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3. In the Dyehouse

Piece Dying The final quality of chenille goods is determined by adhering to the correct practices in the weaving mill or knitting mill, and by the dyeing process. The nature of chenille-the fact that its pile lies in one direction-produces different results with different dyeing processes. It should also be noted that small-scale tests of piece dyeing should be carried out prior to large scale production to ensure that the pile of the chenille yarn is not washing out. Beam dying results in a different surface structure than dyeing in a star dyeing machine. The type of dye process used will be determined by the desired appearance of the final chenille goods. During beam dyeing, the chenille pile does not have a chance to stand up because of the pressure exerted by the various layers of goods. The thermal treatment during dyeing then fixes the pile in its position. This reduces the desirable "reflection effect" of chenille products. The surface can be improved by treatment with a pile rotor. Dyeing on a star dyeing machine is similar to hank dyeing in its higher costs and results. During the dye process, the material is suspended and hangs freely, allowing the pile to stand up. Thermal treatment then fixes the pile in this upright position. The resulting material is soft and voluminous to touch, and the "reflection effect" is more successful than in beam dyeing.

After Piece Dyeing

Shrinkage during the dyeing process will impact the width of the final material. For instance, acrylic goods can shrink 3-5% during dyeing, depending on the structure of the fabric. If the shrinkage factor can be taken into consideration during the manufacturing process, the additional step of using a stenter can be eliminated. For goods manufactured from colored chenille, post-treatment on a stenter can improve the appearance of the material due to the thermal treatment involved. Yarn Dyeing In the case of dyeing on cross-wound packages, the two different cone sizes of 10" 2° 30' and 6" 4° 20' can be used directly, or the cone diameter can be custom-designed (see section 1 above for more information about the various yarn carriers). Tests have shown that the last step of the dye bath, which is pressed through the yarn, should be from the inner side of the package outward. This pushes the inner chenille layer out of the cone perforation and guarantees smooth unwinding of the yarn from the package. Hank dyeing is definitely the best dye process for voluminous and twisted yarns, but is at present used only to a limited degree for chenille.
Hank dyeing is considerably more expensive than other methods, and because of the hank suspension at two points-suspension and strain-an "ironing" or "flattening" effect to the chenille pile can occur.
If hank dyeing is planned, the chenille manufacturer supplies the chenille yarn on cones with a diameter up to 300 mm. Because of the relatively low demand for reeled chenille, chenille manufacturers do not have the necessary machines to supply yarn in hanks. However, dyehouses using hank dyeing have the necessary reeling and winding machinery.

This information is designed as a basic technical guideline for converting chenille yarn in dyehouses. Further information can be obtained by contacting CIMA.

For further technical questions, please e-mail or fax to CIMA's office in Lugano, Switzerland:

CIMA - Chenille International Manufacturers Association
Corso Elvezia 16 C.P. 4511 CH-6904 Lugano (Switzerland)
Tel/Fax: 011 41 91 921 09 91 - - E-mail: cima_intl@hotmail.com

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