MXPA99005690A - A dry laid structure comprising particulate material - Google Patents

Abstract

The present invention relates to a dry laid fibrous structure (40) for absorbing aqueous fluids and/or for providing odor control. The fibrous structure (40) comprises a dry laid fibrous web (22) and a particulate material (42) distributed in the web and are bonded by a thermoplastic polymeric material in finely divided form (48) distributed therein;the fibrous structures (40) are particularly suitable for use in disposable absorbent articles.

Description

STRUCTURE PLACED IN DRY COMPRISING PARTICLE MATERIAL FIELD OF THE INVENTION The present invention relates to dry-laid fibrous structures, preferably designed to absorb aqueous fluids and / or to provide odor control. The structures comprise a dry-laid fibrous web and a particle material distributed in the web and which are joined by a thermoplastic polymer material distributed therein; these are particularly suitable for use in disposable absorbent articles.

BACKGROUND OF THE INVENTION Fibrous structures, particularly fibrous structures for absorbing liquids, are manufactured for many uses, for example, they are incorporated in absorbent articles such as disposable diapers, incontinence pads and catamenial towels as fluid absorption elements or fluid transmission elements. and / or diffusion, for example as absorbent cores that are intended to absorb and retain body fluids. The fibrous structures, and more specifically the fibrous structures used in absorbent articles as fluid absorption or fluid transmission and / or diffusion elements, usually comprise a multiplicity of components to improve their specific performances, for example, the absorbent structures that comprise fibers and a particulate material, such as a gelling absorbent material in the form of particles are known in the art. Additional components may also be included to provide the structure with additional benefits. Dry placement processes and, more specifically, air placement processes are widely used to produce wefts from dry fibers, which in turn are used, for example, as structures to absorb fluids. Particularly, dry laying refers to the formation of carded webs, ie, webs in which the fibers are oriented (carded), in a given direction, while the air laying process refers to the formation of webs with a completely random fiber orientation; the properties of these wefts placed with air are therefore somewhat isotopic. The fibrous webs produced by dry placement processes are soft, flexible and porous and are particularly suitable for use as liquid absorbent structures, in absorbent articles, such as diapers, sanitary napkins, incontinence pads and wipes. Methods for incorporating additional components, for example, in the form of particles within a dry-laid fibrous web are also known in the art; particularly, in U.S. Patent No. 4,765,780, there is disclosed a process and apparatus for forming fibrous webs placed with air, having a multiplicity of components, such as a two-layer absorbent core with a layer having an absorbent material of gelation in the form of particles mixed therein homogeneously, the other layer being substantially free of the particles of gelling absorbent material. Similar techniques can be used to incorporate different types of components into a dry-laid fibrous web, for example, a particulate odor control means in order to provide the absorbent structure constituted by the dry-laid fibrous web the additional benefit of odor control. The manufacturing process of dry laying generally comprises a step of forming and placing the weft and a step of joining and stabilizing the weft; in the processes of dry placement, in fact the fibers can be of any type, for example, cellulosic, synthetic or any combination thereof, which are formed or condensed in a web. In addition, additional components that are not in fiber form can also be incorporated into the fibrous web, for example, a particle material. The resulting plot lacks integrity after the formation and must therefore be stabilized. The different techniques for joining and stabilizing a dry formed web, that is, the mechanical, thermal and chemical bonding processes, are known in the art. The union of a weft structure by chemical bonding is one of the most common methods of bonding within the non-woven industry, and involves the application of a chemical binder to the weft, and the curing of the binder. The most widely used chemical is latex, since it is cheap, versatile, easy to apply and very effective as a binder. Various methods are known for applying the latex binder to the fibrous web, while spraying and stamping for fibrous webs intended for use in absorbent articles are particularly preferred. European patent application EP-A-592 001 discloses a non-woven fabric bonded by means of, for example, a latex binder, comprising "particles" or "globules" of a thermoplastic composition arranged in a discontinuous pattern over less one of its surfaces, and with an odor control material in the powder form, attached to the "thermoplastic particles" or "globules", on the surface of the non-woven fabric. All of the odor control material is fixed to the "thermoplastic particles", in this case, and is present only on the surface of the non-woven structure. European Patent Application EP-A-463 716 describes a dry-laid absorbent structure comprising a fibrous web with a gelling absorbent material therein and which is stabilized by applying a latex coating to at least a surface of the frame. The thermal bonding process is also widely used in order to join a dry laid web; such a web comprises fusible fibers such as bicomponent fibers such as single component fiber or as a mixture with non-fusible fibers, e.g., natural fibers. These are successively melted by heat treatment to join the weft structure. The layered, patterned absorbent structures described in international applications WO 94/01069 and WO 95/17868 typically comprise two independently formed outer fibrous layers, typically two layers of cellulose tissue placed with air, and an intermediate layer comprising particles of gelling absorbent material and particles of the thermoplastic polymer material, the two fibrous layers being joined by the melting of the thermoplastic particles. The fibrous layers are the same already formed and joined when the structure is made in layers, and therefore, they constitute two distinct and separate layers joined together to form the structure in layers, with the particulate material distributed only between the fibrous layers. Both of the chemical and thermal bonding processes and their possible combinations also suffer from certain disadvantages and are applied to dry laid structures, which comprise a particulate material therein, especially when the particulate material is incorporated into the placed structure. in dry form it is concentrated preferably intermediate in the thickness of the weft, therefore, forming a region in the weft in which the fibers constitute a lower percentage. In such cases, a latex composition can penetrate strongly into the thickness of the weft in order to reach the particles, unless it is used in such quantity that it will impart the performances of the total structure, and possibly, will cause interactive interactions with the particle material. On the other hand, the use of fusible fibers, for example, two-component fibers with the subsequent heat treatment does not solve the problem since the fibers may not be distributed among the particles in such quantity to perform an effective bonding action; furthermore recognizing the nature of the fibers as compared to the particulate material, a homogeneous distribution of the fibers between the particulate material is instead difficult to achieve when the particulate material constitutes the upper percentage of the mixture. Heat-fusible fibers, such as two-component fibers, are also expensive. It is therefore an object of the present invention to provide a dry-laid fibrous structure, preferably a fibrous structure placed with air which comprises a dry-laid fibrous web and a particulate material and having good integrity combined with softness. The dry-laid fibrous structure of the present invention can be used as the absorbent structure for absorbing fluids, preferably with the ability to control the additional odor, which is related to the absorbed fluids. It has surprisingly been found that a thermoplastic polymer material in the finely divided form, preferably in the form of particles or powder, can be effectively distributed between the particulate materials and at least partially between the fibers of the weft laid dry. Subsequent treatments melt the thermoplastic polymeric material, and therefore create a framework of discrete bonding points within the web, i.e., between the fibers and the particle material where the thermoplastic polymer material has been distributed in the finely formed form. divided, without substantially modifying the effectiveness of the same particle material, recognizing the very small dimensions of the thermoplastic particles. The use of the thermoplastic polymer material in the finely divided form can also be combined with a traditional latex union, for example, the thermoplastic powder, performs the union preferably of the internal portion of the weft placed in dry, while the application of a small amount of latex stabilizes the surfaces of the dry-laid weft. Alternatively, the dry laid web can be fully bonded by the thermoplastic polymer material in the finely divided form uniformly dispersed within the entire web, and then melted by heat treatment.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a fibrous structure placed in dry; the dry-laid fibrous structure comprises a dry-laid fibrous web having a first surface and a second surface aligned approximately opposite the first surface and a particulate material distributed within the web. The dry-laid fibrous structure further comprises a thermoplastic polymeric material in the finely divided form distributed therein so as to bond the particulate material to the fibers of the dry laid fibrous web.

BRIEF DESCRIPTION OF THE DRAWINGS Although the description concludes with the claims singling 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 accompanying drawings: Figure 1 is a viewed in fragmented side elevation, of an apparatus for making a fibrous structure according to the present invention; Figure 2 is an enlarged cross-sectional view of a fibrous structure according to the present invention; Figure 3 is a schematic fragmentary side elevational view of an apparatus for making an alternate embodiment of a fibrous structure according to the present invention; Figure 4 is an enlarged cross-sectional view of an alternate embodiment of a fibrous structure according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry-laid fibrous structure, preferably to absorb aqueous fluids and / or to provide odor control. The structure is formed by a dry-laid fibrous web, which comprises a particulate material and which is joined by a thermoplastic polymer material distributed therein in a finely divided form. In a preferred embodiment, the structures of the present invention are incorporated into the absorbent articles, preferably as absorbent structures that are intended to absorb and retain the various body fluids. Absorbent articles, and more specifically disposable absorbent articles, refer to articles such as sanitary napkins, disposable diapers, incontinence pads, which are worn by a user adjacent to the body and which are intended to absorb and contain the various fluids bodily discharges from the body (for example, vaginal discharges, menses, sweat and / or urine), and which are intended to be discarded after a single 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 user's anatomy. In a preferred embodiment of the present invention, the dry laid fibrous structure according to the present invention may integrally comprise the absorbent core of a disposable absorbent article, or these may be comprised there as part of the absorbent core or in any case, these they may constitute an element of a disposable absorbent article, for example, intended for the absorption of body fluids, or for odor control, or both. Disposable absorbent articles, such as for example sanitary napkins, pantiliners, incontinence pads, or diapers, typically comprise a fluid-permeable topsheet, a fluid-impermeable backsheet, which may optionally be vapor permeable. water or gas, and an absorbent core comprised between them. The dry-laid fibrous structures of the present invention comprise a particulate material distributed within the web that is typically capable of developing the absorption of aqueous fluids and / or controlling odors, for example, those odors associated with the absorbed fluids. Preferably the particulate material comprises a gelling absorbent material and an odor control medium, both in the form of particles. The fibrous structures of the present invention can be made using conventional equipment designed for dry placement processes, and although the invention is described, here below with particular reference to structures placed with air, it should be understood that other processes are also applicable. dry placement, for example, carding. The invention will be described as a fibrous structure placed with air, which is capable of providing absorption of aqueous fluids, particularly body fluids, and control of odors associated with absorbed fluids being intended to be incorporated as an absorbent structure in a disposable absorbent article, for example, a sanitary napkin. Figure 1 is a simplified schematic illustration of a preferred embodiment for the manufacture of the fibrous structure of the present invention. According to this embodiment, the air forming system, indicated generally by the number 10, includes a distributor unit 12 arranged transversely above a continuous forming screen 14, mounted on the rollers 16 and driven by a suitable motor (not shown). ), and a vacuum means or vacuum cleaner of the screen 18 is placed under the screen. In a conventional air forming system, the upstream of the distributing unit is a defibrator or feeder (not shown), such as a hammer mill or a Rando feeder where the bales, coatings or the like are defibrated, and also the fibers they can be cleaned and / or mixed and if necessary or desired depending greatly on the type of fibers used, the fiber blends used and the final product thought. For example, the fibers of wood pulp can be mixed with synthetic fibers and applied as a mixture by a single distributor or each of the different fibers can be transported by a different distributor towards the screen to form separate layers or sheets. The porous forming screen 14 is essentially coextensive with the distributors, and the vacuum cleaner of the screen 18 under the screen sucks the area current downwards and transports the fibers towards the surface of the screen thus forming the layers or a loose weft 22. In this stage of the process, the screen exhibits little integrity, and the vacuum means retain the loose, fibrous web on the screen. The web 22 has a first surface 6, which faces towards the distributor and a second surface 8, opposite the surface 6, which faces towards the forming screen 14.

It should be understood that the system can be modified to control the composition and thickness of the final product. For example, the distributor unit may comprise a plurality of individual distributors, and although Figure 1 schematically shows two distributors at 12a and 12B this number of distributors and the particular arrangement may be altered or varied depending on factors such as the speed of the machine. , the capacity, the type of fibers and the desired final product. The web 22 formed on the screen 14 has a particle material incorporated therein. In a preferred embodiment, the particulate material comprises a mixture of a gelling absorbent material and an odor control means, both in the form of particles or powder. In a preferred embodiment, as shown in the Figure 1, a dosing unit or feed hopper 24, containing the particulate material is placed at the midpoint of the dispensing unit, i.e., between the distributors 12A and 12B. In the embodiment of Figure 1, the dosing unit 14 receives the different materials from the supply containers 25 and 26, which respectively contain the gelling absorbent material and the odor control means in particulate forms. The dosing unit 24, preferably provides the particulate material in a homogeneous mixture. A thermoplastic polymeric material in the finely divided form, preferably in the powder form, is also added to the fibrous web 22; in a preferred embodiment, the thermoplastic polymeric material in the powder form is supplied to the dosing unit 24, from the container 27 and mixed homogeneously with the particulate material coming from the containers 25 and 26. In this way , the particulate material comprising the thermoplastic material in the powder form is deposited between the layers of fibers placed by each distributor. That is, the particulate material and the thermoplastic polymeric material are discharged from the hopper 24 onto the moving fiber layer placed by the distributor 12A, and the fiber layer placed by the distributor 12B is placed on the particulate material. However, it should be understood that the layers are relatively porous, and therefore the particulate material and the thermoplastic polymeric material tend to distribute a little within the adjacent layers. Therefore, the fibrous layer 22 comprises the particulate material and the thermoplastic polymeric material concentrated in the middle part of the thickness of the weft, forming a region in the weft 22 in which the fibers constitute a lower percentage as compared to the Particle material and thermoplastic polymer material. Where you want, you can mix the material! of particles with the fibers in one or more distributors, such as in the distributor 12A and 12B thereby forming a web with a particulate material internally mixed with one or more of the fibrous layers of the web. However, it is preferred that the particulate material with the thermoplastic polymer material be distributed within the thickness of the weft 22, between the first and the second surface, 6, 8. The weft 22 condensed on the forming wire 14 has very little integrity and requires stabilization. In the embodiment shown in Figure 1, the weft is subjected to a first stabilization step by means of heat treatment at the bonding station 28. The particulate material and the fibers of the wefts 22 which are comprised between the particulate material and at least partially in the two layers are joined together by the application of heat and, optionally, moderate pressure to melt the thermoplastic polymer material in the form of powder mixed with the particulate material constituted by the gelling absorbent material and by means of odor control. The bond between the particle material and the fibers is generated by the fusion of the individual particles of the thermoplastic polymer material in the powder form, as it melts the thermoplastic polymeric material, it forms "bridges" that directly connect the particle material and the fibers. A global surface area of the junctions represents a first fraction of the surface area of the particulate material and of the fibers that are involved in the junction, the characteristics of which remain almost unchanged. Since the thermoplastic polymer material in the powder form can be homogeneously distributed between the particulate material and the fibers comprised therein, the frame 22 can therefore be provided with an effective connection within the portion concerned by the distribution of the thermoplastic polymer material itself: in the embodiment of the present invention achieved by the apparatus of Figure 1, this corresponds to the region of the weft 22 mainly constituted by the particle material with a lower percentage of fibers, intermediate to the first and to the second surface 6 and 8. The gelling absorbent material, which is preferably distributed in the particulate form, can be made from inorganic or organic substances such as cross-linked polymers, all known from the prior art. The odor control means may be any suitable odor control agent known in the art, or any mixture thereof, for example, this may be constituted by zeolite and silica particles. The average dimensions of the particulate material, given as a weight average of the smaller dimensions of the individual particles, may be between 50 microns and 1500 microns, preferably between 100 microns and 800 microns. The thermoplastic polymer material in the finely divided form, for example, in the powder form, has the purpose of joining together the particulate material and, at least partially, the fibers of the absorbent structure placed in dry, melting and forming discrete dots of Separate bond between particles and fibers. The thermoplastic polymer material can also be used in other finely divided forms, for example, in the form of fibrils. As explained above, the bridges forming these junctions can involve the particle material and the fibers of the weft 22. The amount of the thermoplastic polymer material in the finely divided form incorporated within the weft 22 can be between 5g / m2 and 180 g / m2. The thermoplastic polymer material in the finely divided form can preferably be melted at such a temperature that it does not interfere with the characteristics of the other components of the absorbent structure, i.e., the fibers and the particulate material, which comprise the gelling absorbent material and the odor control means in the preferred embodiment. Therefore, the thermoplastic polymeric material must have flow characteristics such as to allow the necessary bonds to be formed quickly. These preferred characteristics can be achieved by a thermoplastic polymer material in the finely divided form having a melt flow index (MFI), evaluated by the method ASTM D 1238-85 under conditions 190 / 2.16, of at least 25g / 10 min., preferably at least 40 g / 10 min, and even more preferably at least 60 g / 10 min. If the fibers of the dry-formed fibrous structure are short cellulose fibers, it is preferable to use a thermoplastic polymeric material composed of high density polyethylene powder with maximum particle dimensions of about 400 microns, characterized by a melt flow index of approximately 50 g / 10 min, in an amount of 12 g / m2 and 90 g / m2. In accordance with the embodiment of the present invention illustrated in Figure 1, the weft 22 can be further joined on one, or preferably both, surfaces 6 and 8 by means of the application of a latex composition. The weft 22 can be first passed between the compression rollers (not shown), which can be heated, to densify the weft, but this step is optional. This densification step can increase the penetration of the latex into the web, and the degree and percentage of densification can vary depending on factors such as the amount of the odor control particles, the basis weight of the web, the desired degree of penetration in the latex in the plot, and the final product thought. After the joining station 28 and the compression rollers (optional), the web is transported to a suitable dispensing means 30, such as a spray nozzle, knife, or roller applicator, or the like where a latex binder is applied. to the first surface 6 of the web 22. A vacuum applied by a screen aspirator 19 placed under the dispensing means and the screen 14, helps to suck the latex into the web. The dispensing or applicator means are essentially coextensive with the width of the weft, and preferably a substantially uniform coating is applied to the weft surface. However, latex can be applied as a random or patterned non-uniform coating, and because the latex is water-based, it will diffuse throughout the weft and will function as a binder when covered. The latex, when cured, imparts integrity to the weft and therefore some latex penetration is required. The limit or degree of penetration of the latex in the web is controlled by controlling the amount of latex applied and by controlling the vacuum applied to the web in which the vacuum helps to pull the latex towards the web. This extension or degree of penetration can be limited to the surface of the weft 22, since the part of the weft 22 comprising the particulate material which is intermediate to the surface 6 and 8 is already bonded by the thermoplastic polymeric material, and therefore any possible negative interference between the composition of the latex and the particulate material is avoided. The amount of the latex composition is also maintained to such a limit that it will not affect the absorbency and softness characteristics of the fibrous web 22. The latex is normally applied as an aqueous emulsion, and may be a thermal hardening plastic. In order to activate the latex, the latex emulsion contains a suitable curing agent or crosslinking agent, and the weft is subsequently coated, in latex it is cured to effect crosslinking. More typically curing is achieved by passing the coated web through a hot air oven or through an air dryer 32, and the temperature typically varies from about 100 ° C to 260 ° C, but this depends on the type of resin specific latex used, the curing agent or the crosslinking agent, the amount of latex, the thickness of the weft, the degree of vacuum and the speed of the machine. It is desirable to coat the second surface 8 of the web 22 with latex as well, and this is easily achieved by the dispensing means 36 as the web 22 is transported over the second web 34 operated around the pulleys 191, 192 193 and 194 The second dispensing means 36 includes a screen aspirator 37. This second latex coating is also cured by passing the screen through a second oven 38 within approximately the same temperature range. The resulting absorbent structure 40 that leaves the last oven, now exhibits sufficient integrity, and can be cut, rolled, packed, etc. The absorbent structure 40 made according to the above process is Illustrated in Figure 2. The absorbent structure 40 comprises randomly distributed fibers 46, such as wood pulp fibers, and the particulate material 42 is distributed within the absorbent structure. The thermoplastic polymer material 48 in the powder form is distributed principally between the particulate material 42 and performs the bonding of the particulate material and at least part of the fibers of the absorbent structure 40, ie, those fibers that are in contact with the thermoplastic polymer material. It will be noted that the particulate material is more concentrated in the middle zone of the absorbent structure, but some particles migrate to other sections of the absorbent structure. Both the first and the second surfaces 6 and 8 of the absorbent web 22 carry a latex coating 50 indicated in the drawings by shading, which has penetrated or impregnated the absorbent structure to some degree and has partially coated some of the fibers. As explained above, the penetration is controlled so as not to affect the characteristics of the particulate material. The fibrous structure of the present invention is strong and absorbent, yet smooth, exhibiting a relatively high tensile strength. It may also be desirable for the preferred absorbent fibrous structures of this type to have a relatively low volume, because a denser absorbent structure, when compared to structures that do not contain latex and of approximately equal absorbent capacity but of higher volume, can be thinner still highly absorbent and consequently less bulky. A reduction in volume which means a reduction in the volume of the absorbent fibrous structure that it is occupying without sacrificing significantly other desired properties is important from the point of view of manufacturing, storage and packaging. Consequently, for the products of the present invention, the basis weight may vary from about 75 g / m2 to about 50 g / m2 to 600 g / m2, and preferably from about 75 g / m2 to 400 g / m2, and more preferably from approximately 250 g / m2 to 350 g / rtf. There may be manufacturing limitations therein in producing an absorbent structure having a lower basis weight of about 50 g / m2, in which this absorbent structure may lack the desired strength. When the base weight exceeds the upper limit, the product may be too rigid and therefore not useful for most applications.

Any of a variety of fibers, including a mixture or combination, can be used within the fibrous structure of this invention. The fibers may be cellulosic, modified cellulosic, or synthetic, and include such fibers as wood pulp, rayon, cellulose acetate cotton, polyester, polyethylene, polypropylene, nylon, and the like. A fibrous structure comprising cellulosic fibers such as wood pulp fibers, is particularly useful as an absorbent structure in products such as sanitary napkins, disposable diapers or cloths because cellulose is liquid absorbent and therefore increases overall absorbency of the structure. Products of this type, i.e. fibrous structures which are also absorbent, also advantageously use a mixture of cellulosic and synthetic fibers, typically comprising about 65% to 95% by weight of cellulosic fibers, and more preferably up to about 20% by weight. % by weight of synthetic fibers. Synthetic fibers, which can be provided in any short length, can improve the strength of the structure. These can also be treated to make them hydrophilic, so as not to diminish the absorbent capacity of the preferred absorbent fibrous structure. The preferred fibrous structures described thus far comprise hydrophilic fibers which are substantially uniform to aqueous fluids, said structures being useful as absorbent structures in disposable absorbent articles. The dry-laid fibrous structures according to the present invention may also comprise hydrophobic fibers only, for example, synthetic fibers. These structures may comprise, for example, as the particulate material an odor control means only, being therefore able to control the odor without absorbing and retaining liquids. Such type of structures may be comprised in disposable absorbent articles as a liquid receiving and transmitting layer, for example, as an acquisition layer comprised between the topsheet and the absorbent core, which is capable of rapidly acquiring body fluid and absorbing fluid. transmit it to the absorbent core, while carrying out an action of odor control with respect to the fluid. A structure according to the present invention comprising hydrophobic synthetic fibers, alone, may also be useful in different applications, for example, as a filter medium. In this way the type of fibers and the particular mixture can be varied depending on the final product. In addition, of the above uses, the absorbent structures of the present invention can be used suitably for incontinence pads, diaper cores, diaper inserts, and for surgical and wound bands, providing the absorbent capacity and / or the odor color, the gelling absorbent material, which preferably constitutes at least part of the particulate material comprised within the dry-laid absorbent structure of the present invention, may comprise any of the known materials (sometimes referred to as "superabsorbents") ), which are widely used in absorbent articles. AGMs are materials that have fluid-absorbing properties. These materials form hydrogels on 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 thereby form hydrogels). These preferred gelling absorbent materials will generally comprise partially neutralized, slightly crosslinked, substantially water-insoluble, hydrogel-forming polymer materials prepared in water, prepared from acid-free, unsaturated, polymerizable monomers. In these materials the polymeric component formed from acid-containing unsaturated monomers comprises the entire gelling agent or can be grafted onto other types of polymer portions such as starch or cellulose. The starch materials grafted with acrylic acid are of the latter type. Thus, preferred gelling absorbent materials include starch grafted with hydrolyzed acrylonitrile, starch grafted with acrylic acid, polyacrylates, maleic anhydride-based copolymers and combinations thereof. Especially preferred gelling absorbent materials are polyacrylates and starch grafted with acrylic acid. The odor control means preferably included within the fibrous structure of the present invention may comprise a wide variety of odor control agents, in order to control unpleasant odors, for example, those odors associated with the fluids absorbed when the structure fibrous is a fluid-absorbing structure. In its preferred use as absorbent cores within the disposable absorbent articles, the absorbent structure of the present invention is intended to absorb body fluids. The various body fluids contain several malodorous chemical compounds including acyclic and cyclic amines, aldehydes, fatty acids and sulfur-containing compounds such as sulfides. For example, the vaginal discharges and sanitary napkins used may contain many malodorous chemical compounds, for example, trimethylamine, pyridine, foraldehyde, isobalérico acid, and methyl mercaptan. Particular malodorous compounds that will be absorbed by the various absorbent articles will vary depending on the person using the absorbent article and the type of absorbed body fluid, i.e., urine, menstrual fluid, vaginal discharge, perspiration, milk, etc. For feminine pads such as sanitary napkins or pantiliners, the length of time the article is worn, the amount of fluid that is absorbed and the exposure of the pad to the different body fluids, will determine what odors can be emitted by the body. absorbent article.

Any suitable odor control agent known in the art can be incorporated into the dry laid fibrous structures of the present invention to provide the structure with the benefit of odor control, for example, toward those odors associated with body fluids. absorbed when the fibrous structure placed in dry is an absorbent structure, preferably incorporated within the absorbent articles. Suitable odor control agents that can be employed in the practice of the present invention can be, for example, water soluble antibacterial compounds. These compounds include, for example, halogenated phenylene compounds (3,093,546), periodic acids (U.S. Patent No. 3,804,094), various copper compounds, especially copper acetate (U.S. Patent No. 4,385,632), various salts of quaternary ammonium, which are well known for their antibacterial properties, for example, cetyl pyridinene chloride and the like. Alternatively, the antibacterial compounds can be used in conjunction with various particle materials which in use and in the presence of moisture release the antibacterial agent. Zeolite materials, such as zeolites which are bactericidal by virtue of having absorbed therein various bacterial cations such as copper, silver and zinc, may advantageously be used in the practice of the invention (patent of United States No. 4,525,410). In a preferred embodiment, the odor control agent is a water-insoluble, particulate odor absorbing material, such as chlorophyll particles, activated control granule, charcoal, freshly ion exchanger (Japanese Patent 87019865), alumina activated, and absorbent zeolite materials, including the well-known molecular sieve zeloites of type A and Z, and the zeolite materials marketed under the trade name of ABSCENTS by Union Carbide Corporation and UOP, and which are typically available as a powder white in the particle size range of 3 to 5 microns. In a known way, the odor control agent can be a water-insoluble, odor-absorbing particulate material, such as chlorophyll particles, activated carbon granules, charcoal, ion-exchange resin (Japanese Patent 87019865). ), activated alumina, and zeolite-absorbing materials, including the well-known "molecular sieve" zeolites, type A and X and zeolite materials marketed under the trade name BCENTS by Union Carbide Corporation and UOP, and which they are typically available as a white powder in the particle size range of 3 to 5 microns. The odor control agents used in the present invention may also comprise other compounds such as cylcodextran, chelating agents, parabens, chitin, pH regulated materials, silica gel, clay, diatomaceous earth, polystyrene rears, starches and the like. For example, chelating agents such as those described in European patent applications Nos. EP 96109178.2 and EP 96109179.0, both filed on June 7, 1996, are particularly preferred. Some partially neutralized hydrogei-forming gel-forming absorbent materials, such as the polyacrylate gelling material and the acrylate-grafted starch gelling material may also be used, preferably in combination with other odor control agents. In addition, 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 inorganic salts of carbonates, bicarbonates, phosphates, bisphosphates, sulfate, bisulfate, borate, 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 International Application No. WO 94/25077. It should be understood that the odor control means that can be preferably employed in the practice of the present invention is not simply the odor control agent per se added to the fibrous structure. In contrast, the odor control means comprises any combination of odor control agents, and optionally other materials such as binders. The binders of the different odor control agents, for example as a binder, can also be used, such as for example an agglomerate of zeolite and silica in the form of particles, such as that described in European Patent Application No. EP 961091758.8. on June 7, 1996. The odor control agent, on the other hand, is the specific odor control compound. Preferably, odor control agents are used in the present invention in the form of particles. Particularly preferred are the odor control means comprising zeolite, silica, preferably in the form of silica gel, gelling absorbent material and combinations thereof, such as the odor control means described in international application 2O 95/26207 , and in the European patent applications EP 96109177.4, EP 96109173.3, EP 96109174.1, EP 96109176.6. For example, a preferred odor control means may be a combination of silica gel particles, zeolite and gelling absorbent material. The weight ratio of the gelling absorbent material to the silica, to the zeolite is preferably in the scale of 1: 5: 1 to 1: 1: 5, preferably 1: 3: 1 to 1: 1: 3, more preferably from 1: 1: 1 a 1: 1.5: 1.5. It has been found that the odor control material can be incorporated into the fibrous structures according to the present invention in an amount ranging from 20 g / m2 to 400 g / rrf, preferably from 100 g / m2 to 300 g / m , more preferably from 150 g / m2 to 250 gVm, with reference to the total surface area of the fibrous structure. Preferably, the fibrous structures of the present invention may comprise from 20% to 80% by weight of odor control medium. The weight of the odor control means which can actually be used in various fibrous structures intended for different uses can easily be determined by the skilled person having in mind the size and type of fibrous structure, and its intended use. The latex is applied as an aqueous emulsion or dispersion, which typically contains from about 45% to 65% solids, and these materials are readily available from various manufacturers. Because the latex emulsions are miscible in water, they can also be diluted, if desired, before being applied to the weft. Also, these latex compositions are thermosettable, and in order to effect crosslinking, they contain a small amount of a suitable crosslinking agent, which are well known chemical agents for this purpose such as N-methylolacrylamide. Any type of latex known in the art that is suitable for the fibrous structures of the present invention may be used, provided that this preferably does not generate detectable odors, especially after curing, since this may be unpleasant for a user, and, moreover, it can at least partially deplete a preferred odor control capability of the fibrous structure before its intended use. The available cross-links are classified by chemical family, and those particularly useful include copolymers of vinyl acetate and acrylic ester, copolymers of ethylene vinyl acetate, copolymers of styrene butadiene, carboxylate, and polyacrylonitriles and sold, for example, under the trade names of Airbond, Airlex, and Vinac of Air Products, Inc., Hycar and Geon of Goordich Chemical Co., and Fulatex of HB Fuller Company. The amount of latex used in the absorbent structure can not be so high as to substantially affect or obscure the effective odor control capacity of the odor control medium, and also the absorbent properties of the hydrophilic fibers, or as to impart a stiffness to the structure to make it impractical. It has been found that the latex can vary from about 5% to 30% by weight of the structure, and preferably from about 10 to 20% by weight. Fibrous structures made in accordance with the present invention exhibit good integrity due to the binding performance by the thermoplastic polymeric material comprised within the structure in the finely divided form, and optionally the latex coating, and still preferably having either an absorbent capacity remarkable or an odor control capacity, or more preferably both of them since the particulate material comprised in the fibrous web, is affected by the binder medium, ie by the thermoplastic polymer material in the finely divided form, and possibly by the latex coating, only to a minimum limit. If a latex binder is used, the penetration depth of the latex within the fibrous web can be controlled by the vacuum applied by means of the screen aspirators placed in correspondence with the dispensing means, and by the selection of the quantity that it applies to the plot. Figure 3 shows a schematic, simplified illustration of an apparatus for developing a preferred alternate embodiment of a dry-laid fibrous structure 59 according to the present invention, for example an absorbent structure, whose structure is illustrated in Figure 4. The apparatus of Figure 3 is similar to the apparatus illustrated in Figure 1, and the same numbers indicate corresponding parts, but in this case the latex application and curing section is missing, since that the total union of the structure is made by the thermoplastic polymer material in the finely divided form incorporated in the weft. As can be seen in Figure 3, the thermoplastic polymeric material, preferably in powder form, contained within the container 27 is supplied to both the feeder 24 and the distributors 12A and 12B. the thermoplastic polymeric material is therefore mixed homogeneously with the particulate material and with the fibers that form the fibrous layers as well. During the subsequent joining step performed in the bonding station 28, the total dry laid structure 59 is thermally stabilized in its total thickness by the melting of the powder of the thermoplastic polymeric material which binds both of the particulate material comprised between the first and the second. second surface 6 and 8, and the fibers of the screen 22.f With reference to Figure 4 the dry-laid absorbent structure 59 comprises fibers f60 and a material of particles 61 constituted by a mixture of a gelling absorbent material and a odor control means internally dispersed in the web, but more concentrated in the middle part of the thickness of the web 22. The thermoplastic polymer material 63 in the powder form is homogeneously distributed within the total fibrous webs forming the absorbent structure placed in dry 59. In additional alternate embodiments of the present invention either the material may be included gelling absorber or the odor control means in the absorbent structure in a form other than the particulate form, for example, fibrous gelling absorbent materials, or odor control means in the form of a solution sprayed on the Absorbent structure, which can be incorporated as long as a particle material is comprised within the absorbent structure. For example, a suitable solution can be sprayed onto the first fibrous layer placed by the distributor 12A in the apparatus illustrated in Figure 1, or on the first surface 6 of the frame 22 of Figure 3, instead of, or in combination with, the particulate odor control means distributed by the hopper 24 within the frame 22. In a further alternate embodiment of the present invention, not illustrated, a latex coating can be applied to the first layer of the weft fibrous, and subsequently cured before the application of the particulate material, on the surface where the particle material will be distributed. One of the layers of the fibrous web, for example, the second layer of the web of Figure 3, can also, in another alternative embodiment, be replaced by a non-woven layer, or by a polymeric film. In the latter case, the polymeric film must be applied to the weft after the bonding station 28 in order to prevent the temperature in the bonding station from possibly melting the polymeric film. A structure of this type can constitute an absorbent element of a disposable absorbent article having therein incorporated an impermeable layer.

Claims (10)

1. A dry-laid fibrous structure, preferably a dry-laid fibrous structure, said structure comprising a dry-laid fibrous web having a first surface and a second surface aligned approximately opposite the first surface, and comprising a particulate material distributed in the weft, said dry laid fibrous structure being characterized in that it further comprises a thermoplastic polymeric material in the finely divided form distributed therein in order to bond the particulate material to the fibers of the dry laid fibrous web.

2. A dry-laid fibrous structure according to claim 1, characterized in that the particulate material comprises a gelling absorbent material.

3. A dry-laid fibrous structure according to any preceding claim, characterized in that the particulate material comprises an odor control means.

4. A dry-laid fibrous structure according to any preceding claim, characterized in that the particulate material is distributed within the thickness of the dry-laid fibrous web, between the first and the second surfaces.

5. A dry-laid fibrous structure according to any preceding claim, characterized in that the thermoplastic polymeric material is in the form of particles or powder.

6. A dry-laid fibrous structure according to any preceding claim, characterized in that the thermoplastic polymeric material is mixed with the particulate material.

7. A dry-laid fibrous structure according to any preceding claim, characterized in that the dry-laid fibrous structure further comprises the latex coating on at least one of the first or second surfaces of said fibrous web.

8. A dry-laid fibrous structure according to any preceding claim, characterized in that the thermoplastic polymeric material provides more bonding of the dry laid fibrous web.

9. A fibrous structure placed in dry of. according to any preceding claim, characterized in that the fibrous structure placed in dry is preferably placed with air.

10. A disposable absorbent article comprising a dry laid fibrous structure according to any preceding claim.