| 摘要 |
PROBLEM TO BE SOLVED: To prevent the separation of a porous PTFE film and to enhance durability by laminating an air-permeable substrate to at least one side of a porous PTFE film which has at least specified values of elongation at break in two directions at right angles to each other and has an air permeability of a specified value or higher. SOLUTION: This filter, used in a dust collector e.g. for recovering cement or a metal powder, is prepared by laminating an air-permeable substrate to at least one side of a porous polytetrafluoroethylene(PTFE) film the values of elongation of which at break in two directions at right angles to each other are both 20% or higher and which has an air permeability in terms of Fraziel number of 4 or higher. Preferably, the porous PTFE film the values of elongation of which at break in two directions at right angles to each other are both 40% or higher and which has an air permeability in terms of Fraziel number of 8 or higher is used. Such a PTFE film is flexible enough to follow the deformation of a filter and does not separate from the substrate.
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