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Common Issues and Functions in the Use of Defoamers
Release Date:
2022-10-11
In industrial production, certain regions that manufacture foam plastics often use defoamers to eliminate the foaming that occurs during processing. Throughout the application of defoamers, numerous challenges may arise; today, we’ll discuss several common issues and their solutions.
In industrial production, certain regions that manufacture foam plastics often employ defoamers to mitigate the adverse effects of foaming during processing. Throughout the application of defoamers, numerous challenges may arise; today, we will discuss several common issues and their corresponding solutions.
I. The Challenge of Defoamer Turbidity
Defoamers do not exist in the system in a dissolved state; they typically remain as a floating phase. Consequently, the choice of hydrophobic particles, methyl silicone oil, and their respective dosages and coloration are particularly critical, leading to variations in defoamer performance. However, as long as the defoaming effect is effective and the foam‑suppression duration is sufficiently long, there is generally no major issue.
II. The Issue of Defoamer’s Foam-Inhibiting Duration
The characteristics of methyl silicone oil in defoamers determine the duration of their foam‑suppressing effect. The water content of the methyl silicone oil, in turn, dictates how long the defoamer remains effective within the process system. The particle size of the defoamer affects its resistance to filtration; excessively large particles or insufficient mixing can lead to the defoamer being removed during filtration. In wastewater treatment, effluent typically undergoes multiple filtration stages; if the defoamer is filtered out at any point, this will compromise both its initial and sustained foam‑suppression performance.
III. The Problem of Ineffectiveness of Defoamers
The reliability challenge of strong acids and strong bases: if the corrosion resistance of an antifoaming agent is inadequate, leading to the dissolution of methyl silicone oil, the antifoam may become ineffective. Additionally, certain components can cause methyl silicone oil to leach into the system, at which point the antifoam no longer functions as an antifoaming agent; it merely remains in the system as a surfactant, resulting in significantly more foam than would occur without any antifoam additive. Proper application of an antifoam can yield twice the results with half the effort. The market offers a wide variety of antifoams, including those for fermentation, wastewater treatment, textile dyeing, and other applications. Therefore, it is essential to select an antifoam tailored to the specific industry; only then will its performance be truly pronounced.
Defoamers are typically formulated through multi-component blending. The performance of the key defoaming agent can be enhanced by tailoring the surfactant blend. Whether a particular formulation is suitable for defoaming or foam suppression depends on its application conditions: for example, a polyether may act as a defoamer under acidic or neutral conditions, but become a foaming agent under alkaline conditions; it remains effective at very low temperatures, yet loses its efficacy at elevated temperatures.
(1) Dosage points for defoamers: In paper mills, defoamers are typically added in the bleaching and washing sections, usually at the pulp washer, thickener, and pulp tank. In the papermaking section, defoamers are generally introduced into the headbox, pulp tank, sizing and stock‑preparation press sections.
(2) Dosage of defoamer: Typically, two types of defoamers are used; the one with higher water content is more cost-effective and economical, and they are added at separate locations far apart. For example, this defoamer is introduced upstream of the refiner, while the other is added in the headbox.
(3) Solutions for defoamer precipitation: For example, amide‑based defoamers can precipitate, leading to clogging of the screen‑plate apertures and, due to poor dispersion, causing paper defects such as fish‑eye spots. Certain defoamers may also interfere with functions like adhesive formulation and performance enhancement. Therefore, in high‑moisture emulsion systems—whether used in high‑ or low‑viscosity calendering coatings—defoamers with excellent foam‑suppressing and foam‑inhibiting properties are essential.
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