Amine Coinitiator Mixture

Abstract

The present invention relates to a coinitiator comprising an aminobenzoate derivative according to formula I, and at least one auxiliary amine, wherein the reactivity and solubility of the coinitiator in UV curable resins are sufficiently high so that the coinitiator can be used in UV radiation curing processes. 1 and R 2 independently represents a methyl or ethyl group; and j, k, l and m are independently 0-20. Formula I

Description

[0001] The present invention relates to amine co-initiator mixtures comprising at least two amines, and in particular to amine co-initiators comprising an aminobenzoate compound as the first component. These co-initiators can be used in coatings and inks.

[0002] Radiation-curable compositions containing acrylates and other similar unsaturated compounds can be polymerized by exposure to ultraviolet (UV) light. For rapid, efficient curing, a photoinitiator is often necessary, which forms free radical species upon irradiation with photons and initiates free radical polymerization of the unsaturated groups, resulting in hardening (curing) of the material.

[0003] Unlike Type I photoinitiators - which cleave upon exposure to UV radiation, thereby generating free radical species capable of initiating polymerization of unsaturated compounds - so-called Type II photoinitiators (not to be confused with the Norrish Type II reaction, which involves intramolecular hydrogen abstraction of a diradical species) are compounds that do not fragment upon exposure to UV radiation and therefore typically will not initiate free radical chain polymerization unless an additional co-initiator is present. The interaction between a Type II photoinitiator and a suitable co-initiator upon exposure to UV radiation results in the generation of free radical species that can initiate polymerization of a UV-curable resin.

[0004] Suitable Type II photoinitiators include diaryl ketones such as benzophenone (e.g. SpeedCure BP-Lambson Limited) or thioxanthones such as 2-isopropylthioxanthone (e.g. SpeedCure 2-ITX-Lambson Limited). Suitable co-initiators may include thiols or, more commonly, tertiary amines. Tertiary amines are particularly useful for surface curing of UV inks and UV coatings because they can react with otherwise inactive peroxyl radicals (which are formed when reacting between free radical species and atmospheric oxygen) to obtain more reactive species that can continue polymerization reactions, thereby reducing the inhibitory effect of oxygen on the surface of inks and coatings (A. Green, "Industrial Photoinitiators: A Technical Guide", Taylor and Francis Group 2010, p. 70).

[0005] In packaging applications, especially in food packaging, radiation curable compositions containing photoinitiators, co-initiators and other additives can be problematic ("Radiation Curing in Packaging", Radtech Report March / April 2006). Residual photoinitiators, co-initiators and other additives, as well as their fragmentation products, can migrate out of the coating or ink if they are not chemically bound to the polymer backbone. This can lead to contamination of any adjacent materials and, in the case of food, can lead to off-flavor and odor problems. Photoactive compounds with low migration potential are therefore constantly sought. Some of these molecules or their fragmentation products may also present toxicity issues in some cases, so it is also important to develop low toxicity additives.

[0006] Diffusion-hindered photoinitiators or co-initiators are photoactive molecules that exhibit low mobility in the cured layer of the curable composition or ink, thereby reducing their tendency to migrate. st As described in the Journal of the American Chemical Society (Ed. London 1996), the ability of a molecule to migrate is often determined by its molecular weight. Therefore, for low migration UV curable inks or coatings, photoactive components with a molecular weight greater than 500 Daltons are preferred. Likewise, the toxicity of any photoactive component is likely to be lower when the molecule is of a higher molecular weight due to their reduced bioavailability; molecules with a molecular weight greater than 500 Daltons are generally preferred because they are less likely to be absorbed into the skin or penetrate into the gastrointestinal tract (Voutchkova et al., Chem. Rev. 2010, 110, 5845-5882).

[0007] Among the most reactive tertiary amines used as co-initiators for Type II photoinitiators are aminobenzoate derivatives such as ethyl 4-(dimethylamino)benzoate (e.g. SpeedCure EDB - Lambson Limited) and 2-ethylhexyl 4-(dimethylamino)benzoate (e.g. SpeedCure EHA - Lambson Limited). Such aminobenzoate derivatives are particularly useful in lithographic ink formulations where ink leveling is critical for their application and where more hydrophilic tertiary amines may not be suitable. In cases where higher concentrations of amine are used to reduce oxygen inhibition, migration is more likely to occur, as a proportion of the amine co-initiator may remain unreacted and therefore not chemically bound to the polymer backbone. Due to the toxicological classification of these compounds, migration has the potential to damage health.

[0008] The use of multifunctional amine co-initiators increases the likelihood that the co-initiator will be chemically bonded to the polymer backbone after curing, thereby reducing the likelihood that the co-initiator molecules will migrate. For multifunctional amine co-initiators with high molecular weights, particularly those with molecular weights >500 Daltons, the migration of any unreacted co-initiator will also be diffusion hindered. Among the high molecular weight, diffusion hindered co-initiators that have been available for low migration applications are oligomeric aminobenzoates such as Omnipol ASA (IGM Resins) and SpeedCure 7040 (Lambson Limited), but these materials are not as photoactive as their small molecule counterparts and can often present solubility issues. Therefore, there continues to be a need to discover new high molecular weight, diffusion hindered tertiary amine co-initiators that exhibit the properties of low migration and low toxicity while also being highly active and having good solubility.

[0009] In a first aspect of the present invention, there is provided a high molecular weight, diffusion hindered amine co-initiator mixture comprising an amine derivative including an aminobenzoate derivative according to Formula I shown below, and one or more auxiliary amines, as defined in claim 1. The mixture exhibits high co-initiator efficiency for initiating UV curing in the presence of a Type II photoinitiator and surprisingly is well soluble in a range of acrylate resins within a suitable concentration range. Furthermore, the solubility of the co-initiator mixture in acrylate resins is often higher than the solubility of the individual multifunctional amine co-initiators when they are not present in such a mixture.

[0010] Formula I

[0011]

[0012] Where R 1 and R2 independently represent a methyl or ethyl group; and

[0013] j, k, l and m independently represent an integer of 0-20.

[0014] A description of the invention is described herein.

[0015] The present invention relates to amine co-initiator mixtures for use in UV light curable compositions. More particularly, the co-initiator mixtures are suitable for use in applications where the properties of low migration, low toxicity and high solubility (particularly in acrylate resins) are particularly desirable.

[0016] The present invention seeks to provide an effective multifunctional, diffusion hindered co-initiator mixture that is particularly useful for low migration coatings and inks and that exhibits good solubility in polymerizable (polymerizable) resin systems. This is achieved by providing a co-initiator mixture comprising an aminobenzoate compound according to formula I, and one or more auxiliary amines.

[0017] Formula I

[0018]

[0019] Where R 1 and R 2 independently represent a methyl or ethyl group; and

[0020] j, k, l and m independently represent an integer of 0-20.

[0021] Often, R. 1 or R 2 At least one of will be methyl, and in some cases R 1 and R 2 Both will be methyl groups, as it has been found that methyl groups provide the greatest activity. In some cases, the N,N-dialkylamino group (-NR 1 R 2 ) is at the 4 position (para) relative to the ester group, although they can also be at the 2 position (ortho position), or the 3 position (meta position), and for comprehensive reasons, the 2 or 4 position is often selected, and the 4 position is the most common. In addition, the N,N-dialkylamino group can be at different positions on different rings, for example, the N,N-dialkylamino group can be at the 4 position on 1, 2, or 3 rings, although often the positioning of the N,N-dialkylamino group will be the 4 position for all 4 rings. Usually, as shown, there will be only a single N,N-dialkylamino group on each ring.

[0022] In one embodiment, the compound of Formula I can be such that j, k, l and m are all equal to zero.

[0023] In another embodiment, the compound of formula I may be an ethoxylated compound. As used herein, the term "ethoxylated compound" means a compound having one or more oxyethylene -[O-CH2-CH2]- units. Thus, the compound of formula I may have at least one of j, k, l and m not equal to 0. In particular, the sum of j+k+l+m may be 1-30, 4-25, or 6-20. More particularly, j, k, l and m independently represent integers of 0-20, 1-10 or 2-5.

[0024] In a particularly preferred embodiment, the coinitiator according to Formula I has a structure according to Formula Ia.

[0025] Formula Ia

[0026]

[0027] wherein n, o, p and q independently represent an integer of 0-20.

[0028] In one embodiment, the compound of Formula Ia can be such that n, o, p and q are all equal to zero.

[0029] In another embodiment, the compound of formula Ia may be an ethoxylated compound. Thus, the compound of formula Ia may have at least one of n, o, p and q not equal to 0. In particular, the sum of n+o+p+q may be 1-30, 4-25, or 6-20. More particularly, n, o, p and q may independently represent an integer of 0-20, 1-10 or 2-5.

[0030] The co-initiator mixture of the present invention includes an auxiliary amine. As used herein, the term "auxiliary amine" means a compound including at least one amine group that can have a beneficial effect on the compound of formula (I). For example, the auxiliary amine can improve the solubility and / or curing efficiency of the compound of formula (I).

[0031] In a preferred embodiment, the auxiliary amine in the coinitiator mixture is an aminobenzoate derivative, which will often be a tertiary amine, such as an N,N-dialkylaminobenzoate derivative. In one embodiment, the auxiliary amine includes at least one, particularly at least 2, more particularly at least 3 aminobenzoate moieties. In particular, the auxiliary amine may include 2-6 aminobenzoate moieties. In particular, the amino group of the aminobenzoate moiety may be a tertiary amino group.

[0032] In one embodiment, the auxiliary amine includes at least one, particularly at least two, more particularly at least three N,N-dialkylaminobenzoate moieties. In particular, the auxiliary amine may include 2-6 N,N-dialkylaminobenzoate moieties. As used herein, the term "N,N-dialkylaminobenzoate moiety" means a group of formula (A):

[0033]

[0034] wherein R' and R" are independently alkyl, particularly methyl or ethyl, more particularly methyl.

[0035] In particular, the N,N-dialkylaminobenzoate moiety of formula (A) may have the N,N-dialkylamino group (—NR′R”) in the 4 position (para position) relative to the ester group.

[0036] The auxiliary amine may have 1, 2, 3, 4, 5 or 6 N,N-dialkylaminobenzoate moieties as follows: wherein the N,N-dialkylamino group is in the 4 position relative to the ester group. The auxiliary amine may also have N,N-dialkylaminobenzoate moieties as follows: wherein the N,N-dialkylamino group is in the 2 position (ortho position) or 3 position (meta position) relative to the ester group. More particularly, all aminobenzoate moieties of the auxiliary amine have the N,N-dialkylamino group in the 4 position.

[0037] The structure of the auxiliary amine will be different from that of the compound of formula I, although more than one compound having structural formula I may be present in the coinitiator. Furthermore, more than one auxiliary amine may be present in the coinitiator, in particular one or more compounds having formulae II-III as described below may be present in addition to or as an alternative to the compounds present in Table 1.

[0038] In a particularly preferred embodiment, the compound according to formula I is present in a mixture with an auxiliary amine (also a coinitiator) according to formula II, including any stereoisomers thereof.

[0039] Formula II

[0040]

[0041] wherein r, s and t independently represent an integer of 0-20.

[0042] In one embodiment, the compound of Formula II can be such that r, s, and t are all equal to zero.

[0043] In another embodiment, the compound of formula II may be an ethoxylated compound. Thus, the compound of formula II may have at least one of r, s and t not equal to 0. In particular, the sum of r+s+t may be 1-30, 4-25, or 6-20. More particularly, r, s and t may independently represent integers of 0-20, 1-10 or 2-5.

[0044] The auxiliary amine may comprise a compound of formula II as defined above.

[0045] In another particularly preferred embodiment, the compound according to formula I is present in a mixture with an auxiliary amine coinitiator according to formula III.

[0046] Formula III

[0047]

[0048] wherein u, v and w independently represent integers of 0-20.

[0049] In one embodiment, the compound of Formula III may have u, v and w all equal to zero.

[0050] In another embodiment, the compound of formula III may be an ethoxylated compound. Thus, the compound of formula III may have at least one of u, v and w not equal to 0. In particular, the sum of u+v+w may be 1-30, 4-25, or 6-20. More particularly, u, v and w may independently represent integers of 0-20, 1-10 or 2-5.

[0051] The auxiliary amine may comprise a compound of formula III as defined above.

[0052] The auxiliary amine may include a compound of formula IV

[0053] Formula IV

[0054]

[0055] wherein x, y, z and z' independently represent an integer of 0-20.

[0056] In one embodiment, the compound of Formula IV can be such that x, y, z, and z' are all equal to zero.

[0057] In another embodiment, the compound of formula IV may be an ethoxylated compound. Thus, the compound of formula IV may have at least one of x, y, z and z' not equal to 0. In particular, the sum of x+y+z+z' may be 1-30, 4-25, or 6-20. More particularly, x, y, z and z' may independently represent integers of 0-20, 1-10 or 2-5.

[0058] The auxiliary amine may include a compound of formula V

[0059] Formula V

[0060]

[0061] wherein a', b' and c' independently represent an integer of 0-20.

[0062] In one embodiment, the compound of Formula V can be such that a', b' and c' are all equal to zero.

[0063] In another embodiment, the compound of formula V may be an ethoxylated compound. Thus, the compound of formula V may have at least one of a', b' and c' not equal to 0. In particular, the sum of a'+b'+c' may be 1-30, 4-25, or 6-20. More particularly, a', b' and c' may independently represent integers of 0-20, 1-10 or 2-5.

[0064] The coinitiator is present as a mixture of a compound of formula I and one or more auxiliary amines. The percentage of the compound according to formula I in the mixture may be in the range of 0.1-99.9 wt %, preferably in the range of 5-95 wt %, more preferably in the range of 70-90 wt %, based on the weight of the coinitiator mixture. Within these ranges, the coinitiator (i.e., the mixture of the compound of formula I and the auxiliary amine) may be formulated to provide a balance between reactivity and solubility. The remainder of the mixture will consist of the auxiliary amine.

[0065] The coinitiator mixture may include 0.1-99.9%, 5-95%, 10-90%, 15-85%, 20-80%, 25-75%, 30-70%, 35-65%, 40-60%, or 45-55% by weight of the compound of Formula I, based on the weight of the coinitiator mixture. The amount of auxiliary amine in the coinitiator mixture may account for the supplementary amount for 100% by weight of the coinitiator mixture. In particular, the coinitiator mixture may include 0.1-99.9%, 5-95%, 10-90%, 15-85%, 20-80%, 25-75%, 30-70%, 35-65%, 40-60%, or 45-55% by weight of the auxiliary amine, based on the weight of the coinitiator mixture.

[0066] Alternatively, the coinitiator mixture may include 0.1-99.9%, 5-95%, 10-90%, 20-90%, 30-90%, 40-90%, 50-90%, 60-90%, 70-90%, or 80-90% by weight of the compound of Formula I, based on the weight of the coinitiator mixture. The amount of auxiliary amine in the coinitiator mixture may constitute a supplementary amount for 100% by weight of the coinitiator mixture. In particular, the coinitiator mixture may include 0.1-99.9%, 5-95%, 10-90%, 10-80%, 10-70%, 10-60%, 10-50%, 10-40%, 10-30%, or 10-20% by weight of the auxiliary amine, based on the weight of the coinitiator mixture.

[0067] Alternatively, the coinitiator mixture may include 0.1-99.9%, 5-95%, 10-90%, 10-80%, 10-70%, 10-60%, 10-50%, 10-40%, 10-30%, or 10-20% by weight of the compound of Formula I, based on the weight of the coinitiator mixture. The amount of auxiliary amine of the coinitiator mixture may constitute a supplementary amount for 100% by weight of the coinitiator mixture. In particular, the coinitiator mixture may include 0.1-99.9%, 5-95%, 10-90%, 20-90%, 30-90%, 40-90%, 50-90%, 60-90%, 70-90%, or 80-90% by weight of the auxiliary amine, based on the weight of the coinitiator mixture.

[0068] The compound of formula I preferably has a molecular weight of greater than 500 Daltons, more preferably greater than 800 Daltons (often in the range 500-1500 Daltons, or in the range 800-1200 Daltons) to ensure controlled migration of the molecule. It is possible that the auxiliary amine has a molecular weight similar to that of the compound of formula I to improve compatibility in the coinitiator (e.g. by providing a compound of similar viscosity). Therefore, the auxiliary amine may also have a molecular weight greater than 500 Daltons, more preferably greater than 800 Daltons (often in the range 500-1500 Daltons, or in the range 800-1200 Daltons).

[0069] Some non-limiting examples of auxiliary amines that may be included in the coinitiator mixture together with the compound according to formula I are given in Table 1.

[0070] Table 1

[0071]

[0072]

[0073]

[0074] In a second aspect of the invention, a co-initiator mixture comprising a compound according to formula I is combined with one or more Type I or Type II photoinitiators to obtain a photoinitiator blend. Preferably, a Type I photoinitiator is present in the photoinitiator blend. Type I photoinitiators are more likely to form a stable mixture with an amine co-initiator with minimal cross-reaction. In addition, a mixture of a Type I photoinitiator and an amine co-initiator may form a liquid blend. Liquid blends are often more convenient to handle than solid mixtures. For ease of formulation, the photoinitiator may be present in solid or liquid form as appropriate.

[0075] Type I or Type II photoinitiators may be selected from benzoins, benzoin ethers, acetophenones, α-hydroxyacetophenones, aminoacetophenones, benzyl, benzyl ketals, anthraquinones, phosphine oxides, acylphosphine oxides, α-hydroxyketones, phenylglyoxylates, α-aminoketones, benzophenones, thioxanthones, xanthones, acridine derivatives, phenazene derivatives, quinoxaline derivatives, triazine compounds, benzoylformates, aromatic oximes, metallocenes, acylsilyl or acylgermyl compounds, camphorquinones, polymeric derivatives thereof, and mixtures thereof.

[0076] In one embodiment, the photoinitiator blend includes a Type II photoinitiator, particularly selected from diaryl ketones such as benzophenone (e.g., SpeedCure BP—Lambson Limited) or 4-benzoyl-4'-methyldiphenyl sulfide (e.g., SpeedCure BMS—Lambson Limited), thioxanthones such as 2-isopropylthioxanthone (e.g., SpeedCure 2-ITX—Lambson Limited), and combinations thereof. For certain low migration applications, diffusion hindered photoinitiators, particularly polymeric benzophenones or thioxanthones such as SpeedCure 7010 (Lambson Limited) or SpeedCure 7005 (Lambson Limited) may be used instead.

[0077] In one embodiment, the photoinitiator blend includes a Type I photoinitiator, specifically selected from acetophenone, α-hydroxyacetophenone such as 2-hydroxy-2-methyl-1-phenylpropanone (e.g. SpeedCure 73—Lambson Limited), aminoacetophenone, phosphine oxides, and mixtures thereof. SpeedCure 73 can advantageously form a liquid formulation with the co-initiators of the present invention, thereby providing processing benefits.

[0078] The co-initiator mixture as defined in the first aspect of the invention may be present in the photoinitiator blend in a total concentration in the range of 1-99 wt %, more preferably in a concentration in the range of 10-90 wt %, most preferably in a concentration in the range of 40-70 wt %, of the total weight of the photoinitiator blend. These ranges provide a suitable balance between reactivity and viscosity.

[0079] In a third aspect of the invention, a radiation curable composition is provided, which comprises the co-initiator mixture of the first aspect of the invention, one or more photoinitiators and one or more polymerizable monomers, oligomers or prepolymers. Typically, the photoinitiator will be a Type I or Type II photoinitiator as described above.

[0080] The radiation curable composition preferably comprises the co-initiator mixture as defined in the first aspect of the present invention in a concentration in the range of 0.1-50 wt.-%, more preferably in the range of 0.5-25 wt.-%, most preferably in the range of 1-10 wt.-%, based on the total weight of the radiation curable composition. The photoinitiator is typically present in the range of 1-5 wt.-% based on the total weight of the radiation curable composition.

[0081] Examples of photoinitiators that can be used in radiation curable compositions with the co-initiator mixture as defined by the present invention include diaryl ketones such as benzophenone (e.g. SpeedCure BP—Lambson Limited) or 4-benzoyl-4'-methyldiphenyl sulfide (e.g. SpeedCure BMS—Lambson Limited), or thioxanthones such as 2-isopropylthioxanthone (e.g. SpeedCure 2-ITX—Lambson Limited), or combinations of these, without limitation. For certain low migration applications, diffusion hindered photoinitiators such as SpeedCure 7010 (Lambson Limited) or SpeedCure 7005 (Lambson Limited) may be used instead.

[0082] The polymerizable monomers, oligomers or prepolymers that can be used in the radiation curable composition together with the co-initiator can include any polymerizable compound known in the art, but preferably are compounds containing monofunctional or multifunctional acrylates or methacrylates because these structures provide good reactivity. Examples would include neopentyl glycol diacrylate, trimethylolpropane triacrylate, di(trimethylolpropane) tetraacrylate, dipentaerythritol pentaacrylate, hydroxyethyl methacrylate or bisphenol A dimethacrylate, and ethoxylated or propoxylated variants thereof, without limitation.

[0083] In one embodiment, the radiation curable composition of the present invention includes a (meth)acrylate(root) functionalized compound. The radiation curable composition may include a mixture of (meth)acrylate(root) functionalized compounds. (Meth)acrylate(root) functionalized compounds can be described as organic compounds with one or more (meth)acrylate(root) functional groups per molecule. (Meth)acrylate(root) functionalized compounds are capable of participating in free radical reactions or anionic reactions, particularly reactions initiated by ultraviolet radiation or electron beam radiation. Such reactions can lead to polymerization or curing, whereby the (meth)acrylate(root) functionalized compound becomes part of a polymeric matrix or polymer chain. In various embodiments of the present invention, the (meth)acrylate(root) functionalized compound may contain one, two, three, four, five or more (meth)acrylate(root) functional groups per molecule. A combination of various (meth)acrylate(root) functionalized compounds containing different numbers of (meth)acrylate(root) groups may be used in the radiation curable composition of the present invention.

[0084] Thus the radiation curable compositions of the present invention may contain one or more (meth)acrylate(s) functional compounds capable of free radical and / or anionic polymerization (curing) initiated by exposure to UV or electron beam radiation. The (meth)acrylate(s) functional compound may be an oligomer or a monomer or a combination of oligomer(s) and monomer(s).

[0085] In one embodiment, the radiation curable composition may include one or more (meth)acrylate(yl) functional monomers, one or more (meth)acrylate(yl) functional oligomers, and mixtures thereof.

[0086] As used herein, the term "(meth)acrylate(yl)-functionalized monomer" means a monomer comprising a (meth)acrylate(yl) group, in particular an acrylate(yl) group. The term "(meth)acrylate(yl)-functionalized oligomer" means an oligomer comprising a (meth)acrylate(yl) group, in particular an acrylate(yl) group.

[0087] Any of the following types of (meth)acrylate functionalized compounds can be used, for example, in the radiation-curable compositions of the present invention: monomers such as (meth)acrylates of aliphatic monoalcohols, alkoxylated (meth)acrylates of aliphatic monoalcohols, (meth)acrylates of aliphatic polyols, alkoxylated (meth)acrylates of aliphatic polyols, (meth)acrylates of aromatic ring-containing alcohols, and alkoxylated (meth)acrylates of aromatic ring-containing alcohols; and oligomers such as epoxy (meth)acrylates, polyether (meth)acrylates, urethane (meth)acrylates, polyester (meth)acrylates, amine- and sulfide-modified derivatives thereof; and combinations thereof.

[0088] In one embodiment, the radiation curable composition includes a (meth)acrylate(yl)functional monomer.The radiation curable composition may include a mixture of (meth)acrylate(yl)functional monomers.

[0089] The (meth)acrylate-functional monomer may have a molecular weight of less than 600 g / mol, specifically 100-550 g / mol, more specifically 200-500 g / mol.

[0090] The (meth)acrylate(ate)-functional monomer may have 1 to 6 (meth)acrylate(ate) groups, specifically 1 to 3 (meth)acrylate(ate) groups, more specifically 1 to 3 acrylate(ate) groups.

[0091] The (meth)acrylate(s) functional monomers may include mixtures of (meth)acrylate(s) functional monomers having different functionalities. For example, the (meth)acrylate(s) functional monomers may include mixtures of (meth)acrylate(s) functional monomers containing a single acrylate(s) or methacrylate(s) group per molecule (referred to herein as "mono(meth)acrylate(s) functional compounds") and (meth)acrylate(s) functional monomers containing 2 or more, preferably 2 or 3, acrylate(s) and / or methacrylate(s) groups per molecule.

[0092] In one embodiment, the (meth)acrylate(root) functionalized monomer includes a mono(meth)acrylate(root) functionalized monomer. The mono(meth)acrylate(root) functionalized monomer can advantageously act as a reactive diluent and reduce the viscosity of the composition of the present invention. Examples of suitable mono(meth)acrylate(root) functionalized monomers include, but are not limited to, mono(meth)acrylates of aliphatic alcohols (wherein the aliphatic alcohol may be linear, branched or alicyclic and may be a monohydric alcohol, a dihydric alcohol or a polyhydric alcohol, provided that only one hydroxyl group is esterified with (meth)acrylate); mono(meth)acrylates of aromatic alcohols (e.g., phenols, including alkylated phenols); mono(meth)acrylate alkyls of alkylaryl alcohols (e.g., benzyl alcohol); oligomeric and polymeric glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, and polypropylene glycol. mono(meth)acrylates); mono(meth)acrylates of monoalkyl ethers of glycols and oligomeric glycols; mono(meth)acrylates of alkoxylated (e.g., ethoxylated and / or propoxylated) aliphatic alcohols (wherein the aliphatic alcohol may be linear, branched or alicyclic and may be a monohydric alcohol, a dihydric alcohol or a polyhydric alcohol, provided that only one hydroxyl group of the alkoxylated aliphatic alcohol is esterified with (meth)acrylate); mono(meth)acrylates of alkoxylated (e.g., ethoxylated and / or propoxylated) aromatic alcohols (e.g., alkoxylated phenols); caprolactone mono(meth)acrylates; and the like.

[0093] The following compounds are specific examples of mono(meth)acrylate(root)functional monomers suitable for use in the radiation-curable compositions of the present invention: methyl(meth)acrylate; ethyl(meth)acrylate; n-propyl(meth)acrylate; n-butyl(meth)acrylate; isobutyl(meth)acrylate; n-hexyl(meth)acrylate; 2-ethylhexyl(meth)acrylate; n-octyl(meth)acrylate; isooctyl(meth)acrylate; n-decyl(meth)acrylate; n-dodecyl(meth)acrylate; tridecyl(meth)acrylate; tetradecyl(meth)acrylate; hexadecyl(meth)acrylate; 2-hydroxyethyl(meth)acrylate; 2- and 3-hydroxypropyl(meth)acrylate; 2-methoxyethyl(meth)acrylate; 2-ethoxyethyl(meth)acrylate; 2- and 3-ethoxypropyl(meth)acrylate; tetrahydrofurfuryl(meth)acrylate; alkoxylated tetrahydrofurfuryl(meth)acrylate; 2-( 2-ethoxyethoxy)ethyl ester; cyclohexyl (meth)acrylate; glycidyl (meth)acrylate; isodecyl (meth)acrylate: 2-phenoxyethyl (meth)acrylate; lauryl (meth)acrylate; alkoxylated phenol (meth)acrylate; alkoxylated nonylphenol (meth)acrylate; cyclic trimethylolpropane formal (meth)acrylate; isobornyl (meth)acrylate; tricyclodecane methanol (meth)acrylate; tert-butyl cyclohexanol (meth)acrylate ; trimethylcyclohexanol (meth)acrylate; diethylene glycol monomethyl ether (meth)acrylate; diethylene glycol monoethyl ether (meth)acrylate; diethylene glycol monobutyl ether (meth)acrylate; triethylene glycol monoethyl ether (meth)acrylate; ethoxylated lauryl (meth)acrylate; methoxy polyethylene glycol (meth)acrylate; hydroxyethyl-butyl carbamate (meth)acrylate; 3-(2-hydroxyalkyl)oxazolidinone (meth)acrylate; and combinations thereof.

[0094] In one embodiment, the (meth)acrylate(root) functionalized monomer may include a (meth)acrylate(root) functionalized monomer containing two or more (meth)acrylate(root) groups per molecule. Examples of suitable (meth)acrylate(root) functionalized monomers containing two or more (meth)acrylate(root) groups per molecule include acrylates and methacrylates of polyhydric alcohols (organic compounds containing two or more, for example, 2-6 hydroxyl groups per molecule). Specific examples of suitable polyhydric alcohols include C 2-20 Alkylene glycol (having C 2-10Alkylene group diols may be preferred, wherein the carbon chain may be branched; for example, ethylene glycol, trimethylene glycol, 1,2-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, tetramethylene glycol (1,4-butylene glycol), 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,12-dodecanediol, cyclohexane-1,4-dimethanol, bisphenol, and hydrogenated bisphenol, and alkoxylated (e.g., ethoxylated and / or propoxylated) derivatives thereof), diethylene glycol, glycerol, alkoxylated glycerol, triethylene glycol, dipropylene glycol, tripropylene glycol, trimethylolpropane, alkoxylated trimethylolpropane, diethylene glycol, dipropylene ... (trimethylolpropane), alkoxylated di(trimethylolpropane), pentaerythritol, alkoxylated pentaerythritol, dipentaerythritol, alkoxylated dipentaerythritol, cyclohexanediol, alkoxylated cyclohexanediol, cyclohexanedimethanol, alkoxylated cyclohexanedimethanol, norbornene dimethanol, alkoxylated norbornene dimethanol, norbornane dimethanol, alkoxylated norbornane dimethanol, polyols containing aromatic rings, cyclohexane-1,4-dimethanol ethylene oxide adduct, bisphenol ethylene oxide adduct, hydrogenated bisphenol ethylene oxide adduct, bisphenol propylene oxide adduct, hydrogenated bisphenol propylene oxide adduct, cyclohexane-1,4-dimethanol propylene oxide adduct, sugar alcohols and alkoxylated sugar alcohols. Such polyhydric alcohols may be fully or partially esterified (with (meth)acrylic acid, (meth)acrylic anhydride, (meth)acryloyl chloride, etc.), provided that they contain at least two (meth)acrylate functional groups per molecule. As used herein, the term "alkoxylated" refers to compounds containing one or more oxyalkylene moieties (e.g., oxyethylene and / or oxypropylene moieties). The oxyalkylene moieties correspond to the general structure -RO-, where R is a divalent aliphatic moiety such as -CH2CH2- or -CH2CH(CH3)-. For example, the alkoxylated compound may contain 1-30 oxyalkylene moieties per molecule.

[0095] Exemplary (meth)acrylate functional monomers containing two or more (meth)acrylate groups per molecule may include ethoxylated bisphenol A di(meth)acrylate; triethylene glycol di(meth)acrylate; ethylene glycol di(meth)acrylate; tetraethylene glycol di(meth)acrylate; polyethylene glycol di(meth)acrylate; 1,4-butanediol diacrylate; 1,4-butanediol dimethacrylate; diethylene glycol diacrylate; diethylene glycol dimethacrylate, 1,6-hexanediol diacrylate; 1,6-hexanediol dimethacrylate; neopentyl glycol diacrylate; neopentyl glycol di(meth)acrylate; polyethylene glycol ( 600) dimethacrylate (where 600 refers to the approximate number average molecular weight of the polyethylene glycol portion); polyethylene glycol (200) diacrylate; 1,12-dodecanediol dimethacrylate; tetraethylene glycol diacrylate; triethylene glycol diacrylate, 1,3-butylene glycol dimethacrylate, tripropylene glycol diacrylate, polybutadiene diacrylate; methylpentanediol diacrylate; polyethylene glycol (400) diacrylate; ethoxylated 2-bisphenol A dimethacrylate; ethoxylated 3-bisphenol A dimethacrylate; ethoxylated 3-bisphenol A diacrylate; cyclohexanedimethanol dimethacrylate; cyclohexanedimethanol diacrylate; ethoxylated 10 Bisphenol A dimethacrylate (where the number following "ethoxylated" is the average number of oxyalkylene moieties per molecule); dipropylene glycol diacrylate; ethoxylated 4-bisphenol A dimethacrylate; ethoxylated 6-bisphenol A dimethacrylate; ethoxylated 8-bisphenol A dimethacrylate; alkoxylated hexanediol diacrylate; alkoxylated cyclohexanedimethanol diacrylate; dodecane diacrylate; ethoxylated 4-bisphenol A diacrylate; ethoxylated 10 Bisphenol A diacrylate; polyethylene glycol (400) dimethacrylate; polypropylene glycol (400) dimethacrylate; metallic diacrylate / salt; modified metallic diacrylate / salt; metallic dimethacrylate / salt; polyethylene glycol (1000) dimethacrylate; methacrylated polybutadiene; propoxylated 2-neopentyl glycol diacrylate; ethoxylated 30 Bisphenol A dimethacrylate; ethoxylated 30Bisphenol A diacrylate; alkoxylated neopentyl glycol diacrylate; polyethylene glycol dimethacrylate; 1,3-butylene glycol diacrylate; ethoxylated 2-bisphenol A dimethacrylate; dipropylene glycol diacrylate; ethoxylated 4-bisphenol A diacrylate; polyethylene glycol (600) diacrylate; polyethylene glycol (1000) dimethacrylate; tricyclodecane dimethanol diacrylate; propoxylated neopentyl glycol diacrylates such as propoxylated 2-neopentyl glycol diacrylate; alkoxylated aliphatic alcohol diacrylates; trimethylolpropane trimethacrylate; trimethylolpropane triacrylate; tris(2-hydroxyethyl)isocyanurate triacrylate; ethoxylated 20 Trimethylolpropane triacrylate; Pentaerythritol triacrylate; Ethoxylated 3-trimethylolpropane triacrylate; Propoxylated 3-trimethylolpropane triacrylate; Ethoxylated 6-trimethylolpropane triacrylate; Propoxylated 6-trimethylolpropane triacrylate; Ethoxylated 9-trimethylolpropane triacrylate; Alkoxylated trifunctional acrylate; Trifunctional methacrylate (root) ester; Trifunctional acrylate (root) ester; Propoxylated 3-glyceryl triacrylate; Propoxylated 5.5 Glyceryl triacrylate; ethoxylated 15 trimethylolpropane triacrylate; trifunctional phosphate; trifunctional acrylate; pentaerythritol tetraacrylate; di-trimethylolpropane tetraacrylate; ethoxylated 4-pentaerythritol tetraacrylate; pentaerythritol polyoxyethylene tetraacrylate; dipentaerythritol pentaacrylate; and pentaacrylate.

[0096] The radiation-curable composition of the present invention may include 10-80%, specifically 15-75%, more specifically 20-70% by weight of (meth)acrylate(radical)-functional monomers, based on the total weight of the radiation-curable composition.

[0097] In one embodiment, the radiation curable composition comprises a (meth)acrylate(yl) functional oligomer.The radiation curable composition may comprise a mixture of (meth)acrylate(yl) functional oligomers.

[0098] The (meth)acrylate(yl)-functionalized oligomer may be selected to enhance the flexibility, strength, and / or modulus, as well as other properties, of the cured polymer prepared using the radiation-curable composition of the present invention.

[0099] The (meth)acrylate(ate)-functional oligomer may have 1 to 18 (meth)acrylate(ate) groups, specifically 2 to 6 (meth)acrylate(ate) groups, more specifically 2 to 6 acrylate(ate) groups.

[0100] The (meth)acrylate-functional oligomer may have a number average molecular weight equal to or greater than 600 g / mol, specifically 800-15,000 g / mol, more specifically 1,000-5,000 g / mol.

[0101] In particular, the (meth)acrylate-functionalized oligomer may be selected from (meth)acrylate-functionalized urethane oligomers (sometimes also referred to as "urethane (meth)acrylate oligomers", "polyurethane (meth)acrylate oligomers", or "carbamate (meth)acrylate oligomers"), (meth)acrylate-functionalized epoxy oligomers (sometimes also referred to as "epoxy (meth)acrylate oligomers"), The present invention also includes (meth)acrylate functionalized polyether oligomers (sometimes also referred to as "polyether (meth)acrylate oligomers"), (meth)acrylate functionalized polydiene oligomers (sometimes also referred to as "polydiene (meth)acrylate oligomers"), (meth)acrylate functionalized polycarbonate oligomers (sometimes also referred to as "polycarbonate (meth)acrylate oligomers"), and (meth)acrylate functionalized polyester oligomers (sometimes also referred to as "polyester (meth)acrylate oligomers"), and mixtures thereof.

[0102] Preferably, the (meth)acrylate(root) functionalized oligomer comprises a (meth)acrylate functionalized urethane oligomer, more preferably an acrylate functionalized urethane oligomer. Advantageously, the (meth)acrylate(root) functionalized oligomer comprises a (meth)acrylate functionalized urethane oligomer having two (meth)acrylate groups, more preferably an acrylate functionalized urethane oligomer having two acrylate groups.

[0103] Exemplary polyester (meth) acrylate oligomers include the reaction products of acrylic acid or methacrylic acid or mixtures thereof or synthetic equivalents with hydroxyl-terminated polyester polyols. The reaction process may be carried out such that all or substantially all of the hydroxyl groups of the polyester polyol have been (meth) acrylated, particularly where the polyester polyol is difunctional. The polyester polyol may be manufactured by the polycondensation reaction of a polyhydroxyl-functional component (particularly a diol) and a polycarboxylic acid-functional compound (particularly a dicarboxylic acid and anhydride). The polyhydroxyl-functional component and the polycarboxylic acid-functional component may each have a linear, branched, alicyclic or aromatic structure and may be used alone or as a mixture.

[0104] Examples of suitable epoxy (meth)acrylates include reaction products of acrylic acid or methacrylic acid or mixtures thereof with epoxy resins (polyglycidyl ethers or esters). The epoxy resins may be selected in particular from bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, brominated bisphenol A diglycidyl ether, brominated bisphenol F diglycidyl ether, brominated bisphenol S diglycidyl ether, epoxy novolac resins, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether, 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylic acid esters, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-1,4-dioxane, adipate bis(3,4-epoxycyclohexyl methyl ester), vinylcyclohexene epoxide, 4-vinylepoxycyclohexane, adipate bis(3,4-epoxy-6-methylcyclohexyl methyl ester), 3,4-epoxy-6-methylcyclohexyl-3',4'-epoxy-6'-methylcyclohexanecarboxylate, methylene bis(3,4-epoxycyclohexyl) alkyl), dicyclopentadiene diepoxide, ethylene glycol di(3,4-epoxycyclohexyl methyl) ether, ethylene bis(3,4-epoxycyclohexane carboxylate), 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, aliphatic polyhydric alcohols such as ethylene glycol that are oxidized by one or more alkylene oxides , propylene glycol, and glycerol, polyglycidyl ethers of polyether polyols obtained by adding propylene glycol, and glycerol, diglycidyl esters of aliphatic long-chain dibasic acids, monoglycidyl ethers of aliphatic higher alcohols, phenol, cresol, butylphenol, or monoglycidyl ethers of polyether alcohols obtained by adding alkylene oxides to these compounds, glycidyl esters of higher fatty acids, epoxidized soybean oil, epoxy butyl stearic acid, epoxy octyl stearic acid, epoxidized linseed oil, epoxidized polybutadiene, etc.

[0105] Suitable polyether (meth) acrylate oligomers include, but are not limited to, condensation products of acrylic acid or methacrylic acid or their synthetic equivalents or mixtures with polyether alcohols (e.g., polyethylene glycol, polypropylene glycol, or polytetramethylene glycol) as polyether polyols. Suitable polyether alcohols may be linear or branched species containing ether bonds and terminal hydroxyl groups. Polyether alcohols may be prepared by ring-opening polymerization of cyclic ethers such as tetrahydrofuran or oxiranes (e.g., ethylene oxide and / or propylene oxide) with initiator molecules. Suitable initiator molecules include water, polyhydroxy functional materials, polyester polyols, and amines.

[0106] Polyurethane (meth)acrylate oligomers (sometimes also referred to as "urethane (meth)acrylate oligomers") suitable for use in the radiation-curable compositions of the present invention include urethanes based on aliphatic, cycloaliphatic and / or aromatic polyester polyols and polyether polyols and aliphatic, cycloaliphatic and / or aromatic polyester diisocyanates and polyether diisocyanates terminated with (meth)acrylate end groups. Suitable polyurethane (meth)acrylate oligomers include, for example, urethane di- and tetraacrylate oligomers based on aliphatic polyesters, urethane di- and tetraacrylate oligomers based on aliphatic polyethers, and urethane di- and tetraacrylate oligomers based on aliphatic polyesters / polyethers.

[0107] Polyurethane (meth) acrylate oligomers can be prepared by reacting aliphatic, alicyclic and / or aromatic polyisocyanates (e.g., diisocyanates, triisocyanates) with terminal OH group type polyester polyols, polyether polyols, polycarbonate polyols, polycaprolactone polyols, polyorganosiloxane polyols (e.g., polydimethylsiloxane polyols), or polydiene polyols (e.g., polybutadiene polyols), or combinations thereof to form isocyanate functionalized oligomers, which are then reacted with hydroxyl functional (meth) acrylates such as hydroxyethyl acrylate or hydroxyethyl methacrylate to provide terminal (meth) acrylate groups. For example, polyurethane (meth) acrylate oligomers can contain two, three, four or more (meth) acrylate functional groups per molecule. Other addition orders can also be practiced to prepare polyurethane (meth) acrylates, as is known in the art. For example, a hydroxyl-functional (meth)acrylate may first be reacted with a polyisocyanate to obtain an isocyanate-functional (meth)acrylate, which may then be reacted with an OH-terminated polyester polyol, a polyether polyol, a polycarbonate polyol, a polycaprolactone polyol, a polydimethylsiloxane polyol, a polybutadiene polyol, or a combination thereof. In another embodiment, a polyisocyanate may first be reacted with a polyol (including any of the aforementioned types of polyols) to obtain an isocyanate-functional polyol, which may then be reacted with a hydroxyl-functional (meth)acrylate to produce a polyurethane (meth)acrylate. Alternatively, all components may be combined and reacted simultaneously.

[0108] Suitable acrylic (meth)acrylate oligomers (sometimes also referred to in the art as "acrylic oligomers") include oligomers that can be described as having an oligomeric acrylic backbone, functionalized with one or more (meth)acrylate groups, which can be at the end of the oligomer or pendant to the acrylic backbone. The acrylic backbone can be a homopolymer, a random copolymer, or a block copolymer composed of repeating units of acrylic monomers. The acrylic monomers can be any monomeric (meth)acrylate such as C1-C6 alkyl (meth)acrylates and functionalized (meth)acrylates such as (meth)acrylates with hydroxyl, carboxylic acid and / or epoxy groups. Acrylic (meth)acrylate oligomers can be prepared using any procedure known in the art, for example, by oligomerizing a monomer at least a portion of which is functionalized with hydroxyl, carboxylic acid and / or epoxy groups (e.g., hydroxyalkyl (meth)acrylates, (meth)acrylic acid, glycidyl (meth)acrylate) to obtain a functionalized oligomer intermediate, which is then reacted with one or more (meth)acrylate-containing reactants to introduce the desired (meth)acrylate functional groups.

[0109] Any of the above types of oligomers may be modified with amines or sulfides (e.g., thiols) according to procedures known in the art. Such amine and sulfide modified oligomers may be prepared, for example, by reacting a relatively small portion (e.g., 2-15%) of the (meth)acrylate functional groups present in the base oligomer with an amine (e.g., a secondary amine) or a sulfide (e.g., a thiol), wherein the modifying compound adds to the carbon-carbon double bond of the (meth)acrylate in a Michael addition reaction.

[0110] The radiation curable composition of the present invention may include 10-80%, specifically 15-75%, more specifically 20-70% by weight of the (meth)acrylate(radical) functional oligomer, based on the total weight of the radiation curable composition.

[0111] The coinitiator mixture according to the invention can be used in any radiation-curable composition including varnishes, lacquers or printing inks. The composition may additionally contain other additives such as dispersants, dispersion synergists, inhibitors, surfactants, or colorants, i.e. pigments or dyes.

[0112] Co-initiators including compounds according to Formula I can be prepared by simple condensation reactions between suitable acid chlorides and two or more alcohols or polyols including di(trimethylolpropane) to provide a mixture of product esters in the same reaction vessel (Scheme 1). The mixture can then be separated and purified using acid-base extraction.

[0113] Solution 1

[0114]

[0115] Where R 1 and R 2 n and m independently represent a methyl or ethyl group and n and m represent an integer. Often n and m will independently be an integer in the range of 1-8, often in the range of 2-4, inclusive.

[0116] Depending on the stoichiometry of the polyol and the acid chloride used, the use of only one polyol, in particular di(trimethylolpropane), can also give mixtures of completely and partially substituted products, thus also leading to product mixtures (Scheme 2).

[0117] Solution 2

[0118]

[0119] Where R 1 and R 2 independently represents a methyl or ethyl group.

[0120] The corresponding ethoxylated compounds are obtainable in an analogous manner using ethoxylated polyols, in particular ethoxylated di(trimethylolpropane).

[0121] Examples of suitable acid chlorides for making co-initiators comprising compounds according to formula I include 4-(dimethylamino)benzoyl chloride, 4-(diethylamino)benzoyl chloride and 4-[ethyl(methyl)amino]benzoyl chloride, or their hydrochlorides.

[0122] Examples of suitable polyols for making co-initiators including compounds according to Formula I include di(trimethylolpropane), trimethylolpropane, glycerol, pentaerythritol, dipentaerythritol, tripentaerythritol, sorbitol, mannitol, glucose, sucrose, neopentyl glycol, any ethoxylated or propoxylated variants thereof, and any stereoisomeric forms thereof, without limitation.

[0123] Alternatively, a coinitiator comprising a compound according to Formula I may be prepared by separately synthesizing (e.g., by reaction of an alcohol with a suitable acid chloride) a compound of Formula I and an auxiliary amine, which may then be combined in the desired ratio, e.g., by dissolving the compounds in a suitable solvent and then removing the solvent to provide a mixture.

[0124] N,N-dimethylaminobenzoic acid esters can be prepared from N,N-dimethylaminobenzoic acid using the methods described above, which can itself be prepared via reductive alkylation of nitrobenzoic acid in the presence of formaldehyde, a suitable reducing agent (e.g., hydrogen) and a suitable catalyst. Acid chlorides can be prepared by reacting carboxylic acids with a suitable chlorinating agent such as thionyl chloride (Scheme 3).

[0125] To prepare the N,N-diethylamino variants of these products, the necessary N,N-diethylaminobenzoic acid intermediate can be prepared via reductive alkylation of nitrobenzoic acid in the presence of acetaldehyde, a reducing agent, and a catalyst. Mixed methyl and ethyl substituted derivatives can be prepared via stepwise alkylation using both formaldehyde and acetaldehyde in sequence.

[0126] Solution 3

[0127]

[0128] Where R represents H or a methyl group

[0129] Alternatively, a mixture of polyfunctional nitrobenzoates can be prepared by esterification of nitrobenzoic acid with one or more polyols (including di(trimethylolpropane)) in the presence of an acid catalyst such as sulfuric acid or p-toluenesulfonic acid (Scheme 4). Reductive alkylation of this mixture of nitrobenzoates using formaldehyde or acetaldehyde in the presence of a suitable reducing agent and catalyst can likewise afford a mixture of dialkylaminobenzoates including compounds according to Formula I (Scheme 5).

[0130] Solution 4

[0131]

[0132] Wherein n and m represent integers. Often n and m will independently be integers in the range of 1-8, often in the range of 2-4, including 2, 3 and 4.

[0133] Solution 5

[0134]

[0135] wherein R represents H or a methyl group and n and m represent integers. Often n and m will independently be integers in the range of 1-8, often in the range of 2-4, inclusive.

[0136] Dialkylaminobenzoate derivatives can also be prepared via nucleophilic aromatic substitution reactions between dialkylamines (e.g., dimethylamine or diethylamine) and fluorobenzoate derivatives in the presence of a suitable base (Scheme 6). Other halogen-substituted aromatic esters such as chlorobenzoates or bromobenzoates, or compounds containing other leaving groups such as iodide or triflate, can also be used under more vigorous conditions or if a cross-coupling catalyst such as a transition metal salt is used.

[0137] Solution 6

[0138]

[0139] Where R 1 and R 2 independently represent a methyl or ethyl group and R 4 represents any substituent.

[0140] Surprisingly, it was found that the coinitiator mixtures prepared using these methods, including compounds according to formula I, are sufficiently soluble in acrylate resins and have broad applicability in UV curing processes, whereas the individual components are not sufficiently soluble to be used alone. Furthermore, the mixtures show high reactivity, despite the high molecular weight of the components in preferred embodiments of the invention.

[0141] Unless otherwise stated, each of the integers described may be used in combination with any other integer, as will be understood by those skilled in the art. In addition, while all aspects of the present invention preferably "include" the features described in relation to that aspect, it is specifically contemplated that they may be "composed of" or "consisting essentially of" those features outlined in the claims. In addition, unless specifically defined herein, all terms are intended to be given their meanings as commonly understood in the art.

[0142] Furthermore, in discussing the present invention, unless stated to the contrary, the disclosure of alternative values ​​for the upper and lower limits of the permitted range for a parameter should be interpreted as an implicit statement that each intermediate value between the smaller and larger alternative values ​​of the parameter is itself also disclosed as a possible value for the parameter.

[0143] Furthermore, unless otherwise indicated, all numerical values ​​appearing in this application are to be understood as being modified by the term "about."

[0144] In order that the present invention can be easily understood, it will be further described hereinafter with reference to the accompanying drawings and specific embodiments.

[0145] Figure 1Illustrate the migration (mobility) of amine co-initiators (amines SpeedCure EDB and SpeedCure 7040, and mixture AM1) into acetonitrile at 60°C for 10 days, averaged from three runs (including standard deviation);

[0146] Figure 2 Illustrates the migration of amine co-initiators (amines SpeedCure EDB and SpeedCure 7040, and mixture AM1) into 50% v / v ethanol in deionized water at 60°C for 10 days, averaged from three runs (including standard deviation); and

[0147] Figure 3 Illustrated are the migration (including standard deviation) of amine co-initiators (amines SpeedCure EDB and SpeedCure 7040, and mixture AM1) into 3% w / v acetic acid in deionized water at 60°C for 10 days, averaged from three runs.

[0148] The following examples relate to the preparation methods of preferred examples of the present invention, and are followed by descriptions of the results of relevant tests performed on the materials. Example

[0149] Material

[0150] All materials used in the examples are readily available from standard commercial sources such as Sigma-Aldrich Company Ltd. and Tokyo Chemical Industry Ltd. unless otherwise stated. Ethoxylated bisphenol A dimethacrylate (EO / phenol 10) and tripropylene glycol diacrylate are available from Sartomer. Ebercryl 40 is available from Allnex.

[0151] Example 1: Synthesis of amine co-initiator component

[0152] Synthesis of 4-(Dimethylamino)benzoyl chloride hydrochloride

[0153]

[0154] At room temperature, N,N-dimethylformamide (7.0mL, 91.0mmol) is added to a stirred suspension of 4-dimethylaminobenzoic acid (300g, 1.82mol) in toluene (1.5L) and the mixture is heated to 65°C. At this temperature, thionyl chloride (158mL, 2.18mol) is added with about 1.5h, and the reaction mixture is heated for another 5h at 60-65°C. During this time, the starting material dissolves, thereby obtaining a two-phase orange solution. Analysis by HPLC shows that the reaction at this stage is complete. Concentration under reduced pressure obtains an acyl chloride as a mixture of hydrochloride and free amine, which is immediately used in the next step.

[0155] Synthesis of amine AC1 (compound of formula Ia)

[0156]

[0157] At room temperature with 30 minutes triethylamine (508mL, 3.64mol) is added to the suspension of 4-(dimethylamino)benzoyl chloride hydrochloride (1.82mol) in toluene (2.5L) being stirred.Di(trimethylolpropane) (118g, 0.473mol) is added once and the mixture is heated to 85 ℃ for 16h.Allow the mixture to cool to room temperature and add water (1L).The layers are separated and the organic layer is washed with water (2x500mL), saturated sodium bicarbonate solution (500mL) and salt solution (500mL).The organic phase is dried (MgSO ), concentrated under reduced pressure and thoroughly dried to obtain the crude product (368g, 96%) as a light cream solid. A portion of the solid (30 g) was recrystallized from boiling ethyl acetate (150 mL) to give the pure product as a colorless solid, which was redissolved in dichloromethane (100 mL), concentrated under reduced pressure and dried thoroughly under vacuum to give the pure product AC1. 1 H NMR (400MHz, CDCl3); 7.87 (d, J = 9.0 Hz, 8H), 6.59 (d, J = 9.0 Hz, 8H), 4.32 (d, J = 1.5 Hz, 8H), 3.51 (s, 4H), 3.01 (s, 24H), 1.62 (q, J = 7.5Hz, 4H), 0.91 (t, J = 7.5Hz, 6H).

[0158] Synthesis of amine AC2 (compound of formula II)

[0159]

[0160] Triethylamine (42.4mL, 303mmol) was added to the stirred suspension of 4-(dimethylamino)benzoyl chloride hydrochloride (151mmol) in toluene (125mL) at room temperature for 10 minutes.Di(trimethylolpropane) (12.6g, 50.5mmol) was added once and the mixture was heated to 85°C for 16h. The mixture was allowed to cool to room temperature and water (50mL) was added. The layers were separated and the organic layer was washed with water (2x50mL), saturated sodium bicarbonate solution (50mL) and brine (50mL). The organic phase was dried (MgSO4) and concentrated under reduced pressure to obtain a crude product. The pure product AC2 (4.7g, 13%) as a colorless solid was obtained by purification by column chromatography (eluting with 50:1 dichloromethane-methanol). 1 H NMR(400MHz, CDCl3);7.98-7.66(m,6H),6.73-6.49(m,6H),4.45-4.15(m,6H),3.62-3.28(m,6H),3.0 2(s,18H),1.62(q,J=7.5Hz,2H),1.46(q,J=7.5Hz,2H),0.96(t,J=7.5Hz,3H),0.86(t,J=7.5Hz,3H).

[0161] Synthesis of amine AC3 (compound of formula III)

[0162]

[0163] Triethylamine (17.0 mL, 121 mmol) was added to a stirred suspension of 4-(dimethylamino)benzoyl chloride hydrochloride (60.6 mmol) in toluene (50 mL) at room temperature over 5 minutes. Trimethylolpropane (2.85 g, 21.3 mmol) was added all at once and the mixture was heated to 90 °C for 16 h. The mixture was allowed to cool to room temperature and water (50 mL) was added. The layers were separated and the organic layer was washed with water (2x50 mL), saturated sodium bicarbonate solution (50 mL) and brine (50 mL). The organic phase was dried (MgSO4) and concentrated under reduced pressure to give the crude product. Recrystallization from 6:1 ethyl acetate-toluene (70 mL) gave the pure product (6.2 g, 51%) as a light cream solid, which was redissolved in dichloromethane (50 mL), concentrated under reduced pressure and dried thoroughly under vacuum to give the pure product AC3. 1H NMR (400MHz, CDCl3): 7.87 (d, J = 9.0Hz, 6H), 6.60 (d, J = 9.0Hz, 6H), 4.41 (s, 6H), 3.01 (s, 18H), 1.72 (q, J = 7.5Hz, 2H), 0.99 (t, J = 7.5Hz, 3H).

[0164] Synthesis of amine AC4 (compound of formula IV)

[0165]

[0166] Triethylamine (17.0 mL, 121 mmol) was added to a stirred suspension of 4-(dimethylamino)benzoyl chloride hydrochloride (60.6 mmol) in toluene (50 mL) at room temperature over 5 minutes. Pentaerythritol (2.15 g, 15.8 mmol) was added in one portion and the mixture was heated to 90 °C for 16 h, during which time solids precipitated. The mixture was allowed to cool to room temperature and tert-butyl methyl ether (70 mL) was added. The solids were collected by filtration and washed with water (100 mL), methanol (100 mL) and tert-butyl methyl ether (50 mL) to give the crude product. Recrystallization from boiling acetonitrile gave the pure product as a cream solid (7.1 g, 62%), which was redissolved in dichloromethane (50 mL), concentrated under reduced pressure and dried thoroughly under vacuum to give the pure product AC4. 1 H NMR (400MHz, CDCl3); 7.88 (d, J = 9.0 Hz, 8H), 6.58 (d, J = 9.0 Hz, 8H), 4.62 (s, 8H), 3.00 (s, 24H).

[0167] Synthesis of amine AC5 (compound of formula V)

[0168]

[0169] Triethylamine (8.5 mL, 60.6 mmol) was added to a stirred suspension of 4-(dimethylamino)benzoyl chloride hydrochloride (30.3 mmol) in toluene (25 mL) at room temperature over 5 minutes. Glycerol (0.85 g, 9.23 mmol) was added all at once and the mixture was heated to 90° C. for 16 h. The mixture was allowed to cool to room temperature and saturated sodium bicarbonate solution (50 mL) was added. The layers were separated and the organic layer was washed with saturated sodium bicarbonate solution (50 mL), water (50 mL) and brine (50 mL). The organic phase was dried (MgSO 4 ) and concentrated under reduced pressure to give the crude product. Recrystallization from boiling acetonitrile gave the pure product (1.28 g, 26%) as a light cream solid, which was redissolved in dichloromethane (30 mL), concentrated under reduced pressure and thoroughly dried under vacuum to give the pure product AC5. 1 H NMR (400MHz, CDCl3); 7.95-7.90 (m, 6H), 6.63-6.61 (m, 6H), 5.74 (p, J = 5.0Hz, 1H), 4.62 (qd, J = 12.0 and 5.0Hz, 4H), 3.02 (s, 18H).

[0170] Example 2: Preparation of Coinitiator Mixture

[0171] Preparation of amine mixture AM1

[0172] An 82:18 mixture of AC1 and AC2 respectively:

[0173]

[0174] Triethylamine (508mL, 3.64mol) was added to a stirred suspension of 4-(dimethylamino)benzoyl chloride hydrochloride (1.82mol) in toluene (2.5L) at room temperature over 30 minutes. Di(trimethylolpropane) (118g, 0.473mol) was added once and the mixture was heated to 85°C for 16h. The mixture was allowed to cool to room temperature and water (1L) was added. The layers were separated and the organic layer was washed with water (2x500mL), saturated sodium bicarbonate solution (500mL) and brine (500mL). The organic phase was dried (MgSO4), concentrated under reduced pressure and thoroughly dried to obtain the product as a light cream solid containing two products AC1 and AC2 (368g, 96% yield) in a ratio of approximately 82:18 (by HPLC area %).

[0175] Preparation of amine mixture AM2

[0176] 50:50 w / w mixture of AC1 and AC2 respectively: Neat solid amines AC1 and AC2 were combined in proportion to obtain a 50:50 w / w mixture and the solid mixture was dissolved in dichloromethane to obtain a homogeneous solution. The solvent was removed under vacuum on a rotary evaporator and the obtained solid was thoroughly dried under vacuum to obtain mixture AM2.

[0177] Preparation of amine mixture AM3

[0178] 25:75 w / w mixture of AC1 and AC2 respectively: Neat solid amines AC1 and AC2 were combined in proportion to give a 25:75 w / w mixture and the solid mixture was dissolved in dichloromethane to give a homogeneous solution. The solvent was removed under vacuum on a rotary evaporator and the resulting solid was thoroughly dried under vacuum to give mixture AM3.

[0179] Preparation of amine mixture AM4

[0180] 85:15 w / w mixture of AC1 and AC3 respectively: Neat solid amines AC1 and AC3 were combined in proportion to obtain a 85:15 w / w mixture and the solid mixture was dissolved in dichloromethane to obtain a homogeneous solution. The solvent was removed under vacuum on a rotary evaporator and the resulting solid was thoroughly dried under vacuum to obtain mixture AM4.

[0181] Preparation of amine mixture AM5

[0182] 85:15 w / w mixture of AC1 and AC4 respectively: Neat solid amines AC1 and AC4 were combined in proportion to obtain a 85:15 w / w mixture and the solid mixture was dissolved in dichloromethane to obtain a homogeneous solution. The solvent was removed under vacuum on a rotary evaporator and the resulting solid was thoroughly dried under vacuum to obtain a mixture AM5.

[0183] Preparation of amine mixture AM6

[0184] 85:15 w / w mixture of AC1 and AC5 respectively: Neat solid amines AC1 and AC5 were combined in proportion to obtain a 85:15 w / w mixture and the solid mixture was dissolved in dichloromethane to obtain a homogeneous solution. The solvent was removed under vacuum on a rotary evaporator and the resulting solid was thoroughly dried under vacuum to obtain a mixture AM6.

[0185] Example 3: Solubility test

[0186] This example illustrates the improved solubility of a coinitiator mixture compared to a single component amine coinitiator composition, thereby illustrating the benefit of providing a composition comprising both a compound of Formula I and an auxiliary amine. For comparison, the solubility of amine mixtures as provided by the present invention (mixtures AM1-AM6 being representative examples thereof) was tested in addition to single component formulations comprising only amines AC1-AC5.

[0187] Prepare the mixture of amine synergists using one of the following methods.

[0188] Solid amines AC1-AC5 or amine mixtures AM1-AM6 were added batchwise in 1% w / w portions to a stirred 5.0 g sample of the following acrylate resins and the sample was stirred at 15-20°C until all solid material was completely dissolved: HDDA (1,6-hexanediol diacrylate), TMPTA (trimethylolpropane triacrylate), TPGDA (tripropylene glycol diacrylate). At the concentrations given below (Tables 2a-2k), all solids remained dissolved at 15-20°C for at least 7 days unless otherwise stated. In cases where solids began to crystallize out of solution during this time, the mixture was warmed to approximately 40°C to redissolve the solids and the concentration was adjusted to the given value by adding additional resin, whereupon the solids remained dissolved at the adjusted concentration at 15-20°C for at least 7 days. Solubility above 10% w / w was not tested in any case. The weight % is based on the total weight of the mixture.

[0189] Table 2a – Amine Coinitiator AC1

[0190] Acrylate Solubility (% w / w at ~15-20°C) HDDA 5 TMPTA 4 TPGDA 3

[0191] Table 2b – Amine Coinitiators AC2

[0192] Acrylate Solubility (% w / w at ~15-20°C) HDDA 10 TMPTA 10 TPGDA 10

[0193] Table 2c – Amine Coinitiators AC3

[0194] Acrylate Solubility (% w / w at ~15-20°C) HDDA <2 TMPTA <2 TPGDA <2

[0195] Although the solid material initially dissolved at 2% w / w, it crystallized out from all three resins within 24 h.

[0196] Table 2d – Amine Coinitiators AC4

[0197] Acrylate Solubility (% w / w at ~15-20°C) HDDA <1 TMPTA <1 TPGDA <1

[0198] The solid material did not dissolve at 1% w / w.

[0199] Table 2e – Amine Coinitiator AC5

[0200] Acrylate Solubility (% w / w at ~15-20°C) HDDA <1 TMPTA <1 TPGDA <1

[0201] The solid material did not dissolve at 1% w / w.

[0202] Table 2f – Amine Mixture AM1

[0203] Acrylate Solubility (% w / w at ~15-20°C) HDDA 10 TMPTA 10 TPGDA 7

[0204] Table 2g – Amine Mixture AM2

[0205] Acrylate Solubility (% w / w at ~15-20°C) HDDA 10 TMPTA 10 TPGDA 10

[0206] Table 2h - Amine Mixture AM3

[0207] Acrylate Solubility (% w / w at ~15-20°C) HDDA 10 TMPTA 10 TPGDA 10

[0208] Table 2i - Amine Mixture AM4

[0209] Acrylate Solubility (% w / w at ~15-20°C) HDDA 6 TMPTA 6 TPGDA 4

[0210] Table 2j – Amine Mixture AM5

[0211] Acrylate Solubility (% w / w at ~15-20°C) HDDA 5 TMPTA 6 TPGDA 3

[0212] Table 2k – Amine Mixture AM6

[0213] Acrylate Solubility (% w / w at ~15-20°C) HDDA 6 TMPTA 6 TPGDA 4

[0214] Surprisingly, the amine mixtures AM1–AM6 exhibited better solubility in acrylate resins than most of the neat amine co-initiators AC1–AC5 and were comparable to AC2 alone.

[0215] Example 4: Curing Experiment

[0216] The following examples illustrate the high cure speed of coinitiators containing compounds of formula I and auxiliary amines. For comparison, the commercially available amine coinitiator SpeedCure EDB (Lambson Limited) and the diffusion-hindered polymeric amine SpeedCure 7040 (Lambson Limited) were also tested. In addition, neat amines AC1-AC5 were tested in addition to the mixtures provided by the present invention (mixtures AM1-AM6 are representative examples thereof).

[0217] The amine co-initiator or co-initiator mixture (0.20 g) was added to a resin mixture (4.0 g) containing 1% w / w SpeedCure 2-ITX (Lambson Limited) and 4% w / w SpeedCure BP (Lambson Limited) in 70:30 ethoxylated bisphenol A dimethacrylate (EO / phenol 10):trimethylolpropane triacrylate at 15-20° C. with stirring until all solid material had dissolved. In cases where the solid amine did not dissolve, these formulations were not tested.

[0218] The formulations were cured at 6 and 24 μm film thicknesses using a Dymax curing instrument under a Hg lamp with a belt speed of approximately 16 m / min. The number of passes under the lamp required to obtain a 'tack free' (TF) coating (as determined when the surface of the coating no longer feels tacky when lightly touched) or complete cure as determined by the 'thumb twist' test (TT) (i.e. until no visible marks are produced when the thumb is pressed firmly down on the coating with a twisting motion) are given in Table 3.

[0219] Table 3

[0220]

[0221]

[0222] *Not cured after 30 passes under lamp

[0223] **The amine was not dissolved in the formulations and therefore these formulations were not tested.

[0224] Clearly, all of the amine mixtures AM1-AM6 are effective amine co-initiators for promoting fast UV cure under these conditions. The mixtures exhibit comparable reactivity to SpeedCure EDB and much higher reactivity than the diffusion hindered polymeric amine co-initiator SpeedCure 7040. Surprisingly, the relatively high molecular weight of the amines present in the mixtures AM1-AM6 did not adversely affect their performance as co-initiators compared to the smaller molecule SpeedCure EDB. Amines AC3-AC5 were not sufficiently soluble in the acrylate resin formulations tested, but the amine mixtures AM1-AM6 were completely soluble at this concentration.

[0225] Example 5: Migration experiment

[0226] The following examples illustrate the potential of using mixtures of amine co-initiators as defined by the present invention as low migration co-initiator systems.

[0227] Formulations containing 90% w / w Ebecryl 40 (Allnex), 4% w / w SpeedCure BP (Lambson Limited), 1% w / w SpeedCure 2-ITX (Lambson Limited) and 5% w / w SpeedCure EDB, SpeedCure 7040 (Lambson Limited) or amine co-initiator mixture AM1 were cured on paper strips at 24 μm films under a Hg lamp until fully cured (as determined by the 'thumb twist' test, see Example 3). The cured paper strips were each cut into approximately 100 cm 2 The size of each paper strip was measured and the mass of cured resin adhered to each paper was recorded. The cured paper strips were each immersed in 15 mL of solvent in a sealed pressure container and kept in an oven at 60°C for 10 days; the solvents used were acetonitrile, 50% v / v ethanol in water, or 3% w / v acetic acid in water. All containers were then allowed to cool to 20-25°C and the paper strips were removed from the simulant solvent. Samples of each solvent were filtered and injected onto an HPLC, and all components dissolved in the solvent were eluted using an appropriate HPLC method. Comparison of the peak area with a previously prepared calibration curve allowed calculation of the mass of amine co-initiator present in the injected volume of solvent, and therefore also allowed calculation of the total amount of dissolved amine dissolved in 15 mL of simulant solvent for each sample. Since SpeedCure 7040 and mixture AM1 contained multiple components, the peak areas of all components in these mixtures were added together. The total amount of amine that has migrated from the cured film into the simulant solvent is expressed as a percentage of the total amount of amine present on each cured tape (taken as 5% of the total amount of cured resin on the tape) in Tables 4-6 and Figure 1-3 All experiments were performed in triplicate and the results were averaged for each amine. SpeedCure 2-ITX and SpeedCure BP (along with other minor impurities) were also seen to migrate from the cured film into the surrounding solvent in each case, but these were not quantified.

[0228] Table 4 - Migration of amine co-initiators into acetonitrile at 60 °C for 10 days, average of three runs

[0229] Amine Coinitiator Migrated amine weight % SpeedCure EDB 47.5 Amine mixture AM1 15.6 SpeedCure 7040 6.3

[0230] Table 5 - Migration of amine co-initiators into 50% v / v ethanol in deionized water at 60 °C for 10 days, average of three runs

[0231] Amine Coinitiator Weight % of migrated amine SpeedCure EDB 42.6 Amine mixture AM1 6.6* SpeedCure 7040 5.6**

[0232] *Some of the coinitiator mixture AM1 was converted to ethyl (4-dimethylamino)benzoate (<0.5%) due to the experimental conditions; this was detected in the solvent and quantified by HPLC. This amount is included in the total migration percentage given. 4-Dimethylaminobenzoic acid was also detected (approximately <0.5% of the total mass of coinitiator in the cured film), but was not precisely quantified.

[0233] **This value includes ethyl (4-dimethylamino)benzoate, which is typically present in some amount in Speedcure 7040, although it is also expected that some of the 7040 has been converted to ethyl (4-dimethylamino)benzoate due to the experimental conditions. 4-Dimethylaminobenzoic acid was not detected.

[0234] Table 6 - Migration of amine co-initiators into 3% w / v acetic acid in deionized water at 60°C for 10 days, average of three runs

[0235] Amine Coinitiator Weight % of migrated amine SpeedCure EDB 3.5 Amine mixture AM1 <0.001* SpeedCure 7040 1.3**

[0236] * None of the components of mixture AM1 were detected in the solvent above this limit. 4-Dimethylaminobenzoic acid was not detected as a potential hydrolysis product of any of these components.

[0237] **4-Dimethylaminobenzoic acid was not detected.

[0238] In all cases, the high molecular weight amine co-initiator mixture AM1, which is a preferred example of the present invention, migrated from the cured film into the surrounding solvent to a much lower extent than the relatively low molecular weight co-initiator SpeedCure EDB. In the case of the food simulant solvents aqueous ethanol and aqueous acetic acid (simulating alcoholic and acidic foods, respectively), the migration of mixture AM1 was much lower than SpeedCure EDB, and no detectable amount of any component of mixture AM1 was detected in the aqueous acetic acid solvent system. In the ethanol / water solvent system, mixture AM1 had migration properties very similar to those of the polymeric amine co-initiator SpeedCure 7040 with a higher average molecular weight, although the mixture AM1 was not polymeric. Therefore, the present invention provides a novel co-initiator system that not only has good solubility in acrylate resins, but also has migration properties similar to those of commercial polymeric amine co-initiators, while also promoting significantly faster UV cure speeds, as demonstrated in the previous examples.

Claims

1. A coinitiator mixture for UV curing comprising at least one aminobenzoate compound according to formula I and at least one auxiliary amine Formula I Wherein in Formula I, R 1 and R 2 independently represent a methyl or ethyl group; and j, k, l and m independently represent an integer of 0-20, Wherein the auxiliary amine comprises at least one aminobenzoate derivative having a different structure from the compound of formula I, wherein the auxiliary amine comprises a compound selected from the following: Formula II wherein r, s and t independently represent an integer from 0 to 20; Formula III Wherein u, v and w independently represent an integer of 0-20; Formula IV wherein x, y, z and z' independently represent an integer of 0-20; Formula V wherein a', b' and c' independently represent an integer from 0 to 20; wherein a and b independently represent integers from 0 to 20; or wherein c, d, e, and f independently represent integers from 0 to 20.

2. The coinitiator of claim 1, wherein the percentage of the compound according to formula I is in the range of 0.1-99.9 wt.-%, based on the weight of the coinitiator mixture.

3. The coinitiator of claim 2, wherein the percentage of the compound according to formula I is in the range of 5-95 wt.-%, based on the weight of the coinitiator mixture.

4. The coinitiator of claim 3, wherein the percentage of the compound according to formula I is in the range of 70-90 wt.-%, based on the weight of the coinitiator mixture.

5. The coinitiator of claim 1, wherein the auxiliary amine is selected from:

6. The coinitiator of any one of claims 1 to 5, wherein R 1 and R 2 It is methyl.

7. The coinitiator according to any one of claims 1 to 5, wherein the N,N-dialkylamino group in formula I is in the 4-position relative to the ester group.

8. The coinitiator according to any one of claims 1 to 5, wherein in compounds according to formula I, j, k, l and m are all equal to 0.

9. The coinitiator according to any one of claims 1 to 5, wherein at least one of the compounds j, k, l and m according to formula I is not equal to 0.

10. The coinitiator of claim 9, wherein the sum of j+k+l+m is 1-30.

11. The coinitiator of claim 10, wherein the sum of j+k+l+m is 4-25.

12. The coinitiator of claim 11, wherein the sum of j+k+l+m is 6-20.

13. The coinitiator of claim 1, wherein j, k, l and m independently represent an integer from 1 to 10.

14. The coinitiator of claim 13, wherein j, k, l and m independently represent an integer from 2 to 5.

15. The coinitiator of any one of claims 1 to 5, wherein the compound according to formula I has a structure according to formula Ia Formula Ia wherein n, o, p and q independently represent an integer of 0-20.

16. The coinitiator of claim 15, wherein in the compound according to formula Ia n, o, p and q are all equal to 0.

17. The coinitiator of claim 15, wherein at least one of n, o, p and q of the compound according to formula Ia is not equal to 0.

18. The coinitiator of claim 17, wherein the sum of n+o+p+q is 1-30.

19. The coinitiator of claim 18, wherein the sum of n+o+p+q is 4-25.

20. The coinitiator of claim 19, wherein the sum of n+o+p+q is 6-20.

21. The coinitiator of claim 15, wherein n, o, p and q independently represent an integer from 1 to 10.

22. The coinitiator of claim 21, wherein n, o, p and q independently represent an integer from 2 to 5.

23. A photoinitiator blend comprising the co-initiator of any one of claims 1 to 22, and one or more Type I or Type II photoinitiators.

24. A radiation curable composition comprising the coinitiator of any one of claims 1 to 22, one or more Type I or Type II photoinitiators and one or more polymerizable monomers, oligomers or prepolymers.

25. The radiation curable composition of claim 24 which is a UV curable coating or ink.

26. The radiation curable composition of claim 24 or 25, further comprising a colorant.

27. A cured material obtained by curing the radiation curable composition according to any one of claims 24 to 26.

28. A low migration cured material obtained by curing the radiation curable composition according to any one of claims 24 to 26.

29. Use of a radiation curable composition according to any one of claims 24 to 26 as ink, lacquer or varnish.

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