Opacity Defects in Thin-Gauge Blown Films Compensated by High-Flow LLDPE Carrier

In coextruded five- and seven-layer blown film lines producing opaque white packaging for dry foods and frozen goods, LyondellBasell POLYBATCH™ White L8350 HSF Concentrate Based In High-Flow LLDPE is dosed into the outer skin or sub-skin layers rather than into barrier core or tie layers. Addition ratios for a 40–60 µm LLDPE/LDPE blown structure fall between 4 wt% and 8 wt%; in multilayer constructions where the pigmented layer represents only 15–25% of total thickness, the layer-specific let-down ratio may reach 10 wt%. The high-flow LLDPE carrier reduces local melt viscosity in the skin layer, which lowers extruder backpressure and improves pigment dispersion across the die gap when a barrier screw with 25:1 L/D to 30:1 L/D is used. Melt temperature at the die is maintained at 190 °C to 215 °C, die gap at 1.6 mm to 2.2 mm, blow-up ratio at 2.2:1 to 3.0:1, and frost line height at 8–10 die diameters. Because TiO₂ loading alters infrared transmission and cooling rate near the frost line, dual-lip air ring cooling with internal bubble cooling is required to prevent bubble oscillation. Opacity after orientation is evaluated by ASTM D1003 and typically falls in the 85–92% range for a 50 µm film; tear resistance is measured by ASTM D1922 and tensile properties by ASTM D882. Food-contact compliance is anchored to FDA 21 CFR 177.1520(c) for olefin polymers and 21 CFR 178.3297 for pigments used in polymers; for European submission, the finished film is evaluated under EU Regulation (EC) No 10/2011 Annex I and III, with migration testing by EN 1186 methods. Terminal products include opaque bread bags, frozen vegetable bags, laminate base films, and white overwrap for dry food packaging.

Cast chill-roll lines producing white hygiene backsheet film at line speeds of 150–350 m/min typically meter POLYBATCH™ White L8350 HSF at 5 wt% to 9 wt% into the main LLDPE stream using a gravimetric feeder. The slot die gap is set at 0.3 mm to 0.6 mm, the air gap at 4–8 cm, chill roll temperature at 16 °C to 24 °C, and melt temperature at 220 °C to 260 °C. The high-flow LLDPE carrier prevents localized TiO₂ agglomeration in thin edges and reduces die-lip deposit formation under high shear, but the finished film is optically opaque; haze measured by ASTM D1003 exceeds 90% at 50 µm, making the material unsuitable for clear windows. When the film is converted into medical device packaging, the finished article is validated under ISO 11607-1:2019 for sterile barrier systems and biological evaluation follows ISO 10993-5:2009; for food-contact hygiene overwrap, compliance remains under FDA 21 CFR 177.1520(c) and EU Regulation (EC) No 10/2011. Terminal products include non-breathable and breathable diaper backsheet film, medical procedure kit overwrap, and white surface protection film for adhesive tape backing.

What Limits Adhesion to Paperboard When POLYBATCH™ White L8350 HSF Is Used in Extrusion Coating at Line Speeds Above 300 m/min?

During extrusion coating of liquid packaging board and flexible packaging paper, POLYBATCH™ White L8350 HSF is metered into the primary LDPE or LLDPE extruder at 5 wt% to 12 wt% to obtain a white pigmented coating weight of 15–25 g/m². Melt temperature is held at 230 °C to 280 °C, die gap at 0.5 mm to 0.8 mm, air gap at 150–250 mm, and chill roll temperature at 15 °C to 25 °C. Paperboard adhesion relies on the oxidation layer formed in the air gap; increasing TiO₂ concentration raises melt heat capacity and can narrow the effective oxidation window, particularly at line speeds above 300 m/min. Quantitative peel strength data for this specific concentrate on clay-coated board are limited in published technical documentation; adhesion must therefore be confirmed on the intended substrate with pilot coating trials using ISO 8510-1 or ASTM D1876 peel test methods. Food-contact compliance for liquid packaging board is assessed under FDA 21 CFR 176.170(c) for paper and paperboard in contact with aqueous and fatty foods and EU Regulation (EC) No 10/2011 for the polymer coating; colorant migration is controlled under 21 CFR 178.3297. Terminal products include white-pigmented liquid packaging board, cupstock, multiwall sack overwrap, and coated release liner base for pressure-sensitive labels.

Room-temperature mould filling of thin-wall polyethylene closures is modified by the high-flow LLDPE carrier when POLYBATCH™ White L8350 HSF is dosed at 1.5 wt% to 4.0 wt% in a reciprocating-screw injection moulding machine with 20:1 L/D to 25:1 L/D and a shut-off nozzle. Melt temperature is set at 200 °C to 240 °C, mould wall temperature at 10 °C to 40 °C, injection pressure between 70 MPa and 120 MPa, and clamp force at 3–5 kN/cm² of projected area. Viscosity reduction from the carrier shortens fill time in thin-wall sections, but in multi-gate closure designs the weld-line strength may decrease; gate counts and positions are adjusted when structural integrity is verified by ASTM D638 tensile testing on machined specimens. Food-contact closures and cups follow FDA 21 CFR 177.1520(c), EU Regulation (EC) No 10/2011, and 21 CFR 178.3297; lightfastness of white pigmentation is checked by ISO 105-B02 when retail packaging exposure is specified. Terminal products include opaque HDPE and LLDPE bottle caps, overcaps, dosing cups, and thin-wall food containers.

When Split-Feeding the Masterbatch into HDPE Accumulator-Head Extrusion Blow Moulding Lines

When HDPE personal care and household chemical bottles are extrusion blow moulded on accumulator-head machines, POLYBATCH™ White L8350 HSF is split-fed at 2 wt% to 5 wt% into the HDPE main stream after the feed throat, with melt temperature controlled at 180 °C to 210 °C. The high-flow LLDPE carrier reduces parison sag at low melt strength, but addition above 6 wt% may reduce environmental stress crack resistance measured by ASTM D1693 on bottle sidewalls. Die gap is set at 1.0 mm to 2.0 mm, blow pressure at 0.6 MPa to 1.0 MPa, and mould temperature at 15 °C to 30 °C. When bottles are specified for dangerous goods transport, drop and leakproofness tests follow 49 CFR 178.603 and ADR 6.1.5; for food-contact bottles, compliance is established under FDA 21 CFR 177.1520(c) and EU Regulation (EC) No 10/2011, and for pharmaceutical solid-dose packers the relevant plastic packaging chapters are USP <661.1> and USP <661.2>. Terminal products include opaque HDPE bottles for personal care emulsions, household chemical trigger bottles, and solid-dose pharmaceutical packers.

Because the high-flow LLDPE carrier reduces viscosity in thick polyethylene sheet extrusion, addition of 3 wt% to 6 wt% POLYBATCH™ White L8350 HSF at melt temperatures of 200 °C to 230 °C with polish roll temperatures of 60 °C to 80 °C is used for white thermoformable sheet of 0.8–2.0 mm thickness, regulated under FDA 21 CFR 177.1520(c) for food-contact trays, dunnage sheet, and bin liners.