BASF’s ecovio 70 PS14H6 Paper Coating Compostable Biopolymer is supplied as a pelletized compound of an aliphatic-aromatic copolyester and renewably sourced polylactic acid, engineered for melt extrusion coating and lamination of paper and paperboard where the finished article must be industrially compostable. The grade is tested against the harmonized scheme of EN 13432, including clause 5.1 biodegradation, clause 5.2 disintegration, clause 5.3 ecotoxicity, and clause 5.4 heavy metals. The numerical prefix 70 refers to the bio-based carbon share determined by ASTM D6866 or ISO 16620-2, although lot-level certificates remain the controlling specification. In pellet form, the material is moisture-sensitive and is normally packaged in sealed aluminium-lined bags with desiccant sachets, with residual moisture controlled to less than 0.1 wt% by ISO 15512 Karl Fischer titration. Processing requires a desiccant dryer with a dew point of -40°C or lower, because moisture above 0.1 wt% at the feed throat initiates hydrolytic chain scission during extrusion and reduces melt strength at the die exit.

Specification control for ecovio 70 PS14H6 is performed through melt viscosity, ash content, water content, and bio-based carbon content. The melt volume-flow rate is measured by ISO 1133-1 at 190°C under a 2.16 kg load, and density by ISO 1183-1. Because the grade is a blend, differential scanning calorimetry by ISO 11357-3 reveals multiple phase transitions: a copolyester melting event and a PLA melting event. The PLA-related crystalline order influences heat-seal initiation and blocking. Ash content, measured by ISO 3451-1, is kept below a low threshold to maintain compostability and reduce die-lip build-up. The product is encountered on production-scale single-screw extrusion-coating lines rather than in blown-film or cast-film operations.

Typical machine configurations include a grooved feed section, a barrier screw with L/D of 24:1 to 30:1, an automated screen changer with 100-mesh packs, and a flat slot die with internal deckle. Melt temperature at the die is commonly maintained at 160–180°C, while the chill roll is held at 18–25°C. The air gap is set between 150 mm and 250 mm to allow melt draw and surface oxidation for polar adhesion to the paper substrate. Under these conditions, coating weights of 12–25 g/m² are applied to paperboard from 250 g/m² to 350 g/m².

Why Does a 70% Renewable-Carbon Paper Coating Grade Require Different Screw Cooling Than PLA Homopolymer?

Operating with the screw temperature profile of a PLA-only coating line creates unstable melt curtains, because the aliphatic-aromatic copolyester segment in ecovio 70 PS14H6 contributes lower shear viscosity and greater melt elasticity than PLA homopolymer. The feed section is typically maintained at 150–160°C, the compression section at 160–170°C, and the metering section at 170–175°C. If the compression section is heated above 180°C to reduce PLA crystallinity, the copolymer fraction may over-plasticize, leading to edge weave and die-lip build-up. Reverse barrel cooling, using water loops in the feed zone, prevents premature pellet bridging and preserves the solids-conveying capacity of the grooved bush. Operators sometimes maintain a 5–8°C reverse temperature gradient from the compression to the feed zone, which is rarely required for LDPE but is critical for this biodegradable polyester compound.

Viscosity data, when measured by ISO 1133-1 under a 2.16 kg load at 190°C, places the melt volume-flow rate in the range typical for paper-coating grades, but complete comparative curves should be taken from the manufacturer’s technical data sheet because published data for this specific configuration is limited. The key processing distinction is not only average viscosity but the shear-thinning character measured on a capillary rheometer at apparent shear rates of 100–1,000 s⁻¹. At these shear rates, the melt transitions from a more Newtonian plateau to power-law thinning, which determines die-pressure drop and the onset of melt fracture at the lip exit. Melt fracture typically appears as regular sharkskin when line speed exceeds 120 m/min and die gap is below 0.5 mm; the correction is to raise the die temperature by 3–5°C or widen the die gap to 0.6–0.8 mm rather than increasing screw speed alone.

Because the compound is sensitive to thermal history, regrind from edge trim and start-up scrap is added at no more than 20 wt%. Reprocessing above this level reduces paper adhesion, increases the gel count, and increases the pinhole density in the finished coating. Gel contamination is assessed by continuous melt filtration using a pressure-rise index on the screen pack; a pressure increase of more than 15 bar over 4 hours is an operational signal to replace the screen before coating-weight variation exceeds ±1 g/m².

Moisture Uptake, Vicat Softening, and Seal Initiation in Paperboard Lidding Applications

In lidding and paper-cup applications, heat-seal initiation and hot-tack are limiting factors. Because the compound contains PLA domains, the seal initiation temperature is higher than that of PBAT-only coatings but lower than that of PLA homopolymer. On cup-stock paper of 280 g/m² coated with 18 g/m² of ecovio 70 PS14H6, seal strengths above 4 N/25 mm are achieved at jaw temperatures of 140–160°C with dwell times of 0.5–1.0 s when measured by ASTM F88. At temperatures above 175°C, the coating may stick to the sealing jaw or transfer to the anvil, producing process shutdown. The transfer is exacerbated by release agents containing fatty amides; therefore, only FDA 21 CFR 174.5-compliant release agents should be sprayed on the jaws at minimum dosage. Published data for specific food-contact migration under high-temperature fill-and-seal conditions is limited, so the product is not recommended for retort pouches or aseptic packaging without line-specific migration testing according to EU Regulation 10/2011.

Moisture uptake is a different operational boundary than for LDPE or PP extrusion coating. Store pellets at relative humidity above 60% for more than 4 hours and residual moisture can rise to 0.15 wt% or higher. Drying should then be extended to 6–8 hours at 70–80°C. Avoid drying above 90°C, because pellet surface tack develops in the drying hopper and blocks the conveying line. The use of hot-air ovens without desiccant is not recommended; the material does not reach the required dew point in such equipment.

Compared with an aqueous barrier-dispersion coating, ecovio 70 PS14H6 requires no anilox roll changes, no oven drying of the coated web, and no coalescing solvent. The melt-extruded coating develops barrier characteristics by solidification on the chill roll, not by particle coalescence. Barrier performance against water vapour is limited relative to LDPE, but the grade is not positioned as a high-barrier replacement. For paper cups and food trays, water-vapour transmission rates above 100 g/m²·day at 38°C and 90% RH are common, and additional barrier layers are needed where moisture penetration is the sole acceptance criterion. The compostability function, rather than an oxygen or water-vapour barrier, is the primary design driver.

Where the Difference from ecovio PS1606 Appears in Layer Distribution and Hot-Tack

Within the manufacturer’s PS paper-coating series, ecovio 70 PS14H6 differs from earlier grades such as PS1606 in the relative proportion of aliphatic-aromatic copolyester to PLA. The higher renewable-carbon fraction is associated with a higher PLA content, which raises the melt’s shear viscosity and reduces blocking at room temperature. The practical result is that coated reels can be stored at warehouse temperatures up to 35°C without blocking, provided the coating weight is below 20 g/m². Above this coating weight, the surface temperature in a tightly wound reel can exceed 45°C, and blocking may occur if winding tension exceeds 400 N/m. In contrast, PBAT-dominated grades with lower PLA content may block at lower reel temperatures but offer higher elongation and may be preferred for deep-draw paperboard forming. The selection between PS14H6 and those grades is not a simple drop-in substitution; it changes the temperature profile, the adhesion window, the seal initiation, and the reel storage behaviour.

In extrusion-coating layer distribution, the higher PLA fraction in ecovio 70 PS14H6 can produce a more defined layer boundary when coextruded with a pure copolymer tie layer. The tie layer, often an aliphatic-aromatic copolyester without PLA, is used when adhesion to aluminium-metallized paper or printed ink is required. A two-layer structure with 5 g/m² tie layer and 15 g/m² ecovio cap layer gives fibre-tearing bonds on unprimed SBS board, but the die feedblock must maintain the tie layer at 160–170°C to prevent viscosity stratification. If the tie layer is too cold, it forms distinct striations visible as matte bands in the coated sheet, and peel strength measured by TAPPI T 537 falls below 2 N/25 mm. This failure mode is not common with uniform PBAT coatings and requires careful feedblock insulation.

Because the grade is intended for industrial composting, the finished paper article must disintegrate within the time specified by EN 13432. In pilot-scale composting tests following ISO 16929, coated paperboard with 15 g/m² of ecovio 70 PS14H6 disintegrates within 12 weeks, but the result depends on screen opening size and the paper-to-polymer ratio. Coating weights above 25 g/m² or laminated double-layer structures can leave polymer agglomerates on the 2 mm screen, delaying disintegration past the specification limit or requiring additional screening in the composting plant. Biodegradation testing according to ISO 14855-2 reports conversion of the organic carbon to carbon dioxide relative to a cellulose positive control over 180 days; the relevant threshold is 90% relative biodegradation for the organic fraction. Heavy-metal concentrations must not exceed the limits in EN 13432 clause 5.4, and the sum of volatile solids must be controlled to avoid false compliance from non-biodegradable fillers.

No two industrial composting facilities use identical residence times or aeration rates, so a certificate of compostability under EN 13432 does not guarantee that a specific coated article will disintegrate in every plant. Operators should verify local acceptance before marketing a coated paper product as compostable, especially when the coating weight is above 20 g/m² or when the paperboard contains wet-strength resins that retard microbial attack. The use of a PLA-rich coating on paper with high wet strength may require extended residence time or mechanical pre-shredding.

During lamination of printed cards and menus, the product is applied as a clear coating to protect water-based inks from scuffing. The coating is run at 180°C melt temperature on a 1,200 mm wide die, with an air gap of 180 mm and a line speed of 80–100 m/min. At line speeds above 120 m/min, curl becomes the primary defect because the coating and paperboard shrink differentially on cooling. Curl measured by ISO 11556 can exceed 15% if the chill roll temperature is below 15°C or if the web is not conditioned at 23°C and 50% RH for 24 hours before printing. Curl control therefore lies less in the polymer itself than in the thermal history of the web and the moisture content of the paperboard, which should be 6–8% before coating.

Substitution of ecovio 70 PS14H6 for a conventional LDPE extrusion coating reduces the carbon footprint but changes the failure mode of the finished package. LDPE coatings fail by tearing and necking under load, while the compostable polyester coating fails by brittle fracture at low temperature and by softening at high temperature. The low-temperature impact resistance of the coated board, measured by a falling-dart method, is lower than that of LDPE-coated stock at -20°C, so freezer-grade paperboard with this coating may crack at crease folds. The operational boundary is therefore cold-chain distribution below -18°C, where a more flexible PBAT-rich grade should be selected. For ambient dry foods and chilled but not frozen products, the grade is processable on existing extrusion-coating lines with only the drying and temperature changes outlined above.

In barrier testing, the oxygen transmission rate of the coated board depends primarily on the paperboard and the dispersion of the coating at the fibre interface. With perfect film formation, the polymer layer itself is not a high oxygen barrier, and oxygen transmission rates remain above 500 cm³/m²·day·atm at 23°C and 0% RH for a 15 g/m² coating. This places the material in the low-to-moderate barrier category compared with EVOH or PVDC, but the paper substrate itself provides some resistance. For oil and grease resistance, the coating is effective at coating weights above 18 g/m² when tested by ASTM F119, with no oil breakthrough at 40°C for 24 hours. Below 12 g/m², pinholes and thin spots reduce the grease barrier and the test must be repeated with production-representative board roughness.

Compound formulations containing this grade should avoid amine-based additives and certain metal stearates because they accelerate hydrolytic degradation and shift the melt viscosity during processing. The aliphatic-aromatic copolyester segment is susceptible to transesterification in the presence of strong nucleophiles, and the PLA segment is sensitive to residual moisture. Therefore, masterbatches and process aids must be checked for compatibility by melt-viscosity monitoring over a 30-minute dwell time at 180°C. A viscosity drop greater than 10% in that period indicates an incompatible additive package. Likewise, drying hoppers must be purged with line air only after desiccant regeneration is complete; wet purge air immediately undoes the drying cycle. The product should not be left in a hot idle die for longer than 10 minutes without purging, because carbonized residue forms at the die lips and impairs coating uniformity.

The manufacturing difference between this grade and general-purpose biodegradable film grades is the lower melt-viscosity plateau and the emphasis on fibre adhesion rather than film tensile properties. In film extrusion, dart impact and tear strength are dominant specification items; in paper coating, the critical responses are peel strength, pinhole density, seal strength, blocking resistance, and curl. ecovio 70 PS14H6 is therefore not specified by tensile modulus or elongation at break alone, but by the interaction between the molten polymer and the paper surface. This interaction is measured by TAPPI T 537 peel strength and by pinhole testing under ASTM F3039. On unprimed kraft paperboard with a surface energy of 40–42 mN/m, peel strengths below 1.5 N/25 mm indicate incomplete wetting or excessive chill-roll cooling. Corona treatment of the paper to 44–48 mN/m is an effective corrective action, but the treated surface must be coated within 24 hours because the surface energy decays. In addition, the presence of mineral oil in recycled board can reduce adhesion and must be monitored when recycled fibre content exceeds 50%.

When the coating is used for compostable paper cups, the process combines paperboard forming, heat sealing of side seams, and top-curl forming. The side-seam seal is made at 150–160°C with ultrasonic or heated-air support, because the PLA-rich coating requires longer heat transfer than a low-density polyethylene coating at the same thickness. If the sealing tool pressure is too low, the seal fails before the paperboard inside ply; if too high, the coating is squeezed out and the seam leaks. The top curl is formed on the cup machine at preheated paperboard temperatures of 70–90°C; at lower temperatures, the coating cracks at the curl radius and gives visible white stress marks. The white marks are cosmetic but indicate coating damage that can reduce liquid hold-out. For this reason, the forming section must be run 20–30% slower than LDPE-coated paperboard of the same basis weight.