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Cellulose
Acetate Flake
Flake is the raw
material for Cigarette Filter Tow, cellulose acetate
and triacetate filament yarns, film, insulation plastic
for screwdrivers handles, writing pens, and frames for
eye glasses.
The compound is
manufactured by acetylation of wood-pulp, a process
whereby cellulose is combined with acetic acid.
Less than 92%,
but at least 74% of the hydroxyl groups of the original
cellulose are acetylated. |
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Manufacturing of Flakes
Cellulose and acetic acid are
mixed in a reactor, where during the activation phase
the cellulose sheets are broken down into fibres. For
the acetylation as such, acetic acid anhydride is added.
At the end of the reaction, a solution of cellulose
triacetate in acetic acid is obtained.
In a subsequent saponification (hydrolysis), the obtained
solution is mixed with water in a separate hydrolysis
tank, where part of the acetylation is reversed. The
reaction is allowed to continue until cellulose-2,5-acetate
(dissolved in acetic acid) is obtained. By diluting
this solution with large amounts of water, cellulose-2,5-acetate
precipitates rapidly in the form of flakes.
Due to their porous structure, the flakes are saturated
with acetic acid. Through intensive washing with water
this acid removed. After the washing process, the flakes
are first freed of water in a roller press and then
in a hot air dryer.
Pictures: above: Acetylation,
below: Saponification
and Precipitation |
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