EP1704131A1 - A method and composition to easily remove metal oxides from substrates - Google Patents

A method and composition to easily remove metal oxides from substrates

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Publication number
EP1704131A1
EP1704131A1 EP05700714A EP05700714A EP1704131A1 EP 1704131 A1 EP1704131 A1 EP 1704131A1 EP 05700714 A EP05700714 A EP 05700714A EP 05700714 A EP05700714 A EP 05700714A EP 1704131 A1 EP1704131 A1 EP 1704131A1
Authority
EP
European Patent Office
Prior art keywords
thioglycolate
solution
substrates
substrate
contact
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP05700714A
Other languages
German (de)
French (fr)
Inventor
Jan Vermeulen
Gino De Rycke
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Bioservices Belgium bvba
Original Assignee
Bioservices Belgium bvba
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from EP04447002A external-priority patent/EP1538135A1/en
Application filed by Bioservices Belgium bvba filed Critical Bioservices Belgium bvba
Priority to EP05700714A priority Critical patent/EP1704131A1/en
Priority claimed from PCT/EP2005/000053 external-priority patent/WO2005068402A1/en
Publication of EP1704131A1 publication Critical patent/EP1704131A1/en
Withdrawn legal-status Critical Current

Links

Definitions

  • the present invention relates to a method and the use therein of chemical compositions to easily remove metaloxides from substrates and their surfaces that are to be considered as not electrically conductive, in particular from stone-like substrates that contain alkaline- 10 earth metals.
  • substrates is meant here in particular natural and artificial stone, marble, blue limestone, cobble stones, boulders.
  • the stone-like materials are meant to include also concrete, cements, mortars, plasters, cured clay or other cementitious compositions (e.g. in mortar joints) comprising e.g. CaCO3 or MgCO3, even in minor amounts.
  • the objects or substrates can have all possible shapes and dimensions, in 15 particular the shape of tiles, flags, bricks, slabs, plates, tubes, posts, profiles or any other building element for pavements, for floors, walls, pillars, roofs, ceilings, containers in a broad sense etc.
  • the metal oxides to be removed often include ferrous oxides, e.g. in the form of rust.
  • the removal of said oxides from the substrates includes in particular such removal from the surfaces of said substrates.
  • metal compounds particularly of 25 metaloxides on their surface or in their body such as e.g. ironoxide (rust).
  • these compounds on or in their surface may be in the form of spilled fertilizers for gardens, spilled moss control products or irrigation water.
  • these compounds can oxidise and thereby cause undesirable brawny stains or spots (rust) on and/or in said surfaces.
  • rust or 30 other coloured oxide spots can be caused on and in the surfaces of such substrates, due to the presence of humid or wet metal objects (e.g.
  • the humidity on these objects may generate the formation of water drops containing the metaloxides (e.g. rust) dissolved therein and leached out from said metal objects comprising e.g. steel, copper, zinc, brass, lead etc. 35 Such drops then may fall down on and contaminate said substrates. Most people want to remove this unwanted discoloration for esthetical reasons.
  • metaloxides e.g. rust
  • etching methods e.g. etching methods.
  • a commonly used method is the treatment with acids, such as oxalic acid, hydrogenchloride and many others.
  • Another method comprises the treatment with reducing compounds, such as e.g. sulfites. Also this method is known by experts in the art not to give complete removal of the metal oxides and hence it offers only unsatisfactory results in most cases.
  • a similar method relates to the application of complexing agents like chelates, ammonia or amines onto the metaloxides in the surfaces of the substrates, however with similar insufficient results.
  • Still another method exists in or comprises the local application of pastas on the contaminated surface areas or spots to let lye-out or leach out the rust during a long time in a non-oxidising environment. This method is, besides the poor result, not at all user-friendly for large or big surfaces.
  • Such a method is disclosed in JP 10068233. It comprises the application of a concentrated solution of ammonium thioglycolate (as a reducing agent) to the surface of stone after drying the surface by far infrared rays.
  • said reducing solution can be kneaded first with a carrier into a paste.
  • the paste is applied to the surface of the stone at the thickness of several mm and the coated position is covered with a resin sheet or a film to protect the applied reducing agent from oxidation.
  • the paste is kept in contact with the surface of the stone for 1 to 2 days.
  • an oxidant such as an oxygen bleaching agent is applied to the surface of the stone for another one or two days.
  • compositions that can be used in a more or less concentrated or diluted form, optionally in the presence of other ingredients with influence on its characteristics, e.g. on its storage life (tenability).
  • the composition has to remain stable, at least under ambient conditions, also after optional additives have been incorporated therein, e.g. to adapt its viscosity, surface tension or odour or any other useful characteristics or properties, preferably without unwanted side-
  • the effective composition according to our invention thus comprises essentially such a solution based on thioglycolic acid and in particular on one or more of its salts.
  • the solution of the salt or mixture of salts of thioglycolic acid are applied on the object or substrate that shows the oxidation. Remarkable and extremely advantageous for the working or application method is the relatively short time limit the composition has to stay on the surface of the substrate material to enable an effective removal treatment.
  • the invention thus provides an easy method to remove oxidative discolorations from non- electrically conductive substrates such as comprising a stone-like material. Said method is in particular provided to remove metaloxides from such stone-like substrate or at least from its surface which stone-like material contains at least one earth-alkaline metal.
  • an aqueous alkaline solution comprising thioglycolate salts, is brought into contact with said metaloxide-containing substrate for a relatively short but sufficient time to allow said solution to react with and bind to said oxides.
  • the concentration of said salts in the solution is preferably between 4 % and 25 % by weight and most preferably in the range from 5% up to and including 20%. Indeed at a lower concentration than 4 % an effective removal is slow and/or difficult. Otherwise, larger concentrations than 25 % do not substantially contribute to an effective removal that outweighs the extra cost for the solution.
  • the contaminated (oxidised) areas in the substrate, in particular in the substrate surface and comprising iron oxide turn into a purple or violet colour after a very short period of time in the range or order of minutes.
  • iron in particularthe iron oxides and most other metal oxides in whatever form present in the treated surface, are embedded in and bonded in complexed form to the compounds of the thioglycolate solution brought into contact with the surface. They have thus left, i.e. are leached out from the object or substrate.
  • the solution is not left too long on the surface because otherwise after time (and certainly after desiccation) mostly there will be the formation and deposition of unsolvable compounds on the surface.
  • the colouring of the applied solution (in case of iron oxides) to purple-violet is a sign that the reaction, at least at the surface of the substrate, is almost completed and that the following method step to remove the formed reaction products (e.g. by rinsing) can and generally must start.
  • the proper contact time between said substrate and said aqueous thioglycolate solution will last in general less than about 45 minutes and preferably not more than 30 minutes, most preferably even not more than 15 minutes, depending i.a. on the temperature of the substrate.
  • the required contact time will generally be longer at a low ambient temperature (e.g. below 10°C) than at say about 20°. Indeed, waiting much longer would have the effect that the reaction products could again start to oxidise and return to a discoloration (with the deposition of unsolvable compounds).
  • a second or third rinsing operation may be necessary or useful.
  • the violet coloured liquor is removed, e.g. wiped away with a rubber mop.
  • some thioglycolate solution may still remain in pores of the substrate surface and react further with the result of the development again of a violet (or pink) colour.
  • this violet rest solution is then removed.
  • the very small quantity of complexed metal oxides that then finally may remain will again oxidise (in the ambient air) but generally they will no longer develop unesthetic rust spots.
  • the aqueous solution, including thioglycolate salts for use in the method will preferably have a pH-value of at least 7 and up to 9 or even higher than 9. Most preferably the pH- range will be between 7 and 9 depending i.a. on the chosen thioglycolates and on their proportion in the alkaline solution.
  • the composition can include salts or other (ionic) derivatives of thioglycolic acid, in particular an alkali thioglycolate such as sodium- or potassium- thioglycolate. It can also comprise ethanol ammonium thioglycolate or a mixture with an alkali thioglycolate and/or ammonium thioglycolate.
  • the composition can be adjusted or ingredients can be added so that an environment-friendly use, e.g. a substantially odourless character is favoured.
  • compositions comprising either a 20% solution of ammonium thioglycolate or a 20% solution of ethanol ammonium thioglycolate, both at a pH between 7 and 9.
  • the latter example offered the supplementary advantage of a low odour level, i.e. where the generally quite malodorous character of ammonium thioglycolate was substantially absent

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Abstract

The invention relates to a method to remove metaloxides from at least the surface of a substrate comprising a stone-like material that contains at least one earth-alkaline metal, wherein an aqueous alkaline solution comprising thioglycolate salts is brought into contact with said metaloxide-containing substrate for a relatively short but sufficient time to allow said solution to react with and bind to said oxides. The surface is subsequently brought into contact with water during at least one rinsing operation and wiped to remove the reaction products comprising the so bonded metaloxides.

Description

A METHOD AND COMPOSITION TO EASILY REMOVE METAL OXIDES FROM SUBSTRATES
5 Technical field
The present invention relates to a method and the use therein of chemical compositions to easily remove metaloxides from substrates and their surfaces that are to be considered as not electrically conductive, in particular from stone-like substrates that contain alkaline- 10 earth metals. With such substrates is meant here in particular natural and artificial stone, marble, blue limestone, cobble stones, boulders. The stone-like materials are meant to include also concrete, cements, mortars, plasters, cured clay or other cementitious compositions (e.g. in mortar joints) comprising e.g. CaCO3 or MgCO3, even in minor amounts. The objects or substrates can have all possible shapes and dimensions, in 15 particular the shape of tiles, flags, bricks, slabs, plates, tubes, posts, profiles or any other building element for pavements, for floors, walls, pillars, roofs, ceilings, containers in a broad sense etc. The metal oxides to be removed often include ferrous oxides, e.g. in the form of rust. The removal of said oxides from the substrates includes in particular such removal from the surfaces of said substrates. 20 Background art
It is generally known that objects like tiles, natural stone surfaces etc. can show discolorations on their surfaces due to the presence of metal compounds, particularly of 25 metaloxides on their surface or in their body such as e.g. ironoxide (rust). Taking outdoor terrazzo pavements as an example, these compounds on or in their surface may be in the form of spilled fertilizers for gardens, spilled moss control products or irrigation water. Indeed, due to environmental humidity, these compounds can oxidise and thereby cause undesirable brawny stains or spots (rust) on and/or in said surfaces. Likewise, rust or 30 other coloured oxide spots can be caused on and in the surfaces of such substrates, due to the presence of humid or wet metal objects (e.g. tools) for a certain time on or in the neighbourhood of these surfaces. Indeed, the humidity on these objects may generate the formation of water drops containing the metaloxides (e.g. rust) dissolved therein and leached out from said metal objects comprising e.g. steel, copper, zinc, brass, lead etc. 35 Such drops then may fall down on and contaminate said substrates. Most people want to remove this unwanted discoloration for esthetical reasons. Next to mechanical methods - such as wiping or wire brushing - that may remove more or less the upper surface layers of the stone like substrates, there exist different non-optimal chemical methods, e.g. etching methods. A commonly used method is the treatment with acids, such as oxalic acid, hydrogenchloride and many others.
These chemical methods have a big disadvantage. Indeed, lots of types of stone, tiles, concrete or cement-containing materials contain substances as e.g. alkaline-earth metal compounds like CaCO3 or Ca(OH)2, the latter specifically in plaster, etc. These compounds are more or less dissolved or affected by the above mentioned acidic compounds or etching agents. This means that the substrates, at least in their surface area, may be damaged and rendered more porous - e.g. by the undesired removal of CaCO3 - so that their quality decreases. These prior art methods have also the other disadvantage . that one can see that in practice not all forms of oxidation (with discoloration) are completely removed by them. So still additional suitable treatments - if available - are necessary to arrive at a more or less acceptable cleaning result for virtually all kinds of oxides. Another method comprises the treatment with reducing compounds, such as e.g. sulfites. Also this method is known by experts in the art not to give complete removal of the metal oxides and hence it offers only unsatisfactory results in most cases.
A similar method relates to the application of complexing agents like chelates, ammonia or amines onto the metaloxides in the surfaces of the substrates, however with similar insufficient results. Still another method exists in or comprises the local application of pastas on the contaminated surface areas or spots to let lye-out or leach out the rust during a long time in a non-oxidising environment. This method is, besides the poor result, not at all user-friendly for large or big surfaces. Such a method is disclosed in JP 10068233. It comprises the application of a concentrated solution of ammonium thioglycolate (as a reducing agent) to the surface of stone after drying the surface by far infrared rays. When the amount of rust contamination in the surface is of a considerable level said reducing solution can be kneaded first with a carrier into a paste. The paste is applied to the surface of the stone at the thickness of several mm and the coated position is covered with a resin sheet or a film to protect the applied reducing agent from oxidation. The paste is kept in contact with the surface of the stone for 1 to 2 days. When a light pink colour appears on the stone surface after this reducing process, an oxidant such as an oxygen bleaching agent is applied to the surface of the stone for another one or two days. This complex method is not at all practicable for an easy, simple, user-friendly and fast cleaning treatment intended by the invention and certainly not for application to large surfaces, e.g. to floors. From the statements above we can thus conclude that there are presently no user-friendly and efficient methods available that completely or almost completely remove oxidation from stone-like substrates that may contain alkaline-earth metais - without damaging these substrates and in particular their surfaces.
Description of the invention
It is now an object of the invention to provide a method and a composition to easily remove metal oxides, preferably all metal oxides excluding those from alkaline and earth- alkaline metals, from substrates as referred to above and using said composition in a simple, effective, rapid and environment-friendly manner or method. It is a further object to provide such a method and composition that at the same time does not damage nor affect, in particular erode said substrates or their surfaces or generate other undesired side effects therein, such as e.g. porosity. It is also an object to provide a simple method that does not require to apply afterwards an oxidising treament with an oxygen bleaching agent.
It is a further object to provide such a method with a composition that can be used in a more or less concentrated or diluted form, optionally in the presence of other ingredients with influence on its characteristics, e.g. on its storage life (tenability). In particular the composition has to remain stable, at least under ambient conditions, also after optional additives have been incorporated therein, e.g. to adapt its viscosity, surface tension or odour or any other useful characteristics or properties, preferably without unwanted side-
' effects.
Now we found out, to our own surprise that aqueous solutions of salts of thioglycolic acid very easily and effectively remove oxidation - and the resulting discoloration, if any - when applied according to the right method as described hereafter. The effective composition according to our invention thus comprises essentially such a solution based on thioglycolic acid and in particular on one or more of its salts.The solution of the salt or mixture of salts of thioglycolic acid are applied on the object or substrate that shows the oxidation. Remarkable and extremely advantageous for the working or application method is the relatively short time limit the composition has to stay on the surface of the substrate material to enable an effective removal treatment. These characteristics and other particularities of the invention appear in the description hereafter, explaining the practical application, only as a non limiting example of its use and implementation in practice. The invention thus provides an easy method to remove oxidative discolorations from non- electrically conductive substrates such as comprising a stone-like material. Said method is in particular provided to remove metaloxides from such stone-like substrate or at least from its surface which stone-like material contains at least one earth-alkaline metal. According to the invention an aqueous alkaline solution, comprising thioglycolate salts, is brought into contact with said metaloxide-containing substrate for a relatively short but sufficient time to allow said solution to react with and bind to said oxides. The concentration of said salts in the solution is preferably between 4 % and 25 % by weight and most preferably in the range from 5% up to and including 20%. Indeed at a lower concentration than 4 % an effective removal is slow and/or difficult. Otherwise, larger concentrations than 25 % do not substantially contribute to an effective removal that outweighs the extra cost for the solution.
In our working method, prior drying of the substrate is not necessary as in the prior art. This is of course a great advantage since it strongly simplifies the method. The nature of the chemical binding between said oxides and said thioglycolate salts is generally a complexing reaction. After said relatively short contact-time limit with the thioglycolate solution the metal oxides (that originally caused the discoloration) are now bonded. To complete the cleaning operation and thus to remove the now bonded oxides with mechanical means, the surface is subsequently wiped, but preferably first brought into contact with water, e.g. by rinsing the surface at least once, to easily remove thereafter by wiping the reaction products comprising the so bonded metaloxides. Actually, two or more rinsing operations may be advantageous with some relatively short interval periods interbetween as will be explained hereafter:
Due to said prompt binding reaction the contaminated (oxidised) areas in the substrate, in particular in the substrate surface and comprising iron oxide, turn into a purple or violet colour after a very short period of time in the range or order of minutes. This means that iron, in particularthe iron oxides and most other metal oxides in whatever form present in the treated surface, are embedded in and bonded in complexed form to the compounds of the thioglycolate solution brought into contact with the surface. They have thus left, i.e. are leached out from the object or substrate. For contamination by metaloxides other than iron oxide there may be a very poor (almost no) or a different discoloration.
It is an important and often essential part in the working method that the solution is not left too long on the surface because otherwise after time (and certainly after desiccation) mostly there will be the formation and deposition of unsolvable compounds on the surface. The colouring of the applied solution (in case of iron oxides) to purple-violet is a sign that the reaction, at least at the surface of the substrate, is almost completed and that the following method step to remove the formed reaction products (e.g. by rinsing) can and generally must start. The proper contact time between said substrate and said aqueous thioglycolate solution will last in general less than about 45 minutes and preferably not more than 30 minutes, most preferably even not more than 15 minutes, depending i.a. on the temperature of the substrate. The required contact time will generally be longer at a low ambient temperature (e.g. below 10°C) than at say about 20°. Indeed, waiting much longer would have the effect that the reaction products could again start to oxidise and return to a discoloration (with the deposition of unsolvable compounds).
Hence, as a consequence, and as mentioned above, a second or third rinsing operation may be necessary or useful. After a first rinsing treatment the violet coloured liquor is removed, e.g. wiped away with a rubber mop. However, some thioglycolate solution may still remain in pores of the substrate surface and react further with the result of the development again of a violet (or pink) colour. With a second rinsing and wiping operation this violet rest solution is then removed. The very small quantity of complexed metal oxides that then finally may remain will again oxidise (in the ambient air) but generally they will no longer develop unesthetic rust spots.
However, if after removal of the coloured solution there are still rust-stains present on the object or substrate (mostly after treatment during a too short time), then the method has to be repeated until a satisfactory result is obtained. This means that, after a first cyle of application of a thioglycolate solution and rinsing steps, a second cyle of such application and rinsing may be applied. This may be in particular useful for treating vertical surfaces.
The aqueous solution, including thioglycolate salts for use in the method will preferably have a pH-value of at least 7 and up to 9 or even higher than 9. Most preferably the pH- range will be between 7 and 9 depending i.a. on the chosen thioglycolates and on their proportion in the alkaline solution.
The composition can include salts or other (ionic) derivatives of thioglycolic acid, in particular an alkali thioglycolate such as sodium- or potassium- thioglycolate. It can also comprise ethanol ammonium thioglycolate or a mixture with an alkali thioglycolate and/or ammonium thioglycolate Finally, as stated above, the composition can be adjusted or ingredients can be added so that an environment-friendly use, e.g. a substantially odourless character is favoured. In a couple of successful but non limitative examples of the invention, compositions were used comprising either a 20% solution of ammonium thioglycolate or a 20% solution of ethanol ammonium thioglycolate, both at a pH between 7 and 9. The latter example offered the supplementary advantage of a low odour level, i.e. where the generally quite malodorous character of ammonium thioglycolate was substantially absent
It will be clear for a person skilled in the art that numerous variations can be prepared of the composition of the aqueous solution within the ranges as claimed hereafter. The ready made solution will generally be available for sale in bottles, optionally provided with sprayguns.

Claims

Claims
1. A method to remove metaloxides from at least the surface of a substrate comprising a stone-like material that contains at least one earth-alkaline metal, wherein an aqueous alkaline solution comprising thioglycolate salts, with a concentration between 4% and 25% by weight of said salts, is brought into contact with said metaloxide-containing substrate for a relatively short but sufficient time to allow said solution to react with and bind to said oxides and wherein the surface is subsequently brought into contact with water and wiped to remove the reaction products comprising the so bonded metaloxides.
2. A method according to claim 1 wherein the subsequent contact with water comprises at least one rinsing operation.
3. A method according to claim 1 wherein the contact time between said substrate and said aqueous solution is less than about 45 minutes and preferably not more than 30 minutes and most preferably not more than 15 minutes.
4. An aqueous solution including thioglycolate salts at an alkaline pH-value for use in the method according to claim 1 wherein the pH-value is at least 7 and up to 9 or even higher than 9.
5. An aqueous solution according to claim 4 wherein said concentration is from 5 % and ' up to 20%.
6. A solution according to claim 4 which comprises an alkali thioglycolate.
7. A solution according to claim 4 comprising ethanol ammonium thioglycolate
8. A solution according to claim 4 comprising a mixture of an alkali thioglycolate, ethanol ammonium thioglycolate andOr ammonium thioglycolate.
EP05700714A 2004-01-06 2005-01-04 A method and composition to easily remove metal oxides from substrates Withdrawn EP1704131A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP05700714A EP1704131A1 (en) 2004-01-06 2005-01-04 A method and composition to easily remove metal oxides from substrates

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP04447002A EP1538135A1 (en) 2003-11-19 2004-01-06 Composition and working method to remove oxides of metals (rust) from surfaces
EP05700714A EP1704131A1 (en) 2004-01-06 2005-01-04 A method and composition to easily remove metal oxides from substrates
PCT/EP2005/000053 WO2005068402A1 (en) 2004-01-06 2005-01-04 A method and composition to easily remove metal oxides from substrates

Publications (1)

Publication Number Publication Date
EP1704131A1 true EP1704131A1 (en) 2006-09-27

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP05700714A Withdrawn EP1704131A1 (en) 2004-01-06 2005-01-04 A method and composition to easily remove metal oxides from substrates

Country Status (1)

Country Link
EP (1) EP1704131A1 (en)

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2005068402A1 *

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