| 摘要 |
Organic isocyanates are recovered from crude reaction mixtures containing them by a process comprising mixing the crude mixture with an inert solvent which dissolves the isocyanate but not the impurities, and separating the two phases so obtained, both phases being liquid throughout the separation. Preferably, the mixture is first distilled to remove a part of the isocyanate and inert diluent used in the isocyanate-forming reaction and, after the separation into phases, the isocyanate is recovered by distillation. Suitable solvents for the separation into phases are saturated aliphatic hydrocarbons of 5-10 carbon atoms, benzene, toluene and dioxane. The isocyanates which may be treated include hexyl isocyanate, tetramethylene diisocyanate, 3,31-diisocyanato dipropyl ether, cyclohexyl isocyanate, tetrahydro-a - and -b -naphthyl isocyanates, benzyl isocyanate, phenyl isocyanate, 3-nitro-4-dodecylphenyl isocyanate, m- and p-phenylene diisocyanates, 1,3,5-benzene triisocyanate and tetrahydrofurfuryl isocyanate. Others are specified also, and reference is made to the treatment of chlorinated isocyanates. Examples are given of the treatment of toluene diisocyanate prepared in known manner from toluene diamine and phosgene. |
