From ancient Egypt to the indigenous peoples of Latin America, ancient civilizations used dyeing techniques, although they are classified as artisanal. Due to the demand and the arrival of the Industrial Revolution in the eighteenth century, the scenario of textile coloring changed and factories began to exploit synthetic dyes on a large scale. From there, many technologies appeared and are still being developed, for example, to increase quality or add properties to products.
One of these technologies was born at the Federal University of Rio Grande do Norte and has just been patented by the National Institute of Industrial Property (INPI). The invention deals with a new process of dyeing by depletion or exhaustion applied to inorganic and organic nanoparticles, with properties and characteristics that surpass those already on the market, as it has the ease of application in an industrial way, since all industries processing textile products currently have equipment that can be used for this process.
This situation is different from most of the processes already on the market, which are limited to laboratory production and small samples. The product is the thesis result of Iris Oliveira da Silva, who at that time was a student at the university and is currently a professor at the institute. She explained that the invention transforms different types of textile substrates, such as knitting, fabrics and non-woven fabrics (TNT), into multifunctional substrates, with potential biomedical application, primarily through protective measures against microbes, germs and UV rays.
Initially, the substrate is chemically treated to remove wax and grease, according to traditional industrial processes such as depilation, cooking and bleaching. They are then “dipped” into a solution with chemically synthesized nanoparticles. Next, industrial dyeing equipment is used so that the nanoparticles are adsorbed – or retained – on the surface of various textile materials. These mineral particles can be inorganic, such as gold and zinc, and organic, in the form of chitosan and keratin nanocapsules.
“This procedure is easy in the sense that the nanoparticle impregnation process facilitates impregnation on an industrial scale using currently in use machines, taking into account only some process parameters. What we have developed belongs to the field of textile processing, more specifically in industrial finishing processes,” explains the scientist. The use of metallic nanoparticles in textile substrates has been the focus of many studies, mainly due to their physical, chemical and optical properties, when presented in nanometer form, being the focus of major companies worldwide.
Along with Íris, co-authors are Rasiah Ladchumananandasivam, José Heriberto Oliveira do Nascimento and Christiane Siqueira de Azevedo Sá. They noted that another distinction of the new technology is the better yield of nanoparticles on the surface of the substrate, compared to other processes such as dip coating and sol-gel, among others, which greatly improve the physical, chemical and optical properties.
Named “The process of depleting organic and inorganic nanoparticles in textile substrates (mesh, cloth and non-woven) using a closed dyeing machine and controlling time, temperature and pressure”, the patent was granted on May 3. Filed in 2015, the property title was at the time associated with the Graduate Program in Mechanical Engineering (PPGEM) and Textile Chemical Process Laboratory, and currently with the Graduate Program in Textile Engineering (PPgET), a Íris Oliveira and Heriberto do Nascimento research development programme.