Macrofoam entrapment during high-speed mixing remains a primary pinhole source in solventless epoxy flooring binders and filled unsaturated polyester castings. KS-7708 is supplied as a hydrophobic defoamer oil formulated for epoxy, polyester, polyurethane, and acrylic resin matrices at addition rates of 0.1–0.5 wt% based on total resin solids. The product combines a polyether-modified polysiloxane block copolymer with a high-flash mineral carrier; this configuration reduces low-shear drainage time in high-viscosity mixing while preserving 20° gloss in isocyanate-cured topcoats. Incoming QC limits include density 0.88–0.92 g/cm³ at 25 °C per ISO 2811-1:2023 and Brookfield viscosity 300–800 mPa·s per ISO 3219:2021. The material is insoluble in water and miscible with aromatic hydrocarbons, ketones, esters, and styrenated resin systems. In comparison with conventional mineral-oil defoamers, the product leaves a narrower surface-active fraction at the air interface after flash-off, which is measurable as a smaller 60° gloss reduction in acrylic clearcoats.

Why is post-mill addition preferred for KS-7708 in amine-cured epoxy flooring compounds?

Post-mill addition is preferred in amine-cured epoxy flooring compounds because high-speed disperser shear converts defoamer droplets into submicron domains that are less effective against macrofoam. In a production disperser with a disc diameter 0.4 times vessel diameter and tip speed 18 m/s, a 25–30 min grinding cycle under 6,000 rpm reduces the defoamer droplet Dv90 from 20–60 μm to below 10 μm. The same lot then shows a 20–30 % higher residual foam height in a 500 mL graduated cylinder test. Addition after pigment dispersion but before resin letdown retains the effective droplet population; the batch is then mixed under low-torque agitation at 400–800 rpm for 15 min. This sequence also prevents amine-blush disruption on vertical epoxy walls because the carrier oil remains in the bulk rather than partitioning to the curing surface. On a 2,000 kg production batch, post-mill addition results in no visible pinholes on cured slabs after 24 h at 23 °C and 50 % relative humidity when the slab is back-lit. Addition directly into the grinding charge is not recommended for clear epoxy coats because the resulting Dv90 below 10 μm requires a 20–40 % dosage increase to restore foam control, which then raises haze and reduces intercoat adhesion.

Urethane floor coats cure through a combination of isocyanurate formation and moisture-driven side reactions; carbon dioxide release during these reactions stabilizes microfoam in solvent-free 2K systems. KS-7708 at 0.2–0.4 wt% on total resin solids is introduced after the polyol and dehydrating agent have been mixed and before isocyanate addition. This timing prevents any reaction with monomeric isocyanate; the hydrophobic carrier contains no active hydrogen, so no stoichiometric loss is detected by ISO 14896:2009 titration on the mixed resin. A dissolver at 1,200 rpm for 10 min is sufficient for incorporation in 2,000 kg production batches. In acrylic-polyol-polyisocyanate clearcoats at 0.3 wt%, 20° gloss retention remains above 95 % relative to control per ISO 2813:2023. Addition above 0.5 wt% may reduce intercoat adhesion after sanding; crosshatch values per ISO 2409:2020 can fall from class 0 to class 1–2 at 0.8 wt% in the same clearcoat system. For pigmented polyurethane floor coats, the upper limit is shifted to 0.5 wt% because the pigment surface area competes with foam lamellae for defoamer droplets.

Acrylic powder coatings and solventborne acrylic topcoats impose a different constraint because excessive defoamer oil migrates into the top 5 μm of the cured film and raises haze. In a solventborne acrylic clearcoat applied at 40–50 μm dry film thickness, KS-7708 at 0.2 wt% yields haze below 1.5 % per ASTM D1003-21. At 0.6 wt%, haze increases to 2.7 % and specular reflection at 60° drops by 4 %. The product is therefore limited to the lower end of the addition range for transparent acrylic applications, while pigmented acrylic primers may tolerate 0.5 wt% without surface defect development.

Performance differences versus polysiloxane paste defoamers in acrylic and polyester topcoats

Three antifoam families differ in droplet persistence, defect risk, and shear sensitivity. Mineral-oil defoamers provide adequate air release at 0.5 wt% but migrate to the air interface during flash-off, reducing 20° gloss and dry-film adhesion in high-solids acrylic topcoats. High-molecular-weight silicone pastes are effective at 0.1 wt% but can produce cratering if not pre-emulsified; their long-term persistence in recoat surfaces often requires sanding or plasma treatment. KS-7708 is supplied as a pre-dispersed block copolymer in a mineral carrier, with a viscosity band that allows direct metering in solventborne and solvent-free production. Table 1 summarizes laboratory comparison in an acrylic polyol-polyisocyanate clearcoat at 0.3 wt% and in a styrenated unsaturated polyester resin at 0.5 wt%.

In unsaturated polyester gel coats applied by air-assisted spray, the polysiloxane paste requires pre-emulsification in styrene at 1:5 to prevent cratering, whereas KS-7708 can be added directly to the resin side at 0.3 wt% under 900 rpm mixing. This distinction reduces batching time by 15–20 min per 1,000 kg batch in production vessels where a separate premix tank is not available.

If KS-7708 is pre-dispersed in styrenated unsaturated polyester before low-pressure RTM

Pre-dispersion in styrene monomer at 1:10 by mass is required for low-pressure resin transfer molding because neat oil addition may not distribute uniformly in a resin viscosity range of 2,000–4,000 mPa·s before injection. A 10 % dilution of KS-7708 in styrene is stirred at 60 rpm for 20 min before being metered into the resin batch. This procedure maintains gel time within ±5 % of the control when measured at 82 °C by ISO 9396:2019. In filled systems containing 200 phr aluminum hydroxide, addition of 0.3 wt% KS-7708 reduces trapped-air void volume in cured castings from 2.1 % to 0.6 %, measured by image analysis of polished sections at 100×. Above 0.6 wt%, the same formulation exhibits a Barcol hardness reduction from 45 to 38 because styrene dilution favors migration toward the mold surface during exotherm. For gel coat-backed polyester parts, the upper addition limit is therefore set at 0.4 wt% unless surface sanding is specified. In comparison, mineral-oil defoamers at the same addition level show phase separation in styrenated resin after 72 h storage at 25 °C, while KS-7708 remains visually homogeneous.

Specification parameters for incoming QC and batch release

Batch-to-batch consistency is monitored against the limits in Table 2. The most critical parameter for automatic metering is viscosity, because volumetric pumps without mass-flow compensation can overdose when viscosity drifts toward the lower end of the specification band. A plunger pump configured for 800 mPa·s fluid will deliver approximately 7–10 % greater mass at 300 mPa·s under the same cycle time. Therefore, positive displacement pumps with mass-flow verification or gravimetric dosing are recommended for addition below 0.3 wt% in continuous coil coating lines.

Regulatory classification for KS-7708 is based on EU CLP under EC 1272/2008 and REACH registration. The product is not considered hazardous for transport under ADR/RID/IMDG because the flash point is above 60 °C. RoHS compliance under 2011/65/EU with delegated directive 2023/1437 is limited to the four heavy-metal categories; no intentionally added cadmium, lead, mercury, or hexavalent chromium is present. Food-contact suitability under FDA 21 CFR 175.300 is applicable only to cured coatings where free defoamer oil migration does not exceed 10 mg/dm². Compatibility with amine-based epoxy curatives is acceptable, but the product should not be pre-mixed with strong oxidizing acids or stored in unlined carbon steel at temperatures above 40 °C for more than 6 months.

What operational boundaries apply when KS-7708 is used in high-film-build epoxy mastics?

High-film-build epoxy mastics containing 60–75 % solids and 100–150 μm dry film thickness require special attention because solvent entrapment and foam cell collapse can create visible craters if the defoamer is added too late. KS-7708 is incorporated at 0.3–0.5 wt% after resin and pigment concentrates are combined but before final solvent adjustment. On a horizontal pug mill with 40 rpm mixing speed, the batch is mixed for 20 min; the temperature is kept below 45 °C to avoid vaporizing the carrier oil and reducing defoamer concentration. In field application, airless spray at 210–250 bar with tip sizes from 0.017–0.021 inch does not re-entrain foam because the defoamer droplet population survives the pressure drop. However, adding the product directly into the spray pot without pre-mixing can cause localized surface defects; transfer lines shorter than 10 m are not sufficient to homogenize the product at ambient temperature. Published data for this specific configuration is limited, but production observations indicate a longer pre-mix time is needed when line temperature is below 15 °C.

Peroxide-catalyzed cure kinetics in acrylic and unsaturated polyester systems with KS-7708

Differential scanning calorimetry screening at 10 °C/min over 25–180 °C shows no significant shift in the peroxide decomposition onset and heat release when the defoamer is added at 0.3 wt% to acrylic and unsaturated polyester resins. The total exotherm variation is within ±3 % of the control, which is inside typical batch variability for methyl ethyl ketone peroxide and benzoyl peroxide systems. The product does not contain acidic or basic scavengers, and the acid value limit of ≤ 2 mg KOH/g prevents interference with tertiary amine accelerators. This behavior differentiates KS-7708 from some phosphoric ester defoamers that can extend gel time by 10–15 % in ambient-cure acrylic systems. In unsaturated polyester resin with 1–2 phr methyl ethyl ketone peroxide, the exotherm peak temperature remains within 2 °C of the control at 0.5 wt% addition.

In continuous coil coating of acrylic-polyester hybrid backers, foam suppression is required to prevent pinholes at line speeds of 80–120 m/min. KS-7708 is metered into the recirculation line at 0.2–0.3 wt% using a mass-flow-controlled pump; the product is pre-diluted with xylene at 1:3 by volume to reduce viscosity below 150 mPa·s for consistent spray atomization. Under these conditions, foam-related pinhole counts on the strip remain below 2 per m², while gloss retention at 60° is maintained above 98 % relative to the undosed control per ISO 2813:2023. Addition above 0.4 wt% in this configuration leads to surface mottling after curing at 204 °C for 40 s, which is the limiting condition for acrylic coil coating grades.