WO1997049792A1

WO1997049792A1 - Low-alkaline mgda-containing dishwasher rinsing agent

Info

Publication number: WO1997049792A1
Application number: PCT/EP1997/003256
Authority: WO
Inventors: Guido Wäschenbach; Paul William Robinson; Laurence Geret
Original assignee: Benckiser N.V.
Priority date: 1996-06-21
Filing date: 1997-06-20
Publication date: 1997-12-31
Also published as: ATE389709T1; EP1113070B1; EP0906407B1; EP0906407A1; CA2258218A1; ES2300287T3; DE59712930D1; EP1113070A2; EP1113070A3; ES2160355T3; ATE205250T1; DE59704543D1

Abstract

The invention provides a dishwasher rinsing agent which contains methyl glycine diacetic acid or its salts as the complexing agent, characaterized in that it does not exceed a pH of 10.4 in 0.5 % aqueous solution. The dishwasher rinsing agent of the invention operates at low pH and can even removal obstinate food remnants which cannot usually be removed with a dishwasher rinsing agent operating at such a pH. The novel rinsing agent has an excellent cleaning action especially on crockery contaminated with both milk and tea residues.

Description

Machine dishwashing detergent containing low alkalinity

The invention relates to machine dishwashing detergents of low alkalinity which contain methylglycinediacetic acid (MGDA) or a salt thereof and which preferably have a reduced bleaching agent content.

Highly alkaline machine dishwashing detergents without bleach with a high proportion of complexing agents are known in the prior art. In the past, they were sold as a means for household dishwashers and are still used today for industrial appliances.

US-A 3,673,098 discloses non-bleaching caustic compositions based on KOH and nitrilotriacetic acid (NTA).

Fr-A 1 590 416 likewise discloses caustic compositions without bleaching agents, which are based on alkali metal hydroxides, pyrophosphates and NTA. Such agents were later formulated without caustic alkalis and the performance loss was compensated for by the addition of chlorine bleach, as exemplified in US-A-3,826,748. These non-caustic alkalis still had a high pH greater than 11.

The trend towards safer and more environmentally friendly agents initially led to the replacement of strong complexing agents by builders and later to a new generation of mildly alkaline dishwashing detergents with a pH of 9 to 11.5, the chlorine bleaching of which was replaced by oxygen bleaching and enzymes.

Good examples of such agents can be found in EP-A-135 226, EP-A-135 227 and EP-A-414 197. In these agents, complexing agents are normally only present in small amounts, if at all.

EP-A-530 635 discloses acidic to mildly alkaline compositions (pH 5-9) which contain no complexing agents and are based on builders, enzymes and optionally oxygen bleaching.

DE-A-3 833 047 discloses acidic compositions (pH 2-6) with hydrolases and builders or complexing agents. The examples disclose compositions with a high NTA or EDTA content (up to 30%). While these compositions can e.g. Eliminate tea residues well, their effect on milk residues is measured on a scale from 0 to 10, but always below 5.

DE-A-3 829 847 and DE-A-4 036 995 disclose the use of other biodegradable complexing agents, such as ß-alaninediacetic acid (ß-ADA) and isoserinediacetic acid (ISDA), in cleaning agents. If these documents contain application examples for machine dishwashing detergents, it is machine dishwashing - 3 -

detergents which have a pH of more than 10.5 in approximately 0.5% aqueous solution.

In addition, these compounds have a significantly less complex effect than NTA and can only replace them in an insufficient way in the finished agent.

DE-A-4 319 935 discloses the use of MGDA in dishwasher detergents without giving an example. In a GDCH lecture on May 30, 1995, one of the inventors of DE-A-4 319 935 published the use of methylglycinediacetic acid (MGDA) as a complexing agent for cleaning equipment parts of the dairy industry on an industrial scale and in dishwashing detergents with a pH in solution of more than 10.5.

The same information can also be found in the "Preliminary technical information, Trilon ^® ES 9964", April 1995, from BASF AG. The dishwashing detergents disclosed there contain 5-30% MGDA and 1.12% active oxygen, with MGDA achieving a result comparable to NTA in the deposit inhibition (formation of calcium carbonate deposits). The effectiveness of the dishwashers on milk residues or tea residues is not mentioned. However, MGDA is said to dissolve calcium phosphate residues better in dairy cleaning than NTA. Dairy cleaning usually works in a strongly alkaline range.

The use of MGDA in laundry detergents is proposed in an article in SÖFW Journal 122, 1996, 392. MGDA is said to have a better effect, in particular in the case of blood-soiled laundry, than phosphonates and, in the case of tea-soiled laundry, has approximately the same action as phosphonates. In the same publication it is disclosed that MGDA in a dishwashing detergent, similar to NTA, shows very good deposit inhibition on glass, metal and porcelain, whereby a dishwashing detergent is disclosed which has a solution in solution provides pH of more than 10.5. It is also suggested to use MGDA for dairy cleaning in very alkaline conditions.

The previously proposed machine dishwashing detergents that use complexing agents therefore have the disadvantage that they either work at higher pH values or do not have sufficient cleaning power for certain food residues, in particular for milk residues and tea residues.

It is an object of the invention to provide a machine dishwashing detergent which not only works at a low pH, but also removes food residues which are difficult to remove and which usually do not satisfactorily remove machine dishwashing detergents operating at such a pH . In particular, such a dishwashing detergent is said to have excellent cleaning performance for dishes which are contaminated by both milk and tea residues. This object is achieved by a machine dishwashing detergent which contains methylglycinediacetic acid or its salts as a complexing agent and is characterized in that it does not exceed a pH of 10.4 in approximately 0.5% aqueous solution.

Milk residues consist of a mixture of denatured proteins (casein), fats, sugars and mineral deposits and consist of around 70% calcium phosphate (Ca3 (PO _ *.) 2). Complexing agents therefore have a significant influence on the removal of milk residues because they dissolve calcium phosphates by complexing the calcium ions.

Tea residues are also based, among other things, on Ca deposits that arise when tea is brewed with hard water. However, tea residues usually place different requirements on a machine dishwashing liquid than Milk residues, which can already be seen from the fact that the detergent disclosed in DE-A 3 833 047 removes tea residues satisfactorily in the acidic range (pH 2-6), but cannot convince with milk residues.

The ability (based on the weight of the complexing agent) to complex calcium ions at a certain pH value depends on the stability constant of the calcium complex (pKc) _r, the acidic character of the complexing agent (PK3) and its molecular weight.

Although MGDA for calcium carbonate at pH 11 has a higher theoretical degree of complexation than NTA (as disclosed in the aforementioned GDCH lecture and which can be calculated theoretically), at pH 7 and 10.4 and a different result for calcium phosphates.

In fact, at pH 10.4 the theoretical degree of complexation for calcium phosphates is 360 mg / g when using NTA and 340 mg / g when using MGDA, and at pH 8 the theoretical values are 510 mg / g for NTA and 490 mg / g for MGDA.

Therefore, based on these theoretical considerations, it follows that MGDA with a dishwashing detergent which provides a pH of less than 10.4 in approximately 0.5% aqueous solution has a less complexing effect on calcium phosphates and should therefore remove milk residues more poorly than is customary NTA.

In the prior art, MGDA was also used only in dishwashing detergents which have a pH of more than 10.4 in approximately 0.5% aqueous solution.

At lower pH values, the use of NTA is more appropriate, but better at such pH values on calcium phosphates Should have a complexing effect as MGDA and also remove tea residues satisfactorily in the acidic range (pH 2-6) (DE-A 38 33 047).

According to the invention, however, it was surprisingly found that dishwashing detergents which contain MGDA and which provide an approximately 0.5% aqueous solution with a pH of up to 10.4 can better remove both tea residues and milk residues and have an overall better dishwashing result as a dishwashing detergent that contains a complexing agent like the common NTA instead of MGDA.

It has also surprisingly been found that in a dishwashing detergent according to the invention which has a sufficient amount of complexing agent MGDA, the amount of oxygen bleaching agent can be reduced without thereby impairing the rinsing performance and in particular the ability to remove milk residues and tea residues. This surprising finding even opens up the possibility of completely dispensing with the use of oxygen bleaching agents if a sufficiently large amount of complexing agent is used.

The dishwashing detergent according to the invention can be liquid or powder and can also be in the form of a single-layer or multilayer tablet. Appropriate dosage forms and methods of obtaining them are known to the person skilled in the art.

The dishwasher detergents according to the invention preferably contain one or more enzymes such as, for example, amylase, protease, lipase or cellulase. The best cleaning results were achieved by the combined use of amylase and protease. These enzymes can be used particularly effectively in the pH ranges described here; For example, the temperature-stable amylase Termamyl (Novo) achieves the optimum of its spectrum of activity at pH 7-8. The enzymes come in Granular form or in solution with commercial concentrations or activities for use, wherein the content of enzymes can be 0.5-6, preferably 1-4% by weight.

Suitable builders are, for example, homo- and copolymeric polycarboxylic acids and their partially or completely neutralized salts, monomeric polycarboxylic acids and hydroxycarboxylic acids and their salts, carbonates, bicarbonates, borates, phosphates, silicates, aluminosilicates and mixtures of such substances.

Preferred salts of the above compounds are the ammonium and / or alkali salts, i.e. the lithium,

Sodium, potassium and rubidium salts and particularly preferably the sodium salt.

Suitable polycarboxylic acids are acyclic, alicyclic, heterocyclic and aromatic carboxylic acids, these containing at least two carboxy groups which are each separated from one another by preferably no more than two carbon atoms.

Polycarboxylates containing two carboxy groups include, for example, water-soluble salts of succinic acid, malonic acid, (ethylenedioxy) diacetic acid, maleic acid, diglycolic acid, tartaric acid, tartronic acid and fumaric acid. Polycarboxylates containing three carboxy groups include, for example, water-soluble citrates. Accordingly, citric acid is suitable as the hydroxycarboxylic acid.

As a special builder for dishwasher detergents, one of aspartic acid can also be used

H00C-CH (NH2) -CH2-COOH derived polymer with monomer units of the formula

to be named.

The homopolymer of acrylic acid is also suitable as the polycarboxylic acid.

In addition to borates such as sodium borate, those borate builders which release borates under the detergent storage conditions or rinsing conditions can also be used as borate builders.

Polyphosphates such as tripolyphosphate, pyrophosphate, orthophosphate and the polymeric metaphosphate are suitable as phosphates. Examples include alkali metal tripolyphosphates, sodium, potassium and ammonium pyrophosphate, sodium and potassium orthophosphate and sodium polymetaphosphate, in which the degree of polymerization preferably ranges from 5 to 21.

Sodium silicates such as sodium disilicate, sodium metasilicate and crystalline layered silicates are suitable as silicates. Sodium aluminosilicates (zeolites) are also suitable.

Further suitable builders are disclosed in WO 95/01416, the content of which is hereby expressly incorporated by reference.

A builder system from the salt of a hydroxycarboxylic acid or from the mixture of a hydroxycarboxylic acid and the salt of a hydroxycarboxylic acid is particularly preferred. Both the hydroxycarboxylic acid and the salt of Hydroxycarboxylic acid can be replaced in whole or in part by tripolyphosphate, although this is not preferred.

The builder system preferably consists of a hydroxypolycarboxylic acid with 2-4 carboxyl groups (or acidic inorganic salts), which can be mixed with its salt to adjust the pH. Citric acid or a mixture of sodium citrate with citric acid is preferably used. Depending on the other constituents of the mixture, suitable for adjusting the required pH according to the invention are e.g. Mixtures with a predominant proportion of citric acid.

The water content of liquid dishwashing detergents can be 40-80% by weight.

The liquid dishwashing detergents also contain 0.2-5.0% by weight, preferably 0.5-2% by weight, of a thickener. High-molecular organic polymers with molecular weights of 5 × 10 to approx. 5 × 10, which are made up of olefinically unsaturated carboxylic acids, are suitable as thickeners. Carboxyvinyl polymers, e.g. by B. F. Goodrich under the production name "Carbopol" on the market proved to be very usable. Inorganic compounds that have thickening properties in this product composition can also be used. Examples of this are natural or synthetic thickeners based on differently structured silicate structures. Their use is described in various patents, e.g. in US-A-4 933 101 or EP-A2- 0 407 187.

For example, nonionic surfactants are suitable as surfactants. These include, for example, water-soluble ethoxylated C.sub.6 g fatty acid alcohols and C.sub.66 mixed ethoxylated / propoxylated fatty acid alcohols and mixtures thereof, and also polyglucosides. Another class of nonionic surfactants includes polyhydroxy fatty acid amides.

Further suitable surface-active agents are disclosed in WO 95/01416, the content of which is hereby expressly incorporated by reference.

The machine dishwashing detergent according to the invention can furthermore contain one or more foam control agents. All foam control agents used in this area, such as silicones and paraffin oil, are suitable for this.

The foam control agents are preferably contained in the dishwasher detergent according to the invention with less than 5% by weight of the total weight of the detergent.

The machine dishwashing detergents according to the invention can preferably contain chlorine-free, active oxygen-releasing bleaching agents such as inorganic perhydrates or organic peracids and their salts as bleaching agents.

Examples of inorganic perhydrates are perborates, percarbonates and persulfates such as peroxymonopersulfate. The inorganic perhydrates are normally alkali metal salts, such as lithium, sodium, potassium or rubidium salts, in particular the sodium salts. The inorganic perhydrates can be present in the detergent as crystalline solids without further protection. For certain perhydrates, however, it is advantageous to use them as granular compositions which are provided with a coating which gives the granular products better storage stability.

The preferred perborate is sodium perborate, which can be present as a monohydrate with the formula NaBθ2H2θ2 or as a tetrahydrate with the formula NaB02H2Ü2 • 3H20. The preferred percarbonate is sodium percarbonate with the formula 2Na2Cθ33H2θ2 • The percarbonate is preferably used in a coated form to increase its stability.

Organic peracids include all organic peracids conventionally used as bleaching agents, including for example perbenzoic acid and peroxycarboxylic acids such as mono- or diperoxyphthalic acid, 2-0ctydiperoxysuccinic acid, diperoxydodecanedicarboxylic acid, diperoxyazelaic acid and imidoperoxycarboxylic acid and optionally their salts.

The machine dishwashing detergent according to the invention may further contain one or more bleach activators. These are preferably used in detergents for dishwashing operations at temperatures in the range below 60 ° C. in order to achieve a sufficient bleaching effect. N- and 0-acyl compounds such as acylated amines, acylated glycolurils or acylated sugar compounds are particularly suitable. N, N, N ', N'-tetraacetylethylenediamine (TAED), pentaacetylglucose (PAG) and tetraacetylglycoluril (TAGU) are preferred. However, catalytically active metal complexes and preferably transition metal complexes are also suitable as bleach activators. Most preferred is TAED.

Further suitable bleach activators are disclosed in WO 95/01416, the content of which is hereby expressly incorporated by reference.

However, by using MGDA at relatively low pH values, the use of bleaching agents can be reduced and the machine dishwashing detergents according to the invention preferably have an oxygen bleaching agent in an amount of less than 1% by weight, based on the active oxygen. The amount of bleach activator used is adjusted accordingly. In one embodiment, the machine dishwashing detergents have a large proportion of MGDA, such as 25% or more, preferably 30% or more, in each case based on the free acid, and an oxygen bleaching agent is dispensed with.

The machine dishwashing detergent according to the invention may further contain a silver / copper corrosion protection agent. This term includes agents that are intended to prevent or reduce the tarnishing of non-ferrous metals, especially silver and copper. Preferred silver / copper anti-corrosion agents are benzotriazole or bis-benzotriazoles and their substituted derivatives.

Other suitable agents are organic and / or inorganic redox-active substances and paraffin oil.

Benzotriazole derivatives are those compounds in which the available substitution sites of the aromatic ring are partially or completely substituted. Suitable substituents are linear or branched Cι_ 20- ^A lkyj.9jr ^{, groups} and hydroxy, thio, phenyl or halogen such as fluorine, chlorine, bromine and iodine. Preferred substituted benzotriazole is tolyltriazole.

Suitable bis-benzotriazoles are those in which the benzotriazole groups are each connected in the 6-position by a group X, in which X is a bond, a straight-chain, optionally substituted with one or more C 1-4 alkyl groups, preferably 1-6 carbon atoms, a cycloalkyl radical having at least 5 carbon atoms, a carbonyl group, a sulfuryl group, an oxygen or a sulfur atom. The aromatic rings of the bis-benzotriazoles can be substituted as defined above for the benzotriazole.

Suitable organic redox-active substances are, for example, ascorbic acid, indole, methionine, an N-mono- (C ₁ -C 4 alkyl) glycine, an N, N-di (C ₁ -C 4 alkyl) glycine, 2- Phenylglycine or a coupler and / or developer compound chosen from the group of diaminopyridines, aminohydroxypyridines, dihydroxypyridines, heterocyclic hydrazones, aminohydroxypyrimidines, dihydroxypyrimidines, tetraaminopyrimidines, triaminohydroxypyrimidines, diamino dihydroxypyrimidines, Dihydroxynaphtaline, naphthols, pyrazolones, hydroxyquinolines, aminoquinolines, primary aromatic amines, which have in the ortho, meta or para position a further free or substituted with Cι ~ C4-alkyl or C2-C4-hydroxyalkyl groups hydroxy or amino groups and the di- or trihydroxybenzenes.

Suitable inorganic redox-active substances are, for example, metal salts and / or metal complexes selected from the group consisting of manganese, titanium, zirconium, hafnium, vanadium, cobalt and cerium salts and / or complexes, in which the metals are in one of the oxidation stages II, III, IV, V or VI are present.

Metal salts and / or metal complexes selected from the group MnSO4, Mn (II) citrate, Mn (II) stearate, Mn (II) acetylacetonate, Mn (II) - [l-hydroxyethane-l, l- diphosphonate], V2O5, V2O4, VO2, Ti0S04, K ₂ TiF ₆ , K ₂ ZrF ₆ , C0SO4, Co (N0 ₃ ) ₂ , Ce (N0 ₃ ) ₃ .

Organic and inorganic redox-active substances which are suitable as silver / copper corrosion protection agents are also mentioned in WO 94/26860 and WO 94/26859, the content of which is hereby incorporated by reference.

Suitable paraffin oil are predominantly branched aliphatic hydrocarbons with a number of carbon atoms in the range from 20 to 50. The paraffin oil is preferably selected from predominantly branched chain C25_45 species with a ratio of cyclic to noncyclic hydrocarbons of 1:10 to 2: 1, preferably of 1: 5 to 1: 1. If a silver / copper corrosion protection agent is present in the machine dishwashing detergent according to the invention, it is preferably present with 0.01 to 5% by weight, particularly preferably with 0.1 to 2% by weight, of the total weight.

In the embodiment of the invention in which the proportion of MGDA in the dishwasher detergent is sufficiently high, such as 25% or more, preferably 30% or more, in each case based on the free acid, so that bleaching agents can be dispensed with, a Silver / copper anti-corrosion agents can be dispensed with.

Other common additions are e.g. Dyes and fragrances and, if appropriate, preservatives for liquid products, for which purpose e.g. Compounds based on isothiazolinone are suitable.

The machine dishwashing detergents according to the invention are not caustic and therefore do not require any particularly secure packaging. A good washing result can be achieved with a relatively low amount of 15-20 g powder or 20-50 ml liquid cleaner. According to current knowledge, all ingredients are neither toxic nor otherwise harmful to health. The cleaning agents described here are therefore also an environmentally friendly and consumer-friendly alternative to the conventional cleaners with complexing agents that work in the strongly basic area.

The methylglycinediacetic acid used according to the invention has the following structural formula:

The methylglycinediacetic acid is particularly preferably used as the free acid or as the sodium or potassium salt and is preferably present in the dishwashing detergent in an amount of 3% to 90%, based on the free acid.

In bleach-free dishwasher detergents based on phosphates as the main constituent of the builder system, the amount of MGDA is preferably at least 5%, based on the free acid.

According to the invention, it is essential that an approximately 0.5% aqueous solution of the washing-up liquid has a pH of not more than 10.4. The pH of an approximately 0.5% aqueous solution of the washing-up liquid according to the invention is preferably from more than 6 to 10.4, particularly preferably from 7 to 10.0.

The following comparison test proves that the dishwashing detergents proposed in the article in SÖFW Journal 122, 1996, 392-397 have a pH of more than 10.4 in 0.5% aqueous solutions. The disclosure of this article is therefore in line with the theoretical expectation that MGDA is an excellent complexing agent at pH values greater than 10.4, but is inferior to the common NTA at pH values 10.4 or below.

Comparison test

In accordance with the disclosure of the article in SÖFW-Journal 122, 1996, 392-397, dishwashing detergents are made from the following ingredients:

Sodium citrate dihydrate

sodium

Sodium bicarbonate

Sodium perborate monohydrate

TAED ^c 13 ^c 15 oxo alcohol + 4 moles PO + 2 moles EO

MGDA (trisodium salt of methylglycinediacetic acid) (77%

Solution in water) = TRILON ES 9964 available from BASF AG The table below shows the amounts of the respective components in g and%. The components were dissolved in one liter of water of 10 ° hardness, and the pH of the solution was determined in each case. The total amount of ingredients (100%) is 4 g each, corresponding to a 0.4% concentration as disclosed in Figure 14 of the article.

MGDA is not commercially available in its pure form and therefore a 77% solution in water was used. A larger amount of the commercially available product had to be used, as shown in the table. Two values are given in the table for MGDA. The first value indicates the amount in g of the commercial product, and the second value corresponds to the corresponding amount of pure substance (100%).

Although the pH of 0.5% solutions of the agents was not determined directly, the pH became 0.4% Solutions determined. With a higher concentration of the cleaner, the solutions of the cleaner will of course have the same or, more likely, higher pH values.

The following example shows that by replacing part of the builder of a machine dishwashing detergent with methylglycinediacetic acid, an excellent washing performance can be achieved at low pH values and, contrary to theoretical expectations, the ability to remove milk residues and tea residues is higher than with other common complexing agents such as NTA. The example illustrates the invention.

example

Liquid dishwashing detergents were prepared with a composition as shown in Table 1 (both in accordance with the invention using MGDA and using the NTA used in the prior art) and their washing performance was determined by means of dishes which were both milk and milk Contained tea residues, determined. In this experiment, DIN Standard No. 44990, Part 2 was essentially followed. A Bosch SMS 5062 dishwasher was used. The water had a hardness of 19 ° dH (3.39 mmol calcium carbonate), the temperature of the water was 65 ° C and 20 ml detergent was used in each case. The results of the wash performance were rated on a scale of 1-5 (5 stands for 100% clean dishes) and are also listed in Table 1.

The non-ionic surfactant is _. is a common, low-foaming ethoxylated and propoxylated fatty alcohol. Common proteases and amylases are used. Table 1

NTA I IMGDA I INTA Π IMGDA Π 1 NTA m l MGDA m I

It can be seen from the results in Table 1 that, surprisingly, in a pH range below 10.4 detergents which contain MGDA, both the removal of milk residues and the removal of tea residues achieve better results than the corresponding detergents which instead of MGDA contain the common NTA.

Claims

claims

1. dishwasher detergent containing methylglycine diacetic acid or salts thereof as complexing agents, characterized in that the agent does not exceed a pH of 10.4 in approximately 0.5% aqueous solution.

2. Machine dishwashing detergent according to claim 1, characterized in that it contains an oxygen bleaching agent in an amount of less than 1% based on the weight of active oxygen.

3. Machine dishwashing detergent according to claim 1 or 2, characterized in that the agent has a pH of 6 to 10.4 in approximately 0.5% aqueous solution.

4. Use of methylglycinediacetic acid or its salts as a complete or partial replacement for builders or complexing agents in machine dishwashing detergents with a pH of not more than 10.4 in approximately 0.5% aqueous solution to improve the ability of both milk residues and tea residues to eliminate.