DE2262611A1 - PROCESS FOR THE TRANSPARENT COLORING OF CELL-GLASS FILMS IN BULK - Google Patents

Description

FARBWERKE HOECHST AKTIENGESELLSCHAFT formerly Master Lucius & Brüning.

File number: HOE 72 / F 388

Date: December 20, 1972 Dr.Ot / cv

Process for the transparent dyeing of cellulose film in the mass

Cell glass foils have so far been colored transparently in the manner of nouns coloring by. Textile materials or by Printing. However, these colorations are not very wet-fast, which is particularly important when these films are used for packaging of food matters. Another possibility for transparent coloring of cellulose glass is to use it of coloring preparations as described in German Patent 1,245,032, however, also show these Dyeings inadequate fastness properties.

There has now been a process for the transparent coloring of cellulose film found, in which a dispersion of a vat dye is made during the production of the films of the viscose solution adds, passes the coagulated film through a reduction bath after passing through the desulphurisation bath, rinses, leads through an oxidation bath and then finishes.

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The method according to the invention is carried out in the following manner. A commercially available vat dye, all representatives of this class, such as those listed in the Color Index, is first dispersed in water. If the dye is present as a dough, it is only necessary to dilute this dough with water. Solid products usually contain dispersing agents and can therefore be easily dispersed in water using a stirrer. The concentration of dye in this dispersion is generally between 5 and 20% by weight. This dye dispersion is then added to the finished viscose and mixed in such an amount that the finished film, depending on the desired color intensity, between 0.1 and 10 wt -.% Contains dye. But you can also inject the aqueous dispersion as such or mixed with a little viscose in the form of a stock solution just before the spinneret into the viscose. The viscose is then forced through the spinning slot into a coagulating bath. The film that forms then runs through further coagulating baths and the descleaning bath. The film is then passed through a reduction bath heated to approx. 60-100 ° C. which contains, for example, 20-100 g sodium dithionite and 20-100 g sodium hydroxide solution (38 ^° Bo) per liter of water. After a short rinsing bath with cold water, the film then runs into an oxidation bath which is adjusted to a content of approx. 1-5 g per liter of active chlorine, for example with sodium hypochlorite. Finally, the film is treated as usual with a plasticizer and dried.

The new process is particularly suitable for dyeing foils, but also for fibers. Except for the viscose process can be done in the same way by the copper-ammonium process work.

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In this way, fully transparent colorations are obtained good fastness properties such as, in particular, wet fastness. Compared to the dyeings with nouns dyes or with dye preparations according to German patent 1 2 ^ 5 032: the dyeings available here are characterized by better lightfastness and bleaching fastness as well as by ' better stability of the dye dispersion in the viscose.

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Example ;

From the commercially available vat dye Vat Orange 1, CI. 59 105, a 20% strength aqueous dispersion was prepared with a high-speed stirrer (600 rpm) for 15 minutes. 25 g of this dispersion were stirred into 1250 g of a spinning viscose with 8 % al-cellulose customary for the production of cell glass and evacuated for 3 hours to remove the air that had been stirred in. Films were drawn, coagulated and regenerated from the viscose pigmented in this way. Immediately after the desulfurization required in the production of cell glass, part of the film was removed for 30 seconds. treated with 60 g / l sodium dithionite and 50 g / l sodium hydroxide solution (38 ⁰ Be) at 85-95 ° C., rinsed with cold water and then oxidized at room temperature with a sodium hypochlorite bath (3 S active chlorine / 1) and then finished as usual. The other part of the foil was finished in the same way, except that the passage through the reduction and oxidation bath was omitted.

The coloristic assessment of the two cellulose films shows that the normally post-treated sample is very opaque, is cloudy-orange in color, while the reduced and reoxidized film has a fully transparent golden-yellow hue having.

A transparent, brilliant red coloration is obtained in the same way if Vat Red I '*, CI. 71 used.

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Claims (1)

Claim; Process for the transparent coloring of cellulose film in the mass, characterized in that a dispersion of a vat dye is added to the viscose solution, the coagulated film after passage through the desulfurization bath leads through a reduction bath, rinses, leads through an oxidation bath and then finishes « 409826/0951