US 3580253 A
Description (OCR text may contain errors)
United States Patent Leo J. Bernardin Appleton, Wis.
Dec. 9, 1968 May 25, 1971 Kimberly-Clark Corporation Neenah, Wis.
inventor Appl. No. Filed Patented Assignee SANITARY NAPKIN AND FLUSHABLE WRAPPER THEREFOR Primary Examiner-Charles F. Rosenbaum Attorneys-Daniel J. Hanlon, Jr. and Raymond J. Miller ABSTRACT: A flushable pad wrapper for sanitary napkins comprising a nonwoven web of cellulosic fibers in which the fibers are bonded together by sodium carboxymethylcellulose acidified to a pH of between 2.2 to 2.0. This wrapper has sufii cient wet strength and abrasion resistance to perform satisfactorily in normal use but disintegrates readily when immersed and agitated in water.
SANITARY NAIKIN AND FLUSHABLE WRAPPER THEREFOR BACKGROUND OF THE INVENTION The disposal of sanitary napkins after use is a problem which could be simplified if their construction was such that the entire element could be flushed away in a conventional toilet system. Ordinarily the absorbent core of sanitary napkins can be so disposed of quite readily, if it is separated from its outer wrapper, sincesuch cores are customarily made of easily disintegratable materials such as wood pulp fluff, cellulose wadding, or absorbent cotton batts. However, the task of removing the outer wrapper is generally considered to be an inconvenient, disagreeable and unsanitary task. As a result the most common method of disposal is to roll up the soiled pad, tie the tab ends, and discard it in a waste basket. Because of odor problems, this method of disposal is generally considered undesirable. Individual disposal bagswith self-sealing means are therefore frequently used for the purpose to avoid residual odor problems.
It would be highly desirable if a pad could be developed which has a wrapper strong enough to withstand tearing and scuffing when worn, but which would disintegrate readily in water, so that the complete structure could be dropped in a toilet and flushed away. This would eliminate the need for stripping the wrapper from the pad before disposing of the latter.
This invention is directed to a wrapper construction which solves that problem.
SUMMARY OF THE INVENTION Sodium carboxymethylcellulose (hereinafter identified as CMC), sometimes referred to as sodium cellulose glycolate, is a water-soluble gum which, among other things, has been used as a binder for some types of nonwoven webs and also for what is known as dissolving paper. CMC swells readily in the presence of moisture and disperses rapidly when contacted with water. In common use as a binder it is applied in solution form having a pH of between 6.58.0.
It is now been found that if, after application as a binder to a nonwoven web of fibers, the CMC is carefully acidified down to a pH of 2.2 to 2.0, washed free of the acidifying solution and dried, the CMC will not. readily swellin the presence of moisture, but will nevertheless dissolve rapidly when dropped in an excess of water such as in a toilet bowl.
A nonwoven web of this type therefore makes an excellent flushable wrapper for sanitary napkins. It will remain intact in the presence of body moisture and fluids, yet will disintegrate into its fibrous components in water.
Accordingly it is the principal object of this invention to provide a flushable wrapper for sanitary napkins.
It is another important object to provide a process for fabricating such a wrapper.
Still another object is toprovide a sanitary napkin construction in which the entire structuremay be disposed of by flushing in conventional toilet systems.
These and other objects and advantages ,will become apparent by reference to the following specification wherein there is described various selected embodiments of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS A wrapper in accordance with this invention was made by forming a lightweight, carded web comprised of 1.5 denier rayon fibers cut to l 9/l6 inches staple length. The weight of the web was about 14 grams per square yard. The web was impregnated by spraying it with a 2 percent CMC solution in an amount to provide a pickup of IO percent-CMC based on the dry fiber weight. The impregnated web was then passed through a squeeze roll nip to distribute theCMC uniformly and then passed through a solution of hydrochloric acid to acidify the CMC. This acid bath treatment was conducted on three separate batches of the CMC bonded web at three predetermined pH levels; i.e., at a pH of 2.0, 2.2 and 2.4, respectively. Each of the impregnated and acidified webs were then washed in de-ionized water and dried by heating. The water need not necessarily be de-ionized, but preferably should not be alkaline in order not to reverse the acidification process. The heating was done at about l05 C., and for a period sufficient to dry but not to embrittle the web.
Sanitary napkins were made using conventional sanitary napkin fillers as the absorbent, and enwrapping these cores with webs having the CMC binder acidified at each of the above-defined pH levels.
These napkins were tested in actual use by a group of panelists. The absorption performance of the napkins having binders acidified to a pH range of 2.0 and 2.2 was in the same range as conventional napkins, while that of the napkin with the binder acidified to a pH range of2.4 was about 25 percent less. The reason for the lower fluid pickup of the napkins wrapped with webs acidified to a pH of 2.4 was not directly explainable, but it is theorized that this may have occurred because the pads were probably worn for shorter periods. The latter may have been due to the fact that end tabs tore off on some pH 2.4 samples, or because on other pH 2.4 samples the binder was softened by body fluids and stuck to the skin.
In the pads acidified to pH 2.2 and pH 2.0 no end tab tearing occurred nor was there any sticking to the skin.
The pad wrappers in all three cases disintegrated rapidly when flushed in excess water in the toilet.
The above results indicated that CMC binder acidified to a pH of between 2.0 and 2.2 is effective as a flushable binder for nonwoven pad wrappers. The acidified CMC in this range is sufficiently stable in the presence of body moisture and menstrual fluids to maintain the wrapper intact during use and disintegrates easily in conventional toilet systems. Above pH 2.2 the CMC swells too easily in the presence of body moisture and fluids, whereby the bonded web does not remain stable enough during use to retain its integrity. In addition the gelatinizing effect of moisture on the CMC in this higher pH range causes it to stick to the body during use, which is another disadvantage.
If the CMC is acidified to a pH substantially below 2.0, the CMC is no longer chemically stable and tends to disintegrate. In addition the highly acid condition of the binder is detrimental to strength and aging properties since it tends to cause degradation of cellulosic fibers such as rayon, especially during oven drying.
This binder system is applicable to cellulosic fibers, in general, including natural and regenerated cellulose. Rayon fibers in the deniers and lengths adapted for carding processes are especially suitable. Minor amounts of synthetic fibers may also be blended into the webs.
While the specific example refers to carded webs as the base material, other methods of forming, such as airlaying, wetforming using papermaking techniques, and the like, may be used.
In the acid bath, other strong mineral acids such as sulfuric or phosphoric may be used.
The type of absorbent filler employed in the complete sanitary napkin is not critical. Preferably of course, it should be of a structure which easily disintegrates in water if the flushable properties of the wrapper are to be fully utilized. The fillers for most commercial napkins are made of woodpulp fluff, creped cellulose wadding, orabsorbent cotton or rayon fiber batts, which will easily disintegrate if separated from their supporting wrappers. Some pads contain plastic film'baffles, but these are generally so small and thin that they crumple easily into a size which passes through conventional plumbing without trouble.
The base fiber webs may have the fibers aligned substantially in one direction, may have the fibers in random isotropic arrangement or may contain crosslaid layers depending upon the strength characteristics desired.
The amount of binder used will depend on the final strength desired as well as on the speed of solution. Pickups as low as ing a nonwoven web of cellulosic fibers bonded by an adhesive comprising sodium carboxymethylcellulose; said binder being acidified to a pH in the range of 2.2 to 2.0.
2. The wrapper of claim 1 in which said fibers are selected from the group consisting of natural cellulose and regenerated cellulose.
3. The wrapper of claim 1 in which said web comprises carded fibers.
4. The wrapper of claim 2 in which said web comprises carded textile length rayon fibers.
5. The wrapper of claim 3 in which said web comprises multiple carded webs crosslaid with respect to one another.
6. The wrapper of claim 1 in which the pH of said binder is 2.2.
7. A sanitary napkin comprising an absorbent core enwrapped with a fluid-pervious wrapper comprising a nonwoven web of textile fibers bonded by an adhesive comprising sodium carboxymethylcellulose; said binder being acidified to a pH in the range of2.2 to 2.0.
8. A sanitary napkin in accordance with claim 7 in which said fibers are selected from the group consisting of natural cellulose and regenerated cellulose.
9. A sanitary napkin in accordance with claim 7 in which said web comprises carded fibers.
10. A sanitary napkin in accordance with claim 8 in which the fibers in said web comprises a carded web of staple length rayon fibers.
l l. A process for producing a flushable wrapper for sanitary napkins which comprises forming a lightweight nonwoven web from cellulosic fibers, impregnating said web with a dilute solution of sodium carboxymethylcellulose, passing said impregnated web through an acidifying solution having a pH of from 2.2 to 2.0, washing said web free of said acidifying solution, and drying said web with heat.
12. The process of claim 11 in which said web is caused to pick up said sodium carboxymethylcellulose in an amount of between about 2 percent and 20 percent by weight of the fibers. I
13. The process of claim 11 in which said web is formed by carding the fibers. I
147 The process of claim 11 in which said web is formed by airlaying the fibers.
' 15. The process of claim 13 in which said carded webs are crosslaid before impregnation and acidification