DE2426116A1 - PROCESS FOR THE PRODUCTION OF METHYLENE BRIDGES POLYARYLAMINES - Google Patents

Description

PATENT LAWYERS

DR.-ING. BY KREISLER DR.-ING. BEAUTIFUL FOREST DR.-ING. TH. MEYER DR. FUES DIPL.-CHEM. ALEK VON KREISLER DIPL-CHEM. CAROLA KELLER DR.-ING. KLÖPSCH DIPL.-ING. SELTING

5KOLNLDEICHMANNHAUs 2426116

Process for the production of methylene bridges

having poly aryl on the inner ■

The preparation of di (aminophenyl) methane and mixtures of this diamine-containing, methylene bridge-containing polyphenyl polyamines by acidic condensation of aniline and formaldehyde has been known for a long time and is described, for example, in US Pat. No. 2,683,730. This reaction has achieved considerable economic importance, since the diamine itself and 'the polymethylene polyamine niches formed in this aniline-formaldehyde condensation and containing this diamine as the main component are not only useful as such in polymer technology as curing agents for epoxy resins and elastomeric polyurethanes, but are also suitable as intermediates in the preparation of the corresponding di- and polyisocyanates by phosgenation.

The diisocyanate thus obtained is widely used for production elastomeric polyurethanes used, while those obtained in the above manner

Nenen polymethylene polyphenyl polyisocyanates are also largely used Production of polyurethane foam compounds are used.

According to the prior art, it is known that bases of the diph'enylmethane series can be prepared by condensation of aromatic amines with aliphatic aldehydes in an acidic, in particular hydrochloric acid, medium, the acids being used in various amounts. The condensation also succeeds in neutral aqueous or alkali-Afkohoüscher solution, whereby D iaminodi aryl methane, corresponding to higher molecular condensation products or cyclic so-called anhydroformal dehydrated bases are obtained, which are then obtained by means of mineral acid at increased. Temperature in the corresponding mineral

acidic salts are converted to diphenymethane bases. To the »409881 / 1221-

Obtaining the free bases must be prepared from the mineral acid salts with the help of alkalis, such as soda or caustic soda, the corresponding free bases of the diphenylmethane series. A major disadvantage of this process is that the mineral acid and the alkali have to be used in larger amounts and undesired salts of these mineral acids and bases are obtained, which of course cannot be used as catalysts, for example. It is obvious that this is uneconomical.

It has now been found that the production of methylene bridges Polyarylamines can be made in an economically simple manner can without the consumption of catalytically active acids or neutralizing agents being necessary. .

It has now been found that the preparation of the methylene bridges having polyarylamines can be highly profitable even without recycling of the catalyst, since several Improvements through a new way of working with regard to consumption of hydrochloric acid and alkali, volume yield and the Formation of undesired N-methyl compounds compared to the prior art can be achieved.

DOS 1 518 4o6 and 2 o49 7o7 describe processes for the preparation of the above-mentioned compounds in which im In the best case, at least 500 kg of NaCl are produced per 1 t of aniline-free product. That means that appropriate Amounts of HCl and alkali are consumed.

With regard to the space yield, the modification of the process plays a particularly important role. After today In the prior art, at least 0.5, but mostly 1 volume of water per 1 volume of aniline is used. This Water becomes part of formaldehyde water, formaldehyde reaction water, Hydrochloric acid water and, if necessary, additional water added to ensure good reaction performance. The necessary equipment must be corrosion-proof against hydrochloric acid, which of course causes great costs.

For the quality of the isocyanates it is crucial that the content of N-methyl compounds is minimal, because otherwise large amounts of so-called saponifiable chlorine are formed. In the process according to the invention, almost no or minimal amounts of N-methyl compounds are formed.

Accordingly, the invention consists of a method of manufacture of polyamines in several stages, which is characterized in that one ■

a) aromatic amines that contain at least one hydrogen atom in the Have amine group and must be unsubstituted in at least one of the positions 2, 4 or the aromatic nucleus and aliphatic

"Reacts aldehydes with one another in the absence of a catalyst and forms so-called precondensates,

b) after the reaction has ended, separates the water present,

-4-0-9-8-8-1 A-V 2-2-4 -

c) 'the pre-condensate thus obtained is in the presence of acid salts of the aromatic amines or their condensation products with saturated aliphatic aldehydes or their mixtures and in polar ones water-soluble organic solvents, optionally in Presence of water, which is indifferent under the reaction conditions remain or in the presence of aqueous mineral acid or aqueous acidic salts of aromatic amines, optionally in the presence of polar, organic solvents which are indifferent under the reaction conditions remain implemented, and the catalyst used is either washed out with water and reused or neutralized with alkali.

In the first step of the process according to the invention, an aromatic amine and the aliphatic aldehyde are brought together in the usual manner in the absence of any acidic or other catalyst and the reaction is carried out essentially in the manner described by Cohn in the Zeitschrift für angewandte Chemie XIV (1901), 311 by. The two reactants are therefore brought together in any suitable manner, preferably with stirring, the aromatic amine being added to the aldehyde or, preferably, the latter being added to the former. Formaldehyde is preferred as the aldehyde. This is preferably used in the form of its aqueous solution, for example as a commercially available 37% solution, but can, if desired, also be used in one of its polymer forms, ie as paraformaldehyde or trioxymethylene. The temperature at which the two reactants are brought together is not important. For the sake of simplicity, this is generally done at room temperature, ie 20 to 25 C, but b
to be worked. AO'9881 / 5221

i.e. 20 to 25 C, but can also be at lower or higher temperatures

The reaction is exothermic, but can readily by suitable inputs' control the rate of addition of the reactants or, if necessary, controlled by cooling from the outside. Although the reaction temperature is not critical in this first stage of the process, it is allowed to prefer

ο
wisely do not rise above about 100 C. Moreover, it has an automatic upper limit insofar as it cannot rise above the boiling point of the reaction mixture containing the water of reaction.

In the further stage, the precondensate obtained in this way is with a Catalyst solution made by dissolving acidic salts of aromatic amines or their condensation products with saturated aliphatic Aldehydes or their mixtures in water-soluble organic polar solvents, optionally in the presence of water, brought together with stirring or other physical methods

and forms a clear solution within minutes. '■

This reaction stage can take place in a wide temperature range. It has proven advantageous to mix at one temperature

ο ο

from 10-100 C _1, preferably at 25-70 C, and allowed to react at this temperature for 1 minute to 360 minutes, preferably 20 to 90 minutes. . *

During this time, the originally existing ones are rearranged Anhydro-formaldehyde and methylene-dianil in to aminobenzy I amines. The formation of diamino-diphenylmethanes is also observed.

For further rearrangement to polyarylemines containing methylene bridges the solution is heated to a temperature of 60 to 150 C, preferably

o ■ ■

wise heated to 70 to 130 C, the practical at this temperature

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carry out full rearrangement to polyarylamines having methylene bridges. At this stage the reaction takes times of 10 minutes to 8 hours, preferably 30 minutes to 3 hours. Higher temperatures mean shorter times.

Any primary aryl amine or mixture of primary aryl amines can be used in the method according to the invention, which is particularly suitable for primary arylamines which have an aromatic nucleus which is unsubstituted in the p-position to the amino group.

Examples of primary arylamines that can be used in the present process are aniline, m-toluidine, o-toluidine, m-, o- and similar isomers of propylaniline, butylaniline, o- and m-anisidine and phenetidine, 2 ₁ 3 _I 5-trimethylaniline, t> 4-naphthylamine, 2,4- and 2,6-xyüdindiamine, 2,4- and 2,6-diethylaniline, 2-methyl-6-ethylaniline, m-benzylaniline, o- and m- Chloroaniline, m-bromoaniline, 2,4- and 2,6-tolylenediamine, i, 5-naphthylenediamine and o- and m-phenylenediamine. . . .

The saturated aliphatic aldehydes include, for example, formaldehyde,

Acetaldehyde and butyraldehyde. Formaldehyde is expediently used in the form of an aqueous solution in the process according to the invention. The commercially available solutions with a concentration of 30-40 % can be used. Formaldehyde generating agents such as paraformaldehyde and trioxane which in situ generate formaldehyde can also be used.

By setting the amine-aldehyde ratio appropriately it is possible to make products that contain varying amounts of diamines and higher polyamines. This is how you can make products which have a large proportion of Oiamine or a smaller one

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Containing proportion of diamine and a larger proportion of triamine or polyamines of higher functionality. In general, the higher the amine-aldehyde ratio, the greater the amount of diamine in the 'product. -'

The ratios of arylamine to formaldehyde in the invention Methods that can be used are of the type known in the art, such as molar ratios of Aiylai-hin / rormaldehyde from about 1.5 / 1 to 12/1. Particularly molar ratios of arylamine / formaldehyde of 1.5 / 1 are suitable up to 4/1.

• ■ "- -

While the lower limit of the aniline-formaldehyde-MoI ratio to be observed is determined by the desire to avoid the formation of undesirable by-products, the upper limit is not critical and depends largely on economic considerations.

Generally speaking, this determines aniline-formaldehyde ratio the ratio of di (aminophenyi) methane to higher polymethyl an-Po Iy phenyl am inen in the end product in the sense that with increasing excess aniline also means more di (aminophenyi) methane in the

Final product is included. Experience has shown that this influence disappears, when the aniline to formaldehyde molar ratio is increased beyond about 8: 1, but apparently without any impairment the advantages of the invention can be exceeded.

Among acidic catalysts are the acidic salts of inorganic ones and organic acids, which at least partially dissociate with the formation of a proton, with the used or in the reaction

.409881 / 1221

to understand formed amines. Examples of inorganic acids are hydrochloric acid and hydrobromic acid, sulfuric acid, phosphoric acid. Examples of organic acids are organic sulfonic acids such as methanesulfonic acid, benzene mono- and disulfonic acids, toluenesulfonic acid and chloroacetic acids. Hydrobromic acid and methanesulfonic acid are preferred. '. '

The serving as catalysts salts may be prior to the reaction or be prepared iri situ. I.

When working with neutralization of the catalyst, the Use of hydrochloric acid preferred. In order to achieve better temperature control, it is advantageous to use this hydrochloric acid with the appropriate equivalent of aniline to implement this aqueous solution as a catalyst for the implementation to be used with precondensate. This reduces the temperature build-up in the mixing zone to a minimum, whereby also has a positive influence on the quality of the finished products in terms of viscosity and the formation of N-methyl compounds will.

As organic water-soluble polar solvents, saturated aliphatic alcohols with 1-4 carbon atoms such as monohydric alcohols, e.g. methyl alcohol, ethyl alcohol, isopropyl alcohol or polyhydric, especially dihydric alcohols, e.g. ethylene glycol, which remain indifferent under the reaction conditions, ie with the amines or

do not react with phenyl nuclei or their mixtures v / er-409881/1221

the. In particular, so-called aprotic solvents can be used such as dimethyl sulfoxide, dimethyl sulfone, tetramethylene sulfone (Sulfolane).

* I

When working with low-boiling alcohols, the catalyst can either be in solid form or dissolved in water or higher-boiling alcohols polar water-soluble organic solvents, such as ethy-

lenglycol and sulfolane, if necessary with the addition of water, re-used or used.

It has been shown that various salts of aromatic amines, or their condensation products, with aldehydes are less soluble or not at all soluble in polar solvents. With the addition of water, these salts dissolve completely and remain completely dissolved even at room temperature.

In terms of process technology, it is much cheaper to use catalysts not in solid form but in the form of their solutions, because this is the case

is easier to use.

The amount of polar water-soluble organic solvents can be varied widely, for example. from 5, in particular 15 wt% to 150, in particular 80 wt%. ·;

The amount of the acidic catalyst can be varied widely and preferably at 0.001-0.5 mol, based on the aromatic amine at 0.01-0.15 MoM. -

The process can be carried out continuously or batchwise will. The catalyst can be reused in both cases

409881/1221 - be.

The method described is particularly interesting for the working method in which the acidic catalyst is washed with water and after removal of excess water for reuse in the Circle is led. ·

It is also possible to add water-immiscible organic solvents during work-up of the reaction mixture in order to prevent it from being washed out to facilitate the catalytic converter.

All organic solvents can be used as such solvents which are immiscible with water, but which dissolve the polyamines and aniline. For example, toluene, benzene, xylene, Pseudocumene and other aromatic solvents can be used. Furthermore, chlorinated hydrocarbons such as dichloromethane, carbon tetrachloride, Chlorobenzene, dichlorobenzene and others are used will. · -.

The conversion in several temperature stages is advantageous for the process, for example in three stages: at about 0 to 40 ° C, at about 40-80 ° C and at about 80-120 ° C. The residence time in the individual stages is. not critical and can vary within wide ranges known per se. For example, the residence time can be 0.5-2 hours.

After the catalyst has been washed out, the organic phase is distilled, the remaining water and aniline, if appropriate the additional solvent, being distilled off first; a phenyl base mixture is obtained which can continue to be worked up in an anhydrous state.

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The reaction may be c), ie the reaction of the precondensate, in several stages, to perform particular two stages, the first stage being between 0 and 7o ° C, preferably from 2o to 60 ⁰ C, and the second stage between 60 and 15o ° C. , preferably 75 to 12o ° C is carried out.

In the present process, the acid used in catalytic amounts for the condensation is formed with water washed out by salts of the polyarylamines containing methylene bridges.

It was to be expected that these acid-bonded methylene bridges containing polyarylamines will have the same composition as those obtained during laundry organic phase.

Surprisingly, it was found that the in the water by Acid-bonded and dissolved methylene bridges polyarylamines have a completely different composition, in particular with regard to the 2-nucleus content and its isomer composition.

It has been found that washing or extraction of the aqueous phase with the starting amine (aniline, toluidine, aniside i.a.) the 4,4-rich reaction product in the aqueous salt can exchange for the starting amine, 4,4-rich Product becomes acid-free.

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It was also found that when this aqueous solution was washed in the heat with pure aniline or in countercurrent is extracted, the polyarylamines can be displaced by aniline, whereby an aqueous salt is obtained, which consists mainly of ahiline chlorohydrate and an organic phase, which has a much higher content of 2-nucleus in the Compared to the original reaction product and has a higher 4,4-content in 2-core. This results in the possibility In addition to the condensation product, a second one with a much higher 2-core content and 4,4-content can be produced. !

The extraction of the aqueous solution with e.g. pure aniline in e.g. a multi-stage extraction column succeeds To displace almost all of the polyamine from the salt and replace it with the starting aniline. If you are interested is to make products with a high 4,4-diamine content (over 95%), it is advantageous to work with amounts of acid from 0.1 to 0.3 mol. In this case two streams are obtained, of which the first is a product of about 50 to 80% binary and about 88 to 93 * 4,4-isomers and the second contains a product with about 80 to 95% binary and about 95 to 100% 4,4-isomers.

The analytical investigations were carried out by means of gas phase chromatography on a 1 m column filled with silicone rubber on a carrier using made of anthracene as a reference substance.

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Examples: example 1

In a double-walled vessel j fitted with a KPG stirrer and connected to a thermostat, 558 g of aniline = 6 mol and at 25 ° C. 218.7 g. 37% formaldehyde = 2.7 mol added dropwise. After the addition is complete, the mixture is stirred at 25 ° C. for a further 2 hours and then heated to 70 ° C. After 10 min. at 70 ° C. and 607 g of precondensate are obtained in addition to 165 g of water of reaction and formaldehyde.

607 gr. Of pre-condensate are then placed in a double-walled vessel

ο
with stirring to 40 C <

solution, consisting of

ο
heated to 40 C with stirring and quickly add 600 gr. of catalyst

440 gr. Sulfolane,
80 gr. Water,
65 gr. Hydrogen chloride acid salt of

Anil in formaldehyde condensation product (0.36 mol. HCI)

admitted. The approach corresponds to a ratio of 1 mol of aniline to 0.45 mol of formaldehyde and 0.06 mol of HCl.

Forms within 1-2 minutes with development of heat

ο a homogeneous solution. This is then at 40 1h and further Maintained at 97 ° C. for 1 h.

ο When the reaction is complete, it is cooled to 75 C and

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washed with water several times. The wash water is collected and cooled. This separates further organic ones Layer that is added to the product.

The wash water is after the addition of sulfolane which has been distilled off evaporated again to approx. 600 gr in a rotary evaporator and used for further implementation.

The organic layer is made up of unreacted aniline, sulfolane and freed residual water under vacuum and examined the product obtained GC.

The product consists of approx. 68% 2-core products and 32 % 3-core and higher condensation products.

The 2-core part consisted of:

91% \ 4-4 di aminodiphenyl methane,

Il

2 7, 6 % 2-4 1, 2% ^V 2-2 0, 08% N-methyl example

It is as in Example 1 but with 75 gr. B rom hydrogen acid salt of aniline-formaldehyde condensation product as a catalyst worked. The composition of the reaction product is similar to Example 1.

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Example 3

In a continuous system similar to scheme 1, 5 liters of aniline are pumped in through line 1 and 1.8 liters of 37 % formaldehyde through line 2. The stirred vessel A is designed for a residence time of 2 hours and 50 C. Then the mixture formed runs into a separator B ₁ where the product

o The product separates into two layers after a residence time of 15 minutes at 75 ° C. The upper reaction and formaldehyde water containing phase is withdrawn through line 4.

The precondensate runs into the stirred vessel C (t = 40 C), where also through line 14 4.7 liters of catalyst solution from the evaporator F to be added.

A homogeneous solution forms after a residence time of 1 hour runs through line 6 into the reaction vessel D. After a

O
The reaction product goes into multi-stage countercurrent extraction for 1 hour at 97 ° C., where the catalyst is washed out with about 3.5 l / h of water.

The organic phase is freed from residual water, sulfolane and aniline in the evaporator G under vacuum.

The aqueous phase becomes after the addition of sulfolane which has been distilled off in the evaporator F again concentrated to approx. 4.7 liters and fed back into the system (C).

40 9 881/1221

The product consists of approx. 68% 2-core, which in turn has the following composition:

2.2 diaminodiphenyl methane 1.1%

2.4 "8.2%

4.4 "90.7%

<0.1% N-methyl

The catalyst solution used in this example had the following composition:

88% by weight sulfolane 9.5 "phenyl base chlorohydrate

2.5 "water,

which corresponds to a molar ratio of anil in / formaldehyde / H Cl of 1: 0.40: 0.06

Example 4

In a double-walled vessel, fitted with a KPG stirrer and connected on a thermostat, 558 g of aniline = 6 mol given and added dropwise at 25 C 218.7 g. 37% formaldehyde = 2.7 mol. After the end of the dropwise addition, another 2 hours

ο ο

stirred at 25 ° C. and then heated to 70 ° C. To It is switched off for 10 minutes at 70 ° C. and 607 g of precondensate is obtained along with 165 g of water of reaction and formaldehyde.

607 gr. Of pre-condensate are then placed in a double-walled vessel 409881/1221

heated to 40 ° C. with stirring and 12 grams of 37% HCl added.

The temperature is kept at 40-45 ° C. when the acid is added. After the addition of acid is complete, the temperature is 45 minutes at 45-50 ° C held and then increased to 97 C and held for 1 hour. When the reaction is complete, the mixture is cooled to 75 ° C. with aqueous NaOH neutralized and then washed several times.

The approach corresponds to 1: 0.45: 0.02.

The organic layer is freed from unreacted aniline and residual water under vacuum and the product obtained is GC examined.

The product consists of approx. 66% 2-core products and 40% 3-core and higher condensation products. The 2-core part consisted of:

91.8 % 4-4 diaminodiphenyl methane, 8.0% 2-4. "

0.2% 2-2 "

<0.1% N-methyl

Example 5

The procedure is as in Example 4, but instead of 12 gr. HCI concentrated 3 gr. Added. This corresponds to a ratio of Äni1 in / formaldehyde / HCl such as 1: 0.45: 0.005.

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The following product is obtained:

84 % 4-4 diaminodiphenyl methane, 11 % x 2-4 "

5 % 2-2 "

<0.05% N-methyl

Example 6

In a continuous system similar to the accompanying drawing are through the line 1 9.3 kg of aniline (100 mol) and pumped in through line 2 3.56 kg of formaldehyde 37%. The stirred vessel A is designed for a residence time of 2 hours

and 30 C. Subsequently, the mixture formed runs into a separator B, where the product settles after a dwell time of

Separates into two layers at 75 ° C. for 15 minutes. The upper phase containing reaction and formaldehyde water is passed through line 4 deducted.

The approach corresponds to 1: 0.411: 0.06.

The precondensate (approx. 10 kg) runs into the stirred vessel C (t = 40 C), where 1.6 kg of catalyst solution, consisting of

600 grams of methanesulfonic acid, 400 grams of water and 600 grams of aniline

join in,.

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The mixture formed is kept in the stirred vessel C at this temperature for about 3/4 hour and then through Line 6 passed into the reaction vessel D. After a residence time of 1 1/2 hours at 99 ° C., the reaction product goes into the multi-stage countercurrent extractor E, where the catalyst is washed out at about 3.5 It per hour.

The aqueous phase is then in the evaporator F again concentrated to approx. 1.3 liters and fed back into the system (C).

The organic phase is in the evaporator G under vacuum Freed residual water and aniline.

The product consists of approx. 66% 2-core, which in turn has the following composition:

2.2 _N D! Aminodiphenylmethane 0.2% 2.4 "6.8%

4.4 \ "93%

N-methyl ^ C 0.1%

Example 7

The precondensate in this example is prepared as in Example 1. 600 g of precondensate and 60 g of methanol are in a Submitted double-walled vessel with stirrer at 25 ° C. For this purpose, a solution consisting of 60 g concentrated (37%) hydrochloric acid,

.4 09881/1221

60 g of methanol, 60 g of aniline within 5 minutes under intensive Cooling added. A homogeneous phase is formed. The product is allowed to react for 20 minutes and then heated to 95.degree. The methanol is in a short column Range between 75 and 95 C distilled off practically quantitatively. The product is allowed to react for 1 hour, then to 70.degree

3
cool and wash 3 times with 300 ecm of water each time. The water

The remaining phase is collected and 3 times with 300 g of aniline at 70.degree washed. The organic phases obtained are collected and washed with pure water.

The two organic phases (the organic reaction product and the aniline wash of the aqueous phase) are removed from the aniline liberated and examined. It was found that the reaction product has about 70% two-core content and this is off

1.1% 2.2 di aminodiphenyl methane 8.9% 2.4 "and

89% 4.4 "

and the aniline exchange phase contains 85% two-core with the composition

0% 2.2 di aminodiphenyl methane 5% 2.4 ■ · and

95% 4.4 "

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Example 8

In a system similar to Scheme 2, line 1 about 5.58 kg of aniline (60 mol) and, through line 2, about 2.43 kg of 37% technical formaldehyde (30 mol) into reactor A

ο
initiated at a temperature of 65 C. The reaction time is set to 30 minutes. The emulsion obtained in this way runs into separator B, from which, after a separation time of 20 minutes, precondensate, about 6 kg per hour, continues to flow into reactor C through line 5. The water of reaction and formaldehyde, which only contains traces of precondensate, runs through line 4 for extraction or into the sewer.

Through line 14 run from the evaporation column F into the Reactor C approx. 3.84 kg per hour of catalyst solution as follows Composition:

about 1.44 kg methanesulfonic acid, 0.9 kg water and 1.5 kg of aniline.

The reaction mixture remains in reactor C for about 40 minutes

ο
a temperature of 40. The solution continues to run into reactor D, in which a residence time of 70 min. And a temperature

O
temperature of 100 C are set.

The product which has reacted completely in this way runs through line 7 into the extraction column E 1, where the product flows in countercurrent is washed with 10 kg of water per hour at 70.

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The overhead stream, consisting of an aqueous solution of the catalyst

O
tors, is cooled to approx. 25 in order to separate out the organic product that is also dissolved. This aqueous solution goes through line 8 into the extraction column E 2, in which this solution is washed in countercurrent at 70 with 5 kg of aniline, which is pumped in through line 16. The organic phases from the columns E 1 and E 2 are passed through the lines 10 or into the evaporation columns G and H and are distilled free of water and aniline.

2.4-rich product passes through line 13 and 4.4-rich product passes through line 18. The composition is as follows:

The 2,4-rich product consists of 65% 2-core, which in turn consists of

0.2% 2-2 diaminodiphenyl methane, 7 % 2-4 "

92.8% 4-4

Il

the 4.4-rich product consists of 87 % 2-core of the composition

0% 2-2 Di ami nod! Phenyl methane, 1.2% 2-4 "

98.8% 4-4 «

The aqueous solution, consisting mainly of amino chlorohydrate goes into the evaporator F, where the excess water is drawn off through 11 and the catalyst through line 14 goes into reactor C.

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Claims (14)

Claims 1 · Process for the production of methylene bridges Polyary I amines in several stages, characterized in that one a) aromatic amines which have at least one hydrogen atom in the amine group and at least in one of the positions 2, 4 or of the aromatic nucleus must be unsubstituted and react aliphatic aldehydes with one another in the absence of a catalyst and forms so-called precondensates, · '. ·' .. b) after the reaction has ended, separates the water present, c) the pre-condensate thus obtained is in the presence of acid salts of aromatic amines or their condensation products with saturated ones aliphatic aldehydes or their mixtures and in polar water-soluble organic solvents, optionally in Presence of water which remains indifferent under the reaction conditions or in the presence of aqueous mineral acid or aqueous acidic salts of aromatic amines, optionally in the presence of polar, organic ones Solvents which under the reaction conditions f _t remains different, and the catalyst used either washed out with water and reused or neutralized with alkali. 2.. Process according to claim 1, characterized in that one. ο the reaction a) at temperatures of about 10-90 C ₁ preferably at 20-30 ° C. -. ·. · '..-. 3.. Process according to Claims "1-2, characterized in that reaction b) is _{carried out at temperatures of about 30-80 C 1,} preferably at 60-70 C. 409881/1221 4 · Process according to claims 1-3, characterized in that the rearrangement reaction is carried out in several stages at different Temperatures and performs in a manner known per se. 5. The method according to claim 1-4, characterized in that the reaction c) in several stages, in particular carried out in two stages, the first stage between 0 and 7o ° C, preferably 2o to 6o ° C, and the! second stage between 6o and 15o ° C, preferably 75 to 12o ° C is carried out. ' 6. The method according to claim 1, characterized in that the polar water-soluble organic solvents aliphatic saturated alcohols with 1 to 4 carbon atoms, in particular monohydric or dihydric alcohols. ; 7. The method according to claim 1 to 6, characterized in that the alcohols are methanol, ethanol, isopropanol or ethylene glycol. , 8. The method according to claim 1-5, characterized in that the polar water-soluble organic solvents non-aprotic solvents, especially dimethyl sulfoxide, dimethyl sulfone or tetramethylene sulf are on. 409881/1221 9. The method according to claim 1-8, characterized in that that o, oo1 to 0.5 mol of acidic catalyst per 1 mol of aromatic amine, preferably o, o1 to 0.15 mol, can be used. '■ 10. The method according to claim 1-9, characterized in that that work is carried out continuously. ; • 11. Method according to claim 1 - 1o, characterized in that that the aliphatic aldehyde is formaldehyde or a formaldehyde generating agent. 12. The method according to claim 1-11, characterized in that that the aromatic amine used is o-toluidine or ortho-chloroaniline, in particular aniline. 13. The method according to claim 1 - 12, characterized in that at molar ratios of arylamine to Al- ' dehydration of about 1.5 to ¹ 1 to 1 to 1 is worked. 14. The method according to claim 1-13, characterized in that that the aqueous phase obtained in stage c) is washed with starting amine. 4 0 9 8 8 1/12 21