Core/Shell Nanofiber Non-Woven

The process of forming a core/shell nanofiber non-woven comprising, in order:

• a) mixing a core thermoplastic polymer, a shell thermoplastic polymer and a matrix thermoplastic polymer in a molten state forming a molten polymer blend, wherein the matrix polymer is soluble in a first solvent, wherein the core and shell polymers are insoluble in the first solvent, wherein the core polymer is not miscible with the shell polymer, wherein the core polymer forms discontinuous regions in the matrix polymer, wherein the shell polymer forms a shell around the discontinuous regions between the core polymer and the matrix polymer and optionally cooling the polymer blend to a temperature below the softening temperature of the core and shell polymers;
• b) subjecting the polymer blend to extensional flow, shear stress, and heat such that the core and shell polymers forms core/shell nanofibers having an aspect ratio of at least 5:1, and wherein less than about 30% by volume of the nanofibers are bonded to other nanofibers, wherein the nanofibers are generally aligned along an axis, wherein at least a portion of the core polymer interpenetrates the shell of the nanofiber and at least a portion of the shell polymer interpenetrates the core of the nanofiber;
• c) cooling the polymer blend with nanofibers to a temperature below the softening temperature of the core and shell polymers to preserve the nanofiber shape forming a first intermediate;
• d) forming the first intermediate into a pre-consolidation formation;
• e) consolidating the pre-consolidation formation at a consolidation temperature forming a second intermediate, wherein the consolidation temperature is above the Tg and of core, shell, and matrix polymers, wherein consolidating the pre-consolidation formation causes core/shell nanofiber movement, randomization, and at least 70% by volume of the core/shell nanofibers to fuse to other core/shell nanofibers;
• and,
• f) applying the first solvent to the second intermediate removing at least a portion of the matrix polymer.

The core/shell nanofiber non-woven formed by the process comprising:

• a) mixing a core thermoplastic polymer, a shell thermoplastic polymer and a matrix thermoplastic polymer in a molten state forming a molten polymer blend, wherein the matrix polymer is soluble in a first solvent, wherein the core and shell polymers are insoluble in the first solvent, wherein the core polymer is not miscible with the shell polymer, wherein the core polymer forms discontinuous regions in the matrix polymer, wherein the shell polymer forms a shell around the discontinuous regions between the core polymer and the matrix polymer and optionally cooling the polymer blend to a temperature below the softening temperature of the core and shell polymers;
• b) subjecting the polymer blend to extensional flow, shear stress, and heat such that the core and shell polymers forms core/shell nanofibers having an aspect ratio of at least 5:1, and wherein less than about 30% by volume of the nanofibers are bonded to other nanofibers, wherein the nanofibers are generally aligned along an axis, wherein at least a portion of the core polymer interpenetrates the shell of the nanofiber and at least a portion of the shell polymer interpenetrates the core of the nanofiber;
• c) cooling the polymer blend with nanofibers to a temperature below the softening temperature of the core and shell polymers to preserve the nanofiber shape forming a first intermediate;
• d) forming the first intermediate into a pre-consolidation formation;
• e) consolidating the pre-consolidation formation at a consolidation temperature forming a second intermediate, wherein the consolidation temperature is above the Tg and of core, shell, and matrix polymers, wherein consolidating the pre-consolidation formation causes core/shell nanofiber movement, randomization, and at least 70% by volume of the core/shell nanofibers to fuse to other core/shell nanofibers;
• and,
• f) applying the first solvent to the second intermediate removing at least a portion of the matrix polymer.