Issued Patents All Time
Showing 1–2 of 2 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4298344 | Age resistant chrome tanning agents | Herbert Knopf, Heinrich Spahrkas | 1981-11-03 |
| 4211529 | Chrome-tanning | Heinrich Spahrkas, Josef Muller, Ernst Komarek | 1980-07-08 |