CA1155863A - Sensitizers for photopolymerisation - Google Patents

Abstract

ABSTRACT
Novel aromatic-aliphatic ketones of the formula:

(I) wherein Ar represents arylene or phenylene-T-phenylene, X
represents substituted amino, hydroxy, optionally substituted alkoxy, optionally substituted phenoxy or alkylated silyloxy and R1 and R2 generally represent optionally substituted alkyl, cycloalkyl or phenylalkyl are disclosed. The compounds (1) are useful as sensitizers for the photopolymerization of unsaturated compounds and for the photochemical crosslinking of polyolefins.

Description

CANADA

Sensitizers for_photopolymerisation The invention relates to the use of aromatic aliphatic ketones which are substituted in the ~-position as sensitizers for the photopolymerisation of unsaturated compounds or for the photochemical crosslinking of poly-olefins, as well as to the photopolymerisable and cross-linkable systems which contain such sensitizers.

Photochemical polymerisation processes have attained substantial importance in the art, especially in those cases where thin layers have to be hardened in a short time, for example in the hardening of varnish coat-ings or in the drying of printing inks. Compared with con-ventional hardening methods, UV irradiation in the presence of photosensitizers has a number of advantages, the most important of which is the great speed of the photohardening.
The speed is heavily dependent on the photosensitizer em-ployed and there has been no lack of attempts to replace the conventional sensitizers by ever better and more effec-tive compounds. Among the most effective photosensitizers are derivatives of benzoin, in particular the benzoin esters described for example in German patent specification Al ~

1~5~63 1,694,149, derivatives of ~-hydroxymethylbenzoin described in German Offenlegungsschrift 1,923,266, and the dialkoxy-acetophenones and benzil monoketals described for example in German Offenlegungsschrift 2,261,383 or 2,232,365.
~-Aminoacetophenones and ~-diaminoacetophenones have re-cently been proposed as photosensitizers in US patent speci-fication 4,04~,034and a-hydroxy-a-alkylolacetophenones and their ethers in German Offenlegungsschrift 2,357,866. The shortcomings of these known photosensitizers are in some cases an insufficient storage life in the dark of the photo-polymerisable systems mixed with such sensitizers. A number of benzoin derivatives tend to cause yellowing of the har-dened compositions. Other sensitizers are insufficiently reac-tive - a feature which is observed in the relatively lengthy hardening times - or their solubility in the photopolymeri-sable systems is too low or they are rapidly rendered in-active by atmospheric oxygen. There is therefore a need in the art for photosensitizers which are readily soluble in the substrate and, while having a good storage life in the dark, initiate the photopolymerisation more rapidly and give a higher polymer yield per unit of time than the known photosensitizers. By using such improved photosensitizers it would be possible to exploit better the expensive in-dustrial UV irradiation plants.

It has been found that compounds of the follow-ing formula I possess the required properties as photo-sensitizers. In particular, they effect a rapid photo-polymerisation and do not have the shortcomings referred to or possess them to a much lesser degree than the known photosensitizers. Furthermore, they are suitable for the photochemical crosslinking of polyolefins. The invention relates to a compound of the formula I, Rl O O R

X - C - C - Ar - C - C - X (I) wherein Ar represents arylene of 6 to 12 carbon atoms or a phenylene-T-phenylene group, wherein T represents -O-, -S-, -SO2-, -CH2- or -CH=CH-, X represents -NR R , OR , -O-Si(R )(R7)2, hydroxymethoxy, (Cl-C4 alkoxy)methoxy, (C2-C8 acyloxy)methoxy or together with Rl represents (C C alkyl)-O(CH2)1 2-' -OCH(C6 C14 y OCH(Cl-C8 alkyl)- or -OCH(C6-C14 aryl)-, R represents alkyl of 1 to 8 carbon atoms optionally substituted by OH, Cl-C4 alkXY~ C2-C8 aCyloxy~ ~Coo-(cl-c4)alkyl or -CN, or represents cycloalkyl of 5 to 6 carbon atoms or phenyl-alkyl of 7 to 9 carbon atoms, R2 has one of the meanings assigned to Rl or represents allyl, methallyl, 2-carbamoyl-ethyl, 2-(N-Cl-C4 alkylcarbamoyl)ethyl, 2-(N,N-di-Cl-C4 alkylcarbamoyl)ethyl, 2-(2-pyridyl)ethyl, 2-l2-oxo-1-pyrrolidinyl)ethyl or 2-(di-O-Cl-C4 alkylphosphono)ethyl, or R and R together represent alkylene of 4 to 6 carbon atoms or oxaalkylene or azaalkylene of 3 to 4 carbon atoms, or R and R are both hydroxymethyl, R3 represents hydrogen, alkyl of 1 to 12 carbon atoms, alkyl of 2 to 4 carbon atoms which is substituted by -OH or -Oalk, or represents allyl, cyclohexyl, phenylalkyl of 7 to 9 carbon atoms, phenyl or phenyl which is substituted by Cl or alk, R4 represents alkyl of 1 to 12 carbon atoms, alkyl of 2 to 4 carbon atoms which is substituted by -OH or -Oalk, or represents allyl, cyclohexyl, phenylalkyl of 7 to 9 carbon atoms, phenyl or phenyl which is substituted by Cl, alk, OH~ -Oalk or -COOalk, wherein alk is a lower alkyl radical of 1 to 4 carbon atoms, R represents alkyl 1 15$863 of l to 12 carbon atoms, alkyl of 2 to 4 carbon atoms which is substituted by -OH or -Oalk, or represents allyl, cyclohexyl or phenylalkyl of 7 to 9 carbon atoms, or together with R represents alkylene of 4 to 5 carbon atoms which can be interrupted by -O-, -NH- or -Nalk-, or together with R2 represents alkylene or phenylalkylene of 1 to 9 carbon atoms or oxaalkylene or azaalkylene of 2 to 3 carbon atoms, and R6 and R7 are the same or different and represent alkyl of l to 4 carbon atoms or phenyl.

Of the substituents listed above, Rl and R
can be alkyl of l to 8 carbon atoms, for example methyl, ethyl, propyl, butyl, hexyl or octyl. R4 and R as alkyl can be unbranched or branched alkyl of 1 to 12 carbon atoms, for example methyl, ethyl, isopropyl, tert.-buty], isoamyl, n-hexyl, 2-ethylhexyl, n-decyl or n-dodecyl.
Alk represents a lower alkyl radical of 1 to 4 carbon atoms, for example methyl, ethyl, isopropyl, n-butyl or tert.-butyl.

Rl and R2 as hydroxyalkyl, alkoxyalkyl or acyl-oxyalkyl can be for example hydroxymethyl, l-hydroxy-ethyl, 2-hydroxyethyl, 2-isopropoxyethyl, l-hydroxyiso-butyl, l-acetyloxybutyl, l-acryloyloxyhexyl, l-hydroxy-octyl, 3-benzoyloxypropyl, methoxymethyl or isobutyloxy-methyl. The acyl radical can be the radical of an aliphatic or aromatic carboxylic acid. Preferably they are l-hydroxy-alkyl radicals and their ethers or esters. R , R4 and R
as hydroxyalkyl or alkoxyalkyl can be for example 2-hydroxyethyl, 2-butoxyethyl, 2-methoxypropyl, 3-hydroxy-propyl or 2-ethoxybutyl. Preferably they are 2-hydroxy-alkyl radicals and the ethers thereof.

R and R2 as CN-substituted alkyl can be for 115~863 example 2-cyanoethyl, 2-cyanopropyl, 4-cyanobutyl, cyano-methyl, 2-cyanohexyl or 4-cyanooctyl. The 2-cyanoethyl radical is preferred.

R and R2 as alkyl substituted by -COOalk can be for example -CH2COOC2H5, -CH2CH2COOCH3, -(CH2)3-COOCH3 or -CH2-CH(C2H5)-COOC4Hg.

R and R as cycloalkyl can be cyclopentyl or cyclohexyl. Rl, R , R3, R and R as phenylalkyl can be for example benzyl, phenylethyl or dimethylbenzyl.

R and R together can represent alkylene or oxa-alkylene or azaalkylene. In this case, Rl and R together with the carbon atom to which they are attached form a cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, tetrahydrofurane, tetrahydropyrane, pyrroli-dine or piperidine ring.

R2 and R together can represent alkylene or phenylalkylene of 1 to 9 carbon atoms or oxaalkylene or azaalkylene. In this case, R2 and R5 together with the carbon atom to which R is attached and the nitrogen atom to which R is attached form a 3- to 6-membered ring, for example an aziridine, azetidine, pyrrolidine, imidaz-olidine, piperidine, piperazine or morpholine ring.

R4 and R5 together can represent alkylene of 4 to 5 carbon atoms which can be interrupted by -O- or -NR14-. In this case, R4 and R5 together with the nitrogen atom to which they are attached form a pyrrolidine, piperi-dine, morpholine, 4-alkylpiperazine, 4-cyanoethyl-piperazine or 4-alkoxycarbonylethylpiperazine ring.

,~ '';

~1SS863 X and R together can represent a -OC~I(Cl-C8 Y ~ 2)1-2 ~ OCH(C6-C14 aryl)-O-(CH2)1 2-~ -OCH-(Cl-C8 alkyl)- or -OCH(C6-C14 aryl)-group. In this case, R and X together with the carbon atom to which they are attached form an oxirane, oxetane, oxolane, tetrahydro-pyrane, 1,3-dioxolane or 1,3-dioxane ring which can be substituted by alkyl or aryl.

Ar can be arylene of 6 to 12 carbon atoms, for example phenylene, naphthylene or diphenylene.

Examples of compounds of the formula I are:
4,4'-bis-(a-hydroxy-isobutyryl~-diphenyl oxide, 4,4'-bis-(a-hydroxy-isobutyryl)-diphenyl, 4,4'-bis-(a-hydroxy--isobutyryl)-diphenyl sulfide, 4,4'-bis-(a-hydroxy-iso-butyryl)-diphenyl methane, 4,4'-bis-(a-piperidino-iso-butyryl)-diphenyl oxide, 4,4'-bis-[a-(isopropylamino)-isobutyryl]-diphenyl, 4,4'-bis-(a-benzoyloxy-isobutyryl)-diphenyl. oxide, 4,4'-bis-(a-hydroxy-isobutyryl)-diphenyl ethene~

~ he compounds of the formula I can be prepared from aromatic-aliphatic ketones by the following reaction steps:

Ar [CO-CHR R ]2 ~ Ar--~CO-CBrR R ]2 ~ C33 12 ~ R 2 ~5863 ~ s HX it is possible to use amines [C.L. Stevens, Ch. Hung Chang, J. Org. Chem. 27 (1962), 4392] or water or carboxylic acids [C.L. Stevens, E. Farkas, J. Am. Chem. Soc.
74 (1952), 618 and C.L. Stevens, S.J. Dykstra, J. Am. Chem.
Soc. 75 (1953), 5976].

In many cases the direct reaction of the ~-bromo-ketones to give compounds of the formula I

O Rl Ar ~ CO CBrRl~ ] ~ Ar ~ C - C- X ]

is also possible, for example with amines, alkali hydroxides or alkali phenoxides. Instead of bromine compounds it is also possible to use the corresponding chlorine compounds.

The resulting hydroxyketones of the formula I
(X=OH) can be etherified or O-silylated by the conventional methods.

Compounds of the formula I, wherein R is a sub-stituted alkyl group, can be obtained from the compounds of the formula Ar-~CO-CH(R )-X]2 by reaction with aldehydes (Rl = hydroxyalkyl) or with a vinyl compound which is cap-able of addition, for example with acrylates or acrylonit-rile. If both R and R are substituted alkyl, then both substituents can be introduced jointly by reaction of a compound Ar-~CO-CH2-X]2 with at least 2 moles of an aldehyde or a vinyl compound. The corresponding alkoxyalkyl and acyl-oxyalkyl groups can be obtained from the hydroxyalkyl groups R and/or R by etherification or esterification.

According to the invention, the compounds of the formula I can be used as sensitizers for the photopoly-merisation of unsaturated compounds or systems which contain such compounds.

Such compounds are for example unsaturated mono-mers, such as esters of acrylic or methacrylic acid, for example methylacrylate, ethylacrylate, n- or tert-butyl-acrylate, isooctylacrylate or hydroxyethylacrylate, methyl-or ethylmethacrylate, ethylene diacrylate, neopentyl dia-crylate, trimethylolpropane trisacrylate, pentaerythritol tetraacrylate or pentaerythritol trisacrylate; acrylo-nitrile, methacrylonitrile, acrylamide, methacrylamide, N-substituted acrylamides and methacrylamides; vinyl esters, such as vinyl acetate, vinyl propionate, vinyl acrylate or vinyl succinate; other vinyl compounds, such as vinyl ethers, styrene, alkyl styrenes, halostyrenes, divinyl benzene, vinyl naphthalene, N-vinylpyrrolidone, vinyl chloride or vinylidene chloride; allyl compounds, such as diallyl phthalate, diallyl maleate, triallyl isocyanurate, triallyl phosphate or ethylene glycol diallyl ether and the mixtures of such unsaturated monomers.

Photopolymerisable compounds are in addition un-saturated oligomers or polymers and the mixtures thereof with unsaturated monomers. These include thermoplastic resins which contain unsaturated groups, such as fumaric acid ester groups, allyl groups or acrylate or methacrylate groups. These unsaturated groups are usually bound through functional groups to the main chain of these linear poly-mers. Mixtures of oligomers with simply and poly-unsaturated monomers are very important. Example~ of such oligomers are unsaturated polyesters, unsaturated acrylic resins and iso-,,,~ ~;,, ,", ~,,, ~155~63 cyanate or epoxide modified acrylate oligomers as well aspolyether acrylate oligomers. Examples of poly-unsaturated compounds are in particular the acrylates of diols and poly-ols, for example hexamethylene diacrylate or pentaerythri-tol tetracrylate. Acrylates are also preferred as simply unsaturated monomers, for example butyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate or 2-hydroxypropyl acrylate. By choosing from the different representatives of the three components, the opportunity is afforded to vary the consistency of the unpolymerised mixture as well as the plasticity of the polymerised resin.

In addition to these three-component mixtures, two-component mixtures especially are of great importance among the polyester resins. These usually consist of an un-saturated polyester and a vinyl compound. The unsaturated polyesters are oligomer esterification products of at least one unsaturated dicarboxylic acid, for example maleic, fumaric or citraconic acid, and usually of at least one saturated dicarboxylic acid, for example phthalic acid, succinic acid, sebacic acid or isophthalic acid, with glycols, for example ethylene glycol, propanediol-1,2, di- or triethylene glycol or tetramethylene glycol r whilst monocarboxylic acids and monoalcohols are generally also used concurrently for the modification. These unsaturated polyesters are normally dissolved in a vinyl or allyl com-pound, styrene being preferably used for this purpose.

Photopolymerisable systems which are used for the different purposes usually contain, in addition to the photopolymerisable compounds and the photosensitizer, a number of other ingredients. It is therefore often customary to add heat inhibitors in order to prever,t a premature poly-merisation, especially during the preparation of the systems by mixing the components. E~ydroquinone, llydroquinone deriva-tives, p-methoxyphenyl, ~-naphthylamine or ~-naphthols are used for example for this purpose. Furthermore, small amounts of UV absorbers can be added, for example those of the benztriazole or benzophenone type.

To increase the storage life in the dark, it is possible to add copper compounds, such as copper naphthenate, copper stearate or copper octoate, phosphorus compounds, such as triphenylphosphine, tributylphosphine, triethyl phosphite, triphenyl phosphite or tribenzyl phosphate, quaternary ammonium compounds, such as tetramethylammonium chloride or, trimethylbenzylammonium chloride, or hydroxyl-amine derivatives, for example N-diethylhydroxylamine. In addition, the photopolymerisable systems can contain chain transfer agents, for example N-methyl-diethanolamine, tri-ethanolamine or cyclohexene.

In order to exclude the inhibiting action of atmospheric oxygen, paraffin or similar wax-like substances are frequently added to photohardening systems. On account of their poor solubility in the polymer, these substances float at the beginning of the polymerisation and form a transparent surface layer which prevents the entry of air.
The atmospheric oxygen can also be deactivated by introduc-ing autoxidisable groups, for example allyl groups, into the resin to be hardened.

Depending on the end-use, photopolymerisable systems also contain fillers, such as silicic acid, talc or gypsum, pigments, dyes, fibres, thixotropic agents or level-ling agents.

Combinations with known photosensitizers, such as benzoin ethers, dialkoxy acetophenones or benzyl ketals, can also be used. Combinations of the photosensitizers of the invention with amines and/or aromatic ketones can be used especially for the photopolymerisation of thin layers and printing inks. Examples of amines are triethylamine, N-methyldiethanolamine, N-dimethylethanolamine or p-di-methylaminobenzoate. Examples of ketones are benzophenone, substituted benzophenone derivatives, Michler's ketone, anthraquinone and anthraquinone derivatives, as well as thioxanthone and the derivatives thereof.

Photohardening is of great importance for print-ing inks, since the drying time of the binder is a decisive factor in the production speed of printing products and should be in the order of fractions of seconds. The sensi-tizers of the invention are also very suitable for photo-hardening systems for the manufacture of printing plates.
Mixtures of soluble linear polyamides with photopolymeris-able monomers, for example acrylamides, and a photosensi-tizer, are usually employed for this purpose~ Films or plates prepared from these systems are exposed vla the negative (or positive) of the original and the unhardened portions are subsequently eluted with a solvent.

A further field of use of UV hardening is metal coating, for example in the varnish coating of metal sheeting for tubes, cans or bottle caps, as well as the UV hardening of plastic coatings, for example of floor or wall coverings based on PVC.

Exemplary of the UV hardening of paper coatings is the colourless varnish coating of labels, gramophone record sleeves or book jackets.

According to the invention, the compounds of the formula I can also be used as sensitizers for the photochemical crosslinking of polyolefins, for example polypropylene, polybutene, polyisobutylene and also copolymers, for example ethylene/propylene copolymers, but preferably polyethylene of low, medium or high density.

The photosensitizers are advantageously used for the above fields of use in amounts of 0.1 to 20% by weight, preferably about 0.5 to 5% by weight, based on the photo-polymerisable or crosslinkable system. The term "system"
is to be understood as meaning the mixture of the photo-polymerisable or crosslinkable compound, the photosensitizer and the other fillers and additives, as it is used in the respective application.

The addition of the photosensitizers to the photo-polymerisable systems is accomplished in general by simple stirring, since most of these systems are fluid or readily soluble. Usually the sensitizers of the invention dissolve in the system, thereby ensuring their uniform distribution and the transparency of the polymers.

The polymerisation is carried out by the known methods of polymerisation by irradiation with light which is rich in shortwave radiation. Suitable light sources are for example mercury medium pressure, high pressure and low pressure lamps, as well as superactinic fluorescent tubes, the emission peaks of which are in the range between 250 and 400 nm.

The following Examples describe the manufacture and use of compounds of the formula I in more detail. Parts and percentages are by weight.

Example l: Manufacture and properties of the compounds of formula I

The compounds listed in Table l were obtained by one or more of the methods A to K.

Method_ A Chlorination of aromatic-aliphatic ketones Ar~C0-CR R H]n + n Cl2 _ Ar~C0-CR R Cl]n + n HCl The ketone is dissolved in an inert solvent, preferably in tetrachloromethane, and the calculated amount of chlorine is introduced into the solution at 40-80C. Nitrogen is then introduced to remove dissolved HCl. Finally, the sol-vent is distilled off. Purification of the chloroketone is usually not necessary and the product can subsequently be reacted by method D, F or H.

Method B Bromination of aromatic-aliphatic ketones Ar~CO-CRlR2H]n + n Br2 ~--~Ar~C0-CR R Br3n + n HBr The calculated amount of bromine is added dropwise at room temperature to a solution of the ketone, for example in CCl4. Working up and further processing are effected as in Method A.

Method C Chlorination with sulfuryl chloride Ar~CO-CRlR2H~ 2 C12 ~ Ar~CO-CRlR--Cl]n + n S02 ~ n HCl The sulfuryl chloride is added dropwise at 40C to a solu-tion of the ketone in CC14. Working up and further process-ing as in Method A.

Method D ~reparation of the epoxide intermediate Ar~CO-CRlR Hal] n + n NaOCH3 -~ArfC - CR R ] n + n NaHal Hal = Cl or Br The haloketone is dissolved in methanol and a solution of the stoichiometric amount of sodium methoxide in methanol is added dropwise at reflux temperature. The methanol is then distilled off and the residue is poured into ice-water and extracted with ether. The ethereal solution is washed with water, dried over Na2S04, dried and concentrated. The residue is purified by recrystallisation or vacuum distil-lation. The epoxide can subsequently be reacted bv Method E
or G.

Method E Hydrolysis of the epoxide 1 .
Ar ~C \CRlR2~ + n H20 H ~ Ar~co-cRlR2oH] +n CH30H

The epoxide is covered with 2 to 5 times its weight of water and the mixture is refluxed for 1 to 2 hours with the addi-tion of a catalytic amount of mineral acid. After cooling, the reaction mixture is extracted with ether. The ethereal solution is washed with water, dried over Na2S04, and con-centrated. The residue (crude hydroxyke,one) is purified by distillation or crystallisation or column chromatography.
The properties of the pure a-hydroxyketones are indicated in Table 1.

Method F a-Hydroxyketones from a-haloketones Ar~CO-CR R Hal~n + n NaOH _ Ar~CO-CR R OH]n + n NaHal The a-haloketone is refluxed in dilute or concentrated sodium hydroxide solution (20% excess of NaOH~. When the hydrolysis is complete (check by chromatography), the crude hydroxyketone is isolated and purified as described in Method E. The pure hydroxyketones are listed in Table 1.

Method G a-Aminoketones from the epoxides Ar~C - CRlR ] n +n R R5NH ~ Ar~CO-CRlR2-~R4R5] +n CH30H

, _ The epoxide is treated with the stoichiometric amount of the amine, either without a solvent or with the addition of a small amount of toluene or xylene, and reacted for about 10 to 20 hours at 100-200C. When using low boiling amines, for example dimethylamine or diethylamine, the reaction is carried out in an autoclave. The reaction mixture is diluted with benzene and extracted with dilute hydrochloric acid.
The aqueous acid solution is made alkaline with NaOH and extracted with ether. The ethereal solution is washed with water, dried over Na2S04 and concentrated. The crude product is purified by distillation or crystallisation. The a-amine-ketones are listed in Table 1.
}'~",' Method_H ~-Aminoketones from the ~-halo~etones Ar~CO-CR R Hal] + 2n R R NH ~ Ar~CO-CR R -NR R ] n + n R R NH2Hal The ~-haloketone, undiluted or diluted with toluene, is mixed with 2 molar equivalents of the amine and the mixture is heated for 10 to 20 hours to 100-200C. When using low boiling amines, for example dimethylamine or diethylamine, the reaction is carried out in an autoclave. Isolation and purification are effected as in Method G.

Method I Introduction of a carbalkoxyethyl group CH2CH2CAlk Ar~CO-CHR -X]n + n CH2 = CH-COOAlk _ Ar~CO-CRl-X ] n The ketone is dissolved in dimethyl sulfoxide. To the solu-tion are then added 1.1 molar equivalents of NaOH in the form of 4N sodium hydroxide solution and, with cooling, 1.1 molar equivalents of acrylate are added dropwise at room temperature. The reaction mixture is diluted with ice-water and extracted with toluene. The toluene solution is washed neutral with water, dried over Na2S04 and concentra-ted. The crude product is purified by column chromatography or crystallisation.

Method K Etherification of hydroxyketones Ar~CO-CRlR -OH] + n R Hal + n NaOH Ar~CO-CR R -OR ]n + n NaHal 1 1558~3 The ~-hydroxyketone is dissolved in about 4 times its weight of dimethyl sulfoxide and, while cooling to 10-20C and with stirring, 1 molar equivalent of the alkyl halide R6Hal and 1 molar equivalent of concentrated sodium hydroxide solution are added dropwise simultaneously from two drip funnels. The reaction mixture is then stirred for 3 hours at room temperature. Precipitated sodium halide is then removed by filtration, the filtrate is washed with water, dried over Na2S04 and concentrated. The crude product is purified by column chromatography, crystallisation or vacuum distillation. Examples of eligible halogen compounds are methyl iodide, isopropyl bromide, allyl bromide, cyclo-hexyl bromide, benzyl chloride or ethyl chloroacetate.

Instead of using an alkyl halide, it is also possible to use a dialkyl sulfate or alkylaryl sulfonate as etherifying reagent.

~ .
_ O o ~- O O
rl ~ O
~n Q .
~ O Q~ X
P-~ R 3 e .o V V V :~
~ . . _____ _ o ~
~o~ ~+
~ e m ~
.

o=y o= C~
~/\. ~/\.
\./ \\./
o .// \ //
l~l l~./ll o=~ o= ' ~ ~ T ~

.a ~ E :1 _ -- . ___ E~
~' ,h 1 1~5863 Example 2: Use as photoinitiator A resin mixture consisting of 70 parts of Ebercyl 593 (polyester acrylate available from UCB, Belgium), 30 parts of trimethylolpropane trisacrylate, O.S part of ByK
300 ~levelling assistant available from ByK-Mallinchrodt, West Germany) and 3 parts of the compound No. l, is applied to glass plates in a layer of 30 - 40,u. After brief exposure to air, hardening is effected with a UV
laboratory device (model PPG/QC-processer) with a UV
lamp of 80 watts/cm. After the UV hardening, the plates are stored for 1/2 hour under normal climatic conditions and then the hardness of the layers is determined using the pendulum device of Konig. If the conveyor belt in the irradiation device has a transpo~tation speed ad 10 m/min the film sample showed a pendulum hardness of 155 sec.
At a speed of 25 m/min the pendulum hardness is 143 sec.

Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A compound of the formula:

(I) wherein Ar represents arylene of 6 to 12 carbon atoms or a phenylene-T-phenylene group, wherein T represents -O-, -S-, -SO2-, -CH2- or -CH=CH-, X represents -NR4R5, OR3, -O-Si(R6)(R7)2, hydroxymethoxy, (C1-C4 alkoxy)methoxy, (C2-C8 acyloxy)methoxy or together with R1 represents OCH(C1-C8 alkyl)-O(CH2)1-2-, -OCH(C6-C14 aryl) -O-(CH2)1-2-, OCH(C1-C8 alkyl)- or -OCH(C6-C14 aryl)-, R1 represents alkyl of 1 to 8 carbon atoms optionally substituted by OH, C1-C4 alkoxy, C2-C8 acyloxy, -COO-(C1-C4)alkyl or -CN, or represents cycloalkyl of 5 to 6 carbon atoms or phenyl-alkyl of 7 to 9 carbon atoms, R2 has one of the meanings assigned to R1 or represents allyl, methallyl, 2-carbamoyl-ethyl, 2-(N-C1-C4 alkylcarbamoyl)ethyl, 2-(N,N-di-C1-C4 alkylcarbamoyl)ethyl, 2-(2-pyridyl)ethyl, 2-(2-oxo-1-pyrrolidinyl)ethyl or 2-(di-O-C1-C4 alkylphosphono)ethyl, or R1 and R2 together represent alkylene of 4 to 6 carbon atoms or oxaalkylene or azaalkylene of 3 to 4 carbon atoms, or R1 and R2 are both hydroxymethyl, R3 represents hydrogen, alkyl of 1 to 12 carbon atoms, alkyl of 2 to 4 carbon atoms which is substituted by -OH or -Oalk, or represents allyl, cyclohexyl, phenylalkyl of 7 to 9 carbon atoms, phenyl or phenyl which is substituted by Cl or alk, R4 represents alkyl of 1 to 12 carbon atoms, alkyl of 2 to 4 carbon atoms which is substituted by -OH

or -Oalk, or represents allyl, cyclohexyl, phenylalkyl of 7 to 9 carbon atoms, phenyl or phenyl which is substituted by Cl, alk, OH, -Oalk or -COOalk, wherein alk is a lower alkyl radical of 1 to 4 carbon atoms, R5 represents alkyl of 1 to 12 carbon atoms, alkyl of 2 to 4 carbon atoms which is substituted by -OH or -Oalk, or represents allyl, cyclohexyl or phenylalkyl of 7 to 9 carbon atoms, or to-gether with R4 represents alkylene of 4 to 5 carbon atoms which can be interrupted by -O-, -NH- or -Nalk-, or to-gether with R2 represents alkylene or phenylalkylene of 1 to 9 carbon atoms or oxaalkylene or azaalkylene of 2 to 3 carbon atoms, and R6 and R7 are the same or different and represent alkyl of 1 to 4 carbon atoms or phenyl.

2. 4,4'-Bis-(.alpha.-hydroxy-isobutyryl)-diphenyl oxide.

3. 4,4'-Bis-(.alpha.-hydroxy-isobutyryl)-diphenyl methane.