MXPA98003495A - Non-woven fabric of multiple length fibers, of multiple deniers, and absorbent article formed from e - Google Patents

Abstract

The present invention is directed to a non-woven fabric which is formed of a network of interconnected thermoplastic fibers, of multiple lengths, multiple deniers. The non-woven fabrics of the present invention provide increased comfort and performance, which are not found in conventional non-woven fabrics, and have been found to be particularly useful as covering materials in sanitary absorbent articles, disposable.

Description

NON-WOVEN FABRIC OF MULTIPLE LENGTH FIBERS, OF MULTIPLE DENIERS. AND ABSORBENT ARTICLE FORMED FROM IT FIELD OF THE INVENTION This invention relates to a new non-woven fabric, the fabric being specifically suited for use as a contact surface with a wearer's body, in disposable absorbent products, surgical bandages, tampons for feminine hygiene, fabric with dust or cleaners and articles Similar. More particularly, the present invention relates to a non-woven fabric, made of a network of interconnected short fibers, wherein the fibers include a blend of at least two series of short fibers, each series having a length that is different from that of the other series in at least two millimeters.

BACKGROUND OF THE INVENTION Medical and disposable absorbent products usually include a body-facing cover or liner material formed of a non-woven fabric. Typical non-woven fabrics are derived from fibers or filaments that are chemically, hydraulically, thermally or mechanically bonded together, and formed by technologies that are known to those skilled in the art, such as, for example, "thermal bonding", "spun bonding". "or" union by means of air ". Said fabrics must be comfortable, able to remain in contact with the internal and external surfaces of the body for prolonged periods, without causing itchy or allergic reactions, and capable of transmitting body fluids to a central absorbent core. In an attempt to provide absorbent articles with cover or liner materials, which remain clean and dry during use, it is conventional to use synthetic fibers, such as polypropylene, polyethylene, polyester and the like. The non-woven fabric covers, made of synthetic fibers up to 3 denier, have been used as covers for disposable, personal absorbent articles. These fabrics, although they have great softness due to the fine denier of their fibers, tend to retain more liquids than desired, due to the small capillary pore size provided by these fine denier fibers. Alternatively, an increase in the denier of the fiber results in decreased fluid retention, but the softness of the fabric is decreased. Therefore, the search for an adequate technical solution still persists.

BRIEF DESCRIPTION OF THE INVENTION It is an object of the present invention to provide a nonwoven fabric that is useful as a cover for personal absorbent articles, for surfaces that are intended to make contact with a user's body. It is another object of the present invention to provide a non-woven fabric having a pleasant touch and marked softness, but at the same time providing increased fluid absorption capabilities. Another object of the present invention is to provide an absorbent article using a non-woven fabric cover, formed of at least two series of short fibers of multiple length; the length of a series being different from that of the other series, by at least two millimeters. A further object of the present invention is to provide an absorbent article using a non-woven fabric cover, formed of at least two series of short fibers, of multiple lengths, and having fibers of more than one denier. These and other objects of the present invention will be better understood in the detailed description that follows. In accordance with the present invention a new non-woven fabric was created, characterized by a network of interconnected short fibers, formed by a mixture of at least two series of short fibers; each set of short fibers having different average fiber lengths. Suitable fibers for use in this invention have a length of at least about 2 mm, and are generally in the range of 2 mm to 100 mm. The fibers of a series have an average fiber length that is greater than an average fiber length of a second series, at least 2 mm. As used herein, the term "fiber length" refers to an average length of a series of fibers. Consequently, short fibers having a length of 32 mm, for example, refer to a series of short fibers having an average length of 32 mm, with a slight distribution of values around that number, usually with a normal statistical distribution. . This distribution can vary up to about ± 20% of the average length of the fiber in the short fibers of the series. As used herein, the terms "nonwoven" and "non-woven fabric" are understood as synonyms. Also as used herein, the term "a single length" refers to a series of short fibers that only have one length. Also as used herein, the term "multiple lengths" refers to a mixture of short fibers having more than one measure of length. As used herein, the term "single denier" refers to a series of fibers or a fabric containing single denier fibers. The term "multiple deniers" refers to a fabric formed from a mixture of two or more series of fibers, each series of fibers with a different value of denier, with respect to the other series. The present invention provides a favorable relationship between the number of fibers per volume of a non-woven fabric and the pleasant feel sensation obtained, while maintaining its fluid absorbency performance. A greater number of fiber ends in a non-woven fabric that is in contact with a wearer of the fabric results in a greater feeling of softness. Thus, a given non-woven fabric, produced by an amount "n" of short fibers, having a length "x", will be perceived by a user as more pleasant to the touch than a non-woven fabric produced by an amount "n / 2"of short fibers that have a length" 2x ". The invention finds an optimized balance between the fluid handling performance of a non-woven fabric (e.g., the rate of liquid transmission in one direction, and the amount of liquid returned in the opposite direction, the masking capacity, the softness , flexibility, etc.) and the number of fiber ends available to give a pleasant touch. In a preferred embodiment, the fibers of the present invention have lengths of between 10 and 80 mm; each length being different by at least 2 mm from the other. Preferably, the fibers have lengths between 15 and 40 mm, each length differing by at least 2 mm and, preferably, by at least 4 mm, from the other. In another preferred embodiment, the fiber mixture of the present invention comprises between 2 and 15 different lengths and, better yet, between 2 and 6 different lengths. In another preferred embodiment, in each fiber series 50% to 99% of the fibers are within 1% of the average length of the fibers of the series; the rest of the fibers of the series being within 20% of the average fiber length of the mixture. Thus, if the average fiber length for a given series of fibers is 10 mm, then 50% to 99% of the fibers in the series are within 1% of that length; the rest of the fibers of the series are within 20% of that length. In the modality that is most preferred among all, from 809% to 90% of the fibers of the series are within 1% of the average length of the fiber; the rest of the fibers of the series being within 10% of this length. In another preferred embodiment, the non-woven fabric is formed by a mixture of fibers having more than one denier and, better yet, each series of short fibers of Specific length comprises at least two different denier; preferably being the values of 2 and 5. With reference to the denier of the fibers of the invention, fibers having a denier of between 1 and 10 are suitable; preferably between 2 and 6. For one and the same fiber length, it is an advantage that between one and the other denier there is a difference of at least one denier, preferably two denier. Advantageously, all fibers having a single denier represent from 10% to 90% of the total amount of fibers of the fiber blend of the invention, preferably from more or less 30 to plus or minus 70%. The non-woven fabrics of the present invention preferably have a basis weight between 25 g to 50 g / m2, preferably on a scale of 30 g / m2 to 35 g / m2 and, most preferred, 35 g / m2 . The non-woven fabrics of the present invention preferably have an apparent thickness between 0.15 and 0.40 mm. An additional benefit provided by the non-woven fabric of the invention is that, for a given basis weight, the thickness of the fabric obtained from a mixture of fibers of multiple lengths and fibers of multiple deniers, is greater than that of a fabric formed with single-length and single-denier fibers, or a fabric formed with single-length fibers and multi-denier fibers, or the product with multi-length fibers and single-denier fibers. Said fabrics additionally provide the feeling of comfort and pleasant touch. The use of multiple denier and multiple length fibers also significantly increases the sensation of a pleasant touch. In addition, according to the present invention, a new absorbent article with a permeable cover is provided for contacting the user's body, comprising a non-woven fabric formed by a network of interconnected thermoplastic fibers of multiple lengths; and the fibers have a mixture or combination of at least two different lengths ranging from 2 to 100 mm, and including a difference of at least 2 mm between them. Additionally in accordance with the present invention a new feminine sanitary napkin with a liquid-permeable cover facing the body is provided; a liner impervious to the liquid facing the garment, and an absorbent core between the liquid permeable cover and the liquid impervious liner; wherein the liquid-permeable cover comprises a non-woven fabric formed by a network of short fibers of multiple lengths, interconnected; wherein the short fibers possess a combination of at least two different lengths, varying between 2 and 100 mm, and comprising a difference between the two lengths of at least 2 mm. The absorbent articles of the present invention absorb body fluids and are useful as disposable articles such asfor example, diapers, feminine sanitary napkins, tampons, bandage fabrics, surgical bandages and cleaning cloths. They can be used as separate items or as necessary parts of disposable belongings or for limited use. Suitable fibers for use in the present invention include, but are not limited to, conventional synthetic short fibers, such as polymeric fibers including polypropylene, acetate, rayon, dyne, nylon, acrylic, Orion, Dacron, Vicara. , polyester, polyethylene, polyacrylate and their mixtures; and preferably are polypropylene fibers. Also in accordance with the present invention is the use of double-component ("core-sheath") fibers, wherein the core polymer of the fiber is different from the polymer of the outer layer of the fiber. Also according to the present invention are fibers of cross section, which are different from circular ones, for example, bilobed fibers, trilobal fibers, etc. The ability to mask the absorbed fluids, in a non-woven fabric, mainly with reference to menstruation, is an important consideration in the development of cover materials for feminine sanitary napkins. It is highly appreciated that said covers have the ability to allow a rapid flow of menstrual fluid into the absorbent material, thereby preventing the vivid and clear display of the fluid that has just been absorbed. Accordingly, the fibers of the non-woven fabric of the present invention are preferably provided with a pigment material of preferably white color, such as, for example, titanium dioxide, calcium carbonate and mixtures thereof. Titanium dioxide is the preferred pigment material. The amount of the pigment material present in the fibers should be sufficient to give the fibers opacity, thereby providing increased capacity in the non-woven fabric to mask the absorbed fluids. The amount of titanium dioxide in the fibers is between 1 and 6 weight percent and, preferably, is between 2 and 3.5 weight percent. When the nonwoven fabric of the invention is used as a cover for a disposable absorbent article, to make contact with the wearer's body, it is usually convenient that said cover has a durable hydrophilic finish, so that the portion of the disposable absorbent article which is in contact with the body of the user, remain hydrophilic after multiple introductions or steps of the liquid. The hydrophilic finishes give a better fluid transport of the body, away from the user; and the body fluids are brought more efficiently into the nearby absorbent core, which results in a cleaner, drier feeling for the wearer. The fibers of the present invention can be provided with a durable hydrophilic finish, by treating the fibers with a surfactant such as, for example, a nonionic surfactant, which can be obtained commercially from ICI Polymer Additives, New Castle, Delaware, USA, under the brand name "ATMER". Other suitable surfactants, without excluding any other, are the sodium salts of dioctyl sulfosuccinate (commercially available from American Cyanamid under the name AEROSOL OT), the nonionic polyoxyethylene sorbitol monolaurate (commercially available from ICI Polymer Additives, New Castle, Delaware, EU., Under the name TWEEN 20) and similar products. Durable hydrophilic finish can be applied to the surface of the fibers by immersing them in an aqueous solution of the desired surfactant, or by spraying an aqueous solution of the desired surfactant onto the surface of the fibers and subsequently drying them. Alternatively, the surfactant can be applied to the non-woven fabric with the aid of a cylinder that is previously wetted with an aqueous solution of the desired surfactant, to make contact with the inner surface of the non-woven fabric, so that the outer surface opposite can retain its original hydrophobic characteristics. Alternatively, internal hydrophilic surfactants, or wetting agents, may be directly incorporated into the thermoplastic polymer during the manufacture of the fibers. Suitable wetting agents include, but are not limited to: nonionic surfactants, based on ethylene oxide / fatty alcohol ether; the propylene oxide ethoxylates with propylene glycol, the fatty esters of sorbitol and glycerol, and other similar products. Any other agents and additives known to those skilled in the art, which result in fibers and, consequently, non-woven fabrics also, with specific properties, can be used without interfering with the purposes of the invention. The non-woven fabrics of the present invention may be formed by conventional processes including "thermal bonding", "resin bonding" and "spin bonding". In all these manufacturing processes the initial step is to form a veil of homogeneously mixed fibers. In general, bundles of fiber series are mixed, each series having different lengths, in an air mixing chamber and, subsequently, the fibers are combed to form a combed veil, or they are randomly placed on a perforated conveyor in order to form a continuous veil. When the thermal sealing process ("thermal bonding") is used, the veil of homogeneously blended fibers can be fed to a calendering station equipped with a hot smooth roller and with a normal raised roller, which binds the fibers and stabilizes the veil to a non-woven fabric. In a chemical sealing process ("resin bonding") the veil of homogeneously mixed fibers is formed, as described above, and is carried through a cylinder equipped with a series of nozzles for spraying water (e.g. , with a pressure of around 1406 kPa), capable of causing a slight entangling of the fibers. Then the water is removed from the veil of entangled fibers, feeding it to a station where it is impregnated with a binding material, which dries up and hardens in a thermal transfer equipment. Alternatively, the fiber web can be sprayed with resin powder, under vacuum, and subsequently dried and cured under forced air passage. Finally, in a "spun bond" process, the homogeneous mixture of fibers of different lengths passes through a series of high pressure water jet, for example, from 3515 kPa to 1.05 MPa, in order to entangle deep the fibers of the veil until a stabilized cloth is obtained. Then the water contained in the cloth is removed and the cloth is dried. All the methods mentioned herein are well known to the skilled person and the selection of one or the other method is not critical, per se, for the invention; of course as long as the resulting non-woven fabrics possess sufficient structural integrity for the fabric to be suitable for use as a cover material for absorbent articles. In general, a non-woven fabric has sufficient structural strength for use as a cover material for absorbent articles, when the tensile strength reaches about 17.95 kg / m. Sufficient structural integrity is generally obtained when the sealing area comprises between 10% and 40% of the total surface area of the fabric; and preferably the seal area is between 15 and 20% of the total surface area of the fabric. It is preferred that the non-woven fabric of the invention be a carded or combed mantle by the "thermal bonding" process for hot sealing, making use of the hot roller calender with relief pattern. As is known, absorbent articles that are used eternally, such as feminine sanitary napkins, generally comprise a liquid-impermeable liner facing the garment; a liquid absorbent core, which is a layer of fiber absorbent material, located on the liner, and a liquid permeable cover, facing the body. Conventional cover materials include non-woven fabrics formed by a network of oriented and interconnected fibers. In accordance with the present invention, a feminine, novel, sanitary absorbent article has been provided with a liquid-permeable cover that is facing the wearer's body; a liner impermeable to the liquid, which is in the opposite direction to the permeable cover and oriented towards the wearer's clothes, and an absorbent core between the permeable cover and the impermeable liner, characterized in that the permeable cover comprises a non-woven fabric formed by a network of short fibers of multiple, interconnected lengths, preferably thermoplastic fibers; the fibers further comprising a mixture of at least two different series of fibers; each series of fibers having different average lengths ranging from 2 to 100 mm; and with a difference between the average fiber length of each series, of at least 2 mm. The liquid permeable cover and the liquid impervious cover are substantially coextensive and are bonded together along the periphery of the absorbent article, by means of thermal fusion, adhesion or any other convenient manner. Preferably the core is adhesively bonded to the impermeable liner by one or more lines of glue. The liquid impermeable liner is on the side of the absorbent article that faces the garment, and may be constituted by any flexible material that is capable of preventing the flow of fluid therethrough. Suitable materials include polypropylene films, polyethylene films, polyester films, polyamide films, vinyl / polyethylene acetate films, polyvinyl chloride films and polyvinylidene films. Laminated and coextruded combinations of the mentioned films can also be used, when such combinations are possible; taking into account its physical and chemical properties. Non-crosslinked films, which are impervious to fluids, and papers lined with hydrophobic materials, may also be used. Films that are barriers against fluids, but that allow the flow of gases, called "breathable films," can also be eroded, such as, for example, polyurethane films and microporosae films, where microporosity is created. by ionizing radiation or by leaching the soluble inclusions, by the use of aqueous or non-aqueous solvents. Fabrics that have fluid repellent surfaces, or have small pores, due to the packing of fibers, or when the pore diameters have been reduced, they can also be used, both individually and together with respiratory films or respiratory barriers. A particularly preferred barrier film is an opaque polyolefin film such as, for example, polyethylene, which is impervious to body fluids, and which has an approximate thickness of 20 microns. Polyester is another suitable liner material, such as, for example, polyethylene terephthalate having an approximate thickness of 4 microns. The absorbent core may be a mass of defibrated pulp fibers, which has a relatively high absorption capacity. The absorber core usually has a rectangle shape and occasionally has side edges that are curved inwards, as in the shape of a watch glass. The absorbent core is slightly smaller than the liner sheet and smaller than the nonwoven cover. The absorbent core can also be a fiber panel with a densified integral layer. In this embodiment it is preferred that the absorbent core is located on the liner sheet of the absorbent article, so that the densified layer could be attached to the liner. The densified layer has the ability to absorb and retain the liquid which is relatively higher than the rest of the aforementioned panel, and which is usually formed by a slight wetting of a panel surface and subsequent compression of the wetted surface. The absorbent article may optionally comprise a multi-layer absorbent structure, which may possess, in addition to the absorbent core, a transfer layer which is a low density layer for accepting and distributing fluid, usually located between the absorbent core and the cover sheet . The transfer layer may comprise materials and structures that are relatively less hydrophilic than the contents of the absorbent core, such as the "meltblown" webs of polyester fibers or polypropylene fibers. Said veils may additionally contain wood pulp within the same. The transfer layers may also contain low density, high-softness nonwoven webs, comprising wood fibers and synthetic fibers, such as polyethylene, polypropylene, polyether, polyacrylonitrile and polyamide. Said soft veils can be stabilized with chemical adhesives, by thermal means such as "by means of air binding". The thickness of the absorbent structure can be uniform over the entire surface, in accordance with the requirements of specific conforability, flexibility and absorption or, alternatively, it can be greater in certain parts. For example, a particularly preferred thickness profile is an absorbent structure that is thicker in the central part than in its peripheral portions. The fluid-impermeable barrier liner, which faces the wearer's garments, may be stabilized or otherwise adhered to the surface of the absorbent structure over its entire length or in areas of discrete seal. The barrier lining, which is oriented towards the wearer's garments, may be attached to the cover sheet in an overlapping configuration, for example, parallel to the sides of the absorbent structure, parallel to the bottom of the absorbent structure, or peripherally sealed by lateral extensions to the absorbent structure.

EXAMPLE A practical example is given below to implement a preferred alternative of the invention; whose sole purpose is to illustrate and give details about it, without creating any limitation, because other possible variations are present for the person skilled in the art, without prejudice to the purposes or meaning of the invention. Four types of non-woven fabrics, manufactured by the "thermal bonding" process, named here A, B, C and D, and their compared properties were evaluated. The raw material was the polypropylene homopolymer, which contains 2.5% by weight of bright titanium dioxide inserted during the manufacture of the fiber, and the density of the fabrics was 35 g / m2. Table 1 below shows the distribution of the number of fibers per square centimeter for each of the fabrics used in the test (the numbers in parentheses show the denier of the corresponding fiber).

TABLE 1 NUMBER OF FIBERS PER SQUARE CENTIMETER Length of Type of fiber non-woven fabric, (mm) A B C D 16 66 (3d) 66 (5d) 20 34 (3d) -._., - _- «. 34 (5d) 32 49 (3d) - "« "-" * "" * "" 49 (5d) 40. 16 (3d) 98 (3d) 393 (2d) 157 (5d) ) 16 (5d) 98 (5d) Total / cm2 339 196 393 157 NOTE: The calculation for the number of fibers per square centimeter was determined by the formula: x = 0.9 g / d c, where: x = number of fibers per square centimeter; g = base weight (grams per square meter) d = denier (grams / 9,000 meters). - (NOTE: The value is averaged if there is more than one denier present) c = length of the fiber (meters).

EXPLANATION FOR COMPARISON Fabric A corresponds to a preferred embodiment of the invention; a non-woven fabric of multiple deniers and of multiple lengths. Fabric B corresponds to a non-woven fabric of multiple deniers and a single length. The fabric C is the reference fabric with respect to the softness, comprising fibers of uniform length of denier 2, while the fabric D is the reference fabric with respect to the low liquid retention, comprising fibers of uniform length of denier 5. Fabrics C and D demonstrate the difficulty of obtaining a non-woven fabric with balanced properties. On the one hand, the softest fabric commonly used in commercial products is fabric C, with a few disadvantages, for example, high liquid retention. Fabric D, on the other hand, formed from higher denier fibers, eliminates the problem of high fluid retention, but is very rough. The following table 2 shows the results of various evaluations referring to fabrics A, B, C and D. The values expressed in each column indicate the relative performance among the four products tested by giving the 1 mark to the worst performance and the 4 mark for the best performance.

TABLE 2 PERFORMANCE MARKS Type of non-woven fabric p A C C D 1. Retention of liquid. 2 3 1 4 2. Adjustment 3 2 4 1 3. Extremae number / cm2 3 2 4 1 4. Return of liquid 2 3 1 3 . Apparent thickness 4 3 1 2 6. Softness 3 2 4 1 Average of the six parameters 2.8 2. 5 2.5 2.0 CONCEPT OF EVALUATED PARAMETERS The evaluated concepts will be explained taking the example of a feminine sanitary napkin, in which the nonwoven fabric, according to the invention, is the cover, that is, the material that is in contact with the wearer's body. 1. Liquid retention This measurement refers to the amount of liquid retained in the fabric after passing through it. The greater the retention of liquid (lower mark) the greater the sensation of moisture transmitted to the body of the user. Therefore, it is a partial measure of the comfort caused by contact with the user's body. 2. - Adjustment This measure refers to the possibility of conforming or adapting the fabric to the wearer's body. For example, a "soft" fabric conforms better to the body (higher brand) than a "hard" fabric. Additionally, the "hard" fabric is rougher than the "soft" fabric. Eeta is another partial measure of the comfort offered to the client. 3. - Quantity of fiber ends per cm2 This measure refers to the pleasant feeling of touch caused by the contact of the ends of the fibers of the fabric on the skin, as previously explained. The greater the number of extremes (maximum mark) the more pleasant the sensation will be. This is another partial measure of the comfort offered to the user. 4. - Return of liquid This measure refers to the amount of liquid that returns to the non-woven fabric after passing through the non-woven fabric, which covers the adjacent absorbent body. The lower the liquid return (higher mark) the lower the moisture sensation transmitted to the user and, among other things, makes the user more certain that the product will not leak. This is mentioned as another partial measure of the comfort offered to the user.

. - Thickness First, this measure refers to a feeling of "paper or paperboard" that can occur for a certain density / thickness ratio. The greater the thickness (higher mark), the lower the "paper or cartonboard" feeling transmitted to the user. Secondly, it also refers to the visual perception of the distance of the fluid absorbed by the adjacent absorbent core and of the surface that makes contact with the body. That is, for the same amount of titanium dioxide, the greater the thickness (higher mark) the more -distinct appears to be the blood absorbed, from the surface. This is another partial measure of the comfort offered to the user. 6. - Softness Softness refers to a measure for the sensation of pleasure to the touch, in a general way, without mentioning any other property of the product that is more specific. It is the sensation transmitted by touching a piece of non-woven fabric. The better the senetration (higher mark), the better the product is. It is also a partial measure of the comfort offered to the user.

ANALYSIS OF THE OBTAINED RESULTS The non-woven fabric A of the invention provided superior performance in all the parameters evaluated, and this fact makes it a superior product compared to conventional non-woven fabrics, because it has no disadvantage that could be detrimental to the fabric. ueo. Fabric C- Considered here as the reference with respect to softness, it is the worst among the four types evaluated, with reference to liquid retention, liquid return and apparent thickness. Fabric D.- Considered here as the reference in relation to the low retention of liquids, it is the worst among the four types evaluated, with regard to its adjustment, the number of ends and the softness. Fabric B. Although it comprises the same scale of gradation of the cloth C, it is satisfactory in reducing the deficiencies of the latter and of the cloth D, but its results are still inferior to those of the non-woven fabric of the invention. In summary, the average value of the non-woven fabric A of the invention, obtained from the evaluation of the various properties, was the highest among the four nonwoven webs. Additionally, no parameter has indicated a totally unfavorable operation (mark 1) in relation to the others.

ANALYTICAL METHODS 1. - LIQUID RETENTION Principle of the method: An amount of synthetic menstrual fluid is placed on a specific area on the surface of a previously weighted nonwoven fabric, which rests on a block of absorbent material. After the fluid flow, the fabric is removed and weighed. The difference between the final weight and the initial weight of the non-woven fabric is considered as liquid retention.

Analytical method data: Synthetic menstrual fluid - formulation described in patent application W01510996, page 37. Amount of synthetic menstrual fluid: 7 ml. specific area on the surface of the non-woven fabric: oval hole (3.9 by 2.5 cm) of an acrylic plate measuring 27 cm by 11 cm by 7.5 cm (weight 276.4 g), which is supported on a non-woven fabric during the test . Block of absorbent material: bleached pulp of long wood fibers; dimensions: 210 by 55 by 12 mm; density: 0.06 g / cm3. Synthetic menstrual fluid discharge: quickly, in a single operation. Time elapsed between the start of the pouring of synthetic menstrual fluid and the operation of weighing the non-woven fabric: 2 minutes. 2. - ADJUSTMENT. Normal test INDA IST 90.3-92 (INDA) = "Association of the Non-Woven Fabrics Industry, United States of America). 3. - NUMBER OF EXTREMES Theoretically provided by twice the number of fibers / cm2. In practice, a small number of ends may not be available because they are clogged in the thermal bonding areas. 4.- RETURN OF LIQUID Principle of the method: An amount of synthetic menstrual fluid is placed on a specific area on the surface of a previously weighted nonwoven fabric, which rests on a block of absorbent material. The moistened area is covered with an absorbent sponge, previously weighed, and placed under a specific pressure for a certain period of time. The fluid mass removed from the block of absorbent material by the absorbent sponge is considered as the return of liquid. The data of the analytical method are the same used in the LIQUID RETENTION method, which include: Absorbent sponge: Extra-absorbent bandage measuring 7.5 cm x 7.5 cm, manufactured by Johnson & Johnson Industria e Commercio, Brazil. Use of pressure: 5 minutes after the entire fluid was passed through the block of absorbent material, it is placed on a hard, flat surface. Two sponges are placed, which are bent four times, on the wet spot. A standard weight of 2.2 kg is placed and with dimensions 5.1 by 10.2 by 5.4 c on the sponges (resting on the surface measuring 5.1 cm by 10.2 cm), which produces an approximate pressure of 4.14 kPa. The weight is removed after 3 minutes, as well as the sponges, which are weighed immediately. The difference in weight between the sponges before and after the absorption of the synthetic menstrual fluid represents the return of fluid.

. - THICKNESS Standard test INDA IST 120.1-92. 6. - SOFTNESS Softness is a subjective measure that is assigned to the samples by relative comparison. A checkered cloth of approximately 10 by 10 cm was cut from each of the four non-woven fabrics tested. The samples were handled freely and the "sensation" with respect to the softness between the samples was determined. It is understood that the above example relates only to the operation illustrated as a specific example of the present invention, and should not be construed as limiting the invention in any way, except as stipulated in the following claims.

Claims (31)

NOVELTY OF THE INVENTION CLAIMS

1. - A nonwoven fabric characterized in that it comprises a network of synthetic, interconnected short fibers; the fibers further comprising a mixture of fibers including a first series of fibers and a second series of fibers; each series of fibers having an average length of 2 mm to 100 mm; wherein the average length of the first series of fibers varies from the average length of the second series of fibers by at least 2 mm.

2. The non-woven fabric according to claim 1, further characterized in that the fibers additionally comprise at least two different deniers.

3. The non-woven fabric according to claim 1, further characterized in that the fibers have lengths between 10 mm and 80 mm; and the length of the first series of fibers varies from the length of the second series of fibers by at least 4 mm.

4. The non-woven fabric according to claim 1, further characterized in that the fibers have lengths between 15 mm and 40 mm, and the length of the first series of fibers varies from the length of the second series of fibers in at least 4 mm

5. The non-woven fabric according to claim 1, further characterized in that the fiber mixture comprises between 2 and 10 series of fibers, and each series of fibers has a different length.

6. The non-woven fabric according to claim 1, further characterized in that the fiber mixture comprises between 2 and 6 series of fibers and each series of fibers has a different length.

7. The non-woven fabric according to claim 1, further characterized in that the first series of fibers comprises from 5% to 90% of the total number of fibers.

8. The non-woven fabric according to claim 1, further characterized in that the first series of fibers comprises from 10% to 50% of the total number of fibers.

9. The non-woven fabric according to claim 2, further characterized in that the fibers comprise a mixture of between 2 and 15 fiber series; each fiber series having a different denier.

10. The non-woven fabric according to claim 9, further characterized in that the fibers comprise a mixture of between 2 and 6 fiber series.

11. The non-woven fabric according to claim 2, further characterized in that the fibers have deniers in the scale between 1 and 10.

The non-woven fabric according to claim 2, further characterized in that the fibers have deniers on a scale between 2 and 6.

13. The nonwoven fabric according to claim 2, further characterized in that the fibers of the first series have a first denier and the fibers of the second series have a second denier; and there is a difference of at least one denier between the fibers of the first series and the fibers of the second series.

14. The non-woven fabric according to claim 2, further characterized in that the first series of fibers further comprises a mixture of fibers; the mixture having a plurality of different deniers.

15. The non-woven fabric according to claim 2, further characterized in that the first series of fibers has the same denier and comprises between 10% and 90% of the total number of fibers of the non-woven fabric.

16. The non-woven fabric according to claim 2, further characterized in that the first series of fibers has the same denier and comprises between 30% and 70% of the total number of fibers in the non-woven fabric.

17. The non-woven fabric according to claim 2, further characterized in that the fibers have lengths ranging from 10 mm to 80 mm, and the length of the first series of fibers varies from the length of the second series of fibers. in at least 4 mm.

18. The non-woven fabric according to claim 2, further characterized in that the fibers have lengths ranging from 15 to 40 mm, and the length of the first series of fibers varies from the length of the second series of fibers at minus 4 mm

19. The nonwoven fabric according to claim 1, further characterized in that the fabric has a density between 25 g / m2 and 35 g / m2.

20. The non-woven fabric according to claim 1, further characterized in that the fabric has an apparent thickness of between 0.15 mm and 0.40 mm.

21. The non-woven fabric according to claim 1, further characterized in that the fibers include a pigment material.

22. The nonwoven fabric according to claim 21, further characterized in that the pigment material is dioxide. titanium in an amount of about 1% to 6% by weight.

23. The non-woven fabric according to claim 22, further characterized in that the titanium dioxide is present in an amount of about 2% to 3.5% by weight.

24. An absorbent article, characterized in that it comprises a cover layer permeable to the liquid, which faces towards the body; a liquid impervious barrier layer facing an article of clothing and an absorbent core between the cover layer and the barrier layer; the cover layer further comprising a non-woven fabric formed of a network of synthetic, interconnected short fibers; the fibers further comprising a mixture of a first series of fibers and a second series of fibers; each series of fibers having an average length of 2 mm to 100 mm; wherein the average length of the first series of fibers varies from the average length of the second series of fibers by at least 2 mm.

25. The absorbent article according to claim 24, further characterized in that the fibers additionally comprise at least two different deniers.

26. The absorbent article according to claim 24, further characterized in that the fibers have lengths between 10 mm and 80 mm and the length of the first series of fibers is greater than the length of the second series of fibers in at least 4 mm.

27. The absorbent article according to claim 24, further characterized in that the fibers have lengths between 15 mm and 40 m, and the length of the first series of fibers is greater than the length of the second series of fibers at minus 4 mm

28. The absorbent article according to claim 24, further characterized in that the non-woven fabric has a density between 25 g / m2 and 35 g / m2.

29. The absorbent article according to claim 24, further characterized in that the non-woven fabric has an apparent thickness of between 0.15 mm and 0.40 mm.

30. - The absorbent article according to claim 29, further characterized in that the non-woven fabric has a basis weight of 35 g / m2.

31. The absorbent article according to claim 24, further characterized in that the absorbent article is selected from the group consisting of sanitary napkins, panty liners, diapers and incontinence devices for adults.