EP0900266B1 - Method of producing compact cleaning agents for industrial dish washing machines - Google Patents

Description

The present invention relates to a method for the control of water-based cleaning agents variable strength based on alkali hydroxide. To set the desired The cleaning agents contain glycol, glycol derivatives with a firm consistency and / or certain alkanolamines and alkali hydroxide in solid form.

Highly alkaline cleaning agents are in a wide variety of forms commercially available, e.g. B. as a powder, as granules, as a liquid, as Melting block or as a tablet made by compression.

Each form of presentation has very specific ones for a defined purpose Advantages and disadvantages. For cleaning textile surfaces or for manual mechanical cleaning of hard surfaces have powder, Granules or liquids have proven to be useful for machine cleaning hard surfaces, e.g. B. machine cleaning of dishes, in addition to powders, Granules or liquids increasingly also produced by pressing Tablets or obtained by melting and then cooling block-shaped cleaners (melting blocks) can be used. Tablets and Melting blocks offer the advantage of precise and precise compared to powders simple dosing, do not dust and are easy to handle.

These advantages can be found, for example, in household dishwashers use, but especially in continuously working commercial dishwashers, in which the items to be cleaned are washed through different washing zones is driven.

It has now been shown that very hard tablets and very hard enamel blocks Have disadvantages. So z. B. breakage of such tablets occur; Tablets damaged in this way naturally no longer offer that Advantage of accurate dosing. Another problem with tablets is that the desired solubility in water cannot always be guaranteed, d. H. Sometimes tablets dissolve too quickly or too slowly. at Enamel blocks can be expected to have a high breaking strength during transport Larger containers have a problem with the dosage of these very solid ones Detergent. They also require both tablets as well Melting blocks have so far been very complex manufacturing processes, especially in the Processing of alkaline melts places particularly high demands on the the materials used and the selected conditions.

A high degree of homogeneity of the cleaners obtained is also particularly desirable but is often difficult to achieve with solid cleaners. This problem occurs with liquid cleaners that can be easily stirred less. He wishes would be the homogeneity of a liquid, a viscous liquid or a stirrable paste, which can then be variably controlled into a solid Rigidity solidifies to its advantages in storage and storage at this stage Use transport and dosage. It would be particularly desirable if the stirrability at temperatures up to about 40 ° C would be maintained, then less temperature-stable components could also be added

The object of the present invention is to provide a process for producing highly alkaline, on alkali metal hydroxide, preferably potassium or sodium hydroxide, particularly preferably sodium hydroxide based cleaning agent of a general kind for textile surfaces, preferably but those for cleaning hard surfaces, e.g. B. dishes, and in particular cleaning agents for the commercial cleaning of dishes to provide the benefits of powders and liquids on the one hand and the On the other hand, combine the advantages of tablets and melting blocks. The means that cleaning agents are to be produced, one of the most varied Have defined solubility, on the other hand, they are stable in transport and storage and, moreover, fast, are easy and precise to dose, they do not dust and without great technical Effort to manufacture and easy to fill. Especially the stirrability in the production and the controlled variable strength of the cleaning agents production and storage would and should offer great advantages be taken into account. A process should be developed as to what it permitted, less temperature-stable substances below 42 if necessary ° C to be incorporated without endangering the other tasks

Of course, the cleaning agents must also be provided at the same time Requirements such as good cleaning power, degreasing power, etc. are met.

The state of the art already includes both higher-viscosity and pasty cleaning agents have been described, as well as solid detergents in tablets or Block form.

For example, in the German published application DE-A-31 38 425 the rheological Behavior of the cleaners described there so described that a gel-like paste by the action of mechanical forces, for example by Shake or apply pressure to a deformable storage bottle or tube or liquefied by means of a metering pump and easily from a spray nozzle expresses.

US Pat. No. 3,607,764 describes glass cleaning agents in solid form, which are diluted into a sprayable solution. These funds include Sodium or potassium hydroxide, sodium or potassium tripolyphosphate, sodium or Potassium pyrophosphate, hydroxycarboxylic acid builder, a water soluble nonionic surfactant, alkylene glycol ether and optionally sodium carbonate. A control of the viscosity or the strength in the sense of the present Invention is not described.

Japanese patent specification JA-A-84/182870 describes solutions of alkali metal hydroxides in glycols or alcohols, which are neutralized with long-chain Carboxylic acids become viscous and a silicone oil is added get pasty consistency, making them used as pastes in leather greasing can be.

Japanese patent specification JA-A-86/296098 describes anhydrous solid cleaning agents based on alkali hydroxides. Here, the alkali carrier in Alkanolamines and water-soluble glycol ethers mixed, creating a solid Cleaner receives. A technical lesson on the variable reduction in strength is not described.

WO-A-95/07976 describes a cleaning agent in tablet form which is particularly suitable for use in commercial dishwashers. In a preferred embodiment, this agent contains the following Components: 40 to 70% alkali metal hydroxide, 20 to 60% sequestering agent, in particular a mixture of sodium tripolyphosphate and sodium tripolyphosphate hexahydrate, 1 to 4% water-soluble polyacrylic acid with a Molecular weight between 2,000 and 20,000, 0.5 to 5% non-ionic surfactant based of EO / PO block copolymers, 1 to 4% propylene glycol, 2.5 to 10% water of hydration and a total of 2 to 6% liquid components. As additional components soda, silicates and bleaches containing active chlorine are possible. For the production first the solid components (soda and tripolyphosphates) with each other mixed and then with the mixture of liquid components (polyacrylic acid dissolved in water, nonionic surfactant and propylene glycol) sprayed. this Premix alkali metal hydroxide and bleach are added and then the The mixture obtained is tableted.

a) wäßrige Alkalimetallhydroxidlauge in einer Menge von 21 bis 70 Gew.-% und

b) zum Aufbau einer erhöhten Viskosität eine Verbindung der Formel I HOCH₂CH(R¹)OR² in der R¹ für ein Wasserstoffatom oder eine Methylgruppe steht und R² unabhängig davon ein Wasserstoffatom, eine C₁ bis C₄-Alkylgruppe, eine Gruppe CH₂CH(R³)OR⁴ oder eine Gruppe CH₂CH(R⁵)OCH₂CH(R⁶)OR⁷ bedeutet, worin R³, R⁵ und R⁶ für Wasserstoffatome oder Methylgruppen und R⁴ und R⁷ für Wasserstoffatome oder C₁ bis C₄-Alkylgruppen stehen, und/oder eine Verbindung der Formel II, HOCH₂CH(R⁸)_3-xNH_x in der R⁸ für ein Wasserstoffatom oder eine Methylgruppe und x für eine der Zahlen 0,1 oder 2 steht,
in einer Gesamtmenge von 0,5 bis 40 Gew.-% vermischt werden und danach festes Alkalimetallhydroxid in einer Menge von bis zu 35 Gew.-% zugegeben wird, wobei alle Gew.-%-Angaben auf das gesamte Reinigungsmittel bezogen sind.

In contrast, the present invention relates to a method for producing a solid cleaning agent with a controllably variable strength, which has a water content in the range from 10 to 35% by weight and contains alkali metal hydroxide and glycol and / or alkanolamines, characterized in that

a) aqueous alkali metal hydroxide solution in an amount of 21 to 70 wt .-% and

b) to build up an increased viscosity, a compound of formula I. HIGH ₂ CH (R ¹ ) OR ² in which R ^{1 represents} a hydrogen atom or a methyl group and R ² independently of it a hydrogen atom, a C ₁ to C ₄ alkyl group, a group CH ₂ CH (R ³ ) OR ⁴ or a group CH ₂ CH (R ⁵ ) OCH ₂ denotes CH (R ⁶ ) OR ⁷ , in which R ³ , R ⁵ and R ^{6 represent} hydrogen atoms or methyl groups and R ⁴ and R ^{7 represent} hydrogen atoms or C ₁ to C ₄ alkyl groups, and / or a compound of the formula II, HIGH ₂ CH (R ⁸ ) _3-x NH _x in which R ^{8 represents} a hydrogen atom or a methyl group and x represents one of the numbers 0, 1 or 2,
are mixed in a total amount of 0.5 to 40% by weight and then solid alkali metal hydroxide is added in an amount of up to 35% by weight, all the% by weight data being based on the total cleaning agent.

For the purposes of the process according to the invention, it is preferred that the aqueous Alkali metal hydroxide solution is a 42 to 55% strength by weight potassium or sodium hydroxide solution, preferably sodium hydroxide solution is used. The aqueous Alkali metal hydroxide solution preferably in an amount of 35 to 55% by weight, based on the detergent used.

Preferred compounds of the formula I are ethylene glycol, 1,2-propylene glycol, Butyl glycol or butyl diglycol and as compounds of the formula II preferably ethanolamine, diethanolamine or triethanolamine used. in this connection it is particularly preferred as the compound of formula I 1,2-propylene glycol and / or use diethanolamine as a compound of formula II. The Compounds of the formulas I and / or II are preferably used in one Total amount of 1 to 10 wt .-%, based on the detergent, used.

In the sense of the method according to the invention, it is further preferred as a solid Alkali metal hydroxide potassium or sodium hydroxide, preferably sodium hydroxide, use. The solid alkali metal hydroxide is preferably in one Amount of 2 to 35 wt .-%, based on the detergent, added.

The solid cleaning agent produced according to the invention achieves in one Penetration test according to ISO 2137 at 20 ° C values up to 25 mm, preferably between 0.1 and 25 mm.

ISO 2137 describes, as also mentioned in the examples, penetration measurements with calibrated metal cylinders whose penetration depths are measured become. The test can still be carried out if the one used there narrowest metal cylinder can still penetrate the substance to be tested. Without The invention is intended to be limited to some comparable consistencies are described, which describe the variably variable strength.

Accordingly, cleaning agents produced in accordance with the invention cannot at 20 ° C.-40 ° C. a container, e.g. B. an inverted open glass. The However, the consistency according to the invention can also take the form of, for example Express cut resistance. Many of the cleaning agents made according to the invention are can still be molded during processing and storage.

The decisive factor for achieving the desired consistency is the one according to the invention Coordination of all ingredients and characteristics.

For example, it has been found that those described in US-A-3,607,764 solid mixtures not simply by successively diluting with water in the solid cleaning agents according to the invention with the desired controllable rheological properties can be transferred.

It was also found that introducing NaOH (liquid) into alcohols or Glycols with the addition of further solid NaOH gives no homogeneous agents.

Conversely, when the composition of the substance is selected according to the invention Surprisingly, no other additives apart from the thickener and Z. B. solid alkali hydroxide, preferably potassium or Sodium hydroxide, particularly preferably sodium hydroxide, necessary to achieve the to achieve the desired solidifying effect in aqueous sodium hydroxide solution. It should also be emphasized that the addition of the substances of the formula I or Formula II together with alkali solution, preferably potassium and sodium hydroxide solution, particularly preferably sodium hydroxide solution alone for the desired controllable strength suffice.

After all, the water content is also a critical parameter; it is between 10 and 35% by weight, advantageously between 20 and 30% by weight.

Due to the high NaOH content, the pH of the invention is Detergent over 13.

However, the cleaning agents produced according to the invention can also be used in Combination with other agents can be used without the inventive variable strength is lost. The cleaning agent works in this sense from alkali, preferably potassium and sodium hydroxide, particularly preferred Sodium hydroxide solution, substance I and / or II and solid alkali hydroxide, preferred Sodium hydroxide as a carrier phase for other ingredients commonly found in cleaners.

Optionally, the cleaning agents can therefore also contain a builder substance an amount of up to 50 wt .-%, preferably 15 to 40 wt .-%, contain.

The builder substance contained in the cleaning agents produced according to the invention can in principle any substance that is considered in the broadest sense of the art for Detergent and cleaning agent suitable builder is known, preferably water-soluble builder substances used.

As builder substances come e.g. B. alkali phosphates in the form of their sodium or Potassium salts can be in question. Examples for this are: Tetrasodium diphosphate, pentasodium triphosphate, so-called sodium hexametaphosphate as well as the corresponding potassium salts or mixtures of sodium hexametaphosphate as well as the corresponding potassium salts or mixtures from sodium and potassium salts.

Furthermore, complexing agents are to be mentioned, such as. B. nitrilotriacetate or ethylenediaminetetraacetate. Soda and borax also count within the scope of the present Invention to builder substances.

Other possible water-soluble builder components are, for example, organic Polymers of native or synthetic origin, especially polycarboxylates. In Examples include polyacrylic acids and copolymers Maleic anhydride and acrylic acid as well as the sodium salts of these polymer acids. Commercial products are e.g. B. Sokalan® CP 5 and PA 30 from BASF, Alcosperse® 175 and 177 from Alco, LMW® 45 N and SPO2 ND from Norsohaas. Suitable native polymers include, for example, oxidized starch (e.g. DE 42 28 786) and polyamino acids such as polyglutamic acid or polyaspartic acid, z. B. from Cygnus, Bayer, Rohm & Haas, Rhône-Poulenc or SRCHEM.

Other possible builder components are naturally occurring hydroxycarboxylic acids such as B. mono-, dihydroxy-succinic acid, α-hydroxypropionic acid, Citric acid, gluconic acid and their salts. Citrates are preferred in Form of trisodium citrate dihydrate used.

Amorphous metasilicates or layered silicates can also be mentioned as builder substances. Crystalline layered silicates are also suitable builders, provided they are sufficiently stable to alkali; Crystalline layered silicates are sold by Hoechst AG (Germany) under the trade name Na-SKS, e.g. B. Na-SKS-1 (Na ₂ Si ₂₂ O ₄₅ .xH ₂ O, Kenyaite), Na-SKS-2 (Na ₂ Si ₁₄ O ₂₉ .xH ₂ O, magadiite), Na-SKS-3 (Na ₂ Si ₈ O ₁₇ .xH ₂ O), Na-SKS-4 (Na ₂ Si ₄ O ₉ .xH ₂ O), makatite), Na-SKS-5 (µ-Na ₂ Si ₂ O ₅ ), Na-SKS -7 (β-Na ₂ Si ₂ O ₅ , natrosilite), Na-SKS-11 (τ-Na ₂ Si ₂ O ₅ ) and Na-SKS-6 (δ-Na ₂ Si ₂ O ₅ ).

Particularly preferred builder substances are those selected from the group Pentasodium triphosphate, trisodium citrate, nitrilotriacetate, ethylenediaminetetraacetate, soda, alkali metasilicate or their mixtures.

Bleaches customary in detergents can also be used in those produced according to the invention Means be included. These can be from the group of bleaches Oxygen base, such as B sodium perborate also in the form of its hydrates, or Sodium percarbonate, or from the group of chlorine-based bleaches, such as N-chloro-p-toluenesulfonamide, Trichloroisocyanuric acid, alkali dichloroisocyanurate, Alkali hypochlorites, and alkali hypochlorite releasing agents, particularly alkali-stable bleaching compositions are preferred. Both can be alkali-stable substances, or by suitable methods such as components stabilized by surface coating or passivation.

Low-foaming surfactants, especially nonionic surfactants, can also be present in an amount of up to 10% by weight, preferably up to 5% by weight. Extremely low-foam connections are usually used. These preferably include C ₁₂ -C ₁₈ alkyl polyethylene glycol polypropylene glycol ethers, each with up to 8 moles of ethylene oxide and propylene oxide units in the molecule. But you can also use other non-foaming non-foaming surfactants, such as. B. C ₁₂ -C ₁₈ alkyl polyethylene glycol-polybutylene glycol ether, each with up to 8 moles of ethylene oxide and butylene oxide units in the molecule and end-capped alkyl polyalkylene glycol mixed ether. It should be emphasized in particular that the cleaning agents produced according to the invention solve the problem even without the addition of these ingredients. But they support cleaning.

Other possible ingredients in the cleaners produced according to the invention are defoamers. These can be used if a chosen surfactant is under under the given circumstances foams too strongly, or acts as a foam suppressant foaming leftovers in the dishwasher. Also Packaging agents such as paraffin oil can be included, although the Properties according to the invention are retained even without their addition.

Optional ingredients are other common detergent ingredients, such as B. dyes or alkali-stable perfume substances.

In principle, abrasive ingredients can be present, preferably however, the cleaning agents produced according to the invention are free of them.

Although in addition thickeners such. B. swellable layered silicates from Montmorillonite type, bentonite, kaolin, talc or carboxymethyl cellulose optional Can be used to vary the strength, they are to be achieved the desired controllable solids properties and the consistency of the Cleaning agents produced according to the invention are not required, d. H. on such Thickeners can be omitted.

Another object of the invention results from the strengthening effect of Compounds of the formulas I and II in combination with solid alkali metal hydroxide, preferably potassium or sodium hydroxide, particularly preferably sodium hydroxide over alkali, preferably potash and sodium hydroxide, particularly preferred Sodium hydroxide solution.

So is a process for thickening aqueous 42 to 55 wt.% Alkali solution, preferably potassium and sodium hydroxide solution, particularly preferably sodium hydroxide solution claimed. The method is characterized in that one NaOH solution with stirring a compound of formula I and / or Adds compound of formula II and thus receives a paste-like preparation that a solid is then added, which is selected from the group of Alkali hydroxides, preferably potassium or sodium hydroxide, particularly preferably 0.1 to 35% by weight of sodium hydroxide or a mixture of these substances, and which is added in order to achieve a controllably variable strength. in the generally the process at 20 ° C to 50 ° C is preferred at 30 to 48 ° C carried out particularly preferably at 38-42 ° C.

Since the solubility of NaOH in water increases at higher temperatures, then the NaOH content in the aqueous solution is also more than 55% by weight be. Accordingly, the NaOH content can be at lower temperatures are also below 42% by weight. The restriction to 42 to 55% by weight NaOH solutions is therefore essentially limited to temperatures from 20 ° C to 25 ° C.

A particular advantage of the invention is that the stirrability and thus associated advantages is already given at room temperature. In some cases, e.g. with a greatly increased viscosity of the thickened alkali solution, preferably potassium and Sodium hydroxide solution, particularly preferably sodium hydroxide solution, can be added before the solid Ingredients should be cheap to reduce the viscosity slightly with the Temperature to go up. The consistency according to the invention can, however almost all cases below 42 ° C, preferably between 38 ° C and 42 ° C realized be, so that less temperature-stable components, such as chlorine-containing bleaching agents incorporated into the cleaning agents produced according to the invention can be.

In a preferred embodiment, after the addition of the Stirring compounds of the formula I and / or II for at least 3 minutes, before adding the sodium hydroxide in solid form.

If the thickened preparation should contain builder substances, these can also from the outset in the alkali lye to be thickened, preferably potash and Sodium hydroxide solution, particularly preferably sodium hydroxide solution, may be included. Preferably however, the builders of the already thickened are increased Temperatures pasty preparation from alkali, preferably potash and Sodium hydroxide solution, particularly preferably sodium hydroxide solution, formula I and / or formula II, and mixed with solid NaOH. Other optional ingredients are also included preferably the already thickened, pasty at elevated temperatures Preparation from alkali solution, preferably potassium and sodium hydroxide solution, particularly preferred Sodium hydroxide solution, formula I and / or formula II, and solid NaOH added.

The cleaning agents produced according to the invention can be used for cleaning Find surfaces, preferably for commercial or private use automatic washing of dishes.

The use of the solid detergents produced according to the invention can, for. B. in the Way that in a container (capacity e.g. 0.5 to 10 kg) Any cleaning agent of controllable strength is sprayed with water and the detergent thus released is used, e.g. B. in a Dishwasher is metered. Here, for example, one of the offers Henkel Hygiene GmbH sold under the name Topmater® P40 Dosing device or a V / VT-2000 solid dosing device sold by Henkel Ecolab on.

The cleaning agent can be produced, for example, in a stirred tank at 20 to 50 ° C, preferably at 30 to 48 ° C, particularly preferably at 38 - 42 ° C respectively. Then the detergent can be at approx. 40 ° C in the Sales containers are filled and to about 20 ° C via a cooling tunnel Achievement of the consistency according to the invention can be cooled.

But also other methods of filling and returning to room temperature are conceivable.

Some of the cleaning agents produced according to the invention harden over time was determined by time-dependent measurements and by the respective Composition of the mixtures is greatly influenced. This leads to Part of mixtures in which after a long period of several days and Weeks in the penetrometer test according to ISO 2137 no more penetration of the cone can be observed. Therefore, the details of the penetration depth refer to the time immediately after or less hours and days after production.

Examples

Detergents (1 kg each) of the following compositions 1 made to 8. 50% aqueous alkali was placed in a 2 liter beaker submitted. While stirring with a propeller stirrer (100 U / m) was 1,2-propylene glycol at 40 ° C. added and after the addition is complete for 5 minutes stirred, then sodium hydroxide was added as a solid alkali hydroxide. If necessary, further solid substances (builder) were subsequently added Stirring added; after the addition was complete, stirring was continued for 5 minutes. The penetration measurements according to ISO 2137 were carried out with a standard cone at room temperature (22 ° C), about 5 hours, 24 hours and 48 hours after the production of the cleaning agents. The values given are mean values from 3 measurements. Because undissolved in the pasty cleaning agents Components of different grain sizes can vary of the measured values of approx. ± 20% possible.

The quantities in the following table relate to mixtures in grams in order to ensure better comparability when the influence of the various components or process steps is considered. B1 B2 B3 B4 B5 B6 B7 B8 caustic soda potassium hydroxide MeOH (50% aq) 57.5 53 53 53 53 39.5 39.5 39.5 1,2 propylene glycol 6 5.5 5.5 5.5 5.5 4 - - Parrafin SIK 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 NaOH (solid) 10 15 15 - 15 30 30 30 Nitrilotriacetic acid 92% 25 25 - 25 25 25 25 - Penetration depth (mm) 5 hours 5.5 2.7 8.3 26.8 2.9 0 0 0 Penetration depth (mm) 24 hours 4.5 2.0 7.0 19.7 2.4 0 0 0 Depth of penetration (mm) 48 hours 3.2 1.8 7.2 17.8 2.9 0 0 0

All mixtures can be stirred homogeneously and filled into containers. The hardening process but is different in speed.

The different components have different effects on the strength and the Variability. This will be briefly explained in the following.

The comparison of examples B1 and B2 shows the influence of the amount of the solid Alkali hydroxide on the variation in strength with a mixture like this from an application point of view makes sense. An increase in the proportion of the fixed Alkali hydroxides lead to an increase in strength (= less penetration depth in the penetrometer test).

Example B3 shows, compared to B2, the influence of the optional additives Builder. Adding these substances leads to an increase in strength, but the consistency according to the invention can also be achieved without a builder.

In example B4 the influence of the solid alkali hydroxide is compared to example B2 Illuminated more precisely: addition of solid sodium hydroxide leads to a desired consolidation.

In experiment B5, the mixture was changed in order compared to B2 produced with the addition of nitrilotriacetic acid and solid NaOH. The Properties according to the invention can still be determined

In experiments B6 and B7 and B8, aqueous KOH was used instead of aqueous NaOH used.

In these examples, the very high proportion of solid NaOH only results very briefly stirrability. The hardening process takes place so quickly that after 5 hours there was no penetration in the penetration test. The invention Properties can, however, be observed if you look in measures shorter intervals after the mixture.

Cleaning agents not obtained according to the invention were produced without the addition of a compound of the formula I or formula II as described above for the cleaning agents prepared according to the invention, but without the addition of a compound of the formula I or formula II or without the addition of solid NaOH. V1 V2 V3 V4 V5 V6 caustic soda 20 25 30 35 90 80 propylene glycol - - - - 10 20 Parrafin SIK - - - - - - Soda calc. 30 20 20 10 - - NaOH (solid) - - - - - - water 20 25 30 35 - - Nitrilotriacetic acid 92% 30 30 20 20 - - Penetration depth (mm) according to ISO 2137 - - - - 19.5 4 V1 does not produce a homogeneous cleaning agent, but rather a moist, lumpy powder.
V2, V3 and V4 are subject to phase separation, ie separation of the aqueous phase, after only 1 day of storage at 25 ° C.
V5 and V6 show in particular the great advantage of adding solid alkali hydroxide, since a consistency according to the invention can only be obtained using large amounts of glycols, and variability when solidifying is at least severely restricted.

Claims (15)

1. A process for the production of a solid detergent of controllably variable strength which has a water content of 10 to 35% by weight and contains alkali metal hydroxide and glycol and/or alkanolamines, characterized in that

   a) aqueous alkali metal hydroxide solution in a quantity of 21 to 70% by weight and

   b) - to build up a high viscosity - a compound corresponding to formula I: HOCH₂CH(R¹)OR²    in which R¹ is a hydrogen atom or a methyl group and R² independently of R¹ is a hydrogen atom, a C_1-4 alkyl group, a group CH₂CH-(R³)OR⁴ or a group CH₂CH(R⁵)OCH₂CH(R⁶)OR⁷, where R³, R⁵ and R⁶ are hydrogen atoms or methyl groups and R⁴ and R⁷ are hydrogen atoms or C_1-4 alkyl groups, and/or a compound corresponding to formula II: [HOCH₂CH(R⁸)_3-xNH_x    in which R⁸ is a hydrogen atom or a methyl group and x is the number 0, 1 or 2,
      in a total quantity of 0.5 to 40% by weight
   are mixed and solid alkali metal hydroxide is subsequently added in a quantity of up to 35% by weight, all percentages by weight being based on the detergent as a whole.
2. A process as claimed in claim 1, characterized in that a 42 to 55% by weight potash or soda lye, preferably soda lye, is used as the aqueous alkali metal hydroxide solution.
3. A process as claimed in claim 1 or 2, characterized in that the aqueous alkali metal hydroxide solution is used in a quantity of 35 to 55% by weight, based on the detergent.
4. A process as claimed in one or more of claims 1 to 3, characterized in that ethylene glycol, 1,2-propylene glycol, butyl glycol or butyl diglycol is used as the compound corresponding to formula I and/or ethanolamine, diethanolamine and triethanolamine is used as the compound corresponding to formula II.
5. A process as claimed in claim 4, characterized in that 1,2-propylene glycol is used as the compound corresponding to formula I and/or diethanolamine is used as the compound corresponding to formula II.
6. A process as claimed in one or more of claims 1 to 5, characterized in that the compounds corresponding to formulae I and/or II are used in a total quantity of 1 to 10% by weight, based on the detergent.
7. A process as claimed in one or more of claims 1 to 6, characterized in that potassium or sodium hydroxide, preferably sodium hydroxide, is used as the solid alkali metal hydroxide.
8. A process as claimed in one or more of claims 1 to 7, characterized in that the solid alkali metal hydroxide is used in a quantity of 2 to 25% by weight, based on the detergent.
9. A process as claimed in one or more of claims 1 to 8, characterized in that a builder is additionally introduced in a quantity of up to 50% by weight and preferably in a quantity of 15 to 40% by weight, based on the detergent as a whole.
10. A process as claimed in claim 9, characterized in that the builder is selected from the group consisting of pentasodium triphosphate, trisodium citrate, nitrilotriacetate, ethylenediamine tetraacetate, soda, alkali metal metasilicate and mixtures thereof.
11. A process as claimed in claim 9 or 10, characterized in that the builder is added to the aqueous alkali metal hydroxide solution at the outset.
12. A process as claimed in claim 9 or 10, characterized in that the builder is added after mixing of the aqueous alkali metal hydroxide solution with compounds corresponding to formula(e) I and/or II and subsequent addition of solid alkali metal hydroxide.
13. A process for solidifying aqueous 42 to 55% by weight alkali metal hydroxide solution, characterized in that compounds corresponding to formula(e) I and/or II as claimed in claim 1 and solid alkali metal hydroxide are added with stirring to the aqueous alkali metal hydroxide solution.
14. A process as claimed in claim 13, characterized in that compounds corresponding formula(e) I and/or II as claimed in claim 1 and 0.1 to 35% by weight of sodium hydroxide in solid form are added with stirring to an aqueous sodium hydroxide solution.
15. A process as claimed in one or more of claims 1 to 14, characterized in that the solution is stirred for at least 3 minutes after addition of the compounds corresponding to formula(e) I and/or formula II and solid sodium hydroxide is then added.