MXPA00005177A - Flushable fibrous structures - Google Patents

Abstract

The present invention relates to a flushable fibrous structure that is particularly useful as a disposable tissue product and as a component (e.g., topsheets) for absorbent articles such as catamenial pads, diapers, incontinent articles and the like. The invention specifically relates to a flushable fibrous structure that has an in-use wet tensile strength of at least about 100g/in. and a disposal wet tensile strength of not more than about 30g/in. The invention also relates to absorbent articles comprising the fibrous structures, and methods for making the structures.

Description

FIBROUS STRUCTURES CAPABLE OF FLOWING AND SPREADING FIELD OF THE INVENTION The present invention relates to fibrous structures capable of flowing and spreading. These fibrous structures may be in the form of either paper or synthetic non-woven material.

BACKGROUND OF THE INVENTION Wet strength is a desirable attribute of many disposable paper products, which must maintain their integrity for a prolonged period of time when they get wet during dedicated use. These products include toilet paper and facial tissue, paper towels, and some of the components of diapers and adult incontinence products, feminine hygiene products such as sanitary napkins, pantiliners and tampons, and the like. A number of resins have been used or disclosed as being useful in providing wet strength to paper products and their components. Certain of these wet strength additives have resulted in paper products with permanent wet strength, i.e., paper which when placed in an aqueous medium retains a substantial part of its initial wet strength over time. Exemplary resins of this type include urea-formaldehyde resins, melamine-formaldehyde resins and polyamide-epichlorohydrin resins. These resins exhibit limited decay of wet strength even in the presence of excess water.

However, permanent wet strength in paper products is often an unnecessary and undesirable property. In fact, due to the permanent wet strength of these products, or their components, paper products are generally discarded after brief periods of use towards land fillers, incinerators, etc. Therefore, these products can have a significant load in the solid waste stream. The desirable alternative of directing used paper products to municipal waste treatment facilities or private septic systems is typically obviated by the inclusion of "non-flowable and spreadable" components, such as top sheets and backsheets. That is, the clogging of these systems may result if the product, or one or more of its components, permanently retains the resistance properties resistant to hydrolysis. Therefore, efforts have been made to provide paper product components, and specifically components of incontinence and personal hygiene products, that have sufficient wet integrity when wetted with the body's aqueous fluids during use, but which lose their integrity when exposed to large amounts of wastewater (as it is found in a typical toilet) so that they pass through the pipe and disintegrate in the municipal / septic systems. Numerous approaches have been suggested to provide reclaimed paper products as having good initial wet strength which decays significantly over time. For example, several suggested approaches for achieving temporary wet strength are described in U.S. Patent No. 3, 556, 932, Coscia et al., Issued January 19, 1971; U.S. Patent No. 3,740,391, Williams et al., issued June 19, 1973; U.S. Patent No. 4,258,849, Miller, issued March 31, 1981; U.S. Patent No. 3,096,228, Day et al., issued July 2, 1983; U.S. Patent No. 4,605,702, Guerro et al., issued August 12, 1986; U.S. Patent No. 4,675,394, Solarek, et al., issued June 23, 1987; U.S. Patent No. 5,509,913, issued April 23, 1996 to Yeo; U.S. Patent No. 4,603,176, Bjorkquist et al., issued July 29, 1986; U.S. Patent No. 4,981, 557, Bjorkquist, issued on the 1st. January 1991; and U.S. Patent No. 5,138,002, Bjorkquist, issued August 11, 1992. Although the art has provided a variety of non-woven synthetic products having varying degrees of wet strength, none have provided paper products exhibiting the combined properties of wet integrity during the use and decay of the waste of these present structures. In particular, there are products with temporary wet strength that exhibit immediate and rapid tension decay when exposed to aqueous fluids. Obviously, rapid decay in the presence of bodily fluids makes these materials unsuitable for use in absorbent articles, which must retain their strength until the time of disposal. Conversely, as discussed above, those paper products that have higher permanent wet strength will not disintegrate even when exposed to large amounts of aqueous liquids. It is therefore an object of this invention to provide fibrous structures capable of flowing and spreading in the form of either paper or synthetic nonwovens that provide initial tensile strength even when subjected to aqueous body fluids. , but which will rapidly disintegrate in the presence of excess amounts of water found during disposal. These structures may be in the form of a paper product such as toilet paper, facial paper, paper towels and the like, or these may be used as a component in personal products, such as top sheets of absorbent article, backsheets and the like. .

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to fibrous structures capable of flowing and spreading having a wet tensile strength during the use of at least about 100 gr. per inch and a wet tensile strength to the waste of no more than about 30 gr. per inch. The invention specifically relates to fibrous structures capable of flowing and spreading comprising a binder which comprises a polymer and a salt to provide the desired characteristics of wet strength in use and when disposed. The polymer, when used in combination with the salt, is relatively insoluble in the aqueous fluids found in use, but is soluble in the presence of excess water, such as that found in a typical sanitary waste system. The invention is further related to products consisting of (for example, tissue products such as facial tissue and toilet paper) or comprising (for example, absorbent articles) fibrous structures capable of flowing and spreading, as well as methods of making the fibrous structures.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a top plan view of a sanitary napkin with portions of the sanitary napkin trimmed to more clearly show the construction of the sanitary napkin.

The Figure is a cross-sectional view of the sanitary napkin of Figure 1 taken along the line of section 2-2.

DETAILED DESCRIPTION OF THE INVENTION I. Definitions As used herein, the term "wet tensile strength in use" means the tensile strength of a fibrous structure, as measured using an electronic voltage tester as described in the Test Methods section. , after a sample of the structure has been soaked in a 5% sodium sulfate solution for 23 minutes at 23 ° C. As used herein, the term "removal wet tension" means the strength resistance of a fibrous structure, as measured using an electronic voltage tester as described in the Test Methods section, after which a sample The structure has been soaked in distilled water in excess for 15 seconds at 23 ° C.

Fibrous structures capable of flowing and spreading The present invention relates to fibrous structures capable of flowing and spreading having a wet tensile strength in use of at least about 100 g / in, preferably at least about 200 g / in, and more preferably at least about 300 g / in In addition, the structures have a wet tensile strength of removal of not more than about 30 g / in, preferably not more than about 25 g / in. The tensile strengths are measured according to the procedure established in the Test Methods section below. Preferred materials for preparing these fibrous structures capable of flowing and spreading are described in detail below. In general, these preferred structures comprise fibers and a binder material wherein the binder material comprises a polymer and a salt.

A. Binder composition In a preferred embodiment of the present invention, the binder component of the fibrous structures comprises a salt and the condensation product of polyvinyl alcohol (hereinafter referred to as "PVA") and one or more substituted or unsubstituted C8 C aldehydes. This condensation product is a polyvinyl-co-acetal alcohol (referred to herein as "PVAA"). The polyvinyl alcohols useful in making the PVAA for this preferred binder are well known in the textile and paper arts, and are commercially available from a variety of sources. These alcohols are manufactured by first polymerizing the vinyl acetate, followed by hydrolysis of the acetate groups to alcohol groups. Commercial grades of PVA vary in the degree of polymerization (ie, molecular weight) and the degree of hydrolysis (ie, the number of acetate groups that are converted to hydroxyl groups). For example, the commercial PVA grades that are available have a degree of hydrolysis of about 88% with respect to those that have a degree of hydrolysis in excess of 99%. Preferred functionalized polymers useful in the present invention are those wherein the PVA material to be acetalized has a degree of hydrolysis of at least about 95%, more preferably at least about 97%, even more preferably at least about 98% and most preferably at least about 99%. In addition, the preferred functionalized polymers are those wherein at least about 8% of the hydroxyl groups of the starting PVA are acetalized. More preferably, the PVAA will have from about 8 to about 20% of the acetalized starting PVAA hydroxyl, more preferably from about 10 to about 16%. To be particularly useful in the present invention, the PVA must be acetalized to such an extent that the PVAA dark point (as determined turbidimetrically by measuring a change in light transmittance) is greater than the temperature of the running water (ie say, greater than about 25 ° C) and is killed by the addition of the salts. Furthermore, in order that the PVAA be sintered conveniently, it is useful that its dark point is at least about 1 ° C above the temperature of the condensation reaction, preferably from about 3 to about 5 ° C. above the temperature of the condensation reaction. This is to facilitate the homogeneous reaction conditions during the formation of the PVAA. An expert artisan will recognize that the level of acetalization of the starting PVA to arrive at a functionalized PVAA polymer that will provide the desired wet strength in use is related to the degree of hydrolysis of the starting PVA, the molecular weight of the starting PVA , the aldehyde starting material, etc. In general, with other things being constant, the degree of acetalization needs to increase as the degree of hydrolysis of the starting material of PVA increases. Also, with other things being constant, as the molecular weight of the PVA starting material increases, it increases the wet tensile strength in use. The determination of the degree of acetalization of a given starting PVA to achieve the wet tensile strength in desired use is a matter of routine experimentation for the skilled artisan and will be dictated in part by the final use of the product, as discussed below. . Preferably, the PVA starting material will have an average molecular weight of at least about 80 kg / mol, more preferably at least about 160 kg / mol. In general, the average molecular weight of the higher polymer, the wet strength in greater use of the corresponding fibrous substrate comprising the binder. The skilled artisan will recognize that the molecular weight of the starting PVA affects its viscosity (higher molecular weights provide higher PVA viscosities), and that the viscosity of the lower PVA will be easier to process in the desired PVAA. However, this does not limit the scope of the invention to the use of "low" molecular weight PVAA. As indicated, to obtain the preferred PVAA material, the PVA starting material is reacted with a substituted or unsubstituted C2-C8 aldehyde, or a mixture of two or more of these aldehydes. Where the aldehyde is substituted, suitable substituents include, for example, C3 alkyl or aryl. Preferably, the aldehyde is a saturated straight-chain substituted one. Also preferred is where the aldehyde has from 2 to 5 carbon atoms, more preferably from 3 to 4 carbon atoms. Specific non-limiting examples of particularly suitable aldehydes for the reaction with the PVA starting material are acetaldehyde, propionaldehyde, butyraldehyde, and mixtures thereof. Particularly preferred is where the aldehyde is propionaldehyde and / or butyraldehyde, most preferably butyraldehyde. In general, the PVAA materials used herein can be prepared by reacting a commercial grade of PVA (eg, Airvol 350® or Airvol 165®, available from Air Products, Allentown, PA) and aldehyde in an aqueous solution at a temperature of about 20 ° C and at a pH of about 2. Representative examples for preparing the PVAA useful herein are set forth below in section VI. Another preferred class of polymer useful in the binder component of the fibrous structures are the homopolymers and copolymers derived from the acrylamide monomers. These polymers have a structure with the following general formula (I) where a) x is > 1; b) and it is > 0; c) R1 and R2 are independently selected from hydrogen and C-C-alkyl (preferably at least one of R1 or R2 is different from hydrogen, more preferably R1 is hydrogen and R2 is C3-C3 alkyl, even more preferably R1 is hydrogen and R 2 is methyl, ethyl, isopropyl or n-propyl); and d) when y is > 1, (i) R3 is -N (R4) (R5), wherein R4 and R5 are independently selected from hydrogen, alkyl and aryl of C Ce (preferably R4 is hydrogen or alkyl of and R5 is CC alkyl, more preferably R 4 is hydrogen or C 3 -C 4 alkyl and R 5 is C 3 -C 4 alkyl); or (ii) R3 is -O- (-CH2-) 2-N (Rd) (R7), wherein z is from 2 to about 4 (preferably 2 or 3, most preferably 2) and R6 and R7 are independently selected of hydrogen, C? -C6 alkyl, and aryl (preferably R6 is hydrogen or Ci-Cs alkyl and R7 is Ci-Cs alkyl, more preferably R6 is d-C3 alkyl and R7 is C1-C3 alkyl) . In those examples where R6 and R7 are both alkyl groups, the resulting tertiary amine will be cationic at neutral pH and the polymer will therefore be readily absorbed by the cellulose, allowing ionic bonding with the anionic carboxyl groups of the cellulose. As such, polymers of this kind can be added to the wet term of the papermaking process, rather than as a separate step after substrate formation. Preferably, the polyacrylamide polymer or copolymer will have an average molecular weight of at least about 50 kg / mol, more preferably at least about 100 kg / mol, even more preferably at least about 200 kg / mol. In general, the homo and / or copolymers derived from acrylamide are prepared by free radical polymerization following a method similar to that described in Macromolecules 1992, 25, 5353-5361, which is incorporated by reference herein. In order to obtain a high molecular weight polymer, however, it is necessary to replace the dioxane with t-butanol as the solvent. Representative examples for preparing the polyacrylamide homo- and copolymers useful herein are set forth below in section VI. In addition to the polymer, the binder component of the present invention comprises an appropriate salt that prevents swelling and / or dissolution of the polymer in the presence of relatively small water-based or water-based fluids, such as are found when used as paper products. or tissue components in absorbent articles. This is the ability to resist swelling in the presence of low levels of water that provide wet strength in use to the fibrous structures of the present invention. Useful salts herein include those which comprise monovalent cations (for example Li +, Na +, K +), divalent cations (for example, Mg + 2, Ca + 2), and trivalent cations (for example, Al + 3). Preferred are the salts comprising monovalent or divalent cations. Preferred salts comprise anions such as citrate, sulfate, chloride, fluoride, bromide, thiosulfate, phosphate, nitrate, acetate, carbonate and bicarbonate. Preferred salts include, but are not limited to sodium citrate, potassium citrate, sodium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, sodium phosphate, potassium phosphate and magnesium chloride. Particularly preferred salts include sodium citrate and sodium sulfate. Because the level of the salt used directly affects the wet strength in use of the binder, the level of salt required for a given fibrous structure of the present invention is dictated in part by the end use of the product comprising the fibrous structure. . That is, where wet tension in relatively low use is required, such as for toilet paper, relatively low salt levels may be required. Conversely, where high wet tension is required, such as for a top sheet in an absorbent article, relatively higher salt levels may be used.

B. Fibers The binder composition is useful for imparting temporary wet strength to a wide variety of paper and paper products. As used herein, the terms "paper" and "paper products" include sheet-shaped masses and molded products containing fibrous materials which may be derived from natural sources, such as wood pulp fibers, or which are synthetically derived.

Fibers of different natural origin are applicable to the invention. Cellulose fibers digested from soft wood (derived from coniferous trees), hardwood (derived from deciduous trees) or cotton waste fibers can be used. The fibers from Esparto, bagasse, kempa, flax and other sources of lignacio fiber and cellulose fibers can also be used as raw material in the invention. For reasons of cost, ease of manufacture and availability, the preferred fibers are those derived from wood pulp (i.e., cellulose fibers). When cellulose fibers are used, the optimal source will depend on the particular type of end use contemplated. Generally wood pulps will be used. Applicable wood pulps include chemical pulps, such as Kraft (ie, sulfate) and sulfite pulps, as well as mechanical pulps including, for example, ground wood, thermomechanical pulp (ie, TMP) and thermomechanical chemical pulp. (that is, CTMP). Completely bleached, partially bleached and unbleached fibers are useful here. This can often be desired to use bleached pulp for its superior brilliance and appearance of consumption. For products such as toilet paper, paper towels and diaper substrates, sanitary napkins, catamenial products, and other similar absorbent paper products, it is especially preferred to use northern softwood pulp fibers due to their characteristics of superior resistance. Also useful in the present invention are fibers derived from recycled paper, which may contain any or all of the above categories as well as other non-fibrous materials such as fillers and adhesives used to facilitate the original papermaking process . The fibrous structures of the present invention can comprise or essentially consist of fibrous material without cellulose, for example, glass fibers and synthetic polymer fibers. The synthetic polymeric fibers used herein include polyolefins, particularly polyethylenes, polypropylenes and copolymers having at least one olefinic constituent. Other materials such as polyesters, polyamides, nylons, scratches, copolymers thereof and combinations of any of the foregoing may be suitable as the fibrous polymeric material.

O Preparation of fibrous structures The fibrous structures of the present invention comprise a temporary wet strength binder (polymer and salt) in combination with the fibers. The polymer is combined with the fibers in a manner which, after addition of the salt, leads to a bonded fiber mass, generally in the form of a sheet containing the fibers. The bonded fiber mass has a wet strength in use that is higher than a corresponding fiber mass without the binder. The fibrous structures of the present invention can be prepared in a variety of ways. However, an important aspect is that the polymer and salt must be added to the fibers separately. That is, while the polymer and salt can be added simultaneously, they should not be mixed before introduction to the fibers. This is dictated by the ability of the salt to precipitate the polymer if the two are combined before the addition to the fibers. Fibrous structures are typically formed by a wet-laid papermaking process. The wet-laid papermaking process typically includes the steps of providing a suspension containing the fibers (the suspension is referred to alternatively herein as a papermaking supply), depositing the fiber suspension on a substrate such as a foraminous forming wire (e.g., a Fourdrinier wire), and placing the fibers in a sheet form while the fibers are in a substantially non-flocculated condition. The step of placing the fibers in the sheet form can be performed by allowing the fluid to drain and press the fibers against the foraminous (dewatered) wire, for example, with a gibed roller, such as the Dandy cylindrical roller. Once placed, the fibrous sheet can then be dried and optionally compacted as desired. In general, the polymer is combined with the fibers by contacting the fibers with the polymer in an aqueous liquid medium and substantially removing the medium from the fibers. The polymer can be combined with the fibers in the wet term of the papermaking process (for example, by adding to the paper supply) or after the paper product is substantially formed (i.e., by the addition in term). dry). In a preferred embodiment, the polymer and the salt are combined with the fibers after the paper product is formed substantially, for example, by spraying or by printing. In this way, the treatment of paper or paper products with the polymer may involve spraying or printing or otherwise applying the polymer to the fibers that has been substantially placed in the preparation of the paper product, for example, by a wet laying process. The placed fibers are preferably sprayed or printed with the polymer in the form of a composition which comprises a liquid solution of the polymer. Water is the preferred solvent. The liquid mixture typically contains from about 1 to about 10% by weight of the polymer and from about 90 to about 99% by weight of the solvent; for example, a mixture of about 5% by weight of the polymer and about 95% by weight of the solvent is suitable. Optionally, a plasticizer may be included in the solution to help provide softness and flexibility to the bonded fibrous structure. In a preferred embodiment, the polymer solution sprayed onto the previously placed fibers. Upon drying, the salt component is added (eg, sprayed) to the fiber / polymer substrate. As indicated, the polymer can be alternately combined with the cellulose fibers in the wet term of a wet-paper-making process. In this way, the polymer can be suitably included in the papermaking supply. The polymer can be added directly to the supply and agitated to cause its dissolution. Alternatively, a solution of the polymer is prepared first and then added to the supply. In any case, depending on the nature of the polymer, it may be necessary to introduce a positive charge into the polymer in such a way that it can easily absorb the anionic cellulose fibers when added to the wet term of the papermaking process. For example, a small amount of 4-dimethylaminobutyraldehyde dimethylacetal can be added together with unsubstituted C2 to C aldehyde while the PVAA is made to provide the positive charge. Alternative to the supply of the positive charge is to heat the polymer / fiber mixture to facilitate retention of the polymer on the fibers of the supply. In those embodiments where the polymer of the binder is cationic under the conditions for combining the polymer and the fibers, the problem of incompatibility with the fibers can be obviated. Where the polymer is combined with the fibers via the wet term addition, the salt solution will preferably be added after the fiber / polymer mixture has dried. . Regardless of whether the polymer is combined with the fibers via the addition of dry term or wet term, the salt may be added concurrently with (although separately) or sequentially from the addition of the polymer. In one embodiment, the polymer and fibers are combined and the formed sheet is allowed to dry.

A salt solution is then added to provide a fibrous structure of the present invention. The polymer is advantageously used in the form of a solution, which can be further diluted with additional solvent, or concentrated. Alternatively, the polymer can be isolated and recovered by removing the solvent, for example, by vacuum and / or evaporation. The polymer can then be used in a temporary wet strength composition and applied to the fibers to impart temporary wet strength to them. These compositions comprise the PVAA polymer, a solvent suitable for substantially dissolving the polymer (preferably in water and / or a plasticizer such as glycerol, sorbitol, etc.), and optionally other papermaking additives as are known in the art. technique (for example, softeners, retention aids). In a preferred embodiment, the treatment is achieved by spraying, printing or otherwise applying the polymer to the fibers placed with such a composition (more preferably by spraying). Spraying tends to provide higher levels of wet tensile strength in use relative to treatment by the wet term in a manual papermaking process. The amount of the polymer that is combined with the cellulose fibers is selected to provide an equilibrium of the wet tensile strength in use, the wet tensile strength of removal, and optionally other properties, including dry strength, consistent with the objects of the invention. The paper products will typically contain from about 0.5 wt% to about 20 wt%, preferably from about 1 wt% to about 15 wt%, more preferably from about 1 wt% to about 10 wt% of the polymer, based on the total weight of the fibrous structure. The wet strength properties of the fibrous structure will depend on its end use (eg, a tissue product or a component of an absorbent article). The composition comprising the polymer is allowed to remain in contact with the fibers for a time and at a temperature sufficient to allow the absorption of the polymer by the fibers and the bond between the polymer and the fibers in such a way that the wet strength develops Significant through the formation of links (internal links are formed in the fibers). When the fibers are treated by spray application on conventional commercial papermaking equipment, the production time, for example, the drying time with paper air (conventionally less than 4 minutes), may need to be increased to allow significant levels of wet strength are developed. The fibers and the polymer can be combined at any pH, although it may be desirable to avoid strongly acidic conditions which could lead to catalyzed hydrolysis of the polymer acid. The paper product being treated with polymer is preferably subjected to a drying step to remove the water and / or any other solvent to develop the wet strength in use. Drying can be achieved by subjecting the paper product to elevated temperatures, for example, in the range of about 85 ° C to about 125 ° C, for a sufficient time to achieve the desired level of dryness, typically at constant weight. The present invention is particularly adapted for paper products or components of paper products, which are to be disposed of in sewer systems. Accordingly, it should be understood that the present invention is applicable to a variety of paper products including, but not limited to, disposable absorbent paper products, such as those used for the home, body, or other cleaning applications. Exemplary paper products thus include tissue paper including toilet tissue and facial tissues, paper towels, core materials for absorbent articles such as feminine hygiene items including sanitary napkins, pantiliners and tampons, diapers, adult incontinence articles and the like, and the materials of the topsheet and / or the backsheet for these absorbent articles. lll. Absorbent articles As used herein, the term "absorbent article" generally refers to devices used to absorb and contain exudates from the body, and more specifically refers to devices that are placed against or close to the user's body to absorb and contain various exudates discharged from the body. The term "absorbent article" is intended to include diapers, catamenial pads, tampons, sanitary napkins, incontinence pads, and the like, as well as bandages and bandages for wounds. The term "disposable" is used herein to describe absorbent articles that are not intended to be washed or restored or reused in another way as an absorbent article (ie, they are intended to be disposed of after limited use, and preferably, to be recycled, composted or otherwise disposed of in an environmentally compatible manner). A "unitary" absorbent article refers to absorbent articles that are formed as a single structure or as separate parts joined together to form a coordinated entity such that separate manipulated parts such as a separate fastener and pad are not required. A preferred embodiment of a unitary disposable absorbent article made in accordance therewith is sanitary napkin 10, shown in Figure 1. As used herein, the term "sanitary napkin" refers to an absorbent article that is worn by women adjacent to the pudendal region, usually external to the urinary genital region, and which is dedicated to absorbing and containing the menstrual fluids and other vaginal discharges of the wearer's body (eg, blood, menstruation, and urine). Interlabial devices that reside partially within and partially external to the wearer's vestibule are also within the scope of this invention. However, it should be understood that the present invention is also applicable to other feminine or catamenial hygiene pads or other absorbent articles such as diapers, incontinence pads and the like, as well as other wefts designed to facilitate the transport of fluid away from the body. surface such as disposable towels, facial papers and the like. It should be understood that the overall size, shape and / or configuration of the absorbent article, if any, in which the fluid transport frames in accordance with the present invention are incorporated, or used in combination with, are not so related. critical or functional with the principles of the present invention. However, these parameters must be considered together with the fluid attempted and the functionality attempted when the appropriate frame configurations are determined. The sanitary napkin 10 is illustrated as having two surfaces, a first surface 10a, sometimes referred to as the surface that is in contact with or gives to the user, a surface that faces toward or is in contact with the body or "body surface". , and the second surface 10b, sometimes referred to as the surface facing toward or in contact with the garment, or "pledge surface". The sanitary towel 10 is shown in Figure 1 as seen from its first surface 10a. The first surface 10a is intended to be carried adjacent to the body of the wearer. The second surface 10b of the sanitary napkin 10 (shown in Figure 2) is on the opposite side and is intended to be placed adjacent to the wearer's undergarment when the sanitary napkin 10 is worn.

The sanitary napkin 10 has two center lines, a longitudinal center line "L" and a transverse center line "T". The term "longitudinal", as used herein, refers to a line, axis or direction in the plane of the sanitary napkin 10 that is generally aligned with (eg, approximately parallel to) a vertical plane that divides a user from standing in left and right body halves when wearing the sanitary napkin 10. The terms "transverse" or "lateral" as used hereThey are interchangeable and refer to a line, axis or direction that is located within the plane of the sanitary napkin 10 that is generally perpendicular to the longitudinal direction. Figure 1 also shows that the sanitary napkin 10 has a periphery 20, which is defined by the outer edges of the sanitary napkin 10 in which the longitudinal edges (or "side edges") are designated 21 and the end edges ( or "end") are designated 22. Figure 1 is a top plan view of a sanitary napkin 10 of the present invention in a substantially planar state with portions of the sanitary napkin that are trimmed to more clearly show the construction of the towel sanitary 10 and with the part of the sanitary napkin 10 facing towards or in contact with the user 10a facing the observer. As shown in Figure 1, the sanitary napkin 10 comprises a liquid-permeable topsheet 12 which is a fibrous structure of the present invention, a liquid-impermeable backsheet 13 bonded to the topsheet 12, an absorbent core 14 placed between the upper sheet 12 and the rear sheet 13, and a secondary upper sheet or acquisition layer 15 placed between the upper sheet 12 and the absorbent core 14. To facilitate the discharge capacity of the total towel, it is preferred that the other components of the article are also comprised of materials capable of flowing and separating. The sanitary napkin 10 preferably includes optional side flaps or "wings" that are folded around the crotch portion of the wearer's panties. The side flaps 24 can serve a number of purposes, including, but not limited to, helping to retain the towel in the proper position while protecting the wearer's panties from being soiled and keeping the sanitary napkin secured to the panty of the wearer. user. Figure 2 is a cross-sectional view of the sanitary napkin 10 taken along the section line 2-2 of Figure 1. As can be seen in Figure 2, the sanitary napkin 10 preferably includes a holding means adhesive 26 for fixing the sanitary napkin to the wearer's undergarment. Removable release liner 27 covers the adhesive fastening means 26 to prevent the adhesive from sticking to a different surface of the crotch portion of the undergarment before use. The topsheet 12 has a first surface 12a and a second surface 12b positioned adjacent to and preferably secured to a first surface 15a of the fluid acquisition layer 15 to promote fluid transport from the topsheet to the acquisition layer. The second surface 15b of the acquisition layer 15 is positioned adjacent to and preferably secured to the first surface 14a of an absorbent core or fluid storage layer 14 to promote fluid transport from the acquisition layer to the absorbent core. The second surface 14b of the absorbent core 14 is positioned adjacent to and preferably secured to the first surface 13a of the backsheet 13. In addition to having a longitudinal direction and a transverse direction, the sanitary napkin 10 also has a "Z" direction or axis, which is the direction proceeding down through the top sheet 12 and towards either the fluid storage layer or the core 14 that may be provided. The aim is to provide a substantially continuous path between the topsheet 12 and the underlying layer or layers of the absorbent article, such that the fluid is entrained in the "Z" direction and away from the topsheet of the article and to its backing layer. final storage. The absorbent core 14 may be any absorbent means that is capable of absorbing or retaining the liquids (e.g., menstruation and / or urine), and is preferably capable of spreading and flowing. As shown in Figures 1 and 2, the absorbent core 14 has a body surface 14a, a garment facing surface 14b, side edges and end edges. The absorbent core 14 can be manufactured in a wide variety of sizes and shapes (eg, rectangular, oval, hourglass, dog bone, asymmetric, etc.) and from a wide variety of liquid absorbent materials commonly used in sanitary napkins and other absorbent articles such as crushed wood pulp which is generally referred to as air felt. Examples of other absorbent materials include creped cellulose wadding; meltblown polymers including coform; chemically hardened, modified or crosslinked cellulose fibers; synthetic fibers such as hooked polyester fibers; peat moss; tissue including tissue wraps and tissue laminates, absorbent foams; absorbent sponges; superabsorbent gelling materials; or any equivalent material or combinations of materials, or mixtures thereof. Again, it is preferred that the absorbent core consist of materials that are capable of flowing and spreading. The configuration in the construction of the absorbent core can also be varied (for example, the absorbent core can have variable zones of gauge (for example, profiled to be thicker in the center), hydrophilic gradients, superabsorbent gradients or density acquisition zones. lesser or lesser average basis weight, or may comprise one or more layers or structures). However, the total absorbent capacity of the absorbent core must be compatible with the design load and intended use of the absorbent article. In addition, the size and absorbent capacity of the absorbent core can be varied to encompass the different uses such as incontinence pads, panty hose, regular sanitary napkins, or night sanitary napkins. Exemplary absorbent structures are described for use as the absorbent core in the present invention in U.S. Patent No. 4,556,146 issued December 3, 1985 to Swanson et al .; U.S. Patent No. B1 4,589,876 (original patent granted May 20, 1986) reexamination issued to Van Tilburg on April 27, 1993; U.S. Patent No. 4,687,478 issued August 18, 1987 to Van Tilburg; U.S. Patent No. 5,009,653 issued April 23, 1991 to Osborn; U.S. Patent No. 5,267,992 issued December 7, 1993 to Van Tilburg; U.S. Patent No. 5,389,094 issued February 14, 1995 to Lavash et al .; U.S. Patent No. 5,460,623 issued October 24, 1995 to Emenaker et al .; U.S. Patent No. 5,489,283 issued February 6, 1996 to Van Tilburg; U.S. Patent No. 5,569,231 issued October 29, 1996 to Emenaker et al .; U.S. Patent No. 5,620,430 issued April 15, 1997 to Bamber; U.S. Patent No. 4,950,264 issued to Osborn on August 21, 1990; U.S. Patent No. 4,610,678 issued to Weisman et al. on September 9, 1986; U.S. Patent No. 4,834,735 issued to Alemany et al. on May 30, 1989; and in European Patent Application No. 0 198 683, The Procter & Gamble Company, published on October 22, 1986 in the name of Duenk, and others. The disclosure of each of these documents is incorporated by reference. The backsheet 13 and the fibrous topsheet 12 are placed adjacent to the garment facing surface and the body facing surface respectively of the absorbent core 14 and are preferably bonded to it and to each other by means of attachment (FIG. not shown) such as those well known in the art. For example, the backsheet 13 and / or the topsheet 12 can be secured to the absorbent core or to each other by a continuous uniform adhesive layer, a patterned adhesive layer or any array of separate lines, spirals or spots of adhesive. Adhesives that have been found to be satisfactory are manufactured by H: B Fuller Company of St. Paul, Minnesota under the designation HL-1258, and by Findlay of Minneapolis, Minnesota, under the designation H-2031. The joining means will preferably comprise an open pattern web of filaments of adhesives as disclosed in US Pat. 4,573,986 issued to Minetola on March 4, 1986, the disclosure of which is incorporated herein by reference. In exemplary bonding means and an open pattern network of filaments comprises several lines of adhesive filaments twisted in a spiral pattern as illustrated by the apparatus and method shown in United States Patent No. 3,911,173 issued to Sprague, Jr. on October 7, 1975; U.S. Patent No. 4,785,996 issued to Zieker, and others on November 22, 1978 and U.S. Patent No. 4,842,666 issued to Werenicz on June 27, 1989. The disclosure of each of these patents are incorporated here by reference. Alternatively, the joining means may comprise heat bonds, pressure joints, ultrasonic joints, mechanical dynamic joints or any other suitable joining means or combinations of these joint means as are known in the art. The backsheet 13 is impervious to liquids (eg, menstruation and / or urine) and is preferably manufactured from a thin film which is capable of flowing and spreading, although other flexible liquid impervious materials may also be used. As used, the term "flexible" refers to materials that are docile and that are more easily conformed to the figure and general outline of the human body. The backsheet 13 prevents the exudates absorbed and contained in the absorbent core from wetting the articles that are in contact with the sanitary pad 10 such as underpants, pajamas, and undergarments. The backsheet 13 can thus comprise a woven or non-woven material, films, or composite materials such as a nonwoven material coated with film. Preferably, the backsheet of the polyethylene film having a thickness of about 0.012 mm to about 0.051 mm. Further, the backsheet 13 can allow vapors to escape from the absorbent core 14 (i.e., breathable) while still preventing the exudates from passing through the backsheet 13. In use, the sanitary napkin 10 can be maintained in the place by any means of support or attachment means (not shown) well known for these purposes. Preferably, the sanitary napkin is placed on the wearer's undergarment or wearer's panties and secured thereto by a fastener such as an adhesive. The adhesive provides a means for securing the sanitary napkin in the crotch portion of a pantyhose. In this way, a part or all of the surface facing the garment or external 13b of the backsheet 13 is coated with adhesive. Any adhesive or glue used in the art for these purposes can be used for the adhesive herein, with pressure sensitive adhesives being preferred. Suitable adhesives are manufactured by H.B. Fuller Company of St. Paul, Minnesota, under the designation 2238. Suitable adhesive fasteners are also disclosed in U.S. Patent No. 4,917,697. Before the sanitary napkin is put into use, the pressure sensitive adhesive is typically covered with a removable release liner 27 in order to prevent the adhesive from drying or adhering to a different surface of the crotch portion of the panty before use. Suitable release liners are also disclosed in the aforementioned U.S. Patent No. 4,917,697. Any of the commercially available release liners commonly used for these purposes may be used herein. A non-limiting example of a suitable release liner is BL30MG-A Silox 4P / O, which is manufactured by Akrosil Corporation of Menasha, Wl. The sanitary napkin 10 of the present invention is used by removing the release liner and subsequently placing the sanitary napkin in a panty so that the adhesive is in contact with the panty. The adhesive holds the sanitary napkin in its position inside the pant during use. In a preferred embodiment of the present invention, the sanitary napkin has two fins 24 each of which are adjacent to and extend laterally from the side edge of the absorbent core. The fins 24 are configured to wrap the edges of the wearer's panties in the crotch region such that the fins are disposed between the edges of the panties and the thighs of the wearer. The fins serve at least two purposes. First, the fins help to avoid the staining of the user's body and the panties by the menstrual fluid, preferably forming a double-walled barrier along the edges of the panty. Second, the flaps are preferably provided with fastening means on their garment surface in such a way that the flaps can be folded back under the pantyhose and attached to the garment side of the pantyhose. In this way, the flaps serve to keep the sanitary napkin properly placed in the pantyhose. The fins can be constructed of various materials including materials similar to the topsheet, the backsheet, tissue, or combinations of these materials. In addition, the flaps can be a separate element attached to the main body of the towel or can comprise extensions of the upper sheet and the back sheet (ie, unitary). A number of sanitary napkins having suitable or adaptable fins for use with the sanitary napkins of the present invention is disclosed in U.S. Patent No. 4,687,478 entitled "Towel-sanitary Towel", which was issued to Van Tilburg on August 18, 1987; and in U.S. Patent No. 4,589,876 entitled "Sanitary Towel" which was issued to Van Tilburg on May 20, 1986. The disclosure of each of these patents is hereby incorporated by reference. In a preferred embodiment of the present invention, an acquisition layer or layer 15 can be placed between the topsheet 12 and the absorbent core 14. The acquisition layer 15 can serve several functions including the wicking effect or capillary action of the Exudates improved on and towards the absorbent core. There are several reasons why the wicking effect or improved capillary action of the exudates is important, including providing a more even distribution of the exudates throughout the absorbent core and allowing the sanitary pad 10 to be made relatively thin. The wick or capillary action effect referred to herein may encompass the transport of liquids in one, two or all directions (ie, in the x-y plane and / or in the z-direction). The acquisition layer may be composed of several different materials including non-woven or woven webs of synthetic fibers including polyester, polypropylene or polyethylene; of natural fibers including cotton or cellulose; mixtures of these fibers; or any of the equivalent materials or combinations of materials. Examples of sanitary napkins having an acquisition layer and an upper sheet are more fully described in U.S. Patent No. 4,950,264 issued to Osborn and in U.S. Patent Application Serial No. 07 / 810,774. , "Absorbent article having fused layers", presented on December 17, 1991 in the name of Cree, and others. The disclosure of each of these references are hereby incorporated by reference. In a preferred embodiment, the acquisition layer may be joined to the topsheet by any of the conventional means for joining webs together, most preferably by fusion bonds as described more fully in the Cree application referred to above.

IV. Wet strength properties With respect to paper tissue, the temporary wet strength polymers of the present invention can be used in any type of tissue paper construction. For example, the tissue paper of the present invention can be homogeneous or multi-layered construction; the tissue paper products made therefrom can be of a single layer or multiple layer construction. The tissue paper preferably has a basis weight of between about 10 g / m2 and about 65 g / m2, and a density of about 0.6 g / cm3 or less. More preferably, the basis weight will be about 40 g / m2 or less and the density will be about 0.3 g / cm3 or less. Most preferably, the density will be between about 0.04 g / cm 3 and about 0.2 g / cm 3. See column 13, line 61 to 67, of U.S. Patent No. 5,059,282 (Ampulski et al.), Issued October 22, 1991, which describes how the density of tissue paper is measured and incorporated by reference here. (Unless otherwise specified, all quantities and weights relative to the paper are on a dry basis.) The tissue paper may be conventionally pressed tissue, patterned densified tissue paper, and non-compacted, densified tissue paper. without pattern These types of tissue paper and methods for making this paper are well known in the art and are described, for example, in U.S. Patent No. 5,334,286, issued August 2, 1994 to D. Phan et al. incorporated herein by reference in its entirety. The fibrous structures formed with the temporary wet strength binder of the present invention tend to have a wet tensile strength in high use and a decay rate of wet strength suitable for the discharge capacity without a significant risk of clog the sewer system under normal conditions of use. The aforementioned tensile properties can be determined as described in the following experimental section.

V. Test Method Section - Wet strength tests The fibrous structures are aged before the stress test a minimum of 24 hours in a conditioned room where the temperature is 22.8 ° C + 2.2 ° C and the relative humidity is 50% + 10%. Both of the wet strength tests in use and disposal are performed on strips of approximately 2.5 cm x 2.7 cm of test material in a conditioned room where the temperature is approximately 22.8 ° C + 2.2 ° C and the relative humidity is 50% + 10%. An electronic voltage tester (model 1122, Instron Corp.) is used and operated at a head speed of approximately 1.3 cm per minute and a reference length of approximately 2.5 cm. The two ends of the test strip are placed in the jaws of the machine and the center of the strip is placed around the stainless steel spigot. The reference to a machine address means that the sample that is tested is prepared in such a way that the 5-inch dimension corresponds to that direction. In this way, for a wet tension resistance in the machine direction (MD), the strips are cut in such a way that the 5-inch dimension is parallel to the manufacturing direction of the fibrous structure machine. For a resistance to wet tension in the transverse direction of the machine (CD), the strips are cut in such a way that the 5-inch dimension is parallel to the cross-machine manufacturing direction of the fibrous structure. Manufacturing directions in the machine direction or transverse to the machine are terms well known in the papermaking art.

The wet tensile strengths in the MD and CD are determined using the above equipment and calculations in a conventional manner. The value reported for the wet tensile strengths in the MD and CD is the arithmetic average of at least eight strips tested for each directional resistance. The wet tensile strength is the arithmetic total of the tensile strength in MD and CD. When using hand-made laboratory sheets, the lengths of inches are cut without taking the orientation into account. The wet tensile strength (in use or removal) is the arithmetic average of the wet strength measured on at least 8 strips. to. Resistance to wet tension in use The wet tensile strength in use is measured by soaking the test strip in a 5% sodium sulfate solution for 2 minutes at 23 ° C, and then measuring the tensile strength by the above description. It is believed that this measurement reflects the conditions that a fibrous structure of the present invention would find when used as a tissue product or as a component in an article for absorbing aqueous fluids. b. Resistance to wet tension elimination The wet tensile strength of removal is measured by soaking a test sample in distilled water for 15 seconds at 23 ° C, followed by measurement by the above description. It is believed that this measurement reflects the conditions that a fibrous structure of the present invention would find when disposed of in a typical sewer system.

The following non-limiting examples are provided to illustrate the present invention. The scope of the invention will be determined by the claims that follow it.

SAW. Representative and comparative examples to. Representative examples EXAMPLE 1 Preparation of a PVAA and a fibrous structure prepared using the PVAA This example illustrates the preparation of a PVAA polymer useful in the binder composition for the fibrous structures of the present invention. The starting PVA has a degree of hydrolysis of about 99%. 2.0 grams of polyvinyl alcohol are added (catalog No. 6, batch No. 6 of Scientific Polymer Products, degree of hydrolysis and average molecular weight in approximate number of 99% and 86 Kg / mol, respectively) to 100 grams of deionized water in a clean 250 mL flask. The flask is gradually heated with stirring until the polymer dissolves. The solution is cooled, and a drop of concentrated H2SO4 previously diluted in 10 mL of deionized water is added. Then add 0.68 grams of propanal (as received from Aldrich chemical). The flask is covered and the mixture is stirred for 22 hours at 23 ° C. The solution exhibits a dark point of 32 ° C. The manual air brush type sprayer is used to spray this solution onto the machine-made paper having a basis weight and a wet tensile strength of 33 g / m2 and < 15 g / in, respectively. The treated paper is dried at 23 ° C at constant weight. The amount of added polymer is 5%, based on the weight of the untreated dry paper. The wet tensions in use and disposal for the treated paper are 284 g / in and < 15 g / in, respectively. In this example, the salt component of the binder composition is introduced via the 5% sodium sulfate solution required for the wet tension resistance test protocol in use. That is, the salt component is not added before the test. (It will be recognized that the addition of the salt prior to the test would still provide superior wet tensile strength in use.) However, it is understood that in most examples (eg, commercial uses or applications) the component salt will be added during the manufacture, and in particular after the addition of the polymer component of the binder, to provide a fibrous structure of the present invention. In this regard, for the purposes of determining whether or not a fibrous structure is within the scope of the accompanying claims, the structure will be tested in accordance with the test methods in the way it is used and / or sold. (ie, if any salt is present in the structure, it will not be removed before the measurement of the wet tensile strength in use or disposal).

EXAMPLE 2 Preparation of a PVAA and a fibrous structure prepared using the PVAA This example illustrates the preparation of another PVAA useful in the binder composition for the fibrous structures of the present invention. The starting PVA has a degree of hydrolysis of about 98-98.8%.

Northern softwood Kraft pulp (NSK) fibers available as Grand Prairie® fibers from Weyerhauser, Inc., Federal Way, WA) are dispersed in water and collected on a Fourdrinier wire using a deckle box. The fibers are dehydrated and dried. The resulting paper sheets have good uniformity and a basis weight of 37 g / m2. 10 grams of Airvol 350 (Air Products, Inc., Allentown, PA) are added at 490 gr. of deionized water in a 1000 mL clean flask and gradually heated with stirring at 95 ° C and maintained for 20 minutes. The solution is cooled, and IN H2SO4 is used to bring the pH to 2.0. Then add 2.15 mL of butanal (as received from Aldrich chemical). The flask is covered and the mixture is stirred for 15 hours at 21-23 ° C. The pH is adjusted to 7.0 - 7.5 with NaOH. The solution exhibits a dark point of 25.0 ° C. The NMR Proton results indicate that the degree of acetalization is 15.5%. A manual air brush type sprayer is used to spray this solution over the handmade paper described above. The sample is a convection oven at 60 ° C at constant weight. The amount of the added polymer is 8%, based on the weight of the untreated dry paper. The tensions in use and disposal are 290 g / in and 11 g / in, respectively. As with Example 1, the salt component of the binder composition is introduced to the fibrous structure of this example via the 5% sodium sulfate solution required for the protocol of the test method in use.

EXAMPLE 3 Preparation of polv (N-isopropilacrylamide) The example illustrates the preparation of a polyacrylamide of formula (I) (y = 0) useful in the binder composition for the fibrous structures of the present invention.

Into a 1 liter round bottom flask is added N-isopropylacrylamide (50.03 g, 0.442 mol), 2,2'-azobis-2-methylpropionitrile (hereinafter "AIBN") (0.3636 g, 0.00221 mol) and t- butanol (250 mL). After the solution is homogeneous, the oxygen is removed by three successive cycles of freezing-pumping-thawing. At the end of the third cycle, the solution is left under positive pressure of argon and placed in an oil bath at 70 ° O, After maintaining the reaction at this temperature for 16 hours, it cools and the contents of the flask are transferred with water to dialysis bags (cut molecular weight 12,000 to 14,000). After dialyzing against water, the contents of the bags are frozen and the poly (N-isopropylacrylamide) is collected by freeze drying A fibrous structure comprising poly (N-isopropylacrylamide) is prepared in the binder composition according to the procedure described in Example 2. A solution of poly (N-isopropylacrylamide) (1.0 wt% in water, exhibiting a dark spot of 32 ° C) (10 mL) is sprayed onto a hand-made sheet of NSK 12 in. 12 in. with a basis weight of 16.5 pounds per square foot (made according to the process described in Example 2) After allowing the water to evaporate for a sufficient time (16 hours), the handmade leaf is sprayed (5.0 mL) with an aqueous solution of 0.6 M sodium sulfate to produce a fibrous structure with a wet tension in use of more than 100 g / in and an elimination stress of less than 30 g / in.

EXAMPLE 4 Preparation of Polv (N-isopropylacrylamide-co-t-butylacrylamide) The example illustrates the preparation of a polyacrylamide copolymer of the formula (I) (and > 1) useful in the binder composition for the fibrous structures of the present invention. Into a 50 mL round bottom flask is added N-isopropylacrylamide (3.592 g, 31.7 mmol), t-butylacrylamide (0.446 g, 3.5 mmol), AIBN (0.0309 G, 0.188 mmol) and t-butanol (20 mL). After the solution is made homogeneous, the oxygen is removed by three successive cycles of freezing, pumping-thawing. At the end of the third cycle, the solution is left under positive argon pressure and placed in an oil bath at 60 ° C. After maintaining the reaction at this temperature for 16 hours, it cools and the contents of the flask are transferred to dialysis bags (interrupted molecular weight of 12,000 to 14,000). After dialyzing against water, the contents of the bags are frozen and the poly (N-isopropylamide-co-butylacrylamide) is collected as a white solid by freeze drying. A fibrous structure comprising poly (N-isopropylacrylamide-co-t-butylacrylamide) is prepared in the binder composition according to the procedure described in Example 3. The fibrous structure has a wet tension in use greater than 100 g / in. and an elimination stress of less than 30 g / in.

EXAMPLE 5 Preparation of polv (N-isopropilacrylamide-co-dimethylaminoethyl acrylate) This example illustrates the preparation of another polyacrylamide copolymer of the formula (I) (and > 1) useful in the binder composition for the fibrous structures of the present invention. This polymer has a cationic character for which absorption is facilitated to cellulosic fibers.

In a 100 mL round bottom flask, N-isopropylacrylamide (9.431 g, 83.3 mmol), N, N-dimethylaminoethyl acrylate (0.3708 g, 2.59 mmol), AIBN (0.0711 g, 0.433 mmol) and t-butanol (50 mL) were added. mL). After the solution becomes homogeneous, the oxygen is removed by three successive cycles of freezing-pumping-thawing. At the end of the third cycle the solution is left under positive argon pressure and placed in an oil bath at 60 ° C. After maintaining the reaction at this temperature for 16 hours, it is cooled and the contents of the flask are transferred to dialysis bags (interrupted molecular weight of 12,000 to 14,000). After dialyzing against water the contents of the bags are frozen and the poly (N-isopropylacrylamide-co-dimethylaminoethyl acrylate) is collected by freeze drying. A fibrous structure comprising poly (N-isopropylacrylamide-co-dimethylaminoethyl acrylate) is prepared in the binder composition according to the procedure described in Example 2. Because the poly (N-isopropylacrylamide-co-dimethylaminoethyl acrylate) is cationic , this can be added to the NSK supply during hand sheet preparation. Consequently, the resulting handmade sheet already contains the polymer, and can be sprayed (5.0 mL) directly with the 0.6 M sodium sulfate to produce a fibrous structure with a wet tension in use greater than 100 g / in and a Elimination stress less than 30 g / in. b. Comparative examples COMPARATIVE EXAMPLE A (PVAB from partially hydrolyzed PVOH) This comparative example demonstrates the low-stress tensile strength of a structure formed using a PVAA formed from a PVA having a relatively low degree of hydrolysis. Northern softwood Kraft pulp fibers (Grand Prairie®) are dispersed in water and collected on a Fourdrinier wire using a deckle box. The fibers are dehydrated and dried. The resulting paper sheets have good uniformity and have a basis weight of 37 g / m2. 10 grams of Airvol 540 (Air Products, Inc.) (hydrolysis degree of approximately 88%) was added to 490 grams of deionized water in a clean 1000 mL flask and gradually heated with stirring at 95 ° C and maintained for 20 minutes. . The solution was cooled and 1N H2SO4 was used to bring the pH to 2.0. (Approximately 1.65 mL of butanal was added (as received from Aldrich chemical)). The flask was covered and the mixture was stirred for 22 hours at 21-23 ° C. The solution had a dark point lower than the ambient temperature. The polymer was collected and dissolved in dimethylsulfoxide (DMSO) slightly acidified at 60 ° C, then cooled. This solution was sprayed on handmade paper. The sample was dried in a convection oven at 60 ° C at constant weight. The amount of the polymer added 13% based on the weight of the untreated dry paper. The tensions in use and disposal were 46 g / in and 8 g / in, respectively.

COMPARATIVE EXAMPLES B TO F Northern softwood Kraft pulp fibers (Grand Prairie®) are dispersed in water and collected on a Fourdrinier wire using a deckle box. The fibers were dehydrated and dried. The resulting paper hand sheets have good uniformity and have a basis weight of 37 grams / m2. Each polymer described in Tables 1 and 2 below was obtained from the commercial source shown, and dissolved in water to give a solution of 2% by weight. Each solution was sprayed on handmade paper. Samples were dried to constant weight at 60 ° C in a convection oven. The amount of polymer added to the paper, based on the weight of the untreated dry paper is shown (varying from 6 to 9%).

Table 1 ^ Polymers shown in Comparative Examples B to F Table 2 Attributes of v results of comparative examples B to F Clearly, these polymers do not provide the combined in-use and elimination stresses that are obtained with the fibrous structures of the present invention. Although the embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, attempts are made to protect all these changes and modifications within the scope of the invention in the appended claims.

Claims (13)

1. A fibrous structure capable of flowing and spreading having a wet tensile strength in use of at least 100 g / in and a wet tensile strength of removal no greater than 30 g / in.

2. The fibrous structure capable of flowing and spreading according to claim 1, characterized in that the structure has a humerus tensile strength in use of at least 200 g / in, preferably at least 300 g / in.

3. The fibrous structure capable of flowing and spreading in accordance with claim 1 or claim 2, characterized in that the structure has a wet tensile strength of removal no greater than 25 g / in.

4. The fibrous structure capable of flowing and spreading according to claim 1, comprising fibers, a salt, and a polymer.

5. The fibrous structure capable of flowing and spreading according to claim 4, characterized in that the polymer is the condensation product derived from the reaction of the polyvinyl alcohol and one or more substituted or unsubstituted C8 C aldehydes.

6. The fibrous structure capable of flowing and spreading according to claim 4 or 5, characterized in that the polymer has a structure according to the formula (I) characterized in that a) x is > 1; b) and it is > 0; c) R1 and R2 are independently selected from hydrogen and C6 alkyl; and d) when y is > 1, (i) R3 is -N (R) (R5), wherein R4 and R5 are independently selected from hydrogen, C ^ Ce alkyl, and aryl; or (ii) R3 is -O- (-CH2-) zN (R6) (R7), wherein z is from 2 to 4 and R6 and R7 are independently selected from hydrogen, C? -C6 alkyl , and aril.

7. A fibrous structure capable of flowing and spreading comprising fibers, a salt, and a polymer which is the condensation product derived from the reaction of the polyvinyl alcohol and one or more substituted or unsubstituted C 1 -Cs aldehydes.

8. The fibrous structure capable of flowing and spreading according to claim 7, characterized in that the polyvinyl alcohol that reacts to form the polymer has a degree of hydrolysis before condensation of at least 95%, preferably at least 98%; and characterized in that the polymer is derived from the condensation of at least 8%, preferably from 10% to 16%, of the hydroxyl groups of starting polyvinyl alcohol.

9. A fibrous structure capable of flowing and spreading comprising fibers, a salt, and a polymer which has the structure according to formula (I) characterized in that a) x is > 1; b) and it is > 0; c) R1 and R2 are independently selected from hydrogen and C? -C3 alkyl; and d) when y is > 1, (i) R3 is -N (R4) (R5), wherein R4 and R5 are independently selected from hydrogen, d-Cß alkyl, and aryl; or (ii) R3 is -O- (-CH2-) z-N (R6) (R7), where z is from 2 to 4 and R6 and R7 are independently selected from hydrogen, C? -C6 alkyl, and aryl.

10. The fibrous structure capable of flowing and spreading according to claim 9, characterized in that y is 0; R1 is hydrogen or C? -C3 alkyl; and R2 is d-C3 alkyl.

11. The fibrous structure capable of flowing and spreading according to claim 9, further characterized in that y is > 1 and a) R3 is -N (R4) (R5) where R4 is hydrogen or C4 alkyl and R5 is CTC4 alkyl; or b) R3 is -O- (-CH2-) z-N (R6) (R7) wherein z is 3 or 3, R6 is hydrogen or C3 alkyl and R7 is C3 alkyl.

12. A disposable absorbent article comprising: A. a liquid-permeable upper sheet; B. a back sheet impervious to liquid; Or an absorbent core placed between the top sheet and the back sheet; characterized in that the top sheet comprises the fibrous structure capable of flowing and spreading from any of claims 1 to 11.

13. A method for making a fibrous structure capable of flowing and spreading having a wet tensile strength in use of at least 100 g / in and an elimination wet tensile strength of not more than 30 g / in, the method comprising the steps of: a) providing (I) fibers and (ii) a first solution comprising a polymer the which has a structure according to the formula (I) characterized in that a) x is > 1; b) and it is > 0; c) R1 and R2 are independently selected from hydrogen and d-Cß alkyl; and d) when y is 1, (i) R3 is -N (R4) (R5), where R4 and R5 are independently selected from hydrogen, d-Cß alkyl, and aryl; or (ii) R3 is -O- (-CH2-) z-N (R6) (R7), wherein z is from 2 to 4 and R6 and R7 are independently selected from hydrogen, C6 alkyl, and aryl; and b) contacting the fibers wthe first solution; c) substantially removing the liquid medium from the fibers to provide a fiber / polymer mixture; and d) contacting the fiber / polymer mixture wa second solution comprising a salt.