Dyeing process of the workwear fabrics

- Aug 10, 2020-

1. Greige inspection and stitching:


A. It is to sew one piece of grey fabric into a large roll or a box car, which is called a cylinder. The quantity of one cylinder is different due to different types of fabrics.


B. The greige inspection is mainly to control the quality of the grey fabric to see if there are abnormalities such as drawn yarn, weft, deadfold, macula, mildew, etc. At the same time, pay attention to check whether the fabric type is consistent with the requirements. Under normal circumstances, a lot number is required for careful inspection.


2. Desizing:


A. In order to make the yarn lint-free when weaving, the yarn is sizing, so it must be desizing before dyeing for colors.


B. If the desizing is not clean, there will be defects such as colored flowers and pulp spots on the fabric surface after dyeing.


C. After desizing, it should be washed with water, otherwise the fabric will have higher pH value and abnormal dyeing will occur.


D. Generally, there are two kinds of desizing methods: in-cylinder desizing and continuous desizing. Generally, the former has better desizing effect but low efficiency.


3. Dyeing:


(1) Chemical fiber dyeing method:


A. Normal temperature jig dyeing: Generally the temperature is below 100℃, mainly used for dyeing semi-gloss nylon taffeta, nylon Oxford, nylon twill, etc. This method is prone to abnormalities such as head and tail chromatic aberration, left-middle-right chromatic aberration, and creases.


B. High temperature jig dyeing: The temperature is generally about 130℃, mainly used for dyeing polyester taffeta, N66, nylon matting cloth, polyester oxford (filament), etc. This method is easy to produce head and tail color difference, left, middle and right color difference, and folding Abnormalities such as marks and color spots.


C. Overflow dyeing: The temperature is about 100℃ to 130℃. It is mainly used to dye polyester such as pongee, peach skin, polyester oxford, taslon, nylon-polyester interweaving, etc. Overflow can also be used for polyester spinning For dyeing, nylon spinning and other dyed wrinkles are also used in this way. This method is prone to abnormalities such as colored flowers, chicken feet marks, and straight strips. 


D. Warp beam dyeing: It is suitable for all kinds of cloth, but it should be used reasonably according to the quality requirements. The dyeing temperature can be controlled from 100℃ to 130℃. This method is easy to produce abnormalities such as shallow edges and layer differences.


(2) Dyeing methods of other cloth types:


A. Cotton fabric dyeing: generally continuous dyeing (requiring large batches), pad dyeing (large batches or small batches), overflow dyeing (medium and small batches). Reactive dyes (better fastness), direct dyes (poor fastness), or vat dyes (the best fastness) can be used.


B, Nylon/Cotton, Cotton/Nylon dyeing: generally use overflow dyeing, first dye cotton and then nylon, dye cotton with reactive dyes, dye nylon with acid dyes (better fastness). There are also one-time dyeing with direct dyes (poor fastness).


C, Polyester/Cotton, Cotton/polyester dyeing: generally use overflow dyeing, dye polyester first and then cotton, disperse dyes for polyester and reactive dyes for cotton (the better fastness). There are also continuous dyeing, one-time dyeing, using direct dyes (poor fastness).


(3) Dyestuff classification:


A. Acid dyes: used for dyeing nylon fabrics, generally fixing to improve color fastness, but also pay attention to the choice of dye combination and the use of reasonable dyeing process. Improper selection of fixing agent or too high dosage will cause hard hand feeling.


B. Disperse dyes: used for dyeing polyester fabrics. Generally, reduction washing is used to improve color fastness. At the same time, attention should be paid to the choice of dye combination and the use of reasonable dyeing processes. Disperse dyes pay special attention to the problem of migration and sublimation fastness.


C. Reactive dyes and direct dyes: belong to low-temperature dyes.



4. Drying:


(Generally divided into roller drying and non-contact drying)


A. There are two types of non-contact drying: non-contact dryer and setting machine. There is no contact between the fabric and the heater, and the purpose of drying is achieved by spraying hot air onto the fabric. It is mainly used for drying overflow dyed products to maintain the fluffy and rich feel of the fabric. The cost is higher than drum drying.


B. Tumble drying: The cloth is in direct contact with the drum, and the drum is heated to achieve the purpose of drying the cloth. Mainly used for jig dyeing and warp beam dyeing products (such as nylon spinning, polyester spinning, nylon oxford, polyester filament oxford, etc.), taslon products can also be dried on a tumble dryer (but only first Bake 60% to 70% dry to avoid too hard hand feeling), and then go to the setting machine to do water repellent processing to increase the water repellency. The drying cost is lower.


5. Interim inspection:


A. The intermediate inspection should test the various color fastness of the fabric, and pay attention to the quality of the fabric surface, such as: crease, color difference (color difference, cylinder difference, match difference), color flower, color point, dirt, oil stain, drawn yarn , Weft files, warp bars, etc.


B. Control defective products not to enter the next section to prevent increased costs. After the fabric is finished and processed, some abnormalities cannot be repaired or it is difficult to repair, so intermediate inspection is very important.


C. Rearrange and stitch the fabric before entering the back section.



6. Modeling:


A. After the fabric is shaped, the physical and chemical properties are relatively stable, for example: shrinkage, width, warp and weft density are not easy to change, and the cloth surface is relatively flat. At the same time, some functional processing can be done in the process of shaping, such as water repellent (waterproof), soft, resin, flame retardant, antistatic, super water repellent (Teflon treatment), moisture wicking, antibacterial and deodorant, etc. .


B. Because the setting temperature is high, attention should be paid to the color change before and after setting, especially some sensitive colors, such as gray, army green, light khaki, etc. Products generally require alignment with the finalized color.


C. Shaping can control the width, warp and weft density, shrinkage rate, etc., especially the control of shrinkage rate, which directly affects the processing cost, so special attention should be paid. (Our order shrinkage requirement is generally washing shrinkage less than 3%, and strict washing shrinkage below 2%). The three main factors that affect the setting effect are the setting temperature, speed and overfeeding.


D. Introduction to several types of processing:


①Water splashing and setting make the fabric waterproof and dustproof;


②The soft setting makes the fabric feel soft and smooth, but pay attention to whether the fabric will slip. Water splashing and soft setting can be done at the same time to make the fabric both waterproof and soft, but the softener will affect the water splash.


③Resin styling is mainly used to fix the yarn and make the hand feel stiff. Some resins contain formaldehyde, so please pay attention to the selection; water repellent and resin styling can be done at the same time, and the resin can promote the water repellent.


④ The flame retardant setting has an auxiliary effect on the flame retardant function of the fabric. Flame retardant can also be used for water repellent setting at the same time, but special attention should be paid to the selection of water repellent, otherwise it will have too much influence on the flame retardant effect.


⑤The antistatic setting makes the fabric have antistatic function, which can be done at the same time as the water spraying setting, but it will affect the water spraying effect.


⑥ Moisture absorption and sweat wicking shaping allows the fabric to quickly absorb sweat, making sportswear more comfortable. It cannot be done at the same time as splashing water.


⑦Antibacterial and deodorant processing is mainly to make the fabric have antibacterial function, which is mainly used in medical facilities.


⑧Super water-splashing setting (also called Teflon treatment): It has better waterproof and dustproof effect than ordinary water-spraying setting, and it also has oil-proof function. Generally speaking, guests will request to pass the DuPont tag.



7. Calendering and gluing:


A. The function of calendering ① soften the hand feel ② make the fabric calendered surface smoother, reduce the gap between the fabric fibers to prevent velvet effect or achieve a higher water pressure when applying glue ③ make the rubberized surface smoother Beautiful ④The calendered surface has a bright effect.


B. The three elements of calendering are temperature, speed and pressure. Calendering will change the color of the fabric.


C. Glue can make the fabric have the functions of waterproof, velvet, windproof, etc. It can also fix the yarn, increase the look and feel, and thicken the feel of the fabric, making the fabric more useful.


D. There are acrylic (also known as AC, PA), PU glue, breathable and breathable glue, which can be processed into transparent glue, white glue, silver glue, color glue, pearl glue, Youli glue and so on. You can also add the corresponding raw materials to the glue to make it have anti-ultraviolet, flame-retardant and anti-yellowing effects.


E. Pay attention to the control of water pressure, hand feel (thickness, softness and hardness), uniformity of the glue, peel strength of the glue, washing resistance (whitening), whiteness, etc. Also pay attention to the glue particles, glue marks, whether it is dry and so on. Pay attention to the effect of the glue surface with the waterstop (PVC strip/PU strip).



8. Laminate PVC: Pay attention to the thickness, feel, peel strength of the adhesive, and the quality of the glue surface.


9. Other processing: dry PU (release paper), composite, PU leather, etc.

 

10. Washing: Some cotton fabric, Nylon/Cotton, Polyester/Cotton also go through washing process. Washing is divided into three types: ordinary washing, soft washing, and enzyme washing (removing the floating hair on the surface of the cotton cloth).


11. Finished inspection: Inspect the quality of the finished product, classify it, and pack it for shipment. Generally, an inspection record and a sheet of difference should be made. Any problems should be reported to the salesman in time to communicate with customers in time.