US3591416A - Method of cleaning ovens - Google Patents

Abstract

AN OVEN WALL CLEANING COMPOSITION HAVING AS THE ACTIVE CLEANING AGENT AN OXIDIZING SALT SUCH AS SODIUM NITRATE, OR OTHER ALKALI METAL OR ALKALINE EARTH METAL, NITRATE, IN COMBINATION WITH A SUFFICIENT AMOUNT OF A CAUSTIC ALKALI, SUCH AS SODIUM HYDROXIDE TO GIVE THE MIXTURE AN ALKALINE REACTION. SUCH MIXTURES ARE APPLIED TO AN OVEN WALL SURFACE THAT HAS BECOME GLAZED WITH HEAT-PRODUCED FATTY RESIDUES, AND CLEANING IS EFFECTED BY HEATING THE TREATED SURFACE T O A SUFFICIENTLY HIGH TEMPERATURE ABOVE ABOUT 230*C., FOR A PERIOD OF TIME SUFFICIENT TO BURNS OFF THE FATTY RESIDUES AND LEAVES THE SURFACE SUBSTANTIALLY CLEAN. THE CLEANNG COMPOSITION CAN BE APPLIED DRY TO A LOWER HORIZONTAL SURFACE OR CAN BE DISPERSED IN A CARRIER, SUCH AS AN AQUEOUS VEHICLE IN THE FORM OF A SATURATED SOLUTION, SLURRY, GEL OR THE LIKE, WITH OR WITHOUT A SURFACTANT, AND APPLIED BY BRUSHING, SPRAYING, WIPING OR RUBBING ONTO THE OTHER OVEN WALL SURFACES.

Description

US. Cl. 134-2 3 Claims ABSTRACT OF THE DISCLOSURE An oven wall cleaning composition having as the active cleaning agent an oxidizing salt such as sodium nitrate, or other alkali metal or alkaline earth metal, nitrate, in combination with a sufiicient amount of a caustic alkali, such as sodium hydroxide to give the mixture an alkaline reaction. Such mixtures are applied to an oven wall surface that has become glazed with heat-produced fatty residues, and cleaning is effected by heating the treated surface to a sufiiciently high temperature, above about 230 C., for a period of time sufiicient to burn off the fatty residues and leave the surface substantially clean. The cleaning composition can be applied dry to a lower horizontal surface or can be dispersed in a carrier, such as an aqueous vehicle in the form of a saturated solution, slurry, gel or the like, with or without a surfactant, and applied by brushing, spraying, wiping or rubbing onto the other oven wall surfaces.

SUMMARY OF THE INVENTION The method of my invention comprises applying a cleaning composition to a metal or other wall surface of home or industrial ovens exposed to the spattering of fats and greases, or other oily substances, and having thereon a heat-produced glaze, film, stain or the like, containing residues from oily substances of vegetable, animal or mineral origin. The method of cleaning is especially applicable to walls of home and industrial ovens formed of aluminum or other metal, whether bare or coated, as with porcelain enamel. During use in cooking, such oven walls are coated over with a glaze of heat-produced residues, which adhere tightly to the interior oven walls to form an unsightly stained coating or film, herein generally referred to as a glaze.

In some of the more modern electrically heated ovens, the glaze can be burned off by raising the temperature of the oven walls sufficiently high, in the neighborhood of 700 to 800 F., to burn off the glaze and leave the wall surfaces substantially clean and of their original color. The burn-off can be satisfactorily carried out without the previous application of any cleaning composition, but a large amount of electricity or gas is consumed in heating up the oven walls to such high temperatures.

The present method is carried out at a substantially lower temperature within the range of about 230 C. to 290 C.

My cleaning composition contains as the active cleaning agent a mixture of an oxidizing salt selected from the group consisting of alkali metal and alkaline earth metal nitrates and caustic alkali, such as caustic soda, in an mount sufficient to impart to the mixture an alkaline reaction.

The selected mixture of a nitrate and caustic alkali can be applied dry, powdered, or in granular form, or dispersed in a suitable aqueous vehicle for application by spraying, brushing, wiping or rubbing onto the glazecoated surface to be cleaned. The surface is then heated to a sufficiently high temperature, within the range of from 230 to 290 C., to burn-off the glaze and leave a clean surface behind. The term burn-off is used in the same sense that it is applied to the results obtained when United States Patent O 3,591,416 Patented July 6, 1971 the walls of an electrically heated cooking oven are brought up to a temperature sufiiciently high to remove unwanted grease stains, coatings and the like.

DETAILED DESCRIPTION OF THE INVENTION The oxidizing salt that I prefer to use in the composition of my invention is sodium nitrate, but other oxidizing salts such as other alkali metal and the alkaline earth metal nitrates can be used, together with a sufficient amount of an alkaline reacting compound, such as sodium hydroxide, to give the composition an alkaline reaction. The following tests indicate that while sodium hydroxide (NaOH) can be used by itself to effect the cleaning of glazed oven walls, it is too corrosive for satisfactory use, but when sodium hydroxide is combined with an alkali metal or an alkaline earth metal nitrate, no corrosive effect results, even on an aluminum surface.

For purposes of simulating the conditions under which glazing of oven walls occurs, the following oven tests were carried out:

Grease alone A 30% solution of No. 2 grease was prepared by mixing 30 grams of No. 2 grease with grams of isobutanol in a 250 ml. Erlenmeyer flask. Solution was brought about by Warming the resulting mixture on a warming plate.

Grease and oil Another 30% solution was prepared, this time by combining 10 grams of No. 2 grease, 20 grams of MC800 oil and 70 grams of isobutanol in a 250 ml. 'Erlenmeyer flask. Solution was again brought about by warming.

Simulated oven tests Tests were made using metal plates each having sixteen depressions, or dimples, therein for receiving the grease and grease plus oil solutions. In each case, 0.4 m1.

of the respective solutions were placed in each of the respective sets of 16 depressions. The test plates were then placed in an oven at 280 to 285 C. for 1 hour 45 minutes each. This resulted in a black crust being formed in each depression, whether containing the solution of grease alone or the solution of grease and oil.

In the next step, a solution of sodium nitrate alone was prepared by dissolving 15.7 grams of sodium nitrate in water and diluting the resulting solution to 900 ml. in a column with distilled water. The sodium nitrate plus sodium hydroxide solution was made by combining 3.1 grams of sodium hydroxide and 12.6 grams of sodium nitrate and diluting to ml. to give a total of 15.7 grams of material dissolved in the resulting solution. Thus, both of the solutions prepared contained 0.0157 gram of material in each 0.1 ml. of solution.

The plates were then treated with the respective materials, the amount of material added to each depression being 1.4 ml. or 0.22 gram in each case.

After being allowed to stand overnight, or other effective equivalent soaking period the respective grease and grease plus oil plates were placed in an oven at 280 C. and removed 2 /2 hours later for evaluation, the temperature of the oven being maintained at 280 C. plus or minus 5 C.

The thus treated test plates were then placed back in the oven at 280285 C. and kept at that temperature for at least one hour and preferably about 2 hours before removal. After removal of the test plates, the plates were allowed to cool and then rinsed with tap water. The evaluation was then made on the percent of clean metal area after treatment, based upon the total area treated. A tabulation of the results obtained is as follows:

TAB LE NO. 1

Percent of clean Treating material (salt surface area after Plate with baked on or salt plus caustic) treatment Grease N Do N From the foregoing tabulation of results it will be evident that while sodium nitrate alone shows a removal of and 70%, respectively, for grease and grease plus oil, the combination of sodium nitrate with sodium hydroxide gives better results, 30 and 90% removal, respectively, with grease alone and with grease plus oil. The higher percent of removal of the burned-on grease, or grease plus oil, residues is believed to be due to the resulting alkalinity of sodium nitrate-caustic soda mixture, but caustic soda alone results in excessive corrosion of the metal plate.

Another set of tests was run, using a stainless steel plate 7%" square, containing 16 circular depressions, each 1 /2" in diameter and A2" in depth. Similar conditions were used as above described, except that a drop of a non-ionic surfactant, Triton X-100 (isooctyl phenyl polyethoxyethanol containing 9-10 ethyleneoxide groups per molecule), was placed in each depression over the glaze before adding the treating solution of NaNO or of NaNO plus NaOH in the total amount of 0.22 gram, as before in the proportions of NaNO to NaOH designated below:

Where two figures for Percent Removal are given, they represent different tests.

As indicated in Table No. 2, the combination NaNO and from 1 to 40% of NaOH by weight of the total performed well in the removal of baked of baked-on grease, which was somewhat more difiicult to remove than was the baked-on grease plus oil. The amount of corrosion was directly proportional to the percentage of NaOH, and above the 50% level of NaOH some corrosion was noticed. The greatest amount of corrosion was exhibited by a solution of NaOH alone, where a 90% and a 98% removal in the case of grease and grease plus oil, respectively, were observed.

Satisfactory results can thus be obtained by using from 1 to 40% of caustic soda (NaOH) by weight of the mixture of sodium nitrate and sodium hydroxide. In place of sodium nitrate, other alkali metal nitrates or alkaline earth metal nitrates and equivalent proportions of sodium hydroxide can be used with satisfactory results if at least 0.01 gram/cm. and preferably 0.02 gram/cm. of the composition is spread over the glazed oven surface.

Accordingly, the composition of my invention preferably utilizes sodium nitrate, together with a sufficient amount of sodium hydroxide to render the mixture alkaline. More broadly stated, however, my invention comprises the use of any alkali metal or alkaline earth metal nitrate in combination with a sufficient quantity of an alkali metal or alkaline earth metal hydroxide to give the mixture an alkaline reaction.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

I claim:

1. The method of cleaning a metal surface having thereon a heat-produced glaze of fatty residues, the steps which comprise spreading over said glazed metal surface so as to adhere thereto an aqueous composition consisting essentially of a salt selected from the group consisting of alkali metal nitrates and alkaline earth metal nitrates and mixtures thereof, and an alkali metal hydroxide in an amount sufficient to impart to said composition an alkaline reaction, and

after allowing said composition to remain spread over said surface for an effective soaking period heating said glazed metal surface with said composition adhering thereto to a sufficiently high temperature between 230 C. and 290 C. for a sufficient length of time to remove said glaze and leave said surface substantially clean.

2; The method as defined by claim 1, wherein the metal surface is an aluminum surface.

3. The method as defined by claim 2, wherein the aluminum surface is the interior surface of a cooking oven, and said glazed metal surface is heated to at least a temperature of about 280 C. for at least about one hour.

References Cited UNITED STATES PATENTS 2,357,970 9/1944 Rath 134-2X 2,674,548 4/1954 Balz 1342 2,674,549 4/ 1954 Balz 134-2 3,046,165 7/1962 Halversen et al. 134-2X 3,085,035 4/1963 Ireland ct al. 1342X 3,375,155 3/1968 Adams 134--2X 3,425,947 2/ 1969 Rausch et al. 134--39X MORRIS O. WOLK, Primary Examiner J. T. ZATARGA, Assistant Examiner US. Cl. X.R. 134-19, 22, 39, 40

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,591, 416 Dated H1116, 1971 Inventor(s) Carl E. Johnson It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 52, cancel "of baked" (first occurrence);

Same column, line 56, change "50" to --5-.

Signed and sealed this 1 1th day of July 1972.

(SEAL) Attest:

EDWARD M'.FLETCHER,JR. ROBERT GOTISCHALK Attesting Officer Commissioner of Patents FORM powso 7 USCOMM-DC wan-poo UTS. GOVERNMENT PIINTlNG OFFICE HUD 0-366-3.