Isocyanate-Free Polyaminal-Polyurethane Foams

Patent Title: SYSTEM FOR DIMENSIONALLY STABLE ISOCYANATE-FREE POLYURETHANE FOAM

 Number/Link: WO2018/005142

Applicant/Assignee:  Dow

Publication date: 4 January 2018

Gist”: Polyaldehydes are reacted with polycarbamates in the presence of an acid catalyst, a metal oxide powder and a blowing agent.

Why it is interesting: According to this invention hydrolytically-stable foams can be prepared from a low molecular weight difunctional aldehyde and a polycarbamate with a functionality of about 3.5 to 4 and an equivalent weight of about 200 to 300, in the presence of a blowing agent and a protic acid as catalyst. Surprisingly the foams are rendered hydrolytically stable by the incorporation of a metal oxide powder with a specific particle size. In the examples polycarbamates are prepared by capping high functionality polyols with methylcarbamate and are then reacted with 1,4-cyclohexanedicarboxaldehyde together with p-toluensulfonic acid as catalyst, HFC245fa as blowing agent and MgO powder. The foams show densities of 130-170 kg/m³ and are said to be useful as sealants.

CHDA

Cyclohexanedicarbaldehyde

PU Sealants using Michael Addition Chemistry

Title: MICHAEL ACCEPTOR-TERMINATED URETHANE-CONTAINING FUEL RESISTANT PREPOLYMERS AND COMPOSITIONS THEREOF

 Number/Link: US2015/0252232

Applicant/Assignee: PRC-DeSoto

Publication date: 10-09-2015

Gist”: A PU prepolymer is capped with Michael accepting groups and then cured with a dithiol

Why it is interesting: This invention is about sulphur containing PU sealants with properties acceptable for the aerospace industry. A bis(vinylsulfonyl)- terminated urethane-polythioether prepolymer is prepared according to the scheme below. The prepolymer can then be cured with a dithiol-ended polyether, catalysed by a tertiary amine.  The compositions have an extended pot life and the curing rate can be controlled by using an encapsulated tert-amine as a controlled-release catalyst.

Michael acceptor-terminated prepolymer preparation according to the invention

Michael acceptor-terminated prepolymer preparation according to the invention

Highly Stable Isocyanate Dispersions

Title: STORAGE-STABLE HYDROPHILIC POLYISOCYANATES

 Number/Link: WO2014/053269   (German)

Applicant/Assignee: Evonik

Publication date: 10-04-2014

Gist”: A uretdion-containing isocyanate prepolymer is reacted with a neutralized aminealkylsulfonic acid to produce a novel hydrophilic (latent) isocyanate which can be used in stable aqueous dispersions.

Why it is interesting: Aqueous dispersions of isocyanates are useful in many applications as adhesives, binders, crosslinkers etc, but usually suffer from a relatively short shelf life.  Dispersions prepared according to the current invention supposedly lose less than 30% of their initial NCO value after 12 weeks storage at 50°C. In an example an aceton-solution of  an IPDI-uretdion prepolymer with an isocyanate content of 1.5% is reacted with the sodium salt of an aminealkylsulfonate in water to an NCO value of 0.1%. After removal of the aceton the resulting dispersion had a latent isocyanate content of 4.5%

Dimerization of isocyanate to uretdion.

Reversible dimerization of isocyanate to uretdion.