GB1595710A

GB1595710A - Thioxanthones

Info

Publication number: GB1595710A
Application number: GB11111/78A
Authority: GB
Original assignee: Sandoz AG
Current assignee: Sandoz AG
Priority date: 1977-03-24
Filing date: 1978-03-21
Publication date: 1981-08-19
Also published as: DE2811755A1; BE865202A; ES468218A1; IT7848479A0; FR2397412A1; CH628343A5; FR2397412B1; JPS53119876A; IT1104615B

Abstract

There is described the preparation of optionally substituted thioxanthones; the process involves reacting appropriate o,o'-dihalobenzophenone with sulphur hydride (hydrogen sulphide) or a sulphide or hydrosulphide. The compounds are useful as photoinitiators.

Description

(54) THIOXANTHONES (71) We, SANDOZ LTD., pf 35 Lichtstrasse, 4002 Basle, Switzerland, a Swiss Body Corporate, do hereby declare the invention, for which we pray that a patent may be granted to us. and the method by which it is to be performed. to be particularly described in and by the following statement: The present invention relates to a process for producing thioxanthones.

According to the present invention there is provided a process for producing thioxanthones comprising reacting an o.o'-dihalobenzophenone with a metal sulphide or hydrosulphide.

Preferably the process of the present invention comprises producing a compound of formula I.

in which each of R1 and R2, independently, is hydrogen, (C1-4) alkyl, (C1-12) alkoxy or halogen, each of m and n, independently is zero, 1,2 or 3, R3, when n is 1, and each R3, when n is 2 or 3, is (C1-4) alkyl, and R4, when m is 1, and each R4, when m is 2 or 3, is (C1-4) alkyl, employing, as the o-o'-dihalobenzophenone, a compound of formula I',

in which R1, R2, R3, R4, m, and n are as defined above, and Hal is halogen.

More preferably, the process of the present invention comprises producing a compound of formula Ia.

in which R1'is (C1-4)alkyl, (C1-8)alkoxy or halogen, R2'is hydrogen or halogen. mis zero or 1, n' is zero, I or 2. and RX and R4 are as defined above, employing, as the o,o'-dihalobenzophenone, a compound of formula I",

in which R1', R2', R3, R4, m', and n' and Hal are as defined above.

Most preferably, the process of the present invention comprises producing a compoud of formula lb,

in which R1 is halogen.

R, is methyl or ethyl. and n" is zero or 1, employing, as the o-o'-dihalobenzophenone, a compound of formula I'

in which R1", R3', n" and Hal are as defined above.

In the above formulae I, I', Ia, I", Ib, and I"', Hal and halogen, the latter as signified by R1, R1' and R1", respectively, mean fluorine, chlorine, bromine or iodine.

A further process according to the invention comprises producing a compound of formula I as above defined employing as the o-o'-dihalobenzophenone a compound of formula I also defined above with proviso than in both the compound of formula I and formula I' when R1 and R3 are (C1-4) alkyl and n is 3 and/or when R2 and R4 are (C1-4)alkyl and m is 3 at least one of the four alkyl groups R1 and R3 or R3 or R1 is methyl or ethyl in each case.

When R1 or R1' is (C1-4)alkyl, this is preferably methyl or butyl, more preferably methyl, and when R1 is (C1-12)alkoxy, this is preferably (C1-8)alkoxy, more preferably (C1-4) alkoxy, and most preferably methoxy.

R1, R1' or R1 as a halogen preferably signifies chlorine or bromine, more preferably chlorine.

When R2 is (C1-4)alkyl,. this is preferably methyl or butyl and when (C1-12)alkoxy, this is preferably methoxy or butoxy, more preferably methoxy.

R1 is preferably alkyl, alkoxy or halogen, more preferably alkoxy or halogen, most preferably halogen.

R2 is preferably hydrogen, alkyl or halogen, more preferably hydrogen or halogen, most preferably hydrogen.

Each of R3 and R4, independently, is preferably methyl or ethyl, more preferably methyl.

Each of m and n, independently, is preferably zero, 1 or 2, more preferably zero or 1. most preferably zero.

Hal is preferably chlorine or bromine, of which chlorine is preferred.

In the process of the present invention, the metal sulphide or hydrosulphide reagent is preferably an alkali metal or alkaline earth metal sulphide, especially sodium sulphide.

In order to convert the maximum amount of the starting o,o'-dihalobenzophenone to the corresponding thioxanthone according to the process of the present invention, the molar ratio of metal sulphide or hydrosulphide to starting o,o'-dihalobenzophenone should be at least 1:1. respectively. Preferably, however, the percentage molar excess of the metal sulphide or hydrosulphide over the amount of the starting o,o'-dihalobenzophenone is up to 20%, more preferably up to 10%, and preferably 2 to 5%.

The process of the present invention is preferably conducted in the presence of a solvent, and the preferred solvents are organic solvents which feature polar groups, more particularly, selected from ether. carbonyl, hydroxyl, cyano, sulphoxide and sulphone groups. More preferably the solvent is one containing one or more polar groups selected from ether, carbonyl, hydroxyl and sulphoxide groups. Even more preferably, the solvent is aprotic. Especially preferred solvents in which the process of the present invention can be conducted are dimethylsulphoxide, N,N-dimethylacetamide, N-methylpyrrolidone, hexamethylphosphoric acid triamide and sulpholane, especially N,N-dimethylacetamide, N-methylpyrrolidone and dimethylsulphoxide. If desired, a solvent mixture may be employed.

The amount of solvent used in relation to the amounts of reagents is not critical, and furthermore the solvent or solvent mixture used need not be in pure form. In one embodiment the reaction mixture is in paste form. e.g. comprising 50 to 100 ml of dimethylsulphoxide per g mole of compound of formula 1'. When dimethylsulphoxide is used as a solvent, this may be accompanied by an alcohol e.g. 2-methoxyethanol. diethyleneglycol mono-methyl ether and/or diethyleneglycol monoethyl ether. Such higher boiling alcohols may themselves be used as solvents as alternatives to dimethyl sulphoxide and to the remaining, previously indicated especially preferred solvents.

In general, the suitable amount and constitution of a solvent depends on factors such as the reaction temperature and the temperature at which the reaction mixture is easily stirrable.

The temperature at which the reaction in solution is effected is also not critical. but in general temperatures in the range of 2() to 25() C are suitable. Preferably the temperature is in the range of 6() to 170 C, more preferably 7()-15() C and most preferably 75-l()50C.

The starting materials of formula I' are either known or can be produced by methods analogous to those for the known compounds from available starting materials, e.g. by Friedel Crafts reaction.

The compounds of formula 11.

in which R1', R2, each R3'independently, the or each R4, independently, and m are as defined above, are new, and form a further part of the present invention.

In such cvompounds, R1', R2, R3', R4 and m have the preferred meanings as given above.

Preferably the compounds of formula II are produced by the process of the present invention.

The compounds produced by the process of the present invention. e.g. of formula I, and the new compounds of formula 11 embraced bv formula 1, hoth classes of compounds conveniently being referred to hereinaftcr as the compounds of the invention. are useful 'is photosensitizing agents for the initiation and acceleration of polymerisation of photopolymerisable formulations. The photo-polymerisable formulations themselves comprise photo-polymerisable systems in association with a photo-sensitizing amount of one or more compounds of the invention. and the systems are caused to photo-polvmerise under the influence of the photo-sensitizing compounds of the invention hy irradiation of the formulation with ultraviolet light of wavelength 250 to 400 nm. Any of the conventional light source providing light of wavelength 250 to 400 nm be employed, such as sunlight or actinic light from e.g. a sun-ray lamp or mercur are lamp.

It is to be understood that the terms ''photo-polymerise' and "photo-pol\mel-isable" are employed herein in a broad sense to incclude e.g. cross-linking of polymeric materials. such materials being referred to as "prepolymers", as well as simple homo-, Co- and terpolymerisation of monomers. The photo-polymerisable systems themselves may contain monomers of one type or a mixture of two or more monomeric types and/or prepolymers.

Photo-polymerisable systems suitable for polymerisation in the presence of the compounds producible by the process of the present invention are in general known, e.g. in the ultraviolet curable coating and printing ink arts. The systems preferably contain unsaturated polymerising species capable of polymerising by a free radical mechanism. The systems may be mono- or multi-component. It is preferred that the system contains at least one multi-functional component, i.e. a component having at least two centres at which polymerisation can occur, to promote photo-initiated cross-linking. In addition, it is preferred that at least one component of the system is an unsaturated carboxylic acid, or a derivative thereof, e.g. an ester or acid anhydride, in particular an a-, ss-unsaturated carboxylic acid, or a derivative thereof, e.g. an ester or acid anhydride, in particular an α,ss-unsaturated carboxylic acid such as acrylic or methacrylic acid, or a derivative thereof, such as an ester or acid anhydrie.

Preferably the system is multi-component and more preferably comprises one or more reactive base prepolymers or one or more reactive base long chain monomers in association with one or more cross-linking monomers. Preferred reactive base prepolymers are selected from unsaturated polyethers, polyesters, polyester-based urethanes and epoxy resins, and saturated or unsaturated such polymers modified by esterification with an unsaturated carboxylic acid, especially preferred examples being acrylated or methacrylated hydroxyfunctional polyethers. polyesters, polyester-based urethanes and epoxy resins, and unsaturated polyesters. Preferred reactive base long chain monomers are selected from acryl derivatives of epoxylated unsaturated fatty acids, especially preferred examples being acryl derivatives of epoxylated linseed oil. The cross-linking monomers are preferably vinyl and allyl monomers. e.g. styrene, the diallyl ether of trimethylol propane, and vinyl and allyl esters such as vinyl acrylate and diallyl maleate and phthalate, acrylated alcohols, e.g. acrylated phenoxyethyl alcohol, and multi-functional acrylates such as acrylated polyols. e.g. acrylated neopentyl glycol and pentaerythritol.

Other agents, e.g. antioxidants. pigments and fillers, may also be employed in the photo-polymerisable formulations. The exact composition of such formulations is not critical and may be varied to suit the intended use.

For increased activitv the compound(s) of the invention in the photo-polymerisable formulation is/are preferably used in association with one or more amines, which contains at least one α-CH, α-CH2 or α-CH3 group. More especially, α-aminopropionic acid derivatives are useful in this regard. Of such derivatives, the compounds of formula III are preferred:

in Which Z is-CN or -CONH2-, either each of R5 and R6 independently, is (C1-14)alkyl or ss-, γ- or #-(C2-4)hydroxyalykl, or R5 and R6 together with the nitrogen atom to which they are attached, form a piperazine, N-(C1-4)alkylpiperazine or morpholine ring or R5 and R6 form a group of formula

wherein Z is as defined above.

These compounds are either known. or cm he produced hv known methods from available starting materials.

Z is preferably -CONH2.

When R5 or R6 is alkyl, this is preferably (C1-4)alkyl, and when either is (C2-4)hydroxyalkyl, this is preferably ss-ydroxyethyl. Preferably each of R5 and R6, independently is (C1-4)alkyl or ss-hydroxyethyl, or R5 and R6, together with the nitrogen to which they are attached, form a piperazine or morpholine group, the latter of these two heterocyclic group being preferred.

Especially preferred examples of the compounds of formula Ill are the compounds of the formulae (a). (b). (c) and (d).

(HOCH2CH)2N-CH2Ch2CN (a), (HocH2cH2) 2N-CH2CH2CCNH2 (b),

Of these four compounds, those of formulae (a), (b) and (c) are the most preferred for use in the photopolymerisable formulations with the compounds of the invention.

In the photo-polymerisable formulations for marketing, the compound(s) of the invention may constitute up to 90% by weight of the formulation. For actual use, the amount of photo-sensitizing compound(s) of the invention present in the photopolymerisable formulations will vary depending on the proposed use. Satisfactory results, however, may be obtained when the compound(s) of the invention is/are employed in an amount from 0,01% to 10%, preferably 1% to 8%, and most preferably 2% to 6%, of the weight of the photo-polymerisable formulation.

When an amine, as indicated hereinbefore, is also present in the formulation, this is preferably employed in equal or approximately equal amount as the compound(s) of the invention.

The photo-polymerisable formulations are of particular interest in ultraviolet curable coatings, e.g. coating lacquers. and in printing inks. e.g. offset lithographic printing inks.

In the following Examples, parts and percentages are by weight and temperatures are in degrees Centigrade.

EXAMPLE 1 A mixture of 14.5 g of 2,2'-5-trichlorobenzophenone and 24 g of sodium sulphide nonahydrate in 40 ml of dimethyl sulphoxide is warmed over a period of 10 minutes to 120 C, during which the mixture becomes dark red in colour. To the mixture at 100 C are then added 50 ml of ethanol and 10 ml of water, and the mixture is cooled to 10 . The resulting precipitate is removed bv suction filtration. washed with 20 ml of ethanol followed by 50 ml of water, and dried at 100-105 . 2-Chlorothioxanthone as a lemon yellow powder wth a m.p. of 153-154 is obtained in a yield of 11.2 g (85% of ther theoretical yield).

In an analogous manner the same product is obtained when 60 of dimethylformamide or 60 g of hexamethyl phosphoramide ([(CH3)2N]3P=O) or 60 g of sulpholane (CH2-CH2-SO2-CH2-CH2) are used instead of dimethylsulphoxide.

Thioxanthone (m.p. 215-217 ) is produced in an analogous manner when a mixture of 12.6 g of 2,2'dichlosobenzophenone and 7.9g of sodium sulphide trihydrate in 20 ml of N-methylpyrrolidone is stirred at about 90 for 1 hour and the product is crystallised out by addition of methanol to the reaction mixture.

In an analogous manner 2.7-dichlorothioxanthone (m.p. 253-254 ) is produced by reacting 32.0 g of 2.2',5,5'-tetrachlorobenzophenone (m.p. 115-117 ) with 24.0 g of sodium sulphide nonahydrate in 100 ml of dimethyl sulphoxide. In this case the exothermic reaction is observed to begin at about 50 EXAMPLE 2 A mixture of 14.5 g of 2,2',5-trichlorobenzophenone and 25 g sodium sulphide nonahydrate in 60 g of 2-methoxyethanolis stirred at 110-115 for one hour. Then the dark mixture is treated at 80 with 30 g of methanol and cooled to 10 . The resulting precipitate is collected by suction filtration, wasched with water, dried and crystallised from toluene with the addition of animal charcoal. The product, 2-chlorothioxanthone, has a m.p. 152-154 .

EXAMPLE 3 a) A mixture of 48.7 g of 1,4-dibromobenzene, 17.5 g of 2-chlorobenzoyl chloride and 13.4 g of aluminium trichloride is stirred for 3 hours with heating from an oil bath at a temperature of 160 , during which 3.4 g of hydrogen chloride are evolved. Thereafter the brown mass at 100 is poured into a solution of 10 g of conc. hydrochloride acid in 100 g of ice-water. To the mixture are added 100 g of chlorobenzone. The organic phase is separated, wasched with water, and the solvent is removed by distillation. Then the residual thick oil is distilled under high vacuum. In this way, a colourless oil, b.p. 190-195 / 0.08 mm of mercury pressure, which solidifies on standing , is produced. The formula of the product Is

Elementary Analysis Calc.; C41.7% H 1.88% Cl 9.4% Br 42.6% Found: C 42.9% H 2.0 % CI 9.3% Br 42.3% b) To a solution of 22.5 g of 2-chloro-2',5'-dibromobenzophenone in 60 g of dimethyl sulphoxide at 50 are added 14.4 g of sodium sulphide nonahydrate. An exothermic reaction immediately starts, during which the temperature rises to 90 and the mixtures is coloured brown. The mixture is stirred at 90 for 1 hour, allowed to cool to 60 , and treated with 60 g of methanol. The resulting precipitate is collected by suction filtration at 10 , wasched with methanol and then water, and dried at 95 . Produced is a pale yellowish powder with a m.p.

159-161 . The formula of the product is

Elementary Analysis Calc.: C53.6% H2.4% Br27.4% S11.0% Found: C54.5% H2.6% Br 26.1% S11.2% EXAMPLE 4 a) The compound of formula

with a m.p. of 108-110 is produced in an analogous manner to that described in Example 3a). b) 17.4 g of the above compound are dissolved in 30.0 g of dimethylacetamide at 80 . To the resulting clear solution are added 6.6 g of sodium sulphide trihydrate, as a result of which the temperature rises to 89 . The mixture is then stirred at 95 for 30 minutes and treated with 100 ml of methanol wherein the product is precipitated out. The product is collected by suction filtration at 25 , washed with water, and dried. Produced are pale yellow crystals with a m.p. of 206-207 . The formula of the product is

In an analogous manner the compounds in the Table are produced from the appropriately substituted 2.2'-dichlorobenzophenone.

No. Compound No. Compound 0 1 g C vCH3 CH3 C)'3 0 oc}l3 0 2 t 5 5 C1 CH3 0 3 CJ)3 6 Cl C'i3 7 7 to CX CH 3 S EXAMPLES A mixture consisting of 60 g of a prepolvmer of the formula

(viscosity ~9000 poise at 77 , see US Patent No. 3.713.864). 35 g of pentaerithritol tetraacrylate, 5 g of 2-chlorothioxantone, and 5 g of dibutylamino ethanol is applied with a spatula on to paper for artificial @@ints in an amount of 3.5 g/m. The applied mixture is hardened under a UV-Mini-Cure apparatus to a non-sticky, shiny film.

The compounds Nos. I to 7 given in the table above can also be used in an analogous manner.

Claims

WHAT WE CLAIM IS:

1. A process for producing a thioxanthone comprising reacting an o,o'dihalobenzophenone with a metansulphide or hydrosulphide.

2. A process according to Claim 1 , comprising producing a compound of formula I.

in which each of R1 and R2, independently, is hydrogen, (C1-4); alkyl, (C1-12). alkoxy or halogen, each of m and n, independently, is zero, 1, 2 or 3.

R3, when n is 1, and each R3, when n is 2 or 3, is (C1-4) alkyl, and R4, when m is 1, and each R4, when m is 2 or 3, is (Cl 4)alkyl, employing, as the o,o'-dihalobenzophenone, a compound of formula I',

in which R1, R2, R1. R1, m and n are as defined above. and Hal is halogen.

3. A process according to Claim 2. in which R1. is alkyl. alkoxy or halogen,

4. A process according to Claim 3. in which R1@ is alkoxy or halogen.

5. A process according to Claim 4. in which R1@ is halogen.

6. A process according to any of Claims 2 to 5. in which R2 is hydrogen. alkyl or halogen.

7. A process according to Claim 6. in which R2 is hydrogen or halogen.

X. A process according to Claim 7. in which R2- ~ is hydrogen.

9. A process according to any of Claims 2 to 8-. in which R3 is methyl or ethyl.

10. A process according to any of Claims 2 to 9. in which R4 is methyl or ethyl.

11. A process according to any of Claims 2 to 10. in which m is zero: I or 2.

12. A process according to Claim I I. in which m is zero or I

13. A process according to Claim 12. in which m is zero.

14. A process according to any of Claims 2 to 13. in which n is zero. I or 2.

15. A process according to Claim 14. in which n is zero or I

16. A process according to Claim 15. in which n is zero.

17. A process according to Claim 2. comprising producing a compound of formula Ia.

in which R1 ia (C1 4)alkyl, (C1-@)alkoxy or halogen.

R2 is hydrogen or halogen. m is zero or 1. n'is zero, 1 or 2, and R3 and R4 are as defined in Claim 2. employing , as the o,o' dihalobenzophenone, a compound of formula I".

in which R1, R2, R3. R4, m@, n@ are as defined above and Hal is halogen.

18. A process according to Claim 17, comprising producing a compound of formula Ib.

in which R1" is halogen, R3 is methyl or ethyl, and n" is zero or 1, employing. as the o,o'-dihalobenzophenone. a compound of formula I"',

in which R1", R3@, n" are as defined above, and Hal is halogen.

19. A process according to any of Claims 2 to 18, in which Hal is chlorine or bromine.

20. A process according to Claim 19. in which Hal is chlorine.

21. A process according to any preceding claim, in which the metal sulphide or hydrosulphide reagent is an alkali metal or alkaline earth metal sulphide.

22. A process according to Claim 21, in which the alkali metal sulphide is sodium sulphide.

23. A process according to any preceding claim, in which the process is conducted in the presence of an organic solvent featuring one or more polar groups selected from ether, carbonyl, hydroxyl, cyano, sulphoxide and sulphone groups.

24. A process according to Claim 23. in which the polar groups are selected from ether, carbonyl, hydroxyl and sulphoxide groups.

25. A process according to any preceding claim. in which the process is conducted in the presence of an aprotic solvent.

26. A process according to any one of Claims 1 to 22, in which the process is conducted in the presence of one or more solvent selected from dimethylsulphoxide, N.N- dimethylacetamide. N-methylpyrrolidone, hexamethylphosphoric acid triamide and sulpholane.

27. A process according to Claim 26, in which the solvents are selected from N,N-dimethylacetamide, N-methylpyrrolidone and dimethylsulphoxide.

28. A process according to any preceding claim. in which the temperature at which the process is conducted is in the range 6() to 170 C.

29. A process according to Claim 28. in which the temperature is in the range 7()-15ü C.

30. A process according to Claim 29. in which the temperature is in the range 75 to 105 C.

31. A process according to Claim 1. substantially as described herein with reference to any one of Examples 1 to 4.

32. A thioxanthone compound whenever produced by a process according to any preceding claim.

33. A compound of formula Il.

in which R1, is (C1-4) alkyl, (C1 8) alkoxy or halogen, R2 is hydrogen, (C1-4) alkyl, (C1-12) alkoxy or halogen, each R3 independently, is methyl or ethyl, m is zero, 1, 2, or 3, and R4, when mis 1, and each R4, when mis 2 or 3, is (C1-4) alkyl.

34. A compound according to Claim 33, in which R, ' is alkoxy or halogen.

35. A compound according to Claim 34, in which Rl ' is halogen.

36. A compound according to any of Claims 33 to 35. in which R2 is hydrogen. alkyl or halogen.

37. A compound according to Claim 36, in which R2 is hydrogen or halogen.

38. A compound according to Claim 37. in which R2 is hydrogen.

39. A compound according to any of Claims 33 to 38, in which the or each R4 is methyl or ethyl.

4(k A compound according to any of Claims 33 to 39. in which m is zero. I or 2.

41. A compound according to Claim 40, in which m is zero or 1.

42. A compound according to Claim 41, in which m is zero.

43. A compound substantially as descrlbcdd herein with reference to any one of Exaniple 4 and compounds Nos. 2. 4 and 6.

44. A process for producing a compound according to any one of Claims 33 to 43. comprising reacting a o.o'-dihalobenzophenonc of formula.

in which R1', R2, and R3'independently, the or each R4. independently. and m are as defined in Claim 33. and Hal is halogen. with a metal sulphide or hydrosulphide.

45. A process according to Claim 44. substantially as described herein with reference to Example 4.

46. A compound according to any one of Claims 33 to 43. whenever produced by a process according to Claim 44 or 45.

47. A photo-polymerisable formulation comprising a photo-polymerisable system in association with a photo-sensitizing amount of one or more compounds of any one of Claims 32 to 43 and 46.

48. A photo-polymerisable formulation according to Claim 47. in which the photopolymerisable system comprises unsaturated polymerising species capable of polymerising by a frce radical mechanism.

49. A photo-polymerisable formulation according to Claim 47 or Claim 48, in which the photo-polymerisable system contains at least one multi-functional component to promote photo-initiated cross-linking.

50. A photo-polymerisable formulation according to any of Claims 47 to 49. in which at least one component is an unsaturated carhoxvlic acid or ;i derivative thereof.

51. A photo-polymerisable formulation according to Claim 50. in which the unsaturated carboxylic acid or derivative thereof is acrylic or methacrylic acid or a derivative thereof.

52. A photo-polymerisable formulation according to any of Claims 47 to 51. in which the photo-polymerisable system comprises one or more reactive base prepolyniers or one or more reactive base long chain monomers in association with one or more cross-linking monomers.

53. A photo-polymerisable formulation accordine to Claim 52. in which the reactive base prepolymers are selected from unsaturated polyethers, polyesters, polyester-based urethanes and epoxy resins, and saturated or unsaturated such polymers modified by esterification with an unsaturated carboxylic acid

54. A photo-polymerisable formulation according to Claim 53. in which the reactive base prepolymers are selected from acrylated or methacrylated hydroxy-functional polyethers. polyesters. polyester-based urethanes and epoxy resins. and unsaturated polyesters.

55. A photo-polymerisable formulation according to any of Claims 52 to 54, in which the reactive base long chain monomers are selected from acryl derivatives of epoxylated unsaturated fatty acids.

56. A photo-polymerisable formulation according to Claim 55, in which the reactive base long chain monomers are selected from acryl derivatives of epoxylated linseed oil.

57. A photo-polymerisable formulation according to any of Claims 52 to 56. in which the cross-linking monomers are selected from vinyl and allyl monomers, acrilated alcohols and multi-functional acrylates.

58. A photo-polymerisable formulation according to Claim 57, in which the crosslinking monomers are selected from styrene, the diallyl ether of trimethylol propane, vinyl acrylate, diallyl maleate, diallyl phthalate, acrylated phenoxyethyl alcohol, acrylated neopentyl glycol and acrylated pentaerythritol.

59. A photo-polymerisable formulation according to any of Claims 47 to 58. comprising one or more amines which contains at least one α-CH group.

60. A photo-polymerisable formulation according to Claim 59, in which the amines are ss-aminopropionic acid derivatives.

61. A photo-polymerisable formulation according to Claim 60, in which the ssaminopropionic acid derivatives are of formula III.

in which Z is -('N ior -( '( )Nl l * either each of R5 and R6, independently is (C1-14)alkyl or ss-γ- or #-(C2-4)hydroxyalkyl, or R5 and R6, together with the nitrogen atom to which they are attached, from a piperazine, N-(C1-4)alkylpiperazine or morpholine ring or R5 or R6 from a group of formula

wherein Z is as defined above.

62. A photio-polymeris;ible formulation according to Claim 61, in which the ss- aminopropionic acid derivatives of formula III are of formulae (a). (b), (c) and (d).

(HOCH2CH2)2N-CH2CH2CN (HOCH2CH2)2N-CH2CH2CONH2

63. A photo-polymerisable formulation according to any of Claims 47 to 62, in which the amount of compound of any of Claims 32 to 43 and 46 present is up to 90% by weight of the formulation.

64. A photo-polymerisable formulation according to Claim 63, in which the amount present is from ().01 to lt)(/r of the weight of the formulation.

65. A photo-polymerisable formulation according to Claim 64, in which the amount present is from 1 to 8% of the weight of the formulation.

66. A photo-polymerisable formulation according to Claim 65. in which the amount present is from 7 to 6% of the weight of the formulation.

67. A photo-polymerisable formulation according to any of Claims 47 to 66. in the form of an ultraviolet curable coating or a printing ink.

68. A photo-polymerisable formulation according to Claim 47. substantially as described herein with reference to Example 5.

69. A method of photo-polymerising a photo-polymerisable system comprising irradiating said system with ultraviolet light of wavelength 25() to 4()() nm in the presence of a photo-sensitizing amount of one or more compounds of any one of Claims 43 to 43 and 46.

70. A method according to Claim 69. substantially as described herein with reference to Example 5.

71. A polymer whenever produced by the method of Claim 69 or C'lain 7().

72. A process according to Claim 1, comprising producing a compound of formula 1. as defined in Claim 2. with the provisos that when R1 and R3 are (C1-4)alkyl and n is 3. and/or when R2 and R4 are (C1-4)alkyl and m is 3. at least one of the four alkyl groups in each case on a benzene ring is methyl or ethyl. employing. as the o.o'-dihalobenzophenone. a compound of formula I', as defined in Claim 2. with the provisos that when R@ and R3 llre (C1-4)alkyl and n is 3. and/or when R2 and R4 are (C, )alkvl and m is 3. at least one of the four alkyl groups in each case on a benzene ring is methyl or ethyl.