silicone defoamer manufacturing process

Silicone defoamers are mainly polydimethylsiloxane (silicone oil) combined with hydrophobic silica, supplied as pure compounds, pastes or – most commonly – water-based emulsions. Production starts with a silicone–silica compound, which is then emulsified. Exact ratios, temperatures and catalysts are proprietary and differ between food-grade and industrial products.

1. Raw Materials

• Base silicone: dimethyl silicone oil (PDMS), 100–100,000 cSt.
• Fillers: fumed or precipitated silica, often hydrophobised in situ, a few percent by weight.
• Emulsifiers: non-ionic surfactants (Span, Tween) matched by HLB.
• Additives: thickeners (CMC, PVA, acrylics), stabilisers, preservatives, pH adjusters.
• Continuous phase: water.

2. Preparing the Silicone Paste / Active Compound

1. Charge silicone oil into the reactor.
2. Add silica with modifiers/catalyst while stirring.
3. Heat to 80–210 °C (often 120–160 °C).
4. Stir 1–6 hours to hydrophobise and disperse the silica.
5. Cool the compound.

3. Emulsification

1. Dissolve emulsifiers in the oil phase (or prepare separate phases).
2. Heat both phases to ~50–70 °C.
3. Prepare the aqueous phase with optional thickener.
4. Combine (oil into water, or by phase inversion).
5. Homogenise at 1,500–3,000+ rpm for 15–30+ minutes.
6. Cool; add preservative and thickener; adjust to pH 6–8.
7. Re-homogenise if needed and rest.
8. Test stability, particle size and defoaming performance.

4. Post-Treatment, QC & Packaging

Viscosity and active content (typically 10–30%+) are adjusted, heat-storage stability is tested, and product is packed in carboys and drums.

Key process notes

• Equipment: temperature-controlled reactors, high-shear mixers, homogenisers.
• Critical factors: silica hydrophobisation, emulsifier choice, shear and temperature control.
• Variations: solvent-based, powder and self-emulsifying grades.

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