Aerosol spray can

History

The aerosol spray canister invented by USDA researchers, Lyle Goodloe and William Sullivan.

The concepts of aerosol probably goes as far back as 1790.^[1] The first aerosol spray can was invented in Oslo in 1926 by Erik Rotheim, a Norwegian chemical engineer.^[1] The patent was sold to a US company for 100,000 Norwegian kroners. The Norwegian Post Office celebrated the invention by issuing a stamp in 1998.^[2]

In 1939, American Julian S. Kahn received a patent for a disposable spray can, but the product remained largely undeveloped. It was not until 1941 that the aerosol spray can was first put to good use by Americans Lyle Goodloe and William Sullivan, who are credited as the inventors of the modern spray can.^[3] Their design of a refillable spray can dubbed the ?bug bomb?, was patented in 1943, and is the ancestor of many popular commercial spray products. Pressurized by liquefied gas, which gave it propellant qualities, the small, portable can enabled soldiers to defend against malaria-carrying bugs by spraying inside tents in the Pacific during World War II.^[4] In 1948, three companies were granted licenses by the United States government to manufacture aerosols. Two of the three companies still manufacture aerosols to this day, Chase Products Company and Claire Manufacturing. The "crimp-on valve", used to control the spray was developed in 1949 by Bronx machine shop proprietor Robert H. Abplanalp.^[3]

Technology (aerosol propellants)

If the can were simply filled with compressed gas, either it would need to be at a dangerously high pressure, or the amount of gas in the can would be small, and would rapidly deplete. Usually the gas is the vapor of a liquid with boiling point slightly lower than room temperature. This means that inside the pressurised can, the vapor can exist in equilibrium with its bulk liquid at a pressure that is higher than atmospheric pressure (and able to expel the payload), but not dangerously high. As gas escapes, it is immediately replaced by evaporating liquid. Since the propellant exists in liquid form in the can, it should be miscible with the payload or dissolved in the payload.

Chlorofluorocarbons (CFCs) were once often used, but since the Montreal Protocol came into force in 1989, they have been replaced in nearly every country due to the negative effects CFCs have on Earth's ozone layer. The most common replacements are mixtures of volatile hydrocarbons, typically propane, n-butane and isobutane. Dimethyl ether (DME) and methyl ethyl ether are also used. All these have the disadvantage of being flammable. Nitrous oxide and carbon dioxide are also used as propellants to deliver foodstuffs (for example, whipped cream and cooking spray). Medicinal aerosols such as asthma inhalers use hydrofluoroalkanes (HFA): either HFA 134a (1,1,1,2,-tetrafluoroethane) or HFA 227 (1,1,1,2,3,3,3-heptafluoropropane) or combinations of the two.

Packaging

A typical paint valve system will have a "female" valve, the stem being part of the top actuator. The valve can be preassembled with the valve cup and installed on the can as one piece, prior to pressure-filling. The actuator is added later.

Packaging that uses a piston barrier system is often used for highly viscous products such as post-foaming hair gels, thick creams and lotions, food spreads and industrial products and sealants. The main benefit of the piston barrier system is that is assures separation of the product from the propellant, maintaining the purity and integrity of the formulation throughout its consumer lifespan. The piston barrier system also provides a controlled and uniform product discharge rate with minimal product retention and is economical.

Another type of dispensing system is the bag-in-can system (or BOV ?bag on valve?). This system separates the product from the pressurizing agent with a hermetically-sealed, multi-layered laminated pouch, which maintains complete formulation integrity so only pure product is dispensed. Among its many benefits, the bag-in-can system extends a product?s shelf life. The bag-on-valve, or ABS, is widely used by sun care marketers for its benefits: all-attitude (360-degree) dispensing, quiet and non-chilling discharge. This bag-in-can system is also used in the packaging of pharmaceutical, industrial, household, pet care and other products that require complete separation between the product and the propellant.

Health concerns

There are two main areas of health concern linked to aerosol cans:

• Deliberate inhalation of the contents to gain a high from the propellant
• The piggy-backing of more dangerous particles into the respiratory tracts

Canned-Air / Spray Dusters are dangerous to inhale. They do not use compressed air, but rather other inert gasses.

See also

• Aerosol paint
• Air pollution
• Freon
• Ozone depletion
• Pesticide application
• Nitrous oxide
• Packaging

References

1. ↑ ^{a b} Bellis, Mary The History of Aerosol Spray Cans
2. ↑
3. ↑ ^{a b}
4. ↑ Core, Jim, Rosalie Marion Bliss, and Alfredo Flores. (September 2005) "ARS Partners With Defense Department To Protect Troops From Insect Vectors". Agricultural Research MagazineVol. 53, No. 9 .

Further reading

• Brody, A. L., and Marsh, K, S., "Encyclopedia of Packaging Technology", John Wiley & Sons, 1997, ISBN 0-471-06397-5
• ASTM D3069 Delivery Rate of Aerosol Products
• ASTM D3065 Flammability of Aerosol Products
• ASTM D3094 Seepage Rate of Aerosol Products

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