NPE 2000 News Wrap-Up: Extrusion

At this year’s NPE, new processes to put wood flour into plastic were virtually everywhere—several even start with undried flour. There was also lots of news at the show in downstream cooling and handling of wood-filled profiles, including the first nitrogen cooling tank.

There were also plenty of technical firsts in foaming at NPE, specifically the first known demonstration of foamed PET; the first micro-foamed polyolefin sheet; and the deployment of a high-tech static mixer/heat exchanger instead of a second cooling extruder for foamed PS production.

News in blown film was somewhat less dramatic and includes the first commercial 10-layer die, more players making side-fed dies with split resin distribution, and advances in surface winders designed to accommodate processor shifts to more exotic resins. A host of foreign machine builders turned up to test the U.S. market as well.

 

Wood’s Hot

There was loads of new process technology at NPE for mixing wood with a variety of plastics. Davis-Standard Corp., Pawcatuck, Conn., showed its counter-rotating, twin-screw Woodtruder at NPE for the first time (see PT, Feb. 2000, p. 16, June 2000, p. 48). The 28:1 L/D extruder mixes wood flour into PE, PP, PVC, ABS and HIPS. The machine features a special venting section to draw moisture. It adds plastic via a side mounted, single-screw extruder and uses no melt pump. Nearly a dozen Woodtruders are on order to make building products and custom profiles.

ExtrusionTek Milacron in Batavia, Ohio, which has historically supplied conical twin-screws to licensees of Strandex’s wood-filled process, introduced what it calls the highest output extruder for wood-filled composites for up to 1700 lb/hr. The CM92 conical counter-rotating twin-screw extruder is fed by a 140-mm diam. twin-screw VMEDS model with a crammer auger for wood flour. The VMEDS (Vertical Material Enhancement Delivery System, which has a vertical integrated feed option) is preheated to 220-240 F with an electrically heated barrel and an atmospheric vent. The preheater screw has an 8:1 L/D to promote good distributive mixing and devolatilization, Milacron says. The system uses no melt pump.

Krupp Werner & Pfleiderer in Ramsey, N.J., displayed a two-machine setup for wood processing. The line at the show featured a co-rotating twin-screw ZSK MegaCompounder. Wood is dried in the first four barrel sections, and polymer is added farther downstream. After moisture is vented, the compounding machine feeds the mixture to a 6-in., 8:1 L/D single-screw extruder furnished by Merritt-Davis Corp., Hamden, Conn., with a new feed section. Output is reportedly 1000 lb/hr. On the show line, the die was from ETI–Extrusion Tooling Inc., Cummings, Ga., and downstream cooling equipment was from ESI–Extrusion Services Inc., Akron, Ohio. W&P says it has three wood-filled processing lines in production and several more on order.Foamed PET

 

Tops Sheet News

Probably a world first and certainly one of the most unusual exhibits at NPE was a demonstration of foamed PET sheet by Sentinel Products Corp., Hyannis, Mass. In an alliance with Davis-Standard, Sentinel, a commercial processor of polyolefin foams, developed an extruder with a series of seven feeding ports for CO2- and nitrogen-based blowing agents. Sentinel’s new process also has a specially designed, patent-pending annular spider die. The die has a computer-controlled, pneumatic internal choke and an internal and external die-gap adjustment system known as Autojust. The die is designed for foamed PS, PET, and PP.

The foamed PET uses very high I.V. of 1.2 compared to. 0.8 for bottle grade PET or 0.62 for recycled or fiber grade PET. The 1.2-I.V. resin is made by only one supplier, Mossi & Ghisolfi Group in Tortona, Italy, using patented solid state “poly-addition” to raise the I.V of virgin or recycled PET. M&G now offers its high I.V. resins in the U.S., supplied from Europe, and says that if U.S. demand grows, it will install poly-addition equipment at its new North American plants. M&G earlier this year bought Shell Chemical’s global PET production, which includes a U.S. and Mexican plant.

At least one other new approach foams PET, too. Eastman Chemical Co., Kingsport, Tenn., has a reactive additive, developed two years ago, which increases melt strength of an 0.8 I.V foam grade as it’s extruded. It’s just now being commercialized for sheet, but has never been displayed.

An equally fascinating foam development from Europe was a new static mixing heat exchanger from Fluitec Georg AG in Winterthur, Switzerland (whose new U.S. rep is Interflow Systems Inc., Plaistow, N.H.). The 10-in.-diam. reactor has heat exchangers inside the X-shaped cross pieces of the static mixer for either heating or cooling fluids. Two years ago, Fluitec installed one in production on a tandem foam PS sheet line, where the unit replaced a cooling extruder. The continuous CSE-XR heat exchanger controls fluid temperature to ±1° F with 1500 lb/hr throughput, Fluitec says.

Other foam developments include the first polyolefin sheet made with MuCell micro-foam technology, developed and licensed by Trexel Inc., Woburn, Mass. A major European packaging company ran trials in France during the week of NPE. It made micro-foamed homopolymer PP sheet with 25% weight reduction (using PP from Amoco BP). Micro-foaming PP makes rigid thermoformable PP sheet without PP’s traditional problem of sagging in thermoforming ovens.

Starting this month, a U.S. packaging processor is commercializing a micro-foamed HDPE tubular package with 30% weight reduction. Foaming polyolefins, which are crystalline, is far more difficult than foaming PS, which is amorphous, Trexel explains. Though the rate of expansion is far less (PS expands 95%) and polyolefins require less aggressive cooling, they need tighter control of the supercritical-fluid blowing agent.

Welex Inc., Blue Bell, Pa., showed new quick-change features on cooling rolls for sheet. They include gears and drives mounted on lever arms for quick release and quick disconnects for cooling water. Welex also showed a new digital hydraulic roll gap control, which it maintains is the first to control pressure independent of position to maintain precise closing pressure on delicate form-fill-seal sheet. (It can also control for position.)

American Kuhne Inc., Norwich, Conn., showed a new water-cooling manifold for its extruders. Its tube-in-tube design cools return water for faster, more efficient cooling, according to the company. Another new feature of the manifold is isolated cooling zones that can be separately shut off and drained.

 

Microlayering

Black Clawson Converting Machinery LLC, Fulton, N.Y., showed a new micro-layered feedblock for cast barrier film and extrusion coating for the first time. It has 14 separate flow channels, which can be subdivided for additional micro layers, i.e., 28 or 56. A three-material wall structure like A-B-C-B-A might use 14 layers—five layers of resin A, one layer of tie resin B, two layers of barrier resin C, one tie layer B, and 5 layers of resin A. The subdivision ensures that resin velocities match, so the die fills evenly. Even though higher-viscosity resin flows more slowly than low-viscosity resin, it apparently travels at the same speed and feeds uniformly when separated into many layers. Multiplication of layers also improves barrier, Black Clawson says.

NewCastle Industries, New Castle, Pa., showed a comparatively inexpensive, polished tungsten carbide chill roll for the first time with a near-mirror finish (1-2 root mean square). Tungsten carbide rolls typically have matte finish or chrome plating for hardness and polish. But chrome adds cost. NewCastle made its first polished tungsten roll last year and has shipped three since. NewCastle also showed a new ContraBend chill roll for the first time with reverse deflection to apply pressure more evenly to sheet. A 66-in. wide ContraBend roll was shown at Welex’s booth.

 

Super Cool Tank

Like all other extrusion processes, PVC profile lines have been limited in output by cooling. Conair, Pittsburgh, displayed new technology to cool profiles cryogenically, raising output potentially from 20% to 200%, Conair says. The 12-ft-long, four-zone tank cools profiles without water, thus eliminating environmental concerns over water disposal. Instead it injects liquid nitrogen, which converts to a gas at -320 F and expands 700 times. This forces oxygen out of each zone and creates a 100% nitrogen gas environment in which high-speed blowers circulate gas at up to 2000 cu ft/min.

Adding a nitrogen cooling tank at the end of water cooling tanks can raise profile output 20-40%, Conair says. Trials replacing all sizing and cooling equipment with nitrogen gas can increase output up to 200% and take up to 40% less floor space, Conair says.

Conair is currently working with two tool makers to develop vacuum calibration systems where nitrogen gas replaces water in the calibrator jacket, too. Nitrogen cooling tanks come in three lengths—8, 12, and 16 ft with two, three, and four zones respectively. Nitrogen cooling tanks, however, cost roughly twice what water-cooled ones do, and nitrogen adds 10-15% to operating costs. But this is recovered by higher throughputs in less than a year, Conair says.

The patent-pending nitrogen cooling technology was developed by Material Enhancement Inc. in Effingham, Ill., which built and installed several lines in the past year before teaming up with Conair.

A typicalinstallation is a high-intensity water tank 14-24 ft long, followed by an 8-16 ft nitrogen cooling tank.

Conair now has orders for six more nitrogen tanks, including an 8-ft, two-zone tank, which will go this month to a major profile extruder in North America to cool wood-filled, foamed profiles. The cryogenic tank follows a dry calibrator and sprayed water tank.

Two suppliers touted more conventional cooling lines that have the capability to cool 2000 lb/hr of dual-strand PVC profiles. Conair showed a new 24-ft-long, high-intensity sprayed water tank, which recirculates up to 360 gal/min. Used with a high-speed puller (but without nitrogen), Conair says it’s the fastest cooling line available.

A&G Extrusion (Actual & Gruber) in Austria (represented in the U.S. by Extrusion Process Marketing Inc., Washington Crossing, Pa.) also displayed PVC profile cooling lines rated at 2000 lb/hr. A&G built the first last October after a year of development, and says it has delivered 40 systems worldwide since. The two strands each have two dry calibrators, followed by 45 ft of vacuum water tank. Product changeovers can be done in minutes using single-hose water and vacuum disconnects.

A new development for polishing PVC profile dies comes from ExtrudeHone in Irwin, Pa. ExtrudeHone makes equipment to clean aluminum extrusion dies and surfaces of used injection molds. In the past year, it has sold systems to polish large, complex PVC profile dies to several window processors. Six months ago ExtrudeHone developed its first prototype specifically for multi-part vinyl profile dies, which was shown at NPE for the first time.

ExtrudeHone’s polishing process forces a silicone polymer medium like “Silly Putty” back and forth through die passages to clean them. This visco-elastic, non-Newtonian fluid flows like liquid when no pressure is applied. But it behaves like a solid when sudden shear force is applied, acting like liquified sandpaper.

CPM Compounding Processing Machinery GmbH from Grossfehn, Germany (represented in the U.S. by Plastic Processing Technologies Inc., Lake Geneva, Wis.) is a five-year-old builder of counter-rotating conical and parallel twins that two years ago introduced a new screw design for PVC profile, siding, and pipe. CPM says it’s the only screw in the world where the continuous flight pitch changes gradually from one zone to another while maintaining a constant screw-to-screw gap throughout the length of the screw. The screw achieves 20-40% higher output at the same amps, CPM says.

 

Corrugators Large and Small

In corrugated pipe, NPE brought out samples of some of the biggest and smallest ever. Corma Inc., Concord, Ont., showed a 70-in.-diam., dual-wall corrugated pipe section for the first time in North America. Made commercially in Japan for three years, it was first shown at K’98 in Germany, and is still believed to be the world’s largest for dual-wall pipe. Corma also displayed European dual-wall PP pipe that’s white inside and black out, with a new coupling made by fusing pipe walls together, staying within the OD of the original pipe.

Unicor Plastic Machinery Inc., Mississauga, Ont., showed the world’s smallest corrugated pipe—a 3-mm-diam. nylon tube. It’s extruded for automotive wire harness on three corrugating lines at General Motor’s Packard Electric division. Previously, the smallest tube was 4 mm of nylon for the same application.

For co-extrusion and striping, American Kuhne brought a new controller, called Akcess 100, manufactured by Facts Inc., Cuyahoga Falls, Ohio. It includes a new mechanism to balance a second extruder with a primary one.

Breyer GmbH Maschinenfabrik in Singen, Germany, showed its tube extruders in the U.S. for the first time. Breyer, which says it has about a third of the U.S. market for cosmetic tubes, exhibited at the previous NPE ’97, but without equipment.

An unusual counter-rotating cross-head tubing die was shown for the first time by Guill Tool & Engineering, West Warwick, R.I. The core and outer surface of the patent-pending die turn in opposite directions. Rotation can add a spiral rib to the tubing and improve strength. The die has been in the field several years, but hadn’t been shown before.

 

10-layer Die Goes Commercial

In blown film, there were no elaborate 7-layer lines displayed this year. Brampton Engineering Inc., Brampton, Ont., however, is building what’s believed to be the world’s first commercial 10-layer die. The company previously built a small 4-in., 10-layer die for its own R&D lab. The new 10-layer streamlined pancake die is 18 in. in diameter and will go to Europe in October to make high-barrier film.

NPE also saw more introductions of side-fed dies, both stack and spiral, with shorter flow channels splitting the flow of one material. Addex Inc., Hingham, Mass., showed its newly commercialized, patent-pending Redi (regular division) die (see PT, Jan. 2000, p. 15) for the first time. The side-fed die is designed to combat the so-called limitations of existing stack dies, notably excessive pressure and layer-to-layer thickness variations.

Kiefel Inc., Wrentham, Mass., which traditionally runs HMW-HDPE lines at NPE, this time operated a three-layer coextrusion line in low-stalk mode. Kiefel also showed a video of a recently developed side-fed spiral die with binary melt distribution, which it says is much more accurate at layer thickness control than a bottom fed die. Kiefel installed the first a year ago, but has none in the U.S. yet.

Other blown film news includes a new electrostatic precipitator from Future Design Inc., Brampton, Ont., jointly developed and patented with Martignoni Elettrotechnica SrL in Italy, which will manufacture them. It is the first designed for blown film lines, Future Design says, fitting between the die and air ring. A vacuum removal system will deliver air-born contamination—gas, fumes, and processing aids—to a filtering system or to the electrostatic precipitator.

Macro Engineering & Technology Inc., Mississauga, Ont., showed a 5-layer blown-film die for PVdC (see PT, May ’99, p. 15). Macro is developing another new stackable die with five layers for seven materials.

Battenfeld Gloucester Engineering Co., Gloucester, Mass., showed a new Windows-based version of its Extrol control system, called Extrol Plus. The PC-based software adds data management functions and communication options like plant networking and internet access. The new control system must be beta tested before it’s available commercially.

NPE also saw several foreign blown film machine builders with machinery in the U.S. for the first time. Uteco SpA in Italy (with U.S. offices in Mt. Prospect, Ill.), primarily a maker of downstream converting equipment, was at NPE with its first blown film line. Uteco later in July showed a 9-layer blown film line at an open house in Italy and is offering Italian-built machines with U.S. electrics.

Black Clawson also demonstrated a blown-film line with a 30:1 L/D extruder and a 16-in. die from Rulli-Standard in Brazil, as part of a new alliance between Rulli and Black Clawson. It’s Black Clawson’s second foray into blown-film machinery (it bought Sano from Milacron in the early ’90s), which is often integrated with its converting equipment. The Rulli line from the show went to Nordflex in Hudson, Wis.

Several blown-film machine suppliers reported new interest in advanced winders, especially with automatic roll handling. Reifenhauser Inc., Ipswich, Mass., has offered fully automatic shaft extraction and reloading with cradles and tracks for over five years, but only in the past year sold four systems in the U.S. Reifenhauser also showed a new center/surface winder to make large rolls of plastic (up to 59 in. diam.), one of the largest ever.

Windmoeller & Hoelscher Corp., Lincoln, R.I., demonstrated robotic roll handling at the show on a center surface winder.

Hosokawa Alpine American, Natick, Mass., designed its first completely robotic roll handling for center surface winders after NPE. Its first robotic winders cost $150,000 and will be delivered by year end, Alpine says.

 

New Screw Designs

Inductametals Corp., Chicago, trademarked a new mixing screw for extrusion and injection molding just before the show. Called UltraMelt, the screw pitch is increased at the end of the transition at the same time that a second transition of root depth is occurring. This results in a shallower than normal metering section. Deliberately changing the root depth at a different rate from the pitch disrupts laminar flow, Inductametals says, and improves mixing and melting.

HPM Corp., Mount Gilead, Ohio, has a new wave screw patented just weeks before the show (U.S. patent 6,056,430 May 2, 2000). Taking HPM’s double wave screw, it introduces a “barrier mating” section, then swaps the primary and barrier flights at the start of the wave section. This keeps unmelted resin in a high shear environment and allows for higher throughput rates, HPM says.

Royal Feed Screws Inc., Windsor, Ont., showed a recently developed “Do-All” PVC screw for the first time in North America. The screw, which was previously shown at K’98 in Germany, has a notch through the mixing flights for improved distributive mixing.

 

Low-Pressure Dual-Belt Process makes Vinyl Sheet

A novel low-pressure, dual-belted scattering process can create non-directional sheet out of powder, chips, and fillers (including wood or other natural fibers) for markets like floor covering. Produced by Samtronic Knobel GmbH in Goeppingen, Germany (represented in the U.S. by Ken Faust, Bath, Pa.), this four-year-old process operates under far lower-pressures than traditional high-pressure steel double-belt methods for making vinyl flooring. The process is also one- fifth the cost of high-pressure systems, Faust says.

In the new process, plastic powder, flake, fillers, and other ingredients are scattered directly onto a Teflon-coated fiberglass belt or onto a film, nonwoven, or paper substrate. Rollers with bristles pick up and hold precise amounts of different-size ingredients from a hopper and deposit them on the belt. Chips and powders can even be deposited in repeating patterns. Excess material is vacuumed off the edge of the belt before the belt passes between dual top and bottom oil-heated platens. Platens are temperature-controlled in zones, and dwell time can be up to 1 min. for a 3-mm-thick sheet, which then passes between cooling platens.

The process is already used in Europe to preheat for traditional high-pressure flooring lines and thus increase output. In the U.S., Mannington Mills in Salem, N.J., is using the technology to create flooring. And two other installations in North Carolina make textile waste into air filter material.