st43

Spray Oct 2014

By Montfort A. Johnsen, Ph.D. Technical Ed itor TTV Single Head Gasser Shaker Lab Model. Photo provided by Gerstung Aerosol, Inc.. October 2014 Spray 43 targeted the Halons, as 1301 and 1211, and the HCFCs, as 22, 142b and 133a. Also included were some “low flammability” solvents, such as alkyl bromides and 1,1,1-trichloroethane. Under its Significant New Aerosol Propellant (SNAP) program, the EPA must approve all new propellants developed for aerosol applications. It not only considers Ozone Depletion Potential (ODP), but tropospheric ozone generation (VOC programs) and GWP, as well. It also reviews these criteria for existing propellants. For example, after a round table meeting on Aug. 1, 2014, centering mainly on the GWP of 1350 for HFC-134a, the EPA is now considering which aerosol applications will still be allowed as of 2016. Health and life safety uses will survive; others will be carefully scrutinized. The number of propellants available to the industry is still impressive, and during the last two years the list has been increased by the introduction of propellant having a carbon-to-carbon double bond. Table One will illustrate those currently available. With such a diversity of propellant pressure and solvent abilities, it is apparent that a diversity of gassing machines is currently in use by the aerosol industry. A further distinction relates to production speed, which currently ranges from one-head (laboratory type) models to very complex 18-head models, “boiler-plated” to produce 20 units per head per minute, or 360-per-minute-per-machine. Early Filling Methods From the beginning of the aerosol industry in 1947 to about 1958, at least several fillers used the socalled “cold fill” process for adding propellants to cans. The early Crown and Continental cans were delivered to fillers without attached bottoms, to be filled inverted. The concentrate and propellant (sometimes mixed in large pressure tanks) were chilled to -40° to -45°F (-40° to -43°C) and poured into the cans. The can bottoms were then hermetically double seamed on to the body flanges. Hot water bathing followed. When the industry converted to the nominal “one inch” mounting cup valve in 1953, the pre-chilled contents were poured through the hole, valves were inserted by manual “valve pokers,” the cans were sealed by crimping and then hot water bathed. The “cold fill” process had many shortcomings. The low-odor kerosenes, often used for insecticides and air fresheners, sometimes turned “slushy” at -40°F temperatures. Water-based products froze and could not be filled. The large HCFC-22 or ammonia based refrigeration system and hot water bath required prodigious amounts of power. Lastly, propellant evaporation, while producing air-free aerosols, was also a significant economic burden. Fortunately, machines for filling liquid propellants backwards through the valve were developed around 1953 by such firms as Alpha Engineering and Kartridg-Pak. They became known as Through-the-Valve (TTV) gassers. The in-line gassers could be used with up to four heads on a two track, double indexing line, producing as fast as about 80 cans per minute with wide-open valves. The more preferred versions were rotaries, where a standard base machine could be equipped with three, six or nine heads. In operation, the cans would be perfectly placed on platforms and the gassing head would descend so that an adapter would engage the valve stem. A piston would then deliver a fixed volume of liquid propellant into the aerosol can. To properly energize the gasser, UTC gassing station. Photo provided by MBC Aerosol. 6 Head Inline TTV Pressure Filler. Photo provided by Gerstung Aerosol, Inc.


Spray Oct 2014
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