Frozen Food Packaging Film From Butene Copolymer Blown Film Resin

Chevron Phillips 6109L is processed as a single-layer web or as the core layer of a three-layer coextrusion for frozen food packaging. The polymer, a butene-copolymer linear low-density polyethylene with a manufacturer’s nominal density of 0.920 g/cm³ under ASTM D1505 and a nominal melt index of 0.9 g/10 min under ASTM D1238 at 190 °C/2.16 kg, is selected where low-temperature toughness and heat-seal integrity must be retained after filling at temperatures as low as -30 °C. Regulatory conformance for direct food contact is governed by 21 CFR 177.1520(c) for olefin polymers and by EU Regulation (EC) No 1935/2004, with overall migration below 10 mg/dm² measured according to EU No 10/2011 Annex I in food simulants appropriate to frozen aqueous and fatty foods. Single-layer formulations typically contain 80–95 wt% 6109L, 5–20 wt% high-pressure LDPE for bubble stability, 0.5–1.5 wt% silica-based antiblock masterbatch, and 0.3–0.8 wt% erucamide slip masterbatch. The downstream blown film process uses a die gap of 1.8–2.5 mm, a blow-up ratio of 2.2:1–3.0:1, a melt temperature of 195–220 °C, and a frost line height of 600–900 mm; on lines equipped with internal bubble cooling and die diameters of 250–400 mm, specific outputs of 1.2–1.8 kg/h per mm of die circumference are common. Below a blow-up ratio of 2.0:1, cross-direction gauge variation increases and bubble flutter introduces visible gauge bands; above 3.0:1, melt extensibility in the low-ductility butene matrix reduces process latitude and increases the frequency of pinholes. Terminal product types include individually quick-frozen vegetable pouches, frozen ready-meal bags, ice cream packaging film, and heat-sealed frozen food pouches.

In agricultural silage cover extrusion, 6109L is dry-blended with high-pressure LDPE and carbon black masterbatch to produce a film that blocks UV transmission and resists puncture during bunker compaction. Where conformance to EN 13206:2017 for thermoplastic silage films is specified, the minimum nominal film thickness of 150 µm and carbon black loading are primary specifications; weathering resistance is assessed after 2,000 h of ISO 4892-2 or ASTM G154 exposure, and film tensile properties are evaluated under ISO 527-3. The formulation at the hopper typically contains 70–85 wt% 6109L, 15–30 wt% high-pressure LDPE, 3–6 wt% carbon black masterbatch, and 2–4 wt% hindered amine light stabilizer-based UV stabilizer masterbatch. Processing is carried out on mono-layer blown film extruders with grooved feed sections and screw L/D ratios of 30:1; die gap is set at 1.8–2.2 mm, blow-up ratio at 2.5:1–3.5:1, and melt temperature at 200–230 °C. The presence of carbon black raises melt viscosity at constant throughput, increasing extrusion pressure by approximately 8–15% compared with unpigmented film; pre-drying the masterbatch at 60–70 °C for 2–3 h is required when storage humidity exceeds 60% RH, because moisture levels above 0.1% generate pinholes and bubble destabilization. Terminal products are black bunker silo covers, silage pit side-sheets, and silo bags, typically at thicknesses of 150–250 µm.

What Limits Heat-Seal Initiation Temperature in Coextruded Sealant Webs?

Coextruded sealant webs for liquid packaging position 6109L in the innermost layer because its butene branching lowers the heat-seal initiation temperature relative to high-pressure LDPE while retaining adequate hot-tack strength measured under ASTM F1921. The regulatory framework for this geometry is 21 CFR 177.1520(c) for the olefin polymer and EU No 10/2011 for the finished plastic multilayer article, with compliance determined by overall migration below 10 mg/dm² and specific migration of any additives below their SML values. The sealant layer formulation consists of 60–85 wt% 6109L and 15–40 wt% high-pressure LDPE; a polyolefin plastomer may be added at 5–10 wt% to further depress seal initiation, while slip and antiblock masterbatches are maintained at 0.3–1.0 wt% to prevent blocking of the wound roll. Published heat-seal data specific to 6109L in triple-layer coextrusion are limited; the seal initiation range cited here derives from butene-copolymer LLDPE films with comparable density and melt index under ASTM F88 at 0.5 s dwell and 2 bar jaw pressure. Seal initiation temperatures in these systems typically occur between 85 °C and 105 °C; below that range, coherent seals do not form, and above 130 °C, seal-through distortion damages the outer printed web. The downstream extrusion process uses a three-layer blown film die with gap of 2.0–2.6 mm, blow-up ratio of 2.0:1–2.8:1, melt temperature of 205–230 °C, and sealant layer thickness ratio of 15–25% of total film thickness; oscillating haul-off or 360° reverse rotation is used to distribute gauge bands. Slip additive levels above 0.8 wt% are to be avoided in the sealant layer because migration to hot sealing jaws builds deposit over extended runs and compromises seal integrity. Terminal products are bag-in-box liners for edible oil, dairy, beverage syrups, and liquid food service packaging.

Where heavy-duty industrial liners are produced on high-stalk blown film lines, the principal process constraints are melt pressure, frost line stability, and extrusion pressure drop across the die. 6109L is used here for its puncture resistance and low-temperature flexibility without requiring over-stabilization for outdoor exposure. Industrial compliance is governed by REACH Regulation (EC) No 1907/2006 Annex XVII and RoHS Directive 2011/65/EU for restricted substances where the liner enters general waste or construction debris streams; mechanical properties are specified under ASTM D882 for tensile, ASTM D1709 for dart impact, and ASTM D1922 for Elmendorf tear. The formulation is kept near-virgin at 80–95 wt% 6109L with 5–20 wt% high-pressure LDPE or clean internally recycled trim; a fluoropolymer process aid masterbatch at 0.2–0.6 wt% is added only when melt fracture occurs at high specific outputs. Extrusion conditions on high-stalk lines include die gap 2.0–3.0 mm, blow-up ratio 2.0:1–3.0:1, stalk height 6–10 die diameters, melt temperature 190–230 °C, and film thickness 100–300 µm. Sustained melt temperatures above 230 °C increase gel formation from oxidized fractions in recycled trim; below 185 °C sharkskin melt fracture becomes visible at high shear rates in the die lip. Terminal products include construction debris bags, chemical shipping liners, building underlay membranes, and heavy-duty side-gusseted sacks.

When 6109L Is Dry-Blended With High-Pressure LDPE for Collation Shrink Film

During collation shrink film production, high-pressure LDPE serves as the continuous phase that provides the required free shrink, while 6109L is added as the dispersed modifier to improve tear propagation resistance and puncture resistance on perforated shrink packs. The blend is confined to 20–40 wt% 6109L and 60–80 wt% high-pressure LDPE; at additions of 6109L above 40 wt%, the natural draw ratio increases and the available shrink force at typical tunnel temperatures falls below the level needed to maintain tight bundle geometry. Slip masterbatch is added at 0.3–0.6 wt%, and antiblock is generally omitted to avoid haze in display packaging. Conformance testing is conducted under ASTM D2732 for unrestrained linear thermal shrinkage and ISO 14616:1997 for shrink properties; tensile properties after orientation are measured under ASTM D882. The downstream double-bubble process uses a first-bubble melt temperature of 190–210 °C, a second-bubble orientation temperature of 115–130 °C, machine-direction draw of 4:1–6:1, transverse draw of 4:1–6:1, and final film thickness of 50–100 µm. At orientation temperatures below 110 °C, the blend shows stress-whitening and poor gauge uniformity; above 135 °C, the orientation loses memory and the shrink value drops below specification. Terminal products are multipack shrink bundles for beverage bottles, canned goods, and pet food trays.

For woven polypropylene sack lamination, 6109L is converted into a thin blown film that is subsequently adhesive-laminated to corona-treated tubular PP fabric as a moisture barrier and print-receptive layer. The relevant industrial compliance for the laminate is REACH Regulation (EC) No 1907/2006 and RoHS Directive 2011/65/EU; where the sack is intended for food contact, the final structure must also meet 21 CFR 177.1520(c) on the polyethylene layer and EU No 10/2011 on the complete laminate. The blown film layer formulation contains 70–85 wt% 6109L, 15–30 wt% high-pressure LDPE, and 3–8 wt% titanium dioxide masterbatch when opacity and print contrast are required. The film is produced at a die gap of 2.0–2.5 mm, blow-up ratio of 2.0:1–3.0:1, melt temperature of 200–220 °C, and thickness of 40–80 µm; it is then laminated to woven PP fabric using a solventless polyurethane adhesive at a coat weight of 1.5–2.5 g/m². Corona treatment of the woven fabric to a surface energy of at least 38 mN/m is required before lamination; below that threshold, peel adhesion measured under ASTM D1876 falls below 2 N/15 mm and the sack fails during automated filling. Terminal product types are valve sacks and open-mouth sacks for pet food, fertilizer, grain, and mineral powders.