Vinac DPN890

Vinac DPN890 is a polyvinyl acetate (PVAc) homopolymer dispersion supplied as a milky white aqueous colloid with a fine particle size distribution. The grade is used for high-speed paper carton forming, paper tube winding, and single-surface wood lamination. It is not a reactive thermoset and does not require a two-component mixing step. In converting equipment, the dispersion is transferred by roll, extrusion, or doctor blade at ambient temperature. Film formation occurs by water loss and coalescence rather than by crosslinking; open time and wet tack therefore depend on substrate porosity, ambient relative humidity, and wet film thickness. The designation DPN890 identifies a medium-viscosity, fine-particle PVAc with an anionic/nonionic stabilizer package. In production specifications, the product is released against solids content, Brookfield viscosity, pH, minimum film formation temperature, glass transition temperature, and density.

The specification envelope is measured against standard test methods and is used to release batches for application on high-speed folder-gluer and tube-winder equipment. Table 1 lists the typical controls for grade DPN890. Limits for residual vinyl acetate monomer and preservative content are reported on the safety data sheet and the food-contact statement where applicable.

For release testing, a 1 kg sample is conditioned at 25 °C for 2 h before viscosity measurement. Brookfield viscosity is measured with an RVT spindle 5 at 20 rpm; values are reported in mPa·s. The pH is measured on the as-received dispersion without dilution. Minimum film formation temperature is determined on a gradient bar over 0–40 °C at 60% relative humidity. A film is considered coalesced when it remains crack-free after 24 h drying at 23 °C and 50% relative humidity.

On high-speed folder-gluer lines processing clay-coated board at 60,000 cartons per hour, the transfer roll applies a wet film of 80–120 µm. The compression section applies 0.2–0.5 MPa for 2–5 s. Under these conditions, the adhesive must wet the clay coating and develop sufficient fiber-tearing tack within the compression window. The high-shear viscosity of DPN890 at 1,000 s⁻¹ is controlled below 2,000 mPa·s to reduce stringing from roller gaps, while the low-shear viscosity remains above 12,000 mPa·s to limit strike-through on uncoated linerboard. In tube winding at 20–30 m/min, the limiting factor is usually drying capacity when exhaust air humidity exceeds 12 g water/kg dry air. Increasing wet film above 150 µm without raising dryer temperature or air flow produces a surface film that traps water and delays full set.

Temperature dependence of viscosity is nonlinear. At 10 °C, low-shear viscosity can increase to 30,000 mPa·s; at 35 °C, it can fall below 8,000 mPa·s. Roll coater settings should be adjusted by measuring effluent temperature at the nip rather than relying on ambient temperature. A heat exchanger on the recirculation loop can hold the dispersion at 20–25 °C; water bath heating above 35 °C can cause premature coalescence on the roll ends and increase coagulum formation. The power-law index n from a shear sweep at 0.1–1,000 s⁻¹ is typically 0.6–0.8, indicating shear thinning. The yield stress is below 5 Pa, so the dispersion levels well after application but does not drip from vertical surfaces at wet film thicknesses below 100 µm.

What Are the Operational Boundaries for Storage, Pumping, and Cleanup?

The product is not freeze-thaw stable. Storage below 5 °C can form coagulum that blocks 100 mesh screens. A tote exposed to -5 °C may exceed 5 µm mean particle size after thawing and should not be returned to service. Long-term storage should be maintained between 5 °C and 35 °C. Mild steel, copper, brass, and galvanized surfaces must be excluded from transfer lines because iron ions above 50 ppm destabilize the anionic stabilizer. Use stainless steel, polyethylene, or PTFE-lined equipment. Air-operated diaphragm pumps with 25 mm ports and 2–3 bar air pressure are preferred. Rotary lobe pumps below 200 rpm are acceptable. Centrifugal pumps above 1,500 rpm can impose local shear above 10,000 s⁻¹ at the impeller tip, causing temporary viscosity loss greater than 30%. Viscosity recovery after shear may require 4 h at rest at 25 °C. Cleanup must occur before the film coalesces; once a film has formed at 35 °C, removal requires warm water at 40–50 °C adjusted to pH above 9 or an approved PVAc solvent. Do not allow the dispersion to dry in pumps or doctor blades.

Foaming can be controlled with polyether-modified polysiloxane defoamers at 0.05–0.20% by weight. Silicone defoamers must be pre-dispersed; local high concentration can create fish eyes in the dried film. If foam is generated in a transfer tank, level sensors should be ultrasonic rather than float-type because a foam blanket reduces apparent density to 0.4–0.6 g/cm³ and may cause false readings.

If Water Resistance Beyond D2 Is Required, the Product Is Displaced by VAE or Acrylic Dispersions

Under EN 204, PVAc homopolymers of this class are normally allocated to durability class D2 for interior use. They are not specified for D3 wet-use bonding or exterior exposure because the polymer lacks ethylene or crosslinkable groups. A VAE dispersion with 10–20% ethylene lowers the glass transition temperature and minimum film formation temperature, allowing application below 5 °C, but it also reduces hardness and may raise creep at 50 °C. An acrylic dispersion improves water whitening resistance but forms weaker hydrogen bonding to cellulose hydroxyl groups, so dry adhesion to high-porosity board can fall by 20–40% unless a tackifying resin is added. Starch-blended PVAc lowers adhesive cost but increases biological oxygen demand in wash water and reduces wet tack under high-speed compression. DPN890 is therefore selected where high initial fiber tear, fast set, low foaming under shear, and compatibility with high-speed roller transfer outweigh exterior durability or low-temperature flexibility. Within the same PVAc family, grades with higher low-shear viscosity may be required for vertical surfaces, but they generally require pump derating or heated transfer lines above 25 °C.

Adhesive performance on beech lap shear according to EN 1465 may be reported as 4.0–6.0 MPa dry; after 4 h cold water soak at 23 °C, the retained strength is typically less than 1.0 MPa, which is why D3 classification is not claimed. On paperboard, the failure mode at 24 h should be substrate fiber tear rather than adhesive film peeling. If film peeling occurs, the wet film is too thick or the substrate surface energy is below 38 mN/m.

Storage Stability and Biocide Compatibility Limits

The dispersion is protected by a biocide package. Contact with cationic flocculants, polyamines, alum, or polyvalent metal salts causes immediate precipitation. Do not blend with chlorine-releasing agents or strong mineral acids; pH below 2.5 hydrolyzes PVAc and releases acetic acid. Ammonia or sodium bicarbonate may be used to raise pH, but addition above 0.5% can move pH above 6.5, where hydrolysis and viscosity drift occur over 48 h. If pH-adjusted material is required, evaluate viscosity every 24 h. In storage tanks, recirculate through a low-shear lobe pump at 50 rpm for 15 min per day rather than using high-speed propeller mixers. A slowly rotating blade at 10 rpm prevents skinning without entraining air. The typical shelf life in sealed original containers is 12 months at 23 °C.

For food-contact applications, the dried adhesive must be behind a functional barrier or comply with FDA 21 CFR 175.105 and EU Regulation 10/2011 overall migration limits. The product is not intended for direct food contact, medical devices, or implants. On production lines with waste-water permits, wash water containing PVAc can be coagulated with 50–100 ppm polyaluminum chloride at pH 4–5 before flotation or filtration. The coagulated solids may be classified as non-hazardous industrial waste if free of heavy metals and residual monomer below local permit limits. Published data for this specific configuration is limited for municipal discharge limits; the operator must verify local consent.