Patents by Inventor Enno Mahlmann

Enno Mahlmann has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 4597909
    Abstract: The present invention is directed to a process for the production of polyamines of the diphenylmethane series having a high diamine content and a low 2,2'-diamino-diphenylmethane content by condensing aniline with formaldehyde in the presence of hydrochloric acid as catalyst, neutralizing the acid catalyst at the end of the condensation reaction and working up the polyamine mixture thus obtained by distillation, characterized in that(a) in a first reaction stage, from 2.0 to 3.5 moles of aniline are reacted with 1 mole of formaldehyde in the presence of hydrochloric acid or a condensation product produced from 2.0 to 3.5 moles of aniline and 1 mole of formaldehyde in the absence of acid catalyst is reacted in the presence of hydrochloric acid at a degree of protonation maintained at 40 to 60% at temperatures below 50.degree. C.
    Type: Grant
    Filed: February 21, 1985
    Date of Patent: July 1, 1986
    Assignee: Bayer Aktiengesellschaft
    Inventors: Berthold Keggenhoff, Enno Mahlmann, Willi Eifler, Gunther Ellendt