Acetate fibre:
Textile fibres which are composed
of ester cellulose are called acetate fibres. Acetate is a manufactured fibre
in which the forming substance is cellulose acetate. Where not less than 92% of
the hydroxyl groups are acetylate may be used as a generic description of the
fibre.
 |
| Acetate fibres |
Flow chart of
manufacturing process:
Purification of
cellulose
↓
Activation
↓
Acetylation
↓
Hydrolysis(for
acetate)
↓
Precipitation
↓
Washing & drying
↓
Blending
↓
Dope preparation
↓
Dry spinning
Manufacturing process of acetate:
The main stages of manufacturing of acetate fibres as
follows:
Purification of cellulose:
The cotton linters are purified
by Kier boiling for 4-10 hrs with alkali solution os Na2CO3 then they are
bleached with NaOCLl. Then the linters washed and dried.
Activation:
In this stage, the pufified cotton linters or
wood pulp are steeped in glacial acetic acid (3:1) at room temperature for easy
acetylation.
Acetylation:
a. Non- solvent: esterification is done by
anhydride in presence of catalytic H2SO4.
b.
Solvent: The typical recipe of solvent process.
-
100 lbs purified cellulose
-
300 lbs acetic anhydride
-
500 lbs glacial acetic acid
-
8-10 lbs H2SO4
-
Temperature 25°-30° C for 8-10 hrs.
Hydrolysis:
Hydrolyze acetylated cellulose is performed by
H2O presence of 95% acetic acid, for 15-20 hrs at high temp of 40°-50° C.
Precipitation:
After hydrolysis, for destroying catalytic H2SO4
Na/Mg/Ca acetate is added.
Washing and drying:
In this step, acetate is washed and
centrifuged so that the amount of water is not exceeding 20% then dried.
Blending:
Beffore dry
blending is performed-
To control
product quality.
To decrease
cost
Dope preparation:
For acetate; 85% acetone +15% ethanol.
For triacetate; 90% methylene chloride+
10% ethanol.
Spinning:
Dry spinning process is applied for acetate, tri acetate
spinning Acetate spinning Acetone and methylene chloride used as solvent.
 |
| Fig: dry spining plant for acetate |
This is academic
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