Flame-retardant heat-insulating coating for battery compartment and preparation method of flame-retardant heat-insulating coating

Abstract

The invention relates to the technical field of preparation of flame-retardant heat-insulating coatings, and discloses a flame-retardant heat-insulating coating for a battery compartment and a preparation method of the flame-retardant heat-insulating coating. The method comprises the following steps: in an inert atmosphere, carrying out high-speed dry mixing on composite flame retardant powder and pretreated hollow heat insulation microspheres to obtain primary functional powder, and carrying out spraying treatment and heat treatment on the primary functional powder through a silane coupling agent to obtain surface modified functional core composite powder; the preparation method comprises the following steps: performing high-shear pre-dispersion on raw materials such as water-based organic silicon-acrylic hybrid resin to form a continuous-phase base solution; adding the functional core composite powder into the base solution in three batches, and carrying out program-controlled high-speed dispersion and temperature control to obtain high-solid-content premixed slurry; and slowly stirring the premixed slurry by a planetary stirring defoaming machine to recombine a structure, and quickly stirring and defoaming in vacuum to finish structuring, thereby obtaining the flame-retardant heat-insulating coating. The coating is suitable for battery compartment protection, and the comprehensive performance is improved through multi-step coordinated regulation and control.

Description

Technical Field

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

[0002] With the rapid development of the new energy industry, the demand for safety protection of battery systems is becoming increasingly prominent. The battery compartment, as the core load-bearing and protective component of the battery, directly affects the operational safety of the battery system due to its fire resistance and heat insulation performance. When extreme situations such as thermal runaway occur, high temperatures and flames can spread rapidly, triggering a chain reaction of safety accidents. Therefore, protective materials used in battery compartments must possess excellent flame-retardant and heat-insulating properties. Flame-retardant and heat-insulating coatings, due to their ease of application and strong adaptability, can form a uniform protective coating on the surface of the battery compartment, making them one of the key materials for improving the safety protection level of battery compartments.

[0003] Currently, existing flame-retardant and heat-insulating coating preparation technologies in the industry have many shortcomings, making it difficult to fully meet the stringent requirements of battery compartments. In the functional powder processing stage, traditional methods often employ simple mechanical mixing, resulting in poor uniformity of the mixing between the composite flame retardant and the hollow heat-insulating microspheres. Furthermore, the lack of effective surface modification of the powder leads to poor compatibility between the powder and the base material, easily causing agglomeration and directly affecting the synergistic flame-retardant and heat-insulating effects of the coating. While some technologies utilize coupling agents for modification, these are mostly immersion processes, leading to waste of processing liquid and uneven surface modification of the powder, which can subsequently cause defects in the internal structure of the coating.

[0004] In the base liquid preparation and powder dispersion stages, existing technologies often employ a single-speed dispersion method, adding functional powders to the base liquid all at once. This can easily lead to excessively high local powder concentrations, insufficient dispersion, and the formation of agglomerates. Simultaneously, the lack of effective temperature control measures during dispersion means that the heat generated by high-shear dispersion can easily cause the system temperature to rise, potentially leading to problems such as additive failure and changes in binder properties, thus affecting the stability of the coating system. Furthermore, in the preparation of some high-solids coatings, unreasonable dispersion processes often result in abnormal system viscosity and poor flowability, increasing the difficulty of application.

[0005] In the degassing process, traditional technologies often employ simple stirring or vacuum degassing methods, which are insufficient to completely eliminate air bubbles in high-solids slurries. Residual air bubbles create pores in the coating, reducing its density and compromising the integrity of the flame-retardant and heat-insulating barrier. This allows heat to easily transfer through the pores, significantly weakening the coating's heat insulation effect. Furthermore, it reduces the bonding strength between the coating and the substrate, affecting the coating's durability.

[0006] To address these issues, the industry has attempted to optimize dispersion equipment and increase additive dosages, but with limited success. Some technologies have tried to improve dispersion by increasing the dispersion speed, but this has exacerbated powder breakage and increased system temperature. Other technologies have improved compatibility by increasing coupling agent dosage, but this has led to higher coating costs and may affect the film-forming properties of the coating. Still other technologies employ complex multi-stage dispersion processes, which can improve dispersion uniformity to some extent, but the processes are cumbersome, require sophisticated equipment, and are not conducive to industrial-scale mass production. Therefore, developing a reasonable process for preparing flame-retardant and heat-insulating coatings that achieves uniform dispersion and effective modification of functional powders, ensures coating system stability and thorough defoaming, and is suitable for battery compartment applications has become an urgent direction for industry development. Summary of the Invention

[0007] The purpose of this invention is to provide a flame-retardant and heat-insulating coating for battery compartments and its preparation method, so as to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides a flame-retardant and heat-insulating coating for battery compartments and a method for preparing the same, the method comprising:

[0009] Step (1): Under an inert atmosphere, the composite flame retardant powder and the pretreated hollow heat insulation microspheres are placed in a high-speed vortex mixer and dry-mixed at 1500~2000 rpm for 5~10 minutes to form a primary functional powder; then, the silane coupling agent is dissolved in anhydrous ethanol to form a treatment solution, which is sprayed onto the surface of the primary functional powder under continuous stirring, and then heat-treated at 80~100℃ for 1~2 hours to obtain a surface-modified functional core composite powder;

[0010] Step (2): Add waterborne organosilicon-acrylic hybrid resin, toughening polymer latex, rheology modifier and dispersant to deionized water, and pre-disperse it at 500~800 rpm for 15~20 minutes using a high shear emulsifier to form a uniform and stable continuous phase base liquid.

[0011] Step (3): The functional core composite powder obtained in step (1) is added to the continuous phase base liquid obtained in step (2) in three batches and dispersed using a high-speed disperser with program control. The dispersion program is as follows: after the first batch of powder is added, it is dispersed at 800~1000 rpm for 10 minutes; after the second batch of powder is added, it is dispersed at 1200~1500 rpm for 15 minutes; after the last batch of powder is added, it is dispersed at 600~800 rpm for 20 minutes. The material temperature is controlled below 40℃ throughout the process by circulating water bath, and finally a high solids content premixed slurry is obtained.

[0012] Step (4): Transfer the high solids premixed slurry obtained in step (3) to a planetary mixer degasser. First, run it in a "slow mixing" mode with a revolution of 30-50 rpm and a rotation of 100-200 rpm for 1-2 hours to promote the reorganization and stabilization of the microstructure of the system. Then switch to a "fast mixing" mode with a revolution of 5-15 rpm and a rotation of 500-800 rpm, and simultaneously turn on the vacuum system. Run it in a vacuum of -0.095 MPa or higher for 15-30 minutes to completely eliminate bubbles and complete the final structuring, thus obtaining a flame-retardant and heat-insulating coating.

[0013] Preferably, in step (1), the composite flame retardant is a compound of surface-coated ammonium polyphosphate and modified magnesium hydroxide, with a mass ratio of 2:1 to 3:1; the hollow heat-insulating microspheres are borosilicate glass microspheres with a particle size distribution D50 of 20 to 50 μm; and the silane coupling agent is γ-aminopropyltriethoxysilane, with an amount of 0.5% to 1.5% of the total mass of the functional powder.

[0014] Preferably, in step (1), the inert atmosphere is nitrogen or argon; the mixing chamber of the high-speed vortex mixer is equipped with a cooling jacket, and the temperature of the chamber is maintained below 25°C during the mixing process; the heat treatment is carried out in a vacuum drying oven, and the heating rate is 2~5°C / minute.

[0015] Preferably, in step (2), the solid content of the aqueous organosilicon-acrylic hybrid resin is 45%~55%, and the glass transition temperature Tg is -10~10℃; the toughening polymer latex is a core-shell structured acrylate emulsion; the rheology modifier is a hydrophobically modified alkali-swellable polyacrylate; the proportions of each component in the continuous phase base liquid, by mass, are: 30~40 parts of aqueous organosilicon-acrylic hybrid resin, 10~15 parts of toughening polymer latex, 0.3~0.8 parts of rheology modifier, 0.2~0.5 parts of dispersant, and 40~50 parts of deionized water.

[0016] Preferably, in step (2), the dispersing agent is a compound of polyether-modified polydimethylsiloxane and low molecular weight sodium polyacrylate, with a mass ratio of 1:1 to 2:1; the rotor-stator gap of the high shear emulsifier is set to 0.2 to 0.5 mm.

[0017] Preferably, in step (3), the mass ratio of the three batches of added functional core composite powder is first batch: second batch: last batch = 1:2:1; the dispersion disc of the program-controlled high-speed disperser is sawtooth type, with a diameter of 1 / 3 to 1 / 2 of the diameter of the dispersion cylinder; the temperature control medium of the circulating water bath is ethylene glycol aqueous solution, with a temperature control accuracy of ±1℃.

[0018] Preferably, in step (3), before each batch of powder is added, the viscosity and pH value of the continuous phase base liquid need to be monitored online to ensure that the viscosity is between 300 and 500 mPa·s (25°C) and the pH value is maintained between 8.0 and 9.0. If it exceeds the range, it needs to be adjusted by adding rheology modifier or pH adjuster before the next batch of powder can be added and dispersed.

[0019] Preferably, in step (4), after the micro-nano structuring maturation step is completed, the properties of the resulting coating need to meet the following requirements: Stormer viscosity 90~110KU, specific gravity 1.35~1.50g / cm³, and fineness ≤50μm (Hegmann fineness meter).

[0020] Preferably, after step (4), the product stabilization treatment is further included in step (5): the matured coating is left to stand and age in a constant temperature environment of 25±2℃ for 24~48 hours, then filtered with a 200-mesh vibrating screen, and filled into an opaque, nitrogen-filled sealed container, and stored in the dark at 10~30℃.

[0021] The present invention also includes a flame-retardant and heat-insulating coating for a battery compartment, which is prepared by the above-mentioned method for preparing a flame-retardant and heat-insulating coating for a battery compartment.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] In the preparation stage of the functional core composite powder, the introduction of an inert atmosphere can prevent the composite flame retardant powder and hollow heat-insulating microspheres from being affected by impurities such as oxygen and moisture during the dry mixing process, ensuring that the original properties of the powder remain unchanged. The application of a high-speed vortex mixer, combined with a rotation speed of 1500~2000 rpm and a dry mixing time of 5~10 minutes, can promote the rapid and uniform mixing of the two powders, forming a primary functional powder with uniform composition. Subsequently, a treatment solution is formed by dissolving a silane coupling agent in anhydrous ethanol and applied to the surface of the primary functional powder by spraying. Compared with the traditional immersion modification, the spraying method can make the treatment solution more evenly cover the powder surface, avoiding over- or under-treatment in some areas. Heat treatment at 80~100℃ for 1~2 hours can promote the full reaction between the silane coupling agent and the powder surface, effectively improve the surface activity of the powder, enhance its compatibility with the subsequent base liquid, and reduce the tendency of the powder to agglomerate in the system.

[0024] In the preparation of the continuous phase base liquid, the aqueous organosilicon-acrylic hybrid resin, toughening polymer latex, rheology modifier, and dispersant are added to deionized water and pre-dispersed for 15-20 minutes at 500-800 rpm using a high-shear emulsifier. Precise control of these process parameters allows for rapid fusion of the various base components, forming a homogeneous and stable continuous phase system. The high-shear action effectively breaks down tiny agglomerates in the base material, ensuring that the rheology modifier and dispersant are uniformly dispersed in the system, fully utilizing their regulatory effects and laying a good foundation for the subsequent addition and dispersion of functional powders. A stable continuous phase base liquid avoids problems such as stratification and sedimentation during subsequent mixing with functional powders, ensuring the overall stability of the coating system.

[0025] The batch-addition and programmed dispersion process of the functional core composite powder demonstrates significant advantages. The first batch of powder is dispersed at 800-1000 rpm for 10 minutes, allowing it to gradually integrate into the base liquid and avoiding excessively high local concentrations and dispersion difficulties caused by a single addition. The second batch, after addition, increases the speed to 1200-1500 rpm and disperses for 15 minutes, further breaking down any potential micro-agglomerates and enhancing dispersion. The final batch, after addition, adjusts the speed to 600-800 rpm and disperses for 20 minutes, ensuring uniform dispersion while preventing damage to the established dispersion system from high speeds. A circulating water bath controls the material temperature below 40℃ throughout the process, effectively preventing heat generation during dispersion from causing additive failure or changes in base material properties, ensuring that all components remain stable. The resulting high-solids premixed slurry exhibits excellent dispersion uniformity and stability, balancing high solids content with superior flowability.

[0026] The segmented operation mode of the planetary agitator degasser optimizes the microstructure of the coating system and completely eliminates air bubbles. First, it operates in a slow agitation mode of 30-50 rpm (revolutionary speed) and 100-200 rpm (rotational speed) for 1-2 hours, promoting further recombination of the components in the premixed slurry and allowing for more thorough integration of functional powders and the base liquid, thus optimizing the microstructure stability of the system. Then, it switches to a fast agitation mode of 5-15 rpm (revolutionary speed) and 500-800 rpm (rotational speed), operating at a vacuum of -0.095 MPa or higher for 15-30 minutes. This rapidly breaks down air bubbles in the slurry while preventing their regeneration under vacuum, completely eliminating air bubbles within the system. Compared to traditional single-stage degassing methods, this segmented degassing process ensures both the stability of the system structure and the effectiveness of degassing, resulting in a dense internal structure with no significant pore defects in the final flame-retardant and heat-insulating coating. Attached Figure Description

[0027] Figure 1 This diagram illustrates the steps of a flame-retardant and heat-insulating coating for a battery compartment and its preparation method, as described in this invention. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to specific embodiments, in order to make the technical solution and advantages of the present invention clearer and easier to understand, rather than to limit the scope of protection of the present invention. All "parts" mentioned in the present invention refer to parts by weight. All raw materials are of industrial grade purity. The anhydrous ethanol, after dehydration by molecular sieve, has a moisture content ≤0.05%. The water-based organosilicon-acrylic hybrid resin, toughening polymer latex, and other polymer materials are all commercially available industrial-grade products, and are used only after laboratory testing confirms that they meet the performance indicators specified in the present invention. The composite flame retardant, hollow heat-insulating microspheres, and other powder materials are all vacuum dried at 80°C for 4 hours to remove moisture before use.

[0029] The core idea of ​​this invention is as follows: By modifying the surface of functional powders with silane coupling agents, optimizing the composition ratio and pre-dispersion process of the continuous phase base liquid, and employing a batch-by-batch gradient speed dispersion strategy to control the dispersion uniformity of functional powders in the base liquid, combined with a two-step structuring treatment of "slow stirring and recombination - fast stirring and degassing" and a finished product stabilization process, a battery compartment coating with excellent flame retardant properties, thermal insulation properties, and mechanical stability is prepared. Examples 1-4 below are preferred embodiments conforming to the technical solution of this invention, while Comparative Examples 1-3 are comparative schemes deviating from the key technical parameters of this invention. Performance comparisons with the examples verify the necessity and superiority of the technical features of this invention.

[0030] The performance testing methods involved in each embodiment and comparative example are as follows:

[0031] 1. Basic performance testing:

[0032] (1) Stormer viscosity: measured at 25°C using a Stormer viscometer in accordance with GB / T 9269-2009 standard, unit is KU;

[0033] (2) Specific gravity: determined by the specific gravity bottle method at 25℃ according to GB / T 6750-2007 standard, the unit is g / cm³;

[0034] (3) Fineness: measured by a Hergmann fineness tester according to GB / T 1724-1979 standard, with units of μm;

[0035] (4) Adhesion: According to GB / T 9286-1998 standard, the cross-cut test method is adopted, the cross-cut spacing is 1mm, and the rating is 0-5. The lower the rating, the better the adhesion.

[0036] 2. Flame retardant performance test:

[0037] (1) Limiting oxygen index (LOI): According to GB / T 2406.2-2009 standard, an oxygen index tester was used, and the sample size was 120mm×10mm×3mm;

[0038] (2) Vertical burning performance: According to UL94-2013 standard, a vertical burning tester was used, and the sample size was 127mm×12.7mm×3mm. The flame retardant rating (V-0, V-1, V-2 or no rating) was evaluated.

[0039] (3) Smoke density: According to GB / T 8627-2007 standard, the smoke density was measured using a smoke density tester at a radiation intensity of 30kW / m², and the maximum smoke density (MSD) was recorded.

[0040] 3. Thermal insulation performance test:

[0041] (1) Thermal conductivity: According to GB / T 10294-2008 standard, the thermal conductivity was measured at 25℃ using a protective hot plate method thermal conductivity meter, and the unit is W / (m·K);

[0042] (2) High temperature insulation effect: The coating is evenly applied to the surface of a 1mm thick cold-rolled steel plate, the dry film thickness is controlled to be 1mm, and it is placed in a high temperature furnace. The furnace temperature is set to 800℃. Thermocouples are used to monitor the temperature of the uncoated surface of the steel plate and the temperature values ​​are recorded at 30min and 60min. The lower the temperature, the better the insulation effect.

[0043] 4. Mechanical properties and stability testing:

[0044] (1) Impact resistance: According to GB / T 1732-1993 standard, a falling ball impact tester was used with an impact energy of 5J to observe whether the sample cracked or fell off;

[0045] (2) Moist heat resistance: According to GB / T 1740-2007 standard, the coated sample was placed in a damp heat chamber at 40℃ and 95% relative humidity for 72h, and the adhesion change was measured after it was taken out.

[0046] (3) Storage stability: Store the coating in a constant temperature environment of 25℃ for 6 months, and observe regularly whether the coating shows stratification or sedimentation. Measure the viscosity change rate before and after storage. Viscosity change rate = (viscosity after storage - viscosity before storage) / viscosity before storage × 100%. The absolute value of the change rate ≤ 5% is qualified.

[0047] Example 1

[0048] See appendix Figure 1 This embodiment describes a method for preparing a flame-retardant and heat-insulating coating for a battery compartment. The specific steps are as follows:

[0049] Step (1): Preparation of functional core composite powder

[0050] Under a nitrogen atmosphere, 20 parts of composite flame retardant powder (surface-coated ammonium polyphosphate and modified magnesium hydroxide in a mass ratio of 2:1) and 10 parts of pretreated hollow heat-insulating microspheres (borosilicate glass microspheres with a particle size distribution D50 of 20 μm) were placed in a high-speed vortex mixer. The mixing chamber of the high-speed vortex mixer was equipped with a cooling jacket, and the chamber temperature was maintained at 22°C during the mixing process. The mixture was dry-mixed at 1500 rpm for 10 minutes to form a primary functional powder. Subsequently, 0.225 parts of silane coupling agent (γ-aminopropyltriethoxysilane) were dissolved in 10 parts of anhydrous ethanol to form a treatment solution. This solution was sprayed onto the surface of the primary functional powder under continuous stirring at a spray rate of 0.5 mL / min. The powder was then transferred to a vacuum drying oven and heated to 80°C at a rate of 2°C / min. The powder was then heat-treated at this temperature for 2 hours to obtain a surface-modified functional core composite powder for later use.

[0051] Step (2): Preparation of continuous phase base liquid

[0052] 30 parts of waterborne organosilicon-acrylic hybrid resin (solid content 45%, glass transition temperature Tg -10℃), 10 parts of toughening polymer latex (core-shell structured acrylate emulsion), 0.3 parts of rheology modifier (hydrophobic modified alkali-swellable polyacrylate), and 0.2 parts of dispersant (polyether modified polydimethylsiloxane and low molecular weight sodium polyacrylate in a mass ratio of 1:1) were added to 50 parts of deionized water. Pre-dispersion was performed using a high-shear emulsifier with a rotor-stator gap of 0.2 mm at 500 rpm for 20 minutes to form a homogeneous and stable continuous phase base liquid. The viscosity of the continuous phase base liquid was measured to be 300 mPa·s (25℃), and the pH value was 8.0, meeting the requirements for subsequent powder addition.

[0053] Step (3): Preparation of high solids premixed slurry

[0054] The functional core composite powder obtained in step (1) was added in three batches to the continuous phase base liquid obtained in step (2) in a mass ratio of first batch: second batch: last batch = 1:2:1. The powder was dispersed using a high-speed disperser with a program-controlled system. The dispersion disc of the disperser was serrated and its diameter was 1 / 3 of the diameter of the dispersion cylinder. Before each batch of powder was added, the viscosity and pH value of the continuous phase base liquid were monitored online to ensure that the parameters met the requirements. The specific dispersion procedure was as follows: after the first batch of 7.5 parts of powder was added, it was dispersed at 800 rpm for 10 minutes; after the second batch of 15 parts of powder was added, it was dispersed at 1200 rpm for 15 minutes; after the last batch of 7.5 parts of powder was added, it was dispersed at 600 rpm for 20 minutes. The material temperature was controlled by a circulating water bath throughout the process. The temperature control medium of the circulating water bath was ethylene glycol aqueous solution, and the temperature control accuracy was ±1℃. The material temperature was maintained below 35℃ throughout the process, and a high solids content premixed slurry was finally obtained.

[0055] Step (4): Structuring and maturation

[0056] The high-solids premixed slurry obtained in step (3) was transferred to a planetary mixer degasser. It was first run in a "slow mixing" mode of 30 rpm revolution and 100 rpm rotation for 2 hours to promote the reorganization and stabilization of the microstructure of the system. Then, it was switched to a "fast mixing" mode of 5 rpm revolution and 500 rpm rotation, and the vacuum system was turned on at the same time. It was run in a vacuum of -0.096 MPa for 30 minutes to completely eliminate bubbles and complete the final structuring, thus obtaining a flame-retardant and heat-insulating coating. The coating performance was sampled and measured: Stormer viscosity 90 KU, specific gravity 1.35 g / cm³, fineness 45 μm, which met the preset requirements.

[0057] Step (5): Finished product stabilization treatment

[0058] After aging, the coating is left to stand in a constant temperature environment of 25±2℃ for 24 hours, then filtered through a 200-mesh vibrating screen. No obvious residue is found during the filtration process. The coating is then filled into an opaque, nitrogen-filled, sealed container and stored at 10℃ away from light.

[0059] Example 2

[0060] This embodiment describes a method for preparing a flame-retardant and heat-insulating coating for a battery compartment. The specific steps are as follows:

[0061] Step (1): Preparation of functional core composite powder

[0062] Under an argon atmosphere, 25 parts of composite flame retardant powder (surface-coated ammonium polyphosphate and modified magnesium hydroxide in a mass ratio of 2.5:1) and 12 parts of pretreated hollow heat-insulating microspheres (borosilicate glass microspheres with a particle size distribution D50 of 35 μm) were placed in a high-speed vortex mixer. The mixing chamber of the high-speed vortex mixer was equipped with a cooling jacket, and the chamber temperature was maintained at 20°C during the mixing process. The mixture was dry-mixed at 1800 rpm for 8 minutes to form a primary functional powder. Subsequently, 0.489 parts of silane coupling agent (γ-aminopropyltriethoxysilane) were dissolved in 15 parts of anhydrous ethanol to form a treatment solution. This solution was sprayed uniformly onto the surface of the primary functional powder under continuous stirring at a spray rate of 0.8 mL / min. The powder was then transferred to a vacuum drying oven and heated to 90°C at a rate of 3°C / min. The powder was then heat-treated at this temperature for 1.5 hours to obtain a surface-modified functional core composite powder for later use.

[0063] Step (2): Preparation of continuous phase base liquid

[0064] 35 parts of waterborne silicone-acrylic hybrid resin (50% solids content, glass transition temperature Tg of 0℃), 12 parts of toughening polymer latex (core-shell structured acrylate emulsion), 0.5 parts of rheology modifier (hydrophobic modified alkali-swellable polyacrylate), and 0.35 parts of dispersant (polyether modified polydimethylsiloxane and low molecular weight sodium polyacrylate in a mass ratio of 1.5:1) were added to 45 parts of deionized water. Pre-dispersion was performed using a high-shear emulsifier with a rotor-stator gap of 0.35 mm at 650 rpm for 18 minutes to form a homogeneous and stable continuous phase base liquid. The viscosity of the continuous phase base liquid was measured to be 400 mPa·s (25℃), and the pH value was 8.5, meeting the requirements for subsequent powder addition.

[0065] Step (3): Preparation of high solids premixed slurry

[0066] The 37 parts of the functional core composite powder obtained in step (1) were added to the continuous phase base liquid obtained in step (2) in three batches according to the mass ratio of first batch: second batch: last batch = 1:2:1. The dispersion was carried out using a high-speed disperser with program control. The dispersion disc of the disperser was serrated and the diameter was 2 / 5 of the diameter of the dispersion cylinder. Before each batch of powder was added, the viscosity and pH value of the continuous phase base liquid were monitored online to ensure that the parameters met the requirements. The specific dispersion program was as follows: after the first batch of 9.25 parts of powder was added, it was dispersed at 900 rpm for 10 minutes; after the second batch of 18.5 parts of powder was added, it was dispersed at 1350 rpm for 15 minutes; after the last batch of 9.25 parts of powder was added, it was dispersed at 700 rpm for 20 minutes. The material temperature was controlled by a circulating water bath throughout the process. The temperature control medium of the circulating water bath was ethylene glycol aqueous solution, and the temperature control accuracy was ±1℃. The material temperature was maintained below 38℃ throughout the process, and a high solids content premixed slurry was finally obtained.

[0067] Step (4): Structuring and maturation

[0068] The high-solids premixed slurry obtained in step (3) was transferred to a planetary mixer degasser. It was first run in a "slow mixing" mode of 40 rpm revolution and 150 rpm rotation for 1.5 hours to promote the reorganization and stabilization of the microstructure of the system. Then, it was switched to a "fast mixing" mode of 10 rpm revolution and 650 rpm rotation, and the vacuum system was turned on at the same time. It was run at a vacuum of -0.098 MPa for 22 minutes to completely eliminate bubbles and complete the final structuring, thus obtaining a flame-retardant and heat-insulating coating. The coating performance was sampled and measured: Stormer viscosity 100 KU, specific gravity 1.42 g / cm³, fineness 40 μm, which met the preset requirements.

[0069] Step (5): Finished product stabilization treatment

[0070] After aging, the coating is left to stand in a constant temperature environment of 25±2℃ for 36 hours, then filtered through a 200-mesh vibrating screen. No obvious residue was found during the filtration process. The coating is then filled into an opaque, nitrogen-filled, sealed container and stored at 20℃ away from light.

[0071] Example 3

[0072] This embodiment describes a method for preparing a flame-retardant and heat-insulating coating for a battery compartment. The specific steps are as follows:

[0073] Step (1): Preparation of functional core composite powder

[0074] Under a nitrogen atmosphere, 30 parts of composite flame retardant powder (surface-coated ammonium polyphosphate and modified magnesium hydroxide in a mass ratio of 3:1) and 15 parts of pretreated hollow heat-insulating microspheres (borosilicate glass microspheres with a particle size distribution D50 of 50 μm) were placed in a high-speed vortex mixer. The mixing chamber of the high-speed vortex mixer was equipped with a cooling jacket, and the chamber temperature was maintained at 25°C during the mixing process. The mixture was dry-mixed at 2000 rpm for 5 minutes to form a primary functional powder. Subsequently, 0.675 parts of silane coupling agent (γ-aminopropyltriethoxysilane) were dissolved in 20 parts of anhydrous ethanol to form a treatment solution. This solution was sprayed onto the surface of the primary functional powder under continuous stirring at a spray rate of 1.0 mL / min. The powder was then transferred to a vacuum drying oven and heated to 100°C at a rate of 5°C / min. The powder was then heat-treated at this temperature for 1 hour to obtain a surface-modified functional core composite powder for later use.

[0075] Step (2): Preparation of continuous phase base liquid

[0076] 40 parts of waterborne silicone-acrylic hybrid resin (55% solids content, glass transition temperature Tg of 10℃), 15 parts of toughening polymer latex (core-shell structured acrylate emulsion), 0.8 parts of rheology modifier (hydrophobic modified alkali-swellable polyacrylate), and 0.5 parts of dispersant (polyether modified polydimethylsiloxane and low molecular weight sodium polyacrylate in a mass ratio of 2:1) were added to 40 parts of deionized water. Pre-dispersion was performed using a high-shear emulsifier with a rotor-stator gap of 0.5 mm at 800 rpm for 15 minutes to form a homogeneous and stable continuous phase base liquid. The viscosity of the continuous phase base liquid was measured to be 500 mPa·s (25℃), and the pH value was 9.0, meeting the requirements for subsequent powder addition.

[0077] Step (3): Preparation of high solids premixed slurry

[0078] The functional core composite powder obtained in step (1) was added in three batches to the continuous phase base liquid obtained in step (2) in a mass ratio of first batch: second batch: last batch = 1:2:1. The powder was dispersed using a high-speed disperser with a program-controlled system. The dispersion disc of the disperser was serrated and its diameter was half the diameter of the dispersion cylinder. Before each batch of powder was added, the viscosity and pH value of the continuous phase base liquid were monitored online to ensure that the parameters met the requirements. The specific dispersion procedure was as follows: after the first batch of 11.25 parts of powder was added, it was dispersed at 1000 rpm for 10 minutes; after the second batch of 22.5 parts of powder was added, it was dispersed at 1500 rpm for 15 minutes; after the last batch of 11.25 parts of powder was added, it was dispersed at 800 rpm for 20 minutes. The material temperature was controlled by a circulating water bath throughout the process. The temperature control medium of the circulating water bath was ethylene glycol aqueous solution, and the temperature control accuracy was ±1℃. The material temperature was maintained below 39℃ throughout the process, and a high solids content premixed slurry was finally obtained.

[0079] Step (4): Structuring and maturation

[0080] The high-solids premixed slurry obtained in step (3) was transferred to a planetary mixer degasser. It was first run in a "slow mixing" mode of 50 rpm revolution and 200 rpm rotation for 1 hour to promote the reorganization and stabilization of the microstructure of the system. Then, it was switched to a "fast mixing" mode of 15 rpm revolution and 800 rpm rotation, and the vacuum system was turned on at the same time. It was run in a vacuum of -0.099 MPa for 15 minutes to completely eliminate bubbles and complete the final structuring, thus obtaining a flame-retardant and heat-insulating coating. The coating performance was sampled and measured: Stormer viscosity 110 KU, specific gravity 1.50 g / cm³, fineness 35 μm, which met the preset requirements.

[0081] Step (5): Finished product stabilization treatment

[0082] After maturation, the coating is left to stand and age in a constant temperature environment of 25±2℃ for 48 hours. Then it is filtered through a 200-mesh vibrating screen. No obvious residue is found during the filtration process. The coating is then filled into an opaque, nitrogen-filled, sealed container and stored in the dark at 30℃.

[0083] Example 4

[0084] This embodiment describes a method for preparing a flame-retardant and heat-insulating coating for a battery compartment. The specific steps are as follows:

[0085] Step (1): Preparation of functional core composite powder

[0086] Under an argon atmosphere, 22 parts of composite flame retardant powder (surface-coated ammonium polyphosphate and modified magnesium hydroxide in a mass ratio of 2.2:1) and 11 parts of pretreated hollow heat-insulating microspheres (borosilicate glass microspheres with a particle size distribution D50 of 30 μm) were placed in a high-speed vortex mixer. The mixing chamber of the high-speed vortex mixer was equipped with a cooling jacket, and the chamber temperature was maintained at 23°C during the mixing process. The mixture was dry-mixed at 1600 rpm for 9 minutes to form a primary functional powder. Subsequently, 0.3465 parts of silane coupling agent (γ-aminopropyltriethoxysilane) were dissolved in 12 parts of anhydrous ethanol to form a treatment solution. This solution was sprayed uniformly onto the surface of the primary functional powder under continuous stirring at a spray rate of 0.6 mL / min. The powder was then transferred to a vacuum drying oven and heated to 85°C at a rate of 2.5°C / min. The powder was then heat-treated at this temperature for 1.8 hours to obtain a surface-modified functional core composite powder for later use.

[0087] Step (2): Preparation of continuous phase base liquid

[0088] 32 parts of waterborne organosilicon-acrylic hybrid resin (solid content 48%, glass transition temperature Tg -5℃), 11 parts of toughening polymer latex (core-shell structured acrylate emulsion), 0.4 parts of rheology modifier (hydrophobic modified alkali-swellable polyacrylate), and 0.25 parts of dispersant (polyether modified polydimethylsiloxane and low molecular weight sodium polyacrylate in a mass ratio of 1.2:1) were added to 48 parts of deionized water. Pre-dispersion was performed using a high-shear emulsifier with a rotor-stator gap of 0.3 mm at 550 rpm for 19 minutes to form a homogeneous and stable continuous phase base liquid. The viscosity of the continuous phase base liquid was measured to be 350 mPa·s (25℃), and the pH value was 8.2, meeting the requirements for subsequent powder addition.

[0089] Step (3): Preparation of high solids premixed slurry

[0090] The functional core composite powder obtained in step (1) was added in three batches to the continuous phase base liquid obtained in step (2) in a mass ratio of first batch: second batch: last batch = 1:2:1. The powder was dispersed using a high-speed disperser with a program-controlled system. The dispersion disc of the disperser was serrated and its diameter was 3 / 8 of the diameter of the dispersion cylinder. Before each batch of powder was added, the viscosity and pH value of the continuous phase base liquid were monitored online to ensure that the parameters met the requirements. The specific dispersion procedure was as follows: after the first batch of 8.25 parts of powder was added, it was dispersed at 850 rpm for 10 minutes; after the second batch of 16.5 parts of powder was added, it was dispersed at 1300 rpm for 15 minutes; after the last batch of 8.25 parts of powder was added, it was dispersed at 650 rpm for 20 minutes. The material temperature was controlled by a circulating water bath throughout the process. The temperature control medium of the circulating water bath was ethylene glycol aqueous solution with a temperature control accuracy of ±1℃. The material temperature was maintained below 36℃ throughout the process, and a high solids content premixed slurry was finally obtained.

[0091] Step (4): Structuring and maturation

[0092] The high-solids premixed slurry obtained in step (3) was transferred to a planetary mixer degasser. It was first run in a "slow mixing" mode of 35 rpm revolution and 120 rpm rotation for 1.8 hours to promote the reorganization and stabilization of the microstructure of the system. Then, it was switched to a "fast mixing" mode of 8 rpm revolution and 550 rpm rotation, and the vacuum system was turned on at the same time. It was run at a vacuum of -0.097 MPa for 25 minutes to completely eliminate bubbles and complete the final structuring, thus obtaining a flame-retardant and heat-insulating coating. The coating performance was sampled and measured: Stormer viscosity 95 KU, specific gravity 1.38 g / cm³, fineness 42 μm, which met the preset requirements.

[0093] Step (5): Finished product stabilization treatment

[0094] After maturation, the coating is left to stand and age in a constant temperature environment of 25±2℃ for 30 hours. Then it is filtered through a 200-mesh vibrating screen. No obvious residue is found during the filtration process. The coating is then filled into an opaque, nitrogen-filled, sealed container and stored in the dark at 15℃.

[0095] Comparative Example 1

[0096] The difference between this comparative example and Example 2 is that the primary functional powder was not subjected to silane coupling agent surface modification treatment in step (1), while the remaining steps and parameters are exactly the same as in Example 2.

[0097] Specific differences in steps: Under nitrogen atmosphere protection, 25 parts of composite flame retardant powder and 12 parts of hollow heat insulation microspheres were placed in a high-speed vortex mixer and dry-mixed at 1800 rpm for 8 minutes to directly obtain functional core composite powder without silane coupling agent treatment or subsequent heat treatment; the raw material ratios and process parameters of the remaining steps (steps 2-5) are the same as in Example 2.

[0098] Comparative Example 2

[0099] The difference between this comparative example and Example 2 is that in step (3), the functional core composite powder is added to the continuous phase base liquid at one time and dispersed by constant speed. The batch gradient speed dispersion strategy is not adopted. The remaining steps and parameters are exactly the same as those in Example 2.

[0100] Specific differences in steps: 37 parts of the functional core composite powder obtained in step (1) are added to the continuous phase base liquid obtained in step (2) at one time, and dispersed at a constant speed of 1350 rpm for 45 minutes using a high-speed disperser. The material temperature is controlled below 38℃ throughout the process by circulating water bath. The raw material ratio and process parameters of the remaining steps (step 1, step 2, step 4, step 5) are the same as those in Example 2.

[0101] Comparative Example 3

[0102] The difference between this comparative example and Example 2 is that: in step (4), only the "fast stirring" degassing treatment is performed, the "slow stirring" microstructure recombination step is omitted, and the product stabilization treatment in step (5) is not performed. The remaining steps and parameters are exactly the same as in Example 2.

[0103] Specific difference steps: The high solids content premixed slurry obtained in step (3) is transferred to a planetary mixer deaerator and directly switched to the "fast mixing" mode with a revolution of 10 rpm and a rotation of 650 rpm. It is run for 22 minutes under a vacuum of -0.098 MPa. After deaeration, the flame-retardant and heat-insulating coating is directly obtained. The subsequent static aging, filtration and nitrogen filling storage steps are not carried out. The performance test is carried out directly after the coating is prepared.

[0104] III. Performance Test Results and Analysis of Examples and Comparative Examples

[0105] The basic performance, flame retardant performance, heat insulation performance and stability of the flame-retardant and heat-insulating coatings for battery compartments prepared in Examples 1-4 and Comparative Examples 1-3 were tested. The test results are recorded in Tables 1, 2 and 3 respectively, and the data in each table are analyzed in detail.

[0106] Table 1: Test Results of Basic Properties and Stability of the Coatings in Examples and Comparative Examples

[0107] Sample No. Staudinger viscosity (KU) Specific gravity (g / cm3) Fineness (pm) Adhesion (grade) Impact resistance Adhesion after wet heat resistance (grade) 6-month storage stability (viscosity change rate) Example 1 90 1.35 45 0 No cracking, peeling 0 2.1% Example 2 100 1.42 40 0 No cracking, peeling 0 1.5% Example 3 110 1.50 35 0 No cracking, peeling 0 1.8% Example 4 95 1.38 42 0 No cracking, peeling 0 2.0% Comparative Example 1 105 1.43 65 2 Slight cracking 3 8.7% Comparative Example 2 102 1.42 58 1 No cracking, peeling 2 6.3% Comparative Example 3 98 1.41 42 1 No cracking, peeling 2 12.5%

[0108] As shown in Table 1, the coatings prepared in Examples 1-4 exhibit excellent basic properties and good stability, with all indicators superior to those of Comparative Examples 1-3. Specifically:

[0109] Regarding basic performance: The Stormer viscosity of Examples 1-4 was 90-110 KU, the specific gravity was 1.35-1.50 g / cm³, and the fineness was 35-45 μm, all meeting the performance requirements preset by this invention; and the fineness was ≤45 μm, far lower than 65 μm of Comparative Example 1 and 58 μm of Comparative Example 2. This is because the examples used silane coupling agent surface modification treatment, which improved the compatibility between the functional powder and the base liquid. At the same time, the batch gradient speed dispersion strategy ensured the uniform dispersion of the powder and avoided powder agglomeration. In contrast, Comparative Example 1 did not undergo surface modification, and the surface polarity of the powder differed greatly from that of the base liquid, making it prone to agglomeration and resulting in increased fineness. Comparative Example 2 was dispersed at high speed in one go, and when the amount of powder added was too large, it was easy to form local agglomeration, making it difficult to disperse completely, which also led to increased fineness.

[0110] In terms of mechanical properties: the adhesion of Examples 1-4 was all grade 0, and the impact resistance showed no cracking or peeling. Even after 72 hours of humid heat aging, the adhesion remained at grade 0. This is attributed to the bridging effect of the silane coupling agent, which binds to the hydroxyl groups on the surface of the functional powder at one end and interacts with the resin molecular chains at the other, significantly improving the bonding force between the coating and the substrate, as well as the interfacial bonding strength within the coating. Simultaneously, the addition of the toughening polymer latex improved the toughness of the coating and enhanced its impact resistance. Comparative Example 1, without surface modification, had weak interfacial bonding between the functional powder and the base liquid, resulting in an adhesion grade of only 2. Slight cracking occurred in the impact resistance, and the adhesion further decreased to grade 3 after humid heat aging. Comparative Example 2, due to uneven powder dispersion, had stress concentration points within the coating, resulting in an adhesion grade of 2 after humid heat aging. Comparative Example 3, omitting the "slow stirring" recombination step, had an unstable microstructure, resulting in an adhesion grade of 1, which also decreased to grade 2 after humid heat aging.

[0111] Regarding storage stability: The viscosity change rate of Examples 1-4 after 6 months of storage was only 1.5%-2.1%, all of which met the qualified standard (≤5%). This is because the "slow stirring" recombination in step (4) formed a stable microstructure in the system, and the static aging, filtration and nitrogen filling storage in step (5) further improved the stability of the finished product and prevented the coating from stratifying and settling during storage. However, Comparative Example 1 was prone to sedimentation during storage due to poor compatibility between the powder and the base liquid, with a viscosity change rate of 8.7%; Comparative Example 2 had an agglomeration phenomenon during storage due to uneven powder dispersion, with a viscosity change rate of 6.3%; Comparative Example 3 omitted the "slow stirring" recombination and finished product stabilization treatment, resulting in an unstable microstructure of the system. After 6 months of storage, the viscosity change rate was as high as 12.5%, and the coating showed obvious stratification and could not be used normally.

[0112] Table 2: Flame retardant performance test results of the coatings in the examples and comparative examples

[0113] Sample No. Limiting oxygen index (LOI) (%) UL94 vertical burning grade Maximum smoke density (MSD) Example 1 32.5 V-0 45 Example 2 36.2 V-0 38 Example 3 38.5 V-0 32 Example 4 34.1 V-0 42 Comparative Example 1 28.3 V-2 68 Comparative Example 2 30.5 V-1 56 Comparative Example 3 31.2 V-1 52

[0114] As shown in Table 2, the flame retardant performance of Examples 1-4 is significantly better than that of Comparative Examples 1-3, and all of them can meet the V-0 flame retardant standard. The specific analysis is as follows:

[0115] Limiting Oxygen Index (LOI): The LOI values ​​of Examples 1-4 were 32.5%-38.5%, significantly higher than those of Comparative Example 1 (28.3%), Comparative Example 2 (30.5%), and Comparative Example 3 (31.2%). This is because the functional core composite powder modified with silane coupling agent in the examples was uniformly dispersed, and the composite flame retardant (ammonium polyphosphate and modified magnesium hydroxide) could fully exert its synergistic flame retardant effect: Ammonium polyphosphate decomposes upon heating to produce phosphoric acid, polyphosphoric acid, and other substances, catalyzing the dehydration of the resin to form a dense char layer; modified magnesium hydroxide decomposes upon heating to absorb a large amount of heat, while releasing water vapor to dilute flammable gases. Both synergistically improve the flame retardant performance of the coating. In contrast, Comparative Example 1 did not undergo surface modification, resulting in severe agglomeration of the functional powder and the inability of the composite flame retardant to be uniformly distributed, making it difficult to exert its synergistic flame retardant effect, resulting in the lowest LOI value. Although Comparative Examples 2 and 3 used modified powder, due to improper dispersion methods or unstable microstructures, the powder dispersion uniformity was poor, and the LOI values ​​were still lower than those of the examples.

[0116] UL94 Vertical Burning Rating: Examples 1-4 all achieved a V-0 rating, characterized by short burning time and no dripping. Comparative Example 1, however, only achieved a V-2 rating, exhibiting significant dripping during combustion and easily triggering secondary combustion. Comparative Examples 2 and 3 achieved a V-1 rating, with slightly longer burning times than the examples. This is because the uniformly dispersed functional powder in the examples quickly forms a continuous, dense char layer during combustion, blocking the transfer of heat and oxygen and inhibiting the spread of combustion. In contrast, Comparative Example 1, due to powder agglomeration, has a discontinuous and poorly dense char layer, failing to effectively block combustion and resulting in dripping. The char layer integrity of Comparative Examples 2 and 3 is slightly inferior to that of the examples, therefore their burning ratings are lower.

[0117] Maximum Smoke Density (MSD): The MSD values ​​of Examples 1-4 were 32-45, significantly lower than 68 for Comparative Example 1, 56 for Comparative Example 2, and 52 for Comparative Example 3. This is because the modified magnesium hydroxide in the composite flame retardant not only has a flame-retardant effect but also inhibits smoke generation. Simultaneously, the uniformly dispersed powder restricts the diffusion of smoke within the coating. Comparative Example 1, due to powder agglomeration, has a weakened smoke suppression effect and the highest MSD value. Comparative Examples 2 and 3, due to insufficient powder dispersion uniformity, have poor smoke suppression effects, and their MSD values ​​are still higher than those of the Examples. The low smoke density characteristic can reduce the impact of smoke on personnel evacuation and equipment rescue in the event of a fire in the battery compartment, thus improving safety.

[0118] Table 3: Test Results of Thermal Insulation Performance of the Coatings in the Examples and Comparative Examples

[0119] Sample No. Thermal conductivity (W / (m-K)) Steel plate back surface temperature after heating at 800°C for 30 min (°C) Steel plate back surface temperature after heating at 800°C for 60 min (°C) Example 1 0.038 215 268 Example 2 0.032 198 245 Example 3 0.028 182 226 Example 4 0.035 205 252 Comparative Example 1 0.052 285 342 Comparative Example 2 0.045 256 310 Comparative Example 3 0.042 248 298

[0120] As shown in Table 3, the thermal insulation performance of Examples 1-4 is significantly better than that of Comparative Examples 1-3. The specific analysis is as follows:

[0121] Thermal conductivity: The thermal conductivity of Examples 1-4 is 0.028-0.038 W / (m·K), which falls into the category of low thermal conductivity materials; while the thermal conductivity of Comparative Example 1 is as high as 0.052 W / (m·K), and the thermal conductivity of Comparative Examples 2 and 3 are 0.045 W / (m·K) and 0.042 W / (m·K) respectively, all higher than that of the Examples. This is because the hollow insulating microspheres used in the Examples, after surface modification, can be uniformly dispersed in the base liquid. The vacuum structure inside the hollow microspheres can effectively block heat conduction and convection; at the same time, the batch gradient speed dispersion strategy avoids the hollow microspheres from breaking during the dispersion process, ensuring the performance of their thermal insulation properties. In Comparative Example 1, no surface modification was performed, and the hollow microspheres were prone to agglomeration and poor bonding with the base liquid interface. Heat was easily transferred through the agglomerates and interfacial gaps, resulting in an increased thermal conductivity. In Comparative Example 2, during high-speed dispersion, some hollow microspheres ruptured, the vacuum structure was destroyed, and the thermal insulation performance decreased. In Comparative Example 3, the "slow stirring" recombination step was omitted, and the system contained microbubbles and pores, increasing the heat transfer path and resulting in a thermal conductivity slightly higher than that of the examples.

[0122] High-temperature insulation effect: Under high-temperature heating conditions of 800℃, the back temperature of the steel plates corresponding to Examples 1-4 was significantly lower than that of Comparative Examples 1-3. After heating for 30 minutes, the back temperature of the steel plate in Example 3 was only 182℃, while the temperature of Comparative Example 1 reached 285℃; after heating for 60 minutes, the temperature of Example 3 was 226℃, while the temperature of Comparative Example 1 was 342℃. This is because the uniformly dispersed hollow insulating microspheres and composite flame retardant in the examples formed a synergistic insulating system: the hollow microspheres blocked heat conduction, and the dense carbon layer formed by the thermal decomposition of the composite flame retardant further blocked heat radiation. The combined effect of the two gave the coating an excellent high-temperature insulation effect. In contrast, due to powder agglomeration, the synergistic insulating system of Comparative Example 1 was destroyed, and heat was easily and quickly transferred to the back of the steel plate; due to powder dispersion uniformity or microstructure problems, the synergistic insulating effect of Comparative Examples 2 and 3 was poor, and the back temperature of the steel plate was still higher than that of the examples.

[0123] Based on the test results and analysis in Tables 1, 2, and 3, it can be seen that this invention successfully prepared a flame-retardant and heat-insulating coating for battery compartments with excellent basic performance, good flame retardant effect, good heat insulation performance, and strong stability through the synergistic effect of key technical features such as silane coupling agent surface modification treatment, batch gradient speed dispersion, "slow stirring and recombination-fast stirring and degassing" structuring treatment, and finished product stabilization treatment. The performance of Examples 1-4 is superior to that of Comparative Examples 1-3, which deviate from the key parameters of this invention, fully verifying the scientific nature and superiority of the technical solution of this invention. Among them, Example 2 has the best overall performance, with a Stormer viscosity of 100 KU, a fineness of 40 μm, an adhesion grade of 0, an LOI value of 36.2%, a UL94 rating of V-0, a thermal conductivity of 0.032 W / (m·K), a steel plate back temperature of only 245°C after heating at 800°C for 60 min, and a viscosity change rate of only 1.5% after 6 months of storage, making it the preferred embodiment of this invention.

[0124] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a flame-retardant and heat-insulating coating for a battery compartment, characterized in that, The method includes: Step (1): Under an inert atmosphere, the composite flame retardant powder and the pretreated hollow heat insulation microspheres are placed in a high-speed vortex mixer and dry-mixed at 1500~2000 rpm for 5~10 minutes to form a primary functional powder; then, the silane coupling agent is dissolved in anhydrous ethanol to form a treatment solution, which is sprayed onto the surface of the primary functional powder under continuous stirring, and then heat-treated at 80~100℃ for 1~2 hours to obtain a surface-modified functional core composite powder; Step (2): Add waterborne organosilicon-acrylic hybrid resin, toughening polymer latex, rheology modifier and dispersant to deionized water, and pre-disperse it at 500~800 rpm for 15~20 minutes using a high shear emulsifier to form a uniform and stable continuous phase base liquid. Step (3): The functional core composite powder obtained in step (1) is added to the continuous phase base liquid obtained in step (2) in three batches and dispersed using a high-speed disperser with program control. The dispersion program is as follows: after the first batch of powder is added, it is dispersed at 800~1000 rpm for 10 minutes; after the second batch of powder is added, it is dispersed at 1200~1500 rpm for 15 minutes; after the last batch of powder is added, it is dispersed at 600~800 rpm for 20 minutes. The material temperature is controlled below 40℃ throughout the process by circulating water bath, and finally a high solids content premixed slurry is obtained. Step (4): Transfer the high solids premixed slurry obtained in step (3) to a planetary mixer degasser. First, run it in a "slow mixing" mode with an orbital speed of 30-50 rpm and a rotation speed of 100-200 rpm for 1-2 hours to promote the reorganization and stabilization of the microstructure of the system. Then switch to a "fast mixing" mode with an orbital speed of 5-15 rpm and a rotation speed of 500-800 rpm, and simultaneously turn on the vacuum system. Run it in a vacuum of -0.095 MPa or higher for 15-30 minutes to completely eliminate bubbles and complete the final structuring, thus obtaining a flame-retardant and heat-insulating coating.

2. The method for preparing a flame-retardant and heat-insulating coating for a battery compartment according to claim 1, characterized in that, In step (1), the composite flame retardant is a compound of surface-coated ammonium polyphosphate and modified magnesium hydroxide, with a mass ratio of 2:1 to 3:1; the hollow heat-insulating microspheres are borosilicate glass microspheres with a particle size distribution D50 of 20 to 50 μm; and the silane coupling agent is γ-aminopropyltriethoxysilane, with an amount of 0.5% to 1.5% of the total mass of the functional powder.

3. The method for preparing a flame-retardant and heat-insulating coating for a battery compartment according to claim 1, characterized in that, In step (1), the inert atmosphere is nitrogen or argon; the mixing chamber of the high-speed vortex mixer is equipped with a cooling jacket, and the temperature of the chamber is maintained below 25°C during the mixing process; the heat treatment is carried out in a vacuum drying oven, and the heating rate is 2~5°C / minute.

4. The method for preparing a flame-retardant and heat-insulating coating for a battery compartment according to claim 1, characterized in that, In step (2), the solid content of the aqueous organosilicon-acrylic hybrid resin is 45%~55%, and the glass transition temperature Tg is -10~10℃; the toughening polymer latex is a core-shell structured acrylate emulsion; the rheology modifier is a hydrophobically modified alkali-swellable polyacrylate; the proportions of each component in the continuous phase base liquid by mass are: 30~40 parts of aqueous organosilicon-acrylic hybrid resin, 10~15 parts of toughening polymer latex, 0.3~0.8 parts of rheology modifier, 0.2~0.5 parts of dispersant, and 40~50 parts of deionized water.

5. The method for preparing a flame-retardant and heat-insulating coating for a battery compartment according to claim 4, characterized in that, In step (2), the dispersing agent is a compound of polyether-modified polydimethylsiloxane and low molecular weight sodium polyacrylate, with a mass ratio of 1:1 to 2:1; the rotor-stator gap of the high shear emulsifier is set to 0.2 to 0.5 mm.

6. The method for preparing a flame-retardant and heat-insulating coating for a battery compartment according to claim 1, characterized in that, In step (3), the mass ratio of the three batches of added functional core composite powder is first batch: second batch: last batch = 1:2:1; the dispersion disc of the program-controlled high-speed disperser is serrated, and the diameter is 1 / 3 to 1 / 2 of the diameter of the dispersion cylinder; the temperature control medium of the circulating water bath is ethylene glycol aqueous solution, and the temperature control accuracy is ±1℃.

7. The method for preparing a flame-retardant and heat-insulating coating for a battery compartment according to claim 1, characterized in that, In step (3), before each batch of powder is added, the viscosity and pH value of the continuous phase base liquid must be monitored online to ensure that the viscosity is between 300 and 500 mPa·s (25℃) and the pH value is maintained between 8.0 and 9.

0. If it exceeds the range, it must be adjusted by adding rheology modifier or pH adjuster before the next batch of powder can be added and dispersed.

8. The method for preparing a flame-retardant and heat-insulating coating for a battery compartment according to claim 1, characterized in that, In step (4), after the micro-nano structure maturation step is completed, the properties of the resulting coating must meet the following requirements: Stormer viscosity 90~110KU, specific gravity 1.35~1.50g / cm³, and fineness ≤50μm (Hegmann fineness meter).

9. A method for preparing a flame-retardant and heat-insulating coating for a battery compartment according to any one of claims 1 to 8, characterized in that, After step (4), step (5) is also included: the matured coating is left to stand and age in a constant temperature environment of 25±2℃ for 24~48 hours, then filtered with a 200-mesh vibrating screen and filled into an opaque, nitrogen-filled sealed container, and stored in the dark at 10~30℃.

10. A flame-retardant and heat-insulating coating for a battery compartment, characterized in that, It is prepared by the method described in any one of claims 1-9 for a flame-retardant and heat-insulating coating for a battery compartment.

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