Ozone bleaching with an organic solvent and mineral acid
AssigneeMacMillan Bloedel Limited
InventorsMarco Solinas, Thomas Howard Murphy, Adriaan Reinhard Pieter van Heiningen, Yonghao Ni
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Abstract
A bleached pulp having a high viscosity for a given permanganate number is formed by pretreating never dried pulp with an organic solvent medium to produce a treated pulp composed of said never dried pulp in the medium and then bleaching that treated pulp using ozone at a pH of 1.5-5 to provide a bleached pulp while reducing the viscosity loss during the ozone bleaching step significantly compared to that what would occur if the medium used in the ozone bleaching were water.
Claims14
A method of producing an ozone bleached pulp having a viscosity equivalent to a viscosity of 20 cp for northern softwoods at a permanganate no. of 6 ml comprising pretreating a never dried pulp with an aqueous organic medium consisting essentially of water, a water miscible organic solvent having a dielectric constant of no more than 40 and a mineral acid by thoroughly mixing said pulp and said aqueous organic medium to produce a treated pulp, said aqueous organic medium in said treated pulp containing at least 10% water and at least 10% of said organic solvent and sufficient of said mineral acid to adjust the pH of said treated pulp to a pH of 1.5 to 5, bleaching said treated pulp with ozone in an ozone bleaching stage at said pH in the range of 1.5 to 5 to provide said ozone bleached pulp having a viscosity equivalent to a viscosity of at least 20 cp at a permanganate number of 6 ml for northern softwood pulp.
Dependencies are inferred from the claim text.