Precautions For The Use Of Defoamers

Defoamers are generally made by compounding multiple components. The performance of the main defoamers can be enhanced by the combination of surfactants. Whether an active substance is suitable for defoaming depends on its application conditions. Stearic acid is a defoamer under acidic conditions; Under alkaline conditions, it is a foaming agent. It is effective at low temperatures, but ineffective at high temperatures.
(1) The addition point of defoamer: In a pulp mill, defoamer is generally added in the bleaching and washing section, usually in the washing machine, thickener, and pulp tank. The defoaming agent in the papermaking section is generally added to the paper machine's pulp box, pulp pool, coating, and sizing and pressing areas.
(2) Dosage of defoamer: Generally, using two types of defoamers is more economical and effective than using one with a higher content. They are added separately in areas that are far apart. For example, one defoamer is added in front of the beater, and another is added in the headbox.
(3) The solution to the precipitation of defoamers: such as amide defoamers, can cause precipitation and block the sieve plate gap, which can cause paper problems such as fisheye spots due to poor dispersion. Some defoamers can also interfere with the effects of gluing and reinforcement. Therefore, the high lotion system has an outstanding defoaming effect in the high and low viscosity napping coatings.