GB2420117A

GB2420117A - Piperazino based multi-functional photoinitiators

Info

Publication number: GB2420117A
Application number: GB0424831A
Authority: GB
Inventors: Shaun Lawrence Herlihy; Brian Rowatt; Robert Stephen Davidson
Original assignee: Sun Chemical Ltd
Current assignee: Sun Chemical Ltd
Priority date: 2004-11-10
Filing date: 2004-11-10
Publication date: 2006-05-17
Also published as: EP1812414A1; AU2005326556A1; JP2013060453A; ZA200703761B; AU2005326556B2; GB0424831D0; US7612122B2; EP1812414B1; CA2587383C; CN101133041B; JP5235413B2; WO2006082477A1; CA2587383A1; CN101133041A; KR20070092228A; JP2008519760A; BRPI0520658B1; US20080045620A1; BRPI0520658A2

Abstract

An aminoacetophenone substituted piperazine compound of formula: <EMI ID=1.1 HE=47 WI=133 LX=413 LY=623 TI=CF> <PC>wherein R<1> is a C1-C10 alkyl group or an optionally substituted benzyl group; R<2> is an alkyl group or the two R<2> groups together with the N to which they are attached form a nitrogen heterocyclic group; Z is selected from C6-C10 arylene groups and groups of formula - (CHR<3>)n-, where R<3> is hydrogen, hydroxyl or a C1-C4 alkyl group, and n is 0-6; Y is carbonyl or -CH2-; Q is a residue of a mono- or polyhydroxy compound; x is 1 to 6; and esters thereof. Preferred possibilities for Q include residues of ethylene glycol, propylene glycol, butylenes glycol, glycerol, 2,2-propanediol, polyethylene glycol, polypropylene glycol, trimethylolpropane, di-trimethylolpropane, pentaerythritol and di-pentaerythritol. These compounds may be useful as multi-functional photoinitiators for use in coating compositions to be cured by radiant energy.

Description

PIPERAZINO BASED PHOTOINITIATOP

The present invention relates to a series of new piperazino compounds which are useful as photoinitiators, preferably multi-functional photoinitiators, for use in coating compositions to be cured by radiant energy, for example ultraviolet radiation. The invention also provides radiation-curable surface coating compositions, including varnishes, lacquers, printing inks and the like, which include at least one of the compounds of the present invention as a photoinitiator.

The compounds of the present invention comprise a polymeric core based on a polyhydroxy compound which is chemically bonded to one or more, preferably two or more, groups including a piperazino ring bonded to a benzene ring.

Photoinitiators used in energy-curable surface coating formulations need to have good cure speed, and particularly good surface curing activity, low odour and good solubility. Moreover, as consumers become increasingly wary of extraneous compounds in foodstuffs, in order to comply with likely future legislation, the tendency of the compounds to migrate and be extracted should also be low. Furthermore, in order for the compounds to be useful in practice, it is necessary that they should be preparable with ease and economically on a commercial scale. It is becoming increasingly difficult to meet all of these requirements.

We have now discovered a series of piperazino compounds of the aminoalkylphenone photoinitiator class which have the potential to achieve low levels of photolysis product migration and low odour from the cured print. Their strong UV chromophores in the UVB region make the aminoalkyiphenones particularly useful in pigmented printing inks.

Other compounds containing piperazino groups have been suggested for use as photoinitjators in US 4321118, US 4582862, and EP 1357117. However, in these compounds, the piperazine ring is not attached directly to an aromatic ring, and the resulting compounds do not absorb UV radiation of the wavelengths used in commercial curing systems so efficiently.

GB 2320027 also discloses compounds similar to those of the present invention, but does not disclose compounds in which a piperazine ring is attached directly to an aromatic ring.

Thus, the present invention consists in a compound of formula (I): R2 I ___ R2 N-C--c/----\ (I) x where: the substituents R1 are individually selected from C1 - C10 alkyl groups and optionally the substituents R2 are individually selected from alkyl groups or, together with the nitrogen atom to which they are attached, represent a nitrogen-containing heterocyclic group; Z is selected from C6 - C10 arylene groups and groups of formula where R3 is a hydrogen atom, a hydroxy group or a C1 - C4 alkyl group, and n is a number from 0 to 6; Y is selected from carbonyl groups and the -CH2---- group; Q is selected from the residues of mono- or polyhydroxy compounds having from 1 to 6 hydroxy groups; and xisanumberfrom 1 to6; and esters thereof.

The invention also provides an energy-curable composition comprising: (a) a polymerjsable monomer, prepolymer or oligomer; (b) a compound of formula (I) or an ester thereof as photo initiator, (c) optionally a pigment.

The invention still further provides a process for preparing an energy cured polymeric composition by exposing this energy-curable composition to radiant energy, especially to ultraviolet radiation.

In the compounds of the present invention where R1 represents an alkyl group, this may be a straight or branched chain alkyl group having from 1 to 10, preferably from 1 to 6, carbon atoms. Examples of such groups include the methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, 2- methylbutyl, 1- ethyipropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1 - methylpentyl, 3,3dimethylbutyl, 2,2-dimethylbutyl, 1,1 -dimethylbutyl, 1,2-dimethylbutyl, 1,3- dimethylbutyl, 2,3-dimethylbutyl, 2-ethylbutyl, hexyl, isohexyl, heptyl, octyl, nonyl and decyl groups, of which the methyl, ethyl, propyl, butyl and hexyl groups are preferred, the methyl and ethyl groups being most preferred.

Where R1 represents a benzyl group, this may be substituted or unsubstituted, but is preferably unsubstituted. If the group is substituted, there is no restriction on the number of substituents, except that imposed by the number of substitutable positions and possibly by steric constraints, however, from 1 to 3 substituents would be common.

Examples of such substituents include: alkyl groups, e.g. those having from 1 to 6 carbon atoms, such as the methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, 2-methylbutyl, 1 -ethylpropyl, 4- methylpentyl, 3- methylpentyl, 2-methylpentyl, 1 -methylpentyl, 3,3-dimethylbutyl, 2,2- dimethylbutyl 1,1 -dimethylbutyl, 1,2-dimethylbutyl 1,3-dimethylbutyl 2,3-dimethylbutyl 2- ethylbutyl, hexyl and isohexyl groups; and alkoxy groups, e.g. those having from I to 6 carbon atoms, such as the methoxy, ethoxy, propoxy, butoxy, sec-butoxy, t-butoxy, pentyloxy and hexyloxy groups. However, the benzyl group is preferably unsubstituted.

Where R2 represents an alkyl group, this may be a straight or branched chain alkyl group, preferably having from I to 6 carbon atoms, such as those exemplified above in relation to substituents on the benzyl group.

Alternatively, the two substituents R2, together with the nitrogen atom to which they are attached, may represent a nitrogen-containing heterocyclic group. Such a group preferably has from 3 to 7 ring atoms, of which at least one, but preferably no more than 3, is a nitrogen atom. Of the remaining ring atoms, at least two are preferably carbon atoms, and one or more, preferably no more than one, are oxygen atoms.

Examples of such heterocyclic groups include the morpholino, piperidino, 1- pyrrolidinyl, 3 -alkyl- 1 -imidazolidinyl, 2-alkyl- 1 -pyrazolidinyl, 4- alkyl- 1 -piperazinyl, 1- pyrrolyl, 1 -imidazolyl and 1 -pyridyl groups, of which the piperidino, morpholino and 4- methyl-i -pip erazinyl groups are preferred.

Where Z represents an arylene group, this may be a benzene ring, attached at the 1,2-, 1,3- or 1,4- positions, i.e. a phenylene group, or a naphthalene ring, attached at the 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7- or 1,8- positions, preferably a benzene ring, attached at the 1,4- positions.

Where Z represents a group of formula (CHR3)n_, and R3 represents a C1 C4 alkyl group, the alkyl group may be a methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl or t-butyl group, preferably a methyl or ethyl group. Most preferably R3 represents a hydrogen atom, or a methyl or ethyl group.

If n in the group of formula -(CHR3)_ is 0, then Z represents a direct bond.

However, n is more preferably a number from 1 to 6, still more preferably from 1 to 3, and still more preferably I or 2 and most preferably 2.

An alternative preferred class of compounds of the present invention are those compounds of formula (I) where Z is a group of formula -(CHR3)_, n is a number from 2 to 6 and one R3 represents a hydrogen atom or a C1 - C4 alkyl group, and the other or others of R3 represent hydrogen atoms.

Y may be a carbonyl group or a -CH2- group, preferably the carbonyl group.

In one embodiment of the present invention, Q represents a group of formula -A-Q', where A represents a group of formula _{O(CHR4CHRS)ajy_, -{O(CH2)bCoJy__ or __[O(CH2)bCO](y..1)4O(CHR4CHRS)}_; and where: R4 and R5 are the same or different and each represents a hydrogen atom or a C1 - C4 alkyl group; a is a number from 1 to 2; b is a number from 4 to 5; and yisanumber from ito 10; xisanumberfrom ito 6; and Q' represents a residue of a mono- or poly- hydroxy compound having from 1 to 6 hydroxy groups.

In the compounds of this embodiment of the present invention, we prefer that A should represent a group of formula _[O(CHR4CHRS)a}y_ where a is an integer from 1 to 2, y is as defined above, and R4 and R5 are the same or different and each represents a hydrogen atom or a C1 - C4 alkyl group. More preferably A represents a group of formula [OCH2CH2}y_, [OCH2CH2CH2CH2}__ or [OCH(CH3)CH2]y__, where y is as defined above, or a group of formula -[O(CH2)bCO]y_ or where b is a number from 4 to 5 and R4, R5 and y are as defined above, y preferably being a number from 1 to 6.

In general, in the compounds of the present invention, y is preferably a number from I to 10, more preferably from 1 to 6. We also prefer compounds of this embodiment in which x is 2 and y is a number from 1 to 10.

The compounds of this embodiment of the present invention are preferably of a generally polymeric nature. The polymeric nature may be provided by either the group represented by Q' or the group represented by A or by both.

The polymeric polyhydroxy residue of formula -A---Q', which forms the core of the compounds of the present invention has a major influence on the behaviour of the compounds. In accordance with the present invention, it is preferred that it should have a polymeric nature, since the resulting compounds tend to be liquid or of low melting point, thus aiding dispersion in the coating composition. Compounds having a similar structure but not polymeric tend to be solid and/or insoluble in these coating compositions. However, we prefer that the core residue, of formula -A-Q', should not have too high a molecular weight, and prefer that the residue of formula -A-Q' should have a molecular weight no greater than 2000, preferably no greater than 1200, still more preferably no greater than 1000, and most preferably no greater than 800.

We particularly prefer that Q' is a residue of a C2 - C6 alkylene glycol or of a polyalkylene glycol, in which the alkylene part has from 2 to 6 carbon atoms. More preferably, Q' is a residue of ethylene glycol, propylene glycol, butylene glycol, glycerol, 2,2-propanedjol, polyethylene glycol, polypropylene glycol, polybutylene glycol, trimethyloipropane, di-trimethyloipropane, pentaerythritol or di- pentaerythrjtol.

It will be appreciated that, when the compounds of the present invention are analysed, the numbers a, b and y in the above formulae need not be integral, and, indeed, it is unlikely that they will be integral, since the compounds of the present invention may be mixtures of several compounds in which the numbers a, b and y differ. In accordance with the present invention, provided that the average value of each of these numbers is as defined above, this will be satisfactory. Of course, for each individual molecule of the compounds of the present invention, a, b and y will be integral, and it might be possible to separate out such individual compounds, but, in practice, mixtures of these compounds are used.

In another preferred embodiment of the present invention, x is 1. In this case, Q is preferably the residue of a compound of formula R6-OH, where R6 represents a C1 - C10 alkyl group or an optionally substituted benzyl group, as exemplified above in relation to R1. More preferably, Q is a C1 - C6 alkoxy group or a phenoxy group. We also particularly prefer, in this embodiment, that Z is a phenylene group.

However, the compounds of the present invention are preferably multifunctional photoinitiators, and so x is preferably greater than 1, i.e. preferably from 2 to 6.

Thus, in an alternative preferred embodiment of the present invention, Q is a residue of a C2 - C6 polyalkylene glycol, in which the alkylene part has from 2 to 6 carbon atoms. Alternatively, Q may be a bis(C1 - C6 hydroxyalkyl) ether, where the two hydroxyalkyl parts may be the same as or different from each other, although they are preferably the same, and each may have one or more hydroxy groups. In this embodiment, Q is preferably a residue of ethylene glycol, propylene glycol, butylene glycol, glycerol, 2,2-propanediol, polyethylene glycol, polypropylene glycol, polybutylene glycol, trimethylolpropane, di-trimethylolpropane, pentaerythritol or di-pentaerythrjtol The compounds of the present invention may be prepared simply, for example by a Michael addition of a compound of formula (II): R 0 R2 I II ___ R2 N-C-c (II) (in which R1 and R2 are as defined above) with an active compound corresponding to the group of formula -(Z-Y)-Q (where Z, Y, x and Q are as defined above). This active compound may, for example, be a compound including a carbon-carbon double bond or an epoxide group, as illustrated in more detail in the Examples appearing hereafter, and is preferably an acrylate or methacrylate.

The composition of the present invention may be formulated as a printing ink, varnish, adhesive or any other coating composition which is intended to be cured by irradiation, whether by ultraviolet or electron beam. Such compositions will normally contain at least a polymerjsable monomer, prepolymer or oligomer, the photoinitiator of the present invention, an amine synergist and optionally a sensitiser, but may also include other components well known to those skilled in the art, for example, waxes, flow aids and, in the case of printing inks, a pigment.

A wide variety of monomers and prepolymers may be subjected to photoinjtjatjon with the photoinitjators of the present invention, and the nature of the monomers and prepolymers is not critical to the present invention.

The radiation-curable monomer or oligomer is preferably an ethylenically unsaturated compound, for example an acrylate or thethacrylate. Examples of suitable acrylate oligomers include aliphatic or aromatic urethane acrylates, polyether acrylates, polyester acrylates and epoxy acrylates (such as bisphenol A epoxy acrylate). Examples of suitable acrylate monomers include hexanediol diacrylate, trimethylolpropane triacrylate, di-trimethyloipropane tetraacrylate, di-pentaerythritol pentaacrylate, polyether acrylates, such as ethoxylated trimethylol propane triacrylate, glycerol propoxylate triacrylate, ethoxylated pentaerythrjtol tetraacrylate, epoxy acrylates such as dianol diacrylate (== the diacrylate of Ebecryl 150 from UCB), glycol diacrylates such as tripropylene glycol diacrylate and alkyl acrylates and methaciylates (such as hexanediol diacrylate, isobomyl acrylate, octadecyl acrylate, lauryl acrylate, stearyl acrylate and isodecyl acrylate, and the corresponding methacrylates).

Also, the compositions of the present invention preferably contain a synergist, such as an aminoacrylate or a dimethylaminobep0j acid ester, as is well known in the art. Preferably the synergist will be a dimethylamjnobeoic acid ester in the case of a printing ink or an aminoacrylate in the case of a varnish. Some inks, such as those used in flexographic printing applications, may contain both amine types.

If desired, in addition to the photoinjtiator compound of the present invention, an additional photoinitjator may be employed, as is well known in the art. Examples of such additional photoinitiators which may be used in the compositions of the present invention include thioxanthones (and derivatives), benzophenones (and derivatives), hydroxyalkyiphenones, xanthones and anthraquinones.

The amounts of the radiation-curable monomer or oligomer, photoinitiator, synergist, sensitiser and optional colorant will vary according to the type of varnish or ink, the particular equipment to be used to apply it and the application. However, typically, the amount of photoinitiator plus amine synergist is from 1% to 15-20% by weight of the total composition.

The compounds of formula (I) are especially suited for use in varnishes and inks, especially printing inks, including lithographic inks. These typically comprise, as additional components to those referred to above, one or more of pigments, waxes, stabilisers, and flow aids, for example as described in "Printing Ink Manual", fourth edition, Leach R. H. et a!. (eds.), Van Nostrand Reinhold, Wokingham, (1988), the disclosure of which is incorporated herein by reference. In particular, the compounds are useful as photoinitiators in printing ink compositions, and so these compositions most preferably include at least one pigment.

Additives which may be used in conjunction with the principal components of the coating formulations of the present invention include stabilisers, plasticisers, pigments, waxes, slip aids, levelling aids, adhesion promoters, surfactants and fillers.

Also other photoinitiators, such as thioxanthone (and derivatives), benzophenone (and derivatives), hydroxyalkylphenones aminoalkyiphenones and anthraquinone (and derivatives) may be included, if desired.

The compounds of the present invention may be included as photoinitiators in coating formulations such are well known in the art, and the precise composition of such formulations will vary depending upon the other components and the intended use, as is well known. However, a typical formulation for an ink coatable by flexography might be: Pigment 8 - 20% Photoinitiator + synergist 4- 10 % Monomer/prepolymer/oljgo5 30 - 90% Additives 0- 10% although inks may have compositions outside these ranges as is well known in the art.

The invention is further illustrated by the following non-limiting Examples.

XAMPLE1 Preparation of 2-benzyI2NNd imethylamino I -[4-piperazjnopheny4 butanone.

H3C CH3 5. Og of 1 -[4-fluorophenyl]- 1 -butanone (O.Ol67moles) S.75g of piperazine (O.O669moles), O.063g of copper (I) iodide and lSml of toluene were mixed in a three necked flask equipped with a stirrer, nitrogen inlet, condenser, nitrogen outlet and a temperature probe. The mixture was heated to reflux for a total of 24 hours under a constant flow of nitrogen gas. The mixture was then cooled to room temperature, after which it was dissolved in 50m1 of dichioromethane The mixture was then extracted with 1 OOml of a saturated aqueous sodium chloride solution and then with 2 x lOOmI of water. The dichioromethane layer was then dried using anhydrous magnesium sulphate. The magnesium sulphate was removed by filtration and the organic solvent was then removed on a rotary evaporator to yield the product.

Product yield S.50g (90.23%) of a yellow solid.

The product was analysed by FT-IR and LCMS.

IR: Aryl C-N 1340cm, MS: m/z fM+1] = 366 (Mw = 365).

EXAMPLE 2

Preparation of 2-methyl-i -14-piperazinophenyjl-2-morphol mo propan-i one. H3C /

HNNCH3 4.2g of 2-methyl- l-[4-fluorophenyl]2morpho1 inopropan.. 1-one (0.01 67moles), 5.75g of piperazine (O.O669moles), O.063g of copper (I) iodide and 15m1 of toluene were mixed in a three necked flask equipped with a stirrer, nitrogen inlet, condenser, nitrogen outlet and a temperature probe. The mixture was heated to reflux for a total of 24 hours under a constant flow of nitrogen gas. The mixture was then cooled to room temperature, after which it was dissolved in 75m1 of dichloromethane. The mixture was then extracted with 1 OOml of a saturated aqueous sodium chloride solution and then with 2 x 1 OOml of water. The dichioromethane layer was then dried using anhydrous magnesium sulphate. The magnesium sulphate was removed by filtration and the organic solvent was then removed on a rotary evaporator to yield the product.

Product yield 4.52g (85.4%) of a yellow solid.

The product was analysed by FT-JR and LCMS.

IR: Aryl C-N 1359cm'.

MS: m/z [M+1] = 318 (Mw = 317).

FXAMPLE3 H,C CH, N/\OQO O.53g PEG200 diacrylate (mol. wt. -258, n = 3 average) (O.OO2O5moles), 1.5g of the product of Example 1 (O.OO4llmoles), toluene lOmI and 0.05g 1,8- diazabicyclo- (5.4.O)undec-7-ene (DBU) (catalyst) were mixed in a round bottomed flask equipped with a stirrer, condenser and temperature probe. The mixture was heated to reflux for a total of 6 hours. The mixture was then cooled and filtered, and then the solvent was removed on the rotary evaporator to yield the product.

Product yield 2.lg of a viscous yellow/orange paste.

The product was analysed by FT-JR and LCMS.

IR: acrylate C=C at 81 Ocm not present, indicating product has formed.

MS: m/z [M+1] = 989 (Mw = 988 difunctjonal product); m/z [M+1] = 624 (Mw = 623 monofunctional fragment).

EXAMPLE 4

H3C CH3 O.4055g trimethylol propane triacrylate (TMPTA, mol. wt. 296) (O. OOl37moles), l.5g of the product of Example 1(0.0041 Imoles), toluene lOmi and O.05g 1, 8- diazabicyclo(5.4O)dec..7..ene (DBU) (catalyst) were mixed in a round bottomed flask equipped with a stirrer, condenser and temperature probe. The mixture was heated to reflux for a total of 6 hours. The mixture was then cooled and filtered, and then the solvent was removed on the rotary evaporator to yield the product.

Product yield 2.OOg of a viscous yellow/orange paste.

IR: acrylate C=C at 81 0cm1 not present, indicating product has formed.

MS: m/z [M+l] = 1027 (Mw = 1026 difunctional fragment); m/z [M+lf = 662 (Mw = 661 monofunctional fragment).

EXAMPLE 5

H3C CH3 O.3616g pentaerythritol tetraacrylate (mol. wt. 352) (O. OOl03moles), 1.5g of the product of Example 1 (0.004 1 Imoles), toluene lOml and 0.05g l,8- diazabicyclo- (5.4.0)undec-7-ene (DBU) (catalyst) were mixed in a round bottomed flask equipped with a stirrer, condenser and temperature probe. The mixture was heated to reflux for a total of 6 hours. The mixture was then cooled and filtered, and then the solvent was removed on the rotary evaporator to yield the product.

Product yield 1.80g viscous yellow/orange paste.

IR: acrylate C=C at 810cm' not present, indicating product has formed.

MS: m/z [M+1j = 1083 (Mw = 1082 difunctional fragment); m/z [M+1} = 718 (Mw = 717 mono functional fragment).

XAMPLE6 a CH3 O.41g PEG200 diacrylate (mol. wt. --258, n = 3 average) (O. OOl59moles), I.Og of the product of Example 2 (O.OO3lSmoles), toluene lOmi and 0.04g l,8- diazabicyclo- (S.4.O)undec-7-ene (DBU) (catalyst) were mixed in a round bottomed flask equipped with a stirrer, condenser and temperature probe. The mixture was heated to reflux for a total of 6 hours. The mixture was then cooled and filtered, and then the solvent was removed on the rotary evaporator to yield the product.

Product yield 1.2g of a viscous yellow/orange paste.

IR: acrylate C=C at 81 Ocm' not present, indicating product has formed.

MS: m/z [M+1] = 893 (Mw = 892 difunctjonal product); m/z [M+1J = 576 (Mw = 575 monofunctjonal fragment).

EXAMPLE 7 a CH3 H3C:3

0.311 2g trimethyloipropane tiiacrylate (TMPTA, mol. wt. 296) (0.001 O5moles), I.Og of the product of Example 2 (O.OO3lSmoles) toluene lOmi and O.04g 1, 8- diazabicyclo(5.4.O)undec7ene (DBU) (catalyst) were mixed in a round bottomed flask equipped with a stirrer, condenser and temperature probe. The mixture was heated to reflux for a total of 6 hours. The mixture was then cooled and filtered, and then the solvent was removed on a rotary evaporator to yield the product.

Product yield 1.1 5g of a viscous yellow/orange paste.

IR: acrylate C=C at 81 0cm not present, indicating product has formed.

MS: m/z [M+1j = 931 (Mw = 930 difunctional fragment); m/z [M+1J = 614 (Mw = 613 monofunctional fragment).

EXAMPLE 8 CH3

0.28g pentaerythiitol tetraacrylate (mol. wt. 352) (O.0008moles), 1.Og of the product of Example 1 (0.0031 5moles), toluene 1 Omi and 0.04g 1,8diazabicyclo- (S.4.O)undec-7-ene (DBU) (catalyst) were mixed in a round bottomed flask equipped with a stirrer, condenser and temperature probe. The mixture was heated to reflux for a total of 6 hours. The mixture was then cooled and filtered, and then the solvent was removed on a rotary evaporator to yield the product.

Product yield 1.2g of a viscous yellow/orange paste.

IR: acrylate C=C at 81 Ocm' not present, indicating product has formed.

MS: m/z [M+1] = 987 (Mw 986 difunctional fragment); m/z [M+l] = 670 (Mw = 669 monofunctional fragment).

EXAMPLE 9

Performance Evaluation In Offset Inks The performance of the new materials was assessed in a black offset ink formulation based on a tn- functional urethane acrylate oligomer. A photoinitiator blend was added as 8% of the overall formulation. The photoinitiator blend comprised methyl o-benzoylbenzoate (MBB), isopropyithioxanthone (ITX), 2-ethyihexyl pdimethyl- aminobenzoate (EHA) and a multi-functional photoinitiator (MFPI), as prepared in one of the preceding Examples. The MFPI was used at a level of 13.5 weight % in the photoinitiator blend.

In the control formulation, the new MFPI was substituted by Irgacure 369 when comparing against the products from Examples 3, 4 and 5, or by Irgacure 907 when comparing against the products from Examples 6, 7 and 8, as would be typical in a normal commercial formulation.

A comparative formulation was also prepared that only comprised methyl obenzoyl benzoate (MBB), isopropyithioxanthone (ITX) and 2-ethylhexyl pdimethyl- aminobenzoate (EHA).

The inks were printed onto a carton board substrate (Incada Silk 260 gsm from Iggesund) to a density of approximately 1.8 using an IGT Cl print proofer. These were cured at 100 rn/mm using a Primarc Maxicure IJV rig fitted with a single 300 W/inch medium pressure mercury lamp, operating at full power to provide good comparison of results. Cure was assessed using a Specac set off blocking test at 10 tons pressure for 5 seconds at each pass. The number of passes to achieve no set off of partially cured ink onto apiece of blank substrate was recorded and is shown in Table 1.

Table I

cure speed of inks Initiator No. of passes to cure Irgacure 369 2

Example 3 3

Example 4 3

Example 5 3

Irgacure 907 2

Example 6 2

Example 7 2-3

Example 8 2-3

Comparative 4-5 formulation The results in Table 1 show that the new MFPI materials give good cure speed.

In the case of Example 6, the cure speed is as good as the standard formulations. In the case of Examples 3, 4, 5, 7 and 8, the cure speed is almost as good as the standard formulations. In all cases the cure speed is better than the comparative formulation.

It should be noted that the results outlined above have been obtained from a direct weight % replacement of the standard photoinitiator by the new materials in the formulation.

Overall, the results show that these novel materials have good photoinitiator activity. These new compounds also have the potential to achieve low levels of photolysis product migration and low odour from the cured print due to the initiator moieties being bound to a high molecular weight core. When these two factors are combined these new materials have considerable advantages over the existing technology.

Claims

CLAIMS: 1. A compound of formula (I): R1 0 where: the substituents R1 are

individually selected from C1 - C10 alkyl groups and optionally the substituents R2 are individually selected from alkyl groups or, together with the nitrogen atom to which they are attached, represent a nitrogencontaining heterocyclic group; Z is selected from C6 - C10 arylene groups and groups of formula -(CHR3)_, where R3 is a hydrogen atom, a hydroxy group or a C1 - C4 alkyl group, and n is a number from 0 to 6; Y is selected from carbonyl groups and the -CH2_-- group; Q is selected from the residues of mono- or poly- hydroxy compounds having from 1 to 6 hydroxy groups; and x is a number from 1 to 6; and esters thereof.
2. A compound according to Claim 1, where at least one of the R1 substituents is a C1 - C6 alkyl group.
3. A compound according to Claim 2, where at least one of the R' substituents is a methyl or ethyl group.
4. A compound according to Claim 2 or Claim 3, where at least one of the R1
5. A compound according to any one of the preceding Claims, where the substituents R2 are individually selected from C1 - C6 alkyl groups.
6. A compound according to Claim 5, where the R2 substituent represents a methyl or ethyl group.
7. A compound according to any one of the preceding Claims, where the R2 substituents, together with the nitrogen atom to which they are attached, represent a 5- to 7- membered nitrogen-containing heterocyclic ring.
8. A compound according to Claim 7, where nitrogen-containing said heterocyclic ring is selected from morpholino, piperidino, 1-pyrrolidinyl, 3-alkyl-1- imidazolidjnyl, 2- alkyl- 1 -pyrazolidinyl, 4-alkyl- I -piperazinyl, I -pyrrolyl, 1 - imidazolyl and 1 -pyridyl groups.
9. A compound according to Claim 8, where said heterocyclic ring is selected from piperidino, morpholino and 4-methyl-i -piperazinyl groups.
10. A compound according to any one of the preceding Claims, where Z is a group of formula (CFJR3)n__, and n is I or 2.
11. A compound according to any one of the preceding Claims, where Z is a group of formula -(CHR3)-_, and n is 2.
12. A compound according to Claim 10 or Claim 11, where R3 is selected from hydrogen atoms, methyl groups and ethyl groups.
13. A compound according to Claim 12, where R3 is a hydrogen atom.
14. A compound according to any one of Claims I to 9, where Z is a group of formula -(CHR3)_, n is a number from 2 to 6 and one R3 represents a hydrogen atom or a C1 - C4 alkyl group, and the other or others of R3 represent hydrogen atoms.
15. A compound according to any one of Claims 1 to 9, where Z is a phenylene group.
16. A compound according to any one of the preceding Claims, wherein Q is a group of formula Ax_Q', where: A is selected from groups of formula _[O(CHR4CHR5)a]y_, [O(CH2)bco}y_ and {O(CH2)bCOJ(yl)[O(CHR4CHRS)aJ_; where: R4 and R5 are individually selected from hydrogen atoms and C1 - C4 alkyl groups; a is a number from I to 2; b is a number from 4 to 5; and yisanumber from Ito 10; x is a number from 1 to 6; and Q' is selected from residues of a mono- or poly- hydroxy compounds having from I to 6 hydroxy groups.
17. A compound according to Claim 16, where y is a number from 3 to 10.
18. A compound according to Claim 17, where A is a group of formula _lIO(CHR4CHRS)ajy_ where a is an integer from I to 2, and y is a number from 1 to

I 10.
19. A compound according to Claim 17, where A is selected from groups of formula -[OCH2CH2]_, -IOCH2CH2CH2CH2J and -[OCH(CH3)CH2J, where y is a number from I to 10.
20. A compound according to Claim 17, where A is a group of formula -{O(CH2)bCojy_, where b is a number from 4 to 5 and y is a number from 1 to 10.
21. A compound according to Claim 17, where A is a group of formula _[O(CH2)bCO](yl)_[O(CHR4CHRS)a]_, where a is a number from 1 to 2, b is a number from 4 to 5 and y is a number from ito 10.
22. A compound according to any one of Claims 16 to 21, where x is 2.
23. A compound according to any one of Claims 16 to 22, where y is a number from 1 to6.
24. A compound according to any one of Claims 16 to 23, where the residue has a molecular weight no greater than 2000.
25. A compound according to Claim 24, where the residue -A--Q' has a molecular weight no greater than 1200.
26. A compound according to Claim 25, where the residue -A---Q' has a molecular weight no greater than 1000.
27. A compound according to Claim 26, where the residue -A-Q' has a molecular weight no greater than 800.
28. A compound according to any one of Claims 16 to 27, where Q' is a residue of a poly(C2 - C6 alkylene) glycol.
29. A compound according to any one of Claims 16 to 27, where Q' is a residue of ethylene glycol, propylene glycol, butylene glycol, glycerol, 2,2-propanediol, polyethylene glycol, polypropylene glycol, polybutylene glycol, trimethylolpropane, di-

I

trimethyloipropane, pentaerythritol or di-pentaerythritol.
30. A compound according to any one of Claims 1 to 15, where x is 1.
31. A compound according to Claim 30, where Q is the residue of a compound of formula R6-OH, where R6 is selected from C1 - C10 alkyl groups and optionally
32. A compound according to Claim 30, where Q is a C1 - C6 alkoxy group or a phenoxy group.
33. A compound according to Claim 31 or Claim 32, where Z is a phenylene group.
34. A compound according to any one of Claims ito 15, where Q is a residue of a poly(C2 - C6 alkylene) glycol.
35. A compound according to Claim 34, where Q is a residue of ethylene glycol, propylene glycol, butylene glycol, glycerol, 2,2-propanediol, polyethylene glycol, polypropylene glycol, polybutylene glycol, trimethylolpropane, di-trimethylolpropane, pentaerythritol or dipentaerythritol.
36. An energy-curable composition comprising: (a) a polymerisable monomer, prepolymer or oligomer; and (b) a compound as claimed in any one of Claims 1 to 35 as photoinitiator.
37. A process for preparing an energy cured polymeric composition by exposing a composition according to Claim 36 to radiant energy.
38. A process according to Claim 37, where the radiant energy is ultraviolet radiation.