First highlights from Interplas.

Although it has become in recent years more narrowly focused on the home processing audience in the United Kingdom, the Birmingham show remains one of the largest international forums for presentation of new plastics technology. Interplas '93 last month showcased several major introductions of primary and auxiliary equipment for injection molding, blow molding, extrusion and compounding. Our two editors just back from the show prepared this quick review of show highlights, to be followed by a more thorough report next month.

IN-MOLD PAINTING

A new one-step Granular Injected Paint Technology (GIPT) for in-mold deposition of an automotive "Class-A" paint finish on thermoplastic parts was demonstrated by Battenfeld GmbH of Germany (represented here by Battenfeld of America, West Warwick, R.I.). The GIPT process is a solid paint system based on research done at the University of Warwick, U.K., and developed jointly by the Rover Group, Evode Powder Coatings (both of the U.K.), and Battenfeld. It's said to be the first commercial means of applying a solvent-free finish to plastics such as PP, meeting the same technical and aesthetic requirements as traditional solvent-based "wet" paints.

(In the U.S., coatings manufacturer Sherwin-Williams Co., Cleveland, has been working for more than six years with Krauss-Maffei Corp., Florence, Ky., and GE Plastics, Pittsfield, Mass., to develop a liquid urethane-based in-mold painting system for injection molded thermoplastics, but has never announced a fully commercial system (see PT, May '92, p. 23).

The new paint system was demonstrated on a Battenfeld 605-ton press with modified twin injection units and nozzles. The system molded black PP hubcaps with a white coating in a 45-50 sec cycle--comparable to that for conventional molding without coating. The part was formed in a single-cavity, cold-runner mold, although Rover reportedly is investigating hot-runner molds for future applications. The solid paint system (a Rover spokesman identifies it only as being polyolefin-based and variable in composition according to the substrate material) is fed into the barrel in pellet form. The paint system is injected slightly ahead of the core material, penetrating the extremities of the cavity and forming a consistent coating along the wall of the mold. According to Evode, the paint uses a binder system that assumes a "pseudo-plastic" state under high-shear conditions. The result is that at the point of injection, the total system is at its lowest possible viscosity. Removal of shear (when it stops flowing) results in a rapid increase in viscosity as well as a partial crosslinking of the resin components.

The new GIPT system is said to be uv and scratch resistant and covers minor blemishes in parts. A uniform layer 35 microns or so thick can be deposited on a range of substrates, including untreated PP, with zero wastage of paint material. Molded components can be taken directly to the automotive assembly line. The coating is available in metallic, pearlescent, and solid finishes, and is recyclable--imperfect parts can be directly regranulated and blended into the substrate, and crosslinked paint particles act as filler. Because the entire process is enclosed in the mold, it eliminates rejects due to airborne contamination. GIPT is said to have lower processing costs than conventional coating methods and eliminates the need to carry large inventories of unpainted parts.

Rover plans to use the technology on selected exterior parts, including hubcaps, in the 1994 model year. The demonstration unit has been sold to Clearplas, a British molder.

In other news, Battenfeld Austria introduced vertical C-frame models of the small Plus hydraulic injection presses first shown last year at K'92 in Dusseldorf (PT, May '93, p. 29). Like the horizontal versions, the new VV series is available in 27.5 and 38.5 tons. It's expected to be introduced in the U.S. following the NPE exhibition in Chicago next June.

'EXTERNAL' GAS INJECTION

A new alternative to conventional internal gas injection is available for license by Gas Injection Ltd., Nantwich, U.K. External Gas Molding (EGM) applies gas pressure to the outer surface of the plastic part during the cooling phase--not forming enclosed channels within the plastic, as in other gas-injection processes. The EGM process injects the gas through contoured, porous metal inserts at certain points in the mold. The porous metal is said to permit passage of the gas but not of molten plastic. Integrally mounted seals allow controlled gas pressure to be applied to localized areas. Delivery of the gas to the mold is tied to consistent accurate timing of the pressure phases and the rate of pressure increase.

The EGM process is said to be appropriate for thin-wall parts or moldings in which it is not feasible to include thicker ribs or sections to achieve the formation of channels required for gas injection. It makes possible the application of pressure to the injected melt remote from material feed points, where it is difficult to apply holding pressure during the cooling phase. It also makes possible displacement of plastic in localized areas to compensate for shrinkage.

PLASMA LEAK TESTER

The most dramatic blow molding news was a truly revolutionary leak-testing system for non-metallic containers from Blow Molding Controls Ltd. of England, which recently established Blow Molding Controls Inc. in Port Washington, Wis. Unlike conventional leak testers, which fill a container with air and detect pressure decay caused by a leak, the new "Plasma" system measures the flow of electrical current between a high-voltage probe inside the container and a grounded metal shield outside. (In essence, the container is used as a capacitor.) The current flow is negligible for a good container, but a hole--no matter how small, the company says--provides a path through which a large current can pass. So far, the dielectric system has been tested on holes as small as 23 microns, and no minimum hole size has been identified. Unlike conventional leak testers, the new device can even find holes covered by a label (though some plastic labels may prove an exception). What's more, the Plasma device can find surface cracks that threaten the integrity of reusable containers: If the crack extends half way through a returnable PET bottle, for example, the dielectric voltage will punch a complete hole through the wall.

Dielectric leak testing is also virtually instantaneous--testing speeds are theoretically limited only by the feeding mechanism. A Plasma device has been tested with a cycle time of 0.1 sec to detect a 0.2-mm hole. A major soft-drink manufacturer (believed to be Coca-Cola Co.) will use the device in Europe to test returnable PET bottles at rates of six bottles per second, or 22,000/hr.

By contrast, conventional leak testers typically require 2-3 sec for a 2-3 liter soft-drink bottle and 20-50 sec to test large drums. Consequently, the detectable hole size is limited by how long the user is willing to wait.

PP & PET STRETCH-BLOW

Bekum (with offices in Williamston, Mich.) demonstrated its new RBU 445 reheat-stretch-blow system, capable of 4500 bottles/hr (a larger version of the 2000/hr RBU 225 introduced at K'92). It can process PET or PP preforms (Bekum is developing a one-button changeover between PP and PET setup programs). A key feature is a new preform heating system to transform uniformly heated preforms to the blow mold.

FOR BLOWN AND CAST FILM

Though recently put up for sale by Cincinnati Milacron, Sano in Batavia, Ohio, says its blown film equipment operations will continue on a "business-as-usual" basis. In fact, technical director Rick Knittel reports a first for the company--blown film lines that feature an automatic profile-control system from Germany's Octagon Process Technology.

Octagon's system exerts control through an air ring that depends on an internal flexible lip to deliver flow to segments of the bubble circumference requiring a thickness adjustment. Knittel says the Octagon system could be installed on Sano's own air rings, minimizing costs to customers. Besides Sano, Addex Inc. of Boston offers the Octagon system on its blown film lines. According to Francis Trost, Octagon's export sales manager, the first U.S. test installation of the Smartlip auto-profiling system was planned for last month.

Image Automation Ltd., which operates in the United States as Sira Inc. of Darien, Conn., has embarked on a quest to drive down the cost of its laser web-inspection systems that identify, classify and document film defects such as gels and holes. At the show, the company displayed its first PC/transputer-based inspection system, called the Fastscan Series 10. The system can "see" about 30 defects/sec, about half as fast as the company's high-end systems. Its resolution would be about 10 mils on a two-meter-wide line. The new PC platform offers easier access to defect information, according to managing director John Claridge. The system's Windows environment shows real-time maps of the defects on the film and provides a full range of SPC/SQC charting as well as graphical representations of the web scans.

The system can be used on any flat web, including post-collapsed blown film. With the Series 10, laser system prices have fallen by half, Claridge says. Still, at around $200,000, Claridge acknowledges that it may still be out of the reach of all but the most sophisticated film processors. But, he adds, a new generation of laser scanners will allow Image Automation to cut its prices by as much as half again in the coming year. In the meantime, the Series 10 can hunt defects with a lower cost CCD camera instead of a laser, while still offering the same sort of SPC/SQC functionality.

In flat-film tooling, Extrusion Dies Inc. (EDI) of Chippewa Falls, Wis., announced a couple of developments not seen on the show floor. The company's Ultraflow I adjustable coextrusion feedblock has been modified to allow external adjustments to the skin layers without changing the slip-in feedblock modules. The external adjustment would be used to "pre-tune" or optimize the flow across the entire slot, according to sales manager Harry Lippert. The slip-in modules will still come into play once the flow has been optimized through external adjustments. Lippert says the system will be most useful for processors who must switch between several coex film structures, especially asymmetrical ones.

Also, EDI has finished work on a new polymer-impregnated chrome plating called UltraChrome. In place of the PTFE it once used, EDI has come up with a way to imbue die components--especially the lips and manifold--with a crosslinked thermoset material. Lippert says the material offers better chemical resistance than PTFE and better release for less polymer buildup. Cost for a 2-meter die is only about $2000 extra.

NEW FOR TUBING AND PIPE

Davis-Standard of Pawcatuck, Conn., now sells dies for coex tubing based on its blown-film coex design, which uses a stackable module for each layer. So far, uses have been in automotive fuel lines and medical tubing. The die "looks like a mini blown film die," says business-area manager Al Hodge, explaining that the modular approach allows thermal isolation of dissimilar layers while maintaining good layer concentricity.

For rigid PVC pipe, Davis-Standard also has introduced its first parallel twin-screw extruder, a 112-mm machine called GP12.

TWIN-SCREW COMPOUNDER

A manufacturer of twin-screw extruder components has come out with its first fully fledged machine. U.S. Extrusion Inc. of Hawthorne, N.J., showed its TSC 30 (30-mm) high-torque, corotating, intermeshing twin-screw machine and announced that it can also offer sizes of 40, 58, 70, 92, and 130 mm as well. All these extruders have modular screw and barrel segments, brushless d-c drives, twin-port vacuum venting, and Barber-Colman MACO 5000 controls.