US 3606887 A
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p 21, 1971 R. J. ROEDER 3,606,887
OVERLAP SEAL AND SUPPORT STRIP FOR A SANITARY NAPKIN WRAPPER Filed Feb. 5, 1970 wfifzizw ark/M United States Patent 3,606,887 OVERLAP SEAL AND SUPPORT STRIP FOR A SANITARY NAPKIN WRAPPER Robert J. Roeder, Appleton, Wis., assignor to Kimberly- Clark Corporation, Neenah, Wis. Filed Feb. 5, 1970, Ser. No. 8,832 Int. Cl. A61f 13/16 U.S. Cl. 128-290R 8 Claims ABSTRACT OF THE DISCLOSURE A sanitary napkin designed for disposal in conventional toilet systems includes a conventional pad enclosed in a fluid pervious wrapper which has longitudinally extending overlapping edges. A layer of hydroxylalkylated cellulose is positioned between the overlapping edges and bonded thereto so that sufficient strength to perform the support function will be available but which layer will readily disintegrate in an excess of water to provide flushability.
This invention relates to sanitary napkins and, more particularly, to a sanitary napkin that is flushable.
Absorbent pads, such as sanitary or catamenial napkins, are customarily enclosed in a fluid pervious wrapper. The wrapper serves several functions, including holding together the various components making up the functional elements of the pad. It may also provide extensions or tabs beyond each end of the pad for attachment of the pad to a suspension device, such as a sanitary belt, whereby the pad may be suitably positioned against the body of a wearer. The wrapper must permit the body exudate to pass through into the absorbent pad under the normal conditions of usage and preferably has little )absorbent capacity itself so that the surface remains relatively dry in use, i.e.absorbed fluids should not wick along fibers in the wrapper.
Various materials have been used for wrappers. These include woven gauze, non-woven adhesively bonded thread webs, woven thread webs adhesively stabilized at the thread intersections, non-woven carded fiber webs, knit fabrics, and the like.
While certain of these wrapper materials have functioned in a satisfactory manner, one universal problem has arisen. Disposability has been a messy, disagreeable task. While the absorbent pad element itself may be easily disposed of by flushing in the conventional toilet system, the pad wrapper must first be separated from the pad and disposed of by other items. Conventional wrappers are generally of woven or knitted construction, or are bonded together by a strong, permanent adhesive to provide the requisite strength in use and therefore cannot be deposited in the toilet system because of the obvious plugging problems which would result. Such wrappers are also generally not biodegradable and even if successfully flushed into a septic system will hasten the need for periodic cleaning. Disposal of the conventional sanitary napkin by flushing therefore involves separating the wrapper from the pad depositing the pad into the toilet system and then separately disposing of the wrapper in a waste basket or by other means.
Previous attempts to provide a flushable pad wrapper have been successful in achieving flushability but only at the expense of other desirable features. If made strong enough to support the pad by tabs alone permeability is reduced and the adhesive dissolves too slowly for rapid flushability. If made sufficiently permeable the wrapper is too Weak for tab support. This problem is 3,596,887 Patented Sept. 21, 1971 particularly acute with respect to full tab napkins which rely completely on tab strength for support.
One approach to this problem is disclosed in U.S. Pat. 3,407,814 to George et al. There, as opposed to the use of a bonded carded web or other relatively inextensible textile materials, the disclosed sanitary napkins utilizes a cover formed from a creped cellulosic fibrous sheet material. While this wrapper itself is flushable, the patent points out that the creped wrapper has an inherent tendency to elongate when placed in tension, as would occur during normal use on the body of the wearer. Also, there is an inherent weakness in the wrapper material due to fiber slippage, particularly when moist with body fluids of the wearer. Accordingly, to provide sufficient strength for use, the patented construction employs a strip of a relatively inextensible material such as a woven textile material or an extruded plastic filament which may then be coated with any type of a suitable adhesive such as a hot melt glue or the like for securing overlapping edges of the wrapper together.
While this adhesively coated reinforcing strip imparts the necessary strength to the creped cellulosic wrapper, the strip itself does not dissolve upon flushing and is not biodegradable. Such strips can therefore hang up in sewer pipes and collect in septic systems.
It is accordingly an object of the present invention to provide a sanitary napkin pad and wrapper therefore which may be readily disposed of in conventional toilet systems.
A more specific object is to provide a flushable wrapper for a sanitary napkin pad which provides sufficient strength to perform a support function but which will readily disintegrate in a conventional toilet system to provide flushability.
A further object is to provide a sanitary napkin pad and flushable pad wrapper which may advantageously be used without any supplemental supporting device.
A still further object is to provide a sanitary napkin pad and flushable pad wrapper which may be economically manufactured.
Other objects and advantages of the invention will be understood by reference to the following specification and accompanying drawings, in which:
FIG. 1 is a perspective view of one embodiment of the present invention and illustrating a sanitary napkin with full tabs at both ends; and
FIG. 2 is a cross-sectional view taken along lines 22 of FIG. 1 and illustrating the structural relationship of absorbent pad, the enclosing wrapper and the reinforcing element.
While the invention will be described in connection with certain preferred embodiments, it should be understood that this invention is not intended to be limited to the particular embodiments disclosed, but on the contrary, it is intended to cover the various modifications and equivalent arrangements included within the spirit and scope of the invention. For example, it should be appreciated that while the present invention is particularly advantageously employed in connection with sanitary napkins which have full tabs which provide the sole strength, the invention is equally applicable to short tab or tabless sanitary napkins.
Turning to the figures, FIGS. 1 and 2 illustrate an exemplary embodiment of the present invention. Thus, the catamenial absorption device of the present invention includes a conventional absorptive pad 10, and a fluid pervious wrapper 12 which encloses the pad and is provided with overlapping edges 14, 14'. Tabs 16 and 16 extend beyond the pad and serve to provide the sole strength for the sanitary napkin when it is held in place in a suspension device. As will hereinafter be described, the overlapping edges 14, 14' are bonded together by a unique material 18 which provides the wrapper with suflficient strength to perform its support function when worn in a moist environment but which will disintegrate readily in an excess of water so that the complete sanitary napkin structure will flush away in a toilet.
Describing the exemplary embodiment in greater detail, the construction of the pad itself is not critical and many suitable constructions are well known. As an example, the absorptive pad can suitably comprise multiple plies of cellulose wadding, wood pulp fluff, cotton fiber batts, absorbent sponges such as regenerated cellulose, each alone or in combination with the others and with various types of synthetic fibers.
The pad wrapper preferably comprises a nonwoven web of textile type, staple fibers bonded with a binder that is water sensitive so that the Wrapper will disintegrate in excess water. A nonwoven web formed of staple fibers of varying lengths and having an average length of about 1 /2 inches may be employed. The web should be relatively lightweight, i.e.less than about one ounce per square yard and preferably about /2 ounce per square yard or less. To provide the requisite strength, the fibers should be oriented in the web to provide a machine direction strength that is generally about four or five times that of the cross direction. A machine direction tensile strength of about 2 pounds per inch of width is satisfactory; however, higher strengths are, of course, preferred.
While any means may be employed to form the base web, the desired strength and weight can be readily obtained by combining a number of carded webs. The denier of the staple fibers may vary from about 1 to about 8, with a denier of less than about 2 being preferred. While rayon fibers are preferred, other types of synthetic fibers may be employed either alone or in combination.
To bond the fibers together to achieve the strength levels required, a water-sensitive adhesive such as polyvinyl alcohol, methyl cellulose, polyvinyl methylether, cellulose glycolate or the like may be employed. The adhesive may be printed on or otherwise applied to provide a discontinuous bonding which is preferred. When such discontinuous bonding is used, it is preferable that less than about 40% of the area of the web be covered with the adhesive and preferably about 25% or less. The weight of the adhesive preferably is about or less by weight of the fibers. Carded webs may also be sprayed or impregnated with adhesive but this gives a stiffer, less satisfactory product.
Polyvinyl alcohol is a preferred binder; and, when this is employed, this may be applied to the web by rotogravure printing employing a polyvinyl alcohol, water solution with from about 5 to solids. A plasticizer such as glycerine or the like may be substituted for a minor percentage of the vinyl alcohol to improve the softness, a substitution of about 5 to 10% generally being sufficient. Polyvinyl alcohols having a percent hydrolysis of from about 79 to 98 and a viscosity (4% water solution at C.) of from about 21 to 28 cps. have been found suitable.
In accordance with the present invention, the overlapping edges of the pad wrapper are bonded together with a layer of a nonionic, water-soluble hydroxylalkylated cellulose which provides the requisite strength for the sanitary napkin in its support function when being worn by the wearer yet which will disintegrate readily in an excess of Water so that the complete napkin structure may be flushed away in a conventional toilet system. Both hydroxyethyl cellulose and hydroxypropyl cellulose may be used. However, it is preferred to employ a hydroxypropyl cellulose such as Klucel (manufactured by Hercules Incorporated, Wilmington, Del.). Such material is normally soluble in water below 40 C., and insoluble at between 40 C. and 45 C. and above. The insolubility temperature or precipitation temperature may be reduced from the 40 to 45 C. range by addition of NaCl or sucrose. Thus it can be adjusted to be insoluble at body temperature or below, depending upon the amounts added while retaining its solubility in excess water at temperatures normally found in sewerage disposal systems. While it is desirable to lower the insolubility characteristics, the normal grade of hydroxypropyl cellulose has been found useful since its solubility in strip or fiber form is little effected by the moist environmental conditions encountered in use while it dissolves readily when submitted to excess water as in a toilet. It was found that even when the reinforcing strip of such hydroxypropyl cellulose was bathed in menstrual fluid during use, it did not lose substantial tensile strength. Nevertheless it did dissolve in water after deposition in a toilet.
The layer of the water-sensitive material may be applied to the wrapper by any of several means. For example, the overlapped seal may be suitably made by heat bonding a /2 inch wide 3-mil. extruded Klucel film to the overlapping edges. The width and thickness of the film strip may vary depending upon strength desired. For example, it may be about /s to /2 inch wide and from 3 to 15 mil. thick. The strip could also be extruded in the form of a cylindrical strand up to about /s inch in diameter. The strip may also be applied by moistening the surfaces with water and pressing in place while applying sutficient heat to remove the moisture. Additionally, the material may be applied from a solution, such as from about an 18% to 50% solids solution, to deposit a weight of material equivalent to the extruded films or strands mentioned above. In accordance with one aspect of the present invention, improved strength can be achieved by employing a cast strand.
The present invention may be readily adapted to commercial production. Suitably, for example, the watersensitive material may be extruded in continuous strand form in the area of overlap as the pad wrapper is being overfolded on itself in a continuous process and the strand may then be heat sealed in place. These materials are thermoplastic at temperatures in the range of from about 210 C. to about 250 C. To obtain a good overlap seal, it is desirable that the temperature used to effect the heat bonding be sufficient to cause the film to shrink and become stiff again after the softening process.
If desired, a minor amount of a plasticizer may be used to further improve the flexibility of the water-sensitive material. For example up to about 30% or more by weight of the material may be substituted by a material such as polyethylene glycol, propylene glycol monostearate, tetrahydrofuryl phosphate may be employed. Any other known plasticizing agent may similarly be employed.
Thus, as has been seen, the present invention provides a sanitary napkin which is designed for disposal in conventional toilet systems. By employing a layer of hydroxyalkylated cellulose to bond the overlapping edges of the fluid pervious wrapper in accordance with the present invention, the Wrapper has ample strength to perform its support function, yet which will readily disintegrate when placed in an excess of water, as in a conventional toilet system.
I claim as my invention:
1. A fiushable catamenial absorption device comprising the combination of an absorbent pad, an excess waterdisintegratable fluid pervious wrapper enclosing the pad and having longitudinally extending overlapping edges with a layer of a hydroxyalkylated cellulose watersensi tive material positioned between the overlapping edges to bond a portion of the overlapped wrapper together.
2. The device of claim 1 wherein the water-sensitive material is hydroxypropyl cellulose.
3. The device of claim 2 wherein the hydroxypropyl cellulose comprises a cast film.
4. The device of claim 1 wherein the wrapper includes full tabs extending from both ends of the absorbent pad.
5. The device of claim 1 wherein the wrapper is comprised of staple fibers discontinuously bonded with a water-sensitive adhesive.
6. The device of claim 5 wherein the adhesive is polyvinyl alcohol.
7. The device of claim 2 wherein the hydroxypropyl cellulose has its insolubility temperature reduced by the addition of sodium chloride.
8. The device of claim 2 wherein the hydroxypropyl cellulose has its insolubility temperature reduced by the addition of sucrose.
References Cited UNITED STATES PATENTS -Beery et a1. 128-290 Brownlee et al. 128-290 Joa 128-290 Morse 128-290 Burgeni 128-290 Joa 128-290 Champaigne, Jr. 128-290 CHARLES F. ROSENBAUM, Primary Examiner