EP3662105A1

EP3662105A1 - Method for removing manganese oxide deposits from textile surfaces

Info

Publication number: EP3662105A1
Application number: EP18789120.5A
Authority: EP
Inventors: Martin Gruber; Thomas APLAS
Original assignee: CHT Germany GmbH
Current assignee: CHT Germany GmbH
Priority date: 2017-10-25
Filing date: 2018-10-17
Publication date: 2020-06-10
Also published as: BR112020004613A2; MX2020002536A; WO2019081290A1; CO2020002330A2

Abstract

The subject matter of the invention is a method for removing manganese oxide deposits from textiles that have been dyed with for example indigo and/or sulphur black and have undergone a bleaching treatment with for example potassium permanganate, wherein mixtures of ascorbic acid and organic carbonic acids are used, and relates to the use of such mixtures for removing manganese oxides.

Description

Process for removing manganese oxide deposits from textile surfaces

The invention relates to a process for the removal of manganese oxide deposits of, for example, indigo and / or sulfur black dyed textiles which have been subjected to a bleaching treatment with, for example, potassium permanganate using mixtures of ascorbic acid and organic carboxylic acids and the use of such mixtures for the removal of manganese oxides.

The continuing trend towards wash out and used-look effects means that most of the denim articles dyed with indigo or other dyes are further processed by washing processes, often in combination with chemical treatments, wholly or locally, usually on exposed areas. brightened or bleached.

Bleaching treatment is often preceded by abrasive scrubbing with enzymes and / or pumice stones. The bleaching treatment itself may be done in a second bath containing a bleaching agent to further lighten the color of the entire article and to enhance light-dark contrasts. In addition, however, the targeted, local brightening of the articles in correspondingly exposed areas is used as an essential means of, for example, making a pair of jeans really to give aesthetic appearance. For this purpose, the denim surface is first locally limited, for example, on the thighs and buttocks, mechanically roughened by grinding. Subsequently, sprayed at these points with a bleaching solution that destroys the dye more or less, depending on the desired intensity of the whitening effect.

A very commonly used bleaching agent to achieve such lightening effects is potassium permanganate. Especially for the partial bleaching of denim articles by spraying, its use is state of the art.

The use of permanganate as a dilute, aqueous solution has advantages in practical application: the bleaching action takes place very rapidly within a few minutes, no elevated temperatures are necessary; the bleach itself is storage stable and the bleaching effect achieved is well reproducible.

However, a disadvantage is, inter alia, that in the oxidation of the indigo itself, the permanganate ion, which is readily soluble in water, is itself converted predominantly into insoluble manganese oxides, especially manganese dioxide (manganese dioxide). As a result, dark to red-brown deposits form on the fabric, which initially mask the bleaching effect and which can not be removed by simple washing with water and surfactant.

Therefore, an additional treatment step is necessary, also referred to as "neutralization", in which the insoluble manganese dioxide is converted into water-soluble manganese salts of lower oxidation states using reducing agents.

Common reducing agents are sulfur compounds such as sodium hydrogen sulfite, sodium metabisulfite, as described for example in US 4,795,476, or sodium dithionite. A disadvantage is a strong odor and a pollution of the wastewater by excess reducing agent due to the high chemical oxygen demand (COD). In addition, because of the enzyme toxicity, the neutralization step can not be used for cellulase treatment.

The also widespread hydroxylammonium salts such as bis (hydroxylammonium) sulfate are classified as presumably carcinogenic and organ damaging and also have a very high aquatic toxicity.

For this reason, several umweit- and user-friendly alternatives for neutralization have been proposed. For example, US Pat. Nos. 5,006,124 and JPH0657627 disclose the use of hydrogen peroxide as a reducing agent for manganese dioxide, in particular in combination with complexing agents. No. 5,205,835 describes the use of a mixture of hydrogen peroxide, peracetic acid and acetic acid (equilibrium peracetic acid).

Although the procedure with complexing agents is basically effective but uneconomical and is not used in practice, because the required amounts of chemicals are relatively high and the treatment must be carried out at elevated temperature in the alkaline, which makes an additional step to pH neutralization required. Although the use of equilibrium peracetic acid avoids these disadvantages, but also the cost is high and storage and use due to the very unpleasant odor are problematic, especially in warmer regions.

A reducing agent with an excellent property profile with regard to environmental compatibility and safety in use is the ascorbic acid (vitamin C) formed in numerous organisms, which is widely used as an antioxidant in food production.

Basically, the suitability of ascorbic acid is known because of its reducing properties for dissolving or removing transition metal oxides. CN1126245 describes the use of ascorbic acid solutions to leach milled manganese ore.

Ascorbic acid solutions with wetting agents are described in DE 2 040 546 as effective for the removal of metal oxide-containing deposits in drinking water tanks.

WO 2014/111267 proposes the use of a combination of ascorbic acid and hydroxyethanediphosphonic acid (HEDP) to remove metal oxides from textiles or textile surfaces. However, the focus here is clearly on the removal of iron oxide or rust particles in order to prevent the catalytic decomposition of hydrogen peroxide in the bleaching of textiles made of cotton, which may affect the bleaching effect or lead to damage to the product up to the formation of holes.

By Khan et al. (Khan et al., Journal of Colloid and Interface Science (2005) 290 (1), 184-189) describes the reduction of colloidally dissolved manganese dioxide by ascorbic acid as being rapid and effective, whereas combination with phosphates is said to inhibit it.

It has been found that by using ascorbic acid and under certain conditions, manganese oxide deposits deposited on the textile material during the bleaching treatment of denim articles with permanganate can be removed quickly and effectively.

Complete removal of colored manganese oxides to achieve a clear shade of blue with a white fiber base and good contrast is possible with pure ascorbic acid treatment, but the amounts needed are high and thus the process is highly uneconomical to the established reducing agents.

The object of the present invention is now to provide a process for the treatment of textiles, which in particular with indigo and / or sulfur black, optionally in combination with other dyes, dyed and then a bleaching treatment, in particular with permanganates, were subjected to the Bleaching treatment incurred deposits or stains with manganese oxides, especially with manganese dioxide to remove. The process is intended to provide comparable results in its cleaning effect as using sulfur-based reducing agents or hydroxylammonium salts, while significantly reducing possible disadvantages and risks for the environment and the user. In particular, no environmentally hazardous or harmful to human health chemicals should be used and an entry of aquatic toxic substances into the wastewater should be excluded. In addition, the method should be feasible with economical quantities quickly and effectively.

In a first embodiment, the object underlying the invention is achieved by a method for removing manganese oxides from textile fabrics, wherein the textile fabrics are treated with a mixture comprising ascorbic acid and at least one further organic carboxylic acid.

The inventive combination of ascorbic acid and at least one other organic carboxylic acid, the effectiveness of ascorbic acid can be drastically increased or the required amounts can be significantly reduced.

For the purposes of the present invention, ascorbic acid means both ascorbic acid (CAS number 50-81-7) and isoascorbic acid (CAS number 89-65-6). Both forms of ascorbic acid each comprise two enantiomers. The term ascorbic acid as used in the context of the present invention thus comprises a total of four isomeric forms. These are called L-ascorbic acid, D-ascorbic acid, L-isoascorbic acid and D-isoascorbic acid. The four mentioned forms can be used alone or in any mixtures, wherein all four forms or only three or two of the isomeric forms can be contained in a mixture.

For example, a racemate of L-ascorbic acid and D-ascorbic acid can be used. However, it is also possible to use, for example, any mixtures of L-ascorbic acid with D-ascorbic acid. For example, it is also possible to use pure L-ascorbic acid or pure D-ascorbic acid.

Similarly, a racemate of L-isoascorbic acid and D-isoascorbic acid can be used. However, it is also possible, for example, to use any mixtures of L-isoascorbic acid with D-isoascorbic acid. For example, it is also possible to use pure L-isoascorbic acid or pure D-isoascorbic acid.

Mixtures of L-ascorbic acid or D-ascorbic acid with L-isoascorbic acid or D-isoascorbic acid are of course included in the present invention.

Suitable organic acid further low molecular weight organic carboxylic acids such as acetic acid, glycolic acid or lactic acid. Particularly effective are chelating polybasic acids such as citric acid, which is believed to have an additional synergistic effect due to its complexing effect on metal ions, without the invention being limited thereto by this theory. In a preferred embodiment of the process according to the invention, textile materials are used which contain manganese oxides which originate from a previous treatment with permanganates.

The treatment according to the invention of the textiles contaminated with manganese oxide can take place in a long liquor in a conventional washing unit, for example a drum washing machine, at room temperature or slightly elevated temperature, for example up to 50 ° C.

The wash liquor is a mixture comprising ascorbic acid and other organic acids in a preferred weight ratio of 1: 9 to 1: 1, in particular in the ratio 1: 5 to 1: 2 added. The amount of acid mixture added is preferably between 0.5 g / l and 5.0 g / l, depending on the degree of soiling of manganese oxide.

In a preferred embodiment, the at least one further organic carboxylic acid is selected from the group of mono-, di- or trifunctional low molecular weight carboxylic acids, in particular those having up to 8 C atoms. Also optionally used further carboxylic acids are preferably derived from the groups mentioned here.

Preferred monofunctional organic carboxylic acids include acetic acid, glycolic acid, lactic acid, formic acid, and propionic acid. Preferred difunctional organic carboxylic acids include tartaric, malonic, maleic, fumaric, oxalic, succinic, oxosuccinic, glutaric, adipic and aspartic acids. Preferred trifunctional organic carboxylic acids include citric acid and (2R, 3S) iso-citric acid. The at least one further organic carboxylic acid is particularly preferably a chelate-forming carboxylic acid. Most preferred is citric acid.

Thickening agents, dyes, wetting agents, dispersants, complexing agents, enzymes and / or further auxiliaries known per se can be added as further additives to the treatment liquor.

In a preferred embodiment, the mixture used according to the invention comprises an aqueous solution which contains ascorbic acid and at least one further organic carboxylic acid, in particular citric acid.

The inventive method is preferably carried out at a temperature of 20 to 60 ° C. Particularly preferred is a temperature between 20 and 40 ° C. The treatment is carried out in a preferred embodiment of the method according to the invention over a period of 5 to 40 minutes, more preferably over a period of 5 to 20 minutes.

Depending on the type of further organic carboxylic acid (s) used, the mixing ratio and the amount of the mixture used, the pH of the liquor is preferably from 3.0 to 6.0. More preferably, the pH of the manganese oxide removing effect is 3.5 to 5.5, and more preferably 4.0 to 5.0.

With the help of the present invention Manganoxidablagerungen or -anschmutzungen of the most diverse textiles or textile materials are removed. In a preferred embodiment, textile fabrics made of cellulose fibers or of cellulose fibers are used in mixture with natural or synthetic fibers which are wholly or partly dyed with different dyes. The process according to the invention is preferably carried out with textile materials which are dyed with indigo and / or sulfur black and, if appropriate, in combination with vat, direct, sulfur or disperse dyestuffs.

The process according to the invention is capable of removing manganese oxide deposits which have arisen both as part of a full bleach with permanganate, for example from a long liquor, and in the case of a local bleach at certain locations of an article, for example in the spray process.

In a further embodiment, the object underlying the invention is achieved by the use of a mixture comprising ascorbic acid and at least one further organic carboxylic acid, in particular citric acid, and optionally water for removing manganese oxides from textile materials.

The effectiveness of the method according to the invention was tested on different denim qualities after a standard full bleaching with potassium permanganate in direct comparison with the prior art Na-metabisulfite and bis (hydroxylammonium) sulfate.

The determination of the effectiveness of the manganese oxide removal was carried out by two different methods: • Colorimetric measurement of the bleached and neutralized samples and determination of the dimension b * or the color difference Ab to CIELAB with Datacolor International SF 600 plus CT, aperture 30 mm LAV, quadruple measurement, calibration standard light D 65. The dimension b * allows the weight of the blue / yellow color component between - 80 (pure blue) and + 80 (pure yellow)

• Content of the bleached and neutralized samples of manganese by determination by ICP-OES (optical emission spectrometry by inductively coupled plasma) according to DIN EN ISO 11885.

EXEMPLARY EMBODIMENTS:

All examples below were carried out with a commercially available denim product, each as raw material (material 1) and after a practice-standard combined pretreatment of stonewashing and desizing (prewashing with pumice stone and enzymes, material 2). Both qualities of goods were subjected to full bleaching with potassium permanganate. For this purpose, the product (complete pants in the piece) was treated for 10 minutes at 40 ° C with 1.5 g / l KMnO ₄ at a liquor ratio (FV) of 1: 10, cold rinsed with water at a FV 1:10 with water , spun and dried in a tumbler.

The material thus uniformly stained with manganese oxide contained on average 4900 ppm manganese with a CIELAB measurement b * = 6.6 (raw material) or 5100 ppm manganese and b * = 10.9 (after pretreatment).

This material was then subjected to a neutralization treatment (10 minutes at 40 ° C, FV 1:10), rinsed and dried. Table 1 gives an overview of the treatments performed. The manganese contents and color distances as a measure of the effectiveness of the treatment are listed in Table 2 (material 1) and Table 3 (material 2).

Comparative Example 1

Treatment only with soft water without neutralizing agent leads to no significant removal of Manganoxidanschmutzung. Accordingly, the manganese contents in both treated materials are Lien 1 and 2 hardly reduced (4820 ppm or 4570 ppm) and the color differences Ab to the untreated material show virtually no change in the yellow-brown hue (0.9 or 0.3)

Comparative Example 2:

After treatment with 1.0 g / l of bis (hydroxylammonium) sulfate, the manganese content is drastically reduced (150 ppm or 160 ppm) and the color difference Ab shows the drastic shift from yellow to blue (-24.6 or -27.0) and thus a very good neutralization effect.

Comparative Example 3

With 1.0 g / l Na-Metabisulfit can also achieve a good neutralization effect. However, the treatment is not equally effective, accordingly, the residual levels of manganese are higher and the blue shade less clear.

Comparative Example 4

With 0.2 g / l L - (+) - ascorbic acid without addition of an organic carboxylic acid, only a small part of the manganese oxide can be removed and the neutralization effect is low.

Comparative Examples 5 and 6:

These examples show the effect of adding acids not according to the invention. The mixing ratio was chosen so that at a level of 0.2 g / l L - (+) - ascorbic acid in the treatment liquor the same pH of 4.5 is achieved as with citric acid. In admixture with the complexing agent hydroxyethanediphosphonic acid (HEDP), although the effect over the same amount of pure ascorbic acid can be noticeably increased, but remains far behind the inventively preferred combination with citric acid with respect to manganese removal and the measured color difference reflects the still clearly visible superposition of the Indigo color by brownstone residues again (Comparative Example 5).

With phosphoric acid as an additive (Comparative Example 6), this finding is even clearer, possibly also due to the formation of sparingly soluble phosphates.

Comparative Examples 7 and 8:

It is clear from these examples that organic carboxylic acids without the addition of ascorbic acid, as well as ascorbic acid alone, do not have a satisfactory neutralization effect; So there is a synergistic effect.

Although citric acid (Comparative Example 7) can probably reduce the manganese content due to the complexing properties with respect to metal ions, the optical effect remains strongly behind the combination with ascorbic acid and the color difference Ab still clearly indicates the brownish-yellow discoloration due to manganese oxide residues.

In the case of acetic acid (Comparative Example 8), optically almost no effect of the treatment is evident (Ab negligible in both materials) and only in material 2 was the manganese content reduced somewhat. Example 1 :

With the same amount of L - (+) - ascorbic acid as in Comparative Example 4 but in combination with citric acid in a mixing ratio of 1: 3 parts by weight, on the other hand, excellent neutralization is achieved, which is absolute in terms of clarity and brilliance of the blue clay with the reference in Comparative Example 2 is comparable.

Example 2:

If this treatment is carried out in accordance with Example 1 with D - (-) - isoascorbic acid under otherwise identical conditions, there are no differences in comparison with Example 1.

Example 3:

Also in combination with acetic acid (mixing ratio 1: 3.5 parts by weight) can be achieved with the same amount of L - (+) - ascorbic a very good neutralization effect, which corresponds in terms of manganese removal and color distance of the reference in Comparative Example 3. In comparison to the citric acid but slightly higher amounts must be added.

VergleichsMischungspH value

Neutralization Concentration example ratio in the fleet

1 only soft water - - 7,4

Bis (hydroxyl

2 - 1.00 [g / l] 5.2 ammonium) sulfate

3 Na metabisulfite - 1.00 [g / l] 3.5

4 L - (+) - ascorbic acid - 0.20 [g / l] 6,6

L - (+) - ascorbic acid +

5 1: 2.4 0.68 [g / l] 4.5

HEDP

L - (+) - ascorbic acid +

6 1: 2.4 0.68 [g / l] 4.5

phosphoric acid

7 only citric acid - 0.60 [g / l] 4,5

8 only acetic acid - 0.76 [g / l] 4,5

example

L - (+) - ascorbic acid +

1 1: 3.0 0.80 [g / l] 4.5

citric acid

D - (-) - isoascorbic acid

2 1: 3.0 0.80 [g / l] 4.5

+ Citric acid

L - (+) - ascorbic acid +

3 1: 3.8 0.96 [g / l] 4.5

acetic acid

Table 1 Overview neutralization treatments

VergleichsMangan¬

Neutralization Manganese content Color difference From example distance

1 soft water only 4820 [ppm] 2.4% 0.3

Bis (hydroxyl

2 150 [ppm] 97.0% -24.6 ammonium) sulfate

3 Na metabisulfite 680 [ppm] 86.2% -22.4

4 L - (+) - ascorbic acid 4080 [ppm] 17.4% -6.5

L - (+) - ascorbic acid +

5 3600 [ppm] 27.1% -17.8

HEDP

L - (+) - ascorbic acid +

6 3310 [ppm] 33.0% -14.7

phosphoric acid

7 only citric acid 2550 [ppm] 48.4% -10.8

8 only acetic acid 4560 [ppm] 7.7% 1.9

example

L - (+) - ascorbic acid +

1 520 [ppm] 89.5% -23.2

citric acid

D - (-) - isoascorbic acid

2 530 [ppm] 89.2% -23.2

+ Citric acid

L - (+) - ascorbic acid +

3,740 [ppm] 85.0% -22.8

acetic acid

Table 2 Results of neutralization treatments on material 1

VergleichsMangan¬

Neutralization Manganese content Color difference From example distance

1 only soft water 4570 [ppm] 11.1% 0.9

Bis (hydroxyl

2 160 [ppm] 96.9% -27.0 ammonium) sulfate

3 Na metabisulfite 1420 [ppm] 72.4% -24.7

4 L - (+) - ascorbic acid 4210 [ppm] 18.1% -12.3

L - (+) - ascorbic acid +

5 3410 [ppm] 33.7% -20.5

HEDP

L - (+) - ascorbic acid +

6 3420 [ppm] 33.5% -18.9

phosphoric acid

7 only citric acid 2030 [ppm] 60.5% -19.2

8 only acetic acid 4090 [ppm] 20.4% -0.1

example

L - (+) - ascorbic acid +

1 860 [ppm] 83.3% -26.3

citric acid

D - (-) - isoascorbic acid

2 840 [ppm] 83.5% -26.1

+ Citric acid

L - (+) - ascorbic acid +

3 1100 [ppm] 78.6% -24.6

acetic acid

Table 3 Results of neutralization treatments on material 2

Claims

claims:

1. A process for the removal of manganese oxides from textile fabrics by treatment with a mixture containing ascorbic acid and at least one further organic carboxylic acid.

2. The method according to claim 1, characterized in that one uses textile materials containing manganese oxides, which optionally originate from a previous treatment with permanganates.

3. The method according to claim 1 or 2, characterized in that the weight ratio of further organic carboxylic acid and ascorbic acid in the mixture in a range of 9 to 1 to 2 to 1.

4. The method according to any one of claims 1 to 3, characterized in that at least one further organic carboxylic acid is selected from the group of mono-, di- or trifunctional low molecular weight carboxylic acids, chelating carboxylic acids and citric acid.

5. The method according to any one of claims 1 to 4, characterized in that the mixture is used in the form of an aqueous solution containing ascorbic acid and at least one further organic carboxylic acid, in particular citric acid.

6. The method according to claim 5, characterized in that the treatment at a temperature of 20 to 60 ° C, in particular from 20 to 40 ° C, takes place.

7. The method according to any one of claims 1 to 6, characterized in that the treatment over a period of 5 to 40 minutes, in particular from 5 to 20 minutes, takes place.

8. The method according to any one of claims 1 to 7, characterized in that the treatment at a pH of 3 to 6, in particular from 3.5 to 5.5, takes place.

9. The method according to any one of claims 1 to 8, characterized in that one uses textile fabrics made of cellulose fibers or cellulose fibers in mixture with natural or synthetic fibers, which are wholly or partially dyed with different dyes.

10. The method according to any one of claims 1 to 9, characterized in that one uses textile fabrics which are dyed with indigo and / or sulfur black, optionally in combination with vat, direct, sulfur or disperse dyes.

11. Use of a mixture containing ascorbic acid and at least one further organic carboxylic acid, in particular citric acid, and optionally water for the removal of manganese oxides of textile materials.