PP Woven Bag Recycling Line:
Shredder to Pellet

The fundamental difference is material structure and contamination type. PE blown film is a thin, continuous sheet with low bulk density — the primary feeding challenge is compacting loose film into a consistent feed stream. PP woven bags are a fabric structure made from stretched polypropylene flat yarn — the primary challenge is breaking down that woven structure before any downstream processing is possible. A standard granulator cannot handle the tensile strength of PP flat yarn; a heavy-duty single-shaft shredder is required. Post-consumer PP woven bags also carry inorganic contamination — cement dust, fertilizer residues, sand — that PE film waste typically does not. This contamination cannot be removed by degassing alone and requires a dedicated wet washing stage before extrusion.

The answer depends entirely on the source of your waste. If your waste is generated inside your own factory — edge trim, raffia tape, roll-change scrap, non-conforming bags that have never been filled — a dry-process system is sufficient. The material is clean and consistent, and a shredder-compactor-extruder configuration will produce acceptable pellets without washing. If your waste comes from external sources — cement bags, fertilizer bags, rice bags, or any bag that has been filled and used — a washing line is not optional. Inorganic contamination from cement dust and fertilizer residues will destroy the extruder screen changer within hours of operation if fed into a dry-process line without prior washing. The cost of a washing line is significantly lower than the cost of repeated screen changer replacements and screw wear.

A cutter compactor is designed for thin PE film — it uses frictional heat to compact loose, lightweight film into a dense mass that can feed into an extruder screw. PP woven bags are a fundamentally different material. The woven polypropylene fabric structure, made from stretched flat yarn, has high tensile strength that a cutter compactor cannot overcome. Attempting to process whole or folded woven bags through a cutter compactor results in wrapping around the rotor, jams and inconsistent output. A heavy-duty single-shaft shredder applies shear force to tear the woven structure into manageable fragments before the compactor stage. The compactor then performs its intended function — densifying the shredded fragments for stable extruder feeding.

After shredding, PP woven bag fragments are still bulky and irregular. Their bulk density is too low for consistent extruder screw feeding — the screw would feed air rather than material, causing surging and inconsistent output. The compactor uses a rotating drum to apply frictional heat to the shredded fragments, pre-plasticizing and densifying them into a compact mass before they enter the extruder. This ensures a stable, continuous feed rate at the target throughput. The compactor is positioned between the shredder output and the extruder inlet, and is a standard component in both dry-process and wet-process PP woven bag recycling configurations.

Two-stage extrusion passes the melt through two separate extruders in sequence. The first stage melts and plasticizes the PP material and performs coarse filtration. The second stage provides an additional vacuum degassing zone and precision filtration pass. For PP woven bag waste — which typically contains ink volatiles, residual moisture and fine contamination even after washing — a single extrusion pass often cannot achieve the degassing and filtration depth required for consistent pellet quality. The second stage homogenizes the melt and removes residual volatiles that the first stage did not capture. For clean in-plant scrap with minimal contamination, a single-stage system may be acceptable. For post-consumer bags and any waste with print coverage or chemical residues, two-stage extrusion is the correct specification.

Yes, with the correct filtration configuration. BOPP-laminated bags introduce a mixed PP/PE material structure — the BOPP coating has a lower melting point than the PP woven base fabric. During extrusion, both components melt and blend into the melt stream. The resulting recycled pellets will have a slightly modified MFI compared to pure PP, which affects their suitability for downstream applications. For injection-molded products, plastic pallets and non-woven applications, this blend is typically acceptable. For re-extrusion into new woven bags, the mixed material may affect tape-drawing performance. Two-stage extrusion with precision melt filtration is required to manage the mixed-material stream and maintain consistent pellet quality. Share your BOPP lamination percentage with LayerQuestar Machinery when requesting a configuration.

FIBC jumbo bags require a separate configuration assessment and cannot be processed on a standard PP woven bag recycling line without modification. The reasons are: FIBC bags are significantly larger and heavier than standard woven bags, requiring a larger-format shredder with higher torque; most FIBCs include PE inner liners, polyester sewing thread and BOPP labels that introduce multiple material streams; and the contamination profile of used FIBCs — particularly those used for chemical, mineral or construction materials — varies widely. A line configured for standard woven bags may be undersized for FIBC volume and incorrectly specified for FIBC contamination. Contact LayerQuestar Machinery with your FIBC waste volume, source industry and estimated contamination level for a dedicated configuration assessment.

Vertical water-ring pelletizing cuts the melt at the die face while a ring of water simultaneously cools and transports the pellets. The vertical orientation is preferred for PP because PP melt has a relatively low viscosity at processing temperature and can drip or deform under gravity in a horizontal die-face setup. The vertical configuration keeps the melt stream stable and produces consistent cylindrical pellets. It is suitable for PP melt in the MFI 1–20 range, which covers the majority of recycled PP woven bag material. Strand pelletizing is an alternative but is more sensitive to melt viscosity variation — a significant disadvantage when processing recycled material with inherent batch-to-batch variation.

For in-plant scrap: calculate your total woven bag production output and multiply by your scrap rate. A woven bag factory producing 50,000 bags per day at an average weight of 80 g per bag generates 4,000 kg of finished product. At a 4% scrap rate, that is 160 kg of recyclable waste per day. If your recycling line runs 8 hours per day, you need a minimum of 20 kg/h output capacity — a small single-stage system. For post-consumer waste recycling: base your calculation on your planned daily waste intake volume, not your production output. Factor in a 15–20% efficiency allowance for washing water, screen changes and startup losses. Share your daily waste volume, operating hours per day and waste type with LayerQuestar Machinery for a specific capacity recommendation.

European brands such as Starlinger and Erema are the appropriate choice for food-contact compliance applications, EU-regulated markets and projects where European certification is a contractual requirement. For industrial non-food-contact PP woven bag recycling, the relevant comparison is between suppliers with documented build standards and those without — not between Chinese and European brands as a category. LayerQuestar Machinery specifies ABB or Innomotics main motors, WC bi-metallic screws with HRC 59–65 surface hardness, OMRON PID temperature control with ±1°C deviation under stable conditions, and conducts a 72-hour continuous factory acceptance test on every line before shipment. These specifications are published and verifiable. The price difference versus European equivalents for non-food-contact industrial applications is substantial — typically a fraction of the European price for the same functional output specification.