Patent GB-811681-A (GB)
Title: Improvements in or relating to the production of substituted ureas
IPC: C07C275/30
Filed: 1957-01-01
Abstract: A method for producing a substituted urea in which an aromatic primary monoamine, which is aniline or a nuclear chlorine substituted mononuclear aryl mono-primary amine which may contain further substituent atoms or groups which are inert under the reaction conditions, is reacted with phosgene and the resultant isocyanate is reacted with a lower alkyl amine represented by the formula: R(R1)NH, where R represents a hydrogen atom or a methyl group and R1 represents an alkyl group having 1 to 4 carbon atoms, to form said substituted ureas, comprises continuously introducing (1) the aromatic amine, (2) an inert organic solvent for said aromatic amine, and (3) phosgene in excess of the stoichiomatric requirement in relation to the said aromatic amine into a first reaction zone containing a body of liquid formed by a previous mixing of phosgene said aromatic amine and solvent for said aromatic amine and maintained at a temperature above 75 DEG  C., whereby phosgene boils off from said body of liquid and a reaction takes place with liberation of gaseous hydrogen chloride, continuously withdrawing said gaseous hydrogen chloride and gaseous phosgene from said reaction zone, condensing the withdrawn phosgene but not the hydrogen chloride and returning the condensed phosgene to said first reaction zone; continuously withdrawing liquid from said body of liquid in said first reaction zone and supplying said withdrawn liquid continuously to a second reaction zone containing a liquid reaction mass formed from liquid so introduced and maintained at a temperature above the boiling-point of said inert organic solvent whereby a portion of said inert organic solvent and substantially all the unused phosgene in said supplied liquid is vaporized and the isocyanate-forming reaction is substantially completed with liberation of hydrogen chloride, removing said hydrogen chloride, vaporized phosgene and gaseous solvent from said second reaction zone; continuously withdrawing from said second reaction zone a portion of said liquid reaction mass in said second reaction zone and feeding said withdrawn liquid along with an amount of said lower alkyl amine in excess of the stoichiometric requirement in relation to the isocyanate in said withdrawn liquid continuously into a third reaction zone wherein said isocyanate reacts with said lower alkyl amine to form said substituted urea, and continuously withdrawing liquid from said third reaction zone and subsequently recovering said substituted urea therefrom.  Optionally the liquid withdrawn from the third reaction zone is continuously transferred to a fourth reaction zone containing a liquid mass formed from previously introduced like liquid and maintained at a temperature above the boiling-point of the inert organic solvent in said transferred liquid, whereby said inert organic solvent boils and unused lower alkyl amine in said transferred liquid vaporizes, said vaporized alkyl amine and gaseous solvent is removed from said fourth reaction zone, and liquid is continuously withdrawn from said liquid mass in said fourth reaction zone and the substituted urea product is subsequently recovered therefrom.  Aromatic amine starting materials mentioned include m- and p-chloro-, 3,4-dichloro -, 3 - chloro - 4- methyl -, 3,5 - dichloro-4-methyl and 3-methyl-4-chloro-anilines.  Alkyl amines mentioned include dimethyl-, monomethyl-, methyl-n-butyl-, n-butyl-, methyl isopropyl-, isopropyl- and methyl sec.-butylamines.  Organic solvents mentioned include toluene, xylene, ethyl benzene, chlorinated aromatic hydrocarbons, e.g. monochlorobenzene, anisole and nitrobenzene.  In examples: an apparatus described with reference to a drawing (not shown) is employed in the preparation of 3-(p-chloroaniline)-1, 1-dimethylurea (I); 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (II); 3-phenyl-1,1-dimethylurea (III); 3-(3,4-dichlorophenyl) - 1 - methyl - 1 - butylurea (IV); and 3 - (p - chlorophenyl) - 1 - n - butylurea (V).  Specifications 691,403 and 692,589 are referred to.