This invention relates to laminates incorporating a fibrous layer, and particularly to disposable absorbent products such as panty shields, sanitary napkins, diapers, absorbent towels, and bed liners.
Panty shields consist essentially of three layers: a permeable layer through which liquid passes, a layer of fibers for absorbing the liquid, and a moisture-barrier layer beneath the fibers. Some means must be provided for holding the fibers together to form a layer so that the laminate does not fall apart, and the layer of fibers must be bonded to the adjoining layers.
Several approaches have been taken in the prior art. One common technique is to seal the fibers within an envelope formed by sealing the permeable and barrier layers together at their perimeters. These layers are typically thermoplastic, and are bonded to each other by application of heat (or with adhesive).
Another approach has been to add thermoplastic powders, fibers, or fibrils to the fibrous layer and to apply heat during lamination to form a supporting web of thermoplastic material throughout the fibrous layer as well as a bond between the thermoplastic web and adjoining, thermoplastic permeable and barrier layers. Typically, the laminate is embossed during application of heat so that bonding occurs primarily in embossed areas.
Crosslinkable latex adhesives have also been employed. The layer of fibers is impregnated with such adhesives during lamination, and the laminate is then cured in drying ovens to form bonds between fibers as well as between the layer of fibers and the adjoining permeable and barrier layers. This is commonly done stepwise in separate operations. Embossing has also been used in such constructions to cause the latex adhesive to migrate into the embossed areas prior to curing.
Absorbent fibrous webs have also been made on specialized equipment that consolidates loose fibers using such techniques as spunlacing, mercerizing, or needle punching to mechanically entangle the fibers into a web. Uniform fibers are generally required, and the mechanical entanglement step must be done off-line (i.e., in a separate manufacturing process not part of the process for assembling the panty shield or other disposable absorbent article).
Hot melt adhesives have been used in the manufacture of laminates. A known technique for applying such adhesives is to apply a coating of the adhesive to one or more layers prior to forming the laminate.