Classic PU Patent of the Month: Polyurethane-Polyurea RIM Elastomers (Bayer 1976)


 Number/Link: DE262295 (German)

Applicant/Assignee: Bayer

Publication date: 24-11-1977

Gist”: Use of DETDA  in one shot PU-PUA RIM.

Why it is interesting: This is the invention that for the first time allowed the production of large reaction injection moulded (RIM) polyurea articles with a very short demould time. Apart from advances in mixing head design which allowed for fast and accurate mixing and advances in mould design, polyurea RIM was made possible by the development of specific diamine chain extenders.  Bayer found that aromatic diamines containing one alkyl group in o-postion to a first amino group and two alkyl groups in o-position to a second amine group, where at least two of the alkyl groups contain 2 or more carbon atoms, have the correct reactivity for a one shot RIM process when used together with conventional polyether polyols, MDI and catalysts. A preferred example of such a diamine is diethyltoluenediamine (DETDA). The use of DETDA in one shot RIM allowed for the production of  parts up to 10 kg with a demould time of 30 seconds.



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