WO2000000527A1

WO2000000527A1 - Water reducible resins containing propoxylated allyl alcohol, their use in water borne coating compositions, and coated articles made therewith

Info

Publication number: WO2000000527A1
Application number: PCT/US1999/011218
Authority: WO
Inventors: Truman F. Wilt; Ronald R. Ambrose; Deborah M. Altman; Ross D. Hunter; Melanie S. Campbell
Original assignee: Ppg Industries Ohio, Inc.
Priority date: 1998-06-26
Filing date: 1999-05-20
Publication date: 2000-01-06
Also published as: AU4091999A

Abstract

This invention relates to hydroxyl-functional, water-reducible resins derived from propoxylated allylic alcohol. The hydroxyl functional, water-reducible resin includes the reaction product of at least the following components: (a) a propoxylated allylic alcohol component including at least one propoxylated allylic alcohol having the structure (I): CH2-CR-CH2-(X)n-OH, wherein R is hydrogen or an alkyl group containing 1 to 4 carbon atoms; X is an oxypropylene group; and n, which represents the average number of oxypropylene groups in the propoxylated allylic alcohol, is a number ranging from 1 to 2; (b) an ethylenically unsaturated monomeric component including at least one free-radically polymerizable, ethylenically unsaturated monomer having a COOH functional group; and (c) a chain transfer agent component. This invention also relates to processes for making such hydroxyl-functional, water-reducible resins; coating compositions which include the same; and articles of manufacture coated therewith - particularly food and beverage cans.

Description

WATER REDUCIBLE RESINS CONTAINING

PROPOXYLATED ALLYL ALCOHOL,

THEIR USE IN WATER BORNE COATING COMPOSITIONS,

AND COATED ARTICLES MADE THEREWITH

FIELD OF THE INVENTION

This invention relates to hydroxyl-functional, water-reducible resins derived from propoxylated allylic alcohol. These hydroxyl functional, water- reducible resins are useful when formulating water borne coating compositions. This invention also relates to processes for making such hydroxyl-functional, water- reducible resins; water borne coating compositions which include the same; and articles of manufacture coated therewith ~ particularly food and beverage cans.

BACKGROUND OF THE INVENTION

Although solvent borne coatings are used extensively, water borne coatings have gained particular importance due, in part, to increasingly stringent environmental regulations which limit emissions of volatile organic compounds (VOCs) that can be released into the atmosphere during coating application and curing processes. In fact, some coating applications are limited strictly to the use of water borne coatings.

Thermoset water borne coating compositions are often desirable over their thermoplastic counterparts because the cured films resulting from the thermoset coatings typically exhibit many excellent physical properties such as heat and chemical resistance, water and humidity resistance and excellent adhesion. Generally, thermoset water borne coating compositions include a water-reducible functional group containing resin which is dissolved or dispersed in water, and a curing agent which contains functional groups which are reactive with the functional groups of the resin. The packaging industry typically requires that the water borne coatings used for application to beer and/or beverage cans must provide cured films which meet a number of demanding requirements such as excellent adhesion, flexibility and extensibility. These requirements are necessary so as to enable a coated can to withstand the very rigorous fabrication and/or subsequent sterilization pasteurization processes.

One example of a particularly rigorous fabrication process in the can body manufacturing process is referred to in the industry as "necking." In this process, the diameter of the can's opened end is reduced so as to minimize the size of the can's upper end/lid. This minimization results in substantial reduction in metal input and, thus, a reduction in overall can costs since a can's end/lid is typically made from a heavier gauge aluminum stock. For example, as described in A Guide to the fine Art of Necking, CAN TECH INTERNATIONAL, November 1996, at pp. 44-47, standard can end diameter has been reduced incrementally over a 20-year period from 211 (2 11/16 inches) to 204 (2 4/16 inches) for beer cans and to 202 (2 2/16 inches) for soft drink cans.

Notwithstanding the cost savings associated therewith, a reduction in a can end's diameter is limited, in part, by certain properties of coatings applied thereover. Typically, can coatings are applied to a formed can body and thermally cured prior to a necking process. In a typical necking process, spinning necking dies or disks are used to reduce the diameter of the coated can's opening by extending or stretching its neck area. During this rigorous necking process, the cured can coating must be able to maintaining adhesion and film continuity. Finally, after the coated can body has undergone the necking process, an end is attached thereto by an edge rolling process which places even further strains on the cured can coating.

U.S. Patent Nos. 5,480,943 and 5,475,073 each disclose hydroxyl functional resins which are copolymers of acrylates and allylic alcohol or propoxylated allylic alcohol. These resins are useful in high solids, solvent borne, thermoset coatings. As such, they are not suitable for use in water borne coating compositions since it is difficult to make such resins water-reducible. U.S. Patent Nos. 5,451,631 and 5,382,642 each disclose copolymers of vinyl aromatic monomers, such as styrene, and propoxylated allylic alcohols. Because of the high proportion of vinyl aromatic monomer, these resins are typically limited for use in high solids, solvent borne coating compositions because they are neither water dispersible nor water soluble.

U.S. Patent No. 5,646,225 discloses a water-reducible resin which includes recurring units of vinyl aromatic monomers, propoxylated allylic alcohol and acrylic acid monomer. That Patent also teaches a process for producing such resins via free-radical polymerization of the above-mentioned monomers, wherein the reaction is conducted in the presence of water to prevent gelation. In addition to the above, the process disclosed in that Patent requires the use of a vacuum or distillation strip of excess and/or unreacted monomer. This step of removing excess and/or unreacted monomer adds significantly to resin's production costs.

Accordingly, it would be advantageous to provide a water-reducible, hydroxyl functional resin which would allow use of the resin in coating compositions employing a variety of curing agents. It would also be advantageous to provide a water-reducible, hydroxyl functional resin which can be utilized in thermoset coating compositions wherein the coating composition can provide cured films which are sufficiently crosslinked but are nonetheless flexible and extensible. Moreover, it would be advantageous to provide coating compositions comprising such a water- reducible, hydroxyl functional resin and a curing agent, said coating composition giving flexible and extensible cured films capable of withstanding the can necking process.

SUMMARY OF THE INVENTION

One object of this invention is to provide a water-reducible, hydroxyl functional resin which can be used in coating compositions employing a variety of curing agents and a process for making the same. Another object of this invention is to provide a water-reducible, hydroxyl functional resin useful in thermoset coating compositions which, when cured, are sufficiently crosslinked yet flexible and extensible.

Still another object of this invention is to provide water borne coating compositions which, when cured, result in films capable of withstanding the can necking and edge rolling processes and processes for making the same.

Yet another object of this invention is to provide a coated article of manufacture whose coating can withstand the vigorous processing conditions to which the coated article is subjected.

These and other objects are achieved by the development of a hydroxy functional, water-reducible resin comprising the reaction product of at least the following components:

(a) a propoxylated allylic alcohol component including at least one propoxylated allylic alcohol having the structure:

CH₂ - CR - CH₂ - (X)„ - OH (I)

wherein R is hydrogen or an alkyl group containing 1 to 4 carbon atoms;

X is an oxypropylene group; and n, which represents the average number of oxypropylene groups in the propoxylated allylic alcohol, is a number ranging from 1 to 2; (b) an ethylenically unsaturated monomeric component including at least one free-radically polymerizable, ethylenically unsaturated monomer having a COOH functional group; and

(c) a chain transfer agent component.

DETAILED DESCRIPTION OF THE INVENTION

This invention includes a number of different embodiments. These embodiments include: a) novel hydroxy functional, water-reducible resins and processes for making the same, b) novel water borne coating compositions, and process for making the same, which include at least one of the aforementioned novel hydroxy functional, water-reducible resins, and c) novel coated articles of manufacture, wherein the coating applied thereover includes at least one of the aforementioned novel water borne coating compositions.

Hydroxy Functional, Water-Reducible Resins and Processes for Making the Same

This embodiment of the invention pertains to a hydroxy functional, water-reducible resin comprising the reaction product of at least the following components: (a) a propoxylated allylic alcohol component including at least one propoxylated allylic alcohol having the structure:

CH₂ - CR - CH₂ - (Λ „ - OH (I)

wherein R is hydrogen or an alkyl group containing 1 to 4 carbon atoms;

X is an oxypropylene group; and n, which represents the average number of oxypropylene groups in the propoxylated allylic alcohol, is a number ranging from 1 to 2;

(b) an ethylenically unsaturated monomeric component including at least one free-radically polymerizable, ethylenically unsaturated monomer having a COOH functional group; and

(c) a chain transfer agent component.

The propoxylated allylic alcohol component useful when practicing this embodiment of the invention includes at least one propoxylated allylic alcohol of the general structure (I). Depending upon the method of synthesis, the oxypropylene group, X, in structure (I), typically has at least one of the following structures: - OCH(CH₃) - CH₂ - (II)

- OCH₂ - CH(CH₃) - (III).

While the average number of oxypropylene groups, n, present in the propoxylated allyl alcohol component ranges from 1 to 2, in many preferred embodiments of this invention, this average number ranges from 1.2 to 1.9; and more preferably from 1.4 to 1.8.

Any suitable propoxylated allyl alcohol can be used when practicing this invention. The selection of suitable propoxylated allyl alcohols can be readily made by those skilled in the art after reading this specification. Examples of such suitable propoxylated allyl alcohols include those prepared by reacting allyl alcohol with up to 2 equivalents of propylene oxide in the presence of a basic catalyst. Specific example of such a propoxylated allyl alcohols are described in U.S. Pat. Nos. 3,268,561, 4,618,703, and 5,382,642, herein incorporated by reference. Acid catalysts can also be employed in the synthesis of suitable propoxylated allyl alcohols. Examples of such are described in J. AM. CHEM. SOC. 71 (1949) 1152.

The propoxylated allyl alcohol component is typically present in the hydroxyl functional, water-reducible resin in an amount ranging from 1 to 40 weight percent. Preferably, the propoxylated allyl alcohol component is present in an amount ranging from 3 to 20 weight percent, and more preferably, in an amount ranging from 5 to 15 weight percent. These weight percentages are based upon the weight of the water-reducible resin's total resin solids.

The hydroxyl functional, water-reducible resins of this invention's embodiment also comprise an ethylenically unsaturated monomeric component which includes at least one free-radically polymerizable, ethylenically unsaturated monomer having a COOH functional group. Generally, such monomers include alpha, beta- ethylenically unsaturated carboxylic acids containing from 3 to 20 carbon atoms.

Any suitable free-radically polymerizable, ethylenically unsaturated monomer which has a COOH functional group can be used when practicing this invention. The selection of suitable free-radically polymerizable, ethylenically unsaturated monomers can be readily made by those skilled in the art after reading this specification. Examples of such suitable ethylenically unsaturated monomers include acrylic acid and methacrylic acid. The ethylenically unsaturated monomeric component is typically present in the hydroxyl functional, water-reducible resin in an amount ranging from 1 to 40 weight percent. Preferably, the ethylenically unsaturated monomeric component is present in an amount ranging from 3 to 30 weight percent, and more preferably, in an amount ranging from 5 to 20 weight percent. These weight percentages are based upon the weight of the water-reducible resin's total resin solids. In addition to the free-radically polymerizable, ethylenically unsaturated monomer(s) having a COOH functional group, the ethylenically unsaturated monomeric component can further comprise at least one "other" free- radically polymerizable, ethylenically unsaturated monomer. If employed, this "other" free-radically polymerizable, ethylenically unsaturated monomer can include alkyl esters of acrylic acid or methacrylic acid, such as ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate and 2-ethylhexyl acrylate; vinyl aromatic compounds; nitriles, such as acryloniturile and methacrylonitrile; vinyl and vinylidene halides, such as vinyl chloride and vinylidene fluoride; vinyl esters, such as vinyl acetate; and acrylamides and methacrylamides, such as N-(butoxymethyl) acrylamide and N-(butoxymethyl) methacrylamide. In one preferred embodiment, the ethylenically unsaturated monomeric component includes at least one such "other" monomer selected from the following group: ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, 2-ethylhexyl acrylate and isobutyl methacrylate. It should be noted that, typically, vinyl aromatic compounds are not preferred for use as a reactant in the hydroxyl functional, water-reducible resin when the resin is employed in coating compositions designed for use in can coating applications. However, for applications where properties such as hydrophobicity are required and properties such as flexibility and extensibility are not so critical, the ethylenically unsaturated monomeric component of the hydroxyl functional, water- reducible resin can include a vinyl aromatic compound.

The term "vinyl aromatic compound" as used herein refers to aromatic compounds that have a

- CH = CH₂ - group connected to an aromatic ring. Such vinyl aromatic compounds include mono-, di- and polyvinyl aromatic monomers. If employed, monovinyl aromatic compounds are preferred.

When the desired properties of a cured coating composition prepared in accordance with this invention are such that require and/or permit the use of vinyl aromatic compounds as part of the hydroxyl functional, water-reducible resin's ethylenically unsaturated monomeric component, any suitable vinyl aromatic compounds can be employed. Examples of such suitable vinyl aromatic compounds include styrene, alkyl-substituted styrenes, halogenated styrenes, α-substituted styrenes (i.e., styrenes wherein the α -hydrogen is substituted with an alkyl group) and mixtures thereof. Specific examples of vinyl aromatic compounds which can be employed include styrene, α-methyl styrene, 4-methylstyrene, 4-tert-butylstyrene, 2,6-dimefhylstyrene, 3-chlorostyrene, 2,4,6-tribromostyrene, vinylnaphthalene, divinylbnezene and mixtures thereof. Of the above, styrenes are preferred. When used, the amount of the "other" free-radically polymerizable, ethylenically unsaturated monomer(s) employed depends, in part, upon the class of compounds in which it belongs. Specifically, if such an "other" ethylenically unsaturated monomer employed belongs to the class of compounds such as alkyl esters of acrylic acid or methacrylic acid, such a monomer is typically present in the hydroxyl functional, water-reducible resin in an amount ranging from 1 to 95 weight percent; preferably from 20 to 90 weight percent; and more preferably, from 40 to 80 weight percent. On the other hand, if such an "other" ethylenically unsaturated monomer employed belongs to the class of compounds which does not include alkyl esters of acrylic acid or methacrylic acid, such a monomer is typically present in the hydroxyl functional, water-reducible resin in an amount ranging from 1 to 40 weight percent; preferably from 3 to 30 weight percent; and more preferably, from 5 to 20 weight percent. All of the aforementioned weight percentages are based upon the weight of the water-reducible resin's total resin solids.

The hydroxyl functional, water-reducible resins of this invention's embodiment also comprise a chain transfer agent component which includes at least one chain transfer agent. Any suitable chain transfer agent can be employed when practicing this invention. The selection of suitable chain transfer agents can be readily made by those skilled in the art after reading this specification. Examples of such suitable chain transfer agents include mercaptans, halomethanes, allyl compounds, solvents such as ketones and alcohols, substituted olefins and alpha substituted styrene. Preferred chain transfer agents are alpha-methyl styrene dimer and tert- dodecyl mercaptan.

The chain transfer agent component is typically present in the hydroxyl functional, water-reducible resin in an amount ranging from 0.5 to 15 weight percent. Preferably, the chain transfer agent component is present in an amount ranging from 1.0 to 10 weight percent, and more preferably, in an amount ranging from 1.5 to 5 weight percent. These weight percentages are based upon the weight of the water- reducible resin's total resin solids.

From the above, it can be seen that, in one preferred embodiment of this invention, the hydroxyl functional, water reducible resin comprises: from about 5 to about 15 weight percent of component (a), wherein n is a number ranging from 1.4 to 1.8; from about 5 to about 20 weight percent of reactant (b) which includes an acrylic acid; and from about 1.5 to about 5 weight percent of reactant (c) which includes at least one compound selected from the group consisting of alpha- methylstyrene dimer and tert-dodecyl mercaptan.

The weight percentages of the above preferred embodiment are based upon the weight of the water-reducible resin's total resin solids. The hydroxyl functional, water-reducible resins of the invention can optionally include a number of other components which afford, either individually or in combination, certain properties to the resin and/or the resulting cured coating made therewith. The identification and selection of these optional components will be known by those skilled in the art after reading this specification. The hydroxyl functional, water-reducible resins of this invention typically have number average molecular weights ranging from 1,000 to 25,000. Preferably, these molecular weights range from 1,500 to 20,000, and more preferably, from 2,000 to 15,000. As referred to herein, molecular weights are determined by gel permeation chromatography using polystyrene standards. The molecular weight of the resulting hydroxyl functional, water- reducible resins can be controlled by any suitable means known to those skilled in the art. One example of such a suitable means includes adjusting the chain transfer agent concentration, the free-radical initiator concentration, and/or the reaction temperature. The hydroxyl functional, water-reducible resins of this invention typically have hydroxyl numbers ranging from 1 to 200 mg. KOH/g. Preferably, these hydroxyl numbers range from 1 to 150 mg. KOH/g., and more preferably, from about 5 to 100 mg. KOH/g.

The hydroxyl functional, water-reducible resins of this invention typically have acid numbers ranging from 25 to 200 mg. KOH/g. Preferably, these acid numbers range from 45 to 150 mg. KOH/g., and more preferably, from 65 to about 125 mg. KOH/g.

The present invention also relates to a method for producing a hydroxyl functional, water-reducible resin as described above. This method includes the following steps:

(a) heating the propoxylated allyl alcohol component described above; and

(b) adding to the heated propoxylated allyl alcohol component at least one of the following compounds: (i) the ethylenically unsaturated monomeric component described above,

(ii) the chain transfer agent component described above, and

(iii) a free radical initiator component.

Specifically, the hydroxyl functional, water-reducible resin is typically prepared by charging the propoxylated allyl alcohol component into a suitable reaction vessel and heating the same to a temperature ranging from 130°C. to 175°C. Preferably, the reaction temperature ranges from 140°C. to 170°C, and more preferably, from 150°C. to 165°C. After the desired reaction temperature is reached, the following components are added: an ethylenically unsaturated monomeric component, a chain transfer agent component, and a free radical initiator component. These components can be added individually, simultaneously, or in any combination thereof. In one preferred embodiment, these components are added simultaneously.

The free radical component employed in the above process includes at least one free radical initiator. Any suitable free radical initiator can be employed when practicing this embodiment of the invention. The selection of suitable free radical initiators can be readily made by those skilled in the art after reading this specification. Specific examples of such suitable free radical initiators include organic peroxides or azo compounds such as benzoyl peroxide, di-tert-amyl peroxide, tert-butyl peroxide and N,N-azobis(isobutyronitrile).

The free-radical initiator component is typically used in an amount ranging from 1 to 10 weight percent. Preferably, the optional free-radical initiator is present in an amount ranging from 2 to 8 weight percent, and more preferably, in an amount ranging from 3 to 6 weight percent. These weight percentages are based upon the weight of the water-reducible resin's total resin solids.

Typically, the polymerization process used to make the hydroxyl functional, water-reducible resin is carried out in the presence of a solvent component. If used, the solvent component includes at least one solvent which can at least partially solubilize monomers employed in the aforementioned polymerization process. Any suitable solvent can be employed when practicing this embodiment of the invention. The selection of suitable solvents can be readily made by those skilled in the art after reading this specification. Examples of such suitable solvents include water, alcohols, ketones, aromatic hydrocarbons, glycol ethers, esters and mixtures thereof. Specific examples of such include ethanol, acetone, methyl ethyl ketone, methyl amyl ketone, xylenes, butyl CELLOSOLVE, ethylene glycol monopropyl ether, propylene glycol monomethyl ether and mixtures thereof.

If employed, the solvent component is typically present during the polymerization process in an amount ranging from 0.5 to 15 weight percent. Preferably, the optional solvent component is present in an amount ranging from 1 to 10 weight percent, and more preferably, in an amount ranging from 2 to 5 weight percent. These weight percentages are based upon the weight of the water-reducible resin's total resin solids. In one preferred embodiment of the invention, the method used to make the hydroxyl functional, water-reducible resin further comprises the steps of neutralizing the resulting hydroxyl functional, water-reducible resin with a neutralizing agent and, dispersing the neutralized, hydroxyl functional, water- reducible resin in water. If the water-reducible resin is neutralized, it can be done by any suitable neutralization process known to those skilled in the art. The selection of a suitable neutralization process can be readily made by those skilled in the art after reading this specification. Typically, neutralization is performed by using an amount of a suitable neutralizing agent which is effective to convert at least a portion of the hydroxyl functional, water-reducible resin's COOH functional groups to salts. Examples of neutralizing agents suitable for use when practicing this embodiment of the invention include alkali metal hydroxides, alkaline earth metal hydroxides, organic amines and ammonia. Preferred neutralizing agents include organic amines such as triethylamine, trimethylamine, diethanolamine, triethanolamine, N, N-dimethylethanolamine, diisopropanolamine, n-octylamine and the like, and mixtures thereof.

If such a neutralization step is employed, typically, at least about 50 percent of the hydroxyl functional, water-reducible resin's COOH functional groups are neutralized. Preferably, the neutralization step neutralizes at least about 75 percent of the hydroxyl functional, water-reducible resin's COOH functional groups, more preferably at least about 90 percent, and even more preferably at least about 95 percent. Water Borne Coating Compositions, and Processes for Making the Same

The present invention also relates to novel coating compositions. These coating compositions include the following components:

(a) a resin component including a hydroxyl functional, water reducible resin as described above; and

(b) a curing agent component.

The curing agent component recited above includes at least one curing agent compound having functional groups which are reactive with the hydroxyl (OH) and/or COOH functional groups of the hydroxyl functional, water-reducible resin. Any suitable curing agent can be employed when practicing this embodiment of the invention. The selection of a suitable curing agents can be readily made by those skilled in the art after reading this specification. General examples of such suitable curing agents include aminoplasts, phenoplasts, (blocked) polyisocyanates, anhydrides and mixtures thereof. Specific examples of suitable aminoplast and phenoplast curing agents include those described in U.S. Pat. No. 3,919,351 at col. 5, line 22 to col. 6, line 25, herein incorporated by reference. Specific examples of suitable (blocked) polyisocyanates curing agents include those described in U.S. Pat. No. 4,546,045 at col. 5, lines 16 to 38; and in U.S. Pat. No. 5,468,802 at col. 3, lines 48 to 60, both herein incorporated by reference. Specific examples of suitable anhydride curing agents include those described in U.S. Pat. No. 4,798,746 at col. 10, lines 16 to 50; and in U.S. Pat. No. 4,732,790 at col. 3, lines 41 to 57, both herein incorporated by reference. Of the above, the preferred curing agents for use when practicing this embodiment of the invention are aminoplasts.

Aminoplasts which can be used when practicing this embodiment of the invention include those which are commercially available from CYTEK Industries, Inc. under the trademark CYMEL^® and from Monsanto Chemical Co. under the trademark RESIMENE ^®. Preferably, the coating compositions prepared in accordance with this invention comprise at least one aminoplast selected from the group consisting of melamine, benzoguanamine and glycoluril resin.

Typically, the resin component is present in the coating compositions prepared in accordance with this embodiment of the invention in an amount ranging of 30 to 80 weight percent. Preferably, the resin component is present in an amount ranging from 40 to 70 weight percent, and more preferably in an amount ranging from 50 to 60 weight percent. On the other hand, the curing agent component is typically in the coating compositions prepared in accordance with this embodiment of the invention in an amount ranging of 5 to 35 weight percent. Preferably, the curing agent component is present in an amount ranging from 10 to 30 weight percent, and more preferably in an amount ranging from 15 to 25 weight percent. These weight percentages are based upon total weight of resin solids in the resulting coating composition.

The coating compositions of the invention can be pigmented or unpigmented. If they are to be pigmented, any suitable pigment known to those skilled in the art can be employed. The selection of a suitable pigments can be readily made by those skilled in the art after reading this specification. General examples of such suitable pigments include opaque, transparent and translucent pigments generally known for use in coating applications. Specific examples of such include titanium dioxide, zinc oxide, antimony oxide, iron oxide, carbon black, phthalocyanine blue and mixtures thereof. Metallic pigments, such as aluminum flake and metal oxide- coated micas, can also be used. Moreover, the coatings made in accordance with this embodiment of the invention can also contain extender pigments such as calcium carbonate, clay, silica, talc, etc.

If a pigment is used, it typically is present in an amount such that the pigment to binder ratio ranges from 0.25: 1 to 1.5: 1. Preferably, if used, pigments are employed such that the pigment to binder ratio ranges from 0.50: 1 to 1.2: 1, and more preferably from 0.75: 1 to 1 : 1

In addition to the foregoing, the coating compositions prepared in accordance with this embodiment of the invention may include at least one of the following optional components: a urethane component, adjuvant resins, lubricating waxes, plasticizers, anti-oxidants, light stabilizers, mildewcides, fungicides, surfactants, flow control additives and catalysts.

As used herein, the term "urethane component" refers to a reactant(s) which include a urethane group(s). In one preferred embodiment, the urethane component includes an aqueous polyurethane dispersion.

Aqueous polyurethane dispersions are well known in the art. Examples of aqueous polyurethane dispersions suitable for use in the coating compositions of the invention include those described in U.S. Patent No. 5,169,895 at column 2, line 3 to column 6, line 40 and at column 7, lines 5 to 62, incorporated herein by reference. Other examples of polyurethane dispersions suitable for use in the coating compositions of the invention include those commercially available from Bayer Corp. under the trade names BAYHYDROL 121, BAYHYDROL 123 and BAYHYDROL XP7028; those commercially available from King Industries, Inc. under the trade name KFLEXXM4316; and those commercially available from Air Products, Inc. under the trade names HYBRID 560 and HYBRID 580.

If such optional components are employed, they are typically in the coating compositions prepared in accordance with this embodiment of the invention in an amount ranging of 1 to 50 weight percent. Preferably, these optional components are present in an amount ranging from 2 to 40 weight percent, and more preferably in an amount ranging from 5 to 30 weight percent. These weight percentages are based upon total weight of resin solids in the resulting coating composition.

The coating compositions prepared in accordance with one embodiment of this invention can be applied to any suitable substrate by any suitable means known to those skilled in the art. Examples of such suitable application means include brushing, dipping, flow coating, roll coating, conventional spraying and electrostatic spraying. Moreover, examples of such suitable substrates overwhich the coatings can be applied include primed and unprimed substrates such as wood, metal, glass, cloth, leather, plastics, foams and the like. Notwithstanding the above, the coating compositions prepared in accordance with one embodiment of this invention are especially suitable for being applied via a roll coating application over ;coiled metal substrates, such as aluminum can body stock.

Although, dependent upon the type of curing agent employed, the coating compositions of the invention can be cured at ambient temperatures, they are typically cured thermally. If thermally cured, the coating compositions are cured at elevated temperatures, typically for 1 to 30 minutes, at a temperature ranging from 250°F. to 500°F. (121 °C. to 260°C), with temperature primarily dependent upon the type of substrate used. Dwell time (i.e., time that the coated substrate is exposed to elevated temperature for curing) is dependent upon the cure temperature used as well as wet film thickness of the applied coating composition. For example, coated automotive elastomeric parts require a long dwell time at a lower cure temperature (e.g., 30 minutes at 250°F. (121°C.)), while coated aluminum beverage cans require a very short dwell time at a very high cure temperature (e.g., 1 minute at 375 ° F. (191°C.)).

The coating compositions of the invention are particularly useful as primers and as color coats (base coats) and/or clear coats in "color-clear composite coatings." The compositions of the invention in the pigmented form can be applied directly to a substrate to form a colored basecoat. The pigmented color coat may also be in the form of a primer for subsequent application of a topcoat or may be a colored topcoat. Alternately, the coating composition of the invention can be unpigmented, in the form of a clearcoat for application over a pigmented color coat (either a primer coat or a colored top coat). When used as a primer coating, thicknesses of 0.4 to 4.0 mils are typical. When used as a basecoat or a color topcoat, coating thicknesses of about 0.1 to 4.0 mils are usual, and when used as a clearcoat, coating thicknesses of about 0.1 to 4.0 mils are generally used.

In applying composite coatings using the coating composition of the present invention, the initially applied pigmented coating can be cured prior to the application of the second coat. Alternatively, the coating can be applied by a wet-on- wet technique in which the second coating is applied to the first coating (usually after a flash time at room temperature or slightly elevated temperature to remove solvent or diluent, but insufficient time to cure the coating) and the two coatings are co-cured in a single step.

Only one of the coatings in the composite coating needs to be based on the coating composition of the present invention. The other coating composition can be based on a film-forming system containing a thermoplastic and/or thermosetting film-forming resin well known in the art such as cellulosics, acrylics, polyurethanes, polyesters including alkyds, aminoplasts, epoxies and mixtures thereof. These film- forming resins are typically formulated with various other coatings ingredients such as pigments, solvents and optional ingredients mentioned above.

Coated Articles of Manufacture

The present invention additionally relates to a coated article. The coated article has at least one coating applied thereover which includes a coating composition prepared in accordance with the earlier mentioned embodiment of this invention.

In one preferred embodiment of this invention, ,the coated article of manufacture includes a coated metal beverage can body, more preferably a coated metal can which has undergone a necking and/or edge rolling process.

EXAMPLES

The following examples illustrate the invention and should not be construed as a limitation on the scope thereof. Unless specifically indicated otherwise, all percentages and amounts are by weight.

PREPARATION OF THE WATER REDUCIBLE, HYDROXYL FUNCTIONAL RESINS CONTAINING PROPOXYLATED ALLYL ALCOHOL

EXAMPLE 1

This example describes the preparation of the hydroxyl functional, water-reducible resin of the invention which has been neutralized to 100% TN with dimethylethanolamine and reduced with water. The water-reducible resin was prepared from a mixture of the following ingredients:

Resin Solids Parts by Weight

Ingredients (percent) (grams)

Charge 1 :

DOWANOL PM¹ — 27.9

Propoxylated allyl alcohol² 7.4 111.5

Charge 2:

DOWANOL PM — 61.5

Di-tert-amyl Peroxide³ — 83.6

Charge 3:

Methyl methacrylate 37.0 557.4

Butyl Acrylate 41.7 627.1

Acrylic Acid 13.9 209.0 α-methyl Styrene Dimer — 27.9

Charge 4:

DOWANOL PM — 43.1

Di-tert-amyl Peroxide — 7.4

Charge 5:

(a) Dimethylethanolamine — 258.3

(b) Deionized Water — 1623.7 1 Propylene glycol methyl ether, available from Dow Chemical Co.

2 Propoxylated allyl alcohol having an average number of oxypropylene units of 1.6, commercially available from ARCO Chemical Co. 3 Free radical initiator, commercially available as Di-t-Amyl Peroxide from Elf

AtoChem.

Charge 1 was added to a suitably equipped laboratory-scale pressure reactor and heated to about 155°C. At this temperature, the concurrent addition of Charges 2 and 3 was begun and the addition was completed over a 3 hour period. At this time, Charge 4 was added to the reaction vessel, followed by a 1 hour hold at which time the heat source was removed and the reaction temperature was allowed to decrease until reaching atmospheric pressure. Charge 5(a) was then added and the resin was cooled further before the addition of Charge 5(b). Deionized water was added as required to reduce resin solids to approximately 42 weight percent based on total resin solids.

The hydroxy functional, water-reducible resin thus prepared had the following physical properties: weight percent resin solids as determined by ASTM- D2369-93 (modified to be run at 110° C.) was 42.5%; viscosity as determined using a Brookfield Viscometer, Model RVT, with a #4 spindle at 20 r.p.m. was 4980 centipoise; pH of 8.95; meq acid was 0.746; meq base was 0.851; weight average molecular weight (Mw) as determined by gel permeation chromatography using a polystyrene standard was 11,667; and percent residual free monomer present as determined by gas chromatography analysis was as follows: 0.03 weight percent propoxylated allyl alcohol; 0.01 weight percent α-methyl styrene dimer; 0.06 weight percent butyl acrylate; and 0.18 weight percent methyl methacrylate.

EXAMPLE 2

This Example describes the preparation of the hydroxyl functional, water-reducible resin of the invention which has been neutralized to 100% TN with dimethylethanolamine and reduced with water. This resin contains a lower level of acrylic acid and a higher level of methyl methacrylate for increased glass transition temperature (T_g) than that of the resin of Example 1. The hydroxyl functional, water- reducible resin was prepared from a mixture of the following ingredients:

Resin Solids Parts by Weight

Ingredients (percent) (grams)

Charge 1:

DOWANOL PM ... 27.2 Propoxylated allyl alcohol 7.41 109.0 Charge 2: DOWANOL PM __. 64.9 Di-tert-amyl Peroxide — 88.3 Charge 3: Methyl methacrylate 68.33 1005.1 Butyl Acrylate 15.0 220.6 Acrylic Acid 9.26 136.2 α-methyl Styrene Dimer — 29.4 Charge 4: DOWANOL PM __. 43.3 Di-tert-amyl Peroxide — 7.4 Charge 5:

(a) Dimethylethanolamine ___ 168.3

(b) Deionized Water 1938.2

The hydroxy functional, water-reducible resin thus prepared had the following physical properties: weight percent resin solids as determined by ASTM- D2369-93 (modified to be run at 110° C.) was 41.4%; viscosity as determined using a Brookfield Viscometer, Model RVT, with a #4 spindle at 20 r.p.m. was 12,460 centipoise; pH of 8.55; meq acid was 0.508; meq base was 0.525; weight average molecular weight (Mw) as determined by gel permeation chromatography using a polystyrene standard was 6,966; and percent residual free monomer present as determined by gas chromatography analysis was as follows: 0.2 weight percent propoxylated allyl alcohol; 0.1 weight percent α-methyl styrene dimer; 0.1 weight percent butyl acrylate; and 0.1 weight percent methyl methacrylate.

EXAMPLE 3

This Example describes the preparation of the hydroxyl functional, water-reducible resin of the invention which has been neutralized to 100% TN with dimethylethanolamine and reduced with water. This resin contains a higher level of methyl methacrylate for increased glass transition temperature (T_g) than that of the resin of Example 1. The hydroxyl functional, water-reducible resin was prepared from a mixture of the following ingredients:

Resin Solids Parts by Weight

Ingredients (percent) (grams)

Charge 1:

DOWANOL PM ___ 27.2 Propoxylated allyl alcohol 7.41 109.0 Charge 2: DOWANOL PM — 64.9 Di-tert-amyl Peroxide — 88.3 Charge 3: Methyl methacrylate 68.33 1005.1 Butyl Acrylate 10.0 147.1 Acrylic Acid 14.26 209.7 α-methyl Styrene Dimer — 29.4 Charge 4: DOWANOL PM __. 43.3 Di-tert-amyl Peroxide — 7.4 Charge 5:

(a) Dimethylethanolamine __. 259.2

(b) Deionized Water 1847.3

Charge 1 was added to a suitably equipped laboratory-scale pressure reactor and heated to about 155°C. At this temperature, the concurrent addition of Charges 2 and 3 was begun and the addition was completed over a 3 hour period. At this time, Charge 4 was added to the reaction vessel, followed by a 1 hour hold at which time the heat source was removed and the reaction temperature was allowed to decrease until reaching atmospheric pressure. Charge 5(a) was then added and the resin was cooled further before the addition of Charge 5(b). Deionized water was added as required to reduce resin solids to approximately 42 weight percent based on total resin solids. The hydroxy functional, water-reducible resin thus prepared had the following physical properties: weight percent resin solids as determined by ASTM- D2369-93 (modified to be run at 110° C.) was 41.7%; viscosity as determined using a Brookfield Viscometer, Model RVT, with a #4 spindle at 20 r.p.m. was 2065 centipoise; pH of 8.90; meq acid was 0.730; meq base was 0.810 weight average molecular weight (Mw) as determined by gel permeation chromatography using a polystyrene standard was 8212; and percent residual free monomer present as determined by gas chromatography analysis was as follows: 0.2 weight percent propoxylated allyl alcohol; 0.1 weight percent α-methyl styrene dimer; 0.1 weight percent butyl acrylate; and 0.2 weight percent methyl methacrylate.

EXAMPLE 4

This Example describes the preparation of a hydroxyl functional, water-reducible resin of the invention which has been neutralized to 100% TN with dimethylethanolamine and reduced with water. This resin contains a higher level (40%o) of the propoxylated allyl alcohol component than do the previous examples. The hydroxyl functional, water-reducible resin was prepared from a mixture of the following ingredients:

Resin Solids Parts by Weight

Ingredients (percent) (grams)

Charge 1:

DOWANOL PM _ 40.7 Propoxylated allyl alcohol 40.0 650.8 Charge 2: DOWANOL PM — 30.9 Di-tert-butyl Peroxide — 44.7 Charge 3: Methyl methacrylate 50.0 813.6 Acrylic Acid 10.0 162.7 Charge 4: DOWANOL PM — 43.6 Di-tert-butyl Peroxide — 8.1 Charge 5:

(a) Dimethylethanolamine — 201.1

(b) Deionized Water 2041.8

Charge 1 was added to a suitably equipped laboratory-scale pressure reactor and heated to about 160°C. At this temperature, the concurrent addition of Charges 2 and 3 was begun and the addition was completed over a 3 hour period. At this time, Charge 4 was added to the reaction vessel, followed by a 1 hour hold at which time the heat source was removed and the reaction temperature was allowed to decrease until reaching atmospheric pressure. Charge 5(a) was then added and the resin was cooled further before the addition of Charge 5(b). Deionized water was added as required to reduce resin solids to approximately 42 weight percent based on total resin solids.

The hydroxy functional, water-reducible resin thus prepared had the following physical properties: weight percent resin solids as determined by ASTM- D2369-93 (modified to be run at 110 °C.) was 41.2%; viscosity as determined using a Brookfield Viscometer, Model RVT, with a #4 spindle at 20 r.p.m. was 416 centipoise; pH of 8.85; meq acid was 0.523; meq base was 0.577; weight average molecular weight (Mw) as determined by gel permeation chromatography using a polystyrene standard was 7624; and percent residual free monomer present as determined by gas chromatography analysis was as follows: 0.68 weight percent propoxylated allyl alcohol; and 0.23 weight percent methyl methacrylate.

EXAMPLE 5

This Example describes the preparation of the hydroxyl functional, water-reducible resin of the invention which has been neutralized to 100% TN with dimethylethanolamine and reduced with water. This resin contains a lower level of acrylic acid than that of the resin of Example 1. The hydroxyl functional, water- reducible resin was prepared from a mixture of the following ingredients:

Resin Solids Parts by Weight

Ingredients (percent) (grams)

Charge 1:

DOWANOL PM — 29.4

Propoxylated allyl alcohol 7.27% 117.7

Charge 2:

DOWANOL PM — 71..4

Di-tert-amyl Peroxide — 97.1

Charge 3:

Methyl methacrylate 236.36% 588.4

Butyl Acrylate 45.45% 735.5

Acrylic Acid 9.09% 147.1 α-methyl Styrene Dimer 1.82% 29.4

Charge 4:

DOWANOL PM — 44.0

Di-tert-amyl Peroxide — 8.1

Charge 5:

(a) Dimethylethanolamine — 181.8

(b) Deionized Water — 2091.2 Charge 1 was added to a suitably equipped laboratory-scale pressure reactor and heated to about 155°C. At this temperature, the concurrent addition of Charges 2 and 3 was begun and the addition was completed over a 3 hour period. At this time, Charge 4 was added to the reaction vessel, followed by a 1 hour hold at which time the heat source was removed and the reaction temperature was allowed to decrease until reaching atmospheric pressure. Charge 5(a) was then added and the resin was cooled further before the addition of Charge 5(b). Deionized water was added as required to reduce resin solids to approximately 42 weight percent based on total resin solids.

The hydroxy functional, water-reducible resin thus prepared had the following physical properties: weight percent resin solids as determined by ASTM- D2369-93 (modified to be run at 110° C.) was 42.3%; viscosity as determined using a Brookfield Viscometer, Model RVT, with a #4 spindle at 20 r.p.m. was 13,200 centipoise; pH of 8.5 ; meq acid was 0.510; meq base was 0.516 weight average molecular weight (Mw) as determined by gel permeation chromatography using a polystyrene standard was 7,579; and percent residual free monomer present as determined by gas chromatography analysis was as follows: 0.02 weight percent propoxylated allyl alcohol; 0.02 weight percent α-methyl styrene dimer; 0.09 weight percent butyl acrylate; and 0.21 weight percent methyl methacrylate.

It should be appreciated that the low values for weight percentages of residual free propoxylated allyl alcohol reported in the gas chromatography analysis data for Examples 1 to 5 above illustrate the essentially complete conversion of all propoxylated allyl alcohol using this method for producing the hydroxyl functional, water-reducible resin of the invention. Hence, this method not only obviates the necessity for an excess of propoxylated allyl alcohol to facilitate a free radical polymerization, but, also, eliminates the need for a vacuum strip step to remove the excess monomer. PREPARATION OF COATING COMPOSITIONS

EXAMPLE A

This example describes the preparation of a clear ("varnish") coating composition of the present invention which contains the hydroxyl functional, water- reducible resin of Example 1. This varnish composition was prepared from a mixture of the following ingredients:

Formula Weight Weight Resin Solids

Ingredients (grams) (grams)

Resin of Example 5 179.5 76.34

CYMEL 303 ' 18.0 18.0

CYCAT 500² 1.3 0.5

SILWET L7602³ 0.3 0.3

Phosphatized Epoxy⁴ 1.6 1.0

Lubricity/ Abrasion Additive⁵ 7.2 3.8

Wetting Additive⁶ 0.4 0.2

Deionized water 62.0 — -

TOTAL 270.2 100.0

1 Hexamethoxymethyl melamine formaldehyde curing agent available from CYTEK

Industries, Inc.

2 Dinonylnaphthalene disulfonic acid catalyst commercially available from King Industries, Inc.

3 Ethylene oxide copolymer, commercially available from OSi Specialties, a subsidiary of Witco Corp.

4 Reaction product of 83 parts EPON 828 (diglydidyl ether of Bisphenol A available from Shell Oil and Chemical Co.) and 17 parts phosphoric acid. 5 52.0 weight percent solids acrylic-wax emulsion of 27 weight percent of a blend of 48 weight percent POLYFLUO 150 (micronized HD polyethylene wax/ polytetrafluoroethylene wax available from Micro Powders) and 52 weight percent SST-3H (polytetrafluoroethylene from Shamrock Tech.); 25 weight percent of a water reducible acrylic resin, (41 weight percent butyl acrylate; 29 weight percent methylmethacrylate; 1 1.5 weight percent acrylic acid; 4.8 weight percent styrene); and 48 weight percent of a solvent blend comprised of 71 weight percent water; 15 weight percent ethylene glycol monobutyl ether; 7.8 weight percent n-butanol; and 6.5 weight percent dimethylethanolamine.

6 Low Tg acrylic polymer (90% butyl acrylate, 10% acrylic acid), neutralized to 100% TN with dimethylethanolamine, 62% resin solids in a solvent blend of approximately 41 weight percent n-butanol; 54 weight percent ethylene glycol monobutyl ether; and 5 weight percent deionized water. EXAMPLE B

This example describes the preparation of a clear ("varnish") coating composition of the present invention which contains the hydroxyl functional, water- reducible resin of Example 4 above, blended with a water reducible acrylic resin which contains no propoxylated allyl alcohol to give a coating composition with an overall level of propoxylated allyl alcohol of 6.4 weight percent based on total weight of resin solids. This varnish composition was prepared from a mixture of the following ingredients:

Formula Weight Weight Resin Solids Ingredients (grams) (grams)

Resin of Example 4 36.4 15.0

Water-reducible acrylic resin¹ 145.0 61.3 CYMEL 303 18.0 18.0 CYCAT 500 1.3 .5 SILWET L7602 .3 .3 Phosphatized Epoxy 1.6 1.0 Lubricity/ Abrasion Additive 7.2 3.79 Wetting Agent .4 .2 Deionized water 60.4 — ._

TOTAL 270.3 ϊoT

1 Solution acrylic resin of 40% methyl methacrylate, 40% butyl acrylate, 20% acrylic acid, neutralized to 100% TN, at 42% solids in a solvent blend of approximately 5% propylene glycol methyl ether (available from Dow Chemical Co.), 13% dimethylethanolamine and 82 % deionized water. EXAMPLE C

This example describes the preparation of a clear ("varnish") coating composition of the present invention which contains the hydroxyl functional, water- reducible resin of Example 1 and an optional urethane additive for enhanced flexibility. This varnish composition was prepared from a mixture of the following ingredients:

Formula Weight Weight Resin Solids

Ingredients (grams) (grams)

Resin of Example 1 127.8 54.0

Urethane additive¹ 54.1 22.0

CYMEL 303 18.4 18.1

CYCAT 500 1.9 0.75

BYK-333² 0.3 0.3

Phosphatized Epoxy 1.5 0.9

Lubricity/ Abrasion Additive³ 5.3 2.7

Wetting Agent 1.1 .7

Deionized water 59 —

Silwet L7602 .26 .26

TOTAL 270.0 100.0

1 Urethane acrylic latex comprised of 40 weight percent urethane soap prepolymer of 13% isopherone diisocyanate; 4 % dimethylol propionic acid; and 22 % FOMREZ 55-56 (polyester, commercially available from Witco Corp.); and

60% acrylic latex comprised of 44% methyl methacrylate; 11% styrene; 2.4% hydroxy propyl methacrylate 2.4% (tert-butylamino)ethyl methacrylate; and 0.5% ethylene glycol dimethacrylate.

2 Polyether modified dimethylpolysiloxane copolymer, commercially available from BYK-Che ie USA.

3 52.8 weight percent solids acrylic-wax emulsion of 30 weight percent of

POLYFLUO 150 (micronized HD polyethylene wax/ polytetrafluoroethylene wax available from Micro Powders); 20 weight percent of a water reducible acrylic resin, (50 weight percent butyl acrylate; 40 weight percent methylmethacrylate; 10 weight percent acrylic acid); and 50 weight percent of a solvent blend comprised of 85 weight percent water; 5 weight percent ethylene glycol monobutyl ether; 5 weight percent n-butanol; and 5 weight percent dimethylethanolamine. EXAMPLE D

This example describes the preparation of a pigmented coating composition ("basecoat") of the present invention which contains the hydroxyl functional, water-reducible resin of Example 1 above. A pigment grind paste, Example D-1 , was first prepared, then that paste was subsequently added to the remaining ingredients, Example D-2, to produce the pigmented coating composition of the invention.

EXAMPLE D-1

The grind paste was prepared from a mixture of the following ingredients:

Formula Weight Weight Resin Solids Ingredients (grams) (grams)

Acrylic dispersion grind vehicle¹ 137.9 78.6

CYMEL 303 15.6 15.6

TiO₂ pigment² 471.1

MPP-620 F³ 5.8 5.8

KADOX 915⁴ 1.9 1.9

Deionized water 102

TOTAL 734 100.0

1 57 weight percent of a water reducible acrylic resin, (41.1 percent butyl acrylate;

28.7 percent methyl methacrylate; 11.5 percent acrylic acid; 4.8 percent styrene; 4.8 percent n-butyl methacrylate; 4.8 percent hydroxyethyl acrylate; and 4.3 percent N-butoxymethyl acrylamide);and 43 weight percent of a solvent blend comprised of 11.2 percent water; 16.2 percent ethylene glycol monobutyl ether; 8.5 percent n-butanol; and 7.1 percent dimethylethanolamine.

2 Titanium dioxide rutile, commercially available as R-900 from E.I. Du Pont de Nemours and Co.

3 Micronized polyethylene wax additive, commercially available from Micro

Powders.

4 Zinc oxide, commercially available from Zinc Corporation of America. The above grind vehicle and CYMEL 303 melamine were mixed under moderate agitation, followed by the incremental addition under cowles agitation of the TiO₂ pigment, the MPP-620 F wax additive and the KADOX 915. After the aforementioned ingredients were thoroughly blended, cowles blade speed was increased and the grinding process continued until a Hegman gauge value of 7 was obtained. The deionized water was added to reduce viscosity.

EXAMPLE D-2

This example describes the preparation of a pigmented coating composition of the invention. The pigment grind paste described above in Example D-1 and the following ingredients were blended under moderate agitation:

Formula Weight Weight Resin Solids

Ingredients (grams) (grams)

Resin of Example 1 149.8 64.9

CYMEL 303 12.3 12.3

CYCAT 600¹ .09 .06

Grind paste of Example D-1 134.2 18.3

Phosphatized Epoxy 7.3 4.5

Mineral spirits 1.67 —

DOWANOL DPM² 1.69 —

Deionized water 28.5 —

TOTAL 335.5 100.0

1 Dodecyl benzene sulfonic acid catalyst, commercially available from King Industries, Inc.

2 Dipropylene glycol monomethyl ether, available from Dow Chemical Co. TESTING PROCEDURES

Panels for testing methyl ethyl ketone (MEK) rubs and hot pencil hardness were prepared as follows: the above varnish coating compositions of Examples A, B, and C were drawn down over bare aluminum can body stock available from American National Can Co. Panels for the flexibility/extensibility- upon- fabrication evaluation were prepared by applying a commercial white ink (CL18600, available from INX International Ink Co.) over can end stock (.0088" gauge aluminum available from ALCOA), followed by the application of the varnish coating compositions of Examples A, B and C using a # 8 wirewound draw bar to provide a cured film weight of about 90 to 110 mg./ can. Coated test panels were cured to a peak metal temperature of about 340°F. (170°C) to represent an on-line decorator bake, followed by a second cure to a peak metal temperature of 380°F. (195°C) to represent the on-line inside spray coating bake. Cured coated panels were tested versus analogous test panels coated with a proprietary clear, varnish control, CC3665V, commercially available from PPG Industries, Inc.

Panels for testing the white basecoat composition for the above properties were prepared as follows: the basecoat of Example D above was applied to aluminum can body stock test panels using a # 10 wirewound draw bar to provide a cured film weight of about 200 to 220 milligrams per can. The basecoat thus applied was then cured to a peak metal temperature of about 340°F. (170°C). The clear varnish, CC3665V, was subsequently applied to the cured basecoat using a # 8 wirewound draw bar to provide a cured film weight of about 90 to 110 milligrams per can. The coated panel was then cured to a peak metal temperature of about 340°F. (170°C). Finally, the test panels thus cured were then subjected to a third bake, simulating the on-line inside spray coating bake, to a peak metal temperature of about 380°F. (195°C). The basecoat/varnish test panels were then tested versus analogous test panels coated with CE3734 / CC3665V, a proprietary waterborne white basecoat/ clear varnish system, commercially available from PPG Industries, Inc. Test panels for the "hiding" evaluation were prepared by applying the white basecoat of Example D above to aluminum can body stock test panels using a wirewound draw bar of a size sufficient to provide a cured film weight of about 210 milligrams per can. The basecoat thus applied was then cured to a peak metal temperature of about 340°F. (170°C).

Flexibility /extensibility was tested by fabricating 28 mm. bottle caps from the cured coated ink/varnish panels using a punch press. The fabricated bottle cap were subjected to a pasteurization process (100°C. deionized water for 10 minutes), then rated for film cracking and or delamination in reference to a similarly fabricated and pasteurized cap coated with a commercial control ink/varnish system. The "hot tack" test gauges the ability of a coating to reach surface cure in a time sufficient to prevent two coated articles from sticking to one another. Quick surface cure is important, particularly for beer and beverage container coatings, to prevent two cans from sticking to one another while exiting the decorator oven. "Hot tack" was tested according to ASTM-D3369.

Extent of cure and solvent resistance was tested according to ASTM- D5402-93 using methyl ethyl ketone (MEK) double rubs. Results are reported as the number of double rubs completed before breaking through the coating to the substrate as compared to the commercial control varnish, 34W14-3F.

Extent of cure and film hardness are properties which were tested using the "hot pencil hardness" test. Pencil hardness was done according to ASTM-D3363, but modified by placing the panel to be tested in a constant temperature water bath containing 1 inch of water at 140° to 150°C. during the testing procedure.

The opacity and whiteness of the basecoat was tested by measuring the Hunter L (HL) values of panels prepared as described above using a color spectrophotometer and plotting the HL values versus the calculated coating weight. (The "Hunter L value" is a numeric representation of the degree of whiteness from the light-dark scale in the Hunter LAB calculation (increasing value indicates greater whiteness)).

A series of basecoat panels was prepared as described above representing various coating weights ranging from 150 to 300 mg/can. Using a punch press, 4 inch² disks were cut from each of the various coating weight panels and actual film weight was determined by measuring weight difference between the coated disk, and the weight of the disk after the coating had been stripped (mg./can = 9 x (initial disk weight - stripped disk weight). Prior to removal of the coating, the Hunter L value of each disk was measured on a color spectrophotometer using a specular included reflectance color eye, CIELAB color equation, a 10° observer, daylight illuminant (MacBeth color-Eye). Hunter L value was plotted versus mg basecoat/can, and compared to the Hunter L value of the control basecoat, CE3734, at the same film weight (210 mg./can).

The following Table 1 illustrates the advantages for flexibility, extent of cure and solvent resistance, hot pencil hardness and basecoat hiding of coating compositions comprised of the water reducible resins containing propoxylated allyl alcohol of the invention.

TABLE 1

It is evident from the foregoing that various modifications, which are apparent to those skilled in the art, can be made to the embodiments of this invention without departing from the spirit or scope thereof. Having thus described the invention, it is claimed as follows.

Claims

That Which Is Claimed Is:

1. A hydroxyl functional, water-reducible resin, comprising the reaction product of at least the following reactants:

(a) a propoxylated allylic alcohol having the structure:

CH₂ - CR - CH₂ - (X)ΓÇ₧ - OH

wherein R is H or an alkyl group containing 1 to 4 carbon atoms, X is an oxypropylene group, and n is a number ranging from 1 to 2,

(b) at least one free-radically polymerizable, ethylenically unsaturated monomer having a COOH functional group; and

(c) a chain transfer agent.

2. The hydroxyl functional, water reducible resin of claim 1 wherein n is a number ranging from 1.4 to 1.8.

3. The hydroxyl functional, water reducible resin of claim 1 wherein reactant (b) comprises at least one COOH functional group containing monomer selected from the group consisting of acrylic acid and methacrylic acid.

4. The hydroxyl functional, water reducible resin of claim 3 wherein reactant (b) further comprises at least one other free-radically polymerizable, ethylenically unsaturated monomer.

5. The hydroxyl functional, water reducible resin of claim 4 wherein the at least one other free-radically polymerizable, ethylenically unsaturated monomer is an alkyl ester of acrylic or methacrylic acid selected from the group consisting of ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, 2-ethylhexyl acrylate, and isobutyl methacrylate.

6. The hydroxyl functional, water reducible resin of claim 1 wherein reactant (c) comprises at least one compound selected from the group consisting of alpha- methyl styrene dimer and tert-dodecyl mercaptan.

7. The hydroxyl functional, water reducible resin of claim 1 wherein reactant (a) is present in an amount ranging from 5 to 15 weight percent, wherein reactant (b) is present in an amount ranging from 5 to 20 weight percent, and wherein reactant (c) is present in an amount ranging from 2 to 5 weight percent, said weight percentages being based on the weight of total resin solids in the hydroxyl functional, water reducible resin.

8. The hydroxyl functional, water-reducible resin of claim 7 wherein n is a number ranging from 1.4 to 1.8.

9. The hydroxyl functional, water reducible resin of claim 7 wherein reactant

(b) comprises from 10 to 20 weight percent of acrylic acid, said weight percentages being based on the weight of total resin solids in the hydroxyl functional, water reducible resin.

10. The hydroxyl functional, water-reducible resin of claim 9 wherein reactant (b) further comprises at least one other free-radically polymerizable, ethylenically unsaturated monomer selected from the group consisting of ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, 2-ethylhexyl acrylate, and isobutyl methacrylate.

11. The hydroxyl functional, water-reducible resin of claim 7 wherein reactant (c) comprises at least one compound selected from the group consisting of alpha- methyl styrene dimer and tert-dodecyl mercaptan.

12. A method for producing a hydroxyl functional, water-reducible resin, said method comprising the following steps:

(a) heating a propoxylated allyl alcohol having the following general structure:

CH₂ - CR - CH₂ - (X)ΓÇ₧ - OH

wherein R is H or an alkyl group containing 1 to 4 carbon atoms, X is an oxypropylene group, and n is a number ranging from 1 to 2; and

(b) adding to said heated propoxylated allyl alcohol an admix of compounds comprising: i. a free-radical initiator component; ii. a free-radically polymerizable, ethylenically unsaturated monomer having a COOH functional group, and iii. a chain transfer agent component.

13. The method of claim 12 further comprising neutralizing the water- reducible resin with a neutralizing agent, and dispersing the neutralized, water- reducible resin in deionized water.

14. The method of claim 12 wherein the admix of compounds in step (b) further comprises at least one other ethylenically unsaturated monomer selected from the group consisting of ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, 2-ethylhexyl acrylate, and isobutyl methacrylate.

15. The method of claim 12 wherein the chain transfer agent comprises at least one compound selected from the group consisting of alpha-methyl styrene dimer and tert-dodecyl mercaptan.

16. The method of claim 12 wherein, in step (a), the propoxylated allylic alcohol is present in an amount ranging from 5 to 20 weight percent, and is heated to a temperature ranging from l35┬░C. to l75┬░C.; and in step (b), the free-radically polymerizable, ethylenically unsaturated monomer having a COOH functional group is present in the second admix of compounds in an amount ranging from 5 to 30 weight percent, said weight percentages being based on the weight of total resin solids in the hydroxyl functional, water reducible resin being produced.

17. The method of claim 16 further comprising neutralizing the resin with a neutralizing agent and dispersing the neutralized resin in deionized water.

18. The method of claim 16 wherein the admix of compounds in step (b) further comprises from 20 to 85 weight percent of at least one other ethylenically unsaturated monomer selected from the group consisting of ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, 2-ethylhexyl acrylate, and isobutyl methacrylate, said weight percentages being based on the weight of total resin solids in the hydroxyl functional, water reducible resin being produced..

19. A coating composition comprising the following:

(a) a hydroxyl functional, water-reducible resin which is the reaction product of at least the following reactants: i. a propoxylated allylic alcohol having the following structure: CH₂ - CR - CH₂ - (X)_n - OH wherein R is H or an alkyl group containing 1 to 4 carbon atoms,

X is an oxypropylene group, and n is a number ranging from 1 to 2; ii. at least one free-radically polymerizable, ethylenically unsaturated monomer having a COOH functional group, and iii. a chain transfer agent; and

(b) a curing agent having functional groups which are reactive with the hydroxyl and/or COOH functional groups of the resin (a).

20. The coating composition of claim 19 wherein n is a number ranging from 1.4 to 1.8.

21. The coating composition of claim 19 wherein reactant (ii) comprises at least one COOH functional group containing monomer selected from the group consisting of acrylic acid and methacrylic acid.

22.. The coating composition of claim 21 wherein reactant (ii) further comprises at least one other free-radically polymerizable, ethylenically unsaturated monomer selected from the group consisting ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, 2-ethylhexyl acrylate, and isobutyl methacrylate.

23. The coating composition of claim 19 wherein reactant (iii) comprises at least one compound selected from the group consisting of alpha-methyl styrene dimer and tert-dodecyl mercaptan.

24. The coating composition of claim 19 wherein component (b) comprises at least one aminoplast.

25. The coating composition of claim 24 wherein said at least one aminoplast comprises at least one compound selected from the group consisting of a melamine- formaldehyde resin, benzoguanamine, glycoluril resin.

26. The coating composition of claim 19 further comprising a urethane component.

27. An article having a coating thereover, said coating comprising the following components: (a) a hydroxyl functional, water reducible resin which is the reaction product of the following reactants: i. a propoxylated allylic alcohol having the structure:

CH₂ - CR - CH₂ - (X)_n - OH wherein R is H or an alkyl group containing 1 to 4 carbon atoms, X is an oxypropylene group, and n is a number ranging from 1 to 2, ii. at least one free-radically polymerizable, ethylenically unsaturated monomer having a COOH functional group, and iii. a chain transfer agent; and

28. The coated article of claim 27 wherein said coated article is a coated metal can.

29. The coated article of claim 28 wherein said coated metal can has undergone a necking process.