The dyeing and finishing of polyester multifilament knitted fabrics is completely different from that of ordinary polyester yarn knitted fabrics. Because the surface area of polyester multifilament yarns is almost 2/5 larger than that of ordinary polyester yarns, so for the same depth of color, the amount of dye used in the former is larger than that in the latter. There are many people, and the process equipment is also different.
The fineness of polyester (PET) yarn is usually expressed by d/f.
For example, ordinary polyester yarn is generally 100d/72f, and the fineness of each of its 72 monofilaments is 1.39d (0.15tex); while polyester multifilament yarn is also 100d, There are more than 100 monofilaments. For example, the more common variety at present is 100d/120f. The thickness of each of these 120 monofilaments is about 0.83d (0.09tex).
Currently, there are two types of knitted fabrics made of polyester multifilament: thick and thin. Thick velvet fabrics are delicate in style, both rigid and soft, and have good breathability; Thin fabric is a T-shirt fabric with a strong texture and smooth feel.
The dyeing and finishing of polyester multifilament knitted fabrics is completely different from that of ordinary polyester yarn knitted fabrics. Because the surface area of polyester multifilament yarns is almost 2/5 larger than that of ordinary polyester yarns, dyeing For the same depth of color, the former uses more dye than the latter, and the process equipment is also different.
The dyeing and finishing processes of two types of polyester multifilament knitted fabrics are as follows:
Thick velvet fabrics
Equipped with cylinder seam head → pre-treatment → dyeing → finishing → heat setting → fleece → shearing → rolling Thin T-shirt fabrics are equipped with cylinder seam head → pre-treatment → high temperature pre-shrinking (clear water (130℃ o:p>
1 Pre-treatment
Ordinary polyester fabrics are generally dyed directly from gray cloth, while polyester multifilament knitted fabrics must be opened to improve the fabric style. . The pre-treatment of polyester multifilament fabric is different from that of polyester island yarn. It mainly uses surfactants to allow various additives to penetrate into the interior of the yarn to achieve a good fiber opening effect and remove oil.
The pretreatment prescription is:
Medicine/(g/L) ordinary medium and dark color
Flake sodium hydroxide (NaOH) 3～5
Fiber opening agent 1.5～2
Scouring agent 1～2
Dispersant 1～1.5
30% hydrogen peroxide 3～5
Pyrubilin 0.5～1
Process conditions liquor ratio 1:10
Rise from 40℃ to 95 at 1℃/min ~98℃, process for 50~60 minutes, wash thoroughly with hot water and cold water → neutralize with acetic acid → wash thoroughly with water.
The advantage of this pre-treatment prescription is that after treatment, the fabric becomes puffy and oil and dirt are removed. The impurities dissolved during the treatment process are not easy to re-stain and are easy to clean. After pre-treatment, high-temperature pre-shrinking and pre-shaping processes are carried out to prevent the fabric from problems such as knotting, clogging, uneven fabric density, difficult width control, and color flowers during dyeing.
2 Dyeing production
Selection of dyeing machines, polyester multifilament It is best to use a high-temperature and high-pressure jet overflow dyeing machine for dyeing knitted fabrics, and an airflow dyeing machine is even better. The structure of polyester fiber is very dense, so when dyeing it needs to rely on higher temperature and pressure to cause the fiber to expand and allow the disperse dye to be fully dyed. If the dyeing machine cannot withstand high temperature and pressure, 1~2g/L carrier can also be added to the dye bath to promote dyeing. Under high temperature and high pressure conditions of 135°C/0.22MPa, the dyeing time is 60 to 90 minutes (from light to dark).
Note: Practice has proved that it is very practical to use this method to test the fineness of disperse dye particles.
Using the same polyester multifilament knitted fabric, different disperse dyes were dyed using the same dyeing method. If the dyeing residue is clear and the fabric is dark in color after drying, it means that the dye particles are fine. In addition, if the pre-treatment of this kind of fabric is insufficient, slurry and oil may remain on the dye base to varying degrees, causing dyeing defects. If corresponding measures are not taken during dyeing, some recessive color flowers may not even be discovered until after heat setting, making it difficult to remedy.
For this reason, four kinds of auxiliaries need to be added to the dyeing recipe of this knitted fabric:
1. Metal ions Dispersant with chelating ability
2. High-efficiency penetrating agent
3. High-temperature leveling agent (suitable for ultra-fine polyester )
4. pH stabilizer (such as ammonium sulfate, ammonium dihydrogen phosphate, etc.).
3 Finishing
This type of knitted fabric must be Only through multi-functional finishing such as softness, dustproof, antistatic, moisture wicking and anti-pilling can it fully reflect its different style and excellent wearing performance from ordinary polyester knitted fabrics, and increase its added value.
Impregnation finishing prescription/%(owf)
Antistatic agent**
Polyester finishing agent**
Moisture absorption and perspiration agent**
Padding finishing prescription/(g/L)
Antistatic agent**
Polyester finishing agent**
Moisture absorbing agent Perspiration**
The above three finishing additives are non-ionic and meet environmental protection requirements.
It can be used in the same bath in the dyeing machine (immersion treatment at 55-65℃ for 15-20 minutes), or it can be padded in the padding tank in front of the heat setting machine. . It must be noted that the dehydration after the dipping treatment is not too dry to avoid excessive loss of additives and affecting the effect. Then carry out opening, loose drying and heat setting. The padding speed should be controlled at 25~30m/min, not too fast. </p
