CH628651A5 - UV radiation-polymerisable mixtures - Google Patents

Description

628 651

2nd

CLAIMS OF THE PATENT Polymerizable mixtures of a) compounds with at least one polymerizable CC multiple bond or mixtures containing such compounds with b) monoketals of aromatic 1,2-diketones as photoinitiators, characterized in that they are not mono- ketals of aromatic 1,2-diketones cyclic asymmetric monoketals of formula I.

A'-C-C-A2

IIA oo o

11

R'R2

(I)

included in what

A1 and A2 are the same or different aromatic radicals which may carry substituents,

R1 and R2 are optionally substituted hydrocarbon radicals having 1 to 12 carbon atoms and R1 and R2 are different radicals.

From DT-OS 22 32 365 are polymerizable mixtures of compounds with at least one polymerizable CC multiple compound or of mixtures containing such compounds with a photoinitiator, optionally with conventional additives, which are used as photoinitiators of monoketals of aromatic 1,2-diketones of the formula

R-A-

OO o

X X '

contain, in which A and A 'substituted by R and R' six-membered aromatic radicals of the same or different types and X and X 'optionally substituted monovalent radicals or X and X' together represent a C2 to C2 alkylene radical known.

New non-cyclic asymmetrical monoketals of aromatic 1,2-diketones have now been found which are easy to prepare and are sufficiently stable in polymerizable mixtures or compositions in their customary processing and storage, on the other hand have good reactivity in the radiation curing of the compositions and at the same time have one produce particularly little yellowing.

The present invention thus relates to mixtures of a) compounds with at least one polymerizable CC multiple bond or mixtures containing such compounds with b) monoketals of aromatic 1,2-diketones as photoinitiators which are polymerizable by UV irradiation and which are characterized in that they are monoketals of aromatic 1,2-diketones contain non-cyclic asymmetric monoketals of the formula (I) below

A'-C-C-A2

R1 and R2 are optionally substituted hydrocarbon radicals with 1 to 12 carbon atoms of different types.

Non-cyclic asymmetrical monoketals of aromatic 1,2-diketones of this type are not yet known. The 5 new photoinitiators contained in the mixtures according to the invention can be prepared simply and advantageously if the aromatic 1,2-diketones (formula II) on which they are based

A'-C-C-A2 (II)

10th

Îf \

OO o

11

R'R2

(I),

wherein A 'and A2 are the same or different, optionally bearing aromatic radicals and

O O

in an organic solvent with an alkylating agent (R ') nX and an alcoholate (R20) mMe, where R1 and R2 have the meaning given above and represent different radicals, n and m are integers from 1 to 3, X is one mono- to tri-basic acid residue and Me represent a metal from the first 3 main groups of the periodic table of the elements.

Suitable aromatic diketones of the formula II are in particular those in which A1 and A2 represent a substituted benzene radical, the substituents being in particular C 1 -C 10 -hydrocarbon radicals such as alkyl or phenyl radicals, C 1 -C 2 -secio-alkoxyalkyl radicals, C 1 -C 10 -alkoxy radicals , Ci to Cö alkylthio or halogen atoms come into question.

Examples of aromatic 1,2-diketones from which the monoketals according to the invention are derived are benzil and substituted benzils such as 4,4'-dimethylbenzil, 4,4'-diisopro-30 pylbenzil, 4,4'-diphenylbenzil, 2,2'-dimethoxybenzil , 4,4'-Dimethoxibenzil, 4-Methylbenzil, 3-Methoxibenzil, 2,2'-Dimethylbenzil, 4-Chloro-4'-phenylbenzil, 4,4'-Dichlor-benzil, 3,3'-Dibrombenzil, 2, 4,2 ', 4'-tetramethylbenzil, 2,4,6-trimethylbenzil, 2,4-dichloro-4'-methylbenzil. The Her-35 position of these benzene derivatives is described in the literature; it can e.g. by oxidation of the corresponding benzoin.

Alkylating agents suitable for the preparation of the asymmetrical monoketals have the formula 40 (R ') nX mentioned and are esters of mono- to tri-basic acids, in particular of acids containing a sulfur, a phosphorus or a halogen atom. Worth mentioning are the esters of sulfuric acid, sulfurous acid, phosphoric acid and phosphorous acid, the esters of hydrohalic acids 45 such as chlorides, bromides and iodides as well as aliphatic and aromatic sulfonic acids such as mesylates, tosylates, brosylates and benzosulfonates. The sulfates, halides and sulfonic acid esters, of which the sulfates and bromides are preferably used, are particularly suitable. Examples of alkylating agents are dimethyl sulfate, diallyl sulfate, dicrotyl sulfate, benzyl bromide or allyl bromide.

The radical R1 is optionally substituted hydrocarbon radicals having 1 to 12 carbon atoms, of which the corresponding alkyl-55 (in particular Ci-to Ce-alkyl-), aralkyl (in particular C? - to C9-) Aralkyl-), alkenyl (especially C3- to Cs-alkenyl-), aralkenyl- (especially C9- or Ci i-aralkenyl-) residues and the groupings Z- (CHR3-CHR4) p- or Z- (CHR3) p -, where p can be a number from 1 to 3, R3 and R4 H or CH3 and Z 60 a halogen atom or OR5, SR5, OAr or S Ar with R5 = Ci to C4 alkyl or Ci to Cs alkoxyalkyl and Ar = six-membered aromatic radical.

The alcoholates used for the preparation of the asymmetrical monoketals are alkylates which do not correspond to the alkylating agent and have radicals R2, e.g. when using dimethyl sulfate, an ethylate such as e.g. Sodium ethylate or potassium ethylate or when used

of allyl bromide e.g. Sodium methylate. Otherwise, the information given above about the radicals R1 applies analogously to the type of radicals R2. The alcoholates of sodium and potassium are preferred.

Organic solvents for the production of the monoketals include aromatic solvents such as benzene or toluene and in particular dimethylformamide and dioxane.

Theoretically, for the preparation of the monoketals 1 / n mol of alkylating agent of the formula (R ') explained above nX are reacted with 1 mol of 1,2-diketone and 1 / m mol of alcoholate of the formula (R20) also explained above, where n and m are the number n or m in the formula of the alkylating agent or alcoholate used to produce the asymmetrical monoacetals of the aromatic 1,2-diketones. In general, however, it is preferred to use some reactants in excess amounts to achieve full conversion. For example, 1 / n to 10 / n mol or more, preferably 1 / n to 4 / n mol, of alkylating agent and 1 / m to 10 / m mol or more, preferably 1 / n to 4 / n, can be used per mole of 1,2-diketone Mol, use alcoholate. A particularly preferred way of working up the reaction solution is to remove the solvent from the reaction mixture after adding water by azeotropic distillation. After this, the water-insoluble monoacetal separates out as a crystalline substance or as an oil in often analytically pure or almost analytically pure form, especially when cooling.

The mixtures or compositions according to the invention expediently contain the monoacetals of the 1,2-diketones mentioned in amounts of from 0.01 to 10 and preferably from 0.05 to about 4% by weight, based on the photosensitive mixture or the photopolymerizable compounds.

Suitable for the mixtures or compositions according to the invention are all compounds with at least one C-C multiple bond which can be excited to polymerize in a mixture with the photoinitiator. Compounds and substances with C-C double bonds, which are e.g. Aryl, carbonyl, amide, ester, carboxy or cyanide groups, halogen atoms or C-C double or C-C triple bonds are activated. Examples include styrene, vinyl toluene, acrylic acid and methacrylic acid and their esters, cyanides or amides, e.g. Acryl amide, N-methylol acrylamide, diether from 1 mol glycol and 2 mol N-methylol acrylamide, methyl methacrylate, methylene-bis-acrylamide, m-phenylene-bis-acrylamide or m-xylylene-bis-acrylamide as well as diurethanes with at least two (meth ) acrylic groupings.

The photopolymerizable compounds, the selection of which is known to the person skilled in the art for the respective intended use of the mixtures, can in a known manner be unsaturated and / or saturated polymers and / or the known additives, such as inhibitors against thermal polymerization, such as hydroquinone or tert-butylhydroquinone , skin-forming substances such as paraffin, flow control agents such as silicone oil, fillers and / or pigments or dyes can be added in the usual amounts. Such mixtures are known to the person skilled in the art and the type and amount of the additives depend in particular on the type of use of the mixtures.

The new photoinitiators in polyester resins have proven particularly useful in the manufacture of UV-curable coatings. Suitable compositions of unsaturated polyester resins consist, for example, of a mixture of (1) 40 to 80 percent by weight of a conventional unsaturated polyester; (2) 60 to 15 percent by weight at least

628 651

a copolymerizable olefinically unsaturated monomer; (3) 0.5 to 5 percent by weight of a photoinitiator and optionally (4) other conventional additives.

Suitable unsaturated polyesters (1) are the usual polycondensation products of polybasic, in particular dihydric, carboxylic acids, which are linked ester-like with polybasic, in particular dihydric alcohols, and optionally additionally contain residues of monohydric carboxylic acids and / or residues of monohydric alcohols and / or residues of hydroxycarboxylic acids.

Suitable olefinically unsaturated monomeric compounds (2) for the unsaturated polyester resins are all conventional monomeric compounds which can be copolymerized with unsaturated polyesters, in particular vinyl aromatics, such as styrene and the esters of acrylic acid or methacrylic acid with alkanols having 1 to 8 carbon atoms, such as tert-butyl acrylic acid or methyl methacrylic acid, and mixtures of these monomers. The mixtures used preferably contain 60 to 15, preferably 50 to 25, percent by weight of component (2).

The new photoinitiators are also advantageous in photopolymerizable compositions which are used for the production of systems for optical information fixing, in particular for the production of photopolymer printing plates or of photoresist layers.

Suitable mixtures with compounds having at least one polymerizable C-C multiple bond are mixtures of about 10 to 60 and preferably 15 to 35 percent by weight of monomers with predominantly at least two photopolymerizable C-C double bonds, e.g. B. di (meth) acrylates of aliphatic diols, bis (meth) acrylic amides of aliphatic or aromatic diamines having 2 to 8 carbon atoms, or monomers which, in addition to at least two (meth) acrylic groups, ester or amide and urethane or urea groups contain, with 90 to 40 and preferably 85 to 65 percent by weight in an organic solvent, such as an alcohol, ketone or an ether, soluble polymers. The polymers used are e.g. Copolyamides, such as those from E-caprolactam, hexamethylene diammonium adipate and p, p'-diaminodicyclohexylmethane adipate, and also soluble polyurethanes, polyureas, butadiene or isoprene copolymers, including block copolymers or soluble cellulose derivatives, are also suitable.

More details about the selection of suitable monomers and / or polymers and / or of mixtures and about their processing are adequately described for the person skilled in the art in the known patent literature.

As radiation sources for the light which triggers the photopolymerization or photocrosslinking of the mixtures, it is particularly advantageous to use those which emit light of a wavelength between 230 and 450 nm. Radiation sources with emission maxima in the range from 300 to 380 nm or those which emit a sufficiently high proportion of light in this wavelength range are primarily suitable. Medium-pressure mercury lamps are particularly suitable, but also high-pressure and low-pressure mercury lamps and superactinic fluorescent tubes. The lamps mentioned can optionally be doped.

Mixtures according to the invention containing the new photoinitiators are suitable for the production of coatings, especially those based on polyester resins, etc. for the production of photopolymer printing plates, for the production of holograms, photoresist lacquers, porome skins, for information fixation in general and for UV-curable. Printing inks. Compared to mixtures containing symmetrical benzil monoacetals of the benzil dimethyl acetal type, they are characterized in that they have a lower ver3

5

10th

IS

20th

25th

30th

35

40

45

50

55

60

65

628 651

4th

cause yellowing of the hardened masses.

The parts and percentages given in the following examples relate to the weight. Parts by volume behave in parts like liters to kilograms.

example 1

To a solution of 52.5 parts of benzil and 68.4 parts of benzyl bromide sulfate in 400 parts by volume of dimethylformamide, 21.6 parts of sodium methylate are added in portions at room temperature with stirring over the course of 3 hours. The reaction mixture is then stirred at room temperature for a further 30 minutes and then stirred into 2,000 parts by volume of water. The precipitate is filtered off, washed with water and dried. Then it is slurried in 150 parts by volume of petroleum ether, suction filtered, washed once with petroleum ether and dried. 62.0 parts of benzilmethylbenzylmonoacetal with a melting point of 83 to 84 ° C. are obtained.

Example 2

To a solution of 52.5 parts of benzil and 63 parts of dimethyl sulfate in 250 parts by volume of dioxane, 34 parts of sodium ethylate are added in portions at room temperature with stirring over the course of one hour. After adding 300 parts by volume of water and 22 parts of solid sodium hydroxide solution, the reaction mixture is heated under reflux for 30 minutes, then 350 parts by volume of dioxane-water azeotrope are distilled off from the reaction mixture and, after cooling to room temperature, the remaining residue is extracted with 150 parts by volume of chloroform. The chloroform extract is mixed with 2 parts of animal charcoal, boiled, filtered and the solvent is evaporated on a rotary evaporator. The oily, largely colorless residue becomes crystalline after some time. Melting point: 52 to 54 ° C.

Example 3

To a solution of 105 parts of benzil and 121 parts of allyl bromide in 500 parts by volume of dimethylformamide, 48 parts of sodium methylate are added in portions at room temperature with stirring over the course of 2.5 hours.

After adding 2,000 parts by volume of water, the reaction mixture is extracted four times with 100 parts by volume of chloroform and the combined chloroform extracts are then washed three times with 200 parts by volume of water. The chloroform phase is concentrated on a rotary evaporator and the residue is then distilled in vacuo. This gives 115 parts of benzilmethylal-lylacetal, which boils at 135 to 136 ° C / 0.3 mm Hg.

Example 4

In an analogous manner, as indicated in Example 3, benzilmethylcrotylmonoacetal is produced with the boiling point of 140 to 145 ° C / 0.3 mm Hg. Yield: 119 parts (80% of theory).

Example 5

An esterification of 431 parts of maleic anhydride and 325 parts of phthalic anhydride with 525 parts of 1,2-propylene glycol produces an unsaturated polyester. After adding 0.01% hydroquinone, a 66% solution in styrene is prepared from the polyester (solution A).

97 parts of solution A are mixed with 3 parts of photoinitiator (solution B). The storage stability (onset of gelation) of this mixture is determined at 60 ° C. with exclusion of light. For the photocuring experiments, 10 parts of a 1% solution of paraffin (softening range 50 to 52 ° C.) in styrene were added to 100 parts of solution B, and the resin was applied to hardboard coated with photo paper using a film puller (gap width 500 μm). After flashing off for about 2 minutes, the films are exposed to fluorescent lamps with a high proportion of UV light, which are arranged at a distance of 4 cm. The curing speed is determined by measuring the pendulum hardness according to König (DIN 53157) and is summarized in Table 1 together with the color measurements of the cured films.

Table 1

Photoinitiator pendulum hardness after color measuring rod, at

Minutes

solution of

60 ° C (hrs)

4th

8th

10th

Films: Yellow-ness index after exposure

Benzilmethylbene

90

104

108

18.5

78

cycloacetal

Benzilmethylallyl -

62

92

99

13.8

56-71

monoacetal

Benzilmethylcrotyl

74

98

104

11.6

not monoacetal

measured

Benzil dimethylmo-

92

105

108

21.1

80-105

noacetal

Example 6

A reaction product of 1 mol of bisphenol A diglycidyl ether with 2 mol of acrylic acid is dissolved 65% in butanediol diacrylate. 3 percent by weight of the photoinitiators listed in Tables 2 and 3 are added to this solution. The clear coats are knife-coated in a layer of 80 μm on white photo paper and irradiated with a high-pressure mercury lamp, output 80 watt / cm arc length. The distance between lamp and lacquer film is 10 cm. The samples are passed under the UV lamp on a conveyor belt that is continuously controllable in its running speed. The transport speed (m / min) is determined at which scratch-resistant curing of the paint films can just be achieved.

“Scratch-resistant curing” is understood to mean that rubbing the lacquer surface vigorously with the fingernail does not interrupt the film surface. Furthermore, the degree of whiteness (according to Berger) is determined on the samples cured at 11 m / min.

Table 2

Photoinitiator max.

Whiteness x

Curing

(n. Berger)

speed (m / min)

Benzoin n-butyl ether

16

93.3

p-tert-butyl-trichloroaceto-

16

94.0

phenone

Benzyl dimethyl ketal

24th

92.7

Benzil methylbenzyl ketal

24th

94.0

x the higher value indicates less yellowing.

After 5 days of storage at 20 ° C and 65 ° C, the clear lacquers mixed with photoinitiators are checked again (see Table 3).

5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

5

Table 3

628 651

Photoinitiator max- curing speed in m / min after 5 days of storage

20 ° C 65 ° C

Benzoin n-butyl ether

14

ex.

polymerizes p-tert-butyl-trichloroaceto-

16

no phenon

Curing

Benzyl dimethyl ketal

24th

24th

Benzil-methyl-benzyl ketal

24th

24th

A urethane acrylate, prepared by reacting 1 gene amine. The solution is placed on a glass plate

Mol of a diisocyanate with 2 mol of hydroxypropyl acrylate, 15 a layer of 20 | xm doctored and as in Example 5

was dissolved 70% in 1,1,1-trimethylolpropane triacrylate, described, exposed. The clear coat hardens with a belt

with 2 weight percent benzilmethyl ethyl ketal and 3 speed of 50 m / min from scratch-resistant.

Weight percent methyl diethanolamine as a chain-transfer

B