Matters needing attention in continuous dyeing of ribbons

The main matters that should be paid attention to in continuous dyeing of ribbons are:

1. Factors of ribbon blanks: First of all, we should pay attention to whether the yarn used in the ribbon blanks is from the same batch, because the "oil" contained in different batches of yarn is different. If it is blended, it will become a factor of the color in the dyeing process; secondly, whether the blank has been pre-treated. The dyeing effect of the refined blank is very good, because the "oil" on the yarn is removed after treatment, and the dye can be directly in contact with the fiber for dyeing without protection.

2. The uniformity of the pressure of the cylinders at both ends of the rollers of the dye tank (or called the roller, dye vat, dyeing machine) The rollers of the ribbon continuous hot-melt dyeing machine generally use pneumatic pressurization, and there is a cylinder on each side of the roller. After the roller runs for a period of time, due to the effect of moisture in the compressed air, the pressure at both ends of the cylinder will be different, resulting in uneven liquid rate of the blank strip and color difference in the middle and edge. In addition, the pressure at both ends of the roller of the roller produces a certain deflection, resulting in inconsistent rolling rate in the middle and edge, and also causing color difference from left to right.

3. The pressure, concentricity and hardness of the dye tank rollers. In production, if you want to minimize the impact of roller pressure on the left, middle and right color difference, then the roller pressure should be controlled above 0.2MPa during ribbon dyeing. Due to the wear of the rollers during the production process, it is required to calibrate and repair the rollers regularly, otherwise it is easy to cause inconsistent rolling due to the non-concentricity of the rollers, resulting in different colors. Rollers with different hardness have different rolling rates. Too hard may lead to insufficient absorption of dyes, and too soft may lead to too large rolling rate, resulting in a large amount of dye migration and color. The appropriate hardness should be determined according to the strip.

4. The influence of infrared pre-drying temperature on webbing After the pre-treatment and padding dyeing process, the polyester webbing is generally subjected to infrared (ray) pre-drying before entering the color box to prevent dye migration during the drying process and avoid dyeing defects such as color flowers and color difference between the front and back sides. When the infrared pre-drying temperature is lower than 80℃, the color difference between the front and back sides of the webbing is large, and it is difficult to meet the customer's use requirements. When the infrared pre-drying temperature reaches above 100℃, the color difference between the front and back sides of the webbing is greatly improved. This is because when the pre-drying reaches above 100℃, the moisture of the webbing is basically evaporated, which greatly reduces the possibility of dye migration. Considering the dyeing production practice and energy consumption, it is more appropriate to control the infrared pre-drying temperature at 100℃-150℃. In production, it is generally determined according to the thickness and liquid rate of the blank strip. The higher the liquid rate of the blank strip, the higher the infrared pre-drying temperature. In actual production, we cannot rely solely on infrared pre-drying temperature to control the color difference between the front and back sides of the ribbon dyeing, especially for sensitive colors such as coffee and dark green. We must use auxiliary agents such as anti-migration agents to achieve good dyeing effects.

5. The influence of the fixing temperature of the baking oven on the color development. Baking color development is an important part of continuous hot-solution dyeing. The uniformity of the fixing temperature of the baking oven plays a key role in controlling the left, middle and right color difference of the ribbon. After the polyester ribbon is pre-baked by infrared rays and then enters the baking oven, the temperature must be kept consistent, otherwise there will be obvious color difference. Tests show that when the temperature difference between the left, middle and right of the baking oven exceeds 2°C, the color of the ribbon changes significantly. Therefore, it is necessary to ensure that the temperature of the baking oven is uniform during dyeing production.

6. The effect of moisture content on the left, middle and right color difference of the ribbon. A certain amount of oil will be added to the polyester filament during the spinning process, so it must be degreased before dyeing. The ribbon is generally dried after pre-dyeing treatment, and the uneven surface temperature of the drying drum will cause differences in the moisture content of the ribbon, which may cause left, middle and right color differences in the ribbon in severe cases. In the dyeing production process, in order to avoid left, middle and right color differences caused by different moisture contents of the ribbon, it is necessary to ensure that the ribbon is thoroughly dried before dipping in the dyeing solution, and the drying drum should be regularly inspected.

7. Other factors that cause color difference As far as production management is concerned, the main factors that affect the left, middle and right color difference of polyester ribbon dyeing are as follows.

(1) The quality of semi-finished raw tapes. Many differences in fabric structure, warp and weft density, warping tension, thickness, etc. will cause color difference in dyeing. Due to the difference in production efficiency between looms and dyeing machines, raw tapes produced by different looms will have color differences when dyed in the same dyeing machine, or even when different batches of raw tapes are dyed in the same dyeing machine. In order to minimize the impact of raw tape quality differences on dyeing color differences, weaving and dyeing must coordinate and coordinate production plans, and at the same time do a good job in raw tape inventory management, and try to achieve "first in, first out".

(2) Machine management The baking oven should be inspected and maintained regularly to ensure the normal operation of the heating equipment (such as heating tubes, burners, etc.), normal heating and temperature control. In the actual production process, the air duct in the box should be kept unobstructed and the filter screen should be kept clean. The adjustment of the tension of the blank strip by the dyeing machine's belt feeding device is very important. The tension of the blank strip before entering the dyeing tank must be basically consistent to ensure the consistency of its liquid carrying rate, thereby ensuring the consistency of color. It is also important to control the tension applied by the dyeing machine to the ribbon. Since the ribbon dyeing machine generally uses 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 failed components should be repaired in time.

(3) The compatibility of dyes and dyes has a great influence on the color difference between the front and back of the ribbon. When different formulas are used to produce the same color number, the color difference between the front and back of the ribbon is quite different. Generally, disperse dyes with the same or similar sublimation fastness and type (S, SE, E type) are selected for compatibility, and the dyeing effect is better. In addition, the auxiliary use of auxiliaries such as anti-migration agents, penetrants and leveling agents also has a certain effect on the control of dyeing color difference, but it needs to be used reasonably.

Based on the above, we need to pay attention to the following points in our daily life:

(1) Factors such as roller pressure, uniformity of oven fixation temperature, infrared pre-drying temperature, moisture content, and anti-migration agent concentration will affect the color difference of continuous hot-solution dyeing of polyester webbing. Generally, the roller pressure is 0.2MPa, the difference between the left, middle and right of the oven temperature does not exceed 2℃, the infrared pre-drying temperature is 100℃, and the anti-migration agent concentration does not exceed 15g/L; the blank strip should be fully dried after pre-treatment to effectively control the color difference of the webbing dyeing.

(2) The quality of the blank tape, machine management and dye formula also have an important impact on the control of dyeing color difference. In the production process of hot-melt dyeing of polyester webbing, it is necessary to systematically control the consistency of the blank tape quality, timely maintain and repair the machine, and reasonably use dyes and auxiliaries to obtain good dyeing effects.