Method for the production of methylenedi(phenylamine and methylenedi(phenyl isocyanate)

• US 6,433,219 B1
• Filed: 09/08/2000
• Issued: 08/13/2002
• Est. Priority Date: 02/07/1998
• Status: Expired due to Term

• Current Assignee: BASF AG (BASF SE)
• Original Assignee: BASF AG (BASF SE)
• Inventors: Penzel, Ulrich, Jacobs, Jan, Schwarz, Hans Volkmar, Seyfert, Wilfried, Scharr, Volker, Ströfer, Eckhard, Schweers, Olaf
• Primary Examiner(s): GORR, RACHEL F
• Application Number:
  US09/601,097
• Time in Patent Office: 704 Days
• Field of Search: 560/347, 560/358, 560/359, 564/330, 564/331, 564/333, 564/334
• US Class Current: 560/347
• CPC Class Codes: C07C 209/78 from carbonyl compounds, e.g. from formaldehyde, and amines having amino groups bound to carbon atoms of six-membered aromatic rings, with formation of methylene-diarylamines
• CPC Class Codes: C07C 211/50 with at least two amino groups bound to carbon atoms of six-membered aromatic rings of the carbon skeleton
• CPC Class Codes: C07C 263/10 by reaction of amines with carbonyl halides, e.g. with phosgene
• CPC Class Codes: C07C 265/12 having isocyanate groups bound to carbon atoms of six-membered aromatic rings
• CPC Class Codes: C07C 265/14 containing at least two isocyanate groups bound to the same carbon skeleton

Abstract

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.

Claims

1. 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.

2. A process as claimed in claim 1, wherein the formaldehyde is added up to an amount of at least 50% of the total amount of formaldehyde to be added at a temperature of the reaction mixture in the circuit of from 20 to 75°

C.

3. A process as claimed in claim 1 or 2, wherein the molar ratio of aniline to acid catalyst is from 1:

0.6 to 1;

0.01.

4. A process as claimed in claim 1, wherein the molar ratio of aniline to the total amount of formaldehyde to be added is from 1.7:

1 to 7.2;

1.

5. A process as claimed in claim 1, wherein the formaldehyde is fed into the circuit via a nozzle or a reaction mixing pump.

6. A process as claimed in claim 1, wherein the reaction is carried out in an apparatus which has

1:

feed lines for aniline and acid catalyst,

2;

feed line for formaldehyde,

3;

at least one reaction mixing pump or nozzle through which the formaldehyde is fed into the apparatus,

4;

at least one reactor with or without

5;

devices for mixing the reaction mixture,

6;

a pipe system which, starting from the reactor, makes circulation of the reaction mixture possible,

7;

a device for heating the reaction mixture and

8;

an optional pump which circulates the reaction mixture in (6) and

9;

at least one connection for taking off the reaction mixture.

7. 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.

8. A process for preparing methylenebis(phenyl isocyanate), MDI, as claimed in claim 7, which comprises phosgenating 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.

9. A process as claimed in claim 8, wherein the crude MDI prepared by phosgenation is purified in such a manner that phosgene and optionally solvent are removed in a first purification step and then the desired monomeric MDI is separated off by distillation and/or by crystallization.

10. 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.

11. 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.

12. A process for preparing polymeric MDI, wherein crude MDI is prepared according to claim 11 and monomeric MDI is separated off from the crude MDI by distillation at pressures of from 2 to 50 mbar and temperatures of from 150 to 250°

C.

13. A process for preparing monomeric MDI, wherein crude MDI is prepared according to claim 11 and the monomeric MDI is separated off from the crude MDI by distillation at pressures of from 2 to 50 mbar and temperatures of from 150 to 250°

C.