Latex coating compositions with reduced flavor-stripping properties

Abstract

This article relates to latex coating compositions with reduced flavor peeling properties. The present invention provides a coating composition for food or beverage cans comprising an emulsified latex polymer formed by polymerizing an olefinically unsaturated monomer component in the presence of an aqueous dispersion of the emulsified latex polymer.

Description

[0001] This application is a divisional application of Chinese patent application No. 201780056296.0, entitled "Latex Coating Composition with Reduced Flavor-Stripping Properties," filed by the applicant, SWIMC Ltd, on July 13, 2017.

[0002] Cross-references to related applications This application claims priority to U.S. Provisional Patent Application No. 62 / 362,729, filed July 15, 2016, entitled “LATEX COATING COMPOSITION HAVINGREDUCED FLAVOR SCALPING PROPERTIES,” which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure relates to coating compositions, including latex emulsion coating compositions, which can be used to form coatings (e.g., spray coatings) for food and beverage containers or other packaging articles. Background Technology

[0004] Various coating compositions have been used to coat the surfaces of food and beverage cans and other packaging articles. For example, metal cans are sometimes coated using a "roll coating" or "sheet coating" operation, in which a suitable composition is applied to a flat roll or sheet of a suitable substrate (e.g., steel or aluminum), which is then cured or otherwise hardened. The coated substrate is then formed into the can end or body. Alternatively, a liquid coating composition can be applied to a shaped article by various means, including spraying, dipping, rolling, etc., and then cured or otherwise hardened.

[0005] Packaging coatings should preferably be able to be applied to the substrate at high speeds and provide the necessary properties for operation in such demanding end-use applications upon curing. For example, the coating should be food-safe, have excellent adhesion to the substrate, possess sufficient flexibility to withstand deflection of the underlying substrate without breaking (e.g., during manufacturing steps or due to damage during transport or use of the packaged product), and resist degradation over extended periods, even when exposed to harsh environments. Coatings that will undergo deformation after curing, such as those applied to cans or end preforms (which will subsequently cure and take their final shape), require particularly good flexibility so that the applied coating remains intact on the substrate after deformation.

[0006] Many packaging coatings currently contain mobile or bound bisphenol A (“BPA”), bisphenol F (“BPF”), bisphenol S (“BPS”), their aromatic glycidyl ether compounds (such as diglycidyl ethers of BPA, BPF, or BPS), or polyvinyl chloride (“PVC”) compounds. While the scientific evidence available to date generally suggests that trace amounts of these compounds that may be released from existing coatings do not pose a health risk to humans, some consumers still believe they may be harmful to human health.

[0007] Furthermore, coating compositions used in food and beverage applications should be resistant to and not cause "flavor scalping." Flavor scalping refers to a loss of quality in packaging due to the absorption of aroma or other flavor components from the packaging, or due to the absorption of unwanted aromas or other flavor components from the food or beverage contained within the packaging.

[0008] As can be understood from the foregoing, what is needed in the art is a packaging container (e.g., a food or beverage can or part thereof) coated with a composition that does not contain extractable amounts of unpleasant compounds, can undergo a challenging coating and curing process to produce a coating with the desired adhesion and flexibility, and does not cause unpleasant flavor peeling. Summary of the Invention

[0009] Some researchers in the packaging field have suggested that increasing the coating Tg would help improve resistance to flavor peeling. However, due to the need to meet other requirements for inner container coatings, such as sprayability, flexibility, no blistering and whitening, resistance to breakage and corrosion, resistance to product components, and avoidance of carbonation loss, it is not feasible to increase the Tg of the packaging film sufficiently to achieve acceptable flavor peeling resistance. As the polymer Tg increases, there is a tendency to sacrifice atomization, substrate coverage, flexibility, and blistering resistance. This invention provides a high Tg polymer that solves the flavor peeling problem while maintaining the expected coating performance and film performance characteristics for inner spray coatings in two-piece metal cans.

[0010] One aspect of the present invention provides a coating composition for food or beverage cans comprising an emulsified latex polymer (i.e., a latex polymer prepared by emulsion polymerization in the presence of an emulsifying polymer having a specific minimum molecular weight), wherein the cured film of the coating composition has a specific minimum glass transition temperature (Tg), and the coating composition is substantially free of each of bisphenol A, bisphenol F, and bisphenol S (including its epoxides). The emulsified latex polymer can be formed by mixing an olefinically unsaturated monomer component with an aqueous dispersion of the emulsifying polymer having a number-average molecular weight (Mn) of at least about 8,500, and then polymerizing the olefinically unsaturated monomer component in the presence of the emulsifying polymer to form the emulsified latex polymer, which, upon drying or otherwise curing, provides a cured or otherwise hardened coating film having a Tg of at least about 40°C. The olefinically unsaturated monomer component can be added to the aqueous dispersion of the emulsifying polymer in an incremental, batchwise, or combined manner (e.g., semi-batch addition). For simplicity, the polymer formed from this olefinically bonded unsaturated monomer component can be referred to as the "component polymer." In the emulsified latex polymer, the emulsifying polymer appears to be fully bonded (e.g., covalently or ionicly bonded) or otherwise fully complexed or entangled with the component polymer, thus preventing extraction from the cured coating. Without being bound by theory, the emulsified latex polymer can be said to possess a multi-level polymer morphology, but is believed not to have a conventional core-shell structure. The disclosed emulsified polymer can be provided or formed in a manner similar to conventional core polymers prior to the formation of the component polymer. However, in a manner more similar to conventional shell polymers, the emulsified polymer can serve as a hydrophilic interface between the emulsified latex polymer and the aqueous dispersion medium after the component polymer is formed.

[0011] The olefinically unsaturated monomer component is preferably a mixture of monomers. In some embodiments, at least one monomer in the mixture is preferably a (meth)acrylate monomer, and at least one monomer is preferably an ethylene oxide-functionalized monomer. More preferably, at least one monomer in the mixture is an ethylene oxide-functionalized α,β-olefinically unsaturated monomer. In some embodiments, based on the weight of the monomer mixture, the amount of the ethylene oxide-functionalized monomer in the olefinically unsaturated monomer component is at least 0.1 wt%. In some embodiments, based on the weight of the monomer mixture, the amount of the ethylene oxide-functionalized monomer in the olefinically unsaturated monomer component is not greater than 30 wt%.

[0012] The emulsifying polymer can be an acid-functionalized or anhydride-functionalized polymer (i.e., a polymer containing acid or anhydride groups) and a salt of an amine, preferably a tertiary amine. In other embodiments, the emulsifying polymer is a polymer having salt-forming groups, which are groups other than acid or anhydride groups (e.g., anionic or cationic salt groups that promote the formation of a stable aqueous dispersion, and salt-forming groups that generate anionic or cationic salt groups when neutralized with a suitable acid or base) or groups formed using a neutralizing agent other than an amine. In other embodiments, the emulsifying polymer contains nonionic aqueous dispersion groups (e.g., polyoxyethylene groups), which contribute to the formation of a stable aqueous dispersion.

[0013] The present invention also provides a method for preparing a coating for a food or beverage can or a portion thereof. The method includes forming a composition comprising an emulsified latex polymer, comprising: forming an aqueous dispersion of the emulsified polymer having a Mn of at least about 8,500 in a carrier comprising water and optionally an organic solvent; mixing an olefinically unsaturated monomer component with the aqueous dispersion; polymerizing the olefinically unsaturated monomer component in the presence of the aqueous dispersion to form the emulsified latex polymer, the emulsified latex polymer providing a cured coating with a Tg of at least about 40°C; and applying the composition comprising the emulsified latex polymer onto a metal substrate before or after forming a portion thereof onto the metal substrate. The olefinically unsaturated monomer component and the emulsified polymer are as described above. In some embodiments, the method may include removing at least a portion of the organic solvent (if present) from the aqueous dispersion after polymerization and before applying the composition to the metal substrate.

[0014] In some embodiments, applying the composition to such a metal substrate includes applying the composition to a metal substrate in the form of a flat roll or sheet, causing the emulsified latex polymer to harden, and forming the substrate into a food or beverage can or a portion thereof. In other embodiments, applying the composition to such a metal substrate includes applying the composition to the metal substrate after the can or a portion thereof has been formed.

[0015] In some embodiments, forming the substrate into a can or a portion thereof includes forming the substrate into a can end or can body. In some embodiments, the can is a two-piece drawn food can, a three-piece food can, a food can end, a thin-walled drawn food or beverage can, a beverage can end, etc. The metal substrate may be, for example, steel or aluminum.

[0016] In some embodiments, the disclosed coating composition contains one or more crosslinking agents, fillers, catalysts, dyes, pigments, toners, extenders, lubricants, corrosion inhibitors, flow control agents, thixotropic agents, dispersants, antioxidants, adhesion promoters, light stabilizers, organic solvents, surfactants, or combinations thereof to provide desired film properties.

[0017] In some embodiments, the composition is substantially free of mobile BPA, mobile BPF, and mobile BPS. In preferred embodiments, the composition is substantially free of these mobile compounds, even more preferably substantially completely free of these mobile compounds, and most preferably completely free of these mobile compounds. In other embodiments, the composition is substantially free of bound BPA, bound BPF, and bound BPS. In preferred embodiments, the composition is substantially free of these bound compounds, even more preferably substantially completely free of these bound compounds, and most preferably completely free of these bound compounds. Furthermore, the coating composition preferably is substantially free of, substantially free of, substantially completely free of, or completely free of structural units derived from diphenols or other polyphenols that have estrogen agonist activity greater than or equal to 4,4'-(propane-2,2-diyl)diphenol. More preferably, the coating composition is substantially free of or completely free of any structural units derived from diphenols or other polyphenols that have estrogen agonist activity greater than or equal to BPS. In some embodiments, the coating composition is substantially free of or completely free of any structural units derived from bisphenols. In some embodiments, the latex polymer or coating composition is epoxy-free, for example, free of polyaromatic polyepoxides.

[0018] In some embodiments, the emulsifying polymer includes acid-functional or anhydride-functional acrylic polymers, acid-functional or anhydride-functional alkyd polymers, acid-functional or anhydride-functional polyester polymers, acid-functional or anhydride-functional polyurethane polymers, acid-functional or anhydride-functional polyolefin polymers, or combinations thereof. Preferably, the emulsifying polymer includes acid-functional acrylic polymers. In some embodiments, the emulsifying polymer is neutralized with a tertiary amine, such as those selected from: trimethylamine, dimethylethanolamine (also known as dimethylaminoethanol), methyldiethanolamine, triethanolamine, ethylmethylethanolamine, dimethylethylamine, dimethylpropylamine, dimethyl3-hydroxy-1-propylamine, dimethylbenzylamine, dimethyl-2-hydroxy-1-propylamine, diethylmethylamine, dimethyl1-hydroxy-2-propylamine, triethylamine, tributylamine, N-methylmorpholine, and mixtures thereof. Preferably, the emulsifying polymer is neutralized by at least 25% of an amine in water.

[0019] In some embodiments, the olefinically unsaturated monomer component is polymerized in the presence of an aqueous dispersion using a water-soluble free radical initiator at a temperature from 0°C to 100°C. In some embodiments, the free radical initiator includes a peroxide initiator. In some embodiments, the free radical initiator includes hydrogen peroxide and benzoin. Alternatively, in some embodiments, the free radical initiator includes a redox initiator system.

[0020] The present invention also provides food cans and beverage cans prepared by the methods described herein. In one embodiment, the present invention provides a food or beverage can comprising: one or more of a body portion or end comprising a metal substrate; and a coating composition disposed thereon, wherein the coating composition comprises the aforementioned emulsified latex polymer dispersed in water.

[0021] definition Unless otherwise stated, the following terms used herein have the meanings provided below.

[0022] The terms “a,” “an,” “the,” “at least one,” and “one or more,” as well as the absence of quantifiers, are used interchangeably. Thus, for example, a coating composition comprising “a” polymer means that the coating composition includes “one or more” polymers.

[0023] The term "aliphatic group" refers to a saturated or unsaturated straight-chain or branched hydrocarbon group. This term is used to include, for example, alkyl, alkenyl, and alkynyl groups. The term "alkyl" refers to a saturated straight-chain or branched hydrocarbon group, including, for example, methyl, ethyl, isopropyl, tert-butyl, heptyl, dodecyl, octadecyl, pentyl, 2-ethylhexyl, etc. The term "alkenyl group" refers to an unsaturated straight-chain or branched hydrocarbon group having one or more carbon-carbon double bonds, such as a vinyl group. The term "alkynyl group" refers to an unsaturated straight-chain or branched hydrocarbon group having one or more carbon-carbon triple bonds. The term "cyclic group" refers to a closed-ring hydrocarbon group, classified as either an alicyclic group or an aromatic group, both of which may contain heteroatoms. The term "alicyclic group" refers to a cyclic hydrocarbon group having properties similar to aliphatic groups.

[0024] The term "Ar" refers to a divalent aryl group (i.e., an arylene group), which is a closed aromatic ring or ring system, such as phenylene, naphthylene, biphenylene, fluorene, and indene, as well as a heteroaryl group (i.e., a closed-ring hydrocarbon in which one or more atoms in the ring are elements other than carbon (e.g., nitrogen, oxygen, sulfur, etc.). Suitable heteroaryl groups include furanyl, thiophene, pyridinyl, quinolinyl, isoquinolinyl, indolyl, isoindolyl, triazolyl, pyrroleyl, tetrazolyl, imidazolyl, pyrazolyl, oxazolyl, thiazolyl, benzofuranyl, benzothiophenyl, carbazoleyl, benzooxazolyl, pyrimidinyl, benzoimidazolyl, quinoxolinyl, benzothiazolyl, naphridinyl, isoxazolyl, isothiazolyl, purine, quinazolinyl, pyrazinyl, 1-oxopyridinyl, pyridazinyl, triazinyl, tetraazinyl, oxadiazolyl, thiadiazolyl, etc. When these groups are divalent, they are usually referred to as "hybridaryl" groups (e.g., furanyl, pyridinyl, etc.).

[0025] The term "bisphenol" refers to a polyphenolic compound containing two phenylene rings, each containing a six-carbon ring and a hydroxyl group attached to a carbon atom of that ring, wherein the two phenylene rings do not share any common atoms.

[0026] The terms “comprising,” “including,” and variations thereof, when used in the specification and claims, are not restrictive.

[0027] The term "crosslinking agent" refers to a molecule that is capable of forming covalent bonds between polymers or between two different regions of the same polymer.

[0028] When used in the context of polymers herein, the term "epoxy-free" means a polymer that does not contain any epoxy backbone segments. Therefore, for example, a polymer made from components containing epoxy resins would not be considered epoxy-free. Similarly, polymers having backbone segments of reaction products of bisphenols (e.g., BPA, BPF, BPS, 4,4'-dihydroxybisphenol, etc.) and haloalcohols (e.g., epichlorohydrin) are not considered epoxy-free.

[0029] The term "emulsified latex polymer" refers to particulate polymeric materials that are stably dispersed in an aqueous medium, preferably without the presence of non-polymeric surfactants to achieve such dispersion.

[0030] The terms “emulsified polymer” and “polymer emulsifier” refer to polymers having at least one hydrophobic moiety (e.g., at least one alkyl, cycloalkyl, or aryl moiety) and at least one hydrophilic moiety (e.g., at least one water-dispersible group).

[0031] The term "food contact surface" refers to the surface of an article (e.g., a food or beverage container) that comes into contact with or is suitable for contact with food or beverage products.

[0032] Groups that may be the same or different are referred to as something "independently". Substitution on organic groups of compounds used in this invention is considered. To simplify the discussion and description of certain terms used in this application, the terms "group" and "fraction" are used to distinguish between chemical materials that are allowed to be substituted or can be substituted and chemical materials that are not allowed or may not be so substituted. Thus, when the term "group" is used to describe a chemical substituent, the chemical material includes unsubstituted groups and those groups (e.g., in the chain (such as in alkoxy)) having O, N, Si, or S atoms and carbonyl or other conventional substitutions. When the term "fraction" is used to describe a chemical compound or substituent, only unsubstituted chemical materials are included. For example, the phrase "alkyl group" includes not only pure open-chain saturated hydrocarbon alkyl substituents, such as methyl, ethyl, propyl, tert-butyl, etc., but also alkyl substituents with other substituents known in the art, such as hydroxyl, alkoxy, alkylsulfonyl, halogen atom, cyano, nitro, amino, carboxyl, etc. Thus, "alkyl group" includes ethers, haloalkyl, nitroalkyl, carboxylalkyl, hydroxyalkyl, sulfonyl, etc. On the other hand, the phrase "alkyl fragment" is limited to including only pure open-chain saturated hydrocarbon alkyl substituents, such as methyl, ethyl, propyl, tert-butyl, etc. As used herein, the term "group" is intended to describe a specific fragment, as well as the broader class of substituted and unsubstituted structures that include that fragment.

[0033] The term "latex polymer" refers to a dispersion or emulsion of polymer particles formed in the presence of water and one or more secondary dispersants or emulsifiers (e.g., the emulsified polymers described above, surfactants, or mixtures thereof), the presence of which is necessary for the formation of the dispersion or emulsion. After polymer formation, the secondary dispersant or emulsifier typically separates from the polymer; however, as in the embodiments of the emulsified latex polymers disclosed herein, it may become, or appear to become, part of the emulsified latex polymer particles during their formation.

[0034] Unless otherwise stated, references to "(meth)acrylate" compounds (where "methyl" is in parentheses) mean that they include acrylates, methacrylates, or both.

[0035] When used in relation to a compound, the term "removable" means that the cured composition (typically a coating weight of about 1 mg / cm³) is removable. 2 When exposed to a test medium under certain defined conditions, the compound can be extracted from the cured composition, depending on the end use. One example of these test conditions is exposing the cured coating to HPLC-grade acetonitrile at 25°C for 24 hours.

[0036] The term "multi-coat system" refers to a coating system that includes at least two coating layers. Conversely, as used herein, "single-coat system" refers to a coating system that includes only a single coating layer.

[0037] When used in the context of coatings being applied to a surface or substrate, the term "on" includes coatings applied directly to the surface or substrate and coatings applied indirectly to the surface or substrate. Thus, for example, a coating applied over an undercoat above a substrate is considered a coating applied to the substrate.

[0038] The term "organic group" refers to a hydrocarbon group (with optional elements other than carbon and hydrogen, such as oxygen, nitrogen, sulfur, and silicon), which is classified as an aliphatic group, a cyclic group, or a combination of aliphatic and cyclic groups (e.g., alkylaryl and aralkyl).

[0039] As used herein, the term "phenylene" refers to a six-carbon aromatic ring (e.g., as in phenyl) that may have any substituents, including, for example, halogen atoms, oxygen atoms, hydrocarbon groups, hydroxyl groups, etc. Thus, for example, the following aryl groups are each phenylene rings: -C6H4-, -C6H3(CH3)-, and -C6H(CH3)2Cl-. Additionally, for example, each aromatic ring of a naphthyl group is a phenylene ring.

[0040] The term "polymer" includes both homopolymers and copolymers (e.g., polymers of two or more different monomers).

[0041] The terms "preferred" and "ideally" refer to embodiments of the invention that may provide certain benefits in certain circumstances. However, other embodiments may also be preferred in the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are useless, and is not intended to exclude other embodiments from the scope of the invention.

[0042] When used in relation to a coating composition or a hardened or cured coating, the term "substantially free of" a specific bound or mobile compound means that the composition or coating contains less than 1,000 parts per million (ppm) of said compound. Similarly, the term "substantially free of" a specific bound or mobile compound means that the composition or coating contains less than 100 parts per million (ppm) of said compound; the term "substantially completely free of" a specific bound or mobile compound means that the composition or coating contains less than 5 parts per million (ppm) of said compound; and the term "completely free of" a specific bound or mobile compound means that the composition or coating contains less than 20 parts per billion (ppb) of said compound. If the above phrases are used without the term "mobile" (e.g., "substantially free of XYZ compounds"), the disclosed composition and coating contain less than the amount of the compound described above, regardless of whether the compound is mobile in the hardened or cured coating or is bound to a component of the hardened or cured coating.

[0043] The term "water-dispersible group" refers to a group that helps to disperse or dissolve a polymer containing these groups in an aqueous medium. Therefore, the term includes water-soluble groups.

[0044] "Water-dispersible" polymers are polymers that can bind to water on their own without the need for secondary dispersants or emulsifiers to obtain an aqueous dispersion or emulsion of polymer particles that has a shelf life of at least one month at normal storage temperatures.

[0045] The range of numbers expressed by the endpoints includes all numbers contained within that range (for example, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0046] The above description of the invention is not intended to describe every disclosed embodiment or every implementation of the invention. The following description illustrates illustrative embodiments in more detail. Throughout the application, guidance is provided by a list of examples, which can be used in various combinations. In each case, the enumerated list is intended only as a representative group and should not be construed as exhaustive. Detailed Implementation

[0047] The disclosed olefinically unsaturated monomer component can use a variety of monomers. Preferred monomers are capable of free radical-initiated polymerization in an aqueous medium. The olefinically unsaturated monomer component preferably contains a monomer mixture, preferably containing at least one ethylene oxide-functionalized olefinically unsaturated monomer (e.g., at least 0.1 wt%, more preferably at least 1 wt%, even more preferably at least 2 wt% of an ethylene oxide-functionalized olefinically unsaturated monomer), more preferably containing at least one ethylene oxide-functionalized α,β-olefinically unsaturated monomer. The presence of at least 0.1 wt% of such an ethylene oxide-functionalized monomer contributes to the stability of the latex. The ethylene oxide-functionalized monomer also contributes to the dispersion of crosslinking in the particles and results in better performance of coating compositions formulated with this polymer latex during curing. Based on the weight of the monomer mixture, the olefinically unsaturated monomer component preferably contains no more than 30 wt%, more preferably no more than 25 wt%, even more preferably no more than 20 wt%, and most preferably no more than 15 wt% of an ethylene oxide-functionalized monomer. Typically, a monomer mixture containing more than 30% by weight of ethylene oxide-functionalized monomers can contribute to reduced membrane performance. While not intended to be theoretically limiting, this is believed to be due to embrittlement caused by excessive crosslinking. In some embodiments, the monomer mixture contains more than 1%, more than 2%, more than 3%, or 5% or more of monomers containing ethylene oxide functional groups.

[0048] Suitable ethylene oxide-functionalized olefinically unsaturated monomers include monomers having a reactive carbon-carbon double bond and an ethylene oxide (i.e., glycidyl) group. Typically, this monomer is a glycidyl ester of an α,β-unsaturated acid or its anhydride (i.e., an ethylene oxide-functionalized α,β-olefinically unsaturated monomer). Suitable α,β-unsaturated acids include monocarboxylic acids and dicarboxylic acids. Examples of such carboxylic acids include, but are not limited to, acrylic acid, methacrylic acid, α-chloroacrylic acid, α-cyanoacrylic acid, β-methacrylic acid (crotonic acid), α-phenylacrylic acid, β-acryloyloxypropionic acid, sorbic acid, α-chlorosorbic acid, angelic acid, cinnamic acid, p-chlorocinnamic acid, β-stearylacrylic acid, itaconic acid, citraconic acid, mesoconic acid, glutaric acid, aconitic acid, maleic acid, fumaric acid, tricarboxyethylene, maleic anhydride, and mixtures thereof.

[0049] Specific examples of suitable monomers containing a glycidyl group are glycidyl (meth)acrylate (i.e., glycidyl methacrylate and glycidyl acrylate), itaconic acid monoglycidyl ester and diglycidyl ester, maleic acid monoglycidyl ester and diglycidyl ester, and fumarate monoglycidyl ester and diglycidyl ester. Allyl glycidyl ether and vinyl glycidyl ether can also be used as ethylene oxide functional monomers. Preferred monomers are glycidyl acrylate (“GA”) and glycidyl methacrylate (“GMA”), with GMA being particularly preferred in some embodiments.

[0050] Ethylene oxide-functionalized olefinically unsaturated monomers preferably react with suitable other monomers within the olefinically unsaturated group via the olefinically unsaturated site (e.g., via vinyl groups). These other monomers include, for example, (meth)acrylates (e.g., alkyl (meth)acrylates, cycloalkyl (meth)acrylates, or aryl (meth)acrylates), vinyl monomers, alkyl esters of maleic acid or fumaric acid, etc. Suitable (meth)acrylates include those having the formula CH2=C(R 1 )-CO-OR 2 Of those, R 1 It is hydrogen or methyl, R 2 Preferably, it contains alkyl, cycloalkyl, or aryl groups with one to sixteen carbon atoms. 2 The group can be substituted by one or more segments, typically one to three segments, such as hydroxyl, halogen, phenyl, and alkoxy segments. Therefore, suitable (meth)acrylates include hydroxyl-functionalized (meth)acrylates, such as hydroxyl-functionalized alkyl (meth)acrylates. In a preferred embodiment, the olefinically unsaturated monomer component comprises at least one alkyl (meth)acrylate.

[0051] In some embodiments, the essential portion of the olefinically unsaturated monomer component (e.g., at least 10 wt%, at least 20 wt%, or at least 30 wt%) is composed of one or more (meth)acrylates, more preferably one or more alkyl (meth)acrylates. In some embodiments, up to about 50 wt%, up to about 40 wt%, or up to about 35 wt% of the olefinically unsaturated monomer component is composed of one or more such (meth)acrylates. The (meth)acrylates are typically esters of acrylic acid or methacrylic acid. Preferably, R 1 It is hydrogen or methyl, R 2 It is an alkyl group having 2-8 carbon atoms. Most preferably, R 1 It is hydrogen or methyl, R 2 It is an alkyl group having 2-4 carbon atoms.

[0052] Suitable examples of (meth)acrylates include, but are not limited to, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, benzyl (meth)acrylate, lauryl (meth)acrylate, isobornyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, hydroxyethyl acrylate (HEA), hydroxyethyl methacrylate (HEMA), and hydroxypropyl (meth)acrylate (HPMA).

[0053] Bifunctional (meth)acrylate monomers can also be used in monomer mixtures. Examples include (meth)acrylate monomers having two carbon-carbon double bonds capable of free radical-initiated polymerization, such as ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, allyl methacrylate, etc.

[0054] Suitable vinyl monomers include styrene, methylstyrene, halostyrene, isoprene, diallyl phthalate, divinylbenzene, conjugated butadiene, α-methylstyrene, vinyltoluene, vinylnaphthalene, and mixtures thereof. Styrene is currently the preferred vinyl monomer, partly due to its relatively low cost and its Tg-enhancing properties, as described below.

[0055] Other suitable polymerizable vinyl monomers for olefinically unsaturated monomer components include acrylonitrile, acrylamide, methacrylamide, methacrylonitrile, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl stearate, N-isobutoxymethylacrylamide, N-butoxymethylacrylamide, etc.

[0056] Other monomers or mixtures of monomers in the mixture constitute the remaining portion of the monomer component, i.e., 70 wt% to 99.9 wt%, preferably 80 wt% to 99 wt%, based on the total weight of the monomer mixture. Preferably, at least 5 wt% of the olefinically unsaturated monomer component, more preferably at least 10 or at least 20 wt%, is selected from (meth)acrylates, more preferably alkyl (meth)acrylates. Preferably, at least 5 wt% of the monomer component, more preferably at least 10 wt%, is selected from vinyl aromatic compounds.

[0057] In the currently preferred embodiment, the olefinic unsaturated monomer component does not include any acrylamide-type monomers (e.g., acrylamide or methacrylamide).

[0058] As described above, the cured coating film has a Tg of at least about 40°C. In some embodiments, the olefinically unsaturated monomer component, the emulsifying polymer, and other monomers are desirablely selected and used in sufficient quantities such that the Tg of the final cured coating film is greater than about 50°C, more preferably greater than about 60°C, even more preferably greater than about 70°C, and in some embodiments, greater than about 80°C. When multiple glass transition temperature values ​​are observed, these listed values ​​may be based on the highest or lowest observed Tg value, and preferably based on the highest observed Tg value. It is also desirable to select ethylene oxide functional monomers and other monomers and use them in sufficient quantities such that the cured coating film Tg of the final cured coating film is less than about 120°C, preferably less than about 115°C, more preferably less than about 110°C, and in some embodiments, less than about 100°C. When multiple glass transition temperature values ​​are observed, these listed values ​​may be based on the highest or lowest observed Tg value, and preferably based on the lowest observed Tg value. The above values ​​can be determined in some embodiments for films prepared in the absence of other components (e.g., coalescing agents, surfactants, and other materials) that may affect the final cured coating Tg.

[0059] The polymer Tg value can be estimated using the following Fox equation: 1 / Tg = W1 / Tg1 + W2 / Tg2 + ... WN / TgN Where 1, 2, ..., N represent the monomers used to prepare the polymer; W1, W2, ..., WN sum to 1, representing the weight fraction of each monomer used to prepare the polymer; Tg1, Tg2, ..., TGN represent the glass transition temperature in Kelvin of the homopolymer of each monomer used to prepare the polymer; Tg is the estimated glass transition temperature of the polymer. Tg values ​​can also be measured, for example, by using dynamic mechanical analysis (DMA) or differential scanning calorimetry (DSC) to evaluate the thermal behavior of cured polymer films.

[0060] An increase in the Tg of an emulsified latex polymer can be achieved by preparing a component polymer using an olefinically unsaturated monomer component containing most or most of a monomer with a high Tg homopolymer. Exemplary examples of such monomers and their homopolymer Tg values ​​include isobutyl methacrylate (53°C, 326 Tg). o K), benzyl methacrylate (54℃, 327℃) o K), sec-butyl methacrylate (60℃, 333) o K), Ethyl methacrylate (65℃, 338℃) o K), Isopropyl methacrylate (81℃, 354℃) o K), dipentaerythritol pentaacrylate (90℃, 363℃) o K), cyclohexyl methacrylate (92℃, 365℃) oK), isobornyl acrylate (94℃, 367℃) o K), bis(trimethylolpropane)tetraacrylate (98℃, 371) o K), diethylene glycol diacrylate (100℃, 373℃) o K), styrene (100℃, 373℃) o K), 1,3-Butanediol diacrylate (100℃, 374℃) o K), pentaerythritol tetraacrylate (103℃, 376℃) o K), pentaerythritol triacrylate (103℃, 376℃) o K), ethoxylated (3)trimethylolpropane triacrylate (103℃, 376℃) o K), dipropylene glycol diacrylate (104℃, 377℃) o K), methyl methacrylate (105℃, 378℃) o K), acrylic acid (106℃, 379) o K), neopentyl glycol diacrylate (107℃, 380℃) o K), Cyclohexanedimethyl diacrylate (110℃, 383℃) o K), isobornyl methacrylate (110℃, 383) o K), phenyl methacrylate (110℃, 383℃) o K), tert-butyl methacrylate (118℃, 391) o K), methacrylic acid (228℃, 501) o K) and tri(2-hydroxyethyl) isocyanurate triacrylate (272℃, 545℃) o K).

[0061] Preferably, the olefinically unsaturated monomer component (i.e., the monomer forming the component polymer) accounts for at least 40% by weight, more preferably at least 50% by weight of the emulsified latex polymer. Preferably, the olefinically unsaturated monomer component accounts for no more than 80% by weight, more preferably no more than 70% by weight of the emulsified latex polymer. These percentages are based on the total weight of the olefinically unsaturated monomer component and the emulsified polymer.

[0062] Various polymers can be used as the disclosed emulsifying polymers. The emulsifying polymer preferably includes an appropriate number of water-dispersible groups to promote the efficient polymerization of the olefinically unsaturated component in an aqueous medium. Preferred emulsifying polymers are acid-containing or anhydride-containing polymers that can be neutralized or partially neutralized with a suitable amine or other suitable base (preferably a "volatile" base that readily evaporates from the coating during curing) to form a salt that can be dissolved or stably dispersed in an aqueous medium. Preferred acid-containing polymers have an acid value of at least 40, more preferably at least 100 mg KOH / g polymer. Preferred acid-containing polymers have an acid value not greater than 400, more preferably not greater than 300 mg KOH / g polymer. When in water, the acid values ​​of anhydride-containing polymers preferably have similar lower and upper limits. The acid value of the acid emulsifying polymer and the ratio of the component polymer to the emulsifying polymer appear to be related; a higher acid value of the emulsifying polymer is preferred when a smaller amount of the emulsifying polymer is present in the final emulsified latex polymer.

[0063] The Mn of the emulsified polymer is at least about 8,500, preferably at least about 9,000, more preferably at least about 9,500, and most preferably at least about 10,000. Although not theoretically limited, an increase in the molecular weight of the emulsified polymer within these limits is shown to contribute to improving the flexibility of the disclosed coating composition after curing, thereby offsetting the reduction in flexibility that may be caused by an increase in Tg. Preferably, the Mn value of the emulsified polymer is not greater than about 50,000 or not greater than about 40,000.

[0064] Preferred emulsifying polymers include those prepared by conventional free radical polymerization techniques from unsaturated acid-functional monomers or anhydride-functional monomers, their salts, and other unsaturated monomers. Further preferred examples include those prepared from at least 15% by weight, more preferably at least 20% by weight, and in some embodiments 30% by weight or more of unsaturated acid-functional monomers or anhydride-functional monomers or their salts, with the remainder being other polymerizable unsaturated comonomers. Other preferred examples include those prepared from less than 60% by weight, more preferably less than 55% by weight, and in some embodiments less than 50% by weight of unsaturated acid-functional monomers or anhydride-functional monomers or their salts. Various acid-functional monomers or anhydride-functional monomers or their salts can be used; their selection depends on the properties of the latex polymer to be ultimately emulsified. Preferably, such monomers are olefinically unsaturated, more preferably α,β-olefinically unsaturated. Suitable olefinically unsaturated acid-functional monomers or anhydride-functional monomers include monomers having reactive carbon-carbon double bonds and acid or anhydride groups or their salts. Preferred monomers of this type have 3 to 20 carbons, at least one unsaturated site, and at least one acid group or anhydride group or a salt thereof.

[0065] Suitable acid-functionalized monomers include olefinically unsaturated monocarboxylic acids and diacarboxylic acids, as well as anhydrides and monoesters of diacarboxylic acids. The selected monomers are preferably readily copolymerizable with any other monomers used to prepare emulsified polymers. Exemplary monocarboxylic acids include those derived from the formula CH2=C(R 3 The ones represented by COOH, where R 3 It is hydrogen or an alkyl group having 1 to 6 carbon atoms. Exemplary dicarboxylic acids include those of formula R. 4 (COOH)C=C(COOH)R 5 and R 4 (R 5 C=C(COOH)R 6 COOH represents those, where R 4 and R 5 It is hydrogen, an alkyl group having 1-8 carbon atoms, a halogen, a cycloalkyl group having 3-7 carbon atoms, or a phenyl group, R 6 It is an alkylene group having 1 to 6 carbon atoms. These acids can also be used as half-esters with alkanols having 1 to 8 carbon atoms.

[0066] Non-limiting examples of useful olefinically unsaturated acid functional monomers include acids such as acrylic acid, methacrylic acid, α-chloroacrylic acid, α-cyanoacrylic acid, crotonic acid, α-soybenic acid, β-acryloyloxypropionic acid, fumaric acid, maleic acid, sorbic acid, α-pyrrolidone, angelic acid, cinnamic acid, p-chlorocinnamic acid, β-stearylacrylic acid, citraconic acid, mesoconic acid, glutaric acid, aconitic acid, tricarboxyethylene, 2-methylmaleic acid, itaconic acid, 2-methylitaconic acid, methylene glutaric acid, etc., or mixtures thereof. Preferred unsaturated acid functional monomers include acrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleic acid, 2-methylmaleic acid, itaconic acid, 2-methylitaconic acid, and mixtures thereof. More preferred unsaturated acid functional monomers include acrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, and mixtures thereof. The most preferred unsaturated acid functional monomers include acrylic acid, methacrylic acid, maleic acid, crotonic acid, and mixtures thereof. Aqueous salts of the above acids may also be used if desired.

[0067] Non-limiting examples of suitable olefinically unsaturated anhydride monomers include compounds derived from the aforementioned acids (e.g., as pure anhydrides or mixtures thereof). Preferred anhydrides include acrylic anhydride, methacrylic anhydride, and maleic anhydride.

[0068] Monomer polymerization is typically carried out in the presence of a free radical initiator via organic solution polymerization to form acid-functionalized or anhydride-functionalized polymers. Although the preparation of acid-functionalized or anhydride-functionalized polymers is conveniently carried out in solution, a bulk process or a process carried out in water can be used if desired.

[0069] Preferably, the acid-functionalized or anhydride-functionalized polymer is an acid-functionalized acrylic polymer. However, in addition to or instead of acid-functionalized or anhydride-functionalized acrylic emulsified polymers, emulsified polymers based on acid-functionalized or anhydride-functionalized alkyd, polyester or polyurethane polymers, polyolefin polymers, or combinations thereof may also be used in the practice of this invention. Polymers as described in U.S. Patents 3,479,310, 4,147,679, and 4,692,491 may be used, but with appropriate selection or modification, emulsified polymers with Mn greater than about 8,500 can be provided.

[0070] Salts (which can be full or partial salts) of emulsified polymers can be formed by neutralizing or partially neutralizing acid groups (whether originally present in the acid-functionalized polymer or formed when an anhydride-functionalized polymer is added to water) or other water-dispersible (e.g., anionic salt-forming) groups in the polymer with a suitable base (e.g., an amine, preferably a tertiary amine). Some examples of suitable tertiary amines are trimethylamine, dimethylethanolamine (also known as dimethylaminoethanol), methyldiethanolamine, triethanolamine, ethylmethylethanolamine, dimethylethylamine, dimethylpropylamine, dimethyl3-hydroxy-1-propylamine, dimethylbenzylamine, dimethyl-2-hydroxy-1-propylamine, diethylmethylamine, dimethyl1-hydroxy-2-propylamine, triethylamine, tributylamine, N-methylmorpholine, and mixtures thereof. Most preferably, triethylamine or dimethylethanolamine is used as the tertiary amine.

[0071] The degree of neutralization required to form the desired polymer salt can vary significantly depending on the amount of acid or other water-dispersible groups contained in the polymer and the solubility or dispersibility of the desired salt. Typically, when dispersing the emulsified polymer in water, at least 25% of the acid groups or other water-dispersible groups in the polymer are neutralized with an amine in water, preferably at least 30%, more preferably at least 35%. Preferably, the emulsified polymer comprises a sufficient number of acid groups, anhydride groups, or other water-dispersible groups to form a stable aqueous dispersion upon neutralization.

[0072] The disclosed water-dispersible groups can be used to replace or supplement acid or anhydride groups. For further discussion of such water-dispersible groups, see, for example, U.S. Patent No. 4,147,679. Some other examples of anionic salt groups include sulfate groups (-OSO3). - ), phosphate group (-OPO3) - ), sulfonate group (-SO2O) - ), phosphinate group (-POO) - ), phosphonate group (-PO3) - ) and their combinations. Some examples of suitable cationic salt groups include: , (Respectively referred to as quaternary ammonium groups, quaternary phosphorus groups, and tertiary sulfate groups) and combinations thereof. Some examples of nonionic water-dispersible groups include hydrophilic groups, such as ethylene oxide groups. Compounds used to introduce the above groups into polymers are known in the art. Some further examples of neutralizing bases used to form anionic salt groups include inorganic and organic bases, such as sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide, and mixtures thereof. Some examples of neutralizing compounds used to form cationic salt groups include organic and inorganic acids, such as formic acid, acetic acid, hydrochloric acid, sulfuric acid, and combinations thereof.

[0073] The amount of salt used to neutralize acid- or anhydride-functionalized emulsified polymers is preferably at least 5% by weight, more preferably at least 10% by weight, and even more preferably at least 15% by weight. The amount of salt used to neutralize acid- or anhydride-functionalized emulsified polymers is preferably no more than 95% by weight, more preferably no more than 50% by weight, and even more preferably no more than 40% by weight. These percentages are based on the total weight of the polymerizable olefinically unsaturated monomer component and the salt of the emulsified polymer. In embodiments where the emulsified polymer includes water-dispersible groups other than the neutralized acid or anhydride groups, the total amount of polymer used in the polymerization generally falls within the above parameters, wherein the above percentages are based on the total weight of the olefinically unsaturated monomer component and the emulsified polymer.

[0074] Unbound by theory, the reaction of tertiary amines with materials containing ethylene oxide groups, when carried out in the presence of water, can provide products containing hydroxyl groups and quaternary ammonium hydroxides. Under preferred conditions, the acid group, ethylene oxide group, and amine form a quaternary salt. This bonding is advantageous because it not only links (e.g., crosslinks) the polymer chains but also promotes the water dispersibility of the resulting linked chains. It should be noted that the acid group and ethylene oxide group can also form esters. Some ester-forming reactions may occur, but these are less desirable when water dispersibility is desired.

[0075] While the exact reaction modality is not fully understood, it is believed that competition between the two reactions may occur; however, this is not limiting. In a preferred embodiment, one reaction involves the reaction of a tertiary amine-neutralized acid-functionalized polymer with an ethylene oxide-functionalized monomer or polymer to form a quaternary ammonium salt. The second reaction involves the esterification of the ethylene oxide-functionalized monomer or polymer with a carboxylic acid or salt. Without being bound by theory, it is believed that the presence of water and the amount of amine favor the formation of a quaternary ammonium salt at the ester bond. High levels of quaternization improve water dispersibility, while high levels of esterification provide higher viscosity and the possibility of gel-like materials.

[0076] Preferably, the emulsifying polymer comprises at least 20% by weight of the emulsified latex polymer, more preferably at least 30% by weight. Preferably, the emulsifying polymer comprises no more than 60% by weight of the emulsified latex polymer, more preferably no more than 50% by weight. These percentages are based on the total weight of the olefinically unsaturated monomer component and the emulsifying polymer.

[0077] Regarding the conditions for emulsion polymerization, the olefinic unsaturated monomer component is preferably polymerized in an aqueous medium using a water-soluble free radical initiator in the presence of a salt of an acid-functional or anhydride-functional emulsified polymer.

[0078] The polymerization temperature is typically between 0 and 100°C, preferably between 30 and 90°C. If thermally initiated, a polymerization temperature of 70 to 90°C, or even more preferably 80 to 85°C, is preferred. If chemically initiated via a redox system, a polymerization temperature of 30 to 60°C, or even more preferably 40 to 50°C, is preferred. The pH of the aqueous medium is typically maintained between 5 and 12.

[0079] The free radical initiator may optionally be selected from one or more water-soluble peroxides known to act as free radical initiators. Examples include hydrogen peroxide and tert-butyl hydroperoxide. Other redox initiator systems well known in the art (e.g., tert-butyl hydroperoxide, isoascorbic acid, and ferrous complexes) may also be used. In some embodiments, a mixture of benzoin and hydrogen peroxide is particularly preferred. Other examples of polymerization initiators that can be used include polymerization initiators that thermally decompose at the polymerization temperature to generate free radicals. Examples include water-soluble and water-insoluble materials, such as 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylpentanitrile), and 1-tert-butyl-azocyanocyclohexane; hydroperoxides other than those already mentioned, such as tert-amyl hydroperoxide, methyl hydroperoxide, and cumene hydroperoxide; and peroxides such as benzoyl peroxide, octyl peroxide, di-tert-butyl peroxide, ethyl 3,3'-di(tert-butylperoxy)butyrate, ethyl 3,3'-di(tert-amylperoxy)butyrate, tert-butylperoxy-2-ethylhexanoate, tert-amylperoxy-2-ethylhexanoate, and tert-butylperoxyneopentate. Pivilates; peresters, such as tert-butyl peracetate, tert-butyl perterephthalate, and tert-butyl perbenzoate; and percarbonates, such as di(1-cyano-1-methylethyl)peroxydicarbonate; superphosphates / salts, etc.; and combinations thereof. Persulfate initiators, such as ammonium persulfate or alkali metal (potassium, sodium, or lithium) salts, may also be used, but these may result in poor water resistance of the cured coating and are therefore not preferred.

[0080] Polymerization initiators can be used alone or as an oxidizing component in a redox system, which preferably also includes a reducing component, such as ascorbic acid, malic acid, glycolic acid, oxalic acid, lactic acid, thioglycolic acid, or alkali metal sulfites, more specifically hydrosulfite, hyposulfite, or metabisulfite, such as sodium dithionite, potassium hyposulfite, and potassium metabisulfite, or sodium formaldehyde sulfoxylate, and combinations thereof. The reducing component is commonly referred to as a promoter or catalyst activator.

[0081] Based on the weight of the monomers to be copolymerized, the initiator and accelerator are preferably used in proportions of about 0.001% to 5% each. If desired, a small amount of accelerator, such as chlorides and sulfates of cobalt, iron, nickel, or copper, may be used. Other examples of redox catalyst systems include tert-butyl hydroperoxide / sodium formaldehyde sulfoxylate / Fe(II) and ammonium persulfate / sodium bisulfite / sodium dithionite / Fe(II). Chain transfer agents may also be used to control the polymer molecular weight if desired.

[0082] Polymerization of olefinically unsaturated monomer components can be carried out in batch, intermittent, or continuous operations in the presence of an aqueous dispersion of emulsified polymer salts. The polymerization components can be added entirely to the polymerization vessel at the beginning, or metered using a proportioning technique. Procedures for implementing either method are familiar to those skilled in the art. Preferably, all or substantially all components are added to the polymerization vessel before polymerization begins.

[0083] As described above, in some embodiments, a “batch” method can be used to polymerize olefinically unsaturated monomer components in the presence of an aqueous dispersion of an emulsified polymer salt. While not wishing to be bound by any theory, batch polymerization of olefinically unsaturated monomer components can produce emulsified latex polymers with higher molecular weights, which can produce desired properties for certain coating end-uses, such as beverage end coatings. In some preferred embodiments, the component polymer itself, without the emulsified polymer, has a Mn of at least about 75,000, more preferably at least about 150,000, or even more preferably at least about 250,000. The upper limit of the Mn of the component polymer is not limited and can be 1,000,000 or higher. However, in some embodiments, the Mn of the component polymer is less than about 1,000,000, or less than about 600,000. In some embodiments (e.g., in the case of batch polymerization of the component polymer), the component polymer exhibits an Mn of at least about 75,000, more preferably at least about 150,000, and even more preferably at least about 250,000.

[0084] The disclosed coating composition preferably comprises at least a film-forming amount of emulsified latex polymer. Typically, the emulsified latex polymer is the dominant component in the coating composition (e.g., >50 wt%, >80 wt%, or >90 wt% of the total resin solids in the coating composition), and in some embodiments is the exclusive film-forming polymer. In a preferred embodiment, the coating composition comprises at least about 5 wt%, more preferably at least about 15 wt%, and even more preferably at least about 25 wt% of emulsified latex polymer, based on the weight of the emulsified latex polymer solids relative to the total weight of the coating composition. Preferably, the coating composition comprises less than about 65 wt%, more preferably less than about 55 wt%, and even more preferably less than about 45 wt% of emulsified latex polymer, based on the weight of the emulsified latex polymer solids relative to the total weight of the coating composition.

[0085] It has been found that coating compositions using the above-described emulsified latex polymers can be formulated using one or more optional curing agents (i.e., crosslinking resins, sometimes referred to as "crosslinking agents"). The resulting crosslinked emulsified latex polymers represent a preferred subclass. The degree of crosslinking can be only partial, which results in the polymer being dispersed in an aqueous carrier, applied to a substrate, and coalescing to form a film, but if dissolved in an organic solvent, the polymer will form a gel that cannot pass through a chromatographic column used for molecular weight measurements. The choice of a specific crosslinking agent generally depends on the specific product being formulated. For example, some coating compositions are highly colored (e.g., gold paints). These coatings can generally be formulated using crosslinking agents that tend to have a pale yellow tint. Conversely, white paints are generally formulated using non-yellowing crosslinking agents or only a small amount of yellowing crosslinking agents. Preferred curing agents are substantially free of mobile or bound BPA, BPF, BPS, and their epoxides, such as bisphenol A diglycidyl ether ("BADGE"), bisphenol F diglycidyl ether ("BFDGE"), and epoxy phenolic resins.

[0086] In some embodiments, the coating composition can be cured without the use of an external crosslinking agent (e.g., phenolic crosslinking agent-free). Additionally, the coating composition may be substantially free of formaldehyde and formaldehyde-containing compounds, essentially free of these compounds, essentially completely free of these compounds, or even completely free of these compounds.

[0087] Any well-known hydroxyl-reactive curing resin can also be used. For example, phenolic and amino plastic curing agents can be used.

[0088] Phenolic plastics comprise condensation products of aldehydes and phenols. Formaldehyde and acetaldehyde are preferred aldehydes. Various phenols can be used, such as phenol, cresol, p-phenylphenol, p-tert-butylphenol, p-tert-amylphenol, and cyclopentylphenol.

[0089] Amino plastic resins are condensation products of aldehydes such as formaldehyde, acetaldehyde, crotonaldehyde, and benzaldehyde with substances containing amino or amide groups such as urea, melamine, and guanidine.

[0090] Examples of suitable crosslinking resins include, but are not limited to, benzoguanamine-formaldehyde resins, melamine-formaldehyde resins, etherified melamine-formaldehyde resins, and urea-formaldehyde resins. Preferably, the crosslinking agent is or includes a melamine-formaldehyde resin. Particularly useful examples of crosslinking agents are fully alkylated melamine-formaldehyde resins, available from Cytec Industries, Inc. under the CYMEL brand. TM Obtained through a 303 commercial purchase.

[0091] Examples of other typically suitable curing agents include capped or uncapped aliphatic, alicyclic, or aromatic di-, tri-, or polyvalent isocyanates, such as hexamethylene diisocyanate (HMDI), cyclohexyl-1,4-diisocyanate, etc. Other examples of typically suitable capped isocyanates include isophorone diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, tetramethylxylene diisocyanate, isomers of xylene diisocyanate, and mixtures thereof. In some embodiments, capped isocyanates with Mn of at least about 300, more preferably at least about 650, and even more preferably at least about 1,000 can be used.

[0092] In some embodiments, polymerized end-capped isocyanates are preferred. Some examples of suitable polymerized end-capped isocyanates include isocyanurates or biurets of diisocyanates, trifunctional "trimers," or mixtures thereof. Examples of suitable end-capped polymerized isocyanates include TRIXENE. TM BI 7951, TRIXENE BI 7984, TRIXENE BI 7963 and TRIXENE BI 7981 (TRIXENE materials are available from Baxenden Chemicals, Ltd., Accrington, Lancashire, England), DESMODUR TMBL 3175A, DESMODUR BL3272, DESMODUR BL3370, DESMODUR BL 3475, DESMODUR BL 4265, DESMODUR PL 340, DESMODUR VP LS 2078, DESMODUR VP LS 2117, and DESMODUR VP LS 2352 (DESMODUR materials are available from Bayer Corp., Pittsburgh, PA, USA), or combinations thereof. Examples of suitable trimers may include trimers prepared from an average of three diisocyanate molecules or trimers prepared from an average of three moles of diisocyanate (e.g., HMDI) reacted with one mole of another compound such as a triol (e.g., trimethylolpropane).

[0093] Examples of suitable blocking agents include malonates such as ethyl malonate and diisopropyl malonate, acetylacetone, ethyl acetoacetate, 1-phenyl-3-methyl-5-pyrazolone, pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole, hydroxylamine, thiophenol, caprolactam, catechol, propanethiol, N-methylaniline, amines (such as diphenylamine, diisopropylamine), phenol, 2,4-diisobutylphenol, methyl ethyl ketoxime, α-pyrrolidone, alcohols (such as methanol, ethanol, butanol and tert-butanol), ethyleneimine, acrylamide, benzotriazoles (such as benzotriazole, 5-methylbenzotriazole, 6-ethylbenzotriazole, 5-chlorobenzotriazole and 5-nitrobenzotriazole), methyl ethyl ketoxime (MEKO), diisopropylamine (DIPA) and combinations thereof.

[0094] The required amount of curing agent (i.e., crosslinking agent) depends on the type of curing agent, the baking time and temperature, and the molecular weight of the emulsified polymer. If used, the crosslinking agent is typically present in an amount of up to 50% by weight, preferably up to 30% by weight, and more preferably up to 15% by weight. Alternatively, if used, the crosslinking agent is typically present in an amount of at least 0.1% by weight, more preferably at least 1% by weight, and even more preferably at least 1.5% by weight. These weight percentages are based on the total weight of the resin solids in the coating composition.

[0095] In some embodiments, the disclosed coating composition comprises at least 5% by weight of a capped polymeric isocyanate based on total resin solids, more preferably about 5% to about 20% by weight of a capped polymeric isocyanate, and even more preferably about 10% to about 15% by weight of a capped polymeric isocyanate.

[0096] The disclosed coating compositions may also include other optional polymers that do not adversely affect the coating composition or the cured coating composition derived therefrom. These optional polymers are typically included in the coating composition as fillers, but they may also be included as crosslinking materials or to provide desired properties. One or more optional polymers (e.g., filler polymers) may be included in an amount sufficient to achieve the intended purpose, but their amount does not adversely affect the coating composition or the cured coating composition derived therefrom.

[0097] These additional polymeric materials can be non-reactive and thus serve only as fillers. Such optional non-reactive filler polymers include, for example, polyesters, acrylic resins, polyamides, polyethers, and phenolic resins. Alternatively, such additional polymeric materials or monomers can react with other components of the composition, such as ethylene oxide-functionalized emulsified latex polymers. If desired, reactive polymers can be incorporated into the disclosed compositions to provide additional functionality for various purposes, including crosslinking. Examples of such reactive polymers include, for example, functionalized polyesters, acrylic resins, polyamides, and polyethers. Preferred optional polymers are substantially free of mobile and bound BPA, BPF, and BPS, and preferably substantially free of aromatic glycidyl ether compounds (e.g., BADGE, BFDGE, and epoxy phenolic resins).

[0098] The disclosed coating compositions may also contain other optional components that do not adversely affect the coating composition or the cured coating composition obtained therefrom. These optional components are typically included in the coating composition to enhance the aesthetics of the composition, facilitate the manufacture, processing, treatment and coating of the composition, and further improve the specific functional properties of the coating composition or the cured coating composition obtained therefrom.

[0099] These optional ingredients include, for example, catalysts, dyes, pigments, tinting agents, extenders, fillers, lubricants, corrosion inhibitors, flow control agents, thixotropic agents, dispersants, antioxidants, adhesion promoters, light stabilizers, surfactants, and mixtures thereof. Each optional ingredient is included in an amount sufficient to achieve its intended purpose, but in an amount that will not adversely affect the coating composition or the resulting cured coating composition.

[0100] A preferred optional component is a catalyst that enhances the curing rate. Examples of catalysts include, but are not limited to, strong acids (e.g., dodecylbenzenesulfonic acid (DDBSA, available from Cytec's CYCAT 600), methanesulfonic acid (MSA), p-toluenesulfonic acid (pTSA), dinonylnaphthalenedisulfonic acid (DNNDSA), trifluoromethanesulfonic acid (trifluoromethanesulfonic acid and triflic acid)), quaternary ammonium compounds, phosphorus compounds, and tin and zinc compounds. Specific examples include, but are not limited to, tetraalkylammonium halides, tetraalkyl or tetraarylphosphonium iodide or phosphonium acetate, tin octoate, zinc octoate, triphenylphosphine, and similar catalysts known to those skilled in the art. If used, the catalyst is preferably present in an amount of at least 0.01% by weight, more preferably at least 0.1% by weight, based on the weight of the nonvolatile material. If used, the catalyst is preferably present in an amount of no more than 3% by weight, more preferably no more than 1% by weight, based on the weight of the nonvolatile material.

[0101] Another useful optional ingredient is a lubricant (e.g., wax), which helps in the manufacture of metal seals by imparting lubricity to the coated metal substrate sheet. Preferred lubricants include, for example, carnauba wax and polyethylene lubricants. If used, the lubricant is preferably present in the coating composition in an amount of at least 0.1% by weight, preferably no more than 2% by weight, and more preferably no more than 1% by weight, based on the weight of the non-volatile material.

[0102] Another useful optional ingredient is a pigment, such as titanium dioxide. If used, the pigment is present in the coating composition in an amount of no more than 70% by weight, more preferably no more than 50% by weight, and even more preferably no more than 40% by weight, based on the total weight of solids in the coating composition.

[0103] Surfactants may optionally be added to the coating composition (e.g., after an emulsified latex polymer has been formed) to facilitate wetting and flow 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, the surfactant is preferably present in an amount of at least 0.01% by weight, more preferably at least 0.1% by weight, based on the resin solids. If used, the surfactant is preferably present in an amount of no more than 10% by weight, more preferably no more than 5% by weight, based on the resin solids. However, the use of surfactants is preferably avoided, as they may contribute to water sensitivity, flavor alteration, or flavor stripping.

[0104] As previously stated, the disclosed coating composition preferably contains water and may also contain one or more optional organic solvents. Preferably, based on the weight of the coating composition, the coating composition contains at least about 70% by weight, more preferably at least about 65% by weight, and even more preferably at least about 60% by weight of water. In some embodiments, based on the weight of the coating composition, the coating composition contains less than about 60% by weight, more preferably less than about 50% by weight, and even more preferably less than about 40% by weight of water.

[0105] In some embodiments, such as certain coil coating applications, the coating composition preferably comprises one or more organic solvents. Exemplary solvents include alcohols such as methanol, ethanol, propanol (e.g., isopropanol), butanol (e.g., n-butanol), and pentanol (e.g., pentanol); glycol ethers such as 2-butoxyethanol, ethylene glycol monomethyl ether (i.e., butyl CELLOSOLVE from Dow Chemical Co.). TM ) and diethylene glycol monomethyl ether (i.e., butylCARBITOL of Dow Chemical Co.) TM ); ketones such as acetone and methyl ethyl ketone (MEK); N,N-dimethylformamide; carbonates such as ethylene carbonate and propylene carbonate; diethylene glycol dimethyl ether; N-methylpyrrolidone (NMP); acetates such as ethyl acetate, ethylene diacetate, propylene glycol monoacetate, propylene glycol diacetate, and ethylene glycol ether acetate; alkyl ethers of ethylene; isoflurane; aromatic solvents such as toluene and xylene; and combinations thereof. Based on the weight of the coating composition, exemplary solvent amounts may be, for example, at least about 10% by weight, more preferably at least about 20% by weight, and even more preferably at least about 25% by weight. In some embodiments, based on the weight of the coating composition, the coating composition contains less than about 70% by weight, more preferably less than about 60% by weight, and even more preferably less than about 45% by weight of organic solvent. While not wishing to be bound by any theory, including appropriate amounts of organic solvent is advantageous for certain coil coating applications to modify the flowability and leveling properties of the coating composition, control foaming, and maximize the linear speed of the coil coater. In addition, the vapor generated by the evaporation of organic solvents during coating curing can be used to fuel the curing oven.

[0106] In some embodiments, such as for certain spraying applications (e.g., for internal spraying of food or beverage cans, including, for example, aluminum beverage cans), the coating composition may have a total solids content of greater than about 10% by weight, more preferably greater than about 15% by weight, and even more preferably greater than about 20% by weight, based on the total weight of the coating composition. In these embodiments, the coating composition may also have a total solids content of less than about 40% by weight, more preferably less than about 30% by weight, and even more preferably less than about 25% by weight, based on the total weight of the coating composition. In some of these embodiments, the coating composition may have a total solids content of from about 18% to about 22% by weight. A carrier (preferably an aqueous carrier containing at least some organic solvent) may constitute the remainder of the coating composition by weight.

[0107] Embodiments of the disclosed coating composition may, for example, contain at least about 10, at least about 15, or at least about 18% by weight and at most about 30, at most about 25, or at most about 23% by weight of an emulsified latex polymer; at least about 45, at least about 55, or at least about 60% by weight and at most about 85, at most about 80, or at most about 70% by weight of water; and at least about 5, at least about 7, or at least about 10% by weight and at most about 20, at most about 16, or at most about 13% by weight of an organic solvent.

[0108] The coating composition preferably has a viscosity suitable for a given coating application. In some embodiments, based on the viscosity test (Ford viscosity, #2 cup, 25°C) described below, the coating composition may have an average viscosity greater than about 20 seconds, more preferably greater than 25 seconds, and even more preferably greater than about 40 seconds. In some embodiments, when performed according to ASTM D1200-88 using a Ford #2 viscosity cup at 25°C, the coating composition may also have an average viscosity less than about 50 seconds, more preferably less than 40 seconds, and even more preferably less than about 30 seconds.

[0109] The disclosed coating compositions can exist as a layer in a single-layer coating system or as one or more layers in a multi-layer coating system. The coating compositions can be used as primers, intermediate coats, topcoats, or combinations thereof. The coating thickness of a particular layer and the overall coating system will vary depending on the coating material used, the substrate, the coating application method, and the end use of the coated article. Single-layer or multi-layer coating systems comprising one or more layers formed by the disclosed coating compositions can have any suitable total coating thickness, typically using mixed unit coating commonly used in the packaging industry, with a coating weight of approximately 1 to approximately 20 mg / in. 2 (msi), more typically from about 1.5 to about 10 msi. Typically, the coating weight of a rigid metal food or beverage can is from about 1 to about 6 msi. In some embodiments where the coating composition is used as an inner coating on rollers (e.g., rollers used with food or beverage products), the coating weight may be about 20 msi.

[0110] Metal substrates used to form rigid food or beverage cans or portions thereof typically have a thickness of about 125 micrometers to about 635 micrometers. Tin-plated steel, cold-rolled steel, and aluminum are commonly used as metal substrates for food or beverage cans or portions thereof. In embodiments where metal foil substrates are used to form, for example, packaging articles, the thickness of the metal foil substrate can be thinner than described above.

[0111] The disclosed coating composition can be applied to a substrate before or after forming the substrate into an article (e.g., a food or beverage container or a portion thereof). In one embodiment, a method of forming a food or beverage can is provided, comprising: applying the coating composition described herein to a metal substrate (e.g., applying the composition to a metal substrate in the form of a flat roll or sheet), curing the composition, and forming (e.g., by stamping) the substrate into a packaging container or a portion thereof (e.g., a food or beverage can or a portion thereof). For example, this method can be used to form two-piece or three-piece cans or portions thereof, such as riveted beverage can ends (e.g., soda or beer cans), having a cured coating of the disclosed coating composition on their surfaces. In another embodiment, a method of forming a food or beverage can is provided, comprising: providing a packaging container or a portion thereof (e.g., a food or beverage can or a portion thereof), applying the coating composition described herein to the interior, exterior, or interior and exterior or a portion thereof of such packaging container (e.g., by spraying, dipping, etc.), and curing the composition.

[0112] As described above, the disclosed coating compositions are particularly suitable for food and beverage cans (e.g., two-piece cans, three-piece cans, etc.). Two-piece cans are manufactured by connecting the can body (typically a drawn metal body) to the can ends (typically drawn metal ends). The disclosed coatings are suitable for food or beverage contact applications and can be used on the interior of such cans. They are particularly suitable for spraying, for liquid coatings on the interior of two-piece thin-walled stretched beverage cans, and for roll coatings on the ends of beverage cans. The disclosed coating compositions can also be used in other applications. These additional applications include, but are not limited to, wash coatings, sheet coatings, and seam coatings (e.g., food can seam coatings). The coating compositions can also be used in medical packaging applications, including, for example, the surfaces of metered-dose inhalers (“MDIs”), including drug-contact surfaces.

[0113] Spraying involves applying a coating composition to a surface, such as the interior of a pre-formed packaging container. Typical pre-formed packaging containers suitable for spraying include food cans, beer and beverage containers, etc. Spraying preferably uses nozzles capable of uniformly coating the interior of the pre-formed packaging container. The sprayed pre-formed container is then heated to remove residual solvents and harden the coating.

[0114] Coil coating is described as a coating of a continuous roll of metal (e.g., steel or aluminum). Once coated, the coated roll undergoes short thermal, UV, or electromagnetic curing cycles for hardening (e.g., drying and curing). Coil coating provides a coated metal (e.g., steel or aluminum) substrate that can be formed into shaped articles such as two-piece drawn food cans, three-piece food cans, food can ends, thin-walled drawn and ironed cans, beverage can ends, and similar products. Wash coating is commercially described as the external coating of two-piece thin-walled stretch (“D&I”) cans with a thin protective coating. The exterior of these D&I cans is “wash-coated” by passing a pre-formed two-piece D&I can under a curtain of coating composition. The cans are inverted, meaning the open end of the can is in a “downward” position as it passes through the curtain. This curtain of coating composition creates a “waterfall-like” appearance. Once the cans have passed under this curtain of coating composition, the liquid coating is effectively applied to the exterior of each can. Excess coating is removed using an “air knife.” Once the required amount of coating has been applied to the exterior of each can, each can is passed through a heat, UV, or electromagnetic curing oven to harden (e.g., dry and cure) the coating. The dwell time of the coated cans in the curing oven range is typically 1 to 5 minutes. The curing temperature within the oven is typically 150 to 220ºC.

[0115] Sheet coating is described as coating individual sheets of various materials (e.g., steel or aluminum) that have been pre-cut into square or rectangular "sheets". These sheets are typically about 1 square meter in size. Once coated, each sheet is allowed to cure. Once hardened (e.g., dried and cured), the coated sheets are collected and ready 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 ends, thin-walled drawn cans, beverage can ends, and so on.

[0116] Side seam coating is described as a liquid coating sprayed onto the welded areas of a formed three-piece food can. When manufacturing three-piece food cans, a rectangular sheet of coating substrate is formed into a cylinder. Since each side of the rectangle is welded by thermal welding, the formation of the cylinder is permanent. Once welded, each can typically requires a layer of liquid coating that protects the exposed “weld” from subsequent corrosion or other effects from the food contained therein. This liquid coating serves this purpose and is called a “side seam strip.” Typically, side seam strips are applied and cured quickly using the residual heat generated during the welding operation, except for small amounts of heat, ultraviolet light, or induction cookers.

[0117] For any of the coating techniques described above, the curing process can be carried out in discrete or combined steps. For example, the substrate can be dried at ambient temperature to leave the coating composition in a largely uncrosslinked state. The coated substrate can then be heated to fully cure the composition. In some cases, the disclosed coating composition can be dried and cured in a single step. Curing conditions will vary depending on the coating method and the intended end use. The curing process can be carried out at any suitable temperature, including, for example, an oven temperature range of about 100°C to about 300°C, and more typically about 177°C to about 250°C. If the substrate to be coated is a metal coil, then curing of the coated coating composition can be carried out, for example, by heating the coated metal substrate to a peak metal temperature (“PMT”) preferably greater than about 177°C for an appropriate period of time. More preferably, the coated metal coil is heated to a PMT of at least about 218°C for an appropriate period of time (e.g., about 5 to 900 seconds).

[0118] Other commercial coating and curing methods were also envisioned, such as electrocoating, extrusion coating, lamination, powder coating, etc.

[0119] Preferred coating compositions exhibit one or more of the properties described in the Examples section. More preferred coating compositions exhibit one or more of the following properties: metal exposure value less than 1 mA; metal exposure value after drop damage less than 1.5 mA; global extraction result less than 50 ppm; less than about 50%, preferably less than about 30%, more preferably less than about 10% aldehyde loss when evaluating flavor peeling (more preferably, for aluminum cans containing carbonated cola, the currently used coating surface exhibits less than about 50%, less than about 30%, or less than about 10% aldehyde loss); adhesion rating of 10; whitening rating of at least 7; slight or no cracking in reverse impact test; no cracking in dome impact test (rating 10); feathering less than 0.2 inches; COF range of 0.055 to 0.3; initial end continuity less than 10 mA (more preferably less than 5, 2, or 1 mA); continuity less than 20 mA after pasteurization or boiling.

[0120] To further illustrate certain aspects of the invention, the invention also provides the following non-limiting embodiments: Implementation Method 1. An article comprising: One or more of the body portion or end portion of a food or beverage can comprising a metal substrate; and A coating composition disposed thereon, wherein the coating composition comprises an emulsified latex polymer, the emulsified latex polymer comprising a reaction product of a component containing an olefinically unsaturated monomer component polymerized in the presence of an aqueous dispersion of an emulsified polymer having a number-average molecular weight (Mn) of at least about 8,500, and the cured film of the coating composition having a glass transition temperature (Tg) of at least about 40°C. The coating composition is substantially free of bisphenol A, bisphenol F and bisphenol S, including each of their epoxides.

[0121] Implementation Method 2. A method comprising: Provided is a coating composition comprising an emulsified latex polymer, the emulsified latex polymer comprising a reaction product of a component containing an olefinically unsaturated monomer component polymerized in the presence of an aqueous dispersion of the emulsified polymer having a number-average molecular weight (Mn) of at least about 8,500, and the cured film of the coating composition having a glass transition temperature (Tg) of at least about 40°C, and wherein the coating composition is substantially free of bisphenol A, bisphenol F, and bisphenol S, including each of their epoxides; and The coating composition is applied to the metal substrate before or after it is formed into a food or beverage can or a portion thereof.

[0122] Embodiment 3. A coating composition comprising: Emulsified latex polymer, said emulsified latex polymer comprising a reaction product of polymerizing a component containing an olefinically unsaturated monomer component in the presence of an aqueous dispersion of an emulsified polymer having a number-average molecular weight (Mn) of at least about 8,500. The cured film of the coating composition has a glass transition temperature (Tg) of at least about 40°C, and The coating composition is substantially free of bisphenol A, bisphenol F and bisphenol S, including each of their epoxides.

[0123] Embodiment 4. An article, method, or coating composition as described in any of the preceding embodiments, wherein the emulsified polymer is solution polymerized in an organic solvent, and preferably, at least a portion of the organic solvent is removed from the aqueous dispersion after polymer formation.

[0124] Embodiment 5. An article, method, or coating composition as described in any of the preceding embodiments, wherein the coating composition comprises a cured coating composition.

[0125] Embodiment 6. An article, method, or coating composition as described in any of the preceding embodiments, wherein the olefinic unsaturated monomer component comprises a monomer mixture, the monomer mixture comprising at least one monomer containing an ethylene oxide functional group.

[0126] Embodiment 7. An article, method, or coating composition as described in Embodiment 6, wherein the monomer mixture comprises at least one α,β-olefinic unsaturated monomer containing an ethylene oxide functional group, in an amount of 0.1% to 30% by weight based on the weight of the monomer mixture.

[0127] Embodiment 8. An article, method, or coating composition as described in any of the preceding embodiments, wherein the emulsified polymer is a polymer salt comprising anionic salt groups, cationic salt groups, or combinations thereof.

[0128] Embodiment 9. An article, method, or coating composition as described in any of the preceding embodiments, wherein the emulsifying polymer comprises acrylic polymers, polyurethane polymers, polyester resins, alkyd resins, polyolefins, or combinations thereof.

[0129] Embodiment 10. An article, method, or coating composition as described in any of the preceding embodiments, wherein the emulsifying polymer comprises an acid-functional or anhydride-functional acrylic polymer or a salt thereof.

[0130] Embodiment 11. An article, method, or coating composition as described in any of the preceding embodiments, wherein the emulsifying polymer comprises an acid-functionalized or anhydride-functionalized polymer and a salt of an amine.

[0131] Embodiment 12. An article, method, or coating composition as described in any of the preceding embodiments, wherein the emulsifying polymer comprises a salt of an acid-functional or anhydride-functional acrylic polymer, a salt of an acid-functional or anhydride-functional polyurethane polymer, a salt of an acid-functional or anhydride-functional polyester polymer, a salt of an acid-functional or anhydride-functional alkyd polymer, a salt of an acid-functional or anhydride-functional polyolefin polymer, or a combination thereof.

[0132] Embodiment 13. An article, method, or coating composition as described in any of the preceding embodiments, wherein the emulsifying polymer comprises a salt of an amine and acid- or anhydride-functionalized acrylic polymer, a salt of an amine and acid- or anhydride-functionalized polyurethane polymer, a salt of an amine and acid- or anhydride-functionalized polyester polymer, a salt of an amine and acid- or anhydride-functionalized alkyd polymer, a salt of an amine and acid- or anhydride-functionalized polyolefin polymer, or a combination thereof.

[0133] Embodiment 14. An article, method, or coating composition as described in any of the preceding embodiments, wherein the number-average molecular weight of the emulsified polymer is 8,500 to 50,000.

[0134] Embodiment 15. An article, method, or coating composition as described in any of the preceding embodiments, wherein the number average molecular weight of the emulsified polymer is 10,000 to 20,000.

[0135] Embodiment 16. An article, method, or coating composition as described in any of the preceding embodiments, wherein, based on the total weight of the olefinically unsaturated monomer component and the emulsified polymer, the olefinically unsaturated component accounts for about 40 to about 80% by weight of the emulsified latex polymer, and the emulsified polymer accounts for about 20 to about 60% by weight of the emulsified latex polymer, and wherein the acid value of the emulsified polymer is about 40 to about 400 mg KOH per gram of emulsified polymer.

[0136] Embodiment 17. An article, method, or coating composition as described in any of the preceding embodiments, wherein, based on the total weight of the olefinically unsaturated monomer component and the emulsified polymer, the olefinically unsaturated component accounts for about 50 to about 70% by weight of the emulsified latex polymer, and the emulsified polymer accounts for about 30 to about 50% by weight of the emulsified latex polymer, and wherein the acid value of the emulsified polymer is about 100 to about 300 mg KOH per gram of emulsified polymer.

[0137] Embodiment 18. An article, method, or coating composition as described in any of the preceding embodiments, wherein the olefinic unsaturated monomer component is polymerized in the presence of the aqueous dispersion using a water-soluble free radical initiator at a temperature of 0°C to 100°C.

[0138] Embodiment 19. An article, method or coating composition as described in any of the preceding embodiments, wherein the cured film of the coating composition has a Tg of at least about 50°C.

[0139] Embodiment 20. An article, method, or coating composition as described in any of the preceding embodiments, wherein the coating composition is substantially free of any structural units derived from bisphenol.

[0140] Embodiment 21. An article, method, or coating composition as described in any of the preceding embodiments, wherein the coating composition is substantially free of halogenated monomers.

[0141] Implementation Method 22. An article, method, or coating composition as described in any of the preceding embodiments, wherein the coating composition exhibits less than 50% aldehyde loss when flavor peeling is evaluated.

[0142] Implementation Method 23. An article, method, or coating composition as described in any of the preceding embodiments, wherein the coating composition exhibits less than 10% aldehyde loss when flavor peeling is evaluated.

[0143] Embodiment 24. An article, method, or coating composition as described in any of the preceding embodiments, wherein the coating composition is present on the food contact surface of the metal substrate.

[0144] Embodiment 25. An article, method, or coating composition as described in any of the preceding embodiments, wherein the coating composition is suitable for forming an internal spray coating on a two-piece thin-walled stretched aluminum beverage can.

[0145] Embodiment 26. An article, method, or coating composition as described in Embodiment 25, wherein the metal substrate is a two-piece thin-walled stretched aluminum can having a coating on its inner surface at a concentration of about 0.16 to about 3.1 mg / cm². 2 (1 to 20 mg / in) 2 The coating weight is sprayed and cured as a continuous coating.

[0146] Embodiment 27. The article, method, or coating composition as described in Embodiment 25, wherein the coating composition: a) Contains 10-40% by weight of emulsified latex polymer; b) Using Ford viscosity cup #2, the viscosity is approximately 20 to approximately 50 seconds at 25°C; c) Based on the total weight of the olefinically unsaturated monomer component and the emulsified polymer, the olefinically unsaturated component accounts for about 40 to about 80% by weight of the emulsified latex polymer, and the emulsified polymer accounts for about 20 to about 60% by weight of the emulsified latex polymer. d) The acid value of the emulsified polymer is about 40 to about 400 mg KOH per gram of emulsified polymer.

[0147] Example 28. An article, method, or coating composition as described in any of the preceding examples, wherein when sprayed onto the interior of a 355ml aluminum beverage can at a coating weight of 100 to 130 mg / can, the coating composition provides a metal exposure value of less than 3.5 mA after a drop damage test.

[0148] Embodiment 29. The article of any of the preceding embodiments, wherein the food or beverage can contains a food or beverage product.

[0149] Embodiment 30. Use of the coating composition as described in any one of Embodiments 3 to 28 for improving the combination of resistance to flavor peeling, adhesion and flexibility of the coating.

[0150] Example The following examples are provided to aid in understanding the invention, but these examples should not be construed as limiting the scope of the invention. Unless otherwise stated, all parts and percentages are by weight.

[0151] Curing conditions For the internal spray coating thickness of the beverage as described below, the curing conditions include maintaining the temperature measured at the dome at 188 to 199°C for 30 seconds.

[0152] For the baking of beverage end rolls with the coating thickness described below, the curing conditions include using a temperature sufficient to provide the peak metal temperature for a specified time (e.g., 10 seconds at 204°C means, for example, 10 seconds in an oven and reaching the peak metal temperature of 204°C).

[0153] The referenced structure is evaluated using the following tests.

[0154] Initial metal exposure This test method determines the amount of uncoated metal on the inner surface of a can. This determination is performed using a conductive solution (1% NaCl in deionized water). The can is coated with 100 to 130 mg / can of this room-temperature conductive solution, and an electrical probe is placed in contact with the outside of the can (uncoated, conductive). A second probe is immersed in the salt solution in the middle of the can's interior. If any uncoated metal is present inside the can, a current is passed between the two probes and recorded as a value on an LED display. The LED displays the transmitted current in milliamperes (mA). The current passed is proportional to the amount of metal not effectively covered by the coating. The goal is to achieve 100% coating coverage inside the can, which would result in an LED reading of 0.0 mA. Preferred coatings result in metal exposure values ​​of less than 3 mA, more preferably less than 2 mA, and even more preferably less than 1 mA. Commercially acceptable metal exposure values ​​are typically less than 1.0 mA on average.

[0155] Metal exposure after drop damage Drop damage resistance measures the ability of a coated container to resist cracking under simulated can drop conditions. As previously described in the initial metal exposure section, the presence of cracks is measured by the current passing through the electrolyte. An electrolyte solution is filled into the coated container, and the initial metal exposure current is recorded. The can is then filled with water and dropped through a tube from a height of 61 cm onto a 33° inclined plane, creating an indentation in the chime area. The can is then rotated 180 degrees, and the process is repeated. The water is then removed from the can, and the metal exposure current is measured again as described above. No change in current (mA) is observed if there is no damage. Typically, an average of 6 or 12 container samples are recorded. The metal exposure current results before and after the drop are reported. The lower the mA value, the better the coating's resistance to drop damage. Preferred coatings provide a metal exposure value of less than 3.5 mA after drop damage, more preferably less than 2.5 mA, and even more preferably less than 1.5 mA.

[0156] Solvent resistance The degree of “curing” or crosslinking of the coating is measured as its resistance to solvents such as methyl ethyl ketone (MEK, available from Exxon, Newark, NJ) or isopropanol (IPA). The test is performed as described in ASTM D 5402-93. The number of bi-friction cycles (i.e., one round trip) is reported.

[0157] Whole extraction Whole-volume extraction tests are designed to estimate the total amount of movable material that may potentially migrate from the coating into food packaged in the coated container. Typically, the coated substrate is subjected to a variety of conditions with water or solvent blends to simulate a given end use. Acceptable extraction conditions and media can be found in paragraphs (d) and (e) of 21 CFR 175.300. The permissible whole-volume extraction limit specified by FDA regulations is 50 parts per million (ppm).

[0158] The extraction procedure is described in paragraph (e)(4)(xv) of 21 CFR 175.300, with the following modifications to ensure worst-case performance: 1) the alcohol content is increased to 10% by weight and 2) the filled container is equilibrated for 10 days at 38°C (100°F). These conditions comply with the FDA publication "Industry Guidelines" for preparing food contact notifications. A 10% by weight aqueous solution of ethanol is filled into the coated beverage can and subjected to pasteurization conditions (66°C, 150°F) for 2 hours, followed by equilibration for 10 days at 38°C (100°F). The amount of extract is determined as described in paragraph (e)(5) of 21 CFR 175.300, and the ppm value is calculated based on the surface area of ​​the can (without end), which is 44 square inches and has a volume of 355 ml. Preferred coatings yield a total extraction result of less than 50 ppm, more preferably less than 10 ppm, and even more preferably less than 1 ppm. Most preferably, the total extraction result is undetectable.

[0159] Flavor peeling The following preparation is used to prepare solutions of three different aldehydes at pH 3, each containing 250 parts per billion (ppb). First, an intermediate aldehyde stock solution (approximately 10,000 ppm) is prepared by diluting known amounts of the aldehydes octanal, nonanal, and decanal in pure (190 proof) ethanol. Next, water acidified to pH 3 is prepared as follows: approximately 600 μl of 75% phosphoric acid is added to 4 liters of deionized (DI) water, ensuring the pH is approximately pH 3 using pH paper. The pH is adjusted to a final pH of approximately 2.5 to 3 using more phosphoric acid or DI water. The known amount of the starting aldehyde solution is added to the acidified water, diluted approximately 40,000 times, to obtain a final concentration of approximately 250 ppb for each of the three aldehydes, in a final volume of 4 L.

[0160] The cured coating was applied to a 16.8cm × 16.8cm square metal plate and cured in an oven at 204°C for 75 seconds to provide a dry film with a coating weight of approximately 1.9 msi. These plates were then inserted into FDA-designated single-sided extraction units, which are based on… Journal of the Association of the Official Analytical Chemists The design and fabrication were slightly modified from those in 47(2):387 (1964). The unit measures 22.9cm × 22.9cm × 1.3cm (9 inches × 9 inches × 0.5 inches) and was fabricated in TEFLON. TM The (DuPont) PTFE spacer has a 15.2cm x 15.2cm (6 inches x 6 inches) opening in the center. This allows for the placement of a 232cm test plate. 2 (36 square inches) or 465 cm 2(72 square inches) exposed to aldehyde solution. This unit contains 300 mL of aldehyde-simulated solvent. When 232 cm 2 (36in) 2 ) or 465cm 2 (72in) 2 When the test specimen was exposed to the solution, the solvent-to-surface area ratio was 1.29 mL / cm². 2 Or 0.65 mL / cm 2 The extraction unit was filled with a solution containing 250 ppb of each aldehyde and kept at 40°C for 3 days.

[0161] Flavor stripping performance was evaluated using gas chromatography (GC) and headspace solid-phase microextraction (HS-SPME). The GC inlet was fitted with a 0.75 mm inner diameter SUPELCO™ (Sigma-Aldrich) liner to minimize peak broadening. For headspace analysis, injection was performed in splitless mode at 250°C for 0.8 min, followed by splitting (1:55) after 0.8 min. The oven temperature was set to 40°C and isothermated for 5 min, then ramped to 220°C at 10°C / min and held at the final temperature for 1 min. Helium was used as the carrier gas at a flow rate of 1.5 mL / min. The injector and detector temperatures were 250°C and 270°C, respectively. The amount of each aldehyde lost from the test solution during storage was measured and reported as a percentage of the original concentration. Flavor stripping was reported as a percentage of aldehyde loss relative to current industry-standard coating formulations.

[0162] Adhesion Adhesion tests were performed to assess whether the coating adhered to the coated substrate. According to ASTM D 3359 - Test Method B, a SCOTCH product purchased from 3M was used. TM 610 tape undergoes adhesion testing. Adhesion is typically rated on a scale of 0-10, where a rating of "10" indicates no adhesion failure, a rating of "9" indicates 90% adhesion retention, a rating of "8" indicates 80% adhesion retention, and so on. For commercially viable coatings, an adhesion rating of 10 is usually required.

[0163] Anti-whitening properties Anti-whitening measures a coating's ability to resist erosion by various solutions. Whitening is typically measured by the amount of water absorbed into the coated film. When a film absorbs water, it usually becomes cloudy or appears white. Whitening is visually measured using a scale of 0-10, where a scale "10" indicates no whitening and a scale "0" indicates the film is completely white. For commercially viable coatings, a whitening rating of at least 7 is generally required, with 9 or higher being optimal.

[0164] Resistance to processing or cooking This is a measure of coating integrity after the coated substrate has been exposed to heat and pressure using a liquid such as water. Not all food and beverage coatings necessarily require retortability, but it is ideal for certain product types packaged under distillation conditions. The process is similar to sterilization or pasteurization testing. This is achieved by subjecting the substrate to heating at 105-130°C and 0.7-1.05 kg / cm². 2 The test was completed under pressure for 15 to 90 minutes. The coated substrate was immersed in DI water and subjected to heating at 121°C (250°F) and 1.05 kg / cm² pressure. 2 Apply pressure for 90 minutes. Then test the adhesion and whitening of the coated substrate as described above. In food or beverage applications requiring cooking performance, a coating that is commercially viable typically requires an adhesion rating of 10 and a whitening rating of at least 7.

[0165] Neck constriction test This test measures the membrane's flexibility and adhesion after a commercial necking process. Necking is performed to facilitate coating at the container ends that allow for sealing. The test involves applying a coating to the container at the recommended membrane thickness and subjecting the container to the recommended baking. Prior to the necking process, when evaluated using the electrolyte solution described above, the sample cans typically have a metal exposure value of <1.0 mA (average for 12 cans). After the necking process, the metal exposure of the cans should not increase compared to the average of 12 unnecked cans. An elevated mA value indicates membrane rupture, which constitutes membrane failure.

[0166] Reforming / Remodeling Experiment This test measures the flexibility and adhesion of the membrane after a commercial reforming process. Reforming or modification is performed to strengthen the tank. The test involves applying a coating to the container at the recommended membrane thickness and subjecting the container to the recommended baking. Before the reforming process, when evaluated using the electrolyte solution as described above, the sample tanks typically have a metal exposure value of <1.0 mA (average of 12 tanks). After the reforming process, the metal exposure of the tank should not increase compared to the average of 12 unreformed tanks. An elevated mA value indicates membrane rupture, which constitutes membrane failure.

[0167] Boiling water test This test simulates the water resistance of the membrane. The coating is applied to a suitable substrate at the target film thickness and baked in cycles. DI water is heated to boiling (100°C) in a container. The test can or plate is placed in the boiling water. After 10 minutes, the test can or plate is removed, rinsed with water, and dried. Cross lines are then drawn on the coating. A 25 mm (1 inch) long piece of transparent 610 tape is applied to the cross line area and immediately removed with a rapid, perpendicular pull motion. The adhesion and whitening of the sample are then evaluated as previously described. The beverage interior coating preferably has an adhesion rating of 10 and a whitening rating of at least 7, preferably at least 9, and most preferably 10.

[0168] Boiling acetic acid test This test simulates the membrane's tolerance when exposed to an acidic medium and is conducted and evaluated as in the boiling water test, but using a mixture of 3 wt% acetic acid and 97 wt% water heated to 100°C for 30 minutes. The beverage interior coating preferably has an adhesion rating of 10 and a whitening rating of at least 7, and most preferably at least 9.

[0169] Citric acid test This test simulates the membrane's resistance to exposure to a 2% citric acid solution at 121°C for 30 minutes. The coating is applied to a suitable substrate at the target film thickness and then cycled through a baking process. The test container or plate is placed in a cooking vessel containing a 2% citric acid solution. The solution is heated to 121°C in the cooking vessel. After 30 minutes, the test container or plate is removed, rinsed with water, and dried. Cross lines are then drawn on the coating, and adhesion and whitening are evaluated as in a boiling water test. The beverage interior coating preferably has an adhesion rating of 10 and a whitening rating of at least 7, and most preferably at least 9.

[0170] Taste - Water Test This test simulates the possibility of odors being imparted by the coating. A trained flavor panel is required for optimal results in this test. Sample canisters or plates are subjected to recommended film thickness and baking conditions. The canisters are rinsed, filled with DI water, covered with aluminum foil, and then immersed in a 63°C water bath. Once the water in the canisters reaches 63°C, they are maintained at that temperature for 30 minutes. After 30 minutes, the canisters are removed and allowed to cool overnight. The water from the canisters is then provided to the flavor panel for testing. A blank consisting only of water is used as a control.

[0171] Glass transition temperature Samples for DSC testing can be prepared by first coating a liquid resin composition onto an aluminum sheet. The sheet is then subjected to Fisher ISOTEMP... TMThe sample was baked in an electric oven at 149°C (300°F) for 20 minutes to remove volatile materials. After cooling to room temperature, the sample was scraped from the plate, weighed in a standard sample pan, and analyzed using the standard DSC hot-cold-hot method. The sample was equilibrated at -60°C, then heated to 200°C at 20°C / min, cooled to -60°C, and then reheated to 200°C at 20°C / min. The glass transition was calculated from the thermogram of the last thermal cycle. The glass transition was measured at the inflection point of the transition. Multiple glass transition temperatures were recorded when multiple transitions were observed.

[0172] Example 1, Sample 1 - Preparation of Acid-Functional Acrylic Polymer Emulsifier No. 1 A premix of 2245.54 parts methacrylic acid (GMAA), 1247.411 parts ethyl acrylate (EA), 1496.931 parts styrene, 1513.425 parts butanol, and 167.575 parts deionized water was prepared in a monomer premix container. In another container, 299.339 parts LUPEROX from Arkema were prepared. TM An initiator premix of LUPEROX 26 initiator and 832.275 parts butanol was added. 1778.649 parts butanol and 87.25 parts deionized water were added to a reaction vessel equipped with a stirrer, reflux condenser, thermocouple, heating and cooling devices, and an inert atmosphere. The reaction vessel was heated to 97–102 °C and refluxed under stirring and an inert atmosphere. Once within this temperature range, 46.442 parts LUPEROX 26 initiator were added. Five minutes after the initiator addition, the monomer premix and initiator premix were simultaneously added to the reaction vessel over two and a half hours, maintaining the temperature range of 97–102 °C, refluxed and cooled as needed. After the premix was added, the monomer premix vessel was rinsed with 96.625 parts butanol and the initiator premix vessel with 22.0 parts butanol, and the two rinse solutions were added to the reaction vessel. Immediately after rinsing, 59.33 parts of a second initiator premix of LUPEROX 26 initiator and 24.0 parts of butanol were added to the reaction vessel within 1 hour, while maintaining the temperature range of 97°C to 102°C. At the end of the addition, the premix vessel was rinsed with 22.0 parts of butanol, and the rinse solution was added to the reaction vessel. Thirty minutes after rinsing the initiator premix vessel, 12.889 parts of LUPEROX 26 initiator were added to the reaction vessel and rinsed with 1.0 part of butanol. The components were allowed to react for another 2 hours, then 47.319 parts of deionized water were added, and the reaction vessel was cooled to below 60°C. This process yielded an acrylic emulsified polymer (i.e., an acrylic polymer emulsifier) ​​with a solids content of ~50.0% NV, an acid value of ~300, a Brookfield viscosity of ~25,000 centipoise, a Mn of ~6300, a Mw of 12,500, and a polydispersity index (PDI) of 2.0. The Tg calculated using the Fox equation is 86℃.

[0173] Example 1, Sample 2 - Preparation of Acid-Functional Acrylic Polymer Emulsifier No. 2 A premix of 115.982 parts GMAA, 249.361 parts EA, 214.567 parts styrene, 47.649 parts butanol, and 4.649 parts deionized water was prepared in a monomer premixing vessel. An initiator premix of 12.756 parts LUPEROX 26 initiator and 6.973 parts butanol was prepared in another vessel. 206.71 parts butanol and 10.14 parts deionized water were added to a reaction vessel equipped with a stirrer, reflux condenser, thermocouples, heating and cooling devices, and an inert atmosphere. The reaction vessel was heated to 97–102 °C and refluxed under stirring and an inert atmosphere. Once within this temperature range, 1.979 parts LUPEROX 26 were added. Five minutes after the addition of LUPEROX 26, the monomer premix and initiator premix were simultaneously added to the reaction vessel over two and a half hours, while maintaining the temperature range of 97–102 °C, refluxed, and cooled as needed. After adding the premix, the monomer premix container was rinsed with 10.46 parts butanol, and the initiator premix container was rinsed with 3.487 parts butanol. Both rinse solutions were then added to the reaction vessel. Immediately after rinsing, a second initiator premix of 2.528 parts LUPEROX 26 initiator and 20.919 parts butanol was added to the reaction vessel over 30 minutes, maintaining the temperature range of 97°C to 102°C. At the end of the addition, the premix container was rinsed with 5.346 parts butanol, and the rinse solution was added to the reaction vessel. Thirty minutes after rinsing the initiator premix container, 0.494 parts LUPEROX 26 initiator was added to the reaction vessel and rinsed with 13.946 parts butanol. The components were allowed to react for another 2 hours, then 69.73 parts butanol and 2.324 parts deionized water were added, and the reaction vessel was cooled to below 60°C. The process yields an acrylic emulsion polymer with a solids content of ~58.0% NV, an acid value of ~130, a Brookfield viscosity of ~22,000 centipoise, a Mn of 12,000, a Mw of 29,500, and a PDI of 2.5. The Tg calculated using the Fox equation is 45°C.

[0174] Example 2, Sample 1 (Low Tg) - Preparation of a low Tg control emulsion No. 1 In a reaction vessel equipped with a stirrer, reflux condenser, thermocouples, heating and cooling devices, and an inert atmosphere, 4754.595 parts of deionized water, 143.835 parts of dimethylethanolamine (DMEOA), and 1633.46 parts of acid-functional acrylic polymer emulsifier No. 1 were added and the mixture was heated to 70°C. In another vessel, 898.642 parts of styrene, 1260.619 parts of butyl acrylate, and 175.122 parts of glycidyl methacrylate were premixed and stirred until homogeneous. According to the Fox equation, this monomer premix containing 38.5 wt% styrene, 54.0 wt% butyl acrylate, and 7.5 wt% glycidyl methacrylate will provide a component polymer with an estimated Tg of -5°C. When the temperature of the reaction vessel was 70°C, 23.031 parts of benzoin and 37 parts of deionized water were added. The contents were then heated to 81°C. At 81°C, a 35% hydrogen peroxide solution was added and rinsed into the reaction vessel with a total of 37.031 parts deionized water. After 5 minutes at this temperature, the monomer premix was uniformly added into the reaction vessel over 30 minutes while maintaining a temperature of 80°C to 83°C. Once the monomer premix was added, the premix vessel was rinsed with 826 parts deionized water and then added to the reaction vessel. Ten minutes after adding the rinse solution, 4 parts benzoin and 3.911 parts 35% hydrogen peroxide solution were added and rinsed with a total of 28 parts deionized water. The reaction was allowed to continue for 45 minutes, then 1.304 parts benzoin and 1.304 parts 35% hydrogen peroxide solution were added and rinsed with a total of 28 parts deionized water. The reaction was carried out for two hours. After two hours, the batch was cooled while 12.602 parts TIGONOX from AkzoNobel were added. TM A-W70 tert-butyl hydroperoxide, 1.738 parts of an aqueous solution containing 7% by weight of an iron-sodium-EDTA (ethylenediaminetetraacetic acid) complex in water, and a premixed solution containing 8.691 parts of isoascorbic acid, 9.343 parts of DMEOA, and 74.742 parts of deionized water, were reacted and washed with 14 parts of deionized water. This process was repeated several times. After cooling, the reaction yielded an emulsified latex polymer containing 30.7-32.7% solids, with a #4 Ford viscosity of 15-100 seconds, an acid value of 60-80, a pH of 6.5-7.5, and a particle size of 0.24-0.34 μm. Due to the partially cross-linked nature of the emulsified latex polymer, its molecular weight could not be determined by gel permeation chromatography.

[0175] Example 2, Sample 2 (High Tg) - Preparation of a high Tg control emulsion No. 1 Using the general method employed in Example 2, Sample 1 (low Tg), the high Tg form of the control No. 1 emulsion was prepared by adjusting the monomer premix ratio to 77.2 wt% styrene, 15.3 wt% butyl acrylate, and 7.5 wt% glycidyl methacrylate. According to the Fox equation, the resulting component polymer had an estimated Tg of 60°C. The emulsified latex polymer contained 31.9% solids, had a #4 Ford viscosity of 35 seconds, an acid value of 69, a pH of 6.9, and a particle size of 0.21 micrometers.

[0176] Example 2, Sample 3 (Low Tg) - Preparation of a low Tg control emulsion No. 2 Using the general method employed in Example 2, Sample 1 (low Tg), the low Tg form of the control No. 2 emulsion was prepared by adding 1485.611 parts of acid-functional acrylic polymer emulsifier No. 1 to a reaction vessel and heating to 35°C. At this temperature, 490.409 parts of deionized water and 143.611 parts of DMEOA were added, followed by 4413.677 parts of deionized water, while maintaining the temperature at 35°C. In another vessel, 898.425 parts of styrene, 1260.147 parts of butyl acrylate, and 174.980 parts of glycidyl methacrylate were premixed and stirred until homogeneous. According to the Fox equation, this monomer premix, containing 38.5 wt% styrene, 54.0 wt% butyl acrylate, and 7.5 wt% glycidyl methacrylate, will provide a component polymer with an estimated Tg of -5°C. The monomer premix was then added to the reaction vessel at 35°C. The premix vessel was then rinsed with 99.988 parts of deionized water, and the rinse solution was added to the reaction vessel. The contents of the reaction vessel were mixed for 30 minutes. After this mixing time, 3.946 parts of TRIGNOX TAHP-W85 tert-amyl hydroperoxide from Akzo Nobel were added to the reaction vessel. The reaction mixture was stirred for 5 minutes, and then over 2 hours, 2.892 parts of isoascorbic acid, 249.971 parts of deionized water, 2.892 parts of DMEOA, and 0.257 parts of an aqueous solution of the iron complex were added to the premix. The temperature of the contents of the reaction vessel increased due to the reaction. Cooling was initiated when the temperature reached 65°C and stopped when the temperature dropped to 60°C. When the premix addition was complete, the premix vessel was rinsed with 773.194 parts of deionized water, and the rinse solution was added to the reaction vessel. The reaction mixture was maintained for 1 hour and cooled to below 49°C. This process yields emulsified latex polymers containing 29.8% to 31.8% solids, with a #4 Ford viscosity of 15-100, an acid value of 60-80, a pH of 6.5-7.5, and a particle size of 0.1-0.5 micrometers. Due to the partially cross-linked nature of the emulsified latex polymers, their molecular weight cannot be determined by gel permeation chromatography.

[0177] Example 2, Sample 4 (High Tg) - Preparation of a high Tg control emulsion No. 2 Using the general methods employed in Examples 2 and 3 (low Tg), the high Tg form of the control No. 2 emulsion was prepared by adjusting the monomer premix ratio to 77.2 wt% styrene, 15.3 wt% butyl acrylate, and 7.5 wt% glycidyl methacrylate. According to the Fox equation, the resulting component polymer had an estimated Tg of 60°C. The emulsified latex polymer contained 31.9% solids, had a #4 Ford viscosity of 35 seconds, an acid value of 69, a pH of 6.9, and a particle size of 0.21 micrometers.

[0178] Coating compositions were prepared from control emulsions No. 1 and 2 in low and high Tg forms, respectively, and applied to the inside of metal beverage containers for curing and evaluation. The coating composition components were added in the order shown in Table 1 under stirring. DMEOA was added as needed to obtain the desired final viscosity. Using typical laboratory conditions and a coating weight of 100 to 130 mg / can, the coating composition was sprayed from below into the interior of 355 ml aluminum cans and cured for 30 seconds at 188 to 199 °C (measured at the top of the can) via a gas oven conveyor according to the typical heating schedule used for this coating. Coating and film properties are shown in Table 2 below.

[0179] Table 1 Spray coating composition

[0180] Table 2 Drop tank, necking and remodeling

[0181] The data in Table 2 show that an increase in the film's Tg value will adversely affect the coating's flexibility.

[0182] Example 3 Preparation of test emulsion Using the general method employed in Example 2 and Sample 3 (low Tg), but with a higher molecular weight emulsifying polymer, 201.394 parts of acidic functional acrylic polymer emulsifier No. 2 and 46.65 parts of deionized water were added to the reaction vessel. Next, 13.661 parts of DMEOA were added over 5–10 minutes while the temperature of the reaction mixture was increased. The DMEOA addition vessel was rinsed with 2.632 parts of deionized water, and the rinse solution was added to the reaction vessel. Then, 354.29 parts of deionized water were added over 30–45 minutes while the reaction vessel was heated to 50°C. In another vessel, 119.898 parts of styrene, 39.248 parts of butyl acrylate, and 16.067 parts of glycidyl methacrylate were premixed and stirred until homogeneous. According to the Fox equation, the monomer premix contains 68.4 wt% styrene, 22.4 wt% butyl acrylate, and 9.2 wt% glycidyl methacrylate, which will provide a component polymer with an estimated Tg of 45°C. The monomer premix is ​​added to the reaction vessel over 20–25 minutes. While the premix vessel is empty, it is rinsed with 171.92 parts deionized water, and the rinse solution is added to the reaction vessel. The reaction vessel is stirred for 15 minutes to homogenize the contents. Next, 0.338 parts TRIGNOX TAHP-W85 tert-amyl hydroperoxide is added, followed by rinsing with 2.369 parts deionized water. The reaction mixture is stirred for 5 minutes, and then over 1 hour, the premix consisting of 0.248 parts isoascorbic acid, 21.398 parts deionized water, 0.248 parts DMEOA, and 0.024 parts an aqueous solution of an iron complex is added. The temperature of the reaction vessel is raised to a maximum of 84°C. When the premix was added, the premixing vessel was rinsed with 6.19 parts of deionized water and allowed to react for 60 minutes while the temperature naturally decreased to 55°C. After 60 minutes, 0.038 parts of TRIGNOX TAHP-W85 tert-amyl hydroperoxide were added, followed by rinsing with 0.263 parts of deionized water. Then, a premix of 0.028 parts of isoascorbic acid, 2.378 parts of deionized water, and 0.028 parts of DMEOA was added, followed by rinsing with 1.69 parts of deionized water. The reaction mixture was maintained at 55°C for 60 minutes and then cooled to below 38°C. This process yielded emulsified latex polymers containing 28.2-30.2% solids, with a #4 Ford viscosity of 15”-100”, an acid value of 40-60, a pH of 7.2-8.2, and a particle size of 0.07-0.14 μm. Due to the partially crosslinked nature of the emulsified latex polymers, their molecular weight could not be determined by gel permeation chromatography. This embodiment uses a higher molecular weight emulsified polymer than that used in Example 2, and a monomer premixing addition technique used in Examples 2, 3 and 4.

[0183] Example 4 Internal spray coating composition The coating compositions prepared using the emulsions from Example 2, Sample 1 (low Tg) (i.e., control emulsion No. 1 in low Tg form), and Example 3 were shown in Table 3 below. The compositions were sprayed onto the inside of metal beverage containers, cured, and evaluated as in Example 2. The coating and film properties are shown in Table 4 below.

[0184] Table 3 Spray Coating Compositions

[0185] Table 4 Coating Application and Film Properties

[0186] The data in Table 4 show that improved resistance to flavor peeling and the desired coating and film properties were achieved by using high Tg coating compositions prepared from high molecular weight emulsified polymers.

[0187] The full disclosures of the patents, patent documents, and publications cited herein are incorporated herein by reference in their entirety, as if each were individually introduced. Various modifications and alterations to the invention will be apparent to those skilled in the art without departing from this invention. It should be understood that the invention is not intended to be unduly limited to the illustrative embodiments and examples described herein, which are presented by way of example only, and the scope of the invention is limited only by the claims.

Claims

1. An article comprising: One or more of the main body or end portion of a food or beverage can containing a metal substrate; and A coating composition disposed thereon, wherein the coating composition comprises an emulsified latex polymer, the emulsified latex polymer comprising a reaction product of a component containing an olefinically unsaturated monomer component polymerized in the presence of an aqueous dispersion of an emulsified polymer having a number-average molecular weight (Mn) of at least about 8,500, and the cured film of the coating composition having a glass transition temperature (Tg) of at least about 40°C. The coating composition is substantially free of bisphenol A, bisphenol F and bisphenol S, including each of their epoxides.

2. A method comprising: Provided is a coating composition comprising an emulsified latex polymer, the emulsified latex polymer comprising a reaction product of a component containing an olefinically unsaturated monomer component polymerized in the presence of an aqueous dispersion of the emulsified polymer having a number-average molecular weight (Mn) of at least about 8,500, and the cured film of the coating composition having a glass transition temperature (Tg) of at least about 40°C, and wherein the coating composition is substantially free of bisphenol A, bisphenol F, and bisphenol S, including each of their epoxides; and The coating composition is applied to the metal substrate before or after it is formed into a food or beverage can or a portion thereof.

3. The article of claim 1 or the method of claim 2, wherein the emulsified polymer is solution polymerized in an organic solvent, and at least a portion of the organic solvent is removed from the aqueous dispersion after polymer formation.

4. The article or method of any of the preceding claims, wherein the coating composition comprises a cured coating composition.

5. The article or method of any of the preceding claims, wherein the olefinic unsaturated monomer component comprises a monomer mixture, the monomer mixture comprising at least one monomer containing an ethylene oxide functional group.

6. The article or method of claim 5, wherein the monomer mixture comprises at least one α,β-olefinic unsaturated monomer containing an ethylene oxide functional group, in an amount of 0.1% to 30% by weight based on the weight of the monomer mixture.

7. The article or method of any of the preceding claims, wherein the emulsified polymer is a polymer salt comprising anionic salt groups, cationic salt groups, or combinations thereof.

8. The article or method of any of the preceding claims, wherein the emulsified polymer comprises acrylic polymers, polyurethane polymers, polyester resins, alkyd resins, polyolefins, or combinations thereof.

9. The article or method of any of the preceding claims, wherein the emulsifying polymer comprises an acid-functional or anhydride-functional acrylic polymer or a salt thereof.

10. The article or method of any of the preceding claims, wherein the emulsifying polymer comprises an acid-functionalized or anhydride-functionalized polymer and a salt of an amine.

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