MXPA97003124A - Incorporation of polycyclicosaromatic compounds in quinacrid procedures - Google Patents

Abstract

The present invention relates to a process for the preparation of quinacridone pigments consisting of a) heating, at a temperature of 80 ° C to 145 ° C, a reaction mixture consisting of i) 2,5-dianilinoterephthalic acid, an acid ester 2,5-dianilino-3,6-dihydroterephthalic, a derivative of 2,5-dianilinoterephthalic acid or a 2,5-dianilino-3,6-dihydroterephthalic acid ester having one or more substituents on at least one aniline ring, or a mixture of substances, ii) 3 to 15 parts by weight, by component (a) (i), of a dehydrating agent, and iii) 0.1 to 15 percent, based on component (a) (i) ), of one or more non-pigment aromatic polycyclic copolymers and / or derivatives thereof, with the proviso that, if component (a) (i) is a 2,5-dianilino-3,6-dihydroterphthalic acid ester or a derivative thereof, the reaction step (a) additionally consists of an oxidation step, b) drowning the reaction mixture of the cover (a) by adding said reaction mixture to 3 to 15 parts by weight, by component (a) (i), of a liquid in which the quinacridone pigment is substantially insoluble, c) isolating the quinacridone pigment; d) if necessary, condition the quinacridone pigment, and e) optionally, mix the quinacridone pigment with one or more quinacrylate derivatives

Description

INCORPORATION OF AROMATIC POLYCYCLIC COMPOUNDS IN QUINACRIDONE PROCEDURES BACKGROUND OF THE INVENTION This invention relates to a process for the preparation of quinacridone pigments having a reduced particle size, better coloristic properties and better rheological properties. The addition of certain aromatic polycyclic compounds and / or their derivatives during quinacridone synthesis provides quinacridone pigments having more intense, brighter and more transparent mass tones, higher metallic luster and better rheological properties. The procedures for the preparation of quinacridone are known. For example, S.S. Labana and L.L. Labana, "Quinacridones", in Chemical Review, 67, 1-18 (1967) and US Patents. 3,157,659, 3,256,285 and 3,317,539. The quinacridones thus obtained, known as crude quinacridone, are, in general, unsuitable for use as pigments and must undergo one or more additional finishing steps to modify the particle size, the shape of the particle or the crystal structure to achieve quality. pigmentary. A preferred method for preparing quinacridones includes the thermal induction of the ring closure of the 2,5-dianilinoterephthalic acid intermediates, as well as their known aniline-substituted derivatives, in the presence of phosphoric acid. For example, U.S. Pat. 3,257,405. After completion of the ring closure, the melt is drowned by pouring it into a liquid in which the quinacridone is substantially insoluble, usually water and / or an alcohol. The resulting crystalline pigment is then further conditioned by solvent treatment or milling in combination with solvent treatment. It is also possible to use 2, 5-dianilino-6,13-dihydroterephthalic acid as a starting material in the ring closure reaction. The resulting dihydroquinacridone must, however, be oxidized and then conditioned. The final particle size of the quinacridone pigments can be controlled by the methods used in both synthesis and post-treatment. For example, quinacridone pigments can be made more transparent by reducing the particle size, or more opaque by increasing the particle size. In known methods, the particle size is generally controlled during pigment precipitation by drowning or during grinding or solvent treatment of the crude pigment. The dyeing strength and transparency of the pigments can also be affected by the solvent treatment. Frequent reference is made to the post-treatment stages that manipulate the particle size of the raw pigments as conditioning methods. Several suitable conditioning methods are known. However, the most commonly used methods include grinding dry crude quinacridone, generally in the presence of undesirably large amounts of an inorganic salt which must then be removed. The pigment quinacridones can also be obtained by premixing the dry raw material first and then treating the ground material with an organic liquid. Other methods include a premixing step, followed by another milling step using water and small amounts of an organic liquid. The pigment quinacridones can also be obtained by heat treatment of the filter cake in large amounts of solvent. Various additives have been added during the grinding, solvent treatment or post-treatment with solvents stages to further improve the properties of the pigment. For example, U.S. Pat. No. 4,455,173 discloses a process in which crude quinacridone pigments are acid-ground or ball-milled and then milled in an organic liquid, preferably in the presence of a 2-phthalimidomethylquinacridone particle size growth inhibitor. U.S. Pat. No. 5,084,100 discloses a method in which crude guinacridone is milled with beads in the presence of aluminum sulfate and esters of alkanedicarboxylic acids. The addition of certain quinacridone derivatives to the ring closure stage has also been discussed. For example, US Pat. 5,368,641 describes the use of various quinacridone derivatives in the manufacture of 2,9-dimethylquinacridone. The present invention, on the other hand, uses classes of certain aromatic polycyclic compounds rather than quinacridones in the step of ring closure. European Patent Application 643 110 discloses the use of quinacridone derivatives during the oxidation of dihydroquinacridone (prepared from 2,5-dianilino-6,13-dihydroterephthalic acid) to quinacridone. The present invention, on the other hand, not only uses aromatic polycyclic compounds other than quinacridones as additives, but also uses the additives in the step of closing the ring. Compounds suitable for the present invention have been described as being useful for treating various pigments, including quinacridones (e.g., British Patent 2,058,813), but such derivatives have previously been added only to fully formed quinacridone pigments. The present invention differs from said methods in that the non-pigment aromatic polycyclic compounds are added during the step of ring closure of the quinacridone synthesis. When added to the ring closure stage and, optionally, also during the finishing step, said compounds can provide quinacridone pigments having desirable color properties which are particularly desirable for automotive finishes. The present invention provides quinacridones of lower particle size which have better yield properties by the addition of certain aromatic polycyclic compounds and / or their derivatives to the step of ring closure of the quinacridone synthesis and, optionally, also to the later stages of conditioning. The addition of said compounds during the synthesis of quinacridone (ie, ring closure) before precipitation gives rise to a more intense and brighter pigment that has better transparency and rheological properties, as well as brighter metal shades. The process of the invention is, in principle, applicable to all methods of manufacturing quinacridone pigments that include an "acid pasting" step, but the greatest refinement is expected in the color properties for ring closure procedures, including the procedures used to prepare solid quinacridone solutions. COMPENDIUM OF THE INVENTION This invention relates to a process for the preparation of quinacridone pigments consisting of: (a) heating, at a temperature of about 80 ° C to about 145 ° C (preferably, 100 ° C to 130 ° C) (preferably for approximately one to about 24 hours), a reaction mixture consisting of (i) 2,5-dianilinoterephthalic acid, an ester of 2,5-dianilino-6,13-dihydrote reftalic acid derivative 2,5-dianilinoterephthalic or a 2,5-dianilino-6,13-dihydroterephthalic acid ester having at least one or more substituents on at least one aniline ring, or a mixture thereof; (ii) about 3 to about 15 parts by weight (preferably, 3 to 10 parts by weight), on the part of component (a) (i), of a dehydrating agent (preferably, polyphosphoric acid), and (iii) about 0.5 to about 15 percent by weight (preferably, 1 to 10 percent by weight), based on component (a) (i), of one or more non-pigment aromatic polycyclic compounds (preferably colorless or substantially colorless) and / or derivatives thereof (preferably, anthraquinone or pyrene derivatives), with the proviso that, if the component 10 (a) (i) is an ester of 2, 5-dianilino- , 13-dihydroterephthalic acid or a derivative thereof, the reaction step (a) additionally consists of an oxidation step (which converts the dihydroquinacridone intermediate initially formed into the corresponding quinacridone); (b) drowning the reaction mixture of step (a) by adding said reaction mixture at about 3 to about 15. parts by weight (preferably 5 to 10 parts by weight), by component (a) (i), of a liquid in which the quinacridone pigment is substantially insoluble; (c) isolating the quinacridone pigment; (d) optionally, conditioning the quinacridone pigment (optionally, in the presence of additional amounts of the non-pigmentary aromatic polycyclic compound and / or derivatives thereof), and (e) optionally mixing (preferably, dry-mixing) the pigment of quinacridone resulting with one or more quinacri derivatives donates. DETAILED DESCRIPTION OF THE INVENTION Quinacridone pigments (by which unsubstituted quinacridone is understood, quinacridone derivatives and solid solutions thereof) are prepared according to the invention by first closing the ring of intermediates of 2,5-dianilinoterephthalic acid, including known aniline-substituted derivatives, heating said terephthalic acid intermediates in the presence of a dehydrating agent (preferably, polyphosphoric acid) and an aromatic polycyclic compound according to the invention, or, less preferably, thermally inducing ring closure in a high point solvent of boiling in the presence of an aromatic polycyclic compound according to the invention. Quinacridone is then drowned and isolated by known methods. The quinacridone pigment is preferably also subjected to further conditioning steps to improve the pigment properties and, if desired, mixed with an additional quinacridone derivative. The method of the invention can be used to prepare unsubstituted uinacridone or substituted quinacridone derivatives in the ring, depending on whether ring closure is carried out using 2,5-dianilinoterephthalic acid or derivatives thereof having one or more substituents in at least one of the two aniline rings. Although essentially any 2, 5-dianilinoterephthalic acid derivative known in the art can be used, particularly preferred 2, 5-dianilinoterephthalic acid derivatives are those in which both aniline moieties are substituted (typically with the same substituent) in the position for groups such as halogen (preferably chloro), C 1 -C 6 alkyl (preferably methyl) and C 1 -C 6 alkoxy (preferably methoxy). It is also possible to use 2, 5-dianilinoterephthalic acid derivatives in which both aniline residues are substituted in the ortho or meta positions. Examples of suitable 2, 5-dianilinoterephthalic acid derivatives include 2,5-di (4-chloroanilino) terephthalic acid, 2,5-di (4-methylanyl-no) terephthalic acid, 2,5-di (4) acid -methoxy-anilino) terephthalic.

It is also possible to use mixtures containing 2, 5-dianilinoterephthalic acid and one or more derivatives thereof or mixtures containing two or more derivatives of 2,5-dianilinoterephthalic acid. The use of said mixtures provides a particularly advantageous method for obtaining solid solutions of quinacridone. Mixtures containing 2, 5-dianilinote-reftalic acid and / or a derivative thereof in combination with a fully formed quinacridone pigment (generally in crude form) can also be frequently used. The ring closure step (a) is carried out in a dehydrating agent, particularly a strong acid such as polyphosphoric acid, polyphosphoric acid esters or sulfuric acid. For example, U.S. Pat. 4,758,665 and S.S. Labana and L.L. Labana, "Quinacrido-nes", in Chemical Reviews, 67, 1-18 (1967). In particular, polyphosphoric acid having a phosphate content equivalent to about 110-120% H3P0 is preferred. When polyphosphoric acid is used, the weight ratio of polyphosphoric acid to the terephthalic acid intermediate is typically from about 3: 1 to about 10: 1 (preferably 4: 1 to 8: 1). Lower ratios can give highly viscous reaction masses, but are generally preferred due to cost considerations.

It is sometimes preferable to use a 2,5-dianilino-6,13-dihydroterephthalic acid ester (preferably, a C 1 -C 6 alkyl ester) or a derivative thereof as a starting material in the ring closure reaction. , after which the resulting dihydroquinacridone must be oxidized and collected. The present invention is also applicable to this variant of quinacridone synthesis. It is, of course, possible to use 2, 5-dianilino-6,13-dihydroterephthalic acid ester mixtures and / or derivatives thereof to obtain solid quinacridone solutions. A critical feature of the invention is the presence of a non-pigmentary aromatic polycyclic compound during the ring closure reaction, the term "non-pigmentary" as used herein means that the compounds are significantly less highly colored and lack good pigment properties compared to the quinacridone pigments with which they are used. That is, that the suitable non-pigment aromatic polycyclic compounds would not have in themselves any practical utility as pigments. Suitable non-pigment aromatic polycyclic compounds may even be colorless or substantially colorless. The term "substantially colorless" does not mean that the aromatic polycyclic compounds must be absolutely devoid of color in the visible region, but instead only means that the aromatic polycyclic compounds are insignificantly colored in comparison with the quinacridone pigments with which are used. For example, the preferred substantially colorless aromatic polycyclic compounds exhibit minor molar (preferably at least an order of magnitude less than) orders of magnitude smaller than those of the quinacridone pigments with which they are used. Suitable aromatic polycyclic compounds include compounds having the following formula (I) Q (A-Y) n (I) wherein Q represents an aromatic polycyclic moiety; A represents linking groups -O-, -S-, -NRa- (where Ra is hydrogen, C 1 -C 12 alkyl, C 2 -C 2 alkenyl, C 5 -C 7 cycloalkyl, C 6 -C 6 aryl or C 7 -C aralkyl aryl? 6), -S02-, -CO-, -Alq- (where -Alq- is C? -C8 alkylene, substituted C? -C8 alkylene, C5-C cycloalkylene or substituted C5-C7 cycloalkylene), or -Ar- ( where -Ar- is C6-C? 0 arylene or C6-C? arylene or substituted), chemically reasonable combinations of said linking groups or a direct bond between Q and Y (preferably -S02-NH-Alk-, -CO- NH-Alq- or direct links); Y represents hydrogen, C? -C12 alkyl, C2-C12 alkenyl, C5-C7 cycloalkyl, C5-C7 cycloalkenyl, C6-C? Aryl, heteroaryl of five or six ring atoms (in which at least one atom of such ring atoms is N, 0, S or a combination thereof and which are optionally fused to one or more additional aromatic rings); aralkyl C7-C6, 0Rb (where Rb is hydrogen, metal or C1-C12 alkyl), -NRcRd (where Rc and Rd are independently hydrogen, C? -C? 2 alkyl, C2-C? 2 alkenyl, C5 cycloalkyl -C7, aryl Cedo or C7-Ci6 aralkyl, or Rc and Rd together are C-C6 alkylene, forming a heterocyclic group, or are aliphatic or aromatic dicarbonyl groups that form an imide, and where Rc and Rd may optionally further contain heteroatoms such as N, 0 or S and, optionally, they can be further substituted with C 1 -C 2 alkyl, C 1 -C 2 alkoxy, C 2 -C 2 alkenyl, C 5 -C 7 cycloalkyl, C 5 -C 7 cycloalkenyl, C 5 cycloalkoxy -C7, C 1 -C 12 aryl, C 6 -C 0 aryloxy, C 7 -C 6 aralkyl, C 7 -C 16 aralkoxy, -OH, halogen, -CN, carboxyl, -C0-NRcRd or -S02-NRcRd), or halogen , and n is from about 0.01 to about 4. Fractional values for n indicate that polycyclic aromatic compounds. they can be used as mixtures of compounds having various degrees of substitution, including the same unsubstituted aromatic polycyclic compound (ie, OH). When more than one group -A-Y is present, the various groups A and Y can, of course, be the same or different from each other. The aromatic residue Q can be derived essentially from any class of non-pigmentary aromatic polycyclic compound, including heteroaromatic compounds in which at least one ring atom is N, O, S or a combination thereof, such as anthracene, phenanthrene, pyrene , chrysene, indole, thiazole, benzimidazole, quinoline, acridone, anthraquinone, phenothiazine, quinazoline, carbazole, benzantrone and perylene. The aromatic polycyclic moiety itself may contain one or more substituents other than the -AY groups, including, for example, halogen (preferably chloro), C?-C6 alkyl (preferably methyl), C?-C6 alkoxy (preferably methoxy) , C5-C7 cycloalkyl, C5-C7 cycloalkoxy, C6-C6 aryl, C6-C10 aryloxy, C7-C6 aralkyl, C7-C6 aralkoxy, aminoalkyl, nitro and cyano. Particularly preferred aromatic polycyclic compounds include anthraquinone or derivatives thereof (particularly salts of mono- and disulfonic acid) or pyrene or derivatives thereof (particularly salts of tetrasulfonic acid). As used herein, the term "C 1 -C 12 alkyl" refers to straight or branched chain aliphatic hydrocarbon groups having from 1 to 12 carbon atoms. Examples of C 1 -C 2 alkyl are methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl and their isomeric forms. The term "C 1 -C 12 alkoxy" refers to straight or branched chain alkyloxy groups having from 1 to 12 carbon atoms. Examples of C 1 -C 2 alkoxy methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy and its isomeric forms are examples. The term "C2-C2 alkenyl" refers to straight or branched chain unsaturated aliphatic hydrocarbon groups having from 2 to 12 carbon atoms and a carbon-carbon double bond. Examples of C 2 -C 2 alkenyl ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl and its isomeric forms are examples. The term "C5-C7 cycloalkyl" refers to cycloaliphatic hydrocarbon groups having from 5 to 7 carbon atoms. Examples of C5-C7 cycloalkyl are cyclopentyl, cyclohexyl and cycloheptyl. the term "C5-O7 cycloalkoxy" refers to cycloalkyloxy groups having from 5 to 7 carbon atoms. Examples of C5-C7 cycloalkoxy are cyclopentyloxy, cyclohexyloxy and cycloheptyloxy. The term "C5-C7 cycloalkenyl" refers to cycloaliphatic hydrocarbon groups having from 5 to 7 carbon atoms and a carbon-carbon double bond. Examples of C5-C7 cycloalkenyl are cyclopentenyl, cyclohexenyl and cycloheptenyl. The term "C 6 -C 0 aryl" refers to phenyl and 1- or 2-naphthyl, as well as phenyl and naphthyl groups substituted with alkyl, alkoxy, halogen, cyano and nitro as defined herein. The term "C 6 -C 0 aryloxy" refers to phenoxy and 1- or 2-naphthoxy, wherein the aryl portion may be optionally substituted as described above for "aryl". The term "heteroaryl" refers to five or six membered aromatic groups wherein at least one ring atom is N, O, S or a combination thereof and which may be optionally fused to one or more additional aromatic rings. Said heteroaryl groups are attached to group A at a ring carbon atom or, when chemically reasonable, at a ring nitrogen atom. Examples of heteroaryl are pyrrolyl, imidazolyl, pyrazolyl, furanyl, thiophenyl, isothiazolyl, pyridinyl, pyrazinyl, pyrimidinyl, pyridazinyl and the like. The term "C 7 -C 6 aralkyl" refers to C 1 -C 6 alkyl substituted with C 6 -C 0 aryl, such that the total number of carbon atoms is from 7 to 16. Examples of C 7 aralkyl are Ci6 benzyl, phenethyl and naphthylmethyl. The term "aralkoxy C7-Ci6p" refers to C?-C6 alkoxy substituted with C ar-Cι aryl, such that the total number of carbon atoms is from 7 to 16. An example of aralkoxy C 7 -C 6 is benzyloxy The term "C?-C 8 alkylene" refers to straight or branched chain difunctional aliphatic hydrocarbon groups having from 1 to 8 carbon atoms, examples of C?-C 8 methylene alkylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene and octylene, as well as their branched isomeric forms. The related term "C-C6 alkylene" refers to straight or branched chain difunctional aliphatic hydrocarbon groups having from 4 to 6 carbon atoms and are attached to the nitrogen atom of the amide through two different carbon atoms to form a heterocyclic ring. Examples of C-C6 butylene alkylene (which forms a pyrrolidino substituent), optionally substituted with a methyl group, and pentylene (which forms a piperidino substituent) are examples. The term "C5-C7 cycloalkylene" refers to difunctional cycloaliphatic hydrocarbon groups having from 5 to 7 carbon atoms. Examples of C5-C7 cycloalkylene are cyclopentylene, cyclohexylene and cycloheptylene. The term "arylene C6-C? 0" refers to phenylene and disubstituted naphthalene, wherein the aryl portion may be optionally substituted as described above for "aril". Examples of halogen are fluorine, chlorine, bromine and iodine. Especially preferred aromatic polycyclic compounds are sulfonic acids having the following formula (II) Q (S02-ORb) n (II) where Q represents an aromatic polycyclic compound, Rb is hydrogen or a metal and n is about 0.01. to about 4. As with the general formula (I), the fractional values for n indicate that the derivatives can be used as mixtures, including mixtures containing the unsubstituted aromatic polycyclic compound. Suitable metals include alkali metals (such as lithium, sodium, and potassium), alkaline earth metals (such as magnesium, calcium, and barium), aluminum, transition metals, and other heavy metals (such as nickel, iron, cobalt, manganese, copper and tin). The remaining pigment Q present in the sulfonic acids and salts of formula (II) may be the same as that described above for the compounds of formula (I), but is preferably anthraquinone and pyrene. Suitable aromatic polycyclic compounds also include sulfonamides having the following formula (III) Q (S02-NH-Alk-NRcRd) n (III) wherein Q represents an aromatic polycyclic compound; Alk represents C? -C8 alkylene or C5-C7 cycloalkylene; Rc and Rd are independently hydrogen, C 1 -C 2 alkyl, C 2 -C 2 alkenyl, C 5 -C 7 cycloalkyl, C 6 -C 6 aryl or C 7 -C 6 aralkyl, or Rc and Rd together are C 4 -C 6 alkylene. which forms a heterocyclic group, and n is from about 0.01 to about 4. Rs and Rd may also contain heteroatoms such as N, 0 or S.

As with the general formula (I), the fractional values for n indicate that the derivatives can be used as mixtures, including mixtures containing the unsubstituted aromatic polycyclic compound. The aromatic residue Q present in the sulfonamides of formula (III) can be the same as that described above for the compounds of formula (I). The aromatic polycyclic compounds of the invention can be added at any point during or before the ring closure step (a). For example, an aromatic polycyclic compound can be added during the preparation of the intermediates 2, 5-dianilinoterephthalic acid provided that the compound is stable to the reaction conditions. The reaction mixture of step (a) is heated to a temperature of about 80 ° C to about 145 ° C (preferably 100 ° C to 130 ° C), preferably for about 1 to about 24 hours (more preferably during 1 12 hours). After completion of the ring closure step (a), the quinacridone pigment is precipitated (i.e., "drowned") in step (b) by adding the strongly acidic melt to a liquid in which the quinacridone pigment is substantially insoluble, preferably water, a water-miscible solvent (such as methanol or other lower aliphatic alcohols) or mixtures thereof. Although it is possible to add the drowning liquid to the acid melt (e.g., US Patent 3,265,699), the present invention is preferably carried out by adding the acid melt to the solvent (compare US Patent 4,100. 162). Suitable drowning liquids include water and / or organic liquids miscible in water, including, for example, lower aliphatic alcohols, such as methanol; ketones and ketoalcohols, such as acetone, methyl ethyl ketone and diacetone alcohol; amides, such as dimethylformamide and dimethylacetamide; ethers, such as tetrahydrofuran and dioxane; alkylene glycols and triols, such as ethylene glycol and glycerol, and other organic liquids of this type known in the art. Other organic liquids may be used, but in general they are less preferred. The temperature of the drowning liquid is usually between about 5 ° C and about 65 ° C. In general, lower drowning temperatures give pigments that have smaller particle sizes. Nevertheless, since the cycle time of the process is also very important (due to the manufacturing cost), a shorter drowning time is preferred. The presence of aromatic polycyclic compound (a) (iii), which acts in part as an inhibitor of particle growth, allows the elevation of the temperature of the solvent during the drowning process, thereby shortening the time without excessive growth of the particle size . It is possible, but less preferred, to include a portion of the polycyclic aromatic compound in the drowning step. The drowned pigment is then isolated in step (c) using methods known in the art, such as filtration, and then dried if desired. Other collection methods known in the art, such as centrifugation or even a simple decanting, are also suitable. The crystalline pigment obtained in step (c) may be conditioned in an eventual step (d) using methods known in the art, such as solvent treatment or milling in combination with solvent treatment. The final particle size of the pigment can be controlled by varying the post-treatment method. For example, more transparent pigments can be made by reducing the particle size, or more opaque by increasing the particle size. Suitable milling methods include dry milling methods such as sand milling, ball milling and the like, with or without additives, or wet milling methods, such as salt kneading, pearl milling and the like in water. or organic solvents, with or without additives. It is possible, although generally less preferred, to include a portion of the aromatic polycyclic compound (preferably less than about 50% of the total amount of non-quinacridonic pigment) in the conditioning step (d). The dyeing strength and transparency of the pigment can also be affected by the solvent treatment carried out by heating a pigment dispersion, often in the presence of additives, in a suitable solvent. Suitable solvents include organic solvents, such as alcohols, esters, ketones and aliphatic and aromatic hydrocarbons and derivatives thereof, and inorganic solvents, such as water. Suitable additives include compositions that decrease or prevent flocculation, increase the stability of the pigment dispersion and reduce the viscosity of the coating, such as polymeric dispersants (or surfactants). For example, US Pat. 4,455,173, 4,758,665, 4,844,742, 4,895,948 and 4,895,949. After having isolated the pigment and, optionally, having conditioned it, the pigment can be mixed (preferably by dry blending) with one or more quinacridone derivatives known in the art. Suitable quinacridone derivatives for step (e) include quinacridone sulfonic acids and sulfonamides analogous to the compounds of formulas (I), (II) and (III) above, except that Q represents a quinacridone residue. Compared to previously known processes, the pigments prepared according to the invention characteristically exhibit more intense (darker) and brighter mass tones, with better transparency and rheological properties together with brighter metallic shades, all of which are highly desirable characteristics of the pigments. of quinacridone, especially when used for automotive applications. Due to their light stability and migratory properties, the quinacridone pigments prepared according to the present invention are suitable for many different pigment applications. For example, the pigments prepared according to the invention can be used as a colorant (or as one of two or more colorants) for pigmented systems very quickly, such as mixtures with other materials, pigment formulations, paints, printing ink, colored paper or colored macromolecular materials. It can be understood that the term "mixture with other materials" includes, for example, mixtures with inorganic white pigments, such as titanium dioxide (rutile) or cement, or other inorganic pigments. Examples of pigment formulations include pastes washed with organic liquids or pastes and dispersions with water, dispersants and, if appropriate, preservatives. Examples of paints in which the pigments of this invention may be used include, for example, physical or oxidative drying lacquers, stove enamels, reactive paints, two-component paints, solvent or water based paints, emulsion paints. for waterproof coatings and tempera paints. The printing paints include those known for use in printing on paper, textiles and tinplate. The macromolecular substances include those of natural origin, such as gums; those obtained by chemical modification, such as acetylcellulose, cellulose butyrate or viscose; or those produced synthetically, such as polymers, polyaddition products and polycondensates. Examples of synthetically produced macromolecular substances include plastic materials, such as polyvinyl chloride, polyvinyl acetate and polyvinyl propionate; polyolefins, such as polyethylene and polypropylene; high molecular weight polyamides; polymers and copolymers of acrylates, methacrylates, acrylonitrile, acrylamide, butadiene or styrene; polyurethanes, and polycarbonates. The materials pigmented with the quinacridone pigments of the present invention may have any desired shape. The pigments prepared according to this invention are highly water resistant, oil resistant, acid resistant, lime resistant, alkali resistant, solvent resistant, stable to overcoat, stable to over spray, stable to sublimation, heat resistant and resistant to vulcanization and still give a very good dyeing performance and are easily dispersible (for example, in plastic materials). The following examples further illustrate the details for the process of this invention. The invention, which is established in the foregoing description, is not limited in spirit or scope by these examples. Those skilled in the art will readily understand that known variations of the conditions of the following procedures can be used. Unless otherwise noted, all temperatures are dropped Celsius and all percentages are percentages by weight. EXAMPLES The pigments prepared according to the Examples were analyzed by transmission electron microscopy using a Zeiss EM 109 instrument. The data were collected under the following conditions: Acceleration voltage: 80 kV. Increase: 100,000 X, 40,000 X and 1,000 X. The particle size data were obtained by the BET method (ie, the St.

Brunauer, P.H. Emmett and E. Teller, J. Amer. Chem. Soc., 60, 309 (1938)). The X-ray diffraction patterns for the pigments prepared according to the invention were obtained using a Siemens D-5000 Spectrometer. The data was collected under the following conditions: Power: 50 kV at 40 mA. Slots: 1.0 mm divergence, 1.0 mm anti-scatter, 0.1 mm detector. Step size: 0.01 °. Step time: 3 seconds. Differences in shade and chromaticity were measured using a Spectral Sensor of Applied Color System (Hunt Associated Laboratories, Fairfax, Virginia).

Solvent based paints tests Solvent based paints tests were carried out using a generic alkyd melamine paint system. The pigment dispersions were prepared using a mixture of 33% alkyd resin AROPLAZlR > 1453-X-50 (Reichhold Chemicals, Inc.), 63% xylene and 4% pigment, which gave a pigment-binding ratio of 4:33 and a total solids content of 37%. the pigment-to-binder ratio was reduced to 1:10 by the addition of 2.3% alkyd resin AR0PLAZ (R) 1453-X-50 and 6.5% RESIMENE (R) 717 melamine resin ( Monsanto Company), which gave a total solids content of 40%. Measurements of mass tone and transparency were made using films applied at 152 μm and 38 μm wet film thickness, respectively, and flash at room temperature for 30 minutes and at 121 ° C for 30 minutes. Dye paints with subtone were prepared from the dispersion described above with a pigment-to-binder ratio of 4:33 by adding 31% of a dispersion prepared from 30% AROPLAZ (R) alkyd resin 1453-X-50, 20% xylene, 5% NUOSPERSE (R) 657 (Hüls America) and 50% pigment Ti02 TI-PURE (R1 R-960 (DuPont); 21% AROPLAZ alkyd resin (R1 1453-X-50 and 7% RESIMENE (R) 717 melamine resin, which gave a pigment-to-binder ratio of 1: 2, a total solids content of 50% and a TiO2-a-pigment ratio of 90:10 The color measurements were made using films applied at 76 μm wet film thickness and flashed at room temperature for 30 minutes and at 121 ° C for 30 minutes. metallic paints from the dispersion described above with a pigment-to-binder ratio of 4:33 using an aluminum paste (which can be obtained as 5251 AR from Silberline Manufacturing Co., Inc.), alkyd resin AR0PLAZÍR) 1453- X-50 and RESIMENE (R) 717 melamine resin in amounts that provided a pigment-to-binder ratio of 1: 9, an aluminum-to-pigment ratio of 20:80 and a total solids content of 41%. The color measurements were made using films applied to 76 μm wet film thickness and flash at room temperature for 30 minutes and at 121 ° C for 30 minutes. Water-based paints tests Water-based paints tests were carried out using an aqueous basecoat / clearcoat system in solvents. Aqueous dispersions were prepared using a mixture of 12.4% AR0L0N (R) 559-G4-70 acrylic resin (Reichhold Chemicals, Inc.), 3.2% SOLSPERSE (R) 27000 hyperdispersant (Zeneca, Inc. ), 1.6% 2-amino-2-methyl-1-propanol (Angus Chemical) and 18% pigment, which gave a pigment-to-binder ratio of 18:12 and a total solids content of 30% The pigment-to-binder ratio was then reduced to 10:40 with AROLON acrylic resin. { R | 559-G4-70 additional (total amount, 26%) and 25% melamine / formaldehyde resin CYMEL (R) 325 (Cytec Industries), which gave a total solids content of 50%. Measurements of mass tone and transparency were performed using films applied at 76 μm and 38 μm wet film thickness, respectively, and allowed to stand at room temperature for fifteen minutes and at 100 ° C for five minutes. Transparent layers were then applied containing a mixture of 80% alkyd resin AROPLAZ (R) 1453-X-50 and 20% melamine / formaldehyde resin CYMEL (R) 325 a. a total solids level of 57% on the base layer at a wet film thickness of 76 μm, left to stand at room temperature for fifteen minutes and at 121 ° C for fifteen minutes. Dye paints with subtone were prepared from the reduced aqueous dispersions described above with a pigment-to-binder ratio of 10:40 by addition of additional AROLON (R) 559-G4-70 acrylic resin, melamine / formaldehyde resin CYMEL () 325 and 35% white dispersion TINT-AYD (R) C-5003 (Daniel Products Company), which gave a pigment-to-binder ratio of 1: 1.1, a total solids content of 55% and a Ti02-a-pigment ratio of 90:10. The color measurements were made using films applied at 38 um thickness of wet film and allowed to stand at room temperature for fifteen minutes and at 100 ° C for five minutes. Transparent layers were then applied and baked as described above. Metal paints were prepared from the dispersion described above with a pigment-aligner ratio of 18:12 using a water dispersible aluminum pigment (which can be obtained as HYDRO PASTE (R) 8726R8726, from Silberline Manufacturing Co., Inc. ), acrylic resin AROLON (R) 559-G4-70 and melamine / formaldehyde resin CYMEL (R1 325 in amounts that gave a pigment-aligante ratio of 1: 2, an aluminum-to-pigment ratio of 20:80 and a total solids content of 43% Color measurements were made using films applied at 38 μm wet film thickness and baked as described above Transparent layers were then applied and baked as described above. In plastic The dispersibility of the pigment in polyvinyl chloride ("CPV") was evaluated by comparing the development of color hot ground and ground cold according to the following procedure. A 50 g portion of flexible CPV was added to a hot two-roll mill (155 ° C) having a narrowing thickness of 25 mils (about 0.6 mm) and melted until uniform. A 0.050 g portion of the test pigment or comparative pigment was sprayed in the constriction over a period of about ten seconds, after which the molten material was cut and rolled in the mill for five minutes. The pigmented sheet was then separated from the mill and placed to cool on a clean flat surface. A piece cut from the resulting sheet was used and allowed to cool to room temperature as a "hot ground" sample for evaluation. A sample cut from the same sheet was placed while still hot in a cold two-roll mill (24 ° C) which had a narrowing thickness of 21 milli-inches (about 0.5 mm), was then bent and He passed through the mill seven times. The cold rolled sheet was melted again in the hot mill until smooth. A sample cut from the resulting sheet was used as a "cold-milled" sample for evaluation. Color development was evaluated using a scale of 1 to 5 based on the difference between the development of hot ground and cold ground color, where 1 represents poor dispersibility (as evidenced by extreme differences in color development) and 5 represents excellent dispersibility (as evidenced by essentially no difference in color development). EXAMPLE 1 Pigment-2,9-dimethylquinacridone according to the invention was prepared with the incorporation of 10% by weight, relative to 2,9-dimethylquinacridone, of anthraquinone in the ring closure reaction. To 300 g of polyphosphoric acid (112% phosphoric acid) heated to 88 ° was added 6.8 g of anthraquinone, followed by 68.2 g of 2,5-di (4-methylanilino) terephthalic acid added thereto. over a period of 35 minutes, keeping the temperature below 120 ° C by adjusting the rate of addition. The mixture was heated at 123 ° C for two hours. After cooling the melt at 93 ° C, it was slowly poured into 494 g of methanol, keeping the temperature below 64 ° C by external cooling and adjusting the speed of addition of the melt. The suspension was heated at reflux for one hour, cooled to less than 60 ° C, diluted with water, filtered and washed until free of acid. The resulting filter cake was resuspended in water. After adjusting the pH to more than 7, 5.5 g of 50% sodium hydroxide was added and the resulting suspension was heated at 90 ° C for one hour. The suspension was cooled, filtered and washed with water until free of alkali and then resuspended in water. After adjusting the pH to 9.5, the suspension was heated at 143 ° C for two hours in a closed system (for example, a pressure reactor) and cooled to 40 ° C. After acidifying the suspension at pH 3.3, an emulsion of 2.2 g of an anionic surfactant, 30 g of a petroleum distillate and 80 g of water was added and the suspension was stirred for three hours. The solid component was collected by filtration and washed with water. The wet cake can be dried or used as such for specific applications. Here, the wet cake was dried in an oven at 60 ° C to give approximately 60 g of 2,9-dimethylquinacridone as a magenta pigment. A water-based paint prepared as described above exhibited better rheological properties when compared to QUINDO (R) Magenta RV-6832 (from Bayer Corporation). EXAMPLE 2 Pigmentary 2,9-dimethylquinacridone was prepared exactly as described in Example 1, except for the use of 5% by weight, relative to the quinacridone, of anthraquinone in the ring closure reaction. 2,9-dimethylquinacridone (56 g) was obtained as a magenta pigment having good dispersibility in PVC. Dispersibility in PVC Sample under test Dispersibility Example 2 2 QUINDO (R) Magenta RV-6832 1-2 Example 3 Pigmentant 2, 9-dimethyl lquinacridone was prepared exactly as described in Example 1, except for the use of 10% by weight, in relation to the quinacridone, of the monohydrated sodium salt of anthraquinone-2-sulfonic acid in the ring closure reaction. 2,3-dimethylquinacridone (56 g) was obtained as a magenta pigment. An alkyd melamine enamel paint prepared as described above exhibited a more intense, brighter and more transparent mass tone compared to a paint prepared using QUINDO < R) Magenta RV-6832. A water-based paint prepared as described above exhibited a more intense and brighter mass tone, with better transparency and higher metallic luster compared to QUIND0 (R1 Magenta RV-6832.Example 4, 2, 9-dimethylquinacridone was prepared. pigment exactly as described in Example 1, except for the use of 10% by weight, in relation to quinacridone, of disodium salt of anthraquinone-2,6-disulfonic acid in the ring closure reaction. 2, 9-dimethylquinacridone (58 g) as a magenta pigment A water-based paint prepared as described above exhibited a brighter mass tone, with better transparency compared to QUINDO (R) Magenta RV-6832. He prepared 2, 9-dimethylquinacridone pigment exactly as described in Example 1, except for the use of 10% by weight, in relation to the quinacridone, of a mixture of anthraquinone and phthalimidome-tilanthraquinone (prepared according to the method of the US Pat. No. 3,275,637), which had a molar ratio of anthraquinone-to-phthalimidomethylanthraquinone of about 9: 1 in the ring closure reaction. 2,9-dimethylqui-nacridone (54 g) was obtained as a magenta pigment. An alkyd melamine enamel paint prepared as described above exhibited a more intense, brighter and more transparent mass tone and reduced viscosity compared to a paint prepared using QUIND0 (R) Magenta RV-6832. A water-based paint prepared as described above exhibited a more intense and brighter mass tone, with better transparency and higher metallic luster compared to QUIND0 (R >; Magenta RV-6832.

EXAMPLE 6 Pigmentary 2,9-dimethylquinacridone was prepared exactly as described in Example 1, except for the use of 10% by weight, relative to quinacridone, of monohydrated sodium salt of anthraquinone-2-sulfonic acid in the reaction of the ring closure and subsequent dry mixing with 9% of N, N-diethyl-aminopropylquinacridone sulfonamide after the conditioning step. 2,9-Dimethylquinacridone was obtained as a magenta pigment. An alkyd melamine enamel paint prepared as described above exhibited a more intense and brighter mass tone, with better transparency and reduced viscosity compared to a paint prepared using QUIND0 (R) Magenta RV-6832. A water-based paint prepared as described above exhibited a more intense and brighter mass tone, with better transparency, stronger metallic luster and reduced viscosity compared to a paint prepared using QUINDO (R> Magenta RV-6832. EXAMPLE 7 Pigmentary 2,9-dimethylquinacridone was prepared exactly as described in Example 1, except for the use of 10% by weight, in relation to quinacridone, of monohydrated sodium salt of anthraquinone-2-sulfonic acid in the ring closure reaction and subsequent dry blending of 9% phthalimidomethyl-quinacridone sulphonic acid (prepared according to the method of US Pat. No. 3,275,637) after the conditioning step. 9-dimethylquinacridone as a magenta pigment An alkyd melamine enamel paint prepared as described above exhibited a more intense and brighter mass tone, with better transparency, in combination ration with a paint prepared using QUINDO (R) Magenta RV-6832. A water-based paint prepared as described above exhibited a more intense, brighter and more transparent mass tone and a stronger metallic gloss compared to a paint prepared using QUINDO (R> Magenta RV-6832. prepared exactly 2,9-dimethylquinacridone pigment as described in Example 1, except for the use of 2% by weight, relative to quinacridone, of N, N-dimethylaminopropylpyrene tetrasulfone-mide in the ring closure reaction 2,9-dimethylquinacridone (56 g) was obtained as a bright magenta pigment.

The N, N-dimethylaminopropylpi-rene tetrasulfonamide additive was prepared by the following method. To 20 g of pirenotetrasulfonic acid (from Bayer AG, Germany) were added 78 g of thionyl chloride over a period of 30 minutes, after which the mixture was stirred vigorously at room temperature for 1.5 hours and at reflux for 30 minutes. After cooling the mixture to room temperature, 30.2 g of dimethylformamide was added and the mixture was heated at reflux for 30 minutes. After stopping the heating, an additional 30 g of thionyl chloride was added. The mixture was heated to reflux and refluxed for two hours, cooled to room temperature with stirring and drowned in 500 ml of stirred ice water. The resulting pirenotetrasulfonyl chloride was collected as 17.4 g (89% of theory) as filter cake. A 5.0 g portion of the pirenotetrasulfonyl chloride was added to a solution of 4.5 g of 3- (dimethylamino) propylamine, 4.5 g of triethylamine and 50 ml of acetone maintained at a temperature below 30 ° C. The reaction was stirred at room temperature for 15 hours, filtered and washed with 100 ml of acetone to give 2.7 g of N, N-dimethylaminopropylpyrene tetrasulfonamide. A water-based paint prepared as described above using the pigment of Example 8 exhibited a more intense and brighter mass tone, with better transparency, compared to a paint prepared using QUINDO (R) Magenta RV-6832. Example 9 Pigment quinacridone according to the invention was prepared with the addition of about 10% by weight, relative to the quinacridone, of tetrasodium salt of pyrene tetrasulfonic acid in the reaction of the ring closure. To 300 g of polyphosphoric acid (117% phosphoric acid) heated to 90 ° was added 6.8 g of tetrasodium salt of pyrene tetrasulfonic acid (prepared by the method described in Justus Liebigs Ann. Chem., 540, 189-210 (1939)), followed by 68.2 g of 2,5-dianilinoterephthalic acid. The mixture was heated at 120-125 ° C for two hours. After cooling the melt at 88 ° C, the acid strength was adjusted to 112% by dropwise addition of phosphoric acid. The resulting melt was slowly poured into 453 g of methanol at 24 ° C. During drowning, the temperature was allowed to rise to 55 ° C, controlling the temperature by external cooling and adjusting the rate of addition of the melt. The suspension was heated to reflux (68-72 ° C) for one hour, diluted with water and stirred at 60 ° C for 30 minutes. The solid component was collected by filtration and washed with water until acid-free. The filter cake was resuspended in water. After adjusting the pH to more than 7, 7.5 g of 50% sodium hydroxide was added and the resulting suspension was heated at 90 ° C for one hour. The suspension was cooled, filtered and washed with water until free of alkali and then re-suspended in water. After adjusting the pH to more than 8.5, 3.2 g of cycloaliphatic carboxylic acid was added. The resulting suspension was heated at about 140-145 ° C for two hours in a closed system, cooled, acidified with phosphoric acid and stirred. The solid component was collected by filtration and washed with water. The wet cake can be dried or used as it is for specific applications. Here, the wet cake was dried in an oven at 60 ° C to obtain approximately 52 g of quinacridone as a bright violet pigment. A water-based paint prepared as described above exhibited a more intense and brighter mass tone, with better transparency and stronger metallic gloss compared to a paint prepared using the pigment of Comparative Example 12. Example 10 Quinacridone was prepared pigment exactly as described in Example 9, except for the use of 10% by weight, relative to the quinacridone, of phthalimidomethylpyrne (prepared according to the method of US Patent 3,275,637) in the reaction of ring closure. Quinacridone (56 g) was obtained as a bright violet pigment. A water-based paint prepared as described above exhibited a more intense and brighter mass tone with better transparency and higher metallic luster as compared to a paint prepared according to the pigment of Comparative Example 12. EXAMPLE 11 Pigment quinacridone was prepared exactly as it has been described in Example 9, except for the use of 10% by weight, relative to quinacri-donona, of sodium salt of anthraquinone sulfonic acid in the ring closure reaction. Quinacridone (56 g) was obtained as a bright magenta pigment. A water-based paint prepared as described above exhibited a more intense and brighter mass tone with better transparency and a much more yellow and brighter metallic dye and hue compared to a paint prepared using the pigment of Comparative Example 12 Example 12 (comparison) Pigment quinacridone was prepared exactly as described in Examples 9 and 10, except for the omission of an additive of the invention from the ring closure reaction. Quinacridone (56 g) was obtained as a bright violet pigment. Example 13 (comparison) Pigment quinacridone was prepared in the absence of a pigment additive of the invention exactly as described in Comparative Example 12 (ie, according to Examples 9 and 10 in the absence of an additive of the invention), except by the dry mixture of quinacridone with 10% tetrasodium salt of pyrene tetrasulfonic acid. A water-based paint prepared as described above exhibited a very light, faded and opaque mass tone and a more faint metallic gloss compared to a paint prepared using the quinacridone prepared according to Example 9 of the invention.

Claims (15)

1. CLAIMS 1. A process for the preparation of quinacridone pigments consisting of (a) heating, at a temperature of 80 ° C to 145 ° C, a reaction mixture consisting of (i) 2,5-dianilinoterephthalic acid, an ester of the 2, 5-dianilino-6,13-dihydrote-reftalic acid, a derivative of 2,5-dianilinoterephthalic acid or a 2,5-dianilino-6,13-dihydroterephthalic acid ester having one or more substituents in at least one ring of aniline, or a mixture of these; (ii) 3 to 15 parts by weight, by component (a) (i), of a dehydrating agent, and (iii) 0.1 to 15 percent, based on component (a) ( i), of one or more non-pigment aromatic polycyclic compounds and / or derivatives thereof, with the proviso that, if component (a) (i) is an ester of 2, 5-dianilino-6, 13- dihydroterephthalic or a derivative thereof, the reaction step (a) additionally consists of an oxidation step; (b) drowning the reaction mixture of step (a) by adding said reaction mixture to 3 to 15 parts by weight, per part of component (a) (i), of a liquid in which the quinacridone pigment is substantially insoluble; (c) isolating the quinacridone pigment; (d) optionally, conditioning the quinacridone pigment, and (e) eventually, mixing the pigment of quinacri dona with one or more quinacridone derivatives.
2. 2. A process according to Claim 1, wherein component (a) (i) is selected from the group consisting of 2,5-dianilinoterephthalic acid, 2,5-di (4-methylanilino) terephthalic acid, 2,5- di (4-methoxyanilinyl) terephthalic acid, 2,5-di (4-chloroanilino) terephthalic acid and mixtures thereof.
3. 3. A process according to Claim 1, wherein the reaction mixture is heated in step (a) at a temperature of 100 ° C to 130 ° C.
4. 4. A process according to Claim 1, wherein the dehydrating agent (a) (ii) is polyphosphoric acid.
5. 5. A process according to Claim 4, wherein from 3 to 10 parts by weight, based on component (a) (i), of polyphosphoric acid are used.
6. 6. A process according to Claim 1, wherein component (a) (iii) is a non-pigmentary aromatic polycyclic compound having the formula Q (A-Y) n wherein Q represents an aromatic polycyclic moiety; A represents a bridge group -0-, -S-, -NRa-, -S02-, -CO-, -Alq- or -Ai: -, a chemically reasonable combination of such bridge groups or a direct link between Q and Y; Y represents hydrogen, C? -C? 2 alkyl, C2-Ci2 alkenyl, C5-C7 cycloalkyl, C5-C7 cycloalkenyl, C6-C? Aryl, heteroaryl having five or six ring atoms wherein at least one of such ring atoms is N, 0, S or a combination thereof, C7-C6 aralkyl, ORb, -NRcRd or halogen; - Alk- is C? -C8 alkylene, substituted Ca-C8 alkylene, C5-C7 cycloalkylene or substituted C5-C7 cycloalkylene; -Ar- is aryl C6-C? Oo arylene C6-C? 0 substituted: Ra is hydrogen, C] -C? 2 alkyl, C2-C? 2 alkenyl, C5-C7 cycloalkyl, C6-C? 0 aryl or aralkyl C7- C? 6; Rb is hydrogen, metal or C? -C? 2 alkyl; Rc and Rd are independently hydrogen, C 1 -C 2 alkyl, C 2 -C 2 alkenyl, C 5 -C 7 cycloalkyl, C 6 -C 6 aryl or C 7 -C 6 aralkyl 6, or Rc and Rd together are C 6 -C 6 alkylene or are groups aliphatic or aromatic dicarbonyl, and wherein Rc and Rd may optionally contain heteroatoms such as N, 0 or S and may also be optionally substituted with C 1 -C 12 alkyl, C 1 -C 2 alkoxy, C 2 -C 2 alkenyl, C 5 cycloalkyl -C7, C5-C7 cycloalkylene, C5-Ccycloalkoxy, C6-C6 aryl, C6-C6 aryloxy, C7-C6 aralkyl, C7-C6 aralkoxy, -OH, halogen, - CN, carboxyl, -CO-NRcRd or - S02-NRcRd, and n is from 0.01 to 4.
7. 7. A process according to Claim 6, wherein Q represents a non-pigmentary aromatic polycyclic moiety derived from an anthracene, phenanthrene, pyrene, chrysene, indole, thiazole, benzimidazole, quinoline, acridone, anthraquinone, phenothiazine, quinazoline, carbazole, benzanthrone or perylene or a derivative thereof substituted with one or more halogen groups, C? -C6 alkyl, C 1 -C 6 alkoxy, C 5 -C 7 cycloalkyl, C 5 -C 7 cycloalkoxy, C 6 -C 0 aryl, C 6 -C 0 aryloxy, C 7 -C 16 aralkyl, C 7 -C 6 aralkoxy, nitro or cyano.
8. 8. A process according to Claim 6, wherein Q is a non-pigmentary aromatic polycyclic moiety, A represents a direct link between Q and Y and Y is hydrogen.
9. 9. A process according to Claim 1, wherein component (a) (iii) is anthraquinone or pyrene.
10. 10. A process according to Claim 1, wherein component (a) (iii) is a non-pigmentary aromatic polycyclic compound having the formula Q (S02-OR) n wherein Q represents an aromatic polycyclic moiety, R is hydrogen or a metal and n is from 0.01 to 4.
11. 11. A process according to Claim 9, wherein Q is anthraquinone or pyrene.
12. 12. A process according to Claim 1, wherein component (a) (iii) is anthraquinone-2-sulfonic acid or a sodium salt thereof, anthraquinone-2,6-disulfonic acid or a sodium salt thereof, phthalimidomethyl-anthraquinone , pyrene tetrasulfonic acid or a sodium salt thereof, or phthalimidomethylpyrne.
13. 13. A process according to Claim 1, wherein the reaction mixture of step (a) is quenched by adding said reaction mixture to water, lower aliphatic alcohol or a mixture thereof.
14. 14. A process according to Claim 1, wherein the reaction mixture of step (a) is quenched by adding said reaction mixture to methanol.
15. 15. A quinacridone pigment prepared by the process according to claim 1. SUMMARY OF THE INVENTION This invention relates to a process for the preparation of quinacridone pigments (a) by heating, at a temperature of from about 80 ° C to about 145 ° C, a reaction mixture containing (i) acid. , 5-dianilinoterephthalic acid, an ester of 2,5-dianilino-6,13-dihydrote reftalic acid and / or a derivative thereof; (ii) from about 3 to about 15 parts by weight, per part of component (a) (i), of a dehydrating agent, and (iii) from about 0.1 to about 15 percent by weight, based on to component (a) (i), of one or more non-pigment aromatic polycyclic compounds and / or derivatives thereof, with the proviso that, if component (a) (i) is 2, 5-dianilino acid ester - 6,13-dihydroterephthalic or a derivative thereof, the reaction step (a) additionally consists of an oxidation step; (b) drowning the reaction mixture of step (a) by adding said reaction mixture to about 3 to about 15 parts by weight, per part of component (a) (i), of a liquid in which the pigment of quina-cridone is substantially insoluble; (c) isolating the quinacridone pigment; (d) optionally, conditioning the quinacridone pigment, and (e) eventually, by mixing the resulting pigment with one or more quinacridone derivatives.