Synergistic stain removal through an alkali metal hydroxide-based detergent composition with novel chelator combination

Abstract

The invention relates to a concentrated detergent composition comprising an alkali metal hydroxide, 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: a) an alkali metal hydroxide, b) an alkali metal tripolyphosphate, and c) at least one complexing agent selected from the group consisting of methylglycinediacetic acid and glutamic acid N,N-diacetic acid, wherein the molar ratio of the sum of glutamic acid N,N-diacetic acid, methylglycinediacetic acid, and alkali metal tripolyphosphate to alkali metal hydroxide is 0.01 to 1; and wherein said detergent composition does not comprise any alkali metal carbonates or amylase enzymes.

2. The concentrated detergent composition according to claim 1, wherein the composition comprises methylglycinediacetic acid and glutamic acid N,N-diacetic acid.

3. The concentrated detergent composition according to claim 1, wherein the molar ratio of alkali metal tripolyphosphate to the sum of alkali metal tripolyphosphate, methylglycinediacetic acid, and glutamic acid N,N-diacetic acid is 0.05 to 0.95.

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

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

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 9 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 of the compounds selected from the group consisting of surfactants, bleaching agents, activating agents, chelating/sequestering agents, silicates, detergent fillers or binding agents, defoaming agents, anti-redeposition agents, protease, lipase, gluconase, cellulase, peroxidase, catalase, dyes, odorants, catalysts, threshold polymers, soil suspension agents, antimicrobials and mixtures thereof.

9. The concentrated detergent composition according to claim 1, wherein the composition further comprises a polyacrylate, polymethacrylate, and/or polymaleate.

10. 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.

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

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

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

14. The method according to claim 12, wherein the warewashing detergent 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 and by digital image analysis, 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 the percentage of stain removal.

(4) To determine the breakpoint concentration of individual complexing agents, cleaning tests were performed with detergent use solutions comprising varying amounts of the complexing agent, 400 ppm NaOH, and 30 ppm polyacrylate (Acusol 445 ND). The breakpoint concentration was defined as the minimum concentration of the complexing agent required to achieve a stain removal of at least 90% in a single washing cycle. Table 1 shows the breakpoint concentrations determined for sodium tripolyphosphate (STPP), the sodium salt of methylglycine diacetic acid (MGDA), and the sodium salt of glutamic acid diacetic acid (GLDA). Please note that, in the following, the amounts of MGDA and GLDA are based on the respective sodium salts.

(5) TABLE-US-00001 TABLE 1 Breakpoint concentrations of different complexing agents. Complexing Breakpoint agent concentration (ppm) STPP 405 MGDA 200 GLDA 225

(6) Based on the individual breakpoint concentrations and assuming that the contributions of individual complexing agents are additive, the theoretically required amount of complexing agents in a detergent composition comprising a mixture of complexing agents can be calculated. For instance, 305 ppm of STPP would theoretically provide 305/405=75% of complexing agent activity needed for breakpoint results. The remaining 25% could theoretically be covered by 0,25×200 ppm=50 ppm MGDA. Alternatively, the remaining 25% could be covered by 33 ppm MGDA (equivalent to 33/200=16.5% of required activity) and 20 ppm GLDA (20/225=8.9%). Table 2 gives the theoretically required amounts of complexing agents in a use solution comprising varying amounts of STPP and at least one additional complexing agent.

(7) TABLE-US-00002 TABLE 2 Theoretically required concentrations of combinations of complexing agents to achieve breakpoint results. STPP MGDA GLDA (ppm) (ppm) (ppm) 305 33 20 275 43 24 278 42 24 278 62 278 70

(8) Cleaning tests were performed with detergent use compositions comprising 400 ppm NaOH, 30 ppm polyacrylate (Acusol 445 ND), varying amounts of STPP, and varying amounts of MGDA and/or GLDA. The resulting soil removal is shown in table 3.

(9) TABLE-US-00003 TABLE 3 Percentage of soil removal after one cleaning cycle with a use solution comprising 400 ppm NaOH, 30 ppm polyacrylate (Acusol 445 ND) and the indicated amounts complexing agents. STPP MGDA GLDA Soil Example (ppm) (ppm) (ppm) removal 1 305 26 16 100% 2 275 23 14  99% 3 278 24 14  99% 4 278 38 100% 5 278 38 100%

(10) The data in table 3 show that 99% of soil removal can be achieved by combinations of complexing agents, even though the individual amounts are lower than the theoretically required minimum (see table 2). In particular, the difference between the theoretically required amount and the actually required amount of MDGA in a STPP/MDGA mixture is 24 ppm (38.7%). In the case of GLDA in a GLDA/STPP mixture the difference is 32 ppm (45.7%).