A breathable polyurethane having an upright moisture vapor transmission rate
(MVTR)
of more than about 500 gms/m2/24 hr comprises:
- (a) poly(alkylene oxide) side-chain units in an amount comprising about
12 wt. % to about 80 wt. % of said polyurethane, wherein (i) alkylene oxide groups
in said poly(alkylene oxide) side-chain units have from 2 to 10 carbon atoms and
are unsubstituted, substituted, or both unsubstituted and substituted, (ii) at
least about 50 wt. % of said alkylene oxide groups are ethylene oxide, and (iii)
said amount of said side-chain units is (i) at least about 30 wt. % when the molecular
weight of said side-chain units is less than about 600 grams/mole, (ii) at least
about 15 wt. % when the molecular weight of said side-chain units is from about
600 to about 1,000 grams/mole, and at least about 12 wt. % when the molecular weight
of said side-chain units is more than about 1,000 grams/mole, and
- (b) poly(ethylene oxide) main-chain units in an amount comprising less
than about 25 wt. % of said polyurethane.
Coatings and films for textiles and other articles and applications using
such polyurethanes have excellent breathability, i.e., high moisture vapor transmission
rates (MVTR).
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