DE1159412B - Process for the production of covalent isocyanates - Google Patents

Description

The present invention relates to a method for making covalent isocyanates from those Elements or inorganic groups that form covalent halides, with the exception of phosphorus and boron.

There has been proposed a process for producing phosphorus triisocyanate in which one Phosphorus trichloride with sodium cyanate or potassium cyanate in the presence of an inert polar solvent implements (German patent application I 18256 IVb / 12o). In addition, attempts have become known Phosphorus triisocyanate using multiple solvents and catalysts made from potassium cyanate to produce, but with no success. The usual method of making these and others inorganic isocyanate is the reaction of SiI bercyanat with the corresponding halide in Benzene solution.

It has now been found that the use of a polar solvent either alone or in admixture with certain non-polar solvents the production of covalent inorganic isocyanates made possible from sodium or potassium cyanates and the corresponding covalent halides.

In accordance with the present invention there is provided a method for making a covalent isocyanate with the general formula

R ₁ M (NCO) _n _,

where R is an optionally substituted alkyl or aryl group and M is an inorganic element or an inorganic element group with the exception of phosphorus and boron, which are capable of forming covalent halides, and η is their covalent valence, where * = 0 or an integer is equal to or less than (n-1), proposed in such a way that one is a mixture of sodium or potassium cyanate and a covalent halide with the general formula

R ₁ MHaI _n _ _x

wherein Hai is a halogen, especially chlorine, in an inert polar solvent or reaction medium, optionally in admixture with a non-polar solvent, which refluxes deposited sodium or potassium halide is then separated off and the liquid phase for removal of the solvent or medium is fractionally distilled.

Polar solvents that can be used in this process are nitriles and ketones, for example acetonitrile, Acetones, esters, nitroparaffins, liquid process for the production of covalent isocyanates

Applicant:

Imperial Chemical Industries Ltd., London

Representative: Dr.-Ing. H. Fincke, Dipl.-Ing. H. Bohr and Dipl.-Ing. S. Staeger, patent attorneys,

Munich 5, Müllerstr. 31

Claimed priority:

Great Britain April 25, 1960 and April 7, 1961 ^χ 5 (No. 14 386)

Harold Crosbie Fielding

and John Maclelland Pollock, Northwich, Cheshire ^ao (Great Britain),

have been named as inventors

Sulfur dioxide, and suitable non-polar solvents for mixing with the polar ones are benzene, Paraffins or corresponding symmetrically substituted chlorinated hydrocarbons.

If a mixture of polar and non-polar solvents is used, the amount of polar 5 percent by weight, preferably an amount of 10 to 20 percent by weight is used. The yield of isocyanate in such a mixed solvent is generally much larger than in a polar solvent alone.

Covalent halides which can react in this way to form the corresponding isocyanates are those of the elements aluminum, silicon, germanium, tin, lead, arsenic, antimony, titanium, vanadium, iron and the groups vanadyl, sulfuryl, thionyl and chromyl. The chlorides and fluorides are generally suitable as halides, provided that the bond is covalent. The halide with the stronger covalent bond is selected. For example, one will choose stannous chloride and not stannous chloride, antimony trichloride instead of trifluoride, whereas the tetrafluoride and tetrachloride of silicon are equally suitable. An example of a covalent halide of the general formula R _x MHaI _n „ _Ä , di-n-butyltin dichloride.

309 769/365

Some of the covalent isocyanates, for example Sn (NCO) ₄ , Ti (NCO) ₄ , cannot be isolated from the reaction solvent because they tend to homopolymerize into insoluble non-volatile solids, but they are actually present in the solution as a result of their Infrared absorption spectra and can be shown by titration with n-butylamine. The usual isocyanate reactions can also be carried out in solution, for example with amines, with the formation of substituted ureas, and with organic hydroxy compounds with the formation of urethanes.

According to the invention, the covalent isocyanates are generally obtained by heating the various Components of the reaction mixture prepared under reflux, whereupon insoluble sodium or Potassium halide is removed by filtration and the filtrate to separate the solvent is fractionally distilled from the product.

While it is necessary that the solvent or reaction medium be inert to the reactants when isolating the covalent isocyanate or should remain in solution as such, it is possible according to another feature of the invention, to use a solvent that can react with the covalent isocyanate as soon as the the latter has been formed. Thus, if it is desired to make the types of connections that for example from the conversion of covalent isocyanates and reactive hydrogen atoms arise, the two necessary stages, namely the production of the isocyanate and its implementation with the reactive hydrogen-containing compound, can be combined into one step.

The invention is illustrated by the following examples:

example 1

132 g of 96% sodium cyanate were placed in a flask equipped with a stirrer, reflux condenser, thermometer and dropping funnel. 500 ecm of dry acetonitrile were added and the stirrer started. 85 g of silicon tetrachloride was slowly added from the dropping funnel in such an amount that the heat of reaction kept the mixture under gentle reflux. After adding the SiCl ₄ , the reflux treatment was continued for 30 hours. The mixture was then filtered, the solid was washed with acetonitrile and the filtrate was distilled. After removing the acetonitrile, 25 g of silicon isocyanate Si (NCO) _{4 were} collected at 187 to 189 ° C. Yield 26%.

A mixture of 20 percent by weight acetonitrile and 80 percent by weight is used as the solvent Benzene, silicon isocyanate is obtained after removal of the solvent at 98 to 103 ° C / 23 to 25 mm in a yield (on NaOCN) of 87%.

Example 2

. 65 g of sodium cyanate were introduced with 500 ecm of acetonitrile into a stirred flask provided with a gas outlet and reflux condenser, wherein the outlet of the reflux condenser was connected to a liquid-air separator. The stirred mixture was brought to reflux and 50 g of silicon tetrafluoride was introduced through the gas inlet. The unreacted silicon tetrafluoride was collected in the liquid-air separator. When all the gas was added, the mixture was refluxed for an additional half an hour, then cooled and filtered. After removing the acetonitrile from the filtrate, about 10 g of silicon isocyanate with a boiling point of 187 to 189 ° C. were obtained. Yield based on NaOCN = 20%.

Example 3

30 grams of powdered dry sodium cyanate were

ίο added to 22 g of distilled antimony trichloride, which in 30 ecm of pure acetonitrile and 120 ecm of dry benzene in one with thermometer and The stirred flask provided with a cooler was dissolved. On heating, the reaction began with high boiling of the Solvent, and after 15 minutes the hot reaction mixture was filtered and the filter cake washed with 50 ecm hot benzene containing 20% acetonitrile. Upon removal of the solvent in vacuo at room temperature remained a viscous gum (120.5 g), which on standing or solidified after adding ether or chloroform. After recrystallization from ether, this gave antimony triisocyanate as white microneedles (17.0 g), which swelled considerably when heated to 160 ° C, but did not melt when heated to 360 ° C.

Example 4

Sodium cyanate (280 g) was stirred in 400 g of liquid sulfur dioxide in a three-necked container which was provided with a sealed stirrer, freezer (-40 ° C.) and dropping funnel. The apparatus was protected from the ingress of atmospheric moisture by a protective tube filled with dry glass wool. Silicon tetrachloride (170 g) was slowly added over 15 minutes to the reaction mixture, which was stirred under reflux for an additional 4 hours, then filtered; the filter cake was _{washed well with liquid SO 2} (2 x 100 g). Then sulfur dioxide was distilled from the filtrate into a cooled receiver; the remaining liquid was distilled at 14 mm and gave silicon tetraisocyanate with a boiling point of 88 ° C./14 mm, yield 140 g (71%).

Example

30.3 g (0.1 mol) of di-n-butyltin dichloride were in Dissolved 30 ecm dry acetonitrile and 120 ecm dry benzene, and add to the stirred solution was 16 g (0.25 mol) of dry ground sodium cyanate added. The reaction mixture was

Stirred for 1 hour at reflux temperature and then filtered hot, the filter cake was with

Washed 2 x 10 ecm hot dry benzene. Evaporation of the filtrate in vacuo gave a pale yellow solid product, which when crystallizing from dry benzene needles (19.3 g) of Di-n-butyltin diisocyanate with a m.p. 96 ° C and bp 115 to 120 ° C at 0.01 to 0.02 mm.

Example 6

40 g of dry, finely powdered potassium cyanate were dissolved in 100 ecm of sulfuryl chloride under vigorous Suspended stirring. A solution of 40 ecm of sulfur trioxide in 100 ecm of sulfuryl chloride became slow added. After a short time, sulfur trioxide developed and the liquid phase began to close boil. The mixture was left without for 45 minutes

The mixture was stirred with warming and then stirred for a further 3 hours at 80 ° C. until no further sulfur trioxide developed. The liquid phase was decanted from the solid residue and distilled to give first a mixture of sulfuryl chloride and pyrosulphuryl and then 5 g of a fraction at 90 ^c C was deposited 20 mm /, which, as an analysis revealed a mixture of sulfuryl and Pyrosulfuryldiisocyanat duration. An analysis of this product resulted in the following values:

Found: C = 12.3%, S = 26.7%, N = 13.8%.

SO ₂ (NCO) ₀ requires: C = 16.2%, S = 21.6%,

N = 18.9%.

S ₂ O ₅ (NCO) ₂ requires: C = 10.5%, S = 28.0%, * 5

N = 12.3% "

This product had a strong absorption band in the infrared spectrum at 2270 cm " ¹ , which is characteristic of the isocyanate group

Claims (4)

PATENT CLAIMS: 1. Process for the preparation of covalent isocyanates of the general formula R _x M (NCO) _n ., ^A 5 where R is an optionally substituted alkyl or aryl group and M is an inorganic element or an inorganic element group with the exception of phosphorus and boron, which are capable of forming covalent halides, and η is their covalent valence, where χ = 0 or an integer is equal to or less than (n -1), characterized in that a mixture of sodium cyanate or potassium cyanate and a covalent halide with the general formula R ₁ MHaL ₁ _ _x wherein Hal is a halogen, especially chlorine, in an inert polar solvent or reaction medium, optionally treated as a mixture with an inert non-polar solvent under reflux, then the precipitated sodium or separates potassium halide and the liquid phase for removing the solvent or the medium is fractionally distilled. 2. The method according to claim 1, characterized in that the non-polar solvent or reaction medium benzene, paraffins or corresponding symmetrically substituted chlorohydrocarbons to get voted. 3. The method according to claim 1 and 2, characterized in that the reflux treatment in a medium containing 10 to 20 percent by weight of a polar solvent or contains the reaction medium. 4. The method according to claim 1 to 3, characterized in that the polar solvent or reaction medium nitriles, in particular acetonitrile, ketones, ethyl acetate or liquid sulfur dioxide to get voted. 1 309 769/365 12.63