Three common technical problems in dyeing and finishing

Comprehensive measures
Specific treatment measures:
1. 100% naoh3% is used for grey cloth before dyeing. Surface active detergent l%. After treatment at 130 ℃ for 60 min, the bath ratio is 1:10 ~ 1:15. The pretreatment method has a certain erosion effect on polyester fiber, but it is very beneficial to remove oligomers. The "Aurora" can be reduced for polyester filament fabrics, and the pilling phenomenon can be improved for medium and short fibers.
2. Controlling the dyeing temperature below 120 ℃ and using appropriate carrier dyeing method can reduce the production of oligomers and obtain the same dyeing depth.
3. Adding dispersive protective colloid additives during dyeing can not only produce leveling effect, but also prevent oligomer from precipitating on the fabric.
4. After dyeing, the dye solution shall be rapidly discharged from the machine at high temperature for a maximum of 5 minutes. Because oligomers are evenly distributed in the dyeing solution at the temperature of 100-120 ℃, when the temperature is below 100 ℃, they are easy to accumulate and precipitate on the dyed products. However, some heavy fabrics are easy to form wrinkles.
5. Dyeing under alkaline conditions can effectively reduce the formation of oligomers and remove the residual oil on the cloth. However, dyes suitable for dyeing under alkaline conditions must be selected.
6. After dyeing, wash with reducing agent, add 32.5% (380be) NaOH 3-5ml / L, sodium sulfate 3-4g / L, treat at 70 ℃ for 30min, then wash cold, hot and cold, and neutralize with acetic acid.

For yarn white powder
1. The thorough method is the high-temperature drainage method.
For example, opening the drain valve immediately after the constant temperature of 130 ° C is completed (120 ° C is OK, but it cannot be lower, because 120 ° C is the conversion point of polyester glass).
● Even so, it seems very simple. In fact, the most important thing is the most difficult problem of safety: the sound and mechanical vibration at the moment of high-temperature liquid discharge is amazing, the aging machinery is easy to crack or loosen the screws, and the mechanical crack dyeing machinery will explode (special attention).
● If you want to modify, you'd better go to the original machinery factory to design the modification. You can't take human life as a trifle.
● There are two kinds of drainage methods: drainage to the water tank and drainage to the atmosphere.
● Pay attention to the back flushing phenomenon after discharge (the experienced dye cylinder manufacturing company knows very well).
● High temperature drainage has the advantage of shortening dyeing, but it is difficult for factories with poor reproducibility.

2. For factories that cannot discharge liquid at high temperature, oligomer detergent can be used to replace the detergent in the reduction cleaning project, but the effect is not 100%
● wash the cylinder frequently after dyeing, and wash the cylinder once after about 5 cylinders of medium and dark colors.
● If there is a large amount of white dust on the current liquid flow dyeing machine, the first priority is to wash the cylinder.

Some also think that salt is cheaper
Some people also think that the price of salt is relatively cheap, and salt can be used instead of Yuanming powder. However, it is better to dye light colors with sodium hydroxide than with salt, and it is better to dye dark colors with salt. Whatever is appropriate must be tested before application.

6. Relationship between dosage of the sodium hydroxide and salt
The relationship between the amount of sodium hydroxide and the amount of salt is as follows:
6 parts anhydrous Na2SO4 = 5 parts NaCl
12 parts of hydrate Na2SO4 · 10h20 = 5 parts of NaCl
Reference materials: 1. Discussion on preventing dyeing spots and spots of polyester knitted fabrics by Chen Hai, Zhu Minmin, Lu Yong and Liu Yongsheng 2. Help for polyester yarn white powder problem by Se Lang.

Causes and solutions of colored flowers
Previously, WeChat specifically talked about the fastness problem, which was the most frequently asked question of Dyers without borders, while the color flower problem was the second most asked question among dyers without borders: the following is a comprehensive arrangement of color flowers, first, the reasons, second, the solutions, and third, the relevant information.

Taken together, the reasons are:
1. Process formulation and operation problems:
Unreasonable formulation process or improper operation will produce color flowers;
Unreasonable process (such as too fast temperature rise and fall)
Poor operation, knotting during dyeing and power failure during dyeing;
Too fast temperature rises and insufficient holding time;
The scouring water is not clean, and the pH value of the cloth surface is uneven;
The oil slurry of the embryonic cloth is large and has not been completely removed after scouring;
Uniformity of pretreatment cloth surface.

2. Equipment problems
Equipment failure
For example, the temperature difference in the oven of the heat setting machine after dyeing polyester with disperse dyes is easy to produce color difference and color flowers, and the insufficient pumping force of the rope dyeing machine is also easy to produce color flowers.
The dyeing capacity is too large and too long;
The dyeing machine runs slowly; A dyed man has no boundaries
The circulation system is blocked, the flow rate is too slow, and the nozzle is not suitable.

3. Raw materials
Uniformity of fiber raw materials and fabric structure.

4. Dye problems
The dyes are easy to aggregate, poor solubility, poor compatibility, and are too sensitive to temperature and pH, which are easy to produce color flowers and color differences. For example, reactive turquoise KN-R is easy to produce color flowers.
Dyeing reasons include poor levelness of dyes, migration of dyes during dyeing and too fine fineness of dyes.

5. Water quality problems
Poor water quality causes the combination of dyes and metal ions or the aggregation of dyes and impurities, resulting in color blooming, light color and no sample.
Improper adjustment of pH value of dyeing bath.

6. Auxiliary problems
Improper dosage of additives; Among the auxiliaries, the auxiliaries related to color flower mainly include penetrant, leveling agent, chelating dispersant, pH value control agent, etc.
Solutions for various colors and flowers
Unevenly cooked flowers are made into colored flowers.
Uneven scouring and uneven removal of impurities on the fabric make the moisture absorption rate of the fabric part different, resulting in color flowers.

Measures
1. The scouring auxiliaries shall be quantitatively injected in batches, and the auxiliaries shall be completely filled. The effect of hydrogen peroxide injection at 60-70 degrees is better.
2. The cooking heat preservation time must be strictly in accordance with the process requirements.
3. The heat preservation shall be continued for a period of time for the dead cloth wrapping treatment.
The scouring water stain is not clear, and the embryonic cloth is stained with alkali, resulting in colored flowers.

Measures
After washing water, i.e., after 10% glacial acetic acid is mixed with residual alkali, wash water again to make the cloth surface ph7-7.5.
 The residual oxygen on the cloth surface is not cleaned after cooking.

Measures
At present, most of them are deaerated with deaerator auxiliaries. In normal procedures, glacial acetic acid is injected quantitatively for 5 minutes, the temperature is raised to 50 ° C for 5 minutes, the deaerator is injected quantitatively with clean water, the temperature is maintained for 15 minutes, and the water sample is taken to measure the oxygen content.
Uneven chemical materials and insufficient dye dissolution cause color blooming.

Measures
First stir in cold water, then dissolve in warm water. Adjust the chemical temperature according to the dye properties. The chemical temperature of normal reactive dyes should not exceed 60 ° C. special dyes should be cooled, such as brilliant blue br_ v. Separate chemical materials can be used, which must be fully stirred, diluted and filtered.

The adding speed of dye promoter (sodium hydroxide or salt) is too fast.

Consequence
Too fast will lead to dye promoters on the surface of the rope like fabric, with different concentrations, resulting in different dye promoters on the surface and inside, and forming color flowers.

Measures
1. The dye shall be added in batches, and each addition shall be slow and uniform.
2. The batch addition should be less than the first time and more than the second time. The interval between each addition is 10-15 minutes to make the dye promotion uniform.
Color fixing agent (alkali agent) is added too quickly and too much, resulting in color blooming.

Measures
1. The normal dropping alkali shall be injected in three times, with the principle of less first and more later. The first dosage is 1% 10. The second dosage is 3% 10. The last dosage is 6% 10.
2. Each addition shall be slow and uniform.
3. The temperature rise speed should not be too fast. The difference in the surface of the rope fabric will cause the difference in the color absorption rate and the color will be flowered. Strictly control the heating rate (1-2 ℃ / min) and adjust the steam volume on both sides.
 The bath ratio is too small, resulting in color difference and color flower.
Now many factories are air cylinder dyeing equipment,
Measures: master the water quantity according to the process requirements.

Soap wash color flower.
The washing water after dyeing is not clear, the pH content is high during soaping, and the temperature rises too fast to produce colored flowers. After the temperature rises to the specified temperature, it shall be kept for a certain time.

Measures:
The washing water is clean and neutralized with acid soaping agent in some factories. It should be run in the dyeing machine for about 10 minutes, and then the temperature should be raised. If it is convenient for sensitive colors such as lake blue and color blue, try to test the pH before soaping.

Of course, with the emergence of new soaps, there are low - temperature soaps on the market, which is another matter
The washing water in the dyeing bath is not clear, resulting in color flowers and spots.
After soaping, the residual liquid is not washed clearly, which makes the concentration of residual color liquid on the surface and inside of the fabric different, and it is fixed on the fabric to form color flowers during drying.

Measures:
After dyeing, wash with enough water to remove floating color.
Color difference (cylinder difference, stripe difference) caused by color addition.
1. Causes of color difference
A. The feeding speed is different. If the amount of dye promotion is small, it will affect whether it is added in several times. For example, if it is added in one time, the time is short, and the dye promotion is insufficient, resulting in color blooming.
B. Uneven rubbing on both sides of the feeding, resulting in strip difference, such as darker on one side and less light on the other side.
C. Holding time
D. Color difference is caused by different methods of color cutting. Requirements: cut samples and match colors in the same way.
For example, after 20 days of heat preservation, the samples are cut for color matching, and the washing degree after cutting is different.
E. The color difference is caused by different bath ratios. Small bath ratio: color depth large bath ratio: color light
F. The degree of post-treatment is different. After treatment is sufficient, floating color removal is sufficient, and the color is lighter than that of insufficient after treatment.
G. There is a temperature difference between the two sides and the middle, resulting in a strip difference
The color addition should be slow, at least 20 minutes for quantitative injection, and 30-40 minutes for sensitive color.

2. Feeding and color tracing.
1) Color light condition:
A. First, check the original process prescription and weigh the dye according to the degree of color difference and the weight of the fabric.
B. The color chasing dye must be sufficiently dissolved, diluted and used after filtration.
C. The color tracing corresponds to feeding under normal temperature, and the feeding is slow and uniform, so as to prevent the operation from being too fast and causing re color.
2) Color depth condition
A. Strengthen soaping and adequate post-treatment.
B. Add Na2CO3 for slight decolorization.
The above content is a comprehensive collection of "dyers", "dyers without borders", and network information, and is compiled by dyers without borders. Please indicate if you reprint it.
3. Color fastness
According to dyebbs According to the statistics of. Com, fastness is the most frequently asked question among all dyeing questions. Dyeing fastness requires high quality of dyed and printed fabrics. The nature or degree of dyeing state variation can be expressed by dyeing fastness. It is related to yarn structure, fabric structure, printing and dyeing method, dye type and external force. Different requirements for color fastness will cause great differences in cost and quality.
1. Six main textile fastness
1. Fastness to sunlight
Sun fastness refers to the degree of discoloration of colored fabrics by sunlight. The test method can be sunlight exposure or sunlight machine exposure. The fading degree of the sample after exposure to sunlight is compared with the standard color sample, which is divided into 8 levels, 8 levels are the best and 1 level is the worst. Fabrics with poor sun fastness should not be exposed to the sun for a long time, and should be placed in a ventilated place to dry in the shade.
2. Rubbing fastness
Rubbing fastness refers to the degree of color loss of dyed fabrics after rubbing, which can be divided into dry rubbing and wet rubbing. The rubbing fastness is evaluated based on the staining degree of white cloth, which is divided into 5 levels (1-5). The larger the value, the better the rubbing fastness. The service life of fabrics with poor rubbing fastness is limited.
3. Washing fastness
Water washing or soaping fastness refers to the degree of color change of dyed fabric after washing with washing liquid. Generally, the gray grading sample card is used as the evaluation standard, that is, the color difference between the original sample and the sample after fading is used for evaluation. Washing fastness is divided into 5 grades, grade 5 is the best and grade 1 is the worst. Fabrics with poor washing fastness should be dry cleaned. If wet cleaning is carried out, double attention should be paid to the washing conditions, such as the washing temperature should not be too high and the washing time should not be too long.
4. Ironing fastness
Ironing fastness refers to the degree of discoloration or fading of dyed fabrics during ironing. The degree of discoloration and fading is evaluated by the staining of the iron on other fabrics at the same time. Ironing fastness is divided into grade 1-5, grade 5 is the best and grade 1 is the worst. When testing the ironing fastness of different fabrics, the iron temperature should be selected.
5. Perspiration fastness
Perspiration fastness refers to the degree of discoloration of dyed fabrics after being soaked in perspiration. The perspiration fastness is generally tested in combination with other color fastness in addition to the separate measurement because the artificial perspiration components are different. Perspiration fastness is divided into 1-5 grades, and the larger the value, the better.
6. Sublimation fastness
Sublimation fastness refers to the degree of sublimation of dyed fabrics during storage. The degree of color change, fading and white cloth staining of the fabric after dry hot-pressing treatment is assessed by gray grading sample card for sublimation fastness. It is divided into 5 grades, with grade 1 being the worst and grade 5 being the best. The dyeing fastness of normal fabrics is generally required to reach grade 3-4 to meet the wearing needs.
2. How to control various fastness
After dyeing, the ability of fabric to keep its original color can be expressed by testing various color fastness. The commonly used indicators for testing the dyeing fastness include the washing fastness, rubbing fastness, sunlight fastness, sublimation fastness and so on.
The better the washing fastness, rubbing fastness, sunlight fastness and sublimation fastness of the fabric, the better the dyeing fastness of the fabric.
The main factors affecting the above fastness include two aspects:
The first is the performance of dyes
The second is the formulation of dyeing and finishing process
The selection of dyes with excellent performance is the basis for improving the dyeing fastness, and the formulation of a reasonable dyeing and finishing process is the key to ensure the dyeing fastness. The two complement each other and cannot be neglected.

Washing fastness
The washing fastness of fabrics includes color fastness to fading and color fastness to staining. Generally, the worse the color fastness of textiles, the worse the color fastness to staining. When testing the color fastness of a textile, the color fastness of the fiber can be determined by testing the color fastness of the fiber to the six commonly used textile fibers (these six commonly used textile fibers usually include polyester, nylon, cotton, acetate, wool, silk, and acrylic).

The tests on the color fastness of six kinds of fibers are generally carried out by an independent professional inspection company with qualification, which is relatively objective and fair.) for cellulose fiber products, the water fastness of reactive dyes is better than.