Patent ID: 7901831

Claim:
A monolayer ion-exchange membrane structured in the thickness comprising ion-exchange sites covalently bonded to a support polymer, the membrane having a mean ion-exchange site density D total of at least 2.5 meq/cm 3 when it is calculated on the total thickness of the membrane, the membrane comprising two surface zones located on either side of a mid-zone, each surface zone having a thickness of not more than 5% of the total thickness of the membrane, in which the surface zones have a mean ion-exchange site density D surface calculated on the thickness of the surface zones of at least 1.05 ×D total , and wherein the support polymer is at least one selected from the group consisting of a polyethylene, a polypropylene, a polyamide, a polyphenylene sulfide, a polyphenylene oxide and a polysulfone.