Precautions for continuous dyeing of webbing

Update:27-12-2021

1. Factors of the original webbing material The original webbing material should firstly pay attention to whether the yarns used are of the same batch, because different batches of yarn contain different "oil" conditions, such as blending, it will become a factor of the color in the dyeing process; secondly, Whether the original blank has been pre-treated, the refining treatment of the original blank has a very good dyeing effect, because after the treatment, the "oil" on the yarn is removed and the dye can be directly contacted with the fiber for dyeing, without protection.

2. Dyeing tank (or pad, dye vat, dyeing machine). The pressure of cylinders at both ends of the roll is uniform. The roll of continuous hot melt dyeing machine for webbing generally adopts pneumatic pressure, and there is a cylinder on each side of the roll. When the rolling mill runs for a period of time, due to the action of the moisture in the compressed air, the pressure at both ends of the cylinder will be different, resulting in uneven liquid entrainment rate of the blank strip and color difference in the edge. In addition, the two ends of the roll of the rolling car are pressurized, which produces a certain degree of deflection, resulting in inconsistent rolling margin between the sides, and also causing color difference between the left and the right.

3. The pressure, concentricity and hardness of the dyeing tank rolls are in production. If you want to minimize the impact of the roll pressure on the left, center and right color difference, the roll pressure should generally be controlled above 0.2MPa during ribbon dyeing. In the production process, due to the wear of the rolls, the rolls are required to be calibrated and repaired regularly. Otherwise, it is easy to cause inconsistent rolls due to the misalignment of the rolls and lead to inconsistencies. Rolls with different hardness have different rolling margins. Too hard may result in insufficient dye absorption, and too soft may result in too large rolling margins and cause a large amount of dye migration to produce patterns. The hardness of the rolls is determined by the strip.

4. The influence of infrared pre-drying temperature on the webbing. After the pre-treatment and pad dyeing solution process, the polyester webbing generally needs to undergo infrared (line) pre-drying before entering the hair color box to prevent dye swimming during the drying process. Shift phenomenon, to avoid dyeing defects such as color blur and chromatic aberration on the front and back. When the infrared pre-baking temperature is lower than 80℃, the color difference between the front and back of the webbing is relatively large, and it is difficult to meet the customer's requirements. When the infrared pre-baking temperature reaches above 100℃, the chromatic aberration of the front and back of the webbing is greatly improved. This is because when the pre-baking reaches 100℃ or higher, the moisture of the webbing is almost completely evaporated, which greatly reduces the possibility of dye migration. Considering dyeing production practice and energy consumption, it is more appropriate to control the infrared pre-baking temperature at 100℃-150℃. The production is generally determined according to the thickness and liquid rate of the blank belt variety. The higher the liquid rate of the blank belt, the higher the infrared pre-baking temperature. In actual production, you can't just rely on the infrared pre-baking temperature to control the color difference between the front and back of the ribbon dyeing, especially the sensitive color numbers such as coffee and dark green. It must be used with anti-migration agents and other additives to achieve good dyeing results.

5. The effect of curing temperature of baking oven on color development Baking color development is an important part of continuous hot melt dyeing. The uniformity of curing temperature of baking oven plays a key role in controlling the color difference between the left, middle and right of the webbing. After the polyester webbing is pre-baked by infrared rays and then enters the baking oven, it is necessary to ensure that the temperature is consistent, otherwise it will produce obvious color difference. Experiments show that the temperature difference between the left, middle and right of the baking oven exceeds 2℃, and the color of the webbing changes significantly. Therefore, it is necessary to ensure that the temperature of the baking oven is uniform during dyeing production.

6. The influence of moisture content on the chromatic aberration of the left, middle and right of the ribbon. Polyester filament will add a certain oil during the spinning process, so it must be de-oiled before dyeing. The webbing is generally dried after dyeing pretreatment, and the uneven surface temperature of the drying cylinder will cause the difference in the moisture content of the blank, and in severe cases, it will cause the color difference between the left, middle and right of the webbing. In the dyeing production process, in order to avoid the left, center and right color difference caused by the different moisture content of the blank strip, it is necessary to ensure that the blank strip is thoroughly dried before the padding solution, and the drying cylinder is regularly inspected and repaired.

7. Other factors that produce chromatic aberration. As far as production management is concerned, the main factors affecting the chromatic aberration of polyester webbing dyeing are as follows.
(1) The quality of the blank belt semi-finished product, fabric structure, warp and weft density, warping tension, thickness and many other differences will cause color difference in dyeing. Due to the difference in production efficiency between looms and dyeing machines, the blank belts produced by different looms are dyed in the same dyeing machine, and even different batches of ribbons are dyed in the same dyeing machine. In order to minimize the impact of the quality difference of the blank belt on the color difference, the weaving and dyeing must be coordinated, and the production plan must be coordinated.

(2) Machine management The baking oven should be regularly overhauled and maintained to ensure the normal operation of heating equipment (such as heating tubes, burners, etc.), normal heating and temperature control. In the actual production process, it is necessary to keep the air duct in the box unobstructed and the filter screen clean. The dyeing machine's belt-in device is very important to adjust the tension of the blank belt. The blank belt tension must be basically the same before entering the dyeing tank to ensure the consistency of its liquid rate and the consistency of the color. It is also important to control the tension exerted by the dyeing machine on the webbing. Because the ribbon dyeing machine generally adopts frequency conversion control to adjust the tension of the entire dyeing machine, it is necessary to ensure that the frequency conversion control signal of each process point is normal, and the malfunctioning device must be repaired in time.

(3) The compatibility of dyestuffs and dyes has a greater influence on the chromatic aberration of the front and back sides of the webbing. When different formulas produce the same color number, the color difference between the front and back of the webbing is quite different. Generally, disperse dyes with the same or similar sublimation fastness and type (S, SE, E) are selected for compatibility, and the dyeing effect is better. In addition, the auxiliary use of anti-migration agents, penetrants and levelling agents, etc., also have a certain effect on the control of dyeing chromatic aberration, but they need to be used rationally.

Based on the above, we need to pay attention to the following points daily
(1) Factors such as the pressure of the roller, the uniformity of the curing temperature of the baking oven, the infrared pre-drying temperature, the moisture content, and the mass concentration of the anti-migration agent will all affect the color difference of the continuous hot melt dyeing of the polyester webbing. Generally choose the roll pressure of 0.2MPa, the temperature of the baking oven does not exceed 2℃, the infrared pre-baking temperature is 100℃, and the mass concentration of anti-migration agent does not exceed 15 g/L; the blank strip should be fully dried after pretreatment. To effectively control the color difference of ribbon dyeing.
(2) The quality of the blank belt, machine management and dyeing and chemical formulations also have an important influence on the control of dyeing chromatic aberration. In the production process of hot melt dyeing of polyester webbing, it is necessary to systematically control the consistency of the quality of the blank belt, do the maintenance and repair of the machine in time, and use dyes and auxiliaries rationally to obtain good dyeing results. Continuous dyeing of webbing is a science and an art, and I would like to discuss and communicate with you.

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