Copolímero de acetato de vinilo de etileno ELVAX 3175

Corrugated case and tray sealing lines using wheel applicators, nozzle dispensers, or slot-coat systems require a thermoplastic melt that develops rapid green strength, delivers clean adhesive cut-off, and provides a compression window in the 0.2–0.5 s range. ELVAX 3175 ethylene vinyl acetate copolymer is supplied with a nominal vinyl acetate content of 28 wt% and a melt mass-flow rate of 6.0 g/10 min when measured under a 2.16 kg load at 190 °C in accordance with ISO 1133-1:2022. A standard hot-melt formulation for corrugated case closing contains 30–35 wt% ELVAX 3175, 35–45 wt% fully hydrogenated C9 hydrocarbon tackifying resin, 20–30 wt% microcrystalline or Fischer-Tropsch wax, and 0.5–1.0 wt% hindered phenolic antioxidant. The EVA fraction increases cohesive strength and adhesion to recycled corrugated medium. The tackifier controls wetting of kraft and clay-coated linerboard. The wax component adjusts open time and set speed. Production-scale melt tanks are operated under nitrogen blanket at 165–175 °C, with adhesive delivered to the applicator at 170–180 °C. When the melt temperature exceeds 200 °C for extended periods, acetic acid is liberated from the vinyl acetate comonomer. This accelerates char formation, increases viscosity drift, and corrodes unalloyed aluminium or bronze machinery components. Viscosity stability is monitored over an 8 h production shift by ASTM D3236 using a Brookfield Thermosel. A viscosity increase greater than 10% relative to the start of the shift indicates thermal degradation and requires a lower setpoint or reduced pre-melt inventory. The adhesive may be used in indirect food packaging applications under FDA 21 CFR 175.105, provided the complete formulation is evaluated for migration limits and functional barrier requirements. In high-humidity plants, EVA pellets are pre-dried at 60 °C for 4 h before melt blending to reduce hydrolytic chain scission and melt viscosity inconsistency.

When 28 wt% Vinyl Acetate Modifies Fully Refined Paraffin Wax

In paraffin wax modification, ELVAX 3175 is introduced at 1.5–6.0 wt% of the total wax compound to increase melt viscosity, reduce cold flow, and improve scuff resistance on board and paper surfaces. The blend is prepared in a jacketed vessel equipped with a low-speed turbine agitator at 135–145 °C. Fully refined paraffin wax is melted first, and EVA pellets are added gradually over 20–30 min. Dispersion is considered complete when the melt clears and agitator torque stabilizes. The modified wax is applied through curtain coaters, roll coaters, or immersion dip tanks at 70–100 °C. Terminal products include wax-coated corrugated containers, fruit and vegetable transport boxes, and moisture-resistant paperboard wraps. Ring-and-ball softening point of the cooled compound is measured according to ASTM E28. Raising the EVA content to 8 wt% increases hardness but may push melt viscosity beyond the operational range of roll-coating equipment. Published data for this specific configuration is limited, and preliminary laboratory blending is required to confirm cloud point and phase compatibility. The cooled wax film is evaluated for blocking resistance and coating continuity on production board. Food-contact suitability for paper and paperboard is assessed under FDA 21 CFR 176.170 when the complete wax formulation is finalised. The EVA component alone does not establish food-contact compliance. Wax containing EVA should not be overheated above 160 °C for repeated cycles because thermal oxidation darkens the blend and reduces water resistance.

What Limits Solvent-Borne EVA Adhesive Drying and Viscosity Stability?

In solvent-borne adhesive production, ELVAX 3175 is dissolved at 25–40 wt% solids in a blend of toluene, methyl ethyl ketone, or acetone. Dissolution is performed in a jacketed closed mixer with explosion-proof drives at 40–60 °C under slow agitation for 4–6 h. Solution viscosity is controlled between 1,000 and 3,000 mPa·s at 25 °C using a Brookfield RVT viscometer at 20 rpm. The adhesive is applied by gravure roll, reverse roll, or knife-over-roll coating to polyester film, aluminium foil, or treated polypropylene. Dry coating weights range from 10–25 g/m². Solvent removal occurs in a multi-zone convection oven with air temperatures from 60 °C at the entrance to 120 °C at the exit. Drying rate is limited by solvent vapour pressure, lower explosion limit, and the solubility of the EVA in the remaining solvent. Compliance with Regulation (EC) No 1907/2006 is required for toluene and ketone handling, and exhaust vapours may require carbon adsorption or thermal oxidation. Viscosity instability appears as a slow increase during storage when the solution is contaminated with moisture, acid, or reactive metal ions. Amine-based additives and strong alkali are avoided because they accelerate ester hydrolysis and release acetic acid, further reducing solution stability. The finished adhesive film retains low-temperature flexibility and adhesion. Terminal products include laminating adhesives for printed flexible packaging and heat-seal coatings for foil lidding.

Polyolefin compounders introduce high-VA EVA at 5–20 wt% into LDPE or LLDPE to improve impact toughness, filler acceptance, and adhesion in masterbatch concentrates. ELVAX 3175 is also used as a carrier resin for pigment and additive masterbatches at 30–50 wt% filler loading. Compounding is conducted in a co-rotating twin-screw extruder with an L/D 40:1 configuration. The barrel profile is set with a feed-zone temperature of 120 °C and a die melt temperature of 180 °C. Venting after the mixing zone removes moisture and low-molecular-weight volatiles. If storage relative humidity exceeds 60%, pre-drying at 60 °C for 4 h is required before extrusion. The polar vinyl acetate comonomer reduces interfacial tension between the polymer phase and mineral fillers such as calcium carbonate or talc. This improves pigment dispersion in carbon black masterbatches and reduces filter pressure rise measured on a screen pack with 100 µm mesh. The carrier resin contributes a melt viscosity that matches the diluent polyolefin, producing uniform strand pelletizing. Resulting compounds are used in injection moulding and film extrusion, with tensile properties measured according to ISO 527-2:2012 and impact resistance determined by ASTM D256. Barrel temperatures above 220 °C produce acetic odour and yellowing, indicating degradation. Long residence times at high temperature are not used. Published data for this specific grade in high-filler systems is limited; pilot-scale compounding trials are advised before commercial scale-up.

Flexible Packaging Tie Resin and Extrusion Lamination Parameters

In coextruded flexible packaging structures, ELVAX 3175 is used as a neat tie layer or modified tie resin where adhesion to aluminium foil, paper, PET, or EVOH is required. The vinyl acetate content of 28 wt% provides polar functionality for adhesion to aluminium oxide surfaces and paper fibres. Extrusion lamination with EVA tie resin is run at melt temperatures between 210 °C and 240 °C. Melt temperature is not raised above 250 °C because degradation risk increases rapidly. A typical extrusion laminating line operates with chill roll cooling, a die-to-nip air gap of 15–25 cm, and a coating weight of 12–25 g/m². Adhesion is measured as peel strength according to ASTM D1876. Coextruded structures can include LDPE/EVA/tie constructions for cheese or frozen food pouches. Food-contact use of the EVA layer is subject to FDA 21 CFR 177.1350 provided migration limits and end-use conditions are respected. The EVA tie layer may be blended with LDPE at 10–30 wt% to adjust melt stability and reduce formulation cost. The blend is prepared by dry tumble mixing before feeding to a single-screw extruder with L/D 24:1 or higher. Neck-in and draw-down are controlled by melt temperature, air gap, and line speed. Line speeds above 300 m/min may induce draw resonance, although published data for this specific grade at very high line speeds is limited. Terminal products include foil-laminated flexible packages, lidding films, and multi-layer barrier pouches.

Bituminous Membrane Modification Requires High-Shear Blending

In production of polymer-modified bituminous waterproofing membranes, ELVAX 3175 is dispersed into oxidised or distilled bitumen at 3–6 wt% of the total binder. The copolymer is added to a high-shear rotor-stator mixer at 175–185 °C. Mixing continues for 60–90 min at rotor tip speeds above 15 m/s. The EVA phase raises the softening point, reduces penetration at service temperature, and improves elastic recovery. Process control includes softening point measurement according to ASTM D36, penetration testing under ASTM D5, and elastic recovery evaluation by ASTM D6084. The modified binder is used to impregnate polyester or fibreglass nonwoven carriers for waterproofing membranes. If the blend is over-sheared or held above 200 °C for more than 4 h, viscosity drift and binder gelation may occur. Compatibility with highly paraffinic bitumen can be limited at this vinyl acetate content, and lower EVA concentration or a compatibility agent may be required. Published data for this specific grade in road asphalt is limited; plant-scale viscosity stability and storage stability tests are necessary before use. The finished waterproofing membrane is evaluated under EN 13707 for flexible sheets used in waterproofing.