Tricolene LLDPE LLB2919 is processed on high-output monolayer blown-film lines equipped with 65–90 mm grooved-feed extruders, L/D ratios of 28:1–30:1, and dual-lip air rings. The technical data sheet lists nominal density at 0.918 g/cm³ and melt flow rate at 2.0 g/10 min under 190°C/2.16 kg per ISO 1133-1:2022, placing the grade in the general-purpose butene-copolymer film envelope. For 75–100 µm heavy-duty shipping sacks, die gap is set at 2.0–2.4 mm, blow-up ratio at 3.0–3.8:1, and melt temperature at 195–210°C. Frost-line height is maintained at 8–10 die diameters to force machine-direction orientation and raise Elmendorf tear in MD. Internal bubble cooling is typically activated once output exceeds 180 kg/h on a 400 mm die. Dart drop impact is measured per ASTM D1709-16a; sack converters commonly require 400 g minimum for 100 µm structures used in UN 13H2 transport packaging. Elmendorf tear is checked per ASTM D1922-15, with TD values typically 2.5–3.5 N at 100 µm for this butene-copolymer class. Tensile strength at break per ASTM D882-18 falls in the range 25–35 MPa MD and 20–30 MPa TD. Sacks are rarely run as 100% LLB2919; 20–30 wt% LDPE is added to improve bubble stability on aging air-ring systems, with the optimal blend ratio determined by pinning bubble diameter variance to ±5 mm.

Why Does Bubble Stability Limit Downgauging in Agricultural Silage Wrap?

Agricultural silage wrap extrusion shifts from conventional heavy-duty sack processing only in additive loading and frost-line control. LLDPE LLB2919, when used as the base resin, is blended with 5–8 wt% white silage masterbatch and 0.5–1.0 wt% UV stabilizer masterbatch containing hindered amine light stabilizers. The masterbatch carrier resin must have a melt index within 0.5 g/10 min of LLB2919 to avoid melt-pressure oscillation. On a 1200 mm die, blow-up ratio is held at 2.2–2.8:1, lower than heavy-duty sacks, because silage film requires high MD tensile strength for round-bale wrapping tension. Film thickness is typically 25 µm, and downgauging below 22 µm without metallocene toughener creates a frost-line instability characterized by bubble chatter and measured gauge variation above ±8% by capacitance gauge. Tensile elongation at break per ISO 527-3:2018 must remain above 350% after 4000 h of accelerated weathering in ISO 4892-2:2013 cycle 1. Puncture resistance is measured by a probe test using ASTM D5748-19; field specifications for 25 µm silage wrap commonly set 12 N minimum penetration force. The finished bale wrap must survive 6–8 wrapping revolutions at 0.4 MPa hydraulic tension without tearing at the film edge.

Pallet unitization stretch film runs as a 15–30 µm cast coextrusion with LLB2919 in the core layer

Cast stretch-film lines with 5-layer feedblock and 2500 mm die width use Tricolene LLDPE LLB2919 in the core layer because its 0.918 g/cm³ density and 2.0 g/10 min MFR permit high line speeds without excessive gel back-pressure. Die gap is set at 0.6–0.8 mm; chill roll temperature is maintained at 20–25°C. The air knife pressure is adjusted to 0.3–0.5 bar to pin the melt curtain. Core layer thickness share is 70% of total gauge. Outer cling layers use ultra-low-density polyolefin or ethylene-vinyl acetate with 2–5 wt% polyisobutylene tackifier through side-arm extrusion. Pre-stretch ratio on pallet wrappers is set between 150% and 250% before wrapping; tear propagation of a 20 µm film is tested per ASTM D1922-15 and should not fall below 1.2 N in TD. Puncture resistance on the wrapped pallet is verified by ASTM D5748-19, with a target of 10 N minimum for an 800 kg pallet load. Film elongation at break per ASTM D882-18 is normally 350–450% in MD. No pre-drying is required if internal moisture content is below 0.03%; higher moisture produces flow marks at the die exit visible as chevrons on the cast film.

When converters laminate LLB2919-based blown film to BOPET or BOPP for frozen seafood packaging, film gauge is typically 40–60 µm. Low-temperature puncture and seal reliability dominate. The LLDPE film is corona-treated to 38–42 mN/m and laminated with solventless polyurethane adhesive at 1.8–2.2 g/m². Lamination bond strength is checked after 24 h cure per ASTM F904-16; frozen-food converters commonly require 6 N/15 mm in the machine direction. Dart impact at -20°C is measured per ASTM D1709-16a Method A on a 50 µm film; values below 90 g indicate inadequate low-temperature toughness or excessive filler in the sealant layer. Heat-seal strength on the laminated structure is evaluated at 120–140°C dwell temperature and 0.3 MPa jaw pressure with a 1 s dwell. Seal-through-contamination performance is improved by blending 15–20 wt% of a 0.905 g/cm³ metallocene LLDPE, which lowers seal initiation temperature by approximately 5–8°C. The finished laminate is converted into form-fill-seal pouches on vertical machines running at 60–80 packs/min; edge tear resistance per ASTM D1922-15 prevents splitting at transverse seal perforations. Food-contact compliance is assessed under FDA 21 CFR 177.1520 and Commission Regulation (EU) No 10/2011 Annex I, with overall migration below 10 mg/dm² per EN 1186-1.

When LLB2919 Carries 20–30 wt% Post-Consumer Recyclate in Retail Carrier Bags

Retail carrier bag extrusion with recycled-content mandates alters screen-pack configuration and bubble cooling. Tricolene LLDPE LLB2919 is used as the virgin let-down resin in blends containing 20–30 wt% post-consumer LLDPE recyclate from stretch film or carrier bag recovery streams. A 150 mm grooved-feed extruder with L/D 30:1 is fitted with a continuous slide-plate screen changer and two screens of 250 µm and 100 µm mesh. Melt temperature is kept below 215°C to avoid thermal degradation of residual adhesive and tackifier in the recyclate. Backpressure increases from 280 bar to 340 bar during screen blockage cycles; the screen change is triggered at 380 bar. Film gauge for retail carrier bags is 18–25 µm. Dart impact per ASTM D1709-16a at 20 µm typically falls from 65 g for virgin LLB2919 film to 45–55 g when 30 wt% recyclate is incorporated. To compensate, bag makers increase gauge by 2–3 µm or add 10 wt% metallocene LLDPE. Elmendorf tear in MD per ASTM D1922-15 is monitored to remain above 0.8 N. The finished T-shirt bag is welded on hot-knife lines at 160–180°C; seal strength per ASTM F88/F88M-21 must exceed 4 N/15 mm to prevent handle failure. No pre-drying is required if recycled flake is stored below 50% relative humidity.

Collation Shrink Film and Bottle Multipack Overwrap

Collation shrink film produced from LLB2919 normally uses a 70 wt% LLB2919 / 30 wt% LDPE-EVA blend on high-stalk blown film lines. Die gap is 1.4–1.8 mm; blow-up ratio is set at 3.0–4.0:1 to generate balanced shrink in both directions. The bubble is collapsed at a frost-line height of 8–12 die diameters. Free shrink is tested per ASTM D2732-16 in hot oil at 120°C; collation overwrap specifications frequently require 12–15% MD and 8–12% TD shrink. Shrink tension is measured per ASTM D2838-18. In the shrink tunnel operating at 165–185°C, the film reaches final pack tightness within 2–4 s. Tear propagation in TD per ASTM D1922-15 must stay below 1.5 N at 38 µm to allow hand-opening of multipack bottles. Sealed overlap joints are produced by hot-wire or impulse sealing at 0.4 MPa jaw pressure. Pinhole resistance in the finished overwrap is checked by ASTM F1306-21. Corona treatment is avoided when the film is printed with flexographic inks; surface tension is maintained at 34–36 mN/m to reduce ink blocking on the back side of the sealed film.

In 12–20 µm can liners, gauge uniformity and low gel count are the primary resin selection variables. LLB2919 is extruded on high-output cast or blown film lines with 0.8 mm cast die gap or 1.2 mm blown die gap. For 15 µm blown can liner film, blow-up ratio is set at 2.5–3.0:1; frost-line height is minimized to 4–6 die diameters to reduce blocking. Slip and anti-block masterbatch is added at 1.5–2.5 wt%, containing 5 wt% erucamide and 15 wt% synthetic silica. The film coefficient of friction is measured per ISO 8295:2018, with static friction below 0.35 targeted for automatic bin-liner dispensers. Dart drop impact of a 15 µm film is measured per ASTM D1709-16a Method A; a value below 35 g leads to field failures during waste compaction. The seal zone on side-weld lines runs at 150–165°C and 0.3 MPa jaw pressure; heat-seal strength per ASTM F88/F88M-21 is kept above 3 N/15 mm. Tear resistance per ASTM D1922-15 in TD is not the dominant variable for can liners, but Elmendorf values below 0.5 N at 15 µm indicate excessive gel contamination or poor blend homogeneity. The finished liner is packed in perforated rolls; roll tightness is adjusted to avoid film stretching beyond 3% residual elongation when dispensed.