WO1998025759A1

WO1998025759A1 - A method for forming a laminate web

Info

Publication number: WO1998025759A1
Application number: PCT/US1997/022947
Authority: WO
Inventors: Denise Jean Bien
Original assignee: The Procter & Gamble Company
Priority date: 1996-12-09
Filing date: 1997-12-05
Publication date: 1998-06-18
Also published as: BR9713693A; KR20000069366A; AU5525398A; CA2274692A1; CA2274692C; EP0942827A1; AU734534B2; JP2000505747A; JP3181924B2; KR100317400B1

Abstract

The present invention pertains, in a preferred embodiment, to a method for forming a laminate web. The method includes the steps of: providing a nonwoven web (22) of fibers exhibiting a surface energy, the nonwoven web (22) having a first surface, a second surface, and a plurality of fluid passageways placing the first and second surfaces in fluid communication with one another; applying a surface treatment (28) to the first surface of the nonwoven web, the surface treatment (28) having a surface energy less than the surface energy of the fibers of the nonwoven web providing an apertured macroscopically expanded three-dimensional polymeric web (200); and joining the nonwoven web of fibers to the apertured macroscopically expanded three-dimensional web (200) to form a laminate web. The laminate web is particularly well suited for use as a topsheet on a disposable absorbent article.

Description

A METHOD FOR FORMING A LAMINATE WEB

FIELD OF THE INVENTION

The present invention relates to a laminate web which is suitable for use as a fluid transport mechanism and a method for making the same. In particular, the laminate web is designed to facilitate fluid transport in a preferential direction from one surface toward another surface and resist fluid transport in the opposite direction.

BACKGROUND OF THE INVENTION It has long been known in the field of disposable absorbent articles that it is extremely desirable to construct absorptive devices, such as disposable diapers, sanitary napkins, incontinence briefs, bandages, wound dressings, and the like, presenting a dry surface feel to the user to improve wearing comfort and to minimize the potential for development of undesirable skin conditions due to the prolonged exposure to moisture absorbed within the article. Accordingly, it is generally desirable to promote rapid fluid transfer in a direction away from the wearer and into a retentive structure, while resisting fluid transfer in the reverse direction.

One viable prior art solution to the aforementioned problem has been to utilize a covering or topsheet on the exposed, wearer-contacting surface of the disposable absorbent article which comprises a nonwoven web. Nonwoven webs formed by nonwoven extrusion processes such as, for example, meltblowing processes and spunbonding processes may be manufactured into products or components of products so inexpensively that the products could be viewed as disposable after only one or a few uses. Nonwoven webs are often used as topsheets on disposable absorbent articles as they exhibit capillary fluid transport characteristics via the three-dimensional capillaries formed by inter-fiber spaces, thereby conducting fluid away from the wearer-contacting surface and into the underlying absorbent structure. Such nonwoven webs also exhibit an aesthetically-pleasing, cloth-like surface appearance and tactile impression due to their fibrous nature.

While nonwoven webs are effective in transporting fluid, their effectiveness is limited in that such capillary structures can only move fluid once it reaches the capillary interior. Fluid which wets and remains on wearer contacting surfaces contributes to a "wet" tactile feeling or impression, and to the extent that such fluid may be colored or opaque also contributes to a "stained" visual impression. Surface textures naturally occurring in the material of the web or imparted thereto in formation further increase the likelihood that residual fluid will be trapped or retained on the wearer-contacting surface rather than entering capillary structures for transport away from the surface. Thus, surface topographies which contribute to desirable visual and tactile impressions when dry can also tend to retain residual fluid on the exposed surface and thus reduced desirability under in-use conditions. As used herein, the term "nonwoven web", refers to a web that has a structure of individual fibers or threads which are interlaid, but not in any regular, repeating manner. Nonwoven webs have been, in the past, formed by a variety of processes, such as, for example, meltblowing processes, spunbonding processes and bonded carded web processes. As used herein, the term "microfibers", refers to small diameter fibers having an average diameter not greater than about 100 microns.

As used herein, the term "meltblown fibers", refers to fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into a high velocity gas (e.g., air) stream which attenuates the filaments of molten thermoplastic material to reduce their diameter, which may be to a microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers.

As used herein, the term "spunbonded fiber", refers to small diameter fibers which are formed by extruding a molten thermoplastic material as filaments from a plurality of fine, usually circular, capillaries of a spinneret with the diameter of the extruded filaments then being rapidly reduced as by, for example, eductive drawing or other well-known spunbonding mechanisms.

As used herein, the term "elastic", refers to any material which, upon application of a biasing force, is stretchable, that is, elongatable, at least about 60 percent (i.e., to a stretched, biased length, which is at least about 160 percent of its relaxed unbiased length), and which, will recover at least 55 percent of its elongation upon release of the stretching, elongation force. A hypothetical example would be a one (1) inch sample of a material which is elongatable to at least 1.60 inches, and which, upon being elongated to 1.60 inches and released, will recover to a length of not more than 1.27 inches. Many elastic materials may be elongated by more than 60 percent (i.e., much more than 160 percent of their relaxed length), for example, elongated 100 percent or more, and many of these materials will recover to substantially their initial relaxed length, for example, to within 105 percent of their initial relaxed length, upon release of the stretching force.

As used herein, the term "nonelastic" refers to any material which does not fall within the definition of "elastic" above. As used herein, the term "extensible" refers to any material which, upon application of a biasing force, is elongatable, at least about 50 percent without experiencing catastrophic failure.

As utilized herein, the term "passageway" is intended to encompass enclosed or at least partially enclosed structures or channels which may communicate fluids. The term fluid passageway is thus intended to encompass the terms "aperture", "channel", "capillary", as well as other similar terms.

Apertured macroscopically expanded three-dimensional polymeric webs are often used as topsheets on disposable absorbent articles as they exhibit good fluid transport properties. However, some users find apertured polymeric webs undesirable despite all of their superior fluid handling capabilities because of the reluctance to place the plastic topsheet in direct contact with their skin.

Therefore, it would be desirable to provide all the benefits of softness and clothlike properties provided by nonwoven webs with the fluid handling superiority provided by the apertured macroscopically expanded three-dimensional polymeric webs.

SUMMARY OF THE INVENTION

The present invention pertains, in a preferred embodiment, to a method for forming a fluid pervious laminate web which exhibits a surface energy gradient. The method comprises the steps of: providing a fluid-pervious nonwoven web of fibers exhibiting a surface energy, the nonwoven web has a first or wearer-contacting surface, a second or garment-facing surface, an initial caliper, and a plurality of fluid passageways placing the first and second surfaces in fluid communication with one another; applying a surface treatment to the first surface of the nonwoven web, the surface treatment having a surface energy less than the surface energy of the fibers of the nonwoven web, thereby creating a plurality of surface energy gradients defined by discontinuous, spaced regions which are adapted to exert a force on a fluid contacting the first surface, such that fluid will be directed toward the fluid passageways for transportation away from the first surface and in the direction of the second surface; providing an apertured macroscopically expanded three-dimensional polymeric web; and joining the nonwoven web of fibers to the apertured macroscopically expanded three-dimensional polymeric web to form a laminate web.

The present invention also pertains to absorbent articles which preferably include a topsheet, a backsheet secured to the topsheet, and an absorbent core positioned between the topsheet and the backsheet, wherein the topsheet comprises the laminate according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the present invention will be better understood from the following description in conjunction with the accompanying drawings, in which like reference numbers identify like elements, and wherein:

FIG. 1 is a schematic representation of an exemplary process for forming a laminate web of the present invention; FIG. 2 is an enlarged, partially segmented, perspective illustration of the nonwoven web portion of the laminate web of the present invention;

FIG. 3 is a further enlarged, partial view of the nonwoven web of FIG. 2; FIG. 4 is an enlarged cross-sectional view of a droplet of liquid on a solid surface, where angle A illustrates the contact angle of the liquid with the solid surface; FIG. 5 is an enlarged cross-sectional view of a droplet of liquid on a solid surface having two different surface energies, thus exhibiting two different contact angles A(a) and A(b);

FIG. 6 is an enlarged cross-sectional view of a droplet of liquid located adjacent a generic capillary exhibiting a surface energy gradient; FIG. 7 is an enlarged perspective illustration of the apertured macroscopically expanded three-dimensional polymeric web portion of the laminate web of the present invention;

FIG. 8 is a cross-sectional illustration of the laminate web of the present invention; FIG. 9 is a top plan view of a sanitary napkin with portions of the sanitary napkin cut away to more clearly show the construction of the sanitary napkin; and

FIG. 10 is a cross-sectional view of the sanitary napkin of FIG. 9 taken along section line 10-10;

DETAILED DESCRIPTION OF THE PRESENT INVENTION Referring to FIG. 1 , there is schematically illustrated at 20 a process for forming a laminate web of the present invention which is suitable for use as a topsheet on a disposable absorbent article. According to the present invention, a nonwoven web 22 is unwound from a supply roll 24 and travels in a direction indicated by the arrows associated therewith as the supply roll 24 rotates in the direction indicated by the arrows associated therewith. The nonwoven web 22 passes beneath sprayer 26 which directs a surface treatment 28 onto a surface of the nonwoven web 22.

The nonwoven web 22 may be formed by known nonwoven extrusion processes, such as, for example, known meltblowing processes or known spunbonding processes, and passed directly beneath sprayer 26 without first being stored on a supply roll.

The nonwoven web 22 may be extensible, elastic, or nonelastic. The nonwoven web 22 may be a spunbonded web, a meltblown web, or a bonded carded web. If the nonwoven web is a web of meltblown fibers, it may include meltblown microfibers. The nonwoven web 22 may be made of natural fibers such as wood, cotton, or rayon, or synthetic fibers such as polypropylene, polyethylene, polyester, ethylene copolymers, propylene copolymers, and butene copolymers, bicomponent fibers, or combinations of natural and synthetic fibers.

The nonwoven web 22 may be a multilayer material having, for example, at least one layer of a spunbonded web joined to at least one layer or a meltblown web, a bonded carded web, or other suitable material. Alternatively, the nonwoven web may be a single layer or material, such as, for example a spunbonded web, a bonded carded web, or a meltblown web.

The nonwoven web 22 may also be a composite made up of a mixture of two or more different fibers or a mixture of fibers and particles. Such mixtures may be formed by adding fibers and/or particulates to the gas stream in which the meltblown fibers are carried so that an intimate entangled co-mingling of meltblown fibers and other materials, e.g., wood pulp, staple fibers and particles occurs prior to collection of the meltblown fibers upon a collecting device to form a coherent web of randomly dispersed meltblown fibers and other materials.

The nonwoven web of fibers should be joined by bonding to form a coherent web structure. Suitable bonding techniques include, but are not limited to, chemical bonding, thermobonding, such as point calendering, hydroentangling, and needling.

The surface treatment 28 is applied to one surface of the nonwoven web 22 in FIG. 1 utilizing sprayer 26. Surface treatments may also be applied to one surface of the nonwoven web by other techniques known in the art such as screen printing, gravure printing, dip coating, etc. Referring now to FIGS. 2 and 3, there is shown a perspective illustration of a nonwoven web 22 having the surface treatment applied to one surface thereof. Nonwoven web 22 is a fluid pervious nonwoven web comprised of individual fibers 60. The nonwoven web 22 preferably has a first or upper surface 61 and a second or lower surface 62. The first surface 61 is spaced from the second surface 62 by an intermediate portion 63. The nonwoven web 22 preferably includes a plurality of passageways 66 placing the first and second surfaces in fluid communication with one another.

The first surface 61 includes a plurality of regions 65 which exhibit a comparatively low surface energy and preferably comprise a low surface energy surface treatment. Preferably, the regions 65 have a relatively low surface energy and a relatively low work of adhesion as compared to the fibers 60 of the nonwoven web which have a relatively high surface energy and a relatively high work of adhesion. Accordingly, the treated nonwoven web 22 exhibits a plurality of surface energy gradients defined by the boundaries of regions 65, i.e., the interfaces between regions 65 and the surrounding fiber surfaces.

As depicted in FIG. 3, the relationship of the regions 65 to the surface topography (including individual fibers protruding upward from the upper surface of the web) is believed to be an important aspect of the present invention. Note the intermittent or discontinuous, spaced nature of the regions with regard to the surface direction of the web and the thickness direction of the web, particularly since the surface treatment as depicted in FIG. 3 is actually a plurality of discrete particles, droplets, or globules which coat portions of individual fibers rather than a bridging or masking of the fibers which would occlude the interfϊber pores. This discontinuity results in the generation of a plurality of small-scale surface energy gradients which are believed to be beneficial from a fluid- movement perspective.

Also clearly depicted in FIG. 3 is the penetration of the surface treatment into and below the first surface 61 of the nonwoven web 22. While the majority of the regions 65 are concentrated near the first surface 61 itself, the treated regions extend downward through the web on a fiber-by-fiber basis to achieve a penetration into the intermediate portion 63. Preferably, regions 65 are concentrated near the first surface 61 and decrease in frequency (increase in spacing) with increasing distance from the first surface, such that more low surface energy regions, and hence more surface energy gradients, are generated at or near the first surface 61 for greater effect on fluids on or near the first surface. On average, therefore, the upper regions of the web near the first surface would exhibit a lower average surface. energy than that exhibited by lower regions of the web nearer to the second surface. The non-occlusion of the interfiber capillaries is believed to be important such that sufficient fluid passageways remain open for fluid transmission to the underlying structure. If the surface treatment is applied too heavily it may tend to occlude the interfiber capillaries thereby blocking fluid transmission to the underlying structure.

In addition, the definition of "fiber" as utilized herein is intended to also encompass a type of fiber structure commonly referred to as a "capillary channel fiber", that is, a fiber having a capillary channel formed therein. Suitable fibers of this variety are described in greater detail in U.S. Patent Nos. 5,200,248, 5,242,644, and 5,356,405, all of which issued to Thompson et al. on April 6, 1993, September 7, 1993, and October 18, 1994, respectively, the disclosures of which are hereby incorporated herein by reference. Fibrous structures formed of such fibers may exhibit not only inter-fiber capillaries and spaces, but also intra-fiber capillary structures.

In accordance with the present invention, the first or wearer-contacting surface 61 of nonwoven web 22 is relatively non-wettable compared to the relatively wettable intermediate portion 63. A useful parameter of wettability is the contact angle that a drop of liquid (gas-liquid interface) makes with the solid surface (gas-solid interface). Typically, a drop of liquid 110 placed on a solid surface 112 makes a contact angle, A, with the solid surface, as seen in FIG. 4. As the wettability of the solid surface by the liquid increases, the contact angle, A, decreases. As the wettability of the solid surface by the liquid decreases, the contact angle, A, increases. The liquid-solid contact angle may be determined from techniques known in the art, such as those described in greater detail in Physical Chemistry of Surfaces, Second Edition, by Arthur W. Adamson (1967), F. E. Bartell and H. H. Zuidema, J. Am. Chem. Soc. 58, 1449 (1936), and J. J. Bikerman, Ind. Eng. Chem., Anal. Ed., 13, 443 (1941), each of which are hereby incorporated herein by reference. More recent publications in this area include Cheng, et al., Colloids and Surfaces 43:151-167 (1990), and Rotenberg, et al., Journal of Colloid and Interface Science 93(1):169-183 (1983), which are also hereby incoφorated herein by reference.

As used herein, the term "hydrophilic" is used to refer to surfaces that are wettable by aqueous fluids (e.g., aqueous body fluids) deposited thereon. Hydrophilicity and wettability are typically defined in terms of contact angle and the surface tension of the fluids and solid surfaces involved. This is discussed in detail in the American Chemical Society publication entitled Contact Angle, Wettability and Adhesion, edited by Robert F. Gould (Copyright 1964), which is hereby incoφorated herein by reference. A surface is said to be wetted by a fluid (hydrophilic) when the fluid tends to spread spontaneously across the surface. Conversely, a surface is considered to be "hydrophobic" if the fluid does not tend to spread spontaneously across the surface. The contact angle depends on surface inhomogeneities (e.g., chemical and physical properties, such as roughness), contamination, chemical/physical treatment of or composition of the solid surface, as well as the nature of the liquid and its contamination. The surface energy of the solid also influences the contact angle. As the surface energy of the solid decreases, the contact angle increases. As the surface energy of the solid increases, the contact angle decreases.

The energy required to separate a liquid from a solid surface (e.g., a film or fiber) is expressed by equation (1):

(1) W = G (l + cos A)

where: W is the work of adhesion measured in erg/_cm2,

G is the surface tension of the liquid measured in dyne/cm, and A is the liquid-solid contact angle measured in degrees. With a given liquid, the work of adhesion increases with the cosine of the liquid-solid contact angle (reaching a maximum where the contact angle A is zero). Work of adhesion is one useful tool in understanding and quantifying the surface energy characteristics of a given surface. Another useful method which could be utilized to characterize the surface energy characteristics of a given surface is the parameter labeled "critical surface tension", as discussed in H. W. Fox, E. F. Hare, and W. A. Zisman, J. Colloid Sci. 8, 194 (1953), and in Zisman, W. A., Advan. Chem. Series No. 43. Chapter 1. American Chemical Society (1964), both of which are hereby incoφorated herein by reference.

Illustrated below in Table 1 is the inverse relationship between contact angle and work of adhesion for a particular fluid (e.g., water), whose surface tension is 75 dynes/cm.

TABLE 1

A (degrees) cos A 1+cos A W (erg/cm^)

0 1 2 150

30 0.87 1.87 140

60 0.5 1.50 1 13

90 0 1.00 75

120 -0.5 0.5 38

150 -0.87 0.13 10

180 -1 0 0

As depicted in Table 1, as the work of adhesion of a particular surface decreases (exhibiting a lower surface energy of the particular surface), the contact angle of the fluid on the surface increases, and hence the fluid tends to "bead up" and occupy a smaller surface area of contact. The reverse is likewise true as the surface energy of a given surface decreases with a given fluid. The work of adhesion, therefore, influences interfacial fluid phenomena on the solid surface.

More importantly, in the context of the present invention, surface energy gradients or discontinuities have been found to be useful in promoting fluid transport. FIG. 5 illustrates a droplet of fluid 110 which is located on a solid surface having two regions 113 and 115 having differing surface energies (indicated by the different cross-hatching for illustrative puφoses). In the situation illustrated in FIG. 5, region 113 exhibits a comparatively lower surface energy than region 115, and hence a reduced wettability for the fluid of the droplet than region 115. Accordingly, the droplet 110 produces a contact angle A(b) at the edge of the droplet contacting region 113 which is greater than the contact angle A(a) produced at the edge of the droplet contacting region 115. It should be noted that although for graphic clarity the points "a" and "b" lie in a plane, the distance "dx" between points "a" and "b" need not be linear, instead representing the extent of droplet/surface contact regardless of the shape of the surface. Droplet 110 thus experiences a surface energy imbalance and hence an external force due to the differences in the relative surface energies (i.e., the surface energy gradient or discontinuity) between regions 113 and 115, which can be represented by the equation (2):

(2) dF = G [cos A(a) - cos A(b)] dx where: dF is the net force on the fluid droplet, dx is the distance between the reference locations "a" and "b",

G is as defined previously, and

A(a), and A(b) are the contact angles A at locations "a" and "b", respectively.

Solving equation (1) for cos A(a) and cos A(b) and substituting into equation (2) yields equation (3):

(3) dF = G [(W(a)/G - 1 ) - (W(b)/G - 1 )] dx

Equation (3) can be simplified to equation (4):

(4) dF = (W(a) - W(b)) dx

The importance of the differential in surface energy between the two surfaces is clearly depicted in equation (4), as is the directly proportional effect that changes in the magnitude of the differential in work of adhesion would have on the magnitude of the force.

More detailed discussions of the physical nature of surface energy effects and capillarity may be found in Textile Science and Technology, Volume 7, Absorbency. edited by Portnoy K. Chatterjee (1985), and Capillarity. Theory and Practice. Ind. Eng. Chem. 61,10 (1969) by A. M. Schwartz, which are hereby incoφorated herein by reference.

Accordingly, the force experienced by a droplet will cause movement in the direction of the higher surface energy. For simplicity and graphic clarity, the surface energy gradient or discontinuity has been depicted in FIG. 5 as a single, shaφ discontinuity or boundary between well-defined regions of constant but differing surface energy. Surface energy gradients may also exist as a continuous gradient or a step-wise gradient, with the force exerted on any particular droplet (or portions of such droplet) being determined by the surface energy at each particular area of droplet contact.

As used herein, the term "gradient" when applied to differences in surface energy or work of adhesion is intended to describe a change in surface energy or work of adhesion occurring over a measurable distance. The term "discontinuity" is intended to refer to a type of "gradient" or transition, wherein the change in surface energy occurs over an essentially zero distance. Accordingly, as used herein all "discontinuities" fall within the definition of "gradient". Also, as used herein the terms "capillary" and "capillarity" are used to refer to passageways, apertures, pores, or spaces within a structure which are capable of fluid transport in accordance with the principles of capillarity generally represented by the Laplace equation (5):

(5) p = 2G (cos A) /R where: p is the capillary pressure;

R is the internal radius of the capillary (capillary radius); and G and A are as defined above.

As noted in Penetration of Fabrics by Emery I. Valko, found in Chapter III of Chem. Aftertreat. Text. (1971), pp. 83-1 13, which is hereby incoφorated herein by reference, for A = 90°, the cosine of A is zero and there is no capillary pressure. For A > 90°, the cosine of A is negative and the capillary pressure opposes the entry of fluid into the capillary. Hence, the capillary walls must be of a hydrophilic nature (A < 90°) for capillary phenomena to occur. Also, R must be sufficiently small for p to have a meaningful value, since as R increases (larger aperture/capillary structure) the capillary pressure decreases. Perhaps at least as important as the presence of surface energy gradients is the particular orientation or location of the gradients themselves with respect to the orientation and location of the capillaries or fluid passageways themselves. More particularly, the surface energy gradients or discontinuities are located in relation to the capillaries such that fluid cannot reside on the first or upper surface without contacting at least one surface energy gradient or discontinuity and thus experience the driving force accompanying the gradient. Fluid moved to or otherwise present at a capillary entrance will preferably contact at least one Z-direction gradient or discontinuity present in the capillary itself near the capillary entrance, and thus experience the Z-direction driving force to drive the fluid into the capillary where capillary forces take over to move the fluid away from the first surface. In a preferred configuration, the capillaries preferably exhibit a low surface energy entrance length and an otherwise higher surface energy capillary wall or surface such that the surface energy gradient or discontinuity is a comparatively small but finite distance below the first surface. In such a location the discontinuity or gradient is positioned such that fluid in contact with the first surface at the edge of the capillary or over the open end of the capillary will have a lower surface or meniscus which will extend downwardly into the open end of the capillary where it will contact the discontinuity. By way of further explanation of this principle, FIG. 6 depicts a droplet 1 10 of a fluid which is located over a generic capillary or fluid passageway. This representation is intended to be sufficiently generic as to represent the concept expressed herein without being limited to a particular web material, design, or construction. Analogously to FIG. 5, the capillary is formed so as to present surfaces 113 and 115 having different surface energies (indicated by the different cross-hatching for illustrative puφoses). As in FIG. 5, the surface energy of surface 113 is at a predetermined level which is comparatively low in comparison with that of surface 115, such that surface 113 is regarded as hydrophobic. Accordingly, the droplet edges in contact with surface 1 13 will exhibit a relatively larger contact angle A such that the droplet edges make a shaφ departure from the interface with surface 113. Surface 115, on the other hand, has a comparatively higher surface energy in comparison with surface 113.

In the situation depicted in FIG. 6, the droplet 110 is located over and extends partially into the entrance of the capillary in a condition where the surface tension forces and gravitational forces are roughly in equilibrium. The lower portion of the droplet which is within the capillary forms a meniscus 117, with its edges in contact with the capillary wall in the region 113 having hydrophobic surface energy characteristics. The surface energy gradient, discontinuity, or transition between surfaces 113 and 115 is particularly determined so as to contact the lower portion of the droplet in the vicinity of the edge of the meniscus 117. The orientation of the droplet and depth of the meniscus of the droplet are determined by such factors as fluid viscosity, fluid surface tension, capillary size and shape, and the surface energy of the upper surface and capillary entrance.

At the instant when the droplet positions itself over the capillary entrance and the lower edge of the droplet contacts the Z-direction surface energy gradient, discontinuity, or transition between surfaces 113 and 1 15, the meniscus 117 which is of a convex shape reverts to a concave-shaped meniscus such as meniscus 119 depicted in dot-dash line form. When the meniscus changes to a concave form such as meniscus 119, the fluid wets the capillary wall in the vicinity of the upper region of the hydrophilic surface 115 and the fluid experiences an external force due to the surface energy differential described above in equation (3). The combined surface energy and capillary pressure forces thus act in concert to draw the fluid into the capillary for capillary fluid transport away from the first surface. As the fluid droplet moves downward into the capillary, the comparatively low surface energy nature of the surface 113 at the upper region of the capillary minimizes the attraction of the fluid to the upper surface and minimizes drag forces on the droplet, reducing the incidence of fluid hang-up or residue on or near the upper surface. Water is used as a reference liquid throughout only as an example for discussion puφoses, and is not meant to be limiting. The physical properties of water are well- established, and water is readily available and has generally uniform properties wherever obtained. The concepts regarding work of adhesion with respect to water can easily be applied to other fluids such as blood, menses and urine, by taking into account the particular surface tension characteristics of the desired fluid.

Referring again to FIG. 3, while the first or wearer-contacting surface 61 of nonwoven web 22 has a relatively low surface energy and a relatively low work of adhesion for a given fluid (e.g., water, or bodily fluids such as menses), the intermediate portions 63 of the nonwoven web 22 preferably have a relatively high surface energy and a relatively high work of adhesion for a given fluid. Since the intermediate portions 63 of the nonwoven web 22 have a relatively higher surface energy as compared to the first surface 61 , the intermediate portions 63 are more wettable than the first surface 61.

The second surface 62 of the nonwoven web 22 preferably has a higher surface energy and a higher work of adhesion for fluid than that of the first surface 61. The surface energy and work of adhesion for fluid of second surface 62 may be the same as that of the intermediate portion 63. In a preferred embodiment, the surface energy and work of adhesion for fluid of the second surface 62 are relatively higher than that of the intermediate portion 63. By having a nonwoven web with a surface energy gradient formed by structures creating a relatively low surface energy adjacent the portion of the web which will be placed adjacent to and in contact with the wearer's skin (i.e., the first surface 61), and a relatively higher surface energy portion located away from contact with the wearer's skin (i.e., the intermediate portion 63), the nonwoven web 22 will be capable of moving a drop of liquid from the portion of the web exhibiting the relatively lower surface energy to the portion of the web exhibiting the relatively higher surface energy. The motion of the drop of liquid is induced by the contact angle differential between the lower surface energy portion and the higher surface energy portion which results in an imbalance in surface tension force acting on the solid-liquid contact plane. With regard to the surface energy gradients of the present invention, it is important to remember that the upper and lower bounds of any such gradient are relative with respect to one another, i.e., the regions of the web whose interface defines a surface energy gradient need not be on different sides of the hydrophobic/hydrophilic spectrum. That is to say, a gradient may be established by two surfaces of diverse degrees of hydrophobicity or diverse degrees of hydrophilicity, and need not necessarily be established with regard to a hydrophobic surface and a hydrophilic surface. Notwithstanding the foregoing, it is preferred that the upper surface of the nonwoven web have a comparatively low surface energy, i.e., that it be generally hydrophobic, in order to maximize the driving force imparted to the incoming fluid and minimize the overall wettability of the wearer- contacting surface.

It should be noted that with regard to FIG. 3, the size and shape of regions 65 have been exaggerated in resolution and thickness for graphic clarity. The randomness and irregularity of such depositions or treatments exceed the limitations of graphic depiction, and hence the illustrations herein are intended to be illustrative and not limiting. Accordingly, the regions 65 depicted in FIG. 3 are preferably also interspersed by even smaller regions which are too small and random to be depicted adequately in such an illustration.

The surface energy gradients of the present invention therefore exist in a unique relationship to the surface features and/or textures of a fluid pervious web made in accordance herewith. As depicted in FIG. 3, the surface energy gradients are preferably constructed by forming regions 65 of low surface energy which interface with surrounding regions of the web which are of a comparatively higher surface energy. Therefore, each region 65 generates a surface energy gradient at its boundary. Accordingly, the greater the number of regions 65, the greater the number of individual surface energy gradients. Regions 65 are preferably discontinuous (i.e., not entirely encapsulating the web) and spaced, leaving intervening regions of higher surface energy. At each gradient, a droplet contacting both surfaces experiences a driving force which imparts some degree of motion to the fluid and reduces the likelihood of fluid stagnation or hangup, particularly on surface topography. Although the regions 65 could be applied in a predetermined pattern, the regions 65 are preferably randomly oriented on the web surfaces, with the randomness increasing the likelihood that the surface energy gradients will be properly positioned so as to affect any particular droplet or quantity of fluid. Randomness is desirable not only across the first surface of the web, but also within the fluid passageways themselves. Accordingly, any particular capillary or passageway may exhibit multiple surface energy gradients defined by regions 65 which may also be located at differing locations in the Z-direction from the first surface. Also, particular fluid passageways may exhibit more or less regions 65 than other fluid passageways, and regions 65 may also be located so as to entirely reside within fluid passageways (i.e., be entirely located between the first and second surfaces).

The regions 65 are also preferably discontinuous in nature with respect to the surface directionality of the web. The discontinuity of a hydrophobic surface treatment applied to a less hydrophobic (or more hydrophilic) substrate such as the web surface results in a pattern of small-scale surface energy gradients in the plane of the surface. Such gradients are to be distinguished from large-scale X-Y gradients of a zonal nature by their smaller relative size vis-a-vis average droplet size and size of web surface details. Accordingly, as used herein the term "small-scale" is intended to refer to surface features, topography, or surface energy gradients which are smaller in magnitude than the average size of a droplet of fluid on the surface in question. Average droplet size is a readily determinable characteristic which may be obtained from empirical observations for given fluids and surfaces.

Without wishing to be bound by theory, improvements in fluid pass-through characteristics are believed to be realized by a reduction in residence time of fluid on the upper surfaces of the web, as well as the movement of fluid from the upper surface into the capillaries for capillary fluid transport. Therefore, it is believed to be desirable for the initial fluid contacting surface of the web to facilitate small-scale movement of fluid (as opposed to larger lateral movement across the web surface) toward the nearest available capillary and then rapidly downward into the underlying structure. The surface energy gradients of the present invention provide the desired Z-direction driving force, as well as the X-Y driving force to impart the desired small-scale fluid movement.

The plurality of small-scale surface energy gradients exhibited by such webs are believed to be beneficial from a fluid-movement perspective. The small-scale gradients aid in the lateral or X-Y movement of fluid droplets formed on the web surface.

In addition, the regions 65, which are smaller in their surface-wise extent than the typical size of the droplet, stream, or rivulet of bodily fluid incident thereon, subject the droplet, stream, or rivulet of bodily fluid to destabilizing forces due to the inevitability of the fluid bridging a surface energy gradient or discontinuity.

While the surface energy gradients of the type herein described could advantageously be employed on non-capillary structures, including the surfaces of such structures as two-dimensional ("planar") films, in accordance with the present invention, it is preferable to employ both small scale X-Y surface energy gradients and small scale Z- direction surface energy gradients of the type herein described to achieve maximum disturbance of fluid and droplet equilibrium and thus minimize fluid residence time and hang-up or residue on the upper regions of the web. Accordingly, the presence of regions 65 may be limited to the first surface of the web, and hence provide X-Y functionality, or limited to the interior of the fluid passageways, but is preferably employed to best advantage both on the first surface of the web and within the fluid passageways.

Accordingly, in nonwoven web structures of the present invention the surface energy gradients provide a synergistic effect in combination with the capillary nature of the structure to provide enhanced fluid transport and handling characteristics. Fluid on the first surface of the web encounters two differing, complementary driving forces in its journey away from the first surface and toward the second or opposing surface of the web, and typically further onward into the interior of the absorbent article. These two forces likewise combine to oppose fluid movement toward the first surface of the web, thus reducing the incidence of rewet and increasing the surface dryness of the web.

A number of physical parameters should be considered in designing a web according to the present invention, more particularly with regard to appropriately sizing and positioning the surface energy gradients for proper fluid handling. Such factors include the magnitude of the surface energy differential (which depends upon the materials utilized), migratability of materials, bio-compatibility of materials, porosity or capillary size, overall web caliper and geometry, surface topography, fluid viscosity and surface tension, and the presence or absence of other structures on either side of the web.

Preferably, the regions 65 of the nonwoven web 22 have a work of adhesion for water in the range of about 0 erg/_cm2 to about 150 erg/_cm2, more preferably in the range of about 0 erg/_cm2 to about 100 erg/_cm2, and most preferably in the range of about 0 erg/_cm2 to about 75 erg/_cm2. Preferably, the remainder of the web surrounding regions 65 has a work of adhesion for water in the range of about 0 erg/_cm2 to about 150 erg/_cm2, more preferably in the range of about 25 erg/_cm2 to about 150 erg/_cm2, and most preferably in the range of about 50 erg/_cm2 to about 150 erg/_cm2.

Preferably, the difference in the work of adhesion for water between the regions 65 and the remainder of the nonwoven web is in the range of about 5 erg/_cm2 to about 145 erg/_cm2, more preferably in the range of about 25 erg/_cm2 to about 145 erg/_cm2, and most preferably in the range of about 50 erg/_cm2 to about 145 erg/_cm2.

A suitable surface treatment is a silicone release coating from Dow Corning of Midland, Michigan available as Syl-Off 7677 to which a crosslinker available as Syl-Off 7048 is added in proportions by weight of 100 parts to 10 parts, respectively. Another suitable surface treatment is a coating of a UV curable silicone comprising a blend of two silicones commercially available from General Electric Company, Silicone Products Division, of Waterford, NY, under the designations UV 9300 and UV 9380C-D1, in proportions by weight of 100 parts to 2.5 parts, respectively. The surface energy of the silicone release coating on the first surface of the nonwoven web is less than the surface energy of the individual fibers 60 forming the nonwoven web 22.

Other suitable treatment materials include, but are not limited to, fluorinated materials such as fluoropolymers (e.g., polytetrafluoroethylene (PTFE), commercially available under the trade name TEFLON®) and chlorofluoropolymers. Other materials which may prove suitable for providing regions of reduced surface energy include Petrolatum, latexes, paraffins, and the like, although silicone materials are presently preferred for use in webs in the absorbent article context for their biocompatibility properties. As used herein, the term "biocompatible" is used to refer to materials having a low level of specific adsoφtion for, or in other words a low affinity for, bio-species or biological materials such as gluco-proteins, blood platelets, and the like. As such, these materials tend to resist deposition of biological matter to a greater extent than other materials under in-use conditions. This property enables them to better retain their surface energy properties as needed for subsequent fluid handling situations. In the absence of biocompatibility, the deposition of such biological material tends to increase the roughness or non-uniformity of the surface, leading to increased drag force or resistance to fluid movement. Consequently, biocompatibility corresponds to reduced drag force or resistance to fluid movement, and hence faster access of fluid to the surface energy gradient and capillary structure. Maintenance of substantially the same surface energy also maintains the original surface energy differential for subsequent or enduring fluid depositions.

Biocompatibility, however, is not synonymous with low surface energy. Some materials, such as polyurethane, exhibit biocompatibility to some degree but also exhibit a comparatively high surface energy. Some low surface energy materials which might otherwise be attractive for use herein, such as polyethylene, lack biocompatibility. Presently preferred materials such as silicone and fluorinated materials advantageously exhibit both low surface energy and biocompatibility.

Suitable surfactants for hydrophilizing or increasing the surface energy of the selected regions of the web to have high surface energy include, for example, ethoxylated esters such as Pegosperse® 200-ML, manufactured by Glyco Chemical, Inc. of Greenwich, Connecticut, ATMER® 645, manufactured by ICI, glucose amides, tri-block copolymers of ethylene oxide and propylene oxide such as Pluronic® PI 03, manufactured by BASF, and copolymers of silicone and ethylene glycol such as DC 190, manufactured by Dow Corning of Midland, Michigan.

While much of the foregoing discussion has focused on the presently preferred approach of beginning with a predominantly hydrophilic web and applying a coating, treatment, or overlying layer of material to generate low surface energy regions and to render the upper portions hydrophobic, it is to be understood that other approaches to generating surface energy gradients are contemplated as well and are within the scope of the present invention. Such approaches would include applying a hydrophilic material (e.g., a hydrophilic latex) to the lower portions of an originally hydrophobic web to generate hydrophilic regions with boundaries at interfaces with hydrophobic web surfaces, forming the web of two or more materials of diverse surface energy characteristics with surface energy gradients formed by boundaries between the respective materials, forming the web of a material predominantly hydrophobic or predominantly hydrophilic and altering the surface chemistry of selected regions thereof by mechanical, electromagnetic, or chemical bombardment or treatment techniques know in the art to thus generate selective surface energy gradients, preferential migration of chemical web components capable of surface energy alteration, treating hydrophobic regions to be temporarily hydrophilic and reveal surface energy gradients in use, etc. After passing beneath sprayer 26 where surface treatment 28 is applied to one surface of the nonwoven web 22, the nonwoven web 22 is joined to an apertured macroscopically expanded three-dimensional polymeric web 200. Apertured macroscopically expanded three-dimensional polymeric web 200 is unwound from supply roll 202 and travels in a direction indicated by the arrows associated therewith as the supply roll 202 rotates in the direction indicated by the arrows associated therewith.

The nonwoven web 22 and the apertured polymeric web 200 are both fed to bonding station 230. Bonding station 230 comprises a pair of opposing pressure applicators 232 and 234. Applicator 232 preferably has a series of protuberances or projections 236 extending outwardly from the surface 238 thereof. Applicator 234 preferably comprises a smooth anvil roller having a cylindrical configuration. An example of a suitable pressure bonding system is disclosed in U.S. Pat. No. 4,919,738 issued to Ball, et al. on April 24, 1990 which is hereby incoφorated herein by reference.

The nonwoven web 22 and the apertured polymeric web 200 may be joined together using other suitable means such as by a uniform continuous layer of adhesive, a patterned layer of adhesive, or an array of separate lines, spirals, or spots of adhesive. Alternatively, the nonwoven web 22 may be joined to the apertured polymeric web 200 by the use of heat bonds, pressure bonds, ultrasonic bonds, or any other suitable means or combinations of these means as are known in the art.

Another example of a suitable bonding mechanism for joining the nonwoven web to the apertured polymeric web is disclosed in U.S. Pat. No. 5,518,801 issued to Chappell, et al. on May 21, 1996 and hereby incoφorated herein by reference.

Figure 7 is an enlarged, partially segmented, perspective illustration of a particularly preferred embodiment of an apertured, macroscopically expanded, three- dimensional, fluid-pervious, polymeric web 200 generally in accordance with the teachings of commonly assigned U.S. Pat. No. 4,342,314 issued to Radel on August 3, 1982, which is hereby incoφorated herein by reference.

Other suitable apertured, macroscopically expanded, three-dimensional polymeric webs are also described in U.S. Pat. No. 3,929,135 issued to Thompson on December 30, 1975; U.S. Pat. No. 4,324,246 issued to Mullane, et al. on April 13, 1982; U.S. Pat. No. 4,463,045 issued to Ahr, et al. on July 31, 1984; and U.S. Pat. No. 5,006,394 issued to Baird on April 9, 1991. Each of these patents are incoφorated herein by reference. The term "macroscopically expanded", when used to describe three-dimensional plastic webs of the present invention, refers to webs, ribbons and films which have been caused to conform to the surface of the three-dimensional forming structure so that both surfaces thereof exhibit a three-dimensional forming pattern of surface aberrations corresponding to the macroscopic cross-section of the forming structure, a surface aberrations comprising the pattern are individually discernible to the normal naked eye, i.e., a normal naked eye having 20/20 vision unaided by an instrument that changes the apparent size or distance of an object or otherwise alters the visual powers of the eye, when the peφendicular distance between the viewer's eye and the plane of the web is about 12 inches. As can be seen in Figure 7, the web's fiber-like appearance is comprised of a continuum of fiber-like elements, the opposed ends of each of the fiber-like elements are interconnected to at least one other of the fiber-like elements. The term "fiber-like", as utilized herein to describe the appearance of plastic webs of the present invention, refers generally to any fine scale pattern of apertures, random or non-random, reticulated or non- reticulated which connote an overall appearance and impression of a woven or nonwoven fibrous web when viewed by the human eye.

In the embodiment disclosed in Figure 7, the interconnected fiber-like elements form a pattern network of pentagonally shaped capillaries 241. The web 200 which exhibits a fiber-like appearance, embodies a three-dimensional microstructure extending from the web's uppermost, wearer-contacting or body surface 242 in plane 243 to its lowermost or garment facing surface 244 in plane 245 to promote rapid fluid transport from the uppermost surface 242 to the lowermost surface 244 of the web without lateral transmission of fluid between adjacent capillaries 241. As utilized herein, the term "microstructure" refers to a structure of such fine scale that its precise detail is readily perceived by the human eye only upon magnification by microscopic or other means well known in the art.

Apertures 247 in the body surface 242 are formed by a multiplicity of intersecting fiber-like elements, e.g., elements 248, 249, 250, 251, and 252 interconnected to one another in the body facing surface of the web. Each fiber-like element comprises a base portion, e.g., base portion 254, located in plane 243. Each base portion, has a sidewall portion, e.g., sidewall portions 256, attached to each edge thereof. The sidewall portions 256 extend generally in the direction of the second surface 244 of the web. The intersecting sidewall portions of the fiber-like elements are interconnected to one another intermediate the first and second surfaces of the web and terminates substantially concurrently with one another in the plane 245 of the second surface.

In the embodiment shown in Figure 7, the interconnected sidewall portions 256 terminate substantially concurrently with one another in the plane of the second surface 245 to form apertures 258 in the second surface 245 of the web. The network of capillaries 241 formed by the interconnected sidewall portions 256 between apertures 247 and 258 allow for free transfer of fluids from the body facing surface of the web directly to the garment facing surface of the web without lateral transmission of the fluid between adjacent capillaries.

Preferred polymeric materials for the web include polyolefins, particularly polyethylenes, polypropylenes and copolymers having at least one olefinic constituent. Other materials such as polyesters, nylons, copolymers thereof and combinations of any of the foregoing may also be suitable. Preferably, the apertured polymeric web 200 is hydrophilic so as to help liquid to transfer therethrough in order to diminish the likelihood that fluids will flow off the apertured web 200 rather than flowing into and being absorbed by the underlying absorbent core. In a preferred embodiment, surfactant is incoφorated into the polymeric materials of the apertured web 200 such as described in U.S. Patent Application Serial No. 07/794,745 entitled "Absorbent Article Having A Nonwoven and Apertured Film Coversheet" filed on November 19, 1991 by Aziz, et al. which is incoφorated herein by reference. Alternatively, the apertured web 200 can be rendered hydrophilic by treating it with a surfactant such as described in U.S. Pat. No. 4,950,254 issued to Osborn on August 21, 1990, which is incoφorated herein by reference.

The laminate web 250 is preferably taken up on wind-up roll 252 and stored. Alternatively, the laminate web 250 may be fed directly to a production line where it is used to form a topsheet on a disposable absorbent article.

Referring now to Figure 8 there is shown a cross-sectional illustration of the laminate web 250 comprising a nonwoven web 22 secured to the three-dimensional apertured web 200. As can be seen in Figure 8, the second surface 62 of the nonwoven web 22 which is secured to the body facing surface 242 of web 200. The first or wearer- contacting surface 61 of the nonwoven web 22 has a relatively low surface energy and a relatively low work of adhesion for a given fluid. The second surface 62 of the nonwoven web 22 preferably has a higher surface energy and a higher work of adhesion for a fluid than that of the first surface 61. The apertured web 200 preferably has a higher surface energy and a higher work of adhesion for a fluid than that of the second surface 62 of the nonwoven web 22. By having a laminate web 250 with the surface energy gradient formed by structures creating a relatively low surface energy adjacent the portion of the laminate which will be placed adjacent to and in contact with the wearer's skin (i.e., the first surface 61), and a relatively higher surface energy portion located away from contact with the wearer's skin (i.e., the apertured web 200), the laminate 250 will be capable of moving a drop of liquid from the portion of the web exhibiting a relatively lower surface energy to the portion of the laminate exhibiting a relatively higher surface energy. It is believed that this resulting surface energy gradient, which enhances the fluid handling properties of the laminate web 250 of the present invention and which makes the laminate well suited for use as a topsheet on an absorbent article.

In addition to the enhanced fluid handling properties, by designing the laminate web so that its relatively lower surface energy portion can be placed in contact with the wearer's skin, the adhesion between the skin and the laminate web is reduced by decreasing the capillary force generated by occlusive body fluids located between the first surface of the laminate web in the wearer's skin by providing a structure with reduced adhesion between the wearer's skin and the web, the sensation or impression of stickiness associated with adhesion to a topsheet is also reduced.

The potential for rewet is also reduced by having a topsheet with a surface energy gradient according to the aforementioned description. As use forces tend to force the collective fluid to rewet or be squeezed out of the absorbent article (e.g., squeezed by compression from the absorbent core towards the first surface of the laminate topsheet), such undesirable movement will be resisted by the first surface of the laminate topsheet which has a relatively low surface energy to repel fluid as it attempts to make its way out of the absorbent article through the openings in the laminate topsheet.

Furthermore, fluid is able to enter the topsheet more quickly due to the driving forces of the surface energy gradients of the topsheet. Fluid is moved in the "Z-direction" toward the lowermost or garment facing surface 244 of the laminate topsheet via the surface energy gradients from the first surface 61 to the relatively higher surface energy of the apertured three-dimensional web 200 of the laminate 250 towards the absorbent core.

REPRESENTATIVE ABSORBENT ARTICLE As used herein, the term "absorbent article" refers generally to devices used to absorb and contain body exudates, and more specifically refers to devices which are placed against or in proximity to the body of the wearer to absorb and contain the various exudates discharged from the body. The term "absorbent article" is intended to include diapers, catamenial pads, tampons, sanitary napkins, incontinent pads, and the like, as well as bandages and wound dressings. The term "disposable" is used herein to describe absorbent articles which are not intended to be laundered or otherwise restored or reused as an absorbent article (i.e., they are intended to be discarded after limited use, and, preferably, to be recycled, composted or otherwise disposed of in an environmentally compatible manner). A "unitary" absorbent article refers to absorbent articles which are formed as a single structure or as separate parts united together to form a coordinated entity so that they do not require separate manipulative parts such as a separate holder and pad. A preferred embodiment of a unitary disposable absorbent article made in accordance herewith is the catamenial pad. sanitary napkin 320, shown in FIG. 9. As used herein, the term "sanitary napkin" refers to an absorbent article which is worn by females adjacent to the pudendal region, generally external to the urogenital region, and which is s intended to absorb and contain menstrual fluids and other vaginal discharges from the wearer's body (e.g., blood, menses, and urine). Interlabial devices which reside partially within and partially external to the wearer's vestibule are also within the scope of this invention. It should be understood, however, that the present invention is also applicable to other feminine hygiene or catamenial pads, or other absorbent articles such as diapers, o incontinent pads, and the like, as well as other webs designed to facilitate fluid transport away from a surface such as disposable towels, facial tissues, and the like.

It is to be understood that the overall size, shape, and/or configuration of the absorbent article, if any, into which fluid transport webs according to the present invention are incoφorated, or utilized in conjunction with, have no criticality or functional s relationship to the principles of the present invention. Such parameters, however, must be considered along with the intended fluid and intended functionality when determining appropriate web configurations and appropriate orientation of surface energy gradients according to the present invention.

Sanitary napkin 3120 is illustrated as having two surfaces such as first surface 0 320a, sometimes referred to as a wearer-contacting or facing surface, a body-contacting or facing surface or "body surface", and second surface 320b, sometimes referred to as a garment-facing or contacting surface, or "garment surface". The sanitary napkin 320 is shown in FIG. 9 as viewed from its first surface 320a. The first surface 320a is intended to be worn adjacent to the body of the wearer. The second surface 320b of the sanitary 5 napkin 320 (shown in FIG. 10) is on the opposite side and is intended to be placed adjacent to the wearer's undergarment when the sanitary napkin 320 is worn.

The sanitary napkin 320 has two centerlines, a longitudinal centerline "L" and a transverse centerline "T". The term "longitudinal", as used herein, refers to a line, axis or direction in the plane of the sanitary napkin 320 that is generally aligned with (e.g., 0 approximately parallel to) a vertical plane which bisects a standing wearer into left and right body halves when the sanitary napkin 320 is worn. The terms "transverse" or "lateral" as used herein, are interchangeable and refer to a line, axis or direction which lies within the plane of the sanitary napkin 320 that it generally peφendicular to the longitudinal direction. FIG. 9 also shows that the sanitary napkin 320 has a periphery 330 5 which is defined by the outer edges of the sanitary napkin 320 in which the longitudinal edges (or "side edges") are designated 331 and the end edges (or "ends") are designated 332. FIG. 9 is a top plan view of a sanitary napkin 320 of the present invention in a substantially flat state with portions of the sanitary napkin being cut away to more clearly show the construction of the sanitary napkin 320 and with the portion of the sanitary napkin 320 which faces or contacts the wearer 320a oriented towards the viewer. As shown in FIG. 9, the sanitary napkin 320 preferably comprises a liquid pervious topsheet

322, a liquid impervious backsheet 323 joined with the topsheet 322, an absorbent core

324 positioned between the topsheet 322 and the backsheet 323, and a secondary topsheet or acquisition layer 325 positioned between the topsheet 322 and the absorbent core 324.

The sanitary napkin 320 preferably includes optional side flaps or "wings" 334 that are folded around the crotch portion of the wearer's panty. The side flaps 334 can serve a number of puφoses, including, but not limited to helping to hold the napkin in proper position while protecting the wearer's panty from soiling and keeping the sanitary napkin secured to the wearer's panty.

FIG. 10 is a cross-sectional view of the sanitary napkin 320 taken along section line 10-10 of FIG. 9. As can be seen in FIG. 10, the sanitary napkin 320 preferably includes an adhesive fastening means 336 for attaching the sanitary napkin 320 to the undergarment of the wearer. Removable release liners 337 cover the adhesive fastening means 336 to keep the adhesive from sticking to a surface other than the crotch portion of the undergarment prior to use. The topsheet 322 has a first surface 322a and a second surface 322b positioned adjacent to and preferably secured to a first surface 325a of the fluid acquisition layer 325 to promote fluid transport from the topsheet to the acquisition layer. The second surface 325b of the acquisition layer 325 is positioned adjacent to and is preferably secured to the first surface 324a of an absorbent core or fluid storage layer 324 to promote fluid transport from the acquisition layer to the absorbent core. The second surface 324b of the absorbent core 324 is positioned adjacent to and is preferably secured to the first surface 323a of the backsheet 323.

In addition to having a longitudinal direction and a transverse direction, the sanitary napkin 320 also has a "Z" direction or axis, which is the direction proceeding downwardly through the topsheet 322 and into whatever fluid storage layer or core 324 that may be provided. The objective is to provide a substantially continuous path between the topsheet 322 and the underlying layer or layers of the absorbent article herein, such that fluid is drawn in the "Z" direction and away from the topsheet of the article and toward its ultimate storage layer. The absorbent core 324 may be any absorbent means which is capable of absorbing or retaining liquids (e.g., menses and/or urine). As shown in FIGS. 9 and 10, the absorbent core 324 has a body surface 324a, a garment facing surface 324b side edges, and end edges. The absorbent core 324 may be manufactured in a wide variety of sizes and shapes (e.g. rectangular, oval, hourglass, dogbone, asymmetric, etc.) and from a wide variety of liquid-absorbent materials commonly used in sanitary napkins and other absorbent articles such as comminuted wood pulp which is generally referred to as airfelt.

5 Examples of other suitable absorbent materials include creped cellulose wadding; meltblown polymers including coform; chemically stiffened, modified or cross-linked cellulosic fibers; synthetic fibers such as crimped polyester fibers; peat moss; tissue including tissue wraps and tissue laminates; absorbent foams; absorbent sponges; superabsorbent polymers; absorbent gelling materials; or any equivalent material or l o combination of materials, or mixtures of these.

The configuration and construction of the absorbent core may also be varied (e.g., the absorbent core may have varying caliper zones (e.g. profiled so as to be thicker in the center), hydrophilic gradients, superabsorbent gradients or lower density or lower average basis weight acquisition zones; or may comprise one or more layers or structures). The is total absorbent capacity of the absorbent core, should, however, be compatible with the design loading and the intended use of the absorbent article. Further, the size and absorbent capacity of the absorbent core may be varied to accommodate different uses such as incontinent pads, pantiliners, regular sanitary napkins, or overnight sanitary napkins.

20 Exemplary absorbent structures for use as the absorbent core in the present invention are described in U.S. Pat. No. 4,950,264 issued to Osborn on August 21 , 1990; U.S. Pat. No. 4,610,678 issued to Weisman et al. on September 9, 1986; U.S. Pat. No. 4,834,735 issued to Alemany et al. on May 30, 1989; and European Patent Application No. 0 198 683, the Procter & Gamble Company, published October 22, 1986 in the name

25 Duenk, et al. The disclosures of each of these patents are incoφorated herein by reference.

A preferred embodiment of the absorbent core 324 has a surface energy gradient similar to the surface energy gradient of the topsheet 322. The body facing surface 324a of the absorbent core and the portion of the absorbent core 324 immediately adjacent the

30 body facing surface 324a preferably has a relatively low surface energy as compared to the garment facing surface 324b which has a relatively high surface energy. It is important to note that while there is a surface energy gradient within the absorbent core 324, the surface energy of the wearer-contacting or the body facing surface 324a of the absorbent core is preferably greater than the surface energy of the garment facing surface 325b of the

35 acquisition layer 325. This relationship is preferred in order that fluid may be pulled or driven from the acquisition layer into the absorbent core. If the surface energy of the body facing surface 324a of the absorbent core were less than that of the garment facing surface 325b of the acquisition layer fluid in the acquisition layer 325 would be repelled by the absorbent core, thus rendering the absorbent core useless.

The backsheet 323 and the topsheet 322 are positioned adjacent the garment facing surface and the body facing surface respectively of the absorbent core 324 and are preferably joined thereto and to each other by attachment means (not shown) such as those well known in the art. For example, the backsheet 323 and/or the topsheet 322 may be secured to the absorbent core or to each other by a uniform continuous layer of adhesive, a patterned layer of adhesive or any array of separate lines, spirals or spots of adhesive. Adhesives which have been found to be satisfactory are manufactured by H.B. Fuller Company of St. Paul, Minnesota under the designation HL-1258, and by Findlay of Minneapolis, Minnesota, under the designation H-2031. The attachment means will preferably comprise an open pattern network of filaments of adhesive as disclosed in U.S. Pat. No. 4,573,986 issued to Minetola et al. on March 4, 1986, the disclosure of which is incoφorated herein by reference. An exemplary attachment means of an open patterned network of filaments comprises several lines of adhesive filaments swirled into a spiral pattern such as illustrated by the apparatus and method shown in U.S. Pat. No. 3,911,173 issued to Sprague, Jr. on October 7, 1975; U.S. Pat. No. 4,785,996 issued to Zieker, et al. on November 22, 1978 and U.S. Pat. No. 4,842,666 issued to Werenicz on June 27, 1989. The disclosures of each of these patents are incoφorated herein by reference. Alternatively, the attachment means may comprise heat bonds, pressure bonds, ultrasonic bonds, dynamic mechanical bonds or any other suitable attachment means or combinations of these attachment means as are known in the art.

The backsheet 323 is impervious to liquids (e.g., menses and/or urine) and is preferably manufactured from a thin plastic film, although other flexible liquid impervious materials may also be used. As used herein, the term "flexible" refers to materials which are compliant and are more readily conformed to the general shape and contours of the human body. The backsheet 323 prevents the exudates absorbed and contained in the absorbent core from wetting articles which contact the sanitary napkin 320 such as pants, pajamas and undergarments. The backsheet 323 may thus comprise a woven or nonwoven material, polymeric films such as thermoplastic films of polyethylene or polypropylene, or composite materials such as a film-coated nonwoven material. Preferably, the backsheet of the polyethylene film having a thickness of from about 0.012 mm (0.5 mil) to about 0.051 mm (2.0 mil). Exemplary polyethylene films are manufactured by Clopay Coφoration of Cincinnati, Ohio, under the designation PI 8- 1401 and by Tredegar Film Products of Terre Haute, Indiana, under the designation XP-9818. The backsheet is preferably embossed and/or matte finished to provide a more clothlike appearance. Further, the backsheet 323 may permit vapors to escape from the absorbent core 324 (i.e., breathable) while still preventing exudates from passing through the backsheet 323.

In use, the sanitary napkin 320 can be held in place by any support means or attachment means (not shown) well-known for such puφoses. Preferably, the sanitary napkin is placed in the user's undergarment or panty and secured thereto by a fastener such as an adhesive. The adhesive provides a means for securing the sanitary napkin in the crotch portion of the panty. Thus, a portion or all of the outer or garment facing surface 323b of the backsheet 323 is coated with adhesive. Any adhesive or glue used in the art for such puφoses can be used for the adhesive herein, with pressure-sensitive adhesives being preferred. Suitable adhesives are manufactured by H. B. Fuller Company of St. Paul, Minnesota, under the designation 2238. Suitable adhesive fasteners are also described in U.S. Patent 4,917,697. Before the sanitary napkin is placed in use, the pressure-sensitive adhesive is typically covered with a removable release liner 337 in order to keep the adhesive from drying out or adhering to a surface other than the crotch portion of the panty prior to use. Suitable release liners are also described in the above-referenced U.S. Patent 4,917,697. Any commercially available release liners commonly used for such puφoses can be utilized herein. A non-limiting example of a suitable release liner is BL30MG-A Silox 4P/O, which is manufactured by the Akrosil Coφoration of Menasha, WI. The sanitary napkin 320 of the present invention is used by removing the release liner and thereafter placing the sanitary napkin in a panty so that the adhesive contacts the panty. The adhesive maintains the sanitary napkin in its position within the panty during use.

In a preferred embodiment of the present invention, the sanitary napkin has two flaps 334 each of which are adjacent to and extend laterally from the side edge of the absorbent core. The flaps 334 are configured to drape over the edges of the wearer's panties in the crotch region so that the flaps are disposed between the edges of the wearer's panties and the thighs. The flaps serve at least two puφoses. First, the flaps help serve to prevent soiling of the wearer's body and panties by menstrual fluid, preferably by forming a double wall barrier along the edges of the panty. Second, the flaps are preferably provided with attachment means on their garment surface so that the flaps can be folded back under the panty and attached to the garment facing side of the panty. In this way, the flaps serve to keep the sanitary napkin properly positioned in the panty. The flaps can be constructed of various materials including materials similar to the topsheet, backsheet, tissue, or combination of these materials. Further, the flaps may be a separate element attached to the main body of the napkin or can comprise extensions of the topsheet and backsheet (i.e., unitary). A number of sanitary napkins having flaps suitable or adaptable for use with the sanitary napkins of the present invention are disclosed in U.S. 4,687,478 entitled "Shaped Sanitary Napkin With Flaps", which issued to Van Tilburg on August 18. 1987; and U.S. 4,589.876 entitled "Sanitary Napkin", which issued to Van Tilburg on May 20, 1986. The disclosure of each of these patents is hereby incoφorated herein by reference. In a preferred embodiment of the present invention, an acquisition layer(s) 325 may be positioned between the topsheet 322 and the absorbent core 324. The acquisition layer 325 may serve several functions including improving wicking of exudates over and into the absorbent core. There are several reasons why the improved wicking of exudates is important, including providing a more even distribution of the exudates throughout the absorbent core and allowing the sanitary napkin 320 to be made relatively thin. The wicking referred to herein may encompass the transportation of liquids in one, two or all directions (i.e., in the x-y plane and/or in the z-direction). The acquisition layer may be comprised of several different materials including nonwoven or woven webs of synthetic fibers including polyester, polypropylene, or polyethylene; natural fibers including cotton or cellulose; blends of such fibers; or any equivalent materials or combinations of materials. Examples of sanitary napkins having an acquisition layer and a topsheet are more fully described in U.S. 4,950,264 issued to Osborn and U.S. Patent Application Serial No. 07/810,774, "Absorbent Article Having Fused Layers", filed December 17, 1991 in the names of Cree, et al. The disclosures of each of these references are hereby incoφorated herein by reference. In a preferred embodiment, the acquisition layer may be joined with the topsheet by any of the conventional means for joining webs together, most preferably by fusion bonds as is more fully described in the above-referenced Cree application.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

Claims

WHAT IS CLAIMED IS:

1. A method for forming a laminate web, said method characterized by the steps of:

(a) providing a nonwoven web of fibers exhibiting a surface energy, said nonwoven web having a first surface, a second surface, and a plurality of fluid passageways placing said first and second surfaces in fluid communication with one another;

(b) applying a surface treatment to the first surface of said nonwoven web, said surface treatment having a surface energy less than the surface energy of the fibers of said nonwoven web surface; and

(c) providing an apertured macroscopically expanded three-dimensional polymeric web; and

(d) joining said nonwoven web of fibers to said apertured macroscopically expanded three-dimensional polymeric web to form a laminate web.

2. The method of Claim 1, wherein said nonwoven web is joined to said apertured macroscopically expanded three-dimensional polymeric web by feeding said webs between a first pressure applicator and a second pressure applicator.

3. The method of Claim 1 , wherein said nonwoven web exhibits a plurality of surface energy gradients defined by discontinuous, spaced regions which are adapted to exert a force on a fluid contacting said first surface, such that such fluid will be directed toward said fluid passageways for transportation away from said first surface and in the direction of said second surface.

4. The method of Claim 3, wherein said discontinuous, spaced regions are also located at least partially within said fluid passageways.

5. The method of Claim 3, wherein at least one fluid passageway exhibits a plurality of said discontinuous, spaced regions located at least partially within said fluid passageway.

6. The method of Claim 3, wherein said discontinuous, spaced regions are randomly distributed over said first surface of said nonwoven web.

7. The method of Claim 3, wherein said discontinuous, spaced regions are randomly located at least partially within said fluid passageways.

8. The method of Claim 7, wherein said discontinuous, spaced regions are randomly located between said first and second surfaces of said nonwoven web.

9. The method of Claim 3, wherein said discontinuous, spaced regions are located within said fluid passageways at random distances from said first surface of said nonwoven web.

10. The method of Claim 3, wherein at least one fluid passageway exhibits a plurality of said discontinuous, spaced regions located at different distances from said first surface of said nonwoven web.