INEOS HDPE ELTEX CAP602 is a high density polyethylene injection moulding grade with a nominal melt flow rate of 6.0 g/10 min (ISO 1133-1:2022) and a nominal density of 0.956 g/cm³ (ISO 1183-1:2019). The grade is positioned for high-cavitation closure production where dimensional repeatability, short-cycle mould release, and food-contact compliance must be satisfied in parallel. CAP602 is supplied as a pelletised virgin resin; the documented application window is injection moulding of closures and caps. Blow moulding, compression moulding, and sheet extrusion are outside the normal published grade envelope. Predrying is not mandatory when pellets are stored at 20 °C to 25 °C and relative humidity below 60%. At relative humidity above 60% or when cold pellets are moved into a warm processing hall, hopper drying at 70 °C for 2 h is applied before feeding to a closed-loop vacuum hopper loader. The following application tracks cover the principal downstream closure segments. Processing values in the table are not universal machine settings; they require adjustment for cavity count, hot-runner balance, and closure mass.

For a single-piece tamper-evident still water closure moulded on a 48-cavity valve-gated hot-runner platform, the shell is moulded either as 100% CAP602 or with a 2.0 wt% white masterbatch in an LLDPE carrier. The masterbatch let-down is controlled to 1.8 wt% to 2.2 wt%. Let-down above 2.2 wt% can shift the tamper-band bridge elongation ratio because the carrier resin reduces local yield stress at the bridge root. Melt temperature is maintained at 220 °C to 230 °C; coolant inlet is set at 12 °C ± 1 °C so that cycle time is short but condensation on the mould face is avoided in a dehumidified clamp hall. Injection screw-tip pressure is 65 MPa to 80 MPa, with a hold pressure of 55 MPa to 65 MPa for 1.6 s to 2.0 s. Cooling time for a 1.9 g closure is 6.0 s to 7.5 s. The production defect that appears first on unbalanced 96-cavity stack tools is cavity-to-cavity mass variation above 0.03 g, which produces intermittent capping torque loss. The terminal article is a short-skirt one-piece beverage cap with a tamper-evident band. Food-contact compliance is anchored to EU Regulation (EU) No 10/2011 overall migration limit of 10 mg/dm² and to US FDA 21 CFR 177.1520(c). No liner is used for still water; the cap is applied to PET bottles under normal filling-line torque control.

What Limits Torque Retention in Carbonated Soft Drink Closures?

Carbonated soft drink shells moulded from CAP602 are processed with a 1.5 wt% to 2.0 wt% slip agent masterbatch in an LLDPE carrier to control removal torque without post-mould calcium stearate dusting. For water carbonated below 3.5 gas volumes, the one-piece HDPE shell may be used without a liner; above 3.5 gas volumes, a separate induction seal foil or EVA liner is required because the HDPE shell alone cannot maintain long-term CO₂ retention. Melt temperature is set at 225 °C to 235 °C, and the upper processing limit is 240 °C. Residence time in the hot runner above 10 min at 240 °C can initiate oxidative chain scission, which reduces environmental stress crack resistance and increases cap-shell leakage in pressure tests. The mould coolant inlet is 10 °C to 14 °C. A 32-cavity stack mould requires a shot-to-shot cushion change of less than 2 mm; a larger cushion shift changes sidewall thickness by 0.05 mm and alters tamper-bridge break torque. The formulation is 100% CAP602 or a 2.0 wt% masterbatch. Slip agent addition above 2.5 wt% has produced cap-shell stress cracking in carbonated bottle storage at 3.0 gas volumes and 38 °C for 28 days. ESCR is evaluated according to ASTM D1693-15, condition B in 10% Igepal CO-630. The terminal product is a threaded closure shell for carbonated water, cola, or a liner-retaining beverage cap. EU 10/2011 OML 10 mg/dm² applies, and the shell must satisfy 21 CFR 177.1520(c) for US food-contact use.

On pasteurized dairy lines, the closure is applied at 4 °C to 7 °C after filling, so the injection mould must produce a thread geometry that does not deform under cold capping torque. CAP602 is run at 100% or with a 4.0 wt% white masterbatch containing 60% TiO₂ in a polyethylene carrier. The let-down ratio is kept below 5.0 wt% to avoid gate blush and thread flatness deviation on a 38 mm dairy neck. Melt temperature is 215 °C to 225 °C; coolant inlet is 8 °C to 10 °C, and the clamp hall is dehumidified to a 6 °C dew point to prevent condensation. Filling of a 64-cavity hot-runner tool with 0.8 mm valve pins occurs in 0.28 s to 0.40 s; holding pressure is 60 MPa to 70 MPa. The principal defect is incomplete thread formation when switch-over is set too late, causing inconsistent application torque on high-density polyethylene dairy bottles. Terminal articles include foil-sealed closures for pasteurized milk, UHT milk, and aseptic flavoured milks. For fatty dairy products, migration testing is performed in 50% ethanol simulant for 10 days at 40 °C under EU Regulation (EU) No 10/2011. The grade is not established for retortable dairy processes above 110 °C because the closure body softens beyond the safe dimensional stability range.

When an Induction Seal Requires Flat Sealing Surface Uniformity in Pharmaceutical Caps

Pharmaceutical oral solid dose closures make one additional demand beyond standard beverage caps: the top sealing land must remain flat after ejection so that induction foil bonding produces a continuous hermetic seal. CAP602 is moulded at 210 °C to 220 °C melt temperature and a mould coolant inlet of 12 °C to 15 °C. The formulation is 100% CAP602; if a white shell is required, a pharmaceutical-grade white concentrate is added at 1.0 wt% to 1.5 wt%. A processing aid masterbatch at 0.5 wt% is permitted only after extractables review because the finished cap must meet USP 661.1 and Ph. Eur. 3.1.4 extractable profiles. The sealing surface is measured with a laser profilometer on a 24-cavity production tool; total indicated runout above 0.10 mm across the 0.7 mm sealing land produces induction seal voids. To hold flatness, the mould uses separate cooling zones for the top deck and plug ring, with top-deck coolant at 10 °C and plug-ring coolant at 14 °C. Hold pressure is 70 MPa to 80 MPa for 1.2 s to 1.8 s. The terminal component is a threaded closure with an aluminium induction seal liner for PET or HDPE bottles. Extraction testing uses purified water at 70 °C for 24 h and an extraction ratio of 3 cm²/mL. The resin must not be compounded with unsaturated rubber impact modifiers or with zinc stearate above 0.1 wt% because these raw materials increase extractable zinc and non-volatile residue beyond pharmaceutical packaging limits.

Tethered Beverage Closures Demand a Different Hinge Packing Sequence

Under Directive (EU) 2019/904 Article 6, tethered beverage closures manufactured from CAP602 require the hinge strap to survive repeated open-close cycles without stress whitening or strap release. The closure is usually moulded as a 100% CAP602 shell or with a 2.0 wt% masterbatch; an LLDPE-rich hinge-modifier concentrate at 3.0 wt% is added only when the tether root has demonstrated crack initiation in pilot production, because it lowers top-deck stiffness. Melt temperature is 220 °C to 230 °C. The filling profile is staged: injection speed of 95 mm/s is used to set the tether root, followed by 40 mm/s packing of the top deck. Holding pressure is 45 MPa to 65 MPa depending on tether thickness; cooling time is 8.0 s to 10.0 s. Ejection temperature above 65 °C at the hinge root creates permanent tensile set in the tether, causing the cap to hang incorrectly under bottle opening. Mould coolant inlet is set at 10 °C to 12 °C. The main production failure is gas entrapment at the tether rib intersection when the cavity is vented with channels shallower than 0.015 mm. The terminal product is a tamper-evident tethered closure for still water or carbonated PET bottles. Compliance includes EU Regulation (EU) No 10/2011 and Directive (EU) 2019/904 Article 6. Because the hinge strap is a stress concentrator, cap validation includes 10 manual open-close cycles followed by a tether retention force check. Published harmonised pass values for tether retention force are product-specific, so each bottle platform requires internal validation rather than a single public test standard.

Cosmetic Flip-Top Hinge Life and Gate Vestige Requirements

Hinge durability in cosmetic flip-top caps depends on gate position, packing pressure, and the masterbatch concentration. CAP602 is processed at 220 °C to 230 °C melt temperature and 10 °C to 12 °C coolant inlet. The compound is 100% CAP602 or a 2.0 wt% to 3.0 wt% colour masterbatch in an LLDPE carrier; for flexible hinge caps, a 1.0 wt% LLDPE-rich modifier masterbatch is added to raise hinge cycle life. Loading above 4.0 wt% combined with colour and modifier reduces thread engagement force because the overall modulus drops. The cap is filled through a fan gate or tunnel gate; the screw uses a two-stage injection profile of 90 mm/s to fill the hinge and 35 mm/s to pack the top deck. Hold pressure is 55 MPa to 70 MPa. The hinge is inspected after 100 open-close cycles at 23 °C; stress whitening at the inner hinge radius is the rejection criterion. Terminal articles are flip-top caps for shampoo, lotion, and personal-care bottles. EU compliance for the packaging article is managed under REACH EC 1907/2006 and EU Packaging and Packaging Waste Directive 94/62/EC for heavy metal limits; the grade is not classified as a hazardous mixture under CLP. If the same cap is used for a cosmetic product, the finished article falls under Cosmetics Regulation EC 1223/2009 packaging compatibility requirements, but food-contact status under EU 10/2011 is not required for this non-food segment.