In blown-film extrusion of industrial refuse sacks and heavy-duty can liners on 70 mm grooved-barrel single-screw extruders with 30:1 L/D screws, 250–400 mm spiral-mandrel dies, and die gaps between 1.6 mm and 2.0 mm, POLYBATCH™ Blue LL40348/4 Concentrate Based In LLDPE is dry-blended with neat LLDPE or an LLDPE/LDPE mixture and fed through gravimetric dosing hoppers at 2.0–4.0 wt%, with the 4.0 wt% figure read from the product suffix /4 as a standard let-down reference rather than a fixed value; melt temperatures of 195–220°C, blow-up ratios of 2.2:1 to 3.0:1, and frost-line heights of 600–900 mm are maintained because the LLDPE carrier can reduce bubble stability when the concentrate is dosed above 4.0 wt% in film gauges below 50 µm. The relevant compliance baseline for non-food sacks is EU Directive 94/62/EC on packaging and packaging waste and, from 12 August 2026, Regulation (EU) 2025/40, with CONEG Model Toxics in Packaging limits for the sum of lead, cadmium, mercury and hexavalent chromium at 100 ppm; if a can liner is intended for short-term contact with dry food, the final film must be verified under Regulation (EU) 10/2011 Annex I with an overall migration limit of 10 mg/dm², and the olefin polymer must satisfy FDA 21 CFR §177.1520(c). Downstream converting includes inline perforation, gusseting, and heat-sealed side welds on bag-making machines, with seal settings of 130–150°C and 0.5–1.0 s dwell. Terminal finished products are heavy-duty refuse sacks in 40–80 µm thickness, contractor cleanup bags, can liners for food-service and institutional waste, and coloured recycling collection bags.

Silage Stretch Film and Greenhouse Cover Light-Transmission Control

The same concentrate, let down at lower loadings of 2.0–3.0 wt% for 25 µm silage stretch film and 2.5–3.5 wt% for 150–200 µm greenhouse cover film, is processed on three-layer blown-film coextrusion lines with 1.8–2.2 mm die gaps, product blow-up ratios of 3.0:1, and frost-line heights between 700 mm and 950 mm; the masterbatch is preferably metered into the middle or outer layer using layer ratios of 20/60/20 or 15/70/15 to preserve total film dart impact and interlayer adhesion while maintaining visual tint. Compliance for bale-wrap films is assessed under EN 13206:2017 for thermoplastic stretch films used for wrapping bales, including tensile strain retention and dart impact; where silage covers and greenhouse films are placed in contact with animal feed or food-producing crops, the finished film is evaluated against Regulation (EU) 10/2011 and relevant national feed-chain requirements. Colour strength is controlled by CIE L*a*b* measurement under D65/10° according to ISO 11664-4, with a batch-to-batch ΔE of 0.8 or less across the roll width at 3.0 wt% dose; full-width scanning on the bubble is required because blue pigmentation can obscure visual gel detection. Terminal products include silage bale wrap, silage pit covers, low-tunnel greenhouse films, and light-diffusing agricultural covers.

If Let-Down Exceeds 4 wt% in Thin-Wall Injection Moulding of Closures

If the concentrate is metered into thin-wall polyolefin closure compounds at let-down ratios above 3.5–4.0 wt%, stock temperature uniformity and pigment dispersion at weld lines become critical; high-speed injection moulding machines with 150–250 t clamping force, 0.8–1.2 mm nominal wall thickness, melt temperatures of 220–240°C, injection velocities of 40–90 mm/s, and hydraulic back pressures of 60–100 bar are used, with a screw L/D of 20:1 to 24:1 and a sliding-ring non-return valve clearance maintained below 0.05 mm to avoid blue streaks. The compliance framework for food-contact closures includes FDA 21 CFR §177.1520(c) for the polyolefin base polymer, FDA 21 CFR §178.3297 for colourants used in polymers, and Regulation (EU) 10/2011 Annex I for overall migration; for non-food detergent or lubricant closures, EU Directive 94/62/EC or its successor Regulation (EU) 2025/40 and CONEG heavy-metal limits at 100 ppm operate as the minimum regulatory baseline. Process limits arise from the LLDPE carrier, which can alter the heat distortion performance of the final HDPE or polypropylene compound when over-dosed; validation under ISO 75-2 is therefore required, and screw recovery time below 1.5 s has been associated with unmelted masterbatch particles and flow-line marking on the closure outer surface. Terminal products include tamper-evident closures for non-carbonated beverages, dispensing caps, sport caps, flip-top closures, and thin-wall containers for cosmetics and household chemicals.

Because parison melt strength and colour dispersion are both sensitive to die-head temperature, extrusion blow-moulding of HDPE/LLDPE bottles using POLYBATCH Blue LL40348/4 is run on shuttle or continuous wheel machines with 50–90 mm extruders at 24:1 L/D, die-head temperatures of 190–210°C, and parison drop times of 1.2–2.0 s; the masterbatch is pre-mixed with HDPE pellets and metered at 2.5–4.5 wt%, with the upper boundary set by visual flow lines in the bottle wall rather than by pigment dispersion failure. Compliance for household chemical and agrochemical packaging starts with REACH Regulation (EC) No 1907/2006 for the polymer and colourant substances and CLP Regulation (EC) No 1272/2008 for classification, while packaging placed on the EU market must meet Directive 94/62/EC or Regulation (EU) 2025/40; if the bottle is used as dangerous-goods packaging, the design and construction are tested under UN Model Regulations Chapter 6.1 for drop, leakproofness and stacking, independent of colour masterbatch. In production, die-head pressure fluctuations below ±0.3 MPa across a 4-hour run indicate stable masterbatch feed; larger fluctuations have been linked to bridging in the hopper when dosing above 4.5 wt% in humid environments above 60% RH, and pre-drying at 70°C for 2 h may be required. Terminal finished products are detergent bottles, agrochemical containers, automotive washer-fluid bottles, and light-industrial chemical packs in 0.7–1.5 mm wall thickness.

Why Does Dosing Shift to 5–6 wt% in Extrusion Coating Versus Blown Film?

Extrusion coating lines running at 200–350 m/min impose a much shorter thermal history and a thinner final colour layer than blown-film extrusion, so POLYBATCH Blue LL40348/4 is let down at 5.0–6.0 wt% in 15–25 g/m² polyethylene coating layers applied to paperboard or aluminium foil; the process employs a 90–120 mm single-screw extruder with 30:1 L/D and a slot die with internal deckle adjustment, melt temperatures of 280–320°C, an air-gap distance of 150–250 mm, and a chill-roll temperature of 10–20°C. The higher let-down is necessary because at 20 µm coating thickness the same pigment concentration produces lower optical density than in 60 µm blown film; qualitative control targets a CIELAB ΔE < 1.0 across the web width under D65/10° according to ISO 11664-4. Compliance for food-contact coated paper and board is assessed under FDA 21 CFR §176.170(c) for aqueous and fatty foods, Regulation (EU) 10/2011 for overall migration and specific migration of colourants, and Good Manufacturing Practice Regulation (EC) No 2023/2006; foil-based pharmaceutical or food laminates require verification of the final multilayer structure, because the colourant is not necessarily authorised for direct contact in all jurisdictions. Downstream, the coated substrate passes through corona treatment at 42–48 dyn/cm and is slit or sheeted; terminal products include liquid packaging board for blue-branded beverages, frozen-food cartons, paper cupstock, and foil sachet laminates.

Rotational Moulding of Intermediate Bulk Container Outer Layers Requires a Different Pigment Dispersal Mechanism

Rotational moulding of blue intermediate bulk containers and water storage tanks with LLDPE-rich powders is carried out on biaxially rotating carousel machines with shot weights of 20–60 kg, oven temperatures of 260–320°C, and cycle times of 30–60 min; POLYBATCH Blue LL40348/4 is dry-tumbled with LLDPE powder at 2.0–3.5 wt% rather than melt-compounded, because the low-shear process cannot duplicate the dispersive mixing of a twin-screw extruder. Published data for LL40348/4 specifically in rotomoulding is limited; the 2.0–3.5 wt% range should be confirmed by impact and colour trial on the intended machine. Compliance for tanks intended for potable water or aqueous food contact includes Regulation (EU) 10/2011 where applicable, FDA 21 CFR §177.1520(c) for the polymer, and national approvals such as BS 6920 for non-metallic materials in contact with water destined for human consumption; for dangerous-goods IBCs, the outer shell forms part of a composite or rigid plastics IBC tested under UN Model Regulations Chapter 6.5 for vibration, top lift, bottom lift, stacking, and leakproofness. Field-scale observations indicate that pigment-rich dry blends can segregate during the heating cycle in high-humidity charging rooms above 60% RH, leading to shade variation across the inner surface; pre-drying of the powder and masterbatch at 50–60°C for 2–3 hours may be required before charging. Terminal products include blue intermediate bulk container outer shells, water storage tanks, marine fenders, and rotomoulded agricultural hoppers.