Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
1999-10-11
2001-10-02
Douyon, Lorna M. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S434000, C510S477000, C510S488000, C134S003000, C134S041000
Reexamination Certificate
active
06297208
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the removal of rust stains and more particularly, an improved formula for the removal of rust stains from toilets, sinks, chrome, clothing, and the like, which stains result from a water source having mineral or metal iron content.
Iron present in home water supplies is a common problem which can cause stains on toilets, sinks, chrome, clothing, driveways, sidewalks and the like. These “rust stains” caused by iron typically appear as an orange-brown color and can be difficult to remove. Stain causing iron in tap water can generally be traced to one of two sources.
First, the water source (e.g., a private well) may have a high mineral content of FeCO
3
, which combines with dissolved CO
2
in the water to form Fe
2+
(aq). In turn, in the presence of oxygen, the Fe
2+
(aq) oxidizes to a Fe
3+
hydrate according to the following equation:
4Fe
2+
(
aq
)+O
2
(
g
)+4H
2
O(
l
)+2
x
H
2
O(
l
)→2Fe
2
O3·
x
H
2
O(
s
)+8H
+(
aq
)
where 2Fe
z
O
3
·xH
2
O(s) is rust, a hydrate of iron (III). The variable amount of water of hydration is represented by x.
Alternatively, solid iron (e.g., from iron based piping) can be oxidized to Fe
2+
(aq) in the presence of oxygen. In turn, the Fe
2+
(aq) can be further oxidized to a Fe
3+
hydrate according to the above equation.
The iron oxides or rust stains formed according to the above formula can have various colors, depending upon the extent of hydration. Iron oxide stains can be colored yellow, orange, brown or even black, for example.
Commercially available cleaners for rust stain removal usually include hydrofluoric acid as the active ingredient. While an effective stain remover, hydrofluoric acid undesirably produces an “etching effect.” The etching effect can be observed on enamel or glazed surfaces consisting of SiO
2
or the like, such as tile and glass. For example, glass surfaces appear foggy and tile loses its shine, or gloss, after exposure to hydrofluoric acid. Further, while commercially available rust stain removal formulas are safe when their directions are followed, a second problem is that hydrofluoric acid can cause severe burns when contacted with human skin, even in extremely small amounts.
An iron stain removal formula which does not produce an etching effect and does not cause severe burns when contacted with the skin, yet has an efficacy the same or nearly the same as known commercially available rust stain removal formulas is desired.
SUMMARY OF THE INVENTION
The present invention provides an effective rust stain removal formula using fluoboric acid as the active ingredient and a method of making same. The inventive formula causes less etching to glazed, glass or enamel surfaces and reduces the problems caused by the hydrofluoric acid used as the active ingredient in prior art rust stain removal formulas.
In one form thereof, the present invention provides a composition for removal of iron stains. The composition is formed from about 1 to 5 percent by weight of ammonium bifluoride, about 1 to 5 percent by weight of boric acid, and about 1 to 5 percent by weight of oxalic acid. The remainder of the composition is water and, optionally, a surfactant and a thickening agent. The ammonium bifluoride and the boric acid initially present in the composition react to form fluoboric acid, the active ingredient.
In a preferred form thereof, the inventive composition further comprises about 1 to 5 percent by weight of citric acid. More preferably, the ammonium bifluoride comprises about 2.5 to 3.5 percent by weight, the boric acid comprises about 2 to 3 percent by weight and the oxalic acid comprises about 3 to 4 percent by weight. Still more preferably, the citric acid comprises about 3 percent by weight, the surfactant comprises about 0.1 to 1.0 percent by weight and the thickening agent comprises about 0.1 to 0.5 percent by weight.
One advantage of the inventive formula is that it reduces the undesirable etching effect produced by prior art formulas which utilize hydrofluoric acid as the active ingredient. While hydrofluoric acid is an effective rust stain remover, it also dissolves silicon dioxide, which is a major component of the glazed and enamel surfaces of bathroom tiles and fixtures. Indeed, hydrofluoric acid is commonly used to etch glass. Consequently, prior art formulas which include hydrofluoric acid undesirably cause bathtubs, tiles and the like to lose their gloss and luster. The present invention utilizes fluoboric acid as the active ingredient instead of hydrofluoric acid. Unlike hydrofluoric acid, fluoboric acid does not etch silicon dioxide, and pure fluoboric acid can even be stored in glass containers at room temperature. Thus, iron stain removal formulas embodying the present invention significantly reduce the problematic etching effect associated with prior art formulas.
Another advantage of the inventive formula is that it reduces the potentially harmful effects associated with the hydrofluoric acid contained in prior art formulas. While prior art formulas which include hydrofluoric acid are safe when their directions are followed, hydrofluoric acid can cause severe and penetrating burns when contacted with the human skin. Burns caused by hydrofluoric acid are typically not noticed until the day following contact when they show as painful sores on the skin. Because the present invention utilizes fluoboric acid, and not hydrofluoric acid, the potentially harmful effects caused by hydrofluoric acid are reduced.
In another form thereof, the present invention provides a method of treating rust stains. The method includes combining a predetermined amount of ammonium bifluoride with water in a container and dissolving the ammonium bifluoride. Then, a predetermined amount of boric acid is added to the container. The contents of the container are mixed, whereby the boric acid and the ammonium bifluoride react to form a formula including fluoboric acid. The formula is then applied to an article having a rust stain thereon to remove the stain.
In a preferred form, the inventive method further comprises adding predetermined amounts of oxalic acid and optionally, citric acid, after the boric acid is added. More preferably, the method includes adding predetermined amounts of detergent and perfume after the boric acid is added. Still more preferably, the container contents are heated and maintained at about 40 to 50 degrees Celsius during adding and mixing of the components. Still more preferably, the method includes the predetermined amount of ammonium bifluoride comprising about 1 to 5 percent by weight of the formula and the predetermined amount of boric acid comprising about 1 to 5 percent by weight of the formula.
An advantage of the inventive method is that the boric acid dissolves completely and does not later precipitate from solution. Thus, the reaction of boric acid and ammonium bifluoride to produce fluoboric acid is achieved.
DETAILED DESCRIPTION
Aqueous cleaning compositions embodying the present invention include, on a weight percentage basis, from about 1% to 5% ammonium bifluoride, preferably from about 2.5% to 3.5%; from about 1% to 5% boric acid, preferably from about 2% to 3%; from about 1% to 5% oxalic acid, more preferably from about 3% to 4%; from about 1% to 5% citric acid, more preferably about 3%; nonionic surfactant from about 0.1% to 1.0%, more preferably from about 0.2% to 0.5%; perfume oil from about 0.05% to 1% wt., preferably about 0.1 wt.; a thickening agent less than 0.5%, preferably about 0.1% to 0.5% wt.; the balance water.
Method of Preparation
The method of preparation described below is for a laboratory size experimental batch, as are all examples given hereinbelow. However, it is to be understood that one of ordinary skill in the art could readily adapt the teachings hereunder to a large-scale commercial production of a formula embodying the present invention.
Step 1.
To a clean, 600 ml PYREX® (or equivalent) beaker graduated to 500 ml capacity in increments
Baker & Daniels
Douyon Lorna M.
Iron Out, Inc.
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