■ Paper making
Whitening of paper can usually be carried out in papermaking links such as beating, sizing and surface coating. The method of adding fluorescent brightener directly to pulp and then making paper is mostly used. It is also economical and practical to add fluorescent whitening agent to the surface sizing solution for paper whitening. The whitening agent tends to stay on the paper surface, and the paper whiteness is easy to adjust.
In the field of food packaging paper, there are stricter regulations. For example, popcorn barrels must be made of food grade white cardboard. In order to reduce costs, some businesses use recycled waste paper for production. However, due to poor pulp quality, they have to add a large number of fluorescent brighteners to achieve aesthetic effect. Under the ultraviolet analyzer, the popcorn barrel mixed with a large amount of fluorescent whitening agent will show a bright and dazzling blue, while the qualified package made of food grade white cardboard will show a natural milky white. Therefore, when people buy paper food packaging such as disposable paper cups, it should be noted that the whiter the paper, the cleaner it is.
■ Detergents
During the wearing process, many clothes become old and yellow due to various reasons (including the loss of part of the fluorescent whitening agent added in the dyeing and finishing stage), such as the whiteness of white clothes decreases, and color clothes are no longer bright. Although surfactants and detergent aids play a role in decontamination, fluorescent whitening agents have no decontamination function. However, under the same decontamination function, clothes washed with appropriate fluorescent whitening agent will appear more bright.
■ Textiles
Fluorescent brighteners have been used in the field of textile fibers for nearly 70 years. Fibers are divided into cellulose fibers, protein fibers and synthetic fibers. Therefore, when using fluorescent whitening agents, you must first understand the chemical composition and physical properties of the fibers in order to select appropriate fluorescent whitening agents. Fluorescent brighteners used in textile fiber industry should meet multiple conditions, such as no damage to fibers and good affinity; It has good water solubility; Good chemical stability; It has good uniform whiteness, etc.
■ Others
With the vigorous development of the plastic industry, people's requirements for the appearance performance of plastic products are increasing. Therefore, the use of fluorescent whitening agents to improve the appearance of plastic products has attracted more and more attention. In addition, fluorescent whitening agents are also used in pearl whitening, paint, leather and other fields.