Process for loading a fibrous slurry with filler

Abstract

A process to load a fibrous slurry with a filler, in particular with calcium carbonate (fiber loading). The loaded fibrous slurry is divided into at least two fractions, a light fraction and a heavy fraction, for which purpose hydrocyclones are used in one embodiment. In this case, the different fractions have a different level of loading, that is to say the quantity of precipitated fillers adhering to the fibers is different in each case. There is the possibility of feeding the less highly loaded fibers back into the loading process, in order to increase the level of loading of this fraction further.

1 . A process for loading a fibrous slurry with a filler, said filler including at least one of calcium carbonate and calcium hydroxide in one of liquid and dry form, the process comprising the steps of:
 introducing at least one of said calcium carbonate and said calcium hydroxide into the fibrous slurry;   precipitating said filler in the fibrous slurry by chemical reaction;   fractionating the fibrous slurry into at least two fractions having a different level of loading; and   treating said at least two fractions differently.   
   
   
       2 . The process according to  claim 1 , wherein said fractionating step further includes the step of applying centrifugal forces. 
   
   
       3 . The process according to  claim 2 , wherein said fractionating step further includes using hydrocyclones. 
   
   
       4 . The process according to  claim 3 , wherein said fractionating step further includes the step of producing a centrifugal field with said hydrocyclones, said centrifugal field being at least as great as 200 times the acceleration due to earth gravity. 
   
   
       5 . The process according to  claim 1 , further comprising the step of forming at least one light fraction having a lower level of loading and at least one heavy fraction having a higher level of loading. 
   
   
       6 . The process according to  claim 5 , further comprising the step of loading said light fraction again. 
   
   
       7 . The process according to  claim 6 , further comprising the step of recirculating said light fraction through the same said loading process. 
   
   
       8 . The process according to  claim 6 , further comprising the step of loading said light fraction in an alternative said loading process. 
   
   
       9 . The process according to  claim 5 , further comprising the step of refining said light fraction and said heavy fraction. 
   
   
       10 . The process according to  claim 5 , further comprising the step of producing a plurality of one of paper and board products using one of said light fraction and said heavy fraction. 
   
   
       11 . The process according to  claim 5 , further comprising the step of producing a plurality of layers in one of paper and board using said light fraction and said heavy fraction. 
   
   
       12 . The process according to  claim 1 , wherein said fibrous slurry is an aqueous fibrous material, in particular aqueous paper stock, having a consistency between 0.1 to 20%. 
   
   
       13 . The process according to  claim 12 , wherein said aqueous fibrous material has a consistency between 2 and 8%. 
   
   
       14 . The process according to  claim 1 , wherein the temperature during said precipitating step is between −15° C. and 120° C. 
   
   
       15 . The process according to  claim 14 , wherein the temperature during said precipitating step is between 20° C. and 90° C. 
   
   
       16 . The process according to  claim 1 , further comprising the step of carrying out said precipitating step using gaseous carbon dioxide. 
   
   
       17 . The process according to  claim 1 , further comprising the step of producing one of rhombohedral, scalenohedral and spherical crystals. 
   
   
       18 . The process according to  claim 17 , wherein the dimentions of said one of rhombohedral, scalenohedral and spherical crystals are between 0.05 and 5 μm. 
   
   
       19 . The process according to  claim 18 , wherein the dementions of said one of rhombohedral, scalenohedral and spherical crystals are between 0.3 and 2.5 μm. 
   
   
       20 . The process according to  claim 1 , further comprising the step of carrying out said loading step at a pressure range of between 0 and 15 bar. 
   
   
       21 . The process according to  claim 20 , further comprising the step of carrying out said loading step at a pressure range of between 0 and 6 bar. 
   
   
       22 . The process according to  claim 1 , further comprising the step of carrying out said loading step at a pH between 6 and 10. 
   
   
       23 . The process according to  claim 22 , further comprising the step of carrying out said loading step at a pH between 6.5 and 9.5. 
   
   
       24 . The process according to  claim 1 , further comprising the step of carrying out said loading step at a dryness between 0.1% and 60%. 
   
   
       25 . The process according to  claim 24 , further comprising the step of carrying out said loading step at a dryness between 15% and 35%. 
   
   
       26 . The process according to  claim 1 , wherein the reaction time of said chemical reaction of said precipitating step is between 0.03 seconds and 1 minute. 
   
   
       27 . The process according to  claim 26 , wherein the reaction time of said chemical reaction of said precipitating step is between 0.05 and 10 seconds.