MXPA97005362A - Coloring preparations leuco de tina in the form of granu - Google Patents

Abstract

The present invention relates to a preparation of leucoindigo dye, in the form of granules, comprising, as essential constituents, leucoindigo and leuco forms of dye derivatives, a hydrosulfite and an alkali metal hydroxide.

Description

COLORING PREPARATIONS LEUCO DE TINA IN THE FORM OF GRANULES The present invention relates to new preparations of vat leuco dyes in the form of granules, comprising, as essential constituents, the vat leuco dye, a reductant and an alkali metal hydroxide. The invention also relates to the production of vat leuco dye preparations and their use in dyeing. Last, but not least, the invention relates to a process for stabilizing dry hydrosulfite against self-ignition. Indigoid dyes (particularly the indigo dye itself and its bromine derivatives, such as indigo or bright indigo) and anthraquinoid dyes (particularly nitroviolantrone (IC Vat Green 9)), are vat dyes that have been known since long ago and used to dye textile materials containing cellulose. For dyeing, the vat dye, which is insoluble in water, must first be converted by reduction (vat treatment) into its reactive leuco form to the fiber, soluble in water, and then it is then oxidized again to the vat dye pigment, insoluble in water, after absorption on the material to be dyed. In known dyeing processes, the vat dye is treated in an alkaline medium by the addition of inorganic reducers, such as hydrosulfite (sodium dithionite) and thiourea dioxide or, alternatively, the addition of organic reductants, such as the hydroxyacetone, in a container placed in front of the dyeing bath. Additional amounts, dependent on the machine, of the reducer during dyeing are used, since a part of the leuco dye is oxidized by contact with the air in the conduits thereof and on the surface of the tub bath and must be treated again in the tub, and that is why the reducer must be added to the dye bath. A disadvantage of the treatment of the vat dye using the reducers, is the high contamination of the effluent of the dyeing by the sulphate (around 3500 to 5000 mg / 1, measured in the effluent of a house of indigo dyes) in the case of the hydrosulfite or by substances that consume oxygen (COD values of approximately 8000 mg of oxygen / liter, measured in the effluent of a house of indigo dyes) in the case of hydroxyacetone. In the case of indigo dye, solid powdery pasty preparations of the leuco form are also described, which, as stabilizers, contain polyhydroxy compounds, such as glycerol and, in particular, compounds derived from sugars, for example molasses. , in mixture with alkali or zinc powder (patents DE 200 914 and 235 047). GB 276 023 also discloses preparations of leuco dyes in powder form, heating a mixture of unreduced vat dye, glycol, alkali, hydrosulfite and sodium sulfate and drying in an open container and subsequent grinding. In the case of the above-mentioned preparations, the sulfate content of the dyeing effluent can be effectively lowered, but, as a rule, these preparations are difficult to dose, since the dry preparations tend to form lumps and only dissolve slowly in the coloring bath. In the last case mentioned. the sulfate contamination is further increased, since sulfate is additionally added to the preparations, which already contain the sulphate produced by the reduction of the dye in the mixture, described above. The patent O-A-94/23114 discloses a dyeing process in which the indigo is used, in a reduced form previously, as an alkaline, aqueous solution obtained during the catalytic hydrogenation. In this way, the contamination of the effluent by the organic substances decreases and the sulphate contamination is reduced to the amount of hydrosulphite necessary as a result of air contact during the dyeing process. A disadvantage, however, is that the leucoin-code dye solution used is sensitive to oxidation and must be handled and stored with the exclusion of oxygen. In addition, the high water load of this solution is an obstacle, both during storage and during transport. Finally, the German patent application 43 27 221, which is not a previous publication, describes preparations of the leucoindigo dye in the form of granules, which contain this leucoindigo dye and an alkali metal hydroxide, as essential components. It is an object of the present invention to obtain preparations of vat leuco dyes, which do not have the aforementioned disadvantages and which can be used advantageously for dyeing. We have now found that this object is achieved by the preparations of vat leuco dyes in the form of granules, which, as essential constituents, contain the vat leuco dye, a reducer and an alkali metal hydroxide. We have additionally found a process for obtaining these preparations of vat leuco dyes, which comprises concentrating an aqueous alkaline solution of a vat leuco dye and a solution or suspension of the reductant in water and / or a water miscible solvent, to dryness , together with the complete mixture and excluding oxygen. Finally, we have found a process for dyeing a textile material, which contains cellulose, which comprises using the preparations of the vat leuco dye. Additionally, we have found a process to stabilize the dry hydrosulfite against self-ignition, which comprises the granulation by spraying an aqueous hydrosulfite solution together with a leuco dye solution of tub, excluding oxygen, in such ratio by weight that the resulting granules contain <50% by weight of hydrosulfite. The preparations, according to the invention, as a rule, contain from 20 to 80% by weight of the vat leuco dye, from 5 to 55% by weight of the reductant and from 3 to 20% by weight of an alkali metal hydroxide. . The vat leuco dyes used can be both the leuco forms of the antrcyquinoid and the leuco forms of indigo vat dyes. Preferred examples of vat dyes with I.C. Vat Green 9 and especially the indigo and tetrabromoindigo (bright indigo). Suitable reducers are, in principle, those which are solid at room temperature and stable at the temperature prevailing during the production of the preparations, according to the invention (even in the presence of alkali). The reducers, both inorganic and organic, are suitable, as they are also suitable for vat dyeing. The reducers can be used individually or in the form of mixtures. Examples of preferred organic reductants that may be mentioned are especially ochidroxycarbonyl compounds, such as a-hydroxyketones, which contain from 4 to 6 carbon atoms, for example, acetoin, glutaroin and adipoin, sugars, both aldose and ketoses, for example glucose, mannose and fructose, and enediols stabilized by an oc-keto function, which contain from 4 to 8 carbon atoms, for example reductive acid and ascorbic acid. A preferred inorganic reductant, which may be mentioned, is especially the hydrosulfite (sodium dithionite), which, at the same time, is also the preferred reductant for leuco dye preparations, according to the invention. Reducers which are also suitable are also the organic salts of iron (II) complexes, in particular those with aliphatic hydroxy compounds, such as those disclosed in DE-A-43 20 867.

Suitable alkali metal hydroxides are, in particular, potassium hydroxide and especially sodium hydroxide. Of course, mixtures of alkali metal hydroxides can also be used. The vat leuco dye is converted by means of the hydroxide into easily soluble alkali metal salts. The forms of leucoindigo, for example, mono- and / or di-salt, depend on the amount of the alkali metal hydroxide. The molar ratio of the vat leuco dye and the alkali metal hydroxide is, therefore, conveniently from about 1: 1 to 1:10, preferably from 1: 1 to the molar ratio necessary for the conversion of all the hydroxyl groups free contained in the salt form. In general, amounts of the reductant that are distinctly below 50% by weight, based on the vat leuco dye, are sufficient for the stabilization of the vat leuco dye during the storage of the granule preparation (protection from reoxidation). However, if a quantity of the reductant in the range of the aforementioned weight ratio for the preparations according to the invention (about 40 to 55% by weight) is selected, that is, based on the vat leuco dye , up to 65% by weight, the reoxidized amount of the vat dye, which is inevitably formed as a result of contact with the air during the dyeing process, can additionally be directly balanced, and thus no further reductant will be added to the dye bath. had. This amount of reducer can be adjusted by the slight variation of the dyeing interval used in each case. Thus, for example, in the case of preparations of the leucoindigo dye of particular interest, the amount of the preferred reducing hydrosulphite, necessary for stabilization, is, as a rule, from 5 to 30% by weight, in particular from 10 to 20% by weight. weight, based on the leucoindigo dye, which corresponds to a preparation having a preferred composition of 55 to 75% by weight of this leucoindigo dye, 10 to 20% by weight of hydrosulfite and 10 to 20% by weight of the hydroxide of alkali metal, while for the simultaneous compensation of the loss as a result of reoxidation during dyeing, amounts of 20 to 55% by weight, especially 25 to 35% by weight of the hydrosulfite, based on the leucoindigo dye, are recommended , which correspond to a preparation having a preferred composition of 40 to 60% by weight of this leucoin-dye colorant, 30 to 40% by weight of the hydrosulphite and 8 to 15% by weight of the alkali metal hydroxide. The dye thus no longer has to have any additional reducer at hand. This is of particular interest for the hydrosulfite reducer, which is customary in vat dyeing, since the hydrosulfite is present as a pure substance, ie not as a mixture with a < 50% by weight, which will be classified as a hazardous substance, in accordance with current safety procedures, due to its tendency to self-ignite and, therefore, is problematic during handling and storage. The use of vat leuco dye preparations, according to the invention, is not only easily dosable, stable in storage (stability in several weeks of storage at 50 ° C, with the admission of air), and the developed preparations contaminate the dye effluent in a distinctly smaller form compared to the use of unreduced vat dye and were rapidly soluble in the dyebath, a manner that was also found simultaneously to convert the hydrosulfite to a safe form suitable for dyeing. Essential for the stabilization of the vat leuco dye against reoxidation is its still permanent mixture with the reducer, which is guaranteed by the formula of granules according to the invention (as a rule, mainly spherical particles are present, which have an average size, in general, of 0.1 to 2 mm, preferably of 0.5 to 1.5 mm). The amount of the reducer, which exceeds the amount needed for stabilization and is only used to compensate the reoxidation during the dyeing, can also be subsequently mixed as a solid to the granules, which are already adequately stabilized by the reducer, it is also possible use a reducer that is different from the content in the granules. These blends can be adapted to the requirements of the particular dyeing interval in a particularly simple manner. In the production of the leucoindigo dye preparations, according to the invention, the aqueous solution, obtained during the preparation of this leucoindigo dye or its derivatives by catalytic hydrogenation, can be advantageously used directly for drying, after drying. removal of the catalyst. The catalytic hydrogenation itself can, in this case, be carried out as generally shown, for example by the reduction of an indigo alkaline paste (typically from 10 to 35% by weight of indigo, from 2 to 10% by weight of the hydroxide of alkali metal), using Raney nickel as a catalyst, at a hydrogen pressure, in general, from 2 to 10 bars and a temperature of, as a rule, 60 to 902C. The leucoindigo solutions obtained, as a rule, contain from 10 to 35, preferably from 15 to 30 and particularly preferred from 20 to 25% by weight of the leucoindigo. In a similar manner, starting from solutions of vat leuco dyes, suitable for dyeing, they can also be obtained in the case of vat anthraquinoid dyes. In the preparation process, according to the invention, the aqueous solutions of the vat leuco dye, together with a solution or suspension of the selected reductant in water and / or a water-miscible solvent, are used excluding oxygen, advantageously after of carrying out the inert state with a protective gas, such as nitrogen, and concentrating to dryness with complete mixing. In the case of the hydrosulfite, for example about 5 to 25, preferably 10 to 15% by weight of the aqueous solutions is recommended for this purpose. The vat leuco dye solution and the reducing solution (or suspension) can be mixed before or during the drying process, but the reductant can also be added directly to the vat leuco dye solution as a solid. The temperature of the product, necessary for drying, depends on whether the process is carried out under reduced pressure or not and is generally 70 to 902C or 105 to 130SC. During the drying process, the complete mixture of the liquid phase and the solid obtained must be guaranteed. Apparatus suitable for the large-scale process are, for example, rotary drum dryers, pallet dryers and mechanically cleaned contact dryers, in which the drying is preferably carried out under reduced pressure (from about 10 to 500 mbar). As a rule, the addition is recommended a time after drying of about 1 to 2 hours, at the drying temperature selected in each case, for actual drying. If appropriate, an additional coarse spray can be made inside or outside the drying apparatus. The process, according to the invention, can also be advantageously carried out in a spray drying plant, such as a spray tower and particularly a fluidized spray bed, in which the water is evaporated by the introduction of hot inert gas , preferably nitrogen. The dry product can thus be obtained directly with the desired particle size. It is recommended to cool the dried product to a temperature of, for example, <50QC, before removing it, in order to avoid re-oxidation in the hot state. With the aid of the process, according to the invention, the new leuco dye preparations of tub can be prepared continuously in the form of granules, in a simple manner ,, In general, the dried products will contain only a small amount (about <4% by weight) of the vat without reducing the vat.

The tub leuco dye preparations, according to the invention, are advantageously suitable for dyeing cellulose-containing textile materials. The dyeings obtained comply fully with the requirements. The contamination of the effluent with the sulfate is drastically reduced, compared to the use of unreduced dyes. Depending on the composition of the selected preparation of the vat leuco dye, the dyeing can also be carried out without the further addition of the reductant to the dyeing bath. EXAMPLES A) Obtaining the preparations of the leucoindi dye or, according to the invention. Example 1 A solution of 13% by weight of the leucoindigo dye (calculated as the free acid), 6% by weight of sodium hydroxide, 4% by weight of hydrosulphite (88% of starch) and 77% by weight of water, it was introduced slowly, at 10 mbar, in a rotary evaporator, made inert with nitrogen, and heated in an oil bath at 1402C, and concentrated to dryness at a rotation speed of 70 rp. After a drying time of 2 hours at the indicated temperature of the 140SC oil bath, the mixture was cooled to < 40SC. After coarse grinding, the granules had an average particle diameter of 1 mm. By extraction with water in a Soxhlet apparatus, an amount less than 1% (by-products and unreduced indigo) of water-insoluble substances was determined. Its composition was "57% by weight of the leucoindigo dye, 17% by weight of hydrosulphite and 26% by weight of sodium hydroxide. Example 2 A solution of 13% by weight of the dye leucoln-dye (calculated as the free acid), 6% by weight of sodium hydroxide, 4% by weight of hydrosulphite and 77% by weight of water, was granulated continuously by spraying in a fluidized bed, made inert with nitrogen, at a fluidized gas velocity of 1.2m / sec. The charge gas temperature was 1303C; the temperature of the waste gas was 902C and corresponds to the temperature of the product in the fluidized bed. The formed granules were removed from the fluidized bed by means of a screw conveyor and pneumatically transported to a storage vessel using a stream of nitrogen to cool to room temperature. The granules of the useful fraction had an average particle diameter of about 1 mm. The amount that was insoluble in the water was < 1% by weight The composition of the granules corresponded to the composition of the granules of Example 1.

Example 3 Similar to Example 1, a solution of 20% by weight of the leucoindigo dye (calculated as the free acid), 5% by weight of sodium hydroxide, 3.5% by weight of acetoin and 71.5% by weight of water, dried at an oil bath temperature of 1202C. In the granules obtained after the subsequent coarse grinding, having an average particle diameter of 1 mm, an amount less than 1% by weight insoluble in water was determined. Example 4 Similar to Example 3, a solution of 23% by weight of the leucoindigo dye (calculated as the free acid), 5% by weight of sodium hydroxide, 2.3% by weight of acetoin and 69.7% by weight of water was dried, The granules obtained, in a similar manner, contained an amount which was insoluble in water, of the < ?% in weigh. Example 5 Similar to Example 3, a solution of the 23% by weight of the leucolndigo dye (calculated as the free acid), 5% by weight of sodium hydroxide, 1.2% by weight of acetoin and 70.8% by weight of water.

The granules obtained, in a similar manner, contained an amount, which was insoluble in water, of < 1% by weight Example 6 Similar to Example 3, a solution of the 21. 5% by weight of the leucoindigo dye (calculated as the free acid), 4.8% by weight of sodium hydroxide, 1.1% by weight of glucose and 72.6% by weight of water. The granules obtained, after a coarse pulverization, had an average particle diameter of 0.8 mm and contained an amount, which was insoluble in water, of <1% by weight. Example 7 1490 g of an aqueous solution containing 21.5% by weight of the leucoindigo dye (320 g, calculated as the free acid), 5% by weight (74 g) of sodium hydroxide and 32 g of molasses, was concentrated to dryness in a Discotherm reactor, at an oil bath temperature of 1202C and a pressure of 30-50 mm Hg. After distilling and separating the solvent, the granules were dried for a further 2 hours at 120 ° C and then cooled to room temperature while maintaining the vacuum. The granules obtained contained an amount which was insoluble in water of < 1% by weight Example 8 Similar to Example 7, 510 g of an aqueous solution containing 23% by weight of the leucoindigo dye (117 g, calculated as the free acid), 5% by weight (25.5 g) of sodium hydroxide and 11.7 g of acid Ascorbic, dried. The granules obtained contained an amount which was insoluble in water, of 1.6% by weight. B) Dyeing with leucoíndiqo dye preparations. according to the invention Example 9 For dyeing, the usual amount of indigo dye was used, which has only one bath with a volume of 2000 liters of liquor, dipping four times and oxidation (4 passes). The yield of untreated cotton yarn, No. 12 and 4000 filaments, was 600 kg / h. The content of the indigo was 1.8%. Under the (standard) production conditions, the leucoindigo dye granules of Example 1 and, in a further dyeing experiment, the granules of this leucoindigo dye of Example 2, were allowed to enter the dye bath continuously in an amount of 23.5. kg / h, during the experimental period of 8 hours, to maintain the stationary (constant) conditions already established.

Using these leucoindigo dye granules, the distribution with separate addition of the reductant and / or base, which is necessary for the standard process, was possible. The dyed yarn had the same shade, depth of color and firmness as a yarn dyed in a conventional manner with the continuous addition of: 65 kg / h of the 20% strength leucoindigo dye solution (calculated as the free acid) kg / h of hydrosulfite at 88% strength 15 liters / hour of a solution of sodium hydroxide at 38S Bé.

Claims (8)

1. CLAIMS 1. A leucoindigo dye preparation, in the form of granules, comprising, as essential constituents, leucoindigo or leuco forms of indigo dye derivatives, a hydrosulfite and an alkali metal hydroxide.
2. 2. A preparation, as claimed in claim 1, which comprises »20 to 80% by weight of the leucoindigo dye, 5 to 55% by weight of the hydrosulfite and 3 to 20% by weight of a metal hydroxide alkaline.
3. 3. A process for obtaining leucoindry dye preparations, as claimed in claims 1 or 2, which comprises concentrating to dryness an aqueous alkaline solution of the leucoindigo or leuco form of an indigo dye derivative, and a solution or suspension of hydrosulfite in water and / or a water-miscible solvent, together with the complete mixture and with the exclusion of oxygen.
4. 4. A method, as claimed in claim 3, which is carried out under an atmosphere of inert gas and / or reduced pressure.
5. A process, as claimed in claims 3 or 4, in which the leucoindigo dye solution and the hydrosulfite solution or suspension are first mixed, or the hydrosulfite is introduced into the leucoindigo dye solution as a solid and then the mixture is subjected to drying.
6. 6. A process, as claimed in claims 3 to 5, which is carried out in a spray-drying plant.
7. 7. A process for dyeing textile material containing cellulose, which comprises using the leucoindigo dye preparations as claimed in claims 1 or 2.
8. 8. A method for stabilizing dry hydrosulfite against self-ignition, which comprises Spray granulation of an aqueous hydrosulfite solution, together with a leucoindigo dye solution, excluding oxygen, in such weight ratio that the resulting granules contain less than 50% by weight of the hydrosulfite.