MXPA06009871A - Disposable absorbent articles with improved fastening performance to hydrophobic materials, particularly microfibre materials - Google Patents

Abstract

The present invention relates to an absorbent article for personal hygiene, especially a sanitary napkin, panty liner and the like, comprising an adhesive for securing said article to the garments of a wearer, especially microfibre garments. Said adhesive has an elastic modulus G'at 0.01 Hz and 25°C of from 1,000 to 10,000 Pa and a loss tangent tand at 0.01 Hz and 25°C of from 0.3 to 2.

Description

DISPOSABLE ABSORBENT ITEMS WITH A BETTER PERFORMANCE OR FIXATION TO HYDROPHOBIC MATERIALS, ESPECIALLY TO MICROFIBRE MATERIALS FIELD OF THE INVENTION The present invention relates to an absorbent article for personal hygiene, in particular to a sanitary napkin, panty-protector and the like, comprising an adhesive for securing that article to a user's garments, in particular to microfiber garments. This adhesive has a plastic modulus G 'at 0.01 Hz and 25 ° C from 1 000 a ,000 Pa and a tangent of loss tand at 0.01 Hz and 25 ° C from 0.3 to 2.

BACKGROUND OF THE INVENTION The use of adhesives to secure disposable absorbent articles for personal hygiene is well known in the industry. Specifically, the use of emulsion-based hot-melt adhesives and adhesives is a general technical standard. The application of emulsion-based adhesives on lower canvases of absorbent articles for attachment to garments is described, for example, in SE-A-374,489. The use of hot melt adhesives for this purpose is described, for example, in EP-A-140,135 or WO 00/61054. Lately, a considerable change in women's clothing habits has been observed. Every day there are more women, especially young people, who no longer wear cotton pants, so common in recent decades, but tend to wear panties made of a specific synthetic fabric material, commonly known as "microfiber." Microfibers are one of the most important recent developments in the fabric industry. These fibers conventionally have less than 1 denier and a transverse diameter commonly of up to 10 μm. Shortly after appearing on the market, microfibers have proven useful especially in the garment industry where they are used to manufacture fabrics that have an exclusive physical and mechanical performance, such as a luxurious look and feel since microfibers are even thinner than silk, together with very adequate characteristics of resistance, uniformity and processing. The resulting very fine and closed knitted and woven fabrics are characterized by their softness to the touch and permeability. Based on this, microfiber fabrics are also used to make panties for women, especially modern panties for young women. Microfiber fabrics have physical characteristics very different from the physical characteristics of conventional cotton fabrics. In particular, this applies to the hydrophobicity that is greater for microfibers and that often also increases when treating microfibers with fluoropolymers, silicones, microwaxes and the like. Therefore, unlike conventional cotton garments, microfiber garments have a practically hydrophobic surface. In addition, the density of the fabrics made of microfibers is considerably higher compared to the density of the cotton fabrics. As a consequence, the void space between the individual microfiber filaments is much smaller compared to the void space in the cotton fabrics. Due to the aforementioned characteristics, conventional adhesives currently available for securing absorbent articles, such as sanitary napkins and pantiliners, to garments do not work properly for microfiber garments. It has been observed that the bonding forces that current panty fixation adhesives (hereafter PFAs) can supply to microfiber garments are too few to reliably hold absorbent articles, especially under of tension, such as for example during physical exercise and the like. Therefore, an object of the present invention is to provide an article to bsorbent with a P FA that can provide a secure connection of the absorbent article to the microfiber garments.

BRIEF DESCRIPTION OF THE INVENTION It has been found that the viscoelastic behavior of the adhesive described by means of the Theological parameters tand, G 'and G "is the key element that must be adjusted to solve the aforementioned problem The present invention provides an absorbent article that is attached to the garment of a user by means of a PFA In particular, the PFA of the absorbent article of the present invention has a modulus of elasticity G 'at 0.01 Hz and 25 ° C of 1000 to 10,000 Pa and a tangent of loss tand at 0.01 Hz and 25 ° C from 0.3 to 2. In a preferred embodiment of the present invention there is provided an absorbent article with a PFA having a tand inside a quadrangle ABCD, where that quadrangle ABCD is defined by graphically plotting the frequency in Hz against the tand at 25 ° C of that adhesive; that quadrangle ABCD has as points A and D a tand of 0.3 and 2, respectively, at a frequency of 0.01 Hz and points B and C at a tand of 0.8 and 4, respectively, at a frequency of 10 Hz. In another modality Preferred of the present invention, the PFA of the absorbent article has a modulus G 'in the rear of a quadrangle A BCD, where that quadrangle ABCD is defined by graphically plotting the frequency in Hz versus the tand at 25 ° C of that adhesive; that quadrangle ABCD has as points A and D a module G 'of 1000 to 10,000, respectively, at a frequency of 0.01 Hz and as points B and C to a module G' of 20,000 and 100,000, respectively, at a frequency of 10 Hz.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a graphical representation of the ranges of the parameters claimed in claim 1, ie tand and G 'at 0.01 Hz and 25 ° C. Figure 2 is a double logarithmic graphical representation of the ranges of parameters claimed in claim 4, ie of tand in a frequency range of 0.01 Hz to 10 Hz at 25 ° C. Figure 3 is a double logarithmic graphical representation of the parameter ranges claimed in claim 6, ie of G 'in a frequency range of 0.01 Hz to 10 Hz at 25 ° C. Figure 4 is a graphical representation of the test results for the four illustrative PFAs investigated herein with respect to the parameters claimed in claim 1. Figure 5 is a graphical representation of the test results for the four illustrative PFAs investigated in the present with respect to the parameters claimed in claim 4. Figure 6 is a graphic representation of the test results for the four illustrative PFAs investigated herein with respect to the parameters claimed in claim 6. Figure 7 illustrates the tape side of the common microfiber material used in the peel force test method described herein. Figure 8 illustrates the PFA side of the common microfiber material used in the peel force test method described herein.

DETAILED DESCRIPTION OF THE INVENTION The term 'absorbent article' is used herein in a very broad sense and includes any article capable of receiving and / or absorbing and / or containing and / or retaining and / or liquids and / or exudates, especially body fluids / exudates. bodily The absorbent article referred to herein typically comprises a liquid-permeable top sheet such as the user-facing layer, a lower water-impermeable sheet as the garment-oriented layer that is preferably permeable to water vapor and / or as and a nucleus to bsorbent included among them. In addition, the absorbent articles, in the context of the present invention, are provided with a means for attachment to the wearer's garment, in particular with an adhesive. Preferred absorbent articles in the context of the present invention are disposable absorbent articles. Typical disposable absorbent articles in accordance with the present invention are absorbent articles used for personal hygiene, for example, baby care items such as diapers; incontinence protectors and transpiration protectors such as protectors for underarm perspiration or hat bands.

Especially preferred disposable absorbent articles are absorbent articles for feminine hygiene such as sanitary napkins and pantiliners. In the present, the term 'body fluid' refers to any liquid produced by the human body, including for example, perspiration, urine, blood, menstrual fluids, vaginal secretions and the like.

The term "disposable" is used herein to describe articles that are not intended to be disposed of or reconstituted or reused in any way as an absorbent article (ie whose destination is to be discarded after being used only once, and preferably are intended to be recycled, become compost or disposed of in some other way compatible with the environment). The term 'use', as used herein, refers to the period that begins when the absorbent article actually comes into contact with the wearer's body. As used herein, the term 'hydrophilic' refers to a material having a contact angle of water in air of less than 90 degrees, while the term 'hydrophobic' refers herein to a material having An air contact angle of 90 degrees or greater. Hydrophobic materials are also known as water repellents. As used herein, 'microfibers' refers to fibers that have a denier of up to 1 (1 denier = 1 g / 9000 m fiber) and a transverse diameter of up to μm. Microfibers are artificial fibers and are typically composed of polyester or polyamide, such as nylon. In the fabric industry, microfibers are used to make very thin closed woven cloth materials and knit fabrics that are characterized by their softness to the touch and permeability. Microfiber fabrics have physical characteristics very different from the physical characteristics of conventional cotton fabrics. In particular, this applies to hydrophobicity which is considerably greater than the hydrophobicity of cotton fibers and which often also increases when treating microfibers with fluoropolymers, silicones, microwaxes and the like. Frequently, microfiber garments also contain elastane / Lycra fibers to provide elasticity. Since the microfibers have a small diameter, the density of the fabrics made with these microfibers is very high compared to the density of the cotton fabrics. The reduced fiber diameter of these microfibers makes the empty space between the individual microfibers very small compared to the empty space in the cotton fabrics. The typical microfibre materials are distributed in the market p. e j., by Dupont under the trade name of Tactel® or by Nylstar under the trade name Meryl®. As mentioned below, in the context of the present invention an absorbent article comprises an adhesive means for attaching this article to the wearer's garments. This adhesive is also referred to as 'panty fixation adhesive' or 'PFA'. The PFA is provided on the surface of the absorbent article of the present invention that is oriented toward the undergarment to secure that article to a wearer's garment. Similarly, if the product is a winged product, the wings may also include PFA on the surface facing the undergarment to secure the wings to the wearer's garment. The PFA useful herein is preferably a pressure sensitive adhesive, among which pressure-sensitive hot melt adhesives are especially preferred. The inventors of the present have found that the fundamental property that an adhesive must have to reliably join a microfiber garment is its viscoelastic behavior. In fact, it is well known on the basis of literature (see, eg, "Viscoelastic Windows of pressure sensitive adhesives" (Viscoelastic windows of pressure sensitive adhesives), E. P. Chang, J. Adhesion, Vol. 34, 1991, pgs. 1 89-200; H andbook of p ressure sensitive adhesive technology (Manual of pressure sensitive adhesive technology), Ed. Satas, 3rd. edition, pages. 171-183; Pocius "Adhesion and adhesive technology" (Adhesive and technology of adhesives), pgs. 216-245) that the performance of adhesives, p. eg, detachment, adhesiveness, friction depends largely on the viscoelastic properties of the adhesive volume. This viscoelastic behavior can be quantified by means of the Theological parameters of elastic modulus G ', viscous modulus G "and tangent of loss tand (that is the relation G'VG'). All these parameters are specific for certain frequencies and can be determined by As a standard ASTM D4440-95 test procedure with flat plates that oscillate at the frequency considered, it should be mentioned that the Theological parameters vary widely with frequency, Secondly, the frequency in the procedure for measuring the parameters Theological simulates some real-life situations, Specifically, a frequency of 0.01 Hz represents a typical union and in particular the typical conditions when using the garment, this means the behavior of the adhesive when it is fixed to the wearer's garment and especially during the use, after the fixation, the removal of an article from a garment, specifically the withdrawal of the article of the user's garment is made with increasing frequency. It has been proven that 10 Hz is a suitable frequency to observe the behavior of the adhesive when removing the item from the garment. At present, the elastic and viscous moduli are determined at a temperature of 25 ° C (77 ° Fahrenheit). The adhesive used as PFA in the present invention must meet the following condition: The loss tangent tand at 0.01 Hz and 25 ° C must be within the range of 0.3 to 2 and the elastic modulus G 'at 0.01 Hz and 25 ° C It must be within the range of 1000 to 10,000 Pa. In fact, for the adhesive to be fixed on the microfiber cloth it is essential that this adhesive can moisten the surface of the microfiber and continue to moisten that surface while using the article. Therefore, we consider rheological properties based on longer times, ie lower frequencies, 0.01 Hz (ie 0.0628 rad / s) very close to the creep frequency. In general, adhesives that do not meet the two conditions set forth in this paragraph will not provide sufficient adhesion to the surface of the microfiber fabric. It has been found that if the tangent of loss tand at 0.01 Hz and 25 ° C is less than 0.4, the adhesive will not be able to flow during the use of the article and will penetrate into the net fiber of the microfiber material thus providing a mechanical grip and an increase of the strength of union; the inventors have found that a tand at 0.01 Hz and 25 ° C up to 2 can guarantee sufficient adhesion to the surface of the microfiber cloth. It has been found that if the elastic modulus G 'at 0.01 Hz and 25 ° C is greater than 10,000 Pa, the adhesive will be too hard and therefore will not bond properly to the surface of the microfiber: in fact, during the use of the article , after applying the pressure adhesive and releasing that pressure, the high elastic modulus allows the elastic relaxation of the adhesive to be greater than the low adhesion to the very hydrophobic microfiber material, and thus the microfiber fibers dehumidify and produce a very low release adhesion. The inventors have found that an elastic modulus G 'at 0.01 Hz and 25 ° C greater than 1000 Pa can guarantee sufficient adhesion to the surface of the microfiber cloth. Adhesive compositions that meet the above criteria can be used as PFA for the absorbent article of the present invention as long as they also meet the common safety requirements for use near human skin and are generally safe after disposing of the article. . In a preferred embodiment, the adhesive to be used as PFA in accordance with the present invention has a tand inside a quadrangle ABCD, where that quadrangle ABCD is defined by plotting tand in front of the frequency in Hz at 25 ° C of that sticker; that quadrangle ABCD has as points A and D a tand of 0.3 and 2, respectively, at a frequency of 0.01 Hz and as points B and C to a tand of 0.8 and 4, respectively, at a frequency of 10 Hz. is less than the AB limits of the window described in this paragraph, the adhesive has a lower ability to flow and therefore reduces its ability to penetrate the spaces between fibers of the microfiber of the garment. Inventors have found that a tand up to the CD limit of Figure 2 can guarantee sufficient adhesion to the surface of the microfiber cloth. In another preferred embodiment, the adhesive to be used as a PFA according to the present invention has a modulus G 'inside a quadrant ABCD, where that quadric ABCD is defined when plotting G' in front of the frequency in Hz at 25 ° C of that adhesive; that quadrangle ABCD has as points A and D a module G 'of 1000 and 10,000, respectively, at a frequency of 0.01 Hz and as points B and C to a module G' of 20,000 and 100,000, respectively, at a frequency of 10 Hz. When the G 'module is above the CD window defined in this paragraph, the adhesive has reduced bonding properties since it is too rigid, in other words too hard. The inventors have found that an elastic modulus G 'greater than the limit AB of Figure 3 can guarantee sufficient adhesion to the surface of the microfiber cloth. In a particularly preferred embodiment of the invention, the adhesive has the two properties defined in the preceding two paragraphs. The graphs of Figures 2, 3, 5 and 6 are represented on a double logarithmic scale commonly used to describe variations in rheological properties over several decades of frequency. Following are examples of suitable adhesives to be used as PFA to securely secure an absorbent article to a microfiber substrate. Examples of commercially available PFA suitable for the present are Bio PSA 7-4560 from Dow Corning which is a silicone adhesive and MF55 from Savare 'which is a block-based adhesive of copolymers. A detailed description of suitable silicone PFA is provided below. As mentioned above, Bio PSA 7-4560 from Dow Corning is part of this PFA class. A suitable class of pressure sensitive adhesive compositions is described in U.S. Pat. no. 4,865,920 and consists of (i) a polysilicate resin blocked at the end with a trimethylsilyl group such as a silicone resin consisting of a resinous benzene-soluble copolymer containing hydroxyl radicals bonded with silicon and consisting essentially of triorganosiloxy units of the formula R3SiO1 2 and tetrafunctional siloxy units of the formula SiO42 with a ratio of about 0.6 to 0.9 triorganosiloxy units for each tetrafunctional siloxy unit present in the copolymer and (ii) a fluid polydiorganosiloxane terminated with silanol (silicone liquid), e.g. eg, a polydimethylsiloxane fluid. U.S. Pat. no. 2,736,721 to Dexter et al. and U.S. Pat. no. 2,814,601 to Currie et al. describe those pressure sensitive adhesive compositions or others of the same type. Other pressure sensitive adhesive compositions suitable for use with the specific ester described herein above are those corresponding to that class or similar classes described in U.S. Pat. no. No. 2,857,356 to Goodwin, Jr. The Goodwin, Jr. patent discloses silicone pressure sensitive adhesive compositions consisting of a mixture of ingredients comprising (i) a cohydrolysis product of a hydrolysable trialkylsilane and an alkylsilicate, wherein the product of cohydrolysis contains a plurality of silicon-bonded hydroxyl groups (silica resin) and (ii) a linear high-viscosity orgnopolysiloxane fluid (silicone liquid) containing silicon-bonded hydroxyl groups.

The silicone resin (i) and the silicone liquid (ii) can optionally be condensed together, for example, by the procedure described in Canadian patent no. 711, 756 of Pail. In that condensation reaction, the silicone resin (i) and the siiicone liquid (ii) are mixed together in the presence of a silanol condensation catalyst and the silicone resin (i) and the silicone liquid (ii) are they condense, for example, by heating under reflux conditions for 1 to 20 hours. Examples of silanol condensation catalysts are the primary, secondary and tertiary mines, the carboxylic acids of these amines and the quaternary ammonium salts. Another class of pressure sensitive adhesive compositions suitable for use with the specific ester described herein above are the compositions disclosed in U.S. Pat. num. 4,591,622 and 4,584,355 to Blizzard et al. no. 4,585,836 to Homan et al. and No. 4,655,767 to Woodard et al. Generally, these pressure sensitive adhesive compositions consist of a mixture of i) a silicone resin and ii) a chemically treated silicone liquid to reduce the content of silicon-bonded hydroxyls in the mixture. Prior to the chemical treatment, these compositions may optionally be condensed as described above. The pressure-sensitive silicone adhesive is prepared simply by mixing the siloxanes (i) and (ii) with the selected ester or esters. The pressure sensitive silicone adhesive compositions are then heated to a suitable viscosity for use as a coating and applied to the surface of the absorbent article facing the undergarment. Optionally, the pressure-sensitive silicone adhesive can be cured. If the pressure-sensitive silicone adhesive is to be treated by curing, that adhesive may also contain a curing catalyst. Preferably, these catalysts remain inactive at room temperature and at temperatures reached during the hot melt coating process. Therefore, those catalysts that are activated at temperatures higher than those of hot melt or are activated when they are exposed to another source of energy, p. eg, UV light or electron beam radiation are suitable. Optionally, the pressure sensitive silicone adhesive may include fillers, such as extension or reinforcing fillers. The ester used to prepare the pressure-sensitive silicone adhesive described in U.S. Pat. no. 2,857,356 of Goodwin as described above has the general formula: O R C - OR ' wherein R is a monovalent hydrocarbon radical having from 2 to 32 carbon atoms and R 'is a monovalent hydrocarbon radical having from 1 to 14 carbon atoms. Preferably, R has from 10 to 19 carbon atoms and R 'has from 1 to 3 carbon atoms. R and R 'are independently selected and therefore may be the same or different. Preferably, the esters for pressure-sensitive hot-melt silicone adhesives are non-flammable and therefore the process is safer when the pressure-sensitive silicone adhesive compositions are applied at elevated temperatures. Flammable materials, as the term is used herein, are those flammable materials in accordance with the definition provided in the Code of Federal Regulations of the United States, title 49, part 173, section 115 (49 CFR 173.115). In summary, a flammable liquid refers to any liquid that has a flash point of less than 37.8 ° C (100 ° F), where the flash point refers to the minimum temperature at which a liquid gives off steam within a Test container with sufficient concentration to form a mixture that can be ignited with air near the surface of the liquid. The CFR provides adequate test conditions to measure the flash point. When flammable esters are used, the coating operation could be done in an inert atmosphere (eg, nitrogen gas) lacking oxygen gas to avoid fire hazards. The ester used should not boil at process temperatures. In general, temperatures greater than about 100 ° C produce acceptable working viscosities with non-emulsifiable, non-combustible silicone adhesives.; For example, they prefer esters that have boiling points above 100 ° C. The esters can be solid or liquid. Although solid esters can be used, they must be at least somewhat soluble in the pressure-sensitive silicone adhesive at the coating temperature. Examples of suitable esters include 1-phenylethylpropionate, ethylnoleic acid ethyl ester, dodecyl acetate, ethyl triacontanoate, octyl acetate, methyl caproate, methyl decanoate, isobutyl acetate, methyl docosanoate, methyl heptadecanoate, palmitate isopropyl, isopropyl myristate, lauric acid methyl ester and mixtures thereof. The esters can be used in amounts of about 1% to 10% by weight, based on the total weight of the silicone resin and the silicone liquid. In general, if the ester is fluid at room temperature, especially when the pressure sensitive adhesive will not cure, preferably the maximum limit of the ester will be about 7%, since when that percentage is higher, the ester may make the pressure-sensitive hot-melt silicone adhesive have a high creep at room temperature and this is not suitable for most applications. Generally, solid esters are preferred if it is desired to use more than about 7% by weight of ester in the pressure-sensitive hot-melt silicone adhesive. Pressure-sensitive silicone adhesives can be made by mixing the ingredients in any order. It may be necessary to complete the reaction or the treatment of the ingredients, p. eg, condensation in accordance with the procedure described in CA 711,756 or chemical treatment in accordance with US Pat. num. 4,591,622 and 4,584,355 before adding the ester. The ester allows the viscosity of the pressure-sensitive hot melt adhesive to decrease at elevated temperatures to a suitable viscosity to coat a substrate without using solvents to be removed. The viscosities suitable for hot melt processing are from about 20-30 Pa.s (20,000-30,000 cp (centipoise)) and, more typically, 30-40 Pa.s (30,000-40,000 cp). Typically, upon heating the pressure-sensitive hot melt silicone adhesives described in this invention to temperatures of about 100 ° C or more (more typically above 150 ° C) suitable viscosities of less than 40 Pa.s (40,000 cp. ) These temperatures suitable for the coating are sufficiently low so that the composition does not decompose. Lower temperatures can produce suitable viscosities for the coating depending on the equipment used, the desired final product and the type and amount of the ester used. For example, the greater the thickness desired for the pressure sensitive adhesive layer, the higher the coating viscosity may be.

The upper canvas The upper canvas is moldable, soft to the touch and does not irritate the wearer's skin.

The upper canvas can also have elastic characteristics that allow it to stretch in one or two directions in portions of the upper canvas or in its entire extension. In addition, the upper canvas is permeable to fluids, which allows fluids (eg, urine or menstrual fluid) to easily penetrate through their layers. A suitable top canvas can be manufactured from a wide variety of materials such as woven and non-woven fabric materials; polymeric materials such as thermoplastic films formed with holes, perforated plastic films and hydroformed thermoplastic films; and thermoplastic canvases. Woven and non-woven fabric materials may be composed of natural fibers (eg, wood or cotton fibers), synthetic fibers (eg, polymer fibers such as polyester, polypropylene or polyethylene) or of a combination of natural and synthetic fibers or bicomponent or multicomponent fibers. Preferred upper canvases for use in the present invention are selected from high-fluff non-woven fabric upper canvases and from upper sheets of films formed with holes. For the upper canvases, films formed with holes are especially preferred since they are permeable to body fluids and yet are not absorbent and have a reduced tendency to allow body fluids to return and rewet the user's skin. Therefore, the surface of the formed film that is in contact with the body remains dry; and in this way it reduces the soiling of the skin and generates a feeling of greater comfort for the wearer. Suitable shaped films are described in U.S. Pat. num. 3,929,135; 4,324,246; 4,342,314; 4,463,045 and 5,006,394. Highly preferred microfilm-formed orifice films are described in US Pat. num. 4,609,518 and 4,629,643. The top canvas that is preferred in the present invention comprises the formed film that is described in one or more of the aforementioned patents and is marketed by The Procter & Gamble Company of Cincinnati, Ohio in sanitary napkins, as "DRI-WEAVE". In the present invention, the use of upper canvases in which the liquid passageways are not uniformly distributed is also contemplated, but these passageways are only in a portion of that canvas. Typically, in these upper canvases, the passageways of liquids would be oriented in such a way that the canvas is permeable to liquids in the center and impervious to the periphery. The body surface of the formed film top sheet may be hydrophilic in order to render the transfer of the liquid particles through the top window faster than when the body surface is not hydrophilic. In a preferred embodiment, the surfactant is incorporated into the polymeric materials of the upper film web formed as described in PCT publication WO 93/09741.

Alternatively, the surface of the body of the upper canvas can be made hydrophilic by treating it with a surfactant as described in U.S. Pat. no. 4,950,254. Another alternative are the so-called hybrid upper canvases that incorporate fibrous and film-like structures. The modalities of those especially useful hybrid top cloths are described in the PCT publications WO 93/09744; WO 93/11725 or WO 93/11726. The upper canvas typically extends through the entire absorbent structure and outside the coextensive area to said structure. The upper canvas can extend and form part of the preferred lateral fins, the lateral wrapping elements or the wings or constitute them in their entirety. When referring to the upper canvas, a multilayer structure or a monolayer structure is contemplated. The hybrid upper canvas mentioned above is designed with multiple layers, but other multi-layer upper canvases are also considered as the primary and secondary upper canvas designs.

Absorbent Core In accordance with the present invention, absorbent cores suitable for use herein may be selected from any absorbent core or core systems known in the industry. As used herein, the term "absorbent core" refers to any layer of material or multiple layers of material whose primary function is to absorb, store and distribute the fluid. According to the present invention, the absorbent core can include the following components: (a) an optional primary fluid distribution layer, preferably together with an optional secondary layer of fluid distribution; (b) a fluid storage layer; (c) an optional fibrous layer ("powder") below the storage layer; and (d) other optional components. a) Primary and secondary fluid distribution layers As an optional component of the absorbent core according to the present invention, a primary fluid distribution layer and a secondary fluid distribution layer can be used. The primary distribution layer is usually below the upper canvas and is in fluid communication with it. The upper canvas transfers the received fluid to the primary distribution layer that distributes it to the storage layer. This transfer of fluid by means of the primary distribution layer takes place not only through the thickness, but also in the direction of the longitudinal and transverse directions of the absorbent product. The optional but also preferred secondary distribution layer is usually below the primary distribution layer and is in fluid communication with it. The purpose of this secondary distribution layer is to easily receive the fluid from the primary distribution layer and transfer it rapidly to the layer of the surrounding layer. This helps the fluid capacity of the underlying storage layer to be fully utilized. The distribution layers can be constituted by any typical material for these distribution layers. b) Fluid storage layer In a position that allows it to be in fluid communication with the primary or secondary distribution layers and usually below them is a fluid storage layer. The fluid storage layer may comprise the usual absorbent materials or combinations thereof. Preferably it comprises absorbent gelling materials which are usually known as "hydrogel", "superabsorbent" and "hydrocolloid" materials in combination with suitable carriers. The absorbent gelling materials can absorb large amounts of aqueous body fluids and, in addition, can retain the fluids absorbed under conditions of moderate pressure. The absorbent gelling materials can be dispersed homogeneously or non-homogeneously in a suitable carrier. Suitable carriers, as long as they are absorbent, can also be used independently. The absorbent gelling materials suitable for use herein generally comprise a polymeric gelling material substantially insoluble in water, hardly crosslinked and partially neutralized. When this material comes in contact with water it forms a hydrogel. These polymeric materials can be prepared from polymerizable, unsaturated and acid-containing monomers well known in the industry. Suitable carriers include materials conventionally used in absorbent structures such as natural, modified or synthetic fibers, in particular modified or unmodified cellulose fibers, in the form of fluff and / or fabrics. Suitable carriers can be used together with the absorbent gelling material; however, they can also be used alone or in combination. In the context of sanitary towels and feminine towels, preference is given to fabrics or laminates of toilet paper. One embodiment of the absorbent structure made in accordance with the present invention comprises a double layer laminate of tissue paper formed by folding the tissue thereon. These layers can be used in the same way, for example, by adhesive molding, by mechanical interlacing or by bands of hydrogen bridges. The absorbent gelling material and other optional material may be distributed between the layers. Modified cellulosic fibers such as fibers can also be used. hardened cellulose. Synthetic fibers may also be used, including fibers made from cellulose acetate, polyvinyl fluoride, polyvinylidene chloride, acrylics (such as Orion), polyvinyl acetate, insoluble polyvinyl alcohol, polyethylene, polypropylene, polyamides (such as nylon), polyesters , bicomponent fibers, tricomponent fibers, mixtures of these and the like. Preferably, the surfaces of the fibers are hydrophilic or are treated to make them hydrophilic. The storage layer may also include fillers, for example, pearlite, diatomaceous earth, vermiculite, etc. to improve fluid retention. If the absorbent gelling material is dispersed in an inhomogeneous form in a carrier, the storage layer can, however, be locally homogeneous, ie, have a distribution gradient in one or more directions within the dimensions of the storage layer . The inhomogeneous distribution can also be applied to laminates of carriers that partially or completely absorb absorbent gelling materials. c) Optional fibrous ("powder") layer An optional component for inclusion in the absorbent core, according to the present invention, is a fibrous layer adjacent to the storage layer and which is normally below it. This underlying fibrous layer is generally referred to as the "powder" layer since it provides a substrate on which absorbent gelling material is deposited in the storage layer during the manufacture of the absorbent core. In cases where the absorbent gelling material is in the form of macrostructures such as fibers, canvases or strips, it is not necessary to include this "powdered" fibrous layer. However, this "powder" layer offers some additional capabilities in fluid handling, for example, rapid fluid displacement along the length of the pad. d) Other optional components of the absorbent structure The absorbent core, in accordance with the present invention, may include other optional components that are normally present in the absorbent webs. For example, a lightweight reinforcing fabric may be placed within or between the respective layers of the absorbent core. These lightweight reinforcing fabrics should have a configuration such that they do not form interfacial barriers for fluid transfer. Given the structural integrity that is common to obtain as a result of thermal bonding, the use of reinforcing fabrics in thermally bonded absorbent structures is generally not required.

Another component that can be included in the absorbent core according to the invention and that is preferably included close to the primary or secondary fluid distribution layer or as part of that layer is an odor control agent.

Lower canvas The lower canvas mainly prevents the exudates absorbed and contained in the absorbent structure from wetting the articles that are in contact with the absorbent product, such as briefs, panties, pajamas and garments. The lower canvas is preferably impermeable to liquids (eg, menstrual fluid and urine) and is preferably made from a thin plastic film, although other flexible and liquid impervious materials may also be used. In this description, the term "flexible" refers to materials that are moldable and that will easily conform to the contours and general shape of the human body. The lower canvas can also have elastic properties that allow it to stretch in one or two directions. The bottom layer is usually extended through the entire absorbent structure and can be extended and formed of the preferred side flaps, the side wrapping elements or the wings or constitute them in their entirety. In accordance with the present invention, the bottom sheet of the absorbent article is preferably permeable such that it is permeable to moisture vapor and therefore comprises at least one gas permeable layer. Suitable gas-permeable layers include two-dimensional, microplanar and macroporous, macroscopically expanded, orifice-formed and monolithic films. According to the present invention, the orifices of that layer can have any configuration, but preferably they are spherical or oblong and their dimension can be different. The holes preferably are evenly distributed across the entire surface of the layer; however, layers that have only certain regions of the surface with holes are also provided. The flat two-dimensional layers of the lower canvas may be formed of any material known in the art, but are preferably made of the commonly available polymeric materials. Suitable materials are, for example, Gortex ™ or Sympatex ™ type materials well known in the industry for their application in so-called permeable garments. Other suitable materials include the XMP-1001 from Minnesota Mining and Manufacturing Company, St. Paul, Minnesota, USA and Exxaire XBF-101 W supplied by Exxon Chemical Company. In this description, the term "flat two-dimensional layer" refers to layers having a depth of less than 1 mm, preferably less than 0.5 mm, where the holes have a uniform average diameter over their entire length and do not protrude from the plane of the layer . The perforated materials that are used as a bottom sheet in the present invention can be produced by any method known in the industry such as those described in EP 293,482 and the references contained therein. On the other hand, the dimensions of the orifices produced by this method can be increased by applying a force through the plane of the lower canvas layer (i.e. stretching the layer). Suitable perforated structure films include films having discrete orifices extending beyond the horizontal plane of the surface of the ply-oriented layer, towards the core, thereby forming protuberances. The protuberances have a hole located at their terminal end. Preferably, the protrusions are funnel-shaped, similar to those described in U.S. 3,929,135. The holes located within the plane and the holes located at the terminal end of the protuberances themselves, may or may not be circular, provided that the cross-sectional dimension or area of the hole at the termination of the protrusion is less than the dimension of the section. transverse or area of the hole located within the surface of the layer facing the garments. Preferably, these perforated structure films are unidirectional such that they have a fluid transport at least practically and if not completely in a direction towards the core. Macroscopically expanded films that are suitable for use herein include films such as those described, for example, in U.S. Pat. num. 4,637,819 and 4,591, 523. Suitable monolithic films include Hytrel ™, distributed by DuPont Corporation, USA, and other materials of this type such as those described in the document Index 93 Congress, Session 7A "Adding Value to Nonwovens" (Adding value to non-woven fabrics) ), JO Cardinal and Y. Trouilhet, Dupont de Nemours international SA, Switzerland such as Pebax ™ available from Elf Atochem (France) and Estañe ™ available from BF Goodrich (Belgium). The lower canvases that are especially preferred in the present invention comprise at least one layer which is selected from the above, such as perforated and microporous structured films and an additional layer which may also be selected from the above-mentioned lower canvases or may be a woven or non-woven fibrous fabric. Most preferably, the ventilated bottom sheet component comprises a microporous film and a perforated structure film or a microporous material and a hydrophobic material of woven or non-woven fabric. Adhesive coated surfaces typically have protective covers that come off before use. Before using the absorbent article, the PFA coated areas are typically protected from unwanted contamination and adhesion to another surface by means of a protective cover such as a silicone-coated release paper, a plastic film or any other easily removable cover. . The protective cover can be provided in one piece or in several pieces, e.g. ex. to cover the individual adhesive areas. It can also fulfill other functions such as the provision of an individualized package for the article or can provide a disposal function. Any protective paper or film distributed in the market can be used. For example, BL 30MG-A SILOX EI / O, BL 30 MG-A SILOX 4P / O distributed by Akrosil Corporation, and M &; W distributed by Gronau in Germany, with the code X-5432. The PFA can be applied to the surface of the lower canvas or the wings that is oriented toward the undergarment by any of the methods well known in the art used for this purpose, such as slot coating, spray printing and printing with rollers. The development of adhesive printing as described, for example, in EP 745,432, EP 745,433 and EP 745,368 has also made it possible for this fixing adhesive to be provided to the panty in any desired form at present and therefore these methods are especially preferred in the present invention. Preferably, the panty fastening adhesive is applied in intermittent patterns, for example, intermittent micrometric dots, intermittent strips, lines or grids or other shapes, such as circles. It is also within the scope of the present invention to apply PFA in a completely randomized pattern, for example, that obtained by means of spray printing.

EXAMPLES Following are two examples of adhesives that meet the rheology criteria of the present invention and that have an adequate adhesion performance in microfiber and cotton. As a reference for comparison, we incorporated two adhesives (HL1461 E from H.B. Fuller, DM0110 from National Starch), which are currently used in sanitary napkins commercialized and which have an adequate performance in cotton, but an unacceptable performance in microfiber material.

For Bio PSA 7-4560 from Dow Corning In this example, the adhesive is coated between a plastic film and a release paper as described below: The coating of the PFA on the outer surface of the film of the lower canvas was done by first applying the PFA on a release paper available from Akrosil with the code BL XXG NL-MGA SILOX D3H / 0 and having a basis weight of 40 g / m2, at an application temperature of 200 ° C. After this coating step, the release paper coated with PFA was transferred to the outer surface of the film of the lower canvas by pressing the PFA-coated surface of the release paper on that outer surface at a pressure of 200 kPa (2 bar). . In that way, the PFA was transferred from the release paper to the film of the lower canvas and then that peelable paper was removed. The PFA was Bio PSA 7-4560 available from Dow Corning and was applied as a complete 50 mm wide coating to a base weight of 20 g / m2. The film was a 25 g / m2 polyethylene film available from Britton Taco with the code ST-012-White. The surface coverage of the PFA was approximately 89% of the coated surface.

For MF55 ex Savare: This example is a pantiprotector made in the following way: The upper canvas is a non-woven SBPP fabric of 21 g / m2 available from BBA Fiberweb (France) with the code SPUN-S BLANC ITEM 111 DIMSET 021 Hl. The core is made of 100 g / m2 air-laid material available from Concert GmbH under code GH100.1008. The lower canvas is a 23 g / m2 SBPP non-woven fabric available from BBA Neuberger with the code BASE F1 023 01 001. The PFAs were applied as a full coat (50 mm wide) directly on the external surface of the lower canvas of non-woven fabric and the PFA had a basis weight of 17 g / m2. In this case, the PFA and release paper were applied in the same manner as in the case of Bio PSA 7-4560 of the previous example, while the application temperature was adjusted to 155 ° C. The surface coverage of the PFA was approximately 45% of the coated surface.

For the other two adhesives (DM0110, HL1461 E): In these two examples the same procedure and the same materials were used as for the Bio PSA 7-4560 from Dow Corning. Only the application temperature of the PFA was adjusted according to the specific adhesive, ie 155 ° C for HL1461E and 190 ° C for DM0110.

In addition, HL1461 has also been applied on the lower nonwoven fabric canvas with the same procedure and materials described for MF-55. The example prepared in this way has provided 1.84 N / 5 cm in cotton and 0.34 N / 5 cm in microfiber.

Test method of detachment force 1. Peeling force in the common cotton material An article of the present invention or a part thereof (hereinafter shows) comprising PFA on its surface facing the undergarment (the sample and the PFA are at room temperature) is placed on a rigid support with the surface that has the PFA facing upwards, away from the support. Then, a plate having an opening, hereinafter referred to as a "measuring window", is placed on the upper part of the surface of the sample comprising the PFA. The dimensions of the sample are selected such that the sample fits at least the measurement window having a dimension of 54 mm (width) x 126 mm (length). The sample will be placed in relation to the measurement window of the plate in such a way that the sample completely fills the measurement window. In a typical execution of this test, the sample is placed in such a way that its midpoint (intersection of the longitudinal and lateral center lines) is congruent with the midpoint of the measurement window and the longitudinal centerlines of the sample and of the measurement window are parallel. The sample is adjusted with handles to the support and it is verified that it has no wrinkles. Then, a piece of cotton (100%) available as Weave Style no. 429W, from Loeffler, Sitter Technic GmbH, Nettersheim, Germany, is placed on top of the surface with the PFA, which is exposed through the measuring window, such that one end of the cotton piece is extend approximately 25 mm from the end of the measuring window with the PFA. The measuring window must be completely covered by the piece of cotton. Then a weight is placed on the sample-cotton combination thus formed for 30 seconds so that the entire combination is covered and the weight is 26-27 g / cm2 to ensure that a smooth and even pressure is exerted on the combination . Then, an apparatus for Zwick tension tests (distributed by Zwick GmbH) is used to measure the detachment force necessary to remove the piece of cotton from the sample. Until now, the support with the sample covered with the piece of cotton is placed in the lower clamp of the apparatus for tension tests and the tail end of the cotton piece (opposite to the 25 mm free that was specified above) is placed in the upper clamp of the apparatus for tension tests. The Zwick tension test apparatus is configured at a speed of 102 cm / min. In general, the jaws have a distance of 250 mm from each other. It is evident that any suitable constant index can be used for the apparatus for voltage tests. The tension tester is turned on within 1 minute after removing the compression weight. The piece of cotton is detached from the sample in a direction parallel to the longitudinal dimension of the measuring window. During the peeling process, the peeling force required to remove the piece of cotton is measured along the displacement of the upper jaw that moved at an angle of 180 ° with the sample. The detachment force is calculated as the average of the force peaks in a 13 cm path. The first 2.5 cm and the last 3.75 cm of the measurement are not considered in the calculation of the detachment force to avoid the influence of acceleration and deceleration.

The previous test, for example, is performed with a sample that has the shape and size of a regular All-Days pantyhose using a support plate with a measuring window of 54 mm (width) x 126 mm (length) and a weight of 2. 1 kg with dimensions of 54 mm x 140 mm. The specialist can easily adjust the method for samples of different sizes. 2. Peel strength in common microfiber material This method is a variation of the previous method used to measure the release resistance of PFA in cotton. This variation has been designed to measure the resistance of PFA to the detachment of microfiber samples instead of rigid cotton samples. Actually, when using a microfiber sample, the sample will stretch during the test; that stretch greatly increases the variability of the previous method used for the cotton material. For this reason, a specific preparation has been designed for a sample of microfiber material that includes an intact microfibre material, such as the rigid cotton sample. Once the microfiber sample has been prepared as described below, the test is performed with the previous method used for the cotton and only the cotton sample is replaced by the blocked microfiber sample. The additional elements necessary for testing the microfiber material are: Tape: P42, 70 mm wide. Available from H-Old s.p.a. - 20010 Bareggio - Ml - Italy - Via Monte Ñero, 35, Tel. +39 0290360612 - Fax +39 0290362186 Roller weight: steel cylinder that weighs 1.14 kg and 6.5 cm wide.

Microfiber samples: 95% nylon, 5% elastane, white, available from Maglificio Brugnoli Giovanni Sp.A. in Busto Arsizio (Va) Italy, with the code Zaffiro B / Fast ZAFF60TN, which has a thickness of 0.7 mm, a base weight of 160 g / m2, dimensions of 457 mm x 76 mm, oriented along the direction of the Fabric jersey pattern (indicated by a black arrow in Figure 7). Figure 7 shows the side of the tape of the microfiber material, ie the side of the microfiber material on which the tape is fixed to block the microfiber sample: as seen on the basis of the figure, that is the textured side showing the own spine pattern of the jersey fabric). The side of the PFA (which will join the PFA) is the most uniform (see Figure 8). The blocked microfiber sample will be prepared as follows: A sample of microfiber is taken and held in such a way that the side of the PFA is below. The microfiber sample is laid on a table. The tape is placed on the microfiber sample in such a way that it covers it. The tape must have the same length as the microfiber sample. • The roller is passed slowly twice at a constant speed on the tape in the direction of the length, both times in the same direction. This causes the tape to adhere to the microfiber sample. When passing the roller, the application of additional pressure should be avoided - only the weight of the roller should be applied. The roller is only used to attach the P42 tape to the microfiber fabric.

In the two methods described above, the average value of 10 measurements under identical conditions was used to obtain a reference point. All documents cited in the Detailed Description of the Invention are incorporated, in the pertinent part, as reference herein. The mention of any document should not be construed as an admission that it constitutes a prior industry with respect to the present invention. While particular embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. In particular, it is evident to the person of skill in the industry that the present The invention applies to microfiber materials that have inherent hydrophobicity and also to other panty materials to which a hydrophobic treatment was applied. It has been intended, therefore, to cover in the appended claims all changes and modifications that are within the scope of the invention.

Claims (8)

1. A disposable absorbent article for personal hygiene; the article has a surface oriented towards the user and a surface oriented towards the undergarment; the surface facing the undergarment comprises an adhesive for securing the article to a wearer's garment, characterized in that the adhesive has an elastic modulus G 'at 0.01 Hz and 25 ° C from 1000 to 10,000 Pa and a loss tangent tand a 0.01 Hz and 25 ° C from 0.3 to

2. The article according to claim 1, further characterized in that the adhesive has an elastic modulus G 'at 0.01 Hz and 25 ° C of 1 500 a 8000 Pa.

3. The article according to any of the preceding claims, further characterized in that the adhesive has a loss tangent tand at 0.01 Hz and 25 ° C from 0.4 to 1.6.

4. The article according to any of the preceding claims, further characterized in that the adhesive has a tand inside a quadrant ABCD wherein the quadrant ABCD is defined by graphically plotting the frequency in Hz versus the tand at 25 ° C. of the adhesive; the quadrangle ABCD has as points A and D a tand of 0.3 and 2, respectively, at a frequency of 0.01 Hz and as points B and C at a tand of 0.8 and 4, respectively, at a frequency of 10 Hz.

5. The article according to any of the preceding claims, further characterized in that the adhesive has a tand inside a quadrangle ABCD, where the quadrangle ABCD is defined by graphically plotting the frequency in Hz versus the tand at 25 ° C. adhesive; the quadrangle ABCD has as points A and D a tand of 0.4 and 1.6, respectively, at a frequency of 0.01 Hz and as points B and C to a tand of 1 and 3, respectively, at a frequency of 10 Hz.

6. The article according to any of the preceding claims, further characterized in that the adhesive has a modulus G 'inside a quadrangle ABCD, where the quadrangle ABCD is defined by graphically plotting the frequency in Hz versus the tand at 25 ° C of the adhesive; the quad ABCD has as points A and D a module G 'of 1000 and 10,000, respectively, at a frequency of 0.01 Hz and as points B and C to a G' module of 20,000 and 100,000, respectively, at a frequency of 10 Hz. The article according to any of the preceding claims, further characterized in that the adhesive has a module G 'inside a quadrant ABCD, where the quadrant ABCD is defined by plotting the frequency in Hz in front of the tand a 25 ° C of the adhesive; the quadrangle ABCD has as points A and D a module G 'of 1500 and 8000, respectively, at a frequency of 0.01 Hz and as points B and C to a module G' of 30,000 and 80,000, respectively, at a frequency of 10 Hz. The article according to any of the preceding claims, further characterized in that the article is a sanitary napkin, a pantyhose, a diaper, a protector for axillary perspiration, a band for a hat or a protection device for incontinence .