Coating compositions for beverage containers

Abstract

The present invention provides a beverage container and a coating method. The beverage container comprises a metal substrate at least partially coated with a coating, wherein the coating is prepared from a composition comprising a binder system, a crosslinking agent and a catalyst.

Description

[0001] Cross-references to related patent applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 038,302, filed on June 12, 2020, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to coating compositions for beverage containers and aqueous coating compositions for interior surfaces of beverage containers. Background Art

[0004] A variety of compositions have been used to coat the surfaces of packaging articles such as beverage containers. For example, metal cans are sometimes coated using coil coating or sheet coating operations, in which a planar coil or sheet of a suitable substrate (such as steel or aluminum metal) is coated with a suitable composition and hardened by curing in an oven. The coated substrate can then be formed into a can end cap or body. Alternatively, the liquid coating composition can be applied to a shaped article by spraying, dipping, roller coating or other suitable application methods and then cured.

[0005] Packaging coatings should preferably be capable of being applied to substrates at high speeds and, when hardened, provide the necessary properties to perform in such demanding end uses. For example, the compositions and coatings should be safe for food contact, have good adhesion to substrates, and resist degradation for long periods of time even when exposed to harsh environments. Many current packaging coatings suffer from one or more performance deficiencies and / or contain extractable amounts of one or more undesirable compounds, particularly when the coatings are exposed to short cure cycles.

[0006] Beverage container end caps, such as easy-open container end caps, are usually the most challenging coating applications in the beverage container coating industry. In some cases, this challenge is due to the strict manufacturing level that the coating and substrate must withstand in the formation of beverage container end caps. For example, beverage container end caps are formed by first applying a coating composition to a flat metal coil (usually an aluminum or steel coil). The beverage container end caps are then stamped from the coated metal coil. If an easy-open container is required, a rivet with a pull tab attached is also formed by the substrate, and such rivets have a very harsh profile. Many packaging coatings (including many coatings suitable for the sidewalls of beverage containers) do not have toughness and flexibility to adapt to the stamping process for forming can end caps and / or rivets, but still show enough corrosion resistance for end use. For existing coatings, there is usually a compromise between the flexibility and corrosion resistance of the coating. That is, a type of coating composition can have enough flexibility to adapt to stamping and rivet formation, but such performance is at the expense of corrosion resistance. These two performance characteristics are usually required in many food and beverage container coatings.

[0007] Existing coatings for achieving the high level of performance required for beverage container end caps are typically BPA and / or epoxy compositions combined with melamine or phenolic crosslinkers. Melamine and phenolic resins are based on formaldehyde monomers. Such components have become less desirable in the packaging field for a variety of reasons. However, when used in the context of coating operations for beverage container end caps, non-epoxide and non-formaldehyde alternatives often have disadvantages in processing and / or performance. Polyolefin dispersions are a substitute for epoxy resin coatings. Polyolefin dispersions have been used as spray coatings for the inner bodies of food or beverage containers; however, when existing polyolefin-based compositions are used in the demanding and challenging manufacture of beverage can end caps that are subject to short cure times, the cure process and existing polyolefin chemistry often fall short of the expected performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figures 1 to 4 are exemplary plan and perspective views of a metal sheet having a simulated pull tab formed thereon for use in feathering evaluation as described in the Examples. Summary of the invention

[0009] The present disclosure provides an aqueous coating composition suitable for use in a beverage container, the beverage container comprising a metal substrate at least partially coated with the aqueous coating composition. In one aspect or embodiment, the aqueous coating composition comprises a carrier fluid, a polyolefin binder system, a crosslinking agent; and a transition metal catalyst, the transition metal catalyst preferably being water dispersible. In some embodiments, the aqueous coating composition is suitable for forming a beverage contact coating of an easy-open end cap of a beverage container. In other embodiments or aspects, the coating composition is an inner beverage can end cap coating composition.

[0010] In other embodiments or aspects, the aqueous coating composition of the previous paragraphs and the following paragraphs of the present disclosure may include one or more optional features or components. These optional features or components may include any combination of the following aspects and / or embodiments: wherein the polyolefin binder system comprises a polyolefin copolymer having structural units derived from reactants including two or more C2 to C10 alpha-olefins; and / or wherein the alpha-olefin is selected from C2 to C6 alpha-olefins; and / or wherein the alpha-olefin is selected from C2 to C4 alpha-olefins; and / or wherein the polyolefin binder system comprises a polyolefin copolymer having structural units derived from reactants including ethylene and one or more C3 to C 10and / or wherein the coating composition comprises an emulsion-polymerizable ethylenically unsaturated monomer component, the emulsion-polymerizable ethylenically unsaturated monomer component optionally being emulsion polymerized in the presence of the polyolefin binder system; and / or wherein the coating composition comprises from about 30 wt % to about 35 wt % total resin solids; and / or wherein the coating composition comprises at least about 50 wt % of one or more polyolefin polymers, based on the total resin solids of the coating composition.

[0011] In yet other aspects or embodiments, the aqueous coating composition of the previous paragraphs and the following paragraphs of the present disclosure may include other optional features or components. These other optional features or components may include any combination of the following aspects and / or embodiments: wherein the crosslinking agent is a nitrogen-containing carboxyl-reactive crosslinking agent; and / or wherein the nitrogen-containing carboxyl-reactive crosslinking agent comprises a hydroxyl group; and / or wherein the nitrogen-containing carboxyl-reactive crosslinking agent comprises at least one amide group, at least one imide group, or a combination thereof; and / or wherein the nitrogen-containing carboxyl-reactive crosslinking agent comprises a β-hydroxyl group relative to the nitrogen atom of the amide bond; and / or wherein the nitrogen-containing carboxyl-reactive crosslinking agent has a structure HO-R1-N(R2)-CO-X-CO-N(R2)-(R1)-OH, wherein R1 and R2 are independently organic groups, X is a divalent organic group, and wherein the hydroxyl group is independently a primary hydroxyl group or a secondary hydroxyl group; and / or wherein the nitrogen-containing carboxyl-reactive crosslinking agent comprises a compound of the following formula:

[0012] And / or wherein the nitrogen-containing carboxyl-reactive crosslinking agent comprises a carbodiimide moiety.

[0013] In other aspects or embodiments, the aqueous coating composition of the previous paragraph or the following paragraph of the content of the present invention may include other optional features or components. These other optional features or components may include any combination of the following aspects and / or embodiments: wherein the transition metal catalyst includes at least one metal selected from aluminum (Al), cobalt (Co), iron (Fe), titanium (Ti), zinc (Zn), zirconium (Zr), or a mixture thereof; and / or wherein the transition metal catalyst includes an organic metal transition metal catalyst, and / or wherein the organic metal transition metal catalyst includes one or more alkoxy ligands, and / or wherein the organic metal transition metal catalyst includes one or more alkoxycarbonyl ligands, and / or wherein the alkoxy ligand or the alkoxycarbonyl ligand includes a C1 to C6 alkyl group, and / or wherein the organic metal transition metal catalyst includes a C1 to C6 alkyl group. The activator is an organic metal transition metal chelate, and / or wherein the transition metal catalyst is selected from titanium acetylacetonate, tetraalkyl titanate, isopropyl orthotitanate, a water-soluble titanium chelate, a triethanolamine chelate of titanium, a tetratriethanolamine chelate of titanium, a lactic acid titanate chelate or a combination thereof, and / or wherein the coating composition comprises at least about 400 ppm of the transition metal catalyst based on the total amount of transition metal in the catalyst relative to the total non-volatile weight of the aqueous coating composition, and / or wherein the coating composition comprises no more than about 800 ppm of the transition metal catalyst based on the total amount of transition metal in the catalyst relative to the total non-volatile weight of the aqueous coating composition.

[0014] In other aspects or embodiments, the aqueous coating composition of the preceding paragraph or the following paragraph of the present disclosure may also include or exhibit any of the following items, alone or in combination: when applied to a cleaned and chromium-free pretreated aluminum plate and cured for 12 seconds to a peak metal temperature of 249°C to achieve a dry film thickness of about 12 grams per square meter and formed into a fully converted 202 standard opening beverage can end, a current of less than 5 milliamperes is passed while exposed to an electrolyte solution containing 1 weight percent NaCl dissolved in deionized water for 4 seconds; and / or wherein when the aqueous coating composition is The aqueous coating composition exhibits a feathering, if any, of 0.5 mm or less when applied to a cleaned, chrome-free pretreated aluminum panel and cured for 12 seconds to a peak metal temperature of 249° C. to achieve a dry film thickness of about 12 g / m²; and / or exhibits a blush rating of at least 6 after pasteurization when applied to a cleaned, chrome-free pretreated aluminum panel and cured for 12 seconds to a peak metal temperature of 249° C. to achieve a dry film thickness of about 12 g / m², and / or wherein the aqueous coating composition has a viscosity of 35 seconds to 60 seconds as measured by ASTM D-1200 using a No. 4 Ford Cup at 25° C.

[0015] In other aspects or embodiments, the aqueous coating composition of the previous paragraph or the following paragraph of the present invention may include other optional features or components. These other optional features or components may include any combination of the following aspects and / or embodiments: wherein the aqueous coating composition has about 30% to about 35% by weight of solids; and / or wherein the carrier fluid includes one or more water-miscible organic solvents, and / or wherein the water-miscible organic solvent includes isopropanol, ethanol, methanol, butanol, amyl alcohol, glycol, glycol ether, glycol ester, acetone, methyl ethyl ketone or tetrahydrofuran or a mixture thereof, and / or wherein the coating composition contains about 15% to about 3.5% by weight of the one or more water-miscible organic solvents, and / or wherein the coating composition contains at least about 5% by weight of one or more organic solvents; and / or wherein the coating composition is substantially free of bisphenol A, bisphenol F or bisphenol A. each of bisphenol S, or any epoxides thereof; and wherein the coating composition is optionally substantially free of styrene; or wherein the coating composition does not contain any bisphenol A, bisphenol F, bisphenol S, their epoxides or styrene, or structural units derived from bisphenol A, bisphenol F, bisphenol S, their epoxides or styrene; and / or wherein the aqueous coating composition is substantially free of formaldehyde or structural units derived from formaldehyde, or does not contain any formaldehyde or structural units derived from formaldehyde; and / or further comprises a lubricant; and / or wherein the lubricant is selected from carnauba wax, polyethylene wax, Fischer-Tropsch wax, fatty acid ester wax, silicone wax, lanolin wax, hydroxyl-functional polysiloxane wax or a combination thereof; and / or wherein the coating composition comprises at least about 25% by weight of water.

[0016] In yet other aspects or embodiments, an article is described herein, wherein the article comprises a metal substrate having a riveted food or beverage can end cap, the riveted food or beverage can end cap having a coating disposed on at least a portion of the riveted beverage can end cap, and wherein the coating is formed by an aqueous coating composition as described in any embodiment and / or aspect of the preceding or following paragraphs of the present disclosure. In other embodiments, the coating exists as an internal food contact coating.

[0017] In other aspects or embodiments, the article of the previous paragraph or the following paragraph of the content of the present invention may include other optional features or components. These other optional features or components may include any combination of the following aspects and / or embodiments: wherein when tested as described herein, the coating allows less than 5 mA of current to pass; and / or wherein when tested as described herein, if any, the coating exhibits a feathering of less than 0.5 mm; and / or wherein the coating has an average dry coating thickness of about 7 microns to about 15 microns, and / or wherein the metal substrate of the food or beverage can end cap has an average thickness of about 175 microns to about 230 microns, and / or wherein the metal substrate of the food or beverage can end cap comprises aluminum or steel, and / or wherein the surface of the metal substrate is pretreated with a chromium-based or non-chromium-based (zirconium-based and acrylic-based) treatment before coating with the aqueous coating composition.

[0018] In yet other aspects or embodiments, a method is described herein, wherein the method comprises applying the aqueous coating composition of any preceding or following embodiment or aspect as described in the preceding or following paragraphs of the Summary of the Invention to a surface of a substrate for forming an end cap for a beverage container, and curing the aqueous coating composition to form a cured coating on the surface of the substrate.

[0019] In other aspects or embodiments, the methods of the preceding or following paragraphs of this Summary of the Invention may include other optional features or components. These other optional features or components may include any combination of the following aspects and / or embodiments: wherein the substrate is aluminum or steel; and / or wherein applying the aqueous coating composition to the surface of the substrate comprises applying the aqueous coating composition to a continuously moving surface traveling at a line speed of about 50 meters / minute to about 400 meters / minute; and / or wherein the curing is performed for an oven cure time of about 8 seconds to about 15 seconds to achieve a peak metal temperature of about 200°C to about 260°C; and / or wherein the applied coating has an average dry coating thickness of about 7 microns to about 15 microns; and / or wherein the substrate has an average thickness of about 175 microns to about 230 microns; and / or further comprising forming a beverage can end cap from the coated substrate, and wherein when tested as described herein, the coating passes less than 5 milliamps of current; and / or further comprising forming a beverage can end cap from the coated substrate, and wherein when tested as described herein, the coating exhibits feathering, if any, of about 0.5 mm or less.

[0020] In yet other aspects or embodiments, the present invention includes a method comprising using the aqueous coating composition of any of the previous aspects or embodiments described in the previous paragraphs or the following paragraphs of the present invention as a beverage can end cap coating composition. In some embodiments, the coating is used as an inner coating on a riveted beverage can end cap.

[0021] In yet other aspects or embodiments, the aqueous coating composition, article or method of any preceding aspect, embodiment or paragraph of the present disclosure is prepared without the use of halogenated monomers, or is substantially free of, completely free of or free of halogenated monomers; and / or wherein the aqueous coating composition forms a coating comprising less than 50 ppm of extractables, if any, when tested according to the Total Extractables Test; and / or wherein the coating comprises less than 50 ppm of extractables, if any, when tested according to the Total Extractables Test.

[0022] definition

[0023] The term "easy-open end cap" refers to a container end cap (usually an end cap for a beverage container or can) that includes (i) a frangible opening portion (which, for some beverage can end caps, serves as a drinking opening) and (ii) a rivet portion for attaching a pull tab thereto so as to open the frangible opening portion to obtain the product contained in the can or container.

[0024] The term "food-contact surface" refers to a surface of an article (eg, a beverage container) that comes in contact with a beverage product or is intended to come in contact with a beverage product.

[0025] The term "organic" or "organic group" means a hydrocarbon group (it has optional elements other than carbon and hydrogen, such as oxygen, nitrogen, sulfur and silicon), which is classified as aliphatic groups, cyclic groups or aliphatic groups and cyclic groups The combination of groups (for example, alkylaryl groups and aralkyl groups). The term "aliphatic group" means a saturated or unsaturated straight or branched hydrocarbon group. For example, the term is used to cover alkyl, alkenyl and alkynyl groups. The term "alkyl group" means a saturated straight or branched hydrocarbon group, including, for example, methyl, ethyl, isopropyl, tert-butyl, heptyl, dodecyl, octadecyl, amyl, 2-ethylhexyl, etc. The term "alkenyl group" means an unsaturated, straight or branched hydrocarbon group with one or more carbon-carbon double bonds, such as a vinyl group. The term "alkynyl group" means an unsaturated, straight or branched hydrocarbon group with one or more carbon-carbon triple bonds.

[0026] In the context of a water-dispersible polymer or a water-dispersible catalyst, the term "water-dispersible" means that the polymer or catalyst can be mixed into water (or an aqueous carrier) to form a stable mixture. For example, a mixture that easily separates into immiscible layers is not a stable mixture. The term "water-dispersible" is intended to include the term "water-soluble". In other words, by definition, a water-soluble polymer or catalyst is also considered to be a water-dispersible polymer or catalyst. As used herein, "water-dispersible" means that the components (e.g., catalyst or polymer components) do not significantly separate after 4 months at room temperature (25°C) or 1 month at elevated temperature (40°C).

[0027] In the context of a dispersible polymer, the term "dispersion" refers to a mixture of a dispersible polymer and a carrier fluid. The term "dispersion" is intended to include the term "solution".

[0028] The group that can be identical or different is referred to as "independently" something. It is expected that the organic group of the compounds of the present invention is substituted. Therefore, when the term "group" is used to describe a chemical substituent, the chemical substance includes an unsubstituted group, and for example, in a chain (such as in an alkoxy group) there is an O, N, Si or S atom and a carbonyl group or other conventionally substituted group. For example, the phrase "alkyl group" is intended to include not only pure open-chain saturated hydrocarbon alkyl substituents, such as methyl, ethyl, propyl, tert-butyl, etc., but also includes the alkyl substituents carrying other substituents known in the art (such as hydroxyl, alkoxy, alkyl sulfonyl, halogen atom, cyano, nitro, amino, carboxyl, etc.). Therefore, for example, "alkyl group" includes ether groups, haloalkyl, nitroalkyl, carboxyalkyl, hydroxyalkyl, sulfoalkyl, etc.

[0029] As used herein, "acrylate resin" means a resin comprising acrylate and / or methacrylate monomers, oligomers and / or polymerizable polymers. As used herein, "(meth)acrylate" is a shorthand reference to acrylate, methacrylate, or a combination thereof, and "(meth)acrylic acid" is a shorthand reference to acrylic acid, methacrylic acid, or a combination thereof. The term "acrylic component" includes any compound, polymer, or organic group formed from or containing an acrylate or methacrylate compound (e.g., acrylic acid or methacrylic acid and their esters). As discussed in further detail below, the acrylic component may also be additionally formed from or contain one or more other vinyl monomers.

[0030] As used herein, "cross-linker" refers to a molecule capable of forming a covalent bond between polymers or between two different regions of the same polymer.

[0031] As used herein, "polymer" and "copolymer" refer to molecules comprising a plurality of similar units bound together by covalent bonds. The terms "polymer" and "copolymer" are interchangeable and may refer to homopolymers formed by repeating units of one structural unit or monomer as well as copolymers that may be formed by different types of structural units or monomers.

[0032] As used herein, "monomer" or reactant generally refers to a compound in a reaction mixture prior to polymerization, and a monomer unit or (alternatively) a repeating unit or structural unit refers to a monomer or reactant in a polymer. Preferably, the various monomers or reactants herein are randomly polymerized monomer units, structural units or repeating units. If the discussion herein relates to a monomer or reactant, it also means the resulting monomer units, structural units or repeating units thereof in a polymer. Similarly, if the discussion relates to a monomer unit, structural unit or repeating unit, it also means a mixture of monomers or reactants used to form a polymer having associative units therein.

[0033] As used herein, the term "substantially free," when used with respect to a composition that may contain a particular compound, means that the composition contains less than 1,000 parts per million (ppm) of the compound, regardless of the context of the compound in the composition (e.g., regardless of whether the compound is present in an unreacted form, in a reacted form as a structural unit of another material, or a combination thereof). The term "substantially free," when used with respect to a composition that may contain a particular compound, means that the composition contains less than 100 parts per million (ppm) of the compound, regardless of the context of the compound in the composition (e.g., regardless of whether the compound is present in an unreacted form, in a reacted form as a structural unit of another material, or a combination thereof). The term "substantially completely free," when used with respect to a coating composition that may contain a particular compound, means that the coating composition contains less than 5 parts per million (ppm) of the compound, regardless of whether the compound is mobile in the coating or bound to a component of the coating. When used in relation to a composition that may contain a particular compound, the term "completely free" means that the composition contains less than 20 parts per billion (ppb) of the compound, regardless of the context of the compound in the composition (e.g., whether the compound is present in an unreacted form, in a reacted form as a structural unit of another material, or a combination thereof). When the phrases "free" or "free of" are used herein (outside the context of the above phrases), "do not contain" or "does not contain", "does not include any", etc., such phrases are not intended to exclude the presence of trace amounts of related structures or compounds that may be present but not intentionally used, such as the presence of environmental contaminants.

[0034] When used herein in the context of a polymer, the term "epoxide-free" refers to a polymer that does not include any "epoxide backbone segments" (i.e., segments formed by the reaction of an epoxy group and a group that can react with an epoxy group). For example, a polymer made from an ingredient that includes an epoxy resin would not be considered to be epoxide-free. Similarly, a polymer having a backbone segment that is a reaction product of a bisphenol (e.g., bisphenol A, bisphenol F, bisphenol S, 4,4'-dihydroxybisphenol, etc.) and a halogenated alcohol (e.g., epichlorohydrin) would not be considered to be epoxide-free. However, a vinyl polymer (e.g., glycidyl methacrylate) formed from a vinyl monomer or oligomer that includes a pendant epoxy moiety would be considered to be epoxide-free because the vinyl polymer would not contain an epoxy backbone segment. A coating composition referred to as "epoxide-free" is not prepared using any polymer or other material having an epoxy backbone segment.

[0035] The terms "adhesion test", "blush resistance test", "fouling resistance test" and "porosity test" refer to the adhesion, blush resistance, fouling resistance and porosity test methods described in the test methods section below, respectively. The adhesion test, blush resistance test, fouling resistance test and porosity test are collectively referred to as "coating property tests". By definition, each of these respective tests is conducted after the coating composition of the present invention is suitably cured and retorted or pasteurized according to the retort method or pasteurization method included in the test methods section below.

[0036] The term "retort" generally refers to conditions associated with food or beverage preservation or sterilization, including temperatures of 100° C. or higher. To achieve temperatures above 100° C., conditions associated with retort also often include pressures in excess of atmospheric pressure. The term "retortable" generally refers to the ability of a coating to withstand exposure to one or more such conditions and still exhibit one or more suitable film or coating properties.

[0037] Feathering is a term used to describe the loss of adhesion of a coating on a pull tab of a food or beverage can or container end closure. When the food or beverage can or container is opened, if the coating loses adhesion on the pull tab, a portion of free film may be present on the opening of the container or can. This portion of free film is considered feathered.

[0038] The terms "preferred" and "preferably" refer to embodiments of the present invention that may provide certain benefits in certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. In addition, the description of one or more preferred embodiments does not imply that other embodiments are unusable, and is not intended to exclude other embodiments from the scope of the present invention.

[0039] As used herein, the term "comprising" and variations thereof do not have a limiting meaning when appearing in the specification and claims. As used herein, "a", "an", "the", "at least one" and "one or more" are used interchangeably. Thus, for example, a coating composition comprising "an" amino crosslinking agent may be interpreted to mean that the coating composition comprises "one or more" amino crosslinking agents. Additionally herein, numerical ranges expressed by endpoints include all values ​​included within the range and all ranges of various endpoints therein (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc. and ranges 1 to 5 include 1 to 4, 1 to 3, 1 to 2, 2 to 5, 2 to 4, etc.).

[0040] The above-mentioned summary of the invention and definition of the present disclosure are not intended to describe each disclosed embodiment or its every kind of implementation. The following description more specifically illustrates exemplary embodiments, aspects or methods. In some places of the full text of this application, guidance is provided by lists of examples, which can be used in various combinations. In each case, the cited lists are only used as representative groups and should not be interpreted as exclusive enumeration. DETAILED DESCRIPTION

[0041] The present disclosure provides aqueous coating compositions for beverage containers, such as their internal food contact surfaces, including easy-open end caps of beverage containers. In other methods, the present disclosure provides beverage containers comprising such aqueous coating compositions, and in other methods, provides a method for applying the aqueous coating composition to a metal substrate suitable for a container (and its container end cap) using a coating application. In one aspect, the aqueous coating composition may at least include a binder system, a crosslinking agent, and a catalyst. In a preferred embodiment, the aqueous coating composition is a coating composition. (Hereinafter, for convenience, the aqueous coating composition of the present disclosure may be referred to as a "coil coating composition", but it should be understood that it may also be applied using a non-coil coating method (e.g., roller coating, spray coating, wash coating, etc.), and may be used, for example, to coat a non-coil metal sheet that is subsequently formed into an easy-open food or beverage can end cap). On the other hand, the present disclosure provides a beverage container and / or its metal substrate, at least a portion of which is coated with an aqueous coil coating composition. In yet other aspects, the present disclosure provides a method for coil coating a beverage container and / or a metal substrate suitable for use in a beverage container, and in particular an easy-open end cap for a beverage container. The method may include forming an aqueous coil coating composition as described herein, and applying the composition to the metal substrate using a coil coating method. Alternatively, the composition herein may also be applied to the metal substrate before or after the metal substrate is formed into a beverage container or portion thereof using other suitable beverage can end cap application techniques.

[0042] In one method, the binder system can be a polyolefin binder system, such as a polyolefin dispersion or an aqueous polyolefin dispersion. The polyolefin binder system can include structural units or monomer units derived from two or more C2 to C12 alpha olefins, and can include other optional structural units and / or other optional binder resins required for a specific application. For example, the binder system of the present invention can include one or more optional structural units or optional binding resins, which include acid functional groups (e.g., carboxyl groups), hydroxyl groups, amines, aldehydes, esters, ethoxylates, ethylene oxide groups or combinations thereof. Preferably, the binder system herein is a water-dispersible binder system.

[0043] The composition of this paper comprises a crosslinking agent. In some methods, the crosslinking agent is a nitrogen-containing carboxyl reactive crosslinking agent. In a preferred method, the crosslinking agent can be a hydroxyalkylamide crosslinking agent. Such crosslinking agents allow the production of a coil coating composition that does not contain formaldehyde and does not contain epoxides, and the coil coating composition has sufficient flexibility and corrosion resistance, while being used as an internal or external coating for a beverage can and particularly a container end cap that includes a rivet. In the method, the crosslinking agent can have any suitable combination of one or more carboxyl reactive functional groups, and more preferably includes two or more such groups. Hydroxyl groups are preferred carboxyl reactive groups. Other suitable carboxyl reactive groups can include thiol groups. In some embodiments, the crosslinking agent includes two or more, three or more, or four or more hydroxyl groups.

[0044] The composition herein also comprises a catalyst. In a preferred method, the catalyst is a water-dispersible (and preferably water-soluble) transition metal catalyst, and more preferably an organometallic transition metal catalyst. In one method, the organometallic catalyst comprises at least one metal selected from aluminum (Al), cobalt (Co), iron (Fe), titanium (Ti), zinc (Zn), zirconium (Zr), or a mixture thereof. The catalyst can be an organometallic catalyst with an organic ligand, such that the catalyst is water-soluble and / or water-dispersible.

[0045] The coil coating compositions herein are suitable for use with metal substrates and coil coating conditions and application methods. In some methods, the metal substrate is a metal commonly used in the beverage packaging industry. In one method, the metal substrate comprises steel, aluminum, or a combination thereof. Preferably, the metal substrate is aluminum, and more preferably chromium-free pretreated aluminum. The metal substrate may be formed as a beverage can end cap and may include a riveted beverage can end cap.

[0046] The unique combination of binder system, crosslinker and catalyst herein enables non-formaldehyde and non-epoxy binder system to achieve the robust performance required for beverage container end cap application even when using short curing cycle. Among other features, this unique combination of components unexpectedly reduces the energy required for crosslinking and simultaneously achieves the high level of product tolerance and flexibility generally required for the internal coating of beverage metal packaging (and especially easy opening end cap). In some methods, this performance can be obtained without the need for melamine and / or formaldehyde crosslinking agents. In addition, the resulting coating can exhibit such beneficial coating properties while also exhibiting excellent feathering properties.

[0047] For coil coating applications and beverage container end caps, the curing process for coil coating applications is typically very short (e.g., a flash peak metal temperature of about 200°C to about 260°C (in other methods, about 230°C to about 260°C) is achieved in about 8 seconds to 20 seconds oven cure time, preferably about 8 seconds to about 15 seconds oven cure time, more preferably about 8 seconds to about 14 seconds oven cure time, and even more preferably about 10 seconds to about 12 seconds oven cure time). Such short flash cure conditions for coil coating production are insufficient to obtain good coating performance in the context of existing polyolefin binder systems unless the unique combination of components discovered herein are used together. In some methods, the coil coating compositions herein do not contain any intentionally added bisphenol components (such as bisphenol A or bisphenol F), do not contain formaldehyde, and are suitable for water-based formulations including the polyolefin-based binder systems herein. In some such methods, the coil coating compositions are also styrene-free and / or epoxide-free. Additional details of the compositions and methods are provided below.

[0048] Binder system:The polyolefin binder system of the aqueous coil coating composition of the present invention preferably comprises a base polymer, the base polymer comprising at least one polyolefin polymer having monomer units or structural units derived from at least a reactant comprising two or more C2-C12 α-olefins, and in some methods comprising an aqueous dispersion of two or more α-olefins. In some such methods, the polyolefin polymer of the binder system is derived from ethylene and one or more C3-C12 α-olefins, and in one example comprises ethylene structural units (or ethylene monomer portions) and C3 to C12 structural units (or C3 to C12 monomer portions). In other such methods, the polyolefin polymer of the binder system is derived from ethylene and one or more C3-C6 α-olefins or C3-C4 α-olefins. In one method, the polyolefin binder system comprises a polyolefin polymer having structural units derived from ethylene and propylene. As used herein, ethylene structural units (or monomeric moieties) generally refer to -H2C-CH2- units within the copolymer chain, which are derived from ethylene molecules or reactants during copolymerization, and similar definitions apply to C3-C12 α-olefin structural units (or monomeric moieties). As used herein, olefins may also generally refer to a olefin having the chemical formula C x H 2x A family of organic compounds called alkenes, where x is the number of carbons and which have double bonds within their structure.

[0049] Based on the total weight of the composition, the coating composition of the present invention comprises about 90% to about 40% by weight of a polyolefin binder system, preferably about 80% to about 50% by weight of a polyolefin binder system, and even more preferably about 70% to about 60% by weight of a polyolefin binder system. In terms of resin solids, based on the total weight of the resin solids in the composition, the coating composition of the present invention comprises about 40% to about 20% by weight of a polyolefin binder system, preferably about 36% to about 23% by weight of a polyolefin binder system, and even more preferably about 32% to about 28% by weight of a polyolefin binder system. The polyolefin polymer may have a number average molecular weight suitable for can coating applications, and may be greater than about 1,000; greater than about 5,000; greater than about 10,000; greater than about 15,000; or even greater than about 50,000.

[0050] In some optional methods, the polyolefin polymer may include about 1 wt % to about 40 wt % of structural units derived from one or more alpha-olefin comonomers. In other methods, the weight percentage of structural units derived from one or more alpha-olefin comonomers is about 1 wt % to about 35 wt %, about 1 wt % to 30 wt %, about 3 wt % to about 27 wt %, about 3 wt % to about 20 wt %, or about 3 wt % to about 15 wt % of units derived from one or more alpha-olefin comonomers.

[0051] The term alpha-olefin refers to an olefin having a double bond in the primary or alpha position in its structure. C2-C12 alpha-olefin monomeric part or structural unit has a carbon number of two to twelve. Therefore, the carbon number of C2-C12 alpha-olefin monomeric part can be 2, 4, 5, 6, 7, 8, 9, 10, 11 or 12. For example, C3-C12 alpha-olefin monomeric part or structural unit can be derived from propylene reactant. In other embodiments, C2-C10 alpha-olefin monomeric part can be derived from reactants, and the reactants include but are not limited to one or more alpha-olefins such as ethylene, propylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-hexene, 1-octene, 1-decene and / or 1-dodecene homopolymers and copolymers (including elastomers). The resulting polymer may be polyethylene, polypropylene, poly-1-butene, poly-3-methyl-1-butene, poly-3-methyl-1-pentene, poly-4-methyl-1-pentene, ethylene-propylene copolymer, ethylene-1-butene copolymer and propylene-1-butene copolymer; copolymers (including elastomers) of α-olefins and conjugated or non-conjugated dienes, such as may be represented by ethylene-butadiene copolymers and ethylene-ethylidene norbornene copolymers; and polyolefins (including elastomers), such as copolymers of two or more α-olefins and conjugated or non-conjugated dienes, such as may be represented by ethylene-propylene-butadiene copolymers, ethylene-propylene-dicyclopentadiene copolymers, ethylene-propylene-1,5-hexadiene copolymers and ethylene-propylene-ethylidene norbornene copolymers; ethylene-vinyl compound copolymers, such as ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, ethylene-vinyl chloride copolymers, ethylene-acrylic acid or ethylene-(meth)acrylic acid copolymers and ethylene-(meth)acrylate copolymers. Suitable polyolefin dispersions for use in the binder system may include polyolefin dispersions in the CANVERA commercial product line from Dow Chemical, such as CANVERA 1340 and 1350 polyolefin dispersions.

[0052] In some embodiments, the polyolefin binder system comprises a base polyolefin polymer that is not easily dispersed in water. Examples of such base polyolefin polymers include higher molecular weight polyolefin polymers that do not include polar functional groups, and may be thermoplastic polymers. Examples include non-functionalized ethylene polymers, non-functionalized propylene polymers, non-functionalized propylene / ethylene copolymers, and copolymers and combinations thereof. Such base polyolefin polymers typically have a number average molecular weight exceeding 10,000, 15,000, 20,000 or even 50,000. In a preferred embodiment, the polyolefin binder system comprises a combination of one or more base polyolefin polymers and a polymer stabilizer and an optional compatibilizer (more preferably a polymer coupling agent). Polymer stabilizers are typically hydrophilic materials that are water-dispersible in themselves. Preferred polymer stabilizers are acid-functional or anhydride-functional. Suitable such polymer stabilizers may include, for example, ethylene (meth) acrylic acid copolymers, such as those sold by Dow Chemical Company with PRIMACOR series products, and any other water-dispersible polymers disclosed herein. Processes and materials for forming stable aqueous dispersions of such polyolefin polymers are disclosed, for example, in US8,193,275 (Moncla et al.), US8,946,329 (Wilbur et al.), US9,169,406 (Wilbur et al.), US8,722,787 (Romick et al.), and US9,938,413 (Romick et al.). In some examples, one or more base polyolefin polymers may be melt blended in a suitable process (e.g., an extrusion process such as Dow's BLUEWAVE process) to produce an aqueous dispersion comprising both the base polyolefin polymer and the polymer stabilizer stably dispersed therein.

[0053] In other methods, the polyolefin binder system may also include other structural units, such as acid functional structural units, or alternatively may include acid functionalized polyolefin polymers, which may be interpolymers of olefin structural units and one or more ethylenically unsaturated organic comonomers as described above. Other functional polymers may be stabilizers or stabilizers and / or surfactants. In one method, comonomers or separate polymers may be (meth) acrylates, vinyl esters and / or ethylenically unsaturated carboxylic acids. In some methods, acid or anhydride functionalized polyolefin polymers and / or structural units may be polymers and / or portions of ethylene interpolymerized with (meth) acrylic acid in the form of ethylene-(meth) acrylic acid polymers.

[0054] The copolymer or structural unit of acid or anhydride functionalization may include structural units or moieties derived from one or more C2-C12 olefins such as ethylene and one or more α,β-ethylenically unsaturated carboxylic acids (such as (meth) acrylic acid) as described above. In other methods, the polymer or binder system may include polar groups as comonomers or grafted monomers. Exemplary polar polyolefins may also include, but are not limited to, acylated or acyl-grafted polyolefin polymers.

[0055] In some methods, suitable acylating agents for providing polar groups or grafting are unsaturated substituted or unsubstituted organic acids or anhydrides, such as maleic or fumaric acid reactants (or their anhydride derivatives) of the following formula I:

[0056]

[0057] Wherein R1 and R2 are the same or different, provided that at least one of R1 and R2 is a group capable of reacting to esterify an alcohol, to form an amide or amine salt with ammonia or an amine, to form a metal salt with a reactive metal or a base-reactive metal compound (ammonia, amine, etc.), or to otherwise act as an acylating agent. Typically, R1 and / or R2 are -OH, -O-hydrocarbyl, -NH2, and R1 and R2 together can be -O- to form an anhydride. In some embodiments, R1 and R2 are such that both carboxyl functional groups can enter into an acylation reaction.

[0058] Maleic anhydride is a suitable acylating agent. Other suitable acylating agents include electron-deficient olefins, such as monophenyl maleic anhydride; monomethyl maleic anhydride, dimethyl maleic anhydride, N-phenyl maleimide and other substituted maleimides; isomaleimide; fumaric acid, maleic acid, alkyl hydrogen maleates and alkyl hydrogen fumarates, dialkyl fumarates and dialkyl maleates, fumaric acid and maleic acid; and maleonitrile and fumaronitrile. Maleic anhydride grafted polyethylene homopolymers or copolymers, maleic anhydride grafted polypropylene homopolymers or copolymers, ethylene-acrylic acid (EAA) and ethylene-methacrylic acid copolymers are suitable binder resins herein, such as those sold under the trademark PRIMACOR TM Commercially available from Dow Chemical Company (and in particular the product PRIMACOR 5980i, which according to Dow literature is an ethylene-acrylic acid copolymer) under the trademark NUCREL TM Commercially available from EI DuPont de Nemours and under the trademark ESCOR TMCommercially available from ExxonMobil Chemical Company and described in U.S. Pat. Nos. 4,599,392; 4,988,781; and 5,938,437. Other examples of polymer stabilizers include, but are not limited to, ethylene ethyl acrylate copolymers, ethylene methyl methacrylate copolymers, ethylene butyl acrylate copolymers, and combinations thereof functionalized as discussed herein. Other ethylene-carboxylic acid copolymers may also be used. One of ordinary skill in the art will recognize that many other useful polymers may also be used.

[0059] The polymer stabilizer may have any suitable acid value, as long as the polymer can be stably dispersed in water. Preferred acid or anhydride functional polymer stabilizers have an acid value of at least about 40, more preferably at least about 55, and even more preferably at least about 70, and optimally at least 100 milligrams (mg) KOH / g polymer. Although the upper range of suitable acid values ​​is not particularly limited, the acid value will generally be less than about 400, less than about 300, or less than about 200 mg KOH / g polymer. The acid value referred to herein may be determined according to BS EN ISO 3682-1998 standard, or alternatively may be determined theoretically based on the reactant monomers.

[0060] In some methods, the coating composition of the present invention may also include an optional compatibilizer. The compatibilizer may assist in the formation of the aqueous dispersion, such as assisting in providing a more uniform dispersion, and / or improving the properties of the cured coating composition. The compatibilizer may also be referred to as a coupling agent or a polymer coupling agent.

[0061] In some methods, the compatibilizer may include a modified or functionalized polymer and an optional low molecular weight compound with a reactive polar group. Examples of compatibilizers include, but are not limited to, modified olefin polymers. Modified olefin polymers may include graft copolymers and / or block copolymers, such as propylene-maleic anhydride graft copolymers. Examples of groups that can modify polymers include, but are not limited to, anhydrides, carboxylic acids, carboxylic acid derivatives, primary and secondary amines, hydroxy compounds, oxazolines and epoxides, and ionic compounds, and combinations thereof. Specific examples of groups that can modify polymers include, but are not limited to, unsaturated cyclic anhydrides and their aliphatic diesters, and diacid derivatives. For example, maleic anhydride and selected from C1-C 10 Straight chain and branched dialkyl maleates, C1-C 10 Linear and branched dialkyl fumarates, itaconic anhydride, C1-C 10 Compounds of linear and branched dialkyl itaconates, maleic acid, fumaric acid, itaconic acid, and combinations thereof. Commercially available examples of compatibilizers include, but are not limited to, those sold under the trade names Polymers available from Clariant Corporation, such as 6452, which is a propylene-maleic anhydride graft copolymer; EXXELOR TM ; and Epolene from Westlake Chemical Company.

[0062] In yet other methods, the polyolefin binder system may also include an ethylenically unsaturated monomer component of emulsion polymerization. In some embodiments, some or all of the ethylenically unsaturated monomer components are polymerized in the presence of an aqueous dispersion of the polyolefin binder system. For further discussion of materials and methods related to ethylenically unsaturated monomer components of emulsion polymerization, see, for example, US9,404,006 (Li) and U.S. Publication 2019 / 0292398 (Gao et al.).

[0063] In a preferred embodiment, no halogenated monomers such as chlorinated vinyl monomers are used to prepare the polyolefin binder system. In a further preferred embodiment, the coating composition is substantially free, completely free, or free of halogenated monomers (whether free or polymerized).

[0064] In an alternative method, the binder system comprises a thermoplastic polyester. For example, and in some optional methods, the aqueous dispersion of the binder system may include a melt blend of one or more polyester resins (such as polyethylene terephthalate polyester resins obtained from suitable dicarboxylic acid components and diol components), one or more stabilizers (such as at least one second polyester or other water-dispersible polymer), one or more neutralizers; and water. Exemplary thermoplastic polyesters are described in, for example, U.S. Pat. No. 2,936,296, U.S. Pat. No. 5,955,565, and U.S. Pat. No. 5,859,116. One or more stabilizers suitable for thermoplastic polyester dispersions may include one or more second polyesters to promote the formation of a stable dispersion. In some methods, the second polyester has a carboxylic acid group and an acid value of about 15 or more based on the solid content of the second polyester, or may be a self-dispersing sulfopolyester. The neutralizer may be a base such as ammonium hydroxide, sodium hydroxide, or potassium hydroxide. Other neutralizers may include lithium hydroxide or sodium hydroxide, carbonates, or amines such as monoethanolamine or 2-amino-2-methyl-1-propanol (AMP). Amines useful in embodiments disclosed herein may include diethanolamine, triethanolamine, and TRIS AMINO TM (each purchased from Angus), NEUTROL TM TE (available from BASF), and triisopropanolamine, diisopropanolamine, and N,N-dimethylethanolamine (each available from Dow Chemical Company, Midland, Mich.). Alternatively, a non-melt blend polyester dispersion may be prepared as described in WO 2018 / 118802.

[0065] Crosslinking agent :In certain embodiments, aqueous coating compositions (typically coil coating compositions) can be formulated using one or more curing agents or crosslinking resins (sometimes referred to as crosslinking agents). The selection of a specific crosslinking agent generally depends on the specific product being formulated. In some cases, for aqueous coating compositions, it is preferred to use certain nitrogen-containing carboxyl-reactive crosslinking agents. Suitable nitrogen-containing carboxyl-reactive crosslinking agents include hydroxyalkylamide crosslinking agents and allow the production of formaldehyde-free aqueous coating compositions comprising the above-mentioned polyolefin binder system having sufficient flexibility to be used as an internal or external coating for food or beverage cans, and in particular as an internal or external coating for easy-open beverage can end caps. Based on the total weight of the composition, the coating composition herein comprises about 30% by weight to about 0.5% by weight of a crosslinking agent, preferably about 20% by weight to about 2% by weight of a crosslinking agent, and even more preferably about 15% by weight to about 3% by weight of a crosslinking agent. In terms of resin solids, the coating compositions herein comprise from about 9 wt % to about 0.15 wt % crosslinker, preferably from about 6 wt % to about 0.6 wt % crosslinker, and even more preferably from about 1.5 wt % to about 0.9 wt % crosslinker, based on the total weight of resin solids in the composition.

[0066] The nitrogen-containing carboxyl-reactive crosslinking agent may have any suitable combination of one or more carboxyl-reactive functional groups, and more preferably includes two or more such groups. Hydroxyl groups are preferred carboxyl-reactive groups. Other suitable carboxyl-reactive groups may include thiol groups. In some embodiments, the nitrogen-containing carboxyl-reactive crosslinking agent includes two or more, three or more, or four or more hydroxyl groups.

[0067] The nitrogen-containing carboxyl reactive crosslinking agent may include any suitable number of nitrogen atoms, although it typically includes two or more nitrogen atoms, and in some embodiments includes a total of two nitrogen atoms. In other embodiments, one or more (and more preferably two or more) nitrogen atoms are present in an amide group, an aziridine group, an imide group, a diimide group, an oxazoline group, a carbamate group, or a combination thereof. In some methods, the nitrogen-containing carboxyl reactive crosslinking agent includes two or more amide groups. In yet other methods, the nitrogen-containing carboxyl reactive crosslinking agent may contain a single amide group, such as a multi-substituted amide group with two or more hydroxyl groups. In a preferred method, the nitrogen-containing carboxyl reactive crosslinking agent includes a β-hydroxyl group relative to the nitrogen atom of the amide bond.

[0068] In certain preferred methods, the nitrogen-containing carboxyl-reactive crosslinking agent includes one or more, and more preferably two or more, groups having the structure of Formula II below:

[0069] HO-R3-N(R4)-C(=O)- (Formula II)

[0070] Wherein each R3 is independently an organic group, and each R4 is independently hydrogen or an organic group. As shown in Formula II, the hydroxyl group depicted can be a primary hydroxyl group, a secondary hydroxyl group or a tertiary hydroxyl group, depending on the structure of R3. In some embodiments, the hydroxyl group is a primary hydroxyl group.

[0071] In formula II, R3 may include any suitable number of carbon atoms, but will typically include 2 to 10 carbon atoms, more typically 2 to 8 carbon atoms, more typically 2 to 6 carbon atoms, and even more typically 2 to 4 carbon atoms. R3 typically includes at least two carbon atoms in the chain, one end of which is connected to the depicted nitrogen atom and the other end is connected to the depicted hydroxyl group. In one embodiment, the depicted hydroxyl group is directly attached to the first carbon atom, which is directly attached to the second carbon, which is directly attached to the depicted nitrogen atom. In some embodiments, R3 is a –(CH2)2- moiety. In yet other methods, R3 is an alkylene group preferably containing 1 to 5 carbon atoms (e.g., methylene, ethylene, n-propylene, sec-propylene, n-butyl, sec-butyl, tert-butylene, pentylene, etc.).

[0072] In some methods, R4 is an organic group including a hydroxyl group. In some such embodiments, R4 has the structure HO-R3-, wherein R3 is as described above. Examples of such R4 groups include hydroxyalkyl groups preferably having 1 to 5 carbon atoms (e.g., hydroxy-ethyl, 3-hydroxy-propyl, 2-hydroxy-propyl, 4-hydroxy-butyl, 3-hydroxy-butyl, 2-hydroxy-2-propyl-methyl, 5-hydroxy-pentyl, 4-hydroxy-pentyl, 3-hydroxy-pentyl, 2-hydroxy-pentyl and pentyl isomers). An example of a nitrogen-containing carboxyl-reactive crosslinking agent including such an R4 group is provided in the following formula III (which is believed to be the structure of the PRIMID XL-552 product commercially available from EMS):

[0073]

[0074] In other embodiments, the nitrogen-containing carboxyl-reactive cross-linking agent is a compound having the structure of Formula IV below:

[0075] (HO-R3-N(R4)-C(=O)) n -X, (Formula IV)

[0076] wherein R3 and R4 are as described above, n is an integer of 2 or greater, and X is a polyvalent organic group. In yet other methods, the nitrogen-containing carboxyl reactive crosslinking agent is a compound having a structure of Formula V

[0077] HO-R3-N(R4)-CO-X-CO-N(R4)-(R3)-OH (Formula V)

[0078] Wherein R3 and R4 of Formula V are independently organic groups, X is a divalent organic group, and wherein the hydroxyl groups are independently primary hydroxyl groups or secondary hydroxyl groups. In some methods, X is an alkylene group. In other methods, X is -(CH2) m -group, wherein (i) m is 1 or greater, 2 or greater, 3 or greater, 4 or greater, and more typically an integer from 2 to 10, and (ii) one or more hydrogens may be replaced by a substituent group (e.g., an organic substituent group). In one embodiment, X is -(CH2)4-.

[0079] In certain embodiments, the hydroxyl group attached to the R3 portion or R4 portion of Formula IV or V is a secondary hydroxyl group or is located in the β position relative to the nitrogen atom, more preferably the nitrogen atom of the amide bond. Thus, for example, in certain embodiments, the nitrogen-containing carboxyl reactive crosslinker is a β-hydroxyalkylamide compound. Some examples of such compounds include: bis[N,N-bis(β-hydroxy-ethyl)]adipamide, bis[N,N-bis(β-hydroxy-propyl)]succinamide, bis[N,N-bis(β-hydroxy-ethyl)]azelamide, bis[N,N-bis(β-hydroxy-propyl)]adipamide, bis[N-methyl-N-(β-hydroxy-ethyl)]oxalamide, and mixtures thereof. The PRIMID QM-1260 product commercially available from EMS is an example of a β-hydroxyalkylamide crosslinker. It is believed that the structure corresponding to the PRIMID QM-1260 product is provided by the following formula VI:

[0080]

[0081] Without wishing to be bound by theory, in some embodiments, the use of β-hydroxyalkylamides (such as those of formula IV, V or VI) is preferred, because an oxazolinium intermediate is formed, which is considered to occur and cause the reactivity of a crosslinking agent and a carboxyl group to be enhanced. Therefore, in some embodiments, nitrogen-containing carboxyl reactive crosslinking agents are preferably capable of forming an oxazolinium intermediate or other carbon-nitrogen heterocyclic intermediates with enhanced reactivity with a carboxyl group. Preferably, such reactive intermediates are formed under the short curing time of typical beverage can end cap coating heat curing conditions. For example, for coating curing conditions, in some embodiments, such reactive intermediates may even be formed under oven baking conditions with a peak metal temperature of about 200°C to about 260°C (in some methods, about 230°C to about 260°C) and during a relatively short oven residence time of only about 8 seconds to about 20 seconds, 8 seconds to 15 seconds, 8 seconds to 12 seconds or even 10 seconds to 12 seconds.

[0082] In a preferred embodiment, the nitrogen-containing carboxyl-reactive crosslinking agent is formed from reactants that do not include formaldehyde.Preferred curing agents are also substantially free of, and preferably do not include, any structural units derived from BPA and aromatic glycidyl ether compounds (eg, BADGE, BFDGE, and epoxy novolacs).

[0083] In yet other methods, the crosslinking agent may include a carbodiimide polymer, or the nitrogen-containing carboxyl reactive crosslinking agent may include a carbodiimide moiety. Exemplary carbodiimide crosslinking agents or portions thereof may include, but are not limited to, aliphatic and / or alicyclic dinitrogen derivatives of carbonic acid. Such crosslinking agents have the structure: R'N=C=NR', wherein R' is independently an aliphatic or alicyclic group. The aliphatic group of R' may be a carbon chain of 1 to 6 carbon atoms. Suitable examples of carbodiimide moieties or crosslinking agents include dibutylcarbodiimide and dicyclohexylcarbodiimide. Polymeric or oligomeric carbodiimide crosslinking agents may also be used. Water-dispersible carbodiimide crosslinkers may be prepared by incorporating small amounts of amines (such as dimethylaminopropylamine) and alkyl sulfonates or sulfates into the carbodiimide structure. Suitable water-dispersible carbodiimides may also be prepared by incorporating polyethylene oxide or polypropylene oxide into the carbodiimide structure.

[0084] Although carboxyl-reactive crosslinkers are preferred for the reasons already discussed, other crosslinkers known for use in can coatings may additionally or alternatively be used. For example, any of the well-known hydroxyl-reactive curing resins may be used. For example, phenoplast, blocked isocyanate, and aminoplast curing agents, and combinations thereof, may be used.

[0085] catalyst :The aqueous coating composition of the present disclosure preferably also comprises a catalyst, which in some methods is a transition metal catalyst. The transition metal catalyst is preferably a water-dispersible (and preferably water-soluble) organometallic transition metal catalyst. The transition metal catalyst preferably comprises at least one metal selected from aluminum (Al), cobalt (Co), iron (Fe), titanium (Ti), zinc (Zn), zirconium (Zr), or mixtures thereof, and in other methods comprises titanium and / or zirconium.

[0086] In the methods, the organometallic transition metal catalyst includes one or more alkoxy ligands bound to a transition metal core or base. In some methods, the one or more ligands are one or more alkoxycarbonyl ligands, wherein the alkoxy or alkoxycarbonyl ligands include a C1 to C6 alkyl group.

[0087] In one method, the catalyst is preferably of the general structure M(OR5) nalkyl titanium oxide or its salt (or other alkyl transition metal oxide), wherein M is a transition metal selected from aluminum (Al), cobalt (Co), iron (Fe), titanium (Ti), zinc (Zn), zirconium (Zr), or a mixture thereof, each R5 is independently a linear or branched organic group generally containing 1 to 6 carbon atoms, and n is an integer from 1 to 4. In other methods, the catalyst is a titanium oxide chelate or its salt (or other transition metal oxide chelate or its salt). In the method, the transition metal chelate suitable for the aqueous coating composition of the present invention has the general structure of the following formula VII

[0088]

[0089] wherein R is an organic group, such as a C1 to C10 straight or branched carbon chain, n is 1 or 2; M is a transition metal preferably selected from aluminum (Al), cobalt (Co), iron (Fe), titanium (Ti), zinc (Zn), zirconium (Zr), or a mixture thereof; X is a divalent organic linking group, such as a straight or branched carbon chain with 2 to 4 carbons; and Y is a functional group having an oxygen or nitrogen atom capable of forming a chelate with the central transition metal M. In the method, Y is a carbonyl, an ester, or a salt thereof.

[0090] In a particular method, the organometallic transition metal catalyst may be selected from titanium acetylacetonate, tetraalkyl titanate, isopropyl orthotitanate, water-soluble titanium chelate salts (such as dihydroxybis[lactic acid (2)-O1O2] titanate (2-) diammonium), titanium triethanolamine chelate, titanium tetratriethanolamine chelate, lactic acid titanate chelate salts, or combinations thereof. Suitable commercially available titanium-containing catalysts may include, for example, those available under the trade names VERTEC IA10, PI2, TAA, TET, and XL900 (all from Johnson Matthey, Chicago Ill.); and TYZOR 131, LA, TE, IAM, and TPT (all from Du Pont deNemours, Wilmington Del.).

[0091] In certain embodiments, the zirconium-containing catalyst is selected from the group consisting of zirconium propionate, zirconium acetate, ammonium zirconium carbonate, zirconate (2)-bis[carbonate (2)-O]dihydroxy-diammonium, zirconium chelate salts (such as tetrakis[[2,2',2"-nitrilotri(ethanol)](1)-N,O]zirconium), sodium zirconium lactate, sodium zirconium glycolate, and combinations thereof. Suitable commercially available zirconium-containing catalysts may include, for example, those available under the trade names BACOTE 20 (MEL Chemicals, Manchester, UK); TYZOR 217 and 218, and TEAZ (all available from Du Pont de Nemours, Wilmington, Del.).

[0092] In preferred embodiments, the coating compositions as disclosed herein may include one or more catalysts at appropriate levels to produce the desired results. In certain such preferred embodiments, the aqueous coating composition includes at least about 150 ppm of a transition metal catalyst, at least about 200 ppm of a catalyst, at least about 300 ppm of a catalyst, or at least about 400 ppm of a catalyst (all based on the total amount of transition metals in the catalyst relative to the total non-volatile weight of the aqueous coating composition). In other methods, the aqueous coating composition also includes no more than about 500 ppm of a transition metal catalyst, no more than about 550 ppm of a catalyst, no more than about 600 ppm of a catalyst, or no more than about 750 ppm of a catalyst (again, all based on the total amount of transition metals in the catalyst relative to the total non-volatile weight of the aqueous coating composition). In yet other methods, the composition includes up to about 1 wt % of a catalyst, and in other methods, about 0.2 wt % to about 1 wt %, or about 0.5 wt % to about 1 wt %, or even 0.5 wt % to about 0.75 wt %.

[0093] Carrier fluid :The aqueous coating composition of this article may also include a carrier fluid or other fluid medium. In some methods, the carrier fluid may be an aqueous carrier fluid. In particular, the carrier fluid medium may be any fluid suitable for coating compositions, and may include water or be water. The coating composition of this article may include about 70% by weight to about 50% by weight of a carrier fluid, such as water (based on the total weight of the composition). In other methods, the composition may include about 90% by weight to about 30% by weight of a carrier fluid, about 85% by weight to about 35% by weight in other methods, and about 80% by weight to about 40% by weight in other methods. In other methods, the coating composition of the present disclosure may include at least about 30% by weight, at least about 25% by weight, or at least about 20% by weight to about 10% by weight or less, about 6% by weight or less, or about 3% by weight or less of a carrier fluid. The carrier fluid may be water, and such percentages herein may reflect the amount of water in the composition.

[0094] In some methods, the amount of the fluid carrier is selected so that the non-volatile solids content of the coating composition is in the range of about 20% to about 40% by weight based on the total weight of the composition. For example, the composition may include a solids content of about 25% to 35% by weight based on the total weight of the composition. In other methods, the solids content of the composition ranges from at least about 40% by weight, at least about 38% by weight, or at least about 38% by weight to about 35% by weight or less, about 33% by weight or less, or about 30% by weight or less.

[0095] In other methods, the carrier fluid may include one or more water-miscible organic solvents. In some methods, the water-miscible organic solvent may include one or more of isopropanol, ethanol, methanol, butanol, amyl alcohol, glycols, glycol ethers, glycol esters, glycol ether esters, mineral spirits, aromatic solvents, acetone, ketones such as methyl ethyl ketone or tetrahydrofuran, or mixtures thereof. If the aqueous coating composition of the present invention is included, the composition may include from about 16% to about 3.6% of one or more water-miscible organic solvents.

[0096] In a preferred embodiment, the carrier fluid includes at least some organic solvents, more preferably at least 5 wt %, or at least 10 wt %, or at least 15 wt % of one or more organic solvents based on the total coating weight. Typically, at least some, if not all, of the one or more organic solvents are water miscible.

[0097] In preferred embodiments, the aqueous coating composition herein is substantially free of each of bisphenol A, bisphenol F, and bisphenol S, and structural units derived therefrom. In certain embodiments, the aqueous coating composition is substantially free of each of bisphenol A, bisphenol F, and bisphenol S, and structural units derived therefrom. In certain embodiments, the aqueous coating composition is substantially completely free of each of bisphenol A, bisphenol F, and bisphenol S, and structural units derived therefrom. In certain embodiments, the aqueous coating composition is completely free of each of bisphenol A, bisphenol F, and bisphenol S, and structural units derived therefrom. For example, the coating composition is substantially bisphenol A, which includes 600 ppm bisphenol A and 600 ppm diglycidyl ether of bisphenol A (BADGE) - whether bisphenol A and BADGE are present in the composition in reacted or unreacted form or a combination thereof.

[0098] In certain embodiments, the aqueous coating compositions herein are substantially free of all bisphenol compounds and structural units derived therefrom. In certain embodiments, the aqueous coating compositions are substantially free of all bisphenol compounds and structural units derived therefrom. In certain embodiments, the aqueous coating compositions are substantially completely free of all bisphenol compounds and structural units derived therefrom. In certain embodiments, the aqueous coating compositions are completely free of all bisphenol compounds and structural units derived therefrom. For example, hydroquinone, resorcinol, catechol, etc. are not bisphenols because these phenolic compounds include only one phenylene ring.

[0099] The amount of bisphenol compounds (e.g., bisphenol A, bisphenol F, and bisphenol S) and structural units derived therefrom can be determined based on the starting ingredients; the test method is not essential, and considering the small amounts of these compounds, parts per million (ppm) can be used instead of weight percentages for convenience. In a preferred embodiment, no bisphenol compounds are used, although trace amounts of bisphenol compounds may be present, for example, due to environmental contamination.

[0100] In preferred embodiments, the aqueous coating composition is substantially free, essentially free, completely free, and free of formaldehyde or structural units derived from formaldehyde. In preferred embodiments, no formaldehyde compounds are used, although trace amounts of formaldehyde compounds may be present, for example due to environmental contamination.

[0101] Although the balance of scientific evidence available to date indicates that the small trace amounts of these compounds that may be released from existing coatings do not pose any health risk to humans, some still consider these compounds to be potentially undesirable. Therefore, some would like to eliminate at least some of these compounds from coatings on food contact surfaces. In addition, it is desirable to avoid the use of components that are unsuitable for such surfaces due to factors such as taste, toxicity or other government regulatory requirements.

[0102] Optional Ingredients : The aqueous coating composition herein may also include other optional polymers that do not adversely affect the coating composition or the cured coating composition produced therefrom. Such optional polymers are typically included in the coating composition as filler materials, although they may be included as crosslinking materials, or provide desired properties. One or more optional polymers (e.g., filler polymers) may be included in an amount sufficient for the intended purpose, but not in an amount that adversely affects the coating composition or the cured coating composition produced therefrom.

[0103] Such optional composition is usually included in the coating composition to enhance the composition aesthetics, promote the manufacture, processing, handling and application of the composition, and / or further improve the coating composition or the specific functional properties of the cured coating composition produced therefrom. In a method, the optional composition includes for example dye, pigment, toner, extender, filler, lubricant, corrosion inhibitor, flow control agent, thixotropic agent, dispersant, antioxidant, tackifier, light stabilizer, surfactant or their mixture. Every kind of optional composition is with the amount that is enough to be used for its intended purpose, but is not included with such amount that adversely affects the coating composition or the cured coating composition produced therefrom.

[0104] The coating composition may include an antioxidant. If an antioxidant is included, the antioxidant may comprise 0.001 wt % to 0.1 wt % of the coating composition, based on the total weight of the coating composition. The antioxidant may help protect the aqueous dispersion, for example, at high curing temperatures. In some methods, the antioxidant may include a hindered phenol, such as, but not limited to, pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, which may be IRGANOX TM 1010 was commercially available from Ciba.

[0105] Another useful optional component can be a lubricant (e.g., wax), which promotes the manufacture of metal closures by imparting lubricity to the metal substrate sheet of coating. Examples of lubricants include, for example, carnauba wax, polyethylene type wax, Fischer-Tropsch wax, fatty acid ester wax, silicone wax, lanolin wax, hydroxy-functional polysiloxane wax (e.g., described in US9,169,406) and combinations thereof. If used, based on the weight of non-volatile materials, one or more lubricants can be present in the coating composition in an amount of at least 0.1 wt %, and not more than 2 wt % in certain embodiments, and not more than 1 wt % in other embodiments. In other methods, lubricants can be provided with an amount in the range of at least about 0.1 wt %, at least about 0.5 wt % or at least about 0.75 wt % to less than 2 wt %, less than 1.5 wt %, less than 1.25 wt % or less than 1 wt %.

[0106] Another useful optional ingredient is a pigment, such as titanium dioxide. If used, one or more pigments may be present in the coating composition in an amount of no greater than 70 wt %, and in certain embodiments no greater than 50 wt %, and in other embodiments no greater than 40 wt %, based on the total weight of solids in the coating composition.

[0107] Surfactants can be optionally added to the coating composition to help the flow and wetting of the substrate. Examples of surfactants include, but are not limited to, nonylphenol polyethers and salts and similar surfactants known to those skilled in the art. If used, based on the weight of resin solids, one or more surfactants can be present in an amount of at least 0.01 wt %, in certain embodiments at least 0.1 wt %. If used, based on the weight of resin solids, one or more surfactants can be present in an amount of no more than 10 wt %, and in certain embodiments no more than 5 wt %.

[0108] In certain embodiments, as a general guide to minimizing potential (e.g., taste and toxicity issues), the hardened coating formed from the aqueous coating composition contains less than 50 ppm, less than 25 ppm, less than 10 ppm, or less than 1 ppm of extractables (if any), if any, when tested according to the Total Extraction Test described in the Examples section. An example of these testing conditions is exposing the hardened coating to a 10 wt % ethanol solution at 121° C. for two hours, followed by exposure to the solution at 40° C. for 10 days.

[0109] In some embodiments, such reduced total extractable values ​​can be obtained by limiting the amount of mobile or potentially mobile species in the hardened coating. This can be achieved, for example, by using pure rather than impure reactants, avoiding the use of hydrolyzable components or bonds, avoiding or limiting the use of low molecular weight additives that may not react effectively into the coating, and using optimized curing conditions, optionally in combination with one or more curing additives. This makes the hardened coatings formed from the coating compositions described herein particularly suitable for food contact surfaces.

[0110] As mentioned above, the coating compositions herein are particularly suitable for beverage containers or cans, or parts or precursors thereof, that are subject to short curing cycles. Two-piece cans are manufactured by joining a can body (typically a drawn metal body) with a can end cap (typically an easy-open can end cap formed of aluminum or steel or sheet material). The coatings of the present invention are suitable for beverage contact situations and can be used for the interior of such cans. They are particularly suitable for roller coating applications or liquid coatings for easy-open beverage can end caps. The coatings herein also provide utility in other applications. These additional applications include, but are not limited to, wash coatings, sheet coatings, and side seam coatings (e.g., food can side seam coatings).

[0111] The coating process is to coat the continuous that is made of metal such as steel or aluminum.Once coated, coating is subjected to short heat, ultraviolet and / or electromagnetic curing cycle, for example, to harden (dry and solidify) coating.Coating provides the metal (for example, steel and / or aluminum) substrate of coating, and it can be manufactured into shaped products, such as two-piece drawn food cans, three-piece food cans, food can end caps, drawn and flattened cans, beverage can end caps etc.The metal substrate for typical coating process has the average thickness of about 175 microns to about 230 microns conventionally.Usually, before coating with coating composition, the surface of metal substrate is pre-treated with chromium-based or non-chromium-based (for example, zirconium-based and acrylic acid-based pretreatment).

[0112] In one example of a coating process, coating can be performed by first providing a substrate (such as aluminum or steel) for forming a food or beverage can end cap. Next, an aqueous coating composition as described herein can be applied to the surface of the substrate (e.g., by roller coating or any other suitable technique). Then, the applied aqueous coating composition is cured at the peak metal temperature for a period of time to form a cured coating on the surface of the substrate. Finally, the coated aluminum or steel substrate is then shaped or stamped into a suitable food or beverage can or can end cap.

[0113] In some methods, conventional roller coating process can be used to apply aqueous coating composition to substrate sheet material continuously online or in batches.In some embodiments, in continuous process, the moving surface of substrate advances with a linear speed of at least about 50 meters / minute, at least about 100 meters / minute, at least about 200 meters / minute or at least about 300 meters / minute.Usually, the linear speed will be less than about 400 meters / minute.For this type of continuously moving surface, aqueous coating composition is applied usually with coating weight and relative thickness, to obtain the average coating thickness of expectation after solidification.In certain embodiments, the average dry film thickness gained on substrate can be at least about 7 microns, at least about 8 microns or at least about 9 microns, and can be at most about 11 microns, at most about 12 microns or at most about 15 microns.Once applied to substrate, any suitable curing mechanism can be adopted.For example, coating composition can be subjected to thermal convection, ultraviolet radiation, electromagnetic magnetic radiation or their combination in curing cycle, and this curing cycle provides the fully drying and curing of coating composition to form the final coating of expectation.

[0114] In some methods, the curing time of the coating composition of the present disclosure is at least about 6 seconds, at least about 10 seconds or at least about 12 seconds, and at most about 15 seconds, at most about 20 seconds, at most about 25 seconds or at most about 30 seconds. Preferably, the curing time is 8 seconds to 15 seconds, 8 seconds to 12 seconds or 10 seconds to 12 seconds. In the case of thermal baking to cure the coating, such curing time refers to the residence time in the oven. In such embodiments, the curing process is generally carried out to achieve a peak metal temperature (PMT) of about 200°C to about 260°C, and about 230°C to about 255°C in other methods.

[0115] Sheet coating can also be used for the compositions herein. Sheet coating is the coating of individual pieces of various materials (e.g., steel or aluminum) that have been pre-cut into square or rectangular "sheets." The typical size of these sheets is about one square meter. Once coated, each sheet is cured. Once hardened (e.g., dried and cured), the sheets of the coated substrate are collected and prepared for subsequent manufacturing. Sheet coating provides a coated metal (e.g., steel or aluminum) substrate that can be successfully manufactured into shaped articles, such as two-piece drawn food cans, three-piece food cans, food can end caps, drawn and flattened cans, beverage can end caps, etc.

[0116] In any of the above-mentioned application methods, the coating composition herein can be applied to the substrate using any suitable procedure, including, for example, spraying, roller coating, coating, curtain coating, dip coating, meniscus coating, conformal coating, blade coating, knife coating, dip coating, slot coating, slide coating, vacuum coating, etc., as well as other types of predetermined amount coating. Other commercial coating application and curing methods are also contemplated, including, for example, electrocoating, extrusion coating, lamination, powder coating (e.g., after spray drying to form a powder), etc.

[0117] Depending on the particular application and article, the coating compositions herein can be applied to a substrate before or after the substrate is formed into an article. In some embodiments, at least a portion of a planar metal substrate (e.g., a metal coil) is coated with a layer of the coating composition of the present invention and then cured before the planar substrate is formed (e.g., stamped) into an article (e.g., an easy-open can end).

[0118] After the coating composition is applied to the substrate, various methods can be used to cure the composition, including, for example, oven baking conventional methods, or any other method that provides a high temperature suitable for curing the coating. The curing process can be carried out in discrete or combined steps. For example, the substrate can be dried at ambient temperature so that the coating composition remains in a mostly uncrosslinked state. The coated substrate can then be heated to fully cure the composition. In some cases, the coating composition of the present invention can be dried and cured in one step.

[0119] Embodiments of liquid polymer coating compositions related to beverage can end caps should preferably exhibit sufficient flexibility in the cured coating composition to accommodate the extreme profile of the rivet portion of the easy-open can end cap. In some methods, the test conducted to determine whether a particular coating can be used as an easy-open can end cap can be a porosity test and a feathering test as described herein. The porosity test indicates the flexibility level of the coating, and measures the ability of the coating to maintain its integrity and substrate adhesion when undergoing the forming process required for producing beverage can end caps. In particular, it is a measure of the presence or absence of cracks or fractures in the inner coating of the formed end cap. Feathering refers to the adhesion loss of the coating adjacent to the drinking port of a beverage can or container end cap, and when present, indicates that a portion of the free film can remain on the opening of the container or can when opened.

[0120] Exemplary coatings of the present invention exhibit one or more of the properties described in the Examples section. In some methods, the coatings of the present disclosure exhibit one or more of the following properties (and in some embodiments, all properties or various combinations of such properties): a metal exposure value of less than 5 milliamperes (mA) or less than 3 milliamperes (mA) (more preferably, less than 2 mA, and even more preferably less than 1 mA) (preferably after forming and stamping the can end cap); an overall extraction result of no more than 50 ppm (more preferably no more than 25 ppm, and even more preferably no more than 10 ppm, and even more preferably no more than 1 ppm of extractables); an adhesion rating of GTO after water pasteurization; no blushing after water pasteurization, although for some cases (on a rating scale of 0 to 10) at least 7, at least 8, or at least 9 is acceptable; MEK solvent resistance of at least 30 double rubs; feathering, if any, of about 0.5 mm or less, in other methods, about 0.4 mm or less, about 0.3 mm or less, about 0.2 mm or less, or about 0.1 mm or less, or no feathering.

[0121] In some methods, when the aqueous coating composition herein is applied to a cleaned and chrome-free pretreated aluminum panel and cured for a 12 second oven cure time to a peak metal temperature of about 249° C. to achieve a dry film thickness of about 12 g / m 2 and formed into a fully converted 202 standard opening beverage can end, the aqueous coating composition herein passes less than 5 mA of current while exposed to an electrolyte solution containing 1 wt % NaCl dissolved in deionized water for 4 seconds.

[0122] In yet other methods, the aqueous coating compositions herein exhibit feathering of 0.5 mm or less, feathering of about 0.4 mm or less, feathering of about 0.3 mm or less, or feathering of about 0.2 mm or less when applied to cleaned and chrome-free pretreated aluminum panels and cured for 12 seconds of oven cure time to a peak metal temperature of 249° C. to achieve a dry film thickness of about 7.5 mg / in2. In preferred embodiments, the aqueous coating compositions herein are able to achieve such excellent feathering properties when cured for no more than 12 seconds.

[0123] In yet other methods, the aqueous coating compositions herein have a viscosity of between 35 seconds and 60 seconds when measured at 25°C using a No. 4 Ford cup as measured via ASTM D-1200.

[0124] The present disclosure also provides a method including using an aqueous coating composition on a metal substrate for metal packaging (e.g., a metal coil or sheet for forming a beverage can end cap). In some cases involving multiple parties, a first party (e.g., a party that manufactures and / or supplies an aqueous coating composition) may provide a second party (e.g., a metal coater (e.g., a coil coater for an easy-open food or beverage can end cap), a can manufacturer, or a brand owner) with instructions, suggestions, or other disclosures about the final use of the packaging coating. Such disclosures may include, for example, instructions for coating a metal substrate for subsequent use in forming a packaging container or portion thereof, coating a metal substrate for a preformed container or portion thereof, preparing an aqueous coating composition for such use, curing conditions or process-related conditions for such coatings, or instructions, suggestions, or other disclosures for a suitable type of packaging product for the resulting coating. Such disclosures may appear, for example, in a technical data sheet (TDS), a safety data sheet (SDS), a regulatory disclosure, a warranty or warranty limitation statement, marketing materials, or a presentation, or appear on a company website. A first party who makes such a disclosure to a second party shall be deemed to have caused the aqueous coating composition to be used on a metal substrate for metal packaging (e.g., a container or an easy-open end cap) even if the second party actually applies the composition to a commercial metal substrate, uses such coated substrate in commerce on a metal substrate for a packaging container, and / or fills such coated container with a product.

[0125] Example

[0126] The following examples are given to illustrate but not to limit the scope of the present invention. Unless otherwise stated in the examples and throughout this disclosure, all parts, ratios and percentages are by weight, and all molecular weights are weight average molecular weights. Unless otherwise stated, all chemicals used are commercially available from, for example, Sigma-Aldrich (St. Louis, MO). One or more of the following test methods are used in the following examples.

[0127] Solvent resistance : The "cure" or degree of crosslinking of the coating is measured as resistance to solvents, such as methyl ethyl ketone (MEK). The test is performed as described in ASTM D 5402-93. The number of double rubs (i.e., one back and forth motion) is reported. Preferably, the MEK solvent resistance is at least 30 double rubs, preferably at least 50 double rubs, and more preferably at least 100 double rubs, although can coatings exhibit very low double rubs in this test and are commercially viable in some cases.

[0128] Anti-whitening: Whitening resistance measures the ability of a coating to resist attack by various solutions after pasteurization or retort. Typically, whitening is measured by the amount of water absorbed into the coated film. When the film absorbs water, it typically becomes cloudy or appears white. Whitening is typically visually assessed using a scale of 0 to 10, where a rating of "10" indicates no whitening and a rating of "0" indicates complete whitening of the film. The whitening rating after pasteurization or retort (as described herein) is preferably at least 6, and more preferably 7 or higher, and most preferably 9 or higher.

[0129] Distillation : The coated substrate is subjected to heat in the range of 105°C to 130°C and a temperature in the range of 0.7 kg / cm 2 Up to 1.05kg / cm 2 The test was achieved by immersing the coated substrate in deionized water and subjected to heat of 121°C (250°F) and 1.05 kg / cm 2 The pressure was maintained for a period of 30 minutes.

[0130] Pasteurization : The test was conducted by immersing the coated substrate in a heated water bath at a temperature ranging from 65°C to 100°C for 5 minutes to 60 minutes. For this evaluation, the coated substrate was immersed in a deionized water bath at 85°C for 30 minutes.

[0131] Feathering :like Figures 1 to 4 As shown in , feathering is measured using a 0.226 mm gauge coated aluminum reference sheet 10, a scoring tool (or equivalent) with a 60 micron scoring width set in a Carver press, a 7X magnifying glass (or equivalent) graded in 0.005 inch increments, an optional 6 inch vise, a 2000 mL beaker (or equivalent), and a thermometer. The sample to be tested is prepared by cutting a 2 inch x 6 inch sheet 10 from the area to be tested. The 2 inch cut must be in the rolling direction (with the metal grain). Using a permanent marker, a straight line can be made along the entire 6 inch edge of the side of the product as a reference for forming a simulated pull tab. Using a permanent marker, make a 1 / 4 inch straight line mark on the side of the product approximately 1 / 2 inch from the top edge of the test sample, and then make five additional 1 / 4 inch straight line marks approximately 1 inch apart along the 6 inch width of the sample to help space the simulated pull tabs apart.

[0132] To test, place the sheet 10 (coated or product side up) between the scoring tool and the anvil in the Carver Press. The first 1 / 4 inch line on the sample matches the black line on the scoring tool. The bottom edge of the sample should be aligned flush with the guide block on the inside of the press. The press rod is manually raised until a force of 5 metric tons is registered on the hydraulic pressure gauge to form a score line 11 that creates a simulated pull tab 12. The sheet 10 is then indexed to the second black line at the top edge of the sample. The press rod is raised again until a force of 5 metric tons is registered on the hydraulic pressure gauge to form another score line 11 that creates a second simulated pull tab 12. Figure 1 As shown generally in FIG. 1 , a total of five simulated pull tabs 12 are repeated along a 6-inch width. Next, a portion 14 of the simulated pull tab 12 is cut or torn approximately 1 / 4 inch by hand or by using a pair of small scissors, such as Figure 2 The pull tab portion 14 can be bent upwardly by 90 degrees.

[0133] Next, the sheet 10 is conditioned, such as by immersing the test sample upright (i.e., with the "legs" facing upward) in a water bath as needed to perform the appropriate test selected, such as immersing a beaker and thermometer in a water bath as needed. Typically, conditioning is performed in deionized water at 85°C for about 45 minutes, followed by cooling with tap water before further testing. Other processing conditions may be used as required for a particular application. For feathering evaluation, one sheet 10 is evaluated at a time by drying each sheet before testing. First, the sheet 10 is turned over so that the coated side 13 faces the operator. The scored leg 14 of each simulated pull tab is facing away from the operator at a 90° angle. The sheet 10 is then placed on a flat surface (if necessary, tape or other fastening methods (i.e., a vise) can be used to secure the edge of the plate to the surface). Each simulated pull tab 12 is then pulled straight 15 away from the operator (parallel to the floor) using a pair of pliers or other devices (not shown) to completely remove the pull tab from the test sample. Figure 3 The simulated tab 12a is shown in the process of being pulled and the simulated tab 12b is removed from the sheet 10. After all five simulated tabs are pulled, the feathering is measured on the end cap 18 of the formed opening 16 of the sample 10 using, for example, a 7X eyepiece marked in 0.005 inch increments, as shown in FIG. Figure 4 The feathering is determined by calculating the average of all five values ​​for each sheet 10.

[0134] Coatings for easy-open beverage can end caps preferably exhibit feathering of less than 0.5 mm, more preferably less than 0.4 mm, most preferably less than 0.3 mm, and optimally 0.2 mm or even less. When properly cured, certain preferred films of the present disclosure exhibit feathering of 0.1 mm or less when tested as described above and when subjected to the short cure cycles described herein.

[0135] Coefficient of Friction (COF) : The coefficient of friction is measured with an Alteck (or equivalent mobility or lubricity tester) using a metal ball moving on the surface of the coating with a pressure of about 2 kg weight. The force required to move the metal ball on the coating is measured and used to calculate its coefficient of friction. The coatings of the present disclosure typically have a coefficient of friction of 0.06 or less and preferably between about 0.04 and 0.06.

[0136] Porosity :Porosity testing is performed by placing the coated beverage can end cap on a cup filled with an electrolyte solution. The cup is inverted to expose the inner coated surface of the can end cap to the electrolyte solution. The amount of current passing through the end cap is then measured. If the coating remains intact (no cracks or breaks) after manufacturing, a minimum current will pass through the end cap. For this evaluation, a fully converted 202 standard open can end cap (which is a "riveted" aluminum beverage can end cap) is exposed to an electrolyte solution containing a deionized water solution of 1 wt % NaCl for 4 seconds. Metal exposure is measured using a WACO Enamel Rater II purchased from the Wilkens-Anderson Company, Chicago, IL, with an output voltage of 6.3 volts. The measured current is reported in milliamperes. End cap continuity is usually tested initially, and then the end cap is tested after pasteurization or retorting. When tested as described above, if the coating passes less than about 10 milliamperes (mA) of current (after the end cap is formed), the coating is considered to meet the porosity test. Preferred coatings pass the initial test at less than 5 milliamps (mA), more preferably less than 2 mA, and even more preferably less than 1 mA. Preferred coatings pass the porosity test after pasteurization at less than 10 mA, more preferably less than 8 mA, and even more preferably less than 5 mA.

[0137] Total Extraction Test : The total extraction test is designed to estimate the total amount of mobile materials that can potentially migrate out of the coating and into the food packaged in the coating tank. Typically, the coated substrate is subjected to water or solvent blends under various conditions to simulate a given end use. Acceptable extraction conditions and media can be found in 21CFR§175.300, paragraphs (d) and (e), which are incorporated herein by reference. If evaluated herein, the extraction procedure is performed according to the Food and Drug Administration (FDA) "Preparation of Premarket Submission for Food Contact Substances: Chemistry Recommendations," (December 2007). The total extraction limit allowed by FDA regulations is 50 parts per million (ppm).

[0138] The single-sided extraction cell was made according to a design found in Journal of the Association of Official Analytical Chemists, 47(2):387 (1964) with minor modifications. The cell was 9 inches by 9 inches by 0.5 inches with a 6 inch by 6 inch open area in the center of the TEFLON spacer. This allowed a 36 in. 2 or 72in 2 The test articles were exposed to food simulating solvent. The cell contained 300 mL of food simulating solvent. When exposed to 36 in 2 and 72in 2 The solvent to surface area ratio for the test article was 8.33 mL / in 2 and 4.16mL / in 2 .

[0139] Test products can be used by The test cells were composed of 0.0082-inch thick 5182 aluminum alloy panels pretreated with 1903 (supplied by Chemetall GmbH, Frankfurt am Main, Germany). These panels were coated with the test coating (completely covering at least the 6-inch by 6-inch area required to fit the test cell) to produce a final dry film thickness of 11 grams per square meter (gsm) after a 10-second cure bake, resulting in a peak metal temperature (PMT) of 242°C. Two test articles were used per cell, with a total surface area of ​​72in 2 / pool. The test article was extracted in quadruplicate using 10% ethanol in water as a food simulation solvent. The test article was processed at 121°C for two hours and then stored at 40°C for 238 hours. The test solution was sampled after 2, 24, 96 and 240 hours. The test article was extracted in quadruplicate using 10% ethanol in water under the conditions listed above.

[0140] Each test solution was evaporated to dryness in a pre-weighed 50 mL beaker by heating on a hot plate. Each beaker was dried in a 250 ° F (121 ° C) oven for a minimum of 30 minutes. The beaker was then placed in a desiccator to cool and then weighed to constant weight. Constant weight is defined as three consecutive weighings that differ by no more than 0.00005 g. A solvent blank using a Teflon sheet in an extraction cell was similarly exposed to the simulant and evaporated to constant weight to correct the weight of the test article extraction residue added by the solvent itself. Two solvent blanks were extracted at each time point and the average weight was used for correction.

[0141] Total non-volatile extracts were calculated as follows: Ex = e / s, and where the variable "Ex" refers to the extraction residue (mg / in 2); "e" refers to the extract per replicate test (mg); and "s" refers to the area of ​​extraction (in 2 ). Preferred coatings give a total extraction result of less than 50 ppm, more preferably less than 10 ppm, and even more preferably less than 1 ppm over all of the above-mentioned tested time periods. Most preferably, the total extraction result is optimally undetectable.

[0142] Example 1

[0143] Polyolefin dispersions were prepared according to the compositions of Table 1 below, providing the weight percentage of each component in the composition being evaluated. For this evaluation, the polyolefin was a commercially available Canvera 1350 product (46% solid) from Dow Chemical, the catalyst was a Tyzor TE product from DuPont, and the crosslinking agent was Primid QM1260 from EMS-Chemie AG. In addition, the sample included 2-dimethylaminoethanol (DMEA) (16.5% by weight in water), and the lubricant was carnauba wax type T3. DMEA was blended with a crosslinking agent and / or with a catalyst.

[0144] Typically, the crosslinking agent (if used) is first dissolved in deionized water with a 0.3 wt % DMEA solution, using moderate stirring for about 30 minutes to obtain a colorless aqueous resin solution, thereby forming a 30 wt % solution of the crosslinking agent in water with DMEA. Then, monoethylene glycol is added, followed by the polyolefin dispersion and any remaining DMEA solution under vortex stirring to minimize solvent shock. Finally, the wax dispersion is added in a post-addition using moderate stirring, and the solids content and viscosity of the formulation are adjusted with water.

[0145] Table 1 :

[0146]

[0147]

[0148] Each of the compositions of Comparative Samples A through C and Inventive Sample D was applied to an aluminum substrate formed into a 202 beverage can end cap (0.0082 inch thick 5182 aluminum alloy with a chromium-free pretreatment (supplied by Chemetall GmbH, Frankfurt am Main, Germany) and a 202 beverage can end cap. 1903). A sufficient amount of sample was applied using a bardown hand coater application method to obtain a 12 g / m2 dry coating weight. The coated panels were cured in a 5-zone laboratory scale oven to achieve a peak metal temperature of 249°C after a 12 second oven residence time. The cured panels were pressed into easy-open scored beverage can end caps with rivets. The test results for feathering, curing, porosity, pasteurization, and retorting as described above are provided in Table 2.

[0149] Table 2

[0150]

[0151] After aging for one month at 40°C, comparative sample A and inventive sample D were retested. After aging, sample A and sample D were re-coated with the aged composition and cured using the same initial baking conditions described above. As shown in Table 4 below, sample D again outperformed sample A in feathering, porosity, pasteurization, and retort.

[0152] Table 4

[0153]

[0154] It should be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless expressly and unambiguously limited to one referent. Thus, for example, reference to "an antioxidant" includes two or more different antioxidants. As used herein, the term "comprising" and its grammatical variations are intended to be non-limiting, such that recitation of items in a list does not exclude other like items that can be substituted or added to the listed items.

[0155] For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers used in the specification and claims expressing quantities, percentages or ratios, and other numerical values, are to be understood in all cases as being modified by the term "about". Therefore, unless otherwise indicated, the numerical parameters listed in the following specification and the appended claims are approximate values ​​that may vary depending on the desired properties sought to be obtained by the present disclosure. At a minimum, and without attempting to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be interpreted in light of the number of reported significant digits and by applying customary rounding techniques.

[0156] It should be understood that each component, compound, substituent or parameter disclosed herein should be interpreted as being disclosed for use alone or in combination with one or more of each and every other component, compound, substituent or parameter disclosed herein.

[0157] It should also be understood that each range disclosed herein will be interpreted as a disclosure of each specific value with the same number of significant digits within the disclosed range. Thus, for example, a range of 1 to 4 will be interpreted as an explicit disclosure of the values ​​1, 2, 3, and 4, as well as any range of such values.

[0158] It should also be understood that each lower limit of each scope disclosed herein should be understood to be disclosed in conjunction with each upper limit in each scope disclosed herein for the same component, compound, substituent or parameter and each specific value in each scope. Therefore, the disclosure is interpreted as the disclosure of all scopes obtained by combining each lower limit of each scope with each upper limit of each scope or with each specific value in each scope, or by combining each upper limit of each scope with each specific value in each scope. That is, it should also be understood that any scope between the end values ​​in a wide range is also discussed herein. Therefore, the scope of 1 to 4 also means the scope of 1 to 3, 1 to 2, 2 to 4, 2 to 3, etc.

[0159] In addition, specific amounts / values ​​of components, compounds, substituents or parameters disclosed in the specification or examples should be understood as a disclosure of the lower or upper limit of the range, and can therefore be combined with any other lower or upper limit or specific amount or value of a range for the same component, compound, substituent or parameter disclosed elsewhere in the application to form a range for a component, compound, substituent or parameter.

[0160] Although specific embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents may occur to applicants or other persons skilled in the art that are not presently foreseeable or may not presently be foreseeable. Accordingly, the appended claims as filed and as they may be amended are intended to cover all such alternatives, modifications, variations, improvements, and substantial equivalents. The entire disclosures of all patents, patent documents, and publications are incorporated herein by reference as if individually incorporated.

Claims

1. An aqueous coating composition for a beverage container, the aqueous coating composition comprising: Carrier fluid; Polyolefin binder system; a cross-linking agent; and Transition metal catalysts; wherein the cross-linking agent is a nitrogen-containing carboxyl-reactive cross-linking agent; The nitrogen-containing carboxyl-reactive crosslinking agent comprises a β-hydroxyl group relative to the nitrogen atom of the amide bond.

2. The aqueous coating composition of claim 1, wherein the transition metal catalyst is water dispersible.

3. The aqueous coating composition of claim 1, wherein the aqueous coating composition is suitable for forming a beverage contact coating of an easy opening end cap of a beverage container.

4. The aqueous coating composition of any one of claims 1 to 3, wherein the polyolefin binder system comprises a polyolefin copolymer having structural units derived from reactants comprising two or more C2 to C10 alpha-olefins.

5. The aqueous coating composition of claim 4, wherein the α-olefin is selected from C2 to C6 α-olefins.

6. The aqueous coating composition of claim 4, wherein the α-olefin is selected from C2 to C4 α-olefins.

7. The aqueous coating composition according to any one of claims 1 to 3, wherein the polyolefin binder system comprises a polyolefin copolymer having a carbonyl group derived from ethylene and one or more C3 to C 10 Structural unit of alpha-olefin reactants.

8. The aqueous coating composition of any one of claims 1 to 3, wherein the polyolefin binder system comprises a polyolefin copolymer having structural units derived from reactants including ethylene and propylene.

9. The aqueous coating composition of any one of claims 1 to 3, wherein the polyolefin binder system comprises an acid-functionalized polyolefin.

10. The aqueous coating composition of claim 9, wherein the acid-functionalized polyolefin is a copolymer having structural units derived from reactants comprising one or more C2 to C10 alpha-olefins and (meth)acrylic acid.

11. The aqueous coating composition of claim 9, wherein the coating composition comprises an emulsion-polymerizable ethylenically unsaturated monomer component, the emulsion-polymerizable ethylenically unsaturated monomer component optionally being emulsion polymerized in the presence of the polyolefin binder system.

12. The aqueous coating composition of any one of claims 1 to 3, wherein the coating composition comprises 30% to 35% by weight total resin solids.

13. The aqueous coating composition of any one of claims 1 to 3, wherein the coating composition comprises at least 50 wt. % of one or more polyolefin polymers, based on total resin solids of the coating composition.

14. The aqueous coating composition of any one of claims 1 to 3, wherein the nitrogen-containing carboxyl-reactive crosslinker comprises at least one imide group.

15. The aqueous coating composition of any one of claims 1 to 3, wherein the nitrogen-containing carboxyl-reactive crosslinker has the structure HO-R1-N(R2)-CO-X-CO-N(R2)-(R1)-OH, wherein R1 and R2 are independently organic groups, X is a divalent organic group, and wherein the hydroxyl groups are independently primary hydroxyl groups or secondary hydroxyl groups.

16. The aqueous coating composition of claim 15, wherein the nitrogen-containing carboxyl-reactive crosslinking agent comprises:

17. The aqueous coating composition of any one of claims 1 to 3, wherein the nitrogen-containing carboxyl-reactive crosslinker comprises a carbodiimide moiety.

18. The aqueous coating composition according to any one of claims 1 to 3, wherein the transition metal catalyst comprises at least one metal selected from aluminum (Al), cobalt (Co), iron (Fe), titanium (Ti), zinc (Zn), zirconium (Zr), or mixtures thereof.

19. The aqueous coating composition of any one of claims 1 to 3, wherein the transition metal catalyst comprises an organometallic transition metal catalyst.

20. The aqueous coating composition of claim 19, wherein the organometallic transition metal catalyst comprises one or more alkoxy ligands.

21. The aqueous coating composition of claim 19, wherein the organometallic transition metal catalyst comprises one or more alkoxycarbonyl ligands.

22. The aqueous coating composition of claim 20 or 21, wherein the alkoxy ligand or the alkoxycarbonyl ligand comprises a C1 to C6 alkyl group.

23. The aqueous coating composition of claim 19, wherein the organometallic transition metal catalyst is an organometallic transition metal chelate.

24. The aqueous coating composition according to any one of claims 1 to 3, wherein the transition metal catalyst is selected from titanium acetylacetonate, tetraalkyl titanate, isopropyl orthotitanate, water-soluble titanium chelate, triethanolamine chelate of titanium, tetratriethanolamine chelate of titanium, lactic acid titanate chelate or a combination thereof.

25. The aqueous coating composition of any one of claims 1 to 3, wherein the coating composition comprises at least 400 ppm of the transition metal catalyst based on the total amount of transition metal in the catalyst relative to the total non-volatile weight of the aqueous coating composition.

26. The aqueous coating composition of any one of claims 1 to 3, wherein the coating composition comprises no more than 800 ppm of the transition metal catalyst based on the total amount of transition metal in the catalyst relative to the total non-volatile weight of the aqueous coating composition.

27. The aqueous coating composition of any one of claims 1 to 3, wherein when the aqueous coating composition is applied to a cleaned and chromium-free pretreated aluminum panel and cured for 12 seconds to a peak metal temperature of 249°C to achieve a dry film thickness of 12 grams per square meter and formed into a fully converted 202 standard opening beverage can end, the aqueous coating composition passes less than 5 milliamps of current while exposed to an electrolyte solution containing 1 weight percent NaCl dissolved in deionized water for 4 seconds.

28. The aqueous coating composition of any one of claims 1 to 3, wherein the aqueous coating composition exhibits feathering of 0.5 mm or less when applied to a cleaned and chrome-free pretreated aluminum panel and cured for 12 seconds to a peak metal temperature of 249°C to achieve a dry film thickness of 12 grams per square meter.

29. The aqueous coating composition of any one of claims 1 to 3, wherein the aqueous coating composition exhibits a blush rating of at least 6 after pasteurization when applied to a cleaned and chrome-free pretreated aluminum panel and cured for 12 seconds to a peak metal temperature of 249°C to achieve a dry film thickness of 12 grams per square meter.

30. The aqueous coating composition of any one of claims 1 to 3, wherein the aqueous coating composition has a viscosity of 35 to 60 seconds at 25°C as measured via ASTM D-1200 using a No. 4 Ford cup.

31. The aqueous coating composition of any one of claims 1 to 3, wherein the aqueous coating composition has 30% to 35% solids by weight.

32. The aqueous coating composition of any one of claims 1 to 3, wherein the carrier fluid comprises one or more water-miscible organic solvents.

33. The aqueous coating composition of claim 32, wherein the water-miscible organic solvent comprises isopropanol, ethanol, methanol, butanol, pentanol, glycols, glycol ethers, glycol esters, acetone, methyl ethyl ketone or tetrahydrofuran or mixtures thereof.

34. The aqueous coating composition of claim 32, wherein the coating composition comprises 15% to 3.5% by weight of the one or more water-miscible organic solvents.

35. The aqueous coating composition of any one of claims 1 to 3, wherein the coating composition comprises at least 5 weight percent of one or more organic solvents.

36. An aqueous coating composition according to any one of claims 1 to 3, wherein the coating composition contains less than 1000 ppm of each of bisphenol A, bisphenol F or bisphenol S, or any epoxides thereof; and wherein the coating composition optionally contains less than 1000 ppm of styrene; or wherein the coating composition does not contain any bisphenol A, bisphenol F, bisphenol S, their epoxides or styrene, or structural units derived from bisphenol A, bisphenol F, bisphenol S, their epoxides or styrene.

37. The aqueous coating composition of any one of claims 1 to 3, wherein the aqueous coating composition contains less than 1000 ppm of formaldehyde or structural units derived from formaldehyde, or does not contain any formaldehyde or structural units derived from formaldehyde.

38. The aqueous coating composition of any one of claims 1 to 3, further comprising a lubricant.

39. The aqueous coating composition of claim 38, wherein the lubricant is selected from carnauba wax, polyethylene-based wax, Fischer-Tropsch wax, fatty acid ester wax, silicone-based wax, lanolin wax, hydroxy-functional polysiloxane wax, or combinations thereof.

40. The aqueous coating composition of any one of claims 1 to 3, wherein the coating composition comprises at least 25% by weight water.

41. The aqueous coating composition of any one of claims 1 to 3, wherein the coating composition is an interior beverage can end coating composition.

42. The aqueous coating composition of any one of claims 1 to 3, wherein the aqueous coating composition is prepared without using a halogenated monomer, contains less than 1000 ppm of a halogenated monomer, contains less than 20 ppb of a halogenated monomer, or contains no halogenated monomer.

43. The aqueous coating composition of any one of claims 1 to 3, wherein the aqueous coating composition forms a coating comprising less than 50 ppm of extractables when tested according to the Total Extraction Test.

44. An article comprising a metal substrate having a riveted food or beverage can end, the riveted food or beverage can end having a coating disposed on at least a portion of the riveted beverage can end, wherein the coating is formed from an aqueous coating composition according to any one of claims 1 to 43, and wherein the surface of the metal substrate is pre-treated with a chromium-based or non-chromium-based treatment prior to coating with the aqueous coating composition.

45. The article of claim 44, wherein the non-chrome based treatment is a zirconium based or acrylic based treatment.

46. ​​The article of claim 44 or 45, wherein the coating is present as an inner food contact coating.

47. The article of claim 44 or 45, wherein the coating allows less than 5 milliamps of current to pass therethrough.

48. The article of claim 44 or 45, wherein the coating exhibits feathering of less than 0.5 mm.

49. The article of claim 44 or 45, wherein the coating has an average dry coating thickness of 7 microns to 15 microns.

50. The article of claim 44 or 45, wherein the metal substrate of the food or beverage can end closure has an average thickness of 175 microns to 230 microns.

51. The article of claim 44 or 45, wherein the metal substrate of the food or beverage can end closure comprises aluminum or steel.

52. The article of claim 44 or 45, wherein the article is prepared without the use of halogenated monomers, contains less than 1000 ppm of halogenated monomers, contains less than 20 ppb of halogenated monomers, or contains no halogenated monomers.

53. The article of claim 44 or 45, wherein the coating comprises less than 50 ppm extractables when tested according to the Total Extraction Test.

54. A method comprising applying an aqueous coating composition according to any one of claims 1 to 43 to a surface of a substrate for forming an end closure for a beverage container, and curing the aqueous coating composition to form a cured coating on the surface of the substrate, and wherein the surface of the metal substrate is pre-treated with a chrome-based or non-chrome-based treatment prior to coating with the aqueous coating composition.

55. The method of claim 54, wherein the non-chrome based treatment is a zirconium based or acrylic based treatment.

56. A method according to claim 54 or 55, wherein the substrate is aluminium or steel.

57. The method of claim 54 or 55, wherein applying the aqueous coating composition to the surface of the substrate comprises applying the aqueous coating composition to a continuously moving surface traveling at a line speed of 50 to 400 meters per minute.

58. A method according to claim 54 or 55, wherein the curing is carried out for an oven cure time of 8 seconds to 15 seconds to achieve a peak metal temperature of 200°C to 260°C.

59. A method according to claim 54 or 55, wherein the applied coating has an average dry coating thickness of 7 microns to 15 microns.

60. The method of claim 54 or 55, wherein the substrate has an average thickness of 175 microns to 230 microns.

61. The method of claim 54 or 55, further comprising forming a beverage can end from the coated substrate, and wherein the coating allows less than 5 milliamps of current to pass therethrough.

62. The method of claim 54 or 55, further comprising forming a beverage can end from the coated substrate, and wherein the coating exhibits feathering of 0.5 mm or less.

63. A method comprising using the aqueous coating composition of any one of claims 1 to 43 as a beverage can end coating composition.

64. The method of claim 63 comprising applying the aqueous coating composition of any one of claims 1 to 43 as an interior coating on a riveted beverage can end.

65. The method of any one of claims 54, 55, 63 and 64, wherein the aqueous coating composition is prepared without using a halogenated monomer, contains less than 1000 ppm of a halogenated monomer, contains less than 20 ppb of a halogenated monomer, or contains no halogenated monomer.

66. The method of any one of claims 54, 55, 63, and 64, wherein the coating comprises less than 50 ppm extractables when tested according to the Total Extraction Test.

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