Method of making porous self-cohered web materials
View Patent ↗The present invention is directed to a method of making implantable bioabsorbable non-woven self-cohered web materials having a high degree of porosity. The web materials are very supple and soft, while exhibiting proportionally increased mechanical strength in one or more directions. The web materials often possess a high degree of loft. The web materials can be formed into a variety of shapes and forms suitable for use as implantable medical devices or components thereof.
1. 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 polymeric 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; and
fully annealing said highly porous self-cohered stretched web while restrained at a maximum stretch.
2. The method of claim 1 wherein the said precursor web material is stretched uni-axially.
3. The method of claim 1 wherein the said precursor web material is stretched bi-axially.
4. The method of claim 1 wherein the said precursor web material is stretched radially.