To prevent leakage of body exudates from absorbent articles such as feminine care pads or napkins and disposable diapers, it is desirable that the exudates not reach the edges of the absorbent material in the article. A xe2x80x9ccenter fillxe2x80x9d strategy is desirable for leakage control, wherein fluids are preferentially held in a central region of the article. Unfortunately, in traditional absorbent articles, there is generally no barrier to bulk flow or capillary wicking from the target region (the place where intake of fluids occurs) to the edges of the article, so leaking from the edges of the article is a persistent problem. Thus, in traditional articles, fluid entering the center of the article still has the potential to travel through absorbent material directly to the sides and leak. Flow from the center to the sides can be especially rapid when the article is compressed, bringing the wet central portion of the article in contact with absorbent material at the sides of the article.
The ability of an absorbent article to promote center fill and reduce leakage depends on the goodness of body fit achieved by the article in use. In sanitary napkins and other absorbent articles, the article as worn is often compressed laterally by the legs of the wearer, causing significant deformation of the article. In many conventional articles, the deformation is random or uncontrolled, resulting in a variety of product configurations that often may be inadequate for good uptake and fluid distribution in the article.
Past efforts to improve body fit and promote liquid uptake in the center of the article have included three-dimensional structures with central humps or elevated central members resting above the plane of a flat absorbent core. The elevated member can be a cylinder or an inverted U-shaped tube, for example. However, the article with an elevated central member can still suffer from leakage and smearing from fluid leaving the sides of the member. Further, deformation of the entire article may be poorly controlled, resulting in poor body fit in many cases even with a central elevated region.
What is needed is an absorbent article with internal barriers to prevent leakage to the sides and offering good control of the deformation of the absorbent material when worn such that absorbent material is placed close to the source of body exudates. What is needed further is a thin absorbent article with good center fill performance that can reduce leakage and offer excellent body fit through the efficient use of a small amount of absorbent material while maintaining comfort.
It has been discovered that a layered absorbent core with a horizontal wicking barrier between two superposed layers provides opportunities for improved leakage prevention, better body fit, and more efficient use of the absorbent material of the core if certain design principles are followed to promote the upward deflection of the central portion of the absorbent core toward the body of the wearer. The design principles require that the absorbent core be divided into two parts, a lower absorbent member and a central absorbent section, with a horizontal wicking barrier separating the two parts to reduce the tendency for fluid to flow through the absorbent material from the central target region of the article toward the longitudinal sides of the article.
Hence, in one aspect, the invention resides in an absorbent article for use on the body of a wearer, the absorbent article having a longitudinal centerline, a transverse centerline, two longitudinal sides, a target zone and a body side, the absorbent article comprising:
a) a liquid impervious backsheet;
b) a liquid pervious topsheet attached to the backsheet;
c) a lower absorbent member disposed above the backsheet, the lower absorbent member comprising a pair of spaced apart, substantially longitudinal crease lines in the target zone disposed on opposite sides of the longitudinal centerline of the article, the pair of crease lines having a distance therebetween;
d) a horizontal wicking barrier disposed above the lower absorbent member;
e) a middle absorbent member having a width less than the distance between the crease lines in the target zone, the middle absorbent member being disposed above the horizontal wicking barrier; and
f) an upper absorbent member having longitudinal sides and a width in the target zone greater than the width of the middle absorbent member and less than the width of the horizontal wicking barrier, disposed above the middle absorbent member and beneath the topsheet.
In another aspect, the invention resides in an absorbent article having a target zone, the absorbent article comprising:
a) a liquid impervious backsheet;
b) a lower absorbent member disposed above the backsheet;
c) a horizontal wicking barrier disposed over the lower absorbent member, the wicking barrier having a width in the target zone;
d) a middle absorbent member disposed above the wicking barrier and having a maximum width in the target zone;
e) an upper absorbent member disposed above the middle absorbent member having a width in the target zone no less than the maximum width of the middle absorbent member in the target zone, the upper absorbent member being predisposed to deflect upward during laterally inward compression of the absorbent article; and
f) a topsheet connected to the backsheet.
In another aspect, the invention resides in an absorbent article having a target zone, a longitudinal direction, a transverse direction, a vertical direction substantially normal to both the longitudinal and transverse directions, and a body side, the absorbent article comprising:
a) a liquid impervious backsheet;
b) a lower absorbent member disposed above the backsheet;
c) a horizontal wicking barrier disposed over the lower absorbent member, the horizontal wicking barrier having a width in the target zone;
d) a pre-shaped upper absorbent member disposed above the horizontal wicking barrier, the pre-shaped upper absorbent member being shaped to define a medial hump therein and to define a voidspace between the horizontal wicking barrier and the medial hump, the pre-shaped upper absorbent member having a width in the target zone no greater than the width in the target zone of the horizontal wicking barrier; and
e) a topsheet disposed above the pre-shaped upper absorbent member and attached to the backsheet.
The voidspace of the above article can optionally but desirably be filled in part with a middle absorbent member including loose fibrous material such as hardwood nits, absorbent particulates, high-bulk fluff pulp, tissue layers, and the like. Generally, the pre-shaped upper absorbent member is geometrically predisposed to flex upward during laterally inward compression.
In another aspect, the invention resides in a method for producing an absorbent article having a longitudinal centerline and a transverse centerline substantially normal to the longitudinal centerline comprising:
a) providing a backsheet;
b) disposing a substantially planar lower absorbent member above the backsheet, the lower absorbent member having a width along the transverse centerline of the article and comprising longitudinal crease lines therein;
c) disposing a horizontal wicking barrier over the lower absorbent member;
d) disposing a middle absorbent member over the horizontal wicking barrier, the middle absorbent member being substantially centered about the longitudinal centerline of the article and having a width substantially less than the width of the lower absorbent member along the transverse centerline of the article;
e) disposing an upper absorbent member over the middle absorbent member, the upper absorbent member having a width along the transverse centerline of the article greater than the width of the middle absorbent member;
f) disposing a topsheet above the upper absorbent member and the lower absorbent member; and
g) securing the topsheet to the backsheet.
In still another aspect, the invention resides in a method for producing an absorbent article having a target zone, comprising:
a) providing a liquid impervious backsheet;
b) disposing a lower absorbent member above the backsheet;
c) disposing a horizontal wicking barrier over the lower absorbent member, the wicking barrier having a width in the target zone;
d) pre-shaping an upper absorbent member to form a pre-shaped upper absorbent member having a medial hump therein, such that a voidspace is defined beneath the medial hump when the pre-shaped upper absorbent member rests on a flat surface with the medial hump placed away from the flat surface;
e) disposing the pre-shaped upper absorbent member above the horizontal wicking barrier with the medial hump away from the horizontal wicking barrier; and
f) disposing a topsheet over the pre-shaped upper absorbent member;
g) and attaching the topsheet to the backsheet.
The absorbent members of the core can be fluff pulp, airlaid webs, multiple layers of tissue, coform, absorbent foams, and the like. The central absorbent section of the absorbent core is above the horizontal wicking barrier and comprises at least two layers, a middle absorbent member preferably centrally located in the absorbent article, and an upper absorbent member that is wider than the middle absorbent member. Desirably, the middle absorbent member is substantially thicker than the upper absorbent member. The upper absorbent member conforms at least in part to the shape of the smaller middle absorbent member such that a medial hump is formed in the absorbent core for improved body fit.
The lower absorbent member desirably provides shaping to control the deformation and fit of the pad and provides additional absorbent capacity in case the central absorbent section cannot retain all of the fluid received. The lower absorbent member may be a single contiguous piece, or may comprise a plurality of discrete sections or layers. The lower absorbent member can be provided with a central void beneath the horizontal wicking barrier to reduce the amount of material in the absorbent article since the central portion of the lower absorbent member may not be needed for fluid retention.
Desirably, the topography of the absorbent article is further enhanced in the target zone by laterally inward compression when worn, giving rise to a substantially W-shaped article in the target zone. Crease lines such as embossments or slits in the lower absorbent member and/or the upper absorbent member promote predominantly longitudinal valley folds in the absorbent core away from the longitudinal centerline. The crease lines help enable the desired deformation of the outer portions of the absorbent core to achieve good body fit, while the medial hump and other central elements help promote upward deflection of absorbent core, also for improved body fit. Thus, there is a positive interaction between the medial hump and the crease lines in the absorbent core that promotes good body fit.
In addition to crease lines to promote downward folding of the article, shaping can also be directed by shaping lines that promote upward folding (e.g., a mountain fold) during lateral compression from the longitudinal sides of the article. A shaping line, if present, should be in the central absorbent section of the article. A shaping line near the longitudinal centerline coupled with two crease lines away from the longitudinal centerline can interact during lateral compression to establish a W-fold geometry in the article.
The entire absorbent core together desirably is soft and flexible to readily conform to the body and to permit deformation of components therein to flex toward the body when the article is worn.
In a preferred embodiment, the good body fit and leakage control capabilities of the present invention derive in part from upward deflection of substantially the entire absorbent core in the central portion of the target zone, meaning that the lower absorbent member and the upper absorbent member are both deflected toward the body, rather than the upper absorbent member alone deflecting toward the body or some other member above the absorbent core deflecting toward the body without the lower absorbent member also deflecting toward the body.
The horizontal wicking barrier plays an important role in promoting center fill and preventing leakage of fluids. The horizontal wicking barrier spans a horizontal distance (even though it may not rest in a single horizontal plane) on the surface of the lower absorbent member beyond the periphery of the upper absorbent member, particularly in the target zone. Thus, the horizontal wicking barrier in the target zone is wider than either of the middle absorbent member and the upper absorbent member to hinder wicking contact between the central absorbent section and the lower absorbent member.
The portion of horizontal wicking barrier on the surface of the lower absorbent member and outside the periphery of the upper absorbent member is the xe2x80x9cledgexe2x80x9d or xe2x80x9cexposed portion of the horizontal wicking barrier.xe2x80x9d The ledge helps prevent wicking contact between the central absorbent section and the adjacent lower absorbent member, even when the article is laterally compressed. It can also redirect flow toward the central absorbent section and enhance the center-fill effect. When fluid is deposited on such a ledge, the fluid can be redirected toward the central absorbent section instead of flowing into the underlying lower absorbent member. In a related embodiment, the ledge can substantially cover all of the body side surface of the lower absorbent member outside the perimeter of the central absorbent section. Thus, the ledge can provide wicking isolation of the central absorbent section from the lower absorbent member even under extreme bunching of the article during dynamic use.
The horizontal wicking barrier is preferably a thin, flexible web or film that does not wick fluid or at least wicks fluid significantly more slowly than the absorbent material of the core. The horizontal wicking barrier desirably is a hydrophobic polyolefin film or web, such as a polyethylene film or a meltblown web. In a preferred embodiment, the wicking barrier is impervious to liquid except where optional apertures have been provided to permit a limited degree of flow from the central absorbent section to underlying portions of the lower absorbent member. Less preferably, the wicking barrier can also comprise in part hydrophobic matter that is used to impregnate or coat a portion of the lower absorbent member to reduce lateral wicking by providing a substantially impervious zone in the lower absorbent member. Such hydrophobic matter can include adhesives and particularly hot melt adhesives added to the absorbent article while molten; wax; silicone-based materials; polyolefins and the like.
The horizontal wicking barrier can be a smooth film with relatively low friction, permitting sliding or motion of portions of the middle absorbent member relative to the horizontal wicking barrier when the article is laterally compressed to improve body fit.
Good body fit can be further promoted by a central rising member disposed in or beneath the absorbent core. The central rising member, described more fully hereafter, deflects upward upon lateral compression from the longitudinal sides of the article. The deflection of the central rising member in turns deflects the upper absorbent member toward the body of the wearer.
The optional central rising member can be any of a variety of structures which deflect upward when laterally compressed from the longitudinal sides, including an absorbent web folded into the shape of the letter xe2x80x9cexe2x80x9d prior to flattening, with a centerline aligned with the longitudinal centerline of the article (the flat cross-bar of the xe2x80x9cexe2x80x9d-shape lying in the transverse direction, normal to the longitudinal centerline of the article). Upon lateral compression from the longitudinal sides of the article, the flattened xe2x80x9cexe2x80x9d shape deflects upwardly, the upper loop of the xe2x80x9cexe2x80x9d shape springing back into the approximate shape of a semicircle to urge the upper surface of the upper absorbent member toward the body of the wearer. Collapsed tubes and other structures disclosed below can also serve as a central rising member.
The central rising member can comprise a thermoplastic deformation element as disclosed by K. B. Buell in U.S. Pat. No. 5,300,055, issued Apr. 5, 1994, but the central rising member can also be non-thermoplastic such as a densified cellulosic web. Thus, the central rising member can have a flexure means, and particularly a longitudinally extending flexure hinge, for inducing the body facing surface of the central rising member to have a convex upward configuration when the sanitary napkin is worn.
Many embodiments of the present invention are intended to be worn in the crotch of a wearer, and thus have crotch regions. However, the present invention can also be applied to other articles such as wound dressings where a crotch region may not exist. In such cases, the article will have a region where fluid intake is intended to occur, termed the xe2x80x9ctarget region.xe2x80x9d The portion of the article including the longitudinal length of the target region and the full transverse width of the article normal to length of the target region is defined herein as the xe2x80x9ctarget zone.xe2x80x9d For articles intended to be worn in the crotch, the terms xe2x80x9ctarget zonexe2x80x9d and xe2x80x9ccrotch regionxe2x80x9d are generally synonymous, whereas xe2x80x9ctarget regionxe2x80x9d generally excludes the portions of the absorbent core near the longitudinal sides since the intended area for fluid intake is generally substantially central to the absorbent article.
Possible uses of the present invention include absorbent articles for intake, distribution, and retention of human body fluids, such as feminine care pads and related catamenial devices or sanitary napkins, including xe2x80x9cultra-thinxe2x80x9d pads, pantiliners and maxipads. Likewise, the present invention can be applied to diapers, disposable training pants, other disposable garments such as swimming garments, incontinence articles, bed pads, bandages, or other absorbent articles. The present invention can also be incorporated in articles adapted for particular portions of garments to be worn on the human body, ostomy bags, and medical absorbents and wound dressings. The articles of the present invention provide significant leakage protection, fluid center-fill absorptive performance, and other desirable attributes for absorbent articles.
Preferably, the pre-shaped upper absorbent member is an airlaid web comprising cellulosic fibers and a binder such as a thermoplastic binder material, a heat-setting resin, or a heat-activated crosslinking agent, wherein the medial hump is formed by thermal molding of the airlaid web, exemplified by using mechanical or pneumatic pressure to deform an airlaid web against a molding surface, followed by application of heat to activate the binder and stabilize the airlaid web so it maintains its shape after removal from the molding surface.
For feminine care pads in particular, the present invention offers surprising advantages in terms of comfort and fit. In sanitary napkins, the upward mound that is created near the longitudinal centerline of the article by the upward motion of the central regions of the absorbent article as directed by shaping lines, does not persist throughout the length of the article, but, as influenced by the shaping lines, terminates just outside the crotch region to permit the article to better conform to the regions outside the crotch area, where an inverted V-shape may be useful in the rear of the article to better conform to the buttocks, and where the article generally should be relatively flat in the transverse direction and curled concave up in the longitudinal direction for best body fit in the front of the pad. Proper shaping of regions outside the crotch region during lateral compression can be achieved by providing additional slits, reinforcing elements, elastic components, or attachment elements to the absorbent core.
As used herein, a material is said to be xe2x80x9cabsorbentxe2x80x9d if it can retain an amount of water equal to at least 100% of its dry weight as measured by the test for Intrinsic Absorbent Capacity given below (i.e., the material has an Intrinsic Absorbent Capacity of at about 1 or greater). Desirably, the absorbent materials used in the absorbent members of the present invention have an Intrinsic Absorbent Capacity of about 2 or greater, more specifically about 4 or greater, more specifically still about 7 or greater, and more specifically still about 10 or greater, with exemplary ranges of from about 4 to about 25 or from about 12 to about 40.
As used herein, the term xe2x80x9cabsorbent articlexe2x80x9d refers to devices which absorb and contain liquids such as body exudates, and, more specifically, refers to devices which are placed against or in proximity to the body of the wearer to absorb and contain the various exudates discharged from the body.
As used herein, xe2x80x9cabsorbent capacityxe2x80x9d refers to the total mass of water that a specified quantity of absorbent material can hold, and is simply the Intrinsic Absorbent Capacity (described hereafter) multiplied by the dry mass of the absorbent material. Thus 10 g of material having an Intrinsic Absorbent Capacity of 5 has an absorbent capacity of 50 g (or about 50 ml of fluid).
As used herein, xe2x80x9cbulkxe2x80x9d and xe2x80x9cdensity,xe2x80x9d unless otherwise specified, are based on an oven-dry mass of a sample and a thickness measurement made at a load of 0.34 kPa (0.05 psi) with a 7.62-cm (three-inch) diameter circular platen. Thickness measurements of samples are made in a TAPPI-conditioned room (50% relative humidity, 23xc2x0 C.) after conditioning for at least four hours. Samples should be flat and uniform under the area of the contacting platen. Bulk is expressed as cc/g and density is the inverse, g/cc.
As used herein, the term xe2x80x9ccellulosicxe2x80x9d is meant to include any material having cellulose as a major constituent, and specifically comprising at least 50 percent by weight cellulose or a cellulose derivative. Thus, the term includes cotton, typical wood pulps, nonwoody cellulosic fibers, cellulose acetate, cellulose triacetate, rayon, thermomechanical wood pulp, chemical wood pulp, debonded chemical wood pulp, milkweed, or bacterial cellulose.
As used herein, xe2x80x9cCentral Elevationxe2x80x9d is defined as the height difference between the center of the upper absorbent member along the transverse centerline of the article and the average height of the longitudinal sides of the upper absorbent member along the transverse centerline of the article at the end of the Vertical Deformation Test as described hereinafter. The Central Elevation for absorbent articles of the present invention can be at least about 0.5 cm, specifically at least about 1 cm, and more specifically at least about 1.2 cm and up to about 10 cm. Desirably, an absorbent article of the present invention exhibits an increase in Central Elevation in the crotch region of at least about 20%, and more specifically at least about 50%, relative to the Central Elevation in the crotch region exhibited by an essentially identical absorbent article without a shaping line.
As used herein, the terms xe2x80x9ccrease linesxe2x80x9d and xe2x80x9cshaping linesxe2x80x9d refer to narrow, elongated sections that promote folding by providing a sudden change in material properties of matter along the line relative to matter on either side of the line. Crease lines and shaping lines, as defined herein, can be generally referred to as xe2x80x9cbending lines.xe2x80x9d Such lines can have a width less than about 5 millimeters (mm), desirably less than about 3 mm, more specifically less than about 2 mm, and most specifically between about 0.5 mm and about 1.5 mm. The geometry and nature of bending lines are described more fully hereafter.
As used herein, the xe2x80x9ccrotch regionxe2x80x9d of an absorbent article refers to the generally central region that will be in contact with the crotch of the user, near the lowermost part of the torso, and resides between the front and rear portions of the article. Typically the crotch region contains the transverse centerline of the article and generally spans approximately 7 to 10 cm in the longitudinal direction.
As used herein, xe2x80x9celastic modulusxe2x80x9d is a measure of slope of stress-strain of a web taken during tensile testing thereof and is expressed in units of kilograms of force. Tappi conditioned samples with a width of 3 inches are placed in tensile tester jaws with a gauge length (span between jaws) of 2 inches. The jaws move apart at a crosshead speed of 10 cm/min and the slope is taken as the least squares fit of the data between stress values of 50 grams of force and 100 grams of force, or the least squares fit of the data between stress values of 100 grams of force and 200 grams of force, whichever is greater. If the sample it too weak to sustain a stress of at least 200 grams of force without failure, an additional ply is repeatedly added until the multi-ply sample can withstand at least 200 grams without failure.
As used herein, the term xe2x80x9cextensiblexe2x80x9d refers to articles that can increase in at least one of their dimensions in the x-y plane by at least 10% and desirably at least 20%. The x-y plane is a plane generally parallel to the faces of the article. The term extensible includes articles that are stretchable and elastically stretchable (defined below). In the case of a sanitary napkin comprising an absorbent core, for example, the article and the absorbent core are desirably extensible both in length and width. The absorbent article, however, may only be extensible in one of these directions, desirably at least in the longitudinal direction. Examples of extensible materials and articles, and their methods of preparation, are disclosed in U.S. Pat. No. 5,611,790, issued Mar. 18, 1997 to Osborn.
As used herein, a bulk material (absorbent matter) is xe2x80x9cflexiblexe2x80x9d if a straight, TAPPI-conditioned (50 percent relative humidity at 23xc2x0 C.) strip of the material 25 cm long with a cross-section of 1 cmxc3x971 cm can be bent 180xc2x0 around a 5-cm diameter rod without breaking and without requiring application of more than 6 Newtons of force to the ends of the strip to cause the bending over a 3-second span of time. The same material is xe2x80x9cshape retaining,xe2x80x9d as used herein, if the strip is held in place on the rod for 5 seconds and then remains bent to an angle of at least 300 after the strip is removed from the rod (i.e., the strip is deformed such that the straight portions at the ends of the strip are at an angle relative to each other of at least 30xc2x0, with a perfectly straight strip defining an angle of 0xc2x0).
As used herein, the term xe2x80x9cflexure-resistantxe2x80x9d refers to an element which will support a bending moment, in contrast to an element which will support only axial forces. Likewise, as used herein, xe2x80x9cflexure resistancexe2x80x9d is a means of expressing the flexibility of a material or article and is measured according to the Circular Bend Procedure described in detail in U.S. Pat. No. 5,624,423, issued Apr. 29, 1997 to Anjur et al., herein incorporated by reference in its entirety. Flexure resistance is actually a measurement of peak bending stiffness modeled after the ASTM D4032-82 Circular Bend Procedure. The Circular Bend Procedure of Anjur et al. is a simultaneous multidirectional deformation of a material in which one face of a specimen becomes concave and the other face becomes convex. The Circular Bend Procedure gives a force value related to flexure-resistance, simultaneously averaging stiffness in all directions. For comfort, the absorbent article desirably has a flexure-resistance of less than or equal to about 1,500 grams, more specifically about 1000 grams or less, more specifically still about 700 grams or less and most specifically about 600 grams or less. For shaping performance, the central absorbent section as well as the lower absorbent member can have a flexure resistance of at least about 30 grams, more specifically at least about 50 grams, and most specifically at least about 150 grams.
As used herein, the term xe2x80x9chorizontal,xe2x80x9d refers to directions in the plane of the article that are substantially parallel to the body-side surface of the article, or, equivalently, substantially normal to the vertical direction of the article, and comprises the transverse direction and the longitudinal direction of the article, as well as intermediate directions. The orientation of components in an article, unless otherwise specified, is determined as the article lies substantially flat on a horizontal surface.
As used herein, xe2x80x9cIntrinsic Absorbent Capacityxe2x80x9d refers to the amount of water that a saturated sample can hold relative to the dry weight of the sample and is reported as a dimensionless number (mass divided by mass). The test is performed according to Federal Government Specification UU-T-595b. It is made by cutting a 10.16 cm long by 10.16 cm wide (4 inch long by 4 inch wide) test sample, weighing it, and then saturating it with water for three minutes by soaking. The sample is then removed from the water and hung by one corner for 30 seconds to allow excess water to be drained off. The sample is then re-weighed, and the difference between the wet and dry weights is the water pickup of the sample expressed in grams per 10.16 cm long by 10.16 cm wide sample. The Intrinsic Absorbent Capacity value is obtained by dividing the total water pick-up by the dry weight of the sample. If the material lacks adequate integrity when wet to perform the test without sample disintegration, the test method may be modified to provide improved integrity to the sample without substantially modifying its absorbent properties. Specifically, the material may be reinforced with up to 6 lines of hot melt adhesive having a diameter of about 1 mm applied to the outer surface of the article to encircle the material with a water-resistant band. The hot melt should be applied to avoid penetration of the adhesive into the body of the material being tested. The corner on which the sample is hung should be reinforced with hot melt adhesive to increase integrity if the untreated sample cannot be hung for 30 s when wet.
As used herein, the term xe2x80x9cpolymeric webxe2x80x9d refers to a porous or nonporous layer primarily composed of polymeric material, and can be a nonwoven web, a plastic film, a polymeric film, an apertured film, or a layer of foam. Polymeric webs can be used as wicking barriers, baffle layers, backsheets, and, if sufficiently liquid pervious, as topsheets of absorbent articles. A polymeric web can consist of about 50 weight percent or more polymeric material, more specifically about 80 weight percent or more polymeric material, and most specifically about 90 weight percent or more polymeric material. Exemplary materials include polyolefins, polyesters, polyvinyl compounds, and polyamides.
The term xe2x80x9csanitary napkinxe2x80x9d, as used herein, refers to an article which is worn by females adjacent to the pudendal region that is intended to absorb and contain the various exudates which are discharged from the body (e.g., blood, menses, and urine). While the present invention is shown and described in the form of a sanitary napkin, it should be understood that the present invention is also applicable to other feminine hygiene or catamenial pads such as pantiliners, or other absorbent articles such as incontinence pads. The term xe2x80x9cfeminine care padxe2x80x9d as used herein is synonymous with sanitary napkin.
The absorbent article comprising an absorbent core can, in addition to being extensible, also be stretchable. The term xe2x80x9cstretchablexe2x80x9d, as used herein, refers to articles that are extensible when stretching forces are applied to the article and offer some resistance to stretching. The terms xe2x80x9celastically stretchablexe2x80x9d or xe2x80x9celastically extensiblexe2x80x9d are intended to be synonymous. These terms, as used herein, mean that when in-plane stretching forces are removed, the article or absorbent fibrous structure will tend to return toward its unextended or unstretched dimensions (or original dimensions). It need not return all the way to its unstretched dimensions, however. It may return to relaxed dimensions between its unstretched dimensions and extended (or stretched dimensions).
As used herein, xe2x80x9cthicknessxe2x80x9d of a fluff pad or other absorbent element refers to thickness measured with a platen-based thickness gauge having a diameter of 7.62 cm at a load of about 0.05 pounds per square inch (psi) [about 35 kilograms per square meter].
As used herein, the term xe2x80x9ctransversexe2x80x9d refers to a direction which lies within the plane of the absorbent article and is generally perpendicular to the longitudinal direction. The z-direction is generally orthogonal to both the longitudinal and transverse centerlines. The term xe2x80x9clateralxe2x80x9d refers to substantially in-plane directions having a predominately transverse component. Likewise, xe2x80x9cinwardly lateral compressionxe2x80x9d refers to compression directed from the longitudinal sides of an article toward the longitudinal centerline thereof.
The degree of elevation of the central absorbent section can be quantified in terms of a Vertical Deformation test. As used herein, xe2x80x9cVertical Deformationxe2x80x9d refers to the height increase experienced by the body-side surface of an absorbent article when the longitudinal sides in the crotch reason are gripped and steadily moved inward toward the longitudinal centerline of the article, decreasing the span between the longitudinal sides by 1.5 cm. The Vertical Deformation test apparatus comprises two clamps having a clamp width (longitudinal length of the clamped portion of the edge of the article) of 5 cm. One clamp is stationary and the other is on a track that permits the clamp to slide to increase or decrease the distance between the clamps while keeping the clamp aligned and parallel to the other clamp. The clamps should be tilted downward at an angle of 20 degrees relative to horizontal, such that both outer edges of the absorbent article are slightly elevated relative to the nearest crease line, thus somewhat simulating the positioning of the outward edges of the absorbent article that may be induced by panties with elevated elastic edges in the crotch region. The clamps are 5 cm above the surface of the track, permitting a pad to be suspended in air between the clamps, gripped in the crotch area such that a portion of the longitudinal sides of the absorbent core are held, with the clamps extending inward no more than about 3 mm from the outer edge of the absorbent core. The article should be held substantially taut in the region between the clamps without damaging the article, such that the crotch region is substantially horizontal before lateral compression begins. At a rate of about 0.5 centimeters per second (cm/s), the slidable clamp is moved smoothly toward the fixed clamp by a distance of 50% of the initial width of the article in the crotch region (or less if the article become incompressible such that more than about 5 kg of force is required to further compress the article). The height of the center of the pad or absorbent article is recorded before the clamp is moved and after the clamp is moved, yielding a difference that is reported as the Vertical Deformation. An increase in height is reported as a positive number, while a decrease is reported as a negative number. Desirably, the Vertical Deformation of the absorbent article is at least about 0.5 cm. Specifically, the Vertical Deformation is at least about 1 cm, and more specifically is at least about 1.5 cm and up to about 10 cm. Desirably, an absorbent article of the present invention exhibits an increase in Vertical Deformation in the crotch region of at least about 20%, and more specifically at least about 50%, relative to the Vertical Deformation in the crotch region exhibited by an essentially identical absorbent article without a shaping line.
As used herein, xe2x80x9cWet Bulkxe2x80x9d is based on a caliper measurement of a sample according to the definition of xe2x80x9cbulkxe2x80x9d above (at 0.344 kPa), except that the conditioned sample is uniformly misted with deionized water until the moistened mass of the sample is approximately 250% of the dry mass of the sample (i.e., the added mass of the moisture is 150% of the dry sample weight). If the sample cannot absorb and retain enough moisture from misting to increase the mass by 150%, then the highest level of achievable moisture add-on below 150% but still above 100% moisture add on should be used. The Wet Bulk in cc/g is calculated as the thickness of the substantially planar moistened sample under a load of 0.344 kPa (0.05 psi) divided by the oven-dry sample basis weight. Absorbent materials in the absorbent members of the present invention can have a Wet Bulk of about 4 cc/g or greater, more specifically about 6 cc/g or greater, more specifically still about 10 cc/g or greater, and most specifically about 15 cc/g or greater, with an exemplary range of from about 5 cc/g to about 20 cc/g.
As used herein, the xe2x80x9cwet:dry ratioxe2x80x9d is the ratio of the geometric mean wet tensile strength divided by the geometric mean dry tensile strength. Geometric mean tensile strength (GMT) is the square root of the product of the machine direction tensile strength and the cross-machine direction tensile strength of the web. Unless otherwise indicated, the term xe2x80x9ctensile strengthxe2x80x9d means xe2x80x9cgeometric mean tensile strength.xe2x80x9d The absorbent webs used in the present invention can have a wet:dry ratio of about 0.1 or greater and more specifically about 0.2 or greater. Tensile strength can be measured using an Instron tensile tester using a 2-inch jaw width, a jaw span of 2 inches, and a crosshead speed of 25.4 centimeters per minute after maintaining the sample under TAPPI conditions for 4 hours before testing. The absorbent webs of the present invention can have a minimum absolute ratio of dry tensile strength to basis weight of about 0.01 gram/gsm, specifically about 0.05 grams/gsm, more specifically about 0.2 grams/gsm, more specifically still about 1 gram/gsm and most specifically from about 2 grams/gsm to about 50 grams/gsm.