KR100272832B1 - Absorbent articles having fluid contact angle gradients - Google Patents

Abstract

The present invention relates to a disposable absorbent article (1) comprising a liquid permeable topsheet (2), an absorbent core (4) and a backsheet (3). The backsheet comprises a fluid permeable polymeric film with unidirectional fluid mobility towards the core, the core comprising a fluid storage layer. The absorbent article exhibits a fluid contact angle gradient across the storage layer and the backsheet.

Description

Absorption product with fluid contact angle gradient {ABSORBENT ARTICLES HAVING FLUID CONTACT ANGLE GRADIENTS}

The primary consumer demand underlying the development of absorbent products, especially sanitary napkins, is a high degree of protection and comfort.

One highly preferred means of improving the comfort of absorbent articles is the use of so-called "breathable backsheets". The breathable backsheet may comprise a perforated molded film having directional fluid transfer such as, for example, disclosed in US Pat. No. 4,591,523. Such perforated breathable backsheets are typically vapor and air permeable to allow gas exchange with the environment. This causes some of the fluid stored in the core to evaporate to increase the circulation of air in the absorbent product. This is particularly beneficial as it reduces the sticky feeling experienced by many wearers during use, especially for extended periods of use.

However, a major disadvantage associated with the use of breathable backsheets in absorbent articles is the increased likelihood of leakage, commonly referred to as wetting onto the user's garment. While these breathable backsheets in principle only permit the movement of gaseous matter and fluid movement in only one direction, physical mechanisms such as ejection, diffusion and capillary action may still occur and as a result the fluid may pass through the backsheet. It will move in the opposite direction to the user's clothing. In particular, this mechanism is exacerbated when the product is used during exercise, during high secretions or for extended periods of time. Indeed, while the breathable backsheet provides excellently improved comfort, in terms of protection it becomes unacceptable, especially under pressure conditions.

Wetting problems with user apparel due to the use of such breathable backsheets in absorbent articles have been recognized in the art. Attempts to solve this problem have focused on using multiple layers of backsheets as illustrated, for example, in US Pat. No. 4,341,216. Similarly, unpublished European patent application 94203230 discloses a breathable absorbent article comprising a breathable backsheet composed of two or more breathable layers which are not attached to each other on the core region. Also unpublished European patent application 94203228 discloses a breathable backsheet for disposable absorbent articles comprising an outer layer of gas permeable hydrophobic polymeric fiber fabric and an inner layer comprising a perforated molded film with directed fluid mobility. It is.

On the one hand, another proposed solution to this problem is to increase the thickness of the absorbent article, which is usually achieved by increasing the core thickness to ensure the desired level of protection.

However, none of the above solutions gave full satisfaction. This is especially true for thin products, ie products where thickness is considered a major variable in product comfort. Thus, there is a dichotomy in the methods that can be used to provide absorbent products with increased comfort, and thus thin breathable products may not provide the desired level of protection.

As a result, there is a need for an absorbent product that provides improved comfort by using a breathable backsheet and having a reduced thickness that maintains the required level of protection.

It has now been found that the use of breathable backsheets in thin sanitary napkins can provide a high level of protection and comfort by creating hydrophobic gradients between the backsheet and the core, which is low surface such as silicone and chlorofluorocarbons. Achieved by the use of energy materials or by low surface energy treatment. In this way, it is believed that physical mechanisms such as diffusion and capillary action are hampered and wettability is completely eliminated or significantly reduced.

A further advantage of the present invention is that the present invention provides a breathable backsheet coated with a hydrophobic material, so that the sheet no longer needs to be entirely synthetic and can be at least partially derived from natural materials. This gives the consumer a significant perceptional benefit, as the product gives a more natural feel when touched.

The use of the surface energy gradient itself is discussed in US application 08 / 442,935, which is not published. The application discloses a fluid moving web, such as a topsheet, exhibiting a surface energy gradient. The web promotes fluid movement in one direction and inhibits movement in the opposite direction. The web includes first and second surfaces separated from one another by an intermediate portion. The first surface of the web has a surface energy less than the surface energy of the middle portion, thereby creating a surface energy gradient. Suitable low surface energy materials include silicones, fluoropolymers and paraffins. The web is particularly suitable as a topsheet for absorbent articles for moving fluid away from the wearer contact surface to the absorbent structure.

Summary of the Invention

A first aspect of the invention relates to a disposable absorbent article comprising a liquid permeable topsheet, absorbent core and backsheet. The core is halfway between the top sheet and the back sheet. The topsheet comprises a liquid permeable polymeric film with unidirectional fluid mobility towards the core, the core comprises a fluid storage layer and the backsheet comprises an outer layer. The core and backsheet each comprise one or more layers, each layer having a wearer facing surface and a garment facing surface, each surface of which has a fluid contact angle. The absorbent article includes a lower portion extending from and to the garment facing side of the fluid storage layer and from there to the garment facing side of the outer layer. The present invention is characterized in that the wearer facing surface of at least one layer of the lower portion has a fluid contact angle that is greater than the fluid contact angle of the adjacent garment facing surface of the adjacent layer.

A second aspect of the invention relates to a garment facing surface of at least one layer of the lower portion having a fluid contact angle greater than that of the wearer facing surface of the same layer.

A further aspect of the invention relates to a method of making an absorbent article as described above comprising applying a low surface energy material to the surface of one or more layers of the lower portion.

Another aspect of the invention is directed to a method of making an absorbent article as described above comprising the step of incorporating a low surface energy material into one of the layers of the lower portion.

The present invention relates to a sanitary napkin having a breathable backsheet with reduced wettability to absorbent articles, in particular to user garments.

1 is a top view of a first embodiment of an absorbent article of the present invention partially cut to show structure.

FIG. 2 is an enlarged cross sectional view of the backsheet of the present invention taken along line 1-1 of FIG.

3 is an enlarged cross-sectional view of a liquid droplet on a surface, where each A represents the contact angle of the surface and the liquid.

4 is an enlarged cross-sectional view of a liquid droplet on a surface having two different surface energies, thus showing two different contact angles A (a) and A (b).

The present invention relates to disposable absorbent articles such as sanitary napkins (1), infant diapers, incontinence products and panty liners. Typically such products comprise a liquid permeable topsheet 2, a backsheet 3, and an absorbent core 4 between the topsheet 2 and the backsheet 3. The top sheet 2, the back sheet 3 and the core 4 have a wearer facing surface and a garment facing surface, respectively. The garment facing surface of the top sheet and the wearer facing surface of the back sheet are joined to each other at the periphery 5 of the absorbent article. In a preferred embodiment of the invention, the absorbent article has a wing, a side wrapping member or a side flap.

Absorbent core

According to the invention, the absorbent core comprises a first portion and a second portion, wherein the first portion (a) has any primary fluid distribution layer (preferably with any secondary fluid distribution layer) ; (b) comprises a fluid storage layer; The second portion may comprise (c) any fiber (“dust”) layer below the storage layer; And (d) other optional components.

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

a. Primary / secondary fluid distribution layer

One optional component of the first portion of the absorbent core according to the invention is the primary fluid distribution layer and the secondary fluid distribution layer. The primary distribution layer typically lies below the top sheet and is in fluid communication with the sheet. The topsheet transfers the captured fluid from the primary distribution layer to the storage layer for final distribution. The movement of the fluid through this primary distribution layer occurs not only through the thickness of the absorbent article but also in the length and width directions. Also an optional but preferred secondary distribution layer typically lies below the primary distribution layer and is in fluid communication with the primary distribution layer. The purpose of this secondary distribution layer is to easily capture the fluid from the primary distribution layer and quickly move it to the underlying storage layer. This makes it possible to make full use of the fluid volume of the underlying storage layer. The fluid distribution layers can include any material typical of the distribution layer.

b. Fluid storage layer

There is a fluid storage layer 6 in fluid communication with the primary or secondary distribution layer and typically underlying the layers. This fluid storage layer may comprise any conventional absorbent material or combinations thereof. An absorbent gelling material, preferably referred to as a "hydrogel", "superabsorbent", "hydrocolloid" material, is preferably included with a suitable carrier.

The absorbent gelling material can absorb large amounts of aqueous body fluids and can also maintain the absorbed fluid under conventional pressure. The absorbent gelling material may be homogeneously or heterogeneously dispersed in a suitable carrier. Suitable carriers can also be used alone as long as they are absorbent.

Absorbent gelling materials suitable for use in the present invention will include mostly partially water insoluble, slightly crosslinked, partially neutralized polymeric gelling materials. The material forms a hydrogel upon contact with water. Such polymeric materials can be prepared from polymerizable unsaturated acid-containing monomers well known in the art.

Suitable carriers are materials commonly used in absorbent structures, for example natural fibers, modified fibers or synthetic fibers, especially modified or unmodified cellulose fibers in the form of fluff and / or tissues. Suitable carriers can be used with the absorbent gelling material, but they can also be used alone or in combination. Most preferred are tissues or tissue laminates associated with sanitary napkins and panty liners.

Embodiments of an absorbent structure made in accordance with the present invention include a two layer tissue stack formed by folding tissue onto the tissue itself. These layers can be bonded to one another, for example by adhesive or mechanical interconnect or hydrogen crosslinking. Absorbent gelling material or other optional material may be included between the layers.

Modified cellulose fibers, such as reinforced cellulose fibers, can also be used. Synthetic fibers may also be used, including cellulose acetate, polyvinyl fluoride, polyvinylidene chloride, acrylics such as Orlon, polyvinyl acetate, insoluble polyvinyl alcohol, polyethylene, polypropylene, polyamides such as nylon ), Polyesters, bicomponent fibers, ternary fibers, and blends thereof. Preferably the fiber surface is hydrophilic or treated hydrophilically. The storage layer may also include filler materials, such as fluoride, diatomaceous earth, vermiculite and the like, to improve liquid retention.

If the absorbent gelling material is heterogeneously dispersed in the carrier, the storage layer may nevertheless be homogeneous locally. That is, the storage layer can have more than one distribution gradient in the dimensions of the storage layer. Heterogeneous distribution may also be referred to as a stack of carriers that partially or completely surround the absorbent gelling material.

c. Optional fiber ("dust") layer

An optional component included in the absorbent core according to the present invention is a fibrous layer adjacent to and typically underlying the storage layer. This lower fibrous layer is typically referred to as a "dust" layer because the layer provides a substrate that adheres the absorbent gelling material in the storage layer during fabrication of the absorbent core. Indeed, where the absorbent gelling material is in the form of a large structure such as a fiber, sheet or strip, such a fiber "dust" layer need not be included. However, this "dust" layer provides some additional fluid-handling capability, such as rapid suction of fluid along the length of the pad.

d. Other optional components of the absorbent structure

The absorbent core according to the present invention may comprise other optional components conventionally present in the absorbent web. For example, the reinforcing scrim may be disposed in or between the individual layers of the absorbent core. Such reinforcing scrims should have a form that does not form an interface barrier to fluid movement. Reinforcement scrims are often not needed for heat bonded absorbent structures, provided they provide structural integrity that usually occurs as a result of thermal bonding.

Another component which may be included in the absorbent core according to the invention and which is provided adjacent to or separate from the primary or secondary fluid distribution layer is preferably an odor inhibitor. Other activated odor inhibitors, particularly those coated with or separately from suitable zeolite or clay materials, are optionally included in the absorbent structure. These components may be included in any desired form, but are often included as discrete particles.

Top sheet

The upper sheet 21 may include a single layer or multiple layers. In a preferred embodiment, the topsheet comprises a first layer 22 providing a wearer facing surface of the topsheet, and a second layer 23 between the first layer and the absorbent structure / core.

The topsheet 21 as a whole and therefore each layer needs to be compliant, soft and not irritate the wearer's skin. It may also have elastic properties to extend in one or two directions. In accordance with the present invention, the topsheet can be used for this purpose and can be made from any materials known in the art, for example nonwovens, films or combinations thereof. In a preferred embodiment of the present invention, one or more layers (preferably the top layer) of the topsheet comprise a liquid permeable perforated polymeric film 22.

Preferably, the top layer is provided by a film material having a perforation that facilitates fluid movement from the wearer facing surface to the absorbent structure, such as described in US Pat. No. 3,929,135; 4,151,240; 4,319,868; 4,324,426; 4,343,314; And 4,591,523.

The topsheet typically extends through the front side of the absorbent structure and may extend to form some or all of the desired side flaps, side wrapping elements, or wings.

Back sheet

The absorbent article according to the present invention comprises a breathable backsheet 24 of unidirectional fluid mobility. The main role of the backsheet is to prevent the excretions absorbed and retained in the absorbent structure from soaking articles in contact with the absorbent article, such as underpants, pants, pajamas and undergarments. However, the backsheet of the absorbent article of the present invention also allows the movement of vapor and air through the air to allow air to circulate in and out of the backsheet.

The term "single direction" as used herein refers to a material that has fluid mobility in at least nearly one direction, but not entirely, in the direction of the core. Fluid directivity can be confirmed using Test Method 3 detailed in the present invention in the Test Method section.

According to the invention, the backsheet preferably comprises at least two layers, a first layer comprising a gas permeable perforated polymeric film 25 and a second comprising a gas permeable fibrous fabric layer 26. Layer. The first and second layers preferably have similar relative pore volumes. The first layer is typically disposed adjacent the core 27 and subsequent layers of the backsheet are typically disposed further away from the core. The backsheet may include additional layers. In all cases the outermost layer furthest from the core is the outer layer. All the layers of the backsheet can be in direct intimate contact with each other substantially.

The perforated first layer 25 of the backsheet comprises a layer having separate perforations 28 extending beyond the horizontal plane of the garment facing surface of the layer towards the core to form the protrusions 29. Each of the protrusions has an orifice located at its terminal end. Preferably the protrusions have a funnel or cone shape similar to those disclosed in US Pat. No. 3,929,135. Perforations located in the plane of the layer and the orifice itself located at the terminal end of the protrusion may be annular or acyclic. In any case, the cross sectional area or dimension of the orifice at the end of the protrusion is less than the cross sectional area or dimension of the perforation located in the plane of the layer. The first layer of the backsheet typically has an open area of at least 5%, preferably 10 to 35% of the total film layer area. The open area of the layer can be measured using Test Method 4 described in detail herein in the Test Method section.

According to the present invention, the first layer 25 of the backsheet can be made from any material known in the art, but is preferably made from a polymeric material that can be commonly obtained.

The second layer of the backsheet comprises a gas permeable fibrous fabric layer 26 composed of polymeric fibers known in the art, for example polymeric nonwovens. The fibrous fibrous layer preferably has a basis weight of 10 to 100 g / m ² , more preferably 15 to 30 g / m ² . The fibers are made of any polymeric material, in particular polyethylene, polypropylene, polyester, polyacetate fibers or mixtures thereof (mixtures between and within fibers), and also blends of synthetic and nonabsorbent natural fibers, or Treated natural fibers such as cotton may also be used. These fibers may preferably be spunbonded, carded or melt blown. Preferably the second layer comprises a matrix of spunbonded fibers covered with meltblown fibers on one side or a matrix of meltblown fibers covered with spinblown fibers on both sides. The second layer of backsheet also comprises at least 5% by weight of the liquid absorbent fibers such that the fibers swell and the interfiber spacing is reduced.

The backsheet typically extends across the front of the absorbent structure and may extend to form some or all of the desired side flaps, side wrapping elements, or wings.

Fluid contact angle

According to a first aspect of the invention, any layer of the lower portion has a wearer facing surface and a garment facing surface, each of the surfaces having a fluid contact angle, wherein at least one wearer facing surface of the layers of the lower portion is It has a fluid contact angle that is greater than the fluid contact angle of the adjacent garment facing surface of the adjacent layer.

According to a second aspect of the invention, any layer of the lower portion has a wearer facing surface and a garment facing surface, each of the surfaces of the layer having a fluid contact angle, wherein at least one garment of the layers of the lower portion is The opposing surface has a fluid contact angle that is greater than the fluid contact angle of the wearer facing surface of the same layer.

In principle, a contact angle gradient can be present between any surface (wearer facing or garment facing) of any layer in the lower part. Thus, the fluid contact angle gradient crosses the wearer and garment facing surface of the same layer or between the garment facing surface of at least one layer of the lower portion and the adjacent surface of the adjacent layer, ie the garment facing surface with the wearer of the first layer of the backsheet. In between, the garment facing surface of the first layer of the backsheet and the wearer facing surface of the second layer, between the wearer and garment facing surface of the second layer of the backsheet, or any subsequent backsheet layers. It is also foreseen to create a continuous gradient of contact angles in the lower part using a combination of these layers where each layer exhibits a specific contact angle relationship.

However, for the sake of brevity, the following discussion will focus on the presence of a clear or increased contact angle gradient between the garment facing surface of the core and the wearer facing surface of the first layer of the backsheet.

Typically, the liquid drop 110 overlying the solid surface 112 creates a contact angle A with the solid surface as shown in FIG. 3. 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. Liquid-solid contact angles are known in the art, such as, for example, Arthur W. Adamson, Physical Chemistry of Surfaces , Second Edition (1967), FE Bartell and HH Zuidema, J. Am. Chem. Soc ., 58, 1449 (1936) and JJ Bikeman, Ind. Eng. Chem., Anal. Ed. , 13, 443 (1941), each of which is incorporated herein by reference. More recent literature in the art includes 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 incorporated herein by reference.

The term "hydrophilic" as used herein is used to refer to surfaces that can be wetted by deposited aqueous fluids (such as aqueous body fluids). Hydrophilicity and wettability are typically defined as the contact angle and surface tension of the fluid and solid surfaces involved. This is discussed in more detail in Robert F. Gould, Contact Angle, Wettability and Adhesion , the American Chemical Society (Copyright 1964) (incorporated herein by reference). The surface is said to be wet (hydrophilic) by the aqueous fluid when the fluid tends to spontaneously spread through the surface. In other words, the surface is considered "hydrophobic" unless the aqueous fluid tends to spontaneously spread through the surface.

Liquid / solid contact angles vary with surface heterogeneity (eg, chemical and physical properties such as roughness), degree of contamination, chemical / physical treatment or composition of the solid surface, as well as the nature of the liquid and its degree of contamination. The surface energy of the solid also affects 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 the liquid from the solid surface (eg film or fiber) is represented by the following equation:

In the above formula,

W is the binding date measured in erg / cm ² (x 10 ⁻³ J / m ² ),

G is the surface tension of the liquid measured in dynes / cm (x 10 ³ N / m),

A is the liquid-solid contact angle measured in.

For a given liquid, the bonding date increases with the cosine of the liquid-solid contact angle (the maximum value is reached when contact angle A is zero).

Bonding is one of the useful means to understand and quantify the surface energy characteristics of a given surface for a given liquid.

Table a is useful to illustrate the relationship between solid-liquid contact angle and bonding days for a particular fluid (eg water, its surface tension is 75 dynes / cm (75 × 10 ⁻³ J / m ² )).

A (。) cos A 1 + cos A W (erg / cm ² (x 10 ^-3 J / m ² )) 0 One 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 -One 0 0

As shown in Table a, when the bonding date of a particular surface decreases (indicative of the lower surface energy of the particular surface), the contact angle of the fluid to the surface increases, thus the fluid becomes "bead" shaped. It tends to occupy a smaller contact surface area. The reverse is also true when the surface energy of a given surface decreases with a given fluid. Therefore, the bonding work affects the interfacial fluid phenomenon on the solid surface.

More importantly, in connection with the present invention, the surface energy gradient or discontinuity exemplified by the fluid contact angle has been found to be useful in preventing fluid movement. 4 illustrates a droplet 110 of fluid lying on a solid surface with two regions 113 and 115 (shown with different hatched marks for illustration) with different surface energies. Under the situation illustrated in FIG. 4, region 113 exhibits relatively lower surface energy than region 115, and thus exhibits reduced wettability for fluid droplets than region 115. Accordingly, the droplet 110 generates a contact angle A (b) at the edge of the droplet contact region 113 larger than the contact angle A (a) generated at the edge of the droplet contact region 115. Although points "a" and "b" are placed on the plane for clarity, the distance "dx" between points "a" and "b" does not have to be a straight line, instead it is a droplet / regardless of the shape of the surface. It should be noted that it indicates the degree of surface contact. Thus, droplet 110 experiences surface energy imbalance and thus experiences external forces due to the difference in relative surface energy (ie surface energy gradient or discontinuity) between regions 113 and 115. The surface energy difference is represented by the following equation (2):

In the above formula,

dF is the total force on the fluid droplet,

dx is the distance between the reference position "a" and "b",

G is as defined above,

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

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

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

Equation (3) can be represented simply by Equation (4):

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

The importance of the surface energy difference between the two surfaces is clearly shown in Equation (4), which indicates that the magnitude change of the difference in bonding days is directly proportional to the magnitude of the force.

A more detailed discussion of the physical properties of surface energy effects and capillaryness can be found in Portnoy K. Chatterjee, Textile Science and Technology , Volume 7, Absorbency (1985) and AM Schwartz, Capilliarity, Theory and Practice, Ind. Eng. Chem. 61, 10 (1969), which is incorporated herein by reference.

Thus, the force experienced by the droplets will in this case cause a shift towards the core in the direction of the surface characterized by higher surface energy. For simplicity and expressive clarity, surface energy gradients or discontinuities are shown in FIG. 4 as a single distinct discontinuity or boundary between well-defined regions with constant but different surface energies. The surface energy gradient may also exist as a continuous or stepped gradient, where the force applied to any particular droplet (or portions of such droplet) is measured by the surface energy at each particular droplet contact area.

As used herein, the term "gradient" refers to a change in surface energy or bonding date that occurs over a measurable distance when applied to a difference in surface energy or bonding date. The term "discontinuity" refers to "gradient" or type of change, where the change in surface energy necessarily takes place over a distance of zero. Accordingly, all "discontinuities" as used herein are included within the definition of "gradient."

The terms "capillary tube" and "capillary tube" as used herein are also used to refer to passages, perforations, pores or spaces within a structure that can move fluid in accordance with the principles generally represented by Laplace equation (5) below. do:

In the above formula,

p is capillary pressure,

R is the inner radius of the capillary (capillary radius),

G and A are as defined above.

See Emery I. Valko, Penetration of Fabrics, Chem. Aftertreat. Text , Chapter III, (1971), pp. 83-113, when A is 90 °, the cosine of A is zero and there is no capillary pressure. If A is greater than 90 °, cosine A is negative and capillary pressure resists fluid entering the capillary. Thus, in the case of hydrophilic aqueous solutions, the capillary walls must be hydrophilic such that a recognizable capillary phenomenon occurs. Also, as R increases (larger perforation / capillary structure), capillary pressure decreases, so R must be small enough for p to have a meaningful value.

Perhaps the specific orientation or placement of the gradient itself relative to the orientation and placement of the capillary or fluid passageway itself is at least as important as the presence of the surface energy gradient.

Water is used only as a reference liquid as an example for discussion purposes and is not intended to be limiting. The physical properties of water are well established and water is readily available and generally has uniform properties wherever it is obtained. The concept of adhesion work with respect to water can be readily applied to other fluids such as blood, menstrual blood and urine by considering the specific surface tension characteristics of the desired fluid.

The backsheet has a surface energy gradient between the core and the backsheet that produces a relatively low surface energy adjacent a portion of the backsheet that is in contact with the absorbent core and a relatively low surface energy portion positioned to contact the wearer's skin. Can prevent fluid droplets from moving from a core exhibiting a relatively high surface energy to a backsheet exhibiting a relatively low surface energy. The movement of the liquid droplets is induced by the contact angle difference between the low and high surface energy portions causing an imbalance of surface tension acting on the liquid-solid contact surface. The resulting surface energy gradient that produces negative capillary pressure is particularly suitable for use in perforated backsheets on absorbent articles, for example backsheets 2,24 on absorbent articles 1.

The possibility of wetting is reduced by having a perforated backsheet having a surface energy gradient according to the foregoing description. While some in-use forces tend to compress the collected fluid from the pad (eg, from the absorbent core toward the bottom surface of the backsheet), this undesirable movement causes fluid to pass through the opening of the backsheet. It will be blocked by the surface of the backsheet with a relatively low surface energy that will push the fluid when it is going outward.

Thus, the fluid is more easily retained in the absorbent core by the driving force of the surface energy gradient between the core and the backsheet.

With regard to the surface energy gradient of the present invention, it is important to keep in mind that the upper and lower limits of any such gradient are relative to each other. In other words, the regions of the backsheet and core where the interface defines the surface energy gradient need not be on faces that differ in hydrophobic / hydrophilic range. That is, the gradient can be established by two surfaces having varying degrees of hydrophobicity or varying degrees of hydrophilicity, and need not be established with hydrophobic surfaces and hydrophilic surfaces. Nevertheless, in order to maximize the driving force imparted to the fluid flowing from the core and to minimize the complete wetting of the backsheet on the garment contact surface, it is desirable that the topsheet of the backsheet has a relatively low surface energy, i.e. is generally hydrophobic. desirable.

Thus, the surface energy gradient in the present invention provides a synergistic effect with the unidirectional fluid movement characteristics of the backsheet to prevent fluid movement through the backsheet. The fluid on the first face of the backsheet faces two different but complementary driving forces that are opposite to its movement from the core toward the backsheet and the garment. These two forces combine similarly to impede fluid movement towards the backsheet, greatly reducing the frequency of wetting.

A number of physical variables must be considered in designing the perforated backsheet and core according to the absorbent article of the present invention, and more particularly the proper size and placement of the surface energy gradient for proper fluid handling. These factors include the size of the surface energy difference, the mobility of the material, the biocompatibility of the material, the porosity or capillary size, the total caliper and geometry, the fluid viscosity and the surface tension, and the presence of other structures on either side of the interface, depending on the material used. Or a member is included.

Preferably the difference in fluid contact angle between two adjacent surfaces providing a surface energy gradient should be at least 10 °, preferably at least 20 °, and surfaces with low surface energy at least 90 °, preferably at least 100 °. More preferably at least 110 ° and most preferably at least 120 °.

According to the invention, the contact angle of the layer can be increased by making the surface more hydrophilic. In order to produce the backsheet shown in FIG. 2 according to the invention, the polyethylene sheet is extruded onto a drum in which a vacuum is formed on the perforated molded film, which is then optionally Thomas, generally on September 28, 1982. US Patent No. 4,351,784 to Thomas et al .; 4,456,570 to Thomas, June 26, 1984; And 4,535,020, issued August 13,1985, to Thomas, the patents of which are incorporated herein by reference. A surface treatment having a relatively low surface energy is then applied to the wearer facing surface of the perforated molded film and preferably cured. Suitable surface treatment agents are Dow Corning's silicone release coatings from Midland, Mich., Commercially available as Sil-Off 7677 with the addition of a commercially available crosslinking agent in a ratio of 100 parts to 10 parts, each as Sil-Off 7048. to be. Other suitable surface treatment agents are UV curable silicones comprising a blend of two silicones, commercially available from General Electric Company, Water Products, New York, Water Products, New York, UV 9300 and UV 9380C-D1, in a ratio of 100 parts to 2.5 parts, respectively. Coating agent. When such a silicone blend is used on a molded film as shown in Fig. 2, a coating application level of 0.25 g or more, preferably 0.5 to 8.0 g per square meter of surface area has been satisfactorily used, but the properties of the backsheet and Other coating levels may be suitable for certain applications depending on the characteristics of the fluid and the like.

Other suitable treatment materials include, but are not limited to, fluorinated materials such as fluoropolymers (e.g., polytetrafluoroethylene (PTFE) sold under the trademark TEFLON) and chlorofluoropolymers. Other materials suitable for reducing surface energy include hydrocarbons such as petrolatum, latex, paraffin, and the like, and silicone materials are currently preferred for use in absorbent products because of their biocompatibility. As used herein, the term "biocompatibility" means a material that has a low level of specific adsorption, or in other words a low affinity for a biological species or biological material such as glycoprotein, platelets, and the like. Such materials tend not to deposit on biological materials to a greater extent than other materials under conditions of use. This property makes it possible to better retain the surface energy properties needed for subsequent fluid handling situations. Without biocompatibility, the deposition of such biological materials increases the roughness or nonuniformity of the surface, increasing the force or resistance to arrest fluid movement. As a result, biocompatibility reduces the resistivity or resistance to fluid movement and thus allows the fluid to access surface energy gradients and capillary structures faster. The original surface energy difference is maintained while maintaining substantially the same surface energy and also during subsequent fluid deposition or deposition.

However, biocompatibility is not synonymous with low surface energy. Some materials, such as polyurethanes, exhibit some degree of biocompatibility but also considerably higher surface energy. Currently preferred materials such as silicon and fluoride materials are those that exhibit both low surface energy and biocompatibility.

Another preferred method of converting a ribbon of polyethylene film to a perforated molded film is to apply a high pressure fluid jet comprising water and the like to one side of the film while applying a vacuum adjacent to the opposite side of the film. . Such methods include commonly assigned US Pat. No. 4,609,518, issued to Curro et al. On September 2, 1986; U.S. Patent 4,629,643 to Curro et al. On December 16, 1986; U.S. Patent No. 4,637,819 to Ouellette et al. On January 20, 1987; US Patent No. 4,681,793, issued to Linman et al. On July 21, 1987; U.S. Patent No. 4,695,422 to Curro et al. On September 22, 1987; U.S. Patent No. 4,778,644 to Curro et al. On October 18, 1988; US Patent No. 4,839,216 to Curro et al. On June 13, 1989; And US Pat. No. 4,846,821, issued July 11, 1989 to Lions et al., All of which are incorporated herein by reference. The perforated molded film may optionally be subjected to a corona release treatment. The silicone release coating may then be added or printed to the first side of the perforated molded film, preferably cured. The surface energy of the siliconized surface is less than the surface energy of the untreated backsheet face.

On the other hand, a low surface energy material may be incorporated into the layer during the fabrication process to render the layer hydrophobic to a layer exhibiting lower surface energy, such as a perforated polymeric backsheet layer. This layer may then be subjected to low surface energy materials on its surface. Typically, the layer comprises at least 5% by weight low surface energy material of the layer.

According to the present invention, absorbent articles are made by connecting various elements such as topsheet, backsheet and absorbent core by any means known in the art. For example, the backsheet and / or topsheet may be connected to the absorbent core or to each other by a constant continuous layer of adhesive, a pattern layer of adhesive or any individual line, spiral or dot arrangement of the adhesive. On the one hand, the elements can be connected by thermal bonding, pressure bonding, ultrasonic bonding, kinetic bonding or any other suitable connection means known in the art and combinations thereof.

In accordance with the present invention, absorbent products can be used for applications such as sanitary napkins, panty liners, adult incontinence products, and infant diapers. Thus, in addition to the components disclosed herein, the absorbent article may include elastic materials, anchoring elements, and the like, depending on the use of the article. The present invention is particularly suitable for sanitary napkins and panty liners.

An absorbent article according to the present invention was prepared as follows.

The backsheet was made from the following raw materials:

a) 14 g / m nonwoven fabric having ^two spunbond layers and a meltblown layer of 14 g / m ² of 28 g / m ² obtained from (co-robin geem beha (Corovin GmbH, Peine, Germany) , under the trade name MD 2005) .

b) Polyethylene molded film according to US Pat. No. 3,929,135 available from Tredegar Film Products, USA. The film has an annular perforation with an open area of 19%, an embossed thickness (funnel height) of 0.48 mm and a drilling diameter for the garment facing surface of 0.465 mm.

The backsheet was prepared by combining the above-described film layer (b) with protruding perforations oriented towards the wearer facing surface of the absorbent article with the nonwoven fabric (a) with the garment facing surface of the absorbent article spinning.

Each test sample was prepared under the same conditions in all respects except subjecting the material forming the intimate fluid contact to the backsheet structure, or a portion thereof, to the backsheet structure. As a test sample, a sanitary pad pad produced under the trade name "Always Ultra Normal", available from Procter & Gamble Schwalbach / Germany, is used in the normal fabrication process except that the backsheet is attached very little to the entire structure. It was made according to. This resulted in a backsheet with the existing impermeable (for liquid and gas) plastic films removed and another breathable backsheet replaced. The structure of the sanitary napkin was the same for all examples except for additional surface treatment (dropping of surface energy of one liquid / solid surface through the silicone coating).

Example 1 (Control):

The breathable backsheet disclosed above comprises a unidirectional (unidirectional) conical perforated film (CPT) made of low density PE produced by Tradega USA manufactured code X-1522, which is comprised of tissue and absorbent gelling material. It is placed in contact with the configured absorbent core. The contacting facing surface of the wearer consists of a nonwoven laminate manufactured under the trade name MD 2005 from Corbin GmbH. The nonwoven laminate is composed of meltblown portion of 14 g / m ² of the spunbond and 14 g / m ^2. No additional surface treatment was applied.

Example 2:

The garment facing surface 30 of the absorbent core tissue (placed in contact with the wearer facing surface 31 of the perforated unidirectional film) from Walkisoft Denmark (Material Code: Metmar Kotka) has a basis weight of about 6 g / It has the same structure as the structure of Example 1 except that it is treated with m ² thermally cured silicone. The silicone is manufactured from Dow Corning USA and marketed as a SYL-OFF 7048 crosslinker / SYL-OFF 7677 release agent coater (mixing ratio 10%: 90%).

Example 3:

The wearer facing surface 31 (placed in contact with the absorbent core tissue 200) made of perforated unidirectional film (CPT) made of low density PE produced by Tredega, produced under manufacture code X-1522, was about the basis weight. It has the same structure as Example 1 except that it is treated with 3 g / m ² of heat cured silicone. The silicone is manufactured from Dow Corning USA and marketed as a SYL-OFF 7048 crosslinker / SYL-OFF 7677 release agent coater (mixing ratio 10%: 90%).

Example 4:

Perforated unidirectional film is made from a blend of low density PE (84%) and silicone (16%) and is supplied by P & G Pescara Technical Center SpA from Tredegar Film Products BV, Holland. It has the same structure as in Example 1 except that it is supplied by request. The material was prepared under conditions comparable to the material produced under code name X-1522.

Example 5:

The perforated unidirectional film (CPT) has the same structure as in Example 3, except that it was made of high density polyethylene (supplied by development code 15112 from Tredega Film Products USA). As in Example 3, the wearer facing surface 31 (placed in contact with the absorbent core tissue) of the perforated unidirectional film (CPT-HDPE) was further treated with heat cured silicone having a basis weight of about 3 g / m ² . It became. The silicone is manufactured from Dow Corning USA and marketed as a SYL-OFF 7048 crosslinker / SYL-OFF 7677 release agent coater (mixing ratio 10%: 90%).

Test Methods

Test Methods 1a and 1b-Wetting Test

Wetting tests are used to evaluate the properties of breathable backsheet or backsheet preparations that impede the movement of body secretions. This can be used as a direct measure of the degree of liquid-impermeability of the porous backsheet for the full range of body secretions by simply changing the composition of the test solution as detailed in the method description below.

Basic principle of the method:

The basic principle of the test is to simulate the in-use load of the disposable absorbent product using body secretions. To do this, for example, a sanitary napkin is prepared and placed flat on a transparent test bench made of windshield. The product is placed with the wearer facing (top) exposed and the garment facing (back) in contact with the test bench. Suspend a liquid transfer system capable of delivering (at one time or in a series of stages as appropriate) any desired amount of the desired test liquid onto the sample to be analyzed.

Place the absorbent filter paper sheet between the outermost surface of the test sample and the transparent test bench. This absorbent filter paper is in intimate contact with the backsheet of the test sample, for example to simulate a diaper / incontinence device in intimate contact with a sanitary napkin or clothing attached to panties. Directly beneath the clear test bench is a mirror so that any change in absorbent filter paper (wet with a colored solution simulating sieve secretion) is observed continuously. For example, if the porous backsheet does not adequately resist liquid migration, the filter paper will be wet with the coloring solution, which can be observed with a mirror. In addition to the time dependence of migration, the size of the transferred solution as weight or preferably the size of the stain on the absorbent filter paper (simulating the panties) can be readily determined.

The test solution is introduced into the test sample through a delivery system calibrated through the sample burette according to the preferred test method described below. Once the pads are filled with the test solution, wait one minute for the solution to be absorbed into the test sample so that the test solution does not accumulate on the topsheet (wearer facing surface).

After waiting for 1 minute, the test sample is placed under a pressure of 70 g / cm 2 (g per square centimeter) which is believed to reflect a more stressful but generally obtainable pressure during use. The test sample is maintained at a pressure of 70 g / cm 2 for a period of 30 minutes or more, for example, the area of colored stain on the blotter paper is measured at 5 minute intervals. The mobility or diffusion process of some body secretions, such as blood, takes a very long time, so measuring over extended periods of time is particularly important.

Understanding the mechanism of wetting failure and ensuring the correct test design will allow us to accurately assess this. For example, a breathable backsheet with a relatively large perforation (more than 200 μm) may be subjected to an extrusion process (such as when a sitting pressure is applied to a liquid through a relatively large perforation) that can occur relatively quickly when the test sample is pressed. More likely to fail. In contrast, porous materials with smaller perforations (less than 200 μm) are more likely to fail by simple diffusion or capillary driven diffusion processes. This process is slower than the extrusion process.

Method 1a: high blowout simulation

This first test design measures the impermeability of the porous backsheet under high load (sudden ejection of test solution) simulations. This in-use simulation is most difficult to control because typically the absorbent core (or structure) needs a finite period of time to function and properly absorb and bind body secretions (this often occurs when prolonged lying or sitting). . For example, the absorbent core and absorbent gelling material composed of cellulose fibers (air felt, tissue) take several minutes until the liquid is properly absorbed and firmly bonded. Unbound secretions, which occupy void or interfiber space, are very fluid and can quickly migrate to the porous backsheet, extrude under pressure, or through the backsheet by capillary forces.

High ejection simulations are performed as described in the general text above for typical sanitary napkins under the following conditions:

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

Ejection volume (ml): 10ml for sanitary napkin

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

Pressurized pressure (after waiting 1 second): 70g / ㎠

Results are reported as stain / wet area per square cm after 5, 10, 20, and 30 minutes have elapsed.

Method 1b: iterative load simulation

In this test design, the impermeability of the breathable backsheet is measured under more typical loading conditions where the body secretions are discharged at one time rather than at one time. Repeated loading simulations performed on a typical sanitary napkin are performed according to the general description above using the following specific conditions:

Specifically, 5 ml of a test solution (see below) located in the middle of the test sample is added to the sample. Wait for 1 minute for the test liquid to be absorbed and apply pressure for 5 minutes. After this period, measure and record the fully wetted size (area). The pressure is soon removed and the sample is loaded again with 5 ml of test solution. Wait another minute for the liquid to be absorbed and pressurize the sample (now containing 10 ml of test solution) for 5 minutes. After this period, measure and record the fully wetted size (area). The pressure is soon removed and the sample is loaded again with a 5 ml third test solution. Wait another minute for the liquid to be absorbed, pressurize the sample (now containing 15 ml of test solution) for 5 minutes and measure the stain size (completely wet) again. Continue this process until the pad is loaded with 20 ml of solution.

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

Ejection volume (ml): Repeat stepwise 5ml for sanitary napkin

Load capacity: 20 ml

Load rate (ml / min): 2.5 (i.e. 5 ml in 2 minutes)

Pressurized pressure (after waiting 1 second): 70g / ㎠

Results are reported as stain / wet area per square cm after 5, 10, 15 and 20 minutes have elapsed.

Type and volume of test solution used in the test method

It is important to match the test solution conditions to the product end use used to facilitate evaluating the breathable backsheet design where possible. Sanitary napkins are designed to contain physiological secretions. These secretions can vary considerably from woman to woman and can contain various levels of fatty acid and detergent types of contaminants by daily hygiene habits (washing, washing, etc.). These components are very fluid and can have very low surface tension. The actual physiological secretion pattern was simulated using artificial menstrual blood derived from sheep blood and mucin with the addition of surfactant as detailed below. The volume of the test solution is sufficiently high that 99% of all in-use ejections are within this range up to 5 ml per single ejection. Similarly, sanitary napkins in use can be repeatedly loaded up to 20 ml (95% of all sanitary napkins fall within this range) and are rarely higher. Typically sanitary napkins have a loading of less than 10 ml (90% of all sanitary napkins).

Although incontinence pads, infant diapers or pantyliners (which are worn by women during or during the physiological period or at the beginning / end of the period) have different requirements from sanitary napkins, test solutions closer to the urine secretion may be used for menstruation. . Nevertheless, body contaminants (fatty acids, surfactants and detergent residues) are still found and the addition of surfactants to synthetic urine solutions corresponds well to the conditions found in use. Since it is very common to use feminine hygiene products (sanitary napkins, panty liners) and light incontinence devices, it is also appropriate to evaluate potential breathable backsheet materials or structures using synthetic urine solutions containing surfactants. The volume is also chosen to reflect the typical conditions under which the product can be used. For diaper or more stressed incontinence applications, the method can be easily modified to simulate more test solution loading volumes and delivery rates.

Preparation of Test Solution: Synthetic Urine + 1% Surfactant (Urea B / 1%)

Synthetic urine, a test solution, is first prepared in a 10 kg masterbatch and, if necessary, smaller amounts are removed and surfactant is added. Each 10 kg urea B batch consists of the following components:

ingredient Chemical formula 10 kg batch Urea 200 g Sodium chloride NaCl 90 g Magnesium sulfate MgSO _{4 7} H ₂ O 11 g Calcium chloride CaCl ₂ 6 g Distilled water H ₂ O 9693 g

All reagents are "reagent grade" and are available from standard chemical suppliers. Additional surfactants are supplied in Peosperse 200ML from Pegesis, USA. For individual measurements, a test solution of 100 ml of urea B / 1% surfactant is typically prepared by mixing 90 ml of urea B solution and 10 ml of surfactant. Urea B / 1% solution should always be mixed to ensure that the components are not separated before use.

Preparation of Test Solution: Artificial Menstrual Blood + 1% Surfactant

Artificial menstrual blood (AMF) is based on the amount of blood that has been modified very similar to human menstrual blood in terms of viscosity, electrical conductivity, surface tension and appearance. In addition, the inventors have introduced typical hygiene practices (and food effects under some limited circumstances) to introduce surfactant (1%) into the test fluid (supplied by Pegesis / USA) to lower the surface tension of blood. Better reflecting this additional surfactant or stress situation that may introduce an unexpected level of fatty acid, for example. Low surface tension menstrual blood is the largest contributor to backsheet wetting failure for breathable absorbent products such as sanitary napkins.

reagent:

1) Double fibrinated amounts of blood can be obtained from Unipath S.p.A {Garbagnate Milanese / Italy}.

2) Lactic acid (85-95% w / w) from J.T. Baker Holland Reagent Grade.

3) Reagent grade potassium hydroxide (KOH) from Sigma Chemical Company USA.

4) Purification of reagent grade phosphate buffered saline from Sigma Chemical Company USA.

5) Reagent grade sodium chloride from Sigma Chemical Company.

6) Stomach mucin of type III (CAS 84082-64-4) from Sigma Chemical Company.

7) distilled water.

Step 1:

Lactic acid powder is dissolved in distilled water to prepare a 9 ± 1% lactic acid solution.

Step 2:

KOH powder was dissolved in distilled water to prepare a 10% potassium hydroxide (KOH) solution.

Step 3:

The indicated tablets are dissolved in 1 L distilled water to prepare a phosphate buffer buffered to pH 7.2.

Step 4:

Prepare a solution with a composition of 460 ± 5 ml of phosphate buffer and 7.5 ± 0.5 ml of KOH solution and slowly heat to 45 ± 5 ° C.

Step 5:

Approximately 30 g of gastric mucin was slowly dissolved (with constant stirring) in the heated (45 ± 5 ° C) solution prepared in step 4 to prepare a viscous solution. Once dissolved, the temperature of the solution is raised to 50-80 ° C. and the mixture is covered for about 15 minutes. The heat is reduced to maintain a relatively constant temperature of 40-50 ° C. and stirring is continued for 2.5 hours.

Step 6:

The solution (from step 5) is withdrawn from the hot plate and cooled to below 40 ° C. Add 2.0 ml of 10% lactic acid solution and mix thoroughly for 2 minutes.

Step 7:

The solution is placed in an autoclave and heated to a temperature of 121 ° C. for 15 minutes.

Step 8:

The solution is cooled to room temperature and diluted 1: 1 with double fibrinated amounts of blood.

Following the preparation of AMF, its viscosity, pH and conductivity are defined so that blood characteristics are in a range close to normal menstrual blood (see H. J. Bussing "zur Biochemie de Menstrualblutes" Zbl Gynaec, 179, 456 (1957)). The viscosity should be in the range of 7 to 8 (unit cStK). The pH should be in the range of 6.9 to 7.5 and the conductivity should be in the range of 10.5 to 13 in mmho. If the viscosity is not within the above range, it cannot be used and a new batch of AMF must be prepared. This may be necessary to control the amount of gastric mucin used. Since it is a natural product, its composition may vary.

For individual measurements, a 100 mL AMF test solution, typically with a surfactant, is prepared by mixing 90 mL of AMF solution (maintained at 25 ° C.) with 10 mL of surfactant. The AMF / 1% surfactant solution should always be mixed to ensure that the components are not separated before use. The solution must be used within 4 hours of preparation.

Method 2: measure the fluid contact angle

The contact angle test is a standard test that evaluates the interfacial properties between solid surfaces and liquid droplets. The contact angle, ie the contact angle that the droplets form on the surface, is a reflection of several interactions. In addition to the properties of liquid-solid interactions, the properties of liquids, their surface tension, the properties of solids and surfaces are considered. In general, droplets on rough surfaces typically exhibit a larger contact angle than droplets on smooth surfaces having the same chemical composition. If a droplet of water exhibits a contact angle of 90 ° or more, the surface is considered "hydrophobic" for the liquid. If the contact angle is less than 90 °, the surface is considered "hydrophilic".

Basic principle of the method:

The contact angle that the liquid makes to the surface can be measured by a variety of techniques, from optical analysis of droplets on the surface to more reliable techniques. The technique used to measure the contact angle is the "Wilhelmy Plate Technique". The principle of this technique is to suspend a solid sample on a water container and slowly drop the sample into the water to a defined depth and then recover it. The retardation force exerted by the water on the material sample at the time of contact (immersion depth 0) is then measured by microbalance and the cosine of the contact angle is determined from the following equation:

In the above formula,

F is the sample force (mg) at zero immersion depth measured by the balance,

P is the perimeter of the sample at the interface, in cm,

ST is the surface tension (dyne cm),

Cos Φ is the cosine of the contact angle,

g is the acceleration of gravity (when measuring position).

The device used to measure the contact angle is an automated "dynamic contact angle analyzer (model DCA-322)" manufactured by Cahn Instruments, Inc., Cerritos CA 90701-2275 U.S.A. For each material to be evaluated (see table), a sample (24 mm x 30 mm) is prepared and attached to the glass slide as specified in the device instructions. Great care should be taken to ensure that the surface of the material sample is not in contact with it to prevent contamination. Each material is measured five times to ensure the accuracy of the measurements and to minimize the impact of variables or surface irregularities during fabrication.

Measurement of contact angle of surface (surface tension reduction treatment) of commonly available materials Example surface Untreated Contact Angle Treated contact angle A Core Tissue (Source: Walkysoft Denmark, Metmar Kotkar) -0 131 B LDPE Film Code X-1522 from Tredega USA 102 121 C LDPE Film Code X-1522-Double Sided from Tredega USA 102 144 D LDPE Film Code X-1522-Unperforated (Tradega Film Products Viv, Netherlands) -Double-sided 80 103 E LDPE + Silicon (8%) film (unperforated) from Tredega Film Products, Netherlands-double-sided 92 NA F LDPE + Silicone (16%) film-sided (source: Tredega Film Products, V) 102 NA G Film Teflon (Unperforated Ribbon) from 3M Corporation USA 130 NA NA = not applicable, material already shows high contact angle

The contact angle of the liquid to the surface and the ability of the porous material to deliver the liquid through the capillary or extrusion process depends on the surface departure or surface structure, the nature of the liquid, and the interaction with the surface as well as the movement mechanism. The test solution used in this test is distilled water which is highly hydrophilic and has a high surface tension. This results in a higher contact angle than those typically found or expected in menstrual or urine type secretions. It is necessary to look carefully at the results of the absolute contact angles detailed in the table. Contact angles greater than 90 ° by water do not imply that the pores of the material exert negative capillary forces on menstrual blood-type secretions. However, increasing the contact angle will act to reduce the degree / efficiency of liquid transfer (via capillary or extrusion) through the material in question.

Wetting Test Results Example Test solution Trial design Untreated Wetability (sqcm) Treated wettability (sqcm) * One Urea B / 1% 1a 41 - AMF / 1% 1a 70 - AMF / 1% 1b 90 - 2 Urea B / 1% 1a 41 0 AMF / 1% 1a 70 0 AMF / 1% 1b 90 20 3 Urea B / 1% 1a 41 1.3 AMF / 1% 1a 70 16 AMF / 1% 1b 90 31 4 Urea B / 1% 1a NA 3 AMF / 1% 1a NA 11 AMF / 1% 1b NA 35 5 Urea B / 1% 1a 18 0 AMF / 1% 1a 30 0 AMF / 1% 1b 40 7

Test Method 3: Unidirectional Flow Test:

Unidirectional flow testing is used to quantify the unidirectional flowability of each side of the perforated film for sieve emissions. As a direct measurement of the degree of porosity, the composition of the test solution can be simply changed as detailed in the method description below to determine the porosity for the full range of body secretions on each surface.

Basic principle of this method:

The basic principle of this test is to evaluate the unidirectional / unidirectional performance of perforated films against liquids simulating sieve secretions. A “excellent perforated film” is a film that exhibits an apparent preponderance of fluid transfer from one surface to another but not in the reverse direction, and the test is repeated by inverting the film. Naturally, "excellent perforated film" will also exhibit minimal fluid mobility in the direction used for the breathable backsheet structure, in addition to the apparent orientation to fluid movement.

In order to assess the directional liquid delivery rate of the perforated film, a simple test is performed to place the liquid saturated absorbent structure on top of the perforated film overlying the absorbent blotting paper stage. Pressure is applied to the entire assembly (saturated absorbent material, film and blotting paper) and the amount of test liquid moved and absorbed onto the blotting paper through the perforated film is measured. In the second experiment, the experiment is repeated with the film direction reversed. Record and evaluate the degree of liquid transfer through surfaces 1 and 2.

Specifically, commercially available filter / blotting papers having dimensions of 12 cm x 12 cm are disclosed in Cartiera Favini S.p.A. In Italy, 10 sheets of Type Abssorbente Bianca "N30" (manufactured by Ditta Bragiola SpA, Perugia, Italy) are weighed and a flat test stand is placed directly below the suspended end. On top of the blotting paper stage is placed a sample of perforated film of dimensions 8.5 cm x 8.5 cm to be evaluated (each surface optionally labeled with surfaces 1 and 2). A fully saturated absorbent material layer is placed on top of the perforated film. The absorbent material simulates a liquid saturated absorbent core using two commercially available airborne absorbent tissues (available as code Metmar Kotka from Walkysoft, Denmark) with a basis weight of 63 gsm (for each sheet). . Each sheet of tissue has a dimension of 5 cm x 5 cm, which is placed symmetrically on top of each other. The tissue structure is then completely immersed in synthetic urine (solution detailed in Method 1) for 1 minute to ensure complete saturation.

The tissue is withdrawn from the liquid and left vertical for 60 seconds to drain excess fluid before placing the tissue directly on the perforated film. This saturated tissue is also placed in the center of the perforated film so that it is in the center of the blotting paper stage.

In the final stage of the test, a windshield block (dimensions 8.5 cm x 8.5 cm) is placed in the upper center of the saturated tissue structure and the weight is automatically lowered to apply a pressure of 130 g / cm ² to the sample for 60 seconds. The drop in weight and time is controlled through simple electronics to ensure reproducibility from one test to the next.

The pressure applied to the entire assembly (saturated absorbent material, film and blotting paper) causes the liquid in saturated tissue to be extruded onto the film, allowing the directivity of liquid migration to liberate through the perforated film and the liquid to travel through the film. To be absorbed by the blotting paper. Once the weight is removed, the layers are separated and the blotting paper is inspected and weighed for liquid wetting. The weight difference (before / after) is recorded and compared to the second experiment where the direction of the perforated film is reversed and the amount of test liquid moved through the perforated film in the reverse direction is measured.

Examples of results for testing perforated films and alternative materials currently available from various companies matter Test solution Surface 1 wettability Surface 2 Wetting Surface 2 treated wettability Example 1 CPT (LDPE) Source Code: X-1522 Tredega Corporation USA 3 g / m ² silicone Urea B / 0% 2.5 1.8 1.1 AMF / 0% 1.4 0.8 0.6 Example 2: CPT (HDPE) Source Code: 15112 Tredega Corporation USA 3 g / m ² silicone Urea B / 0% 2.3 0.8 0.5 AMF / 0% 1.3 0.5 0.3 Example 3: Air laying tissue (2 layers: basis weight of 63 g / m ² of each layer) Source code: Metmar Kotka, Walkysoft Denmark 5 g / m ² silicon underlayer only Urea B / 0% 2.7 2.7 1/1 AMF / 0% 1.7 1.7 0.8

Test solution:

Preparation of Test Solution: Urea B / 0%

The test solution, ie synthetic urine urea B / 0%, is prepared in the same manner as the test solution urea B / 0% except no surfactant is added.

Test Method 4: Measurement of Open Area

Disposable products designed to contain sieve excrement and characterized by breathable backsheets are designed to communicate air and water vapor with the external environment. The degree or efficacy (in terms of the consumer's benefit) of the process can be combined with the open area of the breathable back of the disposable product and in particular the open area of the site that lies close to or partially obstructed by the human body. In this test only the open area of the permeable backsheet is evaluated in terms of ubiquitous levels and averaged levels reflecting the entire product.

Basic principle of this method:

The open area can be measured for all of the material (s) assembled or bonded to form the breathable backsheet structure or for absorbent articles containing the breathable backsheet or structure.

Material: The calculation of the open area for a material is relatively straightforward. Material samples should be best seen under a microscope and recorded in a magnified image or still image. The image can then be placed on a paper sheet of mm scale to simply calculate the number of holes per sqcm and the area of each hole. On the other hand, the image can be digitally scanned to determine the area of the hole per sqcm and the number of holes. The open area is simply defined as the sum of the areas of each hole divided by the total area under analysis.

Absorbent Product: The open area of an absorbent product containing a breathable backsheet is measured by evaluating the "main open area" of the area expected to contribute primarily to efficient communication with the surrounding environment. Breathable areas considered less important are only evaluated as part of the "averaged open area" value of the overall product. For example, in absorbent products, if breathability is provided in areas of the absorbent product that are unlikely to contribute to skin occlusion or areas that are not in close contact with the above, this should not be evaluated as part of the "main open area" calculation.

Step 1:

The product is microscopically examined and quantified and graded if there are different levels of porous areas. If different transmissive regions are present, typically only regions of slight or no transmissivity are typically expected. Nevertheless, if not, each area may be marked for subsequent evaluation.

Step 2:

For each area, microscopically enlarged images or still pictures should be taken. The image can then be placed on a paper sheet of mm scale to simply calculate the number of holes per sqcm and the area of each hole. On the other hand, the image can be digitally scanned to determine the area of the hole per sqcm and the number of holes. The open area is simply defined as the sum of the areas of each hole divided by the total area under analysis:

This analysis is followed for each region with varying porosity or breathability.

The "averaged open area" value of the entire product is then calculated as follows:

Step 3:

The “main opening area” is simply the local opening area calculated in step 2 that is formed in the area of the pad that is expected to contribute most to the benefits of the breathable absorbent product in use. This assessment of major or minor domains is subjective but can be performed in one of two ways.

Evaluation Method 1: The product is worn by a representative group of users (for example, women for sanitary napkins or light incontinence products) and the product is evaluated in proximity to the body and where there is a possible blockage. Evaluate them as major areas and classify them as "main open area" areas if the back side is porous in either of these areas.

Evaluation Method 2: The product is technically evaluated from data bank analysis consistent with specific product features that affect pad suitability (eg, flexibility, product dimensions, thickness, etc.) to the body with known wear characteristics. From this purely technical analysis one can characterize major or minor areas.

Examples of perforated films and alternative materials currently available from various companies are tested and the results are shown in detail in Table 4.

Example matter Hole number N / sqcm Average hole area Opening area% One CPT (LDPE) Supplier Code: X-1522 Tredega Corporation USA 110 Surface 1 0.43 To 47 Surface 2 0.13 To 14 2 EVA-HEX Supplier Code: 4017050 Tredega Corporation USA 99 Surface 1 0.42 To 42 Surface 2 0.16 To 16 3 CPT (HDPE) Supplier Code: X-15112 Tredega Corporation USA 110 Surface 1 0.45 -49 Surface 2 0.16 To 18

The film itself is a three-dimensional film with conical perforations, with very different hole dimensions on each surface. Surface 1 is defined as the surface facing the wearer as a breathable backsheet material in use.

Claims (23)

A disposable absorbent article comprising a liquid permeable topsheet, an absorbent core and a backsheet, wherein the core is intermediate between the topsheet and the backsheet. The backsheet comprises a liquid permeable polymeric film having unidirectional fluid mobility towards the core, the core comprising a fluid storage layer, the backsheet comprising an outer layer, Said core and said backsheet each comprising at least one layer having a wearer facing surface and a garment facing surface, wherein said surfaces of said layers each have a fluid contact angle, The absorbent article has a lower portion extending from there to the garment facing surface of the fluid storage layer and from there to the garment facing surface of the outer layer, Wherein the at least one wearer facing surface of the layers of the lower portion has a fluid contact angle that is greater than the fluid contact angle of the adjacent garment facing surface of the adjacent layer. A disposable absorbent article comprising a liquid permeable topsheet, an absorbent core and a backsheet, wherein the core is intermediate between the topsheet and the backsheet. The backsheet comprises a liquid permeable polymeric film having unidirectional fluid mobility towards the core, the core comprising a fluid storage layer, the backsheet comprising an outer layer, Said core and said backsheet each comprising at least one layer having a wearer facing surface and a garment facing surface, wherein said surfaces of said layers each have a fluid contact angle, The absorbent article has a lower portion extending from there to the garment facing surface of the fluid storage layer and from there to the garment facing surface of the outer layer, Wherein the at least one garment facing surface of said layers of said lower portion has a fluid contact angle greater than that of the wearer facing surface of said same layer. The method of claim 1, Disposable absorbent article wherein at least one of the layers below the storage layer comprises a low surface energy material. The method of claim 3, wherein Disposable absorbent article wherein the low surface energy material is selected from curable silicones, fluoropolymers, hydrocarbons, and mixtures thereof. The method of claim 1, Disposable absorbent article wherein the layer comprises at least 5% by weight of the total low surface energy material of the layer. The method of claim 1, The disposable absorbent article of the garment facing side or the wearer facing side of the layer of the lower part comprises at least 0.25 g of low surface energy material per m ² of said surface. The method of claim 1, The backsheet comprises two layers, wherein the first layer adjacent the core comprises a polymeric film and the outer layer comprises a gas permeable fibrous fabric layer. The method of claim 1, The core comprises two or more portions, wherein the first portion comprises a storage layer and the second portion comprises a fibrous layer, wherein the fibrous layer is adjacent the backsheet. The method of claim 1, And a wearer facing surface of the layer having a fluid contact angle that is at least 10 ° greater than the fluid contact angle of adjacent surfaces. The method of claim 9, Disposable absorbent product with a fluid contact angle greater than 20 ° greater than the fluid contact angle of adjacent surfaces. The method of claim 2, Disposable absorbent product with a fluid contact angle of 90 ° or more on the clothes facing surface of the storage layer. The method of claim 11, A disposable absorbent article, wherein the fluid contact angle of the surface is at least 100 °. The method of claim 1, Disposable absorbent article, preferably having a continuous fluid contact angle gradient in the lower portion. The method of claim 1, Disposable absorbent products that are sanitary napkins or panty liners. The method of claim 2, Disposable absorbent article wherein at least one of the layers below the storage layer comprises a low surface energy material. The method of claim 15, Disposable absorbent article wherein the low surface energy material is selected from curable silicones, fluoropolymers, hydrocarbons, and mixtures thereof. The method of claim 2, The disposable absorbent article of the garment facing side or the wearer facing side of the layer of the lower part comprises at least 0.25 g of low surface energy material per m ² of said surface. The method of claim 2, The backsheet comprises two layers, wherein the first layer adjacent the core comprises a polymeric film and the outer layer comprises a gas permeable fibrous fabric layer. The method of claim 2, The core comprises two or more portions, wherein the first portion comprises a storage layer and the second portion comprises a fibrous layer, wherein the fibrous layer is adjacent the backsheet. The method of claim 2, And a wearer facing surface of the layer having a fluid contact angle that is at least 10 ° greater than the fluid contact angle of adjacent surfaces. The method of claim 20, Disposable absorbent product with a fluid contact angle greater than 20 ° greater than the fluid contact angle of adjacent surfaces. The method of claim 2, Disposable absorbent article, preferably having a continuous fluid contact angle gradient in the lower portion. The method of claim 2, Disposable absorbent products that are sanitary napkins or panty liners.