Abstract: The invention relates to a process for the production of di- and polyisocyanates of the diphenylmethane series and mixtures thereof, in which aniline and formaldehyde are reacted in the presence of an acid catalyst to form di- and polyamines of the diphenylmethane series; the di- and polyamines of the diphenylmethane series are phosgenated, optionally in the presence of a solvent, to obtain a crude di- and polyisocyanate; from the crude di- and polyisocyanate, at least one fraction containing at least 5 wt. % 3-ring and multi-ring MDI and at least one fraction containing at least 95 wt. % 2-ring MDI are separated by distillation, and the acidities of the fraction containing at least 5 wt. % 3-ring MDI and multi-ring MDI, and/or the fraction containing at least 95 wt. % 2-ring MDI are determined analytically; and an acidic compound is added to the fraction containing at least 5 wt. % 3-ring MDI and multi-ring MDI, and/or the fraction containing at least 95 wt.

Abstract: The present invention relates to a process for producing 5-nitro-3,4-dihydro-1(2H)-naphthalinone, 1,5-naphthalenediamine and 1,5-naphthalene diisocyanate, in which 4-(2-nitrophenyl)-n-butyronitrile is converted to 4-(2-nitrophenyl)-n-butyric acid.

Abstract: An aromatic dihydroxy compound conforming to formula 1 is disclosed. Also disclosed are (co)polycarbonates derived from the compound. The novel (co)polycarbonates are characterized by their reduced water uptake and improved flowability.