DE859156C - Process for the preparation of addition products from isocyanates and acidic salts of sulphurous acid - Google Patents

Description

Process for the preparation of addition products from isocyanates and acidic salts of sulphurous acid. The present process relates to the preparation of novel derivatives of isocyanates, the special property of which is that they are readily soluble in water. It has been found that mono- and polyisocyanates can easily be reacted with acidic salts of sulphurous acid: this reaction is accessible to isocyanates of the aliphatic, cycloaliphatic, aromatic and heterocyclic series. Examples include: methyl isocyanate, ethyl isocyanate, hexyl isocyanate, i-chlorhexyl-6-isocyanate, isocyanates of the fatty series, cyclohexyl isocyanate, phenyl isocyanate, tolyl isocyanate, chlorophenyl isocyanate, obtained from glycine ester chlorohydrate by phosgenation available isocyanate, ethylene diisocyanate, butane i, q.-diisocyanate, hexane-i, 6-diisocyanate, thiodipropyl- co; co'-diisoeyanate, cyelohexyt-q., 4'-diisocyanate, Phe- nylene-I, q.-diisocyanate; i-methylbenzene-a, 4.-diiso- cyanate, phenyl-i, 3, 5-triisocyanate and higher poly isocyanates. Occur as acidic salts of sulphurous acid all -the- alkali salts- in question, - such as- e.g. Nattiüm- bisulfite and potassium bisulfite: but also ammonium bisulfite or calcium bisulfite and also formaldehyde Bisulfite compounds can be used with success will. - The best way to work is to remove the isocyanate with the concentrated aqueous solution of the acidic Sulphurous acid salt vigorously stir or shake at room temperature or at a moderately elevated temperature. In some cases it is advisable to use inert organic solvents, preferably those that are miscible with water and can therefore serve as solubilizers, such as. B. tetrahydrofuran, dioxane or glycol monomethyl ether acetate. The implementation usually takes place within a few hours, often even faster and almost quantitatively with a mild heat release. Except for the isocyanates with a particularly low molecular weight, in which the adducts are too easily soluble in water, the new compounds, salted out by the high salt content of the reaction mixture, usually separate out as solid white bodies, which can be differentiated in various ways, e.g. B. can be cleaned by recrystallization from water or alcohols or by salting out. They are often characterized by a great tendency to crystallize. They are all readily soluble in water, and often extremely easily soluble. They are similar to the bisulfite compounds of aldehydes and ketones, e.g. B. in the fact that they still have the reactivity of the original isocyanates in many respects. Regarding their chemical structure, it can be said that they contain exactly one 31o) bisulfite for one isocyanate group, so that one of the following formulas can be assigned to them: It is very surprising that the isocyanates react in the manner indicated in the presence of water. It is known that isocyanates decompose with water to form ureas. In the procedure according to the present invention, this reaction is almost completely suppressed by the novel reaction with bisulfites.

The new adducts can be used to purify and identify isocyanates Find use. They are reactive intermediates for organic syntheses all kinds.

Example i 65 g of i-chlorohexyl-6-isocyanate are stirred at room temperature with zoo cm3 of a 4% sodium bisulfite solution. After about one hour a slight precipitate appears; the reaction mixture heats up to 35 ' , the isocyanate disappearing completely and everything dissolving clearly. When cooling with ice, the new compound separates out in the form of shiny, easily water-soluble flakes. These are suctioned off and washed with saline solution. plan can recrystallize the compound undecomposed from methyl alcohol and thus obtain salt-free. The compound decomposes at 168 to 171 'without melting clearly.

Example 2 20 g of ethyl isocyanate are dissolved in .ioo ciii2 aqueous sodium bisulfite solution dripped in by 40%. The temperature is kept between 2o and 3o 'by cooling. A clear yellow solution of the new addition compound is formed in vacuo can be evaporated to dryness.

Example 3 60 g of cyclohexyl isocyanate are dissolved in 60 cm 3 of dioxane. After adding Zoo cm3 of sodium bisulfite solution (38 'B6 = 4io / oig), the reaction mixture becomes heavily turbinated or shaken. After about: z hours divorce quite suddenly a thick slurry of crystals. -Man dilute with saline solution and suction off. The connection can be recrystallized from a little water of 4.5 '. It decomposes in the process but shear) partially with the separation of isocyanate droplets.

Example q.

Phenyl isocyanate is, as indicated in the previous examples, stirred with an excess of sodium bisulfite solution. Divorced after an hour the first crystals in the form of square flakes, the best are immediately isolated. It is filtered again and again at short intervals and washed the crystals obtained with a little water and tetrahydrofuran.

The adduct is soluble in cold water and can easily be mixed with potassium chloride are salted out. Hot water causes it to form diphenylurea and carbon dioxide destroyed.

Example 5 Zoo cm3 of a 4% sodium bisulfite solution are stirred for 18 hours with a solution of 50 g of hexane- 1,6-diisocyanate in 50 cm3 of glycol monomethyl ether acetate. The cheesy precipitate formed is filtered off with suction (dry: 169 g of salt-containing compound). For cleaning, it is best to dissolve just enough cold water, filter off any slight cloudiness (probably hexamethylene polyurea) and salt out with potassium chloride. The potassium salt crystallizes in snow-white needles. The connection is also stable in water at higher temperatures.

The same compound is obtained if 50 g of hexane-1,6-diisocyanate are stirred with a solution of 100 g of potassium bisulfite in 150 cm3 of water at room temperature for a long time without any further organic solvent.

Example 6 Similar to Example 5, zoo cm3 of an ammonium bisulfite solution of 3o 'B6 stirred together with 50 g of hexane-i, 6-diisocyanate. After a while copious precipitate is diluted with concentrated ammonium chloride solution and sucked off. The ammonium salt of the bisulfite adduct can be used without decomposition from moderately recrystallized in warm water.

Example Zoo cm 'of a sodium bisulfite solution of 38' B6 are with qo g butane-i, q.-diisocyanate shaken vigorously for 12 hours. Those in water easily soluble Bisulfite compound is sucked off with a little ice cold Water and then washed with acetone. 55 g of the pure adduct are obtained.

If the butane-1,4-diisocyanate is replaced by thiodipropyl diisocyanate, the corresponding bisulfite compound is also obtained here, but because of it greater poor solubility in better yield. Example 8 A solution is stirred of 100 g of potassium bisulfite in 150 cm 'of water with 50 g of that from glycine ester chlorohydrate isocyanates obtained by phosgenation. After 12 hours the precipitate formed is suctioned off and recrystallized from dilute methanol. The very shiny crystals decompose at 153 ° without melting clearly.

EXAMPLE g 500 g of potassium bisulfite are dissolved in 1 l of water and this solution is intimately stirred at 15 ° with the mixture of 250 g of i-methylbenzene-2,4-diisocyanate in 500 cm 3 of toluene. The reaction mixture becomes so stiff that it can no longer be stirred at the end of the reaction. The new compound is pressed off, dissolved in water at 0 ° C., minor impurities are filtered off and salted out with potassium chloride. Yield around 52o g.

Example 10 130 g of the solid acetone-sodium bisulfite addition compound are dissolved in 300 cm 2 of water and stirred with 65 g of i-chlorohexyl-6-isocyanate at 30 ° to 35 ° overnight. The isocyanate disappears completely, and an almost clear aqueous solution is obtained which is salted out with common salt. The precipitated leaflets are recrystallized from methanol and the same body is obtained as in Example i from the decomposition point 168 to x71 °.

Example ii 70 g of the solid propionaldehyde bisulfite compound are dissolved in 150 cm 3 of water and stirred with 30 g of i-chlorohexyl-6-isocyanate. The reaction and work-up are carried out as in the previous example. The same well-formed leaflets with a decomposition point of 168 to 171 ° are obtained. Yield 42g.

Example 12 40 g of the acetone-potassium bisulfite adduct are in 5o cm3 Dissolved water. 15 g of hexane, 6-diisocyanate are added and the whole thing is shaken. The thick crystal pulp becomes after 24 hours in just enough water of 60 ° and salted out with potassium chloride. The same addition compound is obtained as in Example 5 in good yield.

Similar results are obtained when using other aldehyde or ketone bisulfite adducts, such as. B. Methyläthylketonkaliumbisulfit or AcetaldehydkaHumbisulfit.

Claims (1)

PATENT CLAIM: Process for the preparation of addition products from isocyanates and acidic salts of sulphurous acid, characterized in that isocyanates are reacted with acidic sulphurous acid salts, advantageously at room temperature or at a moderately elevated temperature.