Absorbent structures of chemically treated cellulose fibers

Abstract

Disclosed are absorbent structures including fibers bound with a polyvalent cation-containing compound and superabsorbent polymer particles. The fibers exhibit an ion extraction factor of at least 5%. Also disclosed are multi-strata absorbent structures, such as disposable absorbent articles, including the treated fibers and SAP particles. Further disclosed are methods for preparing absorbent structures including the treated fibers; structures including fibers combined with a polyvalent cation-containing compound; and methods for treating or coating SAP particles with polyvalent cation-containing compounds.

What is claimed is:  
     
         1 . An absorbent structure, comprising: 
 fibers bound with a polyvalent cation-containing compound, said fibers exhibiting an ion extraction factor of at least 5%; and superabsorbent polymer particles.    
     
     
         2 . The structure of  claim 1  wherein said fibers exhibit an ion extraction factor of at least 25%  
     
     
         3 . The structure of  claim 1  wherein said fibers exhibit an ion extraction factor of at least 50%  
     
     
         4 . The structure of  claim 1  wherein said fibers exhibit an ion extraction factor of at least 90%  
     
     
         5 . The structure of  claim 1  wherein the polyvalent cation is present in an amount greater than 0.25% to 5%, by weight of the fiber.  
     
     
         6 . The structure of  claim 1  wherein the polyvalent cation is present in an amount of between 0.25% and 2.5%, by weight of the fiber.  
     
     
         7 . The structure of  claim 1  wherein the polyvalent cation is present in an amount of between 0.4% and 1.2%, by weight of the fiber.  
     
     
         8 . The structure of  claim 1  wherein the polyvalent cation is a transition metal ion.  
     
     
         9 . The structure of  claim 1  wherein the cation is selected from the group consisting of aluminum, iron, tin and mixtures thereof.  
     
     
         10 . The structure of  claim 1  wherein the polyvalent cation is in the +3 or +4 oxidation state.  
     
     
         11 . The structure of  claim 1  wherein said compound is a polyvalent metal salt.  
     
     
         12 . The structure of  claim 9  wherein said compound is selected from the group consisting of hydroxides of aluminum, iron and tin, and mixtures thereof.  
     
     
         13 . The structure of  claim 9  wherein said compound is selected from the group consisting of water soluble salts of aluminum, iron and tin, and mixtures thereof.  
     
     
         14 . The structure of  claim 1  wherein said fiber is at least 80% alpha cellulose and has a water retention value of at least 80%.  
     
     
         15 . The structure of  claim 14  wherein said fiber is at least 95% alpha cellulose, has a curl of at least 25% and has a water retention value of less than 90%.  
     
     
         16 . The structure of  claim 14  wherein said fiber is crosslinked, has a curl of greater than 50% and has a water retention value of less than 60%.  
     
     
         17 . The structure of  claim 14  wherein said fiber is a cellulose fiber selected from the group consisting of softwood cellulose, hardwood cellulose, cotton, esparto grass, bagasse, hemp, flax, chemically modified cellulose, physically modified cellulose, regenerated cellulose, bacterially generated cellulose, lyocell, cellulose acetate and mixtures thereof.  
     
     
         18 . The structure of  claim 1  wherein said fiber is selected from the group consisting of hydrophobic fibers treated with a surfactant, hydrophobic fibers treated with silica, surface-oxidized hydrophobic fibers, and mixtures thereof.  
     
     
         19 . The structure of  claim 1  wherein said superabsorbent polymer is selected from the group consisting of starch-acrylate graft co-polymers, polyacrylates, carboxymethylcellulose derivatives and mixtures thereof.  
     
     
         20 . The structure of  claim 1  wherein the fiber and polymer are in the form of a mixture.  
     
     
         21 . The structure of  claim 1  wherein said particles are present in an amount greater than 40% by weight of said fibers and particles.  
     
     
         22 . An absorbent structure, comprising: 
 an acquisition stratum; and a storage stratum in fluid communication with the acquisition stratum, said storage stratum including fibers bound with a polyvalent cation-containing compound, said fibers exhibiting an ion extraction factor of at least 5% and superabsorbent polymer particles.    
     
     
         23 . The structure of  claim 22  wherein the polyvalent cation is present in an amount greater than 0.25% to 5%, by weight of the fiber.  
     
     
         24 . The structure of  claim 22  wherein the cation is selected from the group consisting of aluminum, iron, tin and mixtures thereof.  
     
     
         25 . The structure of  claim 22  wherein said superabsorbent polymer is selected from the group consisting of starch-acrylate graft co-polymers, polyacrylates, carboxymethylcellulose derivatives and mixtures thereof.  
     
     
         26 . The structure of  claim 22  wherein said particles are present in an amount greater than 40% by weight of said fibers and particles.  
     
     
         27 . An absorbent structure, comprising: 
 an acquisition stratum; and a storage stratum in fluid communication with the acquisition stratum, said storage stratum including hydrophilic fibers combined with a polyvalent cation-containing compound, and superabsorbent polymer particles.    
     
     
         28 . The structure of  claim 27  wherein the polyvalent cation is present in an amount greater than 0.25% to 5%, by weight of the fiber.  
     
     
         29 . The structure of  claim 27  wherein the cation is selected from the group consisting of aluminum, iron, tin and mixtures thereof.  
     
     
         30 . The structure of  claim 27  wherein said superabsorbent polymer is selected from the group consisting of starch-acrylate graft co-polymers, polyacrylates, carboxymethylcellulose derivatives and mixtures thereof.  
     
     
         31 . The structure of  claim 27  wherein said particles are present in an amount greater than 40% by weight of said fibers and particles.  
     
     
         32 . A disposable absorbent article, comprising: 
 a chassis including a liquid pervious topsheet, and a liquid impervious backsheet; and an absorbent structure between said topsheet and said backsheet, said absorbent structure including:    an acquisition stratum in fluid communication with said topsheet; and a storage stratum in fluid communication with the acquisition stratum, said storage stratum including fibers bound with a polyvalent cation-containing compound, said fibers exhibiting an ion extraction factor of at least 5% and superabsorbent polymer particles.    
     
     
         33 . The article of  claim 32  wherein the polyvalent cation is present in an amount greater than 0.25% to 5%, by weight of the fiber.  
     
     
         34 . The article of  claim 32  wherein the cation is selected from the group consisting of aluminum, iron, tin and mixtures thereof.  
     
     
         35 . The article of  claim 32  wherein said superabsorbent polymer is selected from the group consisting of starch-acrylate graft co-polymers, polyacrylates, carboxymethylcellulose derivatives and mixtures thereof.  
     
     
         36 . The article of  claim 32  wherein said particles are present in an amount greater than 0.25% to 5%, by weight of the fiber.  
     
     
         37 . The article of  claim 32  wherein said article is selected from the group consisting of infant diapers, training pants, adult incontinence briefs, and feminine hygiene pads.  
     
     
         38 . A disposable absorbent article, comprising: 
 a chassis including a liquid pervious topsheet, and a liquid impervious backsheet; and an absorbent structure between said topsheet and said backsheet, said absorbent structure including:    an acquisition stratum in fluid communication with said topsheet; and a storage stratum in fluid communication with the acquisition stratum, said storage stratum including fibers combined with a polyvalent cation-containing compound and superabsorbent polymer particles.    
     
     
         39 . The article of  claim 38  wherein the polyvalent cation is present in an amount greater than 0.25% to 5%, by weight of the fiber.  
     
     
         40 . The article of  claim 38  wherein the cation is selected from the group consisting of aluminum, iron, tin and mixtures thereof.  
     
     
         41 . The article of  claim 38  wherein said superabsorbent polymer is selected from the group consisting of starch-acrylate graft co-polymers, polyacrylates, carboxymethylcellulose derivatives and mixtures thereof.  
     
     
         42 . The article of  claim 38  wherein said particles are present in an amount greater than 0.25% to 5%, by weight of the fiber.  
     
     
         43 . The article of  claim 38 , wherein said article is selected from the group consisting of infant diapers, training pants, adult incontinence briefs, and feminine hygiene pads.  
     
     
         44 . A disposable absorbent article, comprising: 
 a chassis including a liquid pervious topsheet, and a liquid impervious backsheet; and an absorbent structure between said topsheet and said backsheet, said absorbent structure including:    an acquisition stratum in fluid communication with said topsheet, said acquisition stratum including fibers combined with a polyvalent cation-containing compound; and a storage stratum in fluid communication with the acquisition stratum, said storage stratum including fibers and superabsorbent polymer particles.    
     
     
         45 . The article of  claim 44  wherein the polyvalent cation is present in an amount greater than 0.25% to 5%, by weight of the fiber in the storage stratum.  
     
     
         46 . The article of  claim 44  wherein the cation is selected from the group consisting of aluminum, iron, tin and mixtures thereof.  
     
     
         47 . The article of  claim 44  wherein said superabsorbent polymer is selected from the group consisting of starch-acrylate graft co-polymers, polyacrylates, carboxymethylcellulose derivatives and mixtures thereof.  
     
     
         48 . The article of  claim 44  wherein said particles are present in an amount greater than 0.25% to 5%, by weight of the fiber in the storage stratum.  
     
     
         49 . The article of  claim 44  wherein said article is selected from the group consisting of infant diapers, training pants, adult incontinence briefs, and feminine hygiene pads.  
     
     
         50 . A disposable absorbent article, comprising: 
 a chassis including a liquid pervious topsheet, and a liquid impervious backsheet;    and an absorbent structure between said topsheet and said backsheet, said absorbent structure including:    an acquisition stratum in fluid communication with said topsheet; a distribution stratum in fluid communication with the acquisition stratum, said distribution stratum including fibers combined with a polyvalent cation-containing compound; and a storage stratum in fluid communication with the distribution stratum, said storage stratum including fibers and superabsorbent polymer particles.    
     
     
         51 . The article of  claim 50  wherein the polyvalent cation is present in an amount greater than 0.25% to 5%, by weight of the fiber in the storage stratum.  
     
     
         52 . The article of  claim 50  wherein the cation is selected from the group consisting of aluminum, iron, tin and mixtures thereof.  
     
     
         53 . The article of  claim 50  wherein said superabsorbent polymer is selected from the group consisting of starch-acrylate graft co-polymers, polyacrylates, carboxymethylcellulose derivatives and mixtures thereof.  
     
     
         54 . The article structure of  claim 50  wherein said particles are present in an amount greater than 0.25% to 5%, by weight of the fiber in the storage stratum.  
     
     
         55 . The article of  claim 50  wherein said article is selected from the group consisting of infant diapers, training pants, adult incontinence briefs, and feminine hygiene pads.  
     
     
         56 . A method of preparing an absorbent structure, comprising: 
 adjusting the pH of a slurry of cellulose fibers to between 3.8 and 4.2; introducing aluminum sulfate to said slurry; agitating the fiber slurry and increasing the pH to between 5.5 and 5.9; forming a web from said fibers; applying an ionizable acid in an amount of between 0.5% and 5% by weight of the fibers to said web; drying and individualizing the fibers; and introducing superabsorbent polymer particles to the fibers to form an absorbent structure.    
     
     
         57 . The method of  claim 56  wherein said acid is applied by a method selected from the group consisting of spraying, painting and foaming.  
     
     
         58 . The method of  claim 56  further comprising the step of applying a reducing agent to the web.  
     
     
         59 . The method of  58  wherein said reducing agent is applied after said application of said acid.  
     
     
         60 . A method of preparing an absorbent structure, comprising: 
 adjusting the pH of a slurry of cellulose fibers to between 3.8 and 4.2; introducing aluminum sulfate to said slurry;    agitating the fiber slurry and increasing the pH to between 5.5 and 5.9; forming a web from said fibers;    applying aluminum sulfate in an amount of between 6.2% and 6.8% by weight of fibers to said web;    drying and individualizing the fibers; and    introducing superabsorbent polymer particles to the fibers to form an absorbent structure.    
     
     
         61 . The method of  claim 60  wherein said aluminum sulfate is applied by a method selected from the group consisting of spraying, painting and foaming.  
     
     
         62 . The method of  claim 60  further comprising the step of applying a reducing agent to the web.  
     
     
         63 . The method of  60  wherein said reducing agent is applied after said application of said aluminum sulfate application.  
     
     
         64 . A method of preparing an absorbent structure, comprising: 
 mixing superabsorbent polymer particles with an aqueous solution of a polyvalent cation containing compound; drying said mixture above 100° C. until a dry mixture is formed;    crushing the dry mixture to form particles; and introducing said particles into an absorbent structure containing fibers.    
     
     
         65 . A method of preparing an absorbent structure, comprising: 
 forming a slurry of cellulose fibers;    forming a web from from said fibers;    applying aluminum sulfate in an amount of between 6.2% and 7.0% by weight of fibers to said web;    drying and individualizing the fibers; and    introducing superabsorbent polymer particles to the fibers to form an absorbent structure.    
     
     
         66 . The method of  claim 65  wherein said aluminum sulfate is applied by a method selected from the group consisting of spraying, painting and foaming.  
     
     
         67 . The method of  claim 65  further comprising the step of applying a reducing agent to the web.  
     
     
         68 . The method of  67  wherein said reducing agent is applied after said application of said aluminum sulfate application.  
     
     
         69 . The absorbent structure of  claim 1  wherein said fibers form a topsheet.  
     
     
         70 . A absorbent structure, comprising: 
 a non-woven material including fibers bound with a polyvalent cation-containing compound, said fibers exhibiting an ion extraction factor of at least 5%; and    superabsorbent polymer particles.    
     
     
         71 . A method of preparing an absorbent structure, comprising: 
 mixing superabsorbent polymer particles with an non-aqueous solution of a polyvalent cation containing compound;    drying said mixture until a dry mixture is formed; and    introducing said particles into an absorbent structure containing fibers.    
     
     
         72 . The method of  claim 71 , wherein said non-aqueous solution is prepared with a solvent selected from the group consisting of methanol, ethanol, n-propanol, iso-propanol, acetone and mixtures thereof.  
     
     
         73 . The method of  claim 71 , wherein the drying step is conducted at a temperature of less than 100° C.  
     
     
         74 . The method of  claim 71 , wherein the drying step is conducted at a temperature of less than 40° C.  
     
     
         75 . Fibers bound with a polyvalent cation-containing compound, said fibers exhibiting an ion extraction factor of at least 5%.  
     
     
         76 . The fibers of  claim 75  wherein said fibers exhibit an ion extraction factor of at least 25%.  
     
     
         77 . The fibers of  claim 76  wherein said fibers exhibit an ion extraction factor of at least 50%.  
     
     
         78 . The fibers of  claim 77  wherein said fibers exhibit an ion extraction factor of at least 90%.  
     
     
         79 . The fibers of  claim 75  wherein the polyvalent cation is present in an amount greater than 0.25% to 5%, by weight of the fiber.  
     
     
         80 . The fibers of  claim 79  wherein the polyvalent cation is present in an amount of between 0.25% and 2.5%, by weight of the fiber.  
     
     
         81 . The fibers of  claim 80  wherein the polyvalent cation is present in an amount of between 0.4% and 1.2%, by weight of the fiber.  
     
     
         82 . The fibers of  claim 75  wherein the polyvalent cation is a transition metal ion.  
     
     
         83 . The fibers of  claim 75  wherein the cation is selected from the group consisting of aluminum, iron, tin and mixtures thereof.  
     
     
         84 . The fibers of  claim 75  wherein the polyvalent cation is in the +3 or +4 oxidation state.  
     
     
         85 . The fibers of  claim 75  wherein said compound is a polyvalent metal salt.  
     
     
         86 . The fibers of  claim 85  wherein said compound is selected from the group consisting of hydroxides of aluminum, iron and tin, and mixtures thereof.  
     
     
         87 . The fibers of  claim 85  wherein said compound is selected from the group consisting of water soluble salts of aluminum, iron and tin, and mixtures thereof.  
     
     
         88 . The fibers of  claim 75  wherein said fiber is at least 80% alpha cellulose and has a water retention value of at least 80%.  
     
     
         89 . The fibers of  claim 75  wherein said fiber is at least 95% alpha cellulose, has a curl of at least 25% and has a water retention value of less than 90%.  
     
     
         90 . The fibers of  claim 75  wherein said fiber is crosslinked, has a curl of greater than 50% and has a water retention value of less than 60%.  
     
     
         91 . The fibers of  claim 75  wherein said fiber is a cellulose fiber selected from the group consisting of softwood cellulose, hardwood cellulose, cotton, esparto grass, bagasse, hemp, flax, chemically modified cellulose, physically modified cellulose, regenerated cellulose, bacterially generated cellulose, lyocell, cellulose acetate and mixtures thereof.  
     
     
         92 . The fibers of  claim 75  wherein said fiber is selected from the group consisting of hydrophobic fibers treated with a surfactant, hydrophobic fibers treated with silica, surface-oxidized hydrophobic fibers, and mixtures thereof.  
     
     
         93 . An absorbent structure comprising: fibers bound with a polyvalent cation-containing compound, said fibers exhibiting an ion extraction factor of at least 5%; superabsorbent polymer particles; and oxalic acid bound to the fiber.  
     
     
         94 . An absorbent structure comprising: 
 (A) fibers, and    (B) superabsorbent polymer particles having surfaces coated with a polyvalent ion salt containing a polyvalent cation and one or more anions.    
     
     
         95 . The structure of  claim 94 , wherein the polyvalent cation is present in an amount from about 0.25 percent to about 5 percent.  
     
     
         96 . The structure of  claim 95 , wherein the polyvalent cation is present in an amount from about 0.25 percent to about 2.5 percent.  
     
     
         97 . The structure of  claim 96 , wherein the polyvalent cation is present in an amount from about 0.4 percent to about 1.2 percent.  
     
     
         98 . The structure of  claim 94 , wherein the polyvalent cation is a transition metal ion.  
     
     
         99 . The structure of  claim 94 , wherein the polyvalent cation is in the +3 or +4 oxidation state.  
     
     
         100 . The structure of  claim 94 , wherein the polyvalent cation is aluminum, iron, tin, or a mixture thereof.  
     
     
         101 . The structure of  claim 99 , wherein the anion is water soluble.  
     
     
         102 . The structure of  claim 99 , wherein the salt is hydroxide.  
     
     
         103 . The structure of  claim 99 , wherein the anion is sulfate.  
     
     
         104 . The structure of  claim 103 , wherein the salt is aluminum sulfate.  
     
     
         105 . The structure of  claim 94 , wherein the superabsorbent polymer is a starch-acrylate graft co-polymer, a polyacrylate, a carboxymethylcellulose derivative or a mixture thereof.  
     
     
         106 . The structure of  claim 105 , wherein the superabsorbent polymer is a polyacrylate.