Abstract: This article briefly describes the basic categories, properties and applicability of reactive dyes for cellulose fiber exhaust dyeing, aiming at the processing of light, medium, dark, extra dark and sensitive colors by printing and dyeing enterprises, as well as special fastness requirements after dyeing. , comprehensively consider the post-processing environment and fastness standards of the dyed materials, and rationally select various dyes to achieve the best use effect and the lowest production cost.
Reactive dyes are currently the most widely used dyes in cellulose fiber dyeing, and exhaust dyeing is a large-volume and wide-ranging processing method in the knitting printing and dyeing industry. This article will discuss how to select the economical, reasonable and most cost-effective types of reactive dyes in the exhaust dyeing production of cellulose fibers.
1 Performance requirements for reactive dyes in exhaust dyeing
1. Pay attention to the solubility and salt-alkali resistance of reactive dyes
Dip dyeing processing includes a variety of product forms, such as loose fiber dyeing, cheese and hank dyeing, Beam dyeing, liquid flow or aerosol dyeing of gray fabrics, garment dyeing, ribbon dyeing, etc. With the increasing requirements for energy conservation, emission reduction and cost reduction of dyes and chemical materials, a large number of new tube yarn dyeing machines and liquid flow and gas-liquid dyeing machines with a liquor ratio as small as 1:4 are used by many dyeing factories. The resulting effects on reactivity The requirements for dye solubility, salt-alkali resistance, permeability, and dye migration are also getting higher and higher. Therefore, it is recommended that when dyeing workers select new dyes or conduct dye batch sample inspections, in addition to routine testing of color light and strength, they should also conduct solubility and salt-alkali resistance tests. Products with high solubility and excellent salt-alkali resistance should be selected. In order to meet the requirements of small liquor ratio and ensure the success rate of dyeing.
2. Examples of differences in salt and alkali resistance of reactive dyes
With index number C. I. B-19# brilliant blue is an example, the same is C. I. B-19# brilliant blue models include KN-R, R, BH-RH, etc. The model is not important but the key is the salt and alkali resistance. We selected two brilliant blues, KN-R and BH-RH, which are common in the market and have similar color and power distribution, for comparative testing, and put 3 drops of each on the filter paper.
It can be seen that there is a big gap between the two. For example, the above-mentioned KN-R brilliant blue is used as the main color to dye sapphire blue, brilliant green, etc. in a small liquor ratio dyeing machine. Bright purple and other colors, if you don’t pay attention to the material mixing and injection process, such as: refluxing liquefied material, yarn injection material flowing out, adding salt and alkali too quickly, etc., it will easily cause color flowers, layer differences, etc. on the cloth and yarn. If there are dyeing defects such as inconsistent color and poor color fastness, the probability of success will be much higher if you choose BH-Rid, a brilliant blue.
2 Categories and applicability of reactive dyes for dip dyeing
Dip dyeing Categories of reactive dyes
Classified according to the type of reactive radical and conditions of use, the reactive dyes most commonly used for dip dyeing can be divided into approximately five categories.
1. Low-temperature reactive dyes whose active group is dichloro-s-triazine
Product category Commonly used are X type, S/SX type, etc. The recommended dyeing temperature is 30~40℃. This type of dye is highly reactive and sensitive to dyeing temperature and color fixation and holding time. Relatively speaking, the dyeing stability is slightly poor. Currently, it is used in dip dyeing. There are not many applications in China.
2. High-temperature reactive dye whose active group is bis-monochloro-s-triazine
Common product categories are KE type, HE type, etc. The recommended dyeing temperature is 80°C. These dyes generally have low reactivity and stable performance, so they have good level dyeing properties and are more suitable for viscose and mercerized cotton. Dyeing and processing of difficult-to-dye fibers and fabrics such as cotton, spandex, etc. In addition, this type of dye has good alkali bond breaking fastness and is very suitable for use as a post-mercerization dye.
3. Medium-temperature reactive dyes whose active groups are vinyl sulfones
The most common product categories are KN type, etc. The recommended dyeing temperature is 45~60℃, and the reactivity is medium. This type of dye is basically dyed in the form of ß-hydroxyethyl sulfone sulfate. Due to its low directivity to the fiber, level dyeing and dyeing through are better at this time. When the dyeing is close to equilibrium, the dyeing temperature is raised to 60℃ and add alkali agent, at this time the dye is converted into vinyl sulfone form, the directness is greatly increased, and the color fixing process is completed quickly. The most commonly used varieties of vinyl sulfone dyes in exhaust dyeing are C.I.5﹟black, C.I. 21﹟turquoise blue, C.I.19﹟bright blue, etc.
4. Isobi-reactive dyes whose active groups are monochloro-s-triazine and vinyl sulfone respectively
The product categories are named differently, mainly including M type, B type, RR type, BF type, BH type (some), etc. The recommended dyeing temperature is 60~80℃. Due to the synergistic effect of two different active groups, this type of dye has moderate reactivity and good water solubility, level dyeing and dye migration properties. It is suitable for small liquor ratio dyeing. It is the fastest growing and most widely used exhaust dye at present. variety, and of course the advantage of relatively low prices. The disadvantage is that the reactivity of the two active groups is quite different, that is, the reactivity of the monochloro-s-triazine group is much lower than that of the vinyl sulfone group. When fixing, it is easy to cause insufficient color fixation of the former and the latter due to the vinyl sulfone group. The covalent bond formed with the fiber has poor alkali resistance and is prone to hydrolysis and bond breaking, and the final color fixation rate is low.
5. Isobi-reactive dyes whose active groups are monofluoro-s-triazine and vinyl sulfone respectively
Product categories include FN type, FD type, BN type, etc. The recommended dyeing temperature is 60°C. In view of the above-mentioned defect that the reactivity of monochloro-s-triazine is significantly lower than that of vinyl sulfone group, the reactivity of monofluoro-s-triazine is 4-6 times that of monochloro-s-triazine, so it is suitable for ethanol.Since the total dosage is too high and has reached the saturation value of the dye, it is more likely to cause problems such as excessive floating colors and difficulty in soaping and washing. The final result is a decrease in color fastness, especially poor wet rubbing fastness. .
In response to the requirements for dye lifting power and post-dyeing color fastness of extra-deep colors, many reactive dye manufacturers have launched extra-deep or super-deep series of dyes, such as Cibacron S/ W series, Remazol super RGB series, etc., domestic brands such as RI-1 series, BD series, C series, etc. from Zhejiang, Jiangsu and other dye companies. Among the above-mentioned dyes, orange, deep red, navy blue, etc. are a new type of multi-reactive group dyes with intramolecular color matching newly developed in recent years. According to reports, these ultra-deep dyes have 2 to 3 color bodies. A complex with a variety of structural color bodies is formed through a linking group, and then 2 or 3 active groups are connected to the appropriate positions of the complex. The entire dye molecule has good water solubility, moderate substantivity, and high color fixation rate. Extremely high. In addition to dyes such as single-molecule multi-reactive group dyes with intramolecular color matching, most of the dyes such as ultra-dark medium red, deep navy blue, deep black, etc. are compound blending dyes. Generally, 2 or more of the same dyes are used. Dyes with heterobial reactive groups or both divinyl sulfone groups or both intramolecular color combinations are mixed in the best ratio. Since the dye color body and reactive group categories are basically the same, the reactivity, The diffusivity is similar to that of a single molecule, and due to the strong interaction between different dyes, the directness will be improved to a certain extent. The most obvious thing is that the dyeing depth of the dye can be greatly improved, that is, the often said lifting power will be greatly improved. .
Under normal circumstances, a reasonable selection of ultra-dark series dyes can achieve the same depth with 1/2 to 1/3 of ordinary dyes. Due to the higher fixation rate, the floating and hydrolyzed dyes after fixation and heat preservation are less than those using conventional dyes, which can reduce the number and time of soaping and washing, and save production costs such as water, electricity, and steam. Very obvious.
For example, choose a deep purple-red color, and use the combination of conventional single-molecule yellow 3RS, red 3BS, and navy blue BH-2GF with the extra deep series orange BD-R and deep red BD-CB , navy blue BD-G combination and comparison samples of the same color and depth. The respective formulas and predicted costs are shown in Table 3. Comparison of soaping fastness (cotton staining), wet rubbing fastness, residual liquid color, etc. is shown in Figure 3.
It can be seen that when dyeing the same deep purple red, the amount of extra deep series dyes is less than 1/3 of the conventional dyes, and the cost of dye alone is reduced by nearly half, plus post-processing savings In terms of water, electricity, gas and other expenses, the advantages of the extra deep series of dyes are very prominent.
4 Postscript
In short, we should choose the dip dyeing materials reasonably. For reactive dyes, first of all, we hope to understand the chemical structure of the dye itself, especially the types and characteristics of the reactive radicals. Secondly, we should understand the usage occasions and process environment of the dyed materials in the next process, such as whether post-mercerization processing is required, and of course the users. According to various quality requirements of the dyed objects, different series of dyes corresponding to the light, medium and dark colors are selected, and a scientific and reasonable dyeing process is carefully designed. The selection principle of exhaust dyes can be summarized in one sentence: it is necessary to consider the performance stability of the dyeing production process and various quality indicators after dyeing, and also pay close attention to and carefully compare the comprehensive costs of dyes and auxiliaries. We should strive to find the best balance between the two, so that enterprises can obtain the most ideal economic benefits in dyeing and processing.
References:
Song Xinyuan, Shen Yuru. Reactive dye dyeing[M]. Beijing: China Textile Publishing House, 2009.</p
