CA2103822A1 - Improved method and apparatus for incrementally stretching a zero strain stretch laminate web to impart elasticity thereto - Google Patents

Abstract

An improved method and apparatus for incrementally stretching "zero strain" stretch laminate webs to impart elasticity thereto in the direction of initial stretching, at least up to the point of initial stretching. The "zero strain" stretch laminate material (1) is formed of at least two plies of material (4a, 5, 6) which are either intermittenly or substantially continuously secured to one another along at least a portion of their coextensive surfaces while in a substantially untensioned ("zero strain") condition. One of the plies (4a) is stretchable and elastomeric, while the second ply (5, 6) is elongatable, but not necessarily elastomeric. The sec-ond ply will, upon stretching of the laminate, be at least to a degree permanently elongated so that, upon release of the applied tensile forces, it will not return to its original undistorted configuration. This results in z-direction bulking of the laminate web when the applied tension is released as well as subsequent elastic extensibility in the direction of initial stretching, at least up to the point of initial stretching. In a particularly preferred embodiment of the present invention the opposed peripheral edge por-tions of the laminate web to be incrementally stretched are subjected to restraint to restraint to substantially prevent inwardly directed slip-page or contraction thereof in a direction parallel to the direction of stretching. This maximizes the effectiveness of the incremen-tal web stretching operation by forcing the "zero strain" stretch laminate web to undergo the fullest possible degree of elongation during the incremental stretching operation.