Patent ID: 7641054

Claim:
A composite semipermeable membrane comprising a separating functional layer comprising a reactant of polyfunctional amine with polyfunctional acid halide on a porous substrate film, wherein a water-soluble organic material, which comprises a compound or derivative selected from the group consisting of a compound having a formyl group, a derivative of a compound having a formyl group, a compound having an oxilanyl group, a derivative of a compound having a oxilanyl group, a carbonate derivative, a carbamate derivative, and an alkyl halide, is in contact with the separating functional layer, and the separating functional layer has a boron removal ratio of 95% or more, when seawater at 25° C. having a pH of 6.5, a boron concentration of 5 ppm and a TDS concentration of 3.5% by weight is permeated under an operation pressure of 5.5 MPa.