WO2002038680A2

WO2002038680A2 - Process for manufacturing pigmentary quinacridones

Info

Publication number: WO2002038680A2
Application number: PCT/US2001/050642
Authority: WO
Inventors: Edward Sung; Jeremy Putney; George H. Robertson
Original assignee: Sun Chemical Corporation
Priority date: 2000-11-10
Filing date: 2001-11-01
Publication date: 2002-05-16
Also published as: WO2002038680A3; CA2429050A1; EP1334154A2

Abstract

A process for preparing quinacridone pigments involving (a) preparing a reaction mixture of a substituted or unsubstituted 2,5-dianilino-terephthalic acid or ester thereof, and at least about 0.5 parts by weight of acid of a dehydrating agent; (b) combining the reaction mixture through one or more heated zones at a temperature of about 80 C to about 300 C; and (c) mixing the resulting crude quinacridone composition with a liquid in which the quinacridone pigment is substantially insoluble.

Description

PROCESS FOR MANUFACTURING PIGMENTARY QUINACRIDONES

FIELD OF THE INVENTION

This invention relates to an economical continuous process for the preparation of quinacridone pigments having uniform particles of a narrow particle size distribution.

BACKGROUND OF THE INVENTION

Processes for the preparation of quinacridone pigments are known, e.g., S. S. Labana and L. L. Labana, "Quinacridones" in Chemical Review, 67, 1-18 (1967), and U.S. Patent Nos . 3,157,659, 3,256,285, and 3,317,539. The quinacridones thus obtained are known as crude quinacridones and are generally unsuitable for use as they must undergo one or more additional finishing steps to modify their particle size, particle shape, or crystal structure to achieve pigmentary quality.

A preferred method for preparing quinacridones involves thermally inducing ring closure of 2, 5-dianilinoterephthalic acid intermediates, as well as known aniline-substituted derivatives thereof, in the presence of polyphosphoric acid (e.g., U.S. Patent No. 3,257,405) or even sulfuric acid (e.g., U.S. Patent No. 3,200,122 and European Patent Application

863,186). After the ring closure step is complete, the melt intermediate is drowned by pouring it into a liquid in which the crude quinacridone is substantially insoluble, usually water and/or an alcohol. The resultant crystalline quinacridone pigment is further conditioned by solvent treatment or milling in combination with solvent treatment.

The final particle size of a quinacridone pigment can be controlled by methods used in both the synthesis and aftertreatment steps. For example, quinacridone pigments can be made more transparent by reducing their particle size or more opaque by increasing their particle size. In known methods, particle size is generally controlled during precipitation of the pigment by drowning or during the milling or solvent treatment of the crude. The tinctorial strength and transparency of a pigment can also be affected by solvent treatment. Aftertreatment steps that manipulate the crude's particle size are often referred to as conditioning methods .

Although prior art methods can produce quality products, a more efficient process for manufacturing pigmentary quinacridone pigments would be desirable.

SUMMARY OF THE INVENTION

This invention relates to a process for the preparation of quinacridone pigments comprising

(a) preparing a reaction mixture by mixing (i) a 2, 5-terephthalic acid or ester thereof, and

(ii) at least about 0.5:1 to about 10:1 parts by weight of said acid or ester of a dehydrating agent;

(b) processing the reaction mixture through a heated kneader or continuous reactor having one or more heated zones at a temperature of about 80 C to about 300 C;

(c) mixing of the crude quinacridone composition with a liquid in which the quinacridone is substantially insoluble (continuous stream of the liquid can be used for continuous process) 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;

(d) optionally, conditioning the resultant quinacridone pigment; and (e) optionally, blending the resultant quinacridone pigment with one or more quinacridone derivatives .

Other objects and advantages of the present invention will become apparent from the following description and appended claims .

DETAILED DESCRIPTION OF THE INVENTION

Quinacridone pigments (by which is meant unsubstituted quinacridone, quinacridone derivatives, and solid solutions thereof) are prepared according to the invention by ring-closing 2, 5-dianilinoterephthalic acid intermediates, including known derivatives that are substituted in the aniline ring, by heating such terephthalic acid intermediates and derivatives in the presence of a dehydrating agent (preferably polyphosphoric acid) . The quinacridone is then drowned in a batch and optionally in a continuous process. The quinacridone pigment is preferably also subjected to additional conditioning steps to improve pigmentary properties and, if desired, blended with an additional quinacridone derivative.

The process of the invention is used to prepare either unsubstituted or substituted quinacridone derivatives, depending on whether the ring closure is carried out using unsubstituted or substituted 2, 5-dianilinoterephthalic acid (or esters thereof) 2 , 5-dianilinoterephthalic acid derivative (or esters thereof) having one or more substituents in at least one of the two aniline rings. Although essentially any substituted 2, 5-dianilinoterephthalic acid derivatives known in the art can be used, particularly preferred substituted

2, 5-dianilinoterephthalic acid derivative are known in which both aniline moieties are substituted (typically with the same substituent) at the para position with, for example, a halogen (preferably chlorine) , Ci -Cg alkyl (preferably methyl) , and Ci -Cζ alkoxy (preferably methoxy) . It is also possible to use 2, 5-dianilinoterephthalic acid derivatives in which both aniline moieties are substituted in the para, ortho or meta positions. Examples of suitably chloro, methyul and methoxy substituted 2,5-di(para, ortho and meta) anilinoterephthalic acid derivatives include 2, 5-di (4-chloroanilino) terephthalic acid, 2, 5-di (4-methylanilino) terephthalic acid, 2, 5-di (4-methoxyanilino) terephthalic acid.

It is also possible to use mixtures containing 2, 5-dianilinoterephthalic acid and one or more derivatives thereof or mixtures containing two or more

2, 5-dianilinoterephthalic acid derivatives. The use of such mixtures provides a particularly advantageous method for obtaining quinacridone solid solutions. Mixtures containing 2, 5-dianilinoterephthalic acid and/or a derivative thereof in combination with a fully formed quinacridone pigment (generally in crude form) can also be used.

Preparation of the reaction mixture (i.e. the ring-closure step (a)) is carried out by contacting the 2, 5-terephthalic acid or ester thereof with a dehydrating agent, which is particularly a strong acid, such as polyphosphoric acid, acidic esters of polyphosphoric acid, or sulfuric acid, e.g., U.S. Patent No. 4,758,665 and S. S. Labana and L. L. Labana, "Quinacridones" in Chemical Reviews, 67, 1-18 (1967) is used. Polyphosphoric acid, having a phosphate content equivalent to about 110 to 120% H₃PO₄ , is particularly preferred. When using polyphosphoric acid, the weight ratio of polyphosphoric acid to the terephthalic acid intermediate is typically about 0.5:1 to about 10:1 (preferably 1:1 to 2:1) . It is also possible to use about 70 to 100% (preferably 85 to 98%, more preferably 90 to 93%) sulfuric acid as the dehydrating agent. When using sulfuric acid, the weight ratio of sulfuric acid to the terephthalic acid intermediate is similar to that used with the polyphosphoric acid. The components used in step (a) are preferably mixed in an unheated reactor or reactor section or in a heated section of a reactor, provided that when doing so the components are adequately mixed and heated, even when the mixture is viscous. The batch reactor is typically one with a sig a blade mixer and an effective heat transfer jacket. The mixer blades may also be thermostatically controlled. The reactor may be heated or cooled to the desired temperature. The energy required to mix a viscous mass and the exothermic nature of the reaction will normally necessitate heating the initial reaction mixture and then cooling it to maintain the desired temperature range.

As an alternative to batchwise methods, a continuous process is also possible. The reaction compositions of the current invention lend themselves to such continuous processing. The present invention therefore also provides continuous process for preparing and drowning quinacridones using the smaller amounts of dehydrating agent. In addition to allowing the use of smaller quantities of dehydrating agent, which would lower manufacturing costs and reduce environmental impact, the continuous process approach produces a quinacridone pigment having a desirably narrow particle size distribution.

The continuous process reactive components can also be mixed before introduction into the reactor. As used herein, the term "continuous reactor" encompasses any number of reactors through which solids, semi-solids, and melts are passed while being heated and, optionally, while being mixed. Suitable continuous reactors can provide good heat transfer and thorough mixing, even with highly viscous materials. Extruders comprise a particularly preferred type of continuous reactor. Examples of suitable extruders include mixing screw extruders (especially single-screw and double-screw extruders) arranged in single or multiple stages where heating and mixing can take place . The desired throughput rate is, of course, a factor in selecting the capacity of the extruder. Regardless of the means used for mixing, in the continuous process, the reaction mixture is passed through one or more heated zones in which a temperature from about 80 C to about 300 C is maintained, giving rise to an initial crude quinacridone. In general, the batch reactor reaction is exothermic and heating within the mixture becomes particularly pronounced once the temperature reaches about 80 C to about

120 C. The maximum temperature reached in the heated zone is generally dependent not only on the temperature applied externally to the reactor but also on the time during which the reaction mixture is retained in the mixing apparatus (i.e. dwell time) and the nature of the dehydrating agent. Other factors, such as the viscosity of the reaction mixture and thermal stability of the intermediate product formed, should also be considered when selecting the reaction parameters. For example, when using the preferred dehydrating agent polyphosphoric acid, in a temperature range of about 100 C to about 220 C and more preferably, from about 140 C to about 200 C. When using sulfuric acid as the dehydrating agent, the preferred temperature range is about 140 C to about 220 C.

Sulfonation can occur with most of the reactants and such reaction is often undesirable. Nonetheless, in the case of intermediates which are less susceptible to sulfonation in forming 2, 9-dichloroquinacridone, the more economical sulfuric acid dehydration agents can be used.

For continuous processing, multistage heating is often desirable. When using a heating apparatus with more than one heating zone, it is generally preferable to begin the heating process at the lower end of the temperature range, continue the heating process at one or more intermediate temperatures, and complete the heating process at the upper end of the temperature range. In a typical three-zone reactor, for example, the reaction mixture is 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 step (b) that is the time within the batch or continuous reactor, is preferably selected to be sufficiently long to allow the reaction to proceed to completion but not so long as to allow undesirable side reactions produce significant amounts of by-product. In the preferred temperature ranges described above, it is generally possible to achieve essentially complete reaction within approximately fifteen minutes, and some instances less than five minutes. The reaction time is, of course, somewhat dependent on the reaction temperature. The batch reactor tends to require longer residence time due to having a less even temperature profile.

The crude quinacridone composition formed in the reactor is drowned in step (c) by mixing it with a liquid in which the quinacridone is substantially insoluble at a ratio of about 0.5 to about 15 parts by weight, more preferably 1 to 10 parts by weight. This would include water, a water-miscible solvent such as methanol or other lower aliphatic alcohols or mixtures thereof, or water containing a dispersion of a water insoluble solvent. Suitable drowning liquids include water and/or water-miscible organic liquids; 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 such organic liquids known in the art. Solvents used in the water dispersion can be aliphatic or aromatic hydrocarbons. Other organic liquids can be used but are generally less preferred. In the continuous process, this drowning can also take place. Because the dehydrating agent of step (a) (ii) is typically strongly acidic, one can optionally include a basic liquid in the drowning liquid in sufficient quantities to maintain an alkaline medium. The specific liquid used for this purpose is not critical but is generally an alkali metal hydroxide and more preferably a sodium or potassium hydroxide.

Depending on the type of condensation reactor used and the pressure requirements downstream from the reactor, it may be necessary to use a separate feeder to transfer the crude quinacridone composition from the reactor to the drowning apparatus. With this separate feeder, the batch and continuous process for this second stage are similar processes. 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 dilute acid, water, water miscible solvents, or dispersion of water miscible solvents in water: all as described above for conditioning process before being mixed with the drowning liquid. However, the specific design of the mixing apparatus is generally not critical as long as the desired ratio of liquid to crude quinacridone composition is maintained.

For the batch process, adding the same dilute acid, water or solvents to the reactor after completion can facilitate the discharge into the conditioning equipment. These also assist in breaking up the viscous mass.

As previously mentioned, the drowning step (c) can be carried out batchwise by introducing the reaction mixture from step (b) into one or more fixed volumes of the drowning liquid. However, when step (a) is carried out as a continuous reaction, the drowning step (c) , is preferably carried out in a continuous manner. When carrying out the drowning by a continuous process, the drowning liquid is generally introduced as a side stream or a centrally injected stream into the crude quinacridone product stream (even when using excess drowning liquid) using nozzles or other mixing devices known in the art. Although it is possible to use a pipe with a simple tee, it is generally preferable to use a drowning nozzle that reduces at least one of the component streams into one or more thin streams. It is also possible to use other types of nozzles, such as a ring-type nozzles, in which the crude quinacridone composition is introduced at low pressure and the drowning liquid is introduced in thin streams at higher pressure. The two streams can be mixed at the entrance 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 drowning liquid in a continuous stirred reactor or in a series of continuous stirred reactors. Another example of a continuous drowning apparatus is a loop reactor. When flammable liquids, such as low boiling point alcohols, are used, the drown stream can also be mixed with water in a continuous manner to reduce the risk of fire or explosion during isolation.

The drowning systems described above can be used at atmospheric or elevated pressures, although the pressure that is actually used is somewhat dependent on the required temperatures and the boiling points of the liquid components being used. When the equipment is sealed and under pressure, the temperature of the drowning medium can be greater than the boiling point at atmospheric pressure. The liquid streams can even be mixed at or below room temperature to help control the initial heating that occurs during hydrolysis of the acidic reaction mass. Furthermore, lower drowning temperatures tend to give pigments having smaller particle sizes. On the other hand, it may be desirable to use higher temperatures to speed up the hydrolysis or to help increase the particle size during drowning. Because process cycle times can also be important, for example, because of manufacturing cost, shorter residence times in the mixing apparatus are generally preferred. It is possible to include various known additives to the drowning liquid. The optional additives can be any of the customary pigment preparation additives known in the art that serve, for example, to improve color properties, lessen or avoid flocculation, increase pigment dispersion stability, and reduce coating viscosity. Suitable additives include, for example, dispersants or surfactants, metal salts, and various pigment derivatives .

Suitable dispersants include anionic compounds, such as fatty acids (such as stearic or oleic acid) , fatty acid salts (i.e., soaps such as alkali metal salts of fatty acids), fatty acid taurides or N-methytaurides, alkylbenzenesulfonates, alkylnaphthalenesulfonates, alkylphenol polyglycol ether sulfates, naphthenic acids or resin acids (such as abietic acid) ; cationic compounds, such as quaternary ammonium salts, fatty amines, fatty amine ethylates, and fatty amine polyglycol ethers; and nonionic compounds, such as fatty alcohol polyglycol ethers, fatty alcohol polyglycol esters, and alkylphenol polyglycol ethers .

Suitable metal salts include various salts of alkali metals (such as lithium, sodium, and potassium) , alkaline earth metals (such as magnesium, calcium, and barium) , aluminum, transition and other heavy metals (such as iron, nickel, cobalt, manganese, copper, and tin) , including, for example, the halide (especially chloride) , sulfate, nitrate, phosphate, polyphosphate, sulfonate (such as methanesulfonate or p-toluenesulfonate, or even known quinacridone sulfonate derivatives) , and carboxylate salts, as well as the oxides and hydroxides. Suitable pigment additives include organic pigments having one or more sulfonic acid groups, sulfonamide groups, carboxylic acid, carboxamide, and/or (hetero) aryl-containing (cyclo) aliphatic groups. If used, such additives are used in amounts ranging from about 0.05 to 100% by weight (preferably 1 to 30% by weight and more preferably 1 to 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 slurry that can be isolated by various methods known in the art, such as filtration, and then dried if desired. Other isolation methods known in the art, such as centrifugation, microfiltration, or even simple decantation, are also suitable. Preferred isolation methods include continuous filtration using, for example, belt filtration, rotary drum filtration, ultrafiltration, or the like.

Before or after being isolated, the pigment can be conditioned, either batchwise or continuously, in an optional 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 method of aftertreatment . For example, the pigment can be made more transparent by reducing the particle size or made 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, bead-milling, and the like in water or organic solvents, with or without additives.

The tinctorial strength and transparency of the pigment can also be affected by solvent treatment carried out by heating a dispersion of the pigment, 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 lessen or avoid flocculation, increase pigment dispersion stability, and reduce coating viscosity, such as polymeric dispersants (or surfactants), e.g., U.S. Patent Nos . 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 optional ingredients that provide additional improved properties. Examples of such optional ingredients include fatty acids 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[(Cι -C₄ alkyl) benzyl] ammonium salts; plasticizers, such as epoxidized soya bean oil; waxes, such as polyethylene wax; resin acids, such as abietic acid, rosin soap, hydrogenated or dimerized rosin; Cι₂ -Ciβ -paraffin-disulfonic acids; alkylphenols; alcohols, such as stearyl alcohol; amines, such as laurylamine or stearylamine; and aliphatic 1,2-diols, such as dodecane-1, 2-diol . Such additives can be incorporated in amounts ranging from about 0.05 to 100% by weight (preferably 1 to 30% by weight, more preferably 10 to 20% by weight) , based on the amount of pigment.

The resultant pigment is optionally blended (preferably by dry blending) in optional step (e) with one or more pigment derivatives known in the art, particularly sulfonic acid, sulfonamide, and phthalimidomethyl derivatives of quinacridones. Although generally less preferred, such derivatives can also be added during other steps of the claimed invention.

Compared to previously known processes, pigments prepared according to the present invention characteristically have a narrower particle size distribution and excellent color properties that are particularly suited for automotive applications .

Because of their light stability and migration properties, the quinacridone pigments prepared according to the present invention are suitable for many different pigment applications. For example, they can be used as the colorant (or as one of two or more colorants) for very fast 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 flushed pastes with organic liquids or pastes and dispersions with water, dispersants, and if appropriate, preservatives. Paints in which the quinacridone pigments of this invention can be used include, for example, physically or oxidatively drying lacquers, stoving enamels, reactive paints, two-component paints, solvent- or water-based paints, emulsion paints for weatherproof coatings, and distempers. Printing inks include those known for use in paper, textile, and tinplate printing. Macromolecular substances include those of a natural origin, such as rubber; those obtained by chemical modification, such as acetyl cellulose, 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 can have any desired shape or form.

Pigments prepared according to this invention are highly water-resistant, oil-resistant, acid-resistant, lime-resistant, alkali-resistant, solvent-resistant, fast to over-lacquering, fast to over-spraying, fast to sublimation, heat-resistant, and resistant to vulcanizing, yet give a very good tinctorial yield and are readily dispersible (for example, in coating systems.

The following examples further illustrate details for the process of this invention. The invention, which is set forth in the foregoing disclosure, is not to be limited either 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 degrees Celsius and all parts and percentages are parts by weight and percentages by weight, respectively.

Example 1 105 parts of 2, 5-ditoluidino-terephthalic acid (DTTA) are mixed with 210 parts by weight of polyphosphoric acid having a P₂U₅ content of 85.3%. The mixing is done in a sigma blade kneader at room temperature and done so as to wet out dry intermediate, forming a smooth magma. The magma is heated to 120 to 135 C and held, with mixing, at this temperature for 2 hours. The hot magma is hydrolyzed in a vessel containing methanol, this ratio being 10 parts by weight methanol to 1 part by weight 2, 9-dimethylquinacridone, and stirred at high speed for 5 minutes. The resulting slurry is then stirred for one hour at medium speed. The resulting methanol pigment slurry is heated under increased pressure with stirring for 4 hours at a temperature of 120 C. The slurry is then cooled, taken to zero pressure, then filtered and washed with water to a conductivity of 200 microMhos . The resulting quinacridone pigment is reslurried in water and the pH adjusted from 6.5 to 7.0. 1 part by weight mineral spirits to 1 part by weight pigment is added to the water slurry and is stirred for one hour. The pigment is then filtered and washed with water to low conductivity, then dried. The result is a magenta having a clean shade, strong tint, and highly dispersible in polyethylene. Comparative Example 1 As an alternative to hydrolyzing the hot magma in methanol, as was done in Example 1, the hydrolyzation occurs in 10 parts by weight water to 1 part by weight 2, 9-dimethylquinacridone . This mixture is then blended for 5 minutes at high speed and stirred for 3 hours. The resulting pigment slurry is filtered and washed with water until free of acid and having low conductivity. One part by weight pigment is reslurried in 15 parts by weight water, with 1 part 50% by weight sodium hydroxide (NaOH ), 1 part mineral spirits, and 0.03 parts by weight surfactant, and the whole is heated under increased pressure for 5 hours at 150 C. The pigment is then cooled taken to zero pressure, filtered, washed with water to low conductivity, and dried. The resulting pigment is lighter, slightly weaker and dirtier than the methanol struck product of Example 1.

Example 2 150 parts by weight of DTTA and 150 parts by weight of polyphosphoric acid having a P₂Os content of 85.3% are mixed in the same manner as described in Example 1. The magma is heated to 120 to 135 C and mixed at this temperature for 2 hours. Frictional heat is generated near the end of the 2 hour time causing the temperature to rise to 140 to 145 C. The magma is a very flat navy blue shade, and, upon cooling, the magma becomes a semi-solid mass that is ground to a powder. The powder is hydrolyzed and conditioned as in Example 1. The resulting pigment is similar to that obtained in Example 1, but slightly dirtier and weaker with a much yellower tint shade. The omission of mineral spirits product has little effect on the strength, but appears to give a lighter masstone in polyethylene. Example 3

100 parts by weight of 2, 5-dichloroanilino-terephthalic acid (DCTA) are mixed with 200 parts by weight of polyphosphoric acid having a P₂0s content of 85.3%. This is done batch wise at room temperature so as to wet out the dry intermediate, thereby forming a smooth magma. The magma is heated to 120 to 135 C and held, with mixing, at this temperature for 2 hours . The hot magma is hydrolyzed in methanol, this ratio being 10 parts by weight methanol to 1 part by weight 2, 9-dichloroquinacridone and stirred for one hour at medium speed then stirred for 5 minutes at high speed. The resulting pigment slurry is refluxed for 4 hours at 70 C. The pigment is filtered and washed with water to a conductivity of 850 microMhos . The pigment is then reslurried and pH adjusted to 6.5 to 7.0. The pigment is filtered, washed with water to low conductivity, and dried.

Comparative Example 3 Using the finished hot magma obtained in Example 3, it is hydrolyzed in 12 parts by weight water to 1 part by weight 2,9- dichloroquinacridone and stirred for one hour at medium speed then stirred for 5 minutes at high speed. The pigment is filtered and washed with water to low conductivity. One part pigment is reslurried in 15 parts by weight water, with 1 part by weight 50% NaOH, 1 part by weight mineral spirits, and 0.03 parts by weight surfactant, and the whole is heated under increased pressure for 5 hours at 150 C. The pigment slurry is cooled and taken to zero pressure, filtered, washed with water to low conductivity, and dried. The resulting pigment is lighter and stronger when compared with the pigment from Example 3 in polyethylene . Example 4

100 parts by weight of 2, 5-dianilinoterephthalic acid (DATA) and 200 parts by weight of polyphosphoric acid having a P₂U₅ content of 85.3% are mixed in the same manner as described in Example 1. The magma is heated to 120 to 135 C and mixed at this temperature for 2 hours . The hot magma is hydrolyzed in methanol, this ratio being 10 parts by weight methanol to 1 part by weight quinacridone and stirred at high speed for 5 minutes.

The resulting slurry is then stirred for one hour at medium speed. This methanol-pigment slurry is heated under increased pressure for 4 hours at a temperature of 120 C with stirring. The pigment slurry is then cooled, taken to zero pressure, filtered and washed with water to low conductivity. The pigment is reslurried in water and the pH of the slurry adjusted to 7.0 to 8.0. An emulsion containing mineral spirits is added and the slurry is stirred for 40 minutes. The pigment is filtered, washed with water to low conductivity, and dried to give a beta crystal quinacridone.

Comparative Example 4 (a) As an alternative to hydrolyzing the hot magma prepared as described in Example 4, it is hydrolyzed in 10 parts by weight to 1 part by weight quinacridone. This is stirred for 5 minutes at high speed and then stirred for 3 more hours . The pigment is filtered and washed with water to a conductivity of 13000 microMhos . The resulting pigment presscake is then reslurried in 8-12 parts by weight of methanol and heated for 4 to 8 hours at a temperature of 75 to 125 C. The resulting pigment is a gamma crystal phase quinacridone.

Example 5

150 parts of DATA and 150 parts of polyphosphoric acid having a P₂0s content of 85.3% are mixed in the same manner as described in Example 1. The hot magma is heated to 120 to 135 C and mixed at this temperature for 2 hours. The magma is hydrolyzed and conditioned as described in Example 4, and yields the same crystal phase pigments as described in Example 4.

The invention has been described in terms of preferred embodiments thereof, but is more broadly applicable as will be understood by those skilled in the art. The scope of the invention is only limited by the following claims .

Claims

What is claimed is:

1. A continuous process for the preparation of quinacridone pigments comprising:

(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 zones at a temperature of about 80 C to about 300 C to form a crude quinacridone composition;

(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;

(d) optionally, conditioning the resultant quinacridone pigment; and

(e) optionally, blending the resultant quinacridone pigment with one or more quinacridone derivatives.

2. The process according to claim 1, wherein the 2, 5-dianilinoterephthalic acid or ester thereof is 2, 5-dianilinoterephthalic acid or an ester thereof,

2, 5-di (4-chloroanilino) terephthalic acid or an ester thereof, 2, 5-di (4-methylanilino) terephthalic acid or an ester thereof, or 2, 5-di (4-methoxyanilino) terephthalic acid or an ester thereof.

3. The process according to claim 1, wherein in step (c) the continuous stream of the crude quinacridone composition from step (b) is mixed with a continuous stream of the liquid in which the quinacridone pigment is substantially insoluble.

4. The process according to claim 1, wherein the dehydrating agent is polyphosphoric acid or 70 to 100% sulfuric acid.

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

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

7. A batch or continuous process for preparing quinacridone pigments comprising:

(a) preparing a reaction mixture of a para-, ortho- or meta- substituted or unsubstituted 2, 5-dianilino-terephthalic acid or ester thereof, and at least about 0.5 parts by weight of said acid or ester of a dehydrating agent;

(b) combining the mixture in a reactor at a temperature of about 80 C to about 300 C;

(c) mixing the resulting crude quinacridone composition with a liquid in which the quinacridone is substantially insoluble, at a ratio of about 0.5 to about 15 parts by weight of the liquid to 1 part by weight of the crude quinacridone composition;

8. The process according to claim 7, in which the process steps are carried out in a batch mode.

9. The process according to claim 7, in which the process steps are carried out in a continuous mode.

10. The process according to claim 7, wherein the dehydrating agent is polyphosphoric acid or a 70 to 100% sulfuric acid solution.

11. The process according to claim 7, wherein the step (c) liquid is water and/or methanol .

12. The process according to claim 11, wherein the step (c) liquid is water and/or methanol containing an alkali metal hydroxide in sufficient quantities to maintain an alkaline medium.