On 25–50 µm polyethylene blown-film lines producing food-contact packages, LyondellBasell POLYBATCH™ Navajo 10294U/4 Concentrate Based In LLDPE is metered through a gravimetric feeder at 2.5–3.5 wt% into an LLDPE-rich matrix, typically containing 85–100% LLDPE and 0–15% LDPE to maintain sealant-layer tear resistance. The carrier is plastified in a grooved-feed single-screw extruder with L/D 24:1–30:1, barrel profile 170°C–220°C, and screen pack 60/100/60 mesh to trap pigment agglomerates above 50–75 µm. Compliance for food-contact structures is assessed under FDA 21 CFR 177.1520(c), EU Regulation 10/2011 overall migration limit 10 mg/dm², and EU Regulation 2023/2006 GMP; heavy-metal restrictions follow 94/62/EC and CONEG limits of 100 ppm total for lead, cadmium, mercury, and chromium VI. The blown-film die is operated with 1.8–2.2 mm die gap and 2.0:1–2.8:1 blow-up ratio; automatic air-ring cooling and internal bubble control hold frost-line height between 300–500 mm to avoid gauge bands that become visible in pigmented film. Die-lip deposit frequency is monitored at output rates of 80–180 kg/h; converters report that raising letdown above 5 wt% in films below 30 µm increases lip build-up and reduces intervals between screen changes. Finished product types include frozen-food pouches, dry-product liners, and lamination-grade base films for flexible packaging converters.

What Occurs When the Concentrate Is Let Down at 3–5 wt% in Three-Layer Agricultural Greenhouse Film?

Three-layer blown-film lines producing 150–200 µm greenhouse covers typically dose the concentrate at 3–5 wt% into the outer or middle layer, with layer ratios of 1:2:1 or 1:3:1, while an amine-based light-stabilizer masterbatch is kept separate to avoid pigment-HALS interactions that can shift thermochromic behaviour during service. Production equipment includes a 250 mm three-layer spiral die, internal bubble cooling, and a dual-lip air ring; melt temperatures of 200°C–230°C are held at each extruder, and the bubble is operated at a blow-up ratio of 2.2:1–2.6:1 with web width up to 4.2 m. Compliance for agricultural covers is anchored to EN 13206:2017 for thermoplastic covering films, with heavy-metal thresholds under REACH Annex XVII and 94/62/EC; photostability is not contributed by this concentrate unless a separate UV stabilizer system is included. On-line thickness scanning with a capacitance gauge is set to reject longitudinal gauge variation exceeding ±5% of nominal, because letdown fluctuations greater than ±0.3 wt% in a 180 µm film appear as visible streaks after 12 months of outdoor exposure. Finished product types include three-layer greenhouse cladding films, low-tunnel covers, and side-ventilation curtains, where pigment dispersion uniformity must withstand 40°C daytime surface temperatures without exudation.

Flat-die sheet extrusion of 1.5–2.0 mm LLDPE geomembrane containing the concentrate is performed on a single-screw extruder with L/D 30:1–36:1, temperature profile 190°C–235°C, and hydraulic screen changer with 100/200/100 mesh. The concentrate is metered at 2–4 wt% in the surface or identification layer; when coextruded, the coloured layer constitutes 15–20% of total thickness, while the core layer remains uncoloured LLDPE compound. Compliance for containment liners is evaluated under GRI-GM17 for LLDPE geomembranes where project specifications adopt it, with tensile testing under ASTM D6693/D6693M, density under ASTM D1505, and stress crack performance under ASTM D5397; REACH Annex XVII applies to restricted heavy metals. The web passes through a polished chrome chill-roll stack at 40°C–60°C before thickness scanning and automatic gauge control; line speeds are typically 3–6 m/min for 2.0 mm sheet. Pre-drying is not required at 23°C and 50% RH because moisture uptake of the LLDPE carrier is below 0.01 wt%; however, regrind streams above 30 wt% can introduce trapped volatiles and should be limited if surface pinholes are detected. Finished product types include secondary-containment liners, stormwater pond membranes, and temporary landfill cell covers where a non-black marking layer is specified for installation layout.

Rotational Moulding Dry-Blend Uniformity and Surface Colour Development

Dry-blend rotational moulding of LLDPE or LLDPE/MDPE mixtures processed to 35 mesh incorporates the concentrate at 1–2 wt% and mixes in a high-intensity turbo mixer at 100–200 rpm for 10–15 min to reduce pigment streak formation on the mould inner surface. Equipment includes three-arm independent-arm machines with 2.1 m swing, mould rotation ratios of 4:1 primary:secondary, oven temperatures 280°C–300°C, and total cycle times of 18–30 min depending on wall section. Compliance for tank and container applications follows FDA 21 CFR 177.1520(c) where food contact is specified, and EN 71-3 migration limits for toy applications; industrial containers may be qualified under REACH Annex XVII and RoHS Directive 2011/65/EU restricted substances. A processing bottleneck observed on production-scale rotomoulding is dry-blend segregation when the concentrate pellet size differs from the pulverized PE mean particle size by more than 2:1; this produces non-uniform pigment distribution and surface specking after cooling. Forced-air cooling is applied after oven dwell to lower internal air temperature to 90°C before demoulding, which reduces warpage in pigmented parts and stabilizes colour across multiple mould cavities. Finished product types include outdoor storage tanks, agricultural hoppers, portable water-storage containers where food-contact certification is obtained, and recreational hulls.

When High-Shear Injection Moulding Demands Low Plate-Out on PE Caps and Closures

In high-shear injection moulding of polyethylene closures, the LLDPE-based concentrate is metered at 1–3 wt% through a gravimetric hopper loader into a reciprocating screw with L/D 20:1–24:1, barrel profile 200°C–260°C, and back pressure of 0.5–1.5 MPa; injection speeds of 100–200 mm/s and clamp forces between 150–350 t are used on multi-cavity hot-runner tools. Compliance for caps and closures is governed by FDA 21 CFR 177.1520(c) for olefin polymers, EU Regulation 10/2011, and EU Regulation 2023/2006 GMP; heavy-metal content is controlled under 94/62/EC and CONEG. Plate-out on the core side of the tool is a known failure mode when melt temperature exceeds 260°C or residence time exceeds 8 min; production technicians therefore purge at 20-minute intervals during colour changes and monitor gas vent deposits. The process window is narrower for thin-wall closures below 1.0 mm wall section, where increasing letdown above 4 wt% can reduce impact resistance and increase gate blush; published data for this specific formulation in ultra-high-flow LLDPE closure compounds is limited, so a 1.5 wt% starting point is used and adjusted after checking cap hinge flex performance by internal hinge cycling and tensile yield under ASTM D638-14. Finished product types include beverage closures, overcaps for personal-care products, and household chemical caps.

Where coloured outer layers are coextruded over a natural PE core in conduit and pressure-pipe lines, the concentrate is metered into a 45 mm single-screw satellite extruder at 2–5 wt% in the outer layer only; the outer layer typically represents 10–15% of total wall thickness. Barrel temperatures are held at 190°C–220°C, screw speed is maintained to deliver a melt pressure of 100–180 bar at the coextrusion die entry, and the composite pipe enters vacuum calibration sleeves with −0.3 bar vacuum for diameter control. Compliance for coloured pressure pipe is anchored to ISO 4427 for polyethylene pipes and EN 12201-1 for water supply, with heavy-metal restrictions under REACH Annex XVII; for cable conduit, EN 61386 may be referenced for mechanical performance. Because the concentrate carrier is LLDPE, it is preferentially inserted into the outer layer rather than the core to avoid reducing the long-term hydrostatic strength of the pressure-bearing wall; published data for this specific product in high-load gas pipe configurations is limited, so verification of hydrostatic design basis under ISO 9080 is required when substitution exceeds 5 wt% in any pressure-bearing layer. Finished product types include coloured PE pressure pipe for district heating jackets, cable protection conduit, and irrigation lateral pipes.