Pourous fluorocarbon membrane, method for producing thereof and cartridge filter based on said membrane

A method for producing a porous fluorocarbon membrane by dissolving tetrafluoroethylene/vinylidene fluoride copolymer in an organic readily-boiling solvent, mixing the resultant copolymer solution with a precipitating mixture to produce a casting solution, forming said casting solution into a membrane on a continuously moving carrying surface and drying the resulting continuously moving membrane at elevated temperature, wherein porous material having the average pore size within the range of 5.0-500.0 microns and difference by specific weight in any two points of a sample having various sizes of not more than 7% is used as a carrying surface;

• formation is performed by the complete impregnation of porous material moving at a constant speed with heated casting solution of a copolymer comprising 23-25 tetrafluoroethylene and 75-77 weight percent vinylidene fluoride and having the ratio of viscosity of the copolymer solution in acetone, with copolymer content in the solution in the amount of 0.01 g/cm.sup.3, to acetone equal to 2.0-4.0;
• short-term storage of continuously moving porous material while applying the casting solution under the conditions of free evaporation of a portion of solvent for partial hardening of the casting solution and consequent drying of continuously moving porous material is effected in at least three successive drying zones wherein temperature, increasing from one zone to another, is maintained.