CA2686590C

CA2686590C - Stabilized concentrated cleaning solutions and methods of preparing the same

Info

Publication number: CA2686590C
Application number: CA2686590A
Authority: CA
Inventors: Siegfried Bragulla
Original assignee: Ecolab Inc
Current assignee: Ecolab Inc
Priority date: 2007-07-17
Filing date: 2007-07-17
Publication date: 2014-04-01
Anticipated expiration: 2027-07-17
Also published as: CN101679921A; JP2010533765A; AU2007356500B2; EP2164944B1; MX2009013256A; CN101679921B; BRPI0721689A2; EP2164944A1; JP5443351B2; CA2686590A1; WO2009011676A1; AU2007356500A1

Abstract

The invention is directed to stabilized concentrated cleaning solutions comprising a source of hypochlorite ions and to a method for providing the stabilized concentrated cleaning solutions. The stabilized concentrated cleaning solutions according to the invention comprise a hydroxide ion source, hypochlorite ion source, and a chelating agent, and are provided simply by mixing the various components together. The stabilized concentrated cleaning solutions exhibit stability against, e.g., dilution with a diluent comprising amounts of copper, iron, nickel cobalt, etc., as well as storage for periods of from about 10 weeks to up to about 1 year without undergoing visible deterioration and/or a substantial deterioration in efficacy.

Description

- -STABILIZED CONCENTRATED CLEANING SOLUTIONS AND
METHODS OF PREPARING THE SAME
FIELD
The invention is directed to stabilized concentrated cleaning solutions, and to a method of preparing them.
BACKGROUND
Commercial cleaning solutions that effectively clean, sanitize and disinfect are of critical importance in many industrial and institutional settings and indeed are ubiquitous in healthcare, food manufacture, educational, governmental, agricultural, water treatment, etc facilities. Due at least in part to cost considerations, these cleaning solutions are often manufactured and sold in concentrated form and then diluted at a point of use to their usable concentration.
Many of the users of these solutions keep inventory on hand and, as a result, concentrated cleaning solution may sit for an extended period of time prior to use. However, the shelf stability of the concentrated solutions has proven to be limiting in some applications. Although clear when produced, the concentrated solutions can tend to partially decompose, or otherwise deteriorate, to produce visible precipitates when stored for long periods of time. Given the intended use of these products, such visible residue is typically at least aesthetically unacceptable to the customer, and indeed, the precipitates, or precursors thereof, can react with the active components of the concentrated cleaning solution, thereby potentially reducing the efficacy thereof.
According to one theory, the production of such residue is caused or at least facilitated by commercially acceptable levels of impurities present in the raw materials used in the manufacture of the concentrated commercial cleaning

- 2 -solutions. Indeed, many of these raw materials are available at various costs and associated levels of purity, i.e., a raw material solution with fewer impurities may be obtained for greater cost. At some point, the cost for a substantially pure raw material may so erode the profit margin of a product that the product would not be commercially viable to produce. Additionally, in some countries, environmental regulations may limit or prohibit the use of manufacturing processes that would produce substantially pure raw materials. In this instance then, even if a manufacturer would be willing to pay more for a raw material with fewer impurities, such a raw material may simply not be commercially available.
Even in those instances when such concentrated cleaning solutions are used relatively quickly, visible precipitates can yet be formed upon dilution of the concentrated cleaning solution to its usable concentration. Any such precipitates are believed to result from impurities introduced by the diluent and the reaction thereof with components of the cleaning solutions. Even though the water quality of the final user is out of the control of the manufacturer, concentrated cleaning solutions would desirably be provided that could resist or prevent the formation of visible precipitates upon dilution to a usable concentration.
And so, concentrated cleaning solution manufactures have tried several approaches to reduce or eliminate the formation of these visible precipitates in their concentrated solutions. One approach, described in copending PCT
application serial no. PCT/EP2006/061793, involves adding a combination of a phosphono compound and a silicate to the concentrated cleaning solution. Indeed, this approach works very well. However, the utilization of two chemicals may represent an undesirable cost and/or time expense to the manufacturer.
In order to enhance the convenience and customer satisfaction associated with concentrated cleaning solutions, the solutions would desirably be

- 3 -produced so that long-term storage thereof is possible without visible =
deterioration and/or other change in product quality. Desirably, concentrated cleaning solutions could also be rendered more shelf stable in a manner thét is more cost and/or time efficient than previously described.
SUMMARY
concentrated cleaning solutions are provided. The solutions comprise from 1 wt% to about 40 wt% of a source of hydroxide ions, from about 5 wt% to about 80 wt% of a source of hypochlorite ions, and from about 0.0001 wt%
to about 2.00 wt% chelating agent. In certain preferred embodiments, the

- 4 -chelating agent. The chelating agent may be EDTA, MGDA, NTA, IDS, polyacrylate or combinations of these. In certain embodiments, EDTA, =
MGDA or NTA are preferred.
In yet another aspect or the present invention, a method of stabilizing a concentrated cleaning solution comprising a source of hypochlorite ions is provided. The method comprises providing such a solution, providing a chelating agent, and adding the chelating agent to the cleaning solution.
The chelating agent(s) are desirably added to the cleaning solution in amounts so that the concentration of chelating agent provided in the cleaning solution ranges from about 0.0001 wt% to about 2.00 wt%, more typically from about 0.0002 wt% to about 0.5 wt%, and preferably may be present in amounts as low as from about 0.0005 wt% to about 0.05 wt%.
DETAILED DESCRIPTION
The present invention provides stabilized concentrated cleaning solutions, and methods of preparing these solutions. It was recently discovered that concentrated cleaning solutions comprising at least one hypochlorite ion source can tend to form visible precipitates upon prolonged storage, or upon the addition of a diluent comprising impurities. It is believed that the precipitates, generally found to be iron oxide, nickel oxide, copper oxide and/or cobalt oxide, were resulting from the reaction of heavy metal impurities in the starting raw materials or diluent, as the case may be, with the oxidant in the concentrated cleaning solutions. If enough impurities are present, and react with enough of the oxidant, the efficacy of the concentrated cleaning solutions may be reduced. Even if the efficacy remains acceptable, the presence of visible precipitates may be commercially unacceptable in products intended to be used in cleaning applications.
Stabilized concentrated cleaning solutions according to the present invention do not form visible amounts of precipitates after storage at or =

- 5 -about room temperature for periods of at least 10 weeks, 3 months, 6 months or even up to one year. This effect is provided via the inclusion of a small amount(s) of one or more chelating agents to the concentrated cleaning solutions. This result is surprising, because as described in copending PCT application serial no. PCT/EP2006/061793, these same chelating agents were not effective at reducing or preventing the formation of precipitates in these solutions in greater amounts. While not wishing to be bound by any theory, it is believed that at higher concentrations of the chelating agents, greater amounts of heavy metal/chelating agent complexes are formed than are soluble in aqueous solution at storage temperatures, and thus, precipitates will form, albeit precipitates comprising complexed heavy metal impurities.
As shown in the example, at the lower concentrations now employed in the solutions and methods described herein, the chelating agents are extremely effective at reducing or even eliminating the amount of visible precipitates that may form in the cleaning solutions upon prolonged storage. Further, these results are achieved by and large with the use of only one readily commercially available, relatively safe chelating agent in very small amounts, representing a cost and time savings over other known methods of stabilizing these types of cleaning solutions, as well as providing significant advantages in storage and handling safety.
As this phrase is used herein, and as is known in the art, chelating agents are polydentate ligands that reversibly bind to a metal ion typically via two or more hydrogen or ionic bonds. Examples of preferred chelating agents for use in the stabilized concentrated cleaning solutions and methods of preparing them include ethylene diamine tetraacetic acid (EDTA), methylglycinediacetic acid (MG DA), nitrilotriacetic acid (NTA), iminodisuccinate (IDS), polyacrylate, or combinations of these.

6 Surprisingly, and although higher concentrations of the chelating agents do not necessarily provide better, or even the same, beneficial results, very low concentrations of the chelating agents are very effective at providing the concentrated cleaning solutions with the desired stability, i.e., the reduction or even elimination of visible precipitates upon prolonged storage, or upon the addition of a diluent comprising copper, iron, nickel or cobalt impurities.
More particularly, amounts of from about 0.0001 wt% to about 2.00 wt%, more typically from about 0.0002 wt% to about 0.5 wt%, and even in amounts as low as from about 0.0005 wt% to about 0.05 wt% have been found capable of providing the concentrated cleaning solutions with the desired stability.
Stated another way, and when the chelating agent is, e.g., EDTA provided as a 38 wt% solution, amounts ranging from about 0.4 ppm to about 7600 ppm, or from about 0/6 ppm to about 1900 ppm or even from about 1.9 ppm to about 190 ppm, or may be used.
Cost/efficiency considerations may dictate that the no more chelating agent than that required to achieve the desired effect should be used, and indeed, at higher concentrations the chelating agent(s) may not be effective at reducing or eliminating the visible prebipitates that may occur upon storage for prolonged periods of time. For these reasons, amounts of the chelating agent greater than 2.5 wt% based upon the total weight of the stabilized concentrated cleaning solution, should be avoided.
Concentrated cleaning solutions that benefit from application of the present method include those comprising an amount of hypochlorite ions. Sources of hypochlorite ions include, but are not limited to, chlorine, hypochlorite salts, chloramine T, dichloramine T, trichloroisocyanuric acid and any of these, or combinations thereof are suitable for use in the present stabilized concentrated cleaning solutions. Preferably, the stabilized concentrated cleaning solutions comprise one or more hypochlorite salts as the source of

- 7 -hypochlorite ions, and calcium hypochlorite, potassium hypochlorite and/or sodium hypochlorite are particularly preferred. The source of hypochlorite ions in typical concentrated cleaning solutions ranges from about 5 to about 80 wt%, or.from about 20 wt % to about 70 wt%, and more particularly from about 40 wt% to about 60 wt%, and these concentration ranges are suitable for use in the stabilized concentrated cleaning solutions of the present invention.
The bactericidal effect of such concentrated cleaning solutions is provided by hypochlorite ions that are, in turn, formed via the dissociation of hypochlorite salts or hypochlorous acid in water. Hypochlorous acid, in turn, can be formed when chlorine reacts with water in amounts that depend upon the pH of the solution:
Cl 2 + H20 HOCI + HCL
The equilibrium of this reaction, and thus the amount of hypochlorous acid produced, depends on the pH of the solution. In alkaline solution, more hypochlorous acid is produced thereby increasing the bactericidal effect that can be seen.
Accordingly, the stabilized concentrated cleaning solutions of the present invention are also desirably alkaline, and include a sufficient amount of a hydroxide ion source to render them so.
Typically, hydroxide ions are provided in cleaning solutions via the inclusion of one or more caustic, or base, solutions. Such solutions are well known in the art, and any of these may be used, with preference given to sodium hydroxide and potassium hydroxide for their ready availability and ease of use. The source of hydroxide ions is typically included in conventional concentrated cleaning solutions in amounts of from about 1 wt% to about 40 wt%, preferably from about 5 wt% to about 35 wt%, or more typically from about 15 wt% to about 30 wt% of one or more hydroxide ion sources, and

- 8 -these ranges again provide a cleaning solution that would desirably be stabilized against the formation of visible precipitates and thus could benefit from application of the method of the present invention.
For example, then, particular stabilized concentrated cleaning solutions according to the present invention may comprise from about 15 wt% to about 30 wt% hydroxide ion source, such as sodium hydroxide or potassium hydroxide, from about 40 wt% to about 60 wt% hypochlorite ion source, such as sodium hypochlorite, and from about 0.0005 wt% to about 0.05 wt%chelating agent, such as EDTA.
Additionally, stabilized concentrated cleaning solutions according to the present invention may comprise any of the other components typically included in conventional concentrated cleaning solutions. For example, many such solutions include one or more sequestrants, surfactants, corrosion inhibitors, builders, solubilizers, solvents, other additives, or combinations of these.
Sequestrants are typically included in cleaning solutions to reduce or prevent water hardness scaling. Examples of suitable sequestrants that may be included in the present stabilized concentrated cleaning solutions if desired, include, polyphosphates, organic phosponates, citrates, lactic acid, combinations of these and the like.
One or more surfactants may also be included in the stabilized concentrated cleaning solutions to enhance the cleaning performance thereof. Although any type of surfactant, i.e., anionic, cationic, non-ionic or amphoteric, may be added to the present concentrated cleaning solutions without detrimentally impacting the stability thereof, anionic and/or non-ionic surfactants are particularly appropriate for inclusion therein since the stabilized concentrated cleaning solutions may typically be alkaline.
=

- 9 -Examples of anionic surfactants include, but are not limited to, alkyl arene sulfonates, such as alkyl benzene sulfonates, alkyl naphthalene sulfonates, alkylsulfonates, alpha olefin sulfonates or alkyl sulfates. One example of a particularly preferred anionic surfactant that may be included in the present stabilized solutions is sodium lauryl sulfate.
Examplary non-ionic surfactants include ethoxylated and/or propoxylated fatty alcohols or fatty amines, alkyl polyglucosides and aminoxides, or combinations thereof. Aminoxides are preferred, and examples of these include coconut alkyl dimethylamine oxide and lauryl dimethylamine oxide.
Cationic surfactants may also be included in the present cleaning solutions.
Cationic surfactants believed to be capable of providing some cleaning activity when in alkaline solution are exemplified by the quaternary ammonium salts. Preferred quaternary ammonium salts may be saturated or unsaturated and are those derived from trialkanol amines esterified with fatty acids and then quaternized with appropriate alkylation agents.
Amounts of surfactant from about 1 wt% to 30 wt%, preferably from about 2 wt% to about 20 wt% and most preferably from about 4 wt% to about 15 wt% based upon the total weight of the stabilized concentrated solution may be employed.
Solubilizers, typically act to facilitate the dispersion of organic components, including any of the non-critical components such as surfactants, in aqueous solution, and one or more may also optionally be included in the stabilized cleaning solutions. Examples of solubilizers include sodium, potassium, ammonium and alkanol ammonium salts of sulfonates of xylene, toluene, ethylbenzoate, isopropylbenzene, naphthalene or alkyl naphthalene, phosphate esters of alkoxylated alkyl phenols, phosphate esters of alkoxylated alcohols and sodium, potassium and ammonium salts of alkyl sarcosinates, and mixtures of these. If desirably included, the one

- 10 -or more solubilizer(s) may be present in amounts of from about 1 to about 35 wt%, or from about 5 to about 25 wt% and more preferably from about 9 to about 20 wt%.
The stabilized concentrated cleaning solution may also optionally contain one or more of other components commonly used in cleaning solutions including, but not limited to, builders, solvents, and other additives.
Amounts of up to about 20%, or up to about 15 wt%, or even up to about 10% are suitable for each of these.
Examplary builders that may be included in the stabilized concentrated cleaning solutions are sodium carbonate, sodium sesquicarbonate, sodium sulfate, sodium hydrogencarbonate, phosphates like pentasodium triphosphate, or its salt, citric acid or its salt, or combinations of these.
The present invention will now be further illustrated by the following non-limiting examples.

Table 1 shows the storage stability of several exemplary stabilized concentrated cleaning solutions prepared in accordance with the present invention, as well as several comparative solutions. Each solution was prepared by simply mixing the components in the order and amounts indicated. Further, all amounts indicated are weight percents, based on the total weight of the solution.
Once prepared, the solutions were stored at or about room temperature (25 C) and visual evaluations taken at 10 weeks, 3 months, 6 months and 1 year. The evaluations were scaled as follows: 0 = no precipitates, 1 =
minimal precipitates, commercially acceptable, 2 = some precipitates, not commercially acceptable, 3 = many precipitates, not commercially acceptable.

-11 -Table 1 Formula Comp Test Comp Test 2 Comp Test 3 Comp Test 4 Comp Test Test 1 1 2 3 4 5 5 5a Demi H20 46 45.9 24.3 23.95 38 37.95 18 17.95 24.5 24.4 23.5 EDTA 0.05 0.05 0.05 0.05 0.05 . -SokalanTM 1 CP45' BayhibitTM 2 2 0.7 0.7 7 7 2 2 0.5 0.5 0.5 AM(60%) NaOH (50%) 17 17 15 15 35 35 10 10 5 5 5 KOH(50%) 10 10 Na0C1 35 35 60 60 20 20 60 60 70 70 70 (17%) Precipitates 2 0 2 0 3 0 3 0 1 0 0 1 Sokalan CP45 is a polyacrylate and acts as a dispersant in the exemplified solutions 2 Bayhibit AM is a polyphosphonate and acts as a sequestrant in the exemplified solutions As is shown, 0.05% EDTA effectively prevents the formation of visible levels of precipitates in all of the tested solutions.

Table 2 shows the storage stability of several exemplary stabilized concentrated cleaning solutions prepared in accordance with the present invention, as well as a comparative solution. Each solution was prepared by simply mixing the components in the order and amounts indicated.
Further, all amounts indicated are weight percents, based on the total weight of the solution.

- 12 -Once prepared, the solutions were stored at or about room temperature (25 C) and visual evaluations taken at 10 weeks, 3 months, 6 months and 1 year. The evaluations were scaled as follows: 0 = no precipitates, 1 =
minimal precipitates, commercially acceptable, 2 = some precipitates, not commercially acceptable, 3 = many precipitates, not commercially acceptable.
Table 2 Formula 1(Test) 2 3 4 5 6 Demi H20 - 24.5 24.5 24.5 24.5 24.5 24.4 24 23.5 23 22.5 22 EDTA 0 0.0001 0.001 0.005 0.05 0.1 0.5 1.0 1.5 2 2.5 Sokalan 0 0 0 0 0 0 o 0 o o 0 Bayhibit- 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 AM (60%) NaOH 23 (50%) Na0C1 50 Precipitates 3 1 0 0 0 0 o 1 1 1 As shown, at all but one concentration of EDTA, visible precipitates were substantially reduced, or even eliminated, as compared to test solution 1.
Solution 11, with an EDTA concentration of 2.5% showed an unacceptable level of precipitates.

Claims

What is claimed is:

1. A stabilized concentrated cleaning solution comprising:
(i) from about 5 wt% to about 35 wt% hydroxide ion source;
(ii) from about 20 wt% to about 70 wt% hypochlorite ion source; and (iii) from about 0.0002 wt% to about 0.5 wt% chelating agent.

2. The stabilized concentrated cleaning solution of claim 1, comprising (i) from about 15 wt% to about 30 wt% hydroxide ion source;
(ii) from about 40 wt% to about 60 wt% hypochlorite ion source; and (iii) from about 0.0005 wt% to about 0.05 wt% chelating agent.

3. The stabilized concentrated cleaning solution of claim 1, wherein the chelating agent comprises EDTA, MGDA, NTA, IDS, polyacrylate or combinations of these.

4. The stabilized concentrated cleaning solution of claim 2, wherein the chelating agent comprises EDTA, MGDA, NTA or combinations of these.

5. The stabilized cleaning solution of claim 1 or 2, wherein the hydroxide ion source comprises sodium hydroxide, potassium hydroxide or combinations of these.

6. The stabilized cleaning solution of claim 1 or 2, wherein the hypochlorite ion source comprises sodium hypochlorite, potassium hypochlorite or combinations of these.

7. The stabilized concentrated cleaning solution of claim 2, wherein the hypochlorite ion source comprises sodium hypochlorite.

8. The stabilized concentrated cleaning solution of claim 2, wherein the chelating agent comprises EDTA.

9. A method for stabilizing a concentrated cleaning solution comprising an oxidant according to any one of claims 1-6, the method comprising:
(i) providing a concentrated cleaning solution comprising a hypochlorite ion source;
(ii) providing a chelating agent; and (iii) adding the chelating agent to the concentrated cleaning solution.