Coating composition

Abstract

The present invention provides a powder coating composition, preferably an intumescent powder coating composition, the composition comprising: (i) a binder system comprising a binder and a curing agent; wherein the binder is selected from epoxy resin, polyester resin or a combination thereof; (ii) an intumescent component comprising an acid-generating agent, preferably ammonium polyphosphate, and optionally an intumescent agent and / or a carbon donor compound; and (iii) a charging agent comprising carbon fibers.

Description

[0001] introduction

[0002] This invention relates to powder coating compositions, and preferably intumescent powder coating compositions, comprising a binder system, an intumescent component, and a charging agent containing carbon fibers. The invention also relates to containers containing the composition and methods for preparing the composition. Furthermore, the invention relates to coatings containing the composition, substrates coated with the composition, and methods for coating substrates with the composition.

[0003] The present invention also relates to a coating system comprising a primer layer, an expansion layer, and a topcoat layer, wherein the expansion layer comprises the powder coating composition as described above. The present invention further relates to a method for coating a substrate with the coating system, and a kit for preparing the coating system.

[0004] Furthermore, the present invention relates to a battery pack comprising a battery assembly, wherein the battery pack has a coating formed on at least one surface by the coating system. Another aspect of the invention is the use of the coating system for forming a fire-resistant and / or heat-insulating coating on at least one surface of the battery pack. Background Technology

[0005] Driven by growing demand for more environmentally friendly transportation, particularly those with reduced CO2 emissions, electric vehicles have become one of the fastest-growing industries in recent years. Batteries are the heart of electric vehicles.

[0006] Electric vehicles (such as electric cars) typically include a battery pack, which is an assembly comprising multiple battery cells. The battery cells may be arranged in different configurations, but are interconnected to provide the overall battery assembly. Typically, a battery pack includes the battery assembly as well as modules and mounting hardware for holding the battery cells.

[0007] One of the main risks associated with electric vehicles is fire. For example, a fire can occur in the event of a vehicle accident or electrical failure. In this situation, the battery pack may catch fire and burn suddenly. Damaged cells within the battery pack's battery components may also experience uncontrolled increases in temperature and pressure, an effect known as "thermal runaway."

[0008] Naturally, electric vehicle manufacturers are developing technologies to reduce the risks associated with battery pack fires and thermal runaway. These technologies include coatings for battery packs and / or battery pack components that reduce the risk of flame spread in the event of a fire and heat transfer in the event of thermal runaway. Such coatings, for example, can increase the time available for passengers to escape from the vehicle before a catastrophic event occurs. However, at the same time, the demand for energy density in batteries used in the transportation industry is increasing, which means that the internal space of the battery pack is limited. There is a clear conflict between providing effective fire-resistant coverings for battery packs and the need to minimize their size.

[0009] Currently available solutions are not ideal. Heat- and fire-resistant materials such as mica sheets, fiberglass sheets, and ceramic blankets can only provide localized coverage of the battery pack. Adhesives tend to be provided in liquid form, and achieving a consistent coating of suitable thickness within a practical timeframe is challenging, for example, by avoiding long drying times. Solvent-based liquid-expanding coatings are fundamentally undesirable due to the presence of environmentally harmful VOCs and require significant expansion space (e.g., 50-100 times the original thickness) to effectively prevent fire spread.

[0010] Powder coatings are environmentally friendly, containing no VOCs. Furthermore, intumescent powder coatings tend to require significantly less space (e.g., 10-30 times the original thickness) to achieve refractoriness. The challenge with intumescent powder coatings is that they need to be applied with a minimum thickness of 150 μm, and ideally 700 μm, and sometimes even 850 μm, to provide the desired refractoriness. The need for large coating thicknesses stems from the fact that, on the one hand, a relatively large amount of material is needed to compensate for the relatively reduced expansion that occurs upon contact with fire, and on the other hand, to prevent heat transfer to the substrate. The exact required thickness depends particularly on the desired level of refractoriness, such as how long it takes to take effect, and the materials present in the coating.

[0011] Traditional powder coating compositions typically use corona-charged guns for application, achieving coating thicknesses of 150-200 μm. The initial powder deposition rate is very low, meaning a significant amount of powder coating detaches from the substrate. As the powder is recycled through a recycling system, it tends to break down into finer particles, resulting in lower powder utilization as it becomes difficult to adhere particles smaller than 10 μm to the substrate. Furthermore, the electric field created when charged powder coating has already deposited on the substrate repels subsequent powder coatings from adhering to the already deposited powder, and at some point, no more powder can be deposited on the substrate. This is known as back ionization. Consequently, achieving thick powder coatings of approximately 700 μm or greater typically requires multiple spray and curing cycles, which is time-consuming and energy-intensive. While some charging agents (such as polyethylene glycol) can be used to increase the coating thickness achieved in each spraying step, their effectiveness is limited. Clearly, given the time and energy efficiency required, it is desirable to apply the coating in as few steps as possible, ideally in a single step.

[0012] In addition, during normal operation, both the interior and exterior of the battery pack are exposed to high temperatures and humidity. Therefore, another challenge for powder coatings used in this application is to provide fire resistance even when exposed to water (e.g., salt water and hot water). Finally, the powder coating should ideally protect the metals present in the battery pack from corrosion during the battery's lifespan (which can be 10 years). Summary of the Invention

[0013] From a first aspect, the present invention provides a powder coating composition, preferably an intumescent powder coating composition, the composition comprising:

[0014] (i) an adhesive system comprising an adhesive and a curing agent, wherein the adhesive is selected from epoxy resins, polyester resins, or combinations thereof;

[0015] (ii) an expanding component comprising an acidifying agent, preferably ammonium polyphosphate, and optionally an expanding agent and / or a carbon donor compound; and

[0016] (iii) A charging agent comprising carbon fiber.

[0017] In another respect, the present invention provides a method for preparing the powder coating composition as described above, and preferably an intumescent powder coating composition, the method comprising:

[0018] (i) A binder system, an intumescent component, and a charging agent are blended to form a mixture, wherein the binder system comprises a binder and a curing agent, wherein the binder is selected from epoxy resins, polyester resins, or combinations thereof, the intumescent component comprises an acid-generating agent (preferably ammonium polyphosphate) and optionally an intumescent agent and / or a carbon donor compound, and the charging agent comprises carbon fibers; and

[0019] (ii) The mixture is extruded to form granules.

[0020] In another respect, the present invention provides powder coating compositions as defined above, and preferably intumescent powder coating compositions, for use in coating substrates (preferably metal substrates, and still more preferably metal substrates pre-coated with a primer layer).

[0021] In another aspect, the present invention provides a method for coating a substrate (preferably a metal substrate) with a powder coating composition (preferably an intumescent powder coating composition) as defined above, the method comprising:

[0022] (i) applying the powder coating composition as defined above to the substrate, wherein preferably the substrate is pre-coated with a primer layer; and

[0023] (ii) Curing the powder coating composition to form a layer, preferably an expanded layer.

[0024] In another respect, the present invention provides a coating comprising a powder coating composition as defined above, preferably an intumescent powder coating composition, and preferably a cured coating.

[0025] In another respect, the present invention provides a substrate coated with a powder coating composition as defined above, preferably an intumescent powder coating composition or a coating as defined above, preferably a metal substrate.

[0026] In another respect, the present invention provides the use of powder coating compositions as defined above, and preferably intumescent powder coating compositions, in coating systems.

[0027] In another aspect, the present invention provides a method for coating a substrate, preferably a metal substrate, using a coating system, the method comprising:

[0028] (i) Applying a primer composition, preferably a powder primer composition, to the substrate and curing the composition to form a primer layer;

[0029] (ii) Applying the intumescent powder coating composition as defined above to the primer layer and curing the composition to form an intumescent layer; and

[0030] (iii) Apply the topcoat composition, preferably the powder topcoat composition, to the expanded layer and cure it to form the topcoat layer.

[0031] From another perspective, the present invention provides a coating system comprising three layers, preferably consisting of three layers, wherein the coating system comprises:

[0032] (i) A primer layer formed on a substrate, preferably a metal substrate;

[0033] (ii) an expanded layer formed on the primer layer, the expanded layer comprising the powder coating composition as defined above; and

[0034] (iii) A topcoat layer formed on the expanded layer.

[0035] In another aspect, the present invention provides a kit for preparing a coating system as defined above, the kit comprising:

[0036] (i) A first container containing a primer composition, preferably a powder primer composition;

[0037] (ii) a second container containing the intumescent powder coating composition as defined above; and

[0038] (iii) A third container containing a topcoat composition, preferably a powder topcoat composition.

[0039] In another respect, the present invention provides a container for containing an intumescent powder coating composition as described above.

[0040] In another respect, the present invention provides a battery pack including a battery assembly, wherein the battery pack has a coating formed on at least one surface, preferably an inner surface, and the coating is formed by a coating system as defined above.

[0041] In another respect, the present invention provides the use of the coating system as defined above for forming a fire-resistant and / or heat-insulating coating on at least one surface and preferably the inner surface of a battery pack, preferably an electric vehicle battery pack.

[0042] definition

[0043] As used herein, the term "powder coating composition" refers to a dry, free-flowing powder that forms a coating on a surface when applied thereto and heated, for example, for curing. Typically, the average diameter of the particles constituting the powder is 10–120 µm.

[0044] As used herein, the terms "fire-resistant" or "fireproof" coatings refer to coatings that can prevent or limit the rate of fire spread. One mechanism by which the coatings described herein work is by insulating the underlying substrate from heat when exposed to flames or high temperatures, i.e., from heat transfer, thereby protecting the substrate from exceeding a certain temperature or losing its mechanical strength. Therefore, the coatings are also described as providing thermal insulation.

[0045] As used herein, the term "binder system" refers to the overall combination of one or more binders and one or more curing agents present in a coating composition.

[0046] As used herein, the term "curing agent" refers to a compound that, when mixed with an adhesive, produces a cured or hardened coating by creating crosslinks within the polymer upon heating. Sometimes, a curing agent is simply referred to as a hardener.

[0047] As used herein, the terms “curing accelerator,” “accelerator,” and “catalyst” are used synonymously and refer to compounds that increase the rate of the curing reaction that causes a coating to cure or harden.

[0048] As used herein, the term "epoxy" refers to a triatomic cyclic ether.

[0049] As used herein, the term "epoxy" refers to a polymer or oligomer containing epoxy groups and / or modified epoxy groups. Epoxy adhesives will contain at least some epoxy groups. The terms "epoxy" and "epoxide" are used interchangeably.

[0050] As used herein, the term "solid epoxy resin" refers to an epoxy polymer that is solid at ambient temperature and pressure (25°C and 1 atm). Therefore, the term "solid" refers to the physical state of the epoxy adhesive.

[0051] As used herein, the phrase “epoxy equivalent weight” or “EEW” refers to the number of grams of epoxy resin required to provide 1 mole of epoxy groups. It is measured according to ASTM D-1652.

[0052] As used herein, the terms “polyester with carboxyl functional group,” “carboxylic acid polyester,” and “carboxylated polyester” refer to polymers containing ester (-COO-) linking groups and having COOH groups.

[0053] As used herein, the term "AV" or "acid value" refers to the number of mg KOH required to neutralize the base-active groups in 1 g of polymer, and the unit is (mg KOH / g polymer). Acid value can be determined according to ASTM standard test method D974.

[0054] As used herein, the term "expandable component" refers to one or more compounds that contribute to fire resistance and thermal insulation. Preferably, the expandable component includes compounds that expand upon exposure to heat and form a barrier layer that will insulate the structure beneath the coating from fire.

[0055] As used herein, the term acid-generating compound refers to a compound that decomposes to provide acid. It may also be referred to as an acid catalyst.

[0056] As used herein, the term expanding agent refers to a compound that typically produces gas through decomposition. It is used interchangeably with the term foaming agent.

[0057] As used herein, the term "carbon donor compound" refers to a compound that reacts with an acid to form carbonaceous material.

[0058] As used herein, the term "charger" refers to a material that reduces the electric field created by the deposited powder, thereby reducing the repulsion of subsequently coated powder, allowing more powder to be deposited on the substrate for a higher dry film structure.

[0059] As used in this article, the term "carbon fiber" refers to a bundle of crystalline carbon filaments, in which each filament is needle-like and typically has a diameter of 5-10 μm. Generally, carbon filaments are composed of carbon, therefore carbon fibers are composed of carbon.

[0060] As used herein, the term "coating system" refers to a multilayer coating.

[0061] As used herein, the term "primer layer" refers to a coating layer that is in direct contact with and adheres to the substrate.

[0062] As used in this article, the term "topcoat layer" refers to the coating layer that serves as the outermost or final layer.

[0063] As used herein, the term "filler" refers to solid particles. Fillers are typically incorporated into powder coating compositions to increase their volume. Sometimes, fillers are referred to as "increasers."

[0064] As used herein, the term "degassing agent" refers to a compound added to a composition to remove gases (e.g., air, water vapor) and / or promote gas dissolution to prevent the formation of pinholes or bubbles in the formed coating.

[0065] As used herein, the term "leveling agent" refers to a compound added to a powder coating composition during the melting phase to promote powder flow, for example by disrupting weak bonds between particles within the powder and / or by lubricating movement.

[0066] As used herein, the terms "flow additive" or "flow agent" refer to compounds added to powder coating compositions to reduce surface tension and decrease surface defects (such as craters, pinholes, and fish-eye cracks) and improve surface smoothness.

[0067] As used herein, the term "colored pigment" refers to a pigment added to a composition to provide color. Colored pigments include white pigments, such as TiO2.

[0068] As used herein, the term "rheology modifier" refers to a compound that improves the consistency uniformity and coatability of a coating composition.

[0069] As used herein, the term "reinforcing material" refers to a material that typically enhances the robustness of the coating film when it begins to expand under conditions of high temperature or fire, thereby providing longer-lasting protection to the substrate.

[0070] Unless otherwise specified, as used herein, the term “molecular weight” refers to weight-average molecular weight (Mw).

[0071] As used herein, when referring to particles, the term "spherical" encompasses both generally spherical and spherical particles. Generally spherical particles have the same dimensions in each of the x, y, and z dimensions, differing by ±1.2 mm, more preferably ±0.6 mm.

[0072] As used herein, the term “mean diameter” refers to the Z-mean diameter size as determined by using Malvern Mastersizer 3000 according to ISO 22412:2017.

[0073] As used in this article, the term D 50 This refers to the size when 50% of the particles have a diameter smaller than the recorded value.

[0074] Unless otherwise specified, as used herein, when referring to compositions (e.g., coating compositions), the term "weight % (wt%)" means the weight of the individual components in the composition relative to the total weight of the composition. The total weight % of any given coating composition is 100% by weight. Detailed Implementation

[0075] This invention relates to powder coating compositions, and preferably to intumescent powder coating compositions, said compositions comprising:

[0076] (i) an adhesive system comprising an adhesive and a curing agent; wherein the adhesive is selected from epoxy resins, polyester resins, or combinations thereof;

[0077] (ii) an expanding component comprising an acidifying agent, preferably ammonium polyphosphate, and optionally an expanding agent and / or a carbon donor compound; and

[0078] (iii) A charging agent comprising carbon fiber.

[0079] The powder coating compositions of the present invention advantageously produce coatings that can be applied to a thickness of up to 850 µm in a single application. In other words, the powder coating compositions of the present invention can be applied in a single step using a corona gun or a combination of a corona gun and a positive charge gun, followed by curing, to provide a thick coating. This is highly advantageous. Conventional powder coating compositions using a corona charging gun can typically only achieve a coating thickness of 150-200 µm, and to achieve greater coating thicknesses, such as 700 µm, multiple spray and curing cycles must be used. However, it has been unexpectedly discovered that the presence of carbon fibers as a charging agent in the powder coating compositions of the present invention overcomes this problem. It is believed that carbon fibers remove the charge from the deposited powder very quickly, enabling the powder coating to achieve a thickness of 850 µm in a single spray and curing process. Therefore, productivity is improved, and energy savings are achieved because less spraying and heating are required.

[0080] Another advantage of the powder coating composition of the present invention is that it forms a coating that moderately expands upon exposure to heat and / or fire, while still providing fire resistance. Thus, the coating of the present invention can expand to 10-30 times its original film thickness, compared to the 50 to 100 times typically seen with liquid-expanding coatings. This is particularly advantageous when the coating is used, for example, in battery packs where the space available for the coating and its expansion is very limited.

[0081] When the powder coating composition of the present invention is applied to a metal substrate with a coating thickness of 150-850 µm and exposed to a butane flame at a temperature typically of 800-1200°C for 30 minutes, the temperature on the back side of the metal substrate does not exceed 400°C. Therefore, in the presence of fire or high temperatures, the powder coating acts as a metal protective coating by preventing the metal temperature from rising excessively and / or preventing the metal from melting.

[0082] Another advantage of the powder coating composition and coating of the present invention is that, when present in the coating system, the system can withstand exposure to water, including salt water and hot water. This is particularly important when the coating system is used, for example, in EV battery packs (where the battery pack is typically exposed to both high temperature and high humidity conditions during daily use). Given that the expected lifespan of EV batteries is generally more than 10 years, it is crucial that the coating does not degrade under such conditions.

[0083] Powder Coating Composition

[0084] The powder coating composition of the present invention comprises a binder system, which includes a binder and a curing agent. The binder system produces a thermosetting plastic in which irreversible crosslinking exists between the binder and the curing agent, resulting in an insoluble polymer network.

[0085] Based on the total weight of the powder coating composition, the amount of the binder system (i.e., the combined binder and curing agent) present in the powder coating composition of the present invention is preferably 35-67% by weight, more preferably 40-60% by weight, and still more preferably 50-60% by weight.

[0086] The adhesive is selected from epoxy resin, polyester resin, or a combination thereof.

[0087] When the adhesive contains epoxy resin, the curing agent is preferably DICY or OTB.

[0088] In one embodiment, when the adhesive comprises a polyester resin, the curing agent is preferably an epoxy resin.

[0089] In another embodiment, when the adhesive comprises a polyester resin, the curing agent is preferably triglycidyl isocyanurate (TGIC) or β-hydroxyalkylamide (HAA).

[0090] Epoxy resin

[0091] The powder coating composition of the present invention may contain epoxy resin. The epoxy resin is preferably a solid epoxy resin.

[0092] The preferred epoxy equivalent weight (EEW) of the epoxy resin present in the powder coating composition of the present invention is 190-1950 g / eq, and more preferably 380 to 1000 g / eq.

[0093] There are two main types of epoxy resins: glycidyl-based epoxy resins and non-glycidyl-based epoxy resins. Some types of glycidyl-based epoxy resins include glycidyl ether epoxy resins, glycidyl ester epoxy resins, and glycidylamine epoxy resins. Some types of non-glycidyl-based epoxy resins include aliphatic epoxy resins and alicyclic epoxy resins.

[0094] Preferably, the solid epoxy resin present in the powder coating composition of the present invention comprises a glycidyl-based epoxy resin, and more preferably a glycidyl ether epoxy resin. Glycidyl ether epoxy resins are typically prepared by a condensation reaction of a dihydroxy compound with epichlorohydrin. Preferably, the dihydroxy compound is a bisphenol compound. Therefore, preferably, the epoxy resin is a bisphenol-based epoxy resin.

[0095] Representative examples of solid epoxy resins suitable for the powder coating compositions of the present invention include bisphenol A-based epoxy resins, bisphenol F-based epoxy resins, phenolic varnish-modified bisphenol A-based epoxy resins, isocyanate-modified bisphenol A epoxy resins, cresol-phenolic varnish-type epoxy resins, O-cresol epoxy resins, silane-modified bisphenol A epoxy resins, rubber-modified bisphenol A epoxy resins, organosilicon-modified bisphenol A epoxy resins, halogenated bisphenol A epoxy resins, and mixtures thereof. In preferred powder coating compositions, the solid epoxy resin is selected from bisphenol A-based epoxy resins, bisphenol F-based epoxy resins, phenolic varnish-modified bisphenol A-based epoxy resins, isocyanate-modified bisphenol A epoxy resins, cresol-phenolic varnish-type epoxy resins, O-cresol epoxy resins, brominated bisphenol A epoxy resins, and mixtures thereof. In particularly preferred powder coating compositions, the solid epoxy resin is selected from bisphenol A-based epoxy resins, phenolic varnish-modified bisphenol A-based epoxy resins, bisphenol F epoxy resins, isocyanate-modified bisphenol A epoxy resins, brominated bisphenol A epoxy resins, and mixtures thereof. Bisphenol A-based epoxy resins, phenolic varnish-modified bisphenol A-based epoxy resins, and mixtures thereof are particularly preferred.

[0096] The preferred solid epoxy resin (e.g., bisphenol A-based epoxy resin, phenolic varnish-modified bisphenol A-based epoxy resin) present in the powder coating composition of the present invention has an equivalent epoxy weight (EEW) of 190-1950 g / eq, preferably 190-1300 g / eq, more preferably 380-1300 g / eq, and still more preferably 380 to 1000 g / eq. EEW is considered to play an important role in the performance of the coating. Epoxy resins with relatively lower EEW tend to have lower viscosity and better wettability, and thus better adhesion, but too low an EEW leads to sagging and / or bubbles in the final coating. On the other hand, epoxy resins with relatively higher EEW tend to slow down the degassing of air in the coating during its curing. Furthermore, if the EEW of the epoxy resin is too low or too high, the composition is challenging to handle during coating, and the final coating produced by the composition tends to have a poor appearance.

[0097] The epoxy resins suitable for the powder coating compositions of the present invention are commercially available. Representative examples of suitable epoxy resins include KD-213, KD-214C, KD-242K, KD-2200, KD-242G, KD-243G, KD-2103, KD-214M, KD-2203, KD-2104, KD214L, KD-9002, KD-9003, KD-9004, KD-213C, KD-213H, YDB-400, DER6805, NPCN-704, DER 6224, DER 6225, DER 662E, KD-211G, DER 662UH, DER6635, DER 663U, DER 663UE, DER 664, DER 664U, DER 664UE, DER 672UD.ER 6510HT, YDCN-500-90P, BE501H, BE502L, BE502, BE503L, BE503, BE504, BE504H, BE505H, B E507, BEB-400YD-017, BE574P, BFE107, MOE-380, MOE-400, CNE202, CNE220, CNE220H, BE50 2S, BE503S, NPES-901, NPES-901H, NPES-902, NPES-902H, NPES-903K, NPES-903, NPES-903 H, NPES-904, NPES-303, NPES-904H, NPES-304, NPEB-400, NPES-907, NPCN-704 and NPER-450.

[0098] Based on the total weight of the powder coating composition, the amount of epoxy resin present in the powder coating composition of the present invention (e.g., when present in a pure epoxy binder system) is preferably 30-66% by weight, more preferably 43-62% by weight, and still more preferably 46-58% by weight.

[0099] Epoxy curing agent

[0100] The powder coating composition of the present invention includes a curing agent. When the binder present in the binder system contains an epoxy resin, the curing agent reacts with the epoxy resin during curing to form a coating, such as a film coating. Therefore, the curing agent is advantageous in providing coating compositions with acceptable curing times.

[0101] When the binder in the binder system contains epoxy resin, the curing agent present in the powder coating composition preferably includes dicyandiamide (DICY) or its salt, o-tolyl biguanide (OTB), phenolic curing agents, acid anhydrides, imidazole rings, imidazoleline rings, or imidazoleidine rings. More preferably, the curing agent includes DICY, OTB, phenolic curing agents, acid anhydrides (such as 1,2,4,5-phenyltetracarboxylic dianhydride (PMDA)), or imidazoleline rings (preferably 2-phenyl-2-imidazoline).

[0102] DICY is the most widely used crosslinking agent for epoxy powder coatings. It is a white, solid crystalline compound. The amino hydrogen present in the structure of DICY can react with the alkyl oxide ring of epoxy resin. DICY suitable for curing epoxy resins is commercially available. Representative examples of suitable DICYs include Thomas Swan's Casamid DMPF and Anqing F&F Chemicals' CP-1.

[0103] OTBs are derivatives of DICY that provide good solubility in epoxy resins. Commercially available OTBs for curing epoxy resins include Huntsman's HT2844, Anqing F&F Chemical's HT2855, and Thomas Swan's Casamid 710.

[0104] Phenolic curing agents are prepared by stepwise growth through the polymerization of phenol and aldehyde under conditions of phenol excess. They can also be prepared by the condensation of epoxy resin with a molar excess of phenolic compounds. Other methods exist for preparing phenolic end-capping materials for use as crosslinking agents in epoxy resins. Their hydroxyl equivalent weight is typically in the range of 230-260 g / eq. Commercially available phenolic curing agents suitable for curing epoxy resins include Kukdo's KD407 and KD410.

[0105] Low molecular weight acid anhydrides (such as phthalic anhydride, maleic anhydride, trimellitic anhydride, and pyromellitic dianhydride (PMDA)) can be used to cure epoxy resins. PMDA can also react with 2-phenylimidazoline to form matting curing agents for powders. These materials are generally commercially available.

[0106] The imidazoline ring can also be used as a curing agent for epoxy resins. A preferred curing agent for the powder coating compositions of the present invention includes 2-phenyl-2-imidazoline (CAS No.: 936-49-2). 2-phenyl-2-imidazoline suitable for the powder coating compositions of the present invention is commercially available, for example, under the trade name HC31 from Huangshan Huahui Technology Co., Ltd., under the trade name Vestagon B31 from Evonik Degussa Coatings & Colour, and under the trade name MB 31 from Huangshan Deping Chemical Co., Ltd.

[0107] It will be understood that the curing agent and epoxy resin need to react to allow the coating to cure. The appropriate amounts of curing agent and epoxy resin depend on the relative number of reactive groups, i.e., the epoxy groups in the epoxy resin and the amine / reactive groups in the curing agent.

[0108] Preferred curing agents for intumescent coating compositions and intumescent layers are DICY, OTB, 2-phenyl-2-imidazoline, and phenolic curing agents. More preferred curing agents are DICY, OTB, and 2-phenyl-2-imidazoline. Most preferred curing agents are DICY and OTB.

[0109] Generally, based on the amount of epoxy resin present, the amount of DICY or OTB curing agent present in the powder coating composition (in weight %) is preferably 1.5-10% by weight, more preferably 2.5-7% by weight, and still more preferably 3-5% by weight.

[0110] Generally, based on the amount of epoxy resin present, the amount of phenolic curing agent present in the powder coating composition (in weight %) is preferably 10-45% by weight, more preferably 15-40% by weight, and still more preferably 18-35% by weight.

[0111] Generally, based on the amount of epoxy resin present, the amount of anhydride curing agent present in the powder coating composition (in weight %) is preferably 3.5-8.5% by weight, more preferably 4-8% by weight, and still more preferably 4.6-7.5% by weight.

[0112] Generally, based on the amount of epoxy resin present, the amount of 2-phenyl-2-imidazoline curing agent present (in weight %) is preferably 3.0-8.0% by weight, more preferably 3.5-7.5% by weight, and still more preferably 4.0-7.0% by weight.

[0113] Preferably, if the curing agent and epoxy resin are mixed in a ratio such that the curing agent is present in a stoichiometric amount, the stoichiometric amount is calculated based on the number of reactive groups in the curing agent relative to the number of reactive groups present in the epoxy resin, and is 30-120%, more preferably 50-115%, and still more preferably 60-110%.

[0114] Polyester resin

[0115] The powder coating composition of the present invention may contain a polyester resin. When present, the polyester resin is preferably a carboxylated polyester resin, also known as a polyester having carboxyl functional groups, and more preferably a saturated carboxylated polyester resin.

[0116] The acid value of the carboxylated polyester resin present in the powder coating composition of the present invention is preferably 16-80 mgKOH / g, and will depend on the curing agent used.

[0117] The powder coating composition of the present invention can contain two types of carboxylated polyester resins: one that can be cured with TGIC or HAA, and the other that can be cured with epoxy resin. The latter produces a so-called hybrid resin in the binder system.

[0118] Polyester crosslinked with TGIC / HAA

[0119] The carboxylated polyester resin present in the powder coating composition is preferably derived from neopentyl glycol (NPG) and terephthalic acid (TPA) and / or isophthalic acid (IPA). These resins are referred to as outdoor resins. Typically, outdoor resins are cured using triglycidyl isocyanurate (TGIC) or β-hydroxyalkylamide (HAA) or derivatives thereof.

[0120] Typically, the polyester resin present in the powder coating composition of the present invention includes resins from Allnex, DSM, Shenjian, Khua, and Fenglin.

[0121] For example, when the weight ratio of polyester with an acid value of 16-26 mgKOH / g to TGIC is 96:4, suitable polyester resins include DSM's Uralac P3800, Allex's Crycoat 2491-2 and 2452-2, Shenjian's SJ4G, SJ4580 and SJ4868, Khua's GH4405 and GH4408, and Fenglin's FL-2031, FL2032 and FL2034.

[0122] For example, when the weight ratio of polyester with an acid value of 28-38 mgKOH / g to TGIC is 73:7, suitable polyester resins include Khua's GH2219, GH2205, and GH2208; Fenglin's FL-2011, FL-2013, and FL-2017; DSM's Uralac P2400, P5300, and P6300; Allnex's Crycoat 2441-2, 2430-0, and 2498-0; and Shenjian's SJ4E, SJ4ET, and SJ4868.

[0123] For example, when the weight ratio of polyester with an acid value of 46-58 mgKOH / g to TGIC is 90:10, suitable polyester resins include Shenjian's SJ4H, SJ4581 and SJ4803, Khua's GH-4403 and GH-4401, Fenglin's FL-2033, FL-2037 and FL2047, DSM's Uralac P2200, P2240 and P2244, and Allnex's Crycoat 2431-0 and 2490-2.

[0124] For example, when the curing agent is TGIC, the amount of polyester resin present in the powder coating composition is preferably 35-66% by weight, more preferably 43-62% by weight, and still more preferably 48-58% by weight, based on the total weight of the powder coating composition.

[0125] TGIC is the most important curing agent for carboxylated polyesters. It is the most common crosslinking agent for polyester powder coatings used in outdoor applications. Nissan's TEPIC-G, Hustman's PT810, and Huangshan Huahui's TGIC are commercially available in TGIG form.

[0126] Based on the weight of the polyester resin, the amount of TGIC present in the powder coating composition of the present invention is preferably 1.5-13% by weight, more preferably 2-11% by weight, and still more preferably 3-7.8% by weight.

[0127] For example, when the weight ratio of polyester with an acid value of 16-26 mgKOH / g to HAA is 96.5:3.5, suitable polyester resins present in the powder coating composition of the present invention include Khua's GH3301, Fenglin's FL3031 and FL-3032, DSM's Uralac P837, P821 and P836, Allnex's Crycoat 2691-2 and 2670-3, and Shenjian's SJ4B-2, SJ5800 and SJ5811.

[0128] For example, when the weight ratio of polyester with an acid value of 28-38 mgKOH / g to HAA is 95:5, suitable polyester resins present in the powder coating composition of the present invention include Khua's GH3320, GH-3322, and GH-3325; Fenglin's FL-3011 and FL-3012A; Uralac's P812, P855, and P865; Allex's Crycoat 4642-3, E04351, and E04365; and Shenjian's SJ5587 and SJ5701.

[0129] For example, when the weight ratio of polyester with an acid value of 46-58 mgKOH / g to HAA is 93:7, suitable polyester resins present in the powder coating composition of the present invention include Khua's GH4407, Fenglin's FL3033, DSM's Uralac P870 and P877, Allnex's Crycoat 2671-3 and 2655-6, and Shengjian's SJ5801 and SJ5807-4.

[0130] For example, when the curing agent is HAA, the amount of polyester resin present in the powder coating composition is preferably 37-66% by weight, more preferably 45-62% by weight, and still more preferably 50-58% by weight, based on the total weight of the powder coating composition.

[0131] HAA has been developed as an alternative to TGIC. HAA can refer to these three chemicals: N,N,N',N'-tetratetra(2-hydroxyethyl)hexamethylenediamide (EMS's Primid XL552, Nanhai Chemical's T-105), N,N,N',N'-tetratetra(2-hydroxypropyl)hexamethylenediamide (EMS's Primide 1260), or β-hydroxyalkylamide (EMS's Primid 4510). Preferably, N,N,N',N'-tetratetra(2-hydroxyethyl)hexamethylenediamide is used in the powder coating compositions of the present invention.

[0132] Based on the weight of the polyester resin, the amount of HAA present in the powder coating composition of the present invention is preferably 1.0-9.0% by weight, more preferably 1.5-7.5% by weight, and still more preferably 2.5-5.3% by weight.

[0133] Polyester cured with epoxy resin

[0134] BPA epoxy resins crosslinked with carboxylic acid-terminated polyester resins (e.g., Mn in the thousands) are called hybrid powder coatings. Their properties fall between epoxy and polyester resins, producing coatings with intermediate properties. They are largely derived from neopentyl glycol (NPG) and terephthalic acid (TPA), using smaller amounts of other monomers to adjust the Tg to the desired level and increase the degree of polymerization (fn) to greater than two. The acid value of the carboxylated polyester resin can vary, for example, between 28-80 mgKOH / g, depending on the polyester-to-epoxy ratio. The weight ratio of polyester to epoxy resin with an EEW value of 650-750 g / eq can be 50:50; 60:40; and 70:30.

[0135] For example, typical polyester resins (acid value 66-80 mg KOH / g) for 50:50 blended powder coating compositions include DSM's Uralac P5127 and P4055, Allnex's Crycoat 1514-2, 1540-0 and 1573-0, Shenjian's SJ3#-B, SJ3AT and SJ3301, Fenglin's FL-1050, FL-1054 and FL-1058, and Khua's GH-1150, GH-1156 and GH1159.

[0136] For example, typical polyester resins (acid value 45-60 mg KOH / g) for 60:40 blended powder coating compositions include DSM's Uralac P5065, P4260 and P6060, Allnex's Crycoat 1622-0, 1631-0 and 1696-0, Shenjian's SJ5A, SJ5BT-6 and SJ6711, Fenglin's FL-1060, FL-1064 and FL1067, and Khua's GH-1164, GH-1160 and GH-1261.

[0137] For example, typical polyester resins (acid values ​​of 28-38 mg KOH / g) for 70:30 blended powder coating compositions are Uralac P775, P5070 and P5170, Allnex Crycoat 1702-0, 1770-0 and 1781-0, Shenjian SJ6A, SJ6B and SJ7301, Khua GH-1171, GH-1172 and GH-1176, and Fenglin FL-1071, FL-1074 and FL-1176.

[0138] Based on the total weight of the powder coating composition, the amount of polyester resin present in the mixed system of the powder coating composition is preferably 15-60% by weight, more preferably 20-55% by weight, and still more preferably 25-49% by weight. Based on the total weight of the powder coating composition, the amount of epoxy resin present in the mixed system of the powder coating composition is preferably 4-40% by weight, more preferably 6-37% by weight, and still more preferably 8-33.5% by weight.

[0139] Expanded components

[0140] The powder coating composition of the present invention comprises an intumescent component, which includes an acid-generating agent. The acid-generating compound preferably comprises a phosphoric acid source, a sulfonic acid source, or a boric acid source. In other words, the acid-generating compound is preferably capable of generating phosphoric acid, sulfonic acid, or boric acid when exposed to heat, particularly at temperatures above 200°C.

[0141] Examples of acid-generating compounds include: sodium phosphate, potassium phosphate (e.g., potassium tripolyphosphate), ammonium phosphate (e.g., ammonium polyphosphate (APP), ammonium dihydrogen phosphate, diammonium hydrogen phosphate), sodium sulfate, potassium sulfate, ammonium sulfate, magnesium sulfate, p-toluenesulfonic acid, borates (e.g., ammonium pentaborate, zinc borate, sodium borate, lithium borate, aluminum borate, magnesium borate), borosilicate compounds, or any combination thereof.

[0142] In some instances, the acid-producing compounds include phosphate esters of polyhydroxy compounds, or ammonium phosphate (e.g., APP), or ammonium phosphate (melamine phosphate), or any combination thereof.

[0143] A particularly useful acid-generating compound is ammonium polyphosphate. APP compounds are polyphosphates with POP bonds, and can be represented by the following formula:

[0144] [NH4PO3] n

[0145] The average value of n is at least about 10. Particularly useful APP compounds in the coating compositions of the present invention include those with n values ​​> 1000. APPs suitable for the powder coating compositions of the present invention are commercially available from Exolit and may be Clariant's TMAP462, Hefei Zhongke and Ji'nan Jinyintai's APP, and JLS-APP from JLS Chemicals.

[0146] Based on the total weight of the intumescent components in the powder coating composition, the powder coating composition of the present invention preferably contains 27% to 100% by weight, more preferably 43-75% by weight of an acid-generating agent.

[0147] The intumescent component of the powder coating composition of the present invention preferably includes an intumescent agent (also known as a foaming agent). The intumescent agent produces a non-flammable gas, typically nitrogen, when exposed to fire or heat. The produced gas causes the coating to expand, forming a thicker protective layer.

[0148] Suitable examples of commercially available expanding agents include, but are not limited to, nitrogen-containing compounds such as glycine, melamine, melamine salts, melamine derivatives, urea, urea derivatives, dicyandiamide, guanidine, and isocyanurate derivatives, especially melamine. The melamine used in the coating compositions of this invention is commercially available from Rongteng Chemical, Sichuan Jiniang Chemical, Ji'nan Jinyintai Chemical, and Sichuan Meifeng Chemical.

[0149] Melamine derivatives include, for example: melamine-formaldehyde, hydroxymethylated melamine, hexamethoxymethyl melamine, melamine monophosphate, di-melamine phosphate, dihydromelamine phosphate, polyphosphate, melamine pyrophosphate, melamine cyanurate, melamine borate, melam (N2-(4,6-diamino-1,3,5-triazin-2-yl)-1,3,5-triazin-2,4,6-triamine), melem (2,5,8-triamino-1,3,4,6,7,9,9b-heptaazaphenalene), and melon (poly[8-amino-1,3,4,6,7,9,9b-heptaazaphenalene-2,5-diyl)imino).

[0150] Urea derivatives include, for example: N-alkylureas, such as methylurea; N,N′-dialkylureas, such as dimethylurea; and N,N,N′-trialkylureas, such as trimethylurea; guanylurea; guanylurea phosphate; formamide aminourea; guanylurea phosphate; 1,3-diaminourea; diurea; etc.

[0151] The isocyanurate derivatives of interest include tris(2-hydroxyethyl) isocyanurate (THEIC).

[0152] Boron-containing compounds that can be used as expanding agents in this invention include, but are not limited to, boric acid and borates such as ammonium pentaborate, zinc borate, sodium borate, lithium borate, aluminum borate, magnesium borate, and borosilicates.

[0153] Expanding agents may also include monomeric or polymeric compounds, such as mesolaclide, polylactic acid, polysulfone, polycarbonate, polyester, 1,1-diactivated vinyl compounds, or addition polymers of 1,1-diactivated vinyl compounds, or any combination thereof.

[0154] Physical expansion agents, such as expandable graphite and / or gas-doped expandable microspheres, can also be used.

[0155] Based on the total weight of the intumescent components in the powder coating composition, the powder coating composition preferably contains 0% to 64% by weight, more preferably 11% to 43% by weight of an intumescent agent.

[0156] The intumescent component of the powder coating composition of the present invention preferably comprises a carbon donor compound. The carbon donor compound preferably comprises an organic polyhydroxy compound (i.e., an organic polyol) and / or expandable graphite. For example, the carbon donor compound may be pentaerythritol, dipentaerythritol, tripentaerythritol, polysaccharides (e.g., starch, cellulose, glycogen, etc.), disaccharides (e.g., sucrose, lactose, maltose, etc.), monosaccharides (glucose, fructose, galactose, etc.), glycerol, or expandable graphite, or any combination thereof.

[0157] Preferably, the carbon donor is pentaerythritol or dipentaerythritol, especially pentaerythritol. Suitable pentaerythritols are commercially available from Guizhou Kailin Chemical, Hengyang Sanhua Chemical, Jiangsu Sanmu Material, and Anhui Jinhe Chemical.

[0158] Based on the total weight of the intumescent components of the powder coating composition, the powder coating composition preferably contains 0% to 64% by weight of a carbon donor compound, more preferably 11% to 43% by weight of a carbon donor compound.

[0159] Based on the total weight of the powder coating composition, the powder coating composition of the present invention preferably contains 25-63% by weight, more preferably 30-55% by weight, and still more preferably 35-50% by weight of an intumescent component (i.e., acid generator, intumescent agent, and / or carbon donor compound).

[0160] A particularly preferred coating composition of the present invention comprises an intumescent component, said intumescent component comprising ammonium polyphosphate and optionally melamine and / or pentaerythritol. More preferably, the coating composition of the present invention comprises an intumescent component comprising ammonium polyphosphate, melamine, and pentaerythritol.

[0161] Based on the total weight of the intumescent components in the powder coating composition, a preferred powder coating composition of the present invention contains 27-100% by weight, more preferably 43-75% by weight, of ammonium polyphosphate.

[0162] Based on the total weight of the intumescent components in the powder coating composition, another preferred powder coating composition of the present invention contains 0-64% by weight, more preferably 11-43% by weight of melamine.

[0163] Based on the total weight of the intumescent components of the powder coating composition, another preferred powder coating composition of the present invention contains 0-64% by weight, and more preferably 11-43% by weight, pentaerythritol.

[0164] In a preferred powder coating composition of the present invention, based on the weight of the expanding component, the weight ratio of APP:melamine:pentaerythritol is: APP 27-100 wt%:melamine 0-64 wt%:pentaerythritol 0-64 wt%. More preferably, based on the weight of the expanding component, the weight ratio of APP:melamine:pentaerythritol is: APP 43-75 wt%:melamine 11-43 wt%:pentaerythritol 11-43 wt%.

[0165] charging agent

[0166] To achieve greater coating thickness in a single application, the powder coating composition of the present invention includes a charging agent comprising carbon fibers. By incorporating carbon fibers, the charge present on previously deposited powder coating particles can be removed very quickly, thereby making subsequent powder adhere more easily to the powder.

[0167] The length of the carbon fibers present in the powder coating composition of the present invention is preferably 0.1-2 mm, more preferably 0.2-1.6 mm, and still more preferably 0.2-1.2 mm. The diameter of the carbon fibers present in the powder coating composition of the present invention is preferably 1-20 µm, more preferably 3-15 µm, and still more preferably 5-10 µm.

[0168] The resistivity of the carbon fibers present in the powder coating composition of the present invention is preferably 1.0 × 10⁻⁶. -7 -1.0×10 -2 Ω·cm, more preferably 1.0×10 -6 -1.0×10 -2 Ω·cm, and still more preferably 1.0×10 -5 -1.0×10 -2 Ω·cm.

[0169] The carbon fibers suitable for the powder coating compositions of the present invention can be obtained, for example, from Toray, BOS and Lishuo.

[0170] As mentioned above, it is important to remove the charge carried by the particles already deposited on the substrate, thereby avoiding back ionization. Commonly used charging materials are hydroxyl-containing materials such as polyethylene glycol (PEG) 6000-8000, glyceryl monostearate, barium titanate, etc. These materials are usually dispersed at the molecular level in the coating, making the charge removal rate very slow. Without being bound by theory, it is believed that the addition of carbon fibers, as described above, allows the charge present on the previously coated powder coating particles to be removed very quickly, thereby making it easier for subsequently arriving particles to adhere to the already coated powder. Optionally, the powder coating composition of the present invention may contain polyethylene glycol (PEG) 6000-8000, glyceryl monostearate, and / or barium titanate. However, preferably, the powder coating composition of the present invention does not contain polyethylene glycol (PEG) 6000-8000, glyceryl monostearate, or barium titanate.

[0171] Preferably, based on the total weight of the powder coating composition, the amount of carbon fiber in the powder coating composition of the present invention is 2-15% by weight, more preferably 3-8% by weight, and still more preferably 3-7% by weight.

[0172] When the powder coating begins to expand, in addition to providing charge removal, the carbon fibers present in the powder coating composition also act as reinforcing fibers. Preferably, no other reinforcing fibers are used besides carbon fibers. Therefore, preferably, the powder coating composition of the present invention does not contain other inorganic or organic fibers. Typical inorganic fibers include: carbide fibers, such as boron carbide fibers, silicon carbide fibers, niobium carbide fibers, etc.; nitride fibers, such as silicon nitride fibers; boron-containing fibers, such as boron fibers, boride fibers; silicon-containing fibers, such as silicon fibers, alumina-borosilicate fibers, E-glass (non-alkali aluminum borate) fibers, C-glass (non-alkali or low-alkali sodium-calcium-aluminum borosilicate) fibers, A-glass (alkali-sodium-calcium-silicate) fibers, S-glass fibers, inorganic glass fibers, quartz fibers, etc. Glass fibers may include E-glass fibers, C-glass fibers, A-glass fibers, S-glass fibers, etc.

[0173] Colored pigments

[0174] The powder coating composition of the present invention works well without any pigments, but preferably contains at least one colored pigment for aesthetic reasons. The colored pigment can be inorganic or organic.

[0175] Representative examples of inorganic colored pigments suitable for inclusion in the powder coating compositions of the present invention include titanium dioxide, ferro-manganese black, iron oxide red, black pigments, yellow pigments, chromium pigments (e.g., copper-chromium), carbon black, and combinations thereof.

[0176] Representative examples of organic pigments suitable for inclusion in the powder coating compositions of the present invention include phthalocyanine, azo, dioxazine, perylene, anthraquinone, thioindigo, isodibenzanthrone, triphendioxane, quinacridone pigments, vat dye pigments, and combinations thereof.

[0177] Preferred colored pigments used in the powder coating compositions of the present invention are selected from titanium dioxide, iron-manganese black, carbon black, organic red pigments, organic yellow pigments, organic blue pigments, ultramarine blue, and organic green pigments. More preferably, the powder coating compositions of the present invention contain iron-manganese black.

[0178] Suitable colored pigments are commercially available, such as NTR-606, Beablack 2669F, Beablack 2870F, Red 122, DPP Red SR2P, Yellow 139, Sudafest Blue 2789, Blue 51, Green 2730K, and Iron Manganese Black.

[0179] Generally, colored pigments should be included in the powder coating composition in the minimum amount required to provide the desired color. The required amount of colored pigment depends in part on the type of pigment. A technician will be able to determine the appropriate amount for different types of pigments.

[0180] When present, the amount of colored pigment present in the powder coating composition of the present invention is preferably 0-15% by weight, more preferably 0-10% by weight, and still more preferably 0-5% by weight, based on the total weight of the intumescent powder coating composition.

[0181] Preferred powder coating compositions

[0182] A preferred powder coating composition of the present invention comprises:

[0183] (a) An adhesive system comprising an adhesive and a curing agent, selected from the group consisting of: an epoxy resin and a curing agent for said epoxy resin, a polyester resin cured with an epoxy resin, or a polyester resin cured with triglycidyl isocyanurate (TGIC) or β-hydroxyalkylamide (HAA).

[0184] (b) an expandable component, said expandable component comprising ammonium polyphosphate and preferably comprising melamine and / or pentaerythritol; and

[0185] (c) A charging agent containing carbon fibers.

[0186] Another preferred powder coating composition of the present invention comprises:

[0187] (a) 35-67% by weight of an adhesive system comprising a binder and a curing agent, selected from the group consisting of: epoxy resin and curing agent for said epoxy resin, polyester resin cured with epoxy resin, or polyester resin cured with triglycidyl isocyanurate (TGIC) or β-hydroxyalkylamide (HAA).

[0188] (b) 25-63% by weight of an expandable component, said expandable component comprising ammonium polyphosphate and preferably comprising melamine and / or pentaerythritol; and

[0189] (c) 2-15% by weight of carbon fiber,

[0190] All weight percentages are based on the total weight of the coating composition.

[0191] In a preferred powder coating composition of the present invention, the amount of carbon fiber present is 2-15% by weight, preferably 3-8% by weight, and more preferably 3-7% by weight, based on the total weight of the powder coating composition.

[0192] Another preferred powder coating composition of the present invention comprises:

[0193] (a) An adhesive system comprising an epoxy resin and a curing agent for the epoxy resin;

[0194] (b) an expandable component, said expandable component comprising ammonium polyphosphate and preferably comprising melamine and / or pentaerythritol; and

[0195] (c) A charging agent containing carbon fibers.

[0196] In a preferred powder coating composition comprising an epoxy resin according to the present invention, the epoxy resin is selected from bisphenol A epoxy resins, bisphenol F epoxy resins, phenolic varnish-modified bisphenol A epoxy resins, and mixtures thereof.

[0197] In a preferred powder coating composition comprising epoxy resin of the present invention, the equivalent epoxy weight (EEW) of the epoxy resin is 190-1950 g / eq, preferably 190-1300 g / eq, more preferably 380-1300 g / eq, and still more preferably 380 to 1000 g / eq.

[0198] In a preferred powder coating composition comprising epoxy resin of the present invention, the curing agent is selected from DICY, OTB, 2-phenyl-2-imidazoline, phenolic curing agents, or acid anhydrides. In a more preferred powder coating composition comprising epoxy resin of the present invention, the curing agent is selected from DICY, OTB, or 2-phenyl-2-imidazoline, preferably DICY or OTB.

[0199] Another preferred powder coating composition of the present invention comprises:

[0200] (a) 35-67% by weight of an adhesive system comprising an epoxy resin and a curing agent, wherein the epoxy resin is selected from bisphenol A epoxy resins, bisphenol F epoxy resins, phenolic varnish-modified bisphenol A epoxy resins, and mixtures thereof; and the curing agent is selected from DICY, OTB, 2-phenyl-2-imidazoline, phenolic curing agents, or acid anhydrides.

[0201] (b) 25-63% by weight of an expandable component, said expandable component comprising ammonium polyphosphate and preferably comprising melamine and / or pentaerythritol; and

[0202] (c) 2-15% by weight of carbon fiber,

[0203] All weight percentages are based on the total weight of the coating composition.

[0204] Another preferred powder coating composition of the present invention comprises:

[0205] (a) An adhesive system comprising polyester resin and a curing agent, wherein the curing agent is epoxy resin, and the weight ratio of polyester resin to epoxy resin is 50:50, 60:40 or 70:30.

[0206] (b) an expandable component, said expandable component comprising ammonium polyphosphate and preferably comprising melamine and / or pentaerythritol; and

[0207] (c) A charging agent containing carbon fibers.

[0208] Another preferred powder coating composition of the present invention comprises:

[0209] (a) 35-67% by weight of an adhesive system comprising polyester resin and a curing agent, wherein the curing agent is an epoxy adhesive resin, wherein the weight ratio of polyester resin to epoxy resin is 50:50, 60:40 or 70:30.

[0210] (b) 25-63% by weight of an expandable component, said expandable component comprising ammonium polyphosphate and preferably comprising melamine and / or pentaerythritol; and

[0211] (c) 2-15% by weight of a charging agent containing carbon fiber,

[0212] All weight percentages are based on the total weight of the coating composition.

[0213] Another preferred powder coating composition of the present invention comprises:

[0214] (a) An adhesive system comprising polyester resin and a curing agent, wherein the curing agent is TGIC, and the weight ratio of polyester resin to TGIC is from 90:10 to 96.5:3.5;

[0215] (b) an expandable component, said expandable component comprising ammonium polyphosphate and preferably comprising melamine and / or pentaerythritol; and

[0216] (c) A charging agent containing carbon fibers.

[0217] Another preferred powder coating composition of the present invention comprises:

[0218] (a) 35-67% by weight of an adhesive system comprising polyester resin and a curing agent, wherein the curing agent is TGIC, and the weight ratio of polyester resin to TGIC is from 90:10 to 96.5:3.5.

[0219] (b) 25-63% by weight of an expandable component, said expandable component comprising ammonium polyphosphate and preferably comprising melamine and / or pentaerythritol; and

[0220] (c) 2-15% by weight of a charging agent containing carbon fiber,

[0221] All weight percentages are based on the total weight of the coating composition.

[0222] Another preferred powder coating composition of the present invention comprises:

[0223] (a) An adhesive system comprising polyester resin and a curing agent, wherein the curing agent is HAA, and the weight ratio of polyester resin to HAA is from 92.5:7.5 to 97.5:2.5;

[0224] (b) an expandable component, said expandable component comprising ammonium polyphosphate and preferably comprising melamine and / or pentaerythritol; and

[0225] (c) A charging agent containing carbon fibers.

[0226] Another preferred powder coating composition of the present invention comprises:

[0227] (a) 35-67% by weight of an adhesive system comprising polyester resin and a curing agent, wherein the curing agent is HAA, and the weight ratio of polyester resin to HAA is from 92.5:7.5 to 97.5:2.5;

[0228] (b) 25-63% by weight of an expandable component, said expandable component comprising ammonium polyphosphate and preferably comprising melamine and / or pentaerythritol; and

[0229] (c) 2-15% by weight of a charging agent containing carbon fiber,

[0230] All weight percentages are based on the total weight of the coating composition.

[0231] The powder coating composition of the present invention may also contain other components that a person skilled in the art deems necessary for a particular coating, such as colored pigments.

[0232] Method for preparing powder coating compositions

[0233] The present invention also relates to a method for preparing the powder coating composition as described above, and preferably an intumescent powder coating composition, the method comprising:

[0234] (i) A binder system, an intumescent component, and a charging agent are blended to form a mixture, wherein the binder system comprises a binder and a curing agent, wherein the binder is selected from epoxy resins, polyester resins, or combinations thereof, the intumescent component comprises an acid-generating agent, preferably ammonium polyphosphate, and optionally an intumescent agent and / or a carbon donor compound, and the charging agent comprises carbon fibers; and

[0235] (ii) The mixture is extruded to form granules.

[0236] The extruded particles can take any form, such as spherical particles, fragments, or flakes. A preferred method of the invention further includes milling the extruded particles to form a powder. Milling can be performed in any conventional mill to achieve the particle size most suitable for powder coating. Other preferred methods of the invention include sieving the milled particles.

[0237] Therefore, the preferred method of the present invention includes:

[0238] (i) A binder system, an intumescent component and a charging agent are blended to form a mixture, wherein the binder system comprises a binder and a curing agent, wherein the binder is selected from epoxy resins, polyester resins or combinations thereof, the intumescent component comprises an acid-generating agent, preferably ammonium polyphosphate and optionally an intumescent agent and / or a carbon donor compound, and the charging agent comprises carbon fibers;

[0239] (ii) Extruding the mixture to form granules;

[0240] (iii) Grinding the extruded particles to form ground particles; and

[0241] (iv) Screening the milled particles.

[0242] After grinding, it is preferable to sieve to remove coarse particles.

[0243] Optionally, a fluidizing agent (e.g., pyrolytic silica or alumina) may be added during milling and / or sieving.

[0244] Any conventional mixing, extrusion, and milling method can be used. Preferred extrusion conditions are conventional and will generally be maintained at low temperatures, such as below 140°C, to avoid premature curing. Particle size distribution D of the powder coating composition. 50 Preferably in the range of 10 to 120 µm, and still more preferably in the range of 15 to 100 µm. Preferred particle size D 50 The particle size should be at least 30 or 80 µm, and advantageously not exceeding 80 µm, for example, 40 to 70 µm. Typically, the particle size can be determined using a Malvern particle size analyzer.

[0245] Methods for coating substrates

[0246] The present invention also provides a method for coating a substrate, preferably a metal substrate, with the powder coating composition as described above, preferably an intumescent powder coating composition, the method comprising:

[0247] (i) applying the powder coating composition as described above to the substrate, wherein preferably the substrate is pre-coated with a primer layer; and

[0248] (ii) Curing the powder coating composition to form a layer, preferably an expanded layer.

[0249] The powder coating composition of the present invention can be applied to a substrate, optionally pre-coated with a primer, by any conventional powder coating method (e.g., electrostatic spraying). A cold substrate can be coated, for example, in a spray booth. To achieve a high coating thickness of, for example, 850 µm, a positive charge gun (e.g., a tribo gun) that imparts a positive charge to the powder coating through friction between the powder and the gun wall, or the newly developed positive charge gun GM04 by Swiss company Gema, can be used in combination with a corona gun. Preferably, a tribo gun or other positive charge gun is used before corona gun spraying. The powder coating layer, preferably an expanded layer, can optionally be applied using a positive charge gun to achieve a powder thickness of 0-200 µm, followed by corona gun coating to achieve a total coating thickness of, for example, up to 850 µm. After coating, the powder coating composition is cured, for example, in a convection oven, an infrared oven, or a combination of both.

[0250] Once the substrate is coated with the powder coating composition of the present invention, the coating is cured. Curing can be carried out by heating, for example in one of the ovens described above, which allows the particles to melt, fuse, and solidify. Optionally, the powder coating composition of the present invention can be cured by placing the substrate in a post-cure oven.

[0251] Preferably, the dry thickness of the powder coating layer, and more preferably the expanded layer, is 150 to 850 µm, such as 200 to 850 µm, particularly 250 to 850 µm.

[0252] Therefore, the present invention also relates to a coating, preferably a cured coating, the coating comprising the powder coating composition as described above, and preferably an intumescent powder coating composition.

[0253] In addition, the present invention also relates to a substrate, preferably a metal substrate, coated with the powder coating composition as described above, and preferably an intumescent powder coating composition or coating.

[0254] Coating system

[0255] The present invention also relates to a coating system comprising an inflatable layer, said inflatable layer comprising or formed of the powder coating composition as described above. Preferably, the coating system comprises three layers, and more preferably consists of three layers, wherein said coating system comprises:

[0256] (i) A primer layer formed on a substrate, preferably a metal substrate;

[0257] (ii) an expanded layer formed on the primer layer, the expanded layer comprising the powder coating composition as described above; and

[0258] (iii) A topcoat layer formed on the expanded layer.

[0259] As mentioned above, the interior and exterior of the battery pack will be exposed to both high temperatures and temperature variations, as well as high humidity, during use. Therefore, it is important to protect the metals present in the battery pack, such as the battery components, from corrosion during their operational life. This is preferably achieved using a coating system that includes a primer layer, a topcoat layer, and an expansion layer.

[0260] The primer layer is applied to the substrate (typically metal) before (i.e., below) the intumescent layer, protecting it from corrosion and providing good adhesion to both the substrate and the overlying intumescent layer. These properties are primarily achieved through an adhesive system comprising either pure epoxy resin cured with an epoxy curing agent or epoxy resin cured with a carboxylic acid polyester. The topcoat is applied over the intumescent layer, sealing and protecting it, including its water-sensitive components. Under the protection of the topcoat, the fire resistance of the coating system can be maintained for an extended period.

[0261] In fact, by combining the intumescent layer with the primer and topcoat layers in the coating system, the fire resistance of the system remains unchanged even when the resulting coating system is exposed to water, high temperatures, or temperature cycling (i.e., varying conditions that may occur within the battery pack). Therefore, by providing a coating system comprising a primer layer, an intumescent layer, and a topcoat layer, a three-layer powder coating system is provided that is corrosion-resistant, water-resistant, and fire-resistant, and does not loosen, significantly expand, or blister when exposed to water, even at high temperatures.

[0262] Therefore, the present invention provides a coating system, preferably a powder coating system, comprising a primer layer, an expansion layer, and a topcoat layer, the coating system providing all the properties required for a fire-resistant and heat-resistant system for use in / on battery packs and similar energy storage devices or systems.

[0263] The primer powder coating composition is preferably applied to the substrate with a thickness of 30-300 µm, more preferably 50-250 µm, and most preferably 60-200 µm. Therefore, the dry thickness of the primer layer is preferably 30-300 µm, more preferably 50-250 µm, and most preferably 60-200 µm.

[0264] The intumescent powder coating composition is preferably applied over a cured primer layer with a thickness of 150-850 µm, preferably 200-850 µm, and most preferably 250-850 µm. Preferably, the dry thickness of the intumescent layer is 150-850 µm, preferably 200-850 µm, and most preferably 250-850 µm. Uniquely, the intumescent coating composition of the present invention can achieve a coating thickness of 850 µm using a single spraying and curing process. Compared to conventional powder coating compositions and coating methods, the intumescent powder coating composition of the present invention exhibits superior performance, which contributes to energy savings and increased productivity.

[0265] The topcoat composition is preferably applied over the cured and expanded layer with a thickness of 60-300 µm, more preferably 90-300 µm, and most preferably 120-300 µm. Therefore, the dry thickness of the topcoat layer is preferably 60-300 µm, more preferably 90-300 µm, and most preferably 120-300 µm.

[0266] For example, the total dry thickness of a three-layer (primer, expander and topcoat) coating system is preferably 240 µm to 1450 µm, more preferably 340-1400 µm, and even more preferably 430-1350 µm.

[0267] Primer coating composition and primer layer

[0268] The primer layer provides good adhesion of the coating to the substrate, preferably a metal substrate, and also acts as a corrosion barrier, protecting the substrate from corrosion.

[0269] The coating composition used to prepare the primer layer is referred to herein as a primer coating composition. It is preferably a powder coating composition. Preferably, the primer coating composition and primer layer comprise: a binder system comprising a binder selected from epoxy resins, polyester resins, or combinations thereof, and a curing agent. Preferably, the primer coating composition and primer layer comprise fillers.

[0270] Therefore, in the preferred primer coating composition and preferred coating system of the present invention, the primer coating composition and primer layer comprise:

[0271] (i) an adhesive system comprising an adhesive selected from epoxy resins, polyester resins, or combinations thereof, and a curing agent; and

[0272] (ii) Optional filler, preferably feldspar or barium sulfate.

[0273] Based on the total weight of the primer coating composition, the amount of the binder system (i.e., the combined binder resin and curing agent) present in the primer coating composition is preferably 40-90% by weight, more preferably 45-80% by weight, and still more preferably 50-70% by weight.

[0274] The primer coating composition is preferably prepared by a method similar to that described above regarding the powder coating composition of the present invention.

[0275] Epoxy resin

[0276] The primer coating composition and primer layer preferably contain epoxy resin. The epoxy resin is preferably a solid epoxy resin. The epoxy resin present in the primer coating composition and primer layer may be the same as or different from the epoxy resin used in the intumescent powder coating composition and topcoat composition.

[0277] The epoxy equivalent weight (EEW) of the epoxy resin present in the primer coating composition and primer layer is preferably 190-1950 g / eq, more preferably 380 to 1000 g / eq, and still more preferably 380-900 g / eq.

[0278] There are two main types of epoxy resins: glycidyl-based epoxy resins and non-glycidyl-based epoxy resins. Some types of glycidyl-based epoxy resins include glycidyl ether epoxy resins, glycidyl ester epoxy resins, and glycidylamine epoxy resins. Some types of non-glycidyl-based epoxy resins include aliphatic epoxy resins and alicyclic epoxy resins.

[0279] Preferably, the solid epoxy resin present in the primer coating composition and primer layer comprises glycidyl-based epoxy resin, and more preferably glycidyl ether epoxy resin. Glycidyl ether epoxy resin is typically prepared by the condensation reaction of a dihydroxy compound with epichlorohydrin. Preferably, the dihydroxy compound is a bisphenol compound.

[0280] Representative examples of solid epoxy resins suitable for the primer compositions and primer layers of the present invention include bisphenol A-based epoxy resins, bisphenol F-based epoxy resins, phenolic varnish-modified bisphenol A-based epoxy resins, isocyanate-modified bisphenol A epoxy resins, cresol-phenolic varnish-type epoxy resins, O-cresol epoxy resins, silane-modified bisphenol A epoxy resins, rubber-modified bisphenol A epoxy resins, organosilicon-modified bisphenol A epoxy resins, halogenated bisphenol A epoxy resins, and mixtures thereof. In a preferred primer composition and primer layer, the solid epoxy resin is selected from bisphenol A-based epoxy resins, bisphenol F-based epoxy resins, phenolic varnish-modified bisphenol A-based epoxy resins, isocyanate-modified bisphenol A epoxy resins, cresol-phenolic varnish-type epoxy resins, O-cresol epoxy resins, brominated bisphenol A epoxy resins, and mixtures thereof. In a particularly preferred primer composition and primer layer, the solid epoxy resin is selected from bisphenol A-based epoxy resins, phenolic varnish-modified bisphenol A-based epoxy resins, bisphenol F epoxy resins, isocyanate-modified bisphenol A epoxy resins, brominated bisphenol A epoxy resins, and mixtures thereof. Bisphenol A-based epoxy resins, phenolic varnish-modified bisphenol A-based epoxy resins, brominated bisphenol A epoxy resins, and mixtures thereof are particularly preferred.

[0281] The preferred solid epoxy resin (e.g., bisphenol A-based epoxy resin, phenolic varnish-modified bisphenol A-based epoxy resin) present in the primer coating composition and primer layer of the present invention has an equivalent epoxy weight (EEW) of 190-1950 g / eq, more preferably 380-1000 g / eq, and still more preferably 380-900 g / eq. EEW is considered to play an important role in the performance of the coating. Epoxy resins with relatively lower EEW tend to have lower viscosity and better wettability, and thus better adhesion, but too low an EEW leads to sagging and / or bubbles in the final coating. On the other hand, epoxy resins with relatively higher EEW tend to slow down the degassing of air in the coating during its curing. Furthermore, if the EEW of the epoxy resin is too low or too high, the composition is challenging to handle during coating, and the final coating produced by the composition tends to have a poor appearance.

[0282] Suitable epoxy resins are commercially available. Representative examples of suitable epoxy resins include KD-213, KD-214C, KD-242K, KD-2200, KD-242G, KD-243G, KD-2103, KD-214M, KD-2203, KD-2104, KD214L, KD-9002, KD-9003, KD-9004, KD-213C, KD-213H, YDB-400, DER 6805, NPCN-704, DER6224, DER 6225, DER 662E, KD-211G, DER 662UH, DER 6635, DER 663U, DER 663UE, DER 664, DER 664U, DER 664UE, and DER 672U. 6510HT, YDCN-500-90P, BE501H, BE502L, BE502, BE503L, BE503, BE504, BE504H, BE505H, B E507, BEB-400YD-017, BE574P, BFE107, MOE-380, MOE-400, CNE202, CNE220, CNE220H, BE50 2S, BE503S, NPES-901, NPES-901H, NPES-902, NPES-902H, NPES-903K, NPES-903, NPES-903 H, NPES-904, NPES-303, NPES-904H, NPES-304, NPEB-400, NPES-907, NPCN-704 and NPER-450.

[0283] Based on the total weight of the primer coating composition, the primer coating composition preferably contains 30-67% by weight, more preferably 43-62% by weight, and still more preferably 46-58% by weight of epoxy resin.

[0284] Epoxy curing agent

[0285] The primer coating composition and primer layer also contain a curing agent. The curing agent reacts with the epoxy resin during curing to form a coating, such as a film coating. Therefore, the curing agent is advantageous in providing coating compositions with acceptable curing times.

[0286] The curing agent present in the primer coating composition and primer layer preferably comprises dicyandiamide (DICY) or a derivative thereof, OTB, phenolic curing agents, acid anhydrides, imidazole rings, or imidazole rings. More preferably, the curing agent present in the primer coating composition and primer layer comprises DICY, OTB, phenolic curing agents, acid anhydrides, or imidazole rings.

[0287] DICY is the most widely used crosslinking agent for epoxy powder coatings. It is a white, solid crystalline compound. The amino hydrogen present in the structure of DICY can react with the alkyl oxide ring of epoxy resin. DICY suitable for curing epoxy resins is commercially available. Representative examples of suitable DICYs include Thomas Swan's Casamid DMPF and Anqing F&F Chemicals' CP-1.

[0288] OTB is a derivative of DICY that provides good solubility in epoxy resins. Commercially available OTBs include Huntsman's HT2844, Anqing F&F Chemical's HT2855, and Thomas Swan's Casamid 710.

[0289] Phenolic curing agents are prepared by stepwise growth of phenol-aldehyde polymerization under conditions of phenol excess. They can also be prepared by condensation of epoxy resin with a molar excess of phenolic compound. Other methods exist for preparing phenolic end-capping materials for use as crosslinking agents in epoxy resins. Their hydroxyl equivalent weight is typically in the range of 230-260 g / eq. Commercially available phenolic curing agents include Kukdo's KD407 and KD410.

[0290] Low molecular weight acid anhydrides (such as phthalic anhydride, maleic anhydride, trimellitic anhydride, and pyromellitic dianhydride (PMDA)) can be used to cure epoxy resins. PMDA can also react with 2-phenylimidazoline to form matting curing agents for powders. These materials are generally commercially available.

[0291] The imidazoline ring can be used as a curing agent for epoxy resins. A preferred curing agent for primer compositions and primer layers contains 2-phenyl-2-imidazoline (CAS No.: 936-49-2). 2-phenyl-2-imidazoline for primer compositions and primer layers is commercially available, for example, under the trade name HC31 from Huangshan Huahui Technology Co., Ltd., under the trade name Vestagon B31 from Evonik Degussa Coatings & Colour, and under the trade name MB 31 from Huangshan Deping Chemical Co., Ltd.

[0292] It is important to understand that the curing agent and epoxy resin need to react to cure the coating. The appropriate amounts of curing agent and epoxy resin depend on the relative number of reactive groups, i.e., the epoxy groups in the epoxy resin and the reactive groups in the curing agent. Preferably, if these components are mixed in a ratio such that the curing agent is present in a stoichiometric amount, calculated based on the number of reactive groups present in the curing agent relative to the number of reactive groups present in the epoxy resin, this stoichiometric amount is 80-120%, more preferably 90-115%, and still more preferably 100-110%.

[0293] Preferred curing agents for primer compositions and primer layers are DICY, OTB, 2-phenyl-2-imidazoline, and phenolic curing agents. More preferred curing agents are DICY, OTB, and 2-phenyl-2-imidazoline. Most preferred curing agents are DICY and OTB.

[0294] Generally, based on the weight of the epoxy resin present, the amount (in weight %) of DICY or OTB curing agent present in the primer coating composition is preferably 1.5-10% by weight, more preferably 2.5-7% by weight, and still more preferably 3-5% by weight.

[0295] Generally, based on the weight of the epoxy resin present, the amount of phenolic hardener present in the primer coating composition (in weight %) is preferably 10-45% by weight, more preferably 15-40% by weight, and still more preferably 18-35% by weight.

[0296] Generally, based on the weight of the epoxy resin present, the amount of anhydride present in the primer coating composition (in weight %) is preferably 3.5-8.5% by weight, more preferably 4-8% by weight, and still more preferably 4.6-7.5% by weight.

[0297] Generally, based on the weight of the epoxy resin present, the amount of 2-phenyl-2-imidazoline present in the primer coating composition (in weight %) is preferably 3.0-8.0% by weight, more preferably 3.5-7.5% by weight, and still more preferably 4.0-7.0% by weight.

[0298] Polyester resin

[0299] The primer composition and primer layer may contain a polyester resin. When present, the polyester resin is preferably a carboxylated polyester resin, and more preferably a saturated carboxylated polyester resin.

[0300] The carboxylated polyester resin present in the primer coating composition and primer layer is preferably cured with epoxy resin.

[0301] BPA epoxy resins crosslinked with carboxylic acid-terminated polyester resins (e.g., Mn in the thousands) are called hybrid powder coatings. Their properties fall between epoxy and polyester resins, producing coatings with intermediate properties. They are largely derived from neopentyl glycol (NPG) and terephthalic acid (TPA), using smaller amounts of other monomers to adjust the Tg to the desired level and increase the degree of polymerization (fn) to greater than two. The acid value of carboxylated polyester resins can vary between 28-80 mgKOH / g, depending on the weight ratio of polyester to epoxy resin. The weight ratio of polyester to epoxy resin with an EEW value of 650-750 g / eq can be 50:50; 60:40; and 70:30.

[0302] For example, typical polyester resins (acid value 66-80 mg KOH / g) for 50:50 blended powder coating compositions include DSM's Uralac P5127 and P4055, Allnex's Crycoat 1514-2, 1540-0 and 1573-0, Shenjian's SJ3#-B, SJ3AT and SJ3301, Fenglin's FL-1050, FL-1054 and FL-1058, and Khua's GH-1150, GH-1156 and GH1159.

[0303] For example, typical polyester resins (acid value 45-60 mg KOH / g) for 60:40 blended powder coating compositions include DSM's Uralac P5065, P4260 and P6060, Allnex's Crycoat 1622-0, 1631-0 and 1696-0, Shenjian's SJ5A, SJ5BT-6 and SJ6711, Fenglin's FL-1060, FL-1064 and FL1067, and Khua's GH-1164, GH-1160 and GH-1261.

[0304] For example, typical polyester resins (acid values ​​of 28-38 mg KOH / g) for 70:30 blended powder coating compositions are Uralac P775, P5070 and P5170, Allnex Crycoat 1702-0, 1770-0 and 1781-0, Shenjian SJ6A, SJ6B and SJ7301, Khua GH-1171, GH-1172 and GH-1176, and Fenglin FL-1071, FL-1074 and FL-1176.

[0305] Based on the total weight of the primer coating composition, the primer coating composition and primer layer of the coating system preferably contain 15-60% by weight, more preferably 20-55% by weight, and still more preferably 25-49% by weight of polyester resin. Based on the total weight of the primer coating composition, the primer coating composition and primer layer preferably contain 5-45% by weight, more preferably 10-40% by weight, and still more preferably 15-35% by weight of epoxy resin.

[0306] filler

[0307] The primer coating composition and primer layer preferably contain fillers.

[0308] The preferred fillers present in the primer coating composition and primer layer are inorganic fillers. Suitable inorganic filler particles exist in different forms, such as spherical, layered, nodular, and irregular forms.

[0309] D of the fillers present in the primer coating composition and primer layer 50 Preferably 0.5 to 25 μm, more preferably 1-20 μm, still more preferably 1-15 μm, and even more preferably 1-10 μm.

[0310] In a preferred primer composition and primer layer, the filler is selected from barium sulfate, calcium carbonate, mica, wollastonite (calcium metasilicate), nepheline, dolomite, diatomaceous earth, alumina, aluminum hydroxide, kaolin, feldspar, and mixtures thereof, and more preferably barium sulfate (preferably precipitated barium sulfate), kaolin, feldspar, and mixtures thereof. In a particularly preferred primer composition and primer layer, the filler is selected from feldspar, barium sulfate, calcium carbonate, and mixtures thereof.

[0311] Primer compositions and primer layers may contain a single filler or a combination of two or more fillers. In some preferred primer compositions and primer layers, a single filler is present. When a single filler is present, the filler is preferably selected from barium sulfate, wollastonite (calcium metasilicate), nepheline, dolomite, diatomaceous earth, alumina, aluminum hydroxide, feldspar, and mixtures thereof.

[0312] Suitable fillers are commercially available. Representative examples of suitable fillers include Blanc Fine GM-80 from Gemme Speciality Chemicals Co. Ltd., BlancFixe L from Yillong Chemical Group Limited, GL-2500 from Jiangsu Qunxin powder technology Co. Ltd., Specswhite and Micro Mica W1 from Imerys Minerals Ltd., JLH-60D and H6 from Shenzhen Jinhaohui Industrial Development Co. Ltd., GA-1 from Chuzhou Gera Minerals Co. Ltd., and feldspar JYJC-12 from Henan Nonferrous Jinyuan Industrial Co., Ltd.

[0313] Based on the total weight of the primer coating composition, the total amount of filler present in the primer coating composition and the primer layer is preferably 0-55% by weight, more preferably 25-50% by weight, and still more preferably 30-40% by weight.

[0314] Degassing agent

[0315] The primer coating composition and primer layer preferably contain a degassing agent.

[0316] A commercially available degassing agent can be used.

[0317] Representative examples of suitable degassing agents include cyclohexanediol dibenzoate, benzoin, benzoin derivatives, and mixtures thereof. Preferably, the degassing agent is benzoin or a benzoin derivative, and particularly preferably benzoin.

[0318] Suitable degassing agents are available from numerous commercial suppliers. For example, benzoin is available under the trade name Miwon benzoin from Miwon Speciality Chemical Co. Ltd., and as benzoin from Orgamine ChemicalsPVT Ltd. and Ningbo South Sea Chemical Co. Ltd.

[0319] Based on the total weight of the primer coating composition, a preferred primer coating composition and primer layer contain 0.15-0.45% by weight, more preferably 0.17-0.4% by weight, and still more preferably 0.2-0.35% by weight of a degassing agent.

[0320] Flowability Additives

[0321] The primer coating composition and primer layer preferably contain flowability additives. The presence of flowability additives tends to improve surface smoothness, for example, by reducing or eliminating surface defects such as pits, fisheye cracks, and pinholes. This is achieved by improving the melt flow characteristics of the primer coating composition.

[0322] Commonly available flow additives can be used, such as PCL-100 from Kscnt Co. Ltd., Rheoflow PLP 100H(A) from KSChemical Co. Ltd., and Resiflow PV 88 from Worlee-Chemie GmbH.

[0323] Representative examples of suitable flow additives include acrylic resins, silicone compounds, and fluoropolymers. A preferred primer composition and primer layer include a flow additive, which is an acrylic resin.

[0324] Based on the total weight of the primer coating composition, a preferred primer coating composition and primer layer contain 0.01-5% by weight, more preferably 0.1-3% by weight, and still more preferably 0.5-1.5% by weight of flowability additives.

[0325] Colored pigments

[0326] The primer coating composition and primer layer preferably contain at least one colored pigment. The colored pigment can be an inorganic or organic colored pigment.

[0327] Representative examples of inorganic colored pigments suitable for inclusion in primer coating compositions and primer layers include titanium dioxide, iron oxide red, black pigments, yellow pigments, chromium pigments, iron-manganese black, carbon black, and combinations thereof.

[0328] Representative examples of organic pigments suitable for inclusion in primer coating compositions and primer layers include phthalocyanine, azo, dioxazine, perylene, anthraquinone, thioindigo, isoanthrone violet, triphenyldioxane, quinacridone pigments, vat dye pigments, and combinations thereof.

[0329] Preferred colored pigments used in primer coating compositions and primer layers are selected from titanium dioxide, carbon black, organic red pigments, organic yellow pigments, organic blue pigments, ultramarine blue, and organic green pigments.

[0330] Another preferred primer composition and primer layer of the present invention contain less than 5% by weight, more preferably less than 2% by weight, and still more preferably less than 0.8% by weight of carbon black.

[0331] Suitable colored pigments are commercially available, such as NTR-606, Beablack 2669F, Beablack 2870F, Red 122, DPP Red SR2P, Yellow 139, Sudafest blue 2789, Blue 51, Green 2730K, and iron manganese black.

[0332] Generally, colored pigments should be included in the primer coating composition and primer layer in the minimum amount required to provide the desired color. The required amount of colored pigment depends in part on the type of colored pigment. A technician will be able to determine the appropriate amount for different types of pigments.

[0333] When present, the amount of colored pigment present in the primer coating composition and the primer layer is preferably 0.05-30% by weight, more preferably 0.1-25% by weight, and still more preferably 0.3-20% by weight, based on the total weight of the primer coating composition.

[0334] Leveling agent

[0335] The primer coating composition and primer layer preferably contain a leveling agent. Examples of suitable leveling agents include copolymers of methyl acrylate and butyl acrylate. Suitable leveling agents are commercially available, such as BLC701B from Ningbo South Sea Chemical Co., Ltd. and WK701 from Ningbo Wecan Chemical Co., Ltd. Leveling agents improve the melt flow properties of the composition and help eliminate surface defects during curing.

[0336] When present, the amount of leveling agent present in the primer coating composition and the primer layer is preferably 0.01-5% by weight, more preferably 0.1-3% by weight, and still more preferably 0.5-1.5% by weight, based on the total weight of the primer coating composition.

[0337] additive

[0338] The primer coating composition and primer layer optionally include one or more additives. Examples of optionally present additives include amino alcohols, tackifiers, gloss modifiers, drying agents, waxes, ethylene bis-stearamide (EBS), antioxidants, rheology modifiers, matting agents, and surface modifiers. Preferred additives present in the primer coating composition and primer layer are gloss modifiers, rheology modifiers, surface modifiers, matting agents, and mixtures thereof.

[0339] Representative examples of suitable rheology modifiers are hydrogenated castor oil and low-melting-point polyethylene wax.

[0340] Based on the total weight of the primer coating composition, the additional additives are preferably present in an amount of 0-10% by weight, more preferably 0.1-5% by weight, still more preferably 0.2-4% by weight, and particularly preferably 0.5-3% by weight.

[0341] Preferred primer coating composition and primer layer

[0342] A preferred primer composition and primer layer in the coating system of the present invention comprises:

[0343] (i) An adhesive system comprising an adhesive and a curing agent, selected from the group consisting of: an epoxy adhesive resin and a curing agent for said epoxy resin, or a polyester adhesive resin cured with an epoxy adhesive resin.

[0344] (ii) Optional filler, preferably feldspar or barium sulfate.

[0345] Another preferred primer composition and primer layer present in the coating system of the present invention comprises:

[0346] (i) 40-90% by weight of an adhesive system comprising an adhesive resin and a curing agent, selected from the group consisting of: epoxy adhesive resin and curing agent for said epoxy resin, or polyester adhesive resin cured with epoxy adhesive resin.

[0347] (ii) 0-55% by weight of filler, preferably feldspar or barium sulfate; and

[0348] (iii) 0-30% by weight of pigment;

[0349] The percentage by weight is based on the total weight of the primer / coating composition.

[0350] Another preferred primer composition and primer layer present in the coating system of the present invention comprises:

[0351] (i) 50-80% by weight of an epoxy adhesive, wherein the curing agent and epoxy resin are mixed in a ratio such that the curing agent is present in a stoichiometric amount of 50-120%, more preferably 50-100%, and still more preferably 60-90%, calculated based on the number of reactive groups in the curing agent relative to the number of reactive groups present in the epoxy resin; and

[0352] (ii) Optional filler,

[0353] The percentage by weight is based on the total weight of the primer / coating composition.

[0354] Another preferred primer composition and primer layer present in the coating system of the present invention comprises:

[0355] (i) 50-80% by weight of an epoxy resin with an EEW of 190-1950 g / eq and a curing agent, wherein the epoxy resin is selected from the group consisting of bisphenol A epoxy resin type 2-7, bisphenol A epoxy resin type 3, bisphenol F, brominated bisphenol A epoxy resin, o-cresol, and phenolic varnish-modified epoxy resins, and the curing agent is selected from DICY, OTB, 2-phenyl-2-imidazoline, and phenolic curing agents, preferably DICY and OTB, wherein the curing agent and the epoxy resin are mixed in a ratio such that the curing agent is present in a stoichiometric amount calculated based on the number of reactive groups in the curing agent relative to the number of reactive groups present in the epoxy resin, the stoichiometric amount being 50-120%, more preferably 50-100%, and still more preferably 60-90%; and

[0356] (ii) Optional filler,

[0357] The percentage by weight is based on the total weight of the primer / coating composition.

[0358] Another preferred primer composition and primer layer present in the coating system of the present invention comprises:

[0359] (i) 40-90% by weight of an epoxy adhesive resin and a curing agent for the epoxy resin, the curing agent being selected from DICY, OTB, 2-phenyl-2-imidazoline and phenolic curing agents;

[0360] (ii) 0-55% by weight of filler, preferably feldspar or barium sulfate; and

[0361] (iii) 0-30% by weight of pigment;

[0362] The percentage by weight is based on the total weight of the primer / coating composition.

[0363] Another preferred primer composition and primer layer present in the coating system of the present invention comprises:

[0364] (i) 55-65% by weight of an epoxy adhesive resin and a curing agent for the epoxy resin, wherein the curing agent is selected from DICY, OTB and 2-phenyl-2-imidazoline, preferably DICY and OTB;

[0365] (ii) 30-40% by weight of filler, preferably feldspar or barium sulfate; and

[0366] (iii) 0-5% by weight of pigment;

[0367] The percentage by weight is based on the total weight of the primer / coating composition.

[0368] Another preferred primer composition and primer layer present in the coating system of the present invention comprises:

[0369] (i) 40-90% by weight of an adhesive system comprising a polyester adhesive resin cured with an epoxy adhesive resin; and

[0370] (ii) 0-55% by weight of filler, preferably feldspar or barium sulfate,

[0371] The percentage by weight is based on the total weight of the primer / coating composition.

[0372] Another preferred primer composition and primer layer present in the coating system of the present invention comprises:

[0373] (i) An epoxy resin with an EEW of 190-1950 g / eq, wherein the epoxy resin is selected from bisphenol A epoxy resin type 2-7, bisphenol A epoxy resin type 3, bisphenol F, brominated bisphenol A epoxy resin, o-cresol, and phenolic varnish modified epoxy resin; and a polyester resin with an acid value of 28-80 mgKOH / g, wherein the weight ratio of polyester resin to epoxy resin is 50:50, 60:40, or 70:30; and

[0374] (ii) Optional filler.

[0375] Another preferred primer composition and primer layer present in the coating system of the present invention comprises:

[0376] (i) 55-65% by weight of epoxy resin with an EEW of 190-1950 g / eq, wherein the epoxy resin is selected from the group consisting of bisphenol A epoxy resin type 2-7, bisphenol A epoxy resin type 3, bisphenol F, brominated bisphenol A epoxy resin, o-cresol and phenolic varnish modified epoxy resin; and polyester resin with an acid value of 28-80 mgKOH / g, wherein the weight ratio of polyester resin to epoxy resin is 50:50, 60:40 or 70:30;

[0377] (ii) 30-40% by weight of feldspar or barium sulfate; and

[0378] (iii) 0-5% by weight of pigment;

[0379] The percentage by weight is based on the total weight of the primer / coating composition.

[0380] The primer coating composition of the present invention optionally includes other components, such as pigments, degassing agents, flow additives, leveling agents, and additives that a person skilled in the art deems necessary for a particular coating.

[0381] Topcoat composition and topcoat layer

[0382] A topcoat is needed to seal the surface of the expansion layer. Under the protection of the topcoat, the fire resistance will not be compromised throughout the entire lifespan of the electric vehicle.

[0383] The coating composition used to prepare the topcoat layer is referred to herein as a topcoat coating composition. It is preferably a powder coating composition. Preferably, the topcoat coating composition and the topcoat layer comprise: a binder system comprising a binder selected from epoxy resins, polyester resins, or combinations thereof, and a curing agent.

[0384] The topcoat composition and topcoat layer include a binder system. The binder resin is selected from the group consisting of epoxy resins, polyester resins, and / or mixtures thereof. Preferably, the topcoat composition and topcoat layer include fillers.

[0385] Therefore, in the preferred topcoat composition and in the preferred coating system of the present invention, the topcoat composition and the topcoat layer comprise:

[0386] The topcoat layer comprises:

[0387] (i) an adhesive system comprising an adhesive selected from epoxy resins, polyester resins, or combinations thereof, and a curing agent; and

[0388] (ii) Optional filler, preferably feldspar or barium sulfate.

[0389] Based on the total weight of the topcoat composition, the amount of the binder system (i.e., the combined binder resin and curing agent) present in the topcoat composition and the topcoat layer is preferably 40-90% by weight, more preferably 45-80% by weight, and still more preferably 50-70% by weight.

[0390] The topcoat composition is preferably prepared by a method similar to that described above regarding the powder coating composition of the present invention.

[0391] Epoxy resin

[0392] The topcoat composition and topcoat layer preferably contain epoxy resin. The epoxy resin is preferably a solid epoxy resin. The epoxy resins used in the primer layer, expanding layer, and topcoat layer may be the same or different.

[0393] The epoxy equivalent weight (EEW) of the epoxy resin present in the topcoat composition and topcoat layer is 190-1950 g / eq, more preferably 380 to 1000 g / eq, and still more preferably 380-900 g / eq.

[0394] There are two main types of epoxy resins: glycidyl-based epoxy resins and non-glycidyl-based epoxy resins. Some types of glycidyl-based epoxy resins include glycidyl ether epoxy resins, glycidyl ester epoxy resins, and glycidylamine epoxy resins. Some types of non-glycidyl-based epoxy resins include aliphatic epoxy resins and alicyclic epoxy resins.

[0395] Preferably, the solid epoxy resin present in the topcoat composition and topcoat layer comprises glycidyl-based epoxy resin, and more preferably glycidyl ether epoxy resin. Glycidyl ether epoxy resin is typically prepared by the condensation reaction of a dihydroxy compound with epichlorohydrin. Preferably, the dihydroxy compound is a bisphenol compound.

[0396] Representative examples of solid epoxy resins suitable for topcoat compositions and topcoat layers include bisphenol A-based epoxy resins, bisphenol F-based epoxy resins, phenolic varnish-modified bisphenol A-based epoxy resins, isocyanate-modified bisphenol A epoxy resins, cresol-phenolic varnish-type epoxy resins, O-cresol epoxy resins, silane-modified bisphenol A epoxy resins, rubber-modified bisphenol A epoxy resins, organosilicon-modified bisphenol A epoxy resins, halogenated bisphenol A epoxy resins, and mixtures thereof. In a preferred topcoat composition and topcoat layer, the solid epoxy resin is selected from bisphenol A-based epoxy resins, bisphenol F-based epoxy resins, phenolic varnish-modified bisphenol A-based epoxy resins, isocyanate-modified bisphenol A epoxy resins, cresol-phenolic varnish-type epoxy resins, O-cresol epoxy resins, brominated bisphenol A epoxy resins, and mixtures thereof. In a particularly preferred topcoat composition and topcoat layer, the solid epoxy resin is selected from bisphenol A-based epoxy resins, phenolic varnish-modified bisphenol A-based epoxy resins, bisphenol F epoxy resins, isocyanate-modified bisphenol A epoxy resins, brominated bisphenol A epoxy resins, and mixtures thereof. Bisphenol A-based epoxy resins, phenolic varnish-modified bisphenol A-based epoxy resins, brominated bisphenol A epoxy resins, and mixtures thereof are particularly preferred.

[0397] The preferred solid epoxy resin (e.g., bisphenol A-based epoxy resin, phenolic varnish-modified bisphenol A-based epoxy resin) present in the topcoat composition and topcoat layer has an equivalent epoxy weight (EEW) of 190-1950 g / eq, more preferably 380-1000 g / eq, and still more preferably 380-900 g / eq. EEW is considered to play an important role in the performance of the coating. Epoxy resins with relatively lower EEW tend to have lower viscosity and better wettability, and thus better adhesion; however, too low an EEW leads to sagging and / or bubbles in the final coating. On the other hand, epoxy resins with relatively higher EEW tend to slow down the degassing of air in the coating during its curing. Furthermore, if the EEW of the epoxy resin is too low or too high, the composition is challenging to handle during coating, and the final coating produced by the composition tends to have a poor appearance.

[0398] Suitable epoxy resins are commercially available. Representative examples of suitable epoxy resins include KD-213, KD-214C, KD-242K, KD-2200, KD-242G, KD-243G, KD-2103, KD-214M, KD-2203, KD-2104, KD214L, KD-9002, KD-9003, KD-9004, KD-213C, KD-213H, YDB-400, DER 6805, NPCN-704, DER6224, DER 6225, DER 662E, KD-211G, DER 662UH, DER 6635, DER 663U, DER 663UE, DER 664, DER 664U, DER 664UE, and DER 672U. 6510HT, YDCN-500-90P, BE501H, BE502L, BE502, BE503L, BE503, BE504, BE504H, BE505H, B E507, BEB-400YD-017, BE574P, BFE107, MOE-380, MOE-400, CNE202, CNE220, CNE220H, BE50 2S, BE503S, NPES-901, NPES-901H, NPES-902, NPES-902H, NPES-903K, NPES-903, NPES-903 H, NPES-904, NPES-303, NPES-904H, NPES-304, NPEB-400, NPES-907, NPCN-704 and NPER-450.

[0399] Based on the total weight of the topcoat composition, the topcoat composition and topcoat layer of the coating system of the present invention preferably contain 30-67% by weight, more preferably 43-62% by weight, and still more preferably 46-58% by weight of epoxy resin.

[0400] Epoxy curing agent

[0401] The topcoat composition and topcoat layer contain a curing agent. During curing, the curing agent reacts with the epoxy resin to form a coating, such as a film coating. Therefore, the curing agent is advantageous in providing a coating composition with an acceptable curing time.

[0402] The curing agent present in the topcoat composition and topcoat layer preferably comprises DICY or its derivatives, OTB, phenolic curing agents, acid anhydrides, imidazoles, or imidazole rings. More preferably, the curing agent present in the topcoat composition and topcoat layer comprises DICY, OTB, phenolic curing agents, acid anhydrides, or imidazole rings.

[0403] DICY is the most widely used crosslinking agent for epoxy powder coatings. It is a white, solid crystalline compound. The amino hydrogen present in the structure of DICY can react with the oxirane ring of epoxy resin. DICY suitable for curing epoxy resins is commercially available. Representative examples of suitable DICYs include Thomas Swan's Casamid DMPF and Anqing F&F Chemical's CP-1.

[0404] OTB is a derivative of DICY that provides good solubility in epoxy resins. Commercially available OTBs include Hutsman's HT2844, Anqing F&F Chemical's HT2855, and Thomas Swan's Casamid 710.

[0405] Phenolic curing agents are prepared by stepwise growth through the polymerization of phenol and aldehyde under conditions of phenol excess. They can also be prepared by the condensation of epoxy resin with a molar excess of phenolic compound. Other methods exist for preparing phenolic end-capping materials for use as crosslinking agents in epoxy resins. Their hydroxyl equivalent weight is typically in the range of 230-260 g / eq. Commercially available phenolic curing agents include Kukdo's KD407 and KD410.

[0406] Acid anhydrides are low molecular weight acid anhydrides, such as phthalic anhydride, maleic anhydride, trimellitic anhydride, and pyromellitic dianhydride (PMDA), which can be used to cure epoxy resins. PMDA can also react with 2-phenylimidazoline to form matting curing agents for powders. These materials are generally commercially available.

[0407] The imidazoline ring can be used as a curing agent for epoxy resins. A preferred curing agent present in topcoat compositions and topcoat layers comprises 2-phenyl-2-imidazoline (CAS No.: 936-49-2). 2-phenyl-2-imidazoline for use in topcoat compositions and topcoat layers is commercially available, for example, under the trade name HC31 from Huangshan Huahui Technology Co., Ltd., under the trade name Vestagon B31 from Evonik Degussa Coatings & Colour, and under the trade name MB 31 from Huangshan Deping Chemical Co., Ltd.

[0408] It's important to understand that the curing agent and epoxy resin need to react to allow the coating to cure. The appropriate amounts of curing agent and epoxy resin depend on the relative number of reactive groups—that is, the epoxy groups in the epoxy resin and the reactive groups in the curing agent.

[0409] Preferably, these components are mixed in a ratio such that the curing agent is present in a stoichiometric amount, calculated based on the number of reactive groups present in the curing agent relative to the number of reactive groups present in the epoxy resin, which is 80-120%, more preferably 90-115%, and still more preferably 100-110%.

[0410] Preferred curing agents for topcoat compositions and topcoat layers are DICY, OTB, 2-phenyl-2-imidazoline, and phenolic curing agents. More preferred curing agents for topcoat compositions and topcoat layers are DICY, OTB, and 2-phenyl-2-imidazoline, with DICY and OTB being even more preferred.

[0411] Generally, based on the weight of the epoxy resin present, the amount (in weight %) of DICY or OTB curing agent present in the topcoat composition is preferably 1.5-10% by weight, more preferably 2.5-7% by weight, and still more preferably 3-5% by weight.

[0412] Generally, based on the amount of epoxy resin present, the amount of phenolic hardener present in the topcoat composition (in weight %) is preferably 10-45% by weight, more preferably 15-40% by weight, and still more preferably 18-35% by weight.

[0413] Generally, based on the amount of epoxy resin present, the amount of anhydride present in the topcoat composition (in weight %) is preferably 3.5-8.5% by weight, more preferably 4-8% by weight, and still more preferably 4.6-7.5% by weight.

[0414] Generally, based on the amount of epoxy resin present, the amount of 2-phenyl-2-imidazoline present in the topcoat composition (in weight %) is preferably 3.0-8.0% by weight, more preferably 3.5-7.5% by weight, and still more preferably 4.0-7.0% by weight.

[0415] Polyester resin

[0416] The topcoat composition and topcoat layer may contain polyester resin. When present, the polyester resin is preferably a carboxylated polyester resin, and more preferably a saturated carboxylated polyester resin.

[0417] The acid value of the carboxylated polyester resin present in the topcoat composition and topcoat layer of the present invention is preferably 16-80 mg KOH / g, depending on the type of curing agent used.

[0418] The carboxylated polyester resin present in the topcoat composition and topcoat layer can be cured with epoxy resin or TGIC.

[0419] Carboxylated polyester resin cured with epoxy resin

[0420] BPA epoxy resins crosslinked with carboxylic acid-terminated polyester resins (e.g., Mn in the thousands) are called hybrid powder coatings. Their properties fall between epoxy and polyester resins, producing coatings with intermediate properties. They are largely derived from neopentyl glycol (NPG) and terephthalic acid (TPA), with smaller amounts of other monomers used to adjust the Tg to the desired level and increase the degree of polymerization (fn) to greater than two. The acid value of the carboxylated polyester resin can vary between 28-80 mgKOH / g, depending on the weight ratio of polyester to epoxy resin. The weight ratio of polyester to epoxy resin with an EEW value of 650-750 g / eq can be 50:50; 60:40; and 70:30.

[0421] For example, typical polyester resins with an acid value of 66-80 mgKOH / g for 50:50 blended powder coating compositions include DSM's Uralac P5127 and P4055, Allnex's Crycoat 1514-2, 1540-0 and 1573-0, Shenjian's SJ3#-B, SJ3AT and SJ3301, Fenglin's FL-1050, FL-1054 and FL-1058, and Khua's GH-1150, GH-1156 and GH1159.

[0422] For example, in a 60:40 blended powder coating composition, typical polyester resins with an acid value of 46-60 mgKOH / g include DSM's Uralac P5065, P4260, and P6060; Allnex's Crycoat 1622-0, 1631-0, and 1696-0; Shenjian's SJ5A, SJ5BT-6, and SJ6711; Fenglin's FL-1060, FL-1064, and FL1067; and Khua's GH-1164, GH-1160, and GH-1261.

[0423] For example, typical polyester resins with an acid value of 28-38 mgKOH / g for 70:30 mixed powder coating compositions include Uralac P775, P5070 and P5170, Allnex Crycoat 1702-0, 1770-0 and 1781-0, Shenjian SJ6A, SJ6B and SJ7301, Khua GH-1171, GH-1172 and GH-1176, and Fenglin FL-1071, FL-1074 and FL-1176.

[0424] Based on the total weight of the topcoat composition, the topcoat composition and topcoat layer of the coating system preferably contain 15-60% by weight, more preferably 20-55% by weight, and still more preferably 25-49% by weight of polyester resin. Based on the total weight of the topcoat composition, the topcoat composition and topcoat layer of the coating system preferably contain 5-45% by weight, more preferably 10-40% by weight, and still more preferably 15-35% by weight of epoxy resin.

[0425] Carboxylated polyester resin cured using TGIC

[0426] The carboxylated polyester resin present in the topcoat composition and topcoat layer is preferably derived from neopentyl glycol (NPG) and terephthalic acid (TPA) and / or isophthalic acid (IPA). These resins are referred to as outdoor resins. Typically, outdoor resins are cured using triglycidyl isocyanurate (TGIC) or derivatives thereof.

[0427] Typically, the polyester resins present in topcoat compositions and topcoat layers include resins from Allnex, DSM, Shenjian, Khua, and Fenglin.

[0428] For example, when the weight ratio of polyester to TGIC is 96:4, suitable polyester resins with an acid value of 16-26 mgKOH / g include DSM's Uralac P3800, Allex's Crycoat 2491-2 and 2452-2, Shenjian's SJ4G, SJ4580 and SJ4868, Khua's GH4405 and GH4408, and Fenglin's FL-2031, FL2032 and FL2034.

[0429] For example, suitable polyester resins with an acid value of 28-38 mgKOH / g when the weight ratio of polyester to TGIC is 73:7 include Khua's GH2219, GH2205, and GH2208; Fenglin's FL-2011, FL-2013, and FL-2017; DSM's Uralac P2400, P5300, and P6300; Allnex's Crycoat 2441-2, 2430-0, and 2498-0; and Shenjian's SJ4E, SJ4ET, and SJ4868.

[0430] For example, when the weight ratio of polyester to TGIC is 90:10, suitable polyester resins with an acid value of 46-58 mgKOH / g include Shenjian's SJ4H, SJ4581 and SJ4803, Khua's GH-4403 and GH-4401, Fenglin's FL-2033, FL-2037 and FL2047, DSM's Uralac P2200, P2240 and P2244, and Allnex's Crycoat 2431-0 and 2490-2.

[0431] When the curing agent is TGIC, the amount of polyester resin present in the topcoat composition and the topcoat layer is preferably 35-67% by weight, more preferably 43-62% by weight, and still more preferably 48-58% by weight, based on the total weight of the powder coating composition.

[0432] TGIC is the most important curing agent for carboxylated polyesters. It is the most common crosslinking agent for polyester powder coatings used in outdoor applications. Nissan's TEPIC-G, Hustman's PT810, and Huangshan Huahui's TGIC are commercially available forms of TGIC.

[0433] Based on the weight of the polyester resin, the amount of TGIC present in the topcoat composition and topcoat layer is preferably 1.0-5.5% by weight, more preferably 1.5-4.7% by weight, and still more preferably 2.0-4.0% by weight.

[0434] filler

[0435] The topcoat composition and topcoat layer preferably contain fillers.

[0436] The preferred fillers present in the topcoat composition and topcoat layer are inorganic fillers. Suitable inorganic filler particles exist in different forms, such as spherical, layered, nodular, and irregular forms.

[0437] D of fillers present in the topcoat composition and topcoat layer 50 Preferably 0.5 to 25 μm, more preferably 1-20 μm, still more preferably 1-15 μm, and even more preferably 1-10 μm.

[0438] In a preferred topcoat composition and topcoat layer, the filler is selected from barium sulfate, calcium carbonate, mica, wollastonite (calcium metasilicate), nepheline, kaolin, dolomite, diatomaceous earth, alumina, aluminum hydroxide, feldspar, and mixtures thereof, and more preferably barium sulfate (preferably precipitated barium sulfate), kaolin, feldspar, and mixtures thereof. In a particularly preferred topcoat composition and topcoat layer, the filler is selected from barium sulfate, calcium carbonate, feldspar, and mixtures thereof.

[0439] Topcoat compositions and topcoat layers may contain a single filler or a combination of two or more fillers. In some preferred topcoat compositions and topcoat layers, a single filler is present. When a single filler is present, the filler is preferably selected from barium sulfate, wollastonite (calcium metasilicate), nepheline, dolomite, diatomaceous earth, alumina, aluminum hydroxide, feldspar, and mixtures thereof.

[0440] Suitable fillers are commercially available. Representative examples of suitable fillers include Blanc Fine GM-80 from Gemme Speciality Chemicals Co. Ltd., BlancFixe L from Yillong Chemical Group Limited, GL-2500 from Jiangsu Qunxin powder technology Co. Ltd., Specswhite and Micro Mica W1 from Imerys Minerals Ltd., JLH-60D and H6 from Shenzhen JinHaoHui Industrial Development Co. Ltd., GA-1 from Chuzhou Gera Minerals Co. Ltd., and feldspar JYJC-12 from Henan Nonferrous Jinyuan Industrial Co., Ltd.

[0441] Based on the total weight of the topcoat composition, the total amount of filler present in the topcoat composition and the topcoat layer is preferably 0-55% by weight, more preferably 25-50% by weight, and still more preferably 30-40% by weight.

[0442] Degassing agent

[0443] The topcoat composition and topcoat layer preferably contain a degassing agent. Conventional, commercially available degassing agents can be used.

[0444] Representative examples of suitable degassing agents include cyclohexanediol dibenzoate, benzoin, benzoin derivatives, and mixtures thereof. Preferably, the degassing agent is benzoin or a benzoin derivative, and particularly preferably benzoin.

[0445] Suitable degassing agents are available from numerous commercial suppliers. For example, benzoin is available under the trade name Miwon benzoin from Miwon Speciality Chemical Co. Ltd., and as benzoin from Orgamine ChemicalsPVT Ltd. and Ningbo South Sea Chemical Co. Ltd.

[0446] Based on the total weight of the topcoat composition, a preferred topcoat composition and topcoat layer contain 0.15-0.45% by weight, more preferably 0.17-0.4% by weight, and still more preferably 0.2-0.35% by weight of a degassing agent.

[0447] Flowability Additives

[0448] The topcoat composition and topcoat layer preferably contain flowability additives. The presence of flowability additives tends to improve surface smoothness, for example, by reducing or eliminating surface defects such as pits, fisheye cracks, and pinholes. This is achieved by improving the melt flow characteristics of the topcoat composition.

[0449] Commonly available flow additives can be used, such as PCL-100 from Kscnt Co. Ltd., Rheoflow PLP 100H(A) from KSChemical Co. Ltd., and Resiflow PV 88 from Worlee-Chemie GmbH.

[0450] Representative examples of suitable flow additives include acrylic resins, silicone compounds, and fluorine-based polymers. A preferred topcoat composition and topcoat layer include a flow additive, which is an acrylic resin.

[0451] Based on the total weight of the topcoat composition, a preferred topcoat composition and topcoat layer contain 0.01-5% by weight, more preferably 0.1-3% by weight, and still more preferably 0.5-1.5% by weight of flowability additives.

[0452] Colored pigments

[0453] The topcoat composition and topcoat layer preferably contain at least one colored pigment. The colored pigment can be inorganic or organic.

[0454] Representative examples of inorganic colored pigments suitable for inclusion in topcoat compositions and topcoat layers include titanium dioxide, iron oxide red, black pigments, yellow pigments, chromium pigments, iron-manganese black, carbon black, and combinations thereof.

[0455] Representative examples of organic pigments suitable for inclusion in the topcoat compositions of the present invention include phthalocyanine, azo, dioxazine, perylene, anthraquinone, thioindigo, isothanthrone violet (isodibenzanthrone), triphenyldioxane, quinacridone pigments, vat dye pigments, and combinations thereof.

[0456] Preferred colored pigments used in topcoat compositions and topcoat layers are selected from titanium dioxide, carbon black, organic red pigments, organic yellow pigments, organic blue pigments, ultramarine blue, and organic green pigments.

[0457] Another preferred topcoat composition and topcoat layer contain less than 5% by weight, more preferably less than 2% by weight, and still more preferably less than 0.8% by weight of carbon black.

[0458] Suitable colored pigments are commercially available, such as NTR-606, Beablack 2669F, Beablack 2870F, Red 122, DPP Red SR2P, Yellow 139, Sudafest blue 2789, Blue 51, Green 2730K, and iron manganese black.

[0459] Generally, colored pigments should be included in the topcoat composition in the minimum amount required to provide the desired color. The required amount of colored pigment depends in part on the type of pigment. A technician will be able to determine the appropriate amount for different types of pigments.

[0460] When present, the amount of colored pigment present in the topcoat composition and the topcoat layer is preferably 0.05-30% by weight, more preferably 0.1-25% by weight, and still more preferably 0.3-20% by weight, based on the total weight of the topcoat composition.

[0461] Leveling agent

[0462] The topcoat composition and topcoat layer preferably contain a leveling agent. Examples of suitable leveling agents include copolymers of methyl acrylate and butyl acrylate.

[0463] Suitable leveling agents are commercially available, such as BLC701B from Ningbo South Sea Chemical Co., Ltd. and WK701 from Ningbo Wecan Chemical Co., Ltd. Leveling agents improve the melt flow properties of the composition and help eliminate surface defects during curing.

[0464] When present, the amount of leveling agent present in the topcoat composition and the topcoat layer is preferably 0.01-5% by weight, more preferably 0.1-3% by weight, and still more preferably 0.5-1.5% by weight, based on the total weight of the topcoat composition.

[0465] additive

[0466] The topcoat composition and topcoat layer optionally include one or more additives. Examples of optionally present additives include amino alcohols, tackifiers, gloss modifiers, drying agents, waxes, ethylene bis-stearamide (EBS), antioxidants, rheology modifiers, matting agents, and surface modifiers. Preferred additives present in the topcoat composition and topcoat layer are gloss modifiers, rheology modifiers, surface modifiers, matting agents, and mixtures thereof. Representative examples of suitable rheology modifiers are hydrogenated castor oil and low-melting-point polyethylene wax.

[0467] Based on the total weight of the topcoat composition, additional additives are preferably present in the topcoat composition and topcoat layer in an amount of 0-10% by weight, more preferably 0.1-5% by weight, still more preferably 0.2-4% by weight, and particularly preferably 0.5-3% by weight.

[0468] Preferred topcoat composition and topcoat layer

[0469] A preferred topcoat composition and topcoat layer of the coating system of the present invention comprises:

[0470] (i) An adhesive system comprising an adhesive and a curing agent, selected from the group consisting of: an epoxy adhesive resin and a curing agent for said epoxy resin, a polyester adhesive resin cured with an epoxy adhesive resin, or a polyester adhesive resin cured with TGIC; and

[0471] (ii) Optional filler, preferably feldspar or barium sulfate.

[0472] Another preferred topcoat composition and topcoat layer of the coating system of the present invention comprises:

[0473] (i) 40-90% by weight of an adhesive system comprising a binder and a curing agent, selected from the group consisting of: epoxy adhesive resins and curing agents for said epoxy resins, polyester adhesive resins cured with epoxy adhesive resins, or polyester adhesive resins cured with TGIC, and

[0474] (ii) 0-55% by weight of filler, preferably feldspar or barium sulfate;

[0475] The percentage by weight is based on the total weight of the topcoat composition.

[0476] Another preferred topcoat composition and topcoat layer of the coating system of the present invention comprises:

[0477] (i) 40-90% by weight of an adhesive system comprising an adhesive and a curing agent, selected from the group consisting of: epoxy adhesive resin and curing agent for said epoxy resin, polyester adhesive resin cured with epoxy adhesive resin, or polyester adhesive resin cured with TGIC.

[0478] (ii) 0-55% by weight of filler, preferably feldspar or barium sulfate, and

[0479] (iii) 0-30% by weight of pigment;

[0480] The percentage by weight is based on the total weight of the topcoat composition.

[0481] Another preferred topcoat composition and topcoat layer of the coating system of the present invention comprises:

[0482] (i) 40-90% by weight of an epoxy adhesive resin and a curing agent for the epoxy resin, the curing agent being selected from DICY, OTB, 2-phenyl-2-imidazoline and phenolic curing agents;

[0483] (ii) 0-55% by weight of filler, preferably feldspar, and

[0484] (iii) 0-30% by weight of pigment;

[0485] The percentage by weight is based on the total weight of the topcoat composition.

[0486] Another preferred topcoat composition and topcoat layer of the coating system of the present invention comprises:

[0487] (i) 55-65% by weight of an epoxy adhesive resin and a curing agent for the epoxy resin, wherein the curing agent is selected from DICY, OTB and 2-phenyl-2-imidazoline, preferably DICY and OTB;

[0488] (ii) 30-40% by weight of filler, preferably feldspar, and

[0489] (iii) 0-5% by weight of pigment;

[0490] The percentage by weight is based on the total weight of the topcoat composition.

[0491] Another preferred topcoat composition and topcoat layer of the coating system of the present invention comprises:

[0492] (i) 50-80% by weight of an epoxy resin with an EEW of 190-1950 g / eq, said epoxy resin being selected from bisphenol A epoxy resins of types 2-7, bisphenol A epoxy resins of type 3, bisphenol F, brominated bisphenol A epoxy resins, o-cresol and phenolic varnish-modified epoxy resins, and 1-5% by weight of a curing agent selected from DICY, OTB, 2-phenyl-2-imidazoline and phenolic curing agents; and

[0493] (ii) Optional filler,

[0494] The percentage by weight is based on the total weight of the topcoat composition.

[0495] Another preferred topcoat composition and topcoat layer in the coating system of the present invention comprises:

[0496] (i) 55-65% by weight of an epoxy resin with an EEW of 190-1950 g / eq, wherein the epoxy resin is selected from bisphenol A epoxy resin type 2-7, bisphenol A epoxy resin type 3, bisphenol F, brominated bisphenol A epoxy resin, o-cresol and phenolic varnish modified epoxy resin, and a curing agent selected from DICY, OTB and 2-phenyl-2-imidazoline, preferably DICY and OTB;

[0497] (ii) 30-40% by weight of feldspar or barium sulfate; and

[0498] (iii) 0-5% by weight of pigment;

[0499] The percentage by weight is based on the total weight of the primer / coating composition.

[0500] Another preferred topcoat composition and topcoat layer of the coating system of the present invention comprises:

[0501] (i) 40-90% by weight of an adhesive system, said adhesive system comprising a polyester adhesive resin cured with an epoxy adhesive resin;

[0502] (ii) 0-55% by weight of filler, preferably feldspar or barium sulfate;

[0503] The percentage by weight is based on the total weight of the primer / coating composition.

[0504] Another preferred topcoat composition and topcoat layer of the coating system of the present invention comprises:

[0505] (i) An epoxy resin with an EEW of 190-1950 g / eq, wherein the epoxy resin is selected from bisphenol A epoxy resin type 2-7, bisphenol A epoxy resin type 3, bisphenol F, brominated bisphenol A epoxy resin, o-cresol, and phenolic varnish modified epoxy resin; and a polyester resin with an acid value of 28-80 mgKOH / g, wherein the weight ratio of polyester to epoxy resin is 50:50, 60:40, or 70:30; and

[0506] (ii) Optional filler.

[0507] Another preferred topcoat composition and topcoat layer of the coating system of the present invention comprises:

[0508] (i) 40-90% by weight of an adhesive system comprising a polyester adhesive resin cured with TGIC, wherein the weight ratio of polyester resin to TGIC is from 90:10 to 96.5:3.5;

[0509] (ii) 0-55% by weight of filler, preferably feldspar or barium sulfate, and

[0510] (iii) 0-30% by weight of pigment;

[0511] The percentage by weight is based on the total weight of the topcoat composition.

[0512] Another preferred topcoat composition and topcoat layer of the coating system of the present invention comprises:

[0513] (i) 35-67% by weight of polyester resin cured with TGIC with an acid value of 16-58 mgKOH / g, wherein the amount of TGIC is 1-5.5% by weight based on the weight of the polyester resin.

[0514] (ii) 20-30% by weight of filler, preferably feldspar or barium sulfate, and

[0515] (iii) 0-8.4% by weight of pigment;

[0516] The percentage by weight is based on the total weight of the topcoat composition.

[0517] The topcoat composition and topcoat layer of the coating system of the present invention optionally include other components, such as pigments, degassing agents, flow additives and leveling agents, as well as additives that a person skilled in the art deems necessary for a particular coating.

[0518] Preferred coating system

[0519] The coating system of the present invention is preferably resistant to damp heat aging, for example, when the expansion system is placed in a constant temperature and humidity chamber and tested at 85°C and 85% RH for 1000 hours. After the humidity test, the adhesion of the coating is preferably Gt0, and the coating system still passes the fire resistance test, for example, as listed in the examples.

[0520] The coating system of the present invention is preferably resistant to water immersion. For example, when the coating system is immersed in a water bath at a temperature of 40°C for 480 hours, the surface preferably does not bubble or peel off, the adhesion is Gt0, and the coating system still passes the fire resistance test, for example, as listed in the examples.

[0521] The coating system of the present invention preferably exhibits good adhesion to a substrate, preferably a metal substrate, such as an aluminum substrate. Preferably, the coating system passes the cross-cutting test as described in ISO 2409:2013 (E).

[0522] A preferred coating system of the present invention includes:

[0523] - A primer layer comprising a primer coating composition, said primer coating composition comprising:

[0524] (i) An adhesive system comprising an adhesive and a curing agent, selected from the group consisting of: epoxy adhesive resins and curing agents for said epoxy resins, and polyester adhesive resins cured with epoxy adhesive resins; and

[0525] (ii) Optional filler, preferably feldspar or barium sulfate;

[0526] - An expanded layer comprising an expanded powder coating composition, said expanded powder coating composition comprising:

[0527] 1) An adhesive system comprising an adhesive and a curing agent, wherein the adhesive is selected from epoxy resin, polyester resin, or a combination thereof;

[0528] 2) An expandable component, said expandable component comprising ammonium polyphosphate and preferably comprising melamine and / or pentaerythritol; and

[0529] 3) Carbon fiber; and

[0530] - A topcoat layer comprising a topcoat composition, the topcoat composition comprising:

[0531] (i) An adhesive system comprising an adhesive and a curing agent, selected from the group consisting of: epoxy adhesive resins and curing agents for said epoxy resins, polyester adhesive resins cured with epoxy adhesive resins, and polyester adhesive resins cured with TGIC; and

[0532] (ii) Optional filler, preferably feldspar or barium sulfate.

[0533] Another preferred coating system of the present invention includes:

[0534] - A primer layer comprising a primer coating composition, said primer coating composition comprising:

[0535] (i) 40-90% by weight of an adhesive system comprising an adhesive resin and a curing agent, selected from the group consisting of: epoxy adhesive resin and curing agent for said epoxy resin, and polyester adhesive resin cured with epoxy adhesive resin.

[0536] (ii) 0-55% by weight of filler, preferably feldspar or barium sulfate;

[0537] - An expanded layer comprising an expanded powder coating composition, said expanded powder coating composition comprising:

[0538] (a) 35-67% by weight of an adhesive system comprising adhesive resin and curing agent;

[0539] (b) 25-63% by weight of an expandable component, said expandable component comprising ammonium polyphosphate and preferably comprising melamine and / or pentaerythritol; and

[0540] (c) 2-15% by weight of carbon fiber; and

[0541] - A topcoat layer comprising a topcoat composition, the topcoat composition comprising:

[0542] (iii) 40-90% by weight of an adhesive system comprising an adhesive resin and a curing agent, selected from the group consisting of: epoxy adhesive resin and a curing agent for said epoxy resin, polyester adhesive resin cured with epoxy adhesive resin, and polyester adhesive resin cured with TGIC; and

[0543] (iv) 0-55% by weight of filler, preferably feldspar or barium sulfate.

[0544] Another preferred coating system of the present invention includes:

[0545] - A primer layer comprising a primer coating composition, said primer coating composition comprising:

[0546] (i) 40-90% by weight of an adhesive system comprising an epoxy adhesive resin and a curing agent for the epoxy resin;

[0547] (ii) 0-55% by weight of filler, preferably feldspar or barium sulfate;

[0548] - An expanded layer comprising an expanded powder coating composition, said expanded powder coating composition comprising:

[0549] (a) 35-67% by weight of an adhesive system comprising adhesive resin and curing agent;

[0550] (b) 25-63% by weight of an expandable component, said expandable component comprising ammonium polyphosphate and preferably comprising melamine and / or pentaerythritol; and

[0551] (c) 2-15% by weight of carbon fiber; and

[0552] - A topcoat layer comprising a topcoat composition, the topcoat composition comprising:

[0553] (iii) 40-90% by weight of an adhesive system comprising an epoxy adhesive resin and a curing agent for said epoxy resin; and

[0554] (iv) 0-55% by weight of filler, preferably feldspar or barium sulfate.

[0555] The preferred coating system of the present invention consists of three layers.

[0556] Methods of coating substrate

[0557] The present invention also relates to a method for coating a substrate, preferably a metal substrate, using the coating system described above, the method comprising:

[0558] (i) Applying a primer composition, preferably a powder primer composition and more preferably a primer composition as described above, to the substrate and curing the composition to form a primer layer;

[0559] (ii) Applying the intumescent powder coating composition as described above to the primer layer and curing the composition to form an intumescent layer; and

[0560] (iii) Apply the topcoat composition, preferably a powder topcoat composition, and more preferably the topcoat composition as described above, to the expanded layer and cure it to form a topcoat layer.

[0561] In a preferred method, the coating system consists of three layers.

[0562] The primer and topcoat compositions of the coating system can be applied using any conventional powder coating method, such as electrostatic spraying. Cold substrates can be coated, for example, in a spray booth. Coating techniques are well known in the art and will be familiar to those skilled in the art.

[0563] In a preferred method, the primer composition is cured at a temperature of 170-200°C for 10-30 minutes.

[0564] In another preferred method, the intumescent powder coating composition is cured at a temperature of 170-200°C for 10-30 minutes.

[0565] In another preferred method, the topcoat composition is cured at a temperature of 170-200°C for 10-30 minutes.

[0566] The primer and topcoat compositions are cured separately after application. Curing can be performed by heating, such as in one or more ovens, which allows the particles to melt, fuse, and solidify. Optionally, the primer and topcoat compositions can be cured by placing the substrate in a post-curing oven.

[0567] The primer coating composition is preferably applied to the substrate using a corona gun. Preferably, it is applied to a thickness of 30-300 µm, more preferably 50-250 µm, and most preferably 60-200 µm. The substrate coated with the primer coating composition is preferably cured at a temperature of 170-200°C for 10-30 minutes, for example, in a convection oven or alternatively in a convection oven combined with an infrared oven. Preferably, the substrate covered by the primer layer is cooled before the expansion layer is applied.

[0568] The intumescent powder coating composition is preferably applied over a cured primer layer at ambient temperature. Preferably, it is applied using a corona gun, or, if a thickness greater than 350 µm is required, using a combination of a corona gun and a positive charge gun. Preferably, it is applied to a thickness of 150-850 µm, more preferably 200-850 µm, and most preferably 250-850 µm. After application, the intumescent layer is preferably cured in a convection oven, an infrared oven, or a combination of both. Preferably, curing is performed at a (substrate) temperature of 170-200°C for 10-30 minutes, followed by cooling to ambient temperature.

[0569] The topcoat composition is preferably applied over the curing and expanding layer at ambient temperature. Preferably, it is applied using a corona gun or a combination of a corona gun and a positive charge gun. Preferably, it is applied to a thickness of 60-300 µm, more preferably 90-300 µm, and most preferably 120-300 µm. After application, the topcoat layer is preferably cured in a convection oven or alternatively a convection oven combined with an infrared oven at 170-200°C for 10-30 minutes.

[0570] Containers and reagent kits

[0571] The present invention also relates to a container for containing a powder coating composition as described above, preferably an intumescent powder coating composition. Suitable containers include cardboard boxes, plastic bags, cans, and barrels.

[0572] The present invention also relates to a kit for preparing the coating system as described above, the kit comprising:

[0573] (i) A first container containing a primer coating composition, preferably a powder primer coating composition, and more preferably a primer coating composition as described above;

[0574] (ii) a second container containing the expandable powder coating composition as described above; and

[0575] (iii) A third container containing a topcoat composition, preferably a powder topcoat composition, and more preferably a topcoat composition as described above.

[0576] Optionally, the kit also includes instructions for preparing the coating system of the present invention.

[0577] Substrate and product

[0578] The present invention also relates to a substrate coated with an intumescent powder coating composition as described above or a coating system as described above.

[0579] The powder coating compositions and coating systems of the present invention can be applied to any substrate. A preferred substrate is metal, and more preferably, the substrate is aluminum or steel. Particularly preferred is the aluminum or steel surface of a battery pack or other parts of the battery pack, and especially preferred is the aluminum and / or steel surface of a battery pack present in a battery assembly (e.g., a battery assembly for an electric vehicle).

[0580] The substrate (e.g., the aluminum surface of a battery pack) may be partially or completely coated with the powder coating composition or coating system of the present invention. However, preferably, substantially the entire substrate is coated with the powder coating composition or coating system of the present invention. In the case of a battery pack, this preferably includes the entire inner wall of the battery pack and, more preferably, the entire outer wall (except for electrical contacts). In the case of components within the battery pack, this preferably includes cooling panels, side panels, and busbars.

[0581] Therefore, the present invention also provides a battery assembly including a battery pack, wherein the battery pack has a coating formed on at least one surface, preferably an inner surface, and the coating is formed by a coating system as described above.

[0582] When used for battery pack protection, the coating system of this invention can prevent heat generated inside the battery pack from transferring to the outside in the event of thermal runaway, thus slowing or preventing the spread of fire or higher temperatures. Additionally, if the coating system of this invention is applied to the outside of the battery pack, it can prevent heat from a fire generated in the surrounding environment (e.g., another electric vehicle) from transferring from the outside to the inside of the battery pack, thus slowing or preventing the spread of fire or higher temperatures. Overall, this provides improved electric vehicle safety and gives passengers more time to escape in the event of a thermal failure of the EV battery.

[0583] The invention will now be described by way of the following non-limiting embodiments.

[0584] Example

[0585] Material

[0586] The polymers and compounds used in the examples are all commercially available. The polymers and compounds used are summarized in the following table.

[0587] The A4-sized aluminum or steel panels used for test preparation were obtained from Chemetall Lab. If purchased, the metal in the panels had been degreased with alkali, rinsed with water, then treated with 9810 silane and 4707 A2 zirconium oxide, followed by rinsing with water and drying in an oven at a target temperature of 100°C.

[0588]

[0589]

[0590] Preparation of powder coating samples

[0591] Powder coatings (primer, expanding coating, and topcoat) are prepared using the following procedures:

[0592] (1) Place the raw materials into the mixing tank according to the corresponding weight percentages for premixing shown in the table below, where the amount of each component is indicated by weight % unless otherwise specified. Blend in the mixing tank in two stages. The first blending time is 3-5 minutes, the rotation speed is 700 r / min, and the operating temperature is 20-30°C. The second blending time is 3-5 minutes, the rotation speed is 900 r / min, and the operating temperature is 20-30°C. The second blending should be performed immediately after the first blending.

[0593] (2) The premixed raw materials are uniformly melted, mixed, dispersed and extruded using a twin-screw extruder. The extruder temperature is 90-110℃ and the screw frequency is controlled at 30-50 Hz. The extruded mixture is then crushed.

[0594] (3) The crushed material is classified and pulverized by an ACM mill. The frequency of the disc is 25-35 Hz, and the frequency of the classifier is 25-35 Hz.

[0595] (4) Classify (i.e. sieve) the finely pulverized material into particle size D. 50 It is a powder coating with a particle size of 30-80 micrometers.

[0596] Preparation of samples for testing

[0597] Prepare a panel coated with an intumescent coating for testing according to the following steps:

[0598] 1. Place the A4-sized aluminum or steel panel obtained from Chemetall Lab into the spray booth.

[0599] 2. If the desired film thickness can be achieved using only a corona gun, then use this method. If the desired film thickness cannot be achieved using only a corona gun, first apply powder using a positive charge gun, then perform corona gun powder spraying to achieve a film thickness of 360-390 µm. Place the sprayed panel in an oven to cure at 160-200°C for 30-10 minutes.

[0600] Panels coated with only a primer layer or only a topcoat layer

[0601] 1. Place the A4-sized aluminum or steel panel obtained from Chemetall Lab into the spray booth.

[0602] 2. Apply the primer powder coating composition or topcoat powder coating composition to the panel using electrostatic spraying to achieve a film thickness of 80-180 µm. Place the sprayed panel in an oven and cure at 160-200°C for 30-10 minutes.

[0603] Prepare the three-layer coating system for testing according to the following steps:

[0604] 1. Place the A4-sized aluminum or steel panel obtained from Chemetall Lab into the spray booth.

[0605] 2. Apply the primer powder coating composition to the panel using electrostatic spraying to achieve a film thickness of 80-100 µm. Place the sprayed panel in an oven and cure at 160-200°C for 10-30 minutes.

[0606] 3. After cooling, use a positive charge gun, followed by a corona gun, to spray the intumescent powder coating composition onto the cured primer layer, achieving an intumescent film thickness of 360-390 µm. Place the sprayed panel in an oven to cure at 160-200°C for 10-30 minutes.

[0607] 4. After cooling, apply the topcoat powder composition to the cured and expanded layer using electrostatic spraying to achieve a topcoat film thickness of 160-180 µm. Place the sprayed panel in an oven to cure at 160-200°C for 10-30 minutes.

[0608] Prepare a two-coated panel (primer layer + expansion layer) for testing according to the following steps:

[0609] 1. Place the A4-sized aluminum or steel panel obtained from Chemetall Lab into the spray booth.

[0610] 2. Apply the primer powder coating composition to the panel using electrostatic spraying to achieve a film thickness of 80-100 µm. Place the sprayed panel in an oven and cure at 160-200°C for 10-30 minutes.

[0611] 3. After cooling, use a positive charge gun, followed by a corona gun, to spray the intumescent powder coating composition onto the cured primer layer, achieving an intumescent film thickness of 360-390 µm. Place the sprayed panel in an oven to cure at 160-200°C for 10-30 minutes.

[0612] Prepare a two-layer coated panel (expansion layer + topcoat layer) for testing according to the following steps:

[0613] 1. Place the A4-sized aluminum or steel panel obtained from Chemetall Lab into the spray booth.

[0614] 2. After drying, at ambient temperature, use a positive charge gun, then a corona gun, to spray the intumescent powder coating composition onto the panel to achieve a film thickness of 360-390 µm. Place the sprayed panel in an oven to cure at 160-200°C for 10-30 minutes.

[0615] 3. After cooling, apply the topcoat powder composition to the cured and expanded layer using electrostatic spraying, achieving a topcoat film thickness of 160-180 µm. Place the sprayed panel in an oven to cure at 160-200°C for 10-30 minutes.

[0616] How to achieve the maximum thickness of powder coating?

[0617] First, spray the substrate with a positive charge gun, then spray the substrate with an electrostatic gun until the powder coating no longer deposits onto the substrate or the underlying layer.

[0618] To make the test results comparable, the actual film thickness of the test panel was controlled to be between 370 and 390 µm by controlling the amount of powder used or the powder coating time.

[0619] Test methods

[0620] • Fire resistance test (heat insulation time - THI)

[0621] 1. Use clamps to keep the panel vertical, maintaining a 10 cm distance between the butane flame gun and the panel. The flame ignition point should be in the center of the coated panel. Place the temperature probe in the center of the back of the panel, ensuring the flame and probe are in the same position with only the panel between them.

[0622] 2. Turn on the thermometer and ignite the flame gun, ensuring the flame is directed at the center of the coated panel. Adjust the flame intensity to maximum and turn on the timer.

[0623] 3. Record the temperature change over time. If the temperature exceeds 400℃, stop the experiment and record the time.

[0624] • Water immersion test according to ISO 2812-2

[0625] 1. Place the coated panel in a 23°C deionized water bath. ¾ of the panels should be soaked for 480 hours.

[0626] 2. After the test, rinse the coated panel with clean, warm water and dry it immediately at 23°C. Then, acclimate it at 50% relative humidity for 24 hours.

[0627] 3. Conduct fire resistance tests as described above.

[0628] • Damp heat aging double 85 test (water absorption at elevated temperature) according to GB / T 2423.50

[0629] 1. Place the coated panel in a temperature and humidity test chamber, set to 85℃ and 85% relative humidity, and test for 1000 hours.

[0630] 2. After the test, rinse the coated panel with clean, warm water and dry it immediately at 23°C. Then, acclimate it at 50% relative humidity for 24 hours.

[0631] 3. Conduct fire resistance tests.

[0632] • NSS test (neutral salt spray) according to ISO 9227

[0633] 1. Place the coated panel in a salt spray test chamber, set to 35℃ and 5% NaCl, and test for 720 hours.

[0634] 2. After the test, rinse the coated panel with clean, warm water and dry it immediately at 23°C.

[0635] 3. Evaluate whether the corrosion width exceeds 2 mm, and if it exceeds 2 mm, it is judged as failing.

[0636] • Film thickness according to ISO 2808

[0637] 1. Select three points and test the thickness of the membrane using a membrane thickness gauge, wherein the membrane thickness gauge is an ERICHSEN PICOGLOSS 503.

[0638] 2. Take the average of the three points.

[0639] 3. The standard deviation of this method is ± 5 µm.

[0640] • Adhesion according to ISO 4624

[0641] 1. Select the appropriate blade width according to the film thickness (0-60 μm: 1 mm spacing; 61-120 μm: 2 mm spacing; 121-250 μm: 3 mm spacing; over 250 μm: 5 mm spacing).

[0642] 2. Using uniform force, keep the blade perpendicular to the panel and make 6 transverse and longitudinal cuts, each exposing the substrate. The angle between the transverse and longitudinal cut lines is 90°.

[0643] 3. Use a soft brush to gently brush along the grid lines to remove paint debris. Place 3M Scotch 250 tape above the cut panel surface and press it flat on the grid area with your fingers. The tape should be at least 20 mm longer than the grid. Within 5 minutes of leaving the tape on, hold the overhanging end of the tape and smoothly remove it at an angle as close to 60° as possible within 0.5 to 1.0 seconds.

[0644] 4. Determine the result according to ISO2409:2007.

[0645] Epoxy-based intumescent powder coatings

[0646] The intumescent powder coating compositions described in Table 1 below were prepared. Examples 1-9 illustrate intumescent powder coatings comprising different types of epoxy resins cured with DICY. Examples 10-13 illustrate intumescent powder coatings comprising epoxy type 3 resins cured with different types of epoxy curing agents. All intumescent powder coatings were prepared to have a target film thickness of 370-390 µm. The test results are also shown in Table 1, where FF indicates failure to pass the fire resistance test after water immersion, damp heat aging, or NSS testing. This is expected due to the lack of a primer and topcoat.

[0647] As shown in Table 1, the prepared coatings have thicknesses ranging from 372 to 390 µm, which is excellent. Furthermore, all powder coating compositions were able to achieve film thicknesses up to approximately 700 µm using a combination of corona gun spraying and positive charge gun spraying.

[0648] The results showed that epoxy-based intumescent coatings containing ammonium polyphosphate, melamine, pentaerythritol, and carbon fiber exhibited excellent thermal insulation and fire resistance. All coatings were able to maintain a temperature below 400°C on the back of the coated panel for more than 30 minutes.

[0649] The results showed that epoxy-based intumescent powder coatings with different curing agents exhibited good fire resistance by preventing heat transfer to the underlying substrate, although different curing agents provided different levels of fire resistance. The highest level of fire resistance was achieved using DICY as the curing agent for the epoxy resin.

[0650] The results also showed that different epoxy resins provided coatings with different heat insulation properties. The epoxy resins that yielded the best fire resistance were epoxy resins type 2, 3, 3.5, 4, and 7, as well as phenolic varnish resins with an EEW of 500-575.

[0651] Table 1: Epoxy Fire-Retardant / Intumescent Coatings

[0652]

[0653]

[0654] Epoxy and polyester resin coatings

[0655] The intumescent powder coating compositions described in Table 2 below (Examples 14-16) were prepared, comprising different types of binders, particularly epoxy resins and saturated carboxyl-functionalized polyesters. The intumescent powder coatings were prepared to have a target film thickness of 370-390 µm. FF indicates failure to pass the fire resistance test after water immersion, damp heat aging, or NSS testing. This is expected due to the lack of a primer and topcoat.

[0656] Table 2: Fire-retardant coatings with hybrid systems

[0657]

[0658] The prepared coatings have a thickness of 378 to 389 µm, and all intumescent powder coating compositions can achieve a film thickness of up to approximately 700 µm by using a combination of spraying with a corona gun and a positive charge gun.

[0659] The results showed that the intumescent powder coating composition containing a mixture of binder, ammonium polyphosphate, melamine, pentaerythritol, and carbon fiber produced a coating with excellent fire resistance, which was achieved by preventing heat transfer to the underlying substrate. All coatings were able to maintain a temperature below 400°C on the back of the coated panel for more than 30 minutes, with Example 14 exhibiting the strongest performance.

[0660] Polyester resin coatings

[0661] Examples 17-22 described in Table 3 below illustrate intumescent powder coatings containing different types of polyester binders. The powder coatings were prepared to have a target film thickness of 370-390 µm. The test results are also reported in Table 3, where FF indicates failure to pass the fire resistance test after water immersion, damp heat aging, or NSS testing. This is expected due to the lack of a primer and topcoat.

[0662] Table 3: Polyester-based Intumescent / Fire-retardant Coatings

[0663]

[0664] The resulting intumescent powder coatings have a thickness of 378 to 388 µm, and all intumescent powder coating compositions can achieve a film thickness of up to approximately 700 µm by a combination of corona gun and positive charge gun spraying.

[0665] The results showed that pure polyester coatings containing ammonium polyphosphate, melamine, pentaerythritol, and carbon fiber (i.e., polyester as the sole binder) exhibited excellent fire resistance due to their ability to prevent heat transfer to the underlying substrate. All coatings were able to maintain a temperature below 400°C on the back of the coated panel for more than 30 minutes.

[0666] While polyester resins cured with TGIC or HAA meet the critical requirements for thermal insulation, epoxy-based intumescent powder coatings, as described above, perform slightly better.

[0667] Expanded powder coatings with different carbon fiber types and carbon fiber contents

[0668] Examples 24-32 illustrate intumescent powder coating compositions and coatings with different carbon fiber types and contents in epoxy-based binder systems. Comparative Example 1 does not contain carbon fiber but is otherwise very similar to Examples 24-32. The test results are shown in Table 4, where FF indicates failure to pass the fire resistance test after water immersion, damp heat aging, or NSS testing. This is expected due to the lack of a primer and topcoat.

[0669] Table 4: Fire-retardant coatings with different carbon fiber types and carbon fiber contents

[0670]

[0671] The coating thickness (time and / or amount) of Examples 3 and 24-32 was controlled during the application of the powder coating compositions to achieve a target film thickness of 370-390 µm for all examples. In contrast, Comparative Example 1 could not achieve the desired coating thickness. Two coating and curing cycles were required to obtain a film thickness of 376 µm to prepare a comparable coating. The maximum thickness achievable with the composition of CE1 by a single coating is approximately 250 µm.

[0672] The results showed that the intumescent powder coating composition and coating containing a binder (epoxy resin in this case), ammonium polyphosphate, melamine, pentaerythritol, and carbon fiber exhibited excellent fire resistance due to its ability to prevent heat transfer to the underlying substrate. All coatings were able to maintain a temperature below 400°C on the back of the coated panel for more than 30 minutes.

[0673] The results also showed that increasing the carbon fiber content improved the fire resistance of the coating. Additionally, it increased the maximum coating thickness achievable in a single application.

[0674] In addition, longer carbon fiber lengths (e.g., 1 or 2 mm) appear to improve fire resistance and increase the thickness of the coating film.

[0675] Expandable powder coatings with different charging agents

[0676] Table 5 shows Example 33, which compares an intumescent powder coating composition and coating using carbon fiber as a charging agent in an epoxy binder system with those using other conventional charging agents (CE2-CE4). Example 33 was coated to 342 µm using a corona gun, making it comparable to Examples CE2-CE4 in terms of film thickness, as their maximum film thicknesses are in the range of 320-370 µm. The test results are shown in Table 5, where FF indicates failure to pass the fire resistance test after water immersion, damp heat aging, or NSS testing. This is expected due to the lack of a primer and topcoat.

[0677] Table 5: Fire-retardant coatings with different charging agents

[0678]

[0679] The results showed that carbon fiber was a significantly better charging agent than other charging agents (i.e., PEG, glyceryl monostearate, barium titanate) for achieving higher film thicknesses in a single coating. Example 33 achieved a maximum film thickness of 700 µm, compared to Comparative Examples CE2-CE4, which could only achieve a maximum film thickness of 320-370 µm through a single coating.

[0680] Intumescent powder coatings with different ratios of ammonium polyphosphate, melamine, and pentaerythritol

[0681] Examples 34-38 illustrate intumescent powder coatings with different ratios of ammonium polyphosphate, melamine, and pentaerythritol in an epoxy binder system. The intumescent powder coatings were prepared to achieve a target film thickness of 370-390 µm. The test results are shown in Table 6, where FF indicates failure to pass the fire resistance test after water immersion, damp heat aging, or NSS testing. This is expected due to the lack of a primer and topcoat.

[0682] Table 6: Fire-retardant coatings with different ratios of APP, melamine, and pentaerythritol

[0683]

[0684] The results in Table 6 show that ammonium polyphosphate, as the only intumescent component, produces a coating with good thermal insulation properties. Good thermal insulation is achieved with either the combination of ammonium polyphosphate and melamine in the absence of pentaerythritol, or with the combination of ammonium polyphosphate and pentaerythritol in the absence of melamine.

[0685] Intumescent powder coatings in different coating binder systems

[0686] Different primer powder coating compositions and topcoat powder coating compositions were prepared as shown in Tables 7 and 8 below.

[0687] Table 7: Primer Powder Coating Compositions

[0688]

[0689] Table 8: Topcoat Powder Coating Compositions

[0690]

[0691] Examples 39-90 demonstrate the fire resistance of different coating systems. The primer layer was prepared with a target film thickness of 80-100 µm. The intumescent powder coating layer was prepared with a target film thickness of 370-390 µm. The topcoat layer was prepared with a target film thickness of 160-180 µm. The test results are shown in Tables 9-16.

[0692] Table 9: Single Coating Only

[0693]

[0694] Intumescent powder coatings easily passed the thermal insulation test but failed all other tests. On the other hand, both primer powder coatings and topcoat powder compositions passed the water immersion, damp heat aging, and corrosion tests, but failed the thermal insulation test.

[0695] Table 10: Two-layer powder coating system: primer + intumescent coating

[0696]

[0697] The two-layer coating system, consisting of a primer and an expansion layer, exhibited good thermal insulation before different exposure tests, but failed the tests after these tests (FF indicates failure to pass the fire resistance test after water immersion, damp heat aging, or NSS testing). The tested system showed good corrosion resistance.

[0698] Table 11: Two-layer powder coating system: intumescent coating + topcoat

[0699]

[0700] The two-layer coating system, consisting of an expansion layer and a topcoat layer, exhibited good thermal insulation before the exposure tests, but failed the tests afterward (FF indicates failure to pass the fire resistance test after water immersion, damp heat aging, or NSS testing). Additionally, the tested system failed the corrosion test.

[0701] Table 12: Epoxy Primer + Intumescent Coating + Epoxy Topcoat

[0702]

[0703] Note: NC indicates that the fire resistance remains unchanged after exposure, meaning that the insulation requirements are met.

[0704] The three-layer powder coating system according to the present invention was prepared using the compositions shown in Table 12 above. Both the primer and topcoat layers are epoxy-based, while the intumescent layers are based on different binders. For example, the intumescent coating in Example 54 is an epoxy binder cured using DICY, while Example 55 comprises a mixture of polyester resin and epoxy resin, etc.

[0705] All three-layer powder coating systems provided insulation for more than 30 minutes before and after various exposure tests (water immersion test, damp heat aging test, and neutral salt spray test). No change in insulation performance was observed. Furthermore, all three-layer coating systems passed the neutral salt spray test with a corrosion width of less than 2 mm, indicating excellent corrosion resistance.

[0706] Table 13: Epoxy resin primer + epoxy resin expandable type + pure polyester and mixed topcoat

[0707]

[0708] Note: NC indicates that the fire resistance remains unchanged after exposure, meaning that the insulation requirements are met.

[0709] The three-layer powder coating system according to the present invention was prepared using the compositions shown in Table 13 above. Both the primer layer and the expansion layer were epoxy-based and cured using OTB or DICY, respectively. The topcoat layers in Examples 64-66 were mixtures or hybrid systems of different polyester resins and epoxy type 3 resin, while the topcoat layers in Examples 67-69 were pure polyester resins cured using TGIC.

[0710] All three-layer powder coating systems provided insulation for more than 30 minutes before and after various exposure tests (water immersion test, damp heat aging test, and neutral salt spray test). No change in insulation performance was observed. Furthermore, all three-layer systems passed the neutral salt spray test with a corrosion width of less than 2 mm, indicating excellent corrosion resistance.

[0711] Table 14: Mixed Primer + Epoxy Resin Expandable Coating + Topcoat

[0712]

[0713] Note: NC indicates that the fire resistance remains unchanged after exposure, meaning that the insulation requirements are met.

[0714] The three-layer powder coating system according to the present invention was prepared using the compositions shown in Table 14 above. The primer layer was a mixture of polyester resin and epoxy resin, and the expansion layer was epoxy-based, cured using DICY. The topcoat layer of Example 70 was an epoxy resin cured using OTB, the topcoat layers of Examples 71-73 were mixed systems of different polyester resins and epoxy type 3 resin, and the topcoat layers of Examples 74-76 were pure polyester resins cured using TGIC.

[0715] All three-layer powder coating systems provided insulation for more than 30 minutes before and after various exposure tests (water immersion test, damp heat aging test, and neutral salt spray test). No change in insulation performance was observed. Furthermore, all three-layer systems passed the neutral salt spray test with a corrosion width of less than 2 mm, indicating excellent corrosion resistance.

[0716] Table 15: Mixed Primer + Epoxy Resin Expandable Coating + Topcoat

[0717]

[0718] Note: NC indicates that the fire resistance remains unchanged after exposure, meaning that the insulation requirements are met.

[0719] The three-layer powder coating system according to the present invention was prepared using the compositions shown in Table 15 above. The primer layer was a mixture of polyester resin and epoxy resin, and the expansion layer was an epoxy system cured using DICY. The topcoat layer of Example 77 was an epoxy resin cured using OTB, the topcoat layers of Examples 78-80 were mixed systems of different polyester resins and epoxy type 3 resin, and the topcoat layers of Examples 81-83 were pure polyester resins cured using TGIC.

[0720] All three-layer powder coating systems provided insulation for more than 30 minutes before and after various exposure tests (water immersion test, damp heat aging test, and neutral salt spray test). No change in insulation performance was observed. Furthermore, all three-layer systems passed the neutral salt spray test with a corrosion width of less than 2 mm, indicating excellent corrosion resistance.

[0721] Table 16: Mixed Primer + Epoxy Resin Expandable Coating + Topcoat

[0722]

[0723] Note: NC indicates that the fire resistance remains unchanged after exposure, meaning that the insulation requirements are met.

[0724] The three-layer powder coating system according to the present invention was prepared using the compositions shown in Table 16 above. The primer layer was a mixture of polyester resin and epoxy resin, and the expansion layer was an epoxy system cured using DICY. The topcoat layer of Example 84 was an epoxy resin cured using OTB, the topcoat layers of Examples 85-87 were mixed systems of different polyester resins and epoxy type 3 resin, and the topcoat layers of Examples 88-90 were pure polyester resins cured using TGIC.

[0725] All three-layer powder coating systems provided insulation for more than 30 minutes before and after various exposure tests (water immersion test, damp heat aging test, and neutral salt spray test). No change in insulation performance was observed. Furthermore, all three-layer systems passed the neutral salt spray test with a corrosion width of less than 2 mm, indicating excellent corrosion resistance.

[0726] Expansion rate of the three-layer coating system

[0727] The following examples illustrate the expansion rates of a three-layer powder coating system according to the present invention and a commercial liquid expansion coating system. Table 17 below shows the composition of the three-layer powder coating system of the present invention, and compares it with the composition of the liquid coating.

[0728] For comparison with liquid coatings, Jotun's Jotacoate F60 was applied as a primer to a thickness of 85 µm and allowed to dry for one day. Then, Jotun's Steelmaster 120SB was applied as an intumescent coating to a thickness of 395 µm and allowed to dry for seven days. Finally, Jotun's Hardtop XP was applied as a topcoat to a thickness of 165 µm and allowed to dry for one day.

[0729] Table 17: Mixed Primer + Epoxy Resin Expandable Coating + Topcoat

[0730]

[0731] The thickness before exposure was measured using a film thickness gauge, and the thickness after exposure was measured using a vernier caliper.

[0732] The expansion rate of the three-layer powder coating system according to the invention is 13 times its initial film thickness. This is much smaller than that observed with respect to liquid-expanding systems, such as the liquid-expanding coating system described above, which expands to 55 times its initial film thickness. Despite the difference in expansion rates, both systems provide substantially the same thermal insulation performance. Given the limited space in EV battery packs, it is preferable to use an intumescent coating that will provide comprehensive protection using a smaller expansion space.

Claims

1. A powder coating composition, preferably an intumescent powder coating composition, said composition comprising: (i) an adhesive system comprising an adhesive and a curing agent; wherein the adhesive is selected from epoxy resins, polyester resins, or combinations thereof; (ii) an expanding component comprising an acidifying agent, preferably ammonium polyphosphate, and optionally an expanding agent and / or a carbon donor compound; and (iii) A charging agent comprising carbon fiber.

2. The composition according to claim 1, wherein the adhesive comprises an epoxy resin, and the curing agent is selected from DICY, 2-phenyl-2-imidazoline, OTB, PMDA and phenolic curing agents, preferably DICY or OTB.

3. The composition according to any one of the preceding claims, wherein the expanding component comprises an expanding agent, preferably comprising an expanding agent selected from the group consisting of glycine, melamine, melamine salts, melamine derivatives, urea, urea derivatives, dicyandiamide, guanidine, and isocyanurate derivatives, and particularly preferably comprising melamine.

4. The composition according to any of the preceding claims, wherein the expandable component comprises a carbon donor compound selected from pentaerythritol, dipentaerythritol, tripentaerythritol, polysaccharides (e.g., starch, cellulose, glycogen, etc.), disaccharides (e.g., sucrose, lactose, maltose), monosaccharides (e.g., glucose, fructose, galactose), glycerol, or expandable graphite, or any combination thereof, and particularly preferably comprises pentaerythritol.

5. The composition according to any of the preceding claims, wherein the composition comprises an expandable component comprising ammonium polyphosphate and optionally melamine and / or pentaerythritol.

6. The composition according to any of the preceding claims, wherein the length of the carbon fiber is 0.1-2 mm, preferably 0.2-1.6 mm, and still more preferably 0.2-1.2 mm.

7. The composition according to any one of the preceding claims, wherein the carbon fibers are present in an amount of 2-15% by weight, more preferably 3-8% by weight, and still more preferably 3-7% by weight, based on the total weight of the composition.

8. A method for preparing a powder coating composition according to any one of claims 1-7, preferably an intumescent powder coating composition, the method comprising: (i) A binder system, an intumescent component, and a charging agent are blended to form a mixture, wherein the binder system comprises a binder and a curing agent, wherein the binder is selected from epoxy resins, polyester resins, or combinations thereof, the intumescent component comprises an acid-generating agent, preferably ammonium polyphosphate, and optionally an intumescent agent and / or a carbon donor compound, and the charging agent comprises carbon fibers; and (ii) The mixture is extruded to form granules.

9. The use of the powder coating composition according to any one of claims 1-7, and preferably an intumescent powder coating composition, for coating a substrate, preferably a metal substrate, and still more preferably a metal substrate pre-coated with a primer layer.

10. A method for coating a substrate, preferably a metal substrate, with a powder coating composition according to any one of claims 1-7, preferably an intumescent powder coating composition, the method comprising: (i) Applying the powder coating composition according to any one of claims 1-7 to the substrate, wherein the substrate is preferably pre-coated with a primer layer; as well as (ii) Curing the powder coating composition to form a layer, preferably an expanded layer.

11. A coating comprising, preferably an intumescent powder coating composition according to any one of claims 1-7, and preferably a cured coating.

12. A substrate, preferably a metal substrate, coated with a powder coating composition according to any one of claims 1-7, and preferably an intumescent powder coating composition.

13. Use of the powder coating composition according to any one of claims 1-7, and preferably an intumescent powder coating composition, in a coating system.

14. A method for coating a substrate, preferably a metal substrate, using a coating system, the method comprising: (i) Applying a primer composition, preferably a powder primer composition, to the substrate and curing the composition to form a primer layer; (ii) Applying the intumescent powder coating composition according to any one of claims 1-7 to the primer layer and curing the composition to form an intumescent layer; as well as (iii) Apply the topcoat composition, preferably the powder topcoat composition, to the expanded layer and cure it to form the topcoat layer.

15. A coating system comprising three layers, preferably consisting of three layers, wherein the coating system comprises: (i) A primer layer formed on a substrate, preferably a metal substrate; (ii) an expanded layer formed on the primer layer, the expanded layer comprising the powder coating composition according to any one of claims 1-7; and (iii) A topcoat layer formed on the expanded layer.

16. A kit for preparing the coating system according to claim 15, the kit comprising: (i) A first container containing a primer composition, preferably a powder primer composition; (ii) A second container containing the intumescent powder coating composition according to any one of claims 1-7; as well as (iii) A third container containing a topcoat composition, preferably a powder topcoat composition.

17. A container for containing an intumescent powder coating composition according to any one of claims 1-7.

18. Use of the coating system according to claim 15 for forming a fire-resistant and / or heat-insulating coating on at least one surface, preferably an inner surface, of a battery pack, preferably an electric vehicle battery pack.

19. A battery pack including a battery assembly, wherein the battery pack has a coating formed on at least one surface, preferably an inner surface, and the coating is formed by the coating system according to claim 15.

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