After the fabric is bleached, in order to further obtain satisfactory whiteness, or to increase the vividness of some light-colored fabrics, it is usually processed with organic compounds that can emit fluorescence. This compound is called Fluorescent Whitening Agent (Fluorescent Whitening Agent or Fluorescent Whitening Agent
). Brightener). Because it uses optical action to significantly improve the whiteness and vividness of the substrate, it is also called Optical Whitening Agent. At present, optical brighteners are widely used in textile, paper, plastic and synthetic detergent industries. In the process of using fluorescent brightener, just like the dyes used in fiber dyeing, it can be dyed on all kinds of fibers. It can dye paper, cotton, linen and viscose fiber like direct dye on cellulose fiber, dye fiber with acid dye on protein fiber such as wool, dye fiber with cationic dye on acrylic fiber, and dye fiber on polyester and acetate. The fibers are dyed like disperse dyes. Fluorescent brighteners have a history of more than 70 years since IG was officially supplied to the market in 1939. Early synthesized products have now been eliminated, and only part of the newly developed chemical structure has practical value, but the fluorescent brighteners The development is still very rapid. In recent years, with the rapid development of the dyeing and finishing industry, fluorescent whitening agents have been given higher requirements in the application process. For example, resin finishing and whitening in the same bath can simplify the dyeing and finishing process, reduce waste water, and save energy. It is required that the fluorescent whitening agent has certain acid and alkali resistance. Similarly, in the paper industry, whitening and resin coating are required to be carried out in one bath, so it is necessary to produce a brightener that is acid-resistant and does not produce precipitation when encountering aluminum sulfate.
Converting the amorphous products of fluorescent brighteners into crystalline products and increasing the purity as much as possible are the future development directions. Because impurities or by-products in the products will weaken and offset the fluorescent effect, so through conversion and purification, the appearance of the product can be improved. The improvement can improve the whitening effect and prevent yellowing to a certain extent.
The use of multi-component optical brighteners to replace single-component optical brighteners is also one of the development directions, because multi-component brighteners will produce a synergistic effect of optical brightening and improve the whitening effect, so it is more and more popular. attention.
Improving the color fastness of fluorescent brighteners, especially the fastness to sunlight, has become the focus of research. How to improve the fastness to sublimation on synthetic fibers will also become an important research direction.