Patent ID: 7091295
Filing Date: 2006-08-15
Classification: C08F

Abstract:
1. A method for preparing transparent films at 157 nm having a transmittance higher than 50%, comprising the step of preparing solutions in perfluorinated solvents of amorphous perfluorinated polymers, said perfluorinated polymers being free from unstable ionic end groups, said polymers formed of cyclic units deriving from perfluorodioxoles of formula: wherein R′ said polymers optionally containing units deriving from perfluorinated comonomers containing at least one ethylene type unsaturation, optionally containing oxygen atoms; in said polymers the cyclic units deriving from the perfluorodioxoles of formula (IA) being ≧95% by moles; said ionic end groups being determined by means of the following method by using the Fourier Transform IR spectroscopy by FT-IR equipment (256 scannings, resolution 2 cm on a polymer sintered powder pellet having a diameter of 5 mm with a thickness from 50 to 300 micron (1.75–10.5 mg of polymer) a scanning between 4000 cm the optical densities related to the COOH and COF end groups after the reaction with the ammonia vapours, end groups giving rise with this reactant to detectable peaks, are determined; the optical densities are converted into mmoles/kg of polymer obtaining the concentrations of the residual polar end groups as mmoles of polar end groups/kg of polymer: in the polymer spectrum in the correspondence of the wave length of the peaks related to COOH groups and/or COF groups are not shown peaks which are detectable from the irregularities of the base line.