Pigments, the process of their manufacturing and their use

The present invention relates to new hybrid pigments of the class of diketopyrrolo [3,4-c]pyrrole (DPP) pigments, the process of their manufacturing and to their use as pigments.

Diketopyrrolo[3,4-c]pyrrole (DPP) pigments are well known pigments. Known processes for preparing mixed crystals or solid solutions containing a DPP pigment as described e.g. in U.S. Pat. No. 4,783,540 include recrystallization in organic solvents, acid or alkaline precipitation and intensive milling of a mixture containing the corresponding pigment components.

Diketopyrrolo[3,4-c]pyrrole (DPP) pigments are formed by reacting a dialkyl succinate with nitriles in the presence of a strong base. An excess of base is required in order to get good yields. It has now been found that the diketopyrrolo[3,4-c]pyrrole pigment alkali salt suspension, formed during the synthesis, can be mixed with pigments bearing “acid” hydrogens like —NH, —OH or —CONH— groups, and is then able to form metal salts. The excess of base is used for the formation of the metal salt of the pigments bearing “acid” hydrogens like —NH, —OH or —CONH— groups. Thereafter, the mixture of metal salts is precipitated in water or a mixture of water and alcohol, optionally in the presence of additives known in the state of the art to control the particle size distribution. The hybrid pigments are formed thereby. The co-precipitation of the metal salts generates an advantageous interaction of crystals.

This process has the advantage that the final pigment composition is obtained with a fine particle size and doesn't need to be milled. With the hybrid pigments so obtained, it is possible to obtain highly advantageous shifts in shades, which are of great interest. Moreover, the hybrid pigments described in this invention, possess excellent dispersability, high color strength, high weatherability, high saturation and outstanding heat stability in engineering plastics. The pigmentary properties are better than the application properties of the individual components and/or their mechanical mixtures.

The invention provides in one of its aspects the new process for the preparation of hybrid pigments of diketopyrrolo[3,4-c]pyrrole pigments according to the formula (I)

where A and B are each, independently of the other, a radical of the formula (II)

in which R 1 and R 2 are each, independently of the other, hydrogen, halogen, C 1 -C 5 alkyl, nitrile or phenyl;

and of pigments bearing “acid” hydrogens like —NH, —OH or —CONH— groups of the class comprising diketopyrrolo[3,4-c]pyrrole, quinacridone, anthraquinone, benzimidazolone, naphthol AS, monoazo pigments, disazo pigments, disazo condensation pigments, isoindolinone, dioxazine, benzimidazolone triphenodioxazine, thiazine indigo, perinone, quinophthalone and metal complex pigments.

Such pigments bearing “acid” hydrogens like —NH, —OH or —CONH— groups preferably correspond to the formula (III) to (XI)

in which R 3 and R 4 are independently the atoms necessary to complete the formation of a substituted or unsubstituted aromatic or aliphatic carbocyclic or heterocyclic ring system; R 5 and R 6 have the meaning of hydrogen, C 1-4 alkyl or hylogen; R 7 and R 8 have the meaning of C 1-4 alkoxy, nitro, C 1-4 alkoxycarbonyl or phenylaminocarbonyl; and X has the meaning of hydrogen and chloro.

Preferably R 3 and R 4 are independently selected from the residues consisting of

wherein R a is hydrogen, C 1-4 alkyl, halogen, C 1-4 alkoxy or trifluoromethyl; R b and R c are independently of each other, hydrogen or C 1-4 alkyl especially methyl or ethyl, or aryl.

If R a has the meaning halogen, it can be F, Cl or Br, preferably Cl, and such substituent can be present more than once.

In formula (IV) R 5 and R 6 can also have the meaning of phenyl or substituted phenyl.

This process for the preparation of hybrid pigments consists in preparing thediketopyrrolo[3,4-c]pyrrole pigment alkali salt suspension with an excess of base, mixing it with a crude pigment bearing “acid” hydrogens like —NH, —OH or —CONH— groups and after the formation of the metal salt of the pigments bearing “acid” hydrogens like —NH, —OH or —CONH— groups, discharging the mixture of metal salts into water or a mixture of water and alcohol. The two pigment salts are precipitating together and the obtained product is isolated.

In a preferred method, the pigment salt suspension is prepared by mixing a diketopyrrolo[3,4-c]pyrrole pigment alkali salt suspension with a crude pigment bearing “acid” hydrogens like —NH, —OH or —CONH— groups, at a temperature in the order of 30 to 100° C., preferably from 50 to 95° C. The mixture is stirred, preferably at or below 95° C., until it is homogenous.

The hybrid pigment is then precipitated from the pigment metal salts suspension to form a pigment suspension by precipitation methods known in the art. For example, suitable precipitation methods include drowning into water or an alcohol, or adding an alcohol and/or water to the pigment salt suspension. The water and/or alcohol can be used in any desired mixing ratio between 5 and 20 parts by weight per 1 part of the pigment alkali metal salts formed. The presence of a mineral acid such as sulfuric acid or an organic acid, such as acetic acid, in the water and/or an alcohol is advantageous in such precipitation methods.

In a preferred method, the solvent used is an alcohol, in particular a secondary or tertiary alcohol. Preferred tertiary alcohols are tert-butanol and ter-amyl alcohol.

Suitable strong bases include alkali metals; such as lithium, sodium and potassium, and alkali metal alkoxides derived in particular from primary, secondary or tertiary aliphatic alcohols having 1 to 10 carbon atoms. It is also possible to use a mixture of the above mentioned alkali metal alkoxides. Preference is given to using alkali metal alkoxides, the alkali metal being especially sodium or potassium, and the alkoxide is preferably derived from a secondary or tertiary alcohol. A particularly preferred strong base is sodium teramylate. These alkali metal alkoxides can also be prepared in situ by reacting the corresponding alcohol with alkali metal.

In the process of the invention, the strong base can be used in an amount from 0,1 to 10 mol, preferably from 1,6 to 2,0 mol, based on 1 mole of the nitrile compound used as a starting compound for the pigments of formula (I) and corresponding to the formulae

and

in which A and B are each as defined above and both compounds in the nitrile mixture are in molar ratio of 100:0 to 50:50 relative to each other.

The formation of the pigment alkali salts suspension can be carried out at a temperature from 60 to 140° C., preferably from 80 to 120° C.

Preferably, the obtained pigment salts suspension is drowned into water or an alcohol or an alcohol/water mixture. Suitable alcohols are methanol, ethanol, n-propanol, isopropylalcohol, ter-butanol and especially ter-amyl alcohol. The water and/or alcohol can be used in any desired mixing ratio between 5 and 20 parts by weight per 1 part of the pigment alkali metal salt formed. Water or ter-amyl alcohol/water mixtures are particularly suitable for drowning the pigment salts suspension.

One can also use additives known in the state-of-the-art to control the particle size of the pigment composition. It's possible as well to control the particle size of the pigment composition by heating under pressure the final pigment suspension at the end of the precipitation or the pigment salts suspension during the mixing step.

Depending on the pigments and on the drowning conditions, pigments with a particle size below 1.5 microns are obtained.

When the ripening of the hybrid pigment is complete, the conditioned pigment is isolated by filtration, with the presscake being washed with water or an organic solvent, preferably methanol, followed by water and dried. Good results can be obtained by performing the filtration in acidic conditions.

Accordingly, the present invention relates to a process for preparing hybrid pigments comprising a diketopyrrolo[3,4-c]pyrrole pigment compound and a crude pigment bearing “acid” hydrogens like —NH, —OH or —CONH— groups which process comprises

(a) preparing a pigment salt suspension by dissolving a crude pigment bearing “acid” hydrogens like —NH, —OH or —CONH— groups in a diketopyrrolo[3,4-c]pyrrole pigment alkali salt suspension

(b) precipitation from the pigment salts suspension to form a hybrid pigment suspension; and

(c) isolating the hybrid pigment.

The proportion of the diketopyrrolo[3,4-c]pyrrole pigment and the pigment bearing “acid” hydrogens like —NH, —OH or —CONH— groups in the hybrid pigment can vary between 10 and 90% by weight of the “other” pigment with 90 to 10% of diketopyrrolo[3,4-c]pyrrole pigment, in particular between 30 and 70% by weight of the “other” pigment with 70 to 30% of diketopyrrolo[3,4-c]pyrrole pigment, especially between 40 and 60% by weight of the “other” pigment with 60 to 40% of diketopyrrolo[3,4-c]pyrrole pigment.

It is also possible to form ternary hybrid pigments by mixing the diketopyrrolo[3,4-c]pyrrole pigment alkali salt suspension with two pigments bearing “acid” hydrogens like —NH, —OH or —CONH— groups.

A further aspect of the invention consists in providing new hybrid pigments of diketopyrrolo[3,4-c]pyrrole pigments according to formula (I) (as defined above) and of other pigments bearing “acid” hydrogens like —NH, —OH or —CONH— groups belonging to the class comprising anthraquinone, benzimidazolone, naphthol AS, monoazo and disazo pigments, disazo condensation pigments, isoindolinone, dioxazine, benzimidazolone triphenodioxazine, thiazine indigo, perinone, quinophthalone and metal complex pigments.

Preferred hybrid pigments according to the invention are those consisting of a diketopyrrolo[3,4-c]pyrrole pigment and of a pigment according to one of the formulae (III), (IV), (VI), (VII), (VIII), (IX), (X) and (XI) as defined above.

Especially preferred hybrid pigments are those consisting of a diketopyrrolo[3,4-c]pyrrole pigment according to formula (I) and a thiazine indigo pigment according to formula (III) or a benzimidazolone triphenodioxazine pigment according to formula (IV).

The hybrid pigments according to the invention are suitable for the mass pigmentation of suitable substrates including synthetic polymers, synthetic resins and regenerated fibers optionally in the presence of solvents. These substrates more particularly include oil or water and solvent based surface coatings, polyester spinning melts, polyethylene, polystyrene and polyvinyl chloride molding materials, rubber and synthetic leather. Furthermore, the pigments can be used in the manufacture of printing inks, for the mass coloration of paper and for coating and printing textiles.

The hybrid pigments according to the invention are also suitable as colorants in electrophotographic toners and developers, such as one- or two-component powder toners (also called one- or two-component developers), magnetic toners, liquid toners, polymerization toners and specialty toners (literature: L. B. Schein, “Electrophotography and Development Physics”; Springer Series in Electrophysics 14, Springer Verlag, 2 nd Edition, 1992).

Typical toner binders are addition polymerization, polyaddition and polycondensation resins, such as styrene, styrene-acrylate, styrene-butadiene, acrylate, polyester and phenol-epoxy resins, polysulphones, polyurethanes, individually or in combination, and also polyethylene and polypropylene, which may comprise further constituents, such as charge control agents, waxes or flow assistants, or may be modified subsequently with these additives.

The hybrid pigments according to the invention are suitable, furthermore, as colorants in powders and powder coating materials, especially in triboelectrically or electrokinetically sprayable powder coating materials which are used for the surface coating of articles made, for example, from metal, wood, plastic, glass, ceramic, concrete, textile material, paper or rubber (J. F. Hughes, “Electrostatics Powder Coating” Research Studies, John Wiley & Sons, 1984).

Powder coating resins that are typically employed are epoxy resins, carboxyl- and hydroxyl-containing polyester resins, polyurethane resins and acrylic resins, together with customary hardeners. Combinations of resins are also used. For example, epoxy resins are frequently employed in combination with carboxyl- and hydroxyl-containing polyester resins. Typical hardener components (as a function of the resin system) are, for example, acid anhydrides, imidazoles and also dicyanodiamide and its derivatives, blocked isocyanates, bisacylurethanes, phenolic and melamine resins, triglycidyl isocyanurates, oxazolines and dicarboxylic acids.

In addition, the hybrid pigments formed by a process according to the invention are suitable as colorants in ink-jet inks, both aqueous and non-aqueous, and in those inks, which operate in accordance with the hot-melt process. The hybrid pigments are also suitable as colorants in cosmetic compositions.

When applied to the afore-mentioned substrates the co-pigments are found to be resistant to migration and fast to light, and show fastness to washing, chlorite, hypochlorite and peroxide bleaching, rubbing, overspraying and solvents. Notably, the pigments display high tinctorial power, good opacity and good heat stability.

Based on the polymeric material to be mass colored, the co-pigments according to the invention are used in amounts of 0.01 to 30% by weight, preferably of 0.1 to 10% by weight.

There now follows a series of examples which serves to illustrate the invention.

The preparation of a 1% colored PVC sheet is performed as follows: 100 parts of clear PVC are mixed with 0.1 part of pigment (obtained according to Example 1) for 2 minutes. The mixture is passed between two rollers for 5 minutes, the front roller being heated at 130° C. and the rear roller being heated at 135° C. Then the sheet is pressed under a pressure of 25 tones between two chromium-plated steel plates heated at 165° C., for 5 minutes. The pressed sheet is colored with a red shade.

The preparation of a 0.1% colored PVC sheet is performed as follows: 100 parts of PVC-white (0.5% TiO 2 ) are mixed with 0.1 part of pigment for 2 minutes. The mixture is passed between two rollers for 8 minutes, the front roller being heated at 160° C. and the rear roller being heated at 165° C. Then the sheet is pressed under a pressure of 25 tones between two chromium-plated steel plates heated at 160° C., for 5 minutes.

The preparation of the alkydmelamine (AM5) resin coating is performed as follows: 3.6 g of pigment, 26.4 g of clear AM5 (35%) and 85 g of glass beads are stirred in a Skandex stirrer for 30 minutes. 30 g of this preparation are mixed with 60 g of clear AM5 (55.8%). The dispersion is sprayed on a cardboard sheet, air-dried for 15 minutes and baked at 140° C. in an oven for 30 minutes.

The preparation of the alkydmelamine (AM5) resin coating is performed as follows: 3.6 g of pigment, 26.4 parts of clear AM5 (35%) and 85 g of glass beads are stirred in a Skandex stirrer for 30 minutes. 7.5 g p of this preparation are mixed with 20 g of AM5-white (30% TiO 2 ). The dispersion is sprayed on a cardboard sheet, air-dried for 15 minutes and baked at 140° C. in an oven for 30 minutes.