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Title:
AMINOBENZOPHENONES AND PHOTOPOLYMERIZABLE COMPOSITIONS INCLUDING SAME
Document Type and Number:
WIPO Patent Application WO/1998/033764
Kind Code:
A1
Abstract:
Novel benzophenone derivatives and methods of making and using the same are disclosed. The novel compounds can display highly active photoinitiation and photopolymerization properties.

Inventors:
Santobianco, John Gabriel (4957 East Belle Fontaine Beach Road, Ocean Springs, MS, 39564, US)
Muller, August John (2408 Huffman Drive, Mobile, AL, 36693, US)
Bowers Jr., Joseph Stanton (63 South Georgia Avenue, Mobile, AL, 36604, US)
Nagarajan, Rajamani (3230 Cumberland Road, No.14 Ocean Springs, MS, 39564, US)
Application Number:
PCT/US1998/001951
Publication Date:
August 06, 1998
Filing Date:
February 03, 1998
Export Citation:
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Assignee:
FIRST CHEMICAL CORPORATION (1001 Industrial Road, Pascagoula, MS, 39581-3237, US)
Santobianco, John Gabriel (4957 East Belle Fontaine Beach Road, Ocean Springs, MS, 39564, US)
Muller, August John (2408 Huffman Drive, Mobile, AL, 36693, US)
Bowers Jr., Joseph Stanton (63 South Georgia Avenue, Mobile, AL, 36604, US)
Nagarajan, Rajamani (3230 Cumberland Road, No.14 Ocean Springs, MS, 39564, US)
International Classes:
C07C225/22; C08F2/50; G03F7/029; (IPC1-7): C07C225/22; C08F2/50; G03F7/029
Foreign References:
DE2729918A11979-01-18
DE3606155A11987-08-27
DE4303938A11993-08-19
US5428163A1995-06-27
US5378519A1995-01-03
US5229238A1993-07-20
US4507497A1985-03-26
Other References:
PATENT ABSTRACTS OF JAPAN vol. 011, no. 282 (C - 446) 11 September 1987 (1987-09-11)
DATABASE WPI Section Ch Week 9435, Derwent World Patents Index; Class E13, AN 94-283314, XP002066200
DATABASE WPI Section Ch Week 9435, Derwent World Patents Index; Class A41, AN 94-283313, XP002066201
PATENT ABSTRACTS OF JAPAN vol. 012, no. 143 (C - 492) 30 April 1988 (1988-04-30)
DATABASE WPI Section Ch Week 8501, Derwent World Patents Index; Class A89, AN 85-004014, XP002066202
DATABASE WPI Section Ch Week 9607, Derwent World Patents Index; Class A89, AN 96-066076, XP002066203
LESLIE HELLERMAN ET AL.: "Syntheses of Certain Derivatives of Phenylalanine and of Auramine in Studies of Antimalarial Action", JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, vol. 68, no. 10, 17 October 1946 (1946-10-17), DC US, pages 1890 - 1893, XP002066198
ULF PINDUR ET AL.: "[4+2]Cycloaddition of Indole Derivatives with Bismaleimides: a Route to New Biscarbazoles", JOURNAL OF THE CHEMICAL SOCIETY, PERKIN TRANSACTIONS 1, no. 12, 21 June 1997 (1997-06-21), LETCHWORTH GB, pages 1861 - 1867, XP002066199
Attorney, Agent or Firm:
Arroyo, Blas P. (Bell Seltzer Intellectual Property Law Group, ALSTON & BIRD LLP P.O. Drawer 3400, Charlotte NC, 28234, US)
Download PDF:
Claims:
THAT WHICH IS CLAIMED IS:
1. A compound having the Formula (I) wherein: each A is independently selected from the group consisting of hydrogen, lower alkyl, cycloalkyl, aryl, lower alkanol, lower alkoxy, halogen, sulfonyl, alkylsulfonyl, trihaloalkyl, trihaloalkoxy, trihaloalkylthio, polymerizable moiety, and oligomeric moiety, with the proviso that no more than three A are the same lower alkyl; each R is independently selected from the group consisting of hydrogen, lower alkyl, cycloalkyl, aryl, lower alkanol, lower alkoxy, halogen, sulfonyl, alkylsulfonyl, trihaloalkyl, trihaloalkoxy, trihaloalkylthio, polymerizable moiety, and oligomeric moiety; and n is an integer from 1 to 4.
2. The compound of Claim 1, wherein each A is lower alkyl.
3. The compound of Claim 2, wherein three As are methyl and one A is ethyl.
4. The compound of Claim 2, wherein three As are ethyl and one A is methyl.
5. The compound of Claim 2, wherein said compound is selected from the group consisting of 4,4' bis(methylethylamino)benzophenone, 4(dimethylamino) 4'(methylethylamono)benzophenone), and 4 (diethylamino) 4' (methylethylamino) benzophenone.
6. The compound of Claim 1, wherein each R is hydrogen.
7. A compound having the formula wherein: each A is independently selected from the group consisting of lower alkyl, with the proviso that no more than three As are the same lower alkyl; each R is hydrogen; and n is an integer from 1 to 4.
8. A compound having the formula.
9. A photopolymerizable composition comprising a photopolymerizable compound comprising at least one ethylenically unsaturated double bond and a photoinitiator having the Formula (I) wherein: each A is independently selected from the group consisting of hydrogen, lower alkyl, cycloalkyl, aryl, lower alkanol, lower alkoxy, halogen, sulfonyl, alkylsulfonyl, trihaloalkyl, trihaloalkoxy, trihaloalkylthio, polymerizable moiety, and oligomeric moiety, with the proviso that no more than three A are the same lower alkyl; each R is independently selected from the group consisting of hydrogen, lower alkyl, cycloalkyl, aryl, lower alkanol, lower alkoxy, halogen, sulfonyl, alkylsulfonyl, trihaloalkyl, trihaloalkoxy, trihaloalkylthio, polymerizable moiety, and oligomeric moiety; and n is an integer from 1 to 4.
10. The composition of Claim 9, wherein each A is lower alkyl.
11. The composition of Claim 10, wherein three As are methyl and one A is ethyl.
12. The composition of Claim 10, wherein three As are ethyl and one A is methyl.
13. The composition of Claim 10, wherein said compound is selected from the group consisting of 4,4'bis(methylethylamino)benzophenone, 4 (dimethylamino) 4' (methylethylamono) benzophenone), and 4(diethylamino)4'(methylethylamino)benzophenone.
14. The composition of Claim 9, wherein each R is hydrogen.
15. A photopolymerizable composition comprising a photopolymerizable compound comprising at least one ethylenically unsaturated double bond and a photoinitiator having the formula wherein: each A is independently selected from the group consisting of lower alkyl, with the proviso that no more than three As are the same lower alkyl; each R is hydrogen; and n is an integer from 1 to 4.
16. A photopolymerizable composition comprising a photopolymerizable compound comprising at least one ethylenically unsaturated double bond and a photoinitiator having the formula.
17. A method of polymerizing a polymerizable compound comprising at least one ethylenically unsaturated double bond, comprising exposing said compound to ultraviolet radiation in the presence of a compound having the Formula (I) wherein: each A is independently selected from the group consisting of hydrogen, lower alkyl, cycloalkyl, aryl, lower alkanol, lower alkoxy, halogen, sulfonyl, alkylsulfonyl, trihaloalkyl, trihaloalkoxy, trihaloalkylthio, polymerizable moiety, and oligomeric moiety, with the proviso that no more than three A are the same lower alkyl; each R is independently selected from the group consisting of hydrogen, lower alkyl, cycloalkyl, aryl, lower alkanol, lower alkoxy, halogen, sulfonyl, alkylsulfonyl, trihaloalkyl, trihaloalkoxy, trihaloalkylthio, polymerizable moiety, and oligomeric moiety; and n is an integer from 1 to 4.
18. The method of Claim 17, wherein each A is lower alkyl.
19. The method of Claim 18, wherein three As are methyl and one A is ethyl.
20. The method of Claim 18, wherein three As are ethyl and one A is methyl.
21. The method of Claim 18, wherein said compound is selected from the group consisting of 4,4' <BR> <BR> <BR> bis(methylethylamino)benzophenone, 4 (dimethylamino) 4'(methylethylamono)benzophenone), and 4 (diethylamino) 4' (methylethylamino) benzophenone.
22. The method of Claim 17, wherein each R is hydrogen.
23. A method of polymerizing a polymerizable compound comprising at least one ethylenically unsaturated double bond, comprising exposing said compound to ultraviolet radiation in the presence of a compound having the formula wherein: each A is independently selected from the group consisting of lower alkyl, with the proviso that no more than three As are the same lower alkyl; each R is hydrogen; and n is an integer from 1 to 4.
24. A method of polymerizing a polymerizable compound comprising at least one ethylenically unsaturated double bond, comprising exposing said compound to ultraviolet radiation in the presence of a compound having the formula.
Description:
AMINOBENZOPHENONES AND PHOTOPOLYMERI ZABLE COMPOSITIONS INCLUDING SAME Cross-Reference to Related Application This application is related to commonly owned copending Provisional Application Serial No.

60/037,155, filed February 4, 1997.

Field of the Invention This invention relates generally to novel photoactive compounds and methods for using the same.

More particularly, this invention relates to aminobenzophenones and methods of using the same in photoactivatable polymerization systems.

Background of the Invention Ethylenically unsaturated compounds, and in particular acrylate derivatives, can be polymerized by irradiation with ultraviolet.light of wavelength between 200 and 450 nanometers (nm) in the presence of a bimolecular photoinitiating system. The photoinitiating system can include, for example, (1) a benzophenone derivative and (2) a coinitiator or synergist, that is, a molecule which serves as a hydrogen atom donor. The coinitiators or synergists are typically alcohols, tertiary amines or ethers which have available hydrogens attached to a carbon adjacent to a heteroatom.

One commercially available benzophenone derivative useful as a photoinitiator is 4,4'-

bis(dimethylamino)benzophenone, also referred to in the art as "Michler's Ketone;. Michler's Ketone has the following structure: While Michler's Ketone can be useful as a photoinitiator in radiation curing of polymers, it is typically used little in the industry due to its potentially hazardous characteristics.

4,4'-Bis(diethylamino)benzophenone (also referred to as tetraethyl Michler's Ketone) has been proposed as a possible alternative to Michler's Ketone due to its lower toxicity. However, this compound does not exhibit good photoinitiating activity and thus has not been widely adopted as an alternative to Michler's Ketone.

Other Michler's Ketone derivatives are described, for example, in U.S. Patent No. 4,507,497 to Reilly, Jr., which is directed to water soluble Michler's Ketone analogs which include amino groups substituted by R1COOH, in which R1 is an alkylene group having 1 to 8 carbon atoms.

Summary of the Invention It is accordingly an object of the present invention to provide compounds which can be used as photoinitiators in photopolymerization processes. It is also an object of the invention to provide compounds which exhibit useful photoinitiation activity with minimal or no adverse hazardous characteristics. These and other objects of the present invention will become

apparent from the following general and detailed description of the invention.

The objects of the present invention are achieved based on the discovery of novel compounds useful in photopolymerization systems. The compounds can display highly active photoinitiation and photopolymerization properties. The compounds of the invention have a structure according to Formula (I) below: wherein: each A is independently selected from the group consisting of hydrogen, lower alkyl, cycloalkyl, aryl, lower alkanol, lower alkoxy, halogen, sulfonyl, alkylsulfonyl, trihaloalkyl, trihaloalkoxy, trihaloalkylthio, polymerizable moiety, and oligomeric moiety, with the proviso that no more than three A are the same lower alkyl; each R is independently selected from the group consisting of hydrogen, lower alkyl, cycloalkyl, aryl, lower alkanol, lower alkoxy, halogen, sulfonyl, alkylsulfonyl, trihaloalkyl, trihaloalkoxy, trihaloalkylthio, polymerizable moiety, and oligomeric moiety; and n is an integer from 1 to 4.

The present invention also provides photopolymerizable compositions which include the compounds of Formula (I) above as a component thereof, as well as methods for the manufacture of the compounds of Formula (I) and methods for the use of the compounds of Formula (I) in photopolymerization systems.

Detailed Description of the Invention The novel compounds of the invention include compounds according to Formula (I) below: wherein: each A is independently selected from the group consisting of hydrogen, lower alkyl, cycloalkyl, aryl, lower alkanol, lower alkoxy, halogen, sulfonyl, alkylsulfonyl, trihaloalkyl, trihaloalkoxy, trihaloalkylthio, polymerizable moiety, and oligomeric moiety, with the proviso that no more than three A are the same lower alkyl; each R is independently selected from the group consisting of hydrogen, lower alkyl, cycloalkyl, aryl, lower alkanol, halogen, lower alkoxy, sulfonyl, alkylsulfonyl, trihaloalkyl, trihaloalkoxy, trihaloalkylthio, polymerizable moiety, and oligomeric moiety; and n is an integer from 1 to 4.

As used herein, the term lower alkyl refers to linear or branched C1-C8 alkyl, such as but not limited to methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, and the like, optionally substituted with one or more halogen, aryl, arylalkyl, alkylaryl, cycloalkyl, alkoxy, heteratom, and the like. The term cycloalkyl refers to C3 to C6 cyclic alkyl, such as but not limited to cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl, optionally substituted with one or more halogen, aryl, alkyl, arylalkyl, alkylaryl, cycloalkyl, alkoxy, heteratom, and the like. The term alkanol

refers to lower alkyl substituted with one or more hydroxyl groups. The term lower alkoxy refers to lower alkyl substituted with one or more oxygen atoms, including but not limited to methoxy, ethoxy, propoxy, butoxy, and the like. The term alkylsulfonyl refers to lower alkyl substituted with sulfonyl. The terms trihaloalkyl, trihaloalkoxy, and trihaloalkylthio refer to lower alkyl, lower alkoxy and lower alkylthio, respectively, in which hydrogen atoms on the organic group are replaced with halogen, preferably fluorine.

The term aryl refers to C3 to C10 cyclic aromatic groups such as but not limited to phenyl, naphthyl, and the like, optionally substituted with one or more halogen, alkyl, arylalkyl, alkylaryl, cycloalkyl, alkoxy, heteroatom, and the like. The term heteroatom refers to oxygen, nitrogen, sulfur, or phosphorous.

The term polymerizable moiety refers to ethylenically unsaturated moieties known in the art which are capable of reaction with another compound (for example, by a free radical mechanism), such as but not limited to, acrylate and methacrylate moieties.

For example, A can have the structure -(CH2)n-OC(O)-CRH=CH2 wherein n is an integer from 1 to 10 and R is H or lower alkyl. Yet another exemplary polymerizable moiety can be a maleimide moiety wherein: R' is selected from the group consisting of (CH2)n, wherein n is an integer from 0 to 10, optionally substituted with one or more heteroatom in the -CH2- chain; and

each R" is independently selected from the group consisting of hydrogen, lower alkyl, and halogen.

The term oligomeric moiety refers to a moiety including two or more monomer units (dimer, trimer, etc.), such as but not limited to an C2-C20 alkylene or polyalkylene polyol, wherein hydroxy groups of the polyol moiety are optionally alkylated, and preferably an alkylene or polyalkylene polyol derived from ethylene glycol. Other suitable oligomer moieties include C2-C20 alkylene or polyalkylene moieties end capped with trihaloalkyl, and optionally substituted with one. or more halogen atoms along the chain, preferably fluorine. Other exemplary oligomeric moieties include C2-C20 alkylene or polyalkylene moieties including carbonate groups and end capped with lower alkyl.

In one embodiment of the invention, each A of the compound of formula (I) is lower alkyl, preferably methyl or ethyl, with the proviso that no more than three As are the same. In another embodiment of the invention, at least one A is lower alkyl, preferably methyl or ethyl, and at least one other A is a polymerizable moiety or an oligomeric moiety.

Exemplary compounds of the invention in accordance with Formula I include without limitation: 4,4'-bis(methylethylamino)benzophenone 4-(dimethylamino)-4'-(methylethylamino)benzophenone 4-(diethylamino)-4'-(methylethylamino)benzophenone 4,4'-bis(methylethanolamino)benzophenone 4,4'-bis(methylmethylacrylateamino)benzophenone 4,4'-bis(maleimideamino)benzophenone

4-(methylethylamino)-4'-(aliphatic maleimideamino)benzophenone wherein n is an integer from 1 to 20; and the like.

In another embodiment of the invention, photopolymerizable compositions are provided which include a compound of Formula (I) above as a photoinitiator. 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.

Generally the compositions of the invention include ethylenically unsaturated compounds, including monomers, oligomers, polymers, prepolymers, resinous materials, optionally dispersed or dissolved in a suitable solvent that is copolymerizable therewith, and mixtures thereof, which are photopolymerizable when exposed to a source of ultraviolet ("W") radiation.

As will be appreciated by the skilled artisan, the photopolymerizable compounds can be monofunctional, or can include two or more terminal polymerizable ethylenically unsaturated groupings per molecule.

Exemplary photopolymerizable compounds or precursors include, but are not limited to, reactive vinyl monomers, including acrylic monomers, such as acrylic and methacrylic acids, and their amides, esters, salts and corresponding nitriles. Suitable vinyl monomers include, but are not limited to, methyl acrylate, ethyl acrylate, n- or tert-butylacrylate, isooctyl acrylate, methyl methacrylate,

ethylmethacrylate, 2-ethylhexyl methacrylate, butylacrylate, isobutyl methacrylate, the corresponding hydroxy acrylates, i.e., hydroxy ethylacrylate, hydroxy propylacrylate, hydroxy ethylhexyl methacrylate, glycol acrylates, i.e., ethylene glycol dimethacrylate, hexamethylene glycol dimethacrylate, the allyl acrylates, i.e., allyl methacrylate, diallyl methacrylate, the epoxy acrylates, i.e., glycidyl methacrylate, and the aminoplast acrylates, i.e., melamine acrylate. Others such as vinyl acetate, vinyl and vinylidene halides and amides, i.e., methacrylamide, acrylamide, diacetone acrylamide, butadiene, styrene, vinyl toluene, and the like are also included. Prepolymers include acrylated epoxides, polyesters and polyurethanes, and are typically combined with a suitable monomer for viscosity control.

The photopolymerizable compounds may be polymerized to form homopolymers or copolymerized with various other monomers.

The photopolymerizable compound can be present in the compositions of the invention in amounts between about 99.8 and about 90 percent by weight of the composition, preferably between about 99.5 and about 95 percent by weight.

In this aspect of the invention, the compounds of Formula (I) act as photopolymerization initiators. The compounds of Formula (I) are added to the photopolymerizable compound in an amount sufficient to initiate polymerization thereof upon exposure to ultraviolet radiation. The compound of Formula (I) can be one of several photoinitiators in a formulation in which the compounds of Formula (I) may act as sensitizers. Preferably the compounds of Formula (I) are present in the photopolymerizable composition in an amount between about 0.2 and about 10 parts by weight of the composition, and more preferably between about

0.5 and about 5 parts by weight, depending on the specific application.

The use of the compounds of Formula (I) can exhibit photoinitiation activity similar to that of Michler's Ketone, but unexpectedly also have greatly reduced toxicity.

The compositions of the invention can also include any of the various pigments or extenders, organic and inorganic, known in the art. Exemplary pigments or extenders include, but are not limited to, opacifying pigments such as zinc oxide, titania, e.g., anatase and rutile; basic lead sulfate, magnesium silicate, silica, clays, wollastonite, talcs, mica, chromates, iron pigments, wood fluor, microballoons (or microspheres), hard polymer particles, glass fiber or flake. Pigments can be present in the compositions of the invention in conventional amounts, i.e., between about 1 and about 40 percent by weight.

It can also be advantageous to also include as a component of the compositions of the invention a coinitiator or synergist, that is, a molecule which serves as a hydrogen atom donor. Coinitiators or synergists are known in the art, and are typically alcohols, tertiary amines or ethers which have available hydrogens attached to a carbon adjacent to a heteroatom. Such co-initiators are typically present in an amount between about 0.2 and about 25 percent by weight. Suitable compounds include triethanolamine, methyl-diethanolamine, ethyldiethanolamine and esters of dimethylamino benzoic acid. These compounds behave as co-initiators or accelerators for the primary photoinitiators and can increase the efficiency and speed of the polymerization process.

In addition, the compositions of the present invention may contain polymerization inhibitors, fillers, ultraviolet absorbers and organic peroxides.

The compositions of the invention can be applied or deposited to 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. Usually the compositions of the invention are fluid at ordinary operating temperatures (between ambient and up to about 60"C).

The thickness of the deposited composition can vary, depending upon the desired thickness of the resultant cured product. Advantageously, the composition is applied to the substrate surface in an amount sufficient to provide a cured coating having a thickness between about 1 micron and about 250 mils.

Typically, the substrate is coated with the uncured photopolymerizable composition and passed under an ultraviolet providing light beam by a conveyer moving at predetermined speeds. The substrate to be coated can be, for example, metal, mineral, glass, paper, plastic, fabric, ceramic, and the like.

The active energy beams used in accordance with the present invention may be 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, i.e., in the range of about 200 nm and about 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, 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. In one embodiment of the invention, the composition including the compounds of the invention is exposed to ultraviolet radiation having a wavelength of about 200 to about 450 nm.

When polymerized by exposure to W radiation, the compositions of the invention give a substantially tack-free product which is durable for ordinary handling. The compositions of the invention 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.

The compounds of the invention can be prepared from an aniline compound which may be substituted at any position, preferably at any position except the 4 position. The nitrogen atom of the aniline can be substituted using techniques known in the art. For example, the aniline can be alkylated using known techniques. In this regard, the aniline may be converted to an N-ethylaniline by reductive alkylation with acetaldehyde by methods reviewed by Rylander in "Catalytic Hydrogenation over Platinum Metals." The N-ethylaniline may be converted to an N-ethyl, N-methylaniline by subsequent reductive alkylation with formaldehyde. These N-alkylations may also be performed with alcohol reagents by methods known in the art. The order of the N-alkylations may also be reversed in order to firstly form the N-methyl and secondly form the N-ethyl, N-methyl intermediate. The N-ethyl, N-methylaniline may be converted to the 4,4'-bis(methylethylamino)benzophenone by reaction with phosgene in the method of Michler disclosed in

Chemische Berichte in the year 1876, p. 1914. This synthesis is described in detail in the following example of the conversion of N-ethylaniline, which is commercially available from First Chemical Corporation, to the photoinitiator 4, 4' -bis (methylethylamino) benzophenone.

Alternative synthetic routes are disclosed in Japanese Kokai 08-12630 published January 16, 1996 and in German patent 2226039, which teach the formation of a diphenylmethane and subsequent oxidation to form the benzophenone. For example, to prepare MEAB, N- ethylaniline can be reacted with formaldehyde with palladium catalyst to produce N-ethylmethyl aniline, which can be reacted with formaldehyde to give 4,4'- bis(ethylmethylamino)diphenyl methane, which is oxidized using a suitable oxidizing agent, such as chloranil/sodium chlorite. Yet another alternative route is amination of 4,4'-bis(chloro)benzophenone with methylethylamine by the method disclosed in U.S. Patent 2,231,067.

The nitrogen atoms can alternatively be hydroxylated as known in the art, or one can start with hydroxy substituted aniline compounds, such as N-alkyl, N'-hydroxyalkyl anilines, commercially available, for example, from First Chemical Corporation. The hydroxyl functionality is reacted with suitable reagents as known in the art to provide the desired functionality.

For example, a hydroxyl functionality can be reacted with a sulfonyl halide to provide sulfonyl groups. A hydroxyl functionality can alternatively be reacted with acryloyl halide to provide an acrylate group.

In yet another embodiment of the invention, compounds having at least one maleimide unit can be prepared according to techniques known in the art. For example, a suitably substituted aromatic amine can be reacted with maleic anhydride (or a substituted maleic anhydride, such as citraconic anhydride) in a polar

solvent to provide the amic acid. This is followed by an acid catalyzed ring closure to form the imide.

Compounds having maleimide functional groups are described in pending U.S. Provisional Application Serial No. 60/047,729, pending U.S. Application Serial No. 08/917,024, Z.Y. Wang, Synthetic Comm. 20(11) 1607- 1610 (1990); P.O. Tawnet et al., J.Org.Chem. 26, 15 (1961), and U.S. Patent No. 2,542,145, the entire disclosure of each of which is hereby incorporated by reference. See also U.S. Patent Nos. 5,629,356, U.S.

Patent No. 5,468,904 and WO 96/33156, the entire disclosure of which are also incorporated by reference, which are directed to compounds which have polymerizable or oligomeric moieties incorporated therein.

Other compounds which can be converted to a benzophenone include, but are not limited to, N-ethyl-m-toluidine, o-toluidine, m-toluidine, 3-propylaniline, 2,3-dimethylaniline, 2,5-dimethylaniline, 2,6-dimethylaniline, 3,5-dimethylaniline, 2-cyclopentylaniline, o-anisidine, m-anisidine, 2-(methylsulfonyl)aniline, 2-fluoroaniline, 2-chloroaniline, 3-chloroaniline, 2,6-dichloroaniline, 2,3,5,6-tetrachloroaniline, 2-(trifluoromethyl)aniline, 3-(trifluoromethyl)aniline, 2-(trifluoromethoxy)aniline, 2- (trifluoromethyl) thioj aniline, and the like.

The present invention will be further illustrated by the following non-limiting examples.

EXAMPLE 1 Synthesis of 4,4'-Bisfethylmethylamino)benzophenone (MEAB) Ethyl-aniline is methylated by reductive alkylation with formaldehyde using isopropyl alcohol as a solvent at 1000C under 120 psi of H2. After the solvent is stripped the product ethylmethylaniline

(NEMA) is purified by distillation at 1200C at a pressure of 21 mm mercury (Hg). NEMA (80 g, 0.59 mol) is charged to a vessel fitted with a dry-ice condenser and is heated to 50-600C. Phosgene is transferred from a cylinder to a calibrated trap placed in dry-ice.

After condensing 10 mL (14.3 g, 0.145 mol), the trap was connected to the vessel containing NEMA and the phosgene was added over 1 hour. After the addition was complete, the mixture was heated to 120"C and held at this temperature for 1 hour. The mixture was cooled to 50-60"C before 11 g (0.275 mol) of NaOH dissolved in 100 mL of water was added to hydrolyze the unreacted acid chloride. The resulting mixture was then extracted with two 100 mL portions of toluene. The product 4,4'- bis(ethylmethylamino)benzophenone (MEAB) was purified by chromatography on silica gel using toluene as an eluent followed by recrystallization from methylene chloride/hexane. Several grams of highly pure MEMK were obtained. No impurities were detectable by NMR; m.p. 122-124"C. NMR, IR and mass spectra were consistent with the proposed structure.

EXAMPLE 2 Use of MEAB as Photoinitiator Michler's Ketone (also tetramethyl Michler's Ketone or TMMK), tetraethyl Michler's Ketone (also 4,4'-bis(diethylamino)benzophenone or TEMK), and MEAB were tested in curing hexanediol diacrylate compositions. The composition included 1% by weight isopropylthioxanthone, 2% ethyl 4-N,N- dimethylaminobenzoate, 4% benzophenone, 1% aminobenzophenone compound, and the balance hexanediol diacrylate. The composition was applied as a 0.15 inch film to a substrate and cured with a Fusion W Systems "H" bulb with 600 Watts/inch power with a belt speed of 55 feet per minute. MEAB and TMMK both required 10 passes under the lamp to obtain a well-cured hard

polymer, and TEMK required 25 passes. This illustrates that MEAB and TMMK have approximately the same activity, and both are much superior to the tetraethyl compound.

EXAMPLE 3 Comparative Mutagenicity of TMMK TEMK and MEAB Michler's ketone (TMMK) is listed by the National Toxicology Program as "reasonably anticipated to be a carcinogen" based on the results of cancer studies in rats and mice. Seventh Annual Report on Carcinogens, U.S. Dept. Health Human Services, p. 259, 1994. Based on comparisons of mutagenicity studies with animal cancer studies, mutagens are more likely to cause cancer, to produce tumors in multiple organs, and to affect multiple species. Gold, L.S. et al., Mutat.

Res. 286, 75-100 (1993).

Mutagenicity can be measured by a variety of assays. The most commonly used method is the Salmonella/Mammalian-Microsome Reverse Mutation Assay (Ames Test), which commonly uses four or five strains of Salmonella bacteria to detect different types of mutations.

Michler's Ketone has been tested in the Ames Test a number times. Scribner, J.D. et al. Cancer Lett. 9, 117-121 (1980); McCarthy, D.J. et al. Mutat. Res. 119, 7-14 (1983); Dunkel, V.C. et al, Environ. Mutagen. 7 (Suppl. 5), 1-248 (1985); Zeiger, E. et al, Environ.

Mol. Mutagen. 19 (Suppl. 21), 2-141 (1992). In this assay, the bacterial strain which was consistently found to have mutations when adequate concentrations of test material were used was Salmonella typhimurium tester strain TA98, with added mammalian metabolic activation. Dunkel, V.C. et al, Environ. Mutagen. 7 (Suppl. 5), 1-248 (1985); Zeiger, E. et al, Environ.

Mol. Mutagen. 19 (Suppl. 21), 2-141 (1992).

TMMK, TEMK, and MEAB were evaluated for the ability to induce reverse mutations at the histidine locus in the genome of a specific Salmonella typhimurium tester strain in the presence of an exogenous metabolic activation system of mammalian microsomal enzymes derived from AroclorTM-induced rat liver (S9). The tester strain used in the mutagenicity assay was Salmonella typhimurium tester strain TA98 with added activation. The assay was conducted using eight doses of the test article, along with the appropriate vehicle and positive controls in the presence of S9 mix (S9 homogenate was purchased from Molecular Toxicology, Inc., Annapolis, MD 21401, Batch 0646, 43.4 mg of protein per ml). Positive controls were also plated in the absence of S9 mix. All doses of test article, vehicle, and positive controls were plated in triplicate.

1. Test Article Handling The test article TMMK was stored at room temperature. Acetone (CAST 67-64-1, Fisher Scientific Co., Lot 961140) was used as the vehicle. At 20 mg per ml, which was the most concentrated stock solution which could be prepared, the test article formed a clear, light yellow solution. The test article remained a solution in all succeeding dilutions prepared for the mutagenicity assay. The maximum aliquot of acetone which can be used in the test system is 200 jil. Thus, the maximum concentration which could be tested was 4,000 yg per plate. The test article and vehicle controls were plated using a 200 yl plating aliquot. Positive control articles were plated using 50 yl plating aliquot.

The test article TEMK was stored at room temperature. Acetone (CAS# 67-64-1, Fisher Scientific Co., Lot 961140) was used as the vehicle. At 100 mg per ml, which was the most concentrated stock solution

prepared, the test article formed a clear, yellow solution. The test article remained a solution in all succeeding dilutions prepared for the mutagenicity assay. The test article, vehicle controls and positive control articles were plated using a 50 jil plating aliquot.

The test article MEAB was stored at room temperature. Acetone (CAST 67-64-1, Fisher Scientific Co., Lot 961140) was used as the vehicle. At 25 mg per ml, which was the most concentrated stock solution prepared, the test article formed a clear, light yellow solution. The test article remained a solution in all succeeding dilutions prepared for the mutagenicity assay. The test article and vehicle controls were plated using a 200 yl plating aliquot. Positive control articles were plated using a 50 Ul plating aliquot.

2. Mutagenicity Assay The mutagenicity assay results for TMMK, TEMK, and MEAB are presented in Table 1. The data are presented as individual plate counts along with a mean and standard deviation.

The results of the Salmonella/Mammalian-Microsome Reverse Mutation Screening Assay (Ames Test) indicate that TMMK did cause a positive (3.9-fold) increase in the number of revertants per plate with tester strain TA98 in the presence of S9 mix. Test articles TEMK and MEAB did not cause a positive increase in the number of revertants per plate with tester strain TA98 in the presence of S9 mix. Of the three test materials, only TMMK was mutagenic. For aromatic amino or nitro compounds such as these test materials, very few which were not mutagenic in the Ames test have been found to cause tumors in animal cancer studies. Ashby, J. and Tennant, R.W., Mutat. Res. 257, 229-306 (1991). Therefore, these results suggest that MEAB has a lower potential to cause tumors than TMMK.

TABLE 1<BR> MUTAGENICITY ASSAY RESULTS<BR> INDIVIDUAL PLATE COUNTS<BR> REVERTANTS PER PLATE<BR> COMPOUND TMMK TEMK MEAB SAMPLE BACK BACK BACK GROUND GROUND GROUND LAWN* LAWN* LAWN* 1 2 3 1 2 3 1 2 3 MICROSOMES: Rat Liver VEHICLE CONTROL 10 22 30 1 16 36 11 1 9 20 30 1 TEST ARTICLE (DOSE/PLATE) 3.33 µg 14 29 24 1 22 22 30 1 13 21 22 1 10.0 µg 9 19 19 1 30 24 20 1 25 28 11 1 33.3 µg 21 35 37 1 13 23 19 1 24 25 24 1 100 µg 16 12 22 1sp 28 26 24 1 20 18 20 1sp 333 µg 18 23 12 1mp 20 17 19 1sp 21 31 19 1mp 1000 µg 35 26 33 1mp 32 23 17 1mp 36 23 21 1mp 3330 µg 78 82 78 6mp 27 15 25 1mp 27 14 17 1hp 4000 µg 80 70 93 6mp NT NT NT - NT NT NT - 5000 µg NT NT NT - 27 19 19 1mp 23 23 27 1hp POSITIVE CONTROL ** 1053 920 932 1 1264 1032 1133 1 1196 1225 1226 1 ** TA98 2-aminoanthracene 2.5 µg/plate<BR> * Background Lawn Evaluation Codes:<BR> 1 = normal 2 = slightly reduced 3 = moderately reduced<BR> 4 = extremely reduced 5 = absent 6 = obscured by precipitate<BR> sp = slight precipitate mp = moderate precipitate hp = heavy precipitate<BR> (requires hand count) (requires hand count)<BR> NT = Not tested.

TABLE 2<BR> MUTAGENICITY ASSAY RESULTS<BR> SUMMARY<BR> MEAN REVERTANTS PER PLATE WITH STANDARD DEVIATION COMPOUND TMMK TEMK MEAB DOSE/PLATE MEAN S.D. BACKGROUND MEAN S.D. BACKGROUND MEAN S.D. BACKGROUND LAWN* LAWN* LAWN* MICROSOMES: Rat Liver VEHICLE CONTROL 21 10 1 21 13 1 20 11 1 DOSE/PLATE 3.33 µg 22 8 1 25 5 1 19 5 1 10.0 µg 16 6 1 25 5 1 21 9 1 33.3 µg 31 9 1 18 5 1 24 1 1 100 µg 17 5 1sp 26 2 1 19 1 1sp 333 µg 18 6 1mp 19 2 1sp 24 6 1mp 1000 µg 31 5 1mp 24 8 1mp 27 8 1mp 3330 µg 79 2 6mp 22 6 1mp 19 7 1hp 4000 µg 81 12 6mp NT - - NT - 5000 µg NT - - 22 5 1mp 24 2 1hp POSITIVE CONTROL ** 968 74 1 1143 116 1 1216 17 1 ** TA98 2-aminoanthracene 2.5 µg/plate<BR> * Background Lawn Evaluation Codes:<BR> 1 = normal 2 = slightly reduced 3 = moderately reduced<BR> 4 = extremely reduced 5 = absent 6 = obscured by precipitate<BR> sp = slight precipitate mp = moderate precipitate hp = heavy precipitate<BR> (requires hand count) (requires hand count)<BR> NT = Not tested.

The foregoing examples are illustrative of the present invention and are not to be construed as limiting thereof. The invention is defined by the following claims, with equivalents of the claims to be included therein.