Textile Finishing Process
These four processes is the basic process, process will be different depending on specific the product.
1. Bleaching process
(1) Cotton scouring and bleaching process:
Singeing – - desizing – - – bleaching – - – mercerizing
Singeing: Because cotton is short fiber, there are short fluff on the surface of the product.In order to make the fabric beautiful and convenient for future treatment, the first process shoula be singeing.
Desizing: during the warping process, the friction between cotton yarns will cause static electricity, so it should be starch before weaving. After weaving, the pulp will be hard, and after a long time it will be yellow and moldy, so it should be desizing first to ensure the smooth progress of printing and dyeing procedures and feel soft.
The second step is mainly scouring process, the purpose is to remove impurities, oil and cotton shell. The oil pollution can also be added to the oil and other additives.
Bleaching: To rinse fabric so that it turns white. There are impurities in natural fibers, during the textile processing some slurry, oil and contaminated dirt will be added too. The existence of these impurities, not only hinder the smooth progress of dyeing and finishing processing, but also affect the wear performance of the fabric. The purpose of scouring and bleaching is to use chemical and physical mechanical action to remove impurities on the fabric, make the fabric white, soft, with good permeability, and meet the requirements of wearing, to provide qualified semi-products for dyeing, printing, finishing.
Boiling is the use of caustic soda and other boiling additives with fruit gum, waxy substances, nitrogen substances, cottonseed shell chemical degradation reaction, emulsification, swelling, etc., Washing will remove impurities from the fabric.
Bleaching removes natural pigments and make sure the fabric with stable whiteness. In a broad sense, it also includes the use of blue or fluorescent brightening agents to produce optical whitening. Bleaching mainly includes oxidant bleaching and reducing agent bleaching. The principle of oxidant bleaching is to destroy pigment generators to achieve achromatic purpose. The principle of reducing agent bleaching is to produce bleaching by reducing pigment. The processing method of bleaching depends on the variety and bleach agent. There are mainly three categories: leaching bleaching, leaching bleaching and rolling bleaching. Different varieties have different requirements for bleaching.
Mercerizing: Make the fabric shine better and feel softer.
1.1 The process of ordinary fabric and cotton/polyester fabric is basically the same (woven):
Singeing → desizing → bleaching
The bleached fabric is often called white cloth.
1.2 The process of ordinary fabric and cotton/polyester fabric (knitted):
Shrinkage → desizing → bleaching
Alkali shrinkage: Because knitted fabric is not starched, it is relatively loose span, alkali shrinkage will make the fabric tight. This is use the tension balance to flatten the surface of the fabric.
Boiling: similar to desizing process, mainly to remove oil and cotton shell.
Bleach: To rinse the fabric clean
Corduroy process: The fabric is produces by one yarn wound around another yarn to form a loop, and then the coil is cut to form the pile.
1.3 Process: alkali rolling → fleece cutting → desizing → drying → brushing → fleece burning → boiling → bleaching
The purpose of alkali rolling is to make the fabric shrink more tightly; The purpose of cutting is to smooth the suede; The purpose of brushing is to smooth the suede and remove the unevenness after cutting; The purpose of singeing is also to get rid of bumps and bruises.
1.4 the process of polyester cotton fabric is the same as ordinary cotton fabric
1.5 flannelette: mainly cover blankets, underwear for children, the elderly, bed sheets, etc. A mace – like roller is rotated at high speed on the surface of the blanket to pull out the fibers, so that the velvet is not very neat.
(2) Wool (wool fabric) process: washing → charring → bleaching
Wool washing: Because wool is animal fiber, it is dirty, so it should be washed to remove the impurities left on the surface (dirt, grease, sweat, impurities, etc.).
Carbonization: further removal of impurities, dirt.
Carbonization: further removal of impurities, dirt. After washing, if the fabric not clean , there will need acid carbonization to further clean.
Bleaching: To rinse fabric clean.
(3) The process of silk: degumming → bleaching or whitening (whitening and whitening additives)
(4) Polyester cloth:
Filament: alkali reduction → bleaching (same as silk process)
② Staple fiber: singeing → boiling → bleaching (same process as cotton)
Stenter: increase stability; Meet the design requirements; The surface is flat.
2. Dyeing process
(1) The principle of dyeing
A Adsorption: Fiber is a polymer, which is rich in ions, and the dye contained in the combination of different ions, so that the fiber absorbs the dye.
B Infiltration: there are gaps in the fiber, the dye is pressed into or infiltrated into the molecular gaps after high temperature and high pressure to make it colored.
C adhesion: there is no dye affinity factor in the fiber molecule, so the adhesive is added to make the dye stick to the fiber.
Fiber dyeing – color spinning (spinning with color, e.g. snowflake, fancy yarn)
Yarn-dyed (yarn-dyed fabric)
Cloth dyeing — Dyeing (piece dyeing)
Dyes and spinning materials
① Direct dye-dyed cotton, linen, wool, silk and viscose (room temperature dyeing)
Features: The most complete chromatography, the lowest price, the worst fastness, the most simple method.
Formaldehyde is used as an accelerant
Direct dye dyed fabrics are generally added to stabilize the color fastness.
② Reactive dyes – reactive groups in dyes and cotton, hemp, silk, wool and viscose in combination with the active groups.
Features: Bright color, good evenness, fastness, but expensive.
(3) Disperse dyes — special dyes for polyester
The dye molecules are as small as possible to penetrate, and high temperature and pressure are used to promote dye penetration. Therefore, high color fastness.
④ cationic dyes:
A special dye for acrylic fibers. The acrylic fibers are negative ions when spinning, and the cations in the dye are absorbed and colored
B polyester with negative ions, cationic dyes can be dyed at room temperature. This is cationic Polyester (CDP: Can Dye Polyester).
⑤ Acid dye: dyeing wool.
E.g. How should T/C dark cloth be dyed?
Dye the polyester with a disperse dye, then the cotton with a direct dye, and then coat the two colors flat. If you deliberately need color difference, do not set flat.
For light colors, you can only dye one kind of raw material, or polyester or cotton with different dyes.
If the color fastness requirement is high, remove polyester; For those with low requirements, cotton can be dyed.
3. Printing process
(1) Printing by equipment classification:
A. flat screen printing: also known as manual platform printing, also known as screen printing. High-grade fabric pure silk is widely used.
B. round screen printing;
C. roller printing;
D. transfer printing: Dye on paper is sublimated to cloth after high temperature and high pressure to form a pattern
The design is less elaborate. Curtain fabrics are mostly transfer prints.
(2) Classification by method:
A. Dye printing: dyeing with active genes in direct dyes and reactive dyes.
B. coating printing: additives are added into the dye to make the dye combine with the cloth (there is no gene of affinity between cloth and dye in the dye)
C. Anti-printing (dyeing) printing: high-grade fabrics have high requirements for color, and anti-printing should be applied to avoid cross-color.
D. pull-out printing: After the fabric is dyed, some places need to print other colors. The color of raw materials must be removed and then printed in other colors to prevent colors from opposing each other.
E. rotten flower printing: Use strong alkali to rot the yarn at the edge of the printing and form a velvet pattern.
F. Gold (silver) powder printing: gold (silver) powder is used to print fabrics. In fact, it also belongs to paint printing.
H. transfer printing: Dye on paper is sublimated to cloth after high temperature and high pressure to form patterns.
I. spray (liquid) printing: consistent with the principle of color printers.
4. Tidy up
1) General arrangement:
A. feel finishing:
① feel hard, quite. Cotton and linen in large quantities
Soft feel: softener and water can be added
B. Finalize finishing:
② Pre-shrinking: for cotton cloth (washing to shrink) in advance to make the size more stable.
C. appearance finishing:
① calender (calender) fabric luster, after calender cloth surface will harden.
② The embossing is rolled with a press stick
③ Whitening and whitening agent
2) Special treatment: The method to achieve special treatment: adding the corresponding additives before setting, or coating machine with the corresponding coating.
A. Waterproof treatment: a coating machine is used to apply a layer of waterproof material/paint on the fabric; The other is drawing before rolling waterproof agent.
B. Flame retardant treatment: the effect achieved: no open flame, cigarette butts thrown on the fabric to a certain area will be automatically extinguished.
C. Anti-fouling and anti-oil treatment; The principle is the same as waterproofing, the surface is coated with a corresponding layer of material.
D. Anti-mildew, antibacterial treatment: coating, ceramic powder can also be used to do treatment to achieve anti-enzyme, antibacterial effect.
E. anti-UV: The use of anti-UV silk is to prevent the destruction of protein fibers of real silk, and make real silk yellow, other products are anti-UV in the sun. Special noun: UV-CUT
F. Infrared treatment: including infrared resistance and absorption to achieve different effects.
G. Antistatic treatment: the concentrated electrostatic dispersion, not easy to produce sparks.
Other special treatment are: fragrance treatment, pharmaceutical flavor (drug effect) treatment, nutrition treatment, radiation treatment, resin treatment (cotton fabric stiffening, silk wrinkle), wash can wear treatment, reflective treatment, luminous treatment, velvet treatment, fuzz (raising) treatment.
Post time: Mar-13-2023