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The upstream extraction stage (2) is designed preferably as a multi-stage extractor. In the simplest case, the optionally interposed extraction stage (3) is composed of a mixer› separator unit, but multi-stage extraction units are also used here in preference. In the simplest case, the extraction stage (4) is a single-stage mixer-separator unit, but multi-stage extraction units are used in preference. 

The final extraction stage (5) is generally designed as a multi-stage extractor. 

The work-up stages (6) and (7) serve to separate the polyamine fractions which are obtained as distillation resi› dues and are isolated as process products (G) and (N) in the tanks (9) and (10), and for the recovery of the hydrophobic solvent used and of the auxiliary amine used as distillates. 

It has proved expedient to remove adhering traces of acid from the organic phases (D) and (D’) and (L) and (L’) fed to the distillation stages by extraction with water in upstream wash stages (6.0) and (7.0) before their treatment by distil› lation. 

The actual work-up stage (6) generally, comprises an at least two-stage multi-stage distillation of which the first stage (6.1) provides a hydrophobic solvent as distillate (E) from which polyamine has been removed and which is depleted in auxiliary amine in comparison with the inflow product (D) and (D’) and/or (P) and (P’), and of which the final stage (6.2) provides a depleted auxiliary amine as distillate (F) in comparison with (D) and (D’) and/or (P) and (P’). 

The complete separation of hydrophobic solvent and auxiliary amine by distillation is not necessary when carry- ing out the process according to the invention. 

In addition, the first polyamine fraction of the starting mixture (A) contained in stream (D) and (D’) and/or (P) and (P’) is obtained as distillation bottom product (G) in the final distillation stage ( 6.2). 

In the simplest case, the work-up stage (7) comprises a distillation column (7.1) which is designed such that an extensive separation of hydrophobic solvent and auxiliary amine jointly as distillate (M) from the polyamine fraction (N) contained in the inflow to ( 6) takes place by distillation. 

Preferably, however, the work-up stage (7) of the process according to the invention is also designed as a multi-stage distillation on account of the improved use of energy. 

The distillation stage (8) is a device with which water can be removed by distillation from the aqueous phase of the system or from a partial stream of the aqueous phase. Such a stage is not necessary in principle for carrying out the process according to the invention, but because of the resulting advantages the embodiments including a water distillation stage (8) are preferred. 

The aqueous phase containing the acid is practically a closed circuit system, so the stage (8) may, in principle, be inserted in any position of said circuit system. The position of stage (8) following the extraction stage (5) and before entry to the extraction stage ( 4) is the most advantageous and therefore the preferred embodiment. 

The quantity of water removed (X), optionally after being divided up into partial streams and the different use thereof, is returned to the system at a suitable location in the form of the stream (Y) as a whole or in partial streams, so that an extended and optionally branched inherently closed aqueous circuit system is produced. 

The system also includes the wash stages (6.0) and/or (7.0). The latter are extraction stages operating in one or more stages on the counter-current principle. In wash stage 65 (6.0), the organic phase (D) and (D’) and/or (P) and (P’) is freed from adhering traces of acid with a partial stream of • 

(X), and in wash stage (7.0) the organic phase (L) and (L’) is freed from adhering traces of acid with the use of another water partial stream of (X). 

The distillate (X) contaminated with hydrophobic solvent and auxiliary amine is highly suitable for wash stages (6.0) and (7.0). The resulting wash waters generally have a very much lower acid concentration than the actual acid circuit, so these may be recycled without difficulty in the form of stream (Y) or its partial streams; optionally, a partial quan- tity of distillate of (X) may be fed from (8) past the wash stages after (Y) and used to control the varying water content of the aqueous phase in the individual extraction stages. 

The practically quantitative circuit operation of the acid used allows the use of expensive acids such as e.g. meth› anesulphonic acid which in turn, because of its reduced corrosion tendency, permits the use of inexpensive materials in the apparatus of the process according to the invention. 

It has proved advantageous to define the acid content of the aqueous phase, independently of the varying amine content occurring in the aqueous phase of a two-phase system, by means of a so-called "molarity". 

The "molarity" is defined as the theoretical concentration of 100% protonated amine (i.e. same number of acid and amine equivalents) in a volume of aqueous phase reduced mathematically by the proportion of unprotonated amine according to the formula: 

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The molarity thus defined may assume values of up to 6 and is varied in a controlled manner in this range depending on the-product-related in this case-separation task on which the relevant embodiment is based. 

It may also be advantageous within an embodiment of the process according to the invention to operate the individual process stages through which the aqueous phase passes, particularly the extraction stages (2) to (5), with a different molarity in the aqueous phase by withdrawing or adding water from or to the aqueous phase between the individual stages. 

The upper limit of said operating range is technically limited on the one hand by the increasing crystallization tendency of the amine salts with increasing concentration, particularly at high degrees of protonation, and on the other hand by the increasing mutual solubility of the phases in one another, particularly at low degrees of protonation. The degree of protonation represents the ratio of acid equivalents to amine equivalents. The lower limit of said range is limited by economic factors by the decreasing acid content and hence the quantitative decrease in the separating efficiency, i.e. for an outstanding qualitative separating efficiency and without technical difficulties, an increasingly large volume of aqueous phase is required for the separation of a given quantity of amine as the molarity falls. 

According to one variant of the process of the invention, the feeding of the starting polyamine mixture (A) from the storage vessel (1) takes place by mixing with the partial stream (C) and introduction of the mixture into the extrac› tion stage ( 4). 

The stream (C) is generally composed of water, a strong protonic acid, auxiliary amine and optionally polyamine. The acid is present in the form of its salts dissolved in water with auxiliary amine and optionally with polyamine. The amino groups of auxiliary amine and optionally polyamine are always present in (C) in a stoichiometric excess, based on the acid. 

The degree of protonation in (C) is generally 10-90%, for the aniline used preferably as auxiliary amine it is preferably 25-70%. 

