| 摘要 |
Carbamic acid esters, obtained by the reaction between urea or its salts and an aliphatic, cycloaliphatic or aryl-aliphatic monohydric alcohol are separated by subjecting the reaction mixture to steam distillation, during which impurities remain in the liquid phase and are removed to produce a gaseous phase containing an alcohol, water and carbamic acid ester, subsequently separating this composition by distillation into a first fraction containing an alcohol and water, and a second fraction containing water and carbamic acid ester. The alcohol is recovered from the first fraction by a further distillation and the carbamic acid ester is recovered by crystallization. The alcohol may be recycled to the synthesis step and the mother liquor recycled to the steam distillation. Specification 922,859 is referred to.
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