Patent ID: 7850810

Claim:
A method of making a highly porous self-cohered non-woven web comprising: providing a non-woven, precursor web material comprising self-cohering filaments having an order-disorder transition temperature and a crystallization exotherm enthalpy wherein said self-cohering filaments are composed of a partially phase immiscible block copolymer or a blend of polymers or copolymers having sufficient melt miscibility to allow for extrusion into filaments; softening said precursor web material at a temperature above its order-disorder transition temperature and below combinations of heat and time that would lead to a substantial reduction in crystallization exotherm enthalpy of said softened precursor web material; stretching said softened precursor web material in at least one direction at a ratio of at least 2:1 to form an unannealed highly porous self-cohered stretched web with a total volume and void spaces of at least ninety percent of said total volume; partially annealing said highly porous self-cohered stretched web material while restrained at maximum stretch; releasing said highly porous self-cohered stretched web material from restraint at maximum stretch; and increasing loft of said partially annealed highly porous self-cohered stretched web material by fully annealing said stretched web material after restraint on said stretched web material has been reduced.