MXPA98001772A - Sanitary articles with top movie sheets with multip opening size - Google Patents

Abstract

The present invention relates to absorbent articles, particularly sanitary napkins having top sheets of film. In particular, a top sheet of absorbent liquid receiving film comprises openings of at least four different sizes. This range of aperture sizes provides exceptionally good liquid admission performance for the range of liquid viscosities commonly found for liquids, which are absorbed into sanitary towels.

Description

SANITARY ARTICLES WITH TOP MOVIE LEAVES WITH MULTIPLE OPENING SIZES FIELD OF THE INVENTION The present invention relates to absorbent articles, particularly sanitary napkins preferably having top sheets of film. In particular, a top sheet that receives the liquids to be absorbed comprises openings of at least four different sizes. This opening size range provides exceptionally good liquid admission performance for the range of viscosities of liquids commonly found for liquids that are absorbed in sanitary napkins.

BACKGROUND OF THE INVENTION Sanitary articles such as sanitary napkins, baby diapers, absorbent inserts and absorbent articles for adult incontinence are well known in the art. Typically, all of these articles comprise a surface facing the user and a surface facing the garment. The surface that gives to the user receives from the user of these articles the corporal, liquid discharges, such as urine, vaginal discharges or menstruations to be absorbed. In order for the article to store the liquid, the surface it faces towards the user must be permeable to the liquid while maintaining the integrity of the external surface facing the user of the absorbent article. This surface facing the user is provided by a top sheet.

Top sheets well known in the art of absorbent articles are non-woven fabrics, woven fabrics or films. The films have to be made permeable by perforation. Non-woven fabrics or fabrics are made of fibers, which by their nature provide non-linear openings in the direction of liquid transport. Also the larger sizes of openings in the upper sheets of fabric are limited by the requirement to maintain the strength of the material. The films are often made of polymeric material, and typically comprise openings that have been made to provide certain characteristics. These openings may vary in shape and size, but have been commonly provided in a single preferred size and shape. The walls of the openings define the amount of extension, if any, beyond the plane of the thickness of the film and the direction of said extensions. The openings in the film can also be provided in the form of a funnel. Films are generally preferred over fabrics, since they can provide a cleaner surface even if the liquid has passed through, since they do not retain liquids. A typical top sheet made of polyethylene film has been used successfully in sanitary articles and adult incontinence products, also as inserts and baby diapers. A problem that remains is the liquid velocity capable of passing through said top sheet under usual conditions of use due to the total amount of the open area of all the openings and the size and shape of the individual opening in particular. Optionally large openings increase the rate of liquid passage, but they have the potential problem of material stability for the topsheet, at least during the manufacture of the absorbent articles, which is highly undesirable. Also, large openings possibly promote a backflow of absorbed liquid, so called rewetting, which is undesirable. The individual small apertures on the other hand, can not provide the liquid passage characteristics required to allow liquids of high surface attention, high viscosity or solid contents such as clots passing through; This can be a problem in an absolute sense for very small openings or cause a too slow liquid flow rate. It has also been found that the total amount of open area for a given size and shape of aperture is approximately linear in relation to the speed of the liquid passage. Again, the concealment of the liquid that has passed through but also the material strength and other appearance considerations are limited by the degree to the total open area in a top sheet that can be selected. It is also known that the viscosity of liquids disposed on sanitary napkins can very drastically from exceptionally low viscosities, for example, of urine from a person having mild incontinence or stress incontinence syndrome. Low viscosities may also occur for vaginal discharges or menstruation, which comprise small amounts of surfactants. You can find some bodily discharges that comprise natural surfactants, but also residues of washing soaps, which many of the users of these articles regularly use. At the other end of the spectrum, the viscosities of menses change drastically during a woman's period and have already been reported in EP-A-0 205 286 at intervals of 5 to 50 mPas. Viscosities may change over time in the same person and may vary between people compared at a similar stage in a monthly period. It is therefore an object of the present invention to provide a top sheet of sanitary ware film that can adjust to viscosity changes, without the need for different items for different periods. It has been found that this can be achieved by providing upper sheets for disposable absorbent articles having openings of different open areas. These open areas must correspond to a range of the distribution of the viscosity of the liquids that are expected to absorb. It is therefore an object of the present invention to provide absorbent articles having a topsheet with a size distribution of openings.

DESCRIPTION OF THE INVENTION The present invention provides an absorbent article having the benefit of an apertured top sheet for liquids of drastically different viscosities. In particular, the absorbent article comprises a top sheet having a surface facing towards the wearer and a surface facing the garment. The top sheet may comprise multiple layers that are preferably joined together. An absorbent article generally further comprises a backsheet and an absorbent structure, alternatively referred to as an absorbent core, positioned between the top sheet and the back sheet.

Absorbent structure The absorbent structure may include the following components: (a) optionally a primary fluid distribution layer preferably attached with an optional secondary fluid distribution layer (b) a fluid storage layer; (c) optionally a fibrous layer ("dedusting") lying on the storage layer; and (d) other optional components. to). Primary / secondary fluid distribution layer An optional component of the absorbent structure according to the present invention is a primary fluid distribution layer, a secondary fluid distribution layer. The primary distribution layer is typically below the top sheet and is in fluid communication with it. The top sheet transfers the acquired fluid to this primary distribution layer for final distribution to the storage layer. This transfer of fluid through the primary distribution layer occurs not only within the thickness, but also along the longitudinal and wide directions of the absorbent product. The also optional, but preferred secondary distribution layer typically lies below the primary distribution layer and is in fluid communication with it. The purpose of this secondary distribution layer is to quickly acquire the fluid from the primary distribution layer and transfer it rapidly to the underlying storage layer. This helps the fluid capacity of the underlying storage layer to be fully utilized. The fluid distribution layers may be formed of any typical material for these distribution layers. In particular, the fibrous layers maintain the capillaries between the fibers even when they are wet they are useful as distribution layers. b) Fluid storage layer Located in fluid communication with, and typically underlying the primary or secondary distribution layers, is a fluid storage layer. The fluid storage layer may comprise any usual absorbent material or combinations thereof. It preferably comprises gelling absorbent materials usually referred to as "hydrogel" "superabsorbent", hydrocolloid materials in combination with suitable carriers. The gelling absorbent materials are capable of absorbing large quantities of aqueous body fluids, and are also capable of retaining these absorbed fluids under moderate pressures. The gelling absorbent materials can be dispersed homogeneously or non-homogeneously in a suitable carrier. Suitable carriers, provided they are absorbent as such, can also be used alone. Suitable gelling absorbent materials for use herein, most will often comprise a substantially insoluble, slightly crosslinked, partially neutralized polymeric gelling material. This material forms a hydrogel upon contact with water. These polymer materials can be prepared from acid-free, unsaturated polymerizable monomers that are well known in the art. Suitable carriers include materials that are conventionally used in absorbent structures such as natural fibers, modified fibers or synthetic fibers, particularly modified or unmodified cellulose fibers, in the form of fluffed fibers or tissue. Suitable carriers can be used in conjunction with the gelling absorbent material, however, these can also be used alone or in combinations. Tissues or tissue laminates are most preferred in the context of sanitary napkins / panty liners. One embodiment of the absorbent structure made in accordance with the present invention comprises a double-layer tissue laminate formed by folding the tissue over itself. These layers can be bonded together, for example, by adhesive or by mechanical entanglement or by hydrogen bonding bands. The gelling absorbent material or other optional material may be comprised between the layers. Modified cellulose fibers such as hardened cellulose fibers can also be used. Synthetic fibers can also be used and include those made of cellulose acetate, polyvinyl fluoride, polyvinylidene chloride, acrylics (such as Orion), polyvinyl acetate, non-soluble polyvinyl alcohol, polyethylene, polypropylene, polyamides (such as nylon) , polyesters, two-component fibers, three-component fibers, mixtures thereof and the like. Preferably, the surfaces of the fiber are hydrophilic or are treated to be hydrophilic. The storage layer may also include filling materials, such as Perlite, diatomaceous earth, Vermiculite, etc., to improve liquid retention. If the gelling absorbent material is dispersed in a non-homogeneous manner in a carrier, the storage layer can, however, be locally homogeneous, that is, have a distribution gradient in one or more directions within the dimensions of the storage layer. The inhomogeneous distribution can also refer to the laminates of the carriers that enclose the gelling absorbent materials partially or totally. c) Optional fibrous layer "dedusting" An optional component for inclusion within the absorbent structure according to the present invention is a fibrous layer adjacent to, and typically underlying the storage layer. This underlying fibrous layer is typically referred to as a "dedusting" layer as it provides a substrate on which the absorbent gelling material is deposited in the storage layer during the manufacture of the absorbent structure. In fact, in those examples where the gelling absorbent materials are in the form of macrostructure such as fibers, sheets or strips, this fibrous "dedusting" layer need not be included. However, this "dedusting" layer provides some of the additional fluid handling capabilities such as rapid fluid flow along the length of the pad. d). Other optional components of the absorbent structure The absorbent structure according to the present invention can include other optional components normally present in absorbent webs. For example, a reinforcing sheet may be placed within the respective layers, or between the respective layers of the absorbent structure. These reinforcement canvases should be of such configuration as they do not form interfacial barriers for fluid transfer. Given the structural integrity that usually occurs as a result of thermal bonding, reinforcing canvases are not usually required for thermally bonded absorbent structures. Another component that can be included within the absorbent structure according to the present invention and preferably is provided closer to or as part of the primary or secondary fluid distribution layer are the odor control agents. The activated carbon coated with or in addition to other odor control agents, in particular suitable zeolite or clay materials, is optionally incorporated into the absorbent structure. These components can be incorporated in any desired form but are often sensed as discrete particles.

Back sheet The back sheet mainly prevents the exudates absorbed and contained within the absorbent structure from humidifying the articles that come into contact with the absorbent product, such as underpants, briefs, pajamas and undergarments. The backsheet is preferably impervious to liquids (eg, menstruation and / or urine and is preferably manufactured from a thin plastic film, although other flexible liquid-impermeable materials may also be used.) As used herein, The term flexible refers to materials that are docile and that will easily conform to the shape and general outline of the human body.The backsheet can also have elastic characteristics that allow it to stretch in one or two directions.The backsheet typically extends through The entire backing sheet can comprise a woven or non-woven material, polymeric films such as polyethylene thermoplastic films or the entire absorbent structure and can extend into and form part of all or of the preferred side flaps, side wrapping elements or wings. polypropylene, or mixed materials, such as a nonwoven material r Ecubierto with film. Preferably, the backsheet is a polyethylene film having a thickness of from about 0.012 mm to about 0.051 mm. Exemplary polyethylene films are manufactured by Clopay Corporation of Cincinnati, Ohio, under the designation P18-0401 and by Ethyl Corporation, Visqueen Division of Terre Haute, Indiana, under the designation XP-39385. The backsheet is preferably embossed and / or finished without gloss to provide a fabric-like appearance. In addition, the backsheet can allow the vapors to escape from the absorbent structure, i.e., be breathable, while still preventing the exudates from passing through the backsheet. Breathable backsheets comprising several layers can also be used, eg, film structures plus nonwoven web.

The top sheet For the top sheets of multiple layers the term "attached" as used herein, encompasses configurations in which the first layer is directly secured to the second layer by attaching the first layer directly to the second layer; configurations in which the first layer is indirectly secured to the second layer by fixing the first layer to a layer or intermediate layers which in turn are fixed to the second layer. The layers of the topsheet can preferably be joined together by adhesives, sewing, heat and / or pressure bonds, mechanical dynamic bonds, ultrasonic joints, intermeshing or entanglement of the structural elements comprising the layers of the topsheet, such as by extruding a layer on top. another, or by other means known in the art. The upper sheet as a whole and consequently each layer individually needs to be docile, soft to the touch and non-irritating to the wearer's skin. This can also have elastic characteristics that allow it to be stretched in one or two directions. According to the present invention, at least one layer of the upper sheet is provided by a film material having openings which are referred to herein as "oversized openings", "large openings", "medium openings" and "small openings". These openings are provided to facilitate the transport of liquid for liquids of various viscosities coming from the surface facing the user towards the absorbent structure. For measurements with respect to openings in the pass film layer, the plane of the smaller cross-sectional areas should be used, unless otherwise mentioned. The term "aperture size" as used herein refers to the open area.

The "oversized openings" have an individual open area of from more than 1.4 mm2 to 3 mrff. The total open area of the "extra large openings excluding all other openings for liquid transport, should be on the scale from 1% to 25%, preferably from 10% to 20% of the surface area of the upper sheet. Large openings "have an individual open area of more than 0.5 mm2 up to 1.4 mm2 The total open area of the" large openings "excluding all of the other openings for liquid transport, should be on the scale of 1% to 30%, preferably from 5% to 15% of the surface area of the top sheet The "middle openings" have an individual open area of more than 0.1 mm2 to 0.5 mm2 The total open area of the "middle openings" excluding all of the other openings for the liquid transport, should be in the range of 1% to 35%, preferably 10% to 25% of the surface area of the upper sheet.The "small openings" have an individual open area of more than 0 mm2 up to 0.1 mm2 The total area opens rta of the "small openings" excluding all other openings for liquid transport, should be in the range of 0.1% to 5%, preferably from 0.5% to 3% of the surface area of the top sheet. The openings are preferably circular or polygonal substantially. Its shape is limited by having a ratio of the largest / smallest internal length to the smallest in the interval between 1 and 6, preferably, 1 and 3. The total open area of all openings for liquid transport is in the range from 3.1% to 95%, preferably from 10% to 50%, most preferably from 15% to 40% of the total area of the top sheet. The upper sheets can have a homogeneous distribution of the liquid passageways. The latter would have a greater concentration of openings in the area where the liquid is expected to discharge. The openings for the transport of the liquid can be simple holes, but preferably are formed in the film such that the walls the openings extend beyond the plane of the surface of the basic film, that is, the film surface before the film is perforated. The direction of these extended walls in the absorbent article is toward the surface facing the garment of the article. The amount of extension of the walls of the openings must be at least 0.3 mm beyond the film surface from which the walls of the openings hang. Preferably the walls of the openings form funnels or Ventury channels as is well known in the art. To ensure the stability of the material the smaller distance between the extra-large and / or large openings nearby, without considering their particular shape and size, is preferably at least 0.5 mm, preferably 1.5 mm. This distance is measured on the surface of the film on the side closest to the surface facing the user of the absorbent article. The film material is preferably made hydrophilic to the extent that the contact angle is less than 90 ° with distilled water upon the first contact with water. For films, this can be achieved by treatment with surfactant.

For polymeric films treated with a surfactant it has been found that this benefits the use of films where the surfactant is permanently fixed on the film surface. These are so-called film materials with integrated resin surfactant. For these films, even with repeated wetting with distilled water, they would approximately provide the same contact angle as the first contact with distilled water. In another preferred embodiment, the surface facing the user of the topsheet is treated with an agent such that the liquids are directed towards the openings. These agents can be silicone or Teflon which provide the treated surface with a self-cleaning effect. This treatment can be in addition to the treatment with surfactant mentioned above. Films like these are disclosed in EP-0 205 286, EP-0 165 208, EP-0 18 020, EP-0 59 506 or US-3,929,135 which are explicitly referred to as suitable for the top sheet to provide the requirements for comply with the distribution of openings. Other suitable shaped films, also providing the requirement for compliance with the aperture distribution are described in EP-203,820, U.S. Patent 4,324,246, U.S. Patent 4,342,314, U.S. Patent 4,463,045 and U.S. Patent 5,006,394. Particularly preferred micro apertures of the formed film are disclosed in U.S. Patent 4,609,518 and U.S. Patent 4,629,643. These micro-openings can also be included in the upper sheet with the condition that their surface area is smaller than 0.15 mm2, and consequently these provide essentially the breathability. Ways to make these films are well known in the art, and have also been disclosed in the references of the prior art. Also, films that are, prior to piercing, permeable to water vapor but impermeable to liquid can be used in the context of the present invention. If the top sheet comprises multiple layers, the second and subsequent layers may be of the same type as the top sheet previously described with the present invention with a distribution of openings. This can also be provided by other layers of film or by woven or non-woven layers. It is recommended that any additional layer does not present a barrier for liquids. This can be achieved by providing a non-hydrophilicity gradient or a hydrophilicity gradient that conducts the absorbency such that a directing force is created for the liquid towards the absorbent structure. It is also considered desirable that all layers have approximately the same total open area.

Although not wishing to be limited by theory, it is believed that a number of the Reynolds constant can ensure optimal rates of fluid passage. The optimum number of Reynolds depends of course on the absorption speed of the absorbent core. Once this Reynolds number is established for a particular viscosity of liquid, the absorbent core and a size of openings, the theoretically ideal distribution of the opening sizes can be identified by the equation Reynolds number = density Flow rate hydraulic diameter viscosity where - the density is the density of the liquid to be absorbed in units of mass on volume, - flow velocity and the speed of liquid that is absorbed in units of distance on time, - hydraulic diameter can be calculated from the size of the opening as the square root of four times the opening size on Pi. - viscosity is the dynamic viscosity of the liquid that is absorbed in units of pressure per time. With the density being approximately constant (about that of the water) and the flow rate being constant so that the desired diameter distribution becomes approximately linearly proportional to the viscosity and so that the aperture size distribution becomes approximately proportional to the square of the viscosity: opening size - viscosity 2 Following this theory, it is easy to select a viscosity profile, which is expected on the conditions of use for a top sheet opening size distribution that is theoretically ideal. From this theoretically ideal distribution, a practical approach with at least four different aperture sizes can be selected to provide a top sheet according to the present invention. The preferred top sheet according to the present invention can have a greater number of four openings, preferably the "theoretically ideal distribution of openings" is likened by a distribution of 5, 6, 7, 8, 9 or even 10 different sizes of openings Most of the benefits from an opening size distribution are, however, already realized by 5, 6, 7 or 8 different sizes of openings. The distribution must still satisfy the given distribution for the four openings, preferably with a movement towards the center of the distribution.

Claims (1)

1. CLAIMS 1. - An absorbent article comprising an upper sheet, a back sheet and an absorbent structure positioned between the back sheet and the upper sheet, the upper sheet having a surface facing the body and a surface facing the garment, and the upper sheet comprising a layer of through film having small openings, medium openings, medium openings, large openings and extra-large openings for liquid transport, said small openings having a single area in the range of more than 0 mm2 to 0.1 mm2 , said median openings have a single area in the range of more than 0.1 mm2 to 0.5 mm2, said large openings have an individual area in the range of more than 0.5 mm2 to 1.4 mm2, the oversized openings have an individual area in the range of more of 1. 4 mm2 to 3 mm2, said small openings have a total open area in the range of 0.1% to 5% of the total area of said pass film layer, the median openings have a total open area in the range of 1% to 35 % of the total area of said pass film layer, said large apertures have a total open area on the scale of 1% to 30% of the total area of said pass film layer, said extra large apertures have a total open area in the scale from 1% to 25% of the total area of said pitch film layer, said apertures for liquid transport have a larger internal diagonal length and a smaller internal diagonal length, the ratio of said longer internal diagonal length at said shorter internal diagonal length is in the range of 1 to 6. 2 - The absorbent article according to claim 1, wherein the small openings have a total open area in the range of 0.5% to 3% of the total area of said pitch film layer, the middle apertures have a total area in the range of 10% to 25% of the total area of said pitch film layer, the large apertures have a total open area in the range of 5 at 15% of the total area of said pass film layer, the extra-large apertures have a total open area in the range of 10% to 20% of the total area of said pass film layer. 3. The absorbent article according to any of the preceding claims, wherein at least some of the openings for the transport of liquid have internal walls that hang at least 0.3 mm from the surface of said layer of pass film. , said inner walls hanging in a direction towards the absorbent structure of the article. 4. The absorbent article according to any of the preceding claims, wherein the passage film layer has openings for the transport of the liquid of 5, 6, 7, 8, 9 or 10 open areas of different openings. 5. The absorbent article according to any of the preceding claims, wherein the total open area of all openings for the transport of liquid in said pass film layer is in the range of 15% to 40% of the area total of the pass film layer. 6. The absorbent article according to any of the preceding claims, wherein the distance of the smaller edge to the edge between the large and / or extra large openings in the pass film layer is at least 0.5 mm. 7. - The absorbent article according to any of the preceding claims, wherein the top sheet comprises more than one pass layer. 8. The absorbent article according to any of the preceding claims, wherein the openings for the passage of the liquid are distributed homogeneously.