Process for improving particle size distribution of calcium carbonate-comprising material

Process for the preparation of an aqueous suspension comprising at least one calcium carbonate-comprising material, the process comprising the following steps:

• a) providing a substantially dispersant-free aqueous suspension of at least one calcium carbonate-comprising material, and
• b) pre-heating the suspension of step a) to a temperature of from 40 to 95° C. at ambient pressure, and
• c) wet-grinding the pre-heated suspension in at least one grinding step for obtaining an aqueous suspension of at least one wet ground calcium carbonate-comprising material, and
• d) contacting the aqueous suspension before and/or during and/or after wet-grinding step c) and/or before and/or during and/or after removal step e) with at least one base for obtaining an aqueous suspension having a pH measured at 25° C. of ≧9.0, and
• e) removal of at least a part of the particles with a diameter >20 μm in the aqueous suspension of the at least one wet ground calcium carbonate comprising material, and
• f) storing the aqueous suspension obtained after removal step e) at a temperature of from 70 to 140° C. for a period of time of 0.25 to 8 hours, for obtaining an aqueous suspension of at least one calcium carbonate-comprising material having a ratio of particles having an average particle size d80 value to particles having an average particle size d20 value [d80/d20] in the range from 1.5 to 4.0.