Process for the production of N-methylcarbamates

In a process for the preparation of N-methylcarbamates having the formula ##STR7## wherein RO-- is a naphthol or substituted phenol radical, wherein diphenyl carbonate reacts with methylamine to form phenyl-N-methylurethane, phenyl-N-methylurethane is thermally decomposed to form methyl isocyanate and the methyl isocyanate is reacted with a substituted phenol or a naphthol to form the N-methylcarbamate (I), the improvement comprising:

• (a) feeding streams of diphenyl carbonate and methylamine in a molar ratio of from 0.8-1:1 to a first reaction space with a first recycle mixture discharged from the first reaction space and containing phenyl-N-methylurethane, phenol and unreacted diphenyl carbonate;
• (b) reacting diphenyl carbonate and methylamine and the first recycle mixture as a liquid phase at a temperature of from 20.degree. C. to 80.degree. C. in the absence of an organic solvent to form a first reaction product containing phenyl-N-methylurethane, phenol and unreacted diphenyl carbonate;
• (c) feeding to a second reaction space streams of the first reaction product and a second recycle mixture discharged from a third reaction space, the second recycle mixture containing phenyl-N-methylurethane and phenol;
• (d) reacting the streams of the first reaction product and the second recycle mixture in a liquid phase at a temperature of from 180.degree. C. to 220.degree. C. at a pressure of from 200 mmHg to atmospheric pressure in the absence of an organic solvent to partially decompose phenyl-N-methylurethane and thereby obtain a second reaction product containing unreacted phenyl-N-methylurethane and methyl isocyanate;
• (e) forwarding the phenol and unreacted phenyl-N-methylurethane to a third reaction space;
• (f) distilling phenol and unreacted phenyl-N-methylurethane in the third reaction space to thereby obtain phenol and the second recycle mixture;
• (g) feeding methyl isocyanate formed in the second reaction space to a fourth reaction space;
• (h) reacting methyl isocyanate with substituted phenol or naphthol in the fourth reaction space in the presence of an inert organic solvent and a basic catalyst at a temperature of from 0.degree. to 50.degree. C. to thereby obtain N-methylcarbamate.