Brownstock washing on a kraft mill vacuum drum washer at 8–10 rpm becomes unstable when tall oil soaps, dissolved lignin fragments, and black liquor solids form a foam mat that obscures vat level control, raises soda carry-over into the unbleached stock chest, and increases defoamer demand in downstream bleach plants. SY-3060 is diluted with filtered process water and injected continuously into the washer shower header or the filtrate tank suction; typical fatty alcohol defoamer addition reported for this unit operation falls between 0.1 kg/t and 0.5 kg/t dry solids at black liquor solids 15%–22%, pH 12.5–13.5, and temperature 80–90 °C. Continuous feed is preferred over slug addition because pulsed injection produces vat level oscillation, uneven liquor displacement, sheet picking on the drum face, and transient foam collapse that can destabilise the vacuum pump seal water. The washed brownstock is assessed for residual sodium using TAPPI T 625 cm-99 or the mill’s black liquor mass balance; for food-contact board grades, the defoamer must be covered by the mill’s indirect food contact file under FDA 21 CFR 176.170 and BfR Recommendation XXXVI, with extraction data generated according to the applicable national migration protocol. Published data for this specific SY-3060 configuration in kraft mill washing is limited, so the addition rate must be validated against foam height, washer vat level, and residual alkali trend rather than by laboratory foam test alone.

What Happens When SY-3060 Is Introduced to a High-Ash White Water System Using Cationic Polyacrylamide Retention Aid?

On a woodfree copy paper machine running a gap former at 1,200–1,500 m/min, the white water loop often carries 30–45 g/L ash, 1,000–2,500 mg/L dissolved solids, and entrained air from the fan pump and stock approach piping; the air becomes stabilised by fines, pitch, and retention polymers, producing a foam layer on the wire pit and forming fabric streaking. SY-3060 is split-fed after the vacuum deaeration tank or at the suction side of the fan pump, with a typical fatty alcohol defoamer range of 20–200 mg/kg dry fibre trimmed against headbox air content and drainage time measured by ISO 5267-1 Schopper-Riegler. The non-ionic character of SY-3060 avoids direct charge reversal of the cationic polyacrylamide retention aid, but addition above approximately 0.3 kg/t dry fibre can release free fatty alcohol droplets into the short circulation and raise filtrate turbidity, occupy hydrophobic sites on colloidal pitch, and reduce first-pass retention; first-pass retention is derived from mill mass balance or online consistency instruments because no ISO method covers this specific wet-end parameter. The process limit is normally set by felt filling in the press section and by uhle box vacuum trend, since coalesced fatty alcohol droplets can entrap fines and reduce felt permeability. The terminal sheet is cut-size copy paper or offset base paper; formation is checked by the mill beta formation tester, surface uniformity by ISO 8791-2 Bendtsen roughness, and internal sizing by ISO 535 Cobb60. In EU mills, the substance must be covered by a valid REACH registration under EC No 1907/2006 and included in the mill’s food-contact paper validation under EU 1935/2004. The white water system should not be overdosed during cationic demand excursions because the resulting foam collapse may redistribute pitch deposits to the forming fabric and increase sheet holes; this operational boundary is more important than the absolute dosage.

Foam generated in a starch size press service tank is usually a mixed system of degraded starch fines, enzyme-converted thin-boiling starch, and bound air introduced by pneumatic starch transfer or by the size press return line; in a paperboard machine running basis weights of 80–120 g/m², this foam reduces level control, causes uneven starch pickup, and can overload the starch filter screens. SY-3060 is injected into the size press return line or the hold tank at 50–300 ppm on liquid starch volume after the cooked starch has cooled below 90 °C; it is not added upstream of the jet cooker because high-temperature steam shear can invert the fatty alcohol dispersion and reduce foam knockdown in the service tank. The process variable is starch viscosity, held between 20 mPa·s and 60 mPa·s at 60 °C using a Brookfield viscometer, while size pickup is controlled gravimetrically by the metering rod load. The defoamer must not increase water absorption or alter the surface sizing film; mill verification uses ISO 535 Cobb60 and ISO 8791-4 Parker PrintSurf roughness on the sized reel. In white top testliner or folding boxboard production, the terminal product is converted with water-based flexo ink, so the defoamer must not create fish eyes or reduce ink adhesion; printability is checked with ISO 2813 gloss and tape adhesion tests. Overdosing above 500 ppm on starch volume can deposit on the dryer cylinders and reduce heat transfer, so steam demand and can surface temperature are monitored as the upper addition limit. Published data for this specific SY-3060 configuration in size press starch is limited, and the addition threshold should be established by foaming tendency measurement rather than by generic starch defoamer tables.

Foam Film Rupture in High-Solids Coating Colour Under Blade Shear

Under high shear generated by the coating kitchen dispersion blade, a calcium carbonate-based coating colour at 65–72 wt% solids with a synthetic styrene-butadiene binder and co-binder thickener retains fine air bubbles from dispersion; these bubbles pass through the machine screen and burst under the blade, producing skip coating, blade scratches, and microscopic voids in the coated layer. SY-3060 is added to the coating colour make-down tank or before the machine screen at 0.05–0.2 kg/t dry coating solids, with dosage adjusted by vacuum deaeration time and by the number of bubbles retained after high-shear mixing. The defoamer must survive high shear from the dispersion blade and positive displacement pump but still migrate to the air-liquid interface after shear; a fatty alcohol formulation is selected because it provides rapid bubble rupture without increasing coating colour viscosity. The process boundary is the 100–150 µm screen mesh: free fatty alcohol particles above this size can block screen slots and create longitudinal streaks on the coated web. The terminal coated art paper or coated folding boxboard is verified for blade line count, ISO 8791-2 Bendtsen roughness, ISO 2470-1 brightness, and print gloss on a sheet-fed offset press. As a non-silicone fatty alcohol defoamer, SY-3060 reduces the risk of cratering in subsequent varnishing or lamination when compared with silicone-containing defoamers; nevertheless, excess addition can reduce coating holdout and increase motting on high-gloss grades, and the upper limit is set by visual print evaluation under standard lighting.

When SY-3060 Is Fed Only After Flotation Cells in a Deinking Line

Flotation deinking depends on stable froth to carry hydrophobic ink particles away from the fibre stream; any defoamer added before the flotation cells collapses the froth and reduces ink removal efficiency, brightness gain, and yield. In a two-loop deinking plant processing mixed office waste, SY-3060 is therefore injected downstream of the secondary flotation cells, into the washing stage filtrate or the thickener feed, at 0.05–0.2 kg/t dry fibre. The objective is to reduce foam carryover in the disk thickener and screw press and to stabilise the wash filtrate tank, not to eliminate flotation froth. The wash stage operates at pH 7.5–9.0, and the defoamer must not reagglomerate dispersed ink particles or increase dirt count in the thickened stock. Terminal product is deinked market pulp or newsprint furnish, verified for brightness with TAPPI T 452 or ISO 2470-1 and for residual ink with TAPPI T 567 effective residual ink concentration. A key operational boundary is backward transport through shared water loops: if the defoamer reaches the flotation feed, a brightness drop of 1.0 point or more at constant bleaching conditions is an early warning of froth kill. Published data for this specific SY-3060 configuration in flotation deinking is limited; mill validation should include laboratory flotation tests to confirm that the defoamer does not migrate upstream through filtrate reuse.

Dissolved air flotation units treating papermachine excess whitewater and biological sludge often carry a foam layer stabilised by extracellular polymeric substances, fatty soaps, and unsettled fibre fines; the foam can overflow the DAF tank, increase float solids moisture, and raise polymer consumption in downstream dewatering. SY-3060 is dosed into the DAF inlet pipe or the pressurised recycle line at 5–20 ppm on total influent flow; the process target is to compact the float layer and improve float solids release from the scraper without destroying the floc structure. Clarified water turbidity and float solids content after the screw press are the primary control variables; defoamer addition should be reduced if turbidity rises because the defoamer can disperse bound flocs when overdosed. The terminal output is clarified water returned to the mill water system and dewatered sludge for disposal or incineration; compliance is governed by the mill discharge permit under EU 2010/75/EU BREF for pulp and paper, with local TSS and COD limits. An operational boundary is the aerated lagoon or activated sludge basin: residual fatty alcohol carried from the DAF overflow can reduce oxygen transfer efficiency, and if the DAF overflow is recycled to the biological treatment train, oxygen uptake should be checked by ISO 8192 or clean water aeration testing. Published data for this specific SY-3060 configuration in DAF treatment is limited; the effective dose must be established by mill-specific jar tests and float compaction trials.

Peroxide Bleaching Towers and Washer Defoamer Addition Under Alkaline Conditions

When an alkaline peroxide bleach tower is operated at pH 10.5–11.5 and 60–80 °C, the release of oxygen and alkali-solubilised hemicellulose creates foam that perturbs the downstream double-wire press and reduces washer feed consistency. SY-3060 is added to the wash press shower or the tower discharge line at 0.1–0.3 kg/t dry pulp, after the bleach tower retention stage because premature addition can suppress peroxide distribution and reduce brightness response. The defoamer must tolerate residual hydrogen peroxide up to approximately 5 g/L and high alkalinity; oxidative stability should be confirmed by bottle tests with actual bleach filtrate, not by water-based foam tests alone. The process target is stable washer feed and uniform press load, and the terminal product is bleached chemithermomechanical pulp or high-yield deinked pulp for tissue and newsprint; brightness is verified by ISO 2470-1 and residual peroxide by iodometric titration. A limitation is that fatty alcohol dispersions can lose emulsion stability during long residence in strongly alkaline filtrate tanks above pH 12; continuous feed near the washer is therefore preferred over storage in the bleach filtrate tank. Batch-to-batch variance in defoamer emulsion stability should be monitored before changing feed points because unstable dispersion may deposit fatty alcohol on the washer wire and reduce washing efficiency.