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Yarn dyeing

The processing forms of yarn pre-treatment are divided into skein, bobbin (warp beam ) Yarn two kinds.

This section takes cotton bobbin (warp beam) yarn as an example to describe its pre-processing.

1. Refining

(1) Purpose

The process of removing various impurities and refining cellulose using chemical and physical methods. After refining, the hygroscopicity and whiteness of cotton yarn are improved.

(2) Refining agents and functions

1. Caustic soda

2. Auxiliary

(1) Surfactant;

(2) Chelating agent.

(3) Process examples

1. Prescription

Caustic soda 3g/L, organic complexing agent 1g/L,

Penetrant NFD 1g/L

2. Process flow

2. One-step pre-treatment of refining and oxygen bleaching

(1) Properties and bleaching principle of hydrogen peroxide

The scientific name of hydrogen peroxide is hydrogen peroxide (H202). It is a colorless and odorless liquid. It has strong oxidizing ability and can cause a burning sensation on the skin, especially It is a relatively concentrated hydrogen peroxide, so please pay attention to safety when using it.

H202 is unstable and can easily decompose and release oxygen when exposed to light or heat, and may even cause an explosion. It is relatively stable under weakly acidic conditions and decomposes faster in alkaline media. Therefore, hydrogen peroxide should be stored in a dark place under normal temperature and weak acid conditions. Heavy metal ions and dust have a catalytic effect on the decomposition of H202.

(2) Analysis of process conditions affecting H202 bleaching

1. pH value ：The optimal pH value is 10～11

2. Temperature: generally 100~110℃

3. Time

4. Concentration

5. Oxygen bleach stabilizer

(3) Process examples

1. Pure cotton non-mercerized yarn pre-treatment process

Hydrogen peroxide (27. 5%) 0.5～5g/L

Caustic soda 2g/L

Oxygen bleaching stabilizer 0.5～1g/L

Scouring agent 1g/L

Complexing agent 1g/L

2. Pure cotton mercerized yarn pre-treatment process

Hydrogen peroxide (27. 5 %) 1～5g/L

Caustic soda 2～2.5g/L

Oxygen bleaching stability 0.8～1.2g/L

Penetrant 1g/L

Complexing agent 0.5g/L

3. Mercerizing

(1) Mercerizing concept

Refers to the processing process in which cotton yarn is treated with concentrated caustic soda solution or other chemicals under tension, which not only improves the performance of the yarn, but also obtains a silk-like luster.

Fabric woven with mercerized yarn has a soft and plump feel, smooth surface, good gloss, and can Significantly improve the quality of the fabric.

The mercerizing agent is caustic soda Lord.

（二 ) Changes in cotton yarn properties after mercerization

Gloss improvement

Improved adsorption and chemical reaction performance

Eliminates the internal stress of the yarn and improves the strength of the fiber

(3) Analysis of mercerizing process conditions

1． Alkaline concentration: 260～280g/L

2. Lye temperature: low temperature is more favorable

3. Soaking time: 120～150s

4. Tension

5. Debase

(4) Mercerizing equipment

Arm-type skein mercerizing machine

Yarn dyeing

Dyeing refers to the process in which dyes are automatically transferred from the dye liquor to the fibers and form a uniform, strong and bright color on the fibers.

Main indicators:

Uniformity of dyeing color

Dye fastness

Vividness

1. Overview

(1) Dyes and pigments

Dye refers to a colored organic compound that can be dissolved in water or other media to make a dye solution or dispersion, and has an affinity for fibers. It is mainly used for dyeing and printing of textiles.

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