How are synthetic yarns dyed?

Dyeing of polyester fibers

1. The structural characteristics of the fiber: strong hydrophobic fiber, poor hygroscopicity, coupled with high crystallinity, relatively tight structure in the amorphous region, and a high degree of orientation of the macromolecular chain.

2. Characteristics of disperse dyes: It is a kind of non-ionic dyes with small relative molecular weight, simple molecular structure and no water-soluble groups.

3. Dyeing method

High-temperature and high-pressure dyeing method: refers to placing polyester yarn in an airtight container filled with dyeing solution, and dyeing it under the conditions of 120-130ºC and 196.4kPa (2kgf/cm2).

(1) Carrier staining method

(2) Thermosol dyeing method

Dyeing of Polyacrylonitrile Fiber

1. Structural characteristics of the fiber: three monomers are copolymerized, the first monomer is acrylonitrile, with a content of more than 85%, which is the main body of the fiber; the second monomer is methyl acrylate, methyl methacrylate, acetic acid Vinyl ester, etc.; the third monomer is sodium itaconate, sodium propylene sulfonate, etc.

2. Cationic dye: It is a water-soluble dye that can be ionized in aqueous solution to generate pigment cations, so it is called cationic dye. Cationic dyes are the main dyes for acrylic fiber dyeing. They have complete chromatograms, bright colors, high color yield, high light fastness and washing fastness, but poor level dyeing.

Dyeing of polyamide fibers

Commonly used are nylon 66 and nylon 6. Nylon molecules also contain amino and carboxyl groups, which are amphoteric.

Excellent dyeing performance, positively charged in acidic medium, commonly used for dyeing with weak acid dyes or neutral dyes; negatively charged in alkaline medium, can be dyed with cationic dyes. Nylon is a hydrophobic fiber and can be dyed with hydrophobic disperse dyes; the fiber contains reactive groups and can also be dyed with reactive dyes.