MXPA97003554A - Composition of coating for substratesmetali - Google Patents

Abstract

The present invention relates to a coating composition for application to a primed metallic substrate characterized in that: a) 13% to 30% by weight of non-volatile material, of an epoxy novolac resin having an epoxy functionality of 2 to 6 and an epoxy equivalent weight of 100 to 210, b) 40% to 60% by weight of non-volatile material, of a phenolic resin, being a condensation product resulting from a reaction between a phenol and formaldehyde, c) 15% to 30%. %, by weight of non-volatile material of a polyester having a weight average molecular weight of 1,000 to 50,000, d) 5% to 20% by weight, of non-volatile material, of an elastomer, and e) a non-aqueous carrier, wherein the composition has a ratio of epoxy resin novolac to phenolic resin from 25:75 to 33:66 and an elastomer to polyester ratio of 1: 1 to 1: 2, and where the composition is free of a vinyl polymer containing halu

Description

COMPOSITION OF COATING FOR METALLIC SUBSTRATES FIELD OF THE INVENTION The present invention relates to coating compositions for metal substrates, methods for protecting a metal substrate, and metal articles having a protective coating composition applied thereto. The coating composition includes: (1) an epoxy novolac resin, (b) a phenolic resin, (c) a polyester and (d) an elastomer, and is free of vinyl polymers containing halide. The coating composition, after curing, is useful as a final coat of paint for the interior of metal lids and demonstrates excellent flexibility and excellent adhesion to the primer layers and plastisol packing. BACKGROUND OF THE INVENTION It is well known that an aqueous solution in contact with an untreated metal substrate can result in corrosion of the untreated metal substrate. Therefore, a metal article, such as a lid or a metal container for a water-based product, such as a food or drink, is subjected to treatment to become corrosion resistant in order to retard or eliminate the interactions between the water-based product and the metallic article. Generally, corrosion resistance is printed to the metal article, or to a metal substrate in general, by passivating the metal substrate or coating the metal substrate with a corrosion inhibiting coating. Researchers have continuously sought to obtain improved coating compositions that reduce or eliminate corrosion of a metal article and in such a way that they do not adversely affect an aqueous product packaged in the metal article. For example, researchers have sought to improve the impermeability of the coating in order to prevent the ions that cause corrosion, oxygen molecules and water molecules from contracting and interacting with a metallic substrate. Impermeability can be improved by providing a thicker, more flexible and more adhesive coating, but often, the improvement of a particular beneficial property is achieved at the expense of another beneficial property. In addition, practical considerations limit the thickness, adhesive properties and flexibility of a coating applied to a metal substrate. For example, thick coatings are expensive, require a longer curing time, can be aesthetically unpleasant and can adversely affect the process of stamping and molding the coated metal substrate in a useful metal article. Similarly, the coating must be sufficiently flexible so that the continuity of the coating is not destroyed during the stamping and molding of the metal substrate in the desired shape of the metal article. Researchers have also sought coatings that have resistance against chemicals in addition to corrosion inhibition. A useful coating for the interior of a metal lid or container must be able to withstand the solvation properties of the packaged product. If the coating does not have sufficient resistance to chemicals, the coating components can be removed inside the packaged product and adversely affect the product. Even small amounts of components extracted from the coating can adversely affect the sensitive products resulting in an unpleasant taste to the product. The organic solvent based coating compositions provide cured coatings with excellent chemical resistance. These solvent-based compositions include ingredients that are not inherently water soluble, and thus effectively resist the solvation properties of water-based products packaged in the metal container. Epoxy-based coatings and polyvinyl chloride-based coatings have been used to coat the inside of caps and metal containers for food and beverages, because these coatings present an acceptable combination of adhesion, flexibility, resistance to chemicals and inhibition to corrosion. Polyvinyl chloride based coatings and vinyl acetate / vinyl chloride copolymer based coatings (ie, vinyl solution) have also been used as the final paint coat of choice for the interior of metal stages, because these coatings offer excellent adhesion to the plastisol sealing gaskets applied to the final cured paint layer. However, epoxy based coatings and polyvinyl chloride based coatings present serious disadvantages that researchers are still trying to overcome. For example, the polyvinyl chloride-based coating compositions are thermoplastic. The thermoplastic coatings used as the final paint layer of the inner lining of metal lids have inherent performance disadvantages, such as softening during the lid manufacturing process or under food processing conditions. Therefore, coatings compositions having a thermostability character have been investigated. In addition, polyvinyl chloride based coatings or a related vinyl polymer containing halide, such as polyvinylidene chloride, possess the above-listed beneficial properties of chemical resistance and corrosion inhibition, and are inexpensive. However, curing a polyvinyl chloride or a related vinyl polymer containing halide can generate toxic monomers, such as, for example, polyvinyl chloride, a known carcinogen. In addition, the removal of a polyvinyl chloride containing halide, for example by incineration, can also generate toxic monomers. In this way, the vinyl chloride generated poses a potential danger to workers in the manufacturing plants of metal lids and cans, in food processing and packing plants, and in disposal sites. The elimination of polyvinyl chloride and related polymers can also produce carcinogenic dioxins and hydrochloric acid harmful to the environment. Government regulators are acting to eliminate the use of polyvinyl chloride-based coating compositions that are in contact with food, and thereby eliminate the environmental and health problems associated with vinyl polymers containing halides. However, currently the polyvinyl chloride-based compositions remain the predominant coating used to coat the interior of caps and food and beverage containers. To overcome the environmental concerns and performance issues associated with polyvinyl chloride-based coating compositions, epoxy-based coating compositions have recently been used to coat the interior of food and beverage containers. However, epoxy based coatings also have disadvantages. For example, epoxy-based coating compositions are more expensive than polyvinyl chloride-based coating compositions. With respect to a metal lid for a food container, the inside of a metal lid was conventionally coated with three separate coating compositions, that is, a three coat system. First a layer of epoxy / phenolic primer was applied to the metal substrate and cured, then an intermediate vinyl-based coating was applied over the cured primer layer. Finally, after curing the intermediate coating, a final layer of specially formulated paint was applied, capable of adhering to a plastisol sealer on the cured intermediate coating. The plastisol sealer is applied on the final layer of cured paint, and it is formed inside the packaging during the manufacture of the metal lid from a metal sheet that has the three cured layers of the coatings applied to it. Currently two coatings systems are commercially used, but they also have disadvantages. Therefore, researchers are trying to develop an improved system of two coatings to coat the inside of a metal lid. An ideal two coat system maintains corrosion inhibition, reduces the cost of coating application, has improved rheological properties and also improved integrity of the cured film. The savings in cost are shown both in the application of a composition of less coating to the metal substrate and in the time saved by applying only two coatings instead of three coatings of the metal substrate. A system of two coatings for the inside of a metal lid for food, includes a primer layer (ie a sizing) and a final coat of paint. Metal caps are usually used together with a glass or plastic container. The final coat of paint must have sufficient adhesion with the primer coat or otherwise the coating will not work. In order to achieve sufficient adhesion between the coatings, the chemical constitution of the final paint layer was usually ordered by the chemical constitution of the primer layer. Therefore, researchers have sought a "more universal" final coat of paint, that is, a final coat of paint that can be applied to a variety of different primer layers and that has sufficient adhesion between the coatings. This final layer of universal paint would constitute an important advance in the technique. The coatings used inside a metal lid for food must also meet other criteria besides performance. For example, coatings must incorporate components acceptable to the United States Food and Drug Administration (FDA) because the composition of the cured coating is in contact with food products. Therefore, the priming layer and the final cured paint layer require sufficient adhesion to maintain the integrity of the film during the manufacture of the lid. The primed primer layer and the final cured paint layer also require sufficient flexibility to resist fabrication of the lid. Sufficient adhesion of the coating and flexibility are necessary characteristics for the lid to withstand the processing conditions to which it is subjected during the packaging of the product.

Other required performance characteristics of cured coatings include protection against corrosion and adequate adhesion to the plastisol packing applied to the final cured paint coat. Also, the composition of the cured coating requires sufficient chemical resistance and sufficient abrasion, as well as a normal wear resistance. In the manufacture of a metal cover, a metal sheet is coated with the coating compositions, and each coating is cured individually, subsequently the metal sheet is formed according to the design of the metal cover. The covers are manufactured in a variety of sizes ranging from 27 mm (millimeters) to 110 mm in diameter. During manufacturing, a plastisol material is molded into a package, and usually is a polyvinyl chloride-based packing. The packaging is applied over the cured coatings inside the metal lid to ensure an effective seal between the metal lid and the glass container, and to maintain the vacuum condition of the packaged food product. The packaging of the product is carried out under processing conditions in which the plastisol package is softened. When the metal lid is pressed onto the glass container, the threads of the glass container form impressions in the softened plastisol packing.

The metal lid is secured in place by means of the threaded impressions and by the vacuum produced by the subsequent cooling. This type of metal lid is used for baby food containers and other packaged food and beverage products, such as juices and sauces. Other types of caps are designed to be secured to glass containers by means of rings instead of impressions threaded into the plastisol. The compositions of the final coat of paint are based on polyvinyl chloride have been softened both by the conditions of product processing, and by the conditions encountered during the manufacture of the lid, which leads in this way to a failure of the lid . The present invention is focused, in part, on overcoming the failures of these covers. Therefore, researchers have sought a system of two coatings for the interior of metal lids used for vacuum packed food products. Researchers have searched in particular for a final layer of paint without vinyl halide for the interior of metal lids for food and beverages, which retains the beneficial properties of a final layer of paint with vinyl chloride base, such as adhesion, flexibility, resistance to chemicals, inhibition to corrosion and a favorable economy. Researchers have sought in particular a coating composition that demonstrates these beneficial properties and also that it reduces the environmental and toxicological concerns associated with vinyl polymers that contain halide. The systems of two coatings have been investigated and used for the application in the interior of metal covers. The researchers studied and used compositions of final coatings of paints with a cured coating sufficiently flexible so that a coated metal substrate can deform without destroying the continuity of the film. Conventional epoxy resins used in the final paint layers offered good adhesion to plastisol gaskets, but also often provided a rigid cured film, making it difficult or impossible to coat the metal substrate before it was deformed, ie, molded the metal substrate in the metal article, such as a metal cap. Coating a metallic substrate before the formation of the metallic substrate is the current standard industrial practice. For example, the application of P. Palackdharry et al., "Interior Two-Coat System Covers Metal Food Closures" ("Two Interior Coatings System that Covers the Metallic Lids for Food"), Modern Paint and Coatings (Modern Paint and Coatings). June, 1989, pp. 78, 82, and 85, presents a composition of a final paint layer comprising a relatively low amount of phenolic resin, polyester and elastomer in relation to the present composition. Japanese Patent JP 86/038744 has a coating composition for metal cans comprising a polyester, a phenolic resin and an epoxide resin. The composition presented also includes a polyvinyl chloride. The aforementioned patent and publication disclose coating compositions comprising an epoxy resin, a polyester and a phenolic resin. The patent and the publication do not present a composition of a coating comprising an epoxy resin novolac; a polyester; a phenolic resin; and an elastomer in the amounts and percentages disclosed herein, wherein the composition of the coating has no vinyl polymer containing halide. Although the aforementioned patent and publication have compositions of a coating for the interior of a metal food lid, the patent and the publication do not present a composition of a final paint layer that includes an epoxy novolac resin, a resin phenolic, a polyester and an elastomer, where the composition has no vinyl polymer containing halide, and which, after the jury, demonstrates: (1) excellent flexibility; (2) excellent adhesion to the coating of the primer layer; (3) excellent resistance to chemicals and inhibition to corrosion; (4) Excellent adhesion to plastisol packing; and (5) reduced toxicological environmental concerns. As an additional advantage, the coating composition of the current final paint layer is an improved two-coat system, thereby eliminating the time and costs attributed to the application of a conventional third coating to the metal substrate. The present coating composition of the final paint layer can also be used with a variety of types of primer layers without significantly reducing the coating properties. SUMMARY OF THE INVENTION The present invention is focused on a composition of a coating which, after curing, effectively inhibits the corrosion of metallic substrates, is flexible and exhibits excellent adhesion to both a coating of the primer layer and A variety of plastisol gaskets used to secure the vacuum seal of a metal lid to a glass container. The present coating composition includes: an epoxy novolac resin, a phenolic resin, a polyester and an elastomer. The present coating composition is also free of vinyl polymer containing halide, such as for example polyvinyl chloride. However, after curing and degradation, the coating compositions demonstrate excellent adhesion to both the primer coating and the plastisol packing. The composition of the coating effectively inhibits the corrosion of ferrous and non-ferrous metal substrates when the composition is applied as a final coat of paint to a metal substrate, then cured for a sufficient time and at a temperature sufficient to provide a transverse coating . A cured and degraded coating demonstrates sufficient chemical and physical properties to be used as the final coat of paint of a two coat system on the inside of metal lids used in food and beverage packaging. The composition of the coating does not adversely affect the products packaged in a container having a metal cap coated on the inner surface by the cured composition. In particular, the present coating composition includes: (1) from about 13% to about 30%, by weight, of non-volatile material, of an epoxy novolac resin; (b) about 40% to about 60%, by weight, of non-volatile material, of a phenolic resin; (c) about 15% to about 30%, by weight, of non-volatile material, of a polyester; and (d) about 5% to about 20%, by weight, of non-volatile material of an elastomer, wherein the composition is free of vinyl polymer containing halide. According to an important feature of the present invention, the weight ratio of the epoxy resin novolac to the phenolic resin is from about 33:66 to about 25:75. The elastomer and the polyester are present in a ratio of the elastomer to the polyester from about 1: 1 to about 1: 2. The components (a) to (d) are dispersed in a non-aqueous carrier such that the composition of the total coating includes about 20 to about 50%, by weight, of the total composition of components (a), (b), (c) and (d). Other additional components, such as a pigment, a filler or a lubricant can also be included in the composition, and accordingly, increase the percentage of the weight of the total non-volatile material in the composition to more than 50% by weight of the composition of the total coating. As used herein and subsequently, the term "coating composition" is defined as the composition that includes the epoxy novolac resin, the phenolic resin, the polyester, the elastomer, and any optional ingredient dispersed in the aqueous carrier.; the term "cured coating composition" is defined as the adherent polymeric coating resulting from the curing of a coating composition. The cured coating composition includes the epoxy resin, the phenolic resin, the polyester and the elastomer essentially in the amounts in which these ingredients are present in the coating composition, expressed as non-volatile material. Therefore, an important aspect of the present invention is to provide a coating composition that improves the ability of the primer layer to inhibit corrosion of ferrous and non-ferrous metal substrates. After application to a primed metallic substrate as a final coat of paint, and subsequent curing at a sufficient temperature for a sufficient time, the coating composition provides an adherent layer of a cured coating composition. The cured coating composition improves corrosion inhibition, has excellent flexibility and shows excellent adhesion to both a variety of different types of primer layers applied to the metal substrate, and to a variety of different types of plastisol sealant packages applied on the composition of the cured coating. Due to these properties, an improved system of two coatings is available for application to the metal substrate, thus providing economy in time, material and machinery in the coating of a metal substrate. The composition of the coating also offers economy because the composition can be used with a variety of primer layers and plastisol packaging of different chemical types. The cap manufacturers can therefore use the composition of the coating in a more universal range of applications, thus eliminating the need to take inventory of different final paint layers and eliminating the change of application equipment. According to another important aspect of the present invention, the cured coating composition demonstrates excellent flexibility and adhesion with respect to the packing of the plastisol sealant. The excellent adhesion between the cured coating composition and the plastisol sealant package further enhances the vacuum seal between a metal lid and a glass container to maintain the integrity of the product, and the excellent flexibility facilitates the processing of the coated metal substrate in the coated metal article, as for example in the steps of the molding or stamping process, such that the cured coating remains in continuous and close contact with the priming layer on the metal substrate. According to another important aspect of the present invention, the cured coating composition demonstrates excellent flexibility and adhesion even when the coating composition does not include a vinyl polymer containing halide. The conventional coating compositions included a polyvinyl chloride to offer flexibility to the cured coating and provide adhesion to the plastisol packing. However, the presence of polyvinyl chloride adversely affected the heat resistance of the cured composition. The present coating composition, which excludes the halide-containing vinyl polymer, exhibits excellent heat resistance, and surprisingly, excellent flexibility. According to another important aspect of the present invention, a primed metallic substrate coated on at least one surface with a cured coating composition of the present invention can be formed in a metal lid for a glass or plastic container that carries food products. Conventionally, a particular type of final paint layer was applied on a particular primer layer in order to achieve sufficient adhesion between the coatings. The present coating composition overcomes this disadvantage, and offers a cured coating composition that exhibits sufficient adhesion in this coating with a variety of types of primer layers, and with a variety of types of plastisol sealers. These and other aspects and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The composition of a coating of the present invention, after curing, offers a cured coating composition that effectively improves the corrosion inhibition of primed metallic substrates, as for example, but without limitation, aluminum, iron, steel and copper. A composition of the current coating, after curing, also demonstrates excellent adhesion to the primer applied to the metal substrate and to a plastisol packing; excellent resistance to chemicals and scratch resistance; and excellent flexibility. Accordingly, the coating between the primer layer and the final paint layer, i.e., the intermediate coating, is removed. The current coating compositions are therefore useful in an improved two coat system comprising a primer layer and a final paint coat. The coatings of the current coating are especially useful as the final coat of paint of a two coat system for the interior of a metal lid for vacuum packed food products. In general, the current coating composition includes: (a) an epoxy novolac resin; (b) a phenolic resin; (c) a polyester; (d) a metallic substrate; and (e) a non-aqueous carrier. The composition of the coating of the present invention does not contain a vinyl polymer containing a halide. In addition, the composition of the current coating may include optional ingredients that improve the aesthetics of the composition, that facilitate the processing of the composition, or that improve a functional property of the composition. The ingredients of the individual composition are described in more detail below. (a) Novolac Epoxy Resin The coating composition of the present invention includes an epoxy novolac resin in an amount of about 13% to about 30%, and preferably about 15% to about 25%, by weight of non-volatile material. To achieve the overall benefit of the present invention, the coating composition has from about 20% to about 25% of the epoxy novolac resin, by weight of non-volatile material. An epoxy novolac resin useful in the present composition is a polyfunctional epoxide resin having an epoxide functionality of about 2, and preferably greater than about 2, to about 6, and preferably greater than about 2 to about 5. The resin epoxy novolac is a low molecular weight resin having an epoxide equivalent weight (EEW) of about 100 to about 220, and preferably an EEW of about 150 to about 210. Novolac epoxy resins useful in the present invention include for example , but are not limited to, epoxy novolac phenol resins. Novolac phenol epoxy resins are represented by the general structural formula (I where n is approximately 0.2 to approximately 4.

The multifunctional phenol novolac epoxy resins contain a phenolic hydroxyl group per phenyl ring in random combinations para-para ', ortho-para', and ortho-ortho '. The epoxidation with epichlorohydrin comes from the highly functional epoxy phenol novolac resins. The phenol novolac epoxy resin can be a liquid of high viscosity (i.e., n about 0.2) or a solid (i.e., n greater than 3). Non-limiting examples of an epoxy phenol novolac resin useful in the present invention are ARALDITE® EPN 1139 available from CIBA-GEIGY Corp., Hawthorne, NY, and D.E.N. 431, available from Dow Chemical Co., Midland, MI. These novolac phenol epoxy resins have an n-value (of structural formula I) of 0.2, an EEW of 175 and an exoxide functionality of 2.2, and have provided a useful coating composition that effectively inhibits substrate corrosion. metallic Other non-limiting examples of epoxy novolac phenol resins are D.E.N. 438 and ARALDITE® EPN 1138, available from Dow Chemical Co. and CIBA-GEIGY Corp., respectively, and have an n-value of 1.6, an EEW of 178 and an epoxide functionality of 3.6; and D.E.N. 439 available from Dow Chemical Co., with an n value of 1.8, an EEW of 200 and an exoxy functionality of 3.8 Another useful class of novolac epoxy resins are cresol novolac epoxy resins shown in general structural formula (II), where n is from about 1.7 to about 1.4.

The novolac cresol epoxy resins are prepared by the glycidylation of the o-cresol formaldehyde condensates in the same manner as the epoxy novolac phenol resins. The epoxide functionality of cresol epoxy novolac resins is from about 2.7 to about 5.4. Other useful epoxy novolac resins, i.e. the polyfunctional hepoxide resins, include but are not limited to a polynuclear glucidyl-phenol ether resin, such as for example the tetraglycidyl ether of tetrakis (4-hydroxyphenyl) ethane shown in the structural formula (III ), and with an EEW of about 185 to about 210 and a theoretical functionality of the epoxide of four.

A tetraglycidylmethylenedianiline resin exemplified in structural formula (IV), such as NJN.N'JN1-tetraglycidyl-4,4'-diaminophenylmethane, with an EEW of about 117 to about 133 and an epoxide functionality of about 4, can also be used like the epoxy resin novolac.

( In addition, the triglycidyl p-aminophenol resins, available from CIBA-GEIGY Corp., and with an EEW of about 105 to about 114 and an epoxide functionality of about 3 can be used as the epoxy novolac resin.

Another epoxy novolac resin that can be used as an example is a triglycidyl isocyanurate shown in structural formula (V) and having an epoxide functionality of about 3 and an EEW of about 108.

An epoxy novolac resin offers a sufficient number of degradation sites, such that a coating composition can be cured and offer sufficient chemical and physical properties for a cured coating composition. A cured coating composition also demonstrates excellent physical properties, such as scratch resistance, adhesion and flexibility. An epoxy novolac resin also offers a sufficient number of degradation sites in such a way that the cured coating composition has excellent barrier properties (i.e., it has excellent control against corrosion). (b) Phenolic resin In addition to epoxy novolac resin, the coating composition also includes from about 40% to about 60%, and preferably from about 40% to 50%, by weight of non-volatile material, of a phenolic resin. To achieve the overall benefit of the present invention, the coating composition has from about 45% to about 50%, by weight of non-volatile material of a phenolic resin. The phenolic resin is present in an amount sufficient to interlock with the epoxy novolac resin and offer a cured coating composition with sufficient flexibility to resist breakage and with sufficient physical and chemical properties to resist chemical attack and scratching. Generally, the phenolic resin used in the present composition is a condensation product resulting from a reaction between a phenol and a formaldehyde, and has a low molecular weight of from about 1,000 to about 8,000 and preferably from about 3,000 to about 5,000. Phenol or essentially any other compound that includes a hydroxyphenyl moiety, such as, for example, crecillic acid, can be used as the phenol component of the phenolic resin. Non-limiting examples of suitable phenol compounds include phenol, crecillic acid and bisphenol A. Bisphenol A is the preferred phenol component of the phenolic resin. To achieve the full benefit of the present invention, bisphenol A and formaldehyde are used as the components of the phenolic resin. The combination of bisphenol A and formaldehyde provide a phenolic resin which, when incorporated into a coating composition of the present invention, offers excellent adhesion of the coating composition to both the primer layer and a variety of plastisol packaging which can be applied on the coating of the cured composition. The crecillic acid can be included in the phenolic resin to further improve the corrosion inhibiting properties of the coating composition. A phenolic resin taken as an example in the present coating composition includes about 24% by weight of bisphenol A, and about 7% by weight of formaldehyde. This phenolic resin is incorporated into the coating composition present as a solution containing about 50% by weight of the phenolic resin. According to an important feature of the present invention, the epoxy novolac resin and the phenolic resin are present in the coating composition in a weight ratio of the novolac epoxy resin to the phenolic resin of about 25:75 (i.e. : 3) at about 33:66 (i.e., 1: 2), and preferably from about 30:70 to about 40:60. As will be demonstrated below, the properties of the cured coating composition are improved when the ratio of the epoxy resin novolac to the phenolic resin is maintained within this weight range. (c) Polyester In addition to epoxy novolac resin and phenolic resin, the present coating composition includes a polyester to impart flexibility to the cured coating composition. The polyester is present in an amount of from about 15% to about 30%, and preferably from about 15% to about 25%, by weight of non-volatile material. To achieve the full benefit of the present invention, the polyester is present in an amount of about 20% to about 25%, by weight of non-volatile material. The polyester has a molecular weight of from about 1,000 to about 50,000, and preferably from about 1,000 to about 10,000. To achieve the full benefit of the present invention, the polyester has a molecular weight of about 1,500 to about 6,000. The identity of the polyester is not especially limited. However, it is important that a particular polyester have a sufficiently low molecular weight to impart flexibility to the cured coating composition. The polyester is prepared by methods known in the art from a diol, triol, polyol or a mixture thereof and a polybasic anhydride or carboxylic acid, or a mixture thereof. The examples of diols, triols and polyols include, but are not limited to, ethylene glycol, propylene glycol, glycerin, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, neopentyl glycol, pentaerythritol, 1,4-butanediol, tri-ethylolpropane, isopropylidene-bis (p-phenylenediopanol-2) and mixtures thereof. Examples of polybasic carboxylic anhydrides or anhydrides include, but are not limited to, maleic anhydride, maleic acid, fumaric acid, succinic anhydride, succinic acid, adipic acid, phthalic acid, phthalic anhydride, tetrahydrophthalic anhydride, exahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, acelaic acid , cebacic acid, tetrachlorophthalic anhydride, chlordenedic acid, isophthalic acid, trimellitic anhydride, and mixtures thereof. A typical polyester illustrated in Example 1 is prepared by mixing the following ingredients and heating to approximately 210 ° F, and then allowing the temperature to rise to approximately 430 ° F until the acid number is approximately 10. EXAMPLE 1 Polyester The mixture was added and mixed, and the resulting mixture was heated until the acid number reached 7.6. The polyester of Example 1, with an average molecular weight of about 3000, was present in the mixture in an amount of about 75% by weight of non-volatile material. Several groups of the polyester of Example 1 were prepared. These different groups provided a polyester with an average molecular weight of about 1,500 to about 6,000. The polyester of each group provided a coating composition of the present invention useful in an improved coating system. (d) Elastomer In addition to the phenoxy novolac resin, the phenolic resin, and the polyester, the present coating composition includes an elastomer to improve the adhesion of the coating composition to the primer layer and especially to the plastisol packing that is applies to the composition of the cured coating. The elastomer is present in an amount of from about 5% to about 20%, and preferably from about 5% to about 15%, by weight of non-volatile material. To achieve the full benefit of the present invention, the elastomer is present in an amount of about to about 15%, by weight of non-volatile material. An elastomer taken as an example, but not limiting, is a butadiene-acrylonitrile copolymer, such as NIPOL® 1042U, available from Zeon Chemicals, Inc., Cleveland, OH. Other butadiene-acrylonitrile copolymers are NYsyn® 35-8 and NYsyn® 33-8HM, available from DSM Copolymers, Inc., Baton Rouge, LA. Examples of other useful elastomers include, but are not limited to, natural rubber, a butadiene-styrene copolymer, a polybutadiene, an isobutylene-isoprene copolymer, a polychloroprene, a polyurethane, an acrylic elastomer, a styrene-isoprene copolymer, a acrylonitrile-chloroprene copolymer, a vinylpyridine-butadiene copolymer, and mixtures thereof. A preferred elastomer includes an acrylonitrile copolymer. (e) Non-Aqueous Carrier The present coating composition is a non-aqueous composition, wherein the epoxy novolac resin, the phenolic resin, the polyester and the elastomer are dispersed homogeneously in a non-aqueous carrier. It is to be understood that the present coating composition may include a relatively low amount of water, such as up to and about 5% by total weight of the composition, without adversely affecting the composition of the corrosion inhibitor coating, either or after curing. Water can be intentionally added to the composition, or it can be present in a composition inadvertently, such as when water is present in a particular component included in the coating composition. In general, the non-aqueous carrier has sufficient volatility to evaporate essentially completely from the coating composition during the curing process, for example during heating to about 300 ° F to about 400 ° F for about 8 to about 12 minutes . Suitable non-aqueous carriers are known in the chemistry of coating compositions, and include, but are not limited to, glycol ethers, such as ethylene glycol monomethyl ether, ethylene glycol ether monoethyl ether, ethylene glycol monobutyl ether, and monomethyl ether of propylene glycol; ketones, such as cyclohexanone, ethylyl ketones, methyleryl ketones and methyl isoamyl ketone; aromatic hydrocarbons, such as toluene, benzene and xylene; aliphatic hydrocarbons, such as for example mineral spirits, kerosene and naphtha VM & P of high flash point; alcohols, such as isopropyl alcohol, butyl alcohol-n and ethyl alcohol; and aprotic solvents, such as tetrahydrofuran; chlorinated solvents; esters; esters of glycol ether, such as propylene glycol monomethyl ether acetate; and combinations thereof. The non-aqueous carrier is generally included in the composition in an amount sufficient to provide a composition comprising from about 20% to about 50%, by weight of the composition, of the total weight of (a), (b), ( c) and (d). The amount of non-aqueous carrier included in the composition is limited solely according to the desired, or necessary, rheological properties of the composition. Generally, a sufficient amount of non-aqueous carrier is included in the composition of the coating to provide a composition that can be easily processed and that can be applied to a metal substrate in an easy and uniform manner, and that is sufficiently removed from the composition of the coating during curing in the desired curing time. Therefore, essentially any nonaqueous carrier is useful in the present coating composition as long as the non-aqueous carrier disperses and / or adequately solubilizes the components of the composition; be inert with respect to the interaction with the components of the composition; does not adversely affect the stability of the coating composition or the ability of the corrosion inhibiting coating to inhibit corrosion of a metal substrate; and evaporates quickly, almost completely and relatively quickly to offer a cured coating composition that inhibits corrosion of a metal substrate, demonstrates good alignment and flexibility, and has good chemical and physical properties. (f) Other Optional Ingredients A coating composition of the present invention may also include other optional ingredients that do not adversely affect the coating composition or a cured coating composition resulting therefrom. These optional ingredients are known in the art, and are included in a coating composition to improve the aesthetics of the composition; to facilitate the manufacture, processing, handling and application of the composition; and to further improve a particular functional property of a coating composition or a cured coating composition resulting therefrom. These optional ingredients include, for example, colorants, pigments, diluents, fillers, lubricants, anticorrosive agents, flow control agents, thixotropic agents, dispersing agents, antioxidants, adhesion promoters, light stabilizers, and mixtures of the same. Each optional ingredient is included in an amount sufficient to accomplish its intended purpose, but not in amounts that adversely affect a coating composition or a cured coating composition resulting therefrom. A useful optional ingredient is a lubricant, such as lanolin, which facilitates the fabrication of metal caps by printing lubrication to the sheets of the coated metal substrate. A lubricant is present in the coating composition in an amount from 0% to about 2%, and preferably from about 0.1% to about 2%, by weight of non-volatile material. Another useful optional ingredient is a pigment, such as titanium dioxide. A pigment is present in the coating composition in an amount of from 0% to about 50%, and preferably from about 10% to about 50%, by weight of non-volatile material. According to an important feature of the present invention, the present coating composition is free of a vinyl polymer containing halide, such as for example polyvinyl chloride. The phrase "free of a polymer of a vinyl containing halide" is defined as 1.5% or less of a vinyl polymer containing halide, by weight of non-volatile material, as explained below. Conventionally, a polyvinyl chloride was included in the coating composition to improve the economics of the composition and improve the adhesion of a plastisol packing material to the cured coating composition. However, a vinyl polymer containing halide adversely affects the thermal resistance of the cured coating composition. The present composition does not include a vinyl polymer containing halide, yet it has sufficient adhesion in the plastisol packing to avoid failures of the metal lid in the food products. In addition, the present composition shows excellent thermal resistance. According to an important feature of the present invention, a vinyl polymer containing halide is not intentionally added to the coating composition. However, 1.5% or less of the halide-containing vinyl polymer, i.e., up to and about 1.5% by weight of non-volatile material, may be present in the coating composition as an inadvertent ingredient. For example, several elastomers have enamel layers with a vinyl polymer containing halide as an additive. By incorporating an enamel-coated elastomer into the present coating composition, a vinyl polymer containing halide could be introduced into the composition in an amount of up to 1.5% by weight of non-volatile material. This amount of vinyl polymer containing halide does not adversely affect the composition of the cured coating. A coating composition of the present invention is prepared by simply mixing the epoxy resin novolac, the phenolic resin, or polyester, the elastomer, and any optional ingredient, in any desired order, in the non-aqueous carrier with sufficient agitation. The resulting mixture is stirred until all the ingredients of the composition are dispersed homogeneously in the non-aqueous carrier. Then, an additional amount of the non-aqueous carrier can be added to the coating composition to adjust the amount of non-volatile material in the coating composition to a predetermined level. To demonstrate the utility of a coating composition of the present invention, the following examples were prepared, then applied to a metal substrate as the final paint layer, and finally cured to provide a coated metal substrate. Subsequently, the coated metal substrates were tested, in a comparative manner, to be used as a lid in a food or beverage container. The cured coatings were tested for their ability to inhibit the corrosion of a metal substrate; the adhesion to the metallic substrate and the plastisol packing; chemical resistance; flexibility; and the resistance to scratching and the usual wear. The following Example 2 illustrates an important embodiment of a composition of the present invention and its method of manufacture. EXAMPLE 2 including 100% by weight of a polyfunctional epoxy novolac resin; a phenolic resin based on bisphenol A and formaldehyde, including about 50% by weight of nonvolatile material in a solvent mixture including toluene, deionized water and ethylene glycol monobutyl ether to provide about 18.15% by weight of the total composition of the Example 2, of the phenolic resin; the polyester of Example 1, including about 75% polyester by weight of non-volatile material in a solvent mixture including butylcarbitol and water to provide about 8% by weight of the total composition of Example 2 of the polyester; NIPOL® 1042U, available from Zeon Chemicals, Inc., including 100% by weight of a butadiene-acrylonitrile copolymer; Y Lanolin, added as a 29.8% active material.

The composition of Example 2 was prepared by mixing the aromatic solvent, the diacetone alcohol and the diisobutyl ketone in a vessel to form a mixture of the non-aqueous carrier. Subsequently, the elastomer was added to the mixture of the non-aqueous carrier by stirring. Next, the polyester, the epoxy novolac resin, the phenolic resin and the lubricant were each added, individually, to the resulting mixture, by stirring until all the components of the composition were dispersed homogeneously in the mixture. After sufficient mixing, a composition of the present invention was provided, which includes about 40% by weight of non-volatile material. The coating composition of Example 2 was applied to a metal substrate on a primer layer as the final paint layer, subsequently cured for a sufficient time at a sufficient temperature, such as from about 8 to about 12 minutes, to about 350. ° F at about 400 ° F, to provide a composition of the adherent, interlaced and cured coating on the metal substrate. An important function of the cured coating composition of Example 2 is to provide a coating layer that: (1) improves the corrosion inhibition of the metal substrate and (2) provides a coating capable of adhering to the plastisol packing. Conventionally, the primer layer offers sufficient corrosion inhibiting properties to adequately protect the metal substrate. However, the corrosion inhibition was occasionally insufficient when only a final coat of paint was applied over the cured primer layer. Therefore, two final layers of paint (ie, a three-coat system) were often used. In the same way, the primer layers also do not have sufficient adhesion in the plastisol packing to secure the packing in place during the manufacture of the lid or the processing of the food. Surprisingly, it has been discovered that a coating composition of the present invention, after curing, exhibits excellent chemical and physical properties, shows sufficient adhesion to the primer layer to remove the second final paint layer and improves inhibition to the corrosion provided by the primer layer. The present composition also offers excellent adhesion to plastisol packaging. In addition, the cured coating composition provided by a coating composition of the present invention is sufficiently adhesive to a variety of different types of primer layers and plastisol packaging, such that the composition of the coating can be used in a further range. universal applications. The coating composition of Example 2 also offered a cured coating composition that exhibited excellent flexibility. Flexibility is an important property of a cured coating composition because the metallic substrate is coated with a primer layer and a final coat of paint prior to embossing or in some other way molding the metal substrate in a desired metal article., such as a metal container or a metal bottle cap. The plastisol packing, if present, is applied to the final layer of paint during the stamping process. The coated metal substrate undergoes severe deformations during the molding process, and if a cured coating composition lacks sufficient flexibility, the coating can form breaks, or fractures. These ruptures result in corrosion of the metal substrate because the aqueous content of the container or bottle has less access to the metal substrate. In addition, a cured coating composition provided by a composition of the present invention adheres sufficiently, and remains sufficiently adhered, to the primer layer during processing in a metallic article, thereby further enhancing corrosion inhibition.

The advantages described above achieve a composition of the coating of the present invention useful for the application on the inner surface of a variety of metal articles, such as the interior of vacuum-packed metal containers. The present coating composition is especially useful after curing, as a corrosion inhibiting coating on a metal lid for glass or plastic containers that store food products, such as baby food, or food products including volatile acids, such as condiments. , pickles and hot peppers. The compositions of the following Examples 3 to 27, including the comparative examples, were prepared by the general method outlined above in Example 2. The compositions of Examples 3 to 27 were subsequently applied to a metal substrate as a final coat of paint on a primer layer and they healed. The resulting coatings were tested for a variety of properties, including adhesion and coating integrity. EXAMPLE 3 diacetone-alcohol and diisobutyl ketone to provide a solution including 15% by weight of NIPOL® 1042U. The composition of Example 3 was applied to tin-free steel panels, chrome-chromium oxide, in an amount sufficient to provide 10 mg (milligrams) of the coating composition cured by 4 square inches of the surface of the steel panel. The composition of Example 3 was applied on a commercial primer layer. After application to the steel panel, the composition of Example 3 was cured for 10 minutes at 380 ° F. The composition of Example 3 was compared with a composition of the final commercial paint layer used inside the metal lid, ie, MICOFLEX®, a composition based on polyvinyl chloride (ie containing approximately 70% by weight). weight of dispersion vinyl) available from The Dexter Corporation, Waukegan, IL. After curing the coating compositions, the steel panels coated with any of the compositions of Example 3 or MICOFLEX® were fabricated in metal caps of 51 millimeters in diameter. The tests showed that the composition of Example 3 approved the fabrication of the 51 mm diameter lid, the integrity requirements at elevated temperatures and the adhesion tests of compounds. The adhesion tests of compounds were carried out by two methods. The first method includes the application of plastisol to the length of a panel coated in an appropriate manner with an applicator. The pastisol is applied as a strip 0.5 inches wide and 50 mils thick. The panel is then tilted on a 0.25 inch mandrel. Next, perpendicular incision is made through the plastisol and the coating to the metallic substrate, at the point of the greatest curvature of the inclination. The panels are subsequently exposed to the appropriate processing conditions.

A high processing test is carried out by placing the inclined panels in an autoclave and processing for 5 minutes in water heated to 250 ° F. The panels are then removed and examined for: (1) removal of the plastisol from the coating and (2) release of the plastisol and coating of the metal substrate. Any observed detachment is unacceptable and is considered as failure. The panels are also examined for their resistance to relative bonding and the adhesion interface by descaling the plastisol. Empirical classifications from 0 to 5 are assigned to the test panels, where the classification of zero (best) means very difficult to pull and a rating of 5 (worst) means that it is easily peeled off. This high processing test is used as a classification procedure before manufacturing the plastisol coated lids. In the manufactured caps, compound adhesion tests are carried out by vacuum sealing the caps either in water filled containers with 10% distance between the closure face and a certain point or empty glass containers. These packages are exposed to food processing conditions ranging from pasteurization for 30 minutes at 180 ° F in water, to high processing conditions of 90 minutes at 256 ° F and pressure at 38 psi (pounds per square inch). Afterwards, the containers are cooled and their integrity is examined. The containers are tested in a vacuum. The containers are opened and the adhesion of the package to the coating is also examined. Any loss of vacuum, or any movement of plastisol or removal of plastisol is considered as failure. During specific stages of the cap manufacturing process, hot tools may come into contact with the coated metal, in some cases, the coatings may soften and lose their adhesion to the metal substrate, thus leaving sites susceptible to corrosion. Therefore, it is important to maintain the integrity of the film at elevated temperatures. This is stimulated in a test where coated metal panels are exposed to heated tools. The coated panels of the test are placed between an upper die and a lower die. The lower die is fixed and maintained at 300 ° F, while the upper die is mobile and maintained at 500 ° F. The coated panels are placed between the dies, which are then closed under 60 psi air pressure. The coated panels are exposed at different time intervals, and then examined microscopically to check the integrity of the film and adhesion.

The composition of Example 3 also exceeded the performance of MICOFLEX® in a 60-day accelerated corrosion test. The lids were also tested for resistance to rubbing in the processing of dog food, the adhesion of the plastisol packing and the flexibility. The composition of Example 3 passed all these tests. In addition, the vinyl chloride based compositions have presented drying cracking problems during curing. The composition of Example 3 exceeded the performance of the standard vinyl chloride base coat topcoat compositions by exhibiting excellent crack resistance to drying the final paint layer. In a test, the composition of the Example 3 as a final layer of paint inside a metal lid 51 millimeters in diameter. The lids were tested for corrosion resistance using 2% acetic acid. The 2% acetic acid was packed hot in a glass container and sealed immediately with a metal lid. The resulting vacuum after cooling remained intact, and the containers were stored at 100 ° F for one and two months. The results of the test showed that the composition of Example 3 exceeded the performance of the control coating with polyvinyl chloride base having fewer pitting, a lower average pitting depth and a better overall appearance of the metal cap. The composition of Example 3 was pigmented by adding 47 wt.% (Weight percent) of titanium dioxide (Ti? 2) to the composition of Example 3. After application to steel panels and curing, the pigmented version of the Example 3 also passed the performance tests necessary for a final coat of paint for the interior of a metal cover. The following composition of Example 4 was prepared in an essentially identical manner to the method of preparing the composition of Example 2. EXAMPLE 4 In order to add to the properties of a composition of the present invention, the composition of Example 2 was applied to steel panels in a manner identical to the composition of Example 3, and the coated steel panels were fabricated into lids. 51 millimeters in diameter. The composition of Example 2 was applied on a pigmented primer layer. The composition of Example 2 provides a high-gloss final coat of paint that passed the manufacturing tests of the metal cap and exposure to high temperature tools. The cured coating composition also passed the plastisol adhesion test and the 60-day accelerated corrosion test with 2% acetic acid. The cured coating composition of Example 2 demonstrated excellent ability to withstand scratching of the metallic cap pairs and demonstrated improved adhesion. In another test, the composition of Example 2 was compared to a standard composition of the final layer of polyvinyl chloride-based paint in a 60-day accelerated corrosion test on a metal lid 63 millimeters in diameter. The composition of Example 2 was applied on a primer layer with a percentage of 10 mg by 4 square inches. The standard composition with polyvinyl chloride base was applied on the same primer layer at a rate of 35 mg per 4 square inches. In separate tests, the compositions were applied on different types of primer layers. The composition of Example 2, applied at a substantially lower percentage than the final standard paint layer with polyvinyl chloride base, did not present faults in the 24 lids tested for the plastisol adhesion of low processing and did not present faults in the 24 lids tested for high processing plastisol adhesion. The composition of Example 4, which lacks lubricant, performed identically to the composition of Example 2. percentage of non-volatile material in the composition. The compositions of Examples 5-12 were prepared in an identical manner to the composition of Example 2. The compositions of Examples 5 and 6 are essentially identical, with the exception of the adhesion of a lubricant to the composition of Example 6. The composition of Example 6 was applied on a primer coat as a final paint coat to tin-free steel panels, at a percentage of 10 mg by 4 square inches and cured at 380 ° F for 10 minutes. The composition of the cured coating of Example 6 was compared with the final coat compositions of polyvinyl chloride-based paint, including MICOFLEX®. The cured coating composition of Example 6 performed in a manner similar to, or exceeded, the performance of the comparative compositions with polyvinyl chloride base in the high temperature tool tests, the accelerated corrosion tests of 60 days, the tests of wedge curvature and plastisol adhesion tests. In the plastisol adhesion tests, the metal cap coated with the cured coating composition of Example 6 had no failure in 8 panels tested. The metal caps coated with the polyvinyl chloride based compositions failed in the plastisol adhesion tests. The composition of Example 6 was also compared to the composition of Example 12, which is a pigmented version of the composition of Example 6. The composition of Example 12 performed in a manner comparable to the composition of Example 6 as the final paint layer for the interior of metal caps with respect to 60-day corrosion tests and plastisol adhesion tests. In similar tests, the cured coating compositions of Examples 7 and 8 performed well. However, the comparative compositions of Examples 9 and 10 failed in the plastisol adhesion tests. The comparative composition of Example 9 contains very little amount of polyester for sufficient adhesion and flexibility. The comparative composition of Example 10 failed because the weight ratio of the epoxy resin novolac to the phenolic resin is 1: 3.5. The composition of Example 11 provided excellent adhesion of the cured coating composition to both the plastisol packing and the primer layer. The following Examples 13-27 illustrate that the ratio of the weight of the epoxy resin novolac to the phenolic resin, and the ratio of the weight of the elastomer to the polyester, are important with respect to improving the performance of the present coating composition. fifteen IJ empirical scale for the peel strength ranges from 0 to 5, with 5 being the worst classification.

The compositions of Examples 13-27 show that the ratio of the epoxy resin novolac to the phenolic resin should be from about 33:66 to about 25:75, and especially about 33:66, to improve the performance of the composition. The adhesive strength of the coating composition to the plastisol packing decreases outside this weight ratio of the novolac epoxy resin to the phenolic resin. Examples 13-27 also show that at a constant weight ratio of the novolac / phenolic epoxy resin of 33:66, the adhesive strength of the coating composition to the plastisol packing decreases as the weight of the polyester increases. In addition, Examples 13, 22, 23 and 24 show that the adhesive properties of the coating composition decrease when the weight ratio of the elastomer to the polyester is out of the range of about 1: 1 to about 1: 2. It was also noted that if the polyester is present in an amount significantly greater than about 20% by weight of the coating composition, then the exposure resistance of high temperature tools of the cured coating composition, although it is still acceptable, it decreases. The properties demonstrated by a coating composition of the present invention, and a cured coating composition resulting therefrom, show that a vinyl polymer containing halide is not necessary to offer adhesion to a primer layer or a plastisol packing. Therefore, the composition of the present coating is useful as a final coat of paint on the inside of the metal caps, and especially of metal caps for food and beverage containers. The removal of the halide-containing vinyl polymer is important with respect to the elimination of environmental and toxicological concerns associated with these polymers. Surprisingly, the halide-containing vinyl polymer has been removed, and the present composition maintains the beneficial physical and chemical properties associated with the compositions including a vinyl polymer containing halide. The present coating composition can be used in conjunction with a variety of types of primer layers and plastisol packaging. Therefore, the present coating composition has a more universal range of applications. The present coating compositions, unlike the previous compositions, do not require a pigment, such as Ti0, to achieve sufficient performance and integrity of the films. The performance characteristics of the present coating composition are achieved by a new combination of ingredients, which is opposed to the vinyl polymers containing halide and the pigments. The composition of the cured coating also has a high gloss and the wear of the tools is reduced during the manufacture of the metal cap. The present coating composition has superior thermal resistance properties, improved film integrity, and accordingly, improved corrosion resistance properties. These and the aforementioned advantages achieve that the composition of the coating of the present invention is especially useful for the application on the inner surface of a metal lid for food and beverage containers. Obviously, various modifications and variations of the invention can be carried out in accordance with the foregoing, without deviating from the purpose and scope of the same, and therefore only these limitations will be imposed as indicated by the appended claims.

Claims (33)

1. CLAIMS 1. A coating composition for application to a primed metallic substrate that includes: (a) from about 13% to about 30%, by weight of non-volatile material, of an epoxy novolac resin having an epoxide functionality of about 2 to about 6 and an equivalent weight of the epoxide of from about 100 to about 210; (b) about 40% to about 60%, by weight of non-volatile material, of a phenolic resin, (c) about 15% to about 30%, by weight of non-volatile material, of a polyester containing an average molecular weight from about 1,000 to about 50,000; (d) about 5% to about 20%, by weight of non-volatile material, of an elastomer; and (e) a non-aqueous carrier.
2. 2. The composition of the coating of claim 1 wherein the composition is free of a vinyl polymer containing halide.
3. 3. The coating composition of claim 1 wherein the ratio of the epoxy resin novolac to the phenolic resin is from about 25:75 to about 33:66.
4. 4. The coating composition of claim 1 wherein the ratio of the elastomer to the polyester is from about 2: 1 to about 1: 2.
5. 5. The coating composition of claim 1 including in addition 0% to about 2%, by weight of non-volatile material, of a lubricant; and 0% to about 50%, by weight of non-volatile material, of a pigment.
6. 6. The composition of the coating of claim 1 comprising about 15% to about 25%, by weight of non-volatile material, of an epoxy novolac resin.
7. The coating composition of claim 1 wherein the epoxy functionality of the epoxy novolac resin is greater than about 2 to about 5.
8. The coating composition of claim 1 wherein the epoxy resin novolac has a epoxy equivalent weight of about 150 to about 210.
9. 9. The coating composition of claim 1 wherein the epoxy novolac resin is selected from the group consisting of an epoxy phenol novolac resin, a cresol novolac epoxy resin, a resin ether polyglycidyl phenol, a tetraglycidylmethylenedianilin resin, a triglycidyl p-aminophenol resin, a triglycidyl isocyanurate, and mixtures thereof.
10. The composition of claim 1 comprising about 40% to about 50%, by weight of non-volatile material, of the phenolic resin.
11. The composition of claim 1 wherein the phenolic resin has a molecular weight of from about 1,000 to about 8,000.
12. The composition of claim 1 wherein the phenolic resin includes a phenol component selected from the group consisting of phenol, bisphenol a, crecillic acid, and combinations thereof.
13. The composition of claim 1 including about 15% to about 25% by weight of non-volatile material of the polyester.
14. The composition of claim 1 wherein the polyester has a molecular weight of from about 1,000 to about 10,000.
15. 15. The composition of claim 1 wherein the polyester has a molecular weight of from about 1,500 to about 6,000.
16. 16. The composition of claim 1 including about 5% to about 15% by weight of non-volatile material of the elastomer.
17. 17. The composition of claim 1 wherein the elastomer includes an acrylonitrile copolymer.
18. The composition of claim 1 wherein the elastomer is selected from the group consisting of butadiene-acrylonitrile, natural rubber, a butadiene-styrene copolymer, a polybutadiene, an isobutylene-isoprene copolymer, a polysuloprene, a polyurethane, a acrylic elastomer, a styrene-isoprene copolymer, an acrylonitrile-chloroprene copolymer, a vinylpyridine-butadiene copolymer, and mixtures thereof.
19. The composition of claim 1 wherein the composition includes up to about 1.5%, by weight of non-volatile material, of a vinyl polymer containing halide.
20. The composition of claim 3 wherein the ratio of the epoxy resin novolac to the phenolic resin is from about 30:70 to about 40:60.
21. The composition of claim 5 wherein the composition includes about 10% to about 50%, by weight of non-volatile material, of a pigment.
22. 22. The composition of claim 5 wherein the pigment is titanium dioxide.
23. The composition of claim 1 including: (a) from about 20% to about 25%, by weight of non-volatile material, of an epoxy novolac resin having a functionality of more than about 2 to about 6 and a weight epoxide equivalent of about 100 to about 210; (b) about 45% to about 50%, by weight of non-volatile material, of a phenolic resin, (c) about 20% to about 25%, by weight of non-volatile material, of a polyester containing an average molecular weight from about 1,000 to about 10,000; (d) about 10% to about 15%, by weight of non-volatile material, of an elastomer, wherein the composition is free of a vinyl polymer containing halide, and has a ratio of the epoxy resin novolac to the resin phenol from about 30:70 to about 40:60 and a ratio of the elastomer to the polyester from about 1: 1 to about 1: 2.
24. The composition of claim 23 which further includes about 0% to about 2% of a lubricant, and about 10% to about 50% of a pigment, by weight of non-volatile material.
25. 25. A method of coating a metal substrate that includes: (a) applying a coating composition of the primer layer to at least one surface of the metal substrate; (b) heating the metal substrate with the coating composition of the primer applied thereto for a sufficient time and at a temperature sufficient to cure the coating composition of the primer layer and provide a primed metal substrate; (c) applying a coating composition to the primed metallic substrate, wherein this composition of the composition includes: (i) about 13% to about 30%, by weight of non-volatile material, of an epoxy novolac resin having an epoxide functionality from about 2 to about 6 and an equivalent weight of the epoxide of from about 100 to about 210; (ii) about 40% to about 60%, by weight of non-volatile material, of a phenolic resin, (iii) about 15% to about 30%, by weight of non-volatile material, of a polyester having an average molecular weight of from about 1,000 to about 50,000; (iv) about 5% to about 20%, by weight of non-volatile material, of an elastomer; and (v) a non-aqueous carrier; and (d) heating the primed metallic substrate with the coating composition applied thereon for a sufficient time and at a temperature sufficient to remove the nonaqueous carrier from the composition and provide an entangled cured coating composition.
26. 26. The method of claim 25 wherein the composition is free of a vinyl polymer containing halide.
27. The method of claim 25 wherein a ratio of the epoxy resin novolac to the phenolic resin is from about 25:75 to about 33:66 and a ratio of the elastomer to the polyester is from about 1: 1 to about 1: 2.
28. The method of claim 25 which further includes 0% to about 2%, by weight of non-volatile material, of a lubricant; and from 0% to about 50%, by weight of non-volatile material, of a pigment.
29. 29. The method of claim 25 wherein the primed metallic substrate having the coating composition applied thereto is heated for approximately about 12 minutes at a temperature of about 350 ° F to about 400 ° F.
30. 30. A metallic article having at least one surface thereof coated with a primer layer and an adherent layer of a cured coating composition, wherein this cured coating composition results from curing a coating composition including: a) from about 13% to about 30%, by weight of non-volatile material, of an epoxy novolac resin having an epoxide functionality of from about 2 to about 6 and an epoxide equivalent weight of from about 100 to about 210; (b) about 40% to about 60%, by weight of non-volatile material, of a phenolic resin, (c) about 15% to about 30%, by weight of non-volatile material, of a polyester containing an average molecular weight from about 1,000 to about 50,000; (d) about 5% to about 20%, by weight of non-volatile material, of an elastomer; and (e) a non-aqueous carrier.
31. 31. The metal article of claim 30 wherein the composition is free of a vinyl polymer containing halide.
32. 32. The method of claim 30 wherein a ratio of the epoxy resin novolac to the phenolic resin is from about 25:75 to about 33:66 and a ratio of the elastomer to the polyester is from about 1: 1 to about 1. :2. The method of claim 30 which further includes 0% to about 2%, by weight of non-volatile material, of a lubricant; and from 0% to about 50%, by weight of non-volatile material, of a pigment.