International Paper Company

Ted Yuan Tsai

Long Shyong Wang

The invention relates to methods for reducing the amount of halogenated organics produced during a halogen bleaching process for lignocellulosic pulp fibers. According to the disclosed invention, it has been discovered that the use of a chelating agent prior to a non-halogen containing bleaching stage of a pulp bleaching process is effective to increase the brightness of the resulting bleached pulp without the need to increase the amount of halogen compounds required to obtain the same pulp brightness and without adversely affecting the pulp viscosity and yield.

Minimizing chlorinated organics in pulp bleaching processes

In the post-digestion treatment of kraft cellulosic pulp, the improvement comprising subjecting the pulp to a two-phase process in which the two-phases are substantially identical and each phase includes contacting the pulp first with an ozone/oxygen mixture at a temperature below about 60&deg; C. and thereafter with oxygen with the pulp at a temperature above about 65&deg; C.

Two phase ozone and oxygen pulp treatment

A method for improving the preparation of chemical cellulosic wood pulp for use in papermaking, and specifically to enhancement of the quality of a kraft pulp which has been subjected to a chlorine dioxide/chlorine bleaching stage and thereafter subjected to ozonation prior to an extraction stage in the bleaching sequence. The improved pulp of the present invention exhibits reduced total organically bound chlorine residues in the wood pulp and adsorbed organic halides (AOX) in the effluent, and has good brightness and viscosity. The advantages of the present invention may be accomplished by means of a bleaching sequence that employs a minimum of stages, namely (D.fwdarw.C)ZED or D.sub.c ZED with attendant relatively lower capital investment than heretofore possible.

Method of bleaching kraft pulp employing chlorine dioxide/chlorine-ozone

A post-digestion treatment method for cellulosic pulps which reduces the generation of dioxins and other chlorinated organics in the pulp, treatment effluent and/or the paper product produced from the pulp. In the treatment, the pulp, following digestion, is washed with a liquid that is essentially free of dioxins or dioxin precursors and simultaneously adjusted in consistency to at least a medium, and preferably a high consistency. Thereafter, the pulp is contacted with a chlorination agent selected from the group consisting of gaseous chlorine dioxide, gaseous chlorine, and gaseous chlorine dioxide which contains a minor amount of gaseous chlorine.

Post digestion treatment of cellulosic pulp to minimize formation of

In the bleaching of kraft cellulosic pulps employing a stage in which the pulp is contacted simultaneously with gaseous chlorine and ozone, the improvement in which the pulp at a low to high consistency is initially chlorinated with hypochlorous acid and thereafter is contacted substantially simultaneously with gaseous chlorine and ozone. The pulp so processed exhibits enhanced brightness and good viscosity, and the process produces low quantities of environmentally undesirable chlorinated organics. The bleaching sequence of M(C+Z).sub.g ED is disclosed.

Bleaching process for kraft pulp employing high consistency chlorinated

In a multi-stage bleaching sequence for kraft pulps employing a chlorine-containing bleaching agent in the first and final stages thereof and an intermediate alkaline extraction stage, the improvement for enhancing the brightness of the pulp and reducing the quantity of dioxin or chlorinated organics comprising contacting the pulp, in a mixer, at an acidic pH and a temperature of below about 60.degree. C. with a mixture of ozone and oxygen at a pressure of between about 60 and 80 psig wherein the quantity of ozone introduced to the pulp is between about 0.2% and about 0.4%, based on pulp.

Bleaching of kraft cellulosic pulp employing ozone and reduced

A method for removing laser printer and xerographic toner, ink or the like from paper to be recycled comprising pulping the paper to be recycled with water to produce a paper pulp slurry with a consistency of between about 1% and 20%, adjusting the pH of the slurry to between about 6 and about 13, adding between about 0.3 and about 5.0 wt. %, based on the dry weight of the paper, of a surfactant to the slurry, the surfactant having the formula R.sup.1 --R.sup.2 --R.sup.3, wherein R.sup.1 and R.sup.3 are each selected from the group consisting of rosins, rosin dimers and mixtures of rosins and rosin dimers and R.sup.2 is a polyethylene glycol (PEG) having a molecular weight of between about 220 and about 660 Da, and adding between about 0.01 and about 5.0 wt. % of polyacrylic acid to the slurry, maintaining the slurry at a temperature of between about 30.degree. C. and about 120.degree. C. for a period of between about 5 minutes and about 90 minutes, and removing the ink from fibers of the paper as agglomerated particles, the particles having diameters of between about 1 mm and about 3 mm.

Removal of laser printer and xerographic ink from recycle paper

A method of enhancing the quality of a pulp which has been subjected to a chlorine-based bleaching agent, by subjecting the chlorinated pulp to ozonation prior to an extraction stage in the bleaching sequence. The improved pulp of the present invention includes reduction of total organically bound chlorine residues in the wood pulp and adsorbed organic halides (AOX) in the effluent, and has good brightness and viscosity. The advantages of the present invention may be accomplished by means of a bleaching sequence that employs as few as four stages, namely DZED with attendant relatively lower capital investment than heretofore possible.

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Harriman, NY, United States of America

Ted Yuan Tsai