are Geoffrey Holden and Ralph Milkovich. The answer was supplied by Frank Van Haste on Twitter. A quick Google search confirms this, but raises more questions. If seems like the original patent (US 3, 265,765) was filed on January 29, 1962, and yet the Belpre plant was built in 1961. [*] So was the plant originally built for other products that weren't as successful as Kraton? Or maybe there is another scenario: At that time, the US had a 1-year grace period between when a product was made public and when you filed for the patent. Did Shell wait until the last possible minute to file? (I find this implausible). Fortunately, these questions certainly don't bother me near as much as who the inventors were.
[*] That explains why I couldn't find the inventors myself, as I only looked at patents that were filed in the 50's.