WO2007044184A1

WO2007044184A1 - Water soluble photoinitiator

Info

Publication number: WO2007044184A1
Application number: PCT/US2006/036394
Authority: WO
Inventors: Wenfeng Kuang
Original assignee: Albemarle Corporation
Priority date: 2005-10-07
Filing date: 2006-09-19
Publication date: 2007-04-19
Also published as: TW200726744A

Abstract

This invention provides both metal carboxylates and tertiary ammonium carboxylates, in which carboxylates a benzoylphenyl group is present. Also provided are photoinitiator compositions which comprise a) (i) at least one metal carboxylate, in which carboxylate a benzoylphenyl group is present, and/or (ii) at least one tertiary ammonium carboxylate, in which carboxylate a benzoylphenyl group is present; and b) at least one coinitiator comprising at least one benzoyl moiety and at least one aliphatic alcohol moiety. Processes for photopolymerization with these photoinitiator compositions are also provided.

Description

WATER SOLUBLE PHOTOINITIATOR

TECHNICAL FIELD

[0001] This invention relates to photoinitiators which are soluble in water and to aqueous photopolymerization systems.

BACKGROUND [0002] Using light to cure coatings comes with motivations such as environmental compliance, fast cure, improved physical properties and lower applied cost. These motivators translate into benefits of reduced solvent emissions, increased product speed/productivity, product performance, efficiency and cost effectiveness. Ethylenically unsaturated compounds, such as acrylate derivatives, can be polymerized by exposure to radiation, typically ultraviolet light, in the presence of a photoinitiating system. Typically, the photoinitiating system includes (1) a compound capable of initiating polymerization of the ethylenically unsaturated compound upon exposure to radiation (a "photoinitiator") and optionally (2) a coinitiator or synergist, that is, a molecule which serves as a hydrogen atom donor. [0003] A recent development in radiation-induced polymerization is the use of aqueous systems. However, many photoinitiators are at best sparingly soluble in water. It would be desirable to have photoinitiators that are soluble in water. It would be even more desirable to have photoinitiating systems in which both the photoinitiator and the coinitiator are soluble in water.

SUMMARY OF INVENTION [0004] Pursuant to this invention, photoinitiators that are soluble in water and photoinitiator systems that are soluble in water are provided. In particular, this invention provides metal carboxylates and tertiary ammonium carboxylates, which carboxylates have a benzoylphenyl group; these carboxylates are miscible with water. An especially advantageous feature of this invention when using a tertiary ammonium carboxylate is that the tertiary ammonium cation can also act as a coinitiator. Another feature of this invention is that some photoinitiators which are only minimally soluble in water, when blended with a metal carboxylate or a tertiary ammonium carboxylate, which carboxylates have a benzoylphenyl group, are miscible in water. [0005] An embodiment of this invention is a composition which is a metal carboxylate, in which carboxylate a benzoylphenyl group is present.

[0006] Another embodiment of this invention is a composition which is a tertiary ammonium carboxylate, in which carboxylate a benzoylphenyl group is present. [0007] Still another embodiment of this invention is a photoinitiator composition. The photoinitiator composition comprises a) (i) at least one metal carboxylate, in which carboxylate a benzoylphenyl group is present, and/or (ii) at least one tertiary ammonium carboxylate, in which carboxylate a benzoylphenyl group is present; and b) at least one coinitiator comprising at least one benzoyl moiety and at least one aliphatic alcohol moiety. [0008] Yet another embodiment of this invention is a photopolymerizable composition. The photopolymerizable composition comprises at least one tertiary ammonium carboxylate, in which carboxylate a benzoylphenyl group is present; at least one photopolymerizable monomer; and water. [0009] Still another embodiment of this invention is a process which comprises photopolymerizing at least one photopolymerizable monomer by exposing the at least one photopolymerizable monomer to radiation in an aqueous medium in the presence of at least one tertiary ammonium carboxylate, in which carboxylate a benzoylphenyl group is present. [0010] These and other embodiments and features of this invention will be still further apparent from the ensuing description and appended claims.

FURTHER DETAILED DESCRIPTION OF THE INVENTION

[0011] The carboxylates and carboxylic acids used in this invention can be viewed as derivatives of benzophenone. Benzophenone is called a benzoylphenyl group when it is a substituent moiety. It is to be understood that unless stated otherwise, as used throughout this document, the term "benzoylphenyl" includes both substituted and unsubstituted benzoylphenyl groups. As used throughout this document, the term "benzoylphenyl carboxylate," unless otherwise stated, refers collectively to metal carboxylates and tertiary ammonium carboxylates in which the carboxylates have a benzoylphenyl group. The solubilities in water referred to herein are for water without the presence of any co-solvent. [0012] As is well known in the art, carboxylates are anions of carboxylic acids. For example, ortho-benzoyl benzoic acid forms ortho-benzoyl benzoate as its carboxylate. In this invention, the types and preferences regarding carboxylates and the carboxylic acids from which they are made are analogous.

[0013] Preferred benzoylphenyl carboxylates have only one carboxylate group; also preferred are benzoylphenyl carboxylates without substitiients. More preferred carboxylates are benzoyl benzoates (also known as benzophenone carboxylates), with or without substituents. Still more preferred are benzoyl benzoates without substituents (i.e., ortho- benzoyl benzoate, meta-benzoyl benzoate, and para-benzoyl benzoate). A highly preferred benzoylphenyl carboxylate is ortho-benzoyl benzoate. [0014] Metal carboxylates in which carboxylates a benzoylphenyl group is present are compositions of the invention. The metal carboxylate is usually and preferably an alkali metal carboxylate. Preferred alkali metal carboxylates are the lithium earboxylates, the sodium carboxylates, and the potassium carboxylates. More preferred are the sodium carboxylates and the potassium carboxylates. Especially preferred are sodium and potassium carboxylates of a benzoyl benzoic acid (a sodium benzoyl benzoate and a potassium benzoyl benzoate). [0015] Generally, the metal carboxylates of this invention are prepared by mixing together an inorganic base and a benzoylphenyl carboxylic acid in an aqueous medium. Suitable inorganic bases include oxides, hydroxides, acetates, sulfates, carbonates, and bicarbonates, especially of the alkali metals. Examples of suitable bases include sodium oxide, potassium oxide, lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, lithium acetate, lithium carbonate, sodium acetate, sodium bicarbonate, sodium carbonate, potassium acetate, potassium bicarbonate, potassium carbonate, potassium nitrite, potassium sulfite, rubidium carbonate, cesium acetate, and cesium bicarbonate. Mixtures of two or more inorganic bases can be used. Preferred inorganic bases are alkali metal hydroxides; preferred metal hydroxides include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Sodium hydroxide and potassium hydroxide are highly preferred inorganic bases.

[0016] Tertiary ammonium carboxylates in which carboxylates a benzoylphenyl group is present are compositions of the invention. Normally, the tertiary ammonium carboxylates are prepared by mixing together a tertiary amine and a benzoylphenyl carboxylic acid in an aqueous medium. In this invention, each group on the tertiary amine generally has up to about twelve carbon atoms; more preferred are groups having up to about six carbon atoms. The groups on the amine are usually hydrocarbyl groups or groups having at least one available hydrogen atom attached to a carbon atom adjacent to a heteroatom; oxygen is a preferred heteroatom. Amines having a mixture of hydrocarbyl groups and heteroatom-containing groups can be used and are preferred. More preferred tertiary amines are one or a mixture of tertiary alkanolamines having "n" alkanol groups and "3-n" hydrocarbyl groups in the molecule, where n is 1 to 3. Mixtures of two or more tertiary amines can be used; preferred mixtures are those which comprise at least one trihydrocarbylamine and at least one tertiary alkanolamine. The tertiary ammonium cations of the tertiary ammonium carboxylates will have the same groups as just described for the tertiary amines used in making these salts. Non-limiting examples of suitable tertiary amines include N-methyl-N,N-diethanolamine, N- ethyl-N,N-diethanolamine, 1 -dimethylamino-2-propanol, N,N-dimethylisopropanolamine, 2- dimethylamino-2-methyl- 1 -propanol, 3 -dimethylamino- 1 -propanol, 1 -diethylamino-2- propanol, 3 -diethylatήino-1 -propanol, N-butyl-N,N-diethanolamine, triethanolamine, triethylamine, triisopropanolamine, and N-methyldibutylamine. Preferred tertiary amines for forming the tertiary ammonium carboxylates, especially of a benzoyl benzoic acid, include N-ethyl-N,N-diethanolamine; thus, N-ethyl-N,N-diethanolammonium benzoyl benzoate is a particularly preferred tertiary ammonium carboxylate.

[0017] The benzoylphenyl carboxylic acids used to form the carboxylates of this invention can be represented by the structures

where R can be, but is not limited to, an alkyl, ether, ester, amino, or amido group. Preferably, R contains up to about twelve atoms; more preferably, R has about one to about six atoms. It is to be understood that these structural representations are not to be construed to limit the benzoylphenyl-containing carboxylic acids. More than one acid group may be present, and such acid groups may be on the same ring or on separate rings. Substituents can be present on one or both rings of the benzoylphenyl group. Suitable substituent groups include alkyl (preferably C₁ to C₆), alkoxy (preferably having up to about twelve carbon atoms), ether, ester, amino, and/or amido groups, and the like. Examples of substituents groups include, but are not limited to, methyl, ethyl, isopropyl, tert-butyl, pentyl, cyclohexyl, hydroxy, methoxy, ethoxy, trifluoromethyl, amino, methylamino, diethylamino, dibutylamino, nitro, and fluoro groups. [0018] Benzoylphenyl carboxylic acids that can be used in the practice of this invention include ortho-benzoylphenyl acetic acid, meta-benzoylphenyl acetic acid, para-benzoylphenyl acetic acid, 2-(3~benzσylphenyl)propionic acid, 2-m-(p-chlorobenzoyl)phenylpropionic acid, 3-benzoyl-2-methoxyphenyl)acetic acid, (2-amino~3-benzoylphenyl)acetic acid, 4-benzoyl- alpha-methylbenzeneacetic acid, 2-(m-benzoylphenoxy)acetic acid, 2-amino-(4'- chlorobenzoyl)phenylacetic acid, 4-(2-methyl-3-(4-chlorobenzoyl)phenyl)butanoic acid, 2- amino-3-(4-bromobenzoyl)benzeneacetic acid, benzeneacetic acid, 5-(2,4-dichlorobenzoyl)-2- hydroxy-5-(4-fluorobenzoyl)-2-hydroxy-alpha-methylbenzeneacetic acid, 2-(4- methylbenzoyl)benzoic acid, 4-methylbenzophenone-2-carboxylic acid, 2-(4- ethylbenzoyl)benzoic acid, 4-ethylbenzophenone-2-carboxylic acid, 4,4'dimethoxy- benzophenone-2,2'-dicarboxylic acid, benzophenone-4,4'-dicarboxylic acid, benzophenone-

2,2',4-tricarboxylic acid, benzophenone-S^'^^'-tetracarboxylic acid, benzophenone-2,2',5,5'- tetracarboxylic acid, ortho-benzoyl benzoic acid, meta-benzoyl benzoic acid, para-benzoyl benzoic acid, 2-(3,4-dimethyl-benzoyl)-benzoic acid, 2-(2-hydroxy-5-methyl-benzoyl)- benzoic acid, 2-(2,3-difluoro-benzoyl)-benzoic acid, 2-(4-fluoro-3-methyl-benzoyl)-benzoic acid, 2-(2,3,4,5,6-pentamethylbenzoyl)-benzoic acid, 2-(4-hydroxy-3,5-dimethylbenzoyl)- benzoic acid, 2-(2-aminobenzoyl)-benzoic acid, 2-(3,5-bis(trifluoromethyl)benzoyl)-benzoic acid, 2-f4-(dibutylamino)-2-hydroxybenzoyl]benzoic acid, 2-(4-fluorobenzoyl)-benzoic acid, 2-(4-hydroxybenzoyl)-benzoic acid, 2-(4-methylbenzoyl)-benzoic acid, 2-(3-aminobenzoyl)- benzoic acid, 2-(4-diethylamino-2-hydroxybenzoyl)-benzoic acid, 2-benzoyl-4-nitrobenzoic acid, 2-benzoyl-3-nitrobenzoic acid, and the like.

[0019] Preferred benzoylphenyl carboxylic acids are those having only one carboxylic acid group. Also preferred are benzoylphenyl carboxylic acids without substituents. More preferred are benzoyl benzoic acids (also known as benzophenone carboxylic acids) with or without substituents. Still more preferred are benzoyl benzoic acids without substituents (i. e. , ortho-benzoyl benzoic acid, meta-benzoyl benzoic acid, and para-benzoyl benzoic acid). A highly preferred benzoylphenyl carboxylic acid is ortho-benzoyl benzoic acid. [0020] Normally, the water of preparation of a benzoylphenyl carboxylate is difficult to remove entirely, without resorting to strenuous measures (e.g., high vacuum at high temperature). Thus, the benzoylphenyl carboxylate compositions of this invention usually contain water, from about 3 wt% to about 99.5 wt%. Preferably, the water content of the compositions of this invention is in the range of about 5 wt% to about 70 wt%. Expressed from the point of view of the benzoylphenyl carboxylate, a composition of this invention typically contains about 0.1 wt% to about 97 wt% benzoylphenyl carboxylate, and preferably contains about 30 wt% to about 95 wt% benzoylphenyl carboxylate. [0021] For the preparation of the benzoylphenyl carboxylates of this invention, the presence of solvent(s) other than water in the aqueous medium is unnecessary. Similarly, the use of solvent(s) other than water is unnecessary in the photopolymerization processes of the invention described below.

[0022] The photoinitiator compositions of the invention comprise a) (i) at least one metal carboxylate in which a benzoylphenyl group is present, and/or (ii) at least one tertiary ammonium carboxylate in which a benzoylphenyl group is present; and b) at least one coinitiator comprising at least one benzoyl moiety and at least one aliphatic alcohol moiety. Tertiary ammonium carboxylates are preferred benzoylphenyl carboxylates in the photoinitiator compositions of this invention. Mixtures of two or more benzoylphenyl carboxylates can be present in the photoinitiators of this invention. [0023] Photoinitiators are grouped into two classes. Type I photoinitiators are those that undergo photocleavage to yield free-radicals; these photoinitiators produce radicals through a unimolecular fragmentation process. Type II photoinitiators are those that produce initiating radicals through an abstraction process. The benzoyl benzoic acid salts of this invention are Type II photoinitiators. hi Type II (abstraction type) photoinitiator systems, a coinitiator generally must be present. For metal carboxylates of the invention, the presence of a coinitiator is usually necessary. When the photoinitiator is a tertiary ammonium carboxylate, the tertiary ammonium cation can act as a coinitiator; a separate coinitiator is not necessary; however, it is preferred to use a coinitiator with a tertiary ammonium carboxylate. [0024] Coinitiator compounds are sometimes referred to in the art as activators, accelerators, coinitiators, or cosynergists. Suitable coinitiators include Type I photoinitiators, especially coinitiators comprising at least one benzoyl moiety and at least one aliphatic alcohol moiety. The benzoyl moiety of the coinitiator can be substituted or unsubstituted; preferably, it is unsubstituted. Suitable substituents for the benzoyl moiety include hydroxyl, alkyl, alkoxy, ether, ester, amino, and/or amido groups, and the like. Exemplary groups that may be present include those listed above for substituents on the rings of the benzoylphenyl group. The aliphatic alcohol moiety of the coinitiator generally has from about one to about twelve carbon atoms; preferably, there are from about three to about eight carbon atoms. The aliphatic alcohol moiety can be linear, branched, or cyclic, and the hydroxyl group may appear anywhere on the aliphatic alcohol moiety. More than one hydroxyl group may be present on the aliphatic alcohol moiety of the coinitiator. [0025] Examples of Type I initiators for use as coinitiators in the photoinitiator compositions of this invention include but are not limited to 2-hydroxy-2-methyl-l-phenyl- propan-1-one (HMPP)₅ 1-hydroxycyclohexyl phenylketone (HCPK), l-[4-(2-hydroxyethoxy)- phenyl]-2-hydroxy-2-methyl-l-propan-2-one (Irgacure^® 2959, a product of Ciba Specialty Chemicals), benzoin (2-hydroxy-2-phenylacetophenone), anisoin (4,4'-dimethoxybenzoin), alpha-hydroxyacetophenone (benzoylcarbinol), alpha-hydroxy-4'-methoxyacetophenone, 2- hydroxy-2-methyl- 1 -(4-hydroxyethyloxy)phenyl-propan- 1 -one, and 3 -hydroxy- 1 -phenyl- 1 - propanone . Mixtures of any two or more such coinitiators may be used. Particularly preferred coinitiators include 2-hydroxy-2-methyl-l-phenyl-propan-l-one (HMPP) and 1- hydroxycyclohexyl phenyl ketone (HCPK). [0026] Surprisingly, some photoinitiators which are only minimally soluble in water, when blended with a metal carboxylate or a tertiary ammonium carboxylate of this invention, are miscible in water. For example, 2-hydroxy-2-methyl- 1 -phenyl-propan- 1 -one is known to have a solubility of about 0.3% in water; when blended with a benzoylphenyl carboxylate of this invention, its solubility increases to at least about 20%. [0027] The proportions of the components in the photoinitiator compositions of this invention can vary. In cases where a coinitiator is used as a component, typically the ratio on a weight basis will fall in the range of about 0.01 to about 1 part by weight of the coinitiator(s) per part by weight of benzoylphenyl carboxylate(s). Preferred proportions are in the range of about 0.1 to about 0.75 parts by weight of the coinitiator(s) per part by weight of benzoylphenyl carboxylate(s). More preferably, in the range of about 0.3 to about 1 part by weight coinitiator(s) per part by weight of benzoylphenyl carboxylate are present in the photoinitiator composition. Departures from the foregoing ranges of proportions and amounts are permissible whenever deemed necessary or desirable, and are within the scope of this invention.

[0028] A radiation curable formulation can contain several fundamental components, of which can be polymerizable monomers and/or functionalized oligomers, and the photoinitiator(s) and coinitiator(s), as desired or needed. A large variety of additional optional components which can also be part of the formulation include, but are not limited to, pigments, dyes, light stabilizers, radical scavengers, rheological modifiers, special effect agents, adhesion promoters, and the like. Any one or more such optional components may be included in the photopolymerizable compositions of this invention.

[0029] One of the photopolymerizable compositions of this invention comprises water, at least one photopolymerizable monomer, and a photoinitiator composition, which photoinitiator composition comprises a) (i) at least one metal carboxylate in which a benzoylphenyl group is present, and/or (ii) at least one tertiary ammonium carboxylate in which a benzoylphenyl group is present; and b) at least one coinitiator comprising at least one benzoyl moiety and at least one aliphatic alcohol moiety. The amount of water in the photopolymerizable composition can range from about 0.1 wt% to about 99.9 wt%, based on the total weight of the composition. Preferably, water is present in an amount of about 4 wt% to about 95 wt%, based on the total weight of the composition. As is known in the art, as the amount of water in the composition is increased, the heat generated by the photopolymerization reaction is easier to control.

[0030] Another photopolymerizable composition of this invention comprises at least one tertiary ammonium carboxylate of a carboxylic acid in which a benzoylphenyl group is present; at least one photopolymerizable monomer; and water. In the photopolymerizable composition, the amount of water can range from about 0.1 wt% to about 99.9 wt%, based on the total weight of the composition. Preferably, water is present in an amount of about 4 wt% to about 95 wt%, based on the total weight of the composition.

[0031] The total amount of the photoinitiator composition mixed with the substrate monomer or oligomer to be photopolymerized can be varied as long as there is a sufficient amount of photoinitiator composition present to effect the polymerization under the selected polymerization conditions. Compositions of this invention to be subjected to photopolymerization typically contain a total amount of the components of the photoinitiator composition, proportioned as above, in the range of about 0.5 to about 90 wt%, preferably in the range of about 0.5 to about 20 wt%, and more preferably in the range of about 1 to about 10 wt%, based on the combined weight of the monomer and/or oligomer and photoinitiator composition of this invention. Selections within these ranges are typically made to suit the particular application method to be used. Thus, the photopolymerizable compound is usually present in the photopolymerizable compositions of this invention in amounts from about 10 wt% to about 99.5 wt%, preferably is present in amounts from about 80 wt% to about 99.5 wt%, and more preferably is present in amounts from about 90 wt% to about 99 wt%, based on the total weight of the composition.

[0032] The photopolymerizable compositions are useful in any of the types of applications known in the art for photopolymerizations, including as a binder for solids to yield a cured product in the nature of a paint, varnish, enamel, lacquer, stain or ink. The compositions are particularly useful in the production of photopolymerizable surface coatings in printing processes, such as lithographic printing, screen printing, and the like.

[0033] Photopolymerizable monomers for use in the practice of this invention include acrylates, methacrylates, and the like. Non-limiting examples of such acrylate and methacrylate monomers and oligomers include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2- ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, dimethylaniinopropyl acrylate, dimethylaminopropyl methacrylate, diethylaminopropyl acrylate, diethylaminopropyl methacrylate, and the like, as well as mixtures of any two or more thereof. [0034] Polyfunctional monomers and oligomers, i. e. , compounds or oligomers having more than one alpha-beta-ethylenic site of unsaturation, can also be used in the practice of this invention. Non-limiting examples of such substances include ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, tripropylene glycol diacrylate, tripropylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, glycerol diacrylate, glycerol dimethacrylate, aliphatic urethane diacrylate, aliphatic urethane dimethacrylate, aliphatic urethane triacrylate, aliphatic urethane hexaacrylate, aromatic urethane diacrylate, aromatic urethane dimethacrylate, aromatic urethane triacrylate, polyethylene glycol (400) diacrylate, polyethylene glycol (400) dimethacrylate, polyethylene glycol (600) diacrylate, polyethylene glycol (600) dimethacrylate, ethoxylatedneopentylglycol diacrylate, ethoxylated neopentylglycol dimethacrylate, propoxylated neopentyl glycol diacrylate, propoxylated neopentyl glycol dimethacrylate, highly ethoxylated trimethylolpropane triacrylate, highly ethoxylated trimethylolpropane trimethacrylate, ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A dimethacrylate, erythritol tetraacrylate, erythritol tetramethacrylate, ammo-modified epoxy diacrylate, epoxy novolac triacrylate, divinylbenzene, 1,3- diisopropenylbenzene, polyester triacrylate, polyester tetraacrylate, polyester hexaacrylate, and diluted acrylic acrylate oligomers such as Ebecryl 740-40TP, Ebecryl 745, Ebecryl 754, Ebecryl® 1701, Ebecryl® 1701-TP20, and Ebecryl® 1710 (all from Cytec Surface Specialities); anionic and non-ionic waterborne monomers and /or oligomers which contain at least one-unsaturated carbon-carbon double bond and one water-soluble functional group in the molecule (examples of commercial products include Ucecoat™ 7772, Ucecoat™ 6558, Ucecoat™ 7773; all from Cytec Surface Specialties), and the like, as well as mixtures of any two or more thereof. [0035] If desired, alpha,beta-ethylenically unsaturated carboxylic acids can be used in conjunction with acrylate and/or methacrylate monomers, typically for the purpose of providing improved adhesion to certain substrates. Examples of such acids include methacrylic acid, acrylic acid, itaconic acid, maleic acid, beta-carboxyethyl acrylate, beta- carboxyethyl methacrylate, and the like, as well as mixtures of any two or more thereof. Preferred composition of this invention are, however, devoid of such carboxylic acids except as may be present as impurities or as residuals from manufacture.

[0036] Other suitable photopolymerizable monomers that can be used in the practice of this invention include vinyl acetate, vinyl and vinylidene halides and amides, i. e. , methacrylamide, acrylamide, diacetone acrylamide, vinyl and vinylidene esters, vinyl and vinylidene ethers, vinyl and vinylidene ketones, butadiene, vinyl aromatics, i.e., styrene, alkyl styrenes, halostyrenes, alkoxystyrenes, divinyl benzenes, vinyl toluene, and the like are also included. Prepolymers including acrylated epoxides, polyesters and polyurethanes can be combined with a suitable monomer for viscosity control. The photopolymerizable compounds may be polymerized to form homopolymers or copolymerized with various other monomers. [0037] Preferred photopolymerizable monomers for use in the practice of this invention include waterborne acrylates such as anionic monofunctional and/or multifunctional urethane acrylates and methacrylates, monofunctional and/or multifunctional polyether acrylates and methacrylates, monofunctional and/or multifunctional polyester acrylates and methacrylates, monofunctional and/or multifunctional epoxy acrylates and methacrylates, and the like, as well as mixtures of any two or more thereof. [0038] Optionally, pigments and dyes can be used, and often are preferably used, in the photopolymerizable compositions of this invention. Non-limiting examples of pigments and typical amounts used in the formulation include phthalocyanine blue (5 to 50 wt%), titanium dioxide (10 to 80 wt%), carbon black (1 to 50 wt%), or other organic or inorganic pigments employed in the art. Optionally, dyes such as nigrosine black or methylene blue may be used to enhance color or tone (1 to 5 wt%).

[0039] Rheological modifiers can be used and are preferably used to improve the processing properties of the photopolymerizable compositions. Non-limiting examples of rheological modifiers include silicone compounds, fatty acids and their derivatives, organic fluoro compounds, organic salts, polyethers, alcohols, tertiary amines, and polymeric surfactants. Typically, the amount of rheological modifier used will be in the range of about 0.01 to about

5 wt%, depending upon the particular type of rheological modifier(s) employed. [0040] Light stabilizers are another type of optional additive which can be, and preferably are, used in the photopolymerizable compositions of this invention. Non-limiting examples of such light stabilizers include 2-hydroxybenzophenones such as 2,2'-dihydroxy-4,4'- dimethoxylbenzophenone, 2-(2-hydroxyphenyl)benzotriazoles such as 2-(2'- hydroxyphenyl)benzotriazole, sterically-hindered amines such as bis(2,2,6,6-tetramethyl-4- piperidyl)sebacate or bis(2,2,6,6-tetramethyl-4-piperidyl)succinate, oxamides such as 4,4'- dioctyloxyanilide, acrylates such as ethyl α-cyano-β,β-diphenylacrylate or methyl α- carbomethoxycinnanamate, and nickel complexes such as the nickel complex of 2,2'- thiobis[(l,l,3,3-tetramethylbutyl)phenol. Typically the amount used will be in the range of about 0.02 to about 5 wt% depending upon the particular type of light stabilizer employed. [0041] Still another type of optional additive which can be used, and in preferred embodiments is used, in forming the photopolymerizable compositions of this invention is one or more radical scavengers. Non-limiting examples of suitable radical scavengers for such use include hydroquinone, hydroquinone methyl ether, p-tert-butylcatechol, quinoid compounds such as benzoquinone and alkyl-substituted benzoquinones, as well as other radical scavenger compounds known in the art. Typically these components will be used in amounts in the range of about 100 ppm to about 2 percent by weight of the composition. [0042] Adhesion promoters constitute yet another type of optional additive component which can be used in the formation of the photopolymerizable compositions of this invention. Such components typically are silane derivatives such as gamma-aminopropyltriethoxysilane

(DOW A-1100) and equivalent substituted silane products; acid functionally-substituted resins; oligomers or monomers, such as partial esters of phosphoric acid, maleic anhydride, or phthalic anhydride, with or without acrylic or methacrylic unsaturation; and dimers and trimers of acrylic/methacrylic acid. If adhesion promoters are used, the preferred types are other than alpha,beta-ethylenically unsaturated carboxylic acids. If and when used, the concentration thereof is determined empirically by adhesion tests. In general, however, amounts are often in the range of about 0.5 to about 20 wt%, and in more preferred cases in the range of about 2 to about 10 wt% of the total weight of the composition. [0043] There are various ways of conducting photopolymerizations pursuant to this invention. Typically, the substrate is coated with the uncured photopolymerizable composition and passed under a commercially available UV or excimer lamp on a conveyer moving at predetermined speeds. The substrate to be coated can be, for example, metal, wood, mineral, glass, paper, plastic, fabric, ceramic, and the like. For example, a photopolymerizable composition of this invention can be photopolymerized as a thin coating on a travelling web. Alternatively, the photopolymerizable composition can be photopolymerized as an a coating or laminate on a substrate. The photopolymerizable compositions can be applied or deposited on a surface of a substrate using conventional techniques and apparatus. The composition can be applied as a substantially continuous film. Alternatively, the composition can be applied in a discontinuous pattern. The thickness of the deposited composition can vary, depending upon the desired thickness of the resultant cured product. Another variant is where the photopolymerizable composition is photopolymerized as an article or shape while in a mold. In these and other modes of operation, the exposure to radiation for effecting photopolymerization can be continuous or intermittent. [0044] In effecting photopolymerization processes pursuant to this invention, either coherent or non-coherent radiation can be employed. Various sources of such radiation can be employed, such as an ion gas laser (e.g. , an argon ion laser, a krypton laser, a helium:cadmium laser, or the like), a solid state laser (e.g., a frequency-doubled Nd: YAG laser), a semiconductor diode laser, an arc lamp (e.g., a medium pressure mercury lamp, a Xenon lamp, or a carbon arc lamp), and like radiation sources. Exposure sources capable of providing ultraviolet and visible wavelength radiation (with wavelengths typically falling in the range of 200-700 nm) can also be used for the practice of the present invention. Preferred wavelengths are those which correspond to the spectral sensitivity of the initiator being employed. Preferred radiation sources are gas discharge lamps using vapors of mercury, argon, gallium, or iron salts and utilizing magnetic, microwave or electronic ballast; such lamps commonly are medium pressure mercury lamps, or lamps made by Fusion Systems (L e. , D, H, and V lamps).

[0045] Exposure times can vary depending upon the radiation source, and photoinitiator(s) being used. For preferred high speed applications such as in forming thin coatings on paper webs travelling at high linear speeds, times in the range of about 0.005 to about 0.015 second are preferred, hi photopolymerization operations in which the mixture being polymerized is either stationary or moving slowly as on a conveyor belt, longer exposure times (e.g. , in the range of about 0.2 to about 300 seconds can be used.

[0046] The active energy beams used in accordance with the present invention may be visible light or ultraviolet light or may contain in their spectra both visible and ultraviolet light. The polymerization may be activated by irradiating the composition with ultraviolet light using any of the techniques known in the art for providing ultraviolet radiation, L e. , in the range of 200 nm and 450 nm ultraviolet radiation. The radiation may be natural or artificial, monochromatic or polychromatic, incoherent or coherent and should be sufficiently intense to activate the photoinitiators of the invention and thus the polymerization. Conventional radiation sources include fluorescent lamps, excimer lamps, mercury, metal additive and arc lamps. Coherent light sources are the pulsed nitrogen, xenon, argon ion- and ionized neon lasers whose emissions fall within or overlap the ultraviolet or visible absorption bands of the compounds of the invention. [0047] Various photopolymerized compositions, articles and shapes can be produced by use of this invention. Thus the photopolymerized end product can be printed matter on a substrate such as paper, cardboard, or plastic film, etc.; manufactured articles such as handles, knobs, inkstand bases, small trays, rulers, etc.:, and coatings or laminates on substrates such as plywood, metal sheeting, polymer composite sheeting, etc. Thin coated paper and coated card or thin paperboard stock where the coatings are up to about 2 mils in thickness constitute preferred articles produced pursuant to this invention.

[0048] The following examples are presented for purposes of illustration, and are not intended to impose limitations on the scope of this invention.

EXAMPLE 1

[0049] To a three-neck flask equipped with a stirrer and N₂ purge, water and N-methyl-N,N- diethanolamine (MDEA) were added. Stirring and N₂ sparging were then started. Gradually, ortho-benzoyl benzoic acid (OBBA) was added to the flask while keeping the temperature in the flask below 3O⁰C during the OBBA addition. The temperature was kept at or below 30 ° C for 30 minutes after the OBBA addition was finished. The temperature was then increased to 55 ° C and held at 55 ° C for 5 hours. The mixture was then cooled to room temperature and filtered to remove tiny insoluble particles from the mixture. The amounts of reagents used were such that OBBA was 26.2 wt%; MDEA was 13.8 wt%; and water was 60 wt% of the components mixed together. The MDEA salt of OBBA was obtained as a 40 wt% transparent light yellow liquid that resulted. The viscosity of the liquid was about 12 cps at 25⁰C.

EXAMPLE 2

[0050] To a three-neck flask equipped with a stirrer and N₂ purge, water was added. Stirring and N₂ sparging were then started. Gradually, NaOH was added to the flask while keeping the temperature in the flask below 30°C during the NaOH addition. After the NaOH addition was finished, OBBA was gradually added to the flask while keeping the temperature in the flask below 30⁰C during the OBBA addition. The temperature was kept at or below 30 ° C for 30 minutes after the OBBA addition was finished. The temperature was then increased to 55⁰C and held at 55⁰C for 2 hours. The mixture was then cooled to room temperature and filtered to remove tiny insoluble particles from the mixture. The amounts of reagents used were such that OBBA was 34.0 wt%; NaOH was 6.0 wt%; and water was 60 wt% of the components mixed together. The sodium salt of OBB A was obtained as a 40 wt% transparent light yellow liquid that resulted. The viscosity of the liquid was about 10 cps at 25⁰C.

EXAMPLE 3 [0051] To a three-neck flask equipped with a stirrer and N₂ purge, water, N-methyl-N,N- diethanolamine (MDEA)₅ and 2-hydroxy-2-methyl-l-phenyl-propan-l-one (HMPP) were added. Stirring and N₂ sparging were then started. Gradually, ortho-benzoyl benzoic acid (OBBA) was added to the flask while keeping the temperature in the flask below 3O⁰C during the OBBA addition. The temperature was kept at or below 3O⁰C for 30 minutes after the OBBA addition was finished. The temperature was then increased to 55 ° C and held at 55 ° C for 5 hours. The amounts of reagents used were such that OBBA was 35 wt%; MDEA was 20 wt%; water was 10 wt%; and HMPP was 35 wt% of the components mixed together. The MDEA salt of OBBA was obtained as part of the semi-transparent light yellow liquid that resulted. The viscosity of the liquid was about 308 cps at 25⁰C.

EXAMPLE 4

[0052] Several samples were prepared and tested. The samples were made up of varying proportions of a mixture of three monomers, the photoinitiator mixture prepared in Example 3, and N-methyl-N,N-diethanolamine (MDEA). The amounts of monomer mixture, photoinitiator mixture, and MDEA are listed in Table 1 in grams. The three monomers in the monomer mixture were in proportions of 20 g of UCECOAT™ 6558 (an acrylated aliphatic urethane oligomer), 40 g of UCECOAT™ 7773 (an acrylated polyurethane dispersion), and 40 g of UCECOAT™ 7772 (an acrylated polyurethane dispersion); all of these UCECOAT™ monomers are commercial waterborne oligomers of Cytec Surface Specialties. [0053] The components of the samples were mixed together, and the samples were drawn down on Q-Panels of cold rolled steel with #3 draw down wire, after which they were placed in an 80⁰C oven for 5 minutes. The samples were then cured at 100 fpm under a Fusion 600 line H-bulb. The extent of cure was determined by a thumb twist test, and is reported under "surface" in Table 1. The MEK Double Rub Test employed a one-pound hammer wrapped with cheese cloth and saturated with methyl ethyl ketone. The test results indicate how many "double rubs" it took to break through the coating material. Results of the MEK double rub test are summarized in Table 1.

TABLE l

1 = N-methyl-N,N-diethanolamine

2 = Good

3 = Methyl ethyl ketone double rub test

EXAMPLE 5

[0054] Sample C from Example 4 was also used to evaluate the effects of residual water on cure of a 3 micron coating as a function of time in an oven at 80 ° C. The extent of cure was determined by a thumb twist test, and is reported under "surface" in Table 2. The MEK double rub test was conducted as described in Example 4. The KMnO₄ stain test was used to measure the stain resistance of the coating, where a higher number indicates poorer stain resistance. Results of the tests are summarized in Table 2.

TABLE 2

1 = Methyl ethyl ketone double rub test [0055] As used herein, and as will be appreciated by the skilled artisan, the term photopolymerizable composition refers to compositions which harden or cure upon exposure to radiation.

[0056] The photopolymerizable compositions can be applied or deposited on a surface of a substrate using conventional techniques and apparatus. The composition can be applied as a substantially continuous film. Alternatively, the composition can be applied in a discontinuous pattern. The thickness of the deposited composition can vary, depending upon the desired thickness of the resultant cured product. Typically, the substrate is coated with the uncured photopolymerizable composition and passed under a commercially available UV or excimer lamp on a conveyer moving at predetermined speeds. The substrate to be coated can be, for example, metal, wood, mineral, glass, paper, plastic, fabric, ceramic, and the like. [0057] The active energy beams used in accordance with the present invention may be visible light or ultraviolet light or may contain in their spectra both visible and ultraviolet light. The polymerization may be activated by irradiating the composition with the aforementioned energy beams using any of the techniques known in the art for providing radiation, i.e., in the range of 200 nm and 450 nm ultraviolet radiation, or by irradiating the composition with radiation outside of the ultraviolet spectrum. The radiation may be natural or artificial, monochromatic or polychromatic, incoherent or coherent and should be sufficiently intense to activate the photoinitiators of the invention and thus the polymerization. Conventional radiation sources include fluorescent lamps, excimer lamps, mercury, metal additive and arc lamps. Coherent light sources include pulsed nitrogen, xenon, argon ion- and ionized neon lasers whose emissions fall within or overlap the ultraviolet or visible absorption bands of the compounds of the invention. [0058] The compositions are useful in any of the types of applications known in the art for photopolymerizations, including as a binder for solids to yield a cured product in the nature of a paint, varnish, enamel, lacquer, stain or ink. The compositions can also be useful hi the production of photopolymerizable surface coatings in printing processes, such as lithographic printing, flexo printing, screen printing, and the like. [0059] It is to be understood that the reactants and components referred to by chemical name or formula anywhere in this document, whether referred to in the singular or plural, are identified as they exist prior to coming into contact with another substance referred to by chemical name or chemical type (e.g. , another reactant, a solvent, or etc.). It matters not what preliminary chemical changes, transformations and/or reactions, if any, take place in the resulting mixture or solution or reaction medium as such changes, transformations and/or reactions are the natural result of bringing the specified reactants and/or components together under the conditions called for pursuant to this disclosure. Thus the reactants and components are identified as ingredients to be brought together in connection with performing a desired chemical operation or reaction or in forming a mixture to be used in conducting a desired operation or reaction. Also, even though an embodiment may refer to substances, components and/or ingredients in the present tense ("is comprised of, "comprises", "is", etc.), the reference is to the substance, component or ingredient as it existed at the time just before it was first contacted, blended or mixed with one or more other substances, components and/or ingredients in accordance with the present disclosure.

[0060] Also, even though the claims may refer to substances in the present tense (e.g., "comprises", "is", etc.), the reference is to the substance as it exists. at the time just before it is first contacted, blended or mixed with one or more other substances in accordance with the present disclosure.

[0061] Except as may be expressly otherwise indicated, the article "a" or "an" if and as used herein is not intended to limit, and should not be construed as limiting, the description or a claim to a single element to which the article refers. Rather, the article "a" or "an" if and as used herein is intended to cover one or more such elements, unless the text expressly indicates otherwise.

[0062] Each and every patent or other publication or published document referred to in any portion of this specification is incorporated in toto into this disclosure by reference, as if fully set forth herein. [0063] This invention is susceptible to considerable variation within the spirit and scope of the appended claims.

Claims

1. A composition which is a metal carboxylate, in which carboxylate a benzoylphenyl group is present.

2. A composition of Claim 1 wherein said carboxylate is an alkali metal carboxylate.

3. A composition of Claim 2 wherein said carboxylate is a lithium carboxylate, sodium carboxylate, or potassium carboxylate.

4. A composition of Claim 1 wherein said carboxylate has only one carboxylate group.

5. A composition of Claim 1 wherein said carboxylate is a benzoylbenzoate.

6. A composition of Claim 2 wherein said salt is a lithium carboxylate, sodium carboxylate, or potassium carboxylate, and wherein said carboxylate is an unsubstituted benzoylbenzoate.

7. A process for preparing a metal carboxylate of Claim 1, which process comprises mixing together in an aqueous medium at least one inorganic base and at least one carboxylic acid in which a benzoylphenyl group is present.

8. A process of Claim 7 wherein said inorganic base is an alkali metal hydroxide.

9. A process of Claim 8 wherein said alkali metal hydroxide is lithium hydroxide, sodium hydroxide, or potassium hydroxide.

10. A process of Claim 7 wherein said carboxylic acid has only one carboxylic acid group.

11. A process of Claim 7 wherein said carboxylic acid is a benzoylbenzoic acid.

12. A process of Claim 8 wherein said alkali metal hydroxide is lithium hydroxide, sodium hydroxide, or potassium hydroxide, and wherein said carboxylic acid is an unsubstituted benzoylbenzoic acid.

13. A composition which is a tertiary ammonium carboxylate, in which carboxylate a benzoylphenyl group is present.

14. A composition of Claim 13 wherein said tertiary ammonium carboxylate has a tertiary ammonium cation in which each group on said cation has up to about six carbon atoms.

15. A composition of Claiml 3 wherein said tertiary ammonium carboxylate has a tertiary ammonium cation in which at least one group on said cation has at least one available hydrogen atom attached to a carbon atom adjacent to a heteroatom.

16. A composition of Claiml 3 wherein said tertiary ammonium carboxylate has a tertiary ammonium cation in which there are "n" alkanol groups and "3-n" hydrocarbyl groups, where n is 1 to 3.

17. A composition of Claiml 3 which is N-ethyl-N,N-diethanolammonium benzoyl benzoate.

18. A composition of any of Claims 1-6 or 13-17 wherein said composition contains about 3 wt% to about 99.5 wt% water.

19. A composition of any of Claims 1-6 or 13-17 wherein said composition contains about 5 wt% to about 70 wt% water.

20. A process for preparing a tertiary ammonium carboxylate of Claim 13 , which process comprises mixing together in an aqueous medium at least one tertiary amine and at least one carboxylic acid in which a benzoylphenyl group is present.

21. A process of Claim 20 wherein said tertiary amine has up to about six carbon atoms in each group on said amine.

22. A process of Claim 20 wherein said tertiary amine has at least one group on which has at least one available hydrogen atom attached to a carbon atom^" adjacent to a heteroatom.

23. A process of Claim 20 wherein said tertiary amine has V alkanol groups and "3-n" hydrocarbyl groups, where n is 1 to 3.

24. A process of Claim 20 wherein said tertiary amine is N-ethyl-N,N- diethanolamine.

25. A process of Claim 20 wherein said carboxylic acid has only one carboxylic acid group.

26. A process of Claim 20 or 23 wherein said carboxylic acid is a benzoylbenzoic acid.

27. A photoinitiator composition which comprises a) (i) at least one metal carboxylate, in which carboxylate a benzoylphenyl group is present, and/or (ii) at least one tertiary ammonium carboxylate, in which carboxylate a benzoylphenyl group is present; and b) at least one coinitiator comprising at least one benzoyl moiety and at least one aliphatic alcohol moiety.

28. A photopolymerizable composition which comprises a photoinitiator composition of Claim 27, at least one photopolymerizable monomer, and water.

29. A composition of Claim 27 or 28 wherein a) is at least one metal carboxylate.

30. A composition of Claim 29 wherein said carboxylate is a lithium carboxylate, sodium carboxylate, or potassium carboxylate.

31. A composition of Claim 27 or 28 wherein a) is at least one tertiary ammonium carboxylate.

32. A composition of Claim 31 wherein said tertiary ammonium carboxylate has a tertiary ammonium cation in which at least one group on said cation has at least one available hydrogen atom attached to a carbon atom adjacent to a heteroatom.

33. A composition of Claim 31 wherein said tertiary ammonium carboxylate has a tertiary ammonium cation in which there are V alkanol groups and "3-n" hydrocarbyl groups, where n is 1 to 3.

34. A composition of any of Claims 27-33 wherein said benzoyl moiety of said coinitiator is unsubstituted, and wherein said aliphatic alcohol moiety of said coinitiator has from about three to about twelve carbon atoms.

35. A composition of any of Claims 27-33 wherein said coinitiator is 2-hydroxy-2- methyl-1-phenyl-proρan-l-one or 1-hydroxycyclohexyl phenyl ketone.

36. A composition of any of Claims 27-35 wherein there is in the range of about 0.01 to about 10 parts by weight of said coinitiator per part by weight of said carboxylate.

37. A composition of any of Claims 27-35 wherein there is in the range of about 0.3 to about 1 part by weight of said coinitiator per part by weight of said carboxylate.

38. A composition of Claim 28 wherein said photopolymerizable monomer is from about 10 wt% to about 99.5 wt% of the composition, based on the total weight of the composition.

39. A composition of Claim 28 wherein said photopolymerizable monomer is from about 80 wt% to about 99.5 wt% of the composition, based on the total weight of the composition.

40. A composition of Claim 28 wherein said tertiary ammonium carboxylate has a tertiary ammonium cation in which there are n alkanol groups and "3-n" hydrocarbyl groups, where "n" is 1 to 3; wherein there is in the range of about 0.01 to about 10 parts by weight of said coinitiator per part by weight of said carboxylate; and wherein said photopolymerizable monomer is from about 80 wt% to about 99.5 wt% of the composition, based on the total weight of the composition.

41. A photopolymerizable composition which comprises at least one tertiary ammonium carboxylate, in which carboxylate a benzoylphenyl group is present; at least one photopolymerizable monomer; and water.

42. A composition of Claim 41 wherein said tertiary ammonium carboxylate has a tertiary ammonium cation in which at least one group on said cation has at least one available hydrogen atom attached to a carbon atom adjacent to a heteroatom.

43. A composition of Claim 41 wherein said tertiary ammonium carboxylate has a tertiary ammonium cation in which there are "n" alkanol groups and "3-n" hydrocarbyl groups, where n is 1 to 3.

44. A composition of any of Claims 41-43 wherein said photopolymerizable monomer is from about 10 wt% to about 99.5 wt% of the composition, based on the total weight of the composition.

45. A composition of any of Claims 41-43 wherein said photopolymerizable monomer is from about 80 wt% to about 99.5 wt% of the composition, based on the total weight of the composition.

46. A process which comprises photopolymerizing at least one photopolymerizable monomer by exposing said at least one photopolymerizable monomer to radiation in an aqueous medium in the presence of a photoinitiator composition of Claim 27.

47. A process of Claim 46 wherein a) is at least one metal carboxylate.

48. A process of Claim 47 wherein said carboxylate is a lithium carboxylate, sodium carboxylate, or potassium carboxylate.

49. A process of Claim 46 wherein a) is at least one tertiary ammonium carboxylate.

50. A process of Claim 49 wherein said tertiary ammonium carboxylate has a tertiary ammonium cation in which at least one group on said cation has at least one available hydrogen atom attached to a carbon atom adjacent to a heteroatom.

51. A process of Claim 49 wherein said tertiary ammonium carboxylate has a tertiary ammonium cation in which there are V alkanol groups and "3-n" hydrocarbyl groups, where n is 1 to 3.

52. A process of any of Claims 46-51 wherein said benzoyl moiety of said coinitiator is unsubstituted, and wherein said aliphatic alcohol moiety of said coinitiator has from about three to about twelve carbon atoms.

53. A process of any of Claims 46-51 wherein said coinitiator is 2-hydroxy-2- methyl-1-phenyl-propan-l-one or 1-hydroxycyclohexyl phenyl ketone.

54. A process of any of Claims 46-53 wherein there is in the range of about 0.01 to about 10 parts by weight of said coinitiator per part by weight of said carboxylate.

55. A process of any of Claims 46-53 wherein there is in the range of about 0.3 to about 1 part by weight of said coinitiator per part by weight of said carboxylate.

56. A process which comprises photopolymerizing at least one photopolymerizable monomer by exposing said at least one photopolymerizable monomer to radiation in an aqueous medium in the presence of at least one tertiary ammonium carboxylate, in which carboxylate a benzoylphenyl group is present.

57. A process of Claim 56 wherein said tertiary ammonium carboxylate has a tertiary ammonium cation in which at least one group on said cation has at least one available hydrogen atom attached to a carbon atom adjacent to a heteroatom.

58. A process of Claim 56 wherein said tertiary ammonium carboxylate has a tertiary ammonium cation in which there are "n" alkanol groups and "3-n" hydrocarbyl groups, where n is 1 to 3.