JPS6339704B2 - - Google Patents

Description

Claim 1 A method for bleaching fibers using an acidic hydrogen peroxide solution, in which the pH of the acidic hydrogen peroxide solution is kept within the range of 3 to 6 and activated by chlorite and vanadate simultaneously present in the solution. A method for bleaching textiles, characterized by:

2. The method of claim 1, wherein the vanadate is selected from the group consisting of alkali metal vanadates and ammonium vanadates.

3. The method according to claim 1 or 2, wherein the chlorite is sodium chlorite.

4 The amount of vanadate is 0.01 to 1 per oxidation bath.
The method according to any one of claims 1 to 3, wherein the amount is 1g.

5 The amount of vanadate is 0.1 to 1 per oxidation bath.
4. The method according to claim 4, wherein the amount is 0.4 g.

6 The amount of chlorite is 0.1 to 10 per oxidation bath.
The method according to any one of claims 1 to 5, wherein g.

7 The amount of chlorite is 1 to 4 g per oxidation bath
The method according to claim 6.

8. The method according to any one of claims 1 to 7, wherein the bleaching is carried out at a temperature of 30 to 130°C.

9. The method according to claim 8, wherein the temperature is 60 to 90°C.

Description The present invention relates to an improved method of oxidative bleaching carried out in acidic media by the action of hydrogen peroxide.

It is known that the bleaching efficiency of dilute hydrogen peroxide solutions is not very high in acid media and does not normally bleach textiles. For this purpose, hydrogen peroxide or alkali metal peroxides are usually used in an alkaline medium.

Various compounds have been proposed to increase the stability and bleaching efficiency of peroxides in alkaline media. For example, the use of silicates, various magnesium complexes or various other salts is recommended.

However, bleaching in alkaline media is unsuitable for certain fibers such as synthetic fibers.
Additionally, other desirable properties preclude the use of alkaline media even when using fibers such as cellulosic fibers that are not adversely affected by alkaline media. For example, it is desirable to retain the natural fats of vegetable or animal fibers, which are saponified in alkaline media.

The applicant was therefore interested in the problem of industrially improving the bleaching process in acid media by the action of hydrogen peroxide.

For example, various compounds such as metal salts derived from iron or copper can increase the rate of decomposition of hydrogen peroxide baths in acidic media. However, it has been found that this type of activation method is activated by the liberation of oxygen molecules, which has little effect on textile bleaching and therefore cannot be used.

The use of various other compounds has also been proposed, but they do not always provide sufficient bleaching efficiency for bleaching carried out in substantially acidic media using hydrogen peroxide.

The applicant has discovered that the introduction of chlorite and a small amount of vanadate into a dilute acidic hydrogen peroxide solution greatly increases the bleaching efficiency of the acidic oxidizing solution and makes bleaching industrially possible under favorable conditions of PH and temperature. We have experimentally discovered that this can be done.

The use of sodium chlorite alone in the absence of vanadate in acidic hydrogen peroxide solutions does not sufficiently increase the bleaching activity of the acidic medium. In such cases, an improvement in bleaching efficiency can be observed, but it becomes clear that this improvement increases only moderately when bleaching is carried out at relatively high temperatures of 120-130°C. In contrast, in the presence of vanadate, a much greater efficacy of bleaching power is observed and, moreover, this is at a more tolerable temperature where it becomes clear that the bleaching efficiency increases already from a temperature of 40 °C. range.

Furthermore, the bleaching process as described by the Applicant makes it possible to simultaneously bleach and dye fibers, especially synthetic fibers which are usually dyed in the acidic PH range, in one and the same operation.

There is also the possibility of bleaching dyed fabrics in acidic media without the risk of adversely affecting the various dyes, or of enzymatic desizing to economically remove sizing products during the bleaching operation. It offers various other benefits such as:

Therefore, the present invention provides a method for bleaching textiles with an acidic dilute hydrogen peroxide solution, which comprises activating hydrogen peroxide by coexisting a chlorite and an alkali metal vanadate in a bleaching bath. It is on offer.

The acidic PH range of the bleach bath is 3-6, and the temperature is 30
-130°C, preferably 60-90°C.

The vanadate can be selected from the group consisting of alkali metal vanadates and ammonium vanadates. Among the chlorites, preference is given to using sodium chlorite, but other alkali metal chlorites or alkaline earth metal chlorites can also be used.

The amount of hydrogen peroxide required varies widely depending on the particulars of the bleaching operation, for example from 1 to 100 g of 35% hydrogen peroxide per bleach bath.

The required amount of sodium chlorite is 0.1 to 10 g, preferably 1 to 4 g per bleach bath.

The amount of vanadate is 0.01 to 1 per bleach bath.
g, preferably 0.1 to 0.4 g.

The method according to the invention makes it possible to obtain major advantages regarding the treatment and dyeing of various fibers. Among these advantages, the main ones are mentioned: - various fibers which are particularly sensitive to alkaline media, such as synthetic fibers, can all be bleached with hydrogen peroxide, - various dyed textiles can be bleached without decomposing the dye; - simultaneous bleaching and dyeing; - enzymatic desizing during the bleaching operation.

The examples described below are intended to more specifically illustrate the advantages provided by the invention, but are not meant to be limiting in any way.

Example 1 For comparison, raw cotton fiber fabrics are treated using bleaching baths each having the following composition: Bath a: 4 cm ³ /of 35% strength hydrogen peroxide 4 cm ³ /of acetic acid bath b : 4 cm ³ / of 35% concentration hydrogen peroxide 2 cm ³ / of acetic acid 2 g / sodium chlorite bath c: 4 cm ³ / of 35% concentration hydrogen peroxide 2 cm ³ / of acetic acid 2 g / sodium chlorite 0.2 g Sodium vanadate bath d: 4 cm ³ / of 35% strength hydrogen peroxide 2 cm ³ / of acetic acid 0.2 g / of sodium vanadate In all cases, the following conditions are used: Bath ratio 1/10 ( Fiber weight/bath volume ratio) Temperature 90°C Duration 60 minutes After treatment, the various samples are rinsed and then dried.

It is observed that the samples bleached in bath c have a significantly higher degree of whiteness than the samples obtained from the other baths, and furthermore, the removal of the fiber shell is also better.

The whiteness was measured and the following results were shown: Bath a = Whiteness of the sample = 71% Bath B = Whiteness of the sample = 74% Bath C = Whiteness of the sample = 81% Bath d = Whiteness of the sample Degree = 72% Example 2 Fabrics consisting of cellulosic fibers, which have been previously dyed in part with reactive dyes to form dyed fabrics, are each treated with a bleaching bath having the composition described below: Bath a: 3 cm ³ / 35% hydrogen peroxide 2 cm ³ /acetic acid bath b: 3 cm ³ / 35% hydrogen peroxide 2 cm ³ / acetic acid 1.5 g / sodium chlorite 0.2 g / sodium vanadate bath C: 3 cm ³ / of 35% strength hydrogen peroxide 3 g / of sodium silicate 2 cm ³ / of 30% strength caustic soda solution The following operating conditions are used: Bath ratio 1/10 Duration 1 hour Temperature 80 °C After treatment, the fabric is rinsed and Then dry.
The following results were observed from samples from the various baths: Bath a: The undyed fibers are normally bleached and the fiber shell is not removed.

Bath b: very good whiteness. Complete removal of fibrous shell. It is also observed that the various dyes are not affected in any way.

Bath C: Good whiteness. Although the fiber shell is completely removed, a clear deterioration of the dye is observed.

Example 3 A fabric consisting of raw cotton fibers and triacetate fibers is treated with a bleaching bath to which disperse dyes have been added and described below, thereby dyeing the triacetate fibers and bleaching the cellulosic fibers at the same time.

Bath A: 2 cm ³ / of 35% concentration hydrogen peroxide 0.75 g / of sodium chlorite 0.1 g / of sodium vanadate Bath B: 0.5 g / of Disperse Red (Disperse Red) color index Dispersible dye described 2 cm ³ / acetic acid bath c: 0.5 g / dispersible dye 2 cm ³ / acetic acid The temperature of the bath is raised to 80 °C, maintained at this temperature for 20 minutes, then at a temperature of 110 °C Raise to ℃.

Maintain a temperature of 110 °C for 30 minutes, then cool the bath,
Rinse the dyed material.

After dyeing, the samples from bath a are very well dyed in the triacetate section, the cotton fibers are bleached and there is almost no staining due to the disperse dyes.

In contrast, the sample from bath b has a pale, dull color, the cellulosic fibers are not bleached, and severe staining with disperse dyes is observed.

Example 4 A sized raw cotton fiber fabric is treated as described below: The fabric is impregnated by padding in a bath with the following composition: 10 cm ³ /hydrogen peroxide 5 g /chlorous acid Sodium 0.3 g/Sodium vanadate 1 cm ³ / Acetic acid to pH 5 1.5 cm ³ / Diamalt Company Enchirus C
(Enzylase C) After impregnation, the fabric is wrung to retain 90% of the impregnating solution, rolled up, and the rolled fabric is then heated to temperature.
Load into a steam chamber at 80 °C for 90 minutes.

After treatment, the resulting fabric is rinsed and then dried.

After treatment, an average degree of objectivity and good removal of fiber shells are observed. Bleached fabrics also have excellent desizing, which makes them ready for other dyeing or finishing operations.