HK1180292B - High functionality polyesters and coatings comprising the same - Google Patents

Description

High functionality polyesters and coatings comprising same

Technical Field

The invention relates to crosslinkable polyesters, which are produced by free-radical polymerization of the double bonds of unsaturated polyester prepolymers.

Background

Conventional linear and branched polyester resins produced by the polycondensation of polyols and polyacids in different combinations have been widely used in the coatings industry. They have been used to coat a number of metallic and non-metallic substrates used in a variety of different industries. These industries include in particular those in which flexible coatings are desired. Particularly suitable examples include substrates used in the packaging industry, coil coatings, and certain industrial and automotive coatings. Certain coatings, especially in the packaging industry, must be subjected to extreme stresses during the manufacture and use of packaging containers. In addition to flexibility, packaging coatings may also need to be resistant to chemicals, solvents, and pasteurization in the consumer packaging of beer and beverages, and may also need to withstand retort conditions commonly used in food packaging. In the coil coating industry, the coil is unrolled, coated and rewound. The coating used must therefore be sufficiently flexible to withstand the winding process and the subsequent stamping or other forming processes in which the coil is manufactured into the desired workpiece or end product; the durability of the paint on the final workpiece or product is also a factor. Similarly, it is often desirable for coatings used in the automotive industry to exhibit flexibility and durability.

High molecular weight polyesters generally have good flexibility and resistance to mechanical deformation, which can be achieved by controlling the ratio of polyol: the ratio of the polybasic acids and the extent of the reaction. However, these polymers typically have a low average functionality per chain, which limits their further use in coatings. On the other hand, increasing the functionality may result in polyesters having lower molecular weights. The use of low molecular weight polyester resins in coatings can result in poor substrate adhesion, limited compatibility with other types of resins, and/or difficulties in achieving the desired balance of chemical resistance and flexibility.

Polyesters with high levels of functionality without sacrificing molecular weight are therefore desirable.

Disclosure of Invention

The invention relates to crosslinkable polyesters, which are prepared by free-radical polymerization of the double bonds of unsaturated polyester prepolymers. The number average functionality of the unsaturation in the prepolymer is from 0.05 to 25. The invention also relates to a coating comprising such a polyester and a crosslinking agent therefor.

Detailed description of the invention

The invention relates to a polyester which is produced by free-radical polymerization of an unsaturated polyester prepolymer. The polyester is crosslinkable. As used herein, "crosslinkable" and similar terms mean that the polyester is capable of being crosslinked with another compound. That is, the polyester has a functionality that will react with a functionality on another compound, such as a crosslinker. The polyesters of the present invention are thermosetting materials, not thermoplastic.

The polyester is formed by using free radical polymerization, wherein the unsaturation of the prepolymer reacts to form the polyester. Thus, the prepolymer is unsaturated, and the unsaturation is reacted to a desired level or degree during the formation of the polyester. In certain embodiments, the reaction is conducted such that substantially all of the unsaturation is reacted in the formation of the polyester, while in other embodiments, the resulting polyester also contains some degree of unsaturation. For example, the resulting polyester may contain sufficient unsaturation to allow the polyester to react with other functional groups. The prepolymer also contains functional groups other than unsaturation. Such functionality remains largely unreacted during the free radical polymerization. In this way, the polyester obtained has a functionality such that it is crosslinkable. Depending on the prepolymer or prepolymers used, the functionality may be pendant and/or end-capped.

The unsaturated polyester prepolymer may be prepared by any means known in the art, such as polycondensation, by reacting a polyacid, and/or esters and/or anhydrides thereof, with a polyol. As used herein, "polyol" and similar terms refer to compounds having two or more hydroxyl groups. As used herein, "polyacid" and similar terms refer to a compound having two or more acid groups and includes esters and/or anhydrides of the acid. The polyacid and/or polyol is unsaturated. The polyacid and/or polyol may also contain one or more additional functional groups, as discussed above. These additional functional groups may include, for example, hydroxyl, carboxyl, amino, epoxy, and/or silane groups. Such functionality cups are referred to as "additional" functionalities or functional groups, as one skilled in the art will appreciate that the unsaturation of the polyacid and/or polyol already provides the functionality. The additional functional groups may be on the polyacid and/or polyol, and may be on the same or different polyacid and/or polyol containing unsaturation. The additional functionality is selected such that when the polyol and the polyacid are reacted, a prepolymer having functional groups that are terminal and/or pendant is obtained. "terminal functional group," "terminal functionality," and like terms refer to a functional group at the chain end of the prepolymer or resulting polyester, such as any of those listed above. "pendant functional group," "pendant functionality," and like terms refer to functional groups, such as any of those listed above, which are not present at the chain ends of the prepolymer or resulting polyester. However, it is also possible to introduce further functional groups via another monomer as described below, which lead to a functionality on the prepolymer.

Suitable unsaturated polyacids for use in the present invention can be any unsaturated carboxylic acid containing two or more carboxyl groups, and/or esters and/or anhydrides thereof. Examples include, but are not limited to, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, teraconicacid, and/or esters and/or anhydrides thereof. When the polyacid is in the form of an ester, the esters may be formed with any suitable alcohol, for example, through C₁-C₁₈C formed by reaction of an alcohol (e.g., methanol, ethanol, 1-propanol, 1-butanol, 2-butanol, isobutanol, 1-pentanol, and 1-hexanol) with the polybasic acid₁-C₁₈An alkyl ester. Particularly suitable unsaturated polybasic acids are maleic acid, maleic anhydride or C of maleic acid₁-C₆An alkyl ester. Suitable saturated polybasic acids for use in the present invention include, but are not limited to, 1, 3-cyclohexanedicarboxylic acid, 1, 4-cyclohexanedicarboxylic acid, adipic acid, azelaic acid, sebacic acid, succinic acid, glutaric acid, sebacic acid, dodecanedioic acid, and esters and anhydrides thereof. Combinations of unsaturated and/or saturated polyacids can be used. As can be appreciated, in certain embodiments, the polyacid is aliphatic. In certain embodiments, the polybasic acid comprises maleic, fumaric and/or itaconic acid, and/or esters and/or anhydrides thereof, and in other embodiments the polybasic acid comprises maleic, fumaric and/or itaconic acid, and/or esters and/or anhydrides thereof and is substantially, orWhich is completely free of any other monomers. In certain embodiments, the unsaturated carboxylic acid/anhydride/ester comprises 3 to 10 weight percent, such as 4 to 7 weight percent, of the polyester, while in other embodiments it comprises greater than 10 weight percent, such as 15 weight percent or more, of the polyester.

Suitable saturated polyols for use in the present invention may be any polyol known for use in the preparation of polyesters. Examples include, but are not limited to, alkylene glycols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, hexylene glycol, polyethylene glycol, polypropylene glycol, and neopentyl glycol; hydrogenated bisphenol a; cyclohexane diol; propylene glycol (including 1, 2-propanediol, 1, 3-propanediol, butylethylpropylene glycol, 2-methyl-1, 3-propanediol, 2-dimethyl-1, 3-propanediol, 2-ethyl-2-butyl-1, 3-propanediol), butylene glycol (including 1, 4-butanediol, 1, 3-butanediol, and 2-ethyl-1, 4-butanediol), pentylene glycol (including trimethylpentylene glycol and 2-methylpentylene glycol); cyclohexanedimethanol; tricyclodecanedimethanol; hexylene glycol (including 1, 6-hexanediol); caprolactone diol (e.g., -the reaction product of caprolactone and ethylene glycol); hydroxy-alkylated bisphenols; polyether glycols such as poly (oxytetramethylene) glycol; trimethylolpropane, pentaerythritol, dipentaerythritol, trimethylolethane, trimethylolbutane, dimethylolcyclohexane, glycerol, erythritol, and the like. Suitable unsaturated polyols for use in the present invention can be any unsaturated alcohol containing two or more hydroxyl groups. Examples include, but are not limited to, trimethylolpropane triallyl ether, trimethylolethane monoallyl ether, and prop-1-ene-1, 3-diol. Combinations of unsaturated and/or saturated polyols may be used.

The unsaturated polyester prepolymer of the present invention may also include one or more optional additional monomers such as aromatic polyacids, monofunctional acids, fatty acids, esters or anhydrides of any of these acids, aromatic polyols and/or monofunctional alcohols. In certain embodiments, the "additional" functional group may be introduced to the unsaturated polyester prepolymer by the one or more optional additional monomers. That is, the additional functional groups may be on the polyacid and/or the polyol as described above, and/or may be on the one or more optional additional monomers. Thus, this "additional" functionality can be introduced in a variety of ways.

Non-limiting examples of suitable additional monomers include acids, and esters and anhydrides thereof, such as phthalic acid, isophthalic acid, 5-tert-butylisophthalic acid, tetrachlorophthalic acid, tetrahydrophthalic acid, naphthalenedicarboxylic acid, terephthalic acid, hexahydrophthalic acid, methylhexahydrophthalic acid, dimethylterephthalate, trimellitic acid, and cycloaliphatic carboxylic acids (including cyclohexanedicarboxylic acid), endomethylenetetrahydrophthalic acid, tricyclodecanedicarboxylic acid, endoethylenehexahydrophthalic acid, camphoric acid, cyclohexanetetracarboxylic acid and cyclobutanetetracarboxylic acid, C₁-C₁₈Aliphatic carboxylic acids such as acetic acid, propionic acid, butyric acid, caproic acid, oleic acid, linoleic acid, undecanoic acid, lauric acid, isononanoic acid, other fatty acids, and hydrogenated fatty acids of naturally occurring oils, benzoic acid, tert-butylbenzoic acid, and esters and anhydrides thereof.

Non-limiting examples of suitable additional poly-and monofunctional alcohols include hydroxy alkylated bisphenols and aromatic alcohols such as benzyl alcohol and hydroxyethoxybenzene, C₁-C₁₈Aliphatic alcohols such as methanol, ethanol, propanol, hexanol, stearyl alcohol, oleyl alcohol and undecyl alcohol, and aromatic alcohols such as benzyl alcohol and hydroxyethoxybenzene.

The unsaturated polyester prepolymer may be prepared in any manner known in the art and may vary depending on the components used to prepare the prepolymer. For example, in one embodiment of the present invention, a polyacid and a polyol, at least one of which is unsaturated, are reacted to produce an unsaturated polyester prepolymer. This reaction product may then be further reacted with other optional monomers, such as any of those described above; the resulting product will also be an unsaturated polyester prepolymer suitable for use in accordance with the present invention. Examples of unsaturated polyester prepolymers prepared in this manner include polymers in which a diol and maleic anhydride (or fumaric acid) are reacted to produce a maleate (or fumarate) linear polymer in a first stage. It is then reacted with a polyol (e.g., glycerol or trimethylolpropane) and an aliphatic (or cycloaliphatic) polyacid to produce a branched, unsaturated polyester precursor or prepolymer. Linear unsaturated prepolymers can also be prepared in a similar manner using diacids. In another embodiment of the present invention, a polyol and a polyacid, both of which are unsaturated, may be reacted and the reaction product further reacted with the unsaturated monomer. A particularly suitable unsaturated polyester prepolymer prepared in this manner is one in which a diol is reacted with isophthalic acid to give a reaction product having a lower acid number and a higher hydroxyl number. The reaction product may then be further reacted with maleic acid, a maleate ester, or maleic anhydride to introduce unsaturation into the resulting low acid number prepolymer.

The result should be an unsaturated polyester prepolymer regardless of the manner of preparing the unsaturated polyester prepolymer, the order of adding the monomers contained in the prepolymer, and the like. The number average functionality of unsaturation ("Fn") in the prepolymer is from 0.05 to 25.0. In certain embodiments, Fn is 0.1 or greater, e.g., 0.2 or greater, 0.5 or greater, 0.8 or greater, 1.0 or greater, or 1.2 or greater, with an upper limit of 2.0, 2.5, 5.0, 7.0, 9.0, 10 or greater. Any value within this range of 0.05 to 25.0 is within the scope of the present invention. In certain embodiments, the unsaturation will be derived from maleic acid/anhydride and the prepolymer will have an average of 0.2 or greater maleic residues, such as 0.5 or greater, 0.9 or greater or even greater, such as 2.0 or greater.

It will be further understood that the unsaturated polyester prepolymer may have varying degrees of unsaturation within the total Fn range of 0.05 to 25.0, and that there will be a distribution of polymeric materials having varying degrees of unsaturation, varying chain lengths, varying degrees of branching, and varying numbers and/or types of end groups after the polycondensation reaction or other reaction forming the unsaturated polyester prepolymer. The average number of double bonds per unsaturated polyester prepolymer chain can vary depending on the degree of free radical polymerization that is desired to provide the target polyester and the various properties resulting from the resulting polyester. Thus, the number of double bonds per unsaturated polyester prepolymer chain is generally reported as an average value (Fn). The unsaturation in the polyester prepolymer can be deduced, for example, from the residues of maleic acid, maleate esters or maleic anhydride. In certain embodiments, the unsaturated moiety is incorporated substantially all of the way into the chain except at the end or terminus of the prepolymer. In this context "substantially all bound" means that only a trace amount of reaction occurs at the end. In other embodiments, no unsaturation is introduced at the terminus.

The polycondensation reaction to form the unsaturated polyester prepolymer may be conducted in the presence of an esterification catalyst. Any polycondensation catalyst commonly used in the preparation of polyesters may be used. Suitable non-limiting examples of esterification catalysts include tin, titanium, and zinc catalysts such as dibutyltin oxide (DBTO), stannous chloride, stannous oxalate, stannous octoate, butylstannoic acid (stannoic acid), tetra-n-butyltitanate, tetraisopropyl titanate, zinc acetate, and zinc stearate. In certain embodiments, it may also be desirable to include a polymerization inhibitor to inhibit polymerization at the unsaturation; the reaction at the unsaturation may result in a saturated or to a large extent saturated prepolymer. Suitable examples of such inhibitors include, but are not limited to, methyl hydroquinone, and t-butyl hydroquinone.

As noted above, the prepolymers of the present invention will also contain terminal and/or pendant functionalities. In certain embodiments, terminal functionality will occur at substantially all of the terminals, including branched ends. If the terminal and/or pendant functionality comprises hydroxyl groups, the unsaturated polyester prepolymer can have a hydroxyl value of 2 to 500mgKOH/gm, e.g., 10 to 350, 30 to 250, 40 to 200, 50 to 200mgKOH/gm, etc.; if the terminal and/or pendant functionality comprises an acid group, the acid value of the unsaturated polyester prepolymer can be 1 to 400mgKOH/gm, e.g., 10 to 500, 20 to 200, 30 to 250, 30 to 150, 40 to 100mgKOH/gm, and the like. Any value between these broad ranges is also within the scope of the invention.

The unsaturated polyester prepolymer can have a number average molecular weight ("Mn") of 150 to 5000, such as 250 to 2500, and a weight average molecular weight ("Mw") of 250 to 50000, such as 1000 to 20000. Any value between these broad ranges is also within the scope of the invention.

The polyesters of the present invention are formed primarily by free radical polymerization of unsaturated polyester prepolymer chains through reaction at the unsaturation. As in the formation of prepolymers, various reaction products may be formed in the formation of polyesters. While a majority of these reaction products will be formed by reaction of the unsaturation, there will also be at least some reaction between the unsaturation and the additional functionality of the prepolymer. Thus, in certain embodiments, the polydispersity or polydispersity index ("PDI") of the polyester polymer will be 1 or greater, such as 2.0, 10, 50, 200 or greater, or such as between 4 and 40.

The polymerization is carried out in the presence of a free radical initiator. Any free radical initiator commonly used to initiate polymerization of unsaturated compounds containing double bonds can be used in the free radical polymerization. For example, the free radical initiator can be an azo initiator or a peroxide initiator, such as t-butyl peroxy-2-ethylhexanoate, t-butyl peroxybenzoate, t-butyl peroxy-3, 5, 5-trimethylhexanoate, or dibenzoyl peroxide. The ratio of initiator to unsaturated polyester prepolymer can vary depending on the desired degree of chain linkage of the polyester prepolymer chains. For example, the molar ratio of the average number of double bonds of the initiator to the chain of each unsaturated polyester prepolymer can be from 0.0001 to 1.0, e.g., from 0.001 to 0.7, from 0.01 to 0.5, from 0.05 to 0.2, and the like.

The initiator may be added in different portions at different times depending on the degree of control over the polymerization desired. For example, all of the free radical initiator may be added at the beginning of the reaction, the initiator may be in multiple portions and the multiple portions added at different intervals during the reaction, or the initiator may be added in a continuous feed. In some embodiments of the invention, the process may be carried out by using a combination of continuous feed and initiator added in multiple portions. It will be appreciated that adding initiator at fixed intervals or in a continuous feed will result in a process that is better controlled than initially with respect to adding all initiator. Furthermore, if all of the initiator is added at once, the heat generated due to the exothermic reaction may make it difficult to control the temperature.

The temperature at which the free radical polymerization reaction is carried out can vary depending on various factors such as the composition of the unsaturated polyester prepolymer, the initiator, the solvent, and the properties desired for the polyester. Typically, the free radical polymerization of the unsaturated polyester prepolymer is carried out at a temperature of from 30 ℃ to 180 ℃ or higher, for example, from 50 ℃ to 150 ℃, or from 80 ℃ to 130 ℃. In a typical polymerization, such as an acrylic polymerization, a higher concentration of free radical initiator results in polymerization of more chains, each chain having a lower molecular weight. It has been unexpectedly found that in the system of the present invention, especially when maleic acid species are used, the higher the initiator concentration, the higher the molecular weight of the resulting polymer. This is an unexpected result, since the person skilled in the art would not have expected that the polymerization of the invention would have occurred. But too much initiator can lead to gelation. Thus, in certain embodiments, the polyesters of the present invention are ungelled.

Although any means of polymerizing the polyester may be used, free radical polymerization may be carried out using a solution of an unsaturated polyester prepolymer for ease of handling. Any solvent can be used as long as it can dissolve the unsaturated polyester prepolymer and the radical initiator to a sufficient extent to allow the polymerization reaction to proceed efficiently. Typical examples of suitable solvents include butylene glycol, propylene glycol monomethyl ether, methoxypropyl acetate, and xylene. The unsaturated polyester prepolymer may also be formed in a molten (i.e., 100% solids) state, the resulting unsaturated polyester prepolymer cooled, then a suitable solvent and free radical initiator added, followed by free radical polymerization, enabling the formation of the polyester of the present invention having the desired molecular weight and functionality to be carried out in a continuous process. Thus, the polyesters of the present invention may be solid or liquid.

The free-radical polymerization of unsaturated polyesters can also be carried out in water or other aqueous media, i.e.in aqueous mixtures. If the unsaturated polyester prepolymer has sufficient carboxylic acid groups, it can be converted to a water-diluted material by neutralization with a suitable base, or partial neutralization, followed by addition of water. Non-limiting examples of suitable bases for the neutralization reaction include dimethylethanolamine, triethylamine, and 2-amino-2-methylpropanol. The aqueous material may then be polymerized using free radicals as described above. Alternatively, the unsaturated polyester prepolymer may be mixed with a surfactant and/or polymeric stabilizer material, followed by mixing with water, and then free radical polymerization as described above. It will also be apparent to those skilled in the art that these aqueous mixtures may contain additional organic co-solvents, examples of which include, but are not limited to, butanediol, butyl diglycol and propylene glycol monomethyl ether.

As mentioned above, the polyesters of the invention are formed from the double bonds of the unsaturated polyester prepolymer by free radical polymerization. In certain embodiments, the polyesters according to the present invention may be prepared by the reaction of unsaturated polyester prepolymers comprising the same components, while in other embodiments they may be prepared by the reaction of two or more unsaturated polyester prepolymers formed from different components. That is, the first unsaturated polyester prepolymer is reacted with the second unsaturated polyester prepolymer by radical polymerization; however, each prepolymer has some degree of unsaturation, which may be the same or different, and provides the primary vehicle by which the prepolymer is polymerized to form a polyester, the components used to prepare the first and second prepolymers may be different, or may have one or more different components. Further, the first and second copolymers may comprise the same components, but have different functionalities, molecular weights, amounts of each component, and the like; this is sometimes referred to herein as different "ratios". Similarly, the first and second prepolymers each may have the same or different types of terminal functionality. In this embodiment, the resulting polyester tends to have random units derived from each of the prepolymers used. Thus, the present invention encompasses polyesters prepared by free radical polymerization of any number of different types of unsaturated polyester prepolymers described herein. The polymerization of two or more different prepolymers can be carried out using means standard in the art. Polyesters with different properties can be obtained using different prepolymers. In this way, polyesters can be formed which have the desired properties derived from the particular prepolymer used.

The polyesters according to the invention may have a branched or linear configuration. It will be appreciated by those skilled in the art that the polyester configuration will vary depending on the components used to form the prepolymer. For example, a prepolymer component having tri-functionality or greater will generally result in a branched prepolymer and, thus, a branched polyester. The linear prepolymer is prepared from a diol and a diacid. After the radical reaction, the resulting mixture may contain linear and branched structures. In certain embodiments, when producing branched polyesters, branching is primarily obtained by reaction of the unsaturation. In this embodiment, a small amount of branching may be promoted by using a tri-or tetra-hydric alcohol, but the amount of such compounds should be selected so as to avoid gelation. Other characteristics of the polyester will also vary depending on the composition of the prepolymer.

In certain embodiments, the unsaturation may be random along the backbone of the polyester prepolymer. In certain other embodiments of the present invention, there are no double bonds at the end of the prepolymer; that is, the polyester is "substantially free" of terminal unsaturation, e.g., less than 20%, e.g., less than 10% or less than 5%, less than 2% or less than 1%, or completely free of terminal unsaturation. In certain embodiments, the polyester prepolymer is actually a monoester. Such monoesters can be formed if a mono-alcohol is reacted with a polybasic acid, or a mono-acid is reacted with a polyhydric alcohol. Also, because there is often diversity in the formation of polymers, the reaction product comprising the prepolymer will have the primary configuration of a polyester (including diesters), and will also have a monoester. Thus, the "poly" ester prepolymers of the present invention will most likely actually comprise polyesters to a large extent, but also include mixtures of esters of monoesters.

As described above, because the polyester according to the present invention is formed primarily by free radical polymerization of unsaturation in an unsaturated polyester prepolymer, the terminal and/or pendant functional groups will remain largely unreacted in the primary reaction product comprising the polyester of the present invention. These unreacted functional groups can then be crosslinked using another component. Thus, the present invention differs from the prior art in that a gelled polyester, i.e., a broadly reticulated polyester, is formed.

In certain embodiments, it may be desirable to convert some or all of the hydroxyl functionality on the unsaturated polyester prepolymer (e.g., prior to polymerization) and/or on the branched polyester to another functionality. For example, the hydroxyl group can be reacted with a cyclic anhydride to provide acid functionality. Acid esters (acidesters) may also be formed.

In certain other embodiments, the unsaturated polyester prepolymer may include linkages in addition to ester linkages. For example, the polyester prepolymer may also include one or more urethane linkages (urethanelinkage). Urethane linkages can be introduced by reacting an excess of polyol prepolymer or unsaturated polyester polymer with a polyisocyanate. The resulting product will still have terminal functionality and unsaturation, but will have a urethane linkage in addition to the ester linkage. Other chemicals (chemistries) may also be introduced. Thus, in certain embodiments, the unsaturated polyester prepolymer includes one or more linkages in addition to ester linkages.

In certain embodiments, the unsaturated polyester prepolymer specifically excludes a prepolymer formed by reaction with an aldehyde; thus, in this embodiment, acyl succinic acid polyesters are specifically excluded. Similarly, in certain embodiments of the present invention, the use of aldehydes in solvents is specifically excluded.

In certain other embodiments, the use of unsaturated monomers other than the unsaturated polyacid/anhydride of the reaction product is excluded. For example, in certain embodiments, the use of vinyl monomers such as (meth) acrylates, styrene, vinyl halides, and the like, may be excluded. Thus, it will be understood that the branched polyesters of the present invention are not polyester/acrylic graft copolymers widely known in the art.

The polyesters of the present invention, formed primarily by free radical polymerization of unsaturated polyester prepolymers, result in polyesters having higher molecular weights and higher functionalities (per molecule) than conventional polyester resins. In certain embodiments, the increase in molecular weight of the polyester of the present invention relative to the molecular weight of the unsaturated polyester prepolymer may be very significant, while in other embodiments it may be only incremental. Gel permeation chromatography results have confirmed that the molecular weight of different linear and slightly branched polyester prepolymers can be significantly increased by free radical polymerization, resulting in higher molecular weight polyesters according to the invention. Typically, the ratio of the weight average molecular weight ("Mw") of the polyester of the present invention to the Mw of the unsaturated polyester prepolymer is from 1.2 to 500, and in some cases may be greater than 500. The weight average molecular weight of the polyesters of the invention is typically 600 to 10,000,000, for example 1,000 to 7,000,000, 10,000 to 4,000,000, 25,000 to 4,000,000, 50,000 to 4,000,000, 100,000 to 4,000,000, or a combination within any of these ranges. In certain embodiments, the Mw of the polyester is greater than 1,000, such as greater than 5,000, greater than 10,000, greater than 25,000, or greater than 50,000, or greater than 100,000. The molecular weight increase may be controlled by one or more factors, such as the type and/or amount of initiator used, Fn of the unsaturated polyester prepolymer, molecular weight and/or PDI of the unsaturated polyester prepolymer, temperature, and type and/or amount of solvent.

In addition to the molecular weights described above, the polyesters of the present invention also have higher functionality (per molecule) than would be expected from conventional polyesters having such molecular weights. The "average functionality" of the final polyester of the invention may be 2.0 or greater, for example 2.5 or greater, 10 or greater, 50 or greater, or even higher. "average functionality" as used in the context of this application refers to the average number of functional groups on the final polyester. The functionality of the final polyester is measured by the number of "additional" functional groups remaining unreacted in the final polyester and not by the unreacted unsaturation. It has been unexpectedly found that in certain embodiments, for example, the concentration of functional groups as measured by hydroxyl number, acid number, etc. of the final polyester prepolymer is similar to the concentration of functional groups of the polyester prepolymer. This indicates that the terminal and/or pendant functional groups on the prepolymer do not significantly participate in the polymerization reaction. Thus, in certain embodiments, the hydroxyl or acid value of the polyesters of the present invention may be in the same ranges as those given above for the prepolymer.

In certain embodiments, the polyesters of the present invention will have both high functionality, e.g., Mw ≧ 15,000, such as from 20,000 to 40,000, or greater than 40,000, and functionality ≧ 100 mgKOH/gm.

Because the polyester of the present invention includes functionality, it is suitable for use in coating formulations where the functional group is crosslinked with other resins and/or crosslinkers commonly used in coating formulations. The present invention therefore further relates to coating formulations comprising a polyester according to the invention and a crosslinker therefor. The crosslinking agent, or crosslinking resin or agent, may be any suitable crosslinking agent or crosslinking resin known in the art and will be selected to be reactive with the functional groups or groups on the polyester. It will be appreciated that the coating of the present invention is cured by reaction of the additional functionality and the crosslinker, but not by reaction of any unsaturation present in the crosslinkable polyester.

Non-limiting examples of suitable crosslinkers include phenol resins, amino resins, epoxy resins, isocyanate resins, blocked isocyanate resins, beta-hydroxy (alkyl) amide resins, alkylated urethane resins, polyacids, anhydrides (including polymeric anhydrides), organometallic acid-functionalized materials, polyamines, polyamides, aminoplasts, melamine formaldehyde polycondensates, polyurethane crosslinkers, and mixtures thereof. In certain embodiments, the crosslinking agent is a phenolic resin, which includes alkylated phenol/methane resins (functionality ≧ 3) and difunctional o-cresol/formaldehyde resins. These cross-linking agents are commercially available from Hexion as BAKELITE6520LB and BAKELITE7081 LB.

Suitable isocyanates include polyfunctional isocyanates. Examples of the polyfunctional polyisocyanate include aliphatic diisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate, and aromatic diisocyanates such as toluene diisocyanate and 4,4' -diphenylmethane diisocyanate. The isocyanate may be blocked or unblocked. Examples of other suitable polyisocyanates include isocyanurate trimers, allophanates, and uretdiones of diisocyanates and polycarbodiimides, such as those disclosed in U.S. patent application 12/056,304 filed 3.27.2008, the relevant portions of which are incorporated herein by reference. Suitable polyisocyanates are known in the art and are widely available commercially. For example, suitable polyisocyanates are disclosed in U.S. Pat. No. 6,316,119 at column 6, lines 19-36, the excerpt from this paragraph being incorporated herein by reference. Examples of commercially available polyisocyanates include DESMODURVP2078 and DESMODURN3390 sold by bayer corporation, and TOLONATEHDT90 sold by rhodia inc.

Suitable aminoplasts include condensates of amines and/or amides with aldehydes. For example, condensates of melamine with formaldehyde are suitable aminoplasts. Suitable aminoplasts are known in the art. Suitable aminoplasts are disclosed, for example, in U.S. Pat. No. 6,316,119 at column 5, lines 45-55, which extract is incorporated herein by reference.

In preparing the coatings of the present invention, the polyester and crosslinker may be dissolved or dispersed in a single solvent or a mixture of solvents. Any solvent that enables the formulation to be applied to a substrate may be used and these are known to those skilled in the art. Typical examples include water, organic solvents, and/or mixtures thereof. Suitable organic solvents include glycols, glycol ether alcohols, ketones, acetates, mineral spirits, naphthas and/or mixtures thereof. "acetate" includes glycol ether acetates. In certain embodiments, the solvent is a non-aqueous solvent. By "non-aqueous solvent" and like terms, it is meant that less than 50% of the solvent is water. For example, less than 10%, or even less than 5% or 2% of the solvent may be water. It will be understood that a mixture of solvents (including or not including water in an amount less than 50%) may constitute a "non-aqueous solvent". In other embodiments, the coating is aqueous or water-based. This means that 50% or more of the solvent is water. These embodiments have less than 50%, e.g., less than 20%, less than 10%, less than 5%, or less than 2% organic solvent.

In certain embodiments, the coating of the present invention further comprises a curing catalyst. Any curing catalyst for catalyzing a crosslinking reaction between the polyester resin and the crosslinking agent such as phenol resin may be used, and the catalyst is not particularly limited. Examples of such curing catalysts include phosphoric acid, alkylarylsulfonic acid (sulfononicacid), dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and dinonylnaphthalenedisulfonic acid. It will be appreciated that the coatings of the present invention cure primarily through crosslinking between the functional groups on the polyester and a suitable crosslinker or crosslinking resin, and not through reaction of any unsaturation remaining in the polyester.

If desired, the coating composition may include other optional materials known in the art in any component, such as colorants, plasticizers, abrasion resistant particles, antioxidants, hindered amine light stabilizers, UV light absorbers and stabilizers, surfactants, flow control agents, thixotropic agents, fillers, organic cosolvents, reactive diluents, catalysts, milling carriers, and other conventional adjuvants.

As used herein, the term "colorant" refers to any substance that imparts color and/or other opacity and/or other visual effect to the composition. The colorant can be added to the coating, such as discrete particles, dispersions, solutions, and/or flakes. A single colorant or a mixture of two or more colorants can be used in the coating of the present invention.

Exemplary colorants include pigments, dyes, and tints, such as those used in the paint industry and/or those listed in the DryColorManufaturers Association (DCMA), as well as special effect compositions. Colorants can include, for example, finely divided solid powders that are insoluble but wettable under the conditions of use. The colorant may be organic or inorganic and may be agglomerated or non-agglomerated. The colorant may be incorporated into the coating by grinding or simple mixing. The colorants can be incorporated into the coating by milling through the use of a mill base, such as an acrylic mill base, the use of which is familiar to those skilled in the art.

Exemplary pigments and/or pigment compositions include, but are not limited to, carbazole dioxazine crude pigment, azo compounds, monoazo compounds, azide compounds, naphthol AS, salt types (lakes), benzimidazolones, condensates, metal complexes, isoindolinones, isoindolines and polycyclic phthalocyanines, quinacridones, perylenes, tyloxanones, diketopyrrolopyrroles, thioindigo, anthraquinones, indanthrones, anthrapyrimidines, flavanthrones, pyranthrones, anthanthrones, dioxazines, triarylcarbonium, quinophthalone pigments (quinophthalones), diketopyrrolopyrrole red ("DPPBO red"), titanium dioxide, carbon black, carbon fibers, graphite, other conductive pigments and/or fillers, and mixtures thereof. The terms "pigment" and "colored filler" are used interchangeably.

Examples of dyes include, but are not limited to, those based on solvents and/or water, such as acid dyes, azo dyes, basic dyes, direct dyes, disperse dyes, reactive dyes, solvent dyes, sulfur dyes, mordant dyes, e.g., bismuth vanadate, anthraquinone, perylene aluminum, quinacridone, thiazole, thiazine, azo, indigoid dyes, nitro dyes, nitroso dyes, oxazines, phthalocyanine dyes, quinoline, 1, 2-stilbene, and triphenylmethane.

Examples of toners include, but are not limited to, pigments dispersed in water-based or water-dispersible carriers such as AQUA-CHEM896 available from Degussa, inc, charismacolor and maxitoni and trialcolor available from Dispersions division of Accurate, inc.

As noted above, the colorant can be in the form of a dispersion, including but not limited to a nanoparticle dispersion. Nanoparticle dispersions can include one or more highly dispersed nanoparticle colorants and/or colorant particles that produce a desired visible color and/or opaque and/or visual effect. The nanoparticle dispersion may include a colorant, such as a pigment or dye, having a particle size of less than 150nm, such as less than 70nm, or less than 30 nm. Nanoparticles can be produced by milling a starting organic or inorganic pigment using milling media having a particle size of less than 0.5 mm. Exemplary nanoparticle dispersions and methods for making them are shown in U.S. Pat. No. 6,875,800B2, which is incorporated herein by reference. Nanoparticle dispersions can also be produced by crystallization, precipitation, gas phase condensation (gashasescondensation), and chemical attrition (i.e., partial dissolution). To minimize re-aggregation of the nanoparticles in the coating, a dispersion of resin-coated nanoparticles may be used. As used herein, "dispersion of resin-coated nanoparticles" refers to a continuous phase in which discrete "composite microparticles" are dispersed, which includes nanoparticles and a resin coating on the nanoparticles. Examples of dispersions of resin-coated nanoparticles and methods for making them are consistent with the following references: U.S. application publication 2005-0287348A1, filed 24.2004, U.S. provisional application 60/482,167, filed 24.6.2003, and U.S. patent application 11/337,062, filed 20.1.2006, which are also incorporated by reference herein.

Exemplary special effect compositions that can be used include pigments and/or compositions that produce one or more appearance effects such as reflectivity, pearlescent appearance, metallic luster, phosphorescence, fluorescence, photochromism, photosensitivity, thermochromism, goniochromism and/or color change. Additional special effect compositions may provide other perceptible properties, such as opacity or texture. In a non-limiting embodiment, the special effect composition may produce a color shift such that the color of the coating changes when viewed at different angles. Exemplary color effect compositions are found in U.S. Pat. No. 6,894,086, which is incorporated herein by reference. Additional color effect compositions may include transparent coated mica and/or synthetic mica, coated silica, coated alumina, transparent liquid crystal pigments, liquid crystal coatings, and/or any composition in which interference is caused by refractive index differences within the material and not by refractive index differences between the surface of the material and air.

In certain non-limiting embodiments, photosensitive compositions and/or photochromic compositions (which reversibly change its color when exposed to one or more light sources) can be used in the coating compositions described herein. Photochromic and/or photosensitive compositions can be activated by exposure to radiation of a particular wavelength. When the composition becomes excited, the molecular structure changes, the changed structure exhibiting a new color that is different from the original color of the composition. Upon removal of the exposed radiation, the photochromic and/or photosensitive composition is able to return to the ground state, where it returns to the original color of the composition. In one non-limiting embodiment, the photochromic and/or photosensitive composition can be colorless in a non-excited state and exhibit color in an excited state. A complete color change can occur in milliseconds to minutes, for example 20 seconds to 60 seconds. Exemplary photochromic and/or photosensitive compositions include photochromic dyes.

In non-limiting embodiments, the photosensitive composition and/or photochromic composition can be associated with and/or at least partially bonded (e.g., by covalent bonds) to: polymeric materials of polymers and/or polymerizable components. In contrast to some coatings in which the photosensitive composition may migrate out of the coating and crystallize into the substrate, the photosensitive composition and/or photochromic composition (which is associated with and/or at least partially bonded to the polymer and/or polymerizable component) according to non-limiting embodiments of the present invention rarely migrates out of the coating. Exemplary photosensitive and/or photochromic compositions and methods of making them are shown in U.S. application 10/892,919 filed 7, 16, 2004.

In general, the colorant can be present in any amount sufficient to impart the desired visual and/or color effect. The colorant can comprise 1 to 65 weight percent, such as 3 to 40 weight percent, or 5 to 35 weight percent of the composition of the present invention, wherein weight percent is based on the total weight of the composition.

"wear resistant particles" are particles that, when used in a coating, will impart a level of wear resistance to the coating as compared to the same coating without the particles. Suitable wear resistant particles include organic and/or inorganic particles. Examples of suitable organic particles include, but are not limited to, diamond particles, such as diamond dust particles, and particles formed from carbide materials; examples of carbide particles include, but are not limited to, titanium carbide, silicon carbide, and boron carbide. Examples of suitable inorganic particles include, but are not limited to, silica; alumina; aluminum silicate; silicon-aluminum oxide; alkaline aluminum silicate; borosilicate glass; nitrides, including boron nitride and silicon nitride; oxides, including titanium dioxide and zinc oxide; quartz; nepheline (nepheline) black granite (syenite); in the form of zircon, such as zirconia; buddeluyite; and alien stone (eudialyte). Any size of particles may be used, as may mixtures of different particles and/or different size particles. For example, the particles can be microparticles having an average particle size of 0.1 to 50, 0.1 to 20, 1 to 12, 1 to 10, or 3 to 6 microns, or any combination within any of these ranges. The particles may be nanoparticles having an average particle size of less than 0.1 micron, such as from 0.8 to 500, from 10 to 100, or from 100 to 500 nanometers, or any combination within these ranges.

It is to be understood that the polyester and crosslinker of the invention may form all or part of the film-forming resin of the coating. In certain embodiments, one or more other film-forming resins may also be used in the coating. For example, the coating composition can comprise any of a variety of thermoplastic and/or thermosetting compositions known in the art. The coating composition may be a water-based or solvent-based liquid composition, or alternatively, may be in the form of solid particles, i.e. a powder coating.

Thermosetting or curable coating compositions typically comprise a film-forming polymer or resin having functional groups that can react with itself or with a crosslinker. Other film-forming resins can be selected from, for example, acrylic polymers, polyester polymers, polyurethane polymers, polyamide polymers, polyether polymers, polysiloxane polymers, polyepoxy polymers, epoxy resins, vinyl resins, copolymers thereof, and mixtures thereof. In general, these polymers may be any of these types of polymers prepared by any method known to those skilled in the art. The polymers may be solvent-based or water-dispersible, emulsified or of limited water solubility. The functional groups on the film-forming resin can be selected from any of a variety of reactive functional groups including, for example, carboxylic acid groups, amine groups, epoxy groups, hydroxyl groups, thiol groups, carbamate groups, amide groups, urea groups, isocyanate groups (including blocked isocyanate groups), mercapto groups, and combinations thereof. Suitable mixtures of film-forming resins can also be used in the preparation of the coating compositions of the present invention.

The thermosetting coating composition typically comprises a crosslinker that may be selected from any of the crosslinkers described above. In certain embodiments, the coating of the present invention comprises a thermosetting film-forming polymer or resin, and a crosslinker therefor, which may be the same or different from the crosslinker used to crosslink the polyester. In certain other embodiments, thermosetting film-forming polymers or resins having functional groups capable of reacting with themselves are used in a manner that renders the thermosetting coating self-crosslinking.

The coating of the present invention may comprise from 1 wt% to 100 wt%, for example from 10 wt% to 90 wt% or from 20 wt% to 80 wt%, of the polyester of the present invention, in wt% based on the total weight of coating solids. The coating composition of the present invention may further comprise from 0 wt% to 90 wt%, for example from 5 wt% to 60 wt% or from 10 wt% to 40 wt%, of a crosslinker for the branched polyester, in wt% based on the total weight of coating solids. If used, other components comprise from 1 wt% up to 70 wt% or more, based on the total weight of coating solids. Any number within any of these ranges is also within the scope of the invention.

The coating formulation according to the invention may have a significantly increased cure response and/or bending flexibility, and/or a significantly improved mechanical deformation and/or sterilization resistance compared to conventional polyesters.

In certain embodiments of the present invention, the polyester and/or coating comprising the polyester is substantially free of epoxy groups. As used herein, the term "substantially free of epoxy groups" means that the polyester resin and/or coating comprising the same is substantially free of epoxy groups, epoxy residues, oxirane rings or oxirane ring residues, adducts of bisphenol A, BADGE or BADGE, adducts of bisphenol F, BFDGE or BFDGE. In certain other embodiments of the present invention, the polyester and/or coatings comprising the same are substantially free of bisphenols or residues thereof, including bisphenol a, bisphenol F, BADGE, and BFDGE. The polyester and/or coating comprising the same may also be substantially free of polyvinyl chloride or related halide-containing vinyl polymers. By "substantially free" is meant that the polyester and/or coating comprises 10 wt.% or less, such as 5 wt.% or less, 2 wt.% or less, or 1 wt.% or less of the compounds described herein or otherwise known. Thus, it is to be understood that the polyesters and/or coatings according to the present invention may contain trace or small amounts of these components and still be "substantially free" of them. In still other embodiments, the polyester and/or coating comprising the same is completely free of one or more of any of the compounds listed or recited in this paragraph or derivatives thereof.

The coatings of the present invention can be applied to any substrate known in the art, such as automotive substrates, industrial substrates, packaging substrates, wood flooring materials and furniture, apparel, electronic devices including housings and circuit boards, glass and transparencies, and sporting equipment including golf balls, and the like. These substrates may be metallic or non-metallic, for example. The metal substrate comprises tin, steel, tin-plated steel, chrome-passivated steel, galvanized steel, aluminum foil, coiled steel, or other coiled metals. Non-metallic substrates include polymers, plastics, polyesters, polyolefins, polyamides, celluloses, polystyrenes, polyacrylics, poly (ethylene naphthalate), polypropylene, polyethylene, nylons, EVOH, polylactic acid, other "green" polymer substrates, poly (ethylene terephthalate) ("PET"), polycarbonate acrylonitrile butadiene styrene ("PC/ABS"), polyamides, wood, veneer, engineered wood materials, particle board, medium density fiberboard, cement, stone, glass, paper, cardboard, textiles, and synthetic and natural leathers, and the like. The substrate may be treated in some manner, for example to provide visual and/or color effects.

The coatings of the present invention may be applied by any process standard in the art, such as electrocoating, spraying, electrostatic spraying, dipping, roll coating, brush coating, roll coating, flow coating, extrusion, and the like.

The coating may be applied to a dry film thickness of 0.04 mils to 4 mils, such as 0.1 to 2 or 0.7 to 1.3 mils. In other embodiments, the coating may be applied to a dry film thickness of 0.1 mils or greater, 0.5 mils or greater, 1.0 mils or greater, 2.0 mils or greater, 5.0 mils or greater, or even greater. The coating of the present invention may be used alone or in combination with one or more other coatings. For example, the coatings of the present invention may or may not contain colorants and may be used as primers, basecoats, and/or topcoats. For substrates coated with multiple coatings, one or more of these coatings may be a coating as described herein.

It is to be understood that the coatings described herein may be single component ("1K") or multi-component compositions such as two-component ("2K") or more. A 1K composition is understood to mean a composition which, after production, during storage, etc., keeps all coating components in the same container. The 1K coating can be applied to the substrate and cured by any conventional means, such as heat and pressurized air. The coating of the present invention may also be a multi-component coating, which is understood to maintain the various components separately prior to application. As noted above, the coatings of the present invention may be thermoplastic or thermosetting.

In certain embodiments, the coating is a clear coating. Clear coatings are understood to be substantially clear coatings. Thus, the clearcoat can have a tint as long as it does not make the clearcoat opaque to any significant degree or otherwise affect the ability to see the underlying substrate. The clearcoats of the invention can be used, for example, in conjunction with pigmented basecoats. The clear coat may be modified by reaction with a urethane.

In certain other embodiments, the coating is a primer. The primer is typically colored; that is, it will impart some type of color and/or other visual effect to the substrate to which it is applied.

The coating compositions of the present invention may be applied alone or as part of a coating system capable of being deposited onto different substrates as described herein. Such coating systems typically include a plurality of coatings, for example two or more. The coating layer is typically formed when the coating composition deposited onto the substrate is cured by methods known in the art (e.g., by heating). The coating compositions described above can be used in one or more of the coating layers described herein.

In conventional coating systems used in the automotive industry, a preheated substrate is coated with an electrodepositable coating composition. After the electrodepositable coating composition is cured, a primer-surfacer coating composition is applied to at least a portion of the electrodepositable coating composition. The primer-surfacer coating composition is typically applied to the electrodepositable coating and cured prior to applying a subsequent coating composition over the primer-surfacer coating composition. However, in some embodiments, the substrate is not coated with an electrodepositable coating composition. Thus, in these embodiments, the primer-surfacer coating composition is applied directly to the substrate. In other embodiments, the primer-surfacer coating composition is not used in a coating system. Thus, the color-imparting basecoat coating composition may be applied directly onto the cured electrodepositable coating composition.

In certain embodiments, the clearcoat is deposited directly onto at least a portion of the basecoat coating. In certain embodiments, the substantially clear coating composition can include a colorant, but in an amount that does not render the clear coating composition opaque (not substantially clear) after curing. In some cases, the cured composition has a BYK haze value of less than 50, can be less than 35, and often is less than 20, as measured using a BYK haze glossmeter available from BYKChemieUSA.

The coating composition of the present invention can be used in the primer and/or the clear coat as described above.

In certain embodiments, the coatings of the present invention may be used in a single coating system. In a single coat coating system, a single coating layer is applied to a substrate (which may or may not be preheated), which may include one or more layers (as described above) either an electrodepositable coating layer, or a primer-surfacer coating layer. In certain embodiments, the coating compositions of the present invention are used in a single coat coating system.

The coatings of the invention are also particularly suitable for use as packaging coatings. The application of various pretreatments and coatings to packaging has been well established. Such pretreatments and/or coatings may be used in the context of metal cans, where the treatments and/or coatings are used to retard or inhibit corrosion, provide decorative coatings, provide ease of handling during production, and the like. A coating may be applied to the interior of the can to prevent the contents from contacting the metal of the container. Contact between the metal and the food or beverage can, for example, lead to corrosion of the metal container, which can then contaminate the food or beverage. This is true when the contents of the canister are acidic. The coating applied to the interior of the metal also helps prevent corrosion of the can top, which is the area between the product can filling line and the can lid; top corrosion is a significant problem for foods with high salt content. Coatings may also be applied to the exterior of metal cans, and certain coatings of the present invention are particularly suitable for use with coil metal stock, such as coil metal stock used to produce can ends ("can end stock"), and end caps (endcaps) and closures ("cap/closure stock"). Because the coatings designed for can end stock and cover/baffle stock are typically applied prior to cutting and stamping the coil metal stock into sheets, they are typically flexible and ductile. For example, the feedstock is typically double coated. The coated metal stock is then stamped. For can ends, a tab opening score is then formed in the metal and the tab is joined to a separately made pin. The ends are then attached to the can body by an edging process. A similar process is performed on an easy open can end. For easy open can ends, a score substantially around the circumference of the lid enables the lid to be easily opened and removed from the can, typically by pulling on a tab. For the cover/baffle, the cover/baffle stock is typically coated, such as by roll coating, and the cover and baffle are stamped from the stock; however, the cover/baffle may be applied after molding. Can coatings that implement relatively stringent temperature and/or pressure requirements should also be resistant to cracking, impact, corrosion, hazing, and/or blistering.

Accordingly, the present invention further relates to a package at least partially coated with any of the above-described coating compositions. A "package" is anything used to hold another item. It may be made of metal or non-metal, such as plastic or laminate, and may be in any form. In certain embodiments, the package is a laminated body tube. In certain embodiments, the package is a metal can. The term "metal can" includes any type of metal can, container, or any type of receptacle or portion thereof for holding items. One example of a metal can is a food can; the term "food can" as used herein refers to a can, container or any type of receptacle or portion thereof for holding any type of food and/or beverage. The term "metal can" specifically includes food cans and also specifically "can ends" which are typically stamped from can end stock and used in conjunction with beverage packaging. The term "metal can" also includes in particular metal lids and/or closures, such as bottle caps, screw tops and lids of any size and pull-caps and the like. The metal cans can be used to hold other items including, but not limited to, personal care products, insecticidal sprayers, spray paint, and any other compound suitable for packaging in aerosol cans. These cans may include "two-piece cans" and "three-piece cans," as well as drawn and ironed one-piece cans; such unitary canisters are common in aerosol product applications. Packages coated according to the present invention may also include plastic bottles, plastic tubes, sheets and flexible packages such as those produced from PE, PP, PET and the like. The package may hold, for example, food, toothpaste, personal care products, and the like.

The coating may be applied to the interior and/or exterior of the package. For example, the coating may be roll coated onto metal used to produce two-piece food cans, three-piece food cans, can end stock, and/or lid/baffle stock. In certain embodiments, the coating may be applied to the coil or sheet by roll coating; the coating is then cured by heat or radiation and the can end is stamped to produce the final product, i.e., the can end. In other embodiments, the coating is applied to the can ends as an edge coating; the coating may be performed by roll coating. The edge coating acts to reduce friction to improve handling during continuous production and/or processing of the can. In certain embodiments, the coating is applied to the cover and/or baffle; the coating includes, for example, a colored finish applied to the lid at the lid/baffle and/or post, particularly those with score joints at the lid base, pre-and/or post-formed protective varnishes. Decorative can stock can also be partially externally coated with the coatings described herein, and decorative coated can stock is used to form various metal cans.

Packaging according to the present invention may be coated with any of the above compositions by any means known in the art such as spraying, roll coating, dip coating, flow coating, and the like; when the substrate is electrically conductive, the coating may also be applied by electrocoating. Suitable application means may be determined by those skilled in the art depending on the type of package to be coated and the functional type of coating used. If desired, the above-described coating can be applied to a substrate in single or multiple layers by multiple stages of heating between each layer application. After the substrate is coated, the coating composition can be cured by any suitable means.

As used herein, unless otherwise specified, all numbers such as those expressing values, ranges, amounts or percentages are to be considered as being preceded by the word "about", even if the term does not expressly appear. Moreover, any numerical range recited herein is intended to include all lower ranges subsumed therein. Singular encompasses plural and vice versa. For example, although "a" polyester, "an" unsaturated polyester prepolymer, "an" end/side functional group, and "a" crosslinker are used herein, one or more of these components and any other components may be used. As used herein, the term "polymer" refers to oligomers as well as homopolymers and copolymers, and the prefix "poly" refers to two or more. The terms "include", "including" and the like mean including but not limited to. Where ranges have been given, ranges and/or numerical endpoints within these ranges can be incorporated within the scope of the present invention.

Examples

The following examples are intended to illustrate the invention but should not be construed as limiting the invention in any way.

EXAMPLE 1 preparation of unsaturated polyester prepolymer

Four different unsaturated polycondensation prepolymers according to the invention were prepared. The reaction compositions used to prepare the unsaturated polyester prepolymer are shown in table 1 below. Dibutyl tin oxide was used to promote esterification and, in some prepolymers, a small amount of the free radical inhibitor methyl hydroquinone (MEHQ) was added to extend the usable shelf life of the unsaturated polyester prepolymer formed therefrom.

TABLE 1

In table 1 above, MEG is monoethylene glycol; 1,2PD is 1, 2-propanediol; 1,3BD is 1, 3-butanediol; TMP is threeA methylol propane; TPA is terephthalic acid; IPA is isophthalic acid; CHDA is 1, 4-cyclohexanedicarboxylic acid; MAN is maleic anhydride; AA is adipic acid; DBTO is dibutyltin oxide; MEHQ is methyl hydroquinone; and SnCl₂Is stannous chloride.

The above prepolymer was prepared as follows.

Prepolymer A

A. The reactor was charged with 1,3BD, 1,2PG, TMP, TPA, IPA and DBTO catalyst.

B. Heated to a maximum temperature of 240 ℃ under nitrogen bubbling and treated to an acid number of less than 10 for clarity of the resin. The maximum head temperature (maxheadtemperature) of the packed column was maintained at 102 ℃, thereby minimizing the loss of glycol.

C. Cooled to 140 ℃ and sampled to measure the hydroxyl number. Hydroxyl number was adjusted to 178 net (net) using 1,3 BD. Conditioning in diol at 180 ℃ for 2 hours.

D. Cooled to 140 ℃ and filled with AA. A maximum reactor temperature of 170 ℃ was used and again heated to distillation to give a final acid number of 40-42.

E. Cooled to 110 ℃ and charged with butanediol as the solvent for dilution.

Prepolymer B

A. The reactor was charged with 1,3BD, 1,2PG, TMP, TPA, IPA and DBTO catalyst.

B. Heated to a maximum temperature of 240 ℃ under nitrogen bubbling and processed to an acid number of less than 10 for clarity of the resin. The maximum head temperature of the packed column was maintained at 102 ℃ to minimize glycol loss.

C. Cooled to 140 ℃ and sampled to measure the hydroxyl number. The hydroxyl number was adjusted to 176 net using 1,3 BD. The treatment was carried out by conditioning in diol at 180 ℃ for 2 hours.

D. Cooled to 140 ℃ and charged with AA. A maximum reactor temperature of 160 ℃ was used and then heated to distillation to give a final acid number of 40-42.

E. Cooled to 110 ℃ and charged with the solvent for dilution, butanediol, which contains MEHQ inhibitor.

Prepolymer C

A. The reactor was charged with 1,3BD, 1,2PG, TMP, TPA, IPA and DBTO catalyst.

B. Heated to a maximum temperature of 240 ℃ under nitrogen bubbling and treated to an acid number of less than 10 for clarity of the resin. The maximum head temperature of the packed column was maintained at 102 ℃ to minimize glycol loss.

C. Cooled to 140 ℃ and charged with MAN. The maximum reactor temperature of 200 ℃ was used again to bring about distillation and thus an acid number of 60 to 70.

D. Cooled to 120 ℃ and sampled to measure the hydroxyl number. The hydroxyl number was adjusted to 40 net using 1,3 BD. The treatment was carried out by conditioning in diol at 120 ℃ for 2 hours.

E. The maximum reactor temperature of 200 ℃ was used to reheat to distillation, resulting in a final acid number of 40-42.

F. Cooled to 110 ℃ and charged with butanediol as a diluent solvent.

Prepolymers D and E

A. The reactor was charged with 1,3BD, MEG, CHDA, IPA, MAN, MEHQ and DBTO in that order.

B. Heated to a maximum temperature of 200 ℃ under nitrogen bubbling and treated to transparency (acid number about 40-50).

C. The reactor was cooled to 180 ℃ and a sample was taken to measure the hydroxyl number. The hydroxyl numbers (polymer D target hydroxyl number 40-42, polymer E target hydroxyl number 150-153) were adjusted as needed using 1,3 BD.

D. It was heated again to 195 ℃ and 200 ℃ and azeotropic distillation was established by careful addition of xylene.

E. The treatment is carried out until the final acid value is 1-3.

F. Cooled to 135 ℃ and diluted with xylene solvent.

Prepolymer F

A. The reactor was charged with 1,3BD, MEG, TMP, IPA, CHDA (43% of charge) and SnCl₂A catalyst.

B. Heated to a maximum temperature of 230 ℃ under nitrogen sparge and treated to an acid number of less than 10 for clarity of the resin. The maximum head temperature of the packed column was maintained at 102 ℃ to minimize glycol loss.

C. Cooled to 140 ℃ and charged with MeHQ, CHDA (57% of charge), MAN. A maximum reactor temperature of 200 ℃ was used and heated to distillation to an acid number of 70-80.

D. Cooled to 120 ℃ and sampled to measure the hydroxyl number. The hydroxyl number was adjusted to-34.7 net using 1,3 BD. The treatment was carried out at 140 ℃ for 2 hours in glycol.

E. Further heated to distillation and azeotropic distillation was established by careful addition of xylene at 195 ℃ and 200 ℃. Treating until the final acid value is 45-50.

F. Cooled to 110 ℃ and charged with the diluent solvents butanediol and propylene glycol monomethyl ether.

TABLE 2 (calculated parameters)

In Table 2 above, OHV is the total hydroxyl number (mg potassium hydroxide/g prepolymer); AV is the acid number (mg potassium hydroxide/g prepolymer); mn is the number average molecular weight; maleic acid/chain is the average number of double bonds per unsaturated polyester prepolymer chain; and Tg is the glass transition temperature.

The acid value was determined as follows. The sample is dissolved in a suitable solvent. The standard solvent was DMF, or a mixture of xylene/methyl Proxitol 3/1. The indicators used were thymolphthalein (thymolphthalein) for DMF solvent and phenolphthalein for xylene/methyl prototol. The resin solution was titrated to endpoint using 0.1N alcoholic KOH.

The hydroxyl number was determined as follows. A resin sample was dissolved in a precisely known solvent that did not contain hydroxyl groups, but a stoichiometric excess of acetic anhydride dissolved in butyl acetate was added. The solution is then heated so that the acetic anhydride reacts with any hydroxyl groups in the resin. The remaining excess acetic anhydride is then hydrolyzed using pyridine and water. Blank titrations were performed without using a resin sample. The blank and resin solution samples were titrated with a methanolic solution of KOH to determine the net hydroxyl value.

Example 2 preparation of polyester by free radical polymerization of unsaturated polyester prepolymer

Using the unsaturated polyester prepolymer of example 1, polyesters were prepared from their double bonds by radical polymerization of the chains of the unsaturated polyester prepolymer. Unless otherwise indicated, the free radical polymerization step in the following examples was carried out under stirring at 100 ℃ while nitrogen purging was carried out, using tert-butyl peroxy-2-ethylhexanoate as free radical initiator (which has a calculated half-life of 22.9 minutes at 100 ℃). The reaction mixture was held at this temperature for 5 hours after the addition of the initiator. Tests were carried out on the polyester obtained, and the tests and the results obtained are discussed below.

(a) Slightly branched polyesters with calculated maleic functionality/prepolymer chain <1

Free radical polymerization is carried out using two different methods, the first involving the single addition of the free radical initiator and the second involving the multiple addition of the initiator at intervals during the course of the polymerization reaction.

(i) One-time addition of initiator

By reacting at 0.1, 0.2, 0.3 and 0.9:1 initiator radicals: a series of polyester resins were prepared by adding a 50% solution of initiator in butanediol to a 50% solution of branched polyester prepolymer B in butanediol, with the molar ratio of maleic double bonds (R x: C = C). The polyester resins obtained were numbered as polyester 1, polyester 2, polyester 3 and polyester 4 (which were gelled), respectively.

In the preparation of each resin, samples were taken for Gel Permeation Chromatography (GPC) analysis after 1 hour of initiator addition and at the end of the process.

(ii) Multiple addition of initiator

Polyester 5 was prepared as follows: a 50% solution of initiator in butanediol was added to a 50% solution of branched prepolymer B (see tables 1 and 2 above) in butanediol, initiator: the total proportion of maleic double bonds was 0.5:1R C = C, but instead of adding all initiator at once, the initiator was divided into 5 equal amounts of 0.1:1R C = C with 1 hour intervals between each initiator addition. Resin samples were taken for GPC analysis after 1 hour of each initiator addition. These samples were labeled as polyesters 5a, 5b, 5c, 5d and 5e, respectively.

(iii) Control Polymer

Two control polymers were prepared for GPC comparison:

polyester 6: a 50% solution of prepolymer B in butanediol was heated to 100 ℃ and held without initiator for three hours.

Polyester 7: mixing prepolymer A (A)SaturatedPolyester resin with similar calculated number average molecular weight Mn, OHV and AV as a 50% solution of prepolymer B) in butanediol was heated to 100 ℃ and a 50% butanediol solution of initiator (0.3:1) in an amount equal to that in the preparation of polyester 5C of example 2(a) (ii) above was added in three portions at 1 hour intervals.

(b) Higher maleic functionality/chain

To investigate the effect of higher maleic functionality per chain, polyester 8 was prepared using slightly branched polyester prepolymer C at a ratio of R x: C = C of 0.1:1 under the same conditions as used in example 2(a), except that a 60% process solids value was used. After 10 minutes of initiator addition, the polymer started to gel.

Second polymeric polyester 9 was prepared under the same conditions except that the initiator was added to prepolymer C in one shot with a significantly reduced R x C = C to 0.003: 1; samples were taken for GPC 2 hours after initiator addition. The initiator was further added twice at 2 hour intervals at a ratio of R x C = C of 0.006:1 and sampled 2 hours after each addition. The collected samples were labeled as polyester 9a, 9b and 9c, respectively.

(c) Linear polyesters with different starting molecular weights

To investigate the effect of starting polyester chain length, the following resins were prepared for GPC analysis using the same conditions as in example 2(a) (i) with a 0.1:1 ratio of R x C = C, and a mixture of xylene and butanediol as solvents:

● polyester 10-calculated Mn2500 using prepolymer D

● polyester 11-calculated Mn726 using prepolymer E

(d) Different processing temperatures and different initiator types

To demonstrate that this free radical polymerization can be carried out at different process temperatures and with different initiator types, the following resins were also prepared using prepolymer D (see tables 1 and 2 above) at a ratio R x: C = C of 0.1:1 and then analyzed by GPC:

● polyester 12: the polymerization was carried out at 100 ℃ with the initiator tert-butyl peroxy-2-ethylhexanoate, the calculated initiator half-life being 22.9 minutes, the total amount of initiator added in three equal portions at 2 hour intervals, and a sample was taken 2 hours after the final addition.

● polyester 13: the polymerization was carried out at 120 ℃ with the initiator tert-butyl peroxy-2-ethylhexanoate, a calculated initiator half-life of 2.95 minutes, the total amount of initiator added in three equal portions at 2 hour intervals, and a sample was taken 2 hours after the final addition.

● polyester 14: the polymerization was carried out at 80 ℃ with the initiator tert-butyl peroxy-2-ethylhexanoate, the calculated initiator half-life being 223.6 minutes. Due to the much longer initiator half-life, initiator was added in one portion, and after initiator addition, the resin was held at 80 ℃ for 8 hours before sampling.

● polyester 15: the polymerization was carried out at 135 ℃ using tert-butyl peroxybenzoate as initiator, the calculated initiator half-life being 13.0 minutes, the total amount of initiator added in three equal portions at 2 hour intervals, and samples taken 2 hours after the final addition.

● polyester 16: the polymerization was carried out at 100 ℃ using benzoyl peroxide as initiator, the calculated initiator half-life being 22.3 minutes, the total amount of initiator added in three equal portions at 2 hour intervals, and samples taken 2 hours after the final addition.

(e) Polyesters prepared in aqueous mixtures

To demonstrate that this free radical polymerization can be carried out in an aqueous mixture, prepolymer F was used to prepare the following resins (see tables 1 and 2 above). Prepolymer F solution (43.2gm) was mixed with dimethylaminoethanol (2.4gm) and then water (54.4gm) was added and the resulting mixture was used in the polymerization. The polymerization was carried out at 90 ℃ with an R x C = C ratio of 0.1:1 using the initiator tert-butyl peroxy-2-ethylhexanoate, the polymerization was carried out with a calculated initiator half-life of 69.4 minutes, the total amount of initiator added in 1 hour of the feed was kept at 90 ℃ for 2 hours after the addition was completed. Samples were taken at 15 minute intervals during the feed and then at 1 and 2 hour intervals after the feed. Details of these samples 17a, 17b, 17c, 17d, 17e and 17f are given in table 3 below, all showing evidence of an increase in molecular weight from the initial prepolymer.

For the polymers prepared in examples 2(a) to 2(d) above, the weight average molecular weight Mw was determined by GPC (reference polystyrene). The Mw increase factor was calculated compared to each initial prepolymer. These results are listed in table 3 below.

TABLE 3

Note 1 prepolymer D' is a second prepolymer D

Since it was confirmed that the radical polymerization process did not affect other functional groups, hydroxyl and carboxyl groups, the hydroxyl and acid values (0.1: 1R: C = C) of polyester 12 were compared with the starting unsaturated polyester prepolymer D'. The results, given as mgKOH/g of resin, are as follows:

OHV Net AV Total OHV

Prepolymer D' 40.22.142.3

Polyester 1240.02.542.5

The results show that the hydroxyl value does not decrease after radical polymerization, but the acid value increases slightly. However, gas chromatography of polyesters polymerized using higher levels of t-butyl peroxy-2-ethylhexanoate has shown the presence of t-butanol and 2-ethylhexanoic acid in the final polymer. The slight increase in acid number of polyester 12 is more likely due to the formation of 2-ethylhexanoic acid from t-butyl peroxy-2-ethylhexanoate in the process rather than a change in carboxyl groups on the prepolymer.

The GPC results listed in table 3 above confirm that the addition of a free radical initiator to an unsaturated polyester prepolymer according to the present invention produces a polyester having a significantly increased weight average molecular weight Mw over the starting polymer. Together with the fact that the other functional groups on the prepolymer remain relatively unaffected, as explained above, the radical polymerization of the unsaturated polyester prepolymer described in the present invention will enable the obtainment of polyesters having a combination of average functionality and molecular weight, which has not previously been obtainable by other conventional methods. The starting prepolymers may be linear, branched, have different starting molecular weights (chain lengths) and have a different number of double bonds per chain, giving different polyesters obtained according to the invention, and in all cases an increased molecular weight is observed. Also, this increase in weight average molecular weight Mw can be obtained using different types of free radical initiators and at different temperatures.

The weight average molecular weights Mw of the two control resins, polyester 6 (without initiator) and polyester 7 (without double bonds in the starting polyester prepolymer), did not change, indicating that the polymerization is specific for the unsaturated groups in the starting polyester prepolymer in the presence of a free radical initiator, and is not the reason for the process conditions.

Whether the initiator is added in a single addition or in multiple additions, the weight average molecular weight Mw increases with increasing initiator level. However, too high an initiator level resulted in resin gelation, as evidenced in polyester 4(0.9:1R x C = C ratio). Likewise, a higher average number (2.81) of double bonds per prepolymer C chain requires significantly less initiator to reach the weight average molecular weight Mw, almost reaching the gel point (see polyester 9). This indicates that the increase in the weight average molecular weight Mw is also influenced by the average number of double bonds per prepolymer chain.

Example 3 packaging coating of test resin

Some of the free-radically polymerized polyesters prepared in examples 2(a) to 2(d) above, together with various starting polyester prepolymers, were reacted with BAKELITE6520LB, an alkylated phenol/formaldehyde resin (functionality 3) and BAKELITE7081LB, an un-alkylated o-cresol/formaldehyde resin (difunctional), at different levels of phenol resin and at different levels of phosphoric acid catalyst, to give a series of coating formulations according to the present invention. The amounts of resin and phosphoric acid catalyst used and the solvent used are given in the results given below.

The coating formulation thus prepared was applied by wire bar coater to 0.22mm tin plated panels and cured in a laboratory oven. The cure time and temperature were selected to be 4 to 12 minutes and 160 to 200 ℃ with a center point of 8 minutes and 180 ℃, respectively.

The cured panels of the different samples were subjected to the following tests which are commonly used for evaluating packaging coatings:

● Methyl Ethyl Ketone (MEK) rub-for cure and chemical resistance comparison

● wedge bends (WedgeBends) -detection of bend flexibility, film integrity and film network

● Box stretching-for comparison of mechanical deformation

● Sterilization- (90min, at 121 ℃, in water and steam)

MEK rubbing: the panel of cured film was rubbed back and forth in a linear direction (calculated as 1 double rub) using a piece of degreased cotton (cottonwood) impregnated with MEK until the coating had been removed, or up to 200 double rubs. The number of double rubs was recorded.

Wedge bending: a 10cm long by 4cm wide strip of coated panel was formed into a U-shape on a 6mm metal bar, the U-shaped piece was then placed in a conical depression and a 2kg metal weight was dropped onto the test piece from a height of 60cm, forming a wedge. After 2 minutes into the acidified copper sulfate solution, the test piece was rinsed in tap water and visually evaluated for any cracking. The length of the film along this bend without rupture was recorded as a percentage of the total length of the test piece.

Stretching the box: the coated panels were placed in a punch press to produce small square boxes (21 mm deep). The corners of the box were visually evaluated for any paint damage. The results are reported as the average depth of stretch without damage.

And (3) sterilization: the coated panels were placed in a lidded container part filled with tap water, with one half of the panel submerged and the other side of the panel above the water line. The vessel was then placed inside an autoclave and heated to the temperature and duration described. The coating was evaluated for any film defects and scored from 0-10 (0= no defects, 10= severe coating damage).

To evaluate the possible use of the free-radically polymerized resin formulation in water-based coatings, polyester 2, polyester 3 and starting prepolymer B were neutralized with various amounts of dimethylethanolamine and diluted with deionized water.

Test results of packaging coating

The tests were carried out on three resins: prepolymer B (starting polyester prepolymer), polyester 2(0.2: 1R: C = C) and polyester 5(0.5: 1R: C = C) (see tables 1 to 3 above) to measure the properties of the polyester of the invention obtained by free radical polymerization of the starting polyester prepolymer, measured with respect to the starting polyester prepolymer. The tests performed included crosslinking the polyester using two alternative phenolic resins, coating the resulting formulation on a test substrate, curing of the coating formulation, and then comparing the performance of the coatings using standard industry techniques.

(a) Response to catalyst

The catalysts used were: phosphoric acid-millimoles per 100g of resin solids (mmolprphr)

Curing conditions are as follows: 8 minutes at 180 ℃

Base material: 0.22mm2.8/2.8 tin-plated steel

Film weight: 5-6 g/m²(gsm)

Phenol resin: BAKELITE6520LB (functionality ≧ 3)

BAKELITE7081LB (functionality =2)

The content of phenols: 6520LB 25.5% of total binder solids

78081LB 19.3% of total binder solids

And (3) testing: MEK double rub-number of rubs before film removal

Wedge bend-coating without any break%

The results are shown in tables 4 and 5 below.

TABLE 4

TABLE 5

Further tests were also carried out using different amounts of phenol resin.

The catalysts used were: 5 mmole phr phosphoric acid

Curing conditions are as follows: 8 minutes at 180 ℃

Base material: 0.22mm2.8/2.8 tin-plated steel

Film weight: 5-6gsm

Phenol resin: BAKELITE6520LB (functionality ≧ 3)

BAKELITE7081LB (functionality =2)

And (3) testing: MEK double rub-number of rubs before film removal

Wedge bend-coating without any break%

Box draw-through mm (maximum draw 21mm)

The results are shown in tables 6 and 7.

TABLE 6

TABLE 7

As is evident from the MEK rub and wedge bend test results shown in tables 4 and 5, the cure and bending flexibility, which is an indication of the extent of film network structure, improve significantly with increasing molecular weight and functionality/chain of the resin.

For the coatings obtained from polyester 5, which has the highest molecular weight of the polyfunctional phenols, lower levels of phenolic crosslinker are required to obtain an improvement in the film network structure due to the increased functionality/chain in the molecular weight enhanced polyesters of the present invention (see table 6).

The box tensile flexibility of the coatings obtained using the bifunctional phenol crosslinker and the same polyester was also significantly better than the box tensile flexibility obtained using the bifunctional phenol and the lower molecular weight polyester prepolymer 2 (see table 7).

(b) Sterilization resistance (90 min/121 ℃ in tap water)

The catalysts used were: 5 mmole phr phosphoric acid

Curing conditions are as follows: 4-12 minutes at 160-

Base material: 0.22mm2.8/2.8 tin-plated steel

Phenol resin: BAKELITE6520LB (functionality ≧ 3)

BAKELITE7081LB (functionality =2)

The samples giving the highest wedge bend results of the above polyester resins were coated and cured at different temperatures for different times. The coated panel was placed in a Kilner jar with the lower half of the panel immersed in tap water and the upper half of the panel above the water line and sterilized in an autoclave.

And (3) testing: 90 minutes at 121 ℃ in tap water

Visually inspecting vapor exposed and submerged panels

0= no defects, 10= complete film damage

Test resin:

prepolymer B: 14.6%6520LB (sample B-10) was used

32.4%7081LB was used (sample B-17)

Polyester 2: 25.5%6520LB (samples 2-11) was used

19.3%7081LB (samples 2-16) was used

Polyester 5: 25.5%6520LB (samples 5-11)

19.3%7081LB (samples 5-16) was used

The results are shown in tables 8 and 9.

TABLE 8

TABLE 9

Polyester 5, the highest molecular weight and functionality/chain resin, gave a significant improvement in submerged phase performance. Curing at 12 minutes/200 ℃ using a multifunctional phenol actually passed the sterilization test, while the lower molecular weight resin formed using the polyester prepolymer failed either in the vapor phase or the submerged phase.

(c) Conversion to water-based polyesters

The calculated AV for prepolymer B, polyester 2 and polyester 5 was all 42. Starting prepolymer B required 70% neutralization with dimethylethanolamine to produce a clear solution in deionized water. However, the high molecular weight polyesters of the present invention, polyester 2 and polyester 5, when diluted with the same amount of deionized water, require only 50% neutralization to obtain a clear solution. This further confirms that the number of acid groups/chains has increased due to free radical polymerization.

While specific embodiments of the invention have been described for purposes of illustration, it will be apparent to those skilled in the art that numerous changes in the details of the invention may be made without departing from the invention as defined in the appended claims.

Claims (27)

1. A crosslinkable polyester prepared by free radical polymerization of the double bonds of a first unsaturated polyester prepolymer and the double bonds of a second unsaturated polyester prepolymer, wherein the number average functionality of the unsaturation in the prepolymer is from 0.05 to 25,

wherein M of the crosslinkable polyester_W≥1,000。

2. The polyester of claim 1, wherein the number average functionality of the unsaturation in the prepolymer is from 0.1 to 5.0.

3. The polyester of claim 1 wherein M of said crosslinkable polyester_W≥10,000。

4. The polyester of claim 1 wherein M of said crosslinkable polyester_W≥50,000。

5. The polyester of claim 1 wherein the crosslinkable polyester has an average functionality of 2 or greater.

6. The polyester of claim 1, wherein the functional groups on the crosslinkable polyester comprise hydroxyl groups, acid groups, or combinations thereof.

7. The polyester of claim 1, wherein said prepolymer is prepared by polycondensation of a) a polyacid, and/or esters and/or anhydrides thereof, and b) a polyol, wherein a and/or b are unsaturated.

8. The polyester of claim 7, wherein the polybasic acid comprises maleic acid, fumaric acid, and/or itaconic acid, and/or esters and/or anhydrides thereof.

9. The polyester of claim 8, wherein the only unsaturation in the polyester prepolymer is derived from the polyacid.

10. The polyester of claim 1, wherein the prepolymer comprises an aromatic polyacid.

11. The polyester of claim 10, wherein said aromatic polyacid comprises terephthalic acid, isophthalic acid, and/or trimellitic anhydride.

12. The polyester of claim 1, wherein the polyester comprises a copolymer of a first unsaturated polyester prepolymer and a second unsaturated polyester prepolymer, wherein the second unsaturated polyester prepolymer comprises one or more components different from the first polyester prepolymer.

13. The polyester of claim 1, wherein the polyester comprises a copolymer of a first unsaturated polyester prepolymer and a second unsaturated polyester prepolymer, wherein the second unsaturated polyester prepolymer comprises the same components as the first polyester prepolymer but in different proportions of the polyester prepolymer components.

14. The polyester of claim 1, wherein the polyester is not an acyl succinic acid polyester.

15. The polyester of claim 1, wherein said polyester does not comprise (meth) acrylates or residues thereof.

16. The polyester of claim 1, wherein said polyester is branched.

17. The polyester of claim 1, wherein said polyester is linear.

18. A coating, comprising:

a) the polyester of claim 1; and

b) a crosslinking agent therefor.

19. The coating of claim 18, wherein the coating is liquid.

20. The coating of claim 19, wherein the coating is solvent-based.

21. The coating of claim 19, wherein the coating is water-based.

22. The coating of claim 18, wherein the coating is a powder.

23. A substrate at least partially coated with the coating of claim 18.

24. The substrate of claim 23, wherein the substrate is metallic.

25. The substrate of claim 23, wherein the substrate is non-metallic.

26. A package at least partially coated with the coating of claim 18.

27. The package of claim 26, wherein the package is a metal can.