Bimodal precipitated calcium carbonate slurries suitable for paper and board applications, methods for making the same and their uses
The present application relates to aqueous slurries comprising precipitated calcium carbonates having a bimodal particle size distribution with a first maximum in particle size distribution and a second maximum in particle size distribution, as well as methods for making them and their uses.
1. An aqueous slurry comprising precipitated calcium carbonate having a bimodal particle size distribution with
a first maximum in particle size distribution in the range of 1.0 to 3.0 μm as measured by Sedigraph and
a second maximum in particle size distribution in the range of 0.2 to 1.0 μm, as measured by Sedigraph;
wherein the said first maximum in particle size distribution substantially represents aggregated particles, and wherein the said second maximum in particle size distribution represents substantially non-aggregated particles.
2. An aqueous slurry according to claim 1 , wherein the precipitated calcium carbonate is scalenohedral precipitated calcium carbonate.
3. An aqueous slurry according to claim 1 , having a solids content of 60 wt. % or greater.
4. An aqueous slurry according to claim 1 , wherein the precipitated calcium carbonate has a BET surface area in the range of 4 to 12 m 2 /g.
5. An aqueous slurry according to claim 1 , wherein the said aggregated particles are made up of primary particles which are substantially the same size as the substantially non-aggregated particles represented by the said second maximum in particle size distribution.
6. A paper coating composition comprising the aqueous slurry according to claim 1 .
7. An aqueous slurry according to claim 3 , wherein the precipitated calcium carbonate has a BET surface area in the range of 4 to 12 m 2 /g.
8. An aqueous slurry according to claim 5 , wherein
the precipitated calcium carbonate is scalenohedral precipitated calcium carbonate,
the precipitated calcium carbonate has a BET surface area in the range of 4 to 12 m 2 /g, and
the slurry has a solids content of 60 wt.-% or greater.
9. A method comprising coating the surface of an article with an aqueous slurry according to claim 1 .
10. The method of claim 9 , wherein the article comprises a raw paper board, raw carton board, or raw cardboard.
11. The method of claim 10 , wherein the coating step hides the base color of the raw paper board, raw carton board, or raw cardboard.
12. The method of claim 9 , wherein
the article is a base paper, board, carton board, or cardboard, and
the coating step improves the board brightness and/or opacity of the base paper, board, carton board, or cardboard.