Section
| HS Code | 450445 |
| Appearance | Milky white liquid |
| Chemical Type | Silicone (polydimethylsiloxane) antifoam emulsion |
| Active Silicone Content | Approximately 10% |
| Emulsion Type | Oil-in-water |
| Diluent | Water |
| Viscosity At 25 C | Approximately 100–200 mPa·s |
| Specific Gravity At 25 C | Approximately 1.0 |
| Ph At 25 C | Approximately 6.0–7.5 |
| Ionic Nature | Nonionic |
| Water Dispersibility | Readily disperses in water |
| Storage Shelf Life | 12 months from date of manufacture in unopened original container |
| Freeze Thaw Stability | Stable under recommended storage conditions; avoid prolonged freezing |
As an accredited DOWSIL SH 5561 Multi-Purpose Silicone Antifoam Emulsion factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Available in 55-gallon drums and 5-gallon pails, supplied in sealed, clearly labeled containers for safe storage. |
| Container Loading (20′ FCL) | 20′ FCL: DOWSIL SH 5561 antifoam emulsion loaded in palletized drums, securely braced for safe, stable container transport. |
| Shipping | DOWSIL SH 5561 Silicone Antifoam Emulsion ships as a non-regulated, non-hazardous chemical in sealed drums, totes, or pails. Protect containers from physical damage, extreme heat, and freezing. Ensure secure upright loading, proper labeling, and ventilation. Avoid contact with incompatible materials; store and transport per Dow’s safety data sheet guidance. |
| Storage | Store DOWSIL™ SH 5561 antifoam emulsion in its original, tightly sealed container, protected from contamination. Keep at temperatures between 0–50°C (32–122°F). Prevent freezing, as ice formation will damage the emulsion. Avoid excessive heat and direct sunlight. Under proper conditions, shelf life is 12 months from date of manufacture. Always mix gently before use. |
| Shelf Life | Shelf life is 18 months from manufacture when stored unopened in original containers, protected from freezing, below 30°C. |
In vinyl acetate–ethylene (VAE), styrene–butadiene (SB), and acrylic latex reactor systems, stable foam is generated during monomer feed and vacuum stripping because residual soap such as sodium dodecylbenzene sulfonate or alkyl ether sulfates lowers surface tension and stabilizes bubble films. The foam layer reduces effective reactor volume, contaminates condenser overheads, and can destabilize the latex by coalescence at the liquid–foam interface. DOWSIL SH 5561 is introduced post-nucleation at 10–500 ppm based on monomer mass, with typical continuous metering at 50–150 ppm during the stripping phase when residual monomer content is below 0.5 wt%. This addition window prevents interference with micellar nucleation and avoids broadening the particle size distribution. In a jacketed stainless-steel reactor of 10–40 m³ equipped with a turbine agitator at tip speed 2.5–4.0 m/s, the antifoam emulsion is injected into the recirculation loop immediately upstream of the vacuum stripping column, which operates at 60–70°C and 20–30 kPa absolute. Foam carryover is monitored by measuring foam height in the condensate receiver using ASTM D3601-22. Residual monomer in the finished latex must meet ISO 13741-1 gas chromatographic limits, typically below 1000 mg/kg for most dispersion applications. Overdosing beyond 500 ppm can reduce polymerization rate because silicone droplets may scavenge free radicals at the particle surface, and silicone accumulation on reactor internals raises coagulum formation. End products derived from these latexes include architectural coatings, carpet backing, nonwoven binders, and pressure-sensitive adhesives.
High-temperature jet dyeing machines such as Then Airflow, Thies iMaster, or Fong’s Jumboflow circulate dye liquor through venturi nozzles at liquor ratios of 1:6 to 1:12, generating local shear rates above 104 s−1 in the nozzle throat. Conventional silicone emulsions with median droplet diameters exceeding 10 µm can undergo shear-induced coalescence in this recirculation loop, depositing silicone agglomerates on fabric as dark spot defects under disperse dyeing. DOWSIL SH 5561 is applied at 0.05–0.3 g/L of dye bath, equivalent to 0.005–0.03 % owf on weight of fabric, after dyes, leveling agents, and electrolytes are fully dispersed; simultaneous addition with concentrated alkali or reducing agents is avoided to minimize emulsion destabilization. The production sequence for polyester involves pre-scouring, dyeing at 130°C under 1.5–2.0 bar pressure, reduction clearing, and final rinsing; for reactive cotton, dyeing occurs at 60–98°C and the antifoam is added during the rinsing and softening stages. Foam height in the drain trough is typically controlled below 50 mL in the ASTM D3601-22 bottle test after 60 s settling, preventing pump cavitation and dye bath overflow. Textiles destined for Oeko-Tex Standard 100 certification must have residual silicone loadings conforming to Annex 4 limits; the finished article is verified by solvent extraction and GC–MS. End products include dyed woven and knit apparel, automotive upholstery, and technical textiles for filtration.
Returnable bottle washing lines that operate at 75–85°C with 1.5–2.5% w/w NaOH recirculated at 1–3 bar spray pressure experience foam that reduces jet impingement on soiled surfaces and can overflow the caustic bath exit. DOWSIL SH 5561 is continuously metered into the detergent holding tank at 0.01–0.1 mL/L of wash solution, maintaining trough foam height below 10 mm as verified by an ultrasonic level sensor in the trough. In tunnel washers with multiple zones—pre-rinse, caustic soak, caustic spray, warm rinse, final rinse—the antifoam is excluded from the final rinse to prevent silicone film formation on bottle interiors. Over-addition or carryover into final rinse can leave a hydrophobic residue that causes haze on PET surfaces, detected by turbidimetry at 650 nm. Compliance for cleaning agents in food and beverage plants requires adherence to EU Detergent Regulation (EC) No 648/2004, which mandates ultimate biodegradability of surfactants; the polydimethylsiloxane active is not biodegradable under OECD 301B, so its concentration in end-of-pipe wastewater is limited by the local discharge permit. Sanitizing solutions used on food-contact surfaces must meet FDA 21 CFR 178.1010, where residues are permitted at levels not exceeding those established for the specific use pattern. Terminal products are cleaned glass and PET bottles, dairy processing equipment, and returnable crates ready for refilling or reuse.
Paper machine white water loops stabilize foam through dissolved and colloidal substances (DCS), including rosin size, starch, fatty acid soaps, and anionic trash from mechanical pulps. Foam on the forming section creates pinholes and sheet breaks, while silicone antifoam over-addition reduces internal sizing efficiency because silicone migrates to the fiber surface and interferes with rosin–alum retention, a reduction measurable by the Hercules Size Test (TAPPI T 530). DOWSIL SH 5561 is added to the wire pit or white water silo at 10–50 ppm of white water flow, equivalent to 0.1–0.5 kg per tonne of dry fiber, preferably after pressure screens to avoid shear-induced agglomeration. The addition point is selected based on white water retention time of 2–5 min before headbox dilution. Production equipment includes pulpers, hydrocyclones, pressure screens, and a twin-wire former running at 800–1500 m/min with headbox consistency 0.5–1.2%. Overdose above 50 ppm can accumulate silicone on press felts, reducing felt permeability measured by ASTM D737 air permeability and requiring more frequent felt washing cycles. Compliance for food-contact paper and paperboard requires the defoaming agent to be listed in 21 CFR 176.210; end-use extraction testing per 21 CFR 176.170(c) is necessary, and Regulation (EC) No 1935/2004 Article 3 requires no transfer of constituents in quantities endangering human health.
| Regulatory framework | Citation / standard | Scope | Verification basis |
|---|---|---|---|
| US FDA indirect food additive | 21 CFR 176.210 | Defoaming agents used in manufacture of paper and paperboard | End-use extraction testing per 21 CFR 176.170(c) |
| EU framework regulation | Regulation (EC) No 1935/2004 | Materials and articles intended to come into contact with food | Article 3 general safety; no transfer of constituents in quantities endangering human health |
| German BfR recommendation | BfR XXXVI | Paper and board for food contact | Compliance with monomer and additive restrictions specified in the recommendation |
Terminal products include tissue, corrugating medium, linerboard, and printing and writing grades.
High-speed dispersion of waterborne acrylic and polyurethane dispersions entrains air; the surfactant package such as sodium lauryl sulfate, nonylphenol ethoxylates, or polymeric dispersants stabilizes microfoam that appears as pinholes and craters in the dried film. DOWSIL SH 5561 is introduced during the letdown stage at 0.1–0.7% of total formulation weight, equivalent to 0.02–0.3% active silicone, after the pigment grind has been completed and the millbase has cooled below 40°C. Adding the emulsion before high-shear dispersion subjects the silicone droplets to tip speeds above 10 m/s in a Cowles disperser, which can reduce defoaming efficiency by emulsion droplet breakup. The emulsion droplet size should remain below 20 µm to avoid visible craters; this is verified by laser diffraction or by Hegman grind gauge per ISO 1524. Quality control includes foam volume after high-speed mixing measured by ASTM D3601-22, gloss at 60° per ISO 2813, and intercoat adhesion per ASTM D3359. Over-addition beyond 0.7% lowers gloss and increases surface slip, which can compromise overprintability. For architectural coatings in the European Union, Directive 2004/42/EC limits VOC content; the silicone active is non-volatile and does not contribute to VOC emissions. Production lines include a letdown tank with a low-shear propeller at tip speed <3 m/s, a 10–25 µm bag filter, and automated viscosity adjustment. Terminal products include interior and exterior architectural paints, flexographic and gravure inks, and overprint varnishes.
Fine-bubble diffuser systems in activated sludge aeration basins are vulnerable to foam stabilized by extracellular polymeric substances (EPS), surfactants from industrial discharges, and filamentous bacteria such as Microthrix parvicella. In secondary clarifiers, stable foam can overflow weirs and raise total suspended solids (TSS) above discharge permit limits. DOWSIL SH 5561 is dosed into the aeration basin influent or Parshall flume at 0.5–5 mg/L of influent flow for continuous foam control; during severe episodes, slug doses of 10–20 mg/L for 24–48 h are applied. The silicone active is not biodegradable under OECD 301B, so dosing is minimized to avoid biosolids accumulation and potential interference with downstream membrane processes. In membrane bioreactors (MBRs) using PVDF or ceramic membranes, silicone fouling can increase transmembrane pressure and require chemical cleaning; therefore addition is located upstream of fine screens and not directly before membrane tanks. Oxygen transfer efficiency (OTE) in clean water is measured per ASCE 2-06; a surface film of silicone can reduce OTE by reducing bubble coalescence and increasing bubble size. Sludge inhibition potential is evaluated by ISO 8192 activated sludge respiration inhibition test; if respiration inhibition measured by ISO 8192 exceeds the threshold set by the receiving utility or local permit, dosing is reduced. Compliance with EU Urban Waste Water Treatment Directive 91/271/EEC requires treated effluent to meet BOD, COD, and TSS limits. The downstream process includes conventional activated sludge, extended aeration, sequencing batch reactors, and anaerobic digesters operating at 35–37°C with 15–20 day retention. Terminal products are treated wastewater meeting permit limits, biogas with methane content 60–65%, and dewatered biosolids for land application.
Pesticide suspension concentrate (SC) production uses horizontal bead mills charged with 0.6–1.2 mm yttria-stabilized zirconia grinding media; the high-energy milling of active ingredients such as chlorothalonil, mancozeb, or azoxystrobin with anionic dispersants and wetting agents generates persistent foam that reduces mill throughput and can cause cavitation. DOWSIL SH 5561 is added post-milling during letdown at 0.05–0.5% w/w of the formulation, after the millbase has been cooled and transferred to a letdown tank with a low-shear anchor agitator. Adding the antifoam directly to the bead mill feed is avoided because the high shear can destabilize the silicone emulsion and leave silicone deposits on the mill chamber. Formulation quality control includes persistent foam measurement by CIPAC MT 47.1, where foam volume is recorded over a fixed time interval; the acceptance limit is specified in the individual FAO/WHO product specification, and typical commercial SC specifications set the foam volume below 25 mL after 10 min—published data for this specific configuration is limited and limits vary by active ingredient and surfactant system. Rheological stability is measured by ISO 3219 rotational viscometry after 7 days at 54°C. For spray tank applications, DOWSIL SH 5561 is used at 0.01–0.05% v/v of spray mixture to control foam during mixing of water-dispersible granules and emulsifiable concentrates. Over-addition can alter droplet spread factor on leaf surfaces and reduce biological efficacy due to surface tension lowering. Compliance with FAO/WHO specifications for pesticides requires the formulation to meet physicochemical parameters including persistent foam, suspensibility, and wet sieve retention. End products include herbicide, fungicide, and insecticide suspension concentrates, suspo-emulsions, and water-dispersible granules.
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Aqueous foam control in paper wet-end, textile dye bath, and waterborne coating operations is frequently achieved with a water-dilutable silicone emulsion rather than a solvent-borne or powdered defoamer. DOWSIL SH 5561 Multi-Purpose Silicone Antifoam Emulsion is a nonionic, water-continuous emulsion of polydimethylsiloxane fluid and hydrophobic silica. The manufacturer’s technical bulletin lists an active silicone content of 10 wt%, a specific gravity of approximately 1.00 g/cm³ at 25 °C determined according to ISO 2811-1:2016, and a Brookfield viscosity of 1,000–4,000 mPa·s at 25 °C determined according to ASTM D2196-20. The pH is neutral to slightly alkaline, typically 7.0–9.0 when measured by ISO 976:2013, and the product is supplied as a mobile milky white liquid. The nonionic emulsifier package permits co-addition with most anionic and cationic wet-end auxiliaries, provided concentrated electrolytes are not added directly to the emulsion. Storage should be maintained between 5 °C and 40 °C; freezing initiates droplet coalescence and oil separation that is not reversible by re-agitation.
Mineral oil defoamers spread on aqueous lamellae and displace surfactant monolayers, but their performance degrades sharply above 60 °C, and their use introduces hydrocarbon load to aerated lagoons—measurable as an increase in BOD5 by ISO 5815-1:2019. Polyol and EO/PO block copolymer defoamers are hydrophilic, but above their cloud point they phase-separate and below the cloud point they can be solubilized into surfactant micelles; this makes dosing temperature-critical. A polydimethylsiloxane/hydrophobic silica antifoam operates by a different mechanism: the silicone phase exhibits a surface tension of approximately 20–21 mN/m at 25 °C, spreads rapidly on the foam lamella, and creates a hydrophobic silica bridge that ruptures the liquid film. Because the silicone phase is insoluble in the foaming medium, the defoamer remains active over a wider pH and temperature window. Dose requirements are typically 50–300 ppm of the as-supplied emulsion in paper whitewater and textile dye baths, equivalent to 5–30 ppm active silicone. Mineral oil or polyol products may require 1,000–5,000 ppm as-supplied to achieve equivalent knock-down in high-surfactant systems. The water-continuous emulsion eliminates solvent handling and contributes negligible VOC compared with xylene or mineral-spirit antifoam carriers.
On paper machine whitewater loops, the emulsion is best injected downstream of the pressure screen and before the fan pump, using a positive displacement metering pump. An injection quill placed in the pipe center and a downstream static mixer with 6–12 elements provide distribution without exposing the emulsion to high-shear rotor-stator conditions. Metering rates of 50–200 ppm as-supplied are typical for open felt-cleaning showers and saveall tanks; whitewater systems with high retained surfactant may require up to 300 ppm. If the emulsion is injected on the suction side of a centrifugal pump, air entrainment and impeller shear can subdivide droplets below 0.5 µm, producing a stable microemulsion that reduces defoaming efficiency and is difficult to remove in the saveall. In textile jet dyeing, the product is diluted with 10–20 parts water at 20–30 °C and metered into the overflow riser at 0.01–0.05 wt% on bath volume. Addition to the pigment grind in architectural waterborne paint is not recommended; post-letdown dosing at 0.1–0.3 wt% as-supplied preserves the hydrophobic silica and minimizes surface defects.
Textile high-temperature jet dyeing exposes the defoamer to liquor temperatures up to 130 °C, pH 4–11, and rapid circulation. The nonionic character of the emulsifier reduces interaction with acid dyes, reactive dyes, and softeners, but in high-electrolyte dyeing with Glauber’s salt above 80 g/L, emulsion creaming may occur. A pre-dilution of 1:10 with 40–50 °C water and injection into the pressure side of the main circulation pump is typical. If the diluted emulsion separates, lowering electrolyte charge or adding a nonionic co-emulsifier may be required. The multi-purpose designation arises from applicability across jet dyeing, continuous bleaching, and finishing pad baths; it is not a high-active defoamer for recovering a completely flooded foam spill.
Above 500 ppm as-supplied in a closed whitewater loop, the failure mode shifts from foam persistence to hydrophobic contamination. Undispersed silicone droplets can deposit on forming fabrics, pressure-screen foils, and drainage elements, producing a gradual increase in sheet contact angle and a reduction in internal sizing retention. In waterborne coatings, addition rates above 0.5 wt% as-supplied have been associated with craters, pinholes, and intercoat adhesion loss, because the surplus droplets coalesce at the air–water interface during film drying. The response is threshold-dependent rather than linear: at 0.1–0.3 wt%, the droplet population remains below the surface packing limit, while at 0.5–0.7 wt%, macroscopic silicone lenses form. Published data for this specific product at higher loading is limited; mill qualification should therefore use an addition ladder of 100 ppm, 250 ppm, and 500 ppm as-supplied, with a dwell period of at least 15 min after each step. Sheet wettability can be checked by TAPPI T 458, and a contact angle above 90° indicates hydrophobic carryover. Low-shear progressive-cavity pumps are preferred over diaphragm pumps with strong acceleration pulses, because pulsed flow destabilizes the emulsion in the injection line.
Because the continuous phase is water, the product freezes near 0 °C. Storage should be maintained between 5 °C and 40 °C. Heating above 50 °C increases Brownian collision frequency and produces a non-redispersible cream layer; immersion heaters with surface temperatures above 80 °C are not recommended. Prior to sampling, drums should be homogenized by low-shear agitation using an air-driven propeller at 50–100 rpm or by drum tumbling for 10–15 min. For dilution, water at 20–30 °C is added to the emulsion under mild agitation; a 1:10 dilution should remain homogeneous for at least 30 min in the intended process water. If rapid creaming occurs, the water hardness or anionic electrolyte load should be reduced. The product should not be mixed with concentrated cationic fixatives or high-electrolyte dyeing auxiliaries without a jar test, because charge reversal causes immediate coagulation. The use of an in-line strainer with 60–100 µm mesh is normal; finer filtration is not advised because it removes the active silicone droplets.
Defoaming activity depends on the presence of hydrophobic silica particles carried by the silicone oil. The silica particles protrude through the foam lamella and create a local surface-energy defect that accelerates film rupture. Excessive mechanical shear destroys this structured oil–silica network. In high-shear ring homogenizers operating above 15 m/s tip speed, the emulsion droplet size decreases but the silica may be stripped from the oil phase, producing a clear dispersion with poor defoaming performance. The emulsion should therefore be added after the last high-shear unit, not before a homogenizer or a colloid mill. Field checks using a sparge test based on ASTM E2407-04 are used to compare foam height after 60 s of aeration; a sharp foam collapse indicates active hydrophobic silica, while slow drainage without collapse suggests silica deactivation. This distinction is also relevant when comparing DOWSIL SH 5561 with silicone polyether defoamers, which do not rely on hydrophobic silica and are more shear-tolerant but less efficient per unit active silicone in high-foam systems.
In water-miscible metalworking fluid systems, tramp air and high-velocity sump return create stable foam; silicone emulsions are effective at 10–50 ppm as-supplied but can affect filter media. In central systems with drum or belt filters, free silicone oil may blind cellulose or polyester media. A low-dose metering pump and a drain interval of 10–15 min after addition are required before filtration. Published data for this specific product in metalworking fluid filter loops is limited; pilot evaluation on the actual sump is required.
Regulatory and raw-material compatibility statements should be obtained from the current safety data sheet and food-contact clearance supplement. DOWSIL SH 5561 is a silicone emulsion preparation; the polydimethylsiloxane and silica components are generally listed on the TSCA inventory. For European users, the product is controlled under REACH Regulation (EC) No 1907/2006 as a preparation, and specific end-use exposure scenarios should be confirmed from the extended safety data sheet. In process wastewater, the product is not readily biodegradable; aerobic treatment plants should evaluate defoamer load against total suspended solids and BOD5 using ISO 5815-1:2019. Overuse in aeration basins can reduce oxygen transfer efficiency, and pilot testing is required because published data for this specific product in aeration basin environments is limited. If residual silicone is a concern in recycled water loops, a coalescing filter or dissolved air flotation step may be required before discharge. The manufacturer’s bulletin does not list a full droplet-size distribution for this product; therefore, in-line particle monitoring is required for processes where submicron carryover is a concern.
