Why is it difficult to deal with high fastness of disperse dyeing?

The effect of disperse dye dyeing on the heat transfer of disperse dyes is not the redistribution of dyes in the two phases of fiber and surface solvent, but its inherent physical characteristics, which also results in the decrease of color fastness and color variation in dry heat treatment of polyester fabrics after dyeing. Key factors: by analyzing the dyeing temperature, heat treatment temperature and time, the influence of dye sublimation, surfactant and finishing agent, dyeing method and heat setting on the heat transfer of dyes, the pre dyeing high temperature pre-determined, non-contact hot air drying and low temperature soft drying process under 130 ℃ and low temperature slow resin finishing process are adopted as much as possible, The effect of heat transfer of dyes is controlled to a minimum. Polyester fabrics (pure polyester fabrics or polyester cotton, polyester viscose and other interwoven and blended fabrics) are dyed with disperse dyes (especially the deep color is dyed by high temperature and high pressure method), and after dry heat treatment at 130 ℃, such as after dyeing, such as heat drawing setting and resin baking, there are usually different changes in the following three aspects, such as the dyeing fastness (soap washing, friction, sun exposure) is obviously reduced, Generally, the medium dark color decreased by 0.5-1.5; The color light of cloth surface changed to different degrees; The pollution of the cotton adhesive components will increase significantly in the interweaved or blended fabrics such as polyester and cotton. 2. The thermal transfer of disperse dyeing polyester fiber dyed with disperse dyes, during the dry heat treatment, the color fastness and color light variation are decreased. It is the thermal mobility of disperse dyes. The so-called heat transfer refers to the phenomenon that some dyes migrate from the inside of the fiber to the surface of the fiber during the dry heat treatment process above 130 ℃ after dyeing with disperse dyes. It is generally believed that the thermal mobility of disperse dyes is the distribution phenomenon of dyes in the two phases of fibers and solvents attached to the surface of fibers (surfactants, softeners, resins, antifouling agents, antistatic agents, etc.) which dissolve disperse dyes. It is believed that if there is no second phase solvent on the surface of fiber, the thermal migration will not occur. In fact, this interpretation is not in line with the reality. If pure polyester fabric is dyed at high temperature and high pressure, it is not treated after any post treatment, washed with hot water and cold water and dried. It is directly dried and heat treated at 180 ℃ for 35S, and the heat transfer phenomenon is still very obvious. Thermal mobility is a kind of physical property inherent in disperse dyes. It is not a phenomenon of attachment caused by the existence of the second phase solvent. The thermal transfer process of disperse dyes can be explained as follows: ① during the high temperature dyeing, the structure of polyester fiber becomes loose, and the disperse dyes diffuse from the surface of the fiber into the fiber, and mainly act on the polyester fiber by hydrogen bond, dipole gravity and van der Waals force. ② When the dyed fiber is treated at high temperature, the vibration of the molecular chain is intensified due to the higher activity energy of the long chain given by the heat energy, and the microstructure of the fiber is relaxed again, which leads to the weakening of the binding force between some dye molecules and the polyester long chain. Therefore, some dye molecules with high activity energy and higher degree of self-reliance migrate from the inside of the fiber to the surface of the fiber with relatively loose structure, and combine with the fiber surface to form surface dyes or adhere to the adjacent cotton adhesive components. ③ During wet fastness test. The dye which is not strong enough and the dye adhering to the cotton adhesive component can easily get rid of the fiber and enter the solution, polluting the white cloth; Or directly adhere to the test cloth by friction, thus showing the wet fastness and friction fastness of the dye decreased. Why is the fastness of disperse dyeing poor? Disperse dyeing is mainly high temperature and high pressure when dyeing polyester fiber. Although the disperse dye molecules are small, it can not guarantee that all dye molecules enter the fiber during dyeing, some disperse dyes will adhere to the surface of the fiber, resulting in poor fastness. The reduction cleaning is used to improve the fastness and color light of the dye molecules that have not entered the fiber. Polyester fabric is dyed with disperse dyes, especially in medium and dark colors. In order to remove the floating color and the oligomer remaining on the surface of the fabric, and improve the dyeing fastness, it is usually necessary to carry out reduction cleaning after dyeing. Blended fabric generally refers to yarn made of two or more components, so this kind of fabric has the advantages of these two components. And by adjusting the proportion of components, we can obtain more characteristics of one of the components. And blending generally refers to the short fiber blend, that is, the two kinds of fibers with different components are mixed together in the form of short fiber. For example: polyester cotton blended fabric, also known as t/c, cvc.t/r, etc. It is made of polyester staple fiber and cotton fiber or man-made fiber. It has the advantages of: it has the appearance and hand feel of the whole cotton cloth, reduces the luster of polyester fabric and the hand feeling of chemical fiber, and improves the level. The color fastness of polyester fabric is improved. Because polyester cloth is color fastness at high temperature and the color fastness is higher than that of all cotton, the color fastness of polyester cotton blended fabric is also improved compared with that of all cotton. However, to improve the color fastness of polyester cotton, it is necessary to do reduction cleaning (called r/c), and after dispersion after high temperature dyeing. Only after the reduction and cleaning can the ideal color fastness be achieved. The short fiber blending makes the characteristics of each component play evenly. Similarly, other components blending can also play their own advantages to meet some functional or comfort or economic requirements. However, in the high temperature dispersion dyeing, due to the mixing of cotton or human cotton fiber, the dyeing temperature cannot be higher than that of polyester cloth. However, the strength or tear strength of polyester cotton or polyester cotton artificial fiber cloth will decrease sharply under the stimulation of strong alkali or insurance powder, and it is difficult to achieve the quality of products in the following links. The relationship between dyeing mode and heat transfer is that when the dry heat treatment is over 130 ℃, the heat transfer phenomenon is common in the fabric dyed with disperse dyes. But the heat transfer direction of dye is different with different dyeing methods. ① The atmospheric boiling dyeing is light color ring dyeing, and there is little sign of heat transfer from the inside and outside after high temperature dry heat treatment. The dye on the surface of the fiber is like the internal migration or diffusion of the fiber due to the concentration gradient. ② The distribution of dye in the fiber is also a certain degree of concentration gradient. During the high temperature heat treatment, some dye molecules migrate to the inside, and some dye molecules move from the inside of the fiber to the surface of the fiber or into the second phase solvent on the surface of the fiber. ③ The dye has good dye permeability and no gradient in the fiber. So when the heat treatment is high temperature, the dye only moves outward in one direction, which has a great influence on the color light and fastness of dyed fabric, especially dark color. The relationship between heat setting and heat transfer, the heat transfer of dye is the same in the process of high temperature dry heat treatment. The pre dyeing setting has a certain inhibition effect on the heat transfer of the dye in dry heat treatment, but the inhibition effect has a direct relationship with the light color of the fixed blank by 10% ~ 15% (the lighter the color, the less the heat transfer of the dye). Therefore, the effect of the predetermined type on the heat transfer of dyes is not significant. The countermeasures are as follows: 1. The thermal mobility of disperse dyes with different structures is different, so the dyes with lower thermal mobility should be selected when dyeing dark colors. 2. Because the color depth has a significant effect on the thermal mobility of dyes, it is necessary to avoid reaching or exceeding the saturation value of dyeing. When choosing dyes, we should consider not only the size of the heat transfer of the dye itself, but also the strength of its promotion and compatibility and additivity. 3. Because surfactants have obvious promotion effect on the thermal mobility of dyes, the principle of "can not use, less use, and not use when not, should be carefully selected" principle. 4. The dye attached to the surface of the fiber (floating color) will aggravate the influence of the heat transfer on the color fastness of the dyed fabric. Therefore, after dyeing (especially dark color), the reducing agent (reducing agent terlipine) should be used for reducing cleaning to remove floating color completely. 5. Because the commonly used softeners have a serious impact on the thermal mobility of dyes, the softener must be carefully selected when finishing the dyed dyed fabrics (for the softener used for polyester fabrics, the influences on the softness, smoothness, yellowing and the thermal mobility of dyes must be considered at the same time). 6. After finishing the dyed fabric, a layer of resin film is formed on the surface of the fiber, which weakens the influence of the heat transfer of the dye on the color fastness of the dyed fabric. However, the influence on the color light of the dyed fabric is often obvious. In addition to the thermal mobility of dyes, the effect of the effects on some dyes sensitive to metal ions and metal ions from metal salt catalysts in resin layer is also directly related. 7. The heat transfer of disperse dyes and the influence of related factors on the heat transfer are obvious only after dry heat treatment at 130 ℃. That is, heat treatment temperature is the main factor of thermal transfer of disperse dyes. 6. The factors considered in post finishing 1. Try to use pre dyeing high temperature pre dyeing pre-determined type, so that the post dyeing setting tension can be used with mild conditions, but attention should be paid to the light color and the deep edge problem is easy to occur. 2. Try to dry with no contact hot air below 130 ℃, such as the cross guide roller dryer. And avoid drying by contact drying. 3. The low temperature soft drying and drawing process below 130 ℃ is used as far as possible, and the high temperature drying and drawing process is avoided. Fourth, low temperature and slow resin finishing process shall be adopted as far as possible, and high temperature and fast resin finishing process shall be avoided. Other effects are different in the heat transfer tendency of different disperse dyes. The heat transfer of different dyes is different under the same dry heat condition, so the color and light of the dye are changed. 1. The relationship between the dyeing depth and the heat transfer of the fibers is proportional to the heat transfer of disperse dyes. That is, the darker the color is, the greater the heat transfer of the dyes is, the more serious the influence on the quality of the dye is. 2. The relationship between heat treatment temperature and heat transfer is usually the higher the temperature of dry heat treatment after dyeing, the greater the heat transfer of dye, the more serious the influence on the color light and dyeing fastness of dye. The heat transfer of dyes is not large when the heat treatment is below 130 ℃,; The heat transfer of dyes is obviously intensified when the heat treatment is over 130 ℃. 3. The relationship between heat treatment time and heat transfer is within 20-40s, and the migration of dyes increases rapidly with the time; In the range of 40-50s, the increase of the heat transfer of dyes was not obvious; The heat transfer of disperse dyes with low temperature and medium temperature decreased over 50s. Obviously, this is related to the increase of sublimation of dyes. 4. The relationship between the heat sublimation and the heat transfer of dyes is the relationship between some high temperature dyes with good sublimation resistance, some of which have small thermal mobility (such as disperse grey s-bn), while others have great heat transfer (such as disperse red s-3gfl, disperse deep blue HGL, etc.). Some low temperature and medium temperature dyes with poor sublimation resistance (such as disperse red B, Fulong brilliant red e-rln, etc.) have a small thermal mobility, which is closely related to the sublimation of dyes. Therefore, there is no obvious rule between the sublimation and the heat transfer of dyes.