ABSORBENT ARTICLE THAT HAS A SUBSEQUENT SHEET WATERPROOF TO FLUID. BREATHABLEFIELD OF THE INVENTIONThe present invention relates generally to disposable absorbent articles such as disposable diapers, incontinence briefs, incontinence undergarments, incontinence pads, feminine hygiene garments, training pants, fitted garments, and the like, and more particularly to disposable absorbent articles having a breathable back sheet, impervious to the fluid.
BACKGROUND OF THE INVENTIONBabies and other incontinent individuals use disposable absorbent articles such as diapers to receive and contain urine and other exudates from the body. The absorbent articles work both to contain the discharged materials and to isolate these materials from the body of the user and from the garments and bedding of the users. Absorbent articles having many different basic designs are known in the art. It is also known that the exterior of the disposable diapers can be covered with a flexible sheet, impervious to fluid and vapor to prevent any absorbed fluid from passing through the diaper and staining the adjacent articles such as clothing, sheets and the like. These external covers generally referred to as backsheets, are often constructed from a fluid impervious film such as polyethylene. Although these posterior sheets prevent the passage of fluid through the diaper, they can also make the diaper feel hot and uncomfortable to wear because of its impermeability to air and moisture. The backsheets that are vapor permeable are generally known as breathable backsheets and have been described in the art. In general, these backsheets are intended to allow steam to pass through them while delaying, at least to a degree, the user's passage. For example, U.S. Patent No. 3,156,242 issued to Crow, Jr. on November 10, 1964 teaches the use of a microporous film as a breathable backsheet. U.S. Patent No. 3,881,489 issued to Hartwell on May 6, 1975, teaches a breathable backsheet comprising in combination two layers, the first of which is a perforated thermoplastic film with low hollow volume and the second of the which is a porous hydrophobic tissue with high hollow volume. U.S. Patent No. 3,989,867 issued to Sisson on November 2, 1976 teaches a breathable back sheet provided with tapered, recessed protrusions that prevent passage of fluids while allowing vapors to easily pass through. Although these backsheets provide improvements on the waterproof backsheets commonly practiced in the prior art, it has been found that they are not sufficiently impervious to fluid when subjected to normal conditions of use. For example, when used as a backsheet in a disposable diaper, the backsheets can allow the transmission of urine to the impact of a sitting baby. This capacity of the fluid that is forced through these materials results in the transmission of unwanted urine waste through the back sheet of the diaper. Therefore, it is an object of the present invention to provide a backsheet for disposable absorbent article having good containment characteristics, while being breathable to ensure comfort for the wearer.
It is still another object of the present invention to provide a disposable absorbent article having a breathable backsheet that has good containment characteristics when subjected to normal conditions of use. These and other objects of the present invention will be more readily apparent when considered with reference to the following description and when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE INVENTIONThe present invention is directed to disposable absorbent articles, such as disposable diapers having a backsheet at least a portion of which is breathable and impervious to fluid. The disposable absorbent article preferably comprises a containment assembly that includes a fluid pervious topsheet, a backsheet attached to the topsheet, and an absorbent core, disposed between the topsheet and the backsheet. The absorbent core has a pair of opposite longitudinal edges, an inner surface and an outer surface. In some embodiments, at least a portion of the backsheet exhibits substantially zero dynamic fluid transmission when subjected to an impact energy of approximately 1000 joules / m2 and will also exhibit a mass vapor transmission rate of at least about 2000 g / m2 / 24hr. In other embodiments, the entire backsheet will exhibit substantially zero dynamic fluid transmission when subjected to an impact energy of approximately 2000 g / m2 / 24 hr.
BRIEF DESCRIPTION OF THE DRAWINGSAlthough the description concludes with the claims pointing out in a particular way, and claiming differently to the subject matter that is considered as formant of the present invention, it is believed that the invention will be better understood from the following description, which is taken in combination with the accompanying drawings, in which similar designations are used to designate substantially identical elements, and in which: Figure 1 is a plan view of one embodiment of the disposable diaper of the present invention having cut portions for reveal the underlying structure, the inner surface of the diaper is facing the observer; Figure 1A is a simplified plan view of the disposable diaper of the present invention in its non-contracted planar condition showing the various panels or zones of the diaper; Figure 2 is a simplified illustration of an apparatus used to determine the impact value of the fluid; Figure 3 is a plan view of another embodiment of a back sheet of the diaper of the present invention; Fig. 4 is a plan view of another embodiment of a backsheet of the diaper of the present invention; and Figure 5 is a plan view of another embodiment of a back sheet of the diaper of the present invention.
DETAILED DESCRIPTION OF THE INVENTIONAs used herein, the term "absorbent article" refers to devices that absorb and contain exudates from the body, and more specifically refers to devices that are placed against or close to the user's body to absorb and contain the various exudates discharged from the body. The term "disposable" is used herein to describe absorbent articles that are not intended to be washed or otherwise restored or reused as an absorbent article (ie, they are intended to be discarded after a single use, and preferably , to be recycled, composted or otherwise disposed of in an environmentally compatible manner). A "unitary" absorbent article refers to absorbent articles that are formed of separate parts joined together to form a coordinated entity, such that they do not require separate manipulated parts such as a fastener and separate liners. A preferred embodiment of an absorbent article of the present invention,#s the unitary disposable absorbent article, diaper 20, shown in Figure 1. As used herein, the term "diaper" refers to an absorbent article generally worn by infants and incontinent persons that is worn around the user's lower torso . However, it should be understood that the present invention is also applicable to other absorbent articles such as incontinence briefs., incontinence undergarments, diaper liners and fasteners, feminine hygiene garments, training pants, fitted garments, and the like. Figure 1 is a plan view of the diaper 20 of the present invention in its flattened non-contracted state (ie, with the contraction induced by the elastic pulled outward), with parts of the structure being cut to show more clearly the construction of the diaper 20. As shown in Figure 1, the diaper 20 preferably comprises a containment assembly 22 comprising a top sheet 24.; a back sheet 26 attached to the top sheet; and an absorbent core 28 positioned between the topsheet 24 and the backsheet 26. The absorbent core 28 has a pair of opposed longitudinal edges, an inner surface and an outer surface. The diaper preferably further comprises elastic leg features 32; characteristics of elastic waist 34; and a fastening system 36, preferably comprising a pair of securing members 37 and a fastening member 38. The diaper 20 shown in Figure 1 with the part of the diaper 20 facing the wearer, the inner surface 40, facing the observer The diaper 20 is shown in theFigure for having an inner surface 40 (facing the observer in Figure 1), an outer surface 42 opposite the inner surface 40, a rear or rear waist region 44, a front waist region 46 opposite the waist region rear 44, a crotch region 48 positioned between the rear waist region 44 and the front waist region 46, and a periphery that is defined by the outer perimeter, or edges of the diaper 20, in which the lateral or longitudinal edges are designate 50 and the end edges are designated 55. The inner surface 40 of the diaper 20 comprises that part of the diaper 20 which is positioned adjacent the wearer's body during use (i.e., the inner surface 40 is generally formed by at least one part of the upper sheet 24 and other components attached to the upper sheet 24). The outer surface 42 comprises that part of the diaper 20 that is placed away from the wearer's body (i.e., the outer surface 42 is generally formed by at least a portion of the back sheet 26 and other components attached to the back sheet 26). As used herein, the term "attached" encompasses configurations by which one element is directly secured to the other element by fixing the element directly to the other element, and configurations by which the element is indirectly secured to the other element by fixing the element to a member or intermediate members which in turn are fixed to the other element. The rear waist region 44 and the waist front region 46 extend from the extreme edges 52 of the periphery to the crotch region 48. The diaper 20 also has two centerlines, a longitudinal centerline 100 and a transverse centerline 110. The term "longitudinal", as used herein, refers to a line, axis or direction in the plane of the diaper 20 that is generally aligned with (eg, approximately parallel to) a vertical plane that divides a standing user in left and right halves when the diaper 20 is used. The terms "transverse", and "lateral", as used herein, are interchangeable, and refer to a line, axis or direction that is located within the diaper plane, which is generally perpendicular to the longitudinal direction (which divides the user into front and back halves). Figure 1A shows a simplified plan view of the diaper 20 of Figure 1 depicting the various panels and their placement with respect to each other. The term "panel" is used herein to denote an area or element of the diaper. (Although a panel is typically a different area or element, a panel can match (functionally corresponds), a bit with an adjacent panel). The diaper 20 has a crotch region 48 comprising a main panel 80 and a pair of leg panels 82, a front waist region 46 comprising a central panel comprising a middle panel 86 and a waistband panel 88, and side panels 90; and a rear waist region 44 comprising a central panel comprising a middle panel 86 'and a waistband panel 88', and side panels 90 '. The main panel 80 is the part of the diaper 20 from which the other panels emanate. The absorbent core is generally placed within the main panel 80 since the exudates are typically discharged in this region of the diaper, although the absorbent core will also likely extend to the middle panels 86 and 86 '. A leg panel 82 extends generally laterally outwardly from and along each side edge 81 of the main panel 80. Each leg panel 82 generally forms at least a portion of the elastic leg feature. In the front waist region 46 the middle panel 86 of the central panel extends generally longitudinally outwardly from and along each edge 85 of the main panel 80. The waistband panel 88 extends generally longitudinally outwardly., from and along the middle panel 86. The side panels 90 each extend generally laterally outwardly from and along the central panel. In the rear waist region 44, the middle panel 86 'of the central panel extends generally longitudinally outwardly and from along the edge 85 of the main panel 80. The waistband panel 88' extends generally longitudinally outwardly. from and along the panel 86 ', the side panels 90' each extend generally laterally outwardly from and along the central panel. Referring again to Figure 1, the containment assembly 22 of the diaper 20 is shown as comprising the main body (frame) of the diaper 20. The containment assembly 22 preferably comprises a top sheet 24, a back sheet 26 and a core absorbent 28 having a pair of opposite longitudinal edges, an inner surface, an outer surface. The internal surface of the absorbent core generally faces the user's body while the external surface generally faces away from the wearer's body. When the absorbent article comprises a separate fastener and liner, the containment assembly 22 generally comprises the fastener and the liner (i.e., the containment assembly 22 comprises one or more layers of material to define the fastener, while the liner comprises an absorbent composite such as a topsheet, a backsheet, and an absorbent core). For the unitary absorbent articles, the containment assembly 22 preferably comprises the topsheet 24, the backsheet 26 and the absorbent core 28 of the diaper with other features added to form the composite structure of the diaper. Figure 1 shows a preferred embodiment of the containment assembly 22, in which the topsheet 24 and the backsheet 26 have length and width dimensions generally greater than those of the absorbent core 28. The topsheet 24 and the backsheet 26 are extend beyond the edges of the absorbent core 28, to thereby form the periphery of the diaper 20. Although the topsheet 24, the backsheet 26 and the absorbent core 28 can be assembled in a variety of well-known configurations, it is generally describe the exemplary configurations of the containment assembly in U.S. Patent No. 3,860,003 entitled "Shrinkable side portions for disposable diaper", which was issued to Kenneth Buell on January 14, 1975; U.S. Patent No. 5,151,092 entitled "Absorbent article with dynamic elastic waist feature having a predisposed elastic flexion joint", which was issued to Kenneth B. Buell et al. on September 29, 1992, each which are incorporated here by reference. In the embodiment shown in Figure 1, the backsheet 26 preferably comprises a continuous sheet or layer defining the front waist region 46, the rear waist region 44 and the crotch region 48. As used herein, the term "layer" does not necessarily limit the element to a layer of simple material in which a layer can actually comprise laminates or combinations of sheets or webs of the types of materials required. The backsheet 26 has an internal surface and an opposing external surface. The inner surface is that part of the back sheet 26 that is placed adjacent to the absorbent core. The outer surface of the back sheet 26 corresponds to the outer surface 42 of the diaper 20. Since the backsheet 26 preferably defines the front waist region 46, the rear waist region 44 and the crotch region 48, the back sheet 26 also has corresponding regions and panels as defined above (for simplicity, these regions and panels are denoted in the drawings by the same reference numbers as the corresponding diaper regions and panels as shown in Figure 1A). In the embodiment shown in Figure 1, the absorbent core is placed in the main panel 80, since the exudates are typically discharged within this region and extend to the middle panels 86 and 86 '. In the embodiment shown in Figure 1, the absorbent core does not extend to the leg panels 82, the waistband panels 88 and 88 ', or to the side panels 90 and 90'. In other embodiments, the absorbent core may extend to all or some of the leg panels 82, the waistband panels 88 and 88 ', and the side panels 90 and 90'. The backsheet 26 of the present invention is that part of the diaper 20 that is generally positioned away from the user's skin and which prevents the exudates absorbed and contained in the absorbent core 28 from wetting the articles that are in contact with the diaper. 20 such as sheets and undergarments. Therefore, the backsheet 26 is impervious to fluids (eg, urine). In addition to being impermeable to the fluid, the backsheet 26 is also breathable. For disposable diapers, it has been found that breathability is critical for performance especially in hot and humid conditions. When an absorbent article is placed on a wearer, the skin is occluded by the materials forming the absorbent article. This occlusion or obstruction of the skin, especially in hot and humid conditions, prevents evaporation and cooling resulting from the clogged area. The resulting perspiration raises the relative humidity of the air within the absorbent article, resulting in less comfort for the user and the negative benefits perceived by the caregivers. It has been found that the rate of wet vapor transmission of the backsheet is important in reducing the incidence of heat rash and other skin problems associated with high heat and humidity conditions. In order to reduce the moisture and heat formed within the disposable diaper, it has been found that at least a portion of the backsheet 26, and more preferably the entire backsheet 26, must have a mass vapor transmission rate. of at least about 2000 g / m2 / 24hr, and more preferably at least 2500 g / m2 ^ hr., and most preferably at least 3000 g / m2 / 24 hr. The backsheets of the present invention may have uniformly superior mass vapor transmission rates, for example, steam transmission rates in mass of at least 4000 g / m2 / 24 hr. or older The transmission speed of the humid steam is measured by the method established below. An amount of CACI2 is placed inside a cup having a rim. A sample material is placed over the top of the cup and held securely by a ring and retainer gasket. The assembly is then weighed and recorded as the initial weight. The assembly is placed inside a chamber at a constant temperature (40 ° C) and humidity (75% RH) for 5 hours. The assembly is then removed from the chamber and allowed to reach equilibrium for at least 30 minutes at the ambient temperature where the balance is located. The assembly is then weighed and recorded as the final weight. The mass vapor transmission rate (MVTR) is calculated and expressed in g / m2 / 24 hr., Using the following formula:MVTR = (that final - initial weight) x 24.0 Sample area in meters x 5.0 (time inside the camera)Conventional diapers have tried to use breathable materials to reduce moisture inside the vapor. However, it has been found that these materials have not been sufficiently impervious to the fluid when subjected to normal conditions of use, for example, mechanical impact from a sitting baby. The ability of a fluid to be forced through these materials during normal conditions of use results in current respirable products that exhibit unwanted transmission of urine waste through the backsheet. Therefore, it would be desirable to provide a backsheet for use in a disposable absorbent article such as a disposable diaper, which is not only breathable, that is, exhibits an MVTR of at least 2000 g / m2 / 24 hr., it also exhibits substantially zero dynamic fluid transmission when subjected to normal conditions of use, such as when a baby sits. As used herein, "substantially zero dynamic fluid transmission" includes any measured value less than 0.5 g / m2 when a material is subjected to the dynamic fluid impact test method set forth below. The dynamic fluid impact test method below is designed for the energy per area that a baby imparts to a back sheet of the diaper, when it abruptly goes from a standing position to a sitting position. Although other common movements and activities of the baby (for example, rolling on the floor), can also cause leaks by transmitting the edge through the back sheet of the diaper, the sitting action provides a clear mechanical interaction that can be analyzed to gain an quantitative understanding of the actual impact energies involved in the typical conditions of diaper use. The dynamic fluid impact test method uses the apparatus 100 shown in Figure 2. The absorption material 102 weighed to the nearest 0.0001 grams is placed directly on top of the energy absorbing impact pad 103. For this purpose the absorption material 102 may comprise a filter paper No. 2 available from Whatman Laboratory Division, distributed by VWR Scientific of Cleveland OH. The absorption material must be capable of absorbing and retaining simulated urine that passes through the backsheet material that is tested. The energy absorbing impact pad 103 is a cross-linked rubber foam filled with carbon black. The impact pad of 5 inches per square inch has a density of 0.1132 gm / cm3 and a thickness of 0.3125 inches. The impact pad 103 has a Durometer value of A / 30/15 in accordance with ASTM 2240-91. A circular absorbent core material 104 measuring 0.0635 meters in diameter is weighed. For this purpose, the absorbent core material may comprise individualized, cross-linked wood pulp cellulosic fibers, as described in U.S. Patent No. 5,137,537 issued to Herron et al. On August 11,1992. The absorbent core has a basis weight of approximately 228 g / m2. The absorbent core material is then loaded with simulated urine at approximately 10 times its dry weight. This represents an absorbent core sufficiently charged with urine. The absorbent core material must be capable of retaining a sufficient amount of simulated urine, for example, at least about 10 times its dry weight. Accordingly, other absorbent core materials, currently used in commercial diapers as the absorbent core material, can also be used. The simulated urine may comprise distilled water. A section of the material of the back sheet 105 being tested is placed face down with the surface external on a clean and dry cover. The loaded core material 104 is placed directly in the center of the backsheet material 105. The backsheet / core arrangement is then secured to the impact part 107 of the impact arm 108 with a rubber band 109. The arrangement of backsheet / core is positioned in such a manner that the core 104 is adjacent to the inner surface 102 of the impact portion 107. The impact arm 108 is raised to a desired impact angle to provide the desired impact energy. The impact arm 108 is then dropped and a stop watch is activated on impact. Then the arm rests on the filter paper 110 for 10 seconds. The impact arm 108 is then raised and the filter paper 102 is removed and placed on a digital ruler. The mass of the moist filter paper is then registered at the three minute mark. The dynamic fluid transmission value (DFTV) is calculated and expressed in g / m2 using the following formula:DFTV = wet filter paper mass (grams) - mass of dry filter paper (grams) Impact area (m2)The impact area, expressed in m2, is the area of the lower surface 110 of the impact portion 107, the impact area is 0.00317 m2. The material of the absorbent core 104 should have a slightly larger area than that of the impact area of the surface 110. In addition to exhibiting a mass vapor transmission rate of at least about 2000 g / m2 / 24 hr, suitable materials for the backsheet they will also exhibit substantially zero dynamic fluid transmission when subjected to an impact energy of approximately 1000 joules / m2. Preferably, the backsheets of the present invention while exhibiting a mass transmission rate of at least 2000 g / m2 / 24 hr., Will also exhibit substantially zero dynamic fluid transmission when subjected to impact energies of approximately 2000 joules / m2, of approximately 3000 joules / ñn, and approximately 4000 joules / m. The backsheets of the present invention can exhibit substantially zero dynamic fluid transmission when subjected to higher impact energy, for example, impact energies of at least about 5000 joules / m2 or greater. Suitable backsheet materials that exhibit substantially zero dynamic fluid transmission, when subjected to an impact energy of approximately 1000 joules / m2 and also exhibit a mass vapor transmission rate of at least 2000 joules / m2, include a single-layer monolithic film capable of passing sufficient wet steam such as a polyester-based film or may comprise two or more layers such as a polyester-based film extrusion coated onto a non-woven web. The following materials were subjected to the mass vapor transmission rate test and the dynamic fluid impact test described above. Sample A- Exxon Exxair XFB-100W available from Exxon Chemical Company of Buffalo Grove, IL. Sample B- DuPont Hytrel Film Mix # P18-3097 available from Clopay Corporation, Cincinnati, OH. Sample C- DuPont Hytrel Film Mix # P18-3096 available from Clopay Corporation, Cincinnati, OH. Sample D - Breathable test film supplied by Minnesota Mining and Manufacturing Company of Minneapolis-Saint Paul, MN. The results of the mass vapor transmission rate test and the dynamic fluid impact test are established in Table 1. Table 1 Mass vapor transmission rate (MVTR) and Dynamic fluid transmission value (DFTV) Sample MVTR in g / m2 / 24hr DFTV in g / m2 At 100 joules / m2 A 5157 3.96 B 2400 0.28 C 3860 0.40 D 5242 1.22 As can be seen from Table 1, samples of B and C exhibited fluid transmission substantially nil dynamic when subjected to an impact energy of 1000 joules / m2 'and also exhibited a mass vapor transmission rate of at least 2000 joules / m2. Samples B and C would therefore be suitable for use as a backsheet, in a disposable diaper since these would be resipirable and sufficiently impervious to fluid when subjected to normal conditions of use. Samples A and B were sufficiently respirable (that is, they had mass vapor transmission rates of at least 2000 g / m2 / 24 hr), however, they exhibited an unacceptable degree of dynamic fluid transmission when subjected to an impact energy of 1000 joules / m2. Additionally, suitable materials of the backsheet would be those that exhibit substantially zero dynamic fluid transmission when subjected to an impact energy of approximately 2000 g / m2 / 24 hr., And also exhibit a mass vapor transmission rate of at least 2000 g / m2 / 24hr through the spatial separation of these key properties within the structure of the back sheet. For example, selectively perforated or perforated backsheets can be used if the orifice portions have a mass vapor transmission rate of at least about 2000 g / m2 / 24 hr and also exhibit substantially zero dynamic fluid transmission when subjected at an impact energy of approximately 1000 joules / m2. The backsheet 26 is preferably positioned adjacent the outer surface of the absorbent core 28 and is preferably attached thereto by any suitable joining means known in the art. For example, the backsheet 26 can be secured to the absorbent core 28 by a continuous uniform adhesive layer, a patterned adhesive layer, or an array of spiral lines or separate adhesive spots, the adhesives that have been found to be satisfactory are manufactured by HB Fuller Company of ST. Paul, Minnesota and they market as HL-1258. An example of a suitable attachment means comprising an open-pattern network of filaments of adhesive is described in U.S. Patent No. 4,573,986 entitled "Disposable Garment Containment", which was issued to Minetola et al. March 4, 1986. Another suitable joining means comprising several lines of adhesive filaments twisted in a spiral pattern is illustrated by the apparatus and methods shown in United States Patent No. 3,911,173 issued to Sprague, Jr. on October 7, 1975; U.S. Patent No. 4,785,996 issued to Ziecker et al. on November 22, 1978; and U.S. Patent No. 4,842,666 issued to Werenicz on June 27, 1989. Each of these patents is incorporated herein by reference. Alternatively, the joining means may comprise heat bonds, pressure joints, ultrasonic joints, mechanical dynamic joints, or any other suitable joining means or combinations of these joining means as are known in the art. Also contemplated are embodiments of the present invention wherein the absorbent core is not attached to the backsheet 26, and / or to the topsheet 24, in order to provide greater extensibility in the front waist region 46 and in the region of back waist 44. Absorbent core 28 can be any absorbent means that is generally compressible, conformable, non-irritating to the wearer's skin, and capable of absorbing and retaining fluids such as urine and other certain exudates from the body. As shown in Figure 1, the absorbent core 28 has a side facing the garment, a side facing the body, a pair of side edges, and a pair of waist edges. The absorbent core 28 can be manufactured in a wide variety of sizes and shapes (eg, rectangular, hourglass, T-shaped, asymmetric, etc.), and from a wide variety of commonly used fluid-absorbing materials in absorbent diapers and other absorbent articles, such as crushed wood pulp which is generally referred to as an air filter. Examples of other suitable absorbent materials include accreted cellulose wadding; polymers exempted by melting and blowing including coform; chemically hardened, modified and cross-linked cellulosic fibers, tissue, including tissue envelopes, and tissue laminates; absorbent foams; absorbent sponges; superabsorbent polymers; absorbent gelling materials; or any equivalent material or combinations of materials. The configuration and construction of the absorbent core 28 can be varied (e.g., the absorbent core can have varying gauge zones, a hydrophilic gradient, a superabsorbent gradient, or acquisition zones of lower average density and lower average basis weight, or may comprise or more layers or structures).
In addition, the size and absorbent capacity of the absorbent core 28 can also be varied to encompass users ranging from babies to adults. However, the total absorbent capacity of the absorbent core 28 must be compatible with the design load and intended use of the diaper 20. One embodiment of the diaper 20 has a modified, asymmetric, T-shaped absorbent core 28 that has ears in the region. of front waist but a generally rectangular shape in the rear waist region. Exemplary absorbent structures for use as the absorbent core 28 of the present invention which have achieved wide acceptance and commercial success are described in U.S. Patent No. 4,610,678 entitled "High Density Absorbing Structures", issued to Weisman et al. September 9, 1986; U.S. Patent No. 4,673,402 entitled "Absorbent articles with double layer cores", issued to Weisman et al. on June 16, 1987; U.S. Patent No. 4,88,231 entitled "Absorbent core having a dust-off layer", issued to Angstadt on December 19, 1989; and U.S. Patent No. 4,834,735 entitled "High density absorbent members having acquisition zones of lower density and lower basis weight", issued to Alemany et al. on May 30, 1989. The absorbent core may further comprise the system dual core containing a core of acquisition / distribution of chemically hardened fibers placed on an absorbent storage core as detailed in U.S. Patent No. 5,234,423 entitled "Absorbing article with characteristic elastic waist and increased absorbency", issued to Alemany et al. on August 10, 1993; and in U.S. Patent No. 5,147,345, "High Efficiency Absorbent Handling Articles for Incontinence Management," issued to Young, La Von, and Taylor on September 15, 1992. All of these patents are incorporated herein by reference. The topsheet 24 is preferably positioned adjacent the inner surface of the absorbent core 28 and is preferably attached to it and to the backsheet 26 by attachment means (not shown), such as those well known in the art). The attachment means are described with respect to the attachment of the backsheet 26 to the absorbent core 28. In a preferred embodiment of the present invention, the topsheet 24 and the backsheet 26 are directly bonded together at the periphery of the diaper and they are indirectly joined together by joining them directly to the absorbent core 28 by means of a suitable joining means. The topsheet 24 is preferably docile, gentle in feel and non-irritating to the wearer's skin, in addition, the topsheet 24 is preferably fluid permeable allowing the fluids, (eg, urine) to easily penetrate through its thickness. A suitable top sheet 24 can be manufactured from a wide range of materials such as woven and nonwoven materials; polymeric materials such as thermoplastic films formed with openings, plastic films with openings, and hydroformed thermoplastic films; porous foams; cross-linked foams; crosslinked thermoplastic films; and thermoplastic canvases. Suitable woven and nonwoven materials may be composed of natural fibers (eg, wood or cotton fibers), synthetic fibers (eg, polymeric fibers such as polyester fibers, polypropylene to polyethylene), or a combination thereof. natural and synthetic fibers. The topsheet 24 is preferably made of a hydrophobic material to isolate the wearer's skin from the fluids that have passed through the topsheet 24 and which are contained within the absorbent core 28 (ie, to prevent rewetting). If the top sheet 24 is made of a hydrophobic material, at least the surface The top sheet 24 is treated to be hydrophilic in such a way that the fluids will transfer through the top sheet more quickly. This decreases the likelihood that the body exudates will flow out of the topsheet 24 instead of being drawn through the topsheet 24 and absorbed by the absorbent core 28 .. the topsheet 24 can be made hydrophilic by treating it with an agent surfactant. Suitable methods for treating the topsheet 24 with a surfactant include spraying the top sheet material 24 with a surfactant and immersing the material within the surfactant. A more detailed discussion of this treatment and hydrophilic capacity is contained in United States Patent No. 4, 988, 344 entitled "Absorbent articles with multi-layer absorbent layers", issued to Reising et al. On January 29, 1991 and U.S. Patent No. 4,988,345 entitled "Absorbent articles with rapidly-absorbing absorbent cores", issued to Reising et al. January 29, 1991, each of which is incorporated herein by reference. A preferred alternate top sheet comprises a film formed with openings. Films formed with openings are preferred for the topsheet because they are permeable to body exudates not yet absorbent and have a reduced tendency to allow the fluids to pass back through and rewet the user's skin. In this way, the surface of the formed film that is in contact with the body remains dry, thus reducing the staining of the body and creating a more comfortable feeling for the user. Suitable formed films are described in U.S. Patent No. 3,929,135 entitled "Absorbent structures having capillary & amp;; tapered ", which was issued to Thompson on December 30, 1975;No. 4,324,246"Disposable absorbent article having a stain resistant top sheet", which was issued to Mullane et al. On April 13, 1982; U.S. Patent No. 4,342,314 entitled "Elastic plastic weft exhibiting properties in the form of fiber", which was issued to Radel et al. on August 3, 1982; U.S. Patent No. 4,463,045 entitled "Microscopic-expanded three-dimensional plastic screen exhibiting a non-glossy visible surface and a cloth-like impression similar to the fabric", which was issued to Ahr et al. on July 31, 1984; and in U.S. Patent No. 5,006,394"Multilayer Polymer Film", issued to Baird on April 9, 1991. Each of these patents is incorporated herein by reference. It may also be desirable to provide the disposable article of the present invention with expandability or resiliency in all or a portion of the side panels 90. (As used herein, the term "extensible" refers to materials that are able to extend in at least one direction to a certain degree without undue rupture.The terms elasticity and "elastically extensible" refer to extensible materials that have the ability to return to approximately their original dimensions after the force is removed Extending the material As used herein, any material or element described as "extensible" may also be elastically extensible unless otherwise provided). The extendable side panels 90 provide a more comfortable and contour fit by initially comfortably fitting the diaper to the wearer and maintaining this fit throughout the time of use even after the diaper has been loaded with the exudates, since the side panels they will allow them to expand and contract the sides of the diaper. The extensible side panels 90, further provide the most effective application of the diaper 20, since even if the people who place the diaper pulls a side diaper 30 more than the other one during the application (asymmetrically), the diaper 20" self-adjust ", during use. Although the extendable side panels 90 may be constructed in a number of configurations, examples of diapers with extendable side panels are disclosed in U.S. Patent No. 4,857,067 entitled "Disposable diaper having gathered ears", issued to Wood et al. August 15, 1989, United States Patent No. 4,381,781 issued to Sciaraffa, and others on May 3, 1983; U.S. Patent No. 4,938,753 issued to Van Gompel, and others on July 3, 1990; and U.S. Patent No. 5,151,092 issued to Buell et al. on September 29, 1992; each of which are incorporated herein by reference. Extendable side panels, or any other element of the diaper 20 in which stretch or stretch capacity such as waistbands are desirable, may comprise materials that have been "pre-ribbed", or "pre-stretched" mechanics, (i.e. said, subject to a degree of mechanical stretching of localized pattern to permanently lengthen the material), or frames in the form of structural elastic as described in United States Patent No. 5,1518,801 issued to Chappell and others on the 21st. May 1986. The materials may be pre-stretched using deep enhment techniques as are known in the art. Alternatively, the materials may be pre-stretched, directing the material through an incremental mechanical stretching system as described in U.S. Patent No. 5,330,458 issued to Buell et al. On July 19, 1994. materials are then allowed to return to their substantially unstressed condition, thus forming a stretch material with zero tension that is extensible, at least up to the point of the initial stretch. Examples of zero stress materials are disclosed in U.S. Patent No. 2,075,189 issued to Galligan on March 30, 1937; U.S. Patent No. 3,025,199 issued to Harwood on March 13, 1962; United States Patent No. 4,107,364 and 4,209,563, issued to Sisson on August 15, 1978 and June 24,1980, respectively; U.S. Patent No. 4,834,741 issued to Sabee on May 30, 1989; and U.S. Patent No. 5,151,092 issued to Buell et al. on September 29, 1992. All of the above-referenced patents are hereby incorporated by reference. The diaper 20 preferably further comprises elastic leg features 32 to provide improved containment of the fluids of other body exudates. Each elastic leg feature 32 may comprise several different embodiments to reduce leakage of body exudates in body exudates in leg panels 82 (the elastic leg feature may be and is sometimes also referred to as leg bands, side flaps , barrier folds or elastic folds). U.S. Patent No. 3,860,003 discloses a disposable diaper that provides a collapsible leg opening having a side flap and one or more elastic members to provide the elasticized leg fold (packing fold). U.S. Patent No. 4,909,803 entitled "Disposable Absorbent Article Having Elasticized Fins", issued to Aziz et al. On March 20, 1990, discloses a disposable diaper having "upright" elastified fins (bar folds) for improve containment of the leg regions, U.S. Patent No. 4,695,278, entitled "Absorbent Article Having Double Folds" issued to Lawson on September 22, 1987, and U.S. Patent No. 4,795,454, entitled "Absorbent article having double folds resistant to leakage", issued toDragoo on January 3, 1989, describes a disposable diaper that has double folds that include a gusset fold and a barrier fold. U.S. Patent No. 4,704,115 entitled "Disposable waste containment garment", issued to Buell on November 3, 1987"discloses a disposable diaper or an incontinence garment having sidewall leak protection channels. configured to contain the free fluids inside the garment. Each of these patents is incorporated herein by reference. Although each elastic leg feature 32 can be configured to be similar to any of the leg bands, side flaps, barrier folds or elastic folds described above, it is preferred that each elastic leg feature 32 comprises at least one fold internal barrier comprising a barrier fin and a separation element as described in U.S. Patent No. 4,695,278. In a preferred embodiment, the elastic leg feature 32 further comprises an elastic packing gusset 63 with one or more elastic threads 65, positioned outwardly of the barrier fold as described in the aforementioned United States Patent No. 4,695,278 . The diaper 20 preferably further comprises an elastic waist feature 34 which provides for improved fit and containment. The elastic waist feature 34 is that part or area of the diaper 20 that is intended to expand and contract elastically to dynamically adjust to the wearer's waist, the elastic waist feature 34 preferably extends longitudinally outward from at least one of the waist edges of the absorbent core 28, and generally forms at least a portion of the end edge of the diaper 20. Disposable diapers are generally constructed to have two elasticated waistbands, one placed in the posterior waist region and the other placed in the frontal waist region, although you can build diapers with a single elastic waistband. Further, although the elastic waist feature 34 or any of its constituent elements may comprise a separate element secured to the diaper 20, the elastic waist feature 34 may be constructed as an extension of other diaper elements such as the back sheet 26 or the top sheet24, preferably both of the topsheet 24 and the backsheet 26. Modalities are also contemplated wherein the elastic waist feature 34 comprises openings, as described above, to provide breathability in the waist regions. The elastic waist feature 34 can be constructed in a number of different configurations including those described in the United States patent.
No. 4,515,595 entitled "Disposable Diapers with Elastic Backfronts B", issued to Kievit et al. On May 7, 1985, and the previously referenced United States Patent No. 5,151,092 issued to Buell, each of these references being incorporated herein by reference The diaper 20 also comprises a fastening system 36 which forms a lateral closure which maintains the posterior waist region 44 and the waist front region 46 in an overlapping configuration such that lateral stresses are maintained around the circumference of the waist. diaper to maintain the diaper on the wearer, exemplary fastening systems are disclosed in U.S. Patent No. 3,848,594 issued to Buell on November 19, 1974; U.S. Patent No. 4,662,875 issued to Hirotsu and Robertson May 5, 1987; United States Patent No. 4,869,724 issued to Scripps on September 26, 1989; United States Patent; two No. 4,846,815, issued to Scripps on July 11, 1989; U.S. Patent No. 4,894,060, issued to Nestegard on January 16, 1990; U.S. Patent No. 4,946,527, issued to Battrell on August 7, 1990; and U.S. Patent No. 5,326,612 entitled "Non-woven female component for restrainable fastening device and method for making same", issued to David J.K. Goulait on July 5, 1994. Each of these patents are incorporated herein by reference. Figure 3 shows a plan view of an alternative embodiment of the backsheet of the diaper of the present invention, with the part of the backsheet positioned adjacent to the absorbent core facing the viewer. As shown in Figure 3, backsheet 226 comprises two layers 250 and 252. Layers 250 and 252 can be secured together by any suitable joining means known in the art. In this embodiment, layer 250 forms the outer surface of the diaper and layer 252 is placed adjacent to the absorbent core. Since the layer 250 is that part of the backsheet 226 that contacts the user's skin, the layer 250 is preferably smooth and comprises a non-woven web. In addition to being soft, layer 250 is preferably breathable. The layer 250 preferably exhibits a mass vapor transmission rate of at least about 2000 g / m2 / 24hr, more preferably at least about 2500 g / m2 / 24hr, and most preferably at least about3000 g / m2 / 24hr. The layer 250 may have a higher mass vapor transmission rate, for example, the mass vapor transmission rate of at least about 4000 g / m2 / 24 hr., Or greater. Since the layer 250 does not need to prevent leakage of the exudates absorbed and contained within the absorbent core, the selection of the materials that provide the desired softness and breathability is very sparse.
Suitable materials include, but are not limited to, nonwoven webs such as spunbonded webs, meltblown extrudate webs, carded webs and the like. The non-woven webs for the layers 250 may comprise synthetic fibers, natural fibers, multi-component fibers such as bicomponent fibers, or mixtures thereof. The layer 252 is the part of the back sheet 226 that will prevent the exudates absorbed and contained in the absorbent core from moistening the articles that come into contact with the diaper. In order to protect the wearer against unwanted leaks from the absorbed exudates and contained within the absorbent core, the layer 252 must have larger dimensions of width and length than those of the absorbent core. If the layer252 is not large enough, the exudates absorbed and contained in the absorbent core can find their way through the outer layer 250 during normal conditions of use. In the embodiment shown in Figure 3, the absorbent core is preferably placed on the main panel 80 and extends toward the middle panels 86 and 86 '. Accordingly, the layer 252 is placed within the main panel 80 and extends towards the middle panels 86 and 86 '. The layer 252 has length and width dimensions at least as large as those of the absorbent core, and preferably larger than the absorbent core. If desired, the layer 252 may extend beyond the main panel 80 and the middle panels 86 and 86 'to the leg panels 82, the waistband panels 88 and 88', and the side panels 90 and 90 '. In addition, the layer 252 may extend laterally and longitudinally outwardly from the main panel 80 to form part of the periphery of the disposable diaper. Although the layer 250 provides a substantial amount of breathability for the diaper, the layer 252 is also breathable providing additional comfort for the wearer, as noted above, it has been found that breathability is critical for diaper performance. For this purpose, layer 252 must substantially exhibit zero dynamic fluid transmission when subjected to an impact energy of approximately 1000 joules / m2, and exhibit a mass vapor transmission rate of at least about 20,900 g / m2 / 24 hr. Preferably, layer 252 while exhibiting a mass vapor transmission rate of at least about 2000 g / m2 / 24 hr. it will also exhibit substantially zero dynamic fluid transmission when subjected to impact energies of approximately 2000 joules / m2, approximately 3000 joules / m2, and approximately 4000 joules / m. The innermost layer 252 can exhibit substantially zero dynamic fluid transmission when subjected to still higher impact energies, for example impact energies of approximately 5000 joules / m2 or greater. In an alternate embodiment, shown in Figure 4, layer 250 is preferably positioned adjacent to the absorbent core. Figure 4 shows a plan view of the rear sheet of the diaper 226 with the part of the back sheet placed adjacent to the absorbent core facing the viewer. In this embodiment, the layers 250 and 252 together form the outer surface of the diaper. The layer 252 is the part of the back sheet 226 that will prevent the exudates absorbed and contained within the absorbent core from moistening the articles that are in contact with the diaper. In order to provide additional comfort for the user, layer 252 is preferably breathable. For this purpose, layer 252 must exhibit substantially zero dynamic fluid transmission when subjected to an impact energy of approximately 1000 joules / m2 and a mass vapor transmission rate of at least approximately 2000 g / m2 / 24 hr. . Preferably layer 252, although exhibiting a mass vapor transmission rate of at least 2000 g / m2 / 24 hr, will also exhibit substantially zero dynamic bonding fluid transmission when subjected to impact energies of approximately 2000 joules / m2, about 3000 joules / m and about 4000 joules / m2. The outermost layer 252 may exhibit substantially zero dynamic fluid transmission when it is still subjected to higher impact energies, for example, impact energies of at least about 5000 joules / m2 or greater. In order to protect the user against unwanted leaks, the layer 252 must have dimensions of width and length greater than those of the absorbent core. If the layer 252 is not large enough, the exudates absorbed and contained in the absorbent core can be forced through the non-woven layer 250 during normal conditions of use. Thus, layer 252 must at least have length and width dimensions greater than those of the absorbent core and may be desired to form parts of the side edges and end edges of the diaper. In an alternate embodiment, a breathable back sheet of suitable nonwoven / film laminate may be made, such that a portion of the backsheet, (the portion directly behind the absorbent core), contains the portion impervious to the non-respirable fluid, while the outer or lateral portions of the backsheet, (parts of the backsheet extending beyond the absorbent core), contain the respirable portion. In this embodiment, shown in Figure 5 with the part of the backsheet 226 positioned adjacent the absorbent core that faces the observer the layer 250 forms the outer surface of the diaper and the layer 252 is positioned adjacent to the absorbent core. Since the layer 250 is that part of the backsheet 226 that will come into contact with the user's skin, the layer 250 is preferably smooth and comprises a non-woven web. In addition to being soft, layer 250 is also breathable and preferably exhibits a mass vapor transmission rate of at least about 2000 g / m2 / 24 hr., More preferably at least about 2500 g / m2 / 24 hr., and very preferably by I or less approximately 3000 g / m2 / 24hr. Layer 250 may have a higher mass transfer rate, for example, mass vapor transmission rate of at least about 4000 g / m2 / 24 hr or greater. The layer 252 is the part of the back sheet 26 that will prevent the exudates absorbed and contained in the absorbent core from moistening the articles that are in contact with the diaper. Layer 252 need not be breathable, since this function is provided by layer 252. For this purpose, layer 252 must exhibit substantially zero dynamic fluid transmission when subjected to an impact energy of approximately 1000 joules / m2. Preferably, layer 252 will also exhibit substantially zero dynamic fluid transmission when subjected to impact energies of approximately 2000 joules / m2, approximately 3000 joules / m2, and approximately 4000 joules / m2. The innermost layer 252 may exhibit substantially zero dynamic fluid transmission when subjected to higher impact energy, for example at impact energies of at least about 5000 joules / m2 or greater. Although particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications may be made without departing from the spirit and scope of the invention. Therefore, attempts are made to protect all these changes and modifications within the scope of the invention in the appended claims.