In black and white, the power is hard to move. As one of the four great inventions in China, the existence of paper provides a powerful medium for the dissemination of scientific culture and enriches our civilization. Different from the cumbersome papermaking in ancient times, with the rapid development of industrialization, our papermaking technology has become more and more perfect, and one ton of wood chips can produce 500-600 kg of chemical pulp or 700-800 kg of mechanical pulp. However, from wood chips, waste paper and other raw materials to various types of paper we use daily, we still need to go through pulping, cooking, washing, bleaching, dehydration, papermaking, sizing, coating and other processes. During this period, due to processes such as stirring, spraying and the addition of additives, more or less foaming will occur. If the foam is not treated in time, it will cause problems such as foam points and pinholes, which will seriously affect the quality of the paper. At this time, we need process aids: defoamer. Paper defoamer can not only solve the foam problem in the papermaking process, but also improve the quality of coated paper.

1. Pulping and cooking waste liquor (black liquor)
The natural lignin, resinous acid and other substances dissolved in the cooking process of papermaking raw materials are easily foamed after being impacted and stirred. Especially, the turpentine saponified content of pine wood is high, and the foaming phenomenon is especially serious.
The sewage (black liquor) discharged from pulping has high organic content, high temperature and strong alkalinity, so the added defoamer is required to be resistant to alkali and high temperature, and has good stability under the impact of strong water flow. The defoaming agent defoamers quickly, but it is easy to precipitate silicone grease, which causes sticky obstructions, and even causes the filter screen to block, which affects the quality of the slurry.

2. Papermaking wastewater (white water)
In the process of beating and white water closed cycle, air is brought into the slurry to form bubbles due to processes such as stirring, shaking, and spraying, and due to the existence of surface-active additives such as filter aids, wet strength agents, and sizing agents, the formation of Difficult-to-remove scum foam.
The defoamer for papermaking requires rapid defoaming, long-term foam suppression and defoaming under the conditions of high temperature, strong alkali and high shear. The defoaming does not affect the cleanliness of paper and subsequent spraying. The defoamers used in this stage are mostly higher alcohols and polyetheresters.

3. Coating
In the coating process of the coating machine, due to foaming substances such as alkalis and pigments and mechanical stirring, many foams often appear, resulting in uneven paper quality, white spots, rough and dull surface, and blurred printing in the later stage.
The defoamer used in coating will eventually be retained in the paper product, so it is required that the papermaking coating defoamer has good dispersibility, does not affect the viscosity of the coating and printing, does not affect the color of the pigment, and also improves the paper product. gloss, smoothness, and brushing efficiency.

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