Process for the preparation of di- and polyamines from the diphenylmethane series
First Claim
1. A process for the preparation of di- and polyamines of the diphenylmethane series, comprising:
- a) converting aniline and formaldehyde in the absence of an acidic catalyst to a reaction mixture comprising aminal and water, where the formaldehyde to be used comprises at most 2.0% by mass of methanol;
b) removing water at least in part from the reaction mixture obtained in step a), giving an organic phase comprising the aminal;
c) converting the organic aminal-comprising phase obtained in step b), in the presence of an acidic catalyst, to a reaction mixture comprising di- and polyamines of the diphenylmethane series; and
d) neutralizing the reaction mixture comprising di- and polyamines of the diphenylmethane series obtained in step c) and then subjecting the reaction mixture to a work-up comprising washing and distillation;
whereinin step a) at least one auxiliary reagent from at least one of the groups (i) to (v) or at least one auxiliary reagent from exclusively group (vi) is added in the mass fractions stated in each case, the mass fractions referring to the total mass of all of the feed substances used in step a) including the mass of the auxiliary reagents added;
(i) 0.05% by mass to 3.0% by mass of aliphatic alcohols having 1 to 6 carbon atoms,(ii) 0.0001% by mass to 3.0% by mass of alkali metal halides,(iii) 0.0001% by mass to 0.030% by mass of alkali metal hydroxides,(iv) 0.0001% by mass to 1.0% by mass of carboxylic acids having 1 to 4 carbon atoms,(v) 0.0001% by mass to 1.0% by mass of salts of carboxylic acids having 1 to 4 carbon atoms,(vi) 0.1% by mass to 3.0% by mass of cycloaliphatic alcohols having 5 to 7 carbon atoms, where the mass fraction of the auxiliary reagent of group (vi) is selected such that this is greater than 0.5% by mass, based on the total mass of the aniline used in step a) and of the auxiliary reagent of group (vi).
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Abstract
The present invention provides a process for preparing di- and polyamines from the diphenylmethane series by converting aniline and formaldehyde in the absence of an acid catalyst to give aminal and water, removing the aqueous phase and further processing the organic aminal phase to give the di- and polyamines of the diphenylmethane series, in which use of a coalescence aid in the phase separation of the process product obtained in aminal reaction reduces the proportion of water and hence also of water-soluble impurities in the organic phase containing the aminal. The di- and polyamines of the diphenylmethane series obtained by acid-catalyzed rearrangement and workup after further processing of the aminal phase are outstanding suitably for preparation of the corresponding isocyanates.
17 Citations
7 Claims
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1. A process for the preparation of di- and polyamines of the diphenylmethane series, comprising:
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a) converting aniline and formaldehyde in the absence of an acidic catalyst to a reaction mixture comprising aminal and water, where the formaldehyde to be used comprises at most 2.0% by mass of methanol; b) removing water at least in part from the reaction mixture obtained in step a), giving an organic phase comprising the aminal; c) converting the organic aminal-comprising phase obtained in step b), in the presence of an acidic catalyst, to a reaction mixture comprising di- and polyamines of the diphenylmethane series; and d) neutralizing the reaction mixture comprising di- and polyamines of the diphenylmethane series obtained in step c) and then subjecting the reaction mixture to a work-up comprising washing and distillation; wherein in step a) at least one auxiliary reagent from at least one of the groups (i) to (v) or at least one auxiliary reagent from exclusively group (vi) is added in the mass fractions stated in each case, the mass fractions referring to the total mass of all of the feed substances used in step a) including the mass of the auxiliary reagents added; (i) 0.05% by mass to 3.0% by mass of aliphatic alcohols having 1 to 6 carbon atoms, (ii) 0.0001% by mass to 3.0% by mass of alkali metal halides, (iii) 0.0001% by mass to 0.030% by mass of alkali metal hydroxides, (iv) 0.0001% by mass to 1.0% by mass of carboxylic acids having 1 to 4 carbon atoms, (v) 0.0001% by mass to 1.0% by mass of salts of carboxylic acids having 1 to 4 carbon atoms, (vi) 0.1% by mass to 3.0% by mass of cycloaliphatic alcohols having 5 to 7 carbon atoms, where the mass fraction of the auxiliary reagent of group (vi) is selected such that this is greater than 0.5% by mass, based on the total mass of the aniline used in step a) and of the auxiliary reagent of group (vi). - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification