Process for elastic nonwoven undergarment with a stitchbonded outer shell

An improved process for making an anatomically form-fitting elastic undergarment that has a stretchable outer shell which is fabricated with a waist opening and two leg openings, the process comprising cutting and seaming operations performed on an elastic nonwoven sheet to form the outer shell for the garment and optionally attaching to its inner surface an absorbent structure for containment of body exudates, the improvement comprising the steps of

• stitchbonding with an elastic thread under tension a deformable nonwoven layer of weighing 17 to 65 grams per square meter and consisting essentially of substantially non-bonded fibers of 1 to 22 dtex to form an elastic stitchbonded nonwoven sheet comprising an array of parallel spaced-apart rows of elastic strands extending in a length direction of the sheet and being incorporated with the deformable nonwoven layer,
• heat setting the stitchbonded elastic nonwoven sheet while contracting the sheet in a first direction and stretching the sheet in a direction perpendicular to the first direction, to provide a heat-set sheet having an elastic stretch of at least 70% in the first direction and a simultaneous contraction in a direction perpendicular to the first direction of at least 20%, the contraction being at least 20% when the elastic stretch is 70%,
• feeding the heat-set stitchbonded elastic nonwoven sheet to the cutting and seaming operations, in a direction substantially parallel to or perpendicular to the first direction of the sheet, at substantially uniform tension across the width of the sheet, and
• selectively cutting and seaming the heat-set stitchbonded elastic nonwoven sheet in a flat trapezoidal or rectangular geometry with the first direction parallel to the waist direction of the undergarment being fabricated, to form the outer shell with the parallel rows of elastic strands being positioned in substantially the same direction throughout the shell.