Cotton cone yarn dyeing,  process mainly consists of the following five steps:

PRETREATMENT

This step primarily removes natural impurities (cottonseed hulls, waxy substances, etc.) and pigmentum from the yarn, enhancing its whiteness and capillary effect to create conditions for dyeing processing.

 

DYEING

Each type of fiber has its unique dyeing characteristics, and yarn dyeing process is formulated based on  properties of cotton fibers (cellulose fibers) and reactive dyes. The process of package yarn dyeing involves applying pressure to dye solution in cone yarn dyeing machine using a pump, allowing the dye solution to penetrate from inner layer to outer layer of package yarn, thereby achieving uniform dyeing.

 

SOAPING

After dyeing, a large amount of hydrolyzed and unreacted dye remains on the surface of the yarn, which must be removed by adding soaping agent and washing under high temperature conditions (known as soaping). The role of soaping is to remove the floating dye on the yarn, improve the color brightness, and meet the fastness requirements of customers.

 

COLOR FIXATION

After soaping, for dark and medium color, fixing agent is added to achieve the processing requirements of subsequent finishing. The function of fixing agent is to form a protective film on the surface of the yarn to prevent dye from falling off during subsequent finishing processes.

 

SOFTENING

During the dyeing process, natural waxy substances on the yarn surface are destroyed, making the yarn feel harder. Therefore, after dyeing, a certain compound is added to the yarn to reduce friction between yarns, facilitating winding and subsequent weaving processes.

 

Bobbin dyeing technology: subjective reasons cause of non-recurrence of yarn through cone yarn dyeing are roughly as below:  winding quality, dye selection, dyeing process, operating factors, management problems, etc.

 

WINDING QUALITY INFLUENCES REPRODUCIBILITY

(1) Bobbin weight: When dyeing by immersion method, the depth of apparent color depends largely on the weight ratio of dye to yarn. In generally, only the number of bobbin is counted when the yarn is put on the cone yarn carrier, no longer weighed again. Therefore, the winding weight determines weight of loading yarn, be weighted after soft winding. Many factory production practices have proved that even without a fixed length meter, it is completely possible to weigh each bobbin and control the weight within the range of ± 1%. Some dyeing plants use "card" to measure the outside diameter, but because of the large error, it is not suitable. The different size of package yarn after dyeing also will get color difference betweent bobbin yarn.

 

(2) Bobbin winding density: The winding density of soft bobbin with direct relationship to resistance of circulation of dyeing liquor . High density, high resistance. Resistance magnitude affects shape of dyeing liquor circulation resistance curve, then affects main circulation pump, affects the circulation flow of the dye fluid, the circulation frequency of dye fluid and number of cycles within specified time are changed, so the amount of dye on yarn is changed, causing the color of yarn to be deep or shallow.

When some bobbin winding density is too small, sometimes the yarn will be out of the "groove", sometimes caused "collapse", the dye liquid will get "short circuit", not only the yarn is washed and dyed unevenly, but also rest bobbin dye liquid circulation will be reduced and cause light color.

 

(3)"Hole exposure" : Because the bobbin and the beam coil are full of holes for the dye to travel through, when the bobbin is not properly wound, or the reciprocating distance is not enough, "hole exposure" will occur. When dyeing, because the warp shaft is placed vertically in the main body of high pressure cone yarn dyeing machine, if winding is too loose, the yarn will fall due to gravity after wetting at sometimes, resulting in upper "hole exposure". The dye liquor will "short circuit" from the "exposed hole", not only wash the yarn on the end of the bobbin, but also affect the flow capacity of other bobbin.

There are numerous factors that influence the quality of dyed products, chief among them being equipment, dyes and chemicals, processes (procedures, formulations, conditions)  and operational factors. Occasionally, defects in dyeing can also arise due to chance occurrences. Therefore, when analyzing the root causes of quality issues, it's imperative to consider all aspects thoroughly to pinpoint the actual cause, allowing for resolution and prevention of recurring issues. According experience, product quality control measures can be implemented.

 

In this context, let's delve primarily into the impact of dyeing equipment on the quality of dyed products.

 

To achieve superior dyed products, not only must suitable dyes be selected based on the type of fiber and fabric, but also must appropriate textile dyeing machine be paired with customized and rational dyeing processes. Despite advancements in production technology and the continuous improvement of dyeing machinery, quality issues stemming from equipment are still not entirely avoidable.

The primary concern related to yarn dyeing machine and fabric dyeing machine is its operational stability, efactors such as machine speed, drying condition, temperature ramp-up and ramp-down rate, and pressure control. When these parameters are tightly controlled, the dyeing and finishing machinery can ensure consistent color reproduction and reproducibility.

 

Textile dyeing machine pivotal role in achieving even dyeing. To this end, the following requirements are crucial:

 

1. **Strong Dyeing Process Adaptability**: dyeing machine must be capable of accommodating a wide range of process parameters like temperature, pressure, speed, and treatment time, as well as adjustment to dyestuff and chemical, ensuring compatibility with new processes and technologies. This ensures uniform dyeing and meets other quality standards.

 

2. **High Automation Level**: Automated detection and adjustment of key process parameters minimize human errors, enhancing precision control. This ensures the repeatability of processes and stabilizes product quality.

 

3. **Versatility for Multi Processing**: Given the limited resources in dyeing plant and ever-changing market demands,  fabric and yarn dyeing equipment should be versatile, allowing for cost-effective processing of various fabric and yarn types while maintaining dyeing uniformity and meeting other quality criteria.

 

4. **Low-Tension or Loose Running**: Tension is a significant factor affecting dyeing evenness. High or uneven tension can easily lead to quality issues. Hence, dyeing equipment should operate with minimal or uniform tension, preferably in a loose-running mode. It is related with the design of dyeing machine structure.

In addition to the processes and operations defined, the color matching and dyeing levelness of products are intimately tied to the dyeing equipment chosen. The selected equipment must cater to the requirements of various dyeing processes, handle diverse product types, produce high-quality outputs, and be safe, durable, economical, high-speed, efficient, continuous, automated, low-energy consuming and environmentally friendly. In essence, the equipment must guarantee the quality of dyed product.