METHOD FOR BRIGHTENING DYED TEXTILES

Abstract

The invention relates to a method for brightening dyed textiles and to the textiles thereby produced. The method is characterized by treating the materials with an aqueous liquor containing an organic peroxocarboxylic acid having a hydrophobic group, consisting of at least 5 C atoms, as the active component.

Claims

1. A process for brightening dyed textile fabrics by treatment with a bleaching solution that more or less destroys the dye, characterized in that said fabrics are treated with an aqueous solution containing an aromatic organic peroxocarboxylic acid as an active component, under acidic pH conditions.

2. The process according to claim 1, characterized in that an aromatic carboxylic acid with one or more percarboxy groups, optionally substituted with further functional groups, is employed as said peroxocarboxylic acid, for example, monoperoxo-orthophthalic acid, monoperoxo-metaphthalic acid, monoperoxo-paraphthalic acid, monoperoxo-4-methylphthalic acid, and/or monoperoxo-1,8-naphthalic acid.

3. The process according to claim 1, characterized in that said brightening is performed at a pH within a range of from 0 to 7, especially from pH 1 to pH 5.

4. The process according to claim 1, characterized in that said peroxocarboxylic acids are is directly employed in the acid form or as salts, or obtained by the addition of activated carboxylic acid derivatives, such as anhydrides, and a hydrogen peroxide source.

5. The process according to claim 1, characterized in that the pH of the solution is adjusted by mineral acids or organic acids, especially with low volatile acids having a vapor pressure of <20 Pa at 20 C., such as citric acid, maleic acid, lactic acid, phthalic acid, phosphoric acid, sulfuric acid, or hydrogensulfates.

6. The process according to claim 1, characterized in that the dyed fabrics are contacted with a solution containing said peroxocarboxylic acid or salts thereof by a spraying, dipping or coating process.

7. The process according to claim 1, characterized in that said aqueous solution may contain one or more of thickening agents, salts, marking dyes, wetting agents, humectants, dispersing agents and/or other auxiliary agents.

8. The process according to claim 1, characterized in that textile fabrics are made from cellulose fibers or cellulose fibers in admixture with natural or synthetic fibers, and are dyed with dyes selected from the groups of vat, direct or sulfur dyes.

9. The process according to claim 8, characterized in that textile fabrics are dyed with indigo, indigoid dyes or sulfur black, and with combinations of such dyes.

10. (canceled)

11. The process according to claim 3, wherein said pH is within a range of 1 to 5.

12. The process according to claim 3, wherein said pH is within a range of 1.5 to 3.5.

Description

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Surprisingly, it has been found that organic peroxocarboxylic acids, especially certain linear or cyclic aliphatic or aromatic peroxocarboxylic acids or -dicarboxylic acids, that contain hydrophobic pendant groups, preferably alkyl radicals with at least 5 carbon atoms, more preferably with 5 to 30 carbon atoms and even more preferably with chain lengths of from 6 to 10 carbon atoms, have a very high brightening effect on dyed textiles. In particular, indigo and indigoid dyes can be bleached under moderate conditions, so that a local treatment, for example, by spraying, can be performed simply and under practicable conditions.

[0025] The term hydrophobic usually designates the association of non-polar groups or molecules of an aqueous environment. It characterizes substances that do not mix with water and mostly let it roll off on surfaces.

[0026] Non-polar materials, such as fats, waxes, alcohols with long alkyl radicals, i.e., except for methanol, ethanol and propanol, alkanes, alkenes etc., are hydrophobic. When hydrophobic materials are dissolved in water, there is generally a so-called hydrophobic effect, and with some small hydrophobic species, such as methane or xenon, even entropically unfavorable clathrate structures form. Therefore, the solubility of such materials in water is generally low.

[0027] Hydrophobic materials are almost always lipophilic, i.e., they dissolve well in fat and oil. Surfaces exhibiting a contact angle of more than 90 with water are also referred to as hydrophobic. Thus, hydrophobic radicals within the meaning of the present invention include, in particular, a contiguous radical of at least 5 carbon atoms, a carbon chain preferably saturated with hydrogen atoms to form an alkyl radical or aryl radical.

[0028] Particularly preferred as bleaching agents according to the invention are aromatic peroxocarboxylic acids consisting of one or more condensed aromatic rings, optionally substituted with one or more further peroxocarboxylic acid groups at any possible position. These aromatic peroxocarboxylic acids according to the invention may further be substituted with at least one functional group selected from alkyl, aryl, carboxylate, sulfonate, halide, nitro or hydroxy groups at any possible position in the aromatic ring system. As preferred examples, there may be mentioned: mono- or diperoxo-ortho-, -meta- or -paraphthalic acid, mono- or diperoxo-4-methyl-o-phthalic acid, mono- or diperoxo-1,8-naphthalic acid.

[0029] The peroxocarboxylic acids may be employed both in the acid form and as salts, or also be produced in situ by the addition of activated carboxylic acid derivatives (for example, as anhydrides) and a hydrogen peroxide source, or in some other way in the process. As salts, alkali or alkaline earth metal salts are preferably employed, for example, Li, Na, K, Mg or Ca salts.

[0030] Even more surprisingly, it has been found that the treatment can be performed particularly efficiently under acidic pH conditions, although the skilled person knows that peroxocarboxylic acids, for example, peracetic acid, have the highest bleaching efficiency at a pH near the pKs values, i.e., in the neutral to weakly alkaline range. Preferably, the pH of the solution is within a range of from 0 to 7, more preferably within a range of from pH 1 to pH 5, even more preferably within a range of from pH 1.5 to pH 3.5.

[0031] As further additives, native and synthetic thickening agents, salts, such as alkali and alkaline earth metal sulfates, phosphates and, if needed, marking dyes, for example, dyes, wetting agents, humectants, such as glycerol, urea, or dispersing agents or other auxiliary agents are added to the application liquor. The use of dyes (marking agents) serves for a better visual trackability of the course of spraying. This is particularly important to practice, because the purple permanganate strongly colors the spraying solution while the spraying solution according to the invention is basically colorless.

[0032] The above mentioned pH ranges either occur by themselves because of the reactants employed, or may be adjusted by further additives. It is particularly preferred according to the present invention to adjust the pH of the solution with mineral acids or organic acids. Even more preferred in this respect are low volatile acids, i.e., acids having a vapor pressure of <20 Pa at 20 C., such as citric acid, maleic acid, lactic acid, phthalic acid, phosphoric acid, sulfuric acid, or hydrogensulfates.

[0033] A wide variety of methods for contacting the dyed fabrics with the peroxocarboxylic acid are available to those skilled in the art. It is particularly preferred in this respect to contact the dyed fabrics completely or partially with solutions containing peroxocarboxylic acid or salts thereof by a spraying, dipping or coating process.

[0034] By means of the present invention, a wide variety of textiles or textile fabrics can be contacted with the peroxocarboxylic acids. It is particularly preferred in this respect to employ textile fabrics made from cellulose fibers or cellulose fibers in admixture with natural or synthetic fibers, dyed with various dyes. It is particularly preferred according to the present invention to select these dyes from the groups of vat, direct or sulfur dyes.

[0035] The process of the present invention is particularly suitable for textile fabrics dyed with indigo, indigoid dyes or sulfur black, and with combinations of such dyes.

[0036] Another embodiment of the present invention includes bleached textiles obtainable by a process as defined above. Jeans are particularly preferred within the meaning of the definition of such bleached textiles.

[0037] The effect of the liquors according to the invention in a local bleaching treatment was determined in a direct comparison with potassium permanganate, representing the prior art.

[0038] All peroxocarboxylic acids were employed in a concentration that corresponds to approximately three times the normality of a 2% potassium permanganate solution as employed on average today.

[0039] The bleaching effect was determined on two different denim fabrics, each with determining the Y values according to CIE with Datacolor International SF 600 Plus-CT, aperture 30 mm LAV, measurement in quadruplicate, calibration with standard light D 65.

[0040] As the bleaching result, it is preferred according to the invention that >40% of the bleaching effect of a standard KMnO.sub.4 solution was achieved, more preferably >60%, even more preferably >80%.

Examples

Reference Example 1

[0041] On two commercially available denim fabrics (denim 1=not desized, scraping pretreatment with abrasive paper; denim 2=desized, stonewash treatment), a rectangular area of 120 cm.sup.2 was marked and covered with adhesive film at the edges against the adjacent areas. These areas were uniformly sprayed with 2 g each of an aqueous solution of 20 g/l potassium permanganate (0.38 normal), and the fabric specimens were subsequently weighed to determine the quantity applied. After an exposure time of 20 min at room temperature, the fabric specimens were neutralized with 4 g/l sodium bisulfite in a washer-extractor together with untreated denim fabric as ballast at first for 10 min at 50 C. and a liquor ratio of 1:8, then rinsed cold three times at a liquor ratio of 1:10, followed by drying in a tumbler. Of the thus obtained specimens, the Y value according to CIE was measured (Datacolor International SF 600 Plus-CT, aperture 30 mm LAV, measurement in quadruplicate, calibration with standard light D 65) each on and beside the spray-treated area, and the degree of brightening was determined from the difference as Y.

[0042] This yielded values of Y=19.2 for denim 1, and Y=35.0 for denim 2.

Comparative Example 1

[0043] From monoperoxoglutaric acid (MPGA), a 1-normal aqueous solution containing 15% by weight MPGA, 2.5% by weight sodium sulfate and 0.4% by weight xanthan gum thickener was prepared and adjusted to a pH of 2.9 with phosphoric acid. Of this solution, 2.0 g was applied on both standard denim fabrics in the same way as in Reference Example 1. After an exposure time of 20 min at 60 C., the fabric specimen was rinsed in a way analogous to that of Reference Example 1 without neutralization once at 40 C. and once cold at a liquor ratio of 1:10, followed by drying in a tumbler. Of the thus obtained specimens, the Y value according to CIE was measured in a way analogous to that of Reference Example 1 each on and beside the spray-treated area and the degree of brightening was determined from the difference as Y.

[0044] This yielded values of Y=4.7 for denim 1, and Y=8.3 for denim 2.

Comparative Example 2

[0045] By analogy with Comparative Example 1, monoperoxomaleic acid (MPMA) as a 1-normal aqueous solution containing 13.8% by weight MPMA, 2.5% by weight sodium sulfate and 0.4% by weight xanthan gum thickener was applied in equal amounts to both standard denim fabrics, processed in the same way, and measured.

[0046] This yielded values of Y=4.9 for denim 1, and Y=10.5 for denim 2.

Example 1

[0047] By analogy with Comparative Example 1, commercially available magnesium bis(monoperoxophthalate) hexahydrate (MMPP) as a 1-normal aqueous solution containing 25% by weight MMPP, 2.5% by weight sodium sulfate and 0.4% by weight xanthan gum thickener was applied in equal amounts to both standard denim fabrics, processed in the same way, and measured.

[0048] This yielded values of Y=18.7 for denim 1, and Y=34.3 for denim 2.

Example 2

[0049] By analogy with Comparative Example 1, monoperoxophthalic acid (MPPA) as a 1-normal aqueous solution containing 16.8% by weight MPPA, 2.5% by weight sodium sulfate and 0.4% by weight xanthan gum thickener was applied in equal amounts to both standard denim fabrics, processed in the same way, and measured.

[0050] This yielded values of Y=18.1 for denim 1, and Y=32.2 for denim 2.

Comparative Example 3

[0051] By analogy with Comparative Example 1, monoperoxo-cis-cyclohexane-1,2-dicarboxylic acid (MPDCA) as a 1-normal aqueous solution containing 17.5% by weight MPDCA, 2.5% by weight sodium sulfate and 0.4% by weight xanthan gum thickener was applied in equal amounts to both standard denim fabrics, processed in the same way, and measured.

[0052] This yielded values of Y=12.4 for denim 1, and Y=24.5 for denim 2.

Example 4

[0053] By analogy with Comparative Example 1, monoperoxo-4-methylphthalic acid Mg salt (MPMP) as a 1-normal aqueous solution containing 18.4% by weight MPMP, 2.5% by weight sodium sulfate and 0.4% by weight xanthan gum thickener, and in addition 1 g/l of a marking dye was applied in equal amounts to both standard denim fabrics. The marking dye was removed again in the subsequent rinsing steps and only served to make the course of the spraying and the uniformity of the application more visible. The processing and measurement were effected in the same way as in Comparative Example 1.

[0054] This yielded values of Y=18.9 for denim 1, and Y=32.5 for denim 2.

TABLE-US-00001 TABLE 1 Spray application on denim 1 (not desized, abrasive-treated) Tem- Exposure Efficiency perature time CIE relative pH [ C.] [min] Y to KMnO.sub.4 Monoperoxophthalic acid 2.8 60 20 18.7 93% Mg salt Monoperoxophthalic acid 2.8 60 20 18.1 90% Monoperoxomaleic acid 2.8 60 20 4.9 24% Monoperoxo-cis- 2.8 60 20 12.4 61% cyclohexane-1,2- dicarboxylic acid Monoperoxoglutaric 2.8 60 20 4.1 20% acid Monoperoxo-4- 2.8 60 20 18.9 94% methylphthalic acid Mg salt Potassium permanganate 7.0 25 10 20.2 reference

TABLE-US-00002 TABLE 2 Spray application on denim 2 (desized, stonewashed) Tem- Exposure Efficiency perature time CIE relative pH [ C.] [min] Y to KMnO.sub.4 Monoperoxophthalic 2.8 60 20 33.4 95% acid Mg salt Monoperoxophthalic acid 2.8 60 20 32.2 92% Monoperoxomaleic acid 2.8 60 20 10.5 30% Monoperoxo-cis- 2.8 60 20 24.5 70% cyclohexane-1,2- dicarboxylic acid Monoperoxoglutaric acid 2.8 60 20 8.3 24% Monoperoxo-4- 2.8 60 20 32.5 93% methylphthalic acid Mg salt Potassium permanganate 7.0 25 10 35.0 reference

Example 5

[0055] From commercially available magnesium bis(monoperoxophthalate) hexahydrate (MMPP), several 1-normal aqueous solutions containing 25% by weight MMPP, 2.5% by weight sodium sulfate and 0.4% by weight xanthan gum thickener were prepared and adjusted to a pH of from 5.5 to 2.5 with phosphoric acid. Of these solutions, 2.0 g was applied to standard denim fabric 2 in the same way as in Comparative Example 1, processed in the same way, and measured.

[0056] The values of Y obtained thereby are summarized in Table 3.

TABLE-US-00003 TABLE 3 Spray application on denim 2influence of pH Tem- Exposure Efficiency perature time CIE relative pH [ C.] [min] Y to KMnO.sub.4 Monoperoxophthalic 5.5 60 20 10.4 30% acid Mg salt 4.5 60 20 12.2 35% 3.5 60 20 24.5 70% 3.0 60 20 31.0 89% 2.5 60 20 34.1 97% Potassium 7.0 25 10 35.0 permanganate reference

Reference Example 2

[0057] Standard denim fabric 2 was treated on a washer-extractor at a liquor ratio of 1:8 with a liquor containing 15 ml/l Na hypochlorite solution (120 g/l active chlorine) at 50 C. for 15 min. This was followed by rinsing twice with cold soft water at a liquor ratio of 1:10, and subsequently, the fabric was neutralized in 2 steps at first with 4 g/l sodium bisulfite and then with 4 ml/l hydrogen peroxide 35% for 10 min each at a liquor ratio of 1:10 and a temperature of 40 C. After drying in a tumbler, the Y value according to CIE of one specimen was measured (Datacolor International SF 600 Plus-CT, aperture 30 mm LAV, measurement in quadruplicate, calibration with standard light D 65).

[0058] This yielded a value of Y=19.2.

Example 6

[0059] Standard denim fabric 2 was treated on a washer-extractor at a liquor ratio of 1:8 with a liquor containing 20 g/l magnesium bis(monoperoxophthalate) hexahydrate (MMPP) at 60 C. for 20 min after adjusting to pH 3.0 with citric acid. This was followed by rinsing twice with soft water at 40 C. at a liquor ratio of 1:10. After drying in a tumbler, the Y value according to CIE of one specimen was measured (Datacolor International SF 600 Plus-CT, aperture 30 mm LAV, measurement in quadruplicate, calibration with standard light D 65).

[0060] This yielded a value of Y=17.8.