Nippon Paper Industries Co., Ltd.

Shoichi Miyawaki

Hiroshi Abe

Takeshi Nakayama

Akira Isogai

Yuko Iijima

Shiho Tsuji

Shiho Katsukawa

Masahiko Fukazawa

Masayuki Watanabe

Yasunori Nanri

Takeshi Iimori

Tomoaki Koyanagi

Eiji Nishijima

Yutaka Nuruki

Yuji Sato

Naoyuki Tamura

An object of present invention is to provide a method for easily extracting and efficiently recovering xylan from wood. A xylan-containing material is produced by a method comprising steps of: (a) adding an acid and/or carbon dioxide to a black liquor discharged during a soda cooking step of wood chips including hardwood chips to adjust the pH of the black liquor to be in the range of 1 to 9, thereby giving a suspension; (b) dehydrating and washing an insoluble matter generated in the suspension to separately collect the insoluble matter; and (c) adding an organic solvent to the insoluble matter obtained at the step (b) to give a suspension, and separately collecting a xylan-containing material made of the insoluble matter present in the suspension by solid/liquid separation.

Method for producing xylan-containing material

Provided is a method which is capable of producing a cellulose nanofiber dispersion liquid that has a low viscosity and excellent fluidity even at a high concentration, while exhibiting excellent transparency. In a method for producing cellulose nanofibers, wherein a cellulosic starting material is oxidized in water using an oxidant in the presence of an N-oxyl compound and a compound that is selected from the group consisting of a bromide, an iodide and a mixture thereof and the thus obtained oxidized cellulose is defibrated and dispersed, pulp which is obtained by carrying out kraft cooking after a hydrolysis process is used as the cellulosic starting material.

Method for producing cellulose nanofibers

Cellulose nanofibers are produced by means of a method comprising a step (A) of oxidizing a cellulosic starting material in the presence of an N-oxyl compound and a step (B) of forming the oxidized cellulosic starting material into nanofibers by defibrating the oxidized cellulosic starting material, and a step (C) of performing at least one selected from the following steps: a step (C-1) of treating the cellulosic starting material in water having a hydroxide ion concentration of 0.75 to 3.75 mol/L prior to performing the step (A); and a step (C-2) of subjecting the oxidized cellulosic starting material obtained from the step (A) to hydrolysis in an alkaline solution having a pH between 8 and 14 after performing the step (A) and prior to performing the step (B).

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.

Processes for producing cellulose nanofibers

A process for preparing a coated printing paper by applying a coating solution containing a pigment and an adhesive to a base paper, which comprises coating the base paper with the coating solution containing 30 to 90% by weight, based on 100% by weight of pigment components, of rice grain- or spindle-shaped precipitated calcium carbonate as a pigment component, the precipitated calcium carbonate being produced by slaking calcium oxide with a white liquor, followed by causticization with a green liquor, at a causticizing step during pulp production by the sulfate process or the soda process; whereby the coated printing paper free from uneven gloss, mottling, and trapping unevenness, and excellent in ink drying properties and operability with a blade coater is provided.

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Tokyo, Japan

Shoichi Miyawaki