DE102006001773B3 - Preparation of a molded protein composite comprises dispersing the protein in water and in aqueous solution of ionic liquid, applying the solution on a smooth plate and recovering the molded protein composite as foil/membrane - Google Patents

Abstract

Preparation of a molded protein composite comprises finely dispersing the protein in water under application of shearing force; dispersing the moist protein in an aqueous solution of the ionic liquid under addition of stabilizers; conducting the solution to a spinning packet, where the solution traverses through the spin capillary or capillaries and/or the slot of spinning nozzle(s) for precipitating, and/or applying the solution on a smooth plate and regenerating the protein through treatment with a temperated solution and removing the molded protein composite as foil/membrane : Preparation of a molded protein composite comprises finely dispersing the protein in water under application of shearing force, squeezed- or filtered-off; dispersing the moist protein in an aqueous solution of the ionic liquid under addition of stabilizers, removing the water through shearing, supplying of heat and vacuum and then transferring the moist protein into a homogeneous solution; conducting the solution to a spinning packet, where the solution traverses through the spin capillary or capillaries and/or the slot of spinning nozzle(s) and the solution strand transformed to capillaries or to flat- and/or tubular foil are passed through an air gap under delay, precipitating the oriented solution strand by treating with a temperated solution, which is miscible with the ionic liquid, but acts as a precipitating agent for the protein, separating the precipitated solution strand at the end of the precipitating bath course by diverting from or by-passing the precipitation bath and withdrawing the molded protein composite as a filament yarn, fiber-cable and/or -foil/membrane, subjecting the molded protein composite to a single- and/or multi-step precipitation wash and drying or cutting to staple fiber and drying; and/or applying the solution in an evenly distributed manner on a smooth plate with a blade and regenerating the protein through treatment with the temperated solution and removing the molded protein composite as foil/membrane, subjecting the protein in to a single- and/or multi-step precipitation wash and drying.

Description

The The invention relates to a process for the production of moldings Proteins by loosening the Proteins in ionic liquids, in particular 1,3-dialkylimidazolium salts, as well as the product-oriented Processing of these solutions by deformation processes such as spinning, casting and blowing processes for the production of moldings such as fibers, filaments, nonwovens, flat or tubular films, membranes and movies. The inventive method for the production of moldings from proteins is characterized by being the protein in the ionic liquid that triggers solution to moldings deformed, the protein by precipitation in protic solutions regenerates, the solvent through Washing separates and the moldings dries.

proteins in the context of this invention are native, high molecular weight fibrillar or globular Proteins caused by the formation of strong intra- and intermolecular Hydrogen bonds in their structure a poor solubility in aqueous and organic solvents exhibit. fibrillar Protein is preferably the sericin-free silk fibroin of the mulberry silk moth Bombyx mori. Globular proteins are preferred Storage proteins such as corn cider and wheat gluten.

According to the invention according to this Processes prepared and processed may be the proteins alone as well as in combination with others, in the ionic liquid solved and / or therein finely dispersed low and / or high molecular weight inorganic and / or organic substances.

Ionian liquids are melting at low temperatures (<100 ° C) Salts that have virtually no vapor pressure. They have been since 1914 known, but have only recently as a solvent or reaction medium for many syntheses gained importance. Of special interest are thereby compounds with a positive nitrogen atom such. the Ammonium-; Pyridinium and imidazolium cation (P. Wasserscheid, W. Germ angew. Chem. 2000, 112, 3926-3945; J. Dupont et al. Chem. Rev. 2002, 102, 3667; Schilling G. "Ionic Liquids" GIT Laboratory Journal 2004 (4) 372-373).

Out Journal of the American Chemical Society 2004, 126, 14350 is known that certain ionic liquids, based on the imidazolium cation and chloride anion, in an inert Nitrogen atmosphere in the absence of water and at elevated temperature (100 ° C) silk fibroin solve the bombyx mori and this regenerated upon addition of acetonitrile or methanol (D.M. Phillips et al., J. Am. Chem. Soc., 2004, 126, 14350-14351). Statements on the characterization and processing of the fibroin solution by Deforming process such as spinning, casting and blowing process not done.

To the Deforming silk fibroin, as a non-meltable polymer, too Filaments, staple fibers or films / membranes are different Solution spinning process been developed. The solubility of the silk fibroin is known in sulfuric, hydrochloric and phosphoric acids, in hot concentrated formic acid and in hot Sodium and potassium hydroxide solutions (H. Zahn, B. Wulfhorst, M. Steffens "Silk (Mulberry Silk) Tussah Silk" Pulp Tables after Koch, 1994).

In WO03060207 is solving of silk fibroin in formic acid with the addition of calcium chloride, and the processing of the solutions too Fibers (J.P. O'Brien WO03060207). WO02081793 describes the dissolution of amorphous fibroin powder in a mixture of dichloroacetic acid with chloroform and the Spinning this solution too Fibers (C.J. Stephen WO02081793). In the mentioned solvent systems is subject to the dissolved in it Silk fibroin molecular degradation processes that reduce the molecular weight result. A processing of the protein such solutions leads to Product properties with low quality level.

Described is also the dissolution of silk fibroin in concentrated aqueous salt solutions of lithium bromide, calcium chloride, magnesium chloride and thiocyanates of lithium, sodium, magnesium or zinc and various copper salts (H. Zahn Ullmanns Encyclopedia of Industrial Chemistry, Vol. A24, 95-106, VCH Publishers, Inc., 1993; RL Lock, DuPont WO93 / 15244). The processing of saline solutions generally results in poor quality of the filaments and moldings produced therefrom due to the residual salt remaining in the product. Therefore, the removal of the salt before the deformation process is essential. DuPont has developed a process of removing the salt and water from concentrated lithium bromide-containing fibroin solutions in two additional steps to produce a protein solution in 1,1,1,3,3,3-hexafluoro-2-propanol, which can be spun into fibers (RL Lock WO9315244). As an alternative to hexafluoro-2-propanol, hexafluoroacetone hydrate can be used to redissolve silk fibroin after dialysis of a concentrated lithium bromide-containing fibroin solution. (A. Tetsuo WO02072931, J. Yao et al., Macromolecules 2002, 35, 6-9). Due to high visc In the case of hexafluoroacetone hydrate, only solutions with a protein content <10% by mass in the spinning process can be processed.

at both methods, the technological effort by the necessary Dialysis of saline solution and subsequent Drying to remove the water significantly increased.

A by wet spinning process processable solution of the silk fibroin leaves made with a mixture of calcium nitrate tetrahydrate and methanol, but also before the spinning process of a dialysis for removal of the salt (S.-W. Ha et al., Biomacromolecules 2003, 4, 488-496).

DE19841649 describes the dissolution of fibrillar proteins such as the silk fibroin in N-methylmorpholine N-oxide monohydrate at temperatures of 75-160 ° C (K. Heinemann, E. Taeger). For a use of ionic liquids as a solvent for the deformation of proteins / silk into filaments, staple fibers and films / membranes speaks a possible higher thermal stability compared to protein solutions in N-methyl-morpholine N-oxide hydrate, which is above 130 ° C. prone to explosive decomposition.

It There still exists the need for suitable solvent systems to find a technologically simple production of fibroin solutions without Reduction in the molecular weight of the protein, with favorable properties in terms the feasibility of subsequent product-oriented processing of these solutions by deformation processes, such as spinning, casting and blowing processes for the production of moldings such as fibers, filaments, nonwovens, flat or tubular films, membranes and movies, allow.

OBJECT OF THE INVENTION

task The present invention is the provision of a method by the one with high process safety and environmental friendliness simple way to preserve proteins while largely retaining the molecular ones Parameters for moldings such as filaments, staple fibers and films / membranes deformed.

• a) das Protein in Wasser vorquellen lässt und anschließend unter Scherung fein dispergiert, abpresst oder abfiltriert, und das feuchte Protein
• b) in einer wässrigen Lösung der ionischen Flüssigkeit, unter Zusatz von Stabilisatoren dispergiert, unter Scherung, Wärmezufuhr und Vakuum das Wasser entfernt und in eine homogene Lösung überführt,
• c) die Lösung einem Spinnpaket zuführt, wo diese die Spinnkapillare(n) bzw. den Schlitz der Spinndüse(n) passiert und die zu Kapillaren oder zur Flach- bzw. Schlauchfolie verformten Lösungsstrahlen unter Verzug durch einen Luftspalt führt, die orientierten Lösungsstrahlen durch Behandeln mit einer temperierten Lösung, die mit der ionischen Flüssigkeit mischbar für das Protein aber ein Fällungsmittel darstellt, ausfällt, am Ende der Fällbadstrecke durch Ab- oder Umlenken vom Fällbad trennt und den Formkörper als Filamentgarn, Faserkabel bzw. Folie/Membran abzieht, einer ein- bzw. mehrstufigen Fällmittelwäsche unterwirft und trocknet oder zu Stapelfasern schneidet und trocknet, bzw.
• d) die Lösung mit einer Rakel durch gleichmäßiges Verteilen auf einer glatten Platte aufbringt und durch Behandeln mit einer temperierten Lösung, die mit der ionischen Flüssigkeit mischbar für das Protein aber ein Fällungsmittel darstellt, das Protein regeneriert und den Formkörper als Folie/Membran abzieht, einer ein- bzw. mehrstufigen Fällmittelwäsche unterwirft und trocknet.

This object is achieved in the method according to the invention that one

• a) the protein is allowed to pre-swell in water and then finely dispersed under shear, squeezed or filtered off, and the wet protein
• b) in an aqueous solution of the ionic liquid, dispersed with the addition of stabilizers, the water is removed under shear, heat and vacuum and transferred into a homogeneous solution,
• c) the solution feeds a spin pack, where it passes the spinning capillary (s) or the slot of the spinneret (s) and leads to capillaries or flat or tubular film deformed solution jets under delay through an air gap, the solution solution beams by treatment precipitated with a tempered solution which is miscible with the ionic liquid for the protein but precipitating agent, separates from the precipitation bath at the end of the precipitation bath section by stripping or deflecting and withdraws the shaped body as filament yarn, fiber cable or film / membrane. or multi-stage Fällmittelwäsche subjects and dries or cuts into staple fibers and dries, or
• d) applying the solution by means of a doctor blade by evenly spreading on a smooth plate and regenerating the protein by treatment with a tempered solution which is miscible with the ionic liquid for the protein but a precipitating agent and withdraws the shaped body as a film / membrane one- or multi-stage precipitant wash and dried.

Prefers used proteins are in particular the silk fibroin of the Mulberry silk moths Bombyx mori and globular proteins such as maize zein and Wheat gluten.

At the inventive method becomes fibrillar Protein, like silk fibroin, shake well in water until high pitched to the single fiber. After pressing is swollen Fibroin with approx. 80-90 Mass% water before. Powdered, globular protein, such as maize or wheat gluten is dispersed in water and as swollen material filtered off.

Surprisingly let yourself the moist protein material in aqueous Easily convert 1,3-dialkylimidazolium salt into a homogeneous suspension which under shear, heat and vacuum passes after distilling off the water in a homogeneous spinning solution. The temperature range is preferably 80-95 ° C. In which inventive method does not have to be worked in inert nitrogen atmosphere, and it can generally be a much lower temperature for dissolving the Selected protein be as for the release of the dry silk fibroins in anhydrous ionic liquid needed (See D.M. Phillips et al., J. Am. Chem. Soc., 2004, 126, 14350-14351).

The characterization of the dope quality can be done by analyzing the homogeneity of the solution under the polarizing microscope. Rheological measurements on the protein solution provide viscosity data that allow an assessment of the required spinning parameters. The determination of the water content is based on the refractive index.

Of the Particle content and the particle size distribution based on the class width in the spinning solution, which can be determined by means of laser diffraction, allow an additional Characterization of dope quality (see B. Kosan, C. Michels Chemical Fibers Int. 1999, 48, 4, pp. 50-54).

Around preserving the molecular parameters of the protein after dissolving in ionic Liquid and Regenerate following can check the deformation process a characterization by capillary viscometric measurements respectively. For this, the intrinsic viscosities, i. the code numbers for the size of the protein molecules in the dissolved state at infinite dilution, from diluted solutions of the regenerated protein compared to the native, used Protein detected. In the case of silk fibroin, a measurement is made the viscosities in 50% aqueous Lithium bromide.

For a high stability of the molecular weight of the protein for a long time at elevated temperature has an addition of antioxidants such as hydroquinone, p-phenylenediamine, gallic acid esters, tannins, etc. proven. As thermogravimetric analyzes (TGA) and measurements by differential scanning calometry (DSC) show, a good thermal stability of the spinning solutions according to the invention is given up to at least 220 ° C. Thus, the solutions of the invention have a much better thermal stability compared to protein solutions in N-methyl-morpholine N-oxide hydrate (NMO hydrate), which tend above 130 ° C for explosive decomposition (K. Heinemann, E. Taeger DE19841649 ). While in the preparation of protein solutions in NMO hydrate to ensure accurate distillation to reach the monohydrate, resulting in simpler procedure when dissolving in ionic liquids significantly shorter processing times for the preparation of the spinning solution. In addition, compared to NMO hydrate solutions in the ionic liquids, especially in 1,3-dialkylimidazolium acetates, at comparable viscosities that allow processing by spinning processes, a higher mass% content of protein can be solved, resulting in a more effective process and stable moldings leads.

According to the invention preferably concentrated solutions of the protein from at least 10% up to 50%, depending on the resulting solution viscosity, for the preparation of moldings used.

As well proteins can be combined with ionic liquids soluble synthetic and / or natural Dissolve polymers and to moldings deform.

The deformation according to the invention the solution to filaments, staple fibers, flat or tubular films and membranes takes place in a dry-wet extrusion process such that the solution feeds to the spin pack, in a temperature-controlled heat exchanger the required spinning temperature sets, through spinnerets to filaments or foils deformed and leads with delay through a gap to the precipitation bath. The Thread formation can be represented as a two-stage process. In the spinning capillary occurs mainly under the influence of shear stress at constant Temperature a rejuvenation of the solution jet from the inlet to the outlet cross section of the spinning capillary.

in the Gap of defined length occurs under the influence of the axial expansion stress at decreasing Temperature another rejuvenation of the solution jet - the spinning draft - in the ratio of withdrawal and injection speed. The delay of the solution jet in the gap is simultaneously associated with an increase in the thread surface.

According to the invention directs one the oriented solution beams for regenerating the protein by a precipitation bath containing a protic solvent in which the ionic liquid but not the protein soluble is, preferably methanol.

films and membranes can with an inventively prepared solution of the protein in ionic liquid also be prepared such that a defined amount of this viscous solution by means of a squeegee on a smooth, cleaned, tempered surface struck and then the protein in a precipitation bath with protic solvent, preferably methanol, and regenerated sufficient residence time becomes. In a further variant for the deformation of the inventively produced solution The protein can pass through an annular gap nozzle with protic internal and Outdoor bathroom too Blown film blown.

The Membrane properties of the films according to the invention and Membranes are a function of the processing parameters. By variation the protein concentration in the solution, gap size and / or Withdrawal speed can be the layer thickness of the films and membranes to be influenced.

The ionic liquids allow working in a closed solvent circuit. The washed out in the precipitation bath ionic liquid can after distillative concentration as a solution tel be recycled into the circulation.

The inventive method will now be explained with reference to examples.

example 1

The on 3-5 mm length cut silk fibroin of Bombyx mori is dispersed in water, in liquor ratio 1:20 open and allowed to swell for 12 hours. By light pressing is dehydrated to 10% by mass of fibroin. By dispersing 210 g of moist silk fibroin in 61.25 g of 80% aqueous solution of 1-ethyl-3-methyl-imidazolium acetate (EMIMAc) previously containing 0.5% by mass of propyl gallate / sodium hydroxide added as a stabilizer, you get 271.25 g of mash, the after Entry into a kneader under high shear, a temperature from 80-90 ° C and decreasing pressure from 850 to 5 mbar below complete Water removal is transferred into 70 g of a homogeneous solution. The release time is 160 min. The refractive index of the 30% by weight fibroin solution is 1.5107 at 50 ° C. The homogeneity the solution is taken on hand samples under the polarizing microscope controlled. Rheological measurements showed a temperature from 50 ° C one decreasing viscosity from 1140 Pas to 640 Pas in the area of a shear gradient of 0.3-4.2 l / s.

To Regeneration of silk fibroin with methanol gives capillary viscometric Measurements of diluted solutions of the protein in 50% aqueous Lithium bromide an intrinsic viscosity of 20.22 ml / g. The intrinsic viscosity of the starting silk fibroin became determined analogously and is 22.57 ml / g.

Example 2

Analogous Example 1, 17.5 g of silk fibroin with dissolution in 65.6 g of 80% aqueous Solution of 1-butyl-3-methylimidazolium acetate (BMIMAc) at pH 7 in 70 g homogeneous viscous solution with 25 mass% fibroin transferred. The release time is 180 min. The refractive index of the fibroin solution at 50 ° C is 1.5015. The homogeneity of the solution is on Hand-picked samples under the polarizing microscope controlled. Rheological measurements showed a falling at a temperature of 50 ° C. viscosity from 1070 Pas to 698 Pas in the area of a shear rate of 0.3-4.2 l / s.

To Regeneration of silk fibroin with methanol gives capillary viscometric Measurements of diluted solutions of the protein in 50% aqueous Lithium bromide an intrinsic viscosity of 22.42 ml / g. The intrinsic viscosity of the starting silk fibroin became determined analogously and is 22.57 ml / g.

Example 3

Analogous Example 1, 14 g of silk fibroin dissolving in 70 g of 80% aqueous solution of 1-ethyl-3-methyl-imidazolium chloride (EMIMCl) in 70 g homogeneous viscous solution with 20 mass% fibroin transferred. The release time is 140 min. The refractive index of the fibroin solution is 1.5377 at 50 ° C. The homogeneity of the solution will controlled by hand under the polarizing microscope. Rheological measurements showed a linear at a temperature of 50 ° C decreasing viscosity from 977 Pas to 574 Pas in the area of a shear rate of 0.3-4.2 l / s.

To Regeneration of silk fibroin with methanol gives capillary viscometric Measurements of diluted solutions of the protein in 50% aqueous Lithium bromide an intrinsic viscosity of 22.39 ml / g. The intrinsic viscosity of the starting silk fibroin became determined analogously and is 22.57 ml / g.

Example 4

7.0 The finely ground cornstarch is dispersed in water and filtered off. To 78.75 g of an 80% aqueous solution of 1-butyl-3-methyl-imidazolium chloride (BMIMCl) previously containing 0.5% by mass of propyl gallate / sodium hydroxide added as a stabilizer is added in portions, the moist Protein added, so that a homogeneous suspension is formed. These becomes after entry into a kneader under strong shear, one Temperature of 80-90 ° C and decreasing Pressure of 850 to 6 mbar with complete removal of water in 70 g of a homogeneous solution. The release time is 120 min. The refractive index of the 10% by weight zein solution is 1.5229 at 50 ° C. The homogeneity the solution is taken on hand samples under the polarizing microscope controlled. Rheological measurements showed a temperature from 50 ° C a linear decreasing viscosity from 40 Pas to 26 Pas in the range of a shear rate of 0.4-4.2 l / s.

Example 5

8:38 g on 3-5 mm length cut silk fibroins of Bombyx mori are dispersed in water, in the liquor ratio 1:20 open and 12 h swollen. 930 mg of a crushed Eucalyptus pulp (Cuoxam DP 569) is also in water dispersed. There is also so much sodium hydroxide to the cellulose suspension added until a pH of 10 sets.

It is slightly pressed and the wetted materials with 75.9 g of 80% aqueous solution of 1-butyl-3-methyl-imidazolium chloride (BMIMCl) previously mixed with 0.5% by mass of propyl gallate / sodium hydroxide added as a stabilizer. This mash will be after entry into a kneader under high shear, a temperature of 85-95 ° C and decreasing Pressure of 850 to 6 mbar with complete removal of water in 70 g of a homogeneous solution is transferred. The release time is 150 min. The refractive index of the 13.3 percent by mass solution consisting from 90 parts of silk fibroin and 10 parts of cellulose, is 1.5252 at 50 ° C. The homogeneity the solution is taken on hand samples under the polarizing microscope controlled. Rheological measurements showed a temperature from 50 ° C a falling viscosity from 1331 Pas to 513 Pas in the range of a shear rate of 0.3-4.2 l / s.

Example 6

A prepared analogously to Example 2 spinning solution with 20% by mass of silk fibroin in 1-butyl-3-methylimidazolium acetate (BMIMAc), which at 50 ° C has a viscosity of 147-129 Pas at a shear rate of 0.6-4.3 l / s becomes monofilaments in a piston spinning apparatus processed. The tempered in an internally lapped steel cylinder at 35 ° C, bubble-free fibroin solution with a motor-driven piston through spinnerets with diameters of 100 microns or 75 microns (1 / d ratio 3-6) on a Air gap of 15 mm in a precipitation bath, consisting of methanol, pressed. The formed monofilament is about a Umlenkgalette led by the 1 m long precipitation bath to Wickelgalette, where the thread at a defined withdrawal speed (e.g., 2 m / min) is wound up. To the complete Removal of the ionic liquid leave the monofilaments for a further 3 hours in the methanol washing bath and subsequently dried at room temperature.

Example 7

The in Example 5 produced 13.3 percent by weight dope in 1-Butyl-3-methylimidazolium chloride (BMIMCl) is analogous in a piston spinning apparatus Example 6 processed into monofilaments. The spinning temperature is here 65 ° C. It is a take-off speed of up to 10 m / min at the Wickelgalette reached. As a precipitation bath is preferably at 20 ° C tempered methanol used.

Example 8

5 g of the solution prepared in Example 4 of 10 mass of maize in 1-butyl-3-methylimidazolium chloride (BMIMCl) is used for the preparation a membrane by means of a doctor uniformly on a preheated to 80 ° C. Distributed glass plate. The plate is placed in a Fällbadwanne and good covered with methanol to regenerate the protein. After a stay of 2 hours, the plate is removed, dried at room temperature and peeled off the membrane.

Example 9

The in Example 5 produced 13.3 percent by weight dope in 1-Butyl-3-methylimidazolium chloride (BMIMCl) is used in a pressure pump spinning apparatus processed into tubular films. It is tempered in a storage vessel to 65 ° C, bubble-free spinning solution through a ring slot nozzle with a gap diameter of 20 mm and a gap width of 9.5 mm above pressed an air gap of 10 cm in a 3 m long precipitation bath of methanol. In the air gap the tubular film is cross-stretched by compressed air. In the tube interior is a constantly renewed Innenfällbad consisting of methanol, brought in. Under delay, the tube foils in the moist Condition wound up. Between two nip rolls is the tubular film then dried with tempered air.

Claims (9)

Process for the production of shaped articles from proteins, by dissolving them in an ionic liquid, shaping the viscous solution into the shaped article and regenerating the protein, characterized in that a) the protein is finely dispersed in water under shear, pressed or filtered off, and the moist Protein, b) dispersed in an aqueous solution of the ionic liquid, with the addition of stabilizers, under shear, heat and vacuum, the water removed and transferred to a homogeneous solution, c) the solution feeds a spin pack, where this the spin capillary (s) or Passes the slot of the spinneret (s) and leads to the capillaries or the flat or tubular film solution jets warped by an air gap, the solution solution jets by treating with a tempered solution, which miscible with the ionic liquid for the protein but one Precipitant, precipitates, at the end of Fällbadstr corner separates by deflection or deflection of the precipitation bath and the shaped body as filament yarn, fiber cable or film / membrane peels, subjected to a single or multi-stage Fällmittelwäsche and dried or cut into staple fibers and dried, or d) the solution with a doctor blade uniform spreading on a smooth plate and by treatment with a tempered solution, which is miscible with the ionic liquid for the protein but a precipitant regenerating the protein and the shaped body as a foil / membrane, ei ner one-stage or multi-stage Fällmittelwäsche subjects and dries. Method according to claim 1, characterized in that that native, high molecular weight fibrillar or globular proteins, the strong inter- and intramolecular hydrogen bonds form, or mixtures of these proteins with others, in the ionic liquid soluble and / or finely dispersed low and / or high molecular weight organic and / or inorganic substances. Method according to claim 1, characterized in that that as proteins the silk fibroin of the silk moth Bombyx mori, Maiszein or wheat gluten. Method according to claim 1, characterized in that that as an ionic liquid 1,3-Dialkylimidazoliumacetate or 1,3-Dialkylimidazoliumchloride used become. Method according to claim 1, characterized in that that the applied dissolution temperature in the range between 80-130 ° C. Method according to claim 5, characterized in that that the applied dissolution temperature in the range between 80-90 ° C. Method according to claim 1, characterized in that that the spinning solution Stabilizers in the form of organic compounds having at least one conjugated double bond and two hydroxyl, or amino groups contains. Method according to claim 7, characterized in that that the organic compounds used as stabilizers having at least one conjugated double bond and two hydroxyl, or amino groups hydroquinone, phenylenediamine, gallic acid esters or tannins are. Method according to claim 1, characterized in that that one is the ionic liquid from the precipitation bath recycled.