CW-705 PVAc Emulsion

In spiral-wound core lamination and multiwall sack side-seam gluing, the selection of CW-705 is governed by the competing requirements of fast wet tack and low moisture addition to the paper web. The emulsion is adjusted with demineralised water to a Brookfield RVT viscosity of 1800–2500 mPa·s at 25°C, spindle 4, 20 rpm. At line speeds between 80 m/min and 200 m/min, a slot nozzle deposits 4–8 g/m² dry adhesive onto the ply interface. Nip pressure is held at 0.2–0.4 N/mm², giving a compression belt contact time of 1.0–2.5 s. Insufficient wet tack within this contact interval causes seam opening on the mandrel, especially with springback-prone recycled coreboard. A hot-air tunnel at 50–70°C removes edge moisture before rewinding; residual moisture above 8% in the outer plies promotes blocking in the finished roll. Filtration through 100 μm mesh screens is required before the delivery head. Alkaline sizing with surface pH above 8.5 may retard coalescence, while acidic kraft with surface pH below 4.5 accelerates viscosity drift in the return tank. Because the emulsion is anionically stabilised, it must not be combined with cationic wet-strength agents or aluminium sulfate in the same mixing tank.

Compliance for dry food packaging side seams is evaluated under FDA 21 CFR 175.105 and EC 1935/2004. The dried film functions behind a paper or board functional barrier. Organic tin catalysts are not used in the polymerisation of this grade; APEO and phthalate plasticisers should not be added. The end products include spiral-wound cores for BOPP film, multiwall sacks for non-greasy powders, and folding carton side seams. Machine operators should monitor viscosity every 4 h with an inline cup measurement correlated to the Brookfield value; an upward drift greater than 300 mPa·s indicates fibre contamination, low emulsion temperature, or return-tank coagulum formation.

What Limits Open Assembly Time on Flat-Pressed Beech When CW-705 Is Used?

Flat-pressed lamella bonding with CW-705 requires the adhesive film to wet fibre without drying before press closure. Open assembly time on beech at 20°C and 60% RH is commonly 8–15 min. At workshop temperatures above 35°C or under forced air, open time falls below 5 min. Solids content is measured by ISO 3251:2019 at 105°C for 3 h; batch values outside 50–55% alter spread rate and press time. The film is applied with a single-sided roll coater at 120–180 g/m² wet. Lower spread rates starve the joint in gap-filling furniture panels; higher spread rates extend clamp time and increase moisture-related dimensional movement. Wood moisture should be 8–12%, and the emulsion temperature should not fall below 15°C to avoid excessive viscosity.

Press pressure is set at 0.5–1.0 N/mm² for cold pressing at 20°C. Clamp time under these conditions is 20–40 min for softwood and 30–60 min for beech. Heated platen pressing at 55–70°C reduces clamp time to 2–5 min. Radio-frequency curing on continuous automatic lines shortens holding time at the joint to 90–180 s for 30 mm lamella, but moisture distribution must be uniform; localised dry zones cause thermal runaway because PVAc does not absorb RF energy as efficiently as water. Dry shear strength after conditioning for 7 days at 23°C and 50% RH is evaluated to ASTM D905-08. D3 wet strength is assessed under EN 204 after the specified cold-water immersion sequence; the pass value is stated in EN 204 clause 5. The emulsion is not rated D4 and should not be used alone in exterior joinery.

End products include edge-glued pine panels, finger-jointed window frame fillers, and veneer layup on cabinet doors. Batch-to-batch viscosity variation must be tracked with a Brookfield RVT spindle 5 at 20 rpm, 25°C. Viscosity outside 2000–4000 mPa·s may require changes in roll-coater gap or press cycle. Because the polymer is thermoplastic, creep resistance is lower than crosslinked PVAc; the component should not be exposed to continuous load above 50°C in service.

On case-making lines running 20–40 cases/min with hot-melt side glue, CW-705 is used in hinge and board-to-cloth lamination rather than spine gluing. The adhesive is applied by a disc roller at 150–250 g/m² on board, with the emulsion warmed to 18–25°C. Open time on 145 g/m² book cloth must remain above 20 s at 50% RH. Nip pressure is 0.3–0.5 N/mm² for 30–60 s. The water-based system adds moisture to the cover board; a drying tunnel at 40–55°C for 5–10 min is required to prevent cover curl and hinge warpage. Adhesive pH between 4.0 and 6.0 is compatible with most case-making board; alkaline board with surface pH above 8.0 may delay wet set and cause cloth staining through paper permeability.

The main failure mode observed on case-making lines is low-temperature film formation. CW-705 should not be applied below 10°C unless the board is preheated to 20°C and the adhesive is stored at 15–25°C. Viscosity for disc application is adjusted to 2500–4000 mPa·s; dilution with more than 5% water can cause strike-through on uncoated cloth. End products include hardcover case books, presentation folders, magnetic closure boxes, and tray covers. A synthetic thickener should not be used unless the neutraliser is pH-adjusted, because alkali-swellable thickeners may shift the emulsion pH above 6.0 and reduce wet tack. The emulsion is not compatible with cationic antistatic sprays; a nonionic polyether treatment should be applied after the drying tunnel if static control is required.

When Portland Cement Is Modified with a 10% Latex Solids Addition

In cementitious patching and repair mortars, CW-705 is added to the mixing water as an anionic polymer dispersion. The polymer-cement ratio is set between 0.05 and 0.20 on a dry solids basis; a starting point of 0.10 is used for interior non-structural patches. The emulsion must be added after the cement-water paste has formed to avoid flocculation from high pH. A two-stage mixing sequence at 300–500 rpm with a paddle mixer is used: first cement and aggregate are mixed with 80% of the water for 90 s, then the emulsion mixed with the remaining water is added and mixed for 120 s. Final slump is adjusted with a water reducer rather than additional water; excess water raises the water-cement ratio and negates compressive strength. Operators should filter the diluted emulsion through a 250 μm screen before adding it to the mix to remove any skin formed during storage.

Pull-off adhesion is measured to EN 1015-12 after 28 days. The film contributes flexibility and reduces dusting at the feather edge. However, uncrosslinked PVAc re-emulsifies under prolonged wet service; the product is therefore limited to interior patch mortars, skim coats, and gypsum board joint fillers not exposed to immersion. For exterior or below-grade exposure, the formulation must include a hydrophobic or crosslinked copolymer. Compliance for cosmetic patching may reference EN 998-1 for general-purpose mortar; structural repair under EN 1504-3 is not claimed. The emulsion is not compatible with water hardeners containing multivalent metal salts; pre-testing with the specific cement batch is required because high alkali content can destabilise the dispersion before film formation.

Air-Laid Dispersible Nonwoven Binding at 140°C Without Formaldehyde

CW-705 is foam-applied to air-laid or carded webs where the finished fabric must lose tensile strength in water. Binder add-on is controlled between 10% and 18% dry weight on fibre. The emulsion is diluted with demineralised water to 10–15% solids and delivered through a foam generator; foam density is held near 80–120 g/L to avoid strike-through. Drying and film formation take place in a through-air oven at 130–150°C for 10–30 s depending on web weight. Since the cure is coalescence rather than chemical crosslinking, the binder remains water-sensitive; this is intended for dispersible nonwoven applications. Do not add cationic antistatic agents to the binder; the positive charge causes localised coagulum. If antistatic treatment is required, a nonionic polyether may be applied after the drying tunnel.

Dry tensile strength measured by ISO 9073-3 is used as a line-control parameter, but the principal qualification is dispersibility after water immersion. EDANA GD 4 or an equivalent slosh-box procedure is used to measure wet strength retention. Commercial dispersible webs with this binder class typically fall below 30% wet strength retention within 5 min of agitation, though published data for CW-705 in this exact configuration is limited. A slosh-box calibration should be performed before line qualification. The absence of formaldehyde and APEO is required by REACH Annex XVII and voluntary wet-wipe labels; the homopolymer PVAc backbone generally complies when no post-added biocide conflicts with the end-use certification.

End products include dispersible hard-surface wipes, flushable packaging pads, and vacuum cleaner bag intermediary layers. Viscosity in the foam line is maintained at 400–900 mPa·s; foam generators with coarse filter stacks require a defoamer addition below 0.1% to prevent cell collapse on the web. The use of a wetting agent is substrate-dependent; an anionic sulfosuccinate at 0.2–0.5% on emulsion solids improves distribution on hydrophobic synthetic fibre, but the same additive can reduce water resistance of the dried film. Immersion service longer than 5 min exceeds the intended boundary for uncrosslinked CW-705 film.

Nip Pressure Above 0.4 N/mm² Is Required Before Paper Adheres to HDF

The emulsion is metered through a three-roller applicator at 60–100 g/m² wet onto the reverse side of 70–120 g/m² printed paper. The HDF panel is pre-sanded with 180–240 grit and conditioned to 8–10% moisture. Nip pressure is set at 0.4–0.8 N/mm²; line speed is limited to 20–40 m/min to allow the water to wet the paper without causing surface breaks. After lamination, panels are stacked cold with interleaving paper and dried under forced air for 24–48 h before trimming. Edge curl is measured by warpage across a 600 mm diagonal after conditioning at 23°C and 50% RH; acceptable flatness for cabinet production is ≤ 1.0 mm. The adhesive must be filtered through 100 μm mesh before the coating head to prevent anilox or roller staining.

Adhesion is evaluated as 180° peel on a tensile tester with a crosshead speed of 100 mm/min; typical paper-to-MDF with PVAc homopolymer systems fails in paper fibre or MDF subsurface at 2–4 N/mm peel force, but laboratory correlation for CW-705 on the specific HDF grade is required before a warranty limit is set. The bond is moisture-sensitive at high humidity; indoor furniture panels should not be exposed to continuous RH above 85% unless the cut edges are sealed with a melamine edgeband. End products include laminated cabinet backs, drawer bottoms, and flat-pack furniture panels. The emulsion is not suitable for continuous exterior exposure or for direct contact with oiled surfaces commonly found on decorative laminates.