Abstract: 'An improvement is described in the process of preparing polymethylene polyphenyl polyamines by condensing aniline and formaldehyde in the presence of an acid catalyst. The improvement entails adding a minor proportion of a polyamine mixture comprising di(aminophenyl)methanes and oligomeric polymethylene polyphenyl polyamines, collectively known as polymethylene polyphenyl polyamines or polymeric MDA, to an intermediate stage of the condensation reaction where the various intermediately formed aminobenzylamines are present. The process lends itself to either a batch or continuous method for preparing the polyamines.The improvement is actually observed in the polymethylene polyphenyl polyisocyanates derived from the polyamines which have substantially reduced color over those polyisocyanates prepared from polyamines prepared via a prior art method. Such color improvements invariably carry over to polyurethane products derived therefrom.

Abstract: A process has been invented for the preparation of polyaryl polyamines having methylene bridges by condensation of primary arylamines with formaldehyde in the presence of a catalyst. According to the invention, the amount of binuclear compounds and an improved viscosity can be obtained if one adds the remaining amount of primary arylamine immediately after the formaldehyde.

Abstract: A process is described for the preparation of bis(aminophenyl)alkanes and bis(aminophenyl)cycloalkanes which comprises condensing a m-alkylphenol with an alkanone or cycloalkanone and heating the resulting condensation product with an at least stoichiometric amount of an acid addition salt of aniline or a substituted aniline or a mixture of such amines.

Abstract: Through condensation ortho- and para-isomers of methylene dianiline (MDA) as well as PMPPA are produced as condensation products from arylamines, especially from aniline, and formaldehyde in the presence of acid catalysts, in which at least one component is a perfluoro-carbonic acid. From this mixture of the condensation products, 4,4'-MDA (p-isomer) of high purity is obtained by crystallization while the homogeneous aqueous solution obtained is being cooled down. It has been discovered that the 4,4'-MDA salts of the perfluoro-carbonic acids are less soluble in water than the corresponding salts of the o-isomers and the PMPPA.

Abstract: A novel process for making 4,4'-methylene diphenyl diisocyanate and corresponding oligomer in improved selectivity and yield comprises condensing formaldehyde and aniline under neutral or basic conditions to yield an anil condensate, followed by reacting the anil condensate with additional aniline and a protonic salt of aniline to yield 4,4'-methylene dianiline and corresponding oligomer, then followed by conventional phosgenation.

Abstract: An improvement is described in the process of preparing polymethylene polyphenyl polyamines by condensing aniline and formaldehyde in the presence of an acid catalyst in the initial condensation. The improvement enables the amount of acid which has to be neutralized at the end of the reaction to be substantially reduced or eliminated entirely. This is accomplished without sacrifice of the high level of 4,4'-isomer of di(aminophenyl)methane normally present in the diamine content of the polyamines when a mineral acid catalyst is employed in the condensation.

Abstract: The instant invention is directed to a process for the preparation of mixtures of polyamines of the polyamino-polyaryl-polymethylene type whereby the proportion or the ortho-substituted products are substantially increased. This increase is brought about by adding the acid catalyst to the aromatic amine/formaldehyde reaction mixture in two or more stages.