CNOOC & Shell (CSPC Huizhou) HDPE 4261 AG Q 469 is a high-molecular-weight high-density polyethylene blow-moulding resin produced at the CSPC Huizhou olefins site. The designation 4261 identifies the nominal density and melt-flow family for the grade; the AG suffix identifies the additive and pellet-finish package supplied with the base polymer; and Q 469 is a production batch or quality-lot qualifier rather than a separate polymer modifier. The grade is designed for extrusion blow-moulded rigid packaging in which high environmental stress-crack resistance, elevated flexural stiffness, and sufficient melt strength are required simultaneously. Published nominal data for the grade list a density of 0.956 g/cm³ and a melt mass-flow rate of 35 g/10 min at 190°C under a 21.6 kg load. Because the flow value is measured at 21.6 kg rather than 2.16 kg, the resin falls into the high-load melt index classification typical of high-molecular-weight blow-moulding resins rather than standard injection-moulding grades.

The following table compiles representative nominal values from publicly available manufacturer literature. Lot-specific certificates of analysis for Q 469 must govern release decisions.

The F50 value in environmental stress-crack resistance testing is highly surface-sensitive. Scratches, weld lines, or die flow marks nucleate stress cracks; upstream polishing of the die lands and removal of degraded material from the barrel are required to reproduce the published ESCR retention.

What limits the processing window when extruding 4261 AG Q 469?

Extrusion blow moulding of 4261 AG Q 469 is constrained by the lower bound of melt elasticity and the upper bound of thermal degradation. Published processing guidance for the grade places the head and die temperature between 190°C and 225°C, with the barrel profile divided into a feed zone at 180–200°C, a compression zone at 200–220°C, and a metering zone at 210–225°C. On a standard 80 mm single-screw extruder with a 24:1 L/D ratio and a grooved feed section, a barrier screw with a Maddock mixing element is preferred to disperse the high-molecular-weight fraction. Melt temperatures below 190°C increase die swell and parison tension, leading to uncontrolled parison flare at the die exit and non-uniform wall thickness in the pinch-off zone. Melt temperatures above 230°C reduce viscosity to a point where parison sag velocity accelerates; this condition is particularly severe in large-part moulding because the open-parison time may exceed 3 s. Extended thermal exposure above 240°C produces a measurable loss of ESCR and an increase in gel-particle generation, although published data for this specific configuration is limited.

The grade’s high-molecular-weight fraction increases back-pressure at the die head. Processors can monitor the melt pressure upstream of the screen pack; a steady increase of more than 15% at constant screw speed indicates either filter blockage or partial thermal degradation. Screw speed on 80–120 mm extruders is generally kept between 30 and 50 min⁻¹, depending on barrel size and back-pressure setting. At lower screw speeds, the residence-time distribution broadens, and the material may begin to degrade in the screw root; at higher speeds, shear heating dominates and the melt temperature may exceed the set-point by 5–10°C. The die head should be designed with a streamlined flow channel and no dead spots. Accumulation of oxidised material in the die lip region is a known source of gel contamination; purging with a low-MI high-density purge compound after each colour change reduces this risk.

Moisture uptake in the as-supplied pellet is generally below 0.03% and drying is not normally required. However, if pellets are stored in unheated silos at relative humidity above 60% for more than 12 h, surface splay may appear in the flash zone during blow moulding. A hot-air dryer set at 80°C for 2 h restores surface quality. The use of a vented extruder is not recommended for this grade because excessive devolatilisation can strip low-molecular-weight processing aids from the additive package and reduce die-lip lubrication.

For closed-head 200 L industrial drum production, 4261 AG Q 469 is processed on accumulator-head machines with a diverging die bushing and a parison programming cam. Die gap programming is required for variable-wall-thickness parts. A typical 200 L closed-head drum uses a programmed die gap from 2.0 mm at the bottom to 1.5 mm near the top edge to compensate for parison sag; the grade’s melt strength permits stable parison formation at lengths up to 1100 mm on accumulator-head machines. Blow pressure should be set between 0.8 and 1.2 MPa, and mould temperature should be maintained at 15–30°C to achieve acceptable surface gloss and wall-thickness reproducibility. The pinch-off weld is the critical failure zone; the high-molecular-weight fraction in 4261 AG Q 469 allows slower intermolecular disentanglement and produces a more homogeneous weld morphology under the compression force of the pinch-off bar. However, the grade is not inherently barrier-enhanced; for solvent-borne or oxygen-sensitive contents, multi-layer coextrusion with an EVOH or polyamide barrier layer and a modified polyethylene tie layer is required.

In industrial detergent and agrochemical bottle applications, the grade competes with lower-ESCR blow-moulding resins that may cost less but fail earlier under stress-cracking conditions. The commonly used Igepal F50 test under ASTM D1693 uses a 100% surfactant solution and a controlled bending strain; published nominal values for 4261 AG Q 469 exceed 1000 h, while many conventional 0.952-density blow-moulding HDPE grades fall below 300 h under the same conditions. This difference is attributable to molecular weight distribution and comonomer placement rather than to density alone. Consequently, the product may permit downgauging of the wall thickness while maintaining the required top-load and ESCR performance. In 25 L tight-head containers, top-load strength is governed by flexural modulus and wall-thickness distribution; the higher flexural modulus of 4261 AG Q 469 relative to lower-density blow-moulding grades provides a top-load advantage of roughly 10–15% at equal wall thickness, although specific published data for this configuration is limited.

When 4261 AG Q 469 replaces conventional 0.952-density blow-moulding HDPE

When this grade replaces a conventional 0.952-density blow-moulding HDPE, the first observable processing difference is the higher back-pressure and melt pressure at the die head. The high-molecular-weight fraction increases the relaxation time and shifts shear-thinning onset to lower shear rates; screw torque at the same throughput is typically elevated, and the barrel temperature profile should be shifted upward by 5–10°C in the metering zone to maintain throughput. The product also exhibits a wider processing window on parison length because the higher zero-shear viscosity slows sag without requiring excessive die swell. Compared with a lower-density film-blowing or pipe-grade HDPE, 4261 AG Q 469 is not optimised for thin-wall injection moulding or cast film; its HLMI of 35 g/10 min at 21.6 kg indicates a melt that is too viscous for typical injection-spiral flow lengths above 400 mm in conventional moulds. In heavy-wall blow moulding, the higher flexural modulus permits a 10–15% wall-thickness reduction while maintaining top-load strength, provided the ESCR requirement controls the lower thickness limit.

Differences from other HDPE products also appear in screw recovery and purge behaviour. The high-molecular-weight fraction requires a longer screw-recovery time on accumulator-head machines; if the shot size is too large, the accumulator fill time can exceed the cooling time at high production rates. This condition is aggravated by poorly designed check rings or worn screws. In injection blow moulding, the grade is generally unsuitable because it cannot fill small preforms without excessive pressure loss. For large extrusion blow-moulded articles, the higher melt strength reduces parison thinning under its own weight; this is the primary reason the grade is specified for 200 L drums and intermediate bulk containers rather than for small cosmetics bottles.

Molecular architecture and stress-crack resistance controls

The stress-cracking resistance of 4261 AG Q 469 is controlled primarily by molecular weight distribution and short-chain branching placement. In high-molecular-weight HDPE, high ESCR arises from tie-molecule formation between lamellar crystals and from resistance to lamellar pull-out under sub-yield stress. The grade’s melt-flow ratio, expressed as HLMI divided by 2.16 kg MI, is reported in manufacturer literature as approximately 100; this indicates a broadened molecular weight distribution. The broader distribution supports shear thinning during extrusion but also reduces impact toughness at sub-ambient temperatures compared with a more uniform metallocene polyethylene. Therefore, the grade is not recommended for applications requiring low-temperature ductility below -30°C unless the part is redesigned with additional wall thickness or impact modifiers are added.

The comonomer type and placement also influence ESCR. A butene-based short-chain branching pattern generally produces a moderate ESCR improvement; longer chain branches or hexene-based placement may improve ESCR further but often lower flexural modulus. The manufacturer’s formulation for 4261 AG Q 469 is not disclosed, but the combination of 0.956 g/cm³ density and 1000 h F50 ESCR suggests controlled placement of short-chain branches to preserve stiffness while increasing tie-molecule concentration. Processors should not combine this grade with amine-based antistatic masterbatches or certain hindered-amine light stabilisers without compatibility testing; such additives can migrate to the surface and alter die-lip lubrication or act as stress-crack promoters in the finished part.

Regulatory compliance data for 4261 AG Q 469 are supplied in the product safety bulletin. In its natural unpigmented form, the base olefin polymer is typically assessed against EU Regulation (EU) No 10/2011 and US FDA 21 CFR 177.1520 for food-contact olefin polymers. Compliance of the finished article depends on migration testing under the intended food-simulant conditions; the producer’s certificate should be requested for each Q 469 lot because additive package modifications may affect specific migration limits. The grade is not classified as hazardous under REACH and is not expected to contain Substances of Very High Concern at concentrations above 0.1 wt%. RoHS restrictions do not apply to unfilled polyolefin resin, but halogen-free verification against IEC 61249-2-21 may be relevant for electronics packaging applications. Contact with strong oxidising acids, chlorinated hydrocarbons, or long-term UV exposure without carbon black or UV stabiliser addition is outside the recommended service boundary.

In storage and handling, pellets should be kept away from direct sunlight and oxidising agents. The product should be purged thoroughly from the barrel before shutdown; prolonged residence time above 240°C can lead to gel formation and black specks. A shutdown procedure of reducing barrel temperatures to 160°C and filling with a low-MI purge grade is standard. When the resin is transferred pneumatically, the conveying velocity should be low enough to avoid pellet fines and angel-hair formation; high-velocity dilute-phase conveying above 25 m/s can damage the pellet surface and increase the incidence of flow marks in the moulded part. Batch-to-batch variation is controlled within the certificate of analysis, but colour and additive masterbatch additions should be validated for each production lot because the Q 469 qualifier identifies a specific production batch whose stabilisation package may not be identical to earlier lots.