Automatic Dishwashing Composition Comprising Metal Corrosion Inhibitors and Bleaches

Abstract

An automatic dishwashing product comprising a bleaching agent and a compound in accordance with formula (1) or a salt or tautomer thereof, wherein A and B are independently selected from the group consisting of H, OR.sup.1, and NHR.sup.2, wherein R.sup.1 and R.sup.2 are independently selected from the group consisting of H and C.sub.1-C.sub.4 alkyl, with the proviso that A and B are not both H and are not both OH.

Claims

1. An automatic dishwashing product comprising: a bleaching agent, and a compound in accordance with formula (1) or a salt or tautomer thereof: ##STR00018## wherein A and B are independently selected from the group consisting of H, OR.sup.1 and NHR.sup.2, wherein R.sup.1 and R.sup.2 are independently selected from the group consisting of H and C.sub.1-C.sub.4 alkyl, wherein A and B are not both H and are not both OH.

2. The automatic dishwashing product according to claim 1, wherein A is OH and B is NH.sub.2, or wherein A is NH.sub.2 and B is OH.

3. An automatic dishwashing product comprising: a bleaching agent, and a compound in accordance with formula (2) or a salt or tautomer thereof: ##STR00019## wherein X is OR.sup.3 or NHR.sup.3, wherein R.sup.3 is selected from the group consisting of H and C.sub.1-C.sub.4 alkyl.

4. The automatic dishwashing product according to claim 3, wherein the compound in accordance with formula (2) is ##STR00020## or a salt or tautomer thereof.

5. The automatic dishwashing product according to claim 3, wherein X is OH.

6. The automatic dishwashing product according to claim 1, wherein the bleaching agent and the compound in accordance with formula (1), or salt or tautomer thereof, are present in a weight ratio of from 20:1 to 500:1.

7. The automatic dishwashing product according to claim 1, wherein the bleaching agent is an oxygen-releasing bleaching agent.

8. The automatic dishwashing product according to claim 1, wherein the product has a pH of less than 11.5 at 1 wt % aqueous solution at 20° C.

9. The automatic dishwashing product according to claim 1, the automatic dishwashing product further comprising: one or more builders, and/or one or more surfactants, and/or one or more enzymes.

10. The automatic dishwashing product according to claim 1, wherein the product is: in a unit dose form; and/or housed within a water soluble or water dispersible film or container, preferably a polyvinyl alcohol film or container.

11. A method of automatic dishwashing, the method comprising: supplying a product to an automatic dishwasher; and releasing the product or a portion thereof into a wash cycle of the automatic dishwasher, the product comprising a bleaching agent, and a compound having a structure in accordance with formula (1) or (2) or a salt or tautomer thereof.

12. The method according to claim 11, wherein the automatic dishwasher contains silverware and/or copperware.

13. The method according to claim 11, wherein the product is formulated to provide, in use, a cleaning solution having a pH of less than 11.5 at a wash cycle temperature of from 30 to 65° C.

14. The method according to claim 1, wherein in the step of releasing the product or a portion thereof into a wash cycle of the automatic dishwasher, from 0.1 to 6.5 grams of bleaching agent and/or from 1 to 500 milligrams of the compound according to formula (1) or (2) are released into the wash cycle.

15. A method of using a compound according to formula (1) or (2) or a salt or tautomer thereof for reducing corrosion of silver and/or copper by a bleaching agent in an automatic dishwashing process.

16. The automatic dishwashing product according to claim 3, wherein the bleaching agent and the compound in accordance with formula (2), or salt or tautomer thereof, are present in a weight ratio of from 20:1 to 500:1.

17. The automatic dishwashing product according to claim 3, wherein the bleaching agent is an oxygen-releasing bleaching agent.

18. The automatic dishwashing product according to claim 3, wherein the product has a pH of less than 11.5 at 1 wt % aqueous solution at 20° C.

19. The automatic dishwashing product according to claim 3, the automatic dishwashing product further comprising: one or more builders, and/or one or more surfactants, and/or one or more enzymes.

20. The automatic dishwashing product according to claim 3, wherein the product is: in a unit dose form; and/or housed within a water soluble or water dispersible film or container, preferably a polyvinyl alcohol film or container.

Description

EXAMPLE 1

[0096] In order to evaluate the feasibility of the compounds listed below for use in ADW detergents, a base powder formulation without any silver/copper corrosion inhibitors was prepared and tested. To this formulation were added either 27 mg of a TTA powder mix as benchmark level of silver protection or a comparable amount of the test candidates.

[0097] General Methods

[0098] Silver corrosion experiments were conducted using the condition and evaluation scheme outlined below:

Test method: Material Care G404 V18 EU
Machine: modified Miele G 1222 SC GSL

Program: 65° C./65° C.

[0099] Water hardness: 21° dH
Rinse Aid: without rinse aid
Evaluators: 2 trained people

[0100] Scores:

5=no discolouration/shine loss
4=minor discolouration/shine loss
3=discolouration/shine loss visible
2=strong discolouration/shine loss
1=very strong discolouration/shine loss

[0101] All compounds used in the following experiments were obtained from commercial suppliers:

TTA (CAS No. 29385-43-1, Italmatch)

[0102] Indole-6-carboxylic acid (CAS No. 1670-82-2, Alfa Aesar)

Benzimidazole (CAS No. 51-17-2, Sigma Aldrich)

[0103] 5-Benzimidazolecarboxylic acid (CAS No. 15788-16-6, Sigma Aldrich)

Allantoin (CAS No. 97-59-6, Sigma Aldrich)

Guanine (CAS No. 73-40-5, Sigma Aldrich)

[0104] Uric acid (CAS No. 69-93-2, Alfa Aesar)

Cytosine (CAS No. 71-30-7, Alfa Aesar)

Xanthine (CAS No. 69-89-6, Alfa Aesar)

[0105] Phytic acid sodium salt hydrate (CAS No. 14306-25-3, Sigma Aldrich)
Folic acid (CAS No. 59-30-3, Sigma Aldrich)

[0106] The benchmark formulation of base powder for Examples 1 and 2 is shown below:

TABLE-US-00001 Raw Material g/dose Bleach system (Sodium 3.0 Percarbonate, TAED, manganese bleach catalyst) Builders 7.5 Surfactants/polymers 1.7 Sodium Carbonate/bicarbonate 7.5 Enzymes 0.1 Others (Antifoam, Fragrances, Dyes, etc.) rest TOTAL 20.00

[0107] The averaged results are shown in the table below:

TABLE-US-00002 20 g 20 g base base powder + powder 0.027 g 20 g base 20 base powder + 20 g + indole-6- powder + 0.027 g 5- base 0.027 g carboxylic 0.027 g benzimidazole- Test product: powder TTA acid benzimidazole carboxylic acid Silver 21° dH 25 1.0 3.1 1.2 1.1 2.3 tarnishing water cycles 0 5.0 5.0 5.0 5.0 5.0 cycles [00007][00008][00009][00010]

[0108] Whereas Indole-6-carboxylic acid and Benzimidazole both offer only two functional groups for molecular cross-linking and/or metal coordination (in addition to the n-electron system common to all of them), TTA and 5-Benzimidazole-carboxylic acid contain three distinct sites each capable of hydrogen bonding, metal coordination and/or crosslinking.

[0109] In conclusion, Example 1 shows that aromatic compounds for silver surface protection require at least three binding sites in their structure.

EXAMPLE 2

[0110] A selection of nitrogen-rich compounds each comprising an aromatic pi-electron system and several binding sites were evaluated, as well as natural products comprising multiple binding sites (e.g. carboxylic acids, phosphonic acid), using the method and base powder of Example 1. The results are shown in the table below.

TABLE-US-00003 20 g base 20 g base 20 g base powder + 20 base 20 g powder + powder + 0.027 g powder + base 0.027 g 0.027 g phytic acid, 0.027 g Test product: powder TTA folic acid Na-salt guanine Silver 21° dH 25 1.0 3.1 1.2 1.1 2.3 tarnishing water cycles 0 5.0 5.0 5.0 5.0 5.0 cycles [00011][00012][00013]

[0111] While all of these compounds—folic acid, phytic acid sodium salt, and guanine—showed a general improvement of the silver corrosion protection versus the Base Powder, only guanine achieved a comparable performance to TTA.

EXAMPLE 3

[0112] Heterocycles structurally related to guanine were evaluated using the method and base powder of Example 1. The results are shown in the table below.

TABLE-US-00004 20 g base 20 g base 20 g base 20 base 20 g powder + powder + powder + powder + base 0.027 g 0.027 g 0.027 g 0.027 g Test product: powder xanthine uric acid allantoin cytosine Silver 21° dH 25 1.0 1.0 1.0 1.0 1.0 tarnishing water cycles 0 5.0 5.0 5.0 5.0 5.0 cycles [00014][00015][00016][00017]

[0113] It was found that none of the tested materials—xanthine, uric acid, allantoin or cytosine—showed an impact on the corrosion protection profile, despite their close structural relationship to guanine. Without wishing to be bound by theory, it is believed that a balance between Lewis-basic and Lewis-acidic functional groups is required for silver/copper corrosion protection efficacy.

EXAMPLE 4

[0114] Guanine was tested as a silver protecting agent in the following base formulation:

TABLE-US-00005 Raw Material g/dose Bleach system (Sodium Percarbonate, 3.1 TAED, etc.) Builders 6.7 Surfactants/polymers 2.8 Alkali (Sodium Carbonate/bicarbonate) 2.1 Enzymes 0.1 Binders & Distintegrants 1.6 Others (dyes, antifoam, processing aids, rest fragrances) TOTAL 16.9

[0115] Using similar test conditions as in the previous experiments, the base formulation resulted in the formation of a strong black layer on the silver cutlery after only ten wash cycles, which would be unacceptable for use in a consumer household. In comparison, the inventive composition comprising the base formulation and 25 mg guanine resulted in significantly less shine loss and discolouration. Moreover, while the formulations showed a comparable surface deterioration after one wash cycle, guanine enabled corrosion protection over multiple cycles.

[0116] The results are shown in the table below.

TABLE-US-00006 16.9 g base 16.9 g base formulation + Test product: formulation 25 mg guanine Silver 21° dH 10 1.0 2.6 tarnishing water cycles 0 cycles 5.0 5.0

[0117] The foregoing detailed description has been provided by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations in the presently preferred embodiments illustrated herein will be apparent to one of ordinary skill in the art, and remain within the scope of the appended claims and their equivalents.