Classic PU Patent of the Month: ICI on “High EO – Pure MDI” Flexible Foams (1991)

Patent Title: Polyurethane Foams

 Number/Link: EP0547765

Applicant/Assignee: ICI

Publication date: 23-06-1993

Gist”: Flexible foams can be based on 4,4’MDI if the polyol contains 50 to 85% EO

Why it is interesting: The first flexible PU foams were all based on toluene diisocyanate and so-called “conventional polyols” (i.e. almost all-propylene oxide polyols). Attempts to replace TDI by the only other commercially viable diisocyanate (4,4′ MDI) failed because of premature phase separation of the highly symmetrical polyurea ‘hard block’, resulting in unstable foaming. The problem was eventually solved by using prepolymers and polymeric MDI, as mentioned before.  More than 10 years later it was shown that it is possible to make flexible foams with 4,4′-MDI if the polyol is polar enough to prevent early phase separation.  This was established by using polyols with high ethylene oxide content. The resulting foams have superior comfort and durability properties compared to both TDI and MDI flexible foams.

4,4'-MDI

4,4′-MDI

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