Emulsão Dairen DA-391 VAE

Dairen DA-391 is a carboxylated vinyl acetate–ethylene (VAE) copolymer emulsion supplied at 54–56 wt% solids and a Brookfield viscosity of 2 000–4 000 mPa·s (ISO 2555, spindle 3, 20 rpm, 23 °C). The product is stabilised with a polyvinyl alcohol protective colloid system and exhibits a glass transition temperature (Tg, DSC midpoint) near 5 °C, corresponding to a minimum film-forming temperature (MFFT, ISO 2115) of approximately 2 °C without coalescing solvent. The ethylene comonomer content provides permanent internal plasticisation, eliminating the plasticiser migration seen in homopolymer PVAc adhesives. Applications span waterborne wood assembly, paper and packaging lamination, tissue and towel core winding, and carpet secondary backing, where a balance of flexibility, wet tack, and heat resistance is required.

What Differentiates the DA-391 from Conventional Vinyl Acetate Homopolymer Emulsions?

The incorporation of ethylene at a level of 10–20 wt% on the polymer backbone depresses the Tg by approximately 30 °C relative to a comparable molecular-weight PVAc homopolymer. This compositional feature removes the need for dibutyl phthalate, benzoate esters, or other external coalescents that can volatilise or migrate to the bond line, causing embrittlement and loss of adhesion over thermal cycling. In D3 wood adhesive formulations tested per EN 204:2016, DA-391 retains a shear strength above 7 N/mm² after 7 days of storage in standard atmosphere, and after 4 days of immersion in cold water the wet strength remains above 4 N/mm², meeting the D3 durability classification without the use of crosslinking isocyanates. In contrast, a typical PVAc homopolymer of similar viscosity and solids will deliver wet adhesion below 1 N/mm² under identical exposure unless formulated with a separate crosslinker. The lower free monomer residual of DA-391 (<0.1 wt% vinyl acetate monomer per headspace GC) also simplifies compliance with the German AgBB scheme for indoor air quality.

Unplasticised films cast from DA-391 and a standard PVAc homopolymer (Tg ≈ 28 °C) were compared for elongation at break using ASTM D638-14 Type V specimens. The table below summarises the mechanical response.

High-speed lamination of porous substrates on a roller coater running at 120 m/min line speed demands a wet pressure-sensitive tack duration of at least 8 seconds to accommodate web alignment before the nip. DA-391, when formulated with 1.0–2.5 wt% of a hydrophobically modified ethoxylated urethane (HEUR) rheology modifier, develops an open time of 10–12 seconds on 80 g/m² kraft liner under 50 % RH and 23 °C conditions. Production experience on a Kroenert PAK 610 roll coater with a 300 mm engraving roll at a gap setting of 0.15 mm shows that the emulsion’s shear stability, quantified by a ≤ 0.05 % coagulum formation after 30 min of stirring at 3 000 rpm (Cowles blade), prevents screen blinding and reduces cleaning downtime. However, the carboxylation level that imparts adhesion to aluminium foil also elevates the risk of viscosity drift when ammonia is used as a fugitive neutraliser; pH must be maintained between 4.5 and 6.0 using a fixed-buffer system, and mixing with zinc ammonium carbonate-based crosslinkers must occur within 4 hours of application to avoid premature gelation.

In cold-setting wood edge-glueing operations with a pneumatic press applying 0.7 MPa pressure for a minimum of 45 minutes, the emulsion composition’s ethylene segments contribute sufficient backbone mobility that joints on hard maple exhibit a dry shear strength exceeding 10 N/mm² after 24 hours of conditioning at 20 °C. One recurrent processing bottleneck observed on mass-production clamping carousels is the onset of skinning at the nozzle tip when ambient conditions surpass 35 °C and 30 % RH, reducing working life to less than 6 hours; retrofitting application heads with a water-jacketed reservoir maintaining the emulsion at 18–22 °C restores the open assembly time to the target 12 minutes.

Viscosity, pH, and Particle Size Thixotropic Landscape

DA-391 exhibits a low-shear pseudoplastic behaviour; the Brookfield viscosity at 1 rpm may climb to 12 000–15 000 mPa·s, while at 100 rpm the reading drops below 2 000 mPa·s. This profile is beneficial in non-drip vertical applications such as wall panel adhesive but mandates positive-displacement pumping with a Waukesha Universal 2 series pump run below 200 rpm to minimise mechanical shear. The mean volume particle size, as determined by dynamic light scattering (ISO 22412), is 0.8–1.2 μm, conferring deep penetration into low-grammage paper stocks without strike-through at coat weights between 20 and 40 g/m² wet. Freeze–thaw stability is absent; storage below +2 °C will cause irreversible coagulation, and the drum must be brought to 15 °C under slow mixing before transfer.

Bonding polyethylene terephthalate (PET) film to corrugated board for point-of-purchase displays represents a technically demanding application because of the low surface energy of PET. Incorporation of 1.5 phr of an aromatic isocyanate trimer and 3 phr of a chlorinated polypropylene adhesion promoter into a DA-391-based adhesive yields a peel strength of 2.8 N/25 mm (ASTM D1876) after 72 hours of cure at 23 °C. Published data for isocyanate-free VAE formulations on untreated PET typically remain below 1.0 N/25 mm, underscoring the utility of the carboxyl functionality in crosslink reactivity.

When High-Speed Case Sealing Demands Immediate Handling Strength

Automated case and carton sealing lines operating at 80 cycles/min impose a requirement for rapid green strength development. DA-391 formulated with 8 wt% of a rosin ester tackifier dispersion (softening point 85 °C) and 0.3 wt% of a polyacrylamide-based flocculant produces a fibre-tear bond on Kraft within 1.5 seconds of compression at 2 bar. However, this combination reduces the system’s pot life to 3 hours due to shear-induced destabilisation; continuous circulation through a static mixer and a progressive-cavity pump maintains homogeneity but demands purging of the entire fluid path if the line stops for more than 15 minutes. Plant-scale data from a 6‑head Nordson ProBlue® adhesive melter retrofitted for waterborne dispersions confirmed that nozzle stagnation at idle positions can generate agglomerates exceeding 150 μm, which block the 0.4 mm orifice if the system is not gravity-flushed during changeovers.

In spiral-wound paper tube manufacturing, DA-391 competes directly with higher-Tg VAE grades such as DA-101 (Tg ca. 18 °C). The lower Tg of DA-391 improves ply adhesion to recycled linerboard with high post-consumer content, requiring 15 % less coat weight to achieve a burst-strength retention above 90 % per TAPPI T 810. Yet the softer polymer raises the risk of roll-blocking under summer storage conditions exceeding 40 °C core temperature; a practical mitigation is blending DA-391 with 15–20 phr of DA-101 to lift the apparent Tg of the blend to approximately 10 °C while preserving sufficient specific adhesion.

The emulsion is supplied without APEO or alkylphenol ethoxylate surfactants, a feature that aligns with the Nordic Swan Ecolabel criteria for adhesives and with the EC Regulation 1907/2006 Annex XVII entry 46a restriction on nonylphenol ethoxylates. Container sizes include 1 000 L IBCs, 200 L internally coated steel drums, and 20 ton road tanker shipments, each with a recommended shelf life of 6 months from the date of manufacture when stored at 5–30 °C in sealed original containers. Prior to use, a 100 μm in-line filter bag is advised downstream of the drum pump to capture any surface skin that may have formed during storage.

Thermal analysis of films blended with 5 wt% of a 50 % solids rosin ester emulsion reveals a single DSC tan δ peak at 12 °C, confirming miscibility across the measurement range and the absence of phase separation that might compromise cohesive strength at low temperatures. This homogeneity is particularly relevant for freezer-grade case and carton adhesives where bond performance must be maintained at −20 °C; lap-shear values on clay-coated newsback at this temperature remain above 1.2 N/mm², while many competitive VAE emulsions with a higher crystalline fraction exhibit brittle fracture below 0.5 N/mm².