GB2096002A - Sanitary napkin - Google Patents

Abstract

A sanitary napkin comprises a fluid impervious baffle (14) and an absorbent batt (10) containing fusible fibers. The batt (10) has folded longitudinal sides. The napkin retains its shape after absorbing a substantial quantity of fluid. <IMAGE>

Description

SPECIFICATION Sanitary Napkin The present invention relates to a sanitary napkin and particularly to a sanitary napkin containing fusible fibers.

One of the traditional ways of forming a sanitary napkin is to assemble the napkin bottom side up. A fluid pervious covering material is overlaid with an absorbent batt such as wood pulp fluff in such a manner that the edges are coterminous. Super absorbent powder or a sheet of superabsorbent material may be then added if desired. If a sheet containing superabsorbent material is used, it need not be coterminous with the other components. The fluid pervious wrap and absorbent batt are then folded to produce, essentially, a double thickness. A fluid impermeable baffle is then added to maintain the fold in place as well as to provide the necessary fluid barrier to the finished napkin. The napkin resulting from this construction has folded longitudinal edges which are soft and comfortable.

It is also known to introduce fusible fibers into an absorbent batt. U.S. Patent 4,059,114 describes such a combination. As disclosed therein, the fusible fibers are added to increase absorbency by aiding a fluid flow in the interior of the absorbent layer.

There has been proposed a sanitary napkin of reduced thickness intended to absorb as much as the sanitary napkins having conventional thickness. The absorbent component of this napkin has superabsorbent material mixed with the conventional absorbent layer. The remaining absorbent is the conventional cellulosic type. Even with the inclusion of superabsorbent material, this napkin has not performed as well as expected. It has been found that one of the reasons for this is the deformation stresses placed upon the napkin which by its construction it cannot overcome.

During wear, a sanitary napkin is subjected to forces directed inward along the longitudinal axis by the legs of the wearer. These forces also generate a shearing action along the longitudinal axis. It has been found that when conventional absorbents contain a sufficient amount of liquid such as menses and a deformation force is applied, the conventional absorbent does not recover its previous shape. This is true even though the absorbent is wrapped with a nonabsorbent wrapper. Absorbing of menses tends to cause local bunching and distortion along the plane of the napkin. Not only does this produce discomfort due to the distortion of the napkin but it also negatively affects its absorbent properties.

Serious distortion and localized bunching of the wet absorbent material can provide channels directing the fluid towards side runoff or otherwise interfering with the general fluid spread throughout the absorbent material.

View from one aspect the present invention provides a sanitary napkin comprising a fluid impervious baffle and an absorbent batt with fusible fibers which has folded longitudinal sides, said napkin retaining at least 96.5% of its planar area after absorbing one gram of fluid and being worn for one hour.

Viewed from another aspect the present invention provides a sanitary napkin having an absorbent batt folded along the longitudinal edges of the napkin, the absorbent material of the batt containing fusible fibers which in combination wth the folded longitudinal edges provide a resilient absorbent matrix which substantially maintans its shape after substantial fluid absorption. A napkin made in accordance with invention, therefore, can be superior from the standpoint of comform and absorbency when compared to a napkin having equal absorbent bulk and similar superabsorbent capacity.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawing, Figure 1,which is a perspective view, partially in section, of a napkin in accordance with the invention.

As can be seen, in the preferred napkin, an absorbent layer 10 contaning fusible fibers is surrounded by fluid permeable wrap 16 and is folded underneath itself to form closely adjacent edges shown in phantom lines 11. An intermediate absorbent layer of superabsorbent material 13 is positioned generally in the center of the absorbent matrix resting upon the top of the folded surface 12 of the absorbent material 10 and a fluid impermeable baffle 14 is adhesively attached to the bottom of the folded absorbent layer. The transverse ends of the absorbent layer 10 are not sea led at the edges but, instead, are sealed by fusing. The fusing generally appears in the absorbent material as clear, thin semicircular bands 15 which are inset from the napkin ends.By leaving the extreme ends of the napkin unattached, a loose, flexible end results which is more comfortable than an end which is bonded to the very edge.

The napkin has an outer wrap 16 which is integral with the preferred absorbent, and is fused to the absorbent after the absorbent is deposited using the wrap as a support. This is because the particularly preferred material is that described in U.S. Patent 4,100,324. This nonwoven material has a fabric-like finish and is made up of an airformed matrix of thermoplastic polymeric fibers having an average diameter of less than about 10 microns and a multiplicity of individualized wood pulp fibers dispersed throughout the matrix and serving to space the microfibers from each other. The material is formed by initially utilizing a primary air stream with the melt blown microfibers and a secondary air stream containing wood pulp fibers and merging the two under turbulent conditions and subsequently placing the integrated air stream along a forming surface.The fabric-like appearance of this material provides a visually appealing absorbent.

An advantage which is present with this embodiment of the invention is the ability not only to fuse the end of the napkin, but to be able to fuse the fusible fiber containing absorbent to the fluid impermeable baffle layer.

The sanitary napking of this embodiment is characterized both by the presence of the folded longitudinal edges and the inclusion of fusible fibers in the absorbent matrix. Surprisingly, it is this particular combination which provides the basis for the resistance to deformation. A napkin made as described above retains at least 96.5% of its surface area after it has absorbed one gram of menstrual fluid and has been worn for a period of at least one hour. The surface area measured is that which is essentially flat. Subtracted from the surface area are areas which are bunched or distorted out of a plane which is either flat or curvilinear depending upon the overall size of the napkin and the configuration of the wearer. Surprisingly, napkins which have folded edges without fusible fibers permanently distort.

This is also true of napkins having fusible fibers which do not have folded longitudinal edges. These napkins which are generally known as die cut because of the existence of coterminous edges around the periphery of the napkin do not produce the resistance tp permanent deformation and bunching which occurs when fusible fibers are utilized in the folded napkin configuration. Distortion is also particularly acute where neither attribute is present and the product thickness is reduced.

It should be noted that this resistance to deformation is particularly important in napkins of reduced bulk. Napkins which have between 0.2 and 0.5 inches (0.51 and 1.27 cm) of absorbent are particularly resistant to deformation and, in fact, the measurements performed above were performed on such napkins.

In order for the deformation resistance of this invention to be realized however, it is preferable for the absorbent to have a density of at least 20 g/m2.

Increased resistance to deformation is encountered at higher densitites with levels of 150 - 200 g/m2 being currently preferred. Higher densities may add rigidity without substantial added deformation resistance. When napkins having this reduced thickness have superabsorbent material present, the absorbency potential of this type of product is realized because the designed absorbent capacity of the napkin can be fully utilized.

It should be noted that while superabsorbent material is presently preferred, there are other materials having increased absorbency or other desirable properties which can be added as an insert or, it is possible to construct a napkin without the presence of such material. Due to the shape retention capability of a napkin constructed as above the absorbent capacity is utilized with greater efficiency which minimizes the need for extra absorbent.

Claims (7)

1. A sanitary napkin comprising a fluid impervious baffle and an absorbent batt with fusible fibers which has folded longitudinal sides, said napkin retaining at least 96.5% of its planar area after absorbing one gram of fluid and being worn for one hour.

2. A sanitary napkin as claimed in Claim 1 wherein the absorbent is an air laid blend of wood pulp fibers and microfibers.

3. A sanitary napkin as claimed in Claim 1 or 2 wherein a baffle is fused to the absorbent batt.

4. A sanitary napkin as claimed in Claim 1,2 or 3 wherein an absorbent additive material is positioned under the body facing side of the absorbent batt.

5. A sanitary napkin as claimed in any preceding claim wherein the thickness of the absorbent material is between 0.2 and 0.5 inches.

6. A sanitary napkin having an absorbent batt folded along the longitudinal edges of the napkin, the absorbent material of the batt containing fusible fibers which in combination with the folded longitudinal edges provide a resilient absorbent matrix which substantially maintains its shape after substantial fluid absorption.

7. A sanitary napkin substantially as hereinbefore described with reference to the accompanying drawing.