MX2008006189A - Absorbent articles comprising acidic superabsorber and an organic zinc salt - Google Patents

Abstract

The present invention relates to an absorbent article, such as a diaper, panty diaper, sanitary napkin or incontinence device comprising a liquid-permeable topsheet, a liquid-impermeable backsheet and an absorbent core enclosed between said liquid-permeable topsheet and said liquid-impermeable backsheet, wherein said absorbent core comprises a superabsorbent material, characterized in that said superabsorbent material is an acidic superabsorbent material having a pH of 5.5 or less and the absorbent core additionally comprises an organic zinc salt, in particular zinc ricinoleate. The combination of organic zinc salt and acidic superabsorber exerts a synergetic effect in the suppression of basic malodours, such as ammonia.

Description

ABSORBENT ARTICLES COMPRISING ACID SUPERABSORBENT AND AN ORGANIC ZINC SALT The present invention relates to an absorbent article such as a diaper, a trainer brief, a sanitary napkin or an incontinence device comprising an effective odor control system. The present invention relates in particular to such absorbent articles wherein an acidic superabsorbent material and an organic zinc salt such as zinc ricinoleate interact in synergistic form to reduce odors such as ammonia.

TECHNICAL BACKGROUND An important area of development in the area of absorbent articles of the type mentioned above is the control of odorous compounds that are typically formed after the release of body fluids, especially over a long period of time. These compounds include fatty acids, ammonia, amines, sulfur-containing compounds and ketones and aldehydes. They are presented as natural ingredients of body fluids or result from the degradation processes of natural ingredients such as urea, which are often facilitated by microorganisms that appear in the urogenital flora.

Several procedures exist to suppress the formation of unpleasant odors in absorbent articles. WO 97/46188, WO 97/46190, WO 97/46192, WO 97/46193, WO 97/46195, and WO 97/46196 teach, for example, the incorporation of additives or deodorants that inhibit odor such as zeolites and silica. The absorption of body fluids however reduces the ability to inhibit the odor of the zeolites as soon as they become saturated with water, as mentioned for example in WO 98/17239. A second procedure involves the addition of lactobacilli with the intention of inhibiting bacteria that form a foul odor in the product. The incorporation of lactobacilli and their favorable effect are described, for example, in SE 9703669-3, SE 9502588-8, WO 92/13577, SE 9801951-6 and SE 9804390-4. Furthermore, it is known from WO 98/57677, WO 00/35503 and WO 00/35505 that partially neutralized superabsorbent materials (acidic superabsorbent materials) counteract the formation of unpleasant odors in absorbent articles. However, the acidic superabsorbent materials absorb lower amounts of body fluid compared to regular superabsorbent materials (hereinafter also referred to as a superabsorbent polymer, SAP).

Therefore, there is a continuing demand in the art for effective odor control systems in absorbent articles. Specifically, it would be desirable to provide an odor control system that allows to reduce the amount of acidic SAP that is used. DE 10256569 A1 relates to polymers containing the acidic group, crosslinked, which absorb water in the form of alveolar cell foam mainly comprising at least one odor control agent selected from the compounds with an anhydride group, compounds with an acidic group, cyclodextrans, bactericides and surfactants with an HLB value of less than 12. An example of bactericidal compounds are zinc compounds such as zinc chloride. The alveolar cell foams according to DE 10256569 Al to which the odor control agent may be added do not represent acidic superabsorbers. In addition, no organic zinc salt is mentioned in this reference. US 2004/0180093 A1 relates to a polymer composition that includes a polymer containing a hydrophilic amine and a bioactive agent selected from silver, copper and zinc compounds. The examples given for the zinc compound include various inorganic salts, zinc acetate and zinc lactate. This polymeric composition is used in medical articles such as dressings for wounds Acidic superabsorbers are not mentioned. US 2004/0024374 A1 is in the name of the present application and relates to an absorbent article having a skin care composition applied in at least a portion thereof. One among many examples of substances for skin care is zinc ricinoleate. The highly absorbent polymers (SAP) mentioned in this document are also not specific. DE 20 2004 015 738 Ul describes an absorbent agent for the reception of moisture and / or odor, characterized in that the absorption agent consists of a mixture of active carbon and a superabsorbent. The activated carbon can be treated with zinc ricinoleate. Acidic superabsorbers are not mentioned in this document. DE 199 29 106 A1 pertains to a diaper comprising an absorbent body and an absorption agent associated therewith, characterized in that this absorption agent is capable of absorbing ammonia. According to the teaching of this document, this can be achieved by using partially neutralized (acidic) SAPs based on polyacrylic acids. According to one embodiment, active carbon impregnated with zinc salts can also be present. Organic zinc salts are not mentioned in this document. US 2002/0128621 Al, US 6,503,526 Bl and WO 00/10500 also mention zinc salts together with absorbent articles, however as a skin care agent in lotions applied in the liquid permeable liner thereof. From other technical areas, it is further known that organic zinc salts of unsaturated hydroxylated fatty acids such as zinc ricinoleate are deodorant active ingredients (see for example, DE 1792074 Al, DE 2548344 Al and DE 3808114 Al). It is a technical object of the present invention to overcome deficiencies discussed above together with the prior art. It is a further technical object to provide an absorbent article that has an efficient odor control system. It is a further technical object of the present invention to reduce or substantially eliminate the formation of ammonia in absorbent articles.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to an absorbent article, such as a diaper, a trainer brief, a pantiprotector, a sanitary napkin or an incontinence device, comprising a liquid-permeable top sheet, a waterproof backing sheet to liquids and a absorbent core contained between the liquid permeable top sheet and the liquid impervious backing sheet, wherein the absorbent core comprises a superabsorbent material, characterized in that the superabsorbent material is an acidic superabsorbent material having a pH value of 5.5 or less and The absorbent core further comprises an organic zinc salt. In the present specification, the acidic superabsorbent material (SAP) having a pH value of 5.5 or less is often simply referred to as an acidic superabsorbent material (SAP). The present inventors have found that the acidic superabsorbent material and the organic zinc salt, such as zinc ricinoleate interact in synergistic manner in the suppression of unpleasant odors and complete the present invention based on this discovery.

DETAILED DESCRIPTION OF THE INVENTION In all of the specification and the claims, the use of "comprising" is intended to also cover the most limiting meanings "consisting essentially of" and "consisting". As "absorbent article" is meant articles capable of absorbing bodily fluids such as urine, watery stools, female discharge or menstrual fluids. These absorbent articles include, but are not limited to diapers, trainers, panty hose, sanitary napkins or incontinence devices (such as those used, for example, by adults) Such absorbent articles have a liquid permeable topsheet, which during use It faces the body of the wearer. They also comprise a liquid-impermeable support sheet, for example, a plastic film, a non-coated plastic or a hydrophobic nonwoven and an absorbent core contained between the liquid-permeable top sheet and the liquid-impermeable backing sheet. A suitable top sheet can be made from a wide variety of materials such as woven and non-woven materials (e.g., a nonwoven fiber mesh), polymeric materials such as perforated plastic films, e.g., thermoplastic films formed by holes and thermoplastic films hydroformed; porous foams; cross-linked foams; crosslinked thermoplastic films; and thermoplastic canvases. Suitable woven and nonwoven materials may be comprised of natural fibers (e.g., wood or cotton fibers), synthetic fibers (e.g., polymer fibers such as polyester, polypropylene fibers) or polyethylene) or a combination of natural and synthetic fibers. When the top sheet comprises a non-woven mesh, the mesh can be manufactured from a wide number of known techniques. For example, the mesh can be spun, carded, wet laid, melted-blown, hydroentangling, combinations of the above or similar. According to the invention, it is preferred to make use of perforated plastic films (for example, thermoplastic films) or nonwoven materials based on synthetic fibers, for example, those made of polyethylene or polypropylene homo or copolymers and polymer compositions based on the same. Optionally, there is at least one additional layer between the absorbent core and the topsheet and can be made of a hydrophobic and hydrophilic mesh or foamed materials. As "mesh material" is meant structures based on coherent flat fibers of tissue paper, woven or non-woven. The nonwoven material may have the same characteristics as described above for the upper sheets. Specifically, at least one additional layer can contribute to fluid handling, for example, in the form of at least one acquisition / distribution layer. Such structures are taught for example by US 5,558,655, EP 0 640 330 Al, EP 0 631 768 Al or WO 95/01147.

"Foamed materials" are also known in the art and for example are described in EP 0 878 481 Al or EP 1 217 978 Al in the name of the present applicant. The absorbent core, which may be partially or completely surrounded by a filling fabric, comprises an acidic superabsorbent material, optionally in admixture with any other absorbent material which is generally compressible, conformable, non-irritating to the skin of the wearer and capable of absorbing and retain fluids such as urine and other body exudates. Examples for other absorbent materials include a wide variety of liquid absorbent materials commonly used in disposable diapers and other absorbent articles such as shredded wood pulp, which is generally referred to as felt or aerial fluff, as well as pleated cellulose wadding; melted-blown polymers, including a co-form; chemically hardened, modified or cross-linked cellulosic fibers; a fabric, including woven and laminated embroidery; absorbent foams, absorbent sponges, non-acidic superabsorbent polymers (such as superabsorbent fibers), absorbent gelling materials, or any other known absorbent materials or combinations of materials. The term "superabsorbent material" is known well in the art and designates water-insoluble, water-swellable materials capable of absorbing multiple of their own weight in bodily fluids. Preferably, the superabsorbent material is capable of absorbing at least about 10 times its weight, preferably at least about 15 times its weight, in particular at least about 20 times its weight in an aqueous solution containing 0.9 wt.% Of chloride of sodium (under usual measurement conditions where the superabsorbent surface is freely accessible to the liquid that is absorbed). To determine the absorption capacity of the superabsorbent material, the EDANA WSP 241.2 standard test can be used. The superabsorbent material may be in any form suitable for use in absorbent articles including particles, fibers, flakes, spheres and the like, particulate form is preferred. Acidic SAPs are based on homo or copolymers comprising at least one polymerizable unit having an acidic group (eg, a carboxylic acid group or a sulfonic acid group) such as methacrylic acid, acrylic acid, maleic acid, vinylsulfonic acid . The corresponding polymers include, but are not limited to poly (meth) acrylic acids, ethylenemaleic anhydride copolymers, polymers and copolymers of vinylsulfonic acids, starch and anhydride copolymers isobutylenemaleic grafted with acrylic acid. These polymers are preferably crosslinked to produce the insoluble materials substantially in water. According to a preferred embodiment of the present invention, the superabsorbent material is a cross-linked homo or copolymer comprising (meth) acrylic acid units, for example, of the type described in EP 0 391 108 A2. The acidic superabsorbent preferably has a pH value of 3.0 to 5.5, more preferably 3.5 to 5.3 and more preferably 4.1 to 5.2. Therefore, the pH is measured using the standard EDANA WSP 200.2 test. Unlike standard SAPs having a pH which lies, for example, in a range of 5.8 or more, the acidic SAPs used in the present invention have a pH of 5.5 or less, with the preferred ranges as defined in US Pat. the previous paragraph. There are two ways to make acidic SAP. One way is to add an acid, for example, citric acid to a standard SAP, so the pH is reduced. The other method is to maintain a low degree of neutralization. A standard SAP has a high percentage (typically at least 70%) of the acidic groups neutralized under the formation of alkali metal salts. In contrast to this, the acidic SAPs manufactured according to this method have a lower degree of neutralization, typically from 15 to 60%. The degree of neutralization and pH correlate strongly, which implies that the acidity of the SAP can be controlled by the degree of neutralization. In view of the foregoing, it is also preferred that the absorbent core comprising the acidic superabsorbent have a pH value of 3.0 to 5.7, more preferably 3.5 to . 5, in particular 4.1 to 5.4 after moistening with synthetic urine. The pH of the absorbent core can be measured very precisely with the following method involving the preparation of a test absorbent core and a pH measurement using the same.

Method 1: Preparation of absorbent cores for testing The absorbent cores of an absorbent core produced in a model plant were drilled. A standard method of a mat forming a core was used in the production of the core in the model plant. The absorbent core consists of a homogeneous mixture of fluff paste and a superabsorbent material. The absorbent core was compacted to a volume of about 8-10 cm3 / g. The size of the perforated cores was 5 cm in diameter, the weight of it approximately 1.2 g. Method 2: Measurement of pH in an absorbent core An absorbent core having a diameter of about 50 mm was prepared according to Method 1. A predetermined amount of Test 1 liquid was added, 16 ml to all samples, thereafter the absorbent core was allowed to swell for 30 minutes. minutes Subsequently, the pH was measured in liquid removed from the samples, using a surface electrode, Flat bottom, Simple Pore Plane type, Hamilton.

Test Liquid 1 (reference is made in Method 2): Synthetic urine contains the following substances: KCl, NaCl, MgSO4, KH2P04, Na2HP0, NH2CONH2. The pH in this composition is 6.0 ± 0.5. The test liquid used is 16 ml of synthetic urine (as defined above) for a single core absorbent body. The absorbent core preferably comprises at least one layer comprising a mixture of fibers and an acidic superabsorbent material, an organic zinc salt and an optionally non-acidic superabsorbent material. As the non-acidic superabsorbent material (also referred to in the present specification as a standard superabsorbent material) are understood to be superabsorbent materials of the type described above that show a pH of, for example, 5.8 or more. Non-acidic SAPs comprising polymerizable units with acidic groups preferably have a degree of neutralization of at least 70%. The fibers present in the absorbent core are preferably also capable of absorbing body fluid as is the case for hydrophilic fibers. More preferably, the fibers are cellulosic fibers such as fluff wood pulp, cotton, cotton linters, rayon, cellulose acetate and the like, the use of cellulosic fluff pulp is preferred. Fluff cellulose pulp can be mechanical or chemical type, chemical pulp is preferred. In the absorbent core and, if applicable, each layer thereof, the total amount of the superabsorbent material (of the acidic and optionally non-acidic type) is preferably 10 to 70% by weight, more preferably 20 to 65% by weight , in particular from 30 to 60% by weight, for example, from 30 to 50% by weight, based on the weight of the complete mixture of the fibers and superabsorbent materials (without organic zinc salt). The weight ratio of the acidic SAP / non-acidic SAP is not particularly restricted (for example, from 5/95 to 95/5, from 10/90 to 90/10, from 20/80 to 80/20), although it would appear to be that the higher amounts of acidic SAP appear to improve the effect of the present invention. Therefore, the weight ratios of the acidic SAP / non-acidic SAP from 100/0 to 50/50 (eg, from 95/5 to 60/40, from 90/10 to 70/30) can preferably be selected depending on the properties that are achieve Very low amounts of organic zinc salts already cooperate with the acidic SAP in a very efficient odor control. A preferred lower weight limit of organic zinc salt (calculated as zinc) appears to be at least 10"5 g per g of dry acidic SAP., the term "dry" used in relation to the acidic SAP is to be understood so that no water has been added to the acidic SAP and that only the water present in the acidic SAP is the inevitable waste water from the manufacture. More preferably, the organic zinc salt is present in amounts of at least 10 ~ 4 g, even more preferably at least 5 x 10 ~ 4g, even more preferably at least 10"3g. In accordance with the most preferred embodiment, the amount of zinc salt is at least 10"2 g of zinc per g of dry acidic SAP. There is no specific upper limit, although for economic reasons, a point may be reached where it may no longer be useful to further increase the zinc content, for example, to values of 0.1 to 1 g of zinc per g of acidic SAP, if this is not accompanied by an improved odor suppression. For example, when 40% of SAP acidic occurs in the absorbent core, the concentration of the organic salt of zinc may be in the range of 0.03 to 30 weight percent. There are no specific restrictions regarding the organic zinc salt that is used. According to the present invention, zinc salts of organic carboxylic acids having from 2 to 30 carbon atoms, in particular from 12 to 24 carbon atoms, are preferably used. The carboxylic acid group can be attached to aliphatic, aliphatic-aromatic, aromatic-aliphatic, alicyclic or aromatic residues, wherein the aliphatic chain or the alicyclic ring or rings may not be saturated and are optionally substituted, for example, with hydroxy or Cl to C4. These salts include zinc acetate, zinc lactate, zinc ricinoleate and zinc abietate. More preferably, the zinc salt is the zinc salt of an unsaturated hydroxy fatty acid having from 8 to 18 carbon atoms. Although there is no specific restriction with respect to the number of unsaturated double bonds or hydroxy groups, those fatty acids having one or two unsaturated double bonds and one or two hydroxyl groups appear to be preferred. The most preferred embodiment is zinc ricinoleate. According to one embodiment of the present invention, the above-described organic zinc salt, such as zinc ricinoleate is activated by an amino acid as in commercially available TEGO® Sorb A30 (Degussa).

The organic zinc salt used in the present invention may also be capable of removing chemically based amine-based malodorous substances, for example, nicotine in cigarette smoke, thiocompuets, for example, allicin in garlic and onions, and acids, for example , isovaleric acid in human sweat, and butyric acid. For example, the zinc ricinoleate which is, for example, marketed by Degussa under the trademark TEGO® Sorb has the additional smell described eliminating the effect by removing the ammonia. The present invention is also not subject to any limitations with respect to the technique for incorporating the organic zinc salt into the absorbent core. Immersion and atomization are preferred. For example, it is possible to treat the fibers present in the absorbent core, preferably cellulosic fluff pulp with a solution of the organic zinc salt prior to or during mixing with the acidic SAP. According to a preferred embodiment, a solution of the organic zinc salt is sprayed onto the fibers, more preferably onto the sheets of cellulosic fluff paste as obtained from the manufacturer. The organic zinc salt solution can be sprayed onto the fluff pulp sheet directly by the manufacturer of these sheets prior to the supply of the sheets to the manufacturer of the sheets. absorbent articles. This is an especially preferred embodiment since it avoids the extra spraying step of the organic zinc salt solution when the absorbent article is made. Alternatively, the fibers are immersed within the solution. The acidic SAP is then added during or after core formation. Alternatively, a core is formed by conventional techniques from the fibers, preferably cellulosic fluff, the core is sprayed during the formation of the core with the zinc salt solution. The acidic SAP is incorporated either during or after the formation of the core, although the mist of the alreformed absorbent core is less preferred. From the information currently available, it would seem however that the most effective technique for achieving zinc incorporation involves treating an alreformed absorbent core comprising a mixture of acidic SAP, fibers, preferably cellulosic fluff pulp and optionally non-acidic SAP with a solution of the organic zinc salt, in particular the zinc ricinoleate solution. According to a preferred application technique, the solution of the organic zinc salt, in particular zinc ricinoleate, is sprayed on one or both sides of the absorbent core, or one or both sides of the individual layers constituting the same.

The solvent used for this solution can be water, a preferably volatile organic solvent such as ethanol or a mixture of water and a water miscible organic solvent such as ethanol. Preferably, the organic zinc solvent is present in the solution in a relatively high concentration, preferably from 1 to 30% by weight. The use of such concentrated solutions ensures that the absorption capacity of the superabsorbent material does not deteriorate more than necessary. Commercially available solutions of organic zinc salts such as TEGO® Sorb A30 available from Degussa (active content of 30% by weight, zinc ricinoleate activated by an amino acid) can also be used. The support sheets avoid the exudates absorbed by the absorbent layer and which they contain with the article by soiling other external articles that may come into contact with the absorbent article, such as sheets and undergarments. In preferred embodiments, the support sheet is substantially impermeable to liquids (eg, urine) and comprises a laminate of a non-woven and a thin plastic film such as a thermoplastic film having a thickness of about 0.012 mm to approximately 0.051 mm. Suitable backsheet films include those manufactured by Tredegar Industries Inc., of Terre Haute, Ind., And sold under the trademarks X15306, X10962 and X10964. Other materials from Suitable backing sheet can include breathable materials that allow the vapors to escape from the absorbent article while still preventing the exudates from passing through the backing sheet. Exemplary breathable materials may include materials such as woven meshes, non-woven meshes, composite materials such as non-woven meshes coated with film and microporous films. The above elements of an absorbent article can optionally be integrated together with other typical items of absorbent articles in a manner known in the art. The following examples and comparative examples illustrate the present invention.

EXAMPLE 1 The circular test absorbent cores having a weight of approximately 1.2 g and a diameter of 5 cm were drilled from an absorbent core produced in a model plant. A standard mat method that forms a core was used in the production of the core in the model plant. The absorbent core consists of a homogeneous mixture of fluff paste and superabsorbent material. The fluff paste used was 0.72 g of Weyerhauser paste (NB 416) and the absorbent material was 0.48 g of an acidic superabsorbent (pH 5.1) named Z3106 from Degussa. The absorbent core was compressed to a volume of about 8-10 cm3 / g. To the absorbent core was added 1.3 ml of a solution of 3% by weight of zinc ricinoleate (available from Degussa under the trademark TEGO® Sorb A30, 1/10 diluted) either by soaking the solution on the surface (on one side ) or by submerging one side of the core into the solution. 1 week after the treatment, the absorbent body was allowed to absorb 16 ml of synthetic urine according to Method 3 as described below, and then allowed to stand at room temperature. After 4 hours, 6 hours and 8 hours the absorption of the synthetic urine was measured the amount of ammonia developed. Five measurements were averaged as the average value. The results are shown in Table 1.

Method 3: Measurement of ammonia inhibition in absorbent nuclei. The absorbent cores were prepared according to Method 1. Test liquid 2 was prepared. The bacterial suspension of Proteus mirabilis was grown in a nutrient broth at 30 ° C overnight. The grafted cultures were diluted and the bacterial count was determined. The final culture contained approximately 105 organisms by me of the test liquid. The absorbent core was placed in a plastic jar and the test liquid 2 was added to the absorbent core, thereafter the vessel was incubated at 35 ° C for 4, 6 and 8 hours respectively, thereafter the samples were They took from the containers using a manual pump and a tube called Dráger. The ammonia content was obtained as a color change in a scale degree in ppm or a volume percentage.

Test liquid 2: The sterile synthetic urine to which a growth medium for microorganisms has been added. Synthetic urine contains mono and divalent cations and anions and urea and has been prepared according to the information in Geigy, Scientific Tables, Vol. 2, eighth edition, 1981, p. 53. The growth medium for microorganisms is based on information from Hook and FSA media for whole-bacteria. The pH in this mixture is 6.6.

EXAMPLE 2 An absorbent core was formed in the same manner as in Example 1 with the sole exception that the aqueous solution added to the absorbent core, either by soaking the solution on the surface (on one side) or by immersing one side of the core within the solution, contained 6% by weight of zinc ricinoleate.

EXAMPLE 3 An absorbent core was formed in the same manner as in Example 1 with the sole exception that the aqueous solution added to the absorbent core, either by soaking the solution on the surface (on one side) or by immersing one side of the core within the solution contained 0.5% by weight of zinc ricinoleate.

EXAMPLE 4 An absorbent core was formed in the same manner as in Example 1 with the sole exception that the aqueous solution added to the absorbent core, either by soaking the solution on the surface (on one side) or by immersing one side of the core within The solution contained 0.3% by weight of zinc ricinoleate.

REFERENCE EXAMPLE An absorbent body was formed in the same manner as in Example 1 with the sole exception that the acidic superabsorbent was replaced by a conventional non-acidic superabsorbent (XZS 91030.03 available from Dow Chemicals). In addition no treatment with zinc ricinoleate was carried out.

COMPARATIVE EXAMPLE 1 An absorbent core was formed in the same manner as in Example 1, with the sole exception that the acidic superabsorbent was replaced by a non-acidic type (Dow XZS 91030.03, available from Dow chemicals).

COMPARATIVE EXAMPLE 2 An absorbent body was formed in the same manner as in Example 1 with the only difference that a treatment with a zinc ricinoleate solution was not carried out. The results in terms of ammonia formation of the reference example, Comparative Examples 1 and 2 and Examples 1 to 4 are shown in the following Table 1. TABLE 1 x Non-acidic supersorber (Dow Chemicals, XZS 91030.03) 2 Acidic supersorber (Z3106, Degussa) 3 Zincrichinoleate EXAMPLE 5 An absorbent core was formed in the same manner as in Example 1 with the sole exception that the commercially available acidic superabsorbant M7125 (BASF, pH 4.9 ± 0.2) was used in place of Z3106 from Degussa.

COMPARATIVE EXAMPLE 3 An absorbent core was formed in the same manner as in Example 5 with the sole exception that zinc ricinoleate was not added thereto. The results in terms of ammonia formation of Comparative Example 3 and Example 5 are shown in the following table 2.

TABLE 2 1 Acid Absorbent (M7125, BASF) 2 Zinc Richolate The above experiments show that the combined use of an acidic superabsorbent and an organic zinc salt such as zinc ricinoleate suppresses the formation of ammonia to a very surprising degree. In considering the fact that a human being can detect the aroma of ammonia at a concentration of 30 ppm, the present invention ensures that during the use of an absorbent article, no ammonia odor will be perceived by the user.

Claims (12)

1. CLAIMS 1. Absorbent article, such as a diaper, a trainer brief, a sanitary napkin or an incontinence device comprising a liquid-permeable top sheet, a liquid impervious backing sheet and an absorbent core contained between the topsheet permeable to liquid. liquids and the liquid impervious support sheet, wherein the absorbent core comprises a superabsorbent material, characterized in that the superabsorbent material is an acidic superabsorbent material having a pH of 5.5 or less and that the absorbent core further comprises an organic salt of zinc. Absorbent article according to claim 1, wherein the absorbent core comprises a mixture of fibers, in particular cellulose fluff pulp, an acidic superabsorbent material and an optionally non-acidic superabsorbent material. Absorbent core according to claim 1 or 2, wherein the total amount of the acidic and non-acidic superabsorbent material is from 10 to 70% by weight, based on the weight of the core (excluding the organic zinc salt). 4. Absorbent core according to claim 1 or 2, wherein the acidic superabsorbent is present in an amount of at least 50% by weight based on the total amount of superabsorbent materials. An absorbent article according to any one of claims 1 to 4, wherein the amount of organic zinc salt is at least 10 ~ 5 g of Zn per g of the dry acidic superabsorbent material. Absorbent article according to any of claims 1 to 5, which is obtainable by treating the absorbent core with a solution of the organic zinc salt. Absorbent article according to any of claims 1 to 6, wherein the absorbent core has a pH value of 3.0 to 5.7, preferably 3.5 to 5.5, in particular 4.1 to 5.4 after moistening with synthetic urine. An absorbent article according to any of claims 1 to 6, wherein the acidic superabsorbent material has a pH value of 3.0 to 5.5, preferably 3.5 to 5.3 and more preferably of 4. 1 to 5.2. 9. Absorbent article according to any of claims 1 to 8, wherein the acidic superabsorbent material is a crosslinked homo- or copolymer comprising (meth) acrylic acid units. Absorbent article according to any of the preceding claims, wherein the organic zinc salt is selected from zinc salts of carboxylic acids which have from 2 to 30 carbon atoms. Absorbent article according to claim 10, wherein the carboxylic acid represents an unsaturated hydroxy fatty acid having from 8 to 18 carbon atoms. 12. Absorbent article according to claim 11, wherein the zinc salt is zinc ricinoleate.