EP0203523A2 - Alkaline hydroxide-containing compounds in melted block form for machine dish-washing, and process for their preparation - Google Patents

Abstract

The agents contain, besides 5 to 50% by weight of anhydrous sodium hydroxide, alkali metal silicates, water of crystallisation and penta-alkali metal triphosphate, 0.5 to 5% by weight of organic complexing agents to increase the rate of dissolution, especially sodium citrate dihydrate, Na salts of nitrilotriacetic acid, of ethylenediaminetetraacetic acid, of ethylenediaminetetramethylene- tetraphosphonic acid, of diethylenetriaminepentaphosphonic acid, of 1-hydroxyethane-1,1-diphosphonic acid, of 2-phosphonobutane-1,2,4- tricarboxylic acid. Preparation: alkali metal silicate (metasilicate hydrate or waterglass) is heated, where appropriate together with solid sodium hydroxide, at 45 to 48 DEG C, without influencing the autogenous heating occurring thereby. Other components are added while stirring, lastly, when the melting point has fallen to 50 to 55 DEG C, pentasodium triphosphate and organic complexing agents. The still liquid melt is poured into flexible moulds and left to solidify to blocks. Advantages: no aggregation on exposure to moisture, high speed of dissolution on use.

Description

Solid detergents for automatic dishwashing are mainly used in powder or Granular form (agglomerates) offered. The individual particles of these agents have a preferred diameter between 0.01 and 3 mm. A serious disadvantage of this type of solid cleaning agents, especially those used in the field of large-scale commercial use with a content of 10 to 60% by weight of alkali metal hydroxides, is that, due to the hygroscopicity of individual raw materials, small amounts of moisture have a strong tendency to Baked or clumped.

By adding so-called "anticaking" agents, such as. B. paraffin, or by enveloping strongly hygroscopic components, such as. B. the alkali metal hydroxides and sodium metasilicate, with powdery substances such. B. the pentasodium triphosphate or sodium sulfate slight improvements in the baking or. Achieved clumping behavior; Larger amounts of moisture in the form of water or water vapor nevertheless lead to caking or clumping of the powdery or granulated (agglomerated) cleaning agents.

This does not make the cleaning agents unusable, because the effect of the components is retained even after clumping or caking due to the ingress of moisture. For the user, however, the quality of the cleaning agents often appears to be reduced or poor in most cases for optical reasons alone, which leads to complaints.

A disadvantage is the use of cleaning agents which tend to clump or cake when exposed to moisture, in particular in automatic, stocking dosing devices which are used in large numbers in the area of large-scale commercial use of single-tank and multi-tank dishwashers. There are metering disorders in the way that too little cleaning agent is discharged or even mechanical damage to the dispenser system occurs, so that it becomes unusable. The only remedy is to prevent the entry of moisture into the storage container - which, however, cannot be guaranteed in a damp kitchen atmosphere or after cleaning the device with water without special drying of the parts of the storage container and the dosing device.

The clumping or caking of alkaline cleaning agents can be avoided, inter alia, by producing them in block form from the outset and packaging, distributing and using them in a moisture-proof manner.

In US Pat. No. 2,412,819 - melt-block detergents for automatic dishwashing have already been described, which are mixed together by mixing all alkaline-reacting, preferably hydrate-containing active substances, such as. As sodium silicates, pentasodium triphosphate, sodium hydroxide and optionally water, if the preferred water of hydration of the compounds mentioned is not sufficient, and then mildly heating the mixture with stirring to 90 to 100 ° C until a uniformly molten mass is obtained and poured into molds and solidified a dense crystal aggregate.

It has now been found that one can obtain - block-shaped, alkali hydroxide-containing detergents for the mechanical cleaning of dishes with not only good mechanical strength, but also high dissolving speed when used, if they contain alkali silicates, water, preferably in the form of water of crystallization, and optionally pentaalkali metal phosphate and additionally contain organic complexing agents which bring about a strong increase in the dissolution rate.

The invention therefore relates to - melt-block-shaped, alkali hydroxide-containing agents for the mechanical cleaning of dishes containing alkali silicates, water, preferably in the form of water of crystallization, and optionally pentaalkali metal phosphate, which are characterized by a further content of organic complexing agents.

As alkali hydroxide, potassium and, for price reasons, preferably sodium hydroxide are suitable, which are preferably in solid form, ie. H. can be used as flakes, flakes or prills, practically anhydrous or as a monohydrate. The amounts used are from 2 to 70, preferably 5 to 50,% by weight, anhydrous, based on the total composition.

Preferred alkali silicates are alkali metal silicates, anhydrous, but advantageously in the form of sodium metasilicate. 9 H ₂ 0, sodium metasilicate. 6 H ₂ 0 and sodium metasilicate. 5 H ₂ 0 used. The amounts used in the respective form are 2 to 60, preferably 5 to 50,% by weight on the entire mean. However, they can also be partially or completely replaced by water glass solutions, the ratio of Na: 0: SiO _: 1: 1 to 1: 4, preferably 1: 2 to 1: 3.5. Because of the higher silicate content of the water glass, its solutions are used in amounts of 2 to 30, preferably 5 to 15% by weight, based on the total agent.

It has also proven advantageous to add 2 to 50, preferably 5 to 45% by weight, based on the total composition, of pentaalkali metal triphosphate which is used in anhydrous form, as a hexahydrate or as a mixture of hexahydrate with small amounts of anhydrous pentasodium triphosphate, so that a total water content of 5.5 moles is calculated.

Possible solubility-improving organic complexing agents which are a constituent of the - melt-block-shaped cleaning agents according to the invention are polycarboxylic acids, hydroxycarboxylic acids, aminocarboxylic acids, carboxyalkyl ethers, polyanionic polymers, in particular polymeric carboxylic acids and phosphonic acids, these compounds being used in the form of their water-soluble salts. Examples of polycarboxylic acids are dicarboxylic acids of the general formula HOOe- (eH ₂ ) _n -COOH with n = 0 to 8, also maleic acid, methylene malonic acid, citraconic acid, mesaconic acid, itaconic acid, non-cyclic polycarboxylic acids with at least 3 carboxy groups in the molecule, such as, for. B. tricarballylic acid, aconitic acid, ethylene tetracarboxylic acid, 1,1,3,3-propane-tetracarboxylic acid, 1,1,3,3,5,5-penta-hexacarboxylic acid, hexane hexacarboxylic acid, cyclic di- or polycarboxylic acids, such as, for. B. cyclopenta-tetracarboxylic acid, cyclohexane-hexacarboxylic acid, tetrahydrofuran tetracarboxylic acid, phthalic acid, terephthalic acid, benzenetri-, -tetra- or -pentacarboxylic acid and mellitic acid.

Examples of hydroxymono- or polycarboxylic acids are glycolic acid, lactic acid, malic acid, tartronic acid, methyltartronic acid, gluconic acid, glyceric acid, citric acid, tartaric acid, salicylic acid.

Examples of aminocarboxylic acids are glycine, glycylglycine, alanine, asparagine, glutamic acid, aminobenzoic acid, iminodi- or triacetic acid, hydroxyethyliminodiacetic acid, ethylenediaminetetraacetic acid, hydroxyethyl-ethylenediamine-triacetic acid, diethylenetriamine-pentaacetic acid, and higher homologyl carboxylic acid, dieidyl carboxylic acid, the homidyl carboxylic acid, the homidyl carboxylic acid, the homidyl carboxylic acid, the homidyl carboxylic acid, the homidyl carboxylic acid, the homidyl carboxylic acid and the homidyl carboxylic acid, the homidyl carboxylic acid, the homidyl carboxylic acid and the homidyl carboxylate, the homidyl carboxylic acid, the homidyl carboxylic acid, the homidyl carboxylic acid, the homidyl carboxylic acid and the homidyl carboxylic acid, the homidyl carboxylic acid and the homomization of a carboxylic acid with the addition of a homolog. B. acetic acid, succinic acid, tricarballylic acid and subsequent saponification or by condensation of polyamines with a molecular weight of 500 to 10,000 with chloroacetic or bromoacetic salts can be prepared.

Examples of carboxyalkyl ethers are 2,2-oxydisuccinic acid and other ether polycarboxylic acids, in particular polycarboxylic acids containing carboxymethyl ether groups, which include corresponding derivatives of the following polyhydric alcohols or hydroxycarboxylic acids which can be fully or partially etherified with the glycolic acid: glycol, di- or triglycols, glycerol, di or triglycerol, glycerol monomethyl ether, 2,2-dihydroxymethyl propanol, 1,1,1-trihydroxymethylethane, 1,1,1-trihydroxymethyl propane, erythritol, pentaerythritol, glycolic acid, lactic acid, tartronic acid, methyl tartronic acid, glyceric acid, erythronic acid, malic acid, malic acid, citric acid, citric acid, citric acid, citric acid, citric acid, citric acid, Trihydroxyglutaric acid, sugar acid, mucic acid.

The carboxymethyl ethers of sugar, starch and cellulose can be mentioned as transition types to the polymeric carboxylic acids.

Among the polymeric carboxylic acids z. B. the, polymers of acrylic acid, hydroxyacrylic acid, maleic acid, itaconic acid, mesaconic acid, aconitic acid, methylene malonic acid, citraconic acid and the like, the copolymers of the above-mentioned carboxylic acids with one another or with ethylenically unsaturated compounds, such as ethylene, propylene, isobutylene, vinyl alcohol, vinyl methyl ether, furan, Acrolein, vinyl acetate, acrylamide, acrylonitrile, methacrylic acid, crotonic acid etc., such as B. the 1: 1 copolymers of maleic anhydride and ethylene or propylene or furan play a special role.

Further polymeric carboxylic acids of the type of polyhydroxypolycarboxylic acids or polyaldehydopolycarboxylic acids are essentially substances composed of acrylic acid and acrolein units or acrylic acid and vinyl alcohol units, which are obtained by copolymerizing acrylic acid and acrolein or by polymerizing acrolein and subsequent Cannizzaro reaction, optionally in the presence of formaldehyde , are available.

Examples of phosphorus-containing organic complexing agents are alkane polyphosphonic acids, amino and hydroxyalkane polyphosphonic acids and phosphonocarboxylic acids, such as. B. the compounds methanediphosphonic acid, propane-1,2,3-triphosphonic acid, butane-1,2,3,4-tetraphosphonic acid, polyvinylphosphonic acid, 1-aminoethane-1,1-diphosphonic acid, 2-amino-1-phenyl -1,1-diphosphonic acid, aminotrimethylene triphosphonic acid, methylamino or ethylaminodimethylene diphosphonic acid, ethylene diaminotetramethylene tetraphos phonic acid, diethylenetriaminepentamethylenepentaphosphonic acid, 1-hydroxyethane-1,1-diphosphonic acid, phosphonoacetic acid, phosphonopropionic acid, 1-phosphonoethane-1,2-dicarboxylic acid, 2-phosphonopropane-2,3-dicarboxylic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, 2-phosphonobutane-2,3,4-tricarboxylic acid.

A content of sodium citrate dihydrate, the sodium salt of nitrilotriacetic acid, the sodium salt of ethylene diamine tetraacetic acid, the sodium salt of ethylene diamine tetramethylene tetraphosphonic acid, the sodium salt of diethylene triamine pentamethylene pentaphosphonic acid, the sodium salt of 1-hydroxyethane-1,1-triphosphononic acid and is preferred , 2,4-tricarboxylic acid.

The amount of organic complexing agents is 0.1 to 10, preferably 0.5 to 5% by weight, based on the total agent.

The total water content of the - block-shaped, alkali hydroxide-containing cleaning agents from dense crystal aggregates is 10 to 40, preferably 15 to 30 wt .-%. It is preferably introduced by the crystal water content of the alkaline reacting active substances, but optionally also via water glass solutions. The calculations of the water content must therefore be based on these compounds.

As is known, pentasodium triphosphate hydrolyzes in the presence of alkali metal hydroxides. The hydrolysis is increased by elevated temperatures. The procedure described in US Pat. No. 2,412,819 is therefore carried out at the lowest possible melting temperatures of 90 to 100.degree.

It has been shown that it is possible to work at much lower and therefore gentler temperatures of 45 to 70 ° C., preferably 45 to 65 ° C., if, according to the invention, the alkali silicate, as a metasilicate hydrate or as a water glass solution alone or together with solid alkali hydroxide is used or its monohydrate is heated to 45 to 48 ° C without affecting the automatic heating to 60 to 65 ° C that occurs, then with stirring or kneading all other components, preferably hydrate water, of which the last when the melting temperature is about 50 to 55 ° C has dropped, pentasodium triphosphate and / or its hexahydrate and the organic complexing agent are stirred in, and the still liquid melt is poured into arbitrarily designed, preferably flexible molds and solidifies to form blocks therein.

The solidification process takes a few minutes to about an hour depending on the size of the mold. Depending on their composition, the melting blocks are very hard, hard or less hard, but in any case consistently and thoroughly composed and quickly soluble when used.

Examples Example 1:

25 parts by weight of sodium metasilicate. 9 H _: 0 and 40 parts by weight of sodium hydroxide flakes were heated together in a stainless steel vessel with stirring using a Teflon stirrer from outside to about 45 ° C. Then the mixture automatically heated up to 60 to 65 ° C. by the hydration of the sodium hydroxide. Then 20 parts by weight of sodium metasilicate. 5 H _: 0.5 part by weight of anhydrous sodium metasilicate and - finally 10 parts by weight of pentasodium triphosphate with a calculated crystal water content of 5.5 mol were stirred in, a homogeneous, free-flowing melt being obtained which cooled in the process. At a temperature of 55 to 50 ° C, the melt was poured into a wax cardboard cylinder with a height of 3 cm and a diameter of 2 cm, where it solidified after only 10 minutes.

The rate of dissolution of the cleaning agent after solidification was determined in a laboratory apparatus. For this purpose, 15 g of the cleaning agent to be tested, which was in the form of a solid, compact, form-freed cylinder (diameter 2 cm, height approximately 3 cm), were placed in a 250 ml wash bottle according to DIN 12596 made of borosilicate glass. The wash bottle was then closed with a Drechsel wash bottle insert and secured with a cut holder. A water mixture of 50% by volume at 14 ° C. and 16 ° C. was passed through the bottle at a rate of 20 liters per hour and the time in which the shaped body was completely dissolved was determined. The dissolution rate was defined in grams per hour. In the composition according to Example 1, it was 24 grams per hour.

Example 2:

Analogously to Example 1, 6 further melt block cleaners were produced, but the proportion of 5 parts by weight of anhydrous sodium metasilicate by the same amount of X, ie sodium citrate dihydrate (Na citrate 2 H ₂ 0), the Na trium salt of nitrilotriacetic acid (NTA), the sodium salt of ethylenediaminetetraacetic acid - (EDTA), the sodium salt of ethylenediaminetetraphosphonic acid (EDTP), the sodium salt of 1-hydroxyethane-1,1-diphosphonic acid (HEDP) and in particular the sodium salt of 2-phosphonobutane1,2, 4-tricarboxylic acid (PBS) was replaced. The improvements achieved in the dissolving speed are shown in Table 1 below:

Examples 3 to 5:

Melting blocks of the following composition were produced analogously to Example 1, the pentasodium triphosphate and / or the PBS in each case being stirred into the still liquid melt below a temperature of 55 ° C. The dissolution behavior was determined as indicated in Example 1. The results are shown in Table 2. They show that the addition of PBS to melts of any composition leads to a significant improvement in the dissolution behavior:

Claims (4)

1. Melting block-shaped, alkali hydroxide-containing agents for the mechanical cleaning of dishes containing alkali silicates, water, preferably in the form of water of crystallization, and optionally pentaalkali metal phosphate, characterized by a further content of organic complexing agents. 2. Composition according to claim 1, characterized in that as the organic complexing agent sodium citrate dihydrate, the sodium salt of nitrilotriacetic acid, the sodium salt of ethylenediaminetetraacetic acid, the sodium salt of ethylenediaminetetramethylene tetraphosphonic acid, the sodium salt of diethylenetriaminepentaphosphonic acid, the sodium salt of 1-hydroxydiphosphonic acid and the sodium salt 2-phosphonobutane-1,2-4-tricarboxylic acid is contained. 3. Composition according to claim 1, the content of organic complexing agents 0.1 to 10, preferably 0.5 to 5 wt .-%, based on the total composition. 4. A process for the preparation of - melt-block-shaped cleaning agents according to claim 1, characterized in that first the alkali silicate, as a metasilicate hydrate or water glass solution, alone or together with solid alkali metal hydroxide or its monohydrate, is heated to 45 to 48 ° C without the occurring automatic Influence on heating to 60 to 65 ° C, then with stirring or kneading adds all other, preferably hydrate water-containing components, of which finally, when the melting temperature has dropped to about 50 to 55 ° C, stir in pentasodium triphosphate and / or its hexahydrate and the organic complexing agent and pouring the still liquid melt into any shape, preferably flexible, and solidifying it into blocks.