CO-EXTRUSION BLOW MOLDING With A Continuously or Sequentially Foamed Layer Wolfgang Meyer W. Müller USA, Inc. Annual Blow Molding Conference October 6-7, 2014 Chicago, IL
W. Müller GmbH, Troisdorf, Germany W. Müller USA, Agawam, MA Manufacturing Engineering R&D Customer Service
W. Müller USA, Agawam, MA Field Service Sampling up to 7 Layers Parts Service
W. Müller USA, Agawam, MA More than 1,200 extrusion heads installed in North, Central and South America S18/35-80 P-PE, ReCo 3 S5/35-85 P-PE, CoEx 6 S1/160 RV-PE, CoEx 3 Accumulator
Presentation Topics Foam Blow Molding Existing Technologies Our Objective Pilot Project: Foaming of Preform Trilayer Co-Extrusion with Foam Trilayer Sequential Co-Extrusion with Foam
Foam Blow Molding Why? Foam Blow Molding is not a new technology Commercial application are not widespread Reasons for Foam Blow Molding Light-weighting Lower part weight while maintaining rigidity Increased rigidity without adding weight Thermal insulation Noise reduction (from airflow)
Foam Blow Molding Existing Technolgy... is based on continuous extrusion blow molding with chemical or physical blowing agents or a combination thereof. Chemical blowing agents are often unacceptable for food/beverage packaging and automotive applications. Physical blowing agents are preferred. uses nucleating agents to achieve a uniform microcellular structure. Adds cost
Foam Blow Molding Existing Technology... allows gas to escape to the surface causing open pores Not ideal for food and beverage packaging Not suitable for exhaust and fluid carrying ducts Can be solved with trilayer co-extrusion introduces blowing agents in the extruder barrel does not adequately control gas volume injected in each parison of a multi-parison extrusion head tries to make do with existing extrusion heads, seldom designed with flow channels to avoid pressure drop. not suitable for sequential foaming of a parison or a layer
Foam Blow Molding Our Overall Objective Develop a multi-parison trilayer extrusion head for discontinuous/sequential extrusion of a center foam layer with a controllable and consistently repeatable cellular structure in each parison without the use of nucleating agents. Explore potential applications in the industrial/automotive sector Apply expertise gained for applications in the packaging sector
Pilot Project: Foaming of Preform First Steps: Inject gas in the extrusion head instead of in extruder Produce a monolayer foamed preform with a consistently fine cellular structure Push out preform via an accumulator in preparation for sequential foam extrusion. Evaluate Impact of blowing agent on viscosity and melt temperature Length of mixing section Effect of gas pressure and compressor
Pilot Project: Foaming of Preform Equipment: S1/25 T-PE Extrusion Head
Pilot Project: Foaming of Preform Effect of Mixer Length and Gas Pressure (w/ PA) Picture 1 Picture 2 Picture 3 # of Mixing Elements 2 4 4 Melt Pressure Elbow 53 bar 103 bar 192 bar Gas Pressure 45 bar 105 bar 390 bar Melt Pressure Mixer Entry 37 bar 80 bar 171 bar
Pilot Project: Foaming of Preform First Results Nitrogen blowing agent is least costly, environmentally friendlier than CO 2 and suitable for many resins. Blowing agent reduces melt viscosity, material dependant; run with up to 50⁰F lower than normal melt temperatures. Suitable mixers are not commercially available, determined required minimum length of a static mixer Compressor must generate up to 600 bar / 8,700 PSI. The higher the pressure, the finer the cell structure. Flow channel must remain unchanged in size from point of gas injection to extrusion die. Avoid 90⁰ turns.
Pilot Project: Foaming of Preform Pressure Drop To avoid premature expansion, gas must be kept in solution in plastic melt from point of introduction to the bottom of the die Soda bottle example: Closed: -- Gas in solution Open: -- Cells are formed that grow as pressure drops
Trilayer Co-Extrusion with Foam Second Step Objectives: Build a trilayer head with accumulators for the extrusion of each layer Employ a dynamic mixer for dispersion of the blowing agent shortening the mixing section to approx. 1.5 x D Produce trilayer structures with foam only in the middle layer Shorten and optimize dimensions of flow channels for foam Produce a repeatedly fine cellular structure, without the use nucleating agents
Trilayer Co-Extrusion with Foam Layer Structure 1 2 3 1. Outer layer (more flexible) 2. Middle layer, continiuous or partially foamed 3. Inner layer (smooth)
Trilayer Co-Extrusion with Foam Equipment: WTC Extrusion Die 1 WTC Extrusion Die 2 Dynamic Mixer Drive Extruder 35/25D for Inner Layer Accumulator for Inner Layer S1/90 TT SeCo 3 Extrusion Tooling Extruder 40/25D for Foam Layer Accumulator for Foam Layer Shutoff for Foam Layer
Trilayer Co-Extrusion with Foam Equipment: Extruder 40/25D for Foam Layer Shutoff for Foam Layer Accumulator for Foam Layer Secondary Extruder 35/25D for Outer Layer Accumulator for Outer Layer Primary Extruder for Outer Layer Extrusion Tooling S1/90 TT SeCo 3 Dynamic Mixer Drive Extruder 35/25D for Inner Layer Accumulator for Inner Layer Ring Distributor
Trilayer Co-Extrusion with Foam Equipment: Servo-electric WTC S1/90 TT SeCo 3 on test stand Dynamic mixer
Trilayer Co-Extrusion with Foam Second Step Objectives (Cont d): Evaluate Potential weight reduction Gas injectors Foam layer shutoff Ability to start and stop foam and to position repeatedly
Trilayer Co-Extrusion with Foam Duct produced in trilayer continuous co-extrusion
Trilayer Co-Extrusion with Foam Duct produced in trilayer continuous co-extrusion Extruded preform, uninflated (approx. 8mm wall thickness) Blow molded, elongated cells (approx. 3mm wall thickness)
Trilayer Co-Extrusion with Foam Duct produced in trilayer continuous co-extrusion Repeatedly fine, uniform cellular structure Net weight reduced from 260 to 180 grams = 30% Solid outer and inner layer Smooth inner surface Noise from airflow reduced
Trilayer Co-Extrusion with Foam Gas Injector Conical Valve Pros: Opens under N 2 pressure Reliable, safe operation No contamination Cons: Injects large gas bubble Gas not homogenously dispersed via dynamic mixer
Trilayer Co-Extrusion with Foam Gas Injector Sintered Metal Sintered Metal Insert Pros: Pre-disperses gas through very small sintered insert (only 3.14 mm 2 ) Cons: Plastic melt penetrates pores when gas pressure drops and no gas flows. Clogs easily. OK for PE / PP.
Trilayer Co-Extrusion with Foam Gas Injector Combine advantages of both Compressor must meter a precise gas volume Gas must be injected in small controlled doses (x gram N 2 / y gram plastic) For example via oscillating gas jet with up to 5 cycles/s, pre-disperses gas
Trilayer Co-Extrusion with Foam Equipment: Dynamic Mixer Gas Injector Layer 3: Inner Layer 2: Foam Layer 1: Outer (via Ring Distributor) Extrusion Die 2, (opens both layer 2 & 3 now, separately in future) Extrusion Die 1 Mandrel
Trilayer Sequential Co-Extrusion Concept: Sequential Foam Blow Molding Non-foam Connecting Areas Inner Layer Foam Layer Outer Layer
Trilayer Sequential Co-Extrusion Next steps Acquired a new blow molding machine for the lab to move ahead with further developments Test system components Determine limitations Start marketing a sequential trilayer co-extrusion system by mid 2015 Develop a simple continuous trilayer co-extrusion system for consumer packaging applications.
Acknowledgments R&D by... Guido Knipp, Extrusion Head Design Engineer, W. Müller GmbH, Troisdorf, Germany Maik Hentschel, Owner, pro.f.i.t (pro future innovative technology), Bobeck, Germany For providing test materials, thanks to... Borealis (PP) Chevron Phillips (PPS) DuPont (PA) LyondellBassell (HDPE)
Acknowledgments Awards Dr. Reinold Hagen Award 2013, presented by the Dr. Reinhold Hagen Foundation at VDI Symposium Blasformen 2013, Baden Baden Innovation Award 2013, presented by Volksbank Bonn Rhein-Sieg eg
Foam Blow Molding THANK YOU! QUESTIONS?