MXPA00006674A - Continuous production of quinacridone - Google Patents

Abstract

This invention relates to a continuous process for the preparation of quinacridone pigments by (a) preparing a reaction mixture by mixing (i) a 2,5-dianilinoterephthalic acid or ester thereof, and (ii) at least about 0.5 parts by weight, per part of component (a)(i), of a dehydrating agent;(b) passing the reaction mixture through a continuous reactor having one or more heated zonesat a temperature of about 80 DEG C. to about 300 DEG C. to form a crude quinacridone composition;and (c) mixing a continuous stream of the crude quinacridone composition with a liquid in which the quinacridone pigment is substantially insoluble at a ratio of about 0.5 to about 15 parts by weight of the liquid per part by weight of the crude quinacridone composition.

Description

PROCEDURE FOR THE CONTINUOUS PREPARATION OF QUINACRIDONES BACKGROUND OF THE INVENTION This invention relates to an economical continuous process for the preparation of quinacridine pigments having uniform particles of a narrow particle size distribution. Processes are known for the preparation of quina-0 cridone. For example, S.S. Labana and L.L. Labana, "Quinacridos", in Chemical Revie, 67, 1-18 (1967), and US Patents. 3,157,659, 3,256,285 and 3,317,539. The quinacridones thus obtained, known as crude quinacridones, are generally unsuitable for use as pigments and must undergo one or more additional Z stages of finishing to modify the particle size, "the shape of the particle or the crystalline structure in order to achieve a pigmentary quality A preferred method of preparation of the quinacridones involves the thermal induction of the internal ring closure medians of 2,5-dianilinoterephthalic acid, as well as of known aniline-substituted derivatives thereof, in the presence of polyphosphoric acid (e.g., U.S. Patent 3,257,405) or even sulfuric acid (e.g., U.S. Patent 3,200,122 and U.S. Patent Application 863,186) 5 After ring closure is complete, fusion is smothered 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 conditioned by treatment with solvents or grinding in combination with '. n Solvent treatment. The final particle size of the quinacridone pigments can be controlled by the methods used in both the synthesis and the 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 the known methods, the particle size is generally controlled during the pigment precipitation by drowning or during the operation or the solvent treatment of the crude pigment. The dyeing strength and the transparency of the pigments can also be affected by the treatment with solvents. Frequently, reference is made to the post-processing steps that manipulate the particle size of the crude pigments as conditioning methods. Although batch methods can produce a product of good quality, a more efficient continuous process would be desirable. Methods of continuous processes for other types of pigments have been described, in particular for cupric phthacianins and perylenes (see US Patents 2,964,532, 3,188,318 and 5,247,088), but so far they have not been described for the preparation of quinacridones. The present invention provides such a continuous process for preparing and drowning quinacridones using smaller amounts of dehydrating agent than those used in the standard methods, even when such smaller amounts of the dehydrating agents produce high viscosities. In addition to allowing the use of smaller amounts of dehydrating agent, which would reduce As the cost of manufacturing and reduce the environmental impact, the present invention produces quinacridones having a desirably narrow particle size distribution. The pigment particles are also generally smaller than those produced in batch processes and can be conditioned to produce more intense and more transparent pigments. COMPENDIUM OF THE INVENTION This invention relates to a continuous process for the preparation of quinacridone pigments, consists in (a) preparing a reaction mixture by mixing (i) a 2,5-dianilinoterephthalic acid ester thereof and (ii) at least about 0.5 parts by weight (preferably, about 0.5 to about 10 parts by weight, more preferably 1 to 4 parts by weight) by component (a) (i) of a dehydrating agent (preferably, polyhydric acid). lifosphoric); (b) passing the reaction mixture through a continuous reactor having one or more zones heated to a temperature of from about 80 ° C to about 300 ° C (preferably from about 100 ° C to about 220 ° C, more preferably from about 140 ° C to about 200 ° C) to form a crude quinacridine composition; (c) mixing a continuous stream of the crude quinacridone composition with a liquid in which the quinacridone pigment is substantially insoluble (preferably, a continuous stream of the liquid), in a Bowl of about 0.5 to about 15 parts by weight (preferably 1 to 10 parts by weight) of the liquid per part by weight of the crude quinacridone composition; (d) optionally, conditioning the resulting quinacridone pigment, and (e) optionally mixing (preferably dry-blending) the resulting quinacridone pigment with one or more quinacridone derivatives.

DETAILED DESCRIPTION OF THE INVENTION Quinacridone pigments (understood as unsubstituted quinacridone, quinacridone derivatives and solid solutions thereof) are prepared according to the invention by first closing the ring of the intermediates of 2,5-dianilinotere-italic acid intermediates. , including known derivatives which are substituted in the aniline ring, by heating said terephthalic acid intermediates in a continuous process in the presence of a dehydrating agent (preferably polyphosphoric acid). The quinacridone is then drowned, preferably in a continuous process. 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 is used to prepare unsubstituted quinacridone or substituted quinacridone derivatives in the ring, depending on whether the ring closure is carried out using unsubstituted 2,5-dianilinoterephthalic acid (or an ester thereof) or a substituted 2, 5-dianilinoterephthalic acid derivative (or ester thereof) having one or more substitutents in at least one of the aniline rings. Although it can be used In essentially any substituted derivative of the 2,5-dianilinoterephonic acid known in the art, substituted derivatives of 2,5-dianilinoterephthalic acid are particularly preferred those in which both aniline moieties are substituted (typically with the same substituent) 0 in the position for groups such as halogen (preferably, chloro), C? -C6 alkyl (preferably methyl) and C? -C3 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 substituted derivatives of 2,5-dianilinoterephthalic acid include 2, 5-di (4-loroanilino) terephthalic acid, 2,5-di (4-methylanilino) terephthalic acid, and 2,5-di (4-) acid. methoxyanilino) 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-dianilinoterephonic acid and / or a derivative thereof in combination with a fully formed quina-oridone pigment (generally in crude form) can also be frequently used. The step (a) of closing the ring is carried out in a dehydrating agent, particularly a strong acid such as polyphosphoric acid, acid esters of polyphosphoric acid or sulfuric acid. For example, US Pat. 4,758,665 and S.S. Labana and L.L. Labana, "Quinacridones", in Chemical Re-views, 61, 1-18 (1967). Polyphosphoric acid having a phosphate content equivalent to about 110 to 120% H3P0 is particularly preferred. When polyphosphoric acid is used, the weight ratio of polyphosphoric acid to the terephthalic acid intermediate is typically from about 0.5: 1 to about 10: 1 (preferably 1: 1 to 4: 1). It is also possible to use about 70 to 100% (preferably 85 to 98%, more preferably 90 to 93%) of sulfuric acid as the dehydrating agent. When sulfuric acid is used, the ratio of sorne of sulfuric acid to terephthalic acid intermediate is typically from about 0.5: 1 to about 20: 1 (preferably 1: 1 to 6: 1). Although the lower relative amounts of dehydrating agents can give high viscosity reaction masses, the inferring relative quantities are still generally effective. Moreover, even when the viscosities are relatively high, the relative lower amounts of dehydrating agent are generally preferred due to cost considerations. Although not necessary, it is often desirable to use a solvent in step (a) of ring closure. Suitable solvents are liquids in which reagents can be dissolved or suspended and which do not react appreciably with the reagents during ring closure. Examples of suitable solvents include polar solvents, such as dimethylformamide or dimethyl sulfoxide, and non-polar solvents, such as aliphatic or aromatic hydrocarbons and their derivatives. The components used in step (a) are preferably mixed in an unheated section or even in a heated section of the reactor, provided that in doing so, the components are properly mixed and heated, even when the mixture is viscous. The reactive components can also be mixed before they are introduced into the continuous reactor. As used herein, the term "continuous reactor" comprises any number of reactors through which solids, semi-solids and fusions may be passed while being heated and, eventually, while being mixed. Suitable continuous reactors can provide a good thermal transfer and a complete mixture, preferably even with highly viscous materials. The extruders include a particularly preferred type of continuous reactor. Examples of suitable extruders include mixing propeller extruders (especially single-screw and double-screw extruders) arranged in single or multiple stages where heating and mixing can take place. The desired flow rate is, of course, a factor when selecting the extruder capacity.

Regardless of the medium used for mixing, the reaction mixture is passed through one or more heated zones in which a temperature of about 80 ° C to about 300 ° C is maintained, giving rise to a crude, nacridone. initial. In general, the reaction is exothermic and the heating in the mixture becomes particularly pronounced once the temperature reaches about 80 ° C to about 120 ° C. the maximum temperature reached in the heated zone depends, in general, not only on the The temperature applied externally to the reactor, but also the time during which the reaction mixture is retained in the apparatus and the nature of the dehydrating agent. (jiros factors, such as the viscosity of the reaction mixture and the thermal stability of the intermediate product formed / should also be considered when selecting the parameters of the reaction. For example, when the preferred dehydrating agent polyphosphoric acid is used, a preferred range of temperature is from about 100 ° C to about 220 ° C (or, even more preferably, from 0 about 140 ° C to about 200 ° C). When using sulfuric acid as a dehydrating agent, the preferred temperature range is from about 140 ° C to about 220 ° C. Although sulphonation may occur, sulphonated pigment byproducts may generally be removed by washing with water base. On the other hand, as small amounts of sulphonated by-products can sometimes actually improve the rheological and coloristic properties, it is not always necessary to carry out steps to eliminate them or prevent their formation. Temperatures of at least approximately 180 ° C 0 produce a surprisingly less significant sulfonation for at least some quinacridones. Multistage heating is often desirable. When a heating appliance with more than one heating zone is used, it is generally preferable to initiate the heating procedure at the lower end of the temperature range, continue the heating procedure at one or more intermediate temperatures and complete the heating process. heating procedure at the upper end of the '- > J ango of temperature. In a typical three zone reactor, for example, the reaction mixture can be passed through zones maintained at temperatures of about 90 ° C, about 120 ° C and about 180 ° C. The time during which the reaction mixture is heated in Xa step (b) (ie, the time inside the reactor) is preferably selected such that it is sufficiently long to allow the reaction to proceed to completion, but not so prolonged so that significant amounts of by-product are formed by unwanted collateral reactions. In the preferred temperature ranges described above, it is generally possible to achieve an essentially complete reaction in about fifteen minutes and sometimes in less than five minutes. The reaction time is, of course, dependent to a certain extent on the reaction temperature. The crude quinacridone composition formed in the continuous reactor is drowned by mixing a continuous stream of the crude quinacridone composition with a liquid in which quinacridone pigment pig is substantially insoluble, including gua, a water-miscible solvent such as methanol or other lower aliphatic alcohols, or mixtures of those. Suitable drowning liquids include water and / or organic liquids miscible in water, including, for example, lower aliphatic alcohols, such as methanol; cotonates 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 the style known in the art. Other organic liquids may be used, but are generally less preferred. Since the dehydrating agent (a) (ii) is typically strongly acidic, it may be desirable to include a base in the drowning liquid in amounts sufficient to maintain an alkaline medium. The specific base used for this purpose is not critical, but is generally an alkali metal hydroxide (preferably sodium or potassium hydroxide). Depending on the type of reactor used and the pressure requirements downstream of the reactor, it may be necessary to use an independent pump to transfer the crude quinacridone composition from the reactor to the blowing apparatus. It may also be necessary or desirable to improve handling by diluting the crude quinacridone composition with about 1 to about 20 parts of additional acid before being mixed with the drowning liquid. However, in general, the specific design of the mixing apparatus is not critical to the extent that the desired ratio of liquid to crude quinacridone composition is maintained. The drowning step (c) can be carried out in batches by introducing the reaction mixture of the continuous reactor of step (b) into one or more fixed volumes of the drowning liquid. The drowning step, however, is preferably performed in a continuous process. When drowning is carried out by a continuous process, a drowning liquid stream is generally introduced as a side stream or stream injected centrally into the raw quinacridone product stream (even when excess drowning liquid is used) using nozzles or other mixing devices known in the art. Although it is possible to use a pipe with a simple T, it is generally preferable to use a drowning nozzle that reduces at least one of the component streams to one or more thin streams. It is also possible to use other types of nozzles, such as nozzle-type nozzles, into which the quinacridone composition is introduced at low pressure and the drowning liquid is introduced i 'ii thin streams at higher Pressure. The two streams' - >; they can be mixed at the inlet of a high-speed shear pump, such as a rotor-stator type pump. Drowning can also be carried out by mixing the crude quinacridone composition and the drowning liquid in a stirred continuous reactor or in a series of stirred continuous reactors. Another example of a continuous drowning apparatus is a loop reactor. When flammable liquids, such as low boiling alcohols, are used, the drowning stream can also be mixed with water in a continuous manner to reduce the risk of fire or explosion during insulation. All the drowning systems described above can be used at atmospheric or elevated pressures, although the pressure actually used depends in some way on the required temperatures and on the boiling points 0 of the liquids used. When the equipment is sealed and under pressure, the temperature of the drowning medium may be higher than the boiling point at atmospheric pressure. The liquid streams can be included mixed at or below room temperature to help with the initial heating that occurs during the hydrolysis of the acid reaction mass. Moreover, lower drowning temperatures give pigments that have smaller particle sizes. On the other hand, it may be desirable to have higher temperatures to accelerate the hydrolysis or 0 to help increase the particle size during the drowning. Since the cycle times of the process can be important, for example due to the manufacturing cost, shorter dwell times in the mixing apparatus are generally preferred.

It is possible to include various known additives in the drowning liquid. The optional additives can be any of the usual additives for the preparation of pigments known in the art, which serve, for example, to improve the color properties, reduce or avoid the ioculation, increase the stability of the pigment dispersion and reduce the viscosity of the coating. Suitable additives include, for example, dispersants or surfactants, metal oxides and various pigment derivatives, LO Examples of suitable dispersants include anionic compounds, such as fatty acids (such as stearic or oleic acid), salts of fatty acids (ie, soaps such as alkali metal salts of fatty acids), fatty acid tabs or N-methyl taurides, alkyl L5 benzene sulphonates, alkyl naphthalenesulfonates, alkylphenol polyglycol ethers sulfates, naphthenic acids or resin (such as abietic acid), cationic compounds, such as quaternary ammonium salts, fatty amines, fatty amine and amine fatty acids polyglycol ethers, and nonionic corneal compounds, such as polyglycol fatty alcohol ethers, polyglycol fatty alcohol esters and alkylphenol polyglycol ethers As examples of suitable metal salts, -ie include various alkali metal salts (such as Lithium, sodium and potassium), of alkaline earth metals (ta- < magnesium, calcium and barium), aluminum, transition metals and other heavy metals (such as iron, nickel, cobalt, manganese, copper and tin), including, for example, halide salts (especially chloride), sulfate , nitrate, phosphate, polyphosphate, sulfonate (such as methanesul-30-ionnate or toluene sulfonate or even known derivatives of quinacridone sulfonate) and carboxylate, as well as oxides and hydroxides. Examples of suitable pigment additives, eg, include organic pigments having one or more sulfonic acid groups, sulfonamide groups, carboxylic acid, car- < -xamide and / or (cyclo) aliphatic groups containing (heteroary) aryl. If they are used, said additives are emiled in amounts ranging from about 0.05 to 100% by weight (preferably between 1 and 30% by weight and more preferably between 1 and 30% by weight). 10% by weight), based on the amount of pigment. Regardless of the nature of the drowning medium used, the drowned pigment is obtained as a suspension, which can be isolated using methods known in the art. technique, such as filtration, and then dried if desired. Other collection means known in the art are also suitable, such as centrifugation, microfiltration or even a simple decanting. Preferred collection methods include continuous filtration using, for example, L5 belt filtration, rotary drum filtration, ultra-? iltration: > Similar. Before or after its isolation, the pigment may be conditioned, either batchwise or continuously, in an eventual step (d) using methods known in the art, such as solvent treatment or combination milling. treatment with solvents. The final particle size of the pigment can be controlled by varying the post-treatment method. For example, the pigments can be made more transparent 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 mixing with salts, the mill with pearls and the like in water or organic solvents, with and without additives. The dyeing strength and transparency of the pigment may be affected by the solvent treatment carried out by heating a pigment dispersion, Frequently 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 reduce or prevent flocculation, which increase the stability of the pigment dispersion and reduce the viscosity of the coating, such as polymeric dispersants (or surfactants). For example, US Patents 4,455,173, 4,758,665, 4,844,742, 4,895,948 and 4,895,949. During or after the conditioning step, it is often desirable to use various other eventual ingredients that provide better properties. Examples of such optional ingredients include acid grades having at least 12 carbon atoms, such as stearic acid or behenic acid, or corresponding amides, esters or salts, such as magnesium stearate, zinc stearate, aluminum stearate or magnesium behenate; quaternary ammonium compounds, such as tri [alkyl (Ci-C4) benzyl] ammonium salts; plasticizers, such as soybean oil < --¡ > rusty; waxes, such as polyethylene wax; tesin acids, such as abietic acid, rosin soap and hydrogenated or dimerized rosin; 2-C18 disulfonic paraffin acids; alkylphenols; alcohols, such as stearyl alcohol; amines, such as laurylamine or stearylamine, and aliphatic 1,2-diols, such as dodecane-1,2-diol. Said additives can be incorporated in amounts ranging between about 0.05 and 100% by weight (preferably between 1 and 30% by weight, more preferably between 10 and 20% by weight), based on the amount of pigment. The resulting pigment can be mixed (preferably by dry mixing) in the eventual step (e) with one or more pigment derivatives known in the art, particularly sulfonated, sulfonamide and phthalimido-methyl derivatives of quinacridones. Although generally less preferred, said derivatives may be added during other steps of the claimed invention. Compared to previously known processes, the pigments prepared according to the invention typically have a narrow particle size distribution and excellent color properties, which are particularly suitable for automotive applications. Due to their light stability and their gratifying properties, the quinacridone pigments prepared according to the present invention are suitable for many different coating 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 very rapidly pigmented systems, such as mixtures with other materials, pigment formulations, paints, printing ink, colored paper or colored macromolecular materials. The term "mixture with other materials" can be understood to include, 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, heated enamels, reactive paints, two-component paints, solvent or water-based paints, paints in emulsion for watertight and tempered coatings. Printing inks include those known for use in printing on paper, fabrics and tinplate. Macromolecular substances include those of natural origin, such as rubber, - 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 jopropionate; polyolefins, such as polyethylene and polypropylene; high molecular weight polyamides; polymers and copolymers of acrylates, methacrylates, acrylonitrile, acrylamide, butadiene or styrene; polyurethanes, and poly-L carbonates. The materials pigmented with the quinacridone pigments of the present invention may have any desired shape or shape. The pigments prepared according to this invention are highly resistant to water, resistant to oils, resistant to acids, resistant to lime, resistant to alkalis, resist to solvents, stable to overcoat, stable to overspray, stable to sublimation, resistant heat and vulcanization resistant and still give a very good dyeing perfoce and are easily dispersible (for example,, in coating systems). The following examples further illustrate the details for the "process of this invention." The invention, set forth in the foregoing description, is not limited in spirit or scope by these examples. that known variations of the conditions of the following procedures may be used Unless otherwise indicated, all temperatures are degrees Celsius and all parts and percentages are parts by weight and weight percentages, respectively. 1 Comparative procedure in batches Two parts of polyphosphoric acid (117% phosphoric acid) heated to about 90 to 100 ° C were added with one part of 2,5-diaryl ether-terephthalic acid, and the mixture was then slowly heated. It became too viscous to be agitated effectively during the addition, at a temperature of approximately 135 ° C and remained stable.; then at that temperature for 25 minutes. The reaction mixture became extremely thick and was not pourable. Because the mass solidified easily upon cooling, the removal of the crpigment from the reaction vessel for drowning was very difficult. LO Examples 2-4 Continuous reaction and drowning in batches Examples 2 to 4 were carried out using an ei Apa of continuous reaction, but a stage of drowning in batches. E Temple 2 l In a single-inch extr (approximately 20 mm) having a length-to-diameter ratio of approximately 30: 1 and three zones heated to 90 ° C, 120 ° C 180 ° C, 11 were introduced, 7 g per minute of 2,5-dianilinoterephthalic acid and 27.2 g per minute of polyphospho-neo acid (117.7% phosphoric acid). The resulting mass was introduced into water. The resulting solid was collected by filtration and resuspended in water containing sodium hydroxide (pH greater than 10). The suspension was heated at 90 to 95 ° C for one hour, then collected, put on filtration, washed until it became alkali-free and dried to give an 85% yield. Or qumacridone (91.3% purity) . Example 3 Example 2 was repeated using 21.1 g per minute of 2,5-diamlinoterephthalic acid and 27.9 g per minute of 30% phosphoric acid. An 86.1% yield of quinacridone was obtained. which had a purity of 96.6%. Example 4 Example 2 was repeated using 4.6 g per minute of 2,5-di (4-methylanilino) terephthalic acid and 18.9 g per minute of polyphosphoric acid. A yield of 95.6% of 2,9-dimethylquinacridone was obtained. Examples 5-10 Continuous Reaction and Continuous Drowning Examples 5 to 10 were carried out using a continuous reaction step and a continuous drowning step. Example 5 In a 50 mm twin-screw extr heated to 195 ° C, 25 g per minute of 2,5-dianilinoterephthalic acid and 78 g per minute of polyphosphoric acid (117% phosphoric acid) were introduced. The resulting crquinacridone melt contained less than 5% of the starting 2,5-dianilinoterephthalic acid, partially enclosed ring intermediate and other impurities. The melt was pumped through a mixing T into a pressurized pipe heated to 120 ° C, through which 70 g per minute of methanol was passed. After heating for approximately five minutes at 120 ° C, the resulting suspension was passed through a second mixing T, where the heated suspension was mixed with 2320 g of water. The suspension P was passed through heat exchangers to cool the liquid below its boiling point (atmospheric pressure) and allow it to escape from the apparatus by filtration. The filter cake was washed until alkali-free and dried to give quinacridone (yield greater than 95%). Examples 6-9 Examples 6-9 according to the invention were carried out by the method of Example 5, except for the use of the parameters indicated in the following Table. In each example, quinacridone was obtained with a yield of more than 95%. Table Reaction parameters for Examples 6 to 9 Ei. Parameters of the extruder Parameters of drowning APF represents polyphosphoric acid. ADAT represents 2, 5-dianilinoterephthalic acid. Example -10 Example 5 was repeated using 25 grams per minute of 2,5-di (4-methylanilino) terephthalic acid and 51 g per minute of polyphosphoric acid at a processor temperature of 160 ° C, followed by drowning with 100 g per minute of methanol (initial temperature of 25 ° C) heated to 85 ° C. 2,9-dimethylquinacridone was obtained in more than 95% yield.

Claims (6)

Claims

1. A continuous process for the preparation of quinacridone pigments consisting of '• > (a) preparing a reaction mixture by mixing (i) a 2,5-dianilinoterephthalic acid or ester thereof and (ii) at least about 0.5 parts by weight per part (a) (i) of an LO agent dehydrating; (b) passing the reaction mixture through a continuous reactor having one or more zones heated to a temperature of about 80 ° C to about 300 ° C to form a crude cridone quina-L5 composition; '') mixing a continuous stream of the crude quinacridone composition with a liquid in which the quinacridone pigment is substantially insoluble, in a ratio of about 0.5 to about 15 parts by weight of the liquid per part by weight of the composition of crude quinacridone; (d) optionally, conditioning the resulting quinacridone pigment, and 5 (e) optionally, mixing the resulting quinacridone pigment with one or more quinacridone derivatives.

2. A process according to claim 1, wherein the 2,5-oannylinoterephthalic acid or ester thereof is 30,5-dianilinoterephthalic acid or an ester thereof, 2,5- (ii (4-chloroanilino) terephthalic acid or an ester of the latter. same, 2-5-di (4-methylanilino) terephthalic acid or an ester thereof or 2,5-di (4-methoxyanilino) terephthalic acid or an ester thereof.

3. A process according to Claim 1, wherein, in step (c), the direct current of the crude qui-nacridine composition of step (b) is mixed with a direct current of the liquid in which the quinacridone pigment is substantially insoluble.

4. A process according to Claim 1, wherein the dehydrating agent is polyphosphoric acid or 70-100% sulfuric acid.

5. A process according to Claim 1, wherein, in step (c), the liquid is water and / or methanol.

6. A process according to Claim 1, wherein, in step (c), the liquid is water and / or methanol containing an alkali metal hydroxide in amounts sufficient to maintain an alkaline medium.