Eco Friendlier

Posted on February 28, 2014 by

By Jan H. Schut

News at GPEC 2014 (Global Plastics Environmental Conference), coming up on March 12-14 in Orlando, FL, (www.sperecycling.org), by the Environmental Division of the Society of Plastics Engineers, includes a new lignin-rich degradable filler, a process potentially for food-contact PPC, plus new ways to recycle some of the toughest plastic scrap. GPEC runs back-to-back in the same location with the Plastics Recycling Conference 2014, on March 11-12 by Resource Recycling Magazine, Portland, OR, (www.resource-recycling.com), which brings an astonishing 150-plus exhibitors in addition to its program. Here are some highlights.

NEW GREEN MATERIALS

Robert Aldi, adjunct professor of mechanical engineering technology at Rochester Institute of Technology, Rochester, NY, (www.rit.edu) presents “LENS FBM Biomass Waste Stream from Cellulosic Sugar Production Compounded in LDPE.” LENS FBM (lignin-enriched, non-sulfonated fractionated bio-mass) is a new bio-based filler that imparts degradability to plastic film. “Fractionated bio mass” is plant material separated into cellulose, hemicellulose, lignin and other components. The patent-applied-for filler is a fine dark brown powder (down to 5 um) with a slight sweet smell, made from a byproduct of cellulosic sugar, sourced from a Rochester area producer. Cellulosic sugar syrup is refined from cellulose and hemicellulose from wood waste and used for bio-based oils and fuels.

Aldi compounded the FBM filler into masterbatches with LDPE, then molded test samples at different loadings in LDPE. He presents the properties of a compound of 30/70 FBM/LDPE with 2% compatibilizer, which reportedly shows only minimal (2%) loss in ultimate tensile strength. He also presents preliminary test data for 3-layer coex blown film containing the filler. The new filler is being developed by an RIT incubator company, Cedar Creek Products and Technologies, of which Aldi is a co-founder (email: rda9587@rit.edu). Samples of the degradable FBM filler should be available this summer for testing, Aldi says.

Photos courtesy of ALDI

Photos courtesy of ALDI

Bahareh Bahramian, a PhD candidate at the University of Sydney in Australia (sydney.edu.au/engineering/chemical/research/sustainable-technology) presents “Development of an Efficient Process for the Purification of a Renewable Polymer: A Solution for Minimizing Issues in Waste Management.” The reportedly benign process removes zinc catalyst residues from poly (propylene carbonate) to a level that could potentially allow PPC to pass tests for direct food contact. PPC is a biodegradable form of polycarbonate with high oxygen barrier properties, made with alternating CO2 and propylene oxide molecules. If PPC is made with zinc glutarate (or other heavy metal) catalyst, catalyst residues are too high for food contact. U. Sydney’s process reportedly removes more than 80% of zinc residues from PPC to below standard limits. The work is done in collaboration with Cardia Bioplastics in Melbourne, Australia (www.cardiabioplastics.com), which has a subsidiary, CO2 Starch Pty. Ltd., developing degradable blends of PPC and starch. Two U.S. companies also offer PPC, but not as plastic. Empower Materials Inc., New Castle, DE, offers PPC as a niche sacrificial polymer for the electronics industry.  Novomer Inc., Waltham, MA, (www.novomer.com) offers low molecular weight PPC polyols (1000-3000 g/mol) for use in PU foams and adhesives. Novomer, however, touts potential use of higher molecular weight PPC as a barrier layer in food packaging to replace EVOH and nylon, but hasn’t so far done food contact testing. Novomer doesn’t use zinc catalyst and says catalyst residues in its polymers are below 1-2 ppm.

RECLAIMING TOUGH SCRAP

Didem Oner-Deliormanli, research scientist at Dow Chemical Company, Freeport, TX, (www.dow.com), presents “Enhancing the Value of Barrier Film Recycle Stream with Dow’s Novel Compatibilizer Technology.” The patent-applied-for new compatibilizer can combine nylon and EVOH fractions with polyolefins, allowing post-industrial barrier film scrap to be recycled. The compatibilizer, which was announced at last year’s K Show in Germany, uses reactive ultra-high-flow grafted maleic anhydride with a very high melt index of 660. The idea is that this very high flow MAH material breaks EVOH up into smaller particles. The new compatibilizer produces compounds with much smaller domain sizes of nylon and EVOH, better strength and optical properties, Dow reports. Conventional MAH compatibilizers, on the other hand, typically have long polymer chains and very low MIs of only 2-3. Dow is also presenting a paper on “Compatibilization  and Recycling of Post-Industrial Barrier Film Scrap” on the same compatibilizer at the SPE Polyolefins conference in February.

Paul Rothweiler, VP of Technology Development at contract research firm Aspen Research Corp., Maple Grove, MN, (www.aspenresearch.com) presents “Recycled PLA for Retail Applications.”Aspen was the first company to offer post-industrial recycled PLA (poly lactic acid) biopolymer (RPLA001 and RPLA002) two years ago, working with Natureworks LLC, Minnetonka, MN, (www.natureworksllc.com), the major producer of PLA biopolymer. Aspen developed compounds that upgrade industrial PLA trim scrap into new materials, including higher-end alloys and pigmented compounds. PLA scrap is sourced from NatureWorks and includes card stock and form-fill-seal trim, so the material is mostly opaque with some clear. Aspen’s first major commercial application, launched in February, is for colored injection-molding grades of rPLA for egg-shaped containers for chocolates, made for the Eco Eggs division of chocolate wholesaler Maud Borup Inc. Minneapolis, MN (www.ecoeggs.com). Interfacial Solutions LLC (www.interfacialsolutions.com), River Falls, WI, last year also announced its “hyper-branched” post-industrial rPLA at GPEC and won a GPEC Environmental Award. Interfacial Solutions has a National Science Foundation grant to develop the technology, but has not yet licensed it commercially.

EcoEggs

EcoEggs from Maud Borup Inc. use rPLA scrap as a biodegradable source of the traditional plastic Easter egg.
Photo courtesy of EcoEggs/Maud Borup

Among the wealth of exhibitors at the Plastic Recycling Conference, are two unusual new recovery technologies. Environmental Recycling Technologies PLC, Oxford, UK, (www.ertplc.com), acquired the rights to a patented process called Powder Impression Molding, originally developed by US car makers. It’s used to mold thermoplastic parts out of commingled recycled plastic powder.

AMUT s.p.a., Novara, Italy (www.amut.it) has set up a new Ecotech Division to supply sortation equipment to MRFs and PRF’s (plastics recovery facilities), including an “elliptical separator,” consisting of  planks with an elliptical motion that carry light materials like paper and film up and heavy materials down, while sand and gravel fall through. AMUT has five elliptical separators installed in North America, three at PRFs and two at MRFs, with the goal of improving upstream plastic separation.

ballistic 3DSC_0949_Amut

Elliptical separator by AMUT.

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How New Catalysts Are Changing Polypropylene

Posted on February 14, 2014 by

By Jan H. Schut

Plastics made with genuinely new catalysts are hard to spot when resin companies don’t identify them in data sheets or only make them available to test partners. But several unusual new polypropylenes are in plain sight for the first time at the Polyolefins Conference on “The Polyolefin Renaissance” in Houston, February 23-26, hosted by the South Texas section of the Society of Plastics Engineers (www.spe-stx.org).

They’re made with three “new generation” catalysts. One is an unusual dual metallocene catalyst; the other two are “advanced” or “6th generation” Ziegler-Natta PP catalysts, though that isn’t easy to define. Ziegler-Natta catalyst generations are named for internal electron donors, which control the all-important orientation of monomers as they attach to the polymer chain, i.e. isotacticity and molecular weight distribution. (Generation 4 Ziegler-Natta is diethyl phthalate; generation 5 is diether or succinate.)

“Gen 6” catalysts claim higher activity (which benefits the resin company). They also claim to make PP with more stereo-selectivity, more controlled dispersion of monomers, higher purity, lower VOCs, and lower extractables. Some are also non-phthalate, but phthalate isn’t a clear criterion because “Gen 5” Ziegler-Natta catalysts like LyondellBasell Industries’ (www.lyondellbasell.com) diether or succinate have been non-phthalate for years. Phthalate internal donors are a hot button because of pending European regulations which could make PP with even minute phthalate traces a “controlled substance,” an obvious no-no for spunbonded or meltblown PP fibers for infant diapers. Here are the three “new catalyst” PPs.

FIRST PP COPOLYMERS FROM DOW’S ‘CHAIN-SHUTTLING’ DUAL CATALYST

Gary Marchand, research fellow at Dow Chemical Co. (www.dow.com), presents “PP-Based Olefin Block Copolymers as Compatibilizers for PE and PP.” It’s the first technical report on developmental “Intune” PP-based block copolymers made with Dow’s patent-applied-for CGC or chain-grafting catalyst technology (Patent Applic. # WO2005/090425, 26 and 27). Intune PP copolymers, announced at last year’s K Show in Germany, combine isotactic PP segments with crystalline PE segments (actually ethylene propylene copolymers) or with “PE, polyolefin elastomers and polar materials like EVOH and PA,” Dow says, “for blends and multilayer structures.” Intune PPs aren’t commercial yet, but are being tested as compatiblizers for PP/PE blends.

Dow’s chain-shuttling catalysts, introduced at ANTEC 2006, use two distinct catalysts and diethylzinc as the shuttling mechanism in one or more continuous solution reactor (s), Dow says. One metallocene catalyst produces hard blocks, a second hybrid metallocene catalyst produces soft blocks. Blocks form on the two catalysts, detach from them and park on diethylzinc particles before reattaching to new monomer blocks forming on the catalysts. The length of block segments is controlled by the ratio of diethylzinc to ethylene monomer, with a higher ratio making finer blocks, according to Dow presentations, while the overall hard-to-soft ratio is controlled by the relative amounts of the two catalysts.

Dow previously commercialized Infuse PE-based block copolymers, using its chain-shuttling catalyst technology to combine ethylene and octene monomers. Infuse PE block copolymers, introduced in 2008, allow high temperature and stiffness properties to be tuned independently for the first time. Infuse PE has temperature resistance up to the melting point of PE (about 138 °C) with low Tg. Intune PP could also have temperature resistance up to that of PP (potentially up to 163 °C), but Dow has only reported performance in blends. Dow’s CGC catalyst isn’t available for license.

Science Figure 2

Dow’s first developmental PP copolymers from its unusual “chain-shuttling” catalyst are being tested to compatibilize PP and PE. The “chain-shuttling” catalyst commercially makes PE block copolymers, described as having either linear hard-soft blocks or a comb-like structure.

Dow’s first developmental PP copolymers from its unusual “chain-shuttling” catalyst are being tested to compatibilize PP and PE. The “chain-shuttling” catalyst commercially makes PE block copolymers, described as having either linear hard-soft blocks or a comb-like structure.

PP COPOLYMERS FROM BOREALIS’S SIRIUS ZIEGLER-NATTA CATALYST

When Markus Gahleitner, senior group expert for PP at Borealis Polyolefine GmbH in Linz, Austria (www.borealisgroup.com), presents “A Brief History of High-Impact PP Copolymers,” he includes the most complex materials made so far with catalyst from Borealis’s Sirius emulsion process. These are certain BorSoft impact copolymers for medical films with higher purity, lower extractables, lower emissions, and better retention of mechanical and optical properties in steam sterilization, targeting PVC. They replace existing grades with higher property materials, but aren’t identified in data sheets.

The Sirius process was commercialized in 2006 and introduced at Polyolefins in 2009. Borealis uses it commercially to make advanced Ziegler-Natta catalyst for PP with higher activity and PP properties, but still with a phthalate internal donor (diethylhexyl phthalate). The Sirius process makes solid spherical Ziegler-Natta catalyst particles with magnesium chloride support formed in situ, not separately, for an active site structure that makes PP with relatively narrow MWD. “The replication is different even from other spherical catalysts,” Gahleitner notes. “Purity is higher, molecular weight distribution is slightly narrower, similar to diether catalysts, but with higher isotacticity.” Sirius technology is covered by over 60 patents (including U.S. Pat. # 7465775).

Interestingly, the Sirius emulsion process can also make metallocene catalysts for PP. Because emulsion distributes active sites evenly in round catalyst particles, Sirius metallocene catalysts would make heterogeneous PP copolymers with more uniform and evenly distributed soft domains than previous metallocene catalysts. Borealis invested 100 million Euros in a new semi-works Sirius catalyst production plant in Linz, Austria, which started in 2013, in addition to 50 million Euros for a new Innovation Center in Linz, which opened in 2009 for customer product R&D. Sirius Ziegler-Natta catalyst is also used by Borealis’s Borouge joint venture in Abu Dhabi, United Arab Emirates (www.borouge.com).

Borealis’s new 100-million-Euro catalyst plant started up in 2013, using its Sirius emulsion process commercially to make high activity Ziegler-Natta catalyst for high-purity PPs for medical films. The Sirius emulsion process can also make metallocene catalysts for PP.

Borealis’s new 100-million-Euro catalyst plant started up in 2013, using its Sirius emulsion process commercially to make high activity Ziegler-Natta catalyst for high-purity PPs for medical films. The Sirius emulsion process can also make metallocene catalysts for PP.

PP’S FROM W.R. GRACE’S ‘GEN 6’ CATALYST

John Kaarto, principal research scientist at W.R. Grace & Co., Columbia, MD (www.grace.com), presents “Investigations into Spinning Performance of PP from Developmental Catalysts,” describing fiber grades made from Grace’s non-phthalate Consista C601 catalyst. C601was developed by Dow and introduced in 2011 for Unipol gas phase processes. Dow called it the world’s first “Gen 6” Ziegler-Natta catalyst (substituted phenylene aromatic diester), referenced in some 70 patents (including U.S. Pat. # 8288585, WO # 2010078494, and U.S. Pat. Applic. # 20140012035). Grace licensed non-phthalate technology from Dow in 2011 and offered it as Grace’s HYamPP catalyst for isotactic PP. Then in 2013, Grace bought Dow’s Unipol PP catalyst technology and licensing business, including C601.

W.R. Grace recently bought Dow’s Unipol PP catalyst and licensing business, including non-phthalate “Gen 6” Ziegler-Natta catalyst (substituted phenylene aromatic diester). Phthalate catalysts are a hot topic because of pending European restrictions on PP with even trace amounts. Schematic: Patent Applic. WO 2010078494

W.R. Grace recently bought Dow’s Unipol PP catalyst and licensing business, including non-phthalate “Gen 6” Ziegler-Natta catalyst (substituted phenylene aromatic diester). Phthalate catalysts are a hot topic because of pending European restrictions on PP with even trace amounts.
Schematic: Patent Applic. WO 2010078494

The non-phthalate catalyst reportedly makes PP with high isotacticity and broad MWD for a broad PP product line, not just fiber. Grades include homopolymer, random copolymer, impact copolymer and TPO for applications like BOPP, film, pipe, thermoforming, and injection molding including clear articles, Grace says. That’s a lot to make with one catalyst, but C601 can use up to three different external donors to tune products separately, according to Grace publications. Slovnaft a.s. in Bratislava, Slovak Republic, which started up in 2005, makes 100% of its PP production with C601 catalyst for a broad range of products.

C601 reportedly makes standard homopolymers 10%-20% stiffer than Dow’s 4th generation catalyst because of higher isotacticity, allowing down gauging in thermoforming and injection molding. Comonomer distribution is more uniform for better clarity (20% lower haze) in random copolymers. Higher catalyst response to hydrogen also reportedly makes PP impact copolymers with higher melt flow rates and up to 35% lower VOCs. (Hydrogen typically controls molecular weight and increases Ziegler-Natta catalyst activity by three-to-five times, but C601 reportedly requires less hydrogen for higher activity.) C601 has 40%-100% higher activity than Dow’s Gen 4 catalyst, so Grace says it’s cost neutral.

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New Melt Pump Invention Needs No Inlet Pressure

Posted on January 31, 2014 by

By Jan H. Schut

A new melt pump concept-the first counter-rotating twin-screw melt pump-was introduced at last year’s K Show by Henschel GmbH in Kassel, Germany (www.henschel.de). Melt pumps, which create pressure between a co-rotating twin-screw compounding extruder and die, have previously been either counter-rotating gear pumps or single-screw pumps. Henschel’s Xtreamor pump is like neither. It’s distinguished from conventional melt pumps by dramatically lower inlet pressure and lower energy consumption over the entire compounding line.

It’s an unusual development in a mature product like melt pumps, where new technology for decades has been only incremental tweaks. It’s also unusual coming from Henschel, formerly Henschel Antriebstechnik GmbH, a maker of gear boxes. The inventor of the twin-screw pump, Matthias Henke, was part of a management buyout of Henschel’s gear box business in 2006 and in 2011 became 100% owner. His patent pending pump was under development for two years.

The Xtreamor pump is a mechanical pump or feeding mechanism, which “creates a continuous cylinder like a piston in a car,” explains owner/inventor Henke. After each half rotation of the screws, one chamber between the screws is closed and the next is opened, feeding material forward. Material doesn’t flow backward and pulse, as it does in a gear pump, and fill levels can be higher than with a gear pump.

But the big difference is low inlet pressure. The Xtreamor pump can be fed with inlet pressure of 0 to 0.4 bars vs. 24-50 bars of inlet pressure for standard gear pumps and 2-10 bars of inlet pressure for single-screw melt pumps. The twin-screw pump can generate the same exit pressures as other melt pumps of up to 350 bars.

Abb-Fig 1 HMP140

Henschel’s invention of the first counter-rotating twin-screw melt pump could be a game changer in compounding. The Xtreamor pump is fed with zero inlet pressure from a main twin-screw extruder, reducing energy use for the whole compounding line by up to 50%.

Henschel’s invention of the first counter-rotating twin-screw melt pump could be a game changer in compounding. The Xtreamor pump is fed with zero inlet pressure from a main twin-screw extruder, reducing energy use for the whole compounding line by up to 50%.

A compounder in France runs 100-mm and 140-mm Xtreamor twin-screw melt pumps commercially on twin-screw compounding extruders, making up to 84.5% CaCO3-filled LDPE master batches for film, possibly the highest loading in the world.

Temperatures are also cooler in the twin-screw pump. Outlet temperature coming from the main extruder remained at 233 C for CaCO3-filled PE vs. an increase to 244 C for a gear pump and to 252 C for a single-screw melt pump, Henschel reported at the K Show. The Xtreamor pump has electric heating cartridges and water injection barrel cooling. (Gear pumps typically don’t have heating or cooling, though they can, while single-screw melt pumps typically do.)

Don’t  confuse the Xtreamor pump with a counter-rotating twin-screw extruder either. Besides having two counter-rotating screws, there is little similarity. Screws in Henschel’s melt pump have outside/inside diameter ratios of two or higher where screws in counter-rotating twin-screw extruders have OD/ID ratios of 1.45 to 1.85. The twin-screw pump has L/Ds of only 2.3-2.5, where counter-rotating twin-screw extruders have ten times higher L/Ds of 22-32 or more.

Henschel has designed five different screw geometries so far with different depth/diameter ratios and number of screw flights and offers pumps from 60 to 200 mm diameter. The twin-screw melt pump also requires a different gearbox than Henschel has built before. Henschel set up a new unit, Henschel ExtruTec GmbH in Heiligenstadt, Germany (www.xtreamor.com), to build the new pump and plans to have labs set up for customer trials in both Germany and the U.S. later this year. Siegward Rockstedt, former head of Maschinenfabrik S. Rockstedt GmbH in Germany, which built multi-screw compounders, worked with Henschel on the first trials and installations.

The first two Xtreamor melt pumps are in commercial use at compounder JM Polymers in Saint-Romain-Lachalm, France (www.jmpolymers.fr), which has had a 100-mm-diameter Xtreamor melt pump running for a year and a 140-mm melt pump for seven months. Both are on twin-screw extruders compounding CaCO3-filled LDPE master batches for film. JM Polymer’s website offers Cacolin PE master batches with up to 82% CaCO3, one of the highest reported commercial loadings. JM has also made custom formulations for customers with up to 84.5% CaCO3, believed to be the highest in the world. Heritage Plastics Inc., Picayune, Miss. (www.heritage-plastics.com), offers PE master batches with up to 80% CaCO3 and has gone higher for custom formulations.

With operating experience, JM confirms that lower inlet pressure in the twin-screw pump results in dramatic overall energy savings on the main extruder of more than 50%. “Because the upstream co-rotating twin-screw extruder doesn’t have to generate high fill pressures, it allows more of the compounder to be used for mixing, and power consumption is crazily low,” reports Pierre Burdier, technical engineer at JM Technology, which builds JM’s compounding machinery. “The Henschel pump is only 38 kW where a comparable single-screw pump is 110 kW. ROI on the new melt pump was less than a year on the energy savings,” JM’s Burdier notes. “Torque on the main extruder is also 20% less because it doesn’t have to push, only to mix.”

OTHER NEW MELT PUMP TECHNOLOGIES

Two other new melt pump developments also target energy savings and improved flow. At the K Show, Maag Pump Systems in Oberglatt, Switzerland (www.maag.com), part of Dover Pump Solutions Group, introduced a new generation counter-rotating gear pump on which Maag worked for eight years. Generation 6 represents a redesign of every element of the pumps, the company says, “with more compact design, sharply increased volumetric efficiency, and lower pulsation.” It allows up to 50% higher flow rates for the same pump size with half as much material recirculating in the pump, Maag says. The first is in commercial operation.

Nordson Xaloy Inc., New Castle, PA (www.xaloy.com) since 2009 has offered a flexible system of modular bushing inserts on its standard and high pressure gear pumps to optimize flow properties for different polymers. Xaloy has built eight insert variations so far. A specific size pump can have multiple bushing inserts, which can easily be changed, the company says. Flow bore inserts are typically used for thermally sensitive polymers like PC, ePET, and biopolymers.

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First Automatic Sorting of Plastic Film by Polymer

Posted on January 8, 2014 by

By Jan H. Schut

Postconsumer mixed plastic film is at the bottom of the MRF (material recovery facility) waste chain. Both in Europe and the U.S. mixed plastic film, known as “2D 1-7″ (two dimensional film, polymers 1 through 7) is a contaminant that lowers the value of recycled paper. So MRFs typically remove plastic film from the paper stream, either by hand or automatically. Automatic removal of film from paper by near infrared vision sorting isn’t new. It has been done commercially at MRFs in Europe and the U.S. for at least ten years, notes Jonathan Clarke, country manager for the U.K. division of Tomra Sorting AS in Asker, Norway, which makes TiTech NIR sortation devices (www.titech.com).
Mixed film is only a tiny fraction of “2D” MRF material (3%-6% film vs. 94%-97% mixed paper), so it’s typically landfilled or burned. But that could be changing. Interesting investment is going on now in the first installations of automatic high-speed NIR sorting of plastic film not at MRFs, but at plastic recyclers both in Europe and the U.S. Recyclers are sorting to retain PE film and reject other polymer films. The possibility of upgrading commingled MRF plastic and reusing the PE was extensively studied by the Waste & Resources Action Programme in Oxon, U.K. (www.wrap.org.uk) between June and December, 2012.

The WRAP study (www.wrap.org.uk/content/resources-enable-recycling-household-plastic-films) used “2D” paper and plastic film collected at Casepak, Leicester, U.K. (www.casepak.co.uk), a MRF accepting commingled household recyclables including film. Casepak shipped 146 metric tons of paper and film to BS Environnment, a MRF in Nimes, France, with two NIR sorting devices from Pellenc Selective Technologies, Pertuis, France (www.pellencst.com). The first NIR device removed all plastic film (metalized pouches, nylon, HDPE, LDPE, PP, PS and PVC) from the paper. The second NIR separation retained PE film and removed everything else, i.e., remaining paper and non-PE plastic film. BS Environnment sent 2.67 metric tons of sorted PE film to a plastic film recycler in France, Regefilms Sud Ouest in Abidos, which has since gone out of business.

FIRST AUTOSORTING OF PLASTIC FILM BY POLYMER

Pellenc's automatic NIR sorters at Regefilms in France removed all non-PE plastic films from PE film. Regefilms, which since closed, is believed to have been the first recycler with auto sorting of film. Three other film recyclers are now setting up similar sortation.

Pellenc’s automatic NIR sorters at Regefilms in France removed all non-PE plastic films from PE film. Regefilms, which since closed, is believed to have been the first recycler with auto sorting of film. Three other film recyclers are now setting up similar sortation.

Regefilms was chosen for the WRAP test because it had two washing and recycling lines for film, one from Herbold Meckesheim GmbH, Meckesheim, Germany (www.herbold.com) and one from Sorema division of Previero (www.sorema.it), and automatic NIR film sortation from PellencST already in place. Regefilms sourced film from household waste and agricultural film and sold pelletized material to the Barbier Group, a packaging company in Ste. Segolene, France (www.barbiergroup.com), which used the material at up to 80% in trash bags.

Regefilms shredded the baled PE film from the WRAP test, automatically removed remaining paper and unwanted polymer films, then washed and pelletized the PE film, sending 1.79 metric tons of pelletized WRAP material to CeDo Ltd., Telford, U.K. (www.cedo.com), a maker of film and packaging. Pellets sent to CeDo had MFI (g/10 min.) of 0.55-0.58 and density of 0.923-0.926, close to CeDo’s own recycled film of 0.5-0.7 MFI and 0.92-0.94 density. CeDo blended the material into test bags at 40% and 60%.

When Regefilms went into liquidation in June 2013, its recycling machinery and NIR sorters were bought by its major customer, Barbier, and moved to Ste. Segolene, France, where they are expected to start operation again in 2014. PellencST also has four NIR sorting devices at a U.K. film recycling company, which is starting up now, and the first automatic film sorters are on order for the U.S. for a company that makes a recycled-content packing product.

PellencST's Turbosorter moves air over a high speed conveyor at the same speed as the conveyor to pin plastic film and paper to the belt, so plastic film can be removed.

PellencST’s Turbosorter moves air over a high speed conveyor at the same speed as the conveyor to pin plastic film and paper to the belt, so plastic film can be removed.

Tomra has TiTech NIR installations for automatic film removal from paper at numerous MRFs in the U.S. and Europe, including SIM’s Recycling Solutions Inc.’s new MRF in Sunset Park, Brooklyn. SIMS’ Brooklyn MRF started up in December 2013 to process recyclables from New York City’s five boroughs. In the U.K. Tomra has at least three MRF installations, which also make a second separation of PE film from commingled films. These include an installation at Weir Waste Services Ltd., Oldbury, U.K. (www.weirwaste.co.uk), using TiTech’s latest “Autosort 4″ NIR technology. Autosort 4 integrates lighting with scanning and is reportedly cooler and more energy efficient than other NIR systems. Weir separates PE film, bales it, and sells it to film recyclers.

TiTech’s Autosort also reportedly can distinguish between very similar spectrometer wavelengths of HDPE and LDPE. “TiTech units have been doing this for at least six years,”says Tomra’s Clarke. “But only in the last three years has the software improved to allow sufficient accuracy.” It’s impressive that NIR optical film sorting can extract 95% pure PE film from commingled plastic film from MRFs and tell the difference between HDPE and LDPE. But optical sorting still has limitations to overcome. It can’t identify polymers in black film, so black bags have to be removed some other way. Nor can it identify multilayer barrier PE films–it only reads the surface layer. Another problem with film sourced from MRFs may be smell. The WRAP study notes that pelletized “trial PCR had distinct odor when compared to CeDo PCR, which could have impact on its salability.” The test suggests that smelly pellets could be blended in small quantity. WRAP has a new study on potential end markets for MRF PE film (even if it is a little smelly), due in 2014.

TiTech's latest automatic sorting of films is installed at the new SIMS Recycling MRF in Brooklyn, where New York City's curbside recycling is sorted. TiTech's "auto sort 4" combines lighting with scanning for improved energy efficiency.

TiTech’s latest automatic sorting of films is installed at the new SIMS Recycling MRF in Brooklyn, where New York City’s curbside recycling is sorted. TiTech’s “auto sort 4″ combines lighting with scanning for improved energy efficiency.

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Tale of Two New LLDPE Film Recycling Plants

Posted on December 3, 2013 by

By Jan H. Schut

Postconsumer polyethylene film recycling is coming back after a 15-year hiatus with investment in new plants and new R&D. Especially interesting are new processes to clean LLDPE stretch film. Two new plants started up in 2011 with new wash processes to recycle 100% LLDPE stretch film back into film, one for pallet wrap, the other silage wrap. Wisconsin Film & Bag Inc., Shawano, WI (www.wifb.com), devoted five years to bench top R&D in-house to invent a patented hot wash process (U.S. Pat. # 8567702) for postconsumer LLDPE pallet wrap that allows WIFB to reuse the material in translucent monolayer industrial films and can liners. Soreplastic S.A., Tenneville, Belgium (www.soreplastic.com), recycles heavily contaminated LLDPE silage stretch wrap with a single large washing and recycling line making 1200 kg/hour of black film grade material. The trick, the company says, is much finer shredding.

NEW HOT WASH FOR LLDPE PALLET WRAP
Wisconsin Film & Bag’s process for LLDPE pallet wrap is designed to remove paper labels. WIFB uses hot water and surfactant to sterilize film and remove paper fiber. Typically hot water is used with PET flake to remove adhesives, but WIFB uses hot water “to get the pulping action to remove paper,” explains Robert Kulesa, vice president of operations at WIFB. “Adhesives aren’t a problem, they stay with the plastic. But if any contaminants are left after washing, they reattach to the plastic in the dryer because of the tackifiers.”
WIFB processes 90% LLDPE and 10% LDPE. The LLDPE wash line was built by Herbold Meckesheim GmbH, Meckesheim, Germany (www.herbold.com), though the idea to use hot wash for pallet wrap was WIFB’s. The line starts with a Herbold wet grinder with knives modified for LLDPE. It cuts film into large pieces, which go into Herbold’s recently designed VWE 600 prewash unit with three integrated wash sections. The first segment is float/sink to remove rocks while up-currents of water move film to the second segment, which has two conveying screws over a perforated bottom and spray nozzles to rinse sand and paper off the film. The third segment is another float/sink tank to remove fine sand and sediment. Segments can have separate water circuits for very contaminated film.
Film then goes by screw conveyor to a wet grinder, which reduces it to 1.5-2 in. flake. Next comes the proprietary hot surfactant wash (140-190 F according to the patent), followed by hydrocyclones for density separation and mechanical dryers. Because the material is sticky, WIFB releases last moisture in an agglomerator, creating crumbles that are easier to store than thin flakes. Recycled material is used in WIFB’s monolayer ECO Blend industrial films and can liners and in customers’ bags at 25%-50% recycled content.

Wisconsin Film & Bag uses patented hot surfactant washing to recycle 100% LLDPE pallet stretch wrap. It starts with Herbold’s three-part prewash and ends with an agglomerator to create manageable crumbles out of sticky flake and remove last moisture.

Wisconsin Film & Bag uses patented hot surfactant washing to recycle 100% LLDPE pallet stretch wrap. It starts with Herbold’s three-part prewash and ends with an agglomerator to create manageable crumbles out of sticky flake and remove last moisture.

At least one other filmmaker puts recycled pallet wrap at high percentages into can liners and film, but using a dry cleaning process and putting the material into three-layer film. In 2008, Petoskey Plastics Inc., Petoskey, Mich., started its Greencore Recycling division with a new washing and recycling plant in Hartford City, IN (www.greencore.com). Petoskey recycles 36 million lb/year of LLDPE pallet wrap and contaminated LDPE redemption bags from MRFs. The company dry recycles the LLDPE pallet wrap, shredding it and re-pelletizing it with an extruder from Erema GmbH, Ansfelden, Austria (www.erema.at). Paper is removed with continuous melt filtration from Erema’s self-cleaning laser filter, which has some 500,000 laser-drilled holes. The wash line from Tecnofer Ecoimpianti Srl, Caneselli, Italy (www.tecnofer.bis), recycles the contaminated LDPE redemption bags. Recycled material goes into Greencore’s three-layer can liners and bags with up to 70% postconsumer content. Petoskey also dry recycles postconsumer bags and film in closed loops for customers and has done so since 1978.

NEW SHREDDING FOR 100% LLDPE SILAGE WRAP
Soreplastic’s new recycling plant for silage stretch wrap faces much higher contamination than pallet wrap. Silage film comes with up to 60% rocks and dirt. Soreplastic’s input is roughly 40 million lb/year of silage film collected from regional farm groups (which are part owners of Soreplastic). Output is 18 million-20 million lb/year of film-grade black pellets, sold for agricultural film and garbage bags. Soreplastic washes with cold water and no chemicals. Its recycling line starts with a wet shredder from Lindner ReSource GmbH, Grossbottwar, Germany (www.lindner-resource.com), with capacity for up to 15,000 lb/hour. The number and distribution of shredder knives is modified for stretch film. But the big difference is that the shredder cuts film unusually small–down to 2-4 in. pieces. Recycled stretch film is typically shredded to the size of a sheet of paper (bigger pieces reduce wear on knives).
Shredded film then goes to a Sorema wash line, starting with prewashing with a float/sink section to remove rocks and a spray wash section to screen paper out. Then the material goes to a wet grinder to reduce it to 1-1.5 in. flake—again smaller than usual. Film is typically ground into 1.5-2 in. pieces. Flake then goes to a water tank with stirrers to open up clumps of material and on to another float/sink tank for final density separation before friction washing in centrifuges. Friction washing is followed by a screw press to remove water. Soreplastic’s drying system is different from the hot air dryers typically used for HDPE film. Because of stretch film’s stickiness, Soreplastic dries flake mostly mechanically, being careful not to overheat it. Drying starts with a large double centrifuge, followed by mechanical drying.

Among several new postconsumer film recycling plants, Soreplastic in Belgium stands out for the sheer size of its Sorema recycling line with output of 1200 kg/hour from up to 60% contaminated silage stretch film. Soreplastic’s trick is unusually fine shredding.

Among several new postconsumer film recycling plants, Soreplastic in Belgium stands out for the sheer size of its Sorema recycling line with output of 1200 kg/hour from up to 60% contaminated silage stretch film. Soreplastic’s trick is unusually fine shredding.

Soreplastic isn’t the first or only company recycling LLDPE silage stretch film, but it’s believed to run the biggest single recycling line for silage film. British Polythene Industries in the U.K., a producer of LLDPE silage wrap, is the dean of agricultural film recycling with three plants recycling a total of 150 million lb/year of heavily contaminated LLDPE and LDPE agricultural film. BPI’s first plant, which started in Dumphries, Scotland, in 1995, has recycled 100% contaminated LLDPE silage wrap for 15 years. BPI’s newest plant in Rhymney, Wales, which started in 2007, recycles LLDPE silage wrap and LDPE agricultural film separately. The LLDP line starts with a drum washer from Pla.to GmbH in Goerlitz, Germany (www.plato-technology.de), to remove large contaminants. Shredding, washing, grinding and drying systems are from Tecnofer. Recycled film goes to a twin-screw extruder from MAS Maschinen-und-Anlagenbau GmbH, Pucking, Austria (www.mas-austria.com). BPI’s LDPE recycling uses a conventional dry system with manual sorting, size reduction and extrusion by an Erema TVE extruder. BPI uses recycled material in trash bags and construction films.

British Polythene Industries recycles 150 million lb/year of heavily contaminated postconsumer LLDPE silage stretch film and has since 1995. BPI uses Pla.to Technology’s giant Drum Washer to remove stones before Tecnofer washing and recycling lines.

British Polythene Industries recycles 150 million lb/year of heavily contaminated postconsumer LLDPE silage stretch film and has since 1995. BPI uses Pla.to Technology’s giant Drum Washer to remove stones before Tecnofer washing and recycling lines.

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New Moves for Rotating Molds

Posted on November 6, 2013 by

By Jan H. Schut

Two unusual new concepts for cube molds for multi-material injection molding were introduced at the Kunststoff Show (K Show) in Düsseldorf, October 16-23 this year (www.k-online.com). Both alter the normal role of cube molds to move and assemble parts by creating unusual new non-cube structures to transport molded parts for assembly. Separating part transport from the cube neatly allows secondary automation without adding cycle time providing for significantly faster production. Servo-driven rotating molds also cycled faster with more automation than ever before on the show floor, demonstrating new possibilities for durable and medical applications.

Rotating molds with two, three and four sides have been used since the 1950s to mold multi-material parts, sequentially injecting two to as many as six different materials or colors. Four-sided cubes offer much higher automation and output than two-sided rotary stack molds. Cubes are typically dedicated to in-house molding millions of parts a year of small disposables like toothpaste tube shoulders, re-closable lids and soft-touch toothbrushes. Two-sided rotary molds produce lower volumes of larger multi-material parts in the tens and hundreds of thousands for durables like tools, automotive, appliance and electronic parts.

ON TRACK FOR MORE FLEXIBILITY

One of the two new cube concepts is Flexi-Cube launched by G. B. Boucherie N.V., Izegem, Belgium (www.boucherie.com), which has a fixed cube around which light-weight mold inserts or carriers travel on a track. Parts are molded with different material shots on the stationary cube. Because the cube doesn’t turn, it doesn’t have to be square, but can be rectangular, allowing more stations to be added for molding, cooling, and other functions.

Inserts carry parts from station to station around the cube. Boucherie’s K Show announcement describes a solid track “around the cube on which holders with molded parts are traveling. These holders are moved by servo motors, allowing [them] to travel over different distances.”  The patent application (U.S. Pat. Applic. # 20110117233) describes mold inserts that “serve as holders and can be lifted out of partial cavities,” pulling back from the cube just enough to travel freely around it.

Boucherie's new Flexi-Cube

Boucherie’s new Flexi-Cube technology for high-volume, multi-material injection molding has a fixed cube around which light-weight mold inserts travel on a track. The first commercial Flexi-Cube mold was installed in the U.S. last year to make soft-grip razor handles.

The first commercial Flexi-Cube mold, which took seven months to build, was installed in July 2012, in the U.S. It has 24 cavities molding three-component solid razor handles for a snap-fitting razor. There are four sets of molds on the stationary cube and five sets of inserts to move parts around the cube. The extra insert allows a fifth station on the non-operator side for robotic part removal without adding cycle time. The first parting line of the mold has two sets of cavities for the first and second shots of PP. The second parting line has cavities for contact cooling and a third shot of soft-grip TPE. Cycle time for the 10-gram razor handle is only 17 seconds. “Typically a solid razor handle like that would take 25 seconds,” says John Williams, president of Boucherie USA Inc., Knoxville, TN. Boucherie showed a two-cavity prototype in motion at K without molds.

The other unusual new cube molding concept comes from Zahoransky Formenbau GmbH, Freiburg, Germany (www.zahoransky-group.com) and combines multi-component indexing mold plates with a “TURN-stack” rotating assembly cube. The propeller-like indexing mold plates carry either two or three molds, depending on how many materials are being injected. A single-component part uses two plate molds and indexes 180 degrees with one plate always in the molding machine and the other plate transferring parts to the assembly cube. A two-component part uses three mold plates and indexes 120 degrees with two plates always in the molding machine and the third plate transferring parts to the assembly cube. The assembly cube rotates on either a vertical axis, mounted outside the machine base, or a horizontal axis, mounted off the machine platen. The cube can also do other things besides assembly like leak testing or vision inspection.

Zahoransky's new indexing plate molds

Zahoransky’s new indexing plate molds handle one- and two-component parts. Two-component parts move on three 120-degree indexing plates; one-component parts move on two 180-degree indexing plates. The two parts are then assembled on the rotating cube.

The “indexing plate/assembly cube” concept was presented January 2013 by Zahoransky managing director Michael Schmidt at the Molding 2013 conference in New Orleans, sponsored by Executive Conference Management in Dearborn Heights, MI (www.executive-conference.com). The schematic shows two-component parts made on three 120-degree-indexing plate molds and one-component parts made on two 180-degree indexing plate molds. The two parts are transferred to the cube, which indexes and assembles them. Cycle time is determined by the longest time to mold either part. Zahoransky has built a prototype to demonstrate the new technology.

FASTER CUBES, MORE AUTOMATION

Foboha GmbH in Haslach, Germany (www.advaltech.com), set a speed record at K with its patent-applied-for (U.S. Pat. Applic.# 20120328730) all-electric cube, first launched at the Fakuma Show in 2012 in Germany. Arburg GmbH, Lossburg, Germany (www.arburg.com), ran a pilot Foboha mold at K making two-component (HDPE and PP) caps for juice packs with 12 caps per side (4 x 12 + 12) on an Allrounder 720A press with 3200 kN of clamp force.

Foboha's new automation

At the K Show Foboha demonstrated new automation to screw two-part drink caps together. Each cavity molds 8 tops and 8 bottoms. Tops are unscrewed automatically and screwed onto the bottoms, which remain in the mold. Assembled caps are then removed robotically.

“It molded in under six second cycles,” says Hansjoerg Keusgen, head of sales and marketing at Foboha. “That’s a record for sure for cubes.” A servo drive and servo motor allow the cube to turn as the mold opens, for cycle times at the show of 5.6 to 5.7 seconds.

Last year Zahoransky showed a 6.5-second cycle molding three-component drink caps at NPE 2012 in Orlando, FL, using a pilot total integrated manufacturing (TIM) cube with servo drive and servo motor rotation on a press from KraussMaffei Technologies GmbH in Munich, Germany (www.krauss-maffei.com). Cycles for commercial cubes have been reported as short as 7 seconds for two-component toothpaste tube shoulders.

At the K Show Foboha also demonstrated patent-applied-for new technology (U.S. Pat. Applic. # 2012/0088000) to screw two-part drink caps together automatically in the mold for the first time. The demo ran on a standard F-270 all-electric press from Ferromatik Milacron GmbH, Malterdingen, Germany (www.ferromatik.com). The molds have eight bottoms and eight tops per side (4 x 8 + 8) and inject two PPs of similar shrinkage. Caps are automatically unscrewed from the mold and screwed onto the bottoms while the bottoms are still in the mold. Assembled caps are then removed robotically. Cycle time is 10 seconds because the caps are relatively thick.

Reflecting increased interest in rotating molds for durable automotive, appliance and electronics applications, KraussMaffei showed a GX series machine for the first time with a SpinForm swivel plate. It used a two-sided mold to make a demo part with upper and lower PC/ABS blend shells, combining colored and optical grade transparent materials. Then two different polyurea coatings were flowed onto the finished surface in the mold for high gloss finished coat. Finally the parts were assembled robotically with an LED light inside. KraussMaffei introduced its ColorForm PU in-mold coating at K 2010, but says it has reengineered the RIM process since with wear-resistant pumps and more accurate metering.

Engel Austria GmbH, Schwertberg, Austria (www.engelglobal.com), demonstrated servo-driven rotating index plates, without a tiebar or conventional turntable. Engel molded three component drip chambers for blood transfusions at the show on an Engel e-victory hybrid injection molding machine. The molds index 180 degrees, making two parts, one PS and the other PP, assembling them with a filter between, and overmolding them with PP. The complex molds were built by Hack Formenbau Gmbh in Kirchheim, Germany (www.hack-formenbau.de), accommodating 14 separate moving axes driven by servo motors. “It is by far the most movement we have ever integrated into a production cell,” says Georg Steinbichler, vice president of R&D technologies at Engel.

ENGEL's indexing plates

Engel demonstrated indexing plates from Hack Formenbau, which rotate 180 degrees supported by the platen without a rotary table. The production cell uses an astonishing 14 axes of servo driven motion to mold and assemble three-component drip chambers for blood transfusions.

At the K show Zahoransky showed a TIM Light mold for the first time, which adds external assembly automation to single-component parts for lower volumes. The two-platen mold doesn’t rotate or require a tie bar support structure. “Two assembly plates enter the dual-platen mold when open, remove parts from their respective platens, and then slide back out from the mold, where they mate and assemble the parts,” explains Frank Kigyos, CEO of Zahoransky USA Inc., Sugar Grove, IL (www.zahoransky-usa.com). The system takes slightly longer cycle time than Zahoransky’s original TIM cube technology, but costs significantly less. Zahoransky also showed its TIM cube with a central rotating cube to mold and carry parts and two flat external assembly platens in 90-degree positions beside the cube. The external assembly platens included servo-slide pick-and-place units and rotated 180 degrees, providing up to four assembly functions. Outside assembly platens with servo motion can be retooled for different parts.

Ermo Group, Marcille-La-Ville, France (www.ermo-group.com), introduced a one-sided mold for two components with its in-mold assembly system (IMAS) automation. Three other makers of two- and three-component rotating molds also exhibited at K: Braunform GmbH in Bahlingen am Kaiserstuhl, Germany (www.braunform.com); Ferbe Tools AB, Gislaved, Sweden (www.ferbe.se), with “SpinStack” molds licensed from Gram; and Caco Pacific Corp., Covina, CA (www.cacopacific.com) with low inertia technology (LIT).

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Demystifying Energy Saving Devices on Injection Molding Machines

Posted on August 31, 2013 by

By Jan H. Schut

Injection molding machine makers at the upcoming Kunststoff Show in Dusseldorf, Germany, in October are touting energy efficient presses that will save 30%, 50%, even 70% of energy use. But is anything really new? Energy efficient all-electric and hybrid injection molding machines have been available for nearly 30 years, and energy saving devices like servo pumps and barrel insulation have been retrofitted onto injection molding machines for almost as long.

A cynical explanation for the K Show fuss is that after years of slower business conditions, processors are newly aware of the importance of energy saving. There is also a perceived opportunity for all-electric presses in Europe, where all-electric still accounts for only 15%-20% of injection molding machine sales (see chart), while hydraulic and hybrid account for 80%-85%, based on a 2011 study for Euromap, Frankfurt-Main, Germany (www.euromap.org). In Japan roughly 80% of injection molding machine sales are all-electric vs. 20% hydraulic or hybrid, and in the U.S. sales are roughly 50/50, industry sources say.

EUROMAP p44 Chart

Roughly 15%-20% of injection molding machine sales in Europe are all-electric vs. 80%-85% hydraulic or hybrid, according to data from Euromap, the European machinery association. All electric presses in the total European machine population are still only 4.5%. Source: Euromap

How do original equipment manufacturers (OEMs) calculate their energy savings percentages? Typically by comparing energy use for a new efficient machine function with old-fashioned hydraulics for the same function. An injection molding machine has seven main functions that use energy – plastification, barrel heating, platen movement, injection, clamping pressure, ejection, and barrel retraction. All seven can be made more energy efficient than conventional old-fashioned hydraulics, where a standard induction electric motor runs at constant RPM powering 1-2 hydraulic pumps, which runs even when idling.

Energy efficiency, however, isn’t just a machine function. Efficiency, which is typically measured in kilowatt-hours per kilogram (kWh/kg), is different for each molded part and depends on part weight, cycle time, machine size, and machine efficiency. The SKZ Plastic Institute in Wurzburg, Germany (www.skz.de), which researches energy saving potentials for OEMs and performs energy audits, published a study in 2011 that gives a rough idea of how much energy each machine function uses (see pie chart).

SKZ p40 Pie Chart

Energy consumption on an electric 100-ton injection molding machine with hydraulic injection makes 83-gram ABS storage trays with 2-mm thick walls in 16.9 second cycles and specific energy use of 0.384 kWh/kg. Source: SKZ

The SKZ tested a 100-ton mostly electric press with hydraulic injection, molding an 83-gram ABS storage tray in 16.9 second cycles and found that plastification consumed by far the most energy at 48%. Next came barrel heating at 17%, followed by clamp force at 12%, and injection force at 11%. Linear movements to open and close molds and retract the barrel for cooling used only minor amounts of energy – 4% each. So plastification and barrel heating are the big opportunities to save energy.

REX Materials

Uninsulated barrels waste a lot of energy, as this thermal image shows. Rex Materials’ ceramic insulated clamshells with radiant I.R. heating elements can save up to 45-50% of heat energy.

Heat is the only energy user that doesn’t involve movement, so the fixes are different. Insulating the barrel saves “an average of about 25% of heat energy,” says Bernhard Lettner, product manager for large two-platten presses at Engel Austria GmbH in St. Valentin, Austria (www.engelglobal.com). Replacing hydraulic heat with radiant I.R. heating adds cost, but saves even more. “Based on a complete retrofit of a small machine, we expect I.R. ceramics to save 45-50% of heat energy—up to twice as much as insulating blankets,” says Dean Francis, president of Windsor Kunststofftechnologie GmbH in Hanau, Germany (www.windsor-gmbh.com), which retrofits hydraulic presses for energy saving and sells all-electric presses from JSW Plastics Machinery Inc. in Japan (www.jswpmi.com). Cast in insulating ceramic, I.R. elements from Rex Materials Inc., Fowlerville, MI (www.rexmaterials.com), can convert all zones or only the feed zone.

Windsor/JSW

All-electric presses like JSW’s AD110 save 20%-30% energy overall vs. energy efficient servo-hydraulics, which lose that much in conversion from electric to hydraulic and from hydraulic to mechanical energy. All-electric presses save 50% of energy over old-fashioned hydraulics.

OPTIMIZING ELECTRIC MOTOR EFFICIENCY

For both OEMs and retrofits the basic energy saving devices on injection molding machines are variable frequency drives, also known as inverters, and servo drives. Standard AC motors can be retrofitted with variable frequency drives to control motor speed, so the motor turns at exactly the RPM needed to pump the correct oil pressure for the process.

Direct electric power with a variable frequency drive and AC motor will be 50% more energy efficient than old-fashioned hydraulics and 20%-30% more energy efficient than modern servo-hydraulics for any machine function because hydraulics lose 20%-30% in two conversions. First, electric power is converted to hydraulic power; then hydraulic power is converted to mechanical power. Since plastification uses the most energy, converting plastification to electric power saves the most. It also reduces the size of remaining hydraulic pumps needed and the amount of hydraulic oil in a hybrid machine.

Servo motors controlled by servo drives do the same thing as an inverter/AC motor, but are more precise. The kW size of the variable frequency drive and servo drive has to match motor size. Large servo drives and servo motors over 50 kW to 100 kW are expensive because of the high price of copper and rare earth magnets. So a servo drive/servo motor is likely to replace positional motors for energy saving on functions like clamp opening and closing or part removal.

A direct-drive synchronous torque motor instead of an inverter/AC motor with gearbox saves energy lost in the gearbox (1.5%-2% of energy for that function). Oswald Elektromotoren GmbH in Miltenberg, Germany (www.oswald.de) offers torque motors for plastification and clamping up to 70,000 Nm. Etel S.A. in Motiers, Switzerland (www.etel.ch) makes standard torque motors up to 31,000 Nm and larger custom motors.

Electric motors lose about 8% of energy converting rotational power to linear power, typically with a conventional ball screw. Knoedler-Getriebe GmbH in Ostfildern, Germany (www.knoedler-getriebe.de), offers an alternative ZS rack and pinion electric motor, controlled by a variable frequency drive, that also converts rotation to linear movement. Knoedler’s rack and pinion motor can replace a hydraulic cylinder for plastification and injection and is offered for up to 450 ton presses.

Knoedler

Knoedler’s rack and pinion electric motor converts rotation to linear power and is used for energy saving for injection and plastification on all-electric presses up to 450 tons.

More savings are possible with “stop/go” movements like clamp open and close by regenerating electricity from braking. A regenerative inverter AC unit returns that energy to the grid or applies it to other movement. Regeneration can recover 10%-15% of energy for clamp movement with higher recovery for bigger molds, notes Reinhard Schiffers, head of machine technology and tests at KraussMaffei Technologies GmbH in Munich, Germany (www.krauss-maffei.com). Regenerative inverter drives are commercially available from Siemens AG in Erlangen, Germany (www.siemens.com/drives) and Bernecker + Rainer Industrie-Elektronik GmbH (B&R) in Egglesberg, Austria (www.br-automation.com) and are applicable both to hydraulic and all-electric machines and can be retrofitted. Some regenerative devices are also proprietary to OEMs, like a new mechanical fly-wheel system, which Engel will bring to K.

Siemens Sinamics Servo Pump

Siemens Simatics servo hydraulic pumps with a frequency converter and servo motor reportedly save up to 70% energy vs. conventional hydraulic pumps and are used for retrofits.

All-electric presses also have size limits because of the cost of large motors. The largest all-electric press is 3300 clamp tons vs. around 7000 tons for the largest hydraulic presses. Ube Machinery Corp. in Yamaguchi, Japan (www.ubemachinery.co.jp), and JSW have both built 3300-ton all-electric presses for automotive applications. To reach that tonnage electrically, both are believed to use four large motors in sync. Most all-electric machines are less than 350 tons. Over that size, hybrids with servo hydraulics become more cost effective.

OPTIMIZING HYDRAULIC PUMP EFFICIENCY

Another reason hydraulic injection molding is still popular in Europe is that hydraulics have roughly five times higher energy density than electric motors (kW/cu meter). Many existing molds also use hydraulics for core pulls, so on hybrid machines European OEMs typically use hydraulics for injection and for clamp force done with energy efficient servo-hydraulic pumps. The main saving from putting variable speed drives on hydraulics comes from shutting pumps down during cooling time, which can be long for large parts.

Bosch Rexroth AG in Lohr am Main, Germany (www.boschrexroth.com), combines a variable frequency drive with synchronous torque motor for hydraulics control. Siemens offers Simatics servo hydraulic pumps, launched at the K Show in 2010, with a frequency converter and servo motor for retrofits, reportedly saving up to 70% energy vs. conventional hydraulics.

More efficient drives on hydraulic pumps also allow less expensive gear-type hydraulic pumps to be used instead of variable displacement pumps, though not all OEMs agree. Negri Bossi SpA in Milan, Italy (www.negribossi.com) combines a variable frequency drive with a variable volume hydraulic pump on its Canbio VSE press, introduced in 2011, claiming oil output is more consistent. Engel also combines a servo drive/servo motor with a variable displacement pump on two-platen machines. Software optimizes servo motor setting and pivot angle on the variable displacement pump for greater efficiency, Engel says.

Better controlled hydraulics are quieter and cooler. Siemens in a 2012 publication describes retrofitting a hydraulic machine with servo motors, after which hydraulic oil ran 10 degrees C cooler (35 °C down from 45 °C), and oil cooling was “practically no longer required.” Reducing friction in oil lines, manifolds and fittings also saves energy. KraussMaffei’s GX series at K sports a new hydraulic manifold with two valves instead of one and bigger oil lines, which uses 30% less energy with lower oil temperature. And cooler oil lasts longer.

The area with genuinely new developments at K is software and control packages to monitor energy use. B&R, which supplies energy saving servo pumps for injection molding, is introducing APROL EnMon (energy monitoring) pre-installed in its PC to optimize energy use throughout the molding process. ABB Group in Zurich, Switzerland (www.abb.com) this year introduced energy monitoring capabilities in its new ACS 880 drive motors.

OEMs will show new energy optimizing software at K, too. KraussMaffei will introduce MC6 (motion control) software, which automatically optimizes screw speed and other settings for energy efficiency, then asks the operator to check the part and approve the adjustment with an Eco Button feature. Engel will introduce new “ecobalance” software to reduce peak energy consumption automatically. Instead of heating and injecting at the same time with high peak energy use, the software injects first, and then heats gradually.

Will processors get the same energy savings as OEM tests? The short answer is actual energy savings still depend on part size and cycle time, not just energy efficiency. An all-electric machine will be inefficient if it runs low throughput of small parts. Choices between all-electric and servo-hydraulics won’t be resolved soon. “All systems have usefulness,” notes Werner Knoedler, managing director of Knoedler. “The future will need more than one system.”

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