EP0264043B1 - Process for the production of cast products containing alkali hydroxide and optionally active chlorine-containing agents for the mechanical cleaning of dishes - Google Patents

Abstract

The process entails a melt of alkali metal silicates, alkali metal hydroxides and, where appropriate, water being equilibrated by cooling or heating at 50 to 75 DEG C and, at a controlled temperature of 70 to 75 DEG C, an active chlorine compound, e.g. chlorinated isocyanuric acid derivatives, Na monochloroamidosulphonate, N-chloro-p-toluenesulphonamide sodium, being incorporated, plus organic complexing agents. The resulting melt is then homogeneously mixed together with a) anhydrous coarse-particle and b) fine-particle penta(alkali metal) triphosphate (a : b ratio by weight = 6 : 1 - 2 : 1) and, where appropriate, other components in a flow-through mixer, poured into moulds and left to solidify to blocks which have a uniform composition and are stable on storage.

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 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 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.

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. B. sodium silicates, pentasodium triphosphate, sodium hydroxide and optionally water, if the preferred water of hydration of the compounds mentioned is not sufficient, and then mild heating of the mixture with stirring to 90 to 100 ° C. until a uniformly molten mass was obtained and cast in molds and solidified to form a dense crystal aggregate.

However, this does not solve all of the problems because the desired 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 are only open at one point then the detergent is rinsed out by the water flow 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 preformed kernels during the solidification of the 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. Example 13, Table 1, shows that a direct addition of the active chlorine-releasing compound to the melt mass 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.

It was therefore an object to find a process for optionally also incorporating active chlorine carriers in the presence of alkali metal hydroxides in the most homogeneous distribution possible in block-form cleaning agents. At the same time, detergent formulations should also be developed that correspond to the current state of the art powder or granular products for commercial dishwashers, without the pentalkalitriphosphate used being hydrolysed and partially or completely degraded to orthophosphate.

In European patent applications EP-A-203 523 and EP-A-203 526 both published around 03.12.86, a method is described, according to which at low and therefore gentle temperatures of 45 to 70 ° C, preferably 45 to 65 ° C, can work if the alkali silicate, anhydrous, as a metasilicate hydrate and / or as a water glass solution, alone or together with solid alkali hydroxide or its monohydrate, is heated to 45 to 48 ° C without the resulting automatic heating to 60 to 65 ° C influence, then with stirring or kneading all other, preferably hydrate-containing constituents, of which lastly, when the melting temperature has dropped to about 50 to 55 ° C, pentasodium triphosphate and / or its hexahydrate, organic complexing agents or an active chlorine-releasing compound, which stirs in the still liquid melt casts any shape, preferably flexible, and solidifies them into blocks.

The invention now relates to a process for the preparation of alkali metal-containing melt-block-shaped, homogeneous and storage-stable agents for the mechanical cleaning of dishes containing alkali silicates and water, preferably as water of crystallization, pentaalkali metal phosphate and optionally a further content of active chlorine-releasing compounds and / or organic complexing agents characterized in that first a melt consisting of alkali silicates, alkali hydroxides and optionally water is generated and this is tempered by cooling or heating to 50-75 ° C, preferably 55-70 ° C, then optionally under careful control at a temperature of incorporates an active chlorine-releasing compound and / or organic complexing agent below 70 ° C., the melt obtained simultaneously with the pentaalkali metal phosphate fraction and, if appropriate, other customary components for such agents in a continuous mixer g ibt, where the additional solid, powder or granular raw materials are distributed in the melt, and the still liquid overall mixture immediately afterwards poured into arbitrarily designed, preferably flexible molds and solidified into blocks in these.

As a continuous mixer, those can be used which are also suitable for the production of suspensions or pastes. Preferred are those which bring about a homogeneous distribution of the pentasodium triphosphate in the melt with short residence times of less than one minute and the narrowest possible residence time spectrum, for example an injection mixer from FMC.

The feed and discharge lines of the mixer are heated so that their internal temperatures are 50 to 75 ° C and correspond to those of the melt. At higher temperatures, partial degradation of the active chlorine carrier is to be feared others also favor the phosphate breakdown in the melt after pouring into the molds. Lower temperatures can lead to at least partial crystallization of the melt in the batching tank, the metering units, the pipelines or the mixer and thereby cause technical malfunctions.

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. Commercially available, approximately 50% aqueous alkali hydroxide solutions can also be used. Only the water content for the overall composition has to be taken into account. The amounts used are advantageously 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 expediently 0 to 60, preferably 0 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, the ratio of Na₂O: SiO₂ being 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 expediently used in amounts of 0 to 30, preferably 0 to 15,% by weight, based on the total agent.

Suitable organic complexing agents, which can be solubility-improving constituents of the melt-block-shaped cleaning agents, 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.

The amount of organic complexing agents is advantageously 0 to 10, preferably 0 to 5% by weight, based on the total agent.

The various chlorinated compounds of isocyanuric acid, such as Na / K dichloroisocyanurate and Na dichloroisocyanurate dihydrate (Na-DCC-2H₂O), Na monochloramidosulfonate (= N-chlorosulfamate), and N-chloro-ptoluenesulfonamide sodium ( "Chloramine T") are used. Common to all is that they have a hydrolysis constant of about 3. 10⁻⁴ or less (see W.G. Mizuno "Dishwashing", Chapter 21, in particular page 875, Table 7 in "Detergency, Theory and Test Methods", Part 3 (1981), publisher Marcel Dekker, N.Y.).

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

With the highly alkaline composition using commercially available sodium triphosphates which are as water-free as possible and with as little phase I content as possible, well-castable and homogeneously solidifying melting blocks can be obtained with the process according to the invention. An increase in the degree of phosphate maintenance to more than 85% can be achieved if granular phosphates with a low degree of residual moisture (below 2%) and a high individual grain density are used. However, sedimentation of the phosphate granules can occur after the melt suspension has been poured into the mold, since the increase in viscosity of the melt is slowed down by a partial breakdown of the triphosphate.

The blocks are then no longer composed homogeneously, so that a dosage according to the recipe is not guaranteed during use (gradual rinsing of the blocks).

In a preferred variant, commercially available, coarse, granular, low-water to anhydrous phosphates and commercially available, finely divided phosphate qualities are therefore simultaneously incorporated into the melt in order to achieve good levels of phosphate retention and, on the other hand, a homogeneous composition of the melting blocks.

The weight ratio of the two types of phosphate to one another can vary within wide limits. In the case of highly alkaline formulations, ratios of coarse-grained to fine-grained phosphate of approximately 10: 1 to 2: 1, preferably 6: 1 to 3: 1, have proven successful. In the case of low-alkaline formulations, degrees of phosphate maintenance of more than 90% are already achieved even with fine-grained phosphate. A total of 2 to 50, preferably 5 to 45,% by weight of pentaalkali phosphate is expediently used.

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

The solidification process of the melts obtained by the process according to the invention takes from a few minutes to about one hour, depending on the size of the mold and the composition of the mass. Depending on their composition, the finished melting blocks are very hard, hard or less hard, but in any case through and by consistently composed and quickly soluble in use.

Examples Example 1 :

10

Gew.-Teilen Wasserglas N (Na₂0 : Si0₂ = 1 : 3,35; 34,5 %ig),

8

Gew.-Teilen NaOH (50 %ig),

35

Gew.-Teilen NaOH-Prills und

11

Gew.-Teilen MCAS-Lösung (Na-Salz der Monochloramidosulfonsäure konfektioniert in NaOH)

angesetzt, wobei die Zugabe der aktivchlorabspaltenden Verbindung bei einer Temperatur unterhalb von 70 °C erfolgte, und auf 67 °C eingestellt. Die Schmelze wurde bei dieser Temperatur in den beheizten FMC-Mischer (Drehzahl der Mischspirale 800 UpM, Drehzahl der Pulverspirale 800 UpM) gefördert. Bei einem Gesamtdurchsatz von ca. 500 kg/h wurden kontinuierlich 64 Gew.-% Schmelze mit 9 Gew.-% feinteiligem (Triphosphat N® von Hoechst - Knapsack) und 27 Gew.-% grobkörnigem Pentanatriumtriphosphat (Makrophos GH® von Benckiser - Knapsack) vermischt. Die resultierende Schmelzsuspension wurde in flexible Formen für 1 kg-Portionen abgegossen. Nach dem Erstarren und Abkühlen wurden Phosphaterhaltungsgrade von mehr als 70 % festgestellt.A mixture consisting of

10th

Parts by weight of water glass N (Na₂0: Si0₂ = 1: 3.35; 34.5%),

8th

Parts by weight of NaOH (50%),

35

Parts by weight of NaOH prills and

11

Parts by weight of MCAS solution (Na salt of monochloramido sulfonic acid made up in NaOH)

prepared, the addition of the active chlorine-releasing compound being carried out at a temperature below 70 ° C., and adjusted to 67 ° C. At this temperature, the melt was conveyed into the heated FMC mixer (speed of the mixing spiral 800 rpm, speed of the powder spiral 800 rpm). With a total throughput of approx. 500 kg / h, 64% by weight of melt with 9% by weight of finely divided (triphosphate N® from Hoechst - Knapsack) and 27% by weight of coarse-grained pentasodium triphosphate (Makrophos GH® from Benckiser - Knapsack ) mixed. The resulting melt suspension was poured into flexible molds for 1 kg portions. After solidification and cooling, degrees of phosphate retention of more than 70% were found.

Example 2 :

32

Gew.-Teilen Natriummetasilikatnonahydrat

4

Gew.-Teilen NaOH-Prills

11

Gew.-Teilen MCAS-Lösung

22

Gew.-Teilen Natriummetasilikat, wasserfrei

erhalten. Das wasserfreie Metasilikat löste sich während der Rührzeit von ca. 30 Minuten in dieser Rezeptur nur teilweise. Der ungelöste Anteil lag suspendiert vor. Die Schmelze wurde mit 62 °C in den FMC-Mischer geführt, dort mit 31 Gew.-% feinteiligem Pentanatriumtriphosphat vermischt und in 1 kg-Portionen abgegossen. Nach Abkühlen und Erstarren wurde ein Phosphaterhaltungsgrad von etwa 90 % ermittelt.In a stirred kettle, a melt consisting of a mixture was made while increasing the temperature to 62 ° C

32

Parts by weight of sodium metasilicate nonahydrate

4th

Parts by weight of NaOH prills

11

Parts by weight of MCAS solution

22

Parts by weight sodium metasilicate, anhydrous

receive. The water-free metasilicate only partially dissolved in this recipe during the stirring time of approx. 30 minutes. The undissolved portion was suspended. The melt was fed into the FMC mixer at 62 ° C., mixed there with 31% by weight of finely divided pentasodium triphosphate and poured off in 1 kg portions. After cooling and solidification, a degree of phosphate retention of about 90% was determined.

Claims (3)

1. A process for the production of homogeneous, storable detergents for dishwashing machines in the form of fused blocks containing alkali metal hydroxides, alkali metal silicates and water, preferably as water of crystallization, pentaalkali metal triphosphate and, optionally, active chlorine donors and/or organic complexing agents, characterized in that a melt consisting of alkali metal silicates, alkali metal hydroxides and, optionally, water is initially prepared and is kept by cooling or heating at 50 to 75°C, an active chlorine donor and/or organic complexing agents are then incorporated, optionally with careful control, at a temperature below 70°C, the melt obtained is introduced into a flow mixer together with the pentaalkali metal triphosphate and, optionally, other typical components of dishwashing detergents, the additional solid, powder-form or granular raw materials being distributed in the melt, and the still liquid mixture is poured immediately afterwards into preferably flexible moulds of any shape and allowed to solidify therein.
2. A process as claimed in claim 1 characterized in that coarse-particle and fine-particle pentasodium triphosphate in a ratio by weight of 10 : 1 to 2 : 1 and preferably 6 : 1 to 2 : 1 are used as the pentaalkali metal triphosphate.
3. A process as claimed in claims 1 and 2 characterized in that the pentasodium triphosphate used is substantially anhydrous with a low phase-I content.