Celvolit 1496 VAE Emulsão

An aqueous, surfactant-stabilized vinyl acetate-ethylene (VAE) copolymer dispersion with a nominal solids content of 54.5–55.5 % (ISO 3251), Celvolit 1496 exhibits a Brookfield viscosity of 1,500–3,500 mPa·s at 23 °C (spindle 3, 20 rpm, ISO 2555) and a pH of 4.0–5.0. The latex carries an anionic charge, a mean particle size in the range of 0.8–1.5 µm, and a glass transition temperature (Tg, midpoint by DSC per ASTM D3418) centered near 0 °C. The minimum film-forming temperature (MFFT, ASTM D2354) coincides with the Tg, producing a cohesive film at ambient conditions without the addition of external coalescing solvents. Its ethylene segment, integrated at roughly 12–15 wt% in the backbone, internalizes plasticization, which distinguishes this emulsion from conventional poly(vinyl acetate) homopolymers that typically require 5–15 % dibutyl phthalate or comparable plasticizers to achieve similar flexibility. This intrinsic plasticization eliminates the risk of plasticizer migration, a critical factor in food-contact laminating adhesives tested under overall migration limit 10 mg/dm² (EU 10/2011, Annex III).

The product is delivered in bulk road tankers, IBC totes, and 200 L polyethylene drums. Storage stability exceeds 6 months when kept between 5 °C and 40 °C in sealed containers, although repeated freeze-thaw cycles cause irreversible grit formation. When removing material from partially used drums, contamination with shear-degraded coagulum must be avoided; line strainers of 250 µm mesh are routinely installed upstream of roller coaters to capture skins formed through evaporative drying at the container headspace.

Why Does Celvolit 1496 Exhibit Superior Wet Bonding Immediately After Lamination?

Standard VA homopolymer dispersions develop green strength primarily through water evaporation and capillary-driven film formation. In Celvolit 1496, the ethylene sequences depress the elastic modulus of the dispersed phase, increasing free volume and accelerating polymer interdiffusion across the laminate interface even at incomplete water removal. At 15–20 % residual moisture, the cohesive strength measured on a 50 µm dried film applied to corona-treated PET reaches 2.5–3.5 N/25 mm in a 180° peel test (ASTM D903) within 30 seconds of nip pressure, compared with sub-1 N/25 mm values for plasticized homopolymers under equivalent conditions. The rapid setup enables laminating lines with pressure-sensitive adhesive coatings on label face stocks to run at speeds above 150 m/min without blocking in the rewind roll.

Nevertheless, processing has defined electrolyte tolerance limits. Addition of multivalent cations, particularly at concentrations exceeding 0.5 wt% of CaCl₂, collapses the electrostatic stabilization, producing instantaneous coagulation. Zinc-based ionic crosslinkers, despite their fast gelation profile, generate chelate complexes with the residual poly(vinyl alcohol) protective colloid present at 2–4 wt% on dry polymer, causing spontaneous gellation in the feed pan within 20–40 minutes. Plant trials on multi-station laminators (BMB Combilam, 5-roll configuration) confirm that crosslinking with glyoxal at a ratio of 0.5 parts per 100 parts wet adhesive, added in-line via static mixer, raises wet tensile strength (ISO 527-3, specimen type 5) after 24 h immersion from 1.2 MPa to 4.8 MPa without adversely affecting pot life.

Film formation on substrates with compacted starch or calcium carbonate coatings reduces the practical shear adhesion failure temperature (SAFT) ceiling by 12–18 °C relative to aluminium. When a 40 µm wet film is drawn down on 80 g/m² clay-coated board and conditioned at 23 °C, 50 % RH for 7 days, the SAFT (ASTM D4498, 500 g static load) reaches 55–65 °C. On a 25 µm aluminium foil without surface treatment, the value climbs to 72–78 °C. This differential informs the design of heat-sealable packaging where the adhesive layer must withstand hot-fill conditions up to 85 °C — a boundary where a switch to Celvolit 1490, with its +5 °C Tg, is often necessary.

When Glass Transition Temperature Drops Below 0 °C in Pressure-Sensitive Applications

In PSA tapes produced by transfer coating onto siliconized release liner, Celvolit 1496 delivers a loop tack of 3.5–5.2 N/25 mm (FINAT FTM 9) and a 180° dynamic peel adhesion of 4.0–6.0 N/25 mm (FINAT FTM 2) on stainless steel, both measured at 300 mm/min crosshead speed and 23 °C. The near-zero Tg eliminates the embrittlement observed with higher-Tg VAEs at chiller temperatures; at 2 °C, tack retention is 85–92 % of the room-temperature value, whereas plasticized homopolymer dispersions lose 40–50 % of their loop tack under identical conditions owing to plasticizer phase separation. When compared to solvent-borne acrylic PSAs, Celvolit 1496 inherently yields a lower peel on low-energy surfaces such as HDPE — typically 0.8–1.5 N/25 mm — limiting its use to permanent paper labels and general-purpose carton sealing tapes rather than repositionable polyolefin labels.

Tackifiers may be compounded at 5–20 phr on dry polymer basis to boost specific adhesion. Hydrogenated rosin esters with a softening point of 85–95 °C (Ring & Ball, ASTM E28) are preferred; mixing is carried out under high-shear dispersion (rotor-stator, tip speed ≥ 15 m/s) to prevent nucleation of hydrophobic domains above 2 µm. A production-scale trial on a 1,200 mm wide slot-die coater (Nordson Ultracoat) processing an adhesive containing 15 phr Foral 85-E revealed stable coating weight at 20 g/m² dry for over 8 hours run time, with no build-up on the backup roll.

During high-speed lamination of aluminium foil to paperboard in aseptic brick production, the water-release profile becomes a primary process control parameter. On gravure cylinders engraved with 40 lines/cm pyramid cells, a wet coat weight of 6–8 g/m² requires a drying tunnel residence time of 1.8–2.2 seconds at 120 °C air temperature to reduce moisture below 3 % before the combining nip. Premature skin-over in the cylinder cells, observed when the cylinder temperature exceeds 32 °C, necessitates chilled impression rolls and hood exhaust humidity control below 12 g water/kg dry air. At line speeds above 280 m/min, a continuous defoamer dosing system maintaining 0.05–0.1 % mineral oil defoamer on wet adhesive prevents microfoam entrainment that would otherwise appear as pinhole defects in the seam area of finished packages subjected to pinhole integrity testing (ASTM F3039).

Adhesion to untreated polyester films remains a documented performance boundary. Surface energy of unmodified PET of 36–38 mN/m yields peel values below 0.5 N/25 mm on thin-gauge (12 µm) film. Following inline corona treatment to a surface energy ≥ 48 mN/m (dyne pens, ASTM D2578), peel adhesion increases to 3.2–4.8 N/25 mm, though aging under tropical conditions (38 °C, 90 % RH) for 4 weeks causes partial reversion, attributed to migration of oligomeric friction-reducing additives from the film bulk. Published data for this specific configuration is limited; plant-specific validation is therefore required before committing to a lamination structure for retort pouch applications exceeding 121 °C.