Continuous Setting (ACT) heat setting.pptx

Heat setting,

1. CONTENTS Continuous Setting in Superheated Steam Continuous Bisulphite Setting of Wool Setting Wool Yarns During Scouring

2. Continuous Setting in Superheated Steam A widely used machine for continuous setting in dry steam is the Horauf-Suessen GVA yarn heat setting machine . For full setting, it operates at higher temperatures than are required in saturated steam. It can also be used at lower temperatures for bulking high-bulk acrylic or polypropylene yarns, and dry-spun wool yarns. The dry conditions in the unpressurised steam chamber make it unsuitable for twist setting wool yarns. An important feature of the machine is that it allows complete freedom for the yarn to relax and bulk. The general layout of the machine is shown in given figure. Four (or six) ends of yarn are reeled together on four moving ropes to form a continuous hank , and the yarn is transported through the steaming chamber in this form. The path of the tapes allows the yarns to shrink in the early stages of steaming. Figure shows the cantilevered 'mast' with its transport system: the initial cross-section of the hank (A) is changed to (B) to allow relaxation to configuration (C) as the yarn passes through the steam chamber (GKK). In machine six masts are located in parallel through the setting chamber, so that a machine processes “4x6 = 24” or “6X6 = 36” ends of yarn simultaneously. Two general purpose machines are available : The GVA 2500 works with four or six ends of yarn per mast and the GVA 5000 is a high production machine taking six or eight ends per mast .

3. The GVA 2500 PP is dedicated to bulking and setting polypropylene , BCF or spun, and has a different configuration for the ropes on the mast. The GVA Texturing System is for setting frieze yarns . Yarn from the creel passes into a texturing box that develops kinks , and transport through the setting chamber is via a conveyor belt. A mast-type yarn accumulator is located between the setting chamber and the take-up winders.

4. Continuous Bisulphite Setting of Wool The WRONZ Twistset process is carried out continuously on a machine available from ADM Group (formerly Annett and Darling), New Zealand. Yarn from a creel is coiled on to twin mats (18 or 24 ends of yarn in each coil, depending on the model of machine) on a single perforated conveyor that transports them through four wet processing bowls , each with a squeeze head. The coiled yarn is then dried, passes to twin accumulators (to enable the machine to operate continuously during doffing, etc), is uncoiled and wound by multi-head auto-doffing winders. The first bowl of the machine is used for scouring ; the second contains typically 10 g/l sodium metabisulphite adjusted to pH 7 ; and the third and fourth bowls are used for rinsing away residual bisulphite. Treatment with bisulphite is for 2 minutes at 85°C. The function of the bisulphite is to increase the level of ionised thiol groups in the protein of the wool matrix, facilitating thiol-disulphide interchange between the protein chains. Molecular rearrangement takes place through an 'unzipping/rezipping' action, allowing twist stresses to relax.

5. Advantages of Twistset Process An important technical advantage of the Twistset process is that a fairly high level of unbalanced twist (fibre stress) can be applied without yarn kinking occurring, because the yarns are lightly constrained on the conveyor during the process. This enables a higher level of twist set to be achieved than when processing in hank form, where the yarn is not constrained in this way. Another technical advantage is that bisulphite setting provides a mild bleaching action , brightening colours , whereas steam setting tends to dull colours. Claimed processing advantages of the Twistset process include avoidance of multiple handling of yarn, fewer yarn joints and excellent uniformity of treatment.

6. Setting wool yarn during scouring Setting wool yarn during scouring Definition :- Scouring is the washing of wool yarns to remove impurities ( grease,dirt oil etc ) Recipe for scouring of wool yarn Recipe for wool scouring:- Sodium carbonate=2ml Soap =5ml Water = 200ml Temperature=60 degree Celsius Time.=30min PH=8 MLR:1:30 Parameters:- Combines cleaning and setting in a single step. Reduces additional post-scouring treatments. Advantages Limited control over the degree of setting. • Risk of fiber damage if not carefully controlled. Limitations

7. Setting Wool Yarns During Scouring By modifying existing tape, brattice or suction-drum scouring sets, processing conditions analogous to those pertaining in the WRONZ Twistset process can be created. To achieve an adequate residence time , scouring and bisulphite treatment are carried out simultaneously , using the first two bowls. Setting that is adequately uniform for stocked-dyed yarn can readily be achieved. Mixture colours are advantageously brightened.

8. Comparison Techniques Method Process Advantage Challenges Superheated steam setting Heat – based stabilization using steam. High efficiency . Good control over setting. High energy use,Risk of over shrinking. Disulphite setting Chemical- based rearrangement of bonds. Permanent setting. Improve fiber stability. Chemical handling and disposal challenges. Setting during scouring Thermal/Mechanical action during washing. Combine setting and cleaning. Cost- efficient. Limited control. Risk of felting. Comparison technique :-

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