Photoinitiators for photocurable compositions

Abstract

The present invention relates to oligomeric photoinitiating resin, wherein the oligomeric photoinitiating resin comprises m terminal groups according to formula (I) and n terminal groups according to formula (II): wherein m is equal to or greater than 1, n is equal to or greater than 1, m + n is equal to or greater than 3, R1, R2 and R3 are independently selected from hydrogen, a linear C1-C6 alkyl or a branched C3-C6 alkyl, X1, X2, X3, X4 and X5 are independently selected from hydrogen, a linear C1-C6 alkyl, a branched C3-C6 alkyl, C5-C7 cycloalkyl, phenyl, C1-C4 alkoxy, C5-C7 cycloalkoxy or phenoxy, or X1 and X2 together may form an aromatic ring, or X2 and X3 together may form an aromatic ring, each symbol (A) represents a point of attachment, and wherein the oligomeric photoinitiating resin has a weight-average molecular weight Mw greater than 1000 g / mol, whereby the weight-average molecular weight Mw is determined as described in the description.

Description

[0001] PHOTOINITIATORS FOR PHOTOCURABLE COMPOSITIONS

[0002] Technical Field

[0003]

[0001] The present invention relates to photoinitiating resins that are useful as photoinitiators in free radical curable compositions, such as free radical curable coating and ink compositions. The invention further relates to free radical curable compositions comprising such a photoinitiating resin. Further, the invention relates to objects coated with such a free radical curable composition.

[0004] Background

[0005]

[0002] Nowadays coatings are used every day. Examples are items like coatings for transparent food packages, thin foils, paints, and car part finishes. UV curing or free radical photopolymerization is the fastest growing curing technique, with a continuously increasing number of applications. UV curing saves energy and reduces or eliminates solvent emission in comparison with solvent-based systems because most radiation-curable formulations are 100% solid formulations containing reactive oligomers and diluents. The mechanical properties of the cured formulations are generally determined by the oligomers and diluents. Photoinitiators are one of the key components for every photopolymerizable formulation as they generate upon light exposure radicals, which trigger the polymerization.

[0006]

[0003] A major drawback for most photopolymerizable formulations is the amount of unreacted photoinitiator molecules remaining in the cured polymer material. The high conversion rates in a very short time imply that only a few initiator molecules are able to covalently bind to the polymer network. Ways to solve this are for example irradiating for a very long period of time or using small amounts of initiator. Both ways are not suitable for industrial scale applications as short exposure times ensure the required high throughput. A reasonable conversion is normally provided by using an increased percentage of photoinitiator leading to aforementioned increased amounts of unreacted photoinitiator in the cured formulations. Next to migrating out of the cured formulation, the remaining photoinitiators can cause yellowing, generate a variety of byproducts like for example benzaldehyde which can migrate out of the cured formulations as well. Migration is especially problematic when protective and decorative coatings are applied in the field of food packaging, health care, and other all day use items, which can come in contact with humans.

[0007]

[0004] Benzophenone and its derivatives are more commonly used as photoinitiators in the packaging area. However, for benzophenone there is sufficient evidence in animal studies for its carcinogenicity and it is possible carcinogenic to humans (International Agency for Research on Cancer, “some chemicals present in industrial and consumer products, food and drinking water”, vol 101 p285-301). In fact one study (R. Z. Liu, S. A. Mabury,” First Detection of Photoinitiators and Metabolites in Human Sera from United States Donors” Environmental Science and Technology, vol 52(17), pl0089-10096 2018.) revealed that photoinitiators and co-initiators were also found in every single blood serum illustrating that photoinitiators and their photoproducts are omnipresent contaminants. This illustrates the need for free radical curable formulations in which alternative especially oligomeric photoinitiators are used. By using oligomeric photoinitiators, the migratability is dramatically reduced. An example of such an oligomeric photoinitiator is given in WO202 1 / 259924. However, in this application the basis for the oligomeric photoinitiator are still benzophenone derivatives.

[0008]

[0005] A very elegant alternative to benzophenone derivatives has been described in US2020 / 0231531, i.e., a linear polymer based on a-ketoglutaric acid and hexane diol. However, as will be demonstrated, the reactivity of such a system is low.

[0009]

[0006] Consequently, there is a need for oligomeric photoinitiators with increased reactivity in free radical curing processes.

[0010] Brief Summary

[0011]

[0007] Described herein are several aspects and embodiments of the invention. A first aspect is an oligomeric photoinitiating resin comprising a number of terminal groups according to formula (I) and a number of terminal groups according to formula (II) wherein the number of terminal groups according to formula (I) is m and m is equal to or greater than 1; the number of terminal groups according to formula (II) is n and n is equal to or greater than 1; the summed amount of m and n (m + n) is equal to or greater than 3; Ri, R2 and R3 in formula (I) are independently selected from hydrogen or a linear Ci-Ce alkyl or a branched C3-C6 alkyl; Xi, X2, X3, X4 and X5 in formula (II) are independently selected from hydrogen, a linear Ci- Ce alkyl, a branched C3-C6 alkyl, C5-C7 cycloalkyl, phenyl, C1-C4 alkoxy, C5-C7 cycloalkoxy or phenoxy, or Xi and X2 together may form an aromatic ring, or X2 and X3 may form an aromatic ring; each symbol * represents a point of attachment; and the oligomeric photoinitiating resin has a weight-average molecular weight Mwas determined by GPC (THF) greater than 1000 g / mol, whereby the weight-average molecular weight Mw is determined as described further herein.

[0012]

[0008] A second aspect of the current invention is a free radical curable composition comprising at least one oligomeric photoinitiating resin according to any one of the embodiments of the first aspect of the invention. In an embodiment of the second aspect of the current invention, the free radical curable composition is a coating or ink composition.

[0013]

[0009] A third aspect of the current invention is a coating or ink obtained by

[0014] (1) Preparing or providing a free radical curable coating or ink composition according to one of the embodiments of the second aspect of the invention,

[0015] (2) Applying the free radical curable coating or ink composition to a substrate, and

[0016] (3) Free radical curing the free radical curable coating or ink composition with a light source.

[0017] Detailed Description

[0018]

[0010] For all upper and / or lower boundaries of any range given herein, the boundary value is included in the range given, unless specifically indicated otherwise. Thus, when saying from x to y, means including x and y and also all intermediate values.

[0019] [OH] A first aspect of the current invention is an oligomeric photoinitiating resin, wherein the oligomeric photoinitiating resin comprises m terminal groups according to formula (I) and n terminal groups according to formula (II): wherein m is equal to or greater than 1, n is equal to or greater than 1, preferably n is equal to or greater than 2, m + n is equal to or greater than 3, Ri, R2 and R3 are independently selected from hydrogen, a linear Ci-Ce alkyl or a branched C3-C6 alkyl, Xi, X2, X3, X4 and X5 are independently selected from hydrogen, a linear Ci-Ce alkyl, a branched C3-C6 alkyl, C5-C7 cycloalkyl, phenyl, C1-C4 alkoxy, C5-C7 cycloalkoxy or phenoxy, or Xi and X2 together may form an aromatic ring, or X2 and X3 may form an aromatic ring, each symbol represents a point of attachment, and wherein the oligomeric photoinitiating resin has a weight-average molecular weight Mwas determined by GPC (THF) greater than 1000 g / mol, whereby the weight-average molecular weight Mw is determined as described further herein.

[0020]

[0012] It has surprisingly been found that the photoinitiators according to the invention have enhanced reactivity in free radical curable compositions, and thus resulting in a higher cure speed of the free radiation curable composition which is generally illustrated by a higher conversion of the free radical curable groups. The photoinitiators according to the invention can in particular advantageously be applied in free radical curable coating and ink compositions wherein a low migration of chemical species is required.

[0021]

[0013] In view of reduced migratability, the oligomeric photoinitiating resins according to the current invention preferably have a weight-average molecular weight Mwgreater than 1200 g / mol, more preferably greater than or equal to 1300 g / mol. Preferably, the oligomeric photoinitiating resins according to the current invention preferably have a weight-average molecular weight Mwof at most 15000 g / mol, more preferably of at most 12000 g / mol, even more preferably of at most 10000 g / mol. As used herein, weight-average molecular weight Mwis determined with the method as described further herein.

[0022]

[0014] The oligomeric photoinitiating resin according to the current invention comprises at least one terminal group according to formula (I): wherein Ri, R2 and R3 are independently selected from hydrogen or a from a linear Ci-Ce alkyl or from a branched C3-C6 alkyl. Preferably, Ri, R2 and R3 are independently selected from hydrogen or methyl. More preferably Ri, R2 and R3 are hydrogen. In case Ri, R2 and R3 are hydrogen, the terminal functional group according to formula (I) is derived from pyruvic acid with formula:

[0023]

[0015] The oligomeric photoinitiating resin according to the current invention comprises at least one terminal group according to formula (II): wherein Xi, X2, X3, X4 and X5 are independently selected from hydrogen, a linear Ci-Ce alkyl, branched C3-C6 alkyl, C5-C7 cycloalkyl, phenyl, C1-C4 alkoxy, C5-C7 cycloalkoxy or phenoxy, or Xi and X2 together may form an aromatic ring, or X2 and X3 together may form an aromatic ring. In case Xi and X2 together form an aromatic ring, preferably the group according to formula (II) is derived from 1 -naphthalene glyoxylic acid. In case X2 and X3 together form an aromatic ring, preferably the group according to formula (II) is derived from 2-naphthalene glyoxylic acid. Preferably, Xi, X2, X3, X4 and X5 are hydrogen; or Xi, X2, X4 and X5 are hydrogen and X3 is Ci- C4 alkoxy, preferably methoxy, or phenyl; or X2 and X3 together form an aromatic ring. More preferably, Xi, X2, X3, X4 and X5 are hydrogen. The oligomeric photoinitiating resin according to the current invention preferably comprises at least two terminal group according to formula (II).

[0024]

[0016] The sum of the number of terminal groups according to formula (I) (i.e., m) and the number of terminal groups according to formula (II) (i.e., n), i.e., m + n, is equal to or greater than 3. m + n is preferably equal to or greater than 4.

[0025]

[0017] The ratio of the number of terminal groups according to formula (I) (i.e., m) with respect to the number of terminal groups according to formula (II) (i.e., n) is preferably from 0.1 to 2, more preferably the ratio m : n is from 0.2 to 1.5, even more preferably the ratio m : n is from 0.2 to 1, even more preferably the ratio m : n is from 0.25 to 1 as this may result in a further increase of the reactivity of the oligomer photoinitiating resin.

[0026]

[0018] The oligomeric photoinitiating resins of the present invention can be obtained in a process that comprises at least the following steps:

[0027] (1) providing a core oligomer having at least m + n (m + n > 3, preferably m + n > 4) terminal OH functional groups, (2) (trans)esterification of m terminal OH functional groups of the core oligomer with a compound according to formula (lb) and (trans)esterification of n terminal OH functional groups of the core oligomer with a compound according to formula (Uh) : wherein Rs and Re are independently hydrogen or a C1-C4 alkyl; and Ri, R2, R3, Xi, X2, X3, X4 and X5 are as described above.

[0028]

[0019] The (trans)esterification is usually effected with a catalyst known to the skilled in the art, for example an acid catalyst such as for example methane sulfonic acid or sulfuric acid. The formed water (for Rs = H and Re = H) or the formed small alcohol (for Rs = C1-C4 alkyl and Re = C1-C4 alkyl) (methanol, ethanol,. . .) can be removed physically by the help of an entrainer such as toluene, a nitrogen gas stream, or vacuum. In a preferred embodiment, Rs = H and Re = a C1-C4 alkyl, preferably methyl or ethyl. In a more preferred embodiment, Rs = H and Re = H.

[0020] An epoxy resin, such as for example Epikote™ 828 obtainable from Hexion, can be used to scavenge the acid catalyst. Alternatively the resin can be washed to remove the acid catalyst.

[0021] For incorporation of a multitude of functional groups (including at least the m terminal functional groups with formula (I) and the n terminal groups with formula (II)), the core oligomer is preferably a branched oligomer, more preferably a highly branched oligomer, even more preferably a hyperbranched oligomer. Using branched or highly branched or hyper branched oligomers as core oligomer has the advantage that they can have a multitude of terminal groups, preferably hydroxy terminal groups which can be readily modified resulting in oligomeric photoinitiating resins according to the invention. Under highly branched oligomeric photoinitiating resins are understood in the context of the present invention oligomers having a branched structure and a high density of functional groups with formula (I) and (II). Under hyperbranched oligomeric photoinitiating resins are understood in the context of the present invention oligomers having a branched structure and an even higher density of functional groups with formula (I) and (II).

[0029] Core oligomers

[0030]

[0022] The core oligomer can be a polyether, a polyester, a polycarbonate, a polyamide, or a polyacrylic oligomer, and may optionally further comprises urethane linkages. Preferred core oligomers are polyether oligomers optionally further comprising urethane linkages or polyester oligomers optionally further comprising urethane linkages.

[0023] Polyether core oligomers are for example derived from ethoxylated or propoxylated glycerol, ethoxylated or propoxylated trimethylopropane, ethoxylated or propoxylated pentaerythritol, ethoxylated or propoxylated ditrimethylol propane, ethoxylated or propoxylated dipentaerythritol, ethoxylated or propoxylated sorbitol and / or ethoxylated or propoxylated sucrose.

[0031]

[0024] Polyester core oligomers can for example be derived from di- and / or tri acids or their esters, together with polyvalent alcohols such as di, tri, tetrols, hexols and / or octols. Examples of di-acids are adipic acid, succinic acid, ketoglutaric acid, malonic acid, maleic acid, fumaric acid and itaconic acid. An example of a triacid is trimellitic acid (or anhydride). Preferred polyvalent alcohols are the alkoxylated versions, preferably the ethoxylated or propoxylated versions, of butanediol, hexanediol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerol, trimethylol propane, pentaerythritol, di(trimethylol propane), dipentaerythritol, sorbitol and sucrose.

[0032]

[0025] Obviously hydroxyacids and / or esters can also be employed for obtaining a polyester core oligomer, examples are linear hydroxy acids like lactic acid, gamma-hydroxy butyric acid, caprolactone, branched hydroxy acids like citric acid or 2,2-dimethylol propionic acid. The latter might be used to prepare branched core oligomers of which Boltorn™ H2004 and H311 are examples. Branched amide containing cores are for example Hybrane™ cores.

[0033]

[0026] Polyester core oligomers can also be obtained via the so-called anhydride oxetane reaction. An example of such a core oligomer can be obtained by using trimellitic anhydride in combination with trimethyloloxetane.

[0034]

[0027] As mentioned before, the core oligomer can also be an acrylic oligomer having multiple hydroxyl groups. These hydroxy functional oligomers can for example be prepared via radical polymerization from for example hydroxy ethyl (meth)acrylate. The skilled artisan will recognize that other hydroxy functional unsaturated compounds can be used as well. Examples are hydroxybutyl monovinyl ether, hydroxyethyl maleimide, caprolactone acrylate, ethoxylated or propoxylated acrylic acid. The hydroxy functional unsaturated compounds can be oligomerized / polymerized on themselves or copolymerized. For that copolymerization a wide plethora of other unsaturated compounds are available such as for example various (meth) acrylates, styrene, acrylonitrile, and vinyl ethers.

[0035]

[0028] The oligomeric photoinitiating resins according to the invention can also be obtained using a one-pot synthesis in which at least one or more compounds with formula (lb), one or more compounds with formula (lib) and one or more polyvalent alcohols having at least m + n (m + n > 3, preferably m + n > 4) terminal OH functional groups and optionally one or more diacid and / or triacid or esters thereof are reacted in one step. The one or more polyvalent alcohols having at least m + n (m + n > 3, preferably m + n > 4) terminal OH functional groups are preferably alkoxylated, more preferably ethoxylated or propoxylated. Preferred polyvalent alcohols are the alkoxylated versions, preferably the ethoxylated or propoxylated versions, of butanediol, hexanediol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerol, trimethylol propane, pentaerythritol, di(trimethylol propane), dipentaerythritol, sorbitol and sucrose.

[0036]

[0029] The oligomeric photoinitiating resin according to the current invention preferably further comprises free radical polymerizable groups. These free radical polymerizable groups are preferably selected from the group consisting of methacrylates, acrylates, vinyl amides, vinyl ethers, vinyl esters, fumarates, itaconates, maleates and any combination thereof. In the case where fumarates, maleates and / or itaconates are used, these can be present in the oligomeric photoinitiating resin as terminal groups as well as in the core.

[0037]

[0030] More preferably, the oligomeric photoinitiating resin according to the current invention further comprises o terminal groups according to formula (III): wherein o is equal to or greater than 1, m + n + o is equal to or greater than 4, preferably m + n + o is equal to or greater than 5, more preferably m + n + o is equal to or greater than 6, the symbol represents a point of attachment, and

[0038] R4 is hydrogen or a linear Ci-Ce alkyl or a branched C3-C6 alkyl, preferably R4 is hydrogen or methyl, more preferably R4 is hydrogen.

[0039] In case R4 is methyl, the oligomeric photoinitiating resin according to the current invention comprises methacrylate end groups as free radical polymerizable groups. In case R4 is hydrogen, the oligomeric photoinitiating resin according to the current invention comprises acrylate end groups as free radical polymerizable groups. The oligomeric photoinitiating resin according to the current invention can then be obtained in a process that comprises at least the following steps:

[0040] (1) providing a core oligomer having at least m + n + o (m + n + o > 4, preferably m + n + o > 5, more preferably m + n + o > 6) terminal OH functional groups,

[0041] (2) (trans)esterification of m terminal OH functional groups of the core oligomer with a compound according to formula (lb) and (trans)esterification of n terminal OH functional groups of the core oligomer with a compound according to formula (Uh) and (trans)esterification of o terminal OH functional groups of the core oligomer with a compound according to formula (Illb): wherein R4 is hydrogen (the groups according to formula (III) are then acrylate groups) or R4 is methyl (the groups according to formula (III) are then methacrylate groups); and Ri, R2, R3, R4, Rs, Re, Xi, X2, X3, X4 and X5 are as described above.

[0042]

[0031] The oligomeric photoinitiating resin according to the current invention preferably comprises a number of alkoxy groups, preferably ethoxy or propoxy groups, wherein the number of alkoxy groups is at least 4, preferably at least 5, more preferably at least 8, and preferably at most 200, more preferably at most 100, most preferably at most 80.

[0043]

[0032] A second aspect of the current invention is a free radical curable composition comprising at least one oligomeric photoinitiating resin as described above.

[0044]

[0033] The amount of oligomeric photoinitiating resin according to the invention in the composition can vary within wide ranges like from 0.001 wt.% up to 99 wt.%. Preferably the amount of oligomeric photoinitiating resin according to the invention is between 0.05 wt.% and 50 wt.%, relative to the entire weight of the free radical curable composition. The amount of oligomeric photoinitiating resin according to the invention is preferably higher than 0.1 wt.%, more preferably higher that 0.5 wt.% or higher than 1 wt.% or higher than 2 wt.% and preferably lower than 40 wt.% or lower than 35 wt.% or lower than 30 wt.%, relative to the entire weight of the free radical curable composition. Depending on the amount of free radical polymerizable groups in the oligomer photoinitiating resin, higher amounts of oligomeric photoinitiating resin can be suitably employed as well. For example, when the oligomeric photoinitiating resin according to the invention comprises 2 or more acrylate end groups, the oligomeric photoinitiating resin can be considered a free radical curable oligomer by itself and can be used in amounts ranging from 20 to 70 wt.%.

[0045]

[0034] Although in case the oligomeric photoinitiating resin comprises free radical polymerizable groups, other free radical polymerizable compounds are not required, the free radical curable composition preferably further comprises one or more free radical curable oligomers having one or more free radical curable ethylenically unsaturated groups, preferably having one or more (meth)acryloyl groups or vinyl groups. The one or more oligomers having one or more free radical curable ethylenically unsaturated groups preferably have a number-average molecular weight (Mn) equal to or higher than 800 g / mol, more preferably equal to or higher than 1000 g / mol; and preferably lower than or equal to 15000 g / mol, more preferably lower than or equal to 5000 g / mol, whereby the number-average molecular weight Mnis determined as described herein below.

[0046]

[0035] The one or more oligomers having one or more free radical curable ethylenically unsaturated groups are present in the free radical curable composition in an amount of preferably at least 10 wt.%, or at least 15 wt.%, or at least 20 wt.%, and at most 80 wt.%, or at most 75 wt.%, or at most 70 wt.%, relative to the entire weight of the free radical curable composition.

[0047]

[0036] Preferably the free radical curable oligomers are selected from the group consisting of urethane (meth)acrylates, epoxy (meth)acrylates, polyester (meth)acrylates, polyether (meth)acrylates and any mixture thereof. More preferably the free radical curable oligomers are selected from the group consisting of urethane acrylates, epoxy acrylates, polyester acrylates, polyether acrylates and any mixture thereof.

[0048]

[0037] The (meth)acrylate-functionalized oligomer may be selected in order to enhance the flexibility, strength and / or modulus, among other attributes, of a cured polymer prepared using the free radical curable composition of the present invention. The (meth)acrylate functionalized oligomer may have 1 to 18 (meth)acrylate groups, in particular 2 to 6 (meth)acrylate groups, more particularly 2 to 6 acrylate groups. The (meth)acrylate functionalized oligomer may have a number-average molecular weight equal of more than 800 g / mol, in particular from 800 to 15000 g / mol, more particularly from 1000 to 5000 g / mol. In particular, the (meth)acrylate-functionalized oligomers may be selected from the group consisting of (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"), (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"), acrylic (meth)acrylate oligomers and mixtures thereof. Preferably, the (meth)acrylate-functionalized oligomer comprises a (meth)acrylate-functionalized urethane oligomer, more preferably an acrylate-functionalized urethane oligomer. Advantageously, the (meth)acrylate-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. Exemplary polyester (meth)acrylate oligomers include the reaction products of acrylic or methacrylic acid or mixtures or synthetic equivalents thereof with hydroxyl group-terminated polyester polyols. The reaction process may be conducted such that all or essentially all of the hydroxyl groups of the polyester polyol have been (meth)acrylated, particularly in cases where the polyester polyol is difunctional. The polyester polyols can be made by polycondensation reactions of polyhydroxyl functional components (in particular, diols) and polycarboxylic acid functional compounds (in particular, dicarboxylic acids and anhydrides). The polyhydroxyl functional and polycarboxylic acid functional components can each have linear, branched, cycloaliphatic or aromatic structures and can be used individually or as mixtures. 35

[0038] Examples of suitable epoxy (meth)acrylate oligomers include the reaction products of acrylic or methacrylic acid or mixtures thereof with an epoxy resin (polyglycidyl ether or ester). The epoxy resin may, in particular, by selected from bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol 6 diglycidyl ether, brominated bisphenol A diglycidyl ether, brominated bisphenol F diglycidyl ether, epoxy novolak resin, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether, 3, 4-epoxy cyclohexylmethyl 3',4’epoxycyclohexanecarboxylate, 2-(3,4- epoxycyclohexyl-5,5-spire-3,4-epoxy)cyclohexane-l,4- dioxane, bis(3,4- epoxycyclohexylmethyl)adipate, vinylcyclohexene oxide, 4-vinylepoxycyclohexane, bis(3,4- epoxy-6-methylcyclohexylmethyl)adipate,3,4-epoxy-6-methylcyclohexy l-3',4uepoxy-6u methylcyclohexanecarboxylate, methylenebis(3,4-epoxycyclohexane), dicyclopentadiene diepoxide, di (3, 4-epoxy cyclohexylmethyl) ether of ethylene glycol, ethylenebis(3, 4- epoxy cyclohexanecarboxylate), 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polyglycidyl ethers of a polyether polyol obtained by the addition of one or more alkylene oxides to an aliphatic polyhydric alcohol such as ethylene glycol, propylene glycol, and glycerol, diglycidyl esters of aliphatic long-chain dibasic acids, monoglycidyl ethers of aliphatic higher alcohols, monoglycidyl ethers of phenol, cresol, butyl phenol, or polyether alcohols obtained by the addition of alkylene oxide to these compounds, glycidyl esters of higher fatty acids, epoxidized soybean oil, epoxybutylstearic acid, epoxyoctylstearic acid, epoxidized linseed oil, epoxidized polybutadiene, and the like.

[0049]

[0039] Suitable polyether (meth)acrylate oligomers include, but are not limited to, the condensation reaction products of acrylic or methacrylic acid or synthetic equivalents or mixtures thereof with polyetherols which are polyether polyols (such as polyethylene glycol, polypropylene glycol or polytetramethylene glycol). Suitable polyetherols can be linear or branched substances containing ether bonds and terminal hydroxyl groups. Polyetherols can be prepared by ring opening polymerization of cyclic ethers such as tetrahydrofuran or alkylene oxides (e.g., ethylene oxide and / or propylene oxide) with a starter molecule. Suitable starter molecules include water, polyhydroxyl functional materials, polyester polyols and amines.

[0040] Polyurethane (meth)acrylate oligomers (sometimes also referred to as "urethane (meth)acrylate oligomers") suitable for use in the 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 diisocyanates and capped with (meth)acrylate end-groups. Suitable polyurethane (meth)acrylate oligomers include, for example, aliphatic polyester-based urethane di- and tetra-acrylate oligomers, aliphatic polyether- based urethane di- and tetra-acrylate oligomers, as well as aliphatic polyester / polyether-based urethane di- and tetraacrylate oligomers. The polyurethane (meth)acrylate oligomers may be prepared by reacting aliphatic, cycloaliphatic and / or aromatic polyisocyanates (e.g., diisocyanate, triisocyanate) with OH group terminated polyester polyols, poly ether 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-functionalized (meth)acrylates such as hydroxyethyl acrylate or hydroxyethyl methacrylate to provide terminal (meth)acrylate groups. For example, the polyurethane (meth)acrylate oligomers may contain two, three, four or more (meth)acrylate functional groups per molecule. Other orders of addition may also be practiced preparing the polyurethane (meth)acrylate, as is known in the art. For example, the hydroxyl-functionalized (meth)acrylate may be first reacted with a polyisocyanate to obtain an isocyanate-functionalized (meth)acrylate, which may then be reacted with an OH group terminated polyester polyol, polyether polyol, polycarbonate polyol, polycaprolactone polyol, polydimethysiloxane polyol, polybutadiene polyol, or a combination thereof. In yet another embodiment, a polyisocyanate may be first reacted with a polyol, including any of the aforementioned types of polyols, to obtain an isocyanate-functionalized polyol, which is thereafter reacted with a hydroxyl-functionalized (meth)acrylate to yield a polyurethane (meth)acrylate Alternatively, all the components may be combined and reacted at the same time.

[0050]

[0041] Suitable acrylic (meth)acrylate oligomers (sometimes also referred to in the art as "acrylic oligomers") include oligomers which may be described as substances having an oligomeric acrylic backbone which is functionalized with one or (meth)acrylate groups (which may be at a terminus of the oligomer or pendant to the acrylic backbone). The acrylic backbone may be a homopolymer, random copolymer or block copolymer comprised of repeating units of acrylic monomers. The acrylic monomers may be any monomeric (meth)acrylate such as Ci-Ce alkyl (meth)acrylates as well as functionalized (meth)acrylates such as (meth)acrylates bearing hydroxyl, carboxylic acid and / or epoxy groups. Acrylic (meth)acrylate oligomers may be prepared using any procedures known in the art, such as by oligomerizing monomers, at least a portion of which are 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.

[0051]

[0042] The curable composition of the invention may comprise from 10 to 80 wt.%, in particular from 15 to 75 wt.%, more particularly from 20 to 70 wt.% (meth)acrylate- functionalized oligomer, relative to the entire weight of the free radical curable composition.

[0043] For viscosity reasons it might be beneficial that reactive diluents are used. With reactive diluent is meant a compound being able to reduce the viscosity of the formulation while being able to free radically copolymerize. The invention therefore also relates to free radical curable compositions which comprise a reactive diluent. The one or more diluents having one or more, preferably two or more, free radical curable ethylenically unsaturated groups may be present in the free radical curable composition in an amount of at least 1 wt.%, or at least 5 wt.%, or at least 10 wt.%, and in an amount of at most 85 wt.%, or at most 80 wt.%, or at most 75 wt.%, or at most 70 wt.%, relative to the entire weight of the free radical curable composition.

[0052]

[0044] As reactive diluent various acrylic, methacrylic or vinyl functional monomers can be used. Suitable examples are for instance diacrylates or dimethacrylates of diols or of poly etherdiols, such as propoxylated neopentyl glycol diacrylate, 1,6- hexanediol diacrylate, dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), diethylene glycol diacrylate, triethylene glycol diacrylate, triethylenglycol dimethacrylate, neopentylglycol diacrylate, 1,4-butanediol diacrylate (e.g, SR213), alkoxylated aliphatic diacrylate (e.g. SR9209A), alkoxylated hexanediol diacrylate (e.g, SR561, SR562, SR563, SR564 from Sartomer Co., Inc), polyethylene glycol (200) diacrylate (SR259), polyether glycol-200- diacrylate, PEG300-diacrylate, polypropyleneglycol diacrylate, ethoxylated (3) bisphenol-A- diacrylate, BDDA butanediol diacrylate, BDDMA butane diol dimethacrylate or higher functional acrylates such as trimethylolpropane triacrylate (TMPTA), ethoxylated trimethylolpropane triacrylate, TMP3EOTA ethoxylated (3) trimethylolpropane triacrylate, TMP6EOTA ethoxylated (6) trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol(4)-propoxylated triacrylate, pentaerythritol tetraacrylate, , ethoxylated or propoxylated neopentylglycol, propoxylate (4) glycerol triacrylate, tri -functional monomers, such as Laromer types from BASF or Ebecryl 2047 or Ebecryl 12 from Allnex, di-trimethylolpropane tetraacrylate, dipentaerythritol-pentaacrylate (Di-PEPA), dipentaerythritol hexaacrylate (DPHA). Examples of vinyl compounds are compounds like butanediol divinyl ether or as mono functional compound N-vinyl caprolactam. Although mono functional (meth)acrylates like for example lauryl (meth)acrylate, phenoxyethyl (meth)acrylate can be used as well, it is preferred for low migratability to employ reactive diluents with at least two free radical curable ethylenically unsaturated groups. Obviously, mixtures can be used as well.

[0053]

[0045] In a preferred embodiment of the invention, the oligomeric photoinitiating resin further comprises one or more free radical curable ethylenically unsaturated groups, preferably one or more (meth)acryloyl groups or vinyl groups, more preferably at least two (meth)acryloyl groups, even more preferably at least two acryloyl groups; and the free radical curable composition optionally further comprises one or more oligomers having one or more free radical curable ethylenically unsaturated groups, preferably having one or more (meth)acryloyl groups or vinyl groups; and the free radical curable composition further comprises one or more diluents having one or more free radical curable ethylenically unsaturated groups, preferably the one or more diluents having at least least two free radical curable ethylenically unsaturated groups; and the free radical curable composition comprises: the oligomeric photoinitiating resin in an amount of from 3 to 70 wt.%, the oligomer in an amount of from 0 to 80 wt.%, the diluent in an amount of from 10 to 70 wt.%, whereby the amounts are given relative to the entire weight of (i) to (iii).

[0046] To further improve the cure speed, acrylate functional groups as free radical curable ethylenically unsaturated groups are preferred over methacrylate functional groups.

[0054]

[0047] In accordance with a further aspect, the present invention refers to a free radical curable ink composition or free radical curable coating composition comprising: a) at least one binder, b) at least one ethylenically unsaturated compound selected from monomers and / or oligomers, and c) one or more oligomeric photoinitiating resin of the present invention.

[0055]

[0048] If the free radical curable composition is a free radical curable ink composition, it contains at least one pigment. Preferably, the amount of pigment based on the total amount of the free radical curable ink composition, i.e., the composition before curing, is preferably between 0.5 and 50% by weight and more preferably from 3 to 20% by weight. The cured ink composition preferably contains from 0.5 to 50% by weight and more preferably from 3 to 20% by weight of pigment.

[0056]

[0049] In addition to the oligomeric photoinitiating resin according to the invention, other initiators can be employed as well next to various other additives. Examples for such additives are those selected from the group consisting of rheological additives, adhesion promoters, defoamers, slip additives, wetting agents, levelling agents, gloss additives, waxes, wetting agents, curing agents, chelating agents, additional photoinitiators, amine synergists, inhibitors, desiccants, stabilizers, emulsifiers, abrasion resistance additives, plasticizers, antistatic additives, matting agents and arbitrary combinations of two or more of the aforementioned additives.

[0057]

[0050] The free radical curable ink composition or free radical curable coating composition may be formulated so as to be suitable for any known printing technique, such as offset, lithography, intaglio printing, flexographic printing, gravure printing, screen printing, digital printing, inkjet printing, pad printing, transfer printing, letter printing and the like.

[0058]

[0051] Another aspect of the present invention is a process for free radical curing the free radical curable composition of the current invention, which comprises the following steps:

[0059] (1) Preparing or providing a free radical curable composition as described herein above, and

[0060] (2) Free radical curing the free radical curable composition with a light source.

[0061]

[0052] Said light source is preferably a UV light source emitting UV light in at least one of the UVA, UVB and UVC ranges or a LED source emitting light in the range from 350 to 450 nm.

[0062]

[0053] The process preferably comprises the step of applying the free radical curable composition to a substrate prior to free radical curing it.

[0063]

[0054] Another aspect of the present invention is a coating or ink obtained by

[0064] (1) Preparing or providing a free radical curable coating or ink composition as described herein above,

[0065] (2) Applying the free radical curable coating or ink composition to a substrate, and

[0066] (3) Free radical curing the free radical curable coating or ink composition with a light source.

[0067]

[0055] The following examples further illustrate the invention but, of course, should not be construed as in any way limiting its scope.

[0068] Examples

[0069]

[0056] These examples illustrate embodiments of the instant invention. Table 1 describes the various components used to prepare the oligomeric photoinitiating resins and the free radical curable compositions used in the present examples. Table 2 describes the relative amounts of the reagents described in Table 1 which were used to synthesize the oligomeric photoinitiating resins used in the present examples. Tables 3 to 6 report the photoreactivity of the oligomeric photoinitiating resins. Unless otherwise specified, all parts, percentages and ratios are on a weight basis.

[0070] Table 1 - Formulation Components Table 1 continued Preparation of formulations

[0071]

[0057] Unless otherwise specified, each of the formulations described were prepared by conventional methods by using a 50 ml mixing cup suitable for use with a Speedmixer™. The components, adding up to around 10 g in total, were added in the mixing cup. The cup was then closed and vigorously mixed in a Speedmixer™ DAC150FVZ for 5 minutes, stopped, and mixed again for 5 additional minutes via the same method.

[0072] Determination of viscosity

[0073]

[0058] Viscosities were determined on a BROOKFIELD DVNXB5CBG rheometer equipped with 2.5cm diameter / l° cone / plate geometry at 25°C at a shear rate of 100s'1. CPA-40Z spindle (2.4 cm diameter / 0.8° cone / plate geometry) was used for samples with viscosity between 0.65 and 25 Pa.s; CPA-52Z spindle (1.2 cm diameter / 3° cone / plate geometry) was used for sample with viscosity from 25-800 Pa.s.

[0074] Determination of molecular weight by GPC

[0075]

[0059] The number-average molecular weight (Mn) and the weight-average molecular weight (Mw) were measured via SEC calibrated with a set of polystyrene standards with a molecular weight range of from 500 up to 7 xlO6g / mol and using as an eluent stabilized tetrahydrofuran [THF with 0.007- 0.015% w / w butyl-hydroxytoluene (BHT)] modified with 0.8 % acetic acid, at a flow rate of 1 mL / min at 40 °C.

[0076]

[0060] More specifically, 50 mg of an oligomeric photoinitiating resin was dissolved in 5 mL eluent for 16 hours at room temperature without shaking. 10 pL of the solution thus prepared were injected into the system for the measurement.

[0077]

[0061] The SEC measurements were carried out on a Waters GPC system which consisted of: i) a Waters 2414 refractive index detector at 40°C, ii) a Waters Shodex packed Column at 40°C - with four different Shodex packed columns (5000A, 500 A, 150A and 50A pore size) with I / d = 300 / 8 mm and are filled with particles having a particle size of 10 (the 5000A) or 6 pm (the 500A , 150A and 150A column) (1 pm= 1x10-6 m), (supplied by Waters), iii) a Waters 2707 Autosampler - injection system and iv) a Waters 1515 -Isocratic HPLC pump. The n and Mwwere determined by the use of Empower 3 software from Waters. Determination of reactivity using a UV Rig

[0078]

[0062] A 12 micron thick film was prepared from the formulations on a glass plate and cured on a Fusion UV Rig equipped with a high power, water cooled 395nm LED (1.5 W / cm2) using a total dose of 0.8J / cm2or with a Fusion F600 D bulb (IW / cm2) using a total dose of 1 J / cm2or with an Fusion F600 H bulb (lW / cm2) using a total dose of 0.8J / cm2 as determined with an EIT power puck II. After cure the acrylate conversion was determined using IR spectroscopy. The error in the conversion measurement is estimated to be around +5%.

[0079] Determination of photo reactivity using Photo DSC standard procedure

[0080]

[0063] These analyses were performed using a Mettler Toledo DSC3+ equipped with a Photo DSC fixture bearing an Excelitas Omnicure LX 500 385nm LED source (1.7W / cm2) in a nitrogen atmosphere employing around 30 mg of formulation.

[0081]

[0064] The following protocol was used: After calibrating the sample for 150 seconds under nitrogen, the sample was irradiated for 150 seconds. This was followed by a dark period of 50 second followed by a 2ndirradiation for 50 seconds. The 2ndirradiation was performed in order to verify that full conversion has already been achieved during the first irradiation. The reactivity is expressed as time to maximum heat-flow (seconds) and in maximum rate of double bond conversion (in mmol s'1I’1, calculated from the maximum heat-flow (W / g) using 78.5 kJ / mol as reaction enthalpy for acrylates and an assumed density of lkg / 1).

[0082] Determination of reactivity using RT-DMA: Maximum Modulus (G) and T30%>, modulus max values

[0083]

[0065] For RT-DMA, formulations were prepared using 70 parts urethane oligomer 1 (prepared as described below), 30 parts 2-phenoxy ethyl acrylate and 5 parts of the oligomeric photoinitiating resin (prepared as described below). These formulations were analyzed on a TA instruments Rheometer (HR20) equipped with UV curing accessories (320-500 nm, OmniCure® Series 2000). The UV output intensities were calibrated at the sample position using an external radiometer. For the light guide accessory, the intensity (25 mW / cm2) was applied and recorded as total intensity without any filter. Thickness of the sample was 0.25 mm and a single frequency oscillatory measurement was carried out under a control strain of 1% at 5 Hz. Dynamic time sweep experiments were used to monitor the curing process.

[0084] Illumination started after 60 sec of measuring. Reported herein are the maximum modulus and the time to reach 30% of the maximum modulus after start of illumination as measure of cure speed.

[0085] Synthesis of oligomeric photoinitiating resin OIR 1-14 - typical procedure Synthesis of OIR 1

[0086]

[0066] Step 1) A 500 ml reactor equipped with a stirrer, nitrogen inlet, and Dean-Stark set-up was charged with 16.7 g adipic acid (Ad), 102.9 g propoxylated glycerol (POG), 240 g toluene and 0.74 g methane sulphonic acid MSA. The reaction was heated to reflux under a gentle stream of nitrogen and kept at this temperature until reaction water was no longer formed (4hr).

[0087]

[0067] Next (Step 2) 40.2 g pyruvic acid (Py) (and optional phenylglyoxylic acid (PhG) and optional acrylic acid (Ac)) was added, and the reaction mixture was heated to reflux under a gentle stream of nitrogen and kept at this temperature until reaction water was no longer formed (4hr). Next all the toluene was removed by distillation under reduced pressure at a temperature of 95°C. Next 2.7 g Epikote™ 828 was added and the reaction was stirred for another 30 min, cooled down after which OIR 1 was obtained having a viscosity of 4Pa.s at 100s'1.

[0088] Synthesis of OIR 2-14

[0089]

[0068] The synthesis of OIR 2-14 were prepared similar to OIR 1 using amounts as described in table 2.

[0090]

[0069] For example, the structural formula for OIR 5 with idealized structure AdiPP2Py2PhG2Ac2 is in which p + q + x + y is 5.

[0091] Synthesis comparative linear oligomeric example Comp LI

[0092]

[0070] The synthesis has been performed analogous to (R. Taschner, P. Gauss, P. Knaack, R. Liska, “Biocompatible Photoinitiators Based on Poly-a-ketoesters”, Journal of Polymer Science vol 58,p 242-253, (2020) except on similar scale to OIR 2-14) using 100.6 g a-ketoglutaric acid, 89.5 g hexanediol (1.1 molar equivalents), 270 g toluene and 0.7 g MSA. The resulting solid comparative initiator LI, a hydroxy functional linear polyester, had a Mi of 2.6 kg / mol, a Mwof 9.2 kg / mol and a Tmof 46-54°C (1.1 eq).

[0093] Synthesis comparative linear oligomeric example Comp L2

[0094]

[0071] The procedure for LI was repeated using 98.9 g a-ketoglutaric acid, 80.7 g hexanediol (1.01 molar equivalents, analogous to US 2020 / 0231531), 220 g toluene and 0.26 g MSA. After precipitation and evaporation of the remaining solvent, L2, a hydroxy functional linear polyester, was obtained as white powder. The resulting comparative initiator L2 had a Mn of 5.1 kg / mol, a Mwof 17.2 kg / mol and a Tm 40-51°C (l.Oleq).

[0095] Synthesis comparative linear oligomeric example Comp L3

[0096]

[0072] The procedure for LI was repeated using 100.6 g a-ketoglutaric acid, 78.6 g hexanediol (0.96 molar equivalents), 270 g toluene and 0.7 g MSA. Employing this equivalency an acid functional linear polyester was prepared. The resulting solid comparative initiator L3 had a Mnof 3.4 kg / mol, a Mwof 12.1 kg / mol and a Tmof 52-59°C (0.96eq).

[0097] Table 2: Amounts used in the synthesis of OIR1-14, their molecular weights and viscosities.

[0098] Synthesis of urethane oligomer 1

[0099]

[0073] First, a 1 L glass reactor (equipped with a stirrer, air inlet, dropping funnel, and condenser) was purged with dry lean air. Then 2.19 parts of BHT was charged into the reactor, followed by 52.76 parts of TDI, followed by 0.02 parts of acrylic acid. After charging, the reactor was heated to 45 °C. Then half of the specified amount catalyst (i.e., 0.06 g bismuth neodecanoate) followed by 35.43 parts HEA were charged into the reactor whilst stirring. After waiting one (1) hour for the reaction to commence, the temperature was then raised to 60°C. At 60 °C, 700 parts PPG4000 and the second part of the catalyst (i.e., 0.07 g) were added after which the reaction temperature was raised to 85°C which was further maintained for two (2) additional hours.

[0100] After this, two (2) additional hours of reaction time, the quantity of isocyanate (NCO) content was measured by a potentiometric titrator to ensure it was lower than 0.1% relative to the entire weight of the composition. If the isocyanate content was not lower than this value, the mixture was placed back in the reaction chamber in 15-minute additional increments (again at 85 °C) and checked again, with this step repeated until the isocyanate content fell to within the desired range. Finally, the resulting synthesized oligomer 1 with the idealized structure HEA-TDI-PPG4000-TDI-HEA was cooled slowly and discharged for use. (Reference) Examples and Comparative Experiments

[0101] Reference Example 1 and Comparative Experiment A

[0102]

[0074] Formulations were prepared in the speedmixer using 99.5 parts Neorad™ U25-20D and 0.5 parts of various oligomeric photoinitiating resins. Curing was performed on the UV Rig. The results are in table 3 below.

[0103] Table 3: UV Rig curing (dose 1 J / cm2)

[0104]

[0075] This clearly demonstrate that a branched oligomer with a structure according to the reference example yields a more efficient cure process compared to the linear oligomer LI. The high efficiency is especially surprising when comparing the amount of active chromophores present in the formulations. Even with less active chromophores, the curing proceeds much more efficient using the OIR1.

[0105] Reference Example 2-3 and Comparative Experiments B-D

[0106]

[0076] Formulations were prepared in the speedmixer using 70 parts of the urethane oligomer 1, 30 parts of phenoxy ethyl acrylate and 0.5 parts of various oligomeric photoinitiating resins as indicated in Table 4. Curing was performed using photo-DSC employing a 385nm LED. The results are shown in table 4.

[0107] Table 4: Photo-DSC curing

[0108]

[0077] These reference examples and comparative experiments also demonstrate the surprisingly high efficiency of the branched oligomeric photoinitiators with structures according to the reference examples 1 and 2 compared to the linear oligomers L1-L3.

[0109]

[0078] Note that when using ref 2 the amount of pyruvic chromophores is already reduced significantly (to 8.2 mmol / kg resin compared to 15.5 mmol / kg for ref 1). Although this chromophore reduction results in a reduced cure speed compared to ref 1, it is still higher than when using L1-L3.

[0110] Reference Example 4 and Examples 1-3

[0111]

[0079] Formulations for RT-DMA analysis were prepared using 70 parts of urethane oligomer 1, 30 parts of 2-phenoxy ethyl acrylate and 5 parts of oligomeric photoinitiating resin, the cure results using RT-DMA are shown in table 5.

[0112]

[0080] Formulations for a clear varnish OPV were prepared using 36 parts of Neorad™ U25-20D, 59 parts of Agisyn™ 2844 and 10 parts of oligomeric photoinitiating resins. These formulations were cured on the UV Rig in air (H-bulb) and the conversions were determined with IR. The cure results are also shown in table 5. Table 5

[0113]

[0081] This demonstrates that the cure speed of branched oligomeric photoinitiating resins can surprisingly be further enhanced using a combination of pyruvic with phenyl glyoxylic. This further enhancement in cure speed is surprising in light of (P. Gauss, M. Griesser, M. Markovic, A.

[0114] Ovsianikov, G. Gescheidt, P Knaack, R. Liska, Macromolecules 52, 2814 (2019)) as herein it is shown that both ethyl pyruvate and ethyl phenylglyoxylate have the same efficiency.

[0115]

[0082] It also demonstrates that preferably 2 or more phenylglyoxylate units are present in an oligomer.

[0116] Examples 4-11

[0117]

[0083] Preparing formulations and curing of these formulations were performed similar to examples 1 to 3. The results are shown in Table 6.

[0118] Table 6

[0119] These Examples further demonstrate the high curing efficiency using oligomeric photoinitiating resins according to the invention. Example 12 and Reference Example 4: Preparation of a magenta ink formulation

[0120]

[0084] A clay and wax paste was prepared from 22.5 parts ASP™ 200, 2.5 parts Ceraflour 950 and 75 parts Agisyn™ 2830 using the speed mixer.

[0121]

[0085] A magenta ink formulation was prepared from 24.75 parts Agisyn™ 717, 17.55 parts Irgalite® Rubine D 4240, 0.45 parts Genorad 16, and 2.25 parts Solsperse™ 39000. This mixture was turned into a pigment paste using a triple roll mill. Next 25 parts of the clay and wax paste prepared as described above and 30 parts of AdiSP2PyiPhG3Ac3 were added and the formulation was mixed using a speed mixer. AdiSP2PyiPhG3Ac3 was prepared as described above, except that the reaction with Epikote™828 was omitted and replaced by washing with an aqueous sodium sulphate solution. The amount of free acid was found to be low, as shown by the presence of less than 100 ppm of free acrylic acid.

[0122]

[0086] A reference ink formulation was prepared as described above, however, instead of 30 parts AdiSP2PyiPhG3Ac3, 20 parts Agisyn™ 670A2, 4.6 parts Omnipol ASA, 3.3 parts Omnipol TX, 2.0 parts Omnirad TPO-L and 0.1 parts Genorad 16 was used.

[0123]

[0087] The lithographic behavior was evaluated using a LithoTack II using a CTP300 fount (Novomatics). Offset prints were prepared using a IGT Cl -5, 300N, equipped with a rubber blanket roll (IGT testing systems) and subsequently cured with a Hg-bulb using various belt speeds. The results are reported in Table 7.

[0124] Table 7

[0088] The results as shown in Table 7 show that an offset ink with good curing characteristics can be prepared with the oligomeric initiating resin according to the invention, especially since the reference example contains 10 wt.% of photoinitiator.

Claims

What is claimed is:

1. An oligomeric photoinitiating resin, wherein the oligomeric photoinitiating resin comprises m terminal groups according to formula (I) and n terminal groups according to formula (II):wherein m is equal to or greater than 1, n is equal to or greater than 1, m + n is equal to or greater than 3,Ri, R2 and R3 are independently selected from hydrogen, a linear Ci-Ce alkyl or a branched C3-C6alkyl,Xi, X2, X3, X4 and X5 are independently selected from hydrogen, a linear Ci-Ce alkyl, a branched C3-C6 alkyl, C5-C7 cycloalkyl, phenyl, C1-C4 alkoxy, C5-C7 cycloalkoxy or phenoxy, or Xi and X2 together may form an aromatic ring, or X2 and X3 together may form an aromatic ring, each symbol represents a point of attachment, and wherein the oligomeric photoinitiating resin has a weight-average molecular weight Mwgreater than 1000 g / mol, whereby the weight-average molecular weight Mw is determined as described in the description.

2. The photoinitiating resin according to claim 1, wherein the weight-average molecular weight Mwof the photoinitiating resin is greater than 1200 g / mol, more preferably greater than or equal to 1300 g / mol.

3. The photo initiating resin according to claim 1 or 2, wherein Ri, R2 and R3 are independently selected from hydrogen or methyl, more preferably Ri, R2 and R3 are hydrogen.

4. The photoinitiating resin according to any one of the preceding claims, wherein Xi, X2, X3, X4 and X5 are hydrogen, or Xi, X2, X4 and X5 are hydrogen and X3 is C1-C4 alkoxy or phenyl, or X2 and X3 together form an aromatic ring, more preferably Xi, X2, X3, X4 and X5 are hydrogen.

5. The photoinitiating resin according to any one of the preceding claims, wherein the ratio m:n is from 0.1 to 2, more preferably from 0.2 to 1.5, even more preferably from 0.2 to 1, even more preferably from 0.25 to 1.

6. The photoinitiating resin according to any one of the preceding claims, wherein the photoinitiating resin comprises free radical polymerizable groups which are preferably selected from the group consisting of methacrylates, acrylates, vinyl amides, vinyl ethers, vinyl esters, fumarates, itaconates, maleates and any combination thereof, more preferably the free radical polymerizable groups are methacrylates and / or acrylates.

7. The photoinitiating resin according to any one of the preceding claims, wherein the photoinitiating resin comprises o terminal groups according to formula (III):o is equal to or greater than 1, m + n + o is equal to or greater than 4, preferably m + n + o is equal to or greater than 5, more preferably m + n + o is equal to or greater than 6, andR4 is hydrogen or a Ci-Ce alkyl, preferably R4 is hydrogen or methyl, more preferably R4 is hydrogen.

8. The photoinitiating resin according to any one of the preceding claims, wherein n is equal to or greater than 2.

9. The photoinitiating resin according to any one of the preceding claims, wherein the photoinitiating resin comprises a number of alkoxy groups, preferably ethoxy or propoxygroups, wherein the number of alkoxy groups is at least 4, preferably at least 5, more preferably at least 8, and preferably at most 200, more preferably at most 100, most preferably at most 80.

10. A free radical curable composition comprising at least one oligomeric photoinitiating resin according to any of claims 1 to 9.

11. The free radical curable composition according to claim 10, wherein the oligomeric photoinitiating resin is preferably present in an amount of from 0.05 to 50 wt.%, preferably from 0.1 to 40 wt.%, more preferably from 0.1 to 30 wt.%, relative to the entire weight of the free radical curable composition.

12. The free radical curable composition according to claim 10 or 11, wherein the free radical curable composition further comprises one or more oligomers having one or more free radical curable ethylenically unsaturated groups, preferably having one or more (meth)acryloyl groups or vinyl groups.

13. The free radical curable composition according to claim 12, wherein the one or more oligomers having one or more free radical curable ethylenically unsaturated groups are independently selected from urethane (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, poly ether (meth)acrylate oligomers, polyester (meth)acrylate oligomers and any mixture thereof, more preferably the one or more oligomers having one or more free radical curable ethylenically unsaturated groups are urethane (meth)acrylate oligomers, even more preferably the one or more oligomers having one or more free radical curable ethylenically unsaturated groups are urethane acrylate oligomers.

14. The free radical curable composition according to claim 12 or 13, wherein the one or more oligomers having one or more free radical curable ethylenically unsaturated groups have a number-average molecular weight (Mn) from 800 to 15000 g / mol, preferably from 1000 to 5000 g / mol, whereby the number-average molecular weight Mnis determined as described in the description.

15. The free radical curable composition according to any one of claims 12 to 14, wherein the one or more oligomers having one or more free radical curable ethylenically unsaturated groups are present in the free radical curable composition in an amount of at least 10 wt.%, or at least 15 wt.%, or at least 20 wt.%, and at most 80 wt.%, or at most 75 wt.%, or at most 70 wt.%, relative to the weight of the entire free radical curable composition.

16. The free radical curable composition according to any of claims 10 to 15, wherein the free radical curable composition further comprises one or more diluents having one or more free radical curable ethylenically unsaturated groups, preferably at least two free radical curable ethylenically unsaturated groups.

17. The free radical curable composition according to claim 16, wherein the one or more diluents having one or more free radical curable ethylenically unsaturated groups are present in the free radical curable composition in an amount of at least 1 wt.%, or at least 5 wt.%, or at least 10 wt.%, and in an amount of at most 85 wt.%, or at most 80 wt.%, or at most 70 wt.%, relative to the entire weight of the free radical curable composition.

18. The free radical curable composition according to claim 10, wherein the oligomeric photoinitiating resin comprises one or more free radical curable ethylenically unsaturated groups, preferably one or more (meth)acryloyl groups or vinyl groups, more preferably at least two (meth)acryloyl groups; the free radical curable composition optionally further comprises one or more oligomers having one or more free radical curable ethylenically unsaturated groups, preferably having one or more (meth)acryloyl groups or vinyl groups; and the free radical curable composition further comprises one or more diluents having one or more free radical curable ethylenically unsaturated groups, preferably having at least two free radical curable ethylenically unsaturated groups; and wherein the free radical curable composition comprises(i) the oligomeric photoinitiating resin in an amount of from 3 to 70 wt.%,(ii) the oligomer in an amount of from 0 to 80 wt.%,(iii) the diluent in an amount of from 10 to 70 wt.%, whereby the amounts are given relative to the entire weight of (i) to (iii).

19. The free radical curable composition according to any of claims 10 to 18, wherein the free radical curable composition is a coating or ink composition.

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