． Why is it difficult to level-dye yarn with vat dyes when dyeing light beige and bright yellow on a high-temperature and high-pressure dyeing machine? Is high-temperature dyeing feasible?
Answer: When using a high-temperature and high-pressure coloring machine for vat dyes, the quality of dark and medium-colored varieties will basically meet the requirements if the process formula and operation are reasonable. However, when dyeing light colors, it is more difficult to obtain a level dyeing effect. This is because vat dyes have fast dyeing properties during dip dyeing. When dyeing light-colored varieties, especially when using high-temperature and high-pressure dyeing machines, the spinning yarn adopts conditions such as filling type and dye liquor circulation mode and reciprocating twisting method. Yarn dyeing machines are quite different, so the leveling effect is more difficult to manipulate. In the traditional process, the coloring temperature of vat dyes is determined based on the initial dyeing speed of the dye, the equilibrium dyeing rate, the stability of the dye bath during dyeing, etc., and a certain concentration of caustic soda and safety powder in the dye bath is controlled. , B, C and unusual coloring temperatures. However, at these traditional dyeing temperatures, the dye uptake rate is generally fast, and individual dyes are highly sensitive to temperature. At the same time, due to the low temperature during dyeing, the dyes easily aggregate, so it is easy to produce color blooms when dyeing light colors. , color differences, white knots and other dyeing defects. If the coloring temperature is increased appropriately, the following situations may occur.
① Increase the coloring temperature, the initial dyeing rate will be slow, and the affinity of the dye to the fiber will be reduced, thus preventing the color blooming phenomenon caused by instant dyeing.
② As the coloring temperature increases, the activation energy between dye molecules increases, the collision of dye molecules intensifies, and the aggregation tendency decreases, which is beneficial to level dyeing. Increasing the coloring temperature will increase the swelling degree of the fiber and relax the microstructure, which is conducive to the dyeing of the leuco body of the dye.
③ As the coloring temperature increases, the migration of the leuco body of the dye increases, and the leveling effect is better. The relationship between coloring temperature and leucobody migration is shown in Table 4-10.
It can be seen that restoration When dyeing, appropriately increasing the coloring temperature will help improve the level dyeing of light-colored yarns. However, due to the increase in coloring temperature, the insurance powder is consumed too quickly, so the amount of insurance powder should be increased (about Z0% more than the conventional process) or a mixed reducing agent of insurance powder and caraway powder can be used to maintain the dye bath in the later stage of coloring. Sufficient recovery ability. As the dosage of insurance powder increases, the consumption of caustic soda increases, so the dosage of caustic soda should generally be increased by 5G to 10%. So, when using high temperature for coloring, have vat dyes undergone mutation phenomena such as reduction, hydrolysis, dehalogenation, and molecular rearrangement? We believe that most light-colored varieties have low dye concentration
and the content of caustic soda and insurance powder in the dye bath is lower than that in the dry vat, so over-reduction is generally less likely to occur. However, it should be pointed out that the adaptability of various vat dyes to high-temperature coloring is not exactly the same and must be screened experimentally. For example, vat dyes that were originally colored by the C method, because the molecular structure contains amido groups, in order to prevent dye hydrolysis at high temperatures, the coloring temperature should not exceed 60°C. c. The reduced ash M should not exceed 60°C, and the reduced ash BC should not exceed 70°C. When the coloring temperature of vat dyes containing blue anthrone structures exceeds 80°C, they are prone to mutation. The temperature must be strictly controlled or 2g/L glucose or 0.1-0.3g/L nitrous acid must be added to the dye bath. sodium.
Now the high-temperature coloring process, prescription, etc. are introduced as follows.
① Dyeing machine model and specifications: GR-73 high temperature and high pressure dyeing machine, capacity 780L, the yarn used for dyeing is 14 packs of 14.58tex pure cotton bleached bottom yarn.
②Process flow: bleach the bottom yarn, straighten it, straighten it, put it in a cage and wet it with water (90℃×10min) → color → wash → oxidize (use flat and add O 20g) → soap cooking (fat soap 1g/L + soda ash 0.5g/L, 85℃×10min)→wash→out of cage→wash→dehydrate→dry
③Coloring prescription: See Table 4-11.
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Light beige
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Bright yellow
|
||
Dyes and Auxiliaries
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Yu Tank
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Dye pot
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Dry cylinder
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Dye pot
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Ping Ping plus O／g
|
|
20
|
|
20
|
Leveling agent OP-10/g
|
|
400
|
|
400
|
Temperature／℃
|
55
|
80
|
60
|
80
|
Time／min
|
15
|
20
|
15
|
20
|
④Operating requirements: When preparing the dye bath, first add caustic soda to the dye solution. When the temperature rises to 75°C, the scum must be skimmed off in time. When the temperature rises to 80°C, add 1/3 of the specified amount of insurance powder and add the pre-reduced dry powder. Strain the vat dye into the dye vat, add additives and the remaining 1/3 of the insurance powder to dye. During the dyeing process, the flow direction of the dye solution should be constantly changed, mainly from the inside to the outside, to facilitate even dyeing. After dyeing, draining, washing, oxidation and post-treatment require consistent processes.
AAAEHRYJUTUTHYER
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20
15
20
④Operating requirements: When preparing the dye bath, first add caustic soda to the dye solution. When the temperature rises to 75°C, the scum must be skimmed off in time. When the temperature rises to 80°C, add 1/3 of the specified amount of insurance powder and add the pre-reduced dry powder. Strain the vat dye into the dye vat, add additives and the remaining 1/3 of the insurance powder to dye. During the dyeing process, the flow direction of the dye solution should be constantly changed, mainly from the inside to the outside, to facilitate even dyeing. After dyeing, draining, washing, oxidation and post-treatment require consistent processes.
AAAEHRYJUTUTHYER
Disclaimer:
Disclaimer: Some of the texts, pictures, audios, and videos of some articles published on this site are from the Internet and do not represent the views of this site. The copyrights belong to the original authors. If you find that the information reproduced on this website infringes upon your rights, please contact us and we will change or delete it as soon as possible.
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