Patent ID: 7504000

Claim:
A process for the manufacture of a sheet of paper containing paper fibers and calcium carbonate, mostly in the form of calcite crystals directly linked to the paper fibers, wherein said process includes the steps of: providing an aqueous composition containing calcium hydrogen carbonates and/or hydrated and/or dissolved carbon dioxide; adding thereto an aqueous composition which is an aqueous suspension of solid particles of calcium hydroxide, known as milk of lime, so as to precipitate calcium carbonate in the form of vaterite crystals, wherein the calcium hydroxide is in the form of solid particles with an average grading between 0.5 and 2 μm; immediately adding paper fibers; allowing the vaterite crystals to be transformed into calcite crystals upon contact with the fibers; placing this mixture containing the calcite crystals fixed to the fibers onto the wire of the paper-making machine for drainage and formation of the sheet of paper; and processing (if necessary) and drying the sheet of paper thus obtained.