U.S. Pat. No. 6,582,642 discloses a method of producing a sheet form fastener product comprising                a. lengthwise stretching a sheet of heat-softened synthetic resin to pre-orient the molecular structure of the sheet in a longitudinal direction;        b. with a rotating mold roll, molding from said lengthwise-stretched sheet a running web having a base and a multiplicity of discrete fastener elements integral with the base and protruding from at least one side of the base; and        c. thereafter, under conditions in which the web is permanently stretchable, stretching the web widthwise in a manner that permanently stretches the base and increases the widthwise spacing of the fastener elements.        
In a specific embodiment illustrated in FIG. 13 of U.S. Pat. No. 6,582,642, it is suggested to feed a precompressed knitted web into a nip comprising said rotating mold roll thereby creating an integrated laminate comprising the knitted web and the web having a base and a multiplicity of discrete fastening elements integral with the base. The precompressed knitted web does not tend to shorten longitudinally upon stretching the laminate widthwise so that the thickness of the knitted web is not decreased to a major extent. Stretching of non-precompressed knitted webs is furthermore difficult to perform.
U.S. Pat. No. 6,484,371 discloses a mechanical fastener comprising a hook web and a loop material applied to a first major surface of such hook web. The hook web comprises a uniaxially oriented polymeric substrate bearing a plurality of hooks disposed on the second major surface of the hook web opposite to the first major surface. The thickness and/or mechanical strength of the mechanical fastener of U.S. Pat. No. 6,484,371 does not always meet all practical requirements of disposable sanitary articles and, in particular, of sanitary napkins.
Disposable articles such as sanitary napkins comprise a liquid pervious top sheet which is attached towards the body of the wearer, and a liquid impervious back sheet facing away from the body of the wearer. The top sheet and the back sheet sandwich an absorbent core designed to absorb body exudates such as blood, menses, urine and excrements which are discharged from the body.
In a sanitary napkin, the back sheet is intended to be placed adjacent to the wearer's undergarments and may comprise adhesive and/or male mechanical fastening means such as hook fastener elements to securely attach the sanitary napkin to the undergarment which mechanically engages with the hook fastener elements. A back sheet comprising mechanical fastening means preferably is thin and flexible so that it does not significantly contribute to the overall thickness of the sanitary napkin and does not result in discomfort when attached to the wearer's body. The back sheet also preferably exhibits a sufficient mechanical strength and, in particular, a sufficient tensile strength and tear resistance so that it can be safely handled during the manufacturing of the sanitary napkin and during its use without rupturing.
It was therefore an object of the present invention to provide a mechanically stable, thin web material which can be advantageously used, for example, as a back sheet in sanitary napkins. It was another object of the present invention to provide a stretched mechanical fastening web having a low overall thickness and basis weight. The person skilled in the art can easily take other objects of the invention from the following detailed description.
USPTO Backgrounds
USPTO Backgrounds