Multi-stage polymer latex, coating composition containing such latex, and article coated therewith

Abstract

To provide improved coating compositions that are made without intentionally using bisphenol A but that exhibit the stringent balance of coating properties to permit the use of such coating compositions on food or beverage containers.SOLUTION: A coating composition includes a resin system including a multi-stage latex. In some embodiments, the multi-stage latex is formed using a process including emulsion-polymerizing two or more stages in the presence of an aqueous dispersion including a water-dispersible polymer. In specific preferable embodiments, the water-dispersible polymer is a polyether polymer.SELECTED DRAWING: None

Description

Background Art

[0001]

[0001] Bisphenol A has been used to prepare polymers having various properties and uses. For example, bisphenol A may react with epichlorohydrin to provide a polymer useful for packaging coatings. There is a desire to reduce or eliminate the use of polymers derived from certain bisphenol A in food or beverage container coatings. Some alternative coating compositions made without bisphenol A have been proposed, but some of the alternative compositions have exhibited inadequate coating properties such as inadequate corrosion resistance, inadequate flexibility, or inadequate robustness on metal substrates.

[0002]

[0002] The balance of coating performance attributes required to make a coating composition suitable for use as a food or beverage can coating is particularly stringent and different from that of other coating end uses. Thus, coatings designed for other end uses are typically not suitable for use as food or beverage can coatings.

[0003]

[0003] For example, a coating for use on a food or beverage container must avoid inappropriately changing the taste of the packaged food or beverage product and must also avoid flaking or chipping into the packaged product. Also, the coating must be resistant to chemically aggressive food or beverage products (which may have a complex chemical profile including salts, acids, sugars, fats, etc.) over a long period of time (e.g., several years). Also, a food or beverage container coating must adhere well to the substrate beneath it and must remain sufficiently flexible after curing, because the metal substrate may be deformed by subsequent processing and by dents (e.g., due to dropping) during transportation, storage, or use, causing the coating to bend. A brittle coating may crack while being bent, exposing the container's metal to the packaged product, which may sometimes cause leakage into the container. Considering that a large number of food and beverage containers are produced, even a low likelihood of coating defects can cause leakage in a significant number of containers.

[0004]

[0004] Thus, it will be appreciated that there is a need in the art for an improved coating composition that is made without the intentional use of bisphenol A and that exhibits a strict balance of coating properties to enable the use of such a coating composition in food or beverage containers.

Summary of the Invention

[0005]

[0005] In one aspect, the present invention provides an aqueous coating composition comprising a multistage polymer latex having two or more emulsion polymerization stages in an aqueous carrier liquid, the latex having (i) a low Tg emulsion polymerization stage having a calculated Tg that is at least 20 °C lower than the calculated Tg of a high glass transition temperature (“Tg”) emulsion polymerization stage, or (ii) When the calculated Tg of the monomer supplied at the start of polymerization is compared with the monomer supplied at the end of polymerization, it has one or both of the gradient Tgs with a difference of at least 20 °C, Spray-coated on the inner surface of a 355 mL (12 US fluid ounces) No. 211 two-piece drawn and ironed aluminum beverage can at a coating weight of 115 milligrams per can and cured at 188 °C to 199 °C (measured at the can dome) for 55 seconds, the cured coating composition is (iii) a global extraction result of less than 50 ppm, and (iv) when the can is filled with 1% NaCl in deionized water and tested according to the initial metal exposure test method disclosed herein, it exhibits an average metal exposure of less than 3 mA.

[0006]

[0006] In another aspect, the present invention provides an article formed on or to be formed on a container or container component for food or beverage, the article comprising a metal substrate having a coating formed from an aqueous coating composition on at least one surface, the aqueous coating comprises a multi-stage polymer latex having two or more emulsion polymerization stages in an aqueous carrier liquid, the latex (i) a low Tg emulsion polymerization stage having a calculated Tg at least 20 °C lower than the calculated Tg of the high Tg emulsion polymerization stage, or (ii) has one or both of the gradient Tgs with a difference of at least 20 °C when the calculated Tg of the monomer supplied at the start of polymerization is compared with the monomer supplied at the end of polymerization, Spray-coated on the inner surface of a 355 mL (12 US fluid ounces) No. 211 two-piece drawn and ironed aluminum beverage can at a coating weight of 115 milligrams per can and cured at 188 °C to 199 °C (measured at the can dome) for 55 seconds, the cured coating composition is (iii) a global extraction result of less than 50 ppm, and (iv) When the can is filled with 1% NaCl in deionized water and tested according to the initial metal exposure test method disclosed herein, it exhibits an average metal exposure of less than 3 mA.

[0007]

[0007] In another aspect, the present invention provides a method for making a coated food or beverage container or container component, the method comprising (a) spray applying an aqueous coating composition comprising a multi-stage polymer latex having two or more emulsion polymerization stages in an aqueous carrier liquid to the inner surface of a metal food or beverage can having a body portion and an end portion, the latex having (i) a low Tg emulsion polymerization stage having a calculated Tg that is at least 20 °C lower than the calculated Tg of the high Tg emulsion polymerization stage, or (ii) a gradient Tg having a difference of at least 20 °C when the calculated Tg of the monomers supplied at the start of polymerization is compared with the monomers supplied at the end of polymerization, the process having one or both of these (b) curing the coating composition to form a hardened coating, the process comprising The hardened coating has (iii) a global extraction result of less than 50 ppm, and (iv) When the can is filled with 1% NaCl in deionized water and tested according to the initial metal exposure test method disclosed herein, it exhibits an average metal exposure of less than 3 mA.

[0008]

[0008] In another aspect, the present invention provides a method for making a coated food or beverage container or container component, the method comprising (a) applying a coating formed from an aqueous coating composition comprising a multi-stage polymer latex having two or more emulsion polymerization stages in an aqueous carrier liquid to at least one metal substrate surface of a food or beverage container or container component, the latex having (i) a low Tg emulsion polymerization stage having a calculated Tg that is at least 20 °C lower than the calculated Tg of the high Tg emulsion polymerization stage, or (ii) a step having one or both of a gradient Tg with a difference of at least 20 °C when the calculated Tg of the monomer supplied at the start of polymerization is compared with the monomer supplied at the end of polymerization; (b) a step of curing the coating composition to form a hardened coating; comprising The cured coating composition (iii) exhibits a global extraction result of less than 50 ppm, (iv) has a dry coating weight of about 0.6 grams per square meter ("gsm") to about 13 gsm.

[0009]

[0009] In another aspect, the present invention provides an aqueous coating composition, the aqueous coating composition comprises a resin system containing a water-dispersible polymer and two or more emulsion polymerization steps of a multi-stage polymer latex in an aqueous carrier liquid, the water-dispersible polymer is incorporated into the multi-stage polymer latex, blended with the multi-stage polymer latex, or both, and the latex (i) a low Tg emulsion polymerization step having a calculated Tg at least 20 °C lower than the calculated Tg of the high Tg emulsion polymerization step, or (ii) has one or both of a gradient Tg with a difference of at least 20 °C when the calculated Tg of the monomer supplied at the start of polymerization is compared with the monomer supplied at the end of polymerization.

[0010]

[0010] In another aspect, the present invention provides an article formed on or to be formed on a food or beverage container or container component, the article comprising a metal substrate having a coating formed from an aqueous coating composition on at least one surface, the aqueous coating comprises a resin system containing a water-dispersible polymer and two or more emulsion polymerization steps of a multi-stage polymer latex in an aqueous carrier liquid, the water-dispersible polymer is incorporated into the multi-stage polymer latex, blended with the multi-stage polymer latex, or both, and the latex (i) A low-Tg emulsion polymerization stage having a calculated Tg that is at least 20 °C lower than the calculated Tg of the high-Tg emulsion polymerization stage, or (ii) A gradient Tg having a difference of at least 20 °C when comparing the calculated Tg of the monomers supplied at the start of polymerization with the monomers supplied at the end of polymerization, and has one or both of them.

[0011]

[0011] In another aspect, the present invention provides a method for producing a latex dispersion useful for coating a container or a container component of a food or beverage, the method comprising: (a) Providing an aqueous dispersion of a water-dispersible polymer; (b) Emulsion polymerizing two or more stages in the presence of the aqueous dispersion to form a multi-stage polymer latex, the latex comprising: (i) A low-Tg emulsion polymerization stage having a calculated Tg that is at least 20 °C lower than the calculated Tg of the high-Tg emulsion polymerization stage, or (ii) A gradient Tg having a difference of at least 20 °C when comparing the calculated Tg of the monomers supplied at the start of polymerization with the monomers supplied at the end of polymerization, and has one or both of them.

[0012]

[0012] In another aspect, the present invention provides a method for producing a coated container or container component of a food or beverage, the method comprising: (a) Spraying an aqueous coating composition comprising a resin system containing a water-dispersible polymer and two or more emulsion polymerization stages of a multi-stage polymer latex in an aqueous carrier liquid onto the inner surface of a metal food can or beverage can having a body portion and an end portion, wherein the water-dispersible polymer is incorporated into the multi-stage polymer latex, blended with the multi-stage polymer latex, or both, and the latex has: (i) A low-Tg emulsion polymerization stage having a calculated Tg that is at least 20 °C lower than the calculated Tg of the high-Tg emulsion polymerization stage, or (ii) A gradient Tg having a difference of at least 20 °C when comparing the calculated Tg of the monomers supplied at the start of polymerization with the monomers supplied at the end of polymerization, and has one or both of them; (b) Curing the coating composition to form a cured coating.

[0013]

[0013] In another aspect, the present invention provides a method for making a coated food or beverage container or container component, the method comprising: (a) Applying to at least one metallic substrate surface of a food or beverage container or container component a coating formed from an aqueous coating composition comprising a resin system including a water-dispersible polymer and two or more emulsion polymerization stages of a multi-stage polymer latex in an aqueous carrier liquid, wherein the water-dispersible polymer is incorporated into the multi-stage polymer latex, blended with the multi-stage polymer latex, or both, and the latex has (i) a low Tg emulsion polymerization stage having a calculated Tg that is at least 20 °C lower than the calculated Tg of the high Tg emulsion polymerization stage, or (ii) a gradient Tg having a difference of at least 20 °C when comparing the calculated Tg of the monomers supplied at the start of polymerization with the monomers supplied at the end of polymerization, or both; (b) Curing the coating composition to form a cured coating.

[0014]

[0014] In another aspect, the present invention provides an aqueous dispersion comprising a multi-stage polymer latex having two or more emulsion polymerization stages and suitable for use in forming a food contact coating on a metal substrate of a food can or a beverage can. The latex has one or both of: (i) a "low" Tg emulsion polymerization stage having a calculated Tg at least 20°C, at least 30°C, at least 35°C, at least 40°C, at least 50°C, at least 60°C, or at least 70°C lower than the calculated Tg of the "high" Tg emulsion polymerization stage; or (ii) a gradient Tg having a difference of at least 20°C when the calculated Tg of the monomers supplied at the start of polymerization is compared with the monomers supplied at the end of polymerization. In some embodiments, the multi-stage polymer latex is present in a resin system comprising a water-dispersible polymer (e.g., an acrylic polymer, a polyether polymer, a polyolefin polymer, a polyester polymer, a polyurethane polymer, or a mixture or copolymer thereof), and the water-dispersible polymer is incorporated into the multi-stage polymer latex, blended with the multi-stage polymer latex, or both.

[0015]

[0015] In some embodiments, the aqueous coating composition described above comprises an aqueous carrier liquid and a resin system comprising a multi-stage polymer latex having two or more emulsion polymerization stages dispersed in the aqueous carrier. The latex has one or both of: (i) a low Tg emulsion polymerization stage having a calculated Tg at least 20°C, at least 30°C, at least 35°C, at least 40°C, at least 50°C, at least 60°C, or at least 70°C lower than the calculated Tg of the high Tg emulsion polymerization stage; or (ii) a gradient Tg having a difference of at least 20°C when the calculated Tg of the monomers supplied at the start of polymerization is compared with the monomers supplied at the end of polymerization. In some embodiments, when the latex has (i) above, more than 50% by weight of the emulsion polymerization stage preferably has a calculated Tg of at least 40°C, at least 50°C, at least 60°C, at least 70°C, or at least 80°C.

[0016] In some embodiments, the aqueous coating composition includes an aqueous carrier liquid and a resin system including a water-dispersible polymer and two or more emulsion polymerization stages of a multi-stage polymer latex. The water-dispersible polymer is preferably incorporated into the multi-stage polymer latex, blended with the multi-stage polymer latex, or both. The latex preferably has one or both of: (i) a low Tg emulsion polymerization stage having a calculated Tg that is at least 20 °C, at least 30 °C, at least 35 °C, at least 40 °C, at least 50 °C, at least 60 °C, or at least 70 °C lower than the calculated Tg of the high Tg emulsion polymerization stage; or (ii) a gradient Tg having a difference of at least 20 °C when the calculated Tg of the monomers supplied at the start of polymerization is compared to the monomers supplied at the end of polymerization. In some embodiments, one or more of the emulsion polymerization stages are prepared using at least one monomer A of formula (I):

[0017] CH2=C(R )-X 1 -C(CH3) n (R t ) 2 (I) (wherein R 1 is hydrogen or an alkyl group, more typically hydrogen or a methyl group, n is 0 or 1, more typically 1, X, when present, is a divalent linking group, more typically an amide, carbonate, ester, ether, urea, or urethane linkage, even more typically an ester linkage in either direction (i.e., -C(O)-O- or -O-C(O)-), t is from 0 to 3, each R 2 , when present, is independently an organic group which may optionally be branched per se, more typically an alkyl group which may optionally contain one or more heteroatoms (e.g., N, O, P, Si, etc.), and two or more R 2 when present, are independently the same or different organic groups which may optionally be branched per se, more typically an alkyl group which may optionally contain one or more heteroatoms (e.g., N, O, P, Si, etc.). (which may form a cyclic group with each other if desired).

[0018]

[0018] In some embodiments, at least one (meth)acrylate of the following formula (II) is used to prepare one or more of the emulsion polymerization steps. CH2=C(R 3 )-CO-OR 4 (II) (wherein R 3 is hydrogen or methyl, and R 4 is preferably an alkyl group, an alicyclic group, an aryl group, a silane group, or a combination thereof containing 1 to 16 carbon atoms).

[0019]

[0019] In some embodiments, the aqueous coating composition described above comprises an aqueous carrier liquid and a resin system comprising a multi-stage polymer latex having two or more emulsion polymerization steps, and the multi-stage latex is formed by emulsion polymerizing an ethylenically unsaturated monomer in the presence of an aqueous dispersion of a water-dispersible polymer. The latex preferably has one or both of (i) a low Tg emulsion polymerization step having a calculated Tg that is at least 20 °C, at least 30 °C, at least 35 °C, at least 40 °C, at least 50 °C, at least 60 °C, or at least 70 °C lower than the calculated Tg of the high Tg emulsion polymerization step, or (ii) a gradient Tg having a difference of at least 20 °C when comparing the calculated Tg of the monomers supplied at the start of polymerization with the monomers supplied at the end of polymerization. The water-dispersible polymer preferably comprises a polyether polymer.

[0020]

[0020] In some embodiments, the above aqueous coating composition comprises an aqueous carrier liquid and a resin system comprising a multistage polymer latex formed by emulsion polymerization of ethylenically unsaturated monomers in the presence of a water-dispersible polymer (such as an acrylic polymer, a polyether polymer, a polyolefin polymer, a polyester polymer, a polyurethane polymer, or a mixture or copolymer thereof) in two or more stages (such as a low Tg stage and a high Tg stage). The ethylenically unsaturated monomers for emulsion polymerization include two or more (such as 2, 3, 4, or 5) of methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate (such as n- butyl acrylate), and butyl methacrylate (such as n-butyl methacrylate), with at least 80% by weight.

[0021]

[0021] In some embodiments, the above coating composition contains less than about 10% by weight, less than about 5% by weight, less than about 1% by weight of a polyether compound or polymer, or does not contain a polyether compound or polymer. In some embodiments, the above coating composition is substantially free of or does not contain each of bisphenol A, bisphenol F, and bisphenol S. In some embodiments, the above coating composition is substantially free of or does not contain styrene, if desired.

[0022]

[0022] In yet another aspect, a substrate (such as a metal substrate) on which one or more of the above coating compositions are located is also disclosed. In some embodiments, the substrate is a metal food or beverage can or container, or a part thereof (such as a threaded closure lid, the end of a can, the end of a beverage can, the side wall body portion and the bottom end portion of a can, etc.) on which the invention of the disclosed coating composition is applied to the outer surface, inner surface, or a combination of both. Certain embodiments of the coating composition of the present invention have been found to be particularly suitable for spray coating on the inner surface of food or beverage cans, including, for example, aluminum beverage cans.

[0023]

[0023] In yet another aspect, the present invention provides a method for coating a food or beverage can. The method preferably comprises applying one or more of the above coating compositions to the surface of a metal substrate (e.g., by spray coating, roll coating, etc.) before or after shaping the metal substrate into a food or beverage can or a portion thereof.

[0024]

[0024] In yet another aspect, the present invention provides a food-contact multi-stage latex dispersion and a method for making a food-contact multi-stage latex dispersion. In a preferred embodiment, the method comprises providing an aqueous dispersion of a water-dispersible polymer (e.g., an acrylic polymer, a polyether polymer, a polyolefin polymer, a polyester polymer, a polyurethane polymer, or a mixture or copolymer thereof), and emulsion polymerizing two or more latex stages in the presence of the aqueous dispersion to form a multi-stage polymer latex, wherein the latex has one or both of: (i) a low Tg emulsion polymerization stage having a calculated Tg that is preferably at least 20 °C, at least 30 °C, at least 35 °C, at least 40 °C, at least 50 °C, at least 60 °C, or at least 70 °C lower than the calculated Tg of the high Tg emulsion polymerization stage; or (ii) a gradient Tg having a difference of at least 20 °C when comparing the calculated Tg of the monomers supplied at the start of polymerization with the monomers supplied at the end of polymerization.

[0025]

[0025] The above "Summary of the Invention" of the present invention is not intended to describe each and every disclosed embodiment or all implementations of the present invention. The following description more specifically illustrates exemplary embodiments. Throughout the specification, guidance is provided through lists of examples in several places, and the examples can be used in various combinations. In any case, the lists described are only useful as representative groups and should not be construed as limiting or exclusive lists.

[0026]

[0026] Details of one or more additional embodiments of the present invention are described in the following description. Other features, objects, and advantages of the present invention will become apparent from the description and embodiments. Selected definitions

[0027] Unless otherwise specified, the following terms have the meanings provided below when used in this specification.

[0027]

[0028] The terms "a," "an," "the," "at least one," and "one or more" are used interchangeably. Thus, for example, a coating composition containing "a" polyether polymer means that the coating composition contains "one or more" polyether polymers.

[0028]

[0029] The terms "acrylate" and "acrylic" are used broadly herein and include, for example, substances prepared from one or more of acrylic acid, methacrylic acid, or any acrylate or methacrylate compound. Thus, for example, a polyether - acrylate copolymer in which the "acrylate" component consists entirely of polymerized (meth)acrylic acid contains an "acrylate" component even if no (meth)acrylate monomer is used.

[0029]

[0030] The term "bisphenol" refers to a polyvalent polyphenol monomer having two phenylene groups each having a hydroxyl group bonded to a ring carbon atom, and in which the rings of the two phenylene groups do not share any common atoms.

[0030]

[0031] The terms "comprises," "comprising," and their variations do not have a limiting meaning where those terms appear in the description and embodiments.

[0031] ​

[0032] The term "dihydric monophenol" refers to a polyhydric monophenol containing only two hydroxyl groups bonded to an aryl ring or a heteroaryl ring.

[0033] The term "diphenol" refers to a polyphenol in which two phenylene groups each have one hydroxyl group.

[0032]

[0034] The term "easy open end" means (i) a weak opening (which functions as a drinking mouth in some beverage can ends), and (ii) a riveted portion to which a pull tab is attached for the purpose of opening the weak opening and reaching the product contained inside the can, and refers to a can end (typically the end of a food can or a beverage can) including the above.

[0033]

[0035] The term "estrogen activity" or "estrogen agonist activity" refers to the ability of a compound to mimic hormonal activity through interaction with an endogenous estrogen receptor, typically an endogenous human estrogen receptor.

[0034]

[0036] The term "flavor scalping" means that due to damage to the coating film, an aroma or other flavor component is absorbed by the packaging (e.g., the inner beverage can coating), or the food or beverage contained in the packaging absorbs an undesirable aroma or flavor component from the packaging, and refers to a loss of quality in the packaged article resulting from either of the above.

[0035]

[0037] The term "food contact surface" refers to the surface of an article that contacts or is suitable for contacting a food or beverage product (e.g., a container for food or beverage).

[0038] The term "incorporated", when used with respect to a water-dispersible polymer incorporated in a latex polymer or particles, means that the water-dispersible polymer is physically entangled with, impregnated in, or covalently bonded to the polymer particles of the latex such that the water-dispersible polymer and the latex cannot be easily separated using techniques such as washing or separation.

[0036]

[0039] Groups that may be the same or different are referred to as being "independently" something. The term "group" includes single atom moieties. Thus, for example, a halogen atom can be a group.

[0037]

[0040] The term "low molecular weight" refers to a substance that is essentially generally monomeric or oligomeric and has a molecular weight of less than about 2,000 or less than about 1,000. In the case of oligomeric materials containing molecules having various molecular weights, the term "low molecular weight" refers to the number average molecular weight.

[0038]

[0041] When used in "(meth)acrylate" and "(meth)acrylic acid", the term "(meth)" is intended to indicate that either a hydrogen or a methyl group may be bonded to the appropriate carbon atom of the monomer. For example, "ethyl (meth)acrylate" includes both ethyl acrylate, ethyl methacrylate, and mixtures thereof.

[0039]

[0042] When used with respect to a latex polymer, the term "multistage" means that the polymer was made using a discontinuous charge of two or more monomers, a varying (e.g., continuously varying) charge of two or more monomers, or a combination of both a discontinuous charge and a varying charge of two or more monomers. The presence of "seed" particles in an initial latex polymer reaction mixture that represents 10 wt% or less of the latex polymer solids in the final latex is considered to provide no stage of a multistage polymer, whether it is as an inorganic particulate seed (e.g., clay or glass particles), a preformed particulate polymer seed, or a particulate seed polymer formed in situ, nor does it provide a basis for calling a one-stage polymer made using such a seed polymer a multistage polymer. The presence of a separate non-latex polymer in a latex composition is considered to provide no stage of a multistage polymer, nor does it provide a basis for calling a one-stage polymer made using such a separate polymer a multistage polymer.

[0040]

[0043] The term "on" when used in the context of a coating applied on a surface or substrate includes both coatings applied directly or indirectly to the surface or substrate. Thus, for example, a coating applied to an undercoat layer covering a substrate constitutes a coating applied on the substrate.

[0041]

[0044] The term "or" when used with respect to a set of items, options, or other possibilities refers to either an inclusive or an exclusive selection of such items, options, or other possibilities.

[0042]

[0045] The term "phenylene" refers to an aryl ring of 6 carbon atoms (such as in a benzene group) that can have any substituent (including, for example, a hydrogen atom, a hydrocarbon group, an oxygen atom, a hydroxyl group, etc.). Thus, for example, the following aryl groups: -C6H4-, -C6H3(CH3)-, and -C6H(CH3)2(OH)- are each a phenylene ring. In addition, for example, each aryl ring of a naphthalene group is a phenylene ring.

[0043]

[0046] The term "polyhydric phenol" (including dihydric phenol) generally refers to any compound having one or more aryl or heteroaryl groups (more typically, one or more phenylene groups) and at least two hydroxyl groups bonded to the same or different aryl or heteroaryl rings. Thus, for example, both hydroquinone and 4,4'-biphenol are considered polyhydric phenols. As used herein, polyhydric phenols typically have 6 carbon atoms in the aryl ring, although it is contemplated that aryl or heteroaryl groups having other sized rings may be used.

[0044]

[0047] The term "polyhydric monophenol" refers to a polyhydric phenol that (i) includes an aryl or heteroaryl group (more typically, a phenylene group) having at least two hydroxyl groups bonded to an aryl or heteroaryl ring and (ii) does not include any other aryl or heteroaryl ring having a hydroxyl group bonded to the ring.

[0045]

[0048] The term "polyhydric polyphenol" (including bisphenol) refers to a polyhydric phenol that includes two or more aryl or heteroaryl groups each having at least one hydroxyl group bonded to an aryl or heteroaryl ring.

[0046]

[0049] The term "polyphenol" refers to a polyvalent substance having two or more phenylene groups, wherein each phenylene group contains a ring composed of six carbon atoms and a hydroxyl group bonded to a carbon atom of the ring, and the rings of the phenylene groups do not share any atoms.

[0047]

[0050] The term "polymer" includes both homopolymers and copolymers (e.g., polymers of two or more different monomers). Similarly, unless otherwise specified, the use of terms representing polymer classes such as "polyether" is intended to include both homopolymers and copolymers (e.g., polyether - acrylate copolymers).

[0048]

[0051] The terms "preferred" and "preferably" refer to embodiments that may provide certain benefits under certain circumstances. However, in the same or other circumstances, other embodiments may also be preferred. Furthermore, the detailed description of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the present invention.

[0049]

[0052] The term "substantially free of", when used with respect to a coating composition that may contain a particular compound, means that the coating composition contains less than 1,000 parts per million (ppm) of the compound described (equivalent to less than 0.1% by weight), whether the compound is mobile in the coating or bound to a component of the coating. The term "essentially free of", when used with respect to a coating composition that may contain a particular compound, means that the coating composition contains less than 100 parts per million (ppm) of the compound described, whether the compound is mobile in the coating or bound to a component of the coating. The term "essentially completely free of", when used with respect to a coating composition that may contain a particular compound, means that the coating composition contains less than 5 parts per million (ppm) of the compound described, whether the compound is mobile in the coating or bound to a component of the coating. The term "completely free of", when used with respect to a coating composition that may contain a particular compound, means that the coating composition contains less than 20 parts per billion (ppb) of the compound described, whether the compound is mobile in the coating or bound to a component of the coating. The terms "free of" (except in the context of the foregoing phrases), "does not contain", "contains no", and similar phrases, when used in this specification, are not intended to exclude the presence of trace amounts of related structures or compounds that may be present but were not intentionally used, e.g., the presence of environmental contaminants. As will be understood by those skilled in the art, the amount of a compound in a component, polymer, formulation, or other constituent can typically be calculated based on the amount of starting materials used and the yields obtained in making such components, polymers, formulations, or other constituents. can be calculated based on the yields obtained in making such components, polymers, formulations, or other constituents.

[0050]

[0053] A detailed description of a numerical range by endpoints includes all numbers included within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). Further, the disclosure of a range includes the disclosure of all sub-ranges included within the broader range (e.g., 1 to 5 discloses 1 to 4, 1.5 to 4.5, and 4 to 5, etc.).

DETAILED DESCRIPTION OF THE INVENTION

[0051]

[0054] The present invention relates to a coating composition comprising a multi-stage polymer latex, which is particularly suitable for use in formulating packaging coatings, especially food or beverage can coatings. The coating composition of the present invention is preferably an aqueous coating composition, which may optionally contain one or more organic solvents. In a preferred embodiment, the multi-stage polymer latex is formulated in combination with a water-dispersible polymer. Typically, the multi-stage polymer latex is formed in the presence of a water-dispersible polymer. Without being bound by theory, it is believed that the water-dispersible polymer may function as a surfactant to support the formation and stability of the multi-stage polymer latex.

[0052]

[0055] Epoxy acrylate copolymers (also referred to as epoxy acrylic copolymers) having an over-polymerized emulsion polymerized acrylic system have been used in food or beverage can coatings. The epoxy polymer portion of such systems has conventionally been a BPA-based system (e.g., a polymer formed by the reaction of bisphenol A and diglycidyl ether of bisphenol A), and the acrylic system has been rich in styrene content. Generally, it has been understood by those skilled in the art that certain end-use critical coating performance attributes of such conventional epoxy acrylic systems (e.g., sufficient flexibility for food or beverage can coating end-uses) have been primarily or even exclusively derived from the epoxy polymer, and that the acrylic content has primarily functioned as an inexpensive filler to enable minimizing the amount of the more expensive epoxy polymer. Since the acrylic content in such conventional systems was considered to contribute little to the coating performance characteristics, it has been understood by those skilled in the art that the amount of the epoxy polymer in such epoxy acrylic systems should generally be more than about 50 wt% of the entire resin system in order to avoid undue deterioration of the coating properties.

[0053]

[0056] The system of the present invention surprisingly enables the amount of the epoxy polymer used to be dramatically reduced compared to such conventional systems, while still achieving a comparable balance of coating properties in some embodiments without using either BPA or styrene. For example, in the "Examples" section below, a latex resin system is exemplified that exhibits a suitable balance of coating properties with an 80 wt% total "acrylic" polymer content and only 20 wt% polyether polymer content (which may also be referred to as an "epoxy" polymer due to the reactants used to make it). Surprisingly, such results have been achieved without using either BPA or styrene, and generally, BPA and styrene are recognized by those skilled in the art as providing beneficial coating properties that are difficult to reproduce with alternative substances.

[0054]

[0057] In the above paragraph, the term "acrylic" in the context of "acrylic polymer content" is intended to be broadly construed to indicate the amount of ethylenically unsaturated monomers present in the polymerization (emulsion polymerization or other polymerization). Such ethylenically unsaturated monomers are typically vinyl monomers, some or all of which are typically either (meth)acrylic acid or (meth)acrylate. The majority of the acrylic polymer content of the coating composition (e.g., >50 wt%, >60 wt%, >70 wt%, >80 wt%, >90 wt%, etc.) and, in some embodiments, all or substantially all of it comprises emulsion polymerized ethylenically unsaturated monomers (e.g., low Tg and high Tg emulsion polymerization stages). In some embodiments (e.g., embodiments where the water-dispersible polymer is polyether-acrylate, polyester-acrylate, etc.), the acrylic polymer content also typically comprises organically solution polymerized ethylenically unsaturated monomers, including one or more (meth)acrylic acid or (meth)acrylate. In preferred embodiments, the acrylic polymer content, based on the combined weight of the water-dispersible polymer and the monomers used to form the emulsion polymerization stage, constitutes more than 50 wt%, preferably at least 60 wt%, even more preferably at least 65 wt%, even more preferably at least 70 wt%, even more preferably at least 75 wt%, and optimally 80 wt% or more of the resin system. In some embodiments, the resin system constitutes 70 to 100 wt% of the total resin solids in the coating composition.

[0055]

[0058] Although not bound by theory, a preferred balance of coating properties presented by a preferred embodiment of the latex resin system of the present invention, including excellent flexibility, can be achieved by the novel multi-stage structure of the latex resin system, even when using very small amounts of polyether polymers or other water-dispersible polymers. In particular, preferably, a multi-stage latex resin system is used that includes two or more different emulsion polymerization stages having sufficiently different Tg values to achieve the desired balance of coating properties. Such a Tg difference can be achieved via a plurality of approaches, some of which are described below.

[0056]

[0059] Typically, multi-stage latexes do not exhibit a single Tg inflection point when measured via differential scanning calorimetry ("DSC"). For example, the DSC curve of a multi-stage latex prepared using discontinuous charge amounts of two or more monomers can exhibit two or more Tg inflection points. Also, the DSC curve of a multi-stage latex prepared using continuously varying charge amounts of two or more monomers can exhibit no Tg inflection points. As a further explanation, the DSC curve of a one-stage latex prepared using a single monomer charge amount or a non-varying charge amount of two monomers can exhibit only a single Tg inflection point. Occasionally, when only one Tg inflection point is observed, it can be difficult to determine whether the latex represents a multi-stage latex. In such cases, sometimes a further (e.g., lower or higher) Tg inflection point can be detected by more detailed examination, or the synthesis scheme used to prepare the latex can be investigated to determine whether a multi-stage latex is expected to be produced. When evaluating such Tg inflection points, it may be necessary to exclude inflection points of non-latex polymers that may also be present in the latex polymer composition.

[0057]

[0060] In some embodiments, the multi - stage latex polymer is formed from components comprising a "low" Tg ethylenically unsaturated monomer component and a "high" Tg ethylenically unsaturated monomer component. The low Tg and high Tg monomer components can be emulsion polymerized at any relative time with respect to each other. In some embodiments, the low Tg or high Tg monomer component is polymerized during a first stage and the other monomer component is emulsion polymerized during a later second stage after the emulsion polymerization of the first stage is complete. In other embodiments, the emulsion polymerization of the second stage can be initiated before the completion of the emulsion polymerization of the first stage. One or more additional ethylenically unsaturated monomer components of any suitable Tg can also optionally be used and they can be emulsion polymerized before, after, between, or during the polymerization of the low Tg or high Tg monomer components. Thus, in some embodiments, the multi - stage latex polymer can comprise three or more emulsion polymerization stages. However, in some embodiments, the emulsion polymerization portion of the multi - stage latex polymer essentially consists of stages (typically two stages) formed from a high Tg ethylenically unsaturated monomer component and a low Tg ethylenically unsaturated monomer component, respectively.

[0058]

[0061] The low Tg emulsion polymerization stage preferably has a calculated Tg that is at least 20 °C lower, at least 30 °C lower, at least 35 °C lower, at least 40 °C lower, at least 50 °C lower, at least 60 °C lower, or at least 70 °C lower than the calculated Tg of the high Tg emulsion polymerization stage. For convenience, in the following discussion, the term "stage" is used in place of "emulsion polymerization stage". Preferably, more than 50 wt% of the stages present in the multi - stage latex have a calculated Tg of at least 40 °C, at least 50 °C, at least 60 °C, at least 70 °C, or at least 80 °C.

[0059]

[0062] Typically, the high Tg stage will have a calculated Tg above 40 °C, above 45 °C, above 50 °C, above 60 °C, above 70 °C, or above 80 °C. The Tg of the high Tg stage is not particularly limited, but will typically be about 105 °C or less. The low Tg stage will typically have a calculated Tg below 40 °C, more typically below 35 °C, even more typically below 30 °C. In some embodiments, the low Tg stage has a calculated Tg below 20 °C, below 10 °C, below 0 °C, or even -10 °C or less. The low Tg stage will typically have a calculated Tg of about -54 °C or more.

[0060]

[0063] In certain preferred embodiments, the high Tg stage has a calculated Tg above 40 °C, the low Tg stage has a calculated Tg below 40 °C, and the Tg value of the high Tg stage is at least 20 °C higher than the Tg value of the low Tg stage. In some embodiments, the high Tg stage has a calculated Tg above 45 °C, the low Tg stage has a calculated Tg below 35 °C, and the Tg value of the high Tg stage is at least 20 °C higher than the Tg value of the low Tg stage. In some embodiments, the high Tg stage has a calculated Tg above 50 °C and the low Tg stage has a calculated Tg below 30 °C. In some embodiments, the high Tg stage has a calculated Tg above 60 °C and the low Tg stage has a calculated Tg below 20 °C. In some embodiments, the high Tg stage has a calculated Tg above 70 °C and the low Tg stage has a calculated Tg below 10 °C.

[0061]

[0064] The Tg of a particular stage, or combination of stages, can be estimated (i.e., calculated) using the Fox equation. For example, in the case of a polymer made from two monomer feedstocks, the theoretical Tg can be calculated using the Fox equation as follows.

[0062] 1 / Tg = W a / T ga + W b / T gb wherein T ga and T gb are the respective glass transition temperatures of the homopolymers made from monomers "a" and "b", and Wa and W b are the weight fractions of polymers "a" and "b", respectively.

[0063] When additional monomer feed materials "c", "d", etc. are used, the additional fraction W c / T gc 、W d / T gd etc. are added to the right side of the above formula. Unless otherwise stated, the "calculated" stage or copolymer Tg referred to in this specification is calculated using the Fox equation. Also, the calculation is based on all the monomers reacted together to form the stage and not just on a portion of such monomers. If the emulsion polymerized ethylenically unsaturated monomer component (e.g., the monomer mixture used to form a high Tg stage or a low Tg stage) contains more than 5 wt% of one or more monomers that do not have a homopolymer Tg (e.g., because the monomers cannot be homopolymerized), instead of relying on the Fox equation, a one-stage reference latex is made using the same overall monomer composition as the emulsion polymerized ethylenically unsaturated monomer component and the actual Tg can be measured via DSC. If the emulsion polymerized ethylenically unsaturated component contains 5 wt% or less of one or more monomers that do not have a homopolymer Tg, one or more such monomers are ignored and the Tg can be determined by the Fox equation.

[0064]

[0065] In some embodiments, a gradient Tg approach may be used to polymerize a multi-stage latex polymer, or a portion of a multi-stage latex polymer. It should be noted that when the gradient Tg approach is used, it may not be possible to measure the individual Tg of a particular latex polymer, and a particular gradient Tg latex polymer may contain a nearly infinite number of Tg stages. For example, starting with a high Tg monomer composition, and then at a particular point in the polymerization, a low Tg stage monomer composition may be started to be fed to the high Tg stage monomer feedstock (and vice versa). The resulting multi-stage latex polymer will have a gradient Tg from high to low (and vice versa). Such a composition can be prepared using a "power feed" process. Also, gradient Tg polymers may be used with a plurality of multi-stage Tg polymers. As an example, a high Tg monomer feedstock (F1) and a low Tg monomer feedstock (F2) can be prepared. Start feeding F1 into the latex reaction vessel and initiate the polymerization of the high Tg "hard stage" monomer composition. Then, during a particular period while F1 is being fed, F2 is fed to F1, but the F2 feed rate is faster than the overall feed rate of F1 + F2 to the reaction vessel. As a result, when the feeding of F2 to F1 is completed, the overall Tg of the F1 + F2 monomer feed blend becomes a lower Tg "soft stage" monomer composition. When the gradient Tg approach is employed, the composite Tg can be calculated by using the Fox equation for all the monomers in the final copolymer and their respective fractions, regardless of which stage may contain such monomers. In some embodiments, the composite Tg is at least 0 °C, at least 20 °C, at least 30 °C, at least 40 °C, or at least 50 °C. If the monomers used to produce such a gradient Tg latex polymer include one or more monomers that do not have a homopolymer Tg (e.g., because the monomers do not homopolymerize), in a non-power feed method, a non-gradient reference latex can be made using the same overall monomer composition and used to measure the Tg.

[0065]

[0066] In the case of a gradient Tg latex polymer, the theoretical Tg of the copolymer produced from the monomer feedstock at the start of polymerization is calculated using the Fox equation, and the Tg difference can be determined by comparing the result with the calculated theoretical Tg for the copolymer produced from the monomer feedstock at the end of polymerization. In the case of a multi-stage polymer produced using such a gradient Tg approach, the Tg difference when the calculated Tg of the monomer supplied at the start of polymerization of the gradient feed monomer is compared with the monomer supplied at the end of polymerization is preferably at least 20 °C, at least 30 °C, at least 35 °C, at least 40 °C, at least 50 °C, at least 60 °C, or at least 70 °C.

[0066]

[0067] Any suitable weight ratio of the low Tg stage to the high Tg stage can be employed. In some embodiments, a minor to substantially majority of the high Tg stage is employed relative to the low Tg stage. Typically, the weight ratio of the low Tg stage to the high Tg stage (i.e., low Tg stage: high Tg stage) is 5:95 to 95:5, more typically 20:80 to 70:30, even more typically 25:75 to 48:52. The above weight ratios are based on the weights of the ethylenically unsaturated components (typically monomers) used to produce each stage. In certain preferred embodiments, the high Tg stage constitutes more than 50 wt% of the total emulsion polymerization stage (i.e., the combined weight of the low Tg stage, high Tg stage, and any optional additional stages that may be present if desired). Without being bound by theory, internal can coatings that will be exposed to sensitive flavor products (e.g., certain colas where specific flavorants are present at very low concentrations) or chemically aggressive food or beverage products (e.g., high acid, high salt, or high fat) can benefit from including a sufficient amount of a suitable high Tg component (e.g., the high Tg stage). However, the challenge in such situations is to maintain the overall balance of coating properties, including, for example, coating flexibility. Again, without being bound by theory, including a sufficient amount of a suitable low Tg component (e.g., the low Tg stage) can result in undue degradation in other desired coating properties, such as flexibility. It is considered that it can help avoid embrittlement.

[0067]

[0068] Any suitable ethylenically unsaturated monomer or combination of monomers can be used to form each stage of the multi - stage latex polymer. Typically, a mixture of two or more monomers is used to form each stage. In a preferred embodiment, the coating composition comprises at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 75 wt%, or at least 80 wt% of two or more emulsion polymerization stages, based on the total resin solids. In some such embodiments, the coating composition comprises such amounts of high - Tg and low - Tg stages, based on the total amount of reactants used to form the high - Tg and low - Tg stages relative to the total resin solids.

[0068]

[0069] As discussed herein, the resin system may also optionally contain polymerized ethylenically unsaturated monomers polymerized using polymerization techniques other than emulsion polymerization (e.g., free - radical organic solution polymerization). In a preferred embodiment, the total amount of polymerized ethylenically unsaturated monomers constitutes more than 50 wt%, preferably more than 60 wt%, even more preferably more than 70 wt%, and optimally 80 wt% or more of the total resin solids of the coating composition.

[0069]

[0070] In some embodiments, the emulsion - polymerized monomers of the high - Tg and low - Tg stages constitute at least 50 wt%, at least 60 wt%, at least 75 wt%, or at least 85 wt% or more of the total amount of polymerized ethylenically unsaturated monomers present in the coating composition.

[0070]

[0071] The coating composition of the present invention is preferably formulated using a resin system comprising a water-dispersible polymer and two or more emulsion polymerization steps. The water-dispersible polymer can be incorporated into a multi-stage polymer latex, blended with a multi-stage polymer latex, or both. In a preferred embodiment herein, the two or more emulsion polymerization steps are formed by emulsion polymerizing monomers used to create such steps in the presence of the water-dispersible polymer.

[0071]

[0072] It is contemplated that one or more ethylenically unsaturated monomer components can be polymerized separately from the water-dispersible polymer. However, in a preferred embodiment, the ethylenically unsaturated monomer components used to create two or more emulsion polymerization stages are polymerized in an aqueous composition containing the dispersed water-dispersible polymer therein. Preferably, the water-dispersible polymer functions as a "polymer surfactant" that helps support the emulsion polymerization in two or more stages containing the ethylenically unsaturated monomer components. As an example, a polymer that is stably dispersible in an aqueous medium only with the aid of a conventional external surfactant is not considered to be water-dispersible. As a further example, a stage of a latex polymer (e.g., a first stage) that is polymerizable only with the aid of such an external surfactant is not considered to be a water-dispersible polymer of the present specification in itself. In some embodiments, the multi-stage latex is emulsion polymerized in the presence of a water-dispersible polymer without using a conventional non-polymer surfactant (e.g., sodium lauryl sulfate (288.4 g / mol), sodium dodecylbenzenesulfonate (348.5 g / mol), sodium dioctyl sulfosuccinate (444.5 g / mol), amine-neutralized dodecylbenzenesulfonic acid (326.5 g / mol without counting the amine molecular weight), e.g., sodium ethoxylated aliphatic alcohol ether sulfate (1.022 g / mol + ethylene oxide weight) or other such conventional surfactants). Thus, in some embodiments, the emulsion polymerized ethylenically unsaturated monomer components, and often the entire resin system, do not contain and are not derived from low molecular weight non-polymer surfactants, e.g., low molecular weight anionic, cationic or non-ionic surfactants. If any such surfactant is used, the total amount thereof is preferably the total of the polymerizable monomers used to make the latex It is 0.5% by weight or less, more preferably 0.25% by weight or less, and most preferably 0.1% by weight or less, excluding the weight of any monomer used to prepare the seed polymer before or at the start of the polymerization of the latex. Such a surfactant is also preferably an amine-functional surfactant or an amine-neutralized surfactant because amines tend to volatilize from the coating under the baking and curing conditions.

[0072]

[0073] In some embodiments, the multi-stage latex is also, or alternatively, emulsion polymerized in the presence of one or more polymerizable surfactants. Examples of suitable polymerizable surfactants include those disclosed in U.S. Patent Application Publication No. 2002 / 0155235, International Publication No. 2016 / 105504 (A1), in addition to those commercially available under the trade name "REASOAP" from ADEKA Corporation (Tokyo, Japan), under the trade names "NOIGEN" and "HITENOL" from Dai-ichi Kogyo Seiyaku Co., Ltd. (Tokyo, Japan), and under the trade name "SIPOMER" from Solvay Rhodia (Brussels, Belgium). In embodiments containing a polymerizable surfactant, the polymerizable surfactant can constitute more than about 0.1% by weight, more than about 1% by weight, more than about 2% by weight, or more than about 3% by weight, based on the total weight of the reactant monomers. The polymerizable surfactant can also constitute less than about 25% by weight, less than about 20% by weight, less than about 15% by weight, or less than about 10% by weight, based on the total weight of the polymerizable monomers used to prepare the latex and excluding the weight of any monomer used to prepare the seed polymer before or at the start of the polymerization of the latex.

[0073]

[0074] In some embodiments, the emulsion polymerized ethylenically unsaturated monomer component is derived primarily using, or using only, a low molecular weight surfactant, such as a low molecular weight anionic or nonionic surfactant. The concentration of such low molecular weight surfactants can vary depending on the type and concentration of the reactant components, including the presence of any other polymerizable or polymeric surfactants. In embodiments containing a low molecular weight surfactant, the low molecular weight surfactant can constitute more than about 0.01 wt%, more than about 0.05 wt%, or more than about 0.1 wt% based on the total weight of the polymerizable monomers used to make the latex and excluding the weight of any monomers used to make the seed polymer prior to or at the start of polymerization of the latex. The low molecular weight surfactant can also constitute less than about 10 wt%, less than about 7 wt%, or less than about 5 wt% based on the total weight of the polymerizable monomers used to make the latex and excluding the weight of any monomers used to make the seed polymer prior to or at the start of polymerization of the latex.

[0074]

[0075] Any suitable amount of water-dispersible polymer can be used. In preferred embodiments, the weight ratio of the water-dispersible polymer to the emulsion polymerization step is less than 50:50, preferably less than 40:60, and even more preferably less than 30:70, less than 25:75, or less than 20:80.

[0075]

[0076] The water-dispersible polymer can be any suitable polymer or combination of polymers, including, for example, one or more acrylic polymers, polyester polymers, polyether polymers, polyolefin polymers, polysilicon polymers, polyurethane polymers, or copolymers thereof (e.g., polyether-acrylate copolymers, polyester-acrylate copolymers, etc.). Typically, the water-dispersible polymer is not formed in an aqueous medium. Instead, it is formed, for example, in a solvent medium or in a solventless process and can then be made dispersible in an aqueous medium, for example, by neutralizing one or more groups on the polymer to convert such groups into water-dispersible groups. The water-dispersible polymer may have any suitable water-dispersible group. As used herein, the term "water-dispersible group" also includes water-soluble groups. Typically, the water-dispersible polymer includes one or more polar groups, more typically one or more salt groups (e.g., anionic salt groups such as an acid or anhydride group neutralized with a base or cationic salt groups such as a base group neutralized with an acid) or salt-forming groups (e.g., a base group or an acid or anhydride group). In a preferred embodiment, the water-dispersible polymer is preferably an acid or anhydride-functional polymer in which a suitable amount of acid or anhydride groups is neutralized with a suitable base, more preferably a fugitive base (e.g., a nitrogen-containing base such as ammonia or an amine).

[0076]

[0077] ​The water-dispersible polymer may have any suitable acid value as long as the polymer can preferably be stably dispersed in water. Preferred acid or anhydride-functional water-dispersible polymers have an acid value of at least about 40, more preferably at least about 55, and even more preferably at least about 70 milligrams (mg) of KOH per gram of polymer. The upper limit range of the suitable acid value is not particularly limited, but typically, the acid value will be less than about 400 mg of KOH per gram of polymer, more typically less than about 300 mg of KOH per gram of polymer, and even more typically less than about 200 mg of KOH per gram of polymer. The acid value referred to herein may be calculated according to the BS EN ISO 3682-1998 standard or may be theoretically determined based on the reactant monomers.

[0077]

[0078] Examples of neutralized acid groups include carboxylic acid groups or anhydride groups that are at least partially neutralized with a suitable base. Unstable bases are preferred here, nitrogen-containing bases are preferred, and amines (e.g., primary, secondary, or tertiary amines) are particularly preferred. In certain embodiments, the amine is a tertiary amine. Preferably, the tertiary amine is selected from trimethylamine, dimethylethanolamine (also known as dimethylaminoethanol), methyldiethanolamine, triethanolamine, ethylmethylethanolamine, dimethylethylamine, dimethylpropylamine, dimethyl 3-hydroxy-1-propylamine, dimethylbenzylamine, dimethyl 2-hydroxy-1-propylamine, diethylmethylamine, dimethyl 1-hydroxy-2-propylamine, triethylamine, tributylamine, N-methylmorpholine, and mixtures thereof. In certain preferred embodiments, the acid or anhydride-functional polymer is at least 25% neutralized with an amine in water.

[0078]

[0079] In some embodiments, the water-dispersible polymer comprises free radical polymerizable ethylenically unsaturated monomer components (e.g., vinyl addition components containing or not containing styrene). In such preferred embodiments, the vinyl addition components are formed from an ethylenically unsaturated monomer mixture comprising one or more acid or anhydride functional monomers (e.g., methacrylic acid) and typically one or more (meth)acrylates, more typically one or more methacrylates, and even more typically one or more alkyl methacrylates (e.g., ethyl methacrylate or butyl methacrylate), optionally in combination with one or more acrylates or alkyl acrylates (e.g., ethyl acrylate), and the monomer mixture is polymerized in an organic solvent in the presence or absence of the water-dispersible polymer.

[0079]

[0080] In some embodiments, the water-dispersible polymer is a polyether-acrylate copolymer (alternatively referred to as a "polyether-acrylic" copolymer), more preferably an aromatic polyether-acrylate that does not contain any structural units derived from styrene, if desired. In such embodiments, the polyether polymer used to form the polyether-acrylate copolymer preferably constitutes at least 30% by weight, more preferably at least 50% by weight, and even more preferably at least 60% by weight or more of the polyether-acrylate copolymer, based on the total weight of the polyether-acrylate copolymer. Typically, the polyether polymer constitutes less than 95% by weight, more typically less than 90% by weight, and even more typically less than 85% by weight of the polyether-acrylate copolymer.

[0080]

[0081] In some embodiments, the water-dispersible polymer may be a phosphate polymer. Examples of such water-dispersible polymers include reaction products of polymers having oxirane groups, preferably aromatic polyether polymers having oxirane groups, with phosphoric acid or related compounds. Specific examples of such water-dispersible polymers are aromatic polyether phosphate esters. Such phosphorylated polymers may further contain one or more other salt groups in order to achieve the desired molecular weight and water-dispersibility characteristics.

[0081]

[0082] The water-dispersible polymer can have any suitable molecular weight. Typically, the number average molecular weight (Mn) of the water-dispersible polymer, when measured using gel permeation chromatography (“GPC”) and polystyrene standards, will be at least 1,500, at least 2,000, at least 3,000, or at least 4,000. Typically, the water-dispersible polymer will have an Mn of less than 50,000, less than 20,000, less than 10,000, or less than 8,000.

[0082]

[0083] In some embodiments, the polyester polymer has a calculated Tg of at least 30 °C, more preferably at least 60 °C, and even more preferably at least 70 °C or at least 80 °C. Typically, the Tg of the polyether polymer is less than 150 °C, more typically less than 130 °C, and even more typically less than 110 °C. In this context, Tg refers to the Tg value of the polyether polymer alone (e.g., before forming the polyether-acrylate copolymer). In embodiments where the water-dispersible polymer is a polyether-acrylate copolymer formed from a polyether polymer or a component containing a polyether polymer, the polyether polymer typically has a number average molecular weight (Mn) of at least 2,000, more typically at least 3,000, and even more typically at least 4,000. The molecular weight of the polyether polymer may be as high as required for the desired application. However, typically, the Mn of the polyether polymer does not exceed about 11,000. In some embodiments, the Mn of the polyether polymer is about 5,000 to about 8,000. In embodiments where the water-dispersible polymer is a polyether-acrylate copolymer, the molecular weight of the entire polymer may be higher than those described above, but the molecular weight of the polyether polymer portion is typically as described above. However, typically, the Mn of such a polyether-acrylate copolymer is less than about 20,000.

[0083]

[0084] Various acid or anhydride functional monomers or salts thereof can be incorporated into the water-dispersible polymer, and these selections depend on the desired final polymer properties. In some embodiments, such monomers are ethylenically unsaturated, more preferably alpha, beta-ethylenically unsaturated. Suitable ethylenically unsaturated acid or anhydride functional monomers for the present invention include monomers or salts thereof having a reactive carbon-carbon double bond and an acidic or anhydride group. Preferred such monomers have 3 to 20 carbons, at least one site of unsaturation, and at least one acid or anhydride group, or a salt thereof.

[0084]

[0085] Suitable acid-functional monomers include ethylenically unsaturated acids (e.g., monoprotic or diprotic) copolymerizable with other monomers, if desired, used to prepare the polymer, anhydrides or monoesters of dibasic acids. Exemplary monobasic acids are those represented by the structure CH2=C(R 5 )-COOH, where R 5 is hydrogen or an alkyl group of 1 to 6 carbon atoms). Suitable dibasic acids include those of the formula R 6 (COOH)C=C(COOH)R 7 and R 6 (R 6 )C=C(COOH)R 8 COOH, where R 6 and R 7 are each independently hydrogen, an alkyl group of 1 to 8 carbon atoms, halogen, a cycloalkyl group of 3 to 7 carbon atoms, or a phenyl group, and R 8 is an alkylene group of 1 to 6 carbon atoms). Half-esters of these acids with alkanols of 1 to 8 carbon atoms are also suitable.

[0085]

[0086] Examples of useful ethylenically unsaturated acid functional monomers include, for example, acids such as acrylic acid, methacrylic acid, alpha-chloroacrylic acid, alpha-cyanoacrylic acid, crotonic acid, alpha-phenylacrylic acid, beta-acryloxypropionic acid, fumaric acid, maleic acid, sorbic acid, alpha-chlorosorbic acid, angelic acid, cinnamic acid, p-chlorocinnamic acid, beta-stearylacrylic acid, citraconic acid, mesaconic acid, glutaconic acid, aconitic acid, tricarboxyethylene, 2-methylmaleic acid, itaconic acid, 2-methylitaconic acid, methyleneglutaric acid, 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. Most preferred unsaturated acid functional monomers include acrylic acid, methacrylic acid, maleic acid, crotonic acid, and mixtures thereof. Examples of suitable ethylenically unsaturated anhydride monomers include compounds derived from the above acids (e.g., as pure anhydrides or as such mixtures). Preferred anhydrides include acrylic anhydride, methacrylic anhydride, and maleic anhydride. Optionally, aqueous salts of the above acids may be used.

[0086]

[0087] The polyether polymer is a preferred water-dispersible polymer, preferably an aromatic polyether or other polyether rich in cyclic groups, which is preferably substantially free of or does not contain each of BPA, BPF, and BPS (including their epoxides), which is particularly preferred. Such polyether polymers typically contain secondary hydroxyl groups, more typically secondary hydroxyl groups present in the main chain -CH2CH(OH)CH2- segments. In a preferred embodiment, the polyether polymer is derived from components comprising (i) an aliphatic, cycloaliphatic, or aromatic diepoxide and (ii) an extender compound capable of building the molecular weight of the diepoxide to form the polymer. The above (i) and (ii) may react with each other in an appropriate ratio, for example, a stoichiometric ratio of about 1.05:1 to about 1:1.05. In some embodiments, the diepoxide and the extender contain similar structural units (e.g., the residue of the diphenol in the diepoxide and the same diphenol in the extender). In other embodiments, the diepoxide and the extender contain dissimilar structural units (e.g., the residue of the diphenol in the diepoxide and a different diphenol in the extender). In some embodiments, the diepoxide, the extender, or both contain two ring oxygen atoms, and at least one substituent or bond (e.g., a bond to an aryl ring) is located ortho to the ring oxygen atom. In other embodiments, the diepoxide, the extender, or both contain two ring oxygen atoms, and the substituent or bond is located at both ortho-ring positions relative to the ring oxygen atom. In a further embodiment, the diepoxide, the extender, or both contain two ring oxygen atoms, and there are no substituents or bonds located ortho to the ring oxygen atom.

[0087]

[0088] Examples of suitable extender compounds include diols, diacids, and compounds having both an acid and a hydroxyl group. Polyhydric phenols (e.g., dihydric phenols) are preferred extenders, and in certain embodiments, polyhydric monophenols (e.g., dihydric monophenols) are preferred. Examples of dihydric monophenol compounds include catechol and substituted catechols (e.g., 3-methylcatechol, 4-methylcatechol, 4-tert-butylcatechol, etc.); hydroquinone and substituted hydroquinones (e.g., methylhydroquinone, 2,5-dimethylhydroquinone, trimethylhydroquinone, tetramethylhydroquinone, ethylhydroquinone, 2,5-diethylhydroquinone, triethylhydroquinone , tetraethylhydroquinone, tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, etc.); resorcinol and substituted resorcinols (e.g., 2-methylresorcinol, 4-methylresorcinol, 2,5-dimethylresorcinol, 4-ethylresorcinol, 4-butylresorcinol, 4,6-di-tert-butylresorcinol, 2,4,6-tri-tert-butylresorcinol, etc.); and variants and mixtures thereof. Examples of the divalent diphenol compounds include 4,4'-methylenebis(2,6-dimethylphenol) (tetramethylbisphenol F), 4,4'-(ethane-1,2-diyl)bis(2,6-dimethylphenol), 4,4'-butylidenebis(2-t-butyl-5-methylphenol), 4,4'-methylenebis(2,6-di-t-butylphenol), 2,2'-methylenebis(4-methyl-6-t-butylphenol, 4,4'-(ethane-1,2-diyl)bis(2,6-dimethylphenol), tetrabromobisphenol A, 2,2'-biphenol, and other crosslinked divalent phenols having an inter-ring bridging linkage located at the ortho position with respect to the phenolic oxygen atom, etc. Other suitable divalent diphenol compounds include those described in U.S. Patent Application Publication No. 2015 / 0197597(A1) and International Publication No. 2018 / 125895(A1). Although not preferred for use in all examples, bisphenol compounds such as bisphenol A, bisphenol F, and bisphenol S can be used in some end uses, in some jurisdictions, or in combination with other extender compounds, for example, to reduce raw material costs.

[0088]

[0089] Examples of suitable diepoxides include substituted diphenols (e.g., ortho-substituted diphenols such as tetramethylbisphenol F, di-tert-butylhydroquinone, 2,2'-biphenol, and other crosslinked diphenols having an inter-ring bridging linkage located ortho to the phenolic oxygen atom), aromatic diols (e.g., benzenedimethanol, vanillyl alcohol, furandimethanol, etc.), aromatic diacids (e.g., isophthalic acid, terephthalic acid, etc.), aliphatic diols, aliphatic diacids, alicyclic diols (e.g., cyclobutanediols such as 2,2,4,4-tetramethyl-1,3-cyclobutanediol and cyclohexanedimethanol), alicyclic diacids (e.g., cyclobutanedicarboxylic acids such as 2,2,4,4-tetramethyl-1,3-cyclobutanedicarboxylic acid), and diepoxides (e.g., their diglycidyl ethers or esters) of these combinations. Other suitable diepoxides include the diglycidyl ether compounds described in U.S. Patent Application Publication No. 2015 / 0197597 (A1) and International Publication Nos. 2017 / 079437 (A1) and 2018 / 125895 (A1). Although not preferred for use in all examples, diepoxides (e.g., diglycidyl ethers) of bisphenol compounds such as bisphenol A, bisphenol F, and bisphenol S can be used in some end uses, in some jurisdictions, or when mixed with other diepoxides, for example, to reduce raw material costs.

[0089]

[0090] In some embodiments, the water-dispersible polymer is a reaction product of components comprising a diphenol and a diepoxide of the diphenol that have reacted (e.g., at an appropriate ratio (e.g., a stoichiometric ratio of about 1.05:1 to about 1:1.05)).

[0090]

[0091] Examples of suitable polyether polymers include those disclosed in U.S. Patent No. 9,409,219 (B2), U.S. Patent Application Publication Nos. 2015 / 0021323 (A1), 2015 / 0151878 (A1), 2015 / 0197597 (A1), 2016 / 0272576 (A1), 2017 / 0051177 (A1), 2017 / 0096521 (A1), and 2017 / 0096579 (A1), as well as International Publication Nos. 2017 / 079437 (A1) and 2018 / 125895 (A1).

[0091]

[0092] In some embodiments (e.g., those prepared without using a water-dispersible polyether polymer), one or more of the disclosed latex dispersions, resin systems, and aqueous coating compositions do not contain a polyether compound or a polyether polymer. In other embodiments, the total amount of such polyether compounds or polymers is less than 10 wt%, less than 5 wt%, or less than 1 wt% based on the total solids in the dispersion, resin system, or coating composition.

[0092]

[0093] Using techniques well known to those skilled in the art, a polymer that is not reducible in water can be made water-dispersible. In some embodiments, the polymer (e.g., an aromatic polyether polymer or other polymer) is covalently bonded to one or more substances (e.g., monomers, oligomers, or polymers) having one or more water-dispersing groups (e.g., salts or salt-forming groups) to make the polymer water-dispersible. Substances containing salts, salt-forming, or water-dispersing groups are, for example, (i) formed in situ before, during, or after the formation of the polymer, or (ii) preformed or nascent polymers reacted with preformed substances It may be an oligomer or polymer provided. The covalent bond may be achieved by any suitable means, including, for example, a carbon-carbon double bond, a reaction involving hydrogen abstraction (e.g., a reaction involving grafting mediated by benzoyl peroxide via hydrogen abstraction such as those described in U.S. Patent No. 4,212,781), or a reaction of complementary reactive functional groups such as those occurring in a condensation reaction. In one embodiment, the linking compound is utilized to covalently bond a polymer and a substance containing a salt or salt-forming group. In certain preferred embodiments, one or more substances having a salt or salt-forming group are vinyl addition components (e.g., vinyl addition polymers), which are typically acrylic substances (e.g., formed from ethylenically unsaturated monomer components including one or more of (meth)acrylate, (meth)acrylic acid, and the like), more preferably acid or anhydride-functional acrylic substances.

[0093]

[0094] In one embodiment, the water-dispersible polymer may be formed from preformed polymers (e.g., (a) oxirane-functional polymers such as oxirane-functional polyether polymers, and (b) acid-functional polymers such as acid-functional acrylic polymers) in the presence of an amine, more preferably a tertiary amine. Optionally, the acid-functional polymer can be at least partially neutralized by combining it with an amine, more preferably a tertiary amine, prior to reaction with the oxirane-functional polymer.

[0094]

[0095] In another embodiment, the water-dispersible polymer may be formed from an oxirane-functional polymer (more preferably a polyether polymer as described herein) that reacts with an ethylenically unsaturated monomer to form an acid-functional polymer, and this may then be neutralized with a base such as, for example, a tertiary amine. Thus, for example, in one embodiment, the water-dispersible polymer is described in U.S. Patent No. 4,285,847 or 4,212,781, which teach a process for grafting acid-functional acrylic groups to an oxirane-functional polymer (e.g., via the use of benzoyl peroxide), and may be formed according to the teachings of the polymerization of acrylics. In another embodiment, the polymerization of acrylics may be achieved through reaction with unsaturations present in the polymer of the ethylenically unsaturated monomer. For example, for examples of such processes, see U.S. Patent No. 4,517,322 or U.S. Patent Application Publication No. 2005 / 0196629.

[0095]

[0096] In another embodiment, the water-dispersible polymer may be formed having the structure E-L-A, where "E" is the polyether portion of the polymer formed from the polyether polymer, "A" is the polymerized acrylic portion of the polymer, and "L" is the bonding portion of the polymer that covalently bonds E to A. Such a polymer may be, for example, (a) a polyether polymer preferably having about two oxirane groups, and (b) preferably (i) It can be prepared from an unsaturated bond compound having a carbon-carbon double bond, a conjugated carbon-carbon double bond, or a carbon-carbon triple bond and (ii) a functional group capable of reacting with an oxirane group (e.g., a carboxylic acid group, a hydroxyl group, an amino group, an amide group, a mercapto group, etc.). Preferred linking compounds contain 12 or fewer carbon atoms, and sorbic acid is an example of such a preferred linking compound. The acrylic moiety preferably contains one or more salt groups or salt-forming groups (e.g., acid groups such as those present in α,β-ethylenically unsaturated carboxylic acid monomers). Such polymers can be formed, for example, by using polyether polymers free of BPA and BADGE as described in the above-mentioned U.S. Patent No. 9,409,219 (B2), U.S. Patent Application Publication Nos. 2015 / 0021323 (A1), 2015 / 0151878 (A1), 2016 / 0272576 (A1), 2017 / 0051177 (A1), 2017 / 0096521 (A1), 2017 / 0096579 (A1), and International Publication No. 2018 / 125895 (A1), optionally in combination with the substances and techniques disclosed in U.S. Patent No. 5,830,952 or U.S. Patent Application Publication No. 2010 / 0068433 (A1).

[0096]

[0097] In the above approach of making the polymer water-dispersible using an acrylic component, the acrylic component is typically formed from a mixture of ethylenically unsaturated monomers containing one or more α,β-unsaturated carboxylic acids, but any suitable acid or anhydride-functional monomer may be used. One or more α,β-unsaturated carboxylic acids preferably render the polymer water-dispersible after neutralization with a base. Suitable α,β-unsaturated carboxylic acid monomers include any of those already referenced herein. It may be possible to blend a multi-stage latex polymer and a water-dispersible polymer together, but in the preferred embodiments herein, at least some (and in some embodiments all) of the ethylenically unsaturated monomer components are emulsion polymerized in an aqueous dispersion containing at least some water-dispersible polymer.

[0097]

[0098] While not desiring to be bound by theory, it may be possible to achieve desirable coating performance for specific end uses within the food or beverage can coating area with the multi-stage latex of the present invention without the use of any polyether polymer or without the use of any water-dispersible polymer. Nevertheless, preferred embodiments herein include a water-dispersible polymer, and a polyether polymer (e.g., a polyether-acrylate copolymer) is a preferred water-dispersible polymer.

[0098]

[0099] BPA or styrene may be used, but in preferred embodiments herein, the coating composition of the present invention is substantially free of or does not contain one or more of (i) styrene and (ii) bisphenol A (“BPA”), bisphenol F (“BPF”), and bisphenol S (“BPS”). By way of example, a coating composition substantially free of each of BPA, BPF, and BPS will necessarily also be substantially free of each of the diglycidyl ethers of BPA (“BADGE”), BPF, and BPS. In preferred embodiments, the coating composition exhibits a balance of coating properties in the end use of food or beverage can coatings that is comparable to conventional epoxy-acrylate coating systems that utilize appreciable amounts of both BPA and styrene. In some embodiments, the coating composition is substantially free of or does not contain substituted styrene compounds (e.g., alpha-methylstyrene, methylstyrene (e.g., 2-methylstyrene, 4-methylstyrene, vinyltoluene, and the like), dimethylstyrene (e.g., 2,4-dimethylstyrene), trans-beta-styrene, divinylbenzene, and the like). In some embodiments, the coating composition is substantially free of or does not contain vinyl aromatic compounds.

[0099]

[0100] The two or more emulsion polymerization stages may include any combination of one or more (meth)acrylates. Suitable (meth)acrylates include any of those referred to herein, and those having the structure of formula (II) above.

[0100] CH2=C(R 3 )-CO-OR 4 (II) (wherein, R 3 is hydrogen or methyl, and R 4 is preferably an alkyl group, alicyclic group, aryl group, silane group, or a combination thereof containing 1 to 16 carbon atoms).

[0101]

[0101] Optionally, R 4 may be optionally substituted with one or more (e.g., 1 to 3) moieties such as, for example, hydroxy, halo, phenyl, and alkoxy. Examples of suitable (meth)acrylates (including, for example, suitable alkyl (meth)acrylates) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, lauryl (meth)acrylate, isobornyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, etc., substitution variants thereof (e.g., ring substitution variants of benzyl (meth)acrylate or phenyl (meth)acrylate), and isomers and mixtures thereof.

[0102]

[0102] In the following discussion, various weight percentages are provided for the components of two or more emulsion polymerization stages. As will be understood by those skilled in the art, unless specifically indicated to the contrary, these weight percentages are based on the total weight of the reactants (typically monomers) used to form the relevant stages.

[0103]

[0103] Typically, (meth)acrylates (e.g., one (meth)acrylate, or a mixture of two or more (meth)acrylates) will constitute a significant portion of each of the two or more stages. In some embodiments, the (meth)acrylate may be at least 30 wt%, at least 50 wt%, at least 70 wt%, at least 85 wt%, at least 95 wt%, or even 100 wt% of the monomers (and in some embodiments, the aggregate of monomers used to form two or more stages) used to form at least one of the emulsion polymerization stages. The weight percentages described above include all (meth)acrylate monomers present during a particular stage, regardless of whether one or more of the monomers may also be recognized as "Monomer A" as described below. In some embodiments, one or more methacrylate monomers are present in the amounts described in this paragraph.

[0104]

[0104] In some embodiments, alkyl (meth)acrylates may be at least 30 wt%, at least 50 wt%, at least 70 wt%, at least 85 wt%, at least 95 wt%, or even 100 wt% of the monomers (and in some embodiments, the aggregate of monomers used to form two or more stages) used to form at least one of the emulsion polymerization stages. The weight percentages described above include all alkyl (meth)acrylate monomers present, regardless of the fact that all such monomers are also (meth)acrylates, and regardless of whether one or more of the monomers may also be recognized as "Monomer A".

[0105]

[0105] In some embodiments, the monomer(s) used to form at least one of the emulsion polymerization stages (and, in some embodiments, the collection of monomers used to form two or more emulsion polymerization stages) preferably comprises at least 50 wt%, at least 75 wt%, or at least 80 wt% of one or more (e.g., 1, 2, 3, 4, or 5) of methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate (e.g., n-butyl acrylate), and butyl methacrylate (e.g., n-butyl methacrylate). In some embodiments, the monomer(s) used to form at least one of the emulsion polymerization stages (and, in some embodiments, the monomers used to form each of the corresponding two or more emulsion polymerization stages) comprises butyl methacrylate, butyl acrylate, or both. In some embodiments, the monomer(s) used to form at least one emulsion polymerization stage, and, in some embodiments, the monomers used to form each of the corresponding two or more emulsion polymerization stages, comprises both (i) n-butyl methacrylate and one or both of ethyl methacrylate or methyl methacrylate, and (ii), optionally, one or more of ethyl acrylate, methyl acrylate, or n-butyl acrylate.

[0106]

[0106] In some embodiments, most (e.g., >50 wt%, ≧60 wt%, ≧70 wt%, ≧80 wt%, ≧90 wt%, ≧95 wt%, etc.), or even all, of the (meth)acrylates present in the monomers used to form one or more stages (e.g., high Tg stage) are methacrylates, more preferably alkyl methacrylates. Examples of preferred methacrylates include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, and isomers thereof (e.g., t-butyl methacrylate, isobutyl methacrylate, etc.). In addition, di(meth)acrylates and tri(meth)acrylates can be used, and preferred examples include ethanediol dimethacrylate, propanediol dimethacrylate, and butanediol dimethacrylate (e.g., 1,3-butanediol dimethacrylate and 1,4-butanediol dimethacrylate).

[0107]

[0107] Thus, in some embodiments, one or more stages (e.g., high Tg stage, and in some embodiments, the aggregate of monomers used to form two or more emulsion polymerization stages) comprise at least 30 wt%, at least 50 wt%, at least 70 wt%, at least 85 wt%, or at least 95 wt% of one or more alkyl methacrylates.

[0108]

[0108] In some embodiments (e.g., embodiments that do not contain certain styrenes), the monomers used to form at least one of the emulsion polymerization steps include one or more ethylenically unsaturated monomers that contain an alicyclic group, or a hydrocarbon group containing at least 4 carbon atoms (hereinafter collectively referred to as "monomer component A" or "monomer A"), or a mixture of both. Any suitable ethylenically unsaturated monomer A may be used, but such monomers typically include vinyl monomers such as alkyl (meth)acrylates, cycloalkyl (meth)acrylates, vinyl aromatics (e.g., including aryl (meth)acrylates), vinyl esters, and the like. One or more heteroatoms may optionally be present within the alicyclic group or C4+ hydrocarbon group. In some embodiments, only carbon and hydrogen atoms are present within the alicyclic group or C4+ hydrocarbon group. The C4+ hydrocarbon group can have any suitable structure, but in some embodiments a straight or branched straight chain is preferred, and in certain embodiments a straight or branched straight chain group having a longest chain containing at least 3 carbon atoms is particularly preferred. Alkyl (meth)acrylates having the specified groups are preferred such monomers Although an example of A, any suitable type of ethylenically unsaturated monomer having such a group may be used.

[0109] Although not bound by theory, including one or more ethylenically unsaturated monomers containing an alicyclic group or a hydrocarbon group having at least 4 carbon atoms can, among other things, be thought to help impart a preferably high level of hydrophobicity. This may be desirable for a number of reasons, such as enhancing water resistance or retort resistance and helping to reduce the partitioning (“scalping”) of low levels of flavorants present in certain aqueous packaged products (e.g., certain colas) into coatings. Resistance to inappropriate levels of flavor scalping is generally desired for internal can coatings, particularly for internal beverage can coatings that can be used to package products such as certain colas that may contain relatively low flavorant concentrations where significant partitioning of flavorants into the coating can result in a perceptible change in product flavor.

[0110]

[0110] Examples of hydrocarbon groups having 4 or more carbon atoms suitable for inclusion in monomer A include hydrocarbon groups having 4 or more, 5 or more, 6 or more, 7 or more, or 8 or more carbon atoms. Preferred such hydrocarbon groups are butyl, pentyl, hexyl, and their isomers (e.g., n-butyl, sec-butyl, t-butyl, etc.). Some specific examples of such monomer A include n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl methacrylate, 3,5,5-trimethylhexyl (meth)acrylate, their derivatives and isomers, and combinations thereof. In some embodiments, C4 or higher hydrocarbon groups having 4 to 6 carbon atoms are preferred. Without being bound by theory, it is believed that if monomer A contains an excess amount of a monomer A having a long straight-chain carbon chain (e.g., C7 or higher, in certain examples C5 or C6), a latex having an inappropriately low glass transition temperature may result for certain can interior coating applications. For example, any suitable alicyclic group containing a 4-membered ring, 5-membered ring, 6-membered ring, or even a 7-membered ring or higher alicyclic group may be used in monomer A. Also, the alicyclic group may be monocyclic or polycyclic (e.g., bicyclic, tricyclic, tetracyclic, etc.). For example, any suitable polycyclic group containing a bridged polycyclic ring system (e.g., norbornane group), a fused polycyclic ring system, or a combination thereof (e.g., tricyclodecane group) may be used. Typically, the atom(s) constituting the ring(s) is / are carbon atoms, but as discussed above, one or more heteroatoms may also be present within the ring. Examples of monomer A having an alicyclic group include cyclohexyl (meth)acrylate, 4-tert-butylcyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, their variants and isomers, and mixtures thereof.

[0111]

[0111] In some embodiments, butyl (meth)acrylate is the preferred monomer A. In some embodiments, the ethylenically unsaturated monomer component includes both butyl acrylate and butyl methacrylate. In some such embodiments, it may be preferable to use an excess amount of butyl methacrylate relative to the amount of butyl acrylate.

[0112]

[0112] As described above, in some embodiments, one or more of the emulsion polymerization steps are prepared using at least one monomer A of formula (I) below. CH2=C(R 1 )-X n -C(CH3) t (R 2 ) 3-t (I) (wherein, R 1 is hydrogen or an alkyl group, more typically hydrogen or a methyl group, n is 0 or 1, more typically 1, X, when present, is a divalent linking group, more typically an amide, carbonate, ester, ether, urea, or urethane linkage, even more typically an ester linkage in either direction (i.e., -C(O)-O- or -O-C(O)-), t is from 0 to 3, each R 2 is, when present, independently an organic group which may optionally be branched on its own, more typically an alkyl group which may optionally contain one or more heteroatoms (e.g., N, O, P, Si, etc.), and two or more R 2 may optionally form a cyclic group with each other).

[0113]

[0113] In some embodiments, t is 1 and both R 2The total number of carbon atoms present therein is 6, 7, or 8. Examples of such monomer A include VEOVA 9 (Tg 70°C), VEOVA 10 (Tg -3°C), and VEOVA 11 (Tg -40°C) monomers commercially available from Hexion.

[0114]

[0114] In some embodiments, t is 0, 1, or 2, and at least one R 2 is a branched-chain organic group, more typically a branched-chain alkyl group. Thus, for example, in some embodiments, at least one R 2 containing a tertiary or quaternary carbon atom is present. The VEOVA 9 monomer is an example of such a branched monomer.

[0115]

[0115] In some embodiments, at least one of the emulsion polymerization steps (and, in some embodiments, the aggregate of monomers used to form two or more steps) contains at least 30 weight percent ("wt%"), at least 35 wt%, at least 40 wt%, at least 45 wt%, or even 80 wt% or more of one or more monomer A. The upper limit is not limited, but when used, one or more monomer A is typically present in an amount of 100 wt%, more typically less than 80 wt%, even more typically less than 75 wt%, and even more typically less than 65 wt% (during a particular step or in the aggregate of monomers used to form two or more steps).

[0116]

[0116] In some embodiments, the monomers used to form at least one of the emulsion polymerization steps (and, in some embodiments, the aggregate of monomers used to form two or more emulsion polymerization steps) contain at least 4 carbon atoms and have a linear or branched hydrocarbon group with a longest chain length of at least 3 carbon atoms, and contain at least 20 wt%, at least 30 wt%, at least 35 wt%, at least 40 wt%, or even 80 wt% or more of one or more ethylenically unsaturated monomers.

[0117]

[0117] In some embodiments, the monomer used to form at least one of the emulsion polymerization stages comprises one or more ethylenically unsaturated monomers having a C1-C3 hydrocarbon group. The methyl group bonded to the alpha carbon of methacrylic acid is not considered to be such a C1-C3 hydrocarbon group. Similarly, the vinyl group of a vinyl monomer is not considered to be present in such a C1-C3 hydrocarbon group. Preferred such hydrocarbon groups include methyl, ethyl, propyl, and isopropyl groups. Examples of such monomers include alkyl (meth)acrylates where the alkyl group (e.g., the R 4 group) is a C1-C3 alkyl group such as, for example, methyl, ethyl, n-propyl, isopropyl, and mixtures thereof. Preferred such monomers having a C1-C3 hydrocarbon group include methyl methacrylate, ethyl acrylate, ethyl methacrylate, and mixtures thereof. The emulsion polymerization ethylenically unsaturated monomer component can comprise any suitable amount of such monomers, for example, at least 10 wt%, at least 20 wt%, at least 30 wt%, or at least 40 wt%. Typically, one or more ethylenically unsaturated monomers having a C1-C3 hydrocarbon group will constitute less than 70 wt%, more typically less than 60 wt%, and even more typically less than 50 wt%.

[0118] [

[0118] ] A polyfunctional monomer can be used, and a polyethylenically unsaturated monomer is an example of a preferred polyfunctional monomer. Examples of suitable polyethylenically unsaturated (meth)acrylates include ethanediol di(meth)acrylate, propanediol di(meth)acrylate, butanediol di(meth)acrylate (e.g., 1,3-butanediol di(meth)acrylate and 1,4-butanediol di(meth)acrylate), heptanediol di(meth)acrylate, hexanediol di(meth)acrylate, trimethylolethane tri(meth)acrylate trimethylolpropane tri(meth)acrylate, trimethylolbutane tri(meth)acrylate, trimethylolheptane tri(meth)acrylate, trimethylolhexane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, dipropylene glycol di(meth)acrylate, trimethylolhexane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, isosorbide di(meth)acrylate, allyl (meth)acrylate, glycerol dimethacrylate, and mixtures thereof, and polyhydric alcohol esters of acrylic acid or methacrylic acid. Examples of polyethylenically unsaturated monomers other than (meth)acrylates include diallyl phthalate, divinylbenzene, divinyltoluene, divinylnaphthalene, and mixtures thereof.

[0119] [

[0119] ] In some embodiments, the monomer used to form at least one stage (and, in some embodiments, the collection of monomers used to form two or more emulsion polymerization stages) can contain a small amount (e.g., less than 5 wt%, less than 2 wt%, or less than 1 wt%) of an acid or anhydride functional ethylenically unsaturated monomer. Examples of suitable such acid or anhydride functional monomers can include any of those disclosed for use with any acrylate moiety of the polyether-acrylate copolymers disclosed herein.

[0120]

[0120] Further, the ethylenically unsaturated monomer component may also include any other suitable monomer. For example, suitable other vinyl monomers include isoprene, diallyl phthalate, conjugated butadiene, vinyl naphthalene, acrylonitrile, (meth)acrylamide (e.g., acrylamide, methacrylamide, N-isobutoxymethyl acrylamide, N-butoxymethyl acrylamide, etc.), methacrylonitrile, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl stearate, and the like, as well as variants and mixtures thereof.

[0121]

[0121] In some embodiments, the emulsion polymerized ethylenically unsaturated monomer component does not contain any oxirane group-containing monomer.

[0122] In a preferred embodiment herein, the emulsion polymerized ethylenically unsaturated monomer component, more preferably the entire resin system, does not contain and is not derived from any acrylamide-type monomer (e.g., acrylamide or methacrylamide). If any such monomer is used, its total amount is preferably 0.5% by weight or less, more preferably 0.1% by weight or less of the total weight of the polymerizable monomers used to prepare the resin system.

[0122]

[0123] The emulsion polymerized ethylenically unsaturated monomer component may optionally contain one or more vinyl aromatic compounds other than styrene. Such vinyl aromatic compounds include substituted styrene compounds and / or other types of vinyl aromatic compounds (e.g., aryl group-containing ethylenically unsaturated monomers described herein such as benzyl (meth)acrylate). It may also be any deviation). In some embodiments, the monomer used to form at least one stage (and, in some embodiments, the aggregate of monomers used to form two or more emulsion polymerization stages), if any, may contain less than 20% by weight, less than 10% by weight, less than 5% by weight, or less than 1% by weight of vinyl aromatic compounds. In some embodiments, the monomers used to form the latex substantially do not contain or do not contain such compounds.

[0123]

[0124] Regarding the conditions of the emulsion polymerization reaction described herein, two or more stages of the multi-stage latex (e.g., high Tg and low Tg stages) are preferably polymerized in an aqueous medium using a water-soluble free radical reaction initiator in the presence of one or more water-dispersible polymers described herein. Although not preferred herein, it is also conceivable that some (or even all) of the ethylenically unsaturated components of the two or more stages of emulsion polymerization can be polymerized separately and then mixed later with one or more water-dispersible polymers.

[0124]

[0125] The polymerization temperature is typically from 0 °C to 100 °C, preferably from 50 °C to 90 °C, more preferably from 70 °C to 90 °C, and even more preferably from 80 °C to about 85 °C. The pH of the aqueous medium is usually maintained at a pH of 5 to 12.

[0125]

[0126] For example, a free radical reaction initiator can be selected from one or more water-soluble peroxides known to act as free radical reaction initiators. Examples include hydrogen peroxide and t-butyl hydroperoxide. Redox reaction initiator systems well known in the art (e.g., t-butyl hydroperoxide, erythorbic acid, and ferrous iron complex) can also be used. In some embodiments, a mixture of benzoin and hydrogen peroxide is used.

[0126]

[0127] As a further example of a polymerization initiator that can be used, there are polymerization initiators that thermally decompose at the polymerization temperature to generate free radicals. Examples include both water-soluble species and water-insoluble species. Further examples of free radical reaction initiators that can be used include persulfates (such as ammonium persulfate or alkali metal persulfates (potassium, sodium, or lithium)); azo compounds (such as 2,2'-azo-bis(isobutyronitrile), 2,2'-azo-bis(2,4-dimethylvaleronitrile), and 1-t-butyl-azocyclohexane); hydroperoxides (such as t-amyl hydroperoxide, methyl hydroperoxide, and cumene hydroperoxide); peroxides (such as benzoyl peroxide, caprylyl peroxide, di-t-butyl peroxide, ethyl 3,3'-di(t-butylperoxy)butyrate, ethyl 3,3'-di(t-amylperoxy)butyrate, t-amylperoxy-2-ethylhexanoate, and t-butylperoxypivalate); peresters (such as t-butyl peracetate, t-butyl perphthalate, and t-butyl perbenzoate); and percarbonates (such as di(1-cyano-1-methylethyl) peroxydicarbonate); perphosphates; and combinations thereof.

[0127]

[0128] The polymerization initiator can be used alone or as an oxidation component of a redox system, which preferably also includes a reducing component such as, for example, ascorbic acid, malic acid, glycolic acid, oxalic acid, lactic acid, thioglycolic acid, or an alkali metal sulfite, and more specifically, bisulfites, hyposulfites, or metabisulfites (such as sodium bisulfite, potassium hyposulfite, and potassium metabisulfite), or sodium formaldehyde sulfoxylate, and combinations thereof. The reducing component is often referred to as an accelerator or catalyst activator.

[0128]

[0129] (when present) The reaction initiator and accelerator are preferably the monomers to be copolymerized They are used at a ratio of about 0.001% to 5% respectively based on the weight of the monomer. If necessary, a small amount of promoters such as chlorides and sulfates of cobalt, iron, nickel, or copper can be used. Examples of redox catalyst systems include tert-butyl hydroperoxide / sodium formaldehyde sulfoxylate / Fe(II), and ammonium persulfate / sodium bisulfite / sodium metabisulfite / Fe(II).

[0129]

[0130] If necessary, a chain transfer agent can be used to control the molecular weight of the polymer. Exemplary chain transfer agents include mercaptans and other substances well known to those skilled in the art.

[0130]

[0131] The polymerization reaction of ethylenically unsaturated monomers in the presence of an aqueous dispersion of a water-dispersible polymer may be carried out as a batch, intermittent, or continuous operation.

[0132] Typically, an appropriate amount of water and the water-dispersible polymer are charged into the reactor. Typically, the reactor is then heated to the free radical reaction initiation temperature, and then the ethylenically unsaturated monomers of the first stage (e.g., the high Tg stage or the low Tg stage) are charged. Some water-miscible solvent may also be present. At this temperature, a free radical reaction initiator is added and reacted for a certain period at the polymerization temperature, and the remaining ethylenically unsaturated monomer components (if those of the first stage are present) are added incrementally at an addition rate that varies depending on the polymerization temperature, the specific reaction initiator used, and the type and amount of the monomers to be polymerized. After or before the completion of the first stage of polymerization, the ethylenically unsaturated monomers of the second stage (e.g., the other high or low Tg stage) are typically charged into the reactor together with an additional free radical reaction initiator. After all the monomers are charged, the final heating is carried out to complete the polymerization. Then, the reactor is cooled and the latex is recovered. As already discussed, the method may also include emulsion polymerization in one or more additional optional stages at any suitable time (e.g., in addition to the high Tg and low Tg stages). It should be understood that the above methodology is merely illustrative and other suitable processes may also be used.

[0131]

[0133] Optionally, one or more of the emulsion polymerizations in the latex stage may be promoted using a non-polymer surfactant (or emulsifier). Such surfactants may optionally be polymerizable and may be used in place of or in addition to the water-dispersible polymer. Examples of suitable such non-polymer surfactants are provided, for example, in WO 2016 / 105504 (A1) and WO 2017 / 112837 (A1).

[0132]

[0134] As already discussed, in a preferred embodiment, the water-dispersible polymer and two or more emulsion polymerization stages are both present in the latex (e.g., both present in the same latex particles or latex copolymer), and the latex is preferably formed by emulsion polymerizing two or more stages in the presence of the water-dispersible polymer. The water-dispersible polymer and one or more of the emulsion polymerization stages may optionally be covalently bonded to each other. Similarly, two or more emulsion polymerization stages (e.g., high Tg and low Tg stages) may be covalently bonded to each other.

[0133]

[0135] The coating composition of the present invention preferably contains at least a film-forming amount of the resin system described herein, which contains a water-dispersible polymer and two or more emulsion polymerization stages. The coating composition typically contains at least 10 wt%, more typically at least 20 wt%, even more typically at least 50 wt%, and even more typically at least 75 wt%, at least 90 wt%, or at least 95 wt% of the resin system, based on the solid content weight of the water-dispersible polymer and two or more emulsion polymerization stages relative to the total resin solid content weight of the coating composition. The coating composition contains, based on the solid content weight of the water-dispersible polymer and two or more emulsion polymerization stages relative to the total resin solid content weight of the coating composition up to 100 wt%, more typically less than 99 wt%, even more typically less than 95 wt% of the resin system (preferably a latex resin system).

[0134]

[0136] Typically, the resin solids constitute at least 30 wt%, at least 40 wt%, or at least 50 wt% or more of the coating solids. In some embodiments, the resin solids constitute all or substantially all (e.g., more than 90 or 95 wt% or even 100 wt%) of the coating solids.

[0135]

[0137] The coating composition may be formulated from a latex emulsion, optionally containing one or more additives or rheologically modified (e.g., diluted for spray coating applications) for various coating applications. In embodiments where the coating composition contains one or more additives, the additives preferably do not adversely affect the latex emulsion or the cured coating formed from the coating composition. For example, such optional additives may be included in the coating composition to enhance the aesthetic properties of the composition, to facilitate the manufacture, processing, handling, and application of the composition, and to further improve certain functional properties of the coating composition or the cured coating obtained therefrom.

[0136]

[0138] Examples of such optional additives include catalysts, dyes, pigments, toners, extenders, fillers, lubricants, corrosion inhibitors, flow control agents, thixotropic agents, dispersants, antioxidants, adhesion promoters, light stabilizers, curing agents, auxiliary resins, and mixtures thereof. Each optional additive is preferably included in an amount sufficient to achieve the intended purpose but not in an amount that adversely affects the coating composition or the cured coating obtained therefrom.

[0137]

[0139] One preferred optional additive is a catalyst for increasing the cure rate. Examples of catalysts include strong acids (e.g., dodecylbenzenesulfonic acid (DDBSA, available as CYCAT 600 from Cytec), methanesulfonic acid (MSA), p-toluenesulfonic acid (pTSA), dinonylnaphthalenedisulfonic acid (DNNDSA), and triflic acid), quaternary ammonium compounds, phosphorus compounds, and tin, titanium, and zinc compounds, but are not limited thereto. Specific examples include tetraalkylammonium halides, tetraalkyl or tetraarylphosphonium iodides or acetates, tin octoate, zinc octoate, triphenylphosphine, and similar catalysts known to those skilled in the art, but are not limited thereto.

[0138]

[0140] When used, the catalyst is preferably present in an amount of at least about 0.01 wt%, more preferably at least about 0.1 wt%, based on the total solids weight of the coating composition. Further, when used, the catalyst is also preferably present in a nonvolatile amount of about 3 wt% or less, more preferably about 1 wt% or less, based on the total solids weight of the coating composition.

[0139]

[0141] Another useful optional component is a lubricant (e.g., wax), which facilitates the manufacture of metal closures and other fabricated coated articles by imparting lubricity to the sheets of coated metal substrates. Preferred lubricants include, for example, carnauba wax and polyethylene-type lubricants. When used, the lubricant is preferably present in the coating composition in an amount of at least about 0.1 wt%, preferably about 2 wt% or less, more preferably about 1 wt% or less, based on the total solids weight of the coating composition.

[0140]

[0142] Another useful optional component is a siloxane-based or polysilicon-based substance They are organosilicon substances such as etc. Representative examples of such suitable substances are disclosed in International Publication Nos. 2014 / 089410 (A1) and 2014 / 186285 (A1).

[0141]

[0143] Another useful optional component is a pigment such as titanium dioxide. When used, the pigment is present in the coating composition in an amount of about 70% by weight or less, more preferably about 50% by weight or less, still more preferably about 40% by weight or less, based on the total solids weight of the coating composition.

[0142]

[0144] Also, one or more optional curing agents (e.g., crosslinkable resins sometimes referred to as "crosslinking agents") may be incorporated into the coating composition. The selection of a particular crosslinking agent typically depends on the specific product being formulated. For example, some coatings are darkly colored (e.g., a gold coating). These coatings may typically be formulated using a crosslinking agent that itself tends to have a yellowish color. In contrast, white coatings are generally formulated using a non-yellowing crosslinking agent or using only a small amount of a yellowing crosslinking agent. Preferred curing agents are substantially free of or do not contain each of BPA, BPF, BPS, and epoxy novolac.

[0143]

[0145] Any of the well-known hydroxyl-reactive curable resins can be used. For example, phenoplasts, blocked isocyanates, and aminoplast curing agents, and combinations thereof may be used. Further or alternatively, carboxyl-reactive curable resins may be used.

[0144]

[0146] Phenoplast resins include condensation products of aldehydes and phenols. Formaldehyde and acetaldehyde are preferred aldehydes. Various phenols, such as phenol, cresol, p-phenylphenol, p-tert-butylphenol, p-tert-amylphenol, and cyclopentylphenol, can be used.

[0145]

[0147] An aminoplast resin is a condensation product of an aldehyde such as formaldehyde, acetaldehyde, crotonaldehyde, and benzaldehyde with an amino- or amide group-containing substance such as urea, melamine, and benzoguanamine. Examples of suitable aminoplast crosslinkable resins include benzoguanamine-formaldehyde resins, melamine-formaldehyde resins, esterified melamine-formaldehyde, and urea-formaldehyde resins. One specific example of a suitable aminoplast crosslinking agent is a fully alkylated melamine-formaldehyde resin commercially available from Cytec Industries, Inc. under the trademark CYMEL 303.

[0146]

[0148] Examples of other generally suitable curing agents are blocked or unblocked aliphatic, cycloaliphatic, or aromatic, divalent, trivalent, or polyvalent isocyanates such as hexamethylene diisocyanate (HMDI), cyclohexyl-1,4-diisocyanate, and the like. Further examples of generally suitable blocked isocyanates include isophorone diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, tetramethylxylylene diisocyanate, isomers of xylene diisocyanate, and mixtures thereof. In some embodiments, a blocked isocyanate having a number average molecular weight of at least about 300, more preferably at least about 650, and even more preferably at least about 1,000 is used.

[0147]

[0149] Other suitable curing agents can include, for example, benzoxazine-based phenolic resin such as benzoxazine curing agents. Examples of benzoxazine-based curing agents are provided in U.S. Patent Application Publication No. 2016 / 0297994 (A1).

[0148]

[0150] Alkanolamide type hardeners may also be used. Preferred such hardeners include beta-hydroxyalkyl-amide crosslinkers such as those sold under the trademark PRIMID by EMS-CHEMIE AG (e.g., PRIMID XL-552 and QM-1260 products).

[0149]

[0151] The concentration of the curing agent (e.g., crosslinking agent) in the coating composition may depend on the type of curing agent, the time and temperature of baking, and the molecular weight of the copolymer particles. If used, the crosslinking agent is typically present in an amount of about 50% by weight or less, preferably about 30% by weight or less, and more preferably about 15% by weight or less. If used, the crosslinking agent is typically present in an amount of at least about 0.1% by weight, more preferably at least about 1% by weight, and even more preferably at least about 1.5% by weight. These weight percentages are based on the total resin solids weight of the coating composition.

[0150]

[0152] In some embodiments, the coating composition may be cured without the use of an external crosslinker (e.g., without a phenolic crosslinker). Additionally, the coating composition may be substantially free of formaldehyde and formaldehyde-containing materials, more preferably essentially free of these compounds, even more preferably essentially completely free of these compounds, and most preferably completely free or free of these compounds.

[0151]

[0153] As described above, in a preferred embodiment, the disclosed coating composition substantially does not contain or contains none of (i) styrene and (ii) one or more of each of BPA, BPF, and BPS. In addition, the coating composition preferably substantially does not contain, completely does not contain, or contains none of any structural unit derived from a diphenol or other polyphenol having estrogen agonist activity greater than 4,4'-(propan-2,2-diyl)diphenol. More preferably, the coating composition substantially does not contain, completely does not contain, or contains none of any structural unit derived from a diphenol or other polyphenol having estrogen agonist activity greater than BPS. In some embodiments, the coating composition substantially does not contain, completely does not contain, or contains none of any structural unit derived from bisphenol. By way of example, a structural unit derived from an epoxide of bisphenol (e.g., a diglycidyl ether of bisphenol) is considered to be a structural unit derived from bisphenol.

[0152]

[0154] Even more preferably, the coating composition substantially does not contain, completely does not contain, or contains none of any structural unit derived from a diphenol or other polyphenol having estrogen agonist activity greater than 4,4'-(propan-2,2-diyl)bis(2,6-dibromophenol). Most optimally, the coating composition substantially does not contain, completely does not contain, or contains none of any structural unit derived from a diphenol or other polyphenol having estrogen agonist activity greater than 2,2-bis(4-hydroxyphenyl)propanoic acid. The estrogen agonist activity can be evaluated using a suitable, compliant in vitro human estrogen receptor assay, such as the MCF-7 cell proliferation assay ("MCF-7 assay") or another assay that can be used in place of the MCF-7 assay or that can correlate with the MCF-7 assay through the analysis of a common reference compound. For example, for a discussion of such structural units and applicable test methods, see U.S. Patent Application Publication No. 2013 / 0316109 (A1).

[0153]

[0155] In a preferred embodiment, the coating composition is not prepared using a halogenated monomer (whether free or polymerized), such as a vinyl chloride monomer. In a further preferred embodiment, the coating composition is substantially free of, completely free of, or does not contain a halogenated monomer.

[0154]

[0156] The coating composition may also be rheologically modified, if desired, for the application of various coatings. For example, the coating composition may be diluted with an additional amount of an aqueous carrier to reduce the total solids content in the coating composition. Alternatively, a portion of the aqueous carrier may be removed (e.g., evaporated) to increase the total solids content in the coating composition. The final total solids content in the coating composition may vary depending on the application of the specific coating used (e.g., spray coating), the use of the specific coating (e.g., for the inner surface of a can), the coating thickness, and the like.

[0155]

[0157] Optionally, the coating composition may also contain one or more other desired polymers, such as one or more acrylic polymers, alkyd polymers, epoxy polymers, polyolefin polymers, polyurethane polymers, polysilicon polymers, polyester polymers, and copolymers and mixtures thereof.

[0156]

[0158] In some embodiments, such as for the application of certain spray coatings (e.g., an inner spray for food or beverage cans, including aluminum beverage cans), the total solids weight of the coating composition may be greater than about 5%, more preferably greater than about 10%, and even more preferably greater than about 15% based on the total weight of the coating composition. In these embodiments, the total solids weight of the coating composition may also be less than about 40%, more preferably less than about 30%, and even more preferably less than about 25% based on the total weight of the coating composition. In some of these embodiments, the coating composition may have a total solids weight in the range of about 18% to about 22%. The aqueous carrier may constitute the remainder of the weight of the coating composition.

[0157]

[0159] The aqueous carrier of the coating composition includes water and may further include one or more optional organic solvents. In some embodiments, water constitutes more than about 20% by weight, more preferably more than about 35% by weight, and even more preferably more than about 50% by weight of the total weight of the aqueous carrier. In some embodiments, water constitutes 100% by weight or less, more preferably less than about 95% by weight, and even more preferably less than about 90% by weight of the total weight of the aqueous carrier.

[0158]

[0160] Without being bound by theory, including a suitable amount of organic solvent may be beneficial in some embodiments (e.g., for the application of certain coil coatings, to modify the flow and smoothness of the coating composition, control blistering, and maximize the line speed of the coil coater). Thus, in certain embodiments, the organic solvent may constitute more than 0% by weight, more preferably more than about 5% by weight, and even more preferably more than about 10% by weight of the aqueous carrier based on the total weight of the aqueous carrier. In these embodiments, the organic solvent may also constitute less than about 80% by weight, more preferably less than about 65% by weight, and even more preferably less than about 50% by weight of the aqueous carrier based on the total weight of the aqueous carrier. In some embodiments, the organic solvent constitutes less than 40% by weight of the aqueous carrier.

[0159]

[0161] The viscosity of the coating composition is preferably suitable for the application of a given coating. In some embodiments, the average viscosity of the coating composition may be greater than about 20 seconds, more preferably greater than 25 seconds, even more preferably greater than about 30 seconds, based on the viscosity test described below (Ford Viscosity Cup #2 at 25°C). In some embodiments, the average viscosity of the coating composition may also be less than about 80 seconds, more preferably less than 60 seconds, even more preferably less than about 50 seconds, based on the viscosity test described below (Ford Viscosity Cup #2 at 25°C).

[0160]

[0162] The coating composition of the present invention may be applied to various different substrates using various different coating techniques (e.g., spray coating, roll coating, dip coating, immersion, etc.). In a preferred embodiment, the coating composition is applied as an inner spray coating to a container or a part thereof or its components, or to a substrate surface that is part or all of the inside of such a container. As briefly described above, the cured coating formed from the coating composition is particularly suitable for use on metal food and beverage cans (e.g., two-piece cans, three-piece cans, etc.). Two-piece cans (e.g., two-piece beer or soda cans, and certain food cans) are typically manufactured by a drawing and ironing (“D&I”) process and are becoming increasingly popular in the food and beverage industry. The cured coating is also suitable for use in situations where it contacts food or beverage (collectively referred to herein as “food contact”), and may be used on the inside or outside of such cans.

[0161]

[0163] The preferred coating composition of the present invention is particularly suitable for forming an internal coating spray-applied onto aluminum or steel two-piece drawn and ironed beverage or food cans.

[0162]

[0164] The coating composition of the present disclosure may be present as one layer of a single-layer coating system or as one or more layers of a multi-layer coating system. The coating composition may be used as a primer, a mid-coat, a top-coat, or a combination thereof. The coating thickness of a particular layer and of the coating system as a whole will vary depending on the coating material used, the substrate, the coating application method, and the end use of the coated article. A single-layer or multi-layer coating system comprising one or more layers formed from the disclosed coating composition may have any suitable overall coating thickness, but typically the overall average dry coating weight is from about 0.6 grams per square meter ("gsm") to about 13 gsm, more typically from about 1.0 gsm to about 6.5 gsm, and the coating weight selected will often depend on the desired end use. Also, the minimum average dry film weight is important to ensure sufficient coverage while still maintaining suitable coating performance. For example, in the case of beverage cans, a typical minimum dry film weight is about 1.6 grams per square meter (gsm) (corresponding to a coating thickness of about 1.4 micrometers or about 0.055 mils for a typical cured coating density) for beer beverage cans, about 2.3 gsm (corresponding to about 2 micrometers or about 0.079 mils) for soda cans, and about 3.4 gsm (corresponding to about 3 micrometers or about 0.117 mils) for cans intended to be used when packaging "slippery" products such as sports and energy drinks, wine, mixers, and cocktail drinks. The average total coating weight of a coating system for use on a seal (e.g., a threaded metal seal) for a food or beverage container may be 5.2 gsm or less (corresponding to about 4.6 micrometers or about 0.18 mils). For spray-coated tinplate food cans, a typical minimum dry film weight is about 5.4 gsm (corresponding to about 4.8 micrometers or about 0.19 mils).The minimum dry film weights for other uses may be about 7.9 gsm (corresponding to about 6.9 micrometers or about 0.27 mils), about 9.5 gsm (corresponding to about 8.4 micrometers or about 0.33 mils), and about 11.7 gsm (corresponding to about 10.4 micrometers or about 0.41 mils). In certain embodiments where the coating composition is used as an inner coating on a drum (e.g., a drum for use with food or beverage products), a typical minimum dry film weight may be about 13 gsm (corresponding to about 11.7 micrometers or about 0.46 mils). However, for reasons including economy. The maximum dry coating weight for the various uses above may also be less than about 15 gsm (corresponding to about 13.5 micrometers or about 0.53 mils) due to reasons including economy, cure rate, and efficiency.

[0163]

[0165] The metal substrate used in forming a rigid food or beverage can or a part thereof typically has an average thickness in the range of about 125 micrometers to about 635 micrometers. Electrolytic tinplate, cold rolled steel sheet, and aluminum are commonly used as the metal substrate for food or beverage cans or parts thereof. For example, in embodiments where a metal foil substrate is employed in forming a packaging article, the thickness of the metal foil substrate can be made even thinner than the above.

[0164]

[0166] The coating composition of the present disclosure may be applied to a substrate either before or after the substrate is formed into an article such as, for example, a food or beverage container or a part thereof. In one embodiment, a method of forming a food or beverage can or a part thereof is provided, the method 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 coil or sheet), curing the composition, and forming the substrate into a packaging container or a part thereof (e.g., a food or beverage can or a part thereof) (e.g., via stamping). For example, a cured coating of the coating composition of the present disclosure applied on the surface of a two-piece or three-piece can or a part thereof, such as a riveted beverage can end (e.g., a soda or beer can), can be formed by such a method. In another embodiment, a method of forming a food or beverage can is provided, the method comprising providing a packaging container or a part thereof (e.g., a food or beverage can or a part thereof), and applying the coating composition described herein to an inner part, an outer part, or both an inner part and an outer part of such a packaging container or a part thereof (e.g., via spray coating, dipping, etc.), and curing the composition.

[0165]

[0167] After applying the coating composition onto the substrate, the composition can be cured using various processes including, for example, oven baking by either a conventional method or a convection method, or any other method that provides a suitable high temperature for curing the coating. The curing process can be carried out either as an individual step or a combined step. For example, the substrate can be dried at ambient temperature to leave the coating composition mostly uncrosslinked. The coated substrate is then heated to fully cure the composition. In certain situations, the coating composition of the present disclosure may be dried and cured in one step.

[0166]

[0168] The curing conditions vary depending on the method of application and the intended end use. The curing process may be carried out at any suitable temperature, including, for example, oven temperatures in the range of about 100°C to about 300°C, more typically about 177°C to about 250°C. When the substrate to be coated is a metal coil (e.g., a metal coil for forming the ends of beverage cans), for example, the cured coating composition may be cured by heating the coated metal substrate over a suitable period of time, preferably to a peak metal temperature (“PMT”) above about 177°C. More preferably, the coated metal coil is heated to a PMT of at least about 218°C for a suitable period (e.g., about 5 to 900 seconds). The cured (i.e., hardened) coating is preferably a continuous cured coating (i.e., a coating that exhibits a suitably low initial metal exposure value, thereby indicating that the substrate is effectively coated).

[0167]

[0169] In some embodiments, the coating composition is a spray coating composition that can be spray applied onto the inner surface of a food or beverage can (e.g., a two-piece food or beverage can) to effectively and uniformly coat the substrate and form a continuous cured coating.

[0168]

[0170] Preferred Tg values for the cured coating include those 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. Preferred Tg values for the cured coating include those less than about 120°C, more preferably less than about 115°C, even more preferably less than about 110°C, and in some embodiments less than about 100°C.

[0169]

[0171] Further, to prevent or otherwise reduce coating penetration by the intended food or beverage product, the cured coating is preferably suitably hydrophobic. For example, the cured coating can have a contact angle with deionized water of greater than about 80, more preferably greater than about 85, even more preferably greater than about 90 when tested under ambient conditions. In some embodiments, the cured coating may have a contact angle other than the levels described above.

[0170]

[0172] In some embodiments, the cured coating preferably exhibits the desired properties for use as an internal food contact coating (e.g., an inner spray coating) for food and beverage containers. Thus, it is desirable to avoid using substances that are unsuitable for food contact applications due to factors such as concerns about taste or toxicity, or that potentially do not meet the requirements of government regulations. Additionally, for such coatings, it is necessary to select curing chemistries that can impart sufficient hardness and other relevant cured film properties during the relatively short oven cure times (e.g., less than about 1 minute for coil coatings, less than about 2 minutes or less than about 1 minute for inner spray beverage can coatings, and 10 minutes or less for food containers) used in making food and beverage packaging containers and container components. These times are much shorter than those typically used for many other coating end uses. Also, such coatings need to provide sufficient performance at the very thin film weights and thicknesses used for food and beverage coatings. These film weights and thicknesses are often less than 1 / 10 of the film weights and thicknesses used for many other coating end uses.

[0171]

[0173] As a general guideline to minimize concerns about potential flavor and toxicity, cured food contact coatings made from the disclosed multistage latexes preferably exhibit global extraction values of less than about 50 ppm, more preferably less than about 25 ppm, even more preferably less than about 10 ppm, and most preferably less than about 1 ppm, in accordance with the following global extraction test. These global extraction values are stringent enough to exclude typical multistage latex coating compositions used in architectural paints and other residential or industrial coating applications. Reduced global extraction values can be obtained by limiting the amount of species that are mobile or potentially mobile in the cured coating. Thus, typically, using pure rather than impure reactants, avoiding reaction schemes that result in unduly low yields or unwanted side reactions, selecting appropriate stoichiometry to limit the amount of unreacted or unconsumed species including monomers, oligomers, reaction initiators, crosslinking agents, and catalysts, avoiding the presence of readily hydrolyzable species or linkages, using the disclosed water-dispersible polymers rather than conventional low molecular weight emulsion polymerization surfactants for emulsion polymerizing the multistage latex, limiting or avoiding the use of other low molecular weight adjuvants (e.g., low molecular weight antioxidants, biocides, buffers, complexing agents, dispersion aids for pigments or colorants, defoamers, pH adjusters, non-aqueous solvents and co-solvents, and other mobile components that may be associated with various coating adjuvants), and ensuring that complete cure occurs within the planned cure cycle may be desirable.

[0172]

[0174] Further, the cured coating preferably exhibits metal exposure of less than about 5 milliamperes (mA), more preferably less than about 2 mA, even more preferably less than about 1 mA, according to the following initial metal exposure test. The reduced metal exposure value can be obtained by forming a more flexible coating. In the case of conventional latex-based coatings using a one-stage latex, typically there is a trade-off between flexibility and resistance to flavor scalping. That is, acrylics that tend to have acceptable flexibility also tend to scalp flavorings to an unduly high degree, while acrylics that tend to resist scalping flavorings to an unduly high degree also tend to have unduly low flexibility. This trade-off in coating properties is particularly pronounced in acrylics made without using styrene. Without being bound by theory, using a multi-stage latex rather than a one-stage latex in the present invention may reduce the scope of such a trade-off, thereby making it possible to achieve satisfactory flexibility along with sufficient flavor scalping resistance even in acrylics made without using styrene.

[0173]

[0175] For the inner spray coating and for many other food or beverage can coatings, flexibility is particularly important because the coating can flex with the metal substrate during post-curing processing steps (e.g., necking and dome reforming) and when the can is dropped from a reasonable height during transport or use. In some preferred embodiments, the cured coating preferably exhibits metal exposure of less than about 10 mA, more preferably less than about 3.5 mA, even more preferably less than about 2.5 mA, and optimally less than about 1.5 mA, according to the following post-drop damage metal exposure test.

[0174]

[0176] In addition, the coating compositions of the present disclosure also find use in other coating applications. These additional coatings include, but are not limited to, wash coatings, sheet coatings, and side seam coatings (e.g., side seam coatings for food cans). For example, other commercial coating applications and curing methods such as electrocoating, extrusion coating, lamination, powder coating, etc. are also contemplated. The coating composition may also be useful in medical or cosmetic packaging applications, for example, including the surface of a metered dose inhaler ("MDI") including a drug contact surface.

[0175]

[0177] Polymers and coating compositions such as those described in the following examples can be evaluated using a variety of tests including the following. 1. Viscosity Test

[0178] This test measures the viscosity of a latex emulsion or coating composition for rheological purposes such as sprayability and other coating application properties. The test was performed according to ASTM D1200-88 using a Ford Viscosity Cup #2 at 25°C. The results were measured in seconds.

[0176] 2. Curing Conditions

[0179] For the baking of the beverage inner spray, the curing conditions involve maintaining the temperature measured at the can dome at 188°C to 199°C (measured at the can dome) for 55 seconds. For the baking of the food can inner spray, the curing conditions involve maintaining the temperature at the can dome within the range of 208°C to 218°C for 2 minutes. For the baking of the beverage end coil, the curing conditions involve the use of a temperature sufficient to provide a peak metal temperature within the specified time (e.g., 204°C for 10 seconds means, for example, 10 seconds in an oven where the peak metal temperature reaches 204°C).

[0177] 3. Spray Test on the Inner Side of Beverage Cans

[0180] The disclosed coating into the interior of a commercially available preformed aluminum D&I can To facilitate spray application of the ing composition, the viscosity of each coating is reduced such that the flow rate of each coating through a Ford viscosity cup (#2 orifice) is in the range of 20 to 80 seconds. This viscosity measurement is performed at a temperature of 25 °C using a clean and filtered sample of the coating composition. The cans to be tested are conventional 355 mL (12 U.S. fluid ounces) cans of diameter number "211". The coating composition is spray applied at 115 milligrams (dry weight) per can coating weight using a laboratory scale D&I spray unit commercially available from Reynolds DG-250. This laboratory unit is considered to be an effective replication of an industrial D&I beverage can spray unit. The applied coating is cured at 188 °C to 199 °C (measured at the can dome) for 55 seconds using a laboratory scale D&I can oven commercially available from Ross Co.

[0178] 4. Spray Test on the Inner Side of Food Cans

[0181] To facilitate spray application of the disclosed coating composition inside commercially available preformed tin D&I cans, the viscosity of each coating is reduced such that the flow rate of each coating through a Ford viscosity cup (#2 orifice) is in the range of 20 to 80 seconds. This viscosity measurement is performed at a temperature of 25 °C using a clean and filtered sample of the coating composition. The test cans have a height of 0.113 m, a diameter of 0.076 m, and 0.032 m 2It has a trading display of "300×407" corresponding to the internal area. The cans to be tested include the conventional sidewall beading portion that imparts improved pressure collapse resistance to the cans. Additionally, each can may be flanged, which enables effective seaming and closing of cans having commercially available food can ends with an appropriate 300 diameter. The coating composition is spray-applied at 250 - 375 milligrams (dry weight) per can coating weight using a laboratory-scale D&I spray unit commercially available from H.L.Fisher Co. This laboratory unit is considered to be an effective replica of an industrial D&I food can spray unit. The applied coating is cured at 208°C - 218°C (measured in the can) for 2 minutes using a laboratory-scale D&I can oven commercially available from Ross Co.

[0179] 5. Initial Metal Exposure

[0182] This test method, sometimes called the "enamel tester test", evaluates the coverage and integrity of the dry coating on the inner surface of the can by measuring the flow of current through the can and the electrolyte. The can is filled with the electrolyte and the electrodes are submerged in this solution. A constant voltage is applied and the resulting current is measured in milliamperes. The voltage level, exposure time, and electrolyte solution can all be varied as needed and may vary depending on factors including the packaging facility or the packaging end use. In a typical procedure, the internal "inside spray" coating is applied using high-pressure airless spray with a minimum dry film weight of 1.6 grams per square meter (gsm) for beer cans, 2.3 gsm for soda cans, 3.4 gsm for cans intended for packaging "difficult-to-hold" beverage products such as sports drinks, energy drinks, wine, mixers, or cocktails, and 5.4 gsm for tinplate food cans with an inside spray coating.

[0180]

[0183] The coated can is filled with an electrolyte solution at room temperature containing 1 wt% sodium chloride in deionized water, and an electrical probe is attached to the uncoated conductive portion on the outer surface of the can. A second probe is submerged in the center of the electrolyte solution inside the can. A constant voltage of 6.3 VDC is applied continuously for 4 seconds, and the average current is measured in milliamperes using a WACO Enamel Rater II supplied by the Wilkens-Anderson Company or a similar tester. If there are uncoated metal portions on the inner surface of the can, current will flow between these two probes and be displayed by the tester. The observed current is directly proportional to the amount of metal not effectively covered by the coating. The goal is to achieve 100% coating coverage on the inner surface of the can, which will result in a metal exposure value of 0 mA. Preferred coatings give a metal exposure value 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 2 mA on average.

[0181] 6. Metal Exposure after Drop Impact

[0184] Drop impact resistance measures the ability of a coated container to resist cracking after being subjected to conditions that simulate the dropping of a filled can, and can be used for both beverage and food containers. The presence of cracks is measured by the passage of current through the electrolyte solution, as already described in the section on initial metal exposure. The coated container is filled with an electrolyte solution (1% NaCl in deionized water), and the initial metal exposure is recorded. The electrolyte solution is removed, and then the can is filled with tap water at room temperature. For "inside spray" beverage or food cans, the film weight described in the initial metal exposure test can be used.

[0182]

[0185] A water-filled can without a "top" end is dropped, bottom down, through a cylindrical tube having an inner diameter of 2 and 7 / 8 inches (7.3 centimeters) onto an impact wedge (e.g., a beveled plate at an angle of 33 degrees upward). A dent is formed in the edge region where the bottom end of the can contacts the side wall (typically referred to as the "chime" of a beverage can). Position the impact wedge relative to the tube so that a dent is formed in the chime region. Drop the water-filled can through the tube from a height of 24 inches (61 centimeters) (measured between the bottom of the can and the impact point on the impact wedge) onto the beveled plate to create a dent in the chime region. Then rotate the can 180 degrees and repeat the process. As the bottom end of the can contacts the side wall, a dent is formed in the edge region (typically referred to as the "chime" of a beverage can). Position the impact wedge relative to the tube so that a dent is formed in the chime region. Drop the water-filled can through the tube from a height of 24 inches (61 centimeters) (measured between the bottom of the can and the impact point on the impact wedge) onto the beveled plate to create a dent in the chime region. Then rotate the can 180 degrees and repeat the process.

[0183]

[0186] Then, remove the water from the can and measure the metal exposure again as described above. If there is no damage, no change in current (mA) will be observed relative to the initial metal exposure value. Typically, the average of tests on 6 or 12 containers is recorded. Report the metal exposure results before and after dropping as absolute values. The lower the milliampere value, the better the coating's resistance to drop damage. A preferred coating gives a metal exposure value after drop damage of less than 10 mA, a more preferred value is less than 3.5 mA, an even more preferred value is less than 2.5 mA, and an optimum value is less than 1.5 mA.

[0184]

[0187] Drop damage is often reported as the "delta" or "Δ" mA value, which is the difference between the measured current flow after the drop damage test ("metal exposure") and the initial measured current flow before the drop damage (measured using the initial metal exposure test above). Little or no change in the measured current flow (e.g., <1 mA) indicates that the coating has good flexibility for the end use. In the Examples section below, the drop damage Δ values reported in Tables 3 and 4 were performed using standard 12 ounce (355 mL) 211 diameter aluminum beverage cans with an inner spray coating dry film weight of 4.0 gsm (corresponding to 115 mg / can).

[0185] 7. Necking Test

[0188] This test measures the flexibility and adhesion of the film after the following commercial necking process. Necking is performed to facilitate the application of the container end that enables sealing of the container and is commonly performed on beverage cans. The test involves applying a coating to the container at the recommended film thickness and subjecting the container to the recommended firing (see the specifications for the cans, coating, and firing for items 2 - 4 above). Before the necking process, the sample cans typically have a metal exposure value of <1.0 mA (average of 12 cans) when evaluated using the electrolyte solution as described above. After the necking process, the cans should not show an increase in metal exposure compared to the average of 12 non - necked cans. An elevated mA value indicates a tear in the film that constitutes film breakage.

[0186] 8. Adhesion

[0189] An adhesion test is performed to evaluate whether the coating adheres to the substrate being coated. The adhesion test was performed in accordance with ASTM D 3359 - Test Method B using SCOTCH 610 tape available from 3M Company (Saint Paul, Minn). Generally, adhesion is scored on a scale of 0 - 10, where a score of "10" indicates no adhesion failure (best), a score of "9" indicates that 90% of the coating remains adhered, a score of "8" indicates that 80% of the coating remains adhered, and so on. For commercially viable coatings, typically an adhesion score of 10 is desirable.

[0187] 9. Resistance to Whitening

[0190] Alkali resistance measures the ability of a coating to resist attack by various solutions. Typically, alkali is measured by the amount of solution (e.g., water) absorbed by the coated film. When the film absorbs water, it generally becomes cloudy or appears white. Alkali is generally measured visually using a scale of 0 - 10, where a rating of "10" indicates no alkali (best), and a rating of "0" indicates that the film is completely white (worst). For commercially viable coatings, typically, an alkali rating of 7 or higher is desirable, with 9 - 10 being optimal.

[0188] 10. Corrosion Resistance

[0191] These tests measure the ability of a coating to resist attack by solutions of different levels of aggressiveness. Briefly, a given coating is exposed to specific solutions as described below, and then adhesion and alkali resistance are also measured as described respectively below. For each test, the results are given on a scale of 0 - 10 based on adhesion resistance, alkali resistance, or alkali adhesion resistance, with a rating of "10" being the best and a rating of "0" being the worst.

[0189] A. Deionized water

[0192] Heat deionized water to 82 °C. Immerse the coated panel in the heated solution for 30 minutes, then remove, rinse, and dry. Then, evaluate the sample for adhesion and alkali as already described.

[0190] B. Acetic acid solution

[0193] Prepare a 3% deionized aqueous solution of acetic acid (C2H4O2) and heat to 100 °C. Immerse the coated panel in the heated solution for 30 minutes, then remove, rinse, and dry. Then, evaluate the sample for adhesion and alkali as already described.

[0191] C. Citric acid solution

[0194] Prepare a 2% deionized aqueous solution of citric acid (C6H8O7) and heat it while subjecting it to a pressure sufficient for the solution temperature to reach 121°C. Immerse the coated panel in the heated solution for 30 minutes, then remove it, rinse it, and dry it. Then, evaluate the sample for adhesiveness and whitening as previously described.

[0192] 11. Low-Temperature Sterilization

[0195] The pasteurization test determines how well the coating withstands the processing conditions of various types of food products packaged in containers. Typically, the coated substrate is immersed in a water bath and heated at a temperature in the range of 65°C to 100°C for 5 to 60 minutes. For this evaluation, the coated substrate was immersed either in a deionized water bath at 85°C for 45 minutes or in a 3% acetic acid (C2H4O2) solution in deionized water at 100°C for 30 minutes. Then, the coated substrate is removed from the bath and tested for coating adhesion and whitening as described above. A commercially viable coating preferably provides adequate pasteurization resistance with complete adhesiveness (score 10) and a whitening score of 5 or more, optimally 9 - 10.

[0193] 12. Glass Transition Temperature ("Tg")

[0196] Samples for DSC testing may be prepared by first applying the liquid resin composition onto an aluminum sheet panel. Then, the panel is fired in a Fisher ISOTEMP electric oven at 300°F (149°C) for 20 minutes to remove volatile substances. After cooling to room temperature, the sample is scraped from the panel, weighed, placed into a standard sample pan, and analyzed via DSC using a standard heating / cooling / heating method. The sample is equilibrated at -60°C, then heated to 200°C at 20°C per minute, cooled to -60°C, and then heated again to 200°C at 20°C per minute. Calculate the glass transition from the thermogram of the last heating cycle. Measure the glass transition at the inflection point of the transition.

[0194] 13. Flavor Scalping

[0197] Flavor scalping can be evaluated as described in International Publication No. WO 2018 / 013766 (A1) entitled "Latex Coating Composition Having Reduced Flavor Scalping Properties". The amount of each aldehyde lost from the test solution during storage is measured and calculated as a percentage of the original concentration. Flavor scalping is reported as the % of aldehyde lost relative to the current industry standard coating formulation, and a higher reported percentage value is preferred over a lower percentage value.

[0195] 14. Global Extraction

[0198] The global extraction test is designed to estimate the total amount of free substances that can potentially migrate out of the coating and into the food packaged inside the coated can. Typically, the coated substrate is exposed to water or a solvent blend under various conditions to simulate a given end use. Acceptable extraction conditions and media can be found in 21 CFR 175.300(d) and (e). The acceptable global extraction limit as defined by FDA regulations is 50 parts per million (ppm). The extraction procedure used in the present invention is described in 21 CFR 175.300(e)(4)(xv) and has been modified to (1) increase the alcohol (ethanol) content to 10 wt% and (2) hold the filled container at 37.8 °C (100 °F) for a 10-day equilibration period to ensure worst-case performance. These conditions are in accordance with the FDA publication "Guidelines for Industry" regarding the preparation of Food Contact Notifications.

[0196]

[0199] The coated beverage cans were filled with a 10 wt% aqueous ethanol solution, exposed to pasteurization conditions (65.6 °C, 150 °F) for 2 hours, and then subjected to an equilibration period of 10 days at 37.8 °C (100 °F). The amount of extractives was determined according to the description in 21 CFR 175.300(e)(5), and the ppm value was calculated based on a surface area of 44 square inches excluding the ends of the cans, having a volume of 355 milliliters. The global extraction results for the preferred coating are less than 50 ppm, more preferred results are less than 10 ppm, and even more preferred results are less than 1 ppm. Most preferably, the global extraction results are optimally undetectable.

[0197]

[0200] that has been previously used as a packaging coating on a food or beverage container In materials that are not intended for food and beverage packaging (e.g., construction or industrial coating materials), it may be difficult to measure global extraction using the above procedure because the coating material may not have been previously applied at the low coating weights and low viscosities typically required for food and beverage packaging coatings. Also, the coating material may not have been previously thermoset using the oven curing procedures typically used for food and beverage coatings. In such cases, instead, the material is applied to a beverage can as described above, using the coating weights and viscosities disclosed or recommended for its existing use (e.g., its construction or industrial use), and then the coating is dried or otherwise hardened as disclosed or recommended for its existing use, and then, within 1 hour after the material reaches a tack-free state, the dried coating is subjected to the above-described 21 CFR 175.300(e)(4)(xv) extraction procedure with the above-described worst-case modifications to evaluate the material. For example, in a latex wall paint containing a multistage latex, it may be necessary to determine global extraction by applying the paint using the spray application procedure and viscosity recommended by the paint manufacturer, air-drying the applied coating, and then performing the extraction procedure within 1 hour after the coating reaches a tack-free state. Wall paints and other industrial coatings applied, dried, and evaluated in this manner may exceed the described 50 ppm global extraction limit due to incomplete curing and the presence of extractable species such as co-solvents, low molecular weight surfactants, coalescing agents, and other coating material adjuvants.

Example

[0198]

[0201] The present disclosure is specifically described by the following examples, which are intended to be illustrative only, because many modifications and variations within the scope of the present disclosure will become apparent to those skilled in the art. Unless otherwise indicated, all parts and percentages are by weight. The data included in the following tables were generated using the above test methods, unless otherwise stated.

[0199] Example 1 (Example): Preformed Acrylic A

[0202] A monomer premix of 197.35 parts of ice methacrylic acid (MAA), 59.28 of n-butyl methacrylate (BMA), 88.88 parts of ethyl methacrylate (EMA), 44.45 parts of ethyl acrylate (EA), 113.36 parts of butanol, and 12.63 parts of deionized (“DI”) water was prepared in a separate container. An initiator premix of 18.54 parts of LUPEROX 26 initiator and 41.63 parts of n-butanol (“butanol”) was prepared. The reactor was equipped with a stirrer, a reflux condenser, and a thermocouple and could be heated and cooled and blanketed or sparged with an inert gas or nitrogen. 141.39 parts of butanol and 6.94 parts of deionized water were added to the reactor. While stirring, the contents were heated to 97 °C with the vessel blanketed with an inert gas. Once this temperature was reached, 1.03 parts of LUPEROX 26 initiator was added and the batch was held for 5 minutes. After 5 minutes, while maintaining the reactants at 97 °C to 100 °C, the monomer premix and the remaining initiator premix were added to the vessel over a 2-hour period. When the addition was complete, the monomer premix vessel was rinsed into the reactor using 18.06 parts of butanol and the initiator premix vessel was rinsed into the reactor using 6.03 parts of butanol. After holding the batch at 98 °C to 99 °C for 30 minutes, 1.85 parts of LUPEROX 26 initiator was added and rinsed with 1.86 parts of butanol. After holding the batch at 98 °C for 60 minutes, a second addition of 1.85 parts of LUPEROX 26 was added and rinsed with 1.86 parts of butanol. The batch was held at 98 °C to 100 °C for 2 hours. After the 2-hour hold, 235.78 parts of butyl cellosolve and 7.26 parts of deionized water were added and the contents of the reactor were cooled and then removed from the reactor. The resulting acrylic prepolymer gave a polymer having a monomer ratio (parts by weight) of methacrylic acid / butyl methacrylate / ethyl methacrylate / ethyl acrylate of 50.6 / 15.2 / 22.8 / 11.4 and a Fox equation calculated Tg of 90 °C. Butanol to butyl cellosolve The rosolv ratio was ~58 / 42 by weight. The solids content was ~40.3% with an acid value of ~312 mg KOH / g resin and a viscosity of 7700 centipoise.

[0200] Example 2 (Example): Preformed Acrylic B

[0203] Using the process described above for Example 1, a second preformed acrylic was prepared using a monomer weight ratio of methacrylic acid / butyl methacrylate / methyl methacrylate (MMA) / ethyl acrylate of 60 / 15 / 10 / 15 and a Fox equation calculated Tg of 100 °C. The butanol to butyl cellosolve ratio was adjusted to ~76 / 24 by weight. The solids content was ~38.6% with an acid value of ~384 mg KOH / g resin and a viscosity of 28,000 centipoise.

[0201] Example 3 (Example): Aqueous Polyether-Acrylate Copolymer Dispersion

[0204] To a reactor equipped with a stirrer, a reflux condenser, and a thermocouple that can be heated and cooled and blanketed or sparged with an inert gas or nitrogen and vacuum, 1204.12 parts of diglycidyl ether of tetramethylbisphenol F, 295.1 parts of hydroquinone, 0.71 part of ethyltriphenylphosphonium iodide, 35.23 parts of carbitol, and 131.36 parts of butyl cellosolve were added. (A suitable preparation of diglycidyl ether of tetramethylbisphenol F is described, for example, in International Publication No. 2017079437 (A1).) While stirring, the contents were heated to 155 °C with the vessel blanketed with an inert gas. When a vacuum was applied to cause reflux to control the peak temperature to a maximum of 194 °C, the system exothermed to 181 °C. When the peak temperature was reached, a 30-minute hold was started, the temperature was decreased, and the pressure was returned to atmospheric pressure. After the 30-minute hold, 0.08 part of ethyltriphenylphosphonium iodide was added. Samples were taken every 30 minutes until an epoxy value of 0.039 equivalents per 100 grams of solid resin was achieved 1 hour after the peak temperature. At the desired epoxy value, 144.15 parts of butyl cellosolve and 64.15 parts of hexyl cellosolve were added and the temperature was decreased. Then, 1617.58 parts of the preformed acrylic A of Example 1 was added. After adding, the material was rinsed with 92.98 parts of butyl cellosolve. The contents were mixed for 30 minutes while adjusting the temperature to 99 °C. After 30 minutes, 194.43 parts of deionized water was added and the temperature was adjusted to 93 °C. At this temperature, 142.87 parts of dimethylethanolamine (“DMEOA”) was added over 5 minutes. Then, the batch was held at 96 °C to 101 °C for 1 hour. At the end of this time, all external heat was turned off, the stirring was increased, and 1982.62 parts of deionized water was added uniformly over 50 minutes. After adding the water, another 2768.62 parts of deionized water was added over 30 minutes. After all the water was added, the batch was held for 30 minutes to ensure uniformity. Thereby, an aqueous dispersion of a polyether-acrylate copolymer having a solids content of 23.9%, an acid value of 88.7 mgKOH / g resin, a pH of 6.52, a particle size of 0.17 micrometers, and a #4 Ford viscosity of 35 seconds was produced.

[0202] Example 4 (Example): Alternative Aqueous Polyether-Acrylate Copolymer Dispersion

[0205] Added 1202.92 parts of diglycidyl ether of tetramethylbisphenol F, 289.64 parts of hydroquinone, 0.71 part of ethyltriphenylphosphonium iodide, and 165.84 parts of butyl cellosolve to a reactor equipped with a stirrer, a reflux condenser, and a thermocouple that can be heated and cooled and blanketed or sparged with an inert gas or nitrogen and vacuum that can be applied. While stirring, the contents were heated to 145 °C with the vessel blanketed with an inert gas. The system was exothermed to 184 °C. When the peak temperature was reached, holding for 30 minutes was started and the temperature was decreased. After holding for 30 minutes, 0.08 part of ethyltriphenylphosphonium iodide was added. Samples were taken every 30 minutes until an epoxy value of 0.039 equivalents per 100 grams of solid resin was achieved 1 hour after the peak temperature. At the desired epoxy value, 2 Added 36.04 parts of butyl cellosolve and 63.9 parts of hexyl cellosolve and decreased the temperature. Then, 1964.03 parts of the preformed acrylic B of Example 2 was added. The contents were mixed for 15 minutes, then 121.25 parts of deionized water was added. The batch was mixed for an additional 5 minutes, then 174.25 parts of dimethylethanolamine was added over 5 minutes. Then, the batch was held at 98 °C to 101 °C for 90 minutes. At the end of the 90-minute hold, all external heat was turned off, stirring was increased, and 1973.91 parts of deionized water was added uniformly over 50 minutes. After adding the water, another 3807.40 parts of deionized water was added over about 40 minutes. After all the water was added, the batch was held for 30 minutes to ensure uniformity. Thereby, an aqueous dispersion having a solid content of 23.1%, a resin acid value of 113.6 mgKOH g, a pH of 6.52, and a viscosity of ~9100 centipoises was produced.

[0203] Example 5 (Comparative Example): Aqueous Polyether-Acrylate Copolymer Dispersion with a One-Stage Emulsion Polymerization Extension Part

[0206] The contents of the reactor of Example 3 were heated to 85°C. At this temperature, 373.9 parts of butyl methacrylate, 467.79 parts of ethyl methacrylate, and 93.34 parts of butyl acrylate were added over ~60 minutes. The monomers used were butyl methacrylate / ethyl methacrylate / butyl acrylate with a weight ratio of 40 / 50 / 10 and having a Fox equation calculated Tg of 30°C. When the addition of the monomers was complete, the residual monomer mixture was rinsed into the reactor with 345.56 parts of deionized water. With the contents of the reactor at 82°C, 7.33 parts of benzoin and 7.33 parts of 34% hydrogen peroxide were added and rinsed into the reactor with 7.59 parts of deionized water. The batch was held for 2 hours and the temperature was raised to 88°C. After these 2 hours, 2.0 parts of benzoin and 2.0 parts of 34% hydrogen peroxide were added and rinsed into the reactor with 7.59 parts of deionized water. The batch was held for 1 hour, after which 2.0 parts of benzoin and 2.0 parts of 34% hydrogen peroxide were added and rinsed into the reactor with 7.59 parts of deionized water. The batch was held at this temperature for 1 hour and then cooled. This produced an aqueous dispersion with 30.8% solids, an acid value of 63.0, a pH of 6.42, an average particle size of 0.21 micrometers, and a #4 Ford viscosity of 73 seconds.

[0204] Example 6 (Example): Aqueous Polyether-Acrylate Copolymer Dispersion with a Multi-Stage Emulsion Polymerization Extension Part for Reduced Polyether Content

[0207] To a reactor equipped with a stirrer, a reflux condenser, and a thermocouple that can be heated and cooled and blanketed or sparged with an inert gas or nitrogen, 714.34 parts of Example 5 and 189.04 parts of deionized water were added. While stirring, the substance was heated to 75 °C to 82 °C with the vessel blanketed with an inert gas. At this temperature, 8.78 parts of butyl methacrylate, 74.43 parts of ethyl methacrylate, and 4.35 parts of butyl acrylate were added. This was a monomer blend of butyl methacrylate / ethyl methacrylate / butyl acrylate with a weight ratio of 10 / 85 / 5 and having a Fox equation calculated Tg of 51 °C. When the addition of the monomers was complete, the residual monomer mixture was rinsed into the reactor with 4.52 parts of deionized water. With the contents of the reactor at 82 °C, 0.73 part of benzoin and 0.73 part of 34% hydrogen peroxide were added and rinsed into the reactor with 0.76 part of deionized water. The batch was held for 2 hours and the temperature was raised to 85 °C. After these 2 hours, 0.20 part of benzoin and 0.20 part of 34% hydrogen peroxide were added and rinsed into the reactor with 0.76 part of deionized water. The batch was held for 1 hour, then 0.20 part of benzoin and 0.20 part of 34% hydrogen peroxide were added and rinsed into the reactor with 0.76 part of deionized water. The batch was held at this temperature for 1 hour and then cooled. This produced an aqueous dispersion having a solids content of 30.7%, an acid value of 43.2, a pH of 6.48, an average particle size of 0.22 micrometers, and a #4 Ford viscosity of 21 seconds.

[0205] Examples 7 - 9 (Examples): Additional Multi-Stage Latex-Containing Resin Systems

[0208] Using the method described in Example 6, three additional resin-based examples (i.e., Examples 7-9) were prepared. Similar to Example 6, the resin systems of Examples 7-9 were prepared by emulsion polymerizing the high Tg stage ("Stage 2") in the presence of the single-stage latex of Comparative Example 5 to obtain a resin system containing a multi-stage latex. Table 1 below compares these systems and Example 6 against Comparative Example 5, which includes only a single emulsion polymerization stage and a higher polyether concentration. Unless otherwise noted, all amounts in Table 1 are in parts by weight. The weight contributions of the polyether polymer portion and the acrylic polymer portion present in the aqueous polyether-acrylate copolymer dispersion used to make a particular latex are shown separately as "Total % of Polyether" and "% of Preformed Acrylic". The respective weight contributions of the first emulsion polymerization stage and the second emulsion polymerization stage are referred to as "% of Stage 1" and "% of Stage 2", respectively. The total percent of polymerized ethylenically unsaturated monomers (i.e., the contribution from the preformed acrylic and the single-stage or multi-stage latex) is reported as "Total % of Acrylic". In Examples 6-9, Stage 1 corresponds to the low Tg emulsion polymerization stage and Stage 2 corresponds to the high Tg emulsion polymerization stage, and the low Tg stage was emulsion polymerized prior to the high Tg stage.

[0206]

Table 1

[0207] Examples 10 - 19 (Resin System Examples): Additional Multi-Stage Latex-Containing Resin Systems

[0209] The respective resin systems of Examples 10-19 were produced using the following process. The amounts shown are those used to produce Example 13. The respective amounts of the components used in the remaining Examples 10-12 and 14-19 are shown in Table 2 below along with the amounts of Example 13. As shown in Table 2, adjustments were made for the various examples to provide different monomer ratios, different polymer Tgs, and different Stage 2 to Stage 1 ratios.

[0208]

[0210] A reactor equipped with a stirrer, a reflux condenser, and a thermocouple that can be heated and cooled and blanketed or sparged with an inert gas or nitrogen, 39 9.5 parts of Example 4 copolymer and 114.0 parts of deionized water were added. While stirring, the mixture was heated to 81 °C with the container blanketed with an inert gas. At this temperature, 16.25 parts of butyl methacrylate, 16.25 parts of butyl acrylate, and 9.0 parts of methyl methacrylate were added. This is a monomer blend of butyl methacrylate / butyl acrylate / methyl methacrylate with a weight ratio of 39 / 39 / 22 and having a Fox equation calculated Tg of -2 °C. When the addition of the monomers was complete, the residual monomer mixture was rinsed into the reactor with 31.25 parts of deionized water. With the contents of the reactor at 82 °C, 0.75 part of benzoin was rinsed into the reactor with 35.0 parts of deionized water. The batch was heated to 82 °C and 0.75 part of 34% hydrogen peroxide was added. The batch was held for 1 hour and the temperature was raised to 88 °C. After 1 hour of holding, the conversion of the monomers to polymer was determined to be 93%. After an additional 1 hour of holding, a sample was taken and 75 parts of deionized water was added to the reactor. The sample was determined to have 95% of the monomers converted to polymer. The batch was heated to 82 °C and a monomer blend of 11.87 parts of butyl methacrylate, 5.87 parts of butyl acrylate, and 100.75 parts of methyl methacrylate was added. This blend has a ratio of butyl methacrylate / butyl acrylate / methyl methacrylate of 10 / 5 / 85 and a Fox equation calculated Tg of 82 °C. When the addition of the monomers was complete, the residual monomer mixture was rinsed into the reactor with 81.25 parts of deionized water. Then 0.87 part of benzoin and 0.87 part of 34% hydrogen peroxide were added and rinsed into the reactor with 37.0 parts of deionized water. The batch was held for 1 hour, after which 0.12 part of benzoin and 0.12 part of 34% hydrogen peroxide were added and rinsed into the reactor with 7.37 parts of deionized water. The batch was held at this temperature for 90 minutes. Then 0.12 part of benzoin and 0.12 part of 34% hydrogen peroxide were added and rinsed into the reactor with 7.37 parts of deionized water. The batch was held for 2 hours and then cooled. Thereby, a substance was obtained with a solid content of 30.0%, an acid value of 35.8 mg KOH / g resin, and an average particle size of 0.34 microns.

[0209]

[0211] The following Table 2 compares the resin-based compositions of Examples 10 to 19. Unless otherwise specified, all amounts in Table 2 are in parts by weight. In Table 2, the weight contributions of the polyether polymer portion and the acrylic polymer portion are shown using the same nomenclature as used in Table 1. In Examples 10 to 19, Stage 1 corresponds to the low Tg emulsion polymerization stage, Stage 2 corresponds to the high Tg emulsion polymerization stage, and the low Tg stage was emulsion polymerized prior to the high Tg stage.

[0210]

Table 2

[0211] Finishing Examples 6 - 9: Inner Spray Coating Composition

[0212] Inner spray beverage can coating compositions were formulated using the respective resin systems of Comparative Example 5 and Examples 6 to 9. The resulting inner spray coating compositions are shown in Table 3 below as "Finishes" Examples 6 to 9, and specific coating performance characteristics are reported compared to the inner spray coating composition made using Comparative Example 5. The specific finish example numbers correspond to the indicated resin systems incorporated into the inner spray coating composition.

[0212]

Table 3

[0213]

[0213] In Comparative Finish Example 5, two Tg values were observed, with the 44 °C value due to the one-stage latex and the 106 °C value due to the polyether-acrylate copolymer dispersion.

[0214] As shown in Table 3, the inner spray beverage can coating compositions were also formulated using each of the resin systems of Examples 10-19. The resulting inner spray coating compositions are shown in Table 4 below as "finishes" Examples 10-19, and certain coating performance characteristics are reported. The specific finish example numbers correspond to the indicated resin systems incorporated into the inner spray coating compositions.

[0215]

Table 4

[0216]

[0215] As shown by the coating performance data included in Tables 3 and 4, the use of multistage latex enabled a substantial reduction in the polyether polymer concentration, along with an increase in the corresponding acrylic concentration and the maintenance of certain important end-use performance attributes. Those attributes included flexibility, indicated by a small change in the metal exposure value after drop damage, and flavor scalping resistance equivalent to that of the control example (i.e., comparing finish example 13 to control finish example 5, for example). In particular, although the resin system of the control example contained 49 weight percent polyether and 51 weight percent acrylic, while the resin systems of the finish examples contained 20-35 weight percent polyether and 65-80 weight percent acrylic, in some of the finish examples, flexibility comparable to that of the control example was achieved. Surprisingly, good flexibility was also achieved in many finish examples in which the resin system contained as much as 80 weight percent acrylic. This result was important because, as described above, there is typically a trade-off between flexibility and flavor scalping resistance in conventional acrylic systems, particularly acrylics made without the use of styrene.

[0217]

[0216] Similar to those of Examples 10 to 19, additional multi-stage latex systems were also produced that included a small amount of a polyethylenically unsaturated monomer (e.g., 1,4-butanediol dimethacrylate) in one or both of the high Tg stage and the low Tg stage. Inclusion of such a polyethylenically unsaturated monomer was able to improve both the corrosion resistance and the whitening resistance of the inner spray beverage can coating formulated from the resin system, while it was observed that it did not adversely affect either the advantageous drop damage resistance properties or the flavor scalping resistance properties of the coating (data not shown). Such beneficial properties were observed, for example, for resin systems containing from about 2.5 to about 5 weight % of a polyethylenically unsaturated monomer (e.g., 1,4-butanediol dimethacrylate) based on the weight of the polyethylenically unsaturated monomer relative to the total weight of the monomers used to produce all of the emulsion polymerization stages (e.g., the total weight of the monomers used to form the low Tg stage and the high Tg stage).

[0218] Example 20 (Example): Gradient Tg Latex Prepared Using a Low-Molecular-Weight Surfactant

[0217] Add 318.6 parts of deionized water and 9.6 parts of RHODAPON UB (29 - 30% active sodium lauryl sulfate, CAS No. 68585 - 47 - 7, commercially available from Solvay) to a reactor equipped with a stirrer, a reflux condenser, and a thermocouple that can be heated and cooled and blanketed or sparged with an inert gas or nitrogen. While stirring, heat the mixture to 80 °C with the container blanketed with an inert gas. In a separate container, prepare a mixture of 52.8 parts of deionized water, 4.2 parts of RHODAPON UB, 119.4 parts of butyl methacrylate, 29.9 parts of butyl acrylate, 14.9 parts of methyl methacrylate, and 1.7 parts of methacrylic acid. The monomers used are butyl methacrylate / butyl acrylate / methyl methacrylate / methacrylic acid with a weight ratio of 72 / 18 / 9 / 1, which has a Fox - calculated Tg of 9.6 °C. This mixture represents polymerizable monomer pre - emulsion 1 (ME - 1). In a second container, prepare a mixture of 71.3 parts of deionized water, 5.4 parts of RHODAPON UB, 21.7 parts of butyl methacrylate, 10.9 parts of butyl acrylate, 171.6 parts of methyl methacrylate, 19.7 parts of 2 - hydroxyethyl methacrylate (HEMA), and 2.2 parts of methacrylic acid. The monomers used are butyl methacrylate / butyl acrylate / methyl methacrylate / HEMA / methacrylic acid with a weight ratio of 10 / 5 / 75.2 / 8.8 / 1, which has a Fox - calculated Tg of 78.0 °C. This mixture represents polymerizable monomer pre - emulsion 2 (ME - 2), and its HEMA content facilitates film cross - linking using a suitable cross - linking agent (e.g., a phenol resin or a melamine resin). When the reactor temperature reaches 80 °C, add 1.9 parts of ammonium persulfate dissolved in 50 parts of deionized water. After holding for 5 minutes, supply ME - 1 directly into the reactor over 240 minutes. At the same time, supply ME - 2 into the ME - 1 container over 225 minutes. After 240 minutes, rinse the remaining contents of the ME - 1 and ME - 2 containers into the reactor using 40 parts of deionized water. Hold the batch for an additional 30 minutes while cooling to about 70 °C.Once the batch temperature reaches about 70 °C, add a solution of 0.95 parts of tert-butyl hydroperoxide in 25 parts of deionized water, and then immediately follow with a solution of 0.43 parts of erythorbic acid dissolved in 25 parts of deionized water. Hold the batch at this temperature for 30 minutes and then cool. Once the batch has cooled to ≤ 40 °C, add sufficient dimethylaminoethanol to raise the pH to about 8.0. Filter the latex through a 100 micrometer filter bag. The resulting gradient Tg latex should contain about 40% solids and have a pH of about 8.

[0219] Example 21 (Example): Gradient Tg Latex Prepared Using a Low-Molecular-Weight Surfactant

[0218] Add 318.0 parts of deionized water and 10.0 parts of RHODAPON UB to a reactor equipped with a stirrer, reflux condenser, and thermocouple that can be heated and cooled and blanketed or sparged with an inert gas or nitrogen. While stirring, heat the mixture to 80 °C with the vessel blanketed with an inert gas. In a separate container, prepare a mixture of 55.2 parts of deionized water, 4.3 parts of RHODAPON UB, 125.0 parts of butyl methacrylate, 31.3 parts of butyl acrylate, 11.9 parts of methyl methacrylate, 3.9 parts of HEMA, and 1.7 parts of methacrylic acid. The monomers used are butyl methacrylate / butyl acrylate / methyl methacrylate / HEMA / methacrylic acid in a weight ratio of 72 / 18 / 6.8 / 2.2 / 1, which has a Fox equation calculated Tg of 8.9 °C. This mixture represents polymerizable monomer pre-emulsion 1 (ME-1). In a second container, prepare a mixture of 72.2 parts of deionized water, 5.7 parts of RHODAPON UB, 22.4 parts of butyl methacrylate, 11.4 parts of butyl acrylate, 185.6 parts of methyl methacrylate, 6.6 parts of HEMA, and 2.3 parts of methacrylic acid. The monomers used are butyl methacrylate / butyl acrylate / methyl methacrylate / HEMA / methacrylic acid in a weight ratio of 10 / 5 / 81.2 / 2.8 / 1, which has a Fox equation calculated Tg of 81.0 °C. This mixture is the polymerizable monomer pre- Represents Emulsion 2 (ME-2). When the reactor temperature reaches 80 °C, 2.0 parts of ammonium persulfate dissolved in 50 parts of deionized water are added. After holding for 5 minutes, ME-1 is fed directly into the reactor over 240 minutes. At the same time, ME-2 is fed into the ME-1 vessel over 225 minutes. After 240 minutes, 40 parts of deionized water are used to rinse the remaining contents of the ME-1 and ME-2 vessels into the reactor. The batch is held for an additional 30 minutes while cooling to approximately 70 °C. When the batch temperature reaches approximately 70 °C, a solution of 0.97 parts of tert-butyl hydroperoxide in 25 parts of deionized water is added, followed immediately by a solution of 0.44 parts of erythorbic acid dissolved in 25 parts of deionized water. The batch is held at this temperature for 30 minutes and then cooled. When the batch has cooled to ≤ 40 °C, sufficient dimethylethanolamine is added to raise the pH to approximately 8.0. The latex is filtered through a 100 micrometer filter bag. The resulting gradient Tg latex should contain approximately 40% solids and have a pH of approximately 8.

[0220] Example 22 (Example): Gradient Tg Latex Prepared Using a Water-Dispersible Polymer Surfactant

[0219] Into a reactor equipped with a stirrer, a reflux condenser, and a thermocouple, which can be heated and cooled and blanketed or sparged with an inert gas or nitrogen, 399.5 parts of the copolymer of Example 4 and 220.3 parts of deionized water are added. While stirring, the mixture is heated to 82 °C with the vessel blanketed with an inert gas. In a separate vessel, a mixture of 65.15 parts of butyl methacrylate, 16.29 parts of butyl acrylate, 9.05 parts of methyl methacrylate, and 0.75 part of benzoin is prepared. The monomers used are butyl methacrylate / butyl acrylate / methyl methacrylate in a weight ratio of 72 / 18 / 10, which has a Fox equation calculated Tg of 9 °C. This mixture represents the stage 1 polymerizable monomer. In another separate vessel, an initiator solution is prepared by mixing 1.62 parts of 34% hydrogen peroxide and 72 parts of deionized water. In yet another separate vessel, a mixture of 11.87 parts of butyl methacrylate, 5.87 parts of butyl acrylate, 100.75 parts of methyl methacrylate, and 0.87 part of benzoin is prepared. The monomers used are butyl methacrylate / butyl acrylate / methyl methacrylate in a weight ratio of 10 / 5 / 85, which has a Fox equation calculated Tg of 82 °C. This mixture represents the stage 2 polymerizable monomer. When the reactor temperature reaches 81 °C, the stage 1 monomer mixture and the initiator solution are separately fed into the reactor over 240 minutes. At the same time, the stage 2 monomer mixture is fed into the stage 1 monomer mixture over 225 minutes. After 240 minutes, 81.25 parts of deionized water are used to rinse both the stage 1 and 2 monomer mixture vessels into the reactor. With the contents of the reactor at 82 °C, 0.12 part of benzoin and 0.12 part of 34% hydrogen peroxide are added and rinsed into the reactor with 7.37 parts of deionized water. The batch is held for 30 minutes to allow exotherm. After 30 minutes, 0.12 part of benzoin and 0.12 part of 34% hydrogen peroxide are added and rinsed into the reactor with 7.37 parts of deionized water. The batch is held at this temperature for 1 hour and then cooled. The resulting gradient Tg latex should contain about 30% solids, have an acid value of about 36 mg KOH / g, and an average particle size of 0.3 micrometers.

[0221]

[0220] The present invention is further disclosed in the following embodiments.

[0221] 1. An aqueous coating composition comprising a multi-stage polymer latex having two or more emulsion polymerization stages, wherein the latex has (i) a low Tg emulsion polymerization stage having a calculated Tg that is at least 20°C, at least 30°C, at least 35°C, at least 40°C, at least 50°C, at least 60°C, or at least 70°C lower than the calculated Tg of the high Tg emulsion polymerization stage, or (ii) a gradient Tg, or both, provided that when the latex has (i), more than 50% by weight of the emulsion polymerization stage preferably has a calculated Tg of at least 40°C, at least 50°C, at least 60°C, at least 70°C, or at least 80°C, a multi-stage polymer latex and an aqueous carrier liquid, An aqueous coating composition, wherein the aqueous coating composition is a food or beverage can coating composition.

[0222]

[0222] 2. An aqueous coating composition comprising a resin system comprising a water-dispersible polymer and two or more emulsion polymerization stages of a multi-stage polymer latex, wherein the water-dispersible polymer is incorporated into the multi-stage polymer latex, blended with the multi-stage polymer latex, or both, and the latex has (i) a low Tg emulsion polymerization stage having a calculated Tg that is at least 20°C, at least 30°C, at least 35°C, at least 40°C, at least 50°C, at least 60°C, or at least 70°C lower than the calculated Tg of the high Tg emulsion polymerization stage, or (ii) a gradient Tg, or both, a resin system and an aqueous carrier liquid,

[0223]

[0223] 3. The coating composition according to embodiment 2, wherein the monomers used to form two or more emulsion polymerization stages are emulsion polymerized in the presence of a water-dispersible polymer.

[0224] 4. The coating composition according to Embodiment 2 or 3, wherein the water-dispersible polymer comprises an acrylic polymer, a polyether polymer, a polyolefin polymer, a polyester polymer, a polyurethane polymer, or a mixture or copolymer thereof.

[0224]

[0225] 5. An aqueous coating composition, which is a resin system comprising a multi-stage polymer latex having two or more emulsion polymerization stages, wherein the multi-stage latex is formed by emulsion polymerizing an ethylenically unsaturated monomer in the presence of an aqueous dispersion of a water-dispersible polymer, the latex having (i) a low Tg emulsion polymerization stage having a calculated Tg at least 20 °C, at least 30 °C, at least 35 °C, at least 40 °C, at least 50 °C, at least 60 °C, or at least 70 °C lower than the calculated Tg of the high Tg emulsion polymerization stage, or (ii) a gradient Tg, and a water-dispersible polymer comprising a polyether polymer, and an aqueous carrier liquid, The aqueous coating composition, which is a food or beverage can coating composition.

[0225]

[0226] 6. However, when the latex has (i), more than 50% by weight of the emulsion polymerization stage has a calculated Tg of at least 40 °C, at least 50 °C, at least 60 °C, at least 70 °C, or at least 80 °C. The coating composition according to any one of Embodiments 2 to 5.

[0226]

[0227] 7. An aqueous coating composition, A resin system comprising a multi-stage polymer latex formed by emulsion polymerizing ethylenically unsaturated monomers in two or more stages (e.g., a low Tg stage and a high Tg stage) in the presence of a water-dispersible polymer (e.g., a polyether polymer), wherein the emulsion polymerized ethylenically unsaturated monomers comprise two or more (e.g., 2, 3, 4, or 5) of methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate (e.g., n-butyl acrylate), and butyl methacrylate (e.g., n-butyl methacrylate) and contain at least 80% by weight, an aqueous carrier liquid, An aqueous coating composition, wherein the coating composition is a food or beverage can coating composition.

[0227]

[0228] 8. The coating composition according to any one of Embodiments 2 to 7, wherein the resin system contains at least 60% by weight, at least 65% by weight, at least 70% by weight, at least 75% by weight, or at least 80% by weight of units derived from ethylenically unsaturated monomers based on the combined weight of the water-dispersible polymer and the monomers used to form the emulsion polymerization stage.

[0228]

[0229] 9. The coating composition according to any one of Embodiments 1 to 8, wherein the high Tg emulsion polymerization stage has a calculated Tg above 40°C and the low Tg emulsion polymerization stage has a calculated Tg below 40°C.

[0229]

[0230] 10. The coating composition according to any one of Embodiments 1 to 9, wherein the high Tg emulsion polymerization stage has a calculated Tg above 45°C and the low Tg emulsion polymerization stage has a calculated Tg below 35°C.

[0230]

[0231] 11. The coating composition according to any one of Embodiments 1 to 10, wherein the high Tg emulsion polymerization stage has a calculated Tg above 50°C and the low Tg emulsion polymerization stage has a calculated Tg below 30°C.

[0231]

[0232] 12. The coating composition according to any one of Embodiments 1 to 11, wherein the high-Tg emulsion polymerization stage has a calculated Tg exceeding 60°C and the low-Tg emulsion polymerization stage has a calculated Tg less than 20°C.

[0232]

[0233] 13. The coating composition according to any one of Embodiments 1 to 12, wherein the high-Tg emulsion polymerization stage has a calculated Tg exceeding 70°C and the low-Tg emulsion polymerization stage has a calculated Tg less than 10°C.

[0233]

[0234] 14. The coating composition according to any one of Embodiments 1 to 13, wherein the low-Tg emulsion polymerization stage is emulsion polymerized before the high-Tg emulsion polymerization stage.

[0235] 15. The coating composition according to any one of Embodiments 1 to 13, wherein the low-Tg emulsion polymerization stage is emulsion polymerized after the high-Tg emulsion polymerization stage.

[0234]

[0236] 16. The coating composition according to any one of Embodiments 1 to 15, wherein the weight ratio of the low-Tg emulsion polymerization stage to the high-Tg emulsion polymerization stage is in the range of 5:95 to 95:5, 20:80 to 70:30, or 25:75 to 48:52.

[0235]

[0237] 17. The monomer (and, in some embodiments, the aggregate of monomers used to form two or more emulsion polymerization stages) used to form at least one of the emulsion polymerization stages contains at least 30 wt%, at least 50 wt%, at least 70 wt%, at least 85 wt%, or at least 95 wt% (or even 100 wt%) of one or more (meth)acrylates. The coating composition according to any one of Embodiments 1 to 16.

[0236]

[0238] The monomer (and, in some embodiments, the aggregate of monomers used to form two or more emulsion polymerization stages) used to form at least one of the emulsion polymerization stages comprises at least 30% by weight, at least 50% by weight, at least 70% by weight, at least 85% by weight, or at least 95% by weight (or even 100% by weight) of one or more alkyl (meth)acrylates, according to any one of Embodiments 1 to 17 The coating composition according to any one of claims 1 to 17.

[0237]

[0239] 19. The monomer (and, in some embodiments, the aggregate of monomers used to form two or more emulsion polymerization stages) used to form at least one of the emulsion polymerization stages comprises at least 30% by weight, at least 50% by weight, at least 70% by weight, at least 85% by weight, or at least 95% by weight of one or more alkyl methacrylates, according to any one of Embodiments 1 to 18 of the coating composition.

[0238]

[0240] 20. The monomer (and, in some embodiments, the aggregate of monomers used to form two or more emulsion polymerization stages) used to form at least one of the emulsion polymerization stages comprises at least 30% by weight, at least 35% by weight, at least 40% by weight, at least 45% by weight, or even 80% by weight or more of one or more ethylenically unsaturated monomers having an alicyclic group or a linear or branched hydrocarbon group containing at least 4 carbon atoms, according to any one of Embodiments 1 to 19 of the coating composition.

[0239]

[0241] 21. The coating composition according to any one of Embodiments 1 to 20, wherein the monomer (and, in some embodiments, the aggregate of monomers used to form two or more emulsion polymerization stages) used to form at least one of the emulsion polymerization stages contains at least 4 carbon atoms and has a longest chain length of at least 3 carbon atoms, and contains at least 20% by weight, at least 30% by weight, at least 35% by weight, at least 40% by weight, or even 80% by weight or more of one or more ethylenically unsaturated monomers having a linear or branched hydrocarbon group.

[0240]

[0242] 22. The coating composition according to any one of Embodiments 1 to 21, wherein the monomer (and, in some embodiments, the monomers used to form each of the corresponding two or more emulsion polymerization stages) used to form at least one of the emulsion polymerization stages contains one or more C1-C3 alkyl (meth)acrylates.

[0241]

[0243] 23. The coating composition according to Embodiment 22, wherein the one or more C1-C3 alkyl (meth)acrylates include ethyl methacrylate, methyl methacrylate, or a combination thereof.

[0242]

[0244] 24. The coating composition according to any one of Embodiments 20 to 23, wherein the monomer (and, in some embodiments, the monomers used to form each of the corresponding two or more emulsion polymerization stages) used to form at least one of the emulsion polymerization stages contains one or more ethylenically unsaturated monomers having an alicyclic group or a linear or branched hydrocarbon group containing at least 4 carbon atoms, and one or more C1-C3 alkyl (meth)acrylates.

[0243]

[0245] The coating composition according to any one of Embodiments 1 to 6 or 8 to 24, wherein the monomer (and, in some embodiments, the aggregate of monomers used to form two or more emulsion polymerization stages) used to form at least one of the emulsion polymerization stages contains at least 80% by weight of one or more (e.g., 1, 2, 3, 4, or 5) of methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate (e.g., n-butyl acrylate), and butyl methacrylate (e.g., n-butyl methacrylate).

[0244]

[0246] 26. The monomer used to form at least one of the emulsion polymerization stages (and, in some embodiments, the monomer used to form each of the corresponding two or more emulsion polymerization stages) is the coating composition according to any one of Embodiments 1 to 25, which contains butyl methacrylate, butyl acrylate, or both.

[0245]

[0247] 27. The coating composition according to Embodiment 26, wherein the monomer used to form at least one of the emulsion polymerization stages and, in some embodiments, the monomer used to form each of the corresponding two or more emulsion polymerization stages contains both n-butyl methacrylate and one or both of ethyl methacrylate or methyl methacrylate.

[0246]

[0248] 28. The coating composition according to Embodiment 27, wherein the monomer used to form at least one of the emulsion polymerization stages and, in some embodiments, the monomer used to form each of the corresponding two or more emulsion polymerization stages further contains one or more of ethyl acrylate, methyl acrylate, or n-butyl acrylate.

[0247]

[0249] 29. The coating composition according to any one of Embodiments 1 to 28, wherein the monomer used to form at least one of the emulsion polymerization steps contains a polyethylenically unsaturated monomer (for example, polyethylenically unsaturated (meth)acrylate).

[0248]

[0250] 30. The coating composition according to any one of Embodiments 1 to 29, wherein the coating composition substantially contains none, completely contains none, or does not contain each of bisphenol A, bisphenol F, and bisphenol S.

[0249]

[0251] 31. The coating composition according to any one of Embodiments 1 to 30, wherein the coating composition is not prepared using a halogenated monomer, or substantially contains none, completely contains none, or does not contain a halogenated monomer.

[0250]

[0252] 32. The coating composition according to any one of Embodiments 1 to 31, wherein the coating composition substantially contains none, completely contains none, or does not contain styrene, and optionally, also substantially contains none, completely contains none, or does not contain a substituted styrene compound.

[0251]

[0253] 33. The coating composition according to any one of Embodiments 1 to 32, wherein the resin system (and, optionally, the coating composition) substantially contains none, completely contains none, or does not contain a vinyl aromatic compound.

[0252]

[0254] 34. The coating composition according to any one of Embodiments 1 to 33, wherein the calculated Tg of the aggregate of monomers used to form two or more emulsion polymerization steps is at least 0 °C, at least 20 °C, at least 30 °C, at least 40 °C, or at least 50 °C.

[0253]

[0255] The coating composition according to any one of embodiments 1 to 34, wherein the monomers used to form the low-Tg and high-Tg emulsion polymerization stages (and, optionally, any additional optional emulsion polymerization stages) do not include any monomers having no homopolymer Tg.

[0254]

[0256] 36. The coating composition according to any one of embodiments 1 to 35, wherein the monomers used to form the low-Tg and high-Tg emulsion polymerization stages contain less than 5% by weight of monomers having no homopolymer Tg, based on the total weight of the monomers used to form the low-Tg and high-Tg stages, if any. The coating composition according to any one of embodiments 1 to 35.

[0255]

[0257] 37. The coating composition according to any one of embodiments 2 to 36, wherein the resin system consists essentially of a water-dispersible polymer and two or more emulsion-polymerized ethylenically unsaturated monomers.

[0256]

[0258] 38. The coating composition according to any one of embodiments 1 to 37, wherein two or more emulsion polymerization stages consist essentially of a low-Tg and a high-Tg emulsion polymerization stage.

[0259] 39. The coating composition according to any one of embodiments 2 to 36, wherein the water-dispersible polymer contains one or more neutralized acidic or basic groups.

[0257]

[0260] 40. The coating composition according to any one of embodiments 2 to 39, wherein the water-dispersible polymer contains one or more structural units derived from an ethylenically unsaturated monomer, more typically one or more structural units derived from acrylate or methacrylate.

[0258]

[0261] 41. The coating composition according to embodiment 40, wherein the water-dispersible polymer contains one or more structural units derived from an acid or anhydride-functional ethylenically unsaturated monomer.

[0262] 42. The coating composition according to any one of Embodiments 39 to 41, wherein the water-dispersible polymer contains acidic groups or anhydride groups neutralized with one or more ammonia or amines.

[0259]

[0263] 43. The coating composition according to any one of Embodiments 2 to 42, wherein the weight ratio of the water-dispersible polymer to the emulsion polymerization step is less than 50:50, less than 40:60, less than 30:70, less than 25:75, or less than 20:80.

[0260]

[0264] 44. The coating composition according to any one of Embodiments 2 to 43, wherein the water-dispersible polymer contains a polyether polymer having a calculated Tg of at least 60°C, at least 70°C, at least 80°C, or 80 to 110°C.

[0261]

[0265] 45. The coating composition according to any one of Embodiments 2 to 44, wherein the water-dispersible polymer contains an aromatic polyether polymer.

[0266] 46. The coating composition according to any one of Embodiments 2 to 45, wherein the water-dispersible polymer has a number average molecular weight of at least 2,000, at least 3,000, or at least 4,000.

[0262]

[0267] 47. The coating composition according to any one of Embodiments 2 to 46, wherein the water-dispersible polymer contains an organic solution polymerization polymer.

[0268] 48. The coating composition according to any one of Embodiments 2 to 47, wherein the water-dispersible polymer contains a polyether polymer formed from reactants including a spreading agent and a diepoxide.

[0263]

[0269] 49. The coating composition according to Embodiment 48, wherein the diepoxide contains a diepoxide of a dihydric phenol.

[0270] 50. The coating composition according to Embodiment 49, wherein the dihydric phenol contains an ortho-substituted dihydric phenol.

[0264]

[0271] 51. The coating composition according to embodiment 50, wherein the diepoxide of the ortho-substituted diphenol contains the diepoxide of tetramethyl bisphenol F (for example, the diglycidyl ether of tetramethyl bisphenol F).

[0265]

[0272] 52. The coating composition according to embodiment 50, wherein the diepoxide of the ortho-substituted diphenol contains the diepoxide of 2,2'-biphenol or another crosslinked diphenol having an inter-ring crosslinked linking portion located at the ortho position with respect to the phenolic oxygen atom.

[0266]

[0273] 53. The coating composition according to embodiment 48, wherein the diepoxide contains the diepoxide of an aromatic diol (for example, benzenedimethanol, vanillyl alcohol, furandimethanol, etc.), an aromatic diacid (for example, isophthalic acid, terephthalic acid, etc.), an aliphatic diol, an aliphatic diacid, an alicyclic diol (for example, cyclobutanediol such as 2,2,4,4-tetramethyl-1,3-cyclobutanediol), an alicyclic diacid (for example, cyclobutanedioic acid such as 2,2,4,4-tetramethyl-1,3-cyclobutanedicarboxylic acid), or a combination thereof.

[0267]

[0274] 54. The coating composition according to any one of embodiments 48 to 53, wherein the extender contains a diphenol.

[0275] 55. The coating composition according to embodiment 54, wherein the extender contains a diphenol monophenol.

[0268]

[0276] 56. The coating composition according to embodiment 55, wherein the diphenol monophenol contains hydroquinone.

[0277] 57. The coating composition according to embodiment 54, wherein the extender contains 2,2'-biphenol or another crosslinked diphenol having an inter-ring crosslinked linking portion located at the ortho position with respect to the phenolic oxygen atom.

[0269]

[0278] The coating composition according to any one of Embodiments 2 to 50 and 53 to 56, wherein the water-dispersible polymer (and, optionally, the coating composition) substantially does not contain, completely does not contain, or does not contain any structural unit derived from bisphenol.

[0270]

[0279] 59. The coating composition according to any one of Embodiments 2 to 58, wherein the water-dispersible polymer comprises a copolymer containing both a polyether polymer and a vinyl addition component.

[0271]

[0280] 60. The coating composition according to Embodiment 59, wherein the water-dispersible polymer comprises a polyether-acrylate copolymer.

[0281] 61. The coating composition according to Embodiment 59 or 60, wherein the vinyl addition component is formed from a monomer mixture containing both (i) (meth)acrylic acid and (ii) (meth)acrylate.

[0272]

[0282] 62. The coating composition according to Embodiment 60 or 61, wherein the polyether-acrylate copolymer comprises a reaction product of an oxirane-functional polyether polymer reacted with an acid or anhydride-functional acrylate polymer in the presence of a tertiary amine.

[0273]

[0283] 63. The coating composition according to any one of Embodiments 60 to 62, wherein the polyether polymer used to form the polyether-acrylate copolymer constitutes 30 to 95% by weight of the polyether-acrylate copolymer.

[0274]

[0284] 64. The coating composition according to any one of Embodiments 2 to 63, wherein the water-dispersible polymer has an acid value of 40 to 200 mgKOH per gram.

[0285] 65. The coating composition according to any one of Embodiments 2 to 6 4, wherein the water-dispersible polymer contains a secondary hydroxyl group.

[0275]

[0286] 66. The coating composition according to any one of Embodiments 2 to 65, wherein the water-dispersible polymer contains a -CH2CH(OH)CH2- segment.

[0287] 67. The coating composition according to any one of Embodiments 1 to 66, wherein the coating composition substantially does not contain, completely does not contain, or does not contain each of bisphenol A, bisphenol F, and bisphenol S.

[0276]

[0288] 68. The coating composition according to any one of Embodiments 1 to 67, which has a viscosity of 20 to 80 seconds (Ford Cup #2, 25°C) and is an inner spray coating composition for food cans or beverage cans.

[0277]

[0289] 69. When the coating composition is spray-coated on the inner surface of a 355 mL drawn and ironed aluminum beverage can of size 211 at a dry film weight of 115 milligrams per can and cured at 188°C to 199°C (measured at the can dome) for 55 seconds, and then retorted in 2% citric acid under pressure at 121°C, and then tested according to ASTM D 3359 - Test Method B using SCOTCH 610 tape available from 3M Company (Saint Paul, Minn.), it exhibits a lower wall adhesion score of 9 or 10. The coating composition according to any one of Embodiments 1 to 68.

[0278]

[0290] 70. When the coating composition is spray-coated on the inner surface of a 355 mL drawn and ironed aluminum beverage can of size 211 at a dry film weight of 115 milligrams per can and cured at 188°C to 199°C (measured at the can dome) for 55 seconds, it exhibits a contact angle with deionized water of greater than about 80, more preferably greater than about 85, and even more preferably greater than about 90. The coating composition according to any one of Embodiments 1 to 69.

[0279]

[0291] 71. The coating composition according to any one of Embodiments 1 to 70, wherein the resin system constitutes at least 10 wt%, at least 20 wt%, at least 50 wt%, at least 75 wt%, at least 90 wt%, or at least 99 wt% of the coating composition based on the combined weight of the water-dispersible polymer and two or more emulsion polymerization steps with respect to the total weight of the resin solids in the coating composition.

[0280]

[0292] 72. The coating composition according to any one of Embodiments 1 to 71, wherein the coating composition contains a crosslinking agent.

[0293] 73. The coating composition according to Embodiment 72, wherein the crosslinking agent contains a phenoplast.

[0281]

[0294] 74. The coating composition according to any one of Embodiments 1 to 73, wherein the aqueous carrier liquid contains at least 50 wt% of water.

[0295] 75. The coating composition according to any one of Embodiments 1 to 74, wherein the coating composition contains 5 wt% to 40 wt% of solids, more typically 10 wt% to 30 wt% of solids, and 15 wt% to 25 wt% of solids.

[0282]

[0296] 76. The coating composition according to any one of Embodiments 1 to 75, wherein the coating composition contains at least 50 wt% of two or more emulsion polymerization steps based on the total resin solids.

[0283]

[0297] 77. The coating composition according to any one of Embodiments 2 to 76, wherein the coating composition contains the water-dispersible polymer and two or more emulsion polymerization steps at least 50 wt%, at least 75 wt%, at least 90 wt%, or at least 95 wt% based on the combined weight of the water-dispersible polymer and two or more emulsion polymerization steps with respect to the total resin solids. combination weight.

[0284]

[0298] The coating composition according to any one of Embodiments 2 to 77, wherein the total amount of the polymerizable ethylenically unsaturated monomers constitutes more than 50% by weight, preferably more than 60% by weight, even more preferably more than 70% by weight, and optimally 80% by weight or more of the total resin solids of the coating composition.

[0285]

[0299] The coating composition according to Embodiment 78, wherein the total amount of the polymerizable ethylenically unsaturated monomers present in the coating composition, which are composed of at least 50% by weight, at least 60% by weight, at least 75% by weight, or at least 85% by weight of the high-Tg and low-Tg emulsion polymerization monomers.

[0286]

[0300] The coating composition according to any one of Embodiments 2 to 79, wherein the polymerizable ethylenically unsaturated monomers constitute at least 60% by weight, at least 65% by weight, at least 70% by weight, at least 75% by weight, or at least 80% by weight of the total combined weight of the water-dispersible polymer and the polymerizable ethylenically unsaturated monomers.

[0287]

[0301] When the coating composition is spray-coated on the inner surface of a 355 mL No. 211 two-piece drawn and ironed aluminum beverage can at a coating weight of 115 milligrams per can and cured at 188°C to 199°C (measured at the can dome) for 55 seconds, and is tested according to the metal exposure test after drop damage disclosed herein, it gives a metal exposure of less than 3.5 mA. The coating composition according to any one of Embodiments 1 to 80.

[0288]

[0302] When the coating composition is spray-coated on the inner surface of a 355 mL two-piece draw and redraw aluminum beverage can numbered 211 at a coating weight of 115 milligrams per can and cured at 188°C to 199°C (measured at the can dome) for 55 seconds, it can pass the necking and flanging tests as shown by a change in metal exposure after necking of less than 1.0 mA, more preferably a change of less than 0.1 mA, and even more preferably no measurable change. The coating composition according to any one of Embodiments 1 to 81.

[0289]

[0303] A food or beverage can, or a part thereof, having a cured coating formed from the coating composition according to any one of Embodiments 1 to 82, which is located on at least a part of a metal substrate.

[0290]

[0304] The food or beverage can, or a part thereof, according to Embodiment 83, wherein the overall average dry coating film weight is 1.0 to 6.5 grams per square meter.

[0305] The food or beverage can, or a part thereof, according to Embodiment 83 or 84, wherein the metal substrate has an average thickness of 125 to 635 micrometers.

[0291]

[0306] The food or beverage can, or a part thereof, according to any one of Embodiments 82 to 84, wherein the coating is an internal food contact coating of an aluminum beverage can.

[0292]

[0307] The food or beverage can according to any one of Embodiments 83 to 86, wherein the cured coating exhibits a contact angle with deionized water of greater than about 80, more preferably greater than about 85, and even more preferably greater than about 90.

[0293]

[0308] The food or beverage can according to any one of Embodiments 83 to 87, which contains a packaged food or beverage product.

[0309] A method for coating a food or beverage can, comprising applying the coating composition according to any one of Embodiments 1 to 82 to the surface of a metal substrate before or after forming the metal substrate into a food or beverage can or a part thereof.

[0294]

[0310] 90. The method according to Embodiment 89, wherein the coating composition is spray-coated onto the inner surface of a can including a sidewall body portion and an end portion.

[0311] 91. The method according to Embodiment 89 or 90, wherein the can is an aluminum beverage can.

[0295]

[0312] 92. The multistage polymer latex according to Embodiment 1 or any one of the resin systems according to Embodiments 2 to 81.

[0313] 93. A method for producing a latex dispersion that substantially does not contain, completely does not contain, or does not contain each of bisphenol A, bisphenol F, and bisphenol S, and optionally also substantially does not contain, completely does not contain, or does not contain styrene, the method comprising: providing an aqueous dispersion of a water-dispersible polymer (for example, the water-dispersible polymer according to any one of Embodiments 1 to 92); emulsion polymerizing in two or more stages in the presence of the aqueous dispersion to form a multistage polymer latex, the latex having (i) a low Tg emulsion polymerization stage having a calculated Tg that is preferably at least 20 °C, at least 30 °C, at least 35 °C, at least 40 °C, at least 50 °C, at least 60 °C, or at least 70 °C lower than the calculated Tg of the high Tg emulsion polymerization stage, or (ii) a gradient Tg, or both.

[0296]

[0314] 94. The method according to Embodiment 93, wherein the water-dispersible polymer includes a polyether polymer.

[0315] 95. The method according to embodiment 93, wherein the polyether polymer comprises an aromatic polyether polymer having an acidic group neutralized with a base, a basic group neutralized with an acid, or a combination thereof.

[0297]

[0316] 96. The method according to any one of embodiments 93 to 95, wherein the weight ratio of the water-dispersible polymer to the emulsion polymerization step is less than 50:50, less than 40:60, less than 30:70, less than 25:75, or less than 20:80.

[0298]

[0317] 97. The method according to any one of embodiments 93 to 95, wherein the polymerized ethylenically unsaturated monomer constitutes at least 60% by weight, at least 65% by weight, at least 70% by weight, at least 75% by weight, or at least 80% by weight of the total combined weight of the water-dispersible polymer and the polymerized ethylenically unsaturated monomer.

[0299]

[0318] 98. The method according to any one of embodiments 93 to 97, wherein the low Tg emulsion polymerization step is emulsion polymerized before the high Tg emulsion polymerization step.

[0319] 99. The method according to any one of embodiments 93 to 97, wherein the low Tg emulsion polymerization step is emulsion polymerized after the high Tg emulsion polymerization step.

[0300]

[0320] 100. A latex dispersion obtained according to any one of embodiments 93 to 99.

[0321] 101. The emulsion polymerized ethylenically unsaturated monomer component, more preferably The coating composition, can, method, polymer latex, or latex dispersion according to any one of embodiments 1 to 100, wherein the entire latex comprises or is derived from a low molecular weight surfactant of 0.5% by weight or less, more preferably 0.1% by weight or less, based on the total weight of the ethylenically unsaturated monomer component and the polymerizable monomer used to prepare the latex.

[0301]

[0322] 102. A coating composition, can, method, polymer latex, or latex dispersion according to any one of embodiments 1 to 100, wherein the emulsion polymerization ethylenically unsaturated monomer component, more preferably the entire latex, is derived mainly using, or using only, a low molecular weight surfactant.

[0302]

[0323] 103. A coating composition, can, method, polymer latex, or latex dispersion according to any one of embodiments 1 to 102, wherein the emulsion polymerization ethylenically unsaturated monomer component, more preferably the entire latex, is also polymerized, or alternatively polymerized, in the presence of one or more polymerizable surfactants.

[0303]

[0324] 104. A coating composition, can, method, polymer latex, or latex dispersion according to any one of claims 1 to 103, wherein the emulsion polymerization ethylenically unsaturated monomer component, more preferably the entire latex, contains or is derived from acrylamide-type monomers in an amount of 0.5% by weight or less, more preferably 0.1% by weight or less, based on the total weight of the ethylenically unsaturated monomer component and polymerizable monomers used to prepare the latex.

[0304]

[0325] The complete disclosure of all patents, patent applications, and publications (including chemical safety data sheets, technical data sheets, and product brochures for raw materials and components used in the examples), as well as electronically available documents cited herein, are incorporated herein by reference as if individually incorporated. The above detailed description and examples are provided only to assist understanding. They should not be construed as imposing unnecessary limitations. The present invention should not be limited to the exact details shown and described, and modifications obvious to those skilled in the art are included within the scope of the invention as defined in the embodiments. In some embodiments, the invention disclosed herein illustratively may be suitably practiced in the absence of any element not specifically disclosed herein. [1] An aqueous coating composition comprising a resin system comprising a water-dispersible polymer and two or more emulsion polymerization stages of a multi-stage polymer latex in an aqueous carrier liquid, wherein the water-dispersible polymer is incorporated into the multi-stage polymer latex, blended with the multi-stage polymer latex, or both, and the latex has (i) a low Tg emulsion polymerization stage having a calculated Tg at least 20 °C lower than the calculated Tg of the high Tg emulsion polymerization stage, or (ii) a gradient Tg having a difference of at least 20 °C when the calculated Tg of the monomers supplied at the start of polymerization is compared with the monomers supplied at the end of polymerization, an aqueous coating composition having one or both of these. [2] An article formed on or to be formed on a container or container component of food or beverage, the article comprising a metal substrate having a coating formed from an aqueous coating composition on at least one surface, the aqueous coating composition comprising a resin system comprising a water-dispersible polymer and two or more emulsion polymerization stages of a multi-stage polymer latex in an aqueous carrier liquid, wherein the water-dispersible polymer is incorporated into the multi-stage polymer latex, blended with the multi-stage polymer latex, or both, and the latex has (i) a low Tg emulsion polymerization stage having a calculated Tg at least 20 °C lower than the calculated Tg of the high Tg emulsion polymerization stage, or (ii) a gradient Tg having a Tg difference of at least 20 °C when the calculated Tg of the monomers supplied at the start of polymerization is compared with the monomers supplied at the end of polymerization, an article having one or both of these. [3] A method for producing a latex dispersion useful for coating a container or container component of food or beverage, the method comprising (a) providing an aqueous dispersion of a water-dispersible polymer; and (b) emulsion polymerizing two or more stages in the presence of the aqueous dispersion to form a multi-stage polymer latex, the latex having (i) A low-Tg emulsion polymerization stage having a calculated Tg that is at least 20 °C lower than the calculated Tg of the high-Tg emulsion polymerization stage, or (ii) A gradient Tg having a Tg difference of at least 20 °C when comparing the calculated Tg of the monomer supplied at the start of polymerization with the monomer supplied at the end of polymerization, and a process comprising one or both of them. [4] A method for producing a coated food or beverage container or container component, the method comprising: (a) Spraying an aqueous coating composition comprising a resin system containing a water-dispersible polymer and two or more emulsion polymerization stages of a multi-stage polymer latex in an aqueous carrier liquid onto the inner surface of a metal food or beverage can having a body portion and an end portion, wherein the water-dispersible polymer is incorporated into the multi-stage polymer latex, blended with the multi-stage polymer latex, or both, and the latex has (i) A low-Tg emulsion polymerization stage having a calculated Tg that is at least 20 °C lower than the calculated Tg of the high-Tg emulsion polymerization stage, or (ii) A gradient Tg having a Tg difference of at least 20 °C when comparing the calculated Tg of the monomer supplied at the start of polymerization with the monomer supplied at the end of polymerization, and a process comprising one or both of them. (b) Curing the coating composition to form a hardened coating. [5] A method for producing a coated food or beverage container or container component, the method comprising: (a) Applying a coating formed from an aqueous coating composition comprising a resin system containing a water-dispersible polymer and two or more emulsion polymerization stages of a multi-stage polymer latex in an aqueous carrier liquid to at least one metal substrate surface of a food or beverage container or container component, wherein the water-dispersible polymer is incorporated into the multi-stage polymer latex, blended with the multi-stage polymer latex, or both, and the latex has (i) A low-Tg emulsion polymerization stage having a calculated Tg that is at least 20 °C lower than the calculated Tg of the high-Tg emulsion polymerization stage, or (ii) A gradient Tg having a Tg difference of at least 20 °C when the calculated Tg of the monomer supplied at the start of polymerization is compared with the monomer supplied at the end of polymerization, One or both of which are included in the process, (b) Curing the coating composition to form a hardened coating, A method comprising the steps of. [6] The water-dispersible polymer contains an acrylic polymer, a polyether polymer, a polyolefin polymer, a polyester polymer, a polyurethane polymer, or a mixture or copolymer thereof, The composition according to [1], the article according to [2], or the method according to any one of [3] to [5]. [7] The water-dispersible polymer contains a polyolefin polymer, The composition according to [1], the article according to [2], or the method according to any one of [3] to [5]. [8] The water-dispersible polymer contains a polyether polymer, The composition according to [1], the article according to [2], or the method according to any one of [3] to [5]. [9] The water-dispersible polymer contains an aromatic polyether polymer having a calculated Tg of at least 60 °C, The composition according to [1], the article according to [2], or the method according to any one of [3] to [5].

[10] The water-dispersible polymer contains a polyether polymer formed from a reactant containing a spreading agent and an aromatic diol, an aromatic diacid, an aliphatic diol, an aliphatic diacid, an alicyclic diol, an alicyclic diacid, or a combination thereof, The composition according to [1] or [9], the article according to [2] or [9], or the method according to any one of [3] to [5 of 9].

[11] The composition according to [1] or [9], the article according to [2] or [9], or the method according to any one of [3] to [5 of 9], wherein the water-dispersible polymer comprises a polyether polymer formed from a reactant comprising a spreading agent and a diepoxide of an aromatic diol.

[12] The composition according to [1] or [9], the article according to [2] or [9], or the method according to any one of [3] to [5 of 9], wherein the water-dispersible polymer comprises a polyether polymer formed from a reactant comprising a spreading agent and a diepoxide of an ortho-substituted diphenol.

[13] The composition according to any one of [1] or [9] to

[12] , the article according to any one of [2] or [9] to

[12] , or the method according to any one of [3] to [5] or [9] to

[12] , wherein the water-dispersible polymer comprises a polyether-acrylate copolymer.

[14] The composition, article, or method according to any one of [1] to

[13] , wherein the two or more emulsion polymerization steps are emulsion polymerized in the presence of the water-dispersible polymer.

[15] The composition, article, or method according to any one of [1] to

[14] , wherein the two or more emulsion polymerization steps are emulsion polymerized in the presence of one or more polymerizable surfactants.

[16] The composition, article, or method according to any one of [1] to

[14] , wherein the two or more emulsion polymerization steps are emulsion polymerized without using a non-polymer surfactant.

[17] The composition, article, or method according to any one of [1] to

[14] , wherein the multi-stage polymer latex does not contain and is not derived from a low molecular weight surfactant in an amount exceeding 0.5% by weight based on the total weight of the polymerizable monomers used to prepare the latex.

[18] The composition, article, or method according to any one of [1] to

[17] , wherein the water-dispersible polymer has an acid value of 40 to 200 mgKOH per gram.

[19] A composition, article, or method according to any one of [1] to

[18] , wherein the weight ratio of the water-dispersible polymer to the emulsion polymerization stage is less than 40:60.

[20] A composition, article, or method according to any one of [1] to

[19] , wherein the latex has a low Tg emulsion polymerization stage having a calculated Tg of less than 30 °C and a high Tg emulsion polymerization stage having a calculated Tg of more than 50 °C.

[21] A composition, article, or method according to any one of [1] to

[20] , wherein the latex has a low Tg emulsion polymerization stage having a calculated Tg of less than 20 °C and a high Tg emulsion polymerization stage having a calculated Tg of more than 60 °C.

[22] A composition, article, or method according to any one of [1] to

[21] , wherein the latex has a low Tg emulsion polymerization stage having a calculated Tg that is at least 40 °C lower than the calculated Tg of the high Tg emulsion polymerization stage.

[23] A composition, article, or method according to any one of [1] to

[22] , wherein the latex has a low Tg emulsion polymerization stage having a calculated Tg that is at least 60 °C lower than the calculated Tg of the high Tg emulsion polymerization stage.

[24] A composition, article, or method according to any one of [1] to

[23] , wherein more than 50% by weight of the emulsion polymerization stage has a calculated Tg of at least 40 °C.

[25] A composition, article, or method according to any one of [1] to

[24] , wherein two or more of the emulsion polymerization stages are formed from monomers having a calculated Tg of at least 30 °C as a whole.

[26] A composition, article, or method according to any one of [1] to

[25] , wherein the aqueous coating composition contains at least 50% by weight of the two or more emulsion polymerization stages based on the total resin solids.

[27] The composition, article, or method according to any one of [1] to

[26] , wherein the aqueous coating composition contains more than 70% by weight of resin solids from polymerized ethylenically unsaturated monomers based on the total resin solids in the coating composition.

[28] The composition, article, or method according to any one of [1] to

[27] , wherein at least one of the emulsion polymerization steps is formed from monomers containing at least 50% by weight of one or more (meth)acrylates.

[29] The composition, article, or method according to any one of [1] to

[28] , wherein at least one of the emulsion polymerization steps is formed from monomers containing at least 80% by weight of one or more of methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, and butyl methacrylate.

[30] The composition, article, or method according to any one of [1] to

[29] , wherein at least one of the emulsion polymerization steps is formed from monomers containing a polyethylenically unsaturated monomer.

[31] The composition, article, or method according to any one of [1] to

[30] , wherein the latex has a gradient Tg.

[32] The composition, article, or method according to any one of [1] to

[31] , wherein the coating composition is substantially free of each of bisphenol A, bisphenol F, and bisphenol S.

[33] The composition, article, or method according to any one of [1] to

[32] , wherein the coating composition is not prepared using halogenated monomers.

[34] The composition, article, or method according to any one of [1] to

[33] , wherein the coating composition is substantially free of styrene and substituted styrene compounds.

[35] The composition, article, or method according to any one of [1] to

[34] , wherein the coating composition contains, or is derived from, an acrylamide-type monomer in an amount of 0.5% by weight or less based on the total weight of the ethylenically unsaturated monomer component and the polymerizable monomer used for producing the latex.

[36] The composition, article, or method according to any one of [1] to

[35] , wherein the aqueous coating composition further contains a crosslinking agent.

[37] The composition, article, or method according to any one of [1] to

[36] , wherein the aqueous coating composition further contains a phenoplast crosslinking agent.

[38] The composition, article, or method according to any one of [1] to

[37] , wherein the aqueous coating composition has a viscosity of 20 to 80 seconds (Ford Cup #2, 25 °C) and is an inner spray coating composition for food cans or beverage cans.

[39] When the aqueous coating composition is spray-coated on the inner surface of a 355 mL No. 211 two-piece drawn and ironed aluminum beverage can at a coating weight of 115 milligrams per can and cured at 188 °C to 199 °C (measured at the can dome) for 55 seconds, (i) exhibits a global extraction result of less than 50 ppm, and (ii) when the can is filled with 1% NaCl in deionized water and tested according to the initial metal exposure test method disclosed herein, exhibits an average metal exposure of less than 3 mA, the composition, article, or method according to any one of [1] to

[38] .

[40] The composition, article, or method according to any one of [1] to

[39] , wherein the aqueous coating composition is spray-coated on the inner surface of a 355 mL drawn and ironed aluminum beverage can of number 211 at a dry film weight of 115 milligrams per can and cured at 188 °C to 199 °C (measured at the can dome) for 55 seconds, and when retorted in 2% citric acid under pressure at 121 °C and then tested according to ASTM D 3359 - Test Method B, exhibits a lower wall adhesion score of 9 or 10.

[41] The composition, article, or method according to any one of [1] to

[40] , wherein the aqueous coating composition is spray-coated on the inner surface of a two-piece drawn and ironed aluminum beverage can of number 211 with a capacity of 355 mL at a coating weight of 115 milligrams per can and cured at 188 °C to 199 °C (measured at the can dome) for 55 seconds, and when tested according to the post-drop damage metal exposure test disclosed herein, gives a metal exposure of less than 3.5 mA.

[42] The composition, article, or method according to any one of [1] to

[41] , wherein the aqueous coating composition is spray-coated on the inner surface of a two-piece drawn and ironed aluminum beverage can of number 211 with a capacity of 355 mL at a coating weight of 115 milligrams per can and cured at 188 °C to 199 °C (measured at the can dome) for 55 seconds, and can pass the necking and flanging tests as indicated by a change in metal exposure after necking of less than 1.0 mA.

[43] The article according to [2] or the method according to any one of [3] to [5], wherein the coating composition is cured and is on the internal food-contact coating of an aluminum beverage can.

[44] The article according to [2] or the method according to any one of [3] to [5], wherein the coating composition is cured and the container further contains a packaged food or beverage product.

Claims

**Claim 1** An aqueous coating composition comprising a resin system that is sprayable onto a food or beverage container, said resin system comprising a water-dispersible polymer and a multi-stage polymer latex having two or more emulsion polymerization stages in an aqueous carrier liquid, wherein said water-dispersible polymer comprises a polyether polymer, and said water-dispersible polymer is incorporated into said multi-stage polymer latex, blended with said multi-stage polymer latex, or both, and said aqueous carrier liquid comprises more than 5% by weight of an organic solvent based on the total weight of the aqueous carrier liquid, For said latex, the calculated Tg of the high Tg emulsion polymerization stage is above 40°C and below or equal to 105°C, the calculated Tg of the low Tg emulsion polymerization stage is above -54°C and below 40°C, and the calculated Tg of the low Tg emulsion polymerization stage is at least 20°C lower than the calculated Tg of the high Tg emulsion polymerization stage. The above composition. **Claim 2** An article formed on or to be formed on a food or beverage container or container component, said article comprising a metal substrate having a coating formed from an aqueous coating composition on at least one surface, said aqueous coating composition comprising a resin system comprising a water-dispersible polymer and a multi-stage polymer latex having two or more emulsion polymerization stages in an aqueous carrier liquid, wherein said water-dispersible polymer comprises a polyether polymer, and said water-dispersible polymer is incorporated into said multi-stage polymer latex, blended with said multi-stage polymer latex, or both, and said aqueous carrier liquid comprises more than 5% by weight of an organic solvent based on the total weight of the aqueous carrier liquid, For said latex, the calculated Tg of the high Tg emulsion polymerization stage is above 40°C and below or equal to 105°C, the calculated Tg of the low Tg emulsion polymerization stage is above -54°C and below 40°C, and the calculated Tg of the low Tg emulsion polymerization stage is at least 20°C lower than the calculated Tg of the high Tg emulsion polymerization stage. The above article. **Claim 3** The composition according to claim 1 or the article according to claim 2, wherein said water-dispersible polymer comprises a polyolefin polymer. **Claim 4** The composition according to claim 1 or the article according to claim 2, wherein said water-dispersible polymer comprises a polyether-acrylate copolymer. **Claim 5** The composition or article according to any one of claims 1 to 4, wherein said water-dispersible polymer is derived from tetramethyl bisphenol F. ​

6. The composition or article according to any one of claims 1 to 5, wherein the two or more emulsion polymerization steps are emulsion polymerized in the presence of the water-dispersible polymer.

7. The composition or article according to any one of claims 1 to 6, wherein the multi-stage polymer latex does not contain and is not derived from a low molecular weight surfactant in excess of 0.5% by weight, based on the total weight of the polymerizable monomers used to prepare the latex and excluding the weight of any monomers used to prepare a seed polymer before or at the start of polymerization of the latex.

8. The composition or article according to any one of claims 1 to 7, wherein the water-dispersible polymer has an acid value of 40 to 200 mg KOH per gram.

9. The composition or article according to any one of claims 1 to 8, wherein the latex has a low Tg emulsion polymerization step having a calculated Tg of less than 30 °C and a high Tg emulsion polymerization step having a calculated Tg of greater than 50 °C.

10. The composition or article according to any one of claims 1 to 9, wherein the latex has a low Tg emulsion polymerization step having a calculated Tg at least 40 °C lower than the calculated Tg of the high Tg emulsion polymerization step, and more than 50% by weight of the emulsion polymerization steps have a calculated Tg of at least 40 °C.

11. The composition or article according to any one of claims 1 to 10, wherein the aqueous coating composition comprises at least 50% by weight of the two or more emulsion polymerization steps based on the total resin solids, and the aqueous coating composition contains more than 70% by weight of the resin solids from polymerized ethylenically unsaturated monomers based on the total resin solids in the coating composition.

12. The composition or article according to any one of claims 1 to 11, wherein at least one of the emulsion polymerization steps is formed from monomers containing at least 80% by weight of one or more of methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, and butyl methacrylate.

13. The composition or article according to any one of claims 1 to 12, wherein the latex has a gradient Tg.

14. The coating composition does not substantially contain bisphenol A, bisphenol F, and bisphenol S, the coating composition is not prepared using a halogenated monomer, and the coating composition contains 0.5% by weight or less of an acrylamide-type monomer based on the total weight of the ethylenically unsaturated monomer components and polymerizable monomers used to produce the latex, or is derived therefrom, the composition or article according to any one of claims 1 to 13.

15. The composition or article according to any one of claims 1 to 14, wherein the coating composition does not substantially contain styrene and substituted styrene compounds.

16. When the aqueous coating composition is spray-coated on the inner surface of a 355 mL No. 211 two-piece drawn and ironed aluminum beverage can at a coating weight of 115 milligrams per can and cured at 188 °C to 199 °C (measured at the can dome) for 55 seconds, (i) a global extraction result of less than 50 ppm, and (ii) when the can is filled with 1% NaCl in deionized water and tested according to the initial metal exposure test method disclosed herein, an average metal exposure of less than 3 mA, the composition or article according to any one of claims 1 to 15 exhibits.

17. The composition or article according to any one of claims 1 to 16, wherein the coating composition is cured and is on the internal food contact coating of an aluminum beverage can.

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