Science: How carbon dioxide makes dyeing better - polyethylene terephthalate
German scientists say SARAH houulton carbon dioxide can be used as a medium for dyeing, not water.
This can solve one of the biggest problems facing the textile dyeing industry: how to remove the color in the waste water.
There is an urgent need for better methods for the removal of dyes from wastewater.
In the UK, for example, the 1989 water act affected the textile industry by formalizing the "paid for by polluters" principle.
Wolfgang Saus, Dierk Knittel and Eckhard Schollmeyer from the Texas Research Center in krefeldand, Germany, gave a little horizontal thought on the issue.
Instead of cleaning up the waste water, they first thought about the idea of not using water (
Journal of text Research, Volume 135, page).
Instead, the medium they choose is "supercritical" carbon dioxide.
At room temperature and pressure, the substance is either a gas or a liquid, which can become a supercritical fluid by greatly increasing the temperature and pressure.
When it is impossible to zone between gas and liquid, such a situation occurs because the substance is in a state between the two.
Carbon dioxide becomes supercritical at a temperature of about 31 °c and at a pressure of 73 atmospheres.
If the pressure rises further, the ability of the fluid to dissolve the substance increases dramatically.
Saus and his colleagues used this improved solubility to dye many artificial fibers, especially polyester pet (
More common in the name of brands such as Terylene and trevira).
Dyes commonly used for this fiber are generally not soluble in water;
Their solubility can only be improved by adding a large number of other chemicals, such as Surface Active Agents and dispersing agents.
However, when using a supercritical fluid such as carbon dioxide, these chemicals become unnecessary because the dye will dissolve in a supercritical mixture of carbon dioxide.
Because there are fewer chemicals to be removed, the problem of wastewater is reduced.
German researchers stain in a container called anautoclave.
They wrap the sample around the perforated stainless steel pipe and place the dye powder at the bottom of the container.
They then fill the container with carbon dioxide gas, heat the gas to the desired temperature, and increase the pressure by constantly stirring.
Then leave for an hour.
After the pressure is restored to the atmosphere, the carbon dioxide evaporates to make the dyed sample completely dry.
In order to remove the double dye powder, it is sometimes necessary to quickly rinse the sample with acetone.
It turns out that this method is also successful not only for PET, but also for nylon and other man-made fabrics, especially bullets
The traditional method of water can't be proved by dyby.
Germany is currently building a pilot plant for dyeing the PET Yarn spool with this new method.
The new method is currently under construction in Germany.