Process for preparation of di- and polyamines of the diphenylmethane series

• US 10,125,090 B2
• Filed: 06/22/2015
• Issued: 11/13/2018
• Est. Priority Date: 06/24/2014
• Status: Active Grant

• Current Assignee: Covestro Deutschland AG
• Original Assignee: Covestro Deutschland AG
• Inventors: Knauf, Thomas, Wershofen, Stefan, Gruner, Klaus-Gerd, Hartjes, Volker
• Primary Examiner(s): Truong, Duc
• Application Number:
  US15/317,301
• Publication Number:
  US 20170114000A1
• Time in Patent Office: 1,240 Days
• Field of Search: 528269
• 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: C08G 73/0266 Polyanilines or derivatives thereof

Abstract

The invention relates to a method for the preparation of di- and polyamines of the diphenylmethane series, care being taken during the shutdown of the production process that an excess of aniline and respect to formalin is ensured.

Claims

1. A process for preparing diamines and polyamines of the diphenylmethane series (MDA) by reaction of aniline (1) and formaldehyde (2) at a molar ratio of aniline (1) to formaldehyde (2) in normal operation of A/F_{normal operation}, which comprises the steps:

A.I) reacting aniline (1) and formaldehyde (2) in the absence of an acid catalyst (3) in a reactor to form an aminal, where aniline (1) is introduced at a mass flow rate m₁ and formaldehyde (2) is introduced at a mass flow rate m₂ into the reactor and the resulting reaction mixture is subsequently separated into an aqueous phase and an organic, aminal-containing phase; and

A.II) reacting at least part of the organic, aminal-containing phase obtained in step A.I) with acid (3) in a reactor, with the aminal reacting to form diamines and polyamines of the diphenylmethane series;

wherein the following steps are carried out to end the production of the diamines and polyamines of the diphenylmethane series;

A.I.1) reducing the mass flow rate m₂ of the formaldehyde (2) into the reactor of step A.I), commencing at a point in time t₀, until m₂ is zero at a point in time t₁, where t₁>

t₀;

A.I.2) reducing the mass flow rate m₁ of the aniline into the reactor of step A.I) until m₁ is zero at a point in time t₂, where t₂≥

t₁; and

A.II.1) reducing the mass flow rate m₃ of acid (3), until m₃ zero;

and

the reduction of the mass flow rates m₁ and m₂ occurs in such a way that, up to attainment of the point in time t₁, the instantaneous molar ratio of

aniline (1) introduced into the reactor of step A.I)

to

formaldehyde (2) introduced into the reactor of step A.I),

A/F_inst., is always ≥

1.5 and is always ≥

1.05·

A/F_{normal operation}.

2. The process as claimed in claim 1, wherein the steps I) and II) are carried out in the form of a continuous process.

3. The process as claimed in claim 1, wherein the mixture obtained is also discharged from the respective reactor during and/or after step A.I).

4. The process as claimed in claim 1, wherein t₂−

t₁ is >

0 hour.

5. The process as claimed in claim 1, wherein the mass flow rate m₁ is ≥

1000 kg/hour.

6. The process as claimed in claim 1, wherein the mass flow rate m₂ is ≥

300 kg/hour.

7. The process as claimed in claim 1, wherein at least the reactor of step A.I) is at least partly full of aniline after the point in time t₂.

8. The process as claimed in claim 1, wherein the mass flow rate m₃ of acid (3) is reduced at the earliest commencing at the point in time t₁.

9. The process as claimed in claim 8, wherein the mass flow rate m₃ prevailing before step A.I.1) is carried out is maintained up to the point in time t₂.

10. The process as claimed in claim 8, wherein the introduction of further acid (3) is stopped at the point in time t₂.