ExxonMobil mLLDPE C4LL 2002.4RQ is a metallocene-catalysed linear low density polyethylene produced with a butene comonomer. The C4LL designation identifies the comonomer class as butene, while the suffix 2002.4 is conventionally associated with a nominal melt mass-flow rate of 2.0 g/10 min and a density in the 0.916–0.920 g/cm³ band. The resin is supplied as standard cylindrical pellets and is intended for general-purpose film extrusion, particularly where a balance of optical clarity, seal performance, and moderate mechanical strength is required. Manufacturer-issued technical data list a nominal density of 0.918 g/cm³, a melt mass-flow rate of 2.0 g/10 min at 190°C/2.16 kg, a melting peak of 122°C, and a Vicat softening point of 108°C. Tensile yield strength is reported at 10 MPa, and elongation at break exceeds 800% when tested according to ASTM D638-14. The RQ suffix denotes the manufacturing asset and does not by itself identify an additive package; converters should confirm the exact slip, antiblock, or processing-additive formulation from the certificate of analysis. As a metallocene grade, C4LL 2002.4RQ has a narrow molecular weight distribution and more uniform comonomer incorporation than conventional Ziegler-Natta C4 LLDPE, which affects melt rheology, optics, seal initiation, and extractables behaviour.

Table 1 values are typical values from manufacturer literature and are not specification limits. Actual values vary with conversion conditions, additive package, film thickness, and test specimen preparation.

How Does Butene-Comonomer Architecture Influence Performance of C4LL 2002.4RQ?

Short-chain branching from butene creates a linear backbone with ethyl branches. Compared with ethylene homopolymers, the branched architecture suppresses crystallinity and reduces density. Compared with hexene- or octene-containing metallocene grades, the butene branch is shorter and therefore produces a different tie-molecule population during strain hardening. The practical consequence is that C4LL 2002.4RQ can demonstrate good optical properties and low seal-initiation temperature, but its dart impact resistance and Elmendorf tear resistance are generally below those of hexene or octene mLLDPE of equivalent density and melt index. The lower melt temperature and narrow molecular weight distribution also reduce the level of low-molecular-weight extractables; hexane extractables for this density class are typically below 1.5% by weight when measured according to FDA 21 CFR 177.1520 extraction protocols. However, published data for this specific configuration is limited; end-use extraction testing must be performed on the final film structure and not on the base pellet alone.

Because the melt mass-flow rate is 2.0 g/10 min, the grade enters the shear-thinning portion of the viscosity curve at relatively low screw speed. On single-screw blown film lines with 24:1 to 30:1 L/D barrels, recommended barrel temperature set points start at 150°C and rise to 210°C, while melt temperatures are normally held between 190°C and 220°C. A die gap of 1.5 mm to 2.0 mm is common for 25–50 µm films; for films below 20 µm, a 2.0 mm die gap and internal bubble cooling improve bubble stability. The bubble blow-up ratio is typically set at 2.0:1 to 2.5:1. Unlike LDPE-rich formulations, the metallocene C4 resin has lower melt elasticity and requires external bubble stabilisation at high line speeds. No predrying is required when the pellets are stored at less than 60% relative humidity; if exposure exceeds 60% RH, drying at 80°C for 2 h to 4 h in a desiccant hopper dryer is recommended. The melt temperature should not exceed 240°C because the C4LL product can generate decomposition odours and gel accumulation on the die lip. Production-scale observations for similar metallocene C4 LLDPE grades indicate that purging with a high-viscosity polyolefin or commercial purging compound after shutdown is preferred; direct shutdown without purging may leave die-lip build-up.

Film Mechanical, Optical, and Seal-Resin Application Profiles

Tensile and puncture performance are typically evaluated on 25 µm monolayer cast films. The grade is used in form-fill-seal packaging, lidding webs, collation shrink film, frozen food bags, bread bags, and light-to-medium duty carrier bags. Seal-initiation temperature for 25 µm film is approximately 100°C when measured on a laboratory seal machine at 0.5 N/mm² jaw pressure and 0.5 s dwell; this is lower than conventional Ziegler-Natta C4 LLDPE of equivalent density and melt index, allowing faster packaging line speeds. Hot-tack strength follows the same direction and is measured according to ASTM F1921. Optical haze is reduced relative to Ziegler-Natta C4 grades because the narrow molecular weight distribution and uniform branching reduce surface roughness and internal light scattering; the reduction can be 20–30% at equivalent thickness, though film processing conditions determine absolute values. Gloss is typically evaluated according to ASTM D2457-21, and haze according to ASTM D1003-21. The grade is not recommended for retort, hot-fill above 90°C, or boil-in-bag structures because its Vicat softening point is 108°C and mechanical stiffness decreases rapidly above 85°C. In food contact uses, the converter must validate migration under the relevant food simulant conditions; the base polyethylene polymer falls within the olefin polymer class described in FDA 21 CFR 177.1520(c)3.1, but compliance is use-dependent and includes additives, surface treatments, and lamination adhesives.

Compared with autoclave or tubular LDPE of similar density, C4LL 2002.4RQ provides higher tensile yield strength, higher elongation at break, and lower neck-in during cast film extrusion. However, its melt elasticity is lower, so bubble stability in blown film is more sensitive to draw resonance and gauge variation. In coextruded structures, it is frequently blended with 10–20% by weight LDPE to increase melt strength without sacrificing seal performance. Typical conversion applications include light-to-medium duty packaging, lamination film, frozen food bags, bread bags, and collation shrink. In frozen food bags the lower seal initiation improves packing speeds, but the film must be tested for low-temperature impact; polyethylene generally retains toughness to -40°C, but the exact failure mode depends on thickness and seal geometry. For liquid packaging laminates, the grade may be used as a sealant layer where the seal temperature window is critical; manufacturers should test seal strength to ASTM F88 with 0.5 s dwell and 0.5 N/mm² jaw pressure.

When Replacing Ziegler-Natta C4 or C6/C8 Metallocene Grades in Film Structures

Relative to a conventional Ziegler-Natta C4 LLDPE of the same 2.0 g/10 min melt index and 0.918 g/cm³ density, C4LL 2002.4RQ typically shows lower haze, lower seal initiation, and reduced gel count because the metallocene catalyst produces a more uniform comonomer distribution and a narrower high-molecular-weight tail. However, the same narrow distribution reduces melt strength; blown film lines may require a reduction in low-pressure LDPE content or a change in die configuration to maintain bubble stability. Relative to a hexene or octene mLLDPE of equal density, C4LL 2002.4RQ usually provides lower dart impact strength, lower Elmendorf tear strength, and lower puncture resistance in the transverse direction. The selection of butene as the comonomer is therefore economically attractive when the end-use mechanical demand is moderate and seal performance is the primary requirement. Table 2 summarises the directional property differences for film of comparable thickness.

Table 2 is directional and does not assign absolute values because results depend on film thickness, die gap, frost-line height, additive package, and test method. The comparison applies to cast or blown films of equivalent gauge, not to laminates or coated structures.

Compliance status under FDA 21 CFR 177.1520 for olefin polymers applies to the base resin, not to the finished package. The converter must establish that additives, surface treatments, printing inks, and lamination adhesives meet the intended-use requirements. For European Union food contact, the grade may be evaluated under Regulation (EU) No 10/2011 with overall migration testing according to EN 1186-1 and specific migration testing where applicable. REACH registration and RoHS restrictions are product-stewardship documents; the supplier’s safety data sheet should be consulted for exposure limits and disposal requirements. The resin is incompatible with strong oxidising agents and should not be compounded with acid-functional additives that can accelerate polyolefin chain scission during reprocessing. Avoid combination with amine-based processing aids that can disrupt slip additive performance in film; if slip is required, the converter should add a qualified migratory oleamide or erucamide masterbatch at 0.1–0.3% by weight and verify coefficient of friction using ASTM D1894.

Storage at ambient temperatures below 50°C and below 60% relative humidity preserves pellet flow. Long-term storage above 40°C can increase pellet blocking, especially in bulk silos. Silos should be designed for polyethylene pellets with a mass-flow configuration; bulk density is not specified here because the manufacturer’s certificate of analysis should be consulted for the lot-specific value. Re-extrusion of edge trim and start-up scrap is permissible up to 20% by weight in monolayer film, but higher recycle levels can reduce dart impact and increase gel formation. If odour or gel levels rise during recycled-material use, the recycle ratio should be reduced or predrying at 80°C for 2 h should be introduced.