Nippon Paper Industries Co., Ltd.

Shiho Katsukawa

Hiroshi Abe

Akira Isogai

Shoichi Miyawaki

Yuko Iijima

An effluent produced in oxidation of a cellulosic material with an oxidizing agent in the presence of an N-oxyl compound and a bromide and/or iodide is deionized by electrodialysis to an inorganic salt concentration of less than 0.4%, whereby the N-oxyl compound in the effluent is concentrated and recovered. The N-oxyl compound thus recovered can be reused in oxidation of a cellulosic material. Preferably, the effluent is subjected to reduction treatment and ion exchange resin treatment prior to the electrodialysis.

Method for recovery/reuse of N-oxyl compound

A papermaking additive comprising cellulose nanofibers whose aqueous solution at a concentration of 2% (w/v) has a B-type viscosity (60 rpm, 20&#xb0; C.) of 500 to 7000 mPa&#xb7;s, preferably 500 to 2000 mPa&#xb7;s is used to prepare a paper having improved air resistance and smoothness. This additive is prepared by oxidizing a cellulosic material with an oxidizing agent in the presence of (1) N-oxyl compound(s) and (2) bromide, iodide or a mixture thereof to prepare oxidized cellulose, and finely grinding the oxidized cellulose in a wet condition to convert the oxidized cellulose into nanofibers.

Papermaking additive and paper containing the same

Cellulose nanofibers are produced using a 4-hydroxy TEMPO derivative by treating a cellulosic material with an oxidizing agent in water in the presence of a cellulose oxidation catalyst containing an N-oxyl compound to prepare oxidized cellulos, and microfibrillating the oxidized cellulose.

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Tokyo, Japan

Shiho Katsukawa