STABILIZATION OF FLUOROPOLYMER

摘要

PROBLEM TO BE SOLVED: To improve a melt-fabricable fluoropolymer resin contg. a low level of unstable fractions to give a fluoropolymer resin with a high stability and/or a good color by melt extruding the resin in the presence of an alkali metal nitrate. SOLUTION: A melt-fabricable copolymer of tetrafluroethylene and another copolymerizable monomer selected from among many copolymerzable monomers (e.g. hexafluoropropylene) has unstable terminal groups, esp. COOH groups or salt groups thereof, and decomposes during processing. When a fluoropolymer resin having a content of total unstable fraction of 0.3% or lower and a melt viscosity of 0.550×10<3> Pa.s is melt kneaded together with an alkali metal nitrate in an amt. of 20-500 ppm (in terms of potassium nitrate), a fluoropolymer resin improved in color and/or instability due to unstable fractions is obtd. The total unstable fraction is determined as the wt. loss under a controlled high-temp. exposure.