Patent EA-004451-B1 (EA)
Title: Pigment composite and method for the preparation thereof
Inventor: GRONROOS LARS
IPC: C09D7/12
Filed: 2001-04-18
Abstract: 1. A coating element comprising a pigment binder structure granule formed from pigment particles and a binder and, possibly, additives, characterized in that the granule has an essentially rotationally symmetrical shape and it has an inner part and a crust part, the density of the inner part is about 10 to 90 % % of the density of the crust part. 2. The coating element according to claim 1, characterized in that the density of the inner part of the particle granule is about 40 to 80 % of the density of the crust part. 3. The coating element according to claim 2, characterized in that the particle granule consists of pigment particles, the density of which is about 2.4 to 3.1 kg/m<3>, whereby the density of the inner part is about 1.1 to 1.5kg/m<3>, and that of the crust part about 1.7 to 2.0 kg/m<3>. 4. The coating element according to any of the preceding claims, characterized in that the inner part of the particle granule contains coarser pigment particles in relation to the crust part. 5. The coating element according to any of the preceding claims, characterized in that the porosity of the inner part of the particle granule is higher than that of the crust part, the pore volume of the inner part being 10 to 50 % by volume, preferably about 30 volume-%. 6. The coating element according to any of the preceding claims, characterized in that it contains about 1 to 30 weight fractions, preferably about 2 to 20 weight fractions of binder per 100 weight fractions of pigment particles. 7. The coating element according to any of the preceding claims, characterized in that the crust layer comprises pigment particles that are bound to one another through a crosslinked binder, forming a dense film that surrounds the inner part. 8. The coating element according to any of the preceding claims, characterized in containing additives that affect its electrical or optical properties. 9. The coating element according to any of the preceding claims, characterized in that that its particle granule is essentially spherical and its diameter is about 1 to 100 mum, preferably about 5 to 50 mu. 10. The coating element according to any of the preceding claims, characterized in that the composition of the surface layer of the particle granule corresponds to that of the surface layer of the coating before the mechanical treatment that it is subjected to. 11. A method for preparing a coating element, according to which an aqueous slurry is prepared from pigment particles, a binder, and possible additives, which slurry is dried, characterized in that the aqueous slurry is dried in conditions, where the pigment particles are bound to one another through a binding agent, forming rotationally symmetrical particle granules that comprise an inner part and a crust part, the density of the inner part is about 10 to 90 % % of the density of the crust part being smaller than the crust part. 12. The method according to claim 11, characterized in that fine-grained drops are formed from the aqueous slurry, and dried separately from one another. 13. The method according to claim 12, characterized in that drops are formed, the size of which is about 1 to 300 mum, preferably 5 to 100 mum, more preferably 50 mum maximum. 14. The method according to any of claims 11 to 13, characterized in that the aqueous slurry is dried by spray drying. 15. The method according to any of claims 11 to 14, characterized in that the dry content of the aqueous slurry is about 40 to 95 % by weight, preferably about 50 to 90 weight-%. 16. A coated fibrous web comprising a web formed from a lignocellulose-based raw material, a coating layer containing a pigment and a binder being formed at least onto one surface of the web, characterized in that the coating consists of interconnected cells formed from flattened coating elements, the individual cells comprising a film-like layer of pigment/binder, its density part is about 10 to 90 % % of the density of the film-like layer of pigment/binder. 17. The coated fibrous web according to claim 16, characterized in its coating comprising, on the average, 1 to 10 superimposed layers of pigment cells. 18. The coated fibrous web according to claim 16 or 17, characterized in that the coating consists of a layer of coating elements that is mechanically treated, in which layer the originally essentially rotationally symmetrical elements have been flattened under the effect of pressure and/or temperature to form a smooth layer. 19. The coated fibrous web according to any of claims 16 to 18, characterized in that the surface part of the coating consists of the fine-grained and binder-containing surface parts of the mechanically treated elements. 20. The coated fibrous web according to any of claims 16 to 19, characterized in that the inner part of the coating mainly consists of the porous inner parts of the mechanically treated elements. 21. The coated fibrous web according to any of claims 16 to 20, characterized in that the elements that form the surface part of the coating contain additives that affect its electrical or optical properties. 22. A method for coating a fibrous web, according to which -a coating colour containing particle granules is spread at least onto one surface of the fibrous web, characterized by -using particle granules, which are essentially rotationally symmetrical and which comprise an inner part and a crust part, the density of the inner part being lower than the crust part, and -subjecting the web coated with the particle granule-containing coating colour to mechanical treatment to at least partially flatten the granules. 23. The method according to claim 22, characterized in that in connection with the application of the coating slip, a binder such as latex emulsion is added. 24. The method according to claim 22 or 23, characterized in that linear pressure induced by the nip between rotating rolls is exerted on the web coated with the particle granules. 25. The method according to claim 24, characterized in that the pressure exerted on the web coated with the elements is selected so that it is sufficient for flattening the elements but does not cause an essential decrease in the bulk of the fibrous structure of the web. 26. The method according to Claim 24 or 25, characterized in that the nip that induces the pressure is formed from two rolls, of which at least one is heated. 27. A particle granule consisting of plate-like pigment particles and a binder, characterized in that - the granule has an inner part and a crust part, the density of the inner part is about 10 to 90 % % of the density of the crust part. - the surface layer of the granule, forming the crust, consists of a layer that has at least one layer of pigment particles, which have mainly settled with their levels in the direction of the surface of the granule, and the levels of the pigment particles are almost on the same level. 28. The granule according to claim 27, characterized in that there are some binder and pores between the pigment particles that are on the surface. 29. The granule according to claim 27 or 28, characterized in that the relation of the surface areas of the plate-like pigment particles to the surface area of the binder and the pores between the particles is 0.3 to 60: 1, preferably 0.5 to 4: 1. 30. The granule according to any of claims 27 to 29, characterized in that the inner part of the granule is formed from the part of the plate-like pigment particles that is partially in disorder, so that it mainly contains pigment particles, pores, and some binder. 31. The granule according to any of claims 27 to 30, characterized in that the amount of pores from its volume is 15 to 60 %, preferably 30 to 45 %. 32. The granule according to any of claims 27 to 31, characterized in that the plate-like pigment particles are typically silica minerals, which contain alkali metal and/or alkali earth as a cation. 33. The granule according to any of claims 27 to 32, characterized in that the size distribution of the plate-like particles is 60 % < 5 mum minimum, 95 % < 1 mum maximum. 34. The particle granule according to any of claims 27 to 33, characterized in that an organic binder that dissolves in the solvent phase used, or is dispersed in it, is used as a binder. 35. The granule according to any of claims 27 to 34, characterized in that the portion of binder inside the granule is 0.5 to 3 weight-% of the amount of pigment, preferably 1 %. 36. The granule according to any of claims 27 to 35, characterized in that the binder is concentrated on the surface part of the granule, where its amount is 6 to 60 weight-% of the weight of the pigment, preferably about 50 %. 37. The granule according to any of claims 27 to 36, characterized in being plastically deformable under the effect of pressure and/or temperature. 38. A granule for use as a filler for fibrous web according to claims 27-37.