Patent ID: 6809166
Filing Date: 2004-10-26
Classification: B29D,C08F,G02B

Abstract:
Amorphous perfluorinated copolymers, comprising:A) cyclic perfluorinated units deriving from at least two different perfluorinated comonomers, optionally with units deriving from a non cyclic perfluorinated monomer, or which does not cyclize during the polymerization, wherein said amorphous perfluorinated copolymer contains at least one olefinic unsaturation, or B) cyclic perfluorinated units and units deriving from a non cyclic perfluorinated monomer, or which does not cyclize during the polymerization, wherein said amorphous perfluorinated copolymer contains at least one olefinic unsaturation, and wherein said amorphous perfluorinated copolymer has the following combination of properties: substantial absence of unstable polar end groups; said end groups being not detectable in the copolymer, i.e. present in an amount lower than 0.05 mmoles/kg polymer when they are determined by Fourier transform IR spectroscopy by NicoletÂ® Nexus FT-IR equipment at 256 scannings, resolution 2 cmâˆ’1, wherein: on a sintered polymer powder pellet having 5 mm diameter and thickness from 50 to 300 micron, corresponding to a weight of 1.75 and 10.5 mg of polymer, respectively, a scanning between 4,000 cmâˆ’1 and 400 cmâˆ’1 is initially carried out, the pellet being then kept for 12 hours in an environment saturated with ammonia vapours; the IR spectrum is finally recorded under the same conditions of the initial IR spectrum; the two spectra are elaborated by subtracting from the signals of an initial spectrum relating to the untreated sample those corresponding to the specimen spectrum after exposure to ammonia vapours; the â€œdifferenceâ€  spectrum is obtained, which is normalized by the following equation: &OpenCurlyDoubleQuote;Difference&it;â€ƒ&it;spectrum&CloseCurlyDoubleQuote;[pellet&it;â€ƒ&it;weight&it;â€ƒ&it;(g)/pellet&it;â€ƒ&it;area&it;â€ƒ&it;(cm2)]â€ƒthe optical densities related to the end groups which have reacted with the ammonia vapours are measured, which give rise to detectable peaks in the IR spectrum, said end groups being the COOH and COF groups; the optical densities are converted in mmoles/kg polymer using the extinction coefficients shown in Table 1, page 73 of the paper by M. Pianca et al., â€œEnd groups in fluoropolymersâ€ , J. Fluorine Chem. 95 (1999), 71-84 the so found values give the concentrations of the residual polar end groups as mmoles of polar end groups/kg polymer: in the spectrum of the amorphous (per)fluorinated polymers after fluorination bands between 3,600-3,500 or 1,820-1,770 cmâˆ’1 related to COOH groups and/or bands between 1,900-1,830 cmâˆ’1 related to COF groups are not detectable, the method detectability limit being 0.05 mmoles/Kg polymer; polymer Tg higher than 120Â° C., narrow distribution of the monomeric composition of the amorphous perfluorinated copolymer measured according to the following test: the polymer is dissolved at a concentration of 5% w/w in perfluoroheptane solvent, after filtration on PTFE filter having a maximum pore diameter of 0.2 micron, no polymer residue remains on the filter whereby the filter weight before and after filtration remains unchanged.