US 3672993 A
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United States Patent 3,672,993 METHOD AND COMPOSITIONS FOR CLEANING OVENS AND THE LIIGE Harry Ian Mitchell, Rochdale, and Kenneth Tomlinson, Bramhall, England, assignors to Colgate-Palmolive Company, New York, N.Y. No Drawing. Filed July 30, 1970, Ser. No. 59,753
Int. Cl. C23g 1/02 US. Cl. 134-3 9 Claims ABSTRACT OF THE DISCLOSURE A method is provided whereby baked on organic deposits from a surface are readily removable wherein an alkali metal bicarbonate is applied to the .clean surface and subsequent cleaning after soiling is effected by wash- I This invention relates to the cleaning of surfaces, such as the surfaces of ovens, which are subjected to heat and are liable to soiling by baked-on organic deposits.
The soiling matter deposited on ovens, such as domestic cooker ovens, consists of a complex organic mixture of natural fats and other deposits from the cooking of food. When heated at normal oven temperatures, this soiling matter is converted into an infusible polymeric mass in which part of the organic material may also be charred. Detergents, scouring powders and similar cleansing products, even when alkaline (e.g. those containing phosphates), although highly efiicient for removing normal greasy soiling matter, are not usually adequate for removing baked-on soil of the type found in ovens.
The removal of this type of soil is therefore a considerable problem, requiring powerful chemical or physical action. Among the most effective chemical compounds known for this purpose are the caustic alkalis, sodium and potassium hydroxides. Their mode of action is that they react with and hydrolyse natural fats, thus converting them at least partially into their sodium or potassium salts, which are water-soluble and thus easily removed. Commercial products of this type usually contain up to 3% of sodium hydroxide together with other components such as solvents and emulsifiers which promote the efiiciency of the product. They may be applied direct by brush or sponge, or more conveniently by means of an aerosol spray. Products of this type, although efficient in their action, suffer from a number of major disadvantages. The most important disadvantage is'the serious hazard to the eyes and skin arising from the use of caustic alkalis. If inadvertently sprayed in the eyes, a product of this type could cause permanent blindness. It is also common practice for housewives to use rubber gloves when applying a product of this type to avoid damage to the skin. Such products may also damage adjacent surfaces, such as paint, aluminum or wood, onto which they may be inadvertently sprayed. Another disadvantage is that such products when applied to soiled oven surfaces must attack the soiling matter from the outer surface, while the most severe charring and polym erisation is generally present in the interior of the soil 3,672,993 Patented June 27, 1972 layer, adjacent to the oven wall. This makes cleaning more diflicult.
Alkalis less alkaline than caustic sodi, although they would avoid some of the hazards already indicated, are not very effective in hydrolyzing baked-on fat in the short time of application, and consequently are not efficient oven cleaners.
Certain pre-treatment preparations are known which act by forming a physical barrier between the oven wall and the soiling matter, and do not depend on chemical actions. Those preparations are expensive and not very effective.
It is an object of this invention to avoid the disadvantages of the known oven cleaner preparations, and at the same time to provide a simple and effective procedure for oven cleaning.
According to one aspect of the invention a method of cleaning a surface which is subjected to heat and is liable to soiling 'by baked-on organic deposits comprises applying to the clean surface an alkali metal bicarbonate, and washing the surface clean again after such soiling.
According to other aspects of the invention there are provided various compositions for the pre-treatment of such a surface and comprising an alkali metal bicarbonate, an aqueous vehicle and other components as hereinafter described.
According to a further aspect of the invention there is provided a pressurized aerosol-type dispenser containing a solution or suspension of an alkali metal bicarbonate and a propellant.
The principle of the invention is as follows: Alkali metal bicarbonates, which are very mild alkalis, decompose on moderate heating to form the corresponding carbonates which are much stronger alkalis. These carbonates in turn are sutficiently powerful to promote the slow hydrolysis of fats, particularly under the influence of temperature. After application of the alkali metal bicarbonate to the clean oven surface, use of the oven converts it to the corresponding carbonate, which slowly hydrolyses fats deposited on the walls, thereby converting them at least partially into the corresponding soaps which are easily removed with warm Water.
Alkali metal bicarbonates are very mild alkalis which cannot harm the eyes or the skin. They are harmless to painted surfaces, aluminium and wood, all of which may be damaged by caustic alkalis. Since the product is applied -directly on the clean oven walls, it acts first on the fat which is first deposited and is therefore most likely to polymerize and char and be the most intractable.
Oven pre-treatments according to the invention can be effected in a variety of ways, the following being typical examples:
(a) Application of a solution or suspension of alkali metal bicarbonate by means of a sponge, brush or cloth.
(b) Applicable of a solution or suspension of alkali metal bicarbonate by means of a hand operated spray bottle or a hand pump or automatically (e.g., by venture action) by means of a cartridge of compressed gas.
(c) Application of a gel or paste composition containing alkali metal bicarbonate.
(d) Application of a solution or suspension of alkali metal bicarbonate by means of an aerosol type pressurized dispenser.
The ways (b) and (d) are preferred.
Examples of suitable alkali metal bicarbonate are sodium bicarbonate, potassium bicarbonate and mixtures thereof.
The basic material is a solution or suspension of the alkali metal bicarbonate in water. For a solution the amount present is governed by the solubility of'the partic ularsaltjn water. Typical approximate figures are:
Sodium bicarbonate-8% at 20 C. Potassium bicarbonate25% at 20 C.
These and all other percentages are by weight.
On the grounds of cost, sodium bicarbonate is preferred, and a solution of .4% to 7% is sufiicient to give adequate performance. It is possible to produce a stronger material by including additional alkali metal bicarbonate in a suspended form.
Other,materials may be added for imparting desired additional properties. Examples are:
(i) SURFACE-ACTIVE AGENTS Such compounds improve the wetting action, afford moreeveu distribution on the oven walls. They may also act as a mild adhesive improving retention of the filmon the oven wall. Theymay also act as emulsifying agents for water-immiscible propellants used in aerosol dispensers. In so far as they withstand oven heat they may also facilitate washing off of the soil layer. Almost any kind of surface-active agent will perform at least one of these functions to some extent.. However, among the most eflicient are:
Ethoxylated nonyl phenols (especially 8-11 mols ethylene oxide),
Phosphate ester (e.g. Solumin PFN 95 manufactured by Glovers Chemicals Ltd. of England),
Sodium dodecylbenzene sulphonate.
(iii) CORROSION INHIBITORS These may be included to inhibit corrosion of the aerosol can and oven walls. Examples are sodium benzoatefso dium nitrite and mixtures thereof.
(iv) COLORING MATERIALS A coloring material such as a dye or pigment maybe added to afford a visual contrast between the oven wall and the applied composition to facilitate uniform and complete application, or merely to alter the appearance of the resulting dried film which in the absence of added color has a whitish hue. 7
(v) GELLING OR THICKENING AGENTS Materials such as carboxymethyl cellulose may be added to gel or thicken compositions of the type (c) above.
(vi) PROPELLANTS For aerosol type products a wide variety} of propellant substances may be used, such as halocarbons, hydrocarbons, carbon dioxide, nitrous oxide or suitable mixtures thereof, though hydrocarbons are not recommended because of flammability hazards. "t'l The pressurized dispenser is preferably of a type which discharges the product asa spray.
The following examples illustrate the inventiomln each case a base formula is given which may be applied direct weights are used:
' Example I Base formula: Percent Sodium bicarbonate 7 Nonyl phenol polyethoxylate (8-9 ethylene oxides) e.g. Ethylan TU (Lankro chemicals Ltd., England) 1.5
Sodium xylene sulphonate (30%- aqueous soltion) 1.5
- Water 90.
For filling into an aerosol dispenser the following weights are used:
. Percent Base as above 90 Difiuorodichloromethane 5 Tetrafluorodichloroethane 5 "Example II Base formula: Percent Potassium bicarbonate 15.00 Sodium salt of disulphonated dodecyldiphenyloxide (45% aqueous solution) (Dowfax 2A1) Nonylphenol polyethoxylate (8-9 ethylene 1 oxides) e.g. Ethylan TU (Lankro Chemicals Ltd.) 0.15 Water 84.45
For filling into an aerosol dispenser the following 7 Percent Base as above 90 Difiuorodichloromethane 5 Tetrafluorodichloroethane S I A Example III Base formula (with suspended solids): Percent Sodium bicarbonate 16.0 Hydratedsilica (Aerosil 200 Degussa) 1.0
Sodium salt of disulphonated dedecyldiphenyloxide 45% (Dowfax 2A1) 1.0
For filling into an aerosol dispenser the following weights are used:
, I Percent Base as above a 80.0 Difluorodichloromethane 10.0 Tetrafluorodichloroethane 10.0
Products manufactured according to the examples were evaluated by the procedure described below.
Enamelled metal plates 18" x 10" were heated to 100 C. in an oven. The hot plates were removed from theoven and a mask was placed over one half of each plate. The uncovered half of each plate was then treated with the product under test. After drying the plates the whole area was coated evenly with a layer of greasy soiling matter (deep frying cooking fat, lard and tallow to the oven walls by any convenient means. In addition details are given for the application of the same base by means ofanaerosol dispenser. V
were'used as typical soiling materials.) The plates were then heated in an oven for at least24hours at temperatures between 200 and 250, C. After removal from the oventhe plates were cooled. The whole surface of the plates was then washed with a /z% solution of soap in warm'water applied by a sponge. The burnt-on soiling matter was completely removed from thevtreated areas without difliculty. The untreated areas were still heavily soiled with burnt-on fat after the treatment.
What is claimed is:
1. A method of cleaning a surface which is subjected to heat and is liable to soiling by baked-on organic deposits which comprises applying to the clean surface an effective amount of an alkali metal bicarbonate, and washing the surface clean again after such soiling.
2. A method as claimed in claim 1 in which the alkali metal bicarbonate is applied as a solution in an aqueous vehicle.
3. A method as claimed in claim 1 in which the alkali metal bicarbonate is applied as a suspension in an aqueous vehicle.
4. A method as claimed in claim 3 in which the suspension also contains a suspending agent.
5. A method as claimed in claim 1 in which the alkali metal bicarbonate is applied in the form of a gel or paste.
6. A method as claimed in claim 5 in which the gel or paste also contains a gelling or thickening agent.
7. A method as claimed in claim 1 in which the alkali metal bicarbonate is applied in the form of a solution or suspension sprayed from a pressurized container.
8. A method as claimed in claim 1 in which the alkali metal bicarbonate is applied together with a surfaceactive agent.
9. A method as claimed in claim 1 in which the alkali metal bicarbonate is selected from sodium bicarbonate, potassium bicarbonate and mixtures thereof.
References Cited UNITED STATES PATENTS 3,183,110 5/1965 Aler et al 252 3,198,744 8/1965 Cook et a1. 252156 FOREIGN PATENTS 751,361 1/1967 Canada 252156 US. Cl. X.R.