MXPA00000884A - Absorbent articles having a liquid swellable material coated breathable backsheet - Google Patents

Abstract

The present invention relates to absorbent articles such as sanitary napkins and panty liners comprising a topsheet, absorbent core and backsheet which are breathable by the incorporation of a breathable backsheet and have a reduced tendency to exhibit garment wet through. The backsheet comprises at least one air permeable layer such as an apertured formed film or fibrous layer which is applied and preferably coated with a non-soluble, liquid swellable material, such as polyvinyl alcohol. Upon contact with fluid discharge, the material swells and closes the apertures of the layer, thereby reducing air permeability and preventing the passage of liquid through the layer and thus through the backsheet onto the garment of the wearer of the article.

Description

ABSORBENT ARTICLES THAT HAVE A BREATHABLE BACK SHEET COVERED WITH MATERIAL ABLE TO BREATHE WITH WATER FIELD OF THE INVENTION The present invention relates to the provision of breathable backsheets for use in absorbent articles, which are activated when placed in contact with liquids to prevent wetting of the garment through them.

BACKGROUND OF THE INVENTION The primary needs of the consumer which underlie development in the field of absorbent article, particularly catamenials, is the provision of products that provide both a high level of protection and comfort. A means to provide consumer comfort benefits in absorbent articles is by providing breathable products. The breathability is typically concentrated on the incorporation of the so-called "breathable backsheets" in the absorbent articles. The commonly used breathable backsheets are microporous films and films formed with openings having directional fluid transfer as disclosed in, for example, U.S. Patent No. 4 591 523. Both of these types of breathable backsheets are permeable to steam allowing the exchange of gas with the environment. This thus allows the evaporation of a part of the stored fluid within the core and increases the circulation of air within the absorbent article. The latter is particularly beneficial since it reduces the sticky feeling experienced by many users during use, commonly associated with the presence of a film formed with openings or a film-like top sheet, particularly for a prolonged period of time. This is a result of the upper sheets designed to achieve a clean and appearance. These upper sheets tend to be smooth thus reducing the formation or agglomeration of the fluid on the surface of the upper sheet. However, these benefits are achieved at the expense of comfort, particularly under hot and humid conditions, when due to their smooth surface texture, they tend to be sticky to the skin. However, the main disadvantage associated with the use of breathable backsheets in the absorbent articles is the negative effect on the operation of the protection level, by means of leaks known as humidity through them on the garments of the users. Although breathable backsheets in principle only allow the transfer of materials in the gaseous state, physical mechanisms such as extrusion, diffusion and capillary action can still occur and result in the transfer of liquids from the absorbent core through the back sheet and on the clothes of the users. In particular, these mechanisms become more dominant if the product is used during physical exercise, or for heavy discharge charges or for extended periods of time. In this way, although the incorporation of breathable backsheets in the absorbent articles is highly desirable from the point of view of comfort, since the main role of a backsheet still remains in preventing leakage of liquids, these back sheets Breathable can not be incorporated satisfactorily into the products. The problem of rewetting on the users' garments due to the incorporation of said breathable backsheets into the absorbent articles has in fact also been recognized in the art. Attempts to solve the problem mainly reside in the use of multilayer backsheets such as those illustrated in U.S. Patent No. 4 341 216. Similarly, European Patent Number EPO 710 471 discloses a breathable back sheet comprising an outer layer of a gas permeable fibrous polymeric fabric, hydrophobic, and an inner layer comprising a film formed with openings having directional fluid transport. The construction of the backsheet preferably does not have liquid transport or rewet under certain specific test conditions. European patent 710 472 also discloses a breathable back sheet consisting of at least two breathable layers that are not bonded together over the core area. The construction of the backsheet preferably does not have liquid transport or rewet under certain specific test conditions. U.S. Patent No. 4 713 068 discloses a breathable fabric barrier to be used as an outer cover for absorbent articles. The barrier comprises at least two layers, a first layer having a specific basis weight, a specific fiber diameter and pore size, and a second layer comprising a continuous film of polyvinyl alcohol having a specific thickness. The barrier also has a specific transion regime of water vapor and a level of impermeability. However, none of the previously proposed solutions have been able to provide a completely satisfactory solution for the problem of rewetting the breathable backsheet under all conditions. In addition, another problem associated with the backsheets of multiple layers exemplified is an increase in the total thickness of the product and a reduction in flexibility, both of which result in a reduction in the comfort of the product notable to the consumer. A solution proposed alternately to the problem of the rewetting of the breathable backsheet is related to the improvements of the absorbent material in such a way that nothing or almost nothing of the liquid comes into contact with the backsheet, thus preventing rewetting. This is typically obtained by increasing the amount of absorbent material within the core. However, this results in an absorbent article which is extremely thick, which is highly undesirable from the consumer's point of view. Therefore, the absorbent article, while having the required level of protection and still maintaining some of the comfort benefits due to the presence of the breathable backsheet, suffers from a lack of comfort from a different source, in this case the Increased dimension of the article. In addition, the above solution also results in a reduction of the flexibility of the article, particularly evident as an increase in the stiffness of the cross section. However, it was also established that in order to be comfortable for the user the absorbent articles need to be flexible in a cross-sectional manner. It is believed that in the greatest flexibility in the cross section of an article is, the lesser will be noticeable to the user. In this way flexibility is another requirement of the highly desirable comfort of modern absorbent articles. European patent 705 583 and European patent 705 584 propose longitudinally flexible absorbent articles which are permeable to steam. However, the illustrated absorbent articles are typically very thin and do not direct the absorbency of the article or the rewet problem. U.S. Patent No. 5,447,788 discloses a porous non-woven barrier activated with liquid suitable for use in absorbent articles. The barrier includes a fibrous nonwoven web in which at least 50% of the fibers are prepared from a polymer capable of swelling with the liquid, which is not significantly soluble in water such as polyvinyl alcohols capable of to inflate. In the presence of water, the polymers swell to a sufficient extent to substantially block the passage of the liquid through the fibrous nonwoven web. Nevertheless, from the data given in the patent, the passage of the liquids is not substantially blocked and in this way these frames do not eliminate the problem of rewet. Consequently, since the incorporation of the breathable backsheets in the absorbent articles results in the reduction of the level of protection, the additional desirable modifications of the product comfort such as the reduction of the thickness of the product and the improvement of the flexibility of the product. which would further the problem, can not be incorporated into the absorbent article. Therefore, there exists a dichotomy in the means available to provide the increased consumer comfort of absorbent products and acceptable levels of protection. It is therefore an object of the present invention to provide an absorbent article having improved comfort, by providing breathability throughout the absorbent article, which continues to maintain an acceptable level of protection. It has now been found that this object can be obtained by providing an absorbent article having a breathable backsheet which comprises at least one air permeable layer or an apertured layer, such as a woven or nonwoven material of film formed with openings, which comprise and is preferably covered with a non-soluble material, capable of inflating with the liquid. An advantage of the present invention is that the backsheet layer, when in the dry state, allows the transfer of the moist vapor and air and, in its wet state after inflating, the layer maintains at least a degree of permeability Steam moist while preventing the transfer of liquids.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to absorbent articles such as diapers, sanitary napkins, panty liners, incontinence products and the like. Typically these products comprise a liquid permeable top sheet, an absorbent core and a backsheet. The present invention is characterized in that the backsheet is a breathable backsheet and comprises at least one air-permeable or apertured layer, said layer having an upper surface, a lower surface and an inner surface. According to the present invention at least one of the surfaces of the apertured backsheet layer has at least one region thereon, wherein said region of said surface comprises, and preferably is coated with, a non-colored material. soluble, able to swell with the liquid. The present invention thus provides an absorbent article product that provides the circulation of water vapor and the passage of air through the product when and where it is dry and preferably maintains the permeability of water vapor throughout the use of the product. . Moreover, by applying a material capable of inflating onto the backsheet layer with apertures, preferably as a coating, the present invention also provides absorbent articles that have a reduced tendency to exhibit wetting of the garment.

DETAILED DESCRIPTION OF THE INVENTION The absorbent article according to the present invention comprises as an essential component, a breathable backsheet. The backsheet typically extends through the entire absorbent structure and can extend into and form part of all or part of the side flaps, side wrapping elements or wings. The role of the backsheet is primarily to prevent the exudates absorbed and contained within the absorbent structure from wetting the articles that come into contact with the absorbent product such as underpants, shorts, pajamas and undergarments thus acting as a barrier for the transport of fluid. In addition, however, the breathable backsheet of the present invention when dry allows the transfer of at least water vapor and preferably both water vapor and air through it and thus allows circulation of the gases in and out of the back sheet. In addition, however, the backsheet also preferably continues to allow the transfer of water vapor through it after it has been wetted. According to the present invention, the breathable backsheet comprises at least one layer comprising openings, having a surface that gives the user hereinafter referred to as the upper surface, a surface that gives the garment hereinafter referred to as a lower surface and an internal surface. The term "internal surface" as used herein, refers to any surface of said layer that is not the surface facing the user or the surface facing the garment. Typically said inner surface is a surface extending from the surface that gives the garment towards the surface that it gives to the user thus defining an opening. Each of the surfaces that it gives to the user, the surface that it gives to the garment and the internal surface of said layer of the back sheet with openings has corresponding discrete regions on it. The term "region" as used herein, refers to a discrete surface area of said apertured layer, which comprises an application of said non-soluble material, capable of swelling with the liquid. These regions are identified by discrete limits and may comprise a continuous or discontinuous application of said swelling material therein. In accordance with the present invention at least one of said surfaces, preferably the surface that gives the user or the internal surface or a combination of said surface of said layer of the backsheet comprises the regions. According to the present invention, these regions of said surfaces typically comprise from 50% to 100% of the total surface area of each of the surface that it gives to the user, the surface that it gives to the garment or the inner surface, respectively , of said layer of the back sheet with openings. These regions can be located in any position of said surface. Typically, the user-facing surface and the garment-facing surface each have two end portions, two longitudinal side portions and a central portion, and the region or regions are preferably located in at least the portion central of the surface. The term "central portion" as used herein is defined as the area of the surface where the largest liquid discharge occurs during the use of the article. However, said region or regions may also be located in the end portions and the longitudinal side portions of said surface. The number of regions present on said surface will depend on the method of application used to apply the material capable of inflating on the surface, and in this way the surface may comprise a region or a plurality of regions. The regions can thus be distributed in a regular manner in a pattern or irregularly distributed on one or each of the portions of the surface or on a complete surface of the layer. Preferably, the regions repeat regularly over the total surface, or the surface comprises a region extending over the total surface. Surprisingly it has been found that the application of the material capable of swelling on said surface region of the film layer with openings or the fibrous layer allows the material to swell to such a limit that once the layer comes into contact with liquid , the passage of the liquid through the layer is substantially obstructed. Although not bound by theory, it appears that the application of materials capable of inflating to a film with openings or fibrous layer with openings is advantageous because the openings are distributed in a regular manner in all layers. In particular, it is believed that the regular dimensions, geometrical shape and distribution of the openings in all layers allow the layers to close more efficiently. As a result, the penetration of the liquid throughout the entire layer is avoided. In particular, the present invention is especially beneficial in that the swelling material can be applied to the surface of the layer in the areas where maximum liquid discharge is known to occur and thus be effectively placed to close the openings in contact with the liquid. In addition, and embodiments wherein the inner surfaces of the apertured layer are coated, the closure of these apertures can be controlled more effectively. In accordance with the present invention, any known material that can swell when in contact with the liquid is suitable for application to the surface or surfaces of the backsheet layer with openings. The term "inflate" as used herein, refers to a material exhibits expansion when brought into contact with the liquid in at least one direction, i.e., in the transverse direction x, the longitudinal direction and or the vertical direction z , or a material which inflates in any combination of said directions. The term "liquid" as used herein, refers to any fluid that contains at least 75% by weight of water, such as body fluids including urine, menstrual fluid and the like. The term "non-soluble" as used herein, refers to a material that is not soluble in a significant way at body temperature, so that it can be used for the desired function within the absorbent articles. According to the present invention, each layer or layers of the backsheet comprising the material capable of inflating, at least swell the x, y or z direction. Typically, the most suitable materials are isotropic and in such a way that they swell in all three dimensions. According to the test methods described hereinafter, said material swells preferably in such a way that the layer with openings comprising the inflatable material swells in the z-direction of the layer with apertures of the backsheet by at least 25%, preferably at least 50%, more preferably at least 80%. However, swelling in the directions x, e and is also desirable. The incorporation of at least one film layer with openings comprising a material capable of swelling in the breathable backsheet, allows the passage of water vapor and preferably both water vapor and air through it. In this way, before use and while the backsheet remains dry, the absorbent article is at least permeable to water vapor. After being in contact with the liquid, the material swells thus tending to close the openings of said layer of the backsheet. This thus prevents the passage of matter and macroscopic liquids through the backsheet and over the users' undergarments. As a result of swelling of the layer, the air permeability of the layer and consequently the backsheet in general is reduced and is typically negligible once the layer has been wetted. However, an advantage of the present invention is that the passage of the water vapor is not significantly obstructed by the swelling action of the material upon contact with the liquids. Therefore, while air permeability is reduced, the backsheet and consequently the absorbent article is still breathable when wet. In accordance with the present invention, any material exhibiting the ability to swell upon contact with liquids is suitable for use herein. Suitable materials include (as non-limiting examples) polymers such as polyvinyl alcohols having a hydrolysis level of at least 85%, preferably at least 95%, most preferably at least 98%. The polyvinyl alcohols are prepared by hydrolysis of the polyvinyl acetate. The term "hydrolysis level" as used herein refers to the percentage, in moles of substitution of the acetate groups by the hydroxyl groups. Other suitable materials that exhibit an ability to swell upon contact with liquids for use herein include (as non-limiting examples) polymers such as crosslinked acrylic acid and its copolymers, especially in the form of total or partial alkali metal salts, alkaline earth metals as well as aluminum, zinc and iron salts, as well as poly (acidemethacrylic), polyacrylamide, poly (N, N-dimethylacrialamide) and polymethylacrylamide; crosslinked polyvinylpyrrolidone; polyvinylpyrrolidone copolymers, particularly those containing vinyl acetate; polymethyl, polyethyl or polybutyl vinyl ethers also as the polymers derived from vinyl ethers, for example, the copolymers of methyl vinyl ether and maleic anhydride or maleic acid; polyethylene oxide having a molecular weight of about 100,000 to 8,000,000 Daltons; polysaccharides (gums) of natural origin and their semi-synthetic derivatives such as alginic acid and its salts, agar, locust bean gum, Irish moss, gelatin, starch and cellulose derivatives, such as carboxymethyl cellulose and cellulose acetate, pectin, guar gum and xanthan gum; polyethymimine, polycrocrolein; copolymers of maleic anhydride-styrene; styrene-maleic anhydride copolymers; polydimethyl aminoethyl methacrylate; polyalkene polyamines; poly (vinylbenzyltrimethylammonium chloride) as well as similar quaternary ammonium polymers; poly (maleic anhydride); lower molecular weight phenol-formaldehyde resin; urea formaldehyde resin of lower molecular weight also as compatible mixtures of said materials capable of swelling. The preferred swelling materials for use herein are selected from polyvinyl alcohols; polyacrylic acid, its copolymers and its derived salts; natural polysaccharides and their derivatives, also as mixtures thereof. In addition, material mixtures capable of swelling, which may exhibit different levels of swelling capacity with the liquid may also be used. In particular, it has been observed that the swelling capacity of the particular combinations of certain swelling materials increases beyond the sum of the individual components. These combinations of the swelling materials exhibiting such synergy are particularly preferred and include, for example, the combination of polyacrylic acid and natural derivatives of polysaccharide such as locust bean gum. Any of the methods known in the art can be used for the application of a material to a film to a fibrous layer, to apply the material capable of inflating said layer with openings. Suitable methods include coating, spraying and sprinkling. Preferred methods are the transfer coating of the materials capable of swelling with the liquid and the dusting of the materials capable of swelling into particles. The material capable of swelling can be applied to said region of the surface in any physical form including in the liquid form such as melt, in solution, or in emulsion or in the form of a solid, such as particles. Most preferably, the swelling material is applied to the apertured layer as a solid particulate such as granules. The application of particles is particularly preferred for use with the film layers formed with openings. The material capable of swelling is preferably applied to the surface in an undiluted form. However, plasticizing liquids (such as water, glycols, alcohols, etc.) can also be used in order to apply the material to the surface region. Alternatively, binder materials such as carboxymethyl cellulose can also be used for applications when the material capable of swelling is provided in the form of particles. Preferably, the material capable of inflating said surface in the region is applied in such a way that the particle or coating layer resulting from the swelling material has an average thickness of 0.02 mm to 1 mm, preferably 0.1 mm to 0.5 mm. In accordance with the preferred embodiment of the present invention, the material capable of swelling is applied to the regions of said surface, said layer in the form of particles. Preferably, the particles have an average diameter of about 0.01 to 1 mm, preferably from 0.03 mm to 0.5 mm before being in contact with the liquid. Regardless of the manner in which the material capable of swelling is applied to the surface or surfaces of the apertured layer, the material should preferably be applied at a basis weight of 5 g / m2 to 300 g / m2, more preferably 10. g / m2 at 250 g / m2. Depending on the physical and chemical nature of the material capable of inflating and the method used for its application, the material capable of inflating may require the application of an adhesive in order to ensure its fixation or permanent bonding to the surface of the layer. However, preferably, the material capable of inflating does not require the presence of adhesive in order to ensure its retention. This can be achieved by the manner of incorporation of the apertured layer in the construction of the backsheet and the absorbent article itself. Alternatively, capable of inflating can have inherent adhesive properties by itself such that the additional adhesive is not required. These materials include polyvinyl alcohols and polyvinylmethyl ether and other vinyl ethers. Similarly, the apertured layer on which the swelling material is applied may have adhesive properties such that an additional adhesive is not required. In embodiments where an additional adhesive is required, any of the adhesives known in the art may be used and should be selected such as to minimize the effect of said adhesive on the ability of the material to be inflated and the ability of the layer with openings to expand. allow the transfer of water vapor and air. Adhesives suitable for use in the present invention thus include water acrylic adhesives for example Acronal V 205 available from BASF, Germany or EP 5560 F available from Rohm and Haas Co, E.U.A. It is also contemplated within the scope of the present invention to use adhesives that also have an inherent swelling ability when in contact with liquids, such that they can contribute to the closing of the openings of the layer when in contact with water. Suitable adhesives include certain acrylic adhesives. According to the present invention, the adhesive can be applied to the material capable of swelling before its application on the surface or the adhesive can be applied to the surface or surfaces directly before the application capable of inflating. Accordingly, the adhesive can be applied to said region using any method known in the art such as roll coating, transfer, extrusion, spraying, etc. Typically, the apertured layer is applied with 2 g / m2 to 30 g / m2, preferably 5 g / m2 to 15 g / m2 by weight of said adhesive layer. Preferred breathable layers to be used as the backsheets here are those that have both an exchange with the moist vapor and the high air when they are dry, and which preferably maintain a degree of wet vapor permeability once they get wet, while they avoid the exchange of air. According to a preferred embodiment of the present invention, said apertured layer comprising the coating of material capable of swelling has an air permeability when dry of at least 50 1 / (m2s), preferably at least 70 1 / (m2s), most preferably at least 100 1 / (m2s) and retains an air permeability, when wet, as described here after in the test methods, not exceeding 30%, preferably less than 25% of the value of the permeability of air in the dry state. Preferably, each layer capable of swelling with openings has an air permeability when wetted as described herein below in test methods of less than 10 1 / (m2s), and preferably less than 8 1 / (m2s). In accordance with the present invention, the suitable apertured layer comprising the swelling material can be selected from woven fibrous webs, fibrous non-woven webs, two-dimensional microporous film, two-dimensional macroporous film, macroscopically expanded films or films with formed openings. Preferably, at least one, most preferably all of the layers with openings capable of inflating the backsheet are selected from the film with microporous, macroporous, two-dimensional openings, or a film with openings formed. The backsheets according to the present invention having more than one layer comprising a material capable of inflating, can therefore be selected from any of the previously selected forms and can comprise any combination thereof. According to the present invention, the openings of the backsheet layer may be of any configuration, but are preferably spherical or oblong. The openings may also be of varying dimensions, but typically the openings have an average diameter of 5 microns to 600 microns. For example, the two-dimensional flat porous films for use as the layer herein may have openings having diameters of 200 microns to 5 microns. Similarly, the two-dimensional flat microporous layers for use as the layer herein have openings having average diameters of 150 microns to 5 microns, preferably 120 microns to 10 microns, most preferably 90 microns to 15 microns. The flat, two-dimensional macroporous layers have openings having an average diameter of 90 microns to 200 microns. The layers of macroscopically expanded film and the layers with formed openings have openings having an average diameter of 75 microns to 600 microns. The openings are preferably evenly distributed across the total surface of said layer. However, layers having only certain regions of the surface having openings are also contemplated. The suitable two-dimensional flat layers of the backsheet can be made of any material known in the art, but are preferably made from commonly available polymeric materials. Suitable materials are, for example, XMP-1001 from Minnesota Mining and Manufacturing Company, St. Paul, Minnesota, E.U.A. and Exxaire XBF-101W, supplied by Exxon Chemical Company. As used herein, the term "two-dimensional flat layer" refers to the layers having a depth of less than 1 mm, preferably less than 0.05 mm, wherein the openings have a uniform average diameter along their length and which does not protrude from the plane of the layer. Materials with openings for use as a backsheet in the present invention can be produced using any of the methods known in the art, such as described in EPO 293 482 and references herein. Films formed with suitable apertures include films having discrete apertures, which extend beyond the horizontal plane of the garment facing surface of the layer toward the core, thereby forming a bulge. The protuberances have a hole located at their terminal end. Preferably, said protrusions are of a funnel shape, similar to those described in U.S. Patent No. 3,929,135. The openings located within the plane and the holes located at the terminal end of the protrusions themselves may be circular or noncircular, provided with the dimension or cross-sectional area of the hole at the termination of the protuberance that is smaller than the dimension or area in cross section of the opening located inside the surface that gives the clothing of the layer. Preferably, the preformed films with openings are unidirectional such that they have at least substantially, if not completely, a directional transport of fluid to the core. Macroscopically expanded films suitable for use herein include films as described in, for example, U.S. Patent No. 4,637,819 and U.S. Patent No. 4,591,523. Preferably, the swelling material is applied to at least one of the surfaces of one of the coats of the back sheet. In the embodiments of the multiple breathable backsheet where only one of the layers of the backsheet is applied with a swelling material of the present invention, the surface of the layer should be placed towards the absorbent core, preferably in such a way that that the surface does not form the surface that faces the garment of the absorbent article. Most preferably, the layer itself is placed such that it is in direct contact with the absorbent core and the garment facing surface thereof is applied with the material capable of inflating. This ensures that the material capable of inflating is in contact with the fluid as soon as it has passed through the absorbent core and can immediately swell, thus preventing rewetting. The additional backsheet layers can be placed in contact with the user-facing surface or the garment facing the backsheet layer with openings. According to the present invention, the backsheet comprises at least one layer with openings comprising said non-soluble material, capable of swelling with the liquid. However, in addition said backsheet may comprise optional additional layers that do not comprise materials capable of inflating as defined herein. According to the present invention, the backsheet preferably comprises at least two layers and most preferably said backsheet consists of three layers. The additional backsheet layers can be in any form such as woven, non-woven or apertured, polymeric films, such as flat, macro and microporous two-dimensional films, macroscopically expanded films and polymeric films formed with apertures as was described here above. In addition, said additional layers can be of any chemical nature, as described hereinabove and can be formed from synthetic or naturally derived sources or mixtures thereof. According to a preferred embodiment of the present invention, the backsheet comprises at least two layers, a first layer with openings comprising the material capable of inflating and a second layer comprising a polymeric layer that is not capable of inflating comprising a woven fibrous web , a fibrous non-woven web, a porous film with a two-dimensional aperture or a film with apertures formed, most preferably, the second web is a fibrous nonwoven web. According to an alternative embodiment of the present invention, the backsheet consists of three layers, said layer with openings comprising the non-soluble material capable of inflating with the water and a second and a third layers both comprising components that are not capable of inflating , wherein the second layer and the third layer comprise a polymeric fibrous nonwoven material. According to the preferred embodiment of the present invention, the breathable backsheet itself comprising said layer has in the dry state, the air permeability at the levels defined hereinbefore for the layers with openings comprising the material capable of inflating. In accordance with the present invention, the absorbent articles further comprise a topsheet and an absorbent core. The absorbent material or core may be a foamed fibrous absorbent core, comprising hydrogel particles if desired, or laminated tissues with or without particulate materials including hydrogel particles. The fibers of the absorbent core can be any of those known in the art, including cellulose fibers or polymeric fibers made absorbent or even non-absorbent matrix fibers. Also the tissue of basic weight and sufficient absorbency can be used in the absorbent core according to the present invention. Another component that can be included within the absorbent articles of the present invention, particularly within the nucleus are the odor control assets. Suitable actives include zeolites, silica, chelating agents such as ethylenediamine, tetraacetic acid, activated carbon and clays. These components can be incorporated in any form, but preferably as discrete particles. In accordance with the present invention, the topsheet may comprise a single layer or a multiplicity of layers. In a preferred embodiment, the top sheet comprises a first layer that provides the surface that gives the user of the top sheet and a second layer between the first layer and the diagonal absorbent core structure. The top sheet provides a layer through which the liquids that are absorbed penetrate into the absorbent material. The upper sheet as a whole and therefore each layer individually needs to be docile, soft feeling, 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. Typically, the topsheet extends through the entire absorbent structure and can extend into and form part of all or the side flaps, side wrapping elements or preferred wings. In accordance with the present invention, the topsheet can be formed from any of the materials available for this purpose and known in the art, such as non-woven fabrics, films or combinations of both. In a preferred embodiment of the present invention, at least one of the layers of the topsheet comprises a hydrophobic, liquid-permeable, liquid-permeable, apertured film. Preferably, the top layer is provided by a film material having openings that are provided to facilitate the transport of liquid from the surface that gives the user to the absorbent structure, as detailed for example in U.S. Patent No. 3. 929 135, U.S. Patent No. 4,115,240, U.S. Patent No. 4,319,868, U.S. Patent No. 4,324,466, U.S. Patent No. 4,343,144, and U.S. Patent No. 4 591 523. In accordance with the present invention, the absorbent article is constructed by joining the various elements such as the topsheet, the backsheet and the absorbent core by any means well known in the art. For example, the backsheet and / or the topsheet may be attached to the absorbent core or to each other by a uniform, continuous adhesive layer, a patterned adhesive layer, or an array of separate lines, coils, or spots of adhesive. Alternatively, the elements can be joined by heat bonds, pressure joints, ultrasonic joints, dynamic-mechanical joints or any other suitable joining means known in the art and any combination thereof. Preferably the individual breathable backsheet layers are bonded together to reduce and preferably eliminate any reduction in vapor permeability of the backsheet. Similarly, the breathable backsheet itself is bonded to other elements of the absorbent articles to minimize the effect of wet vapor permeability of the backsheet.

In accordance with the present invention, the absorbent article may find utility such as sanitary napkins, panty liners, adult incontinence products and baby diapers, but may also include other items such as armpit pads or collar bands. The present invention finds particular susceptibility as sanitary napkins and liners for panties. Thus, in addition to the components described hereinbefore, the absorbent article may also comprise all those characteristics and parts that are typical for the products within the context of the intended use such as wings and side flaps, adhesive means for the undergarment, paper of detachment, wrapping elements, fastening means and the like, all known in the art.

EXAMPLES TEST METHODS Testing air permeability in individual layers capable of inflating a breathable back sheet The air permeability test is used to determine the ability of a material to circulate / exchange air.

Basic principle of the method The basic principle of the test is to evaluate the resistance of the material to the passage of air. This test measures the volume (or amount) of air flowing through a sample of given dimensions under standard conditions (23 ° C / 50% relative humidity) and under a given pressure difference. The instrument used for the test is: the air permeability meter FX 3300 manufactured by Tex Test Ag, Switzerland. 100 mm square of wet and dry samples are prepared as described below for air permeability measurements. The sample is placed on the device according to the manufacturer's instructions. A suction pump is used to generate a 1210 Pa depression that sucks air through the sample layer. The device measures the volume of the air flow at a constant pressure drop through the holes contained in the sample and the measuring head. Finally, the device generates a value of air permeability in units of "1 / (m2s)". For each material, in the dry state and in the wet state, six samples are measured and the average value of the air permeability is calculated.

Dry and wet samples The term "dry" as used herein refers to a sample material stored at 23 ° C and 50% relative humidity for at least 12 hours. The test is also performed under these conditions. The term wet or wet as used herein refers to a sample material which has been contacted uniformly with 10 cm3 of distilled water at 37 ° C with a pipette. Excess water is removed by gently pressing the sample on blotting paper. The sample left to remain for at least 60 seconds before the test is carried out, the test being carried out within 10 minutes after contact with water.

Swelling test The capacity of the material to be inflated was measured by determining the caliber of a test sample from a backsheet in the dry and wet state. This determines the swelling in the z direction.

A square sample of 100 mm in size of the layer to be tested is prepared for gauge (thickness) measurement in the dry and wet state. The calibres of the sample are measured using a APP thickness measuring device. 51D20, type 02101, supplied by Lorentzen & Wettre, Sweden and following the supplier's instructions. The thickness measuring device registers the caliber of the pressed sample between two measuring plates, when the pressure exerted reaches 20 g / cm2. The average of the three caliber readings of each of the samples is taken. Five samples for each material are tested and the value is the average value of these readings.

Examples of the back sheet layer Example 1 This example is a back sheet composed of two layers, a first layer and a second layer both comprising a polyester nonwoven material, having a basis weight of 40 g / m2, (available from Suominen, Finland, under the code name F 4100/40). The surface that gives the user of the second layer is coated with a water-based acrylic adhesive (available from Rohm and Haas Co., E.U.A. under the code name EP 5560 F, at a basis weight of 10 g / m2). Then powder of an acrylic superabsorbent, base weight of 50 g / m2 (available from Hoechst A.G., Germany under the code name Sanwet 3746-1) is sprinkled on the entire surface that it gives to the user. The surface that gives the garment of the first layer is then placed on the surface that gives the user of the second layer. The first and second layers are held together in position by the use of staples around the circumference of the layers. Permeability in the dry state = 4000 liters / (m2. S) Permeability to the air in the wet state = 4 liters / (m2.) Dry caliber = 850 um Wet gauge = 2390 um% swelling Delta in the z direction = 181% From the above values, it can be seen that the layer of the backsheet exemplified has a negligible air permeability after contact with the liquid and demonstrates a high degree of swelling such that the size of the wet samples it is 181% greater than the caliber of the corresponding dry samples, even after a time of contact with the liquid with the water of 60 seconds.

EXAMPLE 2 The example is identical to Example 1 except that the material capable of swelling is replaced by the locust bean gum powder (available from Franco Vanni, Italy, under the trade name Albagum at a basis weight of 43 g / m2). The powder of locust bean gum is bonded to the surface that it gives to the user of the first layer by applying a water-based acrylic adhesive, (available under the code name EP 5560 F, from Rohm and Haas Co., at a base weight of 6 g / m2). Permeability in the dry state = 7350 liters / (m2. S) Permeability to the air in the wet state = 4 liters / (m2. S) Dry gauge = 8725 um Wet gauge = 1140 um% swelling Delta in the z direct= 38% Example 3 This example is identical to the example except that the second layer has been replaced with a film formed with openings (available from Tredegar Co., USA, under the code S-225 MD 25, which has a basis weight of 25 g / m2 ). The surface that gives the user of the second layer was coated with an adhesive layer of a water-based acrylic adhesive (available under the code name EP 5560 F, from Rohm and Haas Co., USA, at a basis weight of 10 g. / m2), and the powder of locust bean gum (available from Franco Vanni, Italy under the name Albagum) is applied to a basis weight of 14 g / m2. The discontinuous coating of the material capable of swelling with the water has been applied on the surface that gives the user of the film formed with openings, that is, on the surface from which the cones protrude. Air permeability in the dry state = 645 liters / (m2.). Air permeability in the wet state = 24 liters / (m2.) Dry caliber = 800 um Wet gauge = 1050 um% Delta swelling in the z direct= 31% Example 4 This example is identical to Example 3 except that the material capable of swelling has been replaced by a powder of an acrylic superabsorbent (Sanwet 3746-1, available from Hoechst A.G., Germany at a basis weight of 25 g / m2). Air permeability in the dry state = 1090 liters / (m2 .s). Air permeability in the wet state = 134 liters / (m2.). Dry Calibrat= 845 um Wet Calibrat= 1600 um% Delta Swelling in the z direct= 89% Examples 1 and 2 in which the swelling materials are kept placed between non-woven materials, allows general swelling to be measured actual material in the z direct(because these materials are expected to be substantially isotropic, it is reasonable for the same swelling to occur in the x, y, and z direct. It should be noted that for examples 3 and 4, the change in gauge is not a direct measurement of the ability of the inflatable material to be inflated. This is because some of the swelling actually occurs on the inner surface of the film formed by openings and is therefore not directly detectable as an increase in the caliper. Consequently, the percentage change in swelling is not as great as anticipated.

Example 5 In this example the backsheet comprises three layers, a first layer, a second layer and a third layer, the second intermediate layer being the first and third layers. The first and third layers comprise a non-woven polyester material, having a basis weight of 40 g / m2, (available from Suominen, Finland, under the code F 4100/40). The second layer is a film formed with openings (available from Tredegar, under the code S-225 MD 25, which has a basis weight of 25 g / m2) where the cones protrude from the plane of the surface that gives the garment the movie. The surface that gives the garment of the first layer and the surface that gives the user of the third layer are coated with a water-based acrylic adhesive (Acronal V 205 available from BASF, Germany). The material capable of inflating is a superabsorbent material (available from Shokubai, Japan, under the trade name Aqualic L-74) and is sprinkled on the surface that gives the user the second layer, in such a way that the final average weight of the Aqualic L-74 present in a square meter of the film with opening is 95 gr. The three layers are then stapled together and on the periphery. Air permeability in dry state = 510 liters / (m2.). Permeability to the air in wet state 0 7 liters / (m2.s). The swelling test was not carried out in this example. However, from the measurements of air permeability it can be clearly concluded that the openings have closed to minimize air permeability and consequently swelling has occurred as required.

Claims (15)

1. An absorbent article comprising a liquid-permeable topsheet, a backsheet and an absorbent core, the core being positioned between the topsheet and the backsheet and wherein the backsheet is breathable and said backsheet comprises at least one layer compressing openings, the layer having an upper surface, a lower surface and an inner surface and which is characterized in that at least one of said surfaces of the apertured layer has at least one region therein, wherein said region of said surface it comprises, preferably it is covered with, a non-soluble material capable of swelling with the liquid.

2. An absorbent article according to claim 1, wherein said region of the top surface is coated with said material.

3. An absorbent article according to claim 1, wherein said region of the lower surface is coated with said material.

4. An absorbent article according to claim 1, wherein the region of the inner surface comprises said material.

5. An absorbent article according to claim 4, wherein said layer is a film formed with openings.

6. An absorbent article according to claim 5, wherein said material is in the particulate form.

An absorbent article according to any of claims 1 to 3, wherein the apertured layer is selected from films formed with apertures, microporous films, macroporous films, fibrous fabrics and fibrous nonwoven material.

8. An absorbent article according to any of the preceding claims, wherein said material is selected from polyvinyl alcohols, polyacrylic acid, natural polysaccharides and mixtures thereof.

9. An absorbent article according to any of the preceding claims, wherein said layer comprises said material in a basis weight of 5 g / m2 to 300 g / m2.

10. An absorbent article according to any of the preceding claims, said surface further comprises an adhesive in said region.

An absorbent article according to any of the preceding claims, wherein the backsheet comprises at least two layers, the layer with openings comprising said material capable of inflating and a second layer selected from films formed with openings, microporous films , macroporous films, woven and nonwoven materials.

12. An absorbent article according to claim 11, wherein the apertured layer is a film formed with openings and said second layer is a fibrous nonwoven material.

An absorbent article according to claim 11 or 12, wherein the backsheet comprises three layers, wherein said third layer is a fibrous nonwoven material.

An absorbent article according to any of the preceding claims, wherein the apertured layer has an air permeability when dry, as defined in the air permeability test, of not more than 50 1 / (m2. s) and air permeability when wet, as defined in the air permeability test, of no more than 30% air permeability when dry.

15. An absorbent article according to any of the preceding claims, is where article is a sanitary napkin or a panty liner.