EP0569365B1 - Phosphate-free cleaning agent - Google Patents

Abstract

Disclosed is a phosphate-free dishwashing agent containing crystalline sodium disilicate ($g(b)-form) produced hydrothermally from quartz sand and caustic soda by a sintering process.

Description

The invention relates to a phosphate-free cleaning agent, in particular for the mechanical cleaning of dishes, based on crystalline layered sodium disilicates, alkali metal carbonates, oxidizing agents and optionally alkali metal silicates, surfactants, enzymes and polymeric compounds.

For machine cleaning of dishes, it is known to use detergent mixtures which essentially consist of inorganic salts, such as alkali phosphates, alkali silicates and alkali carbonates, and of active chlorine carriers and which, in order to improve the wetting action, may also contain small amounts of nonionic surfactants. These mixtures have a good cleaning ability against all stains at generally normal working temperatures of 50 to 65 ° C. Enzyme-containing dishwashing detergents, such as those described in, for example, have been used to prevent thin deposits that can settle on the surface of the dishes over time and that consist essentially of starch and possibly traces of protein, and which can significantly impair the appearance of the washed dishes DT 1 767 567.

Because of the known environmental influences of the phosphates (water reutrophication), efforts are still being made to develop recipes which contain only small and preferably no phosphate components. It is known, among other things, to replace phosphates with various organic complexing agents which also serve as framework substances and which include, for example, ethylenediaminetetraacetic acid and the like. However, some of these compounds also repeatedly trigger environmental discussions, since they are not biodegradable and are not eliminated in the sewage treatment plants.

Strongly alkaline cleaning agents without phosphate content, based solely on caustic alkalis, have a relatively strong cleaning power compared to all types of soiling, but you have to accept an increased corrosion effect against glass and onglaze decorations.

DE 24 35 479 A1 already discloses phosphate-free dishwashing detergents with reduced corrosion activity, which essentially consist of water-soluble alkali silicates and water-soluble organic complexing agents, such as the water-soluble alkali salts of polyacrylic acid, which has an average molecular weight of about 1000 to 20,000. Similar cleaning agents are known from EP 267 371 B1, which as alkali silicate is a crystalline, layered sodium disilicate of the general formula Na M Si _x O _{2x + 1 .y} H₂O, in which M sodium or Hydrogen, x is a number from 1.9 to 4 and y is a number from 0 to 20, and also contain a polymeric and / or copolymeric carboxylic acid or a salt of this polymeric carboxylic acid and active chlorine carrier as a supplementary structural substance. The anhydrous, crystalline layered sodium disilicates used there have been produced thermally, as described in EP 293 640 A2. The delta modification of the silicate (δ-Na₂Si₂O₅) is predominantly obtained.

Crystalline disilicates with the composition Na₂Si₂O₅ have also been known from the literature for a long time (cf. JG Vail, Soluble Silicates, Vol. 1, ACS Monograph Series (1952), page 142). The various modifications can be obtained by suitable temperature selection via sintering reactions (cf. A. Willgallis and KJ Range in Glastechnischeberichte 37 (1964), pages 194 to 200). The different modifications differ in the corrugation of the silicate layers (see F. Liebau, Acta Cryst., B24 (1968), pages 690 to 699; W. Hoffmann and H.-J. Scheel, Zeitschrift f. Krist., 129 ( 1969), pages 396 to 404).

As is well known, two factors particularly affect the performance of automatic dishwashing detergents. On the one hand, this is the alkalinity of the cleaning liquor, which must be high enough to cause the food residues to swell, and thus the removal of the dirt residues by the To support the water mechanics of the dishwasher, and on the other hand the solubility of the alkali silicates in the liquor, since they help to disperse the solid particles and thus contribute to the dirt-carrying capacity of the liquor.

According to the unpublished patent application DE 39 39 919, the β-Na₂Si₂O₅ can be obtained in a different reaction path, namely hydrothermally, from quartz sand and sodium hydroxide solution and / or aqueous solutions of sodium silicates. It was surprisingly found that this hydrothermally produced β-disilicate, hereinafter referred to as β-h-disilicate, leads to better cleaning performance than the δ modification.

It was also surprisingly found that hydrothermally produced β-disilicates have a significantly higher dissolution rate than the δ-disilicates produced by sintering reactions. It was found that higher proportions of SiO₂ than Na₂O dissolve in the β modifications compared to the δ modification. Since the β-h modification in turn dissolves particularly quickly, a particularly high proportion of dissolved silicate was observed here.

The present invention therefore relates to a phosphate-free cleaning agent, in particular for automatic dishwashing, based on crystalline, layered sodium disilicates, alkali carbonates, oxidizing agents and, if appropriate, alkali silicates, surfactants, enzymes and polymeric compounds, which is characterized in that it is crystalline layered Na disilicate hydrothermally produced Na disilicate of the formula β-h-Na₂Si₂O₅ contain. Any additions of small or very small amounts of alkali phosphates do not lead out of the scope of the invention.

Anhydrous, but also water containing compounds can preferably be used as alkali carbonates. Sodium carbonate and sodium bicarbonate, the amounts of which are 3 to 30, preferably 6 to 15,% by weight, based on the finished composition, are preferred.

Contaminants that are particularly difficult to remove, such as burnt-on food residues, lipstick and tea stains, may require the appropriate use of oxidizing agents such as active oxygen or active chlorine-splitting compounds or enzymes in the cleaner mixtures.

Compounds which release active oxygen are preferably used as the oxidizing agent. The known alkali perborates, persulfates and percarbonate, which can be activated by activators such as, for example, tetraacetylenediamine, tetraacetylglycoluril, pentaacetylglucose or diacetyldioxohexahydrotriazine, but also compounds such as magnesium monoperphthalate, can be used as such, but there is no need to add an activator. Their amounts can be 5 to 10, preferably 6 to 9% by weight, based on the finished agent.

As active chlorine releasing compounds are, for example, trichloroisocyanuric acid or its alkali salts, e.g. As potassium dichloroisocyanurate, sodium dichloroisocyanurate dihydrate into consideration. Furthermore, alkali hypochlorites, such as lithium or sodium hypochlorite, and hypochlorite-containing complex salts, e.g. B. so-called chlorinated phosphates can be used.

Suitable enzymes are obtained from animal and vegetable materials, in particular from digestive ferment, yeast and bacterial strains. They usually represent a complex mixture of different enzymatic active ingredients. Of particular interest are enzymes that break down starches, proteins or fats, such as amylases, proteases and lipases. The enzymes are produced using a wide variety of processes from bacterial strains, fungi, yeast or animal organs. Most of these are enzyme mixtures that have a combined effect, especially on starch and protein. The enzyme preparations obtained from Bacillus subtilis are relatively resistant to alkalis and are not significantly inactivated at temperatures between 45 and 70 ° C, so that they are particularly suitable for use in dishwasher detergents.

The manufacturers set the enzymes to a certain degree of activity, optionally with the addition of blending agents such as sodium sulfate, sodium chloride, alkali phosphates or alkali polyphosphates. The data in LVE / g (Löhlein-Volhard units per gram), IU (international units) and DE / g (Delft units per gram) are common for proteolytic enzymes. Because of the simple analysis method, the activity is often stated in LVE / g. In the dishwashing detergents according to the invention, the proteolytic enzyme activity should be 100 to 5,000, preferably 200 to 2,000 LVE / g. Amylolytic activity is generally reported in SKB / g (Sandstedt-Kneen-Blish units per gram). It should be about 5 to 1,000, preferably 15 to 250, SKB / g in the detergent mixture. The amount of the enzymes to be used in the dishwashing detergents depends on these values.

The foam behavior is decisive for the surfactants that can be used. Low-foam connections are preferred because of the machine mechanics. These are primarily non-ionic surfactants. All compounds known for this area of application, in particular adducts of 4 to 10 moles of ethylene oxide or 2 to 6 moles of ethylene oxide and 2 to 6 moles of propylene oxide with C₁₀- to C₂₀-, preferably C₁₂- to C₁₈-fatty alcohols, each with C₁ - C₄-n-alkyl radicals may be end-capped, and alkyl glucosides having 8 to 18, preferably 8 to 14 carbon atoms in the alkyl radical and 1 to 4, preferably 1 to 1.4, glucoside radicals in the molecule are used.

The total amount of surfactants in the cleaning agent is 0.5 to 5, preferably 1 to 2% by weight.

If the cleaning agents foam too much during use, 0.1 to 6, preferably 0.5 to 4,% by weight of a foam-suppressing compound, preferably from the group of paraffins, hydrophobized silica and bisstearic acid amides, can be added to them. Polymers, especially polycarboxylates, which act as co-builders are also preferably used. Polyacrylic acids and copolymers of maleic anhydride and acrylic acid and the sodium salts thereof are suitable Polymer acids. Commercial products are e.g. B. Sokalan CP 5 and PA 30 from BASF, Alcosperse 175 by 177 from Alco, LMW 45 from NorsoHAAS.

In addition to the constituents mentioned, the claimed mixtures can contain further components, in particular inorganic salts, the sodium sulfate or sodium chloride, as a blending agent. Other possible additives are substances with a buffering action, dyes, perfumes and, if appropriate, enzyme-activating additives, such as ammonium chloride or the like.

If the claimed agents are in powder form, they are packaged in a known manner by grinding and mixing the components. In order to achieve an intimate connection of the powder constituents, it may be appropriate to mix the powder with an aqueous solution of crystallizing salts, e.g. As sodium sulfate, or to spray one of the nonionic surfactants mentioned. This treatment also reduces the tendency of the powder to dust.

The claimed cleaning agent combinations are characterized by a high cleaning ability. They are particularly suitable for removing burnt-on protein-containing food residues, traces of lipstick and tea stains. As far as the mixtures contain enzymes, they are able to prevent the formation of starch deposits on the dish surfaces or to remove existing deposits again. Particularly noteworthy is the low corrosion effect of the claimed mixtures, especially in the case of porcelain on glass decorations. Finally, the greatly reduced and preferably absent phosphate content prevents the possible risk of undesired water re-watering.

The claimed agents can be used both in household dishwashers and in commercial dishwashers. They are added by hand or using suitable dosing devices. In particular, the liquid concentrates are suitable for use in automatic liquid metering devices, as are already common in many cases. The application concentrations in the cleaning liquor are approximately 0.5 - 10 g / l, preferably 2 - 5 g / l, as far as solid or powdery mixtures are concerned.

The rinse program is generally supplemented and ended by a few intermediate rinse cycles with clear water and a rinse cycle with a customary rinse aid following the cleaning cycle. After drying you get a completely clean and hygienically perfect dishes.

Experimental part

• I: δ-Na₂Si₂O₅, das über eine Sinterreaktion gemäß EP-A2-293 640 hergestellt wurde;
• II: β-t-Na₂Si₂O₅, das über eine Sinterreaktion nach Willgallis (60 Stunden, 600 °C, 20% Kristallkeime) hergestellt wurde;
• III: β-h-Na₂Si₂O₅, das über eine hydrothermale Reaktion nach DE 39 39 919 hergestellt wurde.

The following silicates were used:

• I: δ-Na₂Si₂O₅, which was produced by a sintering reaction according to EP-A2-293 640;
• II: β-t-Na₂Si₂O₅, which was produced by a sintering reaction according to Willgallis (60 hours, 600 ° C, 20% crystal seeds);
• III: β-h-Na₂Si₂O₅, which was prepared via a hydrothermal reaction according to DE 39 39 919.

To determine the dissolving behavior of the disilicate, 250 mg (1.37 mmol) of the sample substance was dissolved in 50 ml of water (use concentration 5 g / l) and stirred for 10 or 30 minutes at room temperature. After centrifugation, 40 ml of the supernatant solution were titrated for Na₂O and SiO₂. The results are shown in Table 1 below. It should be noted that one mole of disilicate can release one mole of Na₂O and two moles of SiO₂. The higher dissolution rate of the hydrothermally produced β-h-disilicate, compared to the disilicate obtained via temperature sintering reactions, clearly catches the eye. In all three types of silicate, the alkalinity was released faster than the silicate. The β modifications also showed the higher proportion of dissolved SiO₂ compared to the dissolved Na₂O. With the particularly quickly soluble β-h modification, a particularly high proportion of dissolved silicate was observed. Table 1 Dissolve disilicate in deionized water Disilicate Time (min.) Temp. (° C) Na₂O SiO₂ (mg) (%) (mg) (%) δ 10th 25th 52 61 45 28 30th 25th 57 67 54 32 β-h 10th 25th 59 71 81 49 30th 25th 69 81 107 65 β-t 10th 25th 42 50 61 37 30th 25th 56 66 87 53

The same trends as for demineralized water were observed when dissolving the disilicate in hard water. However, the total amount of disilicate dissolved was lower, since the formation rate of calcium silicates on the surfaces of the crystallites is likely to reduce the rate of dissolution. The tests carried out in water with a calcium hardness of 30 ° d led to the measurement results shown in Table 2 below. Table 2 Dissolve disilicate in 30 ° d Ca²⁺-containing water Disilicate Time (min.) Temp. (° C) Na₂O SiO₂ (mg) (%) (mg) (%) δ 10th 25th 38 45 14 8th 30th 25th 39 46 14 8th β-h 10th 25th 39 46 34 20th 30th 25th 46 55 52 32 β-t 10th 25th 21 24th 16 9 30th 25th 23 26 17th 10th

Since alkalinity is consumed during the rinsing process, for example due to the saponification of fats, it was of interest to know which alkali reserve the cleaning components still have after the alkali has been used. For this purpose, 1% suspensions of the β-h and the δ disilicate were titrated with 0.1 M HCl solution. The hydrochloric acid was added slowly, and after each addition step was waited until a constant pH was reached. The results are shown in Table 3 below. Table 3 Titration of disilicates (100 mg substance, 0.1 M HCl solution) Amount of acid (ml) PH value β-h disilicate δ-disilicate 0 12.40 12.50 10th 12.19 12.35 20th 11.88 12.19 30th 11.13 11.92 40 10.88 11.23 50 10.68 10.54 60 10.43 10.14 70 10.23 9.81 80 9.98 9.44 90 9.69 9.16 100 8.91 8.31 110 3.36 2.96 115 2.61 2.51

Both disilicates have practically the same initial pH value and are neutralized after adding the equivalent amount of hydrochloric acid. However, if you compare the titration curves for β-h- and δ-Na₂Si₂O₅ (see Fig. 1), you can see that the curve in the alkaline range differs significantly. Up to about half the equivalent amount of acids, the δ modification is the more alkaline compound, the difference in pH compared to the β-h curve being up to an entire pH level. After that, the two curves intersect and the β-compound is the more alkaline. Here the differences are more than half a pH level.

Since the β modification is more alkaline after an alkali consumption (due to food residues when rinsing, here simulated by adding acid), this modification has a surprisingly higher alkali reserve, which should result in a better cleaning result. This was actually the case, as the examples below show.

Examples Example 1:

The constituents of the receptors specified below (amounts in% by weight) were converted into granules in the ploughshare mixer while spraying water and subsequent drying. The granules were mixed with the oxidizing agent.

The cleaning performance was determined in a Bosch SMS 6021 dishwasher, using a commercially available phosphate-containing cleaner as standard (sample C). The rinsing conditions were as follows: hard water: 16 ° d, Düsseldorf city water and a detergent dosage from 30 g to 5 l of liquor volume. The soiling was produced according to known standard conditions (see Th. Altenschöpfer in "Seifen, Fette, Anstrichmittel", 73 (1971), pages 459 to 466), and the visual sampling, which was determined in each case from 4 assessments, was carried out on a scale from 0 to 10 Points, where 10 means the best cleaning result. Detergent compositions cleanser A B C. Pentasodium triphosphate - - 35 δ-disilicate 40 - - β-h disilicate - 40 - Soda calc. 6 6 6 Sokalan CP5 ^R 3.5 3.5 - Dehypon LS 45 ^R 1 1 1 Na metasilicate, anhydrous 42 42 42 Sodium perborate monohydrate 7 7 7 water rest rest rest Dehypon LS 54 ^R = Adduct of 5 moles of ethylene oxide and 4 moles of propylene oxide with 1 mole of C _12/14 fatty alcohol Sokalan ^R CP 5 = Maleic anhydride-acrylic acid copolymer, Na salt Cleaning performance cleanser A B C. A B C. Temperature (° C) 50 50 50 65 65 65 milk 8.5 9.0 8.7 9.5 8.7 9.7 Minced meat 7.2 8.8 9.2 8.8 9.5 10.0 Strength 3.3 3.5 3.7 5.3 6.0 7.0 oatmeal 5.5 5.3 4.8 6.7 7.2 7.7

The β-disilicates are preferably used in amounts of 20 to 70, in particular 30 to 60,% by weight.

Example 2:

An important advantage of the β-h-disilicates used according to the invention is that cleaners with a high bulk density can be produced, which is important for the machine-programmed application. Commercial granular cleaners have liter weights between approx. 900 and 1000 g / l. With a dosing recommendation and a dosing box volume of 40 ml (customary on the market), there are amounts of detergent of 36 to 40 g per cleaning cycle. When using cleaner A, due to its low liter weight, there is an underdosing of approx. 20% by mass, which is not to be feared when using the inventive cleaners according to B. are. As a result of a too short dosage, deposits can occur in the machine and on the dishes or a poorer cleaning result can be obtained.

The following bulk densities (g / l) were achieved with the cleaners A and B described in Example 1: Cleaner A Cleaner B 740 950

Claims (1)

1. A phosphate-free dishwashing detergent based on crystalline, layer-form Na disilicates, alkali metal carbonates, oxidizing agents and optionally alkali metal silicates, surfactants, enzymes and polymeric compounds, characterized in that it contains hydrothermally produced Na disilicate corresponding to the formula β-h-Na₂Si₂O₅ as the crystalline layer-form Na disilicate.

Images