| 摘要 |
The production of methylene-di-phenylamine from aniline (A) and formaldehyde (F) with an acid catalyst (C) comprises placing (A) and possibly (C) in a reactor, feeding (F) and possibly (C) through a mixer into a circulation loop containing (A), possibly (C) and possibly (F), and heating to above 75 degrees C after adding at least 50% of the total (F). Independent claims are also included for: (a) mixtures containing methylene-di-phenylamine (MDA) obtained by this process; (b) a process for the production of polyisocyanates by phosgenation of these mixtures; (c) a process for the production of methylene-diphenylisocyanate (MDI) by phosgenation of MDA (obtained as above) at 50-150 degrees C and 0.5-10 bar, optionally in presence of inert solvent; (d) a process for the production of MDI comprising: (1) the semi-continuous process described above using a mol ratio of (A):(C) = (1:0.6)-(1:0.01) and a mol ratio of (A):(total F) = (1.7:1)-(7.2:1), in which the temperature of the circulating mixture is 20-75 degrees C and the mixture is heated for at least 0.2 hour at above 75 degrees C after adding at least 50% of the (F), (2) neutralization, (3) distillation of water and aniline, (4) phosgenation of the purified MDA as in (c) above, (5) removal of phosgene, hydrogen chloride and possibly solvent at below 150 degrees C under vacuum or inert gas, (6) removal of solvent at not above 1900 degrees C and (7) isolation of 2,2'-, 2,4'- and/or 4,4'-MDI and/or mixtures of at least two of these isomers by distillation at 2-50 mbar and 150-250 degrees C and/or by crystallization; and (e) polyisocyanates obtained by these processes. |
