1. Introduction to Filler Masterbatch
Definition:
Filler masterbatch is a pre-dispersed pellet containing inorganic fillers such as calcium carbonate (CaCO₃), talc, TiO₂, barium sulfate, silica powder, and others, incorporated into a polymer matrix during plastic processing.
Functions:
- Cost reduction: Fillers replace a significant portion of resin, reducing material cost.
- Improved physical properties: Enhance rigidity, heat resistance, flame retardancy.
- Density and processing adjustment: Modify weight and melt flow properties of the final product.
Difference from Color Masterbatch:
- Color masterbatch: Low filler content, primary purpose is pigmentation.
- Filler masterbatch: High filler content, primary purpose is cost reduction and improved performance; low pigment content.
2. Characteristics of Filler Masterbatch
- High filler content (typically 70% or more)
- Requires uniform dispersion; processing equipment must ensure high dispersibility, homogeneity, and stable melt flow
- Filler is hard and low-cost; smaller particles increase cost, low-profit per pellet, requiring high production volumes for profitability
- Hygroscopic and fragile, low toughness
3. Applications of Filler Masterbatch
3.1 Film Applications (Blown or Cast Films)
Products: Shopping bags, garbage bags, packaging films, agricultural films
Functions: Reduce cost (CaCO₃ is much cheaper than resin), improve stiffness, opacity, and heat-seal performance
Notes:
- Excess filler can make films brittle
- Uniform dispersion and fine pellets required (CaCO₃ D50 ~1–2 μm)
- No moisture allowed in blown films to prevent bubble formation and breakage
3.2 Injection Molding Applications
Products: Bottles, buckets, household appliance shells
Functions: Increase rigidity and dimensional stability, reduce shrinkage, lower cost
Notes:
- CaCO₃ content typically 20–40% to balance rigidity and impact resistance
- Higher filler content may make products brittle
3.3 Extrusion Applications (Straps, Woven Bags)
Products: Woven bags, bulk bags, packing straps
Functions: Increase stiffness, reduce shrinkage, lower cost
Notes: Keep filler content 5–15%; too high reduces tensile strength and increases breakage risk
3.4 Blow Molding Applications (Hollow Products)
Products: Pesticide bottles, detergent bottles, chemical containers
Functions: Improve rigidity, reduce cost, enhance dimensional stability
Notes: Excess filler can reduce melt strength, causing deformation or collapse
3.5 Sheet, Pipe, and Profile Applications
Products: PP/PE pipes, sheets, trays, plates
Functions: Reduce cost, improve dimensional stability and scratch resistance
Notes: Pipes require impact resistance; construction sheets and trays can tolerate higher filler content
4.Typical Processing Flow
- Powder pre-mixing
- Drying (ensure low moisture)
- Feeding (main polymer + side feed filler for high ratios)
- Extrusion and dispersion (twin-screw or single-screw with kneader as needed)
- Vacuum venting to remove trapped air and volatiles
- Cooling
- Pelletizing (air-cooled, water-ring, or underwater depending on filler type)
- Finished product
5.Key Considerations
- Raw materials: Dry, surface-activated fillers (e.g., stearic acid treatment) prevent clumping and improve dispersion. Coarse powders reduce surface smoothness.
- High filler content (>70%): Use main feed for polymer, side feed for filler; hopper agitation prevents bridging.
- Feeding system: Gravimetric feeders suitable only for ≤70% filler; high-filled masterbatch requires pre-mixing.
- Moisture and volatiles: Vacuum venting prevents pellets with gas voids.
- Moisture-sensitive products: For films, include a dryer when using water-ring hot-cut pelletizing.
- High PP content / high throughput: Use high-low mixer for pre-mixing to ensure uniformity.
6.Selection of Filler Masterbatch Extruders
6.1 Optimal Solution for High-Filled Masterbatch
- Equipment combination: High-speed mixer + Twin-screw extruder (L/D 48–52:1)
- Advantages: High shear ensures uniform filler dispersion; suitable for very high filler content (>70%)
6.2 Alternative Solution for Medium-Low Filler Content
- Equipment combination: Twin-screw extruder (L/D 48:1) + Single-screw extruder (L/D 7–9:1) + Kneader
- Advantages: Flexible, ensures uniform dispersion; suitable for filler content ≤70%
6.3 Pelletizing Recommendations
PP/PE + CaCO₃ (~80%): Air-cooled strand pelletizing system
PP/PE +CaCO₃ (>83%): Brittle; use air-cooled or water-ring hot-cut system, preferably air-cooled hot-cut system to avoid pellet breakage
PP/PE +CaCO₃ (85%): Very brittle; only air-cooled hot-cut system recommended
PP + CaCO₃ (<82%): Air-cooled or underwater pelletizing system
PE + CaCO₃: Flexible melt; all pelletizing methods feasible except water strand pelletizing system
7.Conclusion
Choosing the right filler masterbatch extrusion system ensures:
- Uniform dispersion of high filler content
- Stable extrusion and pelletizing
- High-quality masterbatch suitable for films, injection molding, extrusion, blow molding, and sheets
Recommendations:
- High-filled masterbatch: High-speed mixer + twin-screw extruder (L/D 48–52:1)
- Medium/low-filled masterbatch: Twin-screw + single-screw extruder + kneader
- Pelletizing method should match filler type, ratio, and polymer to avoid pellet breakage
Note: Pre-mixing, moisture control, and proper feeding are critical to ensure stable extrusion, consistent quality, and optimal product performance.
Main Chinese Manufacturers of Twin-Screw Extruders for Filler Masterbatch
Kerke (Nanjing) – A professional twin-screw extruder manufacturer based in Nanjing, focusing on the KTE series, which covers both laboratory and production-scale models. Screw diameters range from 12–93 mm, with output capacities of 0.5–3000 kg/h. Ideal for high CaCO₃ masterbatch production.
Nanjing GS-Mach Intelligent Equipment Co., Ltd. – Offers customized twin-screw extruders suitable for high filler masterbatch production. Screw diameters range from 30–90 mm, with output capacities from a few dozen up to several hundred kg/h. These machines are designed for demanding applications, such as strand pelletizing and high-filler compounding.
Useon and other Jiangsu brands – Representing China’s mid-to-high-end manufacturers, featuring screw diameters of 20–165 mm and output capacities from 2–6000 kg/h. These machines focus on high-torque, wear-resistant performance for demanding filler compounding applications.
Nanjing and Suzhou manufacturers (such as Jent, Yongteng, Meizhilong, etc.) – Specialize in co-rotating parallel twin-screw and high-torque extruders. Screw diameters typically range from 26–92 mm, with output capacities from tens to over a thousand kg/h.
Price Overview (Approximate Range)
Laboratory or small-scale extruders: around USD 15,000–25,000
Medium-capacity machines: approximately USD 40,000–120,000
Large-scale or high-end production lines: USD 200,000–500,000 and above
