Out of well over 300 names I have investigated, the longest name I have found is the origin of the Dutch firm AKZO dyes (next door to my old office in Abingdon).
It is the amalgamation of 3 other companies (no translation available), Algemene Kunstzijlde unie, Koninklijke Zout-kejten and Koniklijke Zwanenberg Organon. The remainders were added together to form Algemene Kunstzijlde Zout Organon. Anyone who can offer a translation will be greatly welcomed.

My Dutch is pretty poor, but here's a try:

Algemene = General
Kunstzijlde = I think this is Kunstzijde - no "L". Would translate to artificial side or man-made stuff, something like that.
Unie = Union/United ?

Koninklijke = Royal
Zout-kejten = Not sure, but zout is salt

Zwanenberg = I think this is a place or town. Literal translation however would be Swan Mountain.
Organon = Organization ?


Re long company names, here's one for your collection:
Freie Arzt und Medizinkasse der Angehörigen der Berufsfeuerwehr und der Polizei Versicherungs Vergleich A.G.
(medical insurance company in Germany providing group benefits coverage to firefighters and police)