Abstract: The invention relates to an improved process for the production of isocyanates by the reaction of an amine or a mixture of two or more amines with phosgene, the improvement involving the phosgene containing less than about 100 ppm of sulfur in elemental or bound form. The inventive process yields light-colored isocyanates that are suitable for the production of polyurethanes or their precursors (e.g. prepolymers) without the treatment processes heretofore required.

Abstract: Di- and polyamines of the diphenylmethane series are prepared by a) mixing a first portion of aniline with an acid catalyst, b) mixing a second portion of aniline with formaldehyde, and c) mixing and reacting the mixtures prepared in each of steps a) and b). The diamines produced by this process may then be phosgenated to produce the corresponding di-/polyisocyanate.

Abstract: The invention provides a process for the preparation of polyamines of the diphenylmethane series. This process comprises a) reacting aniline and formaldehyde in a molar ratio of 1.5:1 to 6:1, in the presence of an acid catalyst at temperatures of 20° C. to 100° C., in which the water content in the acid reaction mixture is <20 wt. % and a degree of protonation of <15% is established, and b) increasing the temperature of the reaction to a temperature of 110° C. to 250° C. when the ratio of the weight contents of p-aminobenzylaniline to 4,4?-MDA in the reaction mixture falls below a value of 1.00.

Abstract: Di- and polyamines of the diphenylmethane series are prepared by a) mixing a first portion of aniline with an acid catalyst, b) mixing a second portion of aniline with formaldehyde, and c) mixing and reacting the mixtures prepared in each of steps a) and b). The diamines produced by this process may then be phosgenated to produce the corresponding di-/polyisocyanate.

Abstract: The invention relates to a process for the production of liquid, storage-stable isocyanate mixtures with a low color index having carbodiimide-(CD) and/or uretone imine (UI) groups, the isocyanate mixtures that can be obtained by this process and their use for the production of blends with other isocyanates or for the production of isocyanate group-containing pre-polymers and also of polyurethane plastics, preferably polyurethane foamed plastics.

Abstract: The invention relates to a method of producing polyisocyanates of the diphenylmethane series including the steps of a) reacting aniline and formaldehyde in the presence of HCl to provide a product mixture containing polyamines of the diphenylmethane series, HCl, aniline and water; b) removing excess aniline and water by distillation to provide a product mixture comprising polyamines of the diphenylmethane series, HCl, no more than 10 wt. % aniline based on the polyamines, and no more than 5 wt. % water based on the polyamines; and c) phosgenating the product mixture in (b).

Abstract: The invention relates to a method of producing polyisocyanates of the diphenylmethane series including the steps of

Abstract: Polyisocyanates of the diphenylmethane series are produced by a) reacting aniline and formaldehyde in the presence of an acidic catalyst to produce a polyamine, b) neutralizing the reaction mixture from step a) with a base at a temperature of more than 110° C. or neutralizing the reaction mixture from step a) with a base and heating the neutralized mixture to a temperature of more than 110° C., and c) phosgenating the polyamine from step b) to convert it to the corresponding polyisocyanate.

Abstract: The invention relates to a process for the preparation of polyamines of the diphenylmethane series, comprising

Abstract: Polyisocyanates of the diphenyl methane series having reduced color values are obtained by a) reacting aniline and formaldehyde in the presence of an acid catalyst to form a polyamine, b) neutralizing the reaction mixture containing polyamine with a base, c) separating the neutralized mixture into the aqueous and the organic phases, d) adding a base to the organic phase and then e) phosgenating the resulting polyamine to produce the corresponding polyisocyanate.

Abstract: Polyisocyanates of the diphenyl methane series having reduced color values are obtained by a) reacting aniline and formaldehyde in the presence of an acid catalyst to form a polyamine, b) neutralizing the reaction mixture containing polyamine with a base, c) separating the neutralized mixture into the aqueous and the organic phases, d) adding a base to the organic phase and then e) phosgenating the resulting polyamine to produce the corresponding polyisocyanate.

Abstract: Polyisocyanates of the diphenylmethane series are produced by a) reacting aniline and formaldehyde in the presence of an acidic catalyst to produce a polyamine, b) neutralizing the reaction mixture from step a) with a base at a temperature of more than 110° C. or neutralizing the reaction mixture from step a) with a base and heating the neutralized mixture to a temperature of more than 110° C., and c) phosgenating the polyamine from step b) to convert it to the corresponding polyisocyanate.