An anhydrous metal cleaning composition and a process for preparation thereof

Abstract

The present invention relates to an anhydrous metal cleaning composition comprising 70-85% w / w of dolomite as an abrasive, 5-15% w / w of China clay as a filler, 0.1-8.0% w / w of a metal oxide, 0.01-6.0% w / w of an alkali metal carbonate, 0.1-12.0% w / w of sand (mica), 0.1-18.0% w / w of citric acid and 5.0-15.0% w / w of oxalic acid or acetic acid, such that the total amount of the components is 100% w / w. The invention also relates to a method of preparing the anhydrous metal cleaning composition. The anhydrous metal cleaning composition work effectively with less or even absence of water and provides a superior cleaning of metal articles.

Description

FIELD OF THE INVENTIONThe invention relates to an anhydrous metal cleaning composition and its processfor preparation.BACKGROUND OF THE INVENTIONMetal utensils such as that made of copper, brass, iron, silver, stainless steel etc.used in household and industrial settings are prone to rusting and corrosion asthese in contact with aqueous fluids. Hence, such metal utensils are required to becleaned before and after use to remove the corrosion or rust that has been formedand deposited on the utensils.WO 2006 / 136774 describes an acidic hard cleaning surface liquid cleaningcomposition comprising formic acid or sulfamic acid, at least one further acidselected from organic or inorganic acid and at least one nonionic surfactant.However, formic acid is considered harmful due its effect upon contact with skin oreyes and upon ingestion.Metal cleaning compositions contain abrasives such as quartz, fine glass dust etc.for cleaning purposes. Cleaning compositions such as abrasive polishes and silverdips are time consuming in use and damage the metal surface from the abrasivedue to their hardness or their possible detrimental effect on other metals.Also, metal cleaning compositions contain surfactants and generally require waterfor cleaning and rinsing of the utensils during use of the composition. However,water may not always be available in quantities required for cleaning utensils. Also,while washing with water, utensils such as those made of copper, silver, and brassare required to be immediately wiped dry after washing to prevent formation of anoxidized metal film on the surface of the utensils that dulls its appearance.However, usually in households, utensils after washings are kept in open air fordrying and are not wiped to remove the water.There is a need for a metal cleaning composition that effectively cleans and shinesthe metal without damaging the metal surface. Also, there is a need for acomposition that can work effectively with less or even absence of water.SUMMARY OF THE INVENTIONThe invention relates to an anhydrous metal cleaning composition comprising 70-85% w / w of dolomite as an abrasive, 5-15% w / w of China clay as a filler, 0.1-8.0%w / w of a metal oxide, 0.01-6.0% w / w of an alkali metal carbonate, 0.1-12.0% w / wof sand (mica), 0.1-18.0% w / w of citric acid and 5.0-15.0% w / w of oxalic acid oracetic acid, such that the total amount of the components is 100% w / w.BRIEF DESCRIPTION OF THE DRAWINGSFigure 1: Graph comparing the ΔE values for composition of Formulation 6 of thepresent invention and its individual components on cleaning of copper articles.Figure 2: Graph comparing the ΔE values for composition of Formulation 7 of thepresent invention and its individual components on cleaning of copper articles.Figure 3: Graph comparing the ΔE values for composition of Formulation 8 of thepresent invention and its individual components on cleaning of copper articles.Figure 4: Graph comparing the ΔE values for composition of Formulation 9 of thepresent invention and its individual components on cleaning of copper articles.Figure 5: Graph comparing the ΔE values for composition of Formulation 10 of thepresent invention and its individual components on cleaning of copper articles.Figure 6: Graph comparing the ΔE values for composition of Formulation 11 of thepresent invention and its individual components on cleaning of copper articles.Figure 7: Graph comparing the ΔE values for composition of Formulation 12 of thepresent invention and its individual components on cleaning of copper articles.Figure 8: Graph comparing the ΔE values for composition of Formulation 6 of thepresent invention and Comparative Formulations A-D on cleaning of copperarticles.Figure 9: Graph comparing the ΔE values for composition of Formulation 6 of thepresent invention and available marketed composition on cleaning of copperarticles.Figure 10: Images of a copper article (glass) before and after cleaning with thecomposition of the present invention.Figure 11: Images of a silver article (glass) before and after cleaning with thecomposition of the present invention.Figure 12: Accelerated stability study data for Formulation 6 of the presentinvention.DETAILED DESCRIPTION OF THE INVENTIONIn an aspect, the invention relates to an anhydrous metal cleaning compositioncomprising 70-85% w / w of dolomite as an abrasive, 5-15% w / w of China clay as afiller, 0.1-8.0% w / w of a metal oxide, 0.01-6.0% w / w of an alkali metal carbonate,0.1-12.0% w / w of sand (mica), 0.1-18.0% w / w of citric acid and 5.0-15.0% w / w ofoxalic acid or acetic acid, such that the total amount of the components is 100%w / w.The term "filler" refers to a compound or substance that is added to aid inpreparation of the composition. The term "abrasive" refers to a compound orsubstance that used to wear away the surface of softer, less resistant materials bygrinding or rubbing. These terms are known to the person skilled in the art.The alkali metal carbonate is selected from sodium carbonate, potassiumcarbonate, lithium carbonate or a combination thereof.The metal oxide is selected from aluminium oxide, zinc oxide, titanium dioxide,chromium dioxide, iron oxide or a combination thereof.The composition optionally includes a colour and a perfume.In an embodiment, the composition comprises 70-85% w / w of dolomite, 5-15% w / wof China clay, 0.5-2% w / w of aluminium oxide, 0.01-3% w / w of sodium carbonate,1-5% w / w of sand (mica), 3-8% w / w of citric acid and 5-10% w / w of oxalic acidsuch that the total amount of the components is 100% w / w.In an embodiment, the anhydrous metal cleaning composition is a powdered solid.The pH of a 10% solution of the composition is in a range of around 4.0-6.0.The metal cleaning composition provides for cleaning the surface of a metalselected from but not limited to brass, copper, silver, aluminium or steel.The metal composition effectively cleans and shines metal articles (for examplebut not limited to utensils) with very less effort. Small trinkets that are normally hardto handle are cleaned efficiently and effectively.The metal cleaning composition cleans heavily decorated silver as easily as plainsilver. The silver is effectively cleaned without the need for polishing thereby,avoiding the mess and labor time required with conventional polishingcompositions.The composition includes mineral abrasives such as dolomite which is a mildabrasive. The metal cleaning composition is free of harsh abrasives such as quartzand is also free of surfactants. Thereby, the composition cleans and shines themetal article without damaging its surface. Also, as the composition does notinclude a surfactant, it can be effectively used to clean and shine metal articleswith less water or even in absence of water. As the composition cleans in absenceof washing with water, it avoids the need to wipe the articles after cleaning. Further,the composition is stable on storage. The components present in the compositionare not harmful to skin. Thereby, the composition is safe to handle while notaffecting the metal being cleaned.In another aspect, the present invention relates to a process for preparing ananhydrous metal cleaning composition. The process comprises forming a mixtureof the abrasive and the filler. Then metal oxide, alkali metal carbonate and sand(mica) are added to the mixture, followed by addition of citric acid and oxalic acidor acetic acid.The process for preparation is quick and easy as there are less ingredients. Theprocess can be easily scaled from a small to a large scale.The process can be carried out in any mixer / blender known for mixing powdercomponents. In an embodiment, the composition is prepared in a ribbon blender.EXAMPLESExample 1The anhydrous metal cleaning composition of the present invention is described inTable 1 below.Table 1Formulation 1Ingredient Quantity (% w / w)Dolomite powder 80China clay (300#) 14.69Aluminium oxide 0.1Sodium carbonate 0.01Sand (mica) 0.1Oxalic acid 5Citric acid 0.1Colour and perfume q.s.Process for Preparation: Dolomite powder and China clay were added into a dryribbon blender and mixed thoroughly. Then aluminium oxide, sodium carbonateand sand (mica) were added and mixed for 15 minutes. Subsequently, oxalic acidand citric acid was added into the ribbon blender followed by colour and mixedthoroughly for 15 to 20 minutes so that no lumps were formed. Then, perfume wasadded into the blender and mixed thoroughly for 15 to 20 minutes.Examples 2-12Tables 2 and 3 describes the anhydrous metal cleaning composition as per theinvention (Formulations 2-12) with varying quantities of the components.Table 2Table 3Formulations 2-12 were prepared by the process described in Example 1.Comparative ExamplesTable 4 describes the composition of Comparative Formulations A-D.Table 4EvaluationI. Evaluation of cleaning effect of composition of the invention and its individualcomponentsFormulations 6-12 of the present invention as described in Tables 2 and 3 above,were tested on rusted copper articles to evaluate the cleaning effect and comparedwith the cleaning effect of its individual components. The evaluation was carriedout in presence and absence of washing with water.The cleaning effect was ascertained by determining the ∆E of the article beforeand after cleaning with the composition. The ∆E value was determined bymeasuring the L, a, and b values of the CIELAB (lab color space) and then applyingEquation 1 below. For better cleaning a higher ∆E is desired. For copper articlesthe metal cleaning composition of the present invention provides a ∆E value in arange of 20.36-21.15.Equation 1Where,L1, a1, and b1 are the values before cleaning;L2, a2, and b2 are the values after cleaning with the composition.The L, a, and b values of the copper article before cleaning was as below:L1 value = 70.44,a1 value = 15.08,10b1 value =25.34.Tables 5-11 below provides the L, a, b and ΔE values of copper article aftercleaning with Formulations 6-12 and its individual components.Table 5Table 6Table 7Table 8Table 9Table 10Table 11A graphical comparison of the ΔE values is shown in Figure 1-7.From the above results it was seen that ΔE value for Formulations 6-12 of thepresent invention was significantly greater than that of its individual components.Thereby, Formulations 6-12 comprising all the components together provided asuperior cleaning of copper articles than the individual components.II. Evaluation of cleaning effect of composition of the invention and ComparativeFormulationsThe cleaning effect of Formulation 6 on rusted copper articles was determined andcompared with that of Comparative Formulations A-D described above in Table 4.The cleaning effect was ascertained by determining the ∆E of the article beforeand after cleaning with the composition as described in point I, above.The L, a, and b values of the copper article before cleaning was as below:L1 value = 66.15,a1 value = 16.31,b1 value = 24.43.Table 12 below provides the L, a, b and ΔE values of copper article after cleaningwith Formulation 6 and the Comparative Formulations A-D.Table 12A graphical comparison of the ΔE values of the compositions is shown in Figure 8.Comparative Formulation A did not contain dolomite, aluminium oxide (metaloxide), oxalic acid or acetic acid, and sand (mica). Comparative Formulation A hadthe lowest ΔE value. This shows that composition with only citric acid as the aciddid not provide a good cleaning.Comparative Formulation B did not contain dolomite, metal oxide, and sand (mica).Comparative Formulation B contained acetic acid and reduced the amount of alkalimetal carbonate and citric acid to almost half of that present in ComparativeFormulation A. Comparative Formulation B had higher ΔE value than ComparativeFormulation A. This shows that composition comprising both citric acid and aceticacid provided a better cleaning than composition containing citric acid as the onlyacid.Comparative Formulation C did not contain dolomite, metal oxide, sodiumcarbonate (alkali metal carbonate), and sand (mica). Comparative Formulation Chad a lower ΔE value than Comparative Formulation B. This shows that presenceof alkali metal carbonate along with citric acid and acetic acid or oxalic acid in thecomposition provided a better cleaning. Also, sodium chloride due to itshygroscopic nature resulted in a poor flowing product upon storage.Comparative Formulation D did not contain metal oxide, oxalic acid or acetic acid,and alkali metal carbonate. Comparative Formulation D had ΔE value which wasmore than 1.5 times of that obtained with Comparative Formulation A. This showsthat presence of dolomite and sand (mica) in the composition provided a bettercleaning.Formulation 6 of the present invention contained aluminium oxide (metal oxide),dolomite, China clay, sodium carbonate (alkali metal carbonate), citric acid, oxalicacid, and sand (mica). This formulation had the highest ΔE value. This shows thatthe composition of the present invention provided superior cleaning and shine ofcopper articles than composition of Comparative Formulations A-D lacking thepresence of all the components.III. Effect of different metal oxides, alkali metal carbonates, and acidA. Metal oxideMetal cleaning compositions with different metal oxides such as aluminiumoxide, chromium dioxide, titanium dioxide, iron oxide and zinc oxide wereevaluated to determine the effect of metal oxides on the cleaning effect of thecomposition.The formulations were prepared based on the composition described inFormulation 6 and aluminium oxide was replaced with chromium dioxide,titanium dioxide, iron oxide or zinc oxide.The cleaning effect was ascertained by determining the ∆E of the copper articlebefore and after cleaning with the composition as described in point I, above.The L, a, and b values of the copper article before cleaning was as below:L1 value = 70.44,a1 value = 15.08,b1 value =25.34.Table 13 below provides the L, a, b and ΔE values of copper article aftercleaning with formulations containing different metal oxides.Table 13From Table 13, it was seen that ΔE value for the compositions containingchromium dioxide, titanium dioxide or iron oxide was similar to that obtained forFormulation 6 containing aluminium oxide. Thus, the composition containingany of the described metal oxides provided a superior cleaning effect.Also, a superior cleaning effect can be achieved by a composition containing acombination of metal oxides.B. Alkali Metal CarbonateMetal cleaning compositions with different alkali metal carbonates such aslithium carbonate, sodium carbonate and potassium carbonate were evaluatedto determine the effect of alkali metal carbonates on the cleaning effect of thecomposition.The formulations were prepared based on the composition described inFormulation 6 and sodium carbonate was replaced with lithium carbonate orpotassium carbonate.The cleaning effect was ascertained by determining the ∆E of the copper articlebefore and after cleaning with the composition as described in point I, above.The L, a, and b values of the copper article before cleaning was as below:L1 value = 70.44,a1 value = 15.08,b1 value =25.34.Table 14 below provides the L, a, b and ΔE values of copper article aftercleaning with formulations containing different alkali metal carbonates.Table 14From Table 14, it was seen that ΔE value for the compositions containingpotassium carbonate or lithium carbonate was similar to that obtained forFormulation 6 containing sodium carbonate. Thus, the composition containingany of the described alkali metal carbonates provided a superior cleaning effect.Also, a superior cleaning effect can be achieved by a composition containing acombination of alkali metal carbonates.C. Acid (Oxalic acid or Acetic acid)Metal cleaning compositions with citric acid in combination with either oxalicacid or acetic acid were evaluated to determine the effect of either of thecombination on the cleaning effect of the composition.The formulations were prepared based on the composition described inFormulation 6 and oxalic acid was replaced with acetic acid.The cleaning effect was ascertained by determining the ∆E of the copper articlebefore and after cleaning with the composition as described in point I, above.The L, a, and b values of the copper article before cleaning was as below:L1 value = 70.44,a1 value = 15.08,b1 value =25.34.Table 15 below provides the L, a, b and ΔE values of copper article aftercleaning with formulations containing different alkali metal carbonates.Table 15From Table 15, it was seen that ΔE value for the compositions containing citric acidin combination acetic acid was similar to that obtained for Formulation 6 containingcitric acid in combination with oxalic acid. Thus, the composition containing eithera either oxalic acid or acetic acid in combination with citric acid provided a superiorcleaning effect.Also, a superior cleaning effect can be achieved by a composition containing bothcitric and oxalic acid in combination with citric acid.IV. Evaluation of cleaning effect of composition of the invention and AvailableMarketed CompositionThe cleaning effect of Formulation 6 on rusted copper articles was evaluated andcompared with that of an available marketed composition (Pitambari shiningpowder).The cleaning effect was ascertained by determining the ∆E of the article beforeand after cleaning with the composition as described in point I, above.The L, a, and b values of the copper article before cleaning was as below:L1 value = 70.44,a1 value = 15.08,b1 value =25.34.Table 16 below provides the L, a, b and ΔE values of copper article after cleaningwith Formulation 6 and the marketed composition.Table 16A graphical comparison of the ΔE values of the compositions is shown in Figure 9.From the results in Table 16, it was seen that Formulation 6 provided a significantlygreater ΔE value and thereby a better cleaning effect of copper articles than themarketed composition.Figure 10 shows the images of a copper glass before and after cleaning withFormulation 6. Figure 11 shows the images of a silver glass before and aftercleaning with Formulation 6. From the figures it was seen that the surface of thearticles was smooth. Thus, the composition of the present invention did notdamage the metal surface.From the results, it can be inferred that the superior cleaning is due to the combinedeffect of presence of dolomite, metal oxide, alkali metal carbonate, citric acid, oxalicor acetic acid and sand (mica) in the anhydrous metal cleaning composition.Stability StudyThe composition of Formulation 6 of the present invention was evaluated forstorage stability by subjecting it to accelerated stability testing. The results of theaccelerated stability studies is shown in Figure 12.As shown in the figure the parameters of physical appearance, bulk density, pH(10% solution) and loss on drying for Formulation 6 after storage up to 3 monthsat temperatures of 8-10°C, 25°C and 45°C were within permissible limits. Thisshows that the Formulation was stable on storage.The foregoing description of the invention has been set merely to illustrate theinvention and is not intended to be limiting. Since modifications of the disclosedembodiments incorporating the spirit and substance of the invention may occur toperson skilled in the art, the invention should be construed to include everythingwithin the scope of the disclosure.

Claims

1. An anhydrous metal cleaning composition comprising 70-85% w / w of dolomite as an abrasive, 5-15% w / w of China clay as a filler, 0.1-8.0% w / w of a metal oxide, 0.01-6.0% w / w of an alkali metal carbonate, 0.1-12.0% w / w of sand (mica), 0.1-18.0% w / w of citric acid and 5.0-15.0% w / w of oxalic acid or acetic acid, such that the total amount of the components is 100% w / w.

2. The composition as claimed in claim 1, wherein the alkali metal carbonate is selected from sodium carbonate, potassium carbonate, lithium carbonate or a combination thereof.

3. The composition as claimed in claim 1, wherein the metal oxide is selected from aluminium oxide, zinc oxide, titanium dioxide, chromium dioxide, iron oxide or a combination thereof.

4. The composition as claimed in claim 1, comprising 70-85% w / w of dolomite, 5-15% w / w of China clay, 0.5-2% w / w of aluminium oxide, 0.01-3% w / w of sodium carbonate, 1-5% w / w of sand (mica), 3-8% w / w of citric acid and 5- 10% w / w of oxalic acid such that the total amount of the components is 100% w / w.

5. The composition as claimed in any one of the claims 1 to 4 wherein the composition is in form of a powdered solid.

6. A process for preparing an anhydrous metal cleaning composition as claimed in claim 1, the process comprising: forming a mixture of the abrasive and the filler; adding the metal oxide, alkali metal carbonate and sand (mica) to the mixture; and adding citric acid and oxalic acid or acetic acid.

7. The composition as claimed in any one of claims 1 to 5 for cleaning a surface of a metal selected from brass, copper, silver, aluminium or steel.