EP0497298B1 - Process for the pad dyeing of cellulose fibers with black sulfur dyes - Google Patents

Description

The present invention is in the technical field of textile dyeing with sulfur dyes.

Sulfur dyes as such can be obtained by melting together suitable organic compounds with elemental sulfur or polysulfides. After coupling with sodium sulfide, the sulfur dyes are applied to the fiber in the form of their alkali-soluble, reduced compounds, where the original dye is re-formed by subsequent oxidation. The majority of all economically important sulfur dyes are black. Among the sulfur black dyes, those with the Color Index collective name C.I. Sulfur Black 1 is of the greatest importance.

Ecology is a problem with conventional dyeing with sulfur black using sodium sulfide or sodium hydrogen sulfide. Sulfide and hydrogen sulfide in the waste water and in the exhaust air are no longer acceptable for the future use of sulfur black. Problems arise from odor nuisance, acute toxicity and high COD values (chemical oxygen demand) in the wastewater.

The sulfide can be contained in the commercially available sulfur dye and / or it can be added in the dyeing application.

There have been many attempts in the last few years with alternative reducing agents in the dyeing application of sulfur dyes and vat dyes. None of these systems was able to solve the ecological problems for all dyes while maintaining or even optimizing a good color yield. Alternative reducing agents are, for example, sodium dithionite (hydrosulfite), Sodium sulfoxylate, sodium formaldehyde sulfoxylate, sodium boranate, hydroxyacetone, glyceraldehyde, thioglycolic acid, formamidine sulfinic acid and glucose.

All of these reducing agents, when stained with C.I. Sulfur Black 1 has disadvantages, especially with pad-steam coloring. You get, for example, an incomplete reduction of the dye (consequence: no color yield), an over-reduction (result: dye destruction), or you need a very precisely dimensioned amount of the reducing agent (consequence: the color tilts if the color parameters change slightly), which is certain practical application prevented.

It is known from glucose, for example, that color yields are always significantly lower than with sulfide and that the black that can be obtained is not very deep in color. Sodium dithionite is known to only have a precisely dimensioned amount which provides a high and reliable color yield and thus a deep black.

Mixtures and reaction products made from glucose and sodium dithionite have also been used to print cellulose fibers with vat dyes (Melliand, Textilberichte 1930, page 286).
However, an ecologically justifiable process for dyeing textiles with sulfur black dyes was still pending.

The object of the present invention was therefore to design the process for the block dyeing of cellulose fibers with sulfur black dyes in an ecologically favorable manner, that is to say while avoiding sulfides as reducing agents and at the same time high color yield, deep black tone, high security and good reproducibility.

This object is achieved in that a mixture based on dithionite with at least one reducing sugar is used as the reducing agent in the alkaline, aqueous dye bath.

Aldotrioses, aldotetroses, aldopentoses and aldehexoses, preferably glucose, which can be in solid form or as syrup / molasses, and their alkali breakdown products and mixtures of these sugars can be used as reducing sugars. Any alkali metal dithionite, advantageously sodium dithionite, can be used as the dithionite.

The mixing ratio can be between 20 parts by weight of reducing sugar / 80 parts by weight of sodium dithionite and 80 parts by weight of reducing sugar / 20 parts by weight of sodium dithionite. The use according to the invention is preferably carried out in a mixing ratio between 40 parts by weight of reducing sugar / 60 parts by weight of sodium dithionite and 60 parts by weight of reducing sugar / 40 parts by weight of sodium dithionite.

The reducing sugar or dithionite (s) can be added either separately or as a finished mixture to the aqueous, alkaline dyeing liquor before the dyeing application. The dye liquor contains as alkali sodium hydroxide, sodium carbonate, potassium hydroxide and / or potassium carbonate, preferably a mixture of sodium hydroxide and sodium carbonate.

In addition to the reducing agent mixture according to the invention, other suitable reducing agents, for example hydroxiacetone, sodium sulfoxylate or formamidine sulfinic acid, may also be present during the coloring.

Textile material which can be dyed by the process according to the invention consists of cellulose fibers, for example cotton, regenerated cellulose, linen, bast fibers and such a textile material which consists of a mixture of cellulose fibers with polyester fibers. The process is particularly suitable for dyeing cotton.

Sulfur black dyes, mixtures of sulfur black dyes with one another or mixtures of one or more sulfur black dyes with one or several suitable colored sulfur dyes can be used. Sulfur black dyes of the type CI Sulfur Black 1 and their mixtures or combinations with one another or with suitable sulfur colorants are preferred, CI Sulfur Black 1 being the main component. CI Sulfur Black 1 can, according to the invention, be in the form of an aqueous dispersion, a water-soluble product of the CI type Soluble Sulfur Black 1 or in the form of an aqueous solution of CI Leuco Sulfur Black 1 and / or Soluble Sulfur Black 1. Products of the CI Soluble Sulfur Black 1 type are particularly preferred.

The process according to the invention can be carried out by a customary one-bath or two-bath pad-steam process with or without intermediate drying, a pad-roll process or a pad-dry process.

Coloring with the mixtures of reducing sugars and sodium dithionite according to the invention can be carried out in the dyeing process with steaming, preferably at temperatures between 100 ° C. and 105 ° C., in the dyeing process with drying process between 100 ° C. and 140 ° C.

In the case of block dyeing using the one-bath-pad-steam process, the alkaline dye liquor contains the dye and the mixture according to the invention of the reducing sugar component and dithionite. The dye liquor is padded onto the material to be dyed, then the material to be dyed is steamed and reoxidized in the usual way with an oxidation liquor.

The two-bath pad-steam process is preferred for the block dyeing of mercerized cotton with suitable water-soluble sulfide-free sulfur dyes. The dye is first padded without alkali and reducing agent, then dried temporarily, padded with alkali and reducing agent and finally fixed by steaming.

For the dyeing of mixtures of cellulose fibers and polyester fibers expediently applied the thermosol / one-bath pad-steam process. The blended fabric is pre-dyed with a conventional disperse dye using the thermosol process. Without intermediate cleaning, an alkaline dye liquor containing the sulfur dye and the reducing agent is padded, then steamed and reoxidized. It has been found that the use of glucose and dithionite according to the invention leads to a substantially better destruction of the disperse dye soiling than sulfide or as glucose alone. When staining with glucose plus dithionite, a reductive intermediate cleaning after thermosolation can be completely dispensed with.

When dyeing according to the present invention, especially when using C.I. Soluble Sulfur Black 1, black coloring with a deep neutral black tone is achieved in a safe, reproducible manner. The black tone that can be achieved when using glucose alone as a reducing agent is weak in color and brownish. Coloring with sodium sulfide as a reducing agent also leads to a weaker and slightly brownish black tone. The color security and reproducibility are fully retained within the specified fluctuation ranges of the chemical quantities. The padding liquor stability is just as good as with sulfidically formulated padding liquors.

The fastness properties which can be achieved by the process according to the invention are better than if dyeing is carried out only with glucose or with sodium sulfide. This applies in particular to the dyeing of mixtures of polyester fibers and cotton using the thermosol / one-bath pad-steam process.

The method according to the invention of sulfide-free or low-sulfide sulfur dyeing can in principle also be used for exhaust dyeings. However, this is not the subject of the present invention.

The following examples serve to explain the inventive concept. Parts mean parts by weight,% mean percent by weight.

Examples

• 1) 100 g of a cotton fabric was padded at about 20 ° C. with a dyeing liquor (liquor absorption 80%), containing 100 g / l of a commercially available powdery dye according to C.I. Soluble Sulfur Black 1, 1 g / l of a commercially available alkali-resistant wetting agent (type secondary alkanesulfonate), 13 g / l sodium hydroxide, 20 g / l anhydrous sodium carbonate, 30 g / l glucose and 30 g / l sodium dithionite. It was steamed for 1 minute at 102 to 103 ° C in an air-free steamer, then rinsed and reoxidized by treatment for 10 minutes at 70 ° C in a liquor containing 2 g / l sodium bromate, 3 cm³ / l acetic acid 60%, 0.1 g / l sodium metavanadate. After rinsing and drying, a deep black color with a clear, bluish black tone was obtained.
• 2) 100 g of a mixed fabric of 50% polyester fibers and 50% cotton were padded at 50 ° C. with a dyeing liquor (liquor absorption 65%), containing 240 g / l of a commercially available liquid dye according to C.I. Soluble Sulfur Black 1, 10 g / l sodium hydroxide, 10 g / l anhydrous sodium carbonate, 25 g / l glucose and 25 g / l sodium dithionite. The mixture was steamed for 90 seconds at 100 ° C., rinsed and reoxidized by treating for 5 minutes at 70 ° C. with a solution containing 3 cm 3 / l hydrogen peroxide 35%, 3 cm 3 / l acetic acid 60% and 1 g / l crystallized sodium acetate. After rinsing and drying, a melange dyeing was obtained from undyed polyester and jet black cotton.
• 3) 100 g of a cotton fabric (terry cloth) were padded at about 20 ° C. and with a liquor absorption of 100% with a dyeing liquor containing 70 g / l of the dye mentioned in Example 1 and 10 g / l of a commercial dye according to CI Sulfur Black 6, also 30 cm³ / l sodium hydroxide 1.36 kg / l (38 ° Bé), 10 g / l potassium carbonate, 100 g / l of a 30% aqueous glucose syrup and 30 g / l sodium dithionite. After steaming at 105 ° C was rinsed and treated for 15 minutes at 40 ° C with an oxidation liquor containing 3 cm³ / l hydrogen peroxide 35%. A deep reddish black color was obtained.
• 4) The dye C.I. Sulfur Black 6 was replaced by an equal amount of C.I. Sulfur Black 7 or 11. An equivalent color was obtained.
• 5) A cotton fabric was padded with 1 liter of a dyeing liquor (liquor absorption 80%), which was made from 200 g of C.I. Leucosulfur Black 1, 1 g of a wetting agent, 80 cm³ sodium hydroxide 1.36 kg / l (38 ° Bé), 15 g galactose, 15 g dextrin and 30 g sodium dithionite. It was steamed, rinsed, reoxidized, dried and a deep black color was obtained.
• 6) A blend of 70% polyester fibers and 30% cotton was, as is usual in practice, with a commercially available dispersion black, based on C.I. Disperse Yellow 114, C.I. Disperse Red 167, C.I. Disperse Blue 79: 1 pre-colored by the Thermosol process. Without intermediate cleaning, padding was carried out at about 20 ° C. with a liquor which was composed as in Example 1. The mixture was then steamed at 100 ° C. to 102 ° C. for 1 minute, rinsed and reoxidized. A black coloration was obtained which, when tested for washing fastness at 60 ° C. using household detergents against multi-fiber tape as an accompanying material, gave a much better result than conventional coloration using C.I. Sulfur Black 1 with sodium sulfide.
• 7) A cellular wool fabric was padded at 20 to 30 ° C. with a dyeing liquor (liquor pick-up 90%) containing 300 g / l of a commercially available liquid dye according to C.I. Soluble Sulfur Black 1, 40 cm³ / l sodium hydroxide 38 ° Bé, 20 g / l anhydrous sodium carbonate, 20 g / l glyceraldehyde and 30 g / l sodium dithionite contained. After steaming, rinsing, reoxidizing and drying, a deep black color was obtained.
• 8) 12 g of glucose and 48 g of sodium dithionite were used and the procedure otherwise described in Example 1. A deep black color was also obtained.
• 9) 40 g of glucose and 10 g of sodium dithionite were used, the dye used in Example 1 by 200 g of a 25% aqueous dispersion of C.I. Sulfur Black 1 replaced and otherwise proceed as described in Example 1. A deep black was also obtained.
• 10) 100 kg of a woven fabric made of mercerized cotton were padded at about 20 ° C. with a liquor containing 350 g / l of a commercially available liquid dye of the C.I. Soluble Sulfur Black 1.5 cm³ / l acetic acid 60%, 3 g / l of a wetting agent, 15 g / l of a commercially available migration inhibitor based on polyacrylate. It was padded with 70% liquor absorption and dried on a hot flue. Then, at about 20 ° C., a chemical liquor containing 50 g / l of the dye pad liquor used, 60 cm 3 / l sodium hydroxide 32.5%, 20 g / l anhydrous sodium carbonate, 20 g / l glucose and 40 g / l sodium dithionite were added a fleet intake of 80%. A brilliant, deep black color was obtained after the customary completion.
• 11) A cotton fabric was padded at 50 to 60 ° C with a liquor (liquor absorption 80%), which 200 g / l of a commercially available dye according to C.I. Leucosulfur Black 1, 25 cm³ / l sodium hydroxide 50%, 40 g / l glucose and 20 g / l sodium dithionite contained. After padding, drying was carried out in an air passage for 20 seconds and then over bombed drying cylinders. A deep black was obtained.

Claims (9)

1. A process for pad-dyeing cellulose fibers with sulfur black dyes, which comprises using in the alkaline, aqueous dyebath a reducing agent comprising a dithionite-based mixture with at least one reducing sugar.
2. The process of claim 1, wherein the reducing sugar used is an aldotriose, aldotetrose, aldopentose or aldohexose, preferably glucose, or an alkali degradation product thereof or a mixture of reducing sugars.
3. The process of claim 1, wherein the dithionite used is an alkali metal dithionite, preferably sodium dithionite.
4. The process of claim 1, wherein the cellulose fibers dyed are cotton, regenerated cellulose or linen, preferably cotton.
5. The process of claim 1, wherein the cellulose fibers are present in a blend with polyester fibers.
6. The process of at least one of claims 1 to 5, wherein the pad-dyeing is carried out as a single-bath or two-bath pad-steam process with or without intermediate drying.
7. The process of at least one of claims 1 to 4, wherein the pad-dyeing is carried out as a pad-dry process.
8. The process of claim 1, wherein the sulfur black dye used is a pure sulfur black dye, preferably a C.I. Sulfur Black 1, a mixture of sulfur black dyes with each other or a mixture of one or more sulfur black dyes with one or more other colored sulfur dyes.
9. The process of claim 8, wherein the C.I. Sulfur Black 1 used comprises one or more products of the type C.I. Leuco Sulfur Black 1 and/or C.I. Soluble Sulfur Black 1, preferably C.I. Soluble Sulfur Black 1.