US Patent 7776214 Membrane element

A membrane element in which, after membrane breakage or deterioration, the filtration plate made of a thermoplastic resin can be reused to replace the membrane with a fresh one. The membrane element comprises a filtration plate made of a thermoplastic resin and, bonded to a peripheral smooth surface thereof, a microporous filter membrane which has fine pores formed therein and employs a nonwoven fabric comprising synthetic resin fibers as a support. A hot plate having a shape corresponding to the peripheral shape of the resinous filtration plate is brought into contact with a peripheral smooth surface of the plate so as to form a recessed part in the surface. The temperature of the hot plate is regulated so as to be not higher than the melting point of the nonwoven fabric serving as the support and not lower than the Vicat softening temperature of the filtration plate made of a thermoplastic resin. The thermoplastic-resin filtration plate is pressed with this hot plate through the microporous filter membrane to bond it to the membrane.