CA2163194A1 - Absorbent article having anti-wicking crimp seal - Google Patents

Abstract

An absorbent article is disclosed for absorbing liquids, including body fluids such as menstrual discharges or urine. The absorbent article has a liquid impermeable backsheet on which is dis-posed an absorbent core, and first and second liquid permeable topsheet lay-ers. The edge of the absorbent core defines a perimeter, and the first and second topsheet layers and the back-sheet each extend laterally beyond the perimeter to define a continuous bor-der segment surrounding the absorbent core. A liquid impermeable seal is formed in the border segment which surrounds the perimeter for preventing lateral migration of liquid from the ab-sorbent core beyond the seal. The seal is formed to extend from an outer surface of the first topsheet layer to an outer surface of the backsheet, for establishing a capillary gradient in the second topsheet layer, thereby inhibiting wicking of fluid therethrough.

Description

2 1 6 3 1 9 4 ~ PCT/USg4/04657 ABSORBENT ARTICLE HAVING ANTI-WICKING
CRIMP SEAL

BACKGROUND OF THE INVENTION
1. Technical Field The present invention relates generally to disposable absorbent articles and, more particularly, to the incol~ol~lion of an anti-wicking crimp seal into the peripheral border of a c~t~mPni~l pad.

2. Back~round Art Disposable abso~ nL articles are co~ llt;lcially available in a wide variety of configurations for the specific purpose of absorbing and retaining discharged body fluids. For example, dk.l)osable diapers and inconlinen~ briefs are inten-led to absorb and contain urine and feces, b~ s are intPnr~P~ to absorb and contain blood and other body eY~J~I~tPs while c~t~mPni~l pads are intPntled to absorb and retain menstrual fluids and other vaginal discharges. Regardless of the specific application, each absorbent article is intP~ .d to isolate the discharged fluids for preventing the underg~merlL~, clothing, bedding etc. surrounding the tiicpoc~hle article from becoming soiled.As is known, the basic structure for most disposable absoll,c.ll articles inrl~ Pc an absc,ll,elll core that is encased between a liquid permeable topsh~t layer and a liquid impervious b~ckch~oet The abso~ lll core generally hl..ol~,o~àles a number of Absoll,erll Gelling Material (AGM) particles. However, apelLul~d film topsheet layers known in the art have generally failed to ~ qll~tPly retain the AGM particles, either before or after they have abso-l,ed liquids. It is therefore desirable to provide an improved topsheet layer for more effectively retaining the AGM particles within the absG,b~ t article.
In addition, it is common for the topsheet layer to be affixed to the backcheet in a manner defining a continuous and relatively thin border segmPnt which ~u~ou~lds the pe.i.l.~t~,l of the thicker absorbent core. Ideally, the disposable article must exhibit good strikethrough and rewet ch~a~;lelislics for permitting the discharged fluid to rapidly pel.~L.ale the topsheet layer while preventing s~lhsequent flow back through the WO 94/27~39 ~ 63 ~ 9 4 I r ` PCTIUS94/04657 topsheet layer. Moreover, the liquid impervious backsheet should isolate the tluid retained in the abso.l,t;ul core from the wearer's unde-~dl...e--ls or clothing. As will be appreciated, numerous variations to the above-noted structure are known in the art for improving a particular functional or comfort characteristic of the disposable absorbent article.
Due to the rapid capillary-type action H~sociHtPd with the strikethrough characteristics of the liquid permeable topsheet layer, the potential exists for lateral migration (i.e., "wicking") of the discharged fluid from the absorbent core toward the peripheral edge of the abso.lt;.l~ article. Such wicking is undesirable in that it may cause soiling of the wearer's unde-g~---~;--Ls and/or clothing in the vicinity surrounding the absorbent article. In an attempt to prevent such lateral migration of discharged fluids, it is known to form a liquid impervious "seam" in the border se~...- ~l of the disposable absorbent article. For example, commomy owned U.S. Pat. No. 4,321,924 issued to Ahr discloses h~co.lJu.alion of a pair of cor.lh~o~ls seams into a ~hHnnPllPd border segmPnt of a C~HIII~ n;HI pad which act as barriers against edge leakage. Thus, while such conventional products perform well for their intPn~Pd purpose, a continuing need exists to develop improvements in the Sliu~Lu~e, method of ~ n~fh~ e~ and cost of bordereddisposable abso.l,t;..L articles.
It is Lh~ ;ru.e an object of the present invention to provide a disposable absorbent article having an improved m~rhHnicm for preventing wicking of fluid from an abso.le..l core toward the edges of a border se~ surrounding the absorbent core.It is another object of the present invention to provide a second liquid p- ...~ahle topsheet layer in the di ,~,osable~ abso.l.~nt article for improved contHinm~nt of the abso.l,.,..~ fibers and/or abso-l,~ gelling material particles within the absorbent core.
Formation of an anti-wicking seal between the first topsheet layer, the second topsheet layer and the bacl~h~oet in the border seg...~.l of the disposable article is effective in inhibiting lateral migration of fluids from the absorbent core.

3 ~ ~ , PCT/US94/04657 SUMMARY OF THE INVENTION
According to the present invention, a disposable absorbent article is provided having an absorbent core, a liquid impermeable b~cl~heet a first liquidpermeable topsheet layer and a second liquid permeable topsheet layer. The absorbent core is disposed between the bacL~h~t and the second topsheet layer, and the second topsheet layer is disposed between the absorbent core and the first topsheet layer. Each of the first and second topsheet layers and the ~a~L~heet extend laterally beyond the perimeter of the absorbent core to define a continuous border segm~'nt surrounding the absorbent core. A liquid impermeable seal ~u~lullnds at least a portion of the perimeter of the absorbent core and is formed in the border segm~ont to extend between the first and second topsheet layers and the backsheet. Moreover, the seal extends from an outer or top surface of the first topsheet layer to an outer or lower surface of the ba-~L ~heet layer, and is adapted to prevent lateral migration of fluid from within the p~.h"t;ler of the absoll,tnL core beyond the seal.
These and various other objects, advantages and features of the present invention will become apl.~e.lL from the following description and claims, when considered in conjunction with the appended drawings.

WO 94127539 . = ~ PCT/US94/04657 BRIEF DESCRIPTION OF THE DRAWINGS
Figure I is a perspective view of a disposable absorbent article incorporating the novel principles of the present invention;
Figure 2 is a cross-sectional view taken along line 2-2 of Figure l;
Figure 3 is an enlarged partial cross-sectional view of a portion of the absorbent article shown in Figure 2;
Figure 4 is a cross-sectional view of ~n alternative embodiment of the present invention;
Figure S is an enlarged partial cross-sectional view of a portion of the absorbent article shown in Figure 4;
Figure 6 is a cross-sectional view of another alternative embodiment of the present invention;
Figure 7 is an enlarged partial cross-sectional view of a portion of the absorbent article shown in Figure 6; and Figure 8 is a pel~Jecli~e view of a disposable absorbent article arranged according to an alternative embodiment of the present invention.

DET~TT.Fn DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following description of the ~rerellèd embodiments is merely exemplary in nature, and is in no way intpndp~ to limit the invention, its application or uses.
With rert;,~,nce to the drdwill~;s, a pler~.led embodiment of the present invention is shown inco.~ ed into a disposable absorbent article, and in particular, a cat~nnPni~i pad. It should be noted that the present invention may also be utilized in other absorbent articles, such as diapers, adult incontinent products and the like. As used herein, the term "disposable absG.l,e,lL article" includes articles for absorbing and retaining liquids, such as those discharged from the human body, and further, which articles are intP.nrlPA to be discarded after a single use. A "c~t~mPni~l pad" is an WO 94127539 ~ PCT/US94/04657 1~ 5 ~31`94 absorbent article worn by females externally to the urogenital region for absorbing and containing menstrual fluids and other vaginal discharges.
A perspective view of a c~t~mPr-i~i pad incorporating the anti-wicking seal of the present invention is depicted in Figure 1. As best seen from Figure 2, c~t~nnP.ni~l pad 10 is constructed of a first liquid permeable topsheet layer 12~ a second liquid permeable topsheet layer 14, an abso~l~ent core 16, and a liquid impermeable b~ ch~t 18. First and second topsheet layers 12 and 14 may be either formed as separate sheets or as multiple plies of one composite material. Absorbent core 16 may be formed of a variety of absorbent materials, and plereIably includes a predetermined amount of "Abso.ben~ Gelling Material" particles 19, commonly referred to as AGM in the art. Absoll,e.l~ core 16 should be flexible, co,l.l,r~,ssible, and colll~l~ble to the wearer. Moreover, the abso-l,t;--~ capacity of the material used in absorbent core 16 must be sllffi~hPnt to absorb and retain the expected liquid loading on c~t~rnPni~l pad 10. In addition, the shape and ~lim~n.cions of abso-L~,nl core 16 are selected to comfortably fit the urogenital region of the female wearer~ Figure I shows a generally hour-glass shaped absoll,e.ll core 16 that provides s~ r~- LQIy fit and protection.
Liquid h.-pe....cable b~CL~l-r~l 18 ple~/enLS Iiquid which has penetrated first topsl.ee~ layer 12 and second topsheet layer 14 and has been absorbed by absorbent core 16 from soiling the und~,r~;~.. e.. L~. of the wearer of ~; l .. o.. i~i pad 10. Racl~chPet 18 is pr~rerably formed of a hydrophobic polyethylene film having a thit l~nPcc approximately within the range of 0.010 to 0.050 millimeters, although other flexible, liquid h..~,.".eable materials may be used. The term "hydrophobic" is used herein to refer to a surface which is not wetted by contact with a liquid. The wetting of materials is generally defined in terms of contact angle and surface tension. These properties are diccnc~ed further in the publication of the American (~hPmil~l Society entitled "Contact Angle, Wettability, and Adhesion", edited by Robert F. Gould, copyright 1964, which is hereby h~co.~or~ed by ref~r~ ce~
First topsheet layer 12 is liquid permeable and contacts the skin of the wea-rer of c~t~mpni~l pad 10~ It should therefore prefe.dbly be compliant, soft. and non-WO 94/27539 2 l 6 3 1 9 4 PCT/US94/04657 irritating to the skin of the wearer. First topsheet layer 12 is preferably formed ofpolyethylene film that is treated with a surfactant to enhance liquid penetration. The term "hydrophilic" is used herein to refer to a surface which is weKed by contact with a liquid.
First topsheet layer 12 preferably has a multiplicity of transversely extending capillaries for encouraging liquid to rapid penèlra~e or strike through first topsheet layer 12 for subsequrnt absorption and retention by abso,Le"L core 16.
Second topsheet layer 14 is preferably formed of~polypropylene which is initially hydrophobic and has been treated with wetting agènts to become hydrophilic.
Second topsheet layer 14 is disposed between first topsheet layer 12 and absorbent core 14 for the purposes of resisting passage and escape of the AGM particles, which would cause a variety of problems.
When in use, c~t~mrni~l pad 10 is prt;re(ably held in place by an undelgallllenl (not shown). A band of adhesive 20 is affixed to a lower or outer surface 22 of bac~heet 18 for adhering to the undelg~"le"l (not shown) to resist movement of c~t~m~ni~l pad 10 out of proper ~lignmrnt with the urogênital region of the female wearer's body. A cover strip 24 may be initially provided for covering and p,ùteeLh~g adhesive band 20, which is removed before use.
As best seen from Figure 2, abso,be..L corê 16 has a lower surface 28 and an upper surfacê 26 and which are respectively disposed adjacent to and contiguous with an upper surface 30 of barL~h~l 18 and a lower surface 32 of second topsheet layer 14.
Moreovêr~ second topsheet layer 14 has an upper surface 34 which is positioned adjacênt to and contiguous with a lower surface 36 of first topsheet layer 12. Finally, first topsheet layer 12 has an upper surface 38 which is placed against the user's body when c.l ~...Pni~l pad 10 is worn.
The lateral edges of abso,l,~;"l core 16 define a pelhll~,ter 40. First and second topsheet layers 12 and 14 and bac~chPet 18 are formed generally without ,,lac.uscopic pelrul~l~ions~ and each have a shape similar to but larger than absorbent core 16. Thus, each of first and second lop~heèl layers 12 and 14, le~ecli~/ely~ and bar~heP~t 18 have a portion which extends outwardly from the pelillleler of absorbent core 16 to WO 94127'.39 PCTIUS94/04657 7 2163l94-define a continuous border segment which encircles absorbent core 16 Border segment 42 is generally relatively narrow, and may extend a distance of approximately 0 25 to 5 millimeters and pr~re-dbly is approximately 3 millimeters wide. However, the width of border 42 may be uniform or vary about the perimeter of pad 10 Moreover, border segment 42 is relatively thin and flexible and is intrn~ed to provide improved protection against soiling of the vicinity surrounding the discharge region, as well as retain AGM
particles within the absorbent article.
In accordance with the present invention, a liquid impermeable seal 44 is provided in border se~ 42 which .u-loullds pe.il-lcL.3~ 40. Thus, seal 44 is adapted to prevent lateral migration (i.e., "wicking") of liquid from perimeter 40 of absorbent core 16, or first and second topsheet layers 12 and 14, through border segment 42 toward the peripheral edges of c~t~mrni~l pad 10, thereby inhibiting premature side soiling of the wearer's underga..,.~,l.L~.. As a result, first topsheet layer 12, second topsheet layer 14 and bae'L-~hlo,et 18 tend to remain relatively free of liquids, regardless of the amount of liquid co-.L~ d in ab50l'Le.lL core 16. Liquid hll~e....cd'Dle seal 44 is p~ -ably disposed laterally inwardly as close as possible to pe.il..el~;f 40 so that a greater portion of border St'~--l' ~1 42 remains dry and unsoiled Seal 44, in its p,ert;..cd application, completely .u..ou..ds pe.i~ ,ter 40 without any gaps which would allow wicking and fluid lealcage In this most p~,f~ ed application, the improved sea. 44 of the present invention is specific~lly directed to inhibiting wicking of fluid through liquid p~. .,.eable second l~.pshc~l layer 14 which is sandwiched between first topsheet layer 12 and backsheet 18 in border seg... ~ 42.
Seal 44 is p--,f~ bly formed by the siml lt~n~us application of pressure, with or without heat, con.lllo~lly referred to as a "crimping" operation. Referring to Figure 3, an upper and lower crimp tool 46 and 48 are shown for concurrently compressing first and second topsheet layers 12 and 14 and backsheet 18 Tools 46 and 48 should be wide enough so as not to cut, mar or tear first tupshee~ Iayer 12 or bacl~heet 18 During the "crimping" process, sufficient pressure, possibly with heat, is L-~re~.td via crimping tools 46 and 48 to melt first topsheet layer 12 and b~rl~h~oet 18, WO 94/27539 PCl[/US94/04657 21 63~94 8 ~

thereby forming a solid yet flexible liquid impermeable seal 44. Thus, the pressure crushes second topsheet layer 14 to at least partially fill the rem~ining capillary spaces therein. First topsheet layer 12 and barLrchçet 18 melt around the material of second topsheet layer 14 creating a barrier for inhibiting wicking therethrough. The portions of the border outside of seal 44 are crimped with discrete spaced-apart bonds. This discrete bonding creates a reverse or negative capillary gradient, whereby any liquids inadvertently passing through seal 44 will tend to be attracted toward the more dense material in the seal 44 area, so any liquid movement outside seal 44 occurs along seal 44, as opposed to toward outer edge of border 42.
In an alternative embodiment of the present invention, second l~,pshee~
layer 14 is formed of hydrophilic non-woven or apertured polyethylene film having a lower melting lelllpeldllre than first top.~heet layer 12 and ba~Lxhret 18. Upon the application of loc~li7ed pres~ule, during the "crimping" process, with or without heat, polyethylene second t~",shee~ layer 14 will melt before first topsheet layer 12 and ba~L~l-~t 18 and will plopa~de and mingle with the material of first topsheet layer 12 and bl~L~hect 18, thus forming a liquid impermeable seal 44 which appears similar on a "acroscopic level to the seal formed by the first p-efell d embodiment of the present invention, in which first ~op:,llec~ Iayer 12 and barL-cheet 18 melt prior to second topsheet layer 14. The crimping process may be varied to cause first and second topsheet layers 12 and 14, as well as ba Lxl,f~ 18, to melt to form seal 44.
A second alternative embodiment of the present invention is shown in Figures 4 and 5, which depict a c~ ni~l pad 50 generally similar to c~t~mfni~l pad 10 of Figures 1 ~rough 3. For p~l~oses of clarity, like ref~ ,nce numerals are used to ~l~sign~t.o, those el~pmpntx of c~t~mpni~l pad 50 that are similar to, or identie~l with, the above-noted elf~mPntx of c~t~mf ni~l pad 10. Pad 50 has a first or inner liquid hnpelllleable seal 52 which is disposed as ciose as possible to pelhlleler 40 of absorbent core 16 and surrounds pelillle~er 40. In addition, c~t~m~ni~l pad 50 is also provided with a second or outer seal 54 for providing additional resict~nre against wicking of liquid that enters border Se~ f"'~l 42 beyond first seal 52. The present invention contemplates the WO 94/27539 = PCT/US94/04657 ~ 9 21 631 9~

possibility of using three or even more seals. As with the preferred embodiments shown in Figures I through 3, second topsheet layer 12 may be formed preferably of hydrophobic polypropylene which is treated with wetting agents to become hydrophilic, or alternatively can be formed of hydrophilic non-woven or apertured polyethylene.
Accordingly, first and second seals 52 and 54 will be formed by the melting of first topsheet layer 12 and b~eL~he~t 18 with the prel~.led selection of polypropylene for second topsheet layer 14, or in the alternative, seals 52 and 54 will be formed by the melting of second topsheet layer 14 in the case of selection of hydrophilic polyethylene for second topsheet layer 14.
Another alternative embodiment of the present invention is depicted in Figures 6 and 7, in which a c~t~m~oni~l pad 56 is constructed 5~hst~nti~ily similar to c~t~m~ni~l pad 50 shown in Figures 4 and 5, and incllld~os a first or inner seal 52 and a second or outer seal 58. In this emhodimp-nt~ outer seal 58 is disposed at the laterally OUI~....OS~ edge of border seg...- -~l 42 defined by first and second topsheet layers 12 and 14, as well as b~L~l~e~l 18. The ~Itern~tive embodiments of the present invention provide for selectively positioning various liquid impervious seals in order to m~ximi7e their effectiveness while ...~ u;,~;.,g comfort and preventing irritation to the wearer.
Yet another alternative embo-limPnt of the present invention is depicted in Figure 8. C~t~mpni~l pad 62 is formed generally similar to pad 10, and has an anterior portion 64, posterior portion 66, and first and second sides edges 68 and 70. Liquid i...pe...,cable seals 72 and 74 are similar to seal 44, but extend only along side edges 68 and 70. It has been found that seals 68 and 70 may be more easily manufactured than seal 44, which completely surrounds core 16.
It should be lln~iprstood that an lmlimitP~d number of configurations of the present invention can be realized. The foregoing tlicrllccion ~licelose~c and describes merely exemplary embodim~ntc of the present invention. One skilled in the art will readily ~ecog--i e from the discussion and from the accompanying drawings and claims that various changes and modifications can be made without departing from the spirit and scope of the invention, as defined in the following claims.

Claims (10)

What is claimed is:

1. An absorbent article for absorbing liquids, comprising a first liquid permeable topsheet layer, a second liquid permeable topsheet layer, a liquid impermeable backsheet, an absorbent core having a perimeter and being disposed between said backsheet and said second topsheet layer, said second topsheet layer being disposed between said absorbent core and said first topsheet layer, wherein said first topsheet layer, second topsheet layer and backsheet each extend laterally beyond the perimeter of said absorbent core to define a continuous border segment surrounding said absorbent core, said absorbent article being characterized in that it comprises a liquid impermeable seal formed in said border segment and surrounding a portion of said perimeter of said absorbent core, said seal extending from an outer surface of said first topsheet layer to an outer surface of said backsheet, wherein said seal is adapted to prevent migration of liquid from said absorbent core laterally outward beyond said seal.

2. The absorbent article of Claim 1 wherein said liquid impermeable seal comprises a first liquid impermeable seal and said absorbent article further comprises a second liquid impermeable seal surrounding and being spaced apart from said first liquid impermeable seal.

3. The absorbent article of Claim 1 wherein a portion of at least one of said first topsheet layer, said second topsheet layer, and said backsheet are melted to form said seal.

4. The absorbent article of claim 1 wherein said first topsheet layer, second topsheet layer and backsheet each extend laterally beyond said seal.

5. The absorbent article of Claim 2 wherein said second seal is disposed at an outer lateral edge of said border.

6. The absorbent article of Claim 1 wherein said seal is formed closer to said perimeter of said absorbent core than to an outer lateral edge of said border.

7. The absorbent article of Claim 1 wherein said seal is formed by applying localized pressure or by simultaneously applying pressure and heat during a crimping operation.

8. The absorbent article of Claim 1 wherein at least one of said first topsheetlayer and said second topsheet layer is formed of a material treated by a process to become hydrophilic.

9. The absorbent article of Claim 1 wherein said absorbent core comprises a plurality of absorbent particles, and said second topsheet layer tends to prevent escape of said absorbent particles from within said article.

10. The absorbent article of Claim 1 wherein said absorbent article has an anterior portion, a posterior portion, a first and second side edge, and said seal extends along said first and second side edges.