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Abstract

A cellulose ether having a low degree of polymerization is used as a base for film-coating pharmaceuticals. The cellulose ether having a low degree of polymerization obtained by causticizing a pulp having a copper number of not more than 0.4 g, adding an etherifying agent to form a cellulose ether having a high degree of polymerization, then refining it with hot water, drying by heating, finely pulverizing the dried cellulose ether and depolymerizing the fine powder has high whiteness and is thus suitable for use as a base for film-coating pharmaceuticals. The viscosity of a 2% aqueous solution of the cellulose having a low degree of polymerization is preferably not more than 20 cSt at 20.degree. C. The cellulose having a low degree of polymerization is selected from methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose and hydroxybutyl methyl cellulose. The cellulose ether having a high degree of polymerization is pulverized within one minute in an impact pulverizer after drying it at a temperature of atmosphere of not more than 100.degree. C. and that of the cellulose ether per se of 40.degree. to 80.degree. C. to control the moisture content thereof to 1 to 5% by weight, and thus a cellulose ether having a low degree of polymerization and high whiteness can be obtained.

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