Airstream dyeing machine
Compared with the traditional overflow dyeing machine, it has significant energy-saving and emission-reduction effects, and basically covers the range of fabric types that the traditional overflow dyeing machine is suitable for. For some new fiber fabrics such as Lycoell, microfiber fabrics, etc., it has a unique dyeing style. In addition, some of the structural features of the air flow dyeing machine provide a very favorable condition for dyes to uniformly dye the fabrics, plus some advanced control technology provided to ensure that the “primary success rate†of the dyeing is above 98%, resulting in significant savings. The energy wasted due to rework and increased productivity.
Air flow dyeing still belongs to the exhaust dyeing process. As with other intermittent dyeing purposes, it is to establish a condition that allows the dye to be uniformly dyed and fixed on the fibers to ensure that the dyed fabrics are dyed according to the required color and fastness. Because the structural characteristics and working process of airflow dyeing machines are quite different from ordinary overflow or jet dyeing machines, familiarizing and mastering these basic features can provide help and guidance for the design of equipment structures, the formulation of dyeing processes and the control of processes.
1 How Airflow Dyeing Machine Works
The air flow dyeing machine adopts the aerodynamic principle to use recycled air instead of water to draw the dyed fabric to make a circular motion. Therefore, compared with the traditional overflow dyeing machine, the dyeing bath ratio is greatly reduced. There are two types of exchanges between fabrics and dyes in airflow dyeing machines: one is air atomization and the other is pressure infiltration. Air atomization is to first atomize and disperse the dye liquor through a special nozzle in the air stream, and then the air stream with the atomized dye liquor exchanges with the dyed fabric and hauls the fabric into circulation. During the exchange process, the atomized dye liquor not only has a large contact area with the fabric, but also has a strong penetration force on the fabric fibers and accelerates the diffusion rate of the dye liquor into the fibers. The nozzle of the THEN air flow dyeing machine used this form. The pressure infiltration mode uses two nozzles, namely a pure air nozzle and a liquid flow nozzle. The flow nozzle is passed through the nozzle at the front and the dyed fabric first, and is exchanged with the dye solution, and then passes through the pick-up roller and then enters the airflow nozzle. The airflow penetrates the dye exposed fabric and accelerates the dyeing during the circulation of the woven fabric. The diffusion rate of liquid to fabric fibers. The nozzles of the Thies airstream dyeing machine in Germany use this form. From the current application situation, most airflow dyeing machines in the form of gas flow atomization have better use effects. This article is also discussed in this type of nozzle airflow dyeing machine.
2 Main features of airflow dyeing machine
2.1 Low bath ratio
The biggest difference between airflow dyeing and ordinary overflow or jet dyeing is the ability to dye at very low bath ratios (1:4 or less). However, this low bath dyeing condition can cause dye-to-fabric dyeing changes. Experiments have shown that the directness of reactive dyes increases with decreasing dye bath ratio. As far as the dyeing process is concerned, while increasing the dye uptake rate, a high fixing rate should also be ensured, which is a basic requirement for achieving a certain color depth and color fastness. It is not possible to completely dye 100% of the dye onto the fabric. There is always some hydrolyzed or accumulated dye attached to the surface of the fabric fibers. If it is not removed, it will peel off during the process of use or washing. Therefore, improving the fastness of dyeing is an important control index of the dyeing process. In addition to the properties of the dye, the fastness of the fabric depends mainly on the degree of dye penetration during the dyeing process and whether the unbleached or hydrolyzed dye has been fully washed. The low bath ratio of airflow dyeing can achieve higher fixation rate without the use of excessive accelerators and fixing agents, while the reduction of fixing agent (such as alkali) can reduce dye hydrolysis. The improvement of the directness of dyes can also reduce the dependence on the accelerants (such as Yuanmingfen, salt and other electrolytes) and increase the dye uptake rate. However, when dyeing with reactive dyes, in order to control the dye uptake rate, airflow dyeing It is generally considered to use less reactive dyes.
2.2 The frequency of fabric and dye exchange is high
Air flow dyeing still belongs to exhaustion. According to the law of exhaustion, the dyed fabrics must be exchanged several times with the dyeing liquor in order to complete the dyeing process. The airstream dyeing is also relying on this method to achieve the dyeing purpose of the fabric. According to Beckmann's theory, the best dye uptake rate for jet dyeing is:
Vopt=I•U
In the formula: I—The dye uptake rate (%) per cycle of the fabric, general experience takes 1-3%:
U—The sum of the cycle frequency of fabrics and dye liquors.
Obviously, the more exchanges of fabrics and dyes per unit time, the more favorable it is to dye and shorten the dyeing process. If the fabric does not produce excessive tension, increase the cycle frequency of the fabric or the cycle frequency of the dye liquor, then both the uniform dye uptake of the fabric and the dyeing time can be shortened. Airflow dyeing Because baths are relatively low, the dyeing fluid has a high frequency of circulation, and the fabric can be circulated at a higher rate due to the lower liquid content. The exchange of high frequency between the two brings favorable conditions for level dyeing, and under the support of a certain dyeing process, it can be completely encapsulated to achieve a rapid dyeing process.
2.3 Dynamic distribution of dye liquor circulation
For some fabrics with a large specific surface area of ​​the fibers, the dye uptake is usually faster, and if the control is not good, the flowers are easily dyed. Therefore, in order to ensure levelness, it is often necessary to control the maximum amount of dye dyed in each cycle of the fabric. Ordinary overflow or jet dyeing machine's fabric running speed is determined by the dye injection volume. The decrease of the dye jetting rate will reduce the fabric running speed, and it will also affect the exchange frequency of fabric and dye liquor. In contrast, the air circulation dyeing machine fabric circulation is relying on air traction, the dye liquid circulation frequency can be independently controlled according to the needs of the process, in changing the dye liquid supply to the fabric, does not affect the fabric cycle frequency. Therefore, according to the characteristics of the fabric and the dyeing process, the dyeing amount of the dye in each cycle of the fabric can be controlled to ensure the quality of deep and light colors.
2.4 Dye-on-fabric dyeing changes
To achieve dyeing of fabrics with dyes, the first is to determine the combination of the dye and the dyed fabric, and the second is to provide the necessary conditions to promote the combination of the two. It is well known that dyes complete the dyeing process by absorbing, diffusing and fixing three basic processes. The fixing process is mainly determined by the interaction between the dye and the fabric, and the time is also longer. The adsorption and diffusion processes are related to the relative movement of the dye liquor and the fabric. Breaking the dynamic balance of the boundary layer and thinning the thickness in time is relying on this relative motion. To complete. The more intense the relative movement of the dye liquor and the fabric, the easier it is to break the dynamic equilibrium of the adsorption and diffusion boundary layer in time, or reduce the thickness of the adsorption and diffusion boundary layer, and can quickly transport the dye to the “emptiness†of the fixed boundary layer.
According to fluid dynamics, the kinematic viscosity of a liquid decreases with increasing temperature, while the kinematic viscosity of air increases with temperature. For airstream dyeing, as the temperature increases, the kinematic viscosity of the dye liquor decreases and the kinematic viscosity of the gas increases, which is more conducive to breaking the boundary layer of the dye bath and reducing the thickness of the dye bath, thereby accelerating the dyeing process of the dye, thereby shortening the dyeing time. . At the same time, the change in kinematic viscosity of the two fluids also provides conditions for increasing the running speed of the fabric, that is, the increase in air viscosity increases the fabric's viscosity when the circulating air volume is constant (the fan power increases). The traction makes the fabric run faster. Such changes in conditions are more conducive to the uniform dyeing of dyes on fabrics.
2.5 Distribution of temperature
The change in temperature during air flow dyeing is still controlled by heating or cooling the dye liquor. Because the bath is relatively low, the fabric in the storage tank and the dye bath absorbed are in a separate state from the free dye bath (circulating dye bath), so the temperature of the fabric passing through the nozzle is always higher than the temperature of the fabric in the storage tank, especially When the temperature rises rapidly to l30°C, the temperature difference between the two places can reach about 10°C. How to control the uniformity of the dyestuffs on the overall fabric during the dyeing process is very important for the airstream dyeing machine. It is usually controlled by the bypass and heating rate of the dye liquor and the cycle speed of the fabric. Therefore, the rapid exchange of fabrics and dye liquors is not only the requirement for uniform distribution of dyes on dyes, but also an important control method for uniform temperature distribution of fabrics.
2.6 steaming process of fabric
In the dyeing and finishing wet processing process, in order to ensure that the fibers of the processed fabric are fully reacted with the auxiliary agent, a steaming process is often used for the fabric. In this way, the fibers of the fabric can be swollen sufficiently to accelerate the diffusion and reaction of the auxiliary into the interior of the fibers of the fabric. In the air flow dyeing machine, the fabric is not immersed in the dye bath in the cloth storage tank. During the process of processing, the cloth falling into the cloth storage tank after passing through the nozzle is actually subjected to a process similar to steaming. This has played an important role in improving the swellability of textile fibers and accelerating the penetration and diffusion of the auxiliaries into the textile fibers. As a result, not only the processing time is shortened, but also the treatment effect is improved, and the characteristics of high efficiency and short flow are achieved.
Shortening the wet processing time of the fabric can not only improve the production efficiency and reduce the energy consumption, but also can reduce the surface damage or tensile deformation caused by the long process of the fabric (mainly the knit fabric containing spandex). Practice has proved that the "first-pass success rate" of fabric wet processing using air flow dyeing machines is very high, which has obvious advantages over conventional overflow dyeing machines.
3 The key technologies of airflow dyeing machine
Like other batch dyeing machines, the air flow dyeing machine can meet the dyeing process conditions, and its principle, structure and function are also based on a certain key technology. From the perspective of machine design and manufacturing, there are several key technologies.
3.1 Aerodynamic circulatory system
Air flow is the main source of power for traction fabric circulation, and it also has the effect of uniform and accelerated dye adsorption on fabrics. A closed loop system is usually composed of fans, airflow nozzles, airflow ducts, and filtration capacity. Fans generally use high-pressure centrifugal fans, and have enough air volume. There are two types of installations, internal and external. The internal measuring structure is compact, and the resistance loss along the air duct is small; the external volume takes up more space and the local resistance loss is small. The rated power of the fan is generally designed to be relatively large, mainly considering that a large fabric needs to ensure sufficient air volume traction. The air volume of the fabric below the mid-thickness is controlled by the frequency conversion to less than 80%; if it is a light-weight fabric, the air volume can even be used up to 50%.
The airflow nozzle is the core part of the airflow dyeing machine, especially the structure formed by the atomization of airflow, which must ensure the atomization effect of the dye liquor and the full contact with the fabric. At the same time, the air flow can also produce expansion effect on the fabric, and constantly change the rope position of the fabric to avoid fabric wrinkles. For this part of the structure, manufacturers have their own patented technology protection.
3.2 Dyeing fluid circulation system
The dye liquor circulatory system is set up to finish dyeing the dyed fabric. The amount of dye dyed in each cycle of the fabric, the temperature difference and the concentration difference between the dye solution contained in the fabric and the main dyeing solution are all controlled by the dye circulation system. Because the bath ratio of the air flow dyeing machine is extremely low, the concentration of the dye liquor is relatively high, and it is very sensitive to temperature and concentration changes. Therefore, the entire dyeing liquid system must be guaranteed through the system structure and control in the temperature change (increase and decrease in temperature). ) and uniformity of concentration change (feed).
The dyebath nozzle is an important unit in the dye liquor circulation system and its role is to provide exchange conditions for fabrics and dye liquors. In the air flow dyeing machine, no matter which kind of nozzle is used, it does not play the role of traction fabric circulation. Its structural form depends on the exchange of fabric and dye liquor. For atomized nozzles, it is required to produce atomization (exactly, refinement of dye liquor); The dyeing nozzle, which is equivalent to a soft jet nozzle, is required to be able to control the amount of fluid in the fabric and ensure the effect of pressure infiltration.
3.3 Wash controlled
The bath ratio of the air flow dyeing machine is very low, and a continuous water washing method is adopted, and the water flow and the temperature control are performed in stages in the water washing process. At the end of the dyeing, the surface of the fabric fibers is mainly distributed with unstained dyes, hydrolyzed dyes, and electrolytes, which must be washed with strong water to accelerate their peeling speed with the fabric fibers. Usually increase the nozzle injection pressure (main pump motor through the frequency conversion to increase the speed), fabric continuous cycle 2 to 3 cycles to meet the requirements. After the intense flow of water acts on the surface of the fabric, the second stage is the removal of hydrolyzed dyes inside the fiber by the action of temperature. This temperature effect is also an indispensable control part for improving the efficiency of water washing. Due to the presence of hydrolyzed dyes on the inner pores of the fibers, the water stream cannot remove them from the fibers. Therefore, the temperature must be increased, the pores in the fibers should be enlarged, and the kinetic energy of molecules moving out of the fibers should be increased, and they should be desorbed from the surface of the fibers. When the first two control stages have been completed, most of the dirt inside and outside the fabric tube has become detached, but there is still a portion attached to the surface of the fabric, which can be removed with lower water flow and temperature. This process control is actually a controlled process and is the primary means of achieving the best results with a low bath ratio.
3.4 Dyeing Process Control
The dyeing process must be controlled by the dyeing process. The temperature of dyeing liquor, the injection of dyes and auxiliaries are all means of controlling the dyeing process. With respect to the relatively large bath conditions of the overflow jet dyeing machine, the air bath dyeing machine has a higher bath temperature ratio and requires higher precision for these control methods. In addition, the change in density of air at room temperature and high temperature, shrinkage of thermoplastic fibers at high temperatures, can also affect the initial set cycle frequency of the fabric. For these changes, process control should be implemented as long as it may affect the leveling of fabrics. Through the detection of fabric motion, dynamic control is performed by PLC and computer.
Dyeing process control has involved the proportional distribution of the dye liquor, giving high- and low-feed control of the fabric. According to the difference in the surface area of ​​the fibers and the amount of water required for dyeing and washing, the amount of liquid in the fabric can be controlled to ensure that the fabric with fast dyeing rate achieves the best leveling effect in the shortest possible time. . Microfiber fabrics dye better under these conditions than spill dyes, and have a "high success rate". Therefore, the control of the dyeing process is another key technology of the air flow dyeing machine. It must be closely combined with the dyeing and dyeing materials, fabric fibers and dyeing process to form a software control system, rather than a simple control of several actions.
4 Airflow Dyeing Machines Common Problems and Solutions
Any dyeing machine inevitably has its own defects, especially the air flow dyeing machine as a new technology is no exception. In the past decade or so, it is basically in experimental exploration, it is also experienced this process. With the emergence of mature technology today. So, what problems may also appear in the air current dyeing machine? The following points are reflected in the application.
4.1 Fabric abrasion and fluffing
In the air flow dyeing process, the fabric runs at a relatively high speed. When entering the nozzle and the cloth guide tube, although it comes in contact with the dye liquor, it is not completely surrounded by the dye liquor like the overflow spray dyeing. Therefore, a large frictional force is generated between the surface of the fabric and the wall of the pipe, and the surface of the fabric is scratched when it is severe. Designers tried to form an air cushion through the air flow and also surrounded the fabric, but this is not the case.
The fluffing or pilling phenomenon of fabrics is mostly due to the external mechanical action (stretching, friction), in addition to the high strength and flex resistance of the fabric fibers and the large surface area of ​​exposed yarns (such as knitted fabrics). Therefore, the current solution is to improve the manufacturing precision of the inner surface of the device, and to eliminate or improve the measures such as reducing the running speed of the fabric and adding a smoothing agent.
4.2 creases of fabric
Air flow dyeing machines usually have a faster cloth speed, and their purpose is to increase the exchange frequency of the fabric and the dyeing liquor and ensure level dyeing. At the same time, the static time of the fabrics in the storage cloth is shortened, and creases of the fabrics are avoided. However, some lightweight, high-count, high-density filament fabrics are prone to scratches when the cloth speed is too fast, and creases are created when the cloth speed is low. For this situation, we need to find a suitable speed.
For some knitted fabrics may appear crease (vertical), the reason is that the knitted fabric in the textile process to form a larger internal stress, if the external warp tension is too large, it is easy to produce warp creases, and in the first time It is formed in the case of water processing (such as pre-treatment). In the subsequent dyeing process, the amount of dye adsorbed on the creases is different, resulting in different shades. To avoid or reduce this phenomenon, in the pre-processing process, the matching relationship between the air volume and the feeding roller line speed must be adopted. After the fabric leaves the guide pipe, there is an expansion process, and the beam position is constantly changed, so that the folding position is rapidly Expand. As long as this process is carried out once, the fabric does not form a permanent crease, so creases will not be formed during the subsequent processing.
4.3 The color fastness of the fabric is reduced
In theory, the use of reactive dyeing dyeing fabric after airflow dyeing the various indicators of color fastness than ordinary spilled dye, which is also confirmed by the majority of the use of good dyeing plants. However, there are individual dyeing factories, especially those who do not really master the air flow dyeing machine, and there has been a decrease in the color fastness. In fact, this is entirely based on the characteristics of the air flow dyeing machine to design the dyeing process, but the simple application of ordinary overflow spray dyeing process. The reason for the analysis is mainly that the dyeing process takes a long time, and it is not enough to have already reached the leveling time. The result is that the dye that has formed a chemical bond with the fiber breaks the bond, but it has not been sufficiently removed during washing. Therefore, it is very important to formulate a process suitable for airflow dyeing, especially for the control of time. It must be taken into account that the same dye and the dyed fabric are dyed in the same color, and the airstream dyeing time is shorter than that of the ordinary overflow dyeing because the fabrics are The exchange rate of the dye liquor is high, and the time taken to complete the same number of exchanges is short.
5 Development trend of airflow dyeing machine
In the process of dyeing water, air flow dyeing machine as a new model with high efficiency, energy saving and environmental protection features will play a positive role in the development of the printing and dyeing industry in the future, at least it can gradually replace the traditional bath is relatively large Spill dyeing machine. Airflow dyeing machines improve their own structure and performance, but also have more functions to be expanded or developed.
5.1 Develop a process that is fully suitable for airflow dyeing
In order to give full play to the advantages of the flow dyeing machine, it is necessary to combine the characteristics of the air flow dyeing machine to develop a corresponding dyeing process, and continuously expand the application range of the dyeing process. Here, equipment, dyestuffs, textile fibers and dyeing processes are required to closely cooperate with each other, and their respective adaptation conditions and requirements are optimally combined. Then intelligent control software is formed. The user only needs to input the relevant basic parameters according to the instructions. It can be done automatically by the device. With the continuous emergence of new textile materials and the improvement of the functional requirements of textiles, it is necessary to develop airflow dyeing processes and equipment functions that meet these finishing requirements.
5.2 Implementing Dynamic Quality Control
The development requirement of this part is that in addition to the automatic control of temperature and feed, it is also possible to determine the optimum operating time and process conditions (including water and Steam consumption); At the same time, parameters such as cloth speed and bath ratio can be automatically set for the gram weight and length of different fabrics to fully ensure the level dyeing of the fabric and the reproducibility of the process. This is an intelligent control system, also known as DQC (DynamJ Quality Control - Dynamic Quality Control) system.
5.3 for fabric finishing
The finishing of fabrics is a process to improve the taking of the fabric, which occupies an increasingly important position in modern textiles. The air flow of the airflow dyeing machine acts on the fabric, and some fabric special styles can be obtained by reacting some finishing aids with the fabric.
5.3.1 Bio-enzyme polishing
In addition to the application of biological enzymes in the desizing of the dyeing and finishing industry, it has now been extended to the surface treatment of fabrics. The Lyocell fiber undergoes a "primary fibrillation" treatment followed by enzymatic treatment followed by "secondary fibrillation" that accompanies the air flow dyeing process, and finally obtains the effect of the peach skin with frost on the surface of the fabric. In addition, some fabrics knitted by biological enzymes can not only improve the surface finish of the fabric, but also be polished. Also get a very good feel. If the singeing process can be replaced by a certain auxiliaries, this will eliminate the exhaust gas emissions caused by the combustion gases and save energy. This also means that the improvement of certain traditional processes will have more significance for energy conservation and emission reduction.
5.3.2 Island Type Microfiber Alkali Solvent Fiber Processing
Sea-island type microfibers are obtained by dissolving sea components of polyester sea-island composite fibers with caustic soda (NaOH), and the completion of this process is usually carried out on a dyeing apparatus. During the process, it is required that the fabric and the treatment solution have intense relative movements. The purpose is to speed up the reaction rate and the degree of progress, and it is required to strictly control the concentration difference of the alkali solution during the reaction. The pretreatment method using airflow dyeing can better meet this requirement.
5.3.3 Mechanical Flexibility
Flax-containing fabrics are generally softened to improve the intake. There are also high-grade towel-like fabrics. People begin to pay attention to ecological environment protection, use as little or no chemical soft auxiliaries as possible, and perform soft processing through the mechanical action of the fabric movement. Air flow dyeing machine uses the vibration and flapping action of its air flow to reduce the rigidity of fabric fiber molecules and improve the softness of the fabric. In fact, the airflow dyeing machine has been accompanied by this effect in the dyeing process, so the fabric processed by the airflow dyeing machine is obviously better than the ordinary overflow dyeing machine in terms of cloth style and feel.
5.3.4 creases or wrinkles on the fabric surface
Some manufacturers used air flow dyeing machines to process ice flocking on flocked fabrics and obtained very good results. This processing method is mainly through the process design, control of the amount of circulating air, fabric speed and temperature, so that under certain conditions, the flocking cloth is controlled by the mechanical tapping and cooling rate so that the flocked cloth surface is originally even and smooth. Produces a uniform and irregular wrinkle imprint, which looks like fine cracks on the ice surface, and has a strong sense of fashion. In addition, through the design of the process parameters, the surface of the chemical fiber fabric is evenly creased to form a man-made fold, which has distinctive clothing personality.
6 Conclusion
As a new type of intermittent dyeing equipment, the airflow dyeing machine has gradually reached a mature stage after more than ten years of improvement and development. In addition to its significant energy-saving and emission-reduction effects, it is significantly superior to ordinary spill-spray dyeing machines in terms of the scope of application of fabrics, and the processing quality and style of fabrics. While bringing good economic benefits to users, it also produced better social benefits. The effect of its use and the range of applicable fabrics have exceeded the imagination of the people. Despite this, there are many features of the airflow dyeing machine that have not been developed. With the development of dyes, fabrics and dyeing processes, the performance and function of air flow dyeing machines will continue to be improved and will be mastered and adopted by more users. All kinds of indications indicate that in the coming years, an era of airstream dyeing will enter, and the printing and dyeing industry will also develop and advance with the application and promotion of this new technology.
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