1. Different gray fabrics
The gray fabric should be scouring or degreased before dyeing, and the sample may not be pre-processed, or the sample processing method may be different from the large sample production in the workshop. The moisture content of gray cloth is different, and the different moisture content of the sample has a greater impact. Due to the different moisture content, the weighing is also different. For this reason, it is required that the gray fabric produced as a sample must be completely consistent with the gray fabric produced in the workshop.
In addition, is the gray fabric pre-processed for pre-shaping? If the large sample gray fabric has been pre-shaped, the small sample gray fabric has not been pre-shaped, or even the large sample and the small sample have been pre-shaped, and different setting temperatures can also cause different color absorption.
2. Differences in dyes
Although the dyes used in the small sample and the dye used in the large sample are of the same variety and strength, different batch numbers or insufficient accuracy in weighing the small sample may cause differences between the small sample and the large sample. It is also possible that the dyes used for large-scale production have agglomerated and become damp, and some dyes are unstable, resulting in a decrease in strength.
3. Dye bath pH values are different
Generally, it is more accurate to grasp the pH value of the dye bath for small samples, but the pH value is unstable or no acid-base buffer is added during the production of large samples. Since the steam is alkaline during dyeing, the pH value rises during the production of large samples. Some disperse dyes such as Containing ester groups, amido groups, cyano groups, etc. are hydrolyzed under high temperature alkaline conditions. There are also some dyes whose carboxyl groups can be ionized under alkaline conditions, increasing their water solubility and reducing their dye uptake rate. When the pH value of most disperse dyes is 5.5 to 6, the color light is normal and stable, and the dye uptake rate is also high.
But when the pH value increases, the color light changes. For example, dyes such as dispersed black s2bl, dispersed dark blue hgl, and dispersed gray m have obvious color changes when the pH value is >7. Sometimes the gray fabric is not fully washed after pre-treatment and becomes alkaline. During dyeing, the pH value of the dye bath increases, which affects the shade.
4. The influence of liquor ratio
When testing small samples, the bath ratio is generally larger [1: (25~40)], while the bath ratio of large samples varies according to different equipment, and is generally 1: (8~15). Some disperse dyes have little dependence on liquor ratio, and some have great dependence. This causes color difference due to the difference in liquor ratio between the small sample and the large sample.
5. Influence of post-processing
Post-processing is one of the causes of chromatic aberration. Especially for medium and dark colors, if reduction cleaning is not performed or the cleaning is not thorough, in addition to floating color, it can also affect the color light and produce a certain color difference. Therefore, the restoration cleaning must be consistent with the small sample and the large sample.
6. Effect of heat setting
Disperse dyes can be divided into high temperature, medium temperature and low temperature types.
When color matching, you should choose the same type of dye. In case of high-temperature type and low-temperature type color matching, you should consider that the setting temperature should not be too high during heat setting to avoid excessive temperature, which will cause some dyes to sublimate and affect the color light, resulting in color difference. The requirements for shaping conditions for small samples and large samples are basically the same.
Because whether the pre-treatment is set or not and the setting conditions (temperature) have a great impact on the color absorption of polyester (the greater the degree of setting, the lower the dyeability), so the fabric used for the small sample must be consistent with the large sample (that is, before production Use workshop semi-finished products to copy samples), this is one of the keys.
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