Feb. 04, 2020
White, a color. White is a symbol of light and peace. In clothing, white means purity! White and black are both neutral, but they are always a popular color. White can be matched with any color. In contrast to black, the white we see can also be called colorless because it reflects all visible light. The wavelength of electromagnetic waves that can be perceived by the average human eye is between 400 and 760 nm, but some people can perceive electromagnetic waves with a wavelength of between 380 and 780 nm. SO, the white objects we see are those that can reflect electromagnetic waves between 380-780nm.
Into the theme, how can textiles be white? Chemical synthetic fibers generally have better whiteness, such as polyester, nylon, viscose, etc. Natural fibers generally contain many pigments, such as cotton, linen, silk, wool, etc. Therefore, natural fibers need to be white to bleach. Taking cotton fiber as an example, the most used in the printing and dyeing industry now is hydrogen peroxide (hydrogen peroxide) bleaching, commonly known as oxygen bleaching. Before, there were sub-bleaching (sodium chlorite) and chlorine bleaching (sodium hypochlorite), sub-bleaching, chlorine Both bleaching and oxygen bleaching belong to oxidative bleaching. They are also sorted in terms of bleaching whiteness and brightness: sub-bleaching> chlorine bleaching> oxygen bleaching, but because of safety, environmental protection, cost, equipment corrosion and other factors, hydrogen peroxide is now widely used. .
For protein fibers such as silk and wool, since strong alkali cannot be used, the method of oxidative bleaching + reduction bleaching is generally used, and the reducing agent is generally used as a safety powder, and the soybean fiber of regenerated synthetic fiber will also use this method. Bleached fibers, yarns, or fabrics are generally called white or bleached.
Popularize the ancient bleaching process: ancient dyers bleached raw silk with strong alkali to remove sericin. Bleached hemp, in ancient times, more often planted with ash and lime repeatedly. Yuan Dynasty's works recorded the "semi-soaked and half-sun bleached" method of bleaching and sown hemp, which is to spread the simmered hemp hemp that has been boiled with lime on a flat reed curtain. It is extremely white. This is to use the ultraviolet rays of sunlight to oxidize the impurities and pigments in the fiber due to the ozone produced by the interface reaction on the water surface, thereby playing a bleaching role. Around this time, a method of sulfur fumigation and bleaching was also invented.
But people were not satisfied with bleaching or white, and they wanted a brighter white, so Optical Brightener invented it. Fluorescent brighteners are also called white fluorescent dyes.
Optical Brightener For Textile
The principle of optical brightener is to absorb the invisible ultraviolet light and emit visible blue light. The Optical Brightener For Textile and the yellow light emitted from the fabric are superimposed to form white light complementaryly, so that the white light emitted by the fabric is increased and can be felt by the naked eye by the time the white fabric becomes noticeably brighter, this is whitening. Fluorescent brightener can absorb invisible ultraviolet light (wavelength range is about 60-380 nm), and convert it into blue or purple visible light with longer wavelength, so it can compensate for unwanted yellowish in the matrix and reflect the ratio The original incident wavelength is more visible light in the range of 400-600 nm, which makes the product appear whiter, brighter and more vivid.
As a white dye, the whitening agent is mostly mixed. For example, the commonly used cotton whitening agent 4BK was first invented by Koreans. The direct dye blue was mixed in the whitening agent. Blue and red light white, direct dye violet is often mixed in the whitening agent.