On a three-layer coextrusion blown film line producing 50 µm–80 µm red-tinted liners and overwraps, LyondellBasell POLYBATCH™ Red LL50283/3 Concentrate Based In LLDPE is dosed gravimetrically into the outer layer at 2.5% to 4.0%, while the core and skin layers run unpigmented LLDPE/LDPE blend. Barrel temperature profile is set from 175 °C at the feed throat to 210 °C at the die adapter, with die temperature maintained at 205 °C to 215 °C. A die gap of 1.8 mm to 2.2 mm and a blow-up ratio of 2.2:1 to 2.8:1 are used; frost-line height is held at 350 mm to 450 mm above the die face to balance bubble stability and cooling. Dispersion quality is checked on-line by monitoring pressure drop across a 100/200/100/40 mesh screen pack; a pressure rise of more than 12% above the clean-screen baseline over a 4 h tracking period indicates pigment agglomerate accumulation and triggers a screen change before die-lip plate-out transfers to the film. Film colour uniformity is evaluated against a CIEDE2000 reference; a total colour difference ΔE00 of ≤0.8 across the web width is specified for print-accurate red packaging. Tensile properties after pigment addition are measured per ASTM D882; typical MD/TD tensile strength at break for 60 µm LLDPE film falls between 25 MPa and 35 MPa, and thorough dispersion is required to avoid lower tearing resistance at pigment agglomerate boundaries. If surface condensation has occurred during warehouse storage, the concentrate is pre-dried at 70 °C to 80 °C for 2 h using a desiccant dryer with dew point below -30 °C before feeding. Addition to polymers containing high levels of migratory slip agents above 1500 ppm erucamide is not recommended without an extended plate-out trial, because low-molecular-weight amides can carry red pigment to the die lip under high shear; published data for this specific product configuration is limited, so a 8 h continuous trial is used to verify performance before commercial film production.

What Limits High-Shear Dispersive Mixing in Thin-Wall Closure Moulding?

In thin-wall injection moulding of high-density polyethylene closures and caps, the concentrate is introduced at 1.5% to 3.0% by gravimetric dosing at the hopper throat. A reciprocating screw with 24:1 L/D and non-return valve is operated at 80 rpm to 120 rpm; barrel temperatures are profiled from 200 °C to 230 °C, with nozzle temperature not exceeding 240 °C. Mould temperature is controlled at 10 °C to 25 °C, and injection pressure typically falls between 70 MPa and 100 MPa for polyolefin caps depending on wall thickness and gate design. Gate blush is the main process risk: in hot-runner moulds with tunnel gates of diameter 0.8 mm to 1.2 mm, excessive pigment concentration or poor distributive mixing can produce a grey-red halo at the gate, measured visually against a reference plate under D65 illumination. If gate blush appears, the first corrective step is to increase melt temperature by 5 °C increments to 235 °C, not to exceed 240 °C. If blush persists, the letdown ratio is reduced to 1.2% and a higher pigment-strength concentrate is recommended. Mould deposit testing is performed by running 5000 cycles and inspecting the cavity vent lands at 30× magnification; red pigment plate-out at the vents indicates excessive shear or inadequate carrier compatibility. Shrinkage and warpage are evaluated per ISO 294-4; a pigment-induced differential shrinkage of 0.3% or greater across the flow direction should trigger a filling-pattern adjustment. For food-contact cap applications, compliance must be confirmed against EU 10/2011 specific migration limits and FDA 21 CFR 178.3290 colourant provisions using product-specific documentation; this document does not establish global food-contact status.

Extrusion blow moulding of red-tinted containers uses lower addition levels than film because the parison is formed under low shear and layered melt streams are not available to dilute concentrated pigment. In shuttle and reciprocating blow moulding machines running HDPE or LLDPE-rich caps, the concentrate is dosed at 1.0% to 2.5% by weight; melt temperature settings at the die head are held between 190 °C and 210 °C, with accumulator-head drool avoided. Weld lines from the parison pinch-off and neck flash are the primary visual defects: they appear as darker red seams when the parison is cooled below 170 °C before mould closing, or when the die gap is below 1.5 mm. The mandrel and bushing land length must be longer than 12 mm for uniform colour distribution; shorter land lengths leave longitudinal streaks on the container. Drop impact performance after colour addition is checked per ASTM D2463-15 on 500 mL bottles at 23 °C; no brittle failure mode should replace ductile deformation as the impact speed increases from 2 m/s to 4 m/s. For non-food containers used in agricultural chemical packaging, the coloured wall is subjected to stress-crack resistance testing per ASTM D1693 in a 10% Igepal CO-630 solution at 50 °C. If the red concentrate is to be used in a multi-layer bottle with a post-consumer recycled middle layer, the outer layer must remain above 0.25 mm to prevent colour bleed-through; published data for this specific product configuration is limited, so a 24 h migration contact test is recommended before production approval.

If Red Concentrate Is Used in Coextruded Pipe Identification Stripes, Layer Thickness Controls Loading

For coextruded high-density polyethylene conduit or pressure pipe where a red identification stripe is required, the concentrate is fed to a dedicated stripe extruder with screw diameter 25 mm to 45 mm and an L/D of 24:1. Because the stripe layer is typically only 0.10 mm to 0.20 mm thick, letdown ratios in the stripe extruder are significantly higher—commonly 6% to 12%—to achieve visible colour in a thin layer, while the core pipe remains unpigmented or black. Melt temperature in the stripe extruder is controlled between 190 °C and 220 °C; temperatures above 230 °C may cause rheological mismatch between the high-pigment stripe compound and the main pipe melt, resulting in die-lip flow instability. The stripe die is a flat or hemispherical coextrusion insert with land length 5 mm to 8 mm; pressure in the stripe channel is monitored and should remain below 25 MPa to avoid interfacial waviness. Colour fastness in outdoor service is tested under ISO 4892-2 method A, cycle 1, using a xenon arc lamp with 0.51 W/m² @ 340 nm; a blue wool scale rating of 7 or greater after 1000 h is generally required for red identification stripes on above-ground conduit, but product-specific data must be requested to confirm this concentrate's lightfastness. Dimensional stability of the pipe is assessed per ISO 2505; the addition of a small stripe layer should not change longitudinal reversion by more than 0.5% at 110 °C. For potable-water contact, compliance with AS/NZS 4020 or KTW-BWGL may be required depending on the target market; red concentrate is placed only in a non-contact stripe or covered by a clear cap layer unless approved test data is available.

Thermoforming Sheet Colour Uniformity and Roll-Stack Plate-Out Control

In sheet extrusion for red thermoformed trays and packaging inserts, the concentrate is let down at 2% to 4% in a single-screw extruder with screw diameter 75 mm to 120 mm and L/D 32:1, feeding a coat-hanger die. Melt temperature at the die is maintained at 210 °C to 230 °C, and the polished three-roll stack is set at 40 °C to 60 °C with a roll gap corresponding to sheet thickness plus 5% for cooling shrinkage. Red pigment plate-out on the middle and lower chill rolls is the most frequent production issue; it appears as pink film transfer after 2 h to 4 h of continuous running when the concentrate dispersion is poor or when the melt temperature is below 200 °C. Roll release can be improved by adding a polyethylene wax masterbatch at 0.5% to 1.0%, but this must be tested for haze development per ASTM D1003. Sheet colour variation across width is quantified using a spectrophotometer with D65 illuminant and 10° observer; ΔE00 should remain below 0.7 across the sheet width for solid red trays. Thermoforming trials are run on a contact-heat machine at sheet surface temperatures of 150 °C to 170 °C; wall-thickness reduction in corners must not drop below 60% of original sheet thickness, and red colour should not shift visibly after 20 s of heating. For food trays, the coloured sheet is tested for overall migration per EN 1186-3 using 95% ethanol and 40 °C for 10 days if fatty-food contact is claimed; specific migration of any colourant decomposition products must be confirmed before commercial supply.

In LLDPE jacketing compounds for red-sheathed power or telecommunication cables, the concentrate is dosed at 2% to 5% at the throat of a single-screw extruder with L/D 24:1 to 30:1, coupled to a pressure die with tubular tip and die land 10 mm. Melt temperature is kept between 170 °C and 200 °C to avoid premature crosslinking in peroxide-containing formulations if the compound is silane-grafted; for silane-crosslinked LLDPE wire coating, a peroxide-free silane masterbatch is used and red colour is added at 2% to 3%. The line speed for sheathing is controlled at 150 m/min to 300 m/min, depending on conductor diameter; spark testing per IEC 62230 at 6 kV to 10 kV detects insulation defects, and colour spots larger than 0.5 mm are grounds for rejection. In coloured cable sheathing, carbon black is generally absent, so UV resistance relies on hindered amine light stabilisers; the red pigment's lightfastness is assessed under ISO 4892-2 with 0.85 W/m² @ 340 nm and 2000 h exposure for outdoor-rated cables. For flame-retardant cable compounds containing metal hydroxides above 60 phr, the carrier dilution effect must be accounted for: at 3% concentrate addition, the polymer content is reduced by roughly 1.5%, which may affect oxygen index by less than 0.5 percentage points but should be verified per ISO 4589-2 before batch sign-off.