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.




Classic PU patent of the Month: PORON ® Foams (1979)

Title: Polyurethane foam product and process of manufacture thereof from thermosetting frothed mixture

 Number/Link: US4216177

Applicant/Assignee: Rogers

Publication date: 5-08-1980

Gist”: Frothed flexible foam

Why it is interesting: PORON is a popular brand of microcellular elastomeric/flexible polyurethane foams produced by Rogers Corporation. The original process, as documented in this patent, is quite simple:  a flexible foam formulation (in the examples) based on TDI, caprolacton diol, polymer polyol, some chain extender, amine catalyst and surfactant is frothed instead of blown with water or a physical blowing agent. The reacting froth is poured on release paper and heated to cure. Release paper can also be applied on top resulting in an integral skin on both sides of the layer. Frothing instead of blowing results in an improved compression set, different hardness-density relationship and a better control over cell structure. A unique material.

PORON foams

PORON foams

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