Process for bleaching chemical pulp simultaneously with chlorine dioxide, peroxide and a reaction catalyst

Abstract

A process for bleaching chemical pulp for paper manufacturing comprising delignifying and bleaching chemical pulp which has been treated by cooking by simultaneous use of chlorine dioxide, a peroxide, and at least one reaction catalyst selected from the group consisting of oxoacids of elements of Groups IV, V and VI and salts of these acids. Formation of organic chlorine compounds as by-products is suppressed by decreasing the amount of chlorine dioxide used in the ECF bleaching process in the first stage, and thus environmental toxicity in the waste water discharged from the bleaching process is decreased. Chemical pulp having a high degree of brightness is economically produced because increase in the production capacity is not required at all or suppressed to the minimum, and the investment cost is reduced to the minimum when the bleaching with chlorine in the first stage is converted into the bleaching with chlorine dioxide which is an ECF bleaching process.

Dependencies are inferred from the claim text.