Flushable Sanitary Napkin

Abstract

A sanitary napkin of simple construction is provided with a barrier sheet effective for preventing menstrual fluid from passing through the absorbent core of the napkin and onto the underside of the napkin cover. The napkin is constructed so as to allow the barrier sheet to be easily removed from the remainder of the napkin which then can be flushed in a conventional water closet. Specifically, a barrier sheet is held in place during manufacture and use by a tissue paper wrapper which is shorter in the longitudinal direction of the napkin than the barrier sheet leaving at least a portion of the barrier sheet unwrapped. This unwrapped portion may be gripped for removing the barrier sheet from the napkin. This tissue wrapper is so chosen as to allow the napkin of this invention to be manufactured by means compatible with conventional manufacturing techniques.

Description

BACKGROUND OF THE INVENTION

This invention relates to sanitary napkins and more particularly, to sanitary napkins having conventional high wet strength, non-woven covers but which can be safely and easily disposed of, subsequent to use, simply by flushing away in an ordinary water closet.

Sanitary napkins usually comprise a highly absorbent core of fibrous material, such as, comminuted wood pulp fibers, regenerated cellulose or modified cellulosic fibers, cotton linters, bleached sulfite, creped wadding and the like, encased in a non-woven fabric cover. A barrier sheet is generally provided between the cover and the bottom of the absorbent core, i. e., the surface worn away from the body, to prevent menstrual fluid from being transferred through the napkin and wetting the underside of the cover.

Such sanitary napkins are, from a functional standpoint, very acceptable, but disposability thereof has been particularly difficult in that they cannot be easily flushed away in a water closet. To be truly flushable, it is necessary that each component of the napkin when attacked by the excess swirling water of a flushing water closet, be sufficiently reduced in bulk to pass, without clogging, through the piping and fixtures of the water closet and its attendant sewer system. Additionally, it is desirable that each component of the napkin be attackable by microbial action in conventional sceptic systems, i.e., to be biodegradable. Unfortunately, most sanitary napkins cannot meet these criteria in respect to at least one component.

The absorbent cores of most conventional napkins easily meet these criteria as they are comprised of biodegradable fibers loosely held together and easily disintergratable by the action of water. Likewise, napkin covers have already been suggested which, while having the requisite wet-strength in use, will disintegrate in a water closet and be biodegradable in a sceptic system. Some problems have arisen in this connection in that such covers tend to disintegrate at a slow rate and retard the disintegration of the core which they encase. This problem has been met by providing a napkin such as that described in U.S. Pat. No. 3,683,919 issued to Mr. M. B. Ells on Aug. 15, 1972 wherein the napkins provided may be readily torn longitudinally into two portions to release the absorbent core from the encasing cover. Thereafter, the core and the cover may be flushed away in a conventional water closet.

The difficult problem in flushing conventional napkins arises when these napkins include a water impervious barrier film between the core and the underside of the napkin cover. These are of necessity insoluble in menstrual fluid and hence generally insoluble in water. Accordingly, they do not disintegrate in a water closet and instead tend to float to the top of the bowl, all of which makes flushing difficult. Additionally, the films are generally made of synthetic polymers such as polyethylene, polypropylene, polyvinyl chloride, polytetracfluoroethyl, etc., which are not biodegradable.

Because of these shortcomings, it has heretofore been difficult to provide a sanitary napkin which incorporates a non-water disintegratable, non-biodegradable film for use as a barrier sheet and yet can be readily disposed of in a water closet.

SUMMARY OF THE INVENTION

In accordance with the present invention, a sanitary napkin of simple construction is provided with a barrier sheet which is effective in preventing menstrual fluid from passing through the absorbent core, and onto the underside of the napkin cover, but which napkin is so constructed as to allow the barrier sheet to be easily and conveniently removed from the remainder of the napkin, so that the remainder may be flushed in a conventional water closet.

Specifically, the napkin of this invention comprises a longitudinally extending, absorbent core of biodegradable, fibrous material adapted to be placed in proximity with the body to receive body fluids. A barrier film, impervious to body fluids, overlies the surface of the core placed away from the body and is adapted to deter the spread of body fluids beyond the absorbent core. To hold the barrier sheet in place, both during manufacture and in use, a tissue paper wrapper is provided, wrapped around the absorbent core and the fluid impervious barrier film. The tissue wrapper is shorter in the longitudinal direction of the core than is the fluid impervious barrier so as to leave unwrapped, at at least one end of the core, a portion of the fluid barrier sufficient to allow the unwrapped portion to be gripped for removing the barrier from the napkin. Preferably, this unwrapped portion should be about one-eighth inch to about 11/2 inches as measured in the longitudinal direction of the core and more preferably, about one-fourth inch to about 1 inch. A non-woven, biodegradable fibrous cover is provided encasing the wrapper, film and core. I have discovered that particular advantage accrues by employing as the tissue wrapper, a relaxed, extensible tissue and preferably one which is extensible to a degree sufficient, under the tension of line manufacturing operations, to extend the full longitudinal length of the core. Specifically, it is advantageous to employ a tissue wrapper having an elongation at break in the longitudinal direction of the napkin of about 25 percent to 125 percent when the tissue is in the range of 8-30 lbs/3,000 sq.ft. Still more preferably the elongation at break should be about 40 percent to about 80 percent when the tissue is in the range of 10-15 lbs/3,000 sq.ft.

The advantage which accrues from the above described napkin construction will become apparent from the following description considered together with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a sanitary napkin of this invention having portions cut away to reveal its internal structure;

FIG. 2 is a longitudinal cross-sectional view of the napkin of FIG. 1, taken along line 2--2;

FIG. 3 is a transverse cross-sectional view of the napkin of FIG. 1, taken along line 3--3 of FIG. 2;

FIG. 4 illustrates the removing of the barrier sheet of the napkin of this invention prior to disposal; and

FIG. 5 illustrates, schematically, a method for fabricating a napkin of this invention.

Referring now particularly to FIGS. 1-3, a sanitary napkin 10 consists of an absorbent longitudinally extending core assembly 12 encased in a cover 14 that extends beyond the ends of the core assembly 12 to provide the usual attachment tabs 20. The longitudinal edges 22 of the cover are overlapped on the bottom of the napkin. A suitable material for the cover 14 is a non-woven fabric such as that generally described in U.S. Pat. No. 3,123,076 issued to H. W. Griswold on Mar. 3, 1964 and which can be made by the method and apparatus shown and described in detail and claimed in U.S. Pat. No. 2,862,255, issued on Dec. 2, 1958 to Kalwaites or in accordance with the teachings of U.S. Pat. No. 3,081,514, issued on Mar. 19, 1963 to Griswold or U.S. Pat. No. 3,081,515 also issued Mar. 19, 1963 to Griswold et al. In general, such non-woven fabrics are formed of cellulosic fibers which becomes oriented predominately in the machine direction and which have high menstrual fluid wet strength and abrasion resistance imported thereto by using a bonding material applied, for example, by printing or impregnation techniques. The non-woven cover 14 is encased about the core assembly 12 so that the fibers, predominately oriented in the machine direction are also oriented essentially parallel to the longitudinal direction of the napkin.

The core assembly 12 comprises a highly absorbent longitudinally extending pad 16, a menstrual liquid impervious barrier sheet 18, and a tissue wrapper 24. The pad 16 consists of fibrous materials such as comminuted wood pulp fibers, regenerated cellulosic fibers, modified cellulosic fibers, cotton linters, bleached sulfite creped wadding and the like or combinations thereof.

The barrier sheet 18 is provided overlying essentially the entire bottom of the pad, i.e., the surface of the pad which, in use, is placed away from the body) and extending down along the sides of the pad 16. The barrier sheet is provided to preclude the flow of menstrual fluid through the pad to the cover and onto the outer bottom surface of the napkin. Preferably, the barrier sheet extends down over the sides of the pad to similarly prevent flow of menstrual fluid onto those surfaces.

The barrier sheet 18 consists of a thin film of menstrual fluid-impervious material such as polyethylene, polypropylene, polyvinyl chloride, polytetrafluoroethylene, polytrifluoro chloroethylene, cellulose acetate, vinyl chloride - vinyl acetate copolymers, etc. These are all generally available in thickness in the range of about 0.2 to about 1 mil and are suitable in these thicknesses for incorporation into the napkin of this invention. In some cases, paper tissue or other normally pervious sheet material may be used if they have first been rendered imprevious by virtue of treating the same with a repellant. Whichever of these materials are used, however, they are each incapable of disintegrating in water and are not biodegradable and so are not suitable for disposal by flushing in a water closet. Notwithstanding these shortcomings, these materials are excellent barriers to the flow of menstrual fluid, are economical, and are readily available. When they are incorporated in a napkin of this invention, their use does not preclude the disposability of the remainder of the napkin in a water closet.

A further characteristic of these barrier films is their smooth surface and low coefficient of friction. This smoothness causes problems during the manufacture of the napkin in that during the high speed assembly encountered in their manufacture, the films tend to slip and hence become displaced from the desired position. The problem of displacement also exists in use and is then further aggravated because that surface of the film in contact with the core is wet and hence even more slippery. To prevent such displacement, the pad and barrier sheet are wrapped in the flexible, fluid pervious tissue wrapper 24 which extends completely around the assembly and holds the barrier sheet in place. The tissue wrapper is light weight and thin so as not to add appreciably to the bulk or cost of the napkin. Preferably, the tissue has a thickness ranging from about 0.6 mils to about 2.0 mils and a basic weight of about 8 to about 30 pounds per 3,000 square feet of paper. In accordance with this instant invention, the tissue wrapper is shorter in the longitudinal direction of the napkin than the barrier sheet thereby leaving a portion 18a of the sheet 18 unwrapped.

In accordance with the teachings of this invention, this unwrapped portion 18a must be of sufficient length to allow the user to grip the barrier film for removal from the remainder of the core assembly, as shown in FIG. 4, where disposal of the napkin is illustrated. The napkin, after use, may be disposed of by flushing in a water closet and will be completely flushable and biodegradable if the barrier film is first removed. As illustrated in FIG. 4, this removal is accomplished by first tearing the cover longitudinally so as to expose the core assembly. The longitudinal tear may be facilitated by the methods described in U.S. Pat. No. 3,683,919 issued to Mr. M. B. Ells on Aug. 15, 1972, whereby the adhesive applied to the overlapped sections of the wrapper to hold same in place is also used as a guide for producing a straight longitudinal tear when disposing of the napkin. Having torn the cover to expose the core assembly, the unwrapped portion of the barrier film may now be gripped and the barrier film pulled free of the remainder of the napkin which can then be flushed and will disintegrate in a water closet. To accomplish this method of removal, the barrier film must be sufficiently exposed when the wrapper is torn to allow the user to grip same. Too little unwrapped length will make removal difficult. Too great an unwrapped length will allow the barrier film to move too freely during manufacturing and use and hence destroy the value and purpose of using a tissue wrapper. Generally, an unwrapped length of about one-eigth inch to 11/2 inches is satisfactory and preferably a length of one-fourth inch to 1 inch gives excellent results.

The napkin configuration of this invention, shown in FIGS. 1-4, would generally appear to be incompatible with current sanitary napkin methods of manufacturing in that because of economic considerations, it is essential that sanitary napkins be manufactured at great speeds, manufacturing lines being operated at the rate of as much as 600 napkins per minute and, accordingly, every effort is made to simplify the assembling steps. It is highly desirable, for example, that the core be completely preassembled before cutting into individual napkin core assemblies, thus eliminating several cutting steps. Current practice then is to deliver to a cutting station, by means of a conveyer belt or the like, a long sliver of absorbent core assembly having the barrier film and the wrapping tissue in place around the absorbent core and making a single cut through the entire cross-section of the core assembly, just prior to applying the non-woven wrapper. This practice would appear to be incompatible with the configuration prescribed herein as it would appear to result in a core assembly wherein the pad, the barrier film and the tissue wrapper are all coextensive in the longitudinal direction of the napkin (the direction of the conveyer).

It has been discovered that this apparent incompatibility may be overcome by taking advantage of the fact that, because the sliver is essentially being pulled through the manufacturing equipment as it moves along the conveyer system, the sliver 26 is generally under tension T in the longitudinal direction until it reaches the cutting station where, upon being cut, the tension is released. In accordance with this invention, a tissue is chosen as the wrapping material to have the property of being extensible under such line tension so as to fully extend along the length of the sliver but which, in the releaxed state, which it assumes after cutting and release of such tension, will retract and reach the configuration shown in FIGS. 1-3. Generally, the line tension is about 0.05 to about 0.3 lbs. per inch of width and hence when the tissue chosen has the properties prescribed herein, satisfactory results occur.

FIG. 5 illustrates the method of manufacturing the napkin core assembly 12 illustrated in FIG. 1-4. Shown therein is a length of sliver 26 moving, from left to right, in the illustration, by means of a conveyer belt or the like. As a result of the fact that the sliver is being pulled through processing equipment, the sliver is under a tensile stress in the longitudinal direction, designated in FIG. 5 by the letter T. Because of this tension, the outer layer of the assembled sliver, tissue 24, is in the extended state. A cutting station, comprising rotating cutter 28 having a blade 29 and opposing cutting surface 30, is provided and is timed with the speed of the conveyer belt to cut the sliver into the required lengths of core assembly. At the instant before blade 29 cuts into the sliver, the tissue, the barrier film and the pad all extend beneath the blade. When the knife cuts through the cross section of the sliver, freeing the cut piece from the line tension T, the trailing edges of the tissue on the cut portion retract, as in cut core assembly 12, to expose the barrier film and pad in accordance with the teachings of the invention. As soon as the leading edges of the cut core pass the knife station, the tension T is similarly released and the tissue on this edge likewise retracts to form a core assembly having uncovered barrier film on both ends of the pad.

It will be apparent to one skilled in the art that many variations and modifications in the above-described specific embodiments may be made without departing from the scope and spirit of the invention. For example, while the invention has been specifically described in terms of a napkin having tabs for securing same in place during use, the invention will apply equally as well to the so-called tabless napkins having other securement means such as, for example, pressure-sensitive tapes, strips and the like as well as to full size and smaller sanitary napkins.

Claims

What is claimed is:

1. A sanitary napkin comprising:

a. an absorbent core of water dispersible fibrous material adapted to be placed in proximity with the body to receive body fluids;

b. a moisture barrier sheet film overlying the surface of said absorbent core worn away from the body and adapted to deter the spread of body fluids beyond said absorbent core;

c. a tissue paper wrapper wrapped around said absorbent core and said waterproof moisture barrier, said tissue paper wrapper comprising a means for removing the barrier and for exposing at least one end of said barrier to provide a grip portion including having said tissue of a recoverable extensible property such that under manufacturing line tension, said tissue is coextensive with the length of said barrier in a longitudinal direction, and in the relaxed non-tension condition is shorter than the length of the barrier in the longitudinal direction; and

d. a non-woven water-dispersible fibrous covering surrounding said wrapper, film and core.

2. The napkin of claim 1 wherein the grip portion is about one-eigth to about 11/2 inches.

3. The napkin of claim 2 wherein the grip portion is about one-fourth to about 1 inch.

4. The napkin of claim 1 wherein said tissue has an elongation at break in the longitudinal direction of the napkin of about 25 to about 125 percent and a weight of about 8 to about 30 lbs. per 3,000 square feet.

5. The napkin of claim 4 wherein said tissue has an elongation at break of about 40 percent to about 80 percent and a weight of about 10 to about 15 lbs. per 3,000 square feet.