Daicel Chemical Industries, Ltd.

Tokuji Tanaka

Kazuhiro Nishioka

Noboru Kamei

Hideo Yabune

Seiichi Ohta

Etsuji Akimoto

The starting pyroxylin is subjected to an acetylation reaction while it is dispersed in a dispersion medium such as toluene and kept in a solid phase state, and acetylated pyroxylin is then separated from a reaction solution by means of filtration, so that an extra portion of anhydrous acetic acid taking no part in the reaction can be immediately recovered. This dispenses with the precipitation process required for a prior art solution reaction, and so eliminates an unstable quality factor due to product particle size variations. In addition, the process of washing the post-reaction crude acetylated pyroxylin is designed to include a washing step at a high temperature of 60&deg; C. to 105&deg; C. and a washing step using a stabilizer-containing washing agent, so that acetylated pyroxylin having improved heat resistance and stability can be provided.

Acetylated pyroxylin

The starting pyroxylin is subjected to an acetylation reaction while it is dispersed in a dispersion medium such as toluene and kept in a solid phase state, and acetylated pyroxylin is then separated from a reaction solution by means of filtration, so that an extra portion of anhydrous acetic acid taking no part in the reaction can be immediately recovered. This dispenses with the precipitation process required for a prior art solution reaction, and so eliminates an unstable quality factor due to product particle size variations. In addition, the process of washing the post-reaction crude acetylated pyroxylin is designed to include a washing step at a high temperature of 60 to 105&deg; C. and a washing step using a stabilizer-containing washing agent, so that acetylated pyroxylin having improved heat resistance and stability can be provided.

Acetylated pyroxylin, and its production process

The invention provides a method for producing acetylated pyroxylin with safety yet at low cost, using inexpensive water-wetted pyroxylin rather than expensive alcohol-wetted pyroxylin. The acetylated pyroxylin is produced by dehydrating the water-wetted pyroxylin in the presence of a nonalcoholic non-solvent for pyroxylin, and then permitting an acetylating agent to act on the dehydrated pyroxylin. According to the first dehydration process, the water-wetted pyroxylin is dispersed in a dispersing medium comprising a nonalcoholic non-solvent for pyroxylin, and then dehydrated by distillation. According to the second dehydration process, a replacing agent comprising a nonalcoholic non-solvent for pyroxylin is added to the water-wetted pyroxylin, and the wetted pyroxylin is then dehydrated by filtration. With either one of these processes, the water-wetted pyroxylin can be dehydrated with safety.

Method for producing acetylated pyroxylin

An optical information recording medium comprising a glass base, a primer coating layer formed on the glass base and a recording layer formed on the primer coating layer is disclosed. The optical information recording medium is characterized in that the primer coating layer comprises a linear acrylic resin having as a repeating unit an atomic group represented by the following formula (1): ##STR1## wherein R.sup.1 is a hydrogen atom or a methyl group and R.sup.2 is an alkyl group having 1 to 4 carbon atoms. A coupling agent may be interposed between the primer coating layer and the recording layer.

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Himeji, Japan

Tokuji Tanaka