Mitsui Chemicals Evolue mLLDPE SP3210 is a metallocene linear low-density polyethylene produced by single-site catalyst polymerization. The resin is supplied as an ethylene-α-olefin copolymer with a nominal melt mass-flow rate of 2.1 g/10 min at 190 °C under 2.16 kg load per ISO 1133-1:2022, and a nominal density of 0.921 g/cm³ at 23 °C per ISO 1183-1:2019. It is intended for cast film, monolayer and coextruded sealant webs, lamination film, and general-purpose flexible packaging. The grade is not a drop-in substitute for autoclave LDPE on high-speed extrusion coating lines because the metallocene architecture lacks long-chain branching; shear-thinning response is less pronounced, and extruder head pressure is higher at equivalent output. In cast film, SP3210 is used at thicknesses from 20 µm to 80 µm, where low seal initiation temperature, low extractables, and optical clarity are required. The resin is also used as a sealant layer in laminated pouches, overwrap, and flow-wrap structures because its uniform short-chain branching distribution supports rapid interfacial fusion at seal bar temperatures below 110 °C.

Nominal Melt Rheology and Physical Property Data for SP3210

The representative values in this section are consolidated from supplier technical data for film-grade evaluations. Cast film tensile and impact data are thickness-dependent; unless otherwise stated, values correspond to 40 µm film produced on a chill-roll cast line with a 0.8 mm die gap and melt temperature of 250 °C. These values should not be interpreted as batch release limits. The narrow molecular weight distribution associated with single-site catalysis reduces melt fracture and improves gloss; however, it also lowers melt extensibility relative to LDPE, which must be managed through die gap and air gap selection. The polydispersity index for this grade is typical of metallocene LLDPE, generally below 3.0.

Typical usage scenarios include monolayer cast wrap at 25 µm for bakery or confectionery packaging, three-layer coextruded sealant webs with a core layer of LDPE or HDPE, and extrusion coating of paper or aluminium foil. In monolayer cast film, the resin is run at 240–250 °C and provides a seal initiation temperature below 110 °C on vertical form-fill-seal lines. In three-layer structures, SP3210 is placed in the skin layer at 10–20 µm; the core may be a Ziegler-Natta LLDPE or recycled material at 20–30 µm. For lamination film, a 20 µm SP3210 layer can be adhesive laminated to PET or BOPP; the low seal initiation and low oligomer content reduce seal bar contamination. In extrusion coating, SP3210 is dry-blended with LDPE in ratios from 50:50 to 80:20; however, above 80 wt% SP3210, neck-in increases and edge trim waste rises. Melt temperature for coating is maintained at 260–270 °C to improve adhesion to aluminium foil, and a corona discharge unit is operated at 2.0–3.0 kW for 10–15 m/min treatment speed to achieve surface energy above 38 mN/m. Published adhesion data for this specific configuration are limited; users typically run a pilot trial to determine optimal air gap and melt temperature for the target substrate.

On cast film lines, SP3210 is processed at melt temperatures between 240 °C and 260 °C. The die and adapter temperatures are typically set 10–15 °C above the melt temperature to prevent flow marks and die-lip deposit formation. On a 90 mm single-screw extruder with a barrier screw and 30:1 L/D, outputs up to 350 kg/h are generally attainable; higher outputs require a 120 mm extruder or a twin-screw side feeder. The die gap is set at 0.7–0.9 mm, and the air gap is maintained at 100–150 mm to limit web flapping and edge curl. Chill roll temperature is controlled at 18–22 °C; higher chill roll temperatures above 30 °C increase blocking tendency and reduce film flatness. Electrostatic pinning is applied across the full die width because the melt has limited long-chain branching and neck-in is greater than LDPE. When SP3210 is coextruded with LDPE or HDPE layers, the melt curtain can be stabilized by blending 10–20 wt% LDPE with a melt mass-flow rate of 4.0 g/10 min and density of 0.919 g/cm³. This blend reduces neck-in and edge bead without shifting seal initiation above 110 °C. Operators should monitor die-lip deposit formation; the narrow molecular weight distribution can produce flow marks at die temperatures below 220 °C, so die temperatures should be maintained above 240 °C.

Why Does Catalyst Architecture Control Seal Initiation Temperature in Cast Sealant Webs?

Single-site metallocene catalysis provides a narrow molecular weight distribution and uniform intermolecular comonomer composition. In cast film sealant layers, seal initiation temperature is governed by the melting of low-crystallinity fractions. For SP3210, the uniform short-chain branching distribution concentrates melting in a narrow temperature window near 105–115 °C, which allows interfacial fusion at seal bar temperatures below 110 °C. In contrast, Ziegler-Natta LLDPE has a broader branching distribution; its low-crystallinity fraction melts earlier, but a high-melting fraction delays seal strength development. The homogeneous comonomer distribution also reduces high-molecular-weight, low-branch molecules that would otherwise increase extractables. In laboratory heat-seal testing, the grade develops 2.0 N/15 mm seal strength at a lower temperature than a conventional butene LLDPE of equivalent density when measured with 0.5 s dwell and 0.2 MPa jaw pressure according to ASTM F2029. Hot tack strength, measured according to ASTM F1921, is also typically higher at 110–120 °C because crystallization after seal jaw release is more uniform. Seal curves generated on a laboratory heat-seal machine show that SP3210 in 40 µm monolayer film reaches a plateau seal strength near 120 °C. Published data for specific film structures are limited; seal performance must be verified on the target packaging line because film gauge, chill roll cooling, and coextruded layer structure alter interfacial temperature history.

When SP3210 replaces a conventional Ziegler-Natta butene LLDPE of similar density in a 40 µm three-layer cast film, the optical haze generally drops from approximately 12–15% to 6–8%, and gloss at 60° increases from around 70 to above 100. The difference arises from reduced surface roughness and fewer high-molecular-weight species that scatter light. The optical improvement is not solely due to density. The single-site catalyst reduces the concentration of high-molecular-weight, high-crystallinity chains that form surface protrusions during film solidification. The same replacement reduces hexane extractables and improves organoleptic performance in food packaging. In extrusion coating, SP3210 does not match the neck-in performance of LDPE because the absence of long-chain branching reduces strain-hardening. A blend of 70 wt% SP3210 and 30 wt% LDPE is typical for coating paper or aluminium foil at line speeds below 200 m/min; the LDPE component imparts draw-down and edge stability, while SP3210 contributes low seal initiation and toughness. Compared with higher-density mLLDPE grades, SP3210 has lower modulus and lower seal initiation temperature; compared with lower-density mLLDPE grades, it gives lower water vapor transmission rate and higher stiffness. The density of 0.921 g/cm³ places it between a 0.915 g/cm³ easy-seal resin and a 0.927 g/cm³ stiff structural resin.

Within the broader Evolue metallocene range, SP3210 is differentiated by its balance of melt flow and density. Lower-melt-flow grades are used in thicker gauge cast film where higher melt strength is required; higher-melt-flow grades are used for thin-gauge extrusion coating. SP3210 occupies the intermediate cast film window, with a density of 0.921 g/cm³ that provides moisture barrier without excessive stiffness. The grade is not a very-low-density metallocene resin in the 0.900–0.910 g/cm³ range, and it is not a high-stiffness grade in the 0.927–0.930 g/cm³ range. Its selection is therefore driven by sealant-layer performance and cast film draw, rather than by monolayer structural modulus. Current certificates of analysis should be obtained for lot-specific melt flow and density before film conversion.

When SP3210 Is Run Without LDPE Blending on High-Speed Cast Film Lines

Without LDPE, SP3210 shows higher extruder pressure than a comparable autoclave LDPE melt index because the metallocene resin has less shear thinning. The effect is measurable on a 90 mm extruder at 200 kg/h: head pressure can be 15–25% higher, and melt curtain instability increases below 40 µm gauge. Edge weave and draw resonance become more severe at line speeds above 150 m/min. Neck-in on an extrusion coating die is greater than LDPE; industrial practice therefore adds 20–30 wt% LDPE to SP3210 for coating structures. In cast film, the addition of LDPE also improves web tracking and reduces blocking on the chill roll, but levels above 30 wt% begin to raise seal initiation temperature and reduce puncture resistance. The selection of LDPE grade should be based on a melt index near 3.0–4.0 g/10 min and a density between 0.918 g/cm³ and 0.920 g/cm³. Lower-density LDPE reduces stiffness, while higher-density LDPE increases haze. When high clarity is required, a metallocene LDPE or a second mLLDPE grade may be used as the coextrusion partner.

Die-lip deposit formation is commonly observed when SP3210 is run at melt temperatures above 270 °C for extended periods, particularly on cast film lines without melt filtration. The deposit consists of oxidized oligomers and can be mitigated by lowering the adapter temperature 5–10 °C, increasing the die gap to 0.9 mm, or adding a fluoropolymer processing aid at 200–400 ppm. If a processing aid is added, the specific grade must comply with FDA 21 CFR 177.1520 or EU 10/2011 for food contact. On cast film lines with a 20/40/60/80 mesh screen pack, pressure should remain below 35 MPa. A melt pump is recommended downstream of the extruder to stabilize output and reduce surge-induced thickness variation to less than ±2%. Extrusion coating of paper and aluminium foil with SP3210 requires careful control of the air gap. Air gaps below 100 mm increase thermal degradation of the substrate and reduce adhesion; air gaps above 200 mm increase neck-in and reduce web edge stability. The use of a back-up roll with a shore hardness of 80–90 A and a surface temperature below 30 °C improves coating thickness uniformity.

Compliance documentation for SP3210 states that the base resin meets the requirements of FDA 21 CFR 177.1520 for olefin polymers used in contact with food, subject to limitations on use levels and additive package. Supplier declarations typically reference EU Regulation (EU) No 10/2011, including overall migration limits of 10 mg/dm² for food contact applications, and REACH registration under EC 1907/2006. The resin is supplied without anti-block or slip additives in the base grade; specific masterbatch formulations must be evaluated for organoleptic and migration contributions. For pharmaceutical blister packaging, users should verify absence of zinc stearate or erucamide interactions with the seal lacquer. SP3210 is not suitable for high-temperature retort structures requiring sustained exposure above 121 °C; it is intended for hot-fill, pasteurization, or dry food packaging where seal temperatures do not exceed 100–110 °C.

Storage, Moisture, and Thermal Stability Boundaries

Predrying is not required for SP3210 under normal ambient storage if pellets remain dry. Condensation from cold silo transfer or high humidity above 60% RH can introduce surface moisture that causes splay in cast film. In such cases, a hopper dryer at 60 °C for 2 h is sufficient. The resin should be extruded with melt temperatures below 280 °C; prolonged residence time above 290 °C promotes oxidative gel formation and carbonized specks. To limit degradation, use a screw with low compression ratio of 2.5:1–3.0:1 and avoid dead spots in the adapter. SP3210 is incompatible with high levels of certain phthalate plasticizers and with strongly acidic or amine-based processing aids that can accelerate catalyst residue hydrolysis or form odor-active compounds. For monolayer food packaging, no more than 15 wt% recycled content should be added unless the specific recycled stream is tested under EU 10/2011 migration protocols. Regrind from SP3210 cast edges can be reintroduced at levels up to 20 wt% if the regrind is free of dust, contamination, and oxidized gels. Higher regrind levels can reduce gloss and increase gel count. A dedusting unit or vacuum loading system with filtration below 250 µm is recommended to prevent fines from accumulating in the hopper.