■ Paper making
Whitening of paper may usually be done during the papermaking process such as beating, sizing, and surface coating. The method of directly adding fluorescent brighteners to pulp and then making paper is mostly used. Adding fluorescent whitening agents to surface sizing solution for paper whitening is also very economical and practical. Whitening agents tend to stay on the surface of the paper, making it easy to adjust the whiteness of the paper.
In the field of food packaging paper, there are stricter regulations. For example, popcorn barrels and other materials must be made of food grade white cardboard. Some businesses use recycled waste paper to reduce costs, but due to poor pulp quality, they have to add a large amount of fluorescent whitening agents to achieve aesthetic effects. Under the UV analyzer, popcorn barrels mixed with a large amount of fluorescent whitening agent will appear bright and dazzling blue, while qualified packaging made of food grade white cardboard will appear naturally milky white. Therefore, when people choose to purchase paper food packaging such as disposable paper cups, they should pay attention that the whiter the paper, the cleaner it is.
■ Detergent
Many clothes become old and yellow during wearing due to various reasons (including the loss of fluorescent whitening agents added during the dyeing and finishing stage), such as a decrease in the whiteness of white clothes and a decrease in the brightness of colored clothes. Although surfactants and cleaning aids play a cleaning role in washing products, fluorescent brighteners themselves do not have a cleaning function. However, under the same decontamination function, clothes washed with laundry detergent with appropriate addition of fluorescent whitening agents will appear more brightly colored.
■ Textiles
Fluorescent brighteners have been used in the field of textile fibers for nearly 70 years. Fibers are divided into three categories: cellulose fibers, protein fibers, and synthetic fibers. Therefore, when using fluorescent brighteners, it is necessary to first understand the chemical composition and physical properties of the fibers in order to select appropriate fluorescent brighteners. Fluorescent brighteners used in the textile fiber industry should meet multiple conditions, such as no damage to the fibers and good affinity with them; Has good water solubility; Has good chemical stability; Has good uniformity and whitening properties.
■ Other
With the vigorous development of the plastic industry, people's requirements for the appearance and performance of plastic products are constantly increasing. Therefore, the use of fluorescent brighteners to improve the appearance of plastic products has received increasing attention. In addition, fluorescent whitening agents are also used in pearl whitening, coatings, leather and other fields.
