Dyeing fabric ribbons is one of the most complex processes in ribbon manufacturing. The color of a ribbon is crucial to be uniform and replicable so that we can achieve the “same color” twice in two different manufacturing batches.
It is never possible for one color to be exactly the same as another due to the complexity of the process (dyes, auxiliaries, temperatures, ribbon materials, pressures…), even though they may appear the same to our eyes.
DYEING PROCESSES FOR FABRIC RIBBONS: TYPES
There are two dyeing processes for fabric ribbons: discontinuous and continuous.
- Discontinuous System (Autoclave)
The discontinuous system for dyeing fabric ribbons is carried out using a pressurized container with the ribbon wound on perforated cones. This requires a previous winding operation.
Once the container is filled with ribbon coils, the water solution with dyes and necessary auxiliaries is pumped through the holes of the coils containing the ribbon in both directions, from outside to inside and from inside to outside.
In this operation, time and temperature are crucial, requiring the skills of a color technician, although in more modern machines, these operations have also been automated.
For this entire process, a large amount of water and energy is needed because, during dyeing, both cold and hot water are required for washing the fabric ribbon.
In this dyeing mode, the drying and finishing of the ribbon are done with processes separate from the dyeing process we just explained.
This discontinuous process has several disadvantages:
- Winding operation before starting the dyeing process.
- A significant amount of energy and water is required.
- Rewinding the ribbon once the dyeing operation is complete.
To finish the dyeing, subsequent processes (drying and finishing) are needed.
- Continuous System
This system is the most used and efficient for dyeing fabric ribbons. It is characterized by its agility compared to the discontinuous process, as the ribbon dyeing operation is reduced to twenty minutes.
The dyeing machine contains all the steps that must be carried out for dyeing fabric ribbons sequentially.
The continuous dyeing process consists of the following steps:
- Submersion of the ribbon in the solution (dyes and auxiliaries) and penetration of the solution into the fabric through pressure (squeeze rolls).
- Prefixing by heating the dye to the fabric at 80ºC (infrared).
- Dyeing process using hot air at a temperature (from 160 to 210ºC) in the case of polyester or using steam (104ºC) in the case of polyamide and cotton.
- Washing to remove dye particles that have not been fixed in the fabric.
- Finishing and drying the ribbon. Drying the fabric ribbon is done by heat between 100 and 110ºC, both in the air system and in the steam system.
The five steps are carried out one after another, hence the name continuous dyeing. The continuous dyeing system has the following advantages compared to the discontinuous system.
- Less energy and water, and consequently, more sustainable.
- More efficient, an automated process where all the necessary steps for dyeing fabric ribbons are carried out one after another.
- Greater visual control of the ribbon throughout the process.
- Standardization of batches by color. The configuration of all processes can be saved and replicated in different batches to achieve the “same color.”
The skills of the color technician are focused on the formulation and study of colors (dyes and auxiliaries) as well as on quality control of different batches and adjustments to replicate colors or studies for the creation of new colors.
The continuous system began to be implemented in the 1960s and was a revolution in ribbon manufacturing.