Yeah; looks to be a 1940 patent by Dupont. Even the trademark is no longer tied to Dupont.
HYPALON - Trademark Information
By DUPONT PERFORMANCE ELASTOMERS LLC
The HYPALON trademark was assigned a Serial Number #71666833 – by the United States Patent and Trademark Office (USPTO). Trademark Serial Number is a unique ID to identify the HYPALON mark in USPTO. The HYPALON mark is filed in the category of Chemical Products . The legal correspondent for HYPALON trademark is JAMES C. WRAY, 1493 CHAIN BRIDGE ROAD SUITE 300, MCLEAN, VA 22101 . The current status of the HYPALON filing is CONTINUED USE NOT FILED WITHIN GRACE PERIOD, UN-REVIVABLE.