High temperature and high pressure dyeing is an important method for dyeing polyester fibers. Due to the dyeing characteristics of polyester fibers and the special method of high temperature and high pressure dyeing, it also has special requirements for leveling agents used for high temperature dyeing. The difference in form category further creates different special requirements for high-temperature levelling agent.
Therefore, in addition to the most basic basic properties such as retarding and shifting dyeing adapted to the high temperature of 130 ° C, there should also be special varieties that meet the dyeing characteristics of various polyester fiber semi-finished products. Otherwise, it will be difficult for specific applications It is very good for each type of personality characteristics in high temperature and high pressure dyeing, which greatly reduces the applicability.
2. Different dyeing characteristics of different fiber semi-finished products
The various types of textile semi-finished products of polyester fiber also have various forms such as loose fiber, yarn and fabric.
Loose fiber dyeing is required for dyeing, yarn dyeing is mainly used for yarn dyeing, followed by sewing and embroidery; fabric dyeing is for garments, home textiles, industrial fabrics, etc.
The dyeing of fabrics is also divided into loose-dip dyeing, open-width roll dyeing and warp beam dyeing.
Although they are also dyed by high-temperature and high-pressure methods, different forms of fiber semi-finished products must be matched to different dyeing equipment that meets the characteristics of their respective forms; otherwise, it will obviously make the textiles serious in style, characteristics, and product quality Damaged, or even to the feasibility of no staining.
The loose dip dyeing machine is suitable for weft-knitted, warp-knitted knitted fabrics, and wool-like woven fabrics.
Open width dyeing is suitable for woven fabrics with no elasticity requirements, especially for thin woven fabrics of artificial silk filaments, which are generally not necessary for this type of machine.
For the grid-like sparse warp knitting fabric (such as mosquito net cloth, etc.), the warp beam dyeing machine is suitable.
Yarns are mainly dyed in the form of bobbins or caged skeins. Although loose fibers are also dyed in cages, there is also a considerable form difference from cage dyeing of yarns.
3. Basic functions and individual requirements of high-temperature levelling agent 3.1 Basic functions of high-temperature levelling agent:
Hydrophobic disperse dyes are suitable for dyeing hydrophobic polyester fibers, but the hydrophobic nature of the dye determines its low water solubility.
In the dyeing process using water as the medium, this should be said to be a matter of contradictory nature.
For this reason, in the commercial disperse dyes, a large amount of surfactants such as a diffusing agent with a ratio of not less than the dye are blended in a large amount.
Generally, it is dye: filler = 1: 1 ~ 1.5.
As a high-temperature leveling agent added in the dyeing work bath, it must also have a certain auxiliary and supplementary effect to promote the suspension and diffusion of the dispersed dye particles in the dyeing work bath and maintain a uniform and stable distribution.
This is especially important for light and medium shades with a small amount of dye, because the amount of light and medium shade dyes is correspondingly less, the diffusing agent brought from the dye is simultaneously reduced, and a high-temperature leveling agent is necessary Provide some compensation.
The leveling of dyeing needs to have the ideal retarding function, which is the functional focus that all leveling agents must have.
However, the level dyeing of disperse dyes for polyester fibers also needs to be combined with a strong transfer dyeing function, because the dyeing of disperse dyes in polyesters does not undergo chemical reactions from beginning to end; and the compact structure of polyester fibers and its extremely dense The surface crystalline layer and other characteristics have played a key role in blocking, and migration dyeing can make up for the vacancy of retarding dyeing on this aspect, especially after reaching the temperature dyeing stage of 130 ℃, the dye in the dyeing bath has been mostly After being dyed onto the fiber, the slow dyeing function has basically completed its mission. At this stage, the transfer dyeing function has become the main role. It will further promote and ensure the effect on the overall goal of the leveling agent.
Therefore, slow dyeing, shift dyeing, and diffusion-assistance are combined to form the most fundamental basic element of high-temperature levelling agent, which is also a basic function that must be possessed in the use of various different dyeing machines.
3.2 Analysis and classification of personalized requirements:
The different dyeing operation modes of different dyeing machines, in turn, have produced individualized special requirements for high-temperature levelling agents.
On the basis of the above basic essential functions, special varieties with low foam type, anti-precipitation type, penetration enhancement type, etc. are also needed to form a series.
3.2.1 Low foam type and its applicability:
For nozzle-type loose fabric dip dyeing machines such as liquid flow and spray, the dyeing bath is vigorously agitated due to the rapid operation of the fabric in the dyeing machine such as liquid flow and spray.
Especially in semi-filled dyeing machines, certain additives and dyes are prone to foaming in this environment.
Leveling agents containing adducts of ethylene oxide make foaming easier.
If the foam continues to increase to a certain degree, it will cause the nozzle to form a foamy air suction, which will reduce the spray pressure and eventually cause the gray cloth to stop passing.
Once stopped, it is very likely to produce color flowers, and wrinkle marks often also occur. The longer the stop, the more serious the consequences.
For this reason, the type of high-temperature levelling agent used in this type of dyeing machine should be of low foam type.
Of course, in terms of subjective wishes, it is better to be bubble-free, but this does not conform to objective reality.
This type of dyeing machine is vigorously stirred from beginning to end, which is very beneficial to maintain a good suspended state of undissolved dye in the dyeing bath, but on the other hand, it is a power source that continuously induces foam. The operation of the bubble is unrealistic and impossible.
Therefore, it is still necessary to use the defoamer in the semi-filled flow and jet dyeing machine.
But it needs to be mentioned that on the fully-filled jet dyeing machine, there is almost no need for foam.
In another type of overflow dyeing machine, because the dyeing operation of the grey cloth is driven by the self-flow of the water without pressurization, the nozzle is not provided, so it is also unnecessary to add an anti-foaming agent.
3.2.2 Anti-precipitation type and its applicability:
For the high temperature and high pressure dyeing machine, the operation of the grey cloth is mechanical transmission, and the amount of foam is more than the operation of the dyeing and the effect of dyeing, and it does not have much influence.
However, the operating characteristics of this type of dyeing machine are that the cloth is not transferred, and the small bath ratio makes the g / l unit concentration of the dye of the same color formula in the dyeing bath much larger than that of the liquid flow, spray type and package, and loose fiber Dyeing machine (generally at least more than double).
These have correspondingly increased the objective conditions for the aggregation and precipitation of suspended dyes in the dye bath, so the occurrence of color spot defects is much greater than the type of dyeing machine equipped with a powerful circulation pump.
Therefore, they are particularly suitable for the use of enhanced diffusion and anti-settling functions.
3.2.3 Intensified penetration type and its applicability:
Packages, caged skeins, loose fiber dyeing machines and other equipment are also equipped with powerful circulating pumps, but they are different from liquid jet dyeing machines in that the fibers are fully immersed in the dyeing bath, and It does not use a nozzle, and it is not very sharp for foam problems and anti-settling requirements.
However, they have the characteristics of the water movement opposite to the dyeing machine and the fiber does not move, and the fiber stack is much thicker than the flow machine, jet machine, dyeing machine, etc., with a single layer of gray fabric as the dyeing operation method In general, including warp beam dyeing machines, in addition to the need for mechanical equipment to have sufficient water penetration ability, high-temperature leveling agent supplements and strengthens the good penetration performance of all fiber layers inside, middle and outside. Levelling of the machine is both important and necessary.
Therefore, it is appropriate for them to use penetration-enhanced high-temperature leveling agent.
4. Conclusion
Leveling is one of the main quality goals of dyeing, so the leveling agent is very important in dyeing.
The high-temperature and high-pressure dyeing of polyester fiber, the variety of textile semi-finished products, and its selectivity in dyeing equipment, also correspondingly bring about the diversity of functional requirements for high-temperature leveling agent.
Therefore, the series design and speciality of the high-temperature levelling agent in design and development are inevitable and necessary, so that it can well meet the needs of various types of production in high-temperature and high-pressure dyeing.
However, it must also be seen that levelling agent is not the only factor that determines levelling.
Factors that affect level dyeing include: selection of specific dye species (compatibility), heating rate, vehicle blocking operation, and equipment status.
Only when reliable control has been made on all influencing factors can the leveling of dyeing be highly stable.
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