Dyeing finishing refers to the process of chemical treatment of textile materials (fibers, yarns fabrics), which is also known as dyeing printing in modern times. Dyeing finishing, together with spinning, weaving knitting, form the whole process of textile production. The quality of dyeing finishing has an important impact on the use value of textiles. The process mainly includes refining, bleaching, dyeing, printing finishing of raw silk fabrics.
Refine
Silk is composed of two monofilaments, the main body of which is silk prion, the outer layer is covered with sericin. Most of the pigments, oils, waxes inorganic salts are found in sericin. These impurities have a great influence on the dyeing effect, so they must be removed before dyeing. In long-term practice, people have mastered the characteristics that sericin is easy to dissolve in hot water under the action of chemicals enzymes, take advantage of this weakness of sericin, put the green silk raw silk into the mixed solution containing soap ( synthetic detergent) soda ash (sodium carbonate) for heating, hydrolyze sericin after heating. After such refining, the sericin is removed the silk prion is preserved, the impurities such as pigment, grease wax are removed, thus the silk products with white color are obtained. Degumming is also called refining. The raw silk after degumming is called cooked silk. The degumming degree of raw silk shall be determined according to the production requirements.
Bleach
The degummed silk fibers should be bleached to remove natural pigments. Otherwise, when dyeing light color, because of the existence of natural pigments, the color of the finished product will change. Silk can be bleached by oxidation reduction of various bleaching agents. The process of silk bleaching with hydrogen peroxide in the presence of catalyst has been reported. Thiourea dioxide is a kind of reduced bleaching agent. Its BOD COD values are low, so it can be used as a non-toxic bleaching agent with low pollution. However, compared with the powder, the powder is still widely used despite its serious pollution. However, the application of TDU is limited due to its high price.
dyeing
After refining, the green silk with pure white color will enter the dyeing stage. Dyeing is to make dye silkworm, green silk other chemical reactions, so that green silk dyed with a variety of colors. Because silk is a kind of protein fiber, which is alkali resistant, dyeing should be carried out in acid near neutral dye solution. The main dyes used for silk fabrics are: acid dyes, reactive dyes, direct dyes vat dyes. The color of the product dyed with acid dyes is bright. After dyeing, it can be treated with cationic fixing agent to improve the washing fastness of the product. Reactive dyes have good washing fastness on silk. The dyeing methods of fabrics vary with the variety of fabrics, for example, crepe yarn fabrics are dyed with rope overflow spray, while fabrics of spinning, silk satin are dyed with flat hanging curling.
printing
After all, a kind of color is monotonous. In addition to dyeing, people also use printing technology to make silk colorful. Printing refers to a process of printing dyes on fabrics according to designed patterns colors. Common printing processes include direct printing, pull out printing anti dyeing. Direct printing is one of the basic printing methods in which the color paste is directly printed on the silk fabric through the screen printing plate. It can be printed with a variety of dyes. Discharge printing, also known as engraving printing, is a process of discharge dyeing with engraving agent. Before printing dyeing, the silk fabrics are first dyed with acid dyes reactive dyes with azo structure, then the engraving (discharge) pulp made of the engraving agent containing the destructive pigment is printed on the colored silk fabrics according to the pattern needs. After steaming, the ground color of the printing pulp is white, which is called "engraving white".
Anti dyeing printing is to print silk fabrics with "anti white" paste "color anti" paste according to patterns, then dye them after drying. Because the pattern part has the "anti white" paste the anti dye agent in the "color anti" paste, it will dye, the rest parts are all colored.
Arrangement
After scouring, dyeing printing, silk fabrics can be finished finally. The finishing process mainly solves the problems of wetness, fold uneven door width left by the previous processes, highlights the softness of silk fabric itself increases its wearing function, mainly using two methods of mechanical finishing chemical finishing. Mechanical finishing includes stretching wefting, steaming calendering; chemical finishing mainly includes adding chemicals, such as softener, antistatic agent, fireproof agent, sand washing agent composed of soda ash trisodium phosphate, so as to achieve the effect of wrinkle prevention, shrinkage prevention, softness compactness. The treated fabrics are only more suitable for wearing, but also broaden the consumption field of silk.
