DE1079583B - Process for the continuous bleaching of textile goods by means of a solution of alkali chlorite - Google Patents

Description

The use of alkali chlorites, especially sodium chloride, for bleaching textiles, in particular Cellulose fibers is known. Various methods have been described which economic and technical problems that arise, especially during continuous operation try to solve.

The fact that alkali chlorites are stable in neutral or alkaline solution, so that their Bleaching effect is blocked, d. H. that no chlorine dioxide develops, nor any other change it occurs that, rather, the decomposition of the alkali metal chlorites only takes place in the presence of acids or others Substances requires activation of the initially neutral or alkaline bleaching solution Acidification.

According to a known method, the bleached material is impregnated with a non-acidic alkali metal chlorite solution and after squeezing to activate the bleaching effect for 1 to 2 minutes of exposure exposed to acidic vapors, for example by treatment with a mixture of formic acid and water vapor. This process has the disadvantage that very severe corrosion occurs in the steaming system.

Another known method describes a continuous method in which for the impregnation a non-acidic alkali or alkaline earth chlorite solution is used, which ester of organic acids were added. By heating up the damp, impregnated bleached material The ester is saponified at around 100 ° C, and the acid released activates the chlorite. Within A good bleaching effect is achieved in this way for 1 to 2 hours. Besides the relatively slow bleaching speed A disadvantage of this process is that the bleaching solution mixed with the esters is also disadvantageous is only stable for a few hours at room temperature.

In the process according to the invention, non-acidic, aqueous solutions of Alkali chlorites are used that contain such salts that only occur at elevated temperatures of 60 ° C and more acidify the chlorite solutions and thereby activate them, and that the pressed goods are heated to at least such activation temperature. Here is the decomposition of the alkali chlorite and thus the effectiveness of the bleaching solution by the acid donors mentioned so-called "potentially acidic salts" brought about. This is done in such a way that through Heating the pressed and still moist textile material to at least 60 ° C, for example by blowing it in by water vapor, the amounts of bleach solution present in it being activated and so on Process for continuous bleaching

of textile goods by means of a solution

of alkali chlorite

Applicant:
Stoffel & Co., St Gallen (Switzerland)

Representative:

Dr. W. Beil and A. Hoeppener, lawyers,
Frankfurt / M.-Höchst, Antoniterstr. 36

Claimed priority:
Switzerland from. September 19, 1956

Ernst Rüedi, Ennenda, Glarus (Switzerland),
has been named as the inventor

the actual bleaching of the impregnated fiber material he follows. "Potentially acidic salts" are to be understood as meaning those salts which are at room temperature and slightly elevated temperatures do not produce acidic solutions and thus do not activate the chlorite bleach bath, which, however, decompose at elevated temperatures of around 60 ° C and above and are strongly acidic will. Examples of such salts are: ammonium salts of strong acids, such as ammonium chloride, Ammonium nitrate, ammonium sulfate, ammonium phosphate and ammonium tar occurred as well as salts of strong acids with weak bases, such as magnesium chloride or calcium chloride.

The salts of strong acids with organic bases, such as triethanolamine chloride, can also be used.

To carry out the process according to the invention, the bleached material is treated with the non-acidic, d. H. neutral or weakly alkaline bleaching solution, which, in addition to alkali metal chlorite, contains the potentially acidic ones mentioned Salt additive and "also preferably contains a wetting agent, soaked, pressed and heated. On in this way the bleaching time can be reduced to less than 1 hour.

It should be mentioned that the use of ammonium chloride and other ammonium salts as Addition to a chlorite bleach solution also in the French

- '909 770/406

French patent 1117 236 is described. However, this process is carried out with an acidic bleaching solution whose _pH value was adjusted with acids. The acidification of the chlorite bleach solution using chlorinated hydrocarbons such as tetrachloroethane, which act as an activating agent when heated, is also unsuitable for bleaching the impregnated material outside the liquor, since such organic activators are not or at most only slightly soluble in the aqueous chlorite solution.

A continuous chlorite bleaching process is described in German patent 945024. Included No activating additives are provided for this process, nor are those with the present one Process achievable beneficial effects, especially with regard to the intensive, fast, uniform and low-corrosion bleaching effect.

example 1

A bleaching liquor to be used according to the invention contains, for example, the following additives:

37.5 g / l sodium chlorite (80%),
5.0 g / l wetting agent,
10.0 g / l ammonium chloride.

The bleaching can e.g. B. be carried out as follows: A cotton fabric is covered on a Jigger desized and washed. This is followed by drainage using a suction machine to 50 ° / »moisture content. The goods are brought up again at the jigger and with a Liquor containing the above-mentioned composition, soaked cold and slightly squeezed off, so that there was a squeeze effect of 100%. The remaining liquor was pumped out and could be used for a new one Lot can be used. The jig was now closed and brought to the reaction temperature of 90 to 95 ° C using direct steam. Well happened four re-docking passes to bring the impregnated fabric to the bleaching temperature of around 90 ° C. Then the goods including the precursors were slowly rotated on a jigger roller for one hour, the jig temperature was constantly kept at 95 ° C by means of saturated steam. After two passages With hot and then cold rinsing, a beautifully white and highly absorbent product was obtained.

Example 2

A raw cotton fabric that has previously been desized using conventional methods is applied a continuation system made of stainless steel soaked with the following bleach solution:

30 g / l sodium chlorite (50%),
2 g / l wetting agent,
4 g / l ammonium sulfate,
6 g / l diammonium phosphate.

The impregnation solution is evenly applied to the surface with a squeeze effect of about 80 ° / o at 40 to 50 ^{p C}

ίο tissues distributed. That way with bleach solution Soaked fabric is heated to 90 to 100 ° C and wound up. Then leave the tissue for 50 to 60 minutes at a temperature of

.... rotate 90 to 100 ° C. It is then neutralized and rinsed. A completely bleached fabric is obtained in which the cotton shells are completely are bleached.

The excellent effects of the process are based in particular on the surprisingly large bleaching

ao speed that is extremely intense and without any Fiber damage running bleaching effect and in the extensive reduction of the risk of corrosion. The bleach itself has no corrosive properties. The formation is in the heating phase of chlorine dioxide relatively low, so that even there corrosion of the stainless steels with simple means can be prevented. In addition, the chlorite solution changes concentration and effectiveness during continuous operation, so that even with large production units there is great uniformity in the "bleaching effect is achieved. The remaining liquor not required for a day can be stored unchanged to be used again later, even after a few days, what a enables considerable savings in expensive chlorite.

Claims (2)

Patent claims: 1. Process for the continuous bleaching of textile goods, especially cellulose fibers, by means of a solution of alkali chlorite, characterized by: -: indicates that a non-acidic, aqueous solution of alkali chlorite is used for impregnation, which contains such salts that the chlorite solutions only at elevated temperatures of 60 ° C and more acidify and thereby activate, and that one. ■ the pressed goods to at least such activation temperature warmed up. 2. The method according to claim 1, characterized in that the impregnation liquor still continues contains a wetting agent. Considered publications:
■ German patents No. 826 437, 903 926,
904 885. © 909 770/406 4.60