MXPA99005686A - A laminated composite absorbent structure comprising odour control means - Google Patents

Abstract

The disclosure relates to a laminated absorbent structure (14) for absorbing aqueous body fluids and for providing odour control. The structure (14) has a first surface (20) intended to receive such fluids and a second surface aligned opposite the first surface (20). The laminated absorbent structure comprises odour controlling material (24) for absorbing odours and an absorbent gelling material (26), with the odour controlling material (24) and the absorbent gelling material (26) being contained between separating containing layers (4, 6). The odour controlling material (24) is also separated from the first surface by the absorbent gelling material (26).

Description

COMPOSITE ABSORBENT STRUCTURE. LAMINATED, THAT COMPRISES ODOR CONTROL MEANS FIELD OF THE INVENTION The present invention relates to laminated absorbent structures comprising an odor control means, suitable for use in absorbent articles, in particular sanitary napkins and pantiliners.

BACKGROUND OF THE INVENTION Disposable absorbent articles are well known and all have absorbent elements for absorbing and retaining bodily fluids; An absorbent element must be able to quickly acquire the liquid and distribute it internally to prevent leaks, and it must also have a good capacity to retain fluids when subjected to normal pressures of use. Although the main focus of the absorbent articles is on the ability of these articles to absorb and retain fluids, another important development area in this field is the control of the odorous compounds contained within the absorbed fluids or their degradation products. There is a wide range of compounds that may be present in an absorbent article during use, which result in the formation of foul compounds. These compounds include fatty acids, ammonium, amines, sulfur-containing compounds and ketones and aldehydes. The art is replete with descriptions of various odor control agents for use in absorbent articles in order to address the problem of malodorous formation.

For example, odor, acid, basic and neutral control agents are known.

Odor control means comprising mixtures of types of odor control agents are widely used in absorbent articles in order to increase the effectiveness of the odor control medium against the various malodorous compounds associated with the use of the absorbent articles that follow the absorption of aqueous body fluids. For example, the European patent discloses an absorbent article comprising an odor control system wherein the neutral odor control particles are selected from carbon, clays, silica, zeolites and molecular sieves. EPO publication 348978 discloses the combination of zeolites and gelling absorbent -? - materials to provide improvements in the control of ammonia odors. Although mixtures of the different odor control agents can perform this action well by controlling the odors associated with the use of absorbent articles, the interactions between certain odor control agents and the absorbed aqueous body fluids or between the different control agents Odors can at least partially impair the effectiveness of the known odor control means. U.S. Patent No. 5,230,950 discloses a process for incorporating an odor control medium in the powder form into a water-insoluble, swellable, hydrophilic polymer in order to achieve a flexible structure containing the control particles. of the odor in a stable form free of dust. The possible interactions between the two incompatible odor control agents can be avoided by incorporating these odor control agents separately into two different substrates of the structure. The odor control compounds described in the patent typically perform their action when the liquid is absorbed by the hydrophilic polymer that incorporates them, and therefore, the liquid can not be prevented from reaching those odor control compounds that can be influenced. in a negative way by the absorbed liquid.

U.S. Patent No. 5,037,412 describes a sanitary article in which the acid control agents of the basic and neutral acid type, which are preferably active in their anhydrous state, are incorporated in such a way that they are not reached by the fluid absorbed, and therefore remain substantially dry, for at least a substantial period of time after the absorption of the fluid by the sanitary article. Odor control agents are mixed together and placed within the sanitary article in locations that are not likely to be reached by the fluid absorbed for a substantial period of time after absorption, for example, between the absorbent core and the backsheet , along the periphery of the posienor sheet itself, or in the center of the absorbent core, or even along its periphery. Although these structures are able to avoid the interactions between the absorbed fluids and the odor control agents that can be negatively influenced by them, they have a complex structure, while at the same time, the odor control means It is a simple mixture of different odor control agents, all of them intended to operate in their dry state. European Patent Application EP-A-510619 discloses an absorbent article comprising an odor control complex that includes a combination of at least two agents selected from the group including zeolites and silica gels. The effectiveness of at least some of the odor control agents can be increased by arranging the liquid absorbent material, typically a fluff of cellulose fibers, between the topsheet and the odor control agents themselves, in order to reduce the exposure from agents to body fluids. The structures described are quite complex and adhere to a combination of several different components and odor control agents, each performing a different task between fluid absorption, pH regulation, and odor control. Moreover, when odor control agents are incorporated in these structures in the form of particles, it is difficult to avoid the loss or spillage of these particles from the structure, both during production and during use within the sanitary product incorporating them. . These structures are, therefore, not suitable for production as a semi-finished product to be sold and stored separately in the form of a continuous structure in the form of a weft, for example, wound on a roll, which can be subsequently fed to a production line of sanitary articles. Consequently there is still a need to provide an absorbent structure comprising an odor control means and which is simple to produce as long as it has a better effectiveness. It has now been observed that this need can be applied by an absorbent structure in which a synergistic effect is achieved between the gelling absorbent material and the different odor control agents, by means of which the performance of the control agents of the odor is increased. odor, which preferably act in dry conditions, and optionally those that are activated in solution. Structures also take advantage of the combined activity of their components by developing two or three actions between fluid absorption, pH stabilization, and odor control. Moreover, they can be produced as a semi-finished product, while being substantially free of the losses or spillage of the incorporated particulate material.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a laminated absorbent structure for absorbing aqueous body fluids and for providing odor control, having a first surface intended to receive body fluids and a surface aligned approximately opposite to the first surface, the first structure laminated absorbent comprising first means of odor control to absorb odors and further comprising a gelling absorbent material. The first odor control means and the gelling absorbent material are each contained between separate containment layers, the first odor control means being separated from the first surface by the gelling absorbent material.

BRIEF DESCRIPTION OF THE DRAWINGS Although the description concludes with the claims, particularly pointing out and claiming differently from the present invention, it is believed that the present invention will be better understood from the following description in combination with the following drawings: Figure 1 is a view in perspective of a laminated structure according to the present invention, with two of the three layers of the containment partially raised; Figure 2 is a sectional view of a laminated structure according to the present invention, similar to that shown in Figure 1, but with four containment layers instead of 3.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to laminated absorbent structures for absorbing aqueous body fluids and for providing control of the odorous compounds contained within the absorbed fluids or their degradation products. Laminated absorbent structures will be described herein in relation to their use in disposable absorbent articles, for example, sanitary napkins or catamenial products, typically as absorbent elements, the laminated absorbent structures of the present invention can integrally constitute the absorbent element of an article. Disposable absorbent, or these may be comprised therein as part of the absorbent element, in any case, these may constitute an element of a disposable absorbent article. Disposable absorbent articles, such as for example sanitary napkins, pantiliners, incontinence pads or diapers, typically comprise a liquid pervious topsheet, a fluid impermeable backsheet, which may optionally be permeable to water vapor and / or to the gas, and an absorbent element comprised between them. The term "sanitary napkin", as used herein, refers to an article that is worn by women adjacent to the pudendal region and that is intended to absorb and contain the various body fluids that are discharged from the body. For example, vaginal discharge, menses, and / or urine) and which is intended to be discarded after a simple use. The term "use" as used herein, refers to the period of time that begins when the absorbent article is actually placed in contact with the wearer's anatomy. According to the present invention, the laminated absorbent structure comprises a first means of odor control and a gelling absorbent material, each contained between separate containment layers, by "separate containment layers", the layers containing between the gelling absorbent material and the first odor control means, at the same time separating them from each other, and which are different from both the gelling absorbent material and the first means of odor control. The development of unpleasant odors, coming from body fluids such as sweat, menstrual blood, vaginal discharges or urine, are basically due to two different causes: a) the malodorous chemical compounds already contained in the body fluids and (b) the chemical compounds malodorous bacteria produced by the bacterial metabolism when the bacteria comes into contact with body fluids for a prolonged period of time. Means for controlling odors associated with body fluids and their incorporation into disposable absorbent articles are widely known in the art., and several odor control agents have been reported in the literature. Different kinds of odor control agents are known in the art according to their different mechanisms of action. Disposable absorbent articles may comprise only one odor control agent or combinations of various odor control agents, optionally belonging to different classes and therefore performing different actions for the control of odors associated with body fluids. A first class of odor control agents is constituted by those compounds that interfere with bacterial metabolism, in order to avoid or reduce the production of the malodorous metabolites of bodily fluids.; These agents can be bacteriocidal or bacteriostats that are typically available as water soluble compounds. A second class of odor control agent comprises those compounds, typically in the form of particles that are capable of absorbing within their structure the odoriferous substances, both those already present in body fluids, as such, and those produced by the body. bacterial metabolism. Another class of odor control agents comprises perfumes that essentially hide unpleasant odors; Moisture-activated encapsulated perfume particles can also be used, in which perfumes are released only when the material is wetted to provide its action during use of the product, and to optionally prevent interaction with other odor absorbing agents prior to that the product is used, if such combination is actually used as the means of odor control. A broader distinction can be made between the odor control agents known in the art. Some odor control agents are preferably active under dry conditions, i.e., when they are not substantially wetted by the absorbed fluids. Moreover, the negative influence of the liquid is even more increased when the pH conditions are far from neutrality, which is very likely to occur in the structures to absorb body fluids, recognizing the degradation of the fluids themselves. Other odor control agents perform their action in solution, and therefore must be moistened by the absorbed fluid. Odor control agents belonging to the aforementioned first kind are typically active in solution; this is true for some perfume substances as well, for example encapsulated perfumes activated by moisture. In contrast, odor control agents of the second class are typically active towards the odorous gaseous compounds related to the fluid absorbed by means of, for example, an absorption mechanism and therefore perform their action best in substantially dry conditions. . With this distinction in mind, any odor control agent known in the art that can be suitably incorporated into absorbent structures for absorbing bodily fluids or any suitable combination thereof, can be used in the laminated absorbent structures of the present invention. , to provide the article incorporating this structure as the element, at least as part of it with the benefit of controlling odors associated with the absorbed bodily fluids. Among the odor control agents that may be employed in the practice of the present invention may be for example water-soluble antibacterial compounds, which are therefore intended to be typically activated in solution. These compounds include, for example, alkylated phenylene compounds (U.S. Patent No. 3,093,546), periodic acids (U.S. Patent No. 3,804,094), various copper compounds, especially copper acetate (U.S. Pat. No. 4,385,632), various quaternary ammonium salts, which are well known for their antibacterial properties, for example, cetyl pyridinium chloride, and the like. In a known manner the odor control agent can be a water-insoluble particulate odor absorbing material such as chlorophyll particles, activated carbon granules, charcoal, ion exchange resin (Japanese patent 87019865), activated alumina. , and absorbent zeolite materials, including well-known zeolites of (molecular sieve) type A and X and zeolite materials marketed under the trade name ABSCENTS by Union Carbide Corporation and UOP, and which are typically available as a white powder on the scale of 3 to 5 microns of particle size, many of these agents are more effective in dry conditions. The odor control agents used in the present invention may also comprise other compounds such as cyclodextrin, chelating agents, barabenes, chitin, pH stabilizing materials, silica gels, clays, diatomaceous earth, polystyrene derivatives, starches, and the like. In addition, the odor control agents may comprise acidic compounds such as ascorbic acid, stearic acid, boric acid, maleic acid polymers, malonic acid, maleic acid, polyacrylic acid and monopotassium phosphate, or basic compounds such as the inorganic salts of carbonates, bicarbonates, phosphate, bisphosphate, sufflate, bisulfate and mixtures thereof, such as those described in U.S. Patent No. 5037412, or as the combination of boric acid and sodium tetraborate described in the international application No. WO 94725077. A distinction between those agents that are more active in dry conditions as compared to agents typically active in solution can be made by a skilled person. It should be understood that the odor control means employed in the practice of the present invention is not simply the odor control agent, per se, added to the absorbent structure. In contrast, the means of odor control comprise any combination of odor control agents and, optionally, other materials such as binders. The binders of the different odor control agents, with a binder, can therefore also be used as, for example, a cementitious binder, and silica in the form of particles, as described in the European patent application EP. 96109175.8, filed June 7, 1996. The odor control agent, on the other hand, is the specific odor control compound. The laminated absorbent structure of the present invention also comprises a gelling absorbent material. As is well known from recent commercial practice, gelling absorbent materials (sometimes referred to as superabsorbent) are widely used in absorbent articles. AGMs are materials that have fluid-absorbing properties. These materials form hydrolyzes upon contact with water, for example, with urine, blood, and the like. A highly preferred type of hydrogel-forming gelling absorbent material is based on polyacids, especially polyacrylic acid. Hydrogel-forming polymeric materials of this type are those which, upon contact with fluids (ie, liquids), such as water or body fluids imbibe these fluids and thus form hydrogels. These preferred gelling absorbent materials will generally comprise partially cross-linked, partially neutralized, hydrogel-forming polymer materials substantially water-insoluble, prepared from acid-containing, unsaturated, polymerizable monomers. In these materials, the polymeric component formed from the acid-containing, unsaturated monomers may comprise the entire gelling agent or may be inserted on hearing types of portions of the polymer such as starch or cellulose. The starch materials grafted with acrylic acid are of the latter type. In this way the preferred gelling absorbent materials include starch grafted with hydrolyzed acrylonitrile, starch grafted with acrylic acid, polyacrylates, maleic anhydrocopolymers and combinations thereof. Particularly preferred gelling absorbent materials are polyacrylates and starch grafted with acrylic acid. Whatever the nature of the components of! polymer of the preferred gelling absorbent materials, these materials will generally be slightly crosslinked. The crosslinking serves to make these preferred hydrogel-forming absorbent materials substantially water-insoluble in water, and the crosslinking also determines in part the gel volume and the extractable characteristics of the polymer of the hydrogels formed therefrom. Suitable crosslinking agents are well known in the art and include, for example, (1) compounds having at least two polymerizable double bonds; (2) compounds having at least one polymerizable double bond and at least one functional group reactive with the acid-containing monomer material; (3) compounds having at least two functional groups that react with the acid-containing monomer materials; and (4) polyvalent metal compounds which can form ionic cross linkages. Crosslinking agents of the above types are described in greater detail in Masuda et al., U.S. Patent No. 4,076,663 issued February 28, 1978. Preferred crosslinking agents are the mono- or poly-esters of mono acids. or polycarboxylic; Nsaturated with polyols, bisacrylamides and di- or triallyl amines. Especially preferred crosslinking agents are N, N'-methylenebenzacrylamide, trimethylol, propane triacrylate and triallylamine. The crosslinking agent will generally comprise about 0.001 per cent mo! at 5 percent mo! of the preferred materials. Sea * preferably, the crosslinking agent will comprise from about 0.01 percent by 3 mole percent of the gelling materials used herein. Preferred, lightly crosslinked hydrogel-forming gelling absorbers will generally be employed in their partially neutralized form. For the purposes described herein, these materials are considered partially neutralized when at least 25 mol%, preferably at least 50 mol% of the monomers used to form the polymer are monomers containing the acid group, which has been neutralized with a cation forming of salt. Suitable salt forming cations include alkali metal, ammonium, substituted ammonium and amines. This percentage of the total monomers used that are neutralized with the monomers containing the acid group is referred to as the "degree of neutralization". Typically, commercial gelling absorbent materials have a degree of neutralization a little less than 90 percent. The preferred gelling absorbent materials used herein, are those that have a relatively high capacity to imbibe the fluids found in the absorbent articles; this capacity can be quantified by referring to the "gel volume" of said gelling absorbent materials. The gel volume can be defined in terms of the amount of synthetic urine absorbed by any given gelling agent and is specified as grams of synthetic urine per gram of gelling agent. The gel volume of the synthetic urine, (see Brandt et al. Below), can be determined by forming a suspension of approximately 0.1 to 0.2 parts of dry gelling absorbent material to be tested with approximately 20 parts of synthetic urine. . This suspension is maintained at room temperature under gentle agitation for about 1 hour, in such a way as to achieve the equilibrium of the swelling. The gel volume (grams of synthetic urine per gram) of gelling absorbent material is then calculated from the weight fraction of the gelling agent in the suspension and the proportion of the liquid volume excluded from the hydrogel formed with respect to the total volume of the suspension. Preferred gelling absorbent materials useful in the present invention will have a gel volume of about 20 to 70 grams, more preferably about 30 to 60 grams of synthetic urine per gram of gelling absorbent material. Another aspect of the highly preferred gelling absorbent materials is related to the level of! Removable polymer material present in said materials. The levels of the extractable polymer can be determined by the contact of a sample of the preferred gelling absorbent material with a synthetic urine solution over a substantial period of time (eg, at least 16 hours), which is needed to reach the extraction equilibrium, by then filtering the hydrogel formed of supernatant liquid, and finally by determining the polymer content of the filtrate. The particular process used to determine the content of the extractable polymer of the gel absorbing agent regulators preferred herein are set forth in Brandt, Goldman and Inglin; U.S. Patent No. 4,654,039, issued March 31, 1987, reissued as 32,649. The gelling absorbent materials which are especially in the absorbent articles of the present, are those that have equilibrium content of extractables in the synthetic urine not more than about 17%, preferably not more than about 10% by weight of the gelling absorbent material. While referring to the arrangement of the containment layers, the laminated absorbent structures of the present invention can be manufactured in various ways well known in the art. Preferably, the laminated absorbent structures according to the present invention are manufactured from a continuous laminated absorbent structure of a type similar to the thin, layered absorbent structures described in the two international applications WO 94/01069 and WO 95/17868. Figure 1 shows a preferred configuration of a laminated absorbent structure 14 formed in accordance with the present invention, with two of the three separate containment layers forming the partially elevated structure to show its construction more clearly. In the laminated absorbent structure of Figure 1, it is possible to distinguish a first surface 20 which is intended to receive, in use, body fluids and a second surface 22 aligned approximately opposite to the first surface twenty; in the embodiment shown in Figure 1, the two surfaces 20 and 22 are substantially parallel to each other. When the laminated absorbent structure is incorporated as an absorbent element in a disposable absorbent article, for example, a sanitary napkin, the first surface 20 is intended to remain, in use, close to the wearer's body, while the second surface 22 is closer to the wearer's garment.

The laminated absorbent structure 14 of Figure 1 comprises first, second and third containment layers, 2, 4 and 6, which are preferably fibrous layers, the containment layer 2, being closer to the first surface 20 of the absorbent structure. laminate 14, while the containment layer 6 is closer to the second surface 22 and the containment layer 4 is intermediate. The fibrous containment layers 2, 4 and 6 have the same width that is constant along the length of the structure 14 and are superposed in such a way that their respective longitudinal edges 8 and 10 coincide; the fibrous containment layers can be made of various materials, such as, paper, wadding, non-woven fabric; these are preferably made of dry-formed layers, generally referred to as "air-laid" layers, of short cellulose fibers having a basis weight of between 20 g / m2 and 150 g / m2. However, alternatively, the fibrous containment layer that is closest to the second surface 22, and which in the embodiment of Figure 1 corresponds to the fibrous containment layer 6, may consist of a dry-formed mixture of cellulose fibers and polyethylene / polypropylene two-component fibers, such as those "sold by Danaklon a / s from Varde, Denmark as AL-Thernlal B and AL-Thermal C. The laminated absorbent structure 14 further comprises a first odor control means 24 and a gelling absorbent material 26, both in the form of particles, each of the odor control means 24 and the gelling absorbent material 26, are contained between the separated containment layers and are preferably in the form of particles or powder.In the embodiment of Figure 1, the first medium odor control 24 is contained between the containment layers 4 and 6, while the gelling absorbent material is contained between the separated containment layers 2 and 4, with the containment layer 4, therefore comprised between the absorbent material of gelation 26, and the odor control means 24.

In a preferred embodiment of the present invention, an inorganic material 12, thermoplastic polymer in finely divided form preferably in particulate form, is comprised between the fibrous layers 2, 4 and 6, and are mixed with both the first odor control means 24 and the gelling absorbent material 26, forming thus two intermediate layers comprised between the fibrous containment layers separated 2, 4 and 6. The width of each intermediate layer is smaller than that of the separated containment layers 2, 4 and 6 extending beyond the intermediate layers forming the portions of the longitudinal edge 16 on their respective longitudinal edges 8 and 10. Each pair of fibrous containment layers 2, 4 and 6 are bonded together, that is, the fibrous layer 2 is bonded to the fibrous layer 4, which in turn is attached to the fibrous layer 6. The bonding of each pair of adjacent fibrous layers is achieved in the region in which the respective intermediate layer is present by application of heat and moderate pressure to melt the particles 12 of the organic, polymeric, thermoplastic material, which are respectively mixed with the particles of the absorbent material of gelation 26 in the intermediate layer between the fibrous containment layers 2 and 4 adjacent, and with the particles of the first odor control means 24 in the intermediate layer between the adjacent fibrous containment layers 4 and 6. The junction between the adjacent fibrous containment layers, separators, is generated by the melting of the individual particles 12 of the polymeric, thermoplastic organic material; as it melts, the polymeric material forms "bridges" optionally comprising particles of gelling absorbent material 26, or of the first odor control means 24, which bridges the adjacent fibrous layers. The overall surface area of the bonding points represents a smaller fraction of the surface area of the fibrous layers 2, 4 and 6, and of the particles of the gelling absorbent material and the odor control medium, the characteristics of which remain this way almost without change. Two continuous lines of adhesive 18 are also applied to the two sides of the intermediate layers on the longitudinal edge regions 16 of each pair of adjacent fibrous layers 2, 4 and 6, to prevent the particles of the gelling absorbent material 26 and of the first odor control means 24 escape from the longitudinal edges of the laminated structure, which corresponds to the superimposed edges of the separating fibrous, containment layers 2, 4 and 6, and also to reinforce the connection between the fibrous layers themselves . Any other means for joining together the separating containment layers, either in the region in which the respective intermediate layer is present, or along the respective longitudinal edges, can also be used in any manner in the alternate modes of the present invention, for example, by means of spray adhesive or by fusion bonding, respectively. The amount of the thermoplastic polymeric organic material, in the finely divided form which can be distributed and mixed in a preferred embodiment with the gelling absorbent mate- rial and control material. of the odor is between 5 g / m2 and 180 g / m2. The polymeric, thermoplastic organic material can preferably be melted at a temperature such that it does not interfere with the characteristics of the other components of the layer structure, ie, the fibrous layers and the particulate material, namely the gelling absorbent material and the means of odor control. Therefore, the thermoplastic material must have flow characteristics such as to allow the necessary bonds to form quickly. These characteristics can be achieved by a polymeric, thermoplastic organic material 7, having a melt flow index, evaluated by the method of ASTM D 1238-85 under conditions of at least 190 / 2.16 preferably at least 25 g / 10. min, and even more preferably at least 40 g / 10 min, and even more preferably at least 60 g / 10 min. If the fibrous layers 2, 4 and 6 are made of a dry-formed short cellulose fiber material, it is preferable to use a thermoplastic polymeric organic material composed of high density polyethylene particles with maximum dimensions of about 400 microns, characterized by a melt flow rate of approximately 50 g / 10 min, of which the amount distributed is between 12 g / m2 and 90 g / m2. Continuous adhesive lines 18 composed between the adjacent fibrous layers on the respective longitudinal edge portions, prevent the particle material forming the intermediate layers from escaping from the longitudinal edges of the structure. Therefore, the laminated structure can be produced separately and stored, for example, as a continuous strip wound on a roll which can then be fed to the production line for disposable absorbent articles, for example, sanitary napkins where Laminated absorbent structures are manufactured 14, from the continuous aminated absorbent structure, in order to be incorporated as absorbent elements in the absorbent articles. Preferably, the first odor control means comprises the odor control agents whose activity is increased, reducing the exposure of the agents to the fluids ie, which are more active when they are not substantially wetted by the absorbed body fluids. Typically the odor control agents that are most sensitive to moisture are those, usually in the form of particles, which are active by means of an absorption mechanism such as for example zeolites and activated carbon. The laminated absorbent structure 14 can be incorporated into a disposable absorbent article, for example, a sanitary napkin as the absorbent member, being comprised between the fluid permeable topsheet and a fluid impermeable backsheet. In use, the laminated absorbent structure 14 incorporated as an absorbent element in a sanitary napkin is reached by the bodily fluids on the first surface 20; the fluid is received by the first fibrous layer 2, and subsequently most of it is absorbed by the layer of the gelling absorbent material 26 contained between the two adjacent containing fibrous layers 2 and 4. The first odor control means 24 between the two fibrous containment layers 4 and 6 can therefore act more effectively against gaseous odorous substances while the influence of moisture on the odor control agents forming the first odor control means is excellently reduced. The gelling absorbent material 26, contained between the pair of the separating containment fibrous layers 2 and 4, is capable of absorbing bodily fluids, and at the same time has itself an odor control capacity related to its regulatory properties. of pH and ion exchange. The gelling absorbent materials are generally able to maintain the pH of the fluid near neutrality in only slightly alkaline conditions, therefore, controlling the formation of alkaline odorous compounds such as ammonia and amines, which are responsible for some unpleasant odors related to the use of absorbent articles. Therefore, a layer of gelling absorbent material contained between the separating containment layers and combined with a first odor control means according to the present invention as described above, not only increases the effectiveness of the odor control means substantially, preventing the first odor control means from being moistened by the absorbed fluids, but also keeping the pH of the absorbed fluid stable at almost neutral values and developing a true odor control action against some alkaline odorous compounds. A further advantage can be achieved in the event that a minor residual amount of liquid must reach the first means of odor control, not only the fact that this amount is very small in any case, in such a way that its possible influence on the The activity of the first odor control means is low, but that the pH value of the fluid that is kept close to the neutrality further reduces this influence towards the first odor control means. A synergistic effect is therefore achieved in a way not expected by the combination of a material! gelling absorbent and a first control means -'.- i or! ^ - within a laminated absorbent structure according to the present invention. The gelling absorbent materials hereinbefore described are typically used in the form of discrete particles. These gelling absorbent materials can be of any desired shape, for example, spherical or hemispherical, cubic, polyhedral in the form of a bar, etc. the shapes that have a larger dimension / larger smaller dimension ratio, like needles and flakes, are also contemplated to be used here. The agglomerates of the particles of the gelling absorbent material can also be used, as well as the gelling absorbent material other than the particulate form, for example, in the fiber form. The size of the particles of the gelling absorbent material can vary over a wide range. For reasons of industrial hygiene, average particle sizes less than about 30 microns are less desirable. Particles having a smaller dimension greater than about 2 mm can also cause a gritty feeling in the absorbent article, which is undesirable from the consumer's aesthetic point of view. In addition, the speed of fluid absorption can be affected by the particle size. Larger particles have very low absorption rates. Preferred for use herein are the particles of the gelling absorbent material substantially all of which have a particle size of about 30 microns to about 2 mm. The "particle size" as used herein means the average weight of the smallest dimension of the individual particles. The amount of the particles of the gelling absorbent material used in the present invention will typically vary from 20 g / m2 to 150 g / m2, preferably from 40 g / m2 to 110 g / m2, more preferably from 55 g / m2 to 85 g / m2. The first odor control means 24 may comprise a simple odor controlling agent, for example, a zeolite, or alternatively a combination of different known odor control agents, preferably of the same type characterized by a better effectiveness in dry conditions A mixture of zeolite and silica gel, both in the particulate form, is particularly preferred as either the silica gel can perform both an odor control activity and an absorption action towards moisture The zeolites can be naturally derived or synthetically manufactured, the preferred synthetic zeolites being for use herein and include zeolite A, zeolite T, etc. zeolite Y, zeolite X, zeolite DAY, zeolite ZSM-5 and mixtures thereof The most preferred are zeolite A and zeolite Y and their In accordance with the present invention, the zeolite is preferably hydrophobic.

This is typically achieved by increasing the molar ratio of the SiO2 content to AI02 such that the ratio of x to y is at least 1, preferably from 1 to 500, most preferably from 1 to 6. The laminated absorbent structure preferably comprises 40 g. / m2 at 90 g / m2, more preferably from 55 g / m to 85 g / m, most preferably from 60 gfrn to 65 g / m2 of said zeolite. The laminated absorbent structure also preferably comprises from 40 g / m2 to 100 g / m2, more preferably from 60 g / m2 to 90 g / m2, more preferably from 60 g / m2 to 65 g / m2 of silica, preferably silica gel , based on a purity of 100%. The ratio of the gelling absorbent material to the silica to zeolite is preferably in the scale of 1: 5: 1 to 1: 1: 5, preferably 1: 3: 1 to 1: 1: 3, most preferably 1: 1. : 1 to 1: 1.5: 1.5. In accordance with the present invention, the weight of the first control means of! The odor that can be used within the laminated absorbent structure can easily be determined by the skilled person having in mind the dimensions of the absorbent article. For example, when used in a sanitary napkin or in a pantyliner, the laminated absorbent structure may comprise from 0.5 grams to 5 grams, preferably from 1 gram to 3 grams, most preferably from 1.5 grams to 2.5 grams of said system. odor control According to the present invention, the laminated absorbent structure 14 may comprise a second odor control means provided in at least one more interposed layer between the first surface 20 of the laminated absorbent structure 14, and the gelling absorbent material 26. Said The second odor control means may comprise one or more optional components such as antimicrobial agents, perfume ingredients, concealing agents, pH regulating systems and chelants all of which are known to those skilled in the art. These optional odor control agents that constitute the second odor control means are preferably active in solution, i.e. when wetted by body fluids. Therefore, these are intended to be reached by the first fluid.

The odor control agents that constitute the second odor control means may be available in different forms, for example, in powder form, or as an aqueous solution. Depending on their preferred form, these may be comprised within the laminated absorbent structure 14 of the present invention in different arrangements. A second means of controlling the odor in the solid form, for example, in the powder form, may be contained between an additional fibrous containment layer, not illustrated in Figure 1, and the first containment layer 2, or alternating, it can be mixed with the gelling absorbent material 26. If the second medium of ßontro! The odor is in the form of an aqueous solution, this may be comprised within the containment layer that is closest to the first surface 20, for example, sprayed onto the fibrous layer 2 of Figure 1. The control agents of the Suitable odors which are used as the second means of odor control are those agents that at least reduce the enzymatic and / or bacterial activity within the absorbed fluid. Chelating agents such as those described in the European patent applications EP 96109178.2 and EP 96D109179.0, both filed on June 7, 996, are particularly preferred. In a preferred alternate embodiment of the present invention, each simple odor control agent that constitutes the first odor control means is contained between the separating containment layers. A preferred embodiment is illustrated in Figure 2, in which a section of the laminated absorbent structure similar to that illustrated in Figure 1 is shown. The first odor control means comprises the same preferred odor control agents already described, ie, zeolite and silica gel in the particulate form, but each odor control agent is currently contained between the separating containment layers, preferably the fibrous layers of the same type described above. With respect to the embodiment of Figure 1, there is an additional separating containment fibrous layer 5, which separates the silica gel particles 23 and the zeolite 256 which constitute the first odor control means 26. The zeolite 25 is disposed closer to the second surface 22 of the laminated absorbent structure 14. The arrangement of each odor control agent different from the first odor control means 26 between the separating containment layers can be ensured in an even better odor control action of the first month of odor control, since possible interferences between the different odor control agents are avoided. Moreover, the body fluid and the moisture absorbing action of the gelling absorbent material 26 and ge! of silica 25, respectively, combined with their intrinsic odor control capabilities increase to an upper limit the effectiveness of zeolite 25 which can therefore act in substantially anhydrous environment. In a preferred embodiment of Figure 2, the silica gel 25 can in fact act as an odor control agent, and a! at the same time be able to absorb the liquid or residual moisture that can reach it from the gelling absorbent material 26 and through the second containment layer 4. A second odor control means can preferably be incorporated into the laminated absorbent structure of the Figure 2, for example, as an aqueous solution sprayed on the first fibrous layer 2, separant, the different odor control agents, can therefore perform their action under the best conditions against the different kinds of odorous substances. The containment layers comprised in the embodiments of the present invention described so far are fibrous layers preferably made of hydrophilic fibers, but these may also comprise non-fibrous layers, provided they are permeable to the fluid or at least to the gas, for example , the layers constituted by one of the polymeric films with openings well known in the art. Although the separating containment layers of the laminated absorbent structures described so far, all have the same width that is constant along the length of the structure, additional embodiments are also possible in which the separating containment layers have different widths, or, also the width of the laminated absorbent structure can vary along the length of the structure itself, so as to provide, for example, an absorbent element configured for a disposable absorbent article, for example, an absorbent article in the shape of Hourglass. Alternatively, one or more hydrophilic separating containment fibrous layers of the laminated absorbent structures illustrated in Figures 1 and 2, preferably one or more of the intermediate containment layers, can be replaced with containment layers made of hydrophobic fibers, by example, synthetic fibers. In a preferred alternate embodiment, the hydrophilic containing layer 5 of the embodiment shown in Figure 2, and optionally the hydrophilic containing layer 4 can be replaced by a layer or layers entirely made of hydrophobic synthetic fibers, bicomponent fibers. The hydrophobic fibrous layers help to prevent the residual fluid from reaching the zeolite particles 25 and the silica particles 23 also if they constitute the containment layer 4 as well, while at the same time, providing the transmission of the gaseous substances, by example the malodorous compounds which can therefore reach the odor control agents of the first odor control means. An intermediate containment layer of synthetic fibers can have a further advantage if it is comprised within a laminated structure of the types described so far. An intermediate containment layer made of synthetic fibers can be used to join the two adjacent containment layers together along the longitudinal edges 16 of the laminate structure 14 by the simple application of heat and pressure, therefore avoiding the use of continuous adhesive lines 18.

Claims (9)

1. A laminated absorbent structure for absorbing aqueous body fluids and for providing odor control, said structure having a first surface intended to receive the fluids and a second surface aligned approximately opposite the first surface, the laminated absorbent structure comprising first control means of the odor to absorb odors and which further comprises a gelling absorbent material, the laminated absorbent structure being characterized in that e. first means of controlling odor and said matter! The gel-absorbing absorbent each is contained between separating containment layers, said first odor control means being separated from the first surface by the gelling-absorbent material.

2. A laminated absorbent structure according to claim 1, characterized in that it comprises a second odor control means provided in at least one additional layer, said additional layer being interposed between the first surface and the gelling absorbent material.

3. A laminated absorbent structure according to claim 2, characterized in that the first means of odor control comprises one or more odor control agents that are active when they are not substantially moistened by body fluids, and said second means of Odor control comprises one or more agents that are active when moistened by body fluids.

4. A laminated absorbent structure according to any preceding claim, characterized in that each of the odor control agents of said first odor control means is contained between the separating containment layers.

5. A laminated absorbent structure according to any of claims 2 to 4, characterized in that each of the odor control agents of the second odor control means is contained between the separating containment layers.

6. A laminated absorbent structure according to any preceding claim, characterized in that the gelling absorbent material and the odor control agents are in the form of particles or powder.

7. A laminated absorbent structure according to any preceding claim characterized in that the containment layers are fibrous layers. A laminated absorbent structure according to any preceding claim characterized in that each said gelling absorbent material and the odor control agent constitute an intermediate layer between a respective pair of containment layers, each intermediate layer also comprising a thermoplastic material , each intermediate layer joining together the respective pair of containment layers. A laminated absorbent structure according to claim 8, characterized in that each respective pair of containment layers extends beyond the intermediate layer contained therebetween, laterally forming the portions of the longitudinal edge, each respective pair of layers of containment being joined together along each edge portion by means of a preferably continuous adhesive line.