HK1194344B - Phosphatized polyesters and coating compositions containing the same - Google Patents

Description

Phosphated polyesters and coating compositions containing same

Technical Field

The present invention relates to phosphated polyesters and coating compositions containing the same. The composition can be used to coat various containers, such as food and beverage containers.

Background

A variety of coatings have been used to coat the surfaces of food and beverage containers. For example, metal cans are sometimes coated using a roll coating or strip coating operation, i.e., flat or coil, or a sheet of a suitable substrate such as steel or aluminum, coated with a suitable composition and cured. The coated substrate is then formed into a can body or can end. Alternatively, the coating composition can be applied to the shaped can, for example, by spraying, and dipping, and then cured. Coatings for food and beverage containers should preferably be capable of high speed application to a substrate and provide the necessary properties upon curing to perform the desired end use. For example, the coating should be safe for food contact and have excellent adhesion to the substrate.

Many coating compositions for food and beverage containers are based on epoxy resins, which are polyglycidyl ethers of bisphenol A. Bisphenol a in packaging coatings, whether as bisphenol a itself (BPA) or a derivative thereof, such as diglycidyl ether of Bisphenol A (BADGE), epoxy novolac resins and polyols prepared from bisphenol a and bisphenol F are problematic. Although current scientific evidence suggests that few trace amounts of BPA or BADGE that may be released from existing coatings would not be a health hazard to humans. However, some people consider these compounds to be harmful to human health. Therefore, it is highly desirable to remove these compounds from coatings for food and beverage containers. Accordingly, it is desirable that packaging coating compositions for food or beverage containers be free of extractable amounts of BPA, BADGE or derivatives of BPA and yet have excellent properties, such as excellent adhesion to substrates.

Summary of The Invention

The present invention provides a coating composition comprising a resin binder and up to 10 wt.% of a phosphatized polyester, and to articles coated with the coating composition.

The phosphatized polyester comprises the reaction product of:

(a) a polyester having Mn of 2000-10,000, a hydroxyl value of 20 to 75, and an acid value of 15 to 25; the polyester is a polycondensate of:

(i) a polyol component comprising a mixture of diols and triols,

(ii) a polyacid component comprising an alpha, beta-ethylenically unsaturated polycarboxylic acid, and

(b) a phosphorus-containing acid.

The coated article comprises:

(a) a substrate, and

(b) a coating layer of the above coating composition deposited on the substrate.

The coating composition can be formulated such that it is substantially free of bisphenol a (bpa) and derivatives thereof, such as bisphenol a diglycidyl ether (BADGE).

Detailed Description

As used herein, unless otherwise specified, an amount, such as a flexibility expressing values, ranges, amounts, or percentages, can be read as if prefaced by the word "about", even if the term does not expressly appear. Furthermore, it should be noted that plural terms and/or phrases encompass their singular equivalents, and vice versa. For example, "a" polymer, "a" crosslinker, and any other component refer to one or more of these components.

When any numerical range of values is recited, such range is understood to include each and every number and/or fraction between the stated minimum and maximum ranges.

The term "polyol" or variations thereof as used herein broadly refers to a material having an average of two or more hydroxyl groups per molecule. The term "polycarboxylic acid" refers to acids and functionalized derivatives thereof, including anhydride derivatives, if any, and lower alkyl esters having 1 to 4 carbon atoms.

The term "polymer" as used herein broadly refers to prepolymers, oligomers, and homopolymers and copolymers. The terms "resin" and "polymer" are used interchangeably.

The terms "acrylic" and "acrylate" are used interchangeably (unless the intended meaning is changed by doing so) and include acrylic acid, anhydrides and derivatives thereof, e.g., their C₁-C₅Alkyl esters, lower alkyl-substituted acrylic acids, e.g. C₁-C₂Substituted acrylic acids, e.g. methacrylic acid, ethacrylic acid, etc., and C thereof₁-C₅Alkyl esters, unless otherwise indicated. The term "(meth) acrylic" or "(meth) acrylate" is intended to encompass the recited materials in the form of acrylic/acrylate and methacrylic/methacrylate, e.g., (meth) acrylate monomers. The term "acrylic polymer" refers to a polymer prepared from one or more acrylic monomers.

As used herein, "a" and "at least one" and "one or more" are used interchangeably. Thus, for example, a coating composition comprising "a" polymer can be interpreted to mean that the coating composition includes "one or more" polymers.

As used herein, molecular weight is determined by gel permeation chromatography using polystyrene standards. Unless otherwise indicated, molecular weights are given on a number average (Mn).

The phosphatized polyester is prepared by reacting a precursor polyester resin with a phosphorus-containing acid. The polyester resin contains hydroxyl functionality and carboxylic acid functionality. The polyester resin typically has a hydroxyl value of from 20 to 75mgKOH per gram of polyester resin and an acid value of from 15 to 20mgKOH per gram of polyester resin; all based on non-volatile solids measurements.

The number average molecular weight (Mn) of the polyester resin was 2000-10,000 g/mol.

Suitable polyester resins are typically prepared by condensation (esterification) according to known methods [ see, e.g., ZenoWicks, jr., frankn.jonesands.peterpappas, organic coatings: ScieneandTechnology, Vol.1, pp.122-132(John Wiley & Sons: New York, 1992) ]. The polyester resins are generally obtained from a mixture of at least one polyfunctional alcohol (polyol), generally a mixture of diols and triols, esterified with a polybasic acid or anhydride. The polyacid component comprises an alpha, beta-ethylenically unsaturated polycarboxylic acid or anhydride.

Polyester resins are typically prepared from mixtures of α, β -ethylenically unsaturated polycarboxylic acids, usually with aromatic and/or aliphatic polycarboxylic acids, and a polyol component, typically a mixture of diols and triols. The polyol and polycarboxylic acid are mixed in the desired proportions and reacted using standard esterification (condensation) procedures to provide a polyester having hydroxyl groups and carboxylic acid in the polyester resin. Triols are typically used to provide branched polyesters, as opposed to linear.

Examples of suitable polycarboxylic acids or anhydrides include, but are not limited to, maleic anhydride, maleic acid, fumaric acid, itaconic acid, phthalic anhydride, isophthalic acid, trimellitic anhydride, terephthalic acid, naphthalene dicarboxylic acid, adipic acid, azelaic acid, succinic acid, sebacic acid, and various mixtures thereof.

When used, the aromatic and/or aliphatic polycarboxylic acids are used in amounts of up to 70% by weight, typically from 50 to 65% by weight, based on the total weight of the polycarboxylic acid or anhydride.

Examples of suitable diols, triols and polyols include, but are not limited to, ethylene glycol, propylene glycol, 1, 3-propanediol, glycerol, diethylene glycol, dipropylene glycol, triethylene glycol, trimethylolpropane, trimethylolethane, tripropylene glycol, neopentyl glycol, pentaerythritol, 1, 4-butanediol, trimethylolpropane, hexanediol, cyclohexanedimethanol, and polyethylene and polypropylene glycols.

As noted above, the polyol component is a mixture of diols and triols. The weight ratio of diol to triol typically ranges from 0.5 to 10: 1.

the equivalent ratio of polyol component to polycarboxylic acid is from 0.9 to 1.1: 1.0.

the phosphorus-containing acid reacted with the polyester resin may be phosphinic acid, phosphonic acid, or preferably phosphoric acid. The phosphoric acid may be in the form of an aqueous solution, for example, an 85 wt% aqueous solution, or may be 100% phosphoric acid or superphosphoric acid. The acid is provided in an amount of about 0.2 to 0.5 equivalents of phosphoric acid per hydroxyl equivalent of the polyester resin, i.e., 0.2 to 0.45P-OH groups per hydroxyl group.

The reaction of the phosphorus-containing acid with the polyester resin is typically carried out in an organic solvent. The organic solvent is typically an aromatic solvent, a ketone or ester having a boiling point of about 65-250 ℃. Examples of suitable solvents include methyl ethyl ketone, methyl isobutyl ketone, butanediol acetate and methoxypropyl acetate. The organic solvent used for the reaction is typically present in an amount of about 20 to 50 weight percent based on the total weight of the phosphorus-containing acid, the polyester resin, and the organic solvent.

The reactants and organic solvent are typically mixed at a temperature of 50 ℃ to 95 ℃ and once the reactants are contacted, the reaction mixture is maintained at a temperature preferably of 90 ℃ to 200 ℃. The reaction is typically allowed to proceed for about 45 minutes to 6 hours.

Phosphatized polyesters are typically used in small amounts in coating compositions where they provide improved adhesion of the resulting coating to the substrate. The phosphatized polyester is typically present in the coating composition in an amount of up to 10 percent by weight, preferably from 0.1 to 5 percent by weight, based on the weight of resin solids in the coating composition. Amounts less than 0.1% by weight result in poor adhesion of the coating composition to the substrate, while amounts greater than 10% by weight have no additional advantage.

In addition to the phosphatized polyester, the coating composition comprises a resinous vehicle, an organic solvent, and other optional ingredients.

The resinous support is preferably an acrylic polymer and/or a polyester polymer. The acrylic polymer is preferably a polymer derived from one or more acrylic monomers. In addition, blends of acrylic polymers may be used. Preferred monomers are acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate and hexyl methacrylate. The acrylic polymer may also contain hydroxyl groups, typically derived from hydroxyl-substituted acrylic or methacrylic esters. Examples include hydroxyethyl acrylate and hydroxypropyl methacrylate. The weight average molecular weight (Mw) of the acrylic polymer component is preferably at least 5,000g/mol, more preferably 15,000-100,000 g/mol.

The acid value of the acrylic polymer is typically from 30 to 70, for example from 40 to 60 mgKOH/g; hydroxyl number of 0-100, e.g. 0-70mg KOH/g, and glass transition temperature (Tg) of-20 to +100 deg.C, e.g. +20 to +70 deg.C.

The polyester polymer is prepared by methods well known in the art, as described above, including the polycondensation reaction of one or more polycarboxylic acids with one or more polyols. Examples of suitable polycarboxylic acids are phthalic acid, isophthalic acid, terephthalic acid, 1, 4-cyclohexanedicarboxylic acid, succinic acid, sebacic acid, methyltetrahydrophthalic acid, methylhexahydrophthalic acid, tetrahydrophthalic acid, dodecanedioic acid, adipic acid, azelaic acid, naphthalenedicarboxylic acid, pyromellitic acid, dimer fatty acids and/or trimellitic acid.

The polyol component is for example selected from diols or triols. Examples of suitable polyols include ethylene glycol, 1, 3-propanediol, diethylene glycol, dipropylene glycol, triethylene glycol, 1, 4-butanediol, 2-methyl-1, 3-propanediol, 1, 4-cyclohexanedimethanol, 1, 6-hexanediol, neopentyl glycol, trimethylolpropane and glycerol. The polyester polymer preferably has a number average molecular weight of 1000-20,000 g/mol.

The polyester polymer typically has an acid number of from 0 to 20, for example from 0 to 5mg KOH/g, a hydroxyl number of from 50 to 200, for example from 70 to 150mg KOH/g, and a glass transition temperature (Tg) of from-20 ℃ to +50 ℃, for example from-10 ℃ to +40 ℃.

Typically, the curing agent is present in a resinous carrier, which reacts with the acrylic and polyester polymers. Suitable curing agents are phenoplasts or phenol-formaldehyde resins, and aminoplast or triazine-formaldehyde resins. The phenol-formaldehyde resin is preferably of the phenolic resole type. Examples of suitable phenols are phenol itself, butyl phenol, xylenol and cresol. Cresol-formaldehyde resins are frequently used, this type typically being etherified with butanol. For the chemistry for preparing phenol resins, reference is made to the editions "the chemistry and application of phenolic resins, vol.v., part i, dr.oldring; john Wiley&Sons/Cita technology Limited, London, 1997. Examples of commercially available phenol resins arePR285 and BR612, and in trademarksTypically those sold under the trade name BAKELITE6581 LB.

Examples of aminoplast resins are those formed by reacting a triazine, such as melamine or benzoguanamine, with formaldehyde. Preferably, these condensates are etherified typically with methanol, ethanol, butanol and mixtures thereof. For chemistry in the preparation and use of aminoplast resins see "the chemistry and application of amino cross linking Agentsolaminoproplast", Vol.V, PartII, p 21 ff., DrEditing; john Wiley&Sons/Cita technology Limited, London, 1998. These resins are given the trade markSuch as MAPRENALMF980, and under the trademarkSuch as CYMEL303 and CYMEL1128, available from cytec industries.

Typically, the acrylic polymer and/or polyester polymer is used in an amount of 40 to 90 weight percent, preferably 30 to 70 weight percent, and the crosslinker is present in an amount of 5 to 50 weight percent, preferably 20 to 40 weight percent, said weight percentages being based on the weight of total resin solids in the coating composition.

Optional ingredients may be included in the coating composition. Typically, the coating composition contains a diluent, such as water, or an organic solvent, or a mixture of water and an organic solvent, to dissolve or disperse the resin binder and the phosphated polyester. The organic solvent is selected to be sufficiently volatile to substantially completely evaporate during the curing process, for example, heating at 175 ℃ 205 ℃ for about 5-15 minutes. Examples of suitable organic solvents are aliphatic hydrocarbons, such as mineral spirits and high flash point VM & P naphtha; aromatic hydrocarbons such as benzene, toluene, xylene and solvent naphtha 100, 150, 200, etc.; alcohols such as ethanol, n-propanol, isopropanol, n-butanol, etc.; ketones such as acetone, cyclohexanone, methyl isobutyl ketone, and the like; esters such as ethyl acetate, butyl acetate, and the like; glycols, such as butylene glycol, glycol ethers, such as methoxypropanol and ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, and the like. Mixtures of various organic solvents may also be used. For aqueous compositions, the resinous support typically has acid groups, such as acid functional acrylic polymers, which are at least partially neutralized with an amine to aid dispersion or dissolution in an aqueous medium. When present, the diluent is used in the coating composition in an amount of about 20 to 83 weight percent, preferably 30 to 70 weight percent, based on the total weight of the coating composition.

Auxiliary resins, such as polyether polyols and polyurethane polyols, may be included in the coating composition to maximize certain properties of the resulting coating. When present, the auxiliary resin is used in an amount of up to 50 weight percent, typically from 2 to 50 weight percent, based on the total weight of resin solids of the coating composition.

Another optional ingredient typically present in the coating composition is a catalyst to increase the rate of curing or crosslinking of the coating composition. Generally, acid catalysts may be used, and are typically present in an amount of about 0.05 to 5 weight percent. Examples of suitable catalysts are dodecylbenzenesulfonic acid, methanesulfonic acid, p-toluenesulfonic acid, dinonylnaphthalene disulfonic acid and phenylphosphonic acid. It has been found that the amount of acid catalyst in the coating composition of the present invention is not as much as would normally be expected due to the presence of the phosphorylated ester. The reaction product is acidic and has been found to aid in curing the coating composition.

Another optional ingredient that may be used is a lubricant, for example, a wax that facilitates the manufacture of metal closures by imparting lubricity to the sheet of coated metal substrate. Preferred lubricants include, for example, carnauba wax and polyethylene-based lubricants. If used, the lubricant is preferably present in the coating composition in at least 0.1 weight percent based on the weight of resin solids in the coating composition.

Another optional ingredient that may be used is a pigment, such as titanium dioxide. If used, the pigment is present in the coating composition in an amount of no greater than 70 weight percent, preferably no greater than 40 weight percent, based on the total weight of solids in the coating composition.

Surfactants may optionally be added to the coating composition to aid in flow and wetting of the substrate. Examples of suitable surfactants include, but are not limited to, nonylphenol polyethers and salts. If used, the surfactant is present in an amount of at least 0.01% and no greater than 10% based on the weight of resin solids of the coating composition.

In certain embodiments, the compositions used in the practice of the present invention are substantially free, may be substantially free, and may be completely free of bisphenol a and derivatives or residues thereof, including bisphenol a ("BPA") and bisphenol a diglycidyl ether ("BADGE"). Such compositions are sometimes referred to as "BPA-free" because BPA, including derivatives or residues thereof, is not intentionally added but may be present in trace amounts due to unavoidable contamination from the environment. The composition can also be substantially free, and can be completely free of bisphenol F and derivatives or residues thereof, including bisphenol F and bisphenol F diglycidyl ether ("BPFG"). As used herein, the term "substantially free" means that the composition contains less than 1000 parts per million (ppm), "substantially free" means less than 100ppm, and "completely free" means less than 20 parts per billion (ppb) of any of the above compounds, derivatives, or residues thereof.

The coating compositions of the present invention can be applied to all types of containers and are particularly suitable for use with food and beverage cans (e.g., two-piece cans, three-piece cans, etc.). In addition to food and beverage containers, the coating composition may also be applied to containers for aerosol applications, such as deodorants and hair sprays.

Two-piece cans are manufactured by joining a can body (typically a drawn metal body) to a can end (typically a drawn metal end). The coating of the present invention is suitable for use in food or beverage contact situations and may be used on the inside or outside of the can. They are suitable for spray coating, liquid coating, wash coating, sheet coating, varnish coating and edge seam coating.

Spraying comprises introducing the coating composition into the interior of a preformed packaging container. Typical preformed packaging containers suitable for spray coating include food cans, beer and beverage containers, and the like. The spray coating preferably uses a nozzle capable of uniformly coating the inside of the preformed packaging container. The sprayed preformed container is then heated to remove residual solvent and harden the coating.

Roll coating is described as the coating of a coil composed of metal (e.g., steel or aluminum), which is typically applied by roll coating. Once coated, the coated coil is subjected to a short thermal, ultraviolet, and/or electromagnetic curing cycle to harden (e.g., dry and cure) the coating. Roll coating provides coated metal (e.g., steel and/or aluminum) substrates that can be fabricated into articles, such as two-piece drawn food cans, three-piece food cans, food can ends, drawn and drawn cans, beverage can ends, and the like.

Wash coating is a thin layer that is commercially described as applying a protective coating to the exterior of a two-piece drawn and ironed ("D & I") can. The exterior of these D & I cans are "wash coated" by passing a preformed two-piece D & I can through a curtain of coating composition. While passing through the curtain, the can is turned over, i.e., the open end of the can is placed in a "down" position. The curtain of coating composition has a "waterfall" appearance. Once the cans pass through the curtain of coating composition, the liquid coating material effectively coats the exterior of each can. Excess coating is removed by using an "air knife". Once the desired amount of coating is applied to the exterior of each can, each can is passed through a thermal, ultraviolet, and/or electromagnetic curing oven to harden (e.g., dry and cure) the coating. The residence time of the coated cans in the curing oven zone is typically 1 minute to 5 minutes. The curing temperature in the oven typically ranges from 150 ℃ to 220 ℃.

Strip coating is described as coating individual pieces of various materials (e.g., steel or aluminum) that are pre-cut into square or rectangular "sheets". Typical dimensions for these sheets are about one square meter. Once coated, each sheet was cured. Once hardened (e.g., dried and cured), the sheet of coated substrate is collected and ready for subsequent fabrication. The web coating provides coated metal (e.g., steel or aluminum) substrates that can be successfully fabricated into shaped articles, such as two-piece drawn food cans, three-piece food cans, food can ends, drawn and drawn cans, beverage can ends, and the like.

The seam coating is described as spraying a liquid coating onto the welded area of a formed three-piece food can. When preparing three-piece food cans, a rectangular piece of coated substrate is formed into a cylinder. The formation of the cylinder is permanent by welding each side of the rectangle by heat welding. Once welded, each can typically requires a layer of liquid coating to protect the exposed "weld area" from subsequent corrosion or other effects on the contained food items. Liquid coatings that do this are called "side seam tapes". Typical seam tapes are spray coated and quickly cured by residual heat from the welding operation as well as a small amount of heat, ultraviolet light, and/or heat from an induction cooker.

Examples

The following examples are provided to aid the understanding of the present invention and should not be construed to limit the scope of the present invention. All parts and weight percentages are by weight unless otherwise indicated.

Example A

Polyesters acidified with phosphorus-containing acids

The phosphatized polyester resin is prepared from a mixture of:

composition (I)	Parts by weight
		2-methyl-1, 3-propanediol	19.90
Trimethylolpropane	3.01
		Isophthalic acid	14.35
Dibutyl tin oxide (catalyst)	0.06
		Maleic anhydride	8.35
Phthalic anhydride	7.30
		Aromatic1001	7.79
Phosphoric acid (85% solvent)	1.11
		Water (W)	0.08
2-butoxyethanol	4.26
		Monobutyl ether of diethylene glycol	33.80

¹Aromatic solvent from ExxonMobile.

The first two ingredients were added to a reaction vessel equipped with a stirrer, nitrogen blanket and a 50 ℃ distillation apparatus set and heated to. Once this temperature was reached, the next four ingredients were added to the vessel and slowly heated to distill. The mixture is esterified under a nitrogen atmosphere at a temperature of 180 ℃ to 240 ℃ for about twelve (12) hours.

When the acid number of the mixture dropped to about 13.00mgKOH/g, the mixture was cooled to about 160 ℃, and then Aromatic100 solvent (i.e., an Aromatic hydrocarbon solvent blend, available from ExxonMobil) was added to perform azeotropic distillation of water produced as a condensation byproduct. Thereafter, the phosphoric acid solution and water were added, and azeotropic distillation of water was continued until the acid value of the mixture dropped below 20 mgKOH/g. The resulting phosphated polyester resin was then dissolved in 2-butoxyethanol and monobutyl ether of diethylene glycol to produce a composition of about 50% by weight solids.

The resulting phosphatized polyester had a number average molecular weight of about 4500, an acid number of about 20, and a hydroxyl number of about 45.

Example B (comparative example)

Reaction product of phosphoric acid and bisphenol A diglycidyl ether

11.01g of 85% orthophosphoric acid and 14.24g of butanol were added to the flask. The mixture was heated to 230 ° F (110 ℃) under an inert blanket of nitrogen. When this temperature was reached, the nitrogen envelope was closed and a premix of 45.64g of bisphenol A diglycidyl ether (0.286 equivalents of phosphoric acid per equivalent of epoxy group) and 22.53g of butanol was added over 2 hours and 10 minutes. The batch temperature was maintained below 245 ° F (118 ℃) during the addition. After the addition was complete, 2.18g of butanol was added to the flask and the temperature was reduced to 219 ° F (104 ℃) and held for an additional 2 hours. An additional 2.76g of butanol was then added to the flask and the resulting reaction product had a resin solids content of 55.92 wt%.

Examples 1 to 3

A series of container coating compositions were prepared based on a binder comprising a polyester polyol and an aminoplast and a phenoplast curing agent. One composition (example 1) contained a phosphated polyester adhesion promoter, the second composition (example 2) contained a bisphenol a diglycidyl ether (BADGE) adhesion promoter, and the third composition (example 3, control) contained no adhesion promoter.

The ingredients were added to the vessel with gentle stirring to form a clear varnish. Each varnish was brush coated onto a zinc treated aluminum plate which was baked in an electric air oven to obtain a peak metal temperature of 450F (232 c). The cured coatings were then evaluated for adhesion and blushing (blushing). The results are shown in Table I below.

TABLE I

Coating Properties

¹Coating weight, milligrams per square inch.

²A cotton pad soaked with Methyl Ethyl Ketone (MEK) was moved back and forth over the coating under constant pressure until the coating was severely damaged. After 100 double rubs, the test was ended.

³Dowfax detergent test: the "Dowfax" test is designed to measure the resistance of the coating to boiling detergent solutions. The solution is prepared by mixing 5ml of Dowfax2A1 (product of Dow chemical) into 3000ml of deionized water. The coated substrate was immersed in boiling Dowfax solution for 15 minutes. The substrates were then rinsed and cooled in deionized water, dried, and then tested and scored for blush and adhesion.

⁴3(3) weight% acetic acid in water.

⁵Method of heat resistance: this is a measure of the coating integrity of the coated substrate after exposure to heat and pressure with a liquid, such as water. For this evaluation, the coated substrate was immersed in deionized water or water at pH 9 and heat at 121 ℃ (250 ° F) and pressure of 1.05kg/cm was applied for 30 minutes. The substrates were then dried and tested for adhesion and blush.

⁶Hair-resistantWhiteness: blush resistance measures the ability of a coating to resist attack by various solutions. Blush is typically measured by water absorbed into the coating film. When the film absorbs water, the film typically becomes cloudy or looks whitish. Blush was measured with a 0-10 eye scale, where a "10" scale indicates no blush and a "0" scale indicates complete whitening of the film.

⁷Adhesion force: adhesion tests were performed to assess whether the coating adhered to the coated substrate. Adhesion testing was performed according to astm d 3359-test method B using Scotch610 tape (3 mccompany available from SaintPaul, Minnesota). Adhesion is generally scored on a scale of 0 to 100, where a "100" score indicates no adhesion failure and a "90" score indicates that 90% of the coating remains adhered.

Claims (20)

1. A liquid coating composition comprising:

(a) a resin binder, a binder resin, and a binder resin,

(b) up to 10 wt.% of a phosphatized polyester comprising the reaction product of:

(i) a polyester having a number average molecular weight (Mn) of 2000-10,000g/mol, a hydroxyl value of 20-75 mgKOH/g, and an acid value of 15-25 mgKOH/g; the polyester comprises the polycondensate of:

(A) a polyol component comprising a mixture of diols and triols,

(B) a polyacid component comprising an alpha, beta-ethylenically unsaturated polycarboxylic acid, and

(ii) a phosphorus-containing acid.

2. The liquid coating composition of claim 1, wherein the polyol component comprises an aliphatic polyol optionally having alkyl branching.

3. The liquid coating composition of claim 2, wherein the triol comprises trimethylolpropane.

4. The liquid coating composition of claim 1, wherein the polyacid component comprises a mixture of aliphatic and/or aromatic polycarboxylic acids and alpha, beta-ethylenically unsaturated polycarboxylic acids.

5. The liquid coating composition of claim 1, wherein the alpha, beta-ethylenically unsaturated polycarboxylic acid comprises maleic acid.

6. The liquid coating composition of claim 1, wherein the phosphorus-containing acid comprises phosphoric acid.

7. The liquid coating composition of claim 1, wherein the phosphorus acid is used in an amount of 0.2 to 0.5 equivalents per equivalent of hydroxyl groups, i.e., 0.2 to 0.5P-OH per hydroxyl group.

8. The liquid coating composition of claim 1, wherein the resin binder comprises an acrylic polymer and/or a polyester polymer.

9. The liquid coating composition of claim 1, further comprising a crosslinker.

10. The liquid coating composition of claim 9, wherein the crosslinker comprises an aminoplast and/or a phenoplast.

11. The liquid coating composition of claim 1, wherein the resin binder is present in an amount of 40 to 90 percent by weight based on the weight of resin solids in the coating composition.

12. The liquid coating composition of claim 9, wherein the crosslinker is present in an amount of 5 to 50 weight percent based on the weight of resin solids in the coating composition.

13. The liquid coating composition of claim 1, containing less than 1000ppm of bisphenol a and derivatives thereof.

14. The liquid coating composition of claim 1, which is completely free of bisphenol a and derivatives thereof.

15. A coated article comprising:

(a) a substrate, and

(b) a coating deposited on the substrate from the liquid coating composition of claim 1.

16. The coated article of claim 15, wherein the substrate is a container.

17. The coated article of claim 16 wherein the substrate is a container for food and beverages.

18. The coated article of claim 15, wherein the substrate is a can.

19. The coated article of claim 18, wherein the liquid coating composition is deposited onto the exterior wall of the can.

20. The coated article of claim 18 wherein the substrate is a can end.