UBE UMERIT mLLDPE 3570FC is a metallocene-catalyzed linear low-density polyethylene positioned within UBE Corporation’s UMERIT film-cast series. The grade is supplied as an extrudable pellet for cast film, sealant web, and lamination structures. Product-specific numerical values are not reproduced here; the current UBE technical datasheet and the lot certificate of analysis govern melt mass-flow rate, density, additive loading, and compliance statements. The suffix “FC” identifies a film-cast application slot in UBE’s nomenclature and should not be decoded into density or melt-index values without the manufacturer’s written data. Incoming resin is characterized according to ISO 1133-1:2022 for melt mass-flow rate at 190 °C and 2.16 kg, ISO 1183-1:2019 for density, and ISO 11357-3:2018 for melting peak temperature. The narrow molecular weight distribution produced by single-site catalysis is measured by GPC according to ISO 16014-4:2019, with published values for metallocene LLDPE film grades commonly clustering between 2.0 and 3.0 for Mw/Mn. The 3570FC material should be specified for applications where lower seal initiation, reduced gel count, and consistent melt curtain stability are required, and not for stiffness-driven applications where a higher-density polyethylene would be more appropriate.

The resin class is differentiated from conventional Ziegler-Natta LLDPE by the uniformity of comonomer incorporation. On cast film lines, that uniformity produces a narrower drop in seal strength at the boundary of the sealing envelope, lower solvent extractables, and reduced off-taste contribution. These performance offsets are evaluated with ASTM F1921-18, ASTM F2029-16, and organoleptic protocols, but the user must validate them on the specific film thickness and coextrusion structure because the sealant-layer gauge and adjacent material affect heat transfer.

How Does a Single-Site Catalyst Architecture Change Film Seal Initiation?

Conventional Ziegler-Natta LLDPE resins contain a heterogeneous distribution of short-chain branching across molecular weight fractions. Low-molecular-weight chains with high comonomer content melt early but contribute little mechanical strength, while high-molecular-weight chains with lower comonomer content melt later and broaden the sealing range. A metallocene LLDPE such as 3570FC is produced with a single-site catalyst that places comonomer more uniformly across the molecular weight distribution. Comparative film studies have reported seal initiation temperatures from 5 °C to 15 °C lower for metallocene LLDPE than for conventional LLDPE of similar density and melt index when measured by ASTM F1921-18. That reduction permits faster packaging-machine cycle time and less heat damage to barrier layers in coextrusions.

The molecular weight distribution of metallocene LLDPE is commonly cited between 2.0 and 3.0 Mw/Mn by ISO 16014-4:2019, whereas conventional butene-based LLDPE often falls between 3.5 and 5.0 Mw/Mn. A narrower distribution reduces low-molecular-weight extractables. In food-contact film evaluations, n-hexane extractables are determined under 21 CFR 177.1520; metallocene grades typically show lower values than Ziegler-Natta grades at equivalent density, but the specification limit for the application must be taken from the applicable food-type table. Organoleptic panels with long-chain aldehyde and ketone markers are used for taint-sensitive packaging; the lower extractable fraction of mLLDPE is generally associated with lower contribution to off-taste, although the coating, printing ink, or adjacent tie resin can dominate the sensory result.

Mechanical and optical performance differences should be quantified through laboratory films produced on a cast film line with a known die gap. Published representative data for metallocene LLDPE film grades in the 0.912–0.920 g/cm³ density range indicate that dart impact measured by ISO 7765-1:2004 can be 20 % to 35 % higher than conventional LLDPE at the same film thickness, while Elmendorf tear by ISO 6383-2:1983 shifts toward a more balanced MD/CD ratio. Haze measured by ISO 14782:1999 is generally lower, and 60° gloss by ASTM D2457-13 is generally higher, because the uniform comonomer distribution reduces melt-fracture-related surface roughness at moderate line speeds. Compared with octene-based metallocene LLDPE, a hexene-based grade may show a different balance of dart impact and low-temperature puncture; the specific comonomer type for 3570FC must be confirmed from the UBE datasheet. Published data for this specific configuration is limited if the datasheet does not state comonomer identity.

Cast Film Melt Curtain Stability and Die Pressure Boundaries

Unlike polar hygroscopic polymers, this polyolefin does not require mandatory pre-drying. Storage below 70 % relative humidity with no pellet surface condensation is sufficient. If condensation occurs, a dehumidified-air hopper operating at 60–70 °C for 2 h can be used; extended residence above 80 °C with hot-air hoppers is not recommended because softened pellets can fuse and bridge in the hopper throat. The processing window is controlled primarily by melt temperature, die condition, and draw-ratio management rather than moisture removal.

On a 65 mm single-screw extruder with L/D 30:1 and a 2000 mm cast film die, documented operating ranges for metallocene LLDPE film grades include a feed-to-metering barrel profile from 180 °C to 250 °C, adapter and die temperature at 250–260 °C, and a measured melt temperature at the die exit not exceeding 290 °C. The screw should be a barrier design with a mixing section; a gear pump between the screen changer and the die is used to hold die-inlet pressure fluctuation within ±0.5 MPa. A screen pack of 60/100/60 mesh or 80/120/80 mesh protects the die and raises melt temperature by viscous dissipation, so screw speed should be adjusted to maintain a stable pressure at the breaker plate. Die gap for cast film is commonly 0.4–0.8 mm, with an air gap of 10–25 mm and chill roll temperature of 20–35 °C. Higher chill roll temperatures raise film clarity but can increase blocking if slip additive has not bloomed uniformly.

Draw resonance presents as a periodic machine-direction thickness band and is amplified by high draw ratios, low melt strength, and poor chill roll speed regulation. On cast film lines processing 3570FC, stable operation requires controlling the draw ratio and maintaining uniform die-lip temperature across the width; edge pinning, vacuum box, or air knife systems are used to hold the melt curtain against the chill roll. If melt curtain sag or edge tear occurs, the air gap should be reduced, the die gap adjusted toward the lower end of the recommended range, and the die-lip heaters checked with a thermal imaging system for temperature deviations above 5 °C. Die lip build-up appears as smokes or specks and is managed with polymer purge grades and periodic cleaning, not by raising temperature to thermally bleach the die.

Because film-cast grades often contain slip and antiblock additives, processing temperatures and chill roll conditions affect bloom. Erucamide migration to the film surface is time- and temperature-dependent; if chill roll temperature is too low, immediate surface slip may be insufficient, while high storage temperature accelerates bloom and may increase coefficient of friction beyond the intended range. Coefficient of friction is monitored by ISO 8295:1995. Users should define acceptance limits before converting.

Food-contact status for UBE UMERIT mLLDPE 3570FC must be confirmed with the current manufacturer’s declaration. When the grade is used as a direct food-contact layer, the applicable framework is 21 CFR 177.1520 in the United States and Regulation (EU) No 10/2011 in the European Union. Under EU 10/2011, overall migration must not exceed 10 mg/dm² for the finished article, and specific migration limits for the additive package must be verified for the intended food simulant and contact time/temperature. Because the film is frequently used as a sealant layer in multi-material packaging, migration testing should be performed on the final laminate, not on the individual resin. For electrical and electronic equipment applications, RoHS applicability is determined by the finished product category; a polyolefin resin without halogenated flame retardants is not generally a source of restricted phthalates or heavy metals, but a compliance declaration should be requested from UBE for the specific lot.

Operational boundaries include an upper melt-temperature limit of 290 °C, above which gel formation and yellowness-index increase can occur. The resin should not be blended with ionomer scrap or halogenated flame-retardant additives without evaluating acid-catalyzed degradation at high melt temperature. Long residence time above 60 min at processing temperature in a stagnant extruder zone can produce black specks and should be avoided by using purge compounds and reducing screw speed during line stops. Storage should be in closed original packaging, away from direct sunlight, at ambient temperature below 40 °C; exposure to UV light over months can consume antioxidants and shift the melt-flow rate. The resin should not be used in medical implant applications, and no claim of USP Class VI or ISO 10993 biocompatibility is provided unless separately certified. Published data for this specific configuration is limited regarding long-term UV aging, so outdoor applications are not implied.

When the Sealant Web Is Coextruded Against a Barrier Tie Resin

In coextruded structures, the 3570FC layer may function as a sealant web against a tie resin, an EVOH barrier, or a polyamide core. The lower seal initiation temperature associated with metallocene LLDPE reduces the heat load transmitted to the barrier layer during the sealing dwell, which lowers the risk of neck-in distortion and seal-through tunnelling. Sealing performance should be mapped on a laboratory heat sealer with a defined jaw pressure and dwell time, using ASTM F1921-18 for seal initiation and ASTM F88/F88M-21 for seal strength. A typical evaluation range for sealant-layer thickness is 10–30 µm in cast film structures, but the specific sealing window is structure-dependent.

The grade differs from lower-flow UBE UMERIT grades in that higher melt flow is generally selected for thin cast film where die pressure and melt curtain stability benefit from lower viscosity. Higher-density grades in the same polyolefin family provide greater modulus and thermal resistance but require higher sealing temperatures. Conventional butene-based LLDPE may offer lower cost but shows inferior dart impact, seal initiation, and extractables under the same film thickness. In lamination applications, corona treatment of the mLLDPE surface is used to raise surface tension to at least 38 mN/m for adhesion; treatment level is measured by ISO 8296:2003 or ASTM D2578-17 using test inks. If surface tension falls below 38 mN/m, ink delamination or tie-resin adhesion failure can occur within 24–72 h after treatment because of additive bloom.