Synergistic stain removal through novel MGDA and GLDA chelator combination

Abstract

The invention relates to a concentrated detergent composition comprising an alkali metal carbonate, methylglycinediacetic acid, glutamic acid N,N-diacetic acid, and alkali metal tripolyphosphate. The composition is particularly suited to remove tea and coffee soil in warewashing applications.

Claims

1. A concentrated detergent composition comprising: alkali metal carbonate, methylglycinediacetic acid, glutamic acid N,N-diacetic acid, and alkali metal tripolyphosphate; wherein the molar ratio of the sum of glutamic acid N,N-diacetic acid, methylglycinediacetic acid and alkali metal tripolyphosphate to alkali metal carbonate is 0.01 to 0.5.

2. The concentrated detergent composition according to claim 1, wherein the molar ratio of methylglycinediacetic acid to alkali metal tripolyphosphate is 0.14 to 14.3.

3. The concentrated detergent composition according to claim 1, wherein the molar ratio of glutamic acid N,N-diacetic acid to the sum of methylglycinediacetic acid and alkali metal tripolyphosphate is 0.03 to 29.

4. The concentrated detergent composition according to claim 1, wherein the composition comprises at least 5% by weight alkali metal carbonate.

5. The concentrated detergent composition according to claim 1, wherein the alkali metal carbonate is sodium or potassium carbonate, sodium or potassium bicarbonate, sodium or potassium sesquicarbonate, or a mixture thereof.

6. The concentrated detergent composition according to claim 1, wherein the alkali metal tripolyphosphate is sodium tripolyphosphate.

7. The concentrated detergent composition according to claim 1, wherein the composition provides a pH of at least 6 when diluted in distilled water at a concentration of 1 g/l and measured at a temperature of 20? C.

8. The concentrated detergent composition according to claim 1, wherein the composition further comprises at least one compound selected from the group consisting of surfactants, bleaching agents, activating agents, additional chelating/sequestering agents, silicates, detergent fillers or binding agents, defoaming agents, anti-redeposition agents, enzymes, dyes, odorants, catalysts, threshold polymers, soil suspension agents, antimicrobials and mixtures thereof.

9. The concentrated detergent composition according to claim 1, wherein the composition is provided in the form of a solid, a powder, a liquid, a gel, or a paste.

10. An aqueous solution comprising 0.1 to 10 g/l of the concentrated detergent composition according to claim 1.

11. A method of warewashing comprising: obtaining the concentrated detergent composition according to claim 1; and introducing the concentrated detergent composition to soiled dishware as a warewashing detergent for the removal of soil comprising oxidized polyphenols and calcium silicates.

12. The method according to claim 11, wherein the concentrated detergent composition is diluted to provide a use solution with a concentration of 0.1 to 10 g/l.

13. The method according to claim 12, wherein the concentrated detergent composition is diluted with water having a hardness of at least 50 mg/l CaCO.sub.3.

14. The method according to claim 11, wherein the concentrated detergent composition is used for the removal of tea and coffee soil.

Description

EXAMPLES

(1) The following examples illustrate the invention by testing the removal of tea and coffee soil from ceramic tiles.

(2) Ceramic tiles (5.1?15.2 cm white, glazed ceramic tiles) were stained with tea soil (Lipton brand tea) according to the following procedure. Hard water having a hardness of >249.9 mg/l CaCO.sub.3 was heated to >71? C. The tea was then mixed into the hot hard water. The ceramic tiles were then immersed into the tea for 1 min and then taken out for 1 min to dry. This procedure was repeated until a stain was formed, which was typically after 25 cycles. The tiles were then cured for 48 hrs at room temperature. At this time the tiles are ready for testing.

(3) Cleaning test were carried out in a standard automatic dishwasher. The cleaning efficiency was evaluated by visually comparing the amount of soil left on the tiles after one full cleaning cycle to the amount of soil on the tiles before the cleaning procedure. The results were rated according to table 1:

(4) TABLE-US-00001 TABLE 1 Rating % of stain removal 1 100 2 80-99.9 3 20-79.9 4 <20 5 no removal

(5) A rating of 1 was considered to be an excellent result. A rating of 2 (at least 80% stain removal) was considered to be an acceptable cleaning performance.

(6) The complexing agents shown in table 2 were tested for their effect on cleaning efficiency. For each complexing agent the theoretical concentration of the 100% active compound required to cover 85.5 mg/l CaCO.sub.3 of water hardness was calculated on the basis of the calcium binding capacity and the activity of the raw materials. The concentration given relates to the respective sodium salts. It should be noted that the calcium binding capacities in table 2 give the amount of CaCO.sub.3 bound by a given amount of the raw material having an activity that can be lower than 100%, as specified in table 2.

(7) TABLE-US-00002 TABLE 2 Ca- Amount of binding 100% active capacity material of raw Activity required for Trade material of raw 85.5 mg/l Complexing agent name (mg/g) material CaCO.sub.3 (mg/l) methylglycinediacetic Trilon M 310 83% 229 acid (MGDA) Granules SG sodium 232 100% 369 tripolyphosphate (STPP) glutamic acid N,N- Dissolvine 138.2 47% 291 diacetic acid (GLDA) 47S iminodisuccinate (IDS) Baypure 111.8 34% 260 CX100

(8) The cleaning efficiency of different detergent formulations containing 1000 mg/l sodium carbonate and varying amounts of complexing agents was tested. All formulations were prepared in water having a hardness of 85.5 mg/l CaCO.sub.3. The concentrations given relate to the concentrations of the 100% active compounds in the use solution.

(9) A first series of tests involved a combination of varying amounts of MGDA, STPP, and GLDA. Based on the calcium binding capacities and activities of the raw materials given in table 2, the theoretical amount of water hardness (expressed in mg/l CaCO.sub.3) covered was calculated for each formulation and was compared to the cleaning effect achieved by the formulation. The test data are shown in table 3.

(10) TABLE-US-00003 TABLE 3 Example 1 2 3 4 5 6 7 8 9 10 GLDA (mg/l) 75 100 100 75 50 25 100 75 50 25 MGDA (mg/l) 100 100 125 125 125 125 125 125 125 125 STPP (mg/l) 100 100 125 125 125 125 100 100 100 100 CaCO.sub.3 82.6 89.9 105.0 97.7 90.4 83.0 99.2 91.9 84.6 77.2 covered theoretically (mg/l) Rating 2 1 1 1 1 1 1 1 1 2

(11) The results showed that with the inventive combination of complexing agents in a carbonate based cleaning solution, acceptable to excellent cleaning results can be achieved even at a total concentration of complexing agents less than what would be theoretical required to cover 85.5 mg/l CaCO.sub.3 of water hardness (examples 1, 6, 9 and 10). The combination of GLDA, MGDA, and STPP in a carbonate based detergent composition therefore exhibits synergy with respect to the cleaning effect. This allow to minimize the total amount of complexing agents used in a detergent composition.

(12) A second series involved the combination of MGDA, STPP, and IDS (table 4).

(13) TABLE-US-00004 TABLE 4 Example 1 2 3 4 5 6 7 8 9 10 IDS (mg/l) 75 100 100 75 50 25 100 75 50 25 MGDA (mg/l) 100 100 125 125 125 125 125 125 125 125 STPP (mg/l) 100 100 125 125 125 125 100 100 100 100 CaCO.sub.3 85.2 93.4 108.6 100.3 92.1 83.9 102.8 94.5 86.3 78.1 covered theoretically (mg/l) Rating 3 2 1 1 1 2 1 2 2 3

(14) The results of the second series showed that the overall cleaning performance of the combination of IDS, MGDA, and STPP is lower than for the combination of GLDA, MGDA, and STPP, even though the total concentrations of complexing agents are the same. This is unexpected as the theoretically required amount of IDS to cover 85.5 mg/l CaCO.sub.3 of water hardness is lower than for GLDA and hence IDS should be more effective than GLDA (table 2). Further, as the total concentration of complexing agents drops below the amount required to fully cover 85.5 mg/l CaCO.sub.3 of water hardness (examples 1 and 10) the cleaning efficiency becomes unacceptable, in contrast to the combination of GLDA, MGDA, and STPP. The combination of IDS, MGDA, and STPP therefore does not exhibit synergy.