(1) Pre-processing part of continuous dyeing:
Hemming:When turning over the seam, pay attention to the hemming of the cloth joints, because the subsequent processes are basically continuous dyeing production.The consequence of not hemming is that if the cloth joints are broken in the steamer during the production process, that is a very troublesome thing.
Desizing is to remove the sizing on the warp yarns when weaving, and thin fabrics can be directly removed by the desizing machine.The cold-batch desizing method is best for the heavy weight and elastic fabrics, and the enzyme desizing will be more thorough.
Singeing:Cotton cloth need to be singed to remove the hairs of different lengths on the yarn count. Thin cloth singeing is enough. For thick yarn cloth such as 7*7, need to add iron plates (also called cylinders) to burn then can be good enough.
Heat setting: pre-treatment and heat setting are only for stretch fabrics, and the widths are different after singing and desizing. Only those smaller than the finished width can be finalized. The pre-treatment setting cannot be larger than the finished width, and it is best to be close to and equal to the finished width. .
Bleaching, as long as you pay attention to the uniformity of whiteness, cotton cloth is generally bleached with hydrogen peroxide, also called oxygen bleaching.
Mercerizing, mercerizing should pay attention to the width of the fabric, if width is too small and does not open, the finishing can not be opened ,also if too large and cannot be retracted back,better contorl it into similar with the finished fabric width,it will shrink a little when do the dyeing, and the pre-shrinking is just controlled. (Note: the pre-treatment of dyed and vulcanized cloth cannot be mercerized, because there is alkali in mercerizing, and dyeing and vulcanization will cause the cloth surface to bloom)
(2) Dyeing part of continuous dyeing:
The dyeing of cotton fabrics is now dominated by continuous dyeing, and the vat dyeing is no longer the mainstream, so I will not introduce it here.
Continuous dyeing is a simple process, because it only needs to pass through a long dyeing machine, but it is also the most difficult process, because the color control of dyeing is not only known, but there are many unknown things in it, such as the stability of dye stuff at different temperatures, the control of the steam, the control of the pressure of the dyeing machine, etc., are very delicate activities.
The continuous dyeing is divided into two parts, the front part for dyeing the colors, and the rear part for fixing the colors. The dyeing method varies according to the different types of dye stuff selected. The dyes are generally reactive, Shilin, vulcanization, and pigment. They have their own advantages and disadvantages, generally The situation depends on the color of the customers and cannot be replaced with each other. Among them, Shilin has the best color fastness, but it is expensive, not suitable for dark colors, and light colors are not bright enough. Except that dyeing dark colors will increase the cost.
In addition, it is difficult to control the dyeing of dark colors relative to reactive dyes, and it is prone to phenomena such as cloth surface defects. The reactive color fastness is worse than Shilin, but the light color is more bright, the dark color is easier to control, and the cost is correspondingly less. The vulcanization is the worst, the color fastness is not very good, the AZO limitation also not up to the standard, but now there is a liquid vulcanization (also called water vulcanization) that AZO limiatation can meet the standard, but the price is also close to Shilin, and the dyeing is not easy to control and cannot be popularized. A few people pursue its fading effect and adopt it. The pigment dyeing is not comparable, and its fading is very serious.
It is the best choice for the pursuit of fading effect after washing clothes. It can be used with Shilin, active and flexibly to obtain different washing effects (general Shilin or active primer, coating surface color, which can solve the white spot problem of single-dyeing coatings. The cost increases accordingly).
The reacte dye, Shilin and vulcanized dyeing front part of the machine is basically the same, to say the difference is that the infrared ray pre-baked one group, two groups or not. The rear part of the machine is completely different. The active one uses salt and soda ash to fix the color, and the Shilin adopts Hydrogen peroxide reduction fixation (so Shihlin is also called vat dyes), while vulcanization needs to be cooked at high temperature for fixation, and the water temperature must be above 95 degrees.
After pigment dyeing is finished, it is determined whether to bake and fix the color according to the fading requirements of the color fastness. The bake temperature is about 195-210 degrees.
Dyeing is impossible to be 100% good. Color repair and peeling are inevitable. Minor adjustments such as if lighter then use the pigment dyeing,darker use the soda method.
(3) After finishing treatment part of continuous dyeing:
Because the cotton fabric has passed the continuous dyeing pre-treatment and dyeing, the warp direction is stretched, the weft direction is contracted, and the hand feel is relatively rough. The finishing is to solve these problems.
Softness and pulling width,if there is no heat setting machine, softness and pulling width should be carried out separately. First, do the softness to improve the hand feel then do the pulling width. Pull the shrinking weft direction apart. With a setting machine, you can do it in one go. But stretch fabrics should use the heat setting machine.
Pre-shrinking, shrink stretched part of the production process through the pre-shrinking machine by the principle of thermal expansion and contraction,shrinks the cloth to the allowable range of clothing cutting, and the elastic cloth is controlled at 3% warp and 5% weft. The non-elastic control is 3% in warp and 3% in weft.
After finishing, according to the requirements of customers, whether the twill fabric needs to adjust up to the standard (generally the weft twill of the plain weave should be controlled within 3%, and the grid should be controlled, preferably close to 0). Weft whether need straightening.
The factory can also use its own equipment, and can also air-soften the fabric, etc. Of course, there is an additional cost.
(4) Finished product inspection part:
The fabric after finishing continuous dyeing need do the tests shrinkage rate, color fastness, and other internal indicators required by customers.and the color indicators are qualified, and the finished product can be inspected. Generally, customers agree with the American four-point standard inspection (the Chinese national standard is similar, But the defects are too complicated and not easy to be memorized and use),and the qualified products tested can be packaged.By here, the dyeing process is over, and the fabric can be sent to the garment factory.
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Great content! Keep up the good work!
thanks good luck!