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Causes and Solutions of Dyeing and Finishing Defects (2)

Views: 1000     Author: Site Editor     Publish Time: 2022-09-07      Origin: Site

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4. Whitening spots

①.Cause analysis

1) Caused by water quality, high hardness of water and many impurities can lead to whitening spots during whitening;

2) Due to the re-sticking of the pulp, whitening spots will occur when the places where the pulp spots appear are brightened;

3) Whitening spots will appear when the surface of the cloth with oil is whitened due to oil stains.

②.Solution

1) For whitening spots caused by water quality, the water treatment should be strengthened during pre-treatment, and chelating dispersants should be added to improve water quality.

2) If it is caused by the re-sticking of the slurry, add an emulsifying desizing agent during desizing to improve the emulsification and dispersibility, and strengthen the water washing after desizing to prevent the slurry from sticking back.

3) If the oil is re-dipped, it is necessary to strengthen the emulsification of oil removal and use an emulsified oil removal agent.

5. Alkaline spot

①.Cause analysis

The scouring liquid contains a lot of impurities, so that the impurities with alkali stick to the fabric; after desizing and mercerizing, it is not dried in time, resulting in air-dry printing and alkali spots.

②. Solution

1) Wash and dry in time after desizing and mercerizing;

2) If the scouring liquid contains many impurities, add a chelating dispersant to the scouring liquid to improve the water quality and prevent the occurrence of alkali spots;

3) Repair of alkaline spots. If it is confirmed that it is an alkaline spot, it can be removed by washing with dilute hot hydrochloric acid.

6. Rust spots

①.Cause analysis

The rust on the grey cloth itself, the dripping of rainwater when the cloth is stored, and the leakage of the iron roof can cause rust spots;

②.Solution

1) When the water is stopped or the production is stopped for a long time, it is necessary to drain the water for a while and add water for production, or wrap the gauze on the mouth of the water pipe, and filter the water before production.

2) If the grey cloth itself has rust, it can be washed with warm oxalic acid solution before pre-treatment. Note that the fabric treated with oxalic acid must be washed with clean water to prevent the fabric from being brittle and damaged, resulting in a decrease in strength.

The method of cleaning rust spots is for reference only:

Oxalic acid 20g/L

Acetic acid (98%) 30ml/L

7. Calcium spots

①.Cause analysis

Mainly due to the hardness of the water. Due to the high hardness of the water and the large amount of calcium and magnesium ions in the water, the precipitation of insoluble calcium and magnesium substances will be formed during scouring, which will attach to the fabric and produce calcium spots; Calcium chlorate, the decomposed lime in the bleaching solution) is not washed, and it is easy to cause calcium spots.

②.Solution

If the printing and dyeing water is hard, add some water softener, sodium hexametaphosphate, CT powder, etc. to soften the water in the pretreatment; in addition, pay attention to washing the calcium remaining on the fabric during bleaching.

If calcium spots are found before dyeing, they can be removed by washing with dilute hot hydrochloric acid.

8. Air dry printing

①.Cause analysis

This air-drying printing is mainly produced after desizing and before oxygen bleaching. The shape of the defect is dotted and irregular horizontal stripes. After such defects are produced, they cannot be covered up in subsequent processes such as whitening and dyeing. These defects are mainly caused by the fact that the pulp is not completely cleaned after desizing, the wet cloth is stacked for too long, and the fabrics exposed to the air surface are partially air-dried.

②. Prevention and solutions

1) Precautions

Reasonably control the production progress, the fabrics after desizing and before the oxygen bleaching machine should not be stacked too much, and the stacking time should not be too long; strengthen the cleaning of fabrics after desizing, if there are too many fabrics after desizing, use plastic film to cover the fabrics Up to prevent the fabric from being partially air-dried to cause air-dry printing.

2) Solution

After the air-drying printing occurs, the fabric that produces the air-drying printing should be re-desized and then oxygen bleached, and the air-drying printing can be removed.


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