The following is included in this e-tech newsletter:

  • Leistritz to exhibit wide ranging twin screw extrusion equipment at NPE 2012
  • Leistritz Pharmaceutical Extrusion Seminar to be held June 20-21, 2012
  • Technical paper: Melt Extrusion – Shaping Drug Delivery in the 21st Century
  • Twin screw tip:  Side stuffing of fillers/fibers
  • Upcoming exhibit/presentation schedule

Leistritz NPE 2012 preview

For free NPE 2012 guest passes see this link,

We will display wide ranging twin screw extrusion technologies at our NPE 2012 exhibit, booth #5975 West Hall, April 2-5, 2012 in Orlando, FL.  A partial list of what will be exhibited includes:

ZSE-50 MAXX twin screw extruder configured for reactive and direct extrusion:  A ZSE-50 MAXX twin screw extruder with the following features will be displayed:

  • Screw set displayed outside the extruder, 51.2 diameter screws and 1.66 OD/ID ratio, segmented screw elements assembled on asymmetrical splined shafts
  • 400 HP motor/1200 screws rpm
  • 52/1 L/D process section with provision for vacuum venting, liquid injection, and downstream side stuffer
  • Unique modular barrel section design with high-wattage cartridge heaters and increased coolant flow that improves heat transfer capabilities
  • Side stuffer for downstream feeding of fillers and fibers into the process melt stream
  • Front end assembly with filtration, gear pump and flex-lip sheeting die

ZSE-50 MAXX to be displayed @ NPE 2012


ZSE-40 MAXX with new swing-gate strand die assembly:  The ZSE-40 MAXX co-rotating twin screw extruder configured for masterbatch and custom compounding will be displayed.  The ZSE-40 MAXX will feature a newly designed LSSK model swing gate strand die assembly with a streamlined transition from the extruder to an oval breaker plate and then to a front-end die plate.  Screens are accessed by a swing bolt assembly, which facilitates removal of the breaker plate and die for cleaning.  A replaceable multi-strand die face plate is integrated into the design. 

LSSK swing gate die attached to ZSE-40 MAXX

Lab-scale twin screw extruder display area:  The following lab-scale twin screw extruder models will be displayed:

  • nano-16 twin screw extruder system:  This unique twin screw extruder features a 1.2 OD/ID ratio and 1 cc/dia. free volume that facilitates processing as little as 20-100 gram batches.  A patented plunger feeder is used that pushes materials into the feed barrel from underneath.  The nano-16 will also utilize a TSCS™ PC-based data acquisition and control package.

nano-16 process section with top, bottom and liquid feed

  • ZSE-18 twin screw extruder: Available with 1200+ screws RPM, the ZSE-18 has 18 mm diameter screws with a 3-½ mm flight depth.  Screws are assembled on high torque splined shafts, and the unit is caster mounted.  A side stuffer will be integrated into the system for downstream addition of fillers and fibers.  The unit will be equipped with an Allen-Bradley PLC and PanelView+ touch-screen for control, data acquisition and trending.
  • Micro-27 modular, multi-mode twin screw extruder:  The Micro-27 twin screw extruder system offers a cost effective alternative for lab-scale installations. A mode convertible gearbox allows the Micro-27 to operate in both co-rotation and counterrotation, a feature that has helped make it the most popular lab-scale twin screw extruder in North America.


At the co-located ANTEC 2012 SPE annual technical conference, Bert Elliott (Leistritz Engineering Manager) will give a presentation entitled Tips for Optimizing Twin-Screw Extrusion.

For additional information on the Leistritz NPE 2012 exhibit, contact Sarah Scovens, Leistritz Marketing Assistant, at 908/685-2333 x614 or














Leistritz will host the seventh annual Pharmaceutical Extrusion Seminar on June 20-21, 2012.  This program combines classroom sessions with “hands-on” twin screw extrusion demonstrations. In addition to Leistritz staff, outside industry experts will present an overview of the latest extrusion developments that are effecting the pharmaceutical industry. 
A preliminary list of topics includes:

  • Twin screw extrusion theory and design
  • Advantages of continuous extrusion as compared to batch processes
  • Staging of unit operations in an extruder to manufacture a dosage form
  • Upstream considerations for feeding, material handling and containment
  • Scale-up of the extrusion process from laboratory to production
  • Downstream systems for pelletizing, spheronization, films and transdermal products
  • Cleaning and maintenance of extrusion equipment in a GMP environment
  • Equipment and process validation practices and documentation
  • Control issues pertaining to CFR 21 part 11 compliance
  • New emerging extrusion technologies being applied to hot melt extrusion
  • Selection of excipients for processing API’s

“Hands-on” demonstrations at Leistritz process laboratory will include:

  • nano-16 twin screw extrusion system processing 50 gram batch samples
  • Film/lamination extrusion system for transdermal or dissolvable film dosage applications
  • Micro-pelletization extrusion system producing ½ mm pellets for direct capsule filling
  • Wet-granulation extrusion technology for high potency/strength tablets
  • Extrusion system for compounding heat/shear sensitive API’s via hot melt extrusion

Classroom sessions are held at the Holiday Inn Select in Clinton, NJ, and extrusion demonstrations at the nearby Leistritz Process Laboratory in Somerville, NJ.

Cost:  Early registration, if received by May 18, 2012, is $820; after this date cost is $920.

For program details see this link:

To register for this program contact Sarah Scovens at 908/685-2333, X614 or e-mail

To download a registration form for the Leistritz Pharmaceutical Extrusion Seminar ...

TECHNICAL PAPER: Melt Extrusion – Shaping Drug Delivery in the 21st Century

Melt extrusion has been an established industrial manufacturing technology for over 50 years in the plastics (and food industries) having been applied to the production of everything from layered trash bags, to space shuttle parts, to synthetic wine corks. However it is only in the last decade that it has emerged as a viable platform for pharmaceutical development.  Today, applications of melt extrusion for pharmaceutical production range from controlled release systems to oral bioavailability enhancement and show potential for small molecules and therapeutic peptides.  Pioneering development activities in the late 1980’s and 1990’s spawned the generation of several amorphous compositions, including Sporanox®, Prograf® and Rezulin®, leading to the general acceptance of solid dispersions.  Driven by the continuing development of solubility limited new chemical entities and industrial aims at continuous commercial manufacturing, melt extrusion has gained acceptance for improving bioavailability and increasing manufacturing efficiencies.  The emergence of novel drug delivery systems and routes of administration have also allowed for the expansion of melt extrusion applications within the pharmaceutical industry.  This review presents an overview of the processing technology and also four major areas of application: bioavailability enhancement; oral controlled release; melt granulation; and the production of advanced controlled release dosage forms.

To download this paper in its’ entirety ...

TECHNICAL TIP:  Side stuffing of powders into a twin screw extruder

Side stuffing of fillers and fibers is commonly used methodology to introduce high-levels of inert materials into the melt stream in a twin screw extruder after plastication.  A loss-in-weight feeder meters the materials to the side stuffer with co-rotating intermeshing twin screws that “push” the fillers into a figure 8 opening in the side of a barrel section. 

The free volume geometry (and rpms) of the side stuffer screws and/or the twin screw extruder screws can be rate limiting factors.   Oftentimes an off-line test of the side stuffer (with the stuffer unbolted from the extruder, discharging into a drum) will feed a high rate of material, but when the stuffer is attached to the extruder, capacity is often limited by extruder screws and/or entrapped air/flashing moisture.  Venting capacities must allow entrapped air and volatiles to “escape” the process section. 

Example air flow in a twin screw extruder

It is also generally a best practice to situate the loss-in-weight feeder as close to the side stuffer feed throat as possible to help maintain the feed density of the fillers.  In terms of extruder screw design, it is best to have flighted elements with a long flight advance at the stuffer location, extending 2 to 4 L/D downstream of the stuffer to forward the melt in the extruder and allow the maximum free volume for the filler to enter. If the screw design causes any “dam-up” of material downstream of the stuffer, this will severely limit the attainable rate and/or filler %. 

2 Loss-in-weight feeders and 2 side stuffers (note relief vents)

Important side stuffing factors

Back-venting: The object of venting is to allow air to escape easily, while preventing large amounts of filler being lost out the vent. The best configuration for this is to have a top vent in the barrel immediately upstream of the side stuffing barrel. Sometimes a small ½-slot vent insert can also be used in the top of the side stuffing barrel

Feeder drop height: The feeder should be positioned as close as possible above the side stuffer, to minimize the drop height. If a fluffy material is allowed to drop through air, it becomes aerated to the point where the bulk density is significantly reduced. This can often limits the throughput rate of the entire line.

Feeder agitation type: Make sure the agitator in the filler feeder is not aerating the material, reducing the bulk density. Many feeder manufacturers have special agitator designs for powders, to preserve bulk density.

Make sure stuffer hopper is vented: Along with the filler, the stuffer also introduces air into the extruder. If you have an open top on the side stuffer chute, then venting is already taken care of. If you have a solid cover on the chute with a round stubup and flex connector to the feeder, it’s important to also have a vent opening.

Ground all hoppers/chutes to drain static electricity: Some materials generate static electricity from friction. If static is present, it can cause powder to cling to the inside surfaces of hoppers and chutes, leading to problems such as caking. If you think this is happening, an easy fix is to run a ground wire (10 gauge wire is recommended) from the chute to a ground on the machine frame.

Compressed air blaster: If caking in the drop chute to side stuffer persists, sometimes a special solution is needed. Hopper vibrators can be used, but are tricky to size and mount. Another device which can be used is a “blaster”. This consists of air jet nozzles strategically placed within the wall of the chute, directed to break up any cakes before they get too large. The air jets get connected to a solenoid valve using poly-tubing, and the solenoid valve is actuated by a repeat cycle timer to set both the blast period and dwell time in between blasts. Upstream of the solenoid valve a small air accumulator tank is specified to provide a sharp pulse of air.

Air blaster drop chute for side stuffer









Industry events where Leistritz will participate

  • NatureWorks™ Innovation Takes Root – 2/20-22/12, Orlando, FL; presentation entitled “Comparing twin screw extrusion systems to process PLA compounds more efficiently”
  • International Polyolefins Conference – 2/26-29/12, Houston, TX; 10’ display
  • SPE Polymer Nanocomposites RETEC – 3/5-7/12, Bethlehem, PA; sponsor
  • NPE & ANTEC 2012 – 4/1-5/12 – Orlando, FL; 2000 sq/ft display (see article above)
  • Polymer Reaction Engineering & Conference – 5/6-10/12, Cancun, Mexico; presentation entitled “Melt extrusion: shaping the pharmaceutical industry in the 21st century”
  • SPE Bioplastics Conference – 5/16-18/12, Seattle, WA; presentation entitled “Processing of bioplastics via twin screw extrusion”
  • PPS Americas Conference 2012, 5/21-24/12, Niagara Falls, Canada; sponsor / keynote presentation by Charlie Martin entitled “Twin screw extrusion systems to process bioplastics”
  • Leistritz Pharmaceutical Extrusion Seminar – 6/20-21/12, Somerville, NJ
  • Controlled Release Society – 7/15-18/12, Quebec City, Canada; poster session relating to foamed dosage forms
  • SPE Color RETEC 2012 Conference – 10/1-2/12, Louisville, KY; tabletop display
  • AAPS 2012 – 10/14-18/12, Chicago, IL; 20’ display
  • Leistritz Twin Screw Extrusion Workshop – 11/28-29/12, Somerville, NJ

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169 Meister Ave.
Somerville, NJ, 08876, USA
ph: 908/685-2333