EP0423487A2 - Rinse aid for dishwashing machines - Google Patents

Abstract

The present invention relates to a process for the production of rinse aids for dishwashing machines in the form of a solid block which dissolves slowly in water and which contains 5-40, preferably 10-20, % by weight of surfactants and 3-50% by weight, preferably 20-40% by weight, of builders and, preferably, 3.0 to 7.0% by weight of suitable carriers and, where appropriate, up to 1% of dyes and/or perfumes and/or a chlorine-releasing substance, where the builder used is a phosphate-free mixture which contains 30-80% by weight of a sodium aluminium silicate of the zeolite A type, and 20-50% of a polymaleate with a molecular weight of 800 - 10,000 and 0-50% of a biodegradable builder.

Description

The present invention relates to a new rinse aid for dishwashers in the form of a solid block which is slowly soluble in water and does not contain any environmentally harmful phosphates.

Modern dishwashing detergents have a more or less sophisticated control system in which, in addition to pre-rinsing, the main cleaning cycle, in which the actual washing-up liquid is used at higher temperatures, one or more rinse-aid cycles are added before the cleaned dishes are dried under the influence of heat. Rinsing should remove residues of detergent that still adheres to the dishes from the main wash cycle. When washing with water, however, water droplets remain on the dishes, which form blind spots of calcium and magnesium salts after drying, particularly in areas with hard water. It has therefore been customary for a long time to add a rinse aid to the last rinse water used for rinsing, which on the one hand contains a surfactant which ensures that the rinsing water can run off the dishes as residue-free as possible and on the other hand contains builder substances which bind calcium and magnesium ions and thereby a deposition of the corresponding carbonates on the dishes is prevented or carbonates which have already precipitated are brought back into solution. In addition, these rinse aids can also contain agents which give the dishes a surface gloss after drying.

Due to their excellent builder properties, polyphosphates, especially tripolyphosphate, have been used almost exclusively for this purpose in the past. Since these substances only have to be added to the rinse aid solution in very low concentrations, it is common practice not to add liquid rinse aid to the rinse water from a suitable control container using a complicated control mechanism, but rather to add a solid block of rinse aid and suitable carriers that have a very slow dissolution rate. to be inserted directly into the washing chamber of the dishwasher, which is either attached to the machine with a separate basket or the fixed block is placed in the cutlery basket of the dishwasher. In this way, the rinse aid is not only introduced into the rinse aid solution itself, but also into the main and pre-rinse, which, however, is not a problem since it improves the cleaning performance there. The low additional effort for the rinse aid is therefore compensated for in price by a correspondingly smaller amount of the main detergent required. By adding suitable carriers, the rinse aid is dispensed so slowly that a single fixed block, for example with an edge length of 2.5 cm, is sufficient to ensure perfect rinse aid through several rinse cycles.

However, phosphates in rinse aid are increasingly undesirable. On the one hand, despite the small amounts that reach the wastewater via rinse aid, their phosphate content contributes to environmental pollution and thus runs counter to the general goal of reducing the phosphate pollution of the rivers.

On the other hand, it has been found that very small amounts of phosphate in hard water do not act as builders and keep the calcium ions in solution, but rather form poorly soluble deposits of calcium phosphate, which are deposited on the dishes as a veil.

From EP-A 0182 461 rinse aid in the form of solid blocks are known which consist of a poorly water-soluble wetting agent, in particular polyoxypropylene-polyoxyethylene block polymer, urea and an additive which is sparingly soluble in water. The rate of dissolution of the wetting agent is promoted by the urea and slowed down by the additive, so that it can be adjusted within further limits. Such builder-free agents are unsuitable for lime-rich water.

Similar rinse aids are known from EP-A 0154421, which consist of polyethylene glycol, alkanolamides, polyoxyethyl alcohols and polyoxyethylamines, the composition and degree of condensation making it possible to adjust the surfactant action and the dissolution rate. These products are also builder-free and cannot be used in lime-rich water.

From EP-A 0139330 rinse aids are known which consist of a natural or artificially produced clay, in particular of the hectorite type, a wetting agent and sodium citrate and isopropyl alcohol and water as a solvent. In all the embodiments described, the mixtures are added to the rinsing water as a solution or suspension, although solid addition as a powder, tablet, block or granulate is also considered. The handling of such substances is therefore problematic.

It was therefore the task of developing a rinse aid in the form of a solid block which slowly dissolves in water, which, in addition to good rinse aid performance, is above all environmentally friendly and phosphate-free and also in lime-rich detergent ser is usable.

This object is achieved by the features characterized in the patent claims.

• Überraschenderweise hat sich herausgestellt, daß dies nicht der Fall ist, wenn der Zeolithbuilder mit einem Polymaleinat einer definierten Größenordnung, d. h. einem Molekulargewicht von 800 - 10.000 vermischt und auf das Geschirr als Klarspülbestandteil aufgebracht wird. Es wird angenommen, daß diese Polymeren dafür sorgen, daß die Zeolithteilchen sich nicht auf der Geschirroberfläche festsetzen können sondern mit dem Spülwasser ablaufen.

It must seem surprising that zeolite can be used as a builder in a rinse aid, since it was actually to be expected that instead of calcium carbonate deposits, deposits of zeolite particles would now be found on the dishes. In order for the calcium and magnesium ions to be largely bound to the builder in excess, the risk that the builder himself remains as a poorly soluble residue on the bare tableware surface is very great.

• Surprisingly, it has been found that this is not the case if the zeolite builder is mixed with a polymaleinate of a defined size, ie a molecular weight of 800-10,000, and applied to the dishes as a rinse aid component. It is believed that these polymers ensure that the zeolite particles cannot adhere to the surface of the dishes but run off with the rinse water.

To a limited extent, another biodegradable builder known per se can be used instead of the aforementioned zeolites. B. complexing acids such as citric acid, tartaric acid, malic acid or gluconic acid and low molecular weight polyacrylates can be used.

In order to achieve a uniform detachment of the rinse aid from the surface of the solid block, this should be homogeneous, which can be achieved most easily by melting all the components together and allowing the melt to solidify in a glass-like manner. H. without the components crystallizing in larger areas, which could lead to cracking and cracking. For this reason, easily meltable water-soluble carriers, such as the polyetylene glycols which are solid at room temperature, are preferred as carriers. In order to control the solubility in water and thus the rate of detachment, other products such as stearic acid, ethanolamide and / or stearic acid amide are added to this carrier.

The surfactants used must be as low-foaming as possible in order to allow the rinsing solution to flow away clearly. In principle, both cationic and anionic as well as nonionic surfactants can be used. Nonionic surfactants are particularly preferred because of their good degradability, in particular fatty alcohol alkoxylates.

The products of the invention may also contain a small amount of dyes or perfumes in order to make the products more attractive to the consumer. Other additives include, for example, chlorine-releasing agents such as sodium dichloroisocyanate, which can bring about additional sterilization of the dishes, electrolyte salts, such as sodium sulfate or sodium chloride, which influence solubility, or other additives known for this purpose, which may also be present in small amounts in the rinse aid according to the invention .

Table 1 below shows the composition of commercial rinse aid containing phosphates and the composition of several rinse aid according to the invention.

The individual rinse aids weigh 45 - 48g and contain traces of a dye (YellowDye) and 1% lemon perfume in addition to the substances listed in the table. Power and degradation speed correspond to the mean values according to the tests in Tables 2 and 3.

Table 2 contains the drying performance of the rinse aid tested according to Tab. 1 in a dishwasher compared to porcelain, glass or cutlery.

• Das Geschirr wurde nach der Hackfleischmethode verunreinigt. Die Auswertung erfolgte visuell, wobei 50 Porzellanteile, 10 Glasteile und 40 Besteckteile pro Versuch beurteilt wurden. Die Bewertung erfolgte nach folgendem Schema:
• 2 = ohne Tropfen
• 1 = 1 - 2 Tropfen oder 1 Tropfenlaufspur
• 0 = mehr als 2 Tropfen
• zusätzlich wurde ausgewertet, ob die Teile einen Belag aufweisen und die prozentuale Trocknung bestimmt.

A Bosch dishwasher (S 710) and 40 g of a standard detergent (S 44) were used at a washing temperature of 65 o C and a water hardness of 18 German degrees of hardness.

• The dishes were contaminated using the minced meat method. The evaluation was carried out visually, with 50 porcelain parts, 10 glass parts and 40 cutlery parts being assessed per experiment. The evaluation was carried out according to the following scheme:
• 2 = without drops
• 1 = 1 - 2 drops or 1 drop running track
• 0 = more than 2 drops
• In addition, it was evaluated whether the parts have a covering and the percentage drying was determined.

• Die Auflösungsgeschwindigkeit wurde in 10 aufeinanderfolgenden Spülcyclen in einer Kenmore-Maschine der Fa. Sears, USA bestimmt. Das Normal-Waschprogramm wurde verwendet und 60 g S 44 Reiniger pro Waschgang zugegeben. Die Wasserhärte betrug 18 D. H. Die in der Tabelle angegebenen Werte stellen Mittelwerte aus 3 bzw. 5 Spülsteinen dar. Die Steine wurden im oberen Spülkorb angeordnet und ihre Position nach jedem Spülgang gewechselt.

Table 3 shows the dissolution rate of these solids in the rinse cycles.

• The dissolution rate was determined in 10 successive rinse cycles in a Kenmore machine from Sears, USA. The normal wash program was used and 60 g of S 44 detergent were added per wash. The water hardness was 18 DH. The values given in the table represent mean values from 3 or 5 washing stones. The stones were arranged in the upper washing basket and their position changed after each washing cycle.

Claims (4)

1.) Rinse aid for dishwashers in the form of a slow-dissolving solid block which 5-40 preferably 10-20% by weight of surfactants and 3-50% by weight, preferably 20-40% by weight of builder and preferably 3.0 to 7.0% by weight of suitable carriers and, if appropriate up to 10% dyes and / or fragrances and / or a chlorine-releasing substance, contains characterized in that a phosphate-free mixture is used as builder, which 30-80% by weight of a zeolite A type sodium aluminum silicate, and 20 - 50% of a polymaleinate with a molecular weight of 800 - 10,000 as well Contains 0 - 50% of a biodegradable builder. 2.) Rinse aid according to claim 1, characterized in that the carrier substances are 5-50, preferably 15-35% by weight polyethylene glycol, 3-40, preferably 15-30% by weight stearic acid ethanolamide and / or 2-20, preferably 5-15 % By weight of stearic fatty acid amide are contained. 3.) Rinse aid according to one of claims 1-2, characterized in that a nonionic surfactant, in particular a fatty alcohol alkoxylate, is used as the surfactant. 4.) Process for the preparation of rinse aid according to one of claims 1-3, characterized in that the carriers and surfactants are melted and mixed together at temperatures up to 60 ° C, after which the builder substances and any other constituents are stirred in, the mixture in molds is poured and solidified.