EP3927879B1 - Method for producing coloured fibrous materials and the use thereof - Google Patents

Description

The invention relates to a process for the production of colored fiber materials based on fiber mixtures containing m-aramid fibers or mixtures containing m-aramid fibers which have been subsequently colored with vat dyes, and the use of the colored fiber materials for the production of articles of clothing.

In terms of quantity, aramid fibers are among the most frequently used fiber types in the field of personal protective clothing, primarily because of their inherently self-extinguishing properties. Known m-aramids are, for example, ^Nomex® from DuPont de Nemours, ^{Teijinconex®} from Teijin or Yantai ^Newstar® from Yantai. A major problem is the dyeing of textiles made of m-aramid fibers and fiber mixtures containing them. In principle, m-aramid fibers can be dyed with selected cationic dyes under high temperature conditions in the exhaust or continuous process (see e.g Fiebig D., Küster B., Herlinger H.: "One possibility for the continuous coloring of poly-m-phenylene isophthalamide", textilpraxis intern. 49 (1994), 260-262, 265, 266 or the DE 10 2009 039 606 B3 ). The prerequisite is that relatively large amounts of carriers (dyeing accelerators) have to be added to the dyebath. This is mainly due to the fact that the glass transition temperatures (T _g ) of m-aramids are very high. For poly-m-phenylene isophthalamide as a typical m -aramid, the T _g is around 270°C. For polymers, the glass transition temperature is the temperature at which the macromolecules get a certain mobility in the amorphous areas. In terms of dyeing, the T _g is relevant in that dye molecules are given the opportunity to diffuse into the fiber interior due to the chain mobility that occurs above the T _g . The effect of a carrier is to promote this chain mobility so that, depending on the carrier concentration, coloring is possible at a significantly lower temperature. After Roberts and Solanki (J. Soc. Dyers Col. 95 (1979), 226 and ibid. 427), the effect of a carrier leads to plasticization of the polymer with a simultaneous reduction in the T _g . A similar effect occurs when solvents are added to the dyebaths that are relevant when spinning the m-aramids, for example dimethylacetamide (see e.g Moore RF, Weigmann HJ: "Dyeability of Nomex Aramid Yarn", Textile Res. J. 56 (1986), 254-260 ), 1,3-dimethylimidazolidinone or selected ionic liquids. However, such admixtures are not suitable for practical use in dyeing.

carrier stains

A piece dyeing of m -aramids is usually carried out at about 120° C., ie under HT (high temperature) conditions, in a weakly acidic medium with the addition of considerable amounts (30-90 g/l) of carrier. Without the addition of a carrier in the dyeing liquor, the cationic dyeings carried out in production today according to the prior art result in textile samples which are weak in color and only dyed on the surface. The carriers used are usually aromatics. Benzyl alcohol, phenoxypropanol or phenoxyethanol, for example, are frequently used. Other compounds that can develop the effect of a carrier are N-cyclohexylpyrrolidone, acetophenone, 1,2,4-trichlorobenzene, 1-methylnaphthalene, o-dichlorobenzene or n-butyl benzoate ( Roberts G. and Solanki R. in J. Soc. dye Col. 95 (1979), 226 and ibid. 427). Due to their generally low solubility in water, the presence of emulsifying agents is necessary so that they can be emulsified in the aqueous dye liquor.

All available carriers are substances that are hazardous to health and the environment. Extensive and expensive measures are therefore necessary in the practice of carrier dyeing in order to minimize emissions of carriers into the air and into the waste water. At the same time, this means critical Emission behavior is a clear limitation with regard to the available dyeing processes. Dyeing is usually carried out in closed apparatus suitable for high temperatures and overpressure. Dyeing in quasi-open systems, such as in a steamer or on a stenter, is practically impossible. A further disadvantage is that the light fastness of the aramid samples dyed with cationic dyes and carriers is poor, which is insufficient for many applications. Disperse dyes which are dyed according to common formulations for disperse dyeing on aramid with the addition of a carrier show a relatively weak color yield. At the same time, the lightfastness is generally poor, even when using highly lightfast disperse dye types (see F. Gähr, S. Berndt in TextilPlus 2018, issue 5/6, pp. 16-19 ).

Fiber pretreatment process

Other alternatives described in the prior art are aimed at pretreating the fiber using suitable measures that trigger an increased affinity of the fiber surface for various dyes. In DE 43 35 717 A1 describes the treatment of aromatic polyamides in an alcoholic solution of a hydrolyzable alkoxysilane such as (3-triethoxysilylpropyl)octadecyldimethylammonium chloride. The finished, cationized fiber material can then be reactively dyed. Disadvantages of the process are, on the one hand, the solvent-based process control, and on the other hand, poor color fastness is obtained due to the cationization and the resulting edge coloring. In Melliand Textilber. 4/2018, 159-161 describes the possibility of equipping aramids with polyvinylamine to improve UV resistance and colorability. However, the color fastness that can be achieved with anionic dyes, in particular light fastness and rubbing fastness, is also unsatisfactory in this process because of the edge coloring. Physical pre-treatment measures, such as fiber activation by plasma, are generally of interest, but here too the color fastness is extremely unsatisfactory. The effect of the plasma is limited to the fiber surface (approx. 4-10 nm), so that edge coloring is the rule and consequently poor fastness results almost inevitably.

Vat and vat pigment dyeing

As an alternative to dyeing with cationic (basic) dyes, approaches for dyeing m-aramids with vat dyes are described in the prior art. Vat dyes are commonly used for cellulosic fiber materials when high color fastness is required. The indanthrene dyes developed by BASF Ludwigshafen, which have excellent light fastness properties, are well known here. The general process principles on which the dyeing of cotton with vat dyes is based are known to those skilled in the art. The first step in the dyeing process is the vatting of the water-insoluble dye using suitable reducing agents in an alkaline medium. The water-soluble, molecularly present and generally yellowish leuco form is formed. The molecules of the leuco form have a high affinity especially for cellulose in alkaline medium, so that they are easily absorbed by the cellulose fibre. After the cellulose has been drawn down, it is oxidized by atmospheric oxygen (or other oxidizing agents), whereby the water-insoluble dye is reformed and firmly anchored in the pore system of the cellulose. The last step of the dyeing is a post-soaping process, in which dyes adhering to the surface are removed and the brilliance of the dyeing is increased. Depending on the redox potential, dye constitution and temperature-dependent affinity of the respective dye to the fiber, different variants of the standard method have been developed. In addition to this standard process, there are also some special vat dyeing procedures that can be of particular interest for the dyeing of synthetic fibers. In the WO 96/04420 A1 describes the dyeing of textiles made from synthetic fibers with vat dyes in an alkaline medium. A Nomex ^® fabric is dyed at 135°C without a carrier. However, very high amounts of alkali and reducing agents have to be used for this, which in turn leads to extremely severe fiber damage.

Gähr and Berndt describe in TextilPlus 2018, issue 5/6, pp. 16-19 a Leuco-HT process, which is based on the cotton vat dyeing process described above. However, for dyeing articles made of 100% m-aramid as well as, for example, Nomex ^® Comfort (93% m-aramid, 5% p-aramid and 2% antistatic fibre), similar to dyeing with cationic dyes, HT conditions (115°C) and the addition of a carrier necessary. The resulting textile samples are deep in color when the carrier is added. Without the addition of a carrier, the lightfastness is, depending on the dye, at a significantly higher level than with cationically dyed aramids. The addition of a carrier to the dyebath generally leads, analogously to cationic dyeing, to significantly improved color yields, but at the same time the carrier results in losses in lightfastness of 1-2 points.

In the U.S. 6,942,706 B2 a process based on vat acids is described for the dyeing of synthetic fibers which is said to be suitable for delivering high depths of color and fastness to washing. Here, the fibers are treated with leuco vat acids under suitable conditions. The decisive factor is maintaining a weakly acidic reducing environment, whereby special reducing agent admixtures coupled with controlled additions of citric acid must be observed. As Gähr and Berndt (see above) found when comparing the different processes, the color depths determined using the K/S values are always lower for the vat acid process than for the leuco-HT process if the carrier is omitted. Furthermore, in the presence of a carrier, the light fastness grades also deteriorate significantly here.

In the DE 10 2015 114 501 A1 a method is described which works without the vatting step. The vat pigments are applied using a pigment padding process and fixed with hot air or superheated steam. Accordingly, the coloring takes place exclusively in the pigment form without the addition of a reducing agent and alkali. Very good light fastness properties are obtained. In order to achieve good color yields, however, the addition of a carrier (benzyl alcohol) is also necessary with this process.

In detail goes from the DE 19 2915 114501 A1 still emphasizes a process for the production of colored textiles based on m-aramid fibers or m-aramid-containing fiber mixtures subsequently dyed with vat dyes, in particular for the production of colored textiles, the textiles, in particular in the form of woven fabrics, knitted goods and fleece, for Coloring with vat dyes are treated by a) applying the vat dyes directly as vat pigment to the fibers of the m-aramid or the fiber mixtures containing m-aramid and then fixing the vat pigment is carried out or b) the vat dyes before bringing them into contact with the m- Aramid fibers or the m-aramid-containing fiber mixtures are converted into the leuco form by adding reducing agents in an alkaline medium, the resulting vat is applied to the textile, the vat dye is formed from the leuco form by oxidation and then the vat dye is fixed to the fibers . The inclusion of urea and/or homologues and/or derivatives of urea in aqueous dispersions containing vat dyes is not addressed.

The state of the art according to the JP 2010 047850 A deals with colored fiber materials based on colored m-aramid fibers or fiber mixtures containing m-aramid fibers, which are colored with vat dyes and irradiated with lasers. The vat dyes selected according to this prior art are characterized in that they have absorption in the wavelength range of a suitable laser. During the laser treatment, this means that the aramid is spontaneously heated to temperatures of 300 to 400°C, i.e. also to temperatures above the glass transition temperature. There is no mention of the possibility of using additional fibers, since such fibers regularly do not survive a laser treatment unscathed.

The EP 0 357 548 A1 relates to a process for dyeing and printing cellulosic fiber materials with vat dyes in the presence of n-diols as reducing agents and alkali, small amounts of organic, water-miscible solvents, for example low molecular weight alcohols, also being used to reduce the vat dyes. An extensive list of organic solvents is given that can be used here, such as low molecular weight alcohols, ketones, ethers, acetates, glycols, glycol ethers, thioglycols, nitriles, pyridines, lactones, lactams, soramede, ureas, sulfones and sulfoxides. Although urea is used, albeit as an adjuvant, EP 0 358 548 A1 no indication that this has a positive effect on the dyeing speed and the depth of shade without impairing the color fastness.

Prior Art Problems

• ein rascher Wechsel auf den vom Kunden gewünschten Farbton ist erschwert,
• viele Farbtöne für die Dichromie- oder Trichromiefärbungen die Voraussetzung sind, sind nicht einstellbar und daher nicht realisierbar,
• es müssen ständig spinngefärbte Fasern in größerer Menge vorgehalten werden, um bei Bedarf, d.h. Auftragseingang, rasch reagieren zu können,
• bei Fasermischungen müssen die Farbtöne beider Fasern meist entsprechend angepasst sein,

spinngefärbte Fasern aus m-Aramid liegen kostenmäßig auf einem etwa doppelt so hohen Preisniveau wie ungefärbte Fasern.All the processes described for the subsequent coloring of m-aramid fibers, whether batchwise or continuously, have the disadvantages, firstly, of poor color absorption if carriers are dispensed with and, secondly, that the dyed textiles have insufficient color fastness properties, in particular one have poor lightfastness. This is the reason why the majority of dyed aramid fibers are still spun-dyed today (>90%), with all the disadvantages that are well known for spun-dyed fibers:

• a quick change to the color desired by the customer is difficult,
• many color shades for which dichroic or trichromatic colorings are a prerequisite, cannot be adjusted and therefore cannot be realised,
• large quantities of spun-dyed fibers must be kept in stock in order to be able to react quickly when required, i.e. when an order is received,
• in the case of fiber mixtures, the color shades of both fibers usually have to be matched accordingly,

Spun-dyed fibers made of m-aramid are about twice as expensive as undyed fibers.

For these reasons, the subject of subsequent coloring of fiber materials containing m-aramid, namely with the necessary high fastness properties and without the use of carriers, enjoys high priority in the textile industry. From an ecological point of view, the use of carriers represents a major problem. These cause a strong odor nuisance at the workplace and require costly measures to minimize emissions and separate disposal of residual fleets containing carriers.

Another problem with carrier dyeing arises when dyeing fiber blends made from m-aramid with other flame-retardant fibers, such as viscose FR, Modal FR or Lyocell FR (FR = flame retardant). The flame-retardant cellulose fibers are often added to the m-aramid fibers for reasons of comfort. Subsequent coloring is done with cationic dyes. As a rule, they contain additives based on phosphorus-sulphur compounds for the purpose of low flammability (see e.g R. Wolf "Flame Retardant Viscose Rayon Containing a Pyrophosphate" in Ind. Eng. Chem. Res. Dev. 20 (1981), 413-420 ). The corresponding additives, which are contained up to a content of 20% by weight based on the cellulose fiber, are successively extracted under the HT conditions of the carrier dyeing necessary for the aramid content. This results in a significant loss of flame resistance of the fiber blend as a whole.

For this reason, too, there is a great desire in practice to be able to access a method that makes the addition of a carrier superfluous.

A further disadvantage of dyeing processes with carriers carried out according to the prior art is that such dyeings in knitted goods lead to unsatisfactory textile properties. Knitted goods are characterized by a significantly higher elasticity than woven fabrics and, especially in the case of clothing textiles, by a lighter and usually softer feel. Knitted fabrics, which include knitwear and hosiery, are much more sensitive to mechanical stress than woven fabrics when subjected to thermal or hydrothermal treatment. They lose their elasticity more quickly, which is expressed in the tensile/elongation test with regard to the hysteresis in a reduced springback force and an increased permanent elongation. These advantageous properties are adversely affected in the course of coloring under HT conditions when the aromatic carriers mentioned are added.

A particular disadvantage of carrier dyeing is that the dyed m-aramid fibers still contain carrier residues that are difficult to remove by simple washing processes at the end of the finishing chain. This means that at least traces of carrier are often still present in the dyed aramid-containing fibres, yarns or textiles when they are delivered to the customer (see example 1).

object of the invention

The object of the present invention is therefore to provide industrial practice with a process for the subsequent coloring of m-aramid fibers and m-aramid-containing fiber mixtures which dispenses with the use of carriers which are harmful to the environment and health and which nevertheless provides good color yields and fastness properties. At the same time, the use of suitable spinning solvents for m-aramids, which act as carrier-like plasticizers, should be ruled out.

Another object of the invention is to achieve dyeings in color shades which, according to the prior art, are usually only achieved on m-aramid via dichromisms or trichromisms, with high fastness properties and without using a carrier.

According to a further object of the invention, the dyeing process according to the invention should also be suitable for lightfast dyeing of knitted goods containing m-aramid, without a significant loss of the elastic properties occurring.

According to a further object, the process according to the invention should be able to be carried out on standard dyeing apparatus and machines in the textile industry. In particular, it should allow working in quasi-open dyeing machines.

Solution

According to the invention, the above objects are achieved by a process for the production of colored fiber materials based on m-aramid fibers or fiber mixtures containing m-aramid fibers dyed subsequently with vat dyes, which is characterized in that the m-aramid fibers are subsequently dyed with vat dyes be colored by a) applying vat dyes in an aqueous dispersion containing urea and/or homologues and/or derivatives of urea directly to the m-aramid fibers or the m-aramid fibers-containing fiber mixtures and then fixing the vat pigment to the Fiber materials is carried out, or b) the vat dyes are converted into the leuco form by adding reducing agents in an alkaline medium, the resulting vat containing urea and/or homologues and/or derivatives of urea and the vat containing the m-aramid fibers or the Fiber mixtures containing m-aramid fibers are brought into contact, the vat dyes are formed by oxidation from the leuco form and the vat dyes are fixed on the fiber materials.

• die Geruchsneutralität,
• eine hervorragende Wasserlöslichkeit, die zum einen den Einsatz von Emulgierhilfsmitteln erübrigt und zum zweiten für eine leichte Auswaschbarkeit des Harnstoffs am Ende der Färbung sorgt,
• seine hydrotropen Eigenschaften, die für die Löslichkeit der handelsüblichen Küpenfarbstoffpigmente förderlich sind und zur Beschleunigung der Farbstoffdiffusion in die m-Aramidfasern beitragen,
• seine hygroskopischen Eigenschaften, die insbesondere bei Farbstofffixierungsprozessen in einem Dämpfer oder auf einem Spannrahmen zum Tragen kommen.
• Die Färbung der m-Aramidfasern kann nach Verfahren der für Küpenfarbstoffe üblichen Färbepraxis durchgeführt werden.

The above objects are therefore achieved according to the invention in that the dyeing with vat dyes is carried out with the simultaneous action of urea and/or homologues and/or derivatives thereof. Surprisingly, it was found that urea has a positive effect on the dyeing speed and the depth of color without impairing the color fastness. Urea is a substance that is well tolerated by the environment and the body. Other benefits of urea include:

• the odor neutrality,
• excellent water solubility, which on the one hand makes the use of emulsifying agents unnecessary and on the other hand ensures that the urea can be easily washed out at the end of the dyeing,
• its hydrotropic properties, which are beneficial for the solubility of commercial vat dye pigments and contribute to the acceleration of dye diffusion into the m-aramid fibers,
• its hygroscopic properties, which are particularly important in dye fixation processes in a steamer or on a stenter.
• The dyeing of the m-aramid fibers can be carried out according to the usual dyeing practice for vat dyes.

An essential feature of the process is therefore the addition of urea and/or suitable homologues and/or derivatives of urea to the actual dyeing liquors. It is essential in process step a) as well as in process step b), the urea and/or one or more suitable homologues and/or derivatives of urea before the first step of the dyeing process, namely before the application of the vat dye pigment (process step a)) or the vat dye in the leuco form (process step b)) on the respective fiber material, so that this or this can develop its effect - analogous to a carrier. With this measure, the use of urea as such is particularly advantageous. However, various urea derivatives are also suitable for replacing this, in whole or in part. When selecting suitable urea derivatives, it is important that they are similar to urea in terms of water solubility. Urea is very soluble in water. At 5°C 97 g/l and at 25°C 1200 g/l dissolve. In order to satisfactorily achieve the benefit sought according to the invention, the water solubility of the homologues and derivatives of urea should not deviate too far from this. A value of 20 g/l at 20°C could be described as the minimum limit. Urea homologues that are still suitable here include biuret, which is readily soluble in hot water but much less soluble in cold water, namely at 20 g/l at 20°C. Also suitable is N,N'-dimethylurea, which is readily soluble in water (765 g/l at 21.5°C). In addition, there are the following urea derivatives based on substitution are suitable: tetramethyl urea, O-alkyl urea.

The invention can undergo a variety of advantageous developments, which will first be discussed below: When carrying out the method according to the invention, the type of fibers that are to be subsequently colored is not critical. It is preferred that the m-aramid fibers and the fiber mixtures containing m-aramid fibers are based on fiber tufts, fiber tows, slivers, rovings, yarns, woven fabrics, knitted goods, in particular knitted and warp-knitted fabrics, braids or fleece. It is particularly preferred if the fiber mixtures containing m-aramid contain other fibers that can be dyed with vat dyes, especially in the form of viscose, modal, lyocell, polyamide and/or polypropylene fibers and/or wool. The further fibers mentioned are advantageously formed in that they are inherently flame-retardant and have an LOI according to ASTM D2863 of at least 23, in particular at least 27. The other fibers are advantageously present as cellulose, regenerated cellulose, aliphatic, aliphatic-aromatic and aromatic polyamide and/or polyester fibers. If other fibers are used, it is advantageous if these account for about 1 to 75% by weight, in particular about 5 to 60% by weight, based on the total weight of the fiber mixtures.

The particle size of the vat dyes in process step a), which are used in pigment form, is not critical. It is expedient if these have a particle size of about 0.1 to 3 μm, preferably about 0.1 to 1.5 μm, in particular about 0.2 to 0.8 μm, in process step a).

The person skilled in the art is not restricted in his choice of vat dyes. It is considered preferred that the vat dyes are used in the form of indigo, indigo derivative, anthraquinone, anthraquinoneoxazole, anthraquinonecarbazole, indanthrone, flavanthrone, benzanthrone or pyranthrone dyes or sulfur dyes. Concretely preferred vat dyes are identified as CI Vat Green 1, Vat Green 13, CI Vat Red 32, CI Vat Red 10, CI Vat Blue 4, CI Vat Blue 20, CI Vat Yellow 28, CI Vat Orange 29, CI Vat Brown 9, CI Vat Black 9 and/or CI Sulfur Black 9 are used.

The invention is also not subject to any critical limitations when the aqueous dispersion is applied in process step a) and the vat in process step b). It is considered preferred that the aqueous dispersion in process step a) and the vat in process step b) are applied continuously with a padder, a squeegee or a doctor blade, or that the contacting with the fiber material is carried out in the form of a discontinuous exhaust process. It is also preferred that the aqueous dispersion in step a) and the vat in step b) contain about 0.1 to 10 mol/l, in particular 1 to 5 mol/l and particularly preferably 2 to 4 mol/l urea and/or Contain urea derivative. For the broader range of about 0.1 to 10 mol/l, the following advantageous framework conditions also apply: 0.4 to 10 mol/l, preferably 0.6 to 10 mol/l and in particular 0.8 to 10 mol/l.

With regard to the concentration of the vat dyes in the aqueous dispersion after process step a) or in the alkaline medium after process step b), it is preferred that in the aqueous dispersion of process step a) the vat dyes are present in a concentration of 1.5 to 110 g/ l, in particular from 5 to 60 g/l, and in the alkaline medium in process step b) in a concentration of from 0.05 to 30 g/l, in particular from 0.2 to 20 g/l. An advantageous development of the process according to the invention consists in carrying out a post-soaping step after formation of the vat dyes in process step b).

After the application or the formation of the vat dyes after process step a) or process step b), it is preferred that the fixing of the vat dyes in process step a) and process step b) is carried out as a) dry heat fixing between 140 and 260 ° C, in particular between 170 and 220°C, (thermosol process), b) steam setting at a temperature between 100 and 160°C, in particular between 110 and 155°C, and/or c) exhaust dyeing between 70 and 150°C, in particular between 98 and 125 °C

In view of the fact that the invention appears particularly advantageous with its effects when no carrier materials are present, it is therefore considered very expedient that when carrying out the process carrier materials, in particular benzyl alcohol, N-cyclohexylpyrrolidone, phenoxypropanol or phenoxyethanol , are largely excluded.

The particular advantage of the process product obtained according to the invention as such is evident in its use. The use for the manufacture of clothing and equipment applies, in particular flame-retardant or fire-retardant textiles for personal protective clothing, in particular for military, fire brigade and police personnel, work clothing, face masks and protective hoods (balaclava), gloves, underwear (long-sleeved -shirts, Long-Johns), covers for hot-air balloons or for use in the contract sector, as particularly preferred.

In accordance with the above preferred embodiments of the invention, the following statements should be understood, which on the one hand relate to further advantageous developments, but are also intended to explain the method according to the invention presented in detail above:
The process according to the invention can be carried out on many standard dyeing apparatus and machines in the textile industry. These include discontinuous processes which are carried out in the form of exhaust or piece dyeing using liquor ratios customary in practice. For example, a jigger, a winch or a dye jet can be used for exhaust dyeing. Other dyeing methods of piece dyeing or yarn dyeing, such as dyeing on the beam or on the bobbin, are particularly advantageous embodiments of the method according to the invention. When working according to the exhaust process, dyeing is preferably carried out from the vat and under HT conditions in suitable overpressure containers. The leuco dye is first vatted in an alkaline medium by adding a reducing agent, then brought into contact with the fiber material and oxidized or fixed after uniform absorption. The alkaline medium is preferably brought to a pH of 9 to 13.5, in particular with sodium hydroxide solution, potassium hydroxide solution and/or ammonia from 10 to 11. The vatting is preferably carried out with a reducing agent in the form of an HT-stable formaldehyde sulfoxylate or hydroxymethane sulfinate. The oxidation or re-oxidation of the leuco dye is preferably carried out using hydrogen peroxide or atmospheric oxygen.

Intermediate measures are possible. Thus, the leuco dye located on the fiber is expediently fixed by means of suitable measures, with various advantageous options being available, such as dry heat fixing, steam fixing and dyeing. These measures are discussed below.

In principle, the above application method corresponds to the prior art, but with the difference that the dyeing liquors contain urea or suitable urea derivatives instead of a carrier. In particular, it is up to the person skilled in the art to carry out the dyeing according to measure b) or also according to measure a), in which extremely finely divided vat pigments are used. Here, therefore, the vatting is dispensed with.

Due to the odor neutrality of urea, however, a continuous procedure is also possible. Here, the fiber materials containing m-aramid are first impregnated with the urea-containing vat dye liquor using a suitable applicator. The dye liquors are also referred to as padding liquors. Padding liquor is understood to be a highly concentrated solution of one or more dyes, with which a textile web is impregnated using a suitable application device. Suitable application devices are, for example, a foulard, a squeegee, roller or doctor blade systems. A padder is preferably used in the method according to the invention.

Process a) is preferred for the continuous procedure. However, working according to method b) is not excluded.

After application and optional pre-drying, the dye is then fixed by heat treatment when working according to the preferred process variant a). The actual fixing reaction of the dye in the m -aramid fiber takes place according to the usual industrial processes using dry heat at temperatures between 150 and 250°C or using superheated steam at 120 to 170°C. The heat treatment is carried out by the usual methods textile equipment. These are known to the person skilled in the art and can be varied in design and adapted to the respective situation in operation. It can be carried out, for example, by the pad steam method (pad steaming method) or by the pad dry method (pad dry heat setting method). These continuous methods can be carried out, for example, with a damper or a clamping frame or a roller skid. During this heat treatment step, urea acts as a moisture-regulating medium due to its hygroscopicity. As a result, a constant moist level on the fiber surface is maintained for a relatively long time, so that drying out is avoided and an environment favorable for dye diffusion is thus maintained.

If process variant b) is used for the continuous process, the dye liquor is vatted before it is applied to the fiber material. The heat treatment is technically carried out according to the possibilities presented in the previous section. The fixation reaction in the fiber occurs through subsequent oxidation of the applied dye by suitable oxidizing agents (see above), thereby converting the dye to its insoluble form.

The m-aramid materials colored by the process according to the invention are distinguished by good to very good color fastness. In contrast to ordinary carriers, the fastness properties are not adversely affected by the addition of urea. This is due to the fact that the urea is completely removed in the washing processes after the dyeing, while more or less large amounts can still be analytically detected with conventional carriers, depending on the intensity of the washing processes (see example 1). Particular carriers to be mentioned are benzyl alcohol, 2-phenoxyethanol, acetophenone, phenols such as o-phenylphenol or chlorocresols. The amount of carrier that can be determined analytically by chromatography in the colored m-aramid fibers produced according to the invention is therefore below the detection limit, but is <0.1 ppm.

Particularly good light fastness grades are possible with the vat pigment process. The combination of a foulard and a tenter is suitable as the preferred process for the vat pigment dyeing of m -aramid. The concentration of the vat dye pigments and the urea in the dye liquor can be varied over a wide range. The concentration of the vat dye pigments is generally based on the usual specifications. These include the depth of color to be achieved and the desired shade. The preferred urea concentration in the padding liquor is between 0.1 mol I ^-1 and 6.5 mol I ^-1 , preferably between 1.5 and 4 mol I ^-1 and particularly preferably between 2.3 and 3.5 mol I ^-1 . It is also particularly advantageous to comply with the following framework conditions: 0.4 to 6.5 moles of I ^-1 , in particular 0.6 to 6.5 moles of I ^-1 , particularly preferably from 0.8 to 6.5 moles of I ^-1 and completely particularly preferably 1 to 6.5 moles of I ^-1 .

In addition to one or more vat dyes, in pigment form or dissolved in the leuco form, and urea and/or urea derivative, the dye liquor according to the invention may contain other auxiliaries. Mention should be made of migration inhibitors, leveling aids, defoamers, softening aids, complexing agents and sequestering agents, and salts. Other additives are not excluded, provided they do not adversely affect the stability of the dye liquor.

A particular advantage of the process according to the invention results when the vat dyes are used in a mixture both in process step a) and in process step b). In contrast to dyeing in the dope, this allows graded bichrome or trichrome dyeings, the realization of which is desirable for the purpose of achieving specific color templates. This means that in addition to special shades, coloring in melange shades is also possible. Dyed m -aramid-containing fiber materials are obtained which are characterized by a light fastness according to DIN EN ISO 105 B-02 (50° C. and 72 h exposure) of at least 4, a wash fastness according to DIN EN ISO 105-C08 of at least 4 and rubbing fastness according to DIN EN ISO 105-X12 dry of at least 2-3. It is particularly advantageous if the light fastness of the m-aramid-containing fiber materials colored according to the invention is at least 4-5, their fastness to washing is at least 4-5 and/or their fastness to rubbing is at least 3. Commercial vat dyes can be used to implement the invention.

When implementing the invention, the person skilled in the art is free to use suitable preliminary tests to select those vat dyes which are particularly advantageous in the context of the invention.

In contrast to spun-dyed fibers, the colored fibers produced by the process according to the invention no longer contain any spinning solvents, since these are largely extracted from the fibers in the course of the dyeing and the subsequent scouring. Spinning solvents which may be mentioned in particular are spinning solvents which are harmful to health or classified as CMR substances, such as dimethylacetamide, dimethylformamide or dimethylimidazolidinone. The spinning solvent content in the m-aramid fibers dyed according to the invention is less than 1 ppm.

A further advantage of the process according to the invention is that the elastic properties of the dyed m-aramid-containing textiles are largely retained. Because of the milder fixing conditions that prevail, the process according to the invention is therefore also particularly suitable for dyeing knitted goods. The effect of carriers leads to increased swelling of the fibers and mobility of the molecular chains of the m-aramids under the hydrothermal conditions of HT dyeing. After drying, knitwear therefore generally has a stiffer handle and reduced elasticity, which is perceived as a problem. By eliminating carriers from the dyeing liquor, this swelling step is no longer necessary in the process according to the invention. Substances with a hydrotropic effect, such as urea, only have a marginal effect on fiber swelling in m-aramid fibers, so that the elasticity of the knitted goods obtained with the claimed dyeing process is largely retained (see Example 6).

When dyeing fiber blends made of m-aramid with other flame-retardant fibers such as Viscose FR, Modal FR or Lyocell FR (FR=flame retardant), the flame retardant added to the cellulose fiber is not extracted. As a result, the flame resistance of the corresponding fiber blends is hardly changed by the dyeing process. Corresponding experiments with numerical data on the value of the Limiting Oxygen Index (LOI) are given in Example 9. The LOI is a measure of the quality of the flame retardant finish. The LOI according to ASTM D2863 gives the limit of the volume fraction of oxygen in an oxygen/nitrogen gas mixture again, in which a textile fabric just barely burns from top to bottom. The higher the LOI value, the better the flame retardant effect. From a LOI of 24 one speaks of flame-retardant properties and with values of 27 and higher of self-extinguishing properties. According to general consensus, inherently flame-retardant fiber materials with the addition "FR" (FR = flame retardant) have an LOI of at least 28. The LOI of common Nomex ^® articles is between 28 and 30.

It seems appropriate to emphasize the basic idea of the invention again. The teaching according to the invention includes urea or a suitable urea derivative as an essential component in the dyeing formulations. Urea and urea derivatives serve as a substitute for the toxic carriers that are usually used. As determined, the required amount used is preferably in a range that is also customary for carriers (50-100 g/l). In this regard, reference is made to Example 2 below (Table 7). The determined maximum in relation to the depth of color is around 2 mol/l urea (corresponding to 120 g/l). It is assumed that the urea - similar to a carrier - promotes fiber swelling and thus dye absorption.

Tests in the range from 6 to 60 g/l (corresponding to 0.1 to 1 mol) showed depths of color for olive (Ci. Wet Vat Green 26) according to Table 7 below. Reference is made to Examples 6 and 7 below for carrying out the tests.

The invention is to be explained in more detail using the following examples.

• Gerät: Xenotest Beta LM der Fa. Atlas
• Lichtechtheit bei 50 °C
• Bewertung nach 72 Stunden Belichtung
• Bestimmung der Waschechtheit nach EN ISO 105-C08:
• Prüfung A1M mit Mehrfaser-Begleitgewebe
• 40°C / 150 ml / 45 min / 10 Stahlkugeln
• 4 g/l Skip-Waschmittel (ohne opt. Aufheller)
• Bestimmung der Reibechtheiten trocken/nass nach EN ISO 105 - X12:
• Begleitgewebe Baumwolle, ISO 105 - F09

The lightfastness was determined in all examples according to DIN EN ISO 105-B02, July 2002:

• Device: Xenotest Beta LM from Atlas
• Light fastness at 50 °C
• Rating after 72 hours exposure
• Determination of wash fastness according to EN ISO 105-C08:
• Test A1M with multi-fiber adjoining fabric
• 40°C / 150 ml / 45 min / 10 steel balls
• 4 g/l skip detergent (without optical brightener)
• Determination of rub fastness dry/wet according to EN ISO 105 - X12:
• Accompanying fabric cotton, ISO 105 - F09

Example 1 (exhaust dyeing of piece goods/process step b)):

• Farbstoffflotte 1 für den Farbton Oliv:
  5% C.I. Vat Green 13, bezogen auf das Gewicht des Fasermaterials
• Farbstoffflotte 2 für den Farbton Pantone:
  2,5% C.I. Vat Brown 9 + 2,1% C.I. Vat Orange 29
• Farbstoffflotte 3 für den Farbton Gelblich-Blau:
  1,7% C.I. Vat Blue 4 + 0,6% C.I. Vat Green 1 + 0,3% C.I. Vat Yellow 28
• Farbstoffflotte 4 für den Farbton dunkeloliv:
  6,0% C.I. Vat Black 9 + 2,5% C.I. Vat Green 1

The dyeings were carried out in the form of exhaust dyeings on the dyeing beam. A knitted fabric called Nomex ^Comfort® , consisting of 93% ^Nomex® , 5% ^Kevlar® and 2% antistatic fibers, was used. Aqueous liquors with the following composition were prepared: The liquors each contained 90 g/l of urea, 6 g/l of stabilized formaldehyde sulfoxylate (Rongal HT reducing agent), 10 ml/l of 32.5% strength by weight sodium hydroxide solution and 2 g/l of a dispersing agent (Naphthalenesulfonate).

• Dye liquor 1 for the shade olive:
  5% CI Vat Green 13 based on the weight of the fiber material
• Dye liquor 2 for the Pantone shade:
  2.5% CI Vat Brown 9 + 2.1% CI Vat Orange 29
• Dye liquor 3 for the shade of yellowish blue:
  1.7% CI Vat Blue 4 + 0.6% CI Vat Green 1 + 0.3% CI Vat Yellow 28
• Dye liquor 4 for the shade dark olive:
  6.0% CI Vat Black 9 + 2.5% CI Vat Green 1

• Färbung:
  • Mit 3°C/min auf 115°C aufheizen, 35 min bei 115°C
  • Abkühlen
• Oxidation:
  4 g/l Wasserstoffperoxid (35%-ig), pH 5, 35 min bei Raumtemperatur.
• Seifen und Spülen:
  • 1. Bad: 1,5 g/l Dispergator, 10 min bei 100°C
  • 2. Bad: 1 g/l anionaktives Tensid, 15 min bei 100°C
  • 3. Bad: deionisiertes Wasser, 10 min bei 100°C
  • 4.-6. Bad: deionisiertes Wasser, 80°C, je 3 min

The goods were dyed in the package (beam) in 400 ml dyeing beakers in a Turbomat (from Ahiba) at a liquor ratio of 1:12.

• Coloring:
  • Heat at 3°C/min to 115°C, 35 min at 115°C
  • cooling down
• Oxidation:
  4 g/l hydrogen peroxide (35%), pH 5, 35 min at room temperature.
• Soaps and rinses:
  • 1st bath: 1.5 g/l dispersant, 10 min at 100°C
  • 2nd bath: 1 g/l anionic surfactant, 15 min at 100°C
  • 3rd bath: deionized water, 10 min at 100°C
  • 4th-6th Bath: deionized water, 80°C, 3 min each

The color depths of the dyeings are shown in the table below based on the K/S value. The values in brackets for the K/S values and light fastness grades stand for the corresponding dyeings without the addition of urea. <u>Table</u> 1a: Color depths (K/S values) and lightfastness grades color liquor Color depth K/S lightfastness grade 1 (olive), 440 nm 4.22 (0.73) 4-5 (3) 2 (Pantone), 500nm 2.60 (0.61) 5 (3-4) 3 (blue-yellow), 600 nm 1.48 (0.35) 5 (4) 4 (dark olive), 600 nm 8.60 (2.70) 5-6 (4)

Comparison example 1:

The dyeings were carried out identically, with the difference that instead of urea in the dye liquor, 70 g/l of benzyl alcohol was added as a carrier (dye liquor "No.-BA"). <u>Table 1 V</u>: Color depths (K/S values) and lightfastness grades for carrier dyeing with benzyl alcohol color liquor Color depth K/S lightfastness grade 1-BA, 440nm 3.72 3-4 2-BA, 500nm 2.06 3-4 3-BA, 600nm 1.35 4 4-BA, 600nm 7.90 4-5

The fiber materials dyed with carrier, oxidized and rinsed were extracted with isopropanol in a Soxhlet extractor and the content of benzyl alcohol in the extracts was determined by means of HPLC. Based on the fiber weight, the amount of benzyl alcohol is on average 0.33% by weight (±0.3% by weight).

Example 2 (yarn dyeing/process step b)):

• Farbstoffflotte 5 für den Farbton Oliv:
  • 5% C.I. Vat Green 13 (bezogen auf das Gewicht des Fasermaterials) 38 ml/l Natronlauge 32,5%-ig
  • 11 g/l Rongal Reducer HT (stab. Formaldehydsulfoxylat)
• Varianten:
  1. a) ohne weiteren Zusatz
  2. b) 30 g/l 2-Phenoxyethanol
  3. c) 150 g/l Harnstoff
• Färbung:
  • Aufheizen der Flotte auf 60°C und dann mit 3°C/min auf 115°C aufheizen 35 min bei 115°C
  • Oxidation, Seifen und Spülen analog Beispiel 1.

Tabelle 2: Farbtiefen (K/S-Werte) und Lichtechtheitsnoten Farbflotte 5 Variante Farbtiefe K/S (440 nm) Lichtechtheitsnote a) 0,81 3-4 b) 3,77 3-4 c) 4,43 4-5 An m-aramid yarn of the designation Yantai ^Newstar® 50/1 Nm wound on a dye bobbin was used. Yarn dyeing was carried out in a laboratory bobbin dyeing machine (Mathis AG, CH-Oberhasli) with a liquor ratio of 1:5.

• Dye liquor 5 for the shade olive:
  • 5% CI Vat Green 13 (based on the weight of the fiber material) 38 ml/l 32.5% sodium hydroxide solution
  • 11 g/l Rongal Reducer HT (stab. formaldehyde sulfoxylate)
• Variants:
  1. a) without further addition
  2. b) 30 g/l 2-phenoxyethanol
  3. c) 150 g/l urea
• Coloring:
  • Heat up the liquor to 60°C and then at 3°C/min to 115°C 35 minutes at 115°C
  • Oxidation, soaping and rinsing analogous to example 1.

<u>Table</u> 2: Color depths (K/S values) and lightfastness grades Color fleet 5 variant Color depth K/S (440 nm) lightfastness grade a) 0.81 3-4 b) 3.77 3-4 c) 4.43 4-5

Example 3 (exhaust dyeing without Verkupuna/process step a)):

Exhaust dyeing was carried out in a Labomat beaker dyeing apparatus from Mathis AG with dye liquor 2 from Example 1 at a liquor ratio of 1:20, but without the additives sodium hydroxide solution and formaldehyde sulfoxylate (Rongal HT reducing agent). The conditions of the dyeing and the soaping/rinsing process were identical, the oxidation step was omitted. The dyeings contained 150 g/l of urea (= liquor 6 ) and 70 g/l of benzyl alcohol (= liquor 6-BA ). <u>Table</u> 3: Color depths (K/S values) and lightfastness grades Color fleet Pantone Color depth K/S (500 nm) lightfastness grade 6 2:15 4-5 6-BA 1.72 3-4

Example 4 (pad steam or pad steam process/process step a)):

Fabric with the designation Nomex ⁽ R) III from DuPont du Nemours consisting of 95% Nomex ^(R) , 5% Kevlar ^(R ) (p-aramid) was used for the tests. The fabric had a basis weight of 262 g/m ² and moderate crystallinity.

• x,y,z g/l Farbstoff
• 150 g/l Harnstoff (= 2,5 Mol/l)
• 2 g/l Dispergator (Naphthalinsulfonat)
• pH 6-7

1. a) Farbton Pantone (braun):
   Farbflotte 7: 30,1 g/l C.I. Vat Brown 9 + 25,3 g/l C.I. Vat Orange 29
2. b) Farbton Oliv:
   Farbflotte 8: 43 g/l C.I. Vat Green 13

The fabric, measuring 45 cm×30 cm, was prewashed in a weakly alkaline medium with the addition of surfactants customary for this purpose and dried. A padding liquor with the following composition was then applied using a foulard:

• x,y,zg/l dye
• 150 g/l urea (= 2.5 mol/l)
• 2 g/l dispersant (naphthalene sulfonate)
• pH 6-7

1. a) Pantone color (brown):
   Dye liquor 7 : 30.1 g/l CI Vat Brown 9 + 25.3 g/l CI Vat Orange 29
2. b) Color olive:
   Dye liquor 8 : 43 g/l CI Vat Green 13

• Flottenaufnahme: jeweils 70%
• Vortrocknung: Dämpfer ohne Feuchte 2 min, 100°C, 20% Gebläse
• Fixierung:
  Dämpfer: 5 min, 155°C, 45% Dampf
• Nachseifen und Spülen erfolgten analog Beispiel 1.

In addition, the liquors without urea were used as a comparison for both shades and dyed analogously (= liquor numbers 9-7 and 9-8).

• Fleet pickup: 70% each
• Pre-drying: Steamer without moisture 2 min, 100°C, 20% fan
• fixation:
  Steamer: 5 min, 155°C, 45% steam
• Soaping up and rinsing were carried out in the same way as in example 1.

Color depth was determined using K/S values; for dye liquor 7 (Pantone) at 500 nm and for dye liquor 8 (olive) at 440 nm. The light fastness grades achieved for the urea-free dye liquors Nos. 9-7 and 9-8 are given in brackets in Table 4b. <u>Table</u> 4a: Color depths (K/S values) color liquor Shade Pantone K/S (500) Shade olive K/S (440 nm) 7 2.37 - 8th - 4.10 9-7 / 9-8 0.82 1:13 dye liquor lightfastness grade 7 (Pantone) 5-6 (4-5) 8 (olive) 5-6 (4)

Comparative example 2 (with carrier):

• Farbflotte 10: 30 g/l 2-Phenoxyethanol
• Farbflotte 11: 70 g/l Benzylalkohol
• Farbstoffflotte Nr. x,y-7: Farbton Pantone
• Farbstoffflotte Nr. x,y-8: Farbton Oliv

Tabelle 4 V a: Farbtiefen (K/S-Werte) Farbstoffflotte Farbton Pantone K/S (500 nm) Oliv K/S (440 nm) 10-7 / 10-8 2,09 3,61 11-7 / 11-8 2,04 3,45 Tabelle 4 V b: Lichtechtheitsnoten Farbstoffflotte Pantone Oliv 10-7 / 10-8 4 3-4 11-7 / 11-8 4 4 The dyeings were carried out with process parameters which are identical to those of Example 4. However, two commercially available carriers were used in the formulations instead of urea.

• Dye liquor 10: 30 g/l 2-phenoxyethanol
• Dye liquor 11: 70 g/l benzyl alcohol
• Dye liquor No. x,y-7: Pantone shade
• Dye liquor No. x,y-8: shade olive

<u>Table 4 V a:</u> Color depths (K/S values) dye liquor Hue Pantone K/S (500nm) Olive K/S (440 nm) 10-7 / 10-8 2.09 3.61 11-7 / 11-8 2.04 3.45 dye liquor Pantone Olive 10-7 / 10-8 4 3-4 11-7 / 11-8 4 4

Example 5: (Dyeing of a highly crystalline m-aramid by the pad-dry, thermosol or pad-dry process on the stenter, process step a))

A fabric with the designation ^Nomex® 450 from DuPont de Nemours was used for the tests, consisting of 100% m-aramid with high crystallinity. The weight per unit area was 140 g/m ² , the yarn count was Nm 60/2. The dyeing formulations corresponded to those from Example 4. The liquor pick-up was 74%. The dyeings were pre-dried and fixed on a tenter at 100° C./2 min, respectively. 180°C / 3 min.

Tabelle 5d: Reibechtheiten Farbflotte trocken nass 7 3-4 3 8 3-4 3 11-7 / 11-8 3-4 / 3 2-3 / 2-3 Soaping up and rinsing were carried out in the same way as in example 1. <u>Table</u> 5a: Color depths (K/S values) dye liquor Hue Pantone K/S (500nm) Shade olive K/S (440 nm) 7 2.76 - 8th - 3.45 9-7 / 9-8 0.46 0.69 11-7 / 11-8 2.41 3.22 dye liquor Hue Pantone Hue olive 7 5 - 8th - 4-5 11-7 / 11-8 4 3-4

color liquor dry wet 7 3-4 3 8th 3-4 3 11-7 / 11-8 3-4/3 2-3 / 2-3

Example 6 Dyeing of a ^Nomex® Comfort knitted fabric on the stenter/process step a)) A ^Nomex® Comfort knitted fabric consisting of 93% ^Nomex® , 5% ^Kevlar® and 2% antistatic fibers was used.

The liquor pickup was 93%. The pre-drying and fixing of the dyeings took place on a tenter at 100° C./2 min and 180° C./3 min. The amount of urea in the liquors was 150 g/l in each case (similarly to Example 4).

Subsequent washing and rinsing were carried out analogously to example 1. <u>Table</u> 6a: Color depths (K/S values) dye liquor Hue Pantone K/S (x nm) Shade olive K/S (440 nm) 7 3.7 - 8th - 4.7 10-7/ 10-8 2.2 0.6 11-7 / 11-8 2.9 4.0 dye liquor Lightfastness Pantone Light fastness olive 7 5-6 - 8th - 5 10-7 / 10-8 4 4 11-7 / 11.8 4 3-4

Hysteresis measurements were carried out on the differently treated knitwear using a tensile tester (universal tensile tester from Zwick). The force at 38% elongation and the residual elongation after relief were determined. In accordance with DIN 53835-13, stretching/relief cycles were carried out with a specified yield strength of 38%. The mean values from 5 individual determinations were determined in each case. <u>Table</u> 6c: Values for force absorption and permanent strain in the hysteresis test (at a maximum strain of 38%) F _38.1 [cN] ε _remainder,1 [%] F _38.2 [cN] ε _remainder,2 [%] starting goods 6,870 9.9 6,000 11.0 colored without additives 5,289 10.9 4,419 12.6 Staining Pantone with urea, No. 7 8,873 11.1 7,519 11.1 Stain Pantone with benzyl alcohol, No. 10-7 4,300 12.4 3,675 12.4 F _38.1 and F _38.2 : force at 38% elongation in the 1st and 2nd cycles, respectively
ε _rest,1 and ε _rest,2 : permanent strain after the 1st or 2nd cycle.

In order to explain:

The higher the force absorption and the smaller the permanent elongation, the better the material behaves in terms of its elastic properties.

Example 7: (concentration series of urea/process step a))

As in example 6, a knitted fabric called ^Nomex® Comfort was used. The procedure was analogous to example 6 with a variable urea concentration in dye liquors 7 and 8. <u>Table</u> 7: Color depths (K/S values) Concentration of urea in the dye liquor [mol/l] Hue Pantone K/S (500nm) Shade olive K/S (440 nm) 0 1:18 0.58 0.1 - 0.6 0.25 - 0.7 0.4 - 1.1 0.7 - 2.5 1 3.43 4.22 2 3.66 4.69 3 3.61 4.50 4 3.30 4.45

Example 8: (dyeing of a fiber mixture)

A fabric made from 63% ^Nomex® /30% viscose FR/5% ^Kevlar® and 2% antistatic fibers with a surface weight of 290 g/m ² and dimensions of 40 cm×30 cm, prewashed, was used.

The two dye liquors 7 and 8 were used. The liquor pickup was 70%. The pre-drying and fixing of the dyeings took place analogously to Example 5 in a tenter at 100° C./2 min or 180° C./3 min.

Furthermore, for both color shades, the liquors without urea but with carrier benzyl alcohol were prepared as a comparison and dyed analogously (= liquor nos. 10-7 and 10-8). <u>Table</u> 8a: Color depths (K/S values) color liquor Pantone K/S (500nm) Olive K/S (440 nm) 7 2.77 - 8th - 3.97 10-7 / 10-8 1.63 2.71 dye liquor Pantone Olive 7 5 - 8th - 4-5 10-7 / 10-8 3-4 3-4

Example 9:

The fiber blend fabric from Example 8 was used and, as described in Example 1 using the vat process, with the urea-containing dye liquor 1 and the benzyl alcohol-containing dye liquor 1-BA in the exhaust process on the dyeing beam (laboratory dyeing machine "Turbomat" from Ahiba) at a liquor ratio of 1:12 colored. For comparison, a dyeing of the fiber material without addition of urea or carrier was dyed under identical parameters (dye liquor 1-0). Then, as described in Example 1, it was oxidized, resoaped and rinsed. After drying and conditioning in a standard climate, the Limiting Oxygen Index of the colored materials was determined in accordance with ASTM D2863. <u>Table</u> 9: Limiting Oxygen Index dye liquor LOI 1 (with urea) 31:6 1 BA 27.9 1-0 33.4

Claims (20)

1. A method for producing coloured fibrous materials on the basis of m-aramid fibres or m-aramid-fibre-containing fibre mixtures subsequently dyed with vat dyes, characterised in that the m-aramid fibres are subsequently dyed with vat dyes by

   a) applying vat dyes in an aqueous dispersion containing urea and/or homologues and/or derivatives of urea directly to the m-aramid fibres or the m-aramid-fibre-containing fibre mixtures, and then carrying out a fixing of the vat pigment on the fibrous materials, or

   b) transforming the vat dyes into the leuco form by the addition of reducing agents in an alkali medium, the resulting vat containing urea and/or homologues and/or derivatives of urea, and bringing the vat into contact with the m-aramid fibres or the m-aramid-fibre-containing fibre mixtures, forming the vat dyes oxidatively from the leuco form, and carrying out a fixing of the vat dyes on the fibrous materials.
2. The method according to claim 1, characterised in that the m-aramid fibres and the m-aramid-fibre-containing fibre mixtures are based on fibre flocks, fibre tows, wool tops, rovings, yarns, woven fabrics, knitted fabrics, especially weft-knitted fabrics and warp-knitted fabrics, braids or non-woven fabric.
3. The method according to claim 1 or claim 2, characterised in that further fibres that can be dyed with vat dyes are contained in the m-aramid-containing fibre mixtures, especially contained in the form of viscose, modal, lyocell, polyamide and/or polypropylene fibres and/or wool, the further fibres preferably being inherently flame-retardant and having an LOI according to ASTM D2863 of at least 23, especially of at least 27.
4. The method according to claim 3, characterised in that the further fibres are present as cellulose fibres, regenerated cellulose fibres, aliphatic, aliphatic-aromatic and aromatic polyamide fibres and/or polyester fibres.
5. The method according to claim 3 or claim 4, characterised in that the further fibres, in relation to the total weight of the fibre mixtures, account for approximately 1 to 75 wt.%, especially approximately 5 to 60 wt.%.
6. The method according to at least one of claims 1 to 5, characterised in that the vat dyes in method step a) have a particle size of approximately 0.1 to 3 pm, especially of approximately 0.2 to 0.8 pm.
7. The method according to at least one of the preceding claims, characterised in that the vat dyes are used in the form of indigo dyes, indigo derivative dyes, anthraquinone dyes, anthraquinone oxazole dyes, anthraquinone carbazole dyes, indanthrone dyes, flavanthrone dyes, benzanthrone dyes or pyranthone dyes or sulphur dyes, the vat dyes preferably being used as C.I. Vat Green 1, Vat Green 13, C.I. Vat Red 32, C.I. Vat Red 10, C.I. Vat Blue 4, C.I. Vat Blue 20, C.I. Vat Yellow 28, C.I. Vat Orange 29, C.I. Vat Brown 9, C.I. Vat Black 9 and/or C.I. Sulphur Black 9.
8. The method according to at least one of the preceding claims, characterised in that the aqueous dispersion in method step a) and the vat in method step b) are applied continuously by a pad, slop pad or a doctor blade or the bringing into contact with the fibrous material is carried out in the form of a discontinuous exhaust method.
9. The method according to at least one of the preceding claims, characterised in that the aqueous dispersion in method step a) and the vat in method step b) contain approximately 0.1 to 10 mol/l, especially 1 to 5 mol/l, and especially preferably 2 to 4 mol/l of urea and/or urea derivative.
10. The method according to one of the preceding claims, characterised in that the aqueous dispersion in method step a) and the vat in method step b) contain approximately 0.4 to 10 mol/l, preferably 0.6 to 10 mol/l, and especially 0.8 to 10 mol/l of urea and/or homologues and/or derivatives of urea.
11. The method according to at least one of the preceding claims, characterised in that the vat dyes are contained in the aqueous dispersion of method step a) in a concentration from 1.5 to 110 g/l, especially from 5 to 60 g/l, and are contained in the alkali medium in method step b) in a concentration from 0.05 to 30 g/l, especially from 0.2 to 20 g/l.
12. The method according to at least one of the preceding claims, characterised in that a post-dyeing soaping step is carried out following the forming of the vat dyes in method step b) .
13. The method according to at least one of the preceding claims, characterised in that the fixing of the vat dyes in method step a) and method step b) is carried out as

    a) dry heat fixing between 140 and 260°C, especially between 170 and 220°C, (Thermosol method),

    b) vapour fixing at a temperature between 100 and 160°C, especially between 110 and 155°C, and/or

    c) exhaust dyeing between 70 and 150°C, especially between 98 and 125°C.
14. The method according to at least one of the preceding claims, characterised in that when carrying out the method carrier materials, especially benzyl alcohol, acetophenone or 2-phenoxyethanol, are largely excluded.
15. Coloured fibrous materials on the basis of dyed m-aramid-fibre-containing fibre mixtures, characterised in that the fibre mixtures, in addition to the m-aramid fibres, also contain further fibres and are dyed with vat dyes and have a content of carriers of less than 15 ppm, especially less than 10 ppm, obtainable by the method according to at least one of claims 1 to 14, wherein the further fibres preferably being present in the form of viscose fibres, modal fibres, lyocell fibres, polyamide fibres, polypropylene fibres, cellulose fibres, regenerated cellulose fibres, aliphatic, aliphatic-aromatic and aromatic polyamide fibres, polyester fibres and/or wool.
16. Coloured fibrous materials according to claim 15, characterised in that the coloured fibrous materials are present in the form of coloured fibre flocks, fibre tows, wool tops, rovings, yarns, woven fabrics, knitted fabrics, especially weft-knitted fabrics and warp-knitted fabrics, braids or non-woven fabric.
17. Coloured fibrous materials according to claim 15 or claim 16, characterised in that the fibre mixtures have a light fastness (according to DIN EN ISO 105 B-02 (50°C and 72 h exposure)) of at least 4.
18. Coloured fibrous materials on the basis of dyed m-aramid fibres, characterised in that the dyed m-aramid fibres are dyed with vat dyes and have a content of carriers of less than 15 ppm, especially less than 10 ppm, and a light fastness (according to DIN EN ISO 105 B-02 (50°C and 72 h exposure)) of at least 4, obtainable by the method according to at least one of claims 1 to 14, wherein the coloured fibrous materials preferably being present in the form of coloured fibre flocks, fibre tows, wool tops, rovings, yarns, woven fabrics, knitted fabrics, especially weft-knitted fabrics and warp-knitted fabrics, braids or non-woven fabric.
19. Coloured fibrous materials according to at least one of claims 15 to 20, characterised in that they have a content of carriers of less than 5 ppm, especially less than 1 ppm.
20. Use of the coloured fibrous materials according to one of claims 15 to 19 or obtainable by a method according to at least one of claims 1 to 14 for the production of clothing and items of equipment, especially of flame-retardant or fire-protection textiles for personal protective clothing, especially for military, fire-fighting and police personnel, of workwear, of face masks and protective hoods (balaclavas), of gloves, of undergarments (long-arm shirts, Long-Johns), of envelopes for hot air balloons, or for use in objects.