Kaolin products and their use

1. A particulate kaolin,

wherein the kaolin has a mean particle size ranging from 0.9 μm to 2.5 μm, and a shape factor of at least 60.

2. The particulate kaolin according to claim 1 , wherein the shape factor is at least 65.

3. A composition comprising filler materials,

wherein the composition comprising filler materials comprises the particulate kaolin according to claim 1 , and

at least one additional filler chosen form hydrous kaolin, calcined kaolin, talc, calcium sulfate and alkaline earth metal carbonates.

4. The composition according to claim 3 , wherein the composition comprises particulate kaolin in amount ranging from at least 50% by weight, relative to the total weight of the composition.

5. The composition according to claim 4 , wherein the composition comprises particulate kaolin in amount ranging from 60% to 80% by weight, relative to the total weight of the composition.

6. The composition according to claim 3 , wherein the at least one additional filler comprises calcium carbonate.

7. The composition according to claim 6 , wherein the calcium carbonate comprises a material obtained from a natural source and processed by grinding.

8. The composition according to claim 6 , wherein the calcium carbonate comprises a material prepared by chemical synthesis.

9. The composition according to claim 8 , wherein at least one additional solid is bonded to the calcium carbonate.

10. The composition according to claim 6 , wherein the calcium carbonate has a mean particle size ranging from 0.5 μm to 1.5 μm.

11. The composition according to claim 10 , wherein the calcium carbonate has a mean particle size ranging from 0.7 μm to 1.3 μm.

12. The composition according to claim 6 , wherein the calcium carbonate has a steepness factor of at least 40.

13. The composition according to claim 12 , wherein the calcium carbonate has a steepness factor of at least 50.

14. The composition according to claim 6 , wherein the calcium carbonate is in the form of a composition containing at least one chemical additive in an amount ranging from greater than 0 to 15% by weight on an active basis,

wherein said at least one chemical additive is capable of stabilizing the carbonate in acidic conditions.

15. The composition according to claim 6 , wherein the particulate kaolin has a mean particle size of at least 1.2 μm, and

wherein the weight ratio of kaolin:calcium carbonate in the composition is at least 50:50.

16. The composition according to claim 15 , wherein the particulate kaolin has a mean particle size ranging from 1.2 μm to 1.7 μm, and

wherein the weight ratio of kaolin:calcium carbonate in the composition ranges from 60:40 to 80:20.

17. The composition according to claim 6 , wherein the particulate kaolin has a mean particle size ranging from 0.9 μm to 1.2 μm, and

wherein the weight ratio of kaolin:calcium carbonate in the composition to 50:50 or less.

18. The composition according to claim 17 , wherein the particulate kaolin has a mean particle size ranging from 1.2 μm to 0.9 μm, and

wherein the weight ratio of kaolin:calcium carbonate ranges from 40:60 to 20:80.

19. A method of making uncoated paper sheets, comprising preparing an aqueous paper-making composition from a pulp and mineral filler particles, and

forming the composition into paper sheets,

wherein the mineral filler particles comprise a composition according to claim 3 .

20. The method according to claim 19 , wherein the paper sheets are calendared by a supercalendar process.

21. The method according to claim 19 , wherein the pulp comprises mechanical pulp in an amount ranging from at least 70% by weight.

22. The method according to claim 19 , wherein the paper sheets are suitable for printing upon by a process chosen from a gravure printing process and an offset printing process.

23. A method of making uncoated paper sheets, comprising

preparing an aqueous paper-making composition from a pulp and mineral filler particles, and

forming the composition into paper sheets,

wherein the mineral filler particles comprise a particulate kaolin according to claim 1 .

24. The method according to claim 23 , wherein the paper sheets are calendared by a supercalendar process.

25. The method according to claim 23 , wherein the pulp comprises mechanical pulp in an amount ranging from at least 70% by weight.

26. The method according to claim 23 , wherein the paper sheets are suitable for printing upon by a process chosen from a gravure printing process and an offset printing process.