co-extrusion blow molding
TRANSCRIPT
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
• 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
W. Müller USA, Agawam, MA
Foam Blow Molding • Existing Technologies • Our Objective
Pilot Project: Foaming of Preform Trilayer Co-Extrusion with Foam Trilayer Sequential Co-Extrusion with Foam
• Topics
Presentation
• 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)
• Why ?
Foam Blow Molding
• … 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
• Existing Technolgy ...
Foam Blow Molding
• … 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
• Existing Technology ...
Foam Blow Molding
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
• 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
• First Steps:
Pilot Project: Foaming of Preform
Pilot Project: Foaming of Preform
S1/25 T-PE Extrusion Head
• Equipment:
• 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
• Nitrogen blowing agent is least costly, environmentally friendlier than CO2 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.
• First Results
Pilot Project: Foaming of Preform
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
• Pressure Drop
Pilot Project: Foaming of Preform
• 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
• Second Step Objectives:
Trilayer Co-Extrusion with Foam
1 2 3
1. Outer layer (more flexible) 2. Middle layer, continiuous or partially foamed 3. Inner layer (smooth)
• Layer Structure
Trilayer Co-Extrusion with Foam
S1/90 TT SeCo 3
Trilayer Co-Extrusion with Foam
Extruder 40/25D for Foam Layer
Extruder 35/25D for Inner Layer
Extrusion Tooling
Shutoff for Foam Layer
WTC Extrusion Die 1 WTC
Extrusion Die 2
Dynamic Mixer Drive
Accumulator for Inner Layer
Accumulator for Foam Layer
• Equipment:
Trilayer Co-Extrusion with Foam
Extruder 40/25D for Foam Layer
Ring Distributor
Dynamic Mixer Drive Accumulator for
Foam Layer
• Equipment:
S1/90 TT SeCo 3
Extruder 35/25D for Inner Layer
Extrusion Tooling
Shutoff for Foam Layer
Accumulator for Inner Layer
Secondary Extruder 35/25D for Outer Layer Accumulator for Outer Layer Primary Extruder for Outer Layer
Trilayer Co-Extrusion with Foam
• Equipment:
S1/90 TT SeCo 3 on test stand Dynamic mixer
Servo-electric WTC
• Evaluate Potential weight reduction Gas injectors Foam layer shutoff Ability to start and stop foam and to position repeatedly
• Second Step Objectives (Cont‘d):
Trilayer Co-Extrusion with Foam
• Duct produced in trilayer continuous co-extrusion
Trilayer Co-Extrusion with Foam
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)
• Duct produced in trilayer continuous co-extrusion
Trilayer Co-Extrusion with Foam
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
• Gas Injector – Conical Valve
Trilayer Co-Extrusion with Foam
Pros: Opens under N2 pressure Reliable, safe operation No contamination
Cons: Injects large gas bubble Gas not homogenously
dispersed via dynamic mixer
• Gas Injector – Sintered Metal
Trilayer Co-Extrusion with Foam
Pros: Pre-disperses gas through
very small sintered insert (only 3.14 mm2)
Cons: Plastic melt penetrates pores
when gas pressure drops and no gas flows.
Clogs easily. OK for PE / PP.
Sintered Metal Insert
• Gas Injector – Combine advantages of both
Trilayer Co-Extrusion with Foam
• Compressor must meter a precise gas volume • Gas must be injected in small controlled doses
(x gram N2 / y gram plastic) For example via oscillating gas jet with up to 5 cycles/s,
pre-disperses gas
• Equipment:
Extrusion Die 2, (opens both layer 2 & 3 now, separately in future)
Extrusion Die 1
Gas Injector Dynamic Mixer
Mandrel
Trilayer Co-Extrusion with Foam
Layer 1: Outer (via Ring Distributor)
Layer 2: Foam
Layer 3: Inner
• Concept: Sequential Foam Blow Molding
Non-foam Connecting Areas
Inner Layer
Outer Layer
Layer
Foam
Trilayer Sequential Co-Extrusion
• Next steps
Trilayer Sequential Co-Extrusion
• 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
THANK YOU!
QUESTIONS?
Foam Blow Molding