ES2729156T3 - Procedure for rinsing dyed fabrics - Google Patents

Abstract

Procedure for lightening dyed textile fabrics, characterized in that the tissues are treated under acidic pH conditions with an aqueous solution containing an aromatic organic peroxycarboxylic acid as the active component.

Description

DESCRIPTION

Procedure for rinsing dyed tissues.

The object of the invention is a process for lightening dyed tissues.

For several years, there has been a continuous and fashionable trend towards the effects of washing and used appearance. This leads to a growing demand for dyed fabrics made of cellulose fibers, in particular denim items dyed with indigo or other dyes, which in additional processing stages are completely clarified or bleached or in certain places by mechanically reinforced washing processes (washing to the stone), often in combination with chemical treatments.

The classic Jean fabric, or also denim, is a ring-dyed yarn fabric and mostly non-dyed weft. Ring dyeing of the spinning fabric is the reason for the typical signs of wear that give jeans their individual appearance in the course of their lives. The only surface adhesion to the thread dye (usually indigo alone or in combination with sulfur black) is gradually eliminated by mechanical abrasion during washing and use and the white fiber core emerges more and more. Especially in exposed areas such as seam crests and wear folds this is increasingly the case

Given that there is a great need on the part of the consumer to buy garments that look worn as new, the provision of the so-called vintage or used look is now one of the most important commercially fashionable effects in the leisure sector.

For this purpose, articles made of ring-dyed fabrics are subjected to abrasive washing with enzymes and / or pumice stones, which produce abrasion everywhere on the article in the washing drum. This treatment is often done in combination with a second bath that contains a bleach to further lighten the color and enhance light and dark contrasts. In addition, however, the local and specific rinsing of items in the corresponding exposed areas is used as an essential means to give jeans a truly authentic look. For this purpose, the surface of the denim is limited locally first, for example, on the thighs and buttocks, and is mechanically scraped by manual sanding. Subsequently, it is sprayed at these points with a bleaching solution that destroys the dye more or less, depending on the desired intensity of the bleaching effect. This creates a deceptively genuine impression of signs of wear or tear on a new denim item.

In general, it is usual to carry out the treatment to lighten the surface of dyed tissues in an aqueous bath in a prolonged liquor with hypochlorites, for example, sodium hypochlorite. With the chlorine bleach, an easy-to-use, economical and efficient bleaching agent is available, with which a large amount of dyes can be oxidatively discolored, among other indigo or indigoid dyes. However, this procedure has the disadvantage that large amounts of wastewater contaminated with AOX (organically bound adsorbable halogens) are generated, which often have to be subsequently treated to meet the officially prescribed limit values. Chlorine is very toxic to aquatic organisms. Therefore, the use of chlorine-based chemicals in environmental and consumer organizations is highly criticized. In principle, the use of hypochlorites is also possible for local rinsing, for example, by spraying. However, in practice, this method is generally not used due to the strong effects of corrosion and chemical attack, as well as the poor ability to control the bleaching effect.

For partial bleaching of denim items in the spraying process, the use of potassium permanganate is the state of the art. However, in the meantime, serious disadvantages have also emerged here. For example, potassium permanganate exhibits high toxicity to aquatic organisms and its massive use leads to high levels of heavy metals in wastewater. According to the Chemical Ban Ordinance (ChemVerV), the release of potassium permanganate in Germany requires proof of use to prevent misuse in the production of explosives or drugs. Similar restrictions exist in many other countries, which makes it difficult to buy potassium permanganate and makes storage difficult. In addition, also in the spray treatment, an additional process step is necessary to remove the resulting manganese dioxide.

As alternatives to hypochlorite and potassium permanganate, various approaches have been proposed, which also have serious disadvantages and could not prevail in practice.

Thus, among others, tank dyes, especially indigo, are converted to the soluble leuco form by reducing agents, are removed from the fiber and the tissue is cleared. For this purpose it is known, among others, the use of sugars such as glucose, as described in EP 0654557 A. However, these processes have the disadvantage that it is necessary to work at high temperatures (> 80 ° C) and high alkalinity (pH> 11). In addition, large amounts of wastewater accumulate, which also have a higher biological and chemical oxygen demand due to the high organic load. This problem also occurs analogously when other reducing agents are used, such as keto compounds, for example, hydroxyacetone. In addition, the reduction processes to produce local bleaching effects are fundamentally inadequate, since it is not possible, as in a Closed washing drum, create a general reducing environment, and therefore the locally produced leuco form is rapidly re-oxidized by atmospheric oxygen.

In addition, the use of ozone as an oxidizing agent for lightening dyed cotton fabrics (EP 0 554648 A) is known, in which this method has the disadvantage that ozone is a very toxic and corrosive gas. As a result, the handling of ozone in technical production procedures is difficult, since the gaseous ozone produced that is administered in a controlled manner to the treatment unit and the excess ozone must be removed again. Local treatments for example of denim items are not possible in this way.

The use of hydrogen peroxide or peracetic acid in rinsing dyed tissues is also known. However, these substances do not serve as a primary bleaching agent but, for example, to neutralize a cotton fabric that has already been rinsed with potassium permanganate or to remove the residue formed from MnO ² (compare WO 92/13987 TO).

US 3,384,596 C describes the use of peroxycarboxylic acids such as monoperoxyxtalic acid and m-chloroperoxybenzoic acid in the presence of alkaline earth salts as an alkaline pH bleaching agent.

US 4,443,352 C proposes the use of monoperoxyxtallic acid and its water soluble salts as a bleaching enhancer component of a powder detergent formulation. As a procedure, the bleach of blemishes in the household wash at alkaline pH is mentioned. In EP 0027693 A an analogous use of the magnesium salt of the monoperoxiftálic acid is claimed.

Document DE 34 00950 A describes the use of the magnesium salt of the monoperoxyxtalic acid in combination with an alkaline bromide and sulfonamides in a detergent formulation also for bleaching stains in household washing at alkaline pH.

WO 95/25195 A proposes the use of a source of hydrogen peroxide in combination with an iron salt at a strongly acidic pH to bleach indigo dyed tissues. This combination has been known as Fenton reagent. The process is very complex and is not economically feasible in practice, because the iron salt must be applied in an upstream treatment stage and must be removed in a subsequent treatment stage using large amounts of complexing agents again. To achieve good effects, a longer treatment time at temperatures of 70 ° C and more is also necessary, which makes this process very energy intensive.

This also applies to an additional proposal for rinsing dyed fabrics: WO 95/20643 A proposes the use of peroxodisulfates as a source of oxygen in combination with a transition metal catalyst. However, peroxodisulfates are subject to the same restrictions as the oxidizing agent according to ChemVerV, such as permanganate and, therefore, are not suitable as an alternative in this regard. In addition, peroxodisulfate solutions, as well as Fenton solutions, are not suitable for local effects by spray application or brushing.

EP 0 176 124 A2 (AT 44 763 E) refers to the use of a water suspension containing as a bleaching component a peroxycarboxylic acid derived from a dicarboxylic acid having 8 to 13 carbon atoms as a pouring bleaching agent.

Document DT 26 20 723 A1 refers to bleaching or cleaning agents, in particular with a bleaching action at low temperatures.

Document DT 26 12587 A1 refers to bleaching preparations comprising a water-soluble aliphatic peroxy compound and a thickener.

EP 0 160 342 A2 describes liquid bleaching solutions comprising aliphatic peroxy compounds as solid, particulate constituents, substantially insoluble in water.

It is also known to rinse the dyed tissues in the presence of an enzyme. Some examples are the use of laccase enzyme and a source of hydrogen peroxide as an oxidizing agent (US 5,851,233 C, WO 96/12846 A). These methods are used in practice, but they have a number of disadvantages. For example, only the indigo content is bleached in denim items, but not the sulfur black that is frequently used. To achieve a strong rinse, several treatment baths are needed, which also makes this process very expensive. In addition, this treatment must be carried out in a prolonged liquor and partial rinsing is not possible, for example, by spraying.

There is currently no alternative method of using potassium permanganate for the treatment of local bleaching of denim items, which finds an application in practice.

The objective of the present invention is, therefore, to provide a method for bleaching dyed fabrics, which on the one hand makes it possible to lighten the tissue in a flat or uniform manner in the desired tone, but on the other hand also limits locally the freely selectable intensity for bleach, for example, by spray or application with Brush. The method should allow results comparable in its lightening effect to those using chlorine bleaching agents or potassium permanganate, and at the same time significantly reduce the possible disadvantages and risks to the environment. In particular, hazardous chemicals for the environment should not be used and the entry of AOX or heavy metals into wastewater should be excluded.

Surprisingly, it has been found that organic peroxycarboxylic acids, in particular certain aliphatic or aromatic aliphatic or linear cyclic peroxycarboxylic acids or dicarboxylic acids containing hydrophobic side groups, preferably alkyl radicals having at least 5 carbon atoms, particularly preferably with 5 to 30 Carbon atoms and more preferably chain lengths of 6 to 10 carbon atoms, have a very high bleaching effect on the dyed tissues. In particular, indigo and indigoid dyes can be bleached under moderate conditions, so that local treatment can be carried out, for example by spraying, in a simple and practical manner.

The term "hydrophobic" generally refers to the association of non-polar groups or molecules of an aqueous environment. This characterizes substances that do not mix with water and usually adopt "pearl form" on surfaces.

Non-polar substances, such as fats, waxes, alcohols with long alkyl radicals - that is, with the exception of methanol, ethanol and propanol - alkanes, alkenes, etc. They are hydrophobic. The dissolution of hydrophobic substances in water generally produces the so-called hydrophobic effect and in some small and hydrophobic species, such as methane or xenon, even entropically unfavorable clathrate structures are formed. Therefore, the solubility of these substances in water is generally low.

Hydrophobic substances are almost always lipophilic, that is, they dissolve well in fat and oil. Surfaces that have a contact angle greater than 90 ° with respect to water are also known as hydrophobic. Hydrophobic radicals in the context of the present invention thus include, in particular, a contiguous radical of at least 5 carbon atoms, a carbon chain, which is preferably saturated with hydrogen atoms to form an alkyl radical or an aryl radical.

The bleaching agents according to the invention are aromatic peroxycarboxylic acids consisting of one or more fused aromatic rings, optionally substituted with one or more additional peroxycarboxylic acid groups in any position. These aromatic peroxycarboxylic acids of the invention can be further substituted with at least one functional group selected from alkyl, aryl, carboxylate, sulfonate, halide, nitro or hydroxy groups at any point in the aromatic ring system. Preferred examples are: mono- or diperoxo-ortho acid, -meta or para-phthalic acid, mono- or diperoxo-4-methyl-o-phthalic acid, mono- or diperoxo-1,8-naphthalene acid. Peroxycarboxylic acids can be used both in acid form and in the form of salts or can also be generated in situ by the addition of activated carboxylic acid derivatives (for example, as anhydrides) and a source of hydrogen peroxide or otherwise in the process . The salts used are preferably alkali or alkaline earth metal salts, for example, salts of Li, Na, K, Mg or Ca.

It has been found, particularly surprisingly, that treatment under acidic pH conditions can be carried out particularly efficiently, although the person skilled in the art knows that peroxycarboxylic acids, for example, peracetic acid, have the highest bleaching efficiency at pH close to the pKa value, that is, at a neutral to weakly alkaline value. In the context of the present invention, textile fabrics are treated under acidic pH conditions. Preferably, the pH of the solution is in the range of pH 1 to pH 5, more preferably in the range of pH 1.5 to pH 3.5.

As additional additives natural and synthetic thickeners, salts such as alkaline and alkaline earth sulfates, phosphates and, if necessary, marking dyes, for example, dyes, wetting agents, humidifiers such as glycerol, urea or dispersants or other adjuvants are added to the application liquor . The use of dyes (markers) serves for the best visual traceability of the spray course. This is particularly significant in practice since the violet permanganate strongly colors the spray solution, while the spray solution according to the invention is basically colorless.

The pH ranges mentioned above are automatically set by the reagents used, but can also be adjusted by other additives. For the purposes of the present invention, the pH of the solution is adjusted particularly preferably with mineral acids or organic acids. Very particularly preferred in this regard are low volatility acids, that is, acids having a vapor pressure <20 Pa at 20 ° C, such as citric acid, maleic acid, lactic acid, Italic acid, phosphoric acid, sulfuric acid or hydrogen sulfates.

Several methods for contacting the colored substances with peroxycarboxylic acid are available to the person skilled in the art in this field. Particularly preferred in this regard, the colored substances are contacted with a solution containing all or part of the peroxycarboxylic acid or its salts by means of a spray, immersion or blow process.

With the help of the present invention, a wide variety of textiles or textile materials can be contacted with peroxycarboxylic acids. Particularly preferred in this regard are woven fabrics made of cellulose fibers or cellulose fibers in admixture with natural or synthetic fibers, which are dyed with a wide variety of dyes. Particularly preferred according to the present invention, these dyes are selected from the groups of tank dyes, direct or sulfur.

The process of the present invention is particularly suitable for textile materials dyed with indigo, indigoid dyes or sulfur black, as well as with combinations of these dyes.

Bleached tissues are also described which can be obtained by a method as defined above. Jeans, as defined by these bleached fabrics, are particularly preferred.

The effect of the liquors according to the invention in the treatment of local bleaching was determined in direct comparison with the state-of-the-art potassium permanganate. All peroxycarboxylic acids were used in a concentration that corresponds to approximately three times the normality of a 2% potassium permanganate solution used today on average.

The bleaching effect was determined in two different denim products, each with the determination of Y values according to CIE with Datacolor International SF 600 Plus-CT, 30 mm LAV aperture, 4-fold measurement, standard calibration light D 65

As a result of bleaching according to the invention, preferably> 40% of the bleaching effect of a standard solution of KMnO ⁴ , particularly preferably> 60%, very particularly preferably> 80% has been achieved.

Exemplary embodiments:

Reference Example 1:

In two commercially available denim products (denim 1 = not sanding, pre-treatment with scraping with sandpaper, denim 2 = sanding, treatment with stone washing) a rectangular area of 120 cm2 was marked and covered with an adhesive film at the edges against adjacent areas. These areas were sprayed uniformly with 2 g each of an aqueous solution of 20 g / l potassium permanganate (0.38 normal) and the fabric samples were weighed to control the amount applied. After a reaction time of 20 minutes at room temperature, the tissue samples were neutralized in an extractor washer together with an untreated denim fabric as first ballast 10 minutes at 50 ° C and a liquor ratio of 1: 8 with 4 g / l of sodium bisulfite, then rinsed 3 times cold in a liquor ratio of 1:10 and then dried in a dryer. In each of the samples thus obtained, the value of Y was measured in accordance with CIE (Datacolor International SF 600 Plus-CT, 30 mm aperture LAV, 4-fold measurement, standard light calibration D 65) on and next to the surface treated by sprinkling and the difference in the degree of rinsing with AY was determined.

Results were obtained for denim 1 of AY = 19.2 and for denim 2 of AY = 35.0.

Comparative Example 1:

From the monoperoxyglutaric acid (MPGS), a normal aqueous solution containing 15% by weight of MPGS, 2.5% by weight of sodium sulfate and 0.4% by weight of xanthan thickener was prepared and adjusted to pH 2.9 with phosphoric acid. Of this solution, 2.0 g were applied to both standard denim products in the same manner as in Reference Example 1. After a contact time of 20 min at 60 ° C, the tissue sample was rinsed analogously to Reference Example 1 without neutralization once at 40 ° C and 1 time cold in a liquor ratio of 1:10 and then dried in a dryer. From the samples thus obtained, the value of Y was measured according to CIE in each case on and next to the surface treated by spraying in the same manner as Reference Example 1, and the difference in the degree of rinse was determined with Y.

Results were obtained for denim 1 of AY = 4.7 and for denim 2 of AY = 8.3.

Comparative Example 2

Monoperoximaleic acid (MPMS) was applied as a normal aqueous solution containing 13.8% by weight of MPMS, 2.5% by weight of sodium sulfate and 0.4% by weight of xanthan thickener, in the same amount to both standard denim products analogously to comparative example 1, prepared and measured in the same way.

Results were obtained for denim 1 of AY = 4.9 and denim 2 of Y = 10.5.

Example 1:

Commercially available magnesium bis-monoperoxyphthalate hexahydrate (MMPP) was applied as a normal aqueous solution containing 25% by weight of MMPP, 2.5% by weight of sodium sulfate and 0.4% by weight of Xanthan thickener, in the same amount to both standard denim products analogously to comparative example 1, prepared and measured in the same way.

Results were obtained for denim 1 of AY = 18.7 and denim 2 of AY = 34.3.

Example 2:

Monoperoxiftalic acid (MPPS) was applied as a normal aqueous solution containing 16.8% by weight of MPPS, 2.5% by weight of sodium sulfate and 0.4% by weight of xanthan thickener, in the same amount a both standard denim products analogously to comparative example 1, prepared and measured in the same way.

Results were obtained for denim 1 of AY = 18.1 and for denim 2 of AY = 32.2.

Example 3:

Similarly as in Example 1, monoperoxy-cis-cyclohexane-1,2-dicarboxylic acid (MPDCS) was applied as a normal aqueous solution containing 17.5% by weight of MPDCS, 2.5% by weight of sodium sulfate and 0.4% by weight of xanthan thickener, in the same amount to both standard denim products analogously to comparative example 1, prepared and measured in the same way.

Results were obtained for denim 1 of AY = 12.4 and for denim 2 of AY = 24.5.

Example 4:

Similarly to Comparative Example 1, the Mg salt of monoperoxy-4-methyl-phthalic acid (MPMP) as a normal aqueous solution 1, containing 18.4% by weight of MPMP, 2.5% by weight of sodium sulfate 0.4% by weight of xanthan thickener as well as 1 g / l of a marking dye was applied in the same amount on both standard denim products. The marking dye was removed in subsequent rinsing steps and only served to make the spraying process and application uniformity more visible. The preparation and measurement were carried out in the same manner as in Comparative Example 1.

Results were obtained for denim 1 of AY = 18.9 and for denim 2 of AY = 32.5.

Table 1: Spray application on denim 1 (not sanded, treated with abrasive)

Example 5:

From commercially available magnesium bis-monoperoxyphthalate hexahydrate (MMPP), several normal 1 aqueous solutions containing 25% by weight of MMPP, 2.5% by weight of sodium sulfate and 0.4% by weight of Xanthan thickener and adjusted to pH values between 5.5 and 2.5 with phosphoric acid. Of these solutions, 2.0 g were applied to standard denim product 2 in the same manner as in Comparative Example 1, they were processed and measured in the same manner.

The AY values obtained are summarized in Table 2.

Table 2: Spray application on denim 1 - Influence of pH

Reference Example 2:

Standard denim product 2 was treated in a centrifugal washing machine at a liquor ratio of 1: 8 with a liquor containing 15 ml / l of Na hypochlorite solution (120 g / l of active chlorine) for 15 minutes at 50 ° C Subsequently, it was rinsed twice with cold soft water in a liquor ratio of 1:10 and finally neutralized in 2 steps first with 4 g / l sodium bisulfite and then with 4 ml / l 35% hydrogen peroxide for 10 minutes at a liquor ratio of 1:10 and a temperature of 40 ° C. After drying in the dryer, the Y value was determined according to CIE (Datacolor International SF 600 Plus-CT, 30 mm LAV aperture, 4-fold measurement, standard D 65 light calibration).

This resulted in a value Y = 19.2

Example 6:

Standard denim product 2 was treated for 20 min at 60 ° C in a centrifugal washing machine at a liquor ratio of 1: 8 with a liquor containing 20 g / L magnesium bis-monoperoxyphthalate hexahydrate (MMPP) with acid-adjusted citrus at a pH value of 3.0. Subsequently, it was rinsed twice with soft water at 40 ° C with a liquor ratio of 1:10. After drying in the dryer, the Y value was determined according to CIE (Datacolor International SF 600 Plus-CT, 30 mm LAV aperture, 4-fold measurement, standard D 65 light calibration). This resulted in a value Y = 17.8

Claims (9)

1. Procedure for lightening dyed textile fabrics, characterized in that the tissues are treated under acidic pH conditions with an aqueous solution containing an aromatic organic peroxycarboxylic acid as the active component. 2. A method according to claim 1, characterized in that, as peroxycarboxylic acid, aromatic carboxylic acid having one or more percarboxylic groups is used, if necessary substituted with other functional groups, for example, monoperoxy-o-phthalic acid, monoperoxy acid m-phthalic, monoperoxy-p-phthalic acid, monoperoxy-4-methylphthalic acid and / or monoperoxy-1,8-naphthalic acid. 3. Method according to one of claims 1 to 2, characterized in that the rinsing is carried out at a pH value in the range of pH 1 to pH 5, in particular from pH 1.5 to pH 3.5. 4. Process according to any one of claims 1 to 3, characterized in that the peroxycarboxylic acids are used directly, in acid form or as salts, or by the addition of activated carboxylic acid derivatives such as anhydrides and a peroxide source of hydrogen. 5. Method according to any one of claims 1 to 4, characterized in that the pH value of the solution is adjusted with mineral acids or organic acids, in particular with low volatility acids having a vapor pressure <20 Pa a 20 ° C, such as citric acid, maleic acid, lactic acid, phthalic acid, phosphoric acid, sulfuric acid or hydrogen sulfates. Method according to any one of claims 1 to 5, characterized in that the dyed fabrics are contacted with peroxycarboxylic acid or with a solution containing its salts by means of a spray, dip or coating process. Method according to any one of claims 1 to 6, characterized in that thickeners, salts, marking dyes, wetting agents, humidifiers, dispersants and / or other adjuvants are added as additional additives in the application liquids. Method according to any one of claims 1 to 7, characterized in that textile fabrics made of cellulose fibers or cellulose fibers mixed with natural or synthetic fibers are used, dyed with dyes selected from the groups of tank dyes, dyes Direct or sulfur dyes. 9. Method according to claim 8, characterized in that textile fabrics that are dyed with indigo, indigoid dyes or sulfur black are used, as well as combinations of these dyes.