Textile dyeing and finishing process
The dyeing and finishing process of textiles is divided into: pretreatment → dyeing (Dye) → printing (Print) → finishing (Aftertreatment/Finished treatment).
01 Pre-processing
1. Pretreatment process of cotton cloth
singeing→desizing→bleaching→mercerizing
Singeing: Because cotton is a short fiber, there are short fluff on the surface of the product, so it should be singed first for the sake of the fabric's beauty and convenience for later processing.
Desizing: When cotton yarn is used as warp thread, it has more friction with the machine, and the friction between cotton yarns is easy to generate static electricity, so it should be sized before weaving. After weaving, the sizing will become hard, and it will turn yellow and moldy after a long time. Therefore, the starch should be removed first to ensure the smooth progress of the printing and dyeing process and soft hand feeling.
The first two steps are mainly the practice process, the purpose is to remove impurities, oil and cotton husks. When removing oil stains, additives such as degreasing spirit can also be added.
Bleaching: Rinse the fabric to make the color whitish. It is a process of drifting.
Mercerized: Make the fabric luster better and feel softer.
The process of ordinary cotton cloth and polyester cotton cloth is basically the same (woven cloth)
Singeing → desizing → bleaching.
It requires a little higher mercerizing. The bleached cloth is often called the white cloth.
The process of ordinary cotton cloth and polyester cotton cloth (knitted cloth)
Alkaline shrinkage → scouring → bleaching
Alkali shrinkage: Because the knitted fabric is not sized when weaving, it is looser and tighter after alkali shrinkage. Use balanced tension to make the surface of the fabric flat.
Scouring: It is similar to the desizing process, mainly to remove oil and cotton shells.
Bleaching: Rinse the fabric.
Process of Corduroy
The cause is that one yarn is wound around another yarn to form a loop, and then the loop is cut to form pile.
Process: soda rolling→cutting→desizing→drying→brushing→singeing→scouring→bleaching
The purpose of alkali rolling is to make the fabric shrink more compact; the purpose of cutting pile is to make the suede surface smooth; the purpose of brushing is also to smooth the suede surface and remove the unevenness after cutting the pile;
Brushed cloth
Mainly covered blankets, children's and old people's underwear, bed sheets, etc. Use a roller like a mace to turn the carpet surface to pull out the fibers, so that the pulled suede is not very neat.
2. Wool (wool fabric) process
Washing→Carbonization→Bleaching
Wool washing: Because wool, etc. is animal fiber, it is relatively dirty, so the impurities (dirt, grease, sweat, impurities, etc.) left on the surface should be removed first after washing.
Carbonization: further remove impurities and dirt. If it is not clean after washing, it is carbonized with acid for further cleaning.
Bleach: Rinse the fabric well.
3. Silk process
Degumming → bleaching or whitening (whitening plus whitening additives)
4. Polyester cloth
① Filament: alkali reduction → bleaching (same process as silk)
②Short fiber: singeing→scouring→bleaching (same process as cotton)
Stenter setting: Stretching, increased dimensional stability; meet design requirements; smooth surface.
02 Dyeing process
1. The principle of dyeing
Adsorption: The fiber is a polymer, which is rich in ions, and combines with the different ions contained in the dye, so that the fiber absorbs the dye.
Penetration: There are gaps in the fiber, and the dye is pressed or infiltrated into the molecular gap after high temperature and high pressure to make it colored.
Adhesion: There is no affinity dye factor in the fiber molecule, so a binder is added to make the dye stick to the fiber.
2. Method
Fiber dyeing - color spinning (add color to spinning, such as snowflake yarn, fancy yarn)
Yarn Dyeing - Yarn Dyed (Yarn Yarn Fabric)
Cloth dyeing - coloring (piece dyeing)
3. Dyes and textile materials
① Direct dyes - dyeing cotton, linen, wool, silk and viscose (dyeing at room temperature)
Features: The most complete color spectrum, the lowest price, the worst fastness, and the simplest method.
Among them, formaldehyde is used as accelerator
Fabrics dyed with direct dyes generally need to be reinforced with colorants to stabilize the color fastness.
②Reactive dyes
The active groups in the dye combine with the active groups in cotton, hemp, silk, wool and viscose.
Features: bright color, good level dyeing, good fastness, but expensive.
③Disperse dyes
Special Dyes for Polyester
The molecule of the dye is as small as possible, which can penetrate into it, and at the same time, high temperature and high pressure are used to promote the penetration of the dye. Therefore, the color fastness is high.
④ Cationic dyes
A special dye for acrylic fiber, when acrylic fiber is spun, it is a negative ion, and it absorbs and colors with the cation in the dye
Adding negative ions to B polyester can be dyed with cationic dyes at room temperature. It is cationic dyeable polyester yarn (CDP: CanDyePolyester).
⑤ acid dye
Dyed wool.
03 Printing process
1. Printing is classified by equipment
Flat screen printing: There are three types of flat screen printing: manual platen type, semi-automatic flat plate, and fully automatic flat screen. Although the output of flat screen printing is low, it is convenient for plate making, with large flower length and many colors. It can print fine patterns, and It does not transfer color, has a large amount of printing paste, and has a three-dimensional effect. It is suitable for printing on woven and knitted fabrics such as silk, cotton, and chemical fibers, and is more suitable for printing small batches of high-end fabrics with many varieties.
Rotary screen printing: Rotary screen printing is a printing method that uses a scraper to print the color paste in the rotary screen onto the fabric under pressure.
Roller printing: the process of printing on fabrics with copper rollers engraved with concave patterns, also known as copper roller printing.
Transfer printing: one of the textile printing methods. It began in the late 1960s. A printing method that first prints a certain dye on other materials such as paper, and then uses hot pressing to transfer the pattern to the fabric. It is mostly used for the printing of chemical fiber knitwear and clothing. Transfer printing goes through processes such as dye sublimation, swimming, melting, and ink layer peeling.
2. Classified by method
Dye printing: direct dyes, active genes in reactive dyes to dye.
Pigment printing: add additives to the dye to combine the dye with the cloth (there is no gene for affinity cloth and dye in the dye)
Anti-printing (dyeing) printing: High-grade fabrics have high requirements for color, so anti-printing printing is used to avoid color cross-over.
Discharge printing: After the fabric is dyed, other colors need to be printed in some places, and the raw material must be unplugged to reveal the white color, and then printed in another color to prevent the colors from offsetting each other.
Burn-out printing: Use strong alkali to rot the yarn on the edge of the printing to form a velvet pattern.
Gold (silver) powder printing: printing on fabrics with gold (silver) powder. In fact, it also belongs to paint printing.
Transfer printing: The dye on the paper is sublimated to the cloth after high temperature and high pressure to form a pattern.
Spray (liquid) printing: It is consistent with the principle of color printers.
04 finishing
1. General arrangement
Hand finishing:
①It feels hard and stiff. Dealing with cotton and linen in large quantities
②Soft hand feeling: add softener and wash with water
Finishing:
①Stenter
②Pre-shrinking: For cotton cloth (shrink after washing), shrink in advance to make the size more stable in the future.
Appearance finishing:
① Calendering (calendering) fabric luster, after calendering, the fabric surface will become hard.
②Crimping with a pressure stick
③Whitening and whitening agent
2. Special treatment
The method to achieve special treatment: add corresponding additives before setting the shape, or use a coating machine to coat with corresponding paint.
Waterproof treatment: use a coating machine to coat a layer of waterproof material/paint on the fabric; the other is rolling waterproof additives before tentering.
Flame retardant treatment: the effect achieved: there is no open flame, and the cigarette butt will be automatically extinguished when it is thrown on the fabric to a certain area.
Anti-fouling and anti-oil treatment: The principle is the same as waterproof, and the surface is coated with a layer of corresponding substances.
Anti-mildew and anti-bacterial treatment: It can be coated or treated with ceramic powder to achieve anti-enzyme and anti-bacterial effects.
Anti-UV: The use of anti-UV in real silk is to prevent the protein fibers of real silk from being damaged, so that the silk will turn yellow, and other products are anti-ultraviolet rays in the sun. Special term: UV-CUT
Infrared treatment: including anti-infrared and infrared absorption to achieve different effects.
Antistatic treatment: Disperse the concentrated static electricity and prevent sparks.