Udo Schweizer's Texturing Pages

The air texturing process was developed about 50 years ago.  However, it took nearly 30 years before the first commercial machine for the production of air jet textured apparel yarns was displayed at ITMA in 1979.  The air texturing process transforms flat multi-filament yarns into yarns with a spun like character.  The similarity to spun yarns has given the textile industry an economically produced product, which - as we know it today - , cannot be matched by any other texturing method.

For the producer of textiles the imminent question would be: "Why took it so long to make a success out of these yarns and which technological improvements were made to get the yarns to be accepted ?"

To answer this, we need to look back to when the first air texturing machines were produced.  From a rather primitive machine concept, machine builders and users gradually learned how to improve the process by adding more feed- and yarn treatment zones.  A breakthrough came in the late 70's when the German textile machinery producer Barmag found that the a way how to produce a suitable air jet textured apparel yarn was to run the yarn after the texturing first through a stabilizing and then through a heat setting zone.  Having the correct machine design and process steps established, predrawing equipment was added, which now enable us to process inexpensive POY economically into high quality yarns.

This combination of process steps resulted in the following important improvements for yarns and fabrics.

High yarn stability
Low and uniform package take-off tension
High bulk
Reduced boiling water shrinkage
Improved soft hand of fabrics
Elimination of the Velcro effect of fabrics
High pilling resistance
Uniform appearance of the fabric
Sizing of warp beams may not be necessary for slower running looms

There are basically 2 types of yarns which can be produced with air texturing.  The first type is a so called parallel yarn and the second type is a core effect yarn.

• The production of parallel yarns is fairly simple.  One or more yarn ends are being fed into the air texturing jet using for all ends exactly the same overfeed.  Normal overfeeds, depending on the enduse for the yarns are between 18% and 30%. Parallel yarns are being used for apparel and cut pile plush fabrics in the automotive sector.
• Core effect yarns are produced out of 2 components, the core yarn and the effect yarn.  Both yarns could be either single of multiple ends.  The core yarn overfeed however is always lower and in some cases very different to the overfeed of the effect yarn. Normal core yarn overfeed is between 5 - 15%.  The effect yarns can be overfed - again depending on the enduse of the final yarn up- to around 400%. Core effect yarns up to about 40% effect yarn overfeed are being used for apparel enduse, e.g. nylon sports wear.  Core effect yarns up to about 120% effect yarn overfeed are being used for upholstery fabrics, mainly in domestic or car seat upholstery.

Air jet textured yarns contribute to lower cost fabrics, because they :

• Can replace expensive natural fibers such as raw silk, wool and cotton and still feel spun like
• Can replace the very expensive fine count spun yarns for dress weight and blouse weight fabrics
• Replace coarse count yarns or heavy denier false twist textured yarns.

Air texturing economics are most favorable when installing a new production.  The investment for air jet texturing is much less than for an equivalent capacity for spun yarns.

Which yarns are required and how are yarns processed on this machine?

POY is preferred because it is less expensive that FOY and because it is available today in a large variety of deniers, cross sections and colors.  Most important for a successful yarn is the number of filaments respectively the denier per filament.  For different end uses, fabric appearance and hand a variety of yarns are being used.  Only in very few cases can yarns with a higher denier per filament than 3 be used.  Today's standard is between 1 and 2 dpf, with the latest most fashionable yarns being more towards 1 or even smaller than 1 den per filament.
The drawing zone must offer for polyester POY a heated pin, godet or plate, some nylon POY can be drawn cold.  In case of core effect yarns each yarn must have its own drawing zone and for technological reasons it is necessary that each yarn has its own heating device.  The temperatures must be hot enough to ensure that the yarns are adequately treated.

In the texturing zone the yarn must first be wetted with water.  This water has several functions.  It removes parts of the spin finish, it opens the individual filaments and it serves as a lubricant inside the air texturing jet.  When processing core effect yarns only the core yarn is wetted.  There are various ways of wetting the yarn.  One is by dipping the yarn into a water bath, which has been established as a well proven method.  Another method is to add water to the yarn via a ceramic application nozzle, the same type as used in filament spinning for the spin finish application.

There are two different types of commercial air jets available.  The first type, which is a venturi type air jet and a more recent development a vortex type of air jet.  Both jets operate at pressures of around 10 bar / 140 psi.  In both cases, the actual texturing happens directly outside the jet in the turbulent supersonic air stream.

The jet producers offer  a variety of jets  for different deniers and yarns.  The air consumption, one of the significant cost factors of the process can so be kept as low as possible.   It is significant to note that the vortex type jets are being marketed for products which require less than 100% jet overfeed, whereas the venturi type of jet can process effect yarn overfeeds up to several hundred per cent.  There are different size needles and venturis available to cater for the various yarns.

Regardless on which jet is being used, a certain irregularity of the texturing effect cannot be avoided.  Sometimes an accumulation of larger loops occurs, or some long flat loops are being formed.  These irregularities, which create havoc in subsequent processes have to be eliminated.
The yarns, even when well formed are still subject to deformation when they are loaded with a small force.  We call this behavior "Instability" and in order to measure the amount of instability various test methods have been formulated.

Solutions have been found to both problems.

In the earlier mentioned stabilizing zone the yarn is  drawn , depending on its construction by an amount normally between 3 to a maximum of around 15%.  What happens now is that the more bulky loops and irregularities are being reduced because we pull the loop size down to a smaller diameter than that, which is produced in the jet.  The drawing also tightens the loops in a similar way as you tighten your shoe laces when you pull on them.  This now produces a yarn of a low instability which is absolutely necessary for subsequent processing.

In the heat setting zone the now stabilized yarn can be slightly overfed so that the yarn and the surface loops can shrink.  This further reduction of loop size proves to be most important for all further processes.  Because with the elimination of the large loops the tendency of large loops to catch or snag is reduced and often totally eliminated.  The usual setting temperatures are 230 - 240 °C for the finer polyester yarns.

Yarn lubrication is a must for most yarns.  Usually 2 - 4% coning oil is applied to the yarn for improved lubricity during weaving or knitting.  Yarns which will be directly dyed are normally not lubricated.

The yarn is taken up on a rather firm package.  It has been found that such packages give the best unwinding characteristics.

I have so far described the production of post stabilized air textured yarn.  Into this concept a design has to be mentioned, which enables the manufacturer to produce also specialty yarns.  For a more staple fiber like yarn with free fiber ends a so called "Texspun" process was developed by Barmag.

This Texspun unit is located in the stabilizing zone.  If the yarn is passed over the special designed rollers of the unit, a certain amount of the loops are torn and free fiber ends, very similar to staple fiber, are being produced.  Such yarns, commercially produced at 400 m/min and faster show not only a higher tenacity but virtually eliminate the dreaded Velcro effect in the final fabrics.  Improvements in fabric hand, cover, run ability and surface uniformity are the result.

Another specialty is the possibility to produce industrial grade yarns.  This is done with a new yarn drawing concept which allows  to produce from inexpensive POY high grade industrial yarns with tenacities of around 7 g/den at approx. 12 % elongation.  Once this yarn is textured as core effect yarn the combined fiber strength is of course lower.  A typical end use would be sewing thread and scrim fabrics.

The current air jet designs of the various jet producers rarely allow speeds in excess of 600 m/min.

Today there is no other staple fiber spinning or texturing process that offers such a wide range of applications as air texturing does.  This concerns:

• the total denier range and filament fineness
• the type of feeding materials and their combinations
• the bulk and structure of the textured yarn

ATY is used for:

• Sportswear
• Leisure wear
• Men's- and ladies wear
• Rainwear
• Automotive fabrics
• Coating fabrics
• Decorating fabrics
• Industrial yarns
• Sewing thread

Air textured yarns are widely being used in woven, warp knitted and circular knitted fabrics.  The preparatory works are very similar to ordinary textured yarns.
Warping
Standard Warpers -- speed should be reduced to 65 - 75% of normal.
Whorl Tension Devices are recommended.
1 - 2% lubricant on yarn in texturing.
Minimize jogging.  This helps keep all ends running from the start.
Slashing  --  A Must.  Yarns need to be protected from weaving stresses and strains.
7 - 8% dry solids pick up.
After-waxing helps protect and lubricate warp yarns during weaving.
Dye streaks can occur without sizing.

Weaving  --  Bottom weights
All loom types are okay.  Air jet type, projectile type and flexible rapier preferred.
Can also use water jet, fly shuttle, rigid rapier.
Firm packages, lubricant on filling to help yarn unwind from package.

Weaving  --  Top weights
Adjacent end hand up is a problem with air jet textured high count warps.
Sleys in 80 - 120 end/inch range can be woven if measures are taken to assist the shed in opening.
Increase warp tension to assist shed in "snapping" open.
Install nip bars behind harnesses to shorten shed length, thus assisting shedding action.
Increase speed to open shed more quickly.

Warp Knitting Air Textured Yarns
Fabrics have been satisfactorily knit.  Yarn preparation includes the addition of 3 - 4% wax emulsion after texturing to minimize plucking on beams.  Yarns should be textured with minimum overfeed to also minimize plucking.

Finishing Fabrics Containing Air Jet Textured Yarns

Relaxation and overfeed are the keys to success.  Air jet textured yarns need to develop their full bulk potential.  Stretching the fabric diminishes the spun like effect.

Suggested Sequence (Wovens)
Open width scour, finishing at a boil.
(Direct Scour in the jet may be used but open width is preferred since it prevents creases during dyeing.)
Jet dye as relaxed as possible at 120 - 130 °C for 1 hour.
(Fabrics containing wool at 100 °C.)
Jet conditions:  Use minimum nozzle pressure, then adjust lifter reel to match nozzle flow.  Ampere gauge should steady and at a minimum.  (This shows that a minimum of energy is being used to move the fabric through the machine thus less tension of the fabric.)
Dry and heat set one pass on a three-zone pin tenter frame.  Use 30 sec. exposure in heat setting at 130 °C with 1 - 2% overfeed.  Set width at minimum needed to remove wrinkles / creases consistent with stretch desired.
Post Finishing - Optional
Combinations of napping, shearing, hot Schreiner calendering, and semi-decating can be used to improve "face" or cover and hand.  Example - light double-action nap one pass each side of fabric, crop shear, heat set, warm Schreiner calender at 110 °C, 40 tons, 1 minute steam, 1 minute vacuum.

Fabric Performance
Fabrics of air jet textured yarns if properly constructed will perform as well as fabrics of false twist textured or spun yarns.

Specialists  and ecologists regard Air Textured Yarns as a truly green product.  Spun dyed POY converted to ATY does not need to be further dyed and requires less steps in finishing, which is a welcome fact to many fabric producers.  Air textured yarns  will yield, when produced correctly, a wonderful spun like hand.  This makes it a perfect spun replacement yarn.  All this would be meaningless if the process would not offer a splendid return on the investment.  The low floor space requirement and the low power consumption coupled with high productivity speak for themselves.
 

I hope that  my explanation has helped you to understand the principle of the texturing process.  There is much more knowledge out there, but unfortunately very little on the web.  I will try to remedy this situation and welcome all suggestions.  Please let me have your comments.

 
 

Last updated May 1, 2002
Copyright Udo P. Schweizer