| abstract |
Polyurethanes (I) are prepd. by (1) reacting molar excess of hexamethylene di-isocyanate (II) with mixt. of trimethylhexanediol (III) and trimethylolpropane (IV) in equiv. ratio (II) to (III) plus (IV) of 10:1 - 1.5:1 to form a NCO gp.-contg. preadduct (2) reacting pre adduct with chain-lengthening mixt. of (III), (IV), and butane-1,4-diol (V) in presence of catalytic amt. of metal cpd., where equiv. ratio (IV) to (III) plus (V) is 1:30-1:5. USE/ADVANTAGE - Embedding material for holllow fibres and flat sheet membranes (e.g., in haemoseparators such as dialysers), and for prepn. of otoplastics (e.g., ear inserts in hearing aids) and of plastic components for cardiac pace makers (all claimed) (I) have good biocompatibility and biostability and water-clear appearance; do not discolour or change in surface structure, or only slightly, on repeated sterilisation; resist ageing; are not sticky; are very stable to light and UV; and have adequate permeability to gases and water vapour. |