MXPA99005949A - Adhesive for secure topical attachment to the skin and comfortable removal - Google Patents

Abstract

The present invention relates to topical adhesives for attachment to the skin. In particular the present invention relates to such topical adhesives which can be employed for attachment to the skin in the area were absorption of bodily liquids is desired. The topical adhesive provides secure attachment and is pleasing to the skin upon application, yet causes no discomfort upon removal. This is achieved by selecting the chemical composition and rheological characteristics of the topical adhesives, particularly the viscous modulus G"in combination with the thickness C of the topical adhesive layer applied to the absorbent article for attachment to the skin.

Description

ADHESIVE FOR TOPIC FIXATION SAFE TO THE SKIN AND PROPER REMOVAL FIELD OF THE INVENTION The present invention relates to topical adhesives for fixing to the skin, said adhesives being provided as a layer. In particular, the present invention relates to these topical adhesives which can be used for fixing to the skin in the area where the absorption of body fluids is desired, particularly for the adhesion of sanitary napkins, pantiliners, adult incontinence products. or pads for oozing. The topical adhesive provides secure fixation and is suitable for application on the skin, yet does not cause discomfort when removed. This is achieved by selecting the characteristics of the topical adhesives, particularly the viscous modulus "G" of the topical adhesive and the thickness C of the topical adhesive layer applied to the article.

BACKGROUND OF THE INVENTION The general prior art in the field of topical adhesives for fixing to the skin was developed particularly in the field of relief bandages, plasters and bandages. However, these articles are typically applied in an emergency situation, where, for example, a wound has occurred on the wearer's skin and absorption of body fluids emanating from the wound is desired. In this context, aspects of the performance of the absorbent article such as the use and easy application and easy removal without pain, discretion are subordinated to criteria such as sterility, healing protection, mechanical protection of the wound. Also the absorbent articles that protect the wound are mainly adhered to the areas of the skin where the body hair can be removed before the application of the article or where little or no hair grows. The present invention relates to topical adhesives that are particularly useful for absorbent articles for the absorption of body fluids, which naturally emanate from the body without a wound. For example, to fix sanitary pads or pantiliners in the genitourinary region. Also, devices that are used, for example, in the genital region or the sweat pads that are used within the region of a person's armpit, can suitably employ the adhesive of the present invention. These topical adhesives have generally been disclosed in the inventorial register established by United States law H1602 or WO 96/33683. Some additional details of the adhesive have been disclosed in PCT publication WO 95/16424. In this document sanitary napkins having a topical adhesive that is applied on the side facing the user of a sanitary napkin along the entire periphery is disclosed. The problem underlying this document is mainly the secure attachment to the skin but it also mentions the problems of disunion of these items after being used without causing undue pain to a user. The disclosure of the international publication WO 95/16424 includes a detailed analysis of the criteria for the topical adhesive with respect to the rheological criteria. However, this document has little respect for the problem of painless removal of these articles since the rheological criteria taught include depilatory compositions, that is, for the removal of the hair, which are commercially available as STREP MIELE ™ sold in Italy by Laboratori Vaj SpA The adhesives for topical fixation mentioned in WO 95/16424 also include the current pressure sensitive adhesives which are used to attach sanitary napkins to undergarments. In addition, this document only identifies the static rheological characteristics but is reserved for the dynamic rheological behavior of a topical adhesive. In WO 96/13238 a frequency model of the topical dependent adhesive is disclosed. Nevertheless, all measurements reported, for example, on page 9 were made at temperatures between less than 60 ° C and 120 ° C and the actual frequency is 0.1 to 100 rad / s. In order to obtain the necessary data at the application temperature (at approximately 20 ° C, typical bath, ie storage temperature) the Williams-Landel-Ferry equation (hereinafter WLF) was used. This WLF equation is empirical and only valid within certain limits, for example, it can not be used to extrapolate temperatures below the glass transition temperature of a polymeric adhesive, also the WLF can not be used on the basis of values obtained below the glass transition temperature. Details about the WLF equation and its applicability in "Principles of Polymer Processing" can be found by Z. Tadmor and C.G. Gogos, published by John Wiley & amp;; Sons or in "Viscoelastic Properties of Polymers", by J.D. Ferry also published by John Wiley & They are. Since this is missing from WO 96/13238 the applicability of the disclosed data can not be achieved. European patent application EP-638 303 discloses the use of a topical adhesive on the lateral folds of sanitary napkins, in order to keep the folds in an upright position. The Swiss publication discloses the use of a very long sanitary napkin having beveled outer edges with a topical adhesive on the four corners of the extreme edges in order to provide an area of external topical adhesive of the pubic hair growth region. Both requests are reserved as regards the adhesive composition. Based on the prior art, it is an object of the present invention to provide a topical adhesive for secure fixation and painless removal of the skin. It is another object of the present invention to ensure that when removing, no residual adhesive will remain on the skin or on the hair. It is still a further object of the present invention that the adhesive for topical fixation does not cause a cold or otherwise unacceptable temperature sensation upon application occurrence despite a temperature difference of the adhesive with respect to the temperature of the skin. In addition to the above objects of the present invention, it is also desirable that topical adhesives provide adhesives additional benefits such as supplies / dispersion of a compound or composition that is beneficial to the skin or to the general body. In addition, topical adhesives that do not affect the natural condition of the skin, for example, which are respirable or water vapor transmitters or water vapor / sweat absorbers, are preferred.

BRIEF DESCRIPTION OF THE INVENTION The present invention will be explained in its use in disposable absorbent articles for topical adhesive attachment to a user of these articles. The article typically has a surface that faces towards the body or the user and an external surface. The article comprises an absorbent core structure between the surface facing the user and the external surface to absorb the fluids emanating from a user, such as urine, feces, menstruation, sweat and vaginal discharge. The topical adhesive allows to fix an article to the wearer's skin, which is provided as a layer having a certain thickness or caliber C measured in millimeters (mm), typically on at least part of the surface facing the user of the article . The detailed analysis of the sequence of common situations that occur from the application of these disposable absorbent articles until the moment of removal of this article, has shown the specific characteristics of the adhesive needed to be preferably met in order to achieve the objectives desired performance, in particular, the initial secure fixation, the secure fixation during use and the final removal without pain. The characteristics that have been considered in this context are the elastic modulus that describes the elastic behavior of the material, and the viscous modulus that describes the viscous behavior of the adhesive material. The viscous behavior of the adhesive can be interpreted to represent an indication of the adhesive's ability to quickly bond and adhere safely. The elastic behavior can be interpreted as a sign or signal of the "firmness" behavior of the adhesive. Its value is also critical for good initial fixation. It is believed that their combination is an indicator of the force required when the removal occurs. The relationship between the elastic modulus and the viscous modulus is considered to be an indication over which the fraction of the removal energy within the adhesive will be dissipated and over which the fraction is available to cause actual removal. In order to provide topical adhesives for initial and prolonged secure fixation and easy / painless removal, the relationship between the elastic modulus and the viscous modulus as well as its dynamic behavior is of key importance. The topical adhesive has an elastic modulus at a temperature of 37 ° C (100 ° Fahrenheit), abbreviated G'37, a viscous modulus at a temperature of 37 ° C (100 ° Fahrenheit) of G "37 and a viscous modulus to a temperature of 25 ° C (77 ° Fahrenheit) The adhesive also has an elastic dynamic behavior defined as? G'37 which is the difference of G'37 at a frequency of 100 fad7sec and G'37 at a frequency of 1 rad / sec and a viscous dynamic behavior g "37 that the difference of G'37 at a frequency of 100 rad / sec and 6" 37 at a frequency of 1 rad / sec. The topical adhesive according to the present invention satisfies to the following conditions • G'37 (1 rad / sec) is on the scale from 1500 Pa to 20000 Pa, preferably 1500 Pa to 15000 Pa, more preferably 3000 Pa to 10000 Pa. • G "37 (1 rad / sec ) is on the scale of 100 Pa to 15000 Pa, preferably 100 Pa to 10000 Pa, more preferably 3000 Pa to 5000 Pa. • the proportion of G'37 (1 rad7sec) / G "37 (1 rad7sec) is on the scale from 3 to 30. • the proportion G '^ (100 rad / sec) -G% 7 (100 rad / sec) G'37 (1 rad / sec) - G" 37 (1 rad / sec) is not less than 0.5, preferably on the scale from 0J to 3, most preferably on the scale from 1 to 1.8 • any of the proportion of? G'37 / G37 (1 rad / sec) does not is greater than 1.5, preferably not greater than unity and most preferably not greater than 0.8, or "G'37 is not greater than 10000 Pa, preferably less than 5000 Pa, more preferably less than 2000 Pa, or both. • the value of the ratio G'37 / G "37 at least for the frequency scale of about 1 rad / sec to 100 rad / sec, should preferably be 3.3 or higher, more preferably 5 higher, more preferably 10 or higher , while not exceeding about 30, preferably 20, anywhere in the frequency range. • the rheological behavior can also be related to the values of the vitreous transition temperature Tg. For the topical adhesives according to the present invention, it should preferably be less than -15 ° C, more preferably less than -20 ° C, and most preferably less than -25 ° C. • The behavior and rheological acceptance of a topical adhesive can also be related to the specific heat capacity. Preferably, the specific heat capacity of the topical adhesive is less than 4 J / gK, more preferably less than 3 J / gK and most preferably less than 2 J / gK. • The behavior and rheological acceptance of a topical adhesive can also be related to the specific heat conductivity of the adhesive. Preferably, the conductivity of the specific heat is as low as possible, preferably between 1 and 0.1 W / m / K, more preferably between 0.6 and 0.1 W / m / K. Provided that the above rheological conditions are satisfied, the adhesives will also satisfy conditions such as sufficient adhesion (to avoid adhesive residue on the skin), which are critical to the commercial use of these adhesives and apparent to those skilled in the art. Adhesive compositions that meet the above criteria can be used as topical adhesives for disposable absorbent articles as long as they also meet the common requirements of being safe to use on human skin or animals during use and generally after disposal. Article. Often the criteria of hygienic appearance and comfortable feeling when in contact are important, such that adhesive compositions that will be transparent or white are preferred, and which avoid an uncomfortable, cold feeling when applied. * The above rheological criteria and other considerations can be satisfied by the compositions of the adhesive, wherein the composition comprises 45%, preferably 51% to 99.5% of a plasticizing compound or composition, which is liquid at 20 ° C, of 0.5 to 20%, preferably 5% to 15% of a polymeric compound or composition that is soluble or capable of swelling in the plasticizer composition or composition and with a tackifying resin in an amount in the range of 0% to 50% % by weight of the composition, preferably from 0% to 600% by weight of the polymeric compound. The plasticizer compound or composition is preferably selected from the group consisting of water, alcohols (preferably glycerol), glycols, polyglycols, liquid polybutenes, oil or combinations thereof. The polymeric compound or composition is preferably selected from the group consisting of block copolymer thermoplastic elastomers, styrene block copolymers and hydrogenated styrene block copolymers, polyacrylics, polyvinyl alcohol, natural gum or gelatins, polyethylene oxide, polyvinylpyrrolidone (PVP ), polyvinyl ethers, cellulose derivatives, or combinations thereof.

According to the present invention it has been found that the ratio between the thickness or gauge C, measured in millimeters (mm), of the layer in which the topical adhesive is provided, typically on at least part of the surface facing the user of the disposable absorbent article, and the viscous module G "25 at about 100 rad / sec of the topical adhesive is relevant to the scope of providing an easy and painless removal of the user's skin, if such topical adhesive is applied on at least part of the surface facing the user of a disposable absorbent article to fix the article to the skin of a user.

The topical adhesive of the present invention provided with a layer having a thickness C is such that the viscous modulus G "25 (100 rad / sec) and the thickness C satisfy the following empirical equation: G "25 < [(4.26 + C) - 1605] Pa and preferably the following empirical equation: G "2S < [(1.53 + C) - 1724] Pa DETAILED DESCRIPTION OF THE INVENTION Adhesive for Topical Fixation The topical adhesive according to the present invention is applied directly to the skin. In a particular application, the adhesive can be used in sanitary napkins which are applied to the genital region of a typically female user around the discharge area of the liquid. The word "skin" according to the present invention is not only related to the specific dermis of the user but includes the mucosal tissue also as the hair that is typically found in the genital region of the users of the sanitary napkins. In order to provide fixation of an article according to the present invention to the skin, it is necessary to provide a certain area on the side of the article that is facing the skin with the topical adhesive. For the various designs of sanitary napkins it is contemplated, but preferably the topical adhesive is provided adjacent to the peripheral edge of the topsheet such that a central area of the article is left without adhesive. This will more appropriately facilitate the placement of the towel in such a way that the region of the liquid-permeable upper sheet is placed adjacent to the hole where the body fluid emanates, such that the liquid emanating is transported immediately towards the absorbent structure of the absorbent article without the possibility of leakage or spillage. The topical adhesive is provided with the preferred pattern, typically on the surface facing the user of the article, as a layer having a thickness or gauge C that is preferably constant. The layer may preferably be continuous or alternately discontinuous, for example, in the form of dots, spirals or strips.

Physical, Rheological and Adhesive Characteristics of a Topical Adhesive Even when topical adhesives similar to pressure sensitive adhesives are used on human skin and mucosal tissues, it is understood that topical adhesive compositions can only with difficulty to be considered typical pressure sensitive adhesives (referred to as PSA hereinafter) on the basis of the most characteristic rheological behaviors that identify these materials. In fact, as the person skilled in the art of adhesives knows, the most characteristic aspect that distinguishes a PSA from other substances that can temporarily stick things (as can, for example, water between two glass plates), is the fact that its rheological parameters and especially the elastic modulus G 'vary greatly with the frequency of the applied stresses. More particularly the G 'of the PSA may increase over some types of magnitude while the frequency of the applied voltages varies from the typical binding frequency to the typical disbudding frequency, i.e. from 1 rad / sec to 100 rad / sec as is indicated below.

As a first consequence, it is inadmissible to define materials destined to be used as "topical adhesives", giving values of the rheological parameters and especially of G 'at a fixed frequency value. This can be misleading because in the absence of other features it will include materials that do not have practical values. It is consequently necessary that the rheological characterization should be based on dynamic considerations. This applies not only to the elastic modulus G 'but also to the viscous modulus G "and consequently also to (d) = G7G' It is well known that the typical PSA does not have only a high variation of G 'through the frequencies considered, but there is also a variation of G "even higher that may be close to or even higher than the value of G ', that is (d) becomes approximately or even higher than 1, particularly in the frequencies that are typical of disunity. Without wishing to be bound by the theory, this can be interpreted as the meaning that a high fraction of the energy applied for the disunion dissipates inside the adhesive (in such a way that it is not effective to cause disunion), while this fact macroscopically causes the recording of a level of the adhesive strength very high. As indicated above, the materials useful as topical adhesives according to the present invention, have rheological characteristics that are measured at a reference temperature of 37 ° C (as the normal body temperature of humans), and within a scale of frequencies. It has been found that upon application of an article such as a sanitary napkin, such as a topical adhesive, adhesive contact is formed at a low frequency, while disbonding occurs at the rate of removal of the article. This speed is expressed as a frequency of 100 rad / sec whereas it has been found that the low frequency of forming the adhesive bond is in the order of 1 rad / sec. Therefore, the range of frequencies to be used in agreement is between 1 and 100 rad / sec. It is believed that the characteristics of the adhesive bond are selected most appropriately at the temperature of the human body. Since the topical adhesive according to the present invention is used directly on the skin and the person skilled in the art is directed to select the composition of the adhesive to have a small specific heat capacity (eg, preferably less than 4 J / g / K), the actual temperature of the topical adhesive will reach 37 ° C very quickly or will still be heated by a human before application. In order to provide good bonding conditions, ie at a frequency of about 1 rad / sec, the absolute values of the elastic modulus should not be too high, otherwise the adhesive is too hard and is not able to bond intimately or molding to the surface to which it is expected to adhere. It is also important to have an absolute value of G "low in order to have a good cohesion that is particularly valuable to be used in the field of sanitary napkins, and to generate when articles are used that are frequently removed and adhered again or replaced, While the material remains soft, and is able to adhere gently to the skin, the ratio of G'37 (1 rad / sec) to G "37 (1 rad / sec) is important to ensure that these two values are balanced when occurring adhesion to the skin. At the same time, the absolute changes of G'37 need to be limited within the range of frequencies considered. Consequently, a low value must be maintained for the ratio of? G'37 (ie, G'37 (100 rad / sec) -G'37 (1 rad / sec)), above G'37 ( 1 rad7sec) in order to maintain the secure fixation of the topical adhesive without causing discomfort during the time or in the removal / delamination. This can also be expressed in absolute terms by keeping the? G'37 below certain values.

Importantly, the ratio of GJ (100 rad / eq) - G'J (100 rad / seq) G'37 (1 rad / sec) -G "37 (1 rad / sec) needs to be sufficiently large to ensure that the dynamic behavior of both the elastic modulus and the viscous modulus be maintained in a relationship that provides safe adhesion and painless and easy removal Finally, the person skilled in the art will also recognize that the vitreous transition temperature Tg of The composition of the adhesive, the specific heat capacity, and the specific heat conductivity are parameters that are useful to more fully define the group of useful topical adhesives.The set of following characteristics should preferably be met by the topical adhesive herein. invention: • G'37 (1 rad / sec) is on the scale from 1500 Pa to 20000 Pa, preferably 1500 Pa to 15000 Pa, more preferably 3000 Pa to 10000 Pa. • G "37 (1 rad / sec) is in the scale of 100 Pa to 15000 Pa, preferably 100 Pa to 10000 Pa, more preferably 3000 Pa to 5000 Pa. • the proportion of G'37 (1 rad7seg) / G "37 (1 rad7seg) is on the scale of 3 to 30. • the GJ ratio (100 rad / secVG ''. ^ (100 rad / sec) G'37 (1 rad / sec) - G "37 (1 rad / sec) is not less than 0.5, preferably on the scale from 0J to 3 , most preferably on the scale of 1 to 1.8 • any of the ratio of? G'37 / G37 (1 rad / sec) is not greater than 1.5, preferably not greater than unity and most preferably not greater than 0.8, or? G'37 is not greater than 10000 Pa, preferably less than 5000 Pa, more preferably less than 2000 Pa, or both. • the value of the ratio G'37"3" 37 at least for the frequency scale of about 1 rad / sec to 100 rad / sec, should preferably be 3.3 or higher, more preferably 5 higher, more preferably 10 or higher , while not exceeding about 30, preferably 20, anywhere in the frequency range. • the rheological behavior can also be related to the values of the vitreous transition temperature Tg. For topical adhesives according to the present invention, it should preferably be less than -15 ° C, more preferably less than 20 ° C, and most preferably less than -25 ° C. • The behavior and rheological acceptance of a topical adhesive can also be related to the specific heat capacity. Preferably, the specific heat capacity of the topical adhesive is less than 4 J / gK, more preferably less than 3 J / gK and most preferably less than 2 J / gK. • The behavior and rheological acceptance of a topical adhesive can also be related to the specific heat conductivity of the adhesive. Preferably, the conductivity of the specific heat is as low as possible, preferably between 1 and 0.1 W / m / K, more preferably between 0.6 and 0.1 W / m / K.

Chemical Characteristics and Composition of a Topical Adhesive In order to provide topical adhesive compositions that meet the requirements of the rheological and physical characteristics of a topical adhesive above, the following formulation criteria should be used. It should be noted that most of the compositions useful as the topical adhesive have a substantially gel-like structure and are preferably gels. This derives from the fact that: the predominant component is the plasticizer, which is a liquid material at room temperature a macromolecular or polymeric component is present in minor amounts against the plasticizer. This form, in the preferred modalities, a three-dimensional network made by the physical and chemical bonds between the molecules. Particularly useful physical links are the bonds present in systems containing block thermoplastic elastomers. More specifically, the compositions typically comprise: from 0.5 to 20%, preferably from 5% to 15%, by weight of a macromolecular polymer substance or a mixture of these substances soluble or capable of swelling in the aforementioned plasticizer (s). As non-limiting examples, these polymeric or macromolecular substances can be natural and / or synthetic, such as natural gums or derivatives such as natural gums and gelatins, their derivatives and alginates; polyacrylics; polyvinyl alcohol; polyethylene oxide; polyvinylpyrrolidone (PVP) or polyvinyl ethers, their copolymers and derivatives; cellulose derivatives; Thermoplastic Block Copolymer Elastomers and preferably Styrenic Block Copolymers and more preferably the hydrogenated grades Styrene / Ethylene-Butylene / Styrene (SEBS), / Styrene / lsoprene / Styrene (SIS), and Styrene / Ethylene-Propylene / Styrene (SEPS) . from 45 to 99.5% by weight, preferably from 51 to 99.5% by weight of a plasticizer or a mixture of plasticizers, which are liquid at room temperature. As non-limiting examples, the plasticizer may be water, various alcohols (such as in particular glycerol), glycols, polyglycols, liquid polybutenes, natural or synthetic oils such as vegetable oils, mineral oils, or combinations thereof. from 0% to 50% by weight of the composition, preferably from 0 to 600% > by weight of a macromolecular polymeric substance of a tackifier resin whose main scope is to form the Tg especially in systems based on synthetic polymers. from 0 to 10%) and more preferably from 0 to 5% by weight of a substance to facilitate and stabilize the gelation of both the hydrophobic and hydrophilic liquid plasticizers. These can be for oil systems, for example, C8 to C22 fatty acids, their metal salts and their polyoxyl derivatives; lanolin derivatives, silica; bentonite, montmorillonite and its derivatives; polyamides, waxes or mixtures thereof. Common additives known in the art as preservatives, antioxidants, anti-ultraviolet agents, pigments, mineral fillers, rheology modifiers, etc., may also be comprised in amounts of up to 10% each. When chemical lattices are formed in the system, a crosslinking agent may be present in amounts of up to 5% by weight. Chemical crosslinking can also be formed by the mutual neutralization of polymers having different functionalities as in the reaction between polyacrylic acids and polysaccharides. The compositions for the topical adhesives can be divided into three families according to the nature of their main component, i.e., normally the plasticizer or liquid plasticizers (s): 1) The hydrophobic compositions in which the plasticizer is typically an oil or mixtures of vegetable and mineral oils and the polymer is usually a synthetic polymer, preferably an elastomer, soluble, or capable of swelling the oil or oils. 2) The mixed phase compositions in which both the hydrophobic and hydrophilic components, possibly both the piastifiers and the polymers, form two or more separate phases. In these cases, an emulsifier / surfactant is preferably present at an adequate level to form stable emulsions between incompatible phases. For topical adhesives according to the present invention, it is preferable that the hydrophobic components are predominant against the hydrophilic components. 3) The hydrophilic compositions in which typically the plasticizer is water / glycerol / glycols and the like and / or mixtures thereof and the polymer phase is of synthetic (for example polyacrylics), or natural (for example natural gums) or mixtures thereof. It is important that, unlike the medical field and prior art cited, hydrophilic compositions are not preferred, although hydrophobic and mixed phase compositions 1) and 2) are preferred in the applications of the present invention. This partly depends on technical reasons in the sense that many of the hydrophilic compositions used in the medical field show elasticity and cohesion too low to be useful in the present application. The other reason for preferring the hydrophobic or easily mixed compositions is that the application of the present invention, particularly in the field of sanitary napkins, will include a likelihood of contacting the topical adhesive with the liquid that is absorbed. Since the liquids are, all of a general aqueous type, in contact with a topical hydrophilic adhesive, it would result in a certain absorption of the body fluids in the topical adhesives. This would then have the result of changing the rheological characteristics and therefore the functionality of the topical adhesive and cause an unhygienic appearance. In addition, the hydrophilic topical adhesive also tends to be perceived as cold and wet which upon application to a human skin is not in line with the typical expectation. Additional problems result from the fact that particular topical adhesives comprising water as the plasticizer have a tendency to dry unless sealed in a waterproof package.

Application of the Topical Adhesive Absorbent articles in which the topical adhesive can be used • in accordance with the present invention, which are provided as a layer having a thickness or gauge C measured in millimeters (mm), can be made by any of the usual manners of the art. The application of the adhesive to the top sheet side of an absorbent article should not cause greater problems for those skilled in the art since it can be provided by any of the well-known techniques commonly used for other adhesives. The total area of the skin or the surface that faces the user of an item that is covered by the topical adhesive should not be greater than 20%, preferably not greater than 10% ». Preferably, the adhesive is near the periphery of the absorbent article and in the case of the upper sheets of film (or when the backsheet is folded over the upper sheet), the adhesive is preferably on a part of the film that is not permeable to liquids. The topical adhesive is provided, typically on at least part of the user-facing surface of the disposable absorbent articles, such as a layer having a thickness or gauge C that is preferably constant, or which may alternatively vary over the surface of interest for the application of the topical adhesive. If possible, the article also provides breathability by being at least permeable to water vapor, preferably permeable to air to prevent it from being poorly ventilated. The breathability, if not supported or maintained by the topical adhesive as such, may be limited to the area of the article where no adhesive is applied. The topical adhesive in an article is preferably protected before use. This protection can be provided by a release liner such as a paper treated with silicone or surfactant, providing easy detachment of the selected topical adhesive. This invention can be beneficially used in disposable absorbent articles that are applied directly to a user's skin. The article normally exhibits absorbency of bodily fluids, the protection of the user's garments against staining is convenient to use, and is easy to produce and pack. The disposable absorbent article is described below with reference to a sanitary napkin or catamenial product, however, pantiprotectors, adult incontinence articles or sweat pads are also included under the term "disposable absorbent articles". The term "sanitary napkin" as used herein, refers to an article that is worn by women adjacent to the pudendal region and which is intended to absorb and contain the various body fluids that are discharged from the body (e.g. vaginal, menstrual and / or urine), and which are intended to be discarded after a single use. A disposable absorbent article is preferably thin, more preferably between 1 and 5mm thick and, either, substantially planar before use or in a preconfigured form. The terms "attached" or "fixed", as used herein, encompass configurations by which a first member is directly connected to a second member and configurations by which a first member is indirectly connected to a second member by connecting the first member to intermediate members who in turn are connected to the second member. In a preferred embodiment, a sanitary napkin of the present invention comprises a liquid permeable upper sheet, a liquid impermeable back sheet attached to the upper sheet, and an intermediate absorbent core to the upper sheet and the back sheet. The sanitary napkin has two main surfaces, a surface that is in contact with the body or that faces the user on which the topical adhesive is applied and a surface that faces the garment or that is in contact with the garment. The top sheet is docile, of soft feeling, and not irritating to the user's skin, the upper sheet may also have elastic characteristics that allow it to be stretched in one or two directions, in parts of the upper sheet, or in its entirety. In addition, the topsheet is permeable to fluid, allowing fluids (eg, menses and / or urine) to easily penetrate through its thickness. The preferred top sheets for use in the present invention are typically selected from the upper nonwoven sheets with raised upper region and upper sheets of film formed with openings. Films formed with openings are especially preferred for the upper sheets because they are permeable to body exudates and not yet absorbent, and have a reduced tendency to allow the fluids to pass back through and rewet the user's skin . In this way, the surface of the formed film that is in contact with the user remains dry, thus reducing the staining of the body and creating a more comfortable feeling for the wearer. Suitable formed films are described in the patent of the States No. 3,929,135, United States Patent No. 4,324,246; U.S. Patent No. 4,342,314; U.S. Patent No. 4,463,045; and United States Patent No. 5,006,394. Top sheets of film formed with particularly preferred micro apertures are disclosed in U.S. Patent No. 4,609,518 and U.S. Patent No. 4,629,643. A preferred top sheet for the present invention comprises the formed film described in one or more of the above patents and sanitary napkins are marketed by The Procter & Gamble Company of Cincinnati, Ohio as "DRI-WEAVE". Topical adhesives are very well used on top sheets that do not have a homogeneous liquid passages distribution but only a part of the top sheet that comprises the liquid passages oriented in such a way that they result in a centrally permeable and peripherally permeable upper sheet to liquids. Another alternative is the so-called hybrid top sheets, which incorporate structures in fibrous and film form, particularly useful embodiments of these hybrid top sheets are disclosed in PCT Publication Nos. WO 93/09744; WO 93/11725 or WO 93/11726. When we refer to the top sheet, a multi-layered structure or a single layer structure is contemplated. The hybrid top sheet mentioned above, is this multi-layered design, but other multi-layered top sheets such as the primary and secondary top sheet designs are also considered. The absorbent core can also comprise multiple layers and provides the function of fluid storage and distribution. Placed in fluid communication with, and typically underlying, the top sheet, is the absorbent core. The core may comprise any normal absorbent material or combinations thereof. This preferably comprises gelling absorbent materials, generally referred to as "hydrogel", "superabsorbent", "hydrocolloid" materials in combination with suitable carriers. The gelling absorbent materials suitable for use herein will often comprise a partially neutralized, lightly crosslinked polymeric gelling material, substantially insoluble in water. This material forms a hydrogel upon contact with water. These polymer materials can be prepared from acid-containing, unsaturated, polymerizable monomers, such as acrylic acid, which are well known in the art. Suitable carriers include materials that are conventionally used in absorbent structures such as natural, modified or synthetic fibers, particularly modified or unmodified cellulose fibers in the form of fluff and / or tissue. Suitable carriers can be used together with the gelling absorbent material, however, they can also be used alone or in combinations. Tissue and tissue laminates are very preferred, in the context of sanitary napkins / linings. One embodiment of the core, particularly useful in the application of the present invention, comprises a laminate of double-layer tissue formed by folding the tissue over itself. These layers can be joined together. The gelling absorbent material or other optional material can be comprised between the layers. The absorbent core may include optional components normally present in the absorbent webs such as odor control agents, in particular suitable zeolites. The backsheet primarily prevents the exudates absorbed and contained within the absorbent core from wetting articles that come into contact with the absorbent product such as underpants, briefs, pajamas, and undergarments.

The backsheet is preferably impermeable to liquids (e.g., menses and / or urine and is usually manufactured from a thin plastic film. The backsheet typically extends through the entire absorbent core and can extend over and become part of the top sheet, bending around the absorbent core. In this manner a preferred configuration of the topsheet as disclosed in U.S. Patent No. 4,342,314, column 16, lines 47 to 62, can be achieved without the requirement of selectively perforating the top sheet. Preferably, the backsheet also provides breathability to the absorbent article by being at least permeable to water vapor, preferably permeable to air. The backsheet may be a laminate, for example, of a combination of microporous film, and / or a non-woven material, and / or film formed with openings. The breathability, if desired, may be limited to the periphery or the center of the backsheet, or this may be throughout the entire back sheet. When the removal phase of a topical adhesive composition for fixing to the skin of a wearer of a disposable absorbent article is particularly considered, it is commonly recognized that good removal conditions, ie at a frequency of approximately 100 rad / sec. , of the topical adhesive applied to at least part of the surface facing the wearer of a disposable absorbent article for securing said article to the wearer's skin, are achieved when the adhesive can be easily removed from the skin, and particularly from the hairs that typically grow on it, where the disposable absorbent article is in contact with the body, without causing pain to the wearer, therefore without sticking too hard when removing from the user's skin and hairs. Moreover, a good removal means that the topical adhesive does not leave residues that remain on the skin or on the hairs. According to the present invention, the ratio between the thickness or gauge C measured in millimeters (mm) of the layer in which the topical adhesive is provided, typically on at least part of the surface facing the wearer of the disposable absorbent article , and the viscous modulus G "25 at 25 ° C and at approximately 100 rad / sec of the topical adhesive given a signal on the painless and easy removal of the topical adhesive from the skin.Without being bound by any theory, it is believed that the values higher than G "25 to 100 rad / sec, which generally corresponds to a superadhesiveness of the composition, a thicker gauge or thickness of the adhesive layer is needed in such a way that the energy applied for the removal is more evenly distributed within the mass of the adhesive, and is therefore transferred smoothly to the skin, thus avoiding spikes of energy that typically cause the user to feel painful. In other words, the thinner layers of the topical adhesive need an adhesive with a G "25 at 100 rad / sec lower to achieve a reduced painful sensation upon removal of the absorbent article In accordance with the present invention, the topical adhesive of the present invention provided as a layer having a thickness C measured in millimeters (mm), is such that the viscous modulus G "25 (100 rad / sec) and the thickness C of the adhesive layer satisfy the following empirical equation: G "25 < [(4.26 + C) - 1605] Pa and preferably the following empirical equation: G "25 < [(1.53 + C) - 1724] Pa While in a preferred embodiment of the present invention, the thickness C of the adhesive layer is constant, this adhesive layer may also have different thickness in different portions of the surface facing the user of the absorbent article where it is applied, always that the aforementioned relation between C and G "25 is in any case fulfilled In order to evaluate the effect of the thickness C of the topical adhesive layer in its relation with the viscous modulus G" 25 (100 rad / sec) of the adhesive Topical of the present invention in the removal of the topical adhesive used for fixing a disposable absorbent article to a user's skin, a Removal Pain Degree Test has been developed. In this test the adhesion of standard substrates was achieved, on which the same topical adhesive has been provided in layers having different thicknesses, on the forearm skin of the members of a sensitive panel, and upon the successive removal the evaluation was carried out. pain in terms of the degree of pain.

Proof of the degree of pain during removal The test of the degree of pain during removal is used to evaluate the pain during the removal of a user's skin from a sample provided with a topical adhesive layer and which was previously fixed to the wearer's skin. The test specifically evaluates the pain by removing each sample as compared to the pain obtained by removing a reference sample constituted by a firm, commercial medical poultice.

Preparation of the sample The test is carried out on rectangular samples of 60 by 20 mm made of a 23 μm thick polyester film, such as that sold by Effegidi SpA of Colorno (Parma, Italy), provided on one side with a continuous layer of the topical adhesive which has a selected thickness applied with an Acumeter Model LH-1 extruder. The reference sample is a 60 x 20 mm sample of a double-sided medical adhesive tape produced by Minnesota Mining and Manufacturing Company under the trade name Medical Tape No. 1524; only one of the two layers of the adhesive is exposed in the reference sample and is used to fix it to the skin during the test.

Testing method A panel of 6 graders was selected for the test. The test is carried out in a climatically controlled laboratory where a temperature of 23 ° C, and a relative humidity of 50. No special treatment of the user's skin is required beyond normal cleaning / washing with soap and water and drying for at least 2 hours before the test to allow it to reach the balance with environmental conditions for the skin. Three different samples A, B and C are evaluated in the test compared to the reference sample R. Each sample is applied by hand by an operator on the inner part of the forearm of the grader, being centered between the elbow and the wrist, with the short side of the sample aligned with the length of the arm. The operator exerts the same pressure on each sample with his palm, which is typically applied so that he adheres the medical plaster to the skin. Each sample is used for the prescribed time, and then removed from the grader skin by the operator with a slow and slow shot. Four series of a reference sample R and the three samples A, B and C each, used and then removed from the user's skin are applied; each sample is used between two subsequent samples of the same series and a wait of 15 minutes between two later series. The reference sample R is always applied, used / withdrawn as the first sample of its respective series. The sequence of application / use / removal of samples A, B, C in each of the first 3 series is random, provided that repetition is not allowed in each series, and the sequence is not repeated in the first three series . In the four series of the four samples one of the samples of A, B, or C, the reference R is always tested twice, always being the first. In general, each sample (A, B, C and R), has to be tested an equal number of times (24 times according to the scheme below). In the tests carried out, the sequences of the four series are in accordance with the following scheme: The graders were asked to evaluate each sample A, B and C using a pain scale ranging from 0 to 10, where 0 corresponds to no pain and 10 corresponds to pain when removing the reference sample R. Pain values for each sample A, B and C were obtained as an average of 24 observations. The results collected from the test were analyzed by means of a statistical analysis program "comparison of samples in pairs of the popular average", which showed that the differences between the pain values of samples A, B and C are statistically significant. The pain upon removal was assessed according to the removal pain test for three different samples A, B and C, each consisting of the same standard substrate on which the same composition of the topical adhesive is provided as a layer uniform of a predetermined constant thickness. A topical adhesive is an oil-based composition containing 10% by weight of Krato G-1651, a styrene / ethylene / butylene / styrene / styrene block copolymer available from Shell Co., 49% by weight of Kaydol, a paraffinic mineral oil available from Witco Co., 40%) by weight of Escorez 5300, a hydrogenated tackifier resin available from Exxon Co., 0.7% by weight of magnesium stearate, a co-gelling agent available from Cerlo Erba, SpA, and 0.3 % by weight of Irganox 1010, an antioxidant available from Ciba Geigy. Finally, the formulation had the following percentage composition: Kraton G-1651 10.0% by weight Kaydol 49.0% by weight Escorez 5300 40.0% by weight Magnesium stearate 0.7% by weight Irganox 1010 0.3% by weight The composition shown has the following rheological properties a 37 ° C. a) Elastic modulus at 1 rad / sec G'37 = 7038 Pa b) Viscous module at 1 rad / sec G "37 = 487 Pa c) Proportion of Elastic and Viscous Modules at 1 rad / sec, G'37 / G "37 = 14.45 d) Proportion of G '^ dOO rad / sec) - G "^ (100 rad / sec) G'37 (1 rad / sec) - G" 37 (1 rad / eg) = 1.11 e) The proportion of? G '37 on G'37 (1 rad / sec) was 0.291, with? G'37 = 20501 Pa. The composition also has a viscous modulus G "25 at 25 ° C and at approximately 100 rad / sec at 4431 Pa. The thickness of the adhesive layers of the three samples and the respective degrees of pain are shown in the following table: The results show that for a given topical adhesive composition, represented by the value of G "25 (100 rad / sec) of 4431 Pa, the increasing thickness values for the topical adhesive layer correspond to reduced degrees of pain upon removal of the topical skin adhesive Of course, the thickness values for the topical adhesive layers comprised in the disposable absorbent articles can be varied according to the empirical equations of the present invention to achieve acceptable degrees of pain upon removal with the different compositions of topical adhesive, and therefore with different values of G "25 (100 rad / sec), within the limits that can be easily determined by the person skilled in the art. In general, in the field of disposable absorbent articles, this limit should not exceed 10 mm. The same is true for the possible selection of preferred topical adhesive compositions having G "25 (100 rad / sec) values that are applied to a layer having a certain preferred thickness in order to reduce the degree of pain upon removal. The skin absorbent article The preferred limits for G "25 (100 rad / sec) of a topical adhesive composition are implicitly defined for example, by the preferred rheological characteristics of the topical adhesive compositions.

Claims (9)

1. A topical adhesive for securing an article to the skin, said topical adhesive being provided as a layer having a thickness C measured in millimeters (mm), said adhesive having an elastic modulus at a temperature of 37 ° C. (100 ° F), G'37) and having a viscous modulus at a temperature of 37 ° C (100 ° F), G "37, and a viscous modulus at a temperature of 25 ° C (77 ° F), G "25, said topical adhesive characterized in that said viscous modulus G" 25 (100 rad / sec) and said thickness C satisfy the following equation: G "25 < [(4.26 + C) • 1605] Pa

2. A topical adhesive according to claim 1, characterized in that said viscous modulus G "25 (100 rad / sec) and said thickness C satisfy the following equation: G" 25 < [(1.53 + C) - 1724] Pa

3. A topical adhesive according to claim 1, characterized in that said adhesive is selected to have: • G'37 (1 rad / sec) on the scale from 1500 Pa to 20000 Pa, preferably 1500 Pa to 15000 Pa, more preferably 3000 Pa to 10000 Pa; • G "37 (1 rad / sec) is on the scale from 100 Pa to 15000 Pa, preferably 100 Pa to 10000 Pa, more preferably 3000 Pa to 5000 Pa • the proportion of G'37 (1 rad7sec) / G" 37 (1 rad7sec) is on the scale of 3 to 30; • the ratio G '^ (100 rad / secVG' (100 rad / sec) G'37 (1 rad / sec) - G "37 (1 rad / sec) is not less than 0.5, preferably on the scale of 0.7 to 3, most preferably on the scale of 1 to 1.8 alternately, either, G'37 (100 rad / sec) - G'37 (1 rad / sec) is not greater than 10000 Pa, preferably less than 5000 Pa, preferably less than 2000 Pa, or the ratio G'37 (100 rad / sec) - G'37 (1 rad / sec) / G'37 (1 rad / sec) is not greater than 1.5, preferably not greater than 1, very preferably not greater than 0.8, or a combination thereof

4. A topical adhesive according to any preceding claim, characterized in that said adhesive is provided as a continuous layer

5. A topical adhesive according to any preceding claim, comprising: from 45% to 99.5%, preferably from 51% to 99.5%, by weight a compound or plasticizer composition which is liquid at 20% C, from 0.5% to 20% by weight of a compound or polymer composition rich that is soluble or swelling in the plasticizer composition or composition; a tackifying resin in an amount of 0% to 50% by weight, preferably 0% to 600% by weight of the compound or polymer composition.

6. The topical adhesive according to claim 5, wherein said plasticizer compound or composition is selected from the following group: water, alcohols, glycols, oil or combinations thereof; and said polymeric compound or composition is selected from the following group: block copolymer thermoplastic elastomers, styrene block copolymers, and hydrogenated styrene block copolymers, polyacrylics, polyvinyl alcohol, natural gum or gelatins, polyethylene oxide, polyvinylpyrrolidone , polyvinyl ethers, cellulose derivatives, or combinations thereof.

7. A topical adhesive according to any of the preceding claims, wherein 80% by weight of the adhesive consists of hydrophobic components and most preferably all of the adhesive components are hydrophobic.

8. A disposable absorbent article such as a sanitary napkin or a panty protector for topical adhesive attachment to a user's skin, said article comprising a topical adhesive according to claim 1 for attachment to the skin.

9. The use of a topical adhesive according to claim 1 in a sanitary napkin or a pantyhose.