Why Is The Small Sample Inconsistent With The Big Sample?

When the polyester knitted fabric is dyed with disperse dyes, why is the small sample inconsistent with the large sample?

The dyeing factory usually plays a small sample in the laboratory. Then, according to the sample production in the workshop, the reasons for the inconsistent color and chromatic aberration between the sample and the big sample may have the following aspects.

First, grey cloth is different.

The dyed fabric should be scoured or deoiled before dyeing, and the sample may not be processed before, or the sample processing method is different from that of the workshop.

The moisture content of grey cloth is different, and the effect of wetting is different from that of small sample.

To this end, it is required that the grey cloth should be exactly the same as the grey cloth produced in the workshop.

In addition, is the pretreatment of grey cloth predefined?

If the bulk fabric has been predefined, the small sample cloth has been predefined, even the large sample and the small sample have been predefined, and the setting temperature is different.

Two. Different dyes

Although the dyes used in the samples are the same as those used in the samples, their varieties and force are the same. But the batch number is not accurate enough when the batch number is different or the sample size is weighed, which may cause the difference between the sample and the bulk sample.

It is also possible that the dyestuffs of bulk samples have been lumped and moistened, and some dyes are unstable.

Three. The pH value of dye bath is different.

Generally, the pH value of the sample is better than that of the control bath, while the pH value of the sample is not stable or the acid base buffer is not stable. When the dyeing zone is alkaline, the pH value increases during the production of large samples, and some disperse dyes such as ester groups, acylamido and cyano groups are hydrolyzed at high temperature and alkaline conditions.

There are also dyes whose carboxyl groups can be ionized under alkaline conditions, water solubility increases and dye uptake decreases.

When most disperse dyes are pH 5.5 to 6, the color light is normal and stable, and the dye uptake rate is higher.

But when the pH value rises, the color light changes.

Such as disperse black s2bl, disperse dark blue HGL, disperse ash m and other dyes at pH >7, the color change obviously.

Sometimes the gray cloth is not fully washed and alkaline before pretreatment. When dyeing, the pH value of dye bath increases, which affects the shade.

Four. The influence of bath ratio

In the small sample test, the bath is larger than the general [1: (25~40)], while the big sample bath varies according to the equipment, generally 1: (8~15).

Disperse dyes have lower dependence on some baths than others, and some of them are highly dependent.

Five. The impact of post-processing.

Post processing is one of the reasons that affect the chromatic aberration.

Especially in medium and dark colors, if it is not cleaned or cleaned, it will affect the shade and produce a certain chromatic aberration besides floating color.

Therefore, the reduction and cleaning must conform to the large sample.

Six, the influence of heat setting

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

The same type of dyes should be selected for coloring. In case of high temperature and low temperature coloring, the setting temperature should not be too high in the heat setting process to avoid excessive temperature, resulting in sublimation of some dyes and color difference.

Small sample and large sample setting requirements are basically the same.

Because of the setting or not, the setting condition (temperature) has a great influence on the color absorp tion of polyester (the greater the setting degree and the lower dye uptake), so the cloth must be the same as the bulk sample (that is to say, the semi-finished product should be reused before commissioning), which is one of the keys.