English Views: 30 Author: Site Editor Publish Time: 2021-12-01 Origin: Site
The pure α-cellulose (called pulp) is extracted from the cellulose raw material, and treated with caustic soda and carbon disulfide to obtain orange-yellow cellulose sodium xanthate, which is then dissolved in dilute sodium hydroxide solution to become viscous The spinning dope is called viscose.
The viscose is filtered, matured (placed at a certain temperature for about 18-30 hours to reduce the degree of esterification of cellulose xanthate), defoamed, and then subjected to wet spinning. The coagulation bath consists of sulfuric acid, sodium sulfate and sulfuric acid. Zinc composition. The cellulose sodium xanthate in the viscose is decomposed by the action of the sulfuric acid in the coagulation bath, and the cellulose is regenerated and precipitated. The obtained cellulose fibers are washed with water, desulfurized, bleached, and dried to become viscose fibers.
Viscose fiber is the oldest regenerated cellulose fiber. The viscose fibers produced are as follows.
(1) Viscose staple fiber
It is made by cutting the fiber bundle made by continuous spinning into a certain length. According to its cut length, it can be divided into three types: cotton type (artificial cotton), wool type (artificial wool) and medium-long fiber. They are mainly used for blending with other fibers, such as polyester/viscose, wool/viscose and other fabrics. Later, in order to improve the strength and elasticity of viscose fiber, a new type of viscose staple fiber with high strength and high wet modulus, namely rich and strong fiber, appeared, which can be used for spinning alone to make artificial cotton fabric.
(2) Viscose filament
Also known as rayon. At present, there are both pure rayon fabrics on the market, such as non-light spinning, light spinning, beautiful silk, rayon soft satin, rayon crepe de chine, etc., as well as rayon and other fibers. For example, Fuchun spinning is a combination of rayon and rayon. The interwoven fabric of rayon yarn, the soft satin quilt is the interwoven fabric of real silk and rayon, and the thread quilt is the interwoven fabric of rayon and cotton yarn.
The viscose fiber structure is not uniform, and there is a skin-core layer structure. The fiber has good moisture absorption performance, the fabric obviously feels thicker and rougher when exposed to water, and the fabric shrinkage rate is relatively large. The chemical properties of viscose fiber are lively, not acid-resistant, and alkali-resistant than cotton. Except for the rich fiber, it cannot withstand mercerizing treatment.
The strength of viscose fiber is low, the elongation is large, the elasticity is poor, especially the wet strength is lower. Therefore, the viscose fiber is not resistant to processing under tension and is easy to wrinkle. It is best to use loose open-width processing. The viscose filament has a smooth surface, poor cohesive force, and low twist. It is easy to scratch during processing, and care must be taken during operation.
The viscose fiber has been washed, impurity-removed and bleached during the manufacturing process, most of the impurities and pigments have been removed, but because the fiber also contains the oil added after spinning, the slurry during the weaving process and During the entire process before scouring and bleaching, the fabric may be stained with stains, etc. Therefore, rayon and rayon fabrics still need to be scoured and bleached to make the fabric have good water absorption, soft feel and white appearance. Provide excellent semi-finished products.
The pretreatment process of rayon and rayon fabric consists of the following processes and has its own characteristics:
①Pre-preparation: The open-width continuous scouring and bleaching equipment for rayon fabrics can be borrowed from cotton. The pre-preparation should include turning, batching, sewing, printing, etc. When sewing the head, the stitches of rayon can be thinner than cotton cloth, and the rayon fabric can be refined in a hanging barrel, and there are unwinding, folding, nail loops, printing, etc. before preparation. When folding, rayon fabrics generally adopt the "S" code, and heavy fabrics such as satin can also be circled.
② Singeing: Artificial cotton can be singed by a gas singeing machine, but it cannot withstand strong friction and does not require brushes and scrapers; because viscose fiber has high moisture absorption, the singeing temperature can be slightly higher than that of cotton, and the speed can be Slower. Rayon fabric does not need singeing.
③Desizing: Desizing is the focus of the pretreatment of rayon and rayon fabrics. When weaving rayon grey cloth, starch slurry is mostly applied. Because acid and alkali have an influence on the strength of rayon fabric, amylase desizing is often used, and the process is the same as cotton desizing. The most commonly used sizing agent for rayon fabrics is animal glue, and chemical sizing agents such as CMC and PVA are also added. These sizing agents can be desizing with alkali agents or detergents. Due to the low pulp content of rayon, it can be carried out along with the refining process. . If starch sizing is used, it can also be refined after desizing.
④ Refining: Artificial cotton does not need refining. Rayon can be refined in refining barrels, or refined with dyeing equipment before dyeing (including desizing).
⑤Bleaching and whitening: There are very few natural pigments in rayon and rayon fabrics, so bleaching is not required.
