Title of Invention	WATER-ABSORBING POLYSACCHARIDE AND METHOD FOR PRODUCING THE SAME
Abstract	Tho invention furttier relates to a -water-absorbent polysocchnride obtainable by thia procesis, a. water-absorbent polysaccuaride, a composite, a process for producing! a txjmpoaito, a composite produced by this process, the use of the watec-absiorbont polysaccharides or of the composites as -well as the use of polyphosphates.

Full Text

The present invention generally relates to a process for producing a water-absorbent polysaccharide, a water-absorbent polysaccharide obtainable by this process, a water-absorbent polysaccharide, a composite, a process for production of a composite^ a composite produced by this process, the use of the water-absorbent polysaccharides or of the composites and the use of polyphosphafes. Most of the absorption materials used today, which are able to absorb in a short time large quantities of liquids (water, urine), are primarily based upon slightly crosslinked synthetic polymers. These include, for example, polymers and co-polymers based upon acrylic acid or acrylamide, which are not based upon renewable materials and are insufficiently or not at all biologically degradable. In the prior art, however, are described numerous water-absorbing polymers which are based upon polysaccharides and which are at least partially biodegradable. The raw materials for the production of superabsorbers based upon polysaccharides are, however, frequently water-soluble and must be converted into the water-insoluble form, in order to be able to use them as superabsorbers for hygiene applications. EP 0 538 904 Al and US 5,247,072 describe soperabsorbers based upon carboxyalkylpolysaccharides. In the process, the carboxyalkylpolysaccharide is dissolved in water and isolated by drying or precipitation and then thermally crossHnked via internal ester bridges by the reaction of the hydroxyl groups of the polysaccharide skeleton with the acidic carboxyl groups. Since this crosslinking reaction is very sensitive to small changes of the pH value, the temperature or the reaction duration, absorbers with widely varying absorption properties are obtained. The materials are characterized by a high absorption capacity under pressure, which, however, fells to a fraction of the original absorption properties within a few weeks, upon Storage of the absorber. In US 5,550,189 are described absorbers based upon carboxyalkylpolysflccharides, in which the aging stability is improved by'addition of multifunctional crosslinkers, such as, e.g. aluminium salts or citric acid. The production of the absorbers occurs from a common, homogeneous aqueous solution of carboxyalkylpolysaccliaride and crosslinker, in which the components are present in low concentration, isolated together and then thermally crosslinked. The synthesis of these absorbers requires a high energy and time consumption, since the aqueous solutions are only of very low concentration. The improvement of the aging stability in the many exemplary embodiments does not correspond to the demands relevant in practice. EP 855 405 Al deals with the problem of the lacking aging stability of the absorption capacity of swellable starch maleates and proposes as solution an attachment of mercapto compounds to the double bond of the maleic acid substituents. The absorption behaviour of the products, in particular under pressure, is very low; In US 4,952,550 the production of an. absorber based upon carboxymethylcellulose is described, wherein the carboxymethylcellulose in water or organic solvent is treated with multivalent metal salts and a hydrophobising component. A thermal crosslinking is not carried out According to the disclosure, the gel blocking in these absorbers is reduced by the hydrophobising component In the processes known from the prior art for crosslinking of polysaccharides, however, besides the partially low aging stability, it is observed that the homogeneous crosslinking of the polysaccharides hinders the biodegradability of the absorber, since the accessibility for microorganisms is reduced by the restricted swelling. Furthermore, in the crosslinking reactions, known from the prior art, the enzymatic breakdown is inhibited by the additionally introduced substituents [Mehltretter et al., Journal of the American Oil Chemists Society, 47 (1970), pages 522-524] In order to improve these disadvantageous properties, it was proposed to limit the crosslinking of the polysaccharide to the surface area, which, however, as a rule leads to products which da indeed have a satisfactory absorption under pressure, however, are frequently characterized by only an unsatisfactory absorption capacity under normal pressure and above all, caused by the restriction of the crosslinking to the surface area, by a low gel strength compared to homogeneously crosslinked polymers. Low gel strength leads to the formation of fine dust parts during processing processes, such as, for example, sieving or conveying, and thereby to health impacts of the workers involved in the production of the superabspibers. WO 02/096953 Al describes a process for producing soperabsorbers based upon surface-modified polycarboxypolysaccharides, in which an unerosslinked polysaccharide is swollen with water to form a hydrogel, the hydrogel is men mechanically comminuted and dried and men the thus-obtained polymer particles are coated with a solution of a crosslinker and subjected to a surface crosslinking. Disadvantageous in the process described in WO 02/096953 Al is, however, that in the formation of me hydrogel an organic solvent must be added to the water, in order to induce the swelling of me polysaccharide. The addition of the organic solvent however leads to the swollen polysaccharide being extremely "slimy*', which makes their further processing significantly more difficult Furthermore, the organic solvents remain at least partially in the end product, which is questionable for ecological reasons. WO 00/21581 Al also discloses a process in which gels made from crosslinked ipolysaccharides are brought into contact with organic solvents, in order to obtain absorbent polysaceharides with improved absorption properties. Disadvantageous in this process is also above all the use of organic solvents. US 5,470,964 describes the production of an absorber based upon acid group-cpntaining polysaccharides at the surface with multivalent metal ions, which has an improved absorption against pressure. Disadvantageous in this process is that for the improved absorption capacity of the absorber against pressure a relatively thick layer of the surface must be crosslinked and mat according to the disclosure this is only possible with prior swelling of the polysaccharide with large quantities of solvent. In the swollen state the multivalent metal ions can then penetrate deeply enough into the surface. In order to achieve this, the polysaccharide is added to an excess of the aqueous metal salt solution, wherein the water excess lies in a 2-fold to 40-fold amount based upon the polysaccharide. By means of the thick crosslinked surface layer, good absorption values against pressure are indeed achieved, the free swell capacity as well as the retention capacity of the absorber is, however, disadvantageous^ reduced. It is further disadvantageous in the described process that the part of the polysaccharide added last to the crosslinker solution in the production process has available less swelling time and a reduced crosslinker concentration, so mat an ^homogeneous distribution of the crosslinker results upon the surface, whereby wide variations of the absorption properties arise. In general the object underlying the invention is to overcome the disadvantages arising from the state of the art It was • thus an object of the present invention to provide biodegradable, superabsorbent polymers based upon renewable raw materials, which do not have the above described deficiencies. In particular, the absorber should have a high long term storage stability, in which the absorption properties remain as far as possible. At the same time it is intended that the absorber particles have a high mechanical stability, in order to avoid the formation of fine dust parts during processing processes such as, for example, sieving or conveying. Furthermore, regarding the absorption behaviour, the absorbers should not tend to gel blocking, in particular in absorption layers comprising a lot of superabsorber (mostly more than 65 wt % based upon the absorbent layer) and besides a high absorption and retention capacity also possess a high absorption capacity against pressure for water and aqueous solutions. In absorbent layers or cores comprising a lot of superabsorber, and diapers comprising these, a wetting through characterized as leakage is often observed. This, and the gel blocking, are usually due to a slimy swollen hydrogel or at least to slimy components of the hydrqgeL An object of this invention is thus to make available a less slimy hydtogel-forming absorbent polymer, which is suitable for use in hygiene articles. For a good absorption and application behaviour it is necessary mat the absorber has a predominantly insoluble character also in an excess of aqueous solution. Furthermore, the absorbers should be characterized by a particularly good biodegradability and be as free as possible from organic solvents. A further object of the invention is to find a production process for such superabsorbent polymers, which is simple, economical and can be reliably carried out, delivers a uniform product quality and in which small quantities of solvents are used and organic solvents are avoided if possible. Furthermore, it should be possible to cany out the process without the use of lexicologically questionable substances. In addition, an object according to the invention consists in improving the biodegradability of hygiene articles such as sanitary napkins, wound dressings, incontinence articles and diapers. A coatribution to the solution of these objects is made by a process for producing a water-absorbing polysaccharide comprising the process steps: the bringing into contact of an urtcrosslinked polysaccharide with -a polyphosphate or with polyphosphoric acid as crosslinking agent in me presence ! of water to form a polysaccharide gel, whereby the polysaccharide swells; crosslinking of me polysaccharide gel. A further aspect of the present invention is formed by a. process for producing a water-absorbing polysaccharide comprising the process steps: the bringing into contact of a polysaccharide with a crosslinking agent in the present of water to form a polysaccharide gel; drying of the polysaccharide gel; whereby at least the bringing into contact occurs in a kneader. It is hereby preferred that in the kneader as homogeneous and intimate mixing of the crosslinking agent with the polysaccharide as possible occurs. It is preferred mat the crosslinking primarily occurs in the drying step. Also in this embodiment of the process according to the invention, the crosslinking agent is preferably a polyphosphate or polyphosphoric acid. It is furthermore preferred in the process according to the invention that the kneader has at least two kneading shafts. Hie at least two kneading shafts have preferably a contour which at least partially reaches into each other. This is preferably elements attached to the kneading shaft such as disks, paddles, anchors or hooks, which form rotation radii seen from the central axis of the kneading shaft, which overlap with the rotation radii of the element arranged at a farther kneading shaft. This can, for example, be achieved by arranging the kneading shafts at least in sections axially parallel to each other and selecting the distance of the central axis of the kneading shaft at the axially parallel section to be so small that the elements formed on the kneading shaft at least partially overlap during operation of the kneading shaft. It is further preferred in the process according to the invention that at least one part of the elements formed on the kneading shaft are arranged and designed hi such a way that these convey the goods to be conveyed at least partially parallel to the central axis of the kneading shaft, wherein the at least two kneading shafts form a conveying channel which runs at least partially axially at least to one of the kneading shafts. In this way, on the one hand, as homogeneous a mixing Of the polysaccharide with me crosslinking agent as possible can be achieved, and the homogeneous mixture comprising the polysaccharide and the crosslinking agent can be continuously conducted to the crosslinking or drying .step which occurs by means of temperature treatment In connection with the homogenisation it is preferred that in the contact step the portion of already reacted crosslinking agent does not lie above 30 wt %, preferably not above 20 wt % and particularly preferably not over 10 wt. % and even more preferably not over 5 wt %, respectively based upon the crosslinking agent The portion of already reacted crosslinking agent can be determined by subtraction of the detenrinable free crosslinking agent from the originally used amount. In an embodiment of the process according to the invention, the bringing into contact of the polysaccharide and crosslinking agent takes place in a kneader, Whereas the crosslinking or drying step following from the bringing into contact occurs in a device being different torn the. kneader, preferably in a belt drier. A comminution step, such as a chopping or milling step can be provided between tile two steps, in order to increase the surface area of the product to be respectively dried or erosslinked It is further preferred that between the temperatures of the bringing into contact for homogenisation and of the drying or respectively crosslinking there is a temperature difference. The two temperatures differ by at least 10°C, preferably by at least 20°C and particularly preferably by at least 40*C as well as even more preferably by at least 80°C. In an embodiment of the process according to the invention, the temperature during the bringing into contact for homogenisation lies within the range from 2 to 40°C, preferably within the range from 10 to 35°G and particularly preferably within the range from 15 to 30°C. To adjust this suitable temperatures, it is preferred that the temperature of the kneader can be controlled. Hither the bousing surrounding the kneading shafts) or the kneading shafts, optionally with the thereupon arranged elements themselves, or both, can be temperature-controlled. In the process according to (he invention, using the kneader, a kneader energy within the range from 0.01 to 1 MJ/kg, preferably within the range from 0.25 to 0.75 MJ/kg and further preferred 0.3 to 0.7 MJ/kg as well as a specific torque of 0.1 to 70 Nm/I, preferably within the range from 5 to 50 Nm/1 and particularly preferably within the range from 10 to 40 MJ/kg can be applied. Suitable kneaders are among others described in DE 195 36 944 Al, US 5,147,135 and DE 195 33 693 Al. In addition, suitable kneaders can he obtained commercially, for example from List AGr Arisdorf; Switzerland It is generally preferred in Hie process according to the invention that the polysaccharide is a non-crosslinked polysaccharide. The crosslinking agent can be any suitable crosslinking agent, whereby polyphosphate or poryphosphoric acid or a mixture of at least two mereof are. particularly preferred It is further preferred according to the invention to combine polyphosphate or poryphosphoric acid with other suitable further crosslinking agents. Suitable further crosslinking agents are, for example, aluminium chloride or citric acid, as described in WO 02/006953 Al, or polyamines, as described in US 6,734,298 BI. By the use of polyphosphates or polyphosphoric acids as crosslinking agent for polysaccharides according to the process according to the invention, water-absorbent porysaccharides are obtainable which distinguish themselves through an excellent absorption and retention capacity for water, aqueous solutions and body fluids. Furthermore, the water-absorbent polysaccharide obtainable by the process according to the invention is storage-stable, substantially free from residual monomers and organic solvents, only soluble in aqueous liquids to & very small degree and to a large degree biodegradable. The polysaccharides used in the process according to the invention are water-soluble or water-swellable and are used in non-crosslinked form. They can be modified with further groups besides the hydroxyl groups, in particular with such groups which improve the water solubility. To such groups belong, for example, the carboxyl group, the carboxylalkyl group, especially preferred the carboxymethyl group, the hydroryalkyl group, in particular the hydroxymethyl group and/or the hydroxyethyl group, whereby the hydroxymethyl group is especially preferred, as well as the phosphate group. Depending upon the functional modification, the polysaccharides used in the process according to the invention can be based upon electrically charged or upon electrically uncharged polysaccharides. A use of a polysaccharide mixture based upon electrically charged and electrically uncharged polysaccharide is also conceivable. Starches or starch derivatives, such as, for example, hydroxypropyl starches, amylose, amylopectin, cellulose or cellulose derivatives such as, for example, ethyl hydroxyethylcellulose or hydroxypropylcellulose or polygalactomartnanes such as, for example, guar or carob seed flour belong, to the electrically uncharged polysaccharides preferred according to the invention. To the electrically charged polysaccharides preferred according to the invention belong in particular polycarboxypolysaccharides. The polycarboxypolysaccharides preferably used in the process according to the invention are derived either from polysaccharides which do not naturally comprise any carboxyl groups and are provided with carboxyl groups by subsequent modification or they already comprise naturally carboxyl groups and are optionally subsequently provided with further carboxyl groups by modification. To the first group of polysaccharide belong, for example, oxidized starches, carboxylated phosphate starches, oxidized cellulose, carboxymethylcellulose or carboxymethyl starches, wherein of these, carboxymethylcellulose (CMC) is particularly preferred. To the preferred polysaccharides which already comprise naturally carboxyl groups, belong, for example, xanthane, alginate or gum Arabic. Particularly preferably according to the invention, polycarboxypolysaccharides such as, for example, carboxymethyl guar, carboxylated hydroxyethyl or hydroxypropyl cellulose, carboxymethyl cellulose and carboxymethyl starches, oxidized starches, xanthane and mixtures of the individual polycarboxypolysaccharides are used as polysaccharide, wherein the use of carboxymethyl cellulose is most preferred. In principle, polycarboxypolysacccharide derivatives with low and high degrees of carboxyl substitution can be used hi the process according to the invention. In a preferred embodiment they have an average degree of carboxyl substitution within the range from 0.3 to 1.5, particularly preferably polycarboxypolvsaccharide derivatives with a degree of substitution within the range from 0.4 to 1.2 are used in the process according to the invention. In a preferred embodiment of the process according to the invention, the polycaiboxvpolysaccharides ere used with an addition of carboxyl groups-free polysaccharides. Preferably, strongly swelling polysaccharides, such as, for example, polygalactomanine or hydroxyalkyl celluloses are employed. The quantities of carboxyl groups-free polysaccharides to be used for modification are determined by the required property profile, preferably 20 wt %, preferably 10 wt. % and particularly preferably 5 wt % are used, based upon the uncrosslinked polycaiboxypolysaccharide. The carboxyl groups-free polysaccharides can be mixed with the uncrosslinked polycarboxypolysaccharide before the bringing into contact with the polyphosphate or the polyphosphoric acid or mixed with the polycarboxypolysaccharide after the bringing into contact of the uncrosslinked pblycarboxypolysaccharide with the polyphosphate or the polyphosphoric acid. It is also conceivable that the carboxyl groups-free polysaccharides are initially brought into contact with the polyphosphate or the polyphosphoric acid or with an aqueous solution comprising the polyphosphate or the polyphosphoric acid and the thus-obtained mixture is men mixed with the polycarboxypolysaccharide. The carboxyl groups of the uncrosslinked polycarboxypolysaccharides preferably used in the process according to the invention are neutralized to at least SO %, preferably to at least 80 % particularly preferably to at least 90 % and more particularly preferably to 100 %. As neutralization agents, alkali hydroxides such as sodium and potassium hydroxide, sodium and potassium carbonates or hydrocarbonates and ammonium hydroxide and amines have proved themselves. The preferred water-soluble polysaecharides used in the process according to the invention have a high average molecular weight in fhe scope of the molecular weight distribution given by the natural polymer construction and thereby also a high solution viscosity in dilute aqueous solution such as, e.g. carboxymethylcellulose prepared from cotton lint. Preferred are polysaecharides with a solution viscosity in one percent aqueous solution of more man 2,000 mPas. If a polycarboxypolysaccharide is used in the process according to the invention, this should have a solution viscosity in one percent aqueous solution of more than 5,000 mPas and particularly preferably of more than 7,000 mPas. Because of the production process, polysaecharides can comprise varyingly high salt amounts as side components. Typical salt contents of carboxymethylcelluloses preferred as polysaecharides according to fhe invention lie at around 0.5 wt % for food qualities, within the range from around 2 wt. % in technical qualities up to 25 to SO wt % for products in applications as protective colloids. Although the water-absorbing polysaecharides obtained by the process according to the invention have a high tolerance with respect to salt load, the uncrosslinked polysaecharides to be used should have a salt quantity of not more man 20 wt. %, preferably not more than 15 wt %, particularly preferably not more than 5 wt % and even more preferably not more than 2 wt % salt, respectively based upon the weight of the unerosslinked polysaccharide used in the process according to the invention. The physical form of the polysaecharides used in the process according to the invention is unimportant for the properties of the water-absorbing polysaecharides obtainable by the process according to the invention. Thus the polysaecharides can be used, e.g. in the form of powders, fine powders, granulates, fibres, flakes, beads or compacts, wherein the use of powdery materials with a particle size within the range of 1 to 2,000 urn is preferred because of tile simple dosability and conveyability. As polyphosphate or polyphosphoric acid preferably chain polyphosphates (catena-phosphates) or ring polyphosphates (cyclophosphates, also described as "metaphosphates") are used, wherein the polyphosphates are the salts and the esters of polyphosphoric acids. Particularly preferred polyphosphates are compounds of (he composition or M^tHzPnOsfru], whereby compounds of the structure are particularly preferred. Among these, compounds of the composition NanHjPnCWi are preferred, such as for example the "Grahamsche salt", the "Maddrettsche salt", the "Kurrvlsche salt" or "Q%on" used in washing agents. Preferred metaphosphates are compounds of the composition M1,, In the above cited formulae M1 stands for monovalent metal, preferably for sodium or potassium, n has preferably a value of at least 2, preferably at least 10 and even more preferably a value of at least 50, wherein a value of 5,000, preferably of 1,000 and particularly preferably of 100 is not exceeded. In a preferred embodiment of the process according to the invention polyphosphates are used which have been prepared by condensation of dihydrogen monophosphates and in which the H atoms of the acidic groups bound as chain groups are not replaced by metal. The particularly preferred polyphosphates have a composition MntHaPaOjnn], wherein M and n have the above detailed meaning. Preferred polyphosphotic acids •which are obtained by the controlled addition of water to P4Oio or by condensation during heating of HjPO* The polyphpsphoric acids preferred according to the invention have the composition H^aPnPsnf i or (HPOsJn, whereby polyphosphoric acids of the composition (HPOsXj are also described as metaphosphoric acids, whereby n preferably has a value of at least 2, particularly preferably at least 10, even more preferably at least 20 and yet more preferably at least 50, wherein preferably a value of 10,000, particularly preferably of 1 ,000 and even more preferably of 1 00 is not exceeded. With increasing value of n, the above-mentioned composition of approaches the composition (HPOs^ of the metaphosphoric acids. It is further preferred according to (he invention that a polyphbsphate or polyphosphoric acid is brought into contact with the uncrosslinked polysaccharide, in a quantity within a range from 0.001 to 20 wt %, preferably in a quantity within a range from 0.01 to 10 wt. % and particularly preferably in a quantity within a range from 0.05 to 5 wL %, respectively based upon the weight of the uncrosslinked polysaccharide. It is also preferred that the polyphosphate or the polyphosphoric acid is brought into contact with the uncrosslinked polysaccharide in the presence of water at a temperature within a range from 1 5 to 60°C, particularly preferably within a range from 18 to 406C and even more preferably within a range from 20 to 30°C. Most preferably, the bringing into, contact of the polyphosphate or the polyphosphoric acid with the polysaccharide occurs at room temperature. The above mentioned polyphosphates or polyphosphoric acids can be used alone or also in combination with other crosslinkers which are not based upon polyphosphates or polyphosphoric acids, for crosslinkmg of the polysaccharide. As additional crosslinkers which are not based upon polyphosphates or polyphosphoric acids are preferred those crosslinkers which are cited in WO 02/096953 Al as covaleat ionic or post crossHnkrng agents, as well $s those crosslinkers winch are cited in WO 00/21581 Al on page 6 in the first paragraph. The weight proportions between these other crosslinkers which are not based upon polyphosphate or polyphosphoric acids and the polyphosphates or polyphosphoric acids lies preferably within a range from 1:0.01 to 1:50, particularly preferably within a range from 1:0.1 to 1:20 and even more preferably within a range from 1:1 to 1:10. The swelling time is dependent upon the temperature at which the polyphosphate or the polyphosphoric acid is brought into contact with the uncrosslinked polysaccharide as well as from the starting compounds employed and can be easily determined by simple pro-experiments. The first process step of the process according to the invention is preferably men finished when no further volume increase of me polysaccharides as a result of the swelling can be observed. Preferably the bringing into contact of the polyphosphate or the polyphosphoric acid with the uncrosslinked polysaccharide occurs for a time period of 1 minute to 48 hours, particularly preferably from 1 hour to 24 hours and even more preferably from 12 to 20 hours. Preferably the bringing into contact with the uncrosslinked polysaccharide with the polyphosphate or with the polyphosphoric acid occurs at a pH value within a range of 7 to 13, particularly preferably within.a range from 7.5 to 12.5 and even more preferably within a range from 8 to 12. This, is particularly the case if a polycarboxypolysaccharide is used as polysaccharide. By adjusting the pH value within the above given pH ranges, an at least partial neutralization of the carboxyl groups present in the polysaccharide occurs. In addition, the polyphosphorie acid is likewise at least partially neutralized. In a particularly preferred embodiment of the process according to the invention, the bringing into contact of the uncrosslinked polysaccharide with the polyphosphate or the polyphosphorie acid occurs in such a way that initially the polyphosphate or the polyphosphorie acid is dissolved or dispersed in water, in the aqueous solution or the aqueous dispersion of the polyphosphate or the polyphosphorie acid, a pH value is adjusted within a range from 7 to 13, preferably from 7.5 to 12.5 and particularly preferably from 8 to 12, and then the aqueous solution or the aqueous dispersion of the polyphosphate or the polyphosphorie acid is brought into contact with an uncrosslinked polysaccharide. In another particular embodiment of the process according to the invention the bringing into contact of the uncrosslinked polysaccharide with the polyphosphate or me polyphosphorie acid occurs in such a way that the uncrosslinked polysaccharide is initially mixed with the polyphosphate or the polyphosphorie acid under dry conditions and the thus-obtained mixture is then brought into contact with water. In mis way, preferably by addition of acids or bases to the water or to the mixture of the polycarboxypolysaccharide and the polyphosphate or the polyphosphorie acid it is assured that the bringing into contact of me uncrosslinked polysaccharide with the polyphosphate or the pqlyphosphpric acid occurs at a pH value within a range from 7 to 13, preferably from 7.5 to 12.5 and particularly preferably from 8 to 12. hi a further preferred embodiment of the process according to the invention the bringing into contact of the uncrosslinked polysaccharide with the polyphosphate or the polyphosphorie acid occurs in such a way that initially the uncrosslinked polysaccharide is brought into contact with water and then the swollen polysaccharide is brought into contact with the polyphosphate or the polyphosphoric acid. It is also thus assured that, preferably by addition of acids or bases to the water or to the polysaccharide which has been brought into contact with the water or to the polyphosphate or the polyphosphoric acid respectively, that the bringing into contact with the uncrossUnked polysacGharide with the polyphosphate or the polyphosphoric acid occurs at a pH value within a range from 7 to 13, preferably from 7.5 to 12.5 and particularly preferably from 8 to 12. It is further preferred according to the invention that the bringing into contact the uncrossUnked polysaccharide with the polyphosphate or the polyphosphoric acid occurs in the. presence of an additive, whereby the additive can be previously combined with the uncrosslinked polysaccharide or with the polyphosphate or the polyphosphoric acid or added to the uncrosslinked polysaccharide which has already been brought into contact with the polyphosphate or the polyphosphoric acid. If the bringing into contact of the uncrossUnked polysaccharide with the polyphosphate or the polyphosphoric acid occurs in such a way that initially an aqueous solution or an aqueous dispersion of the polyphosphate or the polyphosphoric acid is prepared, which is then added to the polysaccharide, then the additive can also be added to the aqueous solution or the aqueous dispersion of the polyphosphate or the polyphosphoric acid. The additives can be added in a quantity within a range from 0.01 to 20 wt %, preferably in a quantity within a range from 0.1 to 10 wt % and particularly preferably in an amount within a range from 1 to 5 wt %, respectively based upon the weight of the uncrossUnked polysaccharide. Preferred additives are anti blocking additives, which improve the processability of the hydrogel produced and which remain at least partially in the product after drying. Preferred anti blocking additives are native or synthetic fibre materials or other materials with a large surface area, e.g. from the group of silica gels and synthetic silicic acids and water-insoluble mineral salts. Further preferred additives are water-soluble additives from me group of bases salts and blowing agents* As blowing agents are selected inorganic or organic compounds which liberate gas raider the influence of catalysts or heat, for example azo and diazo compounds, carbonate salts, ammonium salts or urea. Further additives are pH regulators such as e.g. alkali metal hydroxides, ammonia, basic salts such as e.g. alkali metal carbonates or acetates. Further additives are neutral salts, such as, e.g. alkali metal or alkaline earth metal sulfates or chlorides for regulation of the ionic strength of the solution or of the .salt content of me powdery absorber resin. Furthermore, water-miscible organic solvents, preferably boiling under 100°C can be used as additive in. the aqueous hydrogeL During the following drying these volatile organic solvents substantially escape from the hydrogeL These solvents are then finally volatilised during the subsequent surface post-crbsslinldng. The bringing into contact of the uncrosslinked polysaccharide with the polyphosphate or the polyphosphoric acid in the presence of water can occur continuously or diseontinuoxtsly, preferably continuously. Suitable mixing devices are e.g. discontinuous kneaders such as VAT kneaders, interior mixers or continuous kneaders such as one-, two- or multishaft mixers. During the production of the polysaccharide gel in the first process step of the process according to the invention, the polysaccharide content in the mixture of polysaccharide, water and polyphosphate. or polyphosphoric acid can vary within wide limits, in a preferred embodiment of the process it lies within the range from 5 to 65 wt %, particularly preferably 10 to 50 wt % and even more preferably 15 to 30 wt. %. In a preferred embodiment, respectively the water, the aqueous solution or aqueous dispersion of ue polyphosphate or the polyphosphoric acid is continuously added to me dry raw material polysaccharide, for example in an. extruder, whereby the process is carried out in such a way that me water is present as minority component The mixture of polysaccharide, polyphosphate or polyphosphoric acid and water can additionally comprise according to the invention up to 30 wt. %, preferably up to 20 wt. % of one or more organic solvents which are miscfble with water and immiscible with the polysaccharide. However, preferably, the bringing into contact with the uncrosslinked polysaccharide with the polyphosphate or with the polyphosphoric acid occurs in the absence of an organic solvent It has proven to be particularly favourable if the swollen gel is comminuted before the crosslinking. Through the gel comminution, above all the ratio of gel surface to gel'volume is increased, whereby me following drying step requires substantially less energy input. The process of gel comminution does not underlie any restriction. In a particularly preferred embodiment, the gel comminution occurs by pressing the gel through a breaker plate into gel strands, which can optionally be fragmented into shorter gel strands by 9 cutting apparatus. The. gel consistency can be purposely adjusted via the type and the amount of the addition of polyphosphates or polyphosphoric acids. A use of organic solvents in this regard, as described in WO 02/096953 Al, is here surprisingly riot necessary. In the second step of the process according to the invention the polysaccharide gel or the comminuted polysaccharide gel is crpsslinked to form a crosslmked polysaccharide and preferably dried at the same time to a low residual water content It is also conceivable to first crosslink the polysaecharide gel under conditions which do not lead to a drying of the polysaccharide gel and only then to dry the crosslinked polysacpharide gel. The crosslinking step can follow directly from the pre-swelling, but it is also possible to store the polysaccharide gels or the comminuted polysaccharide gels respectively before further processing, for a longer period of time, e.g. several weeks, without the properties of the therefrom-resulting soperabsorber according to the invention changing. Preferably the polysaccharide gel is crosslinked and thereby preferably dried at the same time at a temperature of 70°C, preferably above 100°C and particularly preferably above 115°C, whereby preferably a crosslinking or drying temperature respectively of300°C, particularly preferably of 250°C and even more preferably of 200°C is not exceeded. It is also conceivable to first dry the polysaccharide gel at lower temperatures than 70°Q preferably under reduced pressure, and only then to heat by increasing the dried polysaccharide to a temperature which enables a crosslinking of the polysaccharide. In principle, the crosslinking step can be carried put at any conceivable temperature, as long as the temperature is high enough to enable an at least partial crosslinking of the polysaccharide gel by the polyphosphate or the polyphosphorie acid and does not exceed a temperature which leads to degradation of the polysaccharide. Attention should be paid with the crosslinking or drying temperatures respectively that the parameters such as the polymer content of the gel, the pH value of the mixture, the mixing process, the crosslinking or drying temperature respectively and the duration of drying influence each other and are preferably selected in conjunction with each other in such a way that during the crosslinking of the polysaccharide with the polyphosphate or the polyphosphorie acid no internal crosslinking of the hydrogel occurs. If, e.g. in the production of the polysaccharide gel an aqueous solution with a pH value below 7 is used, when using polycarboxypolysaccharides a part of the carboxylate groins present in the polysaccharide derivative is converted into :the free acid form, which above all towards the end of the drying can function as internal crosslinkers by means of an esterification with the hydroxyl groups. In order to avoid or as far as possible suppress this, in principle undesired, internal crosslinking, me crosslinking. or drying respectively in these cases occurs preferably at temperatures within the range from 70 to 100°C. The pH value is usually adjusted to 6 or higher. In a preferred embodiment of the invention, for the production of the polysaccharide gel an aqueous solution is selected with a pH value of > 7 and the crosslinking or drying respectively carried out at temperatures above 1104C, preferably above 115tol20°C. Various processes are known for the drying of the polysaceharide gels. Possible processes are, e.g. vapour drying, evaporation drying, radiation drying (example: infrared drying), high frequency drying (example: microwave drying), vacuum drying, freeze drying or spray drying. The drying can thus occur for example according to the thin film drying process, e.g. with the aid of a two axis roll dryer according to the plate drying process, according to which the hydrogel polymer particles are loaded onto plates in several layers in a drying chamber, in which hot air circulates, according to the rotating drum process using roll dryers or according to the conveyor belt process, in the following also described as belt drying. Belt drying, in which trays provided with holes of a circular conveyor in a tunnel is charged with product to be dried and product is dried during the conveying by the blowing of hot air through fee tray holes, represents the most economical drying process for water-swellable hydrophilic hydrogels and is, therefore, preferred. The moisture of the polymer obtained by drying the polysaccharide gel advantageously does not lie above 30 wt %, preferably not above 15 wt % and particularly preferably not above 10 wt. %. If the polysaccliaride gel is produced in a continuous mixer, for example in an extruder, the initial products which are not yet post-erosslmked at the surface can, at pH values of 7 and above, have high retentions of greater than or equal to 40 g/g, which prove to be stable upon tempering above 60 minutes and 120°C and only differ slightly from products which have been prepared with higher pH values. If the hydrogels are prepared, on the other hand, in a batch process, the stability with respect to a tempering increases with increasing pH value of the gel. A preferred pH setting for the formation of hydrogel in the batch process therefore lies at pH 10 or above. In a further embodiment of the process according to the invention, in an additional process step the crosslinked polycarboxypolysaccharide obtained after the drying of the polysaecharide gel or respectively the comminuted polysaceharide gel is milled in a further process step. Through the comminution of the polysaccharide gel as well as by the milling of the dried, crosslinked polycarboxypolysaccharide, paniculate, crosslinked polysaccharides are obtained. For the subsequent milling of the dried polysaccharide gels or respectively the dried and previously comminuted polysaccharide gels it is advantageous to cool the product to be dried in the last section of the preferred belt drying to temperatures By means of the subsequent sieving, the particle size distribution is adjusted, which generally lies between 10 and 3000 urn, preferably between 100 and 2000 um and particularly preferably between 150 and 850um. Particles which are too course can be subjected to the milling again, particles which are too fine can be recycled in the production process. In a particular embodiment of the process according to the invention a further process step follows the drying step or the milling step respectively, in which the particulate, crosslinked polysaccharide is post-crosslinked in the outer part of the particle with a post-crosslinking agent As outer part of the particle is understood preferably each volume element of the particle whose distance to the center of the particle is at least 75 %, preferably at least 85 % and particularly preferably at least 95 % of the outer radius of the polymer particle. The surface crosslinking of the dried, partieulate, crosslinked polycarooxypolysaccharide occurs preferably with 0.001 to 25 wt. %, particularly preferably with 0.1 to 20 wt % of the post-crosslinking agent, respectively based upon the weight of the crosslinked polysaccharide. The post-crosslinking agent is preferably used in the form of a 0.01 to 80 wt %, preferably a 0.1 to 60 wt % solution. The addition of the post-crosshaking agent occurs in. suitable mixing aggregates. These are, for example, Pattersoh-Kelly-mixer, Drais turbulence tnixer, Lodige mixer, Ruberg mixer, worm mixer, plate mixer, fluidised bed mixer or Schugi mixer. After spraying on the solution of the post-crosslinking agent, a temperature treatment step can follow, preferably in a downstream drier, at a temperature between 40 and 250°C, preferably 60 to 200°C and particularly preferably 80 to 160°C over a time period of 5 minutes to 6 hours, preferably 10 minutes to two hours and particularly preferably 10 minutes to 1 hour, whereby solvent parts are removed. The optimal duration of the post-heating can be easily determined for individual crosslinker types with a small number of erpenments. It is limited by the fact that the desired property profile of the superabsorber may be destroyed again as a result of heat damage. The thermal treatment can be carried out in conventional driers or ovens, for example rotary kiln ovens, fluidised bed driers, plate driers, paddle-driers or infrared driers. It has partially proved advantageous that the aqueous solution of the surface post-crosslinker is adjusted before its use to a temperature of 15°C to 100°C, preferably to20BCto60°C. The covalent surface post-crosslinking can optionally be accelerated by catalysts. Compounds which catalyse the esterification reaction between a carboxyl group and a hydroxyl group, such as, for example, hypophosphite, acetyl acetonate mineral acids are preferably used as catalysts, such as e.g. sulphuric acid and Lewis acids. Preferably sulphuric acid and hypophosphite are used. The weight ratio of surface post-crosslinker to crosslinking catalyst is 1:0.001 to 1:1, preferably 1:0.1 to 2:1. In a preferred embodiment the crosslinking catalysts are mixed with the solution of the surface post-crosslinker. A post-crosslinking solution can optionally comprise, up to 70 wt % of one or more additives. Additives are, above all, water-soluble compounds, which lead to the homogeneous distribution of the crosslinker solution on the surface of the absorber, in mat they slow down the penetration of the solvent into the interior of the superabsorber particle as well as reducing the solubility of the particle surface and thereby die tendency of the moist superabsorber particles to stick together. Preferred additives are, besides water-miscible organic solvents such as, for example, ethanql, propanol, 2-propanol, acetone, glycerine, tetrahydrofuran and dioxane, also water-soluble hydrophilic. organic solids, in particular polymers such as, e.g. polyalkylene glycols, polyvinyl alcohols, preferably polyethylene glycols. The post-crosslinking of the outer part can be carried out by ionic or covalent post-crosslinking agents, which react with the functional molecular groups near to tiie surface, preferably carboxyl, carboxylate or hydroxyl groups, preferably by heating. As covalent post-crosslinking agents, which can also be used in combination with ionic crosslinkers, such crosslinkers are used, which react with functional groups of the polysaccharides to form covalent bonds. In a preferred embodiment, crosslinkers are used which can react with the hydroxyl groups, or if using, polycarboxypolysaccharides, with the carboxyl groups of the crosslinked polysaecharide, for example substances comprising add groups. In particular, low molecular polycarboxylic acids and derivatives thereof, such as, e.g. malonic acid, maleic acid, maleic acid anhydride, tartaric acid and polymeric polycarboxylic acids, e.g. based upon (meth)acrylic acid and/or maleic acid are suitable. Preferred are citric acid, butane tetracarboxytic acid and polyacryUc acid, particularly preferably citric acid is used. The polycarboxylic acids can also be used in partially neutralized form, e.g. by partial neutralization with alkali hydroxides or amine bases. Besides these post-crosslinking agents, in particular also polyphosphates and polyphosphoric acids are preferred as post-crosslinking agents, whereby preferably those polyphosphates and polyphosphoric acids are used which have already been cited in the context of the first process step of the process according to the invention. Suitable ionic post-crosslinking agents which can be used alone or in combination with the covalent post-crosslinking agents are salts of at least divalent metal cations, for example alkaline earth cations such as Nig2"1", Ca2+, as well as Ala+, Ti4+, Fe2+/Fe3+, Zn*" or Zr4*, whereby A13+, Ti44" and Zr4* are preferred and Al3* is particularly preferred. Aluminium salts are preferably used in a quantity of 0.2 to 1.0 wt. %, preferably 0.25 to 0.85 wt. %, based upon the crosslinked polysaccharide. The salts of me metal cations can be used alone or mixed with each other. The metal cations in the form of their salts have a sufficient solubility in the solvent used, particularly preferably the metal salts are used with complexed anions such as, e.g. chloride, nitrate, sulphate and acetate. Further'suitable post-crosslinking agents are such ones which can form both covalent and ionic orosslinking bonds, e.g. di- and polyamines which can function as both covalent crosslinkers via amide groups, and as ionic crosslinkers via ammonium salt complexes. In a particularly preferred embodiment of the process according to the invention, polyphosphates or polyphosphoric adds are used as post-crosslinking agent, in another, particularly preferred embodiment, a mixture of polyphosphates or polyphosphoric acids and at least one further of the above-mentioned post-crosslinking agents, which is not based upon polyphosphates or polyphosphoric acids, in particular mixtures of polyphosphates or polyphosphoric acids and ionic post-crosslinking agents are used, whereby mixtures of polyphosphates or polyphosphoric acids and aluminium salts are particularly preferred. hi the use of polyphosphates or polyphosphoric acids as post-crosslinking agent, these are preferably used in the form of an aqueous solution with a pH value within a range from 7 to 13, particularly preferably within a range from 8 to 12. In the use of polyphosphates or polyphosphoric acids as post-crosslinking agent, it is further preferred that the polyphosphates or the polyphosphoric acids are used in a quantity within a range from 0.01 to 10 wt, %, particularly preferably in a quantity within a range from 0.1 to 5 wt. % and particularly preferably in a quantity within a range from 0.3 to 1.5 wt %, respectively based upon the weight of the crosslinked polysaecharides. hi connection with the post-crosslinkuig of the crossHnked polysaccharidea, it is preferred in a particular embodiment of the process according to the invention that the crosslinked polysaceharide is brought into contact with an inorganic material. As inorganic material, any inorganic material, preferably paniculate, known to the skilled person, can. be brought into contact With the crossHnked polysaecharides, which is suitable for modifying the properties of water-absorbent polymers. To the preferred inorganic materials belong silicates, in particular scaffold silicates such as- zeolites or silicates which have been obtained by drying aqueous silicic acid solutions or silica sols, for example the commercially obtainable products such as precipitated silicic acids and pyrogenic silicic acids, for example aerosils, aluminates, titanium dioxides, zinc oxides, day materials and further minerals familiar to the skilled person as well as carbon-containing inorganic materials. Preferred silicates are all natural or synthetic silicates disclosed in "Hollemah and Wiberg, Lehrbuch der Anorganischen Chemie, Walter de Gruyter Verlag, 91* to 100th edition, 1985" on sides 750 to 783, as silicates. The above-cited part of mis textbook is hereby introduced as reference and forms part of the disclosure of the present invention. Particularly preferred silicates are the zeolites. As zeolites, all synthetic or natural zeolites- known to the skilled person can be used. Preferred natural zeolites ate zeolites from the natrolite groups, the harmotone groups, the mddenite groups, the chabasite groups, the faujasite groups (sodalite groups,) or the analcite groups. Examples of natural zeolites are Analcime, Leucite, Pollucite, Wairakite, Bellbergite, Bikitaite, Boggsite, Brewsterite, Ghabazite, Willhendersonite, Cowlesite, Dachiardite, Edingtonite, Epistilbite, Eriomte, Faujasite, Ferrierite, Amicite, Garronite, Gismondine, Gobbinsite, Gmelintte, Gonnardite, Goosecreekite, Harmotome, Phfllipsite, WeHsite, ClinoptiloUte, Heulandite, Laumontite, Levyne, Mazzite, Merlinoite, Montesommaite, Mordenite, Mesolite, Natrolite, Scolecitei Oflretite, Paranatrolite, Paufingite, Perlialite, Barreritc, Stilbite, Stellerite, Thomsonite, Tschemichite oder Yugawaralite. Preferred synthetic zeolites are zeolite A, zeolite X, zeolite Y, zeolite P, or the product ABSCENTS. As zeolites, zeolites of the so called ^medium" ("rnittlere") type can be used, in which, the SiCVAIOz ratio is smaller than 10, particularly preferably the SiCVAlCh ratio of these zeolites lies in a range of 2 to 10. Besides these "medium" zeolites, zeolites of the "high" ("hohe") type can furtheimore be used, to which belong for example the known "molecular sieve" zeolites of the type ZSM as well as p-zeolites. These"high" zeolites are preferably characterized by a SiO2/AlO2 ratio of at least 35, particularly preferably by a Si(VA102 ratio in a range of 200 to 500. As aluminates are preferably used the naturally occurring spinals, in particular common spinal, zinc spinal, iron spinal or chromium spinal. Preferred titanium dioxides are titanium dioxide in the rutile, anatase and brookite crystal forms, as well as iron-containing titanium dioxides such as, for example, ilmenite, calcium-containing titanium dioxide such as titanite or perowskite. Preferred clay materials are those which are disclosed as clay materials in "Holleman and Wiberg, Lehrbucnder Anorganischen Chemie, Walter de Gruyter Verlag,^!81 to 100* edition, 19§5" on pages 783 to 785. The above-cited part of this textbook is hereby introduced as reference and forms part of the disclosure of the present invention. Particularly preferred clay materials are kaolinite, fllite, hatloysite, montmorillonite and talc. Preferred carbonHxmtaining» but not organic materials are those carbons which are cited as graphites in "Hotteman and Wiberg, Lehrbuch der Anorganischen Ohemie, Walter de Gruyter Verlag, 91* to 100* edition, 1985" on pages 705 to 708. The above-cited part of this textbook is hereby introduced as reference and forms part of the disclosure of me present invention. Particularly preferred graphites are artificial graphites such as, for example, coke, pyrographite, active carbon or soot. When using the above-mentipned inorganic materials or mixtures thereof, it is particularly preferred that these materials, in a quantity within a range from 0.1 to 1 wt. %, more preferably in a quantify within a range from O.I to 1 wt %,, more preferably in a quantity within a range from 0.25 to 0,75 wt. % and even more preferably within a range from 0.4 to 0.6 wt. %, based upon the total weight of the crosslinked polysaccharides, are brought into contact with the crosslinked polysaceharides. It is furthermore preferred according to the invention that the inorganic materials have a specific surface area determined according to the BET method within a range from 30 to 850 m2/& preferably within a range from 40 to 500 m2/g, particularly preferably within a range from 100 to 300 m2/g and even more preferably within a range from 150 to 250 m2/g. In general, and in me case mat the inorganic materials are siperaates or aerosils, the surface area lies within a range from 30 to 850 mVg, preferably within a range from 40 to 500 m2/g, particularly preferably wimin a range from 100 to 300 m2/g and is determined using nitrogen in an Areameter according to ISO 5794, Annex D. When using inorganic materials in the form of particles it is further preferred mat at least 90 wt %, preferably at least 95 wt % and even more preferably at least 99 wt. % of the inorganic material has a particle size of less than 200 uon, particularly preferably less than 100 um and even more preferably of less than 1 jim and even more preferably of less than 500 inn and yet more preferably of less than 100 nm. The sipetnates have a particle size within the range of 10 to 180 nm, preferably within the range of 20 to 150 jtm and particularly preferably within the range from 30 to 110 um. The sipemates have, in another embodiment of the process according to the invention, a particle size within fhe range from 1 to 40 urn, preferably within the range from 2 to 30 urn and particularly preferably within the range from 3 to 20 uin. These are respectively the average particle sizes determined according to the Multisizer Capillary Method according to ASTM C690-1992. Aerosils .are characterized by a particle size within the range from 5 to 50 nm, preferably within the range from 8 to 20 nm (such as "Aerosil 200" from Degussa AG). The particle size cart be determined according to ASTM C690-I992 with a multisizer. When using inorganic materials it is farther preferred that the bringing into contact of the crosslinked polysaecharide with the inorganic material preferably occurs in the presence of a "binding agent". This is preferably provided as a solution, when bringing it into contact. This solution is preferably an aqueous solution. As binding agent are considered all organic polymers which appear suitable to the skilled person. Particularly preferred polymers have a melting point according to ISO 11357 within the range from.-15 to 150*0, preferably within the range from -12 to 100QC and particularly preferably within the range from -9 to 90°C. As binding agents polyethylene glycols are preferred. The binding agents are preferably present as a film. This film is located preferably on the surface of the water-absorbing polysaecharide according to the invention. This film preferably has a thickness within the range from 0.001 to 20 nm, preferably within the range from 0.01 to 15 nm, and particularly preferably within the range from 0.1 to 10 nm. The thickness can, for example, be measured by means of suitable microscopes. In mis. case, an average of at least 10 sections should be formed. It is also possible mat the film only covers part of the surface of the water-absorbing polysaccharide according to the invention. Usually suitable as binding agent are polymeric materials wira a molecular weight of more than around 290 g/mol, which have a corresponding melting temperature and at a corresponding application temperature do not show any degradation or other change in molecular structure which would be disadvantageous for the sticking effect The number weight of the molecular weight (Mn) of the polymers which can be used as binding agent, determined by gel permeation chromatography (GPC), preferably lies within the range from 290 and up to 1,000,000, particularly preferably within the range from 1,000 to 100,000 and yet more preferably within the range from 5,000 to 20,000 g/moL The molecular weight distribution of the cited polymers that can likewise be determined by gel permeation chromatography (GPC), can. be monomodal. A polymer usable as binding agent can optionally also have a by- or higher modal distribution. It is further preferred, when using binding agents, that these are used in a quantity within a range from 0.001 to 10 wt. %, preferably 0,01 to 5 wt % and even more preferably O.OS to 2,5 wt. %, based upon the total weight of the crosslinked polysaccharide. If using inorganic materials, optionally in combination with binding agents, these additional components can be brought into contact with the polysacchaiides before the post-crosslmking, during the post-crossUnking or also after the post-crosslinking of the crosslinked polysaccharides, whereby the addition of these components after the post-crosslinking is particularly preferred. If the addition of the inorganic material and the binding agent occurs before the post-crosslinking of the crosslinked polysaccharides, the post-crosslinking and the adhesion of the inorganic material can be carried out at the same time by heating the polysaccharide to a temperature within the range from 100 to 160°C and preferably fjom 120 to 140°C. The invention also relates to a water-absorbent, at least partially neutralized polysaccharide which is obtainable by the above described process. The water-absorbing polysaccharide obtainable by the process according to the invention is characterized by an excellent absorption and retention capacity for water, aqueous solutions and body fluids. At the same time it has available, by means of the targeted crosstinking of the surfaces, a clearly improved absorption capacity for aqueous solution against an external pressure. The water-absorbing polysaccharide obtainable by the process according to the invention is, furthermore, stable upon storage, substantially free from residual monomer parts and organic solvents which frequiently occur in the production of polyacrylates, only slightly soluble in aqueous liquids and, to high degree, biodegradable. The present invention further relates to a particulate, water-absorbent polysaccharide, whereby the polysaccharide is crosslinked with a polyphosphate or with polyphosiphoric acid in a quantity within a range from 0,001 to 20 wt. %, preferably in a quantity within a range from 0.01 to 10 wt % and particularly preferably in a quantity within a range from 0.05 to 5 wt %, respectively based upon the weight of the polysaccharide. The invention additionally relates, in a farther embodiment, to a particulate water-bsorbent polysaccharide, preferably wife at least 5 wt % and particularly preferably at least 90 wt %, respectively based upon the water-absorbent polysaccharide, of a branched polysaccharide, preferably cellulose and/or derivatives thereof whereby the water-absorbing polysaccharide has a surface part coated with an inorganic particle. It can additionally be preferred that the water-absorbent polysaccharide according to the invention also has a binding agent at least in die surface part The water-absorbent polysaccharide according to the invention has inorganic particles preferably in a quantity within the range from 0.001 to 20 and particularly preferably within the range from 0.01 to 10 wt %, respectively based upon the water-absorbent polysaccharide according to the invention. Independent thereof, the water-absorbent polysaccharide according to the invention has binding agent preferably in a quantity within the range from 0.001 to 20 and particularly preferably within me range from 0.01 to 10 wt %, respectively based upon the water-absorbent polysaccharide according to the invention. As polysaccharides are preferred those polysaccharides which have already been cited in connection with the process according to the invention for producing a water-absorbent polysaccharide^ whereby the same is also true for inorganic particles and for binding agents. In a preferred embodiment, the water-absorbent polysaccharide according to the invention is present in an average particle diameter determined according to BELT 420.1-99 within a range from 1 to 2,000 urn, preferably within a range from 100 to 1,000 um and particularly preferably within a range from ISO to 850 urn. It is furthermore preferred mat at least SO wt %, preferably at least 75 wt % and particularly preferably at least 100 wt % of the water-absorbent polysaccharide according to the invention has a particle size determined by sieve analysis within the range from 300 to 600 um. It is further preferred that the particutate water-absorbent polysaccharide according to the invention has at least one, preferably all of the following properties: (al) an AUL value determined according to the herein-described test method at a pressure of 0.9 psi within a range from 10 to 22 g/g, particularly preferably within a range from 12 to 19 g/g and even more preferably within a range from 14 to 17 g/g at a CRC value detennined according to the herein-described test method within a range from > 15 to (o2) an AUL value at a pressure of 0.9 psi determined according to the herein-described test, method within a range from 6 to 20 g/g, particularly preferably within a range from 8 to 17 g/g and even more preferably within a range from 10 to 14 g/g at a CRC value determined according to the herein-described test method within a range from > 20 to (a3) an AUL value at a pressure of 0.9 psi determined according to the herein-described test method within a range from 6 to IS g/g, particularly preferably within a range from 7 to 12 g/g and even more preferably within a range from 8 to 10 g/g at a CRC value detenmned according to the herein-described test method within a range from > 25 to (a4) an AUL value at a pressure of 0.9 psi determined according to the herein-described test method within a range from 5 to 12 g/g, particularly preferably within a range from 6 to 10 g/g and even more preferably within a range from 7 to 9 g/g at a CRC value detenmned according to the herein-described test method of > 30 gfe- In principle, each of the above figures or a combination thereof represents a preferred embodiment of the present invention. Preferred particulate water-absorbent polysaccharides according to the invention are those which are characterized by the following properties or property combinations: ol, o2, o3, o4, oS, 0.6, alo2, ala3, ala4, a2a3, a2a4, a3a4, alo2a3, ala3a4, ct2a3a4, ala2a3a4. It is further preferred that the particulate water-absorbent polysaccharides according to the invention have at least one, preferably all of the following properties: (pi) a biodegradability determined according to the herein-described test method of at least 40 % in 90 days, preferably of at least 50 % in 90 days and even more preferably of at least 65 % in 90 days and even more preferably of at least 75 % in 90 days; (P2) an extractable part determined according to ERT 470.2-99 within a range from 5 to 60 %, preferably within a range from 8 to 30 % and even more preferably within a range from 10 to 20 %; (P3) a value for the Gel Bed Permeability determined according to the herein-described test method within a range from 1 to 500, preferably within a range from 5 to 300 and even more preferably within a range fiom 20 to 200 x 10"' cm2, hi principle, each of the above figures or a combination thereof represents a preferred embodiment of the present invention. Preferred particulate water-absorbent polysaccharides according to the invention are those which are characterized by the following properties or property combinations: 01, P2, P3, plp2, Plp3, P203, Plp2p3. In another embodiment of the water-absorbent polysaccharide according to the invention, a biodegradability determined according to the herein-described test method is present wimin a range from 25 to 50 % in 45 days and Within a range from more than 50 to 90 % in 90 days, preferably of at least 28 % in 45 days and of at least 51 % in .90 days. It is further preferred in connection with the particulate water-absorbing, at least partially neutralized pelysaccharides according to the invention, that these have a "sliminess " determined according, to the herein-described test method, within a range from 1 to 3, preferably within a range from I to 2, and even more preferably ofl. It is further preferred that the particulate water-absorbent polysaccharides according to the invention nave an inner part and an outer part surrounding the inner part, whereby the outer part has a higher degree of erosslinking man the inner part, such that preferably a core-shell structure is formed. The increased erosslinking in the outer part of the crosslinked polysaccharides is preferably achieved by post-crosslinking of reactive groups near the surface. As post-crosslmker for the post-crosslinking are preferred polyphosphates and polyphosphoric acids, whereby those polyphosphates and polyphosphoric acids are particularly preferred which have already been cited in connection with the first process step of the process according to the invention for producing water-absorbent polysaccharides. As outer part of the particle is preferably understood each volume element of the particle whose distance from the center of the particle is at least 75 %, preferably at least .85 % and particularly preferably at least 95 % of the outer radius of me polymer particle. Hie invention further relates to a composite comprising an above-defined water-absorbent polysaceharide and a substrate. Preferably, the water-absorbent polysaccharide according to the invention and the substrate are firmly bound together. As substrate are preferred sheets made from polymers, such as, for example, from polyethylene, polypropylene or polyamide, metals, non-woven materials, fluff; tissues, woven materials, natural or synthetic fibres, or other foams. According to the invention, as composite are preferred sealant materials, cables, absorbent cores as well as diapers and hygiene articles comprising these. The invention further relates to a process for producing a composite, wherein a water-absorbent polysaccharide according to the invention and a substrate and optionally a suitable additive are brought into contact with each other. The bringing into contact preferably occurs by wetlaid and airlaid processes, compacting, extruding and mixing. The invention additionally relates to a composite which is obtainable by the above process. The invention further relates to chemical products, in particular foams, formed bodies, fibres, sheets, films, cables, sealant materials, liquid-absorbing hygiene articles, carriers for plant or fungus growth-regulating agents or plant protection agents, additives for construction materials, packaging materials or soil additives, which comprise the water-absorbent polysaccharide according to the invention for the above-described composite. These chemical products are distinguished in particular by a particularly good biodegradabilrty. In addition, the invention relates to the use of the water-absorbent polysaecharides according to the invention or of the above-described composite in hygiene products, for combating floods, for insulating against water, for regulating the water balance of soils or for treatment of food products. The invention also relates to the use of polyphosphate or polyphosphoric acid for crosslinkhig of an uncrosslinked polysaccharide, wherein those polyphosphates, polyphosphoric acids and polysaceherides are preferred which have already been cited in connection with the first process step of the process according to the invention for producing water-absorbent polysaccharides. The invention is now more closely described by means of test methods and non-limiting examples. TEST METHODS DETERMINATION OF THE GEL BED PERMEABILITY (GBP) This property is determined according to the test methods disclosed in US 6,387,495 Bl. DETERMINATION OF THE OENTOOTJGATION RETENTION CAPACITY (CRC) This property is determined according to the test methods disclosed in EP 6 601 529 Bl. DETERMINATION OF THE ABSORPTION UNDER LOAD (AUL) This property is determined according to the test methods disclosed in EP 0 339 461 Bl, wherein the following loads cited in the tables were used. 4.DETERMINATION OF THE SUMINESS The swollen gel obtained in the determination of the CRC was evaluated in daylight by visioinspection and given the following marks according to the optical impression. Reference is farther made for clarification to the pictures accompanying the individual marks. (Table Remove) 5. DETERMINATEONOPTHZBIODEGRADAHILrrY The biodegradabilhy (mineralization) is determined by the Controlled Composting Test (according, to ISO 14855, ASTM D5338-92, DIN V54900-2). EXAMPLES EXAMPLE 1 1A) PROCESS STEP OF THE PROCESS ACCORDING TO THE INVENTION. Potyphosphoric acid (84 % from the company Clariant, Germany) in a quantity of 0.09 wt %, based upon the amount of sodium carboxymethyl cellulose used, was dissolved hi distuled water and the pH value adjusted with sodium hydroxide to 11.5. The sodium carboxymethylcellulose (Cekol® 100,000 from the company Noviant, Netherlands, with an active substance content of 15 wt %) was homogeneously kneaded into the solution and then chopped ("wolfed"). The chopped gel was men dried at temperatures of 120°C for 150 minutes and then milled to a particle size within a range from 850 um to 150 um. A powder Al was obtained IB) PROCESS STEP OF THE PROCESS ACCORDING TO tHE INVENTION An aqueous solution with a pH of 11.0 comprising 6 wt %, based upon the total weight of the aqueous solution, of polyphosphoric acid as post-crosslinker, is brought into contact with powder Al in an amount of 10 wt %, based upon the total weight of powder Al. The coated pre-product is heated at temperatures of 13D°C for a duration, of SO minutes. A powder Bl is obtained. The powders Al and Bl were characterized by the following properties: TABLE 1 (Table Remove) EXAMPLE 2 2A) PROCESS STEP OF THE PROCESS ACCORDING TO THE INVENTION Example 1A was repeated, wherein in the place of 0.09 wt. %, based upon the amount of sodium carboxymethylcellulose used, Q.I wt % of polyphosphoric acid (814 %, from the company Clariatrt, Germany) was used. A powder A2 is obtained. 2B) PROCESS STEP OF THE PROCESS ACCORDING TO THE INVENTION Example IB wag repeated, wherein the aqueous solution with a pH of 11.0 additionally comprised 0.3 wt %, based upon the amount of powder A2, aerosil 200 from Degussa AG, Germany, and 5 wt % of polyphosphoric acid, based upon the total weight of the aqueous solution, was used and heated at 125PC for 65 minutes. A powder B2 is obtained. The powders A2 and B2 were characterized by the following properties: Table 2 (Table Remove) EXAMPLES 3 A) PROCESS STEP OF THE PROCESS ACCORDING TO THE INVENTION Example 1A was repeated, whereby instead of Cecol*, 100,000, Cecol* 50,000 was used. A powder A3 is obtained. 3B) PROCESS STEP OF THE PROCESS ACCORDING TO THE INVENTION Example IB was repeated, wherein Hie aqueous solution with a pH of 11.0 additionally comprised 03 wt %, based upon the amount of powder A3, of Aerosil 200 of Degussa AG, Germany. In addition, drying was carried out at MW for 110 minutes. A powder B3 is obtained. The powders A3 and B3 were characterized by the following properties: TABLE 3 (Table Remove) EXAMPLE 4 4 A) PRCK^^ STEP OF THE PROCESS ACCORDING TO THE INVENTION Example 1A was repeated, whereby instead of 0.09 wt. %, based upon the amount of sodium carboxymethylcelhilose used, 0.1 wt-% polyphosphoric acid (84 %, from the company Clariant, Germany) was used. A powder A4 is obtained. 4B) PROCESS STEP OF TIDE PRC>CESS ACCORDING TO THE I^rVrENTION Example IB was repeated, wherein the aqueous solution with a pH of 11.0 additionally comprised QJ wt %, based upon the amount of powder A4, of Sipemat 22S of Degussa AG, Germany and wherein it was heated at 125°C for 65 minutes. A powder B4 is obtained. The powders A4 and B4 were characterized by the following properties: TABLE4 (Table Remove) We Claim: 1. A process for producing a water-absorbent polysaccharide, comprising the process steps: the bringing into contact of an uncrosslinked polysaccharide with a polyphosphate or with polyphosphoric acid as crosslinking agent in the presence of water to form a polysaccharide gel; crosslinking of the polysaccharide gel; drying of the polysaccharide gel; wherein the polysaccharide gel is comminuted before the drying and/or wherein the dried, crosslinking polysaccharide is milled, so that particulate, crosslinked polysaccharides are obtained and wherein the particulate, crosslinked polysaccharide is post-crosslinked in the outer part of the particle with a post-crosslinking agent. 2. A process for producing a water-absorbent polysaccharide, comprising the process steps: the bringing into contact of a polysaccharide with a crosslinking agent in the presence of water to form a polysaccharide gel; drying of the polysaccharide gel; wherein at least the bringing into contact occurs in a kneader and wherein the polysaccharide gel is comminuted before the drying and/or wherein the dried, crosslinking polysaccharide is milled, so that particulate, crosslinked polysaccharides are obtained and wherein the particulate, crosslinked polysaccharide is post-crosslinked in the outer part of the particle with a post-crosslinking agent. 3. Process as claimed in claim 2, wherein the crosslinking agent is a polyphosphate or polyphosphoric acid. 4. Process as claimed in claim 2 or 3, wherein the kneader comprises at least two knead shafts. 5. Process as claimed in claim 4, wherein the at least two knead shafts have a contour which at least partially reaches into each other. 6. Process as claimed in claim 4 or 5, wherein the at least two knead shafts form a conveying channel running at least partially axial to one of the knead shafts. 7. Process as claimed in any one of claims 2 to 5, wherein the polysaccharide is an uncrosslinked polysaccharide. 8. Process as claimed in any one of the preceding claims, wherein the polysaccharide is a polycarboxypolysaccharide. 9. Process as claimed in claim 8, wherein the carboxyl groups of the uncrosslinked polycarboxypolysaccharide are neutralised to at least 50 mol%. 10. Process as claimed in any one of the preceding claims, wherein the crosslinking or the drying occurs at a temperature above 70 °C. 11. Process as claimed in any one of the preceding claims, wherein the bringing into contact of the polysaccharide with the crosslinking agent occurs in the absence of an organic solvent. 12. Process as claimed in any one of the preceding claims, wherein the bringing into contact of the crosslinking agent occurs at a pH within a range from 8 to 12. 13. Process as claimed in any one of the preceding claims, wherein the bringing into contact of the polysaccharide with the polyphosphate or with the polyphosphoric acid occurs in such a way that initially the polyphosphate is dissolved in water, a pH within a range from 8 to 12 is set in the aqueous solution of the polyphosphate and then the aqueous solution of the polyphosphate is brought into contact with an uncrosslinked polysaccharide. 14. Process as claimed in any one of the preceding claims, wherein the crosslinking agent is brought into contact with the polysaccharide in an amount within a range from 0.001 to 20 wt.%, based upon the weight of the polysaccharide. 15. Process as claimed in any one of the preceding claims, wherein the polysaccharide comprises a salt content of less than 20 wt.%, based upon the total weight of the polysaccharide. 16. Process as claimed in any one of the preceding claims, wherein the polyphosphate comprises as crosslinking agent the composition MIn+2[PnO3n+1] or MIn[H2PnO3n+1], wherein MI is a monovalent metal and n has a value of at least 2. 17. Process as claimed in any one of the preceding claims, wherein the polyphosphoric acid as crosslinking agent has the composition Hn+2PnO3n+1 or (HPO3)n, in which n has a value of at least 2. 18. Process as claimed in claim or 2, wherein the post-crosslinking agent is used in the form of a 0.01 to 80 wt.% aqueous solution. 19. Process as claimed in claim 1 or claim 2, wherein the post-crosslinking agent is a polyphosphate or polyphosphoric acid. 20. Process as claimed in any one of claims 1 to 19, wherein the post-crosslinking of the crosslinked polysaccharides with the post-crosslinking agent occurs in the presence of inorganic particles. 21. A water-absorbent polysaccharide obtainable by a process as claimed in any one of the preceding claims. 22. A particulate, water-absorbent polysaccharide, wherein the polysaccharide is crosslinked with a polyphosphate or with polyphosphoric acid in an amount within a range from 0.001 to 25 wt.%, based upon the weight of the polysaccharide. 23. Particulate, water-absorbent polysaccharide as claimed in claim 22, wherein the polysaccharide is an at least partially neutralised polycarboxypolysaccharide. 24. Particulate, water-absorbent polysaccharide as claimed in claim 22 or claim 23, wherein the polysaccharide is present in particulate form with a particle diameter within a range from 150 to 850 µm. 25. Particulate, water-absorbent polysaccharide as claimed in any one of claims 21 to24, wherein the polysaccharide has at least one of the following properties: (αl) an AUL value at a pressure of 0.9 psi within a range from 10 to 32 g/g with a CRC value within a range from >15 to (a2) an AUL value at a pressure of 0.9 psi within a range from 6 to 20 g/g with a CRC value within a range from > 20 bis (α3) an AUL-Wert at a pressure of 0.9 psi within a range from 6 to 15 g/g with a CRC value within a range from > 25 to (a4) an AUL-Wert at a pressure of 0.9 psi within a range from 5 to 12 g/g with a CRC value > 30 g/g. 26. A composite comprising a water-absorbent, at least partially neutralised polysaccharide as claimed in any one of claims 21 to 25 and a substrate.

Documents:

7784-delnp-2006-abstract.pdf

7784-DELNP-2006-Claims-(17-04-2012).pdf

7784-delnp-2006-claims.pdf

7784-DELNP-2006-Correspondence Others-(17-04-2012).pdf

7784-DELNP-2006-Correspondence Others-(28-10-2011).pdf

7784-DELNP-2006-Correspondence Others-(29-02-2012).pdf

7784-delnp-2006-correspondence-others (21-04-2008).pdf

7784-DELNP-2006-Correspondence-Others-(1-1-2010).pdf

7784-delnp-2006-Correspondence-Others-(14-09-2012).pdf

7784-delnp-2006-correspondence-others.pdf

7784-delnp-2006-description (complete).pdf

7784-delnp-2006-drawings.pdf

7784-DELNP-2006-Form-1-(17-04-2012).pdf

7784-delnp-2006-form-1.pdf

7784-delnp-2006-Form-13-(17-04-2012)..pdf

7784-delnp-2006-form-18 (21-04-2008).pdf

7784-DELNP-2006-Form-2-(17-04-2012).pdf

7784-delnp-2006-form-2.pdf

7784-DELNP-2006-Form-3-(29-02-2012).pdf

7784-delnp-2006-form-3.pdf

7784-DELNP-2006-Form-5-(17-04-2012).pdf

7784-delnp-2006-form-5.pdf

7784-DELNP-2006-GPA (1-1-2010).pdf

7784-DELNP-2006-GPA-(28-10-2011).pdf

7784-delnp-2006-pct-301.pdf

7784-delnp-2006-pct-304.pdf

7784-delnp-2006-pct-308.pdf

7784-delnp-2006-pct-332.pdf

7784-delnp-2006-pct-409.pdf

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