Celvolit 1468 VAE Emulsão

Celvolit 1468 is an aqueous dispersion of a vinyl acetate-ethylene (VAE) copolymer stabilized with an anionic surfactant system and preserved with a non-formaldehyde-releasing biocide package. The grade is delivered as a milky liquid with a solids fraction of 54–56 wt% (ISO 3251, 105 °C, 2 h), a Brookfield viscosity of 2500–4000 mPa·s (ISO 2555, spindle 3, 20 rpm, 25 °C), and a pH between 4.5 and 5.5 (ISO 976). The minimum film formation temperature (MFFT) determined by DIN ISO 2115 lies at 0–2 °C, allowing film coalescence at ambient temperatures without external coalescents. This distinguishes 1468 from conventional poly(vinyl acetate) homopolymer emulsions, which demand MFFT values exceeding 15 °C and therefore require volatile plasticizers to form coherent films. The ethylene comonomer content, controlled to approximately 10–15 wt% on dry polymer, depresses the glass transition temperature to near 0 °C while imparting permanent flexibility and good adhesion to low-surface-energy substrates such as polyethylene terephthalate and corona-treated polyolefins.

Measuring Non-Volatile Content and Rheological Consistency per ISO 3251 and ISO 2555

Batch conformity is assessed by a gravimetric solids procedure (ISO 3251, 105 ± 2 °C, 2.0 h in a forced-air oven) and by rotational viscometry using a Brookfield LVT or RVT with spindle #3 at 20 rpm and 25.0 ± 0.5 °C. The viscosity range of 2500–4000 mPa·s is engineered for direct transfer from IBC to a coating tray without pre-dilution; however, at shear rates above 5000 s⁻¹ in gear-pump recirculation loops, the dispersion can exhibit shear-induced micro-coagulum, which elevates screen pack pressure on slot-die coater filters. In continuous process setups, a positive-displacement diaphragm pump coupled with a 100 µm mesh in‑line strainer provides adequate protection. The pH window must remain acidic: drifting above 6.0 through contamination with alkaline cleaning agents can destabilize the colloid, causing an inflection in the Zeta potential from approximately −35 mV to less than −20 mV, visible as a progressive rise in 40‑µm sieve residue (ISO 4576).

What Determines Adhesion Performance on Low-Energy Surfaces?

The critical surface tension of dried Celvolit 1468 film measures approximately 38 mN/m (advancing contact angle with water 82°, diiodomethane 54°), which promotes wetting on substrates with surface energies as low as 34 mN/m when applied as a 20 µm dry film. Lap‑shear strength on beech wood (conditioned at 20 °C/65% RH) according to ASTM D1002 gives 8.5–10.5 MPa, with wood failure percentages exceeding 85% when the adhesive is employed in a two‑part system with a water‑emulsifiable isocyanate hardener. On untreated biaxially oriented polypropylene (BOPP) film, the peel adhesion at 180° and 300 mm/min (ISO 29862) reaches 1.2 N/25 mm but falls to 0.2 N/25 mm on fluoropolymer surfaces, confirming that a pretreatment such as corona discharge (40–44 mN/m dyne level) is mandatory for critical bonding. The copolymer’s ethylene segments create a low-modulus interphase that dissipates peel energy; in contrast, a VAE grade with lower ethylene content (e.g., Celvolit 1490, Tg +15 °C) yields higher static shear but substantially lower peel on flexible films.

When Crosslinking Agents Extend Durability Classification to EN 204 D3

Celvolit 1468 alone meets the requirements of durability class D2 per DIN EN 204 (cold press, 20 °C, 7 days conditioning) for interior applications with occasional short‑term water exposure. The addition of a water‑dispersible polyisocyanate (W‑PI) at 5–7 wt% on total dispersion elevates the bonded joints to D3 classification, which demands a wet‑shear strength after 4 h water immersion at 20 °C of at least 2.0 MPa and a dry shear of 10.0 MPa. The pot life of the mixed adhesive drops to 45–60 minutes at 23 °C because the isocyanate groups react with water and residual hydroxyl sites on the poly(vinyl alcohol) protective colloid present at low concentration. This reactivity disqualifies amine‑based rheology modifiers; ammonia or AMP‑95 (aminomethyl propanol) accelerates gelation within 10 minutes, while a hydroxyethyl cellulose thickener (e.g., Cellosize HEC‑10) or an alkali‑swellable acrylic (ASE) adjusted to pH 5.0 with citric acid maintains usable viscosity for the full working window. Hardener additions above 8 wt% cause edge‑curl on 0.3 mm birch veneer due to an increase in crosslink density that raises the film storage modulus E’ (DMA, 1 Hz) from 12 MPa to 90 MPa at 25 °C, a stiffness mismatch that can be documented by ISO 1519 cylindrical mandrel bend testing.

Comparison of Key Values Across Three Latex Grades

The table highlights the trade‑off inherent in ethylene modification: the permanent flexibility and low‑temperature film formation of Celvolit 1468 come at a sacrifice of cohesive strength compared to a homopolymer PVAc. When high shear adhesion and creep resistance dominate the specification—as in structural woodworking beyond D2—a VAE with a higher Tg (e.g., Celvolit 1320) or an additional crosslinker is necessary. The data demonstrate why selecting 1468 as a base for flooring adhesives must be accompanied by filler reinforcement: 40 wt% calcium carbonate (d₅₀ 5 µm) raises the elongation break stress to 2.4 MPa but reduces peel on vinyl tiles, a consequence of increased cohesive strength depressing wet‑out on micro‑rough PVC surfaces.

Formulating with Fillers: Calcium Carbonate Loading Limits and Whitening Resistance

Celvolit 1468 tolerates calcium carbonate addition up to 60 phr (dry weight basis) while retaining measurable adhesive properties; beyond this filler volume concentration, the continuous film matrix becomes insufficient to accommodate particle‑particle contacts, causing a precipitous drop in elongation from ~300% to less than 15% (ISO 527-3) and a near‑total loss of tack. The surfactant stabilization interacts favourably with stearic acid‑coated ground calcium carbonate (GCC) at pH 5.0, but uncoated GCC may sequester emulsifier and elevate the minimum film formation temperature by 2–4 °C. In parquet flooring adhesive formulations filled with 45 phr GCC and 3 phr pyrogenic silica for anti‑slump, the sag resistance (EN 1308) can be held at 0.5 mm for a 10 mm bead when the yield stress exceeds 150 Pa. The system, however, is sensitive to freeze‑thaw cycles: a single cycle to −5 °C produces irreversible viscosity increase to +15 000 mPa·s and grit formation exceeding 200 µm (ISO 4576), a failure mode not observed in the unfilled emulsion that recovers with gentle stirring at 25 °C.