Disperse dyes are a kind of dyes with small molecules and no water soluble groups in structure.When dyeing, it must use dispersant to disperse the dye evenly in the dye solution to dye polyester and other fibers.
Disperse dyes have small molecules and do not containWater soluble group, with the help ofdispersantThe role ofdye liquorIn uniform dispersiondyeing。It can be dyedpolyester，Acetate fibreandPolyamide fibre, becoming a special dye for polyester.
Disperse dyes can be roughly divided intoDisperse orange、Disperse blue、Disperse yellow、Disperse redComposition, several different disperse dyes can be matched in a certain proportion to obtainDisperse black、Disperse green、Disperse violetAnd other disperse dyes.
Disperse dyes In the process of commercial processing, in order to quickly disperse the commercial dyes in water into a uniform and stable colloidal suspension, dye particlesfinenessIt must reach about 1 μ m atSandingAdd dispersant andWetting agentThe post-processing of disperse dyes generally includes sanding, seasoningspray drying Packaging composition.Many are used in post-processing processingauxiliary, such asLignin、MF、Anti settling agent（SOS）、Dustproof agent、Dispersant NNO, plusSodium sulfateAdjust the intensity.
A dye that is slightly soluble in water and highly dispersed in water by the action of dispersant.Disperse dyes do not contain water soluble groups and have low molecular weight. Although the molecules contain polar groups (such as hydroxyl, amino, hydroxyalkane amino, cyanalkane amino, etc.), they are still non-ionic dyes.This kind of dye requires high post-treatment requirements. It can be used only after it is grinded by a grinder in the presence of dispersant and becomes highly dispersed and crystal stable particles.The dye solution of disperse dyes is a uniform and stable suspension.Disperse dyes were produced by Germany in 1922BadenAniline soda company started production, mainly used forpolyesterandAcetate fibreStaining of.At that time, it was mainly used for dyeing acetate fiber.After the 1950s, with the emergence of polyester fiber, it has developed rapidlyDyestuff industryThe major categories of products in.
classification
Disperse dyes (see table)
Disperse dye
According to the molecular structure, it can be divided into azo type, anthraquinone type and heterocyclic type. They are named according to certain principles (see dyes)Dye Index(C.I. for short). ①The azo type has a complete range of chromatographic agents, including yellow, orange, red, purple, blue and other colors.Azo disperse dyes can beazo dyeThe synthetic method is simple in process and low in cost. ②Anthraquinone type has red, purple, blue and other colors. ③Heterocyclic dyes are newly developed dyes with bright colors.The production process of anthraquinone and heterocyclic disperse dyes is complex and the cost is high.
classification
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Disperse dyes can be divided into low temperature type, medium temperature type and high temperature type according to their heat resistance in application.
Low temperature dye
It has low sublimation fastness, good levelness and is suitable for exhaustion dyeing. It is often called E-type dye;
High temperature dyes
High sublimation fastness, but poor levelness, suitable for hot meltingdyeing, called S-type dye;
Intermediate temperature dye
The sublimation fastness is between the above two, also known as SE dye.
Use disperse dyes topolyester fiberWhen dyeing, dyes should be selected according to different dyeing methods.
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The disperse dye has a simple structure and a non-ionic state with very low solubility in water. In order to make the dye disperse well in solution, in addition to grinding the dye particles to below 2 μ m, a large amount of dispersants should be added to make the dyeSuspensionIt is stably dispersed in solution.
Operation method
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becausepolyesterWith strong hydrophobicity, high crystallinity and alignment, small fiber micro gap and difficult wettingPuffingIt is difficult to use conventional methods to make dyes enter the fiber in the form of single molecules to finish the dyeing of polyester. Therefore, special dyeing methods are required.The methods used include carrier method, high temperature and high pressure method and high temperature and hot solution method.These methods make use of different conditions to expand the fiber and increase the interspace between fiber molecules. At the same time, additives are added to improve the diffusion rate of dye molecules, so that dye molecules can continue to diffuse into the expanded and enlarged fiber interspace, and they are fixed with the fiber by intermolecular gravity and hydrogen bond to complete the dyeing of polyester.Because the solubility of disperse dyes in water is extremely low, the dye solution is composed of dyes and dispersants in the solution.To prevent disperse dyes and polyester fibers from producing under high temperature and alkalihydrolysisDisperse dyes are often dyed under weak acid conditions.[2]
1. Carrier staining
The carrier dyeing method is heated under normal pressure.It uses some chemicals that are direct to dyes and fibers. When these chemicals enter the polyester fiber during dyeing, they also carry dye molecules into it. This chemical is called carrier or dye carrier.
The principle of dyeing polyester with carrier isbenzeneThere is a large intermolecular attraction between the ring and the aromatic nucleus in the dye molecule, and polyester can absorb simplehydrocarbonClassphenolThese chemicals become carriers.Because of the interaction between the carrier and polyester, the molecular structure of polyester is relaxed, the fiber gap is increased, and the molecules are easy to enter the fiber.At the same time, because the carrier itself can generate direct attraction with fibers and dye molecules, it can not only help to dissolve dyes, bring dye molecules to the fiber surface, increase the concentration of dyes on the fiber surface, but also reduce thesurface tensionThe moving dye molecules can quickly enter the fiber gap area, improve the diffusion rate of dye molecules, promote the combination of dyes and fibers, and complete the dyeing process.After dyeing, use alkali washing to completely remove the carrier.Common carriers areO-phenylphenol, biphenylsalicylic acidMethyl esters are rarely used because they are toxic and harmful to human body, so they are only introduced here in general.
2. High temperature and high pressure dyeing
High temperature and high pressure dyeing is carried out under high temperature and pressure.The dye uptake rate is very slow within 100 ℃. Even if the dye is dyed in boiling dyeing bath, the uptake rate and percentage are not high, so the pressure must be below 2 atm (2.02 × 105 Pa). The dyeing bath temperature can be raised to 120~130 ℃. As the temperature increases, the chain segments of fiber molecules move violently, resulting in instantaneousporeThe more and more, the faster the diffusion of dye molecules at this time, increasing the diffusion rate of dye to the interior of the fiber, so that the dyeing rate is accelerated until the dye is absorbed and the dyeing is completed.
High temperature and high pressure dyeing of disperse dyes is an important method, which is suitable for low-temperature dyes with low sublimation fastness and small molecular weight.This kind of dyes has good levelness, bright color, good hand feel, and high degree of core penetration. It is suitable for small batch and multi variety production, and is commonly used for dyeing polyester cotton blended fabrics.
High temperature and high pressure dyeing of disperse dyesJiggerAnd injectionOverflow dyeing machine It is suitable for deep color dyeingPH valueGenerally controlled at 5~6, commonly usedacetic acidandAmmonium dihydrogen phosphateTo adjust the pH value.In order to keep the dyeing bath stable, dispersants andHigh temperature leveling agent。
Examples of dyeing process of overflow dyeing machine:
Gray cloth sewing head → pretreatment → dyeing → reduction cleaning → hot water washing → water washing → dehydration cloth spreading → setting.Generally, it can be dyed at 60~70 ℃, gradually heated to 130 ℃ after about 1h, dyed for about 1h, and then fully washed.The color fastness of the dyed product can be maintained by reduction cleaning when dyeing medium dark colors.
3. Hot melt dyeing
Dyeing polyester/cotton fabric with disperse dyes by hot-melt method is similar to that of ordinary dip pad dyeing, which is first treated with dip pad dye solution and then dried, followed by hot-melt treatment.Under the high temperature of 200 ℃, the dye deposited on the fabric can diffuse into the fiber in the form of single molecule, and the dyeing of polyester can be completed in a very short time.If it is polyester cotton blended fabric, the dye on the cotton can be transferred topolyester fiberOn.Hot melt dyeing is the main method of dyeing polyester/cotton blended fabric, which is mainly continuous pad dyeing production, with high production efficiency, especially suitable for mass production.The disadvantage of hot-melt dyeing is that the equipment occupies a large area, and there are certain restrictions on the dyes used. The utilization rate of dyes is lower than that of high-temperature high-pressure dyeing.
Examples of hot-melt dyeing process are as follows (45 × 45 counts, light blue, 65/35 polyester/cotton fine textiles):
(Two dip and two rolling, rolling surplus 65%, room temperature) → pre drying (8O~120 ℃) → hot melting (180~210 ℃, 2~1min) → cotton over dyeing.
In high temperature hot-melt dyeing, attention should be paid to prevent the generation of dyes in pre drying and bakingmigration The hot melt baking stage is an important stage for the transfer of disperse dyes from cotton to polyester. Appropriate hot melt temperature and time should be selected according to the heat resistance of dyes, that is, the sublimation fastness of dyes.In actual dyeing, the transfer of dyes cannot be complete. There is always a part of dyes left on the cotton, causing cotton staining, which can be treated by reduction cleaning or soaping after dyeing.If the cotton part is to be overprinted after the hot melt dyeing, the line can be selected for post-treatment after overprinting.
Main applications
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The main purpose of disperse dyes is toChemical fibreInpolyester(Polyester)acetate fibre(diacetate fiber, triacetate fiber) andPolyamide fibre(nylon)polyacrylonitrile(Acrylic fiber) also has a small number of applications.The chemical fiber textile products printed and dyed with disperse dyes have bright colors, excellent washing fastness and wide applications.Because it is insoluble in waterNatural fiberThe cotton, hemp, wool and silk in theViscose fibreIt is also almost non staining, so chemical fiber blended products usually need to use disperse dyes in combination with other applicable dyes.[3]
Development prospect
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New progress has been made in the use of disperse dyes: ① multi-component disperse dyes are usually mixed by two (or three or four) disperse dyes in a certain proportion, and the dye uptake is improved due to the synergistic effect of the dyes. ②In transfer printing, disperse dyes are made into printing ink, printed on the fabric, and then pressed and dyed at high temperature.This process, also known as non-aqueous printing, has the advantages of energy saving, time saving and convenience. ③Disperse dyes andReactive dyeMixed use can makepolyester cotton, polyester viscose and other blended fabrics are dyed in one bath and one step, which simplifies the printing and dyeing process and improves the printing and dyeing quality.[4]
