CA1202025A - 3-amino-propiophenones - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Aromatic-aliphatic ketones of the formula I

Description

This Application is a divisional of Application 318,328 filed December 20th, 1978.

The invention relates to the use of aromatic aliphatic ketones which are substituted in the a-position as sensitizers for the photopolymerisation of unsaturated compounds or for the photochemical crosslinking of polyolefins, as well as to the photopolymerisable and crosslinkable 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 shor-t time, for example in the hardening of varnish coatings or in the drying of printing inks. Compared with conventional hardening methods, UV irradia-tion in the presence of photosensitizers has a number of advantages, the most important of which is the great speed of the photoharden-ing. The speed is heavily dependent on the photosensi tizer employed and -there has been no lack of attemps to replace the conventional sensitizers by ever better and more effec-tive com-pounds. Among the most effective photosensitizers are derivatives of benzoin, in particular the benzoin ethers described for example in German Patent Specification 1,694,149, derivatives of a-hydrox.ymethylbenzoin described in German Offenlegungsschrift 1,923,266, and the dialkoxyacetophenones and benzil monoketals - 1- ~.~

~2~ )2~

described for example in German Offenlegungsschrift 2,261,383 or

2,232,365. ~-Aminoacetophenones and ~-diaminoacetophenones have recently been proposed as pho-tosensitizers in United States Patent Specification 4,048,034 and c~-hydroxy-~-alkylolacetophenones and their ethers in German Offenleg-mgsschrift 2,357,866. The shortcomings of these known photosensitizers are in some cases an insufficient storage life in the dark of the photopolymerisable systems mixed with such sensitizers. A number of benzoin deriva-tives tend to cause yellowing of the hardened compositions. Other sensitizers are insufficiently reactive - a feature which is observed in the rela-tively lengthy hardening times - or their solubility in the photopolymerisable systems is too low or they are rapidly rendered inactive by atmospheric oxygen. There is there-fore a need in the art for photosensitizers whicn are readily soluble in the substrate and, while having a good storage li fe in the dark, initiate the photopolymerisation more rapidly and give a higher polymer yield per unit of time than the known photo~
sensitizers. By using such improved photosensitizers it would be possible to exploit be tter the expensive industrial UV irradiation plants.
It has been found that compounds of the following formula I possess the required properties as photosensitizers.
In particular, they effect a rapid photopolymerisa-tion and do not have the shortcomings referred to or possess them to a much lesser degree than the known photosensitizers. Furthermore, they are suita;~le for the photochemical crosslinking of polyolefins. The invention relates to the use of the colnpounds of the following formula I R

~2 wherein:
Ar represents (a) phenyl substjtu-ted wi-th -CN, -OH, -alk, -Oalk, -O phenyl, -Salk, -SO2alk, -SO2phenyl, -COOalk, -SO2NH2, -SO2N(alk)2, -NHalk, -N(alk)2 or -NHCOalk, or (b) naphthyl, thienyl, pyridyl, furyl, indanyl, or te'rahydronaphthyl;
R represents Cl to C8 alkyl which is unsubstituted or sub-stituted by -OH, -Oalk, C2-C8acyloxy, -NR R5, -COOalk, -CN-C3-C3-C4alkenyl, C3-C6cycloalkyl, or C7-Cgphenylalkyl;
R has one of the meanings assigned to Rl or represents a -CH2CH2R group, or, together with R , represents a C2-C8 alkyl-ene, C3-Cg-oxa-alkylene or C3-Cg-aza-alkylene group;
R4 represents Cl-C12 alkyl, C2-C4alkyl substituted by -OH, -CN or -Oalk, or C3-C5 alkenyl, cyclohexyl, C7-Cgphenylalkyl, phenyl, or phenyl substituted by -Cl, -alk, -OH, -Oalk, or -COOalk;
R5 represents Cl-C12 alkyl, C2-C4alkyl substituted by -OH, -CN or -Oalk; or C3-C5alkenyl, cyclohexyl or C7-Cgphenylalkyl, or together T"ith R4 represents C4-C5alkylene which can be interrupted by -O- or -NR14-, or together with R2 represents Cl-Cgalkylene or phenylalkylene or C2-C3-oxa or aza-alkylene;

V~Z~

R13 represents -CON~2, CONHalk, -CON(alk)2, -P(O)(Oalk)2, 2-pyridyl or 2-oxo-1-pyridyl;
R represents Cl-C4alkyl, -CH2CH2CN or -CH2CH2COOalk; and alk represents a lower alkyl radical of 1 to 4 carbon a-toms.
These compounds are accordingly aromatic-aliphatic ketones, the ~-carbon atom of which is tertiary and which is substituted by an amino group. The aliphatic residue can also be cycloaliphatic or araliphatic or linked to the aromatic residue with ring closure, which corresponds to the benzocyclic ketones of the formula IV.
Of the substituents listed above, Rl and R2, can be alkyl of 1 to 8 carbon atoms, for example methyl, ethyl, propyl, butyl, hexyl or octyl. R4 and R5 as alkyl can be unbranched or branched alkyl of 1 to 12 carbon atoms, for example methyl, ethyl, isopropyl, tert -butyl, 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.
R and R2 as hydroxyalkyl, alkoxyalkyl or acyloxyalkyl can be for example hydroxymethyl, l-hydroxyethyl, 2-hydroxyethyl, 2-isopropoxyethyl, l-hydroxyisobu-tyl, l-acetyloxybu-tyl, l-acryloyl-oxyhexyl, l-hydroxyoctyl, 3-benzoyloxypropyl, methoxymethyl or isobutyloxymethyl. The acyl racical can be the radical of an aliphatic or arornatic carboxylic acid. Preferably they are l-hydroxyalkyl radicals and their e-thers or esters. R4 and R5 as hydroxyalkyl or alkoxyalkyl can be for example 2-hydroxyethyl, 2-butoxyethyl, 2-methoxypropyl, 3-hydroxypropyl or 2-e-thoxybutyl.

Preferably they are 2-hydroxyalkyl radicals and the ethers there-of.
R and R as alkyl whieh is subs-tituted by -NR R ean be for example dibutylaminomethyl, 2-piperidinoethyl or 2-dimethyl-aminopropyl.
Rl, R , R or R as CN-substitu-ted alkyl ean be for example 2-eyanoe-thyl, 2-cyanopropyl or 4-cyanobutyl, whilst Rl, R2 and R4 ean also be for example cyanomethyl, 2-eyanohexyl or 4-eyanooctyl. The 2-cyanoethyl radical is preferred.
Rl and R2 as alkyl substituted by -COOalk can be for example -CH2COOC2H5, -CH2CH2COOCE13, -(CH2)3-COOCH3 or -CH2-CH(C H )-COOC4H9 R , R2, R and R as alkenyl can be for example allyl, methallyl or 2-butenyl.
Rl and R as cycloalkyl can be cyclopentyl or eyelohexyl.
Rl, R2, R4 and R5 as phenylalkyl ean be for example ben~yl, phenylethyl or dimethylbenzyl.
Ar as aryl or substituted phenyl ean be for example phenyl, naphthyl, isopropylphenyl, phenoxyphenyl, cyanophenyl, hydroxyphenyl, -tolyl, tert -butylphenyl, xylyl, methoxyphenyl, ethoxyphenyl, phenoxyphenyl, methylthiophenyl, butylsulfophenyl, phenylsulfophenyl, ethoxycarbonylphenyl, tert -butoxyearbonyl-phenyl, methylaminosulfophenyl, dipropylaminosulfophenyl, dimethylaminophenyl or acetylaminophenyl.

~, _ ~,Z~

Rl and R2 together can represent alkylene or oxaalkylene or azaalkylene. In this case, Rl and R2 together with the carbon atom to which they are attached form a cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, tetrahydrofurane, tetra-hydropyrane, pyrrolidine or piperidine ring.
R and R5 together can represent alkylene or phenyl-alkylene of 1 to 9 carbon atoms or oxaalkylene or azaalkylene. In this case, R and R5 -together wi-th the carbon atom to which R2 is attached and the nitrogen atom to which R5 is attached form a

3- to 6-membered ring, for example an aziridine, azetidine, pyrrolidine, imidazolidine, piperidine, piperazine or morpholine ring.
R and R 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, piperidine, morpholine, 4-alkylpiper-azine, 4-cyanoethylpiperazine or 4-alkoxycarbonylethylpiperazine ring.
Ar can be arylene of 6 to 12 carbon atoms~ for example phenylene or naphthylene.
Most preferably, the invention is concerned with the use of compounds of the formula I, wherein Ar represents phenyl ~,lhich is unsubstituted or substitu-ted by Cl-C4 alkyl or Oalk, or represents indanyl or tetrahydronaph-thyl, Rl represents Cl-C8-alkyl, R represents Cl-C8alkyl or C3-C4alkenyl, R
represents Cl-C12alkyl, R5 represents Cl-C12alkyl or -together with 2~325 R represents C4-C5alkylene which can be interrupted by -O-or -NR -and R represents Cl-C4alkyl-The most preferred compound according to this inventionis 2-~1orpholino-2-methyl-p-(methylthio)-propiophenone.
These novel compounds can be prepared by methods analo-gous to those for obtaininy the known compounds, whereby different methods are possible.
Accordingly, the compounds of the formula I can be prepared from aromatic-aliphatic ketones by the following reaction steps:
(a) by bromination of a suitable propiophenone; -the bromo compound is converted to the epoxide, which is reacted with an amine:

ArCOCRlR2H ~ Ar-CO-CRlR2Br , Ar-f/ - \CRlR2.__~ ArCOCR R-NR R

(b) as an alternative to (a), the corresponding propiophe-none can be chlorinated rather than bromina-ted, the remaining steps being the same;
(c) by chlorination of a suitable propiophenone, followed by direct reaction witn an amine;
ArCOCRlR2H ~ ArCOCR R Cl -, ArCOCRlR-NR R ;
and (d) as an alternative to (c), the bromo compound can be used.

3.~

Compounds of the formula I, wherein Rl is a subs-titu-ted alkyl group, can be obtained from the compounds of the formula ArCOCR R -NR R by reaction with aldehydes (R = hydroxyalkyl) or with a vinyl compound which is capable of addition, for example with acrylates or acryloni-trile. In the same way, a -Cll2Ci~2-R
group can be introduced as R2, star-ting from a compo~md A-CoCHRl-NR4R5. If both Rl and R are substituted alkyl, then both substituents can be introduced jointly by reaction of a compound ArCOCRlR2NR R5 with at least 2 moles of an aldehyde or a vinyl compound. The corresponding alkoxyalkyl and acyloxyalkyl groups can be obtained from the hydroxyalkyl groups Rl and/or R2 by etherification or esterification.
Compounds in which X together with Rl is a -O-CH (R9) group are ~-oxydoketones and can be obtained by epoxidation of the corresponding ~-vinyl ketones. Reaction of the oxydoketones with secondary amines affords compounds in which either X is OH
and R is an aminoalkyl group, or in which X is NR R and R is a hydroxyalkyl group.
Addition of bromine to the ~-vinyl ketones yields ~J~,e-dibromoketones of the formula ArCOCBrRl-CBralk.
P~eaction of the dibromoketones with one mole of a primary amine yields the corresponding ~-aziridinoketones [J. Am. Chem.
Soc. 65 (lg43), 312], and reaction with 2 moles of a secondary amine yields compounds of the formula I, wherein R is an amino-alkyl radical [J. Am. Chem. Soc. 74 (1952), 1886].

8 ~

Aminoalkyl groups K and/or R can also be introduced by the Mannich reaction, wherein ketones of the formula Ar-CO-CHRl-X or Ar-CO-CH2-X are reacted with 1 or 2 moles of formaldehyde and a secondary amine.
Whereas all these methods of synthesis start from an aromatic-aliphatic ke-tone into which a substituent is introduced in a different manner, it is also possible in specific cases to introduce the substituent during the ketone synthesis by the Friedel-Crafts reaction in accordance with the reaction scheme:
Rl R-X - C - COCl ~ ArH AlC13 Ar- CO -C -X

This presupposes that the substituent X is not attacked under the conditions of the Friedel-Crafts reaction. In this way it is possible for example by using heterocyclic carboxylic acid chlorides to prepare compounds of -the formula I, in which X and R together with the carbon atom to which they are attached form a heteroring.
According to the invention, the compounds of the formula I can be used as sensitizers for the photopolymerisation of unsaturated compounds or systems which contain such compounds.
Such compounds are for example unsaturated monomers, such as esters of acrylic or methacrylic acid, for example methylacrylate, ethylacrylate, n- or tert-butylacrylate, isooctyl-acrylate or hydroxyethylacrylate, methyl- or ethylmethacrylate, g 3~2~

ethylene diacrylate, neopentyl diacrylate, trime-thylolpropane trisacrylate, pentaerythritol tetraacrylate or pentaery-thritol trisacrylate; acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, N-substituted acrylamides and methacrylamides;
vinyl esters, such as vinyl acetate, vinyl propionate, vinyl acrylate or vlnyl succinate; other vinyl compounds, such as vinyl ethers, s-tyrene, alkyl styrenes, ha:Lostyrenes, divinyl benzene, vinyl naph-thalene, N-vinylpyrrolidone, vinyl chloride or vinyl-idene chloride; allyl compounds, such as diallyl phthala-te, diallyl maleate, triallyl isocyanurate, triallyl phosphate or ethylene glycol diallyl ether and the mix-tures of such unsaturated monomers.

Photopolymerisable compounds are in addition un-saturated oligomers or polymers and the mixtures tnereof 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. Examples of such oligomers are unsaturated polyesters, unsaturated acrylic resins and iso-cyanate or epoxide modified acrylate oligomers as well as polyether 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 differen-t 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, whiist monocarboxylic acids and znonoalcohols 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 prevent a premature poly-merisation, especially during the preparation of the systems by mixing the components. Hydroquinone, hydroquinone deriva-tives, p-methoxyphenyl, ~-naphthylamine or ~-naphthols are used for example for this purpose. Furthermore, small amounts of W 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 requently added to photohardening systems. On accounL
of their poor solubility in the po].ymer, these substances float at the beginning of the polymerisation and form a transparent surface layer which prevents the entry of air.

-- 1~ --32~
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 derivatlves, 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 decisi-ve 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;
~ixtures 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 'rom these systems are exposed via the negative (or positive) of the original and the unhardened portions are subsequently eluted with a solvent.

A further field of use of UV hardeniny is meta~ coating, for example in the varnish coating of metal sheetiny 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.
~ xemplary 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 compou~ds of the formula I can also be used as sensitizers for the photochemical crosslinking of polyolefins, for example polypropylene, poly-butene, 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 photopolymerisable or crosslinkable system. The term "system" is to be understood as meaning the mixture of the photopolymerisable 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 ensuriny theix uniform distribution and the transparency of the polymers.
The pol~rnerisation is carried out by the known methods of polyr~risation by irradiation with light which -- 1~ --is rich in shortwave radiation. Suitable light sources ars 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.

3.~ V~

Manufacture and properties of -the compounds used in Examples 1 to 6.
The compounds listed in Table 1 were obtained by one or more of the methods A, B, C, D, G, H and I.
Method A Chlorination of aromatic-aliphatic ketones Ar_co_cRlR2H + n C12 ~ Ar-CO-CR R Cl + n HCl The ketone is dissolved in an inert solvent, preferably in tetra-chloromethane, and the calculated amount of chlorine is introduced into the solution at 40-80C. Nitrogen is -then introduced to remove dissolved HCl. Finally, the solvent is distilled off.
Purification of the chloroketone is usually not necessary and the product can subsequently be .eacted by me-thod D, or H.
Method B Bromination of aromatic-aliphatic ketones Ar_co_cRlR2H + n Br2 ~ Ar-CO-CRlR2Br -~ n ~Br The calculated amount of bromine is added dropwise at room temperature to a solution of the ketone, for example in CC14.
Working up and further processing are effected as in Method A.
Method C Chlorination with sulfuryl chloride Ar_co_cRlR2H 2 2 ~Ar-CO-CR R -Cl + n SO2 + n HCl The sulfuryl chloride is added dropwise at 40C to a solution of the ketone in CC14. Working up and further processing as in Method A.

Method D Preparation of the epoxide intermediate Ar-CO-CR R Hal + n NaOCH3 -~Ar-f - cRlR + n NaHal Hal = Cl or Br The haloketone is dissolved in methanol and a solutlon of the stoichiometric amount of sodium methoxide in me-thanol 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 Na2SO4, dried and concentrated. The residue is purified by recrystallisation or vacuum distillation. The epoxide can sub-sequently be reacted by Method E or G.
Method G ~-Aminoketones from the epoxides Ar-C \ CRlR2 + R4R5NH ~Ar-co-cRlR2-NR4R5 + CH OH

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. ~hen 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 rr7ith water, dried over Na2SO4 and concentrated. The crude product is purified b~ distillation or crystallisation. The ~-amine-ketones are listed in Table 1.
~ 17 -Method H ~-Aminoketones from the ~.-haloketones Ar-CO-CR R Hal f R4R5NII - ~Ar-CO-CRlR2-NR4R5 + R R NH2Hal The ~-ha]oketone, undiluted or dlluted 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 C~l2CH2COOAlk Ar-CO-CHR -X + CH2 = CH-COOAlk Ar-CO-CR -X

The ketone is dissolved in dimethyl sulfoxide. To the solution are then added l.l molar equivalents of NaOH in -the form of 4N
sodium hydroxide solution and, with cooling, l.l 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 Na2SO4 and concentrated. The crude product is purified by column chro~tography or crystallisation.

Com- Formula ~lethod of Purification Physical pound manufacture properties ~ I I
_8 \S~ C -N\ /0 B+D+G dist. bp-o 1 150 *) o Cl~3 ~9 l~ C~ -C ~ N 0 B+D+G cryst. m.p. 110-112 3 \ ~ I \ / (diisopro-3C/ CE13 pyl ether) O CH
31 Cl ~ C t N~ ~ B+H dist. b-p-o 1 150 ) Com- Formula rlethod of Puriflcation Physical poul~d manufacture properties( C) 32 113C \ / t `: : B+D+G dist. Po~l ) 33 1I C-0-~-C t N~ \- B+H do. b.po 2 180 *) o 0 CIJ3 34 \ ~o-o-o\ ~o-C+N\ \- CfEl do. b.po 1 200 =0 ~ --0 113C-S-o~~--ctN\ \ B+D+G do. m.p. 68-71 b-po l 210 *) Cl~
.

*) temperature of the air bath in bulb tube distillation.

Example 1 A resin mixture consisting of 90 parts of Laromer*
LR 8496 (acrylate resin available from BASF, West Germany), 10 parts of hexanediol diacrylate, O.5 part of ByK 300 (levelling assistant available from ByK-Mallinckrodt, West Germany) and 3 parts of photosensitizer for hardening in the air or 0.5 part of photosensitizer for hardening under nitrogen, is applied electro-motively to cardboard boxes with a 15~ helix. After brief expos-ure to air, hardening is effected with a UV device (model PPG-QC-processer) with a UV lamp of 80 wa-tts/cm. The maximum transporta-tion speed at which non-tacky films were obtained in air or under nitrogen for compound No. 29 was 10 m/min under air and 90 m/min under nitrogen.
Example 2 A resin mixture consisting of 70 parts of Ebercyl* 593 (polyester acrylate available from UCB, Belgium), 30 parts of trimethylolpropane trisacrylate, 0.5 part of ByK 300 (levelling assistant available from ByK-Mallinckrodt, West Germany) and 3 parts of photosensitizer, is applied to glass plates in a layer of 30-40 ~. 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.
The hardness values as a function of the transportation speed under the lamp are reported in the following Table.

* Trademarks 3~

. . Pendulum hardness in sec.
Photosensltlzer 10 m/min. 25 m/min.

Claims (2)

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) (I) wherein:
Ar represents (a) phenyl substituted with -CN, -OH, -alk, -Oalk, -O phenyl, -Salk, -SO2alk, -SO2phenyl, -COOalk, -SO2NH2, -SO2N(alk)2, -NHalk, -N(alk)2 or -NHCOalk, or (b) naphthyl, thienyl, pyridyl, furyl, indanyl, or tetrahydronaphthyl;
R1 represents C1 to C8 alkyl which is unsubstituted or sub-stituted by -Oh, -Oalk, C2-C8acyloxy, -NR4R5, -COOalk, -CN-C3-C3-C4alkenyl, C3-C6cycloalkyl, or C7-C9phenylalkyl;
R2 has one of the meanings assigned to R1 or represents a -CH2CH2R13 group, or, together with R1, represents a C2-C8 alkyl-ene, C3-C9-oxa-alkylene or C3-C9-aza-alkylene group;
R4 represents C1-C12 alkyl, C2-C4alkyl substituted by -OH, -CN or -Oalk, or C3-C5 alkenyl, cyclohexyl, C7-C9phenylalkyl, phenyl, or phenyl substituted by -C1, -alk, -OH, -Oalk, or -COOalk;
R5 represents C1-C12alkyl, C2-C4alkyl substituted by -OH, -CN or -Oalk; or C3-C5alkenyl, cyclohexyl or C7-C9phenylalkyl, or together with R4 represents C4-C5alkylene which can be interrupted by -O- or -NR14-, or together with R2 represents Cl-C9alkylene or phenylalkylene or C2-C3-oxa or aza-alkylene;

R13 represents -CONH2, CONHalk, -CON(alk)2, -P(O)(Oalk)2, 2-pyridyl or 2-oxo-1-pyridyl;
R14 represents C1-C4alkyl, -CH2CH2CN or -CH2CH2COOalk; and alk represents a lower alkyl radical of 1 to 4 carbon atoms.

2. 2-Morpholino-2-methyl-p-(methylthio)-propiophenone.