Bentonite for binding impurities during paper production

Abstract

A method for binding impurities in paper production, comprising the following steps: a) provision of a bentonite, the proportion of the monovalent cations, based on the cation exchange capacity (CEC) of the bentonite, being at least 0.7 and the CEC being more than 85 meq/100 g, preferably more than 90 meq/100 g, in particular more than 95 meq/100 g; b) addition of the bentonite according to a) to a paper pulp or fiber suspension; c) binding of the impurities to the bentonite in the pulp or fiber suspension is described.

1 . A method for binding impurities in paper production, comprising the following steps:
 a) providing bentonite, with a proportion of monovalent cations of at least about 0.7 based on the cation exchange capacity (CEC) of the bentonite, wherein the CEC is greater than 85 meq/100 g;   b) adding the bentonite to a paper pulp or fiber suspension; and   c) binding impurities to the bentonite in the pulp or fiber suspension.   
   
   
       2 . The method as claimed in  claim 1 , characterized in that the proportion of the monovalent cations, based on the CEC of the bentonite, is more than 0.8. 
   
   
       3 . The method as claimed in  claim 1 , characterized in that the proportion of calcium and/or magnesium ions in the bentonite, based on the CEC of the bentonite, is less than 0.2. 
   
   
       4 . The method as claimed in  claim 1 , characterized in that the particle size of the bentonite is chosen so that in the wet sieve residue less than 2% by weight, is 45 μm. 
   
   
       5 . The method as claimed in  claim 1 , characterized in that the monovalent cations in the bentonite are selected from the group consisting of sodium, potassium, lithium and mixtures thereof. 
   
   
       6 . The method as claimed in  claim 1 , characterized in that the bentonite is present in particulate form having a median particle size (D50, based on volume) of from 0.5 to 10 μm. 
   
   
       7 . The method as claimed in  claim 1 , characterized in that the addition of the bentonite is effected in the absence of talc. 
   
   
       8 . The method as claimed in  claim 1 , characterized in that the bentonite has a swellability of at least 25 ml/2 g. 
   
   
       9 . The method as claimed in  claim 1 , characterized in that the bentonite has a proportion of iron ions, based on the CEC, of less than about 0.005. 
   
   
       10 . The method as claimed in  claim 1 , characterized in that the bentonite has a BET surface area of less than 100 m 2 /g. 
   
   
       11 . The method as claimed in  claim 1 , characterized in that from about 0.5 to 10 kg of bentonite are added per tonne of paper pulp or fiber suspension (dry weight). 
   
   
       12 . The method as claimed in  claim 1 , characterized in that the paper pulp or fiber suspension contains a groundwood fraction. 
   
   
       13 . The method as claimed in  claim 12 , characterized in that the groundwood fraction in the paper pulp or the fiber suspension is at least 10% by weight, based on the total pulp or fiber suspension (dry weight). 
   
   
       14 . The method as claimed in  claim 1 , characterized in that no additional talc is added to the paper pulp or fiber suspension. 
   
   
       15 . (canceled) 
   
   
       16 . (canceled) 
   
   
       17 . (canceled) 
   
   
       18 . (canceled) 
   
   
       19 . The method as claimed in  claim 1 , wherein the CEC of the bentonite is greater than 95 meq/100 g. 
   
   
       20 . The method as claimed in  claim 1  characterized in that the proportion of the monovalent cations, based on the CEC of the bentonite, is more than 0.85. 
   
   
       21 . The method as claimed in  claim 1  characterized in that the proportion of calcium and/or magnesium ions in the bentonite, based on the CEC of the bentonite, is less than 0.15. 
   
   
       22 . The method as claimed in  claim 1  characterized in that the particle size of the bentonite is chosen so that the wet sieve residue less than 2% by weight is 45 μm. 
   
   
       23 . The method as claimed in  claim 1  characterized in that the bentonite is present in particulate form having a medium particle size (D50, based on volume) of from 2 to 6 μm. 
   
   
       24 . A method for binding hydrophobic impurities in paper production, comprising the following steps:
 a) providing bentonite, with a proportion of monovalent cations of at least about 0.7 based on the cation exchange capacity (CEC) of the bentonite, wherein the CEC is greater than 85 meq/100 g;   b) adding the bentonite to a paper, pulp or fiber suspension; and   c) binding hydrophobic impurities to the bentonite in the pulp and fiber suspension.