A fireproof paint for a power battery box shell, a preparation method and application thereof

Abstract

This invention provides a fire-retardant coating for power battery box housings, its preparation method, and its application. The fire-retardant coating comprises component A and component B. Component A includes MPD-type polyester polyol, ammonium polyphosphate, melamine, aluminum hydroxide, zinc borate, expanded graphite, and refractory filler. Component B includes a curing agent. Through the coordinated combination of the above components, the resulting fire-retardant coating possesses good sprayability, environmental friendliness, low-temperature flexibility, and fire resistance. When used as a fire-retardant coating on the surface of power battery box housings for new energy vehicles, it can ensure the long-term safety of new energy vehicle batteries.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a fire-retardant coating for the housing of a power battery box, its preparation method, and its application. Background Technology

[0002] Whether in production, storage, transportation, operation, or recycling, a high-quality fire protection solution is crucial for the safe use of batteries.

[0003] Traditional fire-retardant materials (mica, heat-resistant blankets, etc.) can effectively isolate heat diffusion and delay battery heat diffusion time, but they have poor heat dissipation, design and construction limitations, and increase vehicle weight, which is not conducive to the development of lightweight vehicles. Therefore, based on the market demand for the safety and lightweighting of power battery packs, new fire-retardant coatings with excellent flame retardancy will become the preferred material for the protection of new energy vehicle batteries.

[0004] The new fire-retardant coating is mainly a two-component epoxy resin type, which is mainly used on the car cover plate. It has excellent fire resistance, heat insulation, weather resistance and salt spray resistance. The automated coating process meets the requirements of large-scale automated production of battery packs, and greatly releases and improves the production capacity of power battery pack production lines. However, existing commercially available fire-retardant coatings have a number of problems, such as: (1) the price is too high, the viscosity is large and the particles are coarse (containing fibers), resulting in poor sprayability and difficulty in construction; (2) a large amount of halogenated flame retardants or organic solvents are added, which are toxic and harmful; (3) the low-temperature flexibility is poor and it is easy to crack; (4) the fire resistance time is short and cannot provide sufficient escape time.

[0005] CN105238222A discloses an environmentally friendly intumescent fire-retardant coating and its preparation method, which consists of two components, A and B. Component A uses epoxy resin as the main film-forming agent and adds an active diluent, catalyst, charring agent, foaming agent, flame retardant, additives, and solvent. Component B consists of a curing agent, curing accelerator, pigments and fillers, additives, refractory fibers, and solvent. However, the fire-retardant coating provided by this invention adds refractory fibers during the preparation process, which makes the production process complex. Moreover, due to the coarse particles of the refractory fibers, the fire-retardant coating has poor sprayability. At the same time, the addition of organic solvents is toxic and harmful, making it unsuitable for large-scale industrial use.

[0006] CN110903738A discloses a flexible solvent-free epoxy fire-retardant coating and its preparation method, comprising component A and component B; wherein, component A includes epoxy resin and modified resin, flame-retardant filler and other additives, and component B includes curing agent, curing accelerator and other filler; this invention improves the toughness of the fire-retardant coating by adding epoxy-modified polysulfide polymer, so that the obtained fire-retardant coating can maintain a certain high and low temperature resistance between -20 and 60℃, but its flexibility is still weaker than that of polyurethane fire-retardant coatings and needs to be further improved.

[0007] CN114644880A discloses a two-component polyurethane fire-retardant coating, its preparation method, and its application. Component A includes 30-50% polyether polyol, 2-10% nonlinear small molecule chain extender, 0.5-2% polyether amine, 10-20% expanded graphite, 5-15% ammonium polyphosphate, 5-15% melamine, 10-25% aluminum hydroxide, 0.2-2% water absorbent, 0.2-2% silane coupling agent, and 0.01-1% catalyst. Component B is a polyisocyanate component. The fire-retardant coating provided by this invention mainly improves the product's anti-sagging properties and flexibility, but does not describe its fire-retardant performance.

[0008] Therefore, developing a fire-retardant coating with excellent fire-resistant properties for power battery box housings remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] In view of the shortcomings of the prior art, the purpose of this invention is to provide a fire-retardant coating for power battery box housing, its preparation method and application. The fire-retardant coating, through the coordinated combination of specific components, has good sprayability, environmental friendliness, low-temperature flexibility and fire resistance, and can be used for power battery box housing of new energy vehicles, which can ensure the long-term safety of new energy vehicle batteries.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a fire-retardant coating for a power battery box housing, the fire-retardant coating comprising component A and component B;

[0012] Component A includes MPD-type polyester polyol, ammonium polyphosphate, melamine, aluminum hydroxide, zinc borate, expanded graphite, and refractory filler.

[0013] Component B includes a curing agent.

[0014] The fire-retardant coating provided by this invention is a two-component polyurethane fire-retardant coating. It overcomes the defects of traditional epoxy fire-retardant coatings, which are prone to cracking and peeling when thickly coated. It not only has excellent fire-retardant performance and sprayability, but also excellent high and low temperature resistance. It can maintain good fire resistance in the range of -40 to 80℃. At the same time, it also has excellent environmental protection and low-temperature flexibility.

[0015] Specifically, firstly, component A of the fire-retardant coating provided by this invention uses hydrolysis-resistant MPD-type polyester polyol, which helps improve the water resistance of the fire-retardant coating; secondly, ammonium polyphosphate and melamine are used synergistically to exert flame-retardant expansion effects; thirdly, aluminum hydroxide and zinc borate are used as inorganic flame-retardant fillers, which can reduce the temperature of the backing plate and improve safety performance after combustion by dehydration; finally, the strength of the char layer is improved by adding refractory fillers, and the fire resistance time of the coating is effectively extended by using expanded graphite.

[0016] In summary, the synergistic effect of the above components results in a fire-retardant coating with good sprayability, low-temperature flexibility, and fire resistance. Furthermore, the raw materials used do not contain toxic or harmful halogenated flame retardants or organic solvents, thus making it environmentally friendly. When used in the casing of power battery boxes for new energy vehicles, it can ensure the long-term safety of new energy vehicle batteries.

[0017] It should be noted that the "MPD type polyester polyol" mentioned in this invention refers to 3-methyl-1,5-pentanediol type polyester polyol.

[0018] Preferably, component A comprises the following components in parts by weight:

[0019]

[0020]

[0021] The amount of MPD-type polyester polyol used can be 31 parts by weight, 32 parts by weight, 33 parts by weight, 34 parts by weight, 35 parts by weight, 36 parts by weight, 37 parts by weight, 38 parts by weight, or 39 parts by weight, etc.; the amount of ammonium polyphosphate used can be 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, or 19 parts by weight, etc.; the amount of melamine used can be 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, or 10 parts by weight, etc.; the amount of aluminum hydroxide used can be... The amounts of zinc borate can be 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, or 10 parts by weight, etc.; the amounts of expanded graphite can be 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, or 1 part by weight, etc.; the amounts of refractory filler can be 17 parts by weight, 19 parts by weight, 21 parts by weight, 23 parts by weight, 25 parts by weight, 27 parts by weight, 29 parts by weight, 31 parts by weight, or 33 parts by weight, etc.

[0022] Preferably, the MPD-type polyester polyol comprises a combination of 2-functionality MPD-type polyester polyol and 3-functionality MPD-type polyester polyol.

[0023] As a preferred technical solution of the present invention, the advantage of selecting a combination of 2-functionality MPD-type polyester polyol and 3-functionality MPD-type polyester polyol is that it can balance the crosslinking strength and curing rate of the fire-retardant coating, so that it can better meet the requirements of the spraying process. If only 2-functionality MPD-type polyester polyol is used, the crosslinking density of the fire-retardant coating will be too low, the coating will be too soft, and the fire resistance will be poor. If only 3-functionality MPD-type polyester polyol is used, the coating of the fire-retardant coating will gel after mixing with the curing agent, making it impossible to apply.

[0024] Preferably, the number average molecular weight of the dual-functionality MPD type polyester polyol is 1000-3000, such as 1200, 1400, 1600, 1800, 2000, 2200, 2400, 2600 or 2800.

[0025] Preferably, the dual-functionality MPD type polyester polyol includes dual-functionality MPD type polyester polyol A and dual-functionality MPD type polyester polyol B, wherein the number-average molecular weights of dual-functionality MPD type polyester polyol A and dual-functionality MPD type polyester polyol B are different.

[0026] As a preferred technical solution of the present invention, the advantage of selecting two functional MPD type polyester polyols A and B with different number average molecular weights for combination is that it helps to further improve the strength of the fire-retardant coating while maintaining a suitable viscosity of the system, which facilitates the subsequent addition of refractory fillers.

[0027] Preferably, the number average molecular weight of the trifunctional MPD type polyester polyol is 1000-2000, such as 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800 or 1900.

[0028] Preferably, the mass ratio of the 2-functionality MPD type polyester polyol A, the 2-functionality MPD type polyester polyol B, and the 3-functionality MPD type polyester polyol is 1:(1-3):(1-2).

[0029] The mass ratio of the difunctional MPD-type polyester polyol A to the difunctional MPD-type polyester polyol B can be 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2, 1:2.2, 1:2.4, 1:2.6, or 1:2.8, etc.; the mass ratio of the difunctional MPD-type polyester polyol A to the trifunctional MPD-type polyester polyol can be 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, or 1:1.9, etc.

[0030] Preferably, the degree of polymerization of the ammonium polyphosphate is >1000, such as 1100, 1200, 1300, 1400, 1500 or 1600.

[0031] Preferably, the water solubility of the ammonium polyphosphate is <0.1 g / 100 cm³. 3 For example, 0.08g / 100cm 3 0.06g / 100cm 3 0.04g / 100cm 3 Or 0.02g / 100cm 3 The test temperature for water solubility was 25℃.

[0032] Preferably, the particle size of the melamine, aluminum hydroxide, zinc borate and filler is all <50μm, for example 45μm, 40μm, 35μm, 30μm, 25μm or 20μm.

[0033] Preferably, the refractory filler comprises a combination of mica powder, kaolin, and wollastonite. Selecting flake-shaped refractory fillers mica powder and kaolin and needle-shaped refractory fillers wollastonite in combination further improves the strength of the carbon layer.

[0034] Preferably, the mica powder content in component A is 5 to 15 parts by weight, such as 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, or 14 parts by weight.

[0035] Preferably, the content of kaolin in component A is 5 to 15 parts by weight, such as 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, or 14 parts by weight.

[0036] Preferably, the content of wollastonite in component A is 5 to 10 parts by weight, such as 6 parts by weight, 7 parts by weight, 8 parts by weight, or 9 parts by weight.

[0037] Preferably, the expanded graphite has a particle size of 300-400 mesh, such as 310 mesh, 320 mesh, 330 mesh, 340 mesh, 350 mesh, 360 mesh, 370 mesh, 380 mesh or 390 mesh.

[0038] Preferably, the expansion ratio of the expanded graphite is 200 to 400 times, such as 220 times, 240 times, 260 times, 280 times, 300 times, 320 times, 340 times, 360 times or 380 times.

[0039] Preferably, component A further comprises 1 to 3 parts by weight (e.g., 1.2 parts by weight, 1.4 parts by weight, 1.6 parts by weight, 1.8 parts by weight, 2 parts by weight, 2.2 parts by weight, 2.4 parts by weight, 2.6 parts by weight, or 2.8 parts by weight, etc.) of a dehydrating agent.

[0040] Preferably, the dehydrating agent comprises molecular sieves and / or calcium oxide.

[0041] Preferably, the curing agent includes polymeric diphenylmethane diisocyanate (polymeric MDI), and more preferably PM200 or Huntsman 2496.

[0042] Preferably, the functionality of the polymeric diphenylmethane diisocyanate is 2.2 to 2.7, such as 2.3, 2.4, 2.5 or 2.6.

[0043] Preferably, the mass ratio of component A to component B is (6-8):1, such as 6.2:1, 6.4:1, 6.6:1, 6.8:1, 7:1, 7.2:1, 7.4:1, 7.6:1 or 7.8:1, etc.

[0044] In a second aspect, the present invention provides a method for preparing a fire-retardant coating for a power battery box housing as described in the first aspect. The preparation method includes: mixing MPD type polyester polyol evenly, adding ammonium polyphosphate, melamine, aluminum hydroxide, zinc borate and refractory filler and mixing, then adding an optional dehydrating agent and mixing, and finally adding expanded graphite and mixing to obtain component A.

[0045] Mix the curing agent evenly to obtain component B.

[0046] Preferably, the preparation method specifically includes: stirring the MPD-type polyester polyol in a high-speed disperser at a speed of 300-500 rpm (e.g., 320 rpm, 340 rpm, or 360 rpm) for 3-5 minutes (e.g., 3.5 minutes, 4 minutes, or 4.5 minutes); adding ammonium polyphosphate, melamine, aluminum hydroxide, zinc borate, and filler; and stirring at a speed of 500-800 rpm (e.g., 550 rpm, 600 rpm, 650 rpm, 700 rpm, or 750 rpm). Stir for 30–60 min (e.g., 35 min, 40 min, 45 min, 50 min, or 55 min) under the conditions of (etc.), then add an optional dehydrating agent and mix. Finally, add expanded graphite and mix for 5–10 min (e.g., 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, or 9 min) at a speed of 300–500 rpm (e.g., 350 rpm, 400 rpm, or 450 rpm) to obtain component A.

[0047] Mix the curing agent evenly to obtain component B.

[0048] Thirdly, the present invention provides a method for using a fire-retardant coating for a power battery box housing as described in the first aspect, the method comprising: mixing component A and component B of the fire-retardant coating, applying it to a substrate, and curing it to complete the use of the fire-retardant coating.

[0049] Preferably, the substrate comprises any one of an electrophoresis plate, an aluminum plate, or a steel plate.

[0050] Preferably, the thickness of the cured coating is 600–1000 μm, such as 700 μm, 800 μm, 900 μm, or 1000 μm.

[0051] Fourthly, the present invention provides an application of the fire-retardant coating as described in the first aspect, the application including its use in the housing of a power battery box for new energy vehicles.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] (1) The fireproof coating for power battery box housing provided by the present invention includes component A and component B. Component A includes MPD type polyester polyol, ammonium polyphosphate, melamine, aluminum hydroxide, zinc borate, expanded graphite and refractory filler. Component B includes curing agent. Through the coordinated combination of the above components, the obtained fireproof coating has good sprayability, environmental protection, low-temperature flexibility and fireproof performance. When used as a fireproof coating on the surface of power battery box housing of new energy vehicles, it can ensure the long-term safety of new energy vehicle batteries.

[0054] (2) Specifically, the fireproof coating provided by the present invention has a back temperature ≤300℃ and a fire resistance time of 30min at a temperature of 1300~1400℃. After 1000h of double 85℃ test and high and low temperature cycle test, the back temperature is still ≤300℃ and the fire resistance time is 30min. Detailed Implementation

[0055] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0056] Unless otherwise specified, the raw materials involved in the specific embodiments of this invention are all conventional materials in the art and can be purchased commercially.

[0057] Example 1

[0058] A fire-retardant coating for the housing of a power battery box, comprising component A and component B in a mass ratio of 6:1;

[0059] The preparation method of component A includes: placing 8.5g of MPD-type polyester polyol A (functionality 2, number-average molecular weight 1000, purchased from Kuraray, Japan, P1010), 17g of MPD-type polyester polyol B (functionality 2, number-average molecular weight 3000, purchased from Kuraray, Japan, P3010), and 12.5g of MPD-type polyester polyol C (functionality 3, number-average molecular weight 1000, purchased from Kuraray, Japan, F1010) into a 500mL metal container, stirring for 5min in a high-speed disperser at 300rpm, and then adding 20g of ammonium polyphosphate (degree of polymerization 1500, water solubility 0.05g / 100cm³). 3 Add water, 5g melamine (average particle size 10μm), 5g aluminum hydroxide (average particle size 10μm), 5g zinc borate (average particle size 10μm), 15g mica powder (average particle size 15μm), 5g kaolin (average particle size 20μm), and 5g wollastonite (average particle size 10μm) to the above metal container. Stir in a high-speed disperser at 500rpm for 40min. Then add 1g calcium oxide and stir evenly. Finally, add 1g expanded graphite (average particle size 325 mesh, expansion ratio 300 times) and stir in a high-speed disperser at 300rpm for 10min. After even dispersion, set aside for later use.

[0060] Component B is polymeric MDI, specifically PM200.

[0061] Example 2

[0062] A fire-retardant coating for the housing of a power battery box, comprising component A and component B in a mass ratio of 7:1;

[0063] The preparation method of component A includes: placing 7.7g of MPD-type polyester polyol A (functionality 2, number-average molecular weight 1000, purchased from Kuraray, Japan, P1010), 15.4g of MPD-type polyester polyol B (functionality 2, number-average molecular weight 3000, purchased from Kuraray, Japan, P3010), and 11.7g of MPD-type polyester polyol C (functionality 3, number-average molecular weight 1000, purchased from Kuraray, Japan, F1010) into a 500mL metal container, stirring in a high-speed disperser at 400rpm for 4min, and then adding 15g of ammonium polyphosphate (degree of polymerization 1500, water solubility 0.05g / 100cm³). 3Add water, 7.5g melamine (average particle size 10μm), 7.5g aluminum hydroxide (average particle size 10μm), 7.5g zinc borate (average particle size 10μm), 10g mica powder (average particle size 10μm), 7.5g kaolin (average particle size 10μm), and 7.5g wollastonite (average particle size 10μm) to the above-mentioned metal container, stir in a high-speed disperser at 650rpm for 45min, then add 2g calcium oxide and stir evenly, finally add 0.7g expanded graphite (average particle size 325 mesh, expansion ratio 350 times), stir in a high-speed disperser at 400rpm for 7.5min, disperse evenly and set aside for later use;

[0064] Component B is polymeric MDI, specifically Huntsman 2496.

[0065] Example 3

[0066] A fire-retardant coating for the housing of a power battery box, comprising component A and component B in a mass ratio of 8:1;

[0067] The preparation method of component A includes: placing 6.9g of MPD-type polyester polyol A (functionality 2, number-average molecular weight 1000, purchased from Kuraray, Japan, P1010), 13.8g of MPD-type polyester polyol B (functionality 2, number-average molecular weight 3000, purchased from Kuraray, Japan, P3010), and 10.8g of MPD-type polyester polyol C (functionality 3, number-average molecular weight 1000, purchased from Kuraray, Japan, F1010) into a 500mL metal container, stirring for 3 minutes in a high-speed disperser at 500rpm, and then adding 10g of ammonium polyphosphate (degree of polymerization 1500, water solubility 0.05g / 100cm³). 3 Add water, 10g melamine (average particle size 10μm), 10g aluminum hydroxide (average particle size 10μm), 10g zinc borate (average particle size 10μm), 5g mica powder (average particle size 10μm), 10g kaolin (average particle size 10μm), and 10g wollastonite (average particle size 10μm) to the above metal container. Stir in a high-speed disperser at 800 rpm for 30 minutes. Then add 3g calcium oxide and stir evenly. Finally, add 0.5g expanded graphite (average particle size 325 mesh, expansion ratio 400 times) and stir in a high-speed disperser at 500 rpm for 5 minutes. After even dispersion, set aside for later use.

[0068] Component B is polymeric MDI, specifically PM200.

[0069] Example 4

[0070] A fire-retardant coating for the housing of a power battery box differs from Example 1 only in that MPD-type polyester polyol A is not added, and the amount of MPD-type polyester polyol B added is 25.5g. Other components, dosages, and preparation methods are the same as in Example 1.

[0071] Example 5

[0072] A fire-retardant coating for the housing of a power battery box differs from Example 1 only in that MPD-type polyester polyol B is not added, and the amount of MPD-type polyester polyol A added is 25.5g. The other components, dosages and preparation methods are the same as in Example 1.

[0073] Example 6

[0074] A fire-retardant coating for the housing of a power battery box differs from Example 1 only in that MPD-type polyester polyol C is not added, the amount of MPD-type polyester polyol A added is 12.5g, and the amount of MPD-type polyester polyol B added is 25.5g. Other components, dosages, and preparation methods are the same as in Example 1.

[0075] Example 7

[0076] A fire-retardant coating for the housing of a power battery box differs from Example 1 only in that MPD-type polyester polyol A and MPD-type polyester polyol B are not added, and the amount of MPD-type polyester polyol C added is 38g. Other components, dosages and preparation methods are the same as in Example 1.

[0077] Example 8

[0078] A fire-retardant coating for the housing of a power battery box differs from Example 1 only in that mica powder is not added, and the amount of kaolin added is 20g. The other components, dosages, and preparation methods are the same as in Example 1.

[0079] Example 9

[0080] A fire-retardant coating for the casing of a power battery box differs from Example 1 only in that kaolin is not added, and the amount of mica powder added is 20g. The other components, dosages, and preparation methods are the same as in Example 1.

[0081] Comparative Example 1

[0082] A fire-retardant coating for the housing of a power battery box differs from Example 1 only in that 38g of polymeric polyol (functionality 2, number average molecular weight 1000, purchased from Shanghai Huide, HP-7710) is used to replace MPD type polyester polyol A, MPD type polyester polyol B and MPD type polyester polyol C. Other components, dosages and preparation methods are the same as in Example 1.

[0083] Comparative Example 2

[0084] A fire-retardant coating for the housing of a power battery box is different from that in Example 1 only in that ammonium polyphosphate is not added, while the other components, dosages and preparation methods are the same as in Example 1.

[0085] Comparative Example 3

[0086] A fire-retardant coating for the housing of a power battery box is different from that in Example 1 only in that melamine is not added, while the other components, dosages and preparation methods are the same as in Example 1.

[0087] Comparative Example 4

[0088] A fire-retardant coating for the housing of a power battery box differs from Example 1 only in that aluminum hydroxide is not added, and the amount of zinc borate added is 10g. The other components, dosages, and preparation methods are the same as in Example 1.

[0089] Comparative Example 5

[0090] A fire-retardant coating for the housing of a power battery box differs from Example 1 only in that zinc borate is not added, and the amount of aluminum hydroxide added is 10g. The other components, dosages, and preparation methods are the same as in Example 1.

[0091] Comparative Example 6

[0092] A fire-retardant coating for the housing of a power battery box differs from Example 1 only in that it does not contain mica powder, kaolin, wollastonite and expanded graphite, while the other components, dosages and preparation methods are the same as in Example 1.

[0093] Comparative Example 7

[0094] A fire-retardant coating for the housing of a power battery box is different from that of Example 1 only in that expanded graphite is not added, while the other components, dosages and preparation methods are the same as those of Example 1.

[0095] Performance testing:

[0096] Components A and B of the fire-retardant coatings provided in the examples and comparative examples were mixed, coated on an electrophoretic plate, and cured at 80°C for 1 hour to obtain a back panel for the following tests.

[0097] (1) High temperature fire resistance: The fireproof sample was tested with a butane spray gun with a flame temperature of 1300-1400℃ for 30 minutes, and the temperature of the back panel was measured.

[0098] (2) High and low temperature cycling performance: After cycling test in high and low temperature cycling test chamber (-40~80℃), fireproof sample is tested with butane spray gun with flame temperature of 1300~1400℃ for 30 minutes, and the temperature of back plate is measured.

[0099] (3) Moist heat resistance: (After the double 85 test), the fireproof sample was tested with a butane spray gun with a flame temperature of 1300-1400℃ for 30 minutes, and the temperature of the back panel was measured.

[0100] (4) Charcoal layer condition: After the fire is over, observe its appearance, including whether it has expanded or burned through.

[0101] The fire-retardant coatings for power battery box housings provided in Examples 1-9 and Comparative Examples 1-7 were tested according to the above test methods. The test results are shown in Table 1.

[0102] Table 1

[0103]

[0104]

[0105] According to the data in Table 1:

[0106] The fire-retardant coatings provided in Examples 1-3 exhibit good fire resistance, high and low temperature resistance, and damp heat resistance after forming a coating. Furthermore, the char layer expands well and there is no burn-through phenomenon.

[0107] Compared to Examples 1-3, the fire-retardant coating provided in Example 4, due to the absence of MPD-type polyester polyol A with a smaller molecular weight, had excessively high viscosity, making it unsuitable for spraying. The fire-retardant coating provided in Example 5, due to the absence of MPD-type polyester polyol B with a larger molecular weight, exhibited decreased fire resistance, high and low temperature resistance, and damp heat resistance after coating formation. The fire-retardant coating provided in Example 6, due to the absence of MPD-type polyester polyol C with three functionalities, had insufficient cross-linking, resulting in decreased fire resistance, high and low temperature resistance, and damp heat resistance after coating formation. The fire-retardant coating provided in Example 7, due to the absence of MPD-type polyester polyols A and B with two functionalities, had excessively high cross-linking density, leading to gelation and affecting construction. The fire-retardant coatings provided in Examples 8 and 9, respectively, lacked mica powder and kaolin, resulting in slightly decreased fire resistance, high and low temperature resistance, and damp heat resistance after coating formation.

[0108] Compared with Examples 1-3, the fire-retardant coating provided in Comparative Example 1, due to the use of conventional polymer polyols, exhibits poor high and low temperature resistance and damp heat resistance after coating formation; the fire-retardant coating provided in Comparative Example 2, lacking ammonium polyphosphate, exhibits extremely low or even no expansion, resulting in almost no fire-retardant performance and extremely high back temperature; the fire-retardant coating provided in Comparative Example 3, lacking melamine, shows low expansion after coating formation, significantly deteriorating fire resistance, high and low temperature resistance, and damp heat resistance; the fire-retardant coatings provided in Comparative Examples 4 and 5... The absence of aluminum hydroxide and zinc borate in the fire-retardant coatings resulted in a slight increase in back temperature, leading to a decrease in fire resistance, high and low temperature resistance, and damp heat resistance after coating formation. The fire-retardant coating in Comparative Example 6, lacking refractory fillers and expanded graphite, exhibited extremely poor fire resistance and a significantly shortened fire resistance time, with burn-through occurring within 5 minutes. In contrast, the fire-retardant coating in Comparative Example 7, with the addition of refractory fillers without expanded graphite, extended the fire resistance time to 20 minutes, but still failed to reach 30 minutes, demonstrating poor fire resistance, high and low temperature resistance, and damp heat resistance.

[0109] The applicant declares that this invention illustrates a fire-retardant coating for a power battery box casing, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection and disclosure scope of this invention.

Claims

1. A fire-retardant coating for the housing of a power battery box, characterized in that, The fire-retardant coating comprises component A and component B; Component A includes MPD-type polyester polyol, ammonium polyphosphate, melamine, aluminum hydroxide, zinc borate, expanded graphite, and refractory filler. Component B includes a curing agent; The MPD-type polyester polyol is a 3-methyl-1,5-pentanediol-type polyester polyol; The MPD-type polyester polyol includes a combination of 2-functionality MPD-type polyester polyol and 3-functionality MPD-type polyester polyol. The number-average molecular weight of the dual-functionality MPD type polyester polyol is 1000~3000. The number-average molecular weight of the trifunctional MPD type polyester polyol is 1000~2000. Component A comprises the following components in parts by weight: 30-40 parts by weight of MPD type polyester polyol; 10-20 parts by weight of ammonium polyphosphate; 5-10 parts by weight of melamine; 5-10 parts by weight of aluminum hydroxide; 5-10 parts by weight of zinc borate; 0.5 to 1 part by weight of expanded graphite; Refractory filler 15~35 parts by weight.

2. The fire-retardant coating according to claim 1, characterized in that, The dual-functionality MPD type polyester polyols include dual-functionality MPD type polyester polyol A and dual-functionality MPD type polyester polyol B, wherein the number-average molecular weights of dual-functionality MPD type polyester polyol A and dual-functionality MPD type polyester polyol B are different.

3. The fire-retardant coating according to claim 2, characterized in that, The mass ratio of the 2-functionality MPD type polyester polyol A, the 2-functionality MPD type polyester polyol B, and the 3-functionality MPD type polyester polyol is 1:(1~3):(1~2).

4. The fire-retardant coating according to claim 1, characterized in that, The degree of polymerization of the ammonium polyphosphate is >1000.

5. The fire-retardant coating according to claim 1, characterized in that, The water solubility of the ammonium polyphosphate is <0.1 g / 100 cm³. 3 .

6. The fire-retardant coating according to claim 1, characterized in that, The particle size of the melamine, aluminum hydroxide, zinc borate, and refractory filler is all <50 μm.

7. The fire-retardant coating according to claim 1, characterized in that, The refractory filler comprises a combination of mica powder, kaolin, and wollastonite.

8. The fire-retardant coating according to claim 7, characterized in that, The mica powder content in component A is 5-15 parts by weight.

9. The fire-retardant coating according to claim 7, characterized in that, The content of kaolin in component A is 5 to 15 parts by weight.

10. The fire-retardant coating according to claim 7, characterized in that, The content of wollastonite in component A is 5 to 10 parts by weight.

11. The fire-retardant coating according to claim 1, characterized in that, The expanded graphite has a particle size of 300-400 mesh.

12. The fire-retardant coating according to claim 1, characterized in that, The expansion ratio of the expanded graphite is 200 to 400 times.

13. The fire-retardant coating according to claim 1, characterized in that, The A component also includes 1 to 3 parts by weight of a dehydrating agent.

14. The fire-retardant coating according to claim 13, characterized in that, The dehydrating agent includes molecular sieves and / or calcium oxide.

15. The fire-retardant coating according to claim 1, characterized in that, The curing agent includes polymeric diphenylmethane diisocyanate.

16. The fire-retardant coating according to claim 15, characterized in that, The functionality of the polymerized diphenylmethane diisocyanate is 2.2 to 2.

7.

17. The fire-retardant coating according to claim 1, characterized in that, The mass ratio of component A to component B is (6~8):

1.

18. A method for preparing a fire-retardant coating for a power battery box housing as described in any one of claims 1 to 17, characterized in that, The preparation method includes: mixing MPD type polyester polyol evenly, adding ammonium polyphosphate, melamine, aluminum hydroxide, zinc borate and refractory filler and mixing, then adding optional dehydrating agent and mixing, and finally adding expanded graphite and mixing to obtain component A; Mix the curing agent evenly to obtain component B.

19. A method of using a fire-retardant coating for a power battery box housing as described in any one of claims 1 to 17, characterized in that, The method of use includes: mixing component A and component B of the fire-retardant coating for power battery box housing as described in any one of claims 1 to 17, applying it to a substrate, and curing it to complete the use of the fire-retardant coating.

20. The method of use according to claim 19, characterized in that, The thickness of the cured coating is 600~1000μm.

21. The application of a fire-retardant coating as described in any one of claims 1 to 17, characterized in that, The applications include the use of the housing surface of power battery boxes for new energy vehicles.

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