Celvolit 1318 VAE Emulsão

Designated as a high-solids, surfactant-stabilized vinyl acetate-ethylene copolymer dispersion, Celvolit 1318 delivers a film-forming temperature minimum of 0 °C without external coalescing aids, a characteristic that directly addresses plasticizer migration failures common to plasticized poly(vinyl acetate) homopolymers. The aqueous emulsion is stabilized with a poly(vinyl alcohol) protective colloid, yielding a nonionic character and a Brookfield viscosity of 2000–4000 mPa·s (spindle 4, 20 rpm, 25 °C, ISO 2555:2018) at a solids content of 54–56 % (ISO 3251). The pH range of 4.0–5.5 (ISO 976) promotes compatibility with acidic catalysts and crosslinkers while avoiding the alkaline hydrolysis pathways that degrade ester linkages in PVAc matrices. Residual monomer content is held below 500 ppm, meeting indirect food contact adhesive stipulations under FDA 21 CFR 175.105 and the monomer control thresholds of the German Blue Angel RAL-UZ 113 for low-emission floor coverings. When compared to carboxylated styrene-butadiene latexes, Celvolit 1318 exhibits markedly lower yellowing after 100 h QUV-B exposure (Δb <2.0 vs. typical Δb 6–8 for SBR), yet its set speed in direct-coat nonwoven applications requires an elevated line temperature of 80–95 °C to achieve full fibre lock within 45 s residence time.

What Distinguishes the Polymer Architecture of Celvolit 1318 from Plasticized PVAc Systems?

The incorporation of approximately 10–15 wt% ethylene into the vinyl acetate backbone lowers the glass transition temperature to ≈0 °C (differential scanning calorimetry, 10 K/min heating rate, second heat) without the deliberate addition of low-molecular-weight plasticizers such as dibutyl phthalate or triacetin. This internal plasticization mechanism eliminates the exudation risk documented in EN 12720:2009 cold-check testing, where external plasticizers migrate to the adhesive-substrate interface and cause a loss in tensile shear strength exceeding 30 % after 12 months at 40 °C. Minimum film formation temperature, determined by the MFFT bar method per ASTM D2354-10, resides at 0–2 °C; below this point the dispersion requires pre-warming of substrate or co-application of 2–4 wt% of a high-boiling coalescent such as 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate. In multi-layer wood bonding following EN 205:2016, press times of 10–15 min at 1.0–1.5 N/mm² yield a shear strength exceeding 6 N/mm² on beech, provided the adhesive blend pH remains below 6.0 and the application temperature is not permitted to fall below the MFFT during open assembly (≤5 min). Attempts to accelerate drying with infrared panels emitting peak wavelengths below 2.5 µm risk surface film formation that traps water beneath, leading to steam blistering in the glue line when board moisture content exceeds 8 %.

Processing Viscosity and Rheological Response Under Production-Scale Pumping

Celvolit 1318 exhibits pseudoplastic flow behaviour typical of colloid-stabilized VAE latices, with a shear-thinning index (η₁₀/η₁₀₀) of 1.8–2.4 measured on a rotational rheometer at 23 °C. When transferred through air-operated double-diaphragm pumps, pulsation-induced cavitation can raise the free monomer content at the pump outlet by 15–20 ppm and initiate microcoagulum formation that obstructs 150 µm slot-die shims. Progressive cavity pumps with elastomeric stators (NBR or EPDM) reduce shear gradient intensity and maintain a steady-state delivery pressure of 2–4 bar at a flow rate of 25 L/min. Thickening with alkali-swellable acrylic emulsions (e.g., 0.3–1.0 dry phr) to an application viscosity of 12 000–18 000 mPa·s (Brookfield, 10 rpm) is required for vertical surface hold-out in wall panel lamination. Over-thickening beyond 25 000 mPa·s creates a Weissenberg rod-climbing effect in the coating pan that entrains air and produces crater densities of 15–30 per m² on the dried film. Defoaming with 0.1–0.3 % of a silicone-free defoamer based on hydrophobic silica in polyglycol is standard practice; silicone-based defoamers exceeding 0.05 % active silicone have been observed to impair wetting on corona-treated polypropylene (44–48 dyn/cm).

In carpet tile pre-coat and secondary backing operations, Celvolit 1318 is compounded with 300–500 phr of calcium carbonate filler (d50 5–15 µm) and applied at a dry add-on of 350–500 g/m². Tuft bind strength, tested per ASTM D1335-21, reaches 18–22 N for loop-pile polyamide 6 constructions when the latex is cured at 130 °C for 8 min in an impingement oven. Storage at 50 °C and 95 % RH for 7 days reduces wet tuft bind by 25–35 % unless a crosslinker such as ammonium zirconium carbonate (1–2 dry phr) or a blocked isocyanate dispersion is incorporated; the addition re-establishes wet strength to 85–90 % of the original dry value. Delamination resistance under ASTM D3936-21 improves from 1.0 N/mm (straight filler-loaded latex) to 1.6–1.8 N/mm with 2 dry phr of a melamine-formaldehyde resin, but formaldehyde-release concerns restrict this approach in European Ecolabel (2016/1349/EU) compliant products.

Adhesion Profile on Low-Energy Substrates and Diffusion Bonding

The surface tension of the liquid emulsion is 37–39 mN/m (Wilhelmy plate, 25 °C), which is insufficient for wetting untreated polyethylene or polypropylene (<32 mN/m). On corona-treated LDPE film (38–42 mN/m), the emulsion spreads to a continuous wet film at a coat weight of 4–6 g/m² (dry), yielding a 180° peel adhesion of 2.5–3.5 N/25 mm (ASTM D903-98, 300 mm/min crosshead speed) to aluminium foil. Peel values drop to below 0.5 N/25 mm if the treatment level decays below 34 mN/m within 72 h of corona exposure, a timeline that mandates in-line treating immediately upstream of the coating station. On plasticized PVC containing 30–40 phr diisononyl phthalate, Celvolit 1318 resists plasticizer-induced tackification for 500 h at 70 °C (according to a modification of ISO 23999:2018), contrasting with typical PVAc homopolymers that undergo full softening within 100–150 h. This resistance is attributed to the ethylene segments reducing the solubility parameter delta toward the Hansen dispersive component of ≈16 MPa¹/², which is less compatible with the phthalate ester solubility zone.

When formulating one-part waterproof wood adhesives for non-structural interior joinery (Category D2 per EN 204:2016), the native water resistance of Celvolit 1318 without crosslinker is sufficient only for D1 classification. To achieve the D2 requirement of ≥4 N/mm² after 4 h cold-water immersion, the blend must incorporate 1.5–2.5 dry parts of a polymeric methylene diphenyl diisocyanate (pMDI) emulsion per 100 parts of VAE solids. The isocyanate—VAE reaction proceeds at a half-life of approximately 20 min at 20 °C (pot life), after which the Brookfield viscosity doubles and the wet adhesive transitions from a thixotropic gel to a stringy, partially gelled mass that cannot be roller-applied. Production schedules must therefore meter the crosslinker inline via a static mixer immediately ahead of the roll coater, a configuration that imposes a maximum working volume of 20 L in the recirculation loop to prevent gel blockages.

Differences Between Celvolit 1318 and Adjacent VAE Grades in Wood and Packaging Bonding

Within the Celvolit VAE portfolio, grade 1318 occupies an intermediate position between the lower-viscosity grade 1316 and the higher-heat-resistance grade 1325. Celvolit 1316 offers a viscosity of 500–1000 mPa·s and a solids content of 54–56 %, making it more suitable for spray application where atomisation air pressures of 2–3 bar require a low-viscosity Newtonian substrate. Celvolit 1325 possesses a Tg of approximately +7 °C and a corresponding MFFT of +7–9 °C, which confers better creep resistance under load at 60 °C (EN 14292:2005) but necessitates coalescent addition for film formation below 10 °C. Celvolit 1318, with its 0 °C MFFT, avoids coalescent demand in applications running at ambient factory temperatures of 15–25 °C, thereby maintaining a VOC content below 0.5 g/L and satisfying the most restrictive category of indoor air quality labelling schemes. In fast-set tube-winding adhesives for spiral paper cores, the absence of a coalescing solvent in 1318 accelerates initial grab, reducing roll-close time from 8 s (for 1325 with 3 % butyl carbitol acetate) to 4–5 s on 110 g/m² kraft paper.

Published data for this specific configuration regarding high-frequency dielectric bonding of PVC edgebanding is limited. However, the dielectric loss factor of unbonded VAE film at 27.12 MHz is approximately 0.02–0.04, which is insufficient for direct radio-frequency activation without the addition of 5–10 % of a conductive filler such as carbon black or a quaternary ammonium salt. In such hybrids, the power absorption increases but the film homogeneity degrades, causing a drop in tensile lap-shear strength from 5.5 N/mm² to below 3.0 N/mm² on beech when filler content surpasses 8 %. Alternative edgebanding approaches therefore prefer a combination of Celvolit 1318 with a thin layer of an EVA hot-melt for instantaneous tack, leaving the VAE to develop water-resistant strength over 24 h.

The emulsion remains susceptible to destabilization upon contact with amine-functional silanes or polyamidoamine hardeners used in two-part epoxy adhesives. Exposure to triethylenetetramine at concentrations as low as 0.1 % on wet adhesive weight induces instantaneous pH shift above 8.5, cleaving acetate groups and causing coagulation within 30 s. Consequently, mixing or layering with epoxy components is not recommended unless a barrier varnish is applied. For structural wood lamination where epoxy topcoats are subsequently applied, an intermediate seal coat of 50 g/m² dry based on a carboxylated nitrile rubber latex is inserted to block amine permeation.