Compositions of calcium carbonates/pigments for paper formulations, showing print through reduction
The present invention relates to mixtures of two distinct porous, stable aggregates and rather coarse PCCs (precipitated) calcium carbonate pigments (such as a composition comprising a blend or mix of one of the two Grade B or Grade C PCCs, in combination with a second, specific S-PCC (S=scalenohedral type PCC) pigment in a ratio appropriately selected between 90/10 and 10/90 percent by dry weight, namely 80/20 and 20/80, with a coarser, third component, which may be a pigment and/or a filler such as natural calcium (ground) carbonate or (most preferably) a PCC (precipitated calcium carbonate), depending on the granulometry of the two fine PCCs the third, coarser component, may be omitted. The main criteria for selecting the said “coarser” pigment is that it should feature a granulometry which does no affect noticeably, when in admixture with the blend PCC Grade B (or PCC Grade C) with S-PCC the finest part of the granulometry data of the blend, and in particular that it should not contribute anything significant to the amount of particles <0.2 μm, preferably nothing <0.3 μm, more preferably nothing <0.5 μm and most preferably nothing <1 μm.
1. A composition comprising a blend or mixture of (i) a Grade B precipitated calcium carbonate (PCC) and/or a Grade C PCC and (ii) a scalenohedral PCC (S-PCC), wherein the Grade B PCC has the following particle size distribution: 98% of particles are <5 microns, 66% of particles are <2 microns, 32% of particles are <1 microns, 12% of particles are <0.5 microns and 6% of particles are <0.2 microns, and wherein the Grade C PCC has the following particle size distribution: 99% of particles are <5 microns, 66% of particles are <2 microns, 35% of particles are <1 microns, 16% of particles are <0.5 microns and 11% of particles are <0.2 microns.
2. The composition according to claim 1 , wherein ratio of (i) and (ii) is between 90/10 and 10/90 percent by dry weight.
3. The composition according to claim 1 , wherein the ratio of (i) and (ii) is between 80/20 and 20/80.
4. The composition according to claim 1 , that comprises Grade C PCC and S-PCC at a ratio of 50/50 by dry weight.
5. The composition according to claim 1 , that comprises Grade B PCC and S-PCC at a ratio of 70/50 by dry weight.
6. The composition according to claim 1 , that comprises Grade B PCC and S-PCC at a ratio of 50/50 by dry weight.
7. The composition according to claim 1 , further comprises an additional mineral filler or pigment.
8. The composition according to claim 7 , wherein the additional mineral filler or pigment is natural calcium (ground) carbonate, PCC, talc, kaolin, titanium oxide (TiO 2 ), clay, or dolomite.
9. The composition according to claim 7 , wherein the additional mineral filler or pigment is PCC.
10. The composition according to claim 7 , wherein the additional mineral filler or pigment is present at less than 10 wt % of the total weight of (i) Grade B PCC and/or Grade C PCC, (ii) S-PCC, and (iii) additional mineral filler or pigment.
11. The composition according to claim 7 , wherein the additional mineral filler or pigment is present at 0.1 to 10 wt % of the total weight of (i) Grade B PCC and/or Grade C PCC, (ii) S-PCC, and (iii) additional mineral filler or pigment.
12. The composition according to claim 7 , wherein the additional mineral filler or pigment is present at 0.5 to 7 wt % of the total weight of (i) Grade B PCC and/or Grade C PCC, (ii) S-PCC, and (iii) additional mineral filler or pigment.
13. The composition according to claim 7 , wherein the additional mineral filler or pigment is present at 2 to 7 wt % of the total weight of (i) Grade B PCC and/or Grade C PCC, (ii) S-PCC, and (iii) additional mineral filler or pigment.
14. The composition according to claim 7 , wherein the additional mineral filler or pigment has a granulometry which does not affect noticeably, when in admixture with (i) Grade B PCC and/or Grade C PCC and (ii) scalenohedral PCC (S-PCC), the amount of particles <0.2 μm.
15. The composition according to claim 7 , wherein the additional mineral filler or pigment has a granulometry which does not affect, when in admixture with (i) Grade B PCC and/or Grade C PCC and (ii) scalenohedral PCC (S-PCC), the amount of particles <0.3 μm.
16. The composition according to claim 7 , wherein the additional mineral filler or pigment has a granulometry which does not affect, when in admixture with (i) Grade B PCC and/or Grade C PCC and (ii) scalenohedral PCC (S-PCC), the amount of particles <0.5 μm.
17. The composition according to claim 7 , wherein the additional mineral filler or pigment has a granulometry which does not affect, when in admixture with (i) Grade B PCC and/or Grade C PCC and (ii) scalenohedral PCC (S-PCC), the amount of particles <1 μm.
18. A fiber-containing pulp comprising the composition according to claim 1 .
19. A paper product comprising the fiber-containing pulp according to claim 18 .
20. The paper product according to claim 19 , which comprises between 0.3 to 5% by dry weight of (i) Grade B PCC and/or Grade C PCC, (ii) scalenohedral PCC (S-PCC), and optionally (iii) an additional mineral filler or pigment that is courser than (i) Grade B PCC and/or Grade C PCC, and (ii) S-PCC.
21. The paper product according to claim 19 , which comprises between 0.5 to 3% by dry weight of (i) Grade B PCC and/or Grade C PCC, (ii) scalenohedral PCC (S-PCC), and optionally (iii) an additional mineral filler or pigment that is courser than (i) Grade B PCC and/or Grade C PCC, and (ii) S-PCC.
22. The paper product according to claim 19 , which comprises between 1 to 2% by dry weight of (i) Grade B PCC and/or Grade C PCC, (ii) scalenohedral PCC (S-PCC), and optionally (iii) an additional mineral filler or pigment that is courser than (i) Grade B PCC and/or Grade C PCC, and (ii) S-PCC.