MXPA97003447A - Polimero cation - Google Patents

Abstract

The present invention relates to a cationic polysaccharide having super absorbent characteristics, the polysaccharide being substituted by quaternary ammonium groups and having a ds of at least 0.5, and the crosslinked polysaccharide being to a sufficient degree that it remains insoluble on ag

Description

CATIONIC POLYMER FIELD OF THE INVENTION The present invention relates to a cationic polymer more particularly a water absorbing polymer of the type commonly referred to as a "super absorbent".

BACKGROUND OF THE INVENTION The substances currently named "super absorbent" are typically slightly cross-linked hydrophilic polymers. Polymers may differ in their chemical nature, but they participate in the properties of being able to absorb and retain quantities, even under moderate pressures, of aqueous fluids equivalent to several times their own weight. For example, super absorbers can typically absorb up to 100 times their own weight, or even more than distilled water. Super absorbents have been suggested for use in many different industrial applications, where they can take advantage of their water absorption and / or water retention properties, and examples include agriculture, the construction industry, the production of alkaline batteries and filters. However, the primary field of application for super absorbers is in the production of sanitary and / or sanitary products, such as disposable sanitary napkins and disposable diapers, either for children or incontinent adults. In such hygienic and / or sanitary products, the super absorbers are used, generally in combination with cellulose fibers, for example, the use of cellulose to absorb body fluids such as menstruation or urine.

However, the absorbent capacity of super absorbers for bodily fluids is dramatically lower than for deionized water. It is generally believed that this effect results from the electrolyte content of bodily fluids, and the effect is often referred to as "salt poisoning". The characteristics of water absorption and water retention of the super absorbers, is due to the presence of ionizable functional groups in the structure of the polymer. These groups can be carboxyl groups, a high proportion of which are in the salt form when the polymer is dry, however, which undergo dissociation and solvation upon contact with water. In the dissociated state, the polymer chain will have a series of functional groups attached to it, whose groups have the same electrical charge and thus repel each other. This leads to an expansion of the polymer structure, which, in turn, allows the additional absorption of water molecules, although this expansion is subject to the coaxions provided by the crosslinks in the polymer structure, which must be sufficient to prevent the dissolution of the polymer. It is assumed that the presence of a significant concentration of electrolytes in the water interferes with the dissociation of the functional groups and directs the effect "Salt poisoning". Although most commercial super absorbers are anionic, it is also possible to produce cationic super absorbers with functional groups which are, for example, quaternary ammonium groups. Such materials also need to be in the salt form to act as super absorbers, and their performance is also affected by the effect of salt poisoning. A cationic super absorbent based on a polysaccharide such as cellulose will have hydroxyl groups of polysaccharides reacted with a reagent (a derivatizing reagent) which converts these hydroxyl groups into a cationic group, for example, a quaternary ammonium group. To be used as a super absorbent, particularly in sanitary and / or sanitary products, it is advantageous that the product should be based on fibrous cellulose, since it can be combined and processed more easily with fluff or cellulose fluff which also has a fibrous character . WO 92/19652 relates to a cationic fibrous polysaccharide which can be obtained by the reaction of fibrous polysaccharides such as cellulose, with an excess of quaternary ammonium compounds containing at least one group capable of reacting with the hydroxyl groups of polysaccharides. Even though the product of WO 92/19652 shows useful properties as a super absorbent, there is a limit to the absorption properties that can be achieved. As explained above, the absorption of water by a super absorbent involves the functional groups attached to the polymer chain and, in principle, the absorption capacity depends on the ratio of functional groups to the rest of the polymer, that is, most of functional groups that introduce the highest repulsion between the polymer chains and the greatest potential for water absorption. On the other hand, although cellulose in its natural state is insoluble in water, the derivation of cellulose, in the particular introduction of hydrophilic groups, tends to increase the solubility in water.

Accordingly, attempts to increase water absorption of the product of WO 92/19652 through the increase of ds would likely direct a water-soluble polymer instead of a super-absorbent which, by definition, should remain insoluble in water. Furthermore, the fibrous form of the material suggests that it is difficult for a bypass agent to gain access to the hydroxyl groups of polysaccharides without destroying the structural firmness of the material. Thus, although WO 92/19652 gives a nominal figure of 0.5 to 1.1 for the degree of substitution ("ds") with the derivatizing agent it is not generally possible to obtain a ds greater than about 0.7, without the activation of the polysaccharides that damages the structural integrity of the polysaccharide fibers, thereby inducing the solubilization of cellulose. The activation may take the form, for example, of applying pressure to force the fibers and expose more potential reaction sites, or the use of a chemical activating agent such as zinc chloride. Example 6 of WO 92/19652 achieves a ds of 1.10 but only by the use of activation with zinc chloride and the product would have been largely soluble. Processes for the cross-linking of cellulose are known using crosslinking agents such as formaldehyde, epichlorohydrin, diepoxides, dicarboxylic acids, dialdehydes and diisocyanates to obtain highly insoluble products in water. However, the presence of a crosslinking agent would increase the molecular weight of the material and thus, in principle, would decrease the super absorbent properties.

Processes for the derivation of cellulose in crystalline or powder form are also known, but these are generally of low molecular weight than the fibrous cellulose with more accessible hydroxylocide groups, in such a way that the different approaches for the derivation of cellulose in the form are applicable. crystalline and powdery than for fibrous cellulose. An object of the present invention is to provide a super absorbent polymer based on a polysaccharide, preferably a fibrous polysaccharide, more preferably fibrous cellulose having improved super absorbent properties. It has now been surprisingly found that such a product can be produced by combining the derivatization of a polysaccharide with an appropriate degree of crosslinking to maintain insolubility in water. The improvement in the super absorbent properties is effected by an increased number of functional groups (higher ds) rather than the excess in value of any effect that the crosslinking agent has on the super absorbent properties, and the product has improved super absorbent properties , for example, as compared to products of the type described in WO 92/19652. In this way, the use of a crosslinking agent makes it possible to control the gel strength of the product, and makes it easier to adapt to the characteristics of the product for those that are required.

DETAILED DESCRIPTION OF THE INVENTION According to one aspect of the present invention, provide a cationic polysaccharide, preferably a fibrous cationic polysaccharide, having super absorbent characteristics, the polysaccharide being substituted by quaternary ammonium groups and having a ds of at least 0.5, preferably from 0.5 to 2.5, and the polysaccharide being cross-linked to a sufficient degree that it remains insoluble in water. The polysaccharide according to the present invention is preferably based on cellulose, more preferably fibrous cellulose, although the invention can also be applied to other polysaccharides such as starch products and natural products based on saccharide units. The present invention can be applied to fibrous cellulose derivatives by any chemical and / or mechanical treatment, for example fibers obtained from purified wood pulp by the sulphate process or the bisulfite process, cellulose fibers obtained from wood pulp by mechanical thermomechanical treatment, beet cellulose, regenerated cellulose or cotton waste. Preferably, the cellulose fibers are obtained from wood pulp purified by the sulphate process, or as soft or "fluffed" cellulose derivatives from mechanical treatment, or wood pulp which are of the type generally used for the preparation of absorbent pad in disposable products, for example, sanitary napkins and hand towels, and diapers. The present invention can also be applied to cellulose powders. The polysaccharide according to the invention can be prepared by a process involving the derivation of a polysaccharide, preferably a fibrous polysaccharide with quaternary ammonium groups and crosslinking with an appropriate crosslinking agent. Derivatization and crosslinking can be carried out generally under similar conditions, in such a way that it is possible to carry out both reactions in a single step. However, the reactions can become competitive in such a way that it is preferred to carry out the derivation reaction as a first step, followed by the crosslinking as a separate second step. This two-step access allows greater control of the reaction in terms of ds, degrees of crosslinking, exceeding of undesirable byproducts, etc. According to another aspect, the present invention provides a process for the production of a cationic polysaccharide, preferably a fibrous cationic polysaccharide having super-absorption characteristics which comprises: (i) reacting a polysaccharide with an excess of a compound of quaternary ammonium containing at least one group capable of reacting with the hydroxyl groups of the polysaccharide to provide a polysaccharide with a ds of at least 0.5; and simultaneously or subsequently (ii) reacting the derivatized polysaccharide with a crosslinking agent to provide a sufficient degree of crosslinking that the product remains insoluble in water. Preferably, the polysaccharide is in fibrous form. Preferably step (ii) is carried out subsequently at step (i) with or without intermediate isolation of the product of step (i). The use of the crosslinking agent in the process according to the present invention improves the yield of the process by reducing the amount of soluble product that is obtained. When the derivatization reaction begins, the polysaccharide substrate is insoluble, but after derivation all or part of the substrate (depending on the degree of substitution) can be taken to be soluble. The crosslinking can crosslink soluble chains of the polymer together or with insoluble chains of the polymer, thereby preventing loss of material by solubilization. The reaction with the quaternary ammonium compound is generally carried out in the presence of a base, and preferably in an aqueous medium. However, other protic or aprotic solvents for example alcohols, preferably lower alkanols such as ethanol, propanol, or isopropanol, or amides such as D F, can also be used, either alone with a mixture with water. Suitable bases include hydroxide and alcohol oxides of alkaline earth metals, for example the hydroxide, methoxide, ethoxide, propoxide, isopropoxide, n-butoxide or t-butoxide of an alkali metal such as potassium, or preferably sodium. The most preferred base is usually sodium hydroxide. Suitable quaternary ammonium compounds can be represented by one of the following formulas (I) and (II): where n is an integer from 1 to 16; X is halogen, in particular fluoro, chloro, bromo or iodo, preferably chloro; Z is an anion which can be inorganic, for example halide (fluorine, chlorine, bromine, or iodine, preferably chlorine), nitrate, nitrite; phosphate or hydroxide, or organic, for example carboxylate such as acetate or propionate; R, R1, R2, R3, which may be the same or different, each being an organic radical, preferably containing up to 10 carbon atoms, or preferably hydrogen; or additionally R2 may represent a group of the formula (III) or (IV): in which p is an integer from 2 to 10; and n, R, R1, R3, x and Z are as defined above. The preferred meaning for each R, R1, R2 and R3 is hydrogen. When one of these groups is an organic radical, it should not contain any substituent that has an unacceptable adverse effect on the derivatization reaction or the subsequent crosslinking reaction, or on the properties of the material produced, for example, the super absorbent properties . Suitable organic groups include alkyl, hydroxyalkyl, alkenyl and aryl. The large organic groups increase the molecular weight of the product, so that smaller groups are preferred. The most preferred organic group is methyl or hydroxymethyl. Many compounds having the above formulas are known, or can be prepared by conventional methods. Some of said compounds are commercially available. Examples of suitable quaternary ammonium compounds include: glycidyltrimethyl ammonium chloride; 2,3-epoxypropyl-N, N, N-trimethylammonium chloride (commercially available from Degussa AG, as a 70% aqueous solution under the tradename QUAB 151 or as the pure compound in solid form under product code 50045 3-Chloro-2-hydroxypropyl-N, N, N-trimethylammonium chloride (commercially available from Degussa AG with a 65% aqueous solution under the tradename QUAB 188; 3-chloro-2-hydroxypropyl-N chloride) , N, N-dimethylethanolammonium commercially available from Degussa AG, with a 65% aqueous solution under the trademark QUAB 218), 1,3-bis- (3-chloro-2-hydroxypropyl-N, N-dimethylammonium dichloride) ) -N-propane (commercially available from Degussa AG as a 65% aqueous solution under the tradename QUAB 388): A particularly preferred quaternary ammonium compound is glycidyltrimethylammonium chloride.The by-pass reaction with the quaternary ammonium compound It can be carried out in a single stage, or as a s or more steps with or without intermediate separation and product purification. In the step or in each of the steps, the reaction is carried out by contacting the base, preferably in an aqueous medium. Typically, the quaternary ammonium compound is used in excess, for example in a molar ratio based on the saccharide units in the polysaccharide from 5: 1 to 40: 1, more particularly from 20: 1 to 40: 1. Where the bypass reaction is carried out in two or more steps, a molar ratio of 10: 1 to 20: 1 is preferably applied in each step. The base, preferably sodium hydroxide, is used in the step or in each step in a molar ratio of 1: 3 to 3: 1 based on the hydroxyl groups in the monosaccharide units, in a molar ratio of 5: 100 to 300: 100, preferably 100: 100 to 300: 100, based on the quaternary ammonium compound, where this is a compound of the formula (I) or from 10: 100 to 50: 100 where this is a compound of the formula (II). The reaction temperature for the step or each of the steps can be from 15 to 120 ° C, preferably from 70 to 100 ° C, and the total reaction time can be for example from 1 to 20 hours. Where the derivation reaction is carried out in two or more steps, the reaction time for each step will generally be from 0.25 to 5 hours, preferably from 0.25 to 2 hours. The derivative product can be isolated and purified by removing the excess alkali by washing until neutral, for example with dilute aqueous sodium chloride, for example 4%. The product can then be converted to the salt form, by treatment with a concentrated excess of acid, for example 4% aqueous hydrochloric acid, and washed until neutral. The product is then dehydrated, for example with acetone and recovered by filtration and / or centrifugation. The derivatized polysaccharides prepared as described above, in which one or more of is hydrogen, can be subsequently converted to the corresponding compound in which one or more of R1, R2 and R3 is a hydrocarbon group by an n-alkylation reaction , for example, with a compound of the formula R5Hal where R5 is an optionally substituted hydrocarbon group, for example alkyl, hydroxyalkyl or alkenyl, and Ha1 is a halogen, more particularly fluoro, bromo or iodo, to effect the quaternization of some of all the ammonium groups. As indicated above, the polysaccharide crosslinked either in the reaction is the derivation reaction or, preferably, subsequent to it. Suitable crosslinking agents for polysaccharides such as cellulose include: formaldehyde; methoxylated nitrogen compounds such as dimethylolurea, dimethylolethyleneurea and dimethylolimidazolidone; dicarboxylic acids, such as maleic acid; dialdehydes, such as glyoxal; diepoxides such as 1, 2: 3,4-diepoxybutane and 1, 2: 5,6-diepoxyhexane; diisocyanates; divinyl compounds such as divinyl sulfone; dihalogenated compounds such as dichloroacetone, dichloroacetic acid, 1,3-dichloropropan-2-ol, dichloroethane, 2,3-dibromo-1-propanol, 2,3-dichloro-1-propanol and 2,2-dichloroethyl ether; halohydrin such as epichlorohydrin; bis (epoxypropyl) ether; vinylcyclohexanedioxane; ethylene glycol bis (epoxypropyl) ether; 1,3-bis (β-hydroxy-r-chloropropoxy) -2-propanol; 1-3-bis (ß-hydroxy-r-chloropropoxy) ethane; methylenebis (acrylamide); N; N'-dimethylol (methylenebis (acrylamide)); triacrilolhexahidrotriazina; acrylamidomethylene chloroacetamide; 2,4,6, -trichloropyrimidine; 2,4,5,6, -tetrachloropyrimidine; cyanuric chloride; triallylcyanurate; phosphoroxichloride; bis (acrylamido) acetic acid For further information regarding the appropriate crosslinking agents reference may be made to U.S. Patent No. 3658613, U.S. Patent No. 3589365, and U.S. Pat. No. 4068068 Preferred crosslinking agents include di-epoxy compounds and halo-epoxy compounds, such as 1,3-bis (glycidylmethylammonium) propanedichlor and epichlorohydrin. Where the crosslinking and derivatization reactions are carried out together, the conditions are as described above for the derivatization reaction. Where the crosslinking reaction is carried out as a subsequent step followed by the derivatization reaction, the reaction conditions are also generally as described above for the derivatization reaction. The amount of crosslinking agent that is necessary will depend on the nature of the agent, the starting materials, and the conditions of the crosslinking reaction. In all cases, the reaction must be such as to provide a degree of crosslinking which imparts the insolubility to the water desired by the polymer, but which does not interfere with the water absorbing properties of the polymer (super absorbent properties), imparted by the polymer group. quaternary ammonium. Preferably, the crosslinking reaction is carried out at a temperature of 15 to 110 ° C, more preferably 35 to 85 for a time of 1 to 20 hours, preferably 2 to 10 hours.

The degree of substitution and the degree of crosslinking can both be controlled by appropriate variation in the amounts of starting materials and the reaction conditions, in particular the concentration of the derivatization and / or the crosslinking agent, reaction time, amount of the base, reaction temperature and the nature of the substrate. Where the process according to the present invention is applied to a polysaccharide other than cellulose, then appropriate modifications to the reaction conditions will be necessary and, for example, it is known that the starch is generally more reactive than cellulose. The process as described above, induces a polysaccharide derivative in base form as a result of the use of the base, (e.g. sodium hydroxide) as a catalyst in the derivatization and crosslinking reactions. In general, the polysaccharide is required in the salt form, and this can be prepared by treatment with a concentrated acid (for example hydrochloric acid) followed by washing with water to a neutral pH. If necessary, the polysaccharide in salt form can be converted to the base form by treatment with a strong base (for example NaOh) followed by washing with water. According to one embodiment of the invention, cellulose, for example in the form of pulp Kraft of cellulose, is derived with glycidyltrimethylammonium chloride, for example up to a ds of about 0.65, and then crosslinked with 1,3-bis dichloride (glycidyldimethylammonium) propane in the presence of sodium hydroxide. The reaction scheme can be represented as follows: 1 SOURCE LATTICE onic 15 2 RETICULATION ClO ClO The crosslinked cationic cellulose according to the present invention can be prepared without a limitation on the tax ds by increasing the water solubility. The material can be used as an absorbent for water or saline in any salt in basic form. During the use of saline absorption, for example, in the form of liquids containing salt such as urine or menstruation, there are considerable advantages in the use of the polysaccharide according to the present invention in basic form. In this case, at the same time that it absorbs the liquid, the polymer also has a desalting effect on the liquid, by virtue of the fact that when placed in salt solution the quaternary ammonium groups in basic form act as a strong anion exchanger and converts spontaneously to the salt form. The absorbent according to the present invention is particularly suitable for use in applications where it is desired to absorb aqueous liquids containing salt. Examples of such liquids include in particular menstruation and urine, and particularly when in fibrous form the absorbent material can be used for filling in catameneal products and diapers, generally in admixture with a fibrous absorbent such as a cellulose fluff. The absorbent according to the present invention, in the form of a base, can also be used in combination with an anionic super absorbent in the form of a free acid or a cation exchanger in the acid form, as described in our co-pending patent applications. ... (internal references Dr 24) and (internal reference DR 26), respectively. According to a further aspect of the present invention, there is provided the use of a cationic polysaccharide, preferably preferably a fibrous cationic polysaccharide, as defined above as an absorbent, more particularly as an absorbent in sanitary and / or sanitary articles.

The invention is illustrated by the following examples: Example 1 10 grams of Kraft pulp cellulose were mixed with 6.7 grams of NaOh and 28 ml of distilled water. The mixture was cooled for 30 minutes in a salt bath on ice and 46.74 grams of glycidyl trimethyl ammonium chloride in 20 ml of distilled water were added. The temperature was maintained at 80 to 85 ° C for 30 minutes with continuous agitation. After this time, the same amount of glycidi Itrimeti lamonium was added in water and again the mixture was maintained at 80 to 85 ° C for 30 minutes with continuous stirring. The procedure was repeated about three times more (a total of 5 additions of glycidyl trimethyl ammonium chloride). The sample was then washed with NaCl (4% in water: 2 liters) and filtered under vacuum using a Buchner filter (vacuum water gum). The sample was transferred to a 5 liter vessel and treated with 2.5 liters of 4% hydrochloric acid, followed by filtration as described above. The sample was then washed with water to a neutral pH, filtered as described above and then dried by the addition of a large amount of acetone. The ds of the product in this step (defined as the number of quaternary ammonium groups per units of anhydroglucose cellulose, and measures as described in WO 92/19652) was 0.65. a) One gram of the derivative was mixed with 5 ml of 19% aqueous sodium hydroxide. 0.88 grams of a 65% aqueous solution of 1,3-bis (glycidyl dimethyl ammonium) dichloride was added under stirring at room temperature and kept under these conditions for 16 hours. The sample was washed with water to a neutral pH and lyophilized. The sample had an absorbency (tea bag test as described below) of 54 (after draining) and 29 (after centrifugation at 60 grams). b) The experiment of (a) before was repeated, but using a number of crosslinking agents reduced by half. The sample had an abosrbence (tea bag test) of 21 (after draining) and 18 (after centrifugation at 60 grams). The tea bag test was performed weighing approximately 0.3 grams of the product in a sachet bag, which was then itself weighed and dipped in 150 ml of liquid (1% NaCl solution or distilled water) in a beaker weevil 250 ml for 1 hour. The envelope was then removed from the liquid, and allowed to drain for 10 minutes, weigh, and then centrifuged at 60 grams for 10 minutes, and weighed again. Absorbency was calculated as follows: A = (Wwet - Wdry) / G where: A = absorbency (after draining or centrifugation); Wwet = weight of the envelope containing the sample after draining or centrifugation (grams); Wdry = weight of the envelope containing the sample before the immersion (grams), G = weight of the sample used for the test (grams). The use of distilled water in the previous test, gives a measurement of the maximum power of swelling considering that the alauda a reduced figure which is more predictive of the behavior of the material in practice.

EXAMPLE 2 (a) 10 grams of cellulose powder (Farmitalia Cario Erba SpA, Rome, Italy) was mixed with 6.5 grams of NaOH dissolved in 28 ml of distilled water. The mixture was quenched for 30 minutes in a salt bath on ice and 46.74 grams of glycidyl trimethyl ammonium chloride in 20 ml of distilled water was added. The temperature was maintained at 80 ° C for 30 minutes, with continuous agitation. The same amount of glycidyl trimethyl ammonium chloride in water was then added, and again the mixture was maintained at 80 ° C for 30 minutes. The procedure was then repeated twice more (a total of 4 additions of glycidyl trimethyl ammonium chloride). The product was purified by the method described in Example 1 and the product had a ds of 0.53. (b) 0.5 grams of the purified product was mixed with 2.5 ml of 19% NaOH and 0.44 ml of 1,3-bis (3-chloro-2-hydroxypropyl) dimethyl ammonium propane dichloride in water, with continuous stirring for 5 hours. hours. The temperature was maintained at 25 ° C and after the addition of 10 ml of distilled water, the temperature was maintained for 16 hours. The gel obtained was purified as described in Example 1 and lyophilized. The product had an absorbency (tea bag test according to example 1) of 50 (after draining) and 39 (after centrifugation).

EXAMPLE 3 (a) The procedure of Example 2 (a) was repeated to produce a different sample of the same product essentially but with a ds of 0.50. (b) The procedure was as in example 2 (b), except that the temperature was maintained at 20 ° C. The product had an absorbency (tea bag test, according to example 1) of 34 (after draining) and 29 (after centrifugation). In summary, the results obtained were as follows: the ds of the intermediates was measured as described in WO 92/19652. The ds of the final product was not measured but it would not be expected to be significantly different from the intermediates.

COMPARATIVE EXAMPLE The product of example 2 of WO 92/19652 had a ds of 0.64, and an absorbency (tea bag test according to example 1) of 42.9 (after draining) and 23.2 (after centrifugation). 0.2 grams of the same product is placed in a teabag envelope in one liter of 0.1 N NaOH (aqueous solution) for 10 hours with mechanical agitation, and then washed with water to neutralize it and dry with acetone to produce the product in the salt-free form, which had an absorbency of 42.9 (after draining) and 23.2 (after centrifugation). The products of example 1 (a) and 1 (b) show improved gel resistances and are obtained in improved yields relative to WO 92/19652. The products of example 2 (b) and 3 (b) were obtained from the intermediates that were soluble.

Claims (26)

1. A cationic polysaccharide having super absorbent characteristics, the polysaccharide being substituted by quaternary ammonium groups and having a ds of at least 0.5, and the crosslinked polysaccharide being to a sufficient degree that it remains insoluble in water. 2. A cationic polysaccharide according to claim 1, wherein the polysaccharide is cellulose. 3. A cationic polysaccharide according to claim 1 or 2, in the fibrous form. 4. A cationic polysaccharide according to any of claims 1 to 3, wherein the quaternary ammonium groups are derivatives of a quaternary ammonium compound of one of the general formulas (I) and (II):

Where n is an integer from 1 to 16; X is halogen; Z "is an inorganic or organic anion;

R, R1, R2 and R3, which may be the same or different, are each hydrogen or an organic radical; or additionally R2 may represent a group of the formula (III) or (IV):

- (CH2) p (III)

(CH (IV) in which p is an integer from 2 to 10; and N, R, R1, R2, R3, X and Z are as described above. 5. A cationic polysaccharide according to claim 4, wherein each R, R1, R2 and R3, is hydrogen to an alkyl, hydroxyalkyl, alkenyl or aryl group, containing up to 10 carbon atoms.

6. A cationic polysaccharide according to claim 5, wherein each of R, R1, R2 and R3 is hydrogen.

7. A cationic polysaccharide according to claim 5 or 6, wherein the quaternary ammonium compound is selected from: glycidyltrimethyl ammonium chloride; "2,3-epoxypropyl-N, N, N-trimethylammonium chloride; 3-chloro-2-hydroxypropyl-N, N, N-trimethylammonium chloride; 3-chloro-2-hydroxypropyl-N, N, N chloride -dimethylethanolammonium 1,3-bis- (3-chloro-2-hydroxypropyl-N, N-dimethylammonium) -N-propane dichloride

8. A cationic polysaccharide according to any of claims 1 to 7, wherein the The crosslinking agent is a diepoxic compound or a haloepoxy compound

9. A cationic polysaccharide according to claim 8 wherein the crosslinking agent is 1-3-bis (glycidyl dimethylammonium) propane or epichlorohydrin dichloride

10. A cationic polysaccharide. according to any one of claims 1 to 9, having a ds of from 0.5 to 2.5

11. A process for the production of a cationic polysaccharide having super absorbent characteristics which comprises: (i) reacting a polysaccharide with an excess of a quaternary ammonium compound that contains at least s a group capable of reacting with the hydroxyl groups of the polysaccharide to provide a polysaccharide with a ds of at least 0.5; and simultaneously or subsequently (ii) reacting the derivatized polysaccharide with a crosslinking agent to provide a sufficient degree of crosslinking that the product remains insoluble in water.

12. A process according to claim 11, wherein the polysaccharide is cellulose.

13. A process according to claim 11 or 12, wherein the polysaccharide is a fibrous polysaccharide.

14. A process according to any of claims 11 to 13, wherein the quaternary ammonium compound is a compound of one of the general formulas (I) and (II): where n is an integer from 1 to 16; X is halogen; Z is an inorganic or organic anion; R, R1, R2, R, which may be the same or different, each being hydrogen or an organic radical; or additionally R2 may represent a group of the formula (III) or (IV): - (CH2 (III) (IV) in which p is an integer from 2 to 10; and n, R, R1, R3, x and Z are as defined above.

15. A process according to claim 14, wherein each R, R, R2 and R3 is hydrogen or an alkyl, hydroxyalkyl, alkenyl or aryl group, containing up to 10 carbon atoms.

16. A process according to claim 15, wherein each R, R1, R2 and R3 is hydrogen.

17. A process according to claim 15 or 16, wherein the quaternary ammonium compound is selected from: glycidyltrimethyl ammonium chloride; 2,3-epoxypropyl-N, N, N-trimethylammonium chloride; 3-chloro-2-hydroxypropyl-N, N, N-trimethylammonium chloride; 3-chloro-2-hydroxypropyl-N, N, N-dimethylethanolammonium chloride; 1,3-bis- (3-chloro-2-hydroxypropyl-N, N-dimethylammonium) -N-propane dichloride.

18. A process according to any of claims 11 to 16, wherein the cross-linking agent is a diepoxy compound or halo-epoxy compound.

19. A process according to claim 18, wherein the cross-linking agent is 1,3-bis (glycidyl dimethylammonium) propane or epichlorohydrin dichloride.

20. A process according to any of claims 11 to 19, wherein step (ii) is carried out subsequent to step (i).

21. A process according to any of claims 11 to 19, wherein the quaternary ammonium compound is used in a molar ratio based on the saccharide units in the polysaccharide from 5: 1 to 40: 1, preferably 20: 1 to 40: 1, or where the reaction is carried out in two or more steps, and the molar ratio of 10: 1 to 20: 1 is applied in each step.

22. A process according to any of claims 11 to 21, wherein the derivatization and crosslinking reactions are carried out in the presence of a base.

23. A process according to claim 22, wherein the base is a metal hydroxide or alkoxide of alkaline earths.

24. A process according to claim 23, wherein the base is sodium hydroxide.

25. The use of the cationic polysaccharide according to any of claims 1 to 10, as an absorbent.

26. The use according to claim 25, as an absorbent in sanitary and / or sanitary articles.