Flame-retardant coating for automobiles and preparation method of flame-retardant coating

Abstract

The invention relates to the technical field of coatings, and discloses a flame-retardant coating for an automobile and a preparation method of the flame-retardant coating. The flame-retardant coating is prepared from the following components in parts by weight: 50 to 55 parts of epoxy resin, 3 to 5 parts of an imidazolyl curing agent, 2 to 4 parts of an epoxy flame retardant, 2 to 3 parts of diaminodiphenyl sulfone, 0.8 to 1.3 parts of titanium dioxide, 0.15 to 0.3 part of a BYK-071 defoaming agent and 0.2 to 0.4 part of a BYK-345 flatting agent. All the components are added into a stirrer and cured at 150-160 DEG C for 2-4 h. The coating adopts a halogen-free flame-retardant system, is environment-friendly, non-toxic, high in flame-retardant efficiency and good in compatibility with a coating matrix, can effectively ensure mechanical properties and decorative properties, and is suitable for coating of an automobile body and an interior.

Description

Technical Field

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

[0002] With the rapid development of the automotive industry, consumers are increasingly demanding higher standards for vehicle safety and environmental friendliness. During driving or parking, accidents such as collisions or short circuits can easily cause fires. Since most materials used in car bodies and interiors are flammable, they can accelerate the spread of fire, seriously threatening the lives of passengers. Therefore, developing automotive coatings with excellent flame-retardant properties is crucial.

[0003] Current automotive coatings primarily employ halogenated flame retardants. While these halogenated flame retardants offer good flame retardancy, they release toxic and harmful gases (such as hydrogen chloride and hydrogen bromide) during combustion. These gases not only harm human health but also pollute the environment, contradicting current environmental protection trends. Furthermore, some halogen-free flame-retardant coatings suffer from low flame-retardant efficiency, poor compatibility with the coating matrix, and compromised mechanical and decorative properties, failing to meet the practical application requirements of automotive coatings. Therefore, given the shortcomings of existing technologies, there is an urgent need to develop a flame-retardant coating for automobiles that is highly efficient, environmentally friendly and non-toxic, has good compatibility with the substrate, and ensures both mechanical and decorative properties, along with its preparation method. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a flame-retardant coating for automobiles and a method for preparing the same. The flame-retardant coating adopts a halogen-free flame-retardant system, is environmentally friendly and non-toxic, has high flame-retardant efficiency, and has good compatibility with the coating matrix. It can effectively ensure the mechanical and decorative properties of the coating and is suitable for coating automobile bodies and interiors.

[0005] To achieve the above objectives, the present invention employs the following technical solution: To achieve the above objectives, the present invention provides the following technical solution: a flame-retardant coating for automobiles, comprising the following weight components: 50-55 parts by weight of epoxy resin, 3-5 parts by weight of imidazole curing agent, 2-4 parts by weight of epoxy flame retardant, 2-3 parts by weight of diaminodiphenyl sulfone, 0.8-1.3 parts by weight of titanium dioxide, 0.15-0.3 parts by weight of BYK-071 defoamer, and 0.2-0.4 parts by weight of BYK-345 leveling agent.

[0006] Furthermore, the preparation method of the imidazole-based curing agent is as follows: Step 1: Add imidazole and p-hydroxybenzyl alcohol to the reaction flask, heat to 155-160℃ and stir for 6-7 hours. After the reaction is completed, cool to room temperature, add ethyl acetate to the cooled solid and vibrate in an ultrasonic environment, then filter and wash with ethyl acetate again to obtain intermediate 1. Step 2: Add intermediate 1 and triethylamine to a reaction flask containing 30-35 mL of dichloromethane solvent, stir to dissolve, place the reaction flask in an ice-water bath, and continue to add phenylphosphodichlorochloride dropwise over 0.5-1 h. Continue to react in an ice-water bath for 10-12 h. After the reaction is complete, filter, collect the reaction solution, extract with brine to further remove triethylamine hydrochloride, enrich dichloromethane, and evaporate to dryness to obtain imidazole curing agent.

[0007] Furthermore, in step one, the ratio of imidazole to p-hydroxybenzyl alcohol is 6.5-6.8g: 2.9-3.1g.

[0008] Furthermore, in step two, the ratio of intermediate 1, triethylamine, and phenylphosphodichloro to the amount of intermediate 1 is 1.55-1.59g: 1.2-1.45g: 1.9-1.96g.

[0009] Furthermore, the preparation method of the epoxy-based flame retardant is as follows: S1. Vanillin and 4-aminophenol were added to 120-130 mL of deionized water and stirred at room temperature for 4-5 h. After the reaction was completed, the mixture was filtered, washed and dried to obtain bisphenol monomer. 10-15 mmol of bisphenol monomer was added to 50-55 mL of ethanol and stirred. 40-50 mmol of diethyl phosphite was added to the mixture. The mixture was heated to 75-80 °C under a nitrogen atmosphere and reacted for 7-9 h. After the reaction was completed, petroleum ether was added, the mixture was cooled and filtered, and washed with ethanol to obtain phosphorus-based bisphenol monomer. S2. Add 8-12 mmol of phosphorobisphenol monomer and 0.01-0.015 g of pyridine to 25-30 mL of anhydrous N,N-dimethylformamide solvent, stir to dissolve, and then add 16-24 mmol of 4-vinylbenzoyl chloride. React at room temperature. After the reaction is completed, concentrate the solution and wash the product with methanol to obtain the alkenylbisphenol intermediate. S3. Add 5-7 mmol of alkenyl bisphenol intermediate to 18-22 mL of dichloromethane, place in an ice-water bath and slowly add 3-4.5 mmol of m-chloroperoxybenzoic acid, control the temperature at 2-5℃, then gradually raise the temperature to room temperature and continue stirring for 5-6 h. After the reaction is complete, wash twice with saturated sodium bicarbonate solution, then wash twice with deionized water, remove water and dry under reduced pressure to remove solvent, and obtain epoxy flame retardant.

[0010] Furthermore, in step S1, the ratio of vanillin to 4-aminophenol is 20-30 mmol: 20-30 mmol.

[0011] Furthermore, in step S2, the reaction time at room temperature is 5-7 hours.

[0012] Further, the process includes the following steps: adding epoxy resin, imidazole curing agent, epoxy flame retardant, diaminodiphenyl sulfone, titanium dioxide, BYK-071 defoamer, and BYK-345 leveling agent into a mixer and curing at 150-160℃ for 2-4 hours to obtain a flame-retardant coating for automobiles.

[0013] Compared with the prior art, the present invention has the following beneficial technical effects: This invention employs a phosphorus-based halogen-free flame retardant system, consisting of an epoxy-based flame retardant and a phosphorus-containing imidazole curing agent. The phosphorus element contained therein forms a dense carbon layer during combustion, blocking oxygen and heat transfer, while simultaneously releasing flame-retardant gases to inhibit flame spread, resulting in a good flame-retardant effect. At the same time, it abandons traditional halogen flame retardants, and no toxic or corrosive gases such as hydrogen chloride or hydrogen bromide are released during combustion.

[0014] In this technical solution, imidazole-based curing agents and diaminodiphenyl sulfone synergistically catalyze curing. The imidazole groups not only react with the epoxy groups of the epoxy resin but also with the epoxy groups in the epoxy flame retardant. This high-density cross-linked network prevents flame retardant migration and precipitation, ensuring flame retardant durability. Simultaneously, the cross-linked network also improves its impact resistance. In this invention, the epoxy resin provides the basic framework, the imidazole groups tightly bond the three components through catalytic cross-linking, and the epoxy flame retardant participates in both cross-linking and provides flame retardant functionality. This deep integration of "curing-matrix-flame retardancy" solves the problem of "contradiction between flame retardant efficiency and mechanical properties / compatibility" in traditional halogen-free flame retardant coatings, while also achieving environmental protection and flame retardant effects. Attached Figure Description

[0015] Figure 1 This is the synthesis reaction formula for intermediate 1. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Epoxy resin: Grade E51.

[0018] Example 1 A flame-retardant coating for automobiles comprises the following components by weight: 50 parts by weight of epoxy resin, 3 parts by weight of imidazole curing agent, 2 parts by weight of epoxy flame retardant, 2 parts by weight of diaminodiphenyl sulfone, 0.8 parts by weight of titanium dioxide, 0.15 parts by weight of BYK-071 defoamer, and 0.2 parts by weight of BYK-345 leveling agent.

[0019] The preparation method of the imidazole-based curing agent is as follows: Step 1: Add 6.5g imidazole and 2.9g p-hydroxybenzyl alcohol to the reaction flask, heat to 155℃ and stir for 6h. After the reaction is completed, cool to room temperature, add ethyl acetate to the cooled solid and vibrate in sonication, then filter and wash with ethyl acetate again to obtain intermediate 1. Step 2: Add 1.55g of intermediate 1 and 1.2g of triethylamine to a reaction flask containing 30mL of dichloromethane solvent, stir to dissolve, place the reaction flask in an ice-water bath, and continue to add 1.9g of phenylphosphodichloro dropwise over 0.5h. Continue to react in an ice-water bath for 10h. After the reaction is complete, filter, collect the reaction solution, extract with brine to further remove triethylamine hydrochloride, enrich dichloromethane, and evaporate to dryness to obtain imidazole curing agent.

[0020] The preparation method of the epoxy-based flame retardant is as follows: S1. Add 20 mmol of vanillin and 20 mmol of 4-aminophenol to 120 mL of deionized water, stir at room temperature for 4 h, filter, wash and dry to obtain bisphenol monomer; add 10 mmol of bisphenol monomer to 50 mL of ethanol, stir and mix, then add 40 mmol of diethyl phosphite, heat to 75 °C under nitrogen atmosphere, react for 7 h, add petroleum ether, cool and filter, wash with ethanol to obtain phosphorus bisphenol monomer; S2. Add 8 mmol of phosphorobisphenol monomer and 0.01 g of pyridine to 25 mL of anhydrous N,N-dimethylformamide solvent, stir to dissolve, and then add 16 mmol of 4-vinylbenzoyl chloride. React at room temperature for 5 h. After the reaction is completed, concentrate the solution and wash the product with methanol to obtain alkenylbisphenol intermediate. S3. Add 5 mmol of alkenyl bisphenol intermediate to 18 mL of dichloromethane, place in an ice-water bath and slowly add 3 mmol of m-chloroperoxybenzoic acid, control the temperature at 2 °C, then gradually raise the temperature to room temperature and continue stirring for 5 h. After the reaction is complete, wash twice with saturated sodium bicarbonate solution, then wash twice with deionized water, remove water and dry under reduced pressure to remove solvent, and obtain epoxy flame retardant.

[0021] Epoxy resin, imidazole curing agent, epoxy flame retardant, diaminodiphenyl sulfone, titanium dioxide, BYK-071 defoamer, and BYK-345 leveling agent were added to a mixer and cured at 150°C for 2 hours to obtain a flame-retardant coating for automobiles.

[0022] Example 2 A flame-retardant coating for automobiles comprises the following components by weight: 55 parts by weight of epoxy resin, 5 parts by weight of imidazole curing agent, 4 parts by weight of epoxy flame retardant, 3 parts by weight of diaminodiphenyl sulfone, 1.3 parts by weight of titanium dioxide, 0.3 parts by weight of BYK-071 defoamer, and 0.4 parts by weight of BYK-345 leveling agent.

[0023] The preparation method of the imidazole-based curing agent is as follows: Step 1: Add 6.8g imidazole and 3.1g p-hydroxybenzyl alcohol to the reaction flask, heat to 160℃ and stir for 7h. After the reaction is completed, cool to room temperature, add ethyl acetate to the cooled solid and vibrate in sonication, then filter and wash with ethyl acetate again to obtain intermediate 1. Step 2: Add 1.59g of intermediate 1 and 1.45g of triethylamine to a reaction flask containing 35mL of dichloromethane solvent, stir to dissolve, place the reaction flask in an ice-water bath, and continue to add 1.96g of phenylphosphodichloro dropwise over 1 hour. Continue to react in an ice-water bath for 12 hours. After the reaction is complete, filter, collect the reaction solution, extract with brine to further remove triethylamine hydrochloride, enrich dichloromethane, and evaporate to dryness to obtain imidazole curing agent.

[0024] The preparation method of the epoxy-based flame retardant is as follows: S1. Add 30 mmol of vanillin and 30 mmol of 4-aminophenol to 130 mL of deionized water, stir at room temperature for 5 h, filter, wash and dry to obtain bisphenol monomer; add 15 mmol of bisphenol monomer to 55 mL of ethanol, stir and mix, then add 50 mmol of diethyl phosphite, heat to 80 °C under nitrogen atmosphere and react for 9 h, then add petroleum ether, cool and filter, wash with ethanol to obtain phosphorus bisphenol monomer. S2. Add 12 mmol of phosphorobisphenol monomer and 0.015 g of pyridine to 30 mL of anhydrous N,N-dimethylformamide solvent, stir to dissolve, and then add 24 mmol of 4-vinylbenzoyl chloride. React at room temperature for 7 h. After the reaction is completed, concentrate the solution and wash the product with methanol to obtain alkenylbisphenol intermediate. S3. Add 7 mmol of alkenyl bisphenol intermediate to 22 mL of dichloromethane, place in an ice-water bath and slowly add 4.5 mmol of m-chloroperoxybenzoic acid, control the temperature at 5 °C, then gradually raise the temperature to room temperature and continue stirring for 6 h. After the reaction is complete, wash twice with saturated sodium bicarbonate solution, then wash twice with deionized water, remove water and dry under reduced pressure to remove solvent, and obtain epoxy flame retardant.

[0025] Epoxy resin, imidazole curing agent, epoxy flame retardant, diaminodiphenyl sulfone, titanium dioxide, BYK-071 defoamer, and BYK-345 leveling agent were added to a mixer and cured at 155°C for 4 hours to obtain a flame-retardant coating for automobiles.

[0026] Example 3 A flame-retardant coating for automobiles comprises the following components by weight: 52 parts by weight of epoxy resin, 4 parts by weight of imidazole curing agent, 3 parts by weight of epoxy flame retardant, 2.5 parts by weight of diaminodiphenyl sulfone, 1.1 parts by weight of titanium dioxide, 0.18 parts by weight of BYK-071 defoamer, and 0.3 parts by weight of BYK-345 leveling agent.

[0027] The preparation method of the imidazole-based curing agent is as follows: Step 1: Add 6.65g imidazole and 3.0g p-hydroxybenzyl alcohol to the reaction flask, heat to 157℃ and stir for 6.5h. After the reaction is completed, cool to room temperature, add ethyl acetate to the cooled solid and vibrate in an ultrasonic environment, then filter and wash with ethyl acetate again to obtain intermediate 1. Step 2: Add 1.94g of intermediate 1 and 1.34g of triethylamine to a reaction flask containing 32mL of dichloromethane solvent, stir to dissolve, place the reaction flask in an ice-water bath, and continue to add 1.12g of phenylphosphodichloroplastrin dropwise over 0.7h. Continue to react in an ice-water bath for 11h. After the reaction is complete, filter, collect the reaction solution, extract with brine to further remove triethylamine hydrochloride, enrich dichloromethane, and evaporate to dryness to obtain imidazole curing agent.

[0028] The preparation method of the epoxy-based flame retardant is as follows: S1. Add 25 mmol of vanillin and 25 mmol of 4-aminophenol to 126 mL of deionized water, stir at room temperature for 5 h, filter, wash and dry to obtain bisphenol monomer; add 12 mmol of bisphenol monomer to 52 mL of ethanol, stir and mix, then add 43 mmol of diethyl phosphite, heat to 78 °C under nitrogen atmosphere, react for 8 h, add petroleum ether, cool and filter, wash with ethanol to obtain phosphorus bisphenol monomer. S2. Add 10 mmol of phosphorobisphenol monomer and 0.012 g of pyridine to 28 mL of anhydrous N,N-dimethylformamide solvent, stir to dissolve, and then add 20 mmol of 4-vinylbenzoyl chloride. React at room temperature for 6 h. After the reaction is completed, concentrate the solution and wash the product with methanol to obtain alkenylbisphenol intermediate. S3. Add 6 mmol of alkenyl bisphenol intermediate to 20 mL of dichloromethane, place in an ice-water bath and slowly add 3.5 mmol of m-chloroperoxybenzoic acid, control the temperature at 4 °C, then gradually raise the temperature to room temperature and continue stirring for 5 h. After the reaction is complete, wash twice with saturated sodium bicarbonate solution, then wash twice with deionized water, remove water and dry under reduced pressure to remove solvent, and obtain epoxy flame retardant.

[0029] Epoxy resin, imidazole curing agent, epoxy flame retardant, diaminodiphenyl sulfone, titanium dioxide, BYK-071 defoamer, and BYK-345 leveling agent were added to a mixer and cured at 155°C for 3 hours to obtain a flame-retardant coating for automobiles.

[0030] Comparative Example 1 The difference between this comparative example and Example 3 is that p-hydroxybenzyl alcohol is used instead of imidazole curing agent.

[0031] Comparative Example 2 The difference between this comparative example and Example 3 is that 4-aminophenol was used instead of the epoxy flame retardant.

[0032] Adhesion test: The adhesion of the coating was tested according to standard GB / T9286-2021; the limiting oxygen index of the material was tested using an oxygen index meter, and the flammability rating of the coating was tested using a horizontal and vertical burner; Impact resistance test: The maximum impact height without damage to the coating was recorded when the drop weight was 500g, according to GB / T1732-2020 "Determination of Impact Resistance of Coating Films", in cm; the pencil hardness of the coating was tested according to GB / T6739-2022; the test results are shown in Table 1.

[0033] Table 1: Performance Tests project Adhesion Limiting oxygen index (%) Vertical flammability rating Maximum impact height (cm) Pencil hardness Example 1 Level 0 34.1 V-0 45.6 2H Example 2 Level 0 35.6 V-0 46.8 2H Example 3 Level 0 33.4 V-0 45.2 2H Comparative Example 1 Level 1 28.6 V-1 32.1 HB Comparative Example 2 Level 1 29.1 V-1 34.4 HB Table 1 shows that in Comparative Example 1, p-hydroxybenzyl alcohol was used instead of the imidazole curing agent. The core function of the imidazole curing agent is to participate in the crosslinking reaction and co-crosslink with the epoxy resin and epoxy flame retardant to construct a high-density network. It acts as a "synergist" for mechanical and flame retardant properties, improving adhesion and impact resistance through chemical bonding, while introducing phosphorus to enhance the flame retardant effect. Due to the absence of this component, all properties decreased. In Comparative Example 2, 4-aminophenol was used instead of the epoxy flame retardant. The core function of the epoxy flame retardant is to act as both a "core carrier" for flame retardant function, providing sufficient phosphorus flame retardant sites, and a "structural unit" of the crosslinking network, ensuring the integrity of the coating structure through the participation of epoxy groups in crosslinking. Due to the replacement of this component, the flame retardant performance was significantly reduced, and the mechanical properties decreased simultaneously.

[0034] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0035] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0036] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments.

Claims

1. A fire-retardant coating for an automobile, characterized by, It comprises the following weight components: 50-55 parts by weight of epoxy resin, 3-5 parts by weight of imidazole-based curing agent, 2-4 parts by weight of epoxy-based flame retardant, 2-3 parts by weight of diamino diphenyl sulfone, 0.8-1.3 parts by weight of titanium white powder, 0.15-0.3 parts by weight of BYK-071 defoaming agent, 0.2-0.4 parts by weight of BYK-345 leveling agent.

2. The fire-retardant coating for an automobile according to claim 1, characterized by The preparation method of the imidazole-based curing agent is: Step one: add imidazole and p-hydroxybenzyl alcohol to a reaction bottle, heat to 155-160 DEG C and stir for 6-7 h, after the end of the reaction, cool to room temperature, add ethyl acetate to the obtained solid and shake in the ultrasonic wave, then filter, wash with ethyl acetate again, and obtain intermediate 1; Step two: add intermediate 1 and triethylamine to a reaction bottle containing 30-35 mL of dichloromethane, stir and dissolve, place the reaction bottle in an ice water bath, continue to add phenyl phosphorodichloridate dropwise, dropwise for 0.5-1 h, continue to react in the ice water bath for 10-12 h, after the end of the reaction, filter, collect the reaction liquid, extract with brine to further remove triethylamine hydrochloride, enrich dichloromethane and spin dry, dry to obtain the imidazole-based curing agent.

3. The fire-retardant coating for an automobile according to claim 2, characterized by In the step one, the amount ratio of imidazole and p-hydroxybenzyl alcohol is 6.5-6.8 g:2.9-3.1 g.

4. The fire-retardant coating for an automobile according to claim 2, characterized by In the step two, the amount ratio of intermediate 1, triethylamine and phenyl phosphorodichloridate is 1.55-1.59 g:1.2-1.45 g:1.9-1.96 g.

5. The fire-retardant paint for an automobile according to claim 1, characterized by The preparation method of the epoxy-based flame retardant is: S1. Add vanillin and 4-aminophenol to 120-130 mL of deionized water, stir at room temperature for 4-5 h, filter, wash and dry to obtain a biphenol-based monomer; add 10-15 mmol of the biphenol-based monomer to 50-55 mL of ethanol, stir and mix, continue to add 40-50 mmol of diethyl phosphite, heat to 75-80 DEG C under nitrogen atmosphere, react for 7-9 h, after the end of the reaction, add petroleum ether, cool and filter, wash with ethanol to obtain a phosphorus-based biphenol monomer; S2. Add 8-12 mmol of the phosphorus-based biphenol monomer and 0.01-0.015 g of pyridine to 25-30 mL of anhydrous N,N-dimethylformamide solvent, stir and dissolve, continue to add 16-24 mmol of 4-vinylbenzoyl chloride, react at room temperature, after the end of the reaction, concentrate the solution, and wash the product with methanol to obtain an alkenyl biphenol intermediate; S3. Add 5-7 mmol of the alkenyl biphenol intermediate to 18-22 mL of dichloromethane, place in an ice water bath, slowly add 3-4.5 mmol of meta-chloroperoxybenzoic acid, control the temperature at 2-5 DEG C, then gradually heat to room temperature, continue to stir for 5-6 h, after the end of the reaction, wash twice with saturated sodium bicarbonate solution, then wash twice with deionized water, remove water, then dry under reduced pressure to remove the solvent to obtain the epoxy-based flame retardant.

6. The fire-retardant coating for an automobile according to claim 5, characterized by In the step S1, the amount ratio of vanillin and 4-aminophenol is 20-30 mmol:20-30 mmol.

7. The fire-retardant coating for an automobile according to claim 5, characterized by In the step S2, the reaction time at room temperature is 5-7 h.

8. A process for the preparation of a fire-retardant coating for automobiles as claimed in any one of claims 1 to 7, characterised in that, The process comprises the following steps: Epoxy resin, imidazole curing agent, epoxy-based flame retardant, diaminodiphenyl sulfone, titanium white, BYK-071 defoaming agent, BYK-345 leveling agent are added into a stirrer, and cured at 150-160℃ for 2-4h to obtain a flame-retardant coating for automobiles.

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