AT526943A4 - CLEANING SOLUTION AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Abstract

The invention relates to an aqueous cleaning solution for removing rouging deposits, containing: - at least one oxidizing agent, wherein the at least one oxidizing agent is a salt of peroxodisulfuric acid; - at least one complexing agent which is suitable for complexing iron(II) ions and/or iron(III) ions; - at least one catalyst, wherein the at least one catalyst is a salt of hydrofluoric acid. In addition, uses of the cleaning solution according to the invention and methods for producing such a cleaning solution are specified within the scope of the invention.

Description

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51373AT

CLEANING SOLUTION AND METHOD FOR THE PRODUCTION THEREOF

FIELD OF INVENTION

The present invention relates to an aqueous cleaning solution for removing rouging deposits that can form on surfaces of corrosion-resistant, stainless steels that come into contact with media. In addition, the invention relates to uses of the cleaning solution according to the invention and to processes for producing

of such a cleaning solution.

STATE OF THE ART

Corrosion-resistant, stainless steels, which are alloyed with a high proportion of at least 11.5% chromium, for example, can corrode after a certain period of use following contact with certain media, in particular hot pure water and/or pure steam. The corrosion products that form

are called “rouging”.

Particularly in production plants, for example in the pharmaceutical industry, the bioprocess industry and the semiconductor industry, as well as in medical technology plants or products that have to be sterilized on a regular basis using hot steam and/or with the help of special chemicals, depending on the application, after a certain period of operation, for example after several months or years, corrosion products in the form of rouging deposits can form on media-contacting surfaces of otherwise corrosion-resistant, stainless steels.

which need to be removed regularly.

In particular, ultrapure water in WFI (Water for Injection) quality, which is used in the aforementioned pharmaceutical, bioprocess, semiconductor and/or medical technology plants, behaves

very aggressive towards stainless steel surfaces of pipes and containers. The associated corrosion effects or rouging deposits that form on the surfaces of such systems that come into contact with the media

or parts of the plant are further enhanced when

Pure steam can be transported in such plants.

Depending on their nature and color, such rouging coatings can be classified according to the American Society of Mechanical Engineers

5 (short: ASME) guideline for Bioprocessing Equipment (BPE) into the following Rouge classes 1, 2 or 3 (see

ASME BPE Guideline, Appendix D):

—- Rouge Class 1: The particulate rouging deposits consist of various iron oxides, mainly hematite (Fe,O3) with small amounts of Fe(II) oxides or hydroxides, and are easier to remove by wiping than other deposits. Such rouging

Rouge Class 1 coverings are predominantly orange, orange-red

or colored brown.

—- Rouge Class 2: Rouging deposits of Rouge Class 2 consist mainly of iron(III) oxide, hematite (Fe,O3), as well as chromium and/or nickel oxides and carbon, usually occur in both particulate and surface-bound form, and are only partially wipeable. The color spectrum of such rouging deposits ranges from orange-red to blue and purple to gray. 20 To remove rouging deposits according to Rouge Class 2, the

Use of suitable cleaning chemicals required.

—- Rouge Class 3: Rouging coatings according to Rouge Class 3 consist mainly of iron(II,III) oxide, magnetite or Fe;0,, and occur as surface-bound layers that are no longer

25 can be wiped off. Particularly when used in pure steam systems up to 180 °C, very solid, closed red to blue-black oxide layers can form. Such particularly stable rouging coatings according to Rouge Class 3, which contain iron (II,III) oxide, can usually only be removed by conventional etching processes.

30, damaging or roughening the underlying steel surface. This is particularly disadvantageous for electropolished surfaces, as rouging deposits form particularly quickly on surfaces roughened by etching.

be able to train again.

35 Without being bound to a theory, rouging seems to be

apparently the media-contacting corrosion-resistant

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Steel surface layer from a chromium oxide-rich passive layer to an iron oxide-rich rouging layer, whereby this process is referred to as "rouge inversion". The rouging deposits that form are therefore a surface corrosion effect, whereby the previously intact, chromium oxide-rich passive layer of a corrosion-resistant steel surface collapses locally due to the environmental conditions, such as contact with hot clean water, and thus leads to increased iron oxide formation as a corrosion effect on the

steel surface.

In addition, rouging particles can detach from their original place of origin due to flow processes and be transported to other locations within a production plant and then

be deposited.

The state of the art already includes various

Cleaning agent for removing rouging deposits.

For example, the publication EP 3 269 844 A1 discloses an aqueous cleaning solution made up of several components for removing so-called blacking deposits on the corresponding media-contacting surfaces of stainless steels. The term “blacking deposits” refers to stubbornly adhering magnetite layers that are dark in color and thus correspond to rouging deposits of rouge class 3. The proposed cleaning solution consists, among other things, of an organic acid in the form of a saturated dicarboxylic acid or hydroxycarboxylic acid, with oxalic acid preferably being used, an oxidizing agent, which is preferably hydrogen peroxide, and

an inorganic fluoride, in particular ammonium bifluoride.

However, the disadvantage of the cleaning solution disclosed in EP 3 269 844 Al is that the calcium and magnesium salts that form during the cleaning process, particularly when oxalic acid is used, are difficult to dissolve. When cleaning steam systems with this cleaning solution, an additional upstream decalcification step of the production system to be cleaned with nitric acid is therefore necessary, which is, however, complex. Furthermore, the cleaning solution disclosed in EP 3 269 844 Al

The disadvantage of the cleaning solution that has become known is that

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Using dicarboxylic acid or hydroxycarboxylic acid, in particular oxalic acid, in combination with an inorganic fluoride, in particular ammonium bifluoride, which decomposes at the prevailing low pH values of less than 2 (pH < 2), a pickling solution is provided which undesirably etches stainless steel surfaces treated with it. The formation of new rouging deposits on steel surfaces roughened by etching processes is thus accelerated. In addition, this cleaning solution is only suitable for one-time use and cannot be reused after the corrosion layer has been removed. Disposing of the contaminated pickling solution is, however, expensive and

problematic for environmental reasons.

The publication WO 2008/119533 A1 relates to a method for removing corrosion layers, which can be used as a derouging solution. The corrosion remover contains both a biological complexing agent and a buffer system with an organic acid, which are mixed together in such a way that the pH value

of the corrosion remover is between about 3 and 6.

One of the disadvantages is that this corrosion remover forms an anti-corrosive protective film on the treated metal surface after the corrosion layer has been removed, which is why the process known from WO 2008/119533 Al is not suitable for cleaning tasks, particularly in the pharmaceutical, bioprocess or

Semiconductor industry is not suitable.

The publication DE 10 2015 114 481 Al relates to an aqueous neutral derouging solution which contains sodium sulfite or potassium sulfite as a reducing agent and a multi-efficient acid which causes a dissolving effect and a complexing effect on metal(II) ions. The derouging solution can contain sodium thioglycolate and/or

contain ascorbic acid.

The use of harmful, toxic and sensitizing (H317) sodium thioglycolate as a component of such a derouging solution is not only disadvantageous for environmental reasons, but also no longer meets the current safety requirements for the use

generic cleaning solutions for removing rouging deposits.

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In the event that ascorbic acid is added to the derouging solution as an additional reducing agent, the reductive properties of the ascorbic acid are overshadowed by the reductive reaction conditions of the other components. To remove stubborn rouging deposits according to Rouge Class 3, the method known from DE 10 2015 114 481 Al is suitable.

In any case, derouging solution is not suitable.

In addition, the publication US 2010/0078040 Al discloses a method for using an aqueous cleaning solution to remove rouging deposits on stainless steels, whereby methylglycine or ethanoldiglycine, for example, can be used as complexing agents. However, the production and handling of this cleaning solution is complicated: the complexing agent is only added later, after an inorganic reducing agent, which preferably contains dithionite or disulfite, has been added to the aqueous solution. To increase the cleaning effect, the aqueous cleaning solution should be sprayed onto the corrosion layer to be removed in an oxygen-free protective gas atmosphere, preferably under a nitrogen blanket. In addition to the complicated handling, another disadvantage is that this cleaning solution has a reductive effect and is not suitable for removing firmly adhering rouging deposits according to Rouge Class 3.

is not suitable.

In summary, the conventional cleaning solutions known from the state of the art for removing rouging deposits have at least the following disadvantages: In some cases, reducing agents are used to produce such conventional cleaning solutions, which are unstable, which is why storing them is complex and expensive. In particular under acidic conditions, the cleaning solutions known from the state of the art can have a corrosive effect or develop an undesirable pickling effect, whereby the steel surfaces to be cleaned are chemically attacked due to undesirable etching processes and new rouging deposits form even more quickly on the steel surfaces that have come into contact with the media after cleaning. In addition,

the cleaning solutions known from the state of the art

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or cleaning process disadvantages regarding

Occupational safety for the people handling it.

TASK OF THE INVENTION

It is therefore the object of the invention to overcome the aforementioned disadvantages of the prior art and to provide an aqueous cleaning solution for derouging, i.e. for removing rouging deposits of Rouge Class 3 on corrosion-resistant, stainless steels, which reliably and selectively dissolves rouging deposits without etching the underlying steel surfaces or roughening them by acid attack. In addition, an aqueous cleaning solution for derouging is to be provided which is easier to produce, store and use than conventional cleaning solutions. Furthermore, the object of the invention is to provide uses of the cleaning solution according to the invention and

A process for preparing such a cleaning solution is given.

DESCRIPTION OF THE INVENTION

To achieve the above-mentioned object of the invention, an aqueous cleaning solution for removing rouging deposits

The cleaning solution contains the following:

—- at least one oxidizing agent, wherein the at least one

The oxidizing agent is a salt of peroxodisulphuric acid;

—- at least one complexing agent capable of binding iron(II) ions

and/or iron(III) ions;

—- at least one catalyst, wherein the at least one catalyst

is a salt of hydrofluoric acid.

In addition to the aforementioned ingredients, the aqueous cleaning solution contains at least a proportion of water. Depending on the application, the cleaning solution according to the invention can be provided as a ready-to-use one-component system with a comparatively larger proportion of water, with the aforementioned components already being present in a diluted aqueous cleaning solution. A ready-to-use cleaning solution

offers the advantage of easy and safe handling and is

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Ready for use immediately without any further dosing or mixing steps

for cleaning rouging surfaces.

Alternatively, the cleaning solution according to the invention can also be provided in the form of a concentrate with a comparatively lower proportion of water, which is diluted accordingly before use by adding water in measured amounts. In this case, the cleaning solution according to the invention in a formulation as a concentrate solution forms a first component of a multi-component system, which must be diluted with water as the second component in a suitable manner in order to obtain a ready-to-use cleaning solution for removing rouging deposits. Providing a cleaning solution according to the invention as a concentrate solution offers the advantage that a comparatively smaller volume of concentrated cleaning agent has to be provided on site for cleaning large production plants in particular than is the case with a ready-to-use diluted solution.

Cleaning solution with a higher water content.

Depending on the composition of such a concentrate solution and the respective storage conditions, in particular the respective storage temperature, the concentrate solution may have a comparatively high viscosity, be present as a suspension with a pasty consistency, or be provided as a saturated solution with a solid solid body, for example in the form of crystalline precipitates. As soon as such a concentrate solution is diluted with the appropriate amount of additional water, any inhomogeneities such as a solid body or precipitate dissolve again, if necessary by stirring the diluted cleaning solution, and a ready-to-use cleaning solution with a homogeneous composition is available.

Disposal.

Due to the simplified storage and logistics, the use of the cleaning solution according to the invention as a cleaning agent concentrate, which is only diluted on site by adding water, can offer cost advantages and a particularly economical and efficient

Enable system cleaning.

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In its basic formulation, the aqueous

Cleaning solution consists of: — a proportion of water;

—- at least one oxidizing agent, wherein the at least one

The oxidizing agent is a salt of peroxodisulphuric acid;

—- at least one complexing agent capable of binding iron(II) ions

and/or iron(III) ions;

—- at least one catalyst, wherein the at least one catalyst

is a salt of hydrofluoric acid.

In further preferred embodiments of the invention, which are set out in the dependent claims and in the following description, the aqueous cleaning solution may further comprise further

Contain components or ingredients.

According to the invention, the at least one oxidizing agent is a salt of peroxodisulphuric acid. Peroxodisulphuric acid H‚,S,Os3 has a strong oxidising effect. Its salts, the peroxodisulphates, are usually extremely easily soluble in water and are used as strong

Oxidizing agents are used.

Examples of salts of peroxodisulphuric acid which may be used in the context of the invention are potassium peroxodisulphate (potassium persulphate, K2S,Os8), sodium peroxodisulphate (sodium persulphate, Na,S,Os) and ammonium peroxodisulphate (ammonium persulphate, (NHı),> S,Os).

Oxidizing agents can be used in the cleaning solution.

The alkali metal salt sodium persulfate mentioned as an example advantageously has a very high solubility of around 550 g/l (at 20°C) in water. In addition, sodium persulfate offers the advantage of high temperature stability and good storage capacity, since the melting temperature of sodium persulfate is around 180°C and thermal decomposition of this salt compound only occurs above this temperature. In conjunction with the high temperature stability, when sodium persulfate is used as an oxidizing agent, a controlled release of the

oxidizing agent in the aqueous cleaning solution.

In comparison, the ammonium salt mentioned as an example begins

Ammonium persulfate already at temperatures of around 120°C,

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thermally decompose and is therefore less storable. However, ammonium persulfate also offers the advantage of a very high

Solubility of about 620 g/l (at 20°C) in water.

Due to their high solubility in water, both sodium persulfate and ammonium persulfate are suitable as oxidizing agents, in particular for the preparation of a cleaning solution according to the invention as a concentrate solution with a

low water content.

In comparison, potassium persulfate has a lower solubility of around 50 g/l (at 20°C) in water. The use of potassium persulfate as an oxidizing agent is therefore particularly suitable for the preparation of a cleaning solution according to the invention in a ready-to-use, diluted formulation with a higher

water content.

According to the invention, the cleaning solution contains at least one complexing agent which is suitable for iron(II) ions and/or

to complex iron(III) ions.

Depending on the individual cleaning task, different complexing agents can be used to complex the iron(II) ions and/or

Iron(III) ions are used.

Ascorbic acid or amino acids can be used as complexing agents. These complexing agents are advantageously naturally occurring substances that are biologically well

are degradable.

Alternatively, salts of methylglycinediacetic acid (abbreviated to MGDA; C,;,H3NNa:06), in particular the trisodium salt of methylglycinediacetic acid, which forms stable chelate complexes with cations with a charge number of at least +2

forms, can be used.

Likewise, salts of iminodisuccinic acid, called iminodisuccinates (abbreviated to IDS), can be used as complexing agents. For example, tetrasodium iminodisuccinate (also: iminodisuccinate tetrasodium salt; C;H/NNa,Os), a sodium salt of iminodisuccinic acid, is a possible complexing agent that is suitable for forming iron(II) ions and/or iron(III) ions.

complex.

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These complexing agents are also characterized by good

Biodegradability and good environmental compatibility.

The cleaning solution according to the invention contains at least one catalyst, wherein the at least one catalyst is a salt of

is hydrofluoric acid.

The salts of hydrofluoric acid or hydrofluoric acid (HF) are called fluorides, are usually particularly soluble in water and have good storage stability. Depending on availability, different fluorides can be used as catalysts in the invention.

be used.

For example, ammonium fluoride (NHıF) or ammonium bifluoride (ammonium hydrogen difluoride; NHıHF>,) as acidic ammonium salts of hydrofluoric acid can be used as catalysts in the cleaning solution. Alternatively, potassium fluoride (KF) or potassium hydrogen difluoride (KHF,) as potassium salts of hydrofluoric acid can be used as catalysts in the cleaning solution. Likewise, sodium fluoride (NaF) or sodium hydrogen difluoride (NaHF,) as sodium salts of hydrofluoric acid can serve as catalysts in the cleaning solution. The aforementioned fluorides that are in question differ in their catalytic effect.

something from each other.

Due to the temperature stability and good storage capacity, it can be advantageous if the at least one oxidizing agent in the cleaning solution according to the invention is a metal salt of peroxodisulphuric acid, preferably potassium persulphate (K,S,O83) or

Sodium persulfate (Na,S,Os), is.

In order to be able to clean particularly stubborn or firmly adhering rouging deposits of rouge class 3, it can be advantageous if the cleaning solution according to the invention contains at least one further

oxidizing agent, preferably hydrogen peroxide (H,O,).

Possible further oxidizing agents which may be contained in or added to an aqueous cleaning solution according to the invention in order to increase its cleaning effect,

Examples are cerium(IV) salt compounds or ozone (0O:).

It can be particularly advantageous if the inventive

Cleaning solution contains hydrogen peroxide or, if necessary,

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Hydrogen peroxide of the cleaning solution according to the invention

is added.

Hydrogen peroxide is readily available, a largely stable liquid compound of hydrogen and oxygen, and acts as a very strong oxidizing agent against most substances, reacting violently with substances such as copper, brass, potassium iodide and thus acting as a powerful bleaching and disinfectant. In aqueous solution with a

low, diluted concentration below 8 wt.% hydrogen peroxide

only general safety rules for handling need to be observed.

Advantageously, the cleaning effect of the cleaning solution according to the invention for removing firmly adhering

Corrosion layers can be further increased.

In a preferred embodiment of the invention, the at least one catalyst in the aqueous cleaning solution may be a metal salt of hydrofluoric acid, preferably potassium hydrogen difluoride (KHF) or

Sodium hydrogen difluoride (NaHF).

Metal salts of hydrofluoric acid are stable during storage and usually easily

soluble.

Potassium hydrogen difluoride is a stable potassium salt of hydrofluoric acid with a melting point of around 240°C and a high solubility of around 180 g/l (at 20°C) in water. Potassium hydrogen difluoride also has the advantage of not breaking down and not lowering the pH value of the cleaning solution even at high process temperatures of, for example, 80°C, which can be set when removing rouging deposits. Sodium hydrogen difluoride as a hygroscopic sodium salt of hydrofluoric acid has a slightly lower melting point of around 160°C and a lower solubility of around 33 g/l (at 20°C) in

Water.

Both alkali metal salts of hydrofluoric acid offer the advantage that the pH value of the cleaning solution remains constant even at higher catalyst concentrations, so that with the inventive

Cleaning solution also in the slightly acidic to pH neutral range at

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pH values, for example, from pH = 5.0 to pH = 7.0

can.

In order to provide a cleaning solution according to the invention that is as gentle as possible, the at least one complexing agent can contain at least one amino acid, preferably glycine HOOC-CH,-NH,,

contain or be.

The use of one or more amino acids as complexing agents in a cleaning solution according to the invention offers the advantage that amino acids can be used in a correspondingly high concentration depending on the layer thickness of the corrosion residues or rouging deposits to be removed, if necessary, without

to noticeably change the pH value of the cleaning solution.

Amino acids such as glutamine or glycine act as

comparatively weak complexing agents for iron(III) ions (Fe**) and can be advantageously used in cleaning solutions according to the invention for removing weak rouging deposits, preferably of rouge class 2

be used.

The use of such a cleaning solution according to the invention with at least one amino acid as a complexing agent offers the advantage of extremely gentle removal of rouging deposits while at the same time causing the least possible side effects for the stainless steel surfaces to be cleaned. An undesirable, aggressive etching of the base material to be cleaned can be avoided if the cleaning solution according to the invention is used correctly in this mild formulation.

can be practically ruled out.

Glutamine has a higher complex formation constant than glycine. The solubility of glutamine in water (at 20°C) is around 35 g/l. As the smallest and simplest amino acid, glycine is preferred as a complexing agent for the cleaning solution according to the invention because thermal decomposition of glycine only begins at temperatures of around 230°C and glycine can therefore be stored particularly stably. In addition, glycine advantageously has a high solubility of around 250 g/l (at 20°C)

in water.

In this embodiment of the invention, in which at least one

Amino acid as a complexing agent for the production of aqueous

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Cleaning solution is used, a cleaning solution for the particularly gentle removal of rouging deposits, especially of rouge class 2, can be provided, which has a pH value of 4.0 to

8.0, preferably a pH of 5.0 to 7.0.

The slightly acidic to essentially neutral pH range of this cleaning solution has clear advantages in terms of occupational safety

when handling such a cleaning solution.

It may be particularly useful if, according to this embodiment of the invention, a ready-to-use cleaning solution is provided as a one-component system,

which cleaning solution has the following composition: —- from 80 to 90 wt.% water,

—- from 1 to 4% by weight, preferably from 2 to 3% by weight, of at least one salt of peroxodisulphuric acid, preferably

Potassium persulfate or sodium persulfate,

—- from 1 to 4% by weight, preferably from 2 to 3% by weight, of at least one salt of hydrofluoric acid, preferably potassium hydrogen difluoride

or sodium hydrogen difluoride,

- from 8 to 12% by weight, preferably from 9 to 11% by weight, at least

an amino acid, preferably glycine.

This ready-to-use cleaning solution is used to gently remove rouging deposits and is particularly practical and safe to use. As already explained in detail, this cleaning solution has a very high temperature stability and a long shelf life, since the ingredients listed can be stored for a long time. As a one-component system, this cleaning solution according to the invention can be provided on site in a pharmaceutical, bioprocess, semiconductor or medical technology plant, for example, in order to remove rouging deposits as required.

to be used for coatings in plant components.

As an alternative to the aforementioned one-component system, it can be advantageous for logistical and economic reasons, especially for applications where large quantities of cleaning solution are required to remove rouging deposits.

the cleaning solution according to the invention as

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Two-component system, whereby the concentrated cleaning solution, i.e. the cleaning solution concentrate, is added before the

Diluted with water has the following composition:

Q

—- from 10 to 20 wt.% water,

—- from 8 to 18% by weight, preferably from 10 to 16% by weight, of at least one salt of peroxodisulphuric acid, preferably

Potassium persulfate or sodium persulfate,

—- from 8 to 18% by weight, preferably from 10 to 16% by weight, of at least one salt of hydrofluoric acid, preferably potassium hydrogen difluoride

or sodium hydrogen difluoride,

—- from 54 to 64% by weight, preferably from 56 to 62% by weight, at least

an amino acid, preferably glycine.

The transport of such a concentrated cleaning solution, i.e. only the cleaning solution concentrate as the first component of a two-component system, is simpler and more cost-effective than when using a ready-to-use cleaning solution as a one-component system. The cleaning solution concentrate is delivered to a pharmaceutical, bioprocess, semiconductor or medical technology plant and made available there, whereby only a reduced storage volume is advantageously required on site. If required, the cleaning solution concentrate can be diluted with water on site to obtain a ready-to-use cleaning solution for removing rouging deposits. When the cleaning solution concentrate is diluted with water, any precipitates in the concentrate dissolve and a homogeneous cleaning solution is obtained that is ready for use. The cleaning solution concentrate can conveniently be stirred while water is being added. Another advantage is the increased storage stability of the concentrated cleaning solution due to the

lower water content.

According to a further embodiment of the invention, in a particularly effective cleaning solution, which is also suitable for removing rouging deposits of rouge class 3, at least one complexing agent ascorbic acid (with the molecular formula C£,H8O6; IUPAC nomenclature: (5R)-5-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxy-5-

hydrofuran-2-one) or contain ascorbic acid.

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The cleaning solution according to the invention, in which ascorbic acid (vitamin C) acts as a complexing agent, can be used in particular for the effective ablation of steam rouge layers of rouge class 3, which adhere firmly to media-contacting surfaces of stainless steel. Ascorbic acid is an excellent complexing agent for iron(II) ions (Fe'") and has the ability to reduce iron(III) ions (Fe) in a so-called inner-sphere reaction to iron(II) ions (Fe'"). The ascorbic acid can then advantageously be oxidized again, for example by hydrogen peroxide (H,O,) and then reused essentially without loss or only with comparatively low consumption (make-up). The use of ascorbic acid as a complexing agent in a cleaning solution according to the invention is therefore not only particularly effective for cleaning particularly firmly adhering corrosion layers or rouging deposits according to Rouge Class 3, but can also be recycled several times in a particularly sustainable manner, which is particularly economical and

is environmentally friendly.

In this embodiment of the invention, a cleaning solution with ascorbic acid as a complexing agent can be provided, which has a pH value of 1.0 to 5.0, preferably a pH

value of 1.5 to 4.5.

For removing heavy rouging deposits of rouge class 3, such as steam rouge, this cleaning solution proves to be

very efficient.

It may be particularly useful if, according to this embodiment of the invention, a ready-to-use cleaning solution as a one-component system has the following

Composition: —- from 82 to 97.5% by weight water,

—- from 0.5 to 4% by weight, preferably from 1 to 3% by weight, of at least one salt of peroxodisulphuric acid, preferably

Potassium persulfate or sodium persulfate,

—- from 0 to 4% by weight, preferably from 0.5 to 3% by weight, of a

further oxidizing agent, preferably hydrogen peroxide,

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—- from 0.5 to 4% by weight, preferably from 1 to 3% by weight, of at least one salt of hydrofluoric acid, preferably potassium hydrogen difluoride

or sodium hydrogen difluoride,

—- from 1.5 to 6% by weight, preferably from 2 to 5% by weight,

Ascorbic acid.

This ready-to-use cleaning solution is very effective for removing heavy rouging deposits of rouge class 3, such as steam rouge. To further increase the cleaning effect, the cleaning solution can be diluted with up to

4 wt.% of a further oxidizing agent. Hydrogen peroxide can preferably be contained in the cleaning solution in a comparatively small proportion of up to 4 wt.%, preferably from 0.5 to 3 wt.%, as a further oxidizing agent. For safety reasons, a proportion of the further oxidizing agent, preferably hydrogen peroxide, can optionally also be added later to the

ready-to-use aqueous cleaning solution.

In particular for applications where large amounts of cleaning solution are required to remove rouging deposits, it may be advantageous in this embodiment of the invention to use the cleaning solution according to the invention as a two-component system, wherein the concentrated cleaning solution contains the following components before being diluted with water:

Composition:

Q

—- from 10 to 20 wt.% water,

—- from 16 to 26% by weight, preferably from 18 to 24% by weight, of at least one salt of peroxodisulphuric acid, preferably

Potassium persulfate or sodium persulfate,

—- from 16 to 26% by weight, preferably from 18 to 24% by weight, of at least one salt of hydrofluoric acid, preferably potassium hydrogen difluoride

or sodium hydrogen difluoride,

—- from 38 to 48% by weight, preferably from 40 to 46% by weight,

Ascorbic acid.

The above mentioned advantages and beneficial effects

referred to.

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For safety reasons, it may be expedient in a further development of the invention if the concentrated cleaning solution is free of hydrogen peroxide. In this variant of the invention, the storage life of the concentrated cleaning solution is advantageously increased, particularly when stored at higher temperatures in poorly

temperature-controlled storage facilities.

The object of the invention mentioned at the outset is also achieved by using a cleaning solution according to the invention according to one of claims 5 to 7, in which the at least one complexing agent contains or is at least one amino acid, preferably glycine HOOC-CH,-NH,, for removing rouging deposits containing iron(III) oxide at a cleaning temperature of 20 to 60°C, preferably

at a cleaning temperature of not more than 50°C.

As already explained above, such rouging coatings containing iron(III) oxide mainly in the form of hematite Fe,O3,

referred to as Rouge Class 2.

The moderate application temperatures mentioned above offer advantages in terms of occupational safety when handling the

cleaning solution according to the invention.

The use of a concentrated cleaning solution according to claim 8, which is adjusted to a proportion of 80 to 90% by weight of water in the diluted cleaning solution by adding water, can be particularly cost-effective and efficient in order to remove rouging deposits containing iron(III) oxide with this diluted, ready-to-use cleaning solution at a cleaning temperature of 20° to 60°C, preferably at a cleaning temperature of at most

50°C, to be removed.

As already explained, the use of a concentrate serves to simplify logistics by reducing the number of transports, but also to increase the storage stability of the concentrated cleaning solution due to the lower

water content.

The object of the invention mentioned at the outset is also achieved by providing a cleaning solution according to the invention according to one of claims 9 to 11, in which the at least one

Complexing agent containing or is ascorbic acid, for the removal of

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Rouging coatings containing iron(II,III) oxide at a cleaning temperature of 20° to 80°C, preferably at a

Cleaning temperature of 30° to 70°C is used.

As already explained above, such rouging coatings, which mainly contain iron(II,III) oxide in the form of magnetite or Fe3z0,

are referred to as Rouge Class 3. The iron(II,III) oxide rich Rouging coatings form particularly firmly surface-bound

Layers that can no longer be wiped off.

The moderate application temperatures compared to the use of conventional cleaning solutions offer advantages in the case of the use of the cleaning solution according to the invention with regard to

Handling and occupational safety.

The use of a concentrated cleaning solution according to claim 12 or 13, which is adjusted by adding water to a proportion of 82 to 97.5% by weight of water in the diluted cleaning solution, can be particularly cost-effective and efficient in order to remove rouging deposits containing iron (II, III) oxide with this diluted, ready-to-use cleaning solution at a cleaning temperature of 20°

up to 80°C, preferably at a cleaning temperature of 30° to

70°C. If necessary, up to 4% by weight of hydrogen peroxide can be added as an additional oxidizing agent to the cleaning solution, which has already been diluted by adding water, in order to further increase the cleaning effect of the diluted, ready-to-use cleaning solution. However, it should be noted that the cleaning solution as a concentrate without any additional oxidizing agent is usually longer lasting than after the addition of

for example hydrogen peroxide H,O.

In order to produce a ready-to-use cleaning solution according to one of claims 5 to 7 from a concentrated cleaning solution according to claim 8, a method according to the invention for producing a cleaning solution is specified, which

which includes the following steps:

—- Providing a concentrated cleaning solution after

Claim 8;

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—- Dilute the concentrated cleaning solution with water until a proportion of 80 to 90 wt.% water in the diluted

cleaning solution is set.

Reference is again made to the advantages of using a cleaning agent concentrate already mentioned above, in particular the simplified logistics and increased

Storage stability of the concentrate.

In an alternative process variant according to the invention, a ready-to-use cleaning solution according to one of claims 9 to 11 can be prepared from a concentrated cleaning solution according to claim 12 or 13, wherein the process according to the invention

includes the following steps:

—- Providing a concentrated cleaning solution according to claim

12 or 13;

—- Dilute the concentrated cleaning solution with water until a proportion of 82 to 97.5 wt.% water in the diluted

cleaning solution is set;

—- If necessary, add up to 4% by weight of hydrogen peroxide

into the diluted cleaning solution.

WAYS OF IMPLEMENTING THE INVENTION

Below are some examples of implementation to

to remove rouging deposits using cleaning solutions according to the invention.

Example A: pH-neutral steam derouging of thin rouging layers

In this example, a vein clamp, i.e. a medical device that was coated with a homogeneous rouging coating with black discoloration according to rouge class 3, was tested with

a cleaning solution according to the invention.

To prepare the cleaning solution, 2 g of potassium hydrogen difluoride KHF,, 2 g of potassium persulfate K,S,O8s and 9 g of glycine were dissolved in 87 g of water at room temperature of around 25°C. The ready-to-use cleaning solution had a pH value of 5.3. The cleaning solution was heated to 50°C and then the blackened

Vein clamp is placed in this heated cleaning solution. After 15

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After 1 min of cleaning time, the vein clamp was removed from the cleaning solution and the dark rouging deposits were completely removed from the vein clamp. The pH value of the used cleaning solution after removal of the vein clamp was determined to be between 4.8 and 4.9. The cleaning solution used contained 87% by weight water, 2% by weight potassium hydrogen difluoride KHF,, 2% by weight potassium persulfate K,S,Os

and 9 wt.% glycine.

Example B: Steam derouging of heavy rouging deposits

In this example, a material sample from a container wall of a steam line operated at around 140°C, which had been in use in a pharmaceutical production plant for more than 20 years, was cleaned with a cleaning solution according to the invention. The material sample to be cleaned had crystalline, surface-bound magnetite deposits on the inside exposed to steam, thus rouging deposits according to Rouge Class 3, which mainly

consist of iron(II,III) oxide, magnetite or Fe;0,,.

To prepare the cleaning solution, 2 g of potassium hydrogen difluoride KHF,, 2 g of potassium persulfate K,S,Os and 5 g of ascorbic acid were completely dissolved in 85 g of water at room temperature of around 25°C. The solution was then mixed with 6 g of a 35% hydrogen peroxide (H,O,) solution. The ready-to-use

Cleaning solution had a pH of 4.3.

The ready-to-use cleaning solution was heated to 80°C and then the material sample of the steam line contaminated with magnetite deposits was placed in this heated cleaning solution. After 60 minutes of cleaning, the material sample was removed from the cleaning solution and the rouging deposits were completely removed. The inside of the steam line exposed to steam was cleaned to a metallic bare finish. The used cleaning solution

had a pH value of 2.7 after removal of the workpiece.

The cleaning solution used contained 89 wt.% water, 2 wt.% potassium persulfate K,S,08s, 2 wt.% potassium hydrogen difluoride KHF,, 2 wt.%

Q

Hydrogen peroxide H,O, and 5 wt.% ascorbic acid.

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Example C: Steam derouging of heavy rouging deposits

In this example, a material sample of a plate heat exchanger was cleaned. On both the steam side, i.e. the side of the plate heat exchanger exposed to hot steam, and on the water side of the material sample to be cleaned opposite the steam side and exposed to water, there were non-wipeable, firmly adhering rouging deposits of rouge class 3. The firmly adhering rouging deposits on the steam side (“steam rouge”) and on the water side of the plate heat exchanger

each had a powdery surface structure.

For the cleaning solution used in Example C, approximately half the concentrations of the previously used in Example B were used.

Cleaning solution used.

To prepare the cleaning solution, 40 g of potassium hydrogen difluoride KHF,, 40 g of potassium persulfate K,S,Os and 100 g of ascorbic acid were completely dissolved in 3700 g of water at room temperature of around 25°C. The solution was then mixed with 120 g of a 35% hydrogen peroxide (H,O,) solution. The ready-to-use

Cleaning solution had a pH of 4.0.

The ready-to-use cleaning solution was heated to 70°C and then the material sample of the plate heat exchanger contaminated with magnetite deposits was placed in this heated cleaning solution. After 60 minutes of cleaning, the material sample was removed from the cleaning solution and the rouging deposits were completely removed except for a few local areas. The used cleaning solution was orange in color and

had a pH value of 2.5 after removal of the workpiece.

The cleaning solution used contained 94.5 wt.% water, 1 wt.% potassium persulfate K,S,O0s, 1 wt.% potassium hydrogen difluoride KHF,, 1 wt.%

Q

Hydrogen peroxide H,O, and 2.5 wt.% ascorbic acid.

The used cleaning solution was then heated again to 60°C and the pre-cleaned material sample of the plate heat exchanger was placed in the heated cleaning solution again for a cleaning period of 120 minutes. After another

Removing the material sample from the cleaning solution showed

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that the previously existing locally adhering rouging deposits were now satisfactorily cleaned after the second cleaning

were.

In addition, another material sample was cleaned in the used cleaning solution: a pipe section of a (black) steam line with external rouging deposits and internal “steam rouge” deposits, each of rouge class 3. This additional material sample was also cleaned at a used cleaning solution temperature of 60°C for a cleaning time of 120 minutes. After cleaning this material sample, the firmly adhering rouging deposits on both sides of the steam line were completely removed. An optical inspection using a microscope showed metallically bright surfaces on

both sides of the steam line.

Claims (1)

15 20 25 30 23 PATENT CLAIMS Aqueous cleaning solution for removing rouging deposits, containing: at least one oxidizing agent, wherein the at least one The oxidizing agent is a salt of peroxodisulphuric acid; at least one complexing agent which is suitable for iron(II) ions and/or iron(III) ions; at least one catalyst, wherein the at least one Catalyst is a salt of hydrofluoric acid. Cleaning solution according to claim 1, characterized in that the at least one oxidizing agent is a metal salt of peroxodisulphuric acid, preferably potassium persulphate (K,S,Os8) or sodium persulfate (Na,S,Os). Cleaning solution according to claim 1 or 2, characterized in that the cleaning solution contains at least one further oxidizing agent, preferably hydrogen peroxide (H,O>) / contains. Cleaning solution according to one of claims 1 to 3, characterized in that the at least one catalyst is a metal salt of hydrofluoric acid, preferably potassium hydrogen difluoride (KHF) or sodium hydrogen difluoride (NaHF,). Cleaning solution according to one of claims 1 to 4, characterized in that the at least one complexing agent contains at least one amino acid, preferably glycine (HOOC-CH,-NH,), contains or is. 10 15 20 25 30 7. 24 Cleaning solution according to claim 5, characterized in that the cleaning solution has a pH value of 4.0 to 8.0, preferably has a pH value of 5.0 to 7.0. Cleaning solution according to one of claims 5 or 6, with the Composition: from 80 to 90 wt.% water, from 1 to 4% by weight, preferably from 2 to 3% by weight, of at least one salt of peroxodisulphuric acid, preferably Potassium persulfate or sodium persulfate, from 1 to 4% by weight, preferably from 2 to 3% by weight, of at least one salt of hydrofluoric acid, preferably Potassium hydrogen difluoride or sodium hydrogen difluoride, from 8 to 12% by weight, preferably from 9 to 11% by weight, at least an amino acid, preferably glycine. Concentrated cleaning solution according to one of claims 5 or 6, with the composition: from 10 to 20 wt.% water, from 8 to 18% by weight, preferably from 10 to 16% by weight, of at least one salt of peroxodisulphuric acid, preferably Sodium persulfate, from 8 to 18% by weight, preferably from 10 to 16% by weight, of at least one salt of hydrofluoric acid, preferably Potassium hydrogen difluoride, from 54 to 64% by weight, preferably from 56 to 62% by weight, at least one amino acid, preferably glycine. Cleaning solution according to one of claims 1 to 4, characterized in that the at least one complexing agent contains or is ascorbic acid ((5R)-5-[(1S)-1,2-dihydroxyethyl]-3,4-dihydroxy5-hydrofuran-2-one). 10. Cleaning solution according to claim 9, characterized in that the cleaning solution has a pH value of 1.0 to 5.0, preferably has a pH value of 1.5 to 4.5. 5 11. Cleaning solution according to one of claims 9 or 10, with the Composition: —- from 82 to 97.5 wt.% water, —- from 0.5 to 4% by weight, preferably from 1 to 3% by weight, of at least one salt of peroxodisulphuric acid, preferably 10 Potassium persulfate or sodium persulfate, —- from 0 to 4% by weight, preferably from 0.5 to 3% by weight, of at least one further oxidizing agent, preferably Hydrogen peroxide, —- from 0.5 to 4% by weight, preferably from 1 to 3% by weight, of at least 15% of a salt of hydrofluoric acid, preferably Potassium hydrogen difluoride or sodium hydrogen difluoride, —- from 1.5 to 6% by weight, preferably from 2 to 5% by weight, Ascorbic acid. 20 12. Concentrated cleaning solution according to one of claims 9 or 10, with the composition: Q —- from 10 to 20 wt.% water, —- from 16 to 26% by weight, preferably from 18 to 24% by weight, of at least one salt of peroxodisulphuric acid, preferably 25 Sodium persulfate, —- from 16 to 26% by weight, preferably from 18 to 24% by weight, of at least one salt of hydrofluoric acid, preferably Potassium hydrogen difluoride, —- from 38 to 48% by weight, preferably from 40 to 46% by weight, 30 Ascorbic acid. 13. Concentrated cleaning solution according to claim 12, characterized characterized in that the concentrated cleaning solution is free 15 20 25 30 14. 15. 16. 17. 18. 26 by another oxidizing agent, preferably free from Hydrogen peroxide. Use of a cleaning solution according to one of claims 5 to 7 for removing rouging deposits containing iron(III) oxide at a cleaning temperature of 20° to 80°C, preferably preferably at a cleaning temperature of no more than 50°C. Use a concentrated cleaning solution after Claim 8 after dilution with water to a proportion of 80 to 90 wt.% water in the diluted cleaning solution, for removing rouging deposits containing iron(III) oxide at a cleaning temperature of 20° to 60°C, preferably at a cleaning temperature of maximum 50°C. Use of a cleaning solution according to one of claims 9 to 11 for removing rouging deposits containing Iron(II,III) oxide at a cleaning temperature of 20° to 80°C, preferably at a cleaning temperature of 30° to 70°C. Use of a concentrated cleaning solution according to claim 12 or 13 after dilution with water to a proportion of 82 to 97.5 wt.% water in the diluted cleaning solution, wherein optionally up to 4 wt.% of at least one further oxidizing agent, preferably hydrogen peroxide, is added to the cleaning solution diluted with water, for removing rouging deposits containing iron (II, III) oxide at a cleaning temperature of 20° to 80°C, preferably at a cleaning temperature of 30° to 70°C. Process for preparing a cleaning solution according to a of claims 5 to 7, comprising the following steps: 27733 15 19. 27 Providing a concentrated cleaning solution after Claim 8; Dilute the concentrated cleaning solution with water until Q a proportion of 80 to 90 wt.% water in the diluted cleaning solution is set. Process for preparing a cleaning solution according to a of claims 9 to 11, comprising the following steps: Providing a concentrated cleaning solution after Claim 12 or 13; Dilute the concentrated cleaning solution with water until a proportion of 82 to 97.5 wt.% water in the diluted cleaning solution is set; If necessary, admixture of up to 4 wt.% of at least one further oxidizing agent, preferably hydrogen peroxide, into the diluted cleaning solution. 15 20 25 30 35 23 A50513/2023 51373AT Reply to the 1st preliminary decision Amended patent claims (fair copy) AMENDED PATENT CLAIMS 1. Aqueous cleaning solution for removing rouging deposits, containing at least one complexing agent to remove iron(II) ions and/or iron(III) ions, characterized in that the cleaning solution continues contains: —- at least one oxidizing agent, wherein the at least one The oxidizing agent is a salt of peroxodisulphuric acid; —- at least one catalyst, wherein the at least one Catalyst is a salt of hydrofluoric acid. 2. Cleaning solution according to claim 1, characterized in that the at least one oxidizing agent is a metal salt of peroxodisulphuric acid, preferably potassium persulphate or Sodium persulfate. 3. Cleaning solution according to claim 1 or 2, characterized in that the cleaning solution contains at least one further oxidizing agent, preferably hydrogen peroxide, contains. 4. Cleaning solution according to one of claims 1 to 3, characterized in that the at least one catalyst is a metal salt of hydrofluoric acid, preferably Potassium hydrogen difluoride or sodium hydrogen difluoride. 5. Cleaning solution according to one of claims 1 to 4, characterized in that the at least one complexing agent contains at least one amino acid, preferably glycine, or is. [MOST RECENTLY SUBMITTED CLAIMS] 6. Cleaning solution according to claim 5, characterized in that the cleaning solution has a pH value of 4.0 to 8.0, preferably has a pH value of 5.0 to 7.0. 7. Cleaning solution according to claim 5 or 6, with which Composition: —- from 80 to 90 wt.% water, —- from 1 to 4% by weight, preferably from 2 to 3% by weight, of at least 10% of a salt of peroxodisulphuric acid, preferably Potassium persulfate or sodium persulfate, —- from 1 to 4% by weight, preferably from 2 to 3% by weight, of at least one salt of hydrofluoric acid, preferably Potassium hydrogen difluoride or sodium hydrogen difluoride, 15 —- from 8 to 12 wt.%, preferably from 9 to 11 wt.%, at least an amino acid, preferably glycine. 8. Concentrated cleaning solution according to claim 5 or 6, with which Composition: 20 —- from 10 to 20 wt.% water, —- from 8 to 18% by weight, preferably from 10 to 16% by weight, of at least one salt of peroxodisulphuric acid, preferably Sodium persulfate, —- from 8 to 18% by weight, preferably from 10 to 16% by weight, of at least one salt of hydrofluoric acid, preferably Potassium hydrogen difluoride, —- from 54 to 64% by weight, preferably from 56 to 62% by weight, at least one amino acid, preferably glycine. 30 9. Cleaning solution according to one of claims 1 to 4, characterized in that the at least one complexing agent Contains or is ascorbic acid. | MOST RECENTLY SUBMITTED CLAIMS } 10. Cleaning solution according to claim 9, characterized in that the cleaning solution has a pH value of 1.0 to 5.0, preferably has a pH value of 1.5 to 4.5. 5 11. Cleaning solution according to claim 9 or 10, with which Composition: —- from 82 to 97.5 wt.% water, —- from 0.5 to 4% by weight, preferably from 1 to 3% by weight, of at least one salt of peroxodisulphuric acid, preferably 10 Potassium persulfate or sodium persulfate, - from 0 to 4% by weight, preferably from 0.5 to 3% by weight, of at least one further oxidizing agent, preferably Hydrogen peroxide, —- from 0.5 to 4% by weight, preferably from 1 to 3% by weight, of at least 15% of a salt of hydrofluoric acid, preferably Potassium hydrogen difluoride or sodium hydrogen difluoride, —- from 1.5 to 6% by weight, preferably from 2 to 5% by weight, Ascorbic acid. 20 12. Concentrated cleaning solution according to claim 9 or 10, with the composition: Q —- from 10 to 20 wt.% water, —- from 16 to 26% by weight, preferably from 18 to 24% by weight, of at least one salt of peroxodisulphuric acid, preferably 25 Sodium persulfate, —- from 16 to 26% by weight, preferably from 18 to 24% by weight, of at least one salt of hydrofluoric acid, preferably Potassium hydrogen difluoride, —- from 38 to 48% by weight, preferably from 40 to 46% by weight, 30 Ascorbic acid. 13. Concentrated cleaning solution according to claim 12, characterized characterized in that the concentrated cleaning solution is free | MOST RECENTLY SUBMITTED CLAIMS ] 15 20 25 30 35 14. 15. 16. 17. 18. 26 by another oxidizing agent, preferably free from Hydrogen peroxide. Use of a cleaning solution according to one of claims 5 to 7 for removing rouging deposits containing iron(III) oxide at a cleaning temperature of 20° to 80°C, preferably at a cleaning temperature of at most 50°C. Use a concentrated cleaning solution after Claim 8 after dilution with water to a proportion of 80 to 90 wt.% water in the diluted cleaning solution, for removing rouging deposits containing iron(III) oxide at a cleaning temperature of 20° to 60°C, preferably at a cleaning temperature of maximum 50°C. Use of a cleaning solution according to one of claims 9 to 11 for removing rouging deposits containing Iron(II,III) oxide at a cleaning temperature of 20° to 80°C, preferably at a cleaning temperature of 30° to 70°C. Use of a concentrated cleaning solution according to claim 12 or 13 after dilution with water to a proportion of 82 to 97.5 wt.% water in the diluted cleaning solution, wherein optionally up to 4 wt.% of at least one further oxidizing agent, preferably hydrogen peroxide, is added to the cleaning solution diluted with water, for removing rouging deposits containing iron (II, III) oxide at a cleaning temperature of 20° to 80°C, preferably at a cleaning temperature of 30° to 70°C. Process for preparing a cleaning solution according to a of claims 5 to 7, comprising the following steps: [MOST RECENTLY SUBMITTED CLAIMS] 15 19. 27 Providing a concentrated cleaning solution after Claim 8; Dilute the concentrated cleaning solution with water until Q a proportion of 80 to 90 wt.% water in the diluted cleaning solution is set. Process for preparing a cleaning solution according to a of claims 9 to 11, comprising the following steps: Providing a concentrated cleaning solution after Claim 12 or 13; Dilute the concentrated cleaning solution with water until a proportion of 82 to 97.5 wt.% water in the diluted cleaning solution is set; If necessary, admixture of up to 4 wt.% of at least one further oxidizing agent, preferably hydrogen peroxide, into the diluted cleaning solution. [ RECENTLY FILED CLAIMS |