DE2759766C2 - - Google Patents

Description

Many reactions in organic chemistry are through Irradiation with visible light or ultraviolet Radiation (UV) accelerated or even made possible in the first place. This includes, for example, cleavage reactions, e.g. B. in the vitamin D series, rearrangement reactions, for. B. cis-trans isomerizations, and addition reactions, e.g. B. of maleic anhydride to benzene. The most technical such addition reactions are, however photochemically initiated polymerization reactions.

All of these reactions require that at least a component of the reaction mixture is capable of this is to absorb the irradiated light or UV. If this component is one of the reactants is, the ractions can be done easily without further additions by irradiating the reaction mixture with light or UV can be performed. Often, however, is not a reaction partner able to make the photochemically effective To absorb radiation to a sufficient extent. In these Cases often become substances called photosensitizers added to the desired reaction do not participate, but are able to irradiate Absorb light or UV and the absorbed To transfer energy to one of the reactants. Essential criteria for the selection of such sensitizers include the type of work to be carried out Response, the ratio of the absorption spectrum of the Sensitizer for the spectral energy distribution of the available Radiation source, the solubility of the sensitizer in the reaction mixture as well as the influencing  of the final product due to residual sensitizer residues and / or the result thereof during the photochemical Reaction products.

So far, mainly benzophenone derivatives, benzoin ethers, benzil monoacetals and α- haloacetophenone derivatives have been used as sensitizers for the photopolymerization of unsaturated compounds. However, these substances have various disadvantages, which significantly limit their technical applicability. This includes, in particular, the property of monomers or prepolymers mixed with compounds from these groups to polymerize without irradiation - in the dark - ie many reaction mixtures with such sensitizers have only a low dark stability. Other compounds from these classes have poor chemical stability; for example, some benzil monoacetals are made from very small amounts of water, e.g. B. split by the humidity in benzil and alcohol. Finally, other of these known sensitizers cause yellowing of the polymers produced with them, which is highly undesirable, particularly in the case of usually colorless plastics or in particular in UV-cured printing inks. The often low solubility of the known sensitizers in the monomers or prepolymers also plays an important role in this last-mentioned field of application. Since printing inks generally contain considerable amounts of colored pigments, which absorb a large part of the radiated energy without being photochemically active, a larger amount of sensitizer must be added here. Here it is often 5 to 10 percent by weight of the reaction mixture, ie the printing ink, whereas otherwise in the absence of coloring additives in the plastics industry 1 to 2 percent by weight is often quite sufficient. This concentration can usually still be achieved with the less soluble known sensitizers. At the concentrations required in printing inks, the known sensitizers often crystallize partially; apart from the fact that the crystallized parts no longer have a sensitizing effect, the resulting crystallites also damage the printing plates, which are made of relatively soft materials, even after some time.

The object of the invention was to provide photosensitizers, especially for photopolymerization unsaturated compounds mixed with the other reactants are stable in the dark, which itself and due to its secondary products no yellowing of the reaction products and cause in the usually subjected to photopolymerization Monomers or prepolymers have the highest possible solubility have. In addition, they are said to be in the wavelength range from 250 to 500 nm, preferably between 300 and 400 nm are the largest possible photosensitizing Possess effectiveness.

According to the invention, this object is achieved by the provision of compounds of general formula I for Solved use as photosensitizers,

in which

R₁hydrogen, phenyl or alkyl or alkoxy with each up to 18 carbon atoms, R₂hydrogen, chlorine, bromine, alkyl or alkoxy each with up to 4 carbon atoms R₃ and R₄alkyl with up to 6 carbon atoms and R₅hydrogen, alkyl or alkanoyl with each mean up to 4 carbon atoms,

with the proviso that

• a) R₅ is not hydrogen, methyl or acetyl, provided R₁ and R₂ are hydrogen and R₃ and R₄ Methyl mean
• b) R₁ is not methyl, methoxy or phenyl, provided R₂ and R₃ are hydrogen and R₃ and R₄ Methyl mean
• c) R₃ and R₄ are not methyl, provided that R₂ 2-methyl and R₁ and R₅ are hydrogen,
• d) R₃ is not methyl or ethyl, if R₁, R₂ and R₅ are hydrogen and R₄ is ethyl.

It has been found that the compounds of general Formula I a good photosensitizing activity for radiation in the wavelength range from 250 to 500 nm own and used in most for photopolymerizations Monomers or prepolymers, e.g. B. based of unsaturated esters such as acrylic acid esters, methacrylic acid esters or maleic acid esters, or styrene are more soluble than most previously used Sensitizers. The solutions of photosensitizers of the general formula I in these monomers and prepolymers usually also have a better one Dark storage stability as, for example, analog solutions of benzoin ethers. Finally, in photopolymerizations with the sensitizers of the general formula I Yellowing of the polymers is not or only to a significant extent to a lesser extent than with the previously used sensitizers observed.  

In view of the common structural features of the previously used Photosensitizers, usually two contain optionally substituted phenyl nuclei, the aromatic systems via one or two carbon atoms are cross-conjugated, it is surprising that the invention Hydroxyalkyl ketones to be used with only an aromatic ring has such a good photosensitizing effect have. Acetophenone and derivatives are also of acetophenone as photosensitizers, in particular for photochemical cycloadditions and been used. Those with connections from this Great results obtained, especially the quantum yields of the sensitized photochemical reactions however, were mostly significantly worse than that for example, results obtained with benzophenone.

For example, acrylic-based paints that are in Presence of sensitizers of formula I photopolymerized were significantly improved hardness on and show no yellowing in comparison to corresponding Varnishes, such as the well-known sensitizer benzoin isopropyl ether or those in the German interpretation texts 17 69 854 and 21 60 692 described benzoin ether derivatives, which in German Offenlegungsschrift 24 32 563 and in U.S. Patent 37 15 293 described dialkoxyacetophenone derivatives or that from Japanese Patent Application Laid-Open No. 51-0 17 802 contain known hydroxy ketone compounds.  

The advantageous properties of the sensitizers according to the invention compared to known from the prior art, for example from the following comparative experiments:

1. Lacquer hardness and yellowing a) Test methodology

80 parts by weight of the solution of an unsaturated acrylic resin in hexanediol diacrylate (content of this about 20%; "Laromer® 8555 ", manufacturer BASF AG, Ludwigshafen) were with 20 weight points Trimethylolpropane triacrylate (manufacturer: BASF AG, Ludwigshafen) and 1.5 parts by weight of the photosensitizer mixed. In the case of solid benzoin isopropyl ether the mixture was briefly heated to 60 ° to complete solution achieve, and then cooled back to 20 °. With the (liquid) Compounds according to the invention could already at room temperature a uniform solution can be made.

A glass plate (10 x 10 cm) was washed with acetone and then coated with the mixture described above (Layer density 50 µm). The coated glass plate was then with a mini-cure device for 0.25 seconds irradiated (manufacturer: Primarc (Jigs & Lamps) Ltd .; exposure 80 W / cm; Belt speeds 20 m / min .; Distance 10 cm).

Immediately afterwards, the hardness of the paint was measured using the pendulum device determined according to König (DIN 53 157).

The vibration test according to this standard is based on that the vibrations of a supporting pendulum The more "soft" the pad is, the more steamed it will be is. The time period in is used as a measure of the damping Seconds (damping duration) in which the deflection of the Pendulum subsides from 6 ° to 3 ° to the vertical.

The intensity of the yellowing was determined in parallel experiments a 200 µm thick lacquer layer applied to glass Epoxy acrylate with a concentration of 5 percent by weight the photosensitizer immediately after curing (as above) judged. A scale of served as a measure of the yellowing 0 (no yellowing) to 7 (strong yellowing); the number 3 in this scale corresponds to a clearly yellowish color.

The results are summarized in the table below.  

Table I

c) Result

The significantly better properties of the 10 according to the invention Compounds compared to the 3 known in the prior art Substances, especially in relation to what can be achieved with them Paint hardness are clearly recognizable.

2. Dark storage stability a) Test methodology

A mixture of was used as the test varnish

80 parts epoxy acrylate,
20 parts of trimethylolpropane triacrylate (TMPTA),

3 parts each of the photosensitizer to be examined were clogged.

The coating systems are used to check the dark storage stability stored at 60 ° C in a drying cabinet.

b) Table II

Photosensitizer change

Compounds according to the invention:
1- (4-tert-butylphenyl) -2-hydroxy-2-methyl-propanone- (1) Unchanged after 20 days 1- (4'-dodecylphenyl) -2-hydroxy-2-methyl-propanone- (1) Unchanged after 20 days

Known substances:
Benzoin isopropyl ether gell after 1 day 1-phenyl-2-hydroxy-propanone- (1) (JP-OS 51/0 17 802) solid after <1 day

c) Result

The significantly better storage stability of the invention Photosensitizers is for the practical Use of crucial importance.  

The invention thus relates to the compounds of the general formula I given above

In the general formula I, the radical R 1 preferably alkyl or alkoxy with up to 18 carbon atoms or phenyl. Particularly preferred R 1 radicals are alkyl groups with up to 12 carbon atoms. The rest R₂ is preferably Hydrogen. But it can also be a chlorine or Be bromine or a methyl or methoxy group, which are in the 2 position, but preferably in the 3-position of the phenyl nucleus.  

Compounds in which both are particularly preferred R₃ and R₄ are alkyl groups, which together are 2 to Contain 10, preferably 2 to 8 carbon atoms.

The rest is preferably hydrogen if one Is alkyl or alkanoyl, of these are methyl, Ethyl and acetyl preferred.

Accordingly, according to the invention, in particular those Compounds of the general formula I are preferred in which at least one of the radicals R₁ to R₅ one of the above has preferred meanings. Some preferred Groups of connections can expressed by the following sub-formulas Ia to In be, which correspond to the general formula I and in which the radicals not specified in the general Formula I have the meaning given, wherein however

in IaR₁ means alkyl with 1-12 C atoms; in IbR₁ means alkyl with 3-12 C atoms; in IcR₂ is hydrogen; in IdR₂ is 3-chloro, 3-bromo, 3-methyl or 3-methoxy; in IeR₁ means alkyl with 1-4 carbon atoms and
R₂ has one of the meanings given in (Ie); in IfR₃ and R₄ are methyl groups; in IgR₃ means ethyl and R₄ n-butyl; in IhR₃ is methyl and R₄ is ethyl; in IiR₅ means hydrogen; in IjR₅ means methyl, ethyl or acetyl; in IkR₁ are alkyl with 3-12 C atoms and R₂ and R₅ are hydrogen; in IlR₁ alkyl with 3-12 C atoms, R₂ is hydrogen and R₃ and R₄ are methyl; in ImR₁ alkyl with 1-12 C atoms, R₂ is hydrogen, R₃ is ethyl and R₄ n-butyl.

The preparation of similar compounds is from Bull. Soc. Chim. France 1967, 1047-1052, J. Amer. Chem. Soc. 75 (1953) 5975-5978 and Zh. Obshch. Khim. 34 (1964), 24-28. A photosensitizing activity of these compounds is however not described in these references nor is it suggested by this. The new Compounds of the general formula I can be analogous to according to those described in the references mentioned Standard methods of organic chemistry are produced will.

In a preferred manufacturing process, a Benzene derivative of the general formula II

wherein R₁ and R₂ have the meaning given above, in the presence of a Lewis acid, for example aluminum chloride, with an α- halocarboxylic acid chloride of the general formula III

wherein R₃ and R₄ have the meaning given above and Hal represents a halogen atom, preferably chlorine or bromine, and the resulting α- halogen ketone of the general formula IV

wherein R₁, R₂, R₃, R₄ and Hal have the meaning given above, in themselves usually saponified to the hydroxyalkylphenone of the general formula (I) (R₅ = H). If R₃ and R₄ are alkyl groups, this saponification is achieved by simply heating the α -halogen ketone (V) with a concentrated solution of an alkali metal hydroxide in a water-miscible solvent such as methanol, ethanol, isopropanol, acetone or dimethyl sulfoxide. If one of the radicals R₃ and R₄ is hydrogen, it is generally advisable to first of all react the α -halogen ketone IV by reaction with a carboxylic acid salt, for example sodium acetate, in an anhydrous organic solvent in an alkanoyloxyalkylphenyl ketone of the general formula I (R₅ = Convert alkanoyl) and, if desired, by hydrolysis in the presence of a weakly basic compound, for example sodium hydrogen carbonate, to convert it into the hydroxyalkyl phenyl ketone I (R₅ = H).

Alkanoyloxyalkyl phenyl ketones of the general formula I (R₅ = alkanoyl) can also by acylation of the hydroxyalkyl phenyl ketones I (R₅ = H) with suitable carboxylic acid derivatives, for example carboxylic acid hydrides or halides getting produced.

The alkoxyalkyl-phenyl ketones of the general formula I (R₅ = alkyl) can be prepared, for example, by reacting the α -halogen ketones IV with an alcoholate, for example sodium ethylate, in an anhydrous organic solvent such as ethanol.

In addition to the Friedel-Crafts reaction of II with III, the α- halogen ketones IV can also be obtained by halogenation, preferably chlorination or bromination, of a phenyl ketone of the general formula V

wherein R₁, R₂, R₃ and R₄ have the meaning given above own, are produced in a conventional manner.  

This method is preferably used when the phenyl ketone V is easily accessible and during halogenation no side reactions, e.g. B. Halogenation benzyl carbon atoms in R₁ and / or R₂ occur.

Furthermore, the hydroxyalkyl phenyl ketones of the general Formula I can be made by a Grignard compound of the general formula VI

wherein R₁, R₂ and Hal have the above meaning own, with a cyanohydrin protected from oxygen of the general formula VII

wherein Sch-O- is resistant to Grignard compounds protected hydroxyl group, for example a tetrahydropyranyl ether group means and R₃ and R₄ the above Have meaning, implement and then the reaction mixture in the usual manner in the presence hydrolyzed an acid.  

The use of the photosensitizers according to the invention success in the usual way for such products. For example, become more unsaturated for photopolymerization Compounds in these materials, their prepolymers or pre-copolymers 0.05 to 15 wt .-%, preferably 0.1 to 12% by weight of one or more compounds of general formula I, optionally together with other, already known photosensitizers solved and these solutions with light or UV radiation from the Wavelength range from 250 to 500 nm, preferably 300 to 400 nm irradiated. As unsaturated compounds, which are photopolymerized with the sensitizers according to the invention can be, all those come into question whose C = C double bonds through, for example Halogen atoms, carbonyl, cyano, carboxy, ester, amide, Ether or aryl groups or by conjugated others Double or triple bonds are activated. Examples for such compounds are vinyl chloride, vinylidene chloride, Acrylic acid methyl ester, acrylonitrile, hydroxyethyl acrylate, cyclohexyl acrylate, Hydroxypropyl acrylate, hydroxyethyl methacrylate, Benzyl acrylate, 2-ethylhexyl acrylate, phenyloxyethyl acrylate, lower alkoxyethoxyacrylate, tetrahydrofurfurylacrylate, N-vinyl pyrrolidone, N-vinyl carbazole, vinyl acetate, Styrene, divinylbenzene, and substituted styrenes. Also polyunsaturated compounds such as trimethylol propane diacrylate, propoxylated bisphenol A diacrylate and dimethacrylate and 1,6-hexanediol diacrylate and pentaerythritol triacrylate can with the sensitizers according to the invention be photopolymerized. As prepolymers and pre-copolymers  come for example unsaturated polyesters, acrylic materials, Epoxy materials, urethanes, silicones, amine polyamide resins and especially acrylated resins such as acrylated Silicone oil, acrylated polyester, acrylated urethanes, acrylated Polyamides, acrylated soybean oil, acrylated Epoxy resin and acrylic acrylic resin in question.

The photopolymerizable compounds or mixtures can by adding known inhibitors in the usual Amounts should be stabilized without affecting the sensitizing effect of photosensitizers according to the invention is significantly impaired. Furthermore, they can Pigments or dyes, such as those in photochemically curing Printing inks are included. In in this case the amount of sensitizer is chosen higher, for example 6 to 12 wt .-%, while for colorless photopolymerizable Products 0.1 to 3% by weight in most Cases are sufficient. As possibly together with known known usable the sensitizers For example, photosensitizers are coming Michler's ketone (4,4′-bis [dimethylamino] benzophenone), 4,4'-bis (diethylamino) benzophenone, p-dimethylaminobenzaldehyde, 4,4'-bis (dimethylamino) benzil, p-dimethylaminobenzophenone, p-dimthylaminobenzoin, p-dimethylaminobenzil, N-substituted 9-acridanones, which in the US Pat. No. 3,661,588 described amino (or phenyl) carbonyl compounds, those described in US Pat. No. 3,552,973 p-aminophenylcarbonyl compounds, acetophenone, propiophenone, Xanthone, benzaldehyde, benzophenone, p-chlorobenzophenone, Biacetyl, benzil, fluorenone, 3-nitro-4-chlorobenzophenone-2-carboxylic acid, Phenanthrenequinone, benzoin and alkyl ether of benzoin, 2-chlorothioxanthone, 10-thioxanthenone, 1-phenyl-1,2-propanedionoxime and the esters and Ether of the same, isatin, anthrone, hydroxypropyl benzoate,  Benzoyl benzoate acrylate, 2,4-dimethylbenzophenone, benzoyl biphenyl, Acenaphthenoquinone or Dibenzosuberon in Question. As radiation sources for the implementation of photopolymerization can be sunlight or artificial spotlights be used. Mercury vapor high or low pressure lamps, xenon and tungsten lamps; Laser light sources can also be used.

The following examples are intended to illustrate the invention. In these examples there are temperatures expressed in degrees Celsius; Concentration and Unless otherwise stated, percentages are based on weight; Pressure data at boiling points are in mbar.

Examples 1 to 6 relate to the preparation of the invention General connections Formula I.  

Example 1

In a suspension of 665 g of aluminum chloride in 2000 ml of 1,2-dichloroethane, 740 g of α- chloroisobutyryl chloride (produced by chlorination of isobutyryl chloride in the presence of catalytic amounts of chlorosulfonic acid and chloroanil) are introduced at 0 °. 1230 g of commercial technical dodecylbenzene (Marlican® from Chemische Werke Huls AG, Marl) are added dropwise to this mixture with vigorous stirring at 0 to 5 °. When the dropwise addition has ended, the reaction mixture is stirred at this temperature for a further 45 minutes and then stirred into a mixture of 1000 g of ice and 400 ml of concentrated hydrochloric acid. The organic layer is separated, washed twice with 300 ml of dilute hydrochloric acid. Dried over calcium chloride and evaporated. The remaining 1- (4'-dodecylphenyl) -2-chloro-2-methyl-propanone- (1) is dissolved in 2000 ml of isopropyl alcohol with stirring and gentle heating. This solution is heated to boiling with 500 ml of 32% aqueous sodium hydroxide solution with stirring for 1 1/2 hours and then poured into 2000 ml of water. The aqueous reaction mixture is extracted with 1000 ml of toluene, the extract is washed with 1000 ml of 10% aqueous sodium chloride solution, dried over sodium sulfate and evaporated. The remaining 1- (4'-dodecylphenyl) -2-hydroxy-2-methyl-propanone- (1) is distilled under reduced pressure; Kp. _0.0133 180-183 °.

The following are produced analogously:

1- (4'-hexylphenyl) -2-hydroxy-2-methyl-propanone- (1),
1- (4'-octylphenyl) -2-hydroxy-2-methyl-propanone- (1),
1- (4'-nonylphenyl) -2-hydroxy-2-methyl-propanone- (1),
1- (4'-hexadecylphenyl) -2-hydroxy-2-methyl-propanone- (1),
1- (4'-octadecylphenyl) -2-hydroxy-2-methyl-propanone- (1),
1- (4'-hexyloxyphenyl) -2-hydroxy-2-methyl-propanone- (1),
1- (4'-octyloxyphenyl) -2-hydroxy-2-methyl-propanone- (1),
1- (4′-dodecylphenyl) -2-hydroxy-2-ethyl-propanone- (1),
1- (4′-dodecylphenyl) -2-hydroxy-2-methyl-propanone- (1),

Example 2

Analogously to Example 1, 133 g of aluminum chloride in 500 ml of dichloroethane from 141 g of α- chloroisobutyl chloride and 92 g of toluene are used to prepare 1- (4′-methylphenyl) -2-chloro-2-methyl-propanone- (1) and the crude product in 500 ml of anhydrous methanol dissolved. A solution of 54 g of sodium methylate in 1500 ml of methanol is added dropwise with stirring, the reaction mixture is heated to 60 ° and then left to stand for 16 hours. The precipitated sodium chloride is then filtered off and the filtrate is evaporated. The remaining 1- (4'-methylphenyl) -2-methoxy-2-methyl-propanone is distilled under reduced pressure; 98.4 g with bp. _0.04 75-77 ° are obtained.

The following are produced analogously:

1- (4′-methylphenyl) -2-ethoxy-2-methyl-propanone- (1),
1- (4'-methylphenyl) -2-butoxy-2-methyl-propanone- (1),
1- (4'-isopropylphenyl) -2-ethoxy-2-methyl-propanone- (1),
1- (4'-pentylphenyl) -2-methoxy-2-methyl-propanone- (1),
1- (4′-methylphenyl) -2-methoxy-2-ethylhexanone (1),
1- (4'-Dodexylphenyl) -2-ethoxy-2-methyl-propanone- (1).

Example 3

Analogously to Example 1, 550 g of 1- (4'-methylphenyl) -2-chloropropanone (1) are prepared with 335 g of aluminum chloride in 1000 ml of dichloroethane from 300 g of toluene and 455 g of α -chloropropionyl chloride. The raw material is dissolved in 3000 ml of ethanol and heated to boiling for 15 hours with 392 g of anhydrous potassium acetate. The reaction mixture is then evaporated under reduced pressure, the residue is taken up in 2500 ml of diethyl ether and filtered. The filtrate is evaporated and the remaining 1- (4'-methylphenyl) -2-acetoxy-propanone- (1) is distilled under reduced pressure; Yield 364 g, bp _0.4 115-122 °.

The following are produced analogously:

4-tert-butyl- a- acetoxy-acetophenone, bp _0.4 140-143 °;
1- (4'-tert-Butylphenyl) -2-acetoxy-2-methyl-propanone- (1), bp _0.4 144-148 °.

Example 4

A solution of 421 g of 1- (3 ′, 4′-dimethylphenyl) -2-acetoxy-propanone- (1) in 3000 ml of isopropyl alcohol with a Solution of 151 g sodium hydrogen carbonate in 1200 ml Water is added and the mixture is stirred for 15 hours heated to boiling. Then the solvent distilled off under reduced pressure, the residue in 500 ml of water taken up and three times with 300 ml each Extracted diethyl ether. The combined ether extracts are dried over sodium sulfate and evaporated.  

The remaining 1- (3 ', 4'-dimethylphenyl) -2-hydroxy-2-methyl-propanone- (1) is distilled under reduced pressure; Yield: 264 g, bp _0.8 88-90 °.

The following are produced analogously:

1- (4'-isopropylphenyl) -2-hydroxy-butanone- (1),
1- (4'-isopropylphenyl) -2-hydroxy-propanone- (1),
1- (4'-tert-butylphenyl) -2-hydroxy-propanone- (1),
1- (4'-Nonylphenyl) -2-hydroxy-hexanone- (1).

Example 5

To a solution of 0.1 mol of acetone cyanohydrin tetrahydropyranyl ether in 50 ml of anhydrous tetrahydrofuran a solution of 0.075 mol of 4-ethoxyphenyl-magnesium bromide in 100 ml anhydrous tetrahydrofuran and added the reaction mixture heated to boiling for another 1.5 hours. Subsequently 100 ml of 10% aqueous sulfuric acid are added, the mixture briefly heated to boiling again and then with 10% aqueous sodium hydroxide solution to a pH of set about 10. The weakly alkaline reaction mixture is shaken three times with 150 ml of diethyl ether, the combined ether extracts are with 100 ml Washed out water, filtered and dried over sodium sulfate. After the ether has been distilled off, 12 g remain  1- (4'-Ethoxyphenyl) -2-hydroxy-2-methyl-propanone- (1).

The following is produced analogously:

1- (4'-Butyloxyphenyl) -2-hydroxy-2-methyl-propanone- (1).

Example 6

• a) 750 g of isobutyryl chloride and then 900 g of tert-butylbenzene are added dropwise to a suspension of 1038 anhydrous aluminum chloride in 3000 ml of dichloroethane at 6-10 ° with ice cooling. The reaction mixture is left to stand at 6 ° for 1 hour and then at room temperature for 15 hours. The mixture is then slowly stirred into a solution of 600 ml of concentrated hydrochloric acid in 2400 ml of ice water, the organic phase is separated off and the aqueous solution is washed out once with 600 ml of dichloroethane. The combined organic phases are washed once with 500 ml of 5% hydrochloric acid and water. Dried over calcium chloride and evaporated. The remaining 1- (4'-tert-butylphenyl) -2-methyl-propanone- (1) is distilled under reduced pressure; Yield: 1085 g, bp _0.133 98-102 °.
• b) In a solution of 1007 g of 1- (4'-tert-butylphenyl) -2-methyl-propanone (1) in 3000 ml of methanol in the presence of 2 ml of concentrated hydrochloric acid and 2 g of iodine at 50 ° with stirring in 550 g of chlorine were introduced over a period of 1.5 hours. The reaction mixture is then stirred at 50 ° for a further 30 minutes and then the solvent is distilled off. The residue is taken up in 1000 ml of toluene and washed neutral and chlorine-free with aqueous sodium hydrogen carbonate solution and aqueous sodium thiosulfate solution. Then the toluene is distilled off and the remaining crude 1- (4'-tert-butylphenyl) -2-hydroxy-2-methyl-propanone- (1) is dissolved in 2000 ml of isopropyl alcohol. 420 ml of 32% aqueous sodium hydroxide solution are added to this solution and the reaction mixture is heated to boiling for 1.5 hours. After cooling, the reaction mixture is shaken with 1000 ml of toluene, the toluene extract is washed with 1000 ml of 10% aqueous sodium chloride solution, dried over calcium chloride and evaporated. The remaining 1- (4'-tert-butylphenyl) -2-hydroxy-2-methylpropanon- (1) is distilled under reduced pressure; Yield: 839 g bp. _0.133 132-135 °.

The following are produced analogously:

1- (4'-ethylphenyl) -2-hydroxy-2-methyl-propanone- (1),
1- (4'-isopropylphenyl) -2-hydroxy-2-methyl-propanone- (1), _{b.p. 0.532} 108-109 °;
1- (3'-chloro-4'-methoxyphenyl) -2-hydroxy-2-methyl-propanone- (1), mp 92-93 °;
1- (3'-bromo-4'-methoxyphenyl) -2-hydroxy-2-methyl-propanone- (1), mp 104-106 °;
1- (3'-chloro-4'-methylphenyl) -2-hydroxy-2-methyl-propanone- (1), b.p. _0.931 130-135 °;
1- (2 ′, 4′-dimethylphenyl) -2-hydroxy-2-methyl-propanone- (1),
1- (4'-methylphenyl) -2-hydroxy-2-ethyl-hexanone (1), bp _0.4 155-158 °;
1- (4'-tert-butylphenyl) -2-hydroxy-2-ethylhexanone- (1), _{b.p. 0.266} 162-166 °;
1- (4'-isopentylphenyl) -2-hydroxy-2-methyl-propanone- (1),
1- (4'-methylphenyl) -2-hydroxy-2-methylbutanone- (1),
1- (4'-isopropylphenyl) -2-hydroxy-2-methyl-butanone- (1),
1- (4'-tert-butylphenyl) -2-hydroxy-2-methyl-butanone- (1),
1- (3 ', 4'-Dimethylphenyl) -2-hydroxy-2-methyl-butanone- (1).

The following Examples 7-10 relate to the use of the photosensitizers according to the invention in the Photopolymerization of unsaturated compounds.

Example 7

20 g each of a commercially available casting resin based on partially polymerized methyl methacrylate and allyl methacrylate (Plexit® MU 51 from Röhm GmbH, Darmstadt) are each with 0.4 g of a sensitizer according to the invention or a commercially available comparison product. After the sensitizer has completely dissolved and even mixing, the samples are sealed Glass bottles stored at 60 ° in the dark. in Samples are started at regular intervals Gelation checked. The ones compiled in the following table Results are a measure of dark storage stability of photopolymerizable mixtures under Use of the various sensitizers.

Table B 7

The results show that photoplymerizable mixtures with the sensitizer according to the invention (experiment 3) have significantly better dark storage stability than that  Mixtures with the known sensitizers (tests 1 and 2).

Example 8

Analogously to example 7, the dark storage stability becomes more photopolymerizable Mixtures of 20 g each of a commercially available Casting resin based on unsaturated polyesters and styrene (Palatal® P 70 from BASF AG, Ludwigshafen) and each 0.4 g of one and two according to the invention known sensitizers determined. The results are compiled in Table B 8:

Table B 8

These results also demonstrate the superior properties of the sensitizer according to the invention.

Example 9

50 g each of a commercially available casting resin based on partially polymerized methyl methacrylate and allyl methacrylate (Plexit® MU 51 from Röhm GmbH, Darmstadt) each with 1.25 g of 1- (4'-tert-butylphenyl) -2-hydroxy-2-methyl-propanone- (1) or benzoin butyl ether as a sensitizer  offset and on glass plates to 250 µm thick layers crossed out. Immediately after painting, the Layers from a distance of 11 cm with a mercury lamp Irradiated for 30 seconds. From both materials a hard layer with a non-sticky surface is formed, those when using the sensitizer according to the invention is colorless clear when using the known benzoin ether on the other hand, has a clearly yellowish color.

Example 10

In a solution of 0.8 g of 1- (4'-tert-butylphenyl) -2-hydroxy-2-methyl-propanone- (1) and 0.8 g of 1- (4'-isopropylphenyl) -2-hydroxy-2-methyl-propanone- (1) in 16.4 g of pentaerythritol triacrylate 2.0 g of blue copper phthalocynanine pigment evenly dispersed. With this dispersion a screen cliché inked and white paper with it printed. The sticky print surface after printing is then 20 seconds from a distance of 11 cm irradiated with a mercury vapor lamp. It a tack-free, smudge-proof print is obtained.

Claims (7)

1. Hydroxyalkylphenyl ketones of the general formula I in whichR₁hydrogen, phenyl or alkyl or alkoxy, each with up to 18 C atoms, R₂hydrogen, chlorine, bromine, alkyl or alkoxy, each with up to 4 C atoms R₃ and R₄alkyl with up to 6 C atoms and R₅hydrogen, alkyl or alkanoyl each with up to 4 carbon atoms, with the proviso that

• a) R₅ is not hydrogen, methyl or acetyl, provided that R₁ and R₂ are hydrogen and R₃ and R₄ are methyl,
• b) R₁ is not methyl, methoxy or phenyl, provided that R₂ and R₃ are hydrogen and R₃ and R₄ are methyl,
• c) R₃ and R₄ are not methyl, provided that R₂ is 2-methyl and R₁ and R₅ are hydrogen,
• d) R₃ is not methyl or ethyl, provided that R₁, R₂ and R₅ are hydrogen and R₄ is ethyl.

2. 1- (4'-isopropylphenyl) -2-hydroxy-2-methyl-propanone- (1); 3. 1- (4'-tert-butylphenyl) -2-hydroxy-2-methyl-propanone- (1); 4. 1- (4'-dodecylphenyl) -2-hydroxy-2-methyl-propanone- (1); 5. 1- (4'-methylphenyl) -2-hydroxy-2-ethyl-hexanaon- (1); 6. 1- (3 ', 4'-dimethylphenyl) -2-hydroxy-2-methyl-propanone- (1); 7. 1- (3'-chloro-4'-methylphenyl) -2-hydroxy-2-methyl-propanone- (1).