New Dyeing Process in 2022(Green Dyeing Technology)-2

The new dyeing process includes new technologies such as waterless dyeing and low-temperature dyeing, in addition to the use of natural dyes and computer-controlled dyeing mentioned in the previous article. Let us now look at the specific situation of these related processes.

​Waterless dyeing process

Waterless dyeing is an important dyeing process to reduce dyeing wastewater, and it has many types.

Solvent dyeing

In the 1960s and 1970s in China, solvent dyeing was studied and popularized. While solvent dyeing has many benefits, some solvents, such as halogenated hydrocarbons, pollute the environment. Furthermore, the solvent recovery equipment must be increased, so it has yet to be popularized and applied.

Supercritical carbon dioxide dyeing

Supercritical carbon dioxide fluid has been used as a dyeing medium in recent years. Its most notable feature is that it does not dye with water. It can generally be washed without water or only lightly after dyeing. And carbon dioxide is vaporized and then converted into a supercritical fluid that can still be reused and is thought to be an ideal dyeing process.
The main issues with current industrial production are the high cost of production equipment and the fact that it is only suitable for non-ionic dyes, such as disperse dyeing synthetic fibers. Furthermore, the dye variety is insufficient, and these deficiencies must be addressed in the future.

Electromagnetic staining

Dyes are formed into charged or magnetic particles, which are then electrostatically or magnetically attracted to textiles in an electric or magnetic field. The dyes on the fabric are then adsorbed, diffused, and fixed in the fibers via thermal baking, steaming, or hot pressing.
After dyeing, the process can be completed simply by general washing or by removing unfixed dyes from the fibers using electric or magnetic fields. This is still preliminary research.

Sublimation dyeing process

Water is not used as a dyeing medium in vapor dyeing, also known as sublimation dyeing. Under higher temperature or vacuum conditions, it sublimates the dye into the gas phase, where it adsorbs and diffuses in the fiber. This method of vacuum metallization has long been used. The difference is that a metal coating only forms a metal film on the surface of an object (such as glass or plastic), whereas dye is not only adsorbed on the surface of the textile during gas phase or sublimation dyeing, but also diffuses into the fiber and becomes fixed in it at a certain temperature. That is, the dyeing process occurs.
This type of dyeing’s dye transfer and dyeing mechanism is similar to that of thermal transfer printing, which requires the dye to have strong sublimation. Currently, it is primarily some non-ionic disperse dyes or dyes that are easily sublimed. Because there is no need to wash with water after dyeing, no waste water is generated, which is good for the environment.

New paint dyeing

The dyeing process of paint does not occur, and the paint is mainly adhered to the fabric by adhesives. The process is simple, which is its main advantage. Whether it’s a single natural or synthetic fiber fabric or a blend of several fibers, it only needs to be painted once. Furthermore, it does not require washing with water or only requires light washing after dyeing, resulting in less waste water and energy savings. The most significant disadvantage is a lack of hand feel, and some adhesives are toxic (eg contain formaldehyde or toxic free monomers).
The first step in researching new paint dyeing is to select safe paints and adhesives, and the second step is to improve the hand feel and color vividness of dyed fabrics. Some paints and adhesives that meet environmental standards are now available. Produce some particularly soft adhesives, or reduce the amount of adhesives, and reasonably control the distribution of the adhesives on the fabrics to improve the feel of the fabric. For example, research and development of adhesive-coated coatings used for dyeing has greatly improved the hand and breathability of textiles, as well as the fastness.

​Conclusion

The global theme of the world’s textile industry entering the twenty-first century, and an important content related to the quality of human existence and sustainable development, is the development of cleaner production in the textile industry, the use of green production methods that are conducive to protecting the ecological environment, and the provision of ecological textiles to consumers. As a result, research into these new dyeing processes is critical.