DE719691C - Process for the production of viscose with normal viscosity from unripened alkali cellulose - Google Patents

Description

In the viscose manufacturing process, if one omits the ripening of the alkali cellulose, one obtains a viscose with too high a viscosity. The purpose of the ripening process is that Adjustment of the viscosity of the viscose to the values required for processing.

It is known that the ripening effect is a function of the ripening temperature and the ripening time and that the effect of oxygen from the air during the ripening process is considerable Role play. In any case, if oxygen is excluded, ripening takes place much more slowly.

Various methods have already been proposed in order to save the aging of the alkali cellulose or to increase it very considerably shorten, which of course is great from the standpoint of economy and space Offers advantages.

According to Dutch patent ^{specification χ} 3 ° 57 and British patent specification 433 414, higher process temperatures are used in order to accelerate ripening. However, these working methods have various disadvantages, for example that the alkali cellulose must be cooled before sulfiding. There is a risk that condensation will form and come into contact with the alkali cellulose, resulting in locally poorly sulfided pieces and thus poorly filtering viscose.

The German patent specification 610 329 proposes the viscosity of unripened alkali

Cellulose produced viscose reduce the fact that a gas that is oxygen is richer than the atmosphere that is brought into action. This is also economic in itself The procedure has disadvantages. Finally, the addition of certain chemicals, including Peroxides, from di- and polyhydric alcohols (German patent 564 8So) and sodium sulfide (German Patent 526480), for immersion liquor or for alkali cellulose recommended, which actually results in a considerable reduction in viscosity can. However, these chemicals are not without unpleasant side effects, their use also entails costs.

The invention now relates to a Working method through which the alkali cellulose ripening is also saved or significantly shortened without the addition of special chemicals and those in normal devices can be carried out without the need for unusually high temperatures are. The way of working makes use of a relatively short-term impact from atmospheric air to the xanthate in a very specific stage of the Sulphidation. This is done in the usual way in the rest of the way Baratten initially only carried out a part of the required amount of sulphidation Carbon disulfide added. After this amount of carbon disulfide through the alkali cellulose is absorbed, without interruption of the rotating movement of the Baratten for a short time air is through the Baratten passed through. Then the air flow is interrupted and the rest Amount of carbon disulfide added for normal completion of the sulfiding process.

Surprisingly, the resulting reduction in viscosity is the viscosity of the viscose much larger than that obtained by passing air over alkali cellulose that has not yet been sulfided or over normally produced xanthate at the same temperature and during the same Time scored.

When changing the ratio of the amounts of carbon disulfide before and after Passing air are added, it follows that the viscosity reduction achieved goes through a strongly protruding maximum, which is reached when the added before the passage of air Amount of carbon disulfide is about 60 to 70% of the total amount.

Below are individual Ver search results as an example reported that are obtained with an unripened alkali cellulose with 15.5% NaOH and 29% cellulose. the Numbers indicate the subsequent viscosity determined with one and the same viscometer produced viscose in seconds. That added to the action of air

The amount of carbon disulfide is in all cases 25% and the total amount is 37% of the dry weight of the cellulose (viscose composition: 4.5% NaOH and 6 ⁰ _{I 6} cellulose).

Table 1

Time of implementation
of air Temperature at which the
Exposure to air took place 30 ° Seconds 85
65 125
65
35 ι hour
2 hours
3 hours
4 hours 25 °

For comparison, the viscosities are given which are obtained on exposure from air to unsulfided alkali cellulose and to normally sulfided with 37% carbon disulfide Xanthate. The exposure time was 3 hours.

Tabel 2 temperature
zy 30 = Seconds Action on Alkalicellu
loose
Action on xanthate
Influence on partially sul-
fidated xanthate ge
according to table 1 279 185
186 135
85 35

It is therefore possible, with almost no special costs and without any change in the A ^ arrangement with the help of a very simple no Change in the implementation of the sulphiding process results in a very considerable reduction to achieve the viscosity. The viscose obtained in this way behaves in everyone Respect normal.

Claims (2)

Patent claims: i. Process for the production of viscose with normal viscosity from un- iao matured alkali cellulose, characterized in that the rest of the normal Sulphidation process carried out wisely and with normal amounts of carbon disulfide The sulfidation is carried out in two stages, with initially only a part of the total amount of carbon disulfide added after the action of this carbon disulfide interrupted and air over the partially sulfided mass and only then is the remaining amount of carbon disulfide added to terminate the sulphidation process. 2. The method according to claim i, characterized in that 60 to 70 ^e / o of the total amount of carbon disulfide is brought to act on the alkali cellulose before air is passed over.