Patent ID: 6881336

Claim:
An improved spiral wound element having: a central collection tube defining an axis and having a plurality of openings along its length to receive permeate; at least one filtration envelope extending outwardly from and wound about said tube, said filtration envelope comprising two sheets of membrane and a permeate carrier sheet sandwiched between said sheets of membrane; said permeate carrier sheet being in direct fluid communication with said openings of said collection tube; at least one feed spacer sheet wound about said collection tube, said feed spacer sheet being in planar contact with the outer surface of at least one filtration envelope; wherein the improvement is characterized in that said feed spacer sheet is a net comprising a first set of substantially parallel filaments crossed with a second set of substantially parallel filaments to form a plurality of parallelograms having an acute angle less than 70°, said net oriented such that a line bisecting said acute angle is approximately parallel to the axis of the central collection tube, and wherein said net has a strand thinning parameter greater than 1.3.