CA1087633A

CA1087633A - Process for the production of polyaryl amines containing methylene bridges

Info

Publication number: CA1087633A
Application number: CA264,973A
Authority: CA
Inventors: Efim Biller
Original assignee: Individual
Current assignee: Individual
Priority date: 1975-11-11
Filing date: 1976-11-05
Publication date: 1980-10-14
Also published as: YU271776A; BR7607527A; IL50857A; IL50857A0; ES453159A1; PT65803B; IE44544L; FR2331575A1; IE44544B1; SE421533B; RO79103A; MX148753A; PT65803A; NL7612539A; LU76153A1; PL104368B1; DK508476A; TR19975A; JPS5260895A; SE7612478L

Abstract

ABSTRACT OF THE DISCLOSURE

This invention is directed to a process for the production of polyaryl amines containing methylene bridges.
These compounds are prepared from aryl amines and formalde-hyde in the presence of acids and water and the catalyst is simultaneously recovered. The polyaryl amine salt solutions produced by conventional methods are mixed with the starting aryl amines to form at least partially hetero-geneous systems, optionally after the addition of water and optionally in the presence of hydrophobic solvents.
Polyaryl amines are exchanged by aryl amines to form on the one hand, mixtures of polyaryl amines and aryl amines and on the other hand, an aqueous solution of the acid in the form of a salt of the aryl amine.

Description

The production of polyamines of the diamino-diphenyl methane series by condensing aromatic amines with formaldehyde in the presence of acid catalysts has been repeatedly described and gives a product differing in composition according to the procedure adopted. Thus, condensation in the presence of weakly acid catalysts or in the presence of traces of strongly acid catalysts gives polyamine mixtures with a high content of 2,4'-diaminodiaryl methanes, whereas polyamines with a high content of 4,4'-diaminodiaryl methanes and, at the same time, a low content of 2,4'-isomers can only be produced in the presence of relatively large quantities of strongly acid catalysts.
For the second of these two cases, it is best to use strong mineral acids, especially hydrochloric acid (DOS No.
1,518,406; DOS No. 2,045,834; DOS No. 2,049,707;
DOS No. 2,301,554; US-PS No. 3,367,969). In conventional processes, however, the advantage of the high selectivity of strongly acid mineral acids for the formation of 4,4'-isomers is obtained st the expense of the loss of the catalyst because, on completion of the reaction, the catalyst has to be removed from the reaction mixture by expensive neutralisation with bases. Another disadvantage of conventional processes is the fact that the salt solutions obtained as a result of this neutralising reaction cannot be put to any worthwhile commercial use and give rise to considerable pollution problems.
It has surprisingly been found that, when aqueo~s polyamine7solutions are mixed with starting aryl amines '' (aryl amines) to form an at least partly heterogeneous ,~ .

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(two-phase) system, the polyamines are displaced or replaced by aryl amines.
Twophases are formed, namely an organic phase (polyaryl amine-aryl amine) and an aqueous phase (aryl amine salt solution).
Accordingly, the present invention relates to a process for the production of polyaryl amines containing methylene bridges from aryl amines and formaldehyde, with simultaneous recovery of the catalyst, distinguished by the fact that polyaryl amine salt solutions produced by any conventional method are mixed with starting aryl amines, optionally after the addition of water, to form, on the one hand, substantially acid-free mixtures of aryl amine and polyaryl amines and, on the other hand, aqueous solutions of the catalyst in the form of a salt of the starting aryl amine.
The condensation reaction which takes place in the continuous or batch process according to the invention may be carried out by conventional methods, the molar ratios of aryl amine to formaldehyde and aryl amine to acid catalyst being variable within wide limits. The molar ratio of aryl amine to formaldehyde is in particular in the range from 10:1 to 1:1 and prefeEbly in the range from 4:1 to 18:1, whilst the molar ratio of aryl amine to catalyst is in the range from 20:1 to 1:1 and preferably in the range from 1:1 to 5:1, this particular molar ratio being the molar ratio between the aryl amine used at the beginning of the process to the acid present in the circuit in the form of aryl amine salts.
In practice, the exchange is effected by repeatedly mixing the aqueous polyamine salt solutions with starting aryl amines, preferably continuously, in countercurrent.
- Two concurrent phenomena occur in the practical application , - ,, ~ ' .
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of the process according to the invention, namely:
1. The reguired exchange of polyamines for aryl amine

2. Extraction of the amine salts by the organic phase.
The second of these two phenomena is undesirable because it is important in terms of process technology to obtain aqueous solutions of the aryl amine salts with maximum concentration. The higher this concentration, the smaller the amount of water which has to be concentrated by evaporation in order to obtain the necessary salt concentration for the initial condensation stage of the process.
In order to suppress extraction, it is necessary to use relatively small quantities of starting aryl amine.
Unfortunately, this adversely affects the replacement or exchange effect.
It has been found that the process according to the invention may be carried out in different ways.
It has been found that, in cases where relatively small quantities of aryl amine are used, it is also necessary to use correspondingly lower concentrations of acid in polyaryl amine salt solutions. The solubility of the aryl amines increases with higher concentrations of acid.
In cases where relatively large quantities of aryl amine are used, two-phase systems are again obtained.
In order to obtain the best possible exchange effect with a mnimal quantity of aryl amine, it is best to circulate the aryl amine in each stage in such a way that, of this liquid, only a part of the quantity which takes part in the exchange in one stage is conveyed into the next stage, whilst the rest is recycled to the same stage. If for example the ratio between the quantities of aqueous polyaryl amine salt solution to be treated and the exchange aryl amine amounts , to 5:1 and if, in each stage, the quanti~y of aryl amine _ 4 _ ~

1~)87~i33 recycled is 4 times the quantity of the aryl amine (inner circuit), the overall ratio between the phases for the same input of aryl amine amounts in each stage to 1:1, which provides for a better exchange effect and also for better phase separation.
It is also possible to keep the ratios between the streams in the stages different because the exchange effects vary in different stages. Exchange is far quicker at the beginning than at the end. It may also be advisable to change the inner circuit from stage to stage.
The at least partial insolubility of the aryl amines in aqueous polyaryl amine salt solutions (prerequisite for exchange) may also be obtained by the addition of hydrophobic (water-insoluble) solvents (WIS). This procedure can only be applied to alimited extent. The presence of relatively large quantities of WIS adversely affects the exchange. It has been found that, although excessively large additions of WIS reduce extraction of the salts, they adversely affect the exchange effect of the polyamines.
It is this which represents the difference from the process according to DT-OS No. 2,238,92 ......... , in which the increase in the quantity of WIS prevents or stops the exchange. This also shows that the exchange presupposes two at least partly heterogeneous phases, the organic phase having to consist predominantly of aryl amine. It is evident that the aryl amines must be soluble to a certain extent in aqueous polyamine salt solutions.
This means that the optimal quantities of the WIS have to be experimentally determined for corresponding apparatus, a compromise having to be found between both concurrent phenomena.
Suitable WIS are any solvents which are immiscible with - .
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water and inert with respect to the reaction products.
Particularly suitabe WIS are benzene and alkyl benzenes, chlorinated hydrocarbons, aliphatic and aromatic hydrocarbons, etc. It is of considerable advantage to use WIS which boil at temperatures in the same range as aniline for example.
Thy are distilled together with excess aniline and re-circulated.
The solubility of aryl amines in water and in acid salt solutions is governed to a large extent by the salt concentration.
According to Landolt-Bornstein II, Vol. 2, Section C:
Losungsgleichgewichte (solution equilibriums) II, page 60~, the equilibriums between aniline and water solution of the aniline hydrochloride areknown. The solubility of the aniline increases to the miscibility stage with the concentration of aniline hydrochloride. For an aniline hydrochloride concentration of approximately 20 %, both ~-phases each contain approximately 20 % of salt.
If the quantity of salt in the aqueous phase is reduced to approximately 6 %, the quantity of salt in the aniline phase decreases to around 1.4 %.
The process may be adapted to these facts by working with different concentrations of salts in the countercurrent installation; with maximum possible salt concentrations on the aqueous phase side and with minimum possible salt concentrations on the organic phase side.
This result may be achieved by introducing the polyaryl amine salt solution into several mixing stages, rather than one mixing stage, in such a way that the highest salt concentration is encountered at about the middle of the exchange installation.
It is also possible to introduce the aqueous polyaryl -- , . ..
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.: .. . . - . . -~087633 amine salt solution into about the middle stage of the multistage installation and to work on one side with starting aryl amine and, on the other side, with water in countercurrent (as is standard practice for example in countercurrent extraction with ~ater as the recycle component).
Another procedure is based on a combination of both processes: to begin with the PA/salt water solution is treated with aryl amine/WIS, giving a 50 to 98 % exchange.
This is followed by treatment with pure aryl amine and completion of the exchange process.
In practice, this means that the WIS is added to the stream of aryl amine either in one stage or in several stages.
The exchange effect may also be enhanced for example by dividing the quantity of aryl amine into two or more streams, introducing these streams into the exchange stages and then combining them in countercurrent. The use of an inner circuit is particularly important in cases where the quantities of aryl amine are small. - -The organic phase thus obtained should contain no more than 30 ppm of acid. This value may readily be obtained by washing with water, for example in a countercurrent extraction installation. The washing water may be used in the exchange installation.
The aqueous phase still contains-dissolved starting aryl ami~. The dissolved starting aryl amine may be removed either azeotropically by stripping (optionally with steam~
or by extraction with hydrophobic solvents. The aqueous phase is then concentrated and introduced into the condensation stage.
The process according to the invention may be carried out with any aromatic amines such as, for example, aniline, : .. - . . . ..

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o-toluidine, m-toluidine, N-methyl aniline, N-ethyl aniline, 2,6-dimethyl aniline, 2,6-diethyl aniline, 2,6-diisopropyl aniline, 2,4-diaminotoluene and any mixtures of these amines.
Aniline is preferably used as the aryl amine in the process accord~g to the invention.
- Water-soluble acids with a pKa-value of less than 1.5 are particularly suitable for use in the process according to the invention. Examples of acids such as these are hydrochloric acid, hydrobromic acid, sulphuric acid, trifluoromethane sulphonic acid, benzene sulphonic acid or phosphoric acid. Preferred catalysts are hydrochloric acid, trifluoroacetic acid and methane sulphonic acid. The above-mentioned acid may also be used in admixture with acid or neutral salts of these acids, such as for example the corresponding ammonium salts or even the corresponding alkali salts. It is of course also possible to use the salts ~rmed from the above-mentioned acids and from the aryl amine used as starting amine as sole catalysts at the very beginning of the process.
The acid condensation mixture may be prepared in known manner by mixing a mixture of aromatic amine and acid catalyst with formaldehyde or formaldehyde donors and heating the precondensates formed to elevated temperatures for rearrangement. Conversely, it is also possible initially to react aromatic amine-with formaldehyde and then to add the catalyst. In both cases, it does not matter whether the reaction is carried out in the presence or absence of water. In either case, the acid condensation mixture is suitable for the process according to the invention.
The quantity of water added is governed primarily by the molar ratio of aryl amine to acid. Water should be added in such a quantity that the solubility of the aryl .

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1~)87633 amines is below a certain limit.
The concentration of salt in water is preferably adjusted to 50 % and, with particular preference, to between 5 % and 40 %.
The water of condensation, the water from the formaldehyde - and also from the addition are preferably removed in a single stage or multistage evaporator under pressure, in the absence of pressure or in vacuo, optionally after removal of the dissolved aryl amine, and are recirculated following removal of the excess.
The exchange may be carried out at room temperature or at a temperature above room temperature, preferably at a temperature between 15C and 35C.
The process according to the invention is distinguished by the following advantages:
- salt-free effluent - no consumption of acid catalyst - elimination of the need fo~ alkali ^ elimination of the need for the neutralisation apparatus - economic advantages.
The exchange process may be carried out in various apparatus either continuously or in batches. It is preferred to use mixer-settlers and countercurrent apparatus.
The density of the phases is influenced by several factors, namely salt concentration in water and in aryl amine and the content of polyaryl amine in aryl amine. The density of the phases is also governed by the catalyst. For example, the polyamines (of the aniline) methane sulphonic acid salt$
in water are lighter than the mixtures of aniline and polyaryl amines.
With a 5 /0 polyamine content, the aqueous solutions of the aniline methane sulphonate are in turn heavier than aniline. Phase reversal occurs. This phenomenon is unfavourabl .. . , ., , . . -- . . :, . ..
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1()1~7~33 in terms of process technology.
Phase reversal may be avoided either by adding WIS or by using acid mixtures as catalysts.
The quantity of aryl amines required for exchange is determined by the composition of the salts (polyamine content), the type of apparatus used and the procedure adopted. In cases where countercurrent installations are used, relatively small quantities are sufficient.
In general, the ratio by volume of the aryl amines to aqueous salt solution may amount to between 5:1 and 1:10 and preferably to between 1:1 and 1:5.
The process may also be used for the production of two products differing from one another in their composition.
In cases where the molar ratio of aryl amine to acids is from 1:0.01 to 0.75, an organic layer separates following the addition of water. Experience has shown that this organic layer has a higher content of 2,2/2,4; 3 and higher nuclear polyamines than the polyamines obtained from salt solutions by aryl amines.
It is possible in this way to produce certain qualities from the outset.
The water may be added in any way: after condensation by straightforward mixing first for washing the polyamine and then for dilution, or some for washing and the rest for dilution. It may also be injected into different stages in several streams.
The present invention will be better understood by reference to the following examples and drawings.
In the drawings, Figures 1 to 4 are diagrammatical representations of suitable apparatus for carrying out the process of the present invention.

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186 g of aniline (2 moles) are introduced into a stirrer-equipped vessel, followed by the addition of 171 g of aqueous HCl (containing 1.5 mole of HCl). The contents of the vessel are then cooled to 25C. After the formaldehyde - has been added, the contents of the vessel are stirred for 1 hour at 25C and then heated to 90C. The rearrangement time ' -. - lOa -A

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1~t8'7633 is 4 hours. The contents of the reaction vessel are then diluted and cooled by the addition of 500 cc of cold water.
A homogeneous aqueous solution containing approximately 20 %
of salt is obtained.
S 600 g of the above solution are mixed 4 times at 25C
with 250 g of aniline, followed by separation. The aqueous phase obtained after the fourth exchange is neutralised with alkali to pH 8, the amine liberated is taken up in chlorofirm and washed twice with w~er. The sample is then analysed by thin layer chromatography (TLC) on silica gel with chloroform-methanol (95:5 % by weight) as eluent.
The free amine from the aqueous phase is found to consist almost comp~tely of aniline. ~lore than 99 % of the polyamine has been exchanged for aniline.
EXA~LE 2 93 g of aniline, 68.6 g of 70 % aqueous methane sulphonic acid and 57.4 g of water are stirred and reacted ,in a stirrer-equipped vessel. The solution is adjusted to 50C, followed by the dropwise addition over a period of 20 minutes of 73 g of 18.5 % formaldehyde.
The ratio of aniline/formaldehyde/methane sulphonic acid is 1:0.45:0.5. The total water content is approximately 50 %.
Thereafter the contents of the vessel are kept for 1 hour at 50C, and then for'2 hours at 70C and finally for 1 hour at 90C.
On completion of the rearrangement, 295 cc of cold, water are introduced and the temperature of the solution adjusted to 23C.
This solution is treated 4 times with 200 g of aniline in the same way as in Example 1.
The ~n layer chromatogram shows that the aqueous _ 1~8'7~ 3 3 solution essentially contains aniline methane sulphonate only.

The condensation product of Example 2 is adjusted with water to a methane sulphonic acid content of 11 %0 There-after 100 g batches of the solution are mixed 5 times at room temperature, followed by separation:
a) 30 g of aniline b) 30 g of aniline + 7.5 g of monochlorobenzene c) 30 g of aniline + 15 g of monochlorobenzene d) 30 g of aniline + 30 g of monochlorobenzene.
After each treatment, a sample of the aqueous phase is neutralised and subjected to thin layer chromatography.
It was found that, in test a), more than 99 % of the polyamines were exchanged after only three treatmen~.
In test b) 98 ~/O after 4 treatments In test c) approximately 80 % after 5 treatments In test d) approximately 50 % after 5 treatments.

The condensation product is adjusted with water to a methane sulphonic acid content of 15 %. This composition is miscible with aniline. Two phases are formed by the addition of WIS.

3 100 g batches of the solution are treated 5 times at room temperature with the following mixtures:
a) 30 g of aniline + 7.5 g of monochlorobenzene b) 30 g of aniline + 30 g of monochlorobenzene c) 30 g of aniline + 30 cc of toluene.
It was found by thin layer chromatography that the exchange level is a) at about 98 % after 5 treatments b) at 50 % after 5 treatments c) at 50 % after 5 treatments.

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11~87633 EXAMPLE 5 (Figure 1) In Figures 1 to 3, U1 - U4 together represent the circuit, M1 ~ M4 are the mixers and S1 - S4 the settlers.
A four-stage countercurrent mixer-settler installation corresponding to Figurè 1 is operated as follows:
650 parts/hour of aqueous solution consisting of 14.7 % of polyamine (methylene dianiline and high PA) 5.6 % of hydrochloric acid (100 ~O) 79.7 % of water are introduced into the mixer 1 through pipe 1.
100 parts/h of aniline are pumped through pipe 2.
The aniline phase is pump-circulated at650 parts per hour in each mixer-settler sta~ge. An aqueous solution containing 14 % of aniliné hydrochloride and substantially free from PA is obtained through pipe 4.
Polyamine/aniline mixture is obtained through pipe 3.
EXAMPLE 5a (Figure 1) The procedure is as in Example 5, the following streams being used: -650 parts/h of anaqueous solution consisting of 16 /O of polyamine (MDA + PA)~ 15 % of methane sulphonic acid and 69 % of water, and 150 parts/hof an organic solution consisting of 120 parts of aniline and 30 parts of o-dichlorobenzene.
The aqueous solution from pipe 4 contains 22 % of a methane sulphonic acid/aniline/MDA-salt., Amine obtained by neutralisation consists of 98 % of aniline and 2 % of MDA.
EXAMPLE 5b (Figure 2) The procedure is as irl Example 5, 90 parts/h of aniline being introduced through pipe 2 and 60 parts/h of a solution consisting of 30 parts of aniline and 30 parts of o-dichloro-benzene through pipe 2a. The salt contained in the aqueous , - 13 -. . . . - : . . ~:

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1~8~ ~3 solution obtained through pipe 4 consists almost entirely of pure aniline methane sulphonate. Polyamine/aniline mixture is obtained through pipe 3.
EXAMPLE 5c (Figure 3) The procedure is as in Example 5, except that 50 parts/h of aniline are introduced through each of the pipes 2 and 2a.
The organic phas~sof stages S3 and S4 are introduced together into the mixer M2 through corrçsponding pipes.
Anaqueous solution containing 16 % of aniline hydrochloride is obtained through pipe 4. The salt is substantially free from MDA.

An exchange installation of the type shown in Figure 4 with 6 exchange stages (5 - 10) (mixer-settler) is operated as follows:
The water used for washing the po~amine/aniline arrives through pipe 12. The condensation solution containing HCl is introduced through the pipes 11a, b, c in such a way that the concentration of HCl is adjusted as follows:
in stage S : 1.5 %
in stage 6 : 3.5 %
in stage 7 :'5.6 %, Aniline arrives through pipe 15a, b, c, the sum of the stream being equal to 25 % by volume of the total sum of 12 + 11a, bj c.
An aniline/polyamine stream 14 containing approximately o,95 /O of HCl and an aqueous solution 13 of the aniline hydrochloride containing approximately 19 ~0 of salt and 5.6 % of aniline are obtained.
The post-extraction stage gives an aniline hydrochloride solution with a concentration of approximately 25 % which is concentrated by evaporation.

f ~ , 1087~33 The aniline/polyamine stream is washed with water in a countercurrent extraction installation and worked up in accordance with the prior art.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In the process wherein an arylamine and formaldehyde are condensed in the presence of aqueous acid to form poly-arylpolyamine salts, and polyarylpolyamine and catalyst are recovered, the improvement which comprises effecting the recovery of polyarylpolyamine by contacting the polyarylpoly-amine salt-containing reaction solution at about 18 to 35°C
with sufficient arylamine to form an aqueous phase and an organic phase, the organic phase comprising polyarylpolyamine and arylamine and the aqueous phase comprising the acid salt of the arylamine, the mixture of reaction solution and aryl-amine containing no more than 50% of a hydrophobic solvent based on the weight of arylamine.

2. A process as claimed in claim 1, wherein water is added to the polyarylpolyamine salt-containing reaction solution prior to contact with the arylamine.

3. A process as claimed in claim 1, wherein the contact with polyarylpolyamine is effected in the presence of a hydrophobic solvent.

4. A process as claimed in claim 1, wherein the ratio by weight of solvent to arylamine amounts to between 0.01 : 1 and 0.5 : l.

5. A process as claimed in claim 1, wherein the contact is effected in a plurality of stages, the organic phase being recirculated.

6. A process as claimed in claim 5, wherein the ratio by volume of organic phase to aqueous phase in each stage amounts to between 20 : 1 and 1 : 10.

7. A process as claimed in claim 3, wherein the exchange is carried out first with a mixture of arylamine and hydrophobic solvent and then with pure arylamine.

8. A process as claimed in claim 5, wherein the composition between arylamine and hydrophobic solvent is different from stage to stage.

9. A process as claimed in claim 5, wherein the final exchange is carried out with a divided arylamine stream, the component streams only being combined after at least two stages.

10. A process as claimed in claim 2, wherein the concen-tration of the salt after dilution of the reacted condensation mixture is adjusted with arylamine to between 2 and 50%
before the exchange.

11. A process as claimed in claim 1, wherein the result-ing solution of polyarylpolyamine in arylamine is washed with water and the washing water is used for diluting the condensa-tion mixture.

12. A process as claimed in claim 1, wherein the aryl-amine is aniline, ?-toluidine, N-methyl aniline, N-ethyl aniline or mixtures thereof.

13. A process as claimed in claim 1, wherein the acid is methane sulphonic acid, trifluoroacetic acid, hydrochloric acid or mixtures thereof.

14. A process as claimed in claim 1, wherein the molar ratio of aromatic amine to formaldehyde amounts to between 10 : 1 and 1 : 1.

15. A process as claimed in claim 1, wherein the molar ratio of aromatic amine to acid amounts to between 20 : 1 and 1 : 1.

16. A process as claimed in claim 5, wherein the aqueous condensation solution is introduced at about the middle exchange stage.

17. A process as claimed in claim 5, wherein the ratio by weight of solvent to arylamine amounts to between 0.01 : 1 and 0.5 : 1, the ratio by volume of organic phase to aqueous phase in each stage amounts to between 20 : 1 and 1 : 10, water is added to the polyarylpolyamine salt-containing reaction solution prior to contact with the arylamine, the concentration of the salt after dilution of the reacted condensation mixture is adjusted with arylamine to between 5 to 30% before the exchange, the arylamine is aniline, ?-toluidine, N-methyl aniline, N-ethyl aniline or mixtures thereof, the acid is methane sulphonic acid, trifluoroacetic acid, hydrochloric acid or mixtures thereof, the molar ratio of aromatic amine to formaldehyde amounts to between 10 : 1 and 1 : 1, and the molar ratio of aromatic amine to acid amounts to between 20 : 1 and 1 : 1.