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AssigneeBASF SE
InventorsEckhard Ströfer, Jan Jacobs, Wilfried Seyfert, Hans Volkmar Schwarz, Olaf Schweers, Volker Scharr, Ulrich Penzel
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A process for preparing methylenedianiline by reacting aniline with formaldehyde in the presence of acid catalysts comprising, in a semicontinuous process, introducing aniline with or without acid catalyst, feeding formaldehyde with or without acid catalyst through a mixing element into a circuit in which aniline with or without acid catalyst and with or without previously added formaldehyde is circulated and, after feeding in at least 50% of the total amount of formaldehyde to be fed in, heating the reaction mixture to a temperature above 75° C. In addition, the invention relates to a process for preparing polyisocyanates by phosgenation of amines obtainable in this manner and to the polyisocyanates obtainable by this process.
A process for preparing methylenedianiline comprising reacting aniline with formaldehyde in the presence of an acid catalyst, further comprising, in a semicontinuous process, introducing said aniline with or without said acid catalyst, feeding formaldehyde with or without acid catalyst through a mixing element into a circuit in which aniline with or without acid catalyst and with or without previously added formaldehyde is circulated and, after feeding in at least 50% of the total amount of formaldehyde to be fed in, heating the reaction mixture to a temperature above 75° C.
A process for preparing polyisocyanates by phosgenation of methylenedianiline, prepared by reacting aniline with formaldehyde in the presence of acid catalysts, further comprising, in a semicontinuous process, introducing said aniline with or without said acid catalyst, feeding formaldehyde with or without acid catalyst through a mixing element into a circuit in which aniline with or without acid catalyst and with or without previously added formaldehyde is circulated and, after feeding in at least 50% of the total amount of formaldehyde to be fed in, heating the reaction mixture to a temperature above 75° C.
A process for preparing methylenebis(phenyl isocyanate), comprising, in a semicontinuous process, introducing aniline and acid catalyst, the molar ratio of aniline to acid catalyst being from 1:0.6 to 1:0.01, feeding formaldehyde through a nozzle or a reaction mixture pump into a circuit in which said aniline and said acid catalyst with or without previously added formaldehyde is circulated at a temperature of from 20 to 75° C., after feeding in at least 50% of the total amount of formaldehyde to be fed in, heating the reaction mixture for a period of at least 0.2 hours at a temperature above 75° C., the molar ratio of the aniline introduced to the total amount of formaldehyde to be added being from 1.7:1 to 7.2:1, neutralizing the resulting methylenedianiline, separating off water and aniline, phosgenating the purified methylenedianiline at a temperature of from 50 to 150° C. and a pressure of from 0.5 to 10 bar in the presence or absence of inert solvents, removing phosgene, HCl and optionally solvent from the crude MDI at a temperature below 150° C. possibly under vacuum or feeding in inert gas, then separating off said solvent from the isocyanate at a temperature of ≦190° C. and then separating off 2,2′-, 2,4′- and/or 4,4′-MDI and/or mixtures comprising at least two of these isomers by distillation at pressures of from 2 to 50 mbar and temperatures of from 150 to 250° C. and/or by crystallization.
A process for preparing monomeric MDI and polymeric MDI comprising crude MDI, wherein, in a semicontinuous process, aniline and acid catalyst are introduced, the ratio of said aniline to said acid catalyst being from 1:0.6 to 1:0.01, formaldehyde is fed through a nozzle or a reaction mixing pump into a circuit in which said aniline and said acid catalyst are circulated at a temperature of from 20 to 75° C., after the complete addition of the formaldehyde the reaction mixture is transferred to a storage vessel, heating for a period of from 0.1 to 120 min at a temperature of from 65 to 100° C., then the reaction mixture is heated in a reactor for a period of from 0.2 to 48 hours at a temperature from 105 to 150° C., the reaction mixture is neutralized at a temperature of from 60 to 110° C., the aqueous phase is separated off by phase separation, unreacted aniline is separated off from the organic phase by distillation, the purified monomeric MDA and polymeric MDA comprising crude MDA is phosgenated in the presence of an inert solvent at a temperature from 50 to 150° C. and a pressure of from 0.5 to 10 bar, phosgene, HCl and if appropriate solvent is removed from the process product, the crude MDI, at a temperature of from 50 to 149° C. and then solvent and, if present, chlorine compounds are separated off at a temperature of from 150 to 209° C.
Dependencies are inferred from the claim text.