NPE 2000 News Wrap-Up: Compounding
Compounding news at NPE included a wealth of new batch and continuous machines to mix in high loadings of wood flour, glass fiber, carbon black, and more exotic fillers. One new batch mixer can melt blend wood-flour compounds without the need for an extruder or continuous mixer. A number of new pelletizers were also introduced.
Fill ’Er Up
Draiswerke, Inc., Mahwah, N.J., showed its unusual high-speed batch mixer for PE and wood flour. The upgraded Gelimat machine is now able to achieve rotor speeds sufficient to melt plastic in less than 20 sec and wet out fillers. The first U.S. application for the 100-liter Gelimat will be making shingles of PE and wood flour.
C.A. Lawton Co., Green Bay, Wis., brought to the show single-screw plasticating technology recently acquired from Kannegiesser KMH in Germany and shown for the first time in the U.S. The process, called Long-Fiber Reinforced Deposition/Compression Molding, is designed to extrude and then compression mold highly glass-filled virgin materials and mixed scrap. But it can also compound flax, hemp, and other natural fibers. It was tested recently for mixing PP and up to 30% flax to make battery cases for Volkswagen AG in Germany.
Buss (America) Inc., Bloomingdale, Ill., has expanded the range of its MKS (Modular Kneader System) mixers. The MKS line now goes up to 20:1 L/D vs. 18:1 before. The longer machine can accommodate two twin-auger side feeders instead of one, and the side-feed ports have been enlarged to a maximum 2 in. diam. This added flexibility lets the kneader compound highly filled engineered resins for the first time, Buss says, making it directly competitive with twin-screw compounders. It also offers higher torque plus electric heating instead of hot oil, so that it can reach temperatures up to 788 F. It is offered with new Maag gear pumps that are designed for abrasive materials.
Also aimed at highly filled compounds is the new Ultima Compounder from Farrel Corp., Ansonia, Conn. Farrel showed a prototype, which pairs a special two-stage Farrel Continuous Mixer (FCM) and a single-screw discharge extruder on one support frame. The company says it provides “the highest dispersive mixing of any compounder yet developed.” A high-torque version has rotor speeds up to 1000 rpm and almost twice the horsepower of a traditional FCM.
The mixer is the equivalent of two FCMs attached end to end. It has two rotors with two wing-shaped mixing sections separated by an adjustable barrier. The first stage is a standard FCM, while the second stage is customized for highly dispersive mixing and downstream addition of mineral fillers or glass. It can also have vacuum venting. After the second mixing stage, melt drops down into the discharge extruder, which also has vacuum venting capability.
This machine is designed for very high loadings of fillers like carbon black or wood flour. With wood flour, moisture levels can be reduced from a starting level of 10% to well below 1% using only atmospheric vents, Farrel says. The machine will be demonstrated at an open house at Farrel this Fall, but won’t be available commercially until the second quarter of 2001.
Century Extruders, Traverse City, Mich., introduced to North America an unusual “ring” mixing extruder developed by 3+ Extruder GmbH in Germany. The machine has a ring of three to 12 corotating, intermeshing screws around a static core. They reportedly generate very low shear and low barrel wear, so the ring extruder is well suited to compounding abrasive fillers. Seven ring extruders have been sold in Europe, including one processing glass-filled nylon.
Twin Screws Rule
Entek Extruders in Lebanon, Ore., is applying for a patent on a twin-screw extrusion compounding process to make materials for next-generation lithium polymer batteries. Entek is also building a new extrusion line to produce separator materials for the lithium batteries used in computers and cell phones. A prototype line has been producing separator material for a year.
NFM/Welding Engineers in Massillon, Ohio, has built a twin-screw compounder that’s so long (60:1 L/D) that its length is broken into three sections that each pivot to give access to the screws for cleaning. This model 58SS corotating compounder uses technology licensed from Toshiba in Japan. Three of these systems are running in Japan.
NFM is also developing a barrel that has a built-in adjustable opening that varies the gap between the screws and barrel for controlled shear in mixing and devolatizing. This mechanism substitutes for a removable blister on the screw.
American Maris, East Brunswick, N.J., showed its recently developed HT (high-torque) Series corotating twin-screw extruder, capable of screw speeds up to 1300 rpm. Maris plans to open a subsidiary in Charlotte later this year.
News in Batch Mixers
Thyssen Henschel Industrietechnik in Germany earlier this year ended its partnership with Henschel Mixers America in Houston and set up its own direct sales and service company, Thyssen Henschel America Inc. in Green Bay, Wis. Thyssen Henschel showed its new CM Container Mixer, which creates a reverse material flow up the center and down the walls of the mixing bowl. The company also introduced a new series of high-torque gearboxes.
Merlin Process Equipment Inc. in Houston (formerly Henschel Mixers America Inc.) launched its own line of batch mixers. Merlin is also building its first twin-screw corotating compounder.
Batch mixers for PVC dryblend from Plas Mec SrL in Italy were shown in the U.S. for the first time by Ferry Industries Inc., Stow, Ohio. Ferry plans to start building Plas Mec Combimix units in coming months. The blenders have cooling jackets and blades impregnated with tungsten carbide. They produce 1500 to 13,000 lb/hr of dryblend.
Farrel, traditionally a maker of very large underwater pelletizers for resin producers, launched a new smaller line for independent compounders. These Hydron pelletizers were developed with TDS Technologies Inc. in Delta, B.C., which will build them for Farrel in three sizes: Hydron 10 for 2200 lb/hr; Hydron 20 for 4400 lb/hr; and Hydron 40 for 8800 lb/hr. Larger models are in development. Instead of hot oil, Hydron pelletizers use less expensive electric heating.
The new Hydron dies have the most concentrated heat available, Farrel says. Electric coils ring the strand holes, and rod heaters concentrate heat at the tips, not along the length of the rods. They also have servo-controlled rather than spring-loaded knife blades for automatic adjustment and more predictable knife wear, says Farrel.
Rieter Corp. U.S.A., Spartanburg, S.C., has redesigned its pelletizers with insertable rotors and a special wear-resistant coating for pelletizing glass-filled materials.
Entek Extruders introduced a quick-release pelletizer die at the show.
Improved clarity and cost competitiveness, added to its inherent heat resistance, are reviving OPP’s prospects in hot-fill barrier containers. But hot-fill PET containers are raising the bar with higher productivity and ‘panel-less’ bottle designs.
Over the past several years, significant innovations have occurred in the area of polypropylene nucleation.
You may be thinking of buying one of the new ‘high-torque/high-speed’ twin-screw compounders in order to raise your output without going to a larger machine. But how much torque or speed do you really need? Underusing a high-powered extruder wastes investment dollars. So look carefully at what is required for the materials you run.