Advances in PVC Compounding Technology with the Oscillating Screw Kneader PVC 2008 by Peter Messmer (Speaker) Andreas Niklaus Hans-Ulrich Siegenthaler
Introduction Overview of the talk Introduction From Vision to Reality Practical Implementation High Flexibility Summary and Outlook PVC 2008 // 2
Introduction History Mr. Erdmenger and Mr. List work on behalf of IG Farbenindustrie in the early 1940 s in the same work group for the Design of Continuous Mixing Machines. Mr. Erdmenger invents and takes a Patent for the Zweiwellenschneckenkneter (ZSK) Mr. Erdmenger finds in Werner & Pfleiderer a mechanical engineering company which is willing to take over his Patent and build the System. Mr. List invents and takes a Patent for the Oscillating Screw Kneader known as Ko-Kneter or Buss Kneader Mr. List finds in Buss a plant engineering company which is willing to take over his Patent and build the System. PVC 2008 // 3
Introduction Dipl.-Ing. Heinz List PVC 2008 // 4
Com poundi ng = Co mb in a t io n a n d Introduction Working Principle Classical Single Screw Extruder - rotation of the screw Buss Kneader - rotation of the screw AND - axial oscillation of the screw Kneading Flight Kneading Pin PVC 2008 // 5
Co m mp o u n d i n g = Co m bi n a ti o n an d Introduction Operating principle Complete covering due to the interaction between Kneading Flights and Pins PVC 2008 // 6
Introduction Self cleaning effect PVC 2008 // 7
PVC 2008 // 8 Introduction
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Com poundi ng = Co mb in a t io n a n d Introduction Shear gradient two plate model γ = Δv s γ: shear gradient Δv: relative velocity s: shear gap PVC 2008 // 10
Introduction Shear between kneading pins and kneading flight Kneading Flight Kneading Pin Shear zone Relaxation reorientation Shear Stock dividing - Local interaction between Kneading pin and Kneading Flight - The stock is divided, sheared reoriented and unified The individual mixing cycles are created by uniform and controlled shear rates. Relative movement PVC 2008 // 11
Introduction Shear Gradient in the Buss Kneader. γ = π D n 60 s s = 1 D 100. γ = π D n 100 60 D = const n γ = constant and moderate PVC 2008 // 12
Introduction Shear Rates in various Types of Machines PVC 2008 // 13
From Vision to Reality Overview of the talk Introduction From Vision to Reality Practical Implementation High Flexibility Summary and Outlook PVC 2008 // 14
From Vision to Reality Vision of the Development Develop a NEW continuous reciprocating screw kneader compounding machine with enhanced performance over existing Buss Technology with following features : Significantly higher specific throughput per machine diameter Lower manufacturing costs per machine diameter Safety, reliability, ease of maintenance and user friendliness PVC 2008 // 15
From Vision to Reality Market Specification of the Development After detailed investigations, our resultant market specification had been summarized as follows: Three times more specific throughput per machine diameter, but without increasing specific manufacturing costs. Improved ratio cost to return on investment. Smaller machine footprint and energy savings. Robust design with wear-resistant processing parts when required. Simplest possible operator interface whilst maintaining processing possibilities. PVC 2008 // 16
From Vision to Reality Practical Implementations Technical investigations Analysis of Test Results Identification of interrelationships Lead to Mathematical simulations of process zones, i.e. Feeding model Shear and transport model Melt forming model (pressure build up/ die plate) PVC 2008 // 17
From Vision to Reality Shear and Transport Model as an Example s 1 α 1 Δr s i Δα α i i Δα r i α n s i v i γ i s n Since the spacing between kneading pins and screw flights continuously changes, computation in finite steps is necessary The sum of the individual energy inputs is computed. The transport model enables the differing transport effects to be mathematically determined. 4. Pin Row 1. Pin Row 3. Pin Row 2. Pin Row Mixing Flight Kneading Flight PVC 2008 // 18
Practical Implementation Overview of the talk Introduction From Vision to Reality Practical Implementation High Flexibility Summary and Outlook PVC 2008 // 19
Practical Implementation Procesing Tasks in the Buss Kneader PVC 2008 // 20
Practical Implementation Enlarged infeed area, Elimination of crammer feeder Big Trap": MK = 1.00 QK = 5.10 Free Feeding of Premix Free ventilation through Pit M M PVC 2008 // 21
Practical Implementation Enlarged, conical feeding zone D Intake D Process S Intake S Process Diameter Ratio: D Intake / D Process = 1.1 Screw Pitch Ratio: S Intake / S Process = 1.4 PVC 2008 // 22
Practical Implementation Mixing and kneading zone The goal of tripling throughput for the same kneader diameter has had consequences: more consistent product transport without losing the mixing optimal exploitation of the available volume Former Labyrinth axial open NEW Improved conveying efficiency of kneading flights by increased pitch Improved conveying stability by The overlapping Birth of 4-Flight flight Technology! Higher number of shear surfaces per L/D Extended design window for process elements PVC 2008 // 23
Practical Implementation Pelletizing Special designed die plates for PVC Flat die plate with groove for screening Pressure optimized die plate for sensible Rigid PVC PVC 2008 // 24
Application Fields Application - Field CABLE - Insulation - Sheathing - Bedding EXTRUSION - Profile -Pipe Plastizised PVC ( P-PVC ) BLOW MOLDING -Bottle - Film & Rigid PVC ( U-PVC ) INJECTION - Shoe - Fitting MEDICAL GRADE - Pouches -Pipes - Fittings -Bottle CALANDERING -Roofing - Film / Sheet - Flooring PVC 2008 // 25
High Flexibility High Flexibility! Kneader size Process length Different types of screw element Easy changing of screw geometry Special designed die plates Multiple dosing possibilities Variation of cutting systems Versatile process conditions PVC 2008 // 26
High Flexibility Kneader sizes & outputs Size [mm] qk 40-90 qk 50-110 qk 67-130 qk 80-160 qk 96-200 qk 110-250 Output [kg/h] 100-220 up to 450 up to 1000 up to 1800 up to 3000 up to 4500 qk 140* 4 flight Kneader the newest generation in PVC compounding * Planned for future PVC 2008 // 27
High Flexibility Process length variations First stage / Kneader -> 10 or 15 L/D Longer version for residence time critical applications Second stage / Discharge -> 4 or 6 L/D Longer version when using screen changer and underwater pelletizer PVC 2008 // 28
Com poundi ng = Co mb in a t io n a n d Different types of elements & Easy access and adaptation of screw geometry High Flexibility The screw consists of individual elements, which can easily be exchanged or replaced. PVC 2008 // 29
High Flexibility Multiple Dosing possibility Feeder for Dry-Blend Feeder for colour pigment M Further components could also be : ----------------------------- SC K water BAR K water SC D water BAR D DIE oil el M -Filler (CaCO3) -Regrind - Elastomer or EVA - Injection of plastiziser PVC 2008 // 30
Cutting systems -> Wet and Dry Die Face Pelletizing High Flexibility Dry Cut Pellet Cooling & Drying Unit Wet Cut Centrifuge Pellet Cooling & Drying Unit Water/Pellet Transport Jet Water Circulation System PVC 2008 // 31
High Flexibility Example of multifunctional screw for a wide field of applications First kneading section Following influences for varying product temperature and gelation degree : Filling ratio -> output to kneader screw speed Temperature Setting of the heating units Dry Blend Temperature Low ratios for temperature sensitive formulations : ( -> T1 deep ) Bottle, IM, shoe, cristall clear, pipe compound (rigid) High ratios for middle to high filled formulations : ( -> T1 higher ) Cable, rigid extrusion, flexible pipe PVC 2008 // 32
Scale Up Process Technology: Scale-up QK Scale-up Procedure: Volumetric G 1 /G 2 = (D 1 /D 2 ) 3 Area G 1 /G 2 = (D 1 /D 2 ) 2 Scale Up Exponent G 1 /G 2 = (D 1 /D 2 ) x x = 3 - α α = f (Md, i, g, w, t, n) Md = torque, i = infeed behaviour, g = degassing, w = heat exchange, t = residence time, n = thermal limits For the quantec series a scale-up exponent between 2.8-3 is established and with it a throughput-increase of x 2 to 2.5 for equivalent screw diameters of the former plant generation PVC 2008 // 33
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Summary and Outlook Summary and Outlook The 4-flight oscillating screw kneader technology has enabled theory to translate into practice for compounding of PVC and heat and shear sensitive products. For equivalent machine sizes 3 times higher output have been achieved. The 4 flight technology has a much lower temperature gradient with increasing screw speed. The analysis and design methods used in this work are now being further refined and applied with similar success to other developments from the Buss kneader stable. PVC 2008 // 35