Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B3/00—Electrolytic production of organic compounds
  • C25B3/20—Processes
  • C25B3/25—Reduction
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06P—DYEING OR PRINTING TEXTILES; DYEING LEATHER, FURS OR SOLID MACROMOLECULAR SUBSTANCES IN ANY FORM
  • D06P5/00—Other features in dyeing or printing textiles, or dyeing leather, furs, or solid macromolecular substances in any form
  • D06P5/20—Physical treatments affecting dyeing, e.g. ultrasonic or electric
  • D06P5/2016—Application of electric energy
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/042—Electrodes formed of a single material
  • C25B11/043—Carbon, e.g. diamond or graphene
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/042—Electrodes formed of a single material
  • C25B11/046—Alloys
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06P—DYEING OR PRINTING TEXTILES; DYEING LEATHER, FURS OR SOLID MACROMOLECULAR SUBSTANCES IN ANY FORM
  • D06P1/00—General processes of dyeing or printing textiles, or general processes of dyeing leather, furs, or solid macromolecular substances in any form, classified according to the dyes, pigments, or auxiliary substances employed
  • D06P1/22—General processes of dyeing or printing textiles, or general processes of dyeing leather, furs, or solid macromolecular substances in any form, classified according to the dyes, pigments, or auxiliary substances employed using vat dyestuffs including indigo
  • D06P1/221—Reducing systems; Reducing catalysts
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06P—DYEING OR PRINTING TEXTILES; DYEING LEATHER, FURS OR SOLID MACROMOLECULAR SUBSTANCES IN ANY FORM
  • D06P1/00—General processes of dyeing or printing textiles, or general processes of dyeing leather, furs, or solid macromolecular substances in any form, classified according to the dyes, pigments, or auxiliary substances employed
  • D06P1/30—General processes of dyeing or printing textiles, or general processes of dyeing leather, furs, or solid macromolecular substances in any form, classified according to the dyes, pigments, or auxiliary substances employed using sulfur dyes
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
  • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
  • C02F1/467—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction
  • C02F1/4676—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction by electroreduction
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
  • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
  • C02F1/46104—Devices therefor; Their operating or servicing
  • C02F1/46109—Electrodes
  • C02F2001/46119—Cleaning the electrodes
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
  • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
  • C02F1/46104—Devices therefor; Their operating or servicing
  • C02F1/46109—Electrodes
  • C02F2001/46133—Electrodes characterised by the material
  • C02F2001/46138—Electrodes comprising a substrate and a coating
  • C02F2001/46142—Catalytic coating
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
  • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
  • C02F1/46104—Devices therefor; Their operating or servicing
  • C02F1/46109—Electrodes
  • C02F2001/46152—Electrodes characterised by the shape or form
  • C02F2001/46157—Perforated or foraminous electrodes
  • C02F2001/46161—Porous electrodes
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2101/00—Nature of the contaminant
  • C02F2101/30—Organic compounds
  • C02F2101/308—Dyes; Colorants; Fluorescent agents

Definitions

• the present invention relates to a process for the electrochemical reduction of reducible dyes.
• EP-A 0 808 920 describes the electrochemical reduction of organic compounds in the presence of a cathode, which comprises a support made of an electrically conductive material and an electrically conductive, cathodically polarized layer formed thereon by being precoated.
• a cathode which comprises a support made of an electrically conductive material and an electrically conductive, cathodically polarized layer formed thereon by being precoated.
• EP-B 0 426 832 describes a process for reducing dyes, according to which, among other things, the poorly soluble indigo can be converted into the soluble form of the leuco indigo by reduction.
• the reduction is carried out in aqueous solution with a pH of> 9 using a reducing agent with a reduct potential of more than 400 mV, which is present in a reduced and oxidized form.
• this reducing agent is characterized in that its redox potential (half-stage potential), increased by the charge transfer overvoltage to at the Returning the cathode of the oxidized form of the reducing agent to the reduced form below the cathode potential.
• indirect electrolysis is carried out in the presence of a mediator, for example iron (TJI) triethanolamine.
• a mediator for example iron (TJI) triethanolamine.
• the iron (TÜ) - triethanolamine is reduced at the cathode to iron ( ⁇ ) -txiethanolan_ ⁇ in and in turn reduces indigo to leucoindigo, whereby, of course, iron ( ⁇ i) triethanolamine is formed, which in turn is reduced at the cathode or is regenerated.
• the present invention relates to a process for the electrochemical reduction of a reducible dye by bringing the reducible dye into contact with a cathode, comprising a support made of an electrically conductive material and an electrically conductive, cathodically polarized layer formed thereon by precoating, characterized in that that the electrochemical reduction is carried out in the presence of a base.
• the catalytically active electrode becomes in the operating state due to the pressure loss at the electrically conductive surface formed by precoating. stabilized cathodically polarized layer.
• the term "in situ” used according to the invention encompasses all variants of such a coating of the material for the cathodically polarized layer, that is to say before, together with or also after the vat dye has been introduced into the Reactor.
• the term “i situ” thus expresses that the cathode is formed in the reduction cell, by means of floating.
• the catalytically active electrode can be suspended again by reversing the flow and removed, for example, by filtration or suction.
• vat dyes are carried out on a system which is suitable for forming and dismantling a catalytically active electrode in the process, only interventions being necessary which are already established in the operational practice of a chemical company, such as switching pumps and actuators.
• Electrically conductive materials are used as carriers for the electrically conductive, cathodically polarized layer.
• materials such as stainless steel, steel, nickel, nickel alloys, tantalum, platinum-coated tantalum, titanium, platinum-coated titanium, graphite, electrode carbon and similar materials and their mixtures are to be mentioned.
• the supports are preferably in the form of permeable porous material, ie the support has pores.
• These can be woven in the form of commercially available filter fabrics made of metal wires or carbon fibers. For example, filter fabrics based on the type of linen weave, twill weave, twill braid weave, braid weave and satin weave are common.
• perforated metal foils, metal felts, graphite felts, edge filters, sieves or porous sintered bodies can also be used as large-area supports in the form of plates or candles.
• the pore size of the support is generally 5 to 300 m, preferably 50 to 200 ⁇ m.
• the supports which can be used in the context of the present process preferably have at least approximately 10%, more preferably at least approximately 20% and in particular approximately 50% free area, the free area being a maximum of approximately 70%. All electrically conductive materials can be used as the electrically conductive material for the electrically conductive, cathodically polarized layer, as long as it is possible to form a layer from these by floating onto the carrier defined above.
• the cathodically polarized layer contains a metal, a conductive metal oxide or a carbon-like material such as e.g. Coal, especially activated carbon, carbon black or graphite, or a mixture of two or more thereof.
• All classic hydrogenation metals in particular the metals of subgroups I, II and VIII of the periodic table, in particular Co, Ni, Fe, Ru, Rh, Re, Pd, Pt, Os, Ir, Ag, Cu, Zn, are preferably used as metals , Pb and Cd.
• Ni, Co, Ag, Fe and Cu preferably as Raney-Ni, Raney-Co, Raney-Ag, Raney-Cu and Raney-Fe, which may be caused by foreign metals such as Mo, Cr, Au, Mn, Hg, Sn or other elements of the periodic table, in particular S, Se, Te, Ge, Ga, P, Pb, As, Bi and Sb can be used.
• the metals used according to the invention are preferably in finely divided and / or activated form.
• conductive metal oxides such as e.g. Magnetite.
• the cathodically polarized layer can also be formed by simply floating the carbon-like material defined above.
• the cathode can be built up in situ in that the abovementioned metals and conductive oxides are washed onto the support in each case on carbon-like materials, in particular activated carbon.
• the present invention thus also relates to a method of the type in question here, the cathodically polarized layer being a metal or a Contains conductive metal oxide or a mixture of two or more thereof, each applied to activated carbon.
• layers which contain Pd / C, Pt / C, Ag / C, Ru / C, Re / C, Rh / C, Ir / C, Os / C and Cu / C should be mentioned, these in turn by Foreign metals or other elements of the periodic table, preferably S, Se, Te, Ge, Ga, P, Pb, As, Bi and Sb can be doped.
• the metals mentioned above can be in the form of nanoclusters, the production of which e.g. in DE-A-44 08 512, on surfaces such as e.g. Metals and carbonaceous materials that are washed onto the carrier.
• the cathodically polarized layer consists of the dye to be reduced.
• this layer can comprise both a metal, a conductive metal oxide or a carbon-like metal, or a mixture of two or more thereof and the dye to be reduced.
• the cathodically polarized layer can contain an electrically conductive reflux material which improves the adhesion of the above-defined metals, metal oxides or nanoclusters to the support or increases the surface area of the cathode, with electrically conductive oxides such as magnetites and carbon, in particular activated carbon, carbon black, carbon fiber and graphite are to be mentioned.
• a cathode is used, which is obtained by first washing the electrically conductive auxiliary material onto the support and then this auxiliary material in situ by reducing salts of metals of I., II. And / or VIII Subgroup is doped with these metals on the coated electrode.
• the salts of the abovementioned metals are preferably metal halides, phosphates, sulfates, chlorides, carbonates, nitrates and the metal salts of organic acids, preferably formates, acetates, propionates and benzoates, in particular preferably acetates used.
• the cathode used according to the invention is constructed in situ by the fact that the above-mentioned. Metals or metal oxides are washed onto the support directly or after the application of the electrically conductive auxiliary material.
• the average particle size of the particles forming the layer defined above and the thickness of the layer is always chosen so that an optimal ratio of filter pressure loss and hydraulic throughput is guaranteed and an optimal mass transfer is possible.
• the average particle size is about 1 to about 400 microns, preferably about 30 to about 150 microns
• the thickness of the layer is generally about 0.05 mm to about 20 mm, preferably about 0.1 to about 5 mm.
• the pore size of the carrier generally exceeds the average diameter of the particles forming the layer, so that two or more particles form bridges over the interstices during the formation of the layer on the carrier, which has the advantage that the formation of the layer on the support does not result in any appreciable flow obstruction for the suspension solution containing the organic compound to be reduced.
• the pore size of the support is about two to about four times the average particle size of the particles forming the layer.
• supports with pore sizes which are smaller than the average particle size of the particles forming the layer can also be used in the context of the present invention, but attention must then be paid very precisely to the flow obstruction emanating from the layer which forms.
• the cathode used according to the invention which is formed in situ by floating the constituents forming the layer on the electrically conductive support, contains, in the case of the reduction of reducible dyes according to the invention, preferably in addition to the cathodically polarized electrically conductive auxiliary material made from the dye to be reduced, which has poor solubility.
• the washed-up layer can be washed away again at specific time intervals in order to achieve better mixing of the dye to be reduced with the electrically conductive auxiliary material. After mixing, it is washed up again. This process can be repeated any number of times during a reduction.
• the cathode according to the invention can also be formed here from the electrically conductive support and a filter layer formed in itself from the respective dye by floating.
• the catalytically active layer After the reduction has ended or when the catalytically active layer has been used up, it can be separated from the support by simply switching the flow direction and disposed of or regenerated independently of the reduction. After the used layer has been completely removed from the system, it is then possible again to coat the support again with the particles forming the layer and, after these particles have been completely suspended, continue to reduce the organic compound.
• the current densities within the process according to the invention are generally about 50 to about 10,000 A / m, preferably about 1,000 to about 4,000 A / m.
• the throughput of the solution containing the dyes to be reduced is generally about 1 to about 4,000 m / (m ⁇ h), preferably about 50
• the pressure loss in the layer at the throughputs used according to the invention is approximately 1 ⁇ 10 Pa to about 2 x 10 Pa, preferably about 2.5 x 10 Pa to about 7.5 x 10 Pa.
• the process according to the invention is generally carried out at temperatures between approximately 0 ° C. to 100 ° C., but temperatures of approximately 40 ° C. to approximately 80 ° C. are preferred.
• the process according to the invention is carried out in basic, i.e. medium is carried out at a pH which is above 7, preferably from 9 to 14 and in particular from 12 to 14.
• a pH which is above 7, preferably from 9 to 14 and in particular from 12 to 14.
• all suitable bases can be used to adjust the basic pH.
• the reaction is particularly preferably carried out at normal pressure and at the temperatures mentioned.
• the type of cell type used, the shape and the arrangement of the electrodes have no decisive influence, so that in principle all cell types customary in electrochemistry can be used.
• Undivided cells with a plane-parallel electrode arrangement or candle-shaped electrodes are preferably used when neither starting materials nor products are disruptively changed by the anode process or react with one another.
• the electrodes are preferably arranged plane-parallel, because in this embodiment a homogeneous current distribution is given with a small electrode gap (1 mm to 10 mm, preferably 3 mm) is.
• the edge splitting element is preferably made of stainless steel, platinum, platinized niobium, titanium, tantalum or nickel.
• Electrodes are preferably used when the catholyte has to be separated from the anolyte, e.g. to rule out chemical side reactions or to simplify the subsequent separation of substances.
• Ion exchange membranes in particular cation exchange membranes, are preferably used, with those membranes which consist of a copolymer of tetrafluoroethylene and a perfluorinated monomer which contains sulfo groups being preferably used.
• the electrodes are preferably also arranged plane-parallel in divided cells, since in this embodiment a homogeneous current distribution is given in the case of small electrode gaps (two gaps each with 0 mm to 10 mm, preferably anodically 0 mm, cathodically 3 mm).
• the separation medium is preferably located directly on the anode.
• Perforated materials such as nets, expanded metal sheets, lamellae, profile webs, grids and smooth sheets can generally be used as electrode materials.
• this takes place in the form of flat surfaces, in the embodiment with candle-shaped electrodes in the form of a cylindrical arrangement.
• anode material or its coating depends on the solvent of the anolyte. So are preferred in organic systems
• Graphite electrodes used while in aqueous systems preferably Materials or coatings with low oxygen overvoltage can be used.
• acidic anolytes are titanium or tantalum carriers with electrically conductive intermediate layers on which electrically conductive mixed oxides of IV. To VI. Subgroup are applied, which are doped with metals or metal oxides of the platinum group to name.
• iron or nickel anodes are preferably used.
• the reduction according to the invention is carried out in the presence of an auxiliary electrolyte.
• the addition of the same serves to adjust the conductivity of the electrolysis solution and to control the selectivity of the reaction.
• the content of the electrolyte is generally at a concentration of approximately 0.1 to approximately 10, preferably approximately 1 to approximately 5% by weight, based in each case on the reaction mixture.
• Neutral salts can be used as auxiliary electrolytes.
• Anions to be mentioned are: fluoride, tetrafluoroborate, sulfonates, such as e.g. Methanesulfonate, benzenesulfonate, toluenesulfonate, sulfates such as e.g. Sulfate, methyl sulfate, ethyl sulfate, phosphates such as e.g. Methyl phosphate, ethyl phosphate, dimethyl phosphate, diphenyl phosphate, hexafluorophosphate, phosphonates, such as e.g. Methylphosphonate methyl ester and phenyl phosphonate methyl ester.
• fluoride tetrafluoroborate
• sulfonates such as e.g. Methanesulfonate, benzenesulfonate, toluenesulfonate
• sulfates such
• organic co-solvents when using organic co-solvents, basic compounds such as e.g. Alkali or alkaline earth metal hydroxides, carbonates, bicarbonates and alcoholates can be used, methylate, ethylate, butylate and isopropylate being preferably used as alcoholate anions.
• basic compounds such as e.g. Alkali or alkaline earth metal hydroxides, carbonates, bicarbonates and alcoholates can be used, methylate, ethylate, butylate and isopropylate being preferably used as alcoholate anions.
• the electrochemical reduction according to the invention can be carried out either continuously or batchwise.
• the cathode is first produced in situ by forming a catalytically active layer on the support by precoating.
• the suspension is flowed through by a suspension of the finely divided metal and / or the conductive metal oxide and or the nanocluster and / or the carbon-like material, that is to say the material which is to be washed up, until essentially the entire amount of the the suspension contained material is located on the carrier. Whether this is the case can be visually recognized, for example, by the fact that the suspension, which is cloudy at the start of the precoat, becomes clear.
• an intermediate layer it is also possible to flow through the carrier provided with an intermediate layer with a solution or a suspension of a metal salt of a metal with which the carrier layer is to be doped, and by applying a suitable voltage to the cell in it To reduce the solution or suspension of existing metal cations in situ at the cathode.
• the organic compound to be reduced is then fed into the system and reduced by introducing a precisely defined amount of current into the system.
• the selectivities are at least 70%, generally above 80% and, in the case of particularly smooth reductions, greater than 95%.
• any used catalyst can be replaced by reversing the direction of flow in the electrolysis cell, as a result of which the washed-on layer loses contact with the support and the catalyst e.g. can be removed by suction or filtration of the suspension containing them.
• the layer can then be built up again as described above and new feed can then be added and reacted.
• the steps of conversion (reduction), renewal of the catalyst and renewed conversion (reduction) can also be carried out alternately, by first producing the cathode as described above by precoating, then the dye to be reduced ??? supplied and this is implemented, after completion of the conversion, the flow direction within the electrolysis cell is changed and the used catalyst, e.g. is removed by filtering, then the cathode is again built up with fresh material forming the cathodically polarized layer and is then further reduced.
• the electrolysis unit consisting of at least one cathode with a common catholyte circuit, is operated stationary as a homogeneously continuous reactor. This means that after the catalyst has been washed once, a defined concentration level of starting materials and products is maintained.
• the reaction solution is continuously pumped in a circuit via the electrochemically active cathode and educt is continuously fed to the circuit, product being continuously removed from this circuit so that the reactor content remains constant over time.
• the starting material is metered in continuously as a solid which is suspended, so that the solution obtained from the dissolved product can be continuously removed.
• At least two electrolysis units are connected in series, the starting material being fed to the first unit and the product being removed from the last unit. This procedure ensures that the concentration in the first electrolysis unit (s) is significantly lower than that in the last unit (s). This means that, on average, higher space-time yields are achieved across all electrolysis units compared to a reaction procedure in which the electrolysis units are operated in parallel.
• the reducible dyes can be selected from a group consisting of vat dyes and sulfur dyes.
• Vat dyes in the context of the present invention are understood to mean in particular indigo and other indigo dyes, anthraquinone dyes and leuco vat dye esters. Sulfur dyes should be mentioned in particular for the reducible dyes.
• indigo 5,5'-dibromoindigo, 5,5 ', 7,7'-tetrabromoindigo, thioindigo, flavanthrene, violanthrene, and the following classes of compounds listed in the cited Ulimann reference:
• Indanthrones and highly condensed ring systems such as dibenzopyrenquinone, Antanthron and Pyranthro: ⁇ .
• the dye used is electrochemically reduced directly at the cathode, which can be avoided by using a mediator.
• the present invention further relates to the use of an electrochemically reduced reducible dye which is prepared by the process according to the invention for dyeing objects.
• the term “objects” in the context of the present invention includes all objects which can be dyed with the dye according to the invention (dyed goods).
• the dye according to the invention includes all objects which can be dyed with the dye according to the invention (dyed goods).
• knitted fabrics and knitted fabrics made from natural or synthetic fibers, wood, plastic, glass and Metal objects can be dyed, and skin and tissue can also be dyed.
• Electrolytic cell split flow type electrolytic cell
• Anode DeNora DSA (anode area: 100 cm 2 )
• Cathode armored braid made of stainless steel material no. 1.4571 (cathode area: 100 cm 2 , pore size: 50 ⁇ m)
• the catholyte consisted of a mixture of 1344 g H 2 O, 28 g H 2 SO (96%), 28 g indigo granules and 10 g Pd / C; 10% Pd content and 10 g BA 1200 (from Anton Richard KG in Graefelfing).
• the test evaluation showed 0.4 g of electrochemically reduced indigo, which corresponds to a yield of 1.4%.
• the catholyte consisted of a mixture of 1344 g of water, 28 g of sodium hydroxide, 28 g of indigo granules, 10 g of Pd / C (10%; BASF E-101, R / D ), 10 g Sigradur K (20-50 ⁇ m) and 10 g BA 1200.
• the two cell compartments were filled and the catholyte heated to 60 ° C.
• the catalyst and the graphite components in a mixture with indigo were then washed to the above-mentioned cathode within 15 minutes.
• the electrolysis was then carried out at 60 ° C. and a current density of 50 mA / cm. After 5 F the experiment was ended.
• the solution was filled under a stream of nitrogen, the catalyst was removed by filtration, made alkaline with sodium hydroxide solution (pH 13) and oxidized by means of air in order to determine the amount of indigo reacted.
• the test evaluation showed 22.4 g of electrochemically reduced indigo, which corresponds to a yield of 80%.
• a commercial wetting agent Purified NF; BASF
• the dyebath which was adjusted to a pH of 11.5, had the following composition:
• the coloration obtained was equivalent in terms of color depth and through-coloration to indigo dyeings produced at the same pH according to the examples from WO 94/23114, which were obtained with indigo or leukoindigo produced according to the prior art.

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• Chemical Kinetics & Catalysis (AREA)
• Textile Engineering (AREA)
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• Hydrology & Water Resources (AREA)
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• Life Sciences & Earth Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Electrodes For Compound Or Non-Metal Manufacture (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
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• 1999
  • 1999-12-22 DE DE19962155A patent/DE19962155A1/de not_active Withdrawn
• 2000
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• 2003
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