MXPA03009796A

MXPA03009796A - Photo-initiator compositions.

Info

Publication number: MXPA03009796A
Application number: MXPA03009796A
Authority: MX
Inventors: Weissman Peter
Original assignee: Ucb Sa
Priority date: 2001-04-27
Filing date: 2002-04-22
Publication date: 2004-06-30
Also published as: JP2004534117A; WO2002088192A1; EP1397393A1; KR20040015181A; CA2445268A1; CN1511166A

Abstract

Photo-initiator blends suitable for radiation curable ink formulations are disclosed which comprise a mixture of three or more photo-initiators, the mixture being a liquid at a temperature at or below ambient; the mixture comprising: (a) a first photo-initiator comprising an optionally substituted hydroxyC1-10 alkylC6-18aryl ketone which is liquid at ambient temperature; (b) a second photo-initiator comprising an optionally substituted hydroxy(cycloC3-10alkyl)C6-18aryl ketone which is solid at ambient temperature; and (c) one or more of the following photo-initiators each of which may be optionally substituted:an alpha aminoacetophenone, a C6-18aryl(((C1-10 alkyl)1-4C6-18arylcarbonyl))1-3 phosphine oxide, a benzophenone; a benzophenone derivative and/or a hydrocarbo (optionally alkyl or aryl) amino benzoate; where, (i) the first photo-initiator (a) and the second photo-initiator (b) are present in the mixture in a weight ratio of from about 0.8 to about 1.2, (ii) the first photo-initiator (a) and the second photo-initiator (b) together comprise from about 15 to about 85 percent by weight of the total mixture.

Description

COMPOSITIONS OF PHOTOINICIATORS DESCRIPTION OF THE INVENTION The present invention relates to improved liquid compositions having use, for example, as photoinitiators, such as inks suitable for use with radiation cured polymers. Inks for use in radiation-cured polymers require a photoinitiator to aid in the initiation of polymerization. It is often necessary or advisable to combine different photoinitiators together in a mixture to improve the sensitivity of the photoinitiator over a wide range of different wavelengths, so that the resulting ink can be cured more easily with the use of incident radiation comprising many different wavelengths. In general, liquid photoinitiators and combinations thereof are more convenient to use. The photoinitiator combinations of the prior art are prepared by combining at high temperatures in an oven to maintain the liquid mixture. However, this is difficult to do and may cause the resulting photoinitiator combinations to be less stable (ie, solid precipitates may form when the photoinitiator is left for extended periods). It would be advisable to provide REF: 151265 compounds and / or combinations of photoinitiators with improved stability; which are substantially liquid at ambient or lower temperatures, which can be mixed together more easily than combinations of the prior art; that are easier to use and / or that can be sent more easily. The invention relates to other aspects of the co-pending application of the applicant EP 01110473.4, the content of which is hereby described, for convenience, and is also incorporated herein by reference. Surprisingly, the applicant has discovered that certain synergistic mixtures of photoinitiators. they form liquid combinations, which solves some or all of the disadvantages, which are described herein. Therefore, generally in accordance with the present invention, a mixture of three or more photoinitiators is provided, the mixture is a liquid at a temperature at or below room temperature; the mixture comprises: (a) a first photoinitiator comprising an optionally substituted C3-.18 alkyl aryl hydroxy alkyl which is liquid at room temperature; (b) a second photoinitiator comprising a hydroxy (C3_10 alkyl) aryl of optionally substituted C6-i8 ketone which is solid at room temperature; and (c) one more of the following photoinitiators, each of which may be optionally substituted: an alpha-aminoacetophenone, an aryl oxide of C6_IB ((((Ci_10 alkyl) i-4 arylcarbonyl of C6-ie)) i- 3 phosphine, a benzophenone; a benzophenone derivative and / or a hydrocarbon amino benzoate (optionally alkyl or aryl); wherein, (i) the first photoinitiator (a) and the second photoinitiator (b) are present in the mixture in a weight ratio of about 0.8 to about 1.2, (ii) the first photoinitiator (a) and the second photoinitiator (b) ) together comprise from about 15 to about 85 weight percent of the total mixture. Preferably, the ambient temperature denotes a temperature of 20 ° C. Preferably, the first photoinitiator (a) comprises hydroxy alkyl of Ci_s aryl of Ce-12 ketone, more preferably hydroxy alkyl of Ci-4 phenyl ketone; with superlative preference 2-hydroxy-2-methyl-1-phenyl-1-propanone (such as that commercially available from CIBA as a clear liquid under the trade name "Darocur 1173"). Preferably, the second photoinitiator (b) comprises hydroxy (C3-6 alkyl) aryl of Ce-12 ketone; more preferably hydroxy (C3_6 alkyl) phenyl ketone; with superlative preference 1-hydroxycyclohexylphenyl ketone (such as that commercially available from CIBA as a white solid under the trade name "Irgacure 184"). Preferably, the third photoinitiator (c) comprises aryl oxide of C6-i2 (((Ci_6 alkyl) 2.3 Ce-12 arylcarbonyl)) 1-2 phosphine; more preferably phenyl ((C 1-4 alkyl) 3-benzoyl) 2-phosphine oxide; preferably superlative phenyl bis (2,4,6-trimethylbenzoyl) phosphine oxide (such as that commercially available from CIBA as a solid under the trade name "Irgacure 819"). In other preferred embodiments, the third photoinitiator (c) is benzophenone or a benzophenone derivative. Preferred benzofon derivatives are EBEC YL P36 (an acrylated derivative of benzophenone) or EBECRYUL P37 (a solid benzophenone derivative), both commercially available from UCB chemicals. Preferably, the weight ratio of the first photoinitiator (a) to the second photoinitiator (b) is from about 0.9 to about 1: 1, more preferably about 1.0. Preferably, the first photoinitiator (a) and the second photoinitiator (b) together comprise from about 60% to about 75% by weight of the total mixture. Preferably, the third photoinitiator (c) comprises from about 25% to about 40% by weight of the total mixture. The terms "optional" and / or "optionally substituted" substituent as used herein (unless they are followed by a list of other substituents) mean one or more of the following groups (or substitution by these groups): carboxy , sulfo, formyl, hydroxy, amino, imino, nitrile, mercapto, cyano, nitro, methyl, methoxy and / or combinations thereof. These optional groups include all chemically possible combinations in the same portion of a plurality (preferably two) of the aforementioned groups (for example, amino and sulfonyl if directly linked together represent a sulphamoyl radical). Preferred optional substituents comprise: carboxy, sulfo, hydroxy, amino, mercapto, cyano, methyl and / or methoxy. The term 'hydrocarbon' can also be used herein to replace other terms such as alkyl or aryl in the present, where the context permits. A hydrocarbon group denotes any univalent or multivalent portion (optionally attached to one or more other portions) consisting of one or more hydrogen atoms and one or more carbon atoms and may comprise saturated, unsaturated and / or aromatic portions. The hydrocarbon groups may comprise one or more of the following groups. The hydrocarbyl groups comprise univalent groups formed by removing a hydrogen atom from a hydrocarbon. The hydrocarbylene groups comprise divalent groups formed by removing two hydrogen atoms from a hydrocarbon, the free valencies of which are not coupled in a double bond. The hydrocarbylidene groups comprise divalent groups (represented by "R2C =") formed by removing two hydrogen atoms from the same carbon atom of a hydrocarbon, the free valencies of which are coupled in a double bond. The hydrocarbylide groups comprise trivalent groups (represented by "RC ="), formed by removing three hydrogen atoms from the same carbon atom of a hydrocarbon, the free valencies of which are coupled in a triple bond. The hydrocarbon groups can also comprise simple saturated carbon to carbon bonds; double and / or triple unsaturated carbon to carbon bonds (eg, alkenyl, and / or alkynyl groups, respectively) and / or aromatic groups (eg, aryl) and, where indicated, may be substituted with other functional groups . The term "alkyl" or its equivalent (eg, "ale") as used herein can be easily replaced, where appropriate and unless the context clearly indicates otherwise, by terms including any other hydrocarbon group such as those described herein (e.g., comprising double bonds, triple bonds, aromatic moieties (such as alkenyl, alkynyl and / or aryl respectively) and / or combinations thereof (e.g., aralkyl) as well as any species of multivalent hydrocarbon linking two or more portions (such as bivalent hydrocarbylene radicals), for example, alkylene). Any radical group or portion mentioned herein (eg, as a substituent) can be a multivalent or monovalent radical unless otherwise mentioned or the context clearly indicates otherwise (eg, a bivalent hydrocarbylene moiety linking two of other portions). However, where indicated herein, such monovalent or multivalent groups may still comprise optional substituents. A group comprising a chain of three or more atoms means a group in which the chain in its entirety or in part can be linear, branched and / or. form a ring (between which spiro and / or fused rings are included). The total number of certain atoms is specified for certain substituents, for example Ci-N hydrocarbon means a hydrocarbon portion comprising 1 to N carbon atoms. In any of the formulas herein, if one or more substituents are not indicated as being attached to any particular atom in a portion (eg, at a particular position along a chain and / or ring), the substituent can replace any H and / or can be located in any available position in the portion that is chemically adequate or effective. Unless the context clearly indicates otherwise, as used herein, the plural forms of the terms herein should be construed as including the singular form and vice versa. The term "comprising" as used herein, shall be understood to mean that the following list is not exhaustive and may or may not include any other suitable additional elements, for example, one or more characteristics, components, ingredients and / or substituents additional, as appropriate. The term 'effective' and / or appropriate 'ov (for example, with reference to the processes, uses, products, materials, formulations, compositions, compounds, monomers, oligomers, polymer precursors and / or polymers used in and / or the present invention) will be understood to denote utility in any one or more of the following uses and / or applications: preparation and / or use of radiation curable formulations, such as inks, and / or photoinitiators for use with such formulations. Such utility can be direct where the material has the properties required for the aforementioned uses and / or indirect where the material has use as a synthetic intermediary and / or diagnostic tool when preparing materials of direct utility. As used herein, the term "suitable" denotes that a functional group is compatible with producing an effective product. Substituents in a repeating unit in any polymers herein may be selected to improve the compatibility of the materials with the polymers and / or resins in which they may be formulated and / or incorporated for the aforementioned uses. Therefore, the size and length of the substituents may be selected to optimize physical entanglement or inter-location with the resin or may or may not include other reactive entities capable of chemically reacting and / or interlacing with those other resins. Certain portions, species, groups, repeating units, compounds, oligomers, polymers, materials, mixtures, compositions and / or formulations comprising and / or used in part of or throughout the invention as described herein, may exist as one or more other forms such as any of those in the following non-exhaustive list: stereoisomers (such as enantiomers (e.g., E and / or Z forms), diastereomers and / or geometric isomers); tautomers (e.g., keto and / or enol forms), conformers, salts, zwitterions, complexes (such as chelates, clathrates, interstitial compounds, ligand complexes, organometallic complexes, non-stoichiometric complexes, solvates and / or hydrates); isotopically substituted forms, polymeric configurations [such as homo or copolymers, random polymers, graft or block polymers, linear or branched polymers (for example, branched star and / or laterally), entangled and / or network polymers, polymers that are they can be obtained from divalent and / or trivalent repeating units, dendrimers, polymers of different tacticity (for example, isotactic, syndiotactic or atactic polymers), polymorphs (such as interstitial forms, crystalline forms and / or amorphous forms), different phases, solid solutions; combinations thereof and / or mixtures thereof. The present invention comprises and / or uses all of these forms that are effective. In another aspect of the present invention, there is provided a composition and / or formulation obtained and / or obtainable by any of the processes of the invention as described herein. Another aspect of the invention comprises a method for preparing an ink comprising the steps of mixing a composition and / or formulation of the invention as described herein, with a suitable vehicle medium and / or grinder. Another aspect of the present invention provides an ink obtained and / or obtainable by the above method. Preferred inks are those suitable for use in lithographic printing, for example, for graphic arts applications. Another aspect of the invention provides the use of a composition and / or formulation of the invention to make an ink, preferably a lithographic ink. Another additional aspect of the invention provides the use of an ink of the invention (preferably a lithographic ink) for printing an article and / or such printed article. Other aspects of the present invention can be given in the claims. The invention will now be illustrated by means of the following non-limiting examples and tests, which are only by way of illustration. Unless otherwise indicated herein, all test results and properties herein were carried out with the use of conventional methods well known to those skilled in the art. The following ingredients are used in the examples herein: 2-hydroxy-2-methyl-1-phenyl-1-propanone (CAS No. 7473-98-5) which is a commercially available photoinitiator of CIBA as a clear liquid under the tradename "Darocur 1173", 1-hydroxycyclohexylphenyl ketone (CAS No. 947-19-3) which is a commercially available photoinitiator of CIBA as a white solid under the trade name "Irgacure 184". Phenyl bis (2,4,6-trimethyl benzoyl) phosphine oxide (CAS No. 162881-26-7) which is a commercially available photoinitiator of CIBA as a solid under the trade name "Irgacure 819". 2-benzyl-2- (dimethylamino) -1- [4- (4-morpholinyl) phenyl] -1-butanone (CAS No. 119313-12-1) which is a commercially available photoinitiator of CIBA as a yellow solid under the trade name "Irgacure 369". Ethyl 4-dimethylaminobenzoate (CAS No. 10287-53-3) which is a commercially available photoinitiator as a white solid under the trade name "Quanticure EPD". 2-isopropylthioxanthone (CAS No. 5495-84-1) which is a commercially available photoinitiator as a yellow solid under the trade name "Quanticure ITX". TMPEOTA, which denotes trimethylolpropane ethoxy triacrylate (CAS No. 28961-43-5) also known as poly (oxy-1,2-ethanediyl), alpha-hydro-omega- [(1-oxo-2-propenyl) oxy], ether with 2-ethyl-2 - (hydroxymethyl) -1 3 -propanediol (3: 1). DPGDA, which denotes dipropylene glycol diacrylate (CAS No. 57472-68-1) also known as 2-propenoic acid, oxybis (methyl-2, l-ethanediyl) ester. BDK, which denotes a benzyl dimethyl ketal of formula which is a solid photoinitiator suitable for UV-curable non-saturated polyester and acrylate-based coatings, and is commercially available from, for example, ChemFirst Fine Chemicals. Benzophenone (CAS No. 119-61-9) is a known commercially available photoinitiator from UCB Chemicals, a white solid under the trade name "Ebecryl BPO". MEHQ, which denotes methyl hydroquinone (CAS no. 150-76-5), an inhibitor also known as the monomethyl ether of hydroquinone, commercially available from Aldrich Chemicals. Acrylated polyester polymer having an average of 5 to 6 acrylate groups per molecule, which is commercially available from UCB Chemicals under the trademark Ebecr l 870. Polyester acrylate oligomer grinding vehicle for flexographic ink, which is commercially available from UCB Chemicals under the trademark Ebecryl 812. Carbon black pigment commercially available from Columbian Chemicals under the tradename Raven 450. Phthalocyanine dye copper available commercially from Ciba, under the trade name Irgalite Blue LGLD. Magenta dye commercially available from Ciba, under the trade name Irgalite Rubine L4BD. Yellow dye commercially available from Ciba, under the trade name Irgalite Yellow BAW. Various combinations of liquid photoinitiators were prepared by mixing the components according to table 1. TABLE 1 (Combinations of photoinitiators) Examples 1 to 6 were prepared on day 1 by combining the components together in the amounts given in table 1, and each example was placed in a refrigerator on day 2. Then, the examples were observed in terms of stability, say, regarding the presence of solid precipitates. The examples were transferred to a freezer at 11:00 a.m. on day 14 (that is, between observations 14 (a) and 14 (b)). The examples were removed from the freezer on day 23, when the experiment was over. The observations made are given in tables 2A and 2B for examples 2 to 6 (example 1 was not tested) and comparative examples Comp. A and B. It can be seen that the combinations were unsatisfactory where the Irgacure 819 was present in an amount of 45% by weight or greater, since significant crystallization was observed from 14 days onwards during the test (Comp. and B). In comparison, examples 2 to 6 show no crystallization or show minimal crystallization during the test, which indicates excellent to good long-term stability. Although it is well known that liquid Darocur 1173 is a good solvent, previously it has only been possible to solubilize 20% by weight of other photoinitiators therein such as Irgacure 819 phosphine oxide. Surprisingly, it has been found that adding an amount approximately equal in weight of the solid Irgacure 184 produces a mixture with synergistic and unexpected properties, since the new mixture is capable of solubilizing 25% or more of other photoinitiators, such as the Irgacure 819 (as shown in tables 2A to 2B) . In Tables 2A and 2B, a check mark indicates that no solid precipitates were observed, ie, the combination was stable.

TABLE 2A Day Ex 2 E] 3 Ex 4 Ex 5 Ex 6 Comp A Comp B 3 • V 7 A stain Leaflets almost begins Tiny in the imperceptible crystals of the liz. vial 8 A spot Lightly begins on the cloudy bottom, crystal jar flasks liz. 9 A stain V It happens crystallized. Start at the bottom of the bottle potential liz., Few spots on the bottom of the bottle 10 A stain A stain It occurs crystallized. It begins tiny in the at the bottom of the crystallized potential of the bottle liz., A few tiny spots bottle sitting on the bottom of the jar 11 A stain A A stain It occurs crystallized. It begins tiny in the spot in the crystal-clear potential background of the tiny vial., Bottle in the bottom of the tiny flask spots sitting on the bottom of the jar TABLE 2B * Transparent; however, the appearance of air bubbles or tiny spots. The performance of the photoinitiator combinations of the present invention for dark color systems was compared with conventional photoinitiators. Various conventional pigment concentrates were prepared (examples B to D) as follows and with reference to table 3. Ebecryl 812 was manually combined with pigment at a level of 30%, then passed continuously through a mill of three rollers to make a pigment concentrate that has a desired Hegman milling value. TABLE 3 Pigment Concentrates For comparison, a formulation of the invention (example 7, see table 4) with the use of combinations of liquid photoinitiators of the invention and a formulation of the prior art (Comp G, see table 5) with the use of a conventional liquid photoinitiator they were used, each one, as vehicles to dilute (diluent formulations) to make inks. Table 4"PI Liquid System" denotes any of the combinations of liquid photoinitiators of the invention given in Examples 1 to 6 of the present. Each diluent was added at 50% to the pigment concentrations in Table 3, and manually combined together, and then dispersed for 15 minutes with Premier Mili Disperser to make an ink final ink compositions are given in Table 6 TABLE ( EXAMPLE 7) TABLE 6 (Ink formulations) The viscosities of the final inks were measured twenty-four hours after preparation with the use of the RheoStress RS150 Haake rheometer. These inks were thrown on a polypropylene substrate (applied on the outside and cleaned with isopropyl) with the use of a Cavanagh printing test printer and cured with UV radiation with the use of the fusion unit equipped with a lamp ( 600 WPI) 75%, 100 RPM at 190.3 mJ / cm2. The ink coatings were bright and examined for color, adhesion and other properties. The results indicate that the inks containing the photoinitiator combinations of the invention have a performance comparable to the prior art, with few important differences in physical properties or performance. The combinations of the invention are easier to prepare and use. The following two combinations of photoinitiators of the invention (examples 11 and 12) were identified from solubility data as being of special use for inks with dark colors. Example 11 is a combination of photoinitiators of the invention comprising Quantacure EPD, Ebecryl BPO, Irgacure 369, Irgacure 184, Quantacure ITX and Darocur 1173; and Example 12 is a combination of photoinitiators of the invention comprising Quantacure EPD, Irgacure 369, Irgacure 184, Quantacure ITX and Darocur 1173 (ie, without the Ebecryl BPO). Control formulations were made comprising the photoinitiator combinations of Examples 11 or 12 with an acrylated polyester polymer having an average of 5 to 6 acrylate groups per molecule (commercially available from UCB Chemicals, under the trademark Ebecryl 870). These formulations were evaluated for reactivity and lithographic properties. Inks in various colors and in black were prepared by adding the combinations of photoinitiators of Examples 11 and 12 in amounts of 10% and 12% by weight of the ink. In addition to the reactivity, basic lithographic properties, such as adhesiveness and water balance, were also measured. The results are given in Table 7 below where Comp M denotes a magenta ink of a similar formulation containing 10% of a conventional photoinitiator. The adhesiveness was measured with the use of an Electronic Ink Meter of Thwing-Albert for 3 minutes at 1200 rpm and at a temperature of 32 ° C. TABLE 7 (More inks) Photoinitiators of Example 11 presented reactivities comparable with Comp. M. Increasing the level of photoinitiator to 12% caused an increase of 71% (on average) in the reactivity for black and cyan inks. The inks using the combination of photoinitiators of Example 12 showed significant reactivity increases with the black and magenta inks compared to Comp M.; however, the cyan ink showed very slow reactivity. An increase in the level of photoinitiator (to 12%) caused a significant increase in the reactivity of the cyan ink. The adhesivities of the ink were similar regardless of the photoinitiator. The inks tested with these combinations of photoinitiators (examples 11 and 12) showed no adverse effects on the conductivity of the source solution (and, therefore, printing capacity) or on the water balance or uptake. Regardless of the photoinitiator, color inks tended to retain more water, while black inks tended to retain less. On the basis of reactivity to reactivity, the inks made from Example 11 appear to be particularly suitable for lithographic applications. The following examples 13 to 15 and the data in tables 8 to 10 show that stable liquid combinations are obtained particularly with mixtures of Irgacure 184 and Darocur 1173. The vehicle to dilute standard consists of TMPEOTA (59.9%), DPGDA (24%), ITX 4 (25%), BDK 4 (25%), EPD 4 (25%), Irg 36S 4 (25%) and MEHQ ( 0.1%).

TABLE 8 Example 13 demonstrates the synergistic effect on solubility of using both Irgacure 184 and Darocur 1173 to form a stable system at room temperature containing EPD, Irgacure 369 and BPO. The samples of Example 13 were made by weighing the individual ingredients in a glass container and heating them in an oven at 60 ° C. Afterwards, the samples were mixed by hand until 100% of the components were in a liquid state and the mixture was homogeneous. The samples were then allowed to cool to room temperature and subsequently transferred to a refrigerator set at 11 ° C. The stability in days was the amount of time spent in the refrigerator before any crystallization or other instability was observed in the mixture. The data in Table 8 clearly demonstrate the superior stability of the mixtures when Irgacure 184 and Darocur 1173 are used together.

TABLE 9 Example 14 demonstrates the synergistic effect on solubility of using both Irgacure 184 and Darocur 1173 to form a stable system at room temperature containing EPD, Irgacure 369 and ITX. The samples of Example 14 were made by weighing the individual ingredients in a glass container and heating them in an oven at 60 ° C. Afterwards, the samples were mixed by hand until 100% of the components were in a liquid state and the mixture was homogeneous. The samples were then allowed to cool to room temperature and subsequently transferred to a refrigerator set at 11 ° C. The stability in days was the amount of time spent in the refrigerator before any crystallization or other instability was observed in the mixture. The data in Table 9 clearly demonstrate the superior stability of the mixtures when Irgacure 184 and Darocur 1173 were used together.

TABLE 10 Example 15 demonstrates the synergistic effect on solubility of using both Irgacure 184 and Darocur 1173 to form a stable system at room temperature containing EPD, Irgacure 369, ITX and BPO. The samples of Example 15 were made by weighing the individual ingredients in a glass container and heating them in an oven at 60 ° C. Afterwards, the samples were mixed by hand until 100% of the components were in a liquid state and the mixture was homogeneous. The samples were then allowed to cool to room temperature and subsequently transferred to a refrigerator set at 11 ° C. The stability in days was the amount of time spent in the refrigerator before any crystallization or other instability was observed in the mixture. The data in Table 10 clearly demonstrate the superior stability of the mixtures when Irgacure 184 and Darocur 1173 are used together. A comparison of Examples 13 to 15 with combinations of prior art photoinitiators illustrates the surprising and unexpected advantages in using Irgacure 184 and Darocur 1173 together to form stable liquid photoinitiator combinations of different chemical classes. TABLE 11 A - Black inks TABLE B - Black inks (continued) The rheology data in Table 11 are for various inks made with ink-like formulations in Example H day table 6- herein, but each of the photoinitiator systems shown in Table 11 is replaced by the system of standard photoinitiators used in the Comp G day table 5. The ink made with the combination of photoinitiators of example 16 has a less good rheology, with a moderate fragility index and a high yield point. In each of the subsequent sample inks made with the photoinitiator combinations of examples 17 to 19, Darocur 1173 and Irgacure 184 are replaced at different levels and, in each case, the rheological performance of the ink is improved by reducing the limit of elasticity, the fragility index, or both. The best performance is obtained with the example 19, where the fragility index is equal to 1 and there is no effort to stress (zero), which indicates almost Newtonian flow conditions, which is the ideal rheological profile for an ink to be used in flexography. This combination of photoinitiators also presents excellent stability. This improvement in rheology, if not fully anticipated as it is, accepted that photoinitiators do not affect the rheology of pigmented systems. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims

CLAIMS Having described the invention as above, the content of the following claims is claimed as property. 1. A formulation comprising a mixture of three or more photoinitiators, the mixture is a liquid at a temperature at or below room temperature; the mixture characterized in that it comprises: (a) a first photoinitiator comprising an optionally substituted C6_18 aryl hydroxy alkyl aryl which is liquid at room temperature; (b) a second photoinitiator comprising a hydroxy (C3_10 alkyl) aryl of optionally substituted C6-yl ketone which is solid at room temperature; and (c) a third photoinitiator comprising one more of the following photoinitiators, each of which may be optionally substituted: an alpha aminoacetophenone, an aryl oxide of Ce_18 (((Ci_ao alkyl) i-4 arylcarbonyl of C6-a)) x_3 phosphine, a benzophenone; a benzophenone derivative and / or a hydrocarbon amino benzoate (optionally alkyl or aryl); wherein, (i) the first photoinitiator (a) and the second photoinitiator (b) are present in the mixture in a weight ratio of about 0.8 to about 1.2, (ii) the first photoinitiator (a) and the second photoinitiator (b) ) together comprise from about 15 to about 85 weight percent of the total mixture. 2. The formulation according to claim 1, characterized in that the first photoinitiator (a) comprises a hydroxy alkyl of C3-aryl of C3-i2 ketone. 3. The formulation according to claim 2, characterized in that the first photoinitiator (a) comprises a hydroxy alkyl of ¾.4 phenyl ketone. 4. The formulation according to claim 3, characterized in that the first photoinitiator (a) comprises 2-hydroxy-2-methyl-1-phenyl-1-propanone. 5. The formulation according to claim 1, characterized in that the second photoinitiator (b) comprises a hydroxy (C3-6 alkyl) aryl of C6-i2 ketone. 6. The formulation according to claim 5, characterized in that the second photoinitiator (b) comprises a hydroxy (C3_6 alkyl) phenyl ketone. 7. The formulation according to claim 6, characterized in that the second photoinitiator (b) comprises l-hydroxycyclohexylphenyl ketone. 8. The formulation according to claim 1, characterized in that the third photoinitiator (c) comprises an aryl oxide of C6-12 (((Ci_6 alkyl) 2-3 C6.12 arylcarbonyl)) i-2 phosphine. 9. The formulation according to claim 8, characterized in that the third photoinitiator (c) comprises an oxide of phenyl ((C 1-4 alkyl) 3 benzoyl) 2-phosphine. The formulation according to claim 9, characterized in that the third photoinitiator (c) comprises phenyl bis (2,4,6-trimethylbenzoyl) phosphine oxide. The formulation according to any of the preceding claims, characterized in that the third photoinitiator (c) is solid at room temperature. The formulation according to any of the preceding claims, characterized in that the weight ratio of the first photoinitiator (a) to the second photoinitiator (b) is from about 0.9 to about 1.1. The formulation according to claim 12, characterized in that the weight ratio of the first photoinitiator (a) to the second photoinitiator (b) is approximately 1.0. The formulation according to any of the preceding claims, characterized in that the first photoinitiator (a) and the second photoinitiator (b) together comprise at least about 60% by weight of the total mixture. 15. The formulation according to claim 14, characterized in that the first photoinitiator (a) and the second photoinitiator (b) together comprise from about 60% to about 75% by weight of the total mixture. 16. The formulation according to any of the preceding claims, characterized in that the third photoinitiator (c) comprises at least about 25% by weight of the total mixture. The formulation according to claim 16, characterized in that the third photoinitiator (c) comprises from about 25% to about 40% by weight of the total mixture. 18. A process characterized in that it comprises the steps of mixing together: (a) a first photoinitiator comprising an optionally substituted C6_18 aryl hydrocarbyl Ci_10 alkyl which is liquid at room temperature; (b) a second photoinitiator comprising a hydroxy (C3_10 alkyl) aryl of optionally substituted C6-i8 ketone which is solid at room temperature; and (c) a third photoinitiator comprising one more of the following photoinitiators, each of which may be optionally substituted: an alpha-aminoacetophenone, an aryl oxide of C6-ai (((Ci_iO alkyl) i-4 arylcarbonyl Cs.18)) i-3 phosphine, a benzophenone, a benzophenone derivative and / or a hydrocarbon amino benzoate (optionally alkyl or aryl); wherein, (i) the first photoinitiator (a) and the second photoinitiator (b) are present in the mixture in a weight ratio of about 0.8 to about 1.2, (ii) the first photoinitiator (a) and the second photoinitiator (b) ) together comprise at least 60% by weight of the total mixture; and (iii) the third photoinitiator (c) comprises at least 25% by weight of the total mixture to form a mixture of three or more photoinitiators, the mixture is a liquid at a temperature at or below room temperature. 19. A formulation obtained and / or characterized in that it can be obtained by the process according to claim 18. 20. A method for preparing a pigmented coating and / or ink characterized in that it comprises the steps of mixing a formulation according to any of claims 1 to 17 or 19 with a suitable vehicle and / or coloring medium. 21. The pigmented coating and / or ink according to claim 20, characterized in that it has a brittleness index of less than or equal to about 10. The pigmented coating and / or ink according to claim 21, characterized in that it has a brittleness index less than or equal to about 5. 23. The pigmented coating and / or ink according to claim 21, characterized in that it has a brittleness index less than or equal to about 2. 2. The pigmented coating and / or ink according to any of claims 20 to 23, characterized in that it has a yield strength less than or equal to about 10 Pa. The pigmented coating and / or ink according to claim 24, characterized because it has a yield strength less than or equal to approximately 5 Pa. 26. The pigmented coating and / or ink according to claim 25, characterized by having a yield strength less than or equal to about 2 Pa. 27. The use of a mixture of: (a) a first photoinitiator comprising an optionally substituted C6-i8 Ci-io-aryl hydroxy alkyl which is liquid at room temperature; (b) a second photoinitiator comprising an optionally substituted C6-yl hydroxy (C3-C10 alkyl cyclo) aryl ester that is solid at room temperature, as an additive for a pigmented coating and / or ink in order to reduce the fragility index and / or limit of elasticity thereof.