A method for forming II-type cellulose, which comprises introducing together a
slurry having water and a I-type cellulose dispersed therein and water in the state
of high temperature and high pressure to a tubular reactor (28) contacting
the I-type cellulose with a hot water in a supercritical state or subcritical state
for a predetermined time in the tubular reactor (28), to thereby cleave
a part of the hydrogen bonds in the I-type cellulose and dissolve the I-type cellulose
into the water in a supercritical state or subcritical state, cooling a cellulose
solution discharged from the tubular reactor (28) in a cooler (30)
to room temperature or lower, followed by allowing to stand, to thereby precipitate
crystals of II-type cellulose having a molecular weight lower than that of the
I-type cellulose, and separating the resultant II-type cellulose from a solvent.
The method allows the preparation of pure II-type cellulose by the use of a simple process.
