Printing and dyeing processing technology of linen products
1. Degumming and bleaching of linen fiber
The hemp fibers used for clothing are mainly ramie, flax and jute, among which ramie and flax are of good quality. Ramie and flax can be purely spun and processed into linen fabrics. After the fabrics are made into garments, they are stiff to wear, absorb moisture and dissipate heat quickly, and are good fabrics for summer clothing.
After the hemp fiber is harvested, the hemp bark is peeled from the hemp stems, and the epidermis is scraped from the hemp bark to obtain the hemp bast, which is dried in the sun to become hemp textile. The raw material of the factory is called raw hemp. Raw hemp contains a large number of impurities, mainly polysaccharide colloid substances. Most of these colloid substances surround the surface of the fibers and glue the fibers together into strong strips. Before spinning, the gum in the bast must be removed and the individual fibers of the linen must be separated from each other. This process is called degumming.
The colloid in hemp fiber is basically an amorphous substance and can be hydrolyzed under the action of alkali, inorganic acid and oxidizing agent. The degumming method is generally “chemical degumming method” or “biological enzymatic degumming method”. Ramie and flax have different degumming methods due to the different gums contained in their fibers.
The process flow of chemical degumming of ramie is:
Tie the handle—→pickle—→rinse —→High-pressure secondary scouring—→Water washing—→Fiber beating—→Acid washing—→Rinse (—→Bleaching—→Scouring)
Zhabang is a hemp of similar quality. Bundle into small handfuls of 0.5-1.0kg in preparation for cooking.
Fiber beating, also known as fiber beating, uses mechanical hammering and water spraying to remove the colloid that has been destroyed by alkali solution from the surface of the fiber to loosen the fiber. ,soft.
Acid washing uses 1-2g/L sulfuric acid to neutralize colored substances such as residual glue on the fiber to further loosen and whiten the fiber.
The process flow of chemical degumming of flax is:
Flax stems —→Select stems and bundles—→Dip—→Dry—→Crush stems—→Beat—→Beat into hemp
Dipping in the process is commonly known as retting, also known as degumming. It uses caustic soda or microorganisms to destroy the colloids in flax fibers.
The scouring and bleaching of linen fabrics is basically similar to that of cotton fabrics, but there are certain differences in process conditions. In particular, the mercerization of ramie fabrics uses semi-mercerization. Since ramie has high crystallinity and orientation, its ability to absorb dyes is much lower than that of cotton. Semi-mercerization can significantly improve the fiber’s ability to absorb dyes, thereby increasing the dye uptake rate. If conventional mercerization is performed, the permeability of ramie will be greatly improved, and the dye will easily penetrate into the fiber, causing the apparent color yield of the ramie fabric to decrease, the strength of the fabric to decrease, and the hand feel to be rough.
The wastewater produced by the degumming of linen fabrics is seriously polluted, and the content of organic pollutants is high.
2. Dyeing of linen fabrics
Because linen is the same as cotton They are all cellulose fibers, so the dyeing process of linen fabrics and the dyes and auxiliaries used are basically the same as those of cotton fabrics. However, due to the high degree of crystallinity and orientation of hemp fiber, it is difficult for dyes to penetrate into the fiber and the coloring rate is poor. Therefore, the dyeing products are mostly light-colored. Compared with cotton fabric dyeing wastewater, the chromaticity is slightly lower.
During the processing of linen fabrics, degumming wastewater and printing and dyeing wastewater are generated. Degumming wastewater is high-concentration organic wastewater and is easier to biodegrade. Printing and dyeing wastewater is similar to that of cotton fabrics.
</p
