lyocell

6/16/2010 Nizam Yaquby - Bahrain 1

Lyocell

[email protected]

NATIONAL TEXTILE UNIVERSITY FAISALABAD

PAKISTAN

Introduction Of Presentation

Manufacturing

Properties

Pretreatment

Fiberillation

Dyeing

Processing Routes

End uses

References

Lyocell Manufacturing

Lyocell is defined as

“ a regenerated cellulosic fiber obtain by spinning of dissolved wood pulp in an organic solvent (NMMO)”.

It is 100% natural regentrated fiber from wood sources

Solvent spinning used for process of manufacturing

Lyocell Manufacturing Main ingredient for Lyocell

– Wood from oak tree or bich

– An amine oxide(N-methylmorpholine N-oxide(NMMO)

– Water

– A finishing agent such as silicon based lubricant

NMMO is used to dissolve the wood pulp obtain from self sustaining resources of harvested trees and it is non toxic and recycled with in the process leading to minimal and harmless effluent

Oak Logs Birch Logs



The Manufacturing Process involve steps

– Preparing the wood pulp

– Dissolving the cellulose in NMMO

– Filtering

– Solvent Spinning (immersed in amine oxide after spinning)

– Drying and finishing

– Cutting staple form and baled

– Recovery of the solvent

Lyocell Manufacturing Some brand name of lyocell

– Tencell® (first Lyocell commercially manufacture by Acrodis in 1988(Courtaulds plc))

– Tencell100® (non fibrillating)( Courtaulds/ Acrodis)

– NewCell® (Akzo Nobel)

– Lenzing Lyocell®(Lenzing)

– Alceru® (TITK)

– Cocel® (Hanil)

Lyocell Manufacturing Process route differenceof tencell and lenzing lyocell

Lyocell Manufacturing Some properties of lyecell

–High strength and tenacity both wet and dry state than viscose and cotton

–High incidence of crystalline area and degree of orientation

– Low shrinkage in water and good dimension stability of garments

–Unique property of fibrillation

LYOCELL MANUFACTURING

High dyeability than cotton and viscose

High strength to alkali than viscose

High swelling capacity that increase with NaOH and decrease with polycarboxylic treatment

Can absorb excess liquid and quickly release it to the atmosphere

High suitability for creation of mill wash , sand wash, used look or peach skin look fabric


Property Tencell Viscose Cotton Polyester

Dry tenacity(cN/Tex) 38-42 22-26 20-24 55-60

Wet tenacity(cN/Tex)

34-38 10-15 26-30 54-58

Dry elongation(%) 14-16 20-25 7-9 25-30

Wet elongation(%)

16-18 25-30 12-14 25-30

Lyocell have good comfort due to less resistance to thermal transmission and higher vapour permeability (good thermal management and moisture management)

Strength and elongation comparison of tencell with other fibres

Tencell absorb 50% more moisture than cotton

0

5

10

15

20

25

Tencell Viscose cotton polyester

MR%



Lyocell key characteristics

–Distinctive soft handle

–Excellent drape

–Silky luster

–High strength

–Good wash ability

Pretreatment of Lyocell

Why Pretreatment?

As lyocell contains impurities as other natural fiber have; so for achieving desirable properties we have to treat the fiber with preliminary processes. Pretreatment, basically removes the undesirable contents of fiber and modifies the fiber in such a way that further following steps are done with great ease.


Contaminations in Lyocell

Following are the impurities of great importance in lyocell fiber:

Contaminations Tencel® A100

Total Ash Content (%) 1.41

Acid insoluble Ash (ppm) 143

Sodium (ppm) 89

Calcium (ppm) 760

Magnesium (ppm) 720


Comparison of Contaminations

Following table gives a comparison chart of contaminations lyocell with cotton and modal:

Cotton Tencel® A100 Modal

Total Ash Content (%) 1.41 0.11 0.21

Acid insoluble Ash (ppm) 143 23 37

Sodium (ppm) 89 590 840

Calcium (ppm) 760 16 20

Magnesium (ppm) 720 4 8

Pretreatment of Lyocell General Requirements in pretreatment

General Requirements in Pre-treatment of woven lyocell include:

» Complete removal of size

» Good absorbency

» Adequate whiteness

» Good dyeability

» Good dimensional stability

» Crease-free fabric

» No abrasion marks

» End-to-end and side-centre-side levelness of treatment

» Good reproducibility


Singeing and Desizing

Lyocell fabrics are singed to remove the protruding fibers and simplify the de-fibrillation process later on. Desizing is normally done in open-width. If the fabric contains only water-soluble sizes, it is washed-only on open-width washing machine or jigger. If starch is present, desizing may be done by enzymatically or oxidatively using cold pad-batch method, open-width washing machine or jigger .

Pretreatment of Lyocell Examples of typical desizing processes

Size Type

Process

Ingredients

Conditions

Wate

r-solu

ble

sizes

Continuous open-width washing machine

2-5 ml/l Wetting agent/ Detergent 1-2 ml/l Sequestrant X g/l Soda Ash or Caustic Soda (depending on type of size)

Temperature 80-95°C Time 1-4 minutes Final hot rinse

Jigger

1-2 ml/l Wetting agent/ Detergent 1-2 ml/l Sequestrant X g/l Soda Ash or Caustic Soda (depending on type of size)

Liquor ratio 1:5 Temperature 80-90°C No. of passes 4 or minimum 30 minutes Final hot rinse

Starch/ W

ater-in

solu

ble

Size

Cold Pad-batch Enzymatic Desizing

2-6 ml/l Amylases Enzyme 3-5 ml/l Wetting agent/ Detergent 1-2 ml/l Sequestrant

Impregnation at 20-60°C Pick-up 100% Dwell time 4-24 hours Final Hot rinse

Jigger

2-4 ml/l Amylases Enzyme 1-2 ml/l Wetting agent/ Detergent 1-2 ml/l Sequestrant

Liquor ratio 1:5 Temperature depending on type of enzyme used Time minimum 30 minutes Addition of enzyme only when suitable temperature reached Final hot rinse


Three-in-One (T-I-O)

Three-in-One (T-I-O) process

may be used for oxidative

desizing, bleaching and

causticizing in one step .

T-I-O

Caustisizing

Bleaching

Oxidative desizing


The position of T-I-O process in the overall processing route is given as follows:

Singeing

T-I-O pre-treatment process primary fibrillation

enzymatic de-fibrillation

Dyeing

Finishing


T-I-O process consists of impregnating the fabric at room temperature with

– 8-15 ml/kg H2O2 (35%)

– 40 g/kg NaOH (100%)

– 8-12 ml/kg “Tinoclarite CBB”

– 3-6 ml/kg “Invatex CRA”

The pick up is adjusted to 100% and the impregnated fabric is batched to dwell for 4-24 hours before a hot wash.

It has been found that fabrics undergone T-I-O process exhibit better colour yield as compared to enzymatically desized fabrics.


Mercerization

Mercerization with NaOH causes increase in degree of lyocell swelling. However, there is a notable decrease in tensile strength when lyocell is treated with strong alkali solutions higher than 7.5 wt% while Mercerization at 10 wt% causes more than 10% weight loss in lyocell fibres.

Pretreatment of Lyocell Effect of concentaration of NaOH on dyeability


Fibrillation

Fibrillation is the partial detachment of microfibrills from the fibers. These microfibrills are typically less than 1 to 4 microns in diameter and give, on one hand, a white “frosty” appearance to the fabric and, on the other had, special peach-skin soft handle. Main causes of lyocell fibrillation tendency are the high wet swelling (approx. 65% increase in volume) of lyocell and weak lateral links between the crystallites rendering it susceptible to mechanical abrasion.

Pretreatment of Lyocell Primary Fibrillation

– Primary fibrillation often results in the presence of long fibrils which are able to entangle and result in fabric pilling.

– A guide process for primary fibrillation is as follows: • load the goods in a suitable jet.

• Pour in 2 g/l suitable lubricant while setting the bath at 60°C.

• Add 2 g/l crease inhibitor and 2-3 g/l soda ash or caustic soda lye.

• Increase the temperature to 80-95°C. Treat the goods for 60-120 minutes.

• Drain off the bath, rinse and neutralize.

Pretreatment of Lyocell Defibrillation or Enzyme Clean

– Defibrillation can be done on the jet machines using acid cellulases enzymes.

– The process is carried out using a suitable cellulases enzyme (1-3% o.w.f.)

– 2 g/l crease inhibitor and 2 g/l lubricant at a liquor ratio of 5:1-10:1

– A strict control of temperature and pH (using buffer system) is ensured before the addition of enzyme.


– The pH and temperature is set as per the enzyme manufacturer’s recommendations.

– The treatment is carried out for 45-90 minutes and then the enzyme is denatured either by raising the temperature or pH by using sodium bicarbonate or sodium carbonate.

– The bath is drained off and the goods are given a final hot rinse.


The benefits of cellulases treatment include:

• Improved softness and surface smoothness

• De-fuzzing

• De-pilling

• Pill prevention

• Improved drapability

• Improved surface appearance after repeated laundering

• Reduced tendency to fibrillate

Pretreatment of Lyocell Secondary Fibrillation

Unlike long-staple irregular primary fibrillation, secondary fibrillation results in the presence of short fibrils which are not usually able to entangle and cause pilling. Secondary fibrillation is usually done after dyeing and finishing.

• Two main effects of the secondary fibrillation are:

– A small pile created on the surface of the fabric, giving the fabric a peach-skin hand

– Fibrils, being a fraction of the size of the fibers, appear much lighter in color than the fibers even when they contain the same amount of dye. This optical effect gives the dusted or mill-wash appearance to the fabric.

Dyeing of Lyocell Fabrics by Exhaust Method

Lyocell fabrics can be dyed by using same classes of dyes and methods as are used for other cellulosic fibers. However, the dyeability of lyocell is higher as compared to that of other conventional cellulosic fibers.


Dye ability of Lyocell vs. Other Cellulosic Fibers

Dyeing of Lyocell Fabrics by Exhaust Method Dye Selection

– Appropriate dye selection is important keeping in view the fact that natural affinity of reactive dyes for lyocell is greater than that for cotton. Those reactive dyes are suitable which are characterized by:

• Excellent exhaustion and fixation

• Good migration properties

• Excellent level dyeing

• Robustness to process variables

• Easy wash-off profile

Bi-functional and tri-functional reactive dyes have been reported to improve the wet abrasion strength of lyocell while non-cross-linking mono-functional dyes are ineffective in that respect.


Main parameters for dyeing lyocell in rope form

• Fabric tube/rope diameter

• Fabric speed

• Rope circulation time

• Differential pressure


• Liquor add-on (in aerodynamic systems), which depends on

– Fabric type (woven or knitted)

– Fabric density

– Fabric GSM (grams per square meter)

– The final fabric appearance required

– Difference in winch speed and fabric speed

– Higher speed differences may cause over-fibrillation


Auxiliaries – Wetting agent (may be omitted if appropriate emulsifiable

yarn lubricants are used)

– Sequestering agent to sequester alkaline earth metals that may be introduced by water or electrolyte

– Electrolyte to increase exhaustion (note: due to high affinity of reactive dyes for lyocell than for cotton, the electrolyte requirement for dyeing lyocell is less than that for dyeing cotton)

– Fabric lubricant with good emulsifying properties

– Alkali for dye fixation

Dyeing of Lyocell Fabrics by Cold Pad-batch Method

Cold pad-batch method has the following characteristics:

• High productivity as compared to exhaust method

• Low energy costs • Low water costs (around 60 l/kg or less as

compared to >100 l/kg in exhaust dyeing) • No use of salt • Low effluent load • Limited fibrillation


• No abrasion marks

• Less crease marks

• Long fixation times

• High cost of correcting faulty shades

• Risk of tailing


Conditions in pad batch dyeing – Good fabric hydrophilicity for ensuring uniform dye uptake – Freedom from residues – Uniform moisture content and temperature (20-25°C) of the

fabric throughout the length and width of the fabric – Small liquor trough for ensuring rapid liquor exchange (in less

than 3 minutes), particularly for dyes of low liquor stability, in order to prevent premature dye hydrolysis and reduce risk of tailing

– Good control of temperature of dye and alkali liquors and the trough temperature for ensuring bath stability


– Use of trichromatic combinations with similar substantivity – Optimum fabric speed to ensure fabric immersion time of

about 1 sec. – Liquor pick-up of 85-100% – Approximately 30-60 sec. air passage after padding and

before batching up, to minimize pressure on the batching roll due to lyocell swelling

– Use of relatively high-diameter foam-covered batching rolls, to provide room for fibre swelling while on the batcher

– A centre wind to ensure constant winding tension on the batching roll

Processing of Lyocell in Garment Form

Processing of lyocell in garment form can be done to obtain different effects such as:

– Mill-wash appearance

– Excellent hand

– Bulk

Main processing routes for processing lyocell garments are:

– Indigo garment wash

– Piece dye for garment wash

– Garment dye

Processing of Lyocell in Garment Form

Route 1: Primary fibrillation of garment → De-fibrillation with enzymes → Dyeing (where secondary fibrillation occurs)

Characteristics of Route 1: • Peach-skin hand • Classic appearance • Good batch to batch

shade reproducibility

Route 2: Dyeing (where primary fibrillation occurs) → de-fibrillation with enzymes → Secondary fibrillation

Characteristics of Route 2: • Peach-skin hand • Distressed look • Poor shade

reproducibility due to use of enzyme after dyeing

Garment Dyeing

Fastness Properties of Dyed Lyocell Fabrics

Washing fastness is comparable with the fastness properties achieved by same dyes on fabrics made from other cellulosic fibers. However, a poor rating may be obtained as compared to other cellulosic fabrics because of fabric fibrillation.

Processing Routes for 100% Lyocell Woven Fabrics

There are tree processing routes for Lyocell

1. Open-width desizing, scouring → Primary fibrillation in a suitable

jet with 1-5 g/l Sodium Carbonate at 90-120°C → Rinsing → De-

fibrillation with cellulase enzymes (typically with 2-4 % o.w.f. at

pH 4.5-5, 55°C ) → Denaturing of Enzyme by increasing

temperature up to 80°C → Rinsing → Dyeing (with reactive dyes

of low reactivity and low-to-medium substantivity) + Secondary

Fibrillation → Rinsing → Soaping/Washing-off → Rinsing →

Softening → Tumble Drying (to enhance peach-skin effect)


1. Typical Processing Route for 100% Lyocell Woven Fabrics


2. Open-width desizing, scouring → Combined primary fibrillation and Dyeing (at 130°C using high-

temperature stable reactive dyes) → Rinsing →

Washing-off/Soaping → Rinsing → Enzyme wash/

De-fibrillation (typically at 55°C) → Denaturing of enzyme (by raising temperature to 80°C) +

Secondary fibrillation → Rinsing → Softening → Tumble Drying (to enhance peach-skin effect)


2. Alternative Route for Processing 100% Lyocell Woven Fabrics, Combining Primary Fibrillation & Dyeing


Open-width desizing, scouring → Combined dye exhaustion (of reactive dyes stable at 130°C) and primary fibrillation → Enzyme Wash/De-fibrillation (typically at 55°C) → Denaturing of enzyme (by raising temperature at 80°C) + dye fixation (by adding alkali, if necessary) + Secondary Fibrillation → Rinse → Washing-off/Soaping → Rinse → Softening → Tumble Drying (to enhance peach-skin effect)


3. An Alternative Route for Processing 100% Lyocell Woven fabrics, Combining Secondary Fibrillation and Dye Fixation


An Alternative Processing Route for Lyocell, including Pad-batch Dyeing


An alternative Processing Route for Lyocell without Secondary Fibrillation


Processing Route for Non-fibrillating Lyocell

End Uses of Lyocell

Main uses for Lyocell • Apparel

– Dresses

– slacks

– coats

– jeans

End Uses of Lyocell

Lyocell is more expensive to produce than cotton or rayon, but is included in many everyday items. Staple fiber are used in apparel items such as

• denim,

• chino,

• underwear

• Other casual wear clothing

• towels.

End Uses of Lyocell

End Uses of Lyocell

Filament fibers are used in items that have a silkier appearance such as women’s clothing and men’s dress shirts. Lyocell can be blended with a variety of other fibers such as silk, cotton, rayon, polyester, linen, nylon, and wool.

End Uses of Lyocell

End Uses of Lyocell

Lyocell is also used in

Conveyer Belt

Specialty Paper

Medical Dressing

End Uses of Lyocell

Tencel is also used for making

baby diaper wipes

Costco/Kirkland is one brand that uses the material.

References

Developments in the Processing of Lyocell Fabris By: Dr. Tanveer Hussain http://www.tencel.at accessed on 14-06-10 http://www.lenzing.com accessed on 14-06-10 J. M. Taylor, M. J. Bradbury and S. Moorhouse, “Dyeing Tencel and Tencel A100 with Poly-Functional Reactive Dyes”, AATCC Review, No. 10 page 21-24 (2001). J. M. Taylor and A. L. Harnden, “An Introduction to Tencel Processing”, International Dyer, August 1997, page 14. K. Gandhi et. al., “A Novel Route for Obtaining ‘Peach Skin Effect’ on Lyocell and its Blends”, AATCC Review, No. 4 page 48-52 (2002)

References

B. Jakob and E. Agster, “Pretreatment and Finishing of Lyocell Woven Fabrics”, International Textile Bulletin, No. 3, page 18-26 (1998).

http://www.everything2.com accessed on 14-06-10

http://www.madehow.com accessed on 14-06-10

http://en.wikipedia.org/wiki/Lyocell accessed on 14-06-10

http://www.fibersource.com accessed on 14-06-10

http://www/

http://www/

http://www/

http://www/

http://www/

http://www/

http://www/

http://www/

http://www/

http://www/

http://www.madehow.com/







http://en.wikipedia.org/wiki/Lyocell







http://www.fibersource.com/







lyocell

Documents