Celvolit 1408 Emulsão de VAE de alto etileno

Celvolit 1408 is a high-ethylene vinyl acetate-ethylene (VAE) copolymer emulsion supplied at a nominal solids content of 55% by weight as determined by ISO 3251. Viscosity measured on a Brookfield RVT viscometer, spindle 4 at 20 rpm and 25 °C, ranges from 1500 to 4000 mPa·s; pH falls between 4.0 and 5.5. The emulsion carries a density of approximately 1.07 g/cm³ and forms transparent films with a minimum film formation temperature (MFFT) of 0 °C per ISO 2115, corresponding to a nominal glass transition temperature near 0 °C by differential scanning calorimetry to ASTM E1356. Its distinguishing feature is the elevated ethylene comonomer content—substantially higher than that of standard vinyl acetate homopolymer or low-ethylene VAE emulsions—which confers intrinsic tack, flexibility, and substrate wet-out without requiring external plasticizers or coalescing solvents.

How Ethylene Content Modulates Adhesive Performance

Ethylene sequences within the copolymer backbone disrupt poly(vinyl acetate) crystallinity, depressing the glass transition temperature while simultaneously reducing the surface energy of the dried film. Conventional VAE emulsions containing 5–8% ethylene exhibit MFFT values of 8–15 °C and typically demand 10–20% dibutyl phthalate or benzoate plasticizer to achieve ambient-temperature film formation and adhesion to untreated polyolefins. Celvolit 1408, with its high-ethylene architecture, eliminates that requirement: a 0 °C MFFT ensures continuous film coalescence at room temperature without coalescing aids, thereby slashing volatile organic compound (VOC) contributions to below 0.5 g/L (calculated per Directive 2004/42/EC). Loop tack measured on untreated polypropylene film following ASTM D6195 typically reaches 2.5–3.5 N/25 mm for an unsupported 25–30 µm dry film, while peel adhesion to low-density polyethylene per ASTM D3330 (180°, 300 mm/min) generates 4.0–5.5 N/25 mm. This immediate adhesion to non-polar substrates is a direct consequence of the ethylene blocks’ ability to migrate to the air–adhesive interface during drying, lowering interfacial tension to 28–32 mN/m as confirmed by contact angle goniometry.

Cohesive strength under static load, assessed by shear adhesion failure temperature (SAFT) to ASTM D4498 on stainless steel with a 25 x 25 mm bond area and 1 kg suspended mass, remains stable up to 80–95 °C when the film is crosslinked via post-addition of 0.3–0.5% polyfunctional aziridine or aluminum acetylacetonate. Without crosslinking, room-temperature shear resistance on polyethylene exceeds 72 hours at 1 kg load, making the base polymer suitable for mounting tapes and removable labels that must avoid edge lifting.

For pressure-sensitive adhesive (PSA) applications requiring direct coating onto untreated polypropylene or cast polyethylene films without corona pre-treatment, the emulsion’s ethylene domains permit spontaneous wet-out. On a slot-die coating line running at 80–120 m/min with a 200–300 µm wet film gap, the low static surface tension of the liquor prevents reticulation and dewetting even on substrates exhibiting 30–32 dynes/cm surface energy. Drying in a three-zone air-floatation oven set to 80 °C /100 °C /120 °C and retention time of 45–60 seconds produces a optically clear, dry film weight of 28–32 g/m². The dried adhesive layer retains its ethylene-driven surface activity, maintaining a peel value drop of less than 15% after 7 days ageing at 40 °C in contact with untreated polyethylene, a storage condition that often induces adhesion loss in plasticizer-containing formulations due to plasticizer migration into the substrate bulk.

Resistance to Plasticizer Migration and VOC Contributions

Flooring adhesives formulated with traditional low-ethylene VAE emulsions frequently suffer from plasticizer exudation into adjacent PVC wear layers, causing staining, dimensional distortion, and loss of adhesive toughness. Celvolit 1408 obviates this degradation pathway because no monomeric plasticizer is present; the molecular-level plasticization is provided solely by the copolymer’s ethylene segments. In a side-by-side migration test conforming to EN 12705 (contact staining of flooring materials), a 3 mm thick adhesive bed cast from a 78 wt% calcium carbonate-filled formulation showed zero visible migration onto a white homogeneous PVC tile after 28 days of contact under 5 kPa pressure at 50 °C, whereas a phthalate-plasticized VAE control produced a distinct yellow halo within 72 hours. Concurrently, total VOC content measured by headspace gas chromatography per ISO 16000-6 fell below 10 µg/m³ after 72 hours of chamber testing, satisfying AgBB and French VOC class A+ emission criteria without the use of formaldehyde scavengers or special low-boiling-point surfactants.

Comparing Plasticizer-Free Emulsions with Traditional Tackified Systems

Acrylic PSAs often rely on hydrogenated rosin ester or hydrocarbon resin tackifiers to achieve peel adhesion on low-energy surfaces comparable to that of a high-ethylene VAE. The table below contrasts key film-formation and adhesive parameters for Celvolit 1408, a representative acrylic waterborne PSA, and a conventional VAE compounded with plasticizer.

The comparison underscores that while acrylic emulsions excel in thermal shear resistance and water-whitening, they demand substantial tackifier addition—often 30–50% of polymer solids—to reach parity with Celvolit 1408 on untreated polyolefins. The high-ethylene VAE therefore occupies a distinct position: intrinsic, plasticizer-free tack on low-energy substrates, coupled with a volatile-free profile that satisfies indoor air quality requirements without the cost or complexity of tackifier dispersions.

When High-Ethylene VAE Replaces Solvent Acrylics in Lamination

Flexible packaging thermal laminating adhesives historically employ solvent-borne polyurethanes or acrylics to achieve bond strengths above 3 N/15 mm on PET/PE and aluminum foil structures. Aqueous VAE emulsions have been limited by slow drying and insufficient bond at 80–100 °C seal temperatures. Celvolit 1408, applied by a 12 BCM engraved gravure cylinder and dried through a 6 m hot-air tunnel at 95 °C air temperature with 2.5 m/s nozzle velocity, deposits 2.5–3.0 g/m² dry adhesive. Laminates tested according to ASTM F904 (T-peel on 53 µm LDPE/354 µm aluminum foil) immediately after lamination at 110 °C nip temperature yield a bond strength of 2.0–2.8 N/15 mm, rising to 3.5–4.0 N/15 mm after 48 hours maturing at room temperature. Crucially, no residual solvent is detectable by gas chromatography with flame-ionization detection (detection limit 0.01 mg/m²), meeting FDA 21 CFR 175.105 specifications for adhesives used in dry food packaging without a functional barrier. The high ethylene content also imparts a broader heat-seal window: acceptable seal strengths are generated from 85 °C to 130 °C, versus a narrow 100–110 °C range typical for medium-ethylene VAEs, thereby improving runnability on horizontal form-fill-seal machines prone to temperature fluctuations.

In carpet tile and luxury vinyl tile (LVT) adhesives, pressure-induced tack development determines early holding power before vitrification of the cementitious or acrylic-encapsulated fillers. A 75 wt% calcium carbonate (particle size D50 ≈ 12 µm) filled compound based on Celvolit 1408 and diluted to 68% solids with water exhibits a pseudoplastic flow profile when measured with a plate-and-cone rheometer at 25 °C: apparent viscosity drops from 120 Pa·s at 0.1 s⁻¹ to 8 Pa·s at 100 s⁻¹. This enables smooth troweling and direct coverage of subfloor irregularities while resisting slump at vertical joints. Open time, determined by tack-roll test per ASTM D4497 at 23 °C /50% RH and 200 µm wet film, extends to 25–30 minutes without the addition of humectants, a consequence of the emulsion’s high polymer softening point that prevents skinning at the air–water interface. The absence of external plasticizers becomes particularly valuable here: when a plasticized control was aged in contact with bitumen-residue subfloors for 90 days at 40 °C, plasticizer migration into the substrate increased creep compliance by a factor of 3–4, while the Celvolit 1408 compound maintained a constant storage modulus G' of 0.8 MPa at 1 Hz in dynamic mechanical analysis.

Stability Limits and Formulation Incompatibilities

The emulsion is colloidally stabilized with a polyvinyl alcohol (PVOH) protective system, which renders it shear-thinning but also imposes operational boundaries. Intensive high-shear mixing via a Cowles dissolver blade at tip speeds above 18 m/s can rupture the PVOH envelope and induce micro-coagulum, visible as grit on a 50 µm Hegmann grind gauge. Optimal incorporation of rheology modifiers, such as alkali-swellable acrylic thickeners, requires pre-neutralization of the thickener to pH 7.5–8.5 before addition to avoid localized pH shock and destabilization of the VAE particle surface. Direct contact with zinc oxide, calcium hydroxide, or strong Lewis acids lowers emulsion pH below 3.5 and accelerates thickening and eventual gelation; the use of a sodium bicarbonate buffer at 0.1–0.2 wt% of formulation weight maintains system pH above 4.5 during compounding. Freeze–thaw stability is poor, as with most VAE emulsions: storage below +5 °C leads to irreversible grit formation; sealed containers must be kept in frost-protected warehouses.

When blending with hydrocarbon resin dispersions to augment tack, compatibility is governed by resin acid number and average particle diameter. Rosin ester dispersions with an acid number below 8 mg KOH/g and anionic stabilization are generally compatible; higher acid numbers can cause hetero-coagulation because of the acidic VAE surface. A simple pre-screening test—tumbling a 90/10 polymer-to-resin dispersion blend for 15 minutes at 500 rpm and passing through a 100 mesh screen—should yield less than 0.1% residue on the screen before scaling up. Tackifier dispersions stabilized with nonylphenol ethoxylates are to be avoided not only for regulatory reasons but also because they interfere with the PVOH colloid, reducing heat-age stability at 50 °C below the 7-day benchmark required by some construction product standards.

Regulatory Reference Matrix