Patent ID: 11878274
Assignee: FUJIFILM CORPORATION
Field: Chemical engineering (Chemistry)
Classification: CPC B  G | IPC B

Claim 17:
18. A filtering device for obtaining a chemical liquid by purifying a liquid to be purified, the filtering device comprising:
an inlet portion;
an outlet portion;
a filter A;
at least one filter B different from the filter A;
a flow path which includes the filter A and the filter B arranged in series and extends from the inlet portion to the outlet portion;
a tank arranged in series with the filter A on an upstream side of the filter A on the flow path;
a filter C which is arranged in series with the tank on an upstream side of the tank in the flow path and has a pore size equal to or greater than 20 nm, and
a return flow path,
wherein the filter A is a porous membrane containing a polyimide-based resin,
the pore size of the filter A is equal to or greater than 0.1 nm and equal to or smaller than 20 nm, and
the pore size of the filter B is equal to or greater than 1 nm and equal to or smaller than 200 nm,
the filter B further includes at least one filter BD that is disposed on the downstream side of the filter A on the flow path and has a pore size smaller than a pore size of the filter A,
the filter BD includes a first resin including at least one resin selected from the group consisting of polyolefin, polyamide, polyfluorocarbon, polystyrene, and polyethersulfone, and a second resin having at least one hydrophilic group, and
the return flow path is configured to return the liquid to be purified to the upstream side of the filter A and a downstream side of the filter C from a downstream side of the filter A on the flow path.