| abstract |
PURPOSE: To obtain titled sheet of high thermal stability (in particular, to high- pressure vapor) free from drop in its filtration rate due to heat, by crystallization treatment, in a specific manner, of fine porous sheet consisting mainly of cellulose acetate. n CONSTITUTION: A cellulose acetate solution is prepared by dissolving a cellulose acetate (cellulose diacetate, cellulose triacetate or a mixture thereof) in a combination of its good, poor and/or non-solvents; said solution being coated or cast on a substrate to form a film followed by drying to make a fine porous sheet with an average pore size 0.01W10μ, porosity 60W90% and film thickness 50W 250μ. This sheet can be crystallized at significantly lower temperatures then those taken in conventional such processes, by performing heat treatment using ≥120°C water or non-aqueous solvent insoluble for cellulose acetate (e.g. ethylene glycol, diethylene glycol dimethyl ether) or saturated vapor therefrom, thus obtaining the objective sheet. n COPYRIGHT: (C)1985,JPO&Japio |