The dyeing and finishing process of cotton knitted fabrics includes scouring and bleaching, dyeing, printing, finishing and other processes. It plays an important role in improving the appearance of knitted fabrics, improving performance, improving product quality, and increasing variety of patterns.
1. Scouring and bleaching The main processes of scouring and bleaching cotton knitted fabrics are: scouring, bleaching, alkali shrinkage, waxing and so on. The processing principles and agents used in scouring, bleaching, etc. are the same as those of cotton cloth, and will not be repeated. However, cotton knitted fabrics are formed by connecting loops, and the gap between the yarns is large, which is easy to deform and cannot withstand large tension. Therefore, loose processing equipment must be used during processing. The following briefly introduces the processes of alkali shrinkage and waxing.
1) Alkali shrinkage: Alkaline shrinkage of cotton knitted fabric is a process in which cotton knitted fabric is treated with concentrated alkali in a relaxed state. Cotton fiber swells in the concentrated caustic soda solution, the fabric shrinks, and the density and elasticity of the fabric increase. For fabric processing such as loose jerseys, alkali shrinkage includes three steps, namely padding with alkali solution, stacking shrinkage and washing to remove alkali.
2) Waxing: After scouring and bleaching cotton knitted fabrics, the friction between the fibers increases after the oil and wax substances of the cotton fibers are removed. When sewing, because the fiber is not easy to slip, the needle is easy to break the fiber and cause the fabric to produce needle holes, which affects the wearing fastness. In order to solve this problem, in addition to strictly controlling the process conditions, a softening treatment, namely waxing, is carried out at the same time, and the dehydrated fabric is dipped into a paraffin wax emulsion, and then dried by deliquation.
2. Dyeing and printing The dyeing and printing of cotton knitted fabrics are basically the same as those of cotton fabrics, so I will not repeat them. Loose processing equipment such as rope dyeing machine should be used for dyeing. The printing adopts manual printing or plain cloth printing.
3. Finishing The finishing of cotton knitted fabrics mainly includes shrink-proof finishing and pile finishing. Cotton knitted fabrics are susceptible to stretching and accumulated deformation during dyeing and finishing. Once washed, the accumulated deformation of the fabric will shrink, causing size changes. Shrink-proof finishing means that the fabric is forced to shrink in the wet and heat relaxed state, so that the size of the fabric is stable. The cotton knitted flannel needs to be raised and finished. Raising finishing is to pull out the fibers in the knitted grey fabric floats to form fluff, making the fabric soft. The hand feels rich and thin, and the warmth retention is enhanced. The varieties of cotton knitted articles are different, and the dyeing and finishing processes are also different.