CA1136641A - Process for the preparation of isocyanic acid esters - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
The invention relates to an improved method for the preparation of isocyanate esters of the general formula (I), R - (NC0)n (I) wherein n is one and R stands for a straight-chained or branched C1- 10 alkyl, benzyl, cyclohexyl, phenyl, halophenyl, methylphenyl or methoxyphenyl group, or n is two and R stands for a hexamethylene, phenylene, methylenebis(phenyl-ene), ethylenebis(phenylene) or methylenebis(halophenylene) group, from the respective amines of the general formula (II), R - (NH2)n wherein R and n are as defined above. According to the invention an amine of the general formula (II) is reacted with a compound of the general formula (III), R'-O-C0-R1 (III) wherein R' stands for chloromethyl, dichloromethyl or trichloromethyl group.
If desired; two compounds of the general formula (II) and/or two compounds of the general formula (III) can be introduced simultaneously into the reaction.
If desired, the reaction is performed in the presence of phosgene. The reac-tants utilized according to the invention are easy to handle, and the required end-products can be obtained with high yields.

Description

1~366~1 The invention relates to a new process for the preparation of iso-cyanic acid esters of the general formula (I), R - (NCO)n (I) wherein n is one and R stands for a straight-chained or branched Cl 10 alkyl, benzyl, cyclohexyl, phenyl, halophenyl, methylphenyl or methoxyphenyl group, or n is two and R stands for a hexamethylene, phenylene, methylenebis(phenylene), ethylenebis(phenylene) or methylenebis(halophenylene) group.
Isocyanic acid esters are very important products of modern chem-ical industry. Great amounts of aromatic isocyanates, particularly toluylene-diisocyanate and diphenylmethane diisocyanate, are utilized for the prepara-tion of polyurethane foams, whereas aromatic monoisocyanates, particularly the halophenylisocyanates, are widely applied as starting substances in the pr~paration of plant protecting agents. Aliphatic monoisocyanates have a similarly wide industrial use.
A large number of publications deal with the preparation of iso-cyanic acid esters. The known methods can be classified essentially into two main groups, i.e. methods utilizing phosgene as reactant and those utilizing other reactants.
Several papers and patent specifications are concerned with methods based on the reaction of phosgene with amines, amine salts or diarylureas. A
comprehensive review of these methods is given in the paper of Babad, H. and Zeiler, A.G. (Chemical Reviews, 73, 75-91 /1973/).
The main difficulty in the processes for the prepara-~r ,~ .

1~3ti~4~

tion of isocyanates by reacting an amine or an amine salt with phosgene is that phosgene, applied as reactant, must not contain chlorine impurity, since otherwise undesired side reactions would occur. Chlorine-free phosgene can be prepared, however, only by liquifying gaseous phosgene and then evaporating the liquid, which requires much energy for cooling.
Several other problems also emerge when performing these reactions on industrial scale. Upon reacting an amine with phosgene, carbamoyl chlorides always form in the reaction mixture, which can be converted into the respective isocyanates at elevated temperatures only. Furthermore, amine hydrochlorides and urea derivatives may form as well, which do not react with phosgene at all, or even at elevated temperatures an incomplete reaction can be initiated. At these high temperatures, however, phosgene is imperfectly soluble in the solvents appliedl making impossible to set the required molar ratio of the reactants.
The introduction of the necessary amount of phosgene at high temperatures involves serious technological problems, too, since a large volume of phosgene gas is to be fed into the reactor. It is also known that at higher temperatures the degree of the thermal dissociation of phosgene increases.
The methods known so far attempted to overcome these difficulties by various means, such as by performing the reaction in many steps at different temperatures, conducting the reaction in vapour phase, applying various catalysts, etc. Thus e.g. according to the method disclosed in the German Democratic Republic patent specification No. 88,315 (March 5, 1972, Magyar Tudomanyos Akademia) isocyanates are prepared in a continuous process by reacting a primary amine or the hydrochloride thereof with phosgene at 0-25C, in the presence of an acid amide catalyst. This method has the disadvantage that the catalyst should be separated from the reaction mixture at the end of the conversion, and the recovery of the catalyst is a complicated and expensive operation.
According to the method disclosed in the Federal Republic of 1~3~

Germany patent specification No. 1,668,109 (November 2, 1972, Bayer) a primary amine is reacted with phosgene in a mixture of an aqueous solution of an inorganic base and a water-immiscible organic solvent, at temperatures between -30C and +35C.
An improved variant of the above method is described in the Federal Republic of Germany patent specification No. 1,809,173 (May 17, 1973, Bayer). According to this method a very short contact time is applied, i.e. the aqueous phase is contacted for a very short time with the organic phase.
It is generally known from the literature that phosgene hydrolyzes quickly in aqueous alkaline media (thus e.g. phosgene is removed from waste gases by aqueous alkali), therefore the above two processes run with very low yields, or they require very expensive automatic control means.
Several processes were disclosed for the preparation of diisocya-nates and various polyisocyanates. The United~States patent specification No. 3,923,732 (December 2, 1975, Olin Corp.) describes the preparation of polyisocyanates by reacting the respective polyamines with phosgene in an inert solvent. The disadvantage of this method is that only polyamines can be applied as starting substances, and mixtures of polyisocyanates are formed as products.
In the methods belonging to the second main group no phosgene is applied for the preparation of isocyanates.
According to the method described in the German Democratic Republic patent specification No. 1,154,090 (March 12, 1964, Bayer) isocyanates are prepared by reacting a dialkyl urea with diphenyl carbonate.
The United States patent specification No. 3,423,448 (January 21, 1969, Sinclair ) discloses a method for the preparation of alkyl isocyanates by reacting the respective alkylhydroxamic acids with thionyl chloride.
According to the method described in the United States patent specification No. 3,017,420 (January 16, 1962, Union Oil Corp.) isocyanates 1~3~

are prepared by reacting an alkali cyanate with an alkyl halide in dimethyl formamide as solvent.
According to the method described in the United States patent specification No. 3,076,007 (January 29, 1963, Union Carbide Corp.) ethylene carbonate is reacted with an amine, and the resulting carbamate is converted into the isocyanate at higher temperatures.
The United States patent specification No. 3,405,159 ~October 8, 1968, Merck ~ Co.) describes a method for the preparation of aliphatic isocyanates by reacting an aliphatic amine with carbon monoxide at super-atmospheric pressure, in the presence of a specially prepared palladium phosphate catalyst.
An alternate method, utilizing carbon monoxide as reactant, is described in the United States patent specification No. 3,523,963 (August 11, 1970, Olin Corp.). In this method carbon monoxide is reacted with an aromatic nitro compound at superatmospheric pressure, in the presence of a special catalyst.
According to the method disclosed in the United States patent specification No. 3,493,596 (February 3, 1970, Universal Oil Products Co.) isocyanates are prepared by oxidizing the respective organic isonitriles with mercury oxide, in the presence of a metal porphyrine or a metal phthalocyanine catalyst.
The United States patent specification No. 3,632,620 (January 4, 1972, Olin Mathleson) describes a method for the preparation of phenyl isocyanate by reacting diphenyl carbodiimide with carbon monoxide under superatmospheric pressure and at elevated temperature, in the presence of a catalyst, such as palladium, rhodium, etc.
The majority of these latter methods utilizing no phosgene in the preparation of isocyanates has the disadvantage that they require special compounds with complicated structures as starting substances. Since such compounds are generally not available on the market, they should be prepared in a separate step, which requires extra investments and renders the process 1~3t;641 less competitive on industrial scale. Moreover, the use of phosgene cannot be eliminated in some of the above processes, since a great number of the starting substances can be prepared only from phosgene.
The yield of the above processes is generally unsatisfactory;
thus e.g. when carbon monoxide is applied as reactant, the isocyanate can be prepared with a yield not exceeding 30-35%.
Now it has been found that the isocyanates of the general formula (I) can be prepared more easily and more economically than before if the respective amine of the general formula (II), R - (NH2)n (II) wherein R and n are as defined above, is reacted with a compound of the general formula (III), R'-0-C0-Cl (III) wherein R' stands for chloromethyl, dichloromethyl or trichloromethyl group, or with a mixture of such compounds, optionally in the presence of phosgene.
Thus, this invention provides a process for the preparation of isocyanate esters of the general formula (I), wherein n is one and R stands for a straight-chained or branched Cl 10 alkyl, benzyl, cyclohexyl, phenyl, halophenyl, methylphenyl or methoxyphenyl group, or n is two and R stands for a hexamethylene, phenylene, methylenebis(phenylene), ethylenebis (phenylene) or methylenebis( halophenylene) group, from amines of the general formula (II), wherein R and n are as defined above, at a temperature of -40C to l300C under a pressure of 0.2 to 200 atmospheres, Characterized in that one or two amines of the general formula (II) are reacted with a compound of the general formula (III), wherein R' stands for chloromethyl, dichloromethyl or trichloromethyl group, or with a mixture thereof, fed into the reaction mixture in liquid state.
The reaction can also be performed under atmospheric `~ - 6 -113~641 or reduced pressure, it is preferred, however, to apply superatmospheric pressure in the process. Depending on the nature of the starting amine, the reaction can be performed at temperatures of -40C to +300C. According to a preferred method the reaction is performed in the presence of a solvent or a solvent mixture. If desired or necessary~ 8 catalyst can be added to the mixture in order to promote the reaction.
It is preferred to apply a chlorinated hydro¢arbon, such as dichloromethane, chloroform, carbon tetrachloride~
chlorobenzene, etc., as solvent.
Of the catalyst applicable in the method of the in-venbion activated carbon, metal chlorides (such as iron chloride, zinc chloride~ etc.) on activated carbon, further_ more acid catalysts, primarily Lewis acids, are to be men-tioned.
~he major advantage of the method according to the invention i~ that the compounds of the general formula (III) sre much more easy to handle than phosgene.
As known, phosgene is a gas above 8C, its volume density is low, its solubility in the solvents apilied decreases considerably with increasing temperature, further_ more phosgene dissociates at higher temperatures. On the other hand, the compounds of the general formula (III) are liquids~ thus their volume densities exceed that of phosgene by orders oi magnitude~ their boiling points are close to the boiling points of the solvents applied, and their solu-bilities~ even at elevated temperatures, are more favourable than that o~ pho~gene. The compounds of the general formula (III) are more stable thermally than phosgene. It is a 1~3~6~:~

" , . .
particular ad~antage that the compounds of the general formula (III) are good solvents for the isocyanates, thus when applying a compound of the general formula (III) as reactant~ isocyanate solutions of higher concentration than the usual 17-17 w/w % can be prepared, which improves the economy of bhe process.
Since the compounds of the general formula (III) are liquids~ they can be ~ed easily, with a simple liquid pump, into the reactors opeerting under superatmospheric pressure, and their concentration can be maintained easily at the value required in the reacbion. These tasks cannot be solved in practice when utilizing gaseous phosgene as rsactant.
~ he compounds of the general formula (III~ have the ~urther advantage that their hydrolysis rates in alkaline media are substantially lower than that o~ phosgene, thus they can be applied in a broader pH rangeO
~ he non-reacted ¢hlorinated chloroformates, applied in excess, can be decomposed thermally and/or catalytically at the end of the reaction, thus they can be separated easily from the crude isocyanate product.
In the known processes starting from an amine and reacting it with phosgene under superatmospheric pressure the reaction mixture is processed generally 90 that the mix-ture is expanded and the individual components are separated from each other under atmospheric pressure. ~he excess Or phosgene and the gaseou~ hydrochloric acid are removed ~rom the reaction mixture generally by passing an inert gas through the solution of the crude isocyanate, and then the solution is distilled in order to separate the isocyanate from the solvent.

113ti6~1 _ 9 _ We have found that gaseous hydrochloric acid and phosgene cen be removed from the reaction mixture more easily if no pressure release and flushin~ i8 applied in the first step of the separation, or if the first step of the separa-tion i~ performed at a presaure even higher than that appliedin the reaction, and only the further steps of purification (and, if required~ the recovery of the solvent) are performed at lower pressures.
It has alsQ been found, unexpectedly, that if a mix-ture of monochloromethyl chloroform3~e and trichloromethylchloroformate i9 reacted with an aromatic amine, diphenyl-methane diisocyanate or polyphenyl-methylene polyi~ocyanates are formed aa end-products. ~hese substance~ are widely used~ es~ential material~ of the plastic industry.
The proce~s of the invention can be conducted either batchwi~e or continuou~ly~ utilising apparatuses commonly applied in the chemi¢al industry.
It i9 preferred to perform the reaction in a con-tinuous way in a pre~surized tube reactor, by; feeding the

2 ~ reacbants into the reactor with a liquid pump.
Ib is also preferred bo use in the reactor a filling with great surface area. As ~illing e.g. the activated carbon catsly~t itself, or a support impregnated with a cataly~t (iron chloride, zinc chloride, etc.) can be used.
~he process of the invention is elucidated in detail by the aid of the following non-limiting ~xamples.
Exam~le 1 20 ml/min. of a 31.1 w/w % carbon tetrachloride solu-tion of butylamine and 20.0 ml/min. of a 52 w/w % carbon tetrachloride ~olution of dichloromethyl chloroformate are 113~6~

fed simultaneously into a tube reactor operatig at 180C and 50 atm. pressure. ~he mixture leaving the reactor i9 fed continuously into a gas/liquid separator connected to the reactor, where 289 ml of a carbon tetrachloride solution 5 containing 24.2 w/w % of butyl isocyanate is separated from the ga~eous substances.
After removing the solvent from the solution 94 g of butyl isocyanate are obtained, thUs the yield is 95 %.
Exam~le 2 20.0 ml/min. of a 31.1 w/w % carbon tetrachloride solution of butylamine and 20.0 ml/min. of a 52 w/w % carbon tetrachloride solubion of dichloromethyl chloroformate are fed simultaneously inbo a tube reactor operating at 130C and 5 atm. pressure. 300 ml of a liquid reaction mixture are 15 separated from the gaseou~ subsbances in the gas/liquid ~epa-rator~ and the liquid is ied into a column filled with activated carbon at 150C under reduced pressure; The carbon tetrachloride solution of butyl isocyanate which leaves the column is separated and purified in the usual manner to obtain 20 92 g (94 %) of butyl isacyanateO

20.0 ml/min. of a 31.1 w/w % carbon tetrachloride solution of but;srlamine and 20.0 ml/min. of a 60.3 w/w % carbon tetrachloride solution of trichloromethyl chlorofo~mate are 25 fed simultaneously into a tube reactor operating at 180C and 50 atm. pres3ure. 280 ml of a carbon tetrachloride solution containing 24.4 w/w % of butyl isocyanate are separated from the gaseous products in the gas/liquid separator connected to the reactor. ~b~e sol~ent is separated from the solute in the usual manner to obtain 93 g (94.5 %) of butyl isocyanate.

1~3~6~L~

Exam~le 4 20.0 ml/min. of a 31.1 w/w % carbon tetrachloride solution of butylamine and 20.0 ml/min. of a 60.3 w/w % carbon tetrachloride solution oi triohloromethyl chloroformate are fed simulta~eously into a tube reactor operating at 120C
and 5 atm. pressure. 300 ml of a liquid reaction mixture are separated from the gaseous products in the continuously openating gas/liquid separator~ and the liquid mixture is fed into a column filled with activated carbon impregnated with zinc ¢hloride. ~his ¢olumn operates at 200C under atmospheric pressure. ~he product i9 separated from the solution leaving the column to obtain 94 g (95 %) of butyl isocyanate.
ExamPle S
- One proceeds as described in Example 4 with the difference that dichloromethane is applied as solvent. After separating the product from the solvent 91 g ~93.5 %) of butyl isocyanate are obtainedO
ExamPle 6 One proceeds as described in Example 4 with the difference thst chloroform is applied as solvent. After se-parating the product from the solvent 92 g (g4 %) of butyl isocyanate are obta~ned.
ExamPle 7 One proceeds as described in Example 4 with the difference that chlorobenzene is applied as solvent. AfOer separating the product from the solvent 94 g (95 %) of butyl isocysna~e are obtained.
Exsm~le 8 One proceeds as described in Example 4 with the difference that o-dichlorobenzene is applied as solv~ntO

After separating the product from the solvent 94 g (95 %) of butyl i~ocyanate are obtained.
Example 9 20.0 ml/min of a 31.1 w/w % carbon tetrachloride solution of butylamine and 20.0 ml/min. of a 41.1 w/w % carbon tetrachloride solution of monochloromethyl chloroformate are fed ~imultaneously into a tube reactor operating at 150C
and 40 atm. pressure. The reaction mixture exiting the re-actor i9 distilled under superatmospheric pressure. In this step 310 ml of a solution containing 20.9 w/w ~0 of butyl isocyanate are separated from the gaseous substance~O ~he product is separated from the solvent and then purified to obtain 91 g (92 %) of butyl isocyanate.
ExamPle 10 20.0 ml/oin. of a 31.1 w/w % carbon tetrachloride solution of butylamine and 2000 ml/min. of a carbon tetra-chloride solution containiDg 30.3 w/w % of phosgene and 30.3 w/w % of trichloromethyl chloroformate are fed simul-taneously into a tube reactor operating at 180C and 50 atm.
pressure. ~he mixture which leaves the reactor is passed through a column filled with activated carbon; thIs colum~
operates at 200C and 5 atm. pressure. ~hereafter 300 ml o~
a solution containil~g 24 w/w % of butyl isocyanate are se-- parated from the gaseous substances in the gas/liquid se-parator. ~he product is separated from the solvent and thon purified to obtain 93 g (94.5 %) of butyl isocyanate.
ExamPle 11 A solution of 198 g of trichloromethyl chloroformate in 200 ml of carbon tetrachloride, 73 g of butylamine and 200 ml of a 10 w/w % aqueous sodium hydroxide solution are 11366~L:l fed into a raund-bottomed flask of 1000 ml capacity, equipped with a stirrer, a thermometer, a droppiDg funnel and a reflux co~denser. The reaction mixture is stirred at -20C for 2 hours, a~d then the aqueous phase is separated.
~he organic phase is dried, evaporated, and the vapours are passed through a column filled with activated carbon, operat-ing at 120& . The carbon tetraehloride solution of butyl isocyanate i~ separated then from the gaseous substances~
the solvent is distilled off, and the residue i9 purified in the usual manner to obtain 96.5 g (97.5 %~ o~ butyl isocyanate.
Ex~m~le 12 One proceed~ as described in ~xample 11 with the difference that 270 ml of a 20 w/w % aqueous sodium carbonate solution i9 substituted for the aqueous sodium hydroxide solubion. 96 g (97 %) of butyl isocyanate are obtained.
Example 13 73 g of butylamine, 198 g of trichloromethyl chloro-iormate and 200 ml of a 10 w/w ~ aqueous sodium hydroxide solution are fed into a round-bottomed flask of 1000 ml capacity~ equipped with a stirrer and a thermometer. The reaction mixture i8 stirred at -20C for 3 hours, thereaiter 101 g of triethylamine are added, and the mixture i9 stirred at -20C for additional 2 hours. The aqueous phase is separat-ed and the organic phase is distilled. 96 g (96 %) of butyl isocyanate are obtained.
Exam~le 14 198 g of trichloromethyl chloroformate, 73 g of butylamine~ 200 ml of o-dichlorobenzene and 200 ml of a 10 w/w % aqueous sodium hydroxide solution are fed into a round-bottomed flask of 1000 ml caE>acity, equipped with a ~l36~
-- l* --stirrer~ A thermometer and a droppi~g funnel. ~hq reaotion mixture i~ sbirred at -20C for 3 hours~ thereafter the organic phase is separated and dried.
10.9 g of tetramethylammonium chloride are added to the organic phase~ and the mixture is boiledO When the evolution of phosgene and hydrochloric acid ceases~ bhe solvent i8 removed from the crude reaction mixture to obtain 96 g (96 %) of butyl isocyanateO
ExamPle 15 20.0 ml/min. of a 10.23 w/w % carbon tetrachloride solu-tion of methylamine and 20.0 ml/min. of a 6003 w/w ~ oarbon tetrachloride solution of trichloromethyl chloroformate are fed simultaneously into a tube reactor operating at 160C
and 50 atm. pressure. ~he product i8 separated ~rom the resulting mixbure in the usual way and thelpuri~ied to obtain 51.3 g (90 %) of methyl isocyanate.
ExamPle 16 20.0 ml/min. of a 39.2 w/~ ~ carbon tetrachloride solu-tion of aniline and 20.0 ml/min. of a 60.3 w/w % carbon tetra-¢hloride solution o~ tri¢hloromethyl chloroformate are fed simulta~eously into a tube reactor operating at 180C and 50 atm. pressure. ~he producb is separated from the crudo rea¢tion mixture in the usual way and then purified to ob-tain 133.4 g (96 %) of phe4yl isocyanate.
Exam~le 17 20.0 ml/min. of a 44.2 w/w ~ carbon tetrachloride ~olu-tion o~ m-chloroaniline and 20.0 ml/min. of a 60.3 w/w %
carbon tetrachloride solution of trichloromethyl chloroformate are fed simultaneously into a tube reactor operating at 180C and 60 atm. pressure. 310 ml of a carbon tetrachloride 1~3~i64~1 solution containing 33.7 w/w % of m-chlorophenyl isocyanate are separated from the gaseous substances in the gas/liquid separator. Thereafter the sol-vent is removed from the mixture to obtain 142.3 g (93%) of m-chlorophenyl isocyanate.
Example 18 20.0 ml/min. of a 40 w/w % carbon tetrachloride solution of cycl~o-hexylamine and 20.0 ml/min. of a 60.3 w/w % carbon tetrachloride solution of trichloromethyl chloroformate are fed simultaneously into a tube reactor op-erating at 170C and 50 atm. pressure. 320 ml of a carbon tetrachloride solution containing 33 w/w % of cyclohexyl isocyanate are separated from the gaseous substances in the gas/liquid separator. Thereafter the solvent is removed from the mixture to obtain 136 g (94%) of cyclohexyl isocyanate.
Example 19 20.0 ml/min. of a 42 w/w % carbon tetrachloride solution of hexa-methylene diamine and 40.0 ml/min. of a 60.3 w/w % carbon tetrachloride solu-tion of trichloromethyl chloroformate are fed simultaneously into a tube re-actor operating at 140C and 50 atm. pressure. 430 ml of a carbon tetrachlor-ide solution containing 28.5 w/w % of hexamethylene diisocyanate are separ-ated from the gaseous by-products. The solvent is removed in the usual way to obtain 156 g (94%) of hexamethylene diisocyanate.
Example 20 20.0 ml/min. of a 45 w/w % carbon tetrachloride solution of tol-uylene diamine (containing 65 w/w % of 2,4-isomer and 35 w/w % of 2,6-isomer) and 40.0 ml/min. of a 60.3 w/w % carbon tetrachloride solution of trichloro-methyl chloroformate are fed simultaneously into a tube reactor ~1366~1 -- 16 _ operating at 190C and 50 atm. pressureO 440 ml of a solution containing 29 w/w % of toluylene diisocyanate are separated from the gaseous by-products in the gas/liquid separator.
The solvent is removed in the usual way to obtain 165 g (95 ~) of toluylene diisocyanate.
Example 21 10.0 ml/min. (7.3 g/min.) of butylamine snd 30.0 ml/min. of trichloromethyl chloroformate are fed simultaneously into a tube reactor operating at 150C and 5 atm. pressure.
The mixture which leaves the reactor is fed into a column filled with activated carbon, operating at 180C and 5 atm.
pressure. Thereafter the gaseous substances are removed in the gas/liguid separator, and the crude product i~ distilled.
91 g ~92 %) of butyl isocyanate are obtained.
Example 22 20.0 ml/min. of a 40 w/w % carbon tetrachloride solution of 4,4'-diphenyl~ethane diamine and 20.0 ml/minO o~
a 60.3 w/w % carbon tetrachloride solution of trichloromethyl chloroformate are fed simultaneously into a tube reactor ?0 operating at 130C and 50 atm. pressureO 320 ml of a solution containing 16.6 w/w % of 4~4~-diphenylmethane diisocyanate are separated from the gaseous by-products. ~he solvent is removed from the solution in the usual way and the product is purified to obtain 70 g (74 %) of the diisocyanate.
ExamPle 23 20.0 ml/min. o~ a 39.16 w/w % carbon tetrachloride solution of aniline and 20.0 ml/min. of a 41.4 w/w ~ carbon tetrachloride solution o~ monochloromethyl chloroformate are fed ~imultaneously into a tube reactor operating ab 130C
and 50 atm. pressure. ~he gaseous by-products are separated,`

113Çi~
-- 17 _ and the resulting solution which contains phenyl isocyanate and 4,4'-diph~nylmethane diisocyanate is distilledO 12 g (9 %) of phenyl isocyanate and 67 g (89 %) of 4,4'-diphenyl-methane diisocyanate are obtained.
Example 24 20.0 ml/min. of a 39016 w/w % carbon tetrachloride solution of aniline and 20.0 ml/min. of a carbon tetrachlor-ide solution containing 20.~2 w/w % of monochloromethyl chloroformate and 30.15 w/w % of trichloromethyl chloroformate are fed simultaneously into a tube reactor operating at 130C and 50 atm. pressure. ~he gaseous by-products are re-moved in the gas/liquid separator, and then the solvent i8 removed from the resulting carbon tetrachloride solution of phenyl isocyanate and 4,4'-diphenylmethane diisocyanate.
The residue is purified in the usual way to obtain 14 g (10 %) of phenyl isocyanate and 64.7 g (85 %) of 4,4'-di-phenylmethane diisocyanate.
ExamPle 25 - 20.0 ml/minO of a carbon tetrachloride solution contai~ing 12.1 w/w % of butylamine and 36 w/w % of aniline and 22.0 ml/min. o$ a solution containing 69 w/w % of tri-chloromethyl chloroformate snd 29 w/w % of monochloromethyl chloroformate are fed simultaneously into a tube reactor operating at 170C and 50 atm. pressure. ~he gaseous by-products are removed in the gas/liquid separator to obtain 8 solution which contains butyl isocyanate, phenyl isocyanate and 4~4'-diphenylmethane diisocyanate.
~he solvent is evaporated, and the isocyanates are separated from each other by distillation. 34 g (94 ~) of butyl isocyanate~ 9 g (10 %) of phenyl isocyanate and 1~36~
_ 18 -92 G (86 %) of 4,4'-diphenylmethane diisoc~anate are obtained.
ExamPle 26 , 20.0 ml/min. of a 31.1 w/w % carbon tetrachloride solu-tion of butylamine and 20.0 ml/min. of a 60.6 w/w % carbon tetrachloride solution of trichloromethyl chloroformate are fed simultaneously into a tube reactor operating at 150C
and 5 atm. pressureO ~he mixture which leaves the reactor is passed through a column filled with activated carbon, operat-ing a~ 180C and 5 atmO pressure. Therea~ter the mixture i~
fed into a gas/liquid separator operating at 80C and 5 atm.
pressure, and 73 g of pure, dry, gaseous hydrochloric acid are lead off from the separabor in every 10 minutes. ~he liquid phase is expanded and distilled at atmospheric pressure, and the phosgene-containing carbon tetrachloride solution i8 recirculated into the column filled with activated carbon.
The product is purified to obtain 93 g (94 %3 of butyl iso-¢yanate.
Exam~le 27 One proceeds as described in Example 26 with the difference bhat o-dichlorobenzene is applied as solventO
92 g ~93 ~) of butyl isocyanste are obtained.
Example 28 One proceeds as described in Example 26 with the difference that the reactants are fed directly into the column filled with activated carbon, operating at 180C and 5 atm.
pressure. 92.5 g (93.5 %) of butyl isocyanate are obtained.
Example 29 One proceeds ss described in ~xample 26 with the difference that 20.0 ml/min. of a 31 w/w % carbon tetrachlor-ide ~olution o~ butylamine~ 2000 ml/min. o~ a 30.3 w/w %

113~i6~1 -- 19 -- .

carbon tetrachloride solution of trichloromethyl chloroformate and 20.0 ml/min. of a 30.4 w/w % carbon tetrachloride solu-tion of phosgene are fed simultaneously into the tube reactor operating at 150C and 5 atm. pressure. After one hour the feeding oi the phosgene solution is cut off~ and the carbon tetrachloride solution of phosgene, obtained in the distilla-tion at atmospheric pressure, is recirculated into the tube reactor. 94 g (95 %) of butyl i~ocyanate are obtained.
Example 30 20.0 ml/min. o~ a 10.23 w/w % carbon tetrachloride solution of methylamine and 20.0 ml/minO of a 60.3 w/w %
carbon tetrachloride solution of trichloromethyl chloroformate are fed into a tube reaotor operating at 150C and 5 atm.
pressure. ~he mixture which leaves the reactor i~ fed into 8 reactor filled with activated carbon, operating at 180C
and 5 atm. pressure. ~hereafter the mixture is fed into a 8? arator operabing at 80C and 5 atm. pressure~ and 22 g (6.6 litres) of dry~ gsseous hydrochloric acid are led ofi from the separator. ~he mixture is then expanded and distilled at atmospheric pressure. The phosgene-containing carbon tetrachloride solution is recirculated into the reactor filled with activated carbon~ and the product is purified.
82.55 g o~ a product consisting of 70 w/w ~ of methylcarbamoyl chloride and 30 w/w % oi methyl isocyanate are obtained~
thus the conversion is 97.6 %.
Example 31 20.0 ml/min. of a 43 w/w % carbon tetrachloride solution oi hexylamine and 20~0 ml/min. of a 60.3 w/w %
carbon tetrachloride solution of trichloromethyl chloroformate are fed simultaneously into a tube reactor operabing at il3 180C and 50 atm. preasure; 300 ml of 9 mixture ~of n-hexyl isocyanate and carbon tetrachloride sre obtained after separating the liquid from the gaseous substances in the llquid/gas separator. ~his mixture is distilled to obtain 101.9 g (91 %) of n-hexyl isocyanate.
ExamPle 32 20.0 ml/min. Or a 23.4 w/w % carbon tetrachloride so~ution of iaopropylamine and 20.0 ml/min. of a 60.3 w/w %
car~Qn tetrachloride solution of trichloromethyl chloroformate are fed aimultaneously into a tube rea¢tor filled with granulsr activ~ted csrbon, operating at 220C and 50 atm. pressure.
The mix~ure which leaves the reactor is fed continuously into a gss/liquid separator, where 2~0 ml o~ a carbon tetra-chloride solution containing isopropyl isocyanabe are ob-tained. ~his ~olution is di~tilled to obtain 68.4 g (94 %) of isopropyl i~ocyanate.
Exam~le 3~ `
~ solution of 44.6 g of 4-chloro-4'-amino-biphenyl in 200 ml o~ dichloromethane and 200 ml of a 20 w/w % di-chloromethane solution Or trichloromethyl chloroformate are red continuously~ within 10 minutes into a tube reactor operating at 120C and 5 atm. pressure. ~he mixture which lea~es the reactor is sub~ected to separation, and the 350 ~1 Or the ~olution obtained i~ distilled. 23 g (90 %) of 4-chloro-biphenyl-4'-isocyanate are obtaincd.
Exam~le 34 20.0 ml/min. of a 37.8 w/w ~ chlorobenzene solution of p-toluidine and 20.0 ml/min. of a 41 w/w % chlorobenzeDe solution Or trichloromethyl chloroformate are fed continuou~ly into a tube reactor filled with activated carbon~ operati~g 1~36~

at 180C. The mixture which leaves the reactor is fed into a gas/liquid sep-arator, and the separated 360 ml of liquid are distilled. 98.6 g (93%) of 4-methylphenyl isocyanate are obtained.
Example 35 20.0 ml/min. of a 46 w/w % o-dichlorobenzene solution of 4-ethyl-aniline and 20.0 ml/min. of a 60.3 w/w % o-dichlorobenzene solution of tri-chloromethyl chloroformate are fed simultaneously and continuously into a tube reactor operating at 150C and 5 atm. pressure. The mixture which leaves the reactor is expanded and fed into a gas/liquid separator to obtain 380 ml of a solution, which is then distilled. 102 g (88%) of 4-ethylphenyl isocyanate are obtained.
Example 36 20.0 ml/min. of a 22.9 w/w % carbon tetrachloride solution of p-anisidine and 20.0 ml/min. of a 60 w/w % carbon tetrachloride solution of trichloromethyl chloroformate are fed simultaneously and continuously into a reactor operating at 180C and 50 atm. pressure. The mixture which leaves the reactor is separated, and the solution is distilled to obtain 102.6 g ~86%) of 4-methoxyphenyl isocyanate.
Example 37 20.0 ml/min. of a 43.2 w/w % chlorobenzene solution of m-phenylene diamine and 30.0 ml/min. of a 65 w/w % o-dichlorobenzene solution of tri-chloromethyl chloroformate are fed simultaneously and continuously into a tube reac~or operating at 150C and 5 atm. pressure. 460 ml of a liquid are separated in the gas/liquid separator, and then the liquid is distilled to obtain 106 g (91.6 %) of m-phenylene diiso-1~l3~69~

cyanate.
Example 38 400 ml of o-dichlorobenzene and 130 ml of trichloromethyl chloro-formate are introduced into a round-bottomed flask of 2500 ml capacity, equipped with a stirrer, a reflux condenser and a thermometer. Thereafter 1000 ml of a 21 w/w % o-dichlorobenzene solution of 4,4'-diamino-dibenzyl are added to the mixture with stirring, whereupon the temperature of the re-action mixture raises above 100C. The resulting mixture is stirred at 130C for 4 hours and then processed by fractional distillation. 201 g (94.8%) of 4,4'-dibenzyl diisocyanate are obtained.
Example 39 400 ml of o-dichlorobenzene and 100 ml of trichloromethyl chloro-formate are introduced into a round-bottomed flask of 2500 ml capacity, equipped with a stirrer, a reflux condenser and a thermometer. 1000 ml of a 27 w/w % o-dichlorobenzene solution of methylenebis-~o-chloroaniline) are added to the mixture with stirring, whereupon the temperature of the reac-tion mixture raises above 100C. At the end of the addition the mixture is stirred at 130 C for 4 hours and then distilled. 230 g (90%) of 3,3'-di-chloro-diphenylmethane-4,4'-diisocyanate are obtained.
Example 40 210 g of ignited sodium carbonate and 100 ml of o-dichlorobenzene are introduced into a round-bottomed flask of 2500 ml capacity, equipped with a stirrer and a thermometer. 100 ml of a 30 w/w % o-dichlorobenzene solution of trichloromethyl chloroformate are added to the mixture under cont1nuous stirring and intense cooling (at -40C) within ,........................ '

3~

one hour. The,reaction mixture i~ stirred then for one furthar hour at 0-20C, thereafter the mixture is filtered and the filtrate i9 distilled to obtain 26 g (92 %) of methyl i80-cyanate.
ExamPle 41 One proceeds as described in Example 4 with the difference that act$vated oarbon impregnated with 0.5 w/w %
of ferric chloride i8 applied as catsly~tO 91 g (92 %) Or butyl isocyanate are obtained.
10 ' ExamPle 42 On0 proceeds as described in Example 4 wibh the diYference that sctivated carbon impregnated with 0.5 w/w %
of aluminium chloride is applied as cabalyst. 89 g ~(90 %) of' butyl isocysns'te are obtai~ed.
ExamPle 43 One proceeds as described in Example 15 wibh the difference that the reactor is operated at 250a under a - pressure of 5 atmospheres. 53 g (93 %) of methyl isocyanate are obtained.
ExamPle 44 20.0 ml/min. of a 31.1 w/w % o-dichlorobenzene 801u-tion of butylamine and 20.0 ml/min. of a 60 w/w % solutien of trichloromethyl chloroformste are fed simultaneously and continuously, through a pre-heater~ into a tube reacbor filled with activated carbon, operati~g at 300& . ~he mixture which leaves the reactor is passed through a separator~ and the separated liquid is distilled. 83 g (85 %~ of butyl iso-cyanate are obtained.
Example 45 20.0 ml/min. of a 36.8 w/w ~ o-dichlorobenzene solu-L

tion of benzylamine and 20.0 ml/min. of a 30 w/w % solution of trichloro-methyl chloroformate are fed simultaneously and continuously, by means of a high-pressure liquid pump, into a tube reactor operating at 180C and 200 atm. pressure. The mixture which leaves the reactor is expanded, passed through a gas/liquid separator, and the separated liquid is distilled. 92 g (86%) of benzyl isocyanate are obtained.
Example 46 20.0 ml/min. of a 33.6 w/w % o-dichlorobenzene solution of aniline and 20.0 ml/min. of a 60.5 w/w % o-dichlorobenzene solution of trichloro-methyl chloroformate are fed simultaneously and continuously into a reactoroperating at 120C and 0.2 atm. pressure. The product is removed continu-ously from the reactor by distillation, and the crude product is purified by fractional distillation. 120 g ~86%) of phenyl isocyanate are obtained.

_ 24 -

Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the preparation of isocyanate esters of the general formula (I), R - (NC0)n (I) wherein n is one and R stands for a straight-chained or branched C1-10 alkyl, benzyl, cyclohexyl, phenyl, halophenyl, methylphenyl or methoxyphenyl group, or n is two and R stands for a hexamethylene, phenylene, methylenebis(phenylene), ethylenebis(phenylene) or methylenebis(halophenylene) group, from amines of the general formula (II), R - (NH2)n (II) wherein R and n are as defined above, at a temperature of -40°C to +300°C
under pressure of 0.2 to 200 atmospheres, characterized in that one or two amines of the general formula (II) are reacted with a compound of the general formula (III), R'-0-C0-C1 (III) wherein R' stands for chloromethyl, dichloromethyl or trichloromethyl group, or with a mixture thereof, fed into the reaction mixture in liquid state.

2. A process as defined in claim 1 wherein the process for the preparation of isocyanate esters of the general formula (I) from amines of the general formula (II) is carried out in the presence of a chlorinated hydrocarbon solvent or a solvent mixture containing a chlorinated hydrocarbon.

3. A process as defined in claim 1 wherein the process for the preparation of isocyanate esters of the general formula (I) from amines of the general formula (II) is carried out in the presence of an activated carbon catalyst.

4. A process as defined in claim 3 wherein the activated carbon catylyst is impregnated with 0.1 to 5 w/w% of a metal halide.

5. A process as defined in claim 1 wherein the process for the preparation of isocyanate esters of the general formula (I) from amines of the general formula (II) is carried out in the presence of an inorganic base or a tertiary amine.