Solution
Turnkey Flexible PVC Cable Compounding & Low-Shear Pelletizing System
Integrated dry-blend mixing and low-shear two-stage extrusion pelletizing solution for flexible PVC cable jacketing and medical-grade compounds.
- Solution scope
- Full-Line Integration
- Flow and installation
- Continuous · Inline
- Capacity
- 350–1200 kg/h
Flexible PVC compounds used in building wire, power cable jacketing, automotive wiring harnesses, and medical tubing represent one of the most demanding compounding applications in polymer engineering. Unlike polyolefins or engineering styrenics, suspension-grade PVC resin is intensely heat-sensitive: prolonged exposure to elevated temperatures triggers autocatalytic dehydrochlorination, releasing corrosive hydrogen chloride (HCl) gas, causing yellow-to-black discoloration, degradation of polymer chains, and catastrophic damage to processing machinery.
Simultaneously, flexible PVC formulations require the incorporation of high volumes of liquid plasticizers (such as DOTP, DINP, DOA, or TOTM, typically 30 to 70 parts per hundred resin), alongside heavy mineral fillers (ground calcium carbonate, precipitated CaCO3, antimony trioxide flame retardants), lubricants, and thermal stabilizers. If liquid plasticizers are fed directly into standard extruders without adequate prior dry-blending and resin pore absorption, severe screw slippage, plasticizer exudation, un-fluxed resin "fish eyes", and chronic processing instability inevitably occur.
To deliver flawless, high-output production without thermal degradation, this integrated solution couples a high-speed heating and cooling combination mixer (SRL-Z series) with a specialized low-shear, two-stage compounding extrusion line (a high-speed co-rotating twin-screw extruder for plasticizing, followed by an air-cooled or water-ring eccentric die-face hot pelletizer). The high-speed hot mixer elevates the batch to 110°C–120°C via aerodynamic friction, opening the porous morphology of the suspension PVC grains to fully absorb liquid plasticizers into a free-flowing "dry blend". The cooling mixer then quenches the blend below 45°C to arrest secondary agglomeration. Downstream, the extrusion system applies precise, low-specific-energy shear, followed by synchronized hot face cutting and multi-stage fluidized-bed cyclone cooling to produce clean, non-tacky, cylindrical or lens-shaped pellets with consistent Shore hardness and zero fish eyes.
The problem
What the section changes
Delivers complete, non-degrading plasticizer absorption and continuous low-shear extrusion to produce zero-fish-eye, thermally stable flexible PVC cable pellets at stable high throughput.
Dónde empieza el cliente
Processors attempting to compound flexible PVC on standard single-stage extruders face frequent thermal scorching, erratic plasticizer “sweating”, and severe surging. When liquid plasticizers are inadequately pre-absorbed into resin pores, liquid pools inside the screw channels, lubricating the barrel walls and destroying conveying friction. Operators are forced to lower screw speeds, leading to excessive residence times in hot zones, triggering hydrochloric acid (HCl) release, severe machine corrosion, and batch rejection due to yellowing or fish eyes.
Por qué ocurre el problema
Suspension PVC resin consists of discrete porous grains (100–150 µm). At room temperature, resin pores are partially closed; adding large volumes of liquid plasticizer directly into an extruder barrel creates an emulsion-like phase boundary. The liquid lubricates the metal flight surfaces, collapsing extruder conveying efficiency while leaving dry resin cores un-plasticized (manifesting as visible fish eyes on extruded cable surfaces).
Furthermore, standard high-shear screws induce localized shear heating in excess of 200°C, accelerating HCl degradation. A successful system requires thermal pre-diffusion in a high-speed mixer to convert liquid and resin into a dry, free-flowing powder, followed by low-shear, controlled-temperature extrusion with minimal residence time.
Producción o estado objetivo
Production of uniform, non-porous, thermally stable flexible PVC pellets with zero fish eyes, uniform plasticizer incorporation, excellent color clarity, and high electrical insulation resistance, ready for direct high-speed cable jacket extrusion.
Process
The steps, in the order the material flows
The equipment named here is maintained on the step it belongs to, so the list and the quotation cannot disagree.
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High-Speed Dry-Blend Pre-Mixing & Plasticizer Absorption
RequiredMixing
Intensely blends PVC resin, stabilizers, and fillers while atomizing liquid plasticizers under controlled aerodynamic frictional heating (115°C–120°C), driving plasticizer molecules deep into the porous PVC resin matrix to form a dry, free-flowing powder.
Función del equipoAerodynamic multi-tier impeller rotating at 25–30 m/s tip speed elevates batch temperature. Liquid injection nozzles atomize pre-weighed plasticizer evenly across the vortex.
Equipos Compounding Mixer
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Fluidized Water-Jacketed Dry-Blend Cooling
RequiredCooling
Rapidly cools the hot dry-blend powder from 115°C down to ≤ 45°C via water-jacketed vessel walls and slow-speed ribbon agitation, arresting thermal degradation and preventing secondary cake formation during intermediate surge storage.
Función del equipoHorizontal cooling mixer with circulating cooling water jacket and helical ribbon agitator gently fluidizes the hot powder without frictional heating.
Equipos Compounding Mixer
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Enclosed Dust-Free Vacuum Pneumatic Feeding
RequiredFeeding and Material Transfer
Pneumatically transfers cooled PVC dry-blend from the mixer discharge hopper into the extruder gravimetric feeding receiver under negative pressure, ensuring completely dust-free plant operation.
Función del equipoStainless steel vacuum receiver with pulsed compressed air jet cleaning across Gortex PTFE membrane filters, discharging directly into the extruder feed throat.
Equipos Vacuum Loader
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Low-Shear Compounding & Multi-Stage Vacuum Degassing
RequiredExtrusion and Melt Processing
Gently plasticizes and homogenizes the pre-blended PVC powder under strictly controlled shear and temperature, followed by high-vacuum degassing to evacuate moisture and trapped air, then builds extrusion pressure through a low-RPM single screw to eliminate shear overheating.
Función del equipoHigh-torque twin-screw plasticizing section equipped with deeply intermeshing screw flights and vacuum devolatilization ports (-0.09 MPa), feeding directly into a single-screw discharge extruder for pressure generation.
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Air-Cooled Die-Face Hot Pelletizing & Inline Classification
RequiredPelletizing
Cuts the plasticized PVC melt at the die face using high-speed rotary knives, immediately cooling the pellets in high-velocity air-conveying ducts and dual cyclone separators, discharging across a linear vibrating screen to eliminate dust and oversized clusters.
Función del equipoSynchronized die-face eccentric hot cutter with water-cooled die plate, pneumatic blower conveying system, multi-tier cyclone cooling receivers, and linear vibrating dedusting screen.
Equipos Linear Vibrating Screen
Material
What goes in, what comes out
Condición y requisitos de alimentación
Suspension-grade PVC resin powder (K-value 65–70, bulk density ~0.50 kg/L); liquid plasticizers (DOTP, DINP, DOA, TOTM, chlorinated paraffin); fine mineral fillers (ground/precipitated CaCO3, antimony trioxide, ATH); thermal stabilizers (eco-friendly Ca-Zn or liquid complex), lubricants, and processing aids.
Condición y límites de salida
Cylindrical or uniform lens-shaped flexible PVC pellets (diameter 3.0 mm ± 0.3 mm, length 3.0 mm ± 0.4 mm). 100% free of un-melted fish eyes, bubbles, and thermal degradation discoloration. Excellent free-flowing behavior with zero sticky agglomeration at packaging temperatures ≤ 40°C. Shore A hardness range 50A to 95A according to formulation recipe.
350–1200 kg/h
Base de las cifras de capacidad
Rated output based on standard 70°C–90°C flexible PVC cable jacketing formulation (100 phr PVC K-67, 45–60 phr DOTP, 30–50 phr ultra-fine coated calcium carbonate, 4 phr Ca/Zn stabilizer, 0.5 phr stearic acid lubricant) running continuously.
Fit
Where this section belongs — and where it does not
The boundaries are part of the solution: they keep a machine from being quoted into a case it cannot serve.
Adecuada cuando
Ideal for wire and cable manufacturers and commercial PVC compounders producing flexible PVC granules (building wire insulation, power cable sheath, automotive wire harness, flexible cords, Shore A 50 to 95).
Suitable for medical tubing, automotive weatherstrip gaskets, and footwear injection molding compound producers requiring high surface smoothness and absolute freedom from un-melted gels.
No adecuada cuando
Not suitable for unplasticized rigid PVC (PVC-U) pipe or window profile powder compounding (which requires specialized conical twin-screw dry-blend extrusion directly to profile dies rather than pelletizing).
Not suitable for cross-linkable silane XLPE or halogen-free flame-retardant (HFFR) compounds requiring high-loading aluminum hydroxide (> 65%) with high-MFI polyolefin carriers.
Condiciones pendientes de confirmar
Suspension PVC resin grade K-value between 65 and 70 (e.g., SG-3 or SG-5) with bulk density ≥ 0.48 kg/L and plasticizer absorption capacity ≥ 25%. Liquid plasticizers pre-filtered and maintained at room temperature (≥ 20°C) or pre-heated.
Site and connections
What the section assumes around it
Servicios auxiliares
- Suministro eléctrico
- 380 V / 415 V / 460 V, 50/60 Hz, 3-Phase AC.
- Agua
- Recirculating cooling water (supply temp ≤ 25°C, pressure 0.3–0.4 MPa, flow rate 15–25 m³/h) for mixer water jackets and barrel heat exchangers.
- Aire comprimido
- 0.6–0.8 MPa dry, filtered plant air; consumption ~0.6 m³/min.
- Extracción y ventilación
- Local negative-pressure dust extraction hoods required above bag dump station and vacuum pump exhaust port (venting outside plant).
Total installed electrical power: 220 kW to 420 kW depending on system throughput selection.
Limitaciones de la planta
- Superficie ocupada
- Approx. 18 m length × 6 m width × 5.5 m height (including overhead mezzanine for mixing unit).
- Altura libre
- Minimum 5.5 meters clear height required above the mixing platform to accommodate raw material loading.
- Entorno
- Standard dry industrial compounding workshop. Ambient temperature 5°C to 40°C. Good cross-ventilation.
Concrete floor must be leveled with load-bearing capacity ≥ 3.5 metric tons/m² for the extrusion and mixer base.
Interfaces
- Mecánico
- Standard DN100 pneumatic conveying piping between mixer discharge and extruder surge hopper; DN150 exhaust venting connection.
- Control
- Siemens S7-1500 PLC architecture with Profinet communication connecting mixer control cabinet, extruder main console, and downstream cooling drives.
- Aguas arriba y aguas abajo
- Upstream: Bag dump station or bulk silo feeding. Downstream: Pneumatic pellet transfer directly to packaging surge hopper.
Targets
What the section is judged on
The numbers are targets agreed per project, not a general promise.
- Fish Eyes / Un-gelled Particles
- 0.00 per 1000 cm² Optical blown/extruded tape inspection per 1000 cm² surface area
- Thermal Stability (Congo Red Test @ 200°C)
- ≥ 100 minutes Congo Red test method per IEC 60811-3-2
- Pellet Shore A Hardness Consistency
- ± 1.0 Shore A Durometer measurement across 20 pellets per batch per ASTM D2240
Cómo se evalúa la aceptación
1. Continuous 8-hour production run achieving ≥ 95% of rated capacity on representative flexible PVC cable compound (e.g., 70 phr DOTP + 30 phr CaCO3).
2. Thermal stability test: Finished pellets subjected to 200°C Congo Red test per IEC 60811-3-2 with thermal stability time exceeding 100 minutes without thermal breakdown.
3. Optical quality: Extruded 0.2 mm tape sample evaluated under light table showing zero visible fish eyes or un-gelled PVC resin particles per 1,000 cm².
4. Pellet geometry: Uniform diameter and length (3.0 mm ± 0.3 mm) with pellet-to-pellet adhesion < 0.05% after continuous fluidized cooling.
Scope of supply
What is in the delivery — and what is not
The confirmed scope is stated in the quotation; this is the boundary of the section as designed.
Incluido en el alcance del suministro
- High-Speed Heating & Cooling Combination Mixer Unit (SRL-Z Series) Mirror-polished SUS304 hot mixer vessel with multi-tier aerodynamic blades, pneumatic discharge flap, and high-efficiency water-jacketed horizontal cooling mixer.
- Automated Liquid Plasticizer Dosing System Positive-displacement dosing pump, mass flowmeter, heating jacket, and pneumatic fine-atomizing spray nozzles.
- Low-Shear Two-Stage Compounding Extrusion System High-speed co-rotating twin-screw extruder for plasticizing coupled to a slow-speed single-screw extruder for pressure generation, complete with bimetallic wear- and corrosion-resistant metallurgy and multi-stage vacuum degassing.
- Air-Cooled Eccentric Die-Face Pelletizing & Fluidized Cooling Skid Synchronized high-speed rotary cutter, water-cooled die plate, pneumatic pellet transport blower, dual cyclone separators, and fluid-bed vibrating cooling bed.
No incluido en el alcance del suministro
- Liquid Plasticizer Bulk Tank Farm External outdoor bulk storage tanks and long-distance underground transfer piping up to mixer day-tanks.
- Building Structural & Ventilation Civil Works Mezzanine structural steel construction, primary building ventilation ducts, and overhead hoists.
- Downstream Finished Pellet Bagging Machine Automated 25kg valve-bag packaging, palletizing, and stretch-wrapping robots (available as an optional separate system).
Before a price
What we confirm before this becomes a quotation
- 01 Detailed Formulation Sheet Base PVC resin grade (K-value), plasticizer types (DOTP, DINP, DOA) and phr loading levels, filler types and loading ratios (CaCO3, ATH), and stabilizer chemistry (Ca/Zn, liquid Ba/Zn, or organotin).
- 02 Finished Pellet Requirements Target Shore A hardness range (e.g., Shore 50A to 95A), cable specification standards (UL, IEC, VDE, RoHS/REACH compliance), and packaging requirements (25 kg bags or bulk octabins).
- 03 Utility Capacities at Site Supplied electrical voltage and transformer rating, chilled water circuit flow rate and cooling tower capacity, and compressed air pressure.
Request a Quote Send these points with your inquiry; the section can then be quoted against your line, not against an assumption.
Photos
The section in the workshop
Photos go here once the section has been built and the material is cleared to publish.
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Placeholder · 1200 × 900 px (4:3)（占位图） Replace with an approved section photos, real workshop or installation views at this size.（按此尺寸替换为正式图片。） -
Placeholder · 1200 × 900 px (4:3)（占位图） Replace with an approved section photos, real workshop or installation views at this size.（按此尺寸替换为正式图片。）
Details
Further details
- Problema de producción principal
- Batch-to-batch variation
- High surface moisture on the material
- Off-spec pellet size and fines
- Sticking and agglomeration