Scratch-resistant flame-retardant insulating powder coating, preparation method thereof and application of scratch-resistant flame-retardant insulating powder coating in rail transit and new energy automobiles

Abstract

The invention discloses a scratch-resistant flame-retardant insulating powder coating, a preparation method thereof and application of the scratch-resistant flame-retardant insulating powder coating in rail transit and new energy automobiles, and relates to the technical field of polysiloxane powder coatings. The scratch-resistant flame-retardant insulating powder coating is prepared from the following raw materials in parts by weight: 100 to 120 parts of polysiloxane epoxy resin, 10 to 20 parts of modified curing agent, 5 to 10 parts of flame retardant, 3 to 6 parts of flexibilizer, 2 to 3 parts of flatting agent, 1 to 2 parts of benzoin and 8 to 10 parts of mica powder. The scratch-resistant flame-retardant insulating powder coating prepared by the invention has good impact resistance, flame retardance, adhesive force and insulating property.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polysiloxane powder coating, in particular to a scratch-resistant flame-retardant insulating powder coating, a preparation method thereof and application thereof in rail transit and new energy vehicles. BACKGROUND

[0002] With the rapid development of rail transit and new energy vehicle industries, the performance requirements of powder coatings are increasingly improved. The conventional powder coatings on the market have significant defects in application. First, the impact resistance of the coating is insufficient, which can easily cause cracks, peeling or scratches during vehicle operation or component assembly due to external impact, directly affecting the long-term protection effect and safety of the components. Second, it is difficult to balance the flame retardation and insulation. Although traditional halogen-based flame retardants have good flame retardation effect, they release toxic gases and reduce the insulation performance, and the insulation materials often cannot meet the strict flame retardation requirements. Third, the adhesion is poor, and the interface between the coating and the substrate is prone to interfacial peeling or cohesive failure, which not only affects the mechanical integrity of the coating system, but also can reduce the uniformity of the coating and the reliability of the overall insulation and flame retardation performance. These problems seriously restrict the application effect of powder coatings in key fields such as new energy vehicle battery packs and rail transit conductive components.

[0003] A Chinese invention patent with publication number CN119859456A discloses a flame-retardant insulating powder coating for new energy vehicles and a preparation method thereof. The components of the flame-retardant insulating powder coating include: 380-384 parts by mass of epoxy resin, 56-58 parts by mass of toughening agent, 5-10 parts by mass of modified flame-retardant filler, 100-101 parts by mass of composite curing agent, 5 parts by mass of leveling agent, 1 part by mass of benzoin, and 0.7 parts by mass of accelerator. The powder coating prepared by the invention has good insulation performance and flame retardation performance, but its impact resistance, adhesion and the like need to be improved. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application aims to provide a scratch-resistant flame-retardant insulating powder coating, a preparation method thereof and application thereof in rail transit and new energy vehicles.

[0005] To achieve the above-mentioned purpose, the present application realizes the following technical solutions: A scratch-resistant flame-retardant insulating powder coating, comprising the following raw materials in parts by weight: polysiloxane epoxy resin 100-120 parts, modified curing agent 10-20 parts, flame retardant 5-10 parts, toughening agent 3-6 parts, leveling agent 2-3 parts, benzoin 1-2 parts, and mica powder 8-10 parts; The modified curing agent is prepared by the following method: S1: Octamethylcyclotetrasiloxane reacts with N-aminoethyl-3-aminopropylmethyldimethoxysilane to generate amino-modified polydimethylsiloxane. S2: Amino-modified polydimethylsiloxane reacts with 4-formyl phthalic acid to generate carboxyl-modified polydimethylsiloxane. S3: Carboxyl-modified polydimethylsiloxane reacts with amino polyethylene glycol hydroxyl groups to generate a modified curing agent.

[0006] In step S1, the molar ratio of octamethylcyclotetrasiloxane to N-aminoethyl-3-aminopropylmethyldimethoxysilane is 1:(1.8-2).

[0007] In step S2, the mass ratio of the amino-modified polydimethylsiloxane to 4-formyl phthalic acid is (5-6):1.

[0008] In step S3, the mass ratio of the carboxyl-modified polydimethylsiloxane to the amino-polyethylene glycol hydroxyl group is (1.1-1.3):1.

[0009] The flame retardant is prepared by the following method: A1: 1-Amino-10-undecene reacts with cyanuric chloride to form a disubstituted compound. A2: The disubstituted compound reacts with 1H,1H-perfluorooctylamine to generate a fluorinated modified compound. A3: Fluorine-modified compounds react with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-sulfides to generate flame retardants.

[0010] In step A1, the molar ratio of 1-amino-10-undecene to cyanuric chloride is 2.1:1.

[0011] In step A2, the molar ratio of the disubstituted compound to 1H,1H-perfluorooctylamine is 1:1.1; in step A3, the molar ratio of the fluorinated modified compound to 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-sulfide is 1:2.1.

[0012] The toughening agent is liquid nitrile rubber; the leveling agent is silica-adsorbed polyacrylate.

[0013] A method for preparing a scratch-resistant, flame-retardant, and insulating powder coating includes the following steps: (1) Weigh out the following by weight: 100-120 parts of polysiloxane epoxy resin, 10-20 parts of modified curing agent, 5-10 parts of flame retardant, 3-6 parts of toughening agent, 2-3 parts of leveling agent, 1-2 parts of benzoin, and 8-10 parts of mica powder. (2) After the polysiloxane epoxy resin, modified curing agent, flame retardant, toughening agent, leveling agent, benzoin and mica powder are mixed evenly, they are extruded by a twin-screw extruder, pressed into sheets and crushed, and then pulverized by a grinding mill to obtain a scratch-resistant, flame-retardant and insulating powder coating.

[0014] Application of a scratch-resistant, flame-retardant, and insulating powder coating in rail transit and new energy vehicles.

[0015] Due to the adoption of the above technical solutions, the beneficial effects of the present invention include: The scratch-resistant, flame-retardant, and insulating powder coating prepared by this invention exhibits excellent impact resistance, flame retardancy, adhesion, and insulation properties. The added modified curing agent, containing siloxane segments, polyether segments, and dynamic Schiff base bonds, synergistically enhances the coating's impact resistance and adhesion. The added flame retardant significantly improves the coating's long-lasting flame retardancy through a multi-synergistic mechanism involving the surface barrier of the fluorocarbon chain and the capture of free radicals by the phosphine-phenanthroline sulfur structure. Detailed Implementation

[0016] The following description, in conjunction with specific embodiments, provides further details, but the present invention is not limited to these embodiments.

[0017] Example 1: Preparation of modified curing agent: S1: Under nitrogen protection, 13.0 g of deionized water, 0.05 g of tetraethylammonium hydroxide, 0.2 mol of octamethylcyclotetrasiloxane, and 0.36 mol of N-aminoethyl-3-aminopropylmethyldimethoxysilane were added to the reactor. The mixture was stirred and stirred until homogeneous. After reflux for 8 h, the temperature was lowered to 50 °C and vacuum was applied for 2 h to remove the byproducts methanol and water. The temperature was then raised to 150 °C and maintained for 30 min to remove tetraethylammonium hydroxide. The mixture was then distilled under reduced pressure at 50 °C for 2 h to obtain amino-modified polydimethylsiloxane. The reaction equation is shown below: .

[0018] S2: Add 200 ml of anhydrous ethanol and 50 g of amino-modified polydimethylsiloxane to the reactor, then add 4 g of 4A molecular sieve (sodium-A type molecular sieve). Slowly add anhydrous ethanol solution of 4-formyl phthalic acid (10 g of 4-formyl phthalic acid dissolved in 100 ml of anhydrous ethanol) to the reactor, adding dropwise for 30 min. After reacting at 70 °C for 6 h, cool to room temperature, filter to remove the molecular sieve, and distill the filtrate under reduced pressure at 60 °C for 2 h. Then add 400 ml of cold n-hexane, stir to precipitate, collect the precipitate by suction filtration, wash with petroleum ether (200 ml of petroleum ether each time), and dry under vacuum at 60 °C for 12 h to obtain carboxyl-modified polydimethylsiloxane. The reaction equation is shown below: .

[0019] S3: Under ice bath conditions, add 200 ml of 1,4-dioxane / water (1,4-dioxane / water (v / v) = 4:1) mixed solvent and 10 g of amino-protected polyethylene glycol hydroxyl (NH2-PEG-OH, number average molecular weight 1000) to the reactor, stir and mix well, then add 2 g of triethylamine and slowly add 2.5 g of di-tert-butyl dicarbonate over 20 min. After the addition is complete, raise the temperature to room temperature and react for 6 h. Then, distill under reduced pressure at 40 °C for 2 h to obtain amino-protected polyethylene glycol hydroxyl. Under ice bath conditions, 200 ml of anhydrous DMF, the amino-protected polyethylene glycol hydroxyl group obtained in the above steps, and 11 g of carboxyl-modified polydimethylsiloxane were added to the reactor and stirred until well mixed. Then, 0.015 mol DCC and 0.02 mol DMAP were added, the mixture was brought to room temperature, and stirred in the dark for 12 h. After filtration, the filtrate was added dropwise to 500 ml of cold anhydrous diethyl ether for 30 min. The mixture was stirred to precipitate the precipitate, which was collected by centrifugation. The precipitate was washed three times with cold diethyl ether (200 ml each time) and dried under vacuum at 70 °C for 2 h to obtain the crude product. Add 200 ml of a mixed solution of dichloromethane / trifluoroacetic acid (dichloromethane / trifluoroacetic acid (v / v) = 9:1) and the crude product obtained in the previous step to the reactor. Stir in an ice-water bath for 30 min, raise to room temperature and continue the reaction for 2 h. Then, distill under reduced pressure at 35 °C for 2 h, dissolve in 150 ml of ice water, adjust the pH to 7 with cold saturated NaHCO3 solution, transfer the reaction solution to a dialysis bag (MWCO = 3000), dialyze with deionized water for 48 h, changing the water every 6 h with 2000 ml each time, and freeze-dry at -50 °C for 12 h to obtain the modified curing agent; the reaction equation is shown below: .

[0020] Example 2: Preparation of modified curing agent: S1: Under nitrogen protection, 14g of deionized water, 0.05g of tetraethylammonium hydroxide, 0.2mol of octamethylcyclotetrasiloxane and 0.38mol of N-aminoethyl-3-aminopropylmethyldimethoxysilane were added to the reactor. The mixture was stirred and stirred until homogeneous. After reflux for 9 hours, the temperature was lowered to 50℃ and vacuum was applied for 2 hours to remove the byproducts methanol and water. The temperature was then raised to 150℃ and maintained for 30 minutes to remove tetraethylammonium hydroxide. The mixture was then distilled under reduced pressure at 50℃ for 2 hours to obtain amino-modified polydimethylsiloxane.

[0021] S2: Add 200 ml of anhydrous ethanol and 55 g of amino-modified polydimethylsiloxane to the reactor, then add 4 g of 4A molecular sieve (sodium-A type molecular sieve). Slowly add anhydrous ethanol solution of 4-formyl phthalic acid (10 g of 4-formyl phthalic acid dissolved in 100 ml of anhydrous ethanol) to the reactor. Add dropwise for 30 min, react at 70 °C for 7 h, cool to room temperature, filter to remove the molecular sieve, distill the filtrate under reduced pressure at 60 °C for 2 h, then add 400 ml of cold n-hexane, stir to precipitate, collect the precipitate by suction filtration, wash with petroleum ether (using 200 ml of petroleum ether each time), and vacuum dry at 60 °C for 12 h to obtain carboxyl-modified polydimethylsiloxane.

[0022] S3: Under ice bath conditions, add 200 ml of 1,4-dioxane / water (1,4-dioxane / water (v / v) = 4:1) mixed solvent and 12 g of amino-protected polyethylene glycol hydroxyl (NH2-PEG-OH, number average molecular weight 1000) to the reactor, stir and mix well, then add 2 g of triethylamine and slowly add 2.5 g of di-tert-butyl dicarbonate over 20 min. After the addition is complete, raise the temperature to room temperature and react for 6 h. Then, distill under reduced pressure at 40 °C for 2 h to obtain amino-protected polyethylene glycol hydroxyl. Under ice bath conditions, 200 ml of anhydrous DMF, the amino-protected polyethylene glycol hydroxyl group obtained in the above steps, and 10 g of carboxyl-modified polydimethylsiloxane were added to the reactor and stirred until well mixed. Then, 0.015 mol DCC and 0.02 mol DMAP were added, the mixture was brought to room temperature, and stirred in the dark for 14 h. After filtration, the filtrate was added dropwise to 500 ml of cold anhydrous diethyl ether for 30 min. The mixture was stirred to precipitate the precipitate, which was collected by centrifugation. The precipitate was washed three times with cold diethyl ether (200 ml each time) and dried under vacuum at 70 °C for 2 h to obtain the crude product. Add 200 ml of a mixed solution of dichloromethane / trifluoroacetic acid (dichloromethane / trifluoroacetic acid (v / v) = 9:1) and the crude product obtained in the previous step to the reactor. Stir in an ice-water bath for 30 min, raise to room temperature and continue the reaction for 2 h. Then, distill under reduced pressure at 35 °C for 2 h and dissolve in 150 ml of ice water. Adjust the pH to 7 with cold saturated NaHCO3 solution. Transfer the reaction solution to a dialysis bag (MWCO = 3000) and dialyze with deionized water for 48 h, changing the water every 6 h with 2000 ml each time. Freeze dry at -50 °C for 12 h to obtain the modified curing agent.

[0023] Example 3: Preparation of modified curing agent: S1: Under nitrogen protection, 15g of deionized water, 0.05g of tetraethylammonium hydroxide, 0.2mol of octamethylcyclotetrasiloxane and 0.4mol of N-aminoethyl-3-aminopropylmethyldimethoxysilane were added to the reactor. The mixture was stirred and stirred until homogeneous. After reflux for 10h, the temperature was lowered to 50℃ and vacuum was applied for 2h to remove the byproducts methanol and water. The temperature was then raised to 150℃ and held for 30min to remove tetraethylammonium hydroxide. The mixture was then distilled under reduced pressure at 50℃ for 2h to obtain amino-modified polydimethylsiloxane.

[0024] S2: Add 200 ml of anhydrous ethanol and 60 g of amino-modified polydimethylsiloxane to the reactor, then add 5 g of 4A molecular sieve (sodium-A type molecular sieve). Slowly add anhydrous ethanol solution of 4-formyl phthalic acid (10 g of 4-formyl phthalic acid dissolved in 100 ml of anhydrous ethanol) to the reactor. Add dropwise for 30 min, react at 70 °C for 8 h, cool to room temperature, filter to remove the molecular sieve, distill the filtrate under reduced pressure at 60 °C for 2 h, then add 400 ml of cold n-hexane, stir to precipitate, collect the precipitate by suction filtration, wash with petroleum ether (200 ml of petroleum ether each time), and vacuum dry at 60 °C for 12 h to obtain carboxyl-modified polydimethylsiloxane.

[0025] S3: Under ice bath conditions, add 200 ml of 1,4-dioxane / water (1,4-dioxane / water (v / v) = 4:1) mixed solvent and 10 g of amino-protected polyethylene glycol hydroxyl (NH2-PEG-OH, number average molecular weight 1000) to the reactor, stir and mix well, then add 2 g of triethylamine and slowly add 2.5 g of di-tert-butyl dicarbonate over 20 min. After the addition is complete, raise the temperature to room temperature and react for 6 h. Then, distill under reduced pressure at 40 °C for 2 h to obtain amino-protected polyethylene glycol hydroxyl. Under ice bath conditions, 200 ml of anhydrous DMF, the amino-protected polyethylene glycol hydroxyl group obtained in the above steps, and 13 g of carboxyl-modified polydimethylsiloxane were added to the reactor and stirred until well mixed. Then, 0.015 mol DCC and 0.02 mol DMAP were added, the mixture was brought to room temperature, and stirred in the dark for 16 h. After filtration, the filtrate was added dropwise to 500 ml of cold anhydrous diethyl ether for 30 min, stirred, and precipitated. The precipitate was collected by centrifugation, washed three times with cold diethyl ether (200 ml each time), and dried under vacuum at 70 °C for 2 h to obtain the crude product. Add 200 ml of a mixed solution of dichloromethane / trifluoroacetic acid (dichloromethane / trifluoroacetic acid (v / v) = 9:1) and the crude product obtained in the previous step to the reactor. Stir in an ice-water bath for 30 min, raise to room temperature and continue the reaction for 2 h. Then, distill under reduced pressure at 35 °C for 2 h and dissolve in 150 ml of ice water. Adjust the pH to 7 with cold saturated NaHCO3 solution. Transfer the reaction solution to a dialysis bag (MWCO = 3000) and dialyze with deionized water for 48 h, changing the water every 6 h with 2000 ml each time. Freeze dry at -50 °C for 12 h to obtain the modified curing agent.

[0026] Example 4: Preparation of flame retardant: A1: Under ice bath conditions, 200 ml of toluene and 0.1 mol of cyanuric chloride were added to the reactor and stirred until homogeneous. 0.21 mol of 1-amino-10-undecene was dissolved in 100 ml of 5 wt% NaOH aqueous solution and added dropwise to the reactor over 1 hour. The reaction was maintained at 0°C for 4 hours, then heated to 40°C and reacted for 6 hours. After cooling to room temperature, the pH was adjusted to 2 using 1 M hydrochloric acid solution. The mixture was then distilled under reduced pressure at 60°C for 3 hours, washed with 100 ml of deionized water, and dried under vacuum at 70°C for 12 hours to obtain the disubstituted compound. The reaction equation is shown below: .

[0027] Its 1H NMR data are as follows: 1 H NMR (400 MHz, Chloroform- d ) δ 6.17 (t, J = 4.6 Hz, 2H), 5.86 –5.66 (m, 2H), 5.23 – 4.87 (m, 4H), 3.52 (td, J = 7.2, 4.6 Hz, 4H), 2.03 (tdt,J = 8.1, 6.8, 1.4 Hz, 4H), 1.71 (p, J = 7.3 Hz, 4H), 1.43 – 1.13 (m, 24H).

[0028] A2: Under nitrogen protection, 200 ml of DMSO (dimethyl sulfoxide), 8 g of NaOH, and 0.1 mol of the disubstituted compound were added to a reaction vessel and stirred until homogeneous. Then, 0.11 mol of 1H,1H-perfluorooctylamine was dissolved in 120 ml of DMSO and added dropwise to the reaction vessel over 30 min. The temperature was raised to 120 °C, and the reaction was allowed to proceed for 10 h. After cooling to room temperature, the reaction solution was slowly added to 500 ml of ice water with stirring. A precipitate formed, which was then filtered, washed with 500 ml of deionized water, and dried under vacuum at 70 °C for 8 h to obtain the fluorinated compound. The reaction equation is shown below: .

[0029] Its 1H NMR data are as follows: 1 H NMR (400 MHz, Chloroform- d ) δ 7.55 (tt, J =6.0, 2.4 Hz, 1H), 6.20 (t, J = 4.6 Hz, 2H), 5.87 – 5.66 (m, 2H), 5.22 – 4.89(m, 4H), 4.52 – 4.24 (m, 2H), 3.52 (td, J = 7.2, 4.6 Hz, 4H), 2.03 (tdt, J =8.1, 6.8, 1.4 Hz, 4H), 1.71 (p, J = 7.3 Hz, 4H), 1.51 – 1.10 (m, 24H).

[0030] A3: Add 500 ml xylene, 0.1 mol of fluorine-modified compound, and 0.21 mol of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-sulfide to the reactor, stir and mix well, heat to 130℃ and react for 10 h, then cool to room temperature. Slowly add the reaction solution dropwise to 1000 mL of ice water for 1 h, stirring to precipitate. Collect the precipitated solid by vacuum filtration, wash with 500 ml of deionized water, and recrystallize three times with toluene (300 ml of toluene each time). Dry under vacuum at 80℃ for 4 h to obtain the flame retardant; the reaction equation is shown below: .

[0031] Its 1H NMR data are as follows: 1 H NMR (400 MHz, Chloroform- d) δ 8.34 (ddd, J =21.6, 7.3, 1.3 Hz, 4H), 7.96 – 7.84 (m, 4H), 7.72 – 7.61 (m, 4H), 7.55 (tt, J= 6.0, 2.4 Hz, 1H), 7.45 – 7.33 (m, 4H), 6.20 (t, J = 4.6 Hz, 2H), 4.41 (tdt,J = 13.0, 5.9, 2.7 Hz, 2H), 3.52 (td, J = 7.2, 4.6 Hz, 4H), 2.35 – 2.12 (m,4H), 1.86 – 1.75 (m, 4H), 1.45 (dq, J = 7.3, 6.6 Hz, 4H), 1.38 – 1.31 (m, 4H), 1.30 – 1.18 (m, 24H).

[0032] Example 5: Preparation of scratch-resistant, flame-retardant, and insulating powder coating: (1) Weigh out: 1000g of polysiloxane epoxy resin, 100g of modified curing agent (prepared in Example 1), 50g of flame retardant (prepared in Example 4), 30g of toughening agent (liquid nitrile rubber), 20g of leveling agent (polyacrylate adsorbed by silica), 10g of benzoin, and 80g of mica powder. (2) After the polysiloxane epoxy resin, modified curing agent, flame retardant, toughening agent, leveling agent, benzoin and mica powder are mixed evenly, they are extruded through a twin-screw extruder. The screw speed of the extruder is 300r / min, the feed temperature of the twin screw is 100℃, and the discharge temperature is 75℃. The extruder is pressed and crushed, and then pulverized by a grinding mill. After pulverization, it is sieved through a 120-mesh sieve to obtain a scratch-resistant, flame-retardant, and insulating powder coating.

[0033] Example 6: Preparation of scratch-resistant, flame-retardant, and insulating powder coating: (1) Weigh out: 1100g of polysiloxane epoxy resin, 150g of modified curing agent (prepared in Example 2), 80g of flame retardant (prepared in Example 4), 45g of toughening agent (liquid nitrile rubber), 25g of leveling agent (polyacrylate adsorbed by silica), 15g of benzoin, and 90g of mica powder. (2) After the polysiloxane epoxy resin, modified curing agent, flame retardant, toughening agent, leveling agent, benzoin and mica powder are mixed evenly, they are extruded through a twin-screw extruder. The screw speed of the extruder is 300r / min, the feed temperature of the twin screw is 100℃, and the discharge temperature is 75℃. The extruder is pressed and crushed, and then pulverized by a grinding mill. After pulverization, it is sieved through a 120-mesh sieve to obtain a scratch-resistant, flame-retardant, and insulating powder coating.

[0034] Example 7: Preparation of scratch-resistant, flame-retardant, and insulating powder coating: (1) Weigh out: 1200g of polysiloxane epoxy resin, 200g of modified curing agent (prepared in Example 3), 100g of flame retardant (prepared in Example 4), 60g of toughening agent (liquid nitrile rubber), 30g of leveling agent (polyacrylate adsorbed by silica), 20g of benzoin, and 100g of mica powder. (2) After the polysiloxane epoxy resin, modified curing agent, flame retardant, toughening agent, leveling agent, benzoin and mica powder are mixed evenly, they are extruded through a twin-screw extruder. The screw speed of the extruder is 300r / min, the feed temperature of the twin screw is 100℃, and the discharge temperature is 75℃. The extruder is pressed and crushed, and then pulverized by a grinding mill. After pulverization, it is sieved through a 120-mesh sieve to obtain a scratch-resistant, flame-retardant, and insulating powder coating.

[0035] Comparative Example 1 The raw material ratio and preparation method of the scratch-resistant flame-retardant insulating powder coating are basically the same as those in Example 6, except that the modified curing agent is replaced with an equal weight of the modified curing agent prepared by the following method: The preparation method of the modified curing agent is basically the same as that in Example 2, except that the octamethylcyclotetrasiloxane in step S1 is replaced with an equimolar amount of hexamethylcyclotrisiloxane.

[0036] Comparative Example 2 The raw material ratio and preparation method of the scratch-resistant flame-retardant insulating powder coating are basically the same as those in Example 6, except that the modified curing agent is replaced with an equal weight of the modified curing agent prepared by the following method: The preparation method of the modified curing agent is basically the same as that in Example 2, except that N-aminoethyl-3-aminopropylmethyldimethoxysilane in step S1 is replaced with an equimolar amount of N-aminoethyl-3-aminopropyltriethoxysilane.

[0037] Comparative Example 3 The raw material ratio and preparation method of the scratch-resistant flame-retardant insulating powder coating are basically the same as those in Example 6, except that the modified curing agent is replaced with an equal weight of the modified curing agent prepared by the following method: The preparation method of the modified curing agent is basically the same as that in Example 2, except that in step S2, 4-formyl phthalic acid is replaced with an equal weight of 2-(4-formylphenyl)acetic acid.

[0038] Comparative Example 4 The raw material ratio and preparation method of the scratch-resistant flame-retardant insulating powder coating are basically the same as those in Example 6, except that the modified curing agent is replaced with an equal weight of the modified curing agent prepared by the following method: The preparation method of the modified curing agent is basically the same as that in Example 2, except that in step S3, the amino polyethylene glycol hydroxyl group (NH2-PEG-OH, number average molecular weight 1000) is replaced with an equal weight of 12-amino-1-n-dodecanool.

[0039] Comparative Example 5 The raw material ratio and preparation method of the scratch-resistant flame-retardant insulating powder coating are basically the same as those in Example 6, except that the modified curing agent is replaced with an equal weight of the modified curing agent prepared by the following method: The preparation method of the modified curing agent is basically the same as that in Example 2, except that in step S3, the amino polyethylene glycol hydroxyl group (NH2-PEG-OH, number average molecular weight 1000) is replaced with an equimolar amount of amino polyethylene glycol hydroxyl group (NH2-PEG-OH, number average molecular weight 2000).

[0040] Comparative Example 6 The raw material ratio and preparation method of the scratch-resistant flame-retardant insulating powder coating are basically the same as those in Example 6, except that the flame retardant is replaced with an equal weight of flame retardant prepared by the following method: The preparation method of the flame retardant is basically the same as that in Example 4, except that 1-amino-10-undecene in step A1 is replaced with an equimolar amount of 1-amino-5-hexene.

[0041] Comparative Example 7 The raw material ratio and preparation method of the scratch-resistant flame-retardant insulating powder coating are basically the same as those in Example 6, except that the flame retardant is replaced with an equal weight of flame retardant prepared by the following method: The preparation method of the flame retardant is basically the same as that in Example 4, except that 1H,1H-perfluorooctylamine in step A2 is replaced with an equimolar amount of 2,2,3,3-tetrafluoropropane-1-amine.

[0042] Comparative Example 8 The raw material ratio and preparation method of the scratch-resistant flame-retardant insulating powder coating are basically the same as those in Example 6, except that the flame retardant is replaced with an equal weight of flame retardant prepared by the following method: The preparation method of the flame retardant is basically the same as that in Example 4, except that the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-sulfide in step A2 is replaced with an equimolar amount of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

[0043] The polysiloxane epoxy resin used in the embodiments and comparative examples of this application is SH-9614 type epoxy modified polysiloxane resin, produced by Hubei Longsheng Sihai New Material Co., Ltd.; the leveling agent is silica-adsorbed polyacrylate, model TP88, produced by Huangshan Debang Powder Material Co., Ltd.; the mica powder is wet-process mica powder with a particle size of 2000 mesh, produced by Lingshou Huajing Mica Co., Ltd.; and the liquid nitrile rubber is model GREEN BABY™ LR810.

[0044] 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-sulfide is prepared by the following method: Under nitrogen protection, 60 ml of toluene and 10.8 g of DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) were added to the reactor and stirred for 25 min to mix evenly. Then, 2.78 g of phosphorus pentasulfide was added, and the temperature was raised to 60 °C and reacted for 2 h. Another 2.78 g of phosphorus pentasulfide was added, and the temperature was lowered to 45 °C and reacted for 15 h. The mixture was then distilled under reduced pressure at 60 °C for 0.5 h. 100 ml of chloroform was added to dissolve the mixture, and 20 ml of saturated sodium bicarbonate solution was slowly added dropwise over 20 min. After the addition was complete, the mixture was stirred for another 30 min. The mixture was allowed to stand and separate into layers. The organic phase was then distilled under reduced pressure at 60 °C for 1 h and dried under vacuum at 70 °C for 2 h to obtain 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-sulfide.

[0045] The scratch-resistant, flame-retardant, and adhesive powder coatings prepared in the examples and comparative examples were tested for impact resistance, flame retardancy, and adhesion. The test results are shown in Table 1.

[0046] Sample preparation: Samples were prepared in accordance with the "HG / T2006-2006 Thermosetting Powder Coatings". The substrate was a carbon steel plate (thickness 0.5 mm, size 150 mm × 100 mm). The coating was uniformly applied to the carbon steel plate by electrostatic spraying, and the coating thickness was 0.06 mm. The prepared sample was placed in a forced-air drying oven and cured at 120°C for 20 min. Then, the temperature was lowered to 23°C and placed at 50% relative humidity for 24 h to obtain the sample.

[0047] Impact resistance test: Referring to GB / T1732-2020 "Test Method for Impact Resistance of Coating Film", a paint film impactor was used to conduct a forward impact test on the scratch-resistant flame-retardant insulating powder coatings prepared in the examples and comparative examples. The cured sample plate was placed flat on the base of the impactor, and a 1kg weight was dropped freely from a height of 30cm to impact the coating. After the test, the sample plate was removed, and the impact point was observed with a magnifying glass for cracks, wrinkles, and peeling. If no cracks, wrinkles, or peeling were observed, the test was repeated at higher positions (each time the height increased by 5cm or multiples of 5cm) until cracks, wrinkles, and peeling were observed. If cracks, wrinkles, and peeling were observed, the test was repeated at lower positions (each time decreasing by 1cm) until no cracks, wrinkles, or peeling were observed. The result is expressed as the maximum height (cm) at which no cracks, wrinkles, or peeling were observed in three tests.

[0048] Flame retardancy test: The scratch-resistant flame-retardant insulating powder coatings prepared in the examples and comparative examples were tested for flame retardancy in accordance with the UL 94 flame retardancy test method and standard. The sample was fixed vertically on the fixture with its longitudinal axis perpendicular. A Bunsen burner (producing a 20mm high blue flame) was used, with the center of the flame aligned with the center point of the lower end of the sample, and ignited for 10 seconds. The flame was removed, and the flaming time (t1) of the sample was recorded. After the afterflame of the sample was extinguished, the same sample was immediately ignited again for 10 seconds. The flame was removed again, and the flaming time (t2) and the afterglow time (t3) of the second flaming time were recorded. Throughout the process, it was observed whether any burning droplets igniting cotton were produced, and whether the flame burned to the clamping end of the fixture. The rating was determined by referring to the judgment indicators in the UL 94 standard.

[0049] Adhesion Test: Referring to GB / T9286-2021 "Cross-cut Test for Paint and Varnish Films", the scratch-resistant, flame-retardant, and insulating powder coatings prepared in the examples and comparative examples were subjected to adhesion tests. A 6×6 grid pattern (1mm spacing, penetrating to the substrate) was cut into the coating film using a cross-cutting tool. Debris was brushed away, and special pressure-sensitive adhesive tape was applied and quickly peeled off. The degree of paint film peeling off in the grid areas was observed. Adhesion was graded from best to worst as 0-5, with 0 representing the best and 5 representing the worst.

[0050] Insulation performance testing: The scratch-resistant and flame-retardant insulating powder coatings prepared in the examples and comparative examples were tested for insulation performance according to "HGT3331-2012 Method for Determination of Volume Resistivity and Surface Resistivity of Insulating Varnish Film". A substrate of 120mm × 100mm × 0.2mm was used. The coating was uniformly applied to the substrate using electrostatic spraying, resulting in a film thickness of 50μm. The prepared samples were placed in a forced-air drying oven and cured at 120℃ for 20 minutes. The temperature was then lowered to 23℃, and the samples were left to stand at 50% relative humidity for 24 hours to obtain the final sample.

[0051]

[0052] As can be seen from Table 1, the scratch-resistant, flame-retardant, and insulating powder coating prepared in this application has good impact resistance, flame retardancy, adhesion, and insulation properties.

[0053] The modified curing agent prepared in this invention contains siloxane segments and polyether segments. The siloxane segments exhibit excellent thermal stability, weather resistance, and low surface energy. Upon impact, the siloxane segments can absorb and dissipate a large amount of impact energy through significant conformational changes, internal rotation, and coiling extension, effectively preventing crack initiation and propagation. The flexible polyether segments can release the internal stress generated during the curing and cooling process of the coating through deformation, avoiding adhesion degradation caused by stress contraction. Their ether bonds can also generate dipole interactions with the surface of the metal substrate, providing strong physical adsorption. Furthermore, the polar groups such as amino groups contained in the curing agent's molecular structure can form strong chemical bonds and hydrogen bonds with the matrix resin (polysiloxane epoxy resin) in the powder coating and polar groups (such as hydroxyl and carboxyl groups) on the substrate surface, enhancing the interfacial bonding between the curing agent and the resin matrix, as well as between the coating and the substrate, thereby significantly improving the coating's adhesion.

[0054] In Comparative Example 5 of this application, when amino-PEG-OH (number-average molecular weight 1000) was replaced with an equimolar amount of amino-PEG-OH (number-average molecular weight 2000), the increased molecular weight of the amino-PEG-OH resulted in a greater polarity and volume fraction of the polyether segments. This disrupted the amphiphilic balance of the entire curing agent molecule, enhancing its hydrophilicity. During the coating's melt curing process, the lower surface energy silica segments still tend to migrate towards the air interface, while the more hydrophilic long-chain polyethers are repelled. This complex migration competition leads to disordered molecular conformation in the interfacial region, preventing the formation of the most effective adhesive interface and reducing the effective contact and interaction strength with the substrate.

[0055] The flame retardant prepared by this invention has a fluorocarbon chain and a phosphonophenanthrene sulfur structure. The fluorocarbon chain has low surface energy and extremely high thermal stability, and tends to be directionally enriched on the coating surface to form a dense protective layer that can isolate oxygen and heat from being transferred inward and inhibit the combustion cycle. The phosphonophenanthrene sulfur structure has physical barrier and chemical reactivity, and can form a dense char layer during combustion to prevent the diffusion of heat, oxygen and combustible gases, thereby improving the flame retardant efficiency.

[0056] Comparative Example 7 uses a flame retardant synthesized with short fluorine-containing segments. The number of fluorine-containing free radicals generated by decomposition is small, the concentration is low, and the lifetime is short. It cannot effectively capture and neutralize enough H· and OH· free radicals to interrupt the chain reaction. The resulting char layer may be sparser, porous, and discontinuous, which leads to a decrease in the gas phase flame retardant mechanism and poor flame retardant effect.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. However, any modifications, alterations, and variations made by those skilled in the art without departing from the scope of the present invention based on the disclosed technical content are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A scratch-resistant, flame-retardant, insulating powder coating, characterized in that, The ingredients include the following parts by weight: 100-120 parts of polysiloxane epoxy resin, 10-20 parts of modified curing agent, 5-10 parts of flame retardant, 3-6 parts of toughening agent, 2-3 parts of leveling agent, 1-2 parts of benzoin, and 8-10 parts of mica powder. The modified curing agent is prepared by the following method: S1: Octamethylcyclotetrasiloxane reacts with N-aminoethyl-3-aminopropylmethyldimethoxysilane to generate amino-modified polydimethylsiloxane. S2: Amino-modified polydimethylsiloxane reacts with 4-formyl phthalic acid to generate carboxyl-modified polydimethylsiloxane. S3: Carboxyl-modified polydimethylsiloxane reacts with amino polyethylene glycol hydroxyl groups to generate a modified curing agent.

2. The scratch-resistant, flame-retardant, and insulating powder coating according to claim 1, characterized in that, In step S1, the molar ratio of octamethylcyclotetrasiloxane to N-aminoethyl-3-aminopropylmethyldimethoxysilane is 1:(1.8-2).

3. The scratch-resistant, flame-retardant, and insulating powder coating according to claim 1, characterized in that, In step S2, the mass ratio of the amino-modified polydimethylsiloxane to 4-formyl phthalic acid is (5-6):

1.

4. The scratch-resistant, flame-retardant, and insulating powder coating according to claim 1, characterized in that, In step S3, the mass ratio of the carboxyl-modified polydimethylsiloxane to the amino-polyethylene glycol hydroxyl group is (1.1-1.3):

1.

5. The scratch-resistant, flame-retardant, and insulating powder coating according to claim 1, characterized in that, The flame retardant is prepared by the following method: A1: 1-Amino-10-undecene reacts with cyanuric chloride to form a disubstituted compound. A2: The disubstituted compound reacts with 1H,1H-perfluorooctylamine to generate a fluorinated modified compound. A3: Fluorine-modified compounds react with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-sulfides to generate flame retardants.

6. The scratch-resistant, flame-retardant, and insulating powder coating according to claim 5, characterized in that, In step A1, the molar ratio of 1-amino-10-undecene to cyanuric chloride is 2.1:

1.

7. The scratch-resistant, flame-retardant, and insulating powder coating according to claim 5, characterized in that, In step A2, the molar ratio of the disubstituted compound to 1H,1H-perfluorooctylamine is 1:1.1; in step A3, the molar ratio of the fluorinated modified compound to 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-sulfide is 1:2.

1.

8. The scratch-resistant, flame-retardant, and insulating powder coating according to claim 1, characterized in that, The toughening agent is liquid nitrile rubber; the leveling agent is silica-adsorbed polyacrylate.

9. A method for preparing a scratch-resistant, flame-retardant, insulating powder coating according to any one of claims 1-8, characterized in that, Includes the following steps: (1) Weigh out the following by weight: 100-120 parts of polysiloxane epoxy resin, 10-20 parts of modified curing agent, 5-10 parts of flame retardant, 3-6 parts of toughening agent, 2-3 parts of leveling agent, 1-2 parts of benzoin, and 8-10 parts of mica powder. (2) After the polysiloxane epoxy resin, modified curing agent, flame retardant, toughening agent, leveling agent, benzoin and mica powder are mixed evenly, they are extruded by a twin-screw extruder, pressed into sheets and crushed, and then pulverized by a grinding mill to obtain a scratch-resistant, flame-retardant and insulating powder coating.

10. The application of the scratch-resistant, flame-retardant, and insulating powder coating according to any one of claims 1-8 in rail transit and new energy vehicles.

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