On each screen, the areas in the design that are not to be penetrated by the dye are covered with lacquer or some other dye-resistant coating. The screens are coated with dye on the back and mounted in the proper sequence above a flat bed. As a belt carries the fabric along from screen to screen, a squeegee or roller presses the dye through the open area of the screen onto the fabric.
The new flat bed machines can have speeds of up to 1, yards per hour for a fabric with a inch design repeat. Faster by far are the recently developed rotary screen printing machines with production speeds of up to 3, yards an hour.
The system combines roller and screen printing, utilizing perforated cylinders instead of flat screens. The color paste is fed inside the cylinders and a small metal roller forces the color through the pores of the cylinder onto the fabric which is moving continuously under the cylinders. As many as 16 colors can be printed on one fabric using this method.
Use of this technique is increasing since the screens or cylinders can be produced less expensively than the engraved copper rollers used in roller printing. Finishing, as the term implies, is the final step in fabric production. In modern machines, circulation is improved at the points of contact between hank and pole.
This leads to better leveling and elimination of irregularities caused by uneven cooling. In package-dyeing machines dye color may be pumped in rather two directions:. Some package-dyeing machines are capable of working under pressure at temperatures up to C.
The winch is the oldest piece of dyeing machine and takes its name from the slated roller that moves an endless rope of cloth or endless belt of cloth at full width through the dye liquor. Pressurized-winch machines have been developed in the U. In an entirely new concept, the Gaston County jet machine circulates fabric in rope form through a pipe by means of a high-pressure jet of dye color.
The jet machine is increasingly important in high-temperature dyeing of synthetic fibers, especially polyester fabrics. Another machine is the jig. It has a V-shaped trough holding the dye color and guide rollers to carry the cloth at full width between two external, powered rollers, the cloth is wound onto each roller alternately, that is, the cloth is first moved forward, then backward through the dye color until dyeing is complete.
Modern machines, automatically controlled and programmed, can be built to work under pressure. The information provided on this website is for educational or information purposes only. Anyone using the information on Fibre2fashion. The views and opinions of the authors who have submitted articles to Fibre2fashion. If you wish to reuse this content on web, print or any other form, please seek for an official permission by writing to us on editorial fibre2fashion.
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Make to Order. Wed, November 24th, Featured Fairs. Get your copy. By: Dg Ladha. View Article Analytics. Methods of Dyeing 1 Bale Dyeing: This is a low cost method to dye cotton cloth.
It is wound onto a perforated beam and the dye is forced through the perforations thereby saturating the yarn with color. It is a hand operation. Several cuts or pieces of cloth are tacked end-to-end and run through in a continuous chain in the dye color.
Pigments can be derived from minerals but can also be made synthetically. Because they are not soluble in water, they can last longer than dyes. To reduce this burden, Huntsman has developed a line of dyes for cotton called Avitera that bonds to the fiber more readily. According to the company, the colors require one-quarter to one-third less water and one-third less energy. Thanks to these extra reactive groups, the dye step lasts about four hours, compared with seven hours for conventional dyes.
Still, it takes a lot of legwork to sell customers on a new suite of dyes. Different regions and countries have different cost structures, he says. Another way to improve the bond between dyes and cotton fibers is a process called cationization.
In North Carolina, textile industry veteran Tony Leonard is taking that approach. Leonard is the inventor and technical director behind ColorZen, a start-up that has developed a cotton pretreatment step. ColorZen treats raw cotton fiber right from the field after the seeds are removed. After treatment, cotton is spun into yarn at customer facilities. It also cuts out almost half the dye compared with processes that call for salts in the dye bath. The company has a partnership with the manufacturing technology firm Jabil to help it scale up its plant in Mebane, N.
It is also in a program run by the apparel start-up incubator Fashion for Good. Hohenstein developed Oeko-Tex, a series of standards and tools for certifying nontoxic textiles. The first version of the standard was called Oeko-Tex for the number of chemicals it tracked. Oeko-Tex certification is now up to more than chemicals. Synthetic indigo, used to make blue jeans blue, is an example of a dye that can release unreacted chemicals downstream of manufacturing.
Indigo is unlike most dyes in that in its unreduced form it is not soluble. So companies like Archroma upgrade it into easier-to-use, prereduced solutions that are more water soluble. The company became concerned after seeing published reports that about metric tons of aniline per year escapes the dyeing process from 70, metric tons of indigo. Archroma developed a technology for prereducing indigo to prevent aniline from carrying through as a contaminant.
Finished textiles colored with the dye contain a nondetectable amount of aniline, whereas competitor dyes can contain up to 2, ppm of the chemical, according to Archroma. Carnahan acknowledges differing views about how big a problem aniline is in the textile industry. It has a better reputation than the category 1 carcinogenic amines that cleave off of azo dyes and were an early target for elimination by clothing brands.
Of course, in the beginning, indigo came from a plant, not a factory. The very first pair of modern-style blue jeans, made by Levi Strauss, debuted in That was about 25 years before chemists developed the synthetic route to indigo dye—with its unappetizing starting materials of aniline, formaldehyde, and hydrogen cyanide.
The ambition at Stony Creek Colors is to return to those early days. Founder Sarah Bellos says a complete life-cycle review of the production and use of synthetic indigo provides plenty of reasons to look again at indigo from plants. Dyeing : Warm temperature, long process time, requires addition of large amounts of salt and alkali fixatives. Washing : Long, energy- and water-intensive process using multiple baths, with at least one at boiling temperature. Washing : Shorter process requiring less energy, water, and chemicals than cotton.
Uses alkali and chemical reducing agent. Washing : Similar to cotton but shorter process, possibly due to less unfixed dye to be removed. Stony Creek is developing varieties of leguminous indigo plants that can provide a high-yield, high-profit crop for Tennessee farmers looking for an alternative to tobacco.
The company is selling all the dye it can make; its goal is to expand U. That could displace 2. Dye houses can reduce natural indigo in bacterial fermentation vats or use more common reducing systems, she adds. Other start-ups have also turned to biology—in particular, engineered microbes—to reduce the use of chemicals in textile dyes.
All that is required to scale up are fermentation tanks and sugar. The idea for Colorifix came out of a biological sensor program in Nepal and Bangladesh. David Nugent and colleagues were in the region to test drinking water wells for arsenic.
They asked local village governments what other substances in their water concerned them. The team was already using color made by microorganisms to act as a sensor for water contaminants. Soon, Nugent says, it became clear the researchers could engineer them to produce natural colors, including anthocyanins and carotenoids. Dyes come in four forms- powders, pastes, crystals, and liquid dispersions. They all get completely dissolved in an aqueous solution like water. When the textile material is dipped into it, the dye molecules get fixed on the fibers.
Basically, the dyeing process is all about absorption and diffusion. Absorption is transferring of dyes from the aqueous solution onto the fabric surface and diffusion is dyes getting diffused into the fibers.
Of course, the temperature and other controlling factors play a major role. This dyeing can be either done by hand or machine. Also, different kinds of dyes are used for different types of fabrics. For example, acid dyes are used to dye wool and silk, the basic dye is used for acrylic fabric, disperse dyes for polyester yarn and cotton can be dyed with a variety of dyes like vat dyes, direct dyes and modern synthetic reactive.
The right dyeing fabric process is:. Singeing and Desizing : They are the first two steps of pre-treatment respectively.
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