Section
| HS Code | 284387 |
| Product Name | SILFOAM SD 670 |
| Product Classification | Anhydrous self-dispersing polyether-modified silicone defoamer |
| Chemical Composition | Polyether-modified silicone active component on an inorganic carrier |
| Physical Form | Dry free-flowing powder |
| Appearance | White to off-white powder |
| Active Content | 100% anhydrous powder formulation with no added water or solvent |
| Moisture Content | Less than 1% |
| Bulk Density | Approximately 650 kg/m³ typical |
| Particle Size | Fine granular powder, typical range 50 to 300 microns |
| Dispersibility In Water | Self-dispersing in water without requiring added surfactant or high shear |
| Solubility In Water | Insoluble as a true solution but readily dispersible |
| Ph Value | Approximately neutral, typically pH 6 to 8 in 1% aqueous dispersion |
| Storage Conditions | Store in original sealed packaging in a cool, dry place below 40°C |
| Shelf Life | At least 12 months under proper storage conditions |
As an accredited SILFOAM SD 670 Anhydrous Self-Dispersing Polyether-Modified Silicone Defoamer factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | SILFOAM SD 670 is supplied in sealed 200 kg steel drums, labeled clearly with product identification and handling precautions for safe storage. |
| Container Loading (20′ FCL) | 20′ FCL loading of SILFOAM SD 670 defoamer in sealed drums, secured, labeled, and ventilated safely per chemical regulations. |
| Shipping | Ship as a non-hazardous liquid in sealed drums or IBC totes. Keep containers upright, dry, and protected from moisture. Store between recommended temperatures to prevent separation. Ensure proper labeling and ventilation. Avoid prolonged exposure to heat or freezing. Follow standard industrial handling procedures for silicone materials. |
| Storage | Store SILFOAM SD 670 in its original, tightly sealed container in a cool, dry, well-ventilated area away from direct sunlight, heat sources, and incompatible oxidizers. Protect from moisture and extreme temperatures; avoid freezing. Keep containers upright to prevent leakage. Follow technical data sheet recommendations for optimal shelf life and product performance. |
| Shelf Life | Store in original container at moderate temperature. Shelf life is 12 months from production date if unopened. |
In waterborne architectural coating production, SILFOAM SD 670 Anhydrous Self-Dispersing Polyether-Modified Silicone Defoamer is introduced at either the pigment grind stage or the final letdown step, depending on where persistent microfoam is observed. The anhydrous composition permits addition without altering the water balance of a viscosity-adjusted tint base, and the self-dispersing polyether-modified siloxane structure eliminates the need for pre-emulsification or high-shear pre-dispersion before the product contacts the aqueous phase. On production-scale high-speed dispersers fitted with Cowles blades operating at tip speeds between 18 m/s and 22 m/s, a dose of 0.1 wt% to 0.3 wt% of total batch mass typically reduces macrofoam in a 2,000 L letdown vessel within 10 min to 15 min. The same dosage range is used in silicate and acrylic plasters when foam generated by cellulose ether swelling interferes with bulk density control. Microfoam persistence is screened in the laboratory with ASTM E2407-04, while pigment grind quality is checked after 24 h via fineness-of-grind gauges. Final film appearance is assessed on glass panels using ISO 2813:2014 at 60° geometry, and low-shear viscosity is monitored under ISO 2884-1:2006 with a Brookfield RVT spindle at 10 min−1 and 23 °C. Overdosing above 0.5 wt% may generate cratering in semi-gloss and silk formulations because excess polyether-modified siloxane at the air-liquid interface suppresses local film coalescence and disturbs surface tension uniformity. The compatibility window narrows when the formulation contains more than 4.0 wt% of high-HLB nonionic surfactants, where micellar partitioning can increase the effective dosage required for defoaming and shorten the persistence time after storage. In tinted architectural paints, defoamer-related color acceptance problems can be monitored by rub-out ΔE values below 0.5 measured with a spectrophotometer using ISO 11664-4 geometry; if ΔE exceeds this threshold, the defoamer dosage or point of addition should be reevaluated.
| Measured parameter | Standard designation | Typical application condition |
|---|---|---|
| Defoaming efficiency | ASTM E2407-04 | Surfactant test solution, 25 °C, 1 h ageing |
| Low-shear viscosity | ISO 2884-1:2006 | Brookfield RVT, 10 min−1, 23 °C |
| Specular gloss | ISO 2813:2014 | 60° geometry, dry film on glass panel |
| Particle size distribution | ISO 13320:2020 | Laser diffraction, wet dispersion |
The limiting factor for defoamer persistence in pigment concentrate letdown is not the initial foam collapse but the gradual loss of dispersed silicone droplets during recirculation through high-shear pumps, in-line filters, and dispenser nozzles. In tint-base manufacturing, a concentrated colorant containing dispersed organic pigments is added to a base paint under a dissolver running at 1,500 rpm to 3,000 rpm; air entrainment at this stage creates foam that can remain after the slurry is transferred to storage. SILFOAM SD 670 is typically dosed into the base paint before colorant addition at 0.05 wt% to 0.2 wt% of the finished tint base, rather than into the colorant itself, because anhydrous self-dispersing silicone species can adsorb partially onto pigment surfaces and lose defoaming activity if added to a 40 % pigment solids concentrate. In volumetric tint dispensers fitted with piston pumps and 2 mm nozzles, air bubbles with diameters below 20 μm can cause metering inaccuracy and color strength drift. Quantitative production-scale data for SILFOAM SD 670 in high-speed colorant letdown is limited; industrial evaluations commonly combine foam-height measurement after 30 min ageing with spectrophotometric color acceptance rub-outs using ΔE tolerances below 0.5 under ISO 11664-4. The defoamer is compatible with most anionic and nonionic dispersant packages but may show reduced persistence when the letdown formulation contains naphthalene sulfonate condensates above 2.0 wt% on pigment mass, because the high electrolyte load compresses the electrical double layer around dispersed droplets and accelerates silicone phase coalescence. If colorant addition is followed by a 24 h storage period, a low-shear paddle mixer at 30 rpm to 60 rpm is generally sufficient to redisperse the defoamer without introducing additional air, provided the temperature remains between 10 °C and 35 °C.
During semibatch acrylic and styrene-acrylic emulsion polymerisation, foam is generated by nitrogen purge, monomer reflux, initiator decomposition, and protein-like surfactants; uncontrolled headspace foam reduces effective reactor capacity and transports polymer particles into overhead condensers, where skinning and cleanup cycles lower campaign productivity. SILFOAM SD 670 is added either to the reactor pre-emulsion before monomer feed or to the finished latex before unreacted monomer stripping. The anhydrous form is particularly relevant in pre-emulsion preparation, where added water can disturb the surfactant-to-monomer ratio in a shear-mixed feed tank. A starting dosage of 50 mg/kg to 300 mg/kg on total batch mass is evaluated in 10 m3 to 25 m3 stainless steel reactors equipped with two-stage pitched-blade turbines at 80 rpm to 120 rpm and jacket temperatures of 75 °C to 85 °C. Defoamer added to the pre-emulsion can alter micellar nucleation because polyether-modified siloxane molecules co-adsorb at the monomer-water interface; this can broaden the final particle size distribution measured by laser diffraction under ISO 13320:2020, especially when the base surfactant concentration is below critical micelle concentration. Post-polymerisation addition at 0.05 wt% to 0.15 wt% on latex mass reduces foam during vacuum stripping at 60 °C to 70 °C and 20 kPa to 30 kPa absolute pressure, but it does not prevent coagulum caused by electrolyte shock or rapid neutralisation with ammonia. Reactor wall fouling and filter screen plugging are therefore controlled only when defoamer dosing is combined with stable monomer feed rates and controlled initiator injection; a diaphragm pump feeding pre-emulsion at 2 L/min to 4 L/min into a 20 m3 reactor is one production-scale configuration where foam-related condenser fouling has been observed to decrease after defoamer introduction. Compatibility with persulfate initiators and with redox systems using sodium metabisulfite and tert-butyl hydroperoxide is generally acceptable at polymerisation pH values between 3 and 9; however, prolonged exposure to pH values above 13 at elevated temperature may hydrolyse the polyether-siloxane linkage and gradually reduce defoaming performance. For high-solids lattices above 55 % solids, the defoamer dose should be established via a pilot-plant foam tower test rather than extrapolated from low-solids laboratory dispersions because the higher viscosity and lower water activity change bubble drainage and coalescence rates.
Water-based flexographic and gravure ink systems running on press at speeds above 200 m/min create foam in recirculating ink trays, anilox rollers, and doctor blade chambers, which leads to pinholes in screen areas, density loss, and dried ink build-up on printing plates. SILFOAM SD 670 is added to finished ink or to the letdown varnish at 0.05 wt% to 0.2 wt% of total ink mass, typically after the final pH adjustment and before packaging. The self-dispersing character ensures that the defoamer does not form a separate oil layer in the ink tray, provided the ink is maintained under gentle recirculation at 20 L/min to 40 L/min through a 100 μm filter. In flexographic units fitted with chambered doctor blades and anilox line screens from 200 L/cm to 400 L/cm, bubble-free transfer is necessary because air pockets smaller than the cell opening can remain trapped in the anilox cells and reduce ink delivery. Viscosity stability is monitored with DIN EN ISO 2431:2019 flow cups; defoamer addition at the recommended dosage typically changes flow time by less than 5 %, but this must be confirmed on a press-side viscometer because ink pH and amine content influence the dispersion state of the polyether-modified siloxane. Overdosing above 0.3 wt% may produce print mottle on low-energy polyethylene or polypropylene films, because siloxane migration to the substrate surface can interfere with wetting and adhesion. Quantitative press-trial data for SILFOAM SD 670 in water-based overprint varnishes is limited; controlled laboratory screening with a flexographic hand proofer and foam-height measurement after 10 min recirculation is the most reliable small-scale predictor. The material remains pourable at temperatures between 5 °C and 40 °C, but storage below 0 °C can increase viscosity temporarily without affecting the chemical activity after thawing and gentle homogenisation.
Aqueous polyvinyl acetate and vinyl acetate-ethylene emulsion adhesives are compounded in z-blade or planetary mixers at temperatures up to 60 °C when starch, dextrin, or borax-complexed plasticisers are incorporated; air entrainment in the high-viscosity paste is difficult to release and can lower final adhesive film clarity and bond strength. SILFOAM SD 670 is dosed at 0.1 wt% to 0.2 wt% of total adhesive mass after the stabiliser hydration step, when the batch temperature has reached 50 °C to 60 °C. In a 500 L sigma-blade mixer running at 40 rpm, the defoamer reduces entrapped air within 20 min to 30 min, but its efficiency decreases when the filler content exceeds 40 wt% calcium carbonate on wet adhesive mass because adsorption onto fresh filler surfaces removes active silicone droplets from the air-water interface. This adsorption boundary is particularly relevant for flooring adhesives and tile adhesives formulated with high mineral loadings. Bond strength after lamination of wood and PVC foil can be evaluated using EN 204 classification for non-structural wood adhesives, but published data for this specific defoamer in filled PVAc systems is limited, so a complete dosing ladder is recommended before production scale-up. The anhydrous nature of SILFOAM SD 670 avoids dilution of high-solids formulations that are sensitive to water addition, and no pre-dispersion is required in most compounding sequences. However, the material should not be combined with concentrated oxidizing agents or with strongly cationic flocculants at pH below 3, because these conditions can destabilise the self-dispersing character and lead to localised silicone separation on mixer walls. When the adhesive is subsequently applied by roll coater at 10 m/min to 30 m/min, air-free film formation is required to avoid pinholes in transparent film layers; defoamer persistence in the wet adhesive after 4 h open time can be evaluated by drawdown on glass plates and visual inspection against a calibrated bubble-size comparator.
Blade coater runnability is controlled by the removal of sub-50 μm air bubbles from high-solids coating colours containing kaolin and ground calcium carbonate at 60 % to 68 % solids, because bubbles that pass under the blade disturb the wet film and produce streaks, scratches, or fibre coverage defects. SILFOAM SD 670 is added to the coating colour at 0.1 wt% to 0.3 wt% on dry pigment mass, either during pigment slurry make-down or after starch or latex binder addition. In high-speed blade coaters operating at 1,200 m/min to 1,800 m/min, the defoamer must provide rapid bubble breakage without creating foam stabilisation at the free surface of the colour supply tank. Recirculation through a screen filter of 80 μm to 150 μm mesh is used to remove agglomerates, but excess shear in centrifugal pumps can reduce defoamer droplet size and shorten persistence; this effect is evaluated by comparing foam height before and after 24 h of continuous recirculation. The polyether-modified siloxane chemistry is compatible with styrene-butadiene, carboxylated styrene-butadiene, and polyvinyl acetate latex binders at typical coating pH values between 7.5 and 9.5, but high levels of anionic polyacrylate dispersants above 0.5 wt% on pigment mass can compete for the air-water interface and require dosage adjustment. No additional wetting agent is normally needed because the defoamer does not form an insoluble surface film; however, overdosing above 0.5 % on dry pigment can increase surface tension non-uniformity and cause ribbing at the blade exit. Coating colour viscosity is monitored with ISO 2884-1:2006 at 100 min−1, and high-shear dewatering behaviour is assessed on a laboratory coater rather than extrapolated from low-shear Brookfield data alone. Quantitative production data for SILFOAM SD 670 in blade coating colours is limited; pilot coater trials with a 200 μm blade gap and 600 m/min to 900 m/min speed provide a more reliable indication of runnability than static foam-height tests.
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SILFOAM SD 670 is an anhydrous self-dispersing polyether-modified silicone defoamer supplied as 100 % active matter. The product is intended for aqueous flexographic and gravure inks, water-based overprint varnishes, emulsion paints, and pigment concentrates where conventional silicone emulsion defoamers can introduce added water, emulsifiers, preservatives, or film haze. Addition rates are typically evaluated in the range 0.05–0.5 wt% on total formulation mass. The anhydrous nature reduces the risk of biologically induced spoilage in stored intermediates and eliminates the formulation-water contribution associated with waterborne defoamer emulsions. Unlike composite silicone defoamers based on hydrophobic silica dispersed in polydimethylsiloxane oil, the polyether modification imparts controlled interfacial activity that allows the defoamer droplet to enter aqueous foam lamellae without an external emulsifier package.
Conventional silicone emulsion defoamers commonly contain 10–30 % water and require surfactant-stabilized droplets, which can migrate to the dried ink or varnish surface and reduce overprintability or block resistance. SILFOAM SD 670 contains no intentionally added water and disperses directly under shear. The defoaming mechanism involves spreading of the silicone phase at the air–water interface of the foam lamella, followed by film thinning and rupture. Polyether substituents provide sufficient hydrophilic character for transport to the interface, while the silicone backbone retains the low surface tension required for lamella destabilization. In comparison to mineral-oil defoamers, the product is less dependent on high oil-phase volume and is less likely to reduce color strength when used at the lower end of the recommended addition range.
Representative physical data from the manufacturer’s technical bulletin are given below. The viscosity is shear-rate dependent and should not be used as a formulation viscosity target because the defoamer is added at low percentages.
| Parameter | Typical value | Method |
|---|---|---|
| Active content | 100 % | Anhydrous product; heat-drying residue |
| Appearance | Slightly yellowish, slightly turbid liquid | Visual inspection |
| Dynamic viscosity at 25 °C | 1,000–2,000 mPa·s | Brookfield rotational viscometry, spindle 3, 20 rpm |
| Density at 25 °C | 0.99–1.03 g/cm³ | ISO 2811-1 |
| Water content | ≤0.5 % | Karl Fischer titration |
| Flash point | >100 °C | EN ISO 2719 |
The product is not a water solution and forms a milky dispersion when stirred into water at 1–5 %. The dispersion is kinetically stable under continuous low-shear agitation but will cream if left undisturbed; redispersion is achieved with low-shear mixing. Storage is recommended in closed containers at 5–30 °C. Brief exposure below 0 °C may increase viscosity without chemically damaging the product, but conditioning at 20–25 °C is required before metering. Published data for repeated freeze–thaw cycling of this specific product is limited.
Self-dispersion arises from the grafted polyether chains on the polysiloxane backbone rather than from added wetting agents. The silicone backbone has limited water solubility, but the polyether segments extend into the aqueous phase and reduce interfacial tension sufficiently to permit droplet formation under shear. The droplet size distribution is controlled by the energy input of the dispersing equipment. A production-scale sawtooth dissolver operating at 15–20 m/s tip speed is generally sufficient to incorporate the product into a resin letdown. High-pressure homogenization can reduce droplet size further, but this is rarely advantageous because excessively fine droplets lose bridging efficiency in coarse foam cells. Published data for the optimum droplet size in a specific millbase is limited; the foam-cell bridging behavior must be checked empirically in each formulation.
The hydrodynamic condition of the letdown vessel is critical. If the defoamer is added to a tank with insufficient agitation, it can form large surface inclusions that later produce craters. A rotor–stator mixer or sawtooth dissolver blade is preferred over a low-shear propeller because the higher shear develops the necessary interfacial area. In production equipment, the product can be metered with a gear pump or progressive cavity pump at 25 °C. At 10 °C, the viscosity may increase, and drum warmers or heated metering lines should be considered. Narrow-diameter static mixers are not suitable as the sole dispersion device because the shear regime is insufficient for reliable self-dispersion.
In water-based flexographic inks based on acrylic resins, SILFOAM SD 670 is commonly incorporated at 0.1–0.3 wt% during letdown after the pigment grind has cooled below 40 °C. Foam control is evaluated by an air-sparging apparatus or a blender test based on ASTM D3519. A film drawdown on polyester or corona-treated polyethylene is used to detect craters, fisheyes, and gloss loss. Gloss retention in overprint varnishes can be measured at 60° geometry in accordance with ISO 2813. Grind fineness is checked with a Hegman gauge per ISO 1524. If the defoamer dose produces a shift of more than 5 µm in Hegman reading or visible surface defects, the dose is reduced or the addition point is moved to the letdown stage.
If the product is added before the pigment grind, it can reduce millbase foaming but may also compete with pigment dispersants at the pigment–water interface. In a production-scale horizontal bead mill, this can appear as a slower reduction in Hegman gauge reading, a higher millbase temperature at the same residence time, or a shift in rheology. When this occurs, the defoamer should be moved to the letdown stage or pre-diluted in a portion of the resin solution to reduce local concentration. Adding at letdown after the grind is preferred for high-gloss systems because the defoamer droplets are not subjected to the full grind residence time and therefore remain large enough to bridge foam lamellae in subsequent printing.
In overprint varnish circulation lines, addition at the make-up tank is preferred over addition into the press return line. Press return lines often contain entrained air, and local shear from centrifugal pumps can emulsify the defoamer into droplets that are too small for efficient foam collapse. The recommended addition point is therefore the mixing tank, not the press sump. Batch-to-batch variance can be reduced by fixing the mixing time, tip speed, and temperature after defoamer addition. A high-shear phase of 5–15 min is usually sufficient after the product has been distributed throughout the batch; prolonged high-shear dispersion is unnecessary and may reduce defoamer efficiency.
In high-gloss water-based overprint varnishes, SILFOAM SD 670 shows compatibility at low addition levels but can produce surface craters above 0.5 wt% depending on the emulsion polymer, coalescent package, and wetting-agent balance. The compatibility boundary is not a universal value. A ladder study from 0.05 wt% to 0.50 wt% in 0.05 wt% increments, evaluated by drawdown and visual inspection for craters, dewetting, and gloss reduction, is used to establish the working limit. In systems containing high levels of low-molecular-weight co-solvents such as propylene glycol n-propyl ether, the working limit may shift downward because co-solvent plasticization increases spreading of the defoamer droplet at the wet film surface.
The product should not be diluted with water and stored as a dilute emulsion for more than a few hours; such dilution reduces self-dispersing stability and may require preservative addition. Avoid prolonged hot storage in strongly alkaline formulations above pH 10, because the polyether chains may undergo oxidative degradation under alkaline conditions. Published data for this specific configuration is limited for long-term storage in highly alkaline pigment concentrates. Regulatory compliance must be verified for each end-use formulation. The product description alone does not convey EU Regulation 10/2011 or FDA food-contact status for the final printed article; the manufacturer’s technical bulletin and safety data sheet should be consulted for current inventory status under REACH and for specific food-contact clearances, if any.
