I found German newspaper articles claiming this, but surely the patents would have expired after more than 20 years?Good question. I got my info from some Solingenfocussed websites.

In English:Nachdem der Solinger Rudolf Osberghaus in den 1930er Jahren Teflonbeschichtete Rasierklingen erfand, wurde dieses Patent im Jahre 1955 an die Fa. Wilkinson verkauft.
Hmmmm.... I need evidence... sounds bogus...After Solingen citizen Rudolf Osberhaus invented the teflon coated razor blade in the 1930s, the patent was sold to the Wilkinson company in 1955.

Zeit Online has a trial login and I managed to find (and download) two articles about Solingen/Osberghaus/Wilkinson/Gillette.Well, then the search is narrowed down to 1939
The Wilkinsoncollaboration was not about patents. The had a joint venture building a razor (cartridge?) factory in/near Solingen, the year this started depends on the source, early 50'-60's. My links no longer work: Zeit Online and Solinger Tagesblatt now require registration.