Coarse pigment addition and high solids slurries for higher coating colour concentrations

Abstract

The present invention relates to an aqueous slurry comprising natural ground calcium carbonate which has a percentage P 5 by weight of particles having a diameter of less than 5.0 μm of from 98.5% to 90%, a percentage P 2 by weight of particles having a diameter of less than 2.0 μm of from 96% to 80%, wherein the ratio of P 2 /P 5 is from 0.98 to 0.85, and wherein the slurry has a solids content of more than 78 wt %.

1 . A process for the preparation of an aqueous slurry having a solids content of more than 78 wt %, comprising the steps of:
 (a) providing a first fraction F1 of a mineral material having a percentage P 5 (F1) by weight of particles having a diameter of less than 5.0 μm of from 75% to 85% and a median particle diameter d 50  of from 2.0 to 3.0 μm,   (b) providing a second fraction F2 of a mineral material having a percentage P 2 (F2) by weight of particles having a diameter of less than 2.0 μm of from 85% to 100% and a median particle diameter d 50  of from 0.3 to 0.65 μm, and   (c) dispersing the first fraction F1 and the second fraction F1 in water.   
     
     
         2 . The process according to  claim 1 , wherein the weight ratio of the first fraction F1 to the second fraction F2 is from 5/95 to 20/80. 
     
     
         3 . The process according to  claim 1 , wherein the first fraction F1 is provided as a dry mineral material. 
     
     
         4 . The process according to  claim 1 , wherein the second fraction F2 is provided as an aqueous slurry. 
     
     
         5 . The process according to  claim 1 , wherein a dispersing agent is added in step (c). 
     
     
         6 . The process according to  claim 1 , wherein the mineral material is calcium carbonate, clay, or a mixture thereof. 
     
     
         7 . The process according to  claim 1 , wherein the mineral matter is natural ground calcium carbonate. 
     
     
         8 . The process according to  claim 1 , wherein the mineral matter is natural ground calcium carbonate obtained from marble, limestone, chalk, or any mixture thereof.