Cupping
The alkaline decoction with or without pressure in textile finishing is called bulging or bulging . The process is used to remove contaminating substances and substances that interfere with subsequent processes in yarns and fabrics made from cellulose fibers , i. H. made of cotton and linen , with the effect of pre-bleaching . The operation was also called Beichen , Bulge or in general simply as bases referred.
In the case of cotton, the notching is used to remove
- Shell parts (remains of the seed coats)
- low molecular weight cellulose content (e.g. immature cotton fibers)
and accompanying substances such as
- Fat and wax
- Pectins
- Proteins
- Calcium - and magnesium - phosphates , aluminum and iron oxides
- Sizing degradation products and residual sizing
- Dirt and dust
- as well as residues of the chemicals applied during rearing and fiber extraction .
The industrial process is carried out under pressure at 110 ° C to 130 ° C and results in a weight loss of 3% to 8%. In addition to the alkali donor (in most cases caustic soda ), caustic alkali-stable wetting agents and surfactants , as well as complexing agents , dispersants and reducing agents are used. When using starch-containing sizing, it must also be desized . The alkaline decoction is only used with poor raw materials, otherwise as a combined bleaching with decoction. Acid pretreatment is an alternative to this process .
In peasant flax processing , beeching was carried out in closed iron kettles (so-called belly kettles ) or in covered wooden tubs . The laundry or ropes of linen to be treated were layered in the belly barrel. At the top came a little sack filled with beech ash, which was poured with hot water. This created a lye that was allowed to seep through the laundry over a dozen times, heating it several times. The dirt particles were loosened and removed. The process took a whole day.
swell
- Real dictionary of Germanic antiquity
- Explanations of the process
- Rouette, H.-K., Handbook Textile Finishing, Technology, Processes, Machines , Deutscher Fachverlag: Frankfurt, (2003); Vol. 2, pp. 61-66