Cautions for continuous dyeing of webbing
The following items should be noted in the continuous dyeing of webbing:
1. Webbing Blanks Factor The first step in a webbing blank is to note whether the yarns used are the same batch, because different batches of yarns contain different “oil” conditions, such as blended yarns, which can become a factor in the color of the dyeing process; Whether the raw material is pretreated or not, the dyeing of the dyed green material after the refining process is very good, because after the treatment, the “oil” on the yarn is removed and the dye can be directly contacted with the fiber without protection.
2. Dyeing tank (or rolling mill, dyeing tank, dyeing machine) The uniform pressure of the cylinder at both ends of the roller The belt rolling machine for continuous hot-melt dyeing machine is generally pneumatically pressurized. There are two cylinders on each side of the roller. When the rolling mill 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 a non-uniform liquid belt rate and a color difference in the edges. In addition, the rollers of the rolling mill are pressurized at both ends, resulting in a certain degree of deflection, resulting in inconsistent rolling margins in the edges, and also causing left, right, and middle chromatic aberrations.
3MPa。 3. Dye groove roller pressure and concentricity, hardness factors in the production, want to roll pressure on the left and right color difference to a minimum, then the general printing of the ribbon pressure roller pressure should be controlled at 0. 2MPa. In the production process, due to the wear of the rollers, it is required to periodically perform calibration and repair on the rollers, otherwise it is easy to cause unevenness due to the unevenness of the rollers resulting in the color. Rollers with different hardness have different rolling allowances. Too hard may result in insufficient absorption of dye. Too soft may lead to a large amount of migration and dye production. How much hardness should be determined according to the tape.
4. Effect of infrared pre-baking temperature on webbing After the polyester webbing undergoes pre-treatment and padding dyeing processes, it is generally subjected to infrared (line) pre-bake treatment before entering the coloring chamber to prevent dye bathing from occurring during the drying process. The phenomenon of shifting, to avoid coloring and color difference between the front and back. When the infrared pre-baking temperature is lower than 80°C, the color difference between the front and back of the webbing is relatively large, and it is difficult to meet the requirements of customers. When the infrared pre-baking temperature reaches above 100°C, the color difference between the front and back of the webbing is greatly improved. This is because when the prebaking reaches above 100°C, the moisture of the webbing is basically evaporated, which greatly reduces the possibility of dye migration. Considering the dyeing production practice and energy consumption, the infrared prebaking temperature is controlled at 100°C-150°C. Production is generally based on the thickness and liquid carrying rate of the type of the blank, the higher the liquid carrying rate of the blank, the higher the infrared pre-baking temperature. In actual production, it is not possible to rely only on the infrared pre-baking temperature to control the color difference between the front and back of the webbing, especially for sensitive colors such as coffee and dark green, and it is necessary to use the anti-migration agent and other additives in order to achieve a good dyeing effect.
The effect of fixing temperature of baking oven on hair color The baking hair color is an important part of continuous hot-melt dyeing. The uniformity of baking oven fixing temperature plays a key role in controlling the left, right, and right chromatic aberration of the webbing. After the polyester webbing is pre-baked by infrared rays and then entered into the bake oven, it is necessary to ensure that the temperature is the same, otherwise a significant color difference will occur. Tests have shown that the temperature difference between the left, middle, and right sides of the baking oven exceeds 2°C, and the color of the ribbon changes significantly. Therefore, the dyeing process must ensure that the baking oven temperature is uniform.
6. The effect of moisture content on the left, right, and right chromatic aberration of the webbing. Polyester filaments are added with a certain amount of oil during the spinning process, so they must be de-oiled prior to dyeing. After the ribbon is dyed, it is generally dried after being processed. The uneven surface temperature of the drying cylinder can cause differences in the moisture content of the web. In severe cases, the left and right chromatic aberrations of the web can be caused. In the dyeing production process, in order to avoid the left-right color difference due to the difference in the moisture content of the green sheet, it is necessary to ensure that the green sheet is completely dried before the pad-dyeing liquid, and the drying cylinder is subjected to periodical overhaul.
7. Other factors that produce color differences In terms of production management, there are mainly the following aspects that affect the left-right color difference of polyester ribbons.
(1) Semi-manufactured quality of semi-finished fabrics The difference in fabric structure, warp and weft density, warping tension, and thickness will cause color difference. Due to the difference in the production efficiency of the loom and the dyeing machine, the green belts produced by different looms are dyed in the same dyeing machine, and even when the different lots of the webbing are dyed in the same dyeing machine, a color difference occurs. In order to minimize the influence of the difference in the quality of the blanks on the color difference of dyeing, weaving and dyeing must be coordinated and the production plan should be coordinated. At the same time, inventory management of the blanks should be carried out to achieve “first-in, first-out”.
(2) The machine management baking oven should be regularly inspected and maintained to ensure normal operation of the heating equipment (such as heat pipe, burner, etc.), normal temperature increase and temperature control. In the actual production process, the air ducts in the box and the filter screen should be kept clean. It is very important for the dyeing machine to enter the tape device to adjust the tension of the tape. Before entering the dyeing tank, the tension of the tape must be basically the same, so as to ensure the consistency of the tape rate and ensure the consistency of color. It is also important to control the tension applied by the dyeing machine to the webbing. Since the webbing dyeing machine generally uses the frequency conversion control method to adjust the tension of the entire dyeing machine, it is necessary to ensure that the frequency conversion control signals of each process point are normal, and that the failed devices should be repaired in time.
(3) The compatibility of dyes with dyes has a great influence on the color difference between the front and back of the webbing. When the different formulas produce the same color number, the color difference between the front and back of the webbing is quite different. Generally, sublimation dyes with the same or similar sublimation fastness and type (S, SE, E type) are selected for compatibility, and the dyeing effect is good. In addition, the use of auxiliary agents such as anti-migration agents, penetrating agents, and leveling agents also has a certain effect on the control of the color difference, but it should be used rationally.
In summary, we need to pay attention to several points in daily life:
(1) The pressure difference of the roller pressure, fixing temperature of the curing oven, infrared prebaking temperature, moisture content, anti-migration concentration and other factors all influence the color difference of the continuous hot-dissolving dyeing of the polyester webbing. Generally choose the roll pressure 0. 2MPa, baking oven temperature difference between the left and right does not exceed 2 °C, infrared pre-baking temperature 100 °C, anti-migration concentration of no more than 15 g / L; before the tape to be fully dried, In order to effectively control the color difference of the ribbon dyeing.
(2) The quality of the blanks, the management of the machine bed, and the formulation of the dyeing and dyeing also have an important influence on the control of the color difference. Polyester webbing hot melt dyeing production process, we must systematically control the consistency of the quality of the ribbon, timely maintenance and maintenance of the machine, the rational use of dyes and auxiliaries, in order to obtain a good dyeing effect.