Grafted crosslinked cellulose

Abstract

Grafted, crosslinked cellulosic materials include cellulose fibers and polymer chains composed of at least one monoethylenically unsaturated acid group-containing monomer (such as acrylic acid) grafted thereto, in which one or more of said cellulose fibers and said polymer chains are crosslinked (such as by intra-fiber chain-to-chain crosslinks). Some of such materials are characterized by a wet bulk of about 10.0-17.0 cm 3 /g, an IPRP value of about 1000 to 7700 cm 2 /MPa·sec, and/or a MAP value of about 7.0 to 38 cm H 2 O. Methods for producing such materials may include grafting polymer chains from a cellulosic substrate, followed by treating the grafted material with a crosslinking agent adapted to effect crosslinking of one or more of the cellulosic substrate or the polymer chains. Example crosslinking mechanisms include esterfication reactions, ionic reactions, and radical reactions, and example crosslinking agents include pentaerythritol, homopolymers of the graft species monomer, and hyperbranched polymers.

What is claimed is: 
     
         1 . A cellulosic material comprising a cellulose fiber and polymer chains composed of at least one monoethylenically unsaturated acid group-containing monomer grafted thereto, wherein one or more of said cellulose fiber and said polymer chains are intra-fiber crosslinked. 
     
     
         2 . The material of  claim 1 , wherein the at least one monoethylenically unsaturated acid group-containing monomer includes acrylic acid. 
     
     
         3 . The material of  claim 1 , characterized by a graft yield of 5-35 weight %. 
     
     
         4 . The material of  claim 3 , characterized by a graft yield of 10-20 weight %. 
     
     
         5 . The material of  claim 1 , wherein the material has a wet bulk at least 6% greater than untreated cellulose fiber. 
     
     
         6 . The material of  claim 1 , wherein the material has a wet bulk of about 10.0-17.0 cm 3 /g. 
     
     
         7 . The material of  claim 1 , wherein the material has an IPRP value of about 1000 to 7700 cm 2 /MPa·sec and a MAP of about 7.0 to 20 cm H 2 O. 
     
     
         8 . The material of  claim 1 , wherein for a given IPRP value y (in cm 2 /MPa·sec) from 1000 to 7700, the MAP value of the material (in cm H 2 O) is within +1-30% of the value of x in the formula y=mx Z ; wherein m is from 600 to 1200, and wherein z is from −0.590 to −0.515. 
     
     
         9 . The material of  claim 7 , characterized in that at a given IPRP value (in cm 2 /MPa·sec) from 800 to 5400, the material has a MAP value that is equal to or higher than the corresponding MAP value possessed by non-grafted, crosslinked cellulose fiber. 
     
     
         10 . The material of  claim 7 , characterized in that at a given MAP value (in cm H 2 O) from 7.0 to 20, the material has an IPRP value that is equal to or higher than the corresponding IPRP value possessed by non-grafted, crosslinked cellulose fiber. 
     
     
         11 . The material  claim 1 , wherein the material has an IPRP value of 5400 cm 2 /MPa·sec or above. 
     
     
         12 . A fibrous cellulosic material comprising cellulose-graft-poly(acrylic) acid having a graft yield of 10-20 weight % and intrafiber wherein two or more grafted polymer chains of poly(acrylic) acid are intra-fiber crosslinked. 
     
     
         13 . The material of  claim 12 , wherein the material has a wet bulk of about 15.0-17.0 cm 3 /g. 
     
     
         14 . The material of  claim 13 , wherein said two or more polymer chains of poly(acrylic) acid are intra-fiber crosslinked by one or more of pentaerythritol and a hyperbranched polymer. 
     
     
         15 . A method of producing a grafted, crosslinked cellulosic material, the method comprising:
 grafting polymer chains of at least one monoethylenically unsaturated acid group-containing monomer from a cellulosic substrate to produce a grafted cellulosic material; and   subsequently crosslinking the grafted cellulosic material by treating the material with a crosslinking agent adapted to effect crosslinking of one or more of the cellulosic substrate or the polymer chains.   
     
     
         16 . The method of  claim 15 , wherein the grafting is performed in situ. 
     
     
         17 . The method of  claim 16 , wherein the grafting includes reacting the at least one monomer with the cellulosic substrate in the presence of a grafting initiator. 
     
     
         18 . The method of  claim 17 , wherein the grafting includes varying one or more of the weight percent of the initiator, and the ratio of the cellulosic substrate to the monomer, to achieve a desired graft yield level. 
     
     
         19 . The method of  claim 15 , wherein the grafting includes using acrylic acid as the at least one monomer. 
     
     
         20 . The method of  claim 15 ,
 wherein the crosslinking includes establishing intra-fiber crosslinks via an esterification reaction, and   wherein the crosslinking agent includes one or more of pentaerythritol, a homopolymer formed of the at least one monoethylenically unsaturated acid group-containing monomer, and a hyperbranched polymer.