New equipment for urethane foaming and RIM recycling.
Among the news is a joint venture to recycle RIM automobile bumpers using a Cannon mixhead that eliminates the surface defects that sometimes occur when powdered RRIM scrap is used as an additive in fresh formulations. Other developments include expanded applications for the company's EasyFroth system; technology for controlling the profiles of foam blocks; and two new metering systems.
While not a brand-new process, recycling RRIM scrap by grinding it into a powder and using it as an additive in fresh RRIM formulations has so far seen only limited applications. Mixing powdered RRIM scrap into fresh formulations historically has caused the powder to interact with the crosslinker DETDA, commonly resulting in irregular cell formation and surface defects. Thus the process has not been suitable for molding appearance parts.
But a Cannon three-component mixing head can reportedly eliminate this problem. To prove its effectiveness, Cannon has joined with Dow Plastics (U.S. headquarters in Midland, Mich.) and Italian automotive RIM processor Maachi SpA in a recycling venture based on this process. Using Cannon equipment and Dow material, Maachi is reincorporating the RRIM material from its rejected bumpers into virgin RIM material used in new bumpers. The Maachi recovery project is believed to be one of the first applications worldwide wherein scrap RIM material is incorporated into the same type of part for which it was originally used, rather than an out-of-sight wheel well or chassis part.
The keys to Maachi's success are the Trio mixing head Cannon developed last year and Dow's technology for crushing and pulverizing RRIM scrap into a powder of uniform particle size. The Trio mixhead handles three separate streams of 1) polyol filled with RRIM powder regrind, 2) isocyanate, and 3) DEDTA blended with other ingredients such as catalyst or internal mold release agent. The jets in the head's mixing chamber are angled at 120|degrees~, guaranteeing perfect homogenization of the three streams, Cannon says. Tests molding automotive door fascias have been able to incorporate as much as 10% RRIM regrind with no sacrifice of appearance, according to Cannon.
To overcome the problems that resulted from random particle sizes in previous elastomer recycling efforts, Dow developed a process that starts with granulating the scrap, followed by pulverization in rotating disc mills. According to Dow, the process reduces the byproducts of normal RRIM molding operations--such as sediment, burrs and paint shavings--into uniform powder with particle sizes from 180 to 300 microns. This powder can be easily incorporated as an additive into fresh RIM formulations, according to both Dow and Cannon.
'EASY' ON THE WHEEL
Cannon's EasyFroth blending unit, developed in the late 1980s (see PT, Feb. '90, p. 35; May '91, p. 102), was originally designed to produce low-density rigid insulation foams using HCFC-22 in place of CFCs. But recently, ECIA, a French manufacturer of urethane automobile parts, has been molding high-quality integral-skin flexible foams for steering wheels using EasyFroth and some other Cannon equipment. ECIA uses the EasyFroth to blend precise amounts of HCFC-22 with formulated polyol immediately before it goes into the machine's tank. Extreme precision is vital, Cannon says, to ensure the consistent foam quality and skin integrity necessary for steering wheels.
FASTER COOLING OF FOAM BLOCKS
In a development that originated in the U.S., Cannon is offering a novel conditioning system said to rapidly cool flexible foam blocks within an enclosed area, reducing the level of auxiliary blowing agent needed and providing 50% reduction in cure time. The Enviro-Cure system is a three-stage process developed by Crain Industries of Fort Smith, Ark., and used in conjunction with Cannon's Vertimax vertical block machines.
The first step in the process uses cooled ambient air drawn through the blocks to cool, dehumidify and remove fumes. The second and third stages cool the block further and remove the remaining fumes and moisture. The process uses fully water-blown formulations and employs a mechanical method of uniformly controlling the cooling rate. By dispersing exotherm heat at a relatively early stage after foaming, foams can be processed with a lower than normal TDI index, Cannon says. A lower TDI index also allows use of higher levels of water in low-density formulations, and reportedly can permit reducing--or in some cases, completely eliminating--auxiliary blowing agents.
EXPANDING MACHINES' ABILITY
Thanks to a new process developed by two European machinery manufacturers, users of high-volume horizontal block foaming systems like the Maxfoam and Varimax systems from Cannon's British unit, Cannon Viking, can now control the top skin profiles of foam blocks. Previous top-profile systems were not practical to use on the high-volume, horizontal machines because the variation in flow speed out of the machines' trough--greater at the center than at the sides--made it difficult to use a top cover.
The new process, called Pintomax, is patented joint development of the Spanish ICOA Group and Unifoam AG of Glarus, Switzerland. Though not yet available in North America, Cannon and the European companies say they hope to introduce it here sometime next year.
Basically, Pintomax works like this: A roller system dispenses a top paper onto the foam chemicals as they leave the machine's trough. The special top paper includes a lubricant, allowing it to conform to the top surface of the foam in spite of variations in flow speed. A blanket placed atop the paper during the rise of the foam and extending beyond full rise and blow-off prevents the film from losing contact with the foam surface. This blanket, which is flexible in the longitudinal direction but relatively stiff transversely, provides a surface against which the foam rises. The conveyor, sidewall and top cover now become a continuous mold.
Cannon says the advantages of adapting its Maxfoam and Varimax systems to use Pintomax include absolutely square block profiles in standard and combustion-modified high-resilience (HR) foams, as well as other foams using standard and PIPA polyols (the latter a suspension of polyurethane particles in a polyol). In addition, the elimination of hard top skin makes flocking easier. More chemicals are converted into prime foam, resulting in a higher block. Fume extraction is easier because most of the gas is confined to sidewalls. Lower tension in the block shoulders improves dimensional stability and leads to conversion gains. And reduced exposure of the fresh foam to atmospheric moisture improves hardness distribution.
When available in this country, equipment to use Pintomax will be offered as either an addition to existing Maxfoam and Varimax machines or as part of new machines. Unifoam AG will license the process.
TWO NEW METERING UNITS
Cannon's new A-System, initially discussed at NPE '91, is a high-pressure, closed-loop metering pump system. Built in a modular format, it can work in conjunction with the previously mentioned EasyFroth metering/premixing unit for incorporation of low-boiling-point blowing agents like the HCFCs and HFCs that are rapidly replacing CFCs. The system's basic configuration includes a tank, metering system, temperature control, mixing head and PLC control. Closed-loop control of the pumps' output rate is optional.
Cannon says the A-System's controller allows machine parameters to be changed on the fly. The company offers software packages for preventive maintenance, troubleshooting, diagnostics, production control, process statistics and monitoring. Controls can be expanded to include "Instant Ratio Detection" with continuous display of component throughput and ratio. It can also be upgraded to a 386-type PC with 14-in., high-resolution color graphic CRT.
The system's metering system uses vibration-dampening supports that lower its noise level and improved seals that Cannon says virtually eliminate leakage problems. The seals, Cannon says, last longer than most other machines, requiring a change about once a year. A quick-change mechanism allows easy access to the external seal block between the motor and pump, letting the user change seals without disassembling the entire pump.
The high-pressure, free-pouring mixhead system can be boom-mounted for manual mold-filling injections, mounted on robots for automatic processes, or on manifolds for fixed-press applications, Cannon says.
Cannon's other new metering system was expected to make its debut at this month's K'92 show in Dusseldorf, Germany. The new version of the HE system is an enhanced, closed-loop controlled piston metering system. An offshoot of the company's first HE machine introduced in 1983, the new HE system has more powerful and sensitive electronic controls, giving it the ability to serve a wider range of applications than its predecessors.
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|Title Annotation:||Technology News|
|Date:||Nov 1, 1992|
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