The core difference between gas-liquid dyeing and air-flow dyeing: From the perspective of heat transfer, the temperature field changes and heat diffusion processes in the dyeing process are analyzed, as well as the impact of temperature field changes on sensitive colors during the dyeing process, and gas-liquid dyeing is discussed Thermal balance conditions of machine and air atomization dyeing machine.
It is pointed out that when dyeing sensitive colors in a gas-liquid dyeing machine, the thermal equilibrium time of the temperature can be shortened by increasing the liquid amount of the fabric, using a front-mounted combined dye liquor nozzle, and utilizing the The extrusion of the fabric by the cloth roller and the osmotic pressure of the air flow produce multiple effects on the heat diffusion of the fabric in a single cycle, providing favorable conditions for the temperature field required for leveling dyeing of sensitive colors.
Gas-liquid dyeing machine and sensitive color
Fabric dip dyeing process , the dyeing of sensitive colors is more difficult and requires higher requirements, which is not only related to the performance of the dye, but also involves equipment performance and process control. Some sensitive color dyes are mainly manifested in the difference in the dyeing rate of each component dye at the same temperature, that is, the sensitivity to temperature is different.
In order to ensure the uniform dyeing of such sensitive dyes, in addition to selecting dyes with good compatibility and adopting certain process controls, it is more important to control the equipment well. Temperature field changing conditions.
The gas-liquid dyeing machine not only incorporates elements of air flow dyeing and ordinary overflow jet dyeing, but also solves the current difficulties in dyeing sensitive colors with air flow dyeing machines. question.
The structural principle of gas-liquid dyeing machine and air flow dyeing machine
Based on the structural principles of the gas-liquid dyeing machine and the air-flow dyeing machine, the changes in the temperature field of the two under the same process conditions were analyzed, and it was pointed out that the large temperature change gradient in the air-flow dyeing process during the sensitive color dyeing process was The temperature difference is the main reason that affects the uniform dyeing of sensitive color dyes; at the same time, the inherent mechanical conditions and structural characteristics of the gas-liquid dyeing machine suitable for sensitive colors are explained.
Temperature field analysis during dyeing process
From the perspective of heat transfer, dyeing It can be regarded as a heat transfer system composed of dye, liquid phase, gas phase and equipment. The collection of temperatures at each point in it is called the temperature field, which is a function of time and space.
The temperature in dyeing is actually a temperature change process, and the temperature distribution changes with time. Therefore, the temperature field of dyeing is an unsteady temperature field.
1. During the heating process of dyeing
There are always gas and liquid phases inside the main cylinder. and temperature differences between fabrics. Tests have shown that the temperature of the dye solution in the nozzle of the airflow dyeing machine and the temperature of the dye solution in the main tank can differ by up to 10°C. This temperature difference has a great impact on the uniform dyeing of some temperature-sensitive dyes. Also during the cooling process, there are also temperature differences between the gas phase, liquid phase and fabric inside the main cylinder. If the temperature difference is too large, the fabric in the gas phase and liquid phase in the master cylinder will cause wrinkles due to uneven shrinkage of the cloth surface.
Although the specific heats of fibers and water are different, fabrics with large water content will be affected by the specific heat of water and increase the heat absorption. That is, absorbing the same heat, its temperature will increase. Lower than fabrics with low moisture content. For this reason, increasing the amount of liquid carried by the fabric during the heating process is beneficial to reducing the temperature difference between the fabric and the liquid phase (dye liquor).
According to the above temperature field changes during the dyeing process, based on the structural characteristics of the gas-liquid dyeing machine and the airflow dyeing machine, analyzing the temperature field changes of the two can explain the gas-liquid dyeing. Why is the machine suitable for dyeing sensitive colors?
2. Temperature field changes of air atomization dyeing machine
To atomize the dye liquor, current airflow dyeing machines mainly use atomization nozzles, and the liquid supply volume of a single tube of fabric in a single cycle is 80 to 100L.
For a standard single tube with a maximum fabric capacity of 250kg, the liquid carrying capacity of the fabric is 32% to 40%, which is lower than that of the overflow dyeing machine. Pure cotton The fabric needs to be circulated 5 to 6 times to reach a higher liquid carrying capacity. Under the conditions of this equipment, when the temperature of the fabric is raised during dyeing, the temperature difference between the fabric in the storage tank and the nozzle is large, which will have a great impact on the dyeing rate of each component in the sensitive color dye, which will seriously affect the dyeing rate. It is difficult to achieve a uniform dyeing rate, so it is not easy to obtain a level dyeing effect.
Since the dye liquor atomization nozzle of the air flow atomization dyeing machine is designed to obtain the so-called dye liquor atomization effect, the fabric is obtained in a single cycle in the nozzle The amount of dye liquor cannot be too large, so the specific heat of the liquid cannot be used to increase the heat absorption of the fabric. Even through the design and control of the dyeing process, the requirements for temperature field changes in sensitive color dyeing cannot be met. Ordinary overflow or jet dyeing machines can basically meet the above requirements. This is because the fabric can obtain a larger amount of liquid in the nozzle, and the temperature gradient changes in the entire dyeing system (including the dyed fabric, dye liquid, air and equipment). Controllable; by controlling the feeding method, it can basically meet the needs of sensitive color dyeing processes.Features that are not available in dyeing machines and overflow or jet dyeing machines.
The osmotic pressure effect of air flow on liquid-laden fabrics
On the fabric During a single cycle, the fabric and dye liquor are exchanged in the nozzle and then enter the air flow nozzle. They will also be affected by the osmotic pressure of the air flow, which accelerates the heat diffusion into the interior of the fiber. At the same time, the dye liquor adsorbed on the fiber surface is redistributed. Improve the uniformity of temperature distribution on the fiber surface.
By analyzing the gas-liquid dyeing and airflow dyeing processes According to the changing rules of the temperature field, it is believed that the structure of the gas-liquid dyeing machine meets the thermal diffusion conditions of the temperature field during the dyeing process, which can reduce the difficulty of controlling sensitive color dyeing. The working principle and structural performance of the equipment determine the processability of the equipment. The temperature field and thermal diffusion conditions of the dyeing process provided by the gas-liquid dyeing machine are currently not available in the air flow dyeing machine and the ordinary overflow dyeing machine. The adaptability of gas-liquid dyeing machines to sensitive colors not only simplifies process design and operation difficulty, but also provides printing and dyeing enterprises with a reliable and improved dyeing quality method. </p