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Why does the detail and the detail of polyester knitted fabric dyeing with disperse dyes not match

2020-03-04 523

The dye factory usually makes the small sample in the laboratory, and then according to the small sample in the workshop to enlarge the sample production, the reasons for the inconsistent color light and color difference between the small sample and the large sample may be as follows.

There are different grey fabrics.

                        . The moisture content of grey cloth is different, and the influence of the moisture content of small sample is great, because of the different moisture content, the weighing is also different. For this reason, it is required that the blank cloth with small sample must be completely consistent with the blank cloth produced in the workshop.

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② different dyes.

   although the dye used for small sample is the same as that used for large sample, its variety and strength are the same, but the difference between small sample and large sample may be caused by different batch number or inaccurate weighing of small sample. It is also possible that the dye used for large-scale production has been caked and damped, and some dyes are not stable, resulting in the decrease of the strength.

③ the pH value of dye bath is different.

Generally, the pH value of dyeing bath for small samples is more accurate, while the pH value of large samples is not stable or acid-base buffer is not added. Due to the alkalinity of steam during dyeing, the pH value rises in the middle of large samples production. Some disperse dyes such as ester group, acylamino group and cyano group are hydrolyzed under the condition of high temperature and alkalinity. There are also some dyes whose carboxyl groups can be ionized in the alkaline condition, the water solubility increases, and the dye uptake decreases. When the pH value of most disperse dyes is 5.5-6, the color light is more normal and stable, and the dye uptake is also higher.

However, when the pH value increases, the color light changes. For example, when the pH value of disperse black s 2BL, disperse dark blue HGL and disperse gray m is more than 7, the color light changes obviously. Sometimes the grey cloth is not washed thoroughly and alkaline after pretreatment, and the pH value of dyeing bath increases when dyeing, which affects the color light.

The influence of bath ratio.

In the small sample test, the bath ratio is generally larger [1: (25-40)], while the large sample bath ratio varies according to the equipment, generally 1: (8-15). Some baths of disperse dyes are less dependent than others, and some of them are more dependent. In this way, the color difference is caused by the difference of bath ratio between small sample and large sample.

   ⑤ the influence of post-treatment.

The post-treatment is one of the reasons that affect the color difference. Especially for medium and dark colors, if no reduction cleaning or unclean cleaning is carried out, in addition to floating color, it can also affect the color light and produce certain color difference. Therefore, the reduction cleaning must be consistent with the small sample and the large sample.

  ⑥ the influence of heat setting.

Disperse dyes can be divided into high temperature type, medium temperature type and low temperature type.

In case of color matching of high temperature type and low temperature type, the setting temperature shall not be too high during heat setting, so as to avoid the influence of sublimation of some dyes on color light and color difference. The setting conditions of small sample and large sample are basically the same.

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