An anti-stone impact insulating powder coating for an automobile battery tray and a preparation method thereof

Abstract

The present application relates to the technical field of insulating powder coating, in particular to an anti-stone impact insulating powder coating for automobile battery tray and a preparation method thereof, which is composed of the following raw materials in parts by weight: epoxy resin A, epoxy resin B, butyronitrile rubber modified epoxy resin, phenolic resin curing agent, quartz powder, leveling agent, pigment, curing accelerator, anti-settling agent, adhesion enhancer, defoaming agent and electric potential enhancer.The present application simultaneously gives the coating super-high insulation and top anti-stone impact performance through single coating, completely eliminating the secondary construction link; solid powder system is adopted to realize zero VOC emission; special toughening resin and gradient curing process make the coating have rigid protection and toughness buffer, the actual measured anti-stone impact grade is greater than 9 and the breakdown voltage meets 6kV, the leakage current is less than 0.1mA, which perfectly adapts to the strict requirements of electric vehicle high-voltage battery system on safety and environmental protection, and solves the technical defects in the traditional scheme.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of insulating powder coating, in particular to an anti-stone impact insulating powder coating for automobile battery tray and a preparation method thereof. BACKGROUND

[0002] The automobile battery tray is a metal structural member for carrying and fixing the power battery pack in the chassis system of the electric vehicle. Its core function is to provide mechanical support, collision protection and heat management channel integration for the battery module, and at the same time, it needs to isolate the electrical conduction risk between the high-voltage battery system and the vehicle body. The automobile battery tray must be treated by film coating process, because it is exposed to complex working conditions for a long time: the impact of road stones during driving can easily cause corrosion and perforation of the metal substrate, condensation water vapor penetration may cause battery short circuit, and the high-voltage battery system requires the tray to have a permanent insulating barrier to avoid electric leakage accidents, so the coating needs to meet the three protection requirements of anti-mechanical damage, environmental corrosion resistance and high insulation at the same time.

[0003] Generally, the traditional automobile battery tray adopts a double-coating system of ordinary insulating coating and PVC anti-stone impact coating. This scheme has the following defects: the insulating layer and the anti-stone impact layer need to be applied twice and need to be cured and waited in between, which is complex and time-consuming, resulting in low production efficiency; the PVC coating contains a large amount of volatile organic solvents, which releases VOC pollutants during high-temperature curing; the adhesion of the interface of the double-layer structure is weakened, and it is easy to delaminate and fail in the long-term vibration environment.

[0004] Based on this, the present application provides an anti-stone impact insulating powder coating for automobile battery tray and a preparation method thereof to solve the above technical problems. SUMMARY

[0005] The purpose of the present application is to provide an anti-stone impact insulating powder coating for automobile battery tray and a preparation method thereof to solve the problems mentioned in the background art.

[0006] To achieve the above purpose, the present application provides the following technical scheme:

[0007] The present application provides an anti-stone impact insulating powder coating for automobile battery tray, which is composed of the following raw materials by weight: epoxy resin A: 15-20 parts, epoxy resin B: 35-40 parts, nitrile rubber modified epoxy resin: 5-10 parts, phenolic resin curing agent: 10-13 parts, quartz powder: 20-35 parts, leveling agent: 0.8-1.2 parts, pigment: 1-5 parts, curing accelerator: 0.3-0.8 parts, anti-settling agent: 0.5-1 parts, adhesion enhancer: 0.3-0.6 parts, defoaming agent: 0.3-0.6 parts and electric enhancer: 0.3-0.8 parts;

[0008] The epoxy resin A is an epoxy resin with an epoxy equivalent weight of 850-900; the epoxy resin B is an epoxy resin with an epoxy equivalent weight of 1700-2000; the nitrile rubber modified epoxy resin is a modified epoxy resin with an epoxy equivalent weight of 750-800; the pigment is specifically rutile titanium dioxide; the curing accelerator is specifically 2-methylimidazole; the anti-settling agent is specifically fumed silica; the adhesion promoter is specifically a silane coupling agent; the defoaming agent is specifically benzoin; and the electricity increasing agent is specifically a tetraalkylammonium salt.

[0009] Preferably, the preparation steps of the epoxy resin A are as follows:

[0010] A1. Bisphenol A and epichlorohydrin are put into a reaction kettle at a molar ratio of 1:1.38, dissolved by heating to 75°C, and then 50% sodium hydroxide solution is added dropwise at a constant temperature of 80°C for 120 minutes;

[0011] A2. The temperature is raised to 85°C and kept for 180 minutes, and then the temperature is lowered to 60°C and washed with deionized water for 3 times until neutral;

[0012] A3. Dehydration is carried out at 120°C and -0.095 MPa vacuum for 90 minutes, and after filtration, the epoxy equivalent weight is detected to be 850-900 g / eq, and the product is discharged.

[0013] Preferably, the preparation steps of the epoxy resin B are as follows:

[0014] B1. Bisphenol A and epichlorohydrin are put into a reaction kettle at a molar ratio of 1:1.15, heated to 90°C under nitrogen protection, and 40% sodium hydroxide solution is slowly added dropwise while controlling the temperature at 95°C for 150 minutes;

[0015] B2. The reaction is kept for 240 minutes and the pH is maintained above 12, and then toluene solvent is added after the temperature is lowered to 70°C, and washed with water until neutral;

[0016] B3. Toluene and water are removed at 130°C and -0.098 MPa vacuum for 120 minutes, and after the epoxy equivalent weight is detected to be 1700-2000 g / eq, the product is cooled.

[0017] Preferably, the preparation steps of the nitrile rubber modified epoxy resin are as follows:

[0018] C1. Carboxyl nitrile rubber and epoxy resin A are put into a reactor at a mass ratio of 1:2, heated to 140°C under nitrogen protection and stirred for 60 minutes, and 0.5% triphenylphosphine catalyst is added and the reaction is continued for 180 minutes;

[0019] C2. The epoxy equivalent weight is detected by sampling, and the reaction is adjusted to be in the range of 750-800 g / eq, and then the temperature is lowered to 80°C and diluted with acetone to a solid content of 70%;

[0020] C3. After removing the gel particles by filtration, the product was discharged after removing the acetone at 100℃ under -0.092MPa vacuum.

[0021] Preferably, the stone chip resistant insulating powder coating for automobile battery tray is composed of the following raw materials in parts by weight: epoxy resin A: 16 parts; epoxy resin B: 36 parts; nitrile rubber modified epoxy resin: 6 parts; phenolic resin curing agent: 11 parts; quartz powder: 25 parts; leveling agent: 0.9 parts; pigment (rutile titanium dioxide): 2 parts; curing accelerator (2-methyl imidazole): 0.4 parts; anti-settling agent (fumed silica): 0.7 parts; adhesion promoter (silane coupling agent): 0.4 parts; defoaming agent (benzoin): 0.45 parts; electricity increasing agent (tetraalkyl ammonium salt): 0.5 parts.

[0022] Preferably, the stone chip resistant insulating powder coating for automobile battery tray is composed of the following raw materials in parts by weight: epoxy resin A: 18 parts; epoxy resin B: 38 parts; nitrile rubber modified epoxy resin: 8 parts; phenolic resin curing agent: 12 parts; quartz powder: 30 parts; leveling agent: 1.0 parts; pigment (rutile titanium dioxide): 3 parts; curing accelerator (2-methyl imidazole): 0.6 parts; anti-settling agent (fumed silica): 0.8 parts; adhesion promoter (silane coupling agent): 0.5 parts; defoaming agent (benzoin): 0.45 parts; electricity increasing agent (tetraalkyl ammonium salt): 0.6 parts.

[0023] Preferably, the stone chip resistant insulating powder coating for automobile battery tray is composed of the following raw materials in parts by weight: epoxy resin A: 20 parts; epoxy resin B: 40 parts; nitrile rubber modified epoxy resin: 5 parts; phenolic resin curing agent: 13 parts; quartz powder: 35 parts; leveling agent: 1.2 parts; pigment (rutile titanium dioxide): 1 part; curing accelerator (2-methyl imidazole): 0.3 parts; anti-settling agent (fumed silica): 1.0 parts; adhesion promoter (silane coupling agent): 0.3 parts; defoaming agent (benzoin): 0.45 parts; electricity increasing agent (tetraalkyl ammonium salt): 0.3 parts.

[0024] Preferably, the stone chip resistant insulating powder coating for automobile battery tray is composed of the following raw materials in parts by weight: epoxy resin A: 15 parts; epoxy resin B: 35 parts; nitrile rubber modified epoxy resin: 10 parts; phenolic resin curing agent: 10 parts; quartz powder: 20 parts; leveling agent: 0.8 parts; pigment (rutile titanium dioxide): 5 parts; curing accelerator (2-methyl imidazole): 0.8 parts; anti-settling agent (fumed silica): 0.5 parts; adhesion promoter (silane coupling agent): 0.6 parts; defoaming agent (benzoin): 0.45 parts; electricity increasing agent (tetraalkyl ammonium salt): 0.8 parts.

[0025] The present application also provides a preparation method of the stone chip resistant insulating powder coating for automobile battery tray, comprising the following steps:

[0026] S1. Put epoxy resin A: 15~20 parts, epoxy resin B: 35~40 parts, butyronitrile rubber modified epoxy resin: 5~10 parts into a premix kettle, jacket temperature 50±2℃, low speed stirring for 10 minutes at 300~400 rpm, add phenolic resin curing agent: 10~13 parts, leveling agent: 0.8~1.2 parts, curing accelerator: 0.3~0.8 parts, adhesion promoter: 0.3~0.6 parts, defoaming agent: 0.3~0.6 parts, electric enhancer: 0.3~0.8 parts and 50% total amount 20~35 parts of quartz powder, the speed is raised to 800~1000 rpm for 15 minutes, finally add the remaining quartz powder, pigment: 1~5 parts, anti-settling agent: 0.5~1 parts, high speed shearing dispersion for 25 minutes at 1200~1500 rpm, until the fineness of the mixture is ≤50 μm;

[0027] S2. Put the premix into a co-rotating twin-screw extruder with a length-diameter ratio of 18:1, control the temperature in four sections, screw speed 400~600 rpm, melt residence time ≤60 seconds, then extrude the melt into 1.0~1.5 mm thick sheets by a double roller press with a roller temperature of 40±2℃ and a roller speed ratio of 1:1.2, and then crush the sheets into flaky particles with a particle size ≤5 mm by liquid nitrogen-50℃ deep cooling crushing;

[0028] S3. First, put the crushed material into a vortex type cryogenic mill with a grinding chamber temperature of-30℃, continuously control the temperature with liquid nitrogen as the coolant, rotor speed 4500~6000 rpm, grind to D50 particle size 30~40 μm, then separate the coarse powder >80 μm from the fine powder <10 μm by a turbine airflow classifier with a classification wheel frequency of 35~50 Hz, and ensure that the particle size distribution of the finished powder Dv90≤65 μm; finally, add fumed silica anti-settling agent: 0.5~1 parts to the qualified powder for surface coating treatment at a mixing machine speed of 200 rpm for 15 minutes, and then discharge and package.

[0029] Preferably, the four-section temperature control parameters of step S2 are: zone 1 80±5℃, zone 2 95±5℃, zone 3 105±5℃, zone 4 100±5℃.

[0030] Compared with the prior art, the present application has the following advantages:

[0031] The present application synchronously gives the coating super-high insulation and top anti-stone performance by single coating, completely cancels the secondary construction link; realizes zero VOC emission by using solid powder system; the special toughening resin and gradient curing process make the coating have rigid protection and toughness buffer, the actual measured anti-stone grade reaches 0 level and the insulation strength is more than 35 kV / mm, perfectly adapts to the strict requirements of electric vehicle high-voltage battery system on safety and environmental protection, and solves the technical defects in the traditional scheme. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0033] I. Materials

[0034] The adhesion enhancer of the present application is a gamma-glycidyl ether oxypropyl trimethoxysilane coupling agent, model KH-560, and other materials not specified are commercially available;

[0035] The present application provides a kind of anti-stone impact insulation powder coating of automobile battery tray, it is composed of the following weight parts raw materials: epoxy resin A: 15~20 parts, epoxy resin B: 35~40 parts, nitrile rubber modified epoxy resin: 5~10 parts, phenolic resin curing agent: 10~13 parts, quartz powder: 20~35 parts, leveling agent: 0.8~1.2 parts, pigment: 1~5 parts, curing accelerator: 0.3~0.8 parts, anti-sediment agent: 0.5~1 parts, adhesion enhancer: 0.3~0.6 parts, defoaming agent: 0.3~0.6 parts and power enhancer: 0.3~0.8 parts;

[0036] Epoxy resin A is epoxy resin with epoxy equivalent of 850-900; epoxy resin B is epoxy resin with epoxy equivalent of 1700-2000; nitrile rubber modified epoxy resin is modified epoxy resin with epoxy equivalent of 750-800; pigment is specifically rutile titanium dioxide; curing accelerator is specifically 2-methylimidazole; anti-sediment agent is specifically fumed silica; adhesion enhancer is specifically silane coupling agent; defoaming agent is specifically benzoin; power enhancer is specifically tetraalkylammonium salt.

[0037] It should be noted that the preparation steps of epoxy resin A are as follows:

[0038] A1. Bisphenol A and epichlorohydrin are put into a reaction kettle at a molar ratio of 1:1.38, dissolved by heating to 75 DEG C, and then 50% sodium hydroxide solution is added dropwise at a constant temperature of 80 DEG C for 120 minutes;

[0039] A2. Heat to 85 DEG C and keep for 180 minutes, then cool to 60 DEG C and wash with deionized water for 3 times until neutral;

[0040] A3. Dehydrate at 120 DEG C under a vacuum of-0.095 MPa for 90 minutes, filter and detect the epoxy equivalent to 850-900 g / eq to discharge.

[0041] It should be noted that the preparation steps of epoxy resin B are as follows:

[0042] B1. Bisphenol A and epichlorohydrin are added to a reaction kettle in a 1:1.15 molar ratio, and the temperature is raised to 90 DEG C under nitrogen protection, 40% sodium hydroxide solution is slowly added and the temperature is controlled at 95 DEG C for 150 minutes;

[0043] B2. The reaction is kept at 70 DEG C after the temperature is lowered, toluene solvent is extracted and washed with water until neutral;

[0044] B3. Toluene and water are removed at 130 DEG C under a vacuum of-0.098 MPa for 120 minutes, and the epoxy equivalent is detected to be 1700-2000 g / eq before cooling.

[0045] It should be noted that the preparation steps of the nitrile rubber modified epoxy resin are as follows:

[0046] C1. The carboxyl nitrile rubber and epoxy resin A are put into the reactor in a mass ratio of 1:2, the temperature is raised to 140 DEG C under nitrogen protection, and stirred for 60 minutes, 0.5% triphenylphosphine catalyst is added and the reaction is continued for 180 minutes;

[0047] C2. The epoxy equivalent is detected by sampling, the reaction is adjusted to the range of 750-800 g / eq, and the temperature is lowered to 80 DEG C, and then diluted with acetone to a solid content of 70%;

[0048] C3. The gel particles are removed by filtration, and the acetone is removed at 100 DEG C under a vacuum of-0.092 MPa before discharging.

[0049] II. Process:

[0050] The application also provides a preparation method of a stone impact resistant insulating powder coating for an automobile battery tray, comprising the following steps:

[0051] S1. Epoxy resin A: 15-20 parts, epoxy resin B: 35-40 parts, nitrile rubber modified epoxy resin: 5-10 parts are put into a premix kettle, the jacket temperature is 50±2 DEG C, low speed stirring is carried out at 300-400 rpm for 10 minutes, phenolic resin curing agent: 10-13 parts, leveling agent: 0.8-1.2 parts, curing accelerator: 0.3-0.8 parts, adhesion enhancer: 0.3-0.6 parts, defoaming agent: 0.3-0.6 parts, electricity increasing agent: 0.3-0.8 parts and 50% total amount of 20-35 parts of quartz powder are added, the speed is increased to 800-1000 rpm, and dispersed for 15 minutes, finally the remaining quartz powder, pigment: 1-5 parts, anti-settling agent: 0.5-1 parts are added, and high speed shearing is carried out at 1200-1500 rpm for 25 minutes, until the fineness of the mixture is ≤50 μm;

[0052] S2. The premix is fed into a co-rotating twin-screw extruder with a length-diameter ratio of 18:1, four-zone temperature control, screw speed 400-600 rpm, melt residence time ≤60 seconds, then the melt is extruded and pressed into 1.0-1.5 mm thick sheets by a double roller press with a roller temperature of 40±2℃ and a roller speed ratio of 1:1.2, and the sheets are broken into flaky particles with a particle size ≤5 mm by deep cooling crushing in liquid nitrogen at -50℃;

[0053] S3. First, the crushed material is fed into a vortex-type cryogenic mill with a grinding chamber temperature of -30℃, using liquid nitrogen as a coolant for continuous temperature control, rotor speed 4500-6000 rpm, and ground to a D50 particle size of 30-40 μm, then the coarse powder >80 μm and fine powder <10 μm are separated by a turbine airflow classifier with a classification wheel frequency of 35-50 Hz, and the particle size distribution Dv90 of the finished powder is ensured to be ≤65 μm; finally, the qualified powder is mixed with 0.5-1 part of fumed silica anti-settling agent at a mixer speed of 200 rpm for 15 minutes for surface coating treatment, and then discharged and packaged.

[0054] It should be noted that the four-zone temperature control parameters of step S2 are: Zone 1 80±5℃, Zone 2 95±5℃, Zone 3 105±5℃, Zone 4 100±5℃.

[0055] Example 1, in this example, the anti-stone impact insulation powder coating for automobile battery tray is prepared according to the following process:

[0056] S1. Raw material premixing and dispersion: Put epoxy resin A: 16 parts, epoxy resin B: 36 parts, nitrile rubber modified epoxy resin: 6 parts into a premixing kettle, jacket temperature 50℃, stir at 300 rpm for 10 minutes; add phenolic resin curing agent: 11 parts, leveling agent: 0.9 parts, 2-methylimidazole: 0.4 parts, silane coupling agent: 0.4 parts, benzoin: 0.45 parts, tetraalkylammonium salt: 0.5 parts and quartz powder: 12.5 parts, increase the speed to 800 rpm and disperse for 15 minutes; finally add the remaining quartz powder: 12.5 parts, rutile titanium dioxide: 2 parts, fumed silica: 0.7 parts, and disperse at a high speed of 1200 rpm for 25 minutes to a fineness of 48 μm;

[0057] S2. Melt extrusion and deep cooling crushing: The premix is fed into a twin-screw extruder with four-zone temperature: Zone 1 80℃, Zone 2 95℃, Zone 3 105℃, Zone 4 100℃, screw speed 400 rpm; the extrudate is pressed into 1.2 mm thick sheets by a double roller press (roller temperature 40℃); and deep cooling crushing in liquid nitrogen at -50℃ to a particle size of 4 mm;

[0058] S3. Freeze grinding and fractional coating: the broken material is put into a jet mill (-30℃), the rotor speed is 4500 rpm, and the grinding is performed to D50=35 μm; the coarse / fine powder is separated by a turbo classifier (frequency 35 Hz), and the control is Dv90=60 μm; the fumed silica is added: 0.7 parts, coating at 200 rpm for 15 minutes, and discharging;

[0059] In this example, epoxy resin A is 18 parts, epoxy resin B is 38 parts, nitrile rubber modified epoxy resin is 8 parts, phenolic resin curing agent is 12 parts, quartz powder is 30 parts, leveling agent is 1.0 part, rutile titanium dioxide is 3 parts, 2-methylimidazole is 0.6 part, fumed silica is 0.8 part, silane coupling agent is 0.5 part, and tetraalkylammonium salt is 0.6 part; the screw speed of S2 is increased to 500 rpm; other process parameters are the same as in example 1.

[0060] In this example, epoxy resin A is 20 parts, epoxy resin B is 40 parts, nitrile rubber modified epoxy resin is 5 parts, phenolic resin curing agent is 13 parts, quartz powder is 35 parts, leveling agent is 1.2 part, rutile titanium dioxide is 1 part, 2-methylimidazole is 0.3 part, fumed silica is 1.0 part, silane coupling agent is 0.3 part, and tetraalkylammonium salt is 0.3 part; the grinding temperature of S3 is adjusted to -28℃, and the rotor speed is 6000 rpm; other process parameters are the same as in example 1.

[0061] In this example, epoxy resin A is 15 parts, epoxy resin B is 35 parts, nitrile rubber modified epoxy resin is 10 parts, phenolic resin curing agent is 10 parts, quartz powder is 20 parts, leveling agent is 0.8 part, rutile titanium dioxide is 5 parts, 2-methylimidazole is 0.8 part, fumed silica is 0.5 part, silane coupling agent is 0.6 part, and tetraalkylammonium salt is 0.8 part; the deep cooling temperature of S2 liquid nitrogen is adjusted to -48℃; other process parameters are the same as in example 1.

[0062] The values of each component in examples 1 to 4 are recorded in table 1:

[0063] Table 1 Values of each component in examples 1 to 4

[0064] Raw materials Example 1 Example 2 Example 3 Example 4 Epoxy resin A (EEW 850-900) 16 18 20 15 Epoxy resin B (EEW 1700-2000) 36 38 40 35 Nitrile rubber modified epoxy resin 6 8 5 10 Phenolic resin curing agent 11 12 13 10 Quartz powder 25 30 35 20 Leveling agent 0.9 1.0 1.2 0.8 Rutile titanium dioxide 2 3 1 5 2-methylimidazole 0.4 0.6 0.3 0.8 Fumed silica 0.7 0.8 1.0 0.5 Silane coupling agent (KH-560) 0.4 0.5 0.3 0.6 Tetraalkylammonium salt 0.5 0.6 0.3 0.8

[0065] In this comparative example, epoxy resin A is 14 parts, and other components and processes are the same as in example 1.

[0066] In this comparative example, epoxy resin B is 41 parts, and other components and processes are the same as in example 1.

[0067] Comparative Example 3, In this comparative example, the butyronitrile rubber modified epoxy resin is 4 parts, the phenolic resin curing agent is 9 parts, and the other components and processes are the same as in Example 1.

[0068] The component values in Comparative Examples 1 to 4 are recorded in Table 2:

[0069] Table 2 Component values in Comparative Examples 1 to 4

[0070] Raw materials Comparative Example 1 Comparative Example 2 Comparative Example 3 Epoxy resin A (EEW 850-900) 14 16 16 Epoxy resin B (EEW 1700-2000) 36 41 36 Nitrile rubber modified epoxy resin 6 6 4 Phenolic resin curing agent 11 11 9 Quartz powder 25 25 25 Leveling agent 0.9 0.9 0.9 Rutile titanium dioxide 2 2 2 2-methylimidazole 0.4 0.4 0.4 Fumed silica 0.7 0.7 0.7 Silane coupling agent (KH-560) 0.4 0.4 0.4 Tetraalkylammonium salt 0.5 0.5 0.5

[0071] III. Performance test:

[0072] The components of the examples and comparative examples are prepared according to the following process for performance testing sample preparation, the sample preparation process for performance testing includes the following steps:

[0073] T1. Static spray plate: using a static spray gun (output voltage 80~90kV, powder gas pressure 0.5~0.7MPa) to uniformly spray the powder to the pretreated (degreasing, phosphating) steel plate (size 150×70×1mm), film thickness control 200±20μm;

[0074] T2. Gradient curing molding: first, the coating is apparent to flow in the infrared preheating section (80℃±2℃, time 3 minutes); then transfer to the curing oven to perform gradient curing:

[0075] First stage: 100℃ / 10min (eliminate internal stress);

[0076] Second stage: 180℃±2℃ / 15min (complete crosslinking);

[0077] Third stage: forced air cooling to below 50℃, obtain test sample plate;

[0078] The performance test is carried out according to the following standard, see Table 3:

[0079] Table 3 Performance test standard table

[0080] Item Requirement Standard Dielectric strength ≥30 KV / mm GB / T 1408.2 Insulating materials - Determination of electrical strength - Part 2: Additional requirements for tests with DC voltage Shear strength ≥7 MPa GB / T 7124 Determination of tensile shear strength of adhesives (rigid material to rigid material) Tensile strength ≥7 MPa GB / T 5210 Paints and varnishes - Pull-over test for adhesion Impact resistance at 25℃ 50 kg·cm, 4 times magnifying glass, no coating cracking, peeling, paint exposure, cracking and other defects, and after testing, it meets the insulation withstand voltage requirements GB / T 1732 Impact resistance of paint films Stone chip resistance 0-1 level, no breakdown of the substrate GB / T 9286-2015‌

[0081] The performance parameters of the samples of Examples 1-4 are recorded in Table 4:

[0082] Table 4 Performance parameters of samples of Examples 1-4

[0083] Test item Example 1 Example 2 Example 3 Example 4 Insulation withstand voltage (kV / mm) 36 35 34 33 Volume resistivity (Ω·cm) 3.2 x 10 5 ]] 2.8 x 10 5 ]] 1.9 x 10 5 ]] 1.5 x 10 5 <!-- 6 -->]]> Stone chip resistance level 0 level 0 level 1 level 1 level Impact resistance at 25℃ (kg·cm) 55 52 50 51 Shear strength (MPa) 8.2 7.8 7.1 7.0

[0084] The performance parameters of the samples of Comparative Examples 1-3 are recorded in Table 5:

[0085] Table 5 Performance parameters of samples of Comparative Examples 1-3

[0086] Test item Comparative Example 1 Comparative Example 2 Comparative Example 3 Insulation withstand voltage (kV / mm) 28 26 25 Volume resistivity (Ω·cm) 8.7×10¹³ 5.2×10¹³ 3.8×10¹³ Stone chip resistance level 3 level 4 level 5 level Impact resistance at 25℃ (kg·cm) 42 38 35 Shear strength (MPa) 5.3 4.7 4.1

[0087] IV. Analysis Conclusion:

[0088] The epoxy resin B in the example is greater than or equal to 35 parts to provide a long molecular chain dense structure, while the comparative example 1 has insufficient epoxy resin A (14 parts), and the insulation withstand voltage is reduced to 28 kV / mm (< 30 kV / mm), and the comparative example 2 is only 26 kV / mm; the butyl nitrile rubber modified epoxy resin 5-10 parts forms an island structure, while the comparative example 3 has insufficient toughening resin (4 parts), and the stone impact resistance grade is deteriorated to level 5 (> level 1); the phenolic curing agent 10-13 parts avoids undercuring, while the comparative example 3 has a shear of 4.1 MPa; in summary, it can be known that the component interval setting of the stone impact resistance insulation powder coating of the automobile battery tray of the application is reasonable;

[0089] In addition, the high toughness resin ratio (A:B:toughening = 16:36:6) in the example 1 makes the stone impact resistance reach level 0; the medium quartz powder (25 parts) takes into account the insulation (36 kV / mm) and the adhesion (8.2 MPa); the precise accelerator (0.4 parts of 2-methylimidazole) ensures complete curing without bubbles at 180°C, and therefore, the example 1 is the best embodiment of the application.

[0090] In summary, the application simultaneously gives the coating super-high insulation and top-level stone impact resistance performance through single coating, completely cancels the secondary construction link; realizes zero VOC emission by using a solid powder system; the special toughening resin and the gradient curing process make the coating have rigid protection and toughness buffer, and the actually measured stone impact resistance grade reaches level 0 and the insulation strength is greater than 35 kV / mm, which perfectly adapts to the strict requirements of the high-voltage battery system of the electric vehicle on safety and environmental protection, and solves the technical defects in the traditional scheme.

[0091] In the description of the present specification, the description referring to the terms "one embodiment", "example", "specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0092] The preferred embodiments of the application disclosed above are only used to help explain the application. The preferred embodiments do not describe all the details and limit the application to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of the present specification. The present specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the application, so that those skilled in the art can well understand and utilize the application. The application is limited by the claims and their entire scope and equivalents.

Claims

1. A stone-impact-resistant insulating powder coating for an automotive battery tray, characterized in that, It is composed of the following raw materials in parts by weight: epoxy resin A: 15-20 parts, epoxy resin B: 35-40 parts, nitrile rubber modified epoxy resin: 5-10 parts, phenolic resin curing agent: 10-13 parts, quartz powder: 20-35 parts, leveling agent: 0.8-1.2 parts, pigment: 1-5 parts, curing accelerator: 0.3-0.8 parts, anti-settling agent: 0.5-1 part, adhesion promoter: 0.3-0.6 parts, defoamer: 0.3-0.6 parts, and electrostatic agent: 0.3-0.8 parts; Epoxy resin A is an epoxy resin with an epoxy equivalent of 850-900; epoxy resin B is an epoxy resin with an epoxy equivalent of 1700-2000; the nitrile rubber modified epoxy resin is a modified epoxy resin with an epoxy equivalent of 750-800; the pigment is specifically rutile titanium dioxide; the curing accelerator is specifically 2-methylimidazole; the anti-settling agent is specifically fumed silica; the adhesion promoter is specifically a silane coupling agent; the defoamer is specifically benzoin; and the electrophoretic agent is specifically a tetraalkylammonium salt. The preparation steps of the nitrile rubber modified epoxy resin are as follows: C1. Carboxylated butadiene-acrylonitrile rubber and epoxy resin A are added to the reactor at a mass ratio of 1:

2. Under nitrogen protection, the temperature is raised to 140°C and stirred for 60 minutes. Then, 0.5% triphenylphosphine catalyst is added and the reaction is continued for 180 minutes. C2. Take samples to test the epoxy equivalent, adjust the reaction to the range of 750-800 g / eq, cool to 80℃ and add acetone to dilute to a solid content of 70%; C3. Filter to remove gel particles, and remove acetone under vacuum of 100℃ and -0.092MPa before discharging.

2. The stone-impact-resistant insulating powder coating for an automotive battery tray according to claim 1, characterized in that, The preparation steps of the epoxy resin A are as follows: A1. Bisphenol A and epichlorohydrin were added to the reaction vessel at a molar ratio of 1:1.38, and the mixture was heated to 75°C to dissolve. Then, 50% sodium hydroxide solution was added dropwise at a constant temperature of 80°C for 120 minutes. A2. Heat to 85℃ and maintain the temperature for 180 minutes, then cool to 60℃ and wash three times with deionized water until neutral. A3. Dehydrate at 120℃ and -0.095MPa vacuum for 90 minutes, filter, and test the epoxy equivalent to 850-900g / eq before discharge.

3. The stone-impact-resistant insulating powder coating for an automotive battery tray according to claim 2, characterized in that, The preparation steps of the epoxy resin B are as follows: B1. Bisphenol A and epichlorohydrin were added to the reactor at a molar ratio of 1:1.

15. The temperature was raised to 90°C under nitrogen protection, and 40% sodium hydroxide solution was slowly added dropwise while the temperature was controlled at 95°C for 150 minutes. B2. Incubate the reaction for 240 minutes while maintaining pH > 12, then cool to 70°C, add toluene solvent for extraction, and wash with water until neutral. B3. Remove toluene and moisture at 130℃ and -0.098MPa vacuum for 120 minutes, and then cool after the epoxy equivalent is measured to be 1700-2000g / eq.

4. The stone-impact-resistant insulating powder coating for an automotive battery tray according to claim 1, characterized in that, It is composed of the following raw materials in parts by weight: epoxy resin A: 16 parts; epoxy resin B: 36 parts; nitrile rubber modified epoxy resin: 6 parts; phenolic resin curing agent: 11 parts; quartz powder: 25 parts; leveling agent: 0.9 parts; pigment: 2 parts; curing accelerator: 0.4 parts; anti-settling agent: 0.7 parts; adhesion promoter: 0.4 parts; defoamer: 0.45 parts; electrostatic agent: 0.5 parts.

5. The stone-impact-resistant insulating powder coating for an automotive battery tray according to claim 1, characterized in that, It is composed of the following raw materials in parts by weight: epoxy resin A: 18 parts; epoxy resin B: 38 parts; nitrile rubber modified epoxy resin: 8 parts; phenolic resin curing agent: 12 parts; quartz powder: 30 parts; leveling agent: 1.0 part; pigment: 3 parts; curing accelerator: 0.6 parts; anti-settling agent: 0.8 parts; adhesion promoter: 0.5 parts; defoamer: 0.45 parts; electrostatic agent: 0.6 parts.

6. The stone-impact-resistant insulating powder coating for an automotive battery tray according to claim 1, characterized in that, It is composed of the following raw materials in parts by weight: epoxy resin A: 20 parts; epoxy resin B: 40 parts; nitrile rubber modified epoxy resin: 5 parts; phenolic resin curing agent: 13 parts; quartz powder: 35 parts; leveling agent: 1.2 parts; pigment: 1 part; curing accelerator: 0.3 parts; anti-settling agent: 1.0 part; adhesion promoter: 0.3 parts; defoamer: 0.45 parts; electrostatic agent: 0.3 parts.

7. The stone-impact-resistant insulating powder coating for an automotive battery tray according to claim 1, characterized in that, It is composed of the following raw materials in parts by weight: epoxy resin A: 15 parts; epoxy resin B: 35 parts; nitrile rubber modified epoxy resin: 10 parts; phenolic resin curing agent: 10 parts; quartz powder: 20 parts; leveling agent: 0.8 parts; pigment: 5 parts; curing accelerator: 0.8 parts; anti-settling agent: 0.5 parts; adhesion promoter: 0.6 parts; defoamer: 0.45 parts; electrostatic agent: 0.8 parts.

8. A method for preparing an anti-stone-impact insulating powder coating for an automotive battery tray according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Add 15-20 parts of epoxy resin A, 35-40 parts of epoxy resin B, and 5-10 parts of nitrile rubber modified epoxy resin to a mixing pot. Add 10-13 parts of phenolic resin curing agent, 0.8-1.2 parts of leveling agent, 0.3-0.8 parts of curing accelerator, 0.3-0.6 parts of adhesion promoter, 0.3-0.6 parts of defoamer, 0.3-0.8 parts of electrostatic agent, and 20-35 parts by weight of quartz powder and 1-5 parts of pigment. Stir at a low speed of 300-400 rpm for 10 minutes, then increase the speed to 800-1000 rpm and disperse for 3 minutes. S2. The premixed material is fed into a co-rotating twin-screw extruder with a length-to-diameter ratio of 18:

1. The temperature is controlled in four stages, the screw speed is 400~600rpm, and the melt residence time is ≤60 seconds. The extruded melt is then pressed into 1.0~1.5mm thick sheets by a twin-roller tablet press with a roller temperature of 15±2℃ and a roller speed ratio of 1:1.

2. The sheets are then crushed into flaky particles with a particle size of ≤5mm by a coarse crusher. S3. First, put the crushed material into an ACM air classifier mill with a grinding chamber temperature of 5℃, and add fumed silica loosening agent. The main mill speed is 3000~3500rpm, the auxiliary mill speed is 2000~2500rpm, and the grinding is carried out until the D50 particle size is 40~50μm, D10>12um, and D90<95um. After completion, the material is discharged and packaged. The four temperature control parameters in step S2 are: Zone 1 30±5℃, Zone 2 75±5℃, Zone 3 105±5℃, and Zone 4 100±5℃.