申请人:Ito Takashi
公开号:US20080073810A1
公开(公告)日:2008-03-27
A dope (
36
) containing TAC and plasticizer is produced. Foreign materials in the dope (
36
) are filtrated by a filtration device (
57
). In the filtration device (
57
), the dope (
36
) flows from an outer passage (
58
a
) to an inner passage (
58
b
) through a filter (
59
). The filter (
59
) has a first layer (
59
a
), a second layer (
59
b
), and a third layer (
59
c
), which are formed of sintered metal fibers. An average diameter of the sintered metal fibers of the first layer (
59
a
) is 8 mm, that of the second layer (
59
b
) is 4 mm, and that of the third layer (
59
c
) is 20 mm. The filter (
59
) is roasted 2 hours at 400° C. and reused. Breakages from the sintered metal fibers in the first and second layers (
59
a
, 59
b
) are filtrated in the third layer (
59
c
).