Hybrid Polyurethane Elastomer

Patent Title:  PROCESS FOR PRODUCING ELASTOMERS

 Number/Link: WO2018069348 (German)

Applicant/Assignee:  Covestro

Publication date: 19 April 2018

Gist”: Unsaturated polycarbonate polyols are reacted with isocyanates together with a peroxide

Why it is interesting: Unsaturated polyethercarbonate polyols are prepared by reacting alkyleneoxides (e.g. PO) together with carbondioxide and an unsaturated monomer like a glycidylether or -ester or cyclooctadienemonoepoxide. These polyols can then be reacted with isocyanates in the presence of  a free-radical initiator like an peroxide. The resulting material can then be crosslinked in a separate step. The hybrid elastomers are said to have improved tensile properties at same or similar hardness.
A related application is WO2018/069350.

glycidylmethacrylate

Glycidylmethacrylate

 

Classic PU Patent of the Month: ICI on MDI Prepolymers and “Cold Cure” Flexible Foams (1978)

Title: Liquid polyisocyanate compositions

 Number/Link:  EP10850

Applicant/Assignee: Imperial Chemical Industries

Publication date: 14-05-1980

Gist”: Liquid compositions from 2,4’/4,4′-MDI  prepolymers and polymeric MDI.

Why it is interesting: The first polyurethane flexible foams were all based on toluene diisocyanate (TDI).  Other commericially available isocyanates like “pure MDI”  (4,4’/ 2,4′- diphenylmethane diisocyanates mixtures) and “crude MDI” (mixtures of MDI and its higher homologues) were not suited for flexible foam production: the former because of it’s high crystallinity and therefore too high melting point and the latter because of its too high functionality.  This classic invention solved the problem by prepolymerizing  a 2,4’/4,4′-MDI mixture with a “flexible” polyol to an NCO content of 8 to 26% and then adding 10-50% of crude MDI to obtain a liquid composition. These liquid MDI compositions allowed the production of cold cure moulded flexible foams and the first MDI-based car seat cushions.

Cold cure moulded car seat cushions

Cold cure moulded car seat cushions

Polyurethane/Polyurea Elastomers from 2,4′-MDI and MDA

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

4,4′-MDA