DE1568844B - Process for the production of an organic isocyanate by phosgenating an amine hydrochloride - Google Patents

Description

3 4

properly suitable for phosgenation, by loading The concentration of the solution of the amine in the

treatment of a thin film of a solution of the inert solvent, hereinafter referred to as

Amine in an inert solvent with chlorine-amine solution can be used to a large extent

hydrogen can be generated. vary, but preferably a solution

The invention thus relates to a method for 5 uses that are between 4 and 16 percent by weight

Production of an organic isocyanate by containing the amine.

Phosgenation of an amine hydrochloride, which The thin film of the amine solution, which is characterized by treating the amine hydrogen with chlorine, can be formed by various hydrochloride by forming a solution of the method, and also the amine in an inert solvent which are produced in different ways in the form of a film with a continuously changing surface of a thin layer with a continuously changing surface.
Surface is present, treated with hydrogen chloride. A thin film of the amine solution and the amine hydrochloride thus formed can be reacted with phosgene to flow downwards over a cooled surface. let that perpendicular or at an angle to the

The heat of reaction of the amine and the chlorine is held horizontally, alternatively the thin Hydrogen is conveniently removed by allowing the thin film to flow along a horizontal top film the solution is cooled. If a very flat area can be brought.

thin solution of the amine is used, the surface of the thin film is covered by the

no cooling to be required. If the amine-sheer flow of the film kept changing, yes

Hydrochloride is generated in this way, the surface can be disturbed further and again

it can be produced in the form of a slurry or suspension by applying agitation or turbulence

very fine particles of the hydrochloride with high bilge in the atmosphere above this surface

Surface obtained in the inert solvent. generated.

This slurry or suspension is suitable which has the inner surface of a cylinder tube

especially for the conversion into the isocyanate, 25 proved to be a suitable surface

and by using them, the disadvantages which the amine solution thin film are formed

which accompany the previous hydrochlorides, can be eroded. The pipe can be vertical, horizontal

avoided or considerably reduced. or be set at an angle. The amine solution

The method according to the invention can be used in the cylindrical tube at one end.

rens in the production of isocyanates, in particular _{given 30} and on the inner wall of the pipe

their polyisocyanates, gives unexpectedly high output, and the desired thin film

and short phosgenation times. can run along the entire length of the inner walls

In the case of isocyanates, at least one of the tube by moving or turbulence within

contain aliphatically bound isocyanate groups, the pipe must be kept flowing. So can

which in the phosgenation stage by the invention 35 a rapidly rotating shaft that in the tube after

Appropriate method achieved reaction speed- down centrally aligned, leaves, arms or

ability particularly surprising with regard to the wipers, which have the surface of the thin

well-known difficulty and slowness of the Phos-Films wiping and moving continuously while they are

generation of the corresponding amines and their salts rotate around the central shaft; the leaves, arms

by known methods. However, the application of the 40 or wiper can be set so that

The method according to the invention actually allows the production of the surface of the thin liquid

The formation of such isocyanates through a continuous film does not touch the surface, only the surface

Procedure that has not previously been found to be practical by walking close to the surface

has proven. disturb. Alternatively, you can have the leaves the wall

The inventive method is particularly _{45 of} the pipe touching the division of the

valuable for the production of organic polyiso-particles of the hydrochloride as they are formed,

cyanates from polyamines that improve at least one ali-. The one through such a rapidly rotating

contain phatically bound amino group. Centrifugal force exerted by the arrangement throws auto-

The matically used in the method according to the invention all particles of the solution or slurry

inert solvent may be any one of those ₅₀ mung, leaving the thin film to the

Be solvent, as is usually the case with Phos pipe walls.

Generation reactions to the division of Isocya- The cylindrical tube can with a jacket

naten can be used. The term "inert" may contain a coolant to prevent a

means inert under the reaction conditions, so cooling of the thin film and the removal of the

that the solvent is inert to hydrogen chloride, _{55 heat of} reaction of the amine and hydrogen chloride

Allow phosgene and the amine among those used.

Reaction conditions must be. For the supply of hydrogen chloride is a

This is preferably in the inlet according to the invention and for the suspension of the hydrochloride

drive an inert solvent to be used at the end of the tube which is the entry point

one in which hydrogen chloride lies opposite the amine solution at low 60, an outlet

Temperatures, e.g. B. room temperature, provided considerably. The stream of hydrogen chloride gas can

is soluble; suitable solvents include either cocurrent or countercurrent to the

Ester solvents such as n-butyl acetate, n-hexyl acetate, flow of the amine solution take place.

Dimethyl carbonate and diethyl carbonate, carbon- When the cylindrical tube is inclined or vertical

Hydrogen, such as toluene and xylene, and halogenated 65, the amine solution flows with the help of gravity

Hydrocarbons such as mono-, di- and trichloro down. When the pipe is in horizontal

benzenes, chlorotoluenes, carbon tetrachloride and layer, the amine charge can be

Trichlorofluoromethane. pumps and the feed pressure is applied

5 6

are effected in order to move the thin film along the pipe to the liquid flow entering at M,

to drive. that the amine solution along the tube A in shape

The pipe does not need to be completely cylindrical with a thin liquid film on the inner upper

to be, but can have tapered sides and flow flat. The reaction of amine and chlorine

have the shape of a truncated cone. 5 hydrogen to form the amine hydrochloride

A type of device that is designed to pass through while the liquid is guided down the pipe the formation of the polyamine hydrochloride flows, and the flow rate and the like are so suitable, is the one that is generally set as thin-film that up to the time at which the susevaporator or thin layer processor means pension from the outlet JV flows out, the whole will. Any of the large number of different io amines is converted into the hydrochloride. The quick one Thin film evaporator or processor that turns the stirrer causes the thin film or are accessible to industry, a surface exposed to hydrogen chloride gas failed in the production of the amine hydrochloride, which is constantly changing.

applied, the only requirement therein being F i g. 5 is an axial section of another type of FIG

insists that while the thin layer of amine-15 thin-film device used to form the

amine hydrochloride dissolves along the processor or evaporator in the process according to the invention

moved and suitable into a fine slurry of amine.

hydrochloride is transferred, it is the chlorine water In Fig. 5, the device consists of a

Substance gas that closes the remainder of the volume of the thin-cylindrical tube A, which fills the layer evaporator or processor at both ends, and is arranged in a vertical position

constantly changing surface presents. One and with a rotatable, centrally aligned

Cooling medium, usually water, can be provided through shaft C, which is located in the stuffing box D.

the jacket of the evaporator. will hold. The shaft C carries coil springs Q,

It is believed that by inventing by arms? as close as possible to the interior

according to the method achieved improvement partial area of the cylindrical tube A are kept,

point to the short residence time in such a The cylindrical tube A is with inlets L and M

Thin film evaporator is due, taking for hydrogen chloride and amine solution and one

the rate of formation of the hydrochloride, outlet JV for amine hydrochloride. A circle-

when the reaction components through the thin-shaped jacket F, which has an inlet G and

Layered evaporator flow, the delay between 30 outlet H for cooling liquid and thermometers for

the formation of the hydrochloride and the phosgene measurement of the temperature of the liquid

brings the hydrochloride to a minimum. surrounds the pipe A.

The drawing shows a device which, when using the device of FIG

the shaft and the springs attached to it are considered to be suitable for carrying out the process according to the invention

Procedure on a small scale has been proven. 35 rotated at high speed, and a thin

F i g. 1 of the drawing is an axial section of a layer of amine solution flowing down the inner surface of the

Device designed to carry out the formation of cylindrical tube down and the surface

of the amine hydrochloride is suitable. the thin layer is through the passage of the

In Fig. 1 the device consists of a coil spring continuously through the thin layer

Reaction vessel that is closed at both ends and is broken and moved. The shaft and the rotatable

senes, cylindrical tube A contains, which with a springs are expedient at speeds

four-blade stirrer B with a clearance in the order of 500 to 1500 rpm

rotated from about 1 mm from the inner surface of tube A.

is provided, which is on a cylindrical tube Die in F i g. The device shown in FIG. 5 can have two

centrally aligned shaft C sits and is contained in the stuffing 45 coil springs on arms at the

bush D and is held by the end bearing E. The rotatable shaft is mounted, or there can be more

cylindrical tube A surrounds an annular man- as two springs are attached so that they are in

tel F operating with an inlet G and an outlet H in close proximity to the inner surface of the tube,

for coolant and a thermometer K for other types of thin film evaporators or

Measuring the temperature of the coolant in the ring 50 processors are also used to manufacture the

shaped jacket is provided. The cylindrical tube of amine hydrochloride suitable in the process

is with an inlet L for hydrogen chloride, a The amine hydrochloride can be at any temperature

Inlet M for the amine solution and an outlet JV within the range of 0 to 100 ° C

for the slurry or suspension of the amine, but one works preferably at Tempe-

hydrochlorids. The outlet JV has a temperature of 10 to 65 ° C. If desired, it can be

Thermometer O is provided to show the temperature of the operation at a pressure above atmospheric pressure

suspension of suspension leaving the reaction vessel to reduce the solubility of hydrogen chloride

Determine amine hydrochloride. to increase in the solvent. To be within the

F i g. Figure 2 is a perspective view of a four-above preferred temperature limit to stay

bladed stirrer, which is suitable for use in the 60, the thin film is cooled appropriately.

Device according to FIG. 1 is suitable. The amine hydrochloride slurry or sweet

If the device shown in Fig. 1 for pension, which from the thin film device

Production of amine hydrochloride is used, flows, contains amine hydrochloride, in which prac-

if hydrogen chloride gas at inlet L and amine table, all amino groups are converted into hydrochloride

solution introduced at inlet M. Coolant is used after 65, and can then go through any of the usual

Requirement applied to the annular cooler. The working methods are phosgenated. So approach-

Stirrer 2? is rotated at about 1000 rpm, and phosgenated wise or continuously. the

Effect of the stirrer together with the pressure continuous type of production of the amine hydro-

chloride in the thin film device makes the Operation particularly suitable for adaptation to a continuous phosgenation process.

The phosgenation stage can be carried out at any pressure desired, which is above or below the operating pressure in the thin-film reactor.

So the amine hydrochloride slurry can be phosgenated or in a single reaction vessel through a number of reaction vessels in series, with the phosgenation being gradual is carried out.

Figure 3 is a flow sheet of a typical process for the continuous production of organic isocyanates according to the invention Proceedings.

In the one shown in FIG. The typical process shown in FIG. 3 flows the amine hydrochloride produced in the thin-film reactor I. to a conventional stirred reactor II operated within the range from 75 to 190 ° C and in which phosgene is introduced.

Working in the higher areas of this temperature range is not necessary, but often desirable when the process is used to prepare organic polyisocyanates, which contain aliphatically bonded isocyanate groups. The overflow goes to another reactor III of similar construction to II, which is operated, for example, in the range from 120 to 200 ° C; at temperatures of up to 160 ° C are normally sufficient for the production of aromatic isocyanates, but in the case of polyisocyanates with aliphatically bound isocyanates it can sometimes be advantageous to work in the higher part of this temperature range.

Depending on the desired throughput and the size of the reactor that you want to use, you can further reactors are added to the series to allow sufficient residence time for safe To offer termination of response. Additional phosgene can be added to the rear reactors as required however, sufficient phosgene often remains dissolved in the solvent from the earlier stages to make further additions in the later reactors unnecessary.

F i g. Figure 4 is a flow sheet of a typical process for the continuous production of organic Polyisocyanates by the process according to the invention with the inclusion of a further reactor IV.

If desired, the reactor II can be equipped with a second thin-film evaporator with similar features like the first to be replaced.

When the phosgenation has ended, the solution obtained is degassed from isocyanate to give hydrogen chloride and to remove excess phosgene and then under reduced pressure to add the solvent remove, heated to suitable temperature. The remaining isocyanate can then be distilled or depending on Wish to be used in raw form.

It was also found that phosgene together with the hydrogen chloride during the formation of the Amine hydrochloride can be introduced without adverse effect on hydrochloride formation. This Embodiment of the present invention permits the formation of a slurry or Suspension of hydrochloride that contains sufficient phosgene to convert it to isocyanate, which takes place on heating, with minimal formation of undesirable by-products.

On organic isocyanates that can be prepared by the process according to the invention, include aromatic, aliphatic, cycloaliphatic and araliphatic isocyanates.

The isocyanates are prepared using appropriate known primary amines as starting materials manufactured.

ίο The method according to the invention has proven to be special applicable to the production of organic polyisocyanates, both aromatic and aliphatic nature, which gives unexpectedly high yields and short phosgenation times.

The rate of reaction achieved by the process according to the invention is particularly surprising with regard to the polyisocyanates which contain aliphatically bonded isocyanate groups, with regard to on the known difficulties and slowness of the phosgenation of aliphatic amines by the known methods. The present invention is also particularly advantageous in that it provides the Allow implementation of a continuous process for the production of aliphatic isocyanates, which was previously not generally possible.

The following examples illustrate the invention without restricting it. All parts and percentages are based on weight unless otherwise specified.

example 1

An 8% (w / w) solution of tolylenediamine in o-dichlorobenzene at 65 ° C is in a Thin film reactor of the type shown in Fig. 1 was introduced at a rate of 8.0 g / min. At the same time, dry hydrogen chloride is poured into the reaction vessel at a rate of 1.6 g / min introduced. The diamine is a mixture of isomers containing about 80% 2.4-, 19.6% 2.6- and 0.4% Contains 3,4-tolylenediamine.

Water at 10 ° C is circulated through the ring-shaped jacket of the thin-film reactor, to dissipate the exothermic heat of the reaction. The reactor used in the above amounts has a length of 30 cm and a radius of 5 cm. The temperature of the reactor effluent is 24 ° C.

The suspension of polyamine hydrochloride flows from the thin-layer reactor into a stirred reactor II (Fig. 3) of the usual design, which is kept at 90 ° C and in which a phosgene stream is continuously with at a rate of 2.0 g / min. The working volume of the second reaction vessel II is about 1500 ecm.

A solution of tolylene diisocyanate flows from reactor II and tolylenebiscarbamyl chloride to a third reactor III (Fig. 3) kept at 120 ° C will. The product which overflows from this reactor runs into a receiving vessel (Fig. 3). This Material is degassed in order to remove remaining hydrogen chloride and remaining phosgene, and the solvent is removed and the product distilled in the usual manner, which is a 93% yield of tolylene diisocyanate results.

Example 2

This example is carried out in a similar manner to Example 1, but instead of chlorinated water

209 524/503

substance a mixture of hydrogen chloride (1.4 g / min) and gaseous phosgene (2.0 g / min) in the thin-film reactor introduced. Another stream of phosgene (0.5 g / min) is introduced into the second reaction vessel II.

A yield of 96 ⁰ zo of tolylene diisocyanate is obtained.

Example 3

This example is carried out in the manner of Example 2, but using crude tolylenediamine is about 76% 2,4-tolylenediamine, 17% 2,6-tolylenediamine, 4% tolylen-o-diamine and 3% contained unidentified tar. After distillation, a yield of 89% of a mixture is obtained of tolylene 2,4- and 2,6-diisocyanate.

Example 4

A 10% (w / w) solution of technical 4,4'-diaminodiphenylmethane in monochlorobenzene 50 ° C. is introduced into a vertical thin-film reactor of the type shown in FIG. 5 type shown at a speed of 8.0 g / min. At the same time, dry hydrogen chloride is entering the reactor at one rate of 0.9 g / min initiated. The diaminodiphenylmethane is produced by condensation of aniline Made with formaldehyde, it contains mostly 4,4'-diaminodiphenylmethane along with something 2,4'-Diaminodiphenylmethane and polyamine of higher functionality.

Water at 50 ° C is circulated through the ring-shaped jacket of the vertical thin-layer reactor in order to control the exothermic heat of reaction. The thin film is continuously wiped by a set of four stainless steel coil springs mounted on cross pieces on a longitudinal shaft as shown in Figure 5 rotating at 900 rpm. The reaction vessel is about 25.4 cm long and 4.6 cm in diameter and has a wiping area of about 365 cm ² . The temperature of the reactor effluent is 50 to 55 ° C.

The suspension of the hydrochloride flows from the thin-layer reaction vessel into the stirred reactor II (Fig. 3) of conventional construction, which is kept at 95 ° C and in which continuously with a A phosgene stream is introduced at a rate of 2.5 g / min. The working volume of the reactor II is about 1500 ecm.

The product flows from reactor II to reactor III (FIG. 3), which is kept at 125.degree. The Product overflowing from this reactor flows into a receiving vessel (FIG. 3). The material that collects in this vessel is approached in the following way:

The material is heated under normal pressure, and half of the monochlorobenzene it contains will be distilled off. Then the pressure is gradually reduced and the temperature is increased to 160 ° C, at what value it is held for 3 hours. The remaining solvent becomes during this Distilled off with heating, and after cooling, the product is obtained as a viscous, dark brown liquid. Its main component is 4,4'-diphenylmethane diisocyanate, however, it contains isomeric diisocyanates and polycyanates of higher functionality together with other impurities.

The analysis shows that the isocyanate content of the product is 91.6%, expressed as diphenylmethane diisocyanate, with a hydrolyzable chlorine content of 0.18%. It is extremely suitable for the production of rigid foams using conventional procedures, e.g. B. from hydroxylated Polyether, catalyst and blowing agents such as halogenated Hydrocarbons.

Example 5A

A 5% (w / w) solution of hexamethylenediamine in trichlorobenzene at about 25 ° C. is introduced into a thin-layer reactor at a rate of 8.0 ml / min the in F i g. 1 introduced with a length of 30 cm and a radius of 5 cm. At the same time, dry hydrogen chloride is fed into the reactor at a rate of 1.0 g / min introduced, and water at 10 ° C is circulated through the annular jacket of the reactor led to dissipate the heat of the exothermic reaction.

The suspension of polyamine hydrochloride flows from the thin-layer reactor into a stirred reactor conventional design, which is kept at 140 ° C and in which a phosgene stream continuously with a Speed of 1 g / min is initiated. When 1000 ml of reaction product formed as an intermediate Are collected in this reactor, the feeds of diamine and hydrogen chloride to the thin film reactor switched off. The temperature of the intermediate reaction product is then within 1 hour increased to 190 ° C and at this temperature, still maintaining the same phosgene stream, Held for 2 hours; at the end of that time has all the suspended solid substance? dissolved, and there remains a clear, orange-brown; Product. The yield of hexamethylene diisocyanate in this crude product, determined by complete distillation from the residues, is 99%.

The following comparative examples 5 B, 5 C and 5 E show known processes for the preparation of hexamethylene diisocyanate. 5 B and 5 C represent two different hydrochloride processes and 5D a »Car bonat «method. A comparison of the reaction times and results of these examples with Example 5 / above shows the advantages of the method according to the invention.

Comparative Example 5B

Hexamethylene diamine dihydrochloride is prepared by slowly stirring a solution of 116 g of hexamethylene diamine in methanol to a solution of 235 g of dry hydrogen chloride v. Methanol is added. The precipitated hydrochloride is filtered off and dried and ground and 90 g are suspended in 510 g of trichlorobenzene in a flask equipped with a stirrer, condenser and gas inlet pipe. The solution is saturated with phosgene at 100.degree. C., and then the temperature is increased to 185-190.degree. C. and maintained at this value while a stream of phosgene is passed through at a rate of about 0.4 g / min. After 6 hours, the phosgene stream is interrupted and the mixture is degassed with a stream of dry nitrogen. The mixture still contains a considerable amount of unreacted hydrochloride, and the analysis shows that the conversion to hexamethylene diisocyanate is only 41%.

Comparative Example 5C

49 g of hexamethylenediamine and 650 g of trichlorobenzene are placed in a flask with equipped with a stirrer, condenser and gas inlet pipe. Dry hydrogen chloride gas is at 20 to 30 ° C initiated until the formation of the hydrochloride has ended. The hydrogen chloride is then through replaced a slow phosgene stream and increased the temperature to 190 ° C as quickly as possible. this requires about IV2 hours since the mixture is medium Temperatures become very gelatinous and difficult to stir. When the temperature reaches 180 ° C, the phosgene speed is increased to about Vz g per minute and the mixture finally with the kept the same phosgene stream at 190 ° C. until it becomes clear. The total phosgenation time in the Heat is 5Va hours and the yield of hexamethylene diisocyanate in the crude product is 92.2%.

Comparative Example 5D
"Carbonate" process

66 g of hexamethylenediamine and 459 g of o-dichlorobenzene are placed in a flask equipped with a stirrer, condenser and gas inlet tube and heated to 80 to 88 ° C. Dry carbon dioxide is introduced until carbonation is complete. This takes about I ³ Aj hours. The mixture is then cooled to 0 ° C. over the course of 1 hour and 90 g of phosgene are passed in for 1 hour while the temperature is kept below 5 ° C. The mixture is heated to 150.degree. To 180.degree. C. over the course of 2.5 hours while passing a slow stream of phosgene through and then stirred under reflux for 11 hours at a rate of phosgene addition of 0.25 g / min. At the end of this time, most of the solid has disappeared and the yield of hexamethylene diisocyanate in the crude product is 95%.

Example 6

A 7.5% (w / w) solution of dodecamethylenediamine in o-dichlorobenzene at about -25 ° C is at a rate of 10 to 15 ml / min in a thin-film reactor in Example 1 used type introduced. At the same time, dry hydrogen chloride is entering the reactor at one rate of 1.1 g / min, and water at 10 ° C is introduced through the annular jacket of the The reaction vessel is circulated to remove the heat from the exothermic reaction.

The suspension of polyamine hydrochloride flows from the thin-layer reactor into a stirred reactor of conventional design, which is kept at 140 ° C. and into which a phosgene stream is continuously introduced at a rate of 0.8 g / min. When 1500 ml of the intermediate reaction product have collected in this reactor, the supply of diamine solution and hydrogen chloride to the thin-film reactor is stopped. The temperature of the intermediate reaction product is then increased to 170 ° C. over the course of one and a half hours and kept at this temperature for I ³ hours while maintaining the same phosgene flow. At the end of this time all of the suspended solid has dissolved and a clear, yellow product remains. The yield of dodeca-

methylene diisocyanate in this crude product, determined by complete distillation from the residues, is 98.7%.

Example 7

A 7% (w / w) solution of m-xylylenediamine in trichlorobenzene at about 25 ° C is at a rate of 9.0 ml / min in a Thin film reactor of the type used in Example 1 introduced. At the same time it becomes dry hydrogen chloride introduced into the reactor at a rate of 0.8 g / min and water is passed through passed the annular jacket of the reactor to remove the heat of the exothermic reaction.

The suspension of polyamine hydrochloride flows from the thin-layer reactor into a stirred reactor of conventional design, which is kept at 160 ° C. and into which a phosgene stream is continuously introduced at a rate of 1 g / min. When 700 ml of the intermediate reaction product have collected in this reactor, the supply of diamine solution and hydrogen chloride to the thin-film reactor is stopped. The temperature of the intermediate reaction product is then increased to 190 ° C. over the course of 1 hour and, at this temperature, still maintaining the same phosgene stream, 3 ¹ A? Held for hours. At the end of this period, the suspended solid has almost dissolved and an orange-brown product remains. The yield of m-xylylene diisocyanate in this crude product, determined by complete distillation from the residues, is 940/0.
When prepared according to a customary procedure, the yield is only 88% after 4 hours of phosgenation in the heat at 190 ° C.

Example 8

A 7% (w / w) solution of p-xylylenediamine in o-dichlorobenzene at about 25 ° C is at a rate of 10.0 ml / min in a Thin film reactor of the type used in Example 1 introduced. At the same time it becomes dry hydrogen chloride introduced into the reactor at a rate of 1.1 g / min, and water at 10 ° C is passed through the circular jacket of the reactor to remove the heat from the exothermic reaction.

The suspension of polyamine hydrochloride flows from the thin-layer reactor into a stirred reactor, as is usual Type that is kept at 150 ° C and in which a phosgene stream continuously with a Speed of 0.8 g / min is initiated.

After 1000 ml of the intermediate reaction product have been collected in this reactor, the feeds of diamine solution and hydrogen chloride to the thin-film reactor are stopped. The temperature the intermediate reaction product is then increased to 170 ° C within 1 hour and, while passing in the same phosgene stream, held at this temperature for 5 hours. At the end During this period, most of the suspended solid has dissolved and remains behind orange brown product. The yield of p-xylylene diisocyanate in this crude product, determined by complete distillation from the residues 86 ° / o.

Example 9

A 5% (w / w) solution of hexamethylenediamine in trichlorobenzene at about 25 ° C is in introduced a thin film reactor similar to that shown in FIG. 1 is shown. At the same time it becomes drier Hydrogen chloride was introduced into the reactor at a rate of 1.0 g / min. Water at about 10 ° C is passed through the annular jacket of the reactor to absorb the heat of the exothermic reaction to dissipate.

The suspension of the diamine hydrochloride flows from the thin-layer reactor into a stirred reactor II (Fig. 4) of conventional design, which is kept at 180 ° C and in which a phosgene stream is continuous

is introduced at a rate of 1 g / min. The working volume of the second reactor is about 1500 ml.

From the reactor II, the intermediate reaction product flows into a third reactor III with a Working volume of about 850 ml, which is maintained at 190 ° C. Phosgene is used in this reactor initiated at a rate of 1 g / min. The reaction product flows from this reactor into a

ίο Final reactor IV with similar characteristics to the reactor III about where the phosgenation is ended. The overflow from reactor IV consists of one crude solution of hexamethylene diisocyanate in trichlorobenzene with only a little suspended solids.

The yield of hexamethylene diisocyanate in this crude product is 94%.

For this purpose 2 sheets of drawings

Claims (8)

1 2 before, and these require longer treatment Claims · ^m ^ phosgene, generally at fairly high levels Temperatures, for conversion to isocyanates. Prolonged treatment of this kind is not only 1 method of making an organic 5 part from the point of view of production speed Isocyanate by phosgenation of an aminity, but also leads to undesirable secondary hydrochloride, characterized in that reactions which result in a loss of yield that the amine hydrochloride is formed by calling. a solution of the amine in an inert amine and polyamine hydrochloride, which after the Solvents which are produced in the form of a thin layer according to known methods are not available with a constantly changing surface, only exist in rough physical form and are treated with hydrogen chloride, which makes it difficult to phosgenate, but rather become formed amine hydrochloride reacts with phosgene. also often under such precipitation conditions 2. The method according to claim 1, obtained in that products result which are not indicates that the treatment of solution 15 is the stoichiometric amount of hydrogen chloride of the amine contained in an inert solvent and a proportion of free amino hydrogen chloride have in a thin film evaporator groups. During the subsequent fer or processor is carried out. Treatment of this coarse hydrochloride with phos- 3. The method according to claim 1, thereby against at elevated temperatures these can free indicates that a thin layer of the 20 amino groups in undesired side reactions, Dissolution of the amine in an inert solution such as formation of urea, with simultaneous medium over the inner wall of a cylindrical loss of yield, participate. Downward flow of the pipe, the chlorine- For these reasons, the production of Contains hydrogen gas, the thin layer isocyanates, especially polyisocyanates, through the amine solution continuously through stirring blades, 25 phosgenation of amine hydrochlorides not in Arms or wipers moved at some extent even though they are carried on rotating rapidly and appearing in the middle of the tube - seem economically attractive at first glance directed shaft are arranged. could. 4. The method according to claim 3, characterized in that the production of aliphatic isocyanates has indicates that a coolant around 30 has proven extremely difficult Outer wall of the cylindrical tube circu- reason of the low speed with which lates. aliphatic amines or their salts are phosgenated 5. Method according to one of the preceding can be. Claims, characterized in that the batch production and phosgenation Solution of the amine in the inert solvent ₃₅ of a low viscosity suspension Contains 4 to 16 percent by weight amine. sions of amine hydrochlorides is in the USA. 6. The method according to one of the preceding patent specification 2 644 007 described, which a VerAnsprüche, characterized in that the drive relates in which the hydrochloride batchwise amine hydrochloride is prepared at a temperature of 0 by the fact that hydrogen chloride in up to 100 ° C, preferably from 10 to 65 ° C, ₄₀ a 120 to 150 ° C warm solution of the polyamine is formed. is initiated. Here the hydrochloride is in 7. The method according to one of the preceding precipitated in a more crystalline state. The claims, characterized in that the formation of the hydrochloride proceeds in high hydrochloride continuously to a phosgeneic degree exothermic, and it is therefore difficult to feed the reagent device. ■ ₄₅ to control temperature, which rises violently 8. Modification of the process after the formation and formation of large crystals of Hydrospruch 1, characterized in that phosgene can lead to chloride that is not easily phosgenic together leave with hydrogen chloride during the ren. Formation of the amine hydrochloride is introduced. It has now been found that if the formation 50 of the hydrochloride is carried out continuously in the form of a film, the problem of stirring a large amount of amine hydrochloride does not occur and it is also not necessary to start the process strongly dilute in order to obtain an appropriate stirring 55 and to carry out movement and mixing, which is easily possible thanks to the thin-film technology is. This also involves heating the amine to a temperature above 120 ° C, as it does The production of organic mono- and polyiso- is given in the USA. Patent 2,644,007, cyanates avoided by phosgenating amine and poly- 60, which has economic advantages, amine hydrochlorides have already been described. They see that the thin-film technology creates a The present invention relates to the phosgenation of continuous operation is possible and which Amine hydrochlorides in an improved physical control of the exothermic reaction extraordinary Lischen shape, which is particularly easy for quick change and achieves even results settlement with phosgene is suitable. Turn 65. Amine hydrochloride, especially polyamine hydro- It has now been found that amine hydrochloride chlorides that are satisfactorily and reproducibly produced by known methods, are mainly in the form of coarse particles, the physical subdivision stood outside the