Highly swellable absorption medium with reduced caking tendency

Abstract

The present invention concerns highly swellable absorption mediums with a reduced caking tendency at high humidity and/or high temperatures, wherein a swellable polymer is coated with a non-ionic, nitrogen-containing surfactant and optionally a Lewis acid and then reacted by heating.

1 . A highly swellable absorption medium with a reduced caking tendency in a moist environment and/or at high temperatures comprising: 
 I a water- or aqueous fluid-absorbing natural polymer modified with acid groups or a water-insoluble, optionally surface cross-linked, water- or aqueous fluid-absorbing cross-linked polymer based on polymerized monomers comprising at least partially neutralized acid groups, which is treated with:    II at least one coating agent selected from the group consisting of nitrogen-containing, non-ionic surfactants;    wherein the mixture formed from components I and II has been heat treated.    
     
     
         2 . The absorption medium according to  claim 1 , wherein the surfactant is at least one compound with general formula I:  
       
         
           
           
               
               
           
         
         in which  
         R 1  is a z-substituted aliphatic residue, preferably a z-substituted, saturated or unsaturated, linear or branched aliphatic C 1  to C 30  hydrocarbon residue, more preferably C 8  to C 22 , which optionally carries aryl residues, preferably a phenyl residue, a z-substituted benzene residue, optionally condensed with five or six-membered rings optionally containing heteroatoms such as oxygen, phosphorus or nitrogen;  
         R 2  is  
         a hydrogen; or  
         an aliphatic residue, preferably a saturated or unsaturated, linear or branched C 2  to C 24  hydrocarbon residue, preferably C 8  to C 22 ;  
         a hydroxyalkylene residue,  
         the hydroxyl group of said hydroxyalkylen residue is preferably an end group and/or optionally alkoxylated with 1 to 50, preferably 1 to 20, more particularly with 1 to 10 alkylene oxide units, preferably ethylene and/or propylene oxide units, and/or said hydroxyl group is optionally esterified with a carbon acid, preferably a C 1 - to C 8 -carbon acid, and  
         the alkylene group of said hydroxyalkylen residue is a C 1 - to C 8 -, preferably C 1 -to C 4 -hydrocarbon group, occurs in the alkylene residue, or a N,N-dihydroxyalkylene-amino-alkylene residue with C 1 -C 4  in each alkylene residue;  
         R 3 , which may be identical or different, has the same meaning as R 2 , provided that with amide compounds, at least one of residues R 2  or R 3  represents a hydroxyalkylene residue or an alkoxylated hydroxyalkylene residue or a corresponding esterified or alkoxylated or esterified and alkoxylated hydroxyalkylene residue with the definition given for R 2  above;  
         n is 0 or 1, preferably 1;  
         and z is a whole number from 1 to 4.  
       
     
     
         3 . The absorption medium according to  claim 1 , wherein polymer I is surface cross-linked.  
     
     
         4 . The absorption medium according to  claim 1 , wherein the coating agent II is used in an amount of 50 to 50000 ppm, preferably 100 to 5000 ppm, particularly preferably 300 to 3000 ppm.  
     
     
         5 . The absorption medium according to  claim 1 , wherein the coated component I is heat treated at a temperature of 100° C. to 250° C., preferably 150° C. to 230° C., particularly preferably 160° C. to 210° C.  
     
     
         6 . The absorption medium according to  claim 1 , wherein coating agent II is a fatty acid alkanolamide or a fatty acid amine according to formula I, which is optionally alkoxylated and/or esterified.  
     
     
         7 . The absorption medium according to  claim 1 , wherein the coating agent II is at least one compound selected from the group consisting of lauric acid monoethanolamide, coconut acid monoethanolamide, stearic acid monoethanolamide, ricinic acid monoethanolamide, undecylenic acid monoethanolamide, lauric acid diethanolamide, coconut acid diethanolamide, soya acid diethanolamide, linoleic acid diethanolamide, laurylmyristic acid diethanolamide, oleic acid diethanolamide, lauric acid isopropanolamide, coconut acid isopropanolamide, oleic acid isopropanolamide, undecylenic acid polydiethanolamide, coconut acid polydiethanolamide, stearylamine, stearyl propylenediamine, coconut acid amine, laurylamine, oleylamine, stearylamine, tallow fat amine; a corresponding ethoxylated and/or propoxylated compound with 1 to 50, preferably 1 to 20 ethylene oxide and/or propylene oxide units and the corresponding esterified compound.  
     
     
         8 . The absorption medium according to  claim 1 , wherein the component I to be coated is in the form of a powder.  
     
     
         9 . The absorption medium according to  claim 1 , wherein the polymer is based on (meth)acrylic acid, the carboxyl groups of which are at least 50 mole % neutralized.  
     
     
         10 . Use of an absorption medium according to  claim 1  in composites for absorbing water and aqueous or serous fluids, preferably body fluids.  
     
     
         11 . Use of an absorption medium according to  claim 1  in hygiene articles, preferably diapers, tampons or feminine pads.  
     
     
         12 . Use of an absorption medium according to  claim 1  in cable sheaths or packaging.  
     
     
         13 . Use of an absorption medium according to  claim 1  as a water storage means in floors or substrates.  
     
     
         14 . Use of an absorption medium according to  claim 1  to store nutrients and active agents and for their controlled release.  
     
     
         15 . A highly swellable absorption medium with a reduced caking tendency in a moist environment and/or at high temperatures comprising: 
 I a water- or aqueous fluid-absorbing natural polymer modified with acid groups or a water-insoluble, optionally surface cross-linked, water- or aqueous fluid-absorbing cross-linked polymer based on polymerized monomers containing at least partially neutralized acid groups, which is treated with:    II at least one coating agent selected from the group consisting of nitrogen-containing, non-ionic surfactants;    wherein the mixture formed from components I and II has been heat treated; and    wherein at least one Lewis acid is used as a further coating agent III.    
     
     
         16 . The absorption medium according to  claim 15 , wherein the coating agents II and III are used in a total amount of 100 to 50000 ppm, preferably 300 to 25000 ppm, particularly preferably 500 to 13000 ppm.  
     
     
         17 . The absorption medium according to  claim 15 , wherein heat treatment of the coated component I is carried out at a temperature of 40° C. to 250° C., preferably 100° C. to 230° C., particularly preferably 130° C. to 210° C.  
     
     
         18 . The absorption medium according to  claim 15 , wherein component I is coated with an aqueous solution of coating agents II and III and caused to react.  
     
     
         19 . The absorption medium according to  claim 15 , wherein the Lewis acid III is an inorganic acid, a water-soluble, saturated or unsaturated organic acid, a water-soluble hydrocarbon acid or a water-soluble acid salt.  
     
     
         20 . The absorption medium according to  claim 19 , wherein the Lewis acid is HCl, H 2 SO 4 , selenium or phosphorus oxyacids, HNO 3 , H 2 SO 2 , H 2 SO 3 , HClO 3 , HBr, acrylic acid, methacrylic acid, formic acid, acetic acid, propionic acid, butyric acid, oxalic acid, malonic acid, succinic acid, lactic acid, maleinic acid, fumaric acid, benzoic acid, phthalic acid, salicylic acid, tartaric acid, citric acid, p- m- or o- toluenesulphonic acid, benzenesulphonic acid, aminomethanesulphonic acid, aminomethanephosphonic acid, water-soluble bromides, chlorides, nitrates, sulphates, phosphates, acetates, formates, oxalates or lactates of aluminium, iron, zinc, antimony, arsenic, tin, copper, magnesium, calcium, chromium, gallium, vanadium, titanium, bismuth, thallium, indium, manganese, nickel, cobalt, beryllium or zirconium or mixtures of two of more of said compounds.  
     
     
         21 . The absorption medium according to  claim 20 , wherein the Lewis acid is sulphuric acid, phosphoric acid, formic acid, acetic acid, citric acid or p-toluenesulphonic acid, aluminium salts or alums and/or hydrates thereof, zinc salts and/or hydrates thereof, magnesium salts and/or different hydrates thereof and/or double salts.  
     
     
         22 . A process for the production of an absorption medium with a reduced caking tendency in a moist environment and/or at high temperatures, comprising the steps of: 
 providing a component I which is a water- or aqueous fluid-absorbing, natural polymer modified with acid groups or a water- or aqueous fluid-absorbing, cross-linked polymer based on polymerized monomers containing at least partially neutralized acid groups;    coating component I with a coating agent selected from the group consisting of nitrogen-containing, non-ionic surfactants as component II and optionally a Lewis acid as component III; and    heat treating the the mixture.    
     
     
         23 . The process according to  claim 22 , further comprising the step of mixing an aqueous solution of the coating agent(s) with component I.  
     
     
         24 . The process according to  claim 22 , further comprising the step of treating the polymer before, during or after its surface cross-linking with an aqueous solution of component II and optional component III, with the addition of heat.  
     
     
         25 . The process according to  claim 22 , further comprising the step of simultaneously transforming the aqueous solution of component II and optional component III and surface cross-linking the polymer.  
     
     
         26 . The process according to  claim 22 , further comprising the step of heating the mixture of components I and II to temperatures of 150° C. to 250° C., preferably 150° C. to 210° C.  
     
     
         27 . The process according to  claim 22 , further comprising the step of heat treating the mixture of components I, II and III to temperatures of 40° C. to 250° C., preferably 100° C. to 230° C., particularly preferably 130° C. to 210° C.  
     
     
         28 . An absorption medium produced by the process defined in  claim 22 .  
     
     
         29 . Diapers, incontinence products for adults, feminine hygiene articles containing absorption mediums, preferably in composites, comprising: 
 I a water- or aqueous fluid-absorbing natural polymer modified with acid groups or a water-insoluble, optionally surface cross-linked, water- or aqueous fluid-absorbing cross-linked polymer based on polymerized monomers containing at least partially neutralized acid groups, which is treated with:    II at least one coating agent selected from the group consisting of nitrogen-containing, non-ionic surfactants;    wherein the mixture formed from components I and II has been heat treated; and    wherein the absorption medium doesn't show anti-caking after at least 3 hours of heat treatment.