Title: POLYURETHANE HAVING LOW VOLUME SHRINKAGE

 Number/Link: US2013/116357

Applicant/Assignee: Bayer

Publication date: 9-05-2013 (priority PCT/DE)

“Gist”: Modified m-XDI mixtures are used to prepare solvent-free polyurethane or polythiourethane with high refractive index, low dispersion and low volume shrinkage.

Why it is interesting: Production of polyurethane and (esp.) polythiourethane for optical applications is well known. Usually araliphatic isocyanates are used, often together with mercapto-functional compounds resulting in materials with high refractive index, low dispersion and low discolouration. Bayer has found that by modifying araliphatic diisocyanates, e.g. m-xylenediisocyanate, by partial trimerization or by partly converting into allophanate or biuret (after adding some diol or water respectively) optical polyurethanes or polythiourethanes can be produced without the use of solvent and with less shrinkage.  The materials are therefore more useful for precision optics.

1,3-bis(isocyanatomethyl)benzene (m-XDI)