WO2001017475A1

WO2001017475A1 - Embossed liner for absorbent article

Info

Publication number: WO2001017475A1
Application number: PCT/US2000/022186
Authority: WO
Inventors: Jaime Braverman; Mir Inayeth Alikhan; David George Crowther; Michael Allen Daley; Emmanuelle Cecile Damay; Eric Mitchell Johns; Jack Nelson Lindon; Susan Carol Paul; David Charles Potts; Philip Anthony Sasse; Eugenio Go Varona
Original assignee: Kimberly-Clark Worldwide, Inc.
Priority date: 1999-09-07
Filing date: 2000-08-14
Publication date: 2001-03-15
Also published as: JP2003508156A; CN1372451A; CN1212819C; MXPA02002447A; AU777296B2; ZA200201004B; AU6904400A; EP1227778A1; KR20020025254A; BR0013678A

Abstract

There is provided a liner for personal care products having at least two layers in face-to-face relation to one another and having at least one concave embossed feature, and preferably an array of such features. These concave features may have different confi gurations such as squares, diamonds, circles or artistic designs. In order to obtain the maximum benefit, however, they should have the necessary depth and distance between each other to allow fluid absorption and at the same time create a physical barrier for the fluid to reduce its spreading. The liner may be made of a combination of a top sheet material, surge layer, and absorbent core embossed together.

Description

EMBOSSED LINER FOR ABSORBENT ARTICLES

FIELD OF THE INVENTION

The invention is related to absorbent personal care products. More particularly, it concerns an absorbent system for disposable articles such as feminine care napkins, diapers and training pants, wound care dressings and bandages, and adult incontinence products, having a liner with modified surface characteristics to improve performance.

BACKGROUND OF THE INVENTION

Disposable products generally have a structure including a top sheet material (also referred to as a cover sheet) an absorbent core and a fluid repellent backing sheet. Some may also have a surge layer or other specialized layers between the top sheet and absorbent core. The structure referred to herein as a "liner" is a combination of at least a first layer (top sheet) and a second layer (surge layer) which are in face-to-face relation.

The function of the top sheet material, since it is the layer in contact with the user's body, is to provide the necessary softness for the user's comfort while wearing the product but, more importantly, it should have the structural characteristics to allow rapid absorbency of the fluids from the user's body. Fast absorbency is important to reduce the possibility of fluid spreading outside the absorbent material periphery and into the wearer's garments, causing undesirable leakage or staining. The absorbent material has the function of desorbing the fluid from the top sheet, preferably distributing it through the absorbent material's length, width and thickness, and retaining it. Top sheet materials are often made from nonwoven fabrics or apertured films. Apertured films can be made by mechanically aperturing a film top sheet with the use of a pattern roll and an anvil roil as described in US Patent 5,536,555 to Zelazoski et al. and US Patent 5,704,101 to Majors, et al. Another material used in this kind of application can be found in US Patent 4,342,314 assigned to the Procter & Gamble Company, in which a vacuum apertured film is described.

A surge layer is most typically interposed between and in intimate, liquid communicating contact with the top sheet and another layer such as a distribution or retention layer. The surge layer is usually adjacent the inner (away from a wearer) surface of the top sheet. It is usually desirable to attach the upper and/or lower surfaces of the surge layer to the top sheet and next layer, respectively, in order to further enhance liquid transfer.

The absorbent cores used in hygienic personal care products are generally made from pulp fibers or pulp fibers mixed with superabsorbent particles. These structures may include binder fibers for integrity as well. The difficult challenge in the design of products to absorb the typical fluids insulted to hygienic products such as feminine care products and infant care products is well known in the industry. In the case of infant care products, the concern is to absorb urine and fecal (BM) discharges, while feminine care products are mainly concerned with menstrual fluids to be absorbed. Due to the differences in viscosity, density and composition of each fluid, each type of personal care product presents a different and complex challenge for the product designer in optimizing the absorption characteristics of each material used in the final product.

One common thread in all of the product designs is that each of them should have the ability to absorb fluid fast, without allowing it to spread outside the absorbent periphery while at the same time keeping the fluid far away from the top sheet and the user's body to reduce the wet sensation and possible skin irritations that a wet top sheet can produce. For these reasons, the structure of any product should to be developed in such a way that each component works well with the others to optimize their use. This means that the absorbent core should have the ability to desorb the top sheet material at a fast rate while having the capability of distributing and retaining the fluid.

A number of patents exist which attempt to address the needed balance between softness and fluid absorption. US Patent 4,323,068 to Aziz, for example, which describes a top sheet material with elevated bosses to isolate the surfaces from the user's body, thereby improving dryness. US Patent 4,041 ,951 to Sanford discloses a top sheet material that contains a multiplicity of depressed areas to isolate the wearer's skin from the moisture of the absorbent. As taught in US Patent 4,323,068, however, the '951 invention has the disadvantage of not having the necessary structural integrity to maintain the material bosses after pressure is applied. U.S Patent 3,934,588 to Mesek describes a nonwoven top sheet made of long and short fibers that provide thinned areas to act as preferential passageways for the fluid absorption. U.S Patent 5,695,595 to Van Hout et al. teaches a process of forming a material with a plurality of thinned regions made in the shape of protrusions that permit the permeation of steam and water vapors. US Patent 4,741 ,941 to Englebert et al. describes a nonwoven web with hollow projections that can be designed to provide the proper structure characteristics to allow fast intake time. All of the references described above show the necessity of modifying the top sheet structure to provide separation of the user's body and the disposable article while providing the necessary absorption for fast fluid transfer to the absorbent core.

There remains a need, however, for a liner for personal care products that will absorb fluid in designated regions and will be capable of retaining its integrity during pressure loads while also keeping its absorbency characteristics. It is an object of this invention to provide a novel structure that enhances the fluid absorption characteristics of highly viscoelastic fluids such as menses or feces (BM) and that also retains its integrity under pressure conditions.

SUMMARY OF THE INVENTION

The objects of the invention are achieved by a liner that will enhance the absorption characteristics of a porous material by modifying its surface. The ideal personal care product would be one that could absorb fluid as fast as it was delivered to the product, without allowing it to spread outside the absorbent periphery. Due to differences in the fluid characteristics observed between insults, however, the election and design of the materials used in a personal care product are quite complicated. The invention described herein, therefore, addresses the fluid absorption characteristics of an absorbent system capable of retaining the fluid and reducing likelihood of leakage while also improving its absorbency characteristics using surface modifications.

The surface modification to absorb viscous fluids, as, for example, menses, urine and BM, is at least one concave feature that is embossed onto a composite structure, although an array of such features is preferred. The composite structure, referred to herein as a liner, is a composite of at least a first layer (top sheet) and a second layer (surge layer) which are in face-to-face relation. A third layer, an absorbent layer, may optionally be present. Any of these elements may have more than one layer. The embossing of concave features on structures made of a top sheet and surge layer alone has shown the best results and is therefore preferred. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows an example of the array of concave features of the liner of the invention Figure 2 shows another example of the array of concave features of the liner of the invention

Figure 3 shows a cross sectional view of a two layer composite with the concave features

Figures 4- 10 show examples of a feminine hygiene product with concave features located in various configurations on the product.

Figure 1 1 shows a three-layer embodiment having concave features.

Figure 12 is a schematic diagram of a rate block apparatus suitable for use in determining fluid intake time of a material or material system.

DEFINITIONS

"Disposable" includes being disposed of after a single use and not intended to be washed and reused.

As used herein and in the claims, the term "comprising" is inclusive or open-ended and does not exclude additional unrecited elements, compositional components, or method steps.

As used herein the term "nonwoven fabric or web" means a web having a structure of individual fibers or threads which are interlaid, but not in an identifiable manner as in a knitted fabric. Nonwoven fabrics or webs have been formed from many processes such as for example, meltblowing processes, spunbonding processes, and bonded carded web processes The basis weight of nonwoven fabrics is usually expressed in ounces of material per square yard (osy) or grams per square meter (gsm) and the fiber diameters useful are usually expressed in microns (Note that to convert from osy to gsm, multiply osy by 33 91) "Spunbonded fibers" refers to small diameter fibers that are formed by extruding 5 molten thermoplastic material as filaments from a plurality of fine capillaries of a spinneret Such a process is disclosed in, for example, US Patent 4,340,563 to Appel et al , and US Patent 3,692,618 to Dorschner et al , US Patent 3,802,817 to Matsuki et al , US Patents 3,338,992 and 3,341 ,394 to Kinney, US Patent 3,502,763 to Hartman, and US Patent 3,542,615 to Dobo et al The fibers may also have shapes such as those described in US l o Patents 5,277,976 to Hogle et al , US Patent 5,466,410 to Hills and 5,069,970 and 5,057,368 to Largman et al , which describe fibers with unconventional shapes

"Conjugate fibers" refers to fibers which have been formed from at least two polymers arranged in substantially constantly positioned distinct zones across the cross- section of the fibers and which extend continuously along the length of the fibers Conjugate

15 fibers are taught in US Patent 5,108,820 to Kaneko et al , US Patent 5,336,552 to Strack et al , and US Patent 5,382,400 to Pike et al

"Bonded carded web" refers to webs that are made from staple fibers which are sent through a combing or carding unit, which separates or breaks apart and aligns the staple fibers in the machine direction to form a generally machine direction-oriented

20 fibrous nonwoven web Such fibers are usually purchased in bales, which are placed in an opener/blender, or picker, which separates the fibers prior to the carding unit Once the web is formed, it then is bonded by one or more of several known bonding methods One such bonding method is powder bonding, wherein a powdered adhesive is distributed through the web and then activated, usually by heating the web and adhesive with hot air Another suitable bonding method is pattern bonding, wherein heated calender rolls or ultrasonic bonding equipment are used to bond the fibers together, usually in a localized bond pattern, though the web can be bonded across its entire surface if so desired. One example of a pattern is the Hansen Pennings or "HP" pattern with about a 30% bond area with about 200 bonds/square inch as taught in U.S. Patent 3,855,046 to Hansen and Pennings. The HP pattern has square point or pin bonding areas wherein each pin has a side dimension of 0.038 inches (0.965 mm), a spacing of 0.070 inches (1.778 mm) between pins, and a depth of bonding of 0.023 inches (0.584 mm). The resulting pattern has a bonded area of about 29.5%. Another typical point bonding pattern is the expanded Hansen Pennings or "EHP" bond pattern, which produces a 15% bond area. Numerous other bonding patterns exist. Another suitable and well-known bonding method, particularly when using conjugate staple fibers, is through-air bonding, wherein hot air is passed through the web, at least partially melting a component of the web to create bonds. "Airlaying" is a well-known process by which a fibrous nonwoven layer can be formed. In the airlaying process, bundles of small fibers having typical lengths ranging from about 3 to about 19 millimeters (mm) are separated and entrained in an air supply and then deposited onto a forming screen, usually with the assistance of a vacuum supply. The randomly deposited fibers then are bonded to one another using, for example, hot air or a spray adhesive.

"Coapertured" refers to a composite wherein (at least two) materials are apertured together to create holes which extend through the layers. An interface is created between the materials which is represented by light contact and/or entanglement and/or interpenetration and/or bonding. The degree or extent of this depends on specific materials composition and process conditions. The apertures which extend through the layers are represented by a fibrous/film-like structure created through melting and some flow of the fiber

"Personal care product" means diapers, training pants, absorbent underpants, adult incontinence products, feminine hygiene products, wound care items like bandages, and other articles

"Feminine hygiene products" means sanitary napkins or pads, tampons and panty- hners

"Target area" refers to the area or position on a personal care product where an insult is normally delivered by a wearer

TEST METHODS

Rate Block Intake Test This test is used to determine the intake time of a known quantity of fluid into a material and/or material system The test apparatus consists of a clear, preferably acrylic, rate block 10 as shown in Figure 12, and a timer or stopwatch A 4 inch by 4 inch (102 mm by 102 mm) piece of liner material 13 to be tested is die cut (The specific liners to be tested are described in the specific examples ) The absorbent 14 used for these studies is described under "Test Materials" below

The rate block 10 is 3 inches (76 2 mm) wide and 2 87 inches (72 9 mm) deep (into the page) and has an overall height of 1 125 inches (28 6 mm) which includes a center area 19 on the bottom of the rate block 10 that projects farther from the main body of the rate block 10 and has a height of 0 125 inches (3 2 mm) and a width of 0 886 inches (22 5 mm) The rate block 10 has a capillary 12 with an inside diameter of 0 186 inches (4 7 mm) that extends diagonally downward from one side 15 to the center line 16 at an angle of 21 8 degrees from the horizontal The capillary 12 may be made by drilling the appropriately sized hole from the side 15 of the rate block 10 at the proper angle beginning at a point 0.726 inches (18.4 mm) above the bottom of the rate block 10; provided, however, that the starting point of the drill hole in the side 15 must be subsequently plugged so that test fluid will not escape there. The top hole 17 has a diameter of 0.312 inches (7.9 mm), and a depth of 0.625 inches (15.9 mm) so that it intersects the capillary 12. The top hole 17 is perpendicular to the top of the rate block 10 and is centered 0.28 inches (7.1 mm) from the side 15. The top hole 17 is the aperture into which the funnel 11 is placed. The center hole 18 is for the purpose of viewing the progression of the test fluid and is actually of an oval shape into the plane of Figure 12. The center hole 18 is centered width-wise on the rate block 10 and has a bottom hole width of 0.315 inches (8 mm) and length of 1.50 inches (38.1 mm) from center to center of 0.315 inch (8 mm) diameter semi-circles making up the ends of the oval. The oval enlarges in size above 0.44 inches (1 1.2 mm) from the bottom of the rate block 10, for ease of viewing, to a width of 0.395 inches (10 mm) and a length of 1.930 inches (49 mm). The top hole 17 and center hole 18 may also be made by drilling.

The sample to be tested is placed over the absorbent 14 and the rate block 10 is placed on top of the two materials. Two ml of an artificial menses fluid as prepared below is delivered into the test apparatus funnel 1 and a timer started. The fluid moves from the funnel 11 into a capillary 12 where it is delivered to the material 13 or material system in the center of the center hole 18. Fluid typically spreads towards the ends of the center hole 18 oval. The timer is stopped when all the fluid is absorbed into the material or material system as observed through the center hole 18 and the capillary 12 in the rate block 10. The intake time for a known quantity of test fluid is recorded for a given material or material system. This value is a measure of a material or materials system's absorbency. Lower intake time represents more absorbent systems. Each type of sample is subjected to five repetitions of testing and the results are averaged to produce a single value.

Rewet Test: This test is used to determine the amount of fluid that will come back to the surface of a top sheet when a load is applied. The amount of fluid that comes back through the surface is called the rewet value. The more fluid that comes to the surface, the larger the rewet value while if a smaller amount of fluid comes back to the surface the rewet value is lower. Lower rewet values are associated with a dryer material and hence a dryer product.

After performing the intake test described above, the material system (top sheet and absorbent or top sheet, surge and absorbent) is placed onto a closed bag which is partially filled with saline solution in order to better distribute the forces on the system. The fluid bag is positioned on top of a lab jack. Two pieces of blotter paper are pre- weighed and placed on top of the material system. The bag, material system and paper are raised against a fixed acrylic plate using the lab jack until a total of 1 psi is applied. The pressure is held fixed for 3 minutes, after which the pressure is removed and the blotter paper is again weighed. The difference in weight between the initial blotter weight and its weight after the test is recorded as the rewet value. Each type of sample is subjected to five repetitions of testing and the results are averaged to produce a single value. Run-off test: The 4 inch by 4 inch (102 mm by 102 mm) material system piece is placed on an acrylic stage that has an inclination angle of 20°. One ml of artificial menses is insulted to the center of the material system with the use of a pipette from a distance of 5 mm. Any fluid that runs off the material sample is collected in a pre-weighed plastic container and the residue left on the acrylic stage is removed with pre-weighed absorbent gauze. The run-off value is obtained by summing the fluid absorbed by the gauze and that retained in the plastic container A lower run-off value implies better fluid absorption Each type of sample is subjected to five repetitions of testing and the results are averaged to produce a single value

Material cahper (thickness) The caiiper or thickness of a material, in inches, is measured at three different pressures, 0 05, 0 20 and 0 50 Psi, using a Frazier spring model compresometer #326 bulk tester with a 2 inch (50 8 mm) foot (Frazier Precision Instrument Corporation , 925 Sweeney Drive , Hagerstown, Maryland 21740 ) Each type of sample is subjected to five repetitions of testing and the results are averaged to produce a single value Artificial Menses Preparation The artificial menses fluid used in the testing was made according to US Patent 5,883,231 from blood and egg white by separating the blood into plasma and red cells and separating the white into thick and thin portions, where "thick" means it has a viscosity after homogenization above about 20 centipoise at 150 sec ¹, combining the thick egg white with the plasma and thoroughly mixing, and finally adding the red cells and again thoroughly mixing A more detailed procedure follows

Blood, in this example defibπnated swine blood, is separated by centrifugmg at 3000 rpm for 30 minutes, though other methods or speeds and times may be used if effective The plasma is separated and stored separately, the buffy coat removed and discarded and the packed red blood cells stored separately as well It should be noted that the blood must be treated in some manner so that it may be processed without coagulating Various methods are known to those skilled in the art, such as defibπnating the blood to remove the clotting fibrous materials, the addition or anti-coagulant chemicals and others The blood must be non-coagulating in order to be useful and any method which accomplishes this without damaging the plasma and red celts is acceptable Jumbo chicken eggs are separated, the yolk and chalazae discarded and the egg white retained. The egg white is separated into thick and thin portions by straining the white through a 1000 micron nylon mesh for about 3 minutes, and the thinner portion discarded. The thick portion of egg white, which is retained on the mesh, is collected and drawn into a 60 cc syringe, which is then placed on a programmable syringe pump and homogenized by expelling and refilling the contents five times. The amount of homogenization is controlled by the syringe pump rate of about 100 ml/min, and the tubing inside diameter of about 0.12 inches. After homogenizing the thick egg white has a viscosity of about 20 centipoise at 150 sec^"1 and is then placed in the centrifuge and spun to remove debris and air bubbles at about 3000 rpm for about 10 minutes

After centrifuging, the thick, homogenized egg white, which contains ovamucin, is added to a 300 cc FENWAL® Transfer pack container using a syringe. Then 60 cc of the swine plasma is added to the FENWAL® Transfer pack container. The FENWAL® Transfer pack container is clamped, all air bubbles removed, and placed in a Stomacher lab blender where it is blended at normal (or medium) speed for about 2 minutes. The FENWAL® transfer pack container is then removed from the blender, 60 cc of swine red blood cells are added, and the contents mixed by hand kneading for about 2 minutes or until the contents appeared homogenous. A hematoc t of the final mixture should show a red blood cell content of about 30 weight percent and generally should be at least within a range of 28-32 weight percent for artificial menses made according to this example. The amount of egg white is about 40 weight percent.

The ingredients and equipment used in the preparation of artificial menses are readily available. Below is a listing of sources for the items used, though of course other sources may be used providing they are approximately equivalent. Blood (swine): Cocalico Biologicals, Inc., 449 Stevens Rd., Reamstown, PA 17567, (717) 336-1990.

Fenwal® Transfer pack container, 300 ml, with coupler, code 4R2014: Baxter Healthcare Corporation, Fenwal Division, Deerfield, IL 60015. Harvard Apparatus Programmable Syringe Pump model no. 55-4143: Harvard

Apparatus, South Natick, MA 01760.

Stomacher 400 laboratory blender model no. BA 7021 , serial no. 31968: Seward Medical, London, England, UK.

1000 micron mesh, item no. CMN-1000-B: Small Parts, Inc., PO Box 4650, Miami Lakes, FL 33014-0650, 1-800-220-4242.

Hemata Stat-ll device to measure hemocrits, serial no. 1 194Z03127: Separation Technology, Inc., 1096 Rainer Drive, Altamont Springs, FL 32714.

DETAILED DESCRIPTION

In a personal care product, the top sheet material is the layer against the wearer's skin and so the first layer in contact with liquid or other exudate from the wearer. The top sheet further serves to isolate the wearer's skin from the liquids held in an absorbent structure and should be compliant, soft feeling and non-irritating. Various materials can be used in forming the bodyside top sheet of the present invention, including apertured plastic films, woven fabrics, nonwoven webs, foams and the like. Nonwoven materials have been found particularly suitable for use in forming the top sheet, including spunbond or meltblown webs of polyolefin, polyester, polyamide (or other like fiber forming polymer) filaments, or bonded carded webs of natural polymers (for example, rayon or cotton fibers) and/or synthetic polymers (for example, polypropylene or polyester) fibers. For example, the top sheet can be a nonwoven spunbond web of synthetic polypropylene filaments. The nonwoven web can have a basis weight ranging from about 10.0 grams per square meter (gsm) to about 68.0 gsm, and more particularly from about 14.0 gsm to about 42.0 gsm, a bulk or thickness ranging from about 0.13 millimeter (mm) to about 1.0 mm, and more particularly from about 0.18 mm to about 0.55 mm, and a density between about 0.025 grams per cubic centimeter (g/cc) and about 0.12 g/cc, and more particularly between about 0.068 g/cc and about 0.083 g/cc. Additionally, the permeability of such nonwoven web can be from about 150 Darcy to about 5000 Darcy. The nonwoven web can be surface treated with a selected amount of surfactant, such as about 0.28% TRITON® X-102 surfactant, or otherwise processed to impart the desired level of wettability and hydrophilicity. If a surfactant is used, it can be applied to the web by any conventional means, such as spraying, printing, brush coating and the like. Nonwoven top sheets are usually made from staple fibers, by, for example, carding or from long fibers by, for example, meltspinning processes. These nonwoven webs are often made from polyolefins or polyesters, and may be conjugate fibers of polypropylene and polyester or polyethylene, for example, set up in different arrangements such as sheath/core, side-by-side, etc. Mixtures of various fibers may also be used. These materials can be bonded with different techniques to provide the necessary mechanical integrity. Such means can include thermal bonding or through-air bonding, ultrasonic bonding or adhesive bonding with latex or other adhesives, entangling with water or by needling, etc. Usually, the top sheet layer is joined to the subsequent layers and the backing sheet with hot melt or latex adhesives, or ultrasonic or mechanical bonding.

The surge layer is most typically interposed between and in intimate, liquid communicating contact with the top sheet and another layer such as a distribution or retention layer. The surge layer is usually subjacent the inner (unexposed) surface of the top sheet. To further enhance liquid transfer, it can be desirable to attach the upper and/or lower surfaces of the surge layer to the top sheet and next layer, respectively. Suitable conventional attachment techniques may be utilized, including without limitation, adhesive bonding (using water-based, solvent-based and thermally activated adhesives), thermal bonding, ultrasonic bonding, needling and pin aperturing, as well as combinations of the foregoing or other appropriate attachment methods. If, for example, the surge layer is adhesively bonded to the top sheet, the amount of adhesive add-on should be sufficient to provide the desired level(s) of bonding, without excessively restricting the flow of liquid from the top sheet into the surge layer. Various foams and woven and nonwoven webs can be used to construct a surge layer. For example, the surge layer may be a nonwoven fabric layer composed of a meltblown or spunbond web of polyolefin filaments. Such nonwoven fabric layers may include conjugate, biconstituent and homopolymer fibers of staple or other lengths and mixtures of such fibers with other types of fibers. The surge layer also can be a bonded carded web or an airlaid web composed of natural and/or synthetic fibers. The bonded carded web may, for example, be a powder bonded carded web, an infrared bonded carded web, or a through-air bonded carded web. The bonded carded webs can optionally include a mixture or blend of different fibers, and the fiber lengths within a selected web may range from about 3 mm to about 60 mm. Exemplary surge layers can have a basis weight of at least about 0.50 ounce per square yard (about 17 grams per square meter), a density of at least about 0.010 gram per cubic centimeter at a pressure of 68.9 Pascals, a bulk of at least about 1.0 mm at a pressure of 68.9 Pascals, a bulk recovery of at least about 75 percent, a permeability of about 500 to about 5000 Darcy, and a surface area per void volume of at least about 20 square centimeters per cubic centimeter. The surge layer may be composed of a substantially hydrophobic material, and the hydrophobic material may optionally be treated with a surfactant or otherwise processed to impart a desired level of wettability and hydrophilicity. The surge layer can have a generally uniform thickness and cross-sectional area. Exemplary surge materials may be found in US Patent numbers 5,879,343 and 5,820,973 to Dodge et al. It is preferred that an array of concave features be present in the practice of the invention. These concave features may have different configurations such as squares, diamonds, circles or artistic designs. In order to obtain the maximum benefit, however, the preferred array of concave features should have the necessary depth and distance between concavities to allow fluid absorption and at the same time create a physical barrier to contain the fluid and reduce its spreading. These concave structures are designed in such a way as to provide a temporary reservoir for the fluid, allowing the top sheet to accept the fluid at its own rate, without allowing the fluid to spread. Currently available products do not have this feature and usually allow the fluid to spread in an erratic path when using materials that have slow intake times. Although a description of a process that produces these results is disclosed here, one skilled in the art may proposed alternative way to achieve similar results. One process that achieves this type of structure is made using a calender unit having an embossing roll and a matching female roll. The materials to be modified are fed through the nip of the calender system at the same time. Heat and pressure (or ultrasonics) permanently emboss the concave features to the materials. This kind of process may be in an off-line operation or can be incorporated into a production line.

In another aspect of the invention, material savings may be achieved by using a narrow surge layer placed particularly in the product target area. This means that the surge (second) layer should be at least a third narrower than the top sheet (first) layer. It is preferred that there be the melting compatibility of the materials used in the creation of the structures of the invention. By "melting compatibility" it is meant that materials may be joined together by heat alone or by heat and pressure. Materials which are not melt compatible may be joined together by other means, such as by entanglement or by the use of adhesives.

When using materials that are melt compatible, after embossing, the composite obtains high mechanical strength that is desired to maintain the material's integrity during use. In a less optimal embodiment wherein the materials are not melt compatible, a hot melt or latex adhesive could be used as an alternative to achieve bonding between layers. In addition to surfactants, other chemical treatments may be added to the material of the invention. One area of increasing consumer interest is in the area of "skin wellness" treatments like, for example, aloe, which is believed by many to positively effect skin health. Other skin wellness chemicals are known in the art.

The preferred embodiment of the invention has an intake value less than 40 seconds, a re-wet value of less than 0.35 grams, a run-off value of less than 0.50 grams, and a caiiper loss under pressure less than 50 percent.

TEST MATERIALS AND PREPARATION

The materials used to demonstrate the invention were the following: A top sheet layer of nonwoven fabric was made by the spunbonding process of 3.5 dpf (denier), 0.6 osy (20.3 gsm) polypropylene fibers containing 8 weight percent of titanium dioxide, (product code 41438, Ampacet Corp., 660 White Plains Rd., Tarrytown, NY) treated with 0.3 weight percent of AHCOVEL® Base N-62 wettable surfactant (ICI Surfactants of Wilmington, Delaware, USA). This fabric had an HP type bonding pattern though the bonding pattern chosen is not critical to the functioning of the invention.

A surge layer was made from a through-air bonded carded web of 100 weight percent polypropylene/polyethylene (PP/PE) sheath-core conjugate fibers having 6 dpf, 0.7 osy (23.7 gsm) with a HR6 finish from the Chisso Corporation (Fiber Division) of Osaka, Japan.

An absorbent was made according to the airlaying process using 250 gsm, 90 weight percent Coosa 0054 pulp and 10 weight percent Kosa (formerly Trevira Inc. and more formerly Hoechst-Celanese) T-255 fiber binder with a density of 0.14 g/cc (unless otherwise specified).

The concave features were applied to the materials with the use of a hot press model OK380 from the Practix MFG Company located at 3416 Cantrell, Practix RD AC, Worth, GA, 30101. The temperature used on the hot plate was 177° C (350° F) with a dwell time of 15 seconds and 50 Psi of pressure. Two sets of plates having a male/female arrangement with a different hole size but equivalent depth were made for the purpose of this testing;

• Plate 1 had an array of projections and holes, each projection having a diameter of 4.5 mm and being separated from each hole by 1 mm. Each hole had a volume of 0.05 cc and a depth of 3 mm. This plate 1 produced a material having what will be referred to as "Feature 1".

• Plate 2 had an array of projections and holes, each projection having a diameter of 8.5 mm and separated from each hole by 1 mm. Each hole had a volume of 0.18 cc and a depth of 3 mm. This plate 2 produced a material having what will be referred to as "Feature 2". EXAMPLES

The following testing matrix has been evaluated to demonstrate the fluid absorption characteristics of each material using the intake, re-wet and run off- test described in the prior section.

1 - Top sheet of spunbond fabric only, no embossing.

2 - Top sheet of spunbond fabric only, embossing of Feature 1.

3 - Top sheet of spunbond fabric only, embossing of Feature 2.

4 - Top sheet of spunbond fabric over surge, no embossing. 5 - Top sheet of spunbond fabric over surge, the combination embossed using

Feature 1.

6 - Top sheet of spunbond fabric over surge, the combination embossed using Feature 2.

7 - Top sheet of spunbond fabric over absorbent core, the combination embossed using Feature 1.

8 - Top sheet of spunbond fabric over absorbent core, the combination embossed using Feature 2.

9 - Top sheet of spunbond fabric over surge and absorbent core, the combination embossed using Feature 1. 10 - Top sheet of spunbond fabric over surge and absorbent core, the combination embossed using Feature 2.

1 1 - Top sheet of spunbond fabric over surge and absorbent core, the combination embossed using Feature 2. Absorbent core density 0.06 g/cc. Structures with the modified surface were created by bonding together via the embossed concave features (where applicable). All the materials were tested using the absorbent core described previously.

Results obtained from testing the materials are shown in Table 1.

TABLE 1

As seen in Table 1 , the absorption of fluid was enhanced by modifying the composite surface. The addition of a surge layer beneath the top sheet material impacted the fluid absorption by greatly reducing its re-wet, this is a result of the additional volume that the surge material provided giving a separation between the absorbent core and the top sheet material. Materials satisfying the needs of this invention have a re-wet of less than 0.40 gms and preferably less than 0.35 gms.

When the concave features are added to the composite liner structure (top sheet/surge), the fluid absorption characteristics are enhanced as seen by the significant intake time reduction obtained in the test. Materials satisfying the needs of this invention have an intake time of less than 50 seconds and preferably less than 40 seconds. As seen in the results, the void volume of the concavity has a direct relationship with the material performance. Although Feature #1 showed improvement compared to the single layer spunbond and to the un-embossed composite, it did not offer the performance advantages of that of Feature #2.

Another feature that has been improved with this invention is the reduction of the fluid run-off. The addition of a surge layer in addition to the concave features was able to reduce significantly the movement of the fluid in the absorbent material, keeping a higher amount of it within the periphery of the absorbent structure. This effect can not be obtained by the un-embossed combination of the top sheet and surge materials alone due to the lack of a physical barrier. Materials satisfying the needs of this invention have a run-off amount of less than 0.60 gms and preferably less than 0.50 gms. The following examples describe the effect of adding the concave features to an absorbent system comprised of top sheet and absorbent material compared to a system comprised of top sheet, surge and absorbent material embossed together.

Table 2

As seen in Table 2, the results show that airlaid absorbent cores with high density (0.14 g/cc) had slower intake times than the single layer system. This is believed to be a result of the increased densification of the absorbent layer, which may slow down the absorption of fluid into the absorbent layer. This effect is also believed to be apparent in the increased intake times of the spunbond/surge/absorbent Examples 9 and 10 versus the similar Examples, 5 and 6 which have no absorbent. Nevertheless, in all the examples, samples with concave features presented lower run-off values compared to the flat systems. One way to improve the slow intake time seen is by using a lower density absorbent core before embossing, as seen in the example using 0.06 g/cc absorbent in which faster intake times and the lowest run-off values were obtained.

As seen from this data, the election of the top sheet, surge and absorbent material has an important role in the functionality of the modified top sheet structure. Adding the concave feature to the three layers described above provides a more stable structure but may compromise the absorption functionality of the system depending on the material elected. The absorbent system may be optimized for a particular application by regulating the degree of compaction and the surfactant type and concentration.

A common requirement for this kind of material structure is its capacity to retain its integrity after use, or after the product has been produced and packaged. Usually, to optimize the space occupied by the products on the shelf, manufacturers have chosen to either bi-fold or tri-fold the products exerting a high-pressure load on the product. For that reason, an evaluation on the thickness lost at different pressures was performed on the different samples.

The results of that evaluation are located in Table 3.

TABLE 3

Table 3 shows that adding the concave feature to the single spunbond top sheet produces a reduction in the material thickness with a load application. This effect is the result of having a hollow embossed feature that loses its integrity easily when load is applied, reducing the capacity to manage the fluid absorption. Contrary to that, having a top sheet and surge system reduces the amount of thickness lost with the load application.

As seen in Table 3, the structure made of top sheet, surge and absorbent core together showed the lowest value of thickness lost of all the samples. This is a result of the structure modification achieved with the process in which the airlaid fiber binders, top sheet and surge are modified together, creating a stable structure. Materials satisfying the needs of this invention have a caiiper loss of less than 60 percent and preferably less than 50 percent between 0.05 and 0.5 psi. Turning now to the drawings, it can be seen that many possible configurations of concavities may be present in a product and yet be within the spirit and intent of the invention. Figures 1 and 2 show a view of a material, in this case a two layer material, having concavities 1 of differing sizes. Figure 3 shows a cross-sectional view of a material comprised of two layers and having concavitiesl . Figures 4-10 show various configurations for feminine hygiene products encompassed by the instant invention. In Figure 4, the concavities 1 are arranged around the periphery of the inner portion 2 of the product. Figure 5 shows the concavities 1 arranged only in the target area 3 of the product. Figure 6 shows concavities 1 having artistic or "whimsical" designs in a slightly expanded target area 3. Figure 7 shows the concavities 1 arranged in an unimaginative row-by-row arrangement. Figure 8 shows a feminine pad having concavities 1 arranged in a random pattern. Figure 9 shows a pattern of large and small concavities 1 arranged in a single product. Figure 10 shows a row arrangement of concavities wherein each concavity is quite small. Figure 1 1 shows a three layer material, which has been embossed with concavities 1 according to the invention.

The concave feature of this invention may vary in size, depth, shape and separation between concavities. The diameter of the features may be up to 10 cm, preferably in a range from 3 to 20 mm in diameter, and still more preferably about 8 mm. The depth may be up to 20 mm, preferably between 1 and 10 mm, and still more preferably about 3 mm. The separation between concavities will depend on the effect desired. Concavities that are more closely packed will provide a more effective fluid barrier by reducing the movement of liquid beyond the liner. The features may also touch, such that they are in liquid communication with each other and so facilitate fluid movement within the liner. It is preferred, however, that the features, depending on their shape, be arranged to have a separation between feature edges of between about 0.5 and 10 mm.

Embodiments of the invention may be prepared with concavities of different shapes and/or sizes. This may be done for purely aesthetic reasons or may be done to produce different absorbent characteristics in various areas of the personal care product. In the case of a diaper, for example, which is exposed to urine and BM, a pattern of smaller concavities may be incorporated into the product in the area most likely to be exposed to urine and a pattern of larger concavities may be incorporated into the product in the area most likely to be exposed to BM, which may at times be runny. Alternatively, the concavities may be applied in only the target area or central region of a product with the likely result being a reduction in spreading. In yet another alternative location, the concavities may be located only on the periphery of a product with the likely result that fluid will be prevented from moving outside of the product. A combination of such features may be designed to improve overall product performance and protection. The exact size, location, etc. depends on the fluid to be handled and the benefit desired. Yet another alternative embodiment may include a liner in which the layers, e.g. top sheet and surge, are coapertured. Such coaperturing may be done in a pattern such that the apertures occur at the bottom of each concavity. The placement of various treatments like surfactants or skin wellness chemicals may also be varied, placing them, for example, only at the bottom of each concavity or only on the underside of the liner. Yet another method of encouraging fluid flow into the concavities is by placing fibers in each concavity perpendicular to the plane of the material. The fibers are capable of directing fluid into the concavity and so reduce the possibility of liquid run-off from the product.

As will be appreciated by those skilled in the art, changes and variations to the invention are considered to be within the ability of those skilled in the art. Such changes and variations are intended by the inventors to be within the scope of the invention.

Claims

What is claimed is:

1. A liner for personal care products comprising a first layer and a second layer, said layers being in face-to-face relation to one another and having at least one concave embossed feature.

2. The liner of claim 1 having an array of discrete concave features.

3. The liner of claim 2 wherein said array of discrete concave features has fibers in at least one concavity in a direction perpendicular to said layers.

4. The liner of claim 2 wherein said first and second layers are bonded together by a method selected from the group consisting of adhesive, mechanical, entanglement, thermal and ultrasonic means.

5. The liner of claim 2 wherein said first and second layers are melt compatible.

6. The liner of claim 2 wherein said first layer has been treated with a wettable surfactant.

7. The liner of claim 6 wherein said concavities each have a bottom and said first layer has been treated with a wettable surfactant at the bottom of each of said concavities.

8. The liner of claim 2 wherein said first layer has been treated with a skin wellness chemical.

9. The liner of claim 2 wherein said first layer comprises a nonwoven web made of polyolefin fibers.

10. The liner of claim 8 wherein said polyolefin is polypropylene.

11. The liner of claim 2 further comprising apertures in said first layer

12. The liner of claim 2 wherein said first and second layers have been coapertured.

13. The liner of claim 2 wherein said first layer is made of a film, apertured by a method chosen from the group consisting of vacuum aperturing and mechanical aperturing.

14. The liner of claim 2 wherein said second layer comprises a bonded carded web of polyolefin fibers, bonded by a method selected from the group consisting of through- air bonding, thermal bonding and adhesive bonding.

15. The liner of claim 13 further comprising conjugated fibers.

16. The liner of claim 2 wherein said second layer is more wettable than said first layer.

17. The liner of claim 2 wherein said second layer comprises a foam.

18. The liner of claim 2 wherein said concave features are located in a target area.

19. The liner of claim 2 having an intake value less than 50 seconds.

20. The liner of claim 2 having a re-wet value of less than 0.40 grams.

21. The liner of claim 2 having a run-off value of less than 0.60 grams.

22. The liner of claim 2 having a caiiper loss under pressure less than 60 percent.

23. The liner of claim 2 wherein said concave features have a diameter of less than 10 cm.

24. The liner of claim 2 wherein said concave features have a depth of less than 20 mm.

25. A feminine hygiene pad comprising the fabric of claim 2.

26. A diaper comprising the fabric of claim 2.

27. An adult incontinence product comprising the fabric of claim 2.

28. A liner for personal care products comprising a first layer and a second layer, said layers being in face-to-face relation to one another and having an array of discrete concave embossed features wherein said liner has an intake value less than 40 seconds, a re-wet value of less than 0.35 grams, a run-off value of less than 0.50 grams and a caiiper loss under pressure less than 50 percent.

29. The personal care product of claim 27 wherein said second layer is at least a third narrower than said first layer.