Daicel Chemical Industries, Ltd.

Hiroshi Ogawa

Toru Ozaki

Hirofumi Sasai

Hisao Fujikawa

Hideo Katsui

The present invention provides a cellulose triacetate which exhibits a satisfactory filtration performance Thus, the present invention provides a cellulose triacetate whose occlusion constant (K) determined by the following method is 70 or less. Method: the cellulose triacetate is dissolved in a solvent mixture of methylene chloride/methanol (9/1 w/w) to form a 16% by weight (as a solid concentration) solution, which is then filtered under a constant pressure at the filtration pressure of 3 kg/cm and the temperature of 25&deg; C. using a muslin filter to determine a filtered volume with the lapse of time, from which the slope of a linear curve represented by t/V&minus;t (wherein t is a filtration time (sec) and V is a filtered volume (ml)) is calculated to obtain an occlusion constant (K) where K&equals;slope&times;2&times;10 .

Cellulose triacetates and methods for producing the cellulose triacetates

An improved process for the preparation of an alkyl vinyl ether/maleic anhydride copolymer in which copolymerization is carried out in an admixture of an ester and an hydrocarbon. The alkyl vinyl ether/maleic anhydride copolymer obtained by this process does not contain any harmful aromatic solvent such as benzene, etc. In addition, the alkyl vinyl ether/maleic anhydride copolymer has a higher apparent bulk density than can be obtained in prior processes.

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Hyogo, Japan

Hiroshi Ogawa