During my time as R&D Director, I developed a specific knowledge of improving aerosol can sealing through minimizing micro leakage. Aerosol can sealing remains one of the most challenging operations in our industry, especially for aluminum cans filled with compressed gas at a high internal pressure. Major aluminum monobloc can innovations have developed over the past 20 years, beginning with shaped cans during the mid-1990s, followed by embossed cans and flat rimmed shoulder cans (also known as transfer rim shoulder cans or TR) in diameters of 45-, 50-, 53- and 57mm. The evolution of European regulations also gave way to new generations of internal coatings. In 1953, Robert Abplanalp of Precision Valve patented the aerosol valve design with a mounting cup as we still know it today. For the past 60 years, the contact between the aerosol can and the valve and the process to create that link have remained basically the same, consisting of a standard 1" opening, a gasket and a valve mounting cup. However, linking together the can, the valve and the cap actuator is a complex process. Industry experts have, since the beginning, taken care to improve process parameters, product tolerance, machine setup, standardization and process/product validation in order to help guarantee product quality and consumer safety. The final product is the result of a commitment to quality from all members of the aerosol industry. Pressurizing the can Since the origins of aerosol packaging, there have always been two major options for pressurizing an aerosol can: 38 Spray November 2015 • Liquefied gases offer a unique advantage in terms of spray regularity, allowing the can to be fully emptied because the pressure remains constant until the liquid gas phase remains in the can. This solution is used mostly for cosmetic and technical products, but some liquefied gases are also used in the pharmaceutical sector. • Compressed gases offer options for food or cosmetic applications. The main gases are Nitrogen (N²), Nitrous Oxide (NO²) or Carbon Dioxide (CO²). However, these options suffer from the compressed gas property itself. During the draining, the pressure does not remain constant enough to enable a consistent spray (or consistent product flow in case of a liquid or gel product). To do so, the internal pressure into the can has to remain sufficiently high to ensure a proper quality until the end of drainage. Therefore, aerosol can fillers using compressed gases to fill aerosol cans have always tried to increase filling pressure specifications. Compressed gas history in aerosol applications It all started in 1950 when a water spray was filled at 5.2 bar with nitrogen; by the early 1960s, several brands were already on the market. In 1989, nitrogen pressure increased to 6.5 bar and since 1990 we’ve seen aerosols filled up to 10 bar. This remains the maximum internal filling pressure in use, but has generated legislation to establish a filling pressure of 10.5 bar at 20°C and a maximum filling pressure of 12 bar at 50°C. Aerosol Cans & High Internal Pressure This paper was originally presented at the Paris Aerosol & Dispensing Forum. Frank Flecheux Director Sprl AERION Packaging & Conseil
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