Abstract: Process for bleaching a chemical paper pulp to a brightness of at least 89° ISO, consisting in subjecting the pulp to a treatment sequence of several stages including a final bleaching stage with hydrogen peroxide in alkaline medium carried out in the presence of at least one stabilising agent and at a consistency of at least 25% by weight of solids, the stages preceding this final stage having purified the pulp so that its manganese content does not exceed 3 ppm by weight with respect to the solids and that the pulp has been delignified beforehand to a kappa number not exceeding 5.

Abstract: A process for the delignification and bleaching of chemical pulp utilizes an acid treatment stage aimed at reducing the quantity of hexene uronic acids present in the pulp by at least 30%, and a pH adjustment stage of the pulp aimed at depositing or redepositing ions of alkaline-earth metals on the fibres of the pulp. The process further includes a washing stage of the pulp and a treatment stage of the pulp with an oxidizing agent. A chelating agent is added to the pulp before and/or during the acid treatment stage and/or before or during the pH adjustment stage or between the pH adjustment stage and washing stage.

Abstract: Process for bleaching a chemical paper pulp by means of a sequence of treatment stages involving at least one stage with an enzyme and at least one stage with a peroxyacid.

Abstract: Process for improving the selectivity of the delignification of a chemical paper pulp by employing a peroxyacid, in which the unbleached pulp originating from the cooking operation is treated with an aqueous solution of this organic peroxyacid in the presence of at least one stabilizer selected from phosphonic acids and their salts.