Area bonded nonwoven fabric from single polymer system

A method of making an area bonded nonwoven fabric comprising the steps of:

• melt extruding a crystallizable amorphous polymer of a single polymer system through one or more spinnerets that form first and second groups of continuous filaments;
• subjecting the first and second groups of continuous filaments to processing conditions that impart stress to the first group of filaments producing stress-induced crystallization such that the filaments are at least partially crystallized, and impart stress to the second group of continuous filaments insufficient to produce stress-induced crystallization such that the filaments remain substantially amorphous;
• depositing the first and second groups of continuous filaments on a collection surface to form a web containing both said partially crystalline first filaments as matrix filaments and said amorphous second filaments as binder filaments;
• heating the web so that the binder filaments soften and fuse to form bonds with one another and with the matrix filaments while maintaining their continuous filamentary form;
• and
• effecting crystallization of the binder filament during the heating step so that in the resulting nonwoven fabric both said matrix filaments and said binder filaments are at least partially crystalline;
• wherein the binder filaments are present in an amount ranging from 5% to 35% by weight, and
• wherein the processing conditions are selected from the group consisting of
• a) subjecting continuous filaments of the first group to stress that induces crystallization, and subjecting continuous filaments of the second group to stress insufficient to induce crystallization, wherein the steps of subjecting the continuous filaments of the first group and continuous filaments of the second group to stress to induce or not induce crystallization comprises extruding the continuous filaments at differing extrusion rates;
• and
• b) subjecting continuous filaments of the first group to stress that induces crystallization, and subjecting continuous filaments of the second group to stress insufficient to induce crystallization, wherein the steps of subjecting the continuous filaments of the first group and continuous filaments of the second group to stress to induce or not induce crystallization comprises providing a reduction in the intrinsic viscosity of the continuous filaments of the first group relative to the intrinsic viscosity of the continuous filaments of the second group.

A method of making a nonwoven fabric comprising the steps of:

• melt extruding a crystallizable amorphous polymer of a single polymer system through one or more spinnerets configured to form bicomponent filaments having first and second polymer components present in distinct portions of the cross section of the filament, wherein the intrinsic viscosity of the polymer in the second component is reduced relative to the intrinsic viscosity of the polymer in the first component;
• attenuating the filaments to cause stress-induced crystallization in the first polymer component of the filaments but without producing stress-induced crystallization in the second polymer component such that the second polymer component remains substantially amorphous;
• depositing the bicomponent filaments on a collection surface to form a web in which the first polymer component of the filaments is partially crystalline and serves as the matrix component of the filaments and the second polymer component of the filament is amorphous and serves as the binder component of the filaments;
• heating the web so that the binder component of the filaments softens and fuses to form bonds with contacting filaments while the filaments maintain their continuous filamentary form;
• and
• effecting crystallization of the binder component of the filaments during the heating step so that in the resulting nonwoven fabric both the matrix component and the binder component of the bicomponent filaments are at least partially crystalline;
• wherein the binder component is present in an amount ranging from 2% to 25% by weight.