WO2005059046A1

WO2005059046A1 - Improved process for the production of printing inks

Info

Publication number: WO2005059046A1
Application number: PCT/EP2004/053188
Authority: WO
Inventors: Stuart Cook Niven; Joyce Wilcox
Original assignee: Ciba Spezialitaetenchemie Holding AG; Ciba SC Holding AG
Current assignee: BASF Schweiz AG
Priority date: 2003-12-10
Filing date: 2004-12-01
Publication date: 2005-06-30
Anticipated expiration: 2006-06-10

Abstract

Process for preparing a polar organic solvent-based printing ink composition which comprises reacting a dye precursor of a cationic indole dye with an organic non-abietyl resin acid, preferably an organic sulfonic acid, in a polar organic solvent suitable for printing inks or in the printing ink medium. The synthesis of the coloured ink via an in-situ generation of the cationic dye offers many procedural advantages such the avoidance of isolation and purification steps for the dye. The printing inks obtained show for example high colour strength and excellent rheological properties and can be used in publication or packaging gravure flexographic, lithographic or letterpress printing processes.

Description

Improved Process for the Production of Printing Inks

The present invention relates to the preparation of organic solvent-based printing ink compositions containing cationic (basic) yellow dyes of the indole class as sole colourant or as toner (toning agent) e.g. for publication gravure or packaging gravure, flexographic, letterpress or lithographic printing processes. The yellow dyes are prepared from their so- called dye precursors (e.g. carbinols) by reacting them with organic acidic components, before or during (in-situ) the process for preparing the printing inks.

Such inks normally use pigments to achieve colouration. Pigments are insoluble crystalline materials. The colour strength of these materials relates directly to the surface area, therefore, in order to increase strength the crystallite size must be reduced. Alternatively the pigment loading can be increased or the ink film thickness increased.

High pigment loading may lead to higher viscosity and may cause difficulty with wetting and dispersion. Poor dispersion results in oversize particles and grit, and further, poor wetting and dispersion also leads to poor strength.

Increased shear rate is normally required during manufacturing to achieve dispersion and overcome viscosity. This can also lead to adverse temperature rises.

High pigment loadings and/or high viscosity can result in poor ink distribution and transfer on the printing press. The film-forming of highly pigmented inks may be disrupted.

And further, the prints obtained from high pigment loaded inks may give poor transparency and gloss.

Increased film thickness gives poorer press mileage with shorter press runs and more frequent ink supply changes. This does not only result in greater expense but can result in prints that are more difficult to dry or cure, that show lower transparency and that lead to reduced printed image definition.

Reducing crystallite size cannot continue indefinitely without massive alteration to the process of pigment synthesis. Reduced crystallite size can result in increased viscosity and reduced flow, can affect the dispersion stability within the ink, and can result in an increased need for surface treatments and additives. Further, reduced crystallite size can lead to high aggregation and poor dispersion and also to increased adsorption of varnish components.

In addition to this, it can be difficult to achieve high levels of transparency due to the particulate nature of the colourant. Furthermore, even for normal strength, the application of significant shear rate (and thus energy, time and equipment investment) is required to prepare pigment based inks.

The use of certain dye precursors (carbinols) for the preparation of organic solvent-based inks is already disclosed e.g. in FATIPEC CONGRESS 1976, 13, 554 where dyes and associated carbinols of the triaryl methane, diarylmethane and xanthene families are combined with coloured pigment compositions containing a so-called printing resin. The use of indole dyes and their carbinols is not mentioned nor is the application to more polar ink solvents.

While the use of the carbinols of the above-mentioned colour families was not fully convincing, it has now been found that by using the dye precursors of a particular group of cationic (yellow) indole dyes for preparing organic solvent-based printing ink compositions, outstanding effects can be achieved.

Accordingly, it is the main object of the present invention to provide a process for the preparation of said printing ink compositions as well as methods of using them.

The current invention offers a novel way to synthesize the coloured ink via an in-situ generation of the dyestuff. Thus an essentially non-coloured non-ionic precursor to the cationic dyestuff is reacted in an organic solvent suitable for said printing inks or in the printing ink medium per se, to generate the dye and consequently the printing ink. These and other objects of the present invention will be described in the following.

Therefore, in a first aspect, there is provided a process for production of an organic solvent- based printing ink composition which comprises reacting (1) a dye precursor of formula (1),

or a mixture thereof, wherein R R₆ are independently of one another hydrogen, substituted or unsubstituted alkyl, alkoxy, cycloalkyl, aryl, heteroaryl or allyl, R₂ and R₃ may be combined together to form a ring, further R₅ and R₆ are independently of one another halogen, cyano, nitro, aryloxy, alkenyl, alkenoxy, alkoxcarbonyl, aryloxycarbonyl, acyloxy, acyl, alkylthio, arylthio, acylamino, alkylsulfonyl, arylsulfonyl or thiocyano, any two of R₅ or any two of R₆ may be combined together to a homocyclic or heterocyclic aromatic or non-aromatic ring, A is -OR, -N(R)_2j -N(R)COR, -N(R)SO₂R, -SR, -S(O)R, -O₂CR, -N(R)CON(R)₂, -OCON(R)_2j -SO₂N(R)₂ or -N(R)COOR, wherein R is Ri, A and Ri may also combine to form a ring, m is an integer of 1 to 5 and n is an integer of 1 to 4, with (2) an organic non-abietyl resin acid, in a polar organic solvent suitable for printing inks or in the printing ink medium.

Preferably, there is used 1 equivalent of acid (2) per carbinol (1) in the inventive process.

Preferably, R-i-R₆ in the carbinol dye precursor of formula (1 ) are independently of one another hydrogen, unsubstitued or substituted alkyl or alkoxy of 1 to 20 carbon atoms, cycloalkyl of 5 to 10 carbon atoms, aryl of 6 to 10 carbon atoms, heteroaryl of 5 to 10 atoms, comprising one or more nitrogen, oxygen or sulfur atoms as ring members, or allyl, R₂ and R3 may be combined together to form a 5 to 7-membered ring, and A, m and n have the meanings indicated. There are many leaving groups (A) possible (as mentioned), but mostly preferrred as substituent A is-OH: then the dye precursors are the carbinols (carbinol bases) of the dyes of formula (2) below. Further A and Ri may also combine to form a ring, which preferably is a 5-or 6-membered ring that may contain - in addition to the nitrogen atom present - further hetero atoms (nitrogen, oxygen, sulfur) and is a non-aromatic or aromatic species. Subsequently a more detailed disclosure of the substituents R R₆ is given: The substituents R R₆ in formula (1) are independently of one another hydrogen; further substituted or unsubstituted alkyl and alkoxy which comprises species of e.g. 1 to 20 carbon atoms, preferably of 1 to 10 carbon atoms, which may be linear or branched. Examples are methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, hexadecyl, octadecyl and the corresponding isomers. The alkoxy species can be listed analogously ._ Preferred are hydrogen and/or the lower alkyl/alkoxy (C C ) species, and mostly preferred are hydrogen, methyl and methoxy.

As to the substituted alky and alkoxy radicals (preferences with regard to the chain lengths as mentioned above) there can be mentioned hydroxyalkyls, halogeno-alkyls (fluoro-, chloro-, bromo-, iodo-), aminoalkyls, cyanoalkyls and arylalkyls, wherein the aryl moiety may be further substituted (e.g. lower alkyl and alkoxy, halogeno, hydroxy, cyano, amino, carboxy, carbonamido), on the one hand, and e.g. arylalkoxy (aryl substituted as mentioned above), on the other hand. The cycloalkyl radicals may contain 5 to 10 ring carbon atoms, preferred are the C₅-C species, viz. cyclopentyl, cyclohexyl, and cycoheptyl, cycohexyl being mostly preferred. Possible substituents may be lower alkyl radicals, preferably methy and ethyl. The aryl radicals may contain e.g. 6 to 10 cabon atoms, preferably comprising phenyl or naphthyl, optionally substituted by hydroxy, halogeno (fluoro-, chloro-, bromo-, iodo-), amino, cyano, carboxy, carbonamido, or sulfo and sulfonamido.

The heteroaryl radicals preferably contain 5 to 10 ring atoms, comprising one or more, for example 1 to 3, nitrogen, oxygen or sulfur atoms. Examples may be imidazolyl, oxazolyl, thiazolyl, thienyl, pyrrolyl, pyrazolyl, triazolyl, pyridinyl, pyridazinyl, pyrimidyl, triazinyl, benzimidazolyl, benzoxazolyl and quinoxalinyl, including isomeric forms. With regard to the monocyclic radicals, those of 5 or 6 ring atoms are preferred.

Substituents may be selected from e.g. hydroxyl, halogen, amino and substituted amino, cyano, carboxyl (including esters and amides), sulfo, sulfonamide, and lower alkyl.

The allyl radical may be optionally substituted by lower alkyl, halogen or cyano.

R₂ and R₃ may be combined together to form a 5 to 7-membered homocyclic or heterocyclic ring, such as cyclopentane, cyclohexane or tetrahydrofurane. Further, the subtituents R₅ and R₆ are independently of one another halogen, cyano, nitro, aryloxy, alkenyl, alkenoxy, alkoxcarbonyl, aryloxycarbonyl, acyloxy, acyl (RCO-), alkylthio, arylthio, acylamino including carboxylamino (carbonamido) R-CO-NH- (R is.g. hydrogen, alkyl or phenyl) and sulfonylamino (sulfamido) R S0₂-NH- (Ri is e.g. alkyl or phenyl), alkylsulfonyl, arylsulfonyl or thiocyano, wherein the number of carbon atoms may be up to 10; depending on the radicals the lower limit may be 1 (alkyl) or 6 (aryl). Any two of R₅ or any two of R₆ may be combined together to form with the rings to which they are attached, annellated ring systems such as homocyclic or heterocyclic aromatic or non- aromatic mono- or bicyclic rings. The annellated rings may contain 6 to 10 ring atoms, and preferably are 5- or 6-membered saturated or unsaturated homocyclic rings (phenylene, cyclopentylene, cyclohexylene); or they contain as heterocyclic rings nitrogen, oxygen and/or sulfur atoms; examples are thienyl, furfuryl, pyrimidyl, pyridinyl, or the group -O-CH₂-O-CH₂-.

The index m is an integer of 1 to 5, preferably 1 to 3 or 1 or 2; the index n is an integer of 1 to 4, preferably 2, and mostly preferred 1.

Mostly preferred are compounds of formula (1) to be used in the inventive process, wherein R R,_! are methyl, R₅ is methyl or methoxy where m is 1 with the remainder being hydrogen, two R₅ together form -O-CH₂-O-CH₂-, R₆ is hydrogen (n is 1 ) and A is -OH.

The dye prescursors of formula (1) are obtained by known methods when preparing cationic dyes.

On the other hand, the dye precursors can also be formed from the dyes of formula (2) by standard literature methods involving sodium hydroxide treatment. Isolation of the non-ionic products (precursors) is then possible by filtration with removal of excess salt by simple washing.

Problems due to variable salt levels in the dyestuff are therefore removed in two ways: Firstly, the level of salt present within the dyestuff is not a great concern during reaction with sodium hydroxide. This is not the case with aqueous based ion-exchange processes for fomation of the dye (complex) of formula (2).

Secondly, being non-ionic and non-water soluble, it is possible to purify the dye (carbinol) precursors by washing such that they are presented to the dye-forming step (almost) salt free. The acid treatment of the dye precursors of formula (1) with the organic non-abietyl resin acids leads to the dyes of formula (2):

or a mixture thereof, wherein Rι-R_β are independently of one another hydrogen, substituted or unsubstituted alkyl, alkoxy, cycloalkyl, aryl, heteroaryl or allyl, R₂ and R₃ may be combined together to form a ring, further R₅ and R₆ are independently of one another halogen, cyano, nitro, aryloxy, alkenyl, alkenoxy, alkoxycarbonyl, aryloxycarbonyl, acyloxy, acyl, alkylthio, arylthio, acylamino, alkylsulfonyl, arylsulfonyl or thiocyano, any two of R₅ or any two of R₆ may be combined together to form a homocyclic or heterocyclic aromatic or non-aromatic ring, m is an integer of 1 to 5, n is an integer of 1 to 4 and X^~ is an organic anion derived from an organic non-abietyl resin acid, which is an organic carboxylic acid, and preferably an organic sulfonic acid.

The term Organic non-abietyl resin acids' - in the context of this invention - means that those acidic species are excluded that are mainly derived from (cyclic) hydrocarbon resins, such as terpenes or terpene based resins, such as colophony or the abietyl family of rosin acids, including chemically modified rosins. These organic non-abietyl resin acids may also be termed in this context as the 'reacting acids': they react (in-situ) with the dye precursors of formula (1 ) to form the dyes of formula (2) which sometimes are also referred to as 'cationic/anionic dye complexes.'

The organic non-abietyl resin acids used inventively - and which form the anion X^~in the dyes of formula (2) - are e.g. organic acids, such as organic carboxylic acids and organic sulfonic acids, of e.g. 6 to 36, preferably 6 to 24, carbon atoms, and which may be aliphatic (linear, branched, saturated, unsaturated) or aromatic species.

The aliphatic acids may be unsubstituted or, furthermore, substituted, for example by lower alkyl (e.g. 2-ethylhexanoic acid); the aromatic acids may be substituted by chlorine, lower alkyl and/or hydroxy (e.g. salicylic acid and 3,5-di-tert.butyl-salicylic acid) or may be polyacids (e.g. 1 ,2,4-benzenetricarboxylic acid).

Further acids may be acid-bearing (carboxylic acid group bearing) esters and amides, including monomers, dimers, oligomers (trimers etc.) and polymers of these such as acrylic acid, polyacrylic acids, polyaspartic acid and polyhydroxystearic acid.

Preferably, the acids are aliphatic or aromatic sulfonic acids of 6 to 24 carbon atoms, such as optionally substituted benzenesulfonic acids. Examples of these are alkyl(Cι-Cι₈) benzene sulfonic acids, such as p-toluene sulfonic acid, p-octylbenzene-sulfonic acid, p- dodecyl benzene sulfonic acid or p-octadecyl benzene sulfonic acid; further alkyl(C₆-C₁₈) sulfonic acids, such as hexyl sulfonic acid or hexadecyl sulfonic acid, and naphthalene sulfonic acid or alkyl(C C₈) naphthalene sulfonic acids.

Further acids may be (partial esters of) phosphoric/phosphonic acids, containing e.g. 8 to 18 carbon atoms in the ester part, such as the monolauryl ester of phosphoric acid, the dioctyl ester of phosphoric acid or dodecylphosphonic acid.

As to further preferences of the substituents in the dyes of formula (2), reference is made to those definitions provided for them in formula (1 ).

The chromophores of the cationic (basic) dyes of formula (2) are e.g. compiled as C.I. Basic Dyes in The Colour Index (C.I.), issued by the Society of Dyers and Colorists and The American Association of Textile Chemists and Colorists. Details of the dyes are disclosed there.

The inventive process may be carried out in a polar organic solvent suitable for printing inks or in the complete printing ink medium. Alternatively, some of the components of the printing ink medium may be present with further suitable components and additives being added later (after the actual reaction step).

As a polarity limit, solvents with dielectric constants greater than 4.5 may be selected in the context of the present invention. These polar organic solvents may be selected from the group consisting of optionally substituted lower alcohols (mono-hydric, aliphatic or aromatic), alkyl esters, ketones, polyhydric alcohols which comprise e.g. (poly)alkylene glycols and triols, (poly)alkylene glycol ethers and esters, halogenated hydrocarbons, solubilising ink vehicle components and monomers (acrylate monomers), as well as mixtures thereof.

Typical alcohols (aliphatic, monohydric) are e.g. Cι-C₄ alkyl alcohols, such as methanol, ethanol, n-propanol, iso-propanol, n-butanol (and ϊsomers); aromatic monohydric alcohols are for example C₇-Cιo alcohols, and the main representative is benzylalcohol (C₇).

Polyhydric alcohols may comprise dihydric alcohols with the representative group of (poly) alkylene glycols, and trihydric alcohols of 3 to 6 carbon atoms, such as glycerol or 1 ,2,6- hexane triol.

Alkylene glycols (including thioglycols) are e.g. C₂-C₆alkylene glycols or thioglycols, such as ethylene glycol, propylene glycol, butylene glycol, 1,5-pentanediol, thiodiglycol, or hexylene glycol.

Polyalkylene glycols, preferably a low molecular weight polyethylene glycol having a molecular weight of from 100 to 800, are e.g. diet ylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400 or polyethylene glycol 600, especially having a molecular weight of from 150 to 400, or a low molecular weight polypropylene glycol, e.g. dipropylene glycol, tripropylene glycol, polypropylene glycol P 400 or polypropylene glycol P 425.

As alkylene glycolethers there can be used C C alkyl ethers of ethylene (propylene) glycol or di-ethylene glycol, such as ethylene glycol monomethyl and monoethylether, the methoxy- propanols (1 -methoxypropan-3-ol, l-methoxypropan-2-ol), 1-ethoxypropan-3-ol, ethyldiglycol or butyldiglycol; and further phenylglycol.

Polyalkylene glycol ethers are e.g. C C₄ alkyl ethers of a polyethylene glycol, e.g. diethylene glycol monobutyl ether, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, 2-[2-(2- methoxyethoxy)ethoxy]ethanol or 2-[2-(2-ethoxyethoxy)ethoxy]ethanol.

Representative alkyl esters are the acetates with 1 to 4, preferably 2 to 4 carbon atoms in the alcohol moiety, such as methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, or butylacetate, and further propyleneglycol monomethylether acetate. Suitable ketones are e.g. aliphatic ketones of 3 to 6 carbon atoms, such as acetone, methylethyl ketone, methyl isobutyl ketone, methylpentyl ketone, diacetonalcohol or cyclohexanone; and further aliphatic/aromatic ketones, such as acetophenone.

The preferred species of the halogenated aliphatic hydrocarbons is trichloromethane (chloroform), and that of the halogenated aromatic hydrocarbons is chlorobenzene.

Monomers of UV-curing inks also class as solvents in this context. Typical examples are, but not exclusively, acrylate monomers, such as 1 ,4-butanediolacrylate, propoxylated glycerol triacrylate and pentaerythritol triacrylate. It is also possible that ink vehicle components or excess organic acid can act as solvent to the reaction.

Preferred polar organic solvents are those selected from the group consisting of said C C₄- alkyl alcohols, benzylalcohol, acetates with 2 to 4 carbon atoms in the alcohol moiety, aliphatic ketones of 3 to 6 carbon atoms, acetophenone, C₂-C₆-alkylene glycols or thioglycols, C C₄ alkyl ethers of ethylene glycol, di-ethyleneglycol or propylene glycol, polyethylene glycols having a molecular weight of rom 100 to 800, and CrC₄-alkyl ethers of polyethylene glycols, and mixtures thereof.

Mostly preferred are said alkyl alcohols, benzylalcohol, acetates, aliphatic ketones, acetophenone and the alkyl ethers of ethylene glycol and propylene glyco, and mixtures thereof.

Solvent mixtures can contain (small) parts of so-called non-polar solvents, such as toluene; examples are ethanol/toluene and methyl ethyl ketone/toluene mixtures..

Alternatively the inventive process may be carried out in the complete printing ink medium or in parts thereof. If only parts are present, the other components needed for a printing ink are added later. What in general is present, is the organic solvent and components that are or form 'ink-vehicles' as defined hereinbelow.

Ink vehicle components are those that are in general known as binders including for example long-oil-, medium-oil- or short oil-alkyd resins, phenol-modified alkyd resins, phenolic resins, rosin-modified phenolic resins, metal resinates, such as copper, zinc or magnesium resinate, petroleum resins, (cyclic) hydrocarbon resins, such as terpene or terpene-phenolic resins, resins based on acrylics, styrenes and vinyl polymers, melamine and epoxy resins, distillate and vegetable oils, and further nitrocellulose, cellulose acetate propionate, polyamide, polyvinylbutyral, polyvinylalcohol, polyvinylacetate, acrylic, propionated acrylic, polyvinylchloride, polyvinyldichloride, chlorinated polyolefin, rosins (rosin acids), modified rosins, such as dimerised and polymerized rosins, hydrogenated, disproportionated and dehydrogenated rosins; further rosin esters, rosin modified maleic, fumaric and phenolic resins, epoxide and maleic resins. The rosins/modified rosins are such that they form part of the ink vehicle components and are not reacted with the dye precursor. This can be ensured by addition of these species to the solvent mixture after reaction of the dyes precursors with the desired acid.

Also possible are solvent based solutions or dispersions of these ink vehicle components.

Furthermore, the printing inks may in addition comprise customary additives known to those skilled in the art. These may be present during reaction according to the inventive process (when carried out in the printing ink medium) or are added later when the reaction is carried out in the not yet complete (partial) printing ink medium.

Typical additives include drying enhancers, drying inhibitors, non-coloured extenders, fillers, opacifiers, antioxidants, waxes, oils, surfactants, rheology modifiers, wetting agents, dispersion stabilizers, strike-through inhibitors and anti-foaming agents; further adherence promoters, cross-linking agents, plasticisers, photoinitiators, deodorants, laking agents, and chelating agents.

Such additives are usually used in amounts of from 0 to 10% by weight, particularly from 0 to 5% by weight, and preferably from 0.01 to 2% by weight, based on the total weight of the printing ink composition.

The inks may also contain pigments as additional colourants. If the pigments are organic pigments they comprise, but not exclusively, such pigments as monoazo, disazo, naphthol, dioxazone, azomethin, azocondensation, metal-complex, nitro, perinone, quinoline, anthraquinone, benzimidazolone, isoindoline, isoindolinone, quinacridone, hydroxyanthraquinone, aminoanthraquinone, anthrapyrimidine, indanthrone, flavanthrone, pyranthrone, antanthrone, isoviolanthrone, diketopyrrolopyrrole, carbazole, perylene, indigo or thioindigo pigments.

Mixtures of the pigments may also be used.

Preferred are organic pigments of the following chemical classes:

Monoazo, disazo, azomethin, naphthol, and metal-complex pigments (e.g. phthalocyanines). For further details as to the organic pigments reference is made to Industrial Organic Pigments, W. Herbst, K. Hunger, 2^nd edition, VCH Verlagsgesellschaft, Weinheim, 1997.

Optionally the organic pigments can be mixed with inorganic pigments which include among others titanium oxide pigments, iron oxide and hydroxide pigments, chromium oxide pigments, spinel type calcined pigments, lead chromate pigments, carbon black and Prussian Blue, and also extenders such as titanium dioxide and china clay. Alternatively, full replacement of organic pigments by inorganic ones is also possible. As an alternative to the inventive process, the preparation can be performed as follows:

This process comprises reacting

(a) the dye precursor of the formula (1) with

(b) the organic non-abietyl resin acid, which is a carboxylic acid, preferably an organic sulfonic acid, dissolved in a polar organic solvent, evaporating off the solvent (under reduced pressure) from that mixture until a dry mixture is obtained, and redissolving the dry mixture in an organic solvent compatible with the desired ink medium, and

(c) adding it to the ink medium

The solvent for the solution (b) must be a solvent wherein both the starting materials (dye precursor and acid) are sufficiently soluble to allow reaction. The organic solvent designated as preferred herein before are most suitable, in particular the ketones (acetone), alkylene glycol ethers and the halogenated hydrocarbons (chloroform). Further, these solvents can be easily removed from the reaction mixture.

The solvents to be used in the redissolving step should be selected from those of the mentioned solvents as preferred which are known as so-called ink solvents, such as aliphatic or aromatic ketones (acetone, methyl ethyl ketone, acetophenone), aliphatic alcohols (methanol, ethanol) and esters (ethyl acetate).

Further, the inventive process additionally comprises mixing a so-called ink vehicle with the combined dry, or wet, or redissolved components (1) (dye precursor), (2) (organic non-abietyl resin acid) and optionally a pigment. These ink vehicles (or parts thereof) are those defined hereinbefore.

Alternatively, the inventive process may be carried out by dry mixing the dye precursor of formula (1 ) with the organic non-abietyl resin acid (2), and then co-dissolving this mixture in a polar organic solvent, as hereinbefore defined.

This wet blend (co-dissolved mixture - as solution or in concentrated form) is a further object of the present invention.

The dry mixture of the dye precursor of formula (1), the organic non-abietyl resin acid (2), and optionally other components used according to this alternative is a further object of the present invention.

Alternatively, the inventive process comprises dry or wet mixing the dye precursor of formula (1), the organic non-abietyl resin acid (2), and an ink vehicle, and then co-dissolving this mixture in a polar organic solvent.

The dry mixture of the dye prcursor of formula (1), the organic non-abietyl resin acid (2), and an ink vehicle used according to this alternative as well as the wet blend (co-dissolved mixture - as solution or in concentrated form) are further objects of the present invention.

As a further alternative, the inventive process comprises incorporating and/or reacting the dye precursor of formula (1), the organic non-abietyl resin acid (2), and optionally further components separately or as dry mix into preformed ink vehicles.

This process can be carried out by extruding the dye precursor of formula (1), the organic non-abietyl resin acid (2), and optionally further components separately or as dry mix into high solids dispersions, solutions or pastes of the ink vehicle.

The extrusion products (containing the dye precursors or dye complexes) obtained according to this process are a further object of the present invention. Processing can also be carried out by predissolving the organic non-abietyl resin acid (2) in the molten ink vehicle or an ink vehicle component by application of shear and/or heat, if necessary. Into this medium the dye precursor of formula (1 ) is dissolved by the application of shear and/or heat, if necessary. Alternatively, both the dye precursor of formula (1 ) and the organic non-abietyl resin acid (2) can be co-dissolved into the ink vehicle in one step.

Further, the inventive process can be carried out, wherein the acidic component (2) and/or the dye precursor of formula (1) constitute a surface treated pigment.

The essential components and the optional components can be reacted (mixed) by any known method using a ball mill, sand mill, bead mill, attrϊtor, continuous horizontal medium dispersing machine, two-roll mill, three-roll mill, pressure kneader, or extruder; further by manual or mechanical shaking, or by low or high shear stirring.

Preparation of the inks according to the present invention is extremely flexible which can allow, as examples, the following manufacturing methods:

- The organic non-abietyl resin acid (2) is fully dissolved in the polar organic solvent followed by, or prior to, the dye precursor (carbinol). The dye solution thus produced is added to a previously prepared ink vehicle solution.

- The organic non-abietyl resin acid (2) and the dye precursor (carbinol) are dry mixed together and then co-dissolved in the polar organic solvent. The dye solution thus produced is added to a previously prepared ink vehicle solution.

- The organic non-abietyl resin acid (2), the dye precursor (carbinol) and the ink vehicle are dry mixed together and then co-dissolved in the polar organic solvent.

In all three cases the level of required shear rate is similar and far less than that required for pigment dispersion. Due to the lower shear rate, the generation of heat within the inks is much reduced.

Due to the simplicity of reaction, many processing possibilities are now open. The production of a coloured ink can now be carried out on any equipment capable of generating low levels of shear rate. The traditional high shear rate approach to pigment dispersion is not required though the possibility of carrying out both in tandem is included. Combination of the dye precursor (carbinol) with the organic non-abietyl resin acid can be carried out in an extruder either dry or with a suitable carrier system. This carrier system may be a solvent or a concentrate of a suitable ink vehicle. Reaction of the dye precursor (carbinol) may be achieved during the extrusion process though this is not essential as this can occur during the later dispersion of the concentrate within the ink solvent.

The dye precursor (carbinol) approach to colouration can be used in conjunction with traditional pigment methodology. As such, further possibilities for both ink and pigment processing are opened.

The dye precursor (carbinol) can also be considered as an agent that reduces the traditional problems of using pigments in liquid ink systems. The high colour strength of the resulting dyestuff allows the use of a lower pigmentation level thus reducing viscosity. The possibility also exists for improved gloss thus allowing an equivalent reduction in binder level.

The printing ink compositions obtained by the inventive process may be employed in any amount effective for the intended purpose. In general good results have been obtained with compositions which comprises by weight

0.1- 25 % of the dye precursor of formula (1),

10 - 50% of the polar organic solvent

0.1 - 25 % of the organic non-abietyl resin acid (2), and 5 - 80 % of an ink vehicle comprising binders and further additives.

It is also possible to produce high solids dispersions for printing inks based on concentrations of the dye of formula (2) of over 50% and even partially reacted pastes of the dye precursor and the the organic non-abietyl resin acid which can be considered as precursors of the the concentrates of up to as much as 100 % of the dye of formula (2).

The compositions may be generally embodied in the following two forms:

(A) A composition containing as components: the dye precursor of formula (1), the organic non-abietyl resin acid (2), solvent and ink vehicle, but no pigment - this composition can be used itself as printing ink where it comprises the whole colourant composition.

(B) A composition containing as components: the dye precursor of formula (1), the organic non-abietyl resin acid (2), ink vehicle and pigment wherein the dye (complex) of formula (2) thus produced serves as a toning agent for the shading, tinting and brightening of predominantly pigment based printing inks (partial colourant composition).

The inventive process provides a new and better method for the formation of the dyes of formula (2) in printing ink compositions, and consequently an improved method for preparing said printing ink compositions. The synthesis of the coloured ink via an in-situ generation of the cationic dye offers many procedural advantages such as the avoidance of isolation and purification steps for the dye (complex).

The printing ink compositions obtained by the inventive process can be used in the corresponding processes for the printing of flat substrates such as publication and packaging gravure, lithographic, letterpress or flexographic printing. These processes are further objects of the present invention.

These processes are used, for example, but not exclusively, for the printing of magazines, newspapers, magazine supplements, catalogs, posters, packaging materials, food wrappings and containers, paper, foil and plastic films.

Advantages of using the inventive compositions over pigment compositions can include high gloss, high transparency, low abrasion, low or more controllable viscosity, high flow, high press mileage and high chroma.

Advantages of the inventive production method include increased accuracy of colorant charge plus reduced bleed, tack and adherence problems which can occur due to excesses of either dye or complexing agent.

The present invention is hereinafter further described with reference to particular examples thereof. It will be appreciated that these examples are presented for illustrative purposes and should not be construed as a limitation on the scope of the invention as herein described.

In the following examples, quantities are expressed as parts by weight or percentages by weight, if not otherwise indicated.

All examples are carried out at room temperature. Reaction time is defined as the time necessary to achieve full solution which indicates full reaction of the dye precursor and the organic non-abietyl resin acid. In general, this reaction time is between 2 and 20 minutes, though can vary depending on the level of agitation applied. Examples

Example 1

4.2 g C.I. Basic Yellow 28 carbinol is combined with 4.0 g dodecylbenzenesulfonic acid, 48 g of a 24% nitrocellulose ink vehicle in ethanol and 42 g of a 3.2:1 ethanol/ethyl acetate blend. The mixture is then mechanically shaken until full solution and dye generation is achieved. The resulting ink shows a strong orange/yellow colouration on printing.

Example 2

4.1g C.I. Basic Yellow 29 carbinol is combined with 4.1g dodecylbenzenesulfonic acid, 48 g of a 24% nitrocellulose ink vehicle in ethanol and 42g of a 3.2:1 ethanol/ethyl acetate blend. The mixture is then mechanically shaken until full solution is achieved. The resulting ink shows a strong yellow colouration on printing.

Example 3

1.28 g C.I. Basic Yellow 29 carbinol is mixed with 1.84 g dodecylbenzenesulfonic acid and 12.13 g ethyl acetate and shaken till full solution is achieved. 12.13 g of a 24% nitrocellulose ink vehicle in ethanol is then added and shaken. The resulting ink shows strong yellow colouration on printing.

Example 4

2.5g C.I. Basic Yellow 28 carbinol and 2.5g dodecylbenzenesulfonic acid are combined in 25 ml diethyleneglycol monobutyl ether giving full solution. 21 g of a 31% solids nitrocellulose ink medium in 5:1 ethanol/ethyl acetate is then added without detrimental effect to the full yellow solution. The ink gives strong orange/yellow colouration on printing.

Example 5

0.5 g C.I.Basic Yellow 28 carbinol is mixed with 0.25 g salicylic acid, 4.85 g ethanol, 2 g ethyl acetate and 4.15g of a 24% nitrocellulose ink vehicle in ethanol giving full yellow solution. The ink gives strong orange/yellow colouration on printing.

Example 6

0.5g C.I. Basic Yellow 28 carbinol is mixed with 0.28 g 1 ,2,4-benzenetricarboxylic acid, 4.85 g ethanol, 2 g ethyl acetate and 4.15 g of a 24% nitrocellulose ink vehicle in ethanol giving full yellow solution. The ink gives strong orange/yellow colouration on printing. - 7 -

Exa ple 7

0.5 g C.l. Basic Yellow 28 carbinol is mixed with 0.25 g para-toluenesulfonic acid monohydrate, 4.85 g ethanol, 2.4 g ethyl acetate and 4.15 g of a 24% nitrocellulose ink vehicle in ethanol giving full yellow solution. The ink gives strong orange/yellow colouration on printing.

Example 8

0.5 g C.l. Basic Yellow 28 carbinol is mixed with 0.5 g salicylic acid, 4.85 g ethyl acetate and 4. 5 g of a 24% nitrocellulose ink vehide in ethanol giving full yellow solution. The ink gives strong orange/yellow colouration on printing.

Example 9

0.5 g C.l. Basic Yellow 28 carbinol is mixed with 1g para-toluenesulfonic acid, 4.85 g ethyl acetate and 4.15 g of a 24% nitrocellulose ink vehicle in ethanol giving full yellow solution. The ink gives strong orange/yellow colouration on printing.

Example 10 0.5 g C.l. Basic Yellow 28 carbinol is mixed with 0.35 g 2-ethylhexanoic acid, 4.85 g ethyl acetate and 4.15 g of a 24% nitrocellulose ink vehicle in ethanol giving full yellow solution. The ink gives strong orange/yellow colouration on printing.

Example 11

0.5 g C.l. Basic Yellow 28 carbinol is mixed with 0.3 g benzoic acid, 4 g ethanol, 1.25 g ethyl acetate, 0.25 g 4-hydroxy-4-methyl-2-pentanone and 4.15 g of a 24% nitrocellulose ink vehicle in ethanol giving full yellow solution. The ink gives strong orange/yellow colouration on printing.

Claims

1. A process for production of an organic solvent-based printing ink composition which comprises reacting (1 ) a dye precursor of formula (1 ),

or a mixture thereof, wherein R Re are independently of one another hydrogen, substituted or unsubstituted alkyl, alkoxy, cycloalkyl, aryl, heteroaryl or allyl, R₂ and R₃ may be combined together to form a ring, further R₅ and R₆ are independently of one another halogen, cyano, nitro, aryloxy, alkenyl, alkenoxy, alkoxcarbonyl, aryloxycarbonyl, acyloxy, acyl, alkylthio, arylthio, acylamino, alkylsulfonyl, arylsulfonyl or thiocyano, any two of R₅ or any two of R₆ may be combined together to a homocyclic or heterocyclic aromatic or non-aromatic ring, A is -OR, -N(R)₂, -N(R)COR, -N(R)SO₂R, -SR, -S(O)R, -0₂CR, -N(R)CON(R)₂, -OCON(R)₂, -

SO₂N(R)₂ or -N(R)COOR, wherein R is Ri, A and Ri may also combine to form a ring, m is an integer of 1 to 5 and n is an integer of 1 to 4, with

(2) an organic non-abietyl resin acid, in a polar organic solvent suitable for printing inks or in the printing ink medium.

2. The process according to claim 1 wherein R β in the dye precursor of formula (1) are independently of one another hydrogen, unsubstituted or substituted alkyl or alkoxy of 1 to 10 carbon atoms, cycloalkyl of 5 to 10 carbon atoms, aryl of 6 to 10 carbon atoms, heteroaryl of 5 to 10 atoms, comprising one or more nitrogen, oxygen or sulfur atoms as ring members, or allyl, R₂ and R₃ may be combined together to form a 5 to 7-membered ring, and A, m and n have the meanings indicated.

3. The process according to any one of claim 1 and 2, wherein the organic non-abietyl resin acids (2) are carboxylic acids of 6 to 36 carbon atoms, organic sulfonic acids of 6 to 24 carbon atoms, partial esters of phosphoric or phosphonic acid, and carboxylic acid group- bearing esters and amides.

4. The process according to any one of claims 1 to 3 wherein the polar organic solvents suitable for printing ink compositions comprise optionally substituted lower monohydric alcohols, alkyl esters, ketones, polyhydric alcohols which comprise (poly)alkylene glycols and triols, (poly)alkylene glycol ethers and esters, halogenated hydrocarbons, solubilising ink vehicle components and monomers (acrylate monomers), as well as mixtures thereof.

5. The process according to any one of claims 1 to 4 wherein the printing ink compositions comprise the polar organic solvents suitable for solvent-based printing inks, ink vehicle components (ink vehicles) and optionally other suitable printing ink additives.

6. The process according to claim 5 wherein the ink vehicles comprise suitable binders or their solvent-based solutions or dispersions.

7. The process according to claim 6 wherein the ink vehicle components comprise long-oil-, medium-oil- or short oil-alkyd resins, phenol-modified alkyd resins, phenolic resins, rosin- modified phenolic resins, metal resinates, such as copper, zinc or magnesium resinate, petroleum resins, (cyclic) hydrocarbon resins, such as terpene or terpene-phenolic resins, resins based on acrylics, styrenes and vinyl polymers, melamine and epoxy resins, distillate and vegetable oils, and further nitrocellulose, cellulose acetate propionate, polyamide, polyvinylbutyral, polyvinylalcohol, polyvinylacetate, acrylic, propionated acrylic, polyvinylchloride, polyvinyldichloride, chlorinated polyolefin, rosins (rosin acids), modified rosins selected from the group consisting of disproportinated, hydrogenated, dehydrogenated, dimerised and polymerized rosins; further rosin esters, rosin modified maleic, fumaric and phenolic resins, epoxide and maleic resins, and solvent based solutions or dispersions of these, with the proviso that the rosins (rosin acids)/modified rosins are not reacted with the dye precursor in that they are added to the solvent mixture after reaction of the dyes precursors with the desired acid.

8. A process according to claim 1 which comprises reacting

(a) the dye precursor of the formula (1) with

(b) the organic non-abietyl resin acid (2) , which is a carboxylic acid, preferably an organic sulfonic acid, dissolved in a polar organic solvent, evaporating off the solvent until a dry mixture is obtained, and redissolving the dry mixture in an organic solvent suitable for the desired printing ink compositions , and

(c) adding it to the printing ink medium.

9. A process according to claim 1, which comprises dry mixing (reacting) the dye precursor of formula (1) with the organic non-abietyl resin acid (2), and then co-dissolving this mixture in a polar organic solvent.

10. A process according to claim 1, which comprises dry mixing the dye precursor of formula (1) with the organic non-abietyl resin acid (2) and an ink vehicle, and then co- dissolving this mixture in a polar organic solvent.

11. A process according to claim 1, which comprises incorporating the dye precursor of formula (1), the organic non-abietyl resin acid (2), and optionally further components separately or as dry mix into preformed ink ve hides.

12. The process according to claim 11, which comprises extruding the dye precursor of formula (1), the organic non-abietyl resin acid (2), and optionally further components separately or as dry mix into high solids dispersions, solutions or pastes of the ink vehicles.

13. A process according to claim 1, which comprises predissolving the organic non-abietyl resin acid (2) in a molten ink vehicle or an ink vehicle component, and dissolving the dye precursor of formula (1) in this medium, both steps being optionally carried out by application of shear rate and/or heat.

14. The process according to claim 13, wherein both the dye precursor of formula (1) and the organic non-abietyl resin acid (2) are co-dissolved in the ink vehicle or the ink vehicle component in one step.

15. The compositions obtained according to the processes of any one of claims 1 to 14.

16. Use of the printing ink compositions obtained according to the processes of any one of claims 1 to 14 in or as printing inks.

17. Use of the solid dispersions, solutions or pastes obtained according to claim 12 in printing inks.

18. Use according to claims 16 and 17 wherein the printing inks are gravure, flexographic, lithographic or letterpress printing inks.

19. Process for printing a flat substrate by employing a printing ink composition prepared according to the processes of any one of claims 1 to 14.

20. Process according to claim 19, wherein the printing process is a publication or packaging gravure, flexographic, lithographic or letterpress printing process.