Description Of The Extruder Thomas I. Butler Blown Film Technology, LLC tbutler@blownfilmtech.com 9/8/2018

Conventional Extruder Grooved Feed Extruders Twin Screw Extruders Extruder Types Conventional Extruder Single screw with a smooth barrel Grooved Feed Extruders Single screw with a grooved feed zone Twin Screw Extruders Co-rotating Counter-rotating Gear Pumps 9/8/2018

Presentation Overview Description of A Single Screw Extruder Single Screw Extruders Smooth Barrel Grooved Barrel Single Screw Mixing 9/8/2018

Requirements for an Extruder Convey pellets into screw channel Compress solid bed/vent gas Melt solid bed Mix/blend to produce homogeneous melt Produce desired melt temperature Produce the pressure required for flow 9/8/2018

Extruder System Drive Motor Reducer Gear T p Pressure Transducers Temperature Thermocouples Heating/Cooling Zones Diameter Length/Diameter 9/8/2018

Extruder Drive Motor Extruder Max. Speed Output Rate Motor inch rpm lb/hr Hp* 2.5 100 - 200 100 - 280 75 3.5 80 - 130 225 - 600 150 4.5 50 - 120 400 - 1200 200 6 50 - 100 750 - 2000 300 * For running 1.0 MI LLDPE 9/8/2018

Drive Coupling Shows one belt Extruder normally have multiple belts Belt Drive Direct Drive Direct Drive 9/8/2018

Gear Reducer Converts motor drive speed of 1750 RPM to useable extruder screw speeds of 40 to 150-200 RPM Conveys sufficient torque (horsepower) to shear, melt and transport materials along screw length. ( > 80% of energy input comes from the motor) Thrust bearing must withstand tremendous rearward forces generated by screw. 9/8/2018

Gear Box Gear reduction ratio range 8 to 25 : 1 100 - 200 rpm 1750 rpm 9/8/2018

Thrust Bearing Assembly connecting the screw to the gear box Tapered roller or Ball Bearing Key Bearings Bearing Assembly connecting the screw to the gear box 9/8/2018

Thrust Bearings 9/8/2018

The Extruder Hopper A hopper is the storage area for all material fed to the extruder. A two hour supply of material is a minimum hopper size. A hopper should be equipped with a gate to start and stop the flow of material. A slight window to observe the level of material A dump/discharge port are usually supplied for quick changes. Gravimetric load cells measure the output rate. 12 9/8/2018

Hopper Loader Frequently, extruder users equip their machines with automatic hopper loaders. These devices, using vacuum or compressed air, transport material from a storage area into the extruder hopper. 9/8/2018

Multi Component Gravimetric Hoppers Loss Weight Feeders Each hopper is mounted to an independent load cell. The weighing system is programmed for simultaneous and proportional metering of each ingredient. 14 9/8/2018

Crammer Feed Throat Crammers help run low bulk density feedstock to increase output and improve stability. It can increase output by as much as 30%. Typical materials Powders Thin, flake regrind 15 9/8/2018

Feed Section Pellet feed from hopper Barrel is flanged Support for screw Barrel is flanged to feed section Cooling channel 9/8/2018

Extruder Barrel with Screw Barrel Diameter Length/Diameter Thermocouples T T T T T p p p p p Pressure Transducers Heating/Cooling Zones 9/8/2018

Screw Design / Barrel Zones Zone Heat/Cool Feed Melt Meter 18 9/8/2018

Thermocouple T ~ DV J type thermocouple Junction Wire Sheath J type thermocouple Two wires (iron & constantan) joined together at end. Temperature is measured as a function of voltage difference Thermocouple must be in direct contact with metal J type thermocouple Two wires (iron & constantan) joined together at end. Temperature is measured as a function of voltage difference 9/8/2018

Zone Temperature Control Heater Blower on Cooling Fins Thermocouple to PID controller 400 9/8/2018

Heater Elements Inside Band 21 9/8/2018

Barrel Heater / Air Cooling 9/8/2018

Liquid-Cooled Band 23 9/8/2018

Variable Depth Thermocouple Located in the adapter pipe 9/8/2018

Pressure Transducer Pressure Transducer Rupture Disk Push rod Capillary Rupture Disk 9/8/2018

Rupture Disk Must be operational at all times. Common Ratings: 5,500 psi 6,500 psi 7,500 psi 10,000 psi 9/8/2018

Screw Design / Barrel Zones Feed Melt Meter Zone Heat/Cool The barrel is divided into multiple temperature zones to insure proper extruder operation. Stability of the temperature controllers is of prime importance in maintaining the final product quality. 27 9/8/2018

Screw Nomenclature Feeding Section (S) Compression Section (C) 9/8/2018 28 Feeding Section (S) Compression Section (C) Metering Section (M) q P Shank D F H L D Screw Diameter L Length q Helix Angle (17.65) P Pitch or Lead F Depth of Feed H Depth of Metering S Length of Feed/D C Length of Compression/D M Length of Metering /D N Screw Speed rpm W Flight Width 9/8/2018

Extruder Barrel Standard Sizes English units (inch of inside diameter) 0.5, 0.75, 1.0, 1.25, 2, 2.5, 3.5, 4.5, 6, 8, 10, 12 Metric units (mm of inside diameter) 20, 30, 40, 50, 60, 70, 90, 120, 150, 200 Common L/D’s 18, 24, 28, 30 , 32, 40 Lab scale Extruders Commercial Extruders 9/8/2018

Screw Types Metering Screws Barrier Screws Grooved Barrel Screws Vented Screws 9/8/2018

Metering Screw 9/8/2018

Barrier Screw DSB-II 9/8/2018

Grooved Feed Housing Feed Section One-piece feed section housing Single-piece feed section High Flow Cooling Channel One-piece Grooved Liner Insert Feed Section One-piece feed section housing One-piece groove liner Intensively water-cooling over grooves (highly turbulent flow) 9/8/2018

Groove-Feed Barrel 9/8/2018

Vented Barrel Extruder A vented barrel provides for the removal of volatiles (moisture, gases, air). The volatiles are remove through an opening in the barrel cylinder. A 2-stage screw is used in vented extruders Vent For Hygroscopic Thermoplastics Vent, dryer, or both May be used. 9/8/2018

Filtering 36 9/8/2018

Breaker Plate/Screen Pack 9/8/2018

Screen Pack Typical Screen Pack: Breaker Plate: 20 /40 / 80 / 40 / 20 Screw 9/8/2018

Screen Pack Opening Sizes Mesh Micron Wire Diameter Inch 20 860 0.0160 406.4 60 230 0.0075 190.5 100 140 0.0045 114.3 150 100 0.0026 66.0 200 75 0.0021 53.3 250 60 0.0016 40.6 325 43 0.0014 35.6 39 9/8/2018

Automatic Screen Changers 40 9/8/2018

Adapter Pipe 41 9/8/2018

Static Mixers Corrugated type – better mixing/more pressure drop Helical twist type – less mixing/less pressure drop 42 9/8/2018

Mixing Sections DISTRIBUTIVE Pineapple Mixer Saxton Mixer Dulmage Mixer Pin Mixer DISPERSIVE Union Carbide Mixer Helical UCC Cavity Transfer Mixer 9/8/2018

Uses for Static Mixers Viscosity decreases at higher temperature Hard to improve mixing at low viscosity Use Static mixers Improve pigment dispersion Improve additive dispersion Improve melt temperature uniformity Problems of static mixers (gels) Increased residence time distribution Stagnant flow channels 44 9/8/2018

Coextrusion Piping Minimize residence time Watch pressure Safety concerns during heat-up 45 9/8/2018

Twin Screw Extruder WP (Werner & Pfleiderer) 9/8/2018

Gear Pump 9/8/2018