The basic principle of the dyeing process flow design is to simplify the production operation as much as possible while ensuring dyeing quality. The goal is to shorten processing time, reduce factors affecting production quality, and maximize production efficiency, following the principle of "necessary and sufficient." The dyeing process flow may vary for the same dye with different fibers or different dyes with the same fiber. For example, the dyeing process for reactive dyes on cotton is different from that on silk, and the process for vat dyes and reactive dyes on cotton is also different. The dyeing process flow design must be based on a thorough understanding of the functions of each processing step and the dyeing principles of the dyes.
In practice, the design of the dyeing process flow primarily focuses on specific process conditions. Due to variations in dyeing processes for different dyes, it is not possible to analyze all of them individually. The following example is based on a basic process flow, emphasizing the design of specific process factors.
Dyeing Process Conditions Design
The fundamental principle of dyeing process conditions design is to minimize damage to fibers and fabrics while ensuring dyeing quality, and maintaining the original characteristics of the fabric such as hand feel and luster.
Pad Dyeing Method
Basic Dyeing Process Flow:
Fabric Pretreatment (or Wetting) ➟ Padding ➟ Dyeing ➟ Water Rinse ➟ Fixation ➜ Post-dyeing Treatment
Pretreatment
Padding Temperature
Nature of the Fiber: Generally, hydrophilic fibers like cellulose fibers and protein fibers exhibit fast dye adsorption at low temperatures. For example, the padding temperature for cotton fabrics is around 40-50°C, while for silk fabrics, it is set between 50-60°C.
Dye Concentration: For deep and dark shades, higher padding temperatures are suitable, while for medium to light shades, lower padding temperatures are preferable.
Directness of the Dye: The padding temperature may vary based on the directness of the dye. Dyes with high directness usually have faster adsorption rates and are suitable for lower padding temperatures.
Heating Rate
Dyeing Temperature
Addition Time of Auxiliaries
Fixation
Post-Dyeing Treatment
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