Patent ID: 6303810
Filing Date: 2001-10-16
Classification: C07F

Abstract:
In a process for preparing bis-silyl ureas of formula (I) R.sup.1 R.sup.2 R.sup.3 -SiNHC(O)NHSi-R.sup.4 R.sup.5 R.sup.6 (I) in which R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6, 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): R.sup.1 R.sup.2 R.sup.3 -Si-NH-Si-R.sup.4 R.sup.5 R.sup.6 (II) in which R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 have the same meanings as in formula (I), the said process comprising conducting 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 said 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, ande) 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;the improvement comprising utilizing as the reaction solvent used in a) and optionally in e) to wash the bis-silyl urea (I) an aliphatic nitrile RCN in which R represents a linear or branched aliphatic hydrocarbon-based radical containing from 1 to 5 carbon atoms.