WO2020053316A1 - Silver protection agent - Google Patents

Abstract

The invention relates to a silver protection agent which comprises bismuth citrate, a degradable carboxylate or a phosphonate, and a salt of methylglycinediacetic acid. Furthermore, a washing agent is disclosed, which comprises the protection agent according to the invention.

Description

 Silver protection agent

The field of the present invention is that of silver protection agents, preferably for detergents, in particular for dishwashing detergents, for protecting silver-containing products during a washing process.

 The silver protection of silver-containing products in general and silver cutlery in particular poses a challenge in catering and household. The silver-containing products can become discolored due to the contact of silver-containing products with sulfur-containing compounds that are present in eggs or onions, for example. Furthermore, the silver over the silver-containing products can come into contact with bleach during a washing process, as a result of which the silver is oxidized to dark gray silver oxide. These processes can lead to undesired discoloration of the silver cutlery, especially with silver cutlery.

 Various silver protection agents are known in the prior art. EP 0 872 543 A2 discloses a detergent with a corrosion protection effect for silver, which has a metal-triazole complex and another triazole.

 WO 1997/003177 A1 also shows a dishwashing machine dishwashing detergent in the form of a tablet, which has a bleaching agent, a bleach activator and a silver and / or copper corrosion protection agent, the silver and / or copper corrosion protection agent not being present in one layer together with the Bleach and the bleach activator is included. As a silver and / or copper anticorrosive agent is according to the

WO 1997/003177 A1 provided, inter alia, benzotriazole.

 EP 0 906 407 B1 discloses a dishwashing detergent which contains methylglycinediacetic acid (MGDA) with a mass fraction of 10% and also works at a low pH. Ben zotriazole is also used as a silver and / or copper corrosion protection agent.

Benzotriazole is partially water-soluble, is drawn onto the surface of the silver-containing product in the course of the washing process and protects this surface from discoloration. What is disadvantageous, however, is that benzotriazole is an environmental toxin and is difficult is degradable. In this context, poorly degradable means slow to no decomposition into smaller molecules with the help of living beings or their enzymes. Benzotriazole is therefore only eliminated to a small extent in sewage treatment plants and reaches large quantities in rivers and lakes. Benzotriazole is classified with H-411 in the hazard and safety instructions of the globally harmonized system for the classification and labeling of chemicals (GHS), which means that benzotriazole is toxic for water organisms with long-term effects.

 It is therefore an object of the present invention to provide a more degradable silver protective agent. In particular, the silver protection agent is to be decomposed biologically by living beings or their enzymes and removed from the environment.

 For this purpose, the present invention provides a silver protection agent that is biodegradable and environmentally friendly. The silver protectant according to the present invention comprises bismuth citrate, a degradable carboxylate or a phosphonate, such as a salt of methylglycinediacetic acid (MGDA). The carboxylate can be a simple molecule or a polymer.

 The silver protection agent according to the invention protects silver-containing products from deposits and / or discoloration during a washing cycle. It can ver for cleaning

dirty silver-containing products the silver protective agent according to the invention dissolved in water alone or together with constituents of detergents, for example in dishwashing detergents or in machine dishwashing detergents, who used the.

 GB 2 311 535 A discloses detergents for reducing deposits which contain an aminotricarboxylic acid, for example MGDA. Among others, the described

Detergents also contain crystal growth inhibitors, for example hydroxyethane diphosphonic acid.

GB 2 297 096 A discloses a composition for dishwashing detergents with reduced tarnishing of silver and good washing performance, comprising an oxygen bleach and a water-soluble bismuth compound. MGDA is not mentioned as a possible component. In the context of the present invention, silver protection leads to particularly good results if the degradable carboxylate is a salt of polyepoxysuccinic acid (PESA), preferably an alkali salt of polyepoxysuccinic acid, in particular the disodium salt of polyepoxysuccinic acid. According to Li, X. et al. : "Effect of Synthesis Process Parameters of PESA on its Scale-inhibiting Performance", Advanced Materials Research Vols. 550-553, 2012, pp. 643-647, PESA is used as an environmentally friendly water treatment agent in cooling water systems to inhibit the formation of deposits.

 US 5,062,962 A and US 5,147,555 A disclose methods for controlling deposit formation in aqueous systems. Although the corrosion protection effect of metallic surfaces of heat exchangers is shown using PESA, neither a detergent nor a silver protection is described in US Pat. No. 5,062,962 or US Pat. No. 5,147,555 A.

 The US 4,654,159 A discloses PESA and the production of PESA as ether hydroxypolycarboxylate from epoxy succinic acid, the use as an ingredient in detergents for the substitution of phosphorus and nitrogen-containing ingredients is shown. The use of PESA as a silver protective agent or the combination of PESA with bismuth citrate or MGDA are not shown in US 4,654,159 A.

 It is advantageous according to the invention if the degradable car boxylate is a salt of iminodisuccinic acid (IDS), preferably an alkali salt of iminodisuccinic acid, in particular the tetranate rium salt of iminodisuccinic acid. The IDS is a complexing agent and biodegradable. Although WO 2009/040544 A1 describes a detergent which can comprise, for example, a salt from MGDA and a salt from IDS as a building material, and which can also have bismuth for the anticorrosive action, but there is no indication of the use of bismuth. Furthermore, MGDA and IDS are elements of a list of components that can be considered as an ingredient and bismuth is an element of a further list of components that are suitable as corrosion inhibitors.

It is also beneficial if the degradable carboxylate is a salt of polyaspartic acid (PASP). Advantages of the PASP are the good water solubility and the good degradability. In a preferred embodiment, the degradable carboxylate is a polymer or copolymer of itaconic acid.

 According to a further preferred embodiment, the phosphonate is a salt of hydroxyethane diphosphonic acid (HEDP), a salt of phosphonobutane tricarboxylic acid (PBTC), a salt of aminotrimethylenephosphonic acid (ATMP) or a salt of diethylenetriaminepentamethylenephosphonic acid (DTPMP).

 According to a particularly preferred embodiment, the salt of methylglycinediacetic acid is an alkali salt of methylglycinediacetic acid, in particular the trisodium salt of methylglycinediacetic acid.

 In a further aspect, the present invention contemplates, instead of the salt of methylglycinediacetic acid, the use of a combination of a salt of polyepoxysuccinic acid, preferably an alkali salt of polyepoxysuccinic acid, in particular the disodium salt of polyepoxysuccinic acid, and an alkali salt of iminodisuccinic acid, in particular the tetranate salt Iminodisuccinic acid. Surprisingly, this combination also protects silver-containing products during a washing process.

 In a further aspect, the present invention relates to a detergent which comprises silver protection, the silver protection comprising bismuth citrate, a degradable carboxylate or a phosphonate, and a salt of methylglycinediacetic acid. The detergent according to the invention is preferably degradable and is particularly suitable for cleaning silver-containing products, in particular silver cutlery, since the silver of the silver-containing products is protected from deposits and / or discoloration and / or oxidation to silver oxide.

 It is favorable if the mass fraction of bismuth citrate, based on the total mass of the detergent, is between 0.01% and 2.5%, preferably between 0.25% and 1%, in particular between 0.4% and 0.6% .

 Furthermore, it is advantageous if the mass fraction of the degradable carboxylate or the phosphonate, based on the total mass of the detergent, is between 0.01% and 20%, preferably between 0.1% and 10%, in particular between 0.5% and 5%, lies.

According to a further preferred embodiment, the Mass fraction of the salt of methylglycinediacetic acid based on the total mass of the detergent between 0.01% and 35%, preferably between 5% and 15%, in particular between 7% and 15%.

 According to a preferred embodiment, the detergent is a machine dishwashing detergent, wherein the machine dishwashing detergent can be in the form of a tab or a powder.

 In the context of the invention, it has been found that in a preferred embodiment the detergent has its full effect at low temperatures below 60 ° C. For this reason, it is advantageous if the detergent according to the invention is used in a dishwasher at temperatures below 60 ° C., preferably below 55 ° C., in particular below 50 ° C.

 The present invention is illustrated by the following example, to which it is of course not limited.

For example:

There were 6 different dishwashing detergents GM 1 to GM 6, which comprise different silver protective agents, 6 tabs of 20 g each being pressed out of the dishwashing detergents GM 1 to GM. Table 1 shows the mass fractions of the constituents of the dishwashing detergents GM 1 to GM 6. The silver protection agents that are part of the dishwashing detergents GM 1 to GM 6 include benzotriazole, bismuth citrate, the sodium salt of the maleic acid-acrylic acid copolymer (MA-AA), the trisodium salt of methylglycinediacetic acid (MGDA), the disodium salt of polyepoxysuccinic acid (PESA) , the tetra sodium salt of iminodisuccinic acid (IDS) and / or a salt of polyaspartic acid (PASP). The remaining constituents of the dishwashing detergents GM 1 to GM 6 are known from the prior art, so that they are not explained in more detail.

The silver protection agent of the dishwashing detergent GM 1 has benzotriazole and MA-AA with mass fractions of 0.3% and 4.45%. The use of benzotriazole is known from the prior art. The silver protective agent of the dishwashing detergent GM 2 contains bismuth citrate and MA-AA with a mass fraction of 0.5% and

4.45% and together with the silver protection agent of dishwashing detergent GM 1 serves as a reference for the embodiments of the silver protection agent according to the invention of dishwashing detergent GM 3 to GM 6.

 The tabs produced from the dishwashing detergents GM 1 to GM 6 were individually placed in a dishwasher loaded with silver cutlery and each carried out 30 washing cycles in a washing program with temperatures between 45 ° C. and 65 ° C. The coating and the discoloration of the silverware was then measured and evaluated using a numerical scale.

The numerical scale has a sequence of numbers from 0 to 10, with 0 points representing a very high deposit and a high degree of discoloration and 10 points no significant deposit and no significant discoloration of the silver cutlery.

 The results from Table 1 show that the formation of deposits on the silver cutlery after 30 rinsing cycles when using the silver protection agent of the dishwashing detergent GM 1 was rated with 7 points.

 The use of bismuth citrate instead of benzotriazole as silver protection in the dishwasher detergent GM 2 leads to a high deposit and to a high discoloration of the silver cutlery after 30 washing cycles. The deposit formation was rated 1.5 points in this series of experiments.

 The use of an embodiment of the silver protective agent according to the invention in the dishwashing agent GM 3, the silver protective agent bismuth citrate, MA-AA and MGDA with mass fractions of 0.5%, 3.3% and 7.5%, leads to 6.5 points on the scale the formation of deposits. Accordingly, the discoloration and the coating of the silver cutlery after cleaning with the dishwashing liquid GM 3 is approximately the same as with the dishwashing liquid GM 1, which comprises benzotriazole.

The dishwashing detergent GM 4 has a further embodiment of the silver protection agent according to the invention, which comprises bismuth citrate, MGDA and PESA with mass fractions of 0.25%, 10.0% and 10.0%. After 30 wash cycles of the wash program, the formation of deposits on the dishwashing detergent GM 4 cleaned silver cutlery with 8 points. Thus, when using the dishwashing agent GM 4 according to the invention, which comprises bismuth citrate, MGDA and PESA, a lower deposit and less discoloration of the treated silverware were found than when using the dishwashing agent GM 1, which has benzotriazole.

 The formation of deposits on the silver cutlery when treated with the dishwasher detergent GM 5 was rated 9 points. The further embodiment of the silver protection agent according to the invention used here has bismuth citrate, MGDA and IDS with mass fractions of 0.25%, 10.0% and 10.0%. Accordingly, the loading and the discoloration of the silver cutlery when using the silver protection agent of the dishwasher detergent GM 5 is significantly lower than when using the dishwasher detergent GM 1, which has benzotriazole.

 The dishwasher detergent GM 6 has a further embodiment of the silver protection agent according to the invention, the bismuth citrate, PESA, IDS and PASP with mass fractions of 0.5%,

5.0%, 20.0% and 8.0%. After 30 wash cycles of the washing program, the build-up of the silver cutlery cleaned with the dishwashing detergent GM 6 was rated with 9 points. Thus, when using the dishwashing agent GM 6, the same results were achieved with regard to the deposit and the discoloration of the silver cutlery as when the dishwashing agent was used with GM 5.

Table 1

Claims

Patent claims 1. Silver protection agent, characterized in that it comprises bismuth citrate, a degradable carboxylate or a phosphonate, and a salt of methylglycinediacetic acid. 2. Silver protective agent according to claim 1, characterized in that the degradable carboxylate is a salt of polyepoxysuccinic acid, preferably an alkali salt of polyepoxysuccinic acid, in particular the disodium salt of polyepoxysuccinic acid. 3. Silver protection agent according to claim 1, characterized in that the degradable carboxylate is a salt of iminodisuccinic acid, preferably an alkali salt of iminodisuccinic acid, in particular the tetrasodium salt of iminodisuccinic acid. 4. Silver protection agent according to claim 1, characterized in that the degradable carboxylate is a salt of polyaspartic acid. 5. Silver protection agent according to claim 1, characterized in that the degradable carboxylate is a polymer or copolymer of itaconic acid. 6. Silver protective agent according to claim 1, characterized in that the phosphonate is a salt of hydroxyethane diphosphonic acid, a salt of phosphonobutane tricarboxylic acid, a salt of aminotrimethylene phosphonic acid or a salt of diethylenetriaminepentamethylenephosphonic acid. 7. Silver protective agent according to one of claims 1 to 6, characterized in that the salt of methylglycinediacetic acid is an alkali salt of methylglycinediacetic acid, in particular the trisodium salt of methylglycinediacetic acid. Silver protection agent according to claim 4, characterized that instead of the salt of methylglycinediacetic acid it comprises a combination of a salt of polyepoxysuccinic acid, preferably an alkali salt of polyepoxysuccinic acid, in particular the disodium salt of polyepoxysuccinic acid, and an alkali salt of iminodisuccinic acid, in particular the tetrasodium salt of iminodisuccinic acid. 9. Detergent, characterized in that it comprises a silver protective agent according to one of claims 1 to 8. 10. Detergent according to claim 9, characterized in that the mass fraction of bismuth citrate, based on the total mass of the detergent, is between 0.01% and 2.5%, preferably between 0.25% and 1%, in particular between 0.4% and 0 , 6%. 11. Detergent according to claim 9 or 10, characterized in that the mass fraction of the degradable carboxylate or the phosphate based on the total mass of the detergent between 0.01% and 20%, preferably between 0.1% and 10%, in particular between 0.5% and 5%. 12. Detergent according to one of claims 9 to 11, characterized in that the mass fraction of the salt of methylglycine diacetic acid based on the total mass of the detergent between 0.01% and 35%, preferably between 5% and 15%, in particular between 7% and 15%. 13. Detergent according to one of claims 9 to 12, characterized in that it is a dishwasher detergent. 14. Use of the detergent according to one of claims 9 to 13 in a dishwasher at temperatures below 60 ° C, before given below 55 ° C, in particular below 50 ° C.