We know that commonly used water-soluble optical brighteners are stilbenes such as optical brighteners VBL and CXT. The optical brightener VBL has two structures, cis and trans, and the trans structure has a good whitening effect. Sunlight and high temperature can transform the trans structure into a cis structure to reduce the whitening effect.
CXT is commonly used in washing powder. It is characterized by a large amount of compounding and a high accumulated washing Baidu. This whitening agent has a whitening effect on cotton, hemp, rayon, polyamide, nylon and protein fibers. The good intensity of whiteness is better than the brightener VBL. Biphenyl fluorescent whitening agent CBS-X. From the molecular formula, it belongs to the stilbene derivative. Its solubility in water is 25g / L at 25 ℃, 300g / L at 95 ℃. The whitening agent has excellent solubility, light resistance, oxygen bleaching agent, chlorine bleaching agent, strong acid and strong alkali performance.
Coumarin fluorescent whitening agents such as SWN are soluble in water and can be used not only for paper whitening, especially for animal fur whitening, which has a good effect.
Three methods of adding fluorescent whitening agent in papermaking
1. Adding in pulp: Add fluorescent whitening agent directly to artificial pulp and then make paper. This method is the most widely used. At the moment of use, first dissolve in 50-60 degrees hot water according to the ratio of 1 part of whitening agent and 20 parts of water, after filtering, dilute with cold water to 2-5g / L, and then add to the pulp. It should be noted that the fluorescent whitening agent cannot be added to the pulp at the same time as aluminum sulfate, otherwise the fluorescent whitening agent will precipitate and affect the whitening effect.
2. For surface sizing: Add fluorescent whitening agent to the surface sizing solution. The amount of whitening agent is 0.01% -0.2%. The use of surface sizing for optical brightener whitening is a very economical whitening method. Because the optical brightener has excellent adsorption to starch, polyvinyl alcohol or carboxymethyl cellulose. Fluorescent brighteners tend to stay on the surface of the paper rather than migrate to the base of the paper. The higher the paper weight, the more obvious the cost advantage of the surface sizing and whitening method.
3. Pigment coating: Use after mixing the optical brightener with the coating pigment. The PH value of the coating liquid is about 9, weakly alkaline, and the whiteness of the white pigment in the coating itself is high.
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Fluorescent brightener production is now sluggish
Post time: Apr-18-2020