THERMALLY STABLE LINKED POLYVINYL FLUORIDE COATING

Abstract

The present disclosure relates to a coating composition comprising polyvinyl fluoride (PVF), an acrylic copolymer comprising groups with amine and / or hydroxyl functionality, and an isocyanate or melamine crosslinker comprising groups reactive towards amine or hydroxyl groups. Also disclosed herein are dried or cured coatings resulting from the coating composition, substrates coated with such coating compositions, the resulting dried and / or cured coated substrates, and methods for coating such substrates.

Description

OBJECT

[0001] The present disclosure relates to polyvinyl fluoride coatings capable of adhering to a wide variety of primers and bare metals. BACKGROUND

[0002] Polyvinyl fluoride (PVF) films are laminated to metal to provide aesthetics and durable protection for metal against harsh environmental conditions such as UV radiation, moisture, and corrosive environments such as exposure to acidic and basic conditions. However, PVF films are available in a limited range of colors, can only be produced in large batch sizes, and require adhesive to adhere to a substrate. Compared to PVF films, coatings made from PVF resin retain much of the same protection and durable aesthetics but can be processed in smaller batch sizes, are easier to apply to the substrate surface, and offer a wider range of aesthetic options. However, due to the inert nature of the PVF polymer, PVF coatings are only capable of adhering to limited types of primers and cannot adhere to bare metal.

[0003] Limited thermal stability is another problem with PVF polymers. In the PVF coating process, a PVF dispersion must be heated to a desired temperature to melt the PVF resin and evaporate the solvent to form a uniform coating. However, if the PVF resin remains at a high temperature for a long period of time, the PVF polymer begins to decompose, causing the PVF coating to appear yellow. Increased thermal stability is desirable to achieve well-fused coatings in a variety of ovens and oven conditions.

[0004] The simplest solution to improve adhesion to a PVF coating is to add acrylic or additional acrylic to the formulation. However, this approach can compromise the desired properties of PVF coatings, such as flexibility, chemical resistance, and weatherability.

[0005] The adhesion of PVF coatings can also be improved by using a primer or by developing the primer. Adding a certain amount of PVF resin to the primer can improve the adhesion of PVF topcoats, as this could improve the wettability of the PVF topcoat on the primer and potentially enhance mechanical interlocking and intermolecular hydrogen bonding. However, developing a PVF-containing primer can be complicated and may increase costs due to the additional amount of PVF resin used.

[0006] Adhesion can also be improved by adjusting process conditions, particularly by preventing primer burn-through during the primer curing process. This approach potentially increases the diffusion of primer components into the topcoat, thereby increasing the adhesion of the topcoat to the primer. However, this may compromise the desired chemical resistance, as the diffused components can alter the topcoat composition.

[0007] In the publications "Tailoring Crosslink Density and Index in 2K Waterborne PVDF Coatings" (Beaugendre et al., Coatingstech 11 (7), 2014) and "A New Approach to Water-based Fluoropolymer-urethane Hybrid Coatings" (Gupta et al., Proc. 2010 American Coatings Conference, Charlotte, NC, April 12-14, 2010), the authors reported on a polyvinylidene fluoride (PVDF) / acrylic resin that can be crosslinked with isocyanates and described that increased adhesion can be achieved using isocyanate crosslinking chemistry. They also described that this crosslinkable PVDF / acrylic system can be applied to and adhere to various window profile substrates, such as primed aluminum, polyester fiberglass composite, and vinyl.

[0008] The thermal stability of thick PVF products produced in a compression molding or sintered extrusion process can potentially be improved by adding epoxy, hindered phenolic compound, alkylarylphosphite, and / or mercaptoarylimidazole (see, e.g., U.S. Patent No. 5,447,975). Other fluoropolymers (e.g., PVDF) used in the coating process exhibit strong stability due to their more highly fluorinated polymer structure, requiring lower amounts of thermal stabilizers in the formulation.

[0009] Thus, there is a need to improve the adhesion of PVF coatings to a wide variety of primer materials as well as to bare metal while maintaining the other beneficial properties of the coatings. SUMMARY

[0010] One aspect relates to a coating composition comprising a polyvinyl fluoride (PVF), an acrylic copolymer comprising groups having amine and / or hydroxyl functionality, and an isocyanate or melamine crosslinker having reactive groups that react with groups having amino or hydroxyl functionality; wherein the weight ratio of the acrylic copolymer to the PVF ranges from about 0.05:1 to about 0.25:1; and wherein the number of reactive groups in the isocyanate or melamine crosslinker is from about 75 to about 125 mol% based on the total number of groups having amine or hydroxyl functionality in the acrylic copolymer. In some embodiments, the coating composition further comprises a pigment component, wherein the weight ratio of the pigment component to the total weight of PVF and acrylic copolymer in the coating composition ranges from about 0.05:1 to about 0.25:1.In some embodiments, the coating composition further comprises an acid scavenging epoxy component, wherein the weight ratio of the acid scavenging epoxy component to the PVF is in the range of about 0.002:1 to about 0.1:1. In some embodiments, the coating composition further comprises an antioxidant component, wherein the weight ratio of the antioxidant component to the PVF is in the range of about 0.002:1 to about 0.1:1; and in some embodiments, the antioxidant component is a phosphate-based antioxidant or a phenolic antioxidant. In some embodiments, the coating composition further comprises one or more solvents, wherein the weight ratio of the solvents to the PVF is in the range of about 2:1 to about 1:1.

[0011] An additional aspect relates to a coating composition comprising (a) about 25 wt. % to about 35 wt. % polyvinyl fluoride (PVF), (b) about 3 wt. % to about 10 wt. % of an acrylic copolymer comprising groups having amine and / or hydroxyl functionality, and (c) about 75 mol. % to about 120 mol. % of an isocyanate or a melamine crosslinker having reactive groups with respect to the groups of the acrylic copolymer having amine and / or hydroxyl functionality. In some embodiments, the coating composition further comprises a weight ratio of a pigment component to the total amount of PVF and acrylic copolymer in the coating composition ranging from about 0.05:1 to about 0.25:1. In some embodiments, the coating composition further comprises from about 0.5 wt. % to about 5 wt. % of an acid scavenger epoxy component. In some embodiments, the coating composition further comprises from about 0.5% to about 5% by weight.-% of an antioxidant component, and in some embodiments, the antioxidant component is a phosphate-based antioxidant or a phenolic antioxidant. In some embodiments, the coating composition further comprises from about 40% to about 60% by weight of one or more solvents.

[0012] Another aspect relates to a substrate at least partially coated with one of the aforementioned coating compositions. In some embodiments, the substrate is a primer, and in some embodiments, the primer is a polyurethane, a polyester, or an acrylic primer. In some embodiments, the substrate is a metal. In some embodiments, the substrate is a cured layer of the aforementioned coating composition. In some embodiments, the coating composition is cured on the substrate.

[0013] Another aspect relates to a method for coating a substrate, comprising applying the aforementioned coating composition to at least a portion of the substrate. In some embodiments, the substrate is coil-coated with the coating composition.

[0014] Another aspect relates to a dry-coated film composition comprising a PVF, an acrylic copolymer comprising groups having amine and / or hydroxyl functionality, and an isocyanate or melamine crosslinker having reactive groups that react with groups having amino or hydroxyl functionality; wherein the weight ratio of the acrylic copolymer to the PVF is in the range of about 0.05:1 to about 0.25:1; and wherein the number of reactive groups in the isocyanate or melamine crosslinker is about 75 to about 125 mol% based on the total number of groups having amine or hydroxyl functionality in the acrylic copolymer. In some embodiments, at least a portion of a primed substrate or a metal substrate is coated with the dry-coated film composition; and in some embodiments, the primer is a polyurethane, a polyester, or an acrylic primer.In some embodiments, the dry-coated film composition results from one of the above-mentioned coated substrates. In some embodiments, the dry-coated film composition is cured.

[0015] An additional aspect relates to a dry-coated film composition comprising (a) about 50 wt.% to about 70 wt.% PVF, (b) about 5 wt.% to about 20 wt.% of an acrylic copolymer comprising amine and / or hydroxyl functional groups, and (c) about 75 mol.% to about 120 mol.% of an isocyanate or melamine crosslinker having reactive groups with respect to the amine and / or hydroxyl functional groups of the acrylic copolymer. In some embodiments, the dry-coated film composition is cured.

[0016] Other objects and advantages will become apparent to one skilled in the art upon reference to the detailed description which follows. DETAILED DESCRIPTION

[0017] The coating compositions disclosed herein improve the adhesion of PVF coatings when applied to a wider variety of primer materials, as well as to bare metal. A coating made with PVF resin enables a metal coil coater to provide a similar level of protection from UV light and corrosive environments in a much more versatile format than PVF films. Customized colors can be produced in smaller batch sizes and applied to a metal coil with or without a corrosion-resistant primer.

[0018] The presently disclosed formulation for a heat-stable crosslinked PVF coating comprises isocyanate or melamine as a crosslinking agent and optionally an acid-scavenging epoxy component and / or an antioxidant component as a heat stabilizer. Isocyanate or melamine can react with amine or hydroxyl groups on the substrate surface, as well as amine or hydroxyl groups in functionalized acrylic, to form a covalently bonded polymer matrix. This formation of covalent bonds provides stronger adhesion of the PVF coating to the substrate surface compared to PVF coatings without crosslinking. Crosslinking in the PVF matrix also makes it difficult to extract the polymer with an organic solvent such as methyl ethyl ketone (MEK). The optional heat stabilizers make the PVF stable at high curing temperatures and for an extended cure time.

[0019] Acrylic resin is known to be soluble in PVDF, while it is insoluble in PVF. Here, the acrylic is expected to form a separate microstructure in the PVF coating compared to the PVDF coating. The result is a well-adhering coating that retains the chemical resistance and flexibility properties of PVF, which are superior to those of PVDF. Definitions

[0020] Numerous terms and abbreviations are used in this disclosure. The following definitions are provided.

[0021] As used herein, the term "about" or "approximately" means within 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1% or less of any value or range.

[0022] The term "comprising" is intended to encompass embodiments covered by the terms "consisting essentially of" and "consisting of." Similarly, the term "consisting essentially of" is intended to encompass embodiments covered by the term "consisting of."

[0023] The indefinite articles “a” and “an” as used in the description and claims of the present invention are to be understood as meaning “at least one” unless clearly stated otherwise.

[0024] For the purposes of the present invention, the phrase "and / or" in the description and claims should be understood to mean "one or both" of the elements thereby connected, i.e., elements that are present together in some cases and separately in other cases. Unless clearly stated otherwise, elements other than those explicitly named by the "and / or" phrase may be present, whether or not related to those explicitly named.Thus, by way of non-limiting example, reference to "A and / or B" when used with open-ended language such as "comprising" may, in one embodiment, refer to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0025] Within the scope of the present invention, in the description and claims, "or" is to be understood as having the same meaning as "and / or" as defined above. For example, when the members of a list are separated, "or" or "and / or" are to be interpreted as inclusive, i.e. the inclusion of at least one, but also more than one, of a plurality or list of elements and, if applicable, additional non-enumerated members. Only terms that clearly indicate something to the contrary, such as "only one of" or "exactly one of" or, when used in the claims, "consisting of", refer to the inclusion of exactly one element of a plurality or list of elements. In general, the term "or" within the scope of the present invention is to be interpreted only as indicating exclusive alternatives (i.e."one or the other, but not both") when preceded by terms of exclusivity, "either," "one of," "only one of," or "exactly one of." "Consisting essentially of," when used in the claims, has the meaning commonly used in patent law.

[0026] As used herein, the term "polyvinyl fluoride" or "PVF" includes homopolymers of vinyl fluoride and also covers copolymers of vinyl fluoride with other monoethylenically unsaturated monomers copolymerizable therewith, wherein vinyl fluoride repeat units constitute at least about 75% of the total copolymer weight. Representative monoethylenically unsaturated monomers useful for this purpose include vinyl esters, such as acetate and stearate, acrylates and methacrylates, such as methyl, ethyl, butyl, and isobutylene methacrylate. Other useful monomers are listed in U.S. Patent No. 3,139,470. PVF can be prepared as described in U.S. Patent No. 3,139,207 and can be fabricated in the form of an oriented film as described in U.S. Patent No. 3,139,470. PVF coatings

[0027] Some embodiments relate to coating compositions comprising a PVF, an acrylic copolymer comprising groups having amine and / or hydroxyl functionality, and an isocyanate or melamine crosslinker having reactive groups that react with groups having amino or hydroxyl functionality; wherein the weight ratio of the acrylic copolymer to the PVF is in the range of about 0.05:1 to about 0.25:1; and wherein the number of reactive groups in the isocyanate or melamine crosslinker is about 75 to about 125 mol% based on the total number of groups having amine or hydroxyl functionality in the acrylic copolymer.

[0028] Some embodiments relate to coating compositions comprising from about 25 wt.% to about 35 wt.% PVF, from about 3 wt.% to about 10 wt.% of an acrylic copolymer comprising groups having amine and / or hydroxyl functionality, and from about 75 mol.% to about 120 mol.% of an isocyanate or a melamine crosslinker having reactive groups with respect to the groups of the acrylic copolymer having amine and / or hydroxyl functionality.

[0029] PVF resin is generally insoluble in conventional solvents at room temperature; however, it can be dispersed in so-called latent solvents. A dispersion of PVF powder is suspended in a latent solvent and heated to a first temperature at which a gel forms, and then to a second temperature at which a solution forms. Latent solvents and other technologies useful for handling PVF are discussed in U.S. Patent Nos. 2,953,818 and 3,139,470.

[0030] Such latent solvents exhibit imperceptible solvent activity for PVF at temperatures below about 90°C, but exhibit solvent activity for PVF at higher temperatures. The latent solvents are relatively volatile, as their boiling point generally ranges between about 90°C and 300°C. In some embodiments, latent solvents are substantially removed by heating at 200°C or less for about 20 minutes. During this heat treatment, water and any volatile non-solvents are removed, and the polymer particles are exposed to the action of an increased concentration of latent solvent at a temperature at which the solvent is an effective solvent.

[0031] In some embodiments, the weight ratio of the acrylic copolymer to the PVF ranges from about 0.05:1 to about 0.25:1, about 0.08:1 to about 0.22:1, about 0.10:1 to about 0.20:1, or about 0.14:1 to about 0.16:1. In some embodiments, the weight ratio of the acrylic copolymer to the PVF is about 0.05:1, about 0.10:1, about 0.15:1, about 0.20:1, or about 0.25:1.

[0032] In some embodiments, PVF is present in the coating composition in the range of about 25 wt% to about 35 wt%, about 26 wt% to about 34 wt%, about 27 wt% to about 33 wt%, about 28 wt% to about 32 wt%, or about 29 wt% to about 31 wt%. In some embodiments, PVF is present in the coating composition in an amount of about 25 wt%, about 27 wt%, about 29 wt%, about 31 wt%, about 33 wt%, or about 35 wt%.

[0033] An acrylic copolymer for use in the present coating compositions is formed by the polymerization of acrylate monomers. Acrylate monomers are based on the structure of acrylic acid, which consists of a vinyl group and a carboxylic acid ester terminus. Typical acrylate monomers are acrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, butyl methacrylate, and the like. Thus, the acrylic copolymer may comprise monomers of acrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, and / or butyl methacrylate.

[0034] Various hydroxy-functional monomers may be used, and in some embodiments, the present coating compositions utilize a hydroxyalkyl ester of a monocarboxylic acid, such as acrylic acid or methacrylic acid. The contemplated alkyl groups are primarily those containing 2-4 carbon atoms and are exemplified by ethyl, propyl, or butyl. In some embodiments, the hydroxy-functional monomer is 2-hydroxyethyl methacrylate. Hydroxyalkyl ethers, such as the hydroxyethyl ether of allyl alcohol, are also useful.

[0035] The hydroxy-functional copolymer, in some embodiments, is the copolymer prepared by solution copolymerization in the presence of a free radical polymerization catalyst of monoethylenically unsaturated monomers, including the required proportion of hydroxyalkyl acrylate. The other monomers, in some embodiments, are acrylic esters and methacrylic esters with alcohols containing 1 to 12 carbon atoms, 1 to 9 carbon atoms, 1 to 6 carbon atoms, 1 to 3 carbon atoms, or 1 to 2 carbon atoms. In some embodiments, the other monomers are at least about 50% methyl methacrylate and the balance hydroxyethyl acrylate, and in some embodiments, about 55% to about 65% methyl methacrylate, about 57% to about 63% methyl methacrylate, methyl methacrylate, or about 59% to about 61% methyl methacrylate and the balance hydroxyethyl acrylate.

[0036] Various amine-functional monomers may be used, and in some embodiments, the present coating compositions utilize an aminoalkyl ester of a monocarboxylic acid, such as acrylic acid or methacrylic acid. The contemplated alkyl groups are primarily those containing 2-4 carbon atoms and are exemplified by ethyl, propyl, or butyl. In some embodiments, the amino-functional monomer is 2-aminoethyl methacrylate.

[0037] The amine-functional copolymer, in some embodiments, is a copolymer prepared by solution copolymerization in the presence of a free radical polymerization catalyst of monoethylenically unsaturated monomers, including the required proportion of aminoalkyl acrylate. The other monomers, in some embodiments, are acrylic esters and methacrylic esters with an amine containing 1 to 12 carbon atoms, 2 to 10 carbon atoms, 4 to 10 carbon atoms, 6 to 10 carbon atoms, 8 to 10 carbon atoms, or 9 to 10 carbon atoms. In some embodiments, the other monomers are acrylic esters and methacrylic esters with an amine containing 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms.In some embodiments, the other monomers are at least about 50% methyl methacrylate and the balance aminoethyl acrylate, and in some embodiments, about 55% to about 65% methyl methacrylate, about 57% to about 63% methyl methacrylate, about 58% to about 62% methyl methacrylate, or about 59% to about 61% methyl methacrylate and the balance aminoethyl acrylate.

[0038] In some embodiments, the acrylic copolymer is present in the coating composition in the range of about 3 wt% to about 10 wt%, about 4 wt% to about 9 wt%, about 5 wt% to about 8 wt%, or about 6 wt% to about 7 wt%. In some embodiments, the acrylic copolymer is present in the coating composition in an amount of about 3 wt%, about 4 wt%, about 5 wt%, about 6 wt%, about 7 wt%, about 8 wt%, about 9 wt%, or about 10 wt%.

[0039] The coating composition further comprises an isocyanate or melamine crosslinker in an amount sufficient to provide from about 75 mol% to about 120 mol% of reactive groups relative to the amine and / or hydroxyl functional groups of the acrylic copolymer.

[0040] Non-limiting examples of isocyanate crosslinkers include monomeric polyisocyanates such as toluene diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and isophorone diisocyanate. In some embodiments, the isocyanate crosslinker is a blocked polyisocyanate, which is a polyisocyanate in which isocyanate groups have reacted with a protecting or blocking agent to form a derivative that dissociates upon heating to remove the protecting or blocking agent and release the reactive isocyanate group. Some examples of suitable blocking agents for polyisocyanates include aliphatic, cycloaliphatic, or monohydric aralkyl alcohols, hydroxylamines, and ketoximes.

[0041] Non-limiting examples of melamine crosslinkers include those sold by Cytec under the trade name CYMEL®, specifically the alkylated melamine-formaldehyde resins CYMEL® 301, 303 and 385.

[0042] In some embodiments, the crosslinker is present in the coating composition in the range of about 75 mol% to about 120 mol%, about 80 mol% to about 115 mol%, about 85 mol% to about 110 mol%, about 90 mol% to about 105 mol%, or about 95 mol% to about 100 mol% of crosslinker having reactive groups with respect to the groups of the acrylic polymer having amine and / or hydroxyl functionality. In some embodiments, the crosslinker is present in the coating composition in an amount of about 75 mol%, about 80 mol%, about 85 mol%, about 90 mol%, about 95 mol%, about 100 mol%, about 105 mol%, about 110 mol%, about 115 mol%, or about 120 mol% of crosslinker having reactive groups with respect to the groups of the acrylic polymer having amine and / or hydroxyl functionality.

[0043] In some embodiments, the coating composition further comprises a pigment component. Suitable pigments can be inorganic or organic color powders of any color, including, but not limited to, a white powder of titanium oxide, pearl white powder, or zinc sulfide; a black powder of cobalt-copper-manganese oxide, copper-manganese oxide, copper-manganese-iron oxide, or iron oxide; a yellow powder of titanium yellow or bismuth yellow; a green powder of cobalt green or chromium oxide; or a blue powder of cobalt-chromium-aluminum oxide or ultramarine. Common types of organic pigments include azo pigments, lake pigments, phthalocyanine pigments, and quinacridone pigments. The color powders can be used individually or in combination to achieve the desired color. The primer and topcoat can employ a color powder of the same color.Alternatively, the primer and topcoat can use different colored powders. For example, the primer can be white, gray, or pale yellow, and the topcoat can be a darker color to mask the color of the primer.

[0044] In some embodiments, the amount of pigment component present in the coating composition provides a weight ratio of the pigment component to the total amount of PVF and acrylic copolymer in the coating composition that ranges from about 0.05:1 to about 0.25:1, about 0.07:1 to about 0.23:1, about 0.09:1 to about 0.21:1, about 0.11:1 to about 0.19:1, about 0.13:1 to about 0.17:1, or about 0.14:1 to about 0.16:1. In some embodiments, the pigment component is present in the coating composition in a weight ratio of the pigment component to the total amount of PVF and acrylic copolymer in the coating composition of about 0.05:1, about 0.10:1, about 0.15:1, about 0.20:1, or about 0.25:1.

[0045] In some embodiments, the coating composition further comprises an acid scavenging epoxy component. Non-limiting examples of suitable acid scavenging epoxies include difunctional bisphenol A / epichlorohydrin-derived epoxy resins and cycloaliphatic glycidyl ethers such as those sold by Miller-Stephenson Chemicals under the tradenames EPON® and EPONEX®, particularly the difunctional bisphenol A / epichlorohydrin-derived epoxy resin EPON® 825, 826, 828, 830, 834, 1001F, 1002F, 1004F, and the cycloaliphatic glycidyl ether EPONEX® 1510.

[0046] In some embodiments, the weight ratio of the acid scavenger epoxy component to the PVF ranges from about 0.002:1 to about 0.1:1, about 0.002:1 to about 0.08:1, about 0.002:1 to about 0.05:1, about 0.002:1 to about 0.025:1, about 0.002:1 to about 0.015:1, about 0.002:1 to about 0.01:1, or about 0.002:1 to about 0.005:1. In some embodiments, the weight ratio of the acid scavenger epoxy component to the PVF is about 0.002:1, about 0.005:1, about 0.01:1, about 0.015:1, about 0.025:1, about 0.05:1, about 0.075:1, or about 0.1:1.

[0047] In some embodiments, the acid scavenging component is present in the coating composition in the range of about 0.5 wt% to about 5 wt%, about 1 wt% to about 4.5 wt%, about 1.5 wt% to about 4 wt%, about 2 wt% to about 3.5 wt%, or about 2.5 wt% to about 3 wt%. In some embodiments, the acid scavenging component is present in the coating composition in an amount of about 0.5 wt%, about 1 wt%, about 2 wt%, about 3 wt%, about 4 wt%, or about 5 wt%.

[0048] In some embodiments, the coating composition further comprises an antioxidant component. In some embodiments, the antioxidant component is a phosphate-based antioxidant, a phenolic antioxidant, or a dialkyl ester of thiodipropionic acid. Non-limiting examples of suitable antioxidants include those sold by BASF under the tradenames IRGANOX® and IRGAPHOS®, particularly the phenolic antioxidant IRGANOX® 1010 and 1035, the dialkyl ester of thiodipropionic acid IRGANOX® PS800 and PS802, and the phosphate-based antioxidant IRGAPHOS® 168. Phosphite ethers such as those sold by the SI Group under the tradename WESTON® are also suitable examples, such as WESTON® TPP.

[0049] In some embodiments, the weight ratio of the antioxidant component to the PVF ranges from about 0.002:1 to about 0.1:1, about 0.005:1 to about 0.08:1, about 0.01:1 to about 0.06:1, about 0.015:1 to about 0.05:1, about 0.02:1 to about 0.04:1. In some embodiments, the weight ratio of the antioxidant component to the PVF is about 0.002:1, about 0.005:1, about 0.01:1, about 0.025:1, about 0.05:1, about 0.075:1, or about 0.1:1.

[0050] In some embodiments, the antioxidant component is present in the coating composition in the range of about 0.5 wt% to about 5 wt%, about 1 wt% to about 4.5 wt%, about 1.5 wt% to about 4 wt%, about 2 wt% to about 3.5 wt%, or about 2.5 wt% to about 3 wt%. In some embodiments, the antioxidant component is present in the coating composition in an amount of about 0.5 wt%, about 1 wt%, about 2 wt%, about 3 wt%, about 4 wt%, or about 5 wt%.

[0051] In some embodiments, the coating composition further comprises one or more solvents. Examples of suitable latent solvents include, but are not limited to, gamma-butyrolactone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, gamma-valerolactone, cyclic butadiene sulfone, tetramethylene sulfone, dimethylsulfolane, hexamethylene sulfone, diallyl sulfoxide, dicyanobutene, adiponitrile, ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, isobutylene carbonate, trimethylene carbonate, N,N-diethylformamide, N,N-dimethyl-gamma-hydroxyacetamide, N,N-dimethyl-gamma-hydroxybutyramide, N,N-dimethylacetamide, N,N-dimethylmethoxyacetamide, N-methylacetamide, N-methylformamide, N,N-dimethylaniline, N,N-dimethylethanolamine, 2-piperidone, N-methyl-2-piperidone, 1-ethyl-2-pyrrolidone, N-isopropyl-2-pyrrolidone, S-methyl-2-pyrrolidone, beta-propiolactone, delta-valerolactone, alpha-angelicalactone,beta-angelicalactone, epsilon-caprolactone, alpha-, beta- and gamma-substituted alkyl derivatives of gamma-butyrolactone, gamma-valerolactone, delta-valerolactone, delta-substituted alkyl derivatives of delta-valerolactone, tetramethylurea, 1-nitropropane, 2-nitropropane, acetonylacetone, Acetophenone, acetylacetone, cyclohexanone, diacetone alcohol, dibutyl ketone, isophorone, mesityl oxide, methyl amyl ketone, 3-methylcyclohexanone, bis(methoxymethyl)urone, methyl acetyl salicylate, diethyl phosphate, butyl carbitol, dimethyl phthalate, diethyl phthalate, ethyl acetoacetate, methyl benzoate, methylene diacetate, methyl salicylate, phenyl acetate, triethyl phosphate, Tris(morpholino)phosphine oxide, N-acetylmorpholine, N-acetylpiperidine, isoquinoline, quinoline, pyridine, xylene, tris(dimethylamido)phosphate, or a combination thereof. In one or more embodiments, the latent solvent may be propylene carbonate, γ-butyrolactone, n-methylpyrrolidone, dimethylacetamide, dimethyl sulfoxide, isophorone, diethyl phthalate,Dimethyl phthalate, dimethylformamide or a combination thereof.

[0052] In one or more embodiments, the latent solvent may be mixed with another organic solvent to form a solvent system. For example, the additional organic solvent may include ethylene glycol monobutyl ether, butyl carbitol, dipropylene glycol butyl ether, propylene glycol methyl ether acetate (PMA), dibasic ester (DBE), toluene, xylene, trimethylbenzene, methyl ethyl ketone, or a combination thereof.

[0053] In some embodiments, the weight ratio of the one or more solvents to the PVF ranges from about 2:1 to about 1:1, about 1.95:1 to about 1.05:1, about 1.9:1 to about 1.2:1, about 1.85:1 to about 1.3:1, about 1.8:1 to about 1.4:1. In some embodiments, the weight ratio of the solvents to the PVF ranges from about 2:1, about 1.75:1, about 1.5:1, about 1.25:1, about 1.15:1, about 1.1:1, about 1.05:1, or about 1:1.

[0054] In some embodiments, the solvent(s) in the coating composition is present in the range of about 40 wt% to about 60 wt%, about 42 wt% to about 58 wt%, about 44 wt% to about 56 wt%, about 46 wt% to about 54 wt%, about 48 wt% to about 52 wt%, or about 49 wt% to about 51 wt%. In some embodiments, the solvent is present in the coating composition in an amount of about 40 wt%, about 45 wt%, about 50 wt%, about 55 wt%, or about 60 wt%.

[0055] The sum of the weight percentages of the components of the PVF coating composition is 100 wt%. Substrat

[0056] The present disclosure also relates to a substrate at least partially coated with the aforementioned coating composition. In some embodiments, the coating composition is applied to at least about 1%, about 5%, about 10%, about 20%, about 50%, about 75%, about 90%, about 95%, about 99%, or more. In some embodiments, the coating composition is applied to an entire substrate.

[0057] In general, as non-limiting examples, a thickness of a single deposited "layer," whether identifiable as a layer or not, of the coating composition may range from less than 1 nm to a few or more nanometers, e.g., about 0.1, 0.5, 1, 2, 5, or 10 nm, to tens or hundreds of nm, e.g., up to or exceeding 50, 100, 500, 600, 800, 900 nm, 1 µm, 5 µm, 10 µm, 20 µm, 40 µm, 50 µm, or more.

[0058] The thicknesses of the individual layers of a coating may be the same, approximately the same, or different. Example coatings may include single deposited layers comprising a layer of clear coating on top of a pigmented coating.

[0059] In some embodiments, the substrate is a primer. Primers form a link between a substrate pretreatment and the coating of the next layer. The composition of the primer will depend on the type of next layer used. Primers require compatibility with various pretreatments and coating systems for the next layer; accordingly, in some embodiments, they may comprise a mixture of resin systems.

[0060] In some embodiments, the primer is a polyurethane, polyester, or acrylic primer. Non-limiting examples of primers include those sold by Sherwin Williams under the trade names Novaprime® and Pro Industrial®, specifically the polyurethane-based primer Novaprime® PU, the polyester primer Novaprime® 871 and HB, and the general-purpose acrylic primer Pro Industrial™ Pro-Cryl®.

[0061] In some embodiments, the substrate is a metal. The substrate may be, for example, cold-rolled steel, stainless steel, metallically coated steel (i.e., hot-dip galvanized steel), aluminum, or the like. The metal may be in the form of a coil, which in some embodiments may have a maximum width of 1.8 m, typically about 1.0 to 1.5 m. The metal substrate may, in some embodiments, have a thickness between 0.17 mm and 3.0 mm. At these thicknesses, the metal may suitably be treated with a coil coating process such as the method according to the present disclosure. In some embodiments, the metal substrate has a thickness between about 0.30 mm and about 1.50 mm, as this is an optimal thickness for a coil coating process in some embodiments.

[0062] When the PVF coating composition is applied to the metal substrate using other processes such as flexographic coating, gravure coating, curtain coating, extrusion coating, or spray coating, the dimensions of the substrate are less important. In these processes, a thin metal substrate may not be required, or it can be reinforced during the coating process, such as with a belt, cylinder, etc. Conversely, in discontinuous processes, it may be practical to apply the PVF coating composition to a thicker metal substrate.

[0063] The metal substrate may optionally be pretreated, for example by degreasing, optionally followed by washing, rinsing, passivation, and drying, and / or the pretreatment may include a chemical pretreatment based on chromium VI, chromium III, or a chromium-free passivating agent. Examples of chromium-free passivating agents are titanium and / or zirconium compounds, particularly complex fluorides of these elements. The pretreatments may include a suitable conversion coating.

[0064] In some embodiments, the substrate is a cured layer of the PVF coating composition described herein.

[0065] In some embodiments, the aforementioned PVF coating composition is cured on the substrate. In such embodiments, a presently disclosed coating composition is at least partially applied to a surface of the substrate to be coated using a suitable process designed to produce a coating having the desired thickness, followed by heat-curing the applied coating composition under controlled conditions, which in some embodiments include an initial heating step to evaporate the latent solvent.

[0066] In some embodiments, the coating composition is applied to the substrate in a coil coating line. Coil coating is a continuous and highly automated industrial process for efficiently coating metal coils. In particular, a coil coating process is a process in which an organic or inorganic coating material is applied to a metal strip in a continuous process that includes cleaning, if necessary, and chemical pretreatment of the metal surface, and the single or multiple application of (liquid) paints or coating powders, either on one or both sides, which are subsequently cured and / or laminated with permanent plastic films. The substrate is output from the roller mills as a coil, i.e., as a longitudinally wound strip. Standard coil weights vary, for example, from 5-6 tons for aluminum and up to approximately 25 tons for steel.The coil is positioned at the beginning of the line and then unwound at a constant speed, undergoing various pretreatment, coating, and hardening processes before being rewound. Two coil accumulators can be located at the beginning and end of the line, enabling continuous operation. This allows new coils to be added (and finished coils removed) via a metal stitching or welding process without having to slow down or stop the line.

[0067] Because the metal is treated in a coil-coating process before being cut and formed, the entire surface is cleaned and treated, providing tightly bonded finishes with reduced effort, reduced cost, and reduced use of chemicals. Coil-coated metal, or pre-coated metal, is more durable and corrosion-resistant than post-painted metal.

[0068] After the coil coating process, the coated metal can be processed, i.e., slit, into slit coils or flat sheets. There are two types of slitting, known as slitting, to produce slit coils: roll slitting and re-slitting. In roll slitting, the coil is treated as a whole (the "roll") and one or more sections are taken from it without an unwinding / re-winding process. In re-slitting, the web is unwound and passed through a machine, passing knives or lasers before being re-wound onto one or more shafts to form narrower rolls. Sheets can be formed into the desired dimensions by further slitting the rolled metal strip that forms the coil or slit coil. Alternatively, the coated metal can be punched, sawn, or processed into desired shapes by other suitable means.

[0069] In some embodiments, the step of curing an at least partially or fully coated substrate forms a cured dry film having a film thickness of, for example, about 0.5 mil to about 6 mil, about 0.75 mil to about 5 mil, about 1 mil to about 4 mil, about 1.25 mil to about 3 mil, about 1.5 mil to about 2 mil. In some embodiments, the film thickness is about 0.5 mil, about 0.75 mil, about 1 mil, about 1.25 mil, about 2.5 mil, or about 5 mil, or about 6 mil.

[0070] The curing step may, in some embodiments, be performed at a temperature in the range of about 160°C to about 300°C, about 180°C to about 280°C, about 200°C to about 260°C, or about 220°C to about 240°C. In some embodiments, the curing step may be performed at a temperature of about 160°C, about 180°C, about 200°C, about 220°C, about 240°C, about 260°C, about 280°C, or about 300°C.

[0071] In some embodiments, the curing step may be performed for a time ranging from about 10 seconds to about 50 seconds, about 15 seconds to about 45 seconds, about 20 seconds to about 40 seconds, about 25 seconds to about 35 seconds, or about 27.5 seconds to about 32.5 seconds. In some embodiments, the curing step may be performed for a time of about 10 seconds, about 15 seconds, about 20 seconds, about 25 seconds, about 30 seconds, about 35 seconds, about 40 seconds, about 45 seconds, or about 50 seconds.

[0072] The fluoropolymer dispersion compositions can be applied to the substrates by a variety of methods, including, among other methods, spraying, brushing, dipping, and roller coating.

[0073] Also provided is a method for spray coating a substrate and the spray-coated substrate. In the present spray coating method, a spray coating apparatus is used to apply the fluoropolymer dispersion composition. The fluoropolymer dispersion composition is often applied such that the wet film thickness ranges from about 1 mil to about 4 mils, about 1.5 mils to about 3.5 mils, about 1.75 mils to about 3.25 mils, about 2 mils to about 3 mils, or about 2.25 mils to about 2.75 mils. In some embodiments, the wet film thickness is about 1 mil, about 1.5 mils, about 2 mils, about 2.5 mils, about 3 mils, about 3.5 mils, or about 4 mils.

[0074] In some embodiments, the coating is cured at a temperature in the range of about 200°C to about 300°C, about 210°C to about 290°C, about 220°C to about 280°C, about 230°C to about 270°C, or about 240°C to about 260°C. In some embodiments, the coating is cured at a temperature of about 200°C, about 220°C, about 240°C, about 250°C, about 260°C, about 280°C, or about 300°C.

[0075] In some embodiments, the coating is cured for a time ranging from about 5 minutes to about 20 minutes, about 7.75 minutes to about 17.5 minutes, or about 10 minutes to about 15 minutes. In some embodiments, the curing step may be performed for a time of about 5 minutes, about 10 minutes, about 15 minutes, or about 20 minutes.

[0076] In some embodiments, the coating is cured to form a cured dry film having a thickness in the range of about 0.3 mil to about 2 mils, about 0.5 mil to about 1.8 mils, about 0.7 mil to about 1.6 mils, about 0.9 mil to about 1.4 mils, about 1 mil to about 1.3 mils, or about 1.1 mil to about 1.2 mils. In some embodiments, the cured dry film has a film thickness of about 0.3 mil, about 0.5 mil, about 0.7 mil, about 0.9 mil, about 1 mil, about 1.1 mil, about 1.3 mil, about 1.5 mil, about 1.7 mil, about 1.9 mil, or about 2 mils. Dry coated film compositions

[0077] Some embodiments relate to dry-coated film compositions comprising a PVF, an acrylic copolymer comprising groups having amine and / or hydroxyl functionality, and an isocyanate or melamine crosslinker having reactive groups that react with groups having amino or hydroxyl functionality; wherein the weight ratio of the acrylic copolymer to the PVF is in the range of about 0.05:1 to about 0.25:1; and wherein the number of reactive groups in the isocyanate or melamine crosslinker is about 75 to about 125 mol% based on the total number of groups having amine or hydroxyl functionality in the acrylic copolymer.

[0078] Some embodiments relate to dry-coated film compositions comprising from about 50 wt. % to about 70 wt. % PVF, from about 3 wt. % to about 10 wt. % of an acrylic copolymer comprising groups having amine and / or hydroxyl functionality, and from about 75 mol. % to about 120 mol. % of an isocyanate or melamine crosslinker having reactive groups with respect to the groups of the acrylic copolymer having amine and / or hydroxyl functionality. In the dry-coated film compositions, the sum of the weight percentages of the non-volatile components of the PVF coating composition is 100 wt. %.

[0079] In some embodiments, the weight ratio of the acrylic copolymer to the PVF ranges from about 0.05:1 to about 0.25:1, about 0.075:1 to about 0.225:1, about 0.10:1 to about 0.20:1, about 0.125:1 to about 0.175:1, or about 0.14:1 to about 0.16:1. In some embodiments, the weight ratio of the acrylic copolymer to the PVF is about 0.05:1, about 0.10:1, about 0.125:1, about 0.15:1, about 0.175:1, about 0.20:1, or about 0.25:1.

[0080] In some embodiments, PVF is present in the dry-coated film composition in the range of about 50 wt% to about 70 wt%, about 52 wt% to about 68 wt%, about 55 wt% to about 65 wt%, about 58 wt% to about 62 wt%, or about 59 wt% to about 61 wt%. In some embodiments, PVF is present in the dry-coated film composition in an amount of about 50 wt%, about 55 wt%, about 60 wt%, about 65 wt%, or about 70 wt%.

[0081] In some embodiments, the acrylic copolymer is present in the dry-coated film composition in the range of about 5 wt% to about 20 wt%, about 7 wt% to about 18 wt%, about 10 wt% to about 15 wt%, about 11 wt% to about 14 wt%, or about 12 wt% to about 13 wt%. In some embodiments, the acrylic copolymer is present in the dry-coated film composition in an amount of about 5 wt%, about 10 wt%, about 15 wt%, or about 20 wt%.

[0082] In some embodiments, the dry-coated film composition is cured. Curing may be achieved as discussed above.

[0083] The other components of the coating composition discussed above, namely an isocyanate or melamine crosslinker having reactive groups, a pigment component, the acid scavenger epoxy component, the antioxidant component, and the solvent, may be present in the dry-coated film composition in amounts and combinations as discussed above for the coating composition. The cured composition differs from the dry-coated film composition in that, upon curing, it comprises the reaction products of the acrylic resin and the crosslinker(s). The weights of the cured components are not expected to differ significantly from those of the unreacted components. In the cured film composition, the sum of the weight percentages of the non-volatile components of the PVF coating composition is 100 wt. %.

[0084] In particular, the applicant incorporates the entire contents of all cited references into the present disclosure. Furthermore, when an amount, concentration, or other value or parameter is specified either as a range or as a list of upper and lower values, this is to be understood as expressly disclosing all ranges formed by any pair of any upper range limit or upper value and any lower range limit or lower value, regardless of whether the ranges are disclosed separately. Whenever a range of numerical values ​​is recited herein, the range is intended to include the endpoints thereof and all integers and fractions within the range, unless otherwise stated.It is not intended to limit the scope of the present disclosure to the specific values ​​recited in defining a range. EXAMPLES

[0085] The present disclosure is further defined in the following examples. It should be understood that these examples, while indicating embodiments of the present disclosure, are provided for illustrative purposes only. Example 1

[0086] A series of cross-linkable PVF coating formulations were developed and tested for their adhesion to various primed or unprimed surfaces. Adhesion was measured using the grid cutter test (ASTM D3359). This test can be performed quickly and easily using an inexpensive grid cutter test kit. A grid pattern is cut into the finished film using a grid cutter, all the way down into the substrate. The test area is then brushed diagonally five times in each direction to remove any loose film / covercoat particles. A special adhesion testing tape is then firmly applied over the grid test area and quickly removed by peeling the tape from the test area to reveal the amount of coating removed from the test tape. The grid test area is then visually compared to ASTM D3359 standards, shown below in Table 1. Table 1 ASTM D3359 classification Percentage of area removed 5B 0% 4B <5% 3B 5-15% 2B 15-35% 1B 35-65% 0B >65%

[0087] A typical formulation for a non-crosslinked PVF coating was tested without an isocyanate crosslinker, and a crosslinked PVF coating with isocyanate was tested at approximately the same acrylic to PVF ratio of 15%. The exact formulation is listed below in Table 2. Table 2 PVF topcoat formulation Comparative example wt.% Example 1 wt.% PVF dispersion in propylene carbonate 65 65,3 60% titanium dioxide dispersion 21 22,5 Acryldispersion 1 11 8,8 33% Irganox™ 1035 solution in 2- 1 1,1 Butoxyethanol acetate (BEA) Propylene carbonate 2 - Isocyanate - 2,1 catalyst - 0,2 Acrylic / PVF 15 15 Pigment / binder 40 40 1. In the comparative example, 30% Paraloid™ B-44 acrylic polymer solution in propylene carbonate was used, available from The Dow Chemical Company of Midland, MI. In Example 1, 50% Setalux DA-450-BA acrylic polymer solution in butyl acetate was used, available from Allnex Resin Company.

[0088] Both the non-crosslinked PVF coating and the crosslinked PVF coating with nearly the same formulation were applied to four different substrate surfaces (polyurethane-primed galvanized steel, polyester-primed galvanized steel, acrylic-primed galvanized steel, and unprimed galvanized steel). It was found that incorporating isocyanate crosslinker into the PVF coating formulation improved adhesion to these tested primed or unprimed substrate surfaces, as shown in Table 3. Table 3 Comparison example 1 Example 1 Polyurethan 2 B 3 B polyester 3 B 5 B Acrylic 5 B 5 B Galvanized steel 3 B 5 B Example 2

[0089] Four formulations with different acrylic-to-PVF ratios (10%, 15%, 20%, and 25% acrylic) were further tested for their adhesion to polyurethane (PU) primer, polyester (PES) primer, acrylic primer, and galvanized steel (Table 4 below). For PU, PES, and galvanized steel, increasing the amount of acrylic resin in the coating formulation resulted in stronger adhesion for both the non-crosslinked and crosslinked coatings. The adhesion of the non-crosslinked PVF topcoat gradually increased from 0B to 5B when the acrylic / PVF ratio was increased from 10% to 25%. The crosslinked coating followed the same trend as the non-crosslinked PVF topcoat, but for each formulation with a specific acrylic-to-PVF ratio, the crosslinked coating with isocyanate crosslinker showed higher adhesion than the non-crosslinked PVF topcoat.This may be due to the fact that the majority of primers or unprimed metal surfaces contain hydroxyl groups, and isocyanate in the cured coating formulation can react with these hydroxyl groups to form covalent urethane bonds. The covalent bonds formed are stronger than the mechanical interlocking and / or intermolecular hydrogen bonding formed in the uncured topcoat. Table 4 Acrylic / PVF (wt%) 10 15 20 25 Pigment / binder (wt%) 40 40 40 40 PU not networked 0 B 2 B 4 B 5B networked 2 B 3 B 5 B 5B PES not networked 0 B 3 B 4 B 5B networked 1 B 5 B 5 B 5B Acrylic not networked 5B - 1 - - networked 5 B 5 B 5 B 5 B Galvanized steel not networked 0 B 1 B 5 B 5B networked 1 B 5 B 5 B 5B 1. "-" means not measured. Example 3

[0090] A methyl ethyl ketone (MEK) rub test (ASTM D4752) for the non-crosslinkable PVF coating (formulation shown below) showed that the blue pigment was extracted, and the MEK left a slight smear on the coating surface. This is possibly due to the non-crosslinked acrylic carrying the blue pigment being dissolved in the MEK. The same MEK rub test was performed on the crosslinked PVF coating (formulation shown below), but extraction of the blue pigment was less pronounced and the white smear was less visible. Crosslinking the acrylic helped to keep the pigment within the polymeric network and allowed for a low level of polymer dissolution in the MEK. Table 5 Comparative Example 3 Non-crosslinked PVF coating (g) Example 3 Crosslinked PVF coating (g) PVF dispersion in propylene carbonate 130 130 TiO2 dispersion 9,3 10,4 Acrylic resin type B-44 (30 %) Seta DA-450 Acrylic resin quantity 21,4 29,25 33% Irganox 1035 in BEA 2 2,4 Blue pigment dispersion 10,4 11 catalyst 0 0,6 Isocyanate 0 6,9 Example 4

[0091] The thermal stability of PVF coatings was investigated using thermogravimetric analysis (TGA). A PVF topcoat containing different heat stabilizers at different dosages (formulation shown in Table 6 below; values ​​are given as weight percentages based on the total weight of the PVF topcoat) was applied to bare metal and then peeled off the metal plate. A sample weighing approximately 0.5 mg was cut from the peeled PVF film and placed in the TGA (TA instrument, TGA 550). The TGA was programmed to heat at 50 °C / min and hold at 250 °C for ~1 h. Table 6 Non-crosslinked PVF topcoat formulation Non-crosslinked PVF wt% Non-crosslinked PVF + 1% Epon Non-crosslinked PVF + 2% Epon Non-crosslinked PVF + 1% TPP Non-crosslinked PVF + 2% TPP Non-crosslinked PVF + 1% Epon + 1% TPP Non-crosslinked PVF + 2% Epon + 2% TPP Non-crosslinked PVDF PVF dispersion (commercially available 44-1010) 65 65 65 65 65 65 64 65 60% titanium dioxide dispersion 21 21 21 21 21 21 20 21 30% Paraloid™ B-44 solution in PC 11 11 11 11 11 11 11 11 33% Irganox™ 1035 solution in BEA 1 1 1 1 1 1 1 1 Propylene carbonate 2 1 _ 1 1 - - - 2 Epon 828 - 1 2 - - 1 2 - TPP - - - 1 2 1 2 - 1. "-" means not present.

[0092] The weight of the PVF sample was recorded in situ as shown in Table 6 below. The decrease in sample weight indicated the instability and degradation of the PVF sample. Typically, the sample weight remains constant at 250 °C for a period of time (stability time), and then the weight decreases as the sample begins to decompose. A decrease in weight at a rate greater than 5% / min indicates the end of the stable period. A formulation based on non-crosslinked PVF (column 2) was tested as a control group, which exhibited a stability time of approximately 3 min. The addition of TPP at 1% and 2% did not improve stability. The addition of 1% epoxy (Epon® Epoxy Resin 828) improved the stability time to ~12 min. Additional epoxy (2%) has no effect on improving stability.Epon® 828 and TPP demonstrated a synergistic effect, as the addition of 1% Epon® 828 and 1% TPP rendered the PVF topcoat stable for ~15 min. Non-crosslinked PVDF topcoat, as a control group, showed no degradation during the 1-hour holding period at 250 °C. Table 7 Non-crosslinked PVF wt.% Non-crosslinked PVF + 1% Epon Non-crosslinked PVF + 2% Epon Non-crosslinked PVF + 1% TPP Non-crosslinked PVF + 2% TPP Non-crosslinked PVF + 1% Epon + 1% TPP Non-crosslinked PVF + 2% Epon + 2% TPP Stable time (min) 3,4 3,4 3,4 11,7 11,7 15 32 b* 2,99 3,35 3,08 -0,48 -0,61 -0,66 -0,74

[0093] Color measurement of the coating at the b* coordinate (blue / yellow) showed a correlation with the thermal stability time measured by TGA (Table 7). Samples with low thermal stability exhibited a positive b* value around 3, consistent with their yellowish color. Yellow color may indicate degradation of the PVF polymer. The addition of Epon® 828 helped improve thermal stability and reduced the b* to negative (blue), indicating less degradation of the PVF polymer. Example 5

[0094] The thermal stability of cross-linked PVF topcoat with different thermal stabilizers (formulation shown in Table 8 below; values ​​are given in grams (g)) was investigated by TGA following the same procedure as in Example 4. Table 8 Mixing recipe Networked PVF Cross-linked PVF + 1% Epon Cross-linked PVF + 1% TPP Cross-linked PVF + 1% TPP + 1% Epon PVF dispersion (45 wt.% PVF resin in propylene carbonate) 40 40 40 40 Acrylic solution (Setalux BA-450) 3,60 3,60 3,60 3,60 Isocyanate 0,84 0,84 0,84 0,84 1% catalyst solution 0,07 0,07 0,07 0,07 33% Irganox 1035 in BEA 0,62 0,62 0,62 0,62 TiO2 dispersion 13,2 13,2 13,2 13,2 Epon 828 0,6 0,6 Weston TPP 0,6 0,6

[0095] Crosslinked PVF topcoat with isocyanate crosslinkers showed a stability time of ~5 min before its weight decreased (Table 9 below). Epoxy (e.g., Epon® 828) added to the crosslinked PVF topcoat increased the stability time to 13 min. The addition of 1% TPP also extended the stability time of the crosslinked PVF topcoat to 20 min, which is different compared to the non-crosslinked PVF topcoat. Adding the combination of 1% Epon® 828 and 1% TPP showed the synergistic effect, exhibiting the longest stability time of 25 min. Table 9 Mixing recipe Networked PVF Cross-linked PVF + 1% Epon Cross-linked PVF + 1% TPP Cross-linked PVF + 1% TPP + 1% Epon Stable time (min) 5 13 25 25 Example 6

[0096] The adhesion of heat-stable cross-linked PVF to various substrates can be further enhanced by increasing the acrylic to PVF ratio in the formulation. With the formulation presented in Table 10, the heat-stable PVF coating can achieve good adhesion (5B) to acrylic primer, polyester primer, polyurethane primer, and bare metal following the ASTM D3359 test. The heat stability of this formulation cannot be directly measured by TGA because the coating cannot be peeled off the substrates. As indirect evidence, the low b* value of this formulation confirmed the good heat stability of the sample. Table 10 Mixing recipe PVF dispersion (45 wt.% PVF resin in propylene carbonate) 40 Acrylic solution (Setalux BA-450) 7,2 Isocyanate 1,69 1% catalyst solution 0,14 33% Irganox 1035 in BEA 0,69 TiO2 dispersion 14,4 Epon 828 0,6 Weston TPP 0,6 Liability Acrylic primer 5B Polyurethane primer 5B Polyester primer 5B Bare metal 5B b* -0,25

[0097] Although certain of the preferred embodiments of the present invention have been described and specifically illustrated above, the invention is not intended to be limited to such embodiments. Various modifications may be made without departing from the scope and spirit of the invention as set forth in the following claims. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 5,447,975

[0008] US 3,139,470 [0026, 0029] US 3,139,207

[0026] US 2,953,818

[0029] Cited non-patent literature

[0000] Tailoring Crosslink Density and Index in 2K Waterborne PVDF Coatings“ (Beaugendre et al., Coatingstech 11 (7), 2014

[0007] A New Approach to Water-based Fluoropolymer-urethane Hybrid Coatings“ (Gupta et al., Proc. 2010 American Coatings Conference, Charlotte, NC, 12.-14. April 2010

[0007]

Claims

[1] Coating composition comprising: (a) a polyvinyl fluoride (PVF); (b) an acrylic copolymer comprising groups having amine and / or hydroxyl functionality; and (c) an isocyanate or melamine crosslinker having reactive groups which react with groups having amino or hydroxyl functionality, wherein: the weight ratio of the acrylic copolymer to the PVF is in the range of 0.05:1 to 0.25:1; and the number of reactive groups in the isocyanate or melamine crosslinker is 75 to 125 mol%, based on the total number of groups with amine or hydroxyl functionality in the acrylic copolymer. [2] The coating composition of claim 1, further comprising a pigment component, wherein the weight ratio of the pigment component to the total weight of PVF and acrylic copolymer in the coating composition is in the range of 0.05:1 to 0.25:

1. [3] The coating composition of claim 1, further comprising an acid scavenger epoxy component, wherein the weight ratio of the acid scavenger epoxy component to the PVF is in the range of 0.002:1 to 0.1:

1. [4] The coating composition of claim 1, further comprising an antioxidant component, wherein the weight ratio of the antioxidant component to the PVF is in the range of 0.002:1 to 0.1:

1. [5] The coating composition of claim 4, wherein the antioxidant component is a phosphate-based antioxidant or a phenolic antioxidant. [6] The coating composition of claim 1, further comprising one or more solvents, wherein the weight ratio of the solvents to the PVF is in the range of 2:1 to 1:

1. [7] A substrate at least partially coated with the coating composition of claim 1. [8] The substrate of claim 7, wherein the coated surface of the substrate is primed. [9] A substrate according to claim 8, wherein a primer is a polyurethane, a polyester or an acrylic primer. [10] The substrate of claim 7, wherein the coated surface of the substrate is a metal. [11] The substrate of claim 7, wherein the coated surface of the substrate is a cured layer of the coating composition of claim 1. [12] A dry coated film composition comprising (a) a polyvinyl fluoride (PVF); (b) an acrylic copolymer comprising groups having amine and / or hydroxyl functionality; and (c) an isocyanate or melamine crosslinker having reactive groups which react with groups having amino or hydroxyl functionality, wherein: the weight ratio of the acrylic copolymer to the PVF is in the range of 0.05:1 to 0.25:1; and the number of reactive groups in the isocyanate or melamine crosslinker is 75 to 125 mol%, based on the total number of groups with amine or hydroxyl functionality in the acrylic copolymer. [13] A dry coated film composition according to claim 12, which is coated on at least a portion of a primed substrate or a metal substrate. [14] The dry coated film composition of claim 13, wherein a primer is a polyurethane, a polyester or an acrylic primer. [15] The dry coated film composition of claim 12 which is cured.