| 摘要 |
PURPOSE: Provided is a process for manufacturing bis-silyl ureas which consists in reacting urea and a disilazane in an aliphatic nitrile and most particularly in acetonitrile. The process is particularly applied to the manufacture of bis(trimethylsilyl)urea from urea and hexamethyldisilazane. CONSTITUTION: In a process for preparing bis-silyl ureas of formula(I): R1R2R3 -SiNHC(O)NHSi-R4R5R6 in which R1, R2, R3, R4, R5 and R6, which may be identical or different, represent a linear or branched aliphatic hydrocarbon-based radical containing a number of carbon atoms ranging from 1 to 5, a phenyl radical, a benzyl radical or a phenethyl radical, which comprises reacting, in a solvent, urea and a disilazane of formula(II): R1R2R3-Si-NH-Si-R4R5R6 in which R1, R2, R3, R4, R5 and R6 have the same meanings as in formula(I), the process comprises the following steps: a) placing in contact, with stirring, a reaction solvent, a disilazane and urea; b) bringing the medium obtained in a) to a sufficient temperature equal to or less than the boiling point of the solvent so as to evolve ammonia; c) providing, from the start of evolution of the ammonia, a temperature equal to or different from that used in b) until virtually all of the ammonia has been evolved, optionally followed by stripping off the residual ammonia with an inert gas; d) cooling the reaction medium; and e) recovering resultant the bis-silyl urea(I), optionally washing it with a solvent identical to or different from the one used in a), and then drying it under reduced pressure. Where, the reaction solvent used in a) and optionally in e) to wash the bis-silyl urea(I) is an aliphatic nitrile RCN in which R represents a linear or branched aliphatic hydrocarbon-based radical containing from 1 to 5 carbon atoms.
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