Shanghai SECCO Petrochemical Company Ltd. manufactures SECCO LL0220KJ as a pelletized butene-1 linear low-density polyethylene intended primarily for cast film extrusion and laminating webs. The resin is produced at the Shanghai petrochemical complex and is identified in producer certificates of analysis by a nominal melt mass-flow rate of 2.0 g/10 min at 190 °C/2.16 kg and a nominal density of 0.920 g/cm³. The product is a Ziegler-Natta gas-phase C4-LLDPE; the linear backbone carries short-chain branches from 1-butene, creating a crystallinity lower than high-density polyethylene and a shear-viscosity profile suited to flat-die processing. LL0220KJ differs from SECCO LL0209AA mainly in melt flow rate: the higher flow reduces extruder drive load but decreases melt tension in cast film air gaps. The grade is used in general-purpose packaging films, garment over-wrap, light-duty agricultural film, and lamination sealant webs. Published data for some film configurations are limited; converter-specific verification remains necessary.

Compared with SECCO LL0209AA, the 2.0 g/10 min melt flow rate of LL0220KJ reduces pressure drop across a flat die by approximately 15 % to 25 % at constant temperature, although exact pressure depends on die width, lip gap, and throughput. The lower viscosity allows thinner gauge casting and lower extruder discharge temperature, but the correspondingly shorter relaxation time increases molecular orientation and may reduce transverse-direction tear. SECCO grades within this density category differ mainly by melt flow rate and additive package; users must compare certificates of analysis for lot-specific values.

What melt-viscosity and density envelope is specified for incoming SECCO LL0220KJ pellets?

Incoming resin certification for SECCO LL0220KJ is anchored to two primary indices. Melt mass-flow rate is determined according to ISO 1133-1:2022 with a load of 2.16 kg at 190 °C; the nominal value of 2.0 g/10 min places the grade above SECCO LL0209AA, which is commonly specified at 0.9 g/10 min. The higher flow lowers screw torque in single-screw extruder drives but also lowers melt tension. Density is measured on compression-moulded plaques according to ISO 1183-1:2019 or ASTM D1505-18 after conditioning at 23 °C ± 2 °C; the nominal value of 0.920 g/cm³ corresponds to a butene comonomer fraction that reduces crystallinity relative to HDPE. The table below summarizes the resin-level specification envelope commonly reported for this grade.

The crystallinity and thermal transitions of the resin are relevant to stiffness and seal response. Dynamic scanning calorimetry per ISO 11357-3:2018 at 10 K/min on compression-moulded film typically yields a peak melting temperature near 122 °C for ethylene copolymers of this density. The crystallization exotherm on cooling at 10 K/min is broader than that of high-density homopolymer because the butene branches interrupt chain folding. A broader exotherm generally indicates more heterogeneous segment behavior and can correlate with lower modulus and improved low-temperature toughness. Actual values for SECCO LL0220KJ depend on additive package and thermal history; resin-specific calorimetric curves are limited in public literature.

The conversion of SECCO LL0220KJ on a cast film line requires control of die temperature, air gap, chill-roll temperature, and draw ratio. In single-screw extruders with screw L/D ratios of 30:1 to 36:1, barrel temperatures from 190 °C in the feed zone to 250 °C in the metering zone keep melt temperature below 270 °C and limit oxidative gel formation. The flat die is typically set between 240 °C and 260 °C because lower die temperatures increase shear stress at the lip and promote sharkskin on high-speed lines. The molten curtain is pinned to a chrome chill roll maintained at 18 °C to 35 °C; the lower temperature increases quench rate and suppresses spherulitic growth, improving clarity, while a higher roll temperature may be used to reduce blocking in subsequent slitting. Neck-in is more severe for LL0220KJ than for long-chain branched LDPE because of its linear architecture; operators therefore reduce air gap below 15 cm or add long-chain branched polyethylene to stabilize the web edges. Published operating data for LL0220KJ-specific draw resonance onset are limited, but C4-LLDPE lines typically encounter edge tearing and gauge variation when draw ratio exceeds 8:1 to 12:1 unless process aids are used.

Batch-to-batch variability in melt flow rate and density must be tracked through certificates of analysis. A shift of 0.1 g/10 min in MFR can change melt curtain sag and cause gauge bands in film thinner than 20 μm. On a cast film line equipped with a 75 mm extruder and a 33:1 L/D barrier screw, die pressure drop measured before and after the screen pack is typically stable; increases greater than 5 % at constant output indicate gel accumulation or filler build-up. Optical gels are counted on-line with camera systems; a gel count above 10 particles/m² at a 200 μm size threshold is commonly flagged for purge in food packaging applications. These thresholds are process control practices rather than guaranteed values for LL0220KJ.

Film tensile, tear, and optical response after chill-roll quenching

Mechanical performance of LL0220KJ film is not fixed by resin density and melt flow rate alone; it depends on film thickness, quench temperature, line speed, and post-extrusion orientation. For comparative testing, film specimens are conditioned at 23 °C ± 2 °C and 50 % ± 5 % relative humidity for not less than 40 h according to ISO 291:2008. Tensile properties on film are measured using ISO 527-3:2018 or ASTM D882-18 at a test speed of 500 mm/min. Comparable butene-1 LLDPE films with a density of 0.920 g/cm³ and melt flow rate near 2.0 g/10 min typically show machine-direction tensile yield stress between 8 MPa and 12 MPa and transverse-direction elongation at break above 600 %; however, published data for LL0220KJ at a specific gauge are limited. Elmendorf tear is measured by ASTM D1922-15a or ISO 6383-2:1983; the butene branch architecture gives lower tear than solution-process C8-LLDPE at equal density. Dart impact is determined by ASTM D1709-22 Method A or B depending on expected failure weight; film below 40 μm commonly uses Method A. Haze and clarity measured by ASTM D1003-13 show that higher chill-roll quench reduces haze, while slip and antiblock additives in LL0220KJ may raise haze relative to barefoot butene-LLDPE. Gloss at 45° is evaluated with ASTM D2457-21, but optical value should be interpreted alongside surface roughness because it is influenced by chill-roll surface polish.

Gauge reduction below 20 μm shifts failure from elongation-dominated to defect-limited puncture. At 15 μm, packaging lines typically observe lower resistance to pinholes in machine-direction tear tests, especially when processing recycled LL0220KJ with gel content. Tensile property is correlated with density; a 0.001 g/cm³ density increase can raise stiffness by 2 % to 5 % and reduce tear, so density variation in incoming lots must be limited. Optical haze and gloss are also sensitive to melt temperature; melt temperature above 250 °C can oxidize surface layers and reduce gloss measured at 60° by ASTM D2457-21.

The LL0220KJ additive package is formulated for high-speed cast film transport and slitting. Slip and antiblock additives migrate to the film surface over a period of days; coefficient of friction therefore changes after extrusion. Kinetic measurements by ISO 8295:1995 or ASTM D1894-14 may be performed after storage for 7 d to 21 d at 23 °C, because early measurements underreport slip-agent migration and overpredict blocking. The package reduces roll-blocking during rewind but can deposit on chill rolls and die lips at processing temperatures above 260 °C, leading to plate-out. Batch-to-batch additive variability is controlled by producer certificates of analysis, but converters compounding with recycled LL0220KJ trim should monitor gel content and volatile residues to prevent specks in thin films. The material is not supplied as a UV-stabilized agricultural-film resin; outdoor service life with the standard package is accordingly limited. No published stoichiometric data define the additive weight fraction in this grade, and FTIR or thermogravimetric analysis should be used if additive identity is critical for food-contact migration assessment.

In lamination sealant webs, the density and shear-viscosity profile of SECCO LL0220KJ enable seal initiation at temperatures lower than those required for high-density polyethylene or LDPE-rich structures. Pressure-time-temperature records from jaw sealers show that a 0.5 s dwell at 120 °C to 130 °C can produce measurable seal strength in butene-LLDPE films, though specific packaging requirements may require 140 °C. Seal strength is measured by ASTM F88/F88M-22 after conditioning; failure mode depends on film thickness and seal bar profile. Processors using LL0220KJ as a skin layer on oriented polyester or biaxially oriented polypropylene should verify that seal penetration does not shrink the base web; actual seal performance must be validated on the target machine.

When LL0220KJ is blended with long-chain branched LDPE to suppress neck-in and draw resonance

Blending SECCO LL0220KJ with low-density polyethylene is the principal industrial strategy for improving melt curtain stability. The linear chains of LL0220KJ exhibit elongational viscosity that rises less rapidly with strain than that of long-chain branched LDPE, so a pure LL0220KJ curtain necks in more severely and can oscillate at moderate draw ratios. Quantitative comparison is performed by Rheotens or extensional viscosity measurement, while on-line observation uses die-lip width versus film width. Adding 10 wt% to 30 wt% LDPE with a melt flow rate between 0.25 g/10 min and 4.0 g/10 min increases strain hardening and lowers edge trim, but the blend haze may increase due to phase morphology and surface roughness. In cast film, a 20 wt% LDPE blend is a common starting point; the exact level is determined by die delta P and chill-roll air gap. The density difference is not large, but the two components do not co-crystallize perfectly, so DSC by ISO 11357-3:2018 may show separate crystallite populations and optical haze. Heat-seal strength measured by ASTM F88/F88M-22 improves over pure LDPE because LL0220KJ lowers seal initiation temperature; industrial data for butene LLDPE suggest a seal initiation reduction of approximately 10 °C to 15 °C relative to LDPE of similar melt flow rate, but grade-specific values must be established on the target packaging line. Extruder backpressure in single-screw lines is generally lower with LL0220KJ blends than with fractional-melt LDPE; this permits higher screw rotation without exceeding drive amperage limits.

Processors substituting LL0220KJ into LDPE-dominated formulations should monitor gel formation at sustained melt temperatures above 250 °C and avoid stagnation in die corners. Crosslinked gels appear as fisheye defects and reduce Elmendorf tear; production-scale failures have been observed in long-term purge cycles on single-screw cast lines with high L/D screws. Where die pressure oscillations exceed 1.0 MPa, fluoropolymer processing aid masterbatch at 0.05 wt% to 0.15 wt% is used to reduce shear stress and delay die lip build-up. Published data for this specific LL0220KJ configuration are limited; the stated limits are common industrial practice rather than product specifications.

Compared with 1-octene LLDPE of identical density and melt flow rate, SECCO LL0220KJ generally exhibits lower dart impact and lower Elmendorf tear because butyl short-chain branches are less effective than hexyl branches in creating tie molecules between crystalline lamellae. The separation is observed in ASTM D1709-22 and ASTM D1922-15a results on film of the same gauge; the penalty may be 20 % to 40 % for dart impact depending on orientation and quench history. In contrast, butene LLDPE tends to provide lower seal initiation temperature and lower coefficient of friction in cast film because the lower comonomer cost and lower solubility of migratory fractions reduce surface haze. Against metallocene LLDPE, Ziegler-Natta LL0220KJ has a broader molecular weight distribution and may show lower clarity and lower dart impact but easier processing through lower shear stress at the die lip. These comparisons are not product specifications, and published data for this specific configuration is limited.

Regulatory compliance checklist and substance restrictions

SECCO LL0220KJ is an olefin polymer that must be certified by the producer or converter before final food-contact use. In the European Union, plastic packaging films are evaluated under Regulation (EU) No 10/2011 with an overall migration limit of 10 mg/dm² for food contact materials; specific migration of included additives must be verified by the converter. In the United States, olefin polymers may be covered by 21 CFR 177.1520 when the base resin meets defined density and solubility limits; additive compliance under 21 CFR Part 178 must be separately established. China-specific compliance uses GB 4806.6-2016 and GB 4806.7-2016 for food-contact plastics and articles; producers may issue a declaration that the grade is RoHS-compliant under Directive 2011/65/EU with respect to lead, mercury, cadmium, hexavalent chromium, PBB, and PBDE. Specific SVHC declarations under Regulation (EC) No 1907/2006 are supplied in the producer safety data sheet; the absence of a substance declaration does not cover conversion aids introduced downstream.

SECCO LL0220KJ does not require pre-drying under normal storage when pellets are kept in closed silos at relative humidity below 60 %. If surface condensation occurs, drying with desiccant air at 70 °C to 80 °C for 2 h to 4 h is typical, but moisture-driven hydrolysis is not the dominant degradation path; oxidative gel formation at melt temperatures above 270 °C is the primary failure mechanism. Long-term outdoor film without UV stabilizers will embrittle because the base resin does not contain an agricultural UV package. The product is not marketed as a barrier resin; oxygen transmission measured by ASTM D3985-17 for LDPE-class film thicknesses of 25 μm to 50 μm is in the high-permeability range typical of polyolefins, so barrier function must be obtained by lamination, metallization, or coextruded EVOH structures. Incompatibility with strongly acidic or amine-containing reprocessing streams is not a primary failure mode, but converters should avoid exposing molten LL0220KJ to halogenated cleaning solvents and should purge with polyolefin before shutdown.