Selection of PE/PP Film Recycling Equipment: Processing Solutions for Agricultural Films/Packaging Films

I. Analysis of Raw Material Characteristics (Premise for Equipment Selection)

1.   Characteristics of Agricultural Films

o    Mainly composed of PE, containing large amounts of impurities: soil, pesticide residues, crop straw, metals, and aging fragments;

o    Uneven thickness, some with degradation additives, resulting in poor toughness and fragility.

2.   Characteristics of Packaging Films

o    Dominated by PE (shopping bags, cling films) and PP (express bags, food packaging), often with composite layers;

o    Impurities mainly include printing inks, label papers, adhesives, and oils, with strong toughness and a tendency to entangle.

II. Core Processing Stages and Equipment Selection

(1) Pretreatment Stage: Targeted Impurity Removal

Core Goal: Reduce wear on subsequent equipment and lower cleaning loads.

1.   Pretreatment Equipment for Agricultural Films

o    Manual sorting station: Remove obvious large impurities (stones, straw) and separate non-PE materials (e.g., PVC mulch films);

o    Magnetic separator: Eliminate ferromagnetic substances mixed in soil;

o    Air separator: Separate lightweight straw from films using specific gravity differences.

2.   Pretreatment Equipment for Packaging Films

o    Near-Infrared (NIR) sorter: Identify and separate PE/PP materials, and remove non-target components in composite films;

o    Label stripper: Soften adhesives via friction or high temperature to separate paper/plastic labels;

o    Manual auxiliary station: Handle packaging with heavy ink or complex structures.

(2) Shredding Stage: Control Particle Size and Prevent Entanglement

Core Goal: Shred films into 5-10cm fragments for subsequent cleaning.

1.   Shredding Equipment for Agricultural Films

o    Prefer dual-shaft shredders (with staggered alloy steel blades):

    §  Advantages: Handle agricultural films containing hard impurities (soil clumps) without jamming; low rotational speed (10-30rpm) reduces dust;

    §  Parameters: Blade gap 0.5-1mm, processing capacity matched to subsequent stages (e.g., 15-22kW power for 1 ton/hour).

2.   Shredding Equipment for Packaging Films

o    Prefer single-shaft shredder + granulator combination:

    §  Single-shaft shredder: Initially shred into 20-30cm strips (anti-entanglement design: blades with hook-shaped protrusions);

    §  Granulator: Secondary shredding to ≤5cm (300-500rpm, serrated blades suitable for tough films).

(3) Cleaning Stage: Deep Stain Removal

Core Goal: Remove soil/pesticides from agricultural films and inks/oils from packaging films, with residual impurities ≤0.1%.

1.   Cleaning Equipment for Agricultural Films

o    Screw washer (primary cleaning): Remove surface loose soil via spiral blade friction + water scouring;

o    Hot alkaline cleaning tank (secondary cleaning): Soak in 80-90℃ alkaline solution for 10-15min to dissolve pesticide residues and oils;

o    Rinsing tank (tertiary cleaning): Rinse residual alkali with clean water, equipped with vibrating screens to separate settled soil.

2.   Cleaning Equipment for Packaging Films

o    Friction washer: Remove surface inks via friction from high-speed rotating paddles;

o    Deinking tank: Add dedicated deinking agents, soak at room temperature for 30min, with optional ultrasonic assistance;

o    High-pressure spray washer: Rinse residual inks with 10-15MPa high-pressure water to reduce black spots during pelletizing.

(4) Drying Stage: Control Moisture Content

Core Goal: Reduce film moisture to ≤1% to avoid bubbles during pelletizing.

1.   Universal Equipment

o    Centrifugal dehydrator: First remove surface moisture via high-speed rotation;

o    Hot air dryer: Subsequent drying with hot air speed 10-15m/s, drying time 5-8min;

o    (Optional) Vibrating fluidized bed dryer: Suitable for large-scale production lines, with 20% higher thermal efficiency than hot air dryers.

(5) Pelletizing Stage: Improve Recycled Material Quality

Core Goal: Produce uniform pellets meeting downstream reprocessing requirements.

1.   Pelletizing Equipment for Agricultural Films

o    Prefer twin-screw extruders:

    §  Advantages: Forced feeding, uniform mixing, and venting sections to remove volatiles;

    §  Configuration: 8-10 heating zones, die temperature 180-200℃, equipped with automatic screen changers.

2.   Pelletizing Equipment for Packaging Films

o    Prefer single-screw extruder + precision filtration system:

    §  Single-screw: Suitable for high-purity PP/PE, with 30:1 length-diameter ratio to enhance plasticization;

    §  Filtration: Dual-station screen changer + melt filter to remove tiny ink particles or residual labels.

III. Key Factors for Equipment Selection

1.   Matching Processing Scale:

o    Small-scale lines (1-5 tons/day): Manual sorting + single-shaft shredder + simple cleaning + single-screw pelletizing;

o    Medium-scale lines (10-30 tons/day): NIR sorting + dual-shaft shredder + automated cleaning line + twin-screw pelletizing;

o    Large-scale lines (≥50 tons/day): Fully automated (including AI sorting) + closed-loop water circulation system + continuous pelletizing line.

2.   Environmental Compliance:

o    Wastewater: Cleaning wastewater must undergo sedimentation + air flotation + biochemical treatment;

o    Waste gas: Pelletizing stages require activated carbon adsorption + photo-oxidation catalytic devices.

3.   End-Use Orientation of Finished Products:

o    For recycled materials used in film blowing (e.g., garbage bags): Enhance cleaning and filtration;

o    For injection molding (e.g., plastic crates): Reduce cleaning intensity, focusing on pelletizing stability.

IV. Typical Solution Examples

• Agricultural Film Recycling Line: Manual sorting → magnetic separation → dual-shaft shredding → screw cleaning → hot alkaline cleaning → rinsing →      centrifugal dehydration → hot air drying → twin-screw pelletizing;

• Packaging Film Recycling Line: NIR sorting → label stripping → single-shaft shredding → granulating → friction cleaning → deinking → high-pressure      spraying → vibrating fluidized bed drying → single-screw pelletizing.

Through targeted equipment selection, efficient recycling of agricultural and packaging films can be achieved. Recycled materials can meet the needs of low-end products and, with refined processing, can even reach food-grade packaging reuse standards.