Aerosol production

The aerosol container has enjoyed commercial success ia a wide variety of product categories. Insecticide aerosols were iatroduced ia the late 1940s. Additional commodities, including shave foams, hair sprays, antiperspirants, deodorants, paints, spray starch, colognes, perfumes, whipped cream, and automotive products, followed ia the 1950s. Mediciaal metered-dose aerosol products have also been developed for use ia the treatment of asthma, migraine headaches, and angiaa. 

Aerosol products are hermetically sealed, ensuring that the contents caimot leak, spill, or be contaminated. The packages can be considered to be tamper-proof. They deUver the product in an efficient manner generating Httie waste, often to sites of difficult access. By control of particle size, spray pattern, and volume deUvered per second, the product can be appHed directiy without contact by the user. For example, use of aerosol pesticides can minimize user exposure and aerosol first-aid products can soothe without applying painful pressure to a wound. Spray contact lens solutions can be appHed directiy and aerosol lubricants (qv) can be used on machinery in operation. Some preparations, such as stable foams, can only be packaged as aerosols. 

Aerosols are unique. The various components are all part of the product, and in the aerosol industry, the formulating chemist must be familiar with the entire package assembly and each of its components. AH aerosols consist of product concentrate, propeUant, container, and valve (including an actuator and dip tube). There are many variations of these components, and only when each component is properly selected and assembled does a suitable aerosol product result. A typical aerosol system is shown in Figure 1. 

Solutions. To dehver a spray, the formulated aerosol product should be as homogeneous as possible. That is, the active ingredients, the solvent, and the propellant should form a solution. Because the widely used halocarbon and hydrocarbon propellants do not always have the desired solubiUty characteristics for all the components in the product concentrate, special formulating techniques using solvents such as alcohols (qv), acetone (qv), and glycols (qv), are employed. 

Chlorofluorocarbons (CFCs). Prior to 1978 most aerosol products contained chlorofluorocarbon propeUants. Since that time, the use of chlorinated fluorocarbons for aerosols has been seriously curtailed. These compounds have been impHcated in the depeletion of the ozone (qv) layer and are considered to be greenhouse gases (see Airpollution Atmospheric modeling). 

In the United States, use of CEC propeUants, designated as PropeUants 11, 12, and 114, is strictly limited to specialized medicinal aerosol products such as metered-dose inhalers. The physical properties and chemical names of these propeUents are given in Table 2. 

Activity or product Aerosol production Intentional Unintentional Evaporation or sublimation Unintentional outgassing... 

Ma.nufa.cture. Finishing sprays are easily prepared as simple solutions of the polymers, neutralizers, plasticizers, fragrance, etc, in ethanol. If water is in the formulation, it must be added last. The aerosol products are filled by the methods described for styling mousses. 

National Aerosol Products Charles Crosbie Laboratories U.S. Technology Composition Materials Co. 

If the dmg is not soluble in the propellant, it is dissolved or dispersed in a Hquid vehicle. The propellant then constitutes the third phase of the system, and the container must be shaken before valve actuation. Emulsified aerosol products like lotions and creams are examples of such systems. 

Over 68 aerosol products containing isopropyl alcohol solvent have been reported (145). Aerosol formulations include hair sprays (146), floor detergents (147), shoe poHshes (148), insecticides (149,150), bum ointments (151), window cleaners, waxes and poHshes, paints, automotive products (eg, windshield deicer), insect repellents, flea and tick spray, air refreshers, disinfectants, veterinary wound and pinkeye spray, first-aid spray, foot fungicide, and fabric-wrinMe remover (152) (see Aerosols). 

Specific advancements ia the chemical synthesis of coUoidal materials are noteworthy. Many types of genera ting devices have been used to produce coUoidal Hquid aerosols (qv) and emulsions (qv) (39—43) among them are atomizers and nebulizers of various designs (30,44—50). A unique feature of produciag Hquid or soHd coUoids via aerosol processes (Table 3) is that material with a relatively narrow size distribution can be routinely prepared. These monosized coUoids are often produced by relying on an electrostatic classifier to select desired particle sizes ia the final stage of aerosol production. 

A number of alternative sizing methods are available, and these are described in Table 8. The American Association of Pharmaceutical Scientists, Inhalation Focus Group conducted a comprehensive review of available methods, which was published in a series of articles identified in the last column of the table. All of the methods described either have been or are currently employed in the development of aerosol products. However, at this time only the inertial samplers, cascade impactors and impingers appear in compendial standards and in regulatory guidelines [44-46], Other methods such as thermal imaging are also under development and may give complementary size information to the current methods. 

Dragoescu, C., Friedlander, S. (1989) Dynamics of the aerosol products of incomplete combustion in urban atmospheres. Aerosol... 

It is present in most of Europe, throughout Africa, the Middle East, most of Asia, and the Americas. It is a highly lethal disease that can affect all warm-blooded animals. This is a biosafety level 2 agent unless there is a high risk of aerosol production then it should be treated as a biosafety level 3 agent. 

Aerosol production and transport over the oceans are of interest in studies concerning cloud physics, air pollution, atmospheric optics, and air-sea interactions. However, the contribution of sea spray droplets to the transfer of moisture and latent heat from the sea to the atmosphere is not well known. In an effort to investigate these phenomena, Edson et al.[12l used an interactive Eulerian-Lagrangian approach to simulate the generation, turbulent transport and evaporation of droplets. The k-e turbulence closure model was incorporated in the Eulerian-Lagrangian model to accurately simulate... 

OTS has focused its control efforts on two other chemicals in addition to PCBs. Working in conjunction with the Food and Drug Administration, EPA used TSCA s Section 6 to prohibit the use of chlorofluorocarbons (CFCs) as propellants in nonessential aerosol products. An advanced notice of proposed rulemaking under TSCA outlined approaches for restricting other uses of CFCs, but the attempt to deal with other CFC uses has been abandoned by the Reagan Administration. 

For aerosol products, the eye should be held open and the substance administered in a single, 1-s burst at a distance of about 4 inches directly in front of the eye. The velocity of the ejected material should not traumatize the eye. The dose should be approximated by weighing the aerosol can before and after each treatment. For other liquids propelled under pressure, such as substances delivered by pump sprays, an aliquot of 0.01 ml should be collected and instilled in the eye as for liquids. 

Table 1 summarises the features of equipment design which influence the risks of odour problems arising from surface spreading. There are numerous combinations of these features to be found in slurry tankers however, tanker design is often directed more to productivity in terms of speed of operating and area of ground covered rather than to minimising odour and aerosol production. 

Equipment design and relative risks of odour and aerosol production... 

Sludges and slurries which have been stabilised, particularly by anaerobic digestion, have no offensive smell, but injection may still be desirable to prevent aerosol production during spreading and for visual and aesthetic reasons. 

Regardless of the type of aerosol products to be radiolabelled, a fimdamental requirement in radiolabelling aerosol products is that the radiolabel must associate with the drug in such a way that not only the radiolabel distribution matches the drug distribution but also that the radiolabel distribution matches that of the unlabelled commercial product. 

All aerosol products identified in the sm( chamber can be reasonably explained in terms of the O Neal and Blumstein and Criegee mechanisms, as is illustrated in Figure 3-11 for Qrclohexene. The major difference between alkenes and cyclic olefins lies in the fact that, after opening of the ( clic olefin double bond, the original number of carbon atoms is conserved and the chain carries both the carbonyl group and the biradical intermediate, whose further reactions lead to the observed difunctional compounds. 

Grosjean, D. Atmospheric reactions of ortho cresol gas phase and aerosol products, Atmos. Environ., 19(8) 1641-1652,1984. Grosjean, D. Photooxidation of methyl sulfide, ethyl sulfide, and methanethiol, Environ. Sci. Technol, 18(6) 460-468,1984a. Grosjean, D. Atmospheric reactions of styrenes and peroxybenzoyl nitrate, ScL Total Environ., 50 41-59, 1985. 

Aerosol products Packaging, propellants, final product assay Raw materials screening Quality control Gas mixture analysis... 

COLLECTION AND DETERMINATION OF DOSES DELIVERED THROUGH THE VALVES OF METERED AEROSOL PRODUCTS... 

The collection and analysis of doses from metered aerosol products has been found to be a tedious, labour-intensive process. Analyst-to-analyst variation in the actuating and collecting of samples from the canisters has been shown to be a significant variable in such determinations. Automation of the testing process conserves analyst time and eliminates all the variables associated with manual testing, thereby producing more consistent results. 

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