Why are fabrics prone to hue problems during the rainy season?

For the printing and dyeing industry, the standard of industrial water is generally used, and the water quality often changes with the season, region and climate change. In particular, the summer rain is relatively sufficient, the water quality changes relatively quickly, and it is easy to have adverse effects on printing and dyeing.

Effect of metal in water on disperse dyeing

Abbreviation for water quality. It marks the physical properties (such as color, turbidity, odor, etc.), the chemistry (content of inorganic and organic matter), and the characteristics of organisms (bacteria, microorganisms, plankton, benthic organisms) and their composition.

In order to evaluate the quality of water bodies, a series of water quality parameters and water quality standards have been stipulated, such as water quality standards for domestic drinking water, industrial water and fishery water. For the printing and dyeing industry, the standard of industrial water is generally used, and the water quality often changes with the season, region and climate change. In particular, the summer rain is relatively sufficient, the water quality changes relatively quickly, and it is easy to have adverse effects on printing and dyeing.

If the content of metal (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 causes of hue change are:

Metal ions combined with dyes;

Metals or metal ions reduce the decomposition of disperse dyes;

The role of metal ions and additives in the dye bath affects the dispersion stability of the dye and reduces the dyeing rate.

Only a few dyes are liable to be combined with metal ions and disperse dyes.

For example, anthraquinone-based disperse dyes, in which anthraquinone-based bright red dyes, due to the combination of metal ions and disperse dyes, change the hue from red to red with blue. The degree of combination of metal ions and dyes is related to the type of metal ions. Fe2 +, Fe3 +, and Cu2 + have a greater effect on dyes. Ca2 + and Mg2 + (the hardness of water generally indicates its concentration) have relatively small effects on dyes, but when the concentration is higher It also adversely affects staining. Zh

When dyeing, in order to prevent the influence of metal ions, a metal chelator can be used. For Fe2 +, Fe3 +, Cu2 +, a metal chelator containing EDTA or NTA effective in an acid-neutral dye bath can be selected. For Ca2 + and Mg2 +, polycarboxylic acid metal chelating agents can be generally used.

However, with the metal ionization reduction reaction, the use of metal chelating agents cannot be solved, and another solution must be found. If the iron powder contained in the dye bath is ionized to Fe2 + and Fe3 +, reducing properties are generated, and the ions are chelated by the metal chelator. Therefore, the use of the metal chelator alone cannot prevent the reduction of the dye.

The use of an oxidant can effectively prevent the reduction, but the dosage is appropriate. When the content of Fe2 + in the dyeing bath is 500 ppm, 1 g / L sodium chlorate can be added. If the amount is too large, the oxidizing property of sodium chlorate will adversely affect the dye, so it is not desirable to use sodium chlorate. When the metal content is small, sodium m-nitrobenzenesulfonate (anti-staining salt S) can be used to prevent reduction.

The acid dyeing bath is easy to cause the reduction of iron powder or Fe2 +. To prevent the dyeing quality problems caused by the reduction, we must pay attention to the selection of water quality and dyeing auxiliary. In addition, the oxygen in the air in the dyeing machine and the oxygen in the dyeing bath help prevent reduction, and the sealed pressure dyeing of the sealed dyeing machine is also very effective.