DE165691C - - Google Patents

Description

• IMPERIAL

PATENT OFFICE.

The method described in patent specification 54626 of class 22 and its additions for the representation of dyes of the indigo series are known to have only a low level technical interest, since the yields of dyestuffs are too low. The same is true also for the process of patent specification 63310 of class 22, according to which the phenylglycine compounds instead of caustic alkalis, only caustic alkalis and quick lime should be used for heating, as these are based on this process The yields achieved are also only small. The phenylglycine compounds apparently decompose for the most part before indoxyl formation takes place.

It has now been found that the alkali salts of phenylglycine, its homologs and derivatives, when heated with sodium oxide and a diluent or. Liquefying agent, such as caustic potash, caustic soda or mixtures of these substances, in a much smoother way in indoxyl bezw. Indoxylderivate transferred than when heating with caustic alkalis alone.

The sodium oxide has a stronger dehydrating effect than the alkalis and therefore finds also indoxyl formation when sodium oxide is used at lower temperatures rather than when condensing with alkalis alone.

The sodium oxide is obtained from metallic sodium.

Example. 30 kg of well-dried, powdered Caustic potash and 10 kg of sodium oxide are heated to about 250 ° and up to thorough mixing, then the mixture is cooled to about 210 ° and added 10 kg of the potassium salt of phenylglycine with stirring; it will be like that heated for a long time until the indoxyl formation no longer increases. The cooled mass is dissolved in water and the indoxyl formed by the introduction of air into indigo convicted. The yield of indigo is z. B. 4.8 kg.

The yield of indigo stays about the same if the reaction takes place at 210 ° is performed at 250 to 260 °.

When heating the same amount of phenylglycine salt with caustic potash or with caustic alkali and Calcium oxide the following yields of indigo are obtained:

ä) I "35 kg of well-dried caustic potash 10 kg phenylglycine potassium salt are entered at 250 to 260 ° and this Temperature melted for 40 minutes with good stirring. Yield of indigo 0.5 kg.

b) 35 kg of anhydrous caustic potash and 8 kg Hot-burned lime is finely ground in a mill, then the mixture to 250 heated to 260 ° and added 10 kg of phenylglycine potassium salt; the crowd can should be stirred well at first, but will become stiff after a while. After 40 minutes long heating the reaction mixture

worked up in the usual way on indigo. Yield of indigo 1.5 kg.

The phenylglycine can be used in the above

Example be replaced by its homologues or derivatives, with homologues or Derivatives of indoxyl can be obtained under otherwise identical working conditions.

One can use the sodium oxide in the example

also rub first with the alkali and the salt of phenylglycine and then the

Heat the mixture slowly to the required temperature.

Claims (1)

Patent claim: Process for the preparation of indoxyl and its derivatives, consisting therein that alkali salts of phenylglycine, its homologues and derivatives are heated with caustic alkalis and sodium oxide.