CS199653B2 - Process for preparing polyarylamines containing methylene bridges - Google Patents

Description

The production of polyamines of the diaminodiphenylmethane series by the condensation of aromatic amines with formaldehyde in the presence of acid catalysts has been described many times and, depending on the production method, provides a product of different composition. Thus, by condensation in the presence of weakly acid catalysts or traces of strongly acid catalysts, mixtures of polyamines with a high proportion of 2,4'-diaminodiarylmethane are obtained, while polyamines with a high proportion of 4,4'-diaminodiarylmethane and at the same time a low content of 2,4'-isomers can be produced. only in the presence of large amounts of strongly acid catalysts. In the latter case, strong mineral acids, such as hydrochloric acid in particular, are best suited. (DOS number 1 518 406, DOS 2 045 834, DOS

No. 049,707, DOS 2,301,554, U.S. Pat

367 969.) The advantage of the high selectivity of strongly acidic mineral acids for the formation of 4,4‘-isomers, however, must be avoided according to methods known in the art because of the loss of the catalyst, since this must be removed from the reaction mixture by expensive base neutralization. A further disadvantage of the prior art method is that the saline solutions which are eliminated by this neutralization reaction cannot in any way be returned to the technical evaluation and entails serious environmental problems.

Surprisingly, it has been found that by mixing the aqueous salt solutions of the polyamines with the starting arylamines (arylamine) in at least a partially heterogeneous (two-phase) system, the polyamines are displaced by arylamines or alternatively replaced by arylamines.

Two phases are formed: organic (polyarylamine-arylamine) and aqueous (saline arylamine).

Accordingly, the present invention provides a process for producing polyarylamines having methylene bridges while recovering the catalyst from arylamines and formaldehyde in the presence of acids and water, wherein the polyarylamine components of the salts of polyarylamines that are present in aqueous solutions after the reaction are exchanged with the starting arylamines, in which case aqueous solutions of polyarylamine salts which, if added with water, have a salt concentration in the aqueous phase of 2 to 50% are present at a concentration at which they form a heterogeneous biphasic system with the starting arylamines. starting arylamines in one or more stages in cocurrent or countercurrent with 15-100 ^{O |} C and process,

139653 wherein the volume ratio of the organic phase to the aqueous phase is 20: 1 to 1: 10, then the organic phase is separated from the aqueous phase and the aqueous phase of the arylamine starting salt is returned to condensation and optionally the polyarylamine phase is washed with water; and the wash water is circulated.

The condensation reaction of the continuous or discontinuous process according to the invention can be carried out by known methods according to the state of the art, wherein the molar ratios of arylamine to acid catalyst can be freely selected in a wide range. Suitable molar ratios of arylamine to formaldehyde are in particular from 10: 1 to 1: 1, preferably from 4: 1 to 18: 1, and from 20: 1 to 1: 1, preferably from 1: 1 to 1, 5: 1, the latter molar ratio being understood as the molar ratio between the arylamine charged at the start of the process and the acid present in the ring in the form of arylamine salts.

The exchange is effected practically by multiple mixing of the aqueous salt solutions of the polyamine with the starting arylamines, preferably continuously, in countercurrent.

There are two competing processes in the process of the invention:

1. the required exchange of polyamines for arylamines,

2. extraction of the amino-salts with the organic phase.

The second phenomenon is undesirable since it is technologically important to obtain aqueous solutions of arylaminosolines with maximum concentration. The higher this is, the less it is necessary to evaporate the water in order to obtain the necessary salt concentration for the initial process condensation.

In order to suppress this extraction, relatively small amounts of the starting arylamine must be used. However, this exacerbates the exchange effect.

It has been found that there are various possibilities to accelerate the process of the invention.

It has been shown that, when working with small amounts of arylamine, reasonably low acid concentrations in the polyamine salt solutions must also be used. At higher acid concentrations, the solubility of arylamine increases. When using more arylamine, two-phase systems are again obtained.

In order to achieve the best exchange effect with a minimum amount of arylamine, it is advantageous to conduct the arylamine at each stage in the cycle, so that only a part of the liquid always participates in one exchange stage, fed to the next stage, of the same degree. For example, if the amounts of the aqueous salt solution of the polyarylamine to be treated and the arylamine to be exchanged at a ratio of 5: 1 are used, and the amount of arylamine fed to each circuit is 4 times the arylamine (inner circuit), the same total amount of arylamine charged in each step is 1: 1, which provides better exchange effect as well as better phase separation.

It is also possible to maintain the ratio between the currents in the stages different, as the exchange effects vary in different stages: at the beginning, the exchange is much faster than at the end. It may also be advantageous to vary the inner circuit step by step.

The at least partial insolubility of arylamine in aqueous salt solutions of polyarylamines (prerequisite for exchange) can also be achieved by the addition of a hydrophobic (water insoluble) solvent (HLM). This process is only of limited use. The presence of larger amounts of hydrophobic solvents affects the exchange negatively: it has been found that too large amounts of added hydrophobic solvents reduce the extraction of salts, but thereby impair the exchange effect of polyamines.

There is shown a difference from the process of DOS 223 892, in which an increase in the amount of hydrophobic solvents prevents or terminates the exchange. This also proves that at least partially heterogeneous phases in the state are a prerequisite for the exchange, and the organic phase must consist mainly of arylamine. It has been shown that there must be some solubility of arylamines in aqueous salt solutions of polyamines.

This means that experimentally optimal hydrophobic solvents must be determined for the corresponding equipment, and a compromise must be found between the two competing processes.

All water-immiscible solvents which are inert to the reaction products are practically useful as hydrophobic solvents. Particularly suitable are: benzene and alkylbenzenes, chlorinated aliphatic and aromatic hydrocarbons, etc. Highly preferred are the use of hydrophobic solvents which are in the boiling range, for example aniline: they distil together with the excess aniline and are circulated.

The solubility of arylamines in water or in acidic salt solutions is highly dependent on the salt concentration.

According to Landolt-Bornstein II, Volume 2 part of Volume C: equilibrium of solution II, page 601, the equilibrium between aniline and an aqueous solution of aniline hydrochloride is known. As the concentration of aniline chloride hydrate increases, the solubility of aniline is increased until miscibility.

At about 20% aniline hydrate, both phases contain about 20% salt.

if the amount of salts in the aqueous phase is reduced to about 6%, the amount of salts in the aniline phase is reduced to about 1.4%.

The process can be adapted to this by operating in a countercurrent device with different salt concentrations; on the aqueous phase with the maximum salt concentration and on the organic phase with the lowest possible salt concentration.

This can be achieved by not delivering the polyarylamine salt solution in one but in several mixing stages so that the highest salt concentration is about in the middle of the exchange device.

Alternatively, the aqueous polyarylamine salt solution is metered into about the middle stage of a multi-stage apparatus and operated in countercurrent with the arylamine starting material and water on the other hand, as is customary in countercurrent extraction, with water such as backflow).

Another way of working comes from a combination of both:

Initially, a mixture of polyamine and aqueous salt solution is treated with a mixture of arylamine with a hydrophobic solvent, resulting in a 50-98% exchange.

It is then treated with pure arylamine and the exchange is complete.

In practice, this means that a hydrophobic solvent is added to the arylamine stream, irrespective of whether this addition is carried out in one or more stages.

The exchange effect can also be increased if, for example, the amount of arylamine is divided into two or more streams, leads to the exchange stages, then is only co-current in countercurrent. Particularly in cases where the amounts of arylamine are small, this use of internal cycle guidance is of importance.

The organic phase thus obtained must not contain more than 30 ppm of acid. By washing with water, for example in a countercurrent extraction device, this value can be easily achieved. The wash water may be used in a replaceable device.

The aqueous phase also contains a dissolved starting arylamine, which can be removed by azeotropic distillation (optionally by steam) or by extraction with hydrophobic solvents. Then, the aqueous phase is concentrated and leads to condensation.

Any aromatic amine may be used in the process of the invention. Examples of this use are: aniline, o-toluidine, m-toluidine, N-methylaniline, N-ethylanlanine,

2,6-dimethylaniline, 2,6-diethylaniline, 2,6-diisoproipyilaniline, 2,4-diaminotoluene, as well as any mixtures consisting of such amines. Preferably aniline is used as arylamine in the process of the invention.

In particular, water-soluble acids having a pKa of less than 1.5 are used in the process according to the invention. Examples of these are hydrochloric acid, hydrobromic acid, sulfuric acid, trifluoromethanesulfonic acid, benzenesulfonic acid or phosphoric acid. Preferred catalysts are hydrochloric acid, trifluoroacetic acid and methanesulfonic acid. Said acids may also be used in admixture with acidic or neutral salts of these acids, such as the corresponding ammonium salts or even the corresponding alkali metal salts. Of course, salts formed initially from said acids as well as from arylamine used as the starting amine can also be used as sole catalysts.

The acidic condensation mixture can be prepared in a manner known per se by mixing a mixture consisting of an aromatic amine and an acid catalyst with formaldehyde or formaldehyde-releasing substances and heating them to higher temperatures to switch the precondensate formed. It is also possible, conversely, first 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 any case, the acidic condensation mixture is suitable for the process of the invention.

The amount of water added depends mainly on the molar ratio of arylamine to acid. Water should be added until the arylamine solubility is below a certain level.

Preferably, the salt concentration in the water is adjusted to 50%, in particular to 5 to 40 percent.

The condensate, water from the formaldehyde as well as the additive are removed after the eventual removal of the dissolved arylamine, preferably in a one- or multi-stage evaporator, under pressure, under pressure or under vacuum, and is subsequently circulated in the ring.

The exchange can be carried out at or above room temperature, preferably at 15 to 35 ° C.

The method according to the invention has the following advantages:

- salt-free waste water, - no acid catalyst is used, - alkali is eliminated, - neutralization apparatus is eliminated, - economic advantages.

Various devices may be used for replacement: continuous or discontinuous. Preferably, liquid extraction devices or countercurrent devices are used.

The specific gravity of the phases is influenced by several factors: the concentration of salts in water or arylamine, as well as the polyarylamine content of the arylamine. The specific gravity also depends on the catalyst. For example, polyamines (aniline J, methanesulfonic acid salts are lighter in water than mixtures of aniline and polyarylamine.

Again, aqueous aniline methanesulfonate solutions with a polyamine content of less than 5% are heavier than aniline. Phases are reversed.

This phenomenon is not technologically pleasant.

Phase reversal can be avoided either by adding a hydrophobic solvent or by using mixtures of acids as catalysts.

The amount of arylamine to be exchanged is determined by the composition of the salts (polyamine content), the type of apparatus, and also the mode of operation.

When working with counterflow devices, smaller quantities are sufficient.

In general, the volume ratio of arylamine to aqueous salt solution may be about 5: 1 to 1: 10, preferably about 1: 1 to 1: 5.

The method can be used to produce two with respect to the composition of different products.

Using a molar ratio of arylamines to acids of 1: 0.01 to 0.75, the organic layer is separated after the addition of water. This has, according to experience, a higher content of aromatic cores 2,2-polyamines, 2,4-polyamines as well as

3-polyamines and higher than polyamines obtained with arylamines from saline solutions.

This makes it possible to produce these in a predetermined quality.

The addition of water can be carried out in any desired manner: after condensation by simple mixing, first to additionally wash the polyamine, then to dilute, or to wash part and the remainder to dilute. It can also be injected to different degrees in multiple streams,

Example 1

186 g of aniline (2 moles) are placed in a stirred vessel and 171 g of aqueous hydrogen chloride (containing 1.5 moles of hydrogen chloride) are added thereto and cooled to 25 ^° C.

After the addition of formaldehyde was complete, the mixture was stirred at 25 ° C for 1 hour and then heated to 90 ° C.

The rearrangement time is 4 hours. It is then diluted with 500 cm ^{3 of} cold water and cooled.

A homogeneous aqueous solution is obtained with about 20% salt.

400 g of the above solution are taken and mixed four times with 250 g of aniline each at 25 ^DEG C. and separated. The aqueous phase is neutralized to pH 8 with alkali to pH 4, the amine liberated is taken up in chloroform and washed twice more with water. The sample is then analyzed by thin layer chromatography on silica gel, eluting with a 95: 5% mixture of chloroform and methanol.

It turns out that the free amine of the aqueous phase consists practically of aniline. Polyamine was more than 99 a / _o exchanged for aniline. Example 2

93 g of aniline and 68.6 g of 70% aqueous metasulfonic acid as well as 57.4 g of water are mixed in the stirring vessel and allowed to react. The solution is set at 50 ° C and 73 g of 18.5% formaldehyde are added dropwise over 20 minutes.

The charge corresponds to a ratio of aniline to formaldehyde and to methanesulfonic acid of 1: 0.45 and 0.5. The total water content is about 50%.

Then maintained for 1 hour at 50 ^DEG C., then for 2 hours at ^70C ° C and 1 hour at 90 ° C.

On completion of the rearrangement, 295 cm ^{3 of} cold water are added and the temperature of the solution is adjusted to 23 ° C.

This solution was treated 4 times with 200 g of aniline, as in Example 1.

Thin layer chromatography showed that only aniline methanesulfonate was present in the aqueous solution.

Example 3

The condensation product of Example 2 was adjusted to 11% methanesulfonic acid with water. Then, at room temperature, they are mixed 5 times with 100 g of solution each time and separated:

and) (b) 30 30 G G aniline aniline + 7.5 G monochlor- C) 30 G aniline + 15 Dec G benzene monochlor- (d) 30 G aniline 4- 30 G benzene monochlor-

benzene

After each treatment, the aqueous phase sample is neutralized and analyzed by thin layer chromatography.

It was found that in experiment a) more than 99% were exchanged after 3-fold processing of the polyamine.

At bj after quadruple processing 98%

c) after processing five times about 80%

(d) after a six-fold treatment, about 50%.

Example 4

The condensation product is adjusted with water to 15% methanesulfonic acid. This setting is miscible with aniline. After addition of the hydrophobic solvent, two phases are formed.

3 batches of 100 g of solution were treated 5 times at room temperature with the following mixtures:

also 30 g aniline + 7.5 g monochlorobenzene bj 30 g aniline 4-30 g monochlorobenzene cj 30 g aniline + 30 cm ³ toluene.

Thin layer chromatography revealed that the exchange of

a) after 5 processing it is about 98%

b) after 5 treatments it is about 50%

c) after about 5 treatments, it is around 50%.

Example 5 (Fig. 1)

In Figures 1 to 3, Ui to U <t represent a circuit,

Mi to M4 mixer and Si to S4 separator (settler).

The four-stage countercurrent extraction apparatus for liquids corresponding to Figure 1 is accompanied by the following:

Through line 1, 650 parts / h of an aqueous solution consisting of:

14.7% polyamine (methylenedianiline and high, PA)

5.6% 100% hydrochloric acid

79.7% water.

100 parts / h of aniline are passed through line 2 and 650 parts / h of aniline phase are pumped through each stage of the liquid extraction apparatus. Line 4 gives an aqueous solution containing 14% aniline chlorohydrate, which is practically free of PA.

Line 3 gives a polyamine-aniline mixture.

Example 5a (Fig. 1)

The procedure is as in Example 5, using the following streams:

650 parts / h of an aqueous solution consisting of% polyamine (methylenedianiline + polyamine),% methanesulfonic acid,% water, and 150 parts / h of an organic solution consisting of 120 parts of aniline and 30 parts of o-dichlorobezene.

The aqueous solution from line 4 contains 22% of a mixture of methanesulfonic acid, aniline and methylenedianiline. The amine obtained by neutralization consists of 98% aniline and 2% methylenedianiline.

Example 5b (Fig. 2)

The procedure is as in Example 5, with 90 parts / h of aniline being fed through line 2 and 60 parts / h through a line 2a containing 30 parts of aniline and 30 parts of o-dichlorobenzene.

The salt obtained in line 4 in aqueous solution consists of practically pure aniline methanesulfonate. Line 3 yields a mixture of polyamine and aniline.

Example 5c (Fig. 3)

The procedure is as in Example 5 except that 50 parts / h of aniline are introduced each time via lines 2 and 2a.

The organic phases of stages S3 and S4 are led through the corresponding lines together to the mixer M2.

Line 4 gives an aqueous solution containing 16% aniline chlorohydrate. The salt is practically free of methylenedianiline.

Example 6

The exchange device according to FIG. 4 with six exchange stages (5 to 10) (liquid extraction device) is operated as follows:

Through line 12, water comes from the additional wash of the polyamine-aniline mixture. The hydrogen chloride condensate is passed through lines 11a, b, c so as to adjust the hydrogen chloride concentration as follows:

step 5 = 1.5%, step 6 = 3.5%, step 7 = 5.6%.

Aniline is passed through lines 15a, b, c, wherein the sum of the currents is 25% by volume of the total sum of 12 + 11a, b, c.

A stream of mixtures of aniline with a polyamine with about 0.95% hydrogen chloride and an aqueous solution of 13 aniline chloride hydrate and about 19% salt and 5.6% aniline is obtained.

After an additional extraction, an aniline chloride hydrate solution of about 25% concentration is obtained which is concentrated.

The stream of aniline and polyamine is additionally washed with water in a countercurrent extraction apparatus and treated according to the prior art method.

Claims (10)

P R E D M E Τ A process for obtaining polyamines having methylene bridges which have been prepared by reacting arylamines and formaldehyde in the presence of acids and water, characterized in that the polyarylamine salt components of the polyarylamine salt present in aqueous solutions after the reaction are exchanged for starting arylamines, wherein In exchange, aqueous solutions of the polyarylamine salts, which, optionally after addition of water, have a salt concentration in the aqueous phase of 2 to 50% and are present in a concentration at which they form a heterogeneous biphasic system with the starting arylamines, are mixed with the starting arylamines in one or more stages or countercurrent at 15 to 100 ° C and processed, with each stage having a volume ratio of organic phase to aqueous phase of 20: 1 to 1: 10, then the organic phase is separated from the aqueous phase and the aqueous phase of the arylamine starting salt is returned to condensation and optionally washing the polyarylamine phase water polyarylamin were separated and the wash water is passed in a circuit. 2. Process according to claim 1, characterized in that the process is carried out at temperatures of 18 to 35 [ ^deg .] C. Method according to Claims 1 and 2, characterized in that, in a continuous process, the organic phase is conducted in a circuit within the individual stages. VYNALEZU 4. A process according to any one of claims 1 to 3, wherein the exchange is carried out first with the starting arylamine and a mixture of hydrophobic solvents and then with the pure starting arylamine. 5. The process of claims 1 to 4 wherein the hydrophobic solvent content of the starting arylamines varies from step to step. Method according to one of Claims 1 to 5, characterized in that the final exchange is carried out with a split stream of the starting arylamines, the partial streams being brought together again only after two or more stages. 7. A method according to any one of claims 1 to 6, wherein the concentration of salt in the aqueous phase is maintained at 5 to 30%. 8. Process according to claim 1, characterized in that solutions of crude salts of polyarylamines containing methanesulfonic acid, trifluoroacetic acid or mixtures thereof are used as acid catalysts. 9. A method according to claims 1 to 8, characterized in that the polyarylamine salt solution is fed to the intermediate exchange stage. 10. A method according to any one of claims 1 to 9, wherein the concentration of the salt of the starting arylamine in the water is maintained at the limit of heterogeneity.