JPS5988451A - Amin continuous high temperature phosgenation - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION It is well known that most organic isocyanates are produced by phosgenation of primary amines, their hydrochlorides or their carbonamidates (Ullman Encyclopedia of Industrial Chemistry). Dictionary (Ullmanns Encyk)
lopadi der Technischench
emi) 4th edition, Vol. 15, p. 350 et seq. ) The most important industrially is the so-called basic phosgenation. At low temperatures, the amine present in the inert solvent reacts with excess phosgene solution, forming the so-called secondary phosgenation.
In step, the carbamoyl chloride desorbs hydrogen chloride at temperatures above 80° C. with the formation of incyanate. Above this temperature, the hydrochloride also reacts to form the isocyanate: 0 n-nH-co-ct+x-NH3ct-4-coct
, →2RIJOO+4Hot The trigger reaction for incyanate formation is the formation of urea from the amine and the already formed carbamoyl chloride or incyanate.

R-NHOOOA+R-NH24R-NH=OO-11
H-R+HC! jR-NOO+R-NH2→R-NH-
Depending on the Co-Nu-R respective amine, these ureas are very difficult to convert to incyanates or not at all. This is particularly true for aliphatic amines and applies particularly well to polyamines. Therefore, this process must be carried out in such a way as to prevent the formation of urea.

The prephosgenation is preferably carried out using a large excess of phosgene at as low a temperature as possible. Therefore, in practice 1. A relatively highly concentrated phosgene solution is charged in excess and the amine in an organic solvent is added.

It is critical to disperse the amine into the phosgene solution as quickly as possible.

Some patent specifications describe special mixing devices. That is, in order to prevent side reactions between the amine and the incyanate that has already formed, “each amine molecule used in the process is temporarily depleted from phosgene before contacting any of the incyanate molecules that have formed. It has been pointed out that this depends on the fact that the invention must be protected (see Toitz Patent No. 1.792.660, column 3, lines 15-19). This cannot be achieved in practice. The most effective mixing device is a mixing nozzle. However, in this case, blockages and precipitation of solids occur which impede the mixing process.

Removal of the heat of reaction generated in strongly exothermic reactions to low temperature levels requires considerable expenditure. In practice, this is mostly carried out continuously and adiabatically, ie at relatively high temperatures (see German Patent No. 1.165.587).

Preparation of highly concentrated phosgene solutions poses safety concerns.

Despite the disadvantages mentioned above, most aromatic amines are subjected to basic phosgenation.

Relatively strong aliphatic amines are even more difficult to phosgenate directly as a base. The formation of urea can be easily avoided if the carbamic acid is used in the prephosgenation instead of the free amine.

In the so-called carbamate process, the carbamic acid salt is first prepared by saturating the amine solution with carbon dioxide; it is sparingly soluble and is present suspended in the solvent. In the subsequent low temperature phosgenation, the same carbamoyl chloride-hydrochloride mixture as in the basic phosgenation is formed under the elimination of Co, R-NH-00-OA+RWH3
CL"+C004→2R-NoO+4 The HOL carbamate method is certainly relatively inexpensive in the case of mixtures of amines or their carbamates with phosgene, but requires a third reaction step, which adds to the cost. It remains that CO2 is required, which can only be recovered from the waste gas by applying .

Most definitely, urea formation is avoided by following the so-called hydrochloride method and by phosgenating the hydrochloride: R-=u, Oze+cOO74-+RNOO+5TI
Ot-stable hydrochloride salts do not react when cold, and even when heated, the rate of reaction is relatively low. However, it has been shown that long reaction times or relatively high temperatures used to shorten reaction times result in side reactions such as chlorine displacement and incyanate polymerization reaching undesirable extents. Therefore, it is difficult to carry out this reaction continuously.

German Patent Application No. 1.56 ill, 844 describes a typical method for such phosgenation. A suspension of the hydrochloride salt of an organic amine is phosgenated in a cascade stirrer with several stages at a relatively high temperature until a clear reaction solution flows out.

As an example of the difficulties that arise, 1,5-diamino-2-
Examples include phosgenation of methylpentane. This diamine is 95% similar to hexamethylene diisocyanate.
US Patent No. , 6
It is known from the specification No. 31.1?8. According to this US patent, the yield increases to 82.7% by using diethyl 7-talate, but this solvent
It has the disadvantage that it is difficult to separate because its boiling point is close to that of the diisocyanate obtained. Furthermore,
It is not very stable under the reaction conditions. Phthalic anhydride is formed which precipitates as a crystalline substance and is a nuisance.

The object of the present invention was to carry out the high-temperature phosgenation step continuously, starting from the hydrochloride process, so that the reaction time is shortened and it can be operated as much as possible in one stage. Another objective was to obtain purer products and better yields under relatively mild reaction conditions.

The present inventors have now demonstrated that a continuously operated high temperature phosgenation process uses a suitable separation device to retain the solids in the reactor and to remove the incyanate produced during the reaction and dissolved in the solvent. It has been found that significant improvements can be made by continuously removing from the reactor.

In continuous operation, a constant solids concentration is established in the reactor, which is varied by increasing and decreasing the feed and discharge.

The feed consists of a mixture of amine hydrochloride or carbamoyl chloride in a suitable solvent.

The effluent contains the isocyanate which is present dissolved in the same solvent which was introduced using the separation device described above.

Since increasing the concentration of solids increases the reaction rate, the highest possible concentration is desired, but this is limited by the fact that a flowable suspension must also be obtained. . Depending on the amine used, the optimum solids concentration will be different. For example, the optimum value for 1,5-diamino-2-methylpentane is around 2G%, while for inphoronediamine only concentrations of about 1% are possible. This is because otherwise the hydrochloride would form lumps.

Embodiments of the method according to the invention are defined in claims 2 to 7.

The process according to the invention is carried out particularly advantageously when using the hydrochloride method. Reaction times can be significantly shortened.

Owing to the mild reaction conditions, ie low reaction temperature and short reaction time, incyanate is obtained in almost quantitative yields and in extremely high purity.

In the case of 1,5-diamino-2-methylpentane, this method first allows for the economical production of diisocyanates. The average residence time is reduced by a factor of 4. In the case of other aliphatic diamines, reaction rates can be obtained by using the hydrochloride method, which would otherwise only be achieved by the pre-phosgenation described above.

Example 4 demonstrates that the method according to the invention can be successfully carried out even if a pre-phosgene reaction has already been carried out.

Separation of the incyanate-containing reaction solution can be carried out in various ways. For example, a portion of the suspension can be removed from the reactor, the solids separated and recycled to the reactor. However, within the reactor itself, the separation is
and before removal of the product, the solids remaining in the reactor continuously. Separation can be done by e.g.
Decantation, centrifugation and hydrozykron are also used. Preferably, the reaction solution is
Separated using a filter.

The process according to the invention is used for the phosgenation of primary aliphatic, cycloaliphatic, araliphatic and aromatic mono- and polyamines having 5 to 18 carbon atoms or technical mixtures thereof. For example, 1,3-bis-(aminomethyl)-benzene, aniline, tolylene diamine-1,6- and -1,4,4,4'diaminodiphenylmethane, octadecylamine, a,'t, 5.
Examples include 9-triaminoundecane and cyclopentylamine. Aliphatic and cycloaliphatic diamines, e.g.
1,6-diamithexane, 1,5-diamino-2-methylpentane, 1,6-diamino-2゜2.4- or -2,4,4-trimethylhexane, 1,9-diamino-5-methylnonane Also preferred are 1-amino-3-aminomethyl-3,5,5-)lyntylcyclohexane.

Suitable solvents are aliphatic and aromatic compounds which are inert under the reaction conditions. They have from 1 to 15 carbon atoms and optionally contain alkyl groups and chlorine atoms as substituents. Examples include toluene, xylene, tetralin and decalin. Preference is given to using chlorobenzene with a boiling point of 160 DEG C. or 0-dichlorobenzene with a boiling point of 170 DEG C. if the reaction is to be carried out at relatively high temperatures. The suspension subjected to the high temperature phosgenation contains 3 to 30 t1, preferably 10 to 201, of solvent per reacted amine.

In particular, most hydrochlorides and carbamoyl chlorides of aliphatic and cycloaliphatic diamines are only slightly soluble in the abovementioned solvents, to the extent that they can be retained quantitatively using separation equipment. On the other hand, if the amine salts are significantly soluble in the solvent, they may exit the reactor along with the incyanate formed. In such cases, the post-reaction is a relief.

In this case too, the method according to the invention is advantageous. Thus, for example, the average residence time for high temperature phosgenation of toluylene diamine is reduced.

After completion of the phosgenation, the isocyanate-containing reaction solution is worked up in the usual manner, as is clear from the other examples.

The diisocyanates obtained according to the invention can be used in many ways and are particularly suitable for the production of polyurethanes, polyureas and polyamides.

Example 1 Isophorone diamine (1-amino-5-aminomethyl-3,5,5
-trimethylcyclohexane) containing 45 g of chlorobenzene solution per hour, and HOt
Gas 15. Introduce a.

The hydrochloride suspension is overflowed into reactor 1, a phosgenation reactor with a capacity of 2 t. 5 per hour at 125°C
0t of phosgene is allowed to flow through. At the bottom outlet, the reaction solution (approximately 500 m
/) are taken out continuously. After separating off the phosgene and hydrogen chloride by distilling under reflux, the sections are distilled off and the incyanate is isolated by distilling under reduced pressure. 1.2% distillation residue remains. The analytical yield is 9a5%.

Example 2 In reactor 1, an apparatus according to Example 1, trimethylhexamethylenediamine (1,6-diami2゜2y4(2,4
, 4) -) isomer mixture of lynchylhexane) 602
300 ml/hour of a chlorobenzene solution containing chlorobenzene were metered in and 12 t of hot gas were introduced. This suspension is continuously flooded into reactor 1, in which high-temperature phosgenation is carried out at 122 DEG C. and with a phosgene feed rate of 50 t/h. A large amount of clear reactor solution (approximately 600 grams) is removed from the bottom of the reactor per hour so that reactor conditions continue to be maintained. Purification is carried out as described in Example 1.

Upon distillation, a 1% residue remains. Analysis shows that the yield is 98% for trimethylhexamethylene diisocyanate.
．． It is 5%.

Example 6 As described in Example 1, reactor I was charged with 92% of 1.9-diamino-5-methylnonane and 1.8-diamino-2.
, 22.5 isomer mixture with 8% of 4-dimethyloctane
300 liters of chlorobenzene solution containing f are metered in per hour and 91 liters of hydrogen chloride gas are introduced. The overflowing suspension is subjected to high-temperature phosgenation in reactor 1 at 122 DEG C. and a phosgene feed rate of 5 ot/h. A large amount of clear reaction solution (approximately 500 mJ) is withdrawn every hour at the bottom of the reactor so that the reactor conditions are maintained. Purification is as in Example 1.
Proceed as described in. 1.1% upon distillation
A residue remains. The analytical yield is 98.5%.

Example 4 A phosgenation apparatus has substantially each of the following capacities: 1=2t,
It consists of five stirring cans connected one behind the other with n=5t and m=50t.

In reactor I, 3 t/h of a chlorobenzene solution containing 150 g of pure 1,5-diamino-2-methylpentane is saturated at 25 DEG C. with excess CO2 to form a carbamate suspension.

This carbamate suspension is flooded into reactor H in which the reaction to form the carbamyl chloride-hydrochloride mixture takes place at 0 DEG C. with excess phosgene. 2007 of phosgene (obtained from waste gas/phosgene + fresh phosgene) is introduced every hour.

Reactor (1) is operated at 125°C.

The phosgene required for the high-temperature phosgenation is contained in the reaction suspension overflowing from reactor (1).

3 L of clear solution are removed per hour corresponding to the feed.

A sieve (made by Chrome-Nickel) is placed before the bottom outlet of the reactor.
Mesh width 0.03 ys, filter area 1807
is present, which keeps all the solids in the reactor. Under these conditions, a solids content of 18% is established in the reactor. For purification, distillation is carried out in the usual manner.

The crude diisocyanate contains only 0.1% of 1(5)-chloro-5(1)-isocyanate)-2-methylpentane as an impurity according to gas chromatography.

The distillation residue is 0.8%, which is 99% according to analysis.
% yield.

Example 5 A phosgenation plant consists of two stirred cans l and l and
Consisting of

In reactor I, 3 t/h of an 0-dichlorobenzene solution containing the technical diamine mixture 1502 is saturated at 30 DEG C. with HOL gas. The amine mixture has the following composition = 1.5-diamino-2-methylpentane 92.3% 1.4-diamino-2-ethylbutane 73% 1.6-diamithexane 0.4% hydrochloride suspension The liquid is continuously flooded into the reactor (2) into which 2001 phosgene (recovered phosgene +
Introduce fresh phosgene). As described in Example 4, 6 L of clear reaction solution are withdrawn per hour. A solids content of 20% is established in the reactor.

The crude diisocyanate contains 0.9% monochloroisocyanate according to gas chromatography. The distillation residue is 57%, and the analytical yield is 95%.

Example 6 As described in Example 1, reactor I was charged with 65% 2°4-diaminotoluene and 65% 2,6-diaminotoluene.
1.000 liters of chlorobenzene solution containing 5% of the isomer mixture 1002 per hour are metered in and 45 t of hydrogen chloride are introduced.

The overflowing suspension was heated at 120°C in reactor
Subject to high temperature phosgenation at a phosgene feed rate of h.

A large amount of transparent reaction solution (approximately 1,000 m
j/h) to maintain the condition of the reactor. Transfer the clear reaction solution to 5 plates and a total of 500
The flow is forced through a heated plate column having a hold up of -. At 125°C, 30'A/hr of phosgene is introduced countercurrently into the liquid stream from below upwards. Subsequent purification is carried out as described in Example 1.

A residue of 6.6% remains upon distillation. The analytical yield is 95.2%.

・　J--co Agent Hikaru Esaki: ; １　　　　　　; (−11

Claims (1)

[Claims] 1. Amine hydrochloride or its mixture with carbamoyl chloride suspended in a solvent with excess phosgene! 78
In the process of continuous high temperature phosgenation at temperatures between 0 and 200°C, preferably between 100 and 180°C, the solids are kept in the reactor using suitable separation equipment and are removed in the solvent produced during the reaction. A process for continuous high temperature phosgenation of amines as described above, characterized in that dissolved incyanate is continuously removed from the reactor. 2. The method according to claim 1, wherein the solids content of the suspension in the reactor is adjusted by controlling the feed rate so that the amount of isocyanate produced per unit time reaches a maximum limit. 3. The method according to claim 1 or 2, wherein the separation is performed using a filter. 4. Process according to any one of claims 1 to 6, characterized in that a suspension having a solids content of 6 to 50%, preferably 10 to 20%, is continuously fed to the reactor. primary aliphatic having 5.5 to 18 carbon atoms,
Claims 1 to 4 for phosgenating cycloaliphatic, araliphatic and aromatic mono- and polyamines
The method described in any of the paragraphs. 6. A process according to claim 5 for phosgenating primary aliphatic diamines having 6.5 to 12 carbon atoms. B. The method according to claim 6 for phosgenating 1,5-diamino-2-methylpentane.