GB1586911A - Water-based coating compositions and their use as coatings for beverage containers - Google Patents

Description

(54) WATER-BASED COATING COMPOSITIONS AND THEIR USE AS COATINGS FOR BEVERAGE CONTAINERS (71) We, PPG INDUSTRIES, INC., a Corporation organised under the laws of the State of Pennsylvania United States of America, of One Gateway Center, Pittsburgh, State of Pennsylvania 15222, United States of America. (Assignees: William Joseph Birkmeyer) do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to water-based coating compositions and their use as coatings for beverage containers.

As a result of the increased emphasis by governments in combating air pollution, the coatings industry is expending considerable effort in eliminating or at least substantially minimizing the emission of solvent vapors to the atmosphere from coating compositions. As a part of this effort, the coatings industry has launched a major effort to develop aqueous or water-based coating compositions in which organic solvents have been completely eliminated or in which the organic solvents constitute only a very minor proportion of the total liquid medium.

In view of the excellent properties of solvent-based epoxy coating compositions for various coating applications, those in the coatings art have been extremely interested in developing aqueous coating compositions derived from epoxy resins. Prior art attempts to develop such compositions involved reacting hydroxy carboxylic acids and epoxy compounds. However, in reacting such compounds, two types of reaction may result due to the chemical nature of the materials used. The hydroxyl groups of the hydroxy acid may react with the epoxide groups to form ether linkages, or the carboxyl group or groups of the acid may react with the epoxide to form ester groups. Both reactions may occur in an uncontrolled reaction to yield products having mixed ether or ester linkages to a non-predetermined degree., Such reaction with the epoxides and acids previously employed have not been tolerable since the ultimate products have not generally been suitable for any practical purpose.

Early efforts to solve these problems involved attempts to optimize the etherification portion of the reaction while minimizing the esterification portion of the reaction. (See, e.g., U.S. Patents Nos. 3*4()4 and 3.41().773). In addition, attempts were made to utilize products containing both ester and ether linkages. (See, e.g., U.S. Patents Nos.

3,707,526 and 3.792.112). However. these efforts were not particularlv successful since compositions produced from these techniques exhibited significant disadvantages including poor cured film saponification resistance. low hydrolysis resistance, and lack of adequate package stability.

It has recently been proposed. as disclosed in U.S. Patent No. 3,960.795. to prepare aqueous-based epoxy resins by a process which involves reacting an epoxy-containing organic material with a compound containing at least one phenolic hydroxyl group and a group hydrolyzable to a carboxyl group following which the resultant composition is hydrolyzed to generate carboxyl groups and then solubilized in known manner by neutralizing at least a portion of the carboxyl groups with a basic compound such as an alkali metal hydroxide or amine. In addition, it has also been proposed,. as described in U.S. Patent No. 4,029,621, to produce aqueous-based epoxy resins by a process which involves reacting an epoxy-containing organic material with a compound containing a mercaptan group and at least one group hydrolyzable to a carboxyl group, following which the resultant composition is hydrolyzed to generate carboxyl groups and then solubilized by neutralizing a portion of the carboxyl groups with a basic compound.

While the processes and products disclosed in the aforementioned patent and application are advantageous in many respects, they also exhibit significant disadvantages. Thus, for example, the processes described in the aforementioned patent and copending applications ordinarily require saponification, neutralization and filtration steps prior to neutralization with the base and solubilization in water. As will be evident, such processes, in view of the number of processing steps and procedures, can be time consuming and costly.

Beer, carbonated and non-carbonated soft drinks, and fruit juices (hereinafter referred to generically as beverages) are often packed in containers made from aluminum, tin-free steel, blackplate or tinplate, which is cold rolled steel to which a thin layer of tin is applied.

Many of these beverages exert corrosive action upon the metal and in order to adequately protect the container and to prevent contamination of the packaged material, a sanitary liner must be applied to the internal surface of the container. However, the use of such liners also presents several problems, one of the most troublesome being the residual turbidity and taste which tends to result from some liner materials.

Because of their relatively taste-free characteristics and other excellent properties, epoxy resins have been extensively employed in sanitary liners in contact with beverages. While such epoxy resins have been extremely useful in the past, they possess a serious disadvantage which materially diminishes their desirability as sanitary liners at this time.

-Thus, these epoxy resins are generally applied from volatile organic solvent solutions at relatively low solids contents and these solvent rich solutions either add to hydrocarbon air pollution or require expensive control equipment.

In recent times the increased emphasis on safety and environmental pollution control has resulted in a need for water-based compositions for such liners. By "water-based" it is meant compositions in solvents consisting predominantly of water, thus greatly reducing the handling and emissions of organic solvent vapors. However, the types of solvent-based epoxy resin liners known and used heretofore have not been readily obtainable as satisfactory water-based systems and, indeed, it has been found that water-based materials as a class often provide liners which impart undesirable turbidity and taste characteristics to beverages, even when the other necessary properties of such liners can be obtained.

The combination of properties which is necessary to successful utilization of any composition for container liners is as follows: A. Properties of the cured liner: 1. Metal Adhesion - Excellent adhesion to metals, including the aluminum, tin-free steel, blackplate and tin plate employed in beverage containers.

2. Taste Characteristics - Taste characteristics at least as good as the best "tasteless" epoxy polymers applied from solvent solutions utilized in the container industry at the present time.

3. Turbidity Resistance - Beverages after packing, pasteurization and storage must not develop undesirable turbidity and loss of appearance due to contact with the liner.

4. Fabricating Properties - Fabricating properties represent a combination of flexibility; extensibility and adhesion so as to permit forming operations to be carried out on the coated metal without cracking or otherwise impairing the continuity of the film.

5. Pasteurization Resistance - Beer is generally pasteurized at a temperature of 15() F.

for 15 to 40 minutes; occasionally during the pasteurization temperatures as high as 16() F.

to 18() F. may be reached.

6. Low Bake Properties - The curing or baking temperature in metal beverage containers should not be excessively high because the exterior of some containers may be coated with lithographic coatings and inks which may discolor and lose their appearance at high temperatures. In addition, some containers employ adhesives as bonding agents and such adhesives may be adversely affected by high baking temperatures.

7. Extrnctability - The liner should not contain undesirable materials which can be extracted from the liner during processing and storage.

S. Intercoat Adhesion - In order to permit use of primer or base coat. if desired, or added coats to repair defects. the liner composition should have good adhesion to itself and other conventionally utilized materials.

B. Properties of the uncured compositon: 1. Application Properties - Application by equipment and methods conventionally employed in the coatings industry. Thus, the composition should be capable of being applied by methods such as dipping, roll coating, spraying and the like. In addition, the composition should be capable of being applied by electrode position if desired.

2. Storage Stability - The coating composition must be in a physical form which permits handling and storage over varying conditions. Water-based compositions in emulsion form, for example, usually are not storage-stable unless additives are employed which generally are undesirable in liners for containers used for comestible products.

We have now found that water-reducible epoxy resins may be prepared by a method which obviates substantially all of the above disadvantages. Thus, water-reducible epoxy resins are prepared by reacting (a) a polyepoxide having a 1,2-epoxide equivalence greater than 1 with (b) an aromatic amino acid containing at least one amine group and one carboxyl group which are both attached to the aromatic ring, wherein the amine group of the acid is preferentially reactive with the epoxy groups of the polyepoxide, the resultant reaction product having unreacted carboxyl groups which when neutralized with a base form anionic salt groups. The resultant product can thus be solubilized (i.e., rendered water-reducible) by neutralizing at least a portion of the acid functionality therein with an amine or other base. Especially valuable amino acids are the aromatic amino acids such as anthranilic acid, p-aminobenzoic acid, m-aminobenzoic acid, and 3-amino-p-toluic acid.

When used in electrodeposition, the compositions herein deposit on the anode. The resultant appropriately crosslinked films, as well as those applied by conventional coating techniques, are characterized by increased cured film saponification resistance, improved hydrolytic stability, improved salt spray resistance and good hardness. Additionally, these compositions have excellent package stability. Since the reaction products contain hydroxyl functionality, a wide variety of conventional crosslinking agents can be employed in formulations with these new resins.

Further, highly useful products can be obtained when the reaction products of the present invention are blended with reactive or non-reactive resins such as water-soluble acrylics, acrylic interpolymer dispersions, acrylic polymer emulsions, aminoplast resins, phenolic resins, polyester resins, blocked or semi-blocked polyisocyanates.

Highly-useful water-based products can be obtained from the reaction products and the above-mentioned resin products which are suitable for use as water-based coating compositions for a variety of protective and decorative coating applications. In a particular embodiment, a water-based coating composition which is suitable for use as an internal sanitary liner for metal beverage containers is formulated by blending the reaction product with an aminoplast resin.

In formulating a coating composition for use as an internal sanitary liner for metal containers in which beverages are to be stored, it is extremely important that cured films produced from such coating compositions do not contan certain materials, even in residual amounts, which can be extracted by the beverage from the cured film. Thus, it has been found that certain additives commonly employed in formulating prior aqueous-based coating compositions may remain in residual amounts in cured films produced from such compositions and that even residual amounts of such additives can adversely affect the characteristics of beverages in contact with such films. For example, residual amounts of such materials as surfactants and dispersion stabilizers commonly employed in formulating aqueous compositions have been found to exert adverse effects on the turbidity and/or taste characteristics of beverages such as beer. Accordingly, in formulating the water-based coating compositions employed in this invention, such materials are avoided.

The water-based coating compositions of the present invention as defined above may also contain as a further component a curing or crosslinking agent.

A wide variety of polyepoxides may be utilized in forming the reaction product component of the compositions herein, provided that they have a 1,2-epoxy equivalence greater than 1.0, that is, in which the average number of 1,2-epoxy groups per molecule is greater than 1.

The polyepoxide can be any of the well-known epoxides, such as, for example, those described in U.S. Patents Nos. 2,467,171; 2,615,007; 2,716,123; 3,030,336; 3,053,855 and 3,075,999. A particularly preferred class of polyepoxides are the polyglycidyl ethers of polyhydric phenols, such as bisphenol-A or bisphenol-F produced, for example, by etherification of a polyhydric phenol with epichlorohydrin or dichlorohydrin in the presence of an alkali.

The phenolic compound may be bis(4-hydroxyphenol)-2, 2-propane, 4,4'dihydroxybenzophenone, bis(4-hydroxyphenyl) 1, 1-ethane, bis(4-hydroxyphenyl)1,1isobutane; bis(4-hydroxytertiary-butyl-phenyl)2,2-propane, bis(2hydroxynaphthyl)methane or 1,5-dihydroxynaphthalene.

Another quite useful class of polyepoxides are produced similarly from Novolak resins or similar polyphenol resins.

Also suitable in some instances are the similar polyglycidyl ethers of polyhydric alcohols which may be delivered from such polyhydric alcohols as ethylene glycol, diethylene glyciol, triethylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol, glycerol, bis(4-hydroxycyclohexyl)-2,2-propane, and the like.

There can also be used polyglycidyl esters of polycarboxylic acids which are produced by the reaction of epichlorohydrin or a similar epoxy compound with an aliphatic or aromatic polycarboxylic acid, such as oxalic acid; succinic acid, glutaric acid, terephthalic acid, 2,6-naphthalene dicarboxylic acid, dimerized linolenic acid and the like. Examples are diglycidyl adipate and diglycidyl phthalate.

In addition, polyepoxides derived from the epoxidation of an olefinically unsaturated alicyclic compound may also be employed. Included are diepoxides comprising in part one or more monoepoxides. These poly-epoxides are non-phenolic and are obtained by epoxidation of alicyclic olefins, for example, by oxygen and selected metal catalysts, by perbenzoic acid, by acetaldehyde monoperacetate, or by peracetic acid. Among such polyepoxides are the epoxyalicyclic ethers and esters, which are well-known in the art.

Polyglycidyl ethers of polyhydric phenols containing oxyalkylene groups may be employed. These can be produced by reacting some of the epoxy groups of the polyglycidyl ether of the polyhydric phenol with a monohydric alcohol containing oxyalkylene groups.

Other epoxy-containing compounds and resins which may be employed include nitrogeneous diepoxides such as disclosed in U.S. Patent No. 3,365,471; epoxy resins from 1,1-methylene bis(5-substituted hydantoin), U.S. Patent No. 3,391,097; bis-imide containing diepoxides, U.S. Patent No. 3,450,711; heterocyclic N,N'-diglycidyl compounds, U.S.

Patent No. 3,503,979; amino epoxy-phosphonates, and the like.

Aromatic amino acids which may be employed in forming the reaction product component of the compositions herein are amino acids which contain at least one amine group and at least one carboxyl group in which the amine group of the amino acid is preferentially reactive with the epoxy groups of the polyglycidyl ether.

It was surprising and unexpected to find in this invention that certain amino acids contain amine groups which are preferentially or selectively reactive with epoxy groups and that such amino acids can be directly reacted with epoxy resins to form reaction products containing free carboxyl groups available for solubilization purposes without first blocking the carboxyl groups of the amino acid as by reaction with an alcohol (i.e., ester formation) or strong base (e.g., NaOH). This was particularly unexpected since previous attempts to prepare such water-reducible products utilizing simple (i.e., short chain) aliphatic amino acids indicated that the epoxy groups of the epoxy resin reacted principally with the carboxyl groups of the amino acid, thereby resulting in a product containing little if any free carboxyl functionality available for solubilization purposes.

The amino acids for use in preparing the reaction product component of the compositions are aromatic amino acids in which the amine group and carboxyl group are both attached to the aromatic ring. Especially preferred amino acids of this type are the aminobenzoic acids, including anthranilic acid, p-aminobenzoic acid and m-aminobenzoic acid, and other aromatic amino acids such as 3-amino-p-toluic acid.

Anthranilic acid is a particularly preferred amino acid for use in forming the reaction product component of the sanitary liner composition because its methyl ester i.e., methyl anthranilate, is a component of naturally-occurring foods such as grape juice and, in addition, the free form of the acid is often present in North American wines. Other amino acids useful in many instances include 3-aminosalicylic acid, 3-amino-4-methoxybenzoic acid, 6-amino-m-toluic acid, 3-amino-4-chlorobenzoic acid, 2-amino-5-nitrobenzoic acid, 2-nitro-5-aminobenzoic acid. In some cases it may be necessary to use a specific solvent chosen to dissolve certain difficult-to-dissolve amino acids, one example being 5aminoisophthalic acid which otherwise does not react.

In reacting the polyepoxide with the amino acid, in general, the equivalent ratio of epoxy groups contained in the polyepoxide to amino groups contained in the aromatic amino acid should be between about 1.0 and 0.20 and 1.0 to 1.25, and preferably 1.0 to 0.5 and 1.0 to 1.0. It is generally preferred that the carboxyl content of the reaction product be at least equivalent, when in an unneutralized state, to an acid value of at least about 15 at 100 percent solids.

In reacting the polyepoxide and the aromatic amino acid, a catalyst may be used, if desired. Suitable catalysts include acid catalysts such as p-toluene-sulfonic acid, butylphosporic acid and methane sulfonic acid. In general, where catalysts are employed, they should be used in amount from 0.01 to 3.0 percent by weight based on total weight of the epoxy-containing material and aromatic amino acid. Usually, it is desirable to react the components at moderately elevated temperatures, and for this purpose, temperatures of from 200 F. to 350 F. are generally acceptable. Of course, it is to be recognized that the reaction temperature can be varied between the lowest temperature at which the reaction reasonablv proceeds and the temperatures indicated above.

It is not absolutely necessary to emplov a solvent in the preparation of the reaction product. for example. when the reactants are mutually soluble and of suitable viscosity but one is usually used in order to provide for more efficient processing. The organic solvent used should be a non-epoxy reactive solvent and. since the finished product is intended to be water-reducible. it is preferred to employ water-miscible or at least partially water-miscible organic solvents. Preferred solvents of this type include the monoalksl ethers of ethylene glycol. propylene glycol and dipropvlene glycol such as. for example.

ethylene glycol monoethyl ether, ethylene glycol monobutyl ether. propylene glycol monomethyl ether and dipropylene glycol monomethyl ether. Mixtures of ihese ether tvpe alcohols and lower alkanols such as ethanol. propanol and isopropyl alcohol may also be employed. Additionally. in some instances. minor proportions of hydrocarbon solvents such as toluene and xylene may be utilized in combination with the preferred solvents.

The reaction products can then be solubilized (i.e.. rendered water-reducible) by neutralizing at least a portion of the carboxyl groups thereof with an amine or other base.

As will be apparent. the term solubilized as employed herein refers to the neutralization or partial neutralization of the acid groups of the reaction product to form the salt or partial salt of the product to thereby render it water-reducible or water-thinnable.

Volatile bases are preferred. particularly when the composition is to be applied by spraying. rolling. dipping or the like (bv volatile bases is meant bases which evaporate at temperatures at or bellow that at which the material is cured). Non-volatile bases. such as alkali metal hydroxides. may be used when application bv electrodeposition or other methods which remove the solubilizing agent are to be used. Amines are the preferred volatile neutralizing agents. although others. such as quaternary ammonium hydroxides.

can be used.

In general. the amines which may be employed herein for neutralization purposes include any of the amines used for solubilizing resin systems knows heretofore including ammonia: alkslamines such as ethylamine. propx lamine. dimethylamine. dibutylamine. triethvlamine and cyclohexylamine: allylamine: alkanolamines such as monoethanolamine. dimethyletha- nolarhine. diethylethanolamine. 2-amino-2-methyl-1-propanol and '-dimeths-l-amino-'- methyl-1-propanol: aralkylamines such as benzylamine: cyclic amines such as morpholine and piperidine and diamines such as ethylene diamine. The preferred amines for use herein are dimethylethanolamine and diethylethanolamine. Mixtures of such solubilizing agents mav also be used. If desired. moderately elevated temperatures may be employed in solubilizing the product. Essentially any amount of solubilizing agent may be utilized as long as the desired degree of water-solubility or water-dispersibilitv is obtained. In general.

the amount of solubilizing agent will be dependent upon the acid value of the reaction product. It is usually preferred to react one equivalent of solubilizing agent per equivalent acid group. although higher and lower amounts may be used. In general. it is preferred to utilize the minimum amount of solubilizing agent to obtain the solubilized product. As noted above. it is often desirable to prepare coating compositions from the reaction products herein in which the liquid medium is a mixture of water and organic solvents This can be conveniently accomplished. as indicated above. by utilizing a water-miscible a water-miscible partially water-miscible organic solvent to first prepare the reaction product in organic solvent solution and then after solubilization with the amine. water can be added to the solution or the reaction product solution can be dissolved or dispersed in water.

For use as sanitary liners for metal containers. a curing or crosslinking agent is included in the compositions. The preferred crosslinking agents include aminoplast resins. phenolic resins and blocked or semi-blocked polyisocyanates.

The aminoplast resins used may be alkylated methklol melamine resins. alkklated methvlol urea. and similar compounds. Products obtained from the reaction of alcohols and formaldehyde with melamine. urea or benzoouanamine are most common and are preferred herein. However. condensation properties of other amines and amides can also be employed. for example. aldehyde condensates of triazines. diazines. triazoles.

guanidines. guanamines and alkyl- and aryl-substituted derixatixes of such compounds.

including alkyl- and aryl-substituted ureas and alkyl and aryl-substituted melamines. Some examples of such compounds are N,N'-dimethylurea, i enzvl-urea. formoguanamine.

acetoguanamine. ammeline. 2-chloro-4.6-diamino- 1 .3.5-triazine. 6-methyl-2 .4- diamino,1,3,5-triazine. 3.5-diaminotriazole. triaminopyrimidine and '-mercapto-4.6 diaminopyridine.

While the aldehyde employed is most often formaldehyde. other similar condensation products can be made from other aldehydes or mixtures thereof. such as acetaldehyde.

crotonaldehyde, acrolein. benzaldehyde. furfural and glyoxal.

The aminoplast resins contain methylol or similar alkylol groups, and in most instances at least a portion of these alkylol groups are etherified by a reaction with an alcohol to provide organic solvent-soluble resins. Any monohydric alcohol can be employed for this purpose, including such alcohols as methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol and monoethers of glycols. The preferred aminoplast resins are substantially etherified with methanol or butanol.

The phenolic resins which may be used as curing agents herein are formed by the condensation of an aldehyde and a phenol. The most used aldehyde is formaldehyde, although other aldehydes, such as acetaldehyde, can also be employed. Aldehyde-releasing agents such as paraformaldehyde and hexamethylenetetramine, can be utilized as the aldehyde agent if desired. Various phenols can be used; for instance, the phenol employed can be phenol per se, a cresol, or a substituted phenol in which a hydrocarbon radical having either a straight chain, a branch'wed chain or a cyclic structure is substituted for a hydrogen in the aromatic ring. Mixtures of phenols are, also often employed. Some specific examples of phenols utilized to produce these resins include p-phenylphenol, p-tert-butylphenol, p-tert-amylphenol, cyclopentylphenol and unsaturated hydrocarbon-substituted phenols, such as monobutenyl phenols containing a butenyl group in the ortho, meta, or para position, and where the double bond occurs in various positions in the hydrocarbon chain.

A common phenolic resin is phenol formaldehyde resin.

Any blocked or semi-blocked organic polyisocyanate may be used as the curing agent herein. The organic polyisocyanates may be blocked with a volatile alcohol, E-caprolactam or ketoximes, and will unblock at elevated temperatures. These curing agents are well-known in the art.

The amounts of curing or crosslinking agents employed in combination with the reaction products herein can vary somewhat depending on desired properties. However, it is preferred to use from about 3 to about 30 percent by weight of the crosslinking agents, based upon the combined total solids weight of the crosslinking agent and reaction product.

As noted above, various other reactive or non-reactive resins other than the aforementioned curing or crosslinking agents may be included in the water-based coating composition. Thus, hydrocarbon resins, such as polybutadiene, maleic anhydride adducts of polybutadiene, styrene-butadiene latices, etc.; water-soluble acrylic resins such as those in U. S. Patent No. 3,403,088; acrylic polymer emulsions; aqueous dispersions of amide-containing acrylic interpolymers; and mixtures thereof may be included. The compositions may also include polyesters and polyamides. When using such modifying materials, such materials generally comprise from 95 to 5 percent by weight, and preferably from 50 to 5 percent by weight, based on total weight of resin solids.

It should be noted that in certain inst carboxylic acid amides, ethylenically unsaturated carboxylic acids and certain ethylenically unsaturated hardening and flexibilizing monomers. Aqueous dispersions of these interpolymers are prepared by neutralizing or partially neutralizing the acid groups of the interpolymer with an amine or other base.

As set forth in U.S. Patent No. 3991216 the preferred materials employed in forming these interpolymers are N-alkoxyalkyl-substituted amides such as N (butoxymethylOacrylamide and N-(butoxymethyl)methacrylamide; ethylenically unsaturated carboxylic acids such as acrylic and methacrylic acid; unsaturated hardening monomers such as styrene, vinyl toluene or alkyl methacrylates having 1 to 4 carbon atoms and unsaturated flexibilizing monomers such as alkyl acrylates having up to 13 carbon atoms and alkyl methacrylates having from 5 to 16 carbon atoms.

The finished water-based coating composition can be prepared in various ways. Thus, for example, the partially neutralized reaction product, usually in organic solvent solution, can be blended with the crosslinking agent and the resultant mixture can then be reduced or thinned with water or, if desired, a mixture of water and water-miscible organic solvents.

Alternatively, the unneutralized reaction product can be blended with the crosslinking agent and solubilizing agent and the resultant mixture can then be reduced with water or a mixture of water and water-miscible organic solvents. Still further, the partially neutralized reaction product can be dissolved in or dispersed in water following which the crosslinking agent can be blended with the mixture.

The liquid medium of the water-based coating compositions used in the invention is an aqueous medium, which ordinarily contains at least 60 percent by weight of water. The liquid medium preferably contains at least 70 percent by weight of water and may contain up to 95 percent by weight of water, the balance being water-miscible or partially water-miscible organic solvents of the type described above.

The water-based coating compositions employed in the invention can be applied by methods conventionally employed in the coatings industry, such as brushing, dipping, roll coating, spraying and electrodeposition and they are particularly adapted to be applied by the methods used to coat containers.

For a detailed description of the aqueous acrylic interpolymer dispersions and their method of preparation, reference can be made to the aforementioned U.S. Patent 3,991,216.

In addition to the components above, the compositions may, if desired, contain other optical ingredients, including any of the pigments ordinarily used in coating compositions of this general class. In addition, various fillers, antioxidants, flow control agents, surfactants, and other such formulating additives may be employed.

The compositions herein can be applied by essentially any coating method, including brushing, spraying, dipping, roll coating, flow coating and electrodeposition. When used in electrodeposition, the compositions deposit on the anode. The compositions may be applied over virtually any substrate, including wood, metals, glass, cloth, plastics, foams, and the like, as well as over various primers, to provide protective and decorative coatings.

They can be used, for example, to coat metal containers.

The invention will be further described in connection with the several examples which follow. These examples are given as illustrative of the invention and are not to be construed as limiting it to their details. All parts and percentages in the examples and throughout the specification are by weight unless otherwise indicated.

Example 1 To a reactor equipped with a heating means, stirrer, thermometer, reflux condenser and means for providing an inert gas blanket were charged 1482.0 grams of Epon 829 (a liquid polyglycidyl ether of Bisphenol A having an epoxide equivalent of about 198, containing an epoxy condensation catalyst, available from Shell Chemical Company) and 616.0 grams of Bisphenol A. The reaction mixture was heated to 280"F. and the heat removed to allow for an exotherm. The maximum temperature reached during exotherm was 390"F. During this period, cooling was applied and the mixture was held above 350"F. for 1 hour. The epoxy equivalent of the polyepoxide produced was 1,015. After the hold period. 600.0 grams of ethylene glycol monoethyl ether (hereinafter ethyl Cellosolve) were added to the reactor.

(CELLOSOLVE is a registered Trade Mark). During this addition, the temperature decreased to 250"F. Heating was then resumed and 5.0 grams of Cyzac 4040 (a 40 percent solution of p-toluene-sulfonic acid in isopropyl alcohol available from American Cyanamid Company) and 302.0 grams of p-aminobenzoic acid were added to the reactor. (CYZAC is a registered Trade Mark). The reaction mixture was then held for 3 hours at a temperature of about 290"F. Following this hold period, 692.0 grams of propylene glycol isobutyl ether were added.

The resultant reaction product had a non-volatile solids content of 64.9 percent, a Gardner-Holdt viscosity of Z10 and an acid value of 33.4 (51.4 at 100 percent solids).

To a 65.5 gram sample of the above reaction product were added 3.5 grams of dimethylethanolamine and 90.2 grams of deionized water with stirring. The resultant composition had a non-volatile solids content of about 26.7 percent and a pH of 8.3 Example 2 To a reactor equipped as in Example 1 were charged 1493.0 grams of Epon 829 and 706.0 grams of Bisphenol A. The reaction mixture was heated to 2800F. and the heat removed to allow for an exotherm (maximum temperature 400"F.). During this period, cooling was applied andvthe mixture was held above 350"F. for 1 hour. The polyepoxide produced had an epoxy equivalent of 1,554. After this hold period, 600.0 grams of ethyl Cellosolve were added to the reactor. During this addition, the temperature decreased to 260"F. Heating was resumed and then 5.0 grams of Cyaz 4040 and 201.0 grams of p-aminobenzoic acid were added. The reaction mixture was then held for 3 hours at 2800F. - 290"F. After this hold period, 692.0 grams of propylene glycol isobutyl ether were added.

The resultant reaction product had a non-volatile solids content of 64.3 percent and an acid value of 22.0 (34.2 at 100 percent solids).

To a 65.5 gram sample of the above reaction product were added 2.3 grams of dimethylethanolamine and 91.4 grams of deionized water with stirring. The resultant composition had a non-volatile solids content of 25.3 and a pH of 8.5.

Example 3 To a reactor equipped as in Example 1 were charged 1,497.0 grams of Epon 829 and 753.0 grams of Bisphenol A. The mixture was heated to 2800F. following which the heat was removed to allow for an exotherm which reached a maximum temperature of 407"F. The reaction mixture was held above 350"F for 1 hour and then cooled to 300"F. The polyepoxide produced had an epoxy equivalent of 1,869. At this point, 600.0 grams of ethylene glycol monobutyl ether (hereinafter butyl Cellosolve) were added to the reactor and the temperature decreased to 260"F. Heating was again resumed and when the temperature reached about 280"F., 5.0 grams of Cyzac 4040 and 150.0 grams of p-aminobenzoic acid were added to the reactor. The reaction mixture was then held for 3 hours at temperature. After the hold period (temperature 280"F.), 692.0 grams of propylene glycol isobutyl ether were added.

The resultant reaction product had a non-volatile solids content of 64.3 percent and an acid value of 16.2 (25.2 at 100 percent solids).

To a 65.5 gram sample of the above reaction product were added 1.7 grams of dimethylethanolamine and 92.0 grams of deionized water with stirring. The resultant composition had a non-volatile solids content of 26.4 percent and a pH of 9.0.

Example 4 To a reactor equipped as in Example 1 were charged 750.0 grams of Epon 829 and 375.0 grams of Bisphenol A. The mixture was heated to 3000F. following which the heat was removed and the mixture allowed to exotherm reaching a maximum temperature of 420"F.

The reaction mixture was held above 350"F. for 1 hour and then cooled to 300"F. At this point, 75.0 grams of anthranilic acid were added and the reaction mixture then held for 2 hours at 310-320"F. The reaction mixture was then cooled and 600.0 grams of butyl Cellosolve was added to the reactor. The resultant reaction product had a non-volatile solids content of 66.2 percent and an acid value of 19.7 (29.8 at 100 percent solids).

To a 100.0 gram sample of the above reaction product (temperature at 1600F.) was added 2.1 grams of dimethylethanolamine with stirring, following which 114.0 grams of deionized water was added. The resultant composition had a non-volatile solids content of about 33.0 percent and a pH of 9.1.

Example 5 To a reactor equipped as in Example 1 were charged 1656.0 grams of Epon 829 and 481.0 grams of Bisphenol A. The mixture was heated to 280"F. and the heat then removed to allow for exotherm (maximum 360"F.). The reaction mixture was then held for 1 hour above 350"F. The product was a polyepoxide having an epoxide equivalent of 522. After the hold period, 600.0 grams of butyl Cellosolve were added to the reaction mixture. After this addition was complete, 10.0 grams of Cyzac 4040 and 263.0 grams of p-aminobenzoic acid were added to the reaction mixture with the temperature at 300"F. The reaction mixture was then held for 3 hours at about 300"F. Following this period, 428.0 grams of butyl Cellosolve were added to the reactor.

The resultant product had a non-volatile solids content of about 70.0 percent and an acid value of 24.8 (35.5 at 100 percent solids).

To a 55.5 gram sample ofthe above reaction product were added 11.2 grams of butyl Cellosolve, 2.2 grams of dimethylethanolamine and 91.1 grams of deionized water. The resultant composition had a non-volatile solids content of 28.9 percent, a Gardner-Holdt viscosity of Z9 - and a pH of 8.25.

Example 6 To a reactor equipped as in Example 1 were charged 1510.0 grams of Epon 829 and 627.0 grams of Bisphenol A. The reaction mixture was heated to 2800F. and the heat was then removed to allow for exotherm (maximum temperature 440"F.) The reaction mixture was then held at above 350"F. for 1 hour. The polyepoxide produced had an epoxy equivalent of 858. Following the hold period, the reaction mixture was cooled to about 380"F. and 600.0 grams of butyl Cellosolve were added. Then, 10.0 grams of Cyzac 4040 and 263.0 grams of p-aminobenzoic acid were added to the reaction mixture (temperature about 2609F.). The reaction mixture was then heated to 300"F. and held for 3 hours at this temperature.

Following this hold period, 428.0 grams of butyl Cellosolve were added to the reactor.

The resultant reaction product had a non-volatile solids content of about 70.0 percent and an acid value of 30.2 (43.1 at 100 percent solids).

To a 57.1 gram sample of the above reaction product were added 9.6 grams of butyl Cellosolve, 2.7 grams of dimethylethanolamine and 90.6 grams of deionized water. The resultant composition had a non-volatile solids content of 27.8 percent, a Gardner-Holdt viscosity of W- and a pH of 8.35.

Example 7 To a reactor equipped as in Example 1 were charged 1,656.0 grams of Epon 829 and 481.0 grams of Bisphenol A. The reaction mixture was heated to 2800F. and the heat then removed to allow for exotherm (maximum temperature 380"F.). The reaction mixture was then held for 1 hour above 350"F. The polyepoxide produced had an epoxy equivalent of 500. After this hold period, 600.0 grams of butyl Cellosolve were added to the reaction mixture and the temperature decreased to about 270"F. After the temperature of the reaction mixture again reached 300"F., 10.0 grams of Cyzac 4040 and 263.0 grams of p-aminobenzoic acid were added. The reaction mixture was then held for 1 hour at this temperature. Following this addition, the contents of the reactor were cooled to about 280"F. and then 428.0 grams of butyl Cellosolve were added.

The resultant reaction product had a non-volatile solids content of about 70.0 percent and an acid value of 28.9 (41.3 at 100 percent solids).

To a 55.5 gram sample of the above reaction product were added 11.2 grams of butyl Cellosolve, 2.7 grams of dimethylethanolamine, and 91.0 grams of deionized water. The resultant composition had a non-volatile solids content of 27.3 percent, a Gardner-Holdt viscosity of Z6 and a pH of 8.75.

Examples 8-11 To a reactor equipped as in Example 1 were charged 3,750.0 grams of Epon 829 and 1,875.0 grams of Bisphenol A. The reaction mixture was heated to 300"F. and the heat was then removed to allow for exotherm, (maximum temperature attained was 404 F.). The reaction mixture was then held for 1 hour above 350"F. The polyepoxide had an epoxy equivalent of 1,616. After this hold period, 1,500.0 grams of butyl Cellosolve were added to the reaction mixture at which time the temperature decreased to about 290"F. After the temperature again reached 300"F., 25.0 grams of Cyzac 4040 and 375.0 grams of p-aminobenzoic acid were added. Following this addition, the reaction mixture was held at about 300"F. for 3 hours. Following this period, 1,730.0 grams of butyl Cellosolve were added to the reactor.

The resultant reaction product had a non-volatile solids content of 64.3 percent, a Gardner-Holdt viscosity of Z10+ and an acid value of 15.7 (24.4 at 100 percent solids).

The above reaction product was neutralized with various basic compounds by admixing the following ingredients: Parts by Weight (Grams) Ingredients Ex. No. 8 9 - 10 11 Reaction product above 61.5 61.5 61.5 61.5 butyl Cellosolve 5.2 5.2 5.2 5.2 dimethylethanolamine 1.5 - - triethylamine - 1.8 NH4OH (28 percent solution in H2O) - - 2.5 2-amino-2-methyl-1 propanol - - - 1.5 deionized water 91.8 91.5 90.8 91.8 The resultant compositions had the following properties: 8 9 10 11 Non-volatile solids content (%) 27.3 27.7 26.7 27.2 Gardner-Holdt viscosity K-L D-E We 24 pH 8.6 9.0 8.7 8.5 Appearance Clear Trans- Clear Clear solution lucent solution solution solution Examples 12-14 To a reactor equipped as in Example 1 were charged 750.0 grams of Epon 829 and 375.0 grams of Bisphenol A. The reaction mixture was heated to 300 F. and the heat was then removed to allow for an exotherm (maximum temperature reached was 400"F.). The mixture was then held above 350"F. for 1 hour. The polyepoxide produced had an epoxy equivalent of 1,800. Following this hold period, 300.0 grams of butyl Cellosolve were added to the reaction mixture with cooling until the temperature reached 300"F. (about 1 hour).

Then, 5.0 grams of Cyzac 4040 and 75.0 grams of p-amino-benzoic acid were added to the reactor. The reaction mixture was then held at 300"F. for about 4 hours. After this hold period, 300.0 grams of butyl Cellosolve were added.

The resultant reaction product had a non-volatile solids content of 67.2 percent and an acid value of 15.3 (22.8 at 100 percent solids).

This reaction product was neutralized by admixing the following ingredients: Parts by Weight (Grams) Ingredients Ex. No. 12 13 14 Reaction product above 100.0 100.0 100.0 butyl Cellosolve 11.8 11.8 dimethylethanolamine 2.4 3.0 3.0 deionized water 109.4 154.4 157.0 The resultant compositions had the following properties: 12 13 14 Non-volatile solids content (%) 29.8 26.3 26.2 pH 8.1 8.7 8.9 Comments Composition Clear solu- Clear solution settled after tion stable stable after aging overnight after aging aging overnight overnight (*due to slightly low level of neutralization) Example 15 To a reactor equipped as in Example A were charged 750.0 grams of Epon 829 and 375.0 grams of Bisphenol A. The reaction mixture was heated to 300"F. and the heat was then removed to allow for an exotherm (maximum temperature 400"F.). The mixture was then held above 350"F. for 1 hour. The resultant polyepoxide had an epoxy equivalent of 1,800.

Following this hold period, 300.0 grams of butyl Cellosolve were added to the reaction mixture with cooling until the temperature reached 300"F. (about 1 hour). Then, 5.0 grams of Cyzac 4040 and 75.0 grams of p-aminobenzoic acid were added to the reactor. The reaction mixture was then held at 3000F. about 4 hours. After this period, 300.0 grams of butyl Cellosolve were added.

The resultant reaction product had a non-volatile solids content of 67.2 percent and an acid value of 15.3 (22.8 at 100 percent solids).

A sample of the above reaction product was solubilized in the following manner: To a reactor equipped with heating means, stirrer, thermometer, and dropping funnel was charged 1,000.0 grams of the reaction product. The reaction product was heated to 145"F. and then 118.0 grams of butyl Cellosolve were added to the reactor with stirring.

After about 20 minutes of stirring, 29.0 grams of dimethylethanolamine were added. After about 30 minutes of stirring, 125.3 grams of deionized water were added dropwise over a 1 hour period. The contents of the reactor were then held for 2 hours at 140-150"F. Following this period, 150.0 grams of deionized water were added to the reactor.

The resultant composition had the following properties: Non-volatile solids content 26.2 percent Gardner-Holdt viscosity Acid Value 6.5 (22.8 at 100 percent solids) pH 8.6 Composition of Liquid Medium (% by weight) Deionized water 74.7 butyl Cellosolve 23.8 dimethylethanolamine 1.5 The following examples illustrate various utilizations of the reaction products herein.

Example 16 A coating composition was prepared by blending the following: Parts by Weight Product of Example 1 159.20 Cymel 303* 7.50 *A highly methylated melamine resin having a non-volatile percentage of 98 minimum, a Gardner-Holdt viscosity at 25"C. of X-Z2, a Gardner color of 2 maximum, and a methylol content of about 1.5 percent, available from American Cyanamid Company. CYMEL is a registered Trade Mark.

The composition was then drawn down on Bonderite 1000 pretreated steel panels (3 mil wet film thickness) and baked at 325"F. for 20 minutes).

(BONDERITE is a registered Trade Mark). The resultant film exhibited excellent properties having a pencil hardness of 4H; a direct impact strength in excess of 160 inch-pounds; a reverse impact strength of 140 inch-pounds and passed 100 acetone double rubs.

Example 17 A coating composition was prepared by the following: Parts by Weight Product of Example 2 159.20 Cymel 303 7.50 The composition was drawn down and baked as in Example 16. The resultant film had a pencil hardness of 3H, a direct and reverse impact strength in excess of 160 inch-pounds, and passed 50 acetone double rubs.

Example 18 A coating composition was prepared by blending the following: Parts by Weight Product of Example 3 159.20 Cymel 303 7.50 The composition was drawn down and baked as in Example 16. The resultant film had a pencil hardness of 3H, a direct and reverse impact strength in excess of 160 inch-pounds and passed 25 acetone double rubs.

Example 19 A pigment paste was prepared by grinding the following ingredients to a number 7.5 Hegman in a steel ball rolling mill: Parts by Weight Resin vehicle* 78.0 Barytes 79.1 Red iron oxide 15.8 Bentone 34 talc 2.1 Blanc fixe 1.1 Fumed litharge 1.1 Carbon black 0.8 Witco 912 surfactant 2.0 Deionized water 20.0 WITCO is a registered Trade Mark.

*A 30 percent solids epoxy-fatty acid ester prepared by reacting a mixture consisting of 64.3 percent Epon 828, a condensation product of epichlorohydrin and Bisphenol A having an epoxide equivalent of about 185-192, commercially available from Shell Chemical Co.; 20.1 percent of Pamolyn 200, a fatty acid composition containing 17 percent by weight oleic acid, 70 percent by weight linoleic acid and 11 percent by weight conjugated linoleic acid, which is commercially available from Hercules, Inc.; and 15.6 percent maleic anhydride.

The pigment paste contains 62.5 percent total solids of which 80 percent is pigment and 20 percent is resinous vehicle.

A coating composition for use as a metal primer was prepared by blending the following ingredients: Parts by Weight Product of Example 15 120.8 Acrylic polymer latex(') 97.2 Bettle 80(2) 7.8 Pigment paste (above) 39.0 Deionized water 15.2 (1) An acrylic polymer emulsion having a total solids content of 38.9 percent by weight and a viscosity of 30 centipoises, prepared by emulsion polymerization of a monomer mixture consisting of 51.0 percent ethyl acrylate, 40.0 percent styrene, 5.0 percent hydroxypropyl acrylate and 4.0 percent acrylic acid in accordance with the procedure described in the specification above.

(2) A butylated urea formaldehyde resin having a solids content of about 96 percent, a Gardner-Holdt viscosity of X-Z3 and a methylol content of less than one percent, commercially available from American Cyanamid Company. BEETLE is a registered Trade Mark.

The primer coating composition was then spray applied to both untreated steel and Bonderite 40 pretreated steel panels. When baked at 325 F. for 30 minutes a film of 1.5 mil thickness was produced. The coated panels were then topcoated with a commercial acrylic enamel coating and evaluated for impact resistance and salt spray resistance utilizing standard impact resistance and salt spray resistance tests. The primer coating on the untreated steel panel exhibited good impact resistance, passing up to 80 inch-pounds while the primer coating on the treated panel had excellent impact resistance, passing over 80 inch-pounds. The primer coating on the untreated steel panels exhibited good salt spray resistance, showing a scribe creepage of 3/16" after 11 days exposure to a 5 percent aqueous salt spray at 100 F. while the treated panel showed excellent salt spray resistance, exhibiting virtually no scribe creepage under the same exposure conditions.

Example 20 A primer coating composition was prepared by blending the following ingredients: Parts by Weight Reaction product of Example 15 120.8 Acrylic polymer latex* 97.2 Beetle 80 7.8 Pigment paste of Example 19 39.0 *An acrylic polymer emulsion having a total solids content of 38.9 percent by weight and a viscosity of 45 centipoises prepared by emulsion polymerization of a monomer mixture consisting of 51.0 percent butyl acrylate, 40.0 percent styrene, 5.0 percent hydroxypropyl acrylate and 4.0 percent acrylic acid, in accordance with the procedure described in the sp ecification above.

The primer coating composition was spray applied to untreated and treated steel panels, baked, topcoated and evaluated for impact resistance as in Example 19.

The primer coating on both the untreated and treated steel panels exhibited excellent impact resistance, passing in excess of 80 inch-pounds and excellent salt spray resistance, showing a scribe creepage of less than 1/8" after 11 days exposure to the salt spray.

Example 21 A water-based coating composition for use as an internal sanitary liner for a metal beverage container was prepared by blending the following ingredients: Ingredients Parts by Weight (Grams) Reaction product used in Examples 8-11 (unneutralized) 1600.00 Cymel 370* 61.50 Triethylamine 54.50 Deionized water 2300.00 Butyl Cellosolve 145.00 *A partially methylated melamine resin having a non-volatile percentage of 88 + 2, a Gardner-Holdt viscosity at 25"C. of A2 - 24, a Gardner color of 1 maximum, and a methylol content of 12 percent, available from American Cyanamid Company.

The resultant water-based coating composition had a non-volatile solids content of 26.0 percent by weight and a No. 4 Ford Cup viscosity of 20.8 seconds. The liquid medium of the composition consisting of 76.1 percent by weight of water and 23.9 percent by weight of organic solvents.

The composition was sprayed into two-piece aluminum cans utilizing a conventional airless gun. The coated cans were cured using a two cycle bake; the first cycle involving baking for 2.5 minutes at 270"F. and the second cycle involving baking for 2.5 minutes at 400"F.

A visual examination of the cans indicated good coating coverage and appearance. The film integrity of each can was evaluated using a standard beverage container coating test referred to in the coating field as an enamel rater quick test. This is a test in which a 1 percent sodium chloride salt solution is placed inside the coated can and a circuit is produced by placing an electrode in the salt solution and a connection on the outside surface of the can. A flow of electrical current will result if there are any bare spots on the coated interior of the can. The current, if present, is measured with an ampmeter in milliamps.

In this test, cans were obtained having film weights of 220 milligrams and 240 milligrams respectively and these produced readings of 19 and 8.5 milliamps respectively. These readings indicate good film integrity.

Other tests run on the coated cans were buffer resistance and beer pasteurization resistance. In the buffer resistance test, a coated sample is placed in a borax buffer solution having a pH of 9.20 and a concentration of 3.8 grams of Na2B407.10H2O per liter of water for 30 minutes at 1600F. and the coating is then checked for blushing, blistering and adhesion failure. The beer pasteurization resistance test is performed and evaluated in the same manner except that the coated sample is placed in beer. In these tests, the cured coatings produced from the above composition exhibited excellent buffer and beer pasteurization resistance.

A sample of the above water-based coating composition was drawn down on treated aluminum in a 3 mil thickness and cured as mentioned above. The cured coating was then tested utilizing several standard tests employed in evaluating container coatings. Test results were as follows: Pencil hardness H Dye stain* 4 Cross hatch adhesion Excellent Wedge bend flexibility 90 mm failure Buffer resistance Excellent Beer pasteurization resistance Excellent Examples 22 & 23 Into a reactor equipped with a heating means, stirrer, reflux condenser and means for providing an inert gas blanket were charged 1493 grams of Epon 829 and 706 grams of Bisphenol A. The reaction mixture was heated to 3000F. and the heat then removed to allow for an exotherm (maximum temperature 399"F.). The reaction mixture was then held for one hour above 350"

Claims (28)

**WARNING** start of CLMS field may overlap end of DESC **. tested utilizing several standard tests employed in evaluating container coatings. Test results were as follows: Pencil hardness H Dye stain* 4 Cross hatch adhesion Excellent Wedge bend flexibility 90 mm failure Buffer resistance Excellent Beer pasteurization resistance Excellent Examples 22 & 23 Into a reactor equipped with a heating means, stirrer, reflux condenser and means for providing an inert gas blanket were charged 1493 grams of Epon 829 and 706 grams of Bisphenol A. The reaction mixture was heated to 3000F. and the heat then removed to allow for an exotherm (maximum temperature 399"F.). The reaction mixture was then held for one hour above 350"F. The polyepoxide produced had an epoxy equivalent of 1582. Following this hold period, 600 grams of butyl Cellosolve were added to the reaction mixture at which time the temperature decreased to 250"F. Then 201 grams of anthranilic acid were added. Following this addition, the reaction mixture was held at about 300"F. for about 3 hours. After this hold period, 692 grams of butyl Cellosolve were added to the reaction. The resultant reaction product had a non-volatile solids content of 64.6 percent and an acid value of 18.6 (28.8 at 100 percent solids). Water-based coating compositions for use as sanitary liners for metal beverage containers were prepared by blending the following ingredients: Ingredients Parts by Weight (grams) Example 22 Example 23 Reaction product above 1400.0 1400.0 Cymel 370 114.2 Cymel 1156* - 114.2 Dimethylethanolamine 38.0 38.0 Deionized water 1500.0 1500.0 *A butylated melamine resin having a non-volatile percentage of 100 percent, a Gardner-Holdt viscosity of Z1-Z4, a Gardner color of 1 maximum, available from American Cyanamid Company. The resultant water-based coating composition of Example 22 had a non-volatile solids content of 32.9 percent by weight while that of Example 23 had a non-volatile solids content of 33.3 percent by weight. The liquid medium of the composition of both examples consisted of 75.0 percent by weight of water and 25.0 percent by weight of organic solvents. The above compositions were drawn down in 3 mil thickness on treated aluminum substrates (i.e., container stock) and the coated substrates were then cured by baking for 2.5 minutes at 4000F. The cured coatings were then evaluated utilizing the same tests as in Example 21. -Test results were as follows: Example No. 22 Example No. 23 Pencil Hardness 3H 2H Dye Stain 4-5 4-5 Cross Hatch Adhesion Excellent Excellent Wedge Bend Flexibility 35 mum!110 mm failure 35 mm/llO mm failure Buffer Resistance Excellent Excellent Beer Pasteurization Resistance Excellent Excellent As an additional test, samples of the compositions of the above examples were sprayed into-two piece aluminum cans, cured and then evaluated for buffer resistance and beer pasteurization resistance using the procedures of Example 21. The cured coatings on the aluminum cans exhibited excellent buffer resistance and beer pasteurization resistance. WHAT WE CLAIM IS:

1. An anionic aqueous composition comprising water and an at least partially based neutralized reaction product of: (a) a polyepoxide having a 1,2-epoxy equivalent greater than 1.0; and (b) an aromatic amino acid containing at least one amine group and at least one

carboxyl group, which are both attached to the aromatic ring, wherein the amine groups of said amino acid are preferentially reactive with the epoxy groups of said polyepoxide, said reaction product having unreacted carboyxl groups which are neutralized with a base to form anionic salt groups.

2. An aqueous composition as claimed in claim 1 wherein the equivalent ratio of epoxy groups in said polyepoxide to amine groups in said aromatic amino acid is from 1:0.20 to 1:1.25.

3. An aqueous composition as claimed in claim 1 or claim 2 wherein said reaction product is at least partially neutralized with a volatile base.

4. An aqueous composition as claimed in claim 3 wherein said volatile base is an amine.

5. An aqueous composition as claimed in any one of claims 1 to 4 wherein said polyepoxide is a polyglycidyl ether of a polyhydric phenol.

6. An aqueous composition as claimed in any one of claims 1 to 5 wherein said aromatic amino acid is anthranilic acid.

7. An aqueous composition as claimed in any one of claims 1 to 5 wherein said aromatic amino acid is p-aminobenzoic acid.

8. An aqueous composition as claimed in any one of claims 1 to 5 wherein said aromatic amino acid is m-aminobenzoic acid.

9. An aqueous composition as claimed in any one of clainis 1 to 8 and further containing a curing agent for said reaction product.

10. An aqueous composition as claimed in claim 9, wherein said curing agent is an aminoplast resin, a phenolic resin or a blocked or semi-blocked polyisocyanate.

11. An anionic aqueous composition cqmprising water and: (a) an at least partially base neutralized reaction product of: (1) a polyepoxide having a 1,2-equivalency of greater than 1.0; and (2) an aromatic amino acid containing at least one amine group and at least one carboxyl group which are both attached to the aromatic ring, wherein the amine groups of said amino acid are preferentially reactive with the epoxy groups of said polyepoxide, said reaction product having unreacted carboxyl groups which are neutralized with base to form anionic salt groups; and (b) a resin selected from hydrocarbon resins, water-soluble acrylic resins, acrylic polymer emulsions, aqueous dispersions of amide-containing acrylic interpolymers, or mixtures thereof.

12. An aqueous composition as claimed in claim 11 further containing a curing agent.

13. An aqueous composition as claimed in claim 11 wherein said composition based on total weight of (a) and (b) contains from 5 to 95 percent by weight of (a) and from 95 to 5 percent by weight of (b).

14. An aqueous composition as claimed in any one of claims 11 to 13 wherein said resin is an acrylic polymer emulsion.

15. An aqueous composition as claimed in any one of claims 11 to 13 wherein said resin is an aqueous dispersion of an amide-containing acrylic interpolymer.

16. An aqueous composition as claimed in any one of claims 11 to 15 and further containing a pigment or pigments.

17. A metal container having an internal surface coated with a cured layer of a water-based coating composition comprising an aqueous medium having dispersed therein: (a) an at least partially base neutralized reaction product of: (1) a polyepoxide having a 1,2-epoxy equivalency of greater than 1.0, and (2) an aromatic amino acid containing at least one amine group and at least one carboxyl group which are both attached to the aromatic ring wherein the amine groups of said amino acid are preferentially reactive with the epoxy groups of said polyepoxide of a polyhydric phenol, said reaction product having unreacted carboxylic acid groups which are neutralized with a base to form anionic salt groups; and (b) from 3 to 30 percent by weight based on the weight of (a) and (b) of a curing agent.

18. A container as claimed in claim 17 wherein said reaction product is at least partially neutralized with a volatile base.

19. A container as claimed in claim 18 wherein said volatile base is an amine.

20. A container as claimed in any one of claims 17 to 19 wherein said aqueous medium of said water-based coating contains at least 60 percent by weight of water.

21. A container as claimed in claim 20 wherein said polyepoxide is a polyglycidyl ether of a polyhydric phenol.

22. A container as claimed in claim 17 wherein said aromatic amino acid is anthranilic acid, p-aminobenzoic acid or m-aminobenzoic acid.

23. A container as claimed in any one of claims 17 to 22 wherein said curing agent is an aminoplast resin, a phenolic resin or a blocked or semi-blocked polyisocyanate.

24. A container as claimed in any one of claims 17 to 23 and further containing a beverage in contact with said cured layer.

25. A container as claimed in claim 24 wherein said beverage is beer, a carbonated or carbonated soft drink or a fruit juice.

26. A coating composition as claimed in claim 1, substantially as hereinbefore described with reference to any one of Examples 1 to 21.

27. A coating composition as claimed in claim 1, substantially as hereinbefore described with reference to Example 22 or 23.

28. A metal container having an internal surface coated with a cured layer of a coating compositon, substantially as hereinbefore described with reference to Example 22 or 23.