Flame-retardant fireproof coating and preparation method thereof

Abstract

The invention relates to the technical field of coatings, and discloses a flame-retardant fireproof coating and a preparation method thereof.The flame-retardant fireproof coating is prepared from, by weight, 100 parts of epoxy resin, 3-12 parts of polyphosphate-indole flame retardant, 6.8-11.5 parts of curing agent and the like; as an intumescent flame retardant, the polyphosphate-indole flame retardant can effectively improve the char-forming property and the mass residual rate of epoxy resin coating cured products, promotes dehydration of a polyaromatic polycyclic structure and an epoxy resin matrix to form an intumescent carbon layer during combustion, remarkably reduces the peak value of the heat release rate, the total heat release amount and the total smoke release, and improves the flame retardance of the epoxy resin coating. The excellent flame retardant property is shown. The 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 a cured product.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and specifically to a flame-retardant and fire-proof coating and a preparation method thereof. Background Art

[0002] Epoxy resin coatings have the advantages of high anti-corrosion performance, good insulation performance, and high mechanical strength, and are widely used. Traditional epoxy resin coatings have problems such as poor flame retardancy and poor toughness, which limit their practical applications in the field of flame retardancy and fire protection. Usually, flame retardants are added to epoxy resin coatings, such as phosphorus-containing flame retardants, intumescent flame retardants, brominated flame retardants, etc.

[0003] Intumescent flame retardants integrate acid source, carbon source and gas source, and have high carbonization performance and high flame retardancy. Commonly used epoxy resin toughening agents include polyethers, organosilicons, substances containing flexible long aliphatic chains, etc. Patent CN113292852B discloses a resin composition containing a phosphorus-containing bisphenol polymer, its preparation method and application. By reacting phenylphosphonyl dichloride or phenyl dichlorophosphate with a tetramethyl bisphenol compound, a phosphorus-containing bisphenol polymer flame retardant is obtained, which improves the properties such as the glass transition temperature and flame retardancy of epoxy resin. However, the patent does not solve the problem of poor toughness such as the impact strength of epoxy resin. Summary of the Invention

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

[0005] The present invention provides a flame-retardant and fire-proof coating, which 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, 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 fire-proof coating is as follows: Add epoxy resin, polyphosphate-indole flame retardant, curing agent, defoaming agent, leveling agent, and wetting agent to a n-butanol solvent, stir and mix evenly to obtain the flame-retardant and fire-proof coating.

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

[0008] Preferably, the preparation method of the polyphosphate-indole flame retardant is as follows: (1) Add 6,12-diphenolyl-5,11-dihydroindolo[3,2-b]carbazole and benzyltriethylammonium chloride to dimethyl sulfoxide, and add an aqueous sodium hydroxide solution and 1-bromoalkane (structural formula: Br-C n H 2n+1),(Stir and react at 20 - 30 °C for 6 - 10 h), add water for dilution, precipitate the sediment, filter by suction, wash with water, and recrystallize the product in a mixed solution of N,N - dimethylformamide and chloroform to obtain the diphenol - based alkyl indole intermediate.

[0009] .

[0010] (2) Add phenyl dichlorophosphate, diphenol - based alkyl indole intermediate, and triethylamine to N,N - dimethylformamide, stir and react at 30 - 50 °C for 12 - 18 h, then add the diphenol - based alkyl indole intermediate again, continue to stir and react for 0.5 - 1 h, pour the solution into water to precipitate the sediment, wash successively with water and ethanol after filtration, and dry to obtain the polyphosphate - indole flame retardant. The reaction formula is: .

[0011] Preferably, in (1), the molar ratio of 6,12 - diphenol - 5,11 - dihydroindolo[3,2 - b]carbazole, benzyltriethylammonium chloride, sodium hydroxide, and 1 - bromoalkane is 1:(0.008 - 0.01):(10 - 12):(2.4 - 2.8).

[0012] Preferably, in (1), the molecular formula of 1 - bromoalkane is Br - C n H 2n+1 , where n is any integer from 10 to 16.

[0013] Preferably, in (2), the molar ratio of phenyl dichlorophosphate, diphenol - based alkyl indole intermediate, and triethylamine is 1:(1.04 - 1.08):(2.1 - 2.2).

[0014] The beneficial technical effects of the present invention: The present invention conducts a phosphoesterification polymerization reaction on the diphenol - based alkyl indole intermediate and phenyl dichlorophosphate to obtain the polyphosphate - indole flame retardant, which contains phosphates and indole nitrogen - containing heterocycles as the acid source and gas source, and at the same time contains a polyaromatic condensed ring structure as the carbon source, forming an intumescent flame retardant. It can effectively improve the char - forming property and mass residue rate of the cured product of the epoxy resin coating. During combustion, it promotes the dehydration of the polyaromatic 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 the escape of smoke, significantly reducing the peak value of the heat release rate, the total heat release, and the total smoke release, showing excellent flame - retardant performance.

[0015] The hydroxyl groups at the ends of the polyphosphate - indole flame retardant of the present invention 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, having less influence on the mechanical properties of the epoxy resin cured product. At the same time, the flame retardant contains a flexible aliphatic long chain, which has a good toughening effect on the epoxy resin, significantly improving the impact strength and toughness of the cured product. Detailed implementation mode

[0016] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present invention.

[0017] Add 0.234 g (2 mmol) of indole, 0.244 g (2 mmol) of p - hydroxybenzaldehyde, and 0.0228 g of the catalyst N,2 - dibromo - 6 - chloro - 3,4 - dihydro - 2H - benzo[e][1,2,4]thiadiazine - 7 - sulfonamide - 1,1 - dioxide (DCDBTSD, the structural formula is ) to 2 mL of acetonitrile, react at 50 °C for 20 min, filter and dry, and recrystallize the product in a mixed solution of N,N - dimethylformamide and chloroform to obtain 6,12 - diphenolic - 5,11 - dihydroindolo[3,2 - b]carbazole. The structural formula is .

[0018] Example 1 (1) Add 5 mmol of 6,12 - diphenolic - 5,11 - dihydroindolo[3,2 - b]carbazole and 0.04 mmol of benzyltriethylammonium chloride to 80 mL of dimethyl sulfoxide. Under a nitrogen atmosphere, add 6 mL of an aqueous solution containing 56 mmol of sodium hydroxide and 12 mmol of 1 - bromotetradecane, stir and react at 20 °C for 10 h, add water for dilution, precipitate a solid, filter by suction, wash with water, and recrystallize the product in a mixed solution of N,N - dimethylformamide and chloroform with a volume ratio of 1:1 to obtain a diphenolic alkyl indole intermediate. The structural formula is: .

[0019] (2) Add 10 mmol of phenyl dichlorophosphate, 10 mmol of diphenylalkyl indole intermediate, and 22 mmol of triethylamine to 100 mL of N,N-dimethylformamide. Stir and react at 50 °C for 12 h, then add 0.8 mmol of diphenylalkyl indole intermediate, continue to stir and react for 0.5 h. Pour the solution into water to precipitate a solid, filter, wash successively with water and ethanol, and dry to obtain a polyphosphate-indole flame retardant.

[0020] (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 defoamer 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 evenly to obtain a flame-retardant and fire-proof coating.

[0021] Example 2 (1) Add 5 mmol of 6,12-diphenyl-5,11-dihydroindolo[3,2-b]carbazole and 0.05 mmol of benzyltriethylammonium chloride to 80 mL of dimethyl sulfoxide. Under a nitrogen atmosphere, add 6 mL of an aqueous solution containing 50 mmol of sodium hydroxide and 12 mmol of 1-bromohexadecane. Stir and react at 25 °C for 10 h, add water for dilution, precipitate a solid, filter by suction, wash with water, and recrystallize the product in a mixed solution of N,N-dimethylformamide and chloroform with a volume ratio of 1:1 to obtain a diphenylalkyl indole intermediate.

[0022] (2) Add 10 mmol of phenyl dichlorophosphate, 10 mmol of diphenylalkyl indole intermediate, and 22 mmol of triethylamine to 90 mL of N,N-dimethylformamide. Stir and react at 40 °C for 12 h, then add 0.4 mmol of diphenylalkyl indole intermediate, continue to stir and react for 1 h. Pour the solution into water to precipitate a solid, filter, wash successively with water and ethanol, and dry to obtain a polyphosphate-indole flame retardant.

[0023] (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 defoamer 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 evenly to obtain a flame-retardant and fire-proof coating.

[0024] Example 3 (1) 5 mmol of 6,12-diphenolic-5,11-dihydroindolo[3,2-b]carbazole and 0.048 mmol of benzyltriethylammonium chloride were added to 80 mL of dimethyl sulfoxide. An aqueous solution containing 60 mmol of sodium hydroxide and 14 mmol of 1-bromodecane were added under a nitrogen atmosphere. The mixture was stirred at 30 °C for 6 h, diluted with water, and a precipitate was formed. The precipitate was filtered, washed with water, and the product was recrystallized from a mixed solution of N,N-dimethylformamide and chloroform with a volume ratio of 1:1 to obtain a diphenolic alkyl indole intermediate.

[0025] (2) 10 mmol of phenyl dichlorophosphate, 10 mmol of diphenolic alkyl indole intermediate, and 21 mmol of triethylamine were added to 100 mL of N,N-dimethylformamide. The mixture was stirred at 30 °C for 18 h, then 0.6 mmol of diphenolic alkyl indole intermediate was added, and stirring was continued for 1 h. The solution was poured into water to form a precipitate, which was filtered and washed successively with water and ethanol, and then dried to obtain a polyphosphate - indole flame retardant.

[0026] (3) 100 g of epoxy resin E44, 12 g of polyphosphate - indole flame retardant, 11.5 g of curing agent triethylenetetramine, 0.8 g of defoamer BYK - A530, 0.6 g of leveling agent TEGO - 2300, and 0.2 g of wetting agent TEGOWet270 were added to 140 mL of n-butanol solvent and stirred evenly to obtain a flame retardant and fireproof coating.

[0027] Comparative Example 1 (1) 100 g of epoxy resin E44, 9.8 g of curing agent diethylenetriamine, 0.5 g of defoamer BYK - A530, 0.4 g of leveling agent TEGO - 2300, and 0.4 g of wetting agent TEGO Wet270 were added to 130 mL of n-butanol solvent and stirred evenly to obtain a coating.

[0028] Comparative Example 2 (1) 10 mmol of phenyl dichlorophosphate, 10 mmol of 4,4'-biphenol, and 22 mmol of triethylamine were added to 100 mL of N,N-dimethylformamide. The mixture was stirred at 50 °C for 12 h, then 0.8 mmol of diphenolic alkyl indole intermediate was added, and stirring was continued for 0.5 h. The solution was poured into water to form a precipitate, which was filtered and washed successively with water and ethanol, and then dried to obtain a polyphosphate flame retardant.

[0029] (2) 100 g of epoxy resin E44, 3 g of polyphosphate flame retardant, 9.8 g of curing agent diethylenetriamine, 0.5 g of defoamer BYK - A530, 0.4 g of leveling agent TEGO - 2300, and 0.4 g of wetting agent TEGO Wet270 were added to 130 mL of n-butanol solvent and stirred evenly to obtain a coating.

[0030] Comparative Example 3 (1) Add 5 mmol of 6,12-diphenolyl-5,11-dihydroindolo[3,2-b]carbazole and 0.04 mmol of benzyltriethylammonium chloride to 80 mL of dimethyl sulfoxide. Under a nitrogen atmosphere, add 6 mL of an aqueous solution containing 56 mmol of sodium hydroxide and 12 mmol of 1-bromopropane. Stir and react at 20 °C for 10 h. Add water for dilution, precipitate, filter by suction, wash with water, and recrystallize the product in a mixed solution of N,N-dimethylformamide and chloroform to obtain a diphenolylalkylindole intermediate. The structural formula is: .

[0031] (2) Add 10 mmol of phenyl dichlorophosphate, 10 mmol of diphenolylalkylindole intermediate, and 22 mmol of triethylamine to 100 mL of N,N-dimethylformamide. Stir and react at 50 °C for 12 h. Then add 0.8 mmol of diphenolylalkylindole intermediate and continue to stir and react for 0.5 h. Pour the solution into water to precipitate, filter, wash successively with water and ethanol, and dry to obtain a polyphosphate-indole flame retardant.

[0032] (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 defoamer 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 evenly to obtain a coating.

[0033] Bake and cure the coating at 80 °C for 3 h, then cure at 130 °C for 3 h, and finally cure at 150 °C for 1 h to make a cast specimen. Test the impact strength according to the method of GB / T 2567-2008.

[0034] Weigh 8 mg of the cast specimen and place it in a thermogravimetric analyzer for thermal performance analysis under a nitrogen atmosphere. The heating rate is 10 °C / min, and the temperature is raised from 30 °C to 800 °C.

[0035] Use a cone calorimeter to conduct cone calorimetry tests on the cast specimen. The sample size is 100 mm × 100 mm × 4 mm, and the heat radiation power is 50 kW / m 2 .

[0036] Table 1 Coating Performance Test

[0037] After testing, compared with the epoxy resin coating of Comparative Example 1, polyphosphate-indole flame retardants were added to Examples 1-3. It contains phosphate ester and indole nitrogen-containing heterocycle, serving as the acid source and gas source, and at the same time contains polyaromatic hydrocarbon condensed ring structure, serving as the carbon source, forming an intumescent flame retardant, which improves the charring property and mass residue rate of the cured coating. 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 the escape of smoke, significantly reducing the peak value of the heat release rate, the total heat release, and the total smoke release, showing excellent flame retardant performance. Moreover, 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 onto the epoxy resin curing system, improving the interfacial bonding strength between the flame retardant and the epoxy resin, having less impact on the mechanical properties of the epoxy resin cured product. At the same time, the flame retardant contains flexible aliphatic long chains, which have a good toughening effect on the epoxy resin, significantly improving the impact strength and toughness of the cured product.

[0038] Compared with Example 1, in Comparative Example 2, diphenyl phosphate and 4,4'-biphenol were reacted to obtain a polyphosphate flame retardant that does not contain an indole nitrogen-containing heterocycle and does not contain a polyaromatic hydrocarbon condensed ring structure, making it difficult to effectively form an intumescent flame retardant, not improving the charring property and mass residue rate of the cured coating well, resulting in a larger peak value of the heat release rate, total heat release, and total smoke release, with poor flame retardant performance. And it does not contain flexible aliphatic long chains, unable to achieve a toughening effect, resulting in a lower impact strength of the epoxy resin cured product.

[0039] In Comparative Example 3, 1-bromopropane was used as the raw material, and the resulting diphenolic alkyl indole intermediate and polyphosphate-indole flame retardant do not contain flexible aliphatic long chains, unable to achieve a toughening effect, resulting in a lower impact strength of the epoxy resin cured product.

[0040] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention based on the concept of the present invention through logical analysis, reasoning, or limited experiments on the basis of the prior art should fall within the protection scope determined by the claims.

Claims

1. A flame retardant and 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 parts by weight of defoaming agent, 0.3-0.6 parts by weight of leveling agent, and 0.2-0.4 parts by weight of wetting agent; The preparation method of the polyphosphate-indole flame retardant is as follows: adding phenyl dichlorophosphate, diphenolyl alkyl indole intermediate and triethylamine to N,N-dimethylformamide, stirring for a first reaction, then adding 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 structural formula of the diphenolyl alkyl indole intermediate is: , n is any integer between 10 and 16.

2. The flame retardant and fireproof coating according to claim 1, characterized in that: The molar ratio of the phenyl dichlorophosphate, the diphenolyl alkyl indole intermediate and triethylamine is 1:(1.04-1.08):(2.1-2.2).

3. 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 hours; the time of the second reaction is 0.5-1 hour.

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

5. The flame retardant and fireproof coating according to claim 1, characterized in that: The preparation method of the diphenolyl alkyl 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 after the reaction, precipitating a precipitate, filtering, washing, and recrystallizing to obtain the diphenolyl alkyl indole intermediate.

6. The flame retardant and fireproof coating according to claim 5, characterized in that: In the preparation method of the diphenolyl alkyl indole intermediate, the reaction temperature is 20-30° C. and the reaction time is 6-10 h.

7. The flame retardant and fireproof coating according to claim 5, characterized in that: The molar ratio of the 6,12-diphenol-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).

8. The flame retardant and fireproof coating according to claim 7, 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.

9. A method for preparing a flame retardant and fireproof coating according to any one of claims 1 to 8, 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 flame retardant and fireproof coating.

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