Main Answer: Laminated woven bags achieve unmatched durability and print clarity through advanced processes—extrusion, drawing, weaving, lamination, coating, printing, and bag-making—each optimized with Starlinger and Windmöller & Hölscher (W&H) machinery for rigorous quality control.
Introduction
Laminated woven bags are indispensable in industries demanding moisture resistance, UV protection, and branding precision, from agriculture to chemicals. Their performance hinges on seven meticulously controlled production stages. This report dissects each process, highlights quality assurance protocols, and underscores how Starlinger and W&H technologies elevate manufacturing standards.
1. Extrusion: Building the Foundation
Extrusion melts polypropylene (PP) resin into a uniform film, dictating the bag’s baseline strength.
Q: How does co-extrusion enhance film performance?
A: Layering PP with polyethylene (PE) or BOPP balances tensile strength and moisture resistance.
Starlinger’s Visco+ extruder uses a dual-layer die to produce films with a PP core (MFI 3–5 g/10 min) and a BOPP outer layer. For example, a 0.08 mm film with ±0.003 mm thickness tolerance ensures consistency in multiwall laminated woven bags for fertilizers.
Quality Control:
- Melt Flow Index (MFI) tests: Verify resin viscosity (3–5 g/10 min at 230°C).
- Laser thickness gauges: Detect deviations exceeding ±0.005 mm.
2. Drawing: Maximizing Tape Strength
The extruded film is slit into tapes and stretched to align polymer chains.
Q: Why is draw ratio critical?
A: A 1:6–1:8 draw ratio optimizes tensile strength (8–10 N/tex) while retaining 15–20% elongation.
W&H’s TA-CON stretching line heats tapes to 160°C and stretches them at 200 m/min. For heavy-duty FIBC bags, this ensures tapes withstand 1-ton loads without snapping.
Quality Control:
- Tensile testers: Confirm break force ≥8 N/tex (ASTM D882).
- Elongation checks: Ensure 15–25% stretch to absorb impacts.