Title: MOLDED POLYURETHANE ELASTOMER PARTS MADE OF DIPHENYLMETHANE DIISOCYANATE-BASED NCO PREPOLYMERS AND METAL SALT COMPLEXES, AND A METHOD FOR PRODUCING SAME

 Number/Link: US2013267655

Applicant/Assignee: Bayer

Publication date: 10-10-2013 (priority PCT/DE)

“Gist”: Molded PU/PUA elastomers are prepared from a 2,4′-MDI based prepolymer cured with blocked MDA

Why it is interesting: A prepolymer with an NCO content between 3 to 7% is prepared from MDI containing more than 97% of the  2,4′ isomer together with a diol with an OH value of about 100.  (e.g a PTMEG or a polycaprolacton).  The prepolymer is then cured with a salt-complexed diphenylmethanediamine (“blocked MDA”). Because of it’s relatively low viscosity and long potlife the system allows for the production of thick-walled, bubble-free molded elastomers.  Probably because there is less premature polyurea phase separation (due the 2,4′-MDI) the system cures homogeneously.

4,4′-MDA