NO156407B - MIXTURES OF HALOGENATED AROMATIC ISOCYANATES WITH DIPHENYLMETAN STRUCTURE. - Google Patents

Abstract

1. Halogenated aromatic isocyanates having an unsymmetrical methyldiphenylmethane or polymethyldiphenylmethane structure of formula : see diagramm : EP0092454,P7,F1 where see diagramm : EP0092454,P7,F2 One of the groups R1 , R2 , R3 , R4 being an NCO group and the others being hydrogen atoms, depending on the values and positions of (X)Y , and (CH3 )Z-1 .

Description

The present invention relates to mixtures of new halogen

pea aromatic isocyanates whose hydrocarbon skeletons have unsymmetrical methyldiphenylmethane or polymethyldiphenyl

methane structure, substituted with one or more halogen atoms.

These mixtures are useful in the production of polyurea-

tanners and especially fireproof foams.

The isocyanates with aromatic hydrocarbon diphenylmethane structure

is already synthesized industrially; it concerns derivatives of diphenylmethane diisocyanate (MDI), commercialized in impure form, i.e. in the form of a mixture of diisocyanates and polyisocyanates, or in pure form after distillation.

In this case, the mixture of isomers which is essentially

contains 4,4'-diphenylmethane diisocyanate solid at water

equal temperature and has a melting point between 30 and 40°C.

The synthesis of polyurethanes is carried out by reacting iso-

the cyanates with polyols. Fireproof grades can be given poly-

more by using halogenated polyols and/or halogenated

nerdy additives. The isocyanates according to the invention have in themselves one or more halogen atoms in the aromatic rings and are thus particularly interesting for the production of polyurethanes with a good resistance to fire.

The isocyanate structures in the mixtures according to the invention

corresponds to the general following formula:

where X = Cl, Br

n = 1, 2

x = 0, 1, 2

y = 1, 2

z = 1, 2, and

one of the groups R^, , R3, R4 is an NCO group and

the others are hydrogen atoms, the amount of NCO in the mixtures being from 4-6.7 equivalents per kg.

The isocyanates are synthesized in three successive reaction stages from a mixture of halogenated aromatic hydrocarbons: a nitration, a hydrogenation and a phosgenation.

The halogenated hydrocarbon structures are produced by Friedel-Crafts condensation in the presence of catalysts which are generally used in these reactions for halogenated benzyl chloride, optionally substituted with a methyl group, with optionally halogenated toluene or xylene used in excess. Various mixtures of halogenated aromatic isomers are thus obtained. Depending on the operating conditions and by regulating the excess of any halogenated toluene or xylene, condensation products with two aromatic nuclei are mainly formed, but trinuclear products can also be formed and all correspond to the general formula:

where X = Cl or Br,

x = 0 to 2,

y = 1 or 2,

z = 1 or 2,

n = 1 or 2.

It is possible to separate the dinuclear isomers from the reaction medium by distillation, but it may be economically advantageous to carry out the synthesis of the isocyanates in the impure reaction mixture. In practice, the reaction product contains between 70 and 95% diaryl condensates.

Among the aromatic hydrocarbons used as a basis for the invention, the isomers of (chlorobenzo)toluene can be synthesized in different ways, but it is preferred to react chlorobenzyl chloride, obtained by controlled photochemical chlorination of monochlorotoluene, with toluene in the presence of a catalyst used in such reactions; thus, in this case, toluene is the only hydrocarbon feedstock. The isomers of (bromobenzyl)toluene are synthesized in the same way from bromobenzyl chloride.

The synthesis of other aromatic hydrocarbons from (polychloro)-methyldiphenylmethane or (polychloro)(polymethyl)-diphenylmethane is known and is described in FR-PS 2,432,199 and its supplement 2,449,954.

The two stages that make up the nitration and then the hydrogenation give amines that correspond to the isocyanate structures obtained according to the invention:

where X = Cl, Br,

n = 1, 2

x = 0, 1, 2,

y = 1, 2,

z = 1, 2 and

one of the groups R'^, R^f R<*>3' R<*>4 is an NF^ group, while the others are hydrogen atoms.

For nitration, a mixture of nitric acid is used

and sulfuric acid with a concentration of at least 85% by weight, preferably at least 95% by weight. The nitric acid can be used in stoichiometric amounts in relation to the aromatic compound. Thus, 1 mole of acid is used for each aromatic nucleus to be nitrated. However, it is advantageous to work in the presence of an excess of nitric acid up to 20% relative to the stoichiometry. The sulfuric acid can be used in an equimolar amount in relation to the nitric acid, but can also be used in excess or deficit. The nitration reaction is carried out at temperatures between 0°C and the boiling temperature of the mixture, generally between 0°C and 50°C, the aromatic compound preferably being dissolved in a solvent such as methylene chloride. The upper organic phase is then separated from the acids, neutralized and evaporated to dryness. It is advisable to work under a nitrogen atmosphere in a reactor equipped with means for efficient stirring and temperature control.

The crude mixture obtained can be hydrogenated as such. However, when the diaryl compounds are to be distilled, it is possible to isolate the main isomers from these by dissolving the mixture in a minimal amount of methylene chloride and to precipitate them using ether or methanol.

The second step is the hydrogenation of the nitro derivatives to

the corresponding amines; there may be chemical, but it is preferred to work under hydrogen pressure in a pressure-resistant reactor equipped with agitators and with conventional control and regulation means in the presence of a catalyst based on nickel, palladium, platinum, ruthenium and the like. In this case, a hydrogenation reactor is used which can work under pressure of up to 100 bar. The reaction can be carried out with a solvent at a temperature

in which the nitro derivative is melted or in conventional hydrogenation solutions such as alcohols, dioxane, ethylene glycol ethers and the like.

Preferably, a catalyst consisting of palladium deposited on a support is used in amounts of between 1 and 10%, which makes it possible to work at temperatures up to between 30 and 100°C and under pressure from 20-50 bar. The molar ratio between dinitro derivative and palladium is not determined, but is preferably between 200 and 3000. After reaction and filtration of the catalyst, any solvent is evaporated off and the obtained mixture of diamine isomers can be used as such or distilled.

The third stage makes use of conventional phosgenation techniques in a reactor equipped with agitators and surrounded by a cooler. The amine mixture is placed in an aromatic chlorinated solvent such as monochlorobenzene or orthodichlorobenzene containing the required amount of phosgene, but the temperature is kept at 0°C. The suspension is then progressively heated; the reaction mixture is homogenized at between 45 and 60°C. The temperature is slowly raised to the boiling point of the mixture and then the solvent is distilled off so that the isocyanates formed can be recovered. These can be distilled if they are sufficiently volatile or used as is. The mixture of amines is preferably placed in the solvent in a concentration of 5-20% and the phosgene is introduced in a stoichiometric amount or in a slight excess. Another method consists in the simultaneous introduction into the reactor of a solution, heated to over 100°C,

of the amines in a chlorinated aromatic solvent and a stream of phosgene dissolved in the same solvent heated to 120°C or above. The reaction is practically immediate.

The isocyanates thus obtained can, according to known methods, give polyurethanes with good properties, especially better ones

flame resistance.

, : The nitrogen derivatives and amines have been analyzed by gas chromatography. As for the nitration products, a 3.17 mm stainless steel column of 1.5 m length was used, packed with a commercially available "Chromosorb W" 80-100 mesh H.P. support, impregnated with 2% XE.60 silicone phase, whether or not commercially available; during the injection the column has a temperature of 100°C and after 5 minutes it is heated to 220°C. Also used is a Pyrex column with inner and outer diameters of 3 and 6 mm and a length of 2 m, filled with SP 2250 phase impregnated in an amount of 3% on a "Supelcoport" 100-120 mesh carrier of commercial available type on which linear temperature programming was carried out with 4°C per minute from 180°C to 280°C.

In the case of the amines, a 2 meter glass column filled with "Chromosorb" W.N.A.W. was used. 60-80 mesh of a commercially available type, impregnated with 5% KOH and 5% "Apiézon N" and the work was carried out isothermally at 220°C.

The nitration or hydrogenation products were identified by combining gas chromatography with mass spectrometry.

In some cases, the major isomer was isolated by trapping them by gas and/or liquid chromatography and they were identified by nuclear magnetic resonance of 13 C and <1>H.

The content of isocyanate functions was assessed by chemical titration with dibutylamine.

EXAMPLE 1

22 g or 0.1 mol .. distilled isomers of (chlorobenzyl)-toluene, prepared by Friedel-Crafts condensation of chlorobenzyl chloride with toluene, are dissolved in 40 ml of methylene chloride. While the temperature is kept at approx. 10°C with stirring, a mixture of 15.5 g of 98.7% nitric acid and 20 ml of 96% sulfuric acid is poured in over the course of one hour. So soon all

mixture is added, the resulting mixture is refluxed for 3 hours and 30 minutes with further stirring and then the whole is cooled. Two phases stand out, a lower acidic phase and an upper organic phase. The organic phase is extracted and the acids are washed twice with methylene chloride. The various organic fractions are combined, neutralized on potassium carbonate and the solvent is evaporated. Thus, 30.5 g of a viscous light yellow product is recovered; when this is analyzed by gas chromatography coupled with mass spectrometry, isomers of (nitrochlorobenzyl) - nitrotoluene are detected. The main component of the mixture is 3,3'-dinitro-4-methyl-4'-chloro-diphenylmethane of the formula: 20 g of this mixture of isomers is placed in the autoclave described above and 200 ml of methanol and 0.2 g of catalyst consisting of 5% palladium on charcoal is added. After the reactor has been flushed with nitrogen, 40 bar hydrogen is introduced and the reactor is heated to 60°C with stirring. After 3 hours and 20 minutes of reaction time, the reactor is allowed to cool and depressurize and the reaction mixture is recovered and filtered to remove catalyst. The methanol is evaporated to dryness and 16 g of a very thick dark-brown product is obtained. Analysis by gas chromatograph coupled with mass spectrometry shows that it contains isomers of (aminochlorobenzyl)-aminotoluene. 12 g of these are added to a solution of 29 g of phosgene in 100 ml of orthodichlorobenzene, while the temperature is kept at 0°C. The whole is then allowed to return to ambient temperature, then heated to 45°C for one hour, to 60°C for one hour and to 100°C for h hour. Finally, by passing through a stream of nitrogen, the temperature is brought to 140°C for 2 hours to remove excess phosgene and formed hydrochloric acid. The solvent is then distilled off in vacuum after the solution has been filtered, after which 13 g of a mixture of isocyanates with an NCO content corresponding to 5 equivalents per kg, whose distillation gives a yellow liquid consisting of a mixture of chlorobenzyltoluene diisocyanates with NCO content: 2 functions per moles, corresponding to the general formula given above,

where X = Cl, x = 0, y = 1, z = 1, n = 1.

EXAMPLE 2

138 g of the mixture of isomers of (chlorobenzyl)-toluenes as prepared in example 1 are dissolved in 240 ml of methylene chloride.

Using the same procedure as in example 1, a mixture of 93 g of 98.3% nitric acid and 120 ml of 96% sulfuric acid is added. The mixture is boiled under reflux in

4 hours and 30 minutes, then cooled, after which the organic phase is extracted. The solvent is evaporated to the limit of the solubility of the dinitration isomers, after which methanol is added and in this way a white solid precipitates which is filtered off and washed with methanol. After drying, 21.5 g of a white solid with a melting point of 183°C are obtained. Analysis by gas chromatography clearly shows the predominant presence of an isomer of dinitro(chlorobenzyl)toluene which is identified by nuclear magnetic resonance to 3,3'-dinitro-1-methyl-4<1->chloro-diphenylmethane:

The methanolic filtrate contains the remainder of this predominant isomer and the other dinitration isomers.

20 g of the precipitate is hydrogenated using the procedure described in example 2 with 200 ml of methanol and 0.4 g of 5% Pd on charcoal. After evaporation of the methanol, 16 g of a paste-like dark brown product is obtained, essentially consisting of

of 3,3'-diamino-4-methyl-4<1->chloro-diphenylmethane.

The phosgenation is then carried out using the procedure as described in example 1 on 10 g of this mixture of amines. thus 12 g of the paste-like brown product is recovered (NCO content: 6 equivalents per kg) which, on distillation under a reduced pressure of 2 mm Hg, gives a paste-like light brown solid completely melting at 64°C and containing about. 66% 4-methyl-4<1->chloro-diphenylmethane-3,3'-diisocyanate (NCO content: 2 equivalents per mol).

EXAMPLE 3

25.1 g or 0.1 mol of a mixture of isomers of (chloro-benzyl) chlorotoluene, synthesized from chlorotoluenes as described in FR-PS 2,432,199, is placed in a stirred 250 ml reactor under a nitrogen atmosphere. 40 ml of methylene chloride is added and, over the course of an hour and between 5 and 15°C, a mixture of 13.5 g of 98.3% nitric acid and 20 ml of 96% sulfuric acid is introduced. The mixture is then heated to 42°C for 3 hours 30 minutes, then cooled and decanted. The upper organic phase is recovered and the lower acidic phase is washed with methylene chloride. The organic extracts obtained from stripping and washing are mixed, neutralized with potassium carbonate and dried with sodium sulfate. A clear, orange-coloured solution is obtained which is evaporated to dryness. In this way, 32 g of very viscous orange-coloured liquid corresponding to a mixture of isomers of (nitrochlorobenzyl)-nitrotoluene is obtained. The main ingredients in the mixture are 2,3'-dinitro-5-methyl-4,2'-dichloro-diphenylmethane with the formula:

2,3'-dinitro-5-methyl-4,4<1->dichloro-diphenylmethane with the formula: 3,3'-dinitro-4-methyl-5,4'-dichloro-diphenylmethane with the formula: 3,3' -dinitro-5-methyl-4,4'-dichloro-diphenylmethane with the formula: 30 g of this liquid is hydrogenated in a stainless steel autoclave equipped with magnetic stirrers in the presence of 0.3 g of 5% palladium on charcoal (ENGELHARD) as catalyst and 300 ml of methanol. The reaction takes 1 hour and 30 minutes under a pressure of 35 bar and at 50°C, then the reactor is emptied and after evaporation of the solvent, 24.5 g of an orange solid is obtained which melts at 45-47°C. Analysis by gas chromatography shows that it consists of isomers of the expected diamine corresponding to the general formula according to the invention, in which X = Cl,

x = 1, y = 1, z = 1, n = 1.

The mixture of amines is phosgenerated using the methods described above. After reaction and evaporation of the solvent, 29 g of an impure mixture of isocyanates are obtained (NCO content: 5.2 equivalents per kg) which, after distillation under a reduced pressure of 2 mm Hg, gives a viscous yellow liquid consisting of isomers of the expected isocyanates (NCO content: 2 functions per mol).

EXAMPLE 4

27.9 g or 0.1 mol of isomers of (chloro-paramethylbenzyl)-chloroparaxylene, prepared by the Friedel-Crafts condensation of chloroparamethylbenzyl chloride by reacting this with chloroparaxylene, are dissolved in 40 ml of methylene chloride. The temperature is kept at approx. 10°C, the mixture is stirred and, over the course of one hour, a mixture of 15.5 g of 98.7% nitric acid and 20 ml of 96% sulfuric acid is added. The mixture is refluxed for 3 hours and 30 minutes and then cooled. The upper organic phase is recovered and the acids are washed with methylene chloride. The organic phases are combined and treated with potassium carbonate, after which the solvent is evaporated. Thus, 36 g of dinitration products are recovered corresponding to the following formula:

20 g of this mixture is hydrogenated using the method described in example 1, with 0.2 l of methanol and 0.4 g of 5% Pd/charcoal as catalyst. After the methanol has been distilled off, 16.5 g of reddish crystalline product with a melting point of 73°C are recovered, essentially corresponding isomers of (amino-chloro-paramethyl-benzyl)-amino-chloro-para-xylene. 15 g of this mixture is phosgenerated using the method described in example 1. After filtering and distilling orthodichlorobenzene, 15 g of an impure brown product with a melting point of 49°C and containing a mixture of the expected isocyanates (NCO content : 4.4 equiv ter per kg), corresponding to the general formula given in the description, where X = Cl, x = 1, y = 1, z = 2, n = 1.

EXAMPLE 5

The Friedel-Crafts condensation of chlorobenzyl chloride with toluene gives, in addition to the diaryl compounds treated in Example 1, condensation products with three aromatic nuclei. Compounds with two nuclei corresponding to the isomers of (chlorobenzyl)toluene can be separated by distillation,

while the triaryl derivatives remain at the bottom of the column.

34 g of a mixture consisting essentially of isomers of bis-(chlorobenzyl)toluene is nitrated according to the procedure described in example 1 using 23.2 g of 98.7% nitric acid and 20.2 ml 96 % sulfuric acid. At the end of the reaction, 48 g of a very viscous reddish product are recovered, of which 20 g are hydrogenated by placing them in an autoclave with 200 ml of methanol and 0.6 g of 5% palladium on charcoal (ENGELHARD) as a catalyst under pressure of 40 bar hydrogen and at 65°C. In this way, 14.5 g of an impure mixture of amines with a melting point of 12 7°C are obtained, which is reacted with 33 g of phosgene as described in example 1. After filtering the reaction mixture with orthodichlorobenzene, the solvent is evaporated and 13 g of an impure product is recovered which melts at 124°C and contains isocyanate isomers according to the general formula according to the invention, where X = Cl, x = O, y = 1, z=logn=2 (NCO content: 4.4 functions per kg) .

EXAMPLE 6

By using the method described in example 1, an impure Friedel-Crafts condensation mixture of chlorobenzene chloride and toluene containing 85% by weight diaryl derivatives and 15% essentially triaryl derivatives is nitrated with 18.7 g of 98.7% nitric acid and 21.5 ml of 96% sulfuric acid. After reaction, 32 g of a semi-solid, semi-viscous nitration product are obtained, of which 20 g are hydrogenated in 200 ml of methanol in the presence of 0.8 g of 5% palladium-on-charcoal

(ENGELHARD) under a hydrogen pressure of 40 bar and at 65°C. After reaction and evaporation of the methanol, 15 g are collected

of an impure mixture of amines which is reacted with 36.2 g of phosgene as described in example 1. After filtering the reaction solution with orthodichlorobenzene, the solvent is evaporated and 13.8 g of a paste-like brown product is recovered and this is allowed to hard cool. Examination of the product by mass spectrometry shows that it contains isomers of diarylisocyanates and triarylisocyanates corresponding to the rough formula in the description where X = Cl, x = 0, y=l, z=logn=log2. This mixture of isocyanates which can be easily poured at 60°C has a content of NCO functions of 5.4 equivalents per kg.

EXAMPLE 7

Using 15.5 g of 98.7% nitric acid and 20 ml of 96% sulfuric acid, 32 g of a mixture of isomers of (dichloro-benzyl)dichlorotoluene produced by Friedel are nitrated under the conditions described in example 1 -Crafts condensation of dichlorobenzyl chloride with dichlorotoluene. 39 g of a very viscous orange colored mixture is obtained. 30 g of this mixture is hydrogenated in the presence of 0.3 g of 5% palladium-on-charcoal (ENGELHARD) in 300 ml of methanol at 60°C under a pressure of 40 bar, giving 25 g of a solid mixture of amines with dark brown color and which phosgenerates under the conditions described above. Finally, 28 g of crude mixture of isocyanates (NCO content: 4.1 equivalents per kg) is obtained corresponding to the general formula given in the description, in which X = Cl, x = 2, y = 2, z = 1, n = 1.

Claims (6)

1. Mixtures of halogenated aromatic isocyanates, characterized in that they consist of mixtures of compounds with an unsymmetrical methyldiphenylmethane or polymethyldiphenylmethane structure with the formula: where X = Cl, Br n = 1,2 x = 0, 1 , 2 y = 1, 2 z = 1, 2 and one of the groups R^ , R£, R^ in R^ is an NCO group, while the others are hydrogen atoms, the amount of NCO in the mixtures being from 4 - 6.7 equivalents per kg. 2. Mixtures of isocyanates according to claim 1, characterized in that they consist of isomers of (chlorobenzyl isocyanate)-toluene isocyanate. 3. Mixtures of isocyanates according to claim 1, characterized in that they consist of isomers of (chlorobenzyl isocyanate)-chlorotoluene isocyanate. 4. Mixtures of isocyanates according to claim 1, characterized in that they consist of isomers of (chloroparamethyl-benzyl-isocyanate)-chloroparaxylene isocyanate. 5. Mixtures of isocyanates according to claim 1, characterized in that they consist of isomers of bis-(chlorobenzyl isocyanate) touenisocyanate. 6. Mixtures of isocyanates according to claim 1, characterized in that they consist of mixtures of isomers of (chlorobenzyl isocyanate)-toluene isocyanate and isomers of bis-(chlorobenzyl isocyanate)-toluene isocyanate.