Acidic and alkaline cleaning compositions for hard surfaces have been used for many years to remove stubborn soils from a variety of surfaces found in household and institutional locations. Such soils include inorganic soils and soils derived from organic sources, such as fats, oils, proteins and carbohydrates. Such soils when heated can form hard tenacious deposits on a variety of surfaces including ceramic, stainless steel, concrete, tile and metal food preparation surfaces. Typical inorganic solids comprise insoluble materials derived from the hardness components of service water including substantially insoluble salts of calcium, magnesium, iron, manganese, etc. Such inorganic salts can be combined in some cases with organic residues which can form large, difficult to remove soil deposits. These soils can be unsightly, can take the form of large deposits of charred or baked-on residue, or large areas of white insoluble soap scum or hardness deposits. These soils can also promote or support the growth of microorganisms that can under certain circumstances contaminate food or other contaminatable materials or surfaces.
A variety of cleaning compositions have been developed to deal with the tenacious organic and organic/inorganic matrix soils common in a variety of surfaces. One particularly useful form of cleaner is an aqueous alkaline cleaner commonly delivered from a pressurized aerosol or pump spray device. These types of cleaners have great utility for a variety of surfaces because the material can be delivered by spray to vertical, overhead or inclined surfaces or to surfaces having a complex curved or convoluted surface while achieving substantially complete coverage of the surface with the spray-on liquid cleaner. Acid spray-on cleaners are also known for removing basic inorganic soils and are becoming more common.
One substantial problem that arises with such spray-on materials relates to an airborne mist or finely divided aerosol generated during the spraying process. The aqueous liquid is converted by the action of propellant or pump action into a spray that is accompanied by a finely divided aerosol or mist. The spray portion contacts and remains on the target surface, while a substantial proportion of the aerosol can remain suspended in the atmosphere.
Such aqueous compositions having a strong acid or strong base cleaning component in the form of a finely divided aerosol or mist can cause respiratory distress in the user. Upon breathing the finely divided aerosol or mist, a very strong and irrepressible choking response is seen in most individuals that come in contact with irritating proportions of the aerosol produced by typical spray-on cleaners. The choking response is inconvenient, reduces cleaning efficiency in a variety of applications and in sensitive individuals can cause asthma attacks, respiratory damage, or other discomfort or injury.
To alleviate, to some degree, the choking response, some products have been formulated with reduced quantities of the strongly alkaline or strongly acid cleaning components to reduce the choking response. Strong caustic has been replaced by reduced alkalinity bases such as bicarbonate or by solvent materials. The reduction in concentration or substitution of these materials can often reduce the cleaning activity and effectiveness of the material when used.
Crotty et al., U.S. Pat. No. 3,644,210, teach an alkaline cleaning material useful for removing burnt-on, baked-on food and grease from cooking surfaces comprising substantial proportions of alkali metal hydroxide in an aqueous cleaning base. Eisen, U.S. Pat. No. 3,779,933, teaches an aqueous alkali metal cleaning composition using clay and organic thickening materials. Mukai et al., U.S. Pat. No. 3,813,343, teach oven cleaning compositions containing an amine or ammonia base combined with dimethyl sulfoxide solvent and other compositions. Wise et al., U.S. Pat. No. 3,829,387, teach caustic cleaning compositions containing substantial proportions of sodium hydroxide, clay thickeners, and solvents in an aqueous base. Dillarstone et al., U.S. Pat. No. 4,214,915, and Canadian Patent No. 1,523,491, teach oven cleaning compositions using a relatively mild base such as sodium carbonate and sodium bicarbonate in an aqueous cleaning material. Culshaw, U.S. Pat. No. 4,676,920, teaches a thickened viscous scouring material using surfactants, abrasives and solvents for soil removal. De Buzzaccarini, U.S. Pat. No. 4,767,563, teach liquid scouring cleaning compositions using solvents, abrasives and surfactants for soil removal from hard surfaces. Cockrell, Jr., U.S. Pat. No. 4,877,691 (International Application No. PCT/US91/05092) teaches a barrier coating composition used to pretreat an oven to promote the subsequent removal of hardened baked-on soils that form on the pretreatment material. Dimond et al., Canadian Patent No. 1,047,903, teach oven cleaning compositions having reduced proportions of sodium hydroxide which are thickened using a bentonite in a substantially aqueous base. Silvester, Canadian Patent No. 1,211,674, teaches an improved oven cleaner using sodium bicarbonate as an alkali, glycerol as a solvent, a clay thickener in an aqueous formulation for oven cleaning. Flannery, United Kingdom Patent No. 2,019,876, teaches an aerosol comprising sodium bicarbonate as an oven cleaner.
The prior art taken as a whole shows that skilled artisans in experimenting with improving acid and alkaline hard surface cleaners, in particular alkaline oven cleaners, have attempted to reduce concentrations of sodium hydroxide to reduce the choking response. Ammonia or an organic base has been used to replace sodium hydroxide in reduced alkaline cleaners. Other relatively mild inorganic basic materials, such as sodium carbonate or sodium bicarbonate have also been used to replace sodium hydroxide. A variety of organic surfactants or glycol, alkyl ether or dimethyl sulfoxide solvent materials have been used to enhance the detergent properties of the reduced alkaline materials.
The prior art taken as a whole has attempted to replace sodium hydroxide to reduce choking response but does not recognize that the choking properties of these cleaners is related to the median particle size of the aerosol. For this reason, no attempt has been made in the prior art to formulate to adjust the particle size of the aerosol to reduce respiratory distress or choking reflex.