2. INTRODUCTION
Lyocell (lyo from Greek: lyein = dissolve, cell from
cellulose)
Man made cellulosic fibres
Produced by regenerating cellulose into fibre form out of
a solution (solvent spinning) of cellulose in an organic
solvent
‘Organic solvent’ - mixture of organic chemicals and
water
‘Solvent spinning’ means dissolving and spinning without
the formation of a derivative
Lenzing AG. is currently (2013) the only major producer
of lyocell fibres
Tencel is the brand name of Lyocell
3. RAW MATERIALS
Cellulose
•
Most abundant natural resource on earth.
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It is obtained form wood pulp.
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Trees like Eucalyptus , bamboo and pine tree are used.
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Eucalyptus is primarily used to produce the Tencel fibre.
4.
NMMO
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Chemically produced from N methyl morpholine and hydrogen peroxide
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Cyclic amine oxides such as N-methyl morpholine oxide have the capacity to
dissolve cellulose in large capacities
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NMMO exists in several degrees of hydration.
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At room temperature it is a crystalline mono hydrate and melts at 72 degrees
•
When heated at 100 C, mono hydrate NMMO is able to dissolve readily several
percentages of high molecular weight cellulose
•
Cellulose dissolution in NMMO is found to depend on:
– The temperature of the solution
– The water content of the mixtures
– The concentration and the degree of
– Polymerisation of the cellulose
5. MANUFACTURING AND PROCESSING
Preparing Wood Pulp
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Hardwood trees are harvested and logs are
taken to mill.
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Wood is cut into small chip and fed into a
chemical digesters which removes lignin and
softens them into wet wood pulp.
•
It is then washed with water, bleached and
dried into huge sheets of cellulose and rolled
onto spools.
6.
Dissolving Cellulose
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Spools of cellulose are unrolled
and broken into one square
inches.
•
It is then loaded into heated
pressurized vessel containing Nmethyl morpholine N-oxide.
•
Cellulose dissolves into a clear
solution.
7.
Filtering
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In Amine Oxide solvent, cellulose is dissolved into a clear solution.
•
It is then pumped out and filtered.
Spinning
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Cellulose is forced through the spinnerets and long strands of fibre comes out.
•
These fibres are then dissolved in dilute Amine Oxide solution and is later
washed with water.
8.
Drying And Finishing
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Fibre is passed through drying area.
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In the drying area, water is evaporated and lubricant is applied which may be
soap, silicone or other agent.
9.
Solvent Recovery
•
After spinning and drying process, dilute solution is taken passed through the
evaporator where water is removed and amine oxide solvent is fed back to the
Dissolving process.
10. PROPERTIES
Soft, strong, absorbent
Fibrillated during wet processing to produce special textures
It has high wet and dry strength, it is stronger than Cotton and Wool.
Wrinkle resistant
Very versatile fabric, dyeable to vibrant colours, with a variety of effects and
textures.
Can be hand washable
Simulates silk, suede, or leather touch
Good drapability
Biodegradable
Fine yarn counts can be spun
11.
Comfort
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Soft, smooth fibre.
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Ideal for apparel that contacts skin.
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Thermal retention is poor.
Appearance Retention
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Resiliency is moderate- Wrinkles but not as severely as rayon.
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Shrinks, but not progressively.
•
May have problems with fuzziness or piling.
12.
Aesthetics
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Lustre, length and diameter can be changed depending upon end use.
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Processed to produce a range of surface effects.
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Offers unusual combinations of strength, opacity, absorbency.
Durability
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Performs more like cotton than rayon.
•
Strongest of cellulosic fibres.
•
Unique combination of soft hand and good durability, produces comfortable,
long-lasting textiles for apparel and interiors.
13.
Care
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Either gently machine- Washable or dry cleaned.
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Sensitive to acids.
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Resistant to mild alkalis.
•
Sensitive to mildew and some insects.
•
High dye affinity.
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High inherent whiteness- Bleaching is not necessary.
14. PHYSICAL STRUCTURE
The physical structure is a more rounded
cross section & smoother longitudinal
appearance than rayon.
Since in the case of Lyocell we are just
dissolving cellulose in NMMO and not
making any cellulose derivatives, it has
a different molecular structure than
other regenerated cellulosic fibres.
The structure is ‘Homogeneous’ and
‘Dense’.
Cross Section
Longitudinal Section
