EP1740659A1 - Process for producing high-purity azo dyes - Google Patents

Abstract

A process for producing high-purity azo dyes is characterised in that (a) at least azo coupling is carried out in a micro-reactor; (b) the azo dye produced in the micro-reactor is brought into intimate contact with an organic solvent from the group of the C3-C6 alcohols, C4-C10 ether alcohols and halogenated aromatic compounds at a temperature from 0 to 60 DEG C; and (c) the azo dye produced in the micro-reactor is subjected to membrane purification in an aqueous or solvent-containing suspension.

Description

Process for the production of high-purity azo colorants

In the context of the present invention, azo dyes mean sparingly soluble azo dyes and azo pigments which are produced by means of the azo coupling reaction from a diazonium salt of an aromatic amine and a CH-acidic compound, hereinafter called the coupling component. Technically, they are manufactured conventionally in a batch process. A common feature of these processes is the need for precise control and compliance with the process parameters: for example, temperature, time, mixing and colorant concentration, for example the suspension concentration in the case of azo pigments, are decisive for the yield, the coloristic properties and the fastness of the azo colorants obtained and their quality consistency. Also, the scale-up of new products from the laboratory scale to the industrial scale in batch processes is complex and can be difficult because, for example, boiler and stirrer geometries or heat transfers have a great influence on the primary grain size, grain size distribution and on the coloristic properties.

Despite all process optimization in the synthesis, conventionally produced azo colorants sometimes still contain residual amounts of unreacted starting materials and by-products formed by side reactions. A high chemical purity is required in particular for azo colorants which are used for non-contact printing processes, such as small office / home office printers. For certain applications, e.g. the coloring of consumer goods, there are special limit values for primary aromatic amines, naphthols and triazenes for the colorants used.

The present invention was based on the object of a technically reliable and cost-effective method for producing azo colorants with a significantly reduced content of undesired secondary components. It has been found that the object of the invention can surprisingly be achieved by combining pigment synthesis using microreaction technology (MRT), solvent washing and membrane purification.

The invention relates to a method for producing high-purity azo colorants, characterized in that

(a) at least the azo coupling is carried out in a microreactor,

(b) the azo colorant produced in the microreactor is brought ₀ -Etheralkohole and halogenated aromatic compounds at a temperature of 0 to 60 ° C in intensive contact with an organic solvent from the group of C-3-C6-AIkohole, the C ₄ -Cι , and

(c) the azo colorant produced in the microreactor is subjected to membrane purification in aqueous or solvent-containing suspension.

Step (c) can also be carried out before step (b).

(a) The synthesis in the microreactor:

The devices described in WO 01/59013 A1 can be used as microreactors. A microreactor is made up of a plurality of platelets stacked on top of one another and connected to one another, on the surfaces of which there are micromechanically produced structures which, in their interaction, form reaction spaces in order to carry out chemical reactions. There is at least one channel through the system connected to the inlet and the outlet.

The flow rates of the material flows are limited in terms of equipment, for example due to the pressures which arise depending on the geometric design of the microreactor. It is desirable for the reaction to proceed to completion in the microreactor, but a residence zone can also follow in order to create a residence time which may be required. The flow rates are expediently between 0.05 and 5 l / min, preferably between 0.05 and 500 ml / min, particularly preferably between 0.05 and 250 ml / min, and in particular between 0.1 and 100 ml / min. The microreaction system is operated continuously, the amounts of fluid mixed in each case being in the micro (μl) to milliliter (ml) range.

The dimensions of the microstructured areas within the reactor are decisive for the production of azo colorants in this microreaction system. These must be selected to be large enough that particulate matter in particular can pass through without problems and so that the channels do not become blocked. The smallest clear width of the microstructures should be about ten times larger than the diameter of the largest pigment particles. Furthermore, appropriate geometric design must ensure that there are no dead water zones, e.g. Dead ends or sharp corners, in which e.g. Can sediment pigment particles are present. Continuous paths with round corners are therefore preferred. The structures must be small enough to take advantage of the inherent advantages of microreaction technology, namely excellent temperature control, laminar flow, diffusive mixing and low internal reaction volume.

The clear width of the solution- or suspension-carrying channels is expediently 5 to 10000 μm, preferably 5 to 2000 μm, particularly preferably 10 to 800 μm, in particular 20 to 700 μm. The clear width of the heat exchanger channels depends primarily on the clear width of the liquid- or suspension-carrying channels and is expediently less than or equal to 10000 μm, preferably less than or equal to 2000 μm, in particular less than or equal to 800 μm. The lower limit of the clear width of the heat exchanger channels is not critical and is limited at most by the pressure increase of the heat exchanger liquid to be pumped and by the need for optimal heat supply or removal. The dimensions of the microreaction system used are: Heat exchanger structures: channel width about 600 μm, channel height: about 250 μm; Mixer and dwell time: channel width approx. 600 μm, channel height approx. 500 μm.

The microreactor is preferably charged with all heat exchanger fluids and reactants from above. The removal of the product and the heat exchanger fluids is preferably also carried out upwards. The eventual addition of third and fourth Liquids involved in the reaction (eg buffer solutions) are realized via a T-branch located directly in front of the reactor, ie one reactant can be mixed with the buffer solution in advance. The required concentrations and flows are preferably checked using precision piston pumps and a computer-controlled control system. The reaction temperature is monitored via integrated sensors and monitored and controlled with the help of the regulation and a thermostat / cryostat.

Mixtures of feedstocks can also be prepared beforehand in micromixers or in upstream mixing zones. Feedstocks can also be metered in downstream mixing zones or in downstream micromixers or reactors. The system used here is made of stainless steel; other materials such as glass, ceramics, silicon, plastics or other metals can also be used.

In addition to the azo coupling, the diazotization, optionally a laking and / or complexing with metal salts can also be carried out in the microreactor. Several of these stages can also be carried out in a corresponding number of microreactors connected in series.

The process according to the invention is suitable for all sparingly soluble azo colorants which can be prepared by azo coupling reaction, for example for azo pigments from the series of monoazo pigments, disazo pigments, β-naphthol and naphthol AS pigments, laked azo pigments, benzimidazolone pigments,

Disazo condensation pigments and metal complex azo pigments; and for azo dyes from the series of disperse dyes.

The process according to the invention also relates to the preparation of precursors of the actual azo colorants by azo coupling reaction. For example, precursors for lacquered azo colorants, i.e. paintable azo colorants, for

Disazo condensation pigments, ie monoazo colorants which can be linked via a bifunctional group or, for example, disazo colorants which can be expanded via an acid chloride intermediate, for formazan dyes or others heavy metal-containing azo colorants, for example copper, chromium, nickel or cobalt-containing azo colorants, ie azo colorants complexable with heavy metals.

The azo colorants which can be prepared by the process according to the invention or the precursors of azo colorants which can be prepared by the process according to the invention are, in the case of azo pigments, in particular C.I. Pigment Yellow 1, 3, 12, 13, 14, 16, 17, 65, 73, 74, 75, 81, 83, 97, 98, 106, 111, 113, 114, 120, 126, 127, 150, 151, 154, 155, 174, 175, 176, 180, 181, 183, 191, 194, 198, 213; Pigment Orange 5, 13, 34, 36, 38, 60, 62, 72, 74; Pigment Red 2, 3, 4, 8, 9, 10, 12, 14, 22, 38, 48: 1-4, 49: 1, 52: 1-2, 53: 1-3, 57: 1, 60, 60: 1, 68, 112, 137, 144, 146, 147, 170, 171, 175, 176, 184, 185, 187, 188, 208, 210, 213, 214, 242, 247, 253, 256, 262, 266, 269; Pigment violet 32; Pigment brown 25; if necessary, their precursors, which are produced by azo coupling reaction.

In the case of azo dyes, it is in particular C.I. Disperse Yellow 3, 23, 60, 211, 241; Disperse Orange 1: 1, 3, 21, 25, 29, 30, 45, 53, 56, 80, 66, 138, 149; Disperse Red 1, 13, 17, 50, 56, 65, 82, 106, 134, 136, 137, 151, 167, 167: 1, 169, 177, 324, 343, 349, 369, 376; Disperse Blue 79, 102, 125, 130, 165, 165: 1, 165: 2, 287, 319, 367; Disperse Violet 40, 93, 93: 1, 95; Disperse Brown 1, 4; and optionally their precursors, which are produced by azo coupling reaction.

The reactants are expediently in the form of aqueous solutions or

Suspensions and preferably in stoichiometric / equivalent amounts fed to the microreactor.

The azo coupling reaction is preferably carried out in aqueous solution or suspension, but it is also possible to use organic solvents, if appropriate in a mixture with water, for example alcohols having 1 to 10 carbon atoms, such as, for example, methanol, ethanol, n-propanol, isopropanol, butanols, such as n-butanol, sec-butanol, tert-butanol, pentanols, such as n-pentanol, 2-methyl-2-butanol, hexanols, such as 2-methyl-2-pentanol, 3-methyl-3-pentanol, 2-methyl-2-hexanoI, 3-ethyl-3-pentanol, octanols, such as 2,4, 4-trimethyl-2-pentanol, cyclohexanol; or glycols, such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, or glycerin; Polyglycols, such as polyethylene glycols or polypropylene glycols; Ethers such as methyl isobutyl ether, tetrahydrofuran or

dimethoxyethane; Glycol ethers, such as monoethyl or monoethyl ether of ethylene or propylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, butyl glycols or methoxybutanol; Ketones such as acetone, diethyl ketone, methyl isobutyl ketone, methyl ethyl ketone or cyclohexanone; aliphatic acid amides such as formamide, dimethylformamide, N-methylacetamide or N, N-dimethylacetamide; Urea derivatives such as tetramethyl urea; or cyclic carboxamides, such as N-methylpyrrolidone, valero- or caprolactam; Esters, such as C1-C6-carboxylic acid alkyl esters, such as butyl formate, ethyl acetate or propyl propionate; or carboxylic acid Ci-Cβ glycol ester; or glycol ether acetates, such as 1-methoxy-2-propyl acetate; or

Phthalic or benzoic acid -CC ₆ alkyl esters, such as ethyl benzoate; cyclic esters such as caprolactone; Nitriles such as acetonitrile or benzonitrile; aliphatic or aromatic hydrocarbons, such as cyclohexane or benzene; or benzene substituted by alkyl, alkoxy, nitro or halogen, such as toluene, xylenes, ethylbenzene, anisole, nitrobenzene, chlorobenzene, o-dichlorobenzene, 1,2,4-trichlorobenzene or bromobenzene; or other substituted aromatics such as benzoic acid or phenol; aromatic heterocycles such as pyridine, morpholine, picoline or quinoline; and hexamethylphosphoric triamide, 1, 3-dimetyl-2-imidazolidinone, dimethyl sulfoxide and sulfolane. The solvents mentioned can also be used as mixtures. Water-miscible solvents are preferably used.

Diazonium salts of aromatic or heteroaromatic amines, such as, for example, aniline, 2-nitroaniline, methyl anthranilate, 2,5-dichloroaniline, 2-methyl-4-chloroaniline, 2-chloroaniline, 2-trifluoromethyl, are used as reactants for the azo coupling reaction. 4-chloroaniline, 2,4,5-trichloroaniline; 3-amino-4-methylbenzamide, 2-methyl-5-chloroaniline, 4-amino-3-chloro-N'-methylbenzamide, o-toluidine, o-dianisidine, 2,2 ', 5,5'-tetrachlorobenzidine , 2-amino-5-methyl-benzenesulfonic acid and 2-amino-4-chloro-5-methyl-benzenesulfonic acid.

The following amine components are of particular interest for azo pigments: 4-methyl-2-nitro-phenylamine, 4-chloro-2-nitro-phenylamine, 3,3'-dichlorobiphenyl-4,4'-diamine, S ^ '- dimethyl -biphenyM ^ '- diamine, 4-methoxy-2-nitro-ρhenylamine, 2-methoxy-4-nitro-phenylamine, 4-amino-2,5-dimethoxy-N-phenylbenzenesulfonamide, 5-amino-isophthalic acid dimethyl ester, anthranilic acid , 2-Trifluoromethyl-phenylamine, 2-Amino-terephthalic acid dimethyl ester, 1, 2-Bis- (2-Amino-phenoxy) -ethane, 2-Amino-4-chloro-5-methyl-benzenesulfonic acid, 2-Methoxyphenylamine, 4- ( 4-amino-benzoylamino) benzamide, 2,4-dinitro-phenylamine, 3-amino-4-chloro-benzamide, 3-amino-4-chloro-benzoic acid, 4-nitrophenylamine, 2,5-dichloro-phenylamine, 4 -Methyl-2-nitro-phenylamine, 2-chloro-4-nitro-phenylamine, 2-methyl-5-nitro-phenylamine, 2-methyl-4-nitro-phenylamine, 2-methyl-5-nitro-phenylamine, 2 -Amino-4-chloro-5-methyl-benzenesulfonic acid, 2-amino-naphthalene-1-sulfonic acid, 2-amino-5-chloro-4-methyl-benzenesulfonic acid, 2-amino-5-chloro-4-methyl -benzenesulfonic acid, 2-amino-5-methyl-benzenesulfonic acid, 2,4,5-trichloro-phenylamine, 3-amino-4-methoxy-N-phenyl-benzamide, 4-amino-benzamide, 2-amino-benzoic acid, methyl ester , 4-Amino-5-methoxy-2, N-dimethyl-benzenesulfonamide, 2-Amino-N- (2,5-dichloro-phenyl) -terephthalic acid monomethyl ester, 2-Amino-benzoic acid butyl ester, 2-Chloro-5- trifluoromethyl-phenylamine, 4- (3-amino-4-methylbenzoylamino) -benzenesulfonic acid, 4-aminino-2,5-dichloro-N-methylbenzenesulfonamide, 4-amino-2,5-dichloro-N, N- dimethyl-benzenesulfonamide,

6-amino-1H-quinazoline-2,4-dione, 4- (3-aminino-4-methoxy-benzoylamino) benzamide and 4-amino-2,5-dimethoxy-N-methyl-benzenesulfonamide, 5-aminobenzimidazolone , 6-Amino-7-methoxy-1,4-dihydroquinoxaline-2,3-dione, 3-amino-4-methyl-benzoic acid (2-chloroethyl ester), 3-amino-4-chloro-benzoic acid isopropyl ester , 3-Amino-4-chloro-benzotrifluoride, 3-Amino-4-methyl-benzoic acid n-propyl ester, 2-Amino-naphthalene-3,6,8-trisulfonic acid, 2-Amino-naphthalene-4,6,8 trisulfonic acid, 2-amino-naphthalene-4,8-disulfonic acid, 2-amino-naphthalene-6,8-disulfonic acid, 2-amino-8-hydroxy-naphthalene-6-sulfonic acid, 1-amino-8-hydroxy-naphthalene-3,6-disulfonic acid, 1-amino-2-hydroxy-benzene-5-sulfonic acid, 1-amino-4- acetylamino-benzene-2-sulfonic acid, 2-aminoanisole, 2-aminomethoxybenzene-ω-methanesulfonic acid, 2-aminophenol-4-sulfonic acid, o-anisidine-5-sulfonic acid, [2- (3-amino-1, 4-dimethoxy- benzenesulfonyl) ethyl] sulfuric acid ester and [2- (1-methyl-3-amino-4-methoxy-benzenesulfonyl) ethyl] sulfuric acid ester.

The following coupling components are of particular interest for azo pigments: acetoacetic acid arylides of the general formula (I),

in which n is a number from 0 to 3 and R ^{1 is} a CrC ₄ alkyl group, such as methyl or ethyl; a -CC ₄ alkoxy group, such as methoxy or ethoxy; a trifluoromethyl group; a nitro group; a halogen atom such as fluorine, chlorine or bromine; an NHCOCH3 group; a S0 ₃ H group; a Sθ ₂ NR ¹⁰ R ¹¹ group in which R ¹⁰ and R ^{11 are the} same or different and are hydrogen or C _ϊ ^ alkyl; a COOR ¹⁰ group in which R ^{10 has} the meaning given above; or can be a COONR ¹² R ¹³ group in which R ¹² and R ³ independently of one another represent hydrogen, C 1 -C ₄ -alkyl or phenyl, the phenyl ring being substituted by two or three identical or different substituents from the group CrC ₄ -Alkyl, -CC ₄ -alkoxy, trifluoromethyl, nitro, halogen, COOR ¹⁰ , where R ^{10 has} the meaning given above, COONR ¹⁰ R ¹¹ , where R ¹⁰ and R ^{11 are} identical or different and have the meaning given above, may be substituted, where n> 1 R ^{1 may be the} same or different;

2-hydroxynaphthalenes of the general formula (II),

in which

X represents hydrogen, a COOH group or a group of the general formula (III), (VI) or (VII);

in which n and R ^{1 are} as defined above; and R ^{20 represents} hydrogen, methyl or ethyl;

Bisacetoacetylated diaminophenyls and biphenyls, N, N'-bis (3-hydroxy-2-naphthoyl) phenylenediamines, the phenyl or biphenyl ring being unsubstituted or having 1, 2, 3 or 4 identical or different radicals CH ₃ , C ₂ H ₅ , OCH ₃ , OC ₂ H ₅ , N0 ₂ , F, Cl, CF ₃ can be substituted; Acetoacetic acid arylides of dinuclear heterocycles of the general formula (IV),

(IV)

in which n and R ^{1 are} as defined above,

Q ¹ , Q ² and Q ^{3 can be the} same or different and N, NR ² , CO, N-CO,

NR ² -CO, CO-N, CO-NR ² , CH, N-CH, NR ² -CH, CH-N, CH-NR ² , CH ₂ , N-CH ₂ ,

NR ² -CH ₂ , CH ₂ -N, CH ₂ -NR ² or S0 ₂ , mean, wherein

R ^{2 represents} a hydrogen atom; for a -CC ₄ alkyl group, such as methyl or ethyl; or represents a phenyl group which is unsubstituted or by halogen, C ₁ -C ₄ -

Alkyl, -CC ₄ alkoxy, trifluoromethyl, nitro, cyano can be substituted one or more times, with the proviso that the combination of Q ¹ , Q ² and Q ³ with the two

Carbon atoms of the phenyl ring gives a saturated or unsaturated, five or six-membered ring; preferably acetoacetic acid arylides of the general formula (Via) and (Vlla),

wherein R ¹ and n are as defined above and R ^{20 is} hydrogen, methyl or ethyl; and pyrazolones of the general formula (V),

in which

R ^{3 is} a group CH ₃ , COOCH ₃ or COOC ₂ H ₅ , R ^{4 is} a group CH3, S0 ₃ H or a chlorine atom, and p is a number from 0 to 3, where p> 1 R ^{4 is the} same or different can be.

For the purposes of the present invention, particular preference is given to the preparation of the so-called anise base pigments of the formula (VI)

wherein

X _{1 is} hydrogen, halogen, in particular chlorine, nitro, carbamoyl, phenylcarbamoyl, sulfamoyl, phenylsulfamoyl or (di) alkylsulfamoyl; X _{2 is} hydrogen or halogen, especially chlorine;

Y is hydrogen, halogen, in particular chlorine, nitro, C 1 -C ₄ alkyl, C 1 -C alkoxy or C 1 -C ₄ alkoxycarbonyl; and Z is hydrogen, phenyl, naphthyl, benzimidazolonyl, or phenyl substituted with halogen, in particular chlorine, nitro, C 1 -C ₄ -alkyl and / or C 1 -C 8 -alkoxy.

In the process according to the invention, the auxiliaries used in the conventional processes, such as, for example, surfactants, pigmentary and non-pigmentary dispersants, fillers, adjusting agents, resins, waxes, defoamers, anti-dust agents, extenders, colorants for shading, preservatives, drying retardants, additives for controlling the rheology, Wetting agents, antioxidants, UV absorbers, light stabilizers, or a combination thereof can be used.

The auxiliaries can be added at any time before, during or after the reaction in the microreactor, all at once or in several portions. The auxiliaries can be added, for example, directly to the solutions or suspensions of the reactants, but also during the reaction in liquid, dissolved or suspended form.

The total amount of auxiliaries added can be 0 to 40% by weight, preferably 1 to 30% by weight, particularly preferably 2.5 to 25% by weight, based on the azo colorant.

Suitable surfactants are anionic or anionic, cationic or cationic and nonionic substances or mixtures of these agents. Examples of surfactants, pigmentary and non-pigmentary dispersants which can be used for the process according to the invention are given in EP-A-1 195 411.

Since maintaining a desired pH value during and after the reaction is often decisive for the quality, buffer solutions can also be added, preferably of organic acids and their salts, such as, for example, formic acid / formate buffer, acetic acid / acetate buffer,

Citric acid / citrate buffer; or of inorganic acids and their salts, such as phosphoric acid / phosphate buffer or carbonic acid / bicarbonate or carbonate buffer. It is also possible with the method according to the invention to use the use of more than one diazonium salt and / or more than one coupling component to produce mixtures or else mixed crystals of azo colorants.

(b) The solvent wash:

The solvent washing according to the invention comprises the absorption of the azo colorant produced in step (a), either directly from the microreactor or after intermediate insulation, e.g. as a press cake (approx. 5 to 30% by weight solids content), in one of the organic solvents mentioned.

Preferred solvents are C ₃ -C ₄ alcohols, glycol ethers and chlorinated benzenes, such as butoxyethanol, ortho-dichlorobenzene, isobutanol, isopropanol, or a mixture thereof. It is also possible to use a pigment suspension treated according to (c).

The amount of solvent is preferably 1 to 30% by volume, in particular 5 to 15% by volume, based on the volume of the pigment suspension, or 1 to 10 times the amount by weight of solvent, based on the weight of the pigment in the press cake. The mixture of pigment suspension or press cake and solvent is preferably at a temperature between 10 ° C and 50 ° C, in particular between 20 ° C and 45 ° C, and preferably for 0.1 to 2 hours, in particular 0.25 to 1 hours, and preferably stirred at normal pressure. Ordinary stirrers such as e.g. Laboratory stirrer in question. In principle, however, an inline dispersing machine, equipped with appropriate dispersing tools, can also be used in the pumping around of the reservoir. Such a dispersing machine firstly ensures intensive mixing of the suspension in the storage vessel, but at the same time it also has a deagglomerating effect, so that any inclusions are exposed.

The solvent-treated azo dye suspension is then filtered and washed or fed directly to the membrane purification (c) without intermediate insulation. (c) Membrane purification:

The membrane purification according to the invention comprises passing an azo colorant suspension obtained from step (a) or from (b) through a membrane system which is designed in such a way that the azo colorant is retained as completely as possible by the membrane. Water or an organic solvent, optionally in a mixture with water, is particularly suitable as the liquid medium. The solids concentration in the suspension is advantageously 1 to 10% by weight, preferably 2 to 5% by weight, based on the total weight of the suspension. The driving force for the transmembrane mass transfer is a pressure difference between the two sides of the membrane. The pressure difference is advantageously 0.5 to 5 bar, preferably 1 to 2 bar. The pressure is measured, for example, by suitable pumps, e.g. Piston pumps. Ceramic or polymer membranes with typical separation limits between 100 and

10 ⁶ g / mol used. Static membrane modules, such as tube or plate modules, or dynamic membrane modules are preferably used. The temperature is advantageously 0 to 100 ° C, in particular 20 to 80 ° C.

The membrane purification can also be carried out as diafiltration. The retentate, i.e. the azo colorant is returned to the original container and the water or solvent content is kept constant by water make-up. With the method according to the invention, the following product improvements can be achieved compared to a conventional, optimized batch process:

Step (a) significantly reduces the content of anise base and mixed triazenes, ie to below the detection limit of 50 ppm, but mostly more than 100 ppm of free aromatic amine and unreacted coupling component, for example naphthol, are still present. Step (b) in combination with step (c) surprisingly brings the free amine and naphthol content below the respective detection limit of 25 ppm and 100 ppm. As a side effect of membrane purification, inorganic salts are also retained.

The secondary component content is determined by customary HPLC methods.

The high-purity azo colorants produced according to the invention are used in particular for coloring electrophotographic toners and developers, such as One or two component powder toners (also called one or two component developers), magnetic toners, liquid toners, latex toners, polymerization toners and special toners, powder coatings, ink jet inks and color filters as well as colorants for electronic inks ("electronic inks" or " e-inks ") or" electronic paper "(" e-paper ").

The invention therefore also relates to a process for coloring electrophotographic toners and developers, characterized in that a high-purity azo colorant prepared in steps (a), (b) and (c) is used in an amount of 0.05 to 30% by weight. %, preferably 0.1 to 15% by weight, based on the total weight of the toner or developer, homogeneously incorporated into a toner binder. Typical toner binders are polymerization, polyaddition and polycondensation resins, such as styrene, styrene-acrylate, styrene-butadiene, acrylate, polyester, phenol-epoxy resins, polysulfones, polyurethanes, individually or in combination, and polyethylene and polypropylene, which also contain other ingredients, such as charge control agents, waxes or flow aids, can contain or be modified afterwards with these additives.

The invention further relates to a method for coloring ink-jet inks, characterized in that a high-purity azo colorant prepared in steps (a), (b) and (c) is present in an amount of 0.5 to 15% by weight %, preferably 1.5 to 8% by weight, based on the total weight of the inkjet ink, homogeneously incorporated into the ink base. Ink-jet inks are those based on water and water, microemulsion inks, UV-curable inks and inks which work according to the hot-melt process.

The ink base of microemulsion inks is based on organic solvents, water and possibly an additional hydrotropic substance (interface mediator).

The ink base of solvent-based ink jet inks is based on organic solvents and / or a hydrotropic compound and optionally a carrier material which is soluble in the “solvent”, such as polyolefins, natural and synthetic rubber, polyvinyl chloride, vinyl chloride / vinyl acetate copolymers , Polyvinyl butyrals, wax / latex systems or combinations thereof. The ink base of UV-curable inks is based on water, organic solvent, a radiation-curable binder and possibly a photoinitiator. The ink base of hot-melt inks is mostly based on waxes, fatty acids, fatty alcohols or sulfonamides which are solid at room temperature and become liquid when heated, the preferred melting range being between about 60 and about 140 ° C.

The invention further relates to a method for coloring color filters, both for additive and for subtractive color generation, characterized in that a high-purity azo colorant prepared in the form of a paste or according to steps (a), (b) and (c) as pigmented photoresists in suitable binders (acrylates, acrylic esters, polyimides, polyvinyl alcohols, epoxies, polyesters, melamines, gelatin, caseine) on the respective LCD components (e.g. TFT-LCD = Thin Film Transistor Liquid Crystal Displays or e.g. (( S) TN-LCD = (Super) Twisted Nematic-LCD) In addition to a high thermal stability, a high pigment purity is also a prerequisite for a stable paste or pigmented photoresist.

The azo colorants produced according to the invention are of course also suitable for coloring natural or synthetic high-molecular organic materials of any kind, such as cellulose ethers and esters, such as ethyl celulose, nitrocellulose, cellulose acetate or cellulose butyrate, natural resins or synthetic resins, such as polymerization resins or condensation resins, for example aminoplasts, in particular urea and melamine-formaldehyde resins, alkyd resins, acrylic resins, phenoplasts, polycarbonates, polyolefins, such as polystyrene, polyvinyl .

Polyacrylonitrile, polyacrylic acid esters, polyamides, polyurethanes or polyesters, rubber, casein, latices, silicones and silicone resins, individually or in mixtures. The high-molecular organic compounds mentioned can be present as plastic compositions, casting resins, pastes, melts or in the form of spinning solutions, lacquers, glazes, foams, inks, inks, stains, paints, emulsion paints or printing inks.

Example 1: C.I. Pigment Red 269

a1) Preparation of an anis base diazonium salt solution:

2532 g of water are initially introduced and 242 g of 3-amino-4-methoxybenzanilide are first stirred homogeneously at room temperature, precipitated with the addition of hydrochloric acid and cooled to 10 ° C. with 1.5 kg of water / ice. When the precipitated hydrochloride is diazotized with 138 ml of sodium nitrite solution (40%), an anisbase-diazo solution which can be easily stirred is finally formed. After adding a clarifying agent, this is filtered off in a receptacle. The excess nitrite is removed by adding amidosulfonic acid.

a2) Preparation of a buffer for the anis base diazonium salt solution: 1884 g of water / ice are introduced, 502 g of acetic acid and 614 g

Sodium hydroxide solution added and the temperature kept at room temperature after the addition of 1 kg of water.

a3) Preparation of a solution of the coupling component (naphthol): 2720 g of water containing a wetting aid are introduced and heated to 80.degree. 328 g of N- (5-chloro-2-methoxyphenyl) -3-hydroxynaphtaline-2-carboxamide are introduced with stirring and dissolved in an alkaline solution. With the addition of a further 2720 g of water / ice, the naphthol AS solution is dissolved Cooled to room temperature. Finally, it is filtered with the addition of a clarifying agent.

a4) Azo coupling in the microreactor: the anis base diazonium salt solution and the naphthol AS solution are pumped into the respective reactant inputs of the microreactor (type: Cytos from CPC-Systems / Frankfurt) at a flow rate of 8 ml / min. In order to achieve the required pH value of 4.8-5.0 for the azo coupling, the reactant solutions are diluted with an acetic acid / acetate buffer prepared according to a2) shortly before the reactor inputs. The buffer solution is also pumped into the feed lines of the microreactor by means of calibrated piston pumps via a T-branch at a flow rate of 6 ml / min. A thermostat is connected to the heat exchanger circuit of the microreactor, which sets the desired reaction temperature from 20 ° C to 35 ° C. The coupled pigment suspension (21 ° C., pH = 5.0) is collected in a storage vessel and subjected to the following solvent washing.

b) Solvent washing:

The pigment suspension obtained from the microreactor is mixed with an amount of butoxyethanol such that the entire slurry contains about 10% by volume of butoxyethanol. The slurry is stirred at a temperature of about 45 ° C for 30 minutes, filtered off and washed with water. After taking the sample, the colorant-solvent-water suspension is subjected to the following membrane purification.

c) membrane purification:

A ceramic multi-channel microfiltration membrane with a nominal separation limit of the separation-selective layer of 60 nm and a membrane area of 0.09 m ^{2 is} used. About 15 kg of the colorant suspension with a pigment content of about 2% by weight are placed in a temperature-controlled storage container. The membrane is subjected to a pressure of about 1.5 bar at ambient temperature on the retentate side. To maintain a constant volume in the To ensure storage tank, the mass of separated permeate is discontinuously replaced by demineralized water.

Under these conditions, it is possible to completely retain the pigment and to reduce the organic secondary components to the values listed in Table 2. The exchange volume (ie volume of demineralized water supplied / volume of pigment suspension used) is approximately 4. The permeate flow is approximately 200 l / (m ² * h * bar).

At the same time, the initial chloride ion content is reduced from 2.5% after 10 hours of diafiltration to 920 ppm and the sulfate content from the initial 0.3% to 30 ppm.

d) Analytics:

The samples taken (0.5 g each) are dried, each with 10 ml

N-methylpyrrolidone added and crushed with ultrasound for 15 min. After adding 20 ml of methanol and grinding again over 15 min

Filtered suspension. 20 μl of the filtrate are introduced into the autosampler of the HPLC system and detected by means of a UV-Vis detector at 240 and 375 nm (Nucleosil 120-5 C18 separation column (length: 25 cm, = 4.6 mm); mobile phase consisting of a buffer (575 mg NH ₄ H ₂ P0 plus 1000 g H ₂ 0 plus 3.0 g NaN ₃ (pH 5.0)) and Methanol ^® Chromasolv in different compositions with a total flow of 1 ml / min).

The contents of secondary components after each step are listed in Table 2: Table 2 shows a comparison of the typical secondary component contents of the conventional batch pigment with the secondary component contents of

Pigments from a synthesis in the microreactor [step a)] with subsequent

Solvent washing [step b)] and membrane cleaning [step c)].

To classify and evaluate the values in Table 2, Table 1 shows the values for the detection limit of the secondary components under consideration. The

Measurement accuracy of the chosen analysis method is approximately ± 5 ppm. Table 1: Detection limits for the secondary components:

Table 2: Comparison of the secondary component contents in the pigment from batch synthesis or microreactor synthesis with subsequent solvent washing and membrane purification.

*: undetectable, i.e. less than the detection limit according to Table 1.

Example 2: C.I. Pigment Red 146

Steps a) - d) were carried out analogously to Example 1. The pigment obtained after step c) contained anise base, chloromethoxyaniline,

Anise base triazene and Naphtol AS from below the respective detection limit. Example 3: Cl Pigment Red 147

Steps a) - d) were carried out analogously to Example 1. The pigment obtained after step c) had an anise base, chloromethoxyaniline, anise base triazene and Naphtol AS content below the respective detection limit.

Comparative Examples 2 and 3:

Average values of a total of 80 batch batches: Anis base 519 ppm

Chloromethoxyaniline 32 ppm

Anise base triazene 446 ppm

Naphtol AS 1, 10%

Example 4: C.I: Pigment Yellow 213

a1) Preparation of a dimethyl aminoterephthalate diazonium salt

Solution:

209 g of dimethyl aminoterephthalate (ATDME) are placed in 270 g of water and stirred homogeneously overnight. The following day, after adding hydrochloric acid, the mixture is cooled to 10 ° C. with water / ice. When the hydrochloride is diazotized with 132 ml of sodium nitrite solution (40%), an ATDME diazo solution which can be easily stirred is finally formed. After adding a clarifying agent, this is filtered off in a receptacle. The excess nitrite is removed by adding amidosulfonic acid.

a2) Preparation of a suspension of the coupling component in water

The coupler N-acetoacetyl-6-methoxy-7-amino-quinoxaldedione-2,3 suspended in water is only dissolved in situ shortly before the actual coupling. a3) Preparation of a buffer for the ATDME diazo solution: 500 g of water are introduced, 432 g of acetic acid and 190 g of sodium hydroxide solution are added, and the temperature is kept at room temperature after the addition of 1 kg of water. Provision of dilute sodium hydroxide solution (0.5 to 5.0 mol / kg) for the azo coupling reaction in the microreactor.

a4) Azo coupling in the microreactor

The ATDME diazo solution and the aqueous coupler suspension are pumped into the respective reactant inputs of the microreactor at a flow rate of 13 ml / min. In order to bring the coupling component suspended in water into solution in situ, diluted sodium hydroxide solution (3%) is also conveyed into the coupler feed line of the microreactor using a calibrated piston pump via a T-branch. In order to achieve the required pH value of 4.0-4.5 for the azo coupling, the ATDME diazo solution is used shortly before

Microreactor inputs diluted with an acetic acid / acetate buffer prepared according to a3). The buffer solution is also conveyed into the diazo feed line of the microreactor by means of a calibrated piston pump via a T-branch at a flow rate of 4 ml / min. A thermostat is connected to the heat exchanger circuit of the microreactor, which sets the desired reaction temperature from 20 ° C to 35 ° C. The coupled pigment suspension is collected in a template and isolated.

Steps b) - d) were carried out analogously to Example 1.

C.I. Pigment Yellow 213 pigment after pigment after [step a)] # 1 [step c)] # 1 iron 78 ppm 20 ppm zinc 12 ppm 7 ppm magnesium 76 ppm 8 ppm sodium 140 ppm 80 ppm calcium 430 ppm 73 ppm aluminum 33 ppm 16 Potassium 29 ppm 22 ppm chloride 168 ppm <50 ppm sulfate 102 ppm <50 ppm phosphate <50 ppm <50 ppm nitrate <50 ppm <50 ppm formate <50 ppm <50 ppm acetate 90 ppm <50 ppm bromide <50 ppm < 50 ppm sulfite <50 ppm <50 ppm nitrite <50 ppm <50 ppm

# 1: target limit <100 ppm

Claims

claims:

1) A method for producing high purity azo colorants, characterized in that (a) at least the azo coupling is carried out in a microreactor, (b) the azo colorant produced in the microreactor with an organic solvent from the group of _C3-C6 alcohols, the C ₄ -Cιo ether alcohols and the halogenated aromatics is brought into intensive contact at a temperature of 0 to 60 ° C, and (c) the azo colorant produced in the microreactor is subjected to membrane purification in an aqueous or solvent-containing suspension.

2) Method according to claim 1, characterized in that first step (a), then step (c) and then step (b) is carried out.

3) Method according to claim 1 or 2, characterized in that step (b) is carried out at a temperature between 20 ° C and 45 ° C.

4) Method according to one or more of claims 1 to 3, characterized in that the organic solvent butoxyethanol, ortho-

Is dichlorobenzene, isobutanol, isopropanol or a mixture thereof.

5) Method according to one or more of claims 1 to 4, characterized in that ceramic or polymer membranes with separation limits between 100 and 10 ⁶ g / mol are used in step (c).

6) Method according to one or more of claims 1 to 5, characterized in that in step (c) the azo colorant is recycled as retentate and the water or solvent content in the suspension is kept constant by water make-up.

7) Method according to one or more of claims 1 to 6, characterized in that the azo colorant is an azo pigment from the group of Monoazo pigments, disazo pigments, β-naphthol and naphthoi AS pigments, lacquered azo pigments, benzimidazolone pigments, disazo condensation pigments and metal complex azo pigments.

8) Method according to one or more of claims 1 to 6, characterized in that the azo colorant is a disperse dye.

9) Method according to one or more of claims 1 to 8, characterized in that the azo colorant is an anise base pigment of the formula (VI),

wherein

Xi is hydrogen, halogen, nitro, carbamoyl, phenylcarbamoyl, sulfamoyl, phenylsulfamoyl or (di) alkylsulfamoyl;

X _{2 is} hydrogen or halogen;

Y is hydrogen, halogen, nitro, -CC alkyl, CC ₄ alkoxy or C ₁ -C ₄ alkoxycarbonyl; and

Z is hydrogen, phenyl, naphthyl, benzimidazolonyl, or phenyl substituted with halogen, nitro, C 1 -C ₄ -alkyl and / or C 1 -C ₄ alkoxy.