An oxygen bleaching method of pulp includes the steps of: adding a solution formulated by a magnesium salt and an activator to an unbleached chemical pulp, stirring to be mixed well, and bleaching by introducing oxygen. The activators are nano zero-valent metals that are conventional, low-cost, and recyclable. These activators can activate low-concentration oxygen at low-temperature in neutral aqueous solution to efficiently generate peroxide anion radicals, so as to promote the generation of hydroperoxide anions and peroxide ions, achieving high efficient delignification. The whole process does not generate waste water, the oxygen consumption is only 50-85% of the original process, the yield is increased by 1.5-2.8% compared with the original system, the pulp brightness is increased to 28-32? SR, and the magnesium salt can be recycled and reused.

The invention provides a method for the application of a bleaching agent to a substrate, the method comprising the treatment of the substrate in an aqueous system comprising a liquid bleaching agent in a closed container, the treatment being carried out at a ratio of liquor to substrate which does not exceed 3:1. Typically, the method is applied to the bleaching of textile fibres and may optionally comprise a bleaching and scouring treatment. The invention also provides a method for the removal of surplus bleaching agents following the bleaching treatment, the method comprising not more than three aqueous wash-off treatments of the substrate. In addition to facilitating the use of much reduced liquor levels, the method also allows for significant reductions to be achieved in usage levels of bleaching agents, auxiliary agents and rinsing agents, thereby reducing generation of waste liquors requiring disposal. Furthermore, treatment temperatures are also significantly lower than for prior art methods, providing yet further benefits in environmental and cost terms.

Process for the delignification and bleaching of pulp, comprising a first bleaching stage with hydrogen peroxide in the presence of a molybdate or tungstate in an acidic aqueous mixture; subsequent to the first bleaching stage, a second bleaching stage with hydrogen peroxide in an alkaline aqueous mixture; and, subsequent to the second bleaching stage, a third bleaching stage with hydrogen peroxide in the presence of a molybdate or tungstate in an acidic aqueous mixture.

The invention relates to a method for reducing pulp viscosity in production of dissolving pulp. The method comprises producing cellulose pulp, whereby the obtained cellulose pulp has a cellulose content of at least 90%, and bleaching the obtained cellulose pulp. The cellulose pulp is treated after bleaching with performic acid.

The present invention relates to compositions for use in an aqueous pulp bleaching process, comprising one or more alkaline earth metal oxides and/or one or more alkaline earth metal hydroxides; one or more alkaline earth metal salts; and optionally, one or more pitch control additives. Methods and kits for the formation of said compositions, are also part of the invention, as is the use of said compositions, methods and kits.

This disclosure relates to improved products containing oxidized cellulose. This disclosure further relates to improved methods of making oxidized cellulose in multi-stage bleaching processes, including, for example, in four-stage and three-stage bleaching processes. This disclosure further relates to products made therefrom, including wipe, tissue, towel, and napkin products.

A modified kraft pulp fiber with unique properties is provided. The modified fiber can be a modified bleached kraft fiber that is almost indistinguishable from its conventional counterpart, except that it has a low degree of polymerization (DP). Methods for making the modified fiber and products made from it are also provided. The method can be a one step acidic, iron catalyzed peroxide treatment process that can be incorporated into a single stage of a multi-stage bleaching process. The products can be chemical cellulose feedstocks, microcrystalline cellulose feedstocks, fluff pulps and products made from them.

Compositions and methods that preserve and enhance the brightness of pulp, and also improve the color of pulp or paper, when applied during different stages of a papermaking process, are disclosed. The compositions and methods maintain or enhance brightness, prevent yellowing, and enhance the performance of paper products. The compositions can include a mixture of reducing agents and can also include optical brighteners, chelants, polycarboxylates, or other additives. The mixture of reducing agents can include a borohydride, such as sodium borohydride, and any other reducing agent, such as a sulfite or bisulfite.

A modified kraft pulp fiber with unique properties is provided. The modified fiber can be a modified bleached kraft fiber that is almost indistinguishable from its conventional counterpart, except that it has a low degree of polymerization (DP). Methods for making the modified fiber and products made from it are also provided. The method can be a one step acidic, iron catalyzed peroxide treatment process that can be incorporated into a single stage of a multi-stage bleaching process. The products can be chemical cellulose feedstocks, microcrystalline cellulose feedstocks, fluff pulps and products made from them.

The present invention relates to an improved process for producing chemical cellulose pulp wherein biopolymers are added immediately before, during or after a bleaching step, depending on pulp characteristics and on process conditions used. The biopolymers according to the present invention are starches chemically modified by an etherification reaction. This treatment results in a differentiated pulp having improved physical, chemical and mechanical properties when compared with cellulose pulps obtained by traditional processes. The use of said biopolymer alters the relations between important pulp properties rendering their application in papermaking process advantageous. This differentiation increases the possibilities of use and also of new applications, including for the substitution of pulps produced from other cellulose sources. Thus, the present invention also relates to methods of making paper, such as printing, writing, decorative, special or tissue-type papers, through the use of the cellulose pulps modified by the above process.