EP0221956A1

EP0221956A1 - Acrylic acid esterification and photopolymerizable compositions containing the acrylated products

Info

Publication number: EP0221956A1
Application number: EP19860903091
Authority: EP
Inventors: George Pasternack
Original assignee: DeSoto Inc
Current assignee: DeSoto Inc
Priority date: 1985-05-22
Filing date: 1986-05-05
Publication date: 1987-05-20
Also published as: WO1986007073A1

Abstract

Procédé de préparation d'un produit de réaction d'un ester à insaturation éthylénique consistant a) à mélanger un composé à fonction époxyde, notamment un polyépoxyde, avec un acide monocarboxylique à insaturation alpha, béta-monoéthylénique, tel que l'acide acrylique, en présence d'une quantité catalytique d'un produit d'addition d'amine tertiaire d'une amine aliphatique ou aromatique possédant au moins un atome d'hydrogène amino, tel que la diéthylamine, avec i) un composé à insaturation éthylénique dont la liaison éthylénique est polarisée et qui peut subir une réaction d'addition du type Michael, ou ii) un composé époxyde; et b) à maintenir ce mélange à la température de réaction jusqu'à ce que la proportion désirée d'acide soit consommée dans une réaction d'estérification. Les compositions de revêtement vulcanisables par une radiation et contenant l'ester résultant et un catalyseur à base d'amine tertiaire possèdent une meilleure odeur, et les compositions vulcanisables aux ultraviolets contenant les mêmes composants vulcanisent plus rapidement et les revêtements ne dégagent pas l'odeur typique d'amine.Process for the preparation of a reaction product of an ethylenically unsaturated ester, comprising a) mixing an epoxy-functional compound, in particular a polyepoxide, with an alpha, beta-monoethylenically unsaturated monocarboxylic acid, such as acrylic acid, in the presence of a catalytic amount of a tertiary amine adduct of an aliphatic or aromatic amine having at least one amino hydrogen atom, such as diethylamine, with i) an ethylenically unsaturated compound whose ethylenic bond is polarized and which can undergo a Michael type addition reaction, or ii) an epoxy compound; and b) maintaining this mixture at the reaction temperature until the desired proportion of acid is consumed in an esterification reaction. Radiation vulcanizable coating compositions containing the resulting ester and a tertiary amine catalyst have a better odor, and ultraviolet vulcanizable compositions containing the same components cure more quickly and the coatings do not give off odor typical amine.

Description

ACRYLIC ACID ESTERIFICATION AND PHOTOPOLYMERIZABLE COMPOSITIONS CONTAINING THE ACRYLATED PRODUCTS

DESCRIPTION Technical Field The present invention relates to the preparation of polyethyleniσally unsaturated esters of epoxγ-functional compounds including polyepoxides having reduced odor and exhibiting improved utility in photopolymerizable coating compositions, especially those curable by exposure to ultraviolet radiation. Background of the Invention

Tertiary alkyl amines, typically triethylamine, have been used to catalyze the acrylation of epoxides; i.e., the formation of an acrylate ester from acrylic acid and an epoxy- functional compound. For example, commonly-owned U.S. Patent No. 3,919,349 to Young et al., describes use of an alkaline catalyst, such as pyridine or triethylamine, to facilitate the esterification of epoxides with acrylic acid in the consumption of the excess acid present after acrylic acid has been used to esterify a polyol.

One advantage of using a relatively volatile tertiary amine, such as triethylamine, as the catalyst is that once the reaction is completed, the amine can be removed from the reaction product, along with any solvent used to dissolve the reactants, by distillation under vacuum. However, even if substantially all of- the tertiary amine is removed by vacuum distillation (or some similar procedure) , enough of the amine remains to impart an objectionable odor to the reaction product. One objective of this invention is to obtain a tertiary amine catalyst that imparts little or no residual odor to the reaction product.

Tertiary amines are also known to facilitate or promote photopolymerization reactions including, for example, the formation of radiation-curable coatings. Again, however, typically utilized tertiary amines-are volatile and create an objectionable odor. This odor can persist in the cured coating, for example to contaminate the contents of a container, such as a metal can, when the cured coating is on the inside surface of the can.

Another objective of this invention is to provide photopolymerizable polyacrylate-containing compositions including a tertiary amine promoter which compositions polymerize to form cured coatings which are substantially free of amine odor. Summary of the Invention

In accordance with this invention, an ethylenically unsaturated ester reaction product is prepared by a method comprising the steps of:

(a) admixing an epoxy-functional compound with an alpha, beta-monoethylenically unsaturated monocarboxylic acid in the presence of a catalytic amount of a tertiary amine adduct of an aliphatic or aromatic amine having at least one amino hydrogen atom with (i) an ethylenically unsaturated compound whose ethylenic bond is polarized and is capable of undergoing a Michael-type addition reaction, or (ii) an epoxide compound; and (b) maintaining the admixture at reaction temperature until the desired esterification reaction is complete, usually evidenced by an acid value of less than about 5.

The epoxy-functional compounds are preferably polyepoxides, and enough of the acid is used so that the esterification process provides polyethylenically unsaturated este^*r reaction products. The reaction products formed by the method of this invention are substantially free of amine odor, and can be used directly in a radiation-curable coating composition. These reaction products are not purified to remove the catalyst used in their production, and thus contain the tertiary amine catalyst used to prepare it. This catalyst is effective to enhance the radiation cure when that cure is achieved by exposure to ultraviolet radiation. Just as catalytic amounts of the adduct are effective to catalyze the esterification reaction, these same catalytic amounts are effective to speed the ultraviolet cure. A radiation-curable coating composition in this invention includes the ethylenically unsaturated ester, the low volatile tertiary amine catalyst used to prepare it, and other radiation-curable 'ethylenically unsaturated materials which one may wish to have present* Ancillary materials may also be present, for example, typical ketonic photoinitiators, such as benzophenone, acetophenone and thioxanthone, which are used to render the composition sensitive to ultraviolet light. In many instances the coating composition will be free of volatile organic solvent, but in some instances such solvents may be present. When a volatile solvent is present, it is normally allowed to evaporate before exposure to the radiation used to effect cure.

A method of forming a cured coating upon a substrate, such as the inner or outer surface of a metal can, is also contemplated herein. Here, a radiation-curable coating composition as described above is applied to a surface of the substrate to form a coated substrate. The coated substrate is thereafter irradiated, as with ultraviolet light, at an intensity and for a time period sufficient to cure the coating, and the tertiary amine adduct present in the coating composition promotes the rate at which the photochemically-induced cure occurs. The cured, coated substrate so produced is substantially free from an amine.odor.

One benefit of the present invention is that the tertiary amine adduct is relatively non-volatile and imparts substantially no odor to the polyethylenically unsaturated polyester, the coating composition containing that polyester or a cured coating prepared from the composition. The present invention also provides the advantage that the substance used to catalyze the preparation of the polyethylenically unsaturated polyester also promotes the ultraviolet cure to which the polyester is subsequently subjected. Thus, the tertiary amine catalyst used in polyester preparation need not be removed from the polyester prior to the compound's later use, and this is a distinct advantage in the production procedure.

Still further benefits and advantages will be apparent to those skilled in the art from the description and examples that follow. Detailed Description of the Invention A. Catalyst The tertiary amine catalyst compounds useful in the present invention comprise an addition reaction product (adduct) of an aliphatic or aromatic amine containing at least one amino hydrogen atom (primary or secondary amine) and (i) an ethylenically unsaturated material whose ethylenic bond is polarized and is capable of undergoing a Michael-type addition reaction, or (ii) an epoxide compound. Such products are known in the art.

Primary and secondary amines; i.e., amines containing at least one amino hydrogen atom, as a class, and especially aliphatic amines, are known to participate in Michael-type addition reactions. Accordingly, any amine capable of undergoing a Michael-type addition reaction is broadly suitable for use in this invention. Monofunctional amines, e.g., those which contain a single amino hydrogen atom, can be illustrated by diethylamine, but other amines like dibutyl amine and dioctyl amine are also useful. Preferably, the amines are aliphatic and include from 2-30 carbon atoms per molecule. The aliphatic amines useful herein may be further illustrated by piperidine, morpholine, piperazine, di- (hydrogenated-coco)amine, and diallylamine. Hydroxy-functional amines such as monoethanolamine, monoisopropanolamine, diethanolamine and. iisopropanolamine are also useful herein.

Amines containing a plurality of amino hydrogen atoms are also useful in this invention. For example, monobutylamine can be reacted with pentaerythritol triacrylate to form mono-, di-, or tri-tertiary a ine-containing reaction products, as well as mixtures thereof, depending upon the stoichiometry of the reaction mixture, as is known. Any of these are useful in this invention, and the unsaturated products are especially useful because these polymerize together with the unsaturated esters which are the prime products of this invention. This more permanently incorporates the tertiary amine products used in this invention into the cured coatings which are formed. It will be understood that the replacement of a proportion of one amine, such as diethylamine, with another amine containing a plurality of amino hydrogen atoms leads to the production of higher molecular weight products and provides, in this manner, a mechanism for controlling the viscosity of the catalyst adduct which is produced. Thus, a small proportion of a primary amine can be used to replace a secondary amine in the reaction mixture used to form the catalyst, and this leads to Michael-type addition products of higher molecular weight, higher viscosity and lower volatility and odor due to the reaction of both primary amino hydrogen atoms. Aromatic amines which can be used are illustrated by aniline, 4, '-diaminodiphenyl methane and diaminodiphenyl ether.

An amine containing a plurality of amino hydrogen atoms, for example ethylamine. butylamine or ethylene diamine, can be used to provide higher molecular weight tertiary amine adducts. These may retain polarized ethylenic bonds. For example, when neopentyl glycol diacrylate is reacted with one-half molar proportion of ethylamine or butylamine, the reaction of these two difunctional reactants leads to the production of polymers. These polymers will have progressively higher molecular weight as the stoichiometric relation of amino hydrogen atoms to polarized monoethylenic unsaturated groups approaches 1:1. The catalysts used in this invention have been illustrated to this point by the use of simple amines, such as monoamines, which may be primary or secondary monoamines. However, polyamines are also useful. When a highly branched structure is desired, it is appropriate to employ polyamines having a high functionality. Such polyamines are illustrated by diethylenetriamine, triethylenetetramine and tetraethylenepentamine. These include terminal two primary amine groups and one or more secondary amine groups spaced along the length of the chain. The presence of amine groups along the length of the chain is not required, as is illustrated by the usefulness of hexamethylenediamine which contains only terminal amine groups. On the other hand, polyamides having terminal amino groups are also quite useful as illustrated by the commercial material Versamid 125 (commercially available from General Mills, Inc, Minneapolis, Minnesota) which is an amine-terminated fatty polyamide. The above-described amines can be used alone or in any desired combination, but it will be understood that when the higher functional amines, and especially those of higher molecular weight, are reacted with an ethylenically unsaturated material or with an epoxide (as discussed hereinafter) , the products are frequently solid and, therefore, must be dissolved for use. Also, if a polyacrylate is used in combination with a polyamine of high functionality, this can lead to the production of insoluble, gelled products that are not desired in this invention. The preferred catalysts are soluble in common organic solvents such as acetone, ethyl acetate, methyl cyclohexane and the like.

Accordingly, a polyacrylate can be used in admixture with a liquid monoacrylate or in admixture with another liquid monoethylenic monomer having a polarized ethylenic bond, such as acrylonitrile, diacetone acrylamide, and the like, to either minimize the cross-link density obtained directly by the Michael-type addition reaction, or as a solvent to dissolve the normally solid Michael-type addition product, or for both purposes.

The ethylenically unsaturated compounds useful herein may be represented by the formula:

H C = C - R

'l '2

R R^

wherein R is a polarizing, strongly electron withdrawing group, and can be:

(a) C(0)OH

(b) C(0)OR³,

(c) CN,

(d) C(0)N(R³) (R⁴) , (e) N0₂,

(f) S0₃R³,

(g) S0₂R³, and . (h) C(0)R³;

R is H or a lower alkyl group that contains 1-4 carbon atoms;

2 R is H, CH- or CN, with the proviso that R² is not CN when R is CN, 0₂, SO_jR³,

SO-R³ or C(0)R³; and R 3 and R4 are the same or different lower alkyl group that contains 1-8 carbon atoms. To illustrate the foregoing, suitable monoethylenically unsaturated materials comprise acrylic acid esters, such as ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, hydroxy alkyl acrylate esters whose alkyl group contains 2-4 carbon atoms such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate, and the corresponding methacrylates. Additional monoethylenically unsaturated materials that are suitable include crotonic acid esters, such as ethyl crotonate, and crotonate derivatives similar to the acrylate derivatives listed above.

Further useful monoethylenically unsaturated compounds having polarized ethylenic bonds include acrylonitrile; methacrylonitrile; acrylamide and methacrylamide as well as their N-substituted derivatives that contain one or two lower alkyl groups such as N-ethylacrylamide,

N,N-dimethylacrylamide, and N-hexylmethacrγlamide; cyanoacrylic acid and cyanomethacrylic acid, as well as their lower alkyl esters such as ethyl cyanoacrylate and 2-ethylhexyl cyanomethacrylate; a vinyl lower alkyl sulfone, such as vinyl ethyl sulfone; and a vinyl lower alkyl ketone such as methyl vinyl ketone and hexyl vinyl ketone.

Since these monoethylenically unsaturated compounds having a polarized ethylenic bond are intended to adduct with the amines previously discussed by a Michael-type addition reaction, those compounds which engage in this reaction easily are preferred. Accordingly, lower alkyl acrylate esters are particularly preferred.

Polyethylenically unsaturated materials suitable for use in the present invention include polyesters of acrylic acid with polyhydric alcohols such as ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, trimethylol propane, glycerine, pentaerythritol, sorbitol and the like.

Thus, for example, ethylene glycol diacrylate, trimethylol propane diacrylate, pentaerythritol triacrylate and tris-hydroxyethyl isocyanurate di- and triacrylates may also be used. Mono- or polyepoxides may also be used to form tertiary amine adducts with the amines noted previously. Thus, monoepoxides such as propylene oxide, butylene oxide, or higher mono-epoxides (preferably not containing more than about 30 carbon atoms) , including olefin oxides containing from 12-16 carbon atoms, such as an epoxidized alpha olefin containing 12 carbon atoms, may be used. Cyclohexene oxide further illustrates the mono-epoxides that may be used to form tertiary amine adducts which are useful herein.

Of the epoxide-containing compounds, mono-epoxides are preferred herein for use in preparing a tertiary amine catalyst. Monoepoxides having a molecular weight of less than about 200, such as propylene oxide and cyclohexene oxide, are particularly preferred.

Polyepoxides of any functionality and molecular weight may also be used. The bisphenol-based diglycidyl ethers are all useful as are tri- and higher functional epoxides. Polyoxy- propylene glycols are also suitable, these being available from Dow Chemical Co. , Midland, Michigan, under trade designations DER^'732 and DER 736. B. Acrylation Reactions

The tertiary amine catalysts described hereinbefore are used as catalysts in the esterification of epoxide compounds with an alpha, beta-monoethylenically unsaturated monocarboxylic acid, such as acrylic, methacrylic or crotonic acids, to form ethylenically unsaturated esters Cacrylation). Esterification of polyepoxides to form polyethylenically unsaturated polyesters is particularly preferred. The ethylenic unsaturation of the epoxy esters thus resides in the carboxylic acid portion of the molecule, as in the acrylate group.

To illustrate the method of this invention, approximately stoichiometric amounts of an epoxide compound, such as a diglycidyl ether of propylene glycol, and an alpha, beta-monoethylenically unsaturated monocarboxylic acid, such as acrylic acid, are admixed in the presence of a tertiary amine catalyst formed by Michael adducting one mole of diethylamine with one mole of ethyl acrylate. The catalyst is used in catalytic amounts, e.g., at least about 0.05% of the weight of the reactants, and the reaction can be carried out in solvent solution, the solvent typically being benzene or toluene. The admixture so obtained is maintained at an appropriate reaction temperature which, generally, can range from about 90°C to about 130°C, preferably from 95°C. to 110°C. until the acid value of the composition is less than about 5. Suitable polyepoxide compounds are diglycidyl ethers of polyols, such as ethylene glycol, butylene glycol, and polyoxypropylene glycols. Dicyclohexyl diepoxides are preferred. Exemplary materials include diglycidyl ethers of bisphenols such as bisphenol A. Commercially available materials of this type are illustrated by the materials sold under the trademarks Epon 828 (Shell Chemical Co., Houston, Texas) and Araldite 6010 (Ciba-Geigy Corp., Ardsley, New York). Those polyepoxides having a molecular weight below about 1000 are particularly preferred. It is preferred to employ aliphatic polyhydric alcohols having a molecular weight below 4000 and containing 2 to 4 hydroxy groups. All the hydroxy groups need not be consumed in the reaction. though this may be done. It is particularly preferred to react glycerin, trimethylol propane or pentaerythritol, as the polyol, with acrylic acid. When polyepoxides are used instead of a polyol, it is preferred to use a diglycidyl ether of a C₂~(_ polyoxyal ylene glycol. It is particularly preferred to react polyoxypropylene diglycidyl ethers containing from about 2 to about 30 oxyalkylene groups with acrylic acid. Illustrative available materials of this type include those sold under the trademarks DER 732 and DER 736 by Dow Chemical Co., Midland, Michigan.

Epoxidized novolacs; i.e., a polyglycidyl ether of a phenol-formaldehyde novolac having an average oxirane functionality greater than 2, e.g., about 2.5 to about 10, and more preferably about 3 to about 6, are also particularly preferred reactants in acrylation reactions. Such materials are well known. Particularly, preferred alpha, beta-monoethylenically unsaturated monocarboxylic acids are acrylic acid and methacrylic acids. Additional useful acids include crotonic acid, itaconic acid, monobutyl fumarate, and the like.

The before-described tertiary amine adducts are utilized in a catalytic amount. Typically, a catalytic amount constitutes about 0.01% to about 3% by weight of the combined weights of the materials which are to be reacted together. Preferably, the catalytic amount is about 0.03% to about 1.0%. Where the acrylation reaction is carried out in a volatile organic solvent, those having a boiling points of about 80°C. to about 120°C. are preferred. Exemplary of such materials are cyclohexane, methyl cyclohexane, which is particularly preferred, toluene and the like. Where a solvent is utilized for the preparation of the polyesters, it is preferred that the solvent be substantially removed prior to the use of the ester product in a coating composition, for these frequently contain no inert volatile solvent. Since the tertiary amine adducts used herein have little volatility, they are not removed when the solvent is evaporated, which is usually carried out under vacuum to minimize the temperature and the tendency for the unsaturated esters to polymerize. C. Radiation-Curable Coating

Composition and Method A radiation-curable coating in this invention comprises the polyethylenically unsaturated esters containing residual relatively high boiling tertiary amine adduct, as previously described. This adduct is present in a catalytic amount, but this is enough to provide a useful improvement in cure speed when ultraviolet light is used for cure. An appropriate photoinitiator is also preferably present, but these are themselves well known. Other ethylenically unsaturated materials may also be present, and these may be solid or liquid and monoethylenic or polyethylenic. The "monomers" include the be ore-described monoethylenically unsaturated materials whose ethylenic bonds are polarized, such as ethyl acrylate, butyl acrylate, phenoxyethyl acrylate, isobornyl acrylate and the corresponding methacrylates. Also included are monomers such as vinyl acetate.

Also included in these "monomers" are polyethylenic polyesters of low molecular weight, like ethylene glycol diacrylate. These are viewed as monomers because they are liquid at room temperature.

"Polymers" include polyethylenic polyurethanes which are well known radiation-curable materials. Since these are frequently solid or of high viscosity, they are combined with liquid materials which may be ethylenically unsaturated and copolymerizable, or with volatile solvents which enable the coating composition to be liquid to enable its application as a coating.

The reaction mixture used in the preparation of the polyethylenic polyester may be used directly in the coating composition after removal of the solvent usually present during such reactions. Of course, the relative amounts of each ingredient can also be altered by addition of one or more of the components, as may be desired.

As indicated, the tertiary amine adduct may be present during the curing of coating compositions by radiation,- in particular, by ionizing or ^• - ultraviolet radiation. When ionizing radiation, such as an electron beam, is used, the tertiary amine adduct can act as a chain transmitting agent. On the other hand, when ketonic photoinitiators, and especially benzophenone, acetophenone or thioxanthone are present, the tertiary amine adducts signficantly enhance the cure speed.

Exemplary photoinitiators include benzophenone, acetophenone, benzoin (and methyl, butyl or isobutyl ethers of benzoin) , and are typically effective at about 0.5 to about weight 6 percent concentrations based on the total weight of the reaction mixture. Thioxanthone (thioxanthen- 9-one) is typically effective at somewhat lower concentrations, but all of this is conventional. All proportions herein are by weight, unless otherwise stated.

Optimum concentrations are a function of the particular composition in which a particular photoinitiator is used as well as of the thickness of the coating, the intensity and wavelength of the ultraviolet energy source and the time of exposure. The amount of particular photoinitiators to use is known to those skilled in the art, and may be referred to as an effective amount.

The present invention also contemplates a method of forming a substrate having a cured coating. In accordance with this method, a before-described radiation-curable coating composition that preferably contains an effective amount of a photoinitiator is provided. The composition is coated on a substrate, such as the surface of a metal as would be used in canning to form a coated substrate, and the coated substrate is irradiated with radiation, such as ultraviolet li^'ght or electron beam radiation, for a time period sufficient for the coating to cure.

In carrying out the curing of coating compositions using a coating composition of the present invention, a 550 watt (2 inch) -medium pressure Hanovia mercury arc quartz lamp (Canrad-Hanovia, Inc. Newark, New Jersey) in an appropriate polished aluminum reflector is suitable for stationary test. A 5 kilowatt (24 inch) Hanovia mercury arc quartz lamp focused into an approximately 1/2 inch band of light using a parabolic polished aluminum reflector is suitable for dynamic testing.

The present invention is further illustrated in the following examples. Example I Preparation of Butyl 3-diethylaminopropionate

A one liter, three-necked flask equipped with a motor driven stirrer, reflux condenser, heating mantle, thermometer and addition funnel is charged with 262.75 grams (2.05 moles) of butyl acrylate. With the stirrer set at medium speed, 146.28 grams (2.0 moles) of diethylamine is added dropwise to the butyl acrylate over a period of about one hour. The contents of the flask increase in temperature from 25 degrees Centigrade (C) to 28 degrees C during the addition. After the addition is completed, the contents of the flask are heated at 40 degrees C for 30 minutes to yield butyl 3- diethylaminopropionate. Example II

Preparation of diethylamine addition product of trimethylolpropane triacrylate

A one liter, three-necked flask, equipped as described in Example I, is charged with 592.64 grams (2 moles) of trimethylol propane triacrylate. With the stirrer set at medium speed, 146.28 grams (2.0 moles) of diethylamine is added dropwise to the trimethylolpropane triacrylate over a period of about one hour. The contents of the flask increase in temperature from 25 degrees C to 30 degrees C during the addition. After the addition is completed, the contents of the flask are heated at 40 degrees C for about 30 minutes to yield the diethylamine addition product of trimethylolpropane triacrylate. Example III

Preparation of 3-diethylamino-2-hydroxypropyl phenyl ether

A one liter, three-necked flask equipped with a motor-driven stirrer, ice-water bath. thermometer and addition funnel is charged with 300.36 grams (2 moles) of phenyl glyσidyl ether. The stirrer is set at medium speed, and the contents of the flask are cooled to about 0 degrees C. Two moles of diethylamine, 146.28 grams, are slowly added to the flask over a period of about one hour. The temperature of the contents of the flask should not be allowed to exceed 10 degrees C during the addition. After the addition is completed, the ice-water bath is removed and the contents of the flask are stirred for a^*n additional 30 minutes to yield 3-diethylamino-2-hydroxypropyl phenyl ether. Example IV Preparation of Pentaerythritol triacrylate

Reagent Grams

1. Pentaerythritol 217.6

2. Glacial acrylic acid 391.6

3. Methyl cyclohexane 203.1

4. o-methoxy phenol 0.24

5. Sulfuric acid 2.03

6. Araldite 6010 (Ciba- 48.4 Geigy Corp., Ardsley, NY)

7. Product from 38.46 (0.104

Example II equiv. of diethylamine)

8. Sodium oleate 1.9

Reagents 1 through 4 are charged to a one-liter flask equipped with a motor-driven stirrer. Dean Stirk water separator, thermometer, heating mantle and air sparge. The mixture is heated to 40 degrees C at which time the sulfuric acid catalyst is added. Water is azeotropically removed at 85-98 degrees C until an acid value of about 20 is reached. Reagents 6, 7 and 8 are charged to the flask and the reaction is continued until an acid value of less than about 5 is achieved.

A vacuum distillation is then performed to remove the solvent.

Claims

WHAT IS CLAIMED IS:

1. A method of preparing an ethylenically unsaturated ester reaction product comprising the steps of: (a) admixing an epoxy-functional compound

- with an alpha, beta-monoethylenically unsaturated monocarboxylic acid in the presence of a catalytic amount of a tertiary amine adduct of an aliphatic or aromatic amine having at least one amino hydrogen 0 atom with

(i) an ethylenically unsaturated compound whose ethylenic bond is polarized and is capable of undergoing a Michael-type addition reaction, or 5 (ii) an epoxide compound; and

(b) maintaining said admixture at reaction temperature until the desired proportion of said acid is consumed ^'in an esterification reaction.

2. A method as recited in claim l^" in which 0 said epoxy-functional compound contains a plurality of esterifiable groups, and sufficient acrylic acid is used to provide a polyester.

3. A method as recited in claim 1 in which the reaction is continued until the acid value is 5 less than about 5 and said amine is an aliphatic amine having from 2-10 carbon atoms per molecule.

4. A method as recited in claim 3 in which said amine is diethylamine.

5. A method as recited in claim 1 in which 0 said ethylenically unsaturated compound whose ethylenic bond is polarized is represented by the formula:

H-C = C - R 5 R¹ R^ wherein R is a polarizing, strongly electron withdrawing group, and can be:

(a) C(0)0H

(b) C(0)0R³,

(c) CN,

( d) C(0)N(R³ ) (R⁴) ,

( e) N0₂ , C f ) S0,R³ ,

3 C g) S0₂R , and

10 ( h) C( 0)R³ ;

R is H or a lower alkyl group that contains 1-4 carbon atoms;

R² is H, CH₃ or CN, with the proviso that R² is not CN when R is CN, N0₂, S0₃R³, 15 S0,R³ or C(0)R³; and

R and R are the same or different lower alkyl group that contains 1-8 carbon atoms.

6. A method as recited in claim 1 wherein said alpha, beta-monoethylenically unsaturated

^' 20 monocarboxylic acid is acrylic acid and a polyepoxide is esterified to convert each epoxide group to an ester group.

7. A method as recited in claim 6 wherein said polyepoxide is selected from a diglycidyl ether

25 of a C₂~C^ polyoxyalkylene glycol and a polyglycidyl ether of a phenol- ormaldehyde novalac having an average oxirane functionality of about 2.25 to about 10.

8. A radiation-curable coating composition 30 comprising the polyester reaction product of claim 1 containing said tertiary amine adduct.

9. A coating composition as recited in claim 8 in which said polyester reaction product is a polyethylenically unsaturated ester of a polyepoxide.

35 10. A coating composition as recited in claim 9 in which said composition is ultraviolet curable and includes an effective amount of a photoinitiator.