Two-component coating composition and single coating system for metal substrates

Abstract

The invention provides a two-component coating composition and a single coating system for a metal substrate. Specifically, the two-component coating composition comprises: a) a film-forming resin composition comprising a phosphate-modified hydroxy acrylic resin and an adhesion promoter; extinction powder; a wax aid; and optionally additional additives; b) a curing system comprising a polyisocyanate. The single coating system according to the present invention is a high performance coating system, which passes the GMW14445 or GWM14698 specification.

Description

Technical Field

[0001] This application relates to the field of coatings, and more particularly to the field of decorative coatings. More specifically, this application relates to a two-component coating composition and a single-coat system for a metal substrate. Background Technology

[0002] In the coatings industry, coatings formed by coating compositions provide both protection and decoration to the target substrate. Metal substrates are a common choice, but applying coating compositions to them can lead to problems such as poor adhesion and inadequate chemical resistance. To address these issues, multi-layer systems are typically used to balance adhesion and chemical resistance, usually consisting of a 2K / 1K / 1.5K primer, a 2K intermediate coat, and a UV / 2K topcoat, or a 2K / 1K / 1.5K primer followed by a UV / 2K topcoat. These multi-layer systems require applying a primer first, allowing it to dry before applying the next coat. This process is complex, time-consuming, labor-intensive, results in high VOC emissions, is inefficient, and often involves high-temperature curing of the coating composition.

[0003] With rising raw material costs and intensifying market competition, customers urgently need a single-coat system to replace current double-coat or multi-coat products. This would significantly reduce raw material and production costs, improve production efficiency and market competitiveness, while also complying with national energy conservation and environmental protection policies and reducing harm to painting workers.

[0004] Therefore, as people's requirements for coatings on metal substrates increase, there is a need for a single-coat system that can be applied to metal substrates and exhibit better performance. This system should not only have excellent adhesion to metal substrates, but also meet appearance requirements and stringent performance requirements (such as chemical resistance, water resistance, and scratch resistance). Summary of the Invention

[0005] This invention provides a two-component coating composition comprising:

[0006] a) A film-forming resin composition comprising:

[0007] Phosphate-modified hydroxyl acrylic resin;

[0008] Adhesion accelerator;

[0009] Matte powder;

[0010] Wax additives; and

[0011] Optional additives may be added;

[0012] b) A curing system containing polyisocyanates.

[0013] In another embodiment, the present invention provides a single-coat system comprising: a cured coating formed from a two-component coating composition according to the present invention; and said system is a high-performance coating system.

[0014] In another embodiment, the present invention provides a method for forming a single-coat system, comprising:

[0015] Provide metal substrates;

[0016] A two-component coating composition is coated onto a substrate, the two-component coating composition comprising...

[0017] a) A film-forming resin composition comprising:

[0018] Phosphate-modified hydroxyl acrylic resin;

[0019] Adhesion accelerator;

[0020] Matte powder;

[0021] Wax additives; and

[0022] Optional additives may be added;

[0023] b) The curing system contains polyisocyanates;

[0024] The metal substrate coated with the two-component coating composition is baked at a temperature of up to 80°C for at least 20 minutes, preferably 20 to 40 minutes, to obtain a cured film;

[0025] The cured film meets the specifications for high-performance coating systems.

[0026] In another embodiment, the present invention provides a coated article comprising:

[0027] Metal substrate; and

[0028] A cured film is placed thereon, the cured film being obtained from a two-component coating composition comprising the following components:

[0029] a) A film-forming resin composition comprising:

[0030] Phosphate-modified hydroxyl acrylic resin;

[0031] Adhesion accelerator;

[0032] Matte powder;

[0033] Wax additives; and

[0034] Optional additives may be added;

[0035] b) The curing system, which contains polyisocyanates.

[0036] The coated articles described herein meet the specifications of high-performance coating systems.

[0037] The inventors were surprised to find that by using phosphate-modified hydroxyl acrylic resin as a film-forming resin, epoxy silane as an adhesion promoter, and polyisocyanate as a curing agent in combination with a specific matting powder, the presence of phosphate functional groups improved the adhesion to the substrate, resulting in a single-coat system that can be used on metal substrates and has excellent adhesion, water resistance, chemical resistance, and scratch resistance.

[0038] The inventors were even more surprised to discover that the two-component coating composition of the present invention can be cured at a relatively low temperature to obtain a single-coat system with excellent performance, which had never been recognized before the present invention.

[0039] Details of one or more embodiments of the present invention are set forth in the following description. Other features, objects, and advantages of the invention will become clear from the description and claims.

[0040] definition

[0041] Unless otherwise specified, the following terms used herein have the meanings provided below.

[0042] Groups, whether the same or different, may be referred to as "independently" something. Substitution on organic groups in the compounds of this invention is also contemplated. To simplify the discussion and presentation of certain terms used throughout this application, the terms "group" and "fraction" are used to distinguish between chemical entities that are permissible or can be substituted and those that are not permissible or cannot be substituted. Thus, when the term "group" is used to describe a chemical substituent, the described chemical material includes unsubstituted groups and groups having, for example, O, N, Si, or S atoms in the chain (as in alkoxy) and having carbonyl or other conventional substitutions. When the term "fraction" is used to describe a compound or substituent, it is intended to include only unsubstituted chemical material. For example, the phrase "alkyl group" is intended to include not only pure open-chain saturated hydrocarbon alkyl substituents (e.g., methyl, ethyl, propyl, tert-butyl, etc.), but also alkyl substituents that also have other substituents known in the art (e.g., hydroxyl, alkoxy, alkylsulfonyl, halogen atom, cyano, nitro, amino, carboxyl, etc.). Therefore, "alkyl group" includes ether groups, haloalkyl groups, nitroalkyl groups, carboxylalkyl groups, hydroxyalkyl groups, sulfonylalkyl groups, and so on. On the other hand, the phrase "alkyl fragment" is limited to those that include pure open-chain saturated hydrocarbon alkyl substituents, such as methyl, ethyl, propyl, tert-butyl, and so on.

[0043] The term "component" refers to any compound that includes a particular characteristic or structure. Examples of components include compounds, monomers, oligomers, polymers, resins, and the organic groups contained therein.

[0044] In this document, the terms “a,” “this,” “at least one,” and “one or more,” as well as those used without quantifiers, are used interchangeably. Thus, for example, a component containing “a” additive can be interpreted as meaning that the component contains “one or more” additives.

[0045] When a composition is described as including or comprising specific components, it is anticipated that optional components not covered by the present invention are not excluded from the composition, and that the composition may be constituted or composed of the components involved. Similarly, when a method is described as including or comprising specific process steps, it is anticipated that optional process steps not covered by the present invention are not excluded from the method, and that the method may be constituted or composed of the process steps involved.

[0046] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, just as any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an undefined range.

[0047] In this document, the term "epoxy equivalent" refers to the mass of epoxy resin containing 1 mol of epoxy groups. Generally, the lower the epoxy equivalent, the more epoxy groups the epoxy resin contains, and the higher its reactivity. In embodiments of the present invention, the epoxy equivalent of the epoxy resin is typically provided by the supplier.

[0048] When used in the context of a substrate, the term "main surface" refers to the surface formed by the length and width dimensions of the substrate and used to provide decoration.

[0049] When used herein, the term "primer" refers to a coating composition that can be applied to a substrate and dried, crosslinked, or otherwise hardened to form a non-sticky, continuous film with adequate adhesion to the substrate surface.

[0050] When used herein, the term "topcoat" refers to a coating composition that can be applied over a primer and dried, crosslinked, or otherwise hardened to form a decorative or protective outermost coating layer. Furthermore, such topcoats are capable of withstanding prolonged outdoor exposure without exhibiting visible, undesirable degradation.

[0051] When used in this document, the term "combined primer and topcoat coating" refers to a coating that combines the traditional primer and topcoat into one, requiring only one coat (one application and one baking) to meet the usage requirements of automotive interior parts and construction machinery.

[0052] The terms "preferred" and "ideally" refer to embodiments of the invention that provide certain benefits in certain circumstances. However, other embodiments may also be preferred in the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of the invention.

[0053] Unless otherwise stated, references to "(meth)acrylate" compounds (where "methyl" is in parentheses) are intended to include acrylate and methacrylate compounds.

[0054] The term "polycarboxylic acid" includes polycarboxylic acids and their anhydrides.

[0055] When used in the context of a coating applied to a surface or substrate, the term "on" includes coatings applied directly or indirectly to a surface or substrate. Thus, for example, a coating applied to a primer layer located on a substrate constitutes a coating applied to that substrate.

[0056] When the term "comprising" and its variations appear in the specification and claims, these terms have no limiting meaning.

[0057] In this invention, the numerical range defined by the endpoints includes all values ​​within that range. For example, the range of 1 to 5 encompasses the values ​​1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc. Moreover, the disclosed numerical range includes all subsets of the wider range. For example, the range of 1 to 5 includes subranges 1 to 4, 1.5 to 4.5, 1 to 2, etc. Detailed Implementation

[0058] This invention provides a two-component coating composition and a single-coat system for metal substrates. On one hand, the single-coat system described herein meets the specifications for high-performance coatings, preferably GMW14445 (Sunscreen and Insect Repellent Resistance) or GWM14698 (Scratch Resistance of Organic Coatings and Self-adhesive Film). Coating systems meeting GMW14445 or GWM14698 specifications exhibit excellent adhesion, water resistance, scratch resistance, and chemical resistance.

[0059] In one embodiment, the present invention provides a two-component coating composition for a metal substrate, comprising: a) a film-forming resin composition comprising: a phosphate-modified hydroxyl acrylic resin; an adhesion promoter; a matting agent; a wax additive; and optionally additional additives; b) a curing system comprising a polyisocyanate.

[0060] Film-forming resin composition

[0061] The term "film-forming resin composition" herein refers to the resin composition constituting the body of the coating formed by the two-component coating composition of the present invention, which may contain phosphate-modified hydroxyl acrylic resin; adhesion promoter; matting agent; wax additive; and optionally additional additives.

[0062] Typically, based on the total weight of the film-forming resin composition, the film-forming resin composition of the present invention comprises at least 55% by weight, at least 60% by weight, at least 65% by weight, at least 70% by weight, and at most 85% by weight, at most 80% by weight, and at most 75% by weight of phosphate ester modified hydroxyl acrylic resin, preferably 55 to 85% by weight of phosphate ester modified hydroxyl acrylic resin.

[0063] Typically, the hydroxyl value (based on solid form) of the phosphate-modified hydroxyl acrylic resin used in the two-component coating compositions of the present invention is at least 60 mg KOH / g, at least 65 mg KOH / g, at least 70 mg KOH / g, and at most 90 mg KOH / g, at most 85 mg KOH / g, at most 80 mg KOH / g, or at most 75 mg KOH / g. Therefore, the hydroxyl value (based on solid form) of the phosphate-modified hydroxyl acrylic resin used in the two-component coating compositions of the present invention is in the range of 60-90 mg KOH / g, preferably in the range of 65-85 mg KOH / g, and more preferably in the range of 65-75 mg KOH / g. Based on the solid weight of the phosphate-modified hydroxyl acrylic resin, the hydroxyl content of the phosphate-modified hydroxyl acrylic resin is at most 5% by weight, preferably at most 4% by weight, and more preferably at most 2% by weight. The hydroxyl groups in phosphate-modified hydroxyl acrylic resin are active functional groups on the resin side chains used for later crosslinking. When the hydroxyl value or hydroxyl content is within the above range, the coating has good adhesion to the metal substrate. At the same time, it has good organic compatibility with wetting and dispersing agents, as well as dispersing pigments and fillers, and is easy to grind and prepare color pastes.

[0064] In one embodiment, the film-forming resin composition according to the present invention comprises a phosphate-modified hydroxy acrylic resin dispersion, i.e., a dispersion of phosphate-modified hydroxy acrylic resin particles in an organic solvent. A variety of organic solvents can be used to formulate the phosphate-modified hydroxy acrylic resin dispersion of the present invention. The solid content of the phosphate-modified hydroxy acrylic resin dispersion is typically in the range of 45-60% by weight. Such a solid content ensures good adhesion of the resulting coating composition to a metal substrate, and after crosslinking with polyisocyanates, the resulting coating exhibits high hardness and good chemical resistance.

[0065] Preferably, the solvents used in this invention include solvents commonly used in the art, including but not limited to aromatic hydrocarbons such as benzene, toluene, and xylene; alcohols such as ethanol, isopropanol, n-butanol, tert-butanol, and ethylhexanol; esters such as ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, and propylene glycol monomethyl ether acetate. Other suitable solvents include ketones such as methyl ethyl ketone, methyl n-pentyl ketone, and methyl isobutyl ketone; glycols such as propylene glycol and diethyl glycol; and glycol ethers such as propylene glycol monomethyl ether and ethylene glycol monomethyl ether. Of course, various mixtures of solvents can be used.

[0066] According to the present invention, the amount of organic solvent can be very low, for example, no more than 30% by weight of organic solvent, preferably no more than 25% by weight of organic solvent, relative to the total weight of the film-forming resin composition, without affecting the preparation of the film-forming resin composition.

[0067] In one embodiment, the film-forming resin composition according to the invention comprises an adhesion promoter. Suitable adhesion promoters for the two-component coating compositions of the invention include, but are not limited to, organofunctional silanes, aminofunctional silanes, halosilanes, silazanes, or combinations thereof. In a preferred aspect, the adhesion promoter is one or more organofunctional silanes.

[0068] In embodiments of the present invention, the adhesion promoter is an organofunctional silane with epoxy functionality.

[0069] In one embodiment, the adhesion promoter has the following general formula:

[0070]

[0071] in

[0072] R1, R2, R4, and R5 are each independently C1-C6 alkyl, C6-C6 alkyl, or C6-C6 alkyl. 10 Aryl, halogen, hydroxyl, C1-C6 alkoxy, C2-C6 enoxy, C6-C 10 Aryloxy, C1-C6 alkyloxy and C6-C10 Aromatic oxy groups, wherein R1, R2, R4, and R5 can be the same or different;

[0073] R3 and R6 are each independently E-R7, wherein E is epoxyethyl, epoxypropyl, or epoxycyclohexyl, preferably epoxypropyl, and R7 is a non-hydrolyzable divalent hydrocarbon group with fewer than 20 carbon atoms or a divalent group with fewer than 20 carbon atoms composed of C, H, N, S, and O atoms (these atoms are the only atoms that can exist in the main chain of the divalent group).

[0074] m is an integer between 0 and 10.

[0075] The epoxy silane used in the embodiments of the present invention can be an epoxy silane represented by general formula 1, wherein R7 is any divalent hydrocarbon group such as methylene, ethylene, decene, cyclohexene, cyclopentene, methylcyclohexene, or 2-ethylbutylene, or an ether group such as -CH2-CH2-O-CH2-CH2-, -(CH2-CH2O)2-CH2-CH2-, or -CH2O-(CH2)3-.

[0076] In embodiments of the invention, the epoxy silane has an epoxy equivalent in the range of 3.8-5.5 eq / 100g, preferably in the range of 4-5 eq / 100g, and more preferably in the range of 4.1-4.8 eq / 100g. The epoxy silane can be a monofunctional epoxy silane or a polyfunctional epoxy silane.

[0077] Examples of monofunctional epoxy silanes include many epoxy-functionalized alkoxysilanes, including glycidyl etheroxymethyltrimethoxysilane, glycidyl etheroxymethyltriethoxysilane, glycidyl etheroxymethyltripropoxysilane, glycidyl etheroxymethyltributoxysilane, β-epoxypropoxyethyltrimethoxysilane, β-epoxypropoxyethyltriethoxysilane, β-epoxypropoxyethyltripropoxysilane, β-epoxypropoxyethyltributoxysilane, β-epoxypropoxyethyltrimethoxysilane, α-epoxypropoxyethyltriethoxysilane, α-epoxypropoxyethyltripropoxysilane, α-epoxypropoxyethyltributoxysilane, γ-epoxypropoxypropyltrimethoxysilane, γ-epoxypropoxyethyltrimethoxysilane, etc. γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltripropoxysilane, γ-glycidoxypropyltributoxysilane, β-glycidoxypropyltrimethoxysilane, β-glycidoxypropyltriethoxysilane, β-glycidoxypropyltripropoxysilane, β-glycidoxypropyltributoxysilane, α-glycidoxypropyltrimethoxysilane, α-glycidoxypropyltriethoxysilane, α-glycidoxypropyltripropoxysilane, α-glycidoxypropyltributoxysilane, α-glycidoxypropyltributoxysilane, γ-glycidoxybutyltrimethoxysilane, δ-glycidoxybutyltriethoxysilane, δ-glycidoxybutyltripropoxysilane, δ-glycidoxybutyltributoxysilane, δ-glycidoxypropyltributoxysilane Butyltrimethoxysilane, γ-epoxypropoxybutyl-triethoxysilane, γ-epoxypropoxybutyltripropoxysilane, γ-epoxypropoxybutyltributoxysilane, δ-epoxypropoxybutyltrimethoxysilane, δ-epoxypropoxybutyltriethoxysilane, δ-epoxypropoxybutyltripropoxysilane, α-epoxypropoxybutyl-trimethoxysilane, α-epoxypropoxybutyl-triethoxysilane, α-epoxypropoxybutyltripropoxysilane, α-epoxypropoxybutyltributoxysilane, (3,4-epoxycyclohexyl)methyltrimethoxysilane, (3,4-epoxycyclohexyl)methyltriethoxysilane, (3,4-epoxycyclohexyl)methyltripropoxysilane, (3,4-epoxycyclohexyl)methyltripropoxysilane, (3,4-epoxycyclohexyl)methyltriethoxysilane Butoxysilane, (3,4-epoxycyclohexyl)ethyltrimethoxysilane, (3,4-epoxycyclohexyl)ethyltriethoxysilane, (3,4-epoxycyclohexyl)ethyltripropoxysilane, (3,4-epoxycyclohexyl)ethyltributoxysilane, (3,4-epoxycyclohexyl)propyltrimethoxysilane, (3,4-epoxycyclohexyl)propyltriethoxysilane, (3,4-epoxycyclohexyl)propyltripropoxysilane, (3,4-epoxycyclohexyl)propyltributoxysilane, (3,4-epoxycyclohexyl)butyltrimethoxysilane, (3,4-epoxycyclohexyl)butyltriethoxysilane, (3,4-epoxycyclohexyl)butyltripropoxysilane, and (3,4-epoxycyclohexyl)butyltributoxysilane.

[0078] As an example of a multifunctional epoxy silane, the oligomers formed from monofunctional epoxy silanes and satisfying general formula 1 can be used.

[0079] The inventors discovered that using a trialkoxysilane containing epoxy propoxy groups (more specifically, a trialkoxysilane with epoxy propoxy groups at the end) as an adhesion promoter can further improve the adhesion between the metal substrate and the cured film. Furthermore, considering its effect of also improving the bonding strength between the inorganic and resin components in the cured film, the improvement in formability and corrosion resistance is significant. Moreover, when adding a trialkoxysilane containing epoxy propoxy groups, the surface tension of the two-component coating composition decreases, improving wettability with the metal substrate, enhancing the coatability of the two-component coating composition, and enabling the formation of a uniform cured film.

[0080] Therefore, preferably, the adhesion promoter is a trialkoxysilane with epoxy functionality, more preferably a trimethoxysilane containing epoxypropoxy, and particularly preferably β-epoxypropoxyethyltrimethoxysilane, γ-epoxypropoxypropyltrimethoxysilane, β-epoxypropoxypropyltrimethoxysilane, α-epoxypropoxypropyltrimethoxysilane, γ-epoxypropoxybutyltrimethoxysilane, δ-epoxypropoxybutyltrimethoxysilane, δ-epoxypropoxybutyltrimethoxysilane, or α-epoxypropoxybutyltrimethoxysilane. Most preferably, the adhesion promoter is γ-epoxypropoxypropyltrimethoxysilane (KBM403 manufactured by Shin-Etsu Chemical Co., Ltd.).

[0081] Based on the total weight of the film-forming resin composition, the content of the adhesion promoter (preferably an epoxy-functionalized organic silane, more preferably an epoxy-functionalized trialkoxysilane, and most preferably a trimethoxysilane containing epoxypropoxy) in the film-forming resin composition is at least 1% by weight, preferably at least 2% by weight, and at most 5% by weight, preferably at most 4% by weight. When the content of the adhesion promoter is less than 1% by weight, no effect on improving the adhesion between the metal substrate and the cured film is observed. In addition, too low a content often leads to a decrease in the bonding force between the inorganic components and the resin components in the cured film, a decrease in the hardness of the cured film, a deterioration in the density of the cured film, and a decrease in formability, adhesion, and corrosion resistance. If the amount of adhesion promoter exceeds 5% by weight, since the effect of improving the adhesion between the metal substrate and the cured film and the effect of improving the bonding force between the inorganic components and the resin components in the cured film have reached their peak, it will become the main reason for the increase in cost. Conversely, excessive content often leads to a decrease in formability, coating adhesion, and corrosion resistance, as well as a decrease in the liquid stability of the film-forming resin composition, resulting in gelation or precipitation.

[0082] Furthermore, the film-forming resin composition according to the present invention includes a matting agent. The matting agent can be one or more commonly used matting agents in the art, such as silica, matting wax paste, and ultrafine talc. The matting principle of these matting agents is that they suspend on the surface of the coating film in the wet state, forming an uneven surface after drying to increase diffuse scattering of light and reduce reflection. However, their loose and porous surface structure results in low mechanical strength, making them easily damaged by external forces, thus causing differences in the gloss of the coating surface. Therefore, in one embodiment of the present invention, the matting agent is surfactant-modified silica, preferably surfactant-modified precipitated silica. Preferably, the volume average particle size of the matting agent is ≤3 μm, more preferably ≤2.5 μm, and even more preferably ≤2 μm. Using a matting agent with a volume average particle size within the above-specified range further improves the adhesion between the coating formed by the two-component coating composition and the metal substrate, and ensures that the tensile properties (tensile strength and elongation) of the coating are sufficiently high.

[0083] Preferably, the oil absorption of the matting powder is at least 200 mL / 100 g, more preferably at least 210 mL / 100 g, even more preferably at least 220 mL / 100 g, and at most 300 mL / 100 g, preferably at most 280 mL / 100 g, and more preferably at most 250 mL / 100 g. With an oil absorption within the above range, the amount of resin used can be reduced, while the amount of filler can be increased. Furthermore, the matting powder with a smaller average particle size fills the voids, thus increasing the solid content, reducing VOCs, and lowering costs. This results in a tough, wear-resistant coating surface with excellent gloss stability. A further preferred matting powder is E-1011 from Tosoh Corporation of Japan, which is easily dispersed, has a good matting effect, and an average particle size of only 1.5 μm.

[0084] It should be noted that in this invention, the "oil absorption" of the matting powder is determined according to JISK5101-13-2 (Picture Test Methods - Part 13: Oil Absorption - Section 2: Boiling Linseed Oil Method). Specifically, the matting powder sample is placed on a glass plate, and boiling linseed oil is slowly dripped from a burette while being stirred and mixed with a spatula. The volume of boiling linseed oil at the moment of rapid softening is taken as the endpoint.

[0085] It should be noted that, in this invention, the "volume average particle size of the matting powder" can be determined using methods known to those skilled in the art.

[0086] Based on the total weight of the film-forming resin composition, the amount of matting agent in the film-forming resin composition, preferably with an oil absorption of at least 200 mL / 100 g, and more preferably with surfactant-modified silica, is at least 1% by weight, at least 2% by weight, preferably at least 3% by weight, more preferably at least 3.5% by weight, and at most 10% by weight, at most 9% by weight, at most 8% by weight, preferably at most 7% by weight, and more preferably at most 6% by weight. When the amount of matting agent is within the above range, the film-forming resin composition exhibits good film-forming properties, thus reducing the likelihood of cured film peeling and improving the adhesion between the coating formed by the two-component coating composition and the metal substrate.

[0087] Furthermore, the film-forming resin composition according to the present invention includes wax additives, preferably ultrafine polytetrafluoroethylene (PTFE) micronized wax aqueous dispersions or ultrafine micronized polytetrafluoroethylene (PTFE) modified polyethylene (PE) waxes, specifically Tianshi PTFE-1003, PTFE-1005, BYK AQUACER 1550R, and CERAFLOUR999. When used in the present invention, these wax additives reduce the surface friction coefficient of the coating, enhance the scratch resistance of the coating, and have strong hydrophobic properties, synergistically enhancing the chemical resistance of the system.

[0088] Based on the total weight of the film-forming resin composition, the amount of wax additive in the film-forming resin composition, preferably ultrafine polytetrafluoroethylene (PTFE) micronized wax aqueous dispersion or ultrafine micronized polytetrafluoroethylene (PTFE) modified polyethylene (PE) wax, is at least 0.01 wt%, preferably at least 0.1 wt%, more preferably at least 0.4 wt%, and at most 1.5 wt%, preferably at most 1.2 wt%, more preferably at most 1.0 wt%.

[0089] If desired, the film-forming resin composition of the present invention may optionally include additional additives that do not adversely affect the coating composition or the cured coating obtained therefrom. Suitable additives include, for example, those agents that improve the processing or manufacturing properties of the composition, or improve specific functional properties or characteristics (such as adhesion to a substrate) of the coating composition or the cured composition obtained therefrom. Additives that may be included are pigments, metal powders or pastes, anti-migration agents, antibacterial agents, chain extenders, curing agents, lubricants, biocides, plasticizers, rheology modifiers, hydrophobic agents, crosslinking agents, defoamers, colorants, antioxidants, preservatives, flow control agents, thixotropic agents, dispersants, leveling agents, UV absorbers, scavengers, thickeners, water-retaining agents, defoamers, pH adjusters, film-forming aids, antifreeze agents, slip agents, water-reducing agents, solvents, or combinations thereof. The amounts of each optional component are sufficient to achieve their intended purpose, but preferably, such amounts do not adversely affect the coating composition or the cured coating obtained therefrom. In a preferred embodiment, the film-forming resin composition of the present invention may include thickeners, defoamers, wetting agents, leveling agents, film-forming aids, dispersants, ultraviolet absorbers, solvents, or any combination thereof as additional additives; more preferably, it may include leveling agents, wetting agents, film-forming aids, ultraviolet absorbers, aqueous media, or any combination thereof as additional additives. Furthermore, the amount of these additives can be determined by those skilled in the art as needed.

[0090] As used herein, the term "aqueous medium" refers to water and various solvents miscible with water, including, but not limited to, water, alcohol solvents, ketone solvents, amide solvents, etc., such as water; methanol, ethanol, propanol, butanol; acetone, butanone, methyl ethyl ketone; dimethylformamide, dimethylacetamide, and combinations thereof. Preferably, the aqueous medium is water. To accelerate the drying speed of the coating composition, a mixture of water and a water-miscible solvent, such as a combination of water and ethanol, a combination of water and acetone, etc., can be used. Those skilled in the art can determine the composition and proportion of the above mixed solvents through simple experiments to obtain a suitable drying speed for the coating composition.

[0091] Examples of film-forming aids include alcohols such as ethylene glycol, propylene glycol, hexanediol, benzyl alcohol, etc.; alcohol esters such as dodecyl alcohol esters; alcohol ethers such as ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol n-propyl ether, propylene glycol butyl ether, dipropylene glycol methyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, tripropylene glycol n-butyl ether, etc.; and alcohol ether esters such as hexanediol butyl ether acetate, etc.

[0092] The film-forming resin composition according to the present invention has good film-forming properties, requiring only a small amount or no film-forming aids to form a film, which greatly reduces the VOC content in the coating and makes the coating more environmentally friendly.

[0093] In one embodiment, the film-forming resin composition includes a leveling agent, a wetting agent, and optionally a UV absorber as additional additives. An example of a leveling agent is BYK 358, available from BYK Corporation. Suitable wetting agents include silicone wetting agents, acetylenic diol wetting agents, or combinations thereof. All types of wetting agents are commercially available. An example of a silicone wetting agent is BYK 346, available from BYK GmbH. An example of a UV absorber is Tinuvin 1130, available from BASF.

[0094] The amount of the additional additive, relative to the total weight of the film-forming resin composition, is in the range of 0 to 15% by weight, preferably in the range of 0.3 to 10% by weight.

[0095] Furthermore, the film-forming resin compositions of the present invention may contain one or more other fillers. As used herein, the term "filler" refers to any volume-increasing agent suitable for coatings, which may be organic or inorganic, for example, in particulate form. There are no particular limitations on the shape of the particles, which may have any suitable shape. The average particle size of the filler may vary over a wide range, for example, from about 10 nanometers to about 50 micrometers. Some fillers, in addition to acting as volume-increasing agents in coatings, impart one or more desired properties to the composition and / or the coating formed from the composition. For example, some fillers may impart a desired color to the composition and the coating obtained from the composition. In this case, such fillers are also referred to as "pigments". Some fillers may improve chemical and / or physical properties, particularly the mechanical properties of the coating obtained from the composition. In this case, such fillers are also referred to as "reinforcing fillers".

[0096] Suitable exemplary fillers include, for example, kaolin, diatomaceous earth, titanium dioxide, calcium carbonate, talc, barium sulfate, magnesium aluminum silicate, and any combination thereof.

[0097] In one embodiment of the present invention, the film-forming resin composition comprises, based on the total weight of the film-forming resin composition:

[0098] 55-85% by weight of phosphate-modified hydroxyl acrylic resin;

[0099] 1-5% by weight of adhesion promoter;

[0100] 1-10% by weight of matting agent;

[0101] 0.01-1.5% by weight of wax additives;

[0102] 8-25% by weight of at least one organic solvent; and

[0103] Additional additives: 0-15% by weight.

[0104] Curing system

[0105] The curing system according to the present invention comprises a polyisocyanate as a curing agent. As used herein, the term "polyisocyanate curing agent" refers to a polyisocyanate compound, an isocyanate oligomer, or a combination thereof. The polyisocyanate curing agent contains two or more isocyanate functional groups, which are capable of undergoing chain extension and crosslinking reactions with the film-forming resin, thereby forming a three-dimensional network structure in the coating.

[0106] Suitable polyisocyanate curing agents include aliphatic polyisocyanates, aromatic polyisocyanates, or any combination thereof. As used herein, the term "aliphatic polyisocyanate" refers to a polyisocyanate compound in which the isocyanate group is directly attached to an aliphatic chain or ring. The term "aromatic polyisocyanate" as used herein refers to a polyisocyanate compound in which the isocyanate group is directly attached to an aromatic ring.

[0107] Examples of suitable polyisocyanate compounds include hexamethylene diisocyanate, dodecamethyl diisocyanate, cyclohexane-1,4-diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, cyclopentane-1,3-diisocyanate, p-phenylene diisocyanate, toluene-2,4-diisocyanate, naphthalene-1,4-diisocyanate, biphenyl-4,4'-diisocyanate, benzene-1,2,4-triisocyanate, xylene-1,4-diisocyanate, xylene-1,3-diisocyanate, diphenylmethane diisocyanate, butane-1,2,3-triisocyanate, or polymethylene polyphenyl polyisocyanate.

[0108] As examples of suitable isocyanate oligomers, polyurethane-type prepolymers of any of the polyisocyanate compounds listed above, polyester-type prepolymers of any of the polyisocyanate compounds listed above, or polyether-type prepolymers of any of the polyisocyanate compounds listed above, and any combination thereof, can be used. Polyurethane-type prepolymers, polyester-type prepolymers, or polyether-type prepolymers can be prepared by any suitable method known to those skilled in the art. For example, polyurethane-type prepolymers can be prepared by reacting a polyol monomer with one or more of the polyisocyanate compounds under suitable conditions; polyester-type prepolymers or polyether-type prepolymers can be prepared by reacting a polyester polyol or polyether polyol with one or more of the polyisocyanate compounds under suitable conditions. Alternatively, any suitable commercial product can be used as a polyurethane-type prepolymer, polyester-type prepolymer, or polyether-type prepolymer.

[0109] Preferred polyisocyanate curing agents are unblocked or blocked polyisocyanates, more preferably unblocked polyisocyanates that are modified with hydrophilic groups and / or at least partially modified with hydrophilic groups, and even more preferably modified with hydrophilic groups.

[0110] In a preferred embodiment of the present invention, the polyisocyanate curing agent is hexamethylene diisocyanate (HDI) trimer.

[0111] As an example of a polyisocyanate curing agent, any suitable commercially available product can be used, such as Coverstro's Desmodur N3790.

[0112] According to the present invention, the amounts of the polyisocyanate crosslinking agent and the film-forming resin composition are selected such that the molar ratio of hydroxyl (OH) to isocyanate (NCO) groups in the resulting system varies within the range of 1:1 to 1:2.5. Generally, when the molar ratio of hydroxyl (OH) to isocyanate (NCO) groups is less than 1:2.5, the operational properties of the resulting two-component coating composition and / or the mechanical properties of the resulting coating may decrease. When the molar ratio of hydroxyl (OH) to isocyanate (NCO) groups is greater than 1:1, the curing performance of the resulting coating is poor. Depending on actual needs, additional inert solvents that do not affect the reactivity of the above-mentioned film-forming resin composition and polyisocyanate curing agent may be added during the preparation of the film-forming resin composition and / or polyisocyanate curing agent, for example, to reduce the viscosity of each component. Therefore, the amounts of the film-forming resin composition and the polyisocyanate curing agent are not limited to the above range and can be adjusted according to actual needs.

[0113] The curing system according to the invention comprises a suitable solvent that is inert to the isocyanate group. Examples of suitable solvents are those used in conventional coating compositions known per se, such as ethyl acetate, butyl acetate, ethylene glycol monomethyl or monoethyl ether acetate, 1-methoxy-2-propyl acetate, 3-methoxy-n-butyl acetate, acetone, 2-butanone, 4-methyl-2-pentanone, cyclohexanone, toluene, xylene, chlorobenzene, and petroleum solvents (e.g., naphtha). (DeutscheEXXONCHEMICALGmbH, Cologne, DE) and (Deutsche ShellChemie GmbH, Eschborn, DE) is a commercially available, relatively highly substituted aromatic hydrocarbon, carbonate (such as dimethyl carbonate, diethyl carbonate, 1,2-ethylene carbonate and 1,2-propyl carbonate), lactone (such as β-propiolactone, γ-butyrolactone, ε-caprolactone and ε-methylcaprolactone), and propylene glycol diacetate, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, ethylene glycol butyl ether acetate, diethylene glycol butyl ether acetate, propylene glycol monomethyl ether acetate, 1,3-dioxane, N-methylpyrrolidone and N-methylcaprolactam, or any mixture of such solvents. Preferably, the solvent is selected from one or more of ethyl acetate, butyl acetate, xylene, toluene, propylene glycol monomethyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol butyl ether acetate, N-methylpyrrolidone, ethylene glycol monobutyl ether, acetone and butanone, and more preferably from one or more of xylene and propylene glycol monomethyl ether acetate.

[0114] The two-component coating composition of this invention uses phosphate-modified hydroxyl acrylic resin as the film-forming resin, epoxy silane as an adhesion promoter, and polyisocyanate as a curing agent, combined with specific silica powder, to obtain a single-coat system that can be used on metal substrates and exhibits excellent adhesion, water resistance, chemical resistance, and scratch resistance. The selected phosphate-modified hydroxyl acrylic resin, with its excellent steric hindrance effect, reduces the penetration of water and chemicals into the coating, thus improving the coating's salt spray resistance. Furthermore, the matting agent in the formulation is surfactant-modified silica, preferably surfactant-modified precipitated silica, which further enhances the adhesion between the coating formed by the two-component coating composition and the metal substrate, and ensures that the tensile properties (tensile strength and elongation) of the coating are sufficiently improved.

[0115] The inventors were surprised to discover that, in addition to their respective conventional functions, the combination of matting powder and wax additives with phosphate-modified hydroxyl acrylic resin had an unexpected effect on the coating's chemical resistance (such as pesticide resistance). Not wanting to be bound by any theory, the inventors speculated that the possible reason was that the selected matting powder, besides its conventional matting function, was inert and acted as a filler in gaps. Combined with the wax additives, this made the coating surface more tough and wear-resistant, resulting in an unexpected effect on pesticide resistance.

[0116] The inventors were also surprised to find that the two-component coating composition according to the invention can be cured at a relatively low temperature to obtain a single-coat system, which had never been recognized before the invention.

[0117] According to the present invention, a two-component coating composition can be prepared by simply mixing the film-forming resin composition and the curing system in a mixing device at a predetermined weight ratio before application.

[0118] Therefore, the second aspect of the present invention provides the application of the above-mentioned two-component coating composition, which can be directly coated on ordinary metal substrates (preferably stainless steel substrates) without the need for surface chemical treatment of the substrate. Since the two-component coating composition of the present invention can be baked at low temperatures and does not require pretreatment, a single coat is sufficient to achieve the decorative and protective functions of the original two- or three-coat system. The operation is simple, production efficiency is high, and the process is energy-saving and efficient. The resulting coating has excellent adhesion, chemical resistance, and abrasion resistance. Furthermore, the single-coat system of the present invention meets GMW14445 or GWM14698 standards.

[0119] The present invention also provides a single-coat system comprising: a cured coating formed from the aforementioned two-component coating composition according to the present invention; and the system is a high-performance coating system.

[0120] According to the two-component coating composition of the present invention, a primer and a topcoat in the traditional sense are combined into one, so that the single-coat system formed by curing the two-component coating composition of the present invention has both high interfacial bonding and high adhesion with the substrate, as well as the decorative properties of the topcoat, which can meet the needs of diverse decoration.

[0121] In one implementation, the system conforms to GMW14445 or GWM14698 specifications.

[0122] Furthermore, the present invention also provides a method comprising:

[0123] Provide metal substrates;

[0124] A two-component coating composition according to the present invention is applied to the metal substrate;

[0125] The metal substrate coated with the two-component coating composition is baked at a temperature of up to 80°C for at least 20 minutes, preferably 20 to 40 minutes, to obtain a cured film;

[0126] The cured film meets the specifications for high-performance coating systems.

[0127] The two-component coating composition of the present invention is practical in a variety of applications. Therefore, embodiments of the present invention also include a coated article comprising:

[0128] Metal substrate; and

[0129] A cured film is placed thereon, the cured film being obtained from a two-component coating composition according to the present invention;

[0130] The coated articles described herein meet the specifications of high-performance coating systems.

[0131] The two-component coating compositions according to the invention can be applied using various methods familiar to those skilled in the art, including spraying (e.g., air-assisted, airless, or electrostatic spraying), brushing, rolling, overcoating, and dipping. In one embodiment of the invention, the mixed two-component coating composition is applied by spraying. The coating composition can be applied to various wet film thicknesses. In embodiments of the invention, the wet film thickness preferably provides a dry film thickness of about 10 to about 40 μm, and more preferably a dry film thickness of about 15 to about 30 μm. The coated coating can be cured by air drying or by accelerating curing using various drying devices familiar to those skilled in the art (e.g., ovens).

[0132] During the curing process, the baking temperature is critical and must be high enough to cause the phosphate-modified hydroxyl acrylic resin present in the film-forming resin composition to react with the polyisocyanate curing agent to form a film. The inventors also surprisingly discovered that the two-component coating composition according to the invention can be cured at relatively low temperatures. For this purpose, the invention does not require very high baking temperatures; a single-coat system satisfying the requirements of a high-performance coating system can be obtained by baking at a temperature of at most 80°C, preferably at most 70°C, more preferably at most 60°C for at least 20 minutes, and preferably for 20 to 40 minutes.

[0133] Substrates that can benefit from coating their surfaces with the two-component coating compositions of the present invention are generally metallic substrates, including, but not limited to, hot-rolled steel, cold-rolled steel, hot-dip galvanized sheet, electro-galvanized sheet, aluminum sheet, tin sheet, various grades of stainless steel, and aluminum-zinc alloy coated steel sheets (e.g., GALVALUME steel sheets or GAL panels).

[0134] The two-component coating composition according to the present invention is a primer-topcoat integrated coating, which means that the traditional primer and topcoat are combined into one, and the coating can meet the usage requirements of automotive interior parts and construction machinery by applying one coating layer (one coating and one baking).

[0135] However, in some embodiments of the present invention, the two-component coating composition of the present invention can be used in conjunction with a primer, in which case the article of the present invention comprises a substrate, a primer layer, and a coating formed by the two-component coating composition of the present invention.

[0136] In other embodiments of the invention, the water-based coating composition of the invention can be applied without a primer, directly coated onto the main surface of the substrate.

[0137] The present invention is described in more detail below through examples. These examples are merely illustrative and should not be construed as limiting the scope of protection of the present invention, as various modifications and variations will be apparent to those skilled in the art within the scope of the present invention. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available and ready for use without further processing.

[0138] Test methods

[0139] Unless otherwise stated, the following test method is used in the following examples.

[0140] Adhesion

[0141] The rating is determined using a cross-cutting method according to the ASTM D3359 standard, and is rated from 5B to 0B, with 5B being the best and 0B being the worst.

[0142] Pencil hardness

[0143] This test is used to measure the hardness of the cured coating. The hardness of the pencil is evaluated using GB / T6739-2006 after the cured coating is baked at 80°C for 30 minutes, with a coating thickness of 20-30 micrometers.

[0144] The data is reported as the pencil hardness of the last successful test performed before the coating cracked. Therefore, for example, if the coating does not crack when tested with a 2H pencil but cracks when tested with a 3H pencil, the coating is reported as having a pencil hardness of 2H.

[0145] Solvent resistance test

[0146] Determined according to the standard test method of ASTM D540293.

[0147] gloss

[0148] This test is used to measure the gloss of the cured coating. The 60° gloss is evaluated using a Sheen pinhole gloss meter according to ASTM D523.

[0149] abrasion resistance

[0150] The test was performed according to the standard test method of HG / T 3655.5-2012.

[0151] Insecticide resistance test

[0152] Determined according to the standard test methods specified in GMW14445 or GWM14698.

[0153] Water boiling resistance test

[0154] This test is used to measure the adhesion of a cured coating to a substrate after boiling in water. The cured coating applied to a metal substrate is baked at 80°C for 30 minutes and then placed in deionized water at 100°C for a specified period. Adhesion tests are performed at time points of 1 hour, 2 hours, 3 hours, and 5 hours in deionized water, as described above, to obtain the appearance / adhesion test results at 80°C*1H, 80°C*2H, 80°C*3H, and 80°C*5H.

[0155] High temperature and high humidity test

[0156] This test measures the adhesion of a cured coating to a substrate after a period of exposure to high temperature and humidity. The cured coating applied to a metal substrate is baked at 80°C for 30 minutes, left for 7 days, and then placed at 85°C and 85% humidity for 150 hours. Adhesion is then tested according to GB / T9286-1998, rated on a scale of 0-5, with 0 being the best and 5 the worst.

[0157] neutral salt spray test

[0158] The test shall be conducted according to the method specified in 5.2 of GB / T10125-2012.

[0159] Chemical resistance

[0160] The tests shall be conducted in accordance with the methods specified in ISO 20433 and ISO 105-A02.

[0161] Insecticide and hand cream / sunscreen properties

[0162] The experiment was conducted according to the methods specified in GMW14445 and GMW14698. The specific experimental method was as follows: a certain amount of reagent was dropped onto the paint film, and then the paint film and reagent were placed together in an 80°C oven for 1 hour. After that, the paint film was removed, the reagent was wiped off, and then the appearance of the paint film was observed to test its scratch resistance.

[0163] Example

[0164] The present invention will now be described in more detail through embodiments. These embodiments are merely illustrative and should not be construed as limiting the scope of protection of the present invention, as various modifications and variations will be apparent to those skilled in the art within the scope of the present invention.

[0165] Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available and ready for use without further processing.

[0166] Preparation and performance testing of two-component coating compositions

[0167] The components are mixed in the following proportions to prepare a two-component coating composition.

[0168] The above-mentioned raw materials were mixed evenly using a disperser to obtain a two-component coating composition. A single coating layer was sprayed onto a stainless steel substrate, baked at 80°C for 30 minutes, and then left at room temperature for 7 days before testing. The test results are shown in the table below.

[0169]

[0170]

[0171] As can be seen from the results in Table 1, the two-component coating composition according to the present invention uses phosphate-modified hydroxyl acrylic resin as the film-forming resin, epoxy silane as an adhesion promoter, and polyisocyanate as a curing agent, combined with specific silica powder as a matting agent. The presence of phosphate functional groups improves the adhesion to the substrate, resulting in a single-coat system that can be used on metal substrates, and exhibits excellent adhesion, water resistance, chemical resistance, and scratch resistance. If a trialkoxysilane containing epoxy propoxy groups (preferably, a trialkoxysilane with epoxy propoxy groups at the end) is used as an adhesion promoter, the adhesion between the metal substrate and the cured film can be further improved. The matting agent in the formulation is surfactant-modified silica, which can further improve the adhesion between the coating formed by the two-component coating composition and the metal substrate.

[0172] The inventors were also surprised to discover that, in addition to their respective conventional functions, the combination of matting powder and wax additives with phosphate-modified hydroxyl acrylic resin had an unexpected effect on the coating's chemical resistance (such as pesticide resistance). Not wanting to be bound by any theory, the inventors speculated that the possible reason is that the selected matting powder, besides its conventional matting function, is inert and acts as a filler in gaps. Combined with the wax additives, this makes the coating surface more tough and wear-resistant, resulting in an unexpected effect on pesticide resistance.

[0173] The inventors were also surprised to find that the two-component coating composition according to the invention can be cured at a relatively low temperature to obtain a single-coat system, which had never been recognized before the invention.

[0174] The foregoing detailed description and embodiments are provided merely for clarity and should not be construed as unnecessarily limiting. The invention is not limited to the precise details shown and described, and obvious variations to those skilled in the art will be included within the scope of the invention as defined by the claims.

[0175] All disclosures of patents, patent applications, publications, and electronically available materials cited herein are incorporated herein by reference. The detailed descriptions and embodiments described above are provided for clarity only and should not be construed as causing unnecessary limitations. The invention is not limited to the precise details shown and described, as variations that will be apparent to those skilled in the art will be included within the scope of the invention as defined in the claims. In some embodiments, the invention exemplarily disclosed herein may be suitably practiced in the absence of any elements not specifically disclosed herein.

Claims

1. A two-component coating composition for a metal substrate, comprising: a) A film-forming resin composition comprising: Phosphate-modified hydroxyl acrylic resin; Adhesion accelerator; Matte powder; Wax additives; and Optional additives may be added; b) A curing system containing polyisocyanates.

2. The two-component coating composition according to claim 1, wherein, The matting powder has an oil absorption capacity of at least 200ml / 100g.

3. The two-component coating composition according to claim 1 or 2, wherein, The matting agent is precipitated silica modified with surfactant, preferably with an average particle size ≤3μm.

4. The two-component coating composition according to any one of the preceding claims, wherein, The wax additive is ultrafine polytetrafluoroethylene (PTFE) micronized wax or ultrafine micronized polytetrafluoroethylene (PTFE) modified polyethylene (PE) wax.

5. The two-component coating composition according to any one of the preceding claims, wherein, based on the solid weight of the phosphate-modified hydroxyl acrylic resin, the hydroxyl content of the phosphate-modified hydroxyl acrylic resin is at most 5% by weight, preferably at most 4% by weight, and more preferably at most 2% by weight.

6. The two-component coating composition according to any one of the preceding claims, wherein, Based on the total weight of the film-forming resin composition, the film-forming resin composition comprises: 55-85% by weight of phosphate-modified hydroxyl acrylic resin; 1-5% by weight of adhesion promoter; 1-10% by weight of matting agent; 0.01-1.5% by weight of wax additives; 8-25% by weight of at least one organic solvent; and Additional additives: 0-15% by weight.

7. The two-component coating composition according to any one of the preceding claims, wherein, The adhesion promoter is an organofunctional silane with epoxy functionality.

8. The two-component coating composition according to claim 7, wherein, The organofunctional silane with epoxy functionality has an epoxy equivalent in the range of 3.8-5.5 eq / 100g.

9. The two-component coating composition according to any one of the preceding claims, wherein, The adhesion promoter has the following general formula: in R1, R2, R4, and R5 are each independently C1-C6 alkyl, C6-C6 alkyl, or C6-C6 alkyl. 10 Aryl, halogen, hydroxyl, C1-C6 alkoxy, C2-C6 enoxy, C6-C 10 Aryloxy, C1-C6 alkyloxy and C6-C 10 Aromatic oxy groups, wherein R1, R2, R4, and R5 can be the same or different; R3 and R6 are each independently E-R7, where E is epoxyethyl, epoxypropyl, or epoxycyclohexyl, and R7 is a non-hydrolyzable divalent hydrocarbon group with fewer than 20 carbon atoms or a divalent group with fewer than 20 carbon atoms composed of C, H, N, S, and O atoms. m is an integer between 0 and 10.

10. The two-component coating composition according to claim 9, wherein, The adhesion promoter is a trimektoxysilane with epoxy functionality, preferably a trimektoxysilane containing epoxypropoxy.

11. The two-component coating composition according to any one of the preceding claims, wherein, The polyisocyanate is selected from one or more of aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates.

12. The two-component coating composition according to any one of the preceding claims, wherein, The polyisocyanate includes hexamethylene diisocyanate (HDI) trimer.

13. The two-component coating composition according to any one of the preceding claims, wherein, The metal substrate is a stainless steel substrate.

14. The two-component coating composition according to any one of the preceding claims, wherein, The two-component coating composition is a topcoat that combines primer and topcoat.

15. A single-coating system comprising: A cured coating formed from the two-component coating composition according to any one of the preceding claims; and the system is a high-performance coating system.

16. The system according to claim 15, wherein, The system has passed the GMW14445 or GWM14698 specifications.

17. A method for forming a single-coat system, comprising: Provide metal substrates; A two-component coating composition according to any one of claims 1 to 14 is coated onto the metal substrate; The metal substrate coated with the two-component coating composition is baked at a temperature of up to 80°C for at least 20 minutes, preferably 20 to 40 minutes, to obtain a cured film; The cured film meets the specifications for high-performance coating systems.

18. A coated article comprising: Metal substrate; and A cured film placed thereon, said cured film being obtained from a two-component coating composition according to any one of claims 1 to 14; The coated articles described herein meet the specifications of high-performance coating systems.

19. The article of claim 18, wherein, The metal substrate is a stainless steel substrate.

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