Thin-Wall Dairy Tub and Food Container Conversion

Sinochem Quanzhou HDPE HMN55180 is deployed in thin-wall injection molding of dairy tubs and food containers where a nominal melt flow rate of 18 g/10 min at 190 °C/2.16 kg under ISO 1133-1 and a nominal density of 0.955 g/cm³ under ISO 1183-1 permit short fill times and sidewall reproducibility in the 0.45–1.20 mm range. The base formulation is 100 parts HMN55180 with a carrier-compatible color masterbatch at 1.0–3.0 wt%, a slip/antiblock masterbatch containing 5% erucamide at 0.5–1.5 wt%, and an antioxidant masterbatch at 0.1–0.3 wt%; reverse-trim regrind may be re-entered at up to 20 wt% only in non-food-contact layers or under a documented closed-loop declaration. Food-contact status is verified against FDA 21 CFR 177.1520(c), EU Regulation (EU) No 10/2011 as amended, and GB 4806.7, with overall migration assessed under GB 31604.8 or EN 1186-1 using 50% ethanol and 3% acetic acid simulants at the listed end-use time-temperature conditions. On accumulator-assisted injection machines with screw L/D ratios of 20:1–25:1 and compression ratios of 2.5:1–3.0:1, melt temperature is held between 220–245 °C, mold temperature between 15–30 °C, injection velocity between 120–250 mm/s, and hot-runner valve gates are maintained above 10⁴ s^-1 shear rate to prevent stringing. Cooling time for 0.7 mm sidewalls on a 48-cavity stack mold is 4.0–8.0 s, but pellet surface moisture or wet regrind can produce splay at screw-back speeds above 150 mm/s; hopper air should therefore remain above the local dew point. Terminal products include margarine and butter tubs, yogurt cups, ice cream containers, takeaway food containers, and snap-on lids.

Closure and overcap molding for still beverages, dairy, and household chemical concentrates uses HMN55180 as the main polyolefin phase because the narrow molecular weight distribution reduces gate freeze delay and permits rapid screw decompression after metering. A typical formulation for tamper-evident or sports-cap designs is 100 parts HMN55180, 2.0–4.0 wt% carrier-compatible color masterbatch, 0.05–0.20 wt% oleamide or erucamide slip additive, and 0.10–0.30 wt% hindered phenol/phosphite antioxidant masterbatch; where a hinged tether strap or flexible tamper-evident band is gated, 5–15 wt% of an ethylene-octene copolymer or linear-low-density polyethylene is substituted for the equivalent mass of HMN55180, with tensile elongation at break verified on the compounded blend by ASTM D638. Food-contact closures are assessed under FDA 21 CFR 177.1520 and EU Regulation (EU) No 10/2011; when post-consumer recyclate is incorporated at 10–30 wt%, environmental stress-cracking resistance must be re-evaluated by ASTM D1693 Condition B because closure threads experience progressive hoop stress after application torque. On 96–128-cavity hot-runner stack molds with clamp force between 3,500 kN and 5,500 kN, melt temperature is kept at 215–235 °C, mold temperature at 10–20 °C, injection speed at 100–250 mm/s, and pack pressure at 30–60 MPa for 0.8–1.5 s; cycle times of 5.5–8.0 s are achieved when gate diameter is limited to 0.6–1.0 mm and pneumatic ejection is trimmed to reduce pull marks on sealing lands. Terminal products include screw caps, snap lids, overcaps, sports caps, and tamper-evident bands.

What Governs Dimensional Stability in Industrial Crate and Pail Molding?

Industrial crate and pail molding shifts the limiting control from melt fill length to packing intensity and differential shrinkage across wall-thickness transitions. HMN55180 is run at 100 parts with 2.0–5.0 wt% color concentrate, 0.2–0.5 wt% antioxidant/processing-stabilizer masterbatch, and, for outdoor handling, 0.3–0.8 wt% HALS-containing UV masterbatch; mechanically recycled HDPE from the converter's own rejected crates may be added up to 30 wt% only after notched Izod impact is rechecked by ISO 180 at 23 °C because pail rims and crate grids experience repeated notched impact in service. Regulatory references for industrial packaging include the UN Model Regulations Chapter 6.1 where the pail or drum is certified for dangerous goods, REACH Annex XVII entries applicable to restricted PAH and phthalate substances, and RoHS Directive 2011/65/EU where the crate is incorporated into electrical storage systems. Production on 800–1,600 t clamp injection machines uses melt temperatures of 210–235 °C, mold temperatures of 20–40 °C, injection pressures of 60–100 MPa, packing pressures of 40–70 MPa for 6–12 s, and screw back pressure of 0.5–1.5 MPa; the projected-area clamp requirement is 4–6 kN/cm² to prevent parting-line flash. Thick sections at handle bosses and pail rims require a stepped packing profile that holds gate pressure until the part mass stabilizes; otherwise sink marks deeper than 0.08 mm appear and fail visual quality criteria. Terminal products include horticultural crates, fish crates, collapsible logistics boxes, paint pails, 5-gal containers, and pallet corner blocks.

Household storage boxes, toy building blocks, and institutional furniture components use HMN55180 when the molder requires a balance of stiffness, drop impact, and rapid ejection from ribbed tools. The blend ratio is 100 parts resin to 2.0–4.0 wt% pigment masterbatch, 0.05–0.20 wt% slip additive where nested parts denest, and 0.10–0.30 wt% antioxidant masterbatch; if high gloss is required, a nucleating masterbatch at 0.05–0.20 wt% is introduced only after the tool has been re-cut for the associated shrinkage reduction of 0.2–0.6 percentage points. Compliance for toys sold in the EU is evaluated under EN 71-3 for migration of elements and REACH Annex XVII for restricted substances; toys sold in the US are assessed under ASTM F963 heavy-metal and mechanical requirements. On single- and twin-platen machines with screw L/D ratios of 20:1–24:1, melt temperature is maintained at 210–240 °C, mold temperature at 15–35 °C, and injection speed at 60–150 mm/s; because mold shrinkage is 1.5–2.5%, draft angles below 0.5° on stacking ribs create ejection marks and audible denesting squeak. Terminal products include stackable storage bins, toy building blocks, toy storage chests, garment hangers, and institutional utility boxes.

When the Grade Is Specified as a Melt Carrier in Polyolefin Masterbatch

When the grade is specified as a melt carrier in polyolefin masterbatch, the high melt flow is used to wet pigment agglomerates and disperse mineral fillers through a twin-screw devolatilization profile without prematurely degrading the colorant. A carrier formulation starts with 20–35 wt% HMN55180, 50–65 wt% pigment or mineral filler, 5–10 wt% low-molecular-weight polyethylene wax, and 0.1–0.5 wt% processing antioxidant/acid scavenger; the pigment-to-carrier ratio is adjusted within this band based on oil number and BET surface area, not set by a fixed rule. The compound is extruded on co-rotating twin-screw lines with L/D ratios of 40:1–48:1, screw speeds of 400–800 rpm, barrel temperatures from 120 °C at the feed throat to 220–230 °C at the die, and underwater pelletizing at 18–25 °C water temperature; melt temperature above 240 °C produces viscosity loss and strand swelling sufficient to shut down die-face pelletizers. The masterbatch must comply with REACH Regulation (EC) No 1907/2006 and, where sold into electrical/electronic articles, RoHS Directive 2011/65/EU; food-contact migration testing is not covered by the masterbatch itself and remains the responsibility of the final article converter. Terminal products are pelletized color concentrates, additive concentrates, and filler masterbatches for non-food injection molding, drip-irrigation pipe, and blown-film extrusion.