DE2717371B2 - Process for the preparation of mixtures from free-flowing sodium and potassium salts of phenylglycine and phenylglycine-o-carboxylic acid - Google Patents

Description

The invention relates to a method for the production of mixtures of free-flowing sodium and Potassium salts of phenylglycine and phenylglycine-o-carboxylic acid by stepwise saponification of the corresponding dinitriles with waste mother liquors.

Phenylglycine salt is the starting product for the production of indigo. The salts are after the Information in DT-PS 120105 or in BIOS Final Report No. 986, page 312 or GB-PS 1119256 produced by saponification of phenylglycine nitrile with aqueous alkali hydroxide. As the phenylglycine salt must be isolated from the solution by evaporation to dryness, is used as the alkali metal hydroxide in the Usually 50% by weight alkali hydroxide solutions.

It has now been found that mixtures of free-flowing sodium and potassium salts of phenylglycine can be used or the phenylglycine-o-carboxylic acid stepwise saponification of the corresponding nitriles with aqueous alkali solutions in the presence of aniline obtained at temperatures between 50 ° C and the boiling point and evaporation of the reaction mixture, if mother liquors are used for saponification, which is the case with alkali hydroxide / alkali amide melts incurred and the - based on the mother liquor - 7 to 30 wt .-% sodium-potassium hydroxide mixture, up to 20% by weight sodium / potassium carbonate and optionally up to 10% by weight of further constituents in addition to smaller amounts of colored constituents and organic decomposition products.

As incurred in alkali hydroxide / alkali amide melts Mother liquors, especially those that come after the oxidation of the indoxyl to indigo during the separation the resulting mother liquor of the indigo formed and the in the production of 2,4-dihydroxychino-Hn resulting mother liquor into consideration.

The mother liquor resulting from the production of indigo is yellow due to flavindine dyes or due to it Decomposition products of indoxyl colored green. The waste liquor resulting from the production of dihydroxyquinoline contains decomposition products and saponification products of the N-acetylanthranilic acid used for production.

These waste eyes usually contain 7 to 30% by weight sodium / potassium hydroxide, up to 20% by weight Carbonate, also optionally up to 10 wt .-% anthranilic acid or dihydroxyquinoline as further components, furthermore metal oxides such as iron oxide (the content data refer to the waste eye). In addition, these waste eyes contain small amounts of colored and organic matter Decomposition products.

Since the waste eyes contain a mixture of sodium and potassium hydroxide, isolating one obtains the mixed salts of phenylglycine corresponding to the saponification products. Have such mixed salts Advantages in the sodium-potassium hydroxide-sodium amide melt according to Heumann-Pfleger for the production of indigo. Because these melts are fluid even after the phenylglycine mixed salt has been added the amount of potassium / sodium hydroxide in the melt can be reduced by 10 to 15%.

The saponification of the phenylglycinnilrils can be carried out either with the stoichiometrically required amount of alkali metal hydroxide or with a 0.1 to 10% excess or excess of alkali metal hydroxide in the waste eye. In the case of an excess of hydroxide, part of the saponification takes place through the alkali metal carbonate present.

Whether an excess of alkali hydroxide, the stoichiometrically required amount or alkali hydroxide in the A deficit is used depends on the material from which the saponification kettle is made. In an iron Apparatus will be the saponification with an excess of 0.1 to 10, preferably from 4 to 7% carry out on alkali hydroxide. If there is a deficit of alkali hydroxide, they are formed during the saponification Carbaminates from the ammonia released during saponification, which are strong against iron have a corrosive effect. In contrast, stainless steel is not attacked, so that in stainless steel apparatus that Saponification of the phenylglycine nitrile can also be carried out with a deficit of alkali metal hydroxide can.

The process is generally carried out so that the phenylglycine nitrile is in the form of the solution is entered in aniline in the waste eye and the saponification is initially started at 40 to 70 ° C. After one hour at this temperature, the reaction mixture is then heated to the boil until all of the nitrile is present is saponified. The saponification takes place in accordance with the information in GB-PS 1119256. After cooling the aniline is extracted with toluene and the aqueous phenylglycine salt solution in the usual way for Evaporated dry.

The phenylglycine mixed salt obtained by the process according to the invention is considerably less dusty than the sodium salt obtained by saponification with pure sodium hydroxide solution. Besides, that's after the The mixed salt obtained according to the invention has excellent flowability, which is why this salt is good can be metered into the melt.

In addition, the inventive method has great ecological value because of the recycling of waste eyes Advantages.

The process according to the invention is further illustrated by the following examples.

example 1

2487 kg of phenylglycine nitrile, which is dissolved in 2100 kg of aniline, is converted into 3990 1 mother liquor from indigo production registered. The mother liquor contains 1000 kg of sodium-potassium hydroxide mixture, 120 kg

Soda and 10 kg of anthranilic acid. The nitrile will accordingly Example 1 of GB-PS 1119256 initially stirred for 1 hour at 50 to 65 ° C, with some of the Nitrile is saponified. The saponification is then brought to an end at the boiling point. Duration: 5 hours.

After cooling to room temperature, the phenylglycine salt solution with toluene to remove the Aniline extracted and the aqueous solution evaporated to dryness.

Yield 3464 kg of the sodium / potassium salt of phenylglycine. Pure content: 94.5%. The yield is: 96% of theory.

Example 2
Proceed as in Example 1 with the sub

decided that the mother liquor from the 2,4-dihydroxyquinoline production was used for saponification. For the saponification of 2487 phenylglycine nitrile, 32001 of the red-brown colored mother liquor, d = 1.26, are used, the 1050 kg of sodium-potassium hydroxide mixture, 100 kg of soda, 25 kg of alkali salts of anthranilic acid, 3 kg of alkali salts of 2,4-dihydroxyquinoline and 1 kg Contains aniline in addition to staining impurities.

The work-up is carried out as in Example 1. The same yield as in Example 1 is obtained with the The difference is that the phenylglycine salt has a slightly stronger yellow color, the quality of the salt mixture is the same as in the salt mixture obtained in Example 1.

Claims (1)

Claim: Process for the preparation of mixtures of free-flowing sodium and potassium salts Phenylglycine and phenylglycine-o-carboxylic acid by stepwise saponification of the corresponding Nitriles with aqueous alkali solutions in the presence of aniline at temperatures between 40 ° C and the boiling temperature and evaporation of the reaction mixture, characterized in that that the saponification is carried out with mother liquors that are used in alkali hydroxide / alkali amide melts incurred and the - based on the mother liquor - 7 to 30 wt .-% sodium / potassium hydroxide mixture, up to 20% by weight of sodium / potassium carbonate and optionally up to 10% by weight of other components in addition to smaller ones Contains quantities of colored components and organic decomposition products.