MX2007006462A - Fibrous structures comprising a nanoparticle additive - Google Patents

Abstract

Fibrous srtuctures comprising an additive, more particularly finished fibrous structures comprising a nanoparticle solid additive, and/or sanitary tissue products comprising such finished fibrous structures, are provided.

Description

FIBROUS STRUCTURES THAT COMPRISE AN ADDITIVE OF NANOPARTICLES FIELD OF THE INVENTION The present invention relates to fibrous structures comprising a nanoparticle additive. More specifically, the present invention relates to finished fibrous structures comprising a solid additive of tissue paper nanoparticles or hygienic products comprising such finished fibrous structures.

BACKGROUND OF THE INVENTION Fibrous structures, especially low density fibrous terminated, soft, fluffed or tissue paper hygienic structures comprising such finished fibrous structures, for example, toilet paper or paper towels or disposable tissues, comprising additives are well known in the art. the industry. Traditionally, additives are incorporated into fibrous structures by adding additives to the fiber pulp before forming the fibrous structures. Other known methods for adding additives to the fibrous structures include the distribution of additives in the fibrous structures by liquid carriers, especially aqueous vehicles. Alternatively, some additives are distributed in the fibrous structures in a contact passage, such as the printing of additives in the fibrous structures by cylinders or rollers, such as gravure rolls, or by placing the additives with brush in the fibrous structures or by the Transfer of additives from wires or tapes / fabrics during the papermaking process. There are problems, both with the product and with the process, in each of the processes of the previous industry described above. In particular, the brush application process binds the additive with the fibrous structure with little precision, so that the average lint index of such fibrous structure is extremely high, and consumers are not willing to accept it willingly. In addition, the additives added to the fibrous structures of the prior industry have a relatively large average particle size. Therefore, there is a need to achieve a fibrous structure, especially a finished fibrous structure and / or a tissue paper hygienic product comprising such a finished fibrous structure, such as toilet paper and / or paper towels, characterized in that the fibrous structure comprises a fiber and a nanoparticle additive.

BRIEF DESCRIPTION OF THE INVENTION The present invention meets the needs described above by providing a fibrous structure comprising a nanoparticle additive. In an example of the present invention, a fibrous structure comprising a solid nanoparticle additive is provided. In another example of the present invention, a single-ply or multi-ply tissue paper hygienic product comprising a finished fibrous structure in accordance with the present invention is provided.

Accordingly, the present invention provides fibrous structures, especially finished fibrous structures comprising a nanoparticle additive and / or tissue paper hygienic products comprising such finished fibrous structures.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a schematic perspective representation of an example of a fibrous structure in accordance with the present invention; Figure 2 is a cross-sectional view of the fibrous structure of Figure 1 taken along line 2-2; Figure 3 is a schematic perspective view of an example of a multi-sheet tissue paper hygiene product in accordance with the present invention with partial trimming to expose the inter-connection between the sheets of the multi-sheet tissue paper hygiene product; Figure 4 is a cross-sectional view of the multi-sheet tissue paper hygienic product of Figure 3 taken along line 4-4; and Figure 5 is an alternative example of the cross-sectional view of the Figure 4 DETAILED DESCRIPTION OF THE INVENTION Definitions As used herein, "additive" means a material that is present in a fibrous structure and / or on it at low levels. For example, an additive is a material that is present in a fibrous structure and / or on it at levels lower than 50% and / or lower than 45% and / or lower than 40% and / or lower than 30% and / or less than 20% and / or less than 10% and / or less than 5% and / or less than 3% and / or less than 1% and / or less than 0.5% to about 0% by weight of the fibrous structure. As used herein, "nanoparticle additive" means an additive having an average particle size of less than about 1 μ? and / or less than about 0.9 μ ?? (900 nm) and / or less than about 0.5 μ? (500 nm) and / or less than approximately 0.4 μ? T? (400 nm), and / or approximately 1 μ ?? at about 0.005 (5 nm) and / or from about 900 nm to about 100 nm and / or from about 800 nm to about 200 nm. As used herein, "solid additive" means an additive capable of being applied to a surface of a fibrous structure in solid form. In other words, the solid additive of the present invention can be directly distributed on a surface of a fibrous structure without being in liquid phase, that is, without the solid additive melting and without suspending the solid additive in a liquid carrier or carrier. . Thus, the solid additive of the present invention does not require a liquid phase or a liquid carrier or carrier for the purpose of being distributed on a surface of a fibrous structure. The solid additive of the present invention can be distributed by a gas or gas combinations. According to the objectives of the present invention, the distribution of an additive, liquid and / or solid, in a fiber pulp used to produce a fibrous structure is not included in this phase. However, such an additive may be present in a finished fibrous structure as long as the finished fibrous structure also comprises a solid additive, as defined herein. Moreover, an additive, liquid and / or solid, distributed to a fibrous structure by a liquid vehicle, such as a latex emulsion, may be present in a finished fibrous structure as long as the finished fibrous structure also comprises a solid additive. , as defined herein. Moreover, an additive, liquid and / or solid, distributed to a fibrous structure terminated by melting, such as a hot melt adhesive, may be present in a finished fibrous structure as long as the fibrous structure also comprises a solid additive, as define in the present. In simple terms, a solid additive is an additive that, when placed in a container, does not take the form of said container. As used herein, "density" or "bulk density" means the mass per unit volume of a material. In fibrous structures, density or bulk density can be calculated by dividing the basis weight of a sample of fibrous structure by the size of the sample of the fibrous structure with the appropriate conversions incorporated therein. The density and / or bulk density used here are expressed in g / cm3. The density of a material, such as a solid additive according to the present invention, is determined according to the density test method described herein. Again, the density units of a material, as used herein, are expressed in g / cm3. As used herein, "average particle size" or "average particle size" of a material, such as a solid additive according to the present invention, is determined according to the average particle size test method. described in this document. As used herein, the units corresponding to the average particle size are expressed in μ? T ?. "Sphericity", represented by the letter "< DS", is a term used herein to refer to the form of a solid additive. The sphericity is defined as follows: 6 ?? < DS = DpSp where Dp is the equivalent spherical diameter of a solid additive, Sp is the surface area of the solid additive and ?? is the volume of said solid additive. The equivalent spherical diameter is defined as the diameter of a sphere that has the same volume as the solid additive. Dp closely approximates the nominal size based on a granulometric analysis or microscopic analysis. Those with knowledge in the industry will perceive that the surface area can be easily determined with adsorption measurements or by the pressure drop in a bed of solid additives. The sphericity varies between 0 and 1. A perfectly spherical solid additive has a sphericity of 1; Deviations from a perfect sphere in flat materials, such as mica, clay or talc, have a much lower sphericity. As used herein, the term "fiber" refers to an elongate particulate whose apparent length is widely greater than its apparent diameter, i.e., has a length to diameter ratio of at least about 10. A fiber may be a solid additive Fibers that do not have a circular cross section are common; the "diameter" in this case can be considered as the diameter of a circle having a cross-sectional area equal to the cross-sectional area of the fiber. More specifically, as used herein, "fiber" is related to paper fibers. The present invention contemplates the use of a variety of papermaking fibers, such as, for example, natural fibers or synthetic fibers, or any other suitable fiber, and any combination thereof. The natural papermaking fibers useful in the present invention include fibers of animal, mineral and vegetable origin and mixtures thereof. The fibers of animal origin can be selected, for example, from the group comprising: wool, silk and mixtures thereof. Fibers of vegetable origin can be derived, for example, from a plant selected from the group comprising: wood, cotton, cotton linters, flax, sisal, abaca, hemp, hesperaloe, jute, bamboo, bagasse, kuzu, corn, sorghum, guaje, maguey, scourer and mixtures of these. Wood fibers, often referred to as wood pulps, include chemical pulps, such as Kraft (sulphate) and sulfite pulps, and also mechanical and semimechanical pulps, including, among others, crushed wood, thermomechanical pulp, and chemomechanical pulp (CMP). , by its abbreviations in English), pulm quimiotermomecánica (CTMP, by its abbreviations in English) and the pulp of sulfite semichemical (NSCS, by its abbreviations in English). However, chemical pulps may be preferred, since they impart a superior feeling of softness to the touch to the sheets of tissue paper made therefrom. Pulps derived from deciduous trees (hereinafter also called "hardwood") and coniferous trees (hereinafter also called "softwood") can be used. Hardwood and softwood fibers may be blended, or alternatively, deposited in layers to provide a layered and / or layered material. U.S. Pat. num. 4,300,981 and 3,994,771 are hereby incorporated by reference for the purpose of disclosing the stratification of hardwood and softwood fibers. Also useful are fibers derived from recycled paper which may comprise one or all of the mentioned fiber categories and other non-fibrous materials such as fillers and adhesives that facilitate the original papermaking process. Wood pulp fibers can be short (characteristic of hardwood fibers) or long (characteristic of softwood fibers). Non-limiting examples of short fibers include fibers derived from a fiber source selected from the group comprising acacia, eucalyptus, maple, oak, poplar, birch, poplar, alder, ash, cherry, elm, American walnut, poplar, gum, walnut, white acacia, sycamore, beech, catalpa, sassafras, melina, albizia, kadam and magnolia. Non-limiting examples of long fibers include fibers derived from pine, spruce, spruce, American larch, pinabete, cypress and cedar. Coniferous fibers obtained by the Kraft process and originating from more northern climates are preferred. They are often referred to as kraft pulps from northern conifers (NSK, for its acronym in English). The synthetic fibers can be selected from the group comprising: wet spun fibers, dry spun fibers, melt spun fibers (including melt blown), synthetic pulp fibers and mixtures thereof. Synthetic fibers can be composed, for example, of cellulose (often referred to as "rayon"); cellulose derivatives such as esters, ether or nitroso derivatives; polyolefins (including polyethylene and polypropylene); polyesters (including polyethylene terephthalate); polyamides (often referred to as "nylon"); acrylics; non-cellulosic polymeric carbohydrates (such as starch, chitin and chitin derivatives such as chitosan); and mixtures of these. "Fiber Length", "Average Fiber Length" and "Fiber Length Weighted Average" are terms that are used interchangeably in the present and are all intended to represent the "Weighted Average Length of Fiber Length" as determined, for example, by means of a FiberKajaani fiber analyzer commercially avaie from Metso Automation, Kajaani, Finland. The instructions supplied with the unit detail the formula used to reach this average. The recommended method for measuring the length of the fiber using this instrument is essentially the same as that detailed by the Fibermanufacturer in its operation manual. The consistencies recommended for loading in the Fiberare somewhat lower than those recommended by the manufacturer as this allows a more reliable operation. Short fiber pulps, as defined herein, should be diluted to 0.02-0.04% before loading into the instrument. Long-fiber pulps, as defined herein, should be diluted to 0.15% - 0.30%. Alternatively, the length of the fiber can be determined by sending the short fibers to an external ratory such as Integrated Paper Services, Appleton, Wisconsin. Non-limiting examples of fibers suitable for use in the present invention include fibers having an average fiber length of less than 5 mm and / or less than about 3 mm and / or less than about 1.2 mm and / or less than about 1.0 mm. and / or from about 0.4 mm to about 5 mm and / or from about 0.5 mm to about 3 mm and / or from about 0.5 mm to about 1.2 mm and / or from about 0.6 mm to about 1.0 mm. As used herein, "fibrous structure" means a structure composed of one or more fibers. Non-limiting examples for making fibrous structures include the wet laying and air laying processes used for paper making. These processes typically include the steps of preparing a fiber composition, often referred to as a fiber slurry in wet, wet or dry laying processes and the subsequent depositing of a plurality of fibers onto a forming wire or band to form a embryonic fibrous structure, the drying and / or joining of the fibers to form a fibrous structure and / or the subsequent processing of the fibrous structure to form a finished fibrous structure. For example, in typical papermaking processes, the finished fibrous structure is that which is wound onto a reel at the end of the manufacturing process, but before its conversion into a tissue paper hygienic product. Those with knowledge in the industry will appreciate that fine paper, such as writing paper and / or other paper that is not particularly suitable for use in tissue paper hygiene products, can be excluded from the scope of the present invention, especially since typical values of lint formation in said "fine" paper is less than 1. In one example, the fibrous structure is a fibrous structure wet laid. A "tissue paper hygiene product" comprises one or more fibrous structures terminated, whether converted or not, and serves as an implement for cleaning after urinating and defecating (toilet paper), for cleaning otorhinolaryngological secretions (disposable tissues) and for absorbent uses. and multifunctional cleaning (absorbent towels). "Base weight" as used herein is the weight per unit area of a sample indicated in g / m2. The basis weight is determined by preparing one or more samples from a given area (m2) and weighing the samples of a fibrous structure according to the present invention and / or a tissue paper hygienic product comprising that fibrous structure on a load balance superior with a minimum resolution of 0.01 g. The balance is protected from drafts and other disturbances using a shield against air currents. The weights are recorded when the readings on the balance are constant. Then the average weight (g) and the average surface area of the samples (m2) are calculated. The basis weight (g / m2) is calculated by dividing the average weight (g) by the average area of the samples (m2). "Machine direction" or "DM" as used herein means the direction parallel to the flow of the fibrous structure through the papermaking machine and / or the equipment to manufacture the product. As used here"cross machine direction" or "CD" refers to the direction perpendicular to the machine direction in the same plane of the fibrous structure and / or tissue paper hygienic product comprising the fibrous structure. The "dry tensile strength" (or simply "tensile strength" as used herein) of a fibrous structure and / or tissue paper hygienic product is measured as described below. of 2.5 cm X 12.7 cm of fibrous structure and / or tissue paper hygienic product A strip is placed on an electronic tensile tester model 1122 distributed by Instron Corp., Canton, assachusetts in a conditioned room at a temperature of approximately 28 ° C ± 2.2 ° C and a relative humidity of 50% ± 10% The approximate crosshead speed for the machine for tensile tests is approximately 51 cm / minute and the reference length is approximately 10.2 cm. Dry tension resistance can be used in any direction.The "total resistance to dry tension" or "TDT" is the total arithmetic result of the tensile strength MD and CD of the strips "elongation under maximum load" (or simply "elongation") as used herein, is determined by the following formula: Length of the fibrous structure ^ - Length of the fibrous structure i Length of the fibrous structure i where Length of the fibrous structure PL is the length of the fibrous structure at maximum load; Length of the fibrous structure i is the initial length of the fibrous structure before its elongation. The length of the fibrous structure PL and the length of the fibrous structure i are observed while performing a voltage measurement as specified above. The apparatus for voltage tests calculates the elongation at maximum load. Basically, the apparatus for tension tests calculates the degree of extensibility by the formula described above.

"Caliber", as used herein, means the macroscopic thickness of a sample. The size of a sample of fibrous structure according to the present invention is determined by cutting a sample of the fibrous structure larger than that of a loading foot surface whose circular surface area is about 20.3 cm2. The sample is confined between a flat horizontal surface and the loading surface of a loading foot. The loading surface of a loading foot applies a confining pressure to the sample of 15.5 g / cm2 (1.45 kPa). The gauge is the resulting space between the flat surface and the loading surface of the loading foot. These measurements can be obtained with an Electronic Thickness Tester VI R, Model II, available from Thwing-Albert Instrument Company, Philadelphia, PA. The caliber measurement is repeated and recorded at least five (5) times to calculate the average caliber. The result is reported in millimeters. As used herein, "surface of a finished fibrous structure" refers to the portion of the finished fibrous structure that is exposed to the environment. In other words, it is the portion of the finished fibrous structure that is not completely surrounded by other portions of that finished fibrous structure. As used herein, "sheet" or "sheets" refers to a finished individual fibrous structure which, optionally, can be placed in a substantially contiguous, face-to-face relationship with other sheets to form a product of fibrous structure and / or a product Hygienic tissue paper finished with multiple sheets. It is also contemplated that a single fibrous structure can efficiently form two "sheets" or multiple "sheets", for example, by folding it over itself. All percentages and proportions are calculated by weight, unless otherwise indicated. All percentages and proportions are calculated based on the total composition, unless otherwise specified.

Unless otherwise specified, all levels of the component or composition are expressed in reference to the active level of that component or composition, and are exclusive of impurities, for example, residual solvents or by-products, which may be present. in commercially available sources.

Finished fibrous structures comprising a solid additive As illustrated in Figure 1, in one example of the present invention, a finished fibrous structure 10 comprises a fiber component 12 containing a fiber 14 and an additive component 16 containing an additive solid 18. The solid additive 18 may be physically and / or chemically bonded to one or more fibers 14. The finished fibrous structure 10 may comprise a first surface 20 and a second surface 22 opposite said first surface 20, as illustrated in FIG. Figure 2. The solid additive 18 may be present on a surface of the finished fibrous structure, such as the first surface 20, at a level greater in weight than within the finished fibrous structure 10, as established in the test method for the determination of surface concentration of a solid additive. For the purpose of better explanation and / or clarity, the solid additives 18 are shown in a dispersed form; however, the concentration of the solid additives 18 in the first surface 20 of the finished fibrous structure 10 and / or in the second surface 22 of the finished fibrous structure 10 can be such that all or almost all of the surface area of the first surface 20 and / or second surface 22 is in contact with solid additives 18. As illustrated in Figure 3, in one example of the present invention, a multi-leaf tissue paper hygienic product 24 comprises a first sheet of a finished fibrous structure 26 and a second sheet of a finished fibrous structure 28. The first sheet 26 comprises a fibrous structure terminated in accordance with the present invention, as illustrated and described in Figures 1 and 2. A surface of the The first sheet 26 comprising the solid additive 18 can form an interior surface of a multi-leaf tissue paper hygiene product 24, as illustrated in Figs. 3 and 4, or an outer surface of the multi-sheet tissue paper hygienic product 24 ', as illustrated in Figure 5. In one example, the second sheet of a finished fibrous structure 28 may comprise a fibrous structure completed in accordance with with the present invention. Its orientation within the multi-sheet tissue paper hygiene product 24 may be similar to or different from the first sheet 26. Although FIGS. 3-5 illustrate a tissue paper hygienic product of only two sheets, those with knowledge in the The industry will perceive that the present invention encompasses other three-sheet and multi-sheet tissue paper sanitary products. The solid additive may be present on a surface of a fibrous structure with a random or uniform pattern. A solid additive may be present on a surface of a fibrous structure terminated with a random pattern, and a different solid additive may be present on a surface with a uniform pattern. Non-limiting types of fibrous structures terminated in accordance with the present invention include conventionally pressed felt fibrous structures, patterned densified fibrous structures, and high volume non-compacted fibrous structures. The fibrous structures can be homogeneous or multi-layered (two or three or more layers), and the tissue paper hygiene products made therefrom can be single or multi-layered. The finished fibrous structures and / or tissue paper hygiene products of the present invention may have a basis weight of from about 10 g / m2 to about 120 g / m2 and / or from about 14 g / m2 to about 80 g / m2 and / or from about 20 g / m2 to about 60 g / m2. The finished fibrous structures and / or the tissue paper hygiene products of the present invention can have a total dry strength strength of greater than about 59 g / cm and / or from about 78 g / cm to about 394 g / cm and / or from about 98 g / cm to about 335 g / cm. The finished fibrous structure and / or tissue paper hygiene products of the present invention may exhibit a density less than about 0.60 g / cm3, and / or less than about 0.30 g / cm3, and / or less than about 0.20 g / cm3, and / or less than about 0.10 g / cm3, and / or less than about 0.07 g / cm3, and / or less than about 0.05 g / cm3, and / or from about 0.01 g / cm3 to about 0.20 g / cm3, and / or from about 0.02 g / cm3 to about 0.10 g / cm3. The finished fibrous structures and / or the tissue paper hygiene products of the present invention may have an elongation at maximum load of at least about 10% and / or at least about 15% and / or at least about 20% and / or from about 10% to about 70% and / or from about 10% to about 50% and / or from about 15% to about 40% and / or about 20% to approximately 40%. The solid additives present in the finished fibrous structures of the present invention and / or the tissue paper hygienic products comprising such finished fibrous structures may be associated with the finished fibrous structures such that little or no such solid additives are dissociated from the fibrous structures finished in the powder form. In one example the finished fibrous structure of the present invention is a densified patterned fibrous structure, characterized in that it has a relatively voluminous region with a relatively low fiber density and an arrangement of densified regions with a relatively high fiber density. The high volume field is characterized as a field of quilted regions. The densified areas are referred to as elbowed regions. Layered regions have a higher density than padded regions. The densified zones may be distinctly separate within the high volume field, or they may be totally or partially interconnected within the high volume field. Generally, from about 8% to about 65% of the surface of the fibrous structure comprises densified elbows; the elbows may have a relative density of at least 125% of the density of the high volume field. The processes for making patterned densified fibrous structures are well known in the industry, as shown in U.S. Pat. num. 3,301, 746, 3,974,025, 4,191, 609 and 4,637,859. The finished fibrous structure may have regions of higher density compared to other regions within the finished fibrous structure, and a solid additive may be present in regions of higher density with a level of weight greater than the weight percentage level of the additive solid in the other regions of the finished fibrous structure. For example, the solid additive may be present in the elbowed regions of a fibrous structure terminated at a different weight percent level of the padded regions of the finished fibrous structure.

Solid additive Some non-limiting examples of suitable solid nanoparticle additives can be selected from the group comprising: fillers, inks, colorants, medicaments, opacifiers, abrasives, adhesives, additives for wet strength, additives for dry strength, auxiliaries for controlling odors (such as activated carbon and / or carbon and / or zeolites), absorbency aids, lotions, softeners, low surface energy particles, surface friction modifying agents, antiviral agents, perfume agents, agents for the Skin care, carbohydrate polymers, antibacterial agents, hydrophobic polymers and mixtures of these. In one example, the solid additive is a hygro-activated material. In other words, the solid additive changes its chemical and / or physical properties when exposed to a certain level of a liquid, such as water. In another example the solid additive is a heat-activated material. In other words, the solid additive changes its chemical and / or physical properties when exposed to a certain temperature. Non-limiting examples of fillers include clays and / or talc. Non-limiting examples of suitable clays include kaolin clays, bentonite clays (e.g., laponite clays commercially available from Southern Clay) and mixtures thereof. The clays can be modified, such as chemically modified and / or physically modified, or they can be unmodified. Non-limiting examples of opacifiers include titanium dioxide. Non-limiting examples of adhesives, which may also function as dry and / or wet strength agents, include thermoplastic polymers, non-limiting examples thereof include polyolefins, polyesters, polyamides, polyurethanes and mixtures of these and / or thermosetting polymers, non-limiting examples thereof include polyesters, polyurethanes, epoxy, and mixtures thereof. Non-limiting examples of absorbency aids include superabsorbent materials these non-limiting examples include cross-linked cellulose ethers, polyacrylates and mixtures thereof. Non-limiting examples of low surface energy particles include fluorocarbon polymer particles, silicone polymer particles, and mixtures thereof. In one example, the fluorocarbon polymer particle comprises polytetrafluoroethylene (PTFE). In one example, the silicone polymer particle comprises polydimethylsiloxane. Non-limiting examples of hydrophobic polymers include anionic, cationic, nonionic and amphoteric polyurethanes; acrylic polyurethane; polyurethane polyvinylpyrrolidones; polyesters, polyester-polyurethanes; polyesteramides; fatty chain polyester, characterized in that the fatty chain comprises at least twelve (12) carbon atoms; polyamide resins; ethylene glycol adipates; polyethylene glycol adipates; reaction products of alkylene oxide and alcohol of random copolymers; polyethylene glycols; polyethylene glycols, and mixtures thereof. Non-limiting examples of carbohydrate polymers include starch, starch derivatives, cellulose, cellulose derivatives, guar, xanthan, arabinogalactan, carrageenan, chitin, chitin derivatives, chitosan, chitosan derivatives, and mixtures thereof. In one example, the density of the solid additive may be less than about 7 g / cm 3 and / or less than about 5 g / cm 3 and / or less than about 4 g / cm 3 and / or less than about 3 g / cm 3 and / or less than about 2 g / cm3 and / or less than about 1 g / cm3 to about 0.001 g / cm3 and / or about 0.01 g / cm3 and / or about 0.1 g / cm3 and / or about 0.5 g / cm3. In one example, the solid additive has a sphericity less than 1 and / or less than about 0.8 and / or less than about 0.6 and / or less than about 0.5 and / or less than about 0.3. The finished fibrous structure may comprise two or more different solid additives. Such different solid additives may differ from each other due to their chemical composition, aspect ratio, average particle size, sphericity and / or density. At least one of the solid additives can function as a fluidizing agent to facilitate fluidization for the purpose of improving the distribution of at least one of the other solid additives on the surface of the fibrous structure. The finished fibrous structure may comprise a solid additive and a fluidifying agent; the fluidizing agent has a density greater than the density of the solid additive, excluding the fluidifying agent. The finished fibrous structure may comprise a solid additive and a fluidifying agent; the fluidizing agent has an average particle size smaller than the average particle size of the solid additive, excluding the fluidizing agent. The finished fibrous structure may comprise a solid additive and a fluidifying agent; the fluidizing agent has a smaller sphericity than the sphericity of the solid additive, excluding the fluidifying agent. In one example, the solid additive comprises a carbohydrate polymer, such as a solid additive of starch and an inorganic mineral, for example, kaolin clay. Generally, clays, such as kaolin clay, have a smaller average particle size; higher density, and a lower sphericity than carbohydrate polymers.

Non-solid additives In addition to the solid additives, the finished fibrous structures of the present invention may comprise suitable non-solid additives, as is known in the industry.

Synthesis Example for Making a Finished Fibrous Structure The following example illustrates the preparation of a tissue paper hygienic product comprising a fibrous structure terminated in accordance with the present invention in a Fourdrinier machine to fabricate fibrous structure on a pilot scale. An aqueous NSK pulp of a consistency of about 3% is formed using a conventional pulp disintegrator and passed through a raw material supply duct to the Fourdrinier inlet box. To impart temporary wet strength to the finished fibrous structure, a 1% dispersion of an additive for temporary wet strength (eg, Parez®) is prepared and added to the NSK raw material supply duct at a sufficient rate as to provide 0.3% additive for temporary wet strength based on the dry weight of the NSK fibers. The absorption of the additive for temporary wet strength is increased by passing the treated pulp through an in-line mixer. An aqueous pulp of eucalyptus fibers of about 3% by weight is formed using a conventional pulp disintegrator. The NSK fibers are diluted with white water at the inlet of a machine head pump to a consistency of approximately 0.15% based on the total weight of the NSK fiber pulp. Likewise, the eucalyptus fibers are diluted with white water at the inlet of a machine head pump to a consistency of approximately 0.15% based on the total weight of the eucalyptus fiber pulp. Both the eucalyptus pulp and the NSK pulp are sent to a stratified entry box that has the ability to keep the pulps as separate streams until they are deposited on the forming mesh fabric of the Fourdrinier machine. The fibrous structure making machine has a stratified entry box having an upper chamber, a central chamber and a lower chamber. The eucalyptus fiber pulp is pumped to the upper and lower chambers of the inlet box and, simultaneously, the NSK fiber pulp is pumped to the central chamber of the inlet box and supplied in superposed relation on the Fourdrinier mesh for forming, on top of it, a three-layer embryonic web, which is constituted by approximately 70% eucalyptus fibers and 30% NSK fibers. This combination achieves an average fiber length of approximately 1.6 mm. The dewatering is carried out through the Fourdrinier mesh, with the help of a deviator and vacuum boxes. The Fourdrinier mesh has a satin sheath configuration of 5 and 87 monofilaments per inch in the machine direction and 76 monofilaments per inch in the cross machine direction, respectively. The Fourdrinier wire speed is approximately 3.81 m / s. The wet embryonic web is transferred from the Fourdrinier wire, with a fiber consistency of about 15% at the transfer point, to a patterned drying fabric. The speed of the pattern drying cloth is equal to the speed of the Fourdrinier wire. The drying fabric is designed to produce densified tissue paper with a pattern with discontinuous, low density deviated areas disposed within a continuous network of high density areas (elbows). This drying fabric is formed by molding an impermeable resin surface onto a mesh of support fibers. The support fabric is a double layer mesh of 45 x 52 filaments. The thickness of the resin mold is approximately 0.3 mm greater than that of the support fabric. The published U.S. patent application no. 2004/0084167 A1 describes a suitable process for making a patterned drying cloth. Greater drainage is achieved by vacuum assisted with drainage until the weave achieves a fiber consistency of approximately 30%.

While remaining in contact with the patterned drying cloth, the weft is pre-dried with through-air presechers until a fiber consistency of about 65% by weight is achieved. After the weft leaves the through-air pre-dryers, the solid additive is applied with a VersaSpray 2 electrostatic applicator and a SureCoat controller from the Nordson Corporation of Amherst, Ohio. The solid additive of this example is a mixture of 85% corn starch and 15% kaolin. The commercial name for corn starch is International PFP from Pocahontas Food Products of Richmond VA. The commercial name for kaolin is WP Dry from Imerys of Roswell, GA. The starch and kaolin are mixed thoroughly and then placed in a hopper model HR-8-80 from Nordson Corporation. A minimum amount of air pressure (from 3.4 kPa to 138 kPa) is used to fluidize the solid additive into the hopper. Enter the configuration of 95 kV and 50 μ? in the SureCoat controller to establish a negative corona load on the tip of the VersaSpray 2 electrostatic applicator. A venturi pump with a 5 mm diameter hole conveys the solid additive from the hopper to the weft. The flow rate of the air pressure of 138 kPa and the air atomization pressure of 103 kPa provide approximately 175 g / min of solid additive output from each venturi pump. Fan spray nozzles with an opening of 2.5 mm X 13 mm are used to direct the flow of the solid additive to the weft. The nozzles are placed 7.6 cm (3") from the weft, orthogonal to the plane of the weft and directed to the trailing edge of a rectangular groove of 1.6 cm (5/8") in a vacuum box located behind the fabric drying with pattern. The horizontal spray of the solid additive is aligned parallel to the transverse direction of the screen. A vacuum of 25.4 cm is applied to the vacuum box. The vacuum captures most of the solid additive that does not remain in the screen. With a first pass retention of 50%, approximately 4 g / m2 of solid additive is applied at 21 g / m2 of fiber. The semi-dry web is transferred to the Yankee dryer and adhered to the surface of said dryer by spraying a creping adhesive. The creping adhesive is an aqueous dispersion with active compounds consisting of approximately 22% polyvinyl alcohol, approximately 11% CREPETROL A3025 and approximately 67% CREPETROL R6390. CREPETROL A3025 and CREPETROL R6390 are commercially available from Hercules Incorporated of Wilmington, Del. The supply index of the creping adhesive to the Yankee dryer surface is about 0.15% of solid adhesives based on the dry weight of the weft. Prior to dry curling with a blade from the Yankee dryer, the fiber consistency increased to approximately 97%. The creping blade has an oblique angle of about 25 degrees and is positioned relative to the Yankee dryer to provide an impact angle of approximately 81 degrees. The Yankee dryer is operated at a temperature of about 177 ° C and at a speed of about 4.1 m / s. The finished fibrous structure is wound on a roller using a drum drum driven on the surface with a surface velocity of about 3.33 m / s. The fibrous structure can then be converted into a hygienic product of two-ply tissue paper having a basis weight of about 50 g / m 2, in one case with a surface coated with a solid additive directed outward, and in a second case with the surface coated with a solid additive directed inwards. The average lint index of the tissue paper hygienic product produced by conversion with the solid additive on the external surface is approximately 3. The lint index of a tissue paper hygienic product made by conversion with the solid additive in the internal surface is approximately 6. A tissue paper hygienic product produced in a similar manner, which omits the passage of the solid additive and equalizes the basis weight by increasing the weight of the NSK and the eucalyptus proportionally, has a lint index. approximately 7.

Test Methods Test method for determining the concentration of solid additive on the surface Any method that quantitatively compares the concentration of the solid additive on the surface with the concentration of the solid additive below said surface is satisfactory to determine whether a fibrous structure meets the needs of the present invention . The ideal method analyzes a relatively thin depth of the fibrous structure corresponding to the surface object of the present and compares the concentration of solid additive found at that depth with the concentration found in the fibrous structure at an equivalent depth that is just below this depth of the surface. Two problems arise when this ideal method is implemented. The first is that the quantitative analysis of the concentration requires determining a relationship between the solid additive and the total material. As the section defining the surface approaches the zero depth, the fraction approaches the indeterminate 0/0. The second problem is that it is recognized that the fibrous structures do not have a smooth surface. The surface is a fractal geometry, which means that the contour that follows the surface becomes increasingly intricate as the observer uses a smaller and smaller scale to analyze it. The definition and the example method below address these problems. For the purposes of the present invention, it can be considered that a part of the fibrous structure resides on the surface of that structure if such structure contains a plane parallel to the center of the structure, and in containing the point in question, the fibrous structure is It divides into two parts in such a way that the mass on the outside of the plane towards the side that is the object of the present is relatively small in comparison with the inner mass towards the center of the structure. For fibrous structures with a homogenous fiber content, the inventors have found it suitable that if such a plane divides the structure into a surface plane, it must have a mass percentage of at least about 2.5% and of about 6.25% at most, as well as a volume plane with a mass percentage of at least about 93.75% and about 97.5% at most. An illustrative test method is the tape method for extracting fiber layers and solid additive from a fibrous structure for the purpose of identifying the stratification of the solid additive. To implement this method, a fibrous structure is selected, usually a sheet of paper, towel or tissue that is clean and free of folds, wrinkles or imperfections. Determine the side that will be the target, the opposite side and the machine direction of the sheet. The side to be the target comprises the area of interest with respect to potentially carrying the solid additive within the scope of the present invention. The opposite side may or may not contain solid additive. With respect to the size, the sample must have a length of approximately 27.9 centimeters to 35.56 centimeters in the cross machine direction and a width of 5.08 centimeters to 15.24 centimeters in the machine direction. The sample of fibrous structure is placed on a flat surface with the side that will be the objective upwards. Then a strip of tape approximately 2.5 centimeters wide is taken from a roll of tape. Generally, a transparent tape such as Scotch® brand adhesive tape is used. In case the adhesive of this tape interferes with the subsequent analysis, it can be replaced with any tape with similar adhesive characteristics. The strip of tape should be approximately 10.16 centimeters longer than the sample. The static is removed from the tape by cleaning the smooth surface of the tape on or with a soft, damp surface or with a current of air. The side of the tape is applied with adhesive, free of static, on the upper surface of the sample to be tested. The tape is centered in the longitudinal direction of the sample and is lowered on the sheet from one end to the other smoothly. Air bags should be avoided. The tape is not pressed or touched on the surface. This tape is labeled as "OBJECTIVE" side. Then, the sample is turned along with the ribbon. The ends of the tape tail adhere to the flat surface. A second strip of tape is applied on the opposite side of the taped sample directly above the first strip of tape. This tape is labeled as "OPPOSITE" side. Then a paper cutter is used to cut a border of 0.317 centimeters from each edge of the sample. A 2000 gram weight is rolled by the length of the ribbon sample on the surface that is the target and on the opposite, once on each side. No pressure is exerted on the weight. The weight is moved at a low and uniform speed over the surface of the sample. Subsequently, the two tapes are separated to an angle of approximately 180 ° at a moderate and uniform speed. The tapes should not be pulled or pulled sharply. The tapes labeled as "OPPOSITE" side can be discarded. The split fiber tape, labeled "OBJECTIVE" side, is located on a flat surface with the fiber surface facing up. The ends of the tail are tapered downwards. A strip of tape of 2.54 centimeters is placed as it was done previously. The steps identified above are followed to separate the 1/2 section of the fiber sheet into two sections of 1/4. Again, the tape labeled "OBJECTIVE" is retained and the other tape can be discarded. A new division is made to separate 1/4 sections into 1/8 cuts. Finally, the 1/8 sections are divided again into 1/16 divisions that section the fibrous structure into layers of fiber (and potentially solid additive) adhered to ribbons. The divisions are identified in a sequence that begins with the side that is the target of the sample, that is, the initial tape is labeled with # 1. The division of 1/16 taken immediately adjacent to # 1 is labeled # 2. Ribbon # 1 contains the surface of the original sample of the fibrous structure. Ribbon # 2 is the reference section of the structure. In summary, if the concentration of solid additive in tape # 1 is greater than that in tape # 2, it is said that the fibrous structure has its maximum concentration of solid additive on the surface. In this case, the concentration is defined as the weight of the solid additive divided by the total weight of the section of interest of the fibrous structure. Given the wide variety of solid additives and fiber components comprised in the present invention, it is not possible to specify a single quantitative analysis technique to determine the weight of the solid additive covering the whole. Those with knowledge in the analytical chemistry industry will recognize that it is possible to use conventional wet analytical chemistry methods or instrumental analysis such as, for example, nuclear magnetic resonance or X-ray fluorescence. It is also possible to use image analysis if the counting and Size of the particles can easily be converted into weight. Precautions must be taken in all cases to avoid interference of the components of the fibrous structure or the determination of solid additive with tape. This may limit the type of tape that can be used if such interference occurs or a combination of methods may be indicated.

Density test method The density of the solid additive (s) is measured with an AccuPyc 1330 pycnometer from Micromeritics, commercially available from the Micromeritics Instrument Company of Norcross, Georgia. A suitable sample container is weighed. 2/3 of the volume of the sample container is filled with the sample of solid additive to be tested. The outer and inner edges are cleaned to remove any residue of solid additive. The sample container is weighed with the solid additive sample and this weight is recorded. The lid of the AccuPyc equipment cell chamber is quickly removed, the sample container is placed inside it and the camera lid is replaced in its place, manually adjusting it. The AccuPyc equipment is configured in such a way that it operates in the following manner: it is purged 10 times with research grade helium at a purge load pressure of 134.5 kPa. A total of 10 series are carried out, with a load pressure for the series of 134.5 kPa and an equilibrium index of 0.034 kPa / min, under precision conditions without use for the series. The analysis is started by entering the identification and the weight of the sample in the AccuPyc. The resulting density of the solid additive sample is reported as an average of 10 series and is expressed in g / cm3.

Average particle size test method The average particle size of the solid additive (s) is measured with a Horiba LA-910 equipment, commercially available from Horiba International Corporation of Irvine, California. Those with knowledge in the industry know that the appropriate and appropriate conditions of use of the Horiba LA-910 equipment consist in running one or more pilot series in the Horiba LA-910 equipment for the solid additive sample. Those with knowledge in the industry can visually determine if the solid additive sample is bimodal or unimodal with respect to particle size. If the sample of solid additive contains accumulations, those who are familiar in the industry will use ultrasound to disintegrate them before running the average particle size test. During the pilot series or series, it can be determined whether the solid additive sample is bimodal or unimodal. In the course of the pilot series, those with knowledge in the industry will be able to determine the appropriate speed of agitation and circulation, and if the average particle size of the sample is less than 10 μ? T ?, the refractive index can be obtained relative of the Horiba database. The instructions of the Horiba LA-910 Instrument manual are followed for the configuration and the instructions for use for the software. The refractive index of the solid additive sample is obtained by testing from the Horiba refractive index database. The appropriate measurement conditions are entered in the instrument. The speed of agitation and circulation is obtained from the pilot series or series; sampling amount 25; standard distribution; dispersing tank B; volume of dispersant 200 mL; dispersant volume per step 10 mL; 10% dilution point; rinsing circulation time 10 seconds; rinsing repeat 1; rinse volume 100 mL; relative refractive index; good lower limit of 88% range; and good upper limit of 92% range. The instrument cell is drained and 150 mL of dispersant is added; it is circulated and sonicated for 2 minutes and shaken. If the cell is clean and the background readings appear flat, a preform is run by pressing "Blank". The sample of solid additive is added to be tested in the cell while the dispersant is agitated and circulates. The solid additive sample is slowly added until the% T of the laser is 90 +/- 2 (about 1 ml_). The sample is allowed to circulate in the cell for 2 minutes. After the sample has circulated for 2 minutes, press "Measure" to analyze it. After the sample has been analyzed, the graphic and the picture are printed. Press "Drain" to drain the cell. The system is rinsed three times with deionized water using agitation and sonication for 30 seconds each time. For subsequent samples, steps 2 - 10 are repeated. The alignment of the laser (four triangles) between each sample should be checked. The results are reported as follows: 1) standard resolution histogram for a unimodal distribution or an intensified resolution histogram for a multimodal distribution; or 2) average particle size (average diameter). All documents cited in the Detailed Description of the Invention are incorporated, in their relevant part, herein as a reference; The citation of any document should not be construed as an admission that it is a prior industry with respect to the present invention. The terms or phrases defined herein prevail even if they have been defined differently in the documents incorporated herein by reference. While particular examples of the present invention have been illustrated and described, it will be apparent to those skilled in the industry that various changes and modifications can be made without departing from the spirit and scope of the invention. It has been intended, therefore, to cover all the changes and modifications within the scope of the invention in the appended claims.

Claims (12)

1. A finished fibrous structure comprising a solid additive of nanoparticles, characterized in that the solid additive is present on the surface of the finished fibrous structure at a higher level by weight than within the finished fibrous structure.

2. The finished fibrous structure according to claim 1, further characterized in that the solid additive of nanoparticles is directly bonded to a fiber of the finished fibrous structure.

3. The finished fibrous structure in accordance with the claim 1, characterized in that the finished fibrous structure has a density lower than 0.10 g / cm3.

4. The finished fibrous structure according to claim 1, further characterized in that the finished fibrous structure has an elongation under maximum load of at least 10%.

5. The finished fibrous structure according to claim 1, further characterized in that the solid additive of nanoparticles is selected from the group comprising: fillers, inks, dyes, medicaments, opacifiers, abrasives, adhesives, auxiliaries for wet strength, auxiliaries for dry strength, auxiliary for odor control, absorbency auxiliaries, lotions, softeners, low surface energy particles, surface friction modifying agents, anti-virus agents, perfume agents, skin care agents, polymers carbohydrate, cellulose, cellulose derivatives, guar, xanthan, arabinogalactan, carrageenan, chitin, chitin derivatives, chitosan, chitosan derivatives, antibacterial agents, hydrophobic polymers, and mixtures thereof.

6. The fibrous structure according to claim 1, further characterized in that the solid additive of nanoparticles is hygroactive and / or thermoactivated.

7. The fibrous structure according to claim 1, further characterized in that the solid nanoparticle additive has an average particle size of less than 900 nm.

8. The finished fibrous structure according to claim 1, further characterized in that the finished fibrous structure comprises a fluidifying agent, further characterized in that the fluidizing agent has a density greater than the density of the solid additive of nanoparticles, excluding the fluidifying agent.

9. The finished fibrous structure according to claim 1, further characterized in that the finished fibrous structure comprises a fluidifying agent, wherein the fluidizing agent has an average particle size smaller than the average particle size of the solid nanoparticle additive, excluding the fluidizing agent.

10. The finished fibrous structure according to claim 1, further characterized in that the finished fibrous structure comprises a fluidifying agent and in that the fluidifying agent has a sphericity smaller than the sphericity of the solid additive of nanoparticles, excluding the fluidifying agent.

11. The finished fibrous structure according to claim 1, further characterized in that the finished fibrous structure is a fibrous structure finished in layers.

12. The use of a finished fibrous structure according to any of the preceding claims in a single-sheet or multi-sheet tissue paper hygienic product