A paper defoamer is not a generic detergent antifoam. Pulp liquor, recycled-fiber surfactants, starch, and coating binders each stabilize foam differently. This guide maps Esteem’s paper defoamers so mill chemists can pick a non-silicone or EO/PO grade by circuit—not by a familiar trade name alone.
Why Foam Costs Mills Real Production
Air in pulp and paper circuits is not cosmetic. Foam reduces washer efficiency (higher soda loss in kraft mills), overflows chests, blinds paper machine felts, and leaves pinholes or fish-eyes in the sheet. In recycled fiber, flotation and wash deinking already use foam on purpose; the rest of the mill then has to kill the foam that escapes into the machine loop.
The chemistry that created the foam matters. Wood soap and black-liquor organics behave unlike coating latex or size-press starch. A defoamer that works in brown stock can crater a coating kitchen. Start from the process map on Esteem’s paper chemicals hub, then specify the circuit.
How Paper Defoamers Work
Commercial paper defoamers enter the foam film, spread, and rupture lamellae. Persistence (anti-foam) is as important as knock-down. Three families dominate mills:
- Silicone emulsions — very efficient, but silicone oil can cause spots, felt filling, and coating defects. Many fine-paper and food-contact grades restrict them.
- Oil / fatty / ester antifoams — mineral-oil or ester carriers with hydrophobic particles. Useful in some stock systems; watch COD and deposit.
- EO/PO copolymers and capped nonionics — water-compatible alkoxylate antifoams that rinse cleaner than silicone. Esteem’s mill range is built mainly in this class, including alkyl-capped grades.
Cloud point, molecular weight, and whether the chain is end-capped decide whether the molecule stays dissolved, clouds out as a defoaming droplet, or acts more like a low-foam surfactant. Related reading: nonionic surfactants and the defoamers and demulsifiers product family.
Where to Apply Defoamer in the Mill
| Circuit | Foam drivers | What to watch | Esteem starting type |
|---|---|---|---|
| Brown-stock washing | Black-liquor soap, high solids, heat | Washer soda loss, deposits on wire | Product 21 P (EO/PO, nonionic) |
| Screen room / deckers | Air entrainment, residual soap | Overflow, consistency swings | Product 209 / Product SDS (non-silicone) |
| Paper machine white water | Starch, fines, recycled surfactants | Felt blinding, sheet holes | Product DF 152B, Product 5100 |
| Hot alkaline pulp processing | High pH, temperature | Persistence vs wash-out | Product 5500 (alkyl-capped EO/PO) |
| Acid circuits / fertilizer-adjacent | Low pH foam | Compatibility with acid salts | OT 70 PG |
Brown-stock washing is the classic kraft pain point: foam holds liquor in the mat and raises soda loss. Product 21 P is positioned as an EO/PO nonionic antifoam for brown-stock washing and black-liquor circuits—use it there, not as a default machine-chest defoamer, until you have mill data.
Silicone Restrictions and Deposit Risk
If converting, coating, or food-contact specifications ban silicone, stay in non-silicone EO/PO. Even where silicone is allowed, overdosing creates spots that look like pitch. Pair foam control with good felt cleaning so you are not using defoamer to hide clothing that is already filled.
Recycled mills should treat deinking foam as a separate brief. Flotation needs controlled froth; the machine loop needs a defoamer. Do not use the same surfactant package for both jobs. See the deinking chemicals guide and de-inking chemicals.
Grade Map: Washer vs White Water vs Acid
Product 209 and Product SDS are the published excellent non-silicone defoamer rows for general mill foam where silicone is restricted. Product 21 P is the brown-stock washing / black-liquor EO/PO nonionic antifoam: enhanced pulp washing and improved liquor recovery sit on that row. Use it on the washer brief, not as a default machine-chest defoamer, until mill data says otherwise. Product DF 152B and Product 5100 are the stock and white-water starting types on this guide’s circuit table. Product 5500 is EO/PO copolymer capped with an alkyl molecule—persistence in hot alkaline pulp processing. OT 70 PG is the acidic-medium defoamer (paper and fertiliser); it is not the alkaline white-water default.
The mill table keeps its own wording on those rows. Do not relabel a non-silicone EO/PO as a silicone emulsion, and do not treat 5100 and 5500 as the same milligram dose. Cloud point and capping decide whether the molecule stays dissolved, clouds out as a defoaming droplet, or acts more like a low-foam surfactant. A low-foam surfactant is designed not to generate foam while it wets; a defoamer collapses foam that already exists. Mills often need both: low-foam surfactants in showers and cleaners, plus a dedicated defoamer in stock and white water.
Deinking Froth vs Machine Foam vs Felt Fill
Recycled mills should treat deinking foam as a separate brief. Flotation needs controlled froth; the machine loop needs a defoamer. Do not use the same surfactant package for both jobs. See the deinking guide. Felt blinding can look like a foam problem: if vacuum is gone because the clothing is filled, more defoamer will not restore dryness. Pair foam control with felt cleaning so you are not hiding a loaded batt.
Start at the low end of the supplier range. Record baseline foam height, washer soda loss, vacuum, and sheet holes. Confirm compatibility with sizing, retention, and coating, then step the dose. A defoamer that works in brown stock can crater a coating kitchen. Name the circuit, furnish, pH, temperature, and whether silicone is allowed. Request a starting grade from the paper defoamers table—not a detergent defoamer from another industry page.
How to Specify a Paper Defoamer with Esteem
- Name the circuit (washer, white water, coating, effluent) and furnish (virgin kraft, OCC, mixed waste, bagasse).
- Give pH, temperature, and whether silicone is allowed.
- List other wet-end chemicals: sizing, retention, biocides, starch.
- State the failure mode: overflow, soda loss, sheet spots, felt fill, coating craters.
- Request a starting grade from the paper defoamers product table and mill-trial instructions.
Related mill chemistry: paper sizing, felt cleaning, bleaching aids, and alkoxylates.
Esteem manufactures these grades in ISO-backed plants with 24/7 QA. For samples, contact the technical team or review custom synthesis when a mill needs a non-catalogue cloud-point window.