fireproof coating.

[0024] Example 2

[0025] (1) Add 5 mmol of 6,12-diphenol-5,11-dihydroindole[3,2-b]carbazole and 0.05 mmol of benzyltriethylammonium chloride to 80 mL of dimethyl sulfoxide. Add 6 mL of an aqueous solution containing 50 mmol of sodium hydroxide and 12 mmol of 1-bromohexadecane in a nitrogen atmosphere. Stir and react at 25°C for 10 h. Add water to dilute the mixture. The precipitate is filtered and washed with water. The product is recrystallized from a mixed solution of N,N-dimethylformamide and chloroform in a volume ratio of 1:1 to obtain a diphenol-alkyl indole intermediate.

[0026] (2) Add 10 mmol of phenyl dichlorophosphate, 10 mmol of diphenolylalkylindole intermediate, and 22 mmol of triethylamine to 90 mL of N,N-dimethylformamide, and stir the mixture at 40°C for 12 h. Then add 0.4 mmol of diphenolylalkylindole intermediate and continue stirring the mixture for 1 h. Pour the solution into water to precipitate the precipitate. After filtering, wash the precipitate with water and ethanol in turn, and dry the mixture to obtain a polyphosphate-indole flame retardant.

[0027] (3) Add 100 g of epoxy resin E44, 7 g of polyphosphate-indole flame retardant, 6.8 g of curing agent ethylenediamine, 1 g of defoaming agent BYK-A530, 0.3 g of leveling agent TEGO-2300, and 0.2 g of wetting agent TEGO Wet270 to 140 mL of n-butanol solvent, stir and mix to obtain a flame retardant and fireproof coating.

[0028] Example 3

[0029] (1) Add 5 mmol of 6,12-diphenol-5,11-dihydroindole[3,2-b]carbazole and 0.048 mmol of benzyltriethylammonium chloride to 80 mL of dimethyl sulfoxide. Add 6 mL of an aqueous solution containing 60 mmol of sodium hydroxide and 14 mmol of 1-bromodecane in a nitrogen atmosphere. Stir and react at 30°C for 6 h. Add water to dilute the mixture. The precipitate is filtered and washed with water. The product is recrystallized from a mixed solution of N,N-dimethylformamide and chloroform in a volume ratio of 1:1 to obtain a diphenol-alkyl indole intermediate.

[0030] (2) Add 10 mmol of phenyl dichlorophosphate, 10 mmol of diphenolylalkylindole intermediate, and 21 mmol of triethylamine to 100 mL of N,N-dimethylformamide, and stir the mixture at 30°C for 18 h. Then add 0.6 mmol of diphenolylalkylindole intermediate and continue stirring the mixture for 1 h. Pour the solution into water to precipitate the precipitate, filter it, wash it with water and ethanol, and dry it to obtain a polyphosphate-indole flame retardant.

[0031] (3) Add 100 g of epoxy resin E44, 12 g of polyphosphate-indole flame retardant, 11.5 g of curing agent triethylenetetramine, 0.8 g of defoaming agent BYK-A530, 0.6 g of leveling agent TEGO-2300, and 0.2 g of wetting agent TEGOWet270 to 140 mL of n-butanol solvent, stir and mix to obtain a flame retardant and fireproof coating.

[0032] Comparative Example 1

[0033] (1) Add 100 g of epoxy resin E44, 9.8 g of curing agent diethylenetriamine, 0.5 g of defoaming agent BYK-A530, 0.4 g of leveling agent TEGO-2300, and 0.4 g of wetting agent TEGO Wet270 to 130 mL of n-butanol solvent, stir and mix to obtain a coating.

[0034] Comparative Example 2

[0035] (1) Add 10 mmol of phenyl dichlorophosphate, 10 mmol of 4,4'-biphenyldiphenol, and 22 mmol of triethylamine to 100 mL of N,N-dimethylformamide, and stir at 50°C for 12 h. Then add 0.8 mmol of diphenolylalkylindole intermediate and continue stirring for 0.5 h. Pour the solution into water to precipitate the precipitate. After filtering, wash with water and ethanol in turn, and dry to obtain a polyphosphate flame retardant.

[0036] (2) Add 100 g of epoxy resin E44, 3 g of polyphosphate flame retardant, 9.8 g of curing agent diethylenetriamine, 0.5 g of defoaming agent BYK-A530, 0.4 g of leveling agent TEGO-2300, and 0.4 g of wetting agent TEGO Wet270 to 130 mL of n-butanol solvent, stir and mix to obtain a coating.

[0037] Comparative Example 3

[0038] (1) Add 5 mmol of 6,12-diphenol-5,11-dihydroindole[3,2-b]carbazole and 0.04 mmol of benzyltriethylammonium chloride to 80 mL of dimethyl sulfoxide. Add 6 mL of an aqueous solution containing 56 mmol of sodium hydroxide and 12 mmol of 1-bromopropane in a nitrogen atmosphere. Stir and react at 20°C for 10 hours. Add water to dilute the mixture, precipitate, filter, and wash with water. The product is recrystallized from a mixed solution of N,N-dimethylformamide and chloroform to obtain a diphenol-alkyl indole intermediate. The structural formula is: .

[0039] (2) Add 10 mmol of phenyl dichlorophosphate, 10 mmol of diphenolylalkylindole intermediate, and 22 mmol of triethylamine to 100 mL of N,N-dimethylformamide, and stir the mixture at 50°C for 12 h. Then add 0.8 mmol of diphenolylalkylindole intermediate and continue stirring the mixture for 0.5 h. Pour the solution into water to precipitate the precipitate. After filtering, wash the precipitate with water and ethanol in turn, and dry it to obtain a polyphosphate-indole flame retardant.

[0040] (3) Add 100 g of epoxy resin E44, 3 g of polyphosphate-indole flame retardant, 9.8 g of curing agent diethylenetriamine, 0.5 g of defoaming agent BYK-A530, 0.4 g of leveling agent TEGO-2300, and 0.4 g of wetting agent TEGOWet270 to 130 mL of n-butanol solvent, stir and mix to obtain a coating.

[0041] The coating was first cured at 80°C for 3 hours, then at 130°C for 3 hours, and finally at 150°C for 1 hour to prepare a casting specimen. Impact strength was tested according to GB / T 2567-2008.

[0042] 8 mg of the casting was weighed and placed in a thermogravimetric analyzer for thermal property analysis in a nitrogen atmosphere at a heating rate of 10°C / min from 30°C to 800°C.

[0043] The casting was subjected to cone calorimetry test using a cone calorimeter with a sample size of 100 mm × 100 mm × 4 mm and a thermal radiation power of 50 kW / m 2 .

[0044] Table 1 Coating performance test

[0045]

[0046] After testing, compared with the epoxy resin coating of Comparative Example 1, Examples 1-3 added a polyphosphate-indole flame retardant, which contains phosphate and indole nitrogen-containing heterocycles as acid sources and gas sources, and contains a polyaromatic hydrocarbon condensed ring structure as a carbon source to form an intumescent flame retardant, thereby improving the carbonization and mass residual rate of the coating cured product. During combustion, it promotes the dehydration of the polyaromatic hydrocarbon condensed ring structure and the epoxy resin matrix to form an intumescent carbon layer, which can inhibit the contact between oxygen and the epoxy resin matrix, prevent heat conduction, inhibit the combustion reaction process, and at the same time play a role in inhibiting smoke escape, significantly reducing the peak heat release rate, total heat release and total smoke release, and showing excellent flame retardant properties. In addition, the terminal hydroxyl groups of the polyphosphate-indole flame retardant react with the epoxy groups of the epoxy resin during the high-temperature thermal curing reaction, thereby grafting the flame retardant into the epoxy resin curing system, improving the interfacial bonding strength between the flame retardant and the epoxy resin, and having less effect on the mechanical properties of the epoxy resin cured product. At the same time, the flame retardant contains flexible long aliphatic chains, which have a good toughening effect on the epoxy resin, significantly improving the impact strength and toughness of the cured product.

[0047] Compared with Example 1, in Comparative Example 2, phenyl dichlorophosphate and 4,4'-biphenol are reacted to obtain a polyphosphate flame retardant that does not contain an indole nitrogen-containing heterocycle or a polyaromatic fused ring structure, making it difficult to effectively form an intumescent flame retardant. The carbonization and mass residual rate of the coating cured product are not well improved, resulting in a large peak heat release rate, a total heat release, and a total smoke release, poor flame retardant properties, and no flexible aliphatic long chain, which cannot have a toughening effect, resulting in a low impact strength of the epoxy resin cured product.

[0048] Comparative Example 3 uses 1-bromopropane as a raw material. The obtained diphenol-based alkyl indole intermediate and polyphosphate-indole flame retardant do not contain flexible aliphatic long chains and cannot play a toughening effect, resulting in low impact strength of the epoxy resin cured product.

[0049] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A flame retardant fireproof coating, characterized in that: The flame retardant and fireproof coating comprises 100 parts by weight of epoxy resin, 3-12 parts by weight of polyphosphate-indole flame retardant, 6.8-11.5 parts by weight of curing agent, 0.5-1 part by weight of defoaming agent, 0.3-0.6 part by weight of leveling agent, and 0.2-0.4 part by weight of wetting agent; The preparation method of the polyphosphate-indole flame retardant comprises: adding phenyl dichlorophosphate, a diphenolyl alkyl indole intermediate, and triethylamine to N,N-dimethylformamide, stirring for a first reaction, then adding the diphenolyl alkyl indole intermediate, continuing stirring for a second reaction, pouring the solution into water to precipitate a precipitate, filtering, washing, and drying to obtain the polyphosphate-indole flame retardant; the molar ratio of the phenyl dichlorophosphate, the diphenolyl alkyl indole intermediate, and the triethylamine is 1:(1.04-1.08):(2.1-2.2); The structural formula of the diphenolyl alkyl indole intermediate is: , n is any integer between 10 and 16, The preparation method of the diphenolylalkyl indole intermediate comprises: adding 6,12-diphenolyl-5,11-dihydroindole[3,2-b]carbazole and benzyltriethylammonium chloride to dimethyl sulfoxide, adding sodium hydroxide aqueous solution and 1-bromoalkane in a nitrogen atmosphere, adding water to dilute the reaction, precipitating the precipitate, filtering, washing, and recrystallizing to obtain the diphenolylalkyl indole intermediate; In the preparation method of the diphenolyl alkyl indole intermediate, the reaction temperature is 20-30° C., and the reaction time is 6-10 hours. The molar ratio of the 6,12-diphenolyl-5,11-dihydroindole[3,2-b]carbazole, benzyltriethylammonium chloride, sodium hydroxide, and 1-bromoalkane is 1:(0.008-0.01):(10-12):(2.4-2.8).

2. The flame retardant and fireproof coating according to claim 1, characterized in that: The temperature of the first reaction is 30-50° C., and the reaction time is 12-18 h; the time of the second reaction is 0.5-1 h.

3. The flame retardant and fireproof coating according to claim 1, characterized in that: The curing agent is ethylenediamine, diethylenetriamine or triethylenetetramine.

4. The flame retardant and fireproof coating according to claim 1, characterized in that: The molecular formula of the 1-bromoalkane is Br-C n H 2n+1 , n is any integer between 10 and 16.

5. A method for preparing a flame retardant and fireproof coating according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: adding epoxy resin, polyphosphate-indole flame retardant, curing agent, defoaming agent, leveling agent and wetting agent into n-butanol solvent, stirring and mixing, and obtaining the flame retardant and fireproof coating.

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