IE44544B1 - A process for the production of polyaryl amines containg methylene bridges - Google Patents

Abstract

This invention is directed to a process for the production of polyaryl amines containing methylene bridges. These compounds are prepared from aryl amines and formaldehyde 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 heterogeneous 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

This invention relates to a process for.the production of polyaryl amines containing methylene bridges.

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 products 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'risomers 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 at 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 neutralisation with a base which is expensive. Another disadvantage of conventional processes is the fact that the salt solutions obtained by this neutralisation cannot be put to any worthwhile commercial use and thus give rise to considerable pollution problems.

It has surprisingly been found.that, when aqueous polyamine product solutions are mixed with starting aryl amines (aryl amines), two phases are formed, namely an organic phase (polyaryl amine-aryl) and an aqueous phase (aryl amine salt solution), in which the polyamines are displaced from the aqueous phase and replaced by aryl ?. 440.14 dill1 ne;..

Accordingly, the present invention relates to a process for the production of polyarylaniines containing methylene bridges, in which a methylene-bridged polyarylamine salt solution, produced by the condensation of arylamines and formaldehyde in the presence of acids and water, is exchanged with a further quantity of arylamine starting material, by mixing the polyarylamine salt solution with the further quantity of arylamine starting material in one or more stages, to form a heterogeneous system, allowing the polyarylamine salt and the arylamine to react together, then separating the aqueous phase and the organic phase and recycling the aqueous aryl amine salt phase to the condensation process.

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 advantageously in the range of from 10:1 to 1:1 and preferably in the range from 4:1 to 1.8:1, whilst the molar ratio of aryl amine to catalyst is in the range of 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 of aryl amine introduced at the beginning of the process to the acid present in the reaction cycle in the form of aryl amine salts. The volume ratio of organic phase to aqueous phase in each stage is preferably from 20:1 to 1:10.

In practice, the exchange is effected by repeatedly mixing the produced aqueous polyamine salt solutions with fresh starting aryl amine, preferably continuously, in countercurrent flow.

Two concurrent phenomena occur in the practical application of the process according to the invention, namely: 1. The required exchange of polyamines of 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 removed by evaporation in order to obtain the necessary salt concentration for the initial condensation stage of the process. 3.

In order to suppress extraction, it is necessary to use relatively small quantities of starting aryl·amine in the exchange stage. Unfortunately, this adversely affects the replacement or exchange effect.

It has been found that the process according to the invention may be carried 5 out in different ways.

It has also been found that, in cases where relatively small quantities of aryl amine are used, it is necessary to use correspondingly lower concentrations of acid in the polyaryl amine salt solutions. The solubility of the aryl amines increases with relatively high 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 minimal quantity of aryl amine, it is best to use a multi-stage process in which the aryl amine is circulated in each stage in such a way that, only a part of the aryl amine 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 volume ratio of the quantities of aqueous polyaryl amine salt solution to be treated and the exchange aryl amine is 1:5 and if, in each stage, the quantity of aryl amine recycled is 4 times the quantity of the aryl amine conveyed to the next stage, 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 ratio of the quantity of aryl amine recycled to the quantity conveyed to the next stage 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 (MIS). This procedure can only be applied to a limited extent. The presence of relatively large quantities of MIS adversely affects the exchange. It has been found that, although excessively large additions of MIS reduce extraction of the salts, they adversely affect the exchange effect of the polyamines. 4. •ί «I S 4 d It is this which represents the difference from the process according to DI-OS No. 2,238,820 in which the increase in the quantity of Wls prevents or stops the exchange. This also shows that the exchange presupposes the existence of two 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 the apparatus used, a compromise having to be found between both concurrent phenomena. A ratio by weight of hydrophobic solvent to aryl amine of from 0.01:10 to 0.5:1 is preferred.

Suitable WIS are any solvents which are immiscible with water and inert with respect to the reaction products. Particularly suitable WIS are benzene and alkyl benzenes, chlorinated hydrocarbons and aliphatic and aromatic hydrocarbons. It is of considerable advantage to use WIS which boil at temperatures in the same range as the starting aryl amines, for example, aniline. They are then distilled together with excess amine and recirculated.

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 11, Vol. 2, Section C: Losungsgleichgewichte (solution equilibriums) 11, page 601, the equilibria between aniline and aqueous solutions of the aniline hydrochloride are known. 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 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 contacting the polyaryl amine salt solution with the aryl amine in 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 amine salt solution into about the middle stage of the multistage -installation and to work with starting aryl amine and with water in countercurrent flow (as is standard practice for example in countercurrent extraction with water as the recycle component).

Another procedure is based on a combination of both processes; to begin with the Pa/aqueous salt 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 amine. 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, 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 according 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 such acids are hydrochloric acid, hydrobromic acid, sulphuric acid, trifluoromethane sulphonic acid, benzene sulphonic acid or phbsphoric acid. Preferred catalysts 6. a>'i> liydtOi.hlm’ir .vid, trlf liiorom t»t h a> id and mrllwne Miiplnuih di id. in»· rtbuvt-niriitlomnl at id·, may also bo used in admixture with their avid or neutral salts such as for example the corresponding ammonium salts or even the corresponding alkali metal salts. It is of course also possible to use the salts formed 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 -0 rearrangement. Conversely, it is also possible initially to react the 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 use in 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 amines is below a certain limit.

The concentration of salt in water is preferably adjusted to between 2 and 50% and, with particular preference, to between 5% and 30%.

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.

The exchange may be carried out at room temperature or at a temperature above room temperature, preferably at a temperature from 15°C to 100°C, more preferably 18°to 35°C.

The process according to the invention is distinguishedby the following advantages :salt-free effluent no consumption of acid catalyst elimination of the need for base elimination of the need for the neutralisation apparatus economic advantages. · 445*4 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 5 concentration in water and in aryl amine and the content of Dolyaryl amine in aryl amine. The density of the Dhases is also governed bv the catalyst. For example, the polyamine (aniline) methane sulphonic acid salts in water are lighter than the mixtures of aniline and polyaryl amines.

With a 5% polyamine content, the aqueous solutions of the aniline methane 10 sulphonate are in turn heavier than aniline. Phase reversal occurs. This phenomenon is unfavourable 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 lb 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.

ZO , 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, polyamines and trinuclear 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 viater 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.

In order that the invention may be more fully understood, the following Examples are given, by way of illustration only:EXAMPLE 1 186 g of aniline (2 moles) are introduced into a stirrer-equipped vessel, followed by the addition of 171g of aqueous HC1 (containing 1.5 mole of HC1).

The contents of the vessel are then cooled to 25°C. After the formaldehyde has been added, the contents of the vessel are stirred for 1 hour at 25°C and then heated to 90°C. The rearrangement time 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. 600 g of the above solution are mixed 4 times at 25°C 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 chloroform and washed twice with water. The sample is then analysed by thin layer chromatography (TLC) on silica gel with chloroform-methanol (95:5% by weight) as eluant.

The free amine from the aqueous phase is found to consist almost completely of aniline. More than 99% of the polyamine has been exchanged for aniline.

EXAMPLE 2 g of aniline, 68.6 g of 70% aqueous methane sulphonic acid and 57.4 g of water are stirred and reacted in a vessel equipped with a stirrer. The temperature of the solution is adjusted to 50°C, 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 50°C and then for 2 hours at 70°C and finally for 1 hour at 90°C.

On completion of the rearrangement, 295 cc of cold water are introduced and the temperature of the solution adjusted to 23°C.

This solution is treated 4 times with 200 g of aniline in the same way as in Example 1. 9. 4 5 4 4 Thin layer chromatography shows that the aqueous solution essentially contains only aniline methane sulphonate.

EXAMPLE 3 The condensation product of example 2 is adjusted with water to a methane sulphonic acid content of 11½. Thereafter 100 g batches of the solution are mixed 5 times at room temperature, followed by separation, with: a) 30 g of aniline b) 30 g of atriline+7.5 g of mono-chlorobenzene c) 30 g of aniline+15 g of mono-chlorobenzene d) 30 g of aniline+30 g of mono-chlorobenzene 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 treatments.

In test b) 98% after 4 treatments In test c) approximately 80% after 5 treatments In test d) approximately 50% after 5 treatments.

EXAMPLE 4 The condensation product of Example 2 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. 100 g batches of the solution are treated 5 times at room temperature with one of 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 . <484 a) at about 98% after 5 treatments b) at 50% after 5 treatments c) at 50% after 5 treatments.

EXAMPLE 5 This Example refers to Figure 1 of the accompanying drawings which is a diagrammatic representation of an arrangement for carrying out the process of the invention.

In this drawing and in Figures 2 and 3 the lines for the flow of material are represented by U]-U4. There are four mixers represented by Mj-M4 and four settlers represented by S]-S4.

A four-stage countercurrent mixer-settler installation corresponding to Figure 1 is operated as follows: 650 parts/hour of aqueous solution consisting of 14.7% of polyamine (methylene dianiline and high PA) .6% of hydrochloric acid (100%) 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 at 650 parts per hour in each mixer-settler stage. An aqueous solution 20 containing 14% of aniline hydrochloride and substantially free from PA is obtained through pipe 4.

Polyamine/aniline mixture is obtained through pipe 3.

EXAMPLE 5a The procedure is the same as in Example 5, the following streams being used: 550 parts/h of an aqueous solution consisting of 16% of polyamine (MDA+PA), % of methane sulphonic acid and 69% of water, and 150 parts/h of 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. 11. 4 5 J 4 EXAMPLE 5b The arrangement used is that shown in Figure 2. The procedure is as in 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-dichlorobenzene through pipe 2a. The salt contained in the aqueous solution obtained through pipe 4 consists almost entirely of pure aniline methane sulphonate. Polyamine/ aniline mixture is obtained through pipe 3.

EXAMPLE 5c The arrangement used is that shown in 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 phases of stages Sg and S4 are introduced together into the mixer Mg through corresponding pipes.

An aqueous solution containing 16$ of aniline hydrochloride is obtained through pipe 4. The salt is substantially free from MDA.

EXAMPLE 6 An exchange installation of the type shown in Figure 4 of the accompanying drawings with 6 exchange stages (5-10} (mixer-settler) is operated as follows: The water used for washing the polyamine/aniline arrives through pipe 12.

The condensation solution containing HCl is introduced through the pipes Ila, b, c in such a way that the concentration of HCl is adjusted as follows: in stage 5:1.5$ 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 $ by volume of the total sum of 12+11a, b, c.

An aniline/polyamine stream 14 containing approximately 0.5$ of HCl and an aqueous solution 13 of the aniline hydrochloride containing approximately 19$ of salt and 5.6$ of aniline are obtained. 12.

The post-extraction stage gives an aniline hydrochloride solution with a concentration of approximately 25% which is concentrated by evaporation.

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

Claims (22)

CLAIMS:
1. I. A process for me production of polyarylamines containing methylene bridges, in which a methylene-bridged polyarylamine salt solution, produced by the condensation of arylamines and formaldehyde in the presence of acids and water, is exchanged with a further quantity of arylamine starting material, by 5 mixing the polyarylamine salt solution with the further quantity of arylamine starting material in one or more stages, to form a heterogeneous system,allowing the pelyarylaffliRe Salt and the aryl amine to react together, then separating the aqueous phase and the organic phase and recycling the aqueous arylamine salt phase to the condensation process. )0
2. 2. A process as claimed in claim 1 in which water is added to the polyaryl amine salt solution.
3. 3. A process as claimed in claim 1 or claim 2 in which hydrophobic solvents are present during mixing.
4. 4. A process as claimed in claim 3 in which the ratio by weight of 15 hydrophobic solvents to aryl amine is from 0.01:10 to 0.5:1.
5. 5. A process as claimed in any of claims 1 to 4 in which the process is operated continuously.
6. 6. A process as claimed in any of claims 1 to 4 in which the ratio by volume of organic phase to aqueous phase in each stage is from 20:1 to 1:10. 20
7. 7. A process as claimed in any of claims 1 to 6 in which the exchange is carried out first with a mixture of aryl amine and hydrophobic solvent and then with pure aryl amine.
8. 8. A process as claimed in any of claims 1 to 7 in which the ratio of aryl amine to hydrophobic solvent is different from stage to stage. 25
9. 9. A process as claimed in any of claims 1 to 8 in v/hich the exchange is carried out with a divided aryl amine stream, the component streams only being combined after two or more stages.
10. 10. A process as claimed in any of claims 1 to 9 in v/hich the concentration of the salt after dilution of the reacted condensation mixture is adjusted with 30 aryl amine to between 2 and 50% before the exchange. 14.
11. 11. A process as claimed in claim 10, in which the concentration of the salt is diluted to 5 to 30% before the exchange.
12. 12. A process as claimed in any of claims 1 to 11 in which the resulting solution of polyamine in aryl amine is washed with water and the washing water is used for diluting the condensation mixture.
13. 13. A process as claimed in any of claims 1 to 12 in which aniline, o-toluidine, N-methyl aniline, N-ethyl aniline or mixtures thereof are used as aromatic amines.
14. 14. A process as claimed in any of claims 1 to 13 in which methane sulphonic acid, trifluoroacetic acid, hydrochloric acid or mixtures thereof are used as the acid catalyst. 15. A process as claimed in any of claims 1 to 14 in which the molar ratio of aromatic amines to formaldehyde is in the range of 10:1 and 1:1.
15. 15. A process as claimed in any of claims 1 to 15 in which the molar ratio of aromatic amine to acid catalyst is in the range of 20:1 and 1:1.
16. 16. 17. A process as claimed in any of claims 1 to 16 in which the exchange is carried out at a temperature of from 15 to 100°C.
17. 17. 18. A process as claimed in claim 17 in which the temperature employed is within the range of 18 to 35°C.
18. 18. 19. A process as claimed in any of claims 1 to 18 in which the polyamine product solution is introduced at approximately the middle exchange stage.
19. 19. 20. A process as claimed in any of claims 1 to 19, in which the concentration of salt is kept at the maximum possible concentration in the aqueous phase and the minimum possible concentration in the organic phase.
20. 20. 21. A process as claimed in claim 1 substantially as herein described with reference to any one of the Examples. 15. 4-45 4 4
21. 21.
22. 22. Polyaryl amines containing methylene bridges when made by the process Claimed in any of claims 1 to 21.