Finally, the First Commercial Thermoformed Bottles

By Jan H. Schut

For decades an incredible amount of inventiveness has been thrown at the challenge of trying to thermoform bottles. The idea was that making bottles out of thin sheet would save 20% to 50% in materials over extrusion blow molding with lower energy, higher output, and easy material and color changes—including barrier—just by changing a roll. Over the years probably a half dozen ingenious technologies were patented, built, announced, and some even exhibited at major trade shows, without ultimately making a commercial bottle.

The string of patents on thermoformed bottles makes fascinating reading. Some are from well-known names in packaging like Hartmut Klocke of the Klocke Group, who applied for a patent on “Thermoforming Packaging” of bottle-like containers in 1981 (German Pat. DE 8135111U1). Others are from relatively unknown inventors like Rudolf Holzleitner, principal of Hol-Pack Verpackungen, Piberbach, Austria (www.hol-pack.at), a processor of PC bottles.

Holzleitner’s patented technology (European Pat. # EP 2091829) resembles twin-sheet thermoforming, but for disposable bottles up to 1.25 liters. One side of the bottle is deep drawn, including the bottle spout. The other side could be flat or half round. Building bottles with unmatched halves opens wonderful design possibilities. The seam between halves could be vertical or horizontal, making two-colored bottles possible horizontally or vertically and even multi-chambered bottles or packs of detachable bottles. Holzleitner got some support from the Austria Wirtschaftsservice Technology and Innovation in Vienna, but not enough to launch the technology, so eventually he let it lapse.

Hol-Pack in Austria invented an ingenious twin-sheet forming technology for up to 1.25 liter bottles. Bottle halves could be formed either horizontally or vertically with novel design options. But the technology failed to attract investors and eventually was dropped.

Hol-Pack in Austria invented an ingenious twin-sheet forming technology for up to 1.25 liter bottles. Bottle halves could be formed either horizontally or vertically with novel design options. But the technology failed to attract investors and eventually was dropped.

Patents for thermoforming large bottles like Holzleitner’s are unusual. The target for most thermoformed bottle technology has been for single portion yogurt and juice drinks as an extension of form-fill-seal machinery. Erca Formseal S.A. in Cortaboeuf, France (www.oystar-group.com), part of Oystar Group in Germany, announced “Open Mold” thermoforming of bottles in 2003, showing it for the first time at the Emballage show in Paris (www.all4pack.fr) in 2010. The patented process (U.S. Pat. # 7585453) reportedly can make 6000-18,000 standard yogurt cups/hour or 9000-16,800 thermoformed bottles/hour with walls 0.7 mm thick for material savings of 20%. The patent describes “a plastic stretching device to reduce the plastic bottom web thickness in the unused thermoforming areas.” But the technology wasn’t in fact material efficient, Erca says, and isn’t being offered now, though research is still going on.

Oystar Erca in France, a maker of form-fill-seal machines, introduced “Open Mold” thermoforming over a decade ago to form small portion yogurt bottles. But the technology wasn’t material efficient and was never commercialized.

Oystar Erca in France, a maker of form-fill-seal machines, introduced “Open Mold” thermoforming over a decade ago to form small portion yogurt bottles. But the technology wasn’t material efficient and was never commercialized.

In 2008, a builder of thermoforming and form-fill-seal machines, Illig Maschinenbau GmbH in Heilbronn, Germany (www.illig.de), got into the market with Bottleform technology, which Illig demonstrated for the first time at Interpack in Dusseldorf, Germany (www.interpack.com) in 2011. A Bottleform BF 70 machine reportedly can make up to 25,000 x 200-ml bottles or cups/hour depending on shape and size, using sheet from 0.4 to 2 mm thick. Bottles can have steep undercuts for necks or even pedestal shapes. The technology can mold partially threaded necks, but the necks couldn’t withstand the torque of screw caps, Illig says, so bottles would be foil sealed and shrink-sleeve labeled. Illig’s process is now also called “Open Mold Forming” because it can thermoform standard cups as well as bottles.

Illig’s technology is a proprietary combination of vacuum forming, pressured sterile air, and plug assist with tooling undercuts to form necks. The BF 70 machine can have up to 20 cavities and use 68% of 26-inch-wide sheet for bottles or for cups. Depth of draw can be up to 5.7 inches with 2:1 draw ratio for bottles from 50 to 200 ml. The machines could be all stainless steel for use with clean, ultra clean or aseptic fillers for Federal Drug Administration approval on food filling lines. Illig’s “Open Mold” forming recently added punch-in-place bottle removal for greater accuracy of bottle lips. Illig hasn’t sold the technology commercially, but says it is in discussion with packaging companies both in Europe and in the U.S.

In 2008 Illig in Germany launched a thermoforming machine for bottles as well as cups, now called “open mold” forming. It combines vacuum forming, pressured air, plug assist and steep undercuts for bottle necks. Illig is in discussions with customers, but hasn’t sold it commercially.

In 2008 Illig in Germany launched a thermoforming machine for bottles as well as cups, now called “open mold” forming. It combines vacuum forming, pressured air, plug assist and steep undercuts for bottle necks. Illig is in discussions with customers, but hasn’t sold it commercially.

FINALLY COMMERCIAL!

Against this backdrop of highly imaginative but ultimately not commercialized R&D, a small startup company in France actually patented, built, and sold machines for what are believed to be the first commercial thermoformed bottles. Agami Technologies in Trappes, France (www.agami-tech.fr), which started in 2009, developed patented film-to-bottle machinery called Roll ‘N Blow (European Pat. # EP 2321113), which doesn’t use tooling undercuts and reportedly saves 30%-50% in material over extrusion blow molding.

The process starts with thin sheet for thermoforming and slits it in the machine direction into strips. The strips are shaped around blow air pipes into cylinders and welded along the open seam to make tubes. Tubes are heated and blown into bottle cavities at low pressure (under 6 bars) and under 150 °C. Because Agami forms bottles from a continuous tube of sheet, not by deep drawing flat sheet, bottle height isn’t limited, and no undercuts are needed. The process can potentially use standard blow mold tooling if the size is right.

The technology is used commercially to make 50-300 ml bottles at 7000-20,000 bottles/hour depending on size and shape, but it could make up to 500 ml bottles, Serac says. Bottles can have foil lids or screw caps and are shrink labeled. The film can also be preprinted before it’s made into bottles.

Serac in France bought start up Agami’s technology to thermoform bottles out of thin sheet. Agami first slits the sheet into strips, and then rolls the strips into tubes, which are heated and blown into bottle cavities. Four machines have been sold for commercial production and one for R&D.

Serac in France bought start up Agami’s technology to thermoform bottles out of thin sheet. Agami first slits the sheet into strips, and then rolls the strips into tubes, which are heated and blown into bottle cavities. Four machines have been sold for commercial production and one for R&D.

Serac Group SAS in La Ferte Bernard, France (www.serac-group.com), a maker of filling and capping machines, initially bought 10% of Agami along with worldwide distributions rights to the machines, which Serac introduced at Interpack in 2011. Serac has sold five machines since, one with two cavities to a U.S. firm for R&D, two machines with four cavities for commercial production in Europe making portion yogurt bottles, and two machines with six cavities, which are being built for a European customer for full production of yogurt bottles. Bottles are made commercially from PS and PP sheet. They could presumably be made from HDPE and PLA sheet too, but these haven’t been tested yet. Six months ago Serac acquired 100% of Agami and plans to introduce the technology for the first time in the U.S. at NPE (www.npe.org) in Orlando, FL, next March.

Two of Serac’s Agami machines are in commercial production in Europe thermoforming bottles in four cavities out of PP and PS sheet for portion yogurt drinks. In the first station, sheet is made into tubes, which are blown into bottles. In the second station bottles are filled and sealed.

Two of Serac’s Agami machines are in commercial production in Europe thermoforming bottles in four cavities out of PP and PS sheet for portion yogurt drinks. In the first station, sheet is made into tubes, which are blown into bottles. In the second station bottles are filled and sealed.

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First Melting with a Flighted Barrel!

By Jan H. Schut

As commercial interest in micro injection molding picks up for high-precision, speck-sized medical and electronic parts, so is R&D. Probably the most unusual development in decades is a novel one-piece melting and injection unit for micro molding, which melts with flights in a stationary barrel, not the rotating shaft. The idea behind the new technology is to reduce melt volume in the barrel, residence time, and risk of thermal degradation.

The technology was invented at the Institute for Plastic Processing (IKV) at RWTH Aachen University in Germany (www.ikv.rwth-aachen.de) and presented for the first time outside of Germany at the SPE’s ANTEC conference in Las Vegas last April (www.4spe.org) by Torben Fischer, a research assistant and PhD candidate at the IKV, and Christian Hopmann, head of the IKV. The technology was first presented at the 29th Polymer Processing Society conference in Nuremberg, Germany (www.pps29.com) in 2013.

Their ANTEC paper describes an “Innovative Plasticizing Method for Micro Injection Molding,” which is a colossal understatement. Plasticizing is done by an “inverse screw” with flights in a stationary barrel, not on the rotor. It’s believed to be the first plastic processing of any kind that melts with stationary flights, not turning ones. The fixed barrel flights correspond to feeding, compression, and metering zones in a conventional screw. Barrel flights are 4 mm deep in the feed zone tapering to 2 mm in the metering zone. So they are nothing like the shallow regular grooves used in the feed sections of some extruders to increase throughput. The 160-mm-long “inverse screw” barrel has an 80-mm feed zone, 48-mm compression zone, and 32-mm metering zone with three temperature zones for compression, metering, and the nozzle.

The IKV in Germany invented an unusual new plasticizing technology with flights built into a stationary barrel and a smooth rotating shaft. The barrel was 3-D printed in two halves with flights that correspond to feeding, compression, and metering zones in a conventional screw.

The IKV in Germany invented an unusual new plasticizing technology with flights built into a stationary barrel and a smooth rotating shaft. The barrel was 3-D printed in two halves with flights that correspond to feeding, compression, and metering zones in a conventional screw.

The flighted barrel allows a much smaller diameter rotor to be used. The IKV has tested shafts as small as 8 mm diameter, whereas 14-15 mm diameters are typically the smallest used in conventional micro injection molding machines (or 12 mm with special micro granules). With a 15-mm diameter screw, a typical injection stroke of three diameters in length makes a shot of roughly 18,000 cubic mm of material—far more than needed for micro injection molded parts. An 8-mm shaft reduces shot volume to 1,200 cubic mm, the IKV presentation says—15 times less.

The “inverse screw” technology is also unusual because it’s a single machine unit with one rotating, reciprocating shaft that melts plastic and feeds molds. Micro injection molding is conventionally done in two units-one melting, one feeding. The Babyplast micro injection molder, built by Chronoplast S.L. in Barcelona since the mid-1980s and distributed by Rambaldi Co. I.T. Srl, Molteno, Lecco, Italy (www.babyplast.com), for example, uses two smooth-bored plungers. The first melts plastic, the second meters it into molds. Other commercial micro-injection molding machines typically use either screw-to-plunger or screw-to-screw processes.

 

BUILDING THE FIRST ‘INVERTED SCREW’

The IKV’s patent-applied-for plasticizing method (German Pat. Applic. # DE102009057729) was invented by Thomas Kamps, a previous doctoral candidate at the IKV. Kamps’s dissertation was actually on vibration in micro molding, presented as “Heating and Plasticizing Thermoplastics with Ultrasound for Micro Injection Molding” (see blog May 30, 2010). In the course of his thesis work, Kamps hypothesized that plastic melting could occur whether flights rotate against a smooth barrel or vice versa.

To prove the concept Kamps built a simple hand-cranked aluminum model and tested it with PP, which showed that it didn’t matter where the movement occurred. Research on the concept was subsequently funded for three years starting in 2011 by the Deutsche Forschungsgemeinschaft, Bonn, Germany (www.dfg.de), together with Arburg GmbH, Lossburg, Germany (www.arburg.com). Fischer did the practical work and built the first motorized test rig as part of his dissertation.

IKV doctoral student Torben Fischer built the first motorized “inverse screw” test rig with a frame and socket construction, allowing different barrel flight, feeding, and shaft geometries to be tested and optimized.

IKV doctoral student Torben Fischer built the first motorized “inverse screw” test rig with a frame and socket construction, allowing different barrel flight, feeding, and shaft geometries to be tested and optimized.

Because they were putting “screw flights” into a barrel for the first time, they built the barrel in two halves out of hardened stainless steel (X5CrNiCuNb16-4), using 3-D laser sintering from BKL Lasertechnik GmbH, Roedental, Germany (www.bkl-lasertechnik.de). The “inverse screw” test unit was driven by a small synchronous torque motor from Beckhoff Automation GmbH, Verl, Germany (www.beckhoff.com), and set up to run continuously like an extruder. Fischer’s ANTEC presentation describes tests done with this initial motorized test rig using PP, PMMA, and POM. The test rig was designed so they could try different shapes and surfaces for the flights and shaft.

They polished the barrel flights, but left the shaft unpolished, just as a conventional screw has polished flights and an unpolished barrel to prevent melt slippage. But there were feeding and pressure issues at first. So the IKV tested also knurled, and lengthwise grooved shafts. Initially no plunger geometries could feed PP and PMMA, which had larger pellets. Pellets bridged in the feed zone of the barrel and wedged into the longitudinal grooves in the shaft. The grooved shaft, however, could process POM, which came in smaller pellet size.

The IKV tested a variety of shaft and barrel feeding geometries with the “inverse screw” and found that a longitudinally grooved shaft and long parallel feed zone were needed to move pellets along the fixed barrel flights. Pellets also had to be small (2.5 mm) in order not to jam.

The IKV tested a variety of shaft and barrel feeding geometries with the “inverse screw” and found that a longitudinally grooved shaft and long parallel feed zone were needed to move pellets along the fixed barrel flights. Pellets also had to be small (2.5 mm) in order not to jam.

The unit also didn’t build up enough pressure before the nozzle for injection. POM melted properly in the feed zone, but the melt still contained air bubbles at the end of the metering zone. So the IKV did more nozzle development and was able to build enough head pressure for injection molding.

The grooved shaft also showed excessive wear on the groove over the feed section. So the feed opening was optimized to prevent jamming by “applying different feed geometries to the upper half barrel shell and analyzing the feed behavior of different pellets,” IKV’s Fischer explains. The feed opening described in the ANTEC paper is the length of one pitch of the barrel flights (11.2 mm). Ultimately the feed opening became three pitches long (33.6 mm). The feed opening is also parallel to the shaft, whereas in conventional injection molding the feed opening is cross-wise to the screw.

Arburg has since built two industrial “inverse screw” prototype molding machines based on its electric Allrounder 270A injection molding machine, the first reciprocating versions of the “inverse screw.” One was given to the IKV in February 2014, officially presented during the IKV’s technology colloquium in March. The other is at Arburg. These prototypes can process PP, PMMA, and POM, provided pellets are small enough (roughly 2.5 mm). The next step now is for the IKV to test Arburg’s industrial prototype against conventional two-step micro injection molding machines to benchmark its performance. The “inverse screw” technology could also potentially be used to melt pellets for 3D printing and is so compact that it would be small enough for desktop 3D printers (see blog Oct. 27, 2014).

Arburg built two industrial prototype reciprocating “inverse screw” machines based on its electric Allrounder 270A injection molding machine. Arbur’s Eduard Duffner presented one to Christian Hopmann, head of the IKV, last March for benchmarking and further R&D.

Arburg built two industrial prototype reciprocating “inverse screw” machines based on its electric Allrounder 270A injection molding machine. Arbur’s Eduard Duffner presented one to Christian Hopmann, head of the IKV, last March for benchmarking and further R&D.

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Micro Extrusion for the Masses

By Jan H. Schut

There’s a new kind of “micro extruder” out there these days. Micro extruders used to mean the smallest size of conventional extruders with screw diameters from 58 to ½ inch for pellet-fed lab models down to ¼ inch for a powder-fed lab model from Randcastle Extrusion Systems Inc., Cedar Grove, NJ (www.randcastle.com), which is probably the smallest.

The new so called micro extruders are an unusual geek product – inexpensive desk top 3D printers, fed by plastic filament from a spool and designed for the broadest possible use. Full sized 3D printers have been around for over 25 years, but they’re large expensive machines bought or leased by mold makers, prototyping service bureaus, and large companies that produce durable products to make prototypes, quick molds, jigs and fixtures for product development and some end use parts for aerospace.

Small desk top 3D printers, also known as micro extruders, are an emerging development since 2009 when an early patent from Stratasys Ltd., Eden Prairie, MN (www.stratasys.com), expired (U.S. Pat. # 5121329). Stratasys developed large industrial “fused deposition” modeling machines using filament, but never built the desktop model. Most new desktop 3D printers, however, are based on Stratasys’ concept for a small programmable filament laying machine. The new machines developed rapidly, many funded over the web by small investors and have become so inexpensive that any business, architect, or designer could afford one. There are supposedly even some home users.

In January 2012, Makerbot Industries LLC, Brooklyn, NY (www.makerbot.com), launched one of the first inexpensive commercial micro extruders, the second generation Replicator for $1,999 with 11.2 x 6.1 x 6 in. build space and 100-micron layer resolution. Stratasys bought Makerbot in 2013. Replicator is now on its fifth generation, and there’s a Replicator Mini for only $1,375 with 5.9 x 5.9 x 5.9 in. build space and 80-micron resolution.

In 2009 3D Systems Inc., Rock Hill, SC (www.3dsystems.com), which builds large 3D printers using laser sintering, acquired assets of Desktop Factory Inc. from Idealab, Pasadena, CA (www.idealab.com). Desktop Factory developed technology to build parts by sintering powdered nylon using a halogen lamp, not laser, but never commercialized the machine. In 2010, 3D Systems also bought Bits from Bytes Ltd., which grew out of the University of Bath in the U.K. (www.bath.ac.uk), and built filament-type desktop 3D printers. Then in January 2012, 3D Systems launched its Cube 3D printer for $1,299, based on filament, not sintering, and in June this year launched Cube3 with 6 x 6 x 6 in. build space for $999.

A wave of over 100 small, inexpensive desktop “micro extruders” appeared after Stratasys’ patent on a compact method for making 3D objects expired in 2009. Makerbot’s Replicator2 was introduced in 2012 for $1,999; Zeepro’s Zim launched in 2013 for only $599.

A wave of over 100 small, inexpensive desktop “micro extruders” appeared after Stratasys’ patent on a compact method for making 3D objects expired in 2009. Makerbot’s Replicator2 was introduced in 2012 for $1,999; Zeepro’s Zim launched in 2013 for only $599.

In October 2013, Zeepro Inc., Stamford, CT (www.zeepro.com), introduced the Zim micro extruder for only $599 with 5.9 x 5.9 x 5.9 in. build space, 80-micron layer resolution, and two print heads. C Enterprise (UK) Ltd., Portishead, Bristol, U.K. (www.cel-robox.com), is developing the CEL-Robox, priced at UK 700 pounds ($910) with 8.3 x 5.9 x 3.9 in. build space, 20-micron layer resolution, and two print heads. Robox and Zim intend their dual print heads potentially to make complex shapes with overhangs using a structural polymer and a sacrificial polymer, which can be washed away later like HIPS, which dissolves in limonene, or PVA, which dissolves in water. 3D Systems’ latest CubePro, introduced in June, has three print heads. Over 100 more desktop 3D printers are available or under development, mostly in China.

BUT ARE THEY EXTRUDERS?

These micro extruders don’t have much in common with conventional extruders. Instead of requiring operators with years of plastics experience, these micro extruders require no plastics experience at all. C Enterprise boasts in its literature that a 5-year-old will be able to operate its Robox. Nor do makers of desktop micro extruders describe how they melt plastic. Stratasys’ patent describes “ratchet teeth” that pull plastic filament into a supply chamber in the print head, where the filament is melted at controlled temperature by an electric cartridge heater. The patent compares the process to a hot glue gun. Colors are changed by changing the print head.

Only one micro extruder, called David (as in Goliath), under development by Sculptify LLC, Columbus, OH (www.sculptify.com), will use lower cost pellets, not filaments. There are only two other full sized 3D printers that use pellets, so David will be unusual among 3D printers of any size. David presumably melts pellets with some kind of screw, though the literature doesn’t say. The hopper holds 1 ¼ lb. of pellets and the “extruder” goes up to 626 °F, an astonishing temperature for a desktop model. Build space is 7.8 x 8.6 x 7.3 in. with 100-micron layer resolution. Head positioning accuracy is described as 8 microns on the x- and y- axes and 3 microns on the z-axis.

One micro extruder model, ‘David’ from Sculptify, may actually use a screw to melt plastic. It’s the only micro extruder that takes pellets, which are less expensive than filaments. David will also be able to use a wide range of plastics, including wood filled composites.

One micro extruder model, ‘David’ from Sculptify, may actually use a screw to melt plastic. It’s the only micro extruder that takes pellets, which are less expensive than filaments. David will also be able to use a wide range of plastics, including wood filled composites.

Typically micro extruder print heads are moved in x, y, z directions by two or three stepper motors, programmed to follow a CAD design and deposit a thin layer of plastic to form a simple part. Their biggest limitation is accuracy, which doesn’t mean accurate layer thickness, but accurate positioning of the print head. Polar 3D LLC, Cincinnati, OH (www.polar3d.com), is developing a micro extruder model with a stationary print head and moving base on a turn table, hoping to improve accuracy. Polar 3D’s printer, which is being beta tested now, will cost $799 with 12.8 x 8 x 14.8 in. build area.

PLA is the preferred material for desktop 3D printing because of its low processing and printing temperature, typically between 390 °F and 450 °F, whereas ABS is printed at 450 F and higher. PLA printing has low odor (a slight sweet smell), where ABS gives off a stronger styrenic smell. Some desktop micro extruders also process ABS, but they require a heated base or build chamber to avoid warping as a part builds and cools, which adds cost. Pirate3D Inc., Palo Alto, CA (www.pirate3d.com), introduced the Buccaneer micro extruder in April this year for only $347 with 5.7 x 5 x 5.9 in. build space and 50-mm resolution, which sounds great except that Pirate3D told investors Buccaneer would use PLA and ABS, but it doesn’t.

New durable filament materials are being introduced all the time. In the New Technology Forum on 3D printing at the Society of Plastics Engineers ANTEC 2014 conference last April, PolyOne Corp, Avon Lake, OH (www.polyone.com), reported on advanced materials for additive manufacturing including glass and carbon fiber composites in engineering polymers. These materials target large 3D printers, which can process ABS, PA 12, PC/ABS, PC, PEI, and PPSU filaments in addition to PLA. Desk top models don’t typically have high heat capabilities, but some new models will. Robox’s components are designed to use nylon and PC as well as PLA. 3D Systems also recently added nylon filament for the Cube and CubePro and says it sees a surge of interest in consumer and commercial use.

NatureWorks LLC, Minnetonka, MN (www.natureworksllc.com), is now developing durable PLA grades for 3D printing, based on existing crystalline formulations for injection molding. “Preliminary results show that these new grades match or exceed the toughness and heat resistance of ABS along with PLA’s traditional printing performance,” says Daniel Sawyer, global leader of new business at NatureWorks, who will present “Innovating with Ingeo Biopolymer for 3D Printing” for the first time at an Upper Midwest SPE Minitech at Century College, White Bear Lake, MN, Nov. 11 (www.uppermidwestspe.org/events.htm).

United Nude shoe stores in New York and London designed their high-fashion “Float” shoes to be made to order in 3D Systems’ Cube or CubePro printers either in the store or at home. Customers choose their size and color combination, and print the shoes out of ABS.

United Nude shoe stores in New York and London designed their high-fashion “Float” shoes to be made to order in 3D Systems’ Cube or CubePro printers either in the store or at home. Customers choose their size and color combination, and print the shoes out of ABS.

Micro extruders are so new that even their most optimistic creators haven’t a clue what they’ll end up being used for. Most are pictured making things like simple trinkets and chess pieces. But it would be a mistake to dismiss them as toys. Sales of 3D micro extruders are growing rapidly, and they’re processing real plastic. In August United Nude shoe stores in New York (www.unitednude.com) launched a line of custom high-fashion shoes made of ABS, called “Float.” Customers build their shoes in the store or at home on Cube or CubePro printers, choosing their own size and color combination.

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Waiting for Bio PBS

By Jan H. Schut

Whatever happened to bio-based poly(butylene succinate)? Bio PBS, based on two new bio monomers, was supposed to be fully commercial by now. PBS is a low molecular weight, biodegradable polyester, which decomposes completely into CO2 and water and is often compared to LDPE or PP. It’s already made commercially from 50/50 petro-based succinic acid and 1,4 butanediol, but the petro route is expensive, so growth is limited.

The bio version is off to a slow start because no one so far has built large scale fermenters for the bio monomers. Five production partnerships were set up 6-8 years ago to ferment bio succinic acid and/or bio BDO, but so far they have built only semi-works plants. Three operate fermenters with combined capacity of only 74 million lb/year of bio succinic acid. A fourth fermenter starts next year with capacity for another 60 million lb/year of bio succinic acid, the biggest so far. A fifth company has technology to ferment bio BDO directly and has licensed it to two large chemical companies, which have done full-scale trials, but neither is in production. Bio BDO can also be made by purifying bio succinic acid.

Several Japanese and Korean companies have made small amounts of petro PBS for years. Showa Denko K.K., Tokyo (www.sdk.co.jp), commercialized Bionolle in the 1990s, developing automotive compounds. Mitsubishi Chemical Corp., Tokyo (www.mitsubishichem-hd.co.jp), introduced GS Pla in 2003 for biodegradable agricultural sheet and film and automotive compounds. IRe Chemical Ltd., Seoul (www.irechem.en.ec21.com), makes EnPol for biodegradable fish nets; and SK Chemicals Co. Ltd., Gyeonggi-do (wwwskchemicals.com), makes Skygreen.

PBS, which is currently made from petro chemicals, is expensive, so it’s used mostly for niches requiring complete degradability like single use food service items, fish nets, and mulch film. Bio PBS should be less expensive. Photos: Mitsubishi Chemical, IRe Chemical

The big PBS capacity, however, is Chinese-reportedly over 200 million lb/year. It is mostly swing plants, which can produce either PBS or PBAT, built with Chinese government grants targeting export of biodegradables to the U.S. and Europe. Kingfa Science & Technology Co., Zhuhai, Guangdong (www.kingfa.net), reportedly has capacity for 68 million lb/year of petro PBS; China New Materials Holdings Ltd., Zibo City, Shandong (www.sdfuwin.com) 55 million lb/year; XinFu Pharmaceutical Co. Ltd., Hangzhou, Zhejiang (www.xinfuchina.com) 28 million lb/year; and He Xing Chemical Co. Ltd., Anqing, Anhui (www.hexinggroup.com) 11 million lb/year. A fifth, Qixiang Tengda Chemical Co. Ltd. in Zibo, Shandong (www.qxgm.com), is reportedly building a whopping 330 million lb/year petro PBS plant to start in 2015, vertically integrated with succinic acid and BDO.

All that petro PBS capacity-potentially nearly 600 million lb/year—is important because it could convert quickly to bio succinic acid once bio is available, since it should cost less. (It supposedly takes 50% less energy to make bio succinic acid than petro.) A few small bio PBS reactors are also being built. PTTMCC Biochem Co. Ltd., a joint venture between PTT PLC Ltd., Bangkok, Thailand (www.pttplc.com) and Mitsubishi, is building a 44 million lb/year bio PBS reactor in Rayong, Thailand, to start in 2Q 2015. Youth Chemical, a unit of Jiangsu Yangnong Chemical Group Co. Ltd., Yangzhou, Jiangsu (www.yangnong.com.cn), started a 22 million lb/year pilot reactor for bio PBS in 2013. So there’s plenty of demand for bio succinic acid just for PBS (succinic acid is also used in paints, polyurethanes, and cosmetics).

So why are the bio monomers lagging? One theory is that the semi-works succinic acid fermentation plants are trying to improve quality before scaling up, aimed at U.S. food contact approval for PBS, which it doesn’t now have. Mitsubishi says its GS Pla qualifies for food contact in Japan and Europe, but not yet in North America. Mitsubishi plans to apply for U.S. food contact approval for products from the Thai plant once it starts up. Single use cutlery and cup lids, common PBS applications, don’t need food contact approval.

There are two potential issues. PBS’s low molecular weight can be raised by reactive chain extension with potential for residues. Showa Denko, for example, uses diisocyanurate for chain extension. There is also low-level sniping among succinic acid producers over yeast vs. bacterial (E. coli) fermentation. The yeast route reportedly requires less cleaning of fermentation equipment to prevent infection and claims higher purity succinic acid. Yeast also produces succinic acid directly, while the bacterial route takes an extra step to convert succinic salt to acid.

Bio based, biodegradable PBS polyester should be commercial by now, but no one makes enough of the necessary bio monomers, bio succinic acid and bio 1,4 butanediol. Plans for big fermenters are announced, but only semi-works sizes have been built. Photos: BioAmber

Bio based, biodegradable PBS polyester should be commercial by now, but no one makes enough of the necessary bio monomers, bio succinic acid and bio 1,4 butanediol. Plans for big fermenters are announced, but only semi-works sizes have been built. Photos: BioAmber

Another issue may be the cost of bio BDO. There are also competing routes to bio BDO–direct bacterial fermentation vs. hydrogenation of bio succinic acid into BDO. Direct fermentation loses 50% of feedstock carbon as waste CO2. Refining bio succinic acid into bio BDO loses 15% of feedstock weight as water and adds the cost of conversion. So opinions vary on which will cost less and whether they will be cost competitive against petro BDO.

UPDATE ON BIO SUCCINIC ACID AND BIO BDO

Here’s a snapshot of the snail’s race. BioAmber Inc., Minneapolis, Minn. (www.bio-amber.com), has run a 6 million lb/year pilot fermenter in Pomacle, France, for four years and is building a 60 million lb/year semi-works fermenter in Sarnia, Ont., in a j/v with Mitsui & Co. (www.mitsui.com) to start in Q2 2015. BioAmber used bacterial fermentation of wheat glucose in France, but will use second generation yeast licensed from Cargill Inc., Minneapolis, MN (www.cargill.com), with corn glucose in Sarnia. BioAmber also plans to build two full-scale fermenters, one for 200 million lb/year of bio BDO to start in late 2017 with expansion for 140 million lb/year of bio succinic acid, and another for 400 million lb/year of bio succinic acid to start in 2020. BioAmber licenses catalyst technology from DuPont Co., Wilmington, DE (www.dupont.com) to hydrogenate bio succinic acid into BDO with 85% yield. Exporter Vinmar International Ltd., Houston, TX (www.vinmar.com) will distribute output from all three plants. BioAmber originally planned to build a large bio succinic acid plant in Thailand with PTTMCC to supply PTTMCC’s bio PBS plant, but PTTMCC will now be supplied from Sarnia where energy and feedstock costs are lower. Bio Amber originally said its bio succinic acid would be competitive with petro succinic acid from $45/barrel oil, but lately says it will be cost equal if oil is at $35/barrel.

Myriant Corp., Quincy, MA (www.myriant.com), started a 30 million lb/year semi-works fermenter for bio succinic acid in Lake Providence, LA, in 2013 using corn glucose as feedstock and bacterial fermentation licensed from the University of Florida, Gainesville (www.ufl.edu). Myriant’s process was developed by ThyssenKrupp Uhde GmbH (www.thyssenkrupp.com) at a pilot plant in Leuna, Germany. Myriant also partnered with Johnson Matthey Davy Technologies Ltd., London, U.K. (www.davyprotech.com), to be sure its bio succinic acid drops into Davy’s single-reactor BDO process to make bio BDO. PTT Global Chemical PLC Ltd. in Thailand (www.pttgcgroup.com), originally 50% owner of Myriant, increased its stake to 86%. Myriant plans to build a second bio succinic acid plant in Louisiana for 140 million lb/year by 2015. Myriant also previously planned two plants in Asia, one with PTT for biosuccinic acid, and another with China National BlueStar Co. Ltd., Beijing, China (www.china-bluestar.com) for Davy process bio BDO.

Succinity GmbH, Dusseldorf, Germany (www.succinity.com), a joint venture of Corbion Purac Biochem BV, Gorinchem, the Netherlands (www.corbion.com), and BASF SE, Ludwigshafen, Germany (www.basf.com), upgraded a 22 million lb/year lactic acid fermenter in Purac’s site in Montmelo, Spain, to make bio succinic acid. The Spanish plant started up in March 2014 using proprietary BASF bacteria. Succinity originally planned a 55 million lb/year succinic acid fermenter in Spain by 2013, but has since announced plans for a 110 million lb/year bio succinic acid fermenter, but hasn’t given a date or site.

Reverdia VOF in Geleen, the Netherlands (www.reverdia.com), a joint venture of Roquette Freres Group, a French starch producer, and Royal DSM NV, Heerlen, the Netherlands (www.dsm.com), started a demo fermenter for bio succinic acid in Lestrem, France, in 2010 (since closed) and a 22 million lb/year semi-works fermenter in Cassano Spinola, Italy, in 2010. Reverdia uses yeast-based fermentation with starch as feedstock and plans a second 100 million lb/year fermenter by 2016, but hasn’t determined the site.

Bio succinic acid, one of two new monomers needed to make bio PBS, can be fermented using either yeast or bacteria. Four companies are developing bio succinic acid, two with yeast and two with bacteria, so competitive claims are flying.           Photo and Figure: Reverdia

Bio succinic acid, one of two new monomers needed to make bio PBS, can be fermented using either yeast or bacteria. Four companies are developing bio succinic acid, two with yeast and two with bacteria, so competitive claims are flying. Photo and Figure: Reverdia

Genomatica Inc., San Diego, CA (www.genomatica.com), has bacterial fermentation to make bio BDO directly and has licensed it to Novamont S.p.A., Novara, Italy (www.novamont.com), and BASF. Novamont is expected to convert a 40 millon lb/year plant in Adria, Italy, to Genomatica’s BDO process this year. BASF used the process for several commercial runs since 2013 and plans to build a 110 million lb/year Genomatica bio BDO plant, “depending on market acceptance,” BASF says. BASF and DSM both make PBT, which could potentially use bio BDO for partial bio content.

So in the next 5-6 years bio, or partially bio, PBS could finally become commercial. That’s a time line of 15-20 years, twice as long as Cargill’s NatureWorks took to launch its PLA biopolymer, which also needed a new bio monomer. PLA wasn’t a drop in polymer for an existing petro plastic like PBS, and there were few alternative suppliers, which made creating a market for PLA a lot more difficult. But NatureWorks lost no time on a semi-works plant. Instead Cargill went straight from a 9 million lb/year pilot fermenter for lactide monomer in 1996 to NatureWorks’ 300 million lb/year PLA plant by 2003, vertically integrating lactic acid, lactide monomer, and PLA. No guts, no glory.

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Thermoplastic Car Bodies Are Ready to Roll

By Jan H.Schut

Two papers given at the Society of Plastics Engineers’ ANTEC 2014 Conference April 28-30 in Las Vegas, NV, (www.4spe.org) describe the development by Volkswagen AG in Wolfsburg, Germany (www.volkswagenag.com), of what is believed to be the first automated process to mass produce finished thermoplastic car body parts. The technology is also likely to be the first multi-process injection molding of a cosmetic exterior car part (see blog May 6, 2014). It combines thermoplastic injection molding, physical foaming, and two-component PU injection molding in one complex tool. VW isn’t talking about small series production either. This is intended for “large scale production” of parts like hoods, spoilers, and mirror housings,possibly as early as next year.

The paper introducing a “Material Concept for Large-Scale Production of Finished Colored External Body Panels in Automobile” was presented by Joerg Hain, a materials research specialist at VW’s research center in Wolfsburg; Achim Schmiemann, a professor at the Institute for Recycling at Ostfalia University of Applied Science, also in Wolfsburg (www.ostfalia.de); and Paulo Bersch, a PhD candidate sponsored by VW. VW’s Hain had previously presented some of the material at the Kunststoffe im Automobilbau 2013 conference in Boeblingen, Germany sponsored by VDI Wissensforum (www.vdi-wissensforum.de).  But ANTEC was its first announcement to a global plastics audience.

VW’s innovation injection molds light weight, foamed PC/ABS body panels, then coats them on one surface with two-component PU in a second cavity of the same tool.  Foamed prototype parts made with mineral-filled PC/ABS and PU-coated weigh 58%less than equivalent steel parts. Unfoamed parts weigh 40% less and cost 30% less, according to the ANTEC paper. The patent-applied-for technology physically foams PC/ABS, impregnated with either nitrogen or CO2 gas in a special, two-compartment feed hopper, which feeds continuously under pressure. This means parts can be molded on conventional injection molding machinery without modification for gas injection into the barrel, allowing VW to use installed commercial machinery. Research on gas-impregnation in the hopper goes back years, including a process called Profoam, developed at the IKV Institute of Plastics Processing RWTH in Aachen,Germany (www.ikv-aachen.de). But VW’s continuous process keeps the entire injection unit including the hopper under pressure, so it loses less gas, says Ostfalia’s Schmiemann.

VW’s multi-process injection molding concept physically foams thermoplastic parts using a pressurized two-compartment hopper and CO2 to impregnate the plastic, then injects a two-component PU coating to make finished exterior car parts in one machine process.

VW’s multi-process injection molding concept physically foams thermoplastic parts using a pressurized two-compartment hopper and CO2 to impregnate the plastic, then injects a two-component PU coating to make finished exterior car parts in one machine process.

After the foamed body panel is molded, the tool opens. The part remains on the moving mold half, which travels to a second cavity, either by sliding or rotating for PU coating. The two PU components (polyol and isocyanate) plus additives and colors are mixed in a mixing head and injected into the space between the second cavity wall and the plastic part to be coated. PU overmolding achieves a Class A surface without release agents directly from the mold, VW’s presentation says. The look of the pigmented PU coating, however, is reportedly far more brilliant and deep than standard auto paint, VW’s Hain says. “We call it ‘piano lacquer.’” The PU coating can reportedly match any standard automotive paint colors except metallics, which are currently being worked on.

Pressure, temperature, and additives are critical to PU surface quality. Pressure in the two component tanks is 180-210 bars; pressure in the mixing head is 140-150 bars;and injection pressure is around 50 bars, VW’s presentation says. VW started with a self-healing PU from Bayer Material Science in Leverkusen, Germany (www.bayer.com) as the basic raw material. Then VW’s Hain worked for three years to develop patent-applied-for additives with several companies under contract to VW to achieve better adhesion of PU to the PC/ABS substrate and better release from the mold without a release agent. Formulation R&D was done in the laboratory at Ostfalia University,which is equipped with two injection molding machines and a two-component PU injection molding machine.  Separately Bayer and Krauss Maffei Technologies GmbH in Munich, Germany (www.kraussmaffeigroup.com), introduced the concept of PC/ABS plastic parts coated with PU in a single multi-process molding machine at K 2013 in Dusseldorf, including self-healing PU coating.

Ostfalia University tested wood-filled ABS with 1-5% chemical blowing agent and 5%, 15%,and 25% wood fiber for car parts and found toughness dropped with more wood and more blowing agent. The photo shows 5% blowing agent and 25% wood, but 1%/25%was optimum.

Ostfalia University tested wood-filled ABS with 1-5% chemical blowing agent and 5%, 15%,and 25% wood fiber for car parts and found toughness dropped with more wood and more blowing agent. The photo shows 5% blowing agent and 25% wood, but 1%/25%was optimum.

TRIALS FOAM LESS EXPENSIVE WOOD-FILLED ABS
Combined cycle time for molding and coating is about 60 seconds, with the PU reaction taking about 30 seconds, in a manufacturing cell planned for 500,000 parts a year, according to a second ANTEC presentation from Ostfalia, also on work done with VW.  The second ANTEC paper on “Coatable Wood Plastic Foams for Automotive Applications,” on the same multi-process technology was from Ostfalia’s Schmiemann and Eric Homey, a post-graduate assistant also at the institute, who now works for VW.  Ostfalia molded and foamed wood-filled ABS with chemical blowing agent. ABS is considerably less expensive than mineral-filled PC/ABS and processes at lower temperature, so ABS can be compounded with natural fiber re-enforcement, which is less expensive than glass- or carbon fibers. Molding temperature for ABS starts at 160 C and goes up to 200 C at the nozzle, Osfalia’s ANTEC paper says.

Ostfalia’s study used ABS with MFR of 8.9 g/10 min. from Samsung SDI Chemicals, Seoul,Korea (www.cdi.samsung.com); soft-wood fibers from Sonae Industria SGPS S.A., Maia, Portugal (www.sonae-industria-tafisa.com); two-component, self-healing PU clear coating (R 7203) from Karl Woerwag Lack- und Farbenfabrik GmbH in Stuttgart, Germany (www.woerwag.de); and an endothermic poly carboxylic acid blowing agent in masterbatch form (Microcell 301) from Momentum International GmbH in Wiesbaden, Germany (www.momentumadditive.com) instead of physical foaming with the special hopper.

VW’s formulation R&D was done in the laboratory of the Institute for Recycling at Ostfalia University in Wolfsburg, which has two injection molding machines and a two-component PU injection machine. VW reported on PC/ABS formulations; Ostfalia presented wood-filled ABS.

VW’s formulation R&D was done in the laboratory of the Institute for Recycling at Ostfalia University in Wolfsburg, which has two injection molding machines and a two-component PU injection machine. VW reported on PC/ABS formulations; Ostfalia presented wood-filled ABS.

Ostfalia tested the strength properties of samples made with 1%, 2%, 3%, 4%, and 5% chemical blowing agent and found that flexural and tensile strength both went down as blowing agent content went up, possibly because of the close proximity of bubbles to fibers. Ostfalia’s research also tested samples with 5%, 15% and 25% wood fiber and found that density, weight,and tensile modulus all went up with higher wood content, while toughness went down. Wood is heavier than ABS with a density of 1.5 g/cm for wood vs 1.04 g/cm for ABS.

Ostfalia researchers found the optimum combination was 25% wood with 1% blowing agent. Physical foaming could also be used, Ostfalia notes, and could make parts up to 20% lighter than unfoamed ABS. Ostfalia has not yet worked on optimizing the PU coating for the ABS substrate. The two presentations were given back-to-back at ANTEC.  Ostfalia’s Schmiemann recalls that it was hard to end the Q&A so the program could continue. “They had to move us out of the meeting room to finish questions in the hall,” he recalls, “and there were still 10-15 people following us asking questions.” Not surprising for such a major new move to thermoplastics in cars.

 

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Is Thermoplastic RTM Close to Commercial?

By Jan H. Schut

For over 10 years R&D has gone on among European car makers, machine builders, material suppliers and research institutes to adapt conventional resin transfer molding machines from thermosets to thermoplastics. Instead of pumping two-component epoxy or PU into a mold to cure, they pump thermoplastic monomer with catalyst and activators into the mold to polymerize in situ. The goal for thermoplastic RTM is to mass produce continuous-glass-fiber-reinforced thermoplastic parts for cars, which would have advantages over thermosets of being tougher, stronger, weldable, and recyclable. T-RTM technologies are mostly focused on in situ molding of PA6 from epsilon-caprolactam monomer.

Because caprolactam has very low viscosity, it wets fiber structures rapidly in about 30 seconds without disturbing their position, achieving high directional fiber content of up to 65 volume %. Caprolactam, which melts at 69 C, comes either in liquid form in heated containers or in flake form. Usually two tanks are used in a modified RTM dosing machine. One tank is for caprolactam with catalyst, the other for caprolactam with activators and additives. The two caprolactam streams are combined typically 1:1 in a specially designed mixing head heated to around 100 C, then pumped into an RTM mold heated to around 150 C. The mix polymerizes in 2-5 minutes, depending on part characteristics and volume.

Caprolactam, however, isn’t easy to work with. It has very low, watery viscosity of 5-10 mPas vs 200-300 mPas for liquid PU, so leaks are an issue with conventional RTM machinery and molds designed for PU. Caprolactam also has to be protected from oxygen and moisture (<0.01%) throughout the in situ process since moisture slows or stops polymerization. So continuous fiber structures have to be predried before they’re put into the mold. PA 6 polymerizes to a solid using an anionic “ring-opening” polymerization reaction at over the melt temperature of the monomer, but below the melt temperature of the polymer.

LOTS OF EUROPEAN R&D

Among others, Porsche AG in Stuttgart, Germany (www.porsche.com), worked with the Fraunhofer Institute for Chemical Technology in Pfinztal, Germany (www.ict.fraunhofer.de), to develop “Cast Polyamide” thermoplastic RTM, shown at the JEC Composites show in Paris in 2006. Porsche and the Fraunhofer showed the process again in 2010 at a composites conference in Germany with a demo trunk liner for a Porsche Carrera 4, which weighed 50% less than an aluminum trunk liner.

Volkswagen AG in Wolfsburg, Germany (www.volkswagenag.com), which bought Porsche in 2012, recently successfully tested high-pressure thermoplastic RTM molding of continuous-glass-filled PA6 “B pillar” reinforcements that could be glued into steel B pillar frames and weigh 36% less than high-strength steel B pillars in production for the North American market. The tests were done in VW’s fiber-reinforced plastics test plant in Wolfsburg, Germany, and reported in Kunststoff magazine in March this year.

First an asymmetrical woven fiber structure with a sizing compatible with anionic polymerization of PA6 was preshaped in a separate mold with a binder, also compatible with caprolactam. Preforms were kept dry in a drying oven from HK-Praezionstechnik GmbH, Oberndorf am Neckar, Germany (www.hk-pt.de), then put into an RTM mold heated to 150 C. Molding was done on an existing 1000-ton injection molding machine, using a two-sided mold, modified to prevent leakage of caprolactam. Caprolactam injection must be moisture-free, so the mold was rinsed with nitrogen each time before filling.

KraussMaffei Technologies GmbH in Munich, Germany (www.kraussmaffeigroup.com), which worked with VW, developed a new high-pressure caprolactam mixing head, electrically heated to about 100 C and pumping with nearly 100 bars of pressure. KraussMaffei also modified its RTM machines for caprolactam with heated hoses to transfer melted caprolactam from dosing tanks to the mixing head. Even coupling pieces in the hoses needed heater cartridges to keep temperature constant. KraussMaffei already built caprolactam mixing heads and dosing machines for NYRIM, a reactive in situ casting process for PA6 copolymers, developed in the 1980s by Monsanto Co., St. Louis, MO (www.monsanto.com), then sold to DSM NV in the Netherlands (www.dsm.com). NYRIM puts caprolactam with activated elastomeric polymer in one tank and caprolactam with catalyst in the other, then mixes them.

Krauss Maffei developed a new high-pressure mixing head and modified RTM machines to mold reactive caprolactam with catalyst and activators in situ into PA6 parts. Thermoplastic RTM could mold series automotive parts with very high directional fiber contents up to 65%.

Hennecke GmbH, Sankt Augustin, Germany (www.hennecke.com), developed an even higher pressure T-RTM system. Hennecke optimized its counter flow RTM mixing head for thermoset PU to mix lower viscosity caprolactam. The high pressure caprolactam mixing head uses more than twice the pressure of Hennecke’s PU mixing head, which is roughly 200 bars. Hennecke’s caprolactam mixing head is self-cleaning only through counter flow.

Henecke

Hennecke developed a very high pressure T-RTM system, adapting its counter flow RTM mixing head to mix much lower viscosity caprolactam. Melted caprolactam has a watery viscosity of only 5-10 mPas, whereas liquid PU has a viscosity of 200-300 mPas.

Engel Austria GmbH, Schwertberg, Austria (www.engelglobal.com), worked with the Fraunhofer-ICT from 2009 to 2011 to develop a high pressure, servo-motor-powered thermoplastic RTM machine based on melting caprolactam flake in a modified injection molding unit, not on dosing liquid caprolactam from tanks. Engel uses an Engel e-victory injection molding machine with two injection units, modified for low viscosity caprolactam with special valves and seals. This was shown for the first time at an Engel open house in June, 2012, along with Engel’s in situ thermoplastic RIM process (see previous blog June 11, 2014), which is also based on injection molding of caprolactam.

Mahr Metering Systems GmbH, Goettingen, Germany (www.mahr.com), adapted a metering machine to process reactive PA for low-pressure T-RTM casting. Mahr also recently developed a new mixing head for caprolactam, catalyst and activator, which is self-cleaning using nitrogen. It was shown for the first time at the JEC Composites show in Paris in March. Mahr’s dynamic mixing head for T-RTM uses high-precision gear pumps for process pressure from 20 up to nearly 50 bars. It is also designed for three components instead of two, allowing caprolactam to be combined with catalyst, activators and colorants separately.

Mahr metering systems

Mahr Metering Systems developed a new low pressure mixing head for caprolactam, catalyst and activator, which is self-cleaning using nitrogen. It’s designed for three components instead of two, allowing caprolactam to be combined with catalyst, activators and colorants separately.

Resin suppliers are working on reactive caprolactam formulations. BASF SE, Ludwigshafen, Germany (www.basf.com) worked with VW and Krauss Maffei to develop reactive PA6 systems with caprolactam, catalyst, activators, and additives,. BASF has also done development work for low-pressure T-RTM with Mahr. Lanxess AG, Koeln, Germany (www.lanxess.com), has done development work with Engel on thermoplastic RIM PA6 (see blog June 11, 2014). Brueggemann Chemical, Heilbronn, Germany (www.brueggemann.com), which acquired DSM’s NYRIM business over a decade ago, has done development work with Hennecke.

No auto maker so far has announced plans to commercialize thermoplastic RTM. Cycle time is apparently still an issue for large production quantities. “Two to three minute cycle time is OK for 100,000 parts a year,” notes a researcher in in situ RTM at a major auto maker, “but not for 200,000 or 300,000 parts a year.” But a spokesperson from BASF thinks the first car parts could be in series production by 2018 or 2019.

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In Situ Molding Is More Than a Possibility

By Jan H. Schut

In situ molding could be the answer to mass producing engineering thermoplastic composites, especially metal-replacing structural parts for future cars. In situ molding mixes melted monomers of a polymer in two parts, one with catalyst, the other with activator, and puts them into a heated mold where they polymerize. For PA6 they polymerize at a temperature over the melt temperature of the monomer, but below the melt temperature of the polymer. The reaction is anionic “ring-opening” addition for PA 6 and PC or conventional chain addition for PA 6.6. Other condensation polymers that could potentially be molded in situ include PMMA, PBT, TPU, and PEK and copolymers are possible.

In situ thermoplastic reaction injection molding has been known for 50 years, primarily for nylon 6, but it’s done by a slow batch casting process with conventional RIM equipment. NYRIM, for example, is a PA6 copolymer system for thermoplastic RIM, commercialized in 1981 by DSM NV in the Netherlands (www.dsm.com), and acquired by Brueggemann Chemicals, Heilbronn, Germany (www.brueggemann.com) over 10 years ago. NYRIM combines caprolactam with different ratios of elastomeric prepolymer (7-40%) and polymerizes them into copolymers in situ using conventional RIM equipment. Caprolactam with activator is heated in one pot, elastomeric prepolymer with catalyst in another. They’re combined in a RIM mixing head and polymerized at low pressure in aluminum molds. It’s a niche process for specialty parts with high strength requirements and short production runs like treads for earth movers.

What’s new is in situ thermoplastic RIM based on conventional injection molding, which can be fully automated and fast enough for mass production for the first time. Three years ago Engel Austria GmbH in Schwertberg, Austria (www.engelglobal.com), built a prototype for the first reactive thermoplastic RIM machine for caprolactam using reciprocating screw injection units instead of heated tanks. Engel worked with the Fraunhofer Institute for Chemical Technology in Pfinztal, Germany (www.ict.fraunhofer.de), to develop the new approach.

The advantage of molding monomers is that they have much lower viscosity than polymers, so monomers can thoroughly impregnate dry continuous or woven fiber structures without disturbing fiber position. In situ molding can thus achieve directional woven fiber contents of up to 65 volume % and mold more complex shapes than viscous polymers. Compared to traditional thermoset RIM molding of epoxy and PU, continuous thermoplastic RIM has other advantages: short cycle times, greater toughness and impact strength, weldability, and recyclability. Below is the latest in thermoplastic RIM developments. The next blog will look at a similar surge of R&D in thermoplastic in situ RTM.

AUTOMATING IN SITU THERMOPLASTIC RIM

Engel’s in situ process for PA6 started as a PhD thesis by Lars Fredrik Berg at the Fraunhofer ICT, supervised by Peter Elsner at the Karlsruhe Institute of Technology in Germany (www.kit.edu), and Georg Steinbichler, head of R&D at Engel. Berg’s thesis, finished in 2011, yielded enabling machine developments, which Engel and the Fraunhofer continued to work on.

Engel built the first thermoplastic RIM machine based on conventional injection molding, with two reciprocating screw injection units instead of heated tanks. A sealing device in the barrel, developed at the Fraunhofer-ICT, meters very low viscosity caprolactam into the mixing head.

Engel built the first thermoplastic RIM machine based on conventional injection molding, with two reciprocating screw injection units instead of heated tanks. A sealing device in the barrel, developed at the Fraunhofer-ICT, meters very low viscosity caprolactam into the mixing head.

In 2011 Engel built a prototype for a commercial thermoplastic RIM machine using a modified tiebarless Engel e-victory reciprocating screw press with two all-electric injection units inclined at a 45 degree angle. One melts epsilon-caprolactam monomer (flake or pellets) with catalyst, the other melts caprolactam with activator. A non-return valve patented by Berg and the Fraunhofer (U.S. Pat. # 8684726) goes onto the end of the reciprocating screws and seals against the inside of the injection barrel, allowing precise feeding and injection of very low viscosity monomers. The two melts are combined in a high pressure mixing head and fed with very low pressure into a mold to cure.

Engel has a patent application on a way to make fiber composites or hybrid components (U.S. Pat. Applic. # 20130181373) using a modified high-pressure mixing head. Engel partnered with Hennecke GmbH, Sankt Augustin, Germany (www.hennecke.com) to optimize Hennecke’s high pressure RTM mixing head for PU for lower viscosity caprolactam instead. Caprolactam has a viscosity of 4mPas, so leakage was an issue. Hennecke developed new dynamic mixing technology for the high pressure, high temperature head for caprolactam. Throughout the molding process, caprolactam also has to be protected against moisture, since moisture absorption impedes or stops polymerization.

ENGEL automotive e-victory 120 combi in-situ-polymerisation 2

Engel’s injection molding machine for in situ RIM is adapted to mold low viscosity caprolactam, wetting out dry fiber inserts. This can achieve PA6 parts with continuous fiber content of up to 65 volume %, like this passenger car brake pedal insert and prototype athletic shin guard.

Engel’s injection molding machine for in situ RIM is adapted to mold low viscosity caprolactam, wetting out dry fiber inserts. This can achieve PA6 parts with continuous fiber content of up to 65 volume %, like this passenger car brake pedal insert and prototype athletic shin guard.

Engel’s injection molding-based RIM process was shown first at an Engel open house in June 2012, molding a continuous fiber PA6 insert for a passenger car brake pedal, developed with ZF Friedrichshafen AG in Friedrichshaven, Germany (www.zf.com). Then the IKV Institute of Plastics Processing RWTH in Aachen, Germany (www.ikv-aachen.de) and 14 partner companies worked with Engel to develop an automated in situ injection molding process combined with TPU overmolding, which was shown for the first time by the IKV at the K 2013 show in Germany. The automated process prototyped an athletic shin guard, starting with a woven fiber glass preform made of multiple layers, consolidated by a binder, robotically trimmed with ultrasonics, dried, and inserted robotically with needle grippers into heated injection molds. Temperature control is critical. Caprolactam melts in the injection barrels at about 70 C, passes through heated runners and the electrically heated mixing head at about 100 C, and into molds heated to about 150-160 C.

The IKV Institute worked with Engel to develop automation for Engel’s thermoplastic RIM press, molding a PA6 shin guard in situ with a continuous glass preform in under 3-minute cycles. It was shown for the first time by the IKV at the K 2013 show in Germany.

The IKV Institute worked with Engel to develop automation for Engel’s thermoplastic RIM press, molding a PA6 shin guard in situ with a continuous glass preform in under 3-minute cycles. It was shown for the first time by the IKV at the K 2013 show in Germany.

The two-cavity in situ molds for the shin guards were built by Schoefer GmbH in Schwertberg, Austria (www.schoefer.at), with a compression edge with silicone seals to contain the low viscosity monomers and to compress the fiber preform at the edges so that no flash forms. The e-caprolactam was specially developed for the application by LanXess AG in Koeln, Germany (www.lanxess.com). Cure time was below 3 minutes. In a separate injection molding machine the shin guards were over-molded on the back with soft-touch TPE.

Auto company interest in in situ molding is also visible. Toyota Motor Corp., Tokyo, Japan (www.toyota-global.com) got a patent years ago for in situ RIM molding of PC (U.S. Patent # 5514322), describing carbonate compounds with catalyst and activators, mixed and fed into a mold to polymerize. The patent says that the anionic addition reaction is controlled by the a third ingredient (BPh3 Lewis acid) so that the reaction starts inside the mold, not before. The patent cites 23 formulations of which the 23rd cures in situ in 4 minutes with thorough impregnating of continuous fibers and makes PC with molecular weight of 17,000. Another Toyota patent (JP Pat. # 194-157769) describes catalysts for in situ molding. It doesn’t appear that Toyota has applied in situ PC technology commercially, though light weight parts for the energy saving Prius would be a good candidate. The Prius-Alpha hybrid minivan already claims to have the largest PC panoramic roof in the world.

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