EP0203526B1 - Compounds in melted block form containing alkaline hydroxide and active chlorine for machine dish-washing, and process for their preparation - Google Patents

Abstract

Detergents for dishwashing machines in the form of fused blocks containing alkali metal hydroxides, alkali metal silicates, and from 0.2 to 4% by weight of active chlorine donors having a hydrolysis constant of 3x10-4 or lower (preferably Na- or K-dichloroisocyanurate, Na-dichloroisocyanurate dihydrate, Na-monochloroamido-sulfonate or Na-N-chloro-p-toluene sulfonic acid amide). The process of making the fused blocks comprises heating metasilicate or waterglass solution with or without solid alkali metal hydroxide to 45 DEG to 48 DEG C., allowing the reaction temperature to rise to 60 DEG to 65 DEG C., adding the remaining ingredients including the active chlorine donor at 50 DEG to 65 DEG C., pouring the still liquid melt into flexible molds and allowing it to solidify into blocks therein. The detergent blocks of the invention have good stability to storage and a high dissolving rate in use.

Description

Solid detergents for automatic dishwashing are mainly offered in powder or granular form (agglomerates). 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. pentasodium triphosphate or sodium sulfate, slight improvements in caking or clumping behavior are achieved; 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 remains after Get clumped or caked as a result of moisture ingress. 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 that tend to clump or cake when exposed to moisture, especially in automatic, stocking dosing devices that 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, but this cannot be guaranteed in a damp kitchen atmosphere or after cleaning the device with water without drying the parts of the storage container and the dosing device.

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

However, this does not solve all problems, because the incorporation of compounds containing active chlorine into strongly alkaline cleaning agents is very difficult.

EP-PS 3 769 describes detergent containers, in particular for machine dishwashing, which contain solid detergent blocks made from water and two solid constituents, at least one of which is an alkaline hydratable compound and which are only open at one point then the detergent through the water flow is washed out in the washing machine. If these cleaning agents are to contain active chlorine compounds in addition to alkali hydroxide, which are necessary for the removal of bleachable soiling, such as, for. B. tea, coffee, fruit juices, etc. are considered, these must preferably be introduced as pre-shaped kernels during the solidification of the heat-dissolved cleaning agent in the still soft mass. To better protect the chlorine carrier, the core should still be coated either with paraffin or with a wax-like mono- and dialkyl ester of polyphosphoric acid. Direct incorporation of compounds containing active chlorine, especially in the presence of high concentrations of alkali metal hydroxide, is not considered feasible. In Example 13, Table 1, it is shown that a direct addition of the active chlorine-releasing compound to the dewaxing solution of the other cleaning components leads to a high loss of active chlorine within 24 hours. The investigated chlorine carriers were Ca (OCl) ₂, LiOCl and Na dichloroisocyanurate dihydrate. Depending on the chlorine carrier, residual chlorine activities between only 3.5 and 17.4% of the initial value were determined.

The incorporation of preformed cores with active chlorine-releasing compounds is feasible, but causes high costs due to labor-intensive production and the necessary raw materials. In addition, there are naturally different solubilities of detergent blocks and their core.

The object was therefore to find ways of introducing active chlorine carriers into block-shaped cleaning agents in the most homogeneous distribution possible in the presence of alkali metal hydroxides. At the same time, detergent formulations should be developed that correspond to the current state of common powder or granular products for commercial dishwashers.

In US Pat. No. 2,412,819, alkali hydroxide-containing, melt-block-like agents for the mechanical cleaning of dishes have been described, which by mixing with all other alkaline-reacting active substances such as. B. sodium silicates and pentasodium triphosphate and optionally water, if the preferred water of hydration of the compounds mentioned is not sufficient, and then gentle heating of the mixture with stirring to 90 to 100 ° C until reaching a uniformly molten mass and its pouring into molds and solidification to a dense Crystal aggregate were manufactured. A possible content of active chlorine-containing compounds in these melt-block-shaped agents has not been mentioned there.

The invention now relates to melt block-shaped, alkali hydroxide-containing, homogeneous and storage-stable agents for the mechanical cleaning of dishes containing alkali silicates and water, preferably as water of crystallization, and optionally pentalkalitriphosphate and is characterized in that it is 0.2 to 4% by weight on the active chlorine content and the entire agent, on an active choir-releasing compound which has a hydrolysis constant of 3. 10 ^-4 or less.

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

Alkali silicates in particular are alkali metal silicates, namely water-free, but advantageously in the form of sodium metasilicate. 9 H₂O, sodium metasilicate. 6 H₂O and sodium metasilicate. 5 H₂O used. The amounts used in the particular form are in particular 2 to 60, preferably 5 to 50,% by weight, based on the total composition. But you can also partially or completely replace the alkali metal silicates with water glass solutions, which Ratio of Na₂O: SiO₂ is 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 in particular 2 to 50, preferably 5 to 45,% by weight, anhydrous, based on the total composition, of pentaalkali metal triphosphate, which is used as 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. However, it can also be used without water, depending on the total water content of the other components.

The various chlorinated compounds of isocyanuric acid, such as Na / K-di-chloroisocyanurate and Na dichloroisocyanurate dihydrate (Na-DCC-2H₂O), Na-monochloramidosulfonate (= N-chlorosulfamate), and N-chloro-p- toluenesulfonamide sodium ("chloramine T") are used. Common to all is that they have a hydrolysis constant of about 3 10 etwa or less (compare WG Mizuno "Dishwashing", Chapter 21, in particular page 875, Table 7 in "Detergency, Theory and Test Methods", Part 3 (1981) , Publisher Marcel Dekker, NY).

They are in amounts of 0.2 to 4, preferably from 0.5 to 2 wt .-%, based on the active chlorine content, the z. B. to be determined by iodometric titration, and the entire mean used.

The total water content of the melt-block-shaped cleaning agents from dense crystal aggregates is 10 to 40, preferably 15 to 30% by weight. It is preferred by the crystal water content of the alkaline active substances, but possibly also introduced 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 is first anhydrous, as a metasilicate hydrate and / or as a water glass solution, alone or together with solid alkali hydroxide or its monohydrate at 45 to 65 ° C until silum bie; warmed without affecting the automatic heating to 60 to 65 ° C, then with stirring or kneading all other, preferably hydrate-containing components, of which last, at temperatures from 50 to 65 ° C, preferably from 55 to 63 ° C, pentasodium triphosphate and / or whose hexahydrate and the active chlorine-releasing compound are stirred in, the still liquid melt is poured into arbitrarily shaped, preferably flexible, molds and solidifies into 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:

A mixture of 50 parts by weight of Na₂SiO₃. 9 H₂O and 50 parts by weight of Na0H prills were heated in a stainless steel vessel with stirring using a Teflon stirrer from outside to 46 to 47 ° C, the elimination of the crystal water and at the same time a temperature increase (60 to 65 ° C) due to the hydration of the Na0H. . After cooling to temperatures below 55 ° C, the chlorine carrier was incorporated into the flowable suspension and poured into wax cardboard molds. Trichloroisocyanuric acid (TICA), sodium di-chloroisocyanurate dihydrate (NaDCC-2 H₂O) and chloramine T (Cl-T) were incorporated as chlorine carriers. The amount of chlorine carrier was chosen so that the same active chlorine content was present in the finished product. This resulted in the following compositions (data in% by weight):

The cast melting bodies had a weight of 25 to 30 g. They were stored in the laboratory and the active chlorine content (A-Cl) was determined in a known manner after appropriate times.

The results show that the cheapest chlorine stability with almost complete retention of active chlorine was observed for chloramine T, while the use of TICA is unsuitable.

Example 2:

10 parts by weight of water glass solution were at 50 to 55 ° C with 50 parts by weight of NaOH. H₂O and 40 parts by weight of anhydrous pentasodium triphosphate and the active chlorine carrier mixed. The suspension was poured into molds where it quickly solidified. TICA and Cl-T were used as active chlorine carriers. The amount of active chlorine carrier was chosen so that the same active chlorine contents were present in the finished product. This resulted in the following compositions (data in% by weight):

As described in Example 1, corresponding storage tests were also carried out here:

Here too, good storage stability is found for chloramine T, while TICA is also unsuitable for use.

Example 3:

12 parts by weight of water glass solution were mixed at room temperature with 55 parts by weight of NaOH prills, the temperature rising to about 65 to 70 ° C. After cooling to about 50 to 55 ° C., the active chlorine-containing component and 33 parts by weight of pentasodium triphosphate were mixed into the solution and the melt was poured in. The sodium salt of N-monochloramidosulfonic acid (MCAS) was stirred in as the active chlorine carrier as an aqueous solution (9.4% active chlorine) and chlorine solution (12.8% active chlorine). The amounts of chlorine carriers used were chosen so that comparable levels of active chlorine were available. This resulted in the following compositions (data in% by weight):

Storage tests were carried out with the cleaner blocks produced, as described in Example 1. Formulation 3c could not be checked as well, since active chlorine contents of less than 40% of the initial value were found immediately after production. Chlorine solution is therefore not suitable as a component of the agents according to the invention.

The results show that the chlorine carrier MCAS can be incorporated in a sufficiently stable manner in a homogeneous distribution.

Example 4:

10 parts by weight of water glass solution (34.5% as in Example 2) with 8 parts by weight of a 50% aqueous NaOH solution were placed in a stainless steel vessel and mixed. 35 parts by weight of solid NaOH in the form of microprills were stirred into the solution, which initially only partially dissolved. After adding 11 parts by weight of an MCAS chlorine carrier solution (cf. Example 3), a homogeneous melt was obtained, the temperature of which was set at 63 ° C. 36 parts by weight of pentasodium triphosphate were then rapidly stirred into the melt. The resulting mass was poured. The material solidified to form stable blocks within 10 - 15 minutes.

Claims (4)

1. Homogeneous and storable detergents for dishwashing machines in the form of fused blocks containing alkali hydroxides, alkali silicates and water, preferably as water of crystallization, and optionally pentaalkali triphos­phate, characterized in that they contain 0.2 to 4% by weight, based on the active chlorine content and on the detergent as a whole, of an active chlorine donor having a hydrolysis constant of 3.10^-4 or lower.

2. Detergents as claimed in claim 1, characterized in that they contain Na- or K-dichloroisocyanurate,.Na-dichlo­roisocyanurate dihydrate, Na-N-monochloroamidosulfonic acid or Na-N-chloro-p-toluene sulfonic acid amide as active chlorine donor.

3. Detergents as claimed in claims 1 and 2, characterized in that they contain the active chlorine donor in quant­ities of from 0.5 to 2% by weight, based on the active chlorine content and on the detergent as a whole.

4. A process for producing the homogeneous, storable detergents in the form of fused blocks containing alkali hydroxides claimed in claim 1, characterized in that the alkali silicate, anhydrous, as metasilicate and/or as waterglass solution, is first heated either on its own or together with solid alkali hydroxide or its monohydrate to 45 to 65°C - without influencing the resulting spontaneous heating to 60 to 65°C - until a melt is formed, all the other constituents, preferably containing water of hydra­tion, including last of all - after the temperature of the melt has fallen to 50 to 65°C and preferably 55 to 63°C - pentasodium triphosphate and/or its hexahydrate, and the active chlorine donor are then introduced with stirring or kneading and the still liquid melt is poured into preferab­ly flexible moulds of any shape and allowed to solidify into blocks therein.