Foam is almost a regular visitor throughout the papermaking process. Pulping and cooking, washing and screening, bleaching, papermaking and even waste liquor treatment all generate large amounts of foam due to mechanical agitation, chemical agents and the natural surface-active substances in the pulp. At best this affects pulp yield and washing efficiency; at worst it causes web breaks, reduced formation uniformity and even a full line shutdown. Choosing the right antifoam for each section is a very practical basic skill in papermaking process management.
Pulping and Papermaking Sections Have Quite Different Requirements
Foam in the pulping section mainly comes from resin, lignin and saponified matter during cooking and washing; the system is high in temperature and strongly alkaline, so the antifoam needs good temperature and alkali resistance and strong foam-breaking ability. Foam in the papermaking section is mostly related to wet-end chemicals such as retention and drainage aids and sizing agents; here, compatibility between the antifoam and the wet-end system is emphasized more, to avoid oily substances forming spots on the sheet or affecting sizing. One product used all the way through often satisfies neither end.
Wet-End Chemicals: Compatibility Is the Hidden Reef
Papermaking uses large amounts of starch, polyacrylamide-type retention aids and various surfactants; these substances change the stability of the foam and may also interact with the antifoam. Improper selection may interfere with retention performance or leave oil spots and white dots on the paper surface. The industry generally recommends running a small-scale wet-end system trial before formal use, to observe its effect on pulp retention and sheet appearance.
Environmental Protection Is Raising the Bar
Papermaking antifoams are shifting from high residue and poor degradability toward low VOC and easy biodegradability. As wastewater discharge standards and green factory assessments tighten, products that combine efficient foam breaking with environmentally friendly characteristics are favored more by paper mills. Only by coordinating antifoam selection with section characteristics, wet-end compatibility and environmental requirements can production remain stable while the grade of the finished product is raised.