EP0094656B1 - Process for simultaneously desizing and bleaching textile materials made of cellulosic fibres - Google Patents

Description

The desizing and bleaching of fabrics with cellulose fibers is usually carried out continuously in several process stages. First, the starch (size) applied before the weaving process is removed, for example with enzymes (amylases). This process is generally followed by treatment with alkali. The fabric is impregnated with solutions which, in addition to sodium hydroxide solution, can also contain surfactants and, if necessary, complexing agents. The fabric is then steamed for up to 60 minutes. If there is no suitable damper available, the effect can also take several hours at room temperature. The alkali and impurities in the cotton are then removed by hot washing and rinsing.

Another step is bleaching with hydrogen peroxide. Here, the fabric is impregnated with a bleaching liquor which, in addition to hydrogen peroxide, also contains alkali in the form of sodium hydroxide solution. The sodium hydroxide solution is required to activate the hydrogen peroxide and the work is carried out to achieve a good balance at pH values above 10, preferably above pH 12. In order to avoid uncontrolled elimination of oxygen (through catalytic decomposition of the hydrogen peroxide), which leads to damage 4-ne So-called stabilizers is necessary. The most common stabilizer is water glass (sodium silicate), which releases oxygen in a controlled manner due to its buffering effect and also prevents catalytic decomposition by incorporating heavy metal ions into its molecular chain. The disadvantage here is that sodium silicate is difficult to remove from the fabric and thus leads to an unpleasant, sandy grip on the fabric. Furthermore, deposits of silicate residues on the machine parts such as rollers, apparatus walls, etc. can easily occur. Therefore, one tries to replace water glass with other, mostly organic stabilizers e.g. based on salts of ethylenediaminetetraacetic acid. However, these stabilizers mostly lack the buffering effect of sodium silicate, so that the release of oxygen is less controlled and the bleaching effects are worse. With this sequence of process stages, one obtains not only a high bleaching effect but also a perfect desizing.

For reasons of rationalization, however, efforts are being made to shorten this 3-stage process, e.g. by no separate desizing. The hydrogen peroxide bleaching gives you a partial oxidative breakdown of the starch and this partial desizing is sufficient for certain articles, e.g. White goods, which are only finished in the following. Peroxidisulfates (such as ammonium, potassium, sodium persulfates) can also be used as further oxidative desizing agents. An addition to the bleaching liquors is not possible, however, because the fiber attack is too strong. Rather, they are used in the alkali stage and a degree of desizing is achieved which also permits the fabrics treated in this way to be used later in the dyeing.

To further shorten the process, it would now be desirable to be able to carry out the required stripping in the bleaching stage and, at the same time, to do without a separate, upstream alkali treatment if possible.

• a) 1 bis 10, vorzugsweise 1 bis 3 g eines Peroxid-Aktivators
• b) 10 bis 80, vorzugsweise 15 bis 60 ml Wasserstoffperoxid,
• c) 1 bis 10, vorzugsweise 3 bis 6 g Harnstoff
• d) 1 bis 10, vorzugsweise 3 bis 6 g eines Tensids und eine schwach alkalisch reagierende Verbindung in einer solchen Menge enthält, daß der pH-Wert der Flotte 7 bis 8 beträgt.

A purely one-step process has now been found which enables simultaneous desizing and bleaching in a fleet. This method consists in treating the textile material with a liquor in 1 liter of water

• a) 1 to 10, preferably 1 to 3 g of a peroxide activator
• b) 10 to 80, preferably 15 to 60 ml of hydrogen peroxide,
• c) 1 to 10, preferably 3 to 6 g of urea
• d) 1 to 10, preferably 3 to 6 g of a surfactant and a weakly alkaline compound in such an amount that the pH of the liquor is 7 to 8.

The process according to the invention is carried out by the processes customary for bleaching, for example in the form of hot or cold bleaching. In the first case, the fabric is impregnated with a liquor of the composition described above, squeezed to a liquor absorption of approximately 60 to 120% by weight and then steamed to a temperature of approx. 40 to 140, preferably 80 to 105 ° C heated. The duration of treatment depends on the respective temperature and can be between about 2 minutes and several hours. In cold bleaching, the impregnated goods are left to stand at room temperature for 8 to 24 hours, preferably 12 to 18 hours, depending on the degree of desizing and bleaching required. In both cases, the goods are finally washed and dried.

Finally, the fabric can also be treated continuously in a long liquor of the composition given above, for example at a liquor ratio of approximately 1:10. The temperature of the bath is about 50 to 95 °, preferably 60 to 85 ° C and the treatment time is about 10 to 40 minutes. In order to maintain a uniform concentration of the chemicals in the liquor, it is advisable to impregnate the incoming web beforehand in the manner described above.

The hydrogen peroxide required for the process according to the invention is preferably used in the form of the commercially available aqueous 35% solution. The above-mentioned limit values of 10 and 80 ml for hydrogen peroxide relate to this concentration. All products that are known to the person skilled in the art under this term are suitable as surfactants. Commercial surfactants are preferably taken from the following groups: sec. Alkanesulfonates, alkylphenol sulfonates, nonylphenol oxethylates and fatty alcohol oxethylates. These surfactants serve for better wetting of the goods with the fleet. Sodium bicarbonate and triethanolamine in particular are used as weakly alkaline compounds. These substances are added to the bleaching and desizing liquor in such an amount that a pH of 7 to 8 is reached in the liquor. As a result of this low pH range compared to a conventional bleaching which is carried out in a strongly alkaline bath, it is also possible to add conventional enzymatic desizing agents to the liquor which are only effective in a pH range from 6.5 to 7.5 are. Such an optional addition of enzymatic desizing agents is particularly recommended for stubborn stains to be removed. It is also possible to add customary oxidative desizing agents, such as ammonium, potassium or sodium peroxidisulfate, to the liquor.

Peroxide activators are all compounds which are already known for this purpose, such as acylated hydroxylamines, acylamines and acylated heterocycles (see text. Praxis Intern. 1974, p. 1392 ff.). Particularly preferred acyl compounds are tetraacetylethylenediamine and tetraacetylglycoluril.

The method according to the invention permits simultaneous desizing and bleaching in a bath, which results in a significant simplification in comparison with the conventional procedure with a separate bleaching and desizing bath. However, it is also possible to pretreat the fabric separately in an alkali bath beforehand. Another major advantage of the process described here is that one only works in the weakly alkaline range. This avoids the risk of damage to the fibers due to degradation, as can occur with conventional bleaching in the strongly alkaline range Stabilizing agents are connected.

Example 1:

• 30 ml/I Wasserstoffperoxid (35 Gew.%)
• 2 g/1 Natriumbicarbonat
• 3 g/I Harnstoff
• 5 g/1 Nonylphenoloxäthylat mit 10 AeO
• 3 g/l Tetraacetylethylendiamin

enthielt. Die Flottenaufnahme betrug 70 Gew.-%.A cotton batiste was impregnated with a fleet after the singeing

• 30 ml / l hydrogen peroxide (35% by weight)
• 2 g / 1 sodium bicarbonate
• 3 g / l urea
• 5 g / 1 nonylphenol oxyethylate with 10 AeO
• 3 g / l tetraacetylethylenediamine

contained. The liquor absorption was 70% by weight.

After impregnation, the fabric was heated to 100 ° C. and stored in a storage device at this temperature for 20 minutes. Then was washed or rinsed on a continuous washing machine 2x at 90 ° C, 2x at 60 ° C and 2x cold. The material had the following data:

Example 2:

• 50 ml/I Wasserstoffperoxid (35 Gew.-%)
• 2 ml/1 Triäthanolamin
• 3 g/1 Harnstoff
• 5 ml/l Tensid (90% Alkansulfonat 30 %ig+10% Nonylphenolpolyglykoläther mit 8 AeO)
• 3 g/1 Tetraacetylethylendiamin
• 1 g/1 Kaliumpersulfat

Die Flottenaufnahme betrug 70%.A shirt fabric made of polyester / cotton 50:50 was impregnated with the following bleaching solution:

• 50 ml / l hydrogen peroxide (35% by weight)
• 2 ml / 1 triethanolamine
• 3 g / 1 urea
• 5 ml / l surfactant (90% alkanesulfonate 30% + 10% nonylphenol polyglycol ether with 8 AeO)
• 3 g / 1 tetraacetylethylenediamine
• 1 g / 1 potassium persulfate

The fleet uptake was 70%.

After impregnation, the fabric was wound up on a dock and left to stand at room temperature for 16 hours. It was then washed out continuously on 2 units of a 6-box washing machine with the addition of 3 ml / l sodium hydroxide solution 50% and 3 ml / l of the surfactant mixture specified above. In 2 further boxes, rinsing was carried out at 60 ° C. and 2xcold.

The fabric showed the following values:

Example 3:

• Imprägnieren mit Behandlungsflotte im Netztrog (Abquetscheffekt 75%);
• Verweilen in der Flotte im Verweilgerät;
• Auswaschen auf einer Wascheinheit bei Kochtemperatur;
• Spülen auf 2 Wascheinheiten bei 60 bzw. 25°C;
• Abquetschen und Trocknen.

8000 m of cotton cord were treated in a sub-fleet storage as follows:

• Impregnation with treatment liquor in the mesh trough (squeezing effect 75%);
• Linger in the fleet in the indwelling device;
• Washing out on a washing unit at cooking temperature;
• Rinsing on 2 washing units at 60 or 25 ° C;
• Squeeze and dry.

• 30 ml/l Wasserstoffperoxid (35 Gew.%)
• 3 g/l Natriumbicarbonat
• 3 g/l Harnstoff
• 3 g/l Tensid (Alkylbenzolsulfonat 70 %ig)
• 3 g/I Tetraacetylethylendiamin

Die Verweilzeit im Flottenspeicher betrug 25 Minuten bei 85°C.The treatment fleet in the mesh trough and in the dwell device had the following composition:

• 30 ml / l hydrogen peroxide (35% by weight)
• 3 g / l sodium bicarbonate
• 3 g / l urea
• 3 g / l surfactant (alkyl benzene sulfonate 70%)
• 3 g / l tetraacetylethylenediamine

The residence time in the liquor store was 25 minutes at 85 ° C.

After washing, rinsing and drying, the fabric had the following values:

Example 4:

• 60 ml/I Wasserstoffperoxid (35 Gew.-%)
• 1 g/I Triethanolamin
• 3 g/l Harnstoff
• 3 g/I Tetraacetylolykoluril
• 3 g/l Alkansulfonat 60 %ig.

After singeing, a cotton nettle was impregnated with a liquor containing 40 g / l caustic soda and 5 g / l surfactant (60% alkane sulfonate) without desizing. The fleet uptake was 85%. After impregnation, the fabric was brought to 100 ° C. with steam and left at this temperature for 20 minutes. It was then washed continuously in a washing machine (2x at 90 ° C, 2x at 60 ° C, 2xcold). After this treatment, the tissue showed a degree of desizing according to the "Tegewa" scale of 1 (1 = no desizing effect, 9 = full desizing). The alkali test was negative. The fabric was then impregnated with the following liquor without intermediate drying:

• 60 ml / l hydrogen peroxide (35% by weight)
• 1 g / l triethanolamine
• 3 g / l urea
• 3 g / l tetraacetylolycoluril
• 3 g / l alkanesulfonate 60%.

The squeezing effect was 90% and the liquor exchange during the impregnation was found to be 85%.

After impregnation, the material was also brought to 100 ° C. with steam and left at this temperature for 30 minutes. It was then washed and rinsed in the manner indicated above.

After the treatment, the goods had the following properties:

Example 5:

• 2 g/l Bakterienamylase (15 000 Effront-Einheiten)

zugesetzt wurden.The same goods were treated in the manner indicated above, with the difference that the bleaching step was additionally

• 2 g / l bacterial amylase (15 000 Effront units)

were added.

With otherwise the same results, the degree of desizing rose to 9.

Claims (4)

1. A process for the simultaneous desizing and bleaching of textile material comprising cellulose fibers, characterized in that the textile material is treated with a liquor containing per liter of water

a) from 1 to 10 grams of a peroxide activator,

b) from 10 to 80 ml of hydrogen peroxide,

c) from 1 to 10 grams of urea,

d) from 1 to 10 grams of a surfactant and a compound of weakly alkaline reaction in such an amount that the pH of the liquor is 7 to 8.

2. The process as claimed in Claim 1, characterized in that the textile material is treated with a liquor containing

a) from 1 to 3 g of tetraacetyl ethylenediamine

b) from 15 to 60 ml of hydrogen peroxide,

c) from 3 to 6 g of urea and

d) from 3 to 6 g of surfactant.

3. The process as claimed in Claim 1, characterized in that the textile material is treated with a liquor containing as surfactant a sec.-alkanesulfonate, alkylphenolsulfonate, nonylphenoloxethylate or fatty alcohol oxethylate, and as compound having a weakly alkaline reaction sodium bicarbonate or triethanolamine.

4. The process as claimed in Claim 1, characterized in that an enzymatic desizing agent is added to the liquor.