Fluorescent Brightener Paper Making Process factors affecting whiteness - Paper, Paper, Paper - Paper Industry

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1 Principles of fluorescent brighteners brightening


Residual lignin as fiber, and chemical pulping process used to make paper yellow shade is always to the principle of optics is that the paper absorbs the natural light of shorter wavelength light, reflected light in the blue-violet visible light is a bit of a lack of which led us to see yellowish paper. The use of optical brighteners is in the ultraviolet (Uv) stimulation, the release of 420 ~ 450nlIl wavelength of fluorescence, to supplement a shortage of blue-violet wavelength of visible light segment, and increase the amount of total reflection of light as the light-sensitive, thus, increase the paper's self-inductance. Optical properties of fluorescent whitening agent is a sense of increasing the role of the white dye, so we called fluorescent whitening agent to optical brighteners, chemical bleaching alone can not achieve satisfactory whiteness, and excessive bleaching will damage fibers Thus, the fluorescent whitening agent is considered the most cost-effective papermaking pharmaceutical white paper.



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2 paper with fluorescent whitening agent of the type and effectiveness of the fluorescent whitening agent with the most paper is anionic direct dyes. General paper may be used in fluorescent brighteners into three categories according to their degree of sulfonation:
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General type: with enough fiber affinity, good pH stability, and starch has good compatibility between, belonging to four sulfonic acid-based fluorescent whitening agents, such as the NT 1 3, NT 1 3 1 B. Direct type: good fiber affinity, fluorescence intensity, with less, it is economic, but the pH stability of the poor, is the second acid-type optical brighteners, such as NT-8.





Coating type: and fiber affinity poor absorption in the fiber is not easy, but it can spread the paint in any condition, in particular, can adapt to all kinds of adhesive, and cationic, high cost, is 6-sulfonic acid fluorescence brightener, such as fluorescent brightener RSB.





Special type: and fiber has a high affinity, excellent weathering performance, refined white paper that can achieve a high degree of acid and alkali resistance are better, but more expensive, such as fluorescent brightener FNW.





3 factors affect the whitening agent whitening effect and Countermeasures


3.1 puree whiteness Higher pulp brightness, whitening agent whitening the better. Only in the high brightness of pulp bleaching agent before the use of more economical and reasonable. For example, the whiteness of magma in the 70% / SO below, the lower the whiteness, whitening effect worse. The same amount of whitening agent, a small value of whiteness. When the puree at 80% ISO brightness are prone to whitening, using 4 ~ 6kg / t paper liquid whitener NT-3 or NT-3 can reach a brightness B 9o% ~ 95% ISO. If the pulp bleaching process equipment subject to conditions, puree whiteness only 75% ISO below recommended NT-8, but must make more than pH 7 before they can have better whitening effect. If deinking recycled paper, taking into account the part of the paper has used whitening agent, whitening agent by adding to significantly improve the general whiteness of finished paper is difficult, choose a special whitening agent trial F1Nw, due to price more costly, should be carefully chosen, NT-3 is also the choice of a B-type product.





3.2 increase from the amount of agent


Certain conditions, puree brightness conditions, brightener on the absolute amount of dry pulp is very important. First of all, with the increase of the amount whitener, whiteness is rapidly increasing, and reached a certain peak. With the increased use of whitening agent after the peak, the peak brightness of little change or even decreased.





When brightener consumption increased from 0 to 0.4%, the brightness increases linearly; but the amount from 0.4% to 0.8%, the whiteness value increased very little. At a time when the cost of whitening agent is increased by one fold! Production brightener consumption reached 12 ~ 16kg / t of paper, but still little change in brightness, is the truth. More than the amount of peak production, then more brightener consumption, does not make sense to improve the whiteness. Of course, in a machine, a particular species of paper, under certain conditions, to reach the peak of the whitener whiteness amount of how much, or a reasonable amount of whitening agent how much the economy, the factory is not the same, to to do some delving into the work. We recommend that the economic content, NT 1 3, NT-3-B is generally 4 ~ 8kg / t paper, NT-8 is generally 3 ~ 6kg / t paper.