Elvax 260 EVA resina de copolímero, grau adesivo

Compounding of Elvax 260 for case and carton sealing is performed in a 200 L jacketed sigma-blade mixer at shell temperatures between 150 °C and 170 °C. The resin enters the batch as a pelletized base with supplier-reported 28 wt% vinyl acetate content and a melt flow rate of 6 g/10 min at 190 °C under 2.16 kg load per ASTM D1238-20. That low MFR restricts capillary penetration into uncoated recycled kraft linerboard, which is the primary failure mechanism leading to bondline starvation when higher-MFR grades are substituted on high-porosity board. The mixer is charged in a sequence that wets the EVA pellets with liquid rosin ester before wax is added, preventing dry wax agglomeration at the oil jacket interface. Blending under nitrogen with a batch residence time below 45 minutes limits acetic acid evolution from vinyl acetate deacetylation; stainless steel wetted surfaces are standard, and brass or copper fittings are excluded because residual acid accelerates metal ion-promoted ester degradation.

Representative production formulation for this grade uses 30–40 wt% Elvax 260, 35–45 wt% rosin ester tackifier with a ring-and-ball softening point of 95–110 °C, 15–25 wt% Fischer-Tropsch wax, and 0.3–0.8 wt% hindered phenolic antioxidant. The high VA content improves adhesion to polar fibre surfaces, but it also narrows the thermal processing window. At die temperatures above 185 °C, viscosity falls sharply and the molten film penetrates the linerboard, reducing the surface adhesive film available for compression set. At die temperatures below 155 °C, the adhesive does not transfer cleanly from a 1.2 m wide slot-die head, producing edge-thin films and variable open time. Across the die width, a thermocouple variation of more than ±5 °C creates measurable differences in coat weight; thermal uniformity is therefore a production acceptance criterion before adhesive application starts. Open time is not defined by a single ISO/ASTM procedure; production lines determine the compression interval window by running a series of delayed compression trials and measuring fibre tear per ASTM D1876-08(2015)e1 and ISO 11339:2022. Compression bond pressure is maintained at 0.3–0.5 MPa for 5–10 seconds; beyond this range no improvement in bond strength is observed. Release viscosity is determined per ASTM D3236-15 at 170 °C because MFR alone does not predict slot-die transfer behaviour. Published data for continuous vertical twin-screw compounding of this specific grade is limited; batch sigma-blade compounding remains the dominant production route.

How Bookbinding Open Time Changes with Tackifier Loading

Spine gluing of perfect-bound book blocks with Elvax 260 is formulated at 24–32 wt% resin, 38–48 wt% rosin ester, 10–18 wt% paraffin wax, and 0.5–1.0 wt% antioxidant. The MFR of 6 g/10 min at 190 °C under 2.16 kg load, as specified in ISO 1133-1:2022, correlates with high cohesive strength after solidification. Increasing tackifier loading above 48 wt% extends open time but shifts the failure mode from fibre tear to cohesive brittleness at shelf temperatures below 10 °C, as observed under ASTM D1876-08(2015)e1 T-peel conditioning. Reducing tackifier below 38 wt% shortens the wetting window on clay-coated cover stock and increases adhesive failure at the cover hinge.

On a perfect-binding line running at 8,000 books/h, the adhesive is delivered through a spine nozzle at 160–170 °C with a film thickness of 0.4–0.8 mm on the block. Open time on coated paperboard at 23 °C and 50% RH is controlled to less than 60 seconds by adjusting tackifier type and line speed. Because open time lacks a single ISO/ASTM method, quality control uses timed nip-interval trials with page pull strength measured per ISO 11339:2022. The low MFR of Elvax 260 prevents deep migration into the spine fibre, preserving the adhesive film at the block surface where cover bonding occurs. Production lines that raise the application temperature to compensate for viscosity above 180 °C induce bubble entrapment in the nozzle manifold; bubble voids reduce spine flex resistance, and published data for this specific grade under repeated flex testing is limited, so internal flex-rig validation is required before sustained production.

Continuous application to 0.4 mm PVC edge banding on a single-sided edgebanding machine is typically performed through a heated roller coater at 170–185 °C. The hot melt is prepared with 28–35 wt% Elvax 260, 35–45 wt% C5/C9 or rosin ester tackifier, 20–30 wt% paraffin wax, and 0.3–0.6 wt% antioxidant. The roller coater applies a film of 0.08–0.15 mm dry thickness to the band before the pressure roller nips the band onto an MDF panel at 0.3–0.6 MPa. Panel surface temperature at the nip is maintained at 40–55 °C; below 40 °C the high-viscosity melt does not transfer sufficient mass, producing skip lines and low peel strength measured per ASTM D903-98(2017). The open time between roller application and nip must remain below 15–20 seconds because surface skinning on the thin film reduces PVC adhesion. Published data for this specific line-speed/open-time configuration is limited; production verification is required when line speed exceeds 25 m/min.

Substrate moisture in MDF above 8% by mass reduces bond strength under ASTM D903-98(2017) by shifting failure from cohesive in the adhesive film to fibre pull-out in the board surface. This behaviour is measured after conditioning at 23 °C and 50% RH for 24 hours. The 28 wt% vinyl acetate content of Elvax 260 provides polarity for the PVC film, while the 6 g/10 min MFR keeps the molten film in the transfer nip without excessive squeeze-out at the band edge. At application temperatures above 190 °C, visible yellowing of the melt occurs and acetic acid release accelerates deacetylation, especially when the coater reservoir is open to air.

When Low-Temperature Deep-Freeze Packaging Requires Cohesive Peel at -20 °C

In frozen-food case sealing, the adhesive film must retain cohesion when the board springs back after compression at -20 °C. Elvax 260 is used at 35–45 wt% with a low-glass-transition aliphatic or cycloaliphatic tackifier at 30–40 wt%, microcrystalline wax at 5–15 wt%, and antioxidant at 0.3–0.8 wt%. The higher resin fraction and reduced wax fraction lower the storage modulus at sub-zero temperature, shifting the failure mechanism from brittle cohesive fracture to ductile yielding of the adhesive film. T-peel specimens are conditioned at -20 °C for 24 hours before testing per ASTM D1876-08(2015)e1; a cohesive failure pattern in the adhesive is preferred over adhesive delamination from the linerboard. Corona-treated LDPE film used for frozen-food lamination is specified at 38–42 dyne/cm surface energy; below that range, even 28 wt% VA content does not provide sufficient polar interaction and adhesive peel fails at the film interface.

The processing window narrows because high resin loading raises melt viscosity. A gear-pump melter set at 165–175 °C is required to deliver the adhesive to a slot die without exceeding 180 °C in the heated hose. If the hose temperature exceeds 180 °C, deacetylation releases acetic acid and the melt odour becomes detectable at the coating head. At temperatures below -30 °C, standard EVA-based adhesives may embrittle; published data for this specific grade in multi-layer PE coextrusions below that temperature is limited, and replacement with a lower-Tg polymer or plasticizer addition requires a formal validation plan.

Corrugated Wax Blending for Curtain Coating: Viscosity Control at Low Addition Levels

Curtain coating of corrugated board with paraffin wax modified by Elvax 260 at 2–8 wt% resin addition improves adhesion of the wax film to the linerboard and reduces flaking during score folding. The blend is prepared at 120–150 °C in a heated melt tank with low-shear agitation; above 150 °C, wax oxidation darkens the melt and raises acid number, which can destabilise the curtain. EVA content above 10 wt% raises melt viscosity beyond the range suitable for a curtain die, producing film thickness variation greater than ±5% across a 2.5 m web. The EVA fraction does not act as the primary moisture barrier; instead it reduces pinhole formation in the wax film that would otherwise compromise MVTR measured per ISO 15106-2:2005 or ASTM E96/E96M-22b. The modified wax layer is tested for adhesion by a tape snap test after score folding; no single ISO standard applies to the score-fold release of wax from linerboard.

For food-contact corrugated board, the final wax coating must meet applicable requirements for paraffin and EVA components under FDA 21 CFR 177.1350 and FDA 21 CFR 176.170, depending on the board construction and end-use conditions. The low addition level of Elvax 260 in this application does not require pre-drying if pellets are stored below 60% RH; pellets exposed to high humidity should be dried at 60 °C for 2–4 hours to prevent steam-driven pinholes in the curtain. Production lines that set the feed throat above 70 °C report bridging of EVA pellets in the feed hopper; a cooled throat section at 40–50 °C is specified for high-throughput extrusion feeding.

What Limits Heat Transfer in Profile Wrapping of 300 g/m² Decorative Films?

On a profile-wrapping line processing MDF profiles with a 0.20 mm PVC décor film, Elvax 260 is applied through a slotted die onto the film at 150–175 °C before wrapping rollers press the film against the profile. The line speed is usually limited to 12–25 m/min. The limiting factor is not the open time of the melt but the heat transfer through the decorative film to the substrate; if the MDF surface temperature falls below 50 °C, initial tack drops below the threshold needed to prevent spring-back at the profile corners. Peel adhesion of the wrapped profile is tested after 24 hours conditioning at 23 °C and 50% RH per ISO 11339:2022. The adhesive formulation for this segment typically contains 25–35 wt% Elvax 260, 30–42 wt% rosin ester tackifier, 18–28 wt% paraffin or Fischer-Tropsch wax, and 0.3–0.6 wt% antioxidant. Published data for this specific grade on profile-wrapping lines with infrared pre-heat banks is limited; process verification by peel testing of wrap corners is required before sustained production.

The 6 g/10 min MFR is low enough to maintain a continuous film between the slotted die and the nip, preventing droplet breakage at line speed despite the absence of solvent. At the same time, the 28 wt% VA content provides polar adhesion to PVC film and pre-primed MDF surfaces. Clean-up of the die lip must be scheduled every 4–6 hours because recirculated hot melt exposed to air forms a thermally oxidised edge bead that transfers to the wrapped profile as a visible surface defect. Thermal degradation is minimised by maintaining the melting tank under a dry nitrogen purge and by limiting the tank temperature to 170 °C when the line is idle.