In monolayer and coextruded blown film used for consumer and industrial packaging, POLYBATCH™ Dark Blue Oil LL40350/4 Concentrate Based In LLDPE is metered at the feed throat with gravimetric dosing units calibrated to ±0.2% accuracy. Standard commercial practice for LLDPE-based color concentrates places the addition between 2 wt% and 4 wt% for films of 20–80 µm; on three-layer coex lines, adding the concentrate to a skin layer representing 20–30% of total thickness generally requires dropping the letdown to 1.0–1.5 wt% to avoid excessive color saturation and die-lip deposit formation. Processing on 50–75 mm grooved-feed extruders with L/D 25–30 at melt temperatures between 180°C and 220°C provides acceptable carrier viscosity match with LLDPE film resins having melt flow rates of 0.8–1.2 g/10 min at 190°C/2.16 kg according to ISO 1133-1:2022. Screen packs of 20/40/60 mesh are fitted before the breaker plate; an increase in screen-pack differential pressure above 1.0 MPa within an 8 h run signals agglomerate retention or carrier incompatibility and requires reducing barrel zone temperatures by 5–10°C before increasing screen surface area. Dispersion quality is checked according to ISO 18553:2002; for film thinner than 50 µm, pigment agglomerates above 50 µm produce visible fisheyes and reduce dart impact. Finished products include printed carrier bags, freezer film, produce bags, and industrial liners. Food-contact articles require finished-article compliance under EU 10/2011 Annex I and II and FDA 21 CFR 178.3290; heavy-metal limits under RoHS Directive 2011/65/EU Annex II must also be confirmed for the pigment package.

What Limits Letdown Ratio in High-Speed Cast Film Extrusion?

Cast film extrusion of LL40350/4 into 15–25 µm stretch film and 25–60 µm hygiene backsheet runs at line speeds from 180–300 m/min, which places a higher shear and thermal history demand on the concentrate than blown film. Letdown is normally reduced to 2–3 wt% because higher addition rates increase surface haze and lower specular gloss, a measurable effect under ASTM D2457-21 at 20° and 60° incidence. On a 45 mm single-screw extruder with L/D 30, barrel zone settings from feed to adapter are typically 180°C, 210°C, 220°C, 230°C, 240°C; melt at the flat die is held at 235–250°C. The LLDPE carrier contributes a small density increase of approximately 0.02–0.05 g/cm³ at 3 wt%, measured by ISO 1183-1:2019, but the main process conflict is quenching rate variation across the web. Chill roll temperature is set at 15–25°C with an air knife and vacuum box to eliminate air entrainment; insufficient contact produces printability defects and uneven pigment distribution in the amorphous surface layer. Published data for LL40350/4 in this specific high-line-speed configuration is limited, so commissioning should include a 24 h screen-pack delta-P trial at the 100–150 kg/h output range, with the upper limit determined by torque rather than melt temperature. Tensile and tear properties are judged by ASTM D882-18 and ASTM D1922-23; final products include hand stretch wrap, machine wrap, construction film, and medical nonwoven backsheet laminates.

Thin-wall closures and containers injection moulded from LLDPE-rich blends with LL40350/4 use LLDPE or LLDPE/HDPE base resins with melt flow rates between 20–40 g/10 min at 190°C/2.16 kg per ISO 1133-1:2022. The concentrate is added at 2–4 wt%; below 2 wt% color intensity varies with screw recovery time and dosage accuracy, while above 4 wt% the LLDPE carrier can reduce injection pressure requirements but increase gate freeze time and shrinkage anisotropy. Reciprocating screws of 20–25 mm diameter with L/D 20–22 and general-purpose metering profiles are used, with injection pressures from 80–110 MPa and hold pressures of 50–70 MPa for 0.5–1.5 s per mm of wall thickness. Barrel temperatures from feed to nozzle are set to 180°C, 200°C, 215°C, 225°C; mold temperatures of 15–30°C allow cycle times of 8–15 s for 1.2–2.0 mm walls. Dimensional stability is checked after 24 h conditioning according to ASTM D955-21; LLDPE-rich formulations usually show shrinkage of 1.5–2.2%, with higher values in the flow direction. Finished parts include overcaps, push-pull closures, thin-wall food containers, and cosmetic packaging. For food-contact grades, compliance must be established on the final article under EU 10/2011 and FDA 21 CFR 178.3290; the concentrate itself is not a food-contact certification and phthalocyanine pigments may be subject to specific migration limits.

When Blow Moulded Containers Require Low-Temperature Impact Retention

Extrusion blow moulding of HDPE containers coloured with LL40350/4 creates a rheological mismatch between the LLDPE carrier and the HDPE matrix that affects parison sag and die swell. In monolayer HDPE bottles, the concentrate is dosed at 2–4 wt%, displacing an equivalent mass of HDPE; at 4 wt% the final article exhibits lower density and flexural modulus, measurable by ISO 1183-1:2019 and ISO 178:2019, but often gains environmental stress crack resistance when tested under ASTM D1693-21 Condition B. Processing on 50–80 mm extruders with L/D 24 uses melt temperatures of 170–200°C and parison temperatures of 190–210°C; die head tooling is set to a die-to-pin diameter ratio of 0.6–0.9 to control parison diameter. Blow air pressure is maintained at 0.5–0.8 MPa, and mould temperatures of 10–20°C prevent surface fold lines. Containers are produced for automotive chemicals, household detergents, and personal care fluids. Low-temperature impact retention at -20°C is typically evaluated by drop tests according to internal protocol; if the part must meet ASTM D2463-15, the HDPE grade and concentrate addition should be fixed before tooling is cut because parison geometry changes with melt elasticity. Regulatory compliance for hazardous goods packaging must be demonstrated on the finished container under applicable transport regulations, and food-contact use requires further verification under EU 10/2011.

For rotational moulding of large LLDPE parts, LL40350/4 is dry blended with ground LLDPE powder at 2–4 wt% before charging to the mould. The LLDPE carrier melts during the heating cycle, but dispersive mixing is not provided by the rotating mould; therefore the concentrate must be pulverized to a particle size distribution matching the base powder, typically 35 mesh or finer, to prevent colour streaks and surface pinholes. Oven temperatures are set at 260–300°C for 20–40 min, with peak internal air temperature maintained between 180–220°C depending on part thickness and resin supplier protocol. The process is inherently low-shear, so pigment dispersion and heat ageing are evaluated by ISO 18553:2002 and by measuring melt flow shift per ISO 1133-1:2022 after the cycle; a shift above 0.4 g/10 min from the specified resin baseline indicates carrier degradation or incomplete homogenization. Finished parts include storage tanks, agricultural hoppers, marine floats, and playground panels. For potable water contact in North America, the final rotomoulded article is subject to NSF/ANSI/CAN 61 and in the EU, EU 10/2011; published data for LL40350/4 in potable water rotomoulding is limited, so certification on the finished article is mandatory before specifying this concentrate.

Melt Filtration and Pressure Build-Up Behaviour on 40 L/D Single-Screw Lines

On 90–120 mm single-screw sheet extrusion lines with L/D 35–40, LL40350/4 is added at 2–4 wt% into monolayer LLDPE or LLDPE/HDPE sheet from 2–6 mm thickness. Melt temperatures are controlled at 200–230°C and three-roll polishing stack temperatures at 60–90°C. The main production bottleneck is melt filtration: the LLDPE carrier has a broader molecular weight distribution than the base HDPE, and screen packs of 40/60/80 mesh can accumulate pigment agglomerates and gelled carrier fragments. A differential pressure above 2.5 MPa across the screen changer signals a need for back-flush or mechanical screen change; failure to monitor this leads to pressure fluctuation at the die lip and thickness variation in the sheet. Thermoformed parts include reusable transit trays, equipment covers, and automotive trunk liners. Automotive interior applications require fogging and odour testing under DIN 75201:2011-04 and VDA 270:2018; volatile organic compounds from the pigment carrier or processing aids may affect results, so pre-production validation is required. Mechanical properties of the formed sheet are tested according to ISO 527-2:2012 and ISO 178:2019; published data for this specific product in 6 mm thermoformed sheet is limited, so corner radius thinning and wall thickness distribution should be mapped during pilot runs.

Dark Blue Jacketing Compounds for Low-Voltage Cable Extrusion

Coloration of polyethylene cable jackets with LL40350/4 is carried out on crosshead extruders of 60–90 mm screw diameter and L/D 25, with melt temperatures from 180°C to 220°C. The concentrate is dosed at 2–4 wt% into LLDPE or LDPE jacket compounds; because cable extrusion runs at line speeds of 50–200 m/min and uses crosshead dies with screen packs of 40/60 mesh, any agglomerate above 50 µm can create a surface protrusion detected by in-line spark testing at 3–6 kV AC depending on insulation thickness. The LLDPE carrier affects elongation at break and cold bend behaviour; jacket compounds are tested according to IEC 60502-1 for low-voltage cables and ISO 527-2:2012 for tensile properties. Dark blue pigments must be selected to avoid heavy-metal content above the maximum concentration values in RoHS Directive 2011/65/EU Annex II; lead, mercury, and hexavalent chromium each have a limit of 0.1 wt%, with cadmium at 0.01 wt%. Final products include low-voltage power cable jackets, data cable sheaths, and underground conduit. When flame-retardant jackets are required, the additive package must be evaluated for interaction with dark blue pigments because some metal hydrate flame retardants can shift the shade and increase plate-out; published data for LL40350/4 in filled FR jackets is limited, and plant-scale color matching is required.