Dic-hercules Chemicals, Inc.

Japan Pmc Corporation

Jisuke Hayashi

A refining assisting agent comprising sulfonated chitosan has been provided. With the addition of the sulfonated chitosan according to the present invention, power needed in the refining can be remarkably reduced compared with that needed in the conventional refining. In addition, the refining assisting additive improves paper strength.

Method of refining woodchips or beating wood pulp with a selectively

There is disclosed a process for preparing a sulfonated chitosan wherein C3/C6-position hydroxyl groups are selectively sulfonated with inexpensive sulfonating agents which comprises dissolving or swelling chitosan in an acetic acid in water, regenerating chitosan with an alkaline aqueous solution, washing the regenerated chitosan with water and then with alcohol, immersing the chitosan in a polar solvent and pressing the solvent out of the same and sulfonating the chitosan with SO.sub.3 -DMF complex or ClHSO.sub.3an -DMF complex in a non-polar solvent. Separation of the product can be easily effected by way of filtration and the like.

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Sapporo, Japan

Jisuke Hayashi