FR2482590A1 - Prepn. of isocyanate ester(s) - from the corresp. amine cpds. using chlorinated methyl chloroformate - Google Patents

Abstract

Isocyanate cpds. of formula R(NCO)n, (in which, when n is 1, R is 1-10C alkyl, benzyl, cyclohexyl, phenyl, halophenyl, methylphenyl or methoxyphenyl, and when n is 2, R is hexamethylene, phenylene, methylene bis(phenylene or halophenylene) or ethylene bisphenylene) are prepd. by reacting one or two amines of formula R(NH)n with >=1 cpds. of formula (I) R1 OCOCl, in which R1 is chloromethyl, di- or tri-chloromethyl. (I) is added to the reaction mixt. in the liq. state. The reaction is carried out at -40 to 300 degrees C and at 0.2-200 atmos. opt. in the presence of an active C catalyst opt. impregnated with 0.1-5% of a metallic halide and/or opt. in the presence of a mineral tert. amino base. The cpds. are used in the prepn. of polyurethanes or if R is aromatic or a mixt. or mono- and trichloromethyl chloroformate is used the prods include polyphenylmethylene polyisocyanates which are used in the plastics industry. The process is simpler and cheaper than previously proposed processes. (I) are easier to handle than phosgene.

Description

The present invention relates to a new process for the preparation of isocyanic acid esters which correspond to the general formula I below
R - (NCO) n (I) in which n is equal to i and
R represents a straight or branched chain alkyl group
in C1 to C10 a benzyl, cyclohexyl, phenyl group,
halophenyl, methylphenyl or methoxyphenyl, or n is 2 and
R represents a hexamethylene, phenylene, methylene group
bis (phenylene) ethylenebis (phenylene) or methylenebis
(halophenylene).

 Isocyanic acid esters are very important products in the modern chemical industry. Large quantities of aromatic isocyanates, in particular toluylene diisocyanate and diphenylmethane diisocyanate, are used for the preparation of polyurethane foams, while aromatic monoisocyanates, in particular halophenylisocyanates, are widely used as starting materials in the preparation of plant protection agents. Aliphatic monoisocyanates also have wide industrial use.

 A large number of publications relate to the preparation of esters of isocyanic acid. The known methods can be classified essentially into two main groups, namely the methods which use phosgene as reagent and those which use other reagents.

Many Articles and Patents are concerned with methods which are based on the reaction of phosgene with amines, amine salts or diarylureas. A
A complete review of these methods is given in the Article by Babad, H. and Zeiler, AG (Cheinical Reviews, 73, 75-91 L1973 /).

The main difficulty with methods for preparing isocyanates by reacting an amine or an amine salt with phosgene is that phosgene, when used as a reagent, should not contain chlorine as an impurity, because if it did, side reactions would occur
undesirable. However, phosgene devoid of chlorine can only be prepared by liquefying phosgene gas, then by evaporating the liquid, which requires a lot of energy for cooling.

 Many other problems also arise when these reactions are carried out on an industrial scale.

During the reaction of an amine with phosgene, carbamoyl chlorides always form in the reaction mixture which can only be converted into the corresponding isocyanates at high temperatures.

In addition, it can also form amine hydrochlorides and urea derivatives, which do not react at all with phosgene, or even at high temperatures an incomplete reaction can start. At these high temperatures, the phosgene is however imperfectly soluble in the solvents used, which makes it impossible to adjust the required molar ratio of the reactants.

Introducing the necessary amount of phosgene
at high temperatures also poses serious technological problems, since a large volume of phosgene
in the gaseous state must be introduced into the reactor. It is also known that at high temperatures, the degree of thermal dissociation of phosgene increases.

 The methods known so far have attempted to overcome these difficulties by various means, in particular by carrying out the reaction in several stages at different temperatures, by carrying out the reaction in the vapor phase, by using various catalysts, etc.

Thus, for example, in accordance with the process described in German Patent No. 88315, isocyanates are prepared in a continuous process by reacting a primary amine or its hydrochloride, with phosgene
at a temperature between 0 and 250C, in the presence of an acid amide as catalyst. This process has the disadvantage of requiring the separation of the catalyst from the reaction mixture at the end of the conversion, and the recovery of the catalyst is a complicated and expensive operation.

 In accordance with the process described in Federal Patent No. 1,668,109, a primary amine is reacted with phosgene in a mixture of an aqueous solution of a mineral base and of an organic solvent immiscible with water, at temperatures between -300C and + 350C.

 An improvement to this process is described in Federal German Patent No. 1,809,173. In accordance with this improvement, a very short contact time is used, that is to say that the aqueous phase is brought into contact with the organic phase, for a very short time.

 It is generally known in the literature that phosgene hydrolyzes rapidly in aqueous alkaline media (thus, for example, that phosgene is separated from waste gases by an aqueous alkali), this is why the two methods above give very low yields, or they require very expensive automatic control means.

 Several processes have been described for the preparation of diisocyanates and of various polyisocyanates.

U.S. Patent No. 3,923,732 describes the preparation of polyisocyanates by quenching the corresponding polyamines with phosgene in an inert solvent. The disadvantage of this process resides in the fact that polyamines can only be used as starting substances and that polyisocyanate mixtures are obtained as end products.

 In the processes which belong to the second main group, phosgene is not used for the preparation of isocyanates.

 In accordance with the process described in Federal German Patent No. 1,154,090, isocyanates are prepared by reacting a dialkylurea with diphenyl carbonate.

 U.S. Patent No. 2,423,448 describes a process for the preparation of alkyl isocyanates by reacting the corresponding alkyl hydroxy acids with thionyl chloride.

In accordance with the process described in the Patent
UNITED STATES OF AMERICA No. 3,017,420, isocyanates are prepared by reacting an alkaline cyanate with an alkyl halide in dimethylformamide as a solvent.

In accordance with the process described in the Patent
UNITED STATES OF AMERICA No. 3,076,007, ethylene carbonate is reacted with an amine, and the resulting carbamate is converted to the isocyanate at elevated temperatures.

 U.S. Patent No. 3,405,159 describes a process for the preparation of aliphatic isocyanates by reacting an aliphatic amine with carbon monoxide at a pressure above atmospheric pressure in the presence of a specially prepared palladium phosphate catalyst.

Another method which uses carbon monoxide as a reagent is described in the U.S. Patent
OF AMERICA No. 3,523,963. In this process, carbon monoxide is reacted with an aromatic nitro compound, at a pressure higher than atmospheric pressure, in the presence of a special catalyst.

In accordance with the process described in the Patent of
UNITED STATES OF AMERICA No. 3,493,596, isocyanates are prepared by oxidizing the corresponding organic isonitriles with mercury oxide, in the presence of a metallic porphyrin or a phthalocyanine as catalyst.

 US Patent No. 3,632,620 describes a process for the preparation of phenyl isocyanate by reacting diphenyl carbodiimide with carbon monoxide, under pressure above atmospheric pressure and at elevated temperatures , in the presence of a catalyst such as palladium, rhodium, etc.

 The majority of these latter methods, which do not use phosgene for the preparation of isocyanates, have the drawback of requiring special compounds which have complicated structures, as starting materials. Since these compounds are generally not available on the market, they must be prepared in a separate step, which requires additional investment and makes the process less competitive on an industrial scale. In addition, the use of phosgene cannot be eliminated in some of the above processes, since many of the starting materials can only be prepared from phosgene.

 The performance of the methods described above is generally unsatisfactory; thus, for example, when carbon monoxide is used as a reactant, the isocyanates can be prepared with a yield which does not exceed 30-35%.

The Applicant has now found that the isocyanates of general formula I can be prepared more easily and more economically than before, if the corresponding amine of general formula II is reacted below
R - (NH2) n (II) in which R and n are as defined above, with a compound of general formula III below
R'-O-CO-C1 (III) in which Ri represents a chloromethyl, dichloromethyl or trichloromethyl group, or with a mixture of these compounds, optionally in the presence of phosgene.

 The reaction can also be carried out at atmospheric pressure or under reduced pressure. It is however preferred to use a pressure higher than atmospheric pressure in the process. Depending on the nature of the starting amine, the reaction can be carried out at temperatures between -4O0C and + 3000C.

 According to a preferred embodiment of the invention, the reaction is carried out in the presence of a solvent or a mixture of solvents. If desired, or if necessary, a catalyst can be added to the mixture to accelerate the reaction.

 It is preferable to use a chlorinated hydrocarbon such as dichloromethane, chloroform, carbon tetrachloride, chlorobenzene, etc. as solvent.

 As catalyst usable in the process which is the subject of the present invention, mention should be made of activated carbon, metal chlorides (such as iron chloride, zinc chloride, etc.) on carbon active, as well as acid catalysts and mainly Lewis acids.

 The essential advantage of the process which is the subject of the present invention lies in the fact that the compounds of general formula III are easier to handle than phosgene.

 As we know, phosgene is a gas above 80C, its density by volume is low, its solubility in the solvents used decreases considerably as the temperature increases, and, moreover, phosgene dissociates at high temperatures.

Contrary to this, the compounds of general formula III are liquids, so that their densities in volume exceed those of phosgene by several orders of magnitude, their boiling points are close to the boiling points of the solvents used and their solubi lite even at high temperatures are much more favorable than that of phosgene. The compounds of general formula III are more thermally stable than phosgene. It is particularly advantageous for the compounds of general formula III to be good solvents for isocyanates, so that when a compound of general formula III is used as reagent, it is possible to prepare isocyanate solutions of concentrations higher than the usual concentrations of 17-17% w / w, which improves the economics of the process.

 As the compounds of general formula III are liquids, they can be introduced easily, using a simple liquid pump, into the reactors, which operate under a pressure higher than atmospheric pressure, and their concentration can be maintained easily to the value required in the reaction. These problems cannot be solved in practice when phosgene gas is used as the reagent.

 The compounds of general formula III have the additional advantage of having hydrolysis rates in alkaline medium significantly lower than that of phosgene, so that they can be used in a much wider pH range.

 The unreacted chlorine chloroformates, used in excess, can be thermally and / or catalytically decomposed at the end of the reaction, so that they can be easily separated from the crude isocyanate obtained as that final product.

 In known processes, which start from an amine and react it with phosgene under a pressure higher than atmospheric pressure, the reaction mixture is generally treated in such a way that the mixture is relaxed and the individual components are separated. 'one of the other at atmospheric pressure. The excess phosgene and gaseous hydrochloric acid are separated from the reaction medium generally by passing an inert gas through the crude isocyanate solution, then distilling the solution in order to separate the isocyanate from the solvent.

The Applicant has now found that gaseous hydrochloric acid and phosgene can be separated from the reaction medium much more easily if the pressure is not relieved and if a purge is not carried out
to the atmosphere during the first stage of the separation, or if the first stage of the separation is carried out at a pressure even higher than that used in the reaction, and if only the other stages of purification (and, if necessary, solvent recovery) are carried out at lower pressures.

 The Applicant has also surprisingly and unexpectedly found that if a mixture of monochloromethyl chloroformate and trichloromethyl chloroformate is reacted with an aromatic amine, diphenylmethane diisocyanate or polyphenylmethylene polyisocyanates are obtained as end products. These substances are essential materials, widely used in the plastics industry.

 The process which is the subject of the present invention can be carried out either batchwise or continuously, using equipment which is usually used in the chemical industry.

 It is preferred to carry out the reaction continuously, in a tubular pressure reactor, by introducing the reagents into the reactor using a liquid pump.

 It is also preferred to use in the reactor a packing having a large specific surface.

Can be used as a packing, for example, the activated carbon catalyst itself, or a support impregnated with a catalyst (iron chloride, zinc chloride, etc.).

 In addition to the foregoing provisions, the invention also comprises other provisions, which will emerge from the description which follows.

The invention will be better understood using the additional description which follows, which refers to examples of implementation of the method which is the subject of the present invention.
It should be understood, however, that these examples of implementation are given solely by way of illustration of the subject of the invention, of which they do not in any way constitute a limitation.

EXAMPLE 1
20 ml / minute of a 31.1% w / w solution of butylamine in carbon tetrachloride and 20.0 ml / minute of a dichloromethyl chloroformate solution of 52% w / w of tetrachloride are simultaneously introduced. carbon, in a tubular reactor which operates at 1800C and at a pressure of 50 atmospheres. The mixture leaving the reactor is continuously introduced into a gas / liquid separator connected to the reactor, in which 289 ml of a solution containing 24.2% w / w butyl isocyanate in carbon tetrachloride are separated from the substances. carbonated.

 After removing the solvent from the solution, 94 g of butyl isocyanate are obtained, so that the yield is 95%.

EXAMPLE 2
Is simultaneously introduced into a tubular reactor operating at 1300C and under a pressure of 5 atmospheres, 20.0 ml / minute of a 31.1% w / w solution of butylamine in carbon tetrachloride and 20.0 ml / minute of a 52% w / w solution of dichloromethyl chloroformate in carbon tetrachloride. 300 ml of a liquid reaction mixture, of gaseous substances, are separated in the gas / liquid separator, and the liquid is introduced into a column filled with activated carbon, at 150 ° C., under reduced pressure. The solution of butyl isocyanate in carbon tetrachloride which leaves the column is separated and purified in the usual manner, to obtain 92 g (94%) of butyl isocyanate.

EXAMPLE 3
Is simultaneously introduced into a tubular reactor operating at 1800C and under a pressure of 50 atmospheres, 20.0 ml / minute of a solution at 31.1% w / w of butylamine in carbon tetrachloride and 20.0 ml / minute of a 60.3 g w / w solution of trichloromethyl chioroformate in carbon tetrachloride. 280 ml of a carbon tetrachloride solution containing 24.4% w / w of butyl isocyanate, of the gaseous products are separated in the gas / liquid separator connected to the reactor. The solvent is separated from the dissolved product in the usual way, to obtain 93 g (94.5%) of butyl isocyanate.

EXAMPLE 4
20.0 ml / minute of a 31.1% w / w solution of butylamine solution in carbon tetrachloride and 20 are simultaneously introduced into a tubular reactor operating at 1200 ° C. and under a pressure of 5 atmospheres. 0 ml / minute of a 60.3% w / w solution of trichloromethyl chloroformate in carbon tetrachloride. 300 ml of a liquid reaction mixture and gaseous products are separated in the gas / liquid separator which operates continuously and the liquid mixture is introduced into a column filled with active carbon impregnated with zinc chloride. This column operates at 2000C at atmospheric pressure. The product is separated from the solution which leaves the column, to obtain 94 g (95%) of butyl isocyanate.

EXAMPLE 5
The procedure is as described in Example 4, with the difference that dichloromethane is used as solvent.

After separating the product from the solvent, 91 g (93.5%) of butyl isocyanate are obtained.

EXAMPLE 6
The procedure is as described in Example 4, except that chloroform is used as solvent. After separating the product from the solvent, 92 g (94%) of butyl isocyanate are obtained.

EXAMPLE 7
The procedure is as described in Example 4, except that chlorobenzene is used as solvent. After separating the product from the solvent, 94 g (95%) of butyl isocyanate are obtained.

EXAMPLE 8 The procedure is as described in Example 4, with the difference that o-dichlorobenzene is used as solvent.

After separating the product from the solvent, 94 g (95%) of butyl isocyanate are obtained.

EXAMPLE 9
Is simultaneously introduced into a tubular reactor operating at 1500C and at a pressure of 40 atmospheres, 20.0 ml / minute of a 31.1% w / w solution of butylamine in carbon tetrachloride and 20.0 ml / minute of a 41.1% w / w solution of monochloromethyl chloroformate in carbon tetrachloride. The reaction mixture which leaves the reactor is distilled under a pressure higher than atmospheric pressure
uric During this step, 310 ml of a solution containing 20.9% .weight / weight of hutyl isocyanate, gaseous substances, are separated. The product is separated from the solvent, then it is purified to obtain 91 g (92)) butyl cyanate.

EXAMPLE 10
Is simultaneously introduced into a tubular reactor operating at 1800C and under a pressure of 50 atmospheres, 20.0 ml / minute of a solution at 31.1% w / w of butylamine in carbon tetrachloride and 20.0 ml / minute of a carbon tetrachloride solution containing 30.3% w / w phosgene and 30.3% w / w trichloromethyl chloroformate.

The mixture which leaves the reactor is passed through a column filled with activated carbon; this column operates at 2000C and under a pressure of 5 atmospheres.

300 ml of a solution containing 24% w / w of butyl isocyanate, of gaseous substances, are then separated in the gas / liquid separator. The product is separated from the solvent, then it is 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 an aqueous solution at 10% w / w of sodium hydroxide is introduced into a round bottom flask d '' a capacity of 1000 ml, equipped with a stirrer, a thermometer, a bromine ball and a reflux condenser. The reaction mixture is stirred at -200C for two hours, then the aqueous phase is separated.

The organic phase is dried, evaporated and the vapors are passed through a column filled with activated carbon, which operates at 1200C. The solution of butyl isocyanate in carbon tetrachloride is then separated from the gaseous substances, the solvent is removed by distillation and the residue is purified in the usual manner to obtain 96.5 g (97.5%) of isocyanate. butyl.

EXAMPLE 12
The procedure is as described in Example 111, except that the aqueous sodium hydroxide solution is replaced by 270 ml of a 20% w / w aqueous solution of sodium carbonate. 96 g (97%) of butyl isocyanate are obtained.

EXAMPLE 13
73 g of butylamine, 198 g of trichloromethyl chloroformate and 200 ml of an aqueous solution at 10% w / w sodium hydroxide are introduced into a round-bottomed flask of 1000 ml capacity, equipped with an agitator. and a thermometer. The reaction mixture is stirred at -200C for three hours, after which 101 g of triethylamine is added thereto, and the mixture is stirred at -200C for two additional hours. The aqueous phase is separated and the organic phase is distilled.

96 g (96%) of butyl isocyanate are obtained.

EXAMPLE 14
198 g of trichloromethyl chloroformate, 73 g of butylamine, 200 ml of o-dichlorobenzene and 200 ml of a 10% w / w aqueous solution of sodium hydroxide are introduced into a 1000 ml round-bottom flask capacity, equipped with an agitator, a thermometer and a bromine ball. The reaction mixture is stirred at -200C for three hours, after which the organic phase is separated and dried.

 10.9 g of tetramethylammonium chloride are added to the organic phase and the mixture is boiled. When the evolution of phosgene and hydrochloric acid ceases, the solvent is removed from the crude reaction mixture, in order to obtain 96 g (96%) of butyl isocyanate.

EXAMPLE 15
20.0 ml / minute of a 10.23% w / w solution of methylamine in carbon tetrachloride and 20.0 ml / min are simultaneously introduced into a tubular reactor operating at 1600 ° C. and at a pressure of 50 atmospheres. of a 60.3% w / w solution of trichloromethyl chloroformate in carbon tetrachloride. The product is separated from the resulting mixture, in the usual manner, then purified to obtain 51.3 g (90%) of methyl isocyanate.

EXAMPLE 16
Is simultaneously introduced into a tubular reactor operating at 1800C and under a pressure of 50 atmospheres, 20.0 ml / minute of a 39.2% w / w solution of aniline in carbon tetrachloride and 20.0 ml / minute of a 60.3% w / w solution of trichloromethyl chloroformate in carbon tetrachloride. The product is separated from the crude reaction mixture in the usual manner, then purified to obtain 133.4 g (96%) of phenyl isocyanate.

EXAMPLE 17
20.0 ml / minute of a 44.2% w / w solution of m-chloroaniline in carbon tetrachloride and 20.0 ml are introduced simultaneously into a tubular reactor operating at 1800C and under a pressure of 60 atmospheres / minute of a 60.3% w / w solution of trichloromethyl chloroformate in car one tetrachloride. 310 ml of a carbon tetrachloride solution containing 33.7% w / w of m-chiorophenyl isocyanate, of gaseous substances, are separated in the gas / liquid separator. The solvent is then removed from the lance, to obtain 142.3 g (93%) of m-chlorophenyl isocyanate.

EXAMPLE 18
Is simultaneously introduced into a tubular reactor operating at 1700C and under a pressure of 50 atmospheres, 20.0 ml / minute of a 40% w / w solution of cyclohexylamine in carbon tetrachloride and 20.0 ml / minute of a 60.3% w / w solution of trichloromethyl chloroformiatede in carbon tetrachloride. 320 ml of a carbon tetrachloride solution containing 33% w / w cyclohexyl isocyanate, gaseous substances, are separated in the gas / liquid separator. The solvent is then removed from the mixture to obtain 136 g (94%) of cyclohexyl isocyanate.

EXAMPLE 19
Is simultaneously introduced into a tubular reactor operating at 1400C and under a pressure of 50 atmospheres, 20.0 ml / minute of a 42% w / w solution of hexamethylenediamine in carbon tetrachloride and 40.0 ml / min of '' a 60.3% w / w solution of trichloromethyl chloroformate in carbon tetrachloride. 430 ml of a carbon tetrachloride solution containing 28.5% w / w hexamethylene diisocyanate, a gaseous by-product, are separated. The solvent is removed in the usual manner, to obtain 156 g (94%) of hexamethylene diisocyanate.

EXAMPLE 20
Is simultaneously introduced into a tubular reactor operating at 1900C and under a pressure of 50 W-mospheres, 20.0 ml / minute of a solution at 45% ids / weight of toluylenediamine (containing 65% weight / weight of isomer 2 , 4- and 35% w / w of the 2,6-) isomer in carbon tetrachloride and 40.0 ml / minute of a 60.3% w / w solution of trichlomethyl chloroformate in tetrachloride carbon. 440 ml of a solution containing 29% w / w toluylene diisocyanate, gaseous by-products, are separated in the gas / liquid separator. The solvent is removed in the usual manner, to obtain 165 g (95%) of toluylene diisocyanate.

EXAMPLE 21
Is simultaneously introduced into a tubular reactor operating at 1500C and under a pressure of 5 atmospheres, 10.0 ml / minute (7.3 g / minute) of butylamine and 30.0 ml / minute of trichloromethyl chloroformate. The mixture which leaves the reactor is introduced into a column filled with activated carbon which operates at 1800C and under a pressure of 5 atmospheres. The gaseous substances are then removed in the gas / liquid separator and the crude product is distilled. 91 g (92%) of butyl isocyanate are obtained.

EXAMPLE 22
Is simultaneously introduced into a tubular reactor operating at 1300C and under a pressure of 50 atmospheres, 20.0 ml / minute of a 40% w / w solution of 4,4'-diphenylmethanediamine in carbon tetrachloride and 20.0 ml / minute of a 60.3% w / w solution of trichloromethyl chloroformate in carbon tetrachloride. 320 ml of a solution containing 16.6% w / w of 4,4'-diphenylmethane diisocyanate are separated from the gaseous by-products. The solvent is removed from the solution in the usual manner and the product is purified to obtain 70 g (74%) of the diisocyanate.

EXAMPLE 23
20.0 ml / minute of a 39.16% w / w solution of aniline in carbon tetrachloride and 20.0 ml / minute of 41.4% w / w solution of chloroformate are simultaneously introduced. of monochloromethyl in carbon tetrachloride, in a tubular reactor which operates at 1300C and under a pressure of 50 atmospheres. The gaseous by-products are separated and the resulting solution is distilled, which contains phenyl isocyanate and 4,49 diphenylmethane diisocyanate. 12 g (9%) of phenyl isocyanate and 67 g (89%) of 4,4'-diphenylmethane diisocyanate are obtained.

EXAMPLE 24
Is simultaneously introduced into a tubular reactor operating at 1300C and under a pressure of 50 aLusphères, 20.0 ml / minute of a solution at 39.16% w / w aniline in carbon tetrachloride and 20 .ml / minute d '' a carbon tetrachloride solution containing 20.52% w / w monochloromethyl chloroformate and 30.15% w / w trichloromethyl chloroformate. The gaseous by-products are removed in the gas / liquid separator, then the solvent is removed from the resulting solution of phenyl isocyanate and 4,4'-diphenylmethane diisocyanate in carbon tetra chloride. The residue is purified to the usual way, to obtain 14 g (10%) of phenyl isocyanate -and 64.7 g (85%) of 4,4'-diphenylmethane diisocyanate.

EXAMPLE 25
Is simultaneously introduced into a tubular reactor operating at 1700C t at a pressure of 50 atmospheres, 20.0 ml / minute of a carbon tetrachloride solutin containing 12.1% weight / weight of butylamine and 36% weight / weight of aniline and 22.0 ml / minute of a solution containing 69% w / w of trichloromethyl chloroformate and 29% w / w of monochloromethyl chloroformate. The gaseous by-products are removed in the gas / liquid separator, to obtain a solution which contains butyl isocyanate, phenyl isocyanate and 4,4'diphenylmethane diisocyanate.

 The 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 92 g (86%) of 4,4'-diphenylmethane diisocyanate are obtained.

EXAMPLE 26
Is simultaneously introduced into a tubular reactor operating at 1500C and under a pressure of 5 atmospheres, 20.0 ml / minute of a 31.1% w / w solution of butylamine in carbon tetrachloride and 20.0 nil / minute of a 60.6% w / w solution of trichloromethyl chloroformate in crone tetrachloride. The mixture which leaves the reactor is passed through a column filled with activated carbon at various temperatures, which operates at 1800 ° C. under a pressure of 5 atmospheres. The mixture is then translated into a gas / liquid separator qu; sanctions at 800C and under a pressure of 5 atmospheres, then 73 g of gaseous hydrochloric acid, pure, anhydrous, are removed from the separator every 10 minutes. The expanded liquid phase is distilled at atmospheric pressure, and the carbon tetrachloride solution containing phosgene is recycled to the column filled with active carbon * The product is purified to obtain 93 g (94 t) of butyl isocyanate.

EXAMPLE 27
The procedure is as described in Example 26, with the difference that o-dichloroboenzene is used as solvent. 92 g (93%) of butyl isocyanate are obtained.

EXAMPLE 28
The procedure is as described in Example 26, with the difference that the reactants are introduced directly into the column filled with activated carbon, which operates at 1800C and under a pressure of 5 atmospheres. 92.5 g (93.5%) of butyl isocyanate are obtained.

EXAMPLE 29
The procedure is as described in Example 26, with the difference that 20.0 ml / minute of a 31% w / w solution of butylamine in carbon tetrachloride, 20.0 ml / minute are simultaneously introduced. of a 30.3% w / w solution of trichloromethyl chloroformate in carbon tetrachloride and 20.0 ml / minute of a 30.4% w / w solution of phosgene in carbon tetrachloride in tubular reactor which operates at 1500C and under a pressure of 5 atmospheres.

After one hour, the introduction of the phosgene solution is stopped and the phosgene in carbon tetrachloride solution which is obtained during distillation at atmospheric pressure is recirculated in the reactor. 94 g (95%) of butyl isocyanate are obtained.

EXAMPLE 30
20.0 ml / minute of a 10.23% w / w solution of methylamine in carbon tetrachloride and 20.0 ml / minute of a 60.3% w / w solution of trichloromethyl cloroformate are introduced. in carbon tetrachloride, in a tubular reactor which operates at 1500C and under a pressure of 5 atmospheres.

The mixture which leaves the reactor is introduced into a reactor filled with activated carbon, which operates at 1800C and under a pressure of 5 atmospheres. The mixture is then introduced into a separator which operates at 800C under a pressure of 5 atmospheres, and 22 g (6.6 liters) of anhydrous hydrochloric acid gas are removed from the separator. The mixture is then expanded and distilled at atmospheric pressure. The carbon tetrachloride solution containing phosgene is recycled to the reactor filled with activated carbon and the product is purified.

82.55 g of a product are obtained, which consists of 70% w / w methylcarbamoyl chloride and 30% w / w methyl isocyanate, so that the conversion was carried out at 97.6%.

EXAMPLE 31
20.0 ml / minute of a 43% w / w solution of hexylamine in carbon tetrachloride and 20.0 ml / min are simultaneously introduced into a tubular reactor which operates at 1800C and at a pressure of 50 atmospheres of a 60.3% w / w solution of trichloromethyl chloroformate in carbon tetrachloride. 300 ml of a mixture of n-hexyl isocyanate and carbon tetrachloride are obtained, after having separated the liquid from the gaseous substances, in the liquid / gas separator. This mixture is distilled to obtain 101.9 g (91%) of n-hexyl isocyanate.

EXAMPLE 32
20.0 ml / minute of a 23.4% w / w solution of isopropylamine in carbon tetrachloride and 20.0 ml / minute of a 60.3% w / w solution of chloroformate are simultaneously introduced. of trichlomethyl in carbon tetrachloride, in a tubular reactor filled with granulated activated carbon, and which operates at 2200C and under a pressure of 50 atmospheres.

The mixture which leaves the reactor is continuously introduced into a gas / liquid separator in which 260 ml of a carbon tetrachloride solution containing isopropyl isocyanate are obtained. This solution is distilled to obtain 68.4 g (94%) of isopropyl isocyanate.

EXAMPLE
A solution of 44.6 g of 4-chloro-4'-amino-biphenyl in 200 ml is continuously introduced, over the course of 10 minutes, into a tubular reactor which operates at 1200C and under a pressure of 5 atmospheres of dichloromethane and 200 ml of a 20% w / w solution of trichloromethyl chloroformate in dichloromethane.

The mixture leaving the reactor is subjected to a separation process and the 350 ml of the solution obtained are distilled. 23 g (90%) of 4-chloro-biphenyl 4 '-isocyanate are obtained.

EXAMPLE 34
20.0 ml / minute of a 37.8% w / w solution of p-toluidine in chlorobenzene and 20.0 ml / ml are continuously introduced into a tubular reactor filled with active charcoal and operating at 1800 ° C. minute of a 41% w / w solution of trichioromethyl chloroformate in chlorobenzene. The mixture which leaves the reactor is introduced into a gas / liquid separator and the 360 ml of liquid which are separated are distilled.

98.6 g (93 t) of 4-niethylphenyl isocyanate are obtained.

EXAMPLE 35
20.0 ml / minute of a 46% w / w solution of 4-ethylaniline in o-dichlorobenzene are introduced simultaneously and continuously into a tubular reactor which operates at 1500 ° C. and under a pressure of 5 atmospheres. 20.0 ml / minute of a 60.3% w / w solution of trichloromethyl chloroformate in o-dichlorobenzene. The mixture which leaves the reactor is expanded and introduced 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 / minute of a 22.9% w / w solution of p-anisidine in carbon tetrachloride and 20 is introduced simultaneously and continuously into a reactor which operates at 1800 ° C. and under a pressure of 50 atmospheres. , 0 ml / minute of a 60% w / w solution of trichloromethyl chloroformate in carbon tetrachloride. 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 / minute of a 43.2% w / w solution of m-phenylenediamine in chlorobenzene and 30 is introduced simultaneously and continuously into a tubular reactor which operates at 1500 ° C. and under a pressure of 5 atmospheres. 0 ml / minute of a 65% w / w solution of trichloromethyl chloroformate in o-dichlorobenzene. 460 ml of a liquid are separated in the gas / liquid separator, then the liquid is distilled to obtain 106 g (91.6%) of m-phenylene diisocyanate.

EXAMPLE 38
400 ml of o-dichlorobenzene and 130 ml of trichloromethyl chloroformate are introduced into a round-bottomed flask of 2500 ml capacity, equipped with an agitator, a reflux condenser and a thermometer. 1000 ml of a 21% w / w solution of 4,4'-diaminobenzyl in o-dichlorobenzene are then added to this mixture, with stirring, after which the temperature of the reaction mixture rises to- above 1000C. The resulting mixture is stirred at 1300C for 4 hours, then it is treated 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 chloroformate are introduced into a round-bottom flask of 2500 ml capacity, equipped with an agitator, a reflux condenser and a thermometer. Jnoo ml of a 27% w / w solution of methylenebis (o-chloroaniline) in 1 'o-dichlorobenzene is added to the mixture, with stirring, after which the temperature of the reaction mixture rises above 1000C. . At the end of the addition, the mixture is stirred at 1300C for 4 hours, then distilled.

230 g (90%) of 4,4'-diisocyanate of 3,3'dichloro-diphenylmethane are obtained.

EXAMPLE 40
210 g of sodium carbonate heated to incandescent and 100 ml of o-dichlorobenzene are introduced into a round bottom flask with a capacity of 2500 ml, equipped with an agitator and a thermometer. 100 nil of a solution at 30 ç weight / weight of trichloromethyl chlorofonnate in o-dichlorobenzene are added to this mixture, with constant stirring and intense cooling (at −400 ° C.), over the space of one hour. The reaction mixture is then stirred for another hour at 0-200C, after which the mixture is filtered and the filtrate is distilled to obtain 26 g ('92 ù) of methyl isocyanate.

EXAMPLE 41
The procedure is as described in Example 4, with the difference that active carbon impregnated with 0.5% w / w ferric chloride is used as catalyst.

91 g (92%) of butyl isocyanate are obtained.

EXAMPLE 42
The procedure is as described in Example 4, except that active carbon impregnated with 0.5% w / w aluminum chloride is used as catalyst. 89 g (90%) of butyl isocyanate are obtained.

EXAMPLE 43
The procedure is as described in Example 15, except that the reactor operates at 2500C under a pressure of 5 atmospheres. 53 g (93%) of methyl isocyanate are obtained.

EXAMPLE 44
Is introduced simultaneously and continuously, through a preheater, into a tubular reactor filled with activated carbon and which operates at 3000C, 20.0 ml / minute of a solution at 31.1 'weight / weight of butylamine in o-dichlorobenzene and 20.0 ml / minute of a 60% w / w solution of trichloromethyl chloroformate.

The mixture which leaves the reactor is passed through a separator and the liquid which separates is distilled. 83 g (85%) of butyl isocyanate are obtained.

EXAMPLE 45
Is introduced simultaneously and continuously using a liquid pump under high pressure, into a reactor which operates at 1800C and under a pressure of 200 atmospheres, 20.0 ml / minute of a 36.8% solution weight / weight of benzylamine in o-dichlorobenzene and 20.0 ml / minute of a 30% weight / weight solution of trichloromethyl chloroformate. The mixture which leaves the reactor is expanded, it is passed through a gas / liquid separator and the liquid which separates is distilled. 92 g (86%) of benzyl isocyanate are obtained.

EXAMPLE 46
Simultaneously and continuously introduced into a reactor which operates at 1200C and under a pressure of 0.2 atmosphere, 20.0 ml / minute of a 33.6% w / w solution of aniline in o -dichlorobenzene and 20.0 ml / minute of a 60.5% w / w solution of trichloromethyl chloroformate in o-dichlorobenzene. The product is continuously removed from the reactor by distillation and the crude product is purified by fractional distillation. 120 g (86%) of phenyl isocyanate are obtained.

 As is apparent from the above, the invention is in no way limited to those of its modes of implementation, embodiment and application which have just been described more explicitly; on the contrary, it embraces all the variants which may come to the mind of the technician in the matter, without departing from the framework, or the scope, of the present invention.

Claims (1)

 CLAIM  Process for the preparation of isocyanic acid esters of general formula I below  R - (NCO) n (I) in which: n is equal to 1 and R represents a straight or branched chain alkyl group  in C1 to C10, a benzyl, cyclohexyl, phenyl group,  halophenyl, methylphenyl or methoxyphenyl, or n is 2 and R represents a hexamethylene, phenylene group,  methylenebis (phenylene), ethylenebis (phenylene) or methylenebis (halophenylene), from amines of general formula II below  R - (NH2) n (II) in which R and n are as defined above, at a temperature between -400C and + 3000C, under a pressure between 0.2 and 200 atmospheres, possibly in the presence of '' a solvent constituted by a chlorinated hydrocarbon or by a mixture of solvents containing a chlorinated hydrocarbon and / or in the presence of an activated carbon catalyst optionally impregnated with 0.1 to 5% w / w of a metal halide and / or optionally in the presence of a mineral base or a tertiary amine, which process is characterized in that one or two amines of general formula II above are reacted with a compound of general formula III below: :  R'-O-CO-Cl (III) in which R 'represents a chloroniethyl, dichloromethyl or trichloromethyl group, or with a mixture of such compounds, introduced into the reaction mixture in the liquid state.