Heatsetting

Heat setting (although heat setting ) is a term from the textile industry and refers to the thermal process usually takes place in steam atmosphere or dry heat to produce fibers, yarns and fabrics dimensional stability and often other desirable properties, such as greater volume, resistance to wrinkles and increased temperature stability to lend.

• 4.1 Carpet Classification
• 4.2 Tip- Definition

• 5.1 autoclave process
• 5.2 Steamatik process
• 5.3 Power - Heat-Set method
• 5.4 TVP process

Target

Very often the Heat setting also serves to give the yarn a better property for subsequent processes. Yarns often tend after fresh spun, cabled or were twisted to increased " snarling tendency ". Through the heatset process can affect or eliminate this property. Especially in the processing stages winding, twisting, weaving, tufting and knitting can be a powerful curling tendency lead to processing difficulties. With yarns for the carpet industry would be in addition to the reduction of the snarling tendency to stabilize or also fix the fiber composite. This applies both to staple fibers as well as continuous filaments (BCF). With synthetic fibers nor the effect is a case that the yarn becomes more volume. This is known as an increase of the pad or in the bulk. In addition, there is a not insignificant amount of fancy yarns, among other things, for the carpet industry, eg for the production of Frieze carpets, shaggy carpets, Trackles carpets or rugs texture, which is submitted to the heatset process. These yarns are usually deformed by a mechanical texturing to arches, wrinkles and curls. Usually this is in a so-called stuffer (English stuffing box, twinrollbox ). To stabilize these permanent mechanical deformations, a Heatsetprozess joins after shaping. All processes with which you want to give one of the pre -mentioned properties with temperature and / or humidity of a textile material, called heatset, Heat setting or set process. Less commonly, the term heat setting. Especially in the carpet industry is referred exclusively by heat setting.

Causes of snarling tendency

The curling tendency, so the cause of the dissolution of the fiber structure in the cut yarn ( e.g. carpets Cutpile ) is based on the technological conditions of the production web and the fiber physical properties. Under technological conditions of the cocoon production is primarily understood the thread torque. The ambition of a rotated string is then to twist when it is hung in a loop freely between two fixed points. He is here from some of its twists that show up in turns, the rotation direction is opposite to the original direction of equilibrium reasons. This is due to the tensions caused by the yarn twist, which indicated Müller in the known distribution. With increasing rotation of the fibers in the yarn body, the rotation counteracting total voltage becomes larger due to the increasing train and compression. It can be so great that the core of the thread is no longer able to compressive stresses occurring and buckles. The yarn curls that is, of the packages sought by a number of turns in the opposite direction - also referred to as negative rotations - a state of equilibrium, which allows cancel the internal torsional stresses. Bends of the yarn is always at such a location is present at the non-uniformity as a result of a small cross-section. This has received a greater number of turns in the spinning process, and thus is subject to high internal stresses, the buckling due to the core thread in the end. Although stronger yarns are rotated less than finer, the inner tension of the yarn count rises opposite. Through the Heat Setting this voltage is more attenuated more, the coarser the yarn count. A further object of Heat Settings is in addition to the reduction of Kräuselvermögens simultaneous fixation of transferred by the rotation of the yarn physical properties of strength and elongation.

Chemical processes

It play, depending on the yarn material with which one has to do it completely different processes from. Examined on precisely the vapors of wool yarns, less so the vapors of synthetic fibers and cotton.

Wool

After the occurrence of vapor occurs abruptly a an effective increase in moisture content of the yarns by Garnaufheizung and by steam condensation. After peak man following phenomena on the strained wool fiber now tripped: The cystine side chain are subjected to the sulfur bridge of hydrolysis, wherein the cystine to cysteine ​​and not isolated sulfonic transitions '.

At the bridges caused by salt formation occurs ionization. Due to the temperature rise occurring during the steaming in the fibers occurs vibration of the molecules, leading to the bursting of the hydrogen bonds; so that residual valences are exposed, which are able to saturate the water dipole. The water then acts as a kind of lubricant between the individual molecules. Thus, the bonds of the main chains between them is canceled by the side chains, the individual polypeptide chains can be shifted against each other and the tensions find their balance. Upon further steaming of the yarn form between the individual blocks of the main chains of new side chains. During the subsequent drying of the yarn, that is, in which take place within the yarn moisture equalization is again effected salt formation and the formation of hydrogen bonds. The individual polypeptide chains are no longer relative to each other and the fibers have regained their former strength, but without the interior to include larger voltages. The yarn or thread rotation is fixed. The morphological structure of the fibers must of course be taken into account by attenuating the voltage compensation. By the wool fiber very quickly the temperature is to break the hydrogen bonds and the water vapor to hydrolyze the cystine bridges available, a relatively fast twist reassurance is possible, which corresponds approximately to the values ​​of a autoklavenberuhigten yarn; said Dämpfqualität of Sewimatic Dämpfverfahrens, with respect to the uniformity of the moisture absorption is much better.

Synthetic fiber

The synthetic fiber we distinguish two fiber regions, the crystalline (ordered ) field and the amorphous ( disordered ) region. In crystalline fiber areas act between the closely parallel to each other polymers physical attraction forces. This acting transverse to the fiber axis forces make up the strength of a fiber. When pressure is applied to the fiber train, then prevent these forces that the fiber tears. The amorphous fiber regions contrast, act as hinges of the fibers. They are responsible for the bending strength of the fiber. In addition, the amorphous portions of the fibers, for example, allow the penetration of water or dye.

What happens during the damping. With increasing heating of the fiber molecules come into increasing their vibration. The influenced by the amount and duration of heating vibration increase cancels the electrical binding forces in the fiber; first in the amorphous regions, and later in the crystalline regions, and finally in the polymers. As in the wool introduced by the spinning tension are now free. When drying or cool the fiber to build the binding forces back on again without that they have in the internal stress.

The problem with synthetic fibers is that the decrease in binding forces only between the so-called glass transition point - the beginning of the conversion of the solid ( frozen ) amorphous portions of the fibers in a viscoelastic; slightly deformable state - and the softening point ( and the crystalline portions of the fibers enter the viscoelastic state above ) takes place, and the synthetic fibers is in a relatively high temperature range.

This fact also explains why wool blends mixed with synthetic fibers, harder to soothe than pure wool. A settling of synthetic fibers is possible only over a temperature range of 85 to 95 ° C. Pure wool can be, however, already at these temperatures very well calm down.

Cotton

Cotton plays with respect to the composite damping a subordinate role, even do not know the exact physical or chemical process in the fiber. Therefore, cotton can be neglected in the considerations.

Application in the carpet industry

Especially with yarns for the carpet industry and here again for carpets that are cut (german cut pile ), the reduction of internal stresses in a significant increase in quality contributes.

Carpet classification

For carpets there are two basic forms. This is the one of the loops carpet (loop pile ) and secondly the cut carpet. Especially with cut-pile carpets and related variants (Saxony, Shag and Frieze ) heatset process is of great importance.

Tip- Definition

When discussing cuts a yarn, the ends rotate similar to a cord or rope on and it creates a kind of " brush". And that's what one wants to avoid the cut carpet and have no case. Such a carpet would have next to a poorer appearance and a shorter service life and, what is more interesting, as scientific studies have shown physiological disadvantages for the " walkers through ". The carpet is not as elastic and absorbs the user's step from not so good, like a carpet, which was geheatsettet. A carpet that was so made ​​of heat-set yarn is thus superior. In general, do you recognize a geheatsetteten carpet to its granular structure, in the jargon we also speak of a " pinpoint tip definition" so a similar appearance of needle tips.

Continuous Heat Setting Process

In the textile industry, several methods are known heatset. The most important are presented here.

Autoclave process

The oldest method is the autoclave. This is usually a batch process. In the autoclave, a distinction between systems that use vacuum and those who work only with pressure. The textile material is introduced in the form of coils or strands into the autoclave. Since almost all autoclave pressures are exposed, they are generally formed in a cylindrical shape and placed in a horizontal position. There are autoclave, which are loaded and unloaded from one side, but also some which are loaded and unloaded from one side of the other side. Autoclave, which are placed in a vertical position, are less common.

Steamatik process

For the automation in spinning Spulverbund (English link spinning ), there are so-called composite damper. The world's first method was the so-called Steamatic process by Resch. In this method, the heat setting operation between a ring spinning machine and the winding machine is held. As soon as the ring spinning machine has completed the spinning operation, the finished spinning cops are automatically supplied to the laminated dampers. There, the spinning cops are attenuated in a vacuum method, and dried again in seconds. Then, the bobbins are supplied to the winding machine where it is then rewound to a cross-wound bobbin.

For the carpet industry are two continuous process application: the Power - Heat-Set method ( developed from the cuties heatset process ) and the TVP method, derived from the autoclave technique.

Power - Heat-Set method

The Power- Heat-Set method, also known as sweetening process, was created in the early 1970s and was one of the first continuous heat setting process worldwide. Method was far revolutionary, as it is not operated as a first method, with saturated steam under pressure, but working with a superheated steam air mixture under atmospheric pressure. On the basis of the treatment process ( superheated steam air mixture ) created entirely new collections of carpets. With the Power - Heat-Set process the fibers or yarns are easily oxidized at its surface by the available oxygen in the air and the higher temperatures. This fine oxidation layer makes later the finished carpet less sensitive to dirt. The dirt particles adhere less well to the fibers.

TVP process

In addition to the Power -Heat -set process there is also the TVP method, which is also one of the continuous process. When TVP process, the yarns are laid on a band and through a lock in a pressure tunnel that can be up to 15 meters long, and introduced in this subject by saturated steam to the heat setting process. At the end of the tunnel, the yarn is run through a sluice from the heatsetting tunnel again. The still hot and wet yarn is then dried and cooled, and fed to the winding process. Up to 36 threads can be processed on this line.

Representation of the process using the example of the Power- Heat-Set process

With the Power -Heat -set process is geheatsettet with superheated steam in an open system at atmospheric pressure. We process all common materials used in the carpet industry for use. This includes mainly polyamide 6, polyamide 66, polypropylene, acrylic, PET, polyester and wool.

The untreated yarn is presented in the form of coils (up to 48 pieces) in a creel. At a rate of up to 700 m / min, the yarn is withdrawn from the coil and fed to the Heatsetprozess. There are two basic transport means for the yarn, on the one hand by feeding the yarn is arranged as a circle or like an "8" flat hangs up on a belt and the Heatsetprozess feeds, or by putting it winds onto ropes, which is arranged as a polygon, the yarn which Heatsetprozess out. At Friezegarnen only the shape of the tape transport is selected. Friezegarne are manufactured using a special Stauckkammer the Twinrollbox. The Heatsetprozess is performed at temperatures of 110 ° C to 200 ° C carried out in a vapor air mixture. After the heatset process, the yarn is again cooled and wound up using a winding machine for coils Typically, the Power - Heat-Set process from 6 working lines, each with 8 threads is (Ends ). This procedure can be a daily production of about 10.5 tons achieve.