In blown-film extrusion of linear low-density polyethylene heavy-duty shipping sacks and industrial can liners, LyondellBasell POLYBATCH™ Deep Red 50389 concentrate based in linear low-density polyethylene is introduced at the feed throat through a gravimetric auger feeder after the base resin hopper. On a single-screw extruder with a barrier screw and L/D of 24:1 to 30:1, the melt temperature is maintained at 190 °C to 220 °C, and the die gap is set between 1.8 mm and 2.4 mm. For film thicknesses from 50 µm to 120 µm, a let-down ratio of 2.0 wt% to 3.5 wt% is typical; below 40 µm, the addition rate may be raised to 4.0 wt% because opacity is primarily controlled by pigment concentration rather than thickness. The bubble is run at a blow-up ratio of 2.0:1 to 3.0:1 and a frost line height of 4 to 8 die diameters to avoid excessive orientation that can produce colour streaks in the red film. Bags of concentrate stored at relative humidity above 60% are pre-dried at 65 °C for 4 h before extrusion to reduce surface moisture streaks. Finished-film colour is measured under illuminant D65 and the 10° observer according to ASTM D2244, with the CIELAB a* coordinate specified as the acceptance limit; gloss is checked by ASTM D523 at 60°. Mechanical integrity is verified by ASTM D1709 for dart drop, ASTM D882 for tensile properties, and ASTM D1922 for Elmendorf tear. Regulatory records normally include EU Directive 94/62/EC heavy-metal limits and REACH Candidate List screening. If the sack or liner is intended for food contact, the processor must verify that the olefin polymer complies with 21 CFR 177.1520 and the colourant falls under 21 CFR 178.3297. The LLDPE carrier maintains compatibility with film-grade LLDPE and low-density polyethylene blends, but outdoor exposure of red film without a separate UV stabiliser package is outside the expected application boundary because organic red pigments alone do not provide adequate weathering resistance.

What Limits Let-Down Ratio in HDPE Blow Moulding of Agrochemical Containers?

In reciprocating-screw and accumulator-head blow moulding machines used for high-density polyethylene chemical containers, the concentrate is metered at 2.0 wt% to 3.0 wt% into virgin or fractional-melt HDPE with a melt flow index below 1.0 g/10 min under ISO 1133-1:2022 at 190 °C and 21.6 kg. The melt temperature at the die head is held between 190 °C and 220 °C. Because the concentrate carrier is linear-low-density polyethylene, its lower zero-shear viscosity and different extensional hardening behaviour relative to high-load-melt-index HDPE can reduce parison hang strength and alter die swell when the let-down exceeds 3.0 wt%. On shuttle machines with a single parison drop length of 600 mm to 900 mm, the operator should verify parison sag with a video-based diameter profiler and, if necking occurs before mould closing, reduce the concentrate addition to 2.0 wt% or blend the concentrate with a higher-viscosity HDPE carrier masterbatch. Container opacity is assessed by total luminous transmittance using ASTM D1003, with many agrochemical specifications requiring less than 2% transmittance at 550 nm. Drop impact, hydraulic leakproofness, and stacking for UN-certified packaging must follow UN Model Regulations Chapter 6.1 and the applicable national provisions such as 49 CFR Part 178 in the United States or ADR/RID in Europe. The finished bottle or jerry can wall thickness is typically 1.0 mm to 2.5 mm, and the red pigment concentration must be adjusted upward for thin-walled areas. Compliance records for crop protection packaging should document heavy-metal content and SVHC status, while food-contact use would require a separate 21 CFR 178.3297 colourant opinion.

When thin-wall polypropylene closure moulds run in high-cavitation hot-runner tools, the red concentrate is added at 1.5 wt% to 3.0 wt% and the melt temperature is set between 230 °C and 250 °C. Injection velocity is commonly 80 mm/s to 180 mm/s, and clamp force on production-scale machines ranges from 1,500 kN to 4,000 kN. The LLDPE carrier is not fully compatible with polypropylene as a molecular blend, but at these low addition levels it disperses as a fine secondary phase and does not normally alter short-term mechanical properties beyond the dilution effect; nevertheless, processors should verify mould shrinkage against a natural-PP reference using ASTM D955 because the pigment and carrier can influence crystallisation rate and post-mould dimensional stability. For closures and overcaps, the target colour is usually specified with a CIELAB L* below 35 and an a* above 40, measured on a benchtop spectrophotometer using ASTM D2244 with a 10 mm aperture. Low-gloss side and top surfaces are measured with ASTM D523 at 60° to detect flow-line shadowing. Food-contact status for polypropylene closures requires base-resin compliance with 21 CFR 177.1520 and colourant compliance with 21 CFR 178.3297; for the European Union, specific migration testing under Regulation (EU) 10/2011 must be completed on the final article, and total migration must remain below 10 mg/dm². Process limitations include residence-time control: at melt temperatures above 250 °C or residence times beyond 10 min, organic red pigment systems can shift yellow, so the processor should purge with natural PP during any moulding interruption.

If Rotational Moulding Replaces Dry Pigment with LLDPE-Based Red Concentrate

In biaxial rotational moulding of large storage tanks, floats, and agricultural hoppers, the red concentrate must be dry-blended with LLDPE or MDPE rotational moulding powder at 2.0 wt% to 3.0 wt% before charging. The concentrate pellets are not milled to the same particle size as the base powder; therefore, a low-shear drum blender or high-intensity mixer is used for 10 min to 20 min, and pellets should be ground to 35 mesh (500 µm) if streaks are observed in the first trial. Oven air temperature is set at 280 °C to 320 °C, while the internal air temperature of the mould typically reaches 190 °C to 220 °C; total cycle time ranges from 30 min to 60 min depending on wall thickness. This long thermal history is the critical process conflict for organic red pigments, and the concentrate’s heat stability should be confirmed by measuring colour shift after a full peak-internal-air-temperature cycle; when published data for this specific configuration are limited, a corner-to-corner colour comparison across the mould is required. Mechanical properties of the moulded part should be tested by ASTM D638 for tensile yield and ASTM D790 for flexural modulus, while rotationally moulded polyethylene upright storage tanks are covered by ASTM D1998. If the tank is intended for potable water or food contact, conformity with NSF/ANSI/CAN 61 or 21 CFR 177.1520 and 21 CFR 178.3297 is not automatic and must be verified with the concentrate supplier. UV-stabilised outdoor grades require a separate hindered-amine light stabiliser package because the red pigment alone does not provide long-term weathering performance.

For extruded polyolefin sheet feeding continuous thermoforming lines, the red concentrate is let down at 2.0 wt% to 4.0 wt% into polypropylene or high-density polyethylene sheet resin, with melt temperatures of 200 °C to 240 °C and a flat die width from 1,200 mm to 2,500 mm. The calender stack temperature is maintained between 70 °C and 90 °C, and sheet thickness ranges from 0.5 mm to 3.0 mm. A screen pack of 40/60/80 mesh is common; if die lines or surface specks appear, the mesh sequence is tightened to 60/80/100, and optical microscopy of the sheet surface is used to confirm that pigment agglomerates remain below 25 µm. Colour uniformity across the sheet width is evaluated by ASTM D2244 with no more than ΔE*ab 1.0 between edge and centre samples. Finished reusable totes, bins, and pallets are tested for tensile yield stress by ASTM D638, flexural modulus by ASTM D790, and notched Izod impact by ASTM D256. Heavy-metal and hazardous-substance documentation should include RoHS 2011/65/EU Annex II and REACH Candidate List verification. One thermoforming-specific limitation is that plug-assisted stretching thins the sidewall and may reduce perceived colour intensity; processors should therefore evaluate the deep-draw regions at the minimum wall thickness specified on the part drawing rather than on flat sheet alone.

Monofilament Tape and Synthetic Turf Fibre: Dispersion and Weathering Boundaries

In water-bath tape extrusion and slit-film monofilament lines for red baler twine, geotextile fibres, and synthetic turf yarn, the concentrate is typically added at 1.5 wt% to 2.5 wt%. Higher addition levels are generally avoided because pigment particles can act as stress concentrators during drawing, reducing elongation at break and increasing the frequency of draw-line breaks. Melt temperature is held at 190 °C to 210 °C for polyethylene and 230 °C to 250 °C for polypropylene, with draw ratios between 5:1 and 8:1 and a water-bath temperature of 30 °C to 45 °C. Melt filtration is critical: tape lines normally use a 60 µm screen, but artificial turf yarn specifications often require filtration at 40 µm to remove agglomerates larger than 25 µm that cause filament failure. Tensile strength and elongation are measured by ASTM D2256 on conditioned yarn samples. For outdoor synthetic turf and fibre applications, accelerated weathering is performed in a xenon-arc apparatus according to ISO 4892-2 method A; a typical technical specification requires 3,000 h exposure with ΔE*ab no greater than 4.0 and a blue-scale rating of at least 7 under ISO 105-B02. This is a stringent boundary for many organic red pigments, and the specific lightfastness of the concentrate should be verified before specifying it for long-life outdoor fibre. The LLDPE carrier is compatible with polyolefin fibre resin at the stated let-down ratios, but the concentrate should not be extended to polyamide or polyester fibre extrusion because the carrier phase would not disperse predictably in those matrices.