WO1991000312A1 - Radiation-curable binding agent systems with alpha-substituted sulphonyl compounds as photo-activators - Google Patents

Abstract

The invention relates to radiation-curable binding agent systems based on radically and/or acid-curable components containing certain alpha-substituted sulphonyl compounds as radical-forming photo-initiators and/or as radiation-activatable latent acid catalysts.

Description

Radiation-curable binder systems with α-substituted sulfonyl compounds as photoactivators

The invention relates to radiation-curable binder systems which contain certain α-substituted sulfonyl compounds as photoactivators. These are binder systems based on free-radically and / or acid-curable components in which the photoactivators according to the invention function as free-radical-forming photoinitiators and / or as radiation-activatable latent acid catalysts.

A large part of the binder systems in paint and coating technology is based on heat-curing materials, in which cross-linking and curing takes place through polycondensation. Base materials capable of polycondensation are usually aminoplast synthetic resins, the thermal curing of which is catalyzed by acids, in particular organic sulfonic acids. A typical and very frequently used acid catalyst is p-toluenesulfonic acid (PTS). However, acid-curable systems have the disadvantage that, if they are mixed with the acid catalyst, they have only a limited shelf life and soon gel if they are not processed within a shorter time. Sulfonic acid catalysts in "blocked" form, for example as amino salts or oxime esters of hydroxamic acids, enable a better one

Storage stability. From these blocked forms, the catalytically active acids can be released by heating to higher temperatures. However, the hardening of the corresponding systems requires a higher level

Energy and time expenditure. In general, thermal curing is very time-consuming, which is disadvantageous for industrial production processes.

In addition to thermal curing, photochemically induced curing has also become very important in coating and coating technology, with special radiation-curable compositions being used which contain photoactivators or photoinitiators for converting the radiation energy. Radiation curing is characterized in particular by high speed and low energy consumption. The most important photopolymerization reaction for practical use is the radical polyaddition of ethylenic double bonds. Corresponding radiation-curable systems are therefore based on materials which contain free-radically polymerizable or crosslinkable ethylenic double bonds and free-radical-forming photoinitiators.

Systems which are thermally acid-catalyzed are in principle also accessible to radiation curing if, instead of the conventional thermal acid catalysts, photochemically activatable latent acid catalysts are used. The catalytically active acid, which effects the actual hardening, expediently promoted by additional supply of thermal energy, must be released from these by exposure to radiation. For this purpose, compounds of the halogen or sulfonyloxyacetophenone type which have been known for some time have the disadvantage of having a corrosive effect, yellowing of the hardened layers or otherwise adversely affecting them; they also have stability and compatibility problems. Recent efforts to reduce the known disadvantages of the acid-catalyzed, thermally curing systems and to utilize therein the advantages of photochemical activation by means of UV radiation are reflected, for example, in EP 192 967. There, sulfonyl derivatives of aromatic-aliphatic ketones, in particular α-sulfonylacetophenone compounds, are disclosed, which can be used as photochemically activatable latent acid catalysts. Compared to the previously known UV acid catalysts, these compounds are said to have more favorable application properties, in particular with regard to influencing the hardened layer and storage stability of the binder system. Furthermore, these compounds can be used as free-radical-generating photoinitiators for free-radically polymerizable binder systems and for hybrid-binder systems based on free-radical and acid-curing constituents.

However, the compounds known from EP 192 967 have the disadvantage that they are only moderately reactive. For a defined curing result, comparatively high radiation outputs and / or long irradiation times are required. In addition, these compounds have the disadvantage that their synthesis is relatively complex and is linked to the use of starting materials and solvents which are not harmless and the formation of harmful by-products. Their industrial production and use from an economic point of view and including today's environmental and occupational safety issues is therefore problematic. The aim of the invention was therefore to find further compounds which can be used as free-radical-forming photoinitiators and as radiation-activatable latent acid catalysts in radiation-curable binder systems based on free-radically and / or acid-curable components. The sought compounds should have a higher reactivity than conventionally used compounds and should be as simple and easy to access as possible.

It has now been found that certain α-substituted

Sulfonyl compounds meet these requirements in an excellent manner.

(I) mit X gleichOR³ oder NR³R⁴, worin These are compounds of the formula I.

(I) with X equal to OR ³ or NR ³ R ⁴ , wherein

R ¹ H, R, RO, R ₂ N, R-CO, R-COO, R ₂ NCO,

R ² R, OR, NR ₂

R ³ H, R

R ⁴ H, R, -CHR ¹ -SO ₂ -R ² and R alkyl, cycloalkyl or aryl, each with up to

10 C atoms, optionally mono- or polysubstituted with OH, halogen, cyano, nitro, alkyl, alkoxy, alkylthio, mono- or bisalkylamino, alkanoyl, alkanoyloxy, alkanoylamido, alkoxycarbonyl, alkylaminocarbonyl, aryloxy, each with up to 6 C atoms means. It was found that the compounds of the formula I initially form free radicals and then, depending on the reaction environment, acidic degradation products by irradiation with UV light of a wavelength in the range between 200 and 450 nm. When used as photoactivators in binder systems based on free-radical and / or acid-curable components, they surprisingly proved to be significantly more reactive than conventional compounds and in particular those

EP 192 967 superior to known sulfonylacetophenone compounds.

The invention thus relates to the 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-radically and / or acid-curable components.

The invention furthermore relates to radiation-curable binder systems based on free-radically and / or acid-curable components which contain an effective amount of at least one compound of the formula I as free-radical-forming photoinitiators and / or as radiation-activatable latent acid catalysts.

The invention furthermore relates to a process for curing binder systems based on free-radically and / or acid-curable components, an effective amount of at least one compound of the formula I being added to them and curing by irradiation with UV light of a wavelength between 200 and 450 nm or by combined irradiation and heating.

Finally, the invention relates to a method for producing a radiation-hardened coating on a substrate, this being done with a binder telsystem based on radical and / or acid-curable components, containing an effective amount of at least one compound of formula I, coated and the curing by irradiation with UV light of a wavelength between 200 and 450 nm or by combined irradiation and heating.

The α-substituted sulfonyl derivatives of the formula I with the meanings given above are essentially compounds known per se. In formula I, the substituent X in the α-position to the sulfonyl group can be a hydroxyl or an amino group, which in turn can itself be substituted. Accordingly, the substructures of sub-formulas Ia, Ib and Ic result with the meanings given above.

 Compounds of sub-formula Ia are preferred because of their structural simplicity and particularly economical accessibility. However, the compounds of sub-formulas Ib and Ic can equally well be used for the purposes of the invention.

Preference is furthermore given to compounds of the formula I or Ia to Ic which have a carbonyl group in the β position relative to the sulfonyl group. Corresponding compounds are particularly preferred:

can be represented by sub-formula Id.

 Typical examples of compounds of the formulas I or

Ia bis Id sind etwa die folgenden:

Ia to Id are about the following:

Phenyl sulfonyl methanol

₃ Benzoyl- (p-acetaminophenylsulfonyl) methanol

₃

p-tolyl sulfonyl methanol

 Benzoyl (methyl sulfonyl) methanol

o-Tolyl-sulfonyl-methanol Benzoyl- (prppyl-sulfonyl) -methanol

p-methoxy-phenyl-sulfonyl-

methanol benzoyl- (dimethylaminosulfonyl) methanol

p-chlorophenyl sulfonyl

methanol benzoyl ethoxy (p-tolyl sulfonyl) methane

p-nitro-phenyl-sulfonyl-

methanol pivaloyl- (p-tolylsulfonyl) - methanol.

ß-naphthyl-sulfonyl-

 methanol (cyclohexylcarbonyl) - (p-tolylsulfonyl) methanol

Di-[(p-tolyl-sulfonyl)-

Di - [(p-tolyl-sulfonyl) -

1- (phenylsulfonyl) ethanol (hydroxymethyl)] benzene

N-(p-Tolyl-sulfonyl-methyl)- 1-(p-Tolyl-sulfonyl)-propanol anilin

N- (p-Tolylsulfonylmethyl) - 1- (p-tolylsulfonyl) propanol aniline

1- (p-tolylsulfonyl) butanol N-methyl-N- (p-tolylsulfonylmethyl) aniline

 (m-nitro-phenyl) - (p-tolyl-di- (p-tolyl-sulfonyl-methyl) -sulfonyl) -methanol amine

(p-nitro-phenyl) - (p-tolyl-methyl-di- (p-tolyl-sulfonyl-sulfonyl) -methanol methyl) -amine

(p-Cyano-phenyl) - (p-tolyl-ethyl-di- (p-tolyl-sulfonylsulfonyl) -methanol methyl) -amine

 Benzoyl- (p-tolylsulfonyl) - (p-cyano-phenyl) - (phenylmethanol amino) - (p-tolylsulfonyl) - methane

 (m-Nitro-benzoyl) - (phenyl-benzoyl- (phenyl-amino) - (p-sulfonyl) -methanol tolyl-sulfonyl) -methane

Benzoyl- (p-methoxy-phenyl-benzoyl- (cyclohexyl-amino) -sulfonyl) -methanol (phenyl-sulfonyl) -methane

p-acetylamino-N- (phenyl-

sulfonyl-methyl) -aniline N-methyl-N- (phenyl-sulfonyl-methyl) -aniline

 (m-nitrophenyl) - (phenylamino) - (p-tolylsulfonyl) methane

The compounds benzoyl- (p-tolyl-sulfonyl) -methanol, (m-nitro-benzoyl) - (phenyl-sulfonyl) -methanol and benzoyl- (p-methoxy-phenyl-sulfo) are particularly preferred nyl) methanol, especially the compound benzoyl- (p-tolyl-sulfonyl) -methanol.

The compounds of the formula I in which X represents an OH group can be formally added products of sulfinic acids to aldehydes according to the reaction scheme

understand. In practice, they are easily accessible in this way and with predominantly excellent yields. If this reaction is carried out in the presence of amines or by subsequent reaction, the corresponding amino compounds can be obtained. Practical information for carrying out syntheses for compounds of the formula I can be found, for example, from:

E. v. Meyer,

 J. Prakt. Chem. 53, 167 (1901) (Lit. 1),

 E.P. Kohler, M. Reimer, J. Amer.

Chem. Soc. 31, 163 (1904) (Ref. 2),

 H. Bredereck, E. Baths,

 Chem. Ber. 87, 128 (1954) (ref. 3),

 H. Bredereck, E. Baths,

 Chem. Ber. 87, 784 (1954) (Ref. 4),

E. Baths, H.D. Hermann,

 Chem. Ber. 88, 40 (1955) (Ref. 5),

 K. Schank,

 Chem. Ber. 99, 48 (1966) (ref. 6),

 K. Schank,

Liebigs Ann. Chem. 716, 87 (1968) (ref. 7).

Numerous compounds of the formula I are also characterized in the work mentioned. According to the invention, the compounds of the formula I can be used very advantageously as radiation activators for curing binder systems. Their particular advantage is that radicals can be liberated from them by the action of radiation and that they can be broken down into radiation-induced acidic cleavage products, which then act as acid catalysts. This acid degradation is also thermally inducible, so that additional promotion or sole triggering of this

Process by exposure to heat is possible.

In accordance with these multifunctional properties, the compounds of the formula I can be used equally as free-radical-forming photoinitiators in binder systems based on free-radically curable components and as radiation-activatable latent acid catalysts in binder systems based on acid-curable components and in mixed systems, so-called hybrid binder systems, which contain free-radical components and acid-curing components.

The compounds of the formula I are used according to the invention as photoactivators in such binder systems by simple mixing with these binder compositions, if appropriate with gentle heating or the addition of minor amounts of solvent to promote homogeneous distribution. The compounds of the formula I are sufficiently effective for common applications and processing processes if they are present in the binder systems in a proportion of 0.1 to 20% by weight. Their proportion is preferably between 1 and 10% by weight; Their use in a proportion of about 2% by weight, based on the total amount of the binder system, is particularly expedient and economical. Depending on the nature of the substituents R ¹ and R ^{2, the} photochemical activation of the compounds of the formula I can be carried out by

Irradiation with UV light with a wavelength between about

200 and 450 nm take place. Compounds of formula I and in particular of sub-formula Id, in which the substituents R ¹ and R ^{2 represent} phenyl or low-substituted phenyl, are particularly effective primarily in the deep to medium UV range, for example between 200 and 300 nm By adding cosensitizers of a known type, such as aromatic ketones, which absorb in longer-wave regions, the sensitivity in the near UV range can be increased if necessary or desired.

Radiation-curable binder systems based on free-radically and / or acid-curable components, in which the compounds of the formula I can be used according to the invention as free-radical-forming photoinitiators and / or radiation-activatable latent acid catalysts, are known per se.

Under a radiation-curable binder system

The basis of free-radically curable components is usually understood to be a mixture which contains at least one ethylenically unsaturated compound which can be photopolymerized by free radicals and, if appropriate, further customary additives. Practically all materials which have olefinically unsaturated double bonds are suitable as free-radically polymerizable components. These can in particular be monomers, oligomers and polymers, each with at least one or expediently with several unsaturated functions of the acrylate or vinyl type. Corresponding materials are known to the expert in great abundance. Examples of such compounds are acrylic compounds, in particular acrylates of aliphatic and aromatic mono- or polyhydroxy compounds, such as (meth) acrylic acid including theirs Salts and amides, (meth) acrylonitrile, (meth) acrylic acid alkyl esters, hydroxyethyl (meth) acrylate, vinyl (meth) acrylate, ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, trimethylol propane di (meth) acrylate, pentaerythritol tri ( meth) acrylate, further vinyl compounds such as vinyl chloride, vinylidene chloride, styrene, divinylbenzene, N-vinylpyrrolidone, N-vinylcarbazole. Examples of higher molecular and polymeric binder components are, for example, acrylated polyester, acrylate, epoxy, urethane, polyamide and silicone resins. Radiation-curable binder systems are predominantly mixtures of several of the listed low molecular weight and high molecular weight unsaturated components.

Acid-curable binder systems, which likewise represent the area of use of the compounds of the formula I according to the invention, are all those systems which contain at least one acid-catalyzed component capable of polycondensation. These are mainly synthetic resin materials based on melamine or urea, which can also be modified in a variety of ways. These materials are familiar to the person skilled in the art; They are manufactured in large quantities and modified for their various properties in their material properties industrially. A typical example of a melamine base material is hexamethoxymethylmelamine. In addition, the acid-curable binder systems can contain any further components in different proportions, as are customary in the technology of aminoplast plastics, for example alkyd, phenol, polyester, acrylic and polyvinyl resins or mixtures thereof.

The compounds of the formula I are suitable as radiation-activatable curing catalysts, in particular also for hybrid binder systems which are acid-catalyzed, polycondensation-capable and free-radically polymerizable parts included. According to the invention, they can be activated purely photochemically and expediently combined photochemically and thermally, whereby they act equally as radical and acid generators and thus effect the curing of the different hybrid system components practically simultaneously. Acid-curable components for such hybrid systems are all materials mentioned above, that is to say materials which can be crosslinked thermally, for example by polycondensation or polyaddition, but not by free radicals. Examples include acid-curable melamine resins and reactive resins that form polyurethane or polyester. Practically all of the materials already mentioned which have olefinically unsaturated double bonds are suitable as free-radically polymerizable components. In hybrid binder systems of this type, the proportion of acid-curable and free-radically polymerizable components can be varied within wide ranges, for example between 10 and 90% by weight. The radiation-curable binder systems can also be in the form of aqueous dispersions, the water content of which is normally removed by brief heating after coating.

The binder systems which can be hardened with the compounds of formula I as photoactivators, whether on the basis of purely free-radically polymerizable, purely acid-hardenable or hybrid-based, can be varied widely in their qualitative and quantitative compositions, and in particular they can also contain further constituents and additives. The proportion of reactive components should expediently not fall below 10% by weight. Inorganic and organic pigments, dyestuffs, Fillers, leveling agents, surface-active agents,

Matting agents, plasticizers, solvents, dispersing aids, other binders and resins, other photoinitiators, spectral sensitizers and coinitiators of a known type, further thermo- or photoreactive radical initiators and cation- or acid-forming catalysts are included.

The coating of substrates, mostly flat

Objects with such binder systems are made in a manner known per se. Corresponding coating technologies and devices are familiar to the person skilled in the art and are generally available.

The application extends primarily to the production of thin layers such as lacquer coatings on all the usual materials and substrates. These can primarily be paper, wood, textile supports, plastic and metal. An important area of application is also the drying or hardening of printing inks and screen printing materials, the latter of which are preferably used in the surface coating or design of, for example, cans, tubes and metal caps.

The binder systems according to the invention containing compounds of the formula I or the coatings produced therewith can be cured by the action of radiation energy, in particular from the UV wavelength range between 200 and 450 nm. The usual high-pressure mercury vapor, medium-pressure or low-pressure lamps as well as xenon and tungsten lamps can be used as beam sources. In certain cases, especially in the case of acid-curable or hybrid binder systems, it is expedient to cure by simultaneous or subsequent addition of

To promote thermal energy. The additional thermal activation takes place in the temperature range customary for acid-catalyzed thermosetting systems. This is approximately between 80 and 150 ° C, preferably between 100 and 120 ° C.

A particularly favorable property of the compounds of the formula I here is that their photochemical and thermal activity can be varied and matched to one another by selective choice of the substituents and the respective sensitivity can be specifically controlled.

The hardening can take place discontinuously as well as continuously. The irradiation time depends on the type of implementation, on the type and amount of the polymerizable materials used, on the type and concentration of the photoactivators used and on the intensity of the light source. When curing radiation from

Coatings it is usually in the range of a few seconds to minutes. Depending on the temperature and the binder system, the duration of any additional heat treatment, which may be expedient, until complete hardening is in the range from minutes to a few hours. The compounds of formula I have comparable radiation activators, in particular those from

EP 192 967 known α-sulfonylacetophenones, the special, not expected advantage that they lead to significantly higher layer hardness under comparable application and processing conditions. Shorter irradiation times are required to achieve certain predetermined layer hardnesses. Furthermore, they are considerably superior to the known radiation-activatable and thermal acid catalysts with regard to the storage stability of the binder systems which have been mixed with them. They also show no tendency to adversely affect the hardened end product, in particular to yellow.

The simple, problem-free accessibility of the compounds of the formula I and their excellent performance properties make them particularly valuable for practical use.

Examples

A. Preparation of compounds of formula I.

The preparation and characterization of compounds of the formula I according to Table 1 below was carried out in accordance with the instructions given in the literature sections mentioned or analogously thereto. All connections made gave correct elemental analysis.

Analogous procedure (compound no. 31) A mixture of 7.6 g (50 mmol) phenylglyoxal hydrate and 4.6 g (50 mmol) aniline in 50 ml THF was stirred for 2 hours at room temperature. Then 7.8 g (50 mmol) of toluenesulfinic acid were added and the mixture was stirred for a further 16 hours. The precipitate was filtered off, washed with ether and uncrystallized from toluene. 9.9 g (27 mmol = 54% of theory) of benzoyl- (phenylamino) - (p-tolylsulfonyl) methane with a melting point of 131.5 ° C. were obtained.

Table 1

Connected Melting Point (° C)

 application no. after found Lit.

 1 Lit. 3 65.5 60

 2 Lit. 1, Lit. 3 96 95

 4 87

 5 Lit. 3 109 111

 6 112

 8 Ref. 2, Ref. 3 52

 9 78-79

 10 Lit. 3 79-80 78

11 Lit. 2, Lit. 3 91.5 110 12 Lit. 2, Lit. 3 109-111 116

 13 92.5

 14 Lit. 6 134 125

 21 Lit. 7 76

 22 Lit. 6 91

 23 Lit. 6 99

 24 128.5

 25 Lit. 3 133 137

 26 Lit. 3 97 95

 27 Lit. 1, Lit. 3 169 171

 28 Lit. 3 159 168

 29 Lit. 3 100 114

 30 155.5

 31 131.5

 33 Lit. 3 160 175

 34 96

 35 (dec.> 90)

Comparative application test

In a paint system (hybrid binder system) consisting of

72 parts by weight of an acrylated, aromatic

 Epoxy resin

 (Laromer EA 81 from BASF), 18 parts by weight of hexanediol diacrylate,

10 parts by weight of hexamethoxymethylmelamine

(Cymel ^® 303 from Dyno Cyanamid), 2% of the compound of the formula I to be tested according to the invention (compound no. 14) or 2% of the reference substance ("DTA", from EP 192967) were in the form of 10% solutions in n-Butanol stirred in evenly.

 The ready-to-use paint samples were then applied to glass plates (10 cm × 10 cm) in a layer thickness of 80 μm and flashed off at room temperature for 10 minutes to remove the solvent.

After flashing off, the coated glass plates were in a UV laboratory dryer (type BE 22 from Beltron) at belt speeds of 2.5 m / min to 40 m / min (exposure times from 1.5 s / m to 24 s / m) passed at a distance of about 10 cm under a medium pressure mercury lamp with an output of 80 W / cm. After the UV radiation, the coated plates were cured in a laboratory drying cabinet at 120 ° C. for 30 minutes. After hardening and cooling, the condition of the surface was determined by sensors and about 20 hours after baking, the pendulum hardness according to König (DIN 53 157) was determined as a measure of the hardening result.

 Table 2 and Figure 1 show the results.

Table 2

Photoactivator curing speed (m / min) Note

 2.5 3.75 5 7.5 10 15 20 40

2% connection 192 185 174 162 138 105 100 62 (a) No. 14 + + + (+) (+) - - - (b)

 176 168 165 144 115 85 75 30 (a)

2% "DME" + + + (+) (+) - - - (b) Remarks:

(a) Pendulum hardness according to DIN 53 157 (in sec), measured 20 hours after thermal curing.

(b) Surface quality immediately after thermal curing

+ = Surface is dry

 (+) = Surface is not completely dry

 - = surface is sticky

It can be seen that considerably harder coatings are obtained over the entire curing speed range with the compound according to the invention than with the comparison substance.

For the production of coatings with a certain pendulum hardness (e.g. of 170 sec), when activated with the compound according to the invention, curing can take place faster than with the comparison substance (e.g. at 6 m / min instead of 4 m / min).

Claims

Claims Radiation-curable binder systems based on free-radically and / or acid-curable components, characterized in that they contain an effective amount of at least one compound of the formula I.

where X is OR ³ or NR ³ R ⁴ , wherein R ¹ H, R, RO, R ₂ N, R-CO, R-COO, R ₂ NCO,

L, OR, NR ₂ MR R ⁴ H, R, -CHR ¹ -SO ₂ -R ² and R alkyl, cycloalkyl or aryl, each with up to  10 carbon atoms, optionally one or more times  substituted with OH, halogen, cyano, nitro,  Alkyl, alkoxy, alkylthio, mono- or bisalkylamino, alkanoyl, alkanoyloxy, alkanoylamido,  Alkoxycarbonyl, alkylaminocarbonyl, aryloxy  each with up to 6 carbon atoms, as radical-forming photoinitiators and / or radiation-activatable latent acid catalysts  contain. 2. Binder systems according to claim 1, characterized in that they preferably 0.1 to 20 wt.%  1 to 10% by weight of compound (s) of the formula I  contain. 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-radically and / or acid-curable components. 4. Process for hardening binder systems  Basis of free-radically and / or acid-curable components, characterized in that an effective amount of at least one compound of the formula I is added to them and the curing by irradiation with UV light of a wavelength between 200 and 450 nm or by combined irradiation and heating beforehand 5. The method 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. A process for producing a radiation-cured coating on a substrate, characterized in that it is coated with a binder system according to claim 1 or 2 and the curing is carried out by irradiation with UV light of a wavelength between 200 and 450 nm or by combined irradiation and heating .