1. Production and removal of oligomers
1. Definition
Oligomers are also called Polymers, oligomers, and short polymers are low-molecular substances with the same chemical structure as polyester fibers that exist inside polyester fibers. They are by-products in the polyester spinning process. Generally, polyester contains 1% to 3% oligomers.
Oligomers are polymers composed of fewer repeating units, and their relative molecular mass is between small molecules and macromolecules. The English word “oligomer” comes from the Greek word oligo, which means “some”. Most polyester oligomers are cyclic compounds formed by three ethyl terephthalates.
2. Influence
The influence of oligomers: color spots and stains are produced on the cloth surface; yarn dyeing produces white color powder.
When the temperature exceeds 120°C, oligomers can dissolve in the dye bath and crystallize out of the solution, combining with the condensed dye. When cooled, it deposits on the surface of machinery or fabrics, causing defects such as stains and spots. Disperse dye dyeing is generally maintained at 130°C for about 30 minutes to ensure the dyeing depth and fastness. Therefore, as a solution, light colors can be kept at 120°C for 30 minutes, while dark colors must be pre-treated before dyeing. In addition, dyeing under alkaline conditions is also an effective method to resolve oligomers.
3. Comprehensive measures
Specific treatment measures:
1. Use 100 %NaOH3%. Surface active detergent 1%. Treat at 130°C for 60 minutes with a liquor ratio of 1:10~1:15. The pre-dyeing treatment method has a certain corrosive effect on the polyester fiber, but it is extremely beneficial for removing oligomers. For polyester filament fabrics, “aurora” can be reduced, and for short fibers, the pilling phenomenon can be improved.
2. Control the dyeing temperature below 120°C and use appropriate carrier dyeing methods to reduce the production of oligomers and achieve the same dyeing depth.
3. Adding dispersing protective colloid additives during dyeing can not only produce a level dyeing effect, but also prevent oligomers from settling on the fabric.
4. After dyeing, the dye liquid is quickly discharged from the machine at high temperature, and the discharge time is up to 5 minutes. Because oligomers are evenly distributed in the dye liquor at a temperature of 100 to 120°C, they tend to accumulate and precipitate on the dyed material when the temperature is below 100°C. However, some heavy fabrics are prone to wrinkles.
5. Dyeing under alkaline conditions can effectively reduce the formation of oligomers and remove residual oil on the cloth surface, but 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, insurance powder 3-4g/L, treat at 70℃ for 30 minutes, then cold wash, hot wash, Wash cold and neutralize with acetic acid.
4. For yarn white powder
1) The thorough method is the high-temperature drainage method.
For example, open the drain valve immediately after the constant temperature of 130°C (120°C is also acceptable, but it cannot be lower, because 120°C is the transition point of polyester glass).
●Although it seems very simple, in fact, the most important issue is safety, which is the most difficult: the sound and mechanical vibration at the moment of high-temperature discharge are alarming, and aging machinery is prone to vibration or cracking of screws. If the dyeing machine is loose or mechanically cracked, the dyeing machine will explode (pay special attention).
●If you want to modify it, it is best to go to the original machinery factory to design and modify it. Do not treat human life as a trivial matter.
●There are two methods of draining liquid: into the water tank and into the atmosphere.
●Pay attention to the backflush phenomenon after the discharge is completed (experienced dye vat manufacturing companies know this very well).
●High-temperature liquid drainage has the advantage of shortening dyeing, but it is very troublesome for factories with poor reproducibility
2) For factories that cannot high-temperature liquid drainage, you can Use Oligomer detergent to replace detergent in the restoration cleaning process, but the effect is not 100%
●After dyeing, wash the tub frequently. For medium and dark colors, wash the tub once after about 5 tubs.
●If the current liquid flow dyeing machine has a lot of white powder dirt, the first priority is to clean the tank.
5. Some people think that table salt is cheaper.
Some people think that table salt is cheaper. Table salt can be used. Daiyuan Mingfen. But for light colors, Yuan Ming powder is better than table salt, and for dark colors, table salt is better. Whatever is appropriate must be tested before application.
6. The relationship between the dosage of Yuanming powder and salt
The relationship between the dosage of Yuanming powder and salt is roughly as follows: 6 servings Anhydrous Na2SO4 = 5 parts NaCl 12 parts hydrated Na2SO4·10H20 = 5 parts NaCl
2. Solutions to the causes of colored flowers
Previously, WeChat specifically talked about the issue of fastness as the most frequently asked question in Dyers Without Borders, and the color flower issue as the second most asked question in Dyers Without Borders: Here is a comprehensive summary of color flowers, one The first is the reason, the second is the solution, and the third is the relevant information.
1. The combined reasons are:
1 Process formulation and operation issues:
Formulation Unreasonable process or improper operation produces color flowers;
Unreasonable process (such as raising and lowering the temperature too quickly)
Poor operation, knotting during dyeing, and power outage during dyeing;
The temperature rises too fast and the holding time is not enough;
The scouring water cannot be washed cleanly, and the PH value of the cloth surface is uneven;
The gray cloth contains a large amount of oil slurry, and it has not been completely washed after scouring. Clear;
The uniformity of the pre-treatment cloth surface
2 Equipment problems:
Equipment failure
eg. After polyester is dyed with disperse dyes, uneven temperatures in the oven of the heat setting machine can easily cause color differences and flakes. Insufficient pump power of the rope dyeing machine can also easily cause chromatic flakes.
The dyeing capacity is too large and too long;
The dyeing machine runs slowly;
The circulation system is clogged and the flow rate is too high.�When proposing specific wash fastness indicators, if specific testing standards can be proposed, it will facilitate smooth communication between the two parties. Although strengthening washing and post-processing can improve the washing fastness of fabrics, it will also increase the emission reduction of dyeing plants. Finding some efficient detergents, rationally formulating dyeing and finishing processes, and strengthening research on short-process processes can not only improve production efficiency, but also contribute to energy conservation and emission reduction.
Rubbing fastness: The rubbing fastness of fabric is the same as the washing fastness, and also includes two aspects: one is dry rubbing fastness, and the other is wet rubbing fastness. Obtain the physical sample cards of the dry rubbing fastness and wet rubbing fastness of the fabric through the detection of the fabric rubbing fastness testing instrument, and compare the fabric discoloration sample card and staining sample card to test the dry rubbing fastness and wet rubbing fastness of the textile. Very convenient.
Usually when testing the rubbing fastness of deep-colored textiles, the dry rubbing fastness grade is generally about 1 grade higher than the wet rubbing fastness grade. Take the black cotton fabric dyed with direct dyes as an example. Although it has undergone effective color fixation treatment, the dry rubbing fastness and wet rubbing fastness levels are not very high, and sometimes it cannot meet customer requirements. In order to improve the rubbing fastness, reactive dyes, vat dyes and insoluble azo dyes are mostly used for dyeing. Strengthening dye screening, strengthening color fixation treatment and soaping are effective measures to improve the rubbing fastness of textiles.
In order to improve the wet rubbing fastness of deep-colored cellulose fiber products, you can choose additives that can specifically improve the wet rubbing fastness of textiles. This can be significantly improved by padding special additives when finalizing the finished product. Improve the wet rubbing fastness of the product. For dark-colored chemical fiber filament products, the wet rubbing fastness of the product can be improved by adding a small amount of fluorine-containing waterproofing agent when finalizing the finished product.
When using acid dyes to dye polyamide fibers with deep colors, the use of special fixatives for nylon can significantly improve the wet rubbing fastness of nylon fabrics with deep colors. For sanded dark-colored products, when testing their wet rubbing fastness, since the shedding of short fibers on the surface of the fabric of sanded products will be more obvious than other products, the wet rubbing fastness grade may be reduced.
Sunlight fastness: Sunlight has wave-particle duality, and sunlight that transfers energy in the form of photons has a strong impact on the molecular structure of the dye. When the basic structure of the color-producing part of the dye structure is destroyed by photons, the color of the light emitted by the dye color body will change, usually becoming lighter in color until it is colorless. The more obvious the color change of the dye is under sunlight conditions, the worse the light fastness of the dye is. In order to improve the light fastness of the dye, dye manufacturers have adopted many methods.
Increasing the relative molecular weight of the dye, increasing the opportunity for internal complexation of the dye, increasing the coplanarity and length of the conjugated system of the dye can relatively improve the light fastness of the dye. For phthalocyanine dyes that can reach level 8 light fastness, adding appropriate metal ions during the dyeing and finishing process to form complexes within the dye molecules can significantly improve the dye’s brightness and light fastness. Spend.
For textiles, choosing dyes with better light fastness is the key to improving the light fastness grade of the product. The effect of improving the light fastness of textiles by changing the dyeing and finishing process is not obvious.
Sublimation fastness: As far as disperse dyes are concerned, since the dyeing principle of polyester fiber is different from other dyes, sublimation fastness can directly express the heat resistance of disperse dyes. For other dyes, testing the ironing fastness of the dye has the same meaning as testing the sublimation fastness of the dye. The sublimation fastness of dyes is not good. Under dry heat, the solid dyes can easily detach directly from the inside of the fiber in a gaseous state. So in this sense, the sublimation fastness of dyes can also indirectly express the ironing fastness of fabrics.
In order to improve the sublimation fastness of dyes, we must start from the following aspects:
The first is the selection of dyes: the relative molecular mass is larger, and the basic structure of the dye is similar to the fiber structure. or similar, can improve the sublimation fastness of textiles.
The second step is to improve the dyeing and finishing process: fully reduce the crystallinity of the crystalline part of the fiber macromolecular structure, increase the crystallinity of the amorphous region, and make the crystallinity of the various regions inside the fiber consistent. After the dye enters the inside of the fiber, it will be more evenly combined with the fiber. This can not only improve the leveling degree, but also improve the sublimation fastness of dyeing. If the crystallinity of each part inside the fiber is not balanced enough and most of the dye stays in the amorphous area with a relatively loose structure, then after extreme external conditions occur, the dye will be more likely to break away from the amorphous area inside the fiber and sublime to the surface of the fabric. , thereby reducing the sublimation fastness of textiles.
The scouring and mercerization of cotton fabrics, and the pre-shrinking and pre-shaping of polyester fabrics are all processing steps that balance the crystallinity within the fiber. The dyeing depth and color fastness of cotton fabrics that have been scoured and mercerized, and polyester fabrics that have been preshrunk and pre-shaped can be significantly improved.
Strengthening post-processing and washing to remove more floating colors on the surface can also significantly improve the sublimation fastness of the fabric. Appropriately lowering the setting temperature during the setting process can significantly improve the sublimation fastness of the fabric. The problem of reduced fabric dimensional stability due to cooling can be compensated by appropriately reducing the setting speed. When selecting finishing agents, you should also pay attention to the impact of auxiliaries on dye fastness. For example, after using cationic softeners for soft finishing of polyester fabrics, the thermal migration of disperse dyes may cause the disperse dyes to fail the sublimation fastness test. Judging from the temperature type of disperse dyes themselves, high-temperature disperse dyes have better sublimation fastness.
The problem of �� can be compensated by appropriately reducing the set speed. When selecting finishing agents, you should also pay attention to the impact of auxiliaries on dye fastness. For example, after using cationic softeners for soft finishing of polyester fabrics, the thermal migration of disperse dyes may cause the disperse dyes to fail the sublimation fastness test. Judging from the temperature type of disperse dyes themselves, high-temperature disperse dyes have better sublimation fastness. </p
