WO2009108552A1

WO2009108552A1 - Low leaching bottle wash additive

Info

Publication number: WO2009108552A1
Application number: PCT/US2009/034383
Authority: WO
Inventors: Holger Theyssen; Hermant Godbole; Stefan Grober; Uday Chaudhari
Original assignee: JohnsonDiversey Inc
Current assignee: Diversey Inc
Priority date: 2008-02-26
Filing date: 2009-02-18
Publication date: 2009-09-03
Anticipated expiration: 2010-08-26
Also published as: CN101952405A; BRPI0908013A2; MX2010009417A; ZA201005932B; CN101952405B

Abstract

A method of reducing leaching of metal from glassware contacted with a caustic wash, the glassware having an applied ceramic label, the method comprising contacting the glassware with a composition comprising EDTA and protective metal ions selected from zinc ions and aluminum ions in a concentration effective to reduce leaching of metal from the glassware.

Description

LOW LEACHING BOTTLE WASH ADDITIVE

INTRODUCTION

[0001] Washing of glass bottles for subsequent reuse often involves soaking the bottles in a caustic solution, e.g. a solution containing sodium hydroxide (NaOH), at elevated temperatures. However, these conditions can result in degradation of the glass and of applied ceramic labels (ACLs) on the bottles. Commonly used wash components, which are added to enhance cleaning, may promote degradation of glass and ACLs. Degradation of ACLs containing metal-based pigments such as zinc-, lead-, cadmium-, aluminum-, or beryllium-based pigments, can lead to release or leaching of metals into the wash solution.

[0002] Leaching of metals from the ACL can cause reduced gloss, fading, and other aesthetic degradation of the labels, which can lead to a high rejection rate of the reused bottles. Increased degradation of ACLs may be unacceptable in that an otherwise useful bottle may be rejected for having a degraded label.

SUMMARY

[0003] The invention provides a method of reducing leaching of metal from glassware contacted with a caustic wash, the glassware having an applied ceramic label, the method comprising contacting the glassware with a composition comprising EDTA and protective metai ions selected from zinc ions and aiuminum ions in a concentration effective to reduce leaching of metal from the glassware,

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1 is a bar graph showing the normalized concentrations of heavy metals (left: Pb; right: Cd) recovered from the combined wash and rinse solutions after treatment of ACL-containing bottles in the listed wash conditions.

[0005] Figure 2 is a bar graph showing the normalized concentrations of heavy metals (left: Pb; right: Cd) in a wash solution containing 0.3% of a commercially-available wash additive concentrate (hereinafter designated Product I) in the presence of various concentrations of aluminum and zinc. [0006] Figure 3 is a bar graph showing the gloss levels of the front and back labels of bottles following various numbers of wash cycles in caustic solution, in the presence or absence of added zinc and aluminum.

[0007] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limited.

DETAILED DESCRIPTION

[0008] Caustic wash solutions for washing glassware are typically high alkaline, and caustic washes are performed at relatively high temperatures. Sequestrants such as ethylenediamine tetraacetic acid (EDTA) are often added to cleaning solutions to enhance cleaning and detergency. For example, sequestrants promote mold removal and chelate metal ions such as calcium and magnesium that are present in hard water and which might otherwise interfere with the cleaning properties of the composition.

[0009] Sequestrants such as EDTA may cause degradation of glassware during a caustic wash, for example by promoting leaching of metals from glassware and ACLs, by causing fading of ACLs, or by reducing gloss of ACLs.

[0010] One approach that has been taken to reduce degradation of glassware and/or ACLs due to caustic washing has been to reduce or eliminate sequestering compounds, particularly EDTA, from cleaning solutions. However, removal of EDTA from the caustic wash leads to reduced detergency that may reduce the effectiveness of the wash. Therefore, there is a need for methods to reduce the metal leaching and related degradation of glassware and ACLs during caustic washes containing EDTA.

[0011] Thus, one aspect of the present invention provides compositions and methods for reducing leaching of metals from glassware during caustic washing, particularly from glassware having applied ceramic labels (ACLs). In particular, the addition of protective metal ions protects glassware against leaching in caustic wash solutions containing chelating agents, including, without limitation, EDTA, EGTA, NTA, DTPA, HElDA, IDS, MGDA, and the like, either alone or in combination with other chelators. In one embodiment, the invention comprises contacting glassware with protective metal ions in concentrations effective to reduce leaching of metals from glassware subjected to a caustic wash containing EDTA.

[0012] The metals that may be leached from the glassware and/or ACLs applied to the glassware can include, for example, lead (Pb), cadmium (Cd), zinc (Zn), aluminum (Ai), beryllium (Be), calcium (Ca) and magnesium (Mg), and combinations thereof. Leaching refers to the removal of the particular metal from the glassware and/or ACL. Leaching may be determined using any suitable method, for example, by measuring the amount of a particular metal in a wash solution that has contacted glassware and/or ACLs.

[0013] Protective metal ions added to the caustic wash solution may include aluminum or zinc ions, used either alone or in combination, in a concentration effective to reduce leaching of metals from glassware containing ACLs.

[0014] A concentration of protective metal ions effective to reduce leaching as used herein is a concentration that is sufficient to reduce leaching of metals from glassware and/or ACLs relative to a suitable control, for example a similar caustic wash conducted without the protective metal ions. Leaching of metals from glassware and/or ACLs may be assessed by measuring the amount of one or more metals of the type ordinarily present in the glassware or ACLs in the wash solution following a caustic wash. Suitably, leaching is reduced by at least about 1%, at least about 2%, at least about 5%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, or at least about 99%. Suitably, the concentration of protective metal ions is effective to reduce adverse effects of caustic washing on glassware and/or ACLs, i.e. to reduce fading of ACLs or to prevent reduced gloss of ACLs, relative adverse effects of caustic washing conducted on glassware and/or ACLs not contacted with protective metals. Fading or gloss of ACL labels may be measured by any suitable means, including those described in the Examples.

[0015] As shown in the Examples below, ACLs exposed to washes according to the methods of the invention exhibit reduced fading and reduced loss of gloss compared with washes conducted in the absence of protective metals. Without being limited as to theory, the reduced fading and reduced loss of gloss is believed to be due to reduced leaching of metals from the ACLs. Leaching of metals from ACL-containing glassware is believed to be correlated with other adverse effects on the glassware and particularly the associated ACLs, e.g. the fading and reduced gloss of the ACLs. The use of protective metal ions as described herein may reduce adverse effects of caustic washing on glassware and/or ACLs by a mechanism unrelated to metal ion leaching. Reduction of adverse effects on glassware and/or ACLs by addition of protective metal ions is encompassed within the present invention regardless of the underlying basis for the reduction.

[0016] In one embodiment, the protective metal ions (i.e. aluminum or zinc alone, or in combination) are added to the wash solution to provide a concentration effective to reduce leaching, reduce ACL fading, or to reduce loss of gloss. It is expected that concentrations of protective metal ions that provide a ratio of the molar concentration of the protective metal ions to the molar concentration of EDTA (molar ratio) is in a range of from about 0.1 to about 9 are expected to be effective. Suitably, molar ratios of protective metal ions to EDTA are in ranges of from about 0.9 to about 9, from about 1 to about 9, from about 1.8 to about 9, or from about 2 to about 9. The molar ratio of protective metal ions to EDTA sequestrant may be at least about 1.1, at least about 1.2, at least about 1.3, at least about 1.4, at least about 1.5, at least about 1.6, at least about 1.7, at least about 1.8, at least about 1.9, or at least about 2.0. As one skilled in the art will appreciate, molar ratios of greater than 9.0 may also be used. !n each case, the aluminum and/or zinc may be provided as a soluble compound including, for example, a soluble salt, which may form a hydroxide of the metal ion. Metals such as aluminum or zinc may be added to the solution in one form, for example as chloride salts, which then form hydroxides in the caustic wash solution.

[0017] Zinc and aluminum may be used in combination, for example, at ratios of zinc to aluminum, by weight, ranging from about 0.1 to.about 10.0. In the examples,- zinc and aluminum were used at a ratio, by weight, of about 2. As one of skill in the art will appreciate, since either aluminum or zinc is effective when used in the absence of the other, other ratios of zinc to aluminum above 10.0 or below 0.1 will also be effective. As in the Examples, zinc and aluminum may be added to the wash as soluble salts and form metal hydroxides. For example, zinc and aluminum may be added to the wash solution as chloride salts, e.g. AICI₃ and ZnCI₂, which may then form hydroxides in the caustic solution.

[0018] Without being limited as to theory, the addition of protective metal ions reduces free EDTA that can leach metal from the glass or ACLs, thus reducing undesired leaching. The interaction between EDTA and zinc or aluminum is sufficiently weak that aluminum and zinc will not interfere with the ability of the EDTA to chelate calcium or magnesium. Therefore, the activity of EDTA is not expected to be diminished by the presence of added aluminum and zinc ions. It is expected that the concentration of protective metal ions needed to reducing leaching may vary depending on the hardness of the water, since the hard water ions (e.g. Ca²⁺ and Mg^2*) will bind to some of the EDTA that is present, thus reducing the amount of the protective metal ions needed to bind free EDTA. [0019] Suitably, EDTA is present during a caustic wash in a concentration effective to afford the desired detergency. Thus, in one embodiment the caustic wash solution contains EDTA at a final concentration of at least about 0.5 millimolar. In other embodiments, EDTA is present at a final concentration of at least about 0.1 millimoiar; at least about 0.2 millimolar; at least about 0.3 millimoiar; at least about 0.4 millimolar; at least about 0.6 millimolar; at least about 0.7 millimoSar; at least about 0.8 millimolar; at least about 0.9 millimolar; at least about 1.0 millimolar; at least about 1.1 millimolar; at least about 1.2 millimolar; at least about 1.3 millimolar; at least about 1.4 millimolar; at least about 1.5 millimolar; at least about 1.6 miilimolar; at least about 1.7 millimolar; at least about 1.8 millimolar; at least about 1.9 millimolar; and at least about 2.0 millimolar.

[0020] As shown in Example 1 below, the inclusion of a molar excess of protective metal ions in the caustic wash solution led to a substantial reduction of leaching (reduced to 30- 40% of the control level) as assessed by the amounts of Pb and Cd in the wash solution. This decrease in leaching was possibly due to a reduction of free available EDTA in the wash solution. The results demonstrate that wash solutions containing a higher molar concentration of aluminum than the molar concentration of EDTA substantially reduce the amount of heavy metai leaching.

[0021] In the Examples, EDTA was added as a tetrasodium salt (Na₄-EDTA). One of skill in the art will appreciate that other forms of EDTA may be used. While the Examples of the present application focus on the use of EDTA, it is expected that the present methods and compositions would be suitable for use with other chelators, in particular chelators that have a high detergency but which cause degradation of glass and/or ACLs.

[0022] In the Examples below, the glassware and ACLs were contacted with the protective metal ions. In general, contacting the glassware and/or ACLs with protective metal ions includes bringing the protective metal ions into contact with the glassware and/or ACLs at some point during the caustic wash. The glassware and/or ACLs may be contacted with the protective metal ions before exposing the glassware and/or ACLs to the caustic wash. Alternatively, the glassware and/or ACLs may be contacted with the protective metal ions at the same time as the glassware and/or ACLs are exposed to the caustic wash, e.g. the protective metal ions may be incorporated into the caustic wash as in the Examples below. In addition, the glassware and/or ACLs may be contacted by the protective metal ions after the glassware and/or ACLs are exposed to the caustic wash solution. The protective metal ions may be incorporated as a separate component into the caustic wash, or the protective metal ions may be incorporated into an additive concentrate. [0023] Caustic wash solutions typically include 2-4% (w/v) of caustic agent and caustic washing is typically conducted at elevated temperatures, for example between 70°C and 8O⁰C₁ although other percentages of caustic agent and other temperatures may be used with the methods of this invention. While in the Examples the caustic wash solution contains sodium hydroxide as the caustic agent, it is anticipated that the methods of the present invention can be used with other alkaline caustic agents, such as potassium hydroxide, under a variety of conditions.

[0024] The following non-limiting Examples are intended to be purely illustrative, and show specific experiments that were carried out in accordance with embodiments of the invention:

EXAMPLE 1

[0025] The following table and graphs show the results of leaching studies that have been conducted in accordance with the present invention. Aluminum and/or zinc have been combined in varying amounts with different amounts of EDTA in a caustic wash solution containing 3% sodium hydroxide, pH > 13. In each experiment, four glass bottles, each having two applied ceramic labels (ACLs) thereon, were soaked in the wash solution at an elevated temperature (75°C) for five hours.

[0026] Each group, or phase, of measurements was performed in parallel with a standard wash additive, Product I, which is a heavy-duty wash additive concentrate containing 24% EDTA (w/v). The caustic wash solution in which the bottles were soaked and a solution used to rinse the bottles after soaking were collected and analyzed for heavy metal content, specifically the amount of lead (Pb) and cadmium (Cd), The concentrations in parts per million (ppm) were determined for the combined caustic wash plus rinse solutions for each set of experiments. To facilitate comparison of results, each phase of experiments includes a control sample obtained with 0.3% Product I in the caustic wash solution without added zinc or aluminum. The Pb and Cd concentrations in these control samples were each set to 10 ppm, and the Pb and Cd concentrations from other experiments within the same phase were normalized to the Pb and Cd levels of the control samples.

[0027] Besides Product i, other commercially-available wash additive concentrates were tested as well, designated Products M-VII. The concentrations of various components of the compounds are listed in Table I. For example, the concentration of EDTA in the concentrated stock solution of each of the additive concentrates is shown in Table I in the column labeled "%EDTA". The stock solution of each additive was combined into the caustic wash solution at a 0.3% final dilution. That is, the stock additive solution was used at a ratio of 3 parts per thousand, for example 3 milliliters of concentrated additive product per liter of final caustic wash solution. The final percentage of EDTA in the caustic wash solution for each experiment is 0.003 times the percentage shown in the column labeled "%EDTA". Thus, for example, in experiment number 3 from Table I below, a 0.3% solution of Product 1 was used, the additive having 24% EDTA. Therefore, the final concentration of EDTA in the soak solution of experiment 3 was 0.072%, or 720 parts per million (ppm), given that a 1% solution equals 10,000 ppm.

[0028] Other components were added to the wash solution in amounts as indicated in Table I, including: sodium gluconate; PBTC (50% solution of phosphono 1,2,4 butanetricarboxyiic acid in water), a scale and corrosion inhibitor; TSP (trisodium phosphate); TEA {Methanol amine); and SMS (sodium metasilicate). The values given in Table I for EDTA₁ sodium gluconate, PBTC, TSP, and TEA are percentages (w/v) of each respective substance in the stock solution of additive product.

[0029] The experiments were conducted in groups, or phases, to test different variables, as listed below:

Trial Sets:

Phase i: Effect of increased levels of EDTA

Phase ii: Influence of TSP and combination of Zn/Al 2:1 ratio

Phase iii: Influence of TEA and metasilicate

Phase Iv: Effect of competitor product

Phase v: Influence of metal gluconates

Phase vi: Influence of non EDTA based formulation (Product VII)

Phase vii: Influence of increased Zn/A! concentrations in absence of gluconate

Phase viii: Influence of decreased Zn/Al concentrations in absence of gluconate

Phase ix: Influence of separate, equimolar Zn/Al additions

Phase x: Influence of increased Al concentrations Table I

NS TSP equivalent to 26% and phosphonate as HEDP 10.5%

SMS Sodium metasilicate n (metal ions/EDTA) = coefficient on mol_M/ TΠOIED_JA [0030] As discussed above, the heavy metal concentrations ("Pb Ind," "Cd Ind") have been normalized to the results obtained using Product I (benchmark, ppm(Pb)=10, ppm(Cd)=10) in each single measurement set. Further, the molar relation between Zn/AI concentration and EDTA-Na₄ has been calculated as: n(metals) / n(EDTA-Na₄), where "n" is the number of moles.

[0031] The graph in Figure 1 shows the amount of heavy metal leaching associated with the use of different additives. Each of the additives contains EDTA except for Product VII, which shows lower levels of leaching. Addition of TEA, SMS, zinc gluconate, or aluminum gluconate at the levels shown did not substantially reduce leaching.

[0032] Easily soluble metal hydroxides have then been tested mainly in a Zn:AI ratio (w/w) of 2:1, although other ratios are possible and are encompassed within the scope of the invention. The graph in Figure 2 shows leaching of Pb and Cd (reported as normalized concentrations of Pb and Cd in the wash plus rinse solutions) associated with use of 0.3% Product I alone or with different additions of Zn/AI. In each case where both zinc and aluminum were added, the metals were present in a ratio relative to one another of 2:1 (w/w). The molar ratio of the combination of metal ions to EDTA-Na₄ is shown in the legend. In addition, results are also shown for experiments in which zinc or aluminum alone were added to the wash solution, in the molar ratios relative to EDTA as shown in the legend.

[0033] Providing a higher molar concentration of metal ions than the molar concentration of EDTA led to a substantial reduction of leaching (30-40%), possibly due to a reduction of free available EDTA in the wash solution. An excess of aluminum resulted in a substantial reduction in heavy metal leaching was seen (Figure 2, "Product I w/Al (1.956)").

EXAMPLE 2

[0034] in this example, assessments have been made of the effects of added zinc and aluminum ions on the gloss of glassware with ACLs as welt as the degree of fading of the ACLs.

[0035] Gloss fading tests with Product I and with addition of slightly excessive amounts of metal ions (n=1.2) have been carried out. Two different sets of glass bottles having ACLs with zinc-based pigments have been tested. Samples from each set of bottles were been soaked in one of two different compositions:

Solution A: 3% NaOH and 0.3% Product I₁ at 80⁰C

Solution B: 3% NaOH; 0.3% Product I; 67 ppm Zn; and 33.5 ppm Al, at 80⁰C.

[0036] The metal ion additions were realized by adding 139.74 mg/liter ZnCl₂ and 299.64 mg/liter AICI₃'6H₂O. At these concentrations of Product I (which has 24% EDTA in the stock solution) and metal ions, the molar concentration of the combination of aluminum and zinc ions is approximately 1.2 times the molar concentration of EDTA.

[0037] The bottles were immersed in either Solution A or Solution B at contact times corresponding to 5, 10, 20, and 30 cycles, where one cycle lasts seven minutes. After treatment, the bottles were rinsed with softened water. The bottles were then evaluated by visual inspection for gloss and fading of the labels. Additionally, the gloss levels on one set of bottles were quantitatively determined using a gloss meter. Table Il summarizes the experiments that were carried out.

[0038] Overall, the results of these experiments showed that the addition of amounts of metal ions in a molar ratio of 1.2 over EDTA (Solution B) led to a substantial reduction of gloss and color fading in the presence of an EDTA-based bottie wash additive. It was observed that gloss fading starts during the first five cycles with EDTA-based wash agents such as Product I (Solution A). Addition of zinc and aluminum ions, as in Solution B, extended the brilliant appearance of an ACL to at least ten cycles.

Table II

[0039] The graph in Figure 3 shows gloss measurements of the front and back ACL labels taken following different lengths of treatment with caustic wash solution, in the presence or absence of added zinc and aluminum ions, as shown in the legend. The graph shows an indication of glossiness of the label, reported as the percentage of incident light that is reflected back from the label. The surface is illuminated at an angle of 60° relative to the surface and the reflection is measured at an angle of 60° relative to the surface on the opposite side of a line normal to the surface.

[0040] Treatment of bottles with caustic wash solution in the absence of added zinc and aluminum ions (Solution A) showed a stronger negative impact on ACL appearance, which was confirmed qualitatively by visual evaluation. Bottles washed treated with added zinc and aluminum (Solution B) showed higher gloss than that of control bottles not contacted with protective metals (Figure 3).

[0041] Qualitative visual assessment indicated that gloss fading of the letters was noticeable after five cycles of caustic wash with Product I alone (Solution A), while addition of a slight excess of zinc and aluminum (Solution B) helped maintain glossiness until ten cycles. After thirty cydes the colors of the bottles washed in the absence of zinc and aluminum (Solution A) exhibited more fading than bottles washed in the presence of added zinc and aluminum (Solution B).

[0042] Similar qualitative effects were observed with other sets of tested bottles that maintained their gloss after being exposed to ten wash cycles in the presence of added zinc and aluminum (Solution B). In contrast, bottles washed without added zinc and aluminum (Solution A) exhibited noticeably reduced gloss after just five cycles. An assessment of the free available EDTA concentration by titration with zinc sulfate solution showed that there was 0.07% Na₄^EDTA in the wash solution having Product I alone, whereas the wash solution having added zinc and aluminum showed no remaining free available (unbound) EDTA.

[0043] Throughout this disclosure, various aspects of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity, and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, as will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof, as well as integral and fractional numerical values within that range. [0044] The above detailed description of the invention is illustrative of certain embodiments of the invention and is not intended to limit the scope of the invention as set forth in the appended claims.

Claims

CLAIMSWhat is claimed is:

1. ethod of reducing leaching of metal from glassware contacted with a caustic wash comprising EDTA, the glassware having an applied ceramic label, comprising: contacting the glassware with a composition comprising protective metal ions selected from zinc ions and aluminum ions, wherein the concentration of protective metal ions is effective to reduce leaching of metal from the glassware.

2. he method of claim 1 , wherein the molar ratio of the protective metal ions to EDTA is >1.

3. he method of claim 1 , wherein the composition comprises zinc ions.

4. The method of claim 1, wherein the composition comprises aluminum ions.

5. The method of claim 1, wherein the composition comprises zinc ions and aluminum ions.

6. The method of claim 5 wherein the ratio (w/w) of zinc ions to aluminum ions is in the range of from about 0.5 to about 3.

7. The method of claim 6, wherein the ratio fw/w) of zinc ions to aluminum is about 2.

8. The method of any of claims 1-7, wherein the molar ratio of the metal ions to EDTA is at least about 1.2.

9. The method of claim 8, wherein the molar ratio of the metal ions to EDTA is at least about 1.5.

10. The method of claim 8, wherein the molar ratio of the metal ions to EDTA is at least about 2.0.

11. The method of any of claims 1 -10, wherein the caustic wash comprises sodium hydroxide.

12. The method of any claims 1-11, wherein the glassware is contacted with the composition for at least a portion of the time that the glassware is contacted with the caustic wash.

13. The method of any of claims 1-12, wherein the glassware is contacted with the composition and the caustic wash substantially simultaneously.

14. The method of any of claims 1-12, wherein the glassware is contacted with the composition prior to contacting the glassware with the caustic wash.

15. The method of any of claims 1-13, wherein the composition is comprised within the caustic wash.

16. The method of claim 15, wherein the concentration of EDTA is effective to enhance cleaning of the glassware.

17. The method of claim 16, wherein the caustic wash comprises at least about 0.1 mϋlimolar EDTA.

18. The method of claim 16, wherein the caustic wash comprises at least about 0.5 millimolar EDTA.

19. The method of claim 16, wherein the caustic wash comprises at least about 1.2 millimoiar EDTA.

20. The method of claim 16, wherein the caustic wash comprises at least about 1.7 miliimolar EDTA.

21. The method of any of claims 1-18, wherein the amount of heavy metal leached from the glassware into the caustic wash is reduced.

22. The method of any of claims 1-19, wherein degradation of the applied ceramic label is reduced.

23. The method of claim 20, wherein degradation comprises reduced gloss or fading.

24. A method of protecting applied ceramic labels on glassware from reduced gloss or fading during caustic washing with a caustic wash solution comprising EDTA, comprising: contacting the glassware with a composition comprising protective metal ions selected from zinc ions and aluminum ions, or a combination thereof, wherein the concentration of protective metal ions is effective to reduce fading or loss of gloss.