Daicel Chemical Industries, Ltd.

Mitsuru Yamashita

Yoshio Onizawa

Akihiro Izuka

Ryosuke Maeda

Seiji Nishioka

Toshifumi Fukui

Kouji Shima

The present invention provides acetic anhydride, a method of purifying crude acetic anhydride, and a method of producing polyoxytetramethylene glycol using acetic anhydride. A method of producing polyoxytetramethylene glycol by ring-opening-polymerizing tetrahydrofuran in the presence of acetic anhydride and an acid catalyst, wherein said ring-opening polymerization is conducted using acetic anhydride having a diketene concentration of 10 ppm or less to produce polyoxytetramethylene glycol.

Acetic anhydride, method of purifying crude acetic anhydride, and method of producing polyoxytetramethylene glycol using acetic anhydride

In a production process of a cellulose acetate which comprises (a) a reduced pressure-acetylation step of acetylating a cellulose under a reduced pressure in the presence of sulfuric acid or other acidic catalyst, with distilling off a gaseous phase component of the reaction system out of the system, and (b) a post-acetylation step of allowing the acetylation to further proceed by increasing the pressure as compared with the pressure of the reduced pressure-acetylation step by means of release of the pressure reduction of the reaction system or the like, the shift operation from the reduced pressure-acetylation step to the post-acetylation step is conducted by taking a distilling rate of a distillate in the reduced pressure-acetylation step as an index to control the reaction temperature of the post-acetylation step. The shift operation from the reduced pressure-acetylation step to the post-acetylation step may also be conducted by taking a distilling rate after the distilling rate in the reduced pressure-acetylation step has reached a maximum value.

Apparatus for acetylating cellulose

Method and apparatus for acetylating cellulose

A process for molding a transparent plastic substrate for a high-density information recording-reading system by injecting molten resin into a molding cavity defined by a pair of mold halves, characterized in that an axial dimension of the molding cavity is increased at least two times between the start of a shot of the molten resin and the end of the pressure-holding stage in an injection molding cycle.

Injection molding process of a plastic substrate for an optical disk

A recording medium for optical high-density data storage and retrievel, comprising a flat transparent plastic substrate characterized by the following relationship between the refractive index (n.sub.z) in the direction perpendicular to the flat surfaces of the transparent substrate, and the refractive indexes (n.sub.x) and (n.sub.y) in the direction parallel to the flat surfaces of the transparent substrate:

Process for producing plastic substrate for optical disks

A recording medium for optical high-density data storage and retrieval, comprising a flat transparent plastic substrate characterized by the following relationship between the refractive index (n.sub.z) in the direction perpendicular to the flat surfaces of the transparent substrate, and the refractive indexes (n.sub.x) and (n.sub.y) in the direction parallel to the flat surfaces of the transparent substrate:

Plastic substrate for optical disk and process for producing the same

Cellulose acetate is effectively prepared from cellulose and acetic anhydride in a solvent of acetic acid in the presence of a catalyst of sulfuric acid, when the reaction system is being evacuated at least before the reaction mixture reaches a boiling point thereof until the reaction completes, so that the vapor evolved from the reaction mixture may be condensed to distill off and the reaction product may be concentrated.

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Himeji, Japan

Mitsuru Yamashita