CHN Energy Baotou (Shenhua Baotou) LLDPE 7042, a butene-comonomer linear low-density polyethylene with nominal melt index 2.0 g/10 min under ASTM D1238 (190 °C, 2.16 kg) and density 0.918–0.922 g/cm³ under ISO 1183-1, enters heavy-duty industrial sack and liner film production as a base resin in mono-layer and three-layer tubular blown film lines. A typical line configuration uses a 65 mm grooved-feed single-screw extruder with L/D 30:1, a 250 mm spiral mandrel die, and a dual-lip air ring with chilled air at 8–12 °C. Barrel temperature profiles are set at 180/200/210/215/220 °C from hopper to adapter, while die zones are held at 220–225 °C; melt temperature at the die entrance is controlled to 210–220 °C. A die gap of 1.8 mm is used for film gauges from 75 µm to 150 µm, with blow-up ratio maintained between 2.3:1 and 2.8:1. Frost line height is set at 600–800 mm above the die lip to balance quench rate and tear anisotropy. For bubble stability and melt strength, 10–20 wt% of a high-pressure LDPE with melt index 0.7–1.0 g/10 min is blended; this addition raises zero-shear viscosity and reduces bubble flutter at high throughput. Film tensile properties determined by ASTM D882 on 100 µm samples typically fall in the range of 30–38 MPa machine-direction break strength and 28–34 MPa transverse-direction break strength. Dart impact by ASTM D1709 Method A for 50 µm film is commonly reported between 85 g and 110 g for butene-LLDPE of this density band. Elmendorf tear by ASTM D1922 shows machine-direction values lower than transverse-direction values when BUR exceeds 2.5:1; reducing BUR to 2.0:1 shifts the MD/TD tear ratio closer to 1.0. Compliance for industrial sack applications is limited to REACH EC 1907/2006 registration and internal heavy-metal specifications; the grade is not normally supplied under a food-contact declaration unless separately confirmed by the producer. Terminal products include fertiliser sacks, resin packaging bags, chemical liner sacks, and construction rubble liners.

Does Butene-LLDPE 7042 Maintain Pre-Stretch Ratios Above 300% on Cast Film Lines?

On a cast stretch film line with a 75 mm smooth-bore extruder, L/D 32:1, and a 0.65 mm slot die gap, 7042 is processed at melt temperature 245–255 °C and chill roll temperature 18–22 °C. The die-to-chill-roll gap is held below 35 mm; air knife pressure is set at 3–5 kPa to suppress neck-in and edge bead formation at line speeds of 450–550 m/min. Gauge variation across 12–20 µm film is maintained within ±1.5% only when chill roll runout is below 5 µm and the die bolt heaters are tuned in zones of 10 mm width. A typical machine-wrap formulation contains 92–94 wt% 7042, 5–6 wt% low-VOC polyisobutylene tackifier masterbatch, and 1–2 wt% silica-based anti-block masterbatch with a 5% silica concentration. Pre-stretch ratios up to 300% on powered prestretch rollers are achievable; above 300% the butene-comonomer resin can exhibit local disengagement from the tackifier phase, reducing cling force measured by ASTM D5458 below 1.5 N and increasing the incidence of film breakage at the wrapper head. Puncture force measured by ASTM D5748 at 20 µm is typically 22–28 N, while tensile elongation at break by ASTM D882 exceeds 350% in the machine direction. Haze measured by ASTM D1003 remains above 8%; therefore the grade is not selected for high-clarity display wrap. Compliance is confined to REACH EC 1907/2006 and RoHS 2011/65/EU heavy-metal restrictions for tackifier and anti-block masterbatches. Terminal products include machine and hand pallet stretch wrap for logistics and warehouse use.

Extrusion lamination of woven polypropylene fabric with 7042 is operated on a 90 mm single-screw extruder with a T-slot die and a 250 mm chill roll set at 12–15 °C. The resin blend contains 20–30 wt% high-pressure LDPE to raise melt strength and reduce draw resonance at coat weights of 12–20 g/m². Die temperature is set at 300–320 °C and web speed is held at 80–150 m/min; melt curtain length is controlled to 100–150 mm. Longer curtains reduce adhesion to the corona-treated woven substrate and promote edge neck-in. Adhesion to untreated woven polypropylene is below 2.0 N/15 mm; corona treatment of the fabric to 40–42 mN/m, measured by ISO 8296, prior to lamination raises peel bond strength to 6–8 N/15 mm when tested by ASTM D1876. Edge trim recycling is operated at 5–8% of total throughput; recycled edge trim is dried below 0.05% moisture to prevent micro-voids in the laminate. Compliance is governed by REACH EC 1907/2006 for laminating additives and inks; food contact is not implied for this configuration unless a specific migration-tested adhesive tie layer is introduced. Terminal products include fertiliser sacks, rice bags, animal feed sacks, and industrial textile laminates.

UV Stabiliser Loading and Anti-Drip Migration Kinetics in Multi-Layer Agricultural Film

Three-layer greenhouse and silage film lines with a 150 mm die and three 50 mm grooved-feed extruders are configured with 7042 as the core layer at 40–60 wt%. The inner and outer layers contain 15 wt% EVA with 18% vinyl acetate for infrared retention, 8–10 wt% UV masterbatch containing 20% hindered amine light stabiliser, and 2–4 wt% anti-drip masterbatch. The core layer is typically 70 wt% 7042 and 30 wt% recycled greenhouse film regrind, screened at 100 µm and dried to below 0.08% moisture. Die gap is 1.6 mm, BUR 2.2–2.6:1, and frost line height 400–500 mm for film gauge 100–200 µm. Migration kinetics of anti-drip additives in butene-LLDPE are slower than in EVA-rich layers; surface beading can appear after 6–10 weeks in high-humidity tunnels if the anti-drip additive is confined to the core layer. Published data for this specific configuration is limited; outdoor ageing trials under ISO 4892-2 accelerated weathering are required to confirm UV stabiliser compatibility. Compliance for agricultural film is assessed under REACH EC 1907/2006; UV stabiliser packages must avoid cadmium-based pigments and comply with 2011/65/EU heavy-metal limits. Terminal products include greenhouse covers, silage bags, and mulch film.

When Flow Length to Wall Thickness Ratio Exceeds 150:1, Injection Speed Must Be Raised

7042 is not a high-flow injection moulding grade; its nominal melt index of 2.0 g/10 min places it outside the 20–50 g/10 min range used for high-speed thin-wall moulding. For thick-walled caps, flexible lids, and collapsible dosing cups with wall sections of 2.5–4.0 mm, a 1500 kN toggle clamp machine with a 30 mm general-purpose screw is operated at melt temperature 215–235 °C, mould temperature 20–30 °C, and injection pressure 70–90 MPa. When the flow length to wall thickness ratio exceeds 150:1, the injection speed is raised to 80–120 mm/s to prevent premature freeze-off; short shots appear when recorded cavity pressure drops below 40 MPa. Hot runner temperatures above 230 °C cause oxidative degradation, resulting in yellowing and acrid odour. A formulation of 100% 7042 provides adequate flexibility for snap-fit lids, but 10 wt% LDPE may be added for improved tear resistance at the hinge zone. Compliance for food-contact closures requires supplier confirmation under Regulation (EU) No 10/2011 and FDA 21 CFR 177.1520(c); migration testing by EN 1186-1 is mandatory for fatty food contact above 40 °C. Terminal products include dosing cups, protective caps, and non-hinged container lids.

Compounding of 7042 as a carrier resin for black masterbatch is performed on a 52 mm co-rotating twin-screw extruder with L/D 44:1 and a side feeder at barrel 6. The resin is dosed at 45–55 wt%, carbon black at 40–45 wt%, and a polyethylene wax dispersant at 5 wt%; screw speed is 400–600 rpm with barrel temperatures 180–215 °C. The melt index of the compounded masterbatch falls to 0.5–1.0 g/10 min at 40% carbon black loading, measured by ASTM D1238. Torque rises sharply above 45% filler loading; side-feeder starvation at the barrel 6 entry produces pressure oscillations exceeding 5% of the die pressure signal. Pelletising is performed by underwater die-face cutting at water temperature 60–70 °C and die plate temperature 200–210 °C. Compliance for electrical and electronic end uses is assessed under RoHS 2011/65/EU for Pb, Cd, Cr(VI), Hg, PBB, and PBDE; carbon black and wax require REACH EC 1907/2006 registration. Terminal products include black masterbatch, filler concentrates, and additive concentrates for film, pipe, and moulding converters.

Can 7042 Meet EU 10/2011 Overall Migration Limits in 30 µm Frozen Food Liners?

When CHN Energy Baotou 7042 is supplied with a food-contact declaration referencing Regulation (EU) No 10/2011 and FDA 21 CFR 177.1520(c), it is processed into 30–80 µm liners on a 55 mm single-screw extruder with L/D 30:1, melt temperature 200–215 °C, BUR 2.0–2.5:1, and die gap 1.4 mm. Overall migration tested by EN 1186-1 in 10% ethanol and 3% acetic acid at 40 °C for 10 days must remain below 10 mg/dm². Butene-LLDPE 7042 is not a barrier resin; oxygen transmission rate at 50 µm under ASTM D3985 at 23 °C and 0% relative humidity typically exceeds 2000 cm³/(m²·day·atm), so frozen food packaging is limited to non-oxygen-sensitive products. For bakery films and frozen pastry liners, the resin is used in 100% form or with 10–20 wt% high-pressure LDPE for bubble stability. Seal initiation temperature by ASTM F88 on 50 µm film is typically 90–100 °C, and hot tack strength is highest at 110–120 °C. The grade is not recommended for fatty or hot-fill food contact above 40 °C unless specific migration tests are completed in the final package configuration. Terminal products include frozen food liners, bakery bags, and non-barrier food pouches.