Mitsui Toatsu Chemicals, Incorporated

Katsuhiko Ito

Toshiaki Takahashi

Yoshihisa Gotoh

Toshihiko Tutumi

Ultrapure water are produced and used by subjecting deionized water, which has been obtained from a deionization step making use of an ion-exchange resin, successively to a sterilization treatment, an activated carbon treatment, an ion-exchange resin treatment and a permeable membrane treatment. The water is fed from each of the steps of the treatments after at least the sterilization tretment (inclusive) to the next step through first piping made of a crystalline polyether ether ketone resin having a recurring unit of the following formula: ##STR1## The thus-produced ultrapure water is then fed through second piping, which is also made of the crystalline polyether ether ketone resin, to and through a use system of the ultrapure water.

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Kawasaki, Japan

Katsuhiko Ito