Method for incrementally stretching a zero strain stretch laminate web to impart elasticity thereto
First Claim
1. An improved method for incrementally stretching a zero strain stretch laminate web to impart elasticity thereto in the direction of stretching, at least up to the point of initial stretching, said method comprising the steps of:
- (a) feeding a zero strain stretch laminate web comprising a substantially untensioned first elastomeric ply intermittently secured to a substantially untensioned second ply comprising a continuous web which is elongatable, but which exhibits less elastic recovery than said first ply, between a pair of opposed pressure applicators having three-dimensional surfaces which at least to a degree are complementary to one another;
(b) restraining the opposed peripheral edge portions of said second elongatable ply adjacent the portion of said zero strain stretch laminate web to be incrementally stretched to substantially prevent slippage or contraction thereof in a direction substantially parallel to the direction of stretching; and
(c) subjecting the portions of said zero strain stretch laminate web located between said opposed points of restraint to incremental stretching, while said second elongatable ply is subject to the restraint applied in step (b), by causing said opposed three-dimensional surfaces of said pressure applicators to mesh with one another at least to a degree, whereby said second elongatable ply is permanently elongated by said incremental stretching so that said laminate web is elastically extensible in the direction of initial stretching, at least up to the point of initial stretching, and the width of said laminate web measured in said direction of stretching is substantially the same as before said initial stretching is applied once the initial incremental stretching forces are removed from said zero strain stretch laminate web.
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Accused Products
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 is formed of at least two plies of material which are either intermittently 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 is stretchable and elastomeric, while the second ply is elongatable, but not necessarily elastomeric. The second 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 portions of the laminate web to be incrementally stretched are subjected to restraint to substantially prevent inwardly directed slippage or contraction thereof in a direction parallel to the direction of stretching. This maximizes the effectiveness of the incremental web stretching operation by forcing the "zero strain" stretch laminate web to undergo the fullest possible degree of elongation during the incremental stretching operation.
890 Citations
26 Claims
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1. An improved method for incrementally stretching a zero strain stretch laminate web to impart elasticity thereto in the direction of stretching, at least up to the point of initial stretching, said method comprising the steps of:
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(a) feeding a zero strain stretch laminate web comprising a substantially untensioned first elastomeric ply intermittently secured to a substantially untensioned second ply comprising a continuous web which is elongatable, but which exhibits less elastic recovery than said first ply, between a pair of opposed pressure applicators having three-dimensional surfaces which at least to a degree are complementary to one another; (b) restraining the opposed peripheral edge portions of said second elongatable ply adjacent the portion of said zero strain stretch laminate web to be incrementally stretched to substantially prevent slippage or contraction thereof in a direction substantially parallel to the direction of stretching; and (c) subjecting the portions of said zero strain stretch laminate web located between said opposed points of restraint to incremental stretching, while said second elongatable ply is subject to the restraint applied in step (b), by causing said opposed three-dimensional surfaces of said pressure applicators to mesh with one another at least to a degree, whereby said second elongatable ply is permanently elongated by said incremental stretching so that said laminate web is elastically extensible in the direction of initial stretching, at least up to the point of initial stretching, and the width of said laminate web measured in said direction of stretching is substantially the same as before said initial stretching is applied once the initial incremental stretching forces are removed from said zero strain stretch laminate web. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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2. An improved method for incrementally stretching a zero strain stretch laminate web to impart elasticity thereto in the direction of stretching, at least up to the point of initial stretching, said method comprising the steps of:
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feeding a zero strain stretch laminate web comprising a substantially untensioned first elastomeric ply substantially continuously secured to a substantially untensioned second ply comprising a continuous web which is elongatable, but which exhibits less elastic recovery than said first ply, between a pair of opposed pressure applicators having three-dimensional surfaces which at least to a degree are complementary to one another; (b) restraining the opposed peripheral edge portions of said second elongatable ply adjacent the portion of said zero strain stretch laminate web to be incrementally stretched to substantially prevent slippage or contraction thereof in a direction substantially parallel to the direction of stretching; and (c) subjecting the portions of said zero strain stretch laminate web located between said opposed points of restraint to incremental stretching, while said second elongatable ply is subject to the restraint applied in step (b), by causing said opposed three-dimensional surfaces of said pressure applicators to mesh with one another at least to a degree, whereby said second elongatable ply is permanently elongated by said incremental stretching so that said laminate web is elastically extensible in the direction of initial stretching, at least up to the point of initial stretching, and the width of said laminate web measured in said direction of stretching is substantially the same as before said initial stretching is applied once the initial incremental stretching forces are removed from said zero strain stretch laminate web.
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20. An improved method for incrementally stretching a continuously moving zero strain stretch laminate web to impart elasticity thereto in the direction of stretching, at least up to the point of initial stretching, said method comprising the steps of:
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(a) continuously feeding a zero strain stretch laminate web comprising a substantially untensioned first elastomeric ply intermittently secured to a substantially untensioned second ply comprising a continuous web which is elongatable, but which exhibits less elastic recovery than said first ply, between a pair of opposed pressure applicators comprising corrugated rolls having an axis of rotation perpendicular to the direction of web travel, said corrugated rolls having three-dimensional surfaces comprising corrugations which at least to a degree are complementary to one another; (b) restraining the opposed peripheral edge portions of said first elastomeric ply and said second elongatable ply adjacent the portion of said continuously moving zero strain stretch laminate web to be incrementally stretched to substantially prevent slippage or contraction thereof in a direction substantially parallel to the direction of stretching; and (c) subjecting the portions of said continuously moving zero strain stretch laminate web located between said opposed points of restraint to incremental stretching, while said first elastomeric ply and said second elongatable ply are subject to the restraint applied in step (b), by causing said opposed three-dimensional surfaces comprising said corrugations on said corrugated rolls to mesh with one another at least to a degree, while said continuously moving zero strain stretch laminate web passes therebetween, whereby said second elongatable ply is permanently elongated by said incremental stretching so that said laminate web is elastically extensible in the direction of initial stretching, at least up to the point of initial stretching, and the width of said laminate web measured in said direction of stretching is substantially the same as before said initial stretching is applied once the initial incremental stretching forces are removed from said zero strain stretch laminate web. - View Dependent Claims (22, 23, 24, 25, 26)
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21. An improved method for incrementally stretching a continuously moving zero strain stretch laminate web to impart elasticity thereto in the direction of stretching, at least up to the point of initial stretching, said method comprising the steps of:
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(a) continuously feeding a zero strain stretch laminate web comprising a substantially untensioned first elastomeric ply substantially continuously secured to a substantially untensioned second ply comprising a continuous wet which is elongatable, but which exhibits less elastic recovery than said first ply, between a pair of opposed pressure applicators comprising corrugated rolls having an axis of rotation perpendicular to the direction of web travel, said corrugated rolls having three-dimensional surfaces comprising corrugations which at least to a degree are complementary to one another; (b) restraining the opposed peripheral edge portions of said first elastomeric ply and said second elongatable ply adjacent the portion of said continuously moving zero strain stretch laminate web to be incrementally stretched to substantially prevent slippage or contraction thereof in a direction substantially parallel to the direction of stretching; and (c) subjecting the portions of said continuously moving zero strain stretch laminate web located between said opposed points of restraint to incremental stretching, while said first elastomeric ply and said second elongatable ply are subject to the restraint applied in step (b), by causing said opposed three-dimensional surfaces comprising said corrugations on said corrugated rolls to mesh with one another at least to a degree, while said continuously moving zero strain stretch laminate web passes therebetween, whereby said second elongatable ply is permanently elongated by said incremental stretching so that said laminate web is elastically extensible in the direction of initial stretching, at least up to the point of initial stretching, and the width of said laminate web measured in said direction of stretching is substantially the same as before said initial stretching is applied once the initial incremental stretching forces are removed from said zero strain stretch laminate web.
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Specification