US20180291227A1

US20180291227A1 - Curable Coating Composition and Packaging Coated with the Same

Info

Publication number: US20180291227A1
Application number: US15/578,031
Authority: US
Inventors: Debra L. Singer; Dary Duhamel; Kam Lun Lock
Original assignee: PPG Industries Ohio Inc
Current assignee: PPG Industries Ohio Inc
Priority date: 2015-05-29
Filing date: 2016-05-26
Publication date: 2018-10-11
Also published as: EP3303485A1; US20180171169A1; WO2016196190A1; WO2016196174A1; CN113416457A; EP3303490A1; US20220025192A1; KR20180002745A; US11091656B2; MX2017015285A; CN107690456B; ES2750820T3; EP3303490B1; CN107683311A; RU2681002C1; CN107690456A

Abstract

A curable coating composition comprising a latex having a reactive functional group and phosphorus acid is disclosed; the coating can be substantially free of crosslinker. Such a coating on a package is also disclosed.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional Patent Application Ser. No. 62/168,040, filed on May 29, 2015, the entirety of which is incorporated by reference, and to U.S. Provisional Patent Application Ser. No. 62/168,134, filed on May 29, 2015, the entirety of which is incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a curable coating composition comprising a latex having a reactive functional group and phosphorus acid and a package coated at least in part with such a coating composition; the coating can be substantially free of crosslinker.

BACKGROUND OF THE INVENTION

The application of various polymeric coatings to metallic substrates, including metal food and beverage containers, to retard or inhibit corrosion is well established. Coatings are applied to the interior of such containers to prevent the contents from contacting the metal of the container. Contact between the metal and the food or beverage can lead to corrosion of the metal container, which can then contaminate the food or beverage. This is particularly true when the contents of the container are acidic in nature, such as tomato-based products and soft drinks.
Certain coatings, particularly in the packaging industry, must undergo extreme stresses in the course of preparation and use of the packaging containers. In addition to flexibility, packaging coatings may also need resistance to chemicals, solvents, and pasteurization processes used in the packaging of beer and other beverages, and may also need to withstand retort conditions commonly employed in food packaging. In addition to corrosion protection, coatings for food and beverage containers should be non-toxic, and should not adversely affect the taste of the food or beverage in the can. Resistance to “popping”, “blushing” and/or “blistering” may also be desired.
Bisphenol A (“BPA”) contributes to many of the properties desired in packaging coating products. The use of BPA and related products such as bisphenol A diglycidyl ether (“BADGE”), however, has recently come under scrutiny in the packaging industry. Substantially BPA-free coatings having properties comparable to coatings comprising BPA are therefore desired. The packaging industry is also interested in eliminating or minimizing other monomers, such as styrene, and components, such as formaldehyde, in coatings.

SUMMARY OF THE INVENTION

The present invention is directed to a curable coating composition comprising: (a) a latex having a reactive functional group; and (b) a phosphorus acid, wherein the composition is substantially free of crosslinker selected from polyisocyanates, aminoplast resins and phenolic resins. Also, the present invention is directed to a curable composition comprising: (a) a latex having a reactive functional group; (b) a phosphorus acid; and (c) a hydroxyalkylamide crosslinker. Packages coated at least in part with such compositions are also within the scope of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to curable compositions such as a coating composition comprising a latex having a reactive functional group and a phosphorus acid. The composition is at least substantially free, but may be essentially free or completely free, of crosslinker selected from polyisocyanates, aminoplast resins and phenolic resins. Also, the composition may contain a hydroxyalkylamide crosslinker. As used in the context of the amount of crosslinker, substantially free means less than 5 wt %, essentially free means less than 2 wt % and completely free means less than 1 wt %, with wt % based on total solid weight of the coating. “Curable” as used herein in reference to a coating composition means that the coating, when cured, forms a self-supporting continuous film on at least a horizontal surface of a substrate upon removal of any diluents or carriers present in the composition or upon curing at ambient conditions or elevated temperature. A “cured” coating according to the present invention is one that has solvent resistance and mechanical resistance and is tack-free; that is, the coating is not tacky when touched and, for example, a fingerprint would not be visible in the coating. It has been surprisingly discovered that use of phosphoric acid in the present coating compositions provides curable coating compositions that can be at least substantially free of an additional film-forming component, such as a crosslinker. This is significant, as cured coatings are typically formed upon reaction of a resin or latex with itself (a “self-crosslinking” resin) or with another component reactive with the functional groups on the resin or latex (a “crosslinker”).
Any latex having any reactive functional group can be used. “Reactive functional group” is used herein to refer to any group that will undergo a chemical reaction with another reactive functional group, including but not limited to hydroxy, epoxy, acid such as carboxylic acid, amine, and/or thio reactive functional groups including mixed groups. Particularly suitable is hydroxyl functionality, either alone or in conjunction with epoxy or carboxylic acid functionality.
The latex can be formed from an ethylenically unsaturated monomer component comprising one or more polymerizable ethylenically unsaturated monomers.
Suitable ethylenically unsaturated monomers and/or oligomers for inclusion in the ethylenically unsaturated monomer component include, for example, ethylenically unsaturated alkyl (meth)acrylates, epoxy-containing ethylenically unsaturated monomers and various vinyl monomers. Examples of ethylenically unsaturated acid are acrylic and methacrylic acid. Typically, they are present in amounts of up to 10, such as 3 to 8 percent by weight based on weight of the emulsion monomer component.
Suitable alkyl(meth)acrylates include, but are not limited to, methyl (meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, isopropyl (meth)acrylate, butyl(meth)acrylate, isobutyl(meth)acrylate, 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, lauryl(meth)acrylate, isobornyl(meth)acrylate, octyl(meth)acrylate and nonyl(meth)acrylate.
The alkyl (meth)acrylates are typically present in amounts of up to 100, such as 20 to 80 percent by weight based on weight of the emulsion monomer component.
Hydroxyalkyl (meth)acrylates can also be used. Examples include hydroxyethyl acrylate (HEA), hydroxyethyl methacrylate (HEMA) and hydroxypropyl(meth)acrylate (HPMA).
The hydroxyalkyl (meth)acrylates are typically present in amounts of up to 30 percent, such as 5 to 15 percent by weight based on weight of the emulsion monomer component.
Difunctional (meth)acrylate monomers may be used in the monomer mixture as well. Examples include ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, allyl methacrylate, and the like. If present, the difunctional (meth)acrylate monomers are present in amounts of up to 5 percent, such as 0.1 to 2 percent by weight based on weight of the emulsion monomer component.
Also, epoxy-containing ethylenically unsaturated monomers such as glycidyl (meth)acrylate can be present in the ethylenically unsaturated monomer component. If present, such monomers can be present in amounts of up to 30, such as 1 to 20 percent by weight based on weight of the ethylenically unsaturated monomer component.
Suitable vinyl monomers include vinyl aromatic monomers, styrene, methyl styrene, alpha-methylstyrene, halostyrene, vinyl toluene, vinyl naphthalene, and mixtures thereof. The ethylenically unsaturated monomer component and/or coatings of the present invention may be completely free of styrene monomers. Other vinyl monomers include vinyl ester, vinyl acetate, vinyl propionate, vinyl butyrate and vinyl stearate. The vinyl monomers, if used, are typically present in amounts of up to 70 percent, such as 10 to 60 percent by weight based on total weight of the emulsion monomer component.
Other suitable polymerizable ethylenically unsaturated monomers include acrylonitrile, acrylamide, methacrylamide, methacrylonitrile, N-isobutoxymethyl acrylamide, N-butoxymethyl acrylamide, conjugated butadiene and isoprene, and mixtures thereof, and which may be present in amounts of up to 30, such as 3 to 20 percent by weight based on total weight of the emulsion monomer component.
The emulsion monomer component is present in amounts of 75 to 99.9, such as 85 to 99.5 percent by weight based on weight of the ethylenically unsaturated monomer component and the reactive polymerizable surfactant.
The coating composition can optionally contain polyolefin base polymers functionalized with a polar group such as an acid group, such as polypropylene or polyethylene homopolymer or copolymer in which the polymer has been modified with carboxylic acid.
The latex of the present invention can be prepared according to methods known in the art. For example, the latex can be prepared by emulsion polymerized techniques in which the ethylenically unsaturated monomer component is emulsified with a surfactant in aqueous medium and the emulsion fed into pre-heated aqueous medium with an initiator.
Any suitable surfactant can be used in latex formulation according to the present invention. The surfactant used in the preparation of the emulsion polymerized latex polymer can be any surfactant capable of polymerizing with the emulsion monomer (“polymerizable surfactant”); that is, the surfactant has at least one moiety that can undergo polymerization with an emulsion monomer. A surfactant having at least one point of unsaturation is one example of a suitable polymerizable surfactant, as the unsaturation of the surfactant can polymerize with unsaturation of an emulsion monomer. The polymerizable surfactant can be polymeric or can be oligomeric. The polymerizable surfactant can have an ionic portion and nonionic portion. The ionic portion can be, for example, acid functional, amine functional and the like. Suitable acid functionality can include, for example, phosphate functionality, sulfonic functionality, and/or carboxylic functionality. The nonionic portion can be aliphatic or aromatic. It may be desired to use a polymerizable surfactant having a nonionic portion that is generally resistant to hydrolysis. Suitable polymerizable surfactants can also be solely nonionic or solely ionic. The polymerizable surfactant can have a weight average molecular weight (“Mw”) as measured by gel permeation chromatography in tetrahydrofuran of at least 200, such as at least 400 or at least 500 or as high as 5,000 or lower, such as 2,000 or lower or 1,000 or lower. The Mw can be, for example, 250 to 850, such as 500 to 700. Use of polymerizable surfactants for packaging coatings is particularly suitable, as the polymerization of the surfactant with the other monomer(s) minimizes the migration of the surfactant into food or beverage. Other suitable surfactants include those that do not polymerize with the monomer(s) in the formation of the latex (non-polymerizable surfactant). The non-polymerizable surfactant may be anionic, nonionic or a combination of the two.
Anionic surfactants suitable for facilitating emulsion polymerizations are well known in the polymer art, and include sodium lauryl sulfate, sodium dodecyl benzene sulfonate, disodium laureth-3 sulfosuccinate, sodium dioctyl sulfosuccinate, sodium di-sec-butyl naphthalene sulfonate, disodium dodecyl diphenyl ether sulfonate, disodium n-octadecyl sulfosuccinate, phosphate esters of branched alcohol ethoxylates, and the like.
The coating composition can optionally contain polyolefin base polymers functionalized with a polar group such as an acid group, such as polypropylene or polyethylene homopolymer or copolymer in which the polymer has been modified with carboxylic acid.
Exemplary polyolefins include, but are not limited to, one or more thermoplastic polyolefin homopolymers or copolymers of one or more alpha-olefins such as ethylene, propylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-hexene, 1-octene, 1-decene, and 1-dodecene, as typically represented by polyethylene, polypropylene, poly-1-butene, poly-3-methyl-1-butene, poly-3-methyl-1-pentene, poly-4-methyl-1-pentene, ethylene-propylene copolymer, ethylene-1-butene copolymer, and propylene-1-butene copolymer. Such exemplary polyolefins may have a molecular weight of greater than 800 grams/mole; for example, greater than 5,000 grams/mole; or in the alternative, greater than 50,000 grams/mole.
The base polymers mentioned above comprise a polar group as either a comonomer or grafted monomer. Exemplary polar polyolefins include, but are not limited to, maleic anhydride grafted polyethylene homopolymer or copolymer, maleic anhydride grafted polypropylene homopolymer or copolymer, ethylene-acrylic acid (EAA) and ethylene-methacrylic acid copolymers, such as those available under the trademarks PRIMACOR™, commercially available from The Dow Chemical Company, NUCREL™, commercially available from E.I. DuPont de Nemours, and ESCOR™, commercially available from ExxonMobil Chemical Company and described in U.S. Pat. Nos. 4,599,392; 4,988,781 and 5,938,437.
The polar polyolefin polymer such as an ethylene-acrylic acid (EAA) or ethylene-methacrylic acid copolymer can be present with the surfactant when the ethylenically unsaturated monomer component is polymerized in the presence of the surfactant, or alternatively, it may be added to the coating composition after polymerization of the ethylenically unsaturated monomer component. The polar polyolefin is typically at least partially neutralized with ammonia or an organic amine.
The polar polyolefin provides enhanced flexibility to the cured coating, which is particularly desirable in coatings for metal can ends and for can bodies that are formed by a deep drawing process. The polar polyolefins are typically present in the coating composition in amounts of 5 to 50, such as 20 to 40 percent by weight based on total weight of the ethylenically unsaturated monomer component, the surfactant and the polar polyolefin.
The polymerization of the surfactant into the latex may also contribute to the flexibility of coatings made from the present latex, although the inventors do not wish to be bound by this. For example, coatings used according to the present invention can have a flexibility as identified by wedge bend testing of 90% or greater or 95% or greater. This is further described in the example section, below.
The average particle size of the latex particles can be 0.05 micron, or greater such as at 0.08 micron or greater or 0.1 micron or greater, and can be up to 1.0 micron or less, such as 0.5 micron or less or 0.2 micron or less. The average particle size can range, for example, from 0.05 to 1.0 micron, such as 0.1 to 0.5 micron, 0.1 to 0.2 micron, or 0.08 to 0.2 micron. The Mw of these particles as measured by gel-permeation chromatography in tetrahydrofuran can be, for example, 50,000 or greater, such as 100,000 or greater or 400,000 or greater, and can be 1,000,000 or less, such as 800,000 or less or 650,000 or less. The average Mw of these particles can range, for example, from 50,000 to 1,000,000, such as 100,000 to 800,000 or 400,000 to 650,000. Higher Mw may increase flexibility and/or resistance of the film coating. Any values within these broad ranges are also within the scope of the present invention, as are higher or lower numbers. Theoretical Tg values, that is, Tg calculated via the Fox Equation, for the latex can be as low as −20° C. or greater, such as 5° C. or greater or 25° C. or greater and as high as 100° C. or lower, such as 80° C. or lower or 40° C. or lower. The Tg can range, for example, from −20° C. to 100° C., such as 25° C. to 80° C. or 5° C. to 40° C.
The compositions according to the present invention can comprise, for example, 50 or greater wt % of the latex having a reactive functional group, such as 80% or greater or 90% or greater, and can have up to 99.9% or less of such latex, such as 95% or less or 85% or less. The amount of latex having a reactive function group in the coating compositions can range, for example, from 10 to 99.9 wt %, such as 20 to 95 wt % or 50 to 95 wt %. Weight percent here is based on the total solid, such as resin solids weight of the coating.
The phosphorus acid used in the present invention can be a phosphinic acid (H₃PO₂), a phosphonic acid (H₃PO₃) and/or a phosphoric acid (H₃PO₄). The phosphoric acid can be in the form of an aqueous solution, for example, an 85 percent by weight aqueous solution, or can be 100 percent phosphoric acid or super phosphoric acid. The phosphorus acid can also be diluted in a water miscible solvent. The amount of phosphorus acid in weight percent used in the present invention reflects the amount of acid itself, and not the combined amount of acid and solvent, if used.
The phosphorus acid can be used in any amount, such as 0.01 wt % or greater, 0.05 wt % or greater or 0.1 wt % or greater and can be used in amounts less than 5 wt %, less than 1 wt % or less than 0.05%, based on total solid such as resin solids weight of the coating. The phosphorus acid can be phosphoric acid used in an amount ranging from 0.1 to 1.0 wt %, based on the total solid such as resin solids weight of the coating.
As noted above, it has been surprisingly discovered that use of a phosphorus acid in the coatings of the present invention provide a curable coating composition having 5 wt % or less crosslinker. Typical crosslinkers for resins or latices having reactive functional groups include polyisocyanates, aminoplast resins and phenolic resins such as those based on benzoguanamine, water-borne isocyanates, phenolics and melamine aminoplasts, all of which are widely commercially available, such as from SI Group or Allenex. “Crosslinker” can specifically refer to amino resins, such as those formed from the reaction of a triazine such as melamine or benzoguanamine with formaldehyde, and/or phenolic resins, such as those formed from the reaction of a phenol with formaldehyde. Non-limiting examples of phenols that may be used to form phenolic resins are resol, phenol, butyl phenol, xylenol and cresol. These crosslinkers generally are formed from and/or degrade to produce at least trace amounts of formaldehyde. Elimination of these crosslinkers can therefore eliminate formaldehyde. Accordingly, the present coating compositions can be completely free of formaldehyde, that is, formaldehyde is not released during curing of the composition.
The compositions of the invention may contain a hydroxyalkylamide crosslinking agent that is particularly effective when used with the phosphorus acid. The hydroxyalkylamides are typically of the structure:
wherein R¹⁰and R¹¹each, independently, represent an electron withdrawing group, such as carbonyl;
Y¹, Y², Y³and Y⁴each, independently, represent a C₁to C₃alkylene group; and
X represents a C₂to C₆alkylene group.
Suitably, each of Y¹, Y², Y³and Y⁴represent an ethylene group.
Suitably, X represents a butylene group.
The crosslinker material may comprise a commercially available beta-hydroxyalkylamide crosslinker, such as, for example, PRIMID XL-552, i.e., N,N,N′,N′-tetrakis(2-hydroxypropyl)adipamide, and PRIMID QM-1260 (available from EMS Chemie).
Besides hydroxyalkylamide crosslinking agents, hydroxyalkylurea crosslinking agents can be used. The hydroxyalkylureas are typically of the structure:
wherein R₂is a substituted or unsubstituted C₁to C₃₆alkyl group, an aromatic group, the residue of an isocyanurate, biuret, allophanate, glycoluril, benzoguanamine and/or polyether amine; wherein each R₁is independently a hydrogen, an alkyl having at least 1 carbon atom, or a hydroxy functional alkyl having 2 or more carbon atoms and at least one R₁is hydroxyalkyl having 2 or more carbon atoms; and n is 2 to 6.
The crosslinker can be used in amounts of 20 wt % or less, 15 wt % or less, and 5 wt % or less, and 1 wt % or greater, 3 wt % or greater, and 10 wt % or greater. Ranges of 3 to 15 wt % can be used. Weight percent is based on total resin solids of the composition.
If desired, the compositions can comprise other optional materials well known in the art of formulating coatings, such as colorants, plasticizers, abrasion-resistant particles, anti-oxidants, hindered amine light stabilizers, UV light absorbers and stabilizers, surfactants, flow control agents, thixotropic agents, fillers, organic cosolvents, reactive diluents, catalysts, grind vehicles, lubricants, waxes and other customary auxiliaries.
As used herein, the term “colorant” means any substance that imparts color and/or other opacity and/or other visual effect to the composition. The colorant can be added to the coating in any suitable form, such as discrete particles, dispersions, solutions and/or flakes. A single colorant or a mixture of two or more colorants can be used in the coatings of the present invention. Suitable colorants are listed in U.S. Pat. No. 8,614,286, column 7, line 2 through column 8, line 65, which is incorporated by reference herein. Particularly suitable for packaging coatings are those approved for food contact, such as titanium dioxide; iron oxides, such as black iron oxide; carbon black; ultramarine blue; phthalocyanines, such as phthalocyanine blue and phthalocyanine green; chromium oxides, such as chromium green oxide; graphite fibrils; ferried yellow; quindo red; and combinations thereof, and those listed in Article 178.3297 of the Code of Federal Regulations, which is incorporated by reference herein.
In general, the colorant can be present in any amount sufficient to impart the desired visual and/or color effect. The colorant may comprise from 1 to 65 weight percent of the present compositions, such as from 3 to 40 weight percent or 5 to 35 weight percent, with weight percent based on the total weight of the compositions.
An “abrasion-resistant particle” is one that, when used in a coating, will impart some level of abrasion resistance to the coating as compared with the same coating lacking the particles. Suitable abrasion-resistant particles include organic and/or inorganic particles. Examples of suitable organic particles include, but are not limited to, diamond particles, such as diamond dust particles, and particles formed from carbide materials; examples of carbide particles include, but are not limited to, titanium carbide, silicon carbide and boron carbide. Examples of suitable inorganic particles, include, but are not limited to, silica; alumina; alumina silicate; silica alumina; alkali aluminosilicate; borosilicate glass; nitrides including boron nitride and silicon nitride; oxides including titanium dioxide and zinc oxide; quartz; nepheline syenite; zircon such as in the form of zirconium oxide; buddeluyite; and eudialyte. Particles of any size can be used, as can mixtures of different particles and/or different sized particles. For example, the particles can be microparticles, having an average particle size of 0.1 to 50, 0.1 to 20, 1 to 12, 1 to 10, or 3 to 6 microns, or any combination within any of these ranges. The particles can be nanoparticles, having an average particle size of less than 0.1 micron, such as 0.8 to 500, 10 to 100, or 100 to 500 nanometers, or any combination within these ranges.
The latex having a reactive functional group and/or coating compositions comprising the same according to the present invention may be substantially free, may be essentially free and/or may be completely free of bisphenol A and derivatives or residues thereof, including bisphenol A and bisphenol A diglycidyl ether (“BADGE”). A latex and/or coating that is substantially bisphenol A free is sometimes referred to as “BPA non intent” because BPA, including derivatives or residues thereof, are not intentionally added but may be present in trace amounts such as because of impurities or unavoidable contamination from the environment. The latex and/or coatings of the present invention can also be substantially free, essentially free and/or completely free of bisphenol F and derivatives or residues thereof, including bisphenol F and bisphenol F diglycidyl ether (“BPFDG”), or any other bisphenol compound. The latex and/or coating comprising the same according to the present invention may be substantially free, essentially free and/or completely free of styrene, and/or may be substantially free, essentially free and/or completely free of phenol. Non-limiting examples of phenols are resol, phenol, butyl phenol, xylenol and cresol. The term “substantially free” means the latex and/or coating compositions contain less than 1000 parts per million (ppm), “essentially free” means less than 100 ppm and “completely free” means less than 20 parts per billion (ppb) of any of the above compounds or derivatives or residues thereof.
The compositions described herein can be applied to any substrates, for example, automotive substrates, industrial substrates, packaging substrates, wood flooring and furniture, apparel, electronics including housings and circuit boards, glass and transparencies, sports equipment including golf balls, and the like. These substrates can be, for example, metallic or non-metallic. Metallic substrates include tin, steel, tin-plated steel, chromium passivated steel, galvanized steel, aluminum, aluminum foil, coiled steel or other coiled metal. Non-metallic substrates including polymeric, plastic, polyester, polyolefin, polyimide, cellulosic, polystyrene, polyacrylic, poly(ethylene naphthalate), polypropylene, polyethylene, nylon, EVOH, polylactic acid, other “green” polymeric substrates, poly(ethyleneterephthalate) (“PET”), polycarbonate, polycarbonate acrylobutadiene styrene (“PC/ABS”), polyimide, wood, veneer, wood composite, particle board, medium density fiberboard, cement, stone, glass, paper, cardboard, textiles, leather, both synthetic and natural, and the like. The substrate can be one that has been already treated in some manner, such as to impart visual and/or color effect.
The coating compositions used in the present invention can be applied by any means standard in the art, such as electrocoating, spraying, electrostatic spraying, dipping, rolling, brushing, roller coating, flow coating, extrusion and the like.
The coating compositions can be applied to a dry film thickness of 0.04 mils or greater, such as 0.1 mil or greater or 0.7 mil or greater and up to 4 mils or less, such as 2 mils or less or 1.3 mils or less, with suitable ranges from 0.04 mils to 4 mils, such as 0.1 to 2 or 0.7 to 1.3 mils. For some applications, the coatings can be applied to a dry film thickness of 0.1 mils or greater, 0.5 mils or greater, 1.0 mils or greater, 2.0 mils or greater, 5.0 mils or greater, or even thicker. For packaging coatings, the dry film thickness can be, for example, 1.0 to 20 microns. The coating compositions of the present invention can be used alone, or in combination with one or more other coating compositions. For example, the coating compositions of the present invention can comprise a colorant or not and can be used as a primer, basecoat, and/or top coat. For substrates coated with multiple coatings, one or more of those coatings can be coatings as described herein.
It will be appreciated that the coatings described herein can be either one component (“1 K”), or multi-component compositions such as two component (“2 K”) or more. A 1 K composition will be understood as referring to a composition wherein all the coating components are maintained in the same container after manufacture, during storage, etc. A 1 K coating can be applied to a substrate and cured by any conventional means, such as by heating, forced air, radiation cure and the like. The present coating compositions can also be multi-component coating compositions, which will be understood as coatings in which various components are maintained separately until just prior to application. The present coatings can be thermoplastic or thermosetting. Thermoset coating compositions are particularly suitable for packaging.
The present coating composition can be applied as a clearcoat. A clearcoat will be understood as a coating that is substantially transparent. A clearcoat can therefore have some degree of color, provided it does not make the clearcoat opaque or otherwise affect, to any significant degree, the ability to see the underlying substrate. The clearcoats of the present invention can be used, for example, in conjunction with a pigmented basecoat. The clearcoat can be modified by reaction with carbamate.
The present coating composition can also be applied as a basecoat used alone or in conjunction with one or more other coatings. A basecoat is typically pigmented; that is, it will impart some sort of color and/or other visual effect to the substrate to which it is applied.
The coating compositions used according to the present invention can be applied alone or as part of a coating system that can be deposited onto the different substrates that are described herein. Such a coating system typically comprises a number of coating layers, such as two or more. A coating layer is typically formed when a coating composition that is deposited onto the substrate is substantially cured by methods known in the art (e.g., by thermal heating). The coating compositions described above can be used in one or more of the coating layers described herein.
In a conventional coating system used in the automotive industry, a pretreated substrate is coated with an electrodepositable coating composition. After the electrodepositable coating composition is cured, a primer-surfacer coating composition is applied onto a least a portion of the electrodepositable coating composition. The primer-surfacer coating composition is typically applied to the electrodepositable coating layer and cured prior to a subsequent coating composition being applied over the primer-surfacer coating composition. However, the substrate may not be coated with an electrodepositable coating composition. Accordingly, the primer-surfacer coating composition is applied directly onto the substrate or the primer-surfacer coating composition is not used in the coating system. Therefore, a color imparting basecoat coating composition can be applied directly onto the cured electrodepositable coating composition.
A clearcoat can be deposited onto at least a portion of the basecoat coating layer. The substantially clear coating composition can comprise a colorant but not in an amount such as to render the clear coating composition opaque (not substantially transparent) after it has been cured. In certain instances, the BYK Haze value of the cured composition is less than 50, can be less than 35, and is often less than 20 as measured using a BYK Haze Gloss meter available from BYK Chemie USA.
The coating compositions according to the present invention may be used in a monocoat coating system. In a monocoat coating system, a single coating layer is applied over a substrate (which can be pretreated or non-pretreated) that can comprise one or more of the following layers (as described above): an electrodepositable coating layer or a primer-surfacer coating layer.
The coating compositions described herein are particularly suitable for use as a packaging coating. The application of various pretreatments and coatings to packaging is well established. Such treatments and/or coatings, for example, can be used in the case of metal cans, wherein the treatment and/or coating may be used, for example, to retard or inhibit corrosion, provide a decorative coating, provide ease of handling during the manufacturing process, and the like. Coatings can be applied to the interior of such cans to prevent the contents from contacting the metal of the container. Contact between the metal and a food or beverage, for example, can lead to corrosion of a metal container, which can then contaminate the food or beverage. This is particularly true when the contents of the can are acidic in nature. The coatings applied to the interior of metal cans also help prevent corrosion in the headspace of the cans, which is the area between the fill line of the product and the can lid; corrosion in the headspace is particularly problematic with food products having a high salt content. Coatings can also be applied to the exterior of metal cans. Certain coatings of the present invention are particularly applicable for use with coiled metal stock, such as the coiled metal stock from which the ends of cans are made (“can end stock”), and end caps and closures are made (“cap/closure stock”). Since coatings designed for use on can end stock and cap/closure stock are typically applied prior to the piece being cut and stamped out of the coiled metal stock, they are typically flexible and extensible. For example, such stock is typically coated on both sides. Thereafter, the coated metal stock is punched. For can ends, the metal is then scored for the “pop-top” opening and the pop-top ring is then attached with a pin that is separately fabricated. The end is then attached to the can body by an edge rolling process. A similar procedure is done for “easy open” can ends. For easy open can ends, a score substantially around the perimeter of the lid allows for easy opening or removing of the lid from the can, typically by means of a pull tab. For caps and closures, the cap/closure stock is typically coated, such as by roll coating, and the cap or closure stamped out of the stock; it is possible, however, to coat the cap/closure after formation. Coatings for cans subjected to relatively stringent temperature and/or pressure requirements may desirably also be resistant to cracking, popping, corrosion, blushing and/or blistering.
Accordingly, the present invention is further directed to a package coated at least in part with any of the coating compositions described above. Accordingly, the present invention is directed to a package coated at least in part with any of the coating compositions described above. A “package” is anything used to contain another item, particularly for shipping from a point of manufacture to a consumer, and for subsequent storage by a consumer. A package will be therefore understood as something that is sealed so as to keep its contents free from deterioration until opened by a consumer. The manufacturer will often identify the length of time during which the food or beverage will be free from spoilage, which typically ranges from several months to years. Thus, the present “package” is distinguished from a storage container or bakeware in which a consumer might make and/or store food; such a container would only maintain the freshness or integrity of the food item for a relatively short period. A package according to the present invention can be made of metal or non-metal, for example, plastic or laminate, and be in any form. An example of a suitable package is a laminate tube. Another example of a suitable package is metal can. The term “metal can” includes any type of metal can, container or any type of receptacle or portion thereof that is sealed by the food/beverage manufacturer to minimize or eliminate spoilage of the contents until such package is opened by the consumer. One example of a metal can is a food can; the term “food can(s)” is used herein to refer to cans, containers or any type of receptacle or portion thereof used to hold any type of food and/or beverage. The term “metal can(s)” specifically includes food cans and also specifically includes “can ends” including “E-Z open ends”, which are typically stamped from can end stock and used in conjunction with the packaging of food and beverages. The term “metal cans” also specifically includes metal caps and/or closures such as bottle caps, screw top caps and lids of any size, lug caps, and the like. The metal cans can be used to hold other items as well, including, but not limited to, personal care products, bug spray, spray paint, and any other compound suitable for packaging in an aerosol can. The cans can include “two piece cans” and “three-piece cans” as well as drawn and ironed one-piece cans; such one piece cans often find application with aerosol products. Packages coated according to the present invention can also include plastic bottles, plastic tubes, laminates and flexible packaging, such as those made from PE, PP, PET and the like. Such packaging could hold, for example, food, toothpaste, personal care products and the like.
The coating compositions can be applied to the interior and/or the exterior of the package. For example, the coating compositions can be rollcoated onto metal used to make a two-piece food can, a three-piece food can, can end stock and/or cap/closure stock. The coating compositions can be applied to a coil or sheet by roll coating; the coating composition is then cured by heating or radiation and can ends are stamped out and fabricated into the finished product, i.e. can ends. The coating compositions can be applied as a rim coat to the bottom of the can; such application can be by roll coating. The rim coat functions to reduce friction for improved handling during the continued fabrication and/or processing of the can. The coating compositions can be applied to caps and/or closures; such application can include, for example, a protective varnish that is applied before and/or after formation of the cap/closure and/or a pigmented enamel post applied to the cap, particularly those having a scored seam at the bottom of the cap. Decorated can stock can also be partially coated externally with the coating compositions described herein, and the decorated, coated can stock used to form various metal cans.
The packages of the present invention can be coated with any of the compositions described above by any means known in the art, such as spraying, roll coating, dipping, flow coating and the like; the coating may also be applied by electrocoating when the substrate is conductive. The appropriate means of application can be determined by one skilled in the art based upon the type of package being coated and the type of function for which the coating is being used. The coatings described above can be applied over the substrate as a single layer or as multiple layers with multiple heating stages between the application of each layer, if desired. After application to the substrate, the coating composition may be cured by any appropriate means.
The coatings can be applied to a dry film thickness of 0.04 mils or greater, such as 0.1 mil or greater or 0.7 mil or greater and up to 4 mils or less, such as 2 mils or less or 1.3 mils or less, with suitable ranges from 0.04 mils to 4 mils, such as 0.1 to 2 or 0.7 to 1.3 mils. For some applications, the coatings can be applied to a dry film thickness of 0.1 mils or greater, 0.5 mils or greater, 1.0 mils or greater, 2.0 mils or greater, 5.0 mils or greater, or even thicker. For packaging coatings, the dry film thickness can be, for example, 1.0 to 20 microns. The coatings of the present invention can be used alone, or in combination with one or more other coatings. For example, the coatings of the present invention can comprise a colorant or not and can be used as a primer, basecoat, and/or top coat. For substrates coated with multiple coatings, one or more of those coatings can be coatings as described herein. For example, a coating such as described herein can be spray applied as a top coat over a roller applied basecoat of a different composition for improvements in organoleptic performance.
As used herein, unless otherwise expressly specified, all numbers such as those expressing values, ranges, amounts or percentages may be read as if prefaced by the word “about”, even if the term does not expressly appear. Also, any numerical range recited herein is intended to include all sub-ranges subsumed therein. Singular encompasses plural and vice versa. For example, although reference is made herein to “a” latex, “a” reactive functional group, “a” latex, “a” latex polymer, “a” phosphorus acid, one or more of each of these and any other components can be used. As used herein, the term “polymer” refers to oligomers and both homopolymers and copolymers, and the prefix “poly” refers to two or more. “Including”, “for example”, “such as” and like terms means including, for example, such as, but not limited to. When ranges are given, any endpoints of those ranges and/or numbers within those ranges can be combined with the scope of the present invention. The terms “acrylic” and “acrylate” are used interchangeably (unless to do so would alter the intended meaning) and include acrylic acids, anhydrides, and derivatives thereof, lower alkyl-substituted acrylic acids, e.g., C₁-C₂substituted acrylic acids, such as methacrylic acid, ethacrylic acid, etc., and their C₁-C₆alkyl esters and hydroxyalkyl esters, unless clearly indicated otherwise. The terms “(meth)acrylic” or “(meth)acrylate” are intended to cover both the acrylic/acrylate and methacrylic/methacrylate forms of the indicated material, e.g., a (meth)acrylate monomer.

EXAMPLES

The following examples are intended to illustrate the present invention and are not intended to limit the invention in any way.

Example 1 Latex Preparation

Latex 1
A total of 14 grams of MAXEMUL 6106 (anionic surfactant commercially available from Croda) was added to an Erlenmeyer flask with 421 grams of deionized water and stirred well. A total of 98 grams of hydroxyethyl methacrylate, 349 grams of styrene, 644 grams of ethyl acrylate and 22 grams of methacrylic acid were added in order to the Erlenmeyer while mixing well. It was mixed until the monomer emulsion showed no separation upon standing. This is referred to below as the monomer premix.
A total of 1431 grams of deionized water was placed into a 5-liter, 4-neck round bottom flask equipped with a stirrer, water-cooled reflux condenser, two addition funnels and a thermocouple. The water was heated to 80° C. with stirring and under a nitrogen gas blanket. A total of 15 grams of the monomer premix was added to the reactor over 2 minutes. A total of 0.5 grams of ammonium persulfate dissolved in 5 grams of water was then added over 1 minute to the reactor. After 20 minutes, 4 grams of ammonium persulfate dissolved in 419 grams of water were added to the flask.
The remaining 1554 grams of the monomer premix and 4.4 grams of ammonium persulfate dissolved in 419 grams of water were added simultaneously to the flask over 150 minutes. At the end of the monomer feed the reaction was maintained at 80° C. for an additional 60 minutes. An aliquot of 4.5 grams of t-butyl peroctoate thinned with 22 grams of Dowanol PM (commercially available from Dow) were added over 5 minutes as a chase initiator to the reactor. The reaction was held with stirring for an additional 60 minutes at 80° C. It was then allowed to cool to <40° C. A total of 11 grams of dimethylethanolamine in 34 grams of water was added over about 5 minutes. The contents of the flask were filtered and filled out into a suitable container. The final latex had a measured solids of 33%, a surface weighted mean particle size of 121 nm, a Brookfield Viscosity of 33 centipoise (#4@60 rpm) and a bluish-white appearance. Unless otherwise indicated, Brookfield Viscosity is measured at 20° C.
Latex 2
A total of 14 grams of MAXEMUL 6106 was added to an Erlenmeyer flask with 421 grams of deionized water and stirred well. A total of 45 grams of glycidyl methacrylate, 279 grams of styrene, 550 grams of ethyl acrylate and 18 grams of methacrylic acid were added in order to the Erlenmeyer while mixing well. It was mixed until the monomer emulsion showed no separation upon standing. This is the monomer premix.
A total of 1145 grams of deionized water was placed into a 5-liter, 4-neck round bottom flask equipped with a stirrer, water-cooled reflux condenser, two addition funnels and a thermocouple. The water was heated to 80° C. with stirring and under a nitrogen gas blanket. A total of 12 grams of the monomer premix was then added to the reactor over 2 minutes. A total of 0.39 grams of ammonium persulfate dissolved in 4 grams of water was added over 1 minute to the reactor. After 20 minutes, 4 grams of ammonium persulfate dissolved in 335 grams of water were added to the flask.
The remaining 1227 grams of the monomer premix and 3.5 grams of ammonium persulfate dissolved in 335 grams of water were added simultaneously to the flask over 150 minutes. At the end of the monomer feed the reaction was maintained at 80° C. for an additional 60 minutes. An aliquot of 3.6 grams of t-butyl peroctoate thinned with 18 grams of Dowanol PM were added over 5 minutes as a chase initiator to the reactor. The reaction was held with stirring for an additional 60 minutes at 80° C. It was then allowed to cool to <40° C. A total of 9 grams of dimethylethanolamine in 28 grams of water was added over about 5 minutes. The contents of the flask were filtered and filled out into a suitable container. The final latex had a measured solids of 33%, a surface weighted mean particle size of 109 nm, a Brookfield Viscosity of 36 centipoise (#4@60 rpm) and a bluish-white appearance.
Latex 3
A total of 11 grams of MAXEMUL 6106 was added to an Erlenmeyer flask with 337 grams of deionized water and stirred well. A total of 45 grams of glycidyl methacrylate, 279 grams of methyl methacrylate, 550 grams of ethyl acrylate and 18 grams of methacrylic acid were added in order to the Erlenmeyer while mixing well. It was mixed until the monomer emulsion showed no separation upon standing. This is the monomer premix.
A total of 1147 grams of deionized water was placed into a 5-liter, 4-neck round bottom flask equipped with a stirrer, water-cooled reflux condenser, two addition funnels and a thermocouple. The water was heated to 80° C. with stirring and under a nitrogen gas blanket. A total of 12 grams of the monomer premix was then added to the reactor over 2 minutes. A total of 0.39 grams of ammonium persulfate dissolved in 4 grams of water was added over 1 minute to the reactor. After 20 minutes, 3.5 grams of ammonium persulfate dissolved in 335 grams of water were added to the flask.
The remaining 1227 grams of the monomer premix and 3.5 grams of ammonium persulfate dissolved in 335 grams of water were added simultaneously to the flask over 150 minutes. At the end of the monomer feed the reaction was maintained at 80° C. for an additional 60 minutes. An aliquot of 3.6 grams of t-butyl peroctoate thinned with 18 grams of Dowanol PM were added over 5 minutes as a chase initiator to the reactor. The reaction was held with stirring for an additional 60 minutes at 80° C. It was then allowed to cool to <40° C. A total of 7 grams of dimethylethanolamine in 22 grams of water was added over about 5 minutes. The contents of the flask were filtered and filled out into a suitable container. The final latex had a measured solids of 33%, a surface weighted mean particle size of 111 nm, a Brookfield Viscosity of 32 centipoise (#4@60 rpm) and a bluish-white appearance.
Latex 4
A total of 24 grams of Rhodapex CO436 (non-polymerizable surfactant ammonium nonyl phenol ether sulfate 58% resin solids in ethanol/water solvent) was added to an Erlenmeyer flask with 421 grams of deionized water and stirred well. A total of 99 grams of hydroxyethyl methacrylate, 349 grams of styrene, 645 grams of ethyl acrylate and 22 grams of methacrylic acid were added in order to the Erlenmeyer while mixing well. It was mixed until the monomer emulsion showed no separation upon standing. This is the monomer premix.
A total of 1422 grams of deionized water was placed into a 5-liter, 4-neck round bottom flask equipped with a stirrer, water-cooled reflux condenser, two addition funnels and a thermocouple. The water was heated to 80° C. with stirring and under a nitrogen gas blanket. A total of 16 grams of the monomer premix was then added to the reactor over 2 minutes. A total of 0.5 grams of ammonium persulfate dissolved in 5 grams of water was added over 1 minute to the reactor. After 20 minutes, 4.4 grams of ammonium persulfate dissolved in 419 grams of water and the remaining 1543 grams of monomer premix were fed into the reactor simultaneously over 150 minutes. At the end of the monomer feed the reaction was maintained at 80° C. for an additional 60 minutes. An aliquot of 4.5 grams of t-butyl peroctoate thinned with 22 grams of Dowanol PM were added over 5 minutes as a chase initiator to the reactor. The reaction was held with stirring for an additional 60 minutes at 80° C. It was then allowed to cool to <40° C. A total of 11 grams of dimethylethanolamine in 34 grams of water was added over about 5 minutes. The contents of the flask were filtered and filled out into a suitable container. The final latex had a measured solids of 32%, a surface weighted mean particle size of 122 nm, a Brookfield Viscosity of 10 centipoise (#4@60 rpm) and a bluish-white appearance.
Latex 5
A total of 24 grams of Rhodapex CO436 was added to an Erlenmeyer flask with 421 grams of deionized water and stirred well. A total of 56 grams of glycidyl methacrylate, 349 grams of styrene, 688 grams of ethyl acrylate and 22 grams of methacrylic acid were added in order to the Erlenmeyer while mixing well. It was mixed until the monomer emulsion showed no separation upon standing. This is the monomer premix.
A total of 1422 grams of deionized water was placed into a 5-liter, 4-neck round bottom flask equipped with a stirrer, water-cooled reflux condenser, two addition funnels and a thermocouple. The water was heated to 80° C. with stirring and under a nitrogen gas blanket. A total of 16 grams of the monomer premix was then added to the reactor over 2 minutes. A total of 0.5 grams of ammonium persulfate dissolved in 5 grams of water was added over 1 minute to the reactor. After 20 minutes, 4.4 grams of ammonium persulfate dissolved in 419 grams of water and the remaining 1543 grams of monomer premix were fed into the reactor simultaneously over 150 minutes. At the end of the monomer feed the reaction was maintained at 80° C. for an additional 60 minutes. An aliquot of 4.5 grams of t-butyl peroctoate thinned with 22 grams of Dowanol PM were added over 5 minutes as a chase initiator to the reactor. The reaction was held with stirring for an additional 60 minutes at 80° C. It was then allowed to cool to <40° C. A total of 11 grams of dimethylethanolamine in 34 grams of water was added over about 5 minutes. The contents of the flask were filtered and filled out into a suitable container. The final latex had a measured solids of 31%, a surface weighted mean particle size of 122 nm, a Brookfield Viscosity of 13 centipoise (#4@60 rpm) and a bluish-white appearance.
Latex 6
A total of 5.6 grams of MAXEMUL 6106 was added to an Erlenmeyer flask with 153 grams of deionized water and stirred well. A total of 23 grams of glycidyl methacrylate, 139 grams of methyl methacrylate, 221 grams of ethyl acrylate, 22 grams of methacrylic acid and 40 grams of hydroxyethyl methacrylate were added in order to the Erlenmeyer while mixing well. The contents were mixed until the monomer emulsion showed no sign of separation upon standing. This is the monomer premix.
A total of 724 grams of deionized water was placed into a 3-liter, 4-neck round bottom flask equipped with a stirrer, water-cooled reflux condenser, two addition funnels and a thermocouple. The water was heated to 80° C. with stirring and under a nitrogen gas blanket. A total of 6 grams of the monomer premix was added to the reactor over 2 minutes. A total of 0.2 grams of ammonium persulfate dissolved in 2 grams of water was then added over 1 minute to the reactor.
After stirring the reaction for 20 minutes, the remaining 599 grams of the monomer premix and 1.8 grams of ammonium persulfate dissolved in 167 grams of water were added simultaneously to the flask over 150 minutes. At the end of the monomer feed the reaction was maintained at 80° C. for an additional 60 minutes. An aliquot of 1.8 grams of t-butyl peroctoate dissolved in 9 grams of Dowanol PM were added over 5 minutes as a chase initiator to the reactor. The reaction was held with stirring for an additional 60 minutes at 80° C. It was then allowed to cool to <40° C. A total of 9 grams of dimethylethanolamine in 28 grams of water was added over about 5 minutes. The contents of the flask were filtered and filled out into a suitable container. The final latex had a measured solids of 30%, a Z-average particle size of 175 nm, a Brookfield Viscosity of 20 centipoise (#4@60 rpm) and a bluish-white appearance.
Latex 7
A total of 4.6 grams of Adeka Reasoap SR-10 was added to an Erlenmeyer flask with 153 grams of deionized water and stirred well. A total of 23 grams of glycidyl methacrylate, 139 grams of methyl methacrylate, 221 grams of ethyl acrylate, 22 grams of methacrylic acid and 40 grams of hydroxyethyl methacrylate were added in order to the Erlenmeyer while mixing well. The contents were mixed until the monomer emulsion showed no sign of separation upon standing. This is the monomer premix.
A total of 722 grams of deionized water was placed into a 3-liter, 4-neck round bottom flask equipped with a stirrer, water-cooled reflux condenser, two addition funnels and a thermocouple. The water was heated to 80° C. with stirring and under a nitrogen gas blanket. A total of 6 grams of the monomer premix was added to the reactor over 2 minutes. A total of 0.2 grams of ammonium persulfate dissolved in 2 grams of water was then added over 1 minute to the reactor.
After stirring the reaction for 20 minutes, the remaining 598 grams of the monomer premix and 1.8 grams of ammonium persulfate dissolved in 167 grams of water were added simultaneously to the flask over 150 minutes. At the end of the monomer feed the reaction was maintained at 80° C. for an additional 60 minutes. An aliquot of 1.8 grams of t-butyl peroctoate dissolved in 9 grams of Dowanol PM were added over 5 minutes as a chase initiator to the reactor. The reaction was held with stirring for an additional 60 minutes at 80° C. It was then allowed to cool to <40° C. A total of 9 grams of dimethylethanolamine in 28 grams of water was added over about 5 minutes. The contents of the flask were filtered and filled out into a suitable container. The final latex had a measured solids of 29%, a volume weighted mean particle size of 145 nm, a Brookfield Viscosity of 22 centipoise (#4@60 rpm) and a bluish-white appearance.
Latex 8
A total of 5.7 grams of sodium dioctyl sulfosuccinate at 75% solids (AOT-75 from Cytec Solvay Group) and 11.4 grams of MAXEMUL 5010 was added to an Erlenmeyer flask with 323 grams of deionized water and stirred well. A total of 47 grams of glycidyl methacrylate, 279 grams of methyl methacrylate, 485 grams of ethyl acrylate, 45 grams of methacrylic acid, and 36 grams of hydroxyethyl acrylate were added in order to the Erlenmeyer while mixing well. The contents were mixed until the monomer emulsion showed no separation upon standing. This is the monomer premix.
A total of 1003 grams of deionized water was placed into a 5-liter, 4-neck round bottom flask equipped with a stirrer, water-cooled reflux condenser, two addition funnels and a thermocouple. The water was heated to 80° C. with stirring and under a nitrogen gas blanket. A total of 0.39 grams of ammonium persulfate dissolved in 3.9 grams of water was then added over 1 minute to the reactor. A total of 12 grams of the monomer premix was then added to the reactor over 2 minutes.
After stirring the reaction for 20 minutes, the remaining 1219 grams of the monomer premix and 3.5 grams of ammonium persulfate dissolved in 335 grams of water were added simultaneously to the flask over 150 minutes. At the end of the monomer feed the reaction was maintained at 80° C. for an additional 60 minutes. An aliquot of 0.9 grams of t-butyl peroctoate dissolved in 4.5 grams of Dowanol PM were added over 5 minutes as a chase initiator to the reactor. The reaction was held with stirring for an additional 60 minutes at 80° C. It was then allowed to cool to <40° C. A total of 18 grams of dimethylethanolamine in 55 grams of water was added over about 5 minutes. The contents of the flask were filtered and filled out into a suitable container. The final latex had a measured solids of 35%, a volume weighted mean particle size of 292 nm, a Brookfield Viscosity of 28 centipoise (#4@60 rpm) and a bluish-white appearance.
Latex 9
A total of 10.7 grams of MAXEMUL 6106 and 3.6 grams of MAXEMUL 5010 was added to an Erlenmeyer flask with 288 grams of deionized water and stirred well. A total of 4 grams of ethylene glycol dimethacrylate, 262 grams of methyl methacrylate, 454 grams of ethyl acrylate, 42 grams of methacrylic acid, and 74 grams of hydroxyethyl acrylate were added in order to the Erlenmeyer while mixing well. The contents were mixed until the monomer emulsion showed no separation upon standing. This is the monomer premix.
A total of 1364 grams of deionized water was placed into a 5-liter, 4-neck round bottom flask equipped with a stirrer, water-cooled reflux condenser, two addition funnels and a thermocouple. The water was heated to 80° C. with stirring and under a nitrogen gas blanket. A total of 11 grams of the monomer premix was then added to the reactor over 2 minutes. A total of 0.37 grams of ammonium persulfate dissolved in 3.7 grams of water was then added over 1 minute to the reactor.
After stirring the reaction for 20 minutes, the remaining 1126 grams of the monomer premix and 3.3 grams of ammonium persulfate dissolved in 314 grams of water were added simultaneously to the flask over 150 minutes. At the end of the monomer feed the reaction was maintained at 80° C. for an additional 60 minutes. An aliquot of 3.3 grams of t-butyl peroctoate dissolved in 17 grams of Dowanol PM were added over 5 minutes as a chase initiator to the reactor. The reaction was held with stirring for an additional 60 minutes at 80° C. It was then allowed to cool to <40° C. A total of 17 grams of dimethylethanolamine in 52 grams of water was added over about 5 minutes. The contents of the flask were filtered and filled out into a suitable container. The final latex had a measured solids of 30%, a volume weighted mean particle size of 121 nm, a Brookfield Viscosity of 42 centipoise (#4@60 rpm) and a bluish-white appearance.
Latex 10
A total of 8 grams of MAXEMUL 6106 was added to an Erlenmeyer flask with 168 grams of deionized water and stirred well. A total of 139 grams of methyl methacrylate, 240 grams of ethyl acrylate, 27 grams of methacrylic acid and 40 grams of hydroxyethyl methacrylate were added in order to the Erlenmeyer while mixing well. The contents were mixed until the monomer emulsion showed no sign of separation upon standing. This is the monomer premix.
A total of 708 grams of deionized water was placed into a 5-liter, 4-neck round bottom flask equipped with a stirrer, water-cooled reflux condenser, two addition funnels and a thermocouple. The water was heated to 80° C. with stirring and under a nitrogen gas blanket. A total of 0.2 grams of ammonium persulfate dissolved in 20 grams of water was added over 1 minute to the reactor. A total of 6 grams of the monomer premix was then added to the reactor over 2 minutes.
After stirring the reaction for 20 minutes, the remaining 616 grams of the monomer premix and 1.8 grams of ammonium persulfate dissolved in 176 grams of water were added simultaneously to the flask over 150 minutes. At the end of the monomer feed the reaction was maintained at 80° C. for an additional 60 minutes. An aliquot of 0.5 grams of ammonium persulfate dissolved in 2.3 grams of water were added over 5 minutes as a chase initiator to the reactor. The reaction was held with stirring for an additional 60 minutes at 80° C. It was then allowed to cool to <40° C. A total of 11 grams of dimethylethanolamine in 33 grams of water was added over about 5 minutes. The contents of the flask were filtered and filled out into a suitable container. The final latex had a measured solids of 29.5%, a Z-average particle size of 124 nm, a Brookfield Viscosity of 76 centipoise (#4@60 rpm) and a bluish-white appearance.

Example 2 Coating Preparation

Coating Example 1

25 g of coating sample 1 were prepared by adding 2.50 g of butanol and 7.73 g of deionized water to 14.77 g of latex 1, made as described above. The mixtures were stirred manually. No phosphorus acid was used in these coatings.

Coating Examples 2-4

25 g of coating samples 2-4 were prepared by adding a 10% solution of phosphoric acid drop by drop to 14.77 g of latex 1 in an amount shown in Table 1. This mixture was stirred manually; then 2.50 g of butanol and 7.70 g of deionized water were added. Formulation of the coatings was completed using the components and amounts also shown in Table 1.

Coating Example 5

25 g of coating sample 5 were prepared by adding 2.50 g of butanol and 7.73 g of deionized water to 14.77 g of latex 2. This mixture was stirred manually. No phosphorus acid was used in these coatings.

Coating Examples 6-8

25 g of coating samples 6-8 were prepared by adding a 10% solution of phosphoric acid drop by drop to 14.77 g of latex 2 in the amount shown in Table 2. The mixtures were stirred manually; then 2.50 g of butanol and 7.70 g of deionized water were added. Formulation of the coatings was completed using the components and amounts also shown in Table 2.

Coating Example 9

25 g of coating sample 9 were prepared by adding 2.50 g of butanol and 7.73 g of deionized water to 14.77 g of latex 3. The mixtures were stirred manually. No phosphorus acid was used in these coatings.

Coating Examples 10-12

25 g of coating samples 10-12 were prepared by adding a 10% solution of phosphoric acid drop by drop to 14.77 g of latex 3 in amounts shown in Table 3. The mixtures were stirred manually; then 2.50 g of butanol and 7.70 g of deionized water were added. Formulation of the coatings was completed using the components and amounts also shown in Table 3.

Coating Example 13

20 g of coating sample 13 was prepared by adding 7.50 g of deionized water to 12.50 g of latex 4. This mixture was stirred manually. No phosphorus acid was used in this coating.

Coating Examples 14-16

20 g of coating samples 14-16 were prepared by adding 0.04 g of a 10% solution of phosphoric acid drop by drop to 12.50 g of latex 4 in an amount shown in Table 4. The mixture was stirred manually; then 7.48 g of deionized water was added. Formulation of the coatings was completed using the components and amounts also shown in Table 4.

Coating Example 17

20 g of coating sample 17 was prepared by adding 7.50 g of deionized water to 12.50 g of latex 5. This mixture was stirred manually. No phosphorus acid was used in this coating.

Coating Examples 18-20

20 g of coating samples 18-20 were prepared by adding 0.04 g of a 10% solution of phosphoric acid drop by drop to 12.50 g of latex 5 in an amount shown in Table 5. The mixture was stirred manually; then 7.07 g of deionized water was added. Formulation of the coatings was completed using the components and amounts also shown in Table 5.

Coating Example 21

20 g of coating sample 21 were prepared by adding 1.80 g of DMAE then 2.17 g of deionized water and 2.60 g of a mix of butanol and pentanol in a 3 to 1 ratio (i.e. 1.95 g of butanol and 0.65 g of pentanol) to 14.77 g of Latex 6, made as described above. The mixtures were stirred manually. No phosphorus acid was used in this coating.

Coating Examples 22-24

20 g of coating samples 22-24 were prepared by adding 1.8 g of DMAE and a 10% solution of phosphoric acid drop by drop to 13.43 g of Latex 6 in an amount shown in Table 6. This mixture was stirred manually; then 2.17 g of deionized water and 2.60 g of the butanol/pentanol (3/1) mix were added. Formulation of the coatings was completed using the components and amounts also shown in Table 6.

Coating Example 25

20 g of coating sample 25 were prepared by adding 1.80 g of DMAE then 2.43 g of deionized water and 2.60 g of butanol to 13.18 g of Latex 7, made as described above. The mixtures were stirred manually. No phosphorus acid was used in this coating.

Coating Examples 26-28

20 g of coating samples 26-28 were prepared by adding 1.8 g of DMAE and a 10% solution of phosphoric acid drop by drop to 13.43 g of Latex 7 in an amount shown in Table 7. This mixture was stirred manually; then 2.17 g of deionized water and 2.60 g of butanol were added. Formulation of the coatings was completed using the components and amounts also shown in Table 7.

Coating Example 29

20 g of coating sample 29 were prepared by adding 0.30 g of DMAE then 5.98 g of deionized water and 2.60 g of a mix of butyl glycol and pentanol in a 4 to 1 ratio (i.e. 2.08 g of butyl glycol and 0.52 g of pentanol) to 11.12 g of Latex 8, made as described above. The mixtures were stirred manually. No phosphorus acid was used in this coating.

Coating Examples 30-32

20 g of coating samples 30-32 were prepared by adding 0.45 g of DMAE and a 10% solution of phosphoric acid drop by drop to 11.12 g of Latex 8 in an amount shown in Table 8. This mixture was stirred manually; then 5.96 g of deionized water and 2.60 g of the butyl glycol/pentanol (4/1) mix were added. Formulation of the coatings was completed using the components and amounts also shown in Table 8.

Coating Example 33

20 g of coating sample 33 were prepared by adding 0.35 g of DMAE then 4.0 g of deionized water and 2.60 g of a mix of butanol and propylene glycol monomethyl ether in a 3 to 1 ratio (i.e. 1.95 g of butanol and 0.65 g of propylene glycol monomethyl ether) to 13.05 g of Latex 9, made as described above. The mixtures were stirred manually. No phosphorus acid was used in this coating.

Coating Examples 34-36

20 g of coating samples 34-36 were prepared by adding 0.35 g of DMAE and a 10% solution of phosphoric acid drop by drop to 13.05 g of Latex 9 in an amount shown in Table 9. This mixture was stirred manually; then 3.98 g of deionized water and 2.60 g of butanol/propylene glycol monomethyl ether (3/1) mix were added. Formulation of the coatings was completed using the components and amounts also shown in Table 9.

Coating Example 37

20 g of coating sample 37 were prepared by adding 3.95 g of deionized water and 2.60 g of a mix of butanol and pentanol in a 3 to 1 ratio (i.e. 1.95 g of butanol and 0.65 g of pentanol) to 13.45 g of latex 10, made as described above. The mixtures were stirred manually. No phosphorus acid was used in this coating.

Coating Examples 38-40

20 g of coating samples 38-40 were prepared by adding a 10% solution of phosphoric acid drop by drop to 13.45 g of latex 10 in an amount shown in Table 10. This mixture was stirred manually; then 3.93 g of deionized water and 2.60 g of butanol/pentanol (3/1) mix were added. Formulation of the coatings was completed using the components and amounts also shown in Table 10.

Coating Examples 41-45

20 g of coating samples 41-45 were prepared by adding a 10% solution of phosphoric acid drop by drop and PRIMID XL-552 to 13.26 g of latex 10 in an amount shown in Table 11. This mixture was stirred manually; then 3.91 g of deionized water and 2.60 g of the butanol/pentanol (3/1) mix were added. Formulation of the coatings was completed using the components and amounts also shown in Table 11.
The properties of the coatings were tested via the following methods. Results are shown in Tables 1-11. The acetic acid sterilization test was performed on all the coatings. The results are shown in Tables A-K.
Test Methods
Test Panel Preparation:
The coating samples were applied onto an ETP panel using a wire wound bar coater to give a 7-9 g/square meter dried coating weight. The substrates were cleaned by MEK before application. The coated panels were stoved in a conveyor oven with 3 controllable heating zones at the following temperature settings: zone 1 145° C.; zone 2 220° C.; zone 3 220° C. at a conveyor speed setting of 2.30 to give a time of 6 minutes.
MEK Rub Test:
The number of reciprocating rubs required to remove the coating was measured using a ball of cotton wool soaked in methyl ethyl ketone (MEK).
Wedge Bend Test:
A 10 cm×4 cm coated panel was bent on a 6 mm steel rod to form a U-shaped strip 10 cm long and 2 cm wide. The U-shaped strip was then placed onto a metal block with a built in tapered recess. A 2 kg weight was dropped onto the recessed block containing the U-shaped strip from a height of 60 cm in order to form a wedge. The test piece was then immersed in a copper sulphate (CuSO₄) solution acidified with hydrochloric acid (HCl) for 2 minutes, followed by rinsing with tap water. The sample was then carefully dried by blotting any residual water with tissue paper. The length of coating without any fracture was measured. The result was quoted in mm passed. The wedge bends were tested in triplicate and the average value was quoted. That is, the results indicate the mm of the 100 mm coating surface that remained in-tact or unbroken upon deformation. A result of 98 therefore means that only 2 mm of the coating out of 100 mm cracked upon deformation.
Acetic Acid Sterilization:
This test was used to determine if the coatings are compatible for use in beverage containers. The coating samples were applied onto aluminum can plate using a wire wound bar coater to give a 7-9 g/square meter dried coating weight. The substrates were cleaned by MEK before application. The coated panels were stoved in a conveyor oven with the following settings: zone 1 145° C.; zone 2 215° C.; zone 3 215° C. and conveyor setting 3.30 to give a through time of 4 minutes.
The coated panels were immersed in a deionized water solution comprising 5% acetic acid inside a Kilner jar and sterilized for 30 minutes at 100° C. in an autoclave. After this time, the coated panels were quickly removed while still hot and rinsed with cold tap water. The portion of the coated panel immersed in acetic acid, was assessed for extent of damage. Five aspects were graded by visual assessment on a scale where 0=no damage and 5=severe damage/defect:

- (A) Gloss surface modification
- (B) Extent of blushing wherein the coating turns hazy due to water trapped in the coating
- (C) Extent of color wherein the coating turns into another color
- (D) Coating adhesion loss (assessed by making a cross hatch on the coating and taping with Scotch 610 tape)
- (E) Blistering of the coating

TABLE 1

Coating Examples 1-4

Coating	Coating	Coating	Coating
1	2	3	4

Latex 1	14.77	14.77	14.77	14.77
Phosphoric acid^‡	—	0.05	0.10	0.19
2-butoxyethanol	2.50	2.50	2.50	2.50
Deionized water	7.73	7.70	7.68	7.63
Total	25.00	25.03	25.05	25.10
Results
MEK Rubs	20	70	100	100
Wedge Bend	98	91	94	89

^‡10 weight % of o-phosphoric acid in deionized water and neutralized at 50% by Dimethylethanolamine (DMAE).

TABLE 2

Coating Examples 5-8 and Test Results

Coating	Coating	Coating	Coating
5	6	7	8

Latex 2	14.77	14.77	14.77	14.77
Phosphoric acid^‡	—	0.05	0.10	0.19
2-butoxyethanol	2.50	2.50	2.50	2.50
Deionized water	7.73	7.70	7.68	7.63
Total	25.00	25.03	25.05	25.10
Results
MEK Rubs	10	20	30	30
Wedge Bend	98	97	97	97

^‡10 weight % of o-phosphoric acid in deionized water and neutralized at 50% by DMAE.

TABLE 3

Coating Examples 9-12 and Test Results

Coating	Coating	Coating	Coating
9	10	11	12

Latex 3	14.77	14.77	14.77	14.77
Phosphoric acid^‡	—	0.05	0.10	0.19
2-butoxyethanol	2.50	2.50	2.50	2.50
Deionized water	7.73	7.70	7.68	7.63
Total	25.00	25.03	25.05	25.10
Results
MEK Rubs	12	70	80	70
Wedge Bend	99	99	98	98

^‡10 weight % of o-phosphoric acid in deionized water and neutralized at 50% by DMAE.

TABLE 4

Coating Examples 13-16 and Test Results

Coating	Coating	Coating	Coating
13	14	15	16

Latex 4	12.50	12.50	12.50	12.50
Phosphoric Acid	—	0.04	0.08	0.16
Deionized water	7.50	7.48	7.46	7.42
Total	20.00	20.02	20.04	20.08
Results
MEK Rubs	5	15	20	70
Wedge Bend	100	99	100	99.3

^‡10 weight % of o-phosphoric acid in deionized water and neutralized at 50% by DMAE.

TABLE 5

Coating Examples 17-20 and Test Results

Coating	Coating	Coating	Coating
17	18	19	20

Latex 5	12.90	12.90	12.90	12.90
Phosphoric Acid	—	0.04	0.08	0.16
Deionized water	7.10	7.08	7.06	7.02
Total	20.00	20.02	20.04	20.08
Results
MEK Rubs	10	20	20	20
Wedge Bend	100	100	100	100

^‡10 weight % of o-phosphoric acid in deionized water and neutralized at 50% by DMAE.

TABLE 6

Coating Examples 21-24

Coating	Coating	Coating	Coating
21	22	23	24

Latex 6	13.43	13.43	13.43	13.43
DMAE	1.8	1.8	1.8	1.8
Phosphoric acid^‡	—	0.04	0.08	0.15
2-butoxyethanol/pentanol	2.60	2.60	2.60	2.60
(3/1)
Deionized water	2.17	2.15	2.13	2.09
Total	20	20.02	20.04	20.07
Results
MEK Rubs	7	13	25	20
Wedge Bend	92.3	88.7	84.7	82

^‡10 weight % of o-phosphoric acid in deionized water and neutralized at 50% by DMAE.

TABLE 7

Coating Examples 25-28 and Test Results

Coating	Coating	Coating	Coating
25	26	27	28

	Latex 7	13.18	13.18	13.18	13.18
	DMAE	1.8	1.8	1.8	1.8
	Phosphoric acid^‡	—	0.04	0.08	0.15
	2-butoxyethanol	2.60	2.60	2.60	2.60
	Deionized water	2.43	2.41	2.39	2.35
	Total	20.01	20.03	20.05	20.08
	Results
	MEK Rubs	38	41	44	30
	Wedge Bend	96	93.3	79.33	93

^‡10 weight % of o-phosphoric acid in deionized water and neutralized at 50% by DMAE.

TABLE 8

Coating Examples 29-32 and Test Results

Coating	Coating	Coating	Coating
29	30	31	32

Latex 8	11.12	11.12	11.12	11.12
DMAE	0.30	0.30	0.30	0.30
Phosphoric acid^‡	—	0.04	0.08	0.15
Butyl glycol/pentanol	2.60	2.60	2.60	2.60
(4/1)
Deionized water	5.98	5.95	5.94	5.91
Total	20	20.02	20.05	20.08
Results
MEK Rubs	39	90	180	140
Wedge Bend	89.7	76.3	79.7	83.7

^‡10 weight % of o-phosphoric acid in deionized water and neutralized at 50% by DMAE.

TABLE 9

Coating Examples 33-36 and Test Results

Coating	Coating	Coating	Coating
33	34	35	36

Latex 9	13.05	13.05	13.05	13.05
DMAE	0.35	0.35	0.35	0.35
Phosphoric acid^‡	—	0.04	0.08	0.15
Butanol/Propylene	2.60	2.60	2.60	2.60
glycol monomethyl
ether (3/1)
Deionized water	4.00	3.98	3.97	3.93
Total	20	20.02	20.05	20.08
Results
MEK Rubs	8	15	17	13
Wedge Bend	97.7	91.7	92.3	91

^‡10 weight % of o-phosphoric acid in deionized water and neutralized at 50% by DMAE.

TABLE 10

Coating Examples 37-40

Coating	Coating	Coating	Coating
37	38	39	40

	Latex 10	13.45	13.45	13.45	13.45
	Phosphoric acid^‡	0	0.04	0.08	0.15
	2-butoxyethanol/	2.60	2.60	2.60	2.60
	pentanol (3/1)
	Deionized water	3.95	3.93	3.91	3.88
	Total	20.00	20.02	20.04	20.08
	Results
	MEK Rubs	6	6	6	2
	Wedge Bend	95.7	93	92.3	97.7

^‡10 weight % of o-phosphoric acid in deionized water and neutralized at 50% by DMAE.

TABLE 11

Coating Examples 41-45 and Test Results

Coating	Coating	Coating	Coating	Coating
41	42	43	44	45

Latex 10	13.26	13.26	12.98	12.70	12.70
PRIMID XL-552	0.17	0.17	0.41	0.66	0.66
Phosphoric acid^‡	0.08	0.15	0.11	0.08	0.15
2-butoxyethanol/	2.60	2.60	2.60	2.60	2.60
pentanol (3/1)
Deionized water	3.91	3.88	3.89	3.91	3.87
Total	20.02	20.06	20.00	19.95	19.99
Results
MEK Rubs	6	10	10	80	27
Wedge Bend	81.7	77.3	81.7	80.3	79

^‡10 weight % of o-phosphoric acid in deionized water and neutralized at 50% by DMAE.

TABLE A

Results of Acetic Acid Sterilization Test on Coatings 1-4

Coating	Coating	Coating	Coating
1	2	3	4

	5% Acetic	A	—	0	0	0
	acid	B	3-4	0	0	0
		C	2	0	0	0
		D	—	5	0	0
		E	5	0	0	0

“—” means that there was no film left.

TABLE B

Results of Acetic Acid Sterilization Test on Coatings 5-8

Coating	Coating	Coating	Coating
5	6	7	8

	5% Acetic	A	—	1	1	1
	acid	B	—	1	1	1
		C	—	0	0	0
		D	—	0	0	0
		E	4	0	0	0

“—” means that there was no film left.

TABLE C

Results of Acetic Acid Sterilization Test on Coatinas 9-12

Coating	Coating	Coating	Coating
9	10	11	12

	5% Acetic	A	—	1	1	0
	acid	B	—	0	0	0
		C	—	0	0	0
		D	—	5	0	0
		E	5d	4	3	1

d means that the film was largely delaminated.
“—” means that there was no film left.

TABLE D

Results of Acetic Acid Sterilization Test on Coatings 13-16

Coating	Coating	Coating	Coating
13	14	15	16

	5% Acetic	A	—	3	0-1	0
	acid	B	—	3	0-1	0
		C	—	0	0	0
		D	—	5	5	0-1
		E	5d	3-4	2-3	0-1

d means that the film was largely delaminated.
“—” means that there was no film left.

TABLE E

Results of Acetic Acid Sterilization Test on Coatings 17-20

Coating	Coating	Coating	Coating
17	18	19	20

	5% Acetic	A	—	—	1	0
	acid	B	—	—	1	0
		C	—	—	0	0
		D	—	—	—	5
		E	5d	5d	2-3	0-1

d means that the film was largely delaminated.
“—” means that there was no film left.

TABLE F

Results of Acetic Acid Sterilization Test on Coatings 21-24

Coating	Coating	Coating	Coating
21	22	23	24

	5% Acetic	A	—	4	1	1
	acid	B	—	4	2-3	1
		C	—	0	0	0
		D	—	4-5	2-3	1-2
		E	5d	4-5	4-5	4

d means that the film was largely delaminated.
“—” means that there was no film left.

TABLE G

Results of Acetic Acid Sterilization Test on Coatings 25-28

Coating	Coating	Coating	Coating
25	26	27	28

5% Acetic	A	0-1	0	0	0
acid	B	1	0-1	0	0
	C	0	0	0	0
	D	1	0-1	0	0
	E	5	0	0	0

TABLE H

Results of Acetic Acid Sterilization Test on Coatings 29-32

Coating	Coating	Coating	Coating
29	30	31	32

	5% Acetic	A	—	3	3	3
	acid	B	—	2	2	2
		C	—	0	0	0
		D	—	2	3	3
		E	5d	5	5	5

d means that the film was largely delaminated.
“—” means that there was no film left.

TABLE I

Results of Acetic Acid Sterilization Test on Coatings 33-36

Coating	Coating	Coating	Coating
33	34	35	36

5% Acetic	A	3	2-3	2-3	2
acid	B	3	2	3	1-2
	C	0	0	0	0
	D	4	3	3	1-2
	E	5	5	5	5

TABLE J

Results of Acetic Acid Sterilization Test on Coatings 37-40

Coating	Coating	Coating	Coating
37	38	39	40

5% Acetic	A	4	2	1-2	1-2
acid	B	4	3	3	3
	C	0	0	0	0
	D	5	3	2-3	2-3
	E	5	5	5	5

TABLE K

Results of Acetic Acid Sterilization Test on Coatings 41-45

Coating	Coating	Coating	Coating	Coating
41	42	43	44	45

5%	A	0-1	0-1	0-1	0	0-1
Acetic	B	2	1	1	0-1	0-1
acid	C	0	0	0	0	0
	D	0-1	0	1	0	1
	E	2	5	5	0	1

The above examples demonstrate that coatings made from a latex polymer prepared with a polymerizable surfactant and an emulsion monomer are suitable for use on packaging but that the use of a phosphorus acid in combination with a hydroxyalkylamide crosslinker in the latex stabilized by polymerizable surfactant results in a notable improvement of the chemical resistance of the film formed. Moreover, with the appropriate choice of surfactant and the amount of added phosphoric acid and crosslinker, an excellent flexibility of the coatings is also demonstrated; such flexibility is particularly desired for packaging applications.
The above examples demonstrate that the use of a phosphorus acid in the coating composition results in a cured film having solvent and mechanical resistance, without the use of a phenolic or amino crosslinker. Examples 9-12 further demonstrate that a latex free from styrene can be used to make a suitable packaging coating. Moreover, the excellent flexibility of coatings 1-5 is also demonstrated; such flexibility is particularly desired for packaging applications.
Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.
Although various embodiments of the invention have been described in terms of “comprising”, embodiments consisting essentially of or consisting of are also within the scope of the present invention.

Claims

1. A curable coating composition comprising:

(a) a latex having a reactive functional group; and

(b) a phosphorus acid,

wherein the composition is substantially free of crosslinkers selected from polyisocyanates, aminoplast resins and phenolic resins.

2. The composition of claim 1, wherein the composition is essentially free or completely free of said crosslinkers.

3. The composition of any of the preceding claims, wherein the reactive functional group comprises a hydroxyl group, an epoxy group, a carboxylic acid or any combination thereof.

4. The composition of any of the preceding claims, further comprising (c) a hydroxyalkylamide crosslinker.

5. The composition of claim 4, wherein the hydroxyalkylamide crosslinker is present in an amount of 1 to 20 weight percent, or 3 to 15 weight percent, or 1 to 15 weight percent, or 1 to 10 weight percent, or 1 to 5 weight percent based on the total weight of resin solids in the composition.

6. The composition of any of the preceding claims which contains 0 to less than 5 weight percent based on total weight of resin solids of the composition of a hydroxyalkylamide crosslinker.

7. The composition of any of claims 4-6, wherein the reactive functional group comprises a carboxylic acid.

8. The composition of any of the preceding claims, wherein the phosphorus acid comprises 0.01 to 5 weight percent, preferably 0.1 to 1 weight percent based on total weight of resin solids of the composition.

9. The composition of any of the preceding claims, wherein the phosphorus acid comprises phosphoric acid.

10. The composition of any of the preceding claims, wherein the composition is substantially free, preferably essentially free, more preferred completely free of styrene, bisphenol A, bisphenol A diglycidyl ether, bisphenol F, bisphenol F diglycidyl ether and/or phenol.

11. The composition of any of the preceding claims, wherein the composition is substantially free, preferably essentially free, more preferred completely free of styrene, bisphenol A, bisphenol A diglycidyl ether, bisphenol F, bisphenol F diglycidyl ether and phenol.

12. The composition of any of the preceding claims, wherein the composition does not release formaldehyde upon curing.

13. A package coated at least in part with a cured coating deposited from a coating composition of any of claims 1-12.

14. The package of claim 13, wherein the package is a metal can, preferably a food can.

15. The package of any of claim 13 or 14 in which the coating composition is applied as a top coat over a basecoat of the same or different composition.

16. The package of any of claim 13 or 14, wherein the coating has flexibility of 90% as measured in a wedge bend test.