Polyester compositions, process for preparing polyester films, polyester films for magnetic recording media and films for capacitors produced from them.

摘要

A process for preparing a polyester composition in which 80 mol% or more of the constituent repeating units are constituted by ethylene terephthalate units or 2,6-naphthalate units and ethylene containing spherical silica particles, comprising : subjecting an esterification reaction terephthalic acid or naphthalene-2,6-dicarboxylic or esters thereof and ethylene glycol, subjecting the reaction product of said esterification reaction to polycondensation reaction in the presence of antimony (Sb) and / or compounds of magnesium (Mg) as a catalyst in an amount defined by the following formulas (4) - (6): 0 Sb 1.5 (4) 0 Mg 10 (5) 0.5 6SB + Mg 15 (6) wherein Sb is the total number of moles of antimony compounds per 10 6 grams of polyester, and Mg is the total number of moles of magnesium compounds per 10 6 grams of the polyester, and adding said spherical silica particles at any stage until the reaction secomplete initial polycondensation, that is, in a stage in which the intrinsic viscosity of the reaction product is 0.2 or less, in an amount of 0.001 to 5% by weight, based on the polyester producing, with said amorphous particles obtained by subjecting alkoxysilane and a hydrolysis reaction and a condensation reaction in the presence of an amine catalyst type, and having an average diameter of 0.01 to 3.0 m and the rate being dispersion diameter of said particles represented by the following formula (1), in the range of 1.1 to 2.7: d10 / d90 (1) wherein d10 is the diameter of the particle when the cumulative number is 10% the total number of said particles, d90 is the diameter of the particle when the cumulative number is 90% of the total number of said particles and d10 and d90 are measured under an electron microscope, said cumulative numbers being calculated comenzan do with the larger particle size.