CA2035460A1 - Radiation-curable binder systems containing .alpha.-substituted sulfonyl compounds as photoactivators - Google Patents

Abstract

Abstract The invention relates to radiation-curable binder systems based on free radical- andtor acid-curable components which contain certain .alpha.-substituted sulfonyl compounds as free radical-forming photoinitiators and/or as radiation-activatable latent acid catalysts.

Description

Merck Patent Gesellschaft mit beschran~ter Haftung 6100 D a r m 8 t a d t Radiation-curable binder sYstems containinq ~-substitu~ed sulfonyl com~ounds as ~hotoacti~ators The invention relate~ to radiation-curable binder systems which contain certain ~-substituted sulfonyl compounds as photoactivators. ~he binder sys~ems are based on free radical- and/or acid-curable components in which the pho~oactivators according to the invention function as free radical-forming photoinitiator~ and/or as radiation-ac~ivatable latent acid catalysts.
A large number of binder systems in paints and coatings technology are ba~ed on heat-curable materials in which cro~slinking and hence curin~ take~ place by polycondensation. Basic ma~erial~ capable of polycondensation are normally aminopla~tic resins, the heat curing of which is catalysed by acids, e~pecially organic sulfonic acids. A typical, very frequen~ly used acid catalyst, is p-toluenesulfonic acid (PTS). However, acid-curable sy~tem~ have ~he drawback that they have only a limited shelf life once they react with ~he acid catalyst, and they gel if they are no~ proce~sed within a short time. Sulfonic acid catalysts in 'blocked' form, either as amino ~alts or a~ oxime esters of hydro~amic acid~, impart be~ter shel~ life. The catalytically active acids may be liberated from the~e blocked form~ by heating at elevated temperature~. By thi~ method, however, the curing o~ the corresponding systems require~
a higher expenditure of energy and time. Heat curing is generally very time-consuming, which is a dlsadvan~age in industrial production proce~ses.
Besides heat cuxing, photochemically induced curing has achieved great significance in paints and coatings technology; in this process special radiation-curable compo~itions are used which contain photoacti-vator~ or photoinitia~ors for converting the radiation ' .: ~ . . , ,;

.
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.
energy. Radiation curing is distingui3hed e~pecially by high reaction rates and low energy needs. The photopoly-merization reaction of greate~ Lmportance in practice is free-radical polyaddition of ethylenic double bond~.
Corresponding radiation-curable systems are therefore based on materials which contain free radîcal-polymerizahle or crosslinkable ekhylenic double bonds and free radical-forming photoinitiatorsO
Systems which undergo acid-catalysed heat curing are in principle also available for radiation curing if photochemically activatable latent acid catalysts are employed instead of the conventional thermal acid catalysts. The catalytically acting acid which effect~
the actual curing, preferably aided by addi~ional input of thermal energy, must be capable of being liberated from these by the action of the radiation. Compound~ of halo- or sulfonyloxyacetophenone type, known for this purpose for some time, have the drawback o~ being cor-rosive, of causing yellowing of the cured ilms or of having other disadvantageous effects; ~hey are further-more associated with problems of ~tabili~y or compatibility of the films.
More recent efforts to le~sen the known drawbacks of the acid catalysed heat-curable system~ and to utilize in them the advantages of photochemical activation by W
radiation are put forward, for example, in EP 192,9671 which discloses sulfonyl derivatives of aromatic-aliphatic ketones, especially of ~-sulfonylacetophenone compounds, which may be used as photochemically activat-able latent acid catalysts. Compared with the previouslyknown W acid catalysts~ these compounds have more favourable application characteri~tics attributed to them, especially a~ regards their efect on the cured film and on the shelf life of the binder sy~tem~. In addition, these compounds may be used as free radical-forming photoinitiator~ for free radical- polymerizable binder systems and for hybrid binder systems based on free radical- or acid-curing components.
The compounds known from EP 192,967 have the :, ' . : ;;' . , :

- 3 - ~ ~35~
drawback, however, of being only moderately reactive. For a given curing resul~, relatively high radia~ion outpu~s and/or prolonged irradia~ion times are required. More-over, these compounds have the drawback that their S synthesis is relatively costly and involves the use of toxic raw materials and solvents and the formation of noxious by-products. ~heir production and u~ilization on an industrial scale is therefore problematic from an economic point of view and with regard to today's la environmental and industrial safety raquirementis.
The ob~ect of ~he invention has therefore been to identify other co~pounds w~ich could be used as free radical-forming photoini~iators and as radiation-activatable latent acid catalysts in radia~ion-curable binder systems based on free radical- and/or acid-curable components.
The desired compounds should a~ the same time be more reactive than the compound~ used conven~ionally in the corresponding situation and be aYailable as sLmply and readily as possible.
We have now found that certain ~-substituted sulfonyl compound3 meet these requirements very well.
- They are compounds of the formula I

1 1 2 tI) . R -C~-SO2-R

X b~ingQ~3 vr NR3R4 in which Rl is H, R, R-O, ~N, R-CO, R-COO, RZNCO, ,~
R2--SO2--CH~

R2 is R, OR, N~, R3 is H, R
R4 is H, R, -CHR1-SO2-RZ
and ' ~35~6~

R is alkyl, cycloalkyl or aryl, each having up to 10 carbon atoms, each being unsubstituted or mono- or polysubsti~uted by OH, halogen, cyano, ni~rol alkyl, alkoxy, alkylthio, monoalkylamino or 5bisalkylaminor alkanoyl, alkanoyloxy, alkanoylamido, alkoxycarbonyl, alkylaminocarbonyl or aryloxy, each substituent having up to 6 carbon atom~.
We have found that the compounds of the formula I, on being irradiated with W liyht of a wavelength 10between 200 and 450 nm, first form free radicals, fol-lowed by acid degradation produc~s, depending on the reaction en~ironmen~. When used as pho~oactivators in binder systems based on radically and/or acid-curable components, they have been found, surprisingly, ~o be 15distinctly more reactive than conventional compound~ and especially the ~ulfollylacetophenone compound~ known from EP l9Z,967.
The invention relates at the ame time to the use of compound3 of the formula I as free radical-forming 20photoinitiator~ and/or radiation-activatable la~ent acid catalysts in binder systems based on free radical- and/or acid-curable component~.
The invention further relates to radiation-curable binder sys~em~ based on free radical- and/or 25acid-curable component~ which contain an effective amount o~ at lea~t one compound of the formula I as free -radical-forming photoinitiator~ and/or as radiation-activatable latent acid cataly~ts.
In addition, the invention relates ko a proces~
30for the curing of binder ~y~tems based on free radical-and/or acid-curable components, wherein an effective amount of at least one compound of the formula I is added to these binder system~ and the curing is effected by irradiation with W light of a wavelength between 200 and 35450 nm or by combined irradiation and heating.
~he invention ~inally relate~ to a process for the production of a radiation cured coatlng on a sub-strate, wherein the sub~trate is coated with a binder system based on free radical- and/or acid-curable : .
. ! : : `. : ,~

- ' - 5 - ~ ~3~
components containing an effective amount of at least one compound of the formula I and the curing is effected by irradiation with W light of a wavelength between 200 and 450 nm or by combined irradiation and heating.
The ~-substituted sulfonyl derivatives of the formula I with the meanings indicated above are essen-tially compounds known per se. In the formula I, ~he sllbstituent X in an ~-position to the sulfonyl group may be a hydroxyl or an amino group which may in turn itself be substituted. Accordingly, we arrive at the substruc-tures of the subformulae Iat Ib and Ic having the mean-ings indicated above.

.~
OR
Rl-CH-SO2R2 (Ia) R1_cH_so2R2 (Ib) Rl -CH~S02R~
N~
R1-CH-SO2R2 (Ic) Compounds of the subformula Ia are preferred because of their structural simplicity and especially because of their economic acce~sibility. However, the compounds of the subformulae Ib and Ic can be used equally well in the sense of the invention.
Compounds of the formulae I and Ia to Ic which are fur~hermore preferred are those having a carbonyl group in a ~-position to the ~ulfonyl group.
The corresponding compounds which can be repre-sented by the subformula Id are particularly preferred.
o OH

R1-C-CH-SO2-R2 (Rl, R2 = R) (Id) . " ' ' .
.

- 6 - ~3~6~
Typical examples of the compounds of the formulae I and Ia to Id include the ollowing:
(1) ~ So2~cH2-oH (17) ~OH
phenylsulfonyl- ~ CO-CH
SO - O -NH-CO-CH
methanol 2 _ 3 benzoyl(p-ace~aminophenyl-~ulfonyl)methanol ( 2 ) CH3~S02-CH2-OH ( 18 ) ~ OH
(~CO Cl{

p-tolylsulfony methanol benzoyl(methyl~ulfonyl)-methanol ( ) ~ CH2 CH2 ~ CO-CH~
o-tolylsulonyl- 2 3 7 methanol benzoyl~propylæulfonyl)-lS me~hanol CH30 ~ S02-CH2-OH (20) ~OH
p-methoxyphenyl- ~ CO-CH~
sulfonylmethanol S02-N(CH3)2 benzoyl(dimethylamino-sulfonyl)methanol Cl ~ S02-CH2-OH (21) ~o-p-chlorophenyl- ~ CO-CH 2 ~
sulfonylmethanol so2 ~ CH3 benzoylethoxy(p-tolylsulfonyl)-me~hane (6) 02N ~ So2-CH2-OH (2~) OH
p-nitrophenyl- (CH ) C-Co-CH' sulfonylmethanol S2 ~ 3 pivaloyl(p-~olylsulfonyl)-methanol (7) ~ S2-CH2-H (23) ~ CO C ~SO ~ CH3 . . , ~
.. . . . . .
... . . .
- . : :,.: :
. : , , , - , .. . .

:.. . ~ , ~ID35~6~

,~ - n a p h t h y 1 -sulfonylmethanol (cyclohexylcarbonyl~-(p-tolylsulfonyl)-methanol ~S02-CH~ (~4) /CH{~CH
CH ~SO `SO {~CH
1- ( phenylsulf- 3 `J 2 2 3 onyl)ethanol di ~ ( p-tolylsulfonyl ) -(hydro~cymethyl)]benzene ~OH
(9) CH3{~S02-CH (25) 2 5 ~-NH-CH2-s02{~cH3 1- (p-tolylsulf-onyl~propanol N-(p-tolyl~ulfonylmethyl)-aniline tlO) ~OH (26) /CH3 CH {~SO -CH (~
3 2 `C3H7 CH2-S02~CH3 1-(p-tolylsulf- N-methyl-N-(p-tolyl3ulf-onyl)butanol onylmethyl)anîline (11) ~-CH NH~ H2 2~ 3 02N S02{~ CH3 CH2-S02{~ CH3 . (m-nitrophenyl)(p- di(p-tolylsulfonylmethyl)-t o 1 y 1 s u 1 f - amim3 onyl)methanol (12) ,OH (28~ ,CH2-so2~;~cH
o2N~CH CH3-N, . 3 S 2~ 3 2 2~CH3 (p-nitrophenyl~(p- methyl-d.i(p-tolyl~ulfonyl-t o 1 y 1 ~ u 1 f - meth~l)amine onyl)methanol ", :' : , , ~ . . . .
- : . , . , ~ :

- 8 _ 2~4~

~13) ~OH (29) ~CH2-S02 ~ -CH3 NC ~ C~sO ~ CH CH2 So2 ~ CH3 (p-cyanophenyl)(p- ethyl-di(p-tolylsulfonyl-t o 1 y 1 s u 1 f - methyl)amine onyl)methanol -CO-CH NC ~ CH
S2 ~ CH3 S2 ~ 3 benzoyl(p-tolyl- (p-cyanophenyl)(ph~nyl-sulfonyl)methanol amino)(p-tolylsulfonyl)-methane (15) /OH (31) NH
O-CO-C~ ~}CO-C~I
02N- S02 ~ 2 ~ 3 (m-nitrobenzoyl)- benzoyl(phenylamino)(p-(phenylsulfonyl)- tolylsulfonyl)methane methanol (16) ,OH (32) /NH
CO-CH ~ ~ CO-CH
S02 ~ 0CH3 \J ~ S02 ~
- henzoyl(p-meth- benzoyl~cyclohexylamino)-oxyphenyl~ulf- (phenylsulfonyl)methane onyl)methanol (33) (34) CH
CH3-CO-NH ~ -SO2-CH2-OH ~ `CH -SO ~
p-acetylamino-N- N-m0thyl-N-(phenylsul-(phenyl~ulfonyl- fonylmethyl)aniline methyl)aniline - 9 - 2~3~

~ -CH ~
O2N S02 ~ 3 (m-nitrophenyl)-(phenylamino)(p-tolylsulfonyl)-methane Particularly preferred are ~he compounds ben zoyl(p-tolylsulfonyl)methanol, (m-nitrobenzoyl)(phenyl-sulfonyl)methanol and benzoyl(p methoxyphenylsulfonyl)-methanol, very particularly ~he compound benzoyl(p-tolylsulfonyl)methanol.
The compounds of the formula I in which X i~ anO~ group can be formally regarded a~ addi~ion products of sulfinic acids to aldehydes according to the reaction scheme OH
Rl-CHO + HSO2-R2 ~ R1-CH-SO2R2 In practice they are likewi~e readily accessible by this route in predominantly excellent yields. ~he correspond-ing amino compounds can be obtained by performing this reaction in the presence of amines as well a~ by a subsequent reaction. Practical procedural information on the syntheses of compounds of the ormula I can be found, for example, in:
E. v. Meyer, J. Prakt. Chem. 53, 167 (1901) (ref. 1) E.P. Kohler, M. Reimer, J. Amer.
Chem. Soc. 31, 163 (1904) (r~. 2) Ho Bredereck, E. Bader, Chem. Ber. 87, 128 (1954) (ref. 3) H.~Bredereck, E. B~der, Chém. Ber. 87, 784 (1954) (re. 4) ,~ .

.
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.. .

- 10~ 5~
E. B~der, H.D. Hermann, Chem. Ber. 88, 40 (1955) (rQ. 5) ~. Schank, Chem. Ber. 99, 48 (1966) (ref. 6) R. Schank, Liebigs Ann. Chem. 716, 87 (1968) ~ref. 7) The numerous compounds of the formula I are characteriæed in the listed references.
According to ~he inventio~, th~ compounds of ~he formula I can be employed very advantageously as radia-tion activators for the curing oi binder sy~tem~. Their particular advantage lies in the fact that it is possib~e not only to liberate free ra~ica~s -f rom th~n by the action of radiation, but al~o to ~ub~ect them to radiation-induced degradation giving acidic degradation products which then ac~ as acid catalysts. This acid degradation can moreover be induced by heat, so that an additional promotion of the proce~ or its sole accomp-lishment by the ac~ion of heat is pos~ible.
In line with the~e mul~ifunctional characteris-tics, the compounds of the formula I can egually be used as free radical~forming photoinitiators in binder ~y~tems based on free radical- curable component~ and a~
radiation-actiYatahle latent acid catalysts in binder systems based on acid-curable component~ as well as in mixed systems~ the so-called hybrid binder 8y8tem8 ~hich contain free radical- and acid-curahle components next to each other.
The use according to the invention of the com-pounds of the formula I as photoactivator~ in such binder system~ i~ carried out by sL~ple mi~ing with these binder COmpQsitiOns ~ using gentle heat if nece~sary or adding small amount-s of solvent to promote homogeneous distribu-tion. The compounds of the formula I are ~ufficiently active for current applications and processing proce~ses, if they are present in the binder systems in an amounk of 0.1 to 20 ~ by weight. Their preferred amount i~ bekween 1 and 10 ~ by weight; the use of these in an amount of about 2 ~ by weight based on the total amount of the '; ~' ,'; '~,'` ` "'; ` , ' .

binder system is particularly preferred and economical.
The photochemical activation of the compound~ of the formula I can be effected by irradiation with W
light of a wavelength between about 200 and 450 nm, depending on ~he nat~re of the substituents R1 and R2.
Compounds of the formula I and in particular of the subformula Id in which the substituent~ Rl and R2 are phenyl or a low-sub~tituted phenyl are particlllarly effective chiefly in the low to middle W range, between about 200 and 300 nm. If necessary or desirable, the sensitivity within a narrow W range can be increased by the addition of cosensitizer~ o known type absorbing in longer-wave range~, such as aromatic ketones.
`` Radiation-curable binder sys~em~ based on free radical- and/or acid-curable components in which ~he compounds of the formula I according to the inventîon may be used as free radical-forming photoinitiator~ and/or radiation-activatable latent acid catalyst~ are known per se.
A radiation-curable binder system ba~ed on free radical- curable components i~ usually under~tood to be a mixture which comprise~ at least one ethylenically unsaturated compound pho~opol~merizable by free radicals and, if appropriate, other customary additive~. Suitable free radical- polymerizable components are practically any materials which contain olefinically unsaturated dou~le bonds. They can be especially monomers, oligomers and polymer~ having in each case at least one or preferably more un~aturated functions of the acrylate or vinyl type. The corxesponding materials are known in large numbers to a person 3killed in the art. Examples of such compounds are acrylic compounds, in particular acrylates of aliphatic and aromakic monohydroxy or polyhydroxy compound~, ~uch as (meth)ac~ylic acid 3s including its salt~ and amide~, (meth)acrylonitrile, alkyl (meth)acrylates, hydroxyethyl (meth)acrylate, vinyl (meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trlmethylolpropane di(meth) acrylate, pentaerythritol tri(meth)acrylate, further also , .
~,'' ', . , ~ .

;~3~4~

vinyl compounds such a~ vinyl chloride, ~inylidene chloride, styrene, divinylbenzene, N-vinylpyrrolidone and N-vinylcarbazole. Example~ of high-molecular and polymeric binder components are acrylated polyester, acrylate, epoxy, ure~hane, polyamide and silicone resins. Radiation-curable binder systems are predominantly mixtures of several of the cited low-molecular and high-molecular unsaturated components.
Acid-curable binder ~ystems which likewise represent the field of use according to the invention of the compounds of the ~ormula I are all those systems which contain at least one acid-catalysed component capable of polycondensation. These are predominantly resin materials based on melamine or urea which can be lS modified in a variety of ways. ~ person 3killed in the art will be aware of these matexial~; they are produced in industry in large amounts, with ~heir characteri~tics modiied for the various areas of application. A typical exampla of a melamine-based material is hexamethoxymeth-ylmelamine. In addition, ~he acid-curable binder ~ystem~
can contain optional other component~ in varying amounts, such as they are customary in the techology of aminoplastic resins, for example alkyd, phenolic, polyester, acrylic and polyvinyl resin~ or mixtures thereof.
The compounds of the formula I are suitable as radiation-activatable curing catalys~ especially also for the hybrid bindex sy~tems which contain acid-ca~a-lysed components capable of polyconden~ation as well as free radical- polymerizable components. According to the invention they may be activated purely photochemically or~ preferably, photochemicallyJthermally in combination;
then they function to an e~ual measure as free radical-and acid generators and thus effect prackically simultaneously the curing of the variou~ components of the hybrid ~ystem. Suitable acid-cuxable components for such hybrid systems axe all the materials already citsd above, likewi3e materials which may be crosslinked by heat, for example by polycondensation or polyaddition, - 13 - 2~3S~6~
but cannot be crossli~ked by means of free radicals.
Examples of these are acid-curable melamine resins and reactive resins forming polyurethanes or polyester~.
Suitable free radical- polymerizable components are practically any of the materials already mentioned which have olefinically unsaturated double bonds. In such hybrid binder systems the amount of acid-curable and free radical- polymerizable components can vary within a wide range, between about 10 and 90 % by weight.
The radiation-curable binder ~ystems may alæo be in the form of aqueous dispersions, whose water content is normally removed by brief heating after the coating has been applied.
The binder system , curable with the compounds of the formula I as photoactivators, whether on a purely radically polymerizable, a purely acid-curable or a hybrid basis, can vary within ~heir qualitative and quantitative composition~ in a wide range and may com-prise in particular other components and additives. In this context ~he amount of reactive components should preferably be not le~ than 10 ~ by weight. Other com-ponents and additives used for the particular purpose in customa~y amount~ may comprise inorganic and oryanic pigments, dyes, filler~, flow control agents, surfac-tants, matting agents, plasticizers, solvent~, auxiliary dispersants, other binder and resins, other photo-ini~iators, spectral sensitizers and co-initiators of known type, other thermoreactive or photoreactive radical initiators and cation-forming or acid-forming catalys~s.
The coating of substrate~, predominantly flat objects, with such binder systems i5 carried out in a manner known per se. A person skilled in the ar~ will be familiar with the appropriate coating technologies and equipment available to him.
Application extend~ chiefly to the production of thin films, for example paint coating~, on all materials and sub~trate~ normally u~ed for thi~ purpose. These can be mainly paper, wood, textile subfltrates, pla~tics and metal. An important area of application i~ al~o the :, . . , - . :
, :' ~3~

drying or curing of printing inks and screen-printing material~, of which the latter are pr~ferahly used in the surface coating or decoration of, for example, cans, ~ube~ and metal closure caps.
The binder systems according ko the invention containing compounds of the formula I or the coatings produced therewith may be cured by the action of radia-tion energy, especially that in the W wavelength range between 200 and 450 nm. Conventional high-pres~ure;
medium-pressure or low-pressure mercury vapour lamps~
such as xenon or tungsken lamps, may be employed as radiation sources.
In certain cases, chiefly in those of acid-curable or hybrid binder systems, it is preferable to promote curing by simultaneous or sub~equent inpu~ of thermal energy. The additional heat activation is carried out in a temperature rhnge which is normal for acid-catalysed heat-curing sy~tem3. Thi~ i~ between about 80 and 150C, preferably between 100 and 120C.
A particularly favourable characteristic of the compounds of the formula I is that their photochemical and thermal activity can be varied and harmonized with each other by a selective choice of the sub~tituent~ and the particular sensitivity can be ~electively controlled.
Curiny can be performed discontinuously as well as continuously. Irradiation time depends on the nature of the process, on the nature and amount of the pol~mer-izable material~ used, on the nature and concentration of the photoactivator~ used and on the inten~ity of the light source. In the radiation curing of coatings, irradiation time is usually between a few seconds to minutes. The time of any additional heat treat~ent which may be preferably carried out, to full curing is from minutes to several hours depending on the temperature and binder system.
Compared with comparable radiation activator~, especially the ~-~ulfonylacetophenones known from EP 192,967, the compound~ of the formula I have the special, unexpected advantage of producing under com-, - - '~ " ~` '~

, ~ - . :, :
, ~: ` ~ ',`` ` `` ' S;4~i~

parable application and processing conditions distinctly grea~er film hardnesses. To achieve given predetermined film hardnessest shorter irradiation ~imes ars reguired.
ThPy are furthermore greatly superior to the known radiation-activatable and thermal acid catalyst~ in respect of shelf life of the binder systems ~reated by them. Also they show no tendency to affect negati~ely the cured end-product, especially as regards yellowing.
The simple, problem-free accessibility of the compounds of the formula I and their outstanding applica-tion characteristics make them particularly valuable in practical use.
Examples A. PreParation of compounds of the formula I
lS The preparation and characterization of compounds of the formula I according to TabIe 1 below wa~ carried out by procedures stated in the cited references or in a similar manner. All the prepared compounds gave correct elemental analyses.

Analoqous procedure (compound No. 31) A mixture of 7.6 g (50 mmol) of phenylglyoxal hydrate and 4.6 g (50 mmol) of aniline was stirred in S0 ml of THF for 2 hours at room temperature. 7.8 g (50 mmol) of toluenesulfinic acid were then added and stir-ring was continued for a further 16 hours. The separatedprecipi$ate was ~iltered by suction, washed with ether and recrystallized from toluene. 9.9 g (27 mmol - 54 ~
of theory) of benzoyl(phenylamino)(p-tolylsulfonyl)meth-ane, melting at 131.5C, were obtained.
Table 1 Compound Prepared ~elting point (C) No. according to foundliterature 1 re~. 3 65.5 60 2 ref. 1, ref. 396 95 ref. 3 109 111 ... ~ . . . .
'1''~
,.~

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., . ; ~ , : .
-: , . :

- 16 - 2~5~
8 ref. 2, ref. 3 52 ref. 3 7g-80 78 11 ref. 2, ref. 3 91.5 110 12 ref. 2, ref. 3 109-111 116 13 92.5 14 ref. 6 134 125 21 ref. 7 76 22 ref. 6 gl 23 ref. 6 99 24 128.5 ref. 3 133 137 26 ref. 3 ~7 95 27 ref. 1, ref. 3 169 171 lS 28 ref. 3 159 168 29 ref. 3 100 114 155.5 31 131.5 33 ref. 3 160 175 (decomp. > 90) B. Application com~arison experiment 2 ~ of th~ compound of the formula I according to the invention under te t (compound No. 14) and 2 % of the comparison substance ('DTA' from EP lg2,967~ a~ a 10 %
~olution in n-butanol were each u~iformly stirred into a paint system (~ybrid binder ~ystem) consisting of 72 part~ by weight of an acrylated aromatic epoxy resin (Laromer~ EA 81 from ~ASF), 18 parts by weight of hexanediol diacrylate, 10 parts by weight of hexamethoxymethylmel~mine tCymel~
303 from Dyno Cyanamid).

(14) ~ Co-C~So2- ~ -CH3 (according to the invention) OH

('DTA') ~ -CO-C-SO2~ ~ CF~3 (from EP 192,967).

. .

~)35~6~

The ready-for-u~e paint samples were ~hen applied to glass panels (10 cm x 10 cm3 at a film thickne~s of 80 ~m and exposed to air for 10 minutes at room ~empera-ture to remove the sol~ent.
After exposure to air the coated glass panels were transported in a W laboratory dryer (model BE 22 from Beltron) at conveyor belt ratei3 of 2.5 mtmin to 40 m/min (i.e. radiation times of 1.5 s/m to 24 s~m) at a distance of about 10 cm under a medi~m-pressure Hg lamp with an output of 80 W/cm.
After irradiation by W, the coated panels were cured in a laboratory drying oven for 30 minutes at 120UC. After curing and cooling, the condition of the surface wa determined by a sensory test and about 20 hours after stoving the K~nig pendulum hardneiss (DIN
53 157) was detexmined as a measure of haxdne3s.
~he results axe shown in ~able 2 and Figure 1.
Table 2 Photoactivator Rate of curing (m/min) Nbte 2.5 3.75 5 7.5 10 15 20 ~0 2 % compound 192 185 174 162 138 105 100 62 (a) No. 14 + + + (+) (+~ _ ~ ~ (b) ~ _ 2 ~ 'DTA' 176 168 165 144 115 85 75 30 (a) + + + (+) (+) ~ b) _ Notes:
(a) Pendulum hardness according to DIN 53 157 (in seconds), measured 20 hour~ after heat curing.
(b) Condition of ~urface immediately after heat curing + = surface is dry (+) = surface ii~ not quike dry - = surface i~ tacky It can be seen that over the whole range of curing rates using the compound according to the i~ven-tion significantly harder coatings are obtained than - . -, 2C~35fl~
_ 18 --using the comparison substancQ.
To prepare coatin~s of the predetermined pendulum hardness (for example 170 seconds), curing can be effsc-ted more rapidly when the compound according to the invention is used for activation than when the comparison substance i9 used (for example at a rate of 6 m/min instead of 4 m/min).

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Claims (6)

Patent Claims

1. Radiation-cuxable binder systems based on free radical- andtor acid-curable compenents, characterized in that they contain an effective amount of at least one compound of the formula I

(I), X being OR3 or NR3R4, in which R1 is H, R, R-O, R2N, R-CO, R-COO, R2NCO, R2 is R, OR, NR2, R3 is H, R
R4 is H, R, -CHR1-SO2-R2 and R is alkyl, cycloalkyl or aryl, each having up to 10 carbon atoms, each being unsubstituted or mono-or multi-substituted by OH, halogen, cyano, nitro, alkyl, alkoxy, alkylthio, monoalkylamino or bis-alkylamino, alkanoyl, alkanoyloxy, alkanoylamido, alkoxycarbonyl, alkylaminocarbonyl or aryloxy, each substituent having up to 6 carbon atoms, as free radical-forming photoinitiators and/or radiation-activatable latent acid catalysts.

2. Binder systems according to Claim 1, charac-terized in that they contain 0.1 to 20 % by weight, preferably 1 to 10 % by weight, of compound(s) of the formula I.

3. Use of compounds of the formula I as free radical-forming photoinitiators and/or radiation-activatable latent acid catalysts in binder systems based on free radical- and/or acid-curable components.

4. Process for the curing of binder systems based on free radical- and/or acid-curable components, charac-terized in that an effective amount of at least one compound of the formula I is added to these binder systems and the curing is effected by irradiation with UV light of a wavelength between 200 and 450 nm or by combined irradiation and heating.

5. Process according to Claim 4, characterized in that 0.1 to 20 % by weight, preferably 1 to 10 % by weight, of compound(s) of the formula I are added.

6. Process for the production of a radiation-cured coating on a substrate, characterized in that the sub-strate is coated with a binder system according to Claim 1 or 2 and the cuxing is effected by irradiation with UV
light of a wavelength between 200 and 450 nm or by combined irradiation and heating.