Denki Kagaku Kogyo Kabushiki Kaisha

Toshiaki Kawanishi

Yoshihiro Mashiko

Koichi Matsunaga

Kazumasa Matsuoto

Koki Goto

Manabu Tsuzuki

Hitoshi Watanabe

A polyvinylacetal resin powder with a low metal content, being excellent in transparency, moisture resistance and electrical insulating properties and having a large specific surface area, and a process for its production, are presented. A polyvinylacetal resin powder obtained by reacting polyvinyl alcohol and an aldehyde in the presence of an acid catalyst, which has an acetalization degree of at least 60 mol %, a specific surface area of from 1.50 to 3.50 m/g, a bulk density of from 0.12 to 0.19 g/cm, an average particle diameter of from 0.5 to 2, 5 &#x3bc;m and a metal content of at most 80 ppm. It is produced, for example, by feeding a reaction fluid containing polyvinyl alcohol, an aldehyde and an acid catalyst into a first reactor, to carry out an acetalization reaction, discharging the reaction fluid wherein the acetalization degree has reached from 10 to 60 mol %, and feeding the same into a second reactor to carry out a further reaction to bring the acetalization degree of polyvinylacetal to at least 65 mol %.

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Niigata, Japan

Toshiaki Kawanishi