Title: Dental and biomedical foams and method
Number/Link: US3903232
Applicant/Assignee: W.R.Grace
Publication date: 2-09-1975
“Gist”: A branched, low NCO prepolymer made from all-EO polyol and TDI or pMDI is reacted with a large surplus of water to make a new class of flexible foams.
Why it is interesting: HYPOL™-type foams are very soft, highly hydrophilic flexible foams which can be produced catalyst-free from a high EO prepolymer and a high surplus of water. Originally the prepolymers were based on all-EO triols or tetrols and TDI 80/20, or -alternatively- PEGs and polymeric MDI. Later these systems were further improved by myself in 1991 using 75% EO triols and 4,4′ MDI. The (after drying) low- to medium density foams are very robust and versatile, can be compressed and restored by adding water, and the specific production process allows to add all kinds of functionalities via the water stream. The HYPOL trademark is currently owned by Dow Chemicals and may encompass a wider range of materials than original.
US3,903,232
Innovation in Polyurethanes 
Mark Smith
/ July 19, 2018I remember Hypol in the 1980’s. Millions of Miss Piggys and Kermits for Avon. Some Med stuff too. I loved playing with it and additives. Glow-In-The-Dark foam. Some of the crew from W.R. Grace were real stick-in-the-ass serious but a couple liked seeing us lowly Mold-Makers having fun.