Method for obtaining a fibrous preparation for immersion-resistant opaque paper

The present invention relates to a method for obtaining a fibrous preparation for manufacturing a paper having significant water repellency and opacity in the dry or wet state, characterised in that it comprises at least the following steps: - suspending fibres in water, - adding calcium salts to the fibres, - adding a source of carbonate salts in the form of an aqueous solution, - stirring the resulting mixture for a time sufficient to allow calcium carbonate particles to be precipitated, - adding a solution of fatty acid salts heated to a temperature which corresponds to the micellisation temperature of the fatty acid salts and takes into account the critical micellar concentration of the fatty acid salts, - stirring the mixture thus obtained for a time sufficient to allow the fatty acids to be absorbed at the surface of the calcium carbonate particles and to obtain the desired fibrous preparation.