For the printing and dyeing industry, industrial water standards are generally used, and water quality often changes with seasons, regions, and climate changes. Especially in summer, when there is relatively abundant rain, water quality changes rapidly and rapidly, which can easily have adverse effects on printing and dyeing.
The influence of metals in water on disperse dye dyeing
Water quality Abbreviation for water quality. It marks the physical (such as color, turbidity, odor, etc.), chemical (inorganic and organic content) and biological (bacteria, microorganisms, plankton, benthic) characteristics and composition of the water body. In order to evaluate the quality of water bodies, a series of water quality parameters and water quality standards are stipulated, such as water quality standards for domestic drinking water, industrial water, and fishery water. For the printing and dyeing industry, industrial water standards are generally used, and water quality often changes with seasons, regions, and climate changes. Especially in summer, when there is relatively abundant rain, water quality changes rapidly and rapidly, which can easily have adverse effects on printing and dyeing.
If the content of metals (such as rust, etc.) or metal ions in the dyeing water exceeds the standard, it will affect the dyeing quality and fail to meet the specified hue requirements.
The main reasons causing hue changes are:
1. The combination of metal ions and dyes;
2. Metals or metal ions cause the reduction and decomposition of disperse dyes;
3. The action of metal ions and auxiliaries in the dye bath affects the dyes The dispersion stability is improved and the dye uptake rate is reduced.
There are only a few dyes that are prone to combine metal ions with disperse dyes.
For example, anthraquinone-type disperse dyes, among which anthraquinone-type bright red dyes, due to the combination of metal ions and disperse dyes, the hue changes from red to red with bluish color. The degree of binding between metal ions and dyes is related to the type of metal ions. Fe2+, Fe3+, and Cu2+ have a greater impact on dyes. Although Ca2+ and Mg2+ (generally expressed by the hardness of water) have a relatively small impact on dyes, when the concentration is high, It will also have adverse effects on dyeing.
In order to prevent the influence of metal ions during dyeing, metal chelating agents can be used. For Fe2+, Fe3+, and Cu2+, metal chelating agents containing EDTA or NTA that are effective in acid-neutral dye baths can be used. For Ca2+ and Mg2+, polycarboxylic acid metal chelating agents can generally be used.
However, the reduction reaction caused by metal ionization cannot be solved with metal chelating agents, and another solution must be found. If the iron powder contained in the dye bath is ionized into Fe2+ and Fe3+, it will produce reducing properties. The ions are chelated by metal chelating agents. Therefore, using only metal chelating agents cannot prevent the dye from being reduced. The use of oxidants can effectively prevent the effects of reduction, but the dosage must be appropriate. When the Fe2+ content in the dye bath is 500ppm, just add 1g/L sodium chlorate. The oxidizing properties of sodium chlorate can have adverse effects on dyes if used in excessive amounts, so the use of sodium chlorate is undesirable. When the metal content is small, sodium m-nitrobenzene sulfonate (anti-staining salt S) can be used to prevent reduction.
Acidic dye baths can easily cause the reduction of iron powder or Fe2+. To prevent dyeing quality problems caused by reduction, attention must be paid to the quality of the dyeing water and the selection of dyeing auxiliaries. In addition, the oxygen in the air inside the dyeing machine and the oxygen in the dye bath help prevent reduction, and the sealed pressure dyeing of the sealed dyeing machine is also very effective. </p
