DE637791C - Process for the finishing of plastics - Google Patents

Description

Some of the plastics or synthetic threads produced by the process of patent 622 851 of cl. 29 b have a yellow or yellowish discoloration and sometimes also a slight opalescence, which does not or only partially disappears with the usual after-treatment with bleach or desulphurisation baths. In some cases the yellow color or the opalescence or both also have an adverse effect on the luster of the plastic or synthetic thread. It has now been found that in the cases in question it is possible to make the yellow color and the opalescence (even if such exist) disappear and to make the plastics or synthetic threads high-gloss and transparent if the plastics or synthetic threads are combined with a warm or hot alkali sulfide solution treated which more alkali sulfide ₀ (as expected Na ₂ S + 9 H ₂ O) as io ° / contains.

The plastics or synthetic threads can be used in the finished state, and the process may be presented dry, moist or wet. However, if desired, you can Include the process in the manufacturing process of the plastic itself, d. H. the the precipitating bath or the circulating wheel or the washing water leaving plastic or Subject artificial thread to the procedure.

If sufficiently strong alkali sulfide solutions are used, the discoloration is so complete, that a previous or subsequent bleaching appears dispensable. However, if desired, it can easily before or after treatment according to the present method.

The plastics or synthetic threads can be tensioned in the present process or subjected to an untensioned condition.

The present process does not exert any detrimental influence on the strength of the Plastics or synthetic threads made of; in many cases it has an elevating effect on them Strengths.

The following exemplary embodiments serve to explain the method according to FIG Invention without, however, limiting its scope thereto.

example 1

Rayon, shown according to Examples I to XVI or XXIV or XXXII of the patent 622 851 of class 29b, which when treated with the generally customary desulphurisation baths (e.g. 0.6 to 10% sodium sulphide solution, calculated as Na ₂ S - \ -g H ₂ O, at 100 ⁰ C) or with 20% sodium sulfide solution, calculated as Na ₂ S + 9 H ₂ O, at 100 ° C not or only partially loses its yellowish color, is in the form of a streak in unbleached and not desulfurized in a state 3o ° / ₀ inserted solution of crystalline sodium sulfide at ioo ° C and herausgenom- to 6g course of about 2 minutes

men, rinsed briefly with hot water, then washed with cold water and dried'.

The clearly yellow g§-, colored or slightly opalescent is completely after the treatment has gained in shine and shows no Ci Opalescence.

Example 2

to procedure as in Example I, but with the difference that instead of 30 ^o / weight sodium sulfide solution is a 58 ° / _o solution of sodium sulfide used crystallized _o;

Example 3

Procedure as in Example 1, but with the difference that instead of 30 ° / _o aqueous sodium sulfide solution, a 20% strength solution is used ^e of crystallized sodium sulphide.

π · 1

Example 4

Procedure as in any of the preceding examples, but with the difference that the rayon after flushing with water io ° / ₀ sulfuric acid is acidified at room temperature and then washed out.

Example 5

Working method as in one of the previous examples, but with the difference that the rayon is bleached and desulfurized in a known manner before treatment with the sodium sulfide solution.

Example 6

Working method as in one of the previous examples, but with the difference that the treatment is carried out in a tense state.

The present method can also be used for plastics, e.g. B. rayon, used who how they are produced according to the method of the patent ι class 29b, from the beginning or after the * 5

icing and / or desulphurising with the aid common very dilute sodium sulphide solution or other desulphurisation bath or agent are white or almost white. By treating according to this method, such silk also acquires valuable properties. For this purpose, the Rayon, which z. B. according to Examples XVII to XXIII of the invention mentioned was treated according to any of the preceding examples.

In the previous examples, you can use another instead of sodium sulfide Use alkali sulfide, e.g. equivalent amounts of potassium sulfide.

The discoloration of those represented by the method of the patent 622 851 cl. 29b Films or finishing layers or coating layers or sheets or tapes or the like, which have a yellowish or yellowish-brown Coloring is done in the same way as in the examples given above for rayon.

Claims (1)

Claim: Process for finishing, in particular for decolorizing plastics or synthetic threads, which are produced according to the process of patent 622 851, characterized in that they are in the dry, moist or wet state with warm or hot alkali metal sulfide solutions that are more than 10 o / _o Alkali sulfide ( _{calculated as Na 2} S -j-9 H ₂ O) contain treated.