New 'eco-logical' RIM equipment.

The polyuretane industry's continuing adaptation to the approaching demise of CFCs is changing not only foam formulations but processing machinery as well. A case in point is RIM equipment, where several recent introductions are designed to accommodate the different processing characteristics of alternative blowing agents such as HCFCs, HFCs and water.

Recycling of reground RIM scrap back into the polyol stream is another "environmental" trend addressed by RIM machine builders. Three-stream systems for this application have been demonstrated by Admiral Equipment, Cannon USA, Elastogran, Hennecke Machinery, Krauss-Maffei, and Linden Industries.

That's not all that's happening in RIM machines, as shown in this report and in this month's news highlights from the K'92 exhibition in Dusseldorf, Germany.

NOT FOR CFCs

Krauss-Maffei Corp., Florence, Ky., recently introduced both the TD-20A preblending unit for high-boiling CFC substitutes (the company's first standard unit of this sort) and a new "Eco" series of its RIM-Star machines. The preblending unit has a pump with a metal diaphragm and is said to be leak-free. It reportedly can handle all CFC substitutes at pressures up to 218 psi. It also can separately recirculate polyol, blowing agent, and/or the blended mixture.

The Eco machines are compact, high-pressure units designed for use in applications where low-pressure RIM equipment has been used in the past. The Eco name stands both for "ecological," since they eliminate the solvent flushing necessary with low-pressure machines, and for "economical." The machines are built in quantity (10-15 at a time) for stock, and offer relatively few options. These features bring them somewhat closer to the cost of a low-pressure machine.

The Eco machines use two variable-displacement metering pumps. The smaller unit, Eco 16/16, has a max. output rate of 1.14 lb/sec, while the larger Eco 40/40 model puts out 2.75 lb/sec.

The Hennecke Div. of Miles Inc., Lawrence, Pa., also has a new "Delta-mat" preblending unit for non-CFC blowing agents. It meters the additive under pressure into a constant flow of polyol in a manner said to be completely leak-free. Hennecke says that rather than pump the gaseous blowing agents into the liquid polyol, the unit uses two differential-flow pumps to "pull" the blowing agent into the polyol. This method prevents leakage and avoids the need for a lot of seals. Accuracy is said to be enhanced because the system actually meters the more viscous polyol rather than the thin, watery blowing agent. This system is said to handle all CFC substitutes, even those that are corrosive in their pure form. The 145-psi, stainless-steel mix tank has a new type of special agitator that eliminates the conventional shaft opening in the tank cover--a source of leakage in conventional systems.

Gusmer, div. of PMC, Inc., Lakewood, N.J., has a one-pass gas-nucleation unit (it can even use air), which does not require recirculation. It uses impingement rather than static mixing of the gaseous blowing agent, and the blend is kept in an accumulator at 175-200 psi, for on-demand feed to the dispensing unit.

Admiral Equipment Co., Akron, Ohio, sub. of Dow Chemical Co., recently commercialized an analytical device for measuring the exact amount of gas (either soluble or inert) that has been added to polyols. An Admiral spokesman says the device is extremely accurate and is being used by makers of RIM automotive fascia and other products relying on the gas nucleation of polyols.

A Krauss-Maffei engineer in Germany says the firm is investigating means of measuring and controlling blowing-agent concentration on-line rather than off-line. The company is evaluating three or four potential solutions.

IMPROVED MIXHEAD

An improved, long-life version of Gusmer's RIM X mixing head eliminates many of the conventional seals used in other heads, replacing them with what Gusmer calls transition blocks inserted between the valve body and the hydraulic cylinders. These blocks are flushable liquid chambers that contain any leakage of chemicals from the valves and prevent their migration into the hydraulic system. By the same token, the inert-fluid-filled chambers ensure that hydraulic fluid cannot contaminate the urethane chemicals. Another improvement Gusmer has made is in the valve coatings to allow the mixhead to operate rapidly without galling of the valves and chambers.

Gusmer expects the new heads to last four times longer than previous versions. Prototypes have been tested in production operations where shot size varies from 50 to 165 g, shot time varies from 0.5 to 1.65 sec, and a shot is made every 5 sec. One mixhead has performed for over 1 million shots, Gusmer says.

Incidentally, Elastogran Machinery (EMB), Wyandotte, Mich., reports that its mixheads are now warranted for half a million shots, and one customer reportedly has delivered about a million shots from one head.

NEW EQUIPMENT AND CONTROLS

Gusmer also recently updated its RimCell variable-ratio, axial-piston, high-pressure metering unit with several new standard features. These include a boom for the mixhead, heat exchangers on the tanks and hydraulic pump, a tank liquid-level display that eliminates the need for a dipstick or sight tube, and automatic shutoff if tank level drops too low. A 100-lb/min system costs $68,500 complete.

Hi-Tec Engineering Inc., Grand Rapids, Mich., has developed a new series of low-flow-rate RIM machines. Called the Accu Flow series, the new machines can continuously meter 3-4 g (0.1-0.14 oz)/sec with an accuracy of |+ or -~0.5%, Hi-Tec says. Acting at the request of an automotive supplier that sought to replace low-pressure equipment, Hi-Tec modified the machine with a 5-mm, flushless mixhead, giving the user an extremely low flow rate combined with a longer shot time and resulting in better repeatability in high-volume production. Low-flow capability is aided by Allen-Bradley controls that regulate hydraulic piston movement up to 10 times more accurately than was possible with most previous RIM machines, Hi-Tec says. Suggested applications for the Accu Flow include gasket production, putting thin coatings on textiles and other substrates, and two-component adhesives, potting and encapsulation.

Hi-Tec has also refined its pump-type continuous metering machines--the Precision Flow series. Enhancements include new variable-speed drives and special high-pressure tank and shaft seals designed to operate with non-CFC blowing agents. The company has also designed a high-pressure, impingement mixhead with external recirculation that's said to be suited to processing components that traditionally "cross over" in internal-recirculation heads.

As noted briefly last month, Cannon USA, Mars, Pa., has a new closed-loop-control version of its HE lance-cylinder machines. This completes the conversion of Cannon's line to standard, rather than proprietary, electronic hardware. The system includes an Allen-Bradley PLC, which communicates via fiber-optic link with an industrially "hardened" 386-type PC operator interface. The latter has a color screen that can display a graphic representation of ratio and shot volume at 3-sec intervals during the course of a shot.

As previously reported, Cincinnati Milacron's U.S. Plastics Machinery Div., Batavia, Ohio, recently adapted the CAMAC XTL control the company has used for the past several years on its conventional injection molding presses to its RIM equipment.

The CAMAC XTL provides for complete digital setup and digital displays. The control has a 9-in. screen with full graphics capability that allows plotting of injection velocities, pressures and ratio. Menu-driven screens guide operators through setups such as clamp sequence and have immediate updating capabilities. Diagnostics and SPC are standard, Milacron says, and the control has internal data storage for as many as 40 mold setups.