Dry spinning is a process to produce cellulose acetate fibers where cellulose is dissolved in a solvent and pumped through a spinneret. As the fibers exit, air evaporates the solvent and the fibers solidify. The raw materials include cellulose from wood pulp or cotton, acetic acid or anhydride, and sulfuric acid catalyst. The process involves reacting the cellulose with acids, dissolving and filtering the precipitate, extruding the solution through a spinneret into fibers as solvent evaporates, and stretching the fibers to increase strength. Cellulose acetate fibers have various applications including clothing fabrics, cigarette filters, and water purification due to their properties such as softness and stability.

1. SYNTHESIS CELLULOSE
ACETATE FIBER
BY DRY SPINNING

2. OUTLINE
 Definition of dry spinning
 Reaction
 Raw materials
 Process
 Characteristics
 Applications
 References

3. Dry spinning
 The polymer is dissolved in
a volatile solvent and the
solution is pumped through
a spinneret (die) with
numerous holes (one to
thousands).
 As the fibers exit the
spinneret, air is used to
evaporate the solvent so
that the fibers solidify

4. Reaction of cellulose acetate
 Molecular: [C6H7O2(OH)3-m(OOCCH3)m], m = 0~3


5. Reaction of cellulose acetate
 Molecular: [C6H7O2(OH)3-m(OOCCH3)m], m = 0~3

6. Raw materials
 CELLULOSE: [C6 H7O2(OH)3]n from pulp
 ACETIC ACID: CH3COOH and ACETIC
ANHYDRIDE: CH3CHO
 SULFURIC ACID: H2SO4

7. Process: Fiber formation
 Purified cellulose from wood pulp or cotton linters.
 Mixed with glacial acetic acid, acetic anhydride and
a catalyst (sulfuric acid).
 Put through a controlled 20 hour partial hydrolysis to
remove the sulfate and the required amount of
acetate molecules to obtain the product’s desired
properties.

8. Process: Fiber formation

9. Process: Fiber formation
 Precipitated as acid-resin flakes
 Flakes is dissolved into acetone
 Solution is filtered

10. Process: Fiber formation
 The liquid substance of
cellulose is forced
through a metal cap
called a spinneret
 The filaments extruded
from the holes in the
spinneret, the liquid
polymer becomes
rubbery and then
solidifies by hot air
 Solvent recovered

11. Process

12. Process: Fiber formation

13. Process: Stretching & Orientation
 While extruded fibers are solidifying, or in some
cases even after they have hardened, the filaments
may be drawn to impart strength
 The filaments are stretched while till plastic to
increase strength
 The filaments are then spun into fiber

14. Characteristics
 Classify: diacetate fiber and triacetate fiber
 Diacetate (acetate): 74% - 92% hydroxyl has been
acetylated
 Triacatate: > 92% hydroxyl has been acetylated

15. Characteristics
 Feels natural and is gentle on the skin
 Elegant gloss and chromogenic quality
 Drapes lightly and flexibly
 Ideal water absorption and quick-drying qualities
 Does not shrink easily, so provides stability for
dimensions and measurements
 Strong pleating durability (triacetate)

16. Applications
 Fabrics: used for linings in suits or coats, for formal
wear including wedding gowns, ribbon

17. Applications
 Filter cigarette tow :good
filtration properties with
good acceptance of the
taste signature, good
biodegradability profile
 Separation technology
Drinking water
purification, waste water
treatment

18. References
 Synthesis of Material: An approach from Chemistry
Dr: Le Minh Thang, HUST, 2008
 www.kpatents.com
 Mitsubishi Rayon Textile Co. LTD
 Wikipedia. Org and other sourses