NO130767B - - Google Patents

Description

Procedure for the production of polyphenyl-

poly.amines with methylene bridges and containing

di-(aminophenyl)methane.

The invention relates to a process for the continuous production of polyphenyl-polyamines with methylene bridges by acid condensation of aniline and formaldehyde.

The acid condensation of aniline and formaldehyde during formation

of a mixture of polyphenyl-polyamines with methylene bridges and containing a larger amount of di-(aminophenyl)-methane is well known, see e.g. U.S. Patents No. 2,938,05<*>+, No. 3,163,666, No. 3,260,751, No. 3,27^,2'47 and No. 3,277-173. The mixture of polyamines can be used for a number of purposes, such as e.g. a starting material for pure di-(^-aminophenyl)-methane (MDA) which is useful as a curing agent for epoxy resins and as a starting material in the preparation of di-(^-aminocyclohexyl)-methane (H-^MDA). Both MDA and H-^MDA are

useful for the production of polyamides, see e.g. respectively the U.S. patent documents no. 2669556 and no. 3^-16302.

The mixture of polyamines can also be phosgenerated by known methods to the corresponding mixture of polymethylene-polyphenyl-polyisocyanates containing methylene-bis-(phenylisocyanate) as the main component. This can, if desired, be extracted from the mixture and is widely used for the production of elastomers and other unfoamed polyurethanes. In addition, the mixture of polymethylene-polyphenyl-polyisocyanates formed by the above-mentioned phosgenation is widely used in the industry for the production of polyurethane foam. A very useful process has recently been described for extracting methylene-bis-(phenylisocyanate) and a mixture of polymethylene-polyphenyl-polyisocyanates continuously and simultaneously from a feed material of polymethylene-polyphenyl-polyisocyanates containing a relatively large amount (65 - 75% by weight methylene bis-(phenyl iso-cyanates), see British Patent No. 1 092 019.

It is for a number of the purposes for which the di-(aminophenyl)-methane and the methylene-bis-(phenylisocyanates),'' obtained as stated above, are to be used for, it is desirable to produce these materials in the form of the essentially pure - isomer (ie at least 98% by weight). The presence of considerable amounts of the corresponding 2,V- and 2,2'-isomers in these materials is undesirable, especially if the materials are to be used for the production of polyamide and polyurethane fibers and filaments.

It has hitherto been necessary to purify the diamine or diisocyanate obtained as. stated above, e.g., by fractionation and fractional crystallisation, etc., to obtain them. desired ^-,<L>f'-isomers free of significant amounts of the corresponding 2,^'- and -2,2'-isomers. Such cleaning methods are difficult to carry out on a technical scale and greatly increase the production costs for the final product.

It has now been shown that it is possible with the present method to directly and continuously produce a mixture of polyamines where the di-(aminophenyl)methane component is present in the form

of the essentially pure h^ K*-isomer (a purity of at least 98% by weight) thereby avoiding the necessity of using an extensive purification of this diamine or of the corresponding diisocyanate into which it is converted by phosgenation. This discovery is of great commercial importance and makes it possible to produce the above-mentioned diamine and diisocyanate with considerable economic savings.

The present method can also be used for the production of polyphenyl-polyamines with methylene bridges which can be phosgenerated for the production of the feed material for the method specified in the above-mentioned British patent document No. 1,092,019. It is thereby possible to use a very economical method for the simultaneous production of essentially pure methylene bis (phenyl isocyanate) and polymethylene polyphenyl polyisocyanates.

These various advantages of the present process represent a clear technical advance compared to known continuous processes for the production of polyphenyl-polyamines with methylene bridges.

The invention relates to a process for the continuous production of polyphenyl-polyamines with methylene bridges and containing di-(aminophenyl)-methane with at least 98% p,p<1->isomer content, by reacting an aqueous solution of free aniline and aniline hydrochloride and formaldehyde, and the method is characterized by the combination of the following steps: a) intimate mixing of rapid streams of an aqueous solution of free aniline and aniline hydrochloride, with a molar ratio between water and aniline of 1.3:1-7.6:1, and aqueous formaldehyde, with a molar ratio between water and formaldehyde of 2.0:1-15.0:1, at a temperature of 0-60°C in a ratio of ^-.0-1.5 mol total aniline per moles of formaldehyde at the inlet of a continuous tubular reactor,

b) feeding the mixed streams through the tubular reactor at such a rate that the streams obtain an average

residence time in the reactor of less than 120 sec., while the temperature of the reaction mixture in the tubular reactor is kept below 75°C,

c) continuous feeding of the reaction mixture from the outlet opening of the tubular reactor to a cooling zone where the reaction mixture

continuously recirculated to keep the temperature of the reaction mixture below 60°C, but above the temperature at which solid material separates from the mixture,

d) continuous removal of the reaction mixture from the cooling zone - at a rate corresponding to that with which the reaction mixture is introduced

in the decoupling zone from the tubular reactor,

e) continuous feeding of the reaction mixture removed from the cooling zone to a final reaction zone where the temperature of the reaction mixture is maintained at 60-120°C, and f) continuous removal of a mixture of polyphenyl-polyamines with methylene bridges from the final reaction zone at a rate corresponding to

the one with which the intermediate reaction mixture is fed from the cooling zone to the final reaction zone.

The invention will be described in more detail with reference to the drawings, where fig. 1 shows a process diagram with the steps used in a particular embodiment of the present method, fig. 2 a cross-section through a special embodiment of a mixing apparatus used in the present method, and fig. 3 a process diagram with the steps used in another special embodiment of the present method.

The present method comprises a new combination of steps which makes it possible to continuously produce polyphenyl-polyamines with methylene bridges. The present method can also be easily adapted for the production of polyphenyl-polyamines with methylene bridges and with wide limits for a content of di-(aminophenyl)-methane. The di-(aminophenyl)methane present in the reaction product is more particularly the essentially pure isomer, i.e. that it contains at least 98% by weight of this isomer. This combination of advantages in the present method is achieved even by a precise regulation of the reaction conditions at the various stages and partly by the new design and the way in which the various stages are carried out.

In the first step of the present method, the aniline, hydrochloric acid and formaldehyde are brought together and mixed in suitable proportional quantities in the form of aqueous solutions. The aniline and hydrochloric acid are premixed and then treated as a single strcim which is mixed with the aqueous formaldehyde solution.

The amount of hydrochloric acid used is less than that necessary to completely neutralize the aniline. The relative amount of hydrochloric acid used is preferably 0.95-05<1>+5 equivalents per equivalent of aniline. The amount of hydrochloric acid used in each particular case depends on the relative amount of di-(aminophenyl)methane which it is desirable to obtain in the final product. The other factors affecting the relative amount of diamine are dealt with below. The Libyan concentrations of hydrochloric acid within the range indicated above are used if a higher concentration of diamine is desired in the final product. Conversely, lower concentrations of hydrochloric acid are used within the range indicated above if a lower concentration of diamine in the final product is desirable.

It appears from the relative amounts stated above that

the aqueous solution of aniline and hydrochloric acid used in the pre-

th step of the present method is a mixture of aniline hydrochloride and free aniline. The total concentration of aniline and aniline hydrochloride in the solution used in this step is of importance. The concentration is such that the molar ratio between water and aniline (as free base and hydrogen chloride) in the supply stream is 1.3:1 - 7.6:l, and preferably 2.1:1 - 3.8:1.

In a similar way, the concentration of formaldehyde in the aqueous solution of this which forms the second supply strbm is of importance and so that the molar ratio between water and formaldehyde is 2.0:1 - 15.0:1, and preferably 2.8:1 - 8,^.:1.

The optimum total amount of water in the mixed feed stream is of importance and is preferably h - 7 moi per mol of aniline or 7-15 mol of water per mol of formaldehyde.

The two supply streams are brought together at relatively high flow rates under conditions which ensure a very efficient mixing of the streams. In fig. 1 shows a process kernel for a method according to the invention. The aniline-hydrochloric acid stream and the formaldehyde stream are brought together in the mixing apparatus 2, which is arranged so that the mixed supply stream flowing from it is led directly to the inlet opening k of the tubular reactor 6. As mixing apparatus 2, a number of different devices which are commonly used can be used within the technique of mixing strommend's liquid. The mixer 2 can e.g. be a standard vane pump which is adapted in such a way that the formaldehyde stream is directed towards the center of the vane and is there injected into the aniline-hydrochloric acid stream which flows through the pump. As a further example of a device that can be used as a mixing device 2, a thin-film reactor mixing nozzle of the type indicated in US patent document No. 3 15L<-> 103 for mixing gaseous fluids can be mentioned Among the types of mixing devices that can be used as the mixing device 2 are the various T-connection devices that are commonly used for mixing fluid drums

A particularly useful mixing device which can advantageously be used as the mixing device 2 is that which is shown in a cross-section in fig.2. At the one in fig. 2, the aniline hydrochloric acid stream is fed through the angle pipe 8 from where it flows directly into the tubular reactor's 6 inlet opening h according to fig. 1. The formaldehyde stream is introduced directly into the aniline-hydrochloric acid stream via the injection tube 10 which is arranged in the angle tube 8 immediately above its knee 12. The tube 10 is in fig. 2 shown arranged so that its axis is essentially concentric with the axis of the lower part of the angle rudder 8 which leads directly to the tube-shaped reactor 6. However, the rudder 10 can, if desired, be arranged so that its axis is parallel to, but not necessarily concentric with, the axis of the lower part of the angle rudder 8.

With the special exit el s-e sf orm according to fig. 2 it is shown that the outlet opening of the injection tube 10 protrudes into the angle tube 8 at such a distance that it clears the knee in the angle tube 8. The arrangement of the outlet opening lh can, however, be varied from a position which essentially coincides with the side wall of the angle tube 8 as the injection tube 10 is quickly through, and to a position where the outlet opening lk- is arranged at a significant distance inside the lower half of the angle rudder 8 outside the special position shown in fig. 2. The most favorable position for the outlet opening lh for any given set of working conditions can be determined by experiment. For a further variation of that in fig. 2, a series of injection rudders 10 can be used instead of the single rudder 10 shown in fig. 2.

According to fig. 1, the relative amounts of the aniline hydrochloric acid stream and the formaldehyde stream which are mixed in the mixing apparatus 2 are determined mainly by the required composition of the mixture of polyphenyl-polyamines with methylene bridges to be produced. As an example, it can be stated that a molar ratio between aniline and formaldehyde of approx. 1.6:1.0 will give a mixture of polyphenyl-polyamines with methylene bridges and containing approx.-.^O weight/? di-(aminophenyl)-methane, see US Patent No. 2,683,730. On the other hand, a molar ratio between aniline and formaldehyde of approx. h:l give a mixture of polyphenyl-polyamines with methylene bridges containing approx. '85 weight/? di-(aminophenyl)-methane, see US Patent No. 2,950,263. Ratios between aniline and formaldehyde within the range between the above two limits give polyphenyl-polyamine mixtures with methylene bridges and a content of di-(aminophenyl)-methane between the two limits stated above. The exact ratios of aniline to formaldehyde necessary to obtain any desired amount of di-(aminophenyl)methane in the methylene-bridged polyphenyl-polyamine mixture can be determined by experiment.

The aniline-hydrochloric acid and formaldehyde drum which is supplied to the mixing apparatus 2 in the necessary relative quantities determined as indicated above, preferably both have a temperature below 50' JC, may be a temperature where fluidity is maintained, for they are mixed. Where the most preferred temperature for the mixing of these streams is 20-M-5°C. The rates at which the two feed streams are introduced into the mixer 2 vary depending on a number of factors, including the capacity of the mixer 2 and the tubular reactor and the desired production volume. The velocities naturally affect the mixing effect in the mixing apparatus 2 and in the reaction mixture as it flows through the then tubular reactor C. The velocity of the supply streams is usually regulated by means of a

any given mixing device 2 in order to thereby essentially avoid any back-mixing in the reaction mixture as it passes into and through the tubular reactor 6. Back-mixing is a term commonly used in the art to denote a mixing of material on a more advanced stage of a process with material at a less advanced stage of the process.

The tubular reactor 6 is shown with a spiral design for the embodiment in fig. 1. However, it should be noted that the design of the reactor 6 is of no importance for carrying out the present method, and any design, including a straight line, can be used. The tubular reactor £.is preferably equipped with a jacket (not shown). The temperature of the reaction mixture as it flows through the reactor 6 is thereby regulated so that it is preferably 0-75°C, and preferably 20-50°C. The flow rate of the reaction mixture and the overall dimensions of the reactor 6 are adjusted so that the average residence time of the reaction mixture in the reactor 6 is not more than approx. 120 sec. The average residence time of the react ion mixture in the reactor

is preferably under 20 sec. The use of a residence time of this low magnitude is decisive for achieving the overall desired result in the present method.

The reaction between formaldehyde and aniline is strongly exothermic.

The above-mentioned residence times in the tubular reactor ensure that the reaction mixture has passed through the reactor 6 before the main exothermic phase of the reaction begins and that it is in the next zone, i.e. the cooling zone shown in fig. 1, for the last specified phase begins.

The one in fig. 1 schematically shown cooling zone comprises a sloyfe 20 with a cooler 16 through which the reaction mixture is continuously recycled using a pump 18. The heater 16 can be of any standard type with the necessary capacity to keep the temperature of the reaction mixture below 60°C , preferably below 50°C. The lower limit for the temperature of the reaction mixture in the cooling zone is determined by the properties of the reaction mixture. The preferred lower working temperature is the lowest temperature at which the reaction mixture can be maintained without solids separating. As indicated above, the reaction mixture is at the maximum exothermic stage when it is in the cooling zone, and the capacity of the dresser 16 must therefore be large.

With a correct setting of the valve 2h which regulates the speed with which the reaction mixture leaves the cooling zone, it is possible to remove the reaction mixture continuously from the cooling zone and transfer it to the final reaction zone at the same speed as the reaction mixture has when it enters the cooling zone from the tubular reactor 6. Thereby, a uniform condition is maintained in the cooling zone. By similarly making a suitable regulation of the flow rates using the valve 2h and by regulating the capacity of the cooling zone, it is possible to vary the average residence time of the reaction mixture in the cooling zone to any desired extent. The average residence time of the reaction mixture in the cooling zone is preferably h - 50 minutes, and preferably 10 - 30 minutes, the final choice being strongly dependent on the temperature maintained in the reaction mixture when it is in the cooling zone, i.e. the lower the temperature in the cooling zone, the longer is generally the permissible average length of stay.

The reaction mixture, which is continuously removed from the cooling zone in the manner indicated above, is then led to a final reaction zone. In this, the reaction mixture is heated to a temperature of 60-120°C, preferably 80-100°C. The heating time is usually sufficient to ensure a complete formation of polyphenyl-polyamines with methylene bridges. It is clear to the person skilled in the art that the higher the reaction temperature used in the final reaction zone, the shorter the time required for complete reaction. The time required for complete reaction at any given temperature can be determined by forsbk0

The final reaction zone can be any suitable reaction container which is equipped with suitable devices for regulating the reaction temperature etc., and it is preferably constructed in such a way that any back-mixing is as small as possible. In a preferred embodiment, the final reaction zone consists of a continuous rudder with a suitable diameter and length for the reaction mixture to have the necessary residence time. The rudder is heated by being surrounded by a suitable heating jacket which keeps the rudder at the desired reaction temperature. If desired, the reaction mixture removed from the cooling zone can be passed directly through a heat exchanger to increase the temperature of the reaction mixture up to or close to the desired reaction temperature for the mixture entering the final reaction zone0 The average residence time of the reaction mixture in the final reaction zone is determined by the conditions stated above. The average length of stay is usually 60 - ^-00 min. depending on the particular reaction temperature used. Longer residence times can be used if desired, but this does not offer any practical advantages. The average residence time is preferably 100-2^0 min.

The reaction mixture is continuously removed from the final reaction zone through valve 26 at the same speed as the reaction mixture has when it enters this zone from the cooling zone via valve 21+. A steady state is thereby maintained in the final reaction zone.

The reaction mixture removed from the final reaction zone is then led to an extraction site where the desired mixture of polyphenyl-polyamines with methylene bridges is extracted in the usual way. The recovery is carried out either batchwise or continuously and usually comprises a neutralization of the reaction mixture by treating it with an excess of a sodium hydroxide solution, followed by a separation of the organic phase and the removal of an excess of aniline from this using a conventional evaporation apparatus0 Depending on the calculated use of the polyamines, part or all of the amount of di-(aminophenyl)methane can be recovered by distillation, preferably using a thin-film vacuum distillation apparatus.

In a modification of the present method as indicated by the process diagram in fig. 3, a further processing step is used between the cooling zone step and the final reaction zone. This further step comprises a holding zone where the reaction mixture is kept at a temperature of 0 - 70°C. The reaction mixture is introduced continuously from the cooling zone into the holding zone and is continuously removed from this at the same speed so that a uniform state is maintained in the holding zone. It has been shown that by keeping the reaction mixture in the residence zone for 30-2>+0 min. at a temperature within the temperature range indicated above, it is possible to greatly increase the overall yield of di-(aminophenyl)methane and the relative amount of ^-,1+' -isomer formed by the present process. Residence times are used within the upper part of the above specified range if the temperature in the residence zone is kept within the lower part of the above specified temperature range, and vice versa.

The residence zone may consist of any of a number of different containers, including cylindrical tanks, towers and continuous rudders, etc. In a preferred embodiment, the residence zone consists of a continuous, tubular container through which the reaction mixture removed from the cooling zone flows in the form of a continuous flow on its way to the final reaction zone. If desired, suitable devices can be used for supplying heat to or removing heat from the tubular container. However, it has generally been shown that a very weak exothermic reaction takes place when the reaction mixture passes through the residence zone, and it is usually unnecessary to take any step to externally regulate the temperature of the reaction mixture during this step.

The present method offers the advantages that (1) it is possible to continuously produce polyphenyl-polyamines with methylene bridges and where the present di-(aminophenyl)-methane component is the essentially pure h, h'-isomer, and (2) that polyphenyl-polyamines with methylene bridges can be produced with this at a very high overall conversion rate. The possibilities for a continuous production, in contrast to a batch production, provide a considerable labor saving and a very strong overall capacity for a plant of a given size. Besides these advantages, the present method offers for the first time the possibility of overcoming a problem which has interfered with previous attempts to develop a continuous method for the acid condensation of aniline and formaldehyde. It has thus far been shown that when streams of aniline and formaldehyde are brought together in the presence of an acid, significant amounts of solid material are deposited from solution. The exact reason for this deposition and the chemical composition of the thus deposited material have not been unequivocally clarified. However, the ledge problem has been so serious that it has caused a rapid clogging of rudders and constricted areas in reaction vessels etc. Such clogging causes that the methods developed so far had to be stopped very soon and prevented the methods from being carried out in a truly continuous manner .

It has now been shown, in contrast to known methods,

that the present method can be carried out continuously over a longer period of time without any significant deposition of solid materials taking place in the reaction vessels. This represents a useful and very unexpected advantage that comes in addition to all the advantages stated above.

Example 1

A continuous process for producing a mixture of polyphenyl-polyamines with polymethylene bridges and containing approx.

70% by weight di-(aminophenyl)methane was prepared as follows:

To mix the aniline-hydrochloric acid stream and the formaldehyde stream, a mixing nozzle of the type described in U.S. Pat. patent document no. 3 l^ h 103. The mixing nozzle was mounted by means of a flange and gasket on one end of a continuous, tube-shaped reactor of 2.5^ cm tubes with a total length of ^5.7 m. The reactor consisted of short rudder sections arranged one above the other in a vertical row with suitable knee sections so that a continuous rudder spiral was formed. The outlet opening of the tubular reactor was via a suitable control valve and line in connection with a recirculation sloyfe containing a centrifugal pump. heat exchanger and a Kynar-lined tank with a capacity of 1893 litres. The waste line from the recycling sludge, which was regulated by one suitable valve, went via a heat exchanger to another continuous tubular reactor. This was made from 7.62 cm steel rudder and was composed of rudder sections mounted in a vertical row and which were connected to each other via knees so that a continuous rudder was formed with a length of approx. 3658 m. The reactor was surrounded by a heated bath. The effluent from the reactor, which was regulated by a valve, was connected to a heat exchanger and via this to a neutralization and separation tank for extraction of the product.

When carrying out the present method using the above-mentioned apparatus, an aniline-hydrochloric acid stream was added in the form of an aqueous solution containing ^9.1 parts by weight of aniline and 15.7 parts by weight of hydrogen chloride per 100 parts by weight solution. The formaldehyde feed stream was a 37% by weight aqueous solution of formaldehyde. The aniline-hydrochloric acid stream was initially supplied to the mixing nozzle at a temperature of 35-50°C in an amount of 10.2 parts by volume per my. The formaldehyde stream was maintained at a temperature of approx.

30°C simultaneously fed a mixing nozzle with an initial rate of 2.163 parts per volume. my. The temperature in the first tubular reactor was regulated so that the temperature of the reaction mixture when it came out through the outlet opening and was led to the cooling-recirculation loop was approx. 70°C. The average residence time in the first tubular reactor was approx. 32 sec. The average temperature of the reaction mixture in the cooling recycle loop was maintained at 35 C at a flow rate in the recycle loop of k-00 parts by volume per min.. The flow rate of the reaction mixture into the slurry and the corresponding flow rate of the reaction mixture out of the slurry was kept at 12.36 volume parts per my.

The temperature of the reaction mixture at the inlet to the final reaction zone was regulated to 66°C by passing the reaction mixture through the heat exchanger. The temperature of the reaction mixture in the tubular end reactor■was kept at approx. 58°C.-' The average residence time for the reaction mixture in the second tubular reactor was approx.

^-00 min. , and the velocity of the product stream out of the reactor was maintained

12^36 volume parts per my. The product from the reactor was cooled to 50°C and then neutralized by adding an excess of an aqueous sodium hydroxide solution. The organic layer was separated and treated in an evaporator to remove excess aniline. The polyamine product thus obtained was analyzed to determine its content of di-(aminophenyl)methane and the <I>f,<L>t-' isomer content in the di-(aminophenyl)methane. The research was carried out in a total time of 2.5 days. 16 hours after the start, the formaldehyde supply rate was covered at 2.22 parts by volume per min., - and the temperature of the reactive ion mixture when it came out of the first tubular reactor was then 67°C. 28 hours after the start, the formaldehyde feed rate was covered at 2.226 parts by volume per my. The temperature of the reaction mixture when it came out of the first tubular reactor was then 72°C. hp-hours after the start, the supply rate of the aniline-hydrochloric acid stream was reduced to 9.12 parts by volume per minute and the formaldehyde flow rate to 2.016 volume parts per minute.

' The table below shows the analysis data which

was obtained for samples of the polyamide product at different stages during the above stated forsdk.

Example 2

A continuous process for producing a mixture of polyphenyl-polyamines with polymethylene bridges and containing approx.

37 - 8% by weight of di-(aminophenyl)methane was carried out as follows:

The same apparatus as described in example 1 was used, but with the exception that (a) the mixing nozzle used there was replaced with a mixing apparatus of the one in fig. 2 shown type, but with several injection tubes 10, (b) the first reaction zone 6 was instead a 1.91 cm tube with a length of 6.1 m and a 2.5<*>+ cm tube with a length of M- 2.7 m connected in series, and (c) a 1.1219 m long section of 7.62 -cm rudder was used as a dwell zone between the cooling zone and the final reaction zone (Fig. 3).

The aniline-hydrochloric acid feed stream was an aqueous solution containing 5<1>+.8 parts by weight aniline and 12.0 parts by weight hydrogen chloride per 100 parts by weight solution. The formaldehyde feed stream was a 37% by weight aqueous formaldehyde solution.

The rate of the aniline-hydrochloric acid feed stream was 20.0 parts by volume per min., and the velocity of the formaldehyde supply stream varied from 5.15 to 5.^ (average 5.28) parts by volume per min0 For the flow rate, the speed was approx. 35 - 50°C. The average temperature of the reaction mixture as it exited the first tubular reactor was 71°C. The average length of stay'! the first tubular reactor was lk-sec., the average temperature of the reaction mixture in the cooling-recirculation slurry <!>f0°C, the flow rate in the recycling slurry h00 volume parts per my. and the flow rate of the reaction mixture into the slurry and out of the slurry

25.28 volume parts per my.

The temperature of the reaction mixture when it came out of the holding zone was 63°C, and the residence time in the holding zone was approx. 55 min. The temperature was covered to 71°C in a heat exchanger, and the temperature of the reaction mixture in the final reaction zone was maintained at 82°C. The average residence time in the final reaction zone was 165 min., and the velocity of the product stream out of the reactor was 25.28 volume parts per my. The product from the final reactor was cooled and treated as described in example 1. Analytical data for samples of the polyamine product at different stages during the above-mentioned experiment are reproduced in Table II.

Example 3

As a continuation of the experiment described in Example 2, the aniline, hydrochloric acid and formaldehyde feed streams were changed without stopping the production, to produce a mixture of polyphenyl-polyamines with polymethylene bridges and containing approx. 6W-69 wt% di-(aminophenyl)methane.

The aniline-hydrochloric acid feed stream was an aqueous solution containing 8.6 parts by weight of aniline and 15.1 parts by weight of hydrogen chloride per 100 parts by weight of solution. The formaldehyde feed stream was one

.37% by weight aqueous formaldehyde solution. The aniline-hydrochloric acid feed rate was initially 20 parts per volume. my. and the formaldehyde supply rate 3?8<!>j- parts by volume per my. The temperature of the supply stream was approx. 35 - 50°C. After 20 hours, the supply rates were reduced to 15 and 2.8 l parts per volume, respectively. min., and the formaldehyde drum was further reduced after 2 hours to 2.7'+ volume parts per my. When the feed rate to the first reaction zone was reduced (20 hours), 2/3 of these feed quantities were fed to a parallel first reaction zone which were fed to the same cooling zone, retention zone and final reaction zone. The temperature of the reaction mixture as it exited the first tubular reactor averaged 62°C, the average temperature of the reaction mixture in the cooling recycle loop was <1>+0°C, and the flow rate in the recycle loop was ^00 parts per volume. my. At steady state, the weight of the flow between the reaction sections corresponded to the sum of the aniline-hydrochloric acid and formaldehyde feed flows. The temperature of the reaction mixture when it came out of the holding zone was approx. 60°C. The temperature was covered to 71°C in a heat exchanger, and the temperature of the reaction mixture in the final reaction zone was maintained at approx. 80°C. The product from the final reaction zone was cooled and treated as described in example 1. Analytical data, feed rates and residence times at different stages during the experiment used above are reproduced in table III»

Example h -

A continuous production of a mixture of polyphenyl-polyamines with polymethylene bridges and containing approx. 6<!>+ - 72% by weight di-(aminophenyl)-methane was carried out as follows: The same apparatus as described in example 2 was used.

The aniline-hydrochloric acid feed stream was an aqueous solution containing 7.7 parts by weight aniline and 15.0 parts by weight hydrogen chloride per 100 parts by weight solution. The formaldehyde feed stream was a 37 wt/? aqueous formaldehyde solution.

The average feed rate for the aniline-hydrochloric acid was 18.7 parts by volume per my. and varied from l^t-.2 to 19.2 volume parts per min., and the formaldehyde supply stream averaged 3.58 volume parts per my. and varied from 2.75 to h, 2 volume parts per min0 The temperature of the supply stream was approx. 35 - 50 C. The average temperature of the reaction mixture when it came out of the first tubular reactor was 56°C. The average residence time in the first tubular reactor was 18 sec., the average temperature of the reaction mixture in the cooling-recirculation sink was <1>+0°C, the flow rate in the recycling sink was h00 volume parts per min., and the flow rate of the reaction mixture into and out of the slurry was 22.28 volume parts per min0

The temperature of the reaction mixture in the holding zone was approx. 58 C and the residence time approx. 63 min. The temperature was covered to 72°C in a heat exchanger, and the temperature of the reaction mixture in the final reaction zone was maintained at approx. 77 - 79°C. The average residence time in the final reaction zone was 189 min., and the product discharge rate from the reactor was 22.28 volume parts per my. The product from the final reactor was cooled and treated as described in example 1. Analytical data for samples of the polyamine product at different stages during the above-mentioned experiment are reproduced in Table IV.

Claims (3)

1. Process for the continuous production of polyphenylpolyamines with methylene bridges and containing di-(aminophenyl)-methane with at least 98% p,p'-isomer content, by reacting an aqueous solution of free aniline and aniline hydrochloride and formaldehyde, characterized by the combination of following steps: a) intimate mixing of rapid streams of an aqueous solution of free aniline hydrochloride, with a molar ratio between water and aniline of 1.3:1 - 7.6:1, and aqueous formaldehyde, with a molar ratio between water and formaldehyde of 2.0:1 - 15.0:1, at a temperature of 0 - 60°C in a ratio of !+.0 - 1.5 mol total aniline per moles of formaldehyde At an inlet opening in a continuous tubular reactor, b) feeding the mixed streams through the tubular reactor at such a speed that the streams have an average residence time in the reactor of less than 120 sec., while the temperature of the reaction mixture in the reactor is kept below 75°C , c) continuous feeding of the reaction mixture from the tubular reactor outlet to a cooling zone where the reaction mixture is continuously recycled to keep the temperature of the reaction mixture below 60°C, but above the temperature at which solid material separates from the mixture, d) continuous removal of the reaction mixture from the cooling zone at a rate corresponding to that with which the reaction mixture is introduced into the cooling zone from the tubular reactor, e) continuous feeding of the reaction mixture removed from the cooling zone to a final reaction zone where the temperature of the reaction mixture is maintained at 60-120°C, and f) continuous removal of a mixture of polyphenyl-polyamines with methylene bridges from the final reaction zone at a rate corresponding to that with which the intermediate reaction mixture is fed from the cooling zone to the final reaction zone. 2. Method according to claim 1, characterized in that an average residence time of less than 20 sec is used in the tubular reactor in the first step of the method. 3. Method according to claim 1 or 2, characterized in that an aqueous solution of free aniline and aniline hydrochloride with a molar ratio between water and aniline of 2.1:1 - 3.8:1 is added to the mixture in the first step and an aqueous formaldehyde solution with a molar ratio between water and formaldehyde of 2.8:1 - 8.M-:1. h. Method according to claims 1-3, characterized in that the reaction mixture is fed from the cooling zone to the slag reaction zone via a holding zone where the reaction mixture is kept at a temperature of <i>+0-70°C for an average residence time of 30-24-0 min .