Compounding & mixing.

You'll see no less than 16 brands of twin-screw compounders, at least six of them new to the U.S. market.

There will be plenty of brand-new compounding machines to investigate at the show, but you'll also want to check out some of the interesting new things being done with existing models. Even though their machines may have changed only subtly, suppliers have broken new ground when it comes to incorporating in-line extrusion processes or adding new instrumentation, controls, and other computer technology.

Look, for example, at Werner & Pfleiderer of Ramsey, N.J. The company will show off a couple of interesting innovations that go on its existing line of twin-screw extruders. First, W&P will introduce an on-line system for evaluating distributive or dispersive mixing performance of various screw-element configurations. The system is based on a split-barrel ZSK extruder with an on-line rheometer and side-stream optical microscope for direct visual observation of the melt. The Evaluator, which is already in use at the Polymer Processing Institute in Hoboken, N.J., comes in a plasticating version or a melt-fed version and can be retrofitted to existing machines.

W&P will also demonstrate new EXCO 3 screw-configuration software for use with the company's ZSK twin-screws. EXCO 3 is a menu-driven program that generates a graphic representation of existing or proposed barrel and screw configurations. Visitors to W&P's booth can try the program and keep a printout of sample screw configurations. W&P will also show a prototype information system for after-sales support of ZSK twin-screw extruders. It stores all drawings, manuals, and bills of materials on CD-ROM for access through a customer's PC.

IN-LINE PROCESSING

Equipment that puts the compounding function in-line with other processes will be an important aspect of the American Leistritz Extruder Corp. exhibit. In general, says sales manager Charles Martin, in-line compounding/processing fits best with materials that either can't stand two heat histories or get a property boost from elimination of a heat history. Martin lists PET and low-durometer TP urethanes as examples.

At the show, Leistritz, located in Somerville, N.J., will demonstrate a complete medical-tubing line built around an 18-mm counterrotating twin-screw extruder. This machine will produce radiopaque olefin catheter tubing after blending HDPE, LDPE, and a barium or bismuth component. Because a twin-screw is not the best of pressure builders, it feeds at a right angle into a modified 0.5-in., 10:1 single-screw machine from Randcastle Extrusion of Cedar Grove, N.J. The line's puller and cutter are from Versa Machinery, also of Somerville. The line should produce catheter tubing at about 2-5 lb/hr.

Another new Leistritz in-line system will be shown as a static display. Built around a ZSE 27-mm multi-mode twin-screw extruder, this line is designed to produce sheeting between 10 and 125 mils thick at rates of 10-60 lb/hr. The line also features a Zenith gear pump and a three-roll stack with 10-in.-wide chill rolls.

According to Martin, what held back in-line processing in the past was control technology. The tubing system on display takes its orders from Leistritz's new Windows-based EMCS controller, which synchronizes the line's various drives and performs other control tasks. Leistritz has applied the same control technology to the in-line sheet system, as well as to fiber and polyvinylbutyral film lines.

Leistritz will also show a new ZSE-40, a modular 40-mm twin-screw that can operate in both counter- and corotating modes.

CONTINUOUS COMPOUNDING

Farrel Corp. of Ansonia, Conn., will introduce the 68-ram model FTX 500 and 37-mm FTX 40, its first twin-screw extruders. Farrel built the machines under license from twin-screw maker S. Rockstedt OHG of Germany. (Farrel canceled previously announced plans to buy the firm outright. See PT, Jan. '93, p. 75). Like the corotating Rockstedt machine Farrel showed at K'92, the new FTX extruders use polygonal mixing sections in place of lobed kneading blocks. Farrel's own machines, however, have been re-engineered to fit into a wider range of applications, according to compounding machinery manager Steve Peterson. Changes include longer barrels and provisions for water cooling.

Farrel will also discuss new twin-screw mixing sections based on rotor twists and helicals from its line of continuous mixers. Though intermeshing, these "rotor derivatives" will run cooler than conventional mixing segments to provide a wider processing window than conventional screw elements, according to Peterson. Farrel will also introduce the CP 250 compact continuous mixer, a 250-kg/hr version of the CP 500 it introduced in '92.

Berstorff Corp. of Charlotte, N.C., will introduce a "pre-engineered." skid-mounted package of ZE 60A-S twin-screw extruder with auxiliary equipment. This single-base system includes the 60-mm extruder, feeders, blender, bag-dump station, dust collector, and controls. Berstorff is also introducing its latest generation of CIM controls, including real-time process monitoring and control with on-line video and visual communications.

Pomini Inc. of Akron, Ohio, will introduce the LCM-AX--short for Long Continuous Mixer-Axial Discharge. This single-stage unit combines twin-screw extrusion and continuous-mixer technology in one machine, requiring less expense and floor space than two separate machines. It employs the corotating intermeshing screws familiar to twin-screw users, but the mixing zone has the rotor-blade profile of a continuous mixer. The unit also has a throttle valve downstream of the rotor section, which allows for fine control of specific-energy input. Because it controls material residence time in the rotor section--much like a gate on a conventional continuous mixer--the valve helps eliminate the need for reconfiguring the twin-screw, according to sales engineering manager Ken Nekola. The LCM-AX comes in a variety of barrel options and lengths, as well as feeding styles.

Along similar lines, Kobelco Stewart Bolling Inc. of Hudson, Ohio, will introduce the Nex-T60A continuous compounder to the U.S. market. It combines a continuous mixer with twin intermeshing, three-tipped rotors, and a single-screw discharge extruder on a common base.

Two European machines will also be at this show for the first time. APV Chemical Machinery of Saginaw, Mich., will show the MP-19 Series twin-screw compounder, a 19-mm benchtop model intended for development work at 4-26 lb/hr. It was shown at Interplas '93 (PT, Jan. '94, p. 50). And Buss (America) Inc. of Bloomingdale, Ill., will show a 70-ram, 13:1 model of the new APC (Advanced Performance Compounder) series of Buss Kneaders, which were unveiled at K'92 (PT, Jan. '93, p. 75). They're tailored for high-throughput compounding of engineering thermoplastics. APC models cost 20% less than the Buss MDK models they replace, although they have 30% greater throughput capacity. The machine at the show will be paired with a tailor-made Maag gear pump.

TWIN-SCREWS FROM NEW SOURCES

NPE will afford an opportunity to get acquainted with new brands of twin-screw compounders and other continuous mixers from around the world.

* American Barmag Corp., Charlotte N.C., will show a model of its DSM twin-screw mixer.

* Ikegai America Corp., Schaumburg, Ill., will show a 30-mm model from its PCM twin-screw series, which runs from 29 to 127 mm in corotating/intermeshing and counterrotating/partially intermeshing versions.

* U.S. Extrusion Inc., Hawthorne N.J., will show for the first time in the U.S. its new line of corotating, intermeshing extruders from 30 to 130 mm (PT, Dec. '93, p. 52).

* Wayne Machine & Die Co. of Totowa, N.J., will introduce its first twin-screw extruder, a 25-mm, 36:1, corotating, intermeshing machine that will be processing a color masterbatch.

* Welding Engineers of Blue Bell, Pa., will display a new 24-mm bench-top corotating, intermeshing twin-screw compounding extruder. It's made by Prism in the U.K. and was first shown at K'92 (PT, Jan. '93, p. 75). It has a split barrel, segmented screws, and 20:1 or 30:1 L/D. Prism builds twin-screws down to 16 mm, 15:1. Welding Engineers will also show a new low-speed 70-mm corotating twin-screw extruder from Italy's ICMA San Giorgio, which WE also represents. Last, the company will show a proprietary reactive extruder of its own counterrotating, non-intermeshing design, a 51-mm machine for finishing condensation polymers such as nylons and polyesters.

* List Inc. of Acton, Mass., will show a newly-modified List AP twin-shaft continuous mixing/kneading reactor designed for viscous, pasty, and shear-sensitive products.

* Charles Ross & Son Co., Hauppauge, N.Y., will introduce a continuous two-roll mill, the Shear Roll Compactor from Condux of Germany. It has rolls up to eight times larger than normal diameter and is designed to provide more shear than conventional two-roll mills or intensive mixers. What's more, the rolls are 5-6 ft long and have spiral grooves that convey material continuously from the feed end, which has hoppers mounted over the roll gap, to the discharge end.

Among other new or recently introduced compounding machines at the show, HPM Corp., Mt. Gilead, Ohio, will display a compounding line built around the company's largest Prodex extruder, a 6-in., 30:1 model with 500-hp motor.

And Processall Inc. of Cincinnati will introduce the Prestovac line of batch-type cross-linking chemical reactors. These operate on a mechanical bed fluidization principle.

NEWS IN PELLETIZING 

Rieter Corp.'s Pelletizing Machinery Group in Spartanburg, N.C. (formerly called Automatik Machinery Corp.), will introduce an unusual fluid-bed pelletizer for cooling and pelletizing polymer strands without using water. Instead, the stainless-steel cooling trough floats strands on a bed of air. The system has the self-stranding provisions of other Rieter pelletizers. The company will also introduce the Primo low-cost strand pelletizer and the Solvo cleaning system for removing polymer residues from hardware. Also to be shown is the USG 900, the "world's largest self-stranding pelletizer," according to group manager Paul Boileau.

Conair Jetro of Bay City, Mich., will introduce the new T2000 Series of strand pelletizers with cutting widths of 6-20 in. It features a patented pivot-opening cutting chamber in which the feed rolls can tilt away from the rotor for complete chamber maintenance. The design's helix-angled rotor has a large root diameter to allow slower rotor speeds.

Henion International, Charlotte, N.C., will introduce an 18-in. dicer capable of producing 10,000 lb/hr of cubes or octahedral pellets.

Accrapak Systems Ltd. of Cheshire, England, will show the Series 900-4 production pelletizer, which has an "overhung rotor" design for easy maintenance. Pelletizing capacity is up to 15 strands. The firm is also showing a bench-model laboratory pelletizer with 5/8-in. feed width and the Model 750-1 Integral pelletizing unit, which includes strand-cooling bath, strand dryer, and pelletizer on a common base.

Gala Industries, Inc. of Eagle Rock, Va., will show the new SLC-6 underwater pelletizer, which features a spring-loaded, self-adjusting blade-to-cutter shaft system for alignment to the die plate. It's for rates up to 6000 lb/hr. A new Easy-Clean low-noise pellet dryer will also be shown.

What to Look For

* Evaluate mixing quality on-line.

* Compound and extrude medical tubing in one step.

* Several new names in twin-screw compounders turn up.

* Liquid-free pelletizer uses no water at all.