Chevron Phillips 7109BKT is a hexene-copolymer LLDPE blown-film resin whose downstream processing routes differ principally by die gap, layer distribution, additive concentration, and regulatory end-use gate. The application scenarios below separate those variables across six industrial conversion environments and state the equipment, test standards, and operating limits that govern each structure.

Heavy-Gauge Industrial Sacks and the Need for Puncture Resistance at Gusset Creases

A three-layer blown-film line configured for form-fill-seal sacks places this hexene copolymer in the core or inner sealant ply, not in a gloss-critical skin layer. The formulation often starts at 65 wt% to 80 wt% 7109BKT, with 20 wt% to 35 wt% LDPE having a melt index below 0.5 g/10 min to increase melt strength and maintain bubble stability at blow-up ratios above 2.8:1. Die gap settings between 1.8 mm and 2.4 mm and melt temperatures between 204°C and 227°C reduce melt fracture while preserving dart impact measured according to ASTM D1709. On a line with 55 mm/65 mm/55 mm screw diameters and an L/D ratio of 30:1, frost-line height is held between 650 mm and 900 mm to balance transverse direction orientation and tear propagation. The finished 160 µm to 220 µm sack body is converted into 25 kg and 50 kg export sacks for polymer pellets, engineering resin powders, and carbon black masterbatches. Gusset creases are the governing failure site; addition of the hexene copolymer above 80 wt% in the core improves puncture propagation resistance but reduces bubble stability, so converters using internal bubble cooling set air temperature between 8°C and 12°C and automatic die control to maintain thickness variation below ±5%. Elmendorf tear in the machine direction, measured with ASTM D1922, becomes the discriminator when sack mass exceeds 35 kg and the film is exposed to pallet-to-pallet abrasion during truck loading.

Among converters supplying individually quick-frozen seafood and vegetable packers, the sealant layer is subjected to surface temperatures that move from 110°C at the sealing jaw to -23°C in cold storage within minutes. The hexene copolymer is commonly placed in the 15 µm to 25 µm sealant ply of a five-layer coextrusion with an EVOH oxygen barrier at 3 µm to 5 µm, tie layers at 4 µm to 6 µm, and a polyamide or stiff LLDPE abuse layer on the outer face. Sealing is controlled under ASTM F88 with fin-seal jaw pressure of 0.35 N/mm² to 0.60 N/mm² and dwell time of 0.3 s to 0.8 s; seal initiation at 95°C to 105°C is typical for blends containing 70 wt% to 85 wt% of this hexene copolymer and 15 wt% to 30 wt% plastomer. The finished 40 µm to 80 µm laminate is converted into pillow packs for IQF shrimp, mixed berries, and diced vegetables. Compliance rests on 21 CFR 177.1520 for the olefin polymer sealant layer and Regulation (EU) No 10/2011 with overall migration below 10 mg/dm² under test conditions for the intended frozen-food use. Cold-temperature impact is assessed with ASTM D1709 dart-drop testing on the finished laminate at -18°C; the failure mode shifts from puncture to brittle fracture when the sealant layer exceeds 80% of the total thickness, which is outside the recommended structure. Anti-fog masterbatch can be incorporated into the sealant ply at 0.5 wt% to 1.0 wt% for visible-pack vegetable applications, but it reduces seal strength at temperatures below 105°C unless dwell time is extended. A converter moving the seal layer below 12 µm observes seal failure at the inner crease after drop tests at -18°C; published data for this specific laminate configuration is limited, and line validation is required.

Why Does Hexene Comonomer Short-Chain Branching Control Tear Performance in Silage Stretch Film?

Extrusion of a monolayer silage film from this hexene copolymer without a UV masterbatch produces a structure that fails brittleness tests after a single season, but the short-chain branching from hexene contributes to the tear propagation resistance required when wrapping high-density round bales. A typical silage film contains 1.0 wt% to 2.5 wt% of a HALS/UV absorber masterbatch in a polyethylene carrier, with the concentrate let down at the feed throat of a 45 mm to 65 mm single-screw extruder running at 150 kg/h to 250 kg/h. Melt temperature is held between 215°C and 235°C, die gap between 1.4 mm and 2.0 mm, and blow-up ratio between 2.5:1 and 3.5:1 to generate the transverse direction elongation needed around the bale shoulders. Film thickness from 25 µm to 150 µm is supplied in 750 mm to 1,500 mm lay-flat widths for round bales and clamp silage covers. Accelerated weathering under ISO 4892-2 with UVA 340 lamps at 0.68 W/m² and 60°C black-panel temperature is used as an incoming QC release for stabilizer masterbatch lots. The terminal products are 12-month and 24-month silage covers, bale wrap, and silo bags; films without the stated stabilizer loading show tensile elongation retention below 50% after 3,000 hours in high UV regions when tested under ISO 527-3. At the low end of the gauge range, transverse tear resistance is improved by orienting the film at blow-up ratios above 3.0:1, but the same setting increases width variability on unguided bubbles. Compliance for the agricultural structure is based on EN 13207 for silage film and the general packaging requirements of 94/62/EC only where the film is subsequently used as a secondary wrap for bagged feed. Machine-direction Elmendorf tear, measured with ASTM D1922, is the primary discriminator at the end of the season because the film must not split during re-wrapping or bale storage on rough concrete.

Liquid bulk liner converting from the same hexene copolymer addresses a different constraint: the seal must survive both 0.15 bar internal pressure cycles and chemical attack from low concentrations of hypochlorite, alcohol, or edible-oil permeation. The resin is used as the 70 µm to 100 µm inner web of a laminated structure carrying reverse-printed polyester or metallized PET on the outside. Web tension is set to 20 N/mm² to 35 N/mm² during lamination; surface treatment is held at 38 dyn/cm to 42 dyn/cm after corona discharge to maintain peel strength above 2.0 N/15 mm measured by ASTM F904. Surface treatment decay below 36 dyn/cm on stored rolls leads to lamination bond loss, so corona treaters are placed in-line immediately before the laminator. For food-contact liners, 21 CFR 177.1520 applies for aqueous, acidic, alcoholic up to 8%, and fatty foods; Regulation (EU) No 10/2011 sets overall migration below 10 mg/dm². Terminal products include 5 L to 20 L bag-in-box liners, wine and edible-oil bladders, and food-service condiment pouches. The critical process limit is seal contamination by fatty products; minimum seal bar temperature of 140°C and dwell of 1.0 s are required after hot-fill at 85°C. Bubble cooling air at 6°C to 10°C and die gap 1.8 mm to 2.2 mm prevent blocked film that would cause missed seals on vertical form-fill-seal lines. The film is not recommended for direct contact with chlorinated solvents above 5% active chlorine at 40°C without a barrier tie layer; prolonged contact with concentrated d-limonene causes sealant swelling that reduces peel strength below the 2.0 N/15 mm threshold.

When Collation Shrink Film Moves from LDPE-Only to a Hexene LLDPE-Rich Blend

Replacing 30 wt% to 50 wt% of a conventional autoclave LDPE with this hexene copolymer in collation shrink alters the heat-seal response, shrink force, and puncture resistance of the final sleeve. The converter typically runs a 55 mm to 75 mm single-screw extruder at 170 kg/h to 300 kg/h with a dual-lip air ring, die gap of 1.2 mm to 1.8 mm, and blow-up ratio of 2.2:1 to 3.0:1. For a 45 µm to 70 µm film, the addition of the hexene copolymer at 35 wt% raises machine-direction shrink tension at 130°C from 0.15 N/mm² to 0.30 N/mm² when measured according to ISO 14616. Too high a LLDPE fraction above 60 wt% produces bubble instability at high frost-line settings and makes shrink force directionality difficult to control on steam tunnels operating at 120°C to 140°C. Excess frost-line height above 750 mm with the LLDPE-rich formulation causes fluctuating layflat width, so automatic bubble cage guides are used on the collation line. Terminal uses are 6-pack and 12-pack beverage can sleeves, cosmetics overwrap, and confectionery multipacks. Converters evaluate free shrink and shrink force with ISO 11501 and ISO 14616 and tensile properties with ISO 527-3. Heavy-metal content in the finished printed film is verified against the sum limit of 100 ppm under EU Packaging Directive 94/62/EC. Puncture resistance of the shrink sleeve is measured with ASTM D5748, and a drop from 1.5 m onto a sharp corner is used as a converter-specific abuse test for beverage multipacks.

On a pallet-containing line operating at 40 pallets per hour, blown stretch-hood film made with the hexene copolymer is drawn over goods at speeds exceeding 7 m/s and must retain sufficient elasticity to return to the pallet foot. The preferred structure is a three-layer blown film with 50 wt% to 70 wt% of the hexene copolymer in the core and outer plies, the balance being metallocene plastomer or LDPE to reduce elongation at break and raise puncture propagation resistance. Gauge runs from 50 µm to 120 µm; high-stalk configurations with frost-line heights above 800 mm and blow-up ratios between 3.5:1 and 4.5:1 give the needed transverse stretch of 60% to 90% during hood application. Hexene copolymer provides higher dart impact and tear propagation than butene-copolymer LLDPE when compared under ASTM D1709 and ASTM D1922, but the film haze is higher; haze is quantified by ASTM D1003, and clarity is not specified for the listed hood applications. Terminal uses are hoods for white-goods distribution, construction material bundles, and glass container palletizing where optical clarity is not required. Puncture resistance is measured by ASTM D5748, tensile by ASTM D882, and cling is not required because the hood is heat-sealed. Ambient temperature in the stretching hall is held above 15°C; below that, the hood loses elastic recovery and fails to lock under the pallet foot. Converters with older extruders below 30:1 L/D report pressure fluctuations above 25 bar when the hexene copolymer fraction exceeds 70 wt% at 220°C, requiring a reduction in screw speed rather than an increase in melt temperature. The lower melt-temperature limit is set at 190°C for this structure; below that, the hexene copolymer fraction above 70 wt% produces high extrusion pressure and visible die lines on the hood surface.