Paper Product with Increased Relative Wet Tensile Strength and Softness, Method for Production and Use Thereof

Abstract

The present invention relates to flat paper products having an increased relative wet strength and softness, a method for the production of the same and also the use of paper products of this type in the form of tissue products. This is achieved by a cross-linkage of the cellulose fibres contained in the paper product with a cationic graft copolymer which is constructed on the basis of polyethyleneoxide- or polyethyleneglycol segments and polyethyleneimine segments.

1 . A paper product having increased relative wet strength and softness containing cellulose fibers which are cross-linked with a graft copolymer comprising a polyethyleneimine segment of the general formula I 
     
       
         
         
             
             
         
       
       x, y and z being chosen such that the molar mass is in the range of 1000 to 2000000 D, and at least one of a polyalkyleneoxide segment and a polyalkyleneglycol segment of the general formula II, 
     
     
       
         
         
             
             
         
       
       with R 1  and R 2  independently of each other C 1 -C 12 -alkyl, and n being chosen such that the molar mass thereof is in the range of 350 to 2000000 D. 
     
   
   
       2 . The paper product according to  claim 1  the graft copolymer has a backbone comprising polyethyleneimine and grafts comprising at least one polyalkyleneoxide and/or at least one polyalkyleneglycol. 
   
   
       3 . The paper product according to  claim 1  wherein the graft copolymer has a backbone comprising at least one polyalkyleneoxide and/or at least one polyalkyleneglycol and grafts comprising polyethyleneimine. 
   
   
       4 . The paper product according to  claim 1  wherein the polyethyleneimine is linear. 
   
   
       5 . The paper product according to  claim 1  wherein the polyethyleneimine is branched. 
   
   
       6 . The paper product according to  claim 1  wherein the polyethyleneimine has a molar mass in the range of 20000 to 1000000 D. 
   
   
       7 . The paper product according to  claim 1  wherein the polyalkyleneglycol is polyethyleneglycol. 
   
   
       8 . The paper product according to  claim 1  wherein the polyalkyleneoxide is polyethyleneoxide. 
   
   
       9 . The paper product according to  claim 1  wherein the polyalkyleneglycol and/or the polyalkyleneoxide has a molar mass in the range of 350 to 1000000 D, in particular 350 to 80000 D. 
   
   
       10 . The paper product according to  claim 1  wherein a terminal hydroxyl group of the polyalkyleneoxide and/or of the polyalkyleneglycol is blocked. 
   
   
       11 . The paper product according to  claim 10  wherein the terminal hydroxy group is blocked with a methoxy, ethoxy, propyloxy, butyloxy and/or benzyloxy group. 
   
   
       12 . A method for the production of flat paper products having an increased relative wet strength and softness from a pulp stock, the method comprising at least one of adding to the pulp stock, adding to the paper product during production, and adding to the paper product after production a graft copolymer comprising a polyethyleneimine segment of the general formula I 
     
       
         
         
             
             
         
       
       x, y and z being chosen such that the molar mass is in the range of 1000 to 2000000 D, and at least one of a polyalkyleneoxide segment and a polyalkyleneglycol segment of the general formula II, 
     
     
       
         
         
             
             
         
       
       with R1 and R2 independently of each other C1-C12-alkyl, and n being chosen such that the molar mass thereof is in the range of 350 to 2000000 D. 
     
   
   
       13 . The method according to  claim 12  wherein said at least one of adding to the pulp stock, adding to the paper product during production, and adding to the paper product after production a graft copolymer comprising a polyethyleneimine segment and at least one of a polyalkyleneoxide segment and a polyalkyleneglycol segment comprises at least one of adding to the pulp stock, adding to the paper product during production, and adding to the paper product after production a graft copolymer having a backbone comprising polyethyleneimine and grafts comprising at least one of a polyalkyleneoxide and a polyalkyleneglycol. 
   
   
       14 . The method according to  claim 12  wherein said at least one of adding to the pulp stock, adding to the paper product during production, and adding to the paper product after production a graft copolymer comprising a polyethyleneimine segment and at least one of a polyalkyleneoxide segment and a polyalkyleneglycol segment comprises at least one of adding to the pulp stock, adding to the paper product during production, and adding to the paper product after production a graft copolymer having a backbone comprising at least one of a polyalkyleneoxide and a polyalkyleneglycol and grafts comprising polyethyleneimine. 
   
   
       15 . The method according to  claim 12  wherein said at least one of adding to the pulp stock, adding to the paper product during production, and adding to the paper product after production a graft copolymer comprising a polyethyleneimine segment and at least one of a polyalkyleneoxide segment and a polyalkyleneglycol segment comprises adding a polyethyleneglycol segment. 
   
   
       16 . The method according to  claim 12  wherein said at least one of adding to the pulp stock, adding to the paper product during production, and adding to the paper product after production a graft copolymer comprising a polyethyleneimine segment and at least one of a polyalkyleneoxide segment and a polyalkyleneglycol segment comprises adding a polyethyleneoxide segment. 
   
   
       17 . The method according to  claim 12  wherein adding a graft copolymer comprising a polyethyleneimine segment comprises adding a polyethyleneimine segment having a weight, relative to the initial compounds, greater than 50% by weight. 
   
   
       18 . The method according to  claim 17  wherein adding a graft copolymer comprising a polyethyleneimine segment comprises adding a polyethyleneimine segment having a weight, relative to the initial compounds, greater than 80% by weight. 
   
   
       19 . The method according to  claim 17  wherein adding a graft copolymer comprising a polyethyleneimine segment comprises adding a polyethyleneimine segment having a weight, relative to the initial compounds, greater than 90% by weight. 
   
   
       20 . The method according to  claim 12  wherein said at least one of adding to the pulp stock, adding to the paper product during production, and adding to the paper product after production a graft copolymer comprising a polyethyleneimine segment and at least one of a polyalkyleneoxide segment and a polyalkyleneglycol segment comprises at least one of adding a polyalkyleneoxide segment having a blocked terminal hydroxyl group and adding a polyalkyleneglycol segment having a blocked terminal hydroxyl group. 
   
   
       21 . The method according to  claim 20  wherein said at least one of adding a polyalkyleneoxide segment having a blocked terminal hydroxyl group and adding a polyalkyleneglycol having a blocked terminal hydroxyl group comprises at least one of adding a polyalkyleneoxide segment having a terminal hydroxyl group blocked by one of a methoxy group, an ethoxy group, a propyloxy group, a butyloxy group and a benzyloxy group, and adding a polyalkyleneglycol having a terminal hydroxyl group blocked by one of a methoxy group, an ethoxy group, a propyloxy group, a butyloxy group and a benzyloxy group. 
   
   
       22 . The method according to  claim 12  further comprising converting a free terminal hydroxy group of said at least one of the polyalkyleneoxide and the polyalkyleneglycol with an epihalogenhydrin into a polyethyleneglycol glycidyl ether and grafting said polyethyleneglycol glycidyl ether onto the polyethyleneimine via the amine groups. 
   
   
       23 . Use of the paper products according to  claim 1  as tissue product.