HU221144B1 - Disposable absorbent article having reduced wet through equipped with a breathable backsheet and method making thereof - Google Patents

Abstract

The present invention relates to a disposable absorbent article having a liquid-permeable topsheet (2), an absorbent core (4) and a backsheet (3), wherein the core (4) is disposed between the topsheet (2) and the backsheet (3); (3) comprises a liquid-permeable polymeric film for unidirectional fluid transfer to the core (4), the core (4) has a single fluid storage layer and the backsheet (3) has an outer layer, each of the core (4) and the backsheet (3) comprising at least one layer, each layer having a wearer-facing surface and a uniform garment-facing surface, each of the layer surfaces having a liquid contact angle, and areas of the absorbent article from the garment-facing area of the liquid storage layer to the garment-facing area of the outer layer; including an extending lower portion, recognizing that the surface of at least one of the layers of the lower portion in the wearer has a greater fluid contact angle than e.g. y is the angle of liquid contact of the surface of the adjacent layer opposite the adjacent garment. In another embodiment, at least one of the layers of the lower portion has a greater liquid contact angle with the surface of the garment facing the surface, the liquid contact angle of the surface of the adjacent layer facing the adjacent wearer. The invention also relates to the manufacture of an absorbent article. ŕ

Description

The present invention relates to a disposable absorbent article such as a sanitary napkin or pant lining having a reduced moisture permeability to the wearer's wear, and to a method for making the absorbent article.

The primary consumer demand that underlies lingerie development in the field of absorbent articles, particularly menstruation pads, is the high level of protection and comfort.

One very desirable tool for improving the comfort of absorbent articles is the use of a breathable backsheet. Breathable backsheets may comprise a direct fluid transfer film formed by a slit as disclosed, for example, in U.S. Patent No. 4,591,523. Backsheets breathing such slits typically allow vapor and air to pass through, allowing for gas exchange with the environment. Thereby, they allow a portion of the fluid stored in the core to be evaporated and air circulated within the absorbent article. This is particularly advantageous as it reduces the feeling of stickiness experienced by many wearers during use, especially over an extended period of time.

However, the major disadvantage associated with the use of breathable backsheets in absorbent articles is the increased likelihood of leakage, commonly referred to as wetting of the wearer's clothing. Although such breathable backsheets permit, in principle, only gaseous material to pass through and only unidirectional fluid passage, physical phenomena such as compression, diffusion, and capillary activity can occur and result in the transfer of these fluids through the backside and to the wearer's clothing. These mechanisms become particularly prevalent when the product is used under high load or over a long period of time under physical exertion. Whilst breathable backs provide excellent comfort, they have unacceptable deficiencies in protection, especially under pressure.

Wetting problems with wearers' clothing due to the inclusion of such breathable backsheets are known in the art. Attempts to overcome this problem mainly involve the use of multilayer backsheets, such as those disclosed in U.S. Patent No. 4,341,216. Similarly, EP-A-0 710 472 discloses breathable absorbent articles comprising a breathable backsheet comprising at least two breathable backsheets which are not interconnected above the absorbent core area. EP-A-0 710 471, also disclosed, discloses a breathable backsheet for disposable absorbent articles comprising a gas-permeable, hydrophobic, polymeric fibrous outer fabric layer and an inner layer formed by a directional fluid transport slot.

Alternatively, another proposed solution to the problem is to increase the thickness of the absorbent articles to achieve the required level of protection, which is usually achieved by increasing the core thickness.

However, none of the previous solutions proved to be fully satisfactory. This is especially the case for thin products, as thickness is also considered to be a key variable affecting product comfort. Thus, there is a duality in the methods available to provide absorbent articles with increased comfort due to the fact that thin breathable products cannot provide the required level of protection.

As a result, there is a need to provide an absorbent article that provides improved comfort by using a breathable backsheet and a thickness that still maintains the desired level of protection.

It has been found that breathable backsheets can be formed in thin sanitary napkins by providing a low surface energy material, such as silicone and chlorofluorocarbons, or by hydrophobicity gradient achieved through low surface energy treatment, providing both high protection and comfort. . In this way, it is believed that physical mechanisms such as diffusion and capillary action are inhibited and that wettability is significantly reduced, if not completely eliminated.

A further advantage of the invention is that it is no longer necessary for this layer to be completely synthetic and may be at least partially natural, since the invention allows the use of breathable backsheets coated with a hydrophobic material. It provides an important and perceptible consumer benefit because the product has a more natural sense of touch.

The use of a surface energy gradient is described, for example, in WO 96/00548. This document discloses fluid transporting webs, such as topsheets, which have surface energy gradients. The web allows for liquid transport in one direction and prevents transportation in the opposite direction. The web comprises first and second surfaces separated by an intermediate portion. The first surface of the web has a lower surface energy than the surface energy of the intermediate portion, resulting in a surface energy gradient. Suitably low surface energy materials include silicone, fluoropolymers and paraffins. The web is particularly suitable for absorbent articles as a topsheet for transporting liquid from the wearer's contact surface to the absorbent structure.

The present invention relates to a disposable absorbent article having a liquid-permeable topsheet, an absorbent core, and a backsheet wherein the core is disposed between the topsheet and the backsheet, the backsheet comprising a liquid-permeable polymeric film for unidirectional fluid transfer to the core. a liquid storage layer and a backsheet having an outer layer, the core and backsheet each having at least one layer wherein each layer has a wearer facing and a clothing facing surface, and each of the layers has a fluid contact angle , and from the area of the absorbent article facing the fluid storage layer clothing to the outer layer clothing

EN 221,144 B1 including an area, and wherein at least one of the layers of the bottom portion has a greater fluid contact angle than the fluid contact surface of an adjacent layer of clothing adjacent to the wearer. angle.

Another embodiment of the present invention is a disposable absorbent article, such as a sanitary napkin or panty liner, having a fluid-permeable topsheet, an absorbent core, and a backsheet wherein the core is disposed between the topsheet and the backsheet; comprising a liquid-permeable polymer film, the core having a fluid storage layer and the backsheet having an outer layer, each core and backsheet comprising at least one layer wherein each layer has a wearer facing surface and a clothing facing surface, and each surface of the layers having a fluid contact angle and extending from the area of the absorbent article to the garment of the liquid storage layer to the garment of the outer layer, including the areas, and at least one of the layers of the lower portion facing the garment has a greater liquid contact angle than the liquid contact angle of the adjacent wearer surface of an adjacent layer.

In yet another aspect, the present invention provides a process for making an absorbent article as described above, wherein at least one of the layers in the lower portion is treated with low surface energy material.

In another aspect, the present invention relates to a process for making an absorbent article as described above, wherein at least one of the layers in the lower portion comprises a low surface energy material.

Detailed Description of the Invention The present invention will be described in detail with reference to the accompanying drawings.

Figure 1 is a plan view of an exemplary embodiment of the absorbent article of the present invention with cutout portions illustrating its internal structure.

Figure 2: Figure 1 of a backsheet according to the invention

I-I is an enlarged cross-sectional view taken along the intersection plane.

Figure 3: An enlarged cross-sectional view of a liquid droplet on a surface, wherein angle A represents the angle of contact of the liquid with the surface.

Figure 4: An enlarged cross-sectional view of two liquid droplets on a surface having two different surface energies, such as two liquid droplets A (a) and A (b).

The present invention relates to absorbent disposable articles such as sanitary napkins 1, baby diapers, incontinence articles and panties.

Such articles typically comprise a liquid-permeable topsheet 2, a backsheet 3 and an absorbent core 4 disposed between the topsheet 2 and the backsheet 3. The topsheet 2, the backsheet 3 and the core 4 each have a face-to-face surface and a face-to-face surface. The garment facing surface of the topsheet 2 and the garment facing surface of the backsheet 3 are joined together at the periphery 5 of the absorbent article. In a preferred embodiment of the invention, the absorbent article may have wings, side wraps, or side projections.

According to the present invention, the absorbent core 4 comprises a first portion and a second portion, the first portion having (a) an optional primary fluid distribution layer, preferably a secondary liquid distribution layer; (b) having a fluid storage layer. The second layer (c) comprises an optional fiber ("dust") layer located below the storage layer; and (d) optionally having other elements.

According to the invention, the absorbent core 4 can be of any thickness depending on the intended use. In a preferred embodiment of the invention, wherein the absorbent article is a sanitary napkin or a panty liner, the core may have a thickness of 15-1 mm, preferably 10-1 mm, most preferably 7-1 mm.

An optional portion of the first portion of the absorbent core 4 of the present invention is a primary liquid distribution layer and a secondary liquid distribution layer. The primary fluid distribution layer is typically located below and in fluid communication with the topsheet 2. The topsheet 2 conveys the absorbed liquid to this primary distribution layer for uniform distribution within the storage layer. This fluid transfer through the primary distribution layer takes place not only in the thickness of the absorbent article but also in its longitudinal and width directions. The optional secondary distribution layer, which may also be used, is typically below and in fluid communication with the primary distribution layer. The purpose of this secondary distribution layer is to rapidly absorb fluid from the primary distribution layer and to transfer it rapidly to the underlying storage layer. This helps to make full use of the liquid capacity of the storage layer below. The liquid distribution layers may comprise any material typical of such distribution layers.

A fluid storage layer 6 is in fluid communication with the primary and secondary distribution layers and is typically located below them. The fluid storage layer 6 is made of any conventional absorbent material or combinations thereof. Preferably, the absorbent gelling materials, commonly referred to as "hydrogel", "superabsorbent", "hydrocolloid", are in combination with suitable carriers.

Absorbent gelling agents are capable of absorbing large amounts of aqueous body exudate, and are capable of holding such absorbed fluids under moderate pressures. The absorbent gelling agent3

The compounds of this invention may be dispersed homogeneously or non-homogeneously in a suitable carrier. Suitable carriers, provided that they are absorbent per se, may be used alone.

The gelling agents suitable for use in the present invention most commonly comprise a substantially water-insoluble, slightly cross-linked, partially neutralized, polymeric gelling agent. This substance forms a hydrogel in contact with water. Such polymeric materials may be prepared from polymerizable, unsaturated, acidic monomers well known in the art.

Suitable carriers include those commonly used in absorbent structures, such as natural, modified or synthetic fibers, in particular modified or unmodified cellulose fibers, in the form of flakes and / or tissues. Suitable carriers may be used in combination with absorbent gelling materials, but may be used alone or in combination. Tissue or tissue laminates are most preferred for sanitary napkins and panty liners.

One embodiment of the absorbent structure of the present invention comprises a bilayer tissue laminate formed by twisting the tissue itself. These layers may be bonded together, for example, by adhesive or mechanical wrapping, or by hydrogen bonding. The absorbent gelling material or other optional material may be included between the layers.

Modified cellulose fibers, such as hardened cellulose fibers, may also be used. Synthetic fibers can also be used and include cellulose acetate, polyvinyl fluoride, polyvinylidene chloride, acrylic species (e.g., Orlon), polyvinyl acetate, insoluble polyvinyl alcohol, containing polyethylene, polypropylene, polyamides (e.g., nylon), polyesters, bicomponent fibers, tri-component fibers, mixtures thereof, and the like. The fiber surfaces are preferably hydrophilic or rendered hydrophilic by treatment. The storage layer includes fillers such as perlite, diatomaceous earth, Vermiculite and the like. it may also include fluid retention enhancement.

However, when the absorbent gelling material is not homogeneously dispersed in a carrier, the storage layer may still be locally homogeneous, i.e. it may have a distribution gradient in one or several directions within the dimensions of the storage layer. The non-homogeneous distribution may also apply to carrier laminates that partially or completely encapsulate absorbent gelling materials.

An optional ingredient for incorporation into the absorbent core 4 of the present invention is a fibrous layer adjacent to and typically below the storage layer. This fibrous layer below is typically equivalent to a "powder" layer on which the absorbent gelling material in the storage layer is deposited during the manufacture of the absorbent core. In cases where the absorbent gelling material is in the form of macrostructures, such as fibers, sheets or strips, this fibrous "dusting" layer need not be applied. However, this "stamen" layer provides some additional fluid control properties, such as rapid absorption of liquid along the length of the cushion.

The absorbent core 4 of the present invention may include other optional components commonly found in absorbent webs, such as reinforcing fabric that may be placed within or between layers of absorbent core 4. Such reinforcing fabric must be of a shape such that it does not interfere with fluid transfer. However, due to the uniform structure formed by heat welding, the use of reinforcing fabrics is usually not required for thermally bonded absorbent structures.

The other component, preferably close to or as part of the primary or secondary liquid distribution layer, which can be placed in the core 4 of the present invention is comprised of deodorants. Activated charcoal or other deodorants may optionally be included in the absorbent structure, particularly zeolite or clay materials. These components may be mixed in any form, but often incorporated as separate particles.

The topsheet 21 (see Figure 2) may comprise a single layer or multiple layers. In a preferred embodiment, the topsheet 21 comprises a first layer 22 which provides a face-to-face surface of the topsheet 21 and a second layer 23 between the first layer 21 and the absorbent structure / core.

The topsheet 21 as a whole, and therefore each layer, must be individually complex, soft in feel, and non-irritating to the wearer's skin. It may also have elastic properties, allowing it to be stretched in one or two directions. According to the invention, the topsheet 21 may be formed from any material available for this purpose and known in the art, such as nonwovens, films and combinations of both. In a preferred embodiment of the invention, at least one of the topsheet layers (preferably the topsheet) comprises a liquid permeable polymeric film 31.

Preferably, the topsheet is provided with a slit film material provided to facilitate fluid transfer from the wearer facing surface to the absorbent structure such as, for example, U.S. Pat. No. 3,929,135; U.S. Pat. Nos. 4,151,240, 4,339,868, 4,334,426, 4,343,314 and 4,591,523.

Typically, the topsheet 21 extends across the entire absorbent structure to the preferred side tabs, side wraps, or wings, all or part of them.

The absorbent articles of the present invention comprise a unidirectional fluid delivery, breathable backsheet 24. The primary role of the backsheet 24 is its megaka4

The B1 is designed to moisten absorbent and retained body exudates to wipe articles in contact with the absorbent article, such as panties, pants, pajamas, and underwear. However, the backsheet 24 of the absorbent article of the present invention also allows the transfer of both humidity and air, and thus air circulation in and out of the backsheet.

As used herein, the term "unidirectional" refers to materials that provide substantially unidirectional fluid transport to the core. Fluid orientation can be identified using Test Method 3, which is detailed herein.

According to the invention, the backsheet 24 preferably comprises at least two layers; a first layer 25 comprising a gas-permeable slit polymer film and a second layer 26 of a gas-permeable fiber. Preferably, the first and second layers 25, 26 have a similar relative void volume. The first layer 25 is typically located adjacent to the core 27, and the subsequent layers of the backsheet 24 are typically located further from the core. The backsheet 24 may comprise additional layers. In each case, the outer layer furthest from the core 27 is the outer layer. All layers of the backsheet 24 are substantially intimate and in direct contact.

The first layer 25 of the slots 25 of the backsheet 24 comprises a layer of discrete slots extending beyond the horizontal plane of the layer to the core 27, thereby forming protrusions. Each protuberance has apertures at its endpoint. The protrusions are preferably in the form of a funnel or cone, as described in U.S. Patent No. 3,929,135. The slots 28 are located in the plane of the first layer 25. The apertures at the end of the protrusions may be circular or non-circular. In any case, the openings at the end of the protrusions have a cross-sectional dimension or area smaller than the cross-sectional dimension or area of the slots 28 located within the plane of the first layer. The first layer 25 of the backsheet 24 typically has an open area greater than 5%, preferably greater than 10-35%, of the total film area. The open area of the first layer 25 may be determined in this specification by Test Procedure 4, which is detailed in the Test Procedures.

According to the invention, the first layer 25 of the backsheet 24 can be made of any material known in the art, but is preferably made of commonly available polymeric materials.

The second layer 26 of the backsheet 24 is a gas-permeable fibrous web consisting of polymer fibers, such as polymeric nonwoven materials known in the art. The fibrous layer preferably has a basis weight of 10-100 g / m ² , more preferably 15-30 g / m ² . The fibers can be made from any polymeric material, in particular polyethylene, polypropylene, polyester, polyacetate fibers or combinations thereof (common and internal fiber combinations), and mixtures of synthetic fibers and non-absorbent natural fibers or treated natural fibers, such as cotton. Preferably, the fibers are braided, carded or melt blown. Preferably, the second layer 26 comprises a network of braided fibers covered with meltblown fibers on one side or alternatively a network of meltblown fibers coated on both sides with braided fibers. The second layer 26 of the backsheet 24 may further comprise at least 5% by weight of the layer of liquid absorbing fiber such that the fibers are swollen and reduce the space between the fibers.

Typically, the backsheet 24 extends throughout the absorbent structure and may enter, or form part or all of, the preferred side tabs, side wraps or wings.

According to a first embodiment of the invention, any of the layers in the lower portion of the absorbent article has a wearer facing surface and a garment facing surface, each of these surfaces having a fluid contact angle, wherein at least one of the layers in the lower portion is facing the wearer. having a greater liquid contact angle than the liquid contact angle of the surface of an adjacent layer facing adjacent clothing.

In a second embodiment of the invention, any layer in the lower portion has a wearer facing surface and a garment facing surface, and each surface of the layers has a liquid contact angle at which at least one of the layers in the lower portion has a larger facing surface. liquid contact angle as the liquid contact angle of the surface of the same layer facing the wearer.

In principle, the liquid contact angular gradient may be present between any surface (wearer or clothing) of any layer in the lower portion. The liquid contact angular gradient is thus across the wearer and clothing surface of the same layer or between at least one layer of clothing and the adjacent surface of an adjacent layer of the lower layer, i.e., the wearer and clothing surface of the first layer 25 of backsheet 24. The second layer 26 may be present between the wearer and clothing surface or any successive backsheet layers. Thus, each of these combinations of layers having a specific fluid contact angle relationship is used to create a continuous gradient.

However, for the sake of simplicity, the description of the invention will then be focused on the differential or increased liquid contact angle gradient between the garment surface of the core 27 and the wearer surface of the first layer 25 of the backsheet 24 (see FIG.

3 and 4).

Applying a drop of liquid 110 to a solid surface 112 typically forms an angle of contact A with the solid surface 112 as shown in FIG. As the solid surface 112 is fluid

EN 221 144 Β1 the angle of contact A decreases. As the wettability of the solid surface 112 decreases with liquid, the contact angle A increases. The liquid contact angle of a solid can be determined by methods known in the art, such as those described by Arthur W. Adamson; in Physical Chemistry of Surfaces, Second Edition, (1967), by F. E. Bartell and Η. H. Zuidema; J. Am. Chem. Soc., 58, 1449 (1936) and J. J. Bikerman; Ind. Eng. Chem. Anal. Ed., 13, 443 (1941). 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.

As used herein, the term "hydrophilic" refers to surfaces that are wetted by aqueous fluids (such as aqueous body exudates) that are deposited on them. Hydrophilicity and wettability are typically defined in terms of the contact angle and surface tension of the liquids and solids involved. This is discussed in detail in "Angié Contact, Wettability and Adhesion," edited by Robert F. Gould of the American Chemical Society (Copyright 1964). A surface is called wettable with an aqueous liquid (hydrophilic) when the liquid spreads on the surface without being forced. On the contrary, a surface is classified as "hydrophobic" if the liquid does not spread on the surface without being forced.

The liquid / solid The contact angle depends on the inhomogeneities of the surface (e.g., chemical and physical properties such as roughness), the chemical / physical treatment or composition of the solid surface, and the nature and impurities of the liquid. The surface energy of the solid also influences the angle of contact A. As the surface energy of the solid decreases, the contact angle A increases. As the surface energy of the solid increases, the contact angle A decreases.

The energy required to separate a liquid from a solid surface (such as a film or fiber) is expressed by equation (1):

W = G (1 + cosA) (1) in which equation

W is the work of adhesion measured at 10 ^-3 Jm ^_2 ,

G is measured in the liquid 10 ^-3 Nm 'in surface tension, and

A is the liquid-solid contact angle in degrees.

For a given fluid, the adhesion work increases with the cosine of the contact angle A of the liquid solid (reaching maximum when contact angle A is zero).

Adhesion work is one useful tool for understanding and quantifying the surface energy characteristics of a given fluid on a given surface.

Table 1 can be used to illustrate the relationship between solid-liquid contact angle and adhesion work for a specific fluid (e.g., water) having a surface tension of 7.5 · 10 ~ ² N / m.

Table 1

The (degrees) cos 1 + cos W (x10 ³ N / m) 0 1 2 150 30 0.87 1.87 140 60 0.5 1.50 113 90 0 1.00 75 120 -0.5 0.5 38 150 -0.87 0.13 10 180 -1 0 0

According to Table 1, as the adhesion work of a specific surface decreases (the specific surface exhibits less surface energy), the contact angle A of the liquid increases on the surface, and therefore the liquid tends to drop (curl) and to have a smaller contact surface. occupying an area. The opposite is equally true, since the surface energy of a given surface is reduced by a given liquid. Adhesion work therefore influences interfacial fluid phenomena on a solid surface.

More importantly, surface energy gradients have been found to be useful in preventing fluid transport, as illustrated by fluid contact angles or discontinuities (interfaces). Figure 4 illustrates a drop of liquid 110 on a solid surface having two areas 113 and 115 having different surface energies (indicated by different cross lines for illustrative purposes). In the position illustrated in Fig. 4, area 113 exhibits a lower surface energy relative to area 115 and, therefore, liquid droplet fluid is less wettable than area 115. Correspondingly, the droplet 110 forms a contact angle A (b) at the edge 113 of the droplet, which is larger than the contact angle A (a) formed at the edge 115 of the droplet. It should be noted that although for the sake of clarity the points "a" and "b" lie flat, the distance "dx" between the points "a" and "b" need not be linear, the degree of droplet / surface contact on the surface instead of being disregarded. The droplet 110 thus has an unbalanced surface energy and therefore, due to relative surface energy differences (i.e., surface energy gradient or discontinuity) between areas 113 and 115, exerts an external force which can be illustrated by equation (2):

dF = G [cosA (a) -cosA (b)] dx, (2) in which equation dF is the net force on the liquid droplet, dx is the distance between the references "a" and "b",

G is as defined above, and

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

HU 221 144 Β1

Solving equation (1) for cosA (a) and cosA (b) and replacing it in equation (2) results in equation (3):

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

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

dF = [W (a) - [W (b)] dx (4).

The importance of the surface energy difference between the two surfaces is clearly described by equation (4), since it has a direct proportional effect on the magnitude of the force that changes the difference in adhesion work.

For a more detailed discussion of surface energy effects and the physical nature of capillary tubing, see Absorbancy (1985) edited by Textile Science and Technology, 7 Portnoy K. Chatterjee (1985) and A. M. Schwartz; Capillarity, Therory and Practice, Ind. Eng. Chem., 61, 10 (1969).

Accordingly, the force exerted by a droplet 110 causes movement toward a surface with a higher surface energy specificity, in this case toward the core. For the sake of simplicity and graphical clarity, the surface energy gradient or discontinuity is shown in Figure 4 as a single sharp surface energy gradient or discontinuity between well defined areas other than surface energy. Surface energy gradients can exist as continuous gradients or step gradients, for any characteristic droplet (or portions thereof), for each specific region of droplet contact, with a force determined by surface energy.

As used herein, the term "gradient", when applied to differences in surface energy or adhesion work, is intended to describe a change in surface energy or adhesion work over a measurable distance. The term "discontinuity" is intended to mean a "gradient" or transition in which a change in surface energy occurs at a substantially zero distance. Accordingly, as used herein, all "discontinuities" fall within the definition of "gradient."

As used herein, the terms "capillary" and "capillary" refer to fluid-carrying transport pathways, gaps, pores or spaces within a structure, in accordance with the Laplace equation (5), which generally represents the principles of capillarity:

p = 2G (cosA) / R, (5) in which p is capillary pressure;

R is the internal radius of the capillary (capillary ray); and

G and A are as defined above.

A = 90 ° The cosine of Z is zero and there is no capillary pressure as Emery I. Valko of Chem. Aftertreat. Tex. (1971) III. in Chapters 83-113. pages, "Penetration of Fabrics". A> 90 ° The cosine is negative and capillary pressure acts in opposition to fluid entering the capillary. The capillary walls must therefore be hydrophilic in nature to produce detectable capillary effects on a hydrophilic aqueous liquid. R must also be small enough for p to be significant, since as R increases (larger gap / capillary structure), capillary pressure decreases.

The specific orientation or location of the gradients themselves with respect to the orientation or location of the capillary or the fluid pathways themselves is perhaps at least as important as the presence of a surface energy gradient.

For reference purposes, and without limitation, water is the only reference liquid. The physical properties of water are well known and water is readily available, and wherever it is obtained, it generally has the same properties. Concerning water, the concepts of adhesion work can be easily applied to other fluids such as blood, menstrual fluid and urine, taking into account the specific surface tension properties of the fluid required.

By providing a relatively low surface energy adjacent to and adjacent to the backsheet 27 adjacent to the absorbent core 27, the backsheet 24 is capable of a liquid drop with a relatively smaller surface energy gradient between the core 27 and backsheet 24 and the skin of the wearer. to prevent movement of the core 27 with relatively higher surface energy to the backsheet 24 with relatively lower surface energy. The movement of the liquid drop is caused by the difference in contact angle A between the smaller surface energy portion and the larger surface energy portion, which is the surface tension acting on the solid-liquid contact plane! resulting in an imbalance of power. It is believed that this obtained surface energy gradient, which results in a negative capillary pressure, is particularly suitable for use with slits 24 on an absorbent article.

The wetting potential is thereby reduced by having a surface energy gradient slit having a backsheet 24 as described above. Because in some applications the applied force tends to squeeze the collected liquid from the pad (e.g., by squeezing it from the absorbent core 27 toward the underside of the backsheet 24), such undesirable movement is prevented by the backsheet 24 having a relatively low surface energy. Through the openings in the rear panel, squeeze the liquid that is trying to escape from the insert.

Due to the driving forces of the surface energy gradient between the backsheet 24 and the core 27, the absorbent core 27 retains the fluid more readily.

With respect to the surface energy gradient of the present invention, it is important to remember that the upper and lower boundaries of any such gradient are relative to one another, i.e., the interfacial areas of backsheet 24 and core 27 defining a surface energy gradient need not be on different sides of the hydrophobic / hydrophilic spectrum. to be. That is, one gradient can be created with two different degrees of hydrophobicity or different

It does not necessarily have to be between a hydrophobic surface and a hydrophilic surface. In spite of the foregoing, it is presently advantageous for the upper surface of the backsheet 24 to have a relatively low surface energy, i.e. generally hydrophobic, to maximize the driving force exerted on the fluid coming from the core 27 and to minimize the total wetting of the backsheet 24.

Accordingly, in the present invention, the surface energy gradient in combination with the unidirectional nature of the fluid transport of the backsheet 24 provides a synergistic effect to prevent fluid transport through the backsheet 24. The fluid on the first surface 25 of the backsheet 24 can count on two different, but additional, driving forces that counteract its movement from the core 27 to the backsheet 24 and the clothing. Similarly, these two forces combine to resist fluid movement toward the backsheet 24, thus greatly reducing the chance of wetting.

The gaps of the absorbent article of the present invention have a number of physical parameters to consider when designing the backsheet 24 and core 27, and more specifically for proper fluid handling, with respect to the proper dimensioning and positioning of surface energy gradients. Such factors include the magnitude of the surface energy difference (depending on the materials used), the migration capability of the materials, the biocompatibility of the materials, porosity or capillary size, total caliper and geometry, liquid viscosity and surface tension and the presence or absence of other structures.

The liquid contact angle difference to provide a surface energy gradient between two adjacent surfaces should preferably be at least 10 °, preferably at least 20 ° and the lower surface energy surface shall be at least 90 °, preferably at least 100 °, more preferably at least 110 °, most preferably at least 120 ° must be at liquid contact angle.

According to the invention, the contact angle A of a layer can be increased by making the surface more hydrophilic. To produce the backsheet 24 of the present invention illustrated in Figure 2, a polyethylene sheet is extruded into a roll, molded into a slit film under vacuum, and then optionally subjected to a corona discharge treatment, generally as described in U.S. Patent Nos. 4,351,784, 4,556,570 and 4,535,020. In accordance with the teachings of U.S. Patent Nos. 4,268,128, all of these patents are incorporated herein by reference. A surface treatment of relatively low surface energy is then applied to the surface of the film facing the wearer and preferably heat treated. Suitable surface treatment with a silicone release coating, available from Dow Comingh of Midland, Michigan, is available as Syl-Off 7677, to which is added a Syl-Off 7048 crosslinker in 100 parts by weight and 10 parts by weight. Another suitable surface treatment is a UV-treatable silicone coating which is commercially available as UV 9300 and UV 9380-C-D1 from the General Electric Company, Silicon Products Division of Waterford,

NY contains a mixture of silicone available in 100 parts by weight and 2.5 parts by weight. When such a silicone mixture is used on a shaped film, such as that shown in Figure 2, at least 0.25 g, preferably 0.5-8.0 g silicone / m ² surface area is applied at a sufficient amount of coating, although other coatings may be appropriate for certain applications, the nature of the backsheet and the properties of the liquid, etc. Depending on.

Other suitable treatment agents include, but are not limited to, fluorinated materials, such as fluoropolymers (e.g., polytetrafluoroethylene) (PTFE), commercially available under the trade name TEFLON) and (chlorofluoride) polymers. Other materials which are suitable for reduced surface energy are hydrocarbons, such as petrolatum, latexes, paraffins, although silicone materials are currently preferred for use in the absorbent article in terms of their biocompatibility. As used herein, the term "biocompatible" refers to substances that have low specific adsorption or, in other words, low affinity for biological species such as glycoproteins, platelets, and the like. These materials, as such, withstand, under conditions of use, greater deposition of biological material than other materials. This property enables them to better retain their surface energy properties as needed for the next fluid treatment situation. In the absence of biocompatibility, the deposition of such biological materials tends to increase surface roughness or unevenness, leading to increased resistance or resistance to fluid movement. Biocompatibility consequently corresponds to a reduced resistance force or resistance to the surface energy gradient and capillary structure against fluid movement and hence to a faster fluid entry. Maintaining essentially the same surface energy also maintains the original surface energy difference.

However, biocompatibility is not related to low surface energy. Some materials, such as polyurethane, show some degree of biocompatibility but also relatively high surface energy. Currently preferred materials, such as silicone and fluorinated materials, preferably exhibit both low surface energy and biocompatibility.

Another preferred method of forming a polyethylene film layer into a slit formed film is, for example, applying a high pressure liquid jet of water to one surface of the film, preferably to the opposite surface of the film using a vacuum. Such methods are described in more detail in U.S. Pat. No. 4,609,518; 4,629,643; 4,637,819; 4,681,793; 4,695,422; 4,778,644; U.S. Patent Nos. 4,839,216 and 4,846,821. The slit formed film may also be subjected to soot release treatment as required. A silicone-releasing coating may then be applied or printed on the first surface of the slit formed film and preferably heat treated. Hi8

The surface energy of the surface treated with lik1 lycon is less than the surface energy of the untreated surface of the backsheet 24.

Alternatively, a layer having a lower surface energy, such as a slit polymer backing layer, may have low surface energy material incorporated during manufacture, making the layer hydrophobic during manufacture. This layer can then have low surface energy material applied to the surface. The layer typically comprises at least 5% by weight of low surface energy material based on its total weight.

According to the invention, the absorbent article is formed by attaching each component, such as the topsheet, the backsheet, and the absorbent core, by any means well known in the art. The backsheet and / or topsheet may be joined to the absorbent core or to each other, for example, by a uniform, continuous layer of adhesive, a layer of adhesive pattern, or by arranging any individual adhesive lines, spirals or spots. Alternatively, the elements may be bonded by heat bonding, pressure bonding, ultrasonic bonding, dynamic mechanical bonding, or any other suitable bonding method known in the art, and any combination thereof.

According to the invention, the absorbent article may be used in sanitary napkins, panty liners, adult incontinence articles and baby diapers. Therefore, in addition to the components described herein, the absorbent article may also include, for example, elastic fasteners, regardless of the use of the article. The invention is particularly applicable to sanitary napkins and panty liners.

The absorbent articles of the present invention are prepared as follows.

The backsheets are made from the following raw material:

(a) a non-woven fabric of 28 g / m ² from Corovin GmbH, Peine, Germany, MD 2005, having a knit layer of 14 g / m ² and a melt bed of 14 g / m ² ,

b) Polyethylene film formulated according to US Patent 3,929,135 available from Tredegar Film Products, USA. The film has circular slits, 19% open area, 0.48 mm embossed thickness (funnel height) and 0.465 mm slit diameter on the surface facing the garment.

The backsheet is made by joining the film layer (b) described above, from which the protruding slots are directed toward the wearer facing surface of the absorbent article, to the nonwoven web (a), which will be molten blown against the garment face of the absorbent article.

Each test sample is prepared under the same conditions in all respects except for specific treatment of the material forming part of the backsheet structure or in close fluid contact therewith. Sanitary napkins for test samples, available under the trade name "Always Ultra Normal" from Procter & Gamble GmbH, Schwalbach / Germany, were manufactured in accordance with standard manufacturing practice, except for a very small attachment of the backsheet to the overall structure. This allows you to remove the original backing made of impermeable plastic (both liquids and gases) and replace it with an alternative breathable backing. The sanitary napkin has the same structure in all examples except for additional surface treatment (reducing the surface energy of a liquid / solid material through a silicone coating).

Example 1

The breathable backsheet consists of a unidirectional (one-way) tapered slit made of low-density PE made by Tredegar USA under serial number X-1522, as described above, and an absorbent core of tissue and absorbent gelling material. contact. The contact surface facing the wearer consists of a nonwoven laminate manufactured by Corovin GmbH in Germany under the trade name MD 2005. The nonwoven laminate consists of 14 g / m ^{2 of} spun and 14 g / m ^{2 of} molding material. No further surface treatments are applied.

Example 2

The same structure as in Example 1, except that the surface of the absorbent core 30 facing the wearer (located in contact with the wearer face of the slit 31 unidirectional film) provided by Walkisoft Denmark (material code: Metmar Kotka) has a basis weight of about 6 g / m ^2. heat-treated silicone. Silicone is a soluble coating made by DOW Corning USA and sold under the trade name SYL-OFF 7048 Crosslinker / SYL-OFF 7677 (mixing ratio 10%: 90%).

Example 3

The structure of Example 1 except that the slit made of low-density PE manufactured by Tredegar USA under serial number X-1522 is exposed to a wearer of 31 films (CPT) (in contact with the absorbent core 30) and has a surface area of approximately 3 g. / m ^{2 of} cured stone treated silicone. Silicone is a soluble coating made by DOW Corning USA and sold under the trade name SYL-OFF 7048 Crosslinker / SYL-OFF 7677 (mixing ratio 10%: 90%).

Example 4

Same structure as Example 1, except that the slits are made of a one-way 31 film (CPT) made from a mixture of low density PE (84%) and silicone (16%), which is manufactured by Tredegar Film Products BV Holland, Technical Center S. p. A. upon request. The material is produced under conditions similar to those of code number X-1522.

Example 5

Same structure as Example 3 except that the slit unidirectional 31 film (CPT) is high density9

It is manufactured from PE 221 144 PE1 (supplied by Tredegar Film Products, USA). The surface facing the wearer (located in contact with the absorbent core 31) is treated with heat treated silicone having a basis weight of about 3 g / m ² as in Example 3. The silicone was manufactured by DOW Corning USA (SYL-OFF 7048 Crosslinker / SYL-OFF 7677, 10% to 90% blending ratio).

Test Procedures la. and lb. Procedure - Moisturization test

The wetting test is used to evaluate the resistance of a breathable backsheet or backsheet to body secretion. By changing the composition of the test solution, it can be used to directly measure the total impermeability of the porous backsheet over the entire range of body exudates.

The principle of the test is to simulate the load on a disposable absorbent article containing body exudates. To achieve this, a product, such as a sanitary napkin, is prepared and smoothed on a transparent test rack made of plexiglass. The product is adjusted upside down (top side) with the wearer facing surface and the back surface facing the garment by contacting the test stand (bottom side). Above the sample to be analyzed is suspended a fluid delivery system capable of delivering any required amount of test fluid required (either by splitting or stepwise as desired).

An absorbent filter paper is placed between the outermost surface of the test sample and the transparent test stand. This absorbent filter paper is in direct contact with the backsheet of the test sample, for example, to simulate a sanitary napkin attached to a panty or a diaper / incontinence device that is in close contact with the clothing. Immediately below the transparent test rack, a mirror is positioned to continuously monitor any change in absorbent filter paper (wetting with colored solutions that simulate body secretions). For example, if the porous backsheet is not sufficiently resistant to fluid transfer, the filter paper will be wetted by the colored solution and observed in the mirror. The amount transferred may be easily recorded, either by weight or, more preferably, by the degree of staining on the absorbent filter paper (simulating panties).

The test solution is passed through a calibrated delivery system, such as a simple burette, to the test sample, according to the required test approach as detailed below. After the cartridge has been filled with the test solution, the solution is allowed to absorb into the test sample for one minute such that the top surface of the topsheet facing the wearer is free of the test solution pots.

After waiting for one minute, the test sample is placed under a pressure of 70 g / cm ² , which is believed to reflect a more pressing pressure than regular pressures during use. The test sample remains at a pressure of 70 g / cm ² for up to 30 minutes and measurements are made at 5 minute intervals, for example to determine the area of the colored spot on the absorbent paper. It is important to perform the measurement over a longer period of time, as some body exudates, such as blood mobility or diffusion, may be relatively time consuming.

Understanding the mechanism of the wetting error and ensuring an accurate test design is important for correct evaluation. For example, a breathable backsheet with relatively large gaps (> 200 μιη) is more likely to fail due to a compression process (for example, seat pressure may push fluid through relatively large gaps), which can occur relatively quickly by applying pressure to the test specimen. Alternatively, as slits are made smaller (<200 µm), simple diffusion or capillary diffusion is more likely to occur. Such processes are slow compared to compression processes.

The la. method (simulating a liquid jet fluid discharge), the impermeability of the porous backsheet is measured during high load simulation (sudden forced discharge of the test solution). This application position is most difficult to control (often occurring after a longer lying down or sitting upright) because the absorbent core (or structure) typically requires a finite amount of time to function and provide satisfactory absorption of body exudates. An absorbent core consisting of cellulosic fibers (airborne, tissue) and absorbent gelling material, for example, requires a few minutes before it is able to absorb fluids sufficiently and tightly bind. Unbound exudates that fill the void volume or spaces within the fiber are highly mobile and can move rapidly to the pressed porous backsheet or pass through the backsheet by capillary forces.

The high-jet fluid-emitting fluid simulation test for a typical sanitary napkin, as detailed in the general description above, may be performed under the following conditions:

Test solution: synthetic urine + 1% surfactant or artificial menstrual fluid + 1% surfactant

Discharge volume (ml): 10 ml for sanitary napkin

Flow rate (ml / min): 10 (ie 10 ml in 60 seconds)

Applied pressure (after 1 minute wait): 70 g / cm ²

After 5, 10, 20 and 30 minutes, the results are reported as spots / wetted areas in cm ² .

The lb. method (repeatable load simulation) is used to measure the impermeability of the breathable backsheet under more typical load conditions where bodily discharge is performed intermittently and rather as a repetitive step rather than a single spill event. The repetitive load simulation test is one

For the sanitary napkin, it is accomplished as detailed in the general description above, under the following specific conditions: The test sample is loaded with a 5 ml test solution (see below) placed in the center of the test sample. Allow the test liquid to absorb for one minute and pressurize the sample for 5 minutes. After this time, the extent (area) of the wetting is measured and recorded. The pressure is immediately released and the sample is again subjected to a second 5 ml test solution load. Allow the test liquid to absorb again for one minute and pressurize the sample (now containing 10 ml of test solution) for 5 minutes. After this time, the extent (area) of the wetting is measured and recorded. The pressure is immediately released and the sample is again subjected to a third 5 ml test solution load. Allow the test liquid to absorb for one minute and apply pressure to the sample (now containing 15 ml of test solution) for 5 minutes. After this time, the stain (wetting) size is again measured. The cycle is continued until the pad is loaded with 20 ml.

Test solution: synthetic urine + 1% surfactant or artificial menstrual fluid + 1% surfactant

Volume of Discharge Fluid (ml): 5 ml loading step for sanitary napkin.

Maximum load: 20 ml

Load rate (ml / min): 2.5 (ie 5 ml in 2 min)

Applied pressure (after 1 minute wait): 70 g / cm ²

After 5, 10, 15 and 20 minutes, the results are reported as spots / wetted areas in cm ² .

The assay solution conditions should be adapted to the final product used to reliably evaluate potential respiratory structures. Sanitary napkins are designed to maintain menstrual discharge. These can be completely different for different women and may contain different amounts of fatty acids and detergent type impurities from daily hygiene practices (washing, washing, etc.). These components are extremely mobile and can have very low surface tension. It has been found that the actual menstrual secretion behavior can be simulated by using artificial menstrual fluid from sheep blood and mucin (animal mucus) by adding the surfactants described in detail below. The volume of test solutions up to 15 ml per spill is large enough to hold 99% of all application spill positions within this range. During use, the sanitary napkin's fluid load is repeatedly up to 20 ml (95% of all sanitary napkins are in this range), but sometimes higher. A sanitary pad typically has a load of 10 ml or less (90% of all pads).

Although incontinence pads, baby diapers or panty liners (pillows worn by a woman at the beginning / end of the period or between pads) have different demands on the sanitary napkin, a test solution approaching urine output can be applied to a sanitary napkin. In addition, physical impurities (fatty acids, surfactant and detergent residues) are also found and it has been found that the addition of a surfactant to the synthetic urine solution is well suited to the conditions of use. As the use of feminine hygiene products (sanitary napkins, panty liners) as a lightweight incontinence device is common practice, it is also suitable for the evaluation of potential respiratory backing materials or structures with a synthetic urine solution containing surfactant. Volumes must be re-selected to reflect the conditions under which the product is likely to be exposed to this application. For diapers or powerful incontinence applications, the procedures can be easily modified to simulate higher test solution volume loads and delivery rates.

Preparation of synthetic urine solution + 1% surfactant (UreaB / 1%).

The synthetic urine assay solution is first prepared in a 10 kg masterbatch, and smaller amounts of surfactant are added as required. Each 10 kg dose of UreaB consists of the following components:

component Formula Quantity/ / 10 kg dose Urine 200 g NaCI NaCl 90g Magnesium sulfate MgSO ₄ water (l / 7) 11g Calcium chloride, q CaCl ₂ 6g Distilled water H ₂ O 9693 g

All reagents are "analytical grade" and available from standard chemical suppliers. In addition, the surfactant is supplied by Peosperse 200 ml, Pegesis, U.S.A. Typically, 100 mL of UreaB / 1% surfactant for each measurement is prepared by mixing 90 mL of UreaB solution with 10 mL of surfactant. The UreaB / 1% surfactant solution should be constantly stirred to ensure that the components do not separate prior to application.

Artificial menstrual fluid (AMF) is based on modified sheep blood, which is modified to resemble human menstrual fluid in viscosity, electrical conductivity, surface tension and appearance. To this test liquid (provided by Pegesis / USA), we add a surfactant (1%) to better reflect stress situations typical of hygienic practice (and in some limited situations, dietary influences), and may include additional surfactants or, for example, fatty acids that may reduce blood surface tension. The smallest surface tension is highest11

Menstrual bleeding contributes to the tendency of the backside of a breathable absorbent article, such as a health article, to become wet.

reagents

1. Fibrous sheep blood available from Unipath S.p.A (Garbagnate Milanese / Italy).

2. Lactic acid from J. T. Baker of Dutch analytical purity (85/95% w / w).

3. Potassium hydroxide (KOH) from Sigma Chemical CO., USA, of analytical purity.

4. Phosphate buffer salt tablets from Sigma Chemical CO., USA, of analytical purity.

5. Sodium chloride from Sigma Chemical CO., USA, of analytical purity.

6. Weeds from Sigma Chemical CO., USA, III. type (CAS 84082-64-4)

7. Distilled water.

1st step

Dissolve lactic acid powder and distilled water to give a 9 ± 1% lactic acid solution.

Step 2

By dissolving KOH powder in distilled water, a 10% potassium hydroxide (KOH) solution is prepared.

Step 3 Phosphate buffer solution buffered to pH 7.2 is prepared by dissolving tablets directly in 1 liter of distilled water.

Step 4

A solution is prepared with the following composition:

- 460 ± 5 ml of phosphate buffer solution,

7.5 ± 0.5 mL of KOH solution and slowly warm to 45 ± 5 ° C.

Step 5

Slow dissolution of about 30 g of weed mucus in a preheated (45 ° C ± 5 ° C) solution prepared in Step 4 to give a mucus solution. Once dissolved, the solution temperature should be raised to 50-80 ° C and the mixture covered for about 15 minutes. The heat is removed to maintain a relatively constant temperature of 40 ° C to 50 ° C and stirring is continued for a period of 2.5 hours.

Step 6

The solution (from step 5) was removed from the hot plate and allowed to cool below 40 ° C. Add 2.0 ml of 10% lactic acid and stir for 2 minutes.

Step 7

The solution was placed in an autoclave and heated to 121 ° C for 15 minutes.

Step 8

The solution was allowed to cool to room temperature and diluted 11 times with diluted sheep blood.

After AMF production, viscosity, pH and conductivity were measured to ensure that blood properties were in the range of normal menstrual blood [see HJ Bussing; "Biochemie des Menstrualblutes" Zbl. Gynaec, 179, 456 (1957)], The viscosity should be in the range of 7-8-10 " ⁶ m ² s- '. The pH should be in the range 6.9-7.5 and the conductivity should be in the range 10.5-13 (mmho). If the viscosity is not within the range specified above, the solution should not be used and a new dose of AMF should be prepared. This may require adjusting the amount of weed mucus applied. As it is a natural product, its composition can vary from one quantity to another.

Typically, for individual measurements, 100 ml of the AMF surfactant test solution is prepared by mixing 90 ml of the AMF solution (kept at 25 ° C) with 10 ml of the surfactant. The AMF / 1% surfactant solution should be constantly stirred to ensure that the components do not separate prior to application. The solution should be used within 4 hours of preparation.

The contact angle test is a standard test for assessing the nature of interaction between a solid surface and a droplet of liquid. The contact angle formed by a droplet on a surface is influenced by a number of interacting factors, including the nature of the liquid, its surface tension, the solid and surface irregularities in addition to the liquid-solid interactions. On a rough surface, a droplet typically has a larger contact angle than a droplet of the same chemical composition on a smooth surface. If a droplet of water has a contact angle greater than 90 °, the surface of the liquid is considered to be "hydrophobic". If the contact angle is less than 90 °, the surface is considered "hydrophilic".

The contact angle formed by a droplet on a surface can be measured by a variety of methods, from both optical analysis of a droplet on a surface to more reliable methods. The method used to measure the contact angle is the "Wilhelmy plate technique". The basic principle of this method is to suspend a sample of solid material over a water vessel and slowly lower the sample to a defined depth in liquid water and then remove it. The retention force of the water on the contact (zero immersion depth) material sample is measured with a micro balance and then the cosine of the contact angle is determined from the following equation:

F = STP-cos0 / g in the equation

F = sample force determined with balance (mg) at zero immersion depth

P = sample circumference at the interface (cm)

ST = surface tension (N / cm) cos0 = cosine of contact angle g = gravitational acceleration (at measuring point)

The apparatus used to measure the contact angle is a "dynamic contact angle analyzer (model DCA-322)" manufactured by Cahn Instruments, Inc., Cerritos CA 90701-2275 USA. For each material evaluated (see table), a sample (24 mm χ 30 mm) is prepared and attached to a glass plate as specified in the equipment manual. We take great care to ensure that the material sample is not touched to prevent contamination of the material surface. Each material is weighed five times to ensure measurement accuracy and to minimize the effect of manufacturing variability or surface irregularities.

HU 221 144 Β1

Table 1

Surface contact angles (after surface tension reduction treatment) of commonly available materials were measured

Sample: Surface contact angle untreated contact angle Handled THE core Fabric Supplied by: Walkisoft Denmark, Metmar Kotkar -zero 131 B LDPE-ftlm, code X-1522 Supplier: TredegarUSA 102 121 C LDPE-ftlm, code X-1522 both sides handled Supplier: TredegarUSA 102 144 D LDPE film, code X -1522, but not perforated: Tredegar Film Products Β. V. Netherlands, both surfaces treated 80 103 E LDPE + silicone (8%) film (non-perforated): Tredegar Film Products Β. V. Netherlands, both surfaces treated 92 So F LDPE + silicone (8%) film - both surfaces treated Tredegar Film Products B.V. The Netherlands 102 So G Teflonftlm (non-slit layer) 3M Corp. USA 130 So

The contact angle of a liquid on a surface and the ability of a porous material to transfer fluid, whether through capillary or compression processes, depend on surface irregularities or surface structure, the nature of the fluid and its interaction with the surface, and the delivery mechanism. The test solution used in this test is distilled water of high hydrophilicity and high surface tension. This leads to contact angles greater than those typically found or expected in menstrual fluids or urinary discharges. As such, the absolute contact results detailed in the table should be carefully considered. An angle of contact with water greater than 90 ° does not indicate that the pores of the material exert a negative capillary force on the substances of menstrual origin.

However, the increase in the contact angle in the material is directed towards reducing the volume / efficiency of the fluid transport (either capillary or compression).

na = not applicable, material already has a large contact angle of 35.

Table 2

Wetness test results

Sample Test solution Test plan Moisturizing (cm ² ) untreated Moisturization (cm ² ) treated * First UreaB / 1% la 41 - AMF / 1% la 70 - AMF / 1% lb 90 - Second UreaB / 1% la 41 zero AMF / 1% la 70 zero AMF / 1% lb 90 20 Third UreaB / 1% la 41 1.3 AMF / 1% la 70 16 AMF / 1% lb 90 31 4th UreaB / 1% la So 3 AMF / 1% la So 11 AMF / 1% lb So 35 5th UreaB / 1% la 18 zero AMF / 1% la 30 zero AMF / 1% lb 40 7

HU 221 144 Β1

The unidirectional flow assay is used to quantify the unidirectional flow properties of individual slit film surfaces against body exudates. It can be used to directly measure pores on each surface over the entire range of bodily additions simply by changing the composition of the test solution.

The principle of the test is to evaluate the unidirectional / one-way performance of slit films on fluids simulating body exudates. A Good Slit Film is a film that has a distinct preference for fluid transport from one surface to another, but not in the opposite direction, and the film has to be reversed and the test repeated. Of course, a good slit film ”, in addition to the differential orientation of the fluid transport, also shows minimal fluid transport in the direction used in the backsheet structure.

To evaluate the fluid transport velocities of a slit in a film direction, a simple test is performed by placing a liquid-saturated absorbent structure on top of a slit film lying on top of an absorbent blend of tissue paper. All equipment (saturated absorbent material, film and blotting paper) is pressurized and the amount of test fluid passing through the slit film and absorbed on the blotting paper is measured. In a second experiment, the film direction is reversed and the experiment is repeated. The amount of liquid passing through surface 1 and surface 2 is measured and evaluated.

Typically, a 10 sheet, 12 cm x 12 cm stack of commercially available filter / blotting paper (manufactured by Cartiera Favini S. p. A., Italy) is weighed and placed flat on a test rack just below a suspended weight. On top of the stack of blotting paper, place a 8.5 cm x 8.5 cm sample of the film to be evaluated (each surface is arbitrarily labeled as a 1 & 2 surface). The absorbent material used to simulate the liquid-saturated absorbent core consists of two layers of a commercially available airborne absorbent fabric having a basis weight of 63 gm (per sheet), under the trade name of Metmar Kotka from Walkisoft, Denmark. Each sheet of said tissue is 5 cm x 5 cm and placed symmetrically on top of each other. The tissue structure is then completely immersed in synthetic urine for a period of 1 minute (see Method 1 for solutions).

The tissue is removed from the fluid and held in an upright position for 60 seconds immediately prior to placing the slit on top of the film to allow the liquid to drain down. Saturated tissue is placed in the center of the film, which is also centered on the blotting paper stack.

In the final stage of the trial, a plexiglass block (8.5 cm x 8.5 cm) is centrally placed on top of the highly saturated tissue structure, the weight is automatically lowered onto the sample, and a pressure of 130 g / cm ^{2 is} applied for 60 seconds. Weight loss and time are controlled from one sample to the next through a simple electronic device to ensure reproducibility.

The pressure exerted on the entire arrangement (saturated absorbent material, film, and blotting paper) causes the liquid in the saturated tissue to be pressed onto the film, and if the slit film has a favorable fluid transfer direction, it passes through the film and is absorbed by the blotting paper. When the weight is removed, the layers are separated and the blotting paper examined for wetting and weighed. The difference in weight (before / after) is recorded and compared to a second assay in which the slit film 35 is reversed and the amount of test fluid passing through the slit film in the reverse direction is measured.

Table 3

Slots currently available from a number of companies were examined for film and alternative material samples, and the results are detailed in Table 3.

Material Test solution Surface 1, wetting 2. surface, wetting Surface 2, treated wetting /. example: CPT (LDPE) Supplier Code: X-1522 UreaB / 0% 2.5 1.8 3 g / m ² Silicone 1.1 Tredegar Corporation USA AMF / 0% 1.4 0.8 0.6 Example 2 CPT (HDPE) Supplier code: 15 112 UreaB / 0% 2.3 0.8 3 g / m ² Silicone 0.5 Tredegar Corporation USA AMF / 0% 1.3 0.5 0.3 Example 3: Aerial fabric (2 layers, each with a basis weight of 63 g / m ² ) Supplier Code: UreaB / 0% 2.7 2.7 5 g / m ² Silicone only lower layer 1.1 Metmar Kotka, Walkisoft Denmark AMF / 0% 1.7 1.7 0.8

Synthetic Urine UreaB / 0% Test Solution is prepared in the same way as UreaB / 0% Test Solution except that no surfactant is added to the test solution.

A disposable article designed to retain body secretion and with a breathable backside feature is designed to allow air and vapor transport through the external environment. The effectiveness of this procedure14

The degree of B1 may be related (to the consumer's benefit) to the open area of disposable breathable hoods, and particularly to open areas near the body or areas where body parts are susceptible to absorption. In this assay, the open area of only one permeable backsheet is evaluated at both localized levels as well as the average of the product as a whole.

The open area may be defined for both materials assembled or combined to form a breathable backsheet or an absorbent article comprising a breathable backsheet or structure.

For materials, the open area calculation is relatively straight. The material sample is best viewed microscopically, and a microscopically magnified image, or rather a photograph, must be recorded. The image can then be placed on a sheet of paper graduated in mm to easily calculate the number of holes per cm ² and the area of each hole. Alternatively, the image can be digitally scanned to determine the number of holes per cm ² and the area of each hole. The open area is simply defined as the sum of each hole area divided by the total area under investigation.

The open area of an absorbent article containing a breathable backsheet is determined primarily by evaluating the "main open area" within the area, which is expected to contribute to an effective interaction with the environment. Breathable areas that are considered to be of minor importance are evaluated only as part of the total product's' average open area value. If the absorbent article has breathing ability in areas that are not in direct contact with the skin, or in areas of the absorbent article that are unlikely to contribute to skin blockage, it is evaluated as part of the "main open area" calculation.

1st step

The product is examined microscopically and, if there are different porosities, they are quantified and classified. If there are areas with different permeabilities, it is usually only to some extent that permeable or non-permeable areas are present. However, if this is not the case, each area should be marked for later evaluation.

Step 2

A microscopic image or rather a photograph of each area should be taken. The image can then be placed on a sheet of paper graduated in mm to easily calculate the number of holes per cm ² and the area of each hole. Alternatively, the image can be digitally scanned to determine the number of holes per cm ² and the area of each hole. The open area is simply defined by dividing the sum of the individual well areas by the total area under investigation.

This analysis is continued for each area of variable porosity or breathability.

The "average open area" value of the whole product is then calculated.

Step 3

The "main open area" is simply the area calculated in step 2 that exists in the areas of the pillow that appear to contribute most to the benefit of a breathable absorbent article in use. This assessment of the main or secondary area is subjective, but it can be done in one of two ways:

Approach 1: The article is worn by a representative group of users (for example, a woman in a sanitary napkin or light incontinence article) and an estimate is made of where the article is in close contact with the body and where the absorption potential may appear. These are evaluated as primary areas, and if the backsheet is porous in any of these areas, they are classified as "main open areas".

Approach 2: The article is purely technically evaluated from a database analysis that fits specific article properties that provide cushion fit to the body (e.g., elasticity, article sizes, thickness, etc.) to determine wear characteristics. From this purely technical analysis, we can characterize primary and secondary areas.

Slots currently available from several companies were examined for film and alternative material samples and the results are detailed in Table 4.

Table 4

Example Material No hole N / cm ² Average lyuktcrülct Open hole area % First CPT (LDPE) Supplier Code: X-1522 Tredegar Corporation USA 110 Surface 1 Surface 2 0.43 0.13 -47 14 ~ Second EVA HEX Supplier Code: 4 017 050 Tredegar Corporation USA 99 Surface 1 Surface 2 0.42 0.16 42 ~ -16 Third CPT (HDPE) Supplier code: 15 112 Tredegar Corporation USA 110 Surface 1 Surface 2 0.45 0.16 46 ~ 18 ~

The previous film is a three-dimensional film with tapered slots, for example, there is a significant difference in hole size on each surface. Surface 1 is defined as the surface 60 facing the wearer when used as a breathable backsheet material.

Claims (15)

PATENT CLAIMS A disposable absorbent article, such as a sanitary napkin or panty liner, having a liquid-permeable topsheet (2), an absorbent core (4) and a backsheet (3), wherein the core (4) is a topsheet (2) and a backsheet (2). 3), the backsheet (3) comprises a liquid permeable polymer film for unidirectional fluid transfer to the core (4), the core (4) having a fluid storage layer (6) and the backsheet (3) having an outer layer, the core (4) and the backsheet (3) each comprising at least one layer wherein each layer has a wearer facing surface and a clothing facing surface, and each surface of the layers has a liquid contact angle and the absorbent article has a a liquid storage layer (6) extending from the garment facing area to the garment facing area of the outer layer, including the areas, characterized in that at least one of the layers of the lower portion has a greater liquid contact angle to the wearer's surface than the liquid contact angle of an adjacent layer to the adjacent clothing. A disposable absorbent article, such as a sanitary napkin or panty liner, having a liquid-permeable topsheet (2), an absorbent core (4), and a backsheet (3), wherein the core (4) is a topsheet (2) and a backsheet (2). 3), the backsheet (3) comprises a liquid-permeable polymeric film for unidirectional fluid transfer to the core (4), the core (4) having a fluid storage layer (6) and the backsheet (3) having an outer layer, the core (4) and the backsheet (3) each comprising at least one layer wherein each layer has a wearer facing surface and a clothing facing surface, and each surface of the layers has a liquid contact angle and the absorbent article has a a liquid storage layer (6) extending from the garment facing area to the garment facing area of the outer layer, including the areas, characterized in that at least one of the layers of the lower portion has a fluid contact angle greater than the liquid contact angle of the adjacent wearer surface of an adjacent layer. A method of making an absorbent article according to any one of claims 1 or 2 by bonding the components together in a known manner, wherein the surface of at least one layer of the lower portion is treated with low surface energy material. 4. A method of making an absorbent article according to claim 1 by joining the components together in a known manner, characterized in that a low surface energy material is incorporated into at least one layer of the lower portion. Disposable absorbent article according to claim 1 or 2, characterized in that at least one of the layers located beneath the fluid storage layer (6) comprises a low surface energy material. 6. The disposable absorbent article of claim 5, wherein the low surface energy material is selected from the group consisting of heat-treatable silicones, fluoropolymers, hydrocarbons, or mixtures thereof. 7. A disposable absorbent article according to claim 1, wherein the bottom layer comprises at least 5% low energy material based on the total weight of the layer. 8. Figures 1, 2, 5 to 7. A disposable absorbent article according to any one of claims 1 to 4, wherein the undergarment surface of the lower layer or the wearer facing surface comprises at least 0.25 g of low surface energy material per m ² of surface. 9, 1, 2, 5 to 8. A disposable absorbent article according to any one of claims 1 to 3, characterized in that the backsheet (3) has two layers, a first layer comprising a polymer film adjacent to the absorbent core (4) and an outer layer of a gas-permeable fibrous fabric. 10, 1-9. A disposable absorbent article according to any one of claims 1 to 3, characterized in that the core (4) has at least two portions, a first portion comprising a storage layer and a second portion comprising a fibrous layer, wherein the fibrous layer is adjacent to the backsheet (3). 11, 1, 2, 5-10. A disposable absorbent article according to any one of claims 1 to 4, wherein the wearer facing surface of the lower layer has a liquid contact angle of at least 10 ° greater than the liquid contact angle of an adjacent surface. 12. A disposable absorbent article according to claim 11, wherein the liquid contact angle is at least 20 ° greater than the liquid contact angle of the adjacent surface. Disposable absorbent article according to claim 2, characterized in that the contact surface of the fluid storage layer (6) facing the garment has a liquid contact angle of at least 90 °. 14. A disposable absorbent article according to claim 13, wherein the surface has a liquid contact angle of at least 100 °. A disposable absorbent article according to claim 1 or 2, characterized in that the lower portion preferably has a continuous liquid contact angle gradient.