MXPA00008740A - Catalyzed oxidation process for preparing quinacridone pigments using a polyalkylene glycol medium - Google Patents

Abstract

A process for preparing an unsubstituted or substituted quinacridone of the formula or a solid solution of quinacridones of the formula (I), wherein X and Y are independently 1 or 2 substituents selected from hydrogen, fluorine, chlorine, C1-C3alkyl, C1-C3alkoxy and COOR wherein R is hydrogen or C1-C10alkyl in which a salt of a corresponding 6,13-dihydroquinacridone of formula II having the same substitutions as the desired quinacridone of formula I, or a mixture of corresponding 6,13-dihydroquinacridones of formula II, is oxidized with an oxygen containing gas in the presence of an aqueous base and a catalytically effective amount of an oxidation catalyst, characterized in that the oxidation is performed in the presence of an polyglycolic reaction medium of formula R1-O- (CH2)m-(CHR1')n-Ox-O-R1"(III).

Description

Oxidation Process to Prepare Quinacridone Pigments The present invention relates to a process for the preparation of quinacridone pigments by the catalysed oxidation of the 6, 13-dihydroquinacridone corresponding to air in a selected organic reaction medium. Quinacridone pigments are known for their attractive magenta and red colors and for their exceptional firmness properties. The technique of how to prepare the quinacridone pigments by oxidation of the corresponding 6,13-dihydroquinacridone is well known. The U.S. patents 2,821,529; U.S. 2,969,366; U.S. 3,148,075 and U.S. No. 3,287,457, for example, disclose the oxidation of a 6,13-dihydroquinacridone to the corresponding quinacridone in an alcoholic medium containing a base and a small amount of water using aromatic nitro compounds, for example, the sodium salt of nitrobenzenesulfonic acid, or similar oxidizing agents. The U.S. Patent No. 2,821,529 describes a process wherein several 6,13-dihydroquinacridones are oxidized by the corresponding quinacridone by heating a mixture containing the dihydroquinacridone and a moderate oxidizing agent in an alkaline reaction medium. The medium is a mixture that contains a larger portion of an organic solvent, usually an alcohol, and a smaller amount of water. The amount of water present in the reaction medium is lower in proportion to the amount of the organic solvent. The literature also describes the processes for oxidizing a dihydroquinacridone with the corresponding quinacridone with the use of molecular oxygen and a quinone compound as the oxidizing agent. A similar reaction is often referred to as an "oxidation in air" because air is a preferred source of molecular oxygen. In general, similar oxidation processes are revealed while taking place in an alkaline medium, usually an organic solvent contains a lower amount of water, in the presence of a quinone compound and molecular oxygen. Molecular oxygen is introduced into the reaction medium by bubbling an oxygen-containing gas through the reaction medium or an oxygen-containing gas is blown onto the surface thereof. Although the literature describes the quinone compound as both a catalyst and an oxidizing agent, U.S. Pat. 3,024,239 discloses that quinone is an oxidizing agent that is reduced to the off-white compound during the oxidation of the corresponding dihydroquinacridone. The molecular oxygen regenerates the quinone so that less than the stoichiometric amount of quinone is required for the reaction to proceed to completion. The patent of the U.S.A. No. 3,475,436 discloses an oxidation process in air wherein the reaction medium contains a larger portion of tetramethylene sulfone and a relatively smaller amount of water. Similar processes using an alkaline medium containing a larger portion of other organic solvents, such as dimethyl sulfoxide, dimethylacetamide, alkanediols, C? ~C3 alcohols of caprolactam and N-alkyl-2-pyrrolidone, usually in the presence of an amount relatively small amount of water, which are also known in the art. Also well known is the oxidation in air of the dihydroquinacridones in an aqueous reaction medium and in the presence of a bivalent metal ion or a quaternary ammonium salt. For example, the patent of the U.S.A. 3,738,988 discloses a process in which an aqueous medium is used and teaches that the oxidation step must be carried out in the presence of bivalent iron, cobalt or nickel ions in order to increase the effectiveness of the oxidation. Japanese Patent 53/904334 discloses oxidation media including Ci-C3 alcohols and aqueous base, together with air. The German patent 3,834,748, and the patent of US Pat. No. 5,093,497 describe the addition of a quaternary ammonium salt for oxidation in both organic and aqueous reaction media. The patent of the U.S.A. 5, 502,192 describes 1 the conversion of 6,13-dihydroquinacridone to the corresponding quinacridone in an aqueous medium via an air oxidation process in which the aqueous reaction medium also contains a relatively minor amount of a polar, non-ionic organic material, which forms a second stage organic liquid in the reaction mixture. In many of the above-mentioned processes, the resulting and reactant products are not generally in solution and consequently must be suspended during the oxidation reaction. The resulting pigments were filtered directly from the reaction mixture. The disadvantages found with these methods include incomplete oxidation, prolonged oxidation reaction cycles and particularly the crude nature of the isolated pigments that are relatively large in particle size. Because of the raw nature of the recovered pigments, additional conditioning steps are required to obtain a commercially acceptable strong clear pigment. Still other patents disclose the use of N-alkyl-2-pyrrolidone (JP 57/119958) or N-methyl-e-caprolactam (Japanese Patent 57/108162), or a mixture of polar solvents (JP 58/147459) together with the base and preferably nitro compounds such as sodium m-nitrobenzenesulfonate as the oxidation agent. Although oxygen and air are mentioned as potential oxidation agents, the yield obtained from quinacridones and quinacridones substituted by such processes are not quantitative due to incomplete or concomitant oxidation on the oxidation of quinacridonaquinone. Additionally, the use of mixtures of solvents and aromatic nitro compounds requires expensive depositions of organic reduction products which must be deposited in an ecologically acceptable manner. Japanese Patent 54/135821 discloses the preparation of quinacridone pigments which involve the oxidation of 6,13-dihydroquinacridone to dimethyl sulfoxide in the presence of water, an alkali and an oxidizing agent such as sodium o-nitrobenzenesulfonate, m- sodium nitrobenzenesulfonate, sulfur powder, selenium, iodine or air to obtain a quinacridone saline solution, which when diluted with a polar solvent or an acid forms a finely divided product. Although this process produces quinacridones directly in pigmentary form, the use of air in said process requires long reaction times and results in the low production of quinacridones as a consequence of the formation of quinacridonaquinone and the presence of residual 6,13-dihydroquinacridone. not rusted. Additionally, only unsubstituted quinacridones that are applicable to this method are described. U.S. 5,286,863 discloses a process for preparing quinacridone pigments in which a 6,13-dihydroquinacridone or a derivative thereof is oxidized at an elevated temperature in the >; presence of a base, a dimethyl sulfoxide medium and a quinone catalyst. This method describes how a direct synthesis of pigment-grade quinacridone is provided which does not require post-synthesis conditioning, without the use of organic oxidizing agents or surface active agents. The patent of the U.S.A. 5,223,624 describes the synthesis of a unique? M-form of quinacridone in which 6,13-dihydroquinacridone is oxidized in a dimethyl sulfoxide medium. Applicants have found that direct oxidation of substituted or unsubstituted 6,13-dihydroquinacridones provide corresponding quinacridones in short reaction times and high yields when the oxidation is conducted in a selected organic reaction medium, more preferably a polyalkylene glycol medium, in presence of an aqueous base, with air or other gas mixture containing oxygen at a temperature below 100 ° C, catalyzed by a quinone or quinone derivative. In addition, the resulting solutions, in compliance with hydrolysis or alcoholysis (immersion). optionally in the presence of an acid, provides quinacridones in a final pigment form that does not require procedures of particle size reduction subsequent to synthesis. The use of a selected organic reaction medium allows direct oxidation of the substituted or unsubstituted 6,13-dihydroquinacridone for the corresponding quinacridone in an ecologically effective manner. For example, without the use of organic oxidizing agents or surface active agents, so that virtually no waste products are generated. The process also allows the introduction of growth inhibitors of the particles directly into the reaction mixture whereby clear pigments, of small particle size, can be obtained directly from the synthesis without requiring mechanical size reduction (eg grinding) ). In addition, it was unexpectedly found that the oxidation to the air of an unsubstituted dihydroquinacridone in a selected organic reaction medium, such as a polyalkylene glycol medium, results in an unsubstituted quinacridone, the polymorphic phase of which is established by the conditions of immersion. Specifically, it has been found that in polyalkylene glycol oxidations submerged in water provides quinacridone, immersed in methanol produces quinacridone ß (with variable levels of phase contamination) and more unexpectedly, provides a poly-type of quinacridone submerged in hot methanol . The oxidation in air of dihydroquinacridones to the corresponding quinacridone in a selected organic reaction medium is both economically attractive and environmentally friendly. The polyalkylene glycol oxidation path directly directs pigment-grade quinacridones that do not require milling or pulverizing operations to reduce particle size. In addition, the air oxidation of the polyalkylene glycol of dihydroquinacridones to the corresponding quinacridone allows one to control the polymorphic state of the resulting pigment by simply altering the immersion conditions. As is clear, many benefits result from the use of the oxidation processes of the present invention. Accordingly, the present invention relates to a process for preparing a quinacridone of the formula I wherein X and Y are 1 or 2 substituents independently selected from the group including H, F, Cl, Cx-C3alkyl and COOR, wherein R is H or C? -C? 0alkyl by oxidation of a salt of the corresponding 6,13-dihydroquinacridone of the formula II which comprises an oxidation step wherein the 6,13-dihydroquinacridone salt is oxidized with air or another mixture of oxygen-containing gas in a reaction medium containing an effective oxidizing amount of a compound represented by the formula (III) R? -0 - [(CH2) m- (CHR1 ') n-0] x-0-R1"(III) wherein RR?' , R? ' ', are, independently of one another, hydrogen or C1-Calkyl, R? and Rx' 'are attached C2-C4alkylene, m and n = 1 to 4, and x = 3 to 1000, in the presence of an aqueous base and a catalyst. Linear compounds, however, are highly preferred for cyclic compounds for practical, environmental and economic reasons.Polyethylene glycol and derivatives thereof are most preferred.Most preferably the dihydroquinacridone salt or mixtures thereof are oxidized with air or other gas mixture containing Oxygen in a polyalkylene glycol medium in the presence of an aqueous base and a catalyst The process of this invention is particularly suitable for the preparation of quinacridone, 2,9-dichloroquinacridone, 2,9-difluoroquinacridone, 4,11-dichloroquinacridone, 4 , 11-difluoroquine cridone, 2,9-dicarboxyquinacridone, 3,10-dichloroquinacridone, 2,9-dimethylquinacridone and 2,9-dimethoxyquinacridone, in addition to any of the other substituted quinacridones which are prep poured from the corresponding 6,13-dihydroquinacridones by means of the processes described. Additionally, the process of this invention is also suitable for the preparation of solid quinacridone solutions such as, for example, those described in U.S. Pat. 3,610,510, U.S. 4,783,540 or U.S.- 4,810,304. In this manner, mixtures of unsubstituted dihydroquinacridone and / or differently substituted 6,13-dihydroquinacridones are co-reacted according to the process of this invention or solutions of oxidized pigments separately from the 6,13-dihydroquinacridones are mixed and the pigments of solid solution are precipitated according to the present invention. Polyalkylene glycol or mixtures thereof having an average molecular weight in the range of 200 to 1000, preferably 200 to 600, more preferably 300 to 400, are especially suitable for use as the reaction medium of the claimed process. Anthraquinone-2-sulfonic acid is used as the catalyst, oxidation dihydroquinacridones in air in both PEG 400 (polyethylene glycol with molecular weight of 400) and PEG 300 were found to result in a commercially important 2, 9-dihydroquinacridone ß-polymorph, considering that when using PEG 200 a mixed phase product is obtained. The polyalkylene glycol (s) suitable for use according to the invention are generally present in technical grade in an amount ranging from 40 to 2 times the weight of 6,13-dihydrbquinacridone and / or its derivatives and preferably from to 3 times the weight of it. Although more than 40 times the weight of polyalkylene glycol can be used to oxidize dihydroquinacridones with excellent yield conversion, it becomes impractical and inefficient to use high amounts of polyalkylene glycol. Surprisingly, it was found that the use of ethylene glycol fails to produce a fully oxidized product. Although it is not desired to link it to any theory, it is believed that both ether linkages in the polyglycols are needed and presumably act as crowned ethers. Bases that prove particularly convenient for this process are, for example, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. In a suitable molar ratio of 6,13-dihydroquinacridone the base is from about 1: 3 to about 1:39, preferably from about 1: 4 to about 1:15. Preferably, the aqueous base used in the oxidation step of the present process is either 50% sodium hydroxide or 45% potassium hydroxide and is used in an amount of 1.0 to 3.0 parts per part of dihydroquinacridone. You can also use more than 3 parts of base in these oxidations, however using more base, and therefore more water, can cause the reaction to become heterogeneous. It is very important to keep the reaction mixture homogeneous; dihydroquinacridone in the form of a salt form and the resulting quinacridone in the form of a salt in solution. The presence of water during the oxidation step is essential for the solubility of the base in the medium of > selected organic reaction. It is preferable to add the base as an aqueous solution. For example, an aqueous solution containing 70-30 parts of an alkaline hydroxide and 30-70 'parts of water, for example commercially available 45% aqueous potassium hydroxide or an aqueous solution of 50% sodium hydroxide, can be used in the oxidation processes of the present invention. An aqueous solution containing 52-30 parts of sodium hydroxide and 30-48 parts of water is most preferably used. Oxidizing agents include mixtures of oxygen-containing gases. For example, mixtures of nitrogen / oxygen or argon / oxygen with at least 2% oxygen. Air is preferably used. The oxygen-containing gas mixture is introduced below or above the surface of the reaction mixture. The oxidation reaction is conducted at temperatures below 150 ° C, preferably at 50-100 ° C and more preferably at 70-90 ° C. Additionally, the oxidation reaction can be conducted under pressure. The presence of catalytic amounts of a quinone and / or derivatives thereof during the oxidation reaction results in obtaining high quinacridone yields at reduced reaction times. The presence of the catalysts and the use of the indicated reaction temperatures and other variables result in quinacridone products that are substantially devoid of over-oxidation products such as quinacridonaquinones that adversely affect the intensity of the resulting quinacridone product. Particularly suitable quinone catalysts are, for example, anthraquinone and its derivatives such as mono and / or dichloroanthraquinone and more preferably anthraquinone-2-sulfonic acid and / or 2,6-disulfonic acid derivatives. The quinone catalyst is present in an amount ranging from 0.005 to 0.25 times the weight of 6,13-dihydroquinacridone or derivative and more preferably from 0.01 to 0.15 times the weight. Again, higher levels of catalyst do not impair the oxidation reaction, but are not required. After the oxidation is complete, the salt generated from the quinacridone dissolves completely in the organic reaction medium. Depending on the amount of dihydroquinacridone used, the reaction mixture can be quite fluid to facilitate the process. Where higher levels of dihydroquinacridone are used, the reaction mixtures tend to be viscous. In such cases it is possible to dilute the reaction mixture after oxidation with a suitable solvent. Preferred solvents are those that are miscible in the reaction mixture and will not initiate precipitation of the pigments from the reaction mixture. For example, it is possible to use the required amounts of water and / or methanol for this purpose. Diluting the reaction mixtures with excess water and / or methanol, has a possibility that the quinacridone pigments may initiate precipitation. Various methods are available to precipitate quinaeridone and / or its derivatives from the saline solution of the pigment. In a preferred process, the reaction mixture is immersed in an alcohol such as methanol, ethanol, n-propanol, isopropanol, n-butanol or its isomers and / or water. As previously noted, it is an advantage of the present process that the polymorphic phase of substituted and unsubstituted quinacridones can be controlled by the selection of the immersion medium. For example, immersing the mixture of the oxidation reaction of 6,13-dihydroquinacridone with the use of water produces an unsubstituted quinacridone of phase a. While the use of alcohols such as methanol provide a commercially important 2, 9-dimethylquinacridone phase β after immersing the reaction mixture of the corresponding dihydroquinacridone. Surprisingly, the use of hot alcohol (from 40 ° C to 97 ° C), particularly refluxed methanol, allows the formation of a desirable non-substituted quinacridone of various types. In another applicable process, the quinacridone pigment is precipitated by the addition of an alcohol and / or water to the reaction mixture. Precipitation can also be initiated using mineral acids such as dilute-, phosphoric-, and sulfuric hydrochloric acid or organic acids such as C2-C8 mono-, di- or tri-carboxylic acids. For example, acetic acid, optionally in conjunction with organic solvents; or by direct introduction • of hydrogen halide gas, for example hydrogen chloride, in the reaction mixture. Depending on the conditions of the selected precipitation, a pigment shape with a transparent particle, small in size (<0.1μm) or a large opaque particle (> 0.2μm) can be obtained. As previously noted, the ability to directly obtain pigments from small particle sizes without the need for mechanical size reduction operations is a definite benefit. Additionally, it is possible to conduct the precipitation in such a way that modifications of the selected crystal of all the quinacridones can be obtained. Such polymorphic modifications are known and described, for example, in Chemical Reviews, 67, 1, 1-18 (1967). In general, more opaque pigments are generated when an alcohol is chosen as the precipitation medium and the resulting pigment in suspension is stirred for 1 to 24 hours at atmospheric pressure or higher and at temperatures of 20 ° C or higher. The particle size of the pigment is controlled by varying the time and temperature of the treatment in the basic solvent mixture. A control of a greater degree of particle size, particularly for small particle pigments, can be exercised by the addition of particle growth inhibitors such as sulfonic acid, phthalimidomethyl amide, imidazolylmethyl-, pyrazolylmethyl-, N- ( dialkylamino-alkyl) sulfartaric acid derived from quinacridone. Such particle growth inhibitors also act under certain conditions as crystal phase directors. Particle growth inhibitors, also known as anti-flocculating agents, are well known, for example, in U.S. Pat. 3,386,843, U.S. 4,310,359, U.S. 4,692,189, EP 321397, EP 321919, and EP 362690.

The particulate growth inhibitors are aggregated in amounts ranging from 0.05 to 15%, preferably from 1 to 8%, and more preferably from 2 to 5% based on the corresponding pigment, it can be then but preferably, before the precipitation of the oxidized pigment. Additionally they can serve to diminish or avoid flocculation, increase the stability of the pigment dispersion and positively affect the rheological characteristics. When the maturation of the pigment crystals is complete, the pigment in its desired pigment form can be isolated by, for example, filtration or centrifugation, the pressure cake being washed with water or an organic solvent, preferably methanol, then with water and dried. Depending on the end use, specific amounts of texture improving agents can be advantageously added to the pigment. Suitable texture improving agents are, in particular, fatty acids of not less than 18 carbon atoms, for example, behenic or stearic acid or amides or metal salts thereof, preferably calcium or magnesium salts, also as plasticizers, waxes , resin acids such as abietic acid or salts thereof, rosin, alkylphenols or aliphatic alcohols such as a stearyl alcohol or vicinal diols such as dodecane-1, 2-diol, and also modified maleate / rosin resins or resins of rosin / fumaric acid or polymeric dispersants. The texture improving agents are preferably added in amounts of 0.1 to 30%, by weight, more preferably 2 to 15% by weight, based on the final product. The compositions of this invention are suitable for use as pigments for coloring high molecular weight organic materials. Examples of high molecular weight organic materials that can be colored or pigmented with the compositions of this invention are cellulose ethers and esters, such as ethylcellulose, nitrocellulose, cellulose acetate, cellulose butyrate, natural resins or synthetic resins such as resins of polymerization or condensation resins, for example to inoplasts, in particular formaldehyde / urea and formaldehyde / melamine resins, alkyd resins, acrylic resins, phenolic plastics, polycarbonates, polyolefins, polystyrene, polyvinyl chloride, polyamides, polyether, polyetherketone, polyurethanes, polyesters, rubber, casein , silicone, silicone resins, individually or in a mixture. The above high molecular weight compounds can be used individually or as mixtures in the form of plastics, centrifuged or melting solutions, varnishes, paints or printing inks. Depending on the final use, it is advantageous to use the pigments as inks for printers in the form of preparations. The compositions of the invention are preferably used in an amount of 0.1 to 30% by weight based on that of the high molecular weight organic material to be pigmented. The pigmentation of the high molecular weight organic compounds with the pigments of the invention is carried out, for example, by the incorporation of such pigments, optionally in the form of a master filler, into the substrates using laminators, powdered or mixed. The pigmented material is then brought into the final desired form by methods which are known per se, for example, calendering, molding, extruding, coating, spinning, melting or injection molding. It is often desirable to incorporate plasticizers into high molecular weight compounds prior to the process in order to produce non-brittle molds or to reduce their brittleness. Suitable plasticizers are, for example, esters of phosphoric acid, italic acid or sebacic acid. The plasticizers can be incorporated before or after working the composition into the polymers. To obtain different shades, it is also possible to add fillers or other chromophoric components such as white, black or colored pigments, in any quantity, for organic compounds of high molecular weight, in addition to the compositions of this invention. For pigment varnishes and printing inks, high molecular weight organic materials and pigments obtained according to the present invention, together with optional additives such as fillers, other pigments, drying materials or plasticizers, are dissolved or finely dispersed in a common organic solvent or a mixture of solvents. The processes may be such that individual components or mixtures thereof are dispersed or dissolved in the solvent and subsequently all components are mixed. The following examples further illustrate the preferred embodiments of this invention. In these examples, all parts given are by weight unless noted otherwise. EXAMPLE 1 To a one liter four-necked round bottom flask equipped with a stirrer, thermometer, gas inlet tube and reflux condenser was added aqueous sodium hydroxide (80 g; 50%), crude 2, 9-dimethyl-6,13-dihydroquinacridone (40.0 g, 1.17 moles), anthraquinone-2-sulfonic acid (4.0 g), 2-phthalimidomethylquinacridone (0.8 g) and polyethylene glycol 400 (360 g). Air was bubbled into the stirred mixture. The reaction mixture was heated with stirring and maintained at 90 ± 2 ° C for 3 hours. The black / deep violet reaction mixture is cooled to 25 ° C. To this mixture methanol (400 ml) was added with vigorous stirring. Part A: One half of the previous slurry was poured into water (1200 ml). The precipitated product was filtered, washed with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to produce 19.6 g of an attractive magenta pigment which was analyzed for 96.9% of 2,9-dimethylquinacridone; 0.1% of 2, 9-dimethyl-6,13-dihydroquinacridone and 0.8% of 2, 9-dimethylquinacridonaquinone. The product shows an X-ray diffraction pattern of a β-polymorph of 2,9-dimethylquinacridone. Part B: The other half of the previous slurry was poured into methanol (1200 ml). The precipitated product was filtered, washed with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to yield 19.4 g of a bright magenta pigment which is analyzed for 98.6% of 2,9-dimethylquinacridone; 0.1% of 2, 9-dimethyl-6,13-dihydroquinacridone and 0.1% of 2,9-dimethylquinacridonaquinone. The product shows an X-ray diffraction pattern of a β-polymorph of 2,9-dimethylquinacridone. Pouring the oxidation slurry into methanol was found to produce a pigment with better crystallinity compared to a pigment that is formed by pouring the slurry into water. Also, the pigment obtained by immersing it in methanol is coloristically more attractive. Example 2 To a one-liter four-necked round bottom flask equipped with a stirrer, thermometer, gas inlet tube and reflux condenser was added aqueous sodium hydroxide (80 g, 50%), 2, Crude 9-dimethyl-6, 13-dihydroquinacridone (40.0 g, 1.17 moles), anthraquinone-2-sulphonic acid (4.0 g), and polyethylene glycol 400 (360 g). Air was bubbled into the stirred mixture. The reaction mixture was heated with stirring and maintained at 90 ± 2 ° C for 3 hours. The black / deep violet reaction mixture is cooled to 25 ° C. and to this mixture is added 2-phthalimido-methylquinacridone (0.8 g). After stirring for H hour, the reaction mixture was poured into methanol (1200 ml) with vigorous stirring. The precipitated product was filtered, washed with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to yield 39.6 g of an attractive magenta pigment which is similar to the pigment of example 1. The product shows an X-ray diffraction pattern of a β-polymorph 2, 9-dimethylquinacridone. As shown, a growth inhibitor can be introduced after the oxidation is complete but before extinguishing the alkali metal salt of the quinacridone to provide a pigment with the desired particle size. Example 3 To a one-liter four-necked round bottom flask equipped with a stirrer, thermometer, gas inlet tube and reflux condenser was added aqueous sodium hydroxide (80 g, 50%), 6, Crude 13-dihydroquinacridone (39.2 g, 1248 moles), anthraquinone-2-sulfonic acid (4.0 g), and polyethylene glycol 400 (360 g) and 2-phthalimidomethylquinacridone (0.8 g). Air was bubbled into the stirred mixture. The reaction mixture was heated with stirring and maintained at 90 ± 2 ° C for 3 hours. The black / deep violet reaction mixture is cooled to 25 ° C. And to this mixture methanol (400 ml) was added with vigorous stirring. Part A: One half of the previous slurry was poured into water (900 ml). After H stirring hour the precipitated product was filtered, washed with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to yield 19.4 g of a deep red color quinacridone pigment (X-ray diffraction). Part B: The other half of the previous slurry was poured into methanol (900 ml). After stirring, the precipitated product was filtered, washed with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to produce 19.4 g of a matt violet pigment which shows a diffraction of a mixture of a and β-quinacridone. Example 4 To a one-liter four-neck round bottom flask equipped with a stirrer, a thermometer, a gas inlet tube and a reflux condenser was added aqueous sodium hydroxide (80 g; 50%), crude 2,9-dichloro-6,13-dihydroquinacridone (39.2 g, 1024 moles), anthraquinone-2-sulfonic acid (4.0 g), 2-phthalimidomethylquinacridone (0.8 g) and polyethylene glycol 400 (360 g). Air was bubbled into the stirred mixture. The reaction mixture was heated with stirring and kept at 90 ° C + 2 ° C for 3 hours. The reaction mixture is dark blue, cooled to 25 ° C. To this mixture methanol (400 ml) was added with vigorous stirring. Part A: One half of the previous slurry was poured into water (900 ml). After 1 hour of stirring the precipitated product was filtered, washed with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to produce 19.4 g of a deep magenta pigment which shows an X-ray diffraction of a? polymorph of 2, 9-dichloroquinacridone of an extremely small particle size. Part B: The other half of the previous slurry was poured into methanol (900 ml). After stirring, the precipitated product was filtered, washed with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to produce 19.4 g of a 2,9-dichloroquinacridone pigment? with a particle of very small size with an attractive deep magenta color.

Example 5 To a one-liter four-neck round bottom flask equipped with a stirrer, thermometer, gas inlet tube and reflux condenser was added aqueous sodium hydroxide (80 g, 50%), 2, Crude 9-dichloro-6, 13-dihydroquinoline (35.3 g, 0.922 mol), crude 6, 13-dihydroquinacridone (3.9 g, 0.012 mol), anthraquinone-2-sulphonic acid (4.0 g), 2-phthalimidomethylquinacridone (0.8 g) and polyethylene glycol 400 (360 g). Air was bubbled into the stirred mixture. The reaction mixture was heated with stirring and maintained at 90 ± 2 ° C for 3 hours. The reaction mixture is dark blue, cooled to 25 ° C. To this mixture methanol (400 ml) was added with vigorous stirring. Part A: One half of the previous slurry was poured into water (900 ml). After stirring, the precipitated product was filtered, washed with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to yield 19.4 g of a deep magenta pigment with X-ray diffraction of a very small particle size the solid solution pigment of 90 / 10 of 2, 9-dichloroquinacridone and unsubstituted quinacridone. Part B: The other half of the previous slurry was poured into methanol (900 ml). After stirring, the precipitated product was filtered, washed with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to yield 19.4 g of a very small particle solution pigment of a 90/10 composition of 2,9-dichloroquinacridone and unsubstituted quinacridone . The pigment achieved has a very attractive deep magenta color. Surprisingly, polyethylene glycol serves as an excellent solvent in the co-oxidation of a variety of substituted and / or unsubstituted dihydroquinacridones resulting in solid solution pigments. It is particularly surprising that the quinacridones generated by the co-oxidation of the dihydroquinacridones do not crystallize as separate entities. Therefore, it is possible to execute step a) separately in a different reactor for each compound of formula (II). Then to combine these reaction mixtures before precipitating them in step b). This advantageously allows more production flexibility, while obtaining similar results. Example 6: To a one-liter, four-neck round bottom flask equipped with a stirrer, a thermometer, a gas inlet tube and a reflux condenser was added aqueous sodium hydroxide (80 g, 50%). , Crude 9-dimethyl-6,13-dihydroquinacridone (40.0 g, 1167 moles), anthraquinone-2-sulfonic acid (4.0 g), and polyethylene glycol 400 (360 g). Air was bubbled into the stirred mixture. The reaction mixture was heated with stirring and maintained at 90 ± 2 ° C for 3 hours. The reaction mixture is dark purple and cooled to 25 ° C. To this mixture methanol (400 ml) was added with vigorous stirring. Part A: One half of the previous slurry was poured into water (900 ml). After% of hour of agitation the precipitated product was filtered, washed with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to produce 19.4 g of a deep magenta pigment which shows an X-ray diffraction pattern of a less crystalline β polymorph- of 2, 9-dichloroquinacridone of a very small particle size. Part B: The other half of the previous slurry was poured into methanol (900 ml). After stirring, the precipitated product was filtered, washed with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to produce 19.4 g of a very small particle pigment with an attractive deep magenta color. The pigment shows an X-ray diffraction pattern of a small size particle of 2,9-dimethylquinacridone of better crystallinity compared to the pigment of Example 6, Part A. Example 7: To a one-liter four-necked round bottom flask equipped with a stirrer, a thermometer, a gas inlet tube and a reflux condenser was added aqueous sodium hydroxide (80 g, 50%), 2,9-dimethyl. -6 crude 13-dihydroquinacridone (39.2 g, 1146 moles), anthraquinone-2-sulfonic acid (4.0 g), 2-phthalimidomethyl quinacridone (0.8 g) and polyethylene glycol 400 (360 g). Air was bubbled into the stirred mixture. The reaction mixture was heated with stirring and maintained at 90 ± 2 ° C for 3 hours. The reaction mixture is dark blue, cooled to 25 ° C. To this mixture methanol (400 ml) was added with vigorous stirring. Part A: One half of the previous slurry was poured into water (900 ml). After stirring, the precipitated product was filtered, washed with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to yield 19.4 g of a deep magenta pigment with X-ray diffraction of an extremely small particle size of 2,9-dimethylquinacridone and in a crystalline state even lower than the pigment of Example 6, Part A. Part B: The other half of the previous slurry was poured into methanol (900 ml). After stirring the precipitated product was filtered, washed with hot water (60CC) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to yield 19.4 g of a particle size significantly lower than 2,9-dimethylquinacridone of an attractively deep magenta color. The X-ray diffraction pattern shows a polymorph β having a lower degree of crystallinity compared to the pigment of Example 6, Part B. Example 8: To a one-liter four-neck round bottom flask equipped with a stirrer, a thermometer , a gas inlet tube and a reflux condenser were added aqueous sodium hydroxide (80 g, 50%), crude 2,9-dimethyl-6,13-dihydroquinacridone (58.8 g, 1719 mol), anthraquinone-2- sulfonic acid (4.0 g), 2-phthalimidomethylquinacridone (1.2 g) and polyethylene glycol 400 (340 g). Air was bubbled into the stirred mixture. The reaction mixture was heated with stirring and maintained at 80 ± 2 ° C for 3 hours. The dark purple reaction mixture was cooled to 25 ° C and poured into methanol (1200 ml) with vigorous stirring. After 1 hour of stirring the precipitated product was filtered, washed with methanol followed by hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to produce 59.6 g of a very attractive deep magenta pigment which exhibits an X-ray diffraction pattern of a significantly smaller particle size similar to the 2, 9-dimethylquinacridone obtained in Example 7, Part B. Oxidations can be carried out in a 15% concentration / loading pigment (even in the presence of a growth inhibitor) resulting in excellent pigments. Example 9: To a four-neck round bottom flask equipped with a stirrer, a thermometer, a gas inlet tube and a reflux condenser was added aqueous sodium hydroxide (80 g, 50%), 2, Crude 9-dimethyl-β, 13-dihydroquinacridone (60.0 g, 1754 moles), anthraquinone-2-sulfonic acid (4.0 g), polyethylene glycol 400 (340 g). Air was bubbled into the stirred mixture. The reaction mixture was heated with stirring and maintained at 80 ± 2 ° C for 3 hours. The dark purple reaction mixture was cooled to 25 ° C and poured into methanol (1200 ml) with vigorous stirring. After 1 hour of stirring the precipitated product was filtered, washed with methanol then with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to produce 59.8 g of a very attractive deep magenta pigment exhibiting an X-ray diffraction pattern of an insignificantly smaller particle size * similar to 2,9-dimethylquinacridone obtained in Example 6, Part B. Oxidations can be carried out in a 15% concentration / loading pigment (even in the presence of a growth inhibitor) which provides excellent pigments. Example 10: To a one-liter four-necked round bottom flask equipped with a stirrer, a thermometer, a gas inlet tube and a reflux condenser was added aqueous sodium hydroxide (80 g, 50%), 2,9-dimethyl. -6 crude 13-dihydroquinacridone (80.0 g, 2339 moles), anthraquinone-2-sulfonic acid (4.0 g), and polyethylene glycol 400 (320 g). Air was bubbled into the stirred mixture. The reaction mixture was heated with stirring and maintained at 80 ± 2 ° C for 3 hours. The dark purple reaction mixture was cooled to 25 ° C and poured into methanol (1200 ml) with vigorous stirring. After stirring the precipitated product was filtered, washed with methanol then with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to produce 59.8 g of a very attractive deep magenta pigment which exhibits an X-ray diffraction pattern of a smaller particle size similar to the 2, 9-dimethylquinacridone obtained in Example 6, Part B. Oxidations can be carried out in a 20% concentration / charge pigment which provides excellent pigments. Example 11: To a one-liter, four-necked round bottom flask equipped with a stirrer, a thermometer, a gas inlet tube and a reflux condenser was added aqueous sodium hydroxide (80 g, 50%), 2, Crude 9-dimethyl-6, 13-dihydroquinacridone (60.0 g, 1754 moles), anthraquinone-2-sulfonic acid (4.0 g), and polyethylene glycol 200 (340 g). Air was bubbled into the stirred mixture. The reaction mixture was heated with stirring and maintained at 80 ± 2 ° C for 3 hours. The dark purple reaction mixture was cooled to 25 ° C and poured into methanol (1200 ml) with vigorous stirring. After of. stirring hour the precipitated product was filtered, washed with methanol then with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to produce 59.8 g of a magenta pigment exhibiting an X-ray diffraction pattern of a small pigment particle size of 2,9. -dimethylquinacridone pigment containing a mixed phase a and β. Oxidation can be effected with PEG 200. Example 12: To a four-neck round bottom flask equipped with a stirrer, a thermometer, a gas inlet tube and a reflux condenser was added aqueous sodium hydroxide ( 80 g, 50%), crude 2, 9-dimethyl-6, 13-dihydroquinacridone (60.0 g, 1754 moles), anthraquinone-2-sulfonic acid (4.0 g), and polyethylene glycol 300 (340 g). Air was bubbled into the stirred mixture. The reaction mixture was heated with stirring and maintained at 80 ± 2 ° C for 3 hours. The dark purple reaction mixture was cooled to 25 ° C and poured into methanol (1200 ml) with vigorous stirring. After stirring the precipitated product was filtered, washed with methanol then with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to produce 59.8 g of a very attractive deep magenta pigment that exhibits an X-ray diffraction pattern of a particle pigment of significantly smaller size similar to the 2, 9-dimethylquinacridone obtained in Example 6, Part B. Oxidations can be carried out in PEG 300 which provides excellent pigments. Example 13: To a one-liter four-necked round bottom flask equipped with a stirrer, a thermometer, a gas inlet tube and a reflux condenser was added aqueous sodium hydroxide (40 g, 50%), 6, Crude 13-dihydroquinacridone (25.0 g, 0.796 moles), anthraquinone-2-sulfonic acid (2.5 g), and polyethylene glycol 400 (2.5 g) and N-methylpyrrolidin-2-one (200 g). Air was bubbled into the stirred mixture. The reaction mixture was heated with stirring and maintained at 90 ± 2 ° C for 3 hours. The deep black-violet reaction mixture is cooled to 70 ° C. To this mixture was added methanol (500 ml) with vigorous stirring.After stirring the precipitated product was filtered, washing with methanol then with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to produce 24.6 g of a matt violet pigment which was analyzed for 96.6 quinacridone; 0.1% of 6, 13-dihydroquinacridone and 1.6% of quinacridonaquinone. The infrared spectrum indicated a mixture of quinacridone and quinacridonaquinone. The product shows an X-ray diffraction pattern of a β-quinacridone phase. Quantities of polyethylene glycol 400 catalysts (with N-methylpyrrolidin-2-one) are shown to improve the purity of the quinacridone resulting from the oxidation of dihydroquinacridone. Example 14: To a four liter round bottom flask equipped with a stirrer, a thermometer, a gas inlet tube and a reflux condenser was added aqueous sodium hydroxide. (44.5 g, 45%), crude 6, 13-dihydroquinacridone (25.0 g, 0.796 moles), anthraquinone-2-sulfonic acid (2.5 g), polyethylene glycol 400 (2.5 g) and N-methylpyrrolidin-2-one (200 g) ). Air was bubbled into the stirred mixture. The reaction mixture was heated with stirring and maintained at 90 ± 2 ° C for 3 hours. The deep black-violet reaction mixture is cooled to 50 ° C. To this mixture methanol (500 ml) was added with vigorous stirring. After stirring the precipitated product was filtered, washed with methanol then with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake was dried in an oven overnight at 80 ° C to produce 24.6 g of a matt violet pigment which is analyzed for 97.3% quinacridone; 0.1% of 6, 13-dihydroquinacridone and 1.0% quinacridonaquinone. The product shows an X-ray diffraction pattern of a β-base quinacridone. Catalyzed oxidation of glycol Dihydroquinacridone polyethylene using potassium hydroxide instead of sodium hydroxide in N-methylpyrrolidin-2-one which produces high purity quinacridone. The above examples are not limiting and numerous variations of specific embodiments described above can be made without departing from the spirit of the invention which is intended to be limited only by the language of the appended claims. Comparative Example 1: To a one-liter four-necked round bottom flask equipped with a stirrer, a thermometer, a gas inlet tube and a reflux condenser was added aqueous sodium hydroxide. (80 g, 50%), crude 2, 9-dimethyl-6,13-dihydroquinacridone (40.0 g; 1. 17 moles), anthraquinone-2-sulfonic acid (4.0 g), 2-phthalimidomethylquinacridone (0.8 g) and ethylene glycol (360 g). Air was bubbled into the stirred mixture. The reaction mixture was heated with stirring and maintained at 90 ± 2 ° C for 0.5 hours. No reaction is observed. The reaction mixture remains pale pink. Essentially, 2,9-dimethyl-6,13-dihydroquinacridone was recovered.

While polyalkylene glycols are particularly useful their monomeric ethylene glycols failed to oxidize dihydroquinacridone. COMPARATIVE EXAMPLE 2 To a one-liter four-necked round bottom flask equipped with a stirrer, a thermometer, a gas inlet tube and a reflux condenser was added aqueous sodium hydroxide (40 g, 50%) Crude 2, 9-dimethyl-6,13-dihydroquinacridone (25.0 g, 0.731 moles), anthraquinone-2-sulfonic acid (2.5 g), and N-methylpyrrolidin-2-one (250 g). Air was bubbled into the stirred mixture. The reaction mixture was heated with stirring and maintained at 80 ± 2 ° C for 3.0 hours. The dark blue reaction mixture was cooled to 50 ° C and poured into aqueous methanol (1200 ml, 50%) cooled to (10 ° C) with vigorous stirring. After stirring the precipitated product was filtered, washed with methanol then with hot water (60 ° C) until the pH of the filtrate was 7.0. The resulting pigment pressure cake is dried overnight in an oven at 80 ° C to produce 24.5 g of a matte magenta pigment which is analyzed for 52.5% of 2,9-dimethylquinacridone; 3.9% 2, 9-dimethyl-6-13-dihydroquinacridone and 8.1% of 2, 9-dimethylquinacridonaquinone. The infrared spectrum and the X-ray diffraction pattern indicate a mixture of previous compounds. The foregoing demonstrates that N-methylpyrrolidin-2-one does not serve as a useful solvent for the oxidation of dimethyldihydroquinacridone.

Comparative Example 3 To a one-liter four-neck round-bottom flask equipped with a stirrer, a thermometer, a gas inlet tube and a reflux condenser was added aqueous sodium hydroxide (40 g, 50%). , Crude 13-dihydroquinacridone (25.0 g, 0.796 moles), anthraquinone-2-sulfonic acid (2.5 g), and N-methylpyrrolidin-2-one (200 g). Air was bubbled into the stirred mixture. The reaction mixture was heated with stirring and maintained at 90 ± 2 ° C for 3.0 hours. The deep violet-black reaction mixture is cooled to 50 ° C. To this mixture methanol (500 ml) was added with vigorous stirring. After vigorous stirring hour the precipitated product was filtered, washed with methanol then with hot water (60CC) until the pH of the filtrate was 7.0. The resulting pigment pressure cake is dried overnight in an oven at 80 ° C to produce 24.6 g of a pale violet phase quinacridone pigment which is analyzed to obtain 94.7% quinacridone; 0.1% of 6,13-dihydroquinacridone and 2.2% quinacridonaquinone. The purity is significantly lower than in example 13 of the present. '

Claims (15)

1. Claims: 1. a process for preparing a substituted or unsubstituted quinacridone of the formula or a quinacridone solution of the formula (I), wherein X and Y in the formula (I) are independently substituents 1 or 2 selected from hydrogen, fluorine, chloride, C? -C3alkyl, C? -C3 alkoxy and COOR wherein R is hydrogen or C? -C? 0 alkyl, said process consists of: a) oxidizing a salt of a corresponding 6,13-dihydroquinacridone of the formula or salts of the corresponding 6,13-dihydroquinacridone of the formula II, with air or another mixture of oxygen-containing gas in a reaction medium comprising an effective amount of an oxidant of a compound represented by the formula R? -0- [(CH2) B_ (CHR! ') N-0]? -0-Ri' '(III) where R? f RA, RA ', are, independently of one another, hydrogen or d-C4alkyl, Rx and RA' are attached C2-C4alkylene, m and n = 1 to 4, and x is 3 to 1000, in the presence of an aqueous base and a catalyst b) precipitating said substituted or unsubstituted quinacridone from the reaction mixture of step a; and c) recovering said substituted or unsubstituted quinacridone. The process of claim 1, wherein said substituted or unsubstituted quinacridone is selected from the group comprising unsubstituted quinacridone, 2,9-dichloroquinacridone, 2,9-difluoroquinacridone, 4,11-dichloroquinacridone, 4, 11 -difluoroquinacridone, 2,9-dicarboxyquinacridone, 3, 10-dichloroquinacridone, 2,9-dimethylquinacridone, 4, 11-dimethylquinacridone and 2,9-dimethoxyquinacridone. 3. The process of claim 1, wherein the salt of a corresponding 6,13-dihydroquinacridone or a corresponding 6,13-dihydroquinacridone sample of the formula II is oxidized with air or some other gas mixture containing oxygen in the a polyalkylene glycol medium in the presence of an aqueous base and a catalyst. 4. The process according to claim 3, wherein said polyalkylene glycol has an average molecular weight of 200 to 600. 5. The process according to claim 3, wherein said polyalkylene glycol is present in an amount of from 40 to about 2 times the weight of 6,13-dihydroquinacridone, preferably from 25 to 3 times the weight of 6,13-dihydroquinacridone. The process according to claim 1, wherein said aqueous base comprises a solution of an alkali metal hydroxide, preferably potassium or sodium hydroxide, more preferably sodium hydroxide. The process according to claim 1, wherein a molar ratio of said base to said 6,13-dihydroquinacridone is from about 1.3 to about 1:39, preferably from about 1: 4 to about 1:15. The process according to claim 1, wherein said oxygen-containing gas is air and said oxidation catalyst is a quinone or a derivative thereof present in an amount of about 0.005 to about 0.25 times the weight of 6, 13-dihydroquinacridone, preferably is present in an amount of about 0.01 to about 0.15 times the weight of 6,13-dihydroquinacridone and is anthraquinone or a derivative thereof, more preferred a derivative anthraquinone selected from monochloroanthraquinone, dichloroanthraquinone, anthraquinone- 2, 6-sulfonic acid, anthraquinone-2-disulfonic acid and mixtures thereof. 9. The process according to claim 1, wherein the oxidation is conducted at a temperature below 150 ° C, preferably from 50 to 100 ° C, more preferred from 70 ° to 90 ° C: 10. The process according to claim 1, wherein said substituted or non-substituted quinacridone is precipitated from said reaction mixture by immersion in water, in an alcohol or in a mixture thereof or by adding water to said reaction mixture. , an alcohol or a mixture thereof. 11. The process according to claim 21, wherein said reaction mixture is introduced into methanol, ethanol, n-propanol, iso-propanol, or n-butanol or an isomer thereof. The process according to claim 1, wherein said substituted or non-substituted quinacridone is precipitated from said reaction mixture by immersion in addition to said reaction mixture in at least one mineral acid, preferably hydrochloric acid, sulfuric acid, or phosphoric acid; an organic acid, preferably acetic acid; or a mixture of them. The process according to claim 1, wherein said substituted or unsubstituted quinacridone is precipitated from said reaction mixture by the introduction of hydrogen chloride gas into said reaction mixture. 14. The process according to claim 1, wherein a solution is prepared. 15. The process according to claim 14, wherein step a) is separately initiated in a different reactor for each 6,13-dihydroquinacridone salt of formula II to form a reaction mixture, and the reaction mixtures are combine before said precipitation step. SUMMARY A process for preparing a substituted or unsubstituted quinacridone of the formula or a solid solution of quinacridones of the formula (I), wherein X and Y are independently 1 or 2 substituents selected from hydrogen, fluorine, chloride, C? -C3alkyl, C? -C3 alkoxy and COOR wherein R is hydrogen or Ci-Cio alkyl, in which a salt of a corresponding 6,13-dihydroquinacridone of the formula II having the same substitutions as the desired quinacridone of the formula I, or a mixture of the corresponding 6,13-dihydroquinacridones of the formula II, are oxidized with oxygen-containing gas in the presence of an aqueous base and a catalytically effective amount of An oxidation catalyst is characterized in that the oxidation is carried out in the presence of a polyglycolic reaction medium of the formula R? -0- [(CH2) m- (CHRi ') n-0] x-0-R? "(III) •