Perfluoropolyethers
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United States of America Patent
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Jun 17, 2008
Grant Date -
Apr 7, 2005
app pub date -
Sep 30, 2004
filing date -
Oct 3, 2003
priority date (Note) -
Expired
status (Latency Note)
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Abstract
Use in optical systems as liquids to transmit light at wave lengths lower than 250 nm, in particular at 157 nm, of perfluoropolyethers having the following formula: X.sub.1--O(CF.sub.2O).sub.n(CF.sub.2CF.sub.2O).sub.m(CF.sub.2CF.sub.2CF.s-ub.2O).sub.p(CF.sub.2CF.sub.2CF.sub.2CF.sub.2O).sub.q--X.sub.2 (I) wherein: the repeating units --CF.sub.2O--, --CF.sub.2CF.sub.2O--, --CF.sub.2CF.sub.2CF.sub.2O--, --CF.sub.2CF.sub.2CF.sub.2CF.sub.2O-- are statistically distributed along the chain; --X.sub.1 and --X.sub.2 are perfluoroalkyl chain end groups equal to or different from each other, having formula --(CF.sub.2).sub.zCF.sub.3 wherein z is 0 or an integer from 1 to 3; n, m, p, q are 0 or integers comprised between 1 and 100, with the proviso that: at least one among n, m, p and q is different from zero; the ratio between the oxygen atoms and the carbon atoms (O/C) is higher than 0.33; wherein the chlorine atoms, determined by .sup.19F-NMR are substantially absent.
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