IE43200B1

IE43200B1 - Flushable sanitary napkin

Info

Publication number: IE43200B1
Application number: IE2236/75A
Authority: IE
Original assignee: Personal Products Co
Priority date: 1974-10-15
Filing date: 1975-10-04
Publication date: 1981-01-14
Also published as: IE43200L; US3913579A; DE2546209A1; CA1043502A; AU8524975A

Abstract

A sanitary napkin is disclosed which includes a flushable absorbent pad and an extremely flushable nonwoven fibrous cover that is bonded with a totally water-soluble resinous binder. The cover is reinforced with hot-melt adhesive means in spaced selected generally rectangular zones to increase the wet strength of the cover in areas of high stress which have the probability of being wetted by menstrual fluid, and the increase in wet strength is achieved without impairing the flushability of the cover. The hot-melt adhesive means is applied in spaced discrete lines in each of the zones and the total area of the zones comprises approximately 30 percent of the total area of the cover.

Description

This invention relates to sanitary napkins.

In the sanitary napkin art, there has been a longstanding need and desire for a completely flushable product, i.e., a sanitary napkin that will readily disintegrate when subjected to excess water and the flushing action of a conventional toilet. This desideratum has been well recognized in the prior art, see for example, U.S. Patent Nos. 3,521,638, 3,550,592, 3,554,788, 3,610,254, 3,616,797 3,654,928 and 3,707,430.

Sanitary napkins have conventionally in the past included a nonwoven fabric cover surrounding an absorbent pad of short cellulosic fibers, with a water-repellant layer being provided between the pad and the cover to prevent menstrual fluid from striking through the product. One of the basic problems in providing complete flushability with such a product is to give the cover of the sanitary napkin adequate wet strength so that the product maintains its structural integrity in the presence of body fluid, while at the same time insuring that the components providing the wet strength characteristics will quickly break-down when subjected to flushing a toilet. Various solutions to this problem have been proposed in the abovementioned patents. However, most of the solutions that have been proposed in the past have been rejected or proven to be unsatisfactory because of either excessive cost, inadequate resistance to wet abrasion, inadequate flushability, inadequate dry and/or wet tensile characteristics, and unsatisfactory softness.

Thus, the need remains for a solution to the problem of providing a commercially feasible completely flushable sanitary napkin.

Like certain of the previously proposed flushable sanitary napkins, the product of the present invention includes an absorbent pad of short cellulosic fibers surrounded by a nonwoven fibrous cover that is bonded with a water-soluble resinous binder. However, the sanitary napkin of the present invention differs significantly from proposed prior art products in that a water-insoluble reinforcing agent is applied to a substantial area (approximately 30%) of the cover. The reinforcing agent is a hot-melt adhesive that is applied to spaced selected zones of the cover which have the greatest probability of being wetted by menstrual fluid, and the hot-melt adhesive is applied in the form of a plurality of spaced discrete lines within each of the zones.

The present invention provides a flushable sanitary napkin comprising: a generally rectangularly shaped in plan view absorbent pad; a nonwoven fibrous cover surrounding said pad, said cover being ractangular in shape when laid out flat and larger in length and width than said p id, the opposite side marginal edges of said cover being folded over said pad and into overlapping relationship with one another, the opposite end edges of said cover extending beyond the ends of said pad and providing attachment t:b means, the cover being bonded with a water-soluble r· sinous binder; and hot-melt adhesive applied to spaced s lected generally rectangular zones of said cover for reinforcing said cover against wear in said zones, a first of said zones being located generally medially of said cover and disposed generally centrally of said pad on the face thereof to be positioned against the body of the wearer, - 4 aaiasji© a second and a third of said zones being spaced generally equally outwardly of said generally medially located zone and disposed in a position adjacent the opposite side edges of the pad, and a fourth of said zones being located along one side marginal edge of said cover and extending from end to end thereof to provide reinforcement in said attachment tab means, the areas of said cover outwardly of said zones being free of said hot-melt adhesive, said cover being disintegratable after soaking in excess water to permit disposal of the napkin by flushing.

Preferably the hot-melt adhesive is applied in lines in each of the reinforced zones of the invention and the lines of adhesive are about 1/8 wide and are spaced from one another from about 1/8 to about 3/8. Preferably, the lines are rectilinear throughout their length and are parallel with one another. The lines are applied to the interior of the cover, i.e., the surface of the cover directly adjacent to the pad, and do not adversely affect the softness and feel of the cover.

Surprisingly, in spite of the relatively substantial amount of the hot-melt adhesive, the cover is readily disintegratable after soaking in excess water to permit disposal of the sanitary napkin by flushing in a conventional toilet. The increased strength imparted to the product by strategic location and distribution of the hot-melt adhesive is achieved with no sacrifice in softness of the product and with an insignificant effect on flushability.

Thus, the present invention provides an economically feasible solution to the troublesome problem that has long plagued skilled workers in the sanitary napkin art, i.e., wet strength and resistance to abrasion in the presence of body fluids and ready disintegratability in the presence of excess water.

The invention will be understood from the following description of an embodiment thereof with reference to the accompanying drawings in which: Fig. 1 is a fragmentary perspective view of a sanitary 4-SSGO napkin formed in accordance with the invention and illustrated in the shape that it assumes while being worn; Fig. 2 is a perspective view of the sanitary 5 napkin illustrated in Fig. 1 in a flat position suitable for packaging, with a portion of the cc-.er being broken away; Fig. 3 is a plan view illustrating the inner surface of cover fabrics laid out flat as manufactured for use with the sanitary napkin of the present invention; Fig. 4 is an enlarged end view of the cover fabric shown in Fig. 3 with the inner surface facing downward; and Fig. 5 is an enlarged cross-sectional view taken generally along lines 5-5 of Fig. 2.

Referring now to the drawings, the sanitary napkin of the present invention includes an absorbent pad or core 12 encased within a fluid pervious cover 14. As can be best seen in Figs. 1 and 5, a barrier sheet 16 overlies the sides and the bottom surface of absorbent pad 12 (the bottom surface being the portion of the napkin facing away from the body of the wearer). Pad 12 is formed of absorbent fibrous material such as comminuted wood pulp fibers, cotton linters, rayon fibers, cotton staple, bleached sulfite linters, and other cellulosic or m .dified cellulosic fibers and the like. The exact s ructure of pad 12 is not critical to the present invention, a .d the pad may include multiple plies and/or densified c llulosic portions, as taught, for example, by U.S. Patents 2,352,260, 3,017,304, 3,060,936 and 3,494,362. It should also be understood that the absorbent core may comprise, in addition to the absorbent pad 12 and barrier sheet 16, a fluid pervious element such as gauze, tissue and the like if increased strength and/or dimensional stability are desired. ->ς Barrier sheet 16 is a thin film which is resistant <33300 to body fluids so as to prevent menstrual fluid from striking through the cover of the sanitary napkin.

The film is dispersible in water and may be constructed as disclosed in U.S. Patent Specification No. 3,800,797.

Other suitable water dispersible films will suggest themselves to those skilled in the art.

Pad 12 in its flat position is generally rectangular in shape, both in cross section and plan view, and the end and side portions of the pad may be rounded for enhanced comfort to the wearer. Cover 14 is also rectangular in shape as can be best seen in Fig. 3, and cover 14 is larger than pad 12 both in length and width, with the pad being generally centrally disposed with respect thereto. The opposite side marginal edges 18 and 20 of cover 14 are folded over pad 12 and into overlapping relationship with one another to encase the pad and to provide tab means 22 and 24 at opposite ends of the napkin for attachment to a support belt circumscribing the hips of the wearer.

Cover 14 is a nonwoven fibrous member bonded with a water-soluble resinous binder so as to be inherently dispersible in excess water. While many different types of fluid pervious nonwoven fabrics are suitable for use as a cover for the sanitary napkin of the present invention, the cover is preferably an apertured nonwoven fabric such as those disclosed in U.S. patents 2,862,251, 3,129,466, 3,193,436, 3,081,515, 3,081,514, 3,081,512, 3,081,500, 3,068,547, 3,059,313, 3,681,182, 3,681,183, 3,681,184 and 3,682,756.

Typical water-soluble polymers, useful as binders for the nonwoven covers include water-soluble vinyl polymers, such as polyvinyl alcohol and polyvinyl pyrrolidone; polymers of acrylic acid and its homologs, such as polyacrylic acid and polymethacrylic acid; modified starches, such as · dextrins, hydroxyethyl starch ethers, amine starches, phosphate starches and starch acetates; cellulose derivatives ££>2ΐΰ - 7 .including carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl hydroxypropyl cellulose, methyl cellulose, ethyl cellulose, and epoxy derivatives oi cellulose; natural gums and alginates, including gum arabic and sodium alginate; polyacrylamide; polyethylene oxide; polyethyleneimine; polyacrylonitrile; and saponified copolymers of ethylene and vinyl acetate.

Cover 14 is reinforced in spaced selected 10 generally rectangular zones hy a water-insoluble hot-melt adhesive to increase the wet strength of the cover in those -areas which have the greatest probability of being wetted l.y menstrual fluid. The term hot-melt as used herein j -·. intended to mean any adhesive base that can be readily softened by moderate heating without degradation of the b.ise itself and which can be melted and applied in molten form to the cover. Typical water-insoluble thermoplastic polymers useful as hot melt adhesives include polyolefins such as low-density polyethylene and polyisobutylene; polyamides, polycarbonates; polyesters; polyurethanes; polystyrene; acrylic polymers; copolymers of ethylene and vinyl acetate; and copolymers of ethylene and ethyl acrylate. As with other types of adhesives, various additives may be added to increase tackiness, flexibility, or flow properties during application. Such adhesives are advantageous in that they contain no water. or expensive solvents that must later be removed and furtherm>re, such adhesives are extremely fast setting because s mole cooling is all that is required to develop bond s rength.

With reference to fig. 3, a first zone 26 is located generally medially cf the cover 14 and second and third zones 2c and 30 are spaced generally equally outwardly from zone 25- zones 2-2 and 30 are generally equal in length and width and are wider and snorter man central zone 26. A fourth zone 32 is provided along cover side marginal edge 18 and extends from end to end thereof, with the zone 32 being generally equal in width to central zone 26.

Zone 26 is provided on the face of the napkin that is to be positioned adjacent the body of the wearer and provides reinforcement in the area that directly receives the body fluid discharge and which is stressed significantly by normal functions of the wearer. Zone 26 extends beyond the end portions of the pad to protect against the possibility of fluid wicking in the cover beyond the ends of the pad. Zones 28 and 30 are generally coextensive in length with the sides of the pad, and provide reinforcement against the considerable abrasion that is imparted to these portions of the cover by rubbing against an undergarment or against the body when the napkin assumes the position shown in Fig. 1. Zone 32 provides reinforcement in the attachment tabs 22 and 24, which are sometimes struck with menstrual fluid by misplacement of the napkin or by an end failure of the pad.

As is evident from Figs. 3 and 4, the hot-melt adhesive in each of zones 26, 28, 30 and 32 is applied in the form of a plurality of spaced discrete lines. And, from Fig. 5, it is clear that the adhesive lines are applied, such as by extruding, to the inside of the cover, i.e., the surface of the cover that faces pad 12. With this arrangement any possible adverse affect on the softness and feel of the cover is minimized. The lines within each of the zones are illustrated as being continuous and rectilinear throughout their length and parallel with one another and with the side marginal edges of the cover. Although it is not perferred, it is contemplated that in certain instances, the lines could be discontinuous and/or curvilinear or non-parallel.

In a most preferred embodiment of the invention, the lines within each of the zones are of equal width and are spaced equally from one another. The overall area of 2ones 26, 28, 30 and 32 represents a significant, although minor, portion of the total area of cover 14, and it has 4S200 been found that when the reinforced zones comprise as much as 30% of the total area of the cover, there is only an insignificant effect on the flushability of the cover, with the result that a sanitary napkin made from such a cover can be readily disposed of in a conventional toilet.

Sanitary napkins constructed in accordance with the invention were prepared for testing by using the pad construction of a commercially available flushable napkin sold as MODESS* flushable feminine napkins., and such pads were wrapped with a nonwoven fabric made with rayon f Lber and bonded with a water-soluble alginate binder Of about 15 percent add-on based on the weight of the web and distributed uniformly in the web. Polyethylene based hot-melt adhesive was applied to the cover in about 6.27 weight percent based on the weight of the web, as a series of lines along the machine direction of the fabric. The hot-melt adhesive lines were approximately 1/8 wide and the spacing therebetween was varied from 1/8 to 3/8 in 1/16 increments. The fabrics were tested for resistance to wet abrasion and flushability, and were compared to a control fabric which was the same fabric without any reinforcement.

In order to simulate and measure in-use wet abrasion, εimples of 7 (machine direction) and 3 (cross direction) o ' cover fabrics as described in the preceding paragraph v re saturated with water and tested on a Stol abrasion t -ster with the motion cf the tester parallel to the m ,chine direction of the fabric. Standard 80 x 80 cotton w is used as the stationary surface, and the area of contact w s a 1-i/2 diameter circle, Samples were abraded in 0, iO, 20, 50 and 100 cycles, dried, and the machine direction tensile strength measured on a Instron tensile tester. The results of the tensile strength are reported in Table I, which also shows the percent loss of tensile strength with -a* φ W V - 10 respect to the 0 cycle reading. All of the reinforced samples showed higher tensile strengths after abrasion at each cycle reading than the control fabric without hot-melt reinforcement. It should be noted that in this test, the maximum loss in tensile strength is never 100 percent because the sample width is greater than the diameter of the abraded area; however, a hole was produced in the center of the sample with the control fabric at 50 cycles which added a 64.9 percent loss of tensile strength.

The data set forth in Table I indicates that a napkin cover bonded with a water-soluble binder performs much better under menstrual conditions when reinforced with hot-melt in the areas which are most subject to wet abrasion. The amount of increase of resistance to wet abrasion is dependent upon the number of hot-melt adhesive lines and the distance between them. The table includes data related to hot-melt adhesive lines spaced apart in a 1/8 to 3/8 range. ΡΠ ΙΌ Η Ο Ο Ο Ο Ο Ω 2 < Ο Ω · Η* Φ 0 ω μι 1 :o ω -J 3*· cP >-3 J * » • » » Φ 1 cn CD σ ys Q F d 1 to cn Ο O 0 0 to 3 W ♦ to l·-1 ω 1 cn cn tn O U- rf 1 4b 4b Μ O rf ώ fi 1 * » • • • φ « 1 Ό σι c O H cr P I to PJ Φ 3 h3 tr Pb H- Φ fi Cj 3 ω 0 rf to ή· 3 cr H· pi Cb • pj σ\ σ. -J 03 w Φ rf Φ » • • • • βι pr cn cn 4b Cu co φ 03 H 4b oo σ. to Φ rf rf w fi 0 Φ 4b 4b CJ ΙΌ tn to 3 4b U) σ to o O to • • • • • rf w to co to Ω Ω 0 pr *< Hl Ω H· rf to Φ Φ to ri 3 . to Φ A Φ K V-J to σ*. -J oo -J f-> Φ C • • • • fi cn 4b pj tn H to Φ cn 'X) to σ to rf P* h Φ H- 4b GO w to 3 3 O cj ΙΌ O lQ • • • • • rf rf tn w 4b o pr pr Φ H· V s *1) Ω Φ pr h-» H* tw 3 H* rf Φ tn σ\ σι σι o H· • « • • • 0 Qj σι O 00 σι tJl 3 to ω cn cn H fi rf Φ 0 Ω »r* Jb tw to rf tn NJ 4b -o O rf p. 1 ♦ « » • 0 >X> C\ σι o s 3 Q a 3 Ω Cb f< Ω pr I—' !—· Pj tn tn σ< o Φ to • • • • • CJ to tr -ό H1 rf Cf .£>. to tv co Φ pr Φ φ a tn lib. 4b H· 03 tn to O )3 3 ® • « » • X3 H· NJ tn «-j -J o • ff ω ω ί+ η ?-9 Φ ω ω rf Η t’P F Ο ω ω rr -7ί tn tn CJ t£? σι ω

Claims

1. A fludiable sanitary napxin comprising: a generally rectangularly shaped in plan view absorbent pad? a nonwoven fibrous cover surrounding the said pad, said cover being rectangular in shape when laid out fiat 5 and larger in length and width than said pad, the opposite side marginal edges of said cover being folded over said pad and into overlapping relationship with one another, the opposite end edges of said cover extending beyond the ends of said pad and providing 10 attachment tab means, the cover being bonded with a water-soluble resinous binder; and hot-melt adhesive applied to spaced selected generally rectangular zones of said cover for reinforcing said cover against wear in said sones, a first of said zones being located 15 generally medially of said cover and disposed generally centrally of said pad on the face thereof to be positioned against the body of the wearer, a second and a third of said zones being spaced generally <= jually outwardly of said generally medially located 2. O z >ne and disposed in a position adjacent the opposite side edges of the pad, and a fourth of said zones b 'ing located along one side marginal edge of said c >ver and extending from end to end thereof to provide r inforcement in said attachment tab means, the areas of 25 s iid cover outwardly of said zones being free of said hot-melt adhesive, said cover being disintegratable after soaking in excess water to permit disposal of the napkin by flushing.

2. A sanitary napxin as set forth in Claim 1 30 wherein said spaced selected zones comprise approximately 30% cf ti-j area of said cover.

3. A sanitary napkin as set forth in Claim 1 wherein said hot-melt adhesive is applied in spaced discrete lines within said zones.

4. A sanitary napkin as set forth in Claim 3 wherein said lines are about 1/8 wide and are spaced from one another by about 3/16.

5. A sanitary napkin as set forth in Claim 1 wherein the total area of said selected zones comprises a minor portion of the total area of said cover, and wherein said hot-melt adhesive is applied in spaced discrete lines within said zones.

6. A sanitary napkin as set forth in Claim 1 wherein said first zone of hot-melt adhesive is at least as long as said pad.

7. A sanitary napkin as set forth in Claim 6 wherein said first zone of hot-melt adhesive extends beyond the ends of said pad.

8. A sanitary napkin as set forth in Claim 1 wherein said second and third zones are generally coextensive in length with the adjacent side edge of the pad.

9. A flushable sanitary napkin comprising: an absorbent pad; a nonwoven fibrous cover surrounding said pad; and hot-melt adhesive applied to spaced selected generally rectangular zones of said cover for reinforcing said cover against wear in said zones, the total area of said selected zones comprising a minor portion of the total area of said cover, a first of said zones being located generally medially of said cover and disposed generally centrally of said pad on the face thereof to be positioned against the body of the wearer, and a second and a third of said zones being spaced generally equally outwardly of said generally medially located zone and disposed in a position adjacent the opposite side edges of the pad, the areas of said cover outwardly of said zones being free of said hot-melt adhesive and each of said zones including a plurality of spaced discrete lines of <32Οϋ - 17 hot-melt adhesive.

10. A sanitary napkin as set forth in Claim 9 in which the opposite end portions of the cover extend beyond the opposite ends of the pad to provide attachment tab means and wherein hot-melt adhesive is applied to the opposite end portions of said cover to reinforce slid attachment tab means.

11. A sanitary napkin as set forth in Claim 10 wherein said cover is rectangular in shape when laid out flat and larger in length and width than said pad, the opposite side marginal edges of said cover being folded over said pad and into overlapping relationship with one another.

12. A sanitary napkin as set forth in Claim 11 wherein said attachment tab means are reinforced by a fourth zone of hot-melt adhesive located along one side marginal edge of said cover and extending from end to end thereof.

13. A sanitary napkin as set forth in Claim 10 wnerein said cover is bonded with a water-soluble resinous binder whereby said cover is disintegratable after soaking in excess water to permit disposal by i ushlng.

14. A flushable sanitary napkin comprising: a g.-neraliy rectangularly shaped in plan view absorbent pad; a nonwoven fibrous cover surrounding said pad, said cover being rectangular in shape when laid out flat and larger in length and width than said pad, the opposite side marginal edges of said cover being folded over said pad and into overlapping relationship with one another, the opposite end edges of said cover extending beyond the ends of said pad and providing attachment tab means, the C'-ver being bonded with a water-soluble resinous binder; and a hot-melt adhesive applied to spaced selected generally rectangular zones of said cover for reinforcing s sid cover against wear in said zones, the total area of Ό2©0 - 18 said zones comprising a minor portion of the total area of said cover, a first of said zones being located generally medially of said cover' and disposed generally centrally of said pad on the face thereof to be positioned against the body of the wearer, a second and a third of said zones being spaced generally equally outwardly of said generally medially located zone and disposed in a position adjacent the opposite side edges of the pad, said first, second and third zones each being at least as long as said pad, and a fourth of said zones being located along one side marginal edge of said cover and extending from end to end thereof to provide reinforcement in said attachment tab means, said hot-melt adhesive being applied in the form of a plurality of spaced discrete lines within each of said zones and the area of said cover outwardly of said zones being free of said hot-melt adhesive, said cover being disintegratable after soaking in excess water to permit disposal of the napkin by flushing.

15. A sanitary napkin as set forth in Claim 14 wherein said second and third zones are generally equal in length, and said first zone is longer than said pad and said second and third zones.

16. A sanitary napkin as set forth in Claim 14 wherein said second and third zones are generally equal in length and width.

17. A sanitary napkin as set forth in Claim 16 wherein said first zone is narrower and longer than said second and third zones.

18. A sanitary napkin as set forth in Claim 17 wherein said lines are about 1/8 wide and are spaced from one another by about 3/16.

19. A sanitary napkin as set forth in Claim 14 wherein each of said lines is continuous throughout its length.

20. A sanitary napkin as set forth in Claim 14 wherein said lines are rectilinear and parallel with one another.

21. A flushabie sanitary napkin substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.